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Linux/Documentation/admin-guide/kernel-parameters.txt

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Diff markup

Differences between /Documentation/admin-guide/kernel-parameters.txt (Version linux-6.11.5) and /Documentation/admin-guide/kernel-parameters.txt (Version linux-6.8.12)


  1         accept_memory=  [MM]                        1         accept_memory=  [MM]
  2                         Format: { eager | lazy      2                         Format: { eager | lazy }
  3                         default: lazy               3                         default: lazy
  4                         By default, unaccepted      4                         By default, unaccepted memory is accepted lazily to
  5                         avoid prolonged boot t      5                         avoid prolonged boot times. The lazy option will add
  6                         some runtime overhead       6                         some runtime overhead until all memory is eventually
  7                         accepted. In most case      7                         accepted. In most cases the overhead is negligible.
  8                         For some workloads or       8                         For some workloads or for debugging purposes
  9                         accept_memory=eager ca      9                         accept_memory=eager can be used to accept all memory
 10                         at once during boot.       10                         at once during boot.
 11                                                    11 
 12         acpi=           [HW,ACPI,X86,ARM64,RIS !!  12         acpi=           [HW,ACPI,X86,ARM64,RISCV64]
 13                         Advanced Configuration     13                         Advanced Configuration and Power Interface
 14                         Format: { force | on |     14                         Format: { force | on | off | strict | noirq | rsdt |
 15                                   copy_dsdt |  !!  15                                   copy_dsdt }
 16                         force -- enable ACPI i     16                         force -- enable ACPI if default was off
 17                         on -- enable ACPI but      17                         on -- enable ACPI but allow fallback to DT [arm64,riscv64]
 18                         off -- disable ACPI if     18                         off -- disable ACPI if default was on
 19                         noirq -- do not use AC     19                         noirq -- do not use ACPI for IRQ routing
 20                         strict -- Be less tole     20                         strict -- Be less tolerant of platforms that are not
 21                                 strictly ACPI      21                                 strictly ACPI specification compliant.
 22                         rsdt -- prefer RSDT ov     22                         rsdt -- prefer RSDT over (default) XSDT
 23                         copy_dsdt -- copy DSDT     23                         copy_dsdt -- copy DSDT to memory
 24                         nospcr -- disable cons !!  24                         For ARM64 and RISCV64, ONLY "acpi=off", "acpi=on" or
 25                                 default _seria !!  25                         "acpi=force" are available
 26                         For ARM64, ONLY "acpi= << 
 27                         "acpi=nospcr" are avai << 
 28                         For RISCV64, ONLY "acp << 
 29                         are available          << 
 30                                                    26 
 31                         See also Documentation     27                         See also Documentation/power/runtime_pm.rst, pci=noacpi
 32                                                    28 
 33         acpi_apic_instance=     [ACPI,IOAPIC,E !!  29         acpi_apic_instance=     [ACPI, IOAPIC]
 34                         Format: <int>              30                         Format: <int>
 35                         2: use 2nd APIC table,     31                         2: use 2nd APIC table, if available
 36                         1,0: use 1st APIC tabl     32                         1,0: use 1st APIC table
 37                         default: 0                 33                         default: 0
 38                                                    34 
 39         acpi_backlight= [HW,ACPI]                  35         acpi_backlight= [HW,ACPI]
 40                         { vendor | video | nat     36                         { vendor | video | native | none }
 41                         If set to vendor, pref     37                         If set to vendor, prefer vendor-specific driver
 42                         (e.g. thinkpad_acpi, s     38                         (e.g. thinkpad_acpi, sony_acpi, etc.) instead
 43                         of the ACPI video.ko d     39                         of the ACPI video.ko driver.
 44                         If set to video, use t     40                         If set to video, use the ACPI video.ko driver.
 45                         If set to native, use      41                         If set to native, use the device's native backlight mode.
 46                         If set to none, disabl     42                         If set to none, disable the ACPI backlight interface.
 47                                                    43 
 48         acpi_force_32bit_fadt_addr [ACPI,EARLY !!  44         acpi_force_32bit_fadt_addr
 49                         force FADT to use 32 b     45                         force FADT to use 32 bit addresses rather than the
 50                         64 bit X_* addresses.      46                         64 bit X_* addresses. Some firmware have broken 64
 51                         bit addresses for forc     47                         bit addresses for force ACPI ignore these and use
 52                         the older legacy 32 bi     48                         the older legacy 32 bit addresses.
 53                                                    49 
 54         acpica_no_return_repair [HW, ACPI]         50         acpica_no_return_repair [HW, ACPI]
 55                         Disable AML predefined     51                         Disable AML predefined validation mechanism
 56                         This mechanism can rep     52                         This mechanism can repair the evaluation result to make
 57                         the return objects mor     53                         the return objects more ACPI specification compliant.
 58                         This option is useful      54                         This option is useful for developers to identify the
 59                         root cause of an AML i     55                         root cause of an AML interpreter issue when the issue
 60                         has something to do wi     56                         has something to do with the repair mechanism.
 61                                                    57 
 62         acpi.debug_layer=       [HW,ACPI,ACPI_     58         acpi.debug_layer=       [HW,ACPI,ACPI_DEBUG]
 63         acpi.debug_level=       [HW,ACPI,ACPI_     59         acpi.debug_level=       [HW,ACPI,ACPI_DEBUG]
 64                         Format: <int>              60                         Format: <int>
 65                         CONFIG_ACPI_DEBUG must     61                         CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
 66                         debug output.  Bits in     62                         debug output.  Bits in debug_layer correspond to a
 67                         _COMPONENT in an ACPI      63                         _COMPONENT in an ACPI source file, e.g.,
 68                             #define _COMPONENT     64                             #define _COMPONENT ACPI_EVENTS
 69                         Bits in debug_level co     65                         Bits in debug_level correspond to a level in
 70                         ACPI_DEBUG_PRINT state     66                         ACPI_DEBUG_PRINT statements, e.g.,
 71                             ACPI_DEBUG_PRINT((     67                             ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
 72                         The debug_level mask d     68                         The debug_level mask defaults to "info".  See
 73                         Documentation/firmware     69                         Documentation/firmware-guide/acpi/debug.rst for more information about
 74                         debug layers and level     70                         debug layers and levels.
 75                                                    71 
 76                         Enable processor drive     72                         Enable processor driver info messages:
 77                             acpi.debug_layer=0     73                             acpi.debug_layer=0x20000000
 78                         Enable AML "Debug" out     74                         Enable AML "Debug" output, i.e., stores to the Debug
 79                         object while interpret     75                         object while interpreting AML:
 80                             acpi.debug_layer=0     76                             acpi.debug_layer=0xffffffff acpi.debug_level=0x2
 81                         Enable all messages re     77                         Enable all messages related to ACPI hardware:
 82                             acpi.debug_layer=0     78                             acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
 83                                                    79 
 84                         Some values produce so     80                         Some values produce so much output that the system is
 85                         unusable.  The "log_bu     81                         unusable.  The "log_buf_len" parameter may be useful
 86                         if you need to capture     82                         if you need to capture more output.
 87                                                    83 
 88         acpi_enforce_resources= [ACPI]             84         acpi_enforce_resources= [ACPI]
 89                         { strict | lax | no }      85                         { strict | lax | no }
 90                         Check for resource con     86                         Check for resource conflicts between native drivers
 91                         and ACPI OperationRegi     87                         and ACPI OperationRegions (SystemIO and SystemMemory
 92                         only). IO ports and me     88                         only). IO ports and memory declared in ACPI might be
 93                         used by the ACPI subsy     89                         used by the ACPI subsystem in arbitrary AML code and
 94                         can interfere with leg     90                         can interfere with legacy drivers.
 95                         strict (default): acce     91                         strict (default): access to resources claimed by ACPI
 96                         is denied; legacy driv     92                         is denied; legacy drivers trying to access reserved
 97                         resources will fail to     93                         resources will fail to bind to device using them.
 98                         lax: access to resourc     94                         lax: access to resources claimed by ACPI is allowed;
 99                         legacy drivers trying      95                         legacy drivers trying to access reserved resources
100                         will bind successfully     96                         will bind successfully but a warning message is logged.
101                         no: ACPI OperationRegi     97                         no: ACPI OperationRegions are not marked as reserved,
102                         no further checks are      98                         no further checks are performed.
103                                                    99 
104         acpi_force_table_verification   [HW,AC !! 100         acpi_force_table_verification   [HW,ACPI]
105                         Enable table checksum     101                         Enable table checksum verification during early stage.
106                         By default, this is di    102                         By default, this is disabled due to x86 early mapping
107                         size limitation.          103                         size limitation.
108                                                   104 
109         acpi_irq_balance [HW,ACPI]                105         acpi_irq_balance [HW,ACPI]
110                         ACPI will balance acti    106                         ACPI will balance active IRQs
111                         default in APIC mode      107                         default in APIC mode
112                                                   108 
113         acpi_irq_nobalance [HW,ACPI]              109         acpi_irq_nobalance [HW,ACPI]
114                         ACPI will not move act    110                         ACPI will not move active IRQs (default)
115                         default in PIC mode       111                         default in PIC mode
116                                                   112 
117         acpi_irq_isa=   [HW,ACPI] If irq_balan    113         acpi_irq_isa=   [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
118                         Format: <irq>,<irq>...    114                         Format: <irq>,<irq>...
119                                                   115 
120         acpi_irq_pci=   [HW,ACPI] If irq_balan    116         acpi_irq_pci=   [HW,ACPI] If irq_balance, clear listed IRQs for
121                         use by PCI                117                         use by PCI
122                         Format: <irq>,<irq>...    118                         Format: <irq>,<irq>...
123                                                   119 
124         acpi_mask_gpe=  [HW,ACPI]                 120         acpi_mask_gpe=  [HW,ACPI]
125                         Due to the existence o    121                         Due to the existence of _Lxx/_Exx, some GPEs triggered
126                         by unsupported hardwar    122                         by unsupported hardware/firmware features can result in
127                         GPE floodings that can    123                         GPE floodings that cannot be automatically disabled by
128                         the GPE dispatcher.       124                         the GPE dispatcher.
129                         This facility can be u    125                         This facility can be used to prevent such uncontrolled
130                         GPE floodings.            126                         GPE floodings.
131                         Format: <byte> or <bit    127                         Format: <byte> or <bitmap-list>
132                                                   128 
133         acpi_no_auto_serialize  [HW,ACPI]         129         acpi_no_auto_serialize  [HW,ACPI]
134                         Disable auto-serializa    130                         Disable auto-serialization of AML methods
135                         AML control methods th    131                         AML control methods that contain the opcodes to create
136                         named objects will be     132                         named objects will be marked as "Serialized" by the
137                         auto-serialization fea    133                         auto-serialization feature.
138                         This feature is enable    134                         This feature is enabled by default.
139                         This option allows to     135                         This option allows to turn off the feature.
140                                                   136 
141         acpi_no_memhotplug [ACPI] Disable memo    137         acpi_no_memhotplug [ACPI] Disable memory hotplug.  Useful for kdump
142                            kernels.               138                            kernels.
143                                                   139 
144         acpi_no_static_ssdt     [HW,ACPI,EARLY !! 140         acpi_no_static_ssdt     [HW,ACPI]
145                         Disable installation o    141                         Disable installation of static SSDTs at early boot time
146                         By default, SSDTs cont    142                         By default, SSDTs contained in the RSDT/XSDT will be
147                         installed automaticall    143                         installed automatically and they will appear under
148                         /sys/firmware/acpi/tab    144                         /sys/firmware/acpi/tables.
149                         This option turns off     145                         This option turns off this feature.
150                         Note that specifying t    146                         Note that specifying this option does not affect
151                         dynamic table installa    147                         dynamic table installation which will install SSDT
152                         tables to /sys/firmwar    148                         tables to /sys/firmware/acpi/tables/dynamic.
153                                                   149 
154         acpi_no_watchdog        [HW,ACPI,WDT]     150         acpi_no_watchdog        [HW,ACPI,WDT]
155                         Ignore the ACPI-based     151                         Ignore the ACPI-based watchdog interface (WDAT) and let
156                         a native driver contro    152                         a native driver control the watchdog device instead.
157                                                   153 
158         acpi_rsdp=      [ACPI,EFI,KEXEC,EARLY] !! 154         acpi_rsdp=      [ACPI,EFI,KEXEC]
159                         Pass the RSDP address     155                         Pass the RSDP address to the kernel, mostly used
160                         on machines running EF    156                         on machines running EFI runtime service to boot the
161                         second kernel for kdum    157                         second kernel for kdump.
162                                                   158 
163         acpi_os_name=   [HW,ACPI] Tell ACPI BI    159         acpi_os_name=   [HW,ACPI] Tell ACPI BIOS the name of the OS
164                         Format: To spoof as Wi    160                         Format: To spoof as Windows 98: ="Microsoft Windows"
165                                                   161 
166         acpi_rev_override [ACPI] Override the     162         acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167                         of 2 which is mandated    163                         of 2 which is mandated by ACPI 6) as the supported ACPI
168                         specification revision    164                         specification revision (when using this switch, it may
169                         be necessary to carry     165                         be necessary to carry out a cold reboot _twice_ in a
170                         row to make it take ef    166                         row to make it take effect on the platform firmware).
171                                                   167 
172         acpi_osi=       [HW,ACPI] Modify list     168         acpi_osi=       [HW,ACPI] Modify list of supported OS interface strings
173                         acpi_osi="string1"        169                         acpi_osi="string1"      # add string1
174                         acpi_osi="!string2"       170                         acpi_osi="!string2"     # remove string2
175                         acpi_osi=!*               171                         acpi_osi=!*             # remove all strings
176                         acpi_osi=!                172                         acpi_osi=!              # disable all built-in OS vendor
177                                                   173                                                   strings
178                         acpi_osi=!!               174                         acpi_osi=!!             # enable all built-in OS vendor
179                                                   175                                                   strings
180                         acpi_osi=                 176                         acpi_osi=               # disable all strings
181                                                   177 
182                         'acpi_osi=!' can be us    178                         'acpi_osi=!' can be used in combination with single or
183                         multiple 'acpi_osi="st    179                         multiple 'acpi_osi="string1"' to support specific OS
184                         vendor string(s).  Not    180                         vendor string(s).  Note that such command can only
185                         affect the default sta    181                         affect the default state of the OS vendor strings, thus
186                         it cannot affect the d    182                         it cannot affect the default state of the feature group
187                         strings and the curren    183                         strings and the current state of the OS vendor strings,
188                         specifying it multiple    184                         specifying it multiple times through kernel command line
189                         is meaningless.  This     185                         is meaningless.  This command is useful when one do not
190                         care about the state o    186                         care about the state of the feature group strings which
191                         should be controlled b    187                         should be controlled by the OSPM.
192                         Examples:                 188                         Examples:
193                           1. 'acpi_osi=! acpi_    189                           1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194                              to 'acpi_osi="Win    190                              to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195                              can make '_OSI("W    191                              can make '_OSI("Windows 2000")' TRUE.
196                                                   192 
197                         'acpi_osi=' cannot be     193                         'acpi_osi=' cannot be used in combination with other
198                         'acpi_osi=' command li    194                         'acpi_osi=' command lines, the _OSI method will not
199                         exist in the ACPI name    195                         exist in the ACPI namespace.  NOTE that such command can
200                         only affect the _OSI s    196                         only affect the _OSI support state, thus specifying it
201                         multiple times through    197                         multiple times through kernel command line is also
202                         meaningless.              198                         meaningless.
203                         Examples:                 199                         Examples:
204                           1. 'acpi_osi=' can m    200                           1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205                              FALSE.               201                              FALSE.
206                                                   202 
207                         'acpi_osi=!*' can be u    203                         'acpi_osi=!*' can be used in combination with single or
208                         multiple 'acpi_osi="st    204                         multiple 'acpi_osi="string1"' to support specific
209                         string(s).  Note that     205                         string(s).  Note that such command can affect the
210                         current state of both     206                         current state of both the OS vendor strings and the
211                         feature group strings,    207                         feature group strings, thus specifying it multiple times
212                         through kernel command    208                         through kernel command line is meaningful.  But it may
213                         still not able to affe    209                         still not able to affect the final state of a string if
214                         there are quirks relat    210                         there are quirks related to this string.  This command
215                         is useful when one wan    211                         is useful when one want to control the state of the
216                         feature group strings     212                         feature group strings to debug BIOS issues related to
217                         the OSPM features.        213                         the OSPM features.
218                         Examples:                 214                         Examples:
219                           1. 'acpi_osi="Module    215                           1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220                              '_OSI("Module Dev    216                              '_OSI("Module Device")' FALSE.
221                           2. 'acpi_osi=!* acpi    217                           2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222                              '_OSI("Module Dev    218                              '_OSI("Module Device")' TRUE.
223                           3. 'acpi_osi=! acpi_    219                           3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224                              equivalent to        220                              equivalent to
225                              'acpi_osi=!* acpi    221                              'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226                              and                  222                              and
227                              'acpi_osi=!* acpi    223                              'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228                              they all will mak    224                              they all will make '_OSI("Windows 2000")' TRUE.
229                                                   225 
230         acpi_pm_good    [X86]                     226         acpi_pm_good    [X86]
231                         Override the pmtimer b    227                         Override the pmtimer bug detection: force the kernel
232                         to assume that this ma    228                         to assume that this machine's pmtimer latches its value
233                         and always returns goo    229                         and always returns good values.
234                                                   230 
235         acpi_sci=       [HW,ACPI,EARLY] ACPI S !! 231         acpi_sci=       [HW,ACPI] ACPI System Control Interrupt trigger mode
236                         Format: { level | edge    232                         Format: { level | edge | high | low }
237                                                   233 
238         acpi_skip_timer_override [HW,ACPI,EARL !! 234         acpi_skip_timer_override [HW,ACPI]
239                         Recognize and ignore I    235                         Recognize and ignore IRQ0/pin2 Interrupt Override.
240                         For broken nForce2 BIO    236                         For broken nForce2 BIOS resulting in XT-PIC timer.
241                                                   237 
242         acpi_sleep=     [HW,ACPI] Sleep option    238         acpi_sleep=     [HW,ACPI] Sleep options
243                         Format: { s3_bios, s3_    239                         Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
244                                   s4_nohwsig,     240                                   s4_nohwsig, old_ordering, nonvs,
245                                   sci_force_en    241                                   sci_force_enable, nobl }
246                         See Documentation/powe    242                         See Documentation/power/video.rst for information on
247                         s3_bios and s3_mode.      243                         s3_bios and s3_mode.
248                         s3_beep is for debuggi    244                         s3_beep is for debugging; it makes the PC's speaker beep
249                         as soon as the kernel'    245                         as soon as the kernel's real-mode entry point is called.
250                         s4_hwsig causes the ke    246                         s4_hwsig causes the kernel to check the ACPI hardware
251                         signature during resum    247                         signature during resume from hibernation, and gracefully
252                         refuse to resume if it    248                         refuse to resume if it has changed. This complies with
253                         the ACPI specification    249                         the ACPI specification but not with reality, since
254                         Windows does not do th    250                         Windows does not do this and many laptops do change it
255                         on docking. So the def    251                         on docking. So the default behaviour is to allow resume
256                         and simply warn when t    252                         and simply warn when the signature changes, unless the
257                         s4_hwsig option is ena    253                         s4_hwsig option is enabled.
258                         s4_nohwsig prevents AC    254                         s4_nohwsig prevents ACPI hardware signature from being
259                         used (or even warned a    255                         used (or even warned about) during resume.
260                         old_ordering causes th    256                         old_ordering causes the ACPI 1.0 ordering of the _PTS
261                         control method, with r    257                         control method, with respect to putting devices into
262                         low power states, to b    258                         low power states, to be enforced (the ACPI 2.0 ordering
263                         of _PTS is used by def    259                         of _PTS is used by default).
264                         nonvs prevents the ker    260                         nonvs prevents the kernel from saving/restoring the
265                         ACPI NVS memory during    261                         ACPI NVS memory during suspend/hibernation and resume.
266                         sci_force_enable cause    262                         sci_force_enable causes the kernel to set SCI_EN directly
267                         on resume from S1/S3 (    263                         on resume from S1/S3 (which is against the ACPI spec,
268                         but some broken system    264                         but some broken systems don't work without it).
269                         nobl causes the intern    265                         nobl causes the internal blacklist of systems known to
270                         behave incorrectly in     266                         behave incorrectly in some ways with respect to system
271                         suspend and resume to     267                         suspend and resume to be ignored (use wisely).
272                                                   268 
273         acpi_use_timer_override [HW,ACPI,EARLY !! 269         acpi_use_timer_override [HW,ACPI]
274                         Use timer override. Fo    270                         Use timer override. For some broken Nvidia NF5 boards
275                         that require a timer o    271                         that require a timer override, but don't have HPET
276                                                   272 
277         add_efi_memmap  [EFI,X86,EARLY] Includ !! 273         add_efi_memmap  [EFI; X86] Include EFI memory map in
278                         kernel's map of availa    274                         kernel's map of available physical RAM.
279                                                   275 
280         agp=            [AGP]                     276         agp=            [AGP]
281                         { off | try_unsupporte    277                         { off | try_unsupported }
282                         off: disable AGP suppo    278                         off: disable AGP support
283                         try_unsupported: try t    279                         try_unsupported: try to drive unsupported chipsets
284                                 (may crash com    280                                 (may crash computer or cause data corruption)
285                                                   281 
286         ALSA            [HW,ALSA]                 282         ALSA            [HW,ALSA]
287                         See Documentation/soun    283                         See Documentation/sound/alsa-configuration.rst
288                                                   284 
289         alignment=      [KNL,ARM]                 285         alignment=      [KNL,ARM]
290                         Allow the default user    286                         Allow the default userspace alignment fault handler
291                         behaviour to be specif    287                         behaviour to be specified.  Bit 0 enables warnings,
292                         bit 1 enables fixups,     288                         bit 1 enables fixups, and bit 2 sends a segfault.
293                                                   289 
294         align_va_addr=  [X86-64]                  290         align_va_addr=  [X86-64]
295                         Align virtual addresse    291                         Align virtual addresses by clearing slice [14:12] when
296                         allocating a VMA at pr    292                         allocating a VMA at process creation time. This option
297                         gives you up to 3% per    293                         gives you up to 3% performance improvement on AMD F15h
298                         machines (where it is     294                         machines (where it is enabled by default) for a
299                         CPU-intensive style be    295                         CPU-intensive style benchmark, and it can vary highly in
300                         a microbenchmark depen    296                         a microbenchmark depending on workload and compiler.
301                                                   297 
302                         32: only for 32-bit pr    298                         32: only for 32-bit processes
303                         64: only for 64-bit pr    299                         64: only for 64-bit processes
304                         on: enable for both 32    300                         on: enable for both 32- and 64-bit processes
305                         off: disable for both     301                         off: disable for both 32- and 64-bit processes
306                                                   302 
307         alloc_snapshot  [FTRACE]                  303         alloc_snapshot  [FTRACE]
308                         Allocate the ftrace sn    304                         Allocate the ftrace snapshot buffer on boot up when the
309                         main buffer is allocat    305                         main buffer is allocated. This is handy if debugging
310                         and you need to use tr    306                         and you need to use tracing_snapshot() on boot up, and
311                         do not want to use tra    307                         do not want to use tracing_snapshot_alloc() as it needs
312                         to be done where GFP_K    308                         to be done where GFP_KERNEL allocations are allowed.
313                                                   309 
314         allow_mismatched_32bit_el0 [ARM64,EARL !! 310         allow_mismatched_32bit_el0 [ARM64]
315                         Allow execve() of 32-b    311                         Allow execve() of 32-bit applications and setting of the
316                         PER_LINUX32 personalit    312                         PER_LINUX32 personality on systems where only a strict
317                         subset of the CPUs sup    313                         subset of the CPUs support 32-bit EL0. When this
318                         parameter is present,     314                         parameter is present, the set of CPUs supporting 32-bit
319                         EL0 is indicated by /s    315                         EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
320                         and hot-unplug operati    316                         and hot-unplug operations may be restricted.
321                                                   317 
322                         See Documentation/arch    318                         See Documentation/arch/arm64/asymmetric-32bit.rst for more
323                         information.              319                         information.
324                                                   320 
325         amd_iommu=      [HW,X86-64]               321         amd_iommu=      [HW,X86-64]
326                         Pass parameters to the    322                         Pass parameters to the AMD IOMMU driver in the system.
327                         Possible values are:      323                         Possible values are:
328                         fullflush - Deprecated    324                         fullflush - Deprecated, equivalent to iommu.strict=1
329                         off       - do not ini    325                         off       - do not initialize any AMD IOMMU found in
330                                     the system    326                                     the system
331                         force_isolation - Forc    327                         force_isolation - Force device isolation for all
332                                           devi    328                                           devices. The IOMMU driver is not
333                                           allo    329                                           allowed anymore to lift isolation
334                                           requ    330                                           requirements as needed. This option
335                                           does    331                                           does not override iommu=pt
336                         force_enable - Force e    332                         force_enable - Force enable the IOMMU on platforms known
337                                        to be b    333                                        to be buggy with IOMMU enabled. Use this
338                                        option     334                                        option with care.
339                         pgtbl_v1     - Use v1     335                         pgtbl_v1     - Use v1 page table for DMA-API (Default).
340                         pgtbl_v2     - Use v2     336                         pgtbl_v2     - Use v2 page table for DMA-API.
341                         irtcachedis  - Disable    337                         irtcachedis  - Disable Interrupt Remapping Table (IRT) caching.
342                                                   338 
343         amd_iommu_dump= [HW,X86-64]               339         amd_iommu_dump= [HW,X86-64]
344                         Enable AMD IOMMU drive    340                         Enable AMD IOMMU driver option to dump the ACPI table
345                         for AMD IOMMU. With th    341                         for AMD IOMMU. With this option enabled, AMD IOMMU
346                         driver will print ACPI    342                         driver will print ACPI tables for AMD IOMMU during
347                         IOMMU initialization.     343                         IOMMU initialization.
348                                                   344 
349         amd_iommu_intr= [HW,X86-64]               345         amd_iommu_intr= [HW,X86-64]
350                         Specifies one of the f    346                         Specifies one of the following AMD IOMMU interrupt
351                         remapping modes:          347                         remapping modes:
352                         legacy     - Use legac    348                         legacy     - Use legacy interrupt remapping mode.
353                         vapic      - Use virtu    349                         vapic      - Use virtual APIC mode, which allows IOMMU
354                                      to inject    350                                      to inject interrupts directly into guest.
355                                      This mode    351                                      This mode requires kvm-amd.avic=1.
356                                      (Default     352                                      (Default when IOMMU HW support is present.)
357                                                   353 
358         amd_pstate=     [X86,EARLY]            !! 354         amd_pstate=     [X86]
359                         disable                   355                         disable
360                           Do not enable amd_ps    356                           Do not enable amd_pstate as the default
361                           scaling driver for t    357                           scaling driver for the supported processors
362                         passive                   358                         passive
363                           Use amd_pstate with     359                           Use amd_pstate with passive mode as a scaling driver.
364                           In this mode autonom    360                           In this mode autonomous selection is disabled.
365                           Driver requests a de    361                           Driver requests a desired performance level and platform
366                           tries to match the s    362                           tries to match the same performance level if it is
367                           satisfied by guarant    363                           satisfied by guaranteed performance level.
368                         active                    364                         active
369                           Use amd_pstate_epp d    365                           Use amd_pstate_epp driver instance as the scaling driver,
370                           driver provides a hi    366                           driver provides a hint to the hardware if software wants
371                           to bias toward perfo    367                           to bias toward performance (0x0) or energy efficiency (0xff)
372                           to the CPPC firmware    368                           to the CPPC firmware. then CPPC power algorithm will
373                           calculate the runtim    369                           calculate the runtime workload and adjust the realtime cores
374                           frequency.              370                           frequency.
375                         guided                    371                         guided
376                           Activate guided auto    372                           Activate guided autonomous mode. Driver requests minimum and
377                           maximum performance     373                           maximum performance level and the platform autonomously
378                           selects a performanc    374                           selects a performance level in this range and appropriate
379                           to the current workl    375                           to the current workload.
380                                                   376 
381         amd_prefcore=                          << 
382                         [X86]                  << 
383                         disable                << 
384                           Disable amd-pstate p << 
385                                                << 
386         amijoy.map=     [HW,JOY] Amiga joystic    377         amijoy.map=     [HW,JOY] Amiga joystick support
387                         Map of devices attache    378                         Map of devices attached to JOY0DAT and JOY1DAT
388                         Format: <a>,<b>           379                         Format: <a>,<b>
389                         See also Documentation    380                         See also Documentation/input/joydev/joystick.rst
390                                                   381 
391         analog.map=     [HW,JOY] Analog joysti    382         analog.map=     [HW,JOY] Analog joystick and gamepad support
392                         Specifies type or capa    383                         Specifies type or capabilities of an analog joystick
393                         connected to one of 16    384                         connected to one of 16 gameports
394                         Format: <type1>,<type2    385                         Format: <type1>,<type2>,..<type16>
395                                                   386 
396         apc=            [HW,SPARC]                387         apc=            [HW,SPARC]
397                         Power management funct    388                         Power management functions (SPARCstation-4/5 + deriv.)
398                         Format: noidle            389                         Format: noidle
399                         Disable APC CPU standb    390                         Disable APC CPU standby support. SPARCstation-Fox does
400                         not play well with APC    391                         not play well with APC CPU idle - disable it if you have
401                         APC and your system cr    392                         APC and your system crashes randomly.
402                                                   393 
403         apic=           [APIC,X86,EARLY] Advan !! 394         apic=           [APIC,X86] Advanced Programmable Interrupt Controller
404                         Change the output verb    395                         Change the output verbosity while booting
405                         Format: { quiet (defau    396                         Format: { quiet (default) | verbose | debug }
406                         Change the amount of d    397                         Change the amount of debugging information output
407                         when initialising the     398                         when initialising the APIC and IO-APIC components.
408                         For X86-32, this can a    399                         For X86-32, this can also be used to specify an APIC
409                         driver name.              400                         driver name.
410                         Format: apic=driver_na    401                         Format: apic=driver_name
411                         Examples: apic=bigsmp     402                         Examples: apic=bigsmp
412                                                   403 
413         apic_extnmi=    [APIC,X86,EARLY] Exter !! 404         apic_extnmi=    [APIC,X86] External NMI delivery setting
414                         Format: { bsp (default    405                         Format: { bsp (default) | all | none }
415                         bsp:  External NMI is     406                         bsp:  External NMI is delivered only to CPU 0
416                         all:  External NMIs ar    407                         all:  External NMIs are broadcast to all CPUs as a
417                               backup of CPU 0     408                               backup of CPU 0
418                         none: External NMI is     409                         none: External NMI is masked for all CPUs. This is
419                               useful so that a    410                               useful so that a dump capture kernel won't be
420                               shot down by NMI    411                               shot down by NMI
421                                                   412 
422         autoconf=       [IPV6]                    413         autoconf=       [IPV6]
423                         See Documentation/netw    414                         See Documentation/networking/ipv6.rst.
424                                                   415 
425         apm=            [APM] Advanced Power M    416         apm=            [APM] Advanced Power Management
426                         See header of arch/x86    417                         See header of arch/x86/kernel/apm_32.c.
427                                                   418 
428         apparmor=       [APPARMOR] Disable or     419         apparmor=       [APPARMOR] Disable or enable AppArmor at boot time
429                         Format: { "0" | "1" }     420                         Format: { "0" | "1" }
430                         See security/apparmor/    421                         See security/apparmor/Kconfig help text
431                         0 -- disable.             422                         0 -- disable.
432                         1 -- enable.              423                         1 -- enable.
433                         Default value is set v    424                         Default value is set via kernel config option.
434                                                   425 
435         arcrimi=        [HW,NET] ARCnet - "RIM    426         arcrimi=        [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436                         Format: <io>,<irq>,<no    427                         Format: <io>,<irq>,<nodeID>
437                                                   428 
438         arm64.no32bit_el0 [ARM64] Unconditiona << 
439                         32 bit applications.   << 
440                                                << 
441         arm64.nobti     [ARM64] Unconditionall    429         arm64.nobti     [ARM64] Unconditionally disable Branch Target
442                         Identification support    430                         Identification support
443                                                   431 
444         arm64.nomops    [ARM64] Unconditionall    432         arm64.nomops    [ARM64] Unconditionally disable Memory Copy and Memory
445                         Set instructions suppo    433                         Set instructions support
446                                                   434 
447         arm64.nomte     [ARM64] Unconditionall    435         arm64.nomte     [ARM64] Unconditionally disable Memory Tagging Extension
448                         support                   436                         support
449                                                   437 
450         arm64.nopauth   [ARM64] Unconditionall    438         arm64.nopauth   [ARM64] Unconditionally disable Pointer Authentication
451                         support                   439                         support
452                                                   440 
453         arm64.nosme     [ARM64] Unconditionall    441         arm64.nosme     [ARM64] Unconditionally disable Scalable Matrix
454                         Extension support         442                         Extension support
455                                                   443 
456         arm64.nosve     [ARM64] Unconditionall    444         arm64.nosve     [ARM64] Unconditionally disable Scalable Vector
457                         Extension support         445                         Extension support
458                                                   446 
459         ataflop=        [HW,M68k]                 447         ataflop=        [HW,M68k]
460                                                   448 
461         atarimouse=     [HW,MOUSE] Atari Mouse    449         atarimouse=     [HW,MOUSE] Atari Mouse
462                                                   450 
463         atkbd.extra=    [HW] Enable extra LEDs    451         atkbd.extra=    [HW] Enable extra LEDs and keys on IBM RapidAccess,
464                         EzKey and similar keyb    452                         EzKey and similar keyboards
465                                                   453 
466         atkbd.reset=    [HW] Reset keyboard du    454         atkbd.reset=    [HW] Reset keyboard during initialization
467                                                   455 
468         atkbd.set=      [HW] Select keyboard c    456         atkbd.set=      [HW] Select keyboard code set
469                         Format: <int> (2 = AT     457                         Format: <int> (2 = AT (default), 3 = PS/2)
470                                                   458 
471         atkbd.scroll=   [HW] Enable scroll whe    459         atkbd.scroll=   [HW] Enable scroll wheel on MS Office and similar
472                         keyboards                 460                         keyboards
473                                                   461 
474         atkbd.softraw=  [HW] Choose between sy    462         atkbd.softraw=  [HW] Choose between synthetic and real raw mode
475                         Format: <bool> (0 = re    463                         Format: <bool> (0 = real, 1 = synthetic (default))
476                                                   464 
477         atkbd.softrepeat= [HW]                    465         atkbd.softrepeat= [HW]
478                         Use software keyboard     466                         Use software keyboard repeat
479                                                   467 
480         audit=          [KNL] Enable the audit    468         audit=          [KNL] Enable the audit sub-system
481                         Format: { "0" | "1" |     469                         Format: { "0" | "1" | "off" | "on" }
482                         0 | off - kernel audit    470                         0 | off - kernel audit is disabled and can not be
483                             enabled until the     471                             enabled until the next reboot
484                         unset - kernel audit i    472                         unset - kernel audit is initialized but disabled and
485                             will be fully enab    473                             will be fully enabled by the userspace auditd.
486                         1 | on - kernel audit     474                         1 | on - kernel audit is initialized and partially
487                             enabled, storing a    475                             enabled, storing at most audit_backlog_limit
488                             messages in RAM un    476                             messages in RAM until it is fully enabled by the
489                             userspace auditd.     477                             userspace auditd.
490                         Default: unset            478                         Default: unset
491                                                   479 
492         audit_backlog_limit= [KNL] Set the aud    480         audit_backlog_limit= [KNL] Set the audit queue size limit.
493                         Format: <int> (must be    481                         Format: <int> (must be >=0)
494                         Default: 64               482                         Default: 64
495                                                   483 
496         bau=            [X86_UV] Enable the BA    484         bau=            [X86_UV] Enable the BAU on SGI UV.  The default
497                         behavior is to disable    485                         behavior is to disable the BAU (i.e. bau=0).
498                         Format: { "0" | "1" }     486                         Format: { "0" | "1" }
499                         0 - Disable the BAU.      487                         0 - Disable the BAU.
500                         1 - Enable the BAU.       488                         1 - Enable the BAU.
501                         unset - Disable the BA    489                         unset - Disable the BAU.
502                                                   490 
503         baycom_epp=     [HW,AX25]                 491         baycom_epp=     [HW,AX25]
504                         Format: <io>,<mode>       492                         Format: <io>,<mode>
505                                                   493 
506         baycom_par=     [HW,AX25] BayCom Paral    494         baycom_par=     [HW,AX25] BayCom Parallel Port AX.25 Modem
507                         Format: <io>,<mode>       495                         Format: <io>,<mode>
508                         See header of drivers/    496                         See header of drivers/net/hamradio/baycom_par.c.
509                                                   497 
510         baycom_ser_fdx= [HW,AX25]                 498         baycom_ser_fdx= [HW,AX25]
511                         BayCom Serial Port AX.    499                         BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512                         Format: <io>,<irq>,<mo    500                         Format: <io>,<irq>,<mode>[,<baud>]
513                         See header of drivers/    501                         See header of drivers/net/hamradio/baycom_ser_fdx.c.
514                                                   502 
515         baycom_ser_hdx= [HW,AX25]                 503         baycom_ser_hdx= [HW,AX25]
516                         BayCom Serial Port AX.    504                         BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517                         Format: <io>,<irq>,<mo    505                         Format: <io>,<irq>,<mode>
518                         See header of drivers/    506                         See header of drivers/net/hamradio/baycom_ser_hdx.c.
519                                                   507 
520         bert_disable    [ACPI]                    508         bert_disable    [ACPI]
521                         Disable BERT OS suppor    509                         Disable BERT OS support on buggy BIOSes.
522                                                   510 
523         bgrt_disable    [ACPI,X86,EARLY]       !! 511         bgrt_disable    [ACPI][X86]
524                         Disable BGRT to avoid     512                         Disable BGRT to avoid flickering OEM logo.
525                                                   513 
526         blkdevparts=    Manual partition parsi    514         blkdevparts=    Manual partition parsing of block device(s) for
527                         embedded devices based    515                         embedded devices based on command line input.
528                         See Documentation/bloc    516                         See Documentation/block/cmdline-partition.rst
529                                                   517 
530         boot_delay=     [KNL,EARLY]            !! 518         boot_delay=     Milliseconds to delay each printk during boot.
531                         Milliseconds to delay  << 
532                         Only works if CONFIG_B    519                         Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
533                         and you may also have     520                         and you may also have to specify "lpj=".  Boot_delay
534                         values larger than 10     521                         values larger than 10 seconds (10000) are assumed
535                         erroneous and ignored.    522                         erroneous and ignored.
536                         Format: integer           523                         Format: integer
537                                                   524 
538         bootconfig      [KNL,EARLY]            !! 525         bootconfig      [KNL]
539                         Extended command line     526                         Extended command line options can be added to an initrd
540                         and this will cause th    527                         and this will cause the kernel to look for it.
541                                                   528 
542                         See Documentation/admi    529                         See Documentation/admin-guide/bootconfig.rst
543                                                   530 
544         bttv.card=      [HW,V4L] bttv (bt848 +    531         bttv.card=      [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545         bttv.radio=     Most important insmod     532         bttv.radio=     Most important insmod options are available as
546                         kernel args too.          533                         kernel args too.
547         bttv.pll=       See Documentation/admi    534         bttv.pll=       See Documentation/admin-guide/media/bttv.rst
548         bttv.tuner=                               535         bttv.tuner=
549                                                   536 
550         bulk_remove=off [PPC]  This parameter     537         bulk_remove=off [PPC]  This parameter disables the use of the pSeries
551                         firmware feature for f    538                         firmware feature for flushing multiple hpte entries
552                         at a time.                539                         at a time.
553                                                   540 
554         c101=           [NET] Moxa C101 synchr    541         c101=           [NET] Moxa C101 synchronous serial card
555                                                   542 
556         cachesize=      [BUGS=X86-32] Override    543         cachesize=      [BUGS=X86-32] Override level 2 CPU cache size detection.
557                         Sometimes CPU hardware    544                         Sometimes CPU hardware bugs make them report the cache
558                         size incorrectly. The     545                         size incorrectly. The kernel will attempt work arounds
559                         to fix known problems,    546                         to fix known problems, but for some CPUs it is not
560                         possible to determine     547                         possible to determine what the correct size should be.
561                         This option provides a    548                         This option provides an override for these situations.
562                                                   549 
563         carrier_timeout=                          550         carrier_timeout=
564                         [NET] Specifies amount    551                         [NET] Specifies amount of time (in seconds) that
565                         the kernel should wait    552                         the kernel should wait for a network carrier. By default
566                         it waits 120 seconds.     553                         it waits 120 seconds.
567                                                   554 
568         ca_keys=        [KEYS] This parameter     555         ca_keys=        [KEYS] This parameter identifies a specific key(s) on
569                         the system trusted key    556                         the system trusted keyring to be used for certificate
570                         trust validation.         557                         trust validation.
571                         format: { id:<keyid> |    558                         format: { id:<keyid> | builtin }
572                                                   559 
573         cca=            [MIPS,EARLY] Override  !! 560         cca=            [MIPS] Override the kernel pages' cache coherency
574                         algorithm.  Accepted v    561                         algorithm.  Accepted values range from 0 to 7
575                         inclusive. See arch/mi    562                         inclusive. See arch/mips/include/asm/pgtable-bits.h
576                         for platform specific     563                         for platform specific values (SB1, Loongson3 and
577                         others).                  564                         others).
578                                                   565 
579         ccw_timeout_log [S390]                    566         ccw_timeout_log [S390]
580                         See Documentation/arch    567                         See Documentation/arch/s390/common_io.rst for details.
581                                                   568 
582         cgroup_disable= [KNL] Disable a partic    569         cgroup_disable= [KNL] Disable a particular controller or optional feature
583                         Format: {name of the c    570                         Format: {name of the controller(s) or feature(s) to disable}
584                         The effects of cgroup_    571                         The effects of cgroup_disable=foo are:
585                         - foo isn't auto-mount    572                         - foo isn't auto-mounted if you mount all cgroups in
586                           a single hierarchy      573                           a single hierarchy
587                         - foo isn't visible as    574                         - foo isn't visible as an individually mountable
588                           subsystem               575                           subsystem
589                         - if foo is an optiona    576                         - if foo is an optional feature then the feature is
590                           disabled and corresp    577                           disabled and corresponding cgroup files are not
591                           created                 578                           created
592                         {Currently only "memor    579                         {Currently only "memory" controller deal with this and
593                         cut the overhead, othe    580                         cut the overhead, others just disable the usage. So
594                         only cgroup_disable=me    581                         only cgroup_disable=memory is actually worthy}
595                         Specifying "pressure"     582                         Specifying "pressure" disables per-cgroup pressure
596                         stall information acco    583                         stall information accounting feature
597                                                   584 
598         cgroup_no_v1=   [KNL] Disable cgroup c    585         cgroup_no_v1=   [KNL] Disable cgroup controllers and named hierarchies in v1
599                         Format: { { controller    586                         Format: { { controller | "all" | "named" }
600                                   [,{ controll    587                                   [,{ controller | "all" | "named" }...] }
601                         Like cgroup_disable, b    588                         Like cgroup_disable, but only applies to cgroup v1;
602                         the blacklisted contro    589                         the blacklisted controllers remain available in cgroup2.
603                         "all" blacklists all c    590                         "all" blacklists all controllers and "named" disables
604                         named mounts. Specifyi    591                         named mounts. Specifying both "all" and "named" disables
605                         all v1 hierarchies.       592                         all v1 hierarchies.
606                                                   593 
607         cgroup_favordynmods= [KNL] Enable or D    594         cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
608                         Format: { "true" | "fa    595                         Format: { "true" | "false" }
609                         Defaults to the value     596                         Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
610                                                   597 
611         cgroup.memory=  [KNL] Pass options to     598         cgroup.memory=  [KNL] Pass options to the cgroup memory controller.
612                         Format: <string>          599                         Format: <string>
613                         nosocket -- Disable so    600                         nosocket -- Disable socket memory accounting.
614                         nokmem -- Disable kern    601                         nokmem -- Disable kernel memory accounting.
615                         nobpf -- Disable BPF m    602                         nobpf -- Disable BPF memory accounting.
616                                                   603 
617         checkreqprot=   [SELINUX] Set initial     604         checkreqprot=   [SELINUX] Set initial checkreqprot flag value.
618                         Format: { "0" | "1" }     605                         Format: { "0" | "1" }
619                         See security/selinux/K    606                         See security/selinux/Kconfig help text.
620                         0 -- check protection     607                         0 -- check protection applied by kernel (includes
621                                 any implied ex    608                                 any implied execute protection).
622                         1 -- check protection     609                         1 -- check protection requested by application.
623                         Default value is set v    610                         Default value is set via a kernel config option.
624                         Value can be changed a    611                         Value can be changed at runtime via
625                                 /sys/fs/selinu    612                                 /sys/fs/selinux/checkreqprot.
626                         Setting checkreqprot t    613                         Setting checkreqprot to 1 is deprecated.
627                                                   614 
628         cio_ignore=     [S390]                    615         cio_ignore=     [S390]
629                         See Documentation/arch    616                         See Documentation/arch/s390/common_io.rst for details.
630                                                   617 
631         clearcpuid=X[,X...] [X86]                 618         clearcpuid=X[,X...] [X86]
632                         Disable CPUID feature     619                         Disable CPUID feature X for the kernel. See
633                         arch/x86/include/asm/c    620                         arch/x86/include/asm/cpufeatures.h for the valid bit
634                         numbers X. Note the Li    621                         numbers X. Note the Linux-specific bits are not necessarily
635                         stable over kernel opt    622                         stable over kernel options, but the vendor-specific
636                         ones should be.           623                         ones should be.
637                         X can also be a string    624                         X can also be a string as appearing in the flags: line
638                         in /proc/cpuinfo which    625                         in /proc/cpuinfo which does not have the above
639                         instability issue. How    626                         instability issue. However, not all features have names
640                         in /proc/cpuinfo.         627                         in /proc/cpuinfo.
641                         Note that using this o    628                         Note that using this option will taint your kernel.
642                         Also note that user pr    629                         Also note that user programs calling CPUID directly
643                         or using the feature w    630                         or using the feature without checking anything
644                         will still see it. Thi    631                         will still see it. This just prevents it from
645                         being used by the kern    632                         being used by the kernel or shown in /proc/cpuinfo.
646                         Also note the kernel m    633                         Also note the kernel might malfunction if you disable
647                         some critical bits.       634                         some critical bits.
648                                                   635 
649         clk_ignore_unused                         636         clk_ignore_unused
650                         [CLK]                     637                         [CLK]
651                         Prevents the clock fra    638                         Prevents the clock framework from automatically gating
652                         clocks that have not b    639                         clocks that have not been explicitly enabled by a Linux
653                         device driver but are     640                         device driver but are enabled in hardware at reset or
654                         by the bootloader/firm    641                         by the bootloader/firmware. Note that this does not
655                         force such clocks to b    642                         force such clocks to be always-on nor does it reserve
656                         those clocks in any wa    643                         those clocks in any way. This parameter is useful for
657                         debug and development,    644                         debug and development, but should not be needed on a
658                         platform with proper d    645                         platform with proper driver support.  For more
659                         information, see Docum    646                         information, see Documentation/driver-api/clk.rst.
660                                                   647 
661         clock=          [BUGS=X86-32, HW] gett    648         clock=          [BUGS=X86-32, HW] gettimeofday clocksource override.
662                         [Deprecated]              649                         [Deprecated]
663                         Forces specified clock    650                         Forces specified clocksource (if available) to be used
664                         when calculating getti    651                         when calculating gettimeofday(). If specified
665                         clocksource is not ava    652                         clocksource is not available, it defaults to PIT.
666                         Format: { pit | tsc |     653                         Format: { pit | tsc | cyclone | pmtmr }
667                                                   654 
668         clocksource=    Override the default c    655         clocksource=    Override the default clocksource
669                         Format: <string>          656                         Format: <string>
670                         Override the default c    657                         Override the default clocksource and use the clocksource
671                         with the name specifie    658                         with the name specified.
672                         Some clocksource names    659                         Some clocksource names to choose from, depending on
673                         the platform:             660                         the platform:
674                         [all] jiffies (this is    661                         [all] jiffies (this is the base, fallback clocksource)
675                         [ACPI] acpi_pm            662                         [ACPI] acpi_pm
676                         [ARM] imx_timer1,OSTS,    663                         [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677                                 pxa_timer,time    664                                 pxa_timer,timer3,32k_counter,timer0_1
678                         [X86-32] pit,hpet,tsc;    665                         [X86-32] pit,hpet,tsc;
679                                 scx200_hrt on     666                                 scx200_hrt on Geode; cyclone on IBM x440
680                         [MIPS] MIPS               667                         [MIPS] MIPS
681                         [PARISC] cr16             668                         [PARISC] cr16
682                         [S390] tod                669                         [S390] tod
683                         [SH] SuperH               670                         [SH] SuperH
684                         [SPARC64] tick            671                         [SPARC64] tick
685                         [X86-64] hpet,tsc         672                         [X86-64] hpet,tsc
686                                                   673 
687         clocksource.arm_arch_timer.evtstrm=       674         clocksource.arm_arch_timer.evtstrm=
688                         [ARM,ARM64,EARLY]      !! 675                         [ARM,ARM64]
689                         Format: <bool>            676                         Format: <bool>
690                         Enable/disable the eve    677                         Enable/disable the eventstream feature of the ARM
691                         architected timer so t    678                         architected timer so that code using WFE-based polling
692                         loops can be debugged     679                         loops can be debugged more effectively on production
693                         systems.                  680                         systems.
694                                                   681 
                                                   >> 682         clocksource.max_cswd_read_retries= [KNL]
                                                   >> 683                         Number of clocksource_watchdog() retries due to
                                                   >> 684                         external delays before the clock will be marked
                                                   >> 685                         unstable.  Defaults to two retries, that is,
                                                   >> 686                         three attempts to read the clock under test.
                                                   >> 687 
695         clocksource.verify_n_cpus= [KNL]          688         clocksource.verify_n_cpus= [KNL]
696                         Limit the number of CP    689                         Limit the number of CPUs checked for clocksources
697                         marked with CLOCK_SOUR    690                         marked with CLOCK_SOURCE_VERIFY_PERCPU that
698                         are marked unstable du    691                         are marked unstable due to excessive skew.
699                         A negative value says     692                         A negative value says to check all CPUs, while
700                         zero says not to check    693                         zero says not to check any.  Values larger than
701                         nr_cpu_ids are silentl    694                         nr_cpu_ids are silently truncated to nr_cpu_ids.
702                         The actual CPUs are ch    695                         The actual CPUs are chosen randomly, with
703                         no replacement if the     696                         no replacement if the same CPU is chosen twice.
704                                                   697 
705         clocksource-wdtest.holdoff= [KNL]         698         clocksource-wdtest.holdoff= [KNL]
706                         Set the time in second    699                         Set the time in seconds that the clocksource
707                         watchdog test waits be    700                         watchdog test waits before commencing its tests.
708                         Defaults to zero when     701                         Defaults to zero when built as a module and to
709                         10 seconds when built     702                         10 seconds when built into the kernel.
710                                                   703 
711         cma=nn[MG]@[start[MG][-end[MG]]]          704         cma=nn[MG]@[start[MG][-end[MG]]]
712                         [KNL,CMA,EARLY]        !! 705                         [KNL,CMA]
713                         Sets the size of kerne    706                         Sets the size of kernel global memory area for
714                         contiguous memory allo    707                         contiguous memory allocations and optionally the
715                         placement constraint b    708                         placement constraint by the physical address range of
716                         memory allocations. A     709                         memory allocations. A value of 0 disables CMA
717                         altogether. For more i    710                         altogether. For more information, see
718                         kernel/dma/contiguous.    711                         kernel/dma/contiguous.c
719                                                   712 
720         cma_pernuma=nn[MG]                        713         cma_pernuma=nn[MG]
721                         [KNL,CMA,EARLY]        !! 714                         [KNL,CMA]
722                         Sets the size of kerne    715                         Sets the size of kernel per-numa memory area for
723                         contiguous memory allo    716                         contiguous memory allocations. A value of 0 disables
724                         per-numa CMA altogethe    717                         per-numa CMA altogether. And If this option is not
725                         specified, the default    718                         specified, the default value is 0.
726                         With per-numa CMA enab    719                         With per-numa CMA enabled, DMA users on node nid will
727                         first try to allocate     720                         first try to allocate buffer from the pernuma area
728                         which is located in no    721                         which is located in node nid, if the allocation fails,
729                         they will fallback to     722                         they will fallback to the global default memory area.
730                                                   723 
731         numa_cma=<node>:nn[MG][,<node>:nn[MG]]    724         numa_cma=<node>:nn[MG][,<node>:nn[MG]]
732                         [KNL,CMA,EARLY]        !! 725                         [KNL,CMA]
733                         Sets the size of kerne    726                         Sets the size of kernel numa memory area for
734                         contiguous memory allo    727                         contiguous memory allocations. It will reserve CMA
735                         area for the specified    728                         area for the specified node.
736                                                   729 
737                         With numa CMA enabled,    730                         With numa CMA enabled, DMA users on node nid will
738                         first try to allocate     731                         first try to allocate buffer from the numa area
739                         which is located in no    732                         which is located in node nid, if the allocation fails,
740                         they will fallback to     733                         they will fallback to the global default memory area.
741                                                   734 
742         cmo_free_hint=  [PPC] Format: { yes |     735         cmo_free_hint=  [PPC] Format: { yes | no }
743                         Specify whether pages     736                         Specify whether pages are marked as being inactive
744                         when they are freed.      737                         when they are freed.  This is used in CMO environments
745                         to determine OS memory    738                         to determine OS memory pressure for page stealing by
746                         a hypervisor.             739                         a hypervisor.
747                         Default: yes              740                         Default: yes
748                                                   741 
749         coherent_pool=nn[KMG]   [ARM,KNL,EARLY !! 742         coherent_pool=nn[KMG]   [ARM,KNL]
750                         Sets the size of memor    743                         Sets the size of memory pool for coherent, atomic dma
751                         allocations, by defaul    744                         allocations, by default set to 256K.
752                                                   745 
753         com20020=       [HW,NET] ARCnet - COM2    746         com20020=       [HW,NET] ARCnet - COM20020 chipset
754                         Format:                   747                         Format:
755                         <io>[,<irq>[,<nodeID>[    748                         <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756                                                   749 
757         com90io=        [HW,NET] ARCnet - COM9    750         com90io=        [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758                         Format: <io>[,<irq>]      751                         Format: <io>[,<irq>]
759                                                   752 
760         com90xx=        [HW,NET]                  753         com90xx=        [HW,NET]
761                         ARCnet - COM90xx chips    754                         ARCnet - COM90xx chipset (memory-mapped buffers)
762                         Format: <io>[,<irq>[,<    755                         Format: <io>[,<irq>[,<memstart>]]
763                                                   756 
764         condev=         [HW,S390] console devi    757         condev=         [HW,S390] console device
765         conmode=                                  758         conmode=
766                                                   759 
767         con3215_drop=   [S390,EARLY] 3215 cons !! 760         con3215_drop=   [S390] 3215 console drop mode.
768                         Format: y|n|Y|N|1|0       761                         Format: y|n|Y|N|1|0
769                         When set to true, drop    762                         When set to true, drop data on the 3215 console when
770                         the console buffer is     763                         the console buffer is full. In this case the
771                         operator using a 3270     764                         operator using a 3270 terminal emulator (for example
772                         x3270) does not have t    765                         x3270) does not have to enter the clear key for the
773                         console output to adva    766                         console output to advance and the kernel to continue.
774                         This leads to a much f    767                         This leads to a much faster boot time when a 3270
775                         terminal emulator is a    768                         terminal emulator is active. If no 3270 terminal
776                         emulator is used, this    769                         emulator is used, this parameter has no effect.
777                                                   770 
778         console=        [KNL] Output console d    771         console=        [KNL] Output console device and options.
779                                                   772 
780                 tty<n>  Use the virtual consol    773                 tty<n>  Use the virtual console device <n>.
781                                                   774 
782                 ttyS<n>[,options]                 775                 ttyS<n>[,options]
783                 ttyUSB0[,options]                 776                 ttyUSB0[,options]
784                         Use the specified seri    777                         Use the specified serial port.  The options are of
785                         the form "bbbbpnf", wh    778                         the form "bbbbpnf", where "bbbb" is the baud rate,
786                         "p" is parity ("n", "o    779                         "p" is parity ("n", "o", or "e"), "n" is number of
787                         bits, and "f" is flow     780                         bits, and "f" is flow control ("r" for RTS or
788                         omit it).  Default is     781                         omit it).  Default is "9600n8".
789                                                   782 
790                         See Documentation/admi    783                         See Documentation/admin-guide/serial-console.rst for more
791                         information.  See         784                         information.  See
792                         Documentation/networki    785                         Documentation/networking/netconsole.rst for an
793                         alternative.              786                         alternative.
794                                                   787 
795                 <DEVNAME>:<n>.<n>[,options]    << 
796                         Use the specified seri << 
797                         The addressing uses DE << 
798                         device, followed by th << 
799                         and the serial port in << 
800                         as documented for the  << 
801                                                << 
802                         The mapping of the ser << 
803                         can be viewed with:    << 
804                                                << 
805                         $ ls -d /sys/bus/seria << 
806                         /sys/bus/serial-base/d << 
807                                                << 
808                         In the above example,  << 
809                         console=00:04:0.0. Not << 
810                         way will only get adde << 
811                         is ready. The use of a << 
812                         the console may be des << 
813                                                << 
814                 uart[8250],io,<addr>[,options]    788                 uart[8250],io,<addr>[,options]
815                 uart[8250],mmio,<addr>[,option    789                 uart[8250],mmio,<addr>[,options]
816                 uart[8250],mmio16,<addr>[,opti    790                 uart[8250],mmio16,<addr>[,options]
817                 uart[8250],mmio32,<addr>[,opti    791                 uart[8250],mmio32,<addr>[,options]
818                 uart[8250],0x<addr>[,options]     792                 uart[8250],0x<addr>[,options]
819                         Start an early, polled    793                         Start an early, polled-mode console on the 8250/16550
820                         UART at the specified     794                         UART at the specified I/O port or MMIO address,
821                         switching to the match    795                         switching to the matching ttyS device later.
822                         MMIO inter-register ad    796                         MMIO inter-register address stride is either 8-bit
823                         (mmio), 16-bit (mmio16    797                         (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824                         If none of [io|mmio|mm    798                         If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825                         to be equivalent to 'm    799                         to be equivalent to 'mmio'. 'options' are specified in
826                         the same format descri    800                         the same format described for ttyS above; if unspecified,
827                         the h/w is not re-init    801                         the h/w is not re-initialized.
828                                                   802 
829                 hvc<n>  Use the hypervisor con    803                 hvc<n>  Use the hypervisor console device <n>. This is for
830                         both Xen and PowerPC h    804                         both Xen and PowerPC hypervisors.
831                                                   805 
832                 { null | "" }                     806                 { null | "" }
833                         Use to disable console    807                         Use to disable console output, i.e., to have kernel
834                         console messages disca    808                         console messages discarded.
835                         This must be the only     809                         This must be the only console= parameter used on the
836                         kernel command line.      810                         kernel command line.
837                                                   811 
838                 If the device connected to the    812                 If the device connected to the port is not a TTY but a braille
839                 device, prepend "brl," before     813                 device, prepend "brl," before the device type, for instance
840                         console=brl,ttyS0         814                         console=brl,ttyS0
841                 For now, only VisioBraille is     815                 For now, only VisioBraille is supported.
842                                                   816 
843         console_msg_format=                       817         console_msg_format=
844                         [KNL] Change console m    818                         [KNL] Change console messages format
845                 default                           819                 default
846                         By default we print me    820                         By default we print messages on consoles in
847                         "[time stamp] text\n"     821                         "[time stamp] text\n" format (time stamp may not be
848                         printed, depending on     822                         printed, depending on CONFIG_PRINTK_TIME or
849                         `printk_time' param).     823                         `printk_time' param).
850                 syslog                            824                 syslog
851                         Switch to syslog forma    825                         Switch to syslog format: "<%u>[time stamp] text\n"
852                         IOW, each message will    826                         IOW, each message will have a facility and loglevel
853                         prefix. The format is     827                         prefix. The format is similar to one used by syslog()
854                         syscall, or to executi    828                         syscall, or to executing "dmesg -S --raw" or to reading
855                         from /proc/kmsg.          829                         from /proc/kmsg.
856                                                   830 
857         consoleblank=   [KNL] The console blan    831         consoleblank=   [KNL] The console blank (screen saver) timeout in
858                         seconds. A value of 0     832                         seconds. A value of 0 disables the blank timer.
859                         Defaults to 0.            833                         Defaults to 0.
860                                                   834 
861         coredump_filter=                          835         coredump_filter=
862                         [KNL] Change the defau    836                         [KNL] Change the default value for
863                         /proc/<pid>/coredump_f    837                         /proc/<pid>/coredump_filter.
864                         See also Documentation    838                         See also Documentation/filesystems/proc.rst.
865                                                   839 
866         coresight_cpu_debug.enable                840         coresight_cpu_debug.enable
867                         [ARM,ARM64]               841                         [ARM,ARM64]
868                         Format: <bool>            842                         Format: <bool>
869                         Enable/disable the CPU    843                         Enable/disable the CPU sampling based debugging.
870                         0: default value, disa    844                         0: default value, disable debugging
871                         1: enable debugging at    845                         1: enable debugging at boot time
872                                                   846 
873         cpcihp_generic= [HW,PCI] Generic port     847         cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
874                         Format:                   848                         Format:
875                         <first_slot>,<last_slo    849                         <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
876                                                   850 
877         cpuidle.off=1   [CPU_IDLE]                851         cpuidle.off=1   [CPU_IDLE]
878                         disable the cpuidle su    852                         disable the cpuidle sub-system
879                                                   853 
880         cpuidle.governor=                         854         cpuidle.governor=
881                         [CPU_IDLE] Name of the    855                         [CPU_IDLE] Name of the cpuidle governor to use.
882                                                   856 
883         cpufreq.off=1   [CPU_FREQ]                857         cpufreq.off=1   [CPU_FREQ]
884                         disable the cpufreq su    858                         disable the cpufreq sub-system
885                                                   859 
886         cpufreq.default_governor=                 860         cpufreq.default_governor=
887                         [CPU_FREQ] Name of the    861                         [CPU_FREQ] Name of the default cpufreq governor or
888                         policy to use. This go    862                         policy to use. This governor must be registered in the
889                         kernel before the cpuf    863                         kernel before the cpufreq driver probes.
890                                                   864 
891         cpu_init_udelay=N                         865         cpu_init_udelay=N
892                         [X86,EARLY] Delay for  !! 866                         [X86] Delay for N microsec between assert and de-assert
893                         of APIC INIT to start     867                         of APIC INIT to start processors.  This delay occurs
894                         on every CPU online, s    868                         on every CPU online, such as boot, and resume from suspend.
895                         Default: 10000            869                         Default: 10000
896                                                   870 
897         cpuhp.parallel=                           871         cpuhp.parallel=
898                         [SMP] Enable/disable p    872                         [SMP] Enable/disable parallel bringup of secondary CPUs
899                         Format: <bool>            873                         Format: <bool>
900                         Default is enabled if     874                         Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
901                         the parameter has no e    875                         the parameter has no effect.
902                                                   876 
903         crash_kexec_post_notifiers                877         crash_kexec_post_notifiers
904                         Run kdump after runnin    878                         Run kdump after running panic-notifiers and dumping
905                         kmsg. This only for th    879                         kmsg. This only for the users who doubt kdump always
906                         succeeds in any situat    880                         succeeds in any situation.
907                         Note that this also in    881                         Note that this also increases risks of kdump failure,
908                         because some panic not    882                         because some panic notifiers can make the crashed
909                         kernel more unstable.     883                         kernel more unstable.
910                                                   884 
911         crashkernel=size[KMG][@offset[KMG]]       885         crashkernel=size[KMG][@offset[KMG]]
912                         [KNL,EARLY] Using kexe !! 886                         [KNL] Using kexec, Linux can switch to a 'crash kernel'
913                         upon panic. This param    887                         upon panic. This parameter reserves the physical
914                         memory region [offset,    888                         memory region [offset, offset + size] for that kernel
915                         image. If '@offset' is    889                         image. If '@offset' is omitted, then a suitable offset
916                         is selected automatica    890                         is selected automatically.
917                         [KNL, X86-64, ARM64, R    891                         [KNL, X86-64, ARM64, RISCV, LoongArch] Select a region
918                         under 4G first, and fa    892                         under 4G first, and fall back to reserve region above
919                         4G when '@offset' hasn    893                         4G when '@offset' hasn't been specified.
920                         See Documentation/admi    894                         See Documentation/admin-guide/kdump/kdump.rst for further details.
921                                                   895 
922         crashkernel=range1:size1[,range2:size2    896         crashkernel=range1:size1[,range2:size2,...][@offset]
923                         [KNL] Same as above, b    897                         [KNL] Same as above, but depends on the memory
924                         in the running system.    898                         in the running system. The syntax of range is
925                         start-[end] where star    899                         start-[end] where start and end are both
926                         a memory unit (amount[    900                         a memory unit (amount[KMG]). See also
927                         Documentation/admin-gu    901                         Documentation/admin-guide/kdump/kdump.rst for an example.
928                                                   902 
929         crashkernel=size[KMG],high                903         crashkernel=size[KMG],high
930                         [KNL, X86-64, ARM64, R    904                         [KNL, X86-64, ARM64, RISCV, LoongArch] range could be
931                         above 4G.                 905                         above 4G.
932                         Allow kernel to alloca    906                         Allow kernel to allocate physical memory region from top,
933                         so could be above 4G i    907                         so could be above 4G if system have more than 4G ram
934                         installed. Otherwise m    908                         installed. Otherwise memory region will be allocated
935                         below 4G, if available    909                         below 4G, if available.
936                         It will be ignored if     910                         It will be ignored if crashkernel=X is specified.
937         crashkernel=size[KMG],low                 911         crashkernel=size[KMG],low
938                         [KNL, X86-64, ARM64, R    912                         [KNL, X86-64, ARM64, RISCV, LoongArch] range under 4G.
939                         When crashkernel=X,hig    913                         When crashkernel=X,high is passed, kernel could allocate
940                         physical memory region    914                         physical memory region above 4G, that cause second kernel
941                         crash on system that r    915                         crash on system that require some amount of low memory,
942                         e.g. swiotlb requires     916                         e.g. swiotlb requires at least 64M+32K low memory, also
943                         enough extra low memor    917                         enough extra low memory is needed to make sure DMA buffers
944                         for 32-bit devices won    918                         for 32-bit devices won't run out. Kernel would try to allocate
945                         default size of memory    919                         default size of memory below 4G automatically. The default
946                         size is platform depen    920                         size is platform dependent.
947                           --> x86: max(swiotlb    921                           --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
948                           --> arm64: 128MiB       922                           --> arm64: 128MiB
949                           --> riscv: 128MiB       923                           --> riscv: 128MiB
950                           --> loongarch: 128Mi    924                           --> loongarch: 128MiB
951                         This one lets the user    925                         This one lets the user specify own low range under 4G
952                         for second kernel inst    926                         for second kernel instead.
953                         0: to disable low allo    927                         0: to disable low allocation.
954                         It will be ignored whe    928                         It will be ignored when crashkernel=X,high is not used
955                         or memory reserved is     929                         or memory reserved is below 4G.
956                                                   930 
957         cryptomgr.notests                         931         cryptomgr.notests
958                         [KNL] Disable crypto s    932                         [KNL] Disable crypto self-tests
959                                                   933 
960         cs89x0_dma=     [HW,NET]                  934         cs89x0_dma=     [HW,NET]
961                         Format: <dma>             935                         Format: <dma>
962                                                   936 
963         cs89x0_media=   [HW,NET]                  937         cs89x0_media=   [HW,NET]
964                         Format: { rj45 | aui |    938                         Format: { rj45 | aui | bnc }
965                                                   939 
966         csdlock_debug=  [KNL] Enable or disabl    940         csdlock_debug=  [KNL] Enable or disable debug add-ons of cross-CPU
967                         function call handling    941                         function call handling. When switched on,
968                         additional debug data     942                         additional debug data is printed to the console
969                         in case a hanging CPU     943                         in case a hanging CPU is detected, and that
970                         CPU is pinged again in    944                         CPU is pinged again in order to try to resolve
971                         the hang situation.  T    945                         the hang situation.  The default value of this
972                         option depends on the     946                         option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
973                         Kconfig option.           947                         Kconfig option.
974                                                   948 
975         dasd=           [HW,NET]                  949         dasd=           [HW,NET]
976                         See header of drivers/    950                         See header of drivers/s390/block/dasd_devmap.c.
977                                                   951 
978         db9.dev[2|3]=   [HW,JOY] Multisystem j    952         db9.dev[2|3]=   [HW,JOY] Multisystem joystick support via parallel port
979                         (one device per port)     953                         (one device per port)
980                         Format: <port#>,<type>    954                         Format: <port#>,<type>
981                         See also Documentation    955                         See also Documentation/input/devices/joystick-parport.rst
982                                                   956 
983         debug           [KNL,EARLY] Enable ker !! 957         debug           [KNL] Enable kernel debugging (events log level).
984                                                   958 
985         debug_boot_weak_hash                      959         debug_boot_weak_hash
986                         [KNL,EARLY] Enable pri !! 960                         [KNL] Enable printing [hashed] pointers early in the
987                         boot sequence.  If ena    961                         boot sequence.  If enabled, we use a weak hash instead
988                         of siphash to hash poi    962                         of siphash to hash pointers.  Use this option if you are
989                         seeing instances of '(    963                         seeing instances of '(___ptrval___)') and need to see a
990                         value (hashed pointer)    964                         value (hashed pointer) instead. Cryptographically
991                         insecure, please do no    965                         insecure, please do not use on production kernels.
992                                                   966 
993         debug_locks_verbose=                      967         debug_locks_verbose=
994                         [KNL] verbose locking     968                         [KNL] verbose locking self-tests
995                         Format: <int>             969                         Format: <int>
996                         Print debugging info w    970                         Print debugging info while doing the locking API
997                         self-tests.               971                         self-tests.
998                         Bitmask for the variou    972                         Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999                         (no extra messages), s    973                         (no extra messages), setting it to -1 (all bits set)
1000                         will print _a_lot_ mo    974                         will print _a_lot_ more information - normally only
1001                         useful to lockdep dev    975                         useful to lockdep developers.
1002                                                  976 
1003         debug_objects   [KNL,EARLY] Enable ob !! 977         debug_objects   [KNL] Enable object debugging
1004                                                  978 
1005         debug_guardpage_minorder=                979         debug_guardpage_minorder=
1006                         [KNL,EARLY] When CONF !! 980                         [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007                         parameter allows cont    981                         parameter allows control of the order of pages that will
1008                         be intentionally kept    982                         be intentionally kept free (and hence protected) by the
1009                         buddy allocator. Bigg    983                         buddy allocator. Bigger value increase the probability
1010                         of catching random me    984                         of catching random memory corruption, but reduce the
1011                         amount of memory for     985                         amount of memory for normal system use. The maximum
1012                         possible value is MAX    986                         possible value is MAX_PAGE_ORDER/2.  Setting this
1013                         parameter to 1 or 2 s    987                         parameter to 1 or 2 should be enough to identify most
1014                         random memory corrupt    988                         random memory corruption problems caused by bugs in
1015                         kernel or driver code    989                         kernel or driver code when a CPU writes to (or reads
1016                         from) a random memory    990                         from) a random memory location. Note that there exists
1017                         a class of memory cor    991                         a class of memory corruptions problems caused by buggy
1018                         H/W or F/W or by driv    992                         H/W or F/W or by drivers badly programming DMA
1019                         (basically when memor    993                         (basically when memory is written at bus level and the
1020                         CPU MMU is bypassed)     994                         CPU MMU is bypassed) which are not detectable by
1021                         CONFIG_DEBUG_PAGEALLO    995                         CONFIG_DEBUG_PAGEALLOC, hence this option will not
1022                         help tracking down th    996                         help tracking down these problems.
1023                                                  997 
1024         debug_pagealloc=                         998         debug_pagealloc=
1025                         [KNL,EARLY] When CONF !! 999                         [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026                         enables the feature a    1000                         enables the feature at boot time. By default, it is
1027                         disabled and the syst    1001                         disabled and the system will work mostly the same as a
1028                         kernel built without     1002                         kernel built without CONFIG_DEBUG_PAGEALLOC.
1029                         Note: to get most of     1003                         Note: to get most of debug_pagealloc error reports, it's
1030                         useful to also enable    1004                         useful to also enable the page_owner functionality.
1031                         on: enable the featur    1005                         on: enable the feature
1032                                                  1006 
1033         debugfs=        [KNL,EARLY] This para !! 1007         debugfs=        [KNL] This parameter enables what is exposed to userspace
1034                         userspace and debugfs !! 1008                         and debugfs internal clients.
1035                         Format: { on, no-moun    1009                         Format: { on, no-mount, off }
1036                         on:     All functions    1010                         on:     All functions are enabled.
1037                         no-mount:                1011                         no-mount:
1038                                 Filesystem is    1012                                 Filesystem is not registered but kernel clients can
1039                                 access APIs a    1013                                 access APIs and a crashkernel can be used to read
1040                                 its content.     1014                                 its content. There is nothing to mount.
1041                         off:    Filesystem is    1015                         off:    Filesystem is not registered and clients
1042                                 get a -EPERM     1016                                 get a -EPERM as result when trying to register files
1043                                 or directorie    1017                                 or directories within debugfs.
1044                                 This is equiv    1018                                 This is equivalent of the runtime functionality if
1045                                 debugfs was n    1019                                 debugfs was not enabled in the kernel at all.
1046                         Default value is set     1020                         Default value is set in build-time with a kernel configuration.
1047                                                  1021 
1048         debugpat        [X86] Enable PAT debu    1022         debugpat        [X86] Enable PAT debugging
1049                                                  1023 
1050         default_hugepagesz=                      1024         default_hugepagesz=
1051                         [HW] The size of the     1025                         [HW] The size of the default HugeTLB page. This is
1052                         the size represented     1026                         the size represented by the legacy /proc/ hugepages
1053                         APIs.  In addition, t    1027                         APIs.  In addition, this is the default hugetlb size
1054                         used for shmget(), mm    1028                         used for shmget(), mmap() and mounting hugetlbfs
1055                         filesystems.  If not     1029                         filesystems.  If not specified, defaults to the
1056                         architecture's defaul    1030                         architecture's default huge page size.  Huge page
1057                         sizes are architectur    1031                         sizes are architecture dependent.  See also
1058                         Documentation/admin-g    1032                         Documentation/admin-guide/mm/hugetlbpage.rst.
1059                         Format: size[KMG]        1033                         Format: size[KMG]
1060                                                  1034 
1061         deferred_probe_timeout=                  1035         deferred_probe_timeout=
1062                         [KNL] Debugging optio    1036                         [KNL] Debugging option to set a timeout in seconds for
1063                         deferred probe to giv    1037                         deferred probe to give up waiting on dependencies to
1064                         probe. Only specific     1038                         probe. Only specific dependencies (subsystems or
1065                         drivers) that have op    1039                         drivers) that have opted in will be ignored. A timeout
1066                         of 0 will timeout at     1040                         of 0 will timeout at the end of initcalls. If the time
1067                         out hasn't expired, i    1041                         out hasn't expired, it'll be restarted by each
1068                         successful driver reg    1042                         successful driver registration. This option will also
1069                         dump out devices stil    1043                         dump out devices still on the deferred probe list after
1070                         retrying.                1044                         retrying.
1071                                                  1045 
1072         delayacct       [KNL] Enable per-task    1046         delayacct       [KNL] Enable per-task delay accounting
1073                                                  1047 
1074         dell_smm_hwmon.ignore_dmi=               1048         dell_smm_hwmon.ignore_dmi=
1075                         [HW] Continue probing    1049                         [HW] Continue probing hardware even if DMI data
1076                         indicates that the dr    1050                         indicates that the driver is running on unsupported
1077                         hardware.                1051                         hardware.
1078                                                  1052 
1079         dell_smm_hwmon.force=                    1053         dell_smm_hwmon.force=
1080                         [HW] Activate driver     1054                         [HW] Activate driver even if SMM BIOS signature does
1081                         not match list of sup    1055                         not match list of supported models and enable otherwise
1082                         blacklisted features.    1056                         blacklisted features.
1083                                                  1057 
1084         dell_smm_hwmon.power_status=             1058         dell_smm_hwmon.power_status=
1085                         [HW] Report power sta    1059                         [HW] Report power status in /proc/i8k
1086                         (disabled by default)    1060                         (disabled by default).
1087                                                  1061 
1088         dell_smm_hwmon.restricted=               1062         dell_smm_hwmon.restricted=
1089                         [HW] Allow controllin    1063                         [HW] Allow controlling fans only if SYS_ADMIN
1090                         capability is set.       1064                         capability is set.
1091                                                  1065 
1092         dell_smm_hwmon.fan_mult=                 1066         dell_smm_hwmon.fan_mult=
1093                         [HW] Factor to multip    1067                         [HW] Factor to multiply fan speed with.
1094                                                  1068 
1095         dell_smm_hwmon.fan_max=                  1069         dell_smm_hwmon.fan_max=
1096                         [HW] Maximum configur    1070                         [HW] Maximum configurable fan speed.
1097                                                  1071 
1098         dfltcc=         [HW,S390]                1072         dfltcc=         [HW,S390]
1099                         Format: { on | off |     1073                         Format: { on | off | def_only | inf_only | always }
1100                         on:       s390 zlib h    1074                         on:       s390 zlib hardware support for compression on
1101                                   level 1 and    1075                                   level 1 and decompression (default)
1102                         off:      No s390 zli    1076                         off:      No s390 zlib hardware support
1103                         def_only: s390 zlib h    1077                         def_only: s390 zlib hardware support for deflate
1104                                   only (compr    1078                                   only (compression on level 1)
1105                         inf_only: s390 zlib h    1079                         inf_only: s390 zlib hardware support for inflate
1106                                   only (decom    1080                                   only (decompression)
1107                         always:   Same as 'on    1081                         always:   Same as 'on' but ignores the selected compression
1108                                   level alway    1082                                   level always using hardware support (used for debugging)
1109                                                  1083 
1110         dhash_entries=  [KNL]                    1084         dhash_entries=  [KNL]
1111                         Set number of hash bu    1085                         Set number of hash buckets for dentry cache.
1112                                                  1086 
1113         disable_1tb_segments [PPC,EARLY]      !! 1087         disable_1tb_segments [PPC]
1114                         Disables the use of 1    1088                         Disables the use of 1TB hash page table segments. This
1115                         causes the kernel to     1089                         causes the kernel to fall back to 256MB segments which
1116                         can be useful when de    1090                         can be useful when debugging issues that require an SLB
1117                         miss to occur.           1091                         miss to occur.
1118                                                  1092 
1119         disable=        [IPV6]                   1093         disable=        [IPV6]
1120                         See Documentation/net    1094                         See Documentation/networking/ipv6.rst.
1121                                                  1095 
1122         disable_radix   [PPC,EARLY]           !! 1096         disable_radix   [PPC]
1123                         Disable RADIX MMU mod    1097                         Disable RADIX MMU mode on POWER9
1124                                                  1098 
1125         disable_tlbie   [PPC]                    1099         disable_tlbie   [PPC]
1126                         Disable TLBIE instruc    1100                         Disable TLBIE instruction. Currently does not work
1127                         with KVM, with HASH M    1101                         with KVM, with HASH MMU, or with coherent accelerators.
1128                                                  1102 
1129         disable_ddw     [PPC/PSERIES,EARLY]   !! 1103         disable_cpu_apicid= [X86,APIC,SMP]
                                                   >> 1104                         Format: <int>
                                                   >> 1105                         The number of initial APIC ID for the
                                                   >> 1106                         corresponding CPU to be disabled at boot,
                                                   >> 1107                         mostly used for the kdump 2nd kernel to
                                                   >> 1108                         disable BSP to wake up multiple CPUs without
                                                   >> 1109                         causing system reset or hang due to sending
                                                   >> 1110                         INIT from AP to BSP.
                                                   >> 1111 
                                                   >> 1112         disable_ddw     [PPC/PSERIES]
1130                         Disable Dynamic DMA W    1113                         Disable Dynamic DMA Window support. Use this
1131                         to workaround buggy f    1114                         to workaround buggy firmware.
1132                                                  1115 
1133         disable_ipv6=   [IPV6]                   1116         disable_ipv6=   [IPV6]
1134                         See Documentation/net    1117                         See Documentation/networking/ipv6.rst.
1135                                                  1118 
1136         disable_mtrr_cleanup [X86,EARLY]      !! 1119         disable_mtrr_cleanup [X86]
1137                         The kernel tries to a    1120                         The kernel tries to adjust MTRR layout from continuous
1138                         to discrete, to make     1121                         to discrete, to make X server driver able to add WB
1139                         entry later. This par    1122                         entry later. This parameter disables that.
1140                                                  1123 
1141         disable_mtrr_trim [X86, Intel and AMD !! 1124         disable_mtrr_trim [X86, Intel and AMD only]
1142                         By default the kernel    1125                         By default the kernel will trim any uncacheable
1143                         memory out of your av    1126                         memory out of your available memory pool based on
1144                         MTRR settings.  This     1127                         MTRR settings.  This parameter disables that behavior,
1145                         possibly causing your    1128                         possibly causing your machine to run very slowly.
1146                                                  1129 
1147         disable_timer_pin_1 [X86,EARLY]       !! 1130         disable_timer_pin_1 [X86]
1148                         Disable PIN 1 of APIC    1131                         Disable PIN 1 of APIC timer
1149                         Can be useful to work    1132                         Can be useful to work around chipset bugs.
1150                                                  1133 
1151         dis_ucode_ldr   [X86] Disable the mic    1134         dis_ucode_ldr   [X86] Disable the microcode loader.
1152                                                  1135 
1153         dma_debug=off   If the kernel is comp    1136         dma_debug=off   If the kernel is compiled with DMA_API_DEBUG support,
1154                         this option disables     1137                         this option disables the debugging code at boot.
1155                                                  1138 
1156         dma_debug_entries=<number>               1139         dma_debug_entries=<number>
1157                         This option allows to    1140                         This option allows to tune the number of preallocated
1158                         entries for DMA-API d    1141                         entries for DMA-API debugging code. One entry is
1159                         required per DMA-API     1142                         required per DMA-API allocation. Use this if the
1160                         DMA-API debugging cod    1143                         DMA-API debugging code disables itself because the
1161                         architectural default    1144                         architectural default is too low.
1162                                                  1145 
1163         dma_debug_driver=<driver_name>           1146         dma_debug_driver=<driver_name>
1164                         With this option the     1147                         With this option the DMA-API debugging driver
1165                         filter feature can be    1148                         filter feature can be enabled at boot time. Just
1166                         pass the driver to fi    1149                         pass the driver to filter for as the parameter.
1167                         The filter can be dis    1150                         The filter can be disabled or changed to another
1168                         driver later using sy    1151                         driver later using sysfs.
1169                                                  1152 
1170         reg_file_data_sampling=                  1153         reg_file_data_sampling=
1171                         [X86] Controls mitiga    1154                         [X86] Controls mitigation for Register File Data
1172                         Sampling (RFDS) vulne    1155                         Sampling (RFDS) vulnerability. RFDS is a CPU
1173                         vulnerability which m    1156                         vulnerability which may allow userspace to infer
1174                         kernel data values pr    1157                         kernel data values previously stored in floating point
1175                         registers, vector reg    1158                         registers, vector registers, or integer registers.
1176                         RFDS only affects Int    1159                         RFDS only affects Intel Atom processors.
1177                                                  1160 
1178                         on:     Turns ON the     1161                         on:     Turns ON the mitigation.
1179                         off:    Turns OFF the    1162                         off:    Turns OFF the mitigation.
1180                                                  1163 
1181                         This parameter overri    1164                         This parameter overrides the compile time default set
1182                         by CONFIG_MITIGATION_    1165                         by CONFIG_MITIGATION_RFDS. Mitigation cannot be
1183                         disabled when other V    1166                         disabled when other VERW based mitigations (like MDS)
1184                         are enabled. In order    1167                         are enabled. In order to disable RFDS mitigation all
1185                         VERW based mitigation    1168                         VERW based mitigations need to be disabled.
1186                                                  1169 
1187                         For details see:         1170                         For details see:
1188                         Documentation/admin-g    1171                         Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1189                                                  1172 
1190         driver_async_probe=  [KNL]               1173         driver_async_probe=  [KNL]
1191                         List of driver names     1174                         List of driver names to be probed asynchronously. *
1192                         matches with all driv    1175                         matches with all driver names. If * is specified, the
1193                         rest of the listed dr    1176                         rest of the listed driver names are those that will NOT
1194                         match the *.             1177                         match the *.
1195                         Format: <driver_name1    1178                         Format: <driver_name1>,<driver_name2>...
1196                                                  1179 
1197         drm.edid_firmware=[<connector>:]<file    1180         drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198                         Broken monitors, grap    1181                         Broken monitors, graphic adapters, KVMs and EDIDless
1199                         panels may send no or    1182                         panels may send no or incorrect EDID data sets.
1200                         This parameter allows    1183                         This parameter allows to specify an EDID data sets
1201                         in the /lib/firmware     1184                         in the /lib/firmware directory that are used instead.
1202                         An EDID data set will !! 1185                         Generic built-in EDID data sets are used, if one of
1203                         connector, if its nam !! 1186                         edid/1024x768.bin, edid/1280x1024.bin,
1204                         the EDID name. Each c !! 1187                         edid/1680x1050.bin, or edid/1920x1080.bin is given
1205                         data set by separatin !! 1188                         and no file with the same name exists. Details and
                                                   >> 1189                         instructions how to build your own EDID data are
                                                   >> 1190                         available in Documentation/admin-guide/edid.rst. An EDID
                                                   >> 1191                         data set will only be used for a particular connector,
                                                   >> 1192                         if its name and a colon are prepended to the EDID
                                                   >> 1193                         name. Each connector may use a unique EDID data
                                                   >> 1194                         set by separating the files with a comma.  An EDID
1206                         data set with no conn    1195                         data set with no connector name will be used for
1207                         any connectors not ex    1196                         any connectors not explicitly specified.
1208                                                  1197 
1209         dscc4.setup=    [NET]                    1198         dscc4.setup=    [NET]
1210                                                  1199 
1211         dt_cpu_ftrs=    [PPC,EARLY]           !! 1200         dt_cpu_ftrs=    [PPC]
1212                         Format: {"off" | "kno    1201                         Format: {"off" | "known"}
1213                         Control how the dt_cp    1202                         Control how the dt_cpu_ftrs device-tree binding is
1214                         used for CPU feature     1203                         used for CPU feature discovery and setup (if it
1215                         exists).                 1204                         exists).
1216                         off: Do not use it, f    1205                         off: Do not use it, fall back to legacy cpu table.
1217                         known: Do not pass th    1206                         known: Do not pass through unknown features to guests
1218                         or userspace, only th    1207                         or userspace, only those that the kernel is aware of.
1219                                                  1208 
1220         dump_apple_properties   [X86]            1209         dump_apple_properties   [X86]
1221                         Dump name and content    1210                         Dump name and content of EFI device properties on
1222                         x86 Macs.  Useful for    1211                         x86 Macs.  Useful for driver authors to determine
1223                         what data is availabl    1212                         what data is available or for reverse-engineering.
1224                                                  1213 
1225         dyndbg[="val"]          [KNL,DYNAMIC_    1214         dyndbg[="val"]          [KNL,DYNAMIC_DEBUG]
1226         <module>.dyndbg[="val"]                  1215         <module>.dyndbg[="val"]
1227                         Enable debug messages    1216                         Enable debug messages at boot time.  See
1228                         Documentation/admin-g    1217                         Documentation/admin-guide/dynamic-debug-howto.rst
1229                         for details.             1218                         for details.
1230                                                  1219 
1231         early_ioremap_debug [KNL,EARLY]       !! 1220         early_ioremap_debug [KNL]
1232                         Enable debug messages    1221                         Enable debug messages in early_ioremap support. This
1233                         is useful for trackin    1222                         is useful for tracking down temporary early mappings
1234                         which are not unmappe    1223                         which are not unmapped.
1235                                                  1224 
1236         earlycon=       [KNL,EARLY] Output ea !! 1225         earlycon=       [KNL] Output early console device and options.
1237                                                  1226 
1238                         When used with no opt    1227                         When used with no options, the early console is
1239                         determined by stdout-    1228                         determined by stdout-path property in device tree's
1240                         chosen node or the AC    1229                         chosen node or the ACPI SPCR table if supported by
1241                         the platform.            1230                         the platform.
1242                                                  1231 
1243                 cdns,<addr>[,options]            1232                 cdns,<addr>[,options]
1244                         Start an early, polle    1233                         Start an early, polled-mode console on a Cadence
1245                         (xuartps) serial port    1234                         (xuartps) serial port at the specified address. Only
1246                         supported option is b    1235                         supported option is baud rate. If baud rate is not
1247                         specified, the serial    1236                         specified, the serial port must already be setup and
1248                         configured.              1237                         configured.
1249                                                  1238 
1250                 uart[8250],io,<addr>[,options    1239                 uart[8250],io,<addr>[,options[,uartclk]]
1251                 uart[8250],mmio,<addr>[,optio    1240                 uart[8250],mmio,<addr>[,options[,uartclk]]
1252                 uart[8250],mmio32,<addr>[,opt    1241                 uart[8250],mmio32,<addr>[,options[,uartclk]]
1253                 uart[8250],mmio32be,<addr>[,o    1242                 uart[8250],mmio32be,<addr>[,options[,uartclk]]
1254                 uart[8250],0x<addr>[,options]    1243                 uart[8250],0x<addr>[,options]
1255                         Start an early, polle    1244                         Start an early, polled-mode console on the 8250/16550
1256                         UART at the specified    1245                         UART at the specified I/O port or MMIO address.
1257                         MMIO inter-register a    1246                         MMIO inter-register address stride is either 8-bit
1258                         (mmio) or 32-bit (mmi    1247                         (mmio) or 32-bit (mmio32 or mmio32be).
1259                         If none of [io|mmio|m    1248                         If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260                         to be equivalent to '    1249                         to be equivalent to 'mmio'. 'options' are specified
1261                         in the same format de    1250                         in the same format described for "console=ttyS<n>"; if
1262                         unspecified, the h/w     1251                         unspecified, the h/w is not initialized. 'uartclk' is
1263                         the uart clock freque    1252                         the uart clock frequency; if unspecified, it is set
1264                         to 'BASE_BAUD' * 16.     1253                         to 'BASE_BAUD' * 16.
1265                                                  1254 
1266                 pl011,<addr>                     1255                 pl011,<addr>
1267                 pl011,mmio32,<addr>              1256                 pl011,mmio32,<addr>
1268                         Start an early, polle    1257                         Start an early, polled-mode console on a pl011 serial
1269                         port at the specified    1258                         port at the specified address. The pl011 serial port
1270                         must already be setup    1259                         must already be setup and configured. Options are not
1271                         yet supported.  If 'm    1260                         yet supported.  If 'mmio32' is specified, then only
1272                         the driver will use o    1261                         the driver will use only 32-bit accessors to read/write
1273                         the device registers.    1262                         the device registers.
1274                                                  1263 
1275                 liteuart,<addr>                  1264                 liteuart,<addr>
1276                         Start an early consol    1265                         Start an early console on a litex serial port at the
1277                         specified address. Th    1266                         specified address. The serial port must already be
1278                         setup and configured.    1267                         setup and configured. Options are not yet supported.
1279                                                  1268 
1280                 meson,<addr>                     1269                 meson,<addr>
1281                         Start an early, polle    1270                         Start an early, polled-mode console on a meson serial
1282                         port at the specified    1271                         port at the specified address. The serial port must
1283                         already be setup and     1272                         already be setup and configured. Options are not yet
1284                         supported.               1273                         supported.
1285                                                  1274 
1286                 msm_serial,<addr>                1275                 msm_serial,<addr>
1287                         Start an early, polle    1276                         Start an early, polled-mode console on an msm serial
1288                         port at the specified    1277                         port at the specified address. The serial port
1289                         must already be setup    1278                         must already be setup and configured. Options are not
1290                         yet supported.           1279                         yet supported.
1291                                                  1280 
1292                 msm_serial_dm,<addr>             1281                 msm_serial_dm,<addr>
1293                         Start an early, polle    1282                         Start an early, polled-mode console on an msm serial
1294                         dm port at the specif    1283                         dm port at the specified address. The serial port
1295                         must already be setup    1284                         must already be setup and configured. Options are not
1296                         yet supported.           1285                         yet supported.
1297                                                  1286 
1298                 owl,<addr>                       1287                 owl,<addr>
1299                         Start an early, polle    1288                         Start an early, polled-mode console on a serial port
1300                         of an Actions Semi So    1289                         of an Actions Semi SoC, such as S500 or S900, at the
1301                         specified address. Th    1290                         specified address. The serial port must already be
1302                         setup and configured.    1291                         setup and configured. Options are not yet supported.
1303                                                  1292 
1304                 rda,<addr>                       1293                 rda,<addr>
1305                         Start an early, polle    1294                         Start an early, polled-mode console on a serial port
1306                         of an RDA Micro SoC,     1295                         of an RDA Micro SoC, such as RDA8810PL, at the
1307                         specified address. Th    1296                         specified address. The serial port must already be
1308                         setup and configured.    1297                         setup and configured. Options are not yet supported.
1309                                                  1298 
1310                 sbi                              1299                 sbi
1311                         Use RISC-V SBI (Super    1300                         Use RISC-V SBI (Supervisor Binary Interface) for early
1312                         console.                 1301                         console.
1313                                                  1302 
1314                 smh     Use ARM semihosting c    1303                 smh     Use ARM semihosting calls for early console.
1315                                                  1304 
1316                 s3c2410,<addr>                   1305                 s3c2410,<addr>
1317                 s3c2412,<addr>                   1306                 s3c2412,<addr>
1318                 s3c2440,<addr>                   1307                 s3c2440,<addr>
1319                 s3c6400,<addr>                   1308                 s3c6400,<addr>
1320                 s5pv210,<addr>                   1309                 s5pv210,<addr>
1321                 exynos4210,<addr>                1310                 exynos4210,<addr>
1322                         Use early console pro    1311                         Use early console provided by serial driver available
1323                         on Samsung SoCs, requ    1312                         on Samsung SoCs, requires selecting proper type and
1324                         a correct base addres    1313                         a correct base address of the selected UART port. The
1325                         serial port must alre    1314                         serial port must already be setup and configured.
1326                         Options are not yet s    1315                         Options are not yet supported.
1327                                                  1316 
1328                 lantiq,<addr>                    1317                 lantiq,<addr>
1329                         Start an early, polle    1318                         Start an early, polled-mode console on a lantiq serial
1330                         (lqasc) port at the s    1319                         (lqasc) port at the specified address. The serial port
1331                         must already be setup    1320                         must already be setup and configured. Options are not
1332                         yet supported.           1321                         yet supported.
1333                                                  1322 
1334                 lpuart,<addr>                    1323                 lpuart,<addr>
1335                 lpuart32,<addr>                  1324                 lpuart32,<addr>
1336                         Use early console pro    1325                         Use early console provided by Freescale LP UART driver
1337                         found on Freescale Vy    1326                         found on Freescale Vybrid and QorIQ LS1021A processors.
1338                         A valid base address     1327                         A valid base address must be provided, and the serial
1339                         port must already be     1328                         port must already be setup and configured.
1340                                                  1329 
1341                 ec_imx21,<addr>                  1330                 ec_imx21,<addr>
1342                 ec_imx6q,<addr>                  1331                 ec_imx6q,<addr>
1343                         Start an early, polle    1332                         Start an early, polled-mode, output-only console on the
1344                         Freescale i.MX UART a    1333                         Freescale i.MX UART at the specified address. The UART
1345                         must already be setup    1334                         must already be setup and configured.
1346                                                  1335 
1347                 ar3700_uart,<addr>               1336                 ar3700_uart,<addr>
1348                         Start an early, polle    1337                         Start an early, polled-mode console on the
1349                         Armada 3700 serial po    1338                         Armada 3700 serial port at the specified
1350                         address. The serial p    1339                         address. The serial port must already be setup
1351                         and configured. Optio    1340                         and configured. Options are not yet supported.
1352                                                  1341 
1353                 qcom_geni,<addr>                 1342                 qcom_geni,<addr>
1354                         Start an early, polle    1343                         Start an early, polled-mode console on a Qualcomm
1355                         Generic Interface (GE    1344                         Generic Interface (GENI) based serial port at the
1356                         specified address. Th    1345                         specified address. The serial port must already be
1357                         setup and configured.    1346                         setup and configured. Options are not yet supported.
1358                                                  1347 
1359                 efifb,[options]                  1348                 efifb,[options]
1360                         Start an early, unacc    1349                         Start an early, unaccelerated console on the EFI
1361                         memory mapped framebu    1350                         memory mapped framebuffer (if available). On cache
1362                         coherent non-x86 syst    1351                         coherent non-x86 systems that use system memory for
1363                         the framebuffer, pass    1352                         the framebuffer, pass the 'ram' option so that it is
1364                         mapped with the corre    1353                         mapped with the correct attributes.
1365                                                  1354 
1366                 linflex,<addr>                   1355                 linflex,<addr>
1367                         Use early console pro    1356                         Use early console provided by Freescale LINFlexD UART
1368                         serial driver for NXP    1357                         serial driver for NXP S32V234 SoCs. A valid base
1369                         address must be provi    1358                         address must be provided, and the serial port must
1370                         already be setup and     1359                         already be setup and configured.
1371                                                  1360 
1372         earlyprintk=    [X86,SH,ARM,M68k,S390 !! 1361         earlyprintk=    [X86,SH,ARM,M68k,S390]
1373                         earlyprintk=vga          1362                         earlyprintk=vga
1374                         earlyprintk=sclp         1363                         earlyprintk=sclp
1375                         earlyprintk=xen          1364                         earlyprintk=xen
1376                         earlyprintk=serial[,t    1365                         earlyprintk=serial[,ttySn[,baudrate]]
1377                         earlyprintk=serial[,0    1366                         earlyprintk=serial[,0x...[,baudrate]]
1378                         earlyprintk=ttySn[,ba    1367                         earlyprintk=ttySn[,baudrate]
1379                         earlyprintk=dbgp[debu    1368                         earlyprintk=dbgp[debugController#]
1380                         earlyprintk=pciserial    1369                         earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381                         earlyprintk=xdbc[xhci    1370                         earlyprintk=xdbc[xhciController#]
1382                         earlyprintk=bios         1371                         earlyprintk=bios
1383                                                  1372 
1384                         earlyprintk is useful    1373                         earlyprintk is useful when the kernel crashes before
1385                         the normal console is    1374                         the normal console is initialized. It is not enabled by
1386                         default because it ha    1375                         default because it has some cosmetic problems.
1387                                                  1376 
1388                         Append ",keep" to not    1377                         Append ",keep" to not disable it when the real console
1389                         takes over.              1378                         takes over.
1390                                                  1379 
1391                         Only one of vga, seri    1380                         Only one of vga, serial, or usb debug port can
1392                         be used at a time.       1381                         be used at a time.
1393                                                  1382 
1394                         Currently only ttyS0     1383                         Currently only ttyS0 and ttyS1 may be specified by
1395                         name.  Other I/O port    1384                         name.  Other I/O ports may be explicitly specified
1396                         on some architectures    1385                         on some architectures (x86 and arm at least) by
1397                         replacing ttySn with     1386                         replacing ttySn with an I/O port address, like this:
1398                                 earlyprintk=s    1387                                 earlyprintk=serial,0x1008,115200
1399                         You can find the port    1388                         You can find the port for a given device in
1400                         /proc/tty/driver/seri    1389                         /proc/tty/driver/serial:
1401                                 2: uart:ST166    1390                                 2: uart:ST16650V2 port:00001008 irq:18 ...
1402                                                  1391 
1403                         Interaction with the     1392                         Interaction with the standard serial driver is not
1404                         very good.               1393                         very good.
1405                                                  1394 
1406                         The VGA output is eve    1395                         The VGA output is eventually overwritten by
1407                         the real console.        1396                         the real console.
1408                                                  1397 
1409                         The xen option can on    1398                         The xen option can only be used in Xen domains.
1410                                                  1399 
1411                         The sclp output can o    1400                         The sclp output can only be used on s390.
1412                                                  1401 
1413                         The bios output can o    1402                         The bios output can only be used on SuperH.
1414                                                  1403 
1415                         The optional "force"     1404                         The optional "force" to "pciserial" enables use of a
1416                         PCI device even when     1405                         PCI device even when its classcode is not of the
1417                         UART class.              1406                         UART class.
1418                                                  1407 
1419         edac_report=    [HW,EDAC] Control how    1408         edac_report=    [HW,EDAC] Control how to report EDAC event
1420                         Format: {"on" | "off"    1409                         Format: {"on" | "off" | "force"}
1421                         on: enable EDAC to re    1410                         on: enable EDAC to report H/W event. May be overridden
1422                         by other higher prior    1411                         by other higher priority error reporting module.
1423                         off: disable H/W even    1412                         off: disable H/W event reporting through EDAC.
1424                         force: enforce the us    1413                         force: enforce the use of EDAC to report H/W event.
1425                         default: on.             1414                         default: on.
1426                                                  1415 
1427         edd=            [EDD]                    1416         edd=            [EDD]
1428                         Format: {"off" | "on"    1417                         Format: {"off" | "on" | "skip[mbr]"}
1429                                                  1418 
1430         efi=            [EFI,EARLY]           !! 1419         efi=            [EFI]
1431                         Format: { "debug", "d    1420                         Format: { "debug", "disable_early_pci_dma",
1432                                   "nochunk",     1421                                   "nochunk", "noruntime", "nosoftreserve",
1433                                   "novamap",     1422                                   "novamap", "no_disable_early_pci_dma" }
1434                         debug: enable misc de    1423                         debug: enable misc debug output.
1435                         disable_early_pci_dma    1424                         disable_early_pci_dma: disable the busmaster bit on all
1436                         PCI bridges while in     1425                         PCI bridges while in the EFI boot stub.
1437                         nochunk: disable read    1426                         nochunk: disable reading files in "chunks" in the EFI
1438                         boot stub, as chunkin    1427                         boot stub, as chunking can cause problems with some
1439                         firmware implementati    1428                         firmware implementations.
1440                         noruntime : disable E    1429                         noruntime : disable EFI runtime services support
1441                         nosoftreserve: The EF    1430                         nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442                         attribute may cause t    1431                         attribute may cause the kernel to reserve the
1443                         memory range for a me    1432                         memory range for a memory mapping driver to
1444                         claim. Specify efi=no    1433                         claim. Specify efi=nosoftreserve to disable this
1445                         reservation and treat    1434                         reservation and treat the memory by its base type
1446                         (i.e. EFI_CONVENTIONA    1435                         (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447                         novamap: do not call     1436                         novamap: do not call SetVirtualAddressMap().
1448                         no_disable_early_pci_    1437                         no_disable_early_pci_dma: Leave the busmaster bit set
1449                         on all PCI bridges wh    1438                         on all PCI bridges while in the EFI boot stub
1450                                                  1439 
1451         efi_no_storage_paranoia [EFI,X86,EARL !! 1440         efi_no_storage_paranoia [EFI; X86]
1452                         Using this parameter     1441                         Using this parameter you can use more than 50% of
1453                         your efi variable sto    1442                         your efi variable storage. Use this parameter only if
1454                         you are really sure t    1443                         you are really sure that your UEFI does sane gc and
1455                         fulfills the spec oth    1444                         fulfills the spec otherwise your board may brick.
1456                                                  1445 
                                                   >> 1446         efi_fake_mem=   nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
                                                   >> 1447                         Add arbitrary attribute to specific memory range by
                                                   >> 1448                         updating original EFI memory map.
                                                   >> 1449                         Region of memory which aa attribute is added to is
                                                   >> 1450                         from ss to ss+nn.
                                                   >> 1451 
                                                   >> 1452                         If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
                                                   >> 1453                         is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
                                                   >> 1454                         attribute is added to range 0x100000000-0x180000000 and
                                                   >> 1455                         0x10a0000000-0x1120000000.
                                                   >> 1456 
                                                   >> 1457                         If efi_fake_mem=8G@9G:0x40000 is specified, the
                                                   >> 1458                         EFI_MEMORY_SP(0x40000) attribute is added to
                                                   >> 1459                         range 0x240000000-0x43fffffff.
                                                   >> 1460 
                                                   >> 1461                         Using this parameter you can do debugging of EFI memmap
                                                   >> 1462                         related features. For example, you can do debugging of
                                                   >> 1463                         Address Range Mirroring feature even if your box
                                                   >> 1464                         doesn't support it, or mark specific memory as
                                                   >> 1465                         "soft reserved".
                                                   >> 1466 
1457         efivar_ssdt=    [EFI; X86] Name of an    1467         efivar_ssdt=    [EFI; X86] Name of an EFI variable that contains an SSDT
1458                         that is to be dynamic    1468                         that is to be dynamically loaded by Linux. If there are
1459                         multiple variables wi    1469                         multiple variables with the same name but with different
1460                         vendor GUIDs, all of     1470                         vendor GUIDs, all of them will be loaded. See
1461                         Documentation/admin-g    1471                         Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462                                                  1472 
1463                                                  1473 
1464         eisa_irq_edge=  [PARISC,HW]              1474         eisa_irq_edge=  [PARISC,HW]
1465                         See header of drivers    1475                         See header of drivers/parisc/eisa.c.
1466                                                  1476 
1467         ekgdboc=        [X86,KGDB,EARLY] Allo !! 1477         ekgdboc=        [X86,KGDB] Allow early kernel console debugging
1468                         Format: ekgdboc=kbd      1478                         Format: ekgdboc=kbd
1469                                                  1479 
1470                         This is designed to b    1480                         This is designed to be used in conjunction with
1471                         the boot argument: ea    1481                         the boot argument: earlyprintk=vga
1472                                                  1482 
1473                         This parameter works     1483                         This parameter works in place of the kgdboc parameter
1474                         but can only be used     1484                         but can only be used if the backing tty is available
1475                         very early in the boo    1485                         very early in the boot process. For early debugging
1476                         via a serial port see    1486                         via a serial port see kgdboc_earlycon instead.
1477                                                  1487 
1478         elanfreq=       [X86-32]                 1488         elanfreq=       [X86-32]
1479                         See comment before fu    1489                         See comment before function elanfreq_setup() in
1480                         arch/x86/kernel/cpu/c    1490                         arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481                                                  1491 
1482         elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1492         elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390]
1483                         Specifies physical ad    1493                         Specifies physical address of start of kernel core
1484                         image elf header and     1494                         image elf header and optionally the size. Generally
1485                         kexec loader will pas    1495                         kexec loader will pass this option to capture kernel.
1486                         See Documentation/adm    1496                         See Documentation/admin-guide/kdump/kdump.rst for details.
1487                                                  1497 
1488         enable_mtrr_cleanup [X86,EARLY]       !! 1498         enable_mtrr_cleanup [X86]
1489                         The kernel tries to a    1499                         The kernel tries to adjust MTRR layout from continuous
1490                         to discrete, to make     1500                         to discrete, to make X server driver able to add WB
1491                         entry later. This par    1501                         entry later. This parameter enables that.
1492                                                  1502 
1493         enable_timer_pin_1 [X86]                 1503         enable_timer_pin_1 [X86]
1494                         Enable PIN 1 of APIC     1504                         Enable PIN 1 of APIC timer
1495                         Can be useful to work    1505                         Can be useful to work around chipset bugs
1496                         (in particular on som    1506                         (in particular on some ATI chipsets).
1497                         The kernel tries to s    1507                         The kernel tries to set a reasonable default.
1498                                                  1508 
1499         enforcing=      [SELINUX] Set initial    1509         enforcing=      [SELINUX] Set initial enforcing status.
1500                         Format: {"0" | "1"}      1510                         Format: {"0" | "1"}
1501                         See security/selinux/    1511                         See security/selinux/Kconfig help text.
1502                         0 -- permissive (log     1512                         0 -- permissive (log only, no denials).
1503                         1 -- enforcing (deny     1513                         1 -- enforcing (deny and log).
1504                         Default value is 0.      1514                         Default value is 0.
1505                         Value can be changed     1515                         Value can be changed at runtime via
1506                         /sys/fs/selinux/enfor    1516                         /sys/fs/selinux/enforce.
1507                                                  1517 
1508         erst_disable    [ACPI]                   1518         erst_disable    [ACPI]
1509                         Disable Error Record     1519                         Disable Error Record Serialization Table (ERST)
1510                         support.                 1520                         support.
1511                                                  1521 
1512         ether=          [HW,NET] Ethernet car    1522         ether=          [HW,NET] Ethernet cards parameters
1513                         This option is obsole    1523                         This option is obsoleted by the "netdev=" option, which
1514                         has equivalent usage.    1524                         has equivalent usage. See its documentation for details.
1515                                                  1525 
1516         evm=            [EVM]                    1526         evm=            [EVM]
1517                         Format: { "fix" }        1527                         Format: { "fix" }
1518                         Permit 'security.evm'    1528                         Permit 'security.evm' to be updated regardless of
1519                         current integrity sta    1529                         current integrity status.
1520                                                  1530 
1521         early_page_ext [KNL,EARLY] Enforces p !! 1531         early_page_ext [KNL] Enforces page_ext initialization to earlier
1522                         stages so cover more     1532                         stages so cover more early boot allocations.
1523                         Please note that as s    1533                         Please note that as side effect some optimizations
1524                         might be disabled to     1534                         might be disabled to achieve that (e.g. parallelized
1525                         memory initialization    1535                         memory initialization is disabled) so the boot process
1526                         might take longer, es    1536                         might take longer, especially on systems with a lot of
1527                         memory. Available wit    1537                         memory. Available with CONFIG_PAGE_EXTENSION=y.
1528                                                  1538 
1529         failslab=                                1539         failslab=
1530         fail_usercopy=                           1540         fail_usercopy=
1531         fail_page_alloc=                         1541         fail_page_alloc=
1532         fail_make_request=[KNL]                  1542         fail_make_request=[KNL]
1533                         General fault injecti    1543                         General fault injection mechanism.
1534                         Format: <interval>,<p    1544                         Format: <interval>,<probability>,<space>,<times>
1535                         See also Documentatio    1545                         See also Documentation/fault-injection/.
1536                                                  1546 
1537         fb_tunnels=     [NET]                    1547         fb_tunnels=     [NET]
1538                         Format: { initns | no    1548                         Format: { initns | none }
1539                         See Documentation/adm    1549                         See Documentation/admin-guide/sysctl/net.rst for
1540                         fb_tunnels_only_for_i    1550                         fb_tunnels_only_for_init_ns
1541                                                  1551 
1542         floppy=         [HW]                     1552         floppy=         [HW]
1543                         See Documentation/adm    1553                         See Documentation/admin-guide/blockdev/floppy.rst.
1544                                                  1554 
1545         forcepae        [X86-32]                 1555         forcepae        [X86-32]
1546                         Forcefully enable Phy    1556                         Forcefully enable Physical Address Extension (PAE).
1547                         Many Pentium M system    1557                         Many Pentium M systems disable PAE but may have a
1548                         functionally usable P    1558                         functionally usable PAE implementation.
1549                         Warning: use of this     1559                         Warning: use of this parameter will taint the kernel
1550                         and may cause unknown    1560                         and may cause unknown problems.
1551                                                  1561 
1552         fred=           [X86-64]              << 
1553                         Enable/disable Flexib << 
1554                         Format: { on | off }  << 
1555                         on: enable FRED when  << 
1556                         off: disable FRED, th << 
1557                                               << 
1558         ftrace=[tracer]                          1562         ftrace=[tracer]
1559                         [FTRACE] will set and    1563                         [FTRACE] will set and start the specified tracer
1560                         as early as possible     1564                         as early as possible in order to facilitate early
1561                         boot debugging.          1565                         boot debugging.
1562                                                  1566 
1563         ftrace_boot_snapshot                     1567         ftrace_boot_snapshot
1564                         [FTRACE] On boot up,     1568                         [FTRACE] On boot up, a snapshot will be taken of the
1565                         ftrace ring buffer th    1569                         ftrace ring buffer that can be read at:
1566                         /sys/kernel/tracing/s    1570                         /sys/kernel/tracing/snapshot.
1567                         This is useful if you    1571                         This is useful if you need tracing information from kernel
1568                         boot up that is likel    1572                         boot up that is likely to be overridden by user space
1569                         start up functionalit    1573                         start up functionality.
1570                                                  1574 
1571                         Optionally, the snaps    1575                         Optionally, the snapshot can also be defined for a tracing
1572                         instance that was cre    1576                         instance that was created by the trace_instance= command
1573                         line parameter.          1577                         line parameter.
1574                                                  1578 
1575                         trace_instance=foo,sc    1579                         trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1576                                                  1580 
1577                         The above will cause     1581                         The above will cause the "foo" tracing instance to trigger
1578                         a snapshot at the end    1582                         a snapshot at the end of boot up.
1579                                                  1583 
1580         ftrace_dump_on_oops[=2(orig_cpu) | =< !! 1584         ftrace_dump_on_oops[=orig_cpu]
1581                           ,<instance>=2(orig_ << 
1582                         [FTRACE] will dump th    1585                         [FTRACE] will dump the trace buffers on oops.
1583                         If no parameter is pa !! 1586                         If no parameter is passed, ftrace will dump
1584                         buffers of all CPUs,  !! 1587                         buffers of all CPUs, but if you pass orig_cpu, it will
1585                         will dump only the bu !! 1588                         dump only the buffer of the CPU that triggered the
1586                         the oops, or the spec !! 1589                         oops.
1587                         its name is passed. M << 
1588                         supported, and instan << 
1589                         instance supports onl << 
1590                         oops by passing 2 or  << 
1591                                               << 
1592                         ftrace_dump_on_oops=f << 
1593                                               << 
1594                         The above will dump o << 
1595                         on CPU that triggered << 
1596                                               << 
1597                         ftrace_dump_on_oops,f << 
1598                                               << 
1599                         The above will dump g << 
1600                         buffer of "foo" insta << 
1601                         of "bar" instance on  << 
1602                                                  1590 
1603         ftrace_filter=[function-list]            1591         ftrace_filter=[function-list]
1604                         [FTRACE] Limit the fu    1592                         [FTRACE] Limit the functions traced by the function
1605                         tracer at boot up. fu    1593                         tracer at boot up. function-list is a comma-separated
1606                         list of functions. Th    1594                         list of functions. This list can be changed at run
1607                         time by the set_ftrac    1595                         time by the set_ftrace_filter file in the debugfs
1608                         tracing directory.       1596                         tracing directory.
1609                                                  1597 
1610         ftrace_notrace=[function-list]           1598         ftrace_notrace=[function-list]
1611                         [FTRACE] Do not trace    1599                         [FTRACE] Do not trace the functions specified in
1612                         function-list. This l    1600                         function-list. This list can be changed at run time
1613                         by the set_ftrace_not    1601                         by the set_ftrace_notrace file in the debugfs
1614                         tracing directory.       1602                         tracing directory.
1615                                                  1603 
1616         ftrace_graph_filter=[function-list]      1604         ftrace_graph_filter=[function-list]
1617                         [FTRACE] Limit the to    1605                         [FTRACE] Limit the top level callers functions traced
1618                         by the function graph    1606                         by the function graph tracer at boot up.
1619                         function-list is a co    1607                         function-list is a comma-separated list of functions
1620                         that can be changed a    1608                         that can be changed at run time by the
1621                         set_graph_function fi    1609                         set_graph_function file in the debugfs tracing directory.
1622                                                  1610 
1623         ftrace_graph_notrace=[function-list]     1611         ftrace_graph_notrace=[function-list]
1624                         [FTRACE] Do not trace    1612                         [FTRACE] Do not trace from the functions specified in
1625                         function-list.  This     1613                         function-list.  This list is a comma-separated list of
1626                         functions that can be    1614                         functions that can be changed at run time by the
1627                         set_graph_notrace fil    1615                         set_graph_notrace file in the debugfs tracing directory.
1628                                                  1616 
1629         ftrace_graph_max_depth=<uint>            1617         ftrace_graph_max_depth=<uint>
1630                         [FTRACE] Used with th    1618                         [FTRACE] Used with the function graph tracer. This is
1631                         the max depth it will    1619                         the max depth it will trace into a function. This value
1632                         can be changed at run    1620                         can be changed at run time by the max_graph_depth file
1633                         in the tracefs tracin    1621                         in the tracefs tracing directory. default: 0 (no limit)
1634                                                  1622 
1635         fw_devlink=     [KNL,EARLY] Create de !! 1623         fw_devlink=     [KNL] Create device links between consumer and supplier
1636                         devices by scanning t    1624                         devices by scanning the firmware to infer the
1637                         consumer/supplier rel    1625                         consumer/supplier relationships. This feature is
1638                         especially useful whe    1626                         especially useful when drivers are loaded as modules as
1639                         it ensures proper ord    1627                         it ensures proper ordering of tasks like device probing
1640                         (suppliers first, the    1628                         (suppliers first, then consumers), supplier boot state
1641                         clean up (only after     1629                         clean up (only after all consumers have probed),
1642                         suspend/resume & runt    1630                         suspend/resume & runtime PM (consumers first, then
1643                         suppliers).              1631                         suppliers).
1644                         Format: { off | permi    1632                         Format: { off | permissive | on | rpm }
1645                         off --  Don't create     1633                         off --  Don't create device links from firmware info.
1646                         permissive -- Create     1634                         permissive -- Create device links from firmware info
1647                                 but use it on    1635                                 but use it only for ordering boot state clean
1648                                 up (sync_stat    1636                                 up (sync_state() calls).
1649                         on --   Create device    1637                         on --   Create device links from firmware info and use it
1650                                 to enforce pr    1638                                 to enforce probe and suspend/resume ordering.
1651                         rpm --  Like "on", bu    1639                         rpm --  Like "on", but also use to order runtime PM.
1652                                                  1640 
1653         fw_devlink.strict=<bool>                 1641         fw_devlink.strict=<bool>
1654                         [KNL,EARLY] Treat all !! 1642                         [KNL] Treat all inferred dependencies as mandatory
1655                         dependencies. This on    1643                         dependencies. This only applies for fw_devlink=on|rpm.
1656                         Format: <bool>           1644                         Format: <bool>
1657                                                  1645 
1658         fw_devlink.sync_state =                  1646         fw_devlink.sync_state =
1659                         [KNL,EARLY] When all  !! 1647                         [KNL] When all devices that could probe have finished
1660                         probing, this paramet    1648                         probing, this parameter controls what to do with
1661                         devices that haven't     1649                         devices that haven't yet received their sync_state()
1662                         calls.                   1650                         calls.
1663                         Format: { strict | ti    1651                         Format: { strict | timeout }
1664                         strict -- Default. Co    1652                         strict -- Default. Continue waiting on consumers to
1665                                 probe success    1653                                 probe successfully.
1666                         timeout -- Give up wa    1654                         timeout -- Give up waiting on consumers and call
1667                                 sync_state()     1655                                 sync_state() on any devices that haven't yet
1668                                 received thei    1656                                 received their sync_state() calls after
1669                                 deferred_prob    1657                                 deferred_probe_timeout has expired or by
1670                                 late_initcall    1658                                 late_initcall() if !CONFIG_MODULES.
1671                                                  1659 
1672         gamecon.map[2|3]=                        1660         gamecon.map[2|3]=
1673                         [HW,JOY] Multisystem     1661                         [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674                         support via parallel     1662                         support via parallel port (up to 5 devices per port)
1675                         Format: <port#>,<pad1    1663                         Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676                         See also Documentatio    1664                         See also Documentation/input/devices/joystick-parport.rst
1677                                                  1665 
1678         gamma=          [HW,DRM]                 1666         gamma=          [HW,DRM]
1679                                                  1667 
1680         gart_fix_e820=  [X86-64,EARLY] disabl !! 1668         gart_fix_e820=  [X86-64] disable the fix e820 for K8 GART
1681                         Format: off | on         1669                         Format: off | on
1682                         default: on              1670                         default: on
1683                                                  1671 
1684         gather_data_sampling=                    1672         gather_data_sampling=
1685                         [X86,INTEL,EARLY] Con !! 1673                         [X86,INTEL] Control the Gather Data Sampling (GDS)
1686                         mitigation.              1674                         mitigation.
1687                                                  1675 
1688                         Gather Data Sampling     1676                         Gather Data Sampling is a hardware vulnerability which
1689                         allows unprivileged s    1677                         allows unprivileged speculative access to data which was
1690                         previously stored in     1678                         previously stored in vector registers.
1691                                                  1679 
1692                         This issue is mitigat    1680                         This issue is mitigated by default in updated microcode.
1693                         The mitigation may ha    1681                         The mitigation may have a performance impact but can be
1694                         disabled. On systems     1682                         disabled. On systems without the microcode mitigation
1695                         disabling AVX serves     1683                         disabling AVX serves as a mitigation.
1696                                                  1684 
1697                         force:  Disable AVX t    1685                         force:  Disable AVX to mitigate systems without
1698                                 microcode mit    1686                                 microcode mitigation. No effect if the microcode
1699                                 mitigation is    1687                                 mitigation is present. Known to cause crashes in
1700                                 userspace wit    1688                                 userspace with buggy AVX enumeration.
1701                                                  1689 
1702                         off:    Disable GDS m    1690                         off:    Disable GDS mitigation.
1703                                                  1691 
1704         gcov_persist=   [GCOV] When non-zero     1692         gcov_persist=   [GCOV] When non-zero (default), profiling data for
1705                         kernel modules is sav    1693                         kernel modules is saved and remains accessible via
1706                         debugfs, even when th    1694                         debugfs, even when the module is unloaded/reloaded.
1707                         When zero, profiling     1695                         When zero, profiling data is discarded and associated
1708                         debugfs files are rem    1696                         debugfs files are removed at module unload time.
1709                                                  1697 
1710         goldfish        [X86] Enable the gold    1698         goldfish        [X86] Enable the goldfish android emulator platform.
1711                         Don't use this when y    1699                         Don't use this when you are not running on the
1712                         android emulator         1700                         android emulator
1713                                                  1701 
1714         gpio-mockup.gpio_mockup_ranges           1702         gpio-mockup.gpio_mockup_ranges
1715                         [HW] Sets the ranges     1703                         [HW] Sets the ranges of gpiochip of for this device.
1716                         Format: <start1>,<end    1704                         Format: <start1>,<end1>,<start2>,<end2>...
1717         gpio-mockup.gpio_mockup_named_lines      1705         gpio-mockup.gpio_mockup_named_lines
1718                         [HW] Let the driver k    1706                         [HW] Let the driver know GPIO lines should be named.
1719                                                  1707 
1720         gpt             [EFI] Forces disk wit    1708         gpt             [EFI] Forces disk with valid GPT signature but
1721                         invalid Protective MB    1709                         invalid Protective MBR to be treated as GPT. If the
1722                         primary GPT is corrup    1710                         primary GPT is corrupted, it enables the backup/alternate
1723                         GPT to be used instea    1711                         GPT to be used instead.
1724                                                  1712 
1725         grcan.enable0=  [HW] Configuration of    1713         grcan.enable0=  [HW] Configuration of physical interface 0. Determines
1726                         the "Enable 0" bit of    1714                         the "Enable 0" bit of the configuration register.
1727                         Format: 0 | 1            1715                         Format: 0 | 1
1728                         Default: 0               1716                         Default: 0
1729         grcan.enable1=  [HW] Configuration of    1717         grcan.enable1=  [HW] Configuration of physical interface 1. Determines
1730                         the "Enable 0" bit of    1718                         the "Enable 0" bit of the configuration register.
1731                         Format: 0 | 1            1719                         Format: 0 | 1
1732                         Default: 0               1720                         Default: 0
1733         grcan.select=   [HW] Select which phy    1721         grcan.select=   [HW] Select which physical interface to use.
1734                         Format: 0 | 1            1722                         Format: 0 | 1
1735                         Default: 0               1723                         Default: 0
1736         grcan.txsize=   [HW] Sets the size of    1724         grcan.txsize=   [HW] Sets the size of the tx buffer.
1737                         Format: <unsigned int    1725                         Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738                         Default: 1024            1726                         Default: 1024
1739         grcan.rxsize=   [HW] Sets the size of    1727         grcan.rxsize=   [HW] Sets the size of the rx buffer.
1740                         Format: <unsigned int    1728                         Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741                         Default: 1024            1729                         Default: 1024
1742                                                  1730 
1743         hardened_usercopy=                       1731         hardened_usercopy=
1744                         [KNL] Under CONFIG_HA    1732                         [KNL] Under CONFIG_HARDENED_USERCOPY, whether
1745                         hardening is enabled     1733                         hardening is enabled for this boot. Hardened
1746                         usercopy checking is     1734                         usercopy checking is used to protect the kernel
1747                         from reading or writi    1735                         from reading or writing beyond known memory
1748                         allocation boundaries    1736                         allocation boundaries as a proactive defense
1749                         against bounds-checki    1737                         against bounds-checking flaws in the kernel's
1750                         copy_to_user()/copy_f    1738                         copy_to_user()/copy_from_user() interface.
1751                 on      Perform hardened user    1739                 on      Perform hardened usercopy checks (default).
1752                 off     Disable hardened user    1740                 off     Disable hardened usercopy checks.
1753                                                  1741 
1754         hardlockup_all_cpu_backtrace=            1742         hardlockup_all_cpu_backtrace=
1755                         [KNL] Should the hard    1743                         [KNL] Should the hard-lockup detector generate
1756                         backtraces on all cpu    1744                         backtraces on all cpus.
1757                         Format: 0 | 1            1745                         Format: 0 | 1
1758                                                  1746 
1759         hashdist=       [KNL,NUMA] Large hash    1747         hashdist=       [KNL,NUMA] Large hashes allocated during boot
1760                         are distributed acros    1748                         are distributed across NUMA nodes.  Defaults on
1761                         for 64-bit NUMA, off     1749                         for 64-bit NUMA, off otherwise.
1762                         Format: 0 | 1 (for of    1750                         Format: 0 | 1 (for off | on)
1763                                                  1751 
                                                   >> 1752         hcl=            [IA-64] SGI's Hardware Graph compatibility layer
                                                   >> 1753 
1764         hd=             [EIDE] (E)IDE hard dr    1754         hd=             [EIDE] (E)IDE hard drive subsystem geometry
1765                         Format: <cyl>,<head>,    1755                         Format: <cyl>,<head>,<sect>
1766                                                  1756 
1767         hest_disable    [ACPI]                   1757         hest_disable    [ACPI]
1768                         Disable Hardware Erro    1758                         Disable Hardware Error Source Table (HEST) support;
1769                         corresponding firmwar    1759                         corresponding firmware-first mode error processing
1770                         logic will be disable    1760                         logic will be disabled.
1771                                                  1761 
1772         hibernate=      [HIBERNATION]            1762         hibernate=      [HIBERNATION]
1773                 noresume        Don't check i    1763                 noresume        Don't check if there's a hibernation image
1774                                 present durin    1764                                 present during boot.
1775                 nocompress      Don't compres    1765                 nocompress      Don't compress/decompress hibernation images.
1776                 no              Disable hiber    1766                 no              Disable hibernation and resume.
1777                 protect_image   Turn on image    1767                 protect_image   Turn on image protection during restoration
1778                                 (that will se    1768                                 (that will set all pages holding image data
1779                                 during restor    1769                                 during restoration read-only).
1780                                                  1770 
1781         hibernate.compressor=   [HIBERNATION] !! 1771         highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1782                                 used with hib << 
1783                                 Format: { lzo << 
1784                                 Default: lzo  << 
1785                                               << 
1786                                 lzo: Select L << 
1787                                 compress/deco << 
1788                                               << 
1789                                 lz4: Select L << 
1790                                 compress/deco << 
1791                                               << 
1792         highmem=nn[KMG] [KNL,BOOT,EARLY] forc << 
1793                         size of <nn>. This wo    1772                         size of <nn>. This works even on boxes that have no
1794                         highmem otherwise. Th    1773                         highmem otherwise. This also works to reduce highmem
1795                         size on bigger boxes.    1774                         size on bigger boxes.
1796                                                  1775 
1797         highres=        [KNL] Enable/disable     1776         highres=        [KNL] Enable/disable high resolution timer mode.
1798                         Valid parameters: "on    1777                         Valid parameters: "on", "off"
1799                         Default: "on"            1778                         Default: "on"
1800                                                  1779 
1801         hlt             [BUGS=ARM,SH]            1780         hlt             [BUGS=ARM,SH]
1802                                                  1781 
1803         hostname=       [KNL,EARLY] Set the h !! 1782         hostname=       [KNL] Set the hostname (aka UTS nodename).
1804                         Format: <string>         1783                         Format: <string>
1805                         This allows setting t    1784                         This allows setting the system's hostname during early
1806                         startup. This sets th    1785                         startup. This sets the name returned by gethostname.
1807                         Using this parameter     1786                         Using this parameter to set the hostname makes it
1808                         possible to ensure th    1787                         possible to ensure the hostname is correctly set before
1809                         any userspace process    1788                         any userspace processes run, avoiding the possibility
1810                         that a process may ca    1789                         that a process may call gethostname before the hostname
1811                         has been explicitly s    1790                         has been explicitly set, resulting in the calling
1812                         process getting an in    1791                         process getting an incorrect result. The string must
1813                         not exceed the maximu    1792                         not exceed the maximum allowed hostname length (usually
1814                         64 characters) and wi    1793                         64 characters) and will be truncated otherwise.
1815                                                  1794 
1816         hpet=           [X86-32,HPET] option     1795         hpet=           [X86-32,HPET] option to control HPET usage
1817                         Format: { enable (def    1796                         Format: { enable (default) | disable | force |
1818                                 verbose }        1797                                 verbose }
1819                         disable: disable HPET    1798                         disable: disable HPET and use PIT instead
1820                         force: allow force en    1799                         force: allow force enabled of undocumented chips (ICH4,
1821                                 VIA, nVidia)     1800                                 VIA, nVidia)
1822                         verbose: show content    1801                         verbose: show contents of HPET registers during setup
1823                                                  1802 
1824         hpet_mmap=      [X86, HPET_MMAP] Allo    1803         hpet_mmap=      [X86, HPET_MMAP] Allow userspace to mmap HPET
1825                         registers.  Default s    1804                         registers.  Default set by CONFIG_HPET_MMAP_DEFAULT.
1826                                                  1805 
1827         hugepages=      [HW] Number of HugeTL    1806         hugepages=      [HW] Number of HugeTLB pages to allocate at boot.
1828                         If this follows hugep    1807                         If this follows hugepagesz (below), it specifies
1829                         the number of pages o    1808                         the number of pages of hugepagesz to be allocated.
1830                         If this is the first     1809                         If this is the first HugeTLB parameter on the command
1831                         line, it specifies th    1810                         line, it specifies the number of pages to allocate for
1832                         the default huge page    1811                         the default huge page size. If using node format, the
1833                         number of pages to al    1812                         number of pages to allocate per-node can be specified.
1834                         See also Documentatio    1813                         See also Documentation/admin-guide/mm/hugetlbpage.rst.
1835                         Format: <integer> or     1814                         Format: <integer> or (node format)
1836                                 <node>:<integ    1815                                 <node>:<integer>[,<node>:<integer>]
1837                                                  1816 
1838         hugepagesz=                              1817         hugepagesz=
1839                         [HW] The size of the     1818                         [HW] The size of the HugeTLB pages.  This is used in
1840                         conjunction with huge    1819                         conjunction with hugepages (above) to allocate huge
1841                         pages of a specific s    1820                         pages of a specific size at boot.  The pair
1842                         hugepagesz=X hugepage    1821                         hugepagesz=X hugepages=Y can be specified once for
1843                         each supported huge p    1822                         each supported huge page size. Huge page sizes are
1844                         architecture dependen    1823                         architecture dependent.  See also
1845                         Documentation/admin-g    1824                         Documentation/admin-guide/mm/hugetlbpage.rst.
1846                         Format: size[KMG]        1825                         Format: size[KMG]
1847                                                  1826 
1848         hugetlb_cma=    [HW,CMA,EARLY] The si !! 1827         hugetlb_cma=    [HW,CMA] The size of a CMA area used for allocation
1849                         of gigantic hugepages    1828                         of gigantic hugepages. Or using node format, the size
1850                         of a CMA area per nod    1829                         of a CMA area per node can be specified.
1851                         Format: nn[KMGTPE] or    1830                         Format: nn[KMGTPE] or (node format)
1852                                 <node>:nn[KMG    1831                                 <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1853                                                  1832 
1854                         Reserve a CMA area of    1833                         Reserve a CMA area of given size and allocate gigantic
1855                         hugepages using the C    1834                         hugepages using the CMA allocator. If enabled, the
1856                         boot-time allocation     1835                         boot-time allocation of gigantic hugepages is skipped.
1857                                                  1836 
1858         hugetlb_free_vmemmap=                    1837         hugetlb_free_vmemmap=
1859                         [KNL] Requires CONFIG    1838                         [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1860                         enabled.                 1839                         enabled.
1861                         Control if HugeTLB Vm    1840                         Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1862                         Allows heavy hugetlb     1841                         Allows heavy hugetlb users to free up some more
1863                         memory (7 * PAGE_SIZE    1842                         memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1864                         Format: { on | off (d    1843                         Format: { on | off (default) }
1865                                                  1844 
1866                         on: enable HVO           1845                         on: enable HVO
1867                         off: disable HVO         1846                         off: disable HVO
1868                                                  1847 
1869                         Built with CONFIG_HUG    1848                         Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1870                         the default is on.       1849                         the default is on.
1871                                                  1850 
1872                         Note that the vmemmap    1851                         Note that the vmemmap pages may be allocated from the added
1873                         memory block itself w    1852                         memory block itself when memory_hotplug.memmap_on_memory is
1874                         enabled, those vmemma    1853                         enabled, those vmemmap pages cannot be optimized even if this
1875                         feature is enabled.      1854                         feature is enabled.  Other vmemmap pages not allocated from
1876                         the added memory bloc    1855                         the added memory block itself do not be affected.
1877                                                  1856 
1878         hung_task_panic=                         1857         hung_task_panic=
1879                         [KNL] Should the hung    1858                         [KNL] Should the hung task detector generate panics.
1880                         Format: 0 | 1            1859                         Format: 0 | 1
1881                                                  1860 
1882                         A value of 1 instruct    1861                         A value of 1 instructs the kernel to panic when a
1883                         hung task is detected    1862                         hung task is detected. The default value is controlled
1884                         by the CONFIG_BOOTPAR    1863                         by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885                         option. The value sel    1864                         option. The value selected by this boot parameter can
1886                         be changed later by t    1865                         be changed later by the kernel.hung_task_panic sysctl.
1887                                                  1866 
1888         hvc_iucv=       [S390]  Number of z/V    1867         hvc_iucv=       [S390]  Number of z/VM IUCV hypervisor console (HVC)
1889                                 terminal devi    1868                                 terminal devices. Valid values: 0..8
1890         hvc_iucv_allow= [S390]  Comma-separat    1869         hvc_iucv_allow= [S390]  Comma-separated list of z/VM user IDs.
1891                                 If specified,    1870                                 If specified, z/VM IUCV HVC accepts connections
1892                                 from listed z    1871                                 from listed z/VM user IDs only.
1893                                                  1872 
1894         hv_nopvspin     [X86,HYPER_V,EARLY]   !! 1873         hv_nopvspin     [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895                         Disables the paravirt !! 1874                                       which allow the hypervisor to 'idle' the
1896                         which allow the hyper !! 1875                                       guest on lock contention.
1897                         on lock contention.   << 
1898                                                  1876 
1899         i2c_bus=        [HW]    Override the     1877         i2c_bus=        [HW]    Override the default board specific I2C bus speed
1900                                 or register a    1878                                 or register an additional I2C bus that is not
1901                                 registered fr    1879                                 registered from board initialization code.
1902                                 Format:          1880                                 Format:
1903                                 <bus_id>,<clk    1881                                 <bus_id>,<clkrate>
1904                                                  1882 
1905         i2c_touchscreen_props= [HW,ACPI,X86]  << 
1906                         Set device-properties << 
1907                         touchscreen, to e.g.  << 
1908                         mounted touchscreens. << 
1909                         submit a drivers/plat << 
1910                         adding a DMI quirk fo << 
1911                                               << 
1912                         Format:               << 
1913                         <ACPI_HW_ID>:<prop_na << 
1914                         Where <val> is one of << 
1915                         Omit "=<val>" entirel << 
1916                         Unsigned number       << 
1917                         Anything else         << 
1918                                               << 
1919                         Examples (split over  << 
1920                         i2c_touchscreen_props << 
1921                         touchscreen-inverted- << 
1922                                               << 
1923                         i2c_touchscreen_props << 
1924                         touchscreen-size-y=10 << 
1925                         firmware-name=gsl1680 << 
1926                                               << 
1927         i8042.debug     [HW] Toggle i8042 deb    1883         i8042.debug     [HW] Toggle i8042 debug mode
1928         i8042.unmask_kbd_data                    1884         i8042.unmask_kbd_data
1929                         [HW] Enable printing     1885                         [HW] Enable printing of interrupt data from the KBD port
1930                              (disabled by def    1886                              (disabled by default, and as a pre-condition
1931                              requires that i8    1887                              requires that i8042.debug=1 be enabled)
1932         i8042.direct    [HW] Put keyboard por    1888         i8042.direct    [HW] Put keyboard port into non-translated mode
1933         i8042.dumbkbd   [HW] Pretend that con    1889         i8042.dumbkbd   [HW] Pretend that controller can only read data from
1934                              keyboard and can    1890                              keyboard and cannot control its state
1935                              (Don't attempt t    1891                              (Don't attempt to blink the leds)
1936         i8042.noaux     [HW] Don't check for     1892         i8042.noaux     [HW] Don't check for auxiliary (== mouse) port
1937         i8042.nokbd     [HW] Don't check/crea    1893         i8042.nokbd     [HW] Don't check/create keyboard port
1938         i8042.noloop    [HW] Disable the AUX     1894         i8042.noloop    [HW] Disable the AUX Loopback command while probing
1939                              for the AUX port    1895                              for the AUX port
1940         i8042.nomux     [HW] Don't check pres    1896         i8042.nomux     [HW] Don't check presence of an active multiplexing
1941                              controller          1897                              controller
1942         i8042.nopnp     [HW] Don't use ACPIPn    1898         i8042.nopnp     [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943                              controllers         1899                              controllers
1944         i8042.notimeout [HW] Ignore timeout c    1900         i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945         i8042.reset     [HW] Reset the contro    1901         i8042.reset     [HW] Reset the controller during init, cleanup and
1946                              suspend-to-ram t    1902                              suspend-to-ram transitions, only during s2r
1947                              transitions, or     1903                              transitions, or never reset
1948                         Format: { 1 | Y | y |    1904                         Format: { 1 | Y | y | 0 | N | n }
1949                         1, Y, y: always reset    1905                         1, Y, y: always reset controller
1950                         0, N, n: don't ever r    1906                         0, N, n: don't ever reset controller
1951                         Default: only on s2r     1907                         Default: only on s2r transitions on x86; most other
1952                         architectures force r    1908                         architectures force reset to be always executed
1953         i8042.unlock    [HW] Unlock (ignore)     1909         i8042.unlock    [HW] Unlock (ignore) the keylock
1954         i8042.kbdreset  [HW] Reset device con    1910         i8042.kbdreset  [HW] Reset device connected to KBD port
1955         i8042.probe_defer                        1911         i8042.probe_defer
1956                         [HW] Allow deferred p    1912                         [HW] Allow deferred probing upon i8042 probe errors
1957                                                  1913 
1958         i810=           [HW,DRM]                 1914         i810=           [HW,DRM]
1959                                                  1915 
1960         i915.invert_brightness=                  1916         i915.invert_brightness=
1961                         [DRM] Invert the sens    1917                         [DRM] Invert the sense of the variable that is used to
1962                         set the brightness of    1918                         set the brightness of the panel backlight. Normally a
1963                         brightness value of 0    1919                         brightness value of 0 indicates backlight switched off,
1964                         and the maximum of th    1920                         and the maximum of the brightness value sets the backlight
1965                         to maximum brightness    1921                         to maximum brightness. If this parameter is set to 0
1966                         (default) and the mac    1922                         (default) and the machine requires it, or this parameter
1967                         is set to 1, a bright    1923                         is set to 1, a brightness value of 0 sets the backlight
1968                         to maximum brightness    1924                         to maximum brightness, and the maximum of the brightness
1969                         value switches the ba    1925                         value switches the backlight off.
1970                         -1 -- never invert br    1926                         -1 -- never invert brightness
1971                          0 -- machine default    1927                          0 -- machine default
1972                          1 -- force brightnes    1928                          1 -- force brightness inversion
1973                                                  1929 
1974         ia32_emulation= [X86-64]                 1930         ia32_emulation= [X86-64]
1975                         Format: <bool>           1931                         Format: <bool>
1976                         When true, allows loa    1932                         When true, allows loading 32-bit programs and executing 32-bit
1977                         syscalls, essentially    1933                         syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
1978                         boot time. When false    1934                         boot time. When false, unconditionally disables IA32 emulation.
1979                                                  1935 
1980         icn=            [HW,ISDN]                1936         icn=            [HW,ISDN]
1981                         Format: <io>[,<membas    1937                         Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982                                                  1938 
1983                                                  1939 
1984         idle=           [X86,EARLY]           !! 1940         idle=           [X86]
1985                         Format: idle=poll, id    1941                         Format: idle=poll, idle=halt, idle=nomwait
1986                         Poll forces a polling    1942                         Poll forces a polling idle loop that can slightly
1987                         improve the performan    1943                         improve the performance of waking up a idle CPU, but
1988                         will use a lot of pow    1944                         will use a lot of power and make the system run hot.
1989                         Not recommended.         1945                         Not recommended.
1990                         idle=halt: Halt is fo    1946                         idle=halt: Halt is forced to be used for CPU idle.
1991                         In such case C2/C3 wo    1947                         In such case C2/C3 won't be used again.
1992                         idle=nomwait: Disable    1948                         idle=nomwait: Disable mwait for CPU C-states
1993                                                  1949 
1994         idxd.sva=       [HW]                     1950         idxd.sva=       [HW]
1995                         Format: <bool>           1951                         Format: <bool>
1996                         Allow force disabling    1952                         Allow force disabling of Shared Virtual Memory (SVA)
1997                         support for the idxd     1953                         support for the idxd driver. By default it is set to
1998                         true (1).                1954                         true (1).
1999                                                  1955 
2000         idxd.tc_override= [HW]                   1956         idxd.tc_override= [HW]
2001                         Format: <bool>           1957                         Format: <bool>
2002                         Allow override of def    1958                         Allow override of default traffic class configuration
2003                         for the device. By de    1959                         for the device. By default it is set to false (0).
2004                                                  1960 
2005         ieee754=        [MIPS] Select IEEE St    1961         ieee754=        [MIPS] Select IEEE Std 754 conformance mode
2006                         Format: { strict | le !! 1962                         Format: { strict | legacy | 2008 | relaxed }
2007                         Default: strict          1963                         Default: strict
2008                                                  1964 
2009                         Choose which programs    1965                         Choose which programs will be accepted for execution
2010                         based on the IEEE 754    1966                         based on the IEEE 754 NaN encoding(s) supported by
2011                         the FPU and the NaN e    1967                         the FPU and the NaN encoding requested with the value
2012                         of an ELF file header    1968                         of an ELF file header flag individually set by each
2013                         binary.  Hardware imp    1969                         binary.  Hardware implementations are permitted to
2014                         support either or bot    1970                         support either or both of the legacy and the 2008 NaN
2015                         encoding mode.           1971                         encoding mode.
2016                                                  1972 
2017                         Available settings ar    1973                         Available settings are as follows:
2018                         strict  accept binari    1974                         strict  accept binaries that request a NaN encoding
2019                                 supported by     1975                                 supported by the FPU
2020                         legacy  only accept l    1976                         legacy  only accept legacy-NaN binaries, if supported
2021                                 by the FPU       1977                                 by the FPU
2022                         2008    only accept 2    1978                         2008    only accept 2008-NaN binaries, if supported
2023                                 by the FPU       1979                                 by the FPU
2024                         relaxed accept any bi    1980                         relaxed accept any binaries regardless of whether
2025                                 supported by     1981                                 supported by the FPU
2026                         emulated accept any b << 
2027                                 if binary mod << 
2028                                                  1982 
2029                         The FPU emulator is a    1983                         The FPU emulator is always able to support both NaN
2030                         encodings, so if no F    1984                         encodings, so if no FPU hardware is present or it has
2031                         been disabled with 'n    1985                         been disabled with 'nofpu', then the settings of
2032                         'legacy' and '2008' s    1986                         'legacy' and '2008' strap the emulator accordingly,
2033                         'relaxed' straps the     1987                         'relaxed' straps the emulator for both legacy-NaN and
2034                         2008-NaN, whereas 'st    1988                         2008-NaN, whereas 'strict' enables legacy-NaN only on
2035                         legacy processors and    1989                         legacy processors and both NaN encodings on MIPS32 or
2036                         MIPS64 CPUs.             1990                         MIPS64 CPUs.
2037                                                  1991 
2038                         The setting for ABS.f    1992                         The setting for ABS.fmt/NEG.fmt instruction execution
2039                         mode generally follow    1993                         mode generally follows that for the NaN encoding,
2040                         except where unsuppor    1994                         except where unsupported by hardware.
2041                                                  1995 
2042         ignore_loglevel [KNL,EARLY]           !! 1996         ignore_loglevel [KNL]
2043                         Ignore loglevel setti    1997                         Ignore loglevel setting - this will print /all/
2044                         kernel messages to th    1998                         kernel messages to the console. Useful for debugging.
2045                         We also add it as pri    1999                         We also add it as printk module parameter, so users
2046                         could change it dynam    2000                         could change it dynamically, usually by
2047                         /sys/module/printk/pa    2001                         /sys/module/printk/parameters/ignore_loglevel.
2048                                                  2002 
2049         ignore_rlimit_data                       2003         ignore_rlimit_data
2050                         Ignore RLIMIT_DATA se    2004                         Ignore RLIMIT_DATA setting for data mappings,
2051                         print warning at firs    2005                         print warning at first misuse.  Can be changed via
2052                         /sys/module/kernel/pa    2006                         /sys/module/kernel/parameters/ignore_rlimit_data.
2053                                                  2007 
2054         ihash_entries=  [KNL]                    2008         ihash_entries=  [KNL]
2055                         Set number of hash bu    2009                         Set number of hash buckets for inode cache.
2056                                                  2010 
2057         ima_appraise=   [IMA] appraise integr    2011         ima_appraise=   [IMA] appraise integrity measurements
2058                         Format: { "off" | "en    2012                         Format: { "off" | "enforce" | "fix" | "log" }
2059                         default: "enforce"       2013                         default: "enforce"
2060                                                  2014 
2061         ima_appraise_tcb [IMA] Deprecated.  U    2015         ima_appraise_tcb [IMA] Deprecated.  Use ima_policy= instead.
2062                         The builtin appraise     2016                         The builtin appraise policy appraises all files
2063                         owned by uid=0.          2017                         owned by uid=0.
2064                                                  2018 
2065         ima_canonical_fmt [IMA]                  2019         ima_canonical_fmt [IMA]
2066                         Use the canonical for    2020                         Use the canonical format for the binary runtime
2067                         measurements, instead    2021                         measurements, instead of host native format.
2068                                                  2022 
2069         ima_hash=       [IMA]                    2023         ima_hash=       [IMA]
2070                         Format: { md5 | sha1     2024                         Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071                                    | sha512 |    2025                                    | sha512 | ... }
2072                         default: "sha1"          2026                         default: "sha1"
2073                                                  2027 
2074                         The list of supported    2028                         The list of supported hash algorithms is defined
2075                         in crypto/hash_info.h    2029                         in crypto/hash_info.h.
2076                                                  2030 
2077         ima_policy=     [IMA]                    2031         ima_policy=     [IMA]
2078                         The builtin policies     2032                         The builtin policies to load during IMA setup.
2079                         Format: "tcb | apprai    2033                         Format: "tcb | appraise_tcb | secure_boot |
2080                                  fail_securel    2034                                  fail_securely | critical_data"
2081                                                  2035 
2082                         The "tcb" policy meas    2036                         The "tcb" policy measures all programs exec'd, files
2083                         mmap'd for exec, and     2037                         mmap'd for exec, and all files opened with the read
2084                         mode bit set by eithe    2038                         mode bit set by either the effective uid (euid=0) or
2085                         uid=0.                   2039                         uid=0.
2086                                                  2040 
2087                         The "appraise_tcb" po    2041                         The "appraise_tcb" policy appraises the integrity of
2088                         all files owned by ro    2042                         all files owned by root.
2089                                                  2043 
2090                         The "secure_boot" pol    2044                         The "secure_boot" policy appraises the integrity
2091                         of files (eg. kexec k    2045                         of files (eg. kexec kernel image, kernel modules,
2092                         firmware, policy, etc    2046                         firmware, policy, etc) based on file signatures.
2093                                                  2047 
2094                         The "fail_securely" p    2048                         The "fail_securely" policy forces file signature
2095                         verification failure     2049                         verification failure also on privileged mounted
2096                         filesystems with the     2050                         filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097                         flag.                    2051                         flag.
2098                                                  2052 
2099                         The "critical_data" p    2053                         The "critical_data" policy measures kernel integrity
2100                         critical data.           2054                         critical data.
2101                                                  2055 
2102         ima_tcb         [IMA] Deprecated.  Us    2056         ima_tcb         [IMA] Deprecated.  Use ima_policy= instead.
2103                         Load a policy which m    2057                         Load a policy which meets the needs of the Trusted
2104                         Computing Base.  This    2058                         Computing Base.  This means IMA will measure all
2105                         programs exec'd, file    2059                         programs exec'd, files mmap'd for exec, and all files
2106                         opened for read by ui    2060                         opened for read by uid=0.
2107                                                  2061 
2108         ima_template=   [IMA]                    2062         ima_template=   [IMA]
2109                         Select one of defined    2063                         Select one of defined IMA measurements template formats.
2110                         Formats: { "ima" | "i    2064                         Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2111                                    "ima-sigv2    2065                                    "ima-sigv2" }
2112                         Default: "ima-ng"        2066                         Default: "ima-ng"
2113                                                  2067 
2114         ima_template_fmt=                        2068         ima_template_fmt=
2115                         [IMA] Define a custom    2069                         [IMA] Define a custom template format.
2116                         Format: { "field1|...    2070                         Format: { "field1|...|fieldN" }
2117                                                  2071 
2118         ima.ahash_minsize= [IMA] Minimum file    2072         ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119                         Format: <min_file_siz    2073                         Format: <min_file_size>
2120                         Set the minimal file     2074                         Set the minimal file size for using asynchronous hash.
2121                         If left unspecified,     2075                         If left unspecified, ahash usage is disabled.
2122                                                  2076 
2123                         ahash performance var    2077                         ahash performance varies for different data sizes on
2124                         different crypto acce    2078                         different crypto accelerators. This option can be used
2125                         to achieve the best p    2079                         to achieve the best performance for a particular HW.
2126                                                  2080 
2127         ima.ahash_bufsize= [IMA] Asynchronous    2081         ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128                         Format: <bufsize>        2082                         Format: <bufsize>
2129                         Set hashing buffer si    2083                         Set hashing buffer size. Default: 4k.
2130                                                  2084 
2131                         ahash performance var    2085                         ahash performance varies for different chunk sizes on
2132                         different crypto acce    2086                         different crypto accelerators. This option can be used
2133                         to achieve best perfo    2087                         to achieve best performance for particular HW.
2134                                                  2088 
2135         init=           [KNL]                    2089         init=           [KNL]
2136                         Format: <full_path>      2090                         Format: <full_path>
2137                         Run specified binary     2091                         Run specified binary instead of /sbin/init as init
2138                         process.                 2092                         process.
2139                                                  2093 
2140         initcall_debug  [KNL] Trace initcalls    2094         initcall_debug  [KNL] Trace initcalls as they are executed.  Useful
2141                         for working out where    2095                         for working out where the kernel is dying during
2142                         startup.                 2096                         startup.
2143                                                  2097 
2144         initcall_blacklist=  [KNL] Do not exe    2098         initcall_blacklist=  [KNL] Do not execute a comma-separated list of
2145                         initcall functions.      2099                         initcall functions.  Useful for debugging built-in
2146                         modules and initcalls    2100                         modules and initcalls.
2147                                                  2101 
2148         initramfs_async= [KNL]                   2102         initramfs_async= [KNL]
2149                         Format: <bool>           2103                         Format: <bool>
2150                         Default: 1               2104                         Default: 1
2151                         This parameter contro    2105                         This parameter controls whether the initramfs
2152                         image is unpacked asy    2106                         image is unpacked asynchronously, concurrently
2153                         with devices being pr    2107                         with devices being probed and
2154                         initialized. This sho    2108                         initialized. This should normally just work,
2155                         but as a debugging ai    2109                         but as a debugging aid, one can get the
2156                         historical behaviour     2110                         historical behaviour of the initramfs
2157                         unpacking being compl    2111                         unpacking being completed before device_ and
2158                         late_ initcalls.         2112                         late_ initcalls.
2159                                                  2113 
2160         initrd=         [BOOT,EARLY] Specify  !! 2114         initrd=         [BOOT] Specify the location of the initial ramdisk
2161                                                  2115 
2162         initrdmem=      [KNL,EARLY] Specify a !! 2116         initrdmem=      [KNL] Specify a physical address and size from which to
2163                         load the initrd. If a    2117                         load the initrd. If an initrd is compiled in or
2164                         specified in the boot    2118                         specified in the bootparams, it takes priority over this
2165                         setting.                 2119                         setting.
2166                         Format: ss[KMG],nn[KM    2120                         Format: ss[KMG],nn[KMG]
2167                         Default is 0, 0          2121                         Default is 0, 0
2168                                                  2122 
2169         init_on_alloc=  [MM,EARLY] Fill newly !! 2123         init_on_alloc=  [MM] Fill newly allocated pages and heap objects with
2170                         zeroes.                  2124                         zeroes.
2171                         Format: 0 | 1            2125                         Format: 0 | 1
2172                         Default set by CONFIG    2126                         Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173                                                  2127 
2174         init_on_free=   [MM,EARLY] Fill freed !! 2128         init_on_free=   [MM] Fill freed pages and heap objects with zeroes.
2175                         Format: 0 | 1            2129                         Format: 0 | 1
2176                         Default set by CONFIG    2130                         Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177                                                  2131 
2178         init_pkru=      [X86] Specify the def    2132         init_pkru=      [X86] Specify the default memory protection keys rights
2179                         register contents for    2133                         register contents for all processes.  0x55555554 by
2180                         default (disallow acc    2134                         default (disallow access to all but pkey 0).  Can
2181                         override in debugfs a    2135                         override in debugfs after boot.
2182                                                  2136 
2183         inport.irq=     [HW] Inport (ATI XL a    2137         inport.irq=     [HW] Inport (ATI XL and Microsoft) busmouse driver
2184                         Format: <irq>            2138                         Format: <irq>
2185                                                  2139 
2186         int_pln_enable  [X86] Enable power li    2140         int_pln_enable  [X86] Enable power limit notification interrupt
2187                                                  2141 
2188         integrity_audit=[IMA]                    2142         integrity_audit=[IMA]
2189                         Format: { "0" | "1" }    2143                         Format: { "0" | "1" }
2190                         0 -- basic integrity     2144                         0 -- basic integrity auditing messages. (Default)
2191                         1 -- additional integ    2145                         1 -- additional integrity auditing messages.
2192                                                  2146 
2193         intel_iommu=    [DMAR] Intel IOMMU dr    2147         intel_iommu=    [DMAR] Intel IOMMU driver (DMAR) option
2194                 on                               2148                 on
2195                         Enable intel iommu dr    2149                         Enable intel iommu driver.
2196                 off                              2150                 off
2197                         Disable intel iommu d    2151                         Disable intel iommu driver.
2198                 igfx_off [Default Off]           2152                 igfx_off [Default Off]
2199                         By default, gfx is ma    2153                         By default, gfx is mapped as normal device. If a gfx
2200                         device has a dedicate    2154                         device has a dedicated DMAR unit, the DMAR unit is
2201                         bypassed by not enabl    2155                         bypassed by not enabling DMAR with this option. In
2202                         this case, gfx device    2156                         this case, gfx device will use physical address for
2203                         DMA.                     2157                         DMA.
2204                 strict [Default Off]             2158                 strict [Default Off]
2205                         Deprecated, equivalen    2159                         Deprecated, equivalent to iommu.strict=1.
2206                 sp_off [Default Off]             2160                 sp_off [Default Off]
2207                         By default, super pag    2161                         By default, super page will be supported if Intel IOMMU
2208                         has the capability. W    2162                         has the capability. With this option, super page will
2209                         not be supported.        2163                         not be supported.
2210                 sm_on                            2164                 sm_on
2211                         Enable the Intel IOMM    2165                         Enable the Intel IOMMU scalable mode if the hardware
2212                         advertises that it ha    2166                         advertises that it has support for the scalable mode
2213                         translation.             2167                         translation.
2214                 sm_off                           2168                 sm_off
2215                         Disallow use of the I    2169                         Disallow use of the Intel IOMMU scalable mode.
2216                 tboot_noforce [Default Off]      2170                 tboot_noforce [Default Off]
2217                         Do not force the Inte    2171                         Do not force the Intel IOMMU enabled under tboot.
2218                         By default, tboot wil    2172                         By default, tboot will force Intel IOMMU on, which
2219                         could harm performanc    2173                         could harm performance of some high-throughput
2220                         devices like 40GBit n    2174                         devices like 40GBit network cards, even if identity
2221                         mapping is enabled.      2175                         mapping is enabled.
2222                         Note that using this     2176                         Note that using this option lowers the security
2223                         provided by tboot bec    2177                         provided by tboot because it makes the system
2224                         vulnerable to DMA att    2178                         vulnerable to DMA attacks.
2225                                                  2179 
2226         intel_idle.max_cstate=  [KNL,HW,ACPI,    2180         intel_idle.max_cstate=  [KNL,HW,ACPI,X86]
2227                         0       disables inte    2181                         0       disables intel_idle and fall back on acpi_idle.
2228                         1 to 9  specify maxim    2182                         1 to 9  specify maximum depth of C-state.
2229                                                  2183 
2230         intel_pstate=   [X86,EARLY]           !! 2184         intel_pstate=   [X86]
2231                         disable                  2185                         disable
2232                           Do not enable intel    2186                           Do not enable intel_pstate as the default
2233                           scaling driver for     2187                           scaling driver for the supported processors
2234                         active                   2188                         active
2235                           Use intel_pstate dr    2189                           Use intel_pstate driver to bypass the scaling
2236                           governors layer of     2190                           governors layer of cpufreq and provides it own
2237                           algorithms for p-st    2191                           algorithms for p-state selection. There are two
2238                           P-state selection a    2192                           P-state selection algorithms provided by
2239                           intel_pstate in the    2193                           intel_pstate in the active mode: powersave and
2240                           performance.  The w    2194                           performance.  The way they both operate depends
2241                           on whether or not t    2195                           on whether or not the hardware managed P-states
2242                           (HWP) feature has b    2196                           (HWP) feature has been enabled in the processor
2243                           and possibly on the    2197                           and possibly on the processor model.
2244                         passive                  2198                         passive
2245                           Use intel_pstate as    2199                           Use intel_pstate as a scaling driver, but configure it
2246                           to work with generi    2200                           to work with generic cpufreq governors (instead of
2247                           enabling its intern    2201                           enabling its internal governor).  This mode cannot be
2248                           used along with the    2202                           used along with the hardware-managed P-states (HWP)
2249                           feature.               2203                           feature.
2250                         force                    2204                         force
2251                           Enable intel_pstate    2205                           Enable intel_pstate on systems that prohibit it by default
2252                           in favor of acpi-cp    2206                           in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253                           instead of acpi-cpu    2207                           instead of acpi-cpufreq may disable platform features, such
2254                           as thermal controls    2208                           as thermal controls and power capping, that rely on ACPI
2255                           P-States informatio    2209                           P-States information being indicated to OSPM and therefore
2256                           should be used with    2210                           should be used with caution. This option does not work with
2257                           processors that are    2211                           processors that aren't supported by the intel_pstate driver
2258                           or on platforms tha    2212                           or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259                         no_hwp                   2213                         no_hwp
2260                           Do not enable hardw    2214                           Do not enable hardware P state control (HWP)
2261                           if available.          2215                           if available.
2262                         hwp_only                 2216                         hwp_only
2263                           Only load intel_pst    2217                           Only load intel_pstate on systems which support
2264                           hardware P state co    2218                           hardware P state control (HWP) if available.
2265                         support_acpi_ppc         2219                         support_acpi_ppc
2266                           Enforce ACPI _PPC p    2220                           Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267                           Description Table,     2221                           Description Table, specifies preferred power management
2268                           profile as "Enterpr    2222                           profile as "Enterprise Server" or "Performance Server",
2269                           then this feature i    2223                           then this feature is turned on by default.
2270                         per_cpu_perf_limits      2224                         per_cpu_perf_limits
2271                           Allow per-logical-C    2225                           Allow per-logical-CPU P-State performance control limits using
2272                           cpufreq sysfs inter    2226                           cpufreq sysfs interface
2273                                                  2227 
2274         intremap=       [X86-64,Intel-IOMMU,E !! 2228         intremap=       [X86-64, Intel-IOMMU]
2275                         on      enable Interr    2229                         on      enable Interrupt Remapping (default)
2276                         off     disable Inter    2230                         off     disable Interrupt Remapping
2277                         nosid   disable Sourc    2231                         nosid   disable Source ID checking
2278                         no_x2apic_optout         2232                         no_x2apic_optout
2279                                 BIOS x2APIC o    2233                                 BIOS x2APIC opt-out request will be ignored
2280                         nopost  disable Inter    2234                         nopost  disable Interrupt Posting
2281                         posted_msi            << 
2282                                 enable MSIs d << 
2283                                                  2235 
2284         iomem=          Disable strict checki    2236         iomem=          Disable strict checking of access to MMIO memory
2285                 strict  regions from userspac    2237                 strict  regions from userspace.
2286                 relaxed                          2238                 relaxed
2287                                                  2239 
2288         iommu=          [X86,EARLY]           !! 2240         iommu=          [X86]
2289                 off                              2241                 off
2290                 force                            2242                 force
2291                 noforce                          2243                 noforce
2292                 biomerge                         2244                 biomerge
2293                 panic                            2245                 panic
2294                 nopanic                          2246                 nopanic
2295                 merge                            2247                 merge
2296                 nomerge                          2248                 nomerge
2297                 soft                             2249                 soft
2298                 pt              [X86]            2250                 pt              [X86]
2299                 nopt            [X86]            2251                 nopt            [X86]
2300                 nobypass        [PPC/POWERNV]    2252                 nobypass        [PPC/POWERNV]
2301                         Disable IOMMU bypass,    2253                         Disable IOMMU bypass, using IOMMU for PCI devices.
2302                                                  2254 
2303         iommu.forcedac= [ARM64,X86,EARLY] Con !! 2255         iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304                         Format: { "0" | "1" }    2256                         Format: { "0" | "1" }
2305                         0 - Try to allocate a    2257                         0 - Try to allocate a 32-bit DMA address first, before
2306                           falling back to the    2258                           falling back to the full range if needed.
2307                         1 - Allocate directly    2259                         1 - Allocate directly from the full usable range,
2308                           forcing Dual Addres    2260                           forcing Dual Address Cycle for PCI cards supporting
2309                           greater than 32-bit    2261                           greater than 32-bit addressing.
2310                                                  2262 
2311         iommu.strict=   [ARM64,X86,S390,EARLY !! 2263         iommu.strict=   [ARM64, X86, S390] Configure TLB invalidation behaviour
2312                         Format: { "0" | "1" }    2264                         Format: { "0" | "1" }
2313                         0 - Lazy mode.           2265                         0 - Lazy mode.
2314                           Request that DMA un    2266                           Request that DMA unmap operations use deferred
2315                           invalidation of har    2267                           invalidation of hardware TLBs, for increased
2316                           throughput at the c    2268                           throughput at the cost of reduced device isolation.
2317                           Will fall back to s    2269                           Will fall back to strict mode if not supported by
2318                           the relevant IOMMU     2270                           the relevant IOMMU driver.
2319                         1 - Strict mode.         2271                         1 - Strict mode.
2320                           DMA unmap operation    2272                           DMA unmap operations invalidate IOMMU hardware TLBs
2321                           synchronously.         2273                           synchronously.
2322                         unset - Use value of     2274                         unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2323                         Note: on x86, strict     2275                         Note: on x86, strict mode specified via one of the
2324                         legacy driver-specifi    2276                         legacy driver-specific options takes precedence.
2325                                                  2277 
2326         iommu.passthrough=                       2278         iommu.passthrough=
2327                         [ARM64,X86,EARLY] Con !! 2279                         [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328                         Format: { "0" | "1" }    2280                         Format: { "0" | "1" }
2329                         0 - Use IOMMU transla    2281                         0 - Use IOMMU translation for DMA.
2330                         1 - Bypass the IOMMU     2282                         1 - Bypass the IOMMU for DMA.
2331                         unset - Use value of     2283                         unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332                                                  2284 
2333         io7=            [HW] IO7 for Marvel-b    2285         io7=            [HW] IO7 for Marvel-based Alpha systems
2334                         See comment before ma    2286                         See comment before marvel_specify_io7 in
2335                         arch/alpha/kernel/cor    2287                         arch/alpha/kernel/core_marvel.c.
2336                                                  2288 
2337         io_delay=       [X86,EARLY] I/O delay !! 2289         io_delay=       [X86] I/O delay method
2338                 0x80                             2290                 0x80
2339                         Standard port 0x80 ba    2291                         Standard port 0x80 based delay
2340                 0xed                             2292                 0xed
2341                         Alternate port 0xed b    2293                         Alternate port 0xed based delay (needed on some systems)
2342                 udelay                           2294                 udelay
2343                         Simple two microsecon    2295                         Simple two microseconds delay
2344                 none                             2296                 none
2345                         No delay                 2297                         No delay
2346                                                  2298 
2347         ip=             [IP_PNP]                 2299         ip=             [IP_PNP]
2348                         See Documentation/adm    2300                         See Documentation/admin-guide/nfs/nfsroot.rst.
2349                                                  2301 
2350         ipcmni_extend   [KNL,EARLY] Extend th !! 2302         ipcmni_extend   [KNL] Extend the maximum number of unique System V
2351                         IPC identifiers from     2303                         IPC identifiers from 32,768 to 16,777,216.
2352                                                  2304 
2353         irqaffinity=    [SMP] Set the default    2305         irqaffinity=    [SMP] Set the default irq affinity mask
2354                         The argument is a cpu    2306                         The argument is a cpu list, as described above.
2355                                                  2307 
2356         irqchip.gicv2_force_probe=               2308         irqchip.gicv2_force_probe=
2357                         [ARM,ARM64,EARLY]     !! 2309                         [ARM, ARM64]
2358                         Format: <bool>           2310                         Format: <bool>
2359                         Force the kernel to l    2311                         Force the kernel to look for the second 4kB page
2360                         of a GICv2 controller    2312                         of a GICv2 controller even if the memory range
2361                         exposed by the device    2313                         exposed by the device tree is too small.
2362                                                  2314 
2363         irqchip.gicv3_nolpi=                     2315         irqchip.gicv3_nolpi=
2364                         [ARM,ARM64,EARLY]     !! 2316                         [ARM, ARM64]
2365                         Force the kernel to i    2317                         Force the kernel to ignore the availability of
2366                         LPIs (and by conseque    2318                         LPIs (and by consequence ITSs). Intended for system
2367                         that use the kernel a    2319                         that use the kernel as a bootloader, and thus want
2368                         to let secondary kern    2320                         to let secondary kernels in charge of setting up
2369                         LPIs.                    2321                         LPIs.
2370                                                  2322 
2371         irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2323         irqchip.gicv3_pseudo_nmi= [ARM64]
2372                         Enables support for p    2324                         Enables support for pseudo-NMIs in the kernel. This
2373                         requires the kernel t    2325                         requires the kernel to be built with
2374                         CONFIG_ARM64_PSEUDO_N    2326                         CONFIG_ARM64_PSEUDO_NMI.
2375                                                  2327 
2376         irqfixup        [HW]                     2328         irqfixup        [HW]
2377                         When an interrupt is     2329                         When an interrupt is not handled search all handlers
2378                         for it. Intended to g    2330                         for it. Intended to get systems with badly broken
2379                         firmware running.        2331                         firmware running.
2380                                                  2332 
2381         irqpoll         [HW]                     2333         irqpoll         [HW]
2382                         When an interrupt is     2334                         When an interrupt is not handled search all handlers
2383                         for it. Also check al    2335                         for it. Also check all handlers each timer
2384                         interrupt. Intended t    2336                         interrupt. Intended to get systems with badly broken
2385                         firmware running.        2337                         firmware running.
2386                                                  2338 
2387         isapnp=         [ISAPNP]                 2339         isapnp=         [ISAPNP]
2388                         Format: <RDP>,<reset>    2340                         Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389                                                  2341 
2390         isolcpus=       [KNL,SMP,ISOL] Isolat    2342         isolcpus=       [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391                         [Deprecated - use cpu    2343                         [Deprecated - use cpusets instead]
2392                         Format: [flag-list,]<    2344                         Format: [flag-list,]<cpu-list>
2393                                                  2345 
2394                         Specify one or more C    2346                         Specify one or more CPUs to isolate from disturbances
2395                         specified in the flag    2347                         specified in the flag list (default: domain):
2396                                                  2348 
2397                         nohz                     2349                         nohz
2398                           Disable the tick wh    2350                           Disable the tick when a single task runs.
2399                                                  2351 
2400                           A residual 1Hz tick    2352                           A residual 1Hz tick is offloaded to workqueues, which you
2401                           need to affine to h    2353                           need to affine to housekeeping through the global
2402                           workqueue's affinit    2354                           workqueue's affinity configured via the
2403                           /sys/devices/virtua    2355                           /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404                           by using the 'domai    2356                           by using the 'domain' flag described below.
2405                                                  2357 
2406                           NOTE: by default th    2358                           NOTE: by default the global workqueue runs on all CPUs,
2407                           so to protect indiv    2359                           so to protect individual CPUs the 'cpumask' file has to
2408                           be configured manua    2360                           be configured manually after bootup.
2409                                                  2361 
2410                         domain                   2362                         domain
2411                           Isolate from the ge    2363                           Isolate from the general SMP balancing and scheduling
2412                           algorithms. Note th    2364                           algorithms. Note that performing domain isolation this way
2413                           is irreversible: it    2365                           is irreversible: it's not possible to bring back a CPU to
2414                           the domains once is    2366                           the domains once isolated through isolcpus. It's strongly
2415                           advised to use cpus    2367                           advised to use cpusets instead to disable scheduler load
2416                           balancing through t    2368                           balancing through the "cpuset.sched_load_balance" file.
2417                           It offers a much mo    2369                           It offers a much more flexible interface where CPUs can
2418                           move in and out of     2370                           move in and out of an isolated set anytime.
2419                                                  2371 
2420                           You can move a proc    2372                           You can move a process onto or off an "isolated" CPU via
2421                           the CPU affinity sy    2373                           the CPU affinity syscalls or cpuset.
2422                           <cpu number> begins    2374                           <cpu number> begins at 0 and the maximum value is
2423                           "number of CPUs in     2375                           "number of CPUs in system - 1".
2424                                                  2376 
2425                         managed_irq              2377                         managed_irq
2426                                                  2378 
2427                           Isolate from being     2379                           Isolate from being targeted by managed interrupts
2428                           which have an inter    2380                           which have an interrupt mask containing isolated
2429                           CPUs. The affinity     2381                           CPUs. The affinity of managed interrupts is
2430                           handled by the kern    2382                           handled by the kernel and cannot be changed via
2431                           the /proc/irq/* int    2383                           the /proc/irq/* interfaces.
2432                                                  2384 
2433                           This isolation is b    2385                           This isolation is best effort and only effective
2434                           if the automaticall    2386                           if the automatically assigned interrupt mask of a
2435                           device queue contai    2387                           device queue contains isolated and housekeeping
2436                           CPUs. If housekeepi    2388                           CPUs. If housekeeping CPUs are online then such
2437                           interrupts are dire    2389                           interrupts are directed to the housekeeping CPU
2438                           so that IO submitte    2390                           so that IO submitted on the housekeeping CPU
2439                           cannot disturb the     2391                           cannot disturb the isolated CPU.
2440                                                  2392 
2441                           If a queue's affini    2393                           If a queue's affinity mask contains only isolated
2442                           CPUs then this para    2394                           CPUs then this parameter has no effect on the
2443                           interrupt routing d    2395                           interrupt routing decision, though interrupts are
2444                           only delivered when    2396                           only delivered when tasks running on those
2445                           isolated CPUs submi    2397                           isolated CPUs submit IO. IO submitted on
2446                           housekeeping CPUs h    2398                           housekeeping CPUs has no influence on those
2447                           queues.                2399                           queues.
2448                                                  2400 
2449                         The format of <cpu-li    2401                         The format of <cpu-list> is described above.
2450                                                  2402 
2451         iucv=           [HW,NET]                 2403         iucv=           [HW,NET]
2452                                                  2404 
2453         ivrs_ioapic     [HW,X86-64]              2405         ivrs_ioapic     [HW,X86-64]
2454                         Provide an override t    2406                         Provide an override to the IOAPIC-ID<->DEVICE-ID
2455                         mapping provided in t    2407                         mapping provided in the IVRS ACPI table.
2456                         By default, PCI segme    2408                         By default, PCI segment is 0, and can be omitted.
2457                                                  2409 
2458                         For example, to map I    2410                         For example, to map IOAPIC-ID decimal 10 to
2459                         PCI segment 0x1 and P    2411                         PCI segment 0x1 and PCI device 00:14.0,
2460                         write the parameter a    2412                         write the parameter as:
2461                                 ivrs_ioapic=1    2413                                 ivrs_ioapic=10@0001:00:14.0
2462                                                  2414 
2463                         Deprecated formats:      2415                         Deprecated formats:
2464                         * To map IOAPIC-ID de    2416                         * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2465                           write the parameter    2417                           write the parameter as:
2466                                 ivrs_ioapic[1    2418                                 ivrs_ioapic[10]=00:14.0
2467                         * To map IOAPIC-ID de    2419                         * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2468                           PCI device 00:14.0     2420                           PCI device 00:14.0 write the parameter as:
2469                                 ivrs_ioapic[1    2421                                 ivrs_ioapic[10]=0001:00:14.0
2470                                                  2422 
2471         ivrs_hpet       [HW,X86-64]              2423         ivrs_hpet       [HW,X86-64]
2472                         Provide an override t    2424                         Provide an override to the HPET-ID<->DEVICE-ID
2473                         mapping provided in t    2425                         mapping provided in the IVRS ACPI table.
2474                         By default, PCI segme    2426                         By default, PCI segment is 0, and can be omitted.
2475                                                  2427 
2476                         For example, to map H    2428                         For example, to map HPET-ID decimal 10 to
2477                         PCI segment 0x1 and P    2429                         PCI segment 0x1 and PCI device 00:14.0,
2478                         write the parameter a    2430                         write the parameter as:
2479                                 ivrs_hpet=10@    2431                                 ivrs_hpet=10@0001:00:14.0
2480                                                  2432 
2481                         Deprecated formats:      2433                         Deprecated formats:
2482                         * To map HPET-ID deci    2434                         * To map HPET-ID decimal 0 to PCI device 00:14.0
2483                           write the parameter    2435                           write the parameter as:
2484                                 ivrs_hpet[0]=    2436                                 ivrs_hpet[0]=00:14.0
2485                         * To map HPET-ID deci    2437                         * To map HPET-ID decimal 10 to PCI segment 0x1 and
2486                           PCI device 00:14.0     2438                           PCI device 00:14.0 write the parameter as:
2487                                 ivrs_ioapic[1    2439                                 ivrs_ioapic[10]=0001:00:14.0
2488                                                  2440 
2489         ivrs_acpihid    [HW,X86-64]              2441         ivrs_acpihid    [HW,X86-64]
2490                         Provide an override t    2442                         Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491                         mapping provided in t    2443                         mapping provided in the IVRS ACPI table.
2492                         By default, PCI segme    2444                         By default, PCI segment is 0, and can be omitted.
2493                                                  2445 
2494                         For example, to map U    2446                         For example, to map UART-HID:UID AMD0020:0 to
2495                         PCI segment 0x1 and P    2447                         PCI segment 0x1 and PCI device ID 00:14.5,
2496                         write the parameter a    2448                         write the parameter as:
2497                                 ivrs_acpihid=    2449                                 ivrs_acpihid=AMD0020:0@0001:00:14.5
2498                                                  2450 
2499                         Deprecated formats:      2451                         Deprecated formats:
2500                         * To map UART-HID:UID    2452                         * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2501                           PCI device ID 00:14    2453                           PCI device ID 00:14.5, write the parameter as:
2502                                 ivrs_acpihid[    2454                                 ivrs_acpihid[00:14.5]=AMD0020:0
2503                         * To map UART-HID:UID    2455                         * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2504                           PCI device ID 00:14    2456                           PCI device ID 00:14.5, write the parameter as:
2505                                 ivrs_acpihid[    2457                                 ivrs_acpihid[0001:00:14.5]=AMD0020:0
2506                                                  2458 
2507         js=             [HW,JOY] Analog joyst    2459         js=             [HW,JOY] Analog joystick
2508                         See Documentation/inp    2460                         See Documentation/input/joydev/joystick.rst.
2509                                                  2461 
2510         kasan_multi_shot                         2462         kasan_multi_shot
2511                         [KNL] Enforce KASAN (    2463                         [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512                         report on every inval    2464                         report on every invalid memory access. Without this
2513                         parameter KASAN will     2465                         parameter KASAN will print report only for the first
2514                         invalid access.          2466                         invalid access.
2515                                                  2467 
2516         keep_bootcon    [KNL,EARLY]           !! 2468         keep_bootcon    [KNL]
2517                         Do not unregister boo    2469                         Do not unregister boot console at start. This is only
2518                         useful for debugging     2470                         useful for debugging when something happens in the window
2519                         between unregistering    2471                         between unregistering the boot console and initializing
2520                         the real console.        2472                         the real console.
2521                                                  2473 
2522         keepinitrd      [HW,ARM] See retain_i    2474         keepinitrd      [HW,ARM] See retain_initrd.
2523                                                  2475 
2524         kernelcore=     [KNL,X86,PPC,EARLY]   !! 2476         kernelcore=     [KNL,X86,IA-64,PPC]
2525                         Format: nn[KMGTPE] |     2477                         Format: nn[KMGTPE] | nn% | "mirror"
2526                         This parameter specif    2478                         This parameter specifies the amount of memory usable by
2527                         the kernel for non-mo    2479                         the kernel for non-movable allocations.  The requested
2528                         amount is spread even    2480                         amount is spread evenly throughout all nodes in the
2529                         system as ZONE_NORMAL    2481                         system as ZONE_NORMAL.  The remaining memory is used for
2530                         movable memory in its    2482                         movable memory in its own zone, ZONE_MOVABLE.  In the
2531                         event, a node is too     2483                         event, a node is too small to have both ZONE_NORMAL and
2532                         ZONE_MOVABLE, kernelc    2484                         ZONE_MOVABLE, kernelcore memory will take priority and
2533                         other nodes will have    2485                         other nodes will have a larger ZONE_MOVABLE.
2534                                                  2486 
2535                         ZONE_MOVABLE is used     2487                         ZONE_MOVABLE is used for the allocation of pages that
2536                         may be reclaimed or m    2488                         may be reclaimed or moved by the page migration
2537                         subsystem.  Note that    2489                         subsystem.  Note that allocations like PTEs-from-HighMem
2538                         still use the HighMem    2490                         still use the HighMem zone if it exists, and the Normal
2539                         zone if it does not.     2491                         zone if it does not.
2540                                                  2492 
2541                         It is possible to spe    2493                         It is possible to specify the exact amount of memory in
2542                         the form of "nn[KMGTP    2494                         the form of "nn[KMGTPE]", a percentage of total system
2543                         memory in the form of    2495                         memory in the form of "nn%", or "mirror".  If "mirror"
2544                         option is specified,     2496                         option is specified, mirrored (reliable) memory is used
2545                         for non-movable alloc    2497                         for non-movable allocations and remaining memory is used
2546                         for Movable pages.  "    2498                         for Movable pages.  "nn[KMGTPE]", "nn%", and "mirror"
2547                         are exclusive, so you    2499                         are exclusive, so you cannot specify multiple forms.
2548                                                  2500 
2549         kgdbdbgp=       [KGDB,HW,EARLY] kgdb  !! 2501         kgdbdbgp=       [KGDB,HW] kgdb over EHCI usb debug port.
2550                         Format: <Controller#>    2502                         Format: <Controller#>[,poll interval]
2551                         The controller # is t    2503                         The controller # is the number of the ehci usb debug
2552                         port as it is probed     2504                         port as it is probed via PCI.  The poll interval is
2553                         optional and is the n    2505                         optional and is the number seconds in between
2554                         each poll cycle to th    2506                         each poll cycle to the debug port in case you need
2555                         the functionality for    2507                         the functionality for interrupting the kernel with
2556                         gdb or control-c on t    2508                         gdb or control-c on the dbgp connection.  When
2557                         not using this parame    2509                         not using this parameter you use sysrq-g to break into
2558                         the kernel debugger.     2510                         the kernel debugger.
2559                                                  2511 
2560         kgdboc=         [KGDB,HW] kgdb over c    2512         kgdboc=         [KGDB,HW] kgdb over consoles.
2561                         Requires a tty driver    2513                         Requires a tty driver that supports console polling,
2562                         or a supported pollin    2514                         or a supported polling keyboard driver (non-usb).
2563                          Serial only format:     2515                          Serial only format: <serial_device>[,baud]
2564                          keyboard only format    2516                          keyboard only format: kbd
2565                          keyboard and serial     2517                          keyboard and serial format: kbd,<serial_device>[,baud]
2566                         Optional Kernel mode     2518                         Optional Kernel mode setting:
2567                          kms, kbd format: kms    2519                          kms, kbd format: kms,kbd
2568                          kms, kbd and serial     2520                          kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569                                                  2521 
2570         kgdboc_earlycon=        [KGDB,HW,EARL !! 2522         kgdboc_earlycon=        [KGDB,HW]
2571                         If the boot console p    2523                         If the boot console provides the ability to read
2572                         characters and can wo    2524                         characters and can work in polling mode, you can use
2573                         this parameter to tel    2525                         this parameter to tell kgdb to use it as a backend
2574                         until the normal cons    2526                         until the normal console is registered. Intended to
2575                         be used together with    2527                         be used together with the kgdboc parameter which
2576                         specifies the normal     2528                         specifies the normal console to transition to.
2577                                                  2529 
2578                         The name of the early    2530                         The name of the early console should be specified
2579                         as the value of this     2531                         as the value of this parameter. Note that the name of
2580                         the early console mig    2532                         the early console might be different than the tty
2581                         name passed to kgdboc    2533                         name passed to kgdboc. It's OK to leave the value
2582                         blank and the first b    2534                         blank and the first boot console that implements
2583                         read() will be picked    2535                         read() will be picked.
2584                                                  2536 
2585         kgdbwait        [KGDB,EARLY] Stop ker !! 2537         kgdbwait        [KGDB] Stop kernel execution and enter the
2586                         kernel debugger at th    2538                         kernel debugger at the earliest opportunity.
2587                                                  2539 
2588         kmac=           [MIPS] Korina etherne    2540         kmac=           [MIPS] Korina ethernet MAC address.
2589                         Configure the RouterB    2541                         Configure the RouterBoard 532 series on-chip
2590                         Ethernet adapter MAC     2542                         Ethernet adapter MAC address.
2591                                                  2543 
2592         kmemleak=       [KNL,EARLY] Boot-time !! 2544         kmemleak=       [KNL] Boot-time kmemleak enable/disable
2593                         Valid arguments: on,     2545                         Valid arguments: on, off
2594                         Default: on              2546                         Default: on
2595                         Built with CONFIG_DEB    2547                         Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596                         the default is off.      2548                         the default is off.
2597                                                  2549 
2598         kprobe_event=[probe-list]                2550         kprobe_event=[probe-list]
2599                         [FTRACE] Add kprobe e    2551                         [FTRACE] Add kprobe events and enable at boot time.
2600                         The probe-list is a s    2552                         The probe-list is a semicolon delimited list of probe
2601                         definitions. Each def    2553                         definitions. Each definition is same as kprobe_events
2602                         interface, but the pa    2554                         interface, but the parameters are comma delimited.
2603                         For example, to add a    2555                         For example, to add a kprobe event on vfs_read with
2604                         arg1 and arg2, add to    2556                         arg1 and arg2, add to the command line;
2605                                                  2557 
2606                               kprobe_event=p,    2558                               kprobe_event=p,vfs_read,$arg1,$arg2
2607                                                  2559 
2608                         See also Documentatio    2560                         See also Documentation/trace/kprobetrace.rst "Kernel
2609                         Boot Parameter" secti    2561                         Boot Parameter" section.
2610                                                  2562 
2611         kpti=           [ARM64,EARLY] Control !! 2563         kpti=           [ARM64] Control page table isolation of user
2612                         user and kernel addre !! 2564                         and kernel address spaces.
2613                         Default: enabled on c    2565                         Default: enabled on cores which need mitigation.
2614                         0: force disabled        2566                         0: force disabled
2615                         1: force enabled         2567                         1: force enabled
2616                                                  2568 
2617         kunit.enable=   [KUNIT] Enable execut    2569         kunit.enable=   [KUNIT] Enable executing KUnit tests. Requires
2618                         CONFIG_KUNIT to be se    2570                         CONFIG_KUNIT to be set to be fully enabled. The
2619                         default value can be     2571                         default value can be overridden via
2620                         KUNIT_DEFAULT_ENABLED    2572                         KUNIT_DEFAULT_ENABLED.
2621                         Default is 1 (enabled    2573                         Default is 1 (enabled)
2622                                                  2574 
2623         kvm.ignore_msrs=[KVM] Ignore guest ac    2575         kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624                         Default is 0 (don't i    2576                         Default is 0 (don't ignore, but inject #GP)
2625                                                  2577 
2626         kvm.eager_page_split=                    2578         kvm.eager_page_split=
2627                         [KVM,X86] Controls wh    2579                         [KVM,X86] Controls whether or not KVM will try to
2628                         proactively split all    2580                         proactively split all huge pages during dirty logging.
2629                         Eager page splitting     2581                         Eager page splitting reduces interruptions to vCPU
2630                         execution by eliminat    2582                         execution by eliminating the write-protection faults
2631                         and MMU lock contenti    2583                         and MMU lock contention that would otherwise be
2632                         required to split hug    2584                         required to split huge pages lazily.
2633                                                  2585 
2634                         VM workloads that rar    2586                         VM workloads that rarely perform writes or that write
2635                         only to a small regio    2587                         only to a small region of VM memory may benefit from
2636                         disabling eager page     2588                         disabling eager page splitting to allow huge pages to
2637                         still be used for rea    2589                         still be used for reads.
2638                                                  2590 
2639                         The behavior of eager    2591                         The behavior of eager page splitting depends on whether
2640                         KVM_DIRTY_LOG_INITIAL    2592                         KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2641                         disabled, all huge pa    2593                         disabled, all huge pages in a memslot will be eagerly
2642                         split when dirty logg    2594                         split when dirty logging is enabled on that memslot. If
2643                         enabled, eager page s    2595                         enabled, eager page splitting will be performed during
2644                         the KVM_CLEAR_DIRTY i    2596                         the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2645                         cleared.                 2597                         cleared.
2646                                                  2598 
2647                         Eager page splitting     2599                         Eager page splitting is only supported when kvm.tdp_mmu=Y.
2648                                                  2600 
2649                         Default is Y (on).       2601                         Default is Y (on).
2650                                                  2602 
2651         kvm.enable_vmware_backdoor=[KVM] Supp    2603         kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652                                    Default is    2604                                    Default is false (don't support).
2653                                                  2605 
2654         kvm.nx_huge_pages=                       2606         kvm.nx_huge_pages=
2655                         [KVM] Controls the so    2607                         [KVM] Controls the software workaround for the
2656                         X86_BUG_ITLB_MULTIHIT    2608                         X86_BUG_ITLB_MULTIHIT bug.
2657                         force   : Always depl    2609                         force   : Always deploy workaround.
2658                         off     : Never deplo    2610                         off     : Never deploy workaround.
2659                         auto    : Deploy work    2611                         auto    : Deploy workaround based on the presence of
2660                                   X86_BUG_ITL    2612                                   X86_BUG_ITLB_MULTIHIT.
2661                                                  2613 
2662                         Default is 'auto'.       2614                         Default is 'auto'.
2663                                                  2615 
2664                         If the software worka    2616                         If the software workaround is enabled for the host,
2665                         guests do need not to    2617                         guests do need not to enable it for nested guests.
2666                                                  2618 
2667         kvm.nx_huge_pages_recovery_ratio=        2619         kvm.nx_huge_pages_recovery_ratio=
2668                         [KVM] Controls how ma    2620                         [KVM] Controls how many 4KiB pages are periodically zapped
2669                         back to huge pages.      2621                         back to huge pages.  0 disables the recovery, otherwise if
2670                         the value is N KVM wi    2622                         the value is N KVM will zap 1/Nth of the 4KiB pages every
2671                         period (see below).      2623                         period (see below).  The default is 60.
2672                                                  2624 
2673         kvm.nx_huge_pages_recovery_period_ms=    2625         kvm.nx_huge_pages_recovery_period_ms=
2674                         [KVM] Controls the ti    2626                         [KVM] Controls the time period at which KVM zaps 4KiB pages
2675                         back to huge pages. I    2627                         back to huge pages. If the value is a non-zero N, KVM will
2676                         zap a portion (see ra    2628                         zap a portion (see ratio above) of the pages every N msecs.
2677                         If the value is 0 (th    2629                         If the value is 0 (the default), KVM will pick a period based
2678                         on the ratio, such th    2630                         on the ratio, such that a page is zapped after 1 hour on average.
2679                                                  2631 
2680         kvm-amd.nested= [KVM,AMD] Control nes    2632         kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2681                         KVM/SVM. Default is 1    2633                         KVM/SVM. Default is 1 (enabled).
2682                                                  2634 
2683         kvm-amd.npt=    [KVM,AMD] Control KVM    2635         kvm-amd.npt=    [KVM,AMD] Control KVM's use of Nested Page Tables,
2684                         a.k.a. Two-Dimensiona    2636                         a.k.a. Two-Dimensional Page Tables. Default is 1
2685                         (enabled). Disable by    2637                         (enabled). Disable by KVM if hardware lacks support
2686                         for NPT.                 2638                         for NPT.
2687                                                  2639 
2688         kvm-arm.mode=                            2640         kvm-arm.mode=
2689                         [KVM,ARM,EARLY] Selec !! 2641                         [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690                         operation.            << 
2691                                                  2642 
2692                         none: Forcefully disa    2643                         none: Forcefully disable KVM.
2693                                                  2644 
2694                         nvhe: Standard nVHE-b    2645                         nvhe: Standard nVHE-based mode, without support for
2695                               protected guest    2646                               protected guests.
2696                                                  2647 
2697                         protected: nVHE-based    2648                         protected: nVHE-based mode with support for guests whose
2698                                    state is k    2649                                    state is kept private from the host.
2699                                                  2650 
2700                         nested: VHE-based mod    2651                         nested: VHE-based mode with support for nested
2701                                 virtualizatio    2652                                 virtualization. Requires at least ARMv8.3
2702                                 hardware.        2653                                 hardware.
2703                                                  2654 
2704                         Defaults to VHE/nVHE     2655                         Defaults to VHE/nVHE based on hardware support. Setting
2705                         mode to "protected" w    2656                         mode to "protected" will disable kexec and hibernation
2706                         for the host. "nested    2657                         for the host. "nested" is experimental and should be
2707                         used with extreme cau    2658                         used with extreme caution.
2708                                                  2659 
2709         kvm-arm.vgic_v3_group0_trap=             2660         kvm-arm.vgic_v3_group0_trap=
2710                         [KVM,ARM,EARLY] Trap  !! 2661                         [KVM,ARM] Trap guest accesses to GICv3 group-0
2711                         system registers         2662                         system registers
2712                                                  2663 
2713         kvm-arm.vgic_v3_group1_trap=             2664         kvm-arm.vgic_v3_group1_trap=
2714                         [KVM,ARM,EARLY] Trap  !! 2665                         [KVM,ARM] Trap guest accesses to GICv3 group-1
2715                         system registers         2666                         system registers
2716                                                  2667 
2717         kvm-arm.vgic_v3_common_trap=             2668         kvm-arm.vgic_v3_common_trap=
2718                         [KVM,ARM,EARLY] Trap  !! 2669                         [KVM,ARM] Trap guest accesses to GICv3 common
2719                         system registers         2670                         system registers
2720                                                  2671 
2721         kvm-arm.vgic_v4_enable=                  2672         kvm-arm.vgic_v4_enable=
2722                         [KVM,ARM,EARLY] Allow !! 2673                         [KVM,ARM] Allow use of GICv4 for direct injection of
2723                         injection of LPIs.    !! 2674                         LPIs.
2724                                               << 
2725         kvm-arm.wfe_trap_policy=              << 
2726                         [KVM,ARM] Control whe << 
2727                         KVM VMs. Traps are al << 
2728                         CPU architecture.     << 
2729                                               << 
2730                         trap: set WFE instruc << 
2731                                               << 
2732                         notrap: clear WFE ins << 
2733                                               << 
2734         kvm-arm.wfi_trap_policy=              << 
2735                         [KVM,ARM] Control whe << 
2736                         KVM VMs. Traps are al << 
2737                         CPU architecture.     << 
2738                                               << 
2739                         trap: set WFI instruc << 
2740                                               << 
2741                         notrap: clear WFI ins << 
2742                                                  2675 
2743         kvm_cma_resv_ratio=n [PPC,EARLY]      !! 2676         kvm_cma_resv_ratio=n [PPC]
2744                         Reserves given percen    2677                         Reserves given percentage from system memory area for
2745                         contiguous memory all    2678                         contiguous memory allocation for KVM hash pagetable
2746                         allocation.              2679                         allocation.
2747                         By default it reserve    2680                         By default it reserves 5% of total system memory.
2748                         Format: <integer>        2681                         Format: <integer>
2749                         Default: 5               2682                         Default: 5
2750                                                  2683 
2751         kvm-intel.ept=  [KVM,Intel] Control K    2684         kvm-intel.ept=  [KVM,Intel] Control KVM's use of Extended Page Tables,
2752                         a.k.a. Two-Dimensiona    2685                         a.k.a. Two-Dimensional Page Tables.  Default is 1
2753                         (enabled). Disable by    2686                         (enabled). Disable by KVM if hardware lacks support
2754                         for EPT.                 2687                         for EPT.
2755                                                  2688 
2756         kvm-intel.emulate_invalid_guest_state    2689         kvm-intel.emulate_invalid_guest_state=
2757                         [KVM,Intel] Control w    2690                         [KVM,Intel] Control whether to emulate invalid guest
2758                         state. Ignored if kvm    2691                         state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2759                         as guest state is nev    2692                         as guest state is never invalid for unrestricted
2760                         guests. This param do    2693                         guests. This param doesn't apply to nested guests (L2),
2761                         as KVM never emulates    2694                         as KVM never emulates invalid L2 guest state.
2762                         Default is 1 (enabled    2695                         Default is 1 (enabled).
2763                                                  2696 
2764         kvm-intel.flexpriority=                  2697         kvm-intel.flexpriority=
2765                         [KVM,Intel] Control K    2698                         [KVM,Intel] Control KVM's use of FlexPriority feature
2766                         (TPR shadow). Default    2699                         (TPR shadow). Default is 1 (enabled). Disable by KVM if
2767                         hardware lacks suppor    2700                         hardware lacks support for it.
2768                                                  2701 
2769         kvm-intel.nested=                        2702         kvm-intel.nested=
2770                         [KVM,Intel] Control n    2703                         [KVM,Intel] Control nested virtualization feature in
2771                         KVM/VMX. Default is 1    2704                         KVM/VMX. Default is 1 (enabled).
2772                                                  2705 
2773         kvm-intel.unrestricted_guest=            2706         kvm-intel.unrestricted_guest=
2774                         [KVM,Intel] Control K    2707                         [KVM,Intel] Control KVM's use of unrestricted guest
2775                         feature (virtualized     2708                         feature (virtualized real and unpaged mode). Default
2776                         is 1 (enabled). Disab    2709                         is 1 (enabled). Disable by KVM if EPT is disabled or
2777                         hardware lacks suppor    2710                         hardware lacks support for it.
2778                                                  2711 
2779         kvm-intel.vmentry_l1d_flush=[KVM,Inte    2712         kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780                         CVE-2018-3620.           2713                         CVE-2018-3620.
2781                                                  2714 
2782                         Valid arguments: neve    2715                         Valid arguments: never, cond, always
2783                                                  2716 
2784                         always: L1D cache flu    2717                         always: L1D cache flush on every VMENTER.
2785                         cond:   Flush L1D on     2718                         cond:   Flush L1D on VMENTER only when the code between
2786                                 VMEXIT and VM    2719                                 VMEXIT and VMENTER can leak host memory.
2787                         never:  Disables the     2720                         never:  Disables the mitigation
2788                                                  2721 
2789                         Default is cond (do L    2722                         Default is cond (do L1 cache flush in specific instances)
2790                                                  2723 
2791         kvm-intel.vpid= [KVM,Intel] Control K    2724         kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2792                         Identification featur    2725                         Identification feature (tagged TLBs). Default is 1
2793                         (enabled). Disable by    2726                         (enabled). Disable by KVM if hardware lacks support
2794                         for it.                  2727                         for it.
2795                                                  2728 
2796         l1d_flush=      [X86,INTEL,EARLY]     !! 2729         l1d_flush=      [X86,INTEL]
2797                         Control mitigation fo    2730                         Control mitigation for L1D based snooping vulnerability.
2798                                                  2731 
2799                         Certain CPUs are vuln    2732                         Certain CPUs are vulnerable to an exploit against CPU
2800                         internal buffers whic    2733                         internal buffers which can forward information to a
2801                         disclosure gadget und    2734                         disclosure gadget under certain conditions.
2802                                                  2735 
2803                         In vulnerable process    2736                         In vulnerable processors, the speculatively
2804                         forwarded data can be    2737                         forwarded data can be used in a cache side channel
2805                         attack, to access dat    2738                         attack, to access data to which the attacker does
2806                         not have direct acces    2739                         not have direct access.
2807                                                  2740 
2808                         This parameter contro    2741                         This parameter controls the mitigation. The
2809                         options are:             2742                         options are:
2810                                                  2743 
2811                         on         - enable t    2744                         on         - enable the interface for the mitigation
2812                                                  2745 
2813         l1tf=           [X86,EARLY] Control m !! 2746         l1tf=           [X86] Control mitigation of the L1TF vulnerability on
2814                               affected CPUs      2747                               affected CPUs
2815                                                  2748 
2816                         The kernel PTE invers    2749                         The kernel PTE inversion protection is unconditionally
2817                         enabled and cannot be    2750                         enabled and cannot be disabled.
2818                                                  2751 
2819                         full                     2752                         full
2820                                 Provides all     2753                                 Provides all available mitigations for the
2821                                 L1TF vulnerab    2754                                 L1TF vulnerability. Disables SMT and
2822                                 enables all m    2755                                 enables all mitigations in the
2823                                 hypervisors,     2756                                 hypervisors, i.e. unconditional L1D flush.
2824                                                  2757 
2825                                 SMT control a    2758                                 SMT control and L1D flush control via the
2826                                 sysfs interfa    2759                                 sysfs interface is still possible after
2827                                 boot.  Hyperv    2760                                 boot.  Hypervisors will issue a warning
2828                                 when the firs    2761                                 when the first VM is started in a
2829                                 potentially i    2762                                 potentially insecure configuration,
2830                                 i.e. SMT enab    2763                                 i.e. SMT enabled or L1D flush disabled.
2831                                                  2764 
2832                         full,force               2765                         full,force
2833                                 Same as 'full    2766                                 Same as 'full', but disables SMT and L1D
2834                                 flush runtime    2767                                 flush runtime control. Implies the
2835                                 'nosmt=force'    2768                                 'nosmt=force' command line option.
2836                                 (i.e. sysfs c    2769                                 (i.e. sysfs control of SMT is disabled.)
2837                                                  2770 
2838                         flush                    2771                         flush
2839                                 Leaves SMT en    2772                                 Leaves SMT enabled and enables the default
2840                                 hypervisor mi    2773                                 hypervisor mitigation, i.e. conditional
2841                                 L1D flush.       2774                                 L1D flush.
2842                                                  2775 
2843                                 SMT control a    2776                                 SMT control and L1D flush control via the
2844                                 sysfs interfa    2777                                 sysfs interface is still possible after
2845                                 boot.  Hyperv    2778                                 boot.  Hypervisors will issue a warning
2846                                 when the firs    2779                                 when the first VM is started in a
2847                                 potentially i    2780                                 potentially insecure configuration,
2848                                 i.e. SMT enab    2781                                 i.e. SMT enabled or L1D flush disabled.
2849                                                  2782 
2850                         flush,nosmt              2783                         flush,nosmt
2851                                                  2784 
2852                                 Disables SMT     2785                                 Disables SMT and enables the default
2853                                 hypervisor mi    2786                                 hypervisor mitigation.
2854                                                  2787 
2855                                 SMT control a    2788                                 SMT control and L1D flush control via the
2856                                 sysfs interfa    2789                                 sysfs interface is still possible after
2857                                 boot.  Hyperv    2790                                 boot.  Hypervisors will issue a warning
2858                                 when the firs    2791                                 when the first VM is started in a
2859                                 potentially i    2792                                 potentially insecure configuration,
2860                                 i.e. SMT enab    2793                                 i.e. SMT enabled or L1D flush disabled.
2861                                                  2794 
2862                         flush,nowarn             2795                         flush,nowarn
2863                                 Same as 'flus    2796                                 Same as 'flush', but hypervisors will not
2864                                 warn when a V    2797                                 warn when a VM is started in a potentially
2865                                 insecure conf    2798                                 insecure configuration.
2866                                                  2799 
2867                         off                      2800                         off
2868                                 Disables hype    2801                                 Disables hypervisor mitigations and doesn't
2869                                 emit any warn    2802                                 emit any warnings.
2870                                 It also drops    2803                                 It also drops the swap size and available
2871                                 RAM limit res    2804                                 RAM limit restriction on both hypervisor and
2872                                 bare metal.      2805                                 bare metal.
2873                                                  2806 
2874                         Default is 'flush'.      2807                         Default is 'flush'.
2875                                                  2808 
2876                         For details see: Docu    2809                         For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877                                                  2810 
2878         l2cr=           [PPC]                    2811         l2cr=           [PPC]
2879                                                  2812 
2880         l3cr=           [PPC]                    2813         l3cr=           [PPC]
2881                                                  2814 
2882         lapic           [X86-32,APIC,EARLY] E !! 2815         lapic           [X86-32,APIC] Enable the local APIC even if BIOS
2883                         disabled it.             2816                         disabled it.
2884                                                  2817 
2885         lapic=          [X86,APIC] Do not use    2818         lapic=          [X86,APIC] Do not use TSC deadline
2886                         value for LAPIC timer    2819                         value for LAPIC timer one-shot implementation. Default
2887                         back to the programma    2820                         back to the programmable timer unit in the LAPIC.
2888                         Format: notscdeadline    2821                         Format: notscdeadline
2889                                                  2822 
2890         lapic_timer_c2_ok       [X86,APIC,EAR !! 2823         lapic_timer_c2_ok       [X86,APIC] trust the local apic timer
2891                         in C2 power state.       2824                         in C2 power state.
2892                                                  2825 
2893         libata.dma=     [LIBATA] DMA control     2826         libata.dma=     [LIBATA] DMA control
2894                         libata.dma=0      Dis    2827                         libata.dma=0      Disable all PATA and SATA DMA
2895                         libata.dma=1      PAT    2828                         libata.dma=1      PATA and SATA Disk DMA only
2896                         libata.dma=2      ATA    2829                         libata.dma=2      ATAPI (CDROM) DMA only
2897                         libata.dma=4      Com    2830                         libata.dma=4      Compact Flash DMA only
2898                         Combinations also wor    2831                         Combinations also work, so libata.dma=3 enables DMA
2899                         for disks and CDROMs,    2832                         for disks and CDROMs, but not CFs.
2900                                                  2833 
2901         libata.ignore_hpa=      [LIBATA] Igno    2834         libata.ignore_hpa=      [LIBATA] Ignore HPA limit
2902                         libata.ignore_hpa=0      2835                         libata.ignore_hpa=0       keep BIOS limits (default)
2903                         libata.ignore_hpa=1      2836                         libata.ignore_hpa=1       ignore limits, using full disk
2904                                                  2837 
2905         libata.noacpi   [LIBATA] Disables use    2838         libata.noacpi   [LIBATA] Disables use of ACPI in libata suspend/resume
2906                         when set.                2839                         when set.
2907                         Format: <int>            2840                         Format: <int>
2908                                                  2841 
2909         libata.force=   [LIBATA] Force config    2842         libata.force=   [LIBATA] Force configurations.  The format is a comma-
2910                         separated list of "[I    2843                         separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2911                         PORT and DEVICE are d    2844                         PORT and DEVICE are decimal numbers matching port, link
2912                         or device.  Basically    2845                         or device.  Basically, it matches the ATA ID string
2913                         printed on console by    2846                         printed on console by libata.  If the whole ID part is
2914                         omitted, the last POR    2847                         omitted, the last PORT and DEVICE values are used.  If
2915                         ID hasn't been specif    2848                         ID hasn't been specified yet, the configuration applies
2916                         to all ports, links a    2849                         to all ports, links and devices.
2917                                                  2850 
2918                         If only DEVICE is omi    2851                         If only DEVICE is omitted, the parameter applies to
2919                         the port and all link    2852                         the port and all links and devices behind it.  DEVICE
2920                         number of 0 either se    2853                         number of 0 either selects the first device or the
2921                         first fan-out link be    2854                         first fan-out link behind PMP device.  It does not
2922                         select the host link.    2855                         select the host link.  DEVICE number of 15 selects the
2923                         host link and device     2856                         host link and device attached to it.
2924                                                  2857 
2925                         The VAL specifies the    2858                         The VAL specifies the configuration to force.  As long
2926                         as there is no ambigu    2859                         as there is no ambiguity, shortcut notation is allowed.
2927                         For example, both 1.5    2860                         For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928                         The following configu    2861                         The following configurations can be forced.
2929                                                  2862 
2930                         * Cable type: 40c, 80    2863                         * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931                           Any ID with matchin    2864                           Any ID with matching PORT is used.
2932                                                  2865 
2933                         * SATA link speed lim    2866                         * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934                                                  2867 
2935                         * Transfer mode: pio[    2868                         * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936                           udma[/][16,25,33,44    2869                           udma[/][16,25,33,44,66,100,133] notation is also
2937                           allowed.               2870                           allowed.
2938                                                  2871 
2939                         * nohrst, nosrst, nor    2872                         * nohrst, nosrst, norst: suppress hard, soft and both
2940                           resets.                2873                           resets.
2941                                                  2874 
2942                         * rstonce: only attem    2875                         * rstonce: only attempt one reset during hot-unplug
2943                           link recovery.         2876                           link recovery.
2944                                                  2877 
2945                         * [no]dbdelay: Enable    2878                         * [no]dbdelay: Enable or disable the extra 200ms delay
2946                           before debouncing a    2879                           before debouncing a link PHY and device presence
2947                           detection.             2880                           detection.
2948                                                  2881 
2949                         * [no]ncq: Turn on or    2882                         * [no]ncq: Turn on or off NCQ.
2950                                                  2883 
2951                         * [no]ncqtrim: Enable    2884                         * [no]ncqtrim: Enable or disable queued DSM TRIM.
2952                                                  2885 
2953                         * [no]ncqati: Enable     2886                         * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2954                                                  2887 
2955                         * [no]trim: Enable or    2888                         * [no]trim: Enable or disable (unqueued) TRIM.
2956                                                  2889 
2957                         * trim_zero: Indicate    2890                         * trim_zero: Indicate that TRIM command zeroes data.
2958                                                  2891 
2959                         * max_trim_128m: Set     2892                         * max_trim_128m: Set 128M maximum trim size limit.
2960                                                  2893 
2961                         * [no]dma: Turn on or    2894                         * [no]dma: Turn on or off DMA transfers.
2962                                                  2895 
2963                         * atapi_dmadir: Enabl    2896                         * atapi_dmadir: Enable ATAPI DMADIR bridge support.
2964                                                  2897 
2965                         * atapi_mod16_dma: En    2898                         * atapi_mod16_dma: Enable the use of ATAPI DMA for
2966                           commands that are n    2899                           commands that are not a multiple of 16 bytes.
2967                                                  2900 
2968                         * [no]dmalog: Enable     2901                         * [no]dmalog: Enable or disable the use of the
2969                           READ LOG DMA EXT co    2902                           READ LOG DMA EXT command to access logs.
2970                                                  2903 
2971                         * [no]iddevlog: Enabl    2904                         * [no]iddevlog: Enable or disable access to the
2972                           identify device dat    2905                           identify device data log.
2973                                                  2906 
2974                         * [no]logdir: Enable     2907                         * [no]logdir: Enable or disable access to the general
2975                           purpose log directo    2908                           purpose log directory.
2976                                                  2909 
2977                         * max_sec_128: Set tr    2910                         * max_sec_128: Set transfer size limit to 128 sectors.
2978                                                  2911 
2979                         * max_sec_1024: Set o    2912                         * max_sec_1024: Set or clear transfer size limit to
2980                           1024 sectors.          2913                           1024 sectors.
2981                                                  2914 
2982                         * max_sec_lba48: Set     2915                         * max_sec_lba48: Set or clear transfer size limit to
2983                           65535 sectors.         2916                           65535 sectors.
2984                                                  2917 
2985                         * [no]lpm: Enable or     2918                         * [no]lpm: Enable or disable link power management.
2986                                                  2919 
2987                         * [no]setxfer: Indica    2920                         * [no]setxfer: Indicate if transfer speed mode setting
2988                           should be skipped.     2921                           should be skipped.
2989                                                  2922 
2990                         * [no]fua: Disable or    2923                         * [no]fua: Disable or enable FUA (Force Unit Access)
2991                           support for devices    2924                           support for devices supporting this feature.
2992                                                  2925 
2993                         * dump_id: Dump IDENT    2926                         * dump_id: Dump IDENTIFY data.
2994                                                  2927 
2995                         * disable: Disable th    2928                         * disable: Disable this device.
2996                                                  2929 
2997                         If there are multiple    2930                         If there are multiple matching configurations changing
2998                         the same attribute, t    2931                         the same attribute, the last one is used.
2999                                                  2932 
3000         load_ramdisk=   [RAM] [Deprecated]       2933         load_ramdisk=   [RAM] [Deprecated]
3001                                                  2934 
3002         lockd.nlm_grace_period=P  [NFS] Assig    2935         lockd.nlm_grace_period=P  [NFS] Assign grace period.
3003                         Format: <integer>        2936                         Format: <integer>
3004                                                  2937 
3005         lockd.nlm_tcpport=N     [NFS] Assign     2938         lockd.nlm_tcpport=N     [NFS] Assign TCP port.
3006                         Format: <integer>        2939                         Format: <integer>
3007                                                  2940 
3008         lockd.nlm_timeout=T     [NFS] Assign     2941         lockd.nlm_timeout=T     [NFS] Assign timeout value.
3009                         Format: <integer>        2942                         Format: <integer>
3010                                                  2943 
3011         lockd.nlm_udpport=M     [NFS] Assign     2944         lockd.nlm_udpport=M     [NFS] Assign UDP port.
3012                         Format: <integer>        2945                         Format: <integer>
3013                                                  2946 
3014         lockdown=       [SECURITY,EARLY]      !! 2947         lockdown=       [SECURITY]
3015                         { integrity | confide    2948                         { integrity | confidentiality }
3016                         Enable the kernel loc    2949                         Enable the kernel lockdown feature. If set to
3017                         integrity, kernel fea    2950                         integrity, kernel features that allow userland to
3018                         modify the running ke    2951                         modify the running kernel are disabled. If set to
3019                         confidentiality, kern    2952                         confidentiality, kernel features that allow userland
3020                         to extract confidenti    2953                         to extract confidential information from the kernel
3021                         are also disabled.       2954                         are also disabled.
3022                                                  2955 
3023         locktorture.acq_writer_lim= [KNL]        2956         locktorture.acq_writer_lim= [KNL]
3024                         Set the time limit in    2957                         Set the time limit in jiffies for a lock
3025                         acquisition.  Acquisi    2958                         acquisition.  Acquisitions exceeding this limit
3026                         will result in a spla    2959                         will result in a splat once they do complete.
3027                                                  2960 
3028         locktorture.bind_readers= [KNL]          2961         locktorture.bind_readers= [KNL]
3029                         Specify the list of C    2962                         Specify the list of CPUs to which the readers are
3030                         to be bound.             2963                         to be bound.
3031                                                  2964 
3032         locktorture.bind_writers= [KNL]          2965         locktorture.bind_writers= [KNL]
3033                         Specify the list of C    2966                         Specify the list of CPUs to which the writers are
3034                         to be bound.             2967                         to be bound.
3035                                                  2968 
3036         locktorture.call_rcu_chains= [KNL]       2969         locktorture.call_rcu_chains= [KNL]
3037                         Specify the number of    2970                         Specify the number of self-propagating call_rcu()
3038                         chains to set up.  Th    2971                         chains to set up.  These are used to ensure that
3039                         there is a high proba    2972                         there is a high probability of an RCU grace period
3040                         in progress at any gi    2973                         in progress at any given time.  Defaults to 0,
3041                         which disables these     2974                         which disables these call_rcu() chains.
3042                                                  2975 
3043         locktorture.long_hold= [KNL]             2976         locktorture.long_hold= [KNL]
3044                         Specify the duration     2977                         Specify the duration in milliseconds for the
3045                         occasional long-durat    2978                         occasional long-duration lock hold time.  Defaults
3046                         to 100 milliseconds.     2979                         to 100 milliseconds.  Select 0 to disable.
3047                                                  2980 
3048         locktorture.nested_locks= [KNL]          2981         locktorture.nested_locks= [KNL]
3049                         Specify the maximum l    2982                         Specify the maximum lock nesting depth that
3050                         locktorture is to exe    2983                         locktorture is to exercise, up to a limit of 8
3051                         (MAX_NESTED_LOCKS).      2984                         (MAX_NESTED_LOCKS).  Specify zero to disable.
3052                         Note that this parame    2985                         Note that this parameter is ineffective on types
3053                         of locks that do not     2986                         of locks that do not support nested acquisition.
3054                                                  2987 
3055         locktorture.nreaders_stress= [KNL]       2988         locktorture.nreaders_stress= [KNL]
3056                         Set the number of loc    2989                         Set the number of locking read-acquisition kthreads.
3057                         Defaults to being aut    2990                         Defaults to being automatically set based on the
3058                         number of online CPUs    2991                         number of online CPUs.
3059                                                  2992 
3060         locktorture.nwriters_stress= [KNL]       2993         locktorture.nwriters_stress= [KNL]
3061                         Set the number of loc    2994                         Set the number of locking write-acquisition kthreads.
3062                                                  2995 
3063         locktorture.onoff_holdoff= [KNL]         2996         locktorture.onoff_holdoff= [KNL]
3064                         Set time (s) after bo    2997                         Set time (s) after boot for CPU-hotplug testing.
3065                                                  2998 
3066         locktorture.onoff_interval= [KNL]        2999         locktorture.onoff_interval= [KNL]
3067                         Set time (s) between     3000                         Set time (s) between CPU-hotplug operations, or
3068                         zero to disable CPU-h    3001                         zero to disable CPU-hotplug testing.
3069                                                  3002 
3070         locktorture.rt_boost= [KNL]              3003         locktorture.rt_boost= [KNL]
3071                         Do periodic testing o    3004                         Do periodic testing of real-time lock priority
3072                         boosting.  Select 0 t    3005                         boosting.  Select 0 to disable, 1 to boost
3073                         only rt_mutex, and 2     3006                         only rt_mutex, and 2 to boost unconditionally.
3074                         Defaults to 2, which     3007                         Defaults to 2, which might seem to be an
3075                         odd choice, but which    3008                         odd choice, but which should be harmless for
3076                         non-real-time spinloc    3009                         non-real-time spinlocks, due to their disabling
3077                         of preemption.  Note     3010                         of preemption.  Note that non-realtime mutexes
3078                         disable boosting.        3011                         disable boosting.
3079                                                  3012 
3080         locktorture.rt_boost_factor= [KNL]       3013         locktorture.rt_boost_factor= [KNL]
3081                         Number that determine    3014                         Number that determines how often and for how
3082                         long priority boostin    3015                         long priority boosting is exercised.  This is
3083                         scaled down by the nu    3016                         scaled down by the number of writers, so that the
3084                         number of boosts per     3017                         number of boosts per unit time remains roughly
3085                         constant as the numbe    3018                         constant as the number of writers increases.
3086                         On the other hand, th    3019                         On the other hand, the duration of each boost
3087                         increases with the nu    3020                         increases with the number of writers.
3088                                                  3021 
3089         locktorture.shuffle_interval= [KNL]      3022         locktorture.shuffle_interval= [KNL]
3090                         Set task-shuffle inte    3023                         Set task-shuffle interval (jiffies).  Shuffling
3091                         tasks allows some CPU    3024                         tasks allows some CPUs to go into dyntick-idle
3092                         mode during the lockt    3025                         mode during the locktorture test.
3093                                                  3026 
3094         locktorture.shutdown_secs= [KNL]         3027         locktorture.shutdown_secs= [KNL]
3095                         Set time (s) after bo    3028                         Set time (s) after boot system shutdown.  This
3096                         is useful for hands-o    3029                         is useful for hands-off automated testing.
3097                                                  3030 
3098         locktorture.stat_interval= [KNL]         3031         locktorture.stat_interval= [KNL]
3099                         Time (s) between stat    3032                         Time (s) between statistics printk()s.
3100                                                  3033 
3101         locktorture.stutter= [KNL]               3034         locktorture.stutter= [KNL]
3102                         Time (s) to stutter t    3035                         Time (s) to stutter testing, for example,
3103                         specifying five secon    3036                         specifying five seconds causes the test to run for
3104                         five seconds, wait fo    3037                         five seconds, wait for five seconds, and so on.
3105                         This tests the lockin    3038                         This tests the locking primitive's ability to
3106                         transition abruptly t    3039                         transition abruptly to and from idle.
3107                                                  3040 
3108         locktorture.torture_type= [KNL]          3041         locktorture.torture_type= [KNL]
3109                         Specify the locking i    3042                         Specify the locking implementation to test.
3110                                                  3043 
3111         locktorture.verbose= [KNL]               3044         locktorture.verbose= [KNL]
3112                         Enable additional pri    3045                         Enable additional printk() statements.
3113                                                  3046 
3114         locktorture.writer_fifo= [KNL]           3047         locktorture.writer_fifo= [KNL]
3115                         Run the write-side lo    3048                         Run the write-side locktorture kthreads at
3116                         sched_set_fifo() real    3049                         sched_set_fifo() real-time priority.
3117                                                  3050 
3118         logibm.irq=     [HW,MOUSE] Logitech B    3051         logibm.irq=     [HW,MOUSE] Logitech Bus Mouse Driver
3119                         Format: <irq>            3052                         Format: <irq>
3120                                                  3053 
3121         loglevel=       [KNL,EARLY]           !! 3054         loglevel=       All Kernel Messages with a loglevel smaller than the
3122                         All Kernel Messages w << 
3123                         console loglevel will    3055                         console loglevel will be printed to the console. It can
3124                         also be changed with     3056                         also be changed with klogd or other programs. The
3125                         loglevels are defined    3057                         loglevels are defined as follows:
3126                                                  3058 
3127                         0 (KERN_EMERG)           3059                         0 (KERN_EMERG)          system is unusable
3128                         1 (KERN_ALERT)           3060                         1 (KERN_ALERT)          action must be taken immediately
3129                         2 (KERN_CRIT)            3061                         2 (KERN_CRIT)           critical conditions
3130                         3 (KERN_ERR)             3062                         3 (KERN_ERR)            error conditions
3131                         4 (KERN_WARNING)         3063                         4 (KERN_WARNING)        warning conditions
3132                         5 (KERN_NOTICE)          3064                         5 (KERN_NOTICE)         normal but significant condition
3133                         6 (KERN_INFO)            3065                         6 (KERN_INFO)           informational
3134                         7 (KERN_DEBUG)           3066                         7 (KERN_DEBUG)          debug-level messages
3135                                                  3067 
3136         log_buf_len=n[KMG] [KNL,EARLY]        !! 3068         log_buf_len=n[KMG]      Sets the size of the printk ring buffer,
3137                         Sets the size of the  !! 3069                         in bytes.  n must be a power of two and greater
3138                         n must be a power of  !! 3070                         than the minimal size. The minimal size is defined
3139                         minimal size. The min !! 3071                         by LOG_BUF_SHIFT kernel config parameter. There is
3140                         LOG_BUF_SHIFT kernel  !! 3072                         also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141                         is also CONFIG_LOG_CP !! 3073                         that allows to increase the default size depending on
3142                         parameter that allows !! 3074                         the number of CPUs. See init/Kconfig for more details.
3143                         depending on the numb << 
3144                         for more details.     << 
3145                                                  3075 
3146         logo.nologo     [FB] Disables display    3076         logo.nologo     [FB] Disables display of the built-in Linux logo.
3147                         This may be used to p    3077                         This may be used to provide more screen space for
3148                         kernel log messages a    3078                         kernel log messages and is useful when debugging
3149                         kernel boot problems.    3079                         kernel boot problems.
3150                                                  3080 
3151         lp=0            [LP]    Specify paral    3081         lp=0            [LP]    Specify parallel ports to use, e.g,
3152         lp=port[,port...]       lp=none,parpo    3082         lp=port[,port...]       lp=none,parport0 (lp0 not configured, lp1 uses
3153         lp=reset                first paralle    3083         lp=reset                first parallel port). 'lp=0' disables the
3154         lp=auto                 printer drive    3084         lp=auto                 printer driver. 'lp=reset' (which can be
3155                                 specified in     3085                                 specified in addition to the ports) causes
3156                                 attached prin    3086                                 attached printers to be reset. Using
3157                                 lp=port1,port    3087                                 lp=port1,port2,... specifies the parallel ports
3158                                 to associate     3088                                 to associate lp devices with, starting with
3159                                 lp0. A port s    3089                                 lp0. A port specification may be 'none' to skip
3160                                 that lp devic    3090                                 that lp device, or a parport name such as
3161                                 'parport0'. S    3091                                 'parport0'. Specifying 'lp=auto' instead of a
3162                                 port specific    3092                                 port specification list means that device IDs
3163                                 from each por    3093                                 from each port should be examined, to see if
3164                                 an IEEE 1284-    3094                                 an IEEE 1284-compliant printer is attached; if
3165                                 so, the drive    3095                                 so, the driver will manage that printer.
3166                                 See also head    3096                                 See also header of drivers/char/lp.c.
3167                                                  3097 
3168         lpj=n           [KNL]                    3098         lpj=n           [KNL]
3169                         Sets loops_per_jiffy     3099                         Sets loops_per_jiffy to given constant, thus avoiding
3170                         time-consuming boot-t    3100                         time-consuming boot-time autodetection (up to 250 ms per
3171                         CPU). 0 enables autod    3101                         CPU). 0 enables autodetection (default). To determine
3172                         the correct value for    3102                         the correct value for your kernel, boot with normal
3173                         autodetection and see    3103                         autodetection and see what value is printed. Note that
3174                         on SMP systems the pr    3104                         on SMP systems the preset will be applied to all CPUs,
3175                         which is likely to ca    3105                         which is likely to cause problems if your CPUs need
3176                         significantly diverge    3106                         significantly divergent settings. An incorrect value
3177                         will cause delays in     3107                         will cause delays in the kernel to be wrong, leading to
3178                         unpredictable I/O err    3108                         unpredictable I/O errors and other breakage. Although
3179                         unlikely, in the extr    3109                         unlikely, in the extreme case this might damage your
3180                         hardware.                3110                         hardware.
3181                                                  3111 
                                                   >> 3112         ltpc=           [NET]
                                                   >> 3113                         Format: <io>,<irq>,<dma>
                                                   >> 3114 
3182         lsm.debug       [SECURITY] Enable LSM    3115         lsm.debug       [SECURITY] Enable LSM initialization debugging output.
3183                                                  3116 
3184         lsm=lsm1,...,lsmN                        3117         lsm=lsm1,...,lsmN
3185                         [SECURITY] Choose ord    3118                         [SECURITY] Choose order of LSM initialization. This
3186                         overrides CONFIG_LSM,    3119                         overrides CONFIG_LSM, and the "security=" parameter.
3187                                                  3120 
                                                   >> 3121         machvec=        [IA-64] Force the use of a particular machine-vector
                                                   >> 3122                         (machvec) in a generic kernel.
                                                   >> 3123                         Example: machvec=hpzx1
                                                   >> 3124 
3188         machtype=       [Loongson] Share the     3125         machtype=       [Loongson] Share the same kernel image file between
3189                         different yeeloong la    3126                         different yeeloong laptops.
3190                         Example: machtype=lem    3127                         Example: machtype=lemote-yeeloong-2f-7inch
3191                                                  3128 
3192         maxcpus=        [SMP,EARLY] Maximum n !! 3129         max_addr=nn[KMG]        [KNL,BOOT,IA-64] All physical memory greater
                                                   >> 3130                         than or equal to this physical address is ignored.
                                                   >> 3131 
                                                   >> 3132         maxcpus=        [SMP] Maximum number of processors that an SMP kernel
3193                         will bring up during     3133                         will bring up during bootup.  maxcpus=n : n >= 0 limits
3194                         the kernel to bring u    3134                         the kernel to bring up 'n' processors. Surely after
3195                         bootup you can bring     3135                         bootup you can bring up the other plugged cpu by executing
3196                         "echo 1 > /sys/device    3136                         "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197                         only takes effect dur    3137                         only takes effect during system bootup.
3198                         While n=0 is a specia    3138                         While n=0 is a special case, it is equivalent to "nosmp",
3199                         which also disables t    3139                         which also disables the IO APIC.
3200                                                  3140 
3201         max_loop=       [LOOP] The number of     3141         max_loop=       [LOOP] The number of loop block devices that get
3202         (loop.max_loop) unconditionally pre-c    3142         (loop.max_loop) unconditionally pre-created at init time. The default
3203                         number is configured     3143                         number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204                         of statically allocat    3144                         of statically allocating a predefined number, loop
3205                         devices can be reques    3145                         devices can be requested on-demand with the
3206                         /dev/loop-control int    3146                         /dev/loop-control interface.
3207                                                  3147 
3208         mce             [X86-32] Machine Chec    3148         mce             [X86-32] Machine Check Exception
3209                                                  3149 
3210         mce=option      [X86-64] See Document    3150         mce=option      [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
3211                                                  3151 
3212         md=             [HW] RAID subsystems     3152         md=             [HW] RAID subsystems devices and level
3213                         See Documentation/adm    3153                         See Documentation/admin-guide/md.rst.
3214                                                  3154 
3215         mdacon=         [MDA]                    3155         mdacon=         [MDA]
3216                         Format: <first>,<last    3156                         Format: <first>,<last>
3217                         Specifies range of co    3157                         Specifies range of consoles to be captured by the MDA.
3218                                                  3158 
3219         mds=            [X86,INTEL,EARLY]     !! 3159         mds=            [X86,INTEL]
3220                         Control mitigation fo    3160                         Control mitigation for the Micro-architectural Data
3221                         Sampling (MDS) vulner    3161                         Sampling (MDS) vulnerability.
3222                                                  3162 
3223                         Certain CPUs are vuln    3163                         Certain CPUs are vulnerable to an exploit against CPU
3224                         internal buffers whic    3164                         internal buffers which can forward information to a
3225                         disclosure gadget und    3165                         disclosure gadget under certain conditions.
3226                                                  3166 
3227                         In vulnerable process    3167                         In vulnerable processors, the speculatively
3228                         forwarded data can be    3168                         forwarded data can be used in a cache side channel
3229                         attack, to access dat    3169                         attack, to access data to which the attacker does
3230                         not have direct acces    3170                         not have direct access.
3231                                                  3171 
3232                         This parameter contro    3172                         This parameter controls the MDS mitigation. The
3233                         options are:             3173                         options are:
3234                                                  3174 
3235                         full       - Enable M    3175                         full       - Enable MDS mitigation on vulnerable CPUs
3236                         full,nosmt - Enable M    3176                         full,nosmt - Enable MDS mitigation and disable
3237                                      SMT on v    3177                                      SMT on vulnerable CPUs
3238                         off        - Uncondit    3178                         off        - Unconditionally disable MDS mitigation
3239                                                  3179 
3240                         On TAA-affected machi    3180                         On TAA-affected machines, mds=off can be prevented by
3241                         an active TAA mitigat    3181                         an active TAA mitigation as both vulnerabilities are
3242                         mitigated with the sa    3182                         mitigated with the same mechanism so in order to disable
3243                         this mitigation, you     3183                         this mitigation, you need to specify tsx_async_abort=off
3244                         too.                     3184                         too.
3245                                                  3185 
3246                         Not specifying this o    3186                         Not specifying this option is equivalent to
3247                         mds=full.                3187                         mds=full.
3248                                                  3188 
3249                         For details see: Docu    3189                         For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250                                                  3190 
3251         mem=nn[KMG]     [HEXAGON,EARLY] Set t !! 3191         mem=nn[KMG]     [HEXAGON] Set the memory size.
3252                         Must be specified, ot    3192                         Must be specified, otherwise memory size will be 0.
3253                                                  3193 
3254         mem=nn[KMG]     [KNL,BOOT,EARLY] Forc !! 3194         mem=nn[KMG]     [KNL,BOOT] Force usage of a specific amount of memory
3255                         of memory Amount of m !! 3195                         Amount of memory to be used in cases as follows:
3256                         as follows:           << 
3257                                                  3196 
3258                         1 for test;              3197                         1 for test;
3259                         2 when the kernel is     3198                         2 when the kernel is not able to see the whole system memory;
3260                         3 memory that lies af    3199                         3 memory that lies after 'mem=' boundary is excluded from
3261                          the hypervisor, then    3200                          the hypervisor, then assigned to KVM guests.
3262                         4 to limit the memory    3201                         4 to limit the memory available for kdump kernel.
3263                                                  3202 
3264                         [ARC,MICROBLAZE] - th    3203                         [ARC,MICROBLAZE] - the limit applies only to low memory,
3265                         high memory is not af    3204                         high memory is not affected.
3266                                                  3205 
3267                         [ARM64] - only limits    3206                         [ARM64] - only limits memory covered by the linear
3268                         mapping. The NOMAP re    3207                         mapping. The NOMAP regions are not affected.
3269                                                  3208 
3270                         [X86] Work as limitin    3209                         [X86] Work as limiting max address. Use together
3271                         with memmap= to avoid    3210                         with memmap= to avoid physical address space collisions.
3272                         Without memmap= PCI d    3211                         Without memmap= PCI devices could be placed at addresses
3273                         belonging to unused R    3212                         belonging to unused RAM.
3274                                                  3213 
3275                         Note that this only t    3214                         Note that this only takes effects during boot time since
3276                         in above case 3, memo    3215                         in above case 3, memory may need be hot added after boot
3277                         if system memory of h    3216                         if system memory of hypervisor is not sufficient.
3278                                                  3217 
3279         mem=nn[KMG]@ss[KMG]                      3218         mem=nn[KMG]@ss[KMG]
3280                         [ARM,MIPS,EARLY] - ov !! 3219                         [ARM,MIPS] - override the memory layout reported by
3281                         reported by firmware. !! 3220                         firmware.
3282                         Define a memory regio    3221                         Define a memory region of size nn[KMG] starting at
3283                         ss[KMG].                 3222                         ss[KMG].
3284                         Multiple different re    3223                         Multiple different regions can be specified with
3285                         multiple mem= paramet    3224                         multiple mem= parameters on the command line.
3286                                                  3225 
3287         mem=nopentium   [BUGS=X86-32] Disable    3226         mem=nopentium   [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288                         memory.                  3227                         memory.
3289                                                  3228 
3290         memblock=debug  [KNL,EARLY] Enable me !! 3229         memblock=debug  [KNL] Enable memblock debug messages.
3291                                                  3230 
3292         memchunk=nn[KMG]                         3231         memchunk=nn[KMG]
3293                         [KNL,SH] Allow user t    3232                         [KNL,SH] Allow user to override the default size for
3294                         per-device physically    3233                         per-device physically contiguous DMA buffers.
3295                                                  3234 
3296         memhp_default_state=online/offline/on    3235         memhp_default_state=online/offline/online_kernel/online_movable
3297                         [KNL] Set the initial    3236                         [KNL] Set the initial state for the memory hotplug
3298                         onlining policy. If n    3237                         onlining policy. If not specified, the default value is
3299                         set according to the     3238                         set according to the
3300                         CONFIG_MEMORY_HOTPLUG    3239                         CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301                         option.                  3240                         option.
3302                         See Documentation/adm    3241                         See Documentation/admin-guide/mm/memory-hotplug.rst.
3303                                                  3242 
3304         memmap=exactmap [KNL,X86,EARLY] Enabl !! 3243         memmap=exactmap [KNL,X86] Enable setting of an exact
3305                         E820 memory map, as s    3244                         E820 memory map, as specified by the user.
3306                         Such memmap=exactmap     3245                         Such memmap=exactmap lines can be constructed based on
3307                         BIOS output or other     3246                         BIOS output or other requirements. See the memmap=nn@ss
3308                         option description.      3247                         option description.
3309                                                  3248 
3310         memmap=nn[KMG]@ss[KMG]                   3249         memmap=nn[KMG]@ss[KMG]
3311                         [KNL, X86,MIPS,XTENSA !! 3250                         [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312                         Region of memory to b    3251                         Region of memory to be used is from ss to ss+nn.
3313                         If @ss[KMG] is omitte    3252                         If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314                         which limits max addr    3253                         which limits max address to nn[KMG].
3315                         Multiple different re    3254                         Multiple different regions can be specified,
3316                         comma delimited.         3255                         comma delimited.
3317                         Example:                 3256                         Example:
3318                                 memmap=100M@2    3257                                 memmap=100M@2G,100M#3G,1G!1024G
3319                                                  3258 
3320         memmap=nn[KMG]#ss[KMG]                   3259         memmap=nn[KMG]#ss[KMG]
3321                         [KNL,ACPI,EARLY] Mark !! 3260                         [KNL,ACPI] Mark specific memory as ACPI data.
3322                         Region of memory to b    3261                         Region of memory to be marked is from ss to ss+nn.
3323                                                  3262 
3324         memmap=nn[KMG]$ss[KMG]                   3263         memmap=nn[KMG]$ss[KMG]
3325                         [KNL,ACPI,EARLY] Mark !! 3264                         [KNL,ACPI] Mark specific memory as reserved.
3326                         Region of memory to b    3265                         Region of memory to be reserved is from ss to ss+nn.
3327                         Example: Exclude memo    3266                         Example: Exclude memory from 0x18690000-0x1869ffff
3328                                  memmap=64K$0    3267                                  memmap=64K$0x18690000
3329                                  or              3268                                  or
3330                                  memmap=0x100    3269                                  memmap=0x10000$0x18690000
3331                         Some bootloaders may     3270                         Some bootloaders may need an escape character before '$',
3332                         like Grub2, otherwise    3271                         like Grub2, otherwise '$' and the following number
3333                         will be eaten.           3272                         will be eaten.
3334                                                  3273 
3335         memmap=nn[KMG]!ss[KMG,EARLY]          !! 3274         memmap=nn[KMG]!ss[KMG]
3336                         [KNL,X86] Mark specif    3275                         [KNL,X86] Mark specific memory as protected.
3337                         Region of memory to b    3276                         Region of memory to be used, from ss to ss+nn.
3338                         The memory region may    3277                         The memory region may be marked as e820 type 12 (0xc)
3339                         and is NVDIMM or ADR     3278                         and is NVDIMM or ADR memory.
3340                                                  3279 
3341         memmap=<size>%<offset>-<oldtype>+<new    3280         memmap=<size>%<offset>-<oldtype>+<newtype>
3342                         [KNL,ACPI,EARLY] Conv !! 3281                         [KNL,ACPI] Convert memory within the specified region
3343                         from <oldtype> to <ne    3282                         from <oldtype> to <newtype>. If "-<oldtype>" is left
3344                         out, the whole region    3283                         out, the whole region will be marked as <newtype>,
3345                         even if previously un    3284                         even if previously unavailable. If "+<newtype>" is left
3346                         out, matching memory     3285                         out, matching memory will be removed. Types are
3347                         specified as e820 typ    3286                         specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348                         3 = ACPI, 12 = PRAM.     3287                         3 = ACPI, 12 = PRAM.
3349                                                  3288 
3350         memory_corruption_check=0/1 [X86,EARL !! 3289         memory_corruption_check=0/1 [X86]
3351                         Some BIOSes seem to c    3290                         Some BIOSes seem to corrupt the first 64k of
3352                         memory when doing thi    3291                         memory when doing things like suspend/resume.
3353                         Setting this option w    3292                         Setting this option will scan the memory
3354                         looking for corruptio    3293                         looking for corruption.  Enabling this will
3355                         both detect corruptio    3294                         both detect corruption and prevent the kernel
3356                         from using the memory    3295                         from using the memory being corrupted.
3357                         However, its intended    3296                         However, its intended as a diagnostic tool; if
3358                         repeatable BIOS-origi    3297                         repeatable BIOS-originated corruption always
3359                         affects the same memo    3298                         affects the same memory, you can use memmap=
3360                         to prevent the kernel    3299                         to prevent the kernel from using that memory.
3361                                                  3300 
3362         memory_corruption_check_size=size [X8 !! 3301         memory_corruption_check_size=size [X86]
3363                         By default it checks     3302                         By default it checks for corruption in the low
3364                         64k, making this memo    3303                         64k, making this memory unavailable for normal
3365                         use.  Use this parame    3304                         use.  Use this parameter to scan for
3366                         corruption in more or    3305                         corruption in more or less memory.
3367                                                  3306 
3368         memory_corruption_check_period=second !! 3307         memory_corruption_check_period=seconds [X86]
3369                         By default it checks     3308                         By default it checks for corruption every 60
3370                         seconds.  Use this pa    3309                         seconds.  Use this parameter to check at some
3371                         other rate.  0 disabl    3310                         other rate.  0 disables periodic checking.
3372                                                  3311 
3373         memory_hotplug.memmap_on_memory          3312         memory_hotplug.memmap_on_memory
3374                         [KNL,X86,ARM] Boolean    3313                         [KNL,X86,ARM] Boolean flag to enable this feature.
3375                         Format: {on | off (de    3314                         Format: {on | off (default)}
3376                         When enabled, runtime    3315                         When enabled, runtime hotplugged memory will
3377                         allocate its internal    3316                         allocate its internal metadata (struct pages,
3378                         those vmemmap pages c    3317                         those vmemmap pages cannot be optimized even
3379                         if hugetlb_free_vmemm    3318                         if hugetlb_free_vmemmap is enabled) from the
3380                         hotadded memory which    3319                         hotadded memory which will allow to hotadd a
3381                         lot of memory without    3320                         lot of memory without requiring additional
3382                         memory to do so.         3321                         memory to do so.
3383                         This feature is disab    3322                         This feature is disabled by default because it
3384                         has some implication     3323                         has some implication on large (e.g. GB)
3385                         allocations in some c    3324                         allocations in some configurations (e.g. small
3386                         memory blocks).          3325                         memory blocks).
3387                         The state of the flag    3326                         The state of the flag can be read in
3388                         /sys/module/memory_ho    3327                         /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389                         Note that even when e    3328                         Note that even when enabled, there are a few cases where
3390                         the feature is not ef    3329                         the feature is not effective.
3391                                                  3330 
3392         memtest=        [KNL,X86,ARM,M68K,PPC !! 3331         memtest=        [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
3393                         Format: <integer>        3332                         Format: <integer>
3394                         default : 0 <disable>    3333                         default : 0 <disable>
3395                         Specifies the number     3334                         Specifies the number of memtest passes to be
3396                         performed. Each pass     3335                         performed. Each pass selects another test
3397                         pattern from a given     3336                         pattern from a given set of patterns. Memtest
3398                         fills the memory with    3337                         fills the memory with this pattern, validates
3399                         memory contents and r    3338                         memory contents and reserves bad memory
3400                         regions that are dete    3339                         regions that are detected.
3401                                                  3340 
3402         mem_encrypt=    [X86-64] AMD Secure M    3341         mem_encrypt=    [X86-64] AMD Secure Memory Encryption (SME) control
3403                         Valid arguments: on,     3342                         Valid arguments: on, off
3404                         Default: off             3343                         Default: off
3405                         mem_encrypt=on:          3344                         mem_encrypt=on:         Activate SME
3406                         mem_encrypt=off:         3345                         mem_encrypt=off:        Do not activate SME
3407                                                  3346 
3408                         Refer to Documentatio    3347                         Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3409                         for details on when m    3348                         for details on when memory encryption can be activated.
3410                                                  3349 
3411         mem_sleep_default=      [SUSPEND] Def    3350         mem_sleep_default=      [SUSPEND] Default system suspend mode:
3412                         s2idle  - Suspend-To-    3351                         s2idle  - Suspend-To-Idle
3413                         shallow - Power-On Su    3352                         shallow - Power-On Suspend or equivalent (if supported)
3414                         deep    - Suspend-To-    3353                         deep    - Suspend-To-RAM or equivalent (if supported)
3415                         See Documentation/adm    3354                         See Documentation/admin-guide/pm/sleep-states.rst.
3416                                                  3355 
                                                   >> 3356         mfgpt_irq=      [IA-32] Specify the IRQ to use for the
                                                   >> 3357                         Multi-Function General Purpose Timers on AMD Geode
                                                   >> 3358                         platforms.
                                                   >> 3359 
3417         mfgptfix        [X86-32] Fix MFGPT ti    3360         mfgptfix        [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418                         the BIOS has incorrec    3361                         the BIOS has incorrectly applied a workaround. TinyBIOS
3419                         version 0.98 is known    3362                         version 0.98 is known to be affected, 0.99 fixes the
3420                         problem by letting th    3363                         problem by letting the user disable the workaround.
3421                                                  3364 
3422         mga=            [HW,DRM]                 3365         mga=            [HW,DRM]
3423                                                  3366 
3424         microcode.force_minrev= [X86]            3367         microcode.force_minrev= [X86]
3425                         Format: <bool>           3368                         Format: <bool>
3426                         Enable or disable the    3369                         Enable or disable the microcode minimal revision
3427                         enforcement for the r    3370                         enforcement for the runtime microcode loader.
3428                                                  3371 
                                                   >> 3372         min_addr=nn[KMG]        [KNL,BOOT,IA-64] All physical memory below this
                                                   >> 3373                         physical address is ignored.
                                                   >> 3374 
3429         mini2440=       [ARM,HW,KNL]             3375         mini2440=       [ARM,HW,KNL]
3430                         Format:[0..2][b][c][t    3376                         Format:[0..2][b][c][t]
3431                         Default: "0tb"           3377                         Default: "0tb"
3432                         MINI2440 configuratio    3378                         MINI2440 configuration specification:
3433                         0 - The attached scre    3379                         0 - The attached screen is the 3.5" TFT
3434                         1 - The attached scre    3380                         1 - The attached screen is the 7" TFT
3435                         2 - The VGA Shield is    3381                         2 - The VGA Shield is attached (1024x768)
3436                         Leaving out the scree    3382                         Leaving out the screen size parameter will not load
3437                         the TFT driver, and t    3383                         the TFT driver, and the framebuffer will be left
3438                         unconfigured.            3384                         unconfigured.
3439                         b - Enable backlight.    3385                         b - Enable backlight. The TFT backlight pin will be
3440                         linked to the kernel     3386                         linked to the kernel VESA blanking code and a GPIO
3441                         LED. This parameter i    3387                         LED. This parameter is not necessary when using the
3442                         VGA shield.              3388                         VGA shield.
3443                         c - Enable the s3c ca    3389                         c - Enable the s3c camera interface.
3444                         t - Reserved for enab    3390                         t - Reserved for enabling touchscreen support. The
3445                         touchscreen support i    3391                         touchscreen support is not enabled in the mainstream
3446                         kernel as of 2.6.30,     3392                         kernel as of 2.6.30, a preliminary port can be found
3447                         in the "bleeding edge    3393                         in the "bleeding edge" mini2440 support kernel at
3448                         https://repo.or.cz/w/    3394                         https://repo.or.cz/w/linux-2.6/mini2440.git
3449                                                  3395 
3450         mitigations=                             3396         mitigations=
3451                         [X86,PPC,S390,ARM64,E !! 3397                         [X86,PPC,S390,ARM64] Control optional mitigations for
3452                         CPU vulnerabilities.     3398                         CPU vulnerabilities.  This is a set of curated,
3453                         arch-independent opti    3399                         arch-independent options, each of which is an
3454                         aggregation of existi    3400                         aggregation of existing arch-specific options.
3455                                                  3401 
3456                         Note, "mitigations" i    3402                         Note, "mitigations" is supported if and only if the
3457                         kernel was built with    3403                         kernel was built with CPU_MITIGATIONS=y.
3458                                                  3404 
3459                         off                      3405                         off
3460                                 Disable all o    3406                                 Disable all optional CPU mitigations.  This
3461                                 improves syst    3407                                 improves system performance, but it may also
3462                                 expose users     3408                                 expose users to several CPU vulnerabilities.
3463                                 Equivalent to    3409                                 Equivalent to: if nokaslr then kpti=0 [ARM64]
3464                                                  3410                                                gather_data_sampling=off [X86]
3465                                                  3411                                                kvm.nx_huge_pages=off [X86]
3466                                                  3412                                                l1tf=off [X86]
3467                                                  3413                                                mds=off [X86]
3468                                                  3414                                                mmio_stale_data=off [X86]
3469                                                  3415                                                no_entry_flush [PPC]
3470                                                  3416                                                no_uaccess_flush [PPC]
3471                                                  3417                                                nobp=0 [S390]
3472                                                  3418                                                nopti [X86,PPC]
3473                                                  3419                                                nospectre_bhb [ARM64]
3474                                                  3420                                                nospectre_v1 [X86,PPC]
3475                                                  3421                                                nospectre_v2 [X86,PPC,S390,ARM64]
3476                                                  3422                                                reg_file_data_sampling=off [X86]
3477                                                  3423                                                retbleed=off [X86]
3478                                               << 
3479                                                  3424                                                spec_store_bypass_disable=off [X86,PPC]
3480                                                  3425                                                spectre_bhi=off [X86]
3481                                                  3426                                                spectre_v2_user=off [X86]
3482                                                  3427                                                srbds=off [X86,INTEL]
3483                                                  3428                                                ssbd=force-off [ARM64]
3484                                                  3429                                                tsx_async_abort=off [X86]
3485                                                  3430 
3486                                 Exceptions:      3431                                 Exceptions:
3487                                                  3432                                                This does not have any effect on
3488                                                  3433                                                kvm.nx_huge_pages when
3489                                                  3434                                                kvm.nx_huge_pages=force.
3490                                                  3435 
3491                         auto (default)           3436                         auto (default)
3492                                 Mitigate all     3437                                 Mitigate all CPU vulnerabilities, but leave SMT
3493                                 enabled, even    3438                                 enabled, even if it's vulnerable.  This is for
3494                                 users who don    3439                                 users who don't want to be surprised by SMT
3495                                 getting disab    3440                                 getting disabled across kernel upgrades, or who
3496                                 have other wa    3441                                 have other ways of avoiding SMT-based attacks.
3497                                 Equivalent to    3442                                 Equivalent to: (default behavior)
3498                                                  3443 
3499                         auto,nosmt               3444                         auto,nosmt
3500                                 Mitigate all     3445                                 Mitigate all CPU vulnerabilities, disabling SMT
3501                                 if needed.  T    3446                                 if needed.  This is for users who always want to
3502                                 be fully miti    3447                                 be fully mitigated, even if it means losing SMT.
3503                                 Equivalent to    3448                                 Equivalent to: l1tf=flush,nosmt [X86]
3504                                                  3449                                                mds=full,nosmt [X86]
3505                                                  3450                                                tsx_async_abort=full,nosmt [X86]
3506                                                  3451                                                mmio_stale_data=full,nosmt [X86]
3507                                                  3452                                                retbleed=auto,nosmt [X86]
3508                                                  3453 
3509         mminit_loglevel=                         3454         mminit_loglevel=
3510                         [KNL,EARLY] When CONF !! 3455                         [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511                         parameter allows cont    3456                         parameter allows control of the logging verbosity for
3512                         the additional memory    3457                         the additional memory initialisation checks. A value
3513                         of 0 disables mminit     3458                         of 0 disables mminit logging and a level of 4 will
3514                         log everything. Infor    3459                         log everything. Information is printed at KERN_DEBUG
3515                         so loglevel=8 may als    3460                         so loglevel=8 may also need to be specified.
3516                                                  3461 
3517         mmio_stale_data=                         3462         mmio_stale_data=
3518                         [X86,INTEL,EARLY] Con !! 3463                         [X86,INTEL] Control mitigation for the Processor
3519                         MMIO Stale Data vulne    3464                         MMIO Stale Data vulnerabilities.
3520                                                  3465 
3521                         Processor MMIO Stale     3466                         Processor MMIO Stale Data is a class of
3522                         vulnerabilities that     3467                         vulnerabilities that may expose data after an MMIO
3523                         operation. Exposed da    3468                         operation. Exposed data could originate or end in
3524                         the same CPU buffers     3469                         the same CPU buffers as affected by MDS and TAA.
3525                         Therefore, similar to    3470                         Therefore, similar to MDS and TAA, the mitigation
3526                         is to clear the affec    3471                         is to clear the affected CPU buffers.
3527                                                  3472 
3528                         This parameter contro    3473                         This parameter controls the mitigation. The
3529                         options are:             3474                         options are:
3530                                                  3475 
3531                         full       - Enable m    3476                         full       - Enable mitigation on vulnerable CPUs
3532                                                  3477 
3533                         full,nosmt - Enable m    3478                         full,nosmt - Enable mitigation and disable SMT on
3534                                      vulnerab    3479                                      vulnerable CPUs.
3535                                                  3480 
3536                         off        - Uncondit    3481                         off        - Unconditionally disable mitigation
3537                                                  3482 
3538                         On MDS or TAA affecte    3483                         On MDS or TAA affected machines,
3539                         mmio_stale_data=off c    3484                         mmio_stale_data=off can be prevented by an active
3540                         MDS or TAA mitigation    3485                         MDS or TAA mitigation as these vulnerabilities are
3541                         mitigated with the sa    3486                         mitigated with the same mechanism so in order to
3542                         disable this mitigati    3487                         disable this mitigation, you need to specify
3543                         mds=off and tsx_async    3488                         mds=off and tsx_async_abort=off too.
3544                                                  3489 
3545                         Not specifying this o    3490                         Not specifying this option is equivalent to
3546                         mmio_stale_data=full.    3491                         mmio_stale_data=full.
3547                                                  3492 
3548                         For details see:         3493                         For details see:
3549                         Documentation/admin-g    3494                         Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550                                                  3495 
3551         <module>.async_probe[=<bool>] [KNL]      3496         <module>.async_probe[=<bool>] [KNL]
3552                         If no <bool> value is    3497                         If no <bool> value is specified or if the value
3553                         specified is not a va    3498                         specified is not a valid <bool>, enable asynchronous
3554                         probe on this module.    3499                         probe on this module.  Otherwise, enable/disable
3555                         asynchronous probe on    3500                         asynchronous probe on this module as indicated by the
3556                         <bool> value. See als    3501                         <bool> value. See also: module.async_probe
3557                                                  3502 
3558         module.async_probe=<bool>                3503         module.async_probe=<bool>
3559                         [KNL] When set to tru    3504                         [KNL] When set to true, modules will use async probing
3560                         by default. To enable    3505                         by default. To enable/disable async probing for a
3561                         specific module, use     3506                         specific module, use the module specific control that
3562                         is documented under <    3507                         is documented under <module>.async_probe. When both
3563                         module.async_probe an    3508                         module.async_probe and <module>.async_probe are
3564                         specified, <module>.a    3509                         specified, <module>.async_probe takes precedence for
3565                         the specific module.     3510                         the specific module.
3566                                                  3511 
3567         module.enable_dups_trace                 3512         module.enable_dups_trace
3568                         [KNL] When CONFIG_MOD    3513                         [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
3569                         this means that dupli    3514                         this means that duplicate request_module() calls will
3570                         trigger a WARN_ON() i    3515                         trigger a WARN_ON() instead of a pr_warn(). Note that
3571                         if MODULE_DEBUG_AUTOL    3516                         if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
3572                         will always be issued    3517                         will always be issued and this option does nothing.
3573         module.sig_enforce                       3518         module.sig_enforce
3574                         [KNL] When CONFIG_MOD    3519                         [KNL] When CONFIG_MODULE_SIG is set, this means that
3575                         modules without (vali    3520                         modules without (valid) signatures will fail to load.
3576                         Note that if CONFIG_M    3521                         Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577                         is always true, so th    3522                         is always true, so this option does nothing.
3578                                                  3523 
3579         module_blacklist=  [KNL] Do not load     3524         module_blacklist=  [KNL] Do not load a comma-separated list of
3580                         modules.  Useful for     3525                         modules.  Useful for debugging problem modules.
3581                                                  3526 
3582         mousedev.tap_time=                       3527         mousedev.tap_time=
3583                         [MOUSE] Maximum time     3528                         [MOUSE] Maximum time between finger touching and
3584                         leaving touchpad surf    3529                         leaving touchpad surface for touch to be considered
3585                         a tap and be reported    3530                         a tap and be reported as a left button click (for
3586                         touchpads working in     3531                         touchpads working in absolute mode only).
3587                         Format: <msecs>          3532                         Format: <msecs>
3588         mousedev.xres=  [MOUSE] Horizontal sc    3533         mousedev.xres=  [MOUSE] Horizontal screen resolution, used for devices
3589                         reporting absolute co    3534                         reporting absolute coordinates, such as tablets
3590         mousedev.yres=  [MOUSE] Vertical scre    3535         mousedev.yres=  [MOUSE] Vertical screen resolution, used for devices
3591                         reporting absolute co    3536                         reporting absolute coordinates, such as tablets
3592                                                  3537 
3593         movablecore=    [KNL,X86,PPC,EARLY]   !! 3538         movablecore=    [KNL,X86,IA-64,PPC]
3594                         Format: nn[KMGTPE] |     3539                         Format: nn[KMGTPE] | nn%
3595                         This parameter is the    3540                         This parameter is the complement to kernelcore=, it
3596                         specifies the amount     3541                         specifies the amount of memory used for migratable
3597                         allocations.  If both    3542                         allocations.  If both kernelcore and movablecore is
3598                         specified, then kerne    3543                         specified, then kernelcore will be at *least* the
3599                         specified value but m    3544                         specified value but may be more.  If movablecore on its
3600                         own is specified, the    3545                         own is specified, the administrator must be careful
3601                         that the amount of me    3546                         that the amount of memory usable for all allocations
3602                         is not too small.        3547                         is not too small.
3603                                                  3548 
3604         movable_node    [KNL,EARLY] Boot-time !! 3549         movable_node    [KNL] Boot-time switch to make hotplugable memory
3605                         NUMA nodes to be mova    3550                         NUMA nodes to be movable. This means that the memory
3606                         of such nodes will be    3551                         of such nodes will be usable only for movable
3607                         allocations which rul    3552                         allocations which rules out almost all kernel
3608                         allocations. Use with    3553                         allocations. Use with caution!
3609                                                  3554 
3610         MTD_Partition=  [MTD]                    3555         MTD_Partition=  [MTD]
3611                         Format: <name>,<regio    3556                         Format: <name>,<region-number>,<size>,<offset>
3612                                                  3557 
3613         MTD_Region=     [MTD] Format:            3558         MTD_Region=     [MTD] Format:
3614                         <name>,<region-number    3559                         <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615                                                  3560 
3616         mtdparts=       [MTD]                    3561         mtdparts=       [MTD]
3617                         See drivers/mtd/parse    3562                         See drivers/mtd/parsers/cmdlinepart.c
3618                                                  3563 
                                                   >> 3564         mtdset=         [ARM]
                                                   >> 3565                         ARM/S3C2412 JIVE boot control
                                                   >> 3566 
                                                   >> 3567                         See arch/arm/mach-s3c/mach-jive.c
                                                   >> 3568 
3619         mtouchusb.raw_coordinates=               3569         mtouchusb.raw_coordinates=
3620                         [HW] Make the MicroTo    3570                         [HW] Make the MicroTouch USB driver use raw coordinates
3621                         ('y', default) or coo    3571                         ('y', default) or cooked coordinates ('n')
3622                                                  3572 
3623         mtrr=debug      [X86,EARLY]           !! 3573         mtrr=debug      [X86]
3624                         Enable printing debug    3574                         Enable printing debug information related to MTRR
3625                         registers at boot tim    3575                         registers at boot time.
3626                                                  3576 
3627         mtrr_chunk_size=nn[KMG,X86,EARLY]     !! 3577         mtrr_chunk_size=nn[KMG] [X86]
3628                         used for mtrr cleanup    3578                         used for mtrr cleanup. It is largest continuous chunk
3629                         that could hold holes    3579                         that could hold holes aka. UC entries.
3630                                                  3580 
3631         mtrr_gran_size=nn[KMG,X86,EARLY]      !! 3581         mtrr_gran_size=nn[KMG] [X86]
3632                         Used for mtrr cleanup    3582                         Used for mtrr cleanup. It is granularity of mtrr block.
3633                         Default is 1.            3583                         Default is 1.
3634                         Large value could pre    3584                         Large value could prevent small alignment from
3635                         using up MTRRs.          3585                         using up MTRRs.
3636                                                  3586 
3637         mtrr_spare_reg_nr=n [X86,EARLY]       !! 3587         mtrr_spare_reg_nr=n [X86]
3638                         Format: <integer>        3588                         Format: <integer>
3639                         Range: 0,7 : spare re    3589                         Range: 0,7 : spare reg number
3640                         Default : 1              3590                         Default : 1
3641                         Used for mtrr cleanup    3591                         Used for mtrr cleanup. It is spare mtrr entries number.
3642                         Set to 2 or more if y    3592                         Set to 2 or more if your graphical card needs more.
3643                                                  3593 
3644         multitce=off    [PPC]  This parameter    3594         multitce=off    [PPC]  This parameter disables the use of the pSeries
3645                         firmware feature for     3595                         firmware feature for updating multiple TCE entries
3646                         at a time.               3596                         at a time.
3647                                                  3597 
3648         n2=             [NET] SDL Inc. RISCom    3598         n2=             [NET] SDL Inc. RISCom/N2 synchronous serial card
3649                                                  3599 
3650         netdev=         [NET] Network devices    3600         netdev=         [NET] Network devices parameters
3651                         Format: <irq>,<io>,<m    3601                         Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652                         Note that mem_start i    3602                         Note that mem_start is often overloaded to mean
3653                         something different a    3603                         something different and driver-specific.
3654                         This usage is only do    3604                         This usage is only documented in each driver source
3655                         file if at all.          3605                         file if at all.
3656                                                  3606 
3657         netpoll.carrier_timeout=                 3607         netpoll.carrier_timeout=
3658                         [NET] Specifies amoun    3608                         [NET] Specifies amount of time (in seconds) that
3659                         netpoll should wait f    3609                         netpoll should wait for a carrier. By default netpoll
3660                         waits 4 seconds.         3610                         waits 4 seconds.
3661                                                  3611 
3662         nf_conntrack.acct=                       3612         nf_conntrack.acct=
3663                         [NETFILTER] Enable co    3613                         [NETFILTER] Enable connection tracking flow accounting
3664                         0 to disable accounti    3614                         0 to disable accounting
3665                         1 to enable accountin    3615                         1 to enable accounting
3666                         Default value is 0.      3616                         Default value is 0.
3667                                                  3617 
3668         nfs.cache_getent=                        3618         nfs.cache_getent=
3669                         [NFS] sets the pathna    3619                         [NFS] sets the pathname to the program which is used
3670                         to update the NFS cli    3620                         to update the NFS client cache entries.
3671                                                  3621 
3672         nfs.cache_getent_timeout=                3622         nfs.cache_getent_timeout=
3673                         [NFS] sets the timeou    3623                         [NFS] sets the timeout after which an attempt to
3674                         update a cache entry     3624                         update a cache entry is deemed to have failed.
3675                                                  3625 
3676         nfs.callback_nr_threads=                 3626         nfs.callback_nr_threads=
3677                         [NFSv4] set the total    3627                         [NFSv4] set the total number of threads that the
3678                         NFS client will assig    3628                         NFS client will assign to service NFSv4 callback
3679                         requests.                3629                         requests.
3680                                                  3630 
3681         nfs.callback_tcpport=                    3631         nfs.callback_tcpport=
3682                         [NFS] set the TCP por    3632                         [NFS] set the TCP port on which the NFSv4 callback
3683                         channel should listen    3633                         channel should listen.
3684                                                  3634 
3685         nfs.delay_retrans=                       3635         nfs.delay_retrans=
3686                         [NFS] specifies the n    3636                         [NFS] specifies the number of times the NFSv4 client
3687                         retries the request b    3637                         retries the request before returning an EAGAIN error,
3688                         after a reply of NFS4    3638                         after a reply of NFS4ERR_DELAY from the server.
3689                         Only applies if the s    3639                         Only applies if the softerr mount option is enabled,
3690                         and the specified val    3640                         and the specified value is >= 0.
3691                                                  3641 
3692         nfs.enable_ino64=                        3642         nfs.enable_ino64=
3693                         [NFS] enable 64-bit i    3643                         [NFS] enable 64-bit inode numbers.
3694                         If zero, the NFS clie    3644                         If zero, the NFS client will fake up a 32-bit inode
3695                         number for the readdi    3645                         number for the readdir() and stat() syscalls instead
3696                         of returning the full    3646                         of returning the full 64-bit number.
3697                         The default is to ret    3647                         The default is to return 64-bit inode numbers.
3698                                                  3648 
3699         nfs.idmap_cache_timeout=                 3649         nfs.idmap_cache_timeout=
3700                         [NFS] set the maximum    3650                         [NFS] set the maximum lifetime for idmapper cache
3701                         entries.                 3651                         entries.
3702                                                  3652 
3703         nfs.max_session_cb_slots=                3653         nfs.max_session_cb_slots=
3704                         [NFSv4.1] Sets the ma    3654                         [NFSv4.1] Sets the maximum number of session
3705                         slots the client will    3655                         slots the client will assign to the callback
3706                         channel. This determi    3656                         channel. This determines the maximum number of
3707                         callbacks the client     3657                         callbacks the client will process in parallel for
3708                         a particular server.     3658                         a particular server.
3709                                                  3659 
3710         nfs.max_session_slots=                   3660         nfs.max_session_slots=
3711                         [NFSv4.1] Sets the ma    3661                         [NFSv4.1] Sets the maximum number of session slots
3712                         the client will attem    3662                         the client will attempt to negotiate with the server.
3713                         This limits the numbe    3663                         This limits the number of simultaneous RPC requests
3714                         that the client can s    3664                         that the client can send to the NFSv4.1 server.
3715                         Note that there is li    3665                         Note that there is little point in setting this
3716                         value higher than the    3666                         value higher than the max_tcp_slot_table_limit.
3717                                                  3667 
3718         nfs.nfs4_disable_idmapping=              3668         nfs.nfs4_disable_idmapping=
3719                         [NFSv4] When set to t    3669                         [NFSv4] When set to the default of '1', this option
3720                         ensures that both the    3670                         ensures that both the RPC level authentication
3721                         scheme and the NFS le    3671                         scheme and the NFS level operations agree to use
3722                         numeric uids/gids if     3672                         numeric uids/gids if the mount is using the
3723                         'sec=sys' security fl    3673                         'sec=sys' security flavour. In effect it is
3724                         disabling idmapping,     3674                         disabling idmapping, which can make migration from
3725                         legacy NFSv2/v3 syste    3675                         legacy NFSv2/v3 systems to NFSv4 easier.
3726                         Servers that do not s    3676                         Servers that do not support this mode of operation
3727                         will be autodetected     3677                         will be autodetected by the client, and it will fall
3728                         back to using the idm    3678                         back to using the idmapper.
3729                         To turn off this beha    3679                         To turn off this behaviour, set the value to '0'.
3730                                                  3680 
3731         nfs.nfs4_unique_id=                      3681         nfs.nfs4_unique_id=
3732                         [NFS4] Specify an add    3682                         [NFS4] Specify an additional fixed unique ident-
3733                         ification string that    3683                         ification string that NFSv4 clients can insert into
3734                         their nfs_client_id4     3684                         their nfs_client_id4 string.  This is typically a
3735                         UUID that is generate    3685                         UUID that is generated at system install time.
3736                                                  3686 
3737         nfs.recover_lost_locks=                  3687         nfs.recover_lost_locks=
3738                         [NFSv4] Attempt to re    3688                         [NFSv4] Attempt to recover locks that were lost due
3739                         to a lease timeout on    3689                         to a lease timeout on the server. Please note that
3740                         doing this risks data    3690                         doing this risks data corruption, since there are
3741                         no guarantees that th    3691                         no guarantees that the file will remain unchanged
3742                         after the locks are l    3692                         after the locks are lost.
3743                         If you want to enable    3693                         If you want to enable the kernel legacy behaviour of
3744                         attempting to recover    3694                         attempting to recover these locks, then set this
3745                         parameter to '1'.        3695                         parameter to '1'.
3746                         The default parameter    3696                         The default parameter value of '0' causes the kernel
3747                         not to attempt recove    3697                         not to attempt recovery of lost locks.
3748                                                  3698 
3749         nfs.send_implementation_id=              3699         nfs.send_implementation_id=
3750                         [NFSv4.1] Send client    3700                         [NFSv4.1] Send client implementation identification
3751                         information in exchan    3701                         information in exchange_id requests.
3752                         If zero, no implement    3702                         If zero, no implementation identification information
3753                         will be sent.            3703                         will be sent.
3754                         The default is to sen    3704                         The default is to send the implementation identification
3755                         information.             3705                         information.
3756                                                  3706 
3757         nfs4.layoutstats_timer=                  3707         nfs4.layoutstats_timer=
3758                         [NFSv4.2] Change the     3708                         [NFSv4.2] Change the rate at which the kernel sends
3759                         layoutstats to the pN    3709                         layoutstats to the pNFS metadata server.
3760                                                  3710 
3761                         Setting this to value    3711                         Setting this to value to 0 causes the kernel to use
3762                         whatever value is the    3712                         whatever value is the default set by the layout
3763                         driver. A non-zero va    3713                         driver. A non-zero value sets the minimum interval
3764                         in seconds between la    3714                         in seconds between layoutstats transmissions.
3765                                                  3715 
3766         nfsd.inter_copy_offload_enable=          3716         nfsd.inter_copy_offload_enable=
3767                         [NFSv4.2] When set to    3717                         [NFSv4.2] When set to 1, the server will support
3768                         server-to-server copi    3718                         server-to-server copies for which this server is
3769                         the destination of th    3719                         the destination of the copy.
3770                                                  3720 
3771         nfsd.nfs4_disable_idmapping=             3721         nfsd.nfs4_disable_idmapping=
3772                         [NFSv4] When set to t    3722                         [NFSv4] When set to the default of '1', the NFSv4
3773                         server will return on    3723                         server will return only numeric uids and gids to
3774                         clients using auth_sy    3724                         clients using auth_sys, and will accept numeric uids
3775                         and gids from such cl    3725                         and gids from such clients.  This is intended to ease
3776                         migration from NFSv2/    3726                         migration from NFSv2/v3.
3777                                                  3727 
3778         nfsd.nfsd4_ssc_umount_timeout=           3728         nfsd.nfsd4_ssc_umount_timeout=
3779                         [NFSv4.2] When used a    3729                         [NFSv4.2] When used as the destination of a
3780                         server-to-server copy    3730                         server-to-server copy, knfsd temporarily mounts
3781                         the source server.  I    3731                         the source server.  It caches the mount in case
3782                         it will be needed aga    3732                         it will be needed again, and discards it if not
3783                         used for the number o    3733                         used for the number of milliseconds specified by
3784                         this parameter.          3734                         this parameter.
3785                                                  3735 
3786         nfsaddrs=       [NFS] Deprecated.  Us    3736         nfsaddrs=       [NFS] Deprecated.  Use ip= instead.
3787                         See Documentation/adm    3737                         See Documentation/admin-guide/nfs/nfsroot.rst.
3788                                                  3738 
3789         nfsroot=        [NFS] nfs root filesy    3739         nfsroot=        [NFS] nfs root filesystem for disk-less boxes.
3790                         See Documentation/adm    3740                         See Documentation/admin-guide/nfs/nfsroot.rst.
3791                                                  3741 
3792         nfsrootdebug    [NFS] enable nfsroot     3742         nfsrootdebug    [NFS] enable nfsroot debugging messages.
3793                         See Documentation/adm    3743                         See Documentation/admin-guide/nfs/nfsroot.rst.
3794                                                  3744 
3795         nmi_backtrace.backtrace_idle [KNL]       3745         nmi_backtrace.backtrace_idle [KNL]
3796                         Dump stacks even of i    3746                         Dump stacks even of idle CPUs in response to an
3797                         NMI stack-backtrace r    3747                         NMI stack-backtrace request.
3798                                                  3748 
3799         nmi_debug=      [KNL,SH] Specify one     3749         nmi_debug=      [KNL,SH] Specify one or more actions to take
3800                         when a NMI is trigger    3750                         when a NMI is triggered.
3801                         Format: [state][,regs    3751                         Format: [state][,regs][,debounce][,die]
3802                                                  3752 
3803         nmi_watchdog=   [KNL,BUGS=X86] Debugg    3753         nmi_watchdog=   [KNL,BUGS=X86] Debugging features for SMP kernels
3804                         Format: [panic,][nopa !! 3754                         Format: [panic,][nopanic,][num]
3805                         Valid num: 0 or 1        3755                         Valid num: 0 or 1
3806                         0 - turn hardlockup d    3756                         0 - turn hardlockup detector in nmi_watchdog off
3807                         1 - turn hardlockup d    3757                         1 - turn hardlockup detector in nmi_watchdog on
3808                         rNNN - configure the  << 
3809                                               << 
3810                         When panic is specifi    3758                         When panic is specified, panic when an NMI watchdog
3811                         timeout occurs (or 'n    3759                         timeout occurs (or 'nopanic' to not panic on an NMI
3812                         watchdog, if CONFIG_B    3760                         watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813                         To disable both hard     3761                         To disable both hard and soft lockup detectors,
3814                         please see 'nowatchdo    3762                         please see 'nowatchdog'.
3815                         This is useful when y    3763                         This is useful when you use a panic=... timeout and
3816                         need the box quickly     3764                         need the box quickly up again.
3817                                                  3765 
3818                         These settings can be    3766                         These settings can be accessed at runtime via
3819                         the nmi_watchdog and     3767                         the nmi_watchdog and hardlockup_panic sysctls.
3820                                                  3768 
3821         no387           [BUGS=X86-32] Tells t    3769         no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
3822                         emulation library eve    3770                         emulation library even if a 387 maths coprocessor
3823                         is present.              3771                         is present.
3824                                                  3772 
3825         no4lvl          [RISCV,EARLY] Disable !! 3773         no4lvl          [RISCV] Disable 4-level and 5-level paging modes. Forces
3826                         Forces kernel to use  !! 3774                         kernel to use 3-level paging instead.
3827                                                  3775 
3828         no5lvl          [X86-64,RISCV,EARLY]  !! 3776         no5lvl          [X86-64,RISCV] Disable 5-level paging mode. Forces
3829                         kernel to use 4-level    3777                         kernel to use 4-level paging instead.
3830                                                  3778 
                                                   >> 3779         noaliencache    [MM, NUMA, SLAB] Disables the allocation of alien
                                                   >> 3780                         caches in the slab allocator.  Saves per-node memory,
                                                   >> 3781                         but will impact performance.
                                                   >> 3782 
3831         noalign         [KNL,ARM]                3783         noalign         [KNL,ARM]
3832                                                  3784 
3833         noapic          [SMP,APIC,EARLY] Tell !! 3785         noaltinstr      [S390] Disables alternative instructions patching
                                                   >> 3786                         (CPU alternatives feature).
                                                   >> 3787 
                                                   >> 3788         noapic          [SMP,APIC] Tells the kernel to not make use of any
3834                         IOAPICs that may be p    3789                         IOAPICs that may be present in the system.
3835                                                  3790 
3836         noautogroup     Disable scheduler aut    3791         noautogroup     Disable scheduler automatic task group creation.
3837                                                  3792 
3838         nocache         [ARM,EARLY]           !! 3793         nocache         [ARM]
3839                                                  3794 
3840         no_console_suspend                       3795         no_console_suspend
3841                         [HW] Never suspend th    3796                         [HW] Never suspend the console
3842                         Disable suspending of    3797                         Disable suspending of consoles during suspend and
3843                         hibernate operations.    3798                         hibernate operations.  Once disabled, debugging
3844                         messages can reach va    3799                         messages can reach various consoles while the rest
3845                         of the system is bein    3800                         of the system is being put to sleep (ie, while
3846                         debugging driver susp    3801                         debugging driver suspend/resume hooks).  This may
3847                         not work reliably wit    3802                         not work reliably with all consoles, but is known
3848                         to work with serial a    3803                         to work with serial and VGA consoles.
3849                         To facilitate more fl    3804                         To facilitate more flexible debugging, we also add
3850                         console_suspend, a pr    3805                         console_suspend, a printk module parameter to control
3851                         it. Users could use c    3806                         it. Users could use console_suspend (usually
3852                         /sys/module/printk/pa    3807                         /sys/module/printk/parameters/console_suspend) to
3853                         turn on/off it dynami    3808                         turn on/off it dynamically.
3854                                                  3809 
3855         no_debug_objects                         3810         no_debug_objects
3856                         [KNL,EARLY] Disable o !! 3811                         [KNL] Disable object debugging
3857                                                  3812 
3858         nodsp           [SH] Disable hardware    3813         nodsp           [SH] Disable hardware DSP at boot time.
3859                                                  3814 
3860         noefi           [EFI,EARLY] Disable E !! 3815         noefi           Disable EFI runtime services support.
                                                   >> 3816 
                                                   >> 3817         no_entry_flush  [PPC] Don't flush the L1-D cache when entering the kernel.
3861                                                  3818 
3862         no_entry_flush  [PPC,EARLY] Don't flu !! 3819         noexec          [IA-64]
3863                                                  3820 
3864         noexec32        [X86-64]                 3821         noexec32        [X86-64]
3865                         This affects only 32-    3822                         This affects only 32-bit executables.
3866                         noexec32=on: enable n    3823                         noexec32=on: enable non-executable mappings (default)
3867                                 read doesn't     3824                                 read doesn't imply executable mappings
3868                         noexec32=off: disable    3825                         noexec32=off: disable non-executable mappings
3869                                 read implies     3826                                 read implies executable mappings
3870                                                  3827 
3871         no_file_caps    Tells the kernel not     3828         no_file_caps    Tells the kernel not to honor file capabilities.  The
3872                         only way then for a f    3829                         only way then for a file to be executed with privilege
3873                         is to be setuid root     3830                         is to be setuid root or executed by root.
3874                                                  3831 
3875         nofpu           [MIPS,SH] Disable har    3832         nofpu           [MIPS,SH] Disable hardware FPU at boot time.
3876                                                  3833 
3877         nofsgsbase      [X86] Disables FSGSBA    3834         nofsgsbase      [X86] Disables FSGSBASE instructions.
3878                                                  3835 
3879         nofxsr          [BUGS=X86-32] Disable    3836         nofxsr          [BUGS=X86-32] Disables x86 floating point extended
3880                         register save and res    3837                         register save and restore. The kernel will only save
3881                         legacy floating-point    3838                         legacy floating-point registers on task switch.
3882                                                  3839 
                                                   >> 3840         nohalt          [IA-64] Tells the kernel not to use the power saving
                                                   >> 3841                         function PAL_HALT_LIGHT when idle. This increases
                                                   >> 3842                         power-consumption. On the positive side, it reduces
                                                   >> 3843                         interrupt wake-up latency, which may improve performance
                                                   >> 3844                         in certain environments such as networked servers or
                                                   >> 3845                         real-time systems.
                                                   >> 3846 
3883         no_hash_pointers                         3847         no_hash_pointers
3884                         [KNL,EARLY]           << 
3885                         Force pointers printe    3848                         Force pointers printed to the console or buffers to be
3886                         unhashed.  By default    3849                         unhashed.  By default, when a pointer is printed via %p
3887                         format string, that p    3850                         format string, that pointer is "hashed", i.e. obscured
3888                         by hashing the pointe    3851                         by hashing the pointer value.  This is a security feature
3889                         that hides actual ker    3852                         that hides actual kernel addresses from unprivileged
3890                         users, but it also ma    3853                         users, but it also makes debugging the kernel more
3891                         difficult since unequ    3854                         difficult since unequal pointers can no longer be
3892                         compared.  However, i    3855                         compared.  However, if this command-line option is
3893                         specified, then all n    3856                         specified, then all normal pointers will have their true
3894                         value printed. This o    3857                         value printed. This option should only be specified when
3895                         debugging the kernel.    3858                         debugging the kernel.  Please do not use on production
3896                         kernels.                 3859                         kernels.
3897                                                  3860 
3898         nohibernate     [HIBERNATION] Disable    3861         nohibernate     [HIBERNATION] Disable hibernation and resume.
3899                                                  3862 
3900         nohlt           [ARM,ARM64,MICROBLAZE !! 3863         nohlt           [ARM,ARM64,MICROBLAZE,MIPS,PPC,SH] Forces the kernel to
3901                         busy wait in do_idle(    3864                         busy wait in do_idle() and not use the arch_cpu_idle()
3902                         implementation; requi    3865                         implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
3903                         to be effective. This    3866                         to be effective. This is useful on platforms where the
3904                         sleep(SH) or wfi(ARM,    3867                         sleep(SH) or wfi(ARM,ARM64) instructions do not work
3905                         correctly or when doi    3868                         correctly or when doing power measurements to evaluate
3906                         the impact of the sle    3869                         the impact of the sleep instructions. This is also
3907                         useful when using JTA    3870                         useful when using JTAG debugger.
3908                                                  3871 
3909         nohugeiomap     [KNL,X86,PPC,ARM64,EA !! 3872         nohugeiomap     [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3910                                                  3873 
3911         nohugevmalloc   [KNL,X86,PPC,ARM64,EA !! 3874         nohugevmalloc   [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
3912                                                  3875 
3913         nohz=           [KNL] Boottime enable    3876         nohz=           [KNL] Boottime enable/disable dynamic ticks
3914                         Valid arguments: on,     3877                         Valid arguments: on, off
3915                         Default: on              3878                         Default: on
3916                                                  3879 
3917         nohz_full=      [KNL,BOOT,SMP,ISOL]      3880         nohz_full=      [KNL,BOOT,SMP,ISOL]
3918                         The argument is a cpu    3881                         The argument is a cpu list, as described above.
3919                         In kernels built with    3882                         In kernels built with CONFIG_NO_HZ_FULL=y, set
3920                         the specified list of    3883                         the specified list of CPUs whose tick will be stopped
3921                         whenever possible. Th    3884                         whenever possible. The boot CPU will be forced outside
3922                         the range to maintain    3885                         the range to maintain the timekeeping.  Any CPUs
3923                         in this list will hav    3886                         in this list will have their RCU callbacks offloaded,
3924                         just as if they had a    3887                         just as if they had also been called out in the
3925                         rcu_nocbs= boot param    3888                         rcu_nocbs= boot parameter.
3926                                                  3889 
3927                         Note that this argume    3890                         Note that this argument takes precedence over
3928                         the CONFIG_RCU_NOCB_C    3891                         the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
3929                                                  3892 
3930         noinitrd        [RAM] Tells the kerne    3893         noinitrd        [RAM] Tells the kernel not to load any configured
3931                         initial RAM disk.        3894                         initial RAM disk.
3932                                                  3895 
3933         nointremap      [X86-64,Intel-IOMMU,E !! 3896         nointremap      [X86-64, Intel-IOMMU] Do not enable interrupt
3934                         remapping.               3897                         remapping.
3935                         [Deprecated - use int    3898                         [Deprecated - use intremap=off]
3936                                                  3899 
3937         noinvpcid       [X86,EARLY] Disable t !! 3900         nointroute      [IA-64]
                                                   >> 3901 
                                                   >> 3902         noinvpcid       [X86] Disable the INVPCID cpu feature.
3938                                                  3903 
3939         noiotrap        [SH] Disables trapped    3904         noiotrap        [SH] Disables trapped I/O port accesses.
3940                                                  3905 
3941         noirqdebug      [X86-32] Disables the    3906         noirqdebug      [X86-32] Disables the code which attempts to detect and
3942                         disable unhandled int    3907                         disable unhandled interrupt sources.
3943                                                  3908 
3944         noisapnp        [ISAPNP] Disables ISA    3909         noisapnp        [ISAPNP] Disables ISA PnP code.
3945                                                  3910 
3946         nokaslr         [KNL,EARLY]           !! 3911         nojitter        [IA-64] Disables jitter checking for ITC timers.
                                                   >> 3912 
                                                   >> 3913         nokaslr         [KNL]
3947                         When CONFIG_RANDOMIZE    3914                         When CONFIG_RANDOMIZE_BASE is set, this disables
3948                         kernel and module bas    3915                         kernel and module base offset ASLR (Address Space
3949                         Layout Randomization)    3916                         Layout Randomization).
3950                                                  3917 
3951         no-kvmapf       [X86,KVM,EARLY] Disab !! 3918         no-kvmapf       [X86,KVM] Disable paravirtualized asynchronous page
3952                         fault handling.          3919                         fault handling.
3953                                                  3920 
3954         no-kvmclock     [X86,KVM,EARLY] Disab !! 3921         no-kvmclock     [X86,KVM] Disable paravirtualized KVM clock driver
                                                   >> 3922 
                                                   >> 3923         nolapic         [X86-32,APIC] Do not enable or use the local APIC.
3955                                                  3924 
3956         nolapic         [X86-32,APIC,EARLY] D !! 3925         nolapic_timer   [X86-32,APIC] Do not use the local APIC timer.
3957                                                  3926 
3958         nolapic_timer   [X86-32,APIC,EARLY] D !! 3927         nomca           [IA-64] Disable machine check abort handling
3959                                                  3928 
3960         nomce           [X86-32] Disable Mach    3929         nomce           [X86-32] Disable Machine Check Exception
3961                                                  3930 
3962         nomfgpt         [X86-32] Disable Mult    3931         nomfgpt         [X86-32] Disable Multi-Function General Purpose
3963                         Timer usage (for AMD     3932                         Timer usage (for AMD Geode machines).
3964                                                  3933 
3965         nomodeset       Disable kernel modese    3934         nomodeset       Disable kernel modesetting. Most systems' firmware
3966                         sets up a display mod    3935                         sets up a display mode and provides framebuffer memory
3967                         for output. With nomo    3936                         for output. With nomodeset, DRM and fbdev drivers will
3968                         not load if they coul    3937                         not load if they could possibly displace the pre-
3969                         initialized output. O    3938                         initialized output. Only the system framebuffer will
3970                         be available for use.    3939                         be available for use. The respective drivers will not
3971                         perform display-mode     3940                         perform display-mode changes or accelerated rendering.
3972                                                  3941 
3973                         Useful as error fallb    3942                         Useful as error fallback, or for testing and debugging.
3974                                                  3943 
3975         nomodule        Disable module load      3944         nomodule        Disable module load
3976                                                  3945 
3977         nonmi_ipi       [X86] Disable using N    3946         nonmi_ipi       [X86] Disable using NMI IPIs during panic/reboot to
3978                         shutdown the other cp    3947                         shutdown the other cpus.  Instead use the REBOOT_VECTOR
3979                         irq.                     3948                         irq.
3980                                                  3949 
3981         nopat           [X86,EARLY] Disable P !! 3950         nopat           [X86] Disable PAT (page attribute table extension of
3982                         pagetables) support.     3951                         pagetables) support.
3983                                                  3952 
3984         nopcid          [X86-64,EARLY] Disabl !! 3953         nopcid          [X86-64] Disable the PCID cpu feature.
3985                                                  3954 
3986         nopku           [X86] Disable Memory     3955         nopku           [X86] Disable Memory Protection Keys CPU feature found
3987                         in some Intel CPUs.      3956                         in some Intel CPUs.
3988                                                  3957 
3989         nopti           [X86-64,EARLY]        !! 3958         nopti           [X86-64]
3990                         Equivalent to pti=off    3959                         Equivalent to pti=off
3991                                                  3960 
3992         nopv=           [X86,XEN,KVM,HYPER_V, !! 3961         nopv=           [X86,XEN,KVM,HYPER_V,VMWARE]
3993                         Disables the PV optim    3962                         Disables the PV optimizations forcing the guest to run
3994                         as generic guest with    3963                         as generic guest with no PV drivers. Currently support
3995                         XEN HVM, KVM, HYPER_V    3964                         XEN HVM, KVM, HYPER_V and VMWARE guest.
3996                                                  3965 
3997         nopvspin        [X86,XEN,KVM,EARLY]   !! 3966         nopvspin        [X86,XEN,KVM]
3998                         Disables the qspinloc    3967                         Disables the qspinlock slow path using PV optimizations
3999                         which allow the hyper    3968                         which allow the hypervisor to 'idle' the guest on lock
4000                         contention.              3969                         contention.
4001                                                  3970 
4002         norandmaps      Don't use address spa    3971         norandmaps      Don't use address space randomization.  Equivalent to
4003                         echo 0 > /proc/sys/ke    3972                         echo 0 > /proc/sys/kernel/randomize_va_space
4004                                                  3973 
4005         noreplace-smp   [X86-32,SMP] Don't re    3974         noreplace-smp   [X86-32,SMP] Don't replace SMP instructions
4006                         with UP alternatives     3975                         with UP alternatives
4007                                                  3976 
4008         noresume        [SWSUSP] Disables res    3977         noresume        [SWSUSP] Disables resume and restores original swap
4009                         space.                   3978                         space.
4010                                                  3979 
                                                   >> 3980         nosbagart       [IA-64]
                                                   >> 3981 
4011         no-scroll       [VGA] Disables scroll    3982         no-scroll       [VGA] Disables scrollback.
4012                         This is required for     3983                         This is required for the Braillex ib80-piezo Braille
4013                         reader made by F.H. P    3984                         reader made by F.H. Papenmeier (Germany).
4014                                                  3985 
4015         nosgx           [X86-64,SGX,EARLY] Di !! 3986         nosgx           [X86-64,SGX] Disables Intel SGX kernel support.
4016                                                  3987 
4017         nosmap          [PPC,EARLY]           !! 3988         nosmap          [PPC]
4018                         Disable SMAP (Supervi    3989                         Disable SMAP (Supervisor Mode Access Prevention)
4019                         even if it is support    3990                         even if it is supported by processor.
4020                                                  3991 
4021         nosmep          [PPC64s,EARLY]        !! 3992         nosmep          [PPC64s]
4022                         Disable SMEP (Supervi    3993                         Disable SMEP (Supervisor Mode Execution Prevention)
4023                         even if it is support    3994                         even if it is supported by processor.
4024                                                  3995 
4025         nosmp           [SMP,EARLY] Tells an  !! 3996         nosmp           [SMP] Tells an SMP kernel to act as a UP kernel,
4026                         and disable the IO AP    3997                         and disable the IO APIC.  legacy for "maxcpus=0".
4027                                                  3998 
4028         nosmt           [KNL,MIPS,PPC,S390,EA !! 3999         nosmt           [KNL,MIPS,PPC,S390] Disable symmetric multithreading (SMT).
4029                         Equivalent to smt=1.     4000                         Equivalent to smt=1.
4030                                                  4001 
4031                         [KNL,X86,PPC] Disable    4002                         [KNL,X86,PPC] Disable symmetric multithreading (SMT).
4032                         nosmt=force: Force di    4003                         nosmt=force: Force disable SMT, cannot be undone
4033                                      via the     4004                                      via the sysfs control file.
4034                                                  4005 
4035         nosoftlockup    [KNL] Disable the sof    4006         nosoftlockup    [KNL] Disable the soft-lockup detector.
4036                                                  4007 
4037         nospec_store_bypass_disable              4008         nospec_store_bypass_disable
4038                         [HW,EARLY] Disable al !! 4009                         [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
4039                         Store Bypass vulnerab << 
4040                                                  4010 
4041         nospectre_bhb   [ARM64,EARLY] Disable !! 4011         nospectre_bhb   [ARM64] Disable all mitigations for Spectre-BHB (branch
4042                         history injection) vu    4012                         history injection) vulnerability. System may allow data leaks
4043                         with this option.        4013                         with this option.
4044                                                  4014 
4045         nospectre_v1    [X86,PPC,EARLY] Disab !! 4015         nospectre_v1    [X86,PPC] Disable mitigations for Spectre Variant 1
4046                         (bounds check bypass)    4016                         (bounds check bypass). With this option data leaks are
4047                         possible in the syste    4017                         possible in the system.
4048                                                  4018 
4049         nospectre_v2    [X86,PPC_E500,ARM64,E !! 4019         nospectre_v2    [X86,PPC_E500,ARM64] Disable all mitigations for
4050                         for the Spectre varia !! 4020                         the Spectre variant 2 (indirect branch prediction)
4051                         prediction) vulnerabi !! 4021                         vulnerability. System may allow data leaks with this
4052                         leaks with this optio !! 4022                         option.
4053                                               !! 4023 
4054         no-steal-acc    [X86,PV_OPS,ARM64,PPC !! 4024         no-steal-acc    [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV] Disable
4055                         Disable paravirtualiz !! 4025                         paravirtualized steal time accounting. steal time is
4056                         is computed, but won' !! 4026                         computed, but won't influence scheduler behaviour
4057                                                  4027 
4058         nosync          [HW,M68K] Disables sy    4028         nosync          [HW,M68K] Disables sync negotiation for all devices.
4059                                                  4029 
4060         no_timer_check  [X86,APIC] Disables t    4030         no_timer_check  [X86,APIC] Disables the code which tests for
4061                         broken timer IRQ sour    4031                         broken timer IRQ sources.
4062                                                  4032 
4063         no_uaccess_flush                         4033         no_uaccess_flush
4064                         [PPC,EARLY] Don't flu !! 4034                         [PPC] Don't flush the L1-D cache after accessing user data.
4065                                                  4035 
4066         novmcoredd      [KNL,KDUMP]              4036         novmcoredd      [KNL,KDUMP]
4067                         Disable device dump.     4037                         Disable device dump. Device dump allows drivers to
4068                         append dump data to v    4038                         append dump data to vmcore so you can collect driver
4069                         specified debug info.    4039                         specified debug info.  Drivers can append the data
4070                         without any limit and    4040                         without any limit and this data is stored in memory,
4071                         so this may cause sig    4041                         so this may cause significant memory stress.  Disabling
4072                         device dump can help     4042                         device dump can help save memory but the driver debug
4073                         data will be no longe    4043                         data will be no longer available.  This parameter
4074                         is only available whe    4044                         is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
4075                         is set.                  4045                         is set.
4076                                                  4046 
4077         no-vmw-sched-clock                       4047         no-vmw-sched-clock
4078                         [X86,PV_OPS,EARLY] Di !! 4048                         [X86,PV_OPS] Disable paravirtualized VMware scheduler
4079                         scheduler clock and u !! 4049                         clock and use the default one.
4080                                                  4050 
4081         nowatchdog      [KNL] Disable both lo    4051         nowatchdog      [KNL] Disable both lockup detectors, i.e.
4082                         soft-lockup and NMI w    4052                         soft-lockup and NMI watchdog (hard-lockup).
4083                                                  4053 
4084         nowb            [ARM,EARLY]           !! 4054         nowb            [ARM]
4085                                                  4055 
4086         nox2apic        [X86-64,APIC,EARLY] D !! 4056         nox2apic        [X86-64,APIC] Do not enable x2APIC mode.
4087                                                  4057 
4088                         NOTE: this parameter     4058                         NOTE: this parameter will be ignored on systems with the
4089                         LEGACY_XAPIC_DISABLED    4059                         LEGACY_XAPIC_DISABLED bit set in the
4090                         IA32_XAPIC_DISABLE_ST    4060                         IA32_XAPIC_DISABLE_STATUS MSR.
4091                                                  4061 
4092         noxsave         [BUGS=X86] Disables x    4062         noxsave         [BUGS=X86] Disables x86 extended register state save
4093                         and restore using xsa    4063                         and restore using xsave. The kernel will fallback to
4094                         enabling legacy float    4064                         enabling legacy floating-point and sse state.
4095                                                  4065 
4096         noxsaveopt      [X86] Disables xsaveo    4066         noxsaveopt      [X86] Disables xsaveopt used in saving x86 extended
4097                         register states. The     4067                         register states. The kernel will fall back to use
4098                         xsave to save the sta    4068                         xsave to save the states. By using this parameter,
4099                         performance of saving    4069                         performance of saving the states is degraded because
4100                         xsave doesn't support    4070                         xsave doesn't support modified optimization while
4101                         xsaveopt supports it     4071                         xsaveopt supports it on xsaveopt enabled systems.
4102                                                  4072 
4103         noxsaves        [X86] Disables xsaves    4073         noxsaves        [X86] Disables xsaves and xrstors used in saving and
4104                         restoring x86 extende    4074                         restoring x86 extended register state in compacted
4105                         form of xsave area. T    4075                         form of xsave area. The kernel will fall back to use
4106                         xsaveopt and xrstor t    4076                         xsaveopt and xrstor to save and restore the states
4107                         in standard form of x    4077                         in standard form of xsave area. By using this
4108                         parameter, xsave area    4078                         parameter, xsave area per process might occupy more
4109                         memory on xsaves enab    4079                         memory on xsaves enabled systems.
4110                                                  4080 
4111         nr_cpus=        [SMP,EARLY] Maximum n !! 4081         nps_mtm_hs_ctr= [KNL,ARC]
                                                   >> 4082                         This parameter sets the maximum duration, in
                                                   >> 4083                         cycles, each HW thread of the CTOP can run
                                                   >> 4084                         without interruptions, before HW switches it.
                                                   >> 4085                         The actual maximum duration is 16 times this
                                                   >> 4086                         parameter's value.
                                                   >> 4087                         Format: integer between 1 and 255
                                                   >> 4088                         Default: 255
                                                   >> 4089 
                                                   >> 4090         nptcg=          [IA-64] Override max number of concurrent global TLB
                                                   >> 4091                         purges which is reported from either PAL_VM_SUMMARY or
                                                   >> 4092                         SAL PALO.
                                                   >> 4093 
                                                   >> 4094         nr_cpus=        [SMP] Maximum number of processors that an SMP kernel
4112                         could support.  nr_cp    4095                         could support.  nr_cpus=n : n >= 1 limits the kernel to
4113                         support 'n' processor    4096                         support 'n' processors. It could be larger than the
4114                         number of already plu    4097                         number of already plugged CPU during bootup, later in
4115                         runtime you can physi    4098                         runtime you can physically add extra cpu until it reaches
4116                         n. So during boot up     4099                         n. So during boot up some boot time memory for per-cpu
4117                         variables need be pre    4100                         variables need be pre-allocated for later physical cpu
4118                         hot plugging.            4101                         hot plugging.
4119                                                  4102 
4120         nr_uarts=       [SERIAL] maximum numb    4103         nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
4121                                                  4104 
4122         numa=off        [KNL, ARM64, PPC, RIS !! 4105         numa=off        [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123                         Disable NUMA, Only se !! 4106                         set up a single NUMA node spanning all memory.
4124                         spanning all memory.  << 
4125                                                  4107 
4126         numa_balancing= [KNL,ARM64,PPC,RISCV,    4108         numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127                         NUMA balancing.          4109                         NUMA balancing.
4128                         Allowed values are en    4110                         Allowed values are enable and disable
4129                                                  4111 
4130         numa_zonelist_order= [KNL, BOOT] Sele    4112         numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131                         'node', 'default' can    4113                         'node', 'default' can be specified
4132                         This can be set from     4114                         This can be set from sysctl after boot.
4133                         See Documentation/adm    4115                         See Documentation/admin-guide/sysctl/vm.rst for details.
4134                                                  4116 
4135         ohci1394_dma=early      [HW,EARLY] en !! 4117         ohci1394_dma=early      [HW] enable debugging via the ohci1394 driver.
4136                         See Documentation/cor    4118                         See Documentation/core-api/debugging-via-ohci1394.rst for more
4137                         info.                    4119                         info.
4138                                                  4120 
4139         olpc_ec_timeout= [OLPC] ms delay when    4121         olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140                         Rather than timing ou    4122                         Rather than timing out after 20 ms if an EC
4141                         command is not proper    4123                         command is not properly ACKed, override the length
4142                         of the timeout.  We h    4124                         of the timeout.  We have interrupts disabled while
4143                         waiting for the ACK,     4125                         waiting for the ACK, so if this is set too high
4144                         interrupts *may* be l    4126                         interrupts *may* be lost!
4145                                                  4127 
4146         omap_mux=       [OMAP] Override bootl    4128         omap_mux=       [OMAP] Override bootloader pin multiplexing.
4147                         Format: <mux_mode0.mo    4129                         Format: <mux_mode0.mode_name=value>...
4148                         For example, to overr    4130                         For example, to override I2C bus2:
4149                         omap_mux=i2c2_scl.i2c    4131                         omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150                                                  4132 
4151         onenand.bdry=   [HW,MTD] Flex-OneNAND    4133         onenand.bdry=   [HW,MTD] Flex-OneNAND Boundary Configuration
4152                                                  4134 
4153                         Format: [die0_boundar    4135                         Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4154                                                  4136 
4155                         boundary - index of l    4137                         boundary - index of last SLC block on Flex-OneNAND.
4156                                    The remain    4138                                    The remaining blocks are configured as MLC blocks.
4157                         lock     - Configure     4139                         lock     - Configure if Flex-OneNAND boundary should be locked.
4158                                    Once locke    4140                                    Once locked, the boundary cannot be changed.
4159                                    1 indicate    4141                                    1 indicates lock status, 0 indicates unlock status.
4160                                                  4142 
4161         oops=panic      [KNL,EARLY]           !! 4143         oops=panic      Always panic on oopses. Default is to just kill the
4162                         Always panic on oopse << 
4163                         process, but there is    4144                         process, but there is a small probability of
4164                         deadlocking the machi    4145                         deadlocking the machine.
4165                         This will also cause     4146                         This will also cause panics on machine check exceptions.
4166                         Useful together with     4147                         Useful together with panic=30 to trigger a reboot.
4167                                                  4148 
4168         page_alloc.shuffle=                      4149         page_alloc.shuffle=
4169                         [KNL] Boolean flag to    4150                         [KNL] Boolean flag to control whether the page allocator
4170                         should randomize its  !! 4151                         should randomize its free lists. The randomization may
4171                         used to enable/disabl !! 4152                         be automatically enabled if the kernel detects it is
4172                         the flag can be read  !! 4153                         running on a platform with a direct-mapped memory-side
                                                   >> 4154                         cache, and this parameter can be used to
                                                   >> 4155                         override/disable that behavior. The state of the flag
                                                   >> 4156                         can be read from sysfs at:
4173                         /sys/module/page_allo    4157                         /sys/module/page_alloc/parameters/shuffle.
4174                         This parameter is onl << 
4175                                                  4158 
4176         page_owner=     [KNL,EARLY] Boot-time !! 4159         page_owner=     [KNL] Boot-time page_owner enabling option.
4177                         Storage of the inform    4160                         Storage of the information about who allocated
4178                         each page is disabled    4161                         each page is disabled in default. With this switch,
4179                         we can turn it on.       4162                         we can turn it on.
4180                         on: enable the featur    4163                         on: enable the feature
4181                                                  4164 
4182         page_poison=    [KNL,EARLY] Boot-time !! 4165         page_poison=    [KNL] Boot-time parameter changing the state of
4183                         poisoning on the budd    4166                         poisoning on the buddy allocator, available with
4184                         CONFIG_PAGE_POISONING    4167                         CONFIG_PAGE_POISONING=y.
4185                         off: turn off poisoni    4168                         off: turn off poisoning (default)
4186                         on: turn on poisoning    4169                         on: turn on poisoning
4187                                                  4170 
4188         page_reporting.page_reporting_order=     4171         page_reporting.page_reporting_order=
4189                         [KNL] Minimal page re    4172                         [KNL] Minimal page reporting order
4190                         Format: <integer>        4173                         Format: <integer>
4191                         Adjust the minimal pa    4174                         Adjust the minimal page reporting order. The page
4192                         reporting is disabled    4175                         reporting is disabled when it exceeds MAX_PAGE_ORDER.
4193                                                  4176 
4194         panic=          [KNL] Kernel behaviou    4177         panic=          [KNL] Kernel behaviour on panic: delay <timeout>
4195                         timeout > 0: seconds     4178                         timeout > 0: seconds before rebooting
4196                         timeout = 0: wait for    4179                         timeout = 0: wait forever
4197                         timeout < 0: reboot i    4180                         timeout < 0: reboot immediately
4198                         Format: <timeout>        4181                         Format: <timeout>
4199                                                  4182 
4200         panic_on_taint= [KNL,EARLY]           !! 4183         panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4201                         Bitmask for condition << 
4202                         Format: <hex>[,nouser    4184                         Format: <hex>[,nousertaint]
4203                         Hexadecimal bitmask r    4185                         Hexadecimal bitmask representing the set of TAINT flags
4204                         that will cause the k    4186                         that will cause the kernel to panic when add_taint() is
4205                         called with any of th    4187                         called with any of the flags in this set.
4206                         The optional switch "    4188                         The optional switch "nousertaint" can be utilized to
4207                         prevent userspace for    4189                         prevent userspace forced crashes by writing to sysctl
4208                         /proc/sys/kernel/tain    4190                         /proc/sys/kernel/tainted any flagset matching with the
4209                         bitmask set on panic_    4191                         bitmask set on panic_on_taint.
4210                         See Documentation/adm    4192                         See Documentation/admin-guide/tainted-kernels.rst for
4211                         extra details on the     4193                         extra details on the taint flags that users can pick
4212                         to compose the bitmas    4194                         to compose the bitmask to assign to panic_on_taint.
4213                                                  4195 
4214         panic_on_warn=1 panic() instead of WA    4196         panic_on_warn=1 panic() instead of WARN().  Useful to cause kdump
4215                         on a WARN().             4197                         on a WARN().
4216                                                  4198 
4217         panic_print=    Bitmask for printing     4199         panic_print=    Bitmask for printing system info when panic happens.
4218                         User can chose combin    4200                         User can chose combination of the following bits:
4219                         bit 0: print all task    4201                         bit 0: print all tasks info
4220                         bit 1: print system m    4202                         bit 1: print system memory info
4221                         bit 2: print timer in    4203                         bit 2: print timer info
4222                         bit 3: print locks in    4204                         bit 3: print locks info if CONFIG_LOCKDEP is on
4223                         bit 4: print ftrace b    4205                         bit 4: print ftrace buffer
4224                         bit 5: print all prin    4206                         bit 5: print all printk messages in buffer
4225                         bit 6: print all CPUs    4207                         bit 6: print all CPUs backtrace (if available in the arch)
4226                         bit 7: print only tas << 
4227                         *Be aware* that this     4208                         *Be aware* that this option may print a _lot_ of lines,
4228                         so there are risks of    4209                         so there are risks of losing older messages in the log.
4229                         Use this option caref    4210                         Use this option carefully, maybe worth to setup a
4230                         bigger log buffer wit    4211                         bigger log buffer with "log_buf_len" along with this.
4231                                                  4212 
4232         parkbd.port=    [HW] Parallel port nu    4213         parkbd.port=    [HW] Parallel port number the keyboard adapter is
4233                         connected to, default    4214                         connected to, default is 0.
4234                         Format: <parport#>       4215                         Format: <parport#>
4235         parkbd.mode=    [HW] Parallel port ke    4216         parkbd.mode=    [HW] Parallel port keyboard adapter mode of operation,
4236                         0 for XT, 1 for AT (d    4217                         0 for XT, 1 for AT (default is AT).
4237                         Format: <mode>           4218                         Format: <mode>
4238                                                  4219 
4239         parport=        [HW,PPT] Specify para    4220         parport=        [HW,PPT] Specify parallel ports. 0 disables.
4240                         Format: { 0 | auto |     4221                         Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241                         Use 'auto' to force t    4222                         Use 'auto' to force the driver to use any
4242                         IRQ/DMA settings dete    4223                         IRQ/DMA settings detected (the default is to
4243                         ignore detected IRQ/D    4224                         ignore detected IRQ/DMA settings because of
4244                         possible conflicts).     4225                         possible conflicts). You can specify the base
4245                         address, IRQ, and DMA    4226                         address, IRQ, and DMA settings; IRQ and DMA
4246                         should be numbers, or    4227                         should be numbers, or 'auto' (for using detected
4247                         settings on that part    4228                         settings on that particular port), or 'nofifo'
4248                         (to avoid using a FIF    4229                         (to avoid using a FIFO even if it is detected).
4249                         Parallel ports are as    4230                         Parallel ports are assigned in the order they
4250                         are specified on the     4231                         are specified on the command line, starting
4251                         with parport0.           4232                         with parport0.
4252                                                  4233 
4253         parport_init_mode=      [HW,PPT]         4234         parport_init_mode=      [HW,PPT]
4254                         Configure VIA paralle    4235                         Configure VIA parallel port to operate in
4255                         a specific mode. This    4236                         a specific mode. This is necessary on Pegasos
4256                         computer where firmwa    4237                         computer where firmware has no options for setting
4257                         up parallel port mode    4238                         up parallel port mode and sets it to spp.
4258                         Currently this functi    4239                         Currently this function knows 686a and 8231 chips.
4259                         Format: [spp|ps2|epp|    4240                         Format: [spp|ps2|epp|ecp|ecpepp]
4260                                                  4241 
4261         pata_legacy.all=        [HW,LIBATA]      4242         pata_legacy.all=        [HW,LIBATA]
4262                         Format: <int>            4243                         Format: <int>
4263                         Set to non-zero to pr    4244                         Set to non-zero to probe primary and secondary ISA
4264                         port ranges on PCI sy    4245                         port ranges on PCI systems where no PCI PATA device
4265                         has been found at eit    4246                         has been found at either range.  Disabled by default.
4266                                                  4247 
4267         pata_legacy.autospeed=  [HW,LIBATA]      4248         pata_legacy.autospeed=  [HW,LIBATA]
4268                         Format: <int>            4249                         Format: <int>
4269                         Set to non-zero if a     4250                         Set to non-zero if a chip is present that snoops speed
4270                         changes.  Disabled by    4251                         changes.  Disabled by default.
4271                                                  4252 
4272         pata_legacy.ht6560a=    [HW,LIBATA]      4253         pata_legacy.ht6560a=    [HW,LIBATA]
4273                         Format: <int>            4254                         Format: <int>
4274                         Set to 1, 2, or 3 for    4255                         Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275                         the secondary channel    4256                         the secondary channel, or both channels respectively.
4276                         Disabled by default.     4257                         Disabled by default.
4277                                                  4258 
4278         pata_legacy.ht6560b=    [HW,LIBATA]      4259         pata_legacy.ht6560b=    [HW,LIBATA]
4279                         Format: <int>            4260                         Format: <int>
4280                         Set to 1, 2, or 3 for    4261                         Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281                         the secondary channel    4262                         the secondary channel, or both channels respectively.
4282                         Disabled by default.     4263                         Disabled by default.
4283                                                  4264 
4284         pata_legacy.iordy_mask= [HW,LIBATA]      4265         pata_legacy.iordy_mask= [HW,LIBATA]
4285                         Format: <int>            4266                         Format: <int>
4286                         IORDY enable mask.  S    4267                         IORDY enable mask.  Set individual bits to allow IORDY
4287                         for the respective ch    4268                         for the respective channel.  Bit 0 is for the first
4288                         legacy channel handle    4269                         legacy channel handled by this driver, bit 1 is for
4289                         the second channel, a    4270                         the second channel, and so on.  The sequence will often
4290                         correspond to the pri    4271                         correspond to the primary legacy channel, the secondary
4291                         legacy channel, and s    4272                         legacy channel, and so on, but the handling of a PCI
4292                         bus and the use of ot    4273                         bus and the use of other driver options may interfere
4293                         with the sequence.  B    4274                         with the sequence.  By default IORDY is allowed across
4294                         all channels.            4275                         all channels.
4295                                                  4276 
4296         pata_legacy.opti82c46x= [HW,LIBATA]      4277         pata_legacy.opti82c46x= [HW,LIBATA]
4297                         Format: <int>            4278                         Format: <int>
4298                         Set to 1, 2, or 3 for    4279                         Set to 1, 2, or 3 for Opti 82c611A on the primary
4299                         channel, the secondar    4280                         channel, the secondary channel, or both channels
4300                         respectively.  Disabl    4281                         respectively.  Disabled by default.
4301                                                  4282 
4302         pata_legacy.opti82c611a=        [HW,L    4283         pata_legacy.opti82c611a=        [HW,LIBATA]
4303                         Format: <int>            4284                         Format: <int>
4304                         Set to 1, 2, or 3 for    4285                         Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305                         channel, the secondar    4286                         channel, the secondary channel, or both channels
4306                         respectively.  Disabl    4287                         respectively.  Disabled by default.
4307                                                  4288 
4308         pata_legacy.pio_mask=   [HW,LIBATA]      4289         pata_legacy.pio_mask=   [HW,LIBATA]
4309                         Format: <int>            4290                         Format: <int>
4310                         PIO mode mask for aut    4291                         PIO mode mask for autospeed devices.  Set individual
4311                         bits to allow the use    4292                         bits to allow the use of the respective PIO modes.
4312                         Bit 0 is for mode 0,     4293                         Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313                         All modes allowed by     4294                         All modes allowed by default.
4314                                                  4295 
4315         pata_legacy.probe_all=  [HW,LIBATA]      4296         pata_legacy.probe_all=  [HW,LIBATA]
4316                         Format: <int>            4297                         Format: <int>
4317                         Set to non-zero to pr    4298                         Set to non-zero to probe tertiary and further ISA
4318                         port ranges on PCI sy    4299                         port ranges on PCI systems.  Disabled by default.
4319                                                  4300 
4320         pata_legacy.probe_mask= [HW,LIBATA]      4301         pata_legacy.probe_mask= [HW,LIBATA]
4321                         Format: <int>            4302                         Format: <int>
4322                         Probe mask for legacy    4303                         Probe mask for legacy ISA PATA ports.  Depending on
4323                         platform configuratio    4304                         platform configuration and the use of other driver
4324                         options up to 6 legac    4305                         options up to 6 legacy ports are supported: 0x1f0,
4325                         0x170, 0x1e8, 0x168,     4306                         0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326                         of individual ports c    4307                         of individual ports can be disabled by setting the
4327                         corresponding bits in    4308                         corresponding bits in the mask to 1.  Bit 0 is for
4328                         the first port in the    4309                         the first port in the list above (0x1f0), and so on.
4329                         By default all suppor    4310                         By default all supported ports are probed.
4330                                                  4311 
4331         pata_legacy.qdi=        [HW,LIBATA]      4312         pata_legacy.qdi=        [HW,LIBATA]
4332                         Format: <int>            4313                         Format: <int>
4333                         Set to non-zero to pr    4314                         Set to non-zero to probe QDI controllers.  By default
4334                         set to 1 if CONFIG_PA    4315                         set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335                                                  4316 
4336         pata_legacy.winbond=    [HW,LIBATA]      4317         pata_legacy.winbond=    [HW,LIBATA]
4337                         Format: <int>            4318                         Format: <int>
4338                         Set to non-zero to pr    4319                         Set to non-zero to probe Winbond controllers.  Use
4339                         the standard I/O port    4320                         the standard I/O port (0x130) if 1, otherwise the
4340                         value given is the I/    4321                         value given is the I/O port to use (typically 0x1b0).
4341                         By default set to 1 i    4322                         By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342                         0 otherwise.             4323                         0 otherwise.
4343                                                  4324 
4344         pata_platform.pio_mask= [HW,LIBATA]      4325         pata_platform.pio_mask= [HW,LIBATA]
4345                         Format: <int>            4326                         Format: <int>
4346                         Supported PIO mode ma    4327                         Supported PIO mode mask.  Set individual bits to allow
4347                         the use of the respec    4328                         the use of the respective PIO modes.  Bit 0 is for
4348                         mode 0, bit 1 is for     4329                         mode 0, bit 1 is for mode 1, and so on.  Mode 0 only
4349                         allowed by default.      4330                         allowed by default.
4350                                                  4331 
4351         pause_on_oops=<int>                      4332         pause_on_oops=<int>
4352                         Halt all CPUs after t    4333                         Halt all CPUs after the first oops has been printed for
4353                         the specified number     4334                         the specified number of seconds.  This is to be used if
4354                         your oopses keep scro    4335                         your oopses keep scrolling off the screen.
4355                                                  4336 
4356         pcbit=          [HW,ISDN]                4337         pcbit=          [HW,ISDN]
4357                                                  4338 
4358         pci=option[,option...]  [PCI,EARLY] v !! 4339         pci=option[,option...]  [PCI] various PCI subsystem options.
4359                                                  4340 
4360                                 Some options     4341                                 Some options herein operate on a specific device
4361                                 or a set of d    4342                                 or a set of devices (<pci_dev>). These are
4362                                 specified in     4343                                 specified in one of the following formats:
4363                                                  4344 
4364                                 [<domain>:]<b    4345                                 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365                                 pci:<vendor>:    4346                                 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366                                                  4347 
4367                                 Note: the fir    4348                                 Note: the first format specifies a PCI
4368                                 bus/device/fu    4349                                 bus/device/function address which may change
4369                                 if new hardwa    4350                                 if new hardware is inserted, if motherboard
4370                                 firmware chan    4351                                 firmware changes, or due to changes caused
4371                                 by other kern    4352                                 by other kernel parameters. If the
4372                                 domain is lef    4353                                 domain is left unspecified, it is
4373                                 taken to be z    4354                                 taken to be zero. Optionally, a path
4374                                 to a device t    4355                                 to a device through multiple device/function
4375                                 addresses can    4356                                 addresses can be specified after the base
4376                                 address (this    4357                                 address (this is more robust against
4377                                 renumbering i    4358                                 renumbering issues).  The second format
4378                                 selects devic    4359                                 selects devices using IDs from the
4379                                 configuration    4360                                 configuration space which may match multiple
4380                                 devices in th    4361                                 devices in the system.
4381                                                  4362 
4382                 earlydump       dump PCI conf    4363                 earlydump       dump PCI config space before the kernel
4383                                 changes anyth    4364                                 changes anything
4384                 off             [X86] don't p    4365                 off             [X86] don't probe for the PCI bus
4385                 bios            [X86-32] forc    4366                 bios            [X86-32] force use of PCI BIOS, don't access
4386                                 the hardware     4367                                 the hardware directly. Use this if your machine
4387                                 has a non-sta    4368                                 has a non-standard PCI host bridge.
4388                 nobios          [X86-32] disa    4369                 nobios          [X86-32] disallow use of PCI BIOS, only direct
4389                                 hardware acce    4370                                 hardware access methods are allowed. Use this
4390                                 if you experi    4371                                 if you experience crashes upon bootup and you
4391                                 suspect they     4372                                 suspect they are caused by the BIOS.
4392                 conf1           [X86] Force u    4373                 conf1           [X86] Force use of PCI Configuration Access
4393                                 Mechanism 1 (    4374                                 Mechanism 1 (config address in IO port 0xCF8,
4394                                 data in IO po    4375                                 data in IO port 0xCFC, both 32-bit).
4395                 conf2           [X86] Force u    4376                 conf2           [X86] Force use of PCI Configuration Access
4396                                 Mechanism 2 (    4377                                 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397                                 the function,    4378                                 the function, IO port 0xCFA, also 8-bit, sets
4398                                 bus number. T    4379                                 bus number. The config space is then accessed
4399                                 through ports    4380                                 through ports 0xC000-0xCFFF).
4400                                 See http://wi    4381                                 See http://wiki.osdev.org/PCI for more info
4401                                 on the config    4382                                 on the configuration access mechanisms.
4402                 noaer           [PCIE] If the    4383                 noaer           [PCIE] If the PCIEAER kernel config parameter is
4403                                 enabled, this    4384                                 enabled, this kernel boot option can be used to
4404                                 disable the u    4385                                 disable the use of PCIE advanced error reporting.
4405                 nodomains       [PCI] Disable    4386                 nodomains       [PCI] Disable support for multiple PCI
4406                                 root domains     4387                                 root domains (aka PCI segments, in ACPI-speak).
4407                 nommconf        [X86] Disable    4388                 nommconf        [X86] Disable use of MMCONFIG for PCI
4408                                 Configuration    4389                                 Configuration
4409                 check_enable_amd_mmconf [X86]    4390                 check_enable_amd_mmconf [X86] check for and enable
4410                                 properly conf    4391                                 properly configured MMIO access to PCI
4411                                 config space     4392                                 config space on AMD family 10h CPU
4412                 nomsi           [MSI] If the     4393                 nomsi           [MSI] If the PCI_MSI kernel config parameter is
4413                                 enabled, this    4394                                 enabled, this kernel boot option can be used to
4414                                 disable the u    4395                                 disable the use of MSI interrupts system-wide.
4415                 noioapicquirk   [APIC] Disabl    4396                 noioapicquirk   [APIC] Disable all boot interrupt quirks.
4416                                 Safety option    4397                                 Safety option to keep boot IRQs enabled. This
4417                                 should never     4398                                 should never be necessary.
4418                 ioapicreroute   [APIC] Enable    4399                 ioapicreroute   [APIC] Enable rerouting of boot IRQs to the
4419                                 primary IO-AP    4400                                 primary IO-APIC for bridges that cannot disable
4420                                 boot IRQs. Th    4401                                 boot IRQs. This fixes a source of spurious IRQs
4421                                 when the syst    4402                                 when the system masks IRQs.
4422                 noioapicreroute [APIC] Disabl    4403                 noioapicreroute [APIC] Disable workaround that uses the
4423                                 boot IRQ equi    4404                                 boot IRQ equivalent of an IRQ that connects to
4424                                 a chipset whe    4405                                 a chipset where boot IRQs cannot be disabled.
4425                                 The opposite     4406                                 The opposite of ioapicreroute.
4426                 biosirq         [X86-32] Use     4407                 biosirq         [X86-32] Use PCI BIOS calls to get the interrupt
4427                                 routing table    4408                                 routing table. These calls are known to be buggy
4428                                 on several ma    4409                                 on several machines and they hang the machine
4429                                 when used, bu    4410                                 when used, but on other computers it's the only
4430                                 way to get th    4411                                 way to get the interrupt routing table. Try
4431                                 this option i    4412                                 this option if the kernel is unable to allocate
4432                                 IRQs or disco    4413                                 IRQs or discover secondary PCI buses on your
4433                                 motherboard.     4414                                 motherboard.
4434                 rom             [X86] Assign     4415                 rom             [X86] Assign address space to expansion ROMs.
4435                                 Use with caut    4416                                 Use with caution as certain devices share
4436                                 address decod    4417                                 address decoders between ROMs and other
4437                                 resources.       4418                                 resources.
4438                 norom           [X86] Do not     4419                 norom           [X86] Do not assign address space to
4439                                 expansion ROM    4420                                 expansion ROMs that do not already have
4440                                 BIOS assigned    4421                                 BIOS assigned address ranges.
4441                 nobar           [X86] Do not     4422                 nobar           [X86] Do not assign address space to the
4442                                 BARs that wer    4423                                 BARs that weren't assigned by the BIOS.
4443                 irqmask=0xMMMM  [X86] Set a b    4424                 irqmask=0xMMMM  [X86] Set a bit mask of IRQs allowed to be
4444                                 assigned auto    4425                                 assigned automatically to PCI devices. You can
4445                                 make the kern    4426                                 make the kernel exclude IRQs of your ISA cards
4446                                 this way.        4427                                 this way.
4447                 pirqaddr=0xAAAAA        [X86]    4428                 pirqaddr=0xAAAAA        [X86] Specify the physical address
4448                                 of the PIRQ t    4429                                 of the PIRQ table (normally generated
4449                                 by the BIOS)     4430                                 by the BIOS) if it is outside the
4450                                 F0000h-100000    4431                                 F0000h-100000h range.
4451                 lastbus=N       [X86] Scan al    4432                 lastbus=N       [X86] Scan all buses thru bus #N. Can be
4452                                 useful if the    4433                                 useful if the kernel is unable to find your
4453                                 secondary bus    4434                                 secondary buses and you want to tell it
4454                                 explicitly wh    4435                                 explicitly which ones they are.
4455                 assign-busses   [X86] Always     4436                 assign-busses   [X86] Always assign all PCI bus
4456                                 numbers ourse    4437                                 numbers ourselves, overriding
4457                                 whatever the     4438                                 whatever the firmware may have done.
4458                 usepirqmask     [X86] Honor t    4439                 usepirqmask     [X86] Honor the possible IRQ mask stored
4459                                 in the BIOS $    4440                                 in the BIOS $PIR table. This is needed on
4460                                 some systems     4441                                 some systems with broken BIOSes, notably
4461                                 some HP Pavil    4442                                 some HP Pavilion N5400 and Omnibook XE3
4462                                 notebooks. Th    4443                                 notebooks. This will have no effect if ACPI
4463                                 IRQ routing i    4444                                 IRQ routing is enabled.
4464                 noacpi          [X86] Do not     4445                 noacpi          [X86] Do not use ACPI for IRQ routing
4465                                 or for PCI sc    4446                                 or for PCI scanning.
4466                 use_crs         [X86] Use PCI    4447                 use_crs         [X86] Use PCI host bridge window information
4467                                 from ACPI.  O    4448                                 from ACPI.  On BIOSes from 2008 or later, this
4468                                 is enabled by    4449                                 is enabled by default.  If you need to use this,
4469                                 please report    4450                                 please report a bug.
4470                 nocrs           [X86] Ignore     4451                 nocrs           [X86] Ignore PCI host bridge windows from ACPI.
4471                                 If you need t    4452                                 If you need to use this, please report a bug.
4472                 use_e820        [X86] Use E82    4453                 use_e820        [X86] Use E820 reservations to exclude parts of
4473                                 PCI host brid    4454                                 PCI host bridge windows. This is a workaround
4474                                 for BIOS defe    4455                                 for BIOS defects in host bridge _CRS methods.
4475                                 If you need t    4456                                 If you need to use this, please report a bug to
4476                                 <linux-pci@vge    4457                                 <linux-pci@vger.kernel.org>.
4477                 no_e820         [X86] Ignore     4458                 no_e820         [X86] Ignore E820 reservations for PCI host
4478                                 bridge window    4459                                 bridge windows. This is the default on modern
4479                                 hardware. If     4460                                 hardware. If you need to use this, please report
4480                                 a bug to <linu    4461                                 a bug to <linux-pci@vger.kernel.org>.
4481                 routeirq        Do IRQ routin    4462                 routeirq        Do IRQ routing for all PCI devices.
4482                                 This is norma    4463                                 This is normally done in pci_enable_device(),
4483                                 so this optio    4464                                 so this option is a temporary workaround
4484                                 for broken dr    4465                                 for broken drivers that don't call it.
4485                 skip_isa_align  [X86] do not     4466                 skip_isa_align  [X86] do not align io start addr, so can
4486                                 handle more p    4467                                 handle more pci cards
4487                 noearly         [X86] Don't d    4468                 noearly         [X86] Don't do any early type 1 scanning.
4488                                 This might he    4469                                 This might help on some broken boards which
4489                                 machine check    4470                                 machine check when some devices' config space
4490                                 is read. But     4471                                 is read. But various workarounds are disabled
4491                                 and some IOMM    4472                                 and some IOMMU drivers will not work.
4492                 bfsort          Sort PCI devi    4473                 bfsort          Sort PCI devices into breadth-first order.
4493                                 This sorting     4474                                 This sorting is done to get a device
4494                                 order compati    4475                                 order compatible with older (<= 2.4) kernels.
4495                 nobfsort        Don't sort PC    4476                 nobfsort        Don't sort PCI devices into breadth-first order.
4496                 pcie_bus_tune_off       Disab    4477                 pcie_bus_tune_off       Disable PCIe MPS (Max Payload Size)
4497                                 tuning and us    4478                                 tuning and use the BIOS-configured MPS defaults.
4498                 pcie_bus_safe   Set every dev    4479                 pcie_bus_safe   Set every device's MPS to the largest value
4499                                 supported by     4480                                 supported by all devices below the root complex.
4500                 pcie_bus_perf   Set device MP    4481                 pcie_bus_perf   Set device MPS to the largest allowable MPS
4501                                 based on its     4482                                 based on its parent bus. Also set MRRS (Max
4502                                 Read Request     4483                                 Read Request Size) to the largest supported
4503                                 value (no lar    4484                                 value (no larger than the MPS that the device
4504                                 or bus can su    4485                                 or bus can support) for best performance.
4505                 pcie_bus_peer2peer      Set e    4486                 pcie_bus_peer2peer      Set every device's MPS to 128B, which
4506                                 every device     4487                                 every device is guaranteed to support. This
4507                                 configuration    4488                                 configuration allows peer-to-peer DMA between
4508                                 any pair of d    4489                                 any pair of devices, possibly at the cost of
4509                                 reduced perfo    4490                                 reduced performance.  This also guarantees
4510                                 that hot-adde    4491                                 that hot-added devices will work.
4511                 cbiosize=nn[KMG]        The f    4492                 cbiosize=nn[KMG]        The fixed amount of bus space which is
4512                                 reserved for     4493                                 reserved for the CardBus bridge's IO window.
4513                                 The default v    4494                                 The default value is 256 bytes.
4514                 cbmemsize=nn[KMG]       The f    4495                 cbmemsize=nn[KMG]       The fixed amount of bus space which is
4515                                 reserved for     4496                                 reserved for the CardBus bridge's memory
4516                                 window. The d    4497                                 window. The default value is 64 megabytes.
4517                 resource_alignment=              4498                 resource_alignment=
4518                                 Format:          4499                                 Format:
4519                                 [<order of ali    4500                                 [<order of align>@]<pci_dev>[; ...]
4520                                 Specifies ali    4501                                 Specifies alignment and device to reassign
4521                                 aligned memor    4502                                 aligned memory resources. How to
4522                                 specify the d    4503                                 specify the device is described above.
4523                                 If <order of     4504                                 If <order of align> is not specified,
4524                                 PAGE_SIZE is     4505                                 PAGE_SIZE is used as alignment.
4525                                 A PCI-PCI bri    4506                                 A PCI-PCI bridge can be specified if resource
4526                                 windows need     4507                                 windows need to be expanded.
4527                                 To specify th    4508                                 To specify the alignment for several
4528                                 instances of     4509                                 instances of a device, the PCI vendor,
4529                                 device, subve    4510                                 device, subvendor, and subdevice may be
4530                                 specified, e.    4511                                 specified, e.g., 12@pci:8086:9c22:103c:198f
4531                                 for 4096-byte    4512                                 for 4096-byte alignment.
4532                 ecrc=           Enable/disabl    4513                 ecrc=           Enable/disable PCIe ECRC (transaction layer
4533                                 end-to-end CR    4514                                 end-to-end CRC checking). Only effective if
4534                                 OS has native    4515                                 OS has native AER control (either granted by
4535                                 ACPI _OSC or     4516                                 ACPI _OSC or forced via "pcie_ports=native")
4536                                 bios: Use BIO    4517                                 bios: Use BIOS/firmware settings. This is the
4537                                 the default.     4518                                 the default.
4538                                 off: Turn ECR    4519                                 off: Turn ECRC off
4539                                 on: Turn ECRC    4520                                 on: Turn ECRC on.
4540                 hpiosize=nn[KMG]        The f    4521                 hpiosize=nn[KMG]        The fixed amount of bus space which is
4541                                 reserved for     4522                                 reserved for hotplug bridge's IO window.
4542                                 Default size     4523                                 Default size is 256 bytes.
4543                 hpmmiosize=nn[KMG]      The f    4524                 hpmmiosize=nn[KMG]      The fixed amount of bus space which is
4544                                 reserved for     4525                                 reserved for hotplug bridge's MMIO window.
4545                                 Default size     4526                                 Default size is 2 megabytes.
4546                 hpmmioprefsize=nn[KMG]  The f    4527                 hpmmioprefsize=nn[KMG]  The fixed amount of bus space which is
4547                                 reserved for     4528                                 reserved for hotplug bridge's MMIO_PREF window.
4548                                 Default size     4529                                 Default size is 2 megabytes.
4549                 hpmemsize=nn[KMG]       The f    4530                 hpmemsize=nn[KMG]       The fixed amount of bus space which is
4550                                 reserved for     4531                                 reserved for hotplug bridge's MMIO and
4551                                 MMIO_PREF win    4532                                 MMIO_PREF window.
4552                                 Default size     4533                                 Default size is 2 megabytes.
4553                 hpbussize=nn    The minimum a    4534                 hpbussize=nn    The minimum amount of additional bus numbers
4554                                 reserved for     4535                                 reserved for buses below a hotplug bridge.
4555                                 Default is 1.    4536                                 Default is 1.
4556                 realloc=        Enable/disabl    4537                 realloc=        Enable/disable reallocating PCI bridge resources
4557                                 if allocation    4538                                 if allocations done by BIOS are too small to
4558                                 accommodate r    4539                                 accommodate resources required by all child
4559                                 devices.         4540                                 devices.
4560                                 off: Turn rea    4541                                 off: Turn realloc off
4561                                 on: Turn real    4542                                 on: Turn realloc on
4562                 realloc         same as reall    4543                 realloc         same as realloc=on
4563                 noari           do not use PC    4544                 noari           do not use PCIe ARI.
4564                 noats           [PCIE, Intel-    4545                 noats           [PCIE, Intel-IOMMU, AMD-IOMMU]
4565                                 do not use PC    4546                                 do not use PCIe ATS (and IOMMU device IOTLB).
4566                 pcie_scan_all   Scan all poss    4547                 pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
4567                                 only look for    4548                                 only look for one device below a PCIe downstream
4568                                 port.            4549                                 port.
4569                 big_root_window Try to add a     4550                 big_root_window Try to add a big 64bit memory window to the PCIe
4570                                 root complex     4551                                 root complex on AMD CPUs. Some GFX hardware
4571                                 can resize a     4552                                 can resize a BAR to allow access to all VRAM.
4572                                 Adding the wi    4553                                 Adding the window is slightly risky (it may
4573                                 conflict with    4554                                 conflict with unreported devices), so this
4574                                 taints the ke    4555                                 taints the kernel.
4575                 disable_acs_redir=<pci_dev>[;    4556                 disable_acs_redir=<pci_dev>[; ...]
4576                                 Specify one o    4557                                 Specify one or more PCI devices (in the format
4577                                 specified abo    4558                                 specified above) separated by semicolons.
4578                                 Each device s    4559                                 Each device specified will have the PCI ACS
4579                                 redirect capa    4560                                 redirect capabilities forced off which will
4580                                 allow P2P tra    4561                                 allow P2P traffic between devices through
4581                                 bridges witho    4562                                 bridges without forcing it upstream. Note:
4582                                 this removes     4563                                 this removes isolation between devices and
4583                                 may put more     4564                                 may put more devices in an IOMMU group.
4584                 config_acs=                   << 
4585                                 Format:       << 
4586                                 <ACS flags>@<p << 
4587                                 Specify one o << 
4588                                 specified abo << 
4589                                 and separated << 
4590                                 capabilities  << 
4591                                 unchanged bas << 
4592                                 flags.        << 
4593                                               << 
4594                                 ACS Flags is  << 
4595                                   bit-0 : ACS << 
4596                                   bit-1 : ACS << 
4597                                   bit-2 : ACS << 
4598                                   bit-3 : ACS << 
4599                                   bit-4 : ACS << 
4600                                   bit-5 : ACS << 
4601                                   bit-6 : ACS << 
4602                                 Each bit can  << 
4603                                   '0' – for << 
4604                                   '1' – for << 
4605                                   'x' – unc << 
4606                                 For example,  << 
4607                                   pci=config_ << 
4608                                 would configu << 
4609                                 ACS to enable << 
4610                                 Translation B << 
4611                                 Validation un << 
4612                                 or firmware s << 
4613                                               << 
4614                                 Note: this ma << 
4615                                 and may put m << 
4616                 force_floating  [S390] Force     4565                 force_floating  [S390] Force usage of floating interrupts.
4617                 nomio           [S390] Do not    4566                 nomio           [S390] Do not use MIO instructions.
4618                 norid           [S390] ignore    4567                 norid           [S390] ignore the RID field and force use of
4619                                 one PCI domai    4568                                 one PCI domain per PCI function
4620                                                  4569 
4621         pcie_aspm=      [PCIE] Forcibly enabl !! 4570         pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
4622                         Management.              4571                         Management.
4623                 off     Don't touch ASPM conf !! 4572                 off     Disable ASPM.
4624                         configuration done by << 
4625                 force   Enable ASPM even on d    4573                 force   Enable ASPM even on devices that claim not to support it.
4626                         WARNING: Forcing ASPM    4574                         WARNING: Forcing ASPM on may cause system lockups.
4627                                                  4575 
4628         pcie_ports=     [PCIE] PCIe port serv    4576         pcie_ports=     [PCIE] PCIe port services handling:
4629                 native  Use native PCIe servi    4577                 native  Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630                         even if the platform     4578                         even if the platform doesn't give the OS permission to
4631                         use them.  This may c    4579                         use them.  This may cause conflicts if the platform
4632                         also tries to use the    4580                         also tries to use these services.
4633                 dpc-native      Use native PC    4581                 dpc-native      Use native PCIe service for DPC only.  May
4634                                 cause conflic    4582                                 cause conflicts if firmware uses AER or DPC.
4635                 compat  Disable native PCIe s    4583                 compat  Disable native PCIe services (PME, AER, DPC, PCIe
4636                         hotplug).                4584                         hotplug).
4637                                                  4585 
4638         pcie_port_pm=   [PCIE] PCIe port powe    4586         pcie_port_pm=   [PCIE] PCIe port power management handling:
4639                 off     Disable power managem    4587                 off     Disable power management of all PCIe ports
4640                 force   Forcibly enable power    4588                 force   Forcibly enable power management of all PCIe ports
4641                                                  4589 
4642         pcie_pme=       [PCIE,PM] Native PCIe    4590         pcie_pme=       [PCIE,PM] Native PCIe PME signaling options:
4643                 nomsi   Do not use MSI for na    4591                 nomsi   Do not use MSI for native PCIe PME signaling (this makes
4644                         all PCIe root ports u    4592                         all PCIe root ports use INTx for all services).
4645                                                  4593 
4646         pcmv=           [HW,PCMCIA] BadgePAD     4594         pcmv=           [HW,PCMCIA] BadgePAD 4
4647                                                  4595 
4648         pd_ignore_unused                         4596         pd_ignore_unused
4649                         [PM]                     4597                         [PM]
4650                         Keep all power-domain    4598                         Keep all power-domains already enabled by bootloader on,
4651                         even if no driver has    4599                         even if no driver has claimed them. This is useful
4652                         for debug and develop    4600                         for debug and development, but should not be
4653                         needed on a platform     4601                         needed on a platform with proper driver support.
4654                                                  4602 
4655         pdcchassis=     [PARISC,HW] Disable/E    4603         pdcchassis=     [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656                         boot time.               4604                         boot time.
4657                         Format: { 0 | 1 }        4605                         Format: { 0 | 1 }
4658                         See arch/parisc/kerne    4606                         See arch/parisc/kernel/pdc_chassis.c
4659                                                  4607 
4660         percpu_alloc=   [MM,EARLY]            !! 4608         percpu_alloc=   Select which percpu first chunk allocator to use.
4661                         Select which percpu f << 
4662                         Currently supported v    4609                         Currently supported values are "embed" and "page".
4663                         Archs may support sub    4610                         Archs may support subset or none of the selections.
4664                         See comments in mm/pe    4611                         See comments in mm/percpu.c for details on each
4665                         allocator.  This para    4612                         allocator.  This parameter is primarily for debugging
4666                         and performance compa    4613                         and performance comparison.
4667                                                  4614 
4668         pirq=           [SMP,APIC] Manual mp-    4615         pirq=           [SMP,APIC] Manual mp-table setup
4669                         See Documentation/arc    4616                         See Documentation/arch/x86/i386/IO-APIC.rst.
4670                                                  4617 
4671         plip=           [PPT,NET] Parallel po    4618         plip=           [PPT,NET] Parallel port network link
4672                         Format: { parport<nr>    4619                         Format: { parport<nr> | timid | 0 }
4673                         See also Documentatio    4620                         See also Documentation/admin-guide/parport.rst.
4674                                                  4621 
4675         pmtmr=          [X86] Manual setup of    4622         pmtmr=          [X86] Manual setup of pmtmr I/O Port.
4676                         Override pmtimer IOPo    4623                         Override pmtimer IOPort with a hex value.
4677                         e.g. pmtmr=0x508         4624                         e.g. pmtmr=0x508
4678                                                  4625 
4679         pmu_override=   [PPC] Override the PM    4626         pmu_override=   [PPC] Override the PMU.
4680                         This option takes ove    4627                         This option takes over the PMU facility, so it is no
4681                         longer usable by perf    4628                         longer usable by perf. Setting this option starts the
4682                         PMU counters by setti    4629                         PMU counters by setting MMCR0 to 0 (the FC bit is
4683                         cleared). If a number    4630                         cleared). If a number is given, then MMCR1 is set to
4684                         that number, otherwis    4631                         that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4685                         remains 0.               4632                         remains 0.
4686                                                  4633 
4687         pm_debug_messages       [SUSPEND,KNL]    4634         pm_debug_messages       [SUSPEND,KNL]
4688                         Enable suspend/resume    4635                         Enable suspend/resume debug messages during boot up.
4689                                                  4636 
4690         pnp.debug=1     [PNP]                    4637         pnp.debug=1     [PNP]
4691                         Enable PNP debug mess    4638                         Enable PNP debug messages (depends on the
4692                         CONFIG_PNP_DEBUG_MESS    4639                         CONFIG_PNP_DEBUG_MESSAGES option).  Change at run-time
4693                         via /sys/module/pnp/p    4640                         via /sys/module/pnp/parameters/debug.  We always show
4694                         current resource usag    4641                         current resource usage; turning this on also shows
4695                         possible settings and    4642                         possible settings and some assignment information.
4696                                                  4643 
4697         pnpacpi=        [ACPI]                   4644         pnpacpi=        [ACPI]
4698                         { off }                  4645                         { off }
4699                                                  4646 
4700         pnpbios=        [ISAPNP]                 4647         pnpbios=        [ISAPNP]
4701                         { on | off | curr | r    4648                         { on | off | curr | res | no-curr | no-res }
4702                                                  4649 
4703         pnp_reserve_irq=                         4650         pnp_reserve_irq=
4704                         [ISAPNP] Exclude IRQs    4651                         [ISAPNP] Exclude IRQs for the autoconfiguration
4705                                                  4652 
4706         pnp_reserve_dma=                         4653         pnp_reserve_dma=
4707                         [ISAPNP] Exclude DMAs    4654                         [ISAPNP] Exclude DMAs for the autoconfiguration
4708                                                  4655 
4709         pnp_reserve_io= [ISAPNP] Exclude I/O     4656         pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710                         Ranges are in pairs (    4657                         Ranges are in pairs (I/O port base and size).
4711                                                  4658 
4712         pnp_reserve_mem=                         4659         pnp_reserve_mem=
4713                         [ISAPNP] Exclude memo    4660                         [ISAPNP] Exclude memory regions for the
4714                         autoconfiguration.       4661                         autoconfiguration.
4715                         Ranges are in pairs (    4662                         Ranges are in pairs (memory base and size).
4716                                                  4663 
4717         ports=          [IP_VS_FTP] IPVS ftp     4664         ports=          [IP_VS_FTP] IPVS ftp helper module
4718                         Default is 21.           4665                         Default is 21.
4719                         Up to 8 (IP_VS_APP_MA    4666                         Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720                         may be specified.        4667                         may be specified.
4721                         Format: <port>,<port>    4668                         Format: <port>,<port>....
4722                                                  4669 
4723         possible_cpus=  [SMP,S390,X86]        << 
4724                         Format: <unsigned int << 
4725                         Set the number of pos << 
4726                         regular discovery mec << 
4727                                               << 
4728         powersave=off   [PPC] This option dis    4670         powersave=off   [PPC] This option disables power saving features.
4729                         It specifically disab    4671                         It specifically disables cpuidle and sets the
4730                         platform machine desc    4672                         platform machine description specific power_save
4731                         function to NULL. On     4673                         function to NULL. On Idle the CPU just reduces
4732                         execution priority.      4674                         execution priority.
4733                                                  4675 
4734         ppc_strict_facility_enable               4676         ppc_strict_facility_enable
4735                         [PPC,ENABLE] This opt !! 4677                         [PPC] This option catches any kernel floating point,
4736                         Altivec, VSX and SPE     4678                         Altivec, VSX and SPE outside of regions specifically
4737                         allowed (eg kernel_en    4679                         allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738                         There is some perform    4680                         There is some performance impact when enabling this.
4739                                                  4681 
4740         ppc_tm=         [PPC,EARLY]           !! 4682         ppc_tm=         [PPC]
4741                         Format: {"off"}          4683                         Format: {"off"}
4742                         Disable Hardware Tran    4684                         Disable Hardware Transactional Memory
4743                                                  4685 
4744         preempt=        [KNL]                    4686         preempt=        [KNL]
4745                         Select preemption mod    4687                         Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746                         none - Limited to con    4688                         none - Limited to cond_resched() calls
4747                         voluntary - Limited t    4689                         voluntary - Limited to cond_resched() and might_sleep() calls
4748                         full - Any section th    4690                         full - Any section that isn't explicitly preempt disabled
4749                                can be preempt !! 4691                                can be preempted anytime.
4750                                contended spin << 
4751                                explicitly pre << 
4752                                                  4692 
4753         print-fatal-signals=                     4693         print-fatal-signals=
4754                         [KNL] debug: print fa    4694                         [KNL] debug: print fatal signals
4755                                                  4695 
4756                         If enabled, warn abou    4696                         If enabled, warn about various signal handling
4757                         related application a    4697                         related application anomalies: too many signals,
4758                         too many POSIX.1 time    4698                         too many POSIX.1 timers, fatal signals causing a
4759                         coredump - etc.          4699                         coredump - etc.
4760                                                  4700 
4761                         If you hit the warnin    4701                         If you hit the warning due to signal overflow,
4762                         you might want to try    4702                         you might want to try "ulimit -i unlimited".
4763                                                  4703 
4764                         default: off.            4704                         default: off.
4765                                                  4705 
4766         printk.always_kmsg_dump=                 4706         printk.always_kmsg_dump=
4767                         Trigger kmsg_dump for    4707                         Trigger kmsg_dump for cases other than kernel oops or
4768                         panics                   4708                         panics
4769                         Format: <bool>  (1/Y/    4709                         Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
4770                         default: disabled        4710                         default: disabled
4771                                                  4711 
4772         printk.console_no_auto_verbose=          4712         printk.console_no_auto_verbose=
4773                         Disable console logle    4713                         Disable console loglevel raise on oops, panic
4774                         or lockdep-detected i    4714                         or lockdep-detected issues (only if lock debug is on).
4775                         With an exception to     4715                         With an exception to setups with low baudrate on
4776                         serial console, keepi    4716                         serial console, keeping this 0 is a good choice
4777                         in order to provide m    4717                         in order to provide more debug information.
4778                         Format: <bool>           4718                         Format: <bool>
4779                         default: 0 (auto_verb    4719                         default: 0 (auto_verbose is enabled)
4780                                                  4720 
4781         printk.devkmsg={on,off,ratelimit}        4721         printk.devkmsg={on,off,ratelimit}
4782                         Control writing to /d    4722                         Control writing to /dev/kmsg.
4783                         on - unlimited loggin    4723                         on - unlimited logging to /dev/kmsg from userspace
4784                         off - logging to /dev    4724                         off - logging to /dev/kmsg disabled
4785                         ratelimit - ratelimit    4725                         ratelimit - ratelimit the logging
4786                         Default: ratelimit       4726                         Default: ratelimit
4787                                                  4727 
4788         printk.time=    Show timing data pref    4728         printk.time=    Show timing data prefixed to each printk message line
4789                         Format: <bool>  (1/Y/    4729                         Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
4790                                                  4730 
4791         proc_mem.force_override= [KNL]        << 
4792                         Format: {always | ptr << 
4793                         Traditionally /proc/p << 
4794                         overridden without re << 
4795                         restrict that. Can be << 
4796                         - 'always': tradition << 
4797                         - 'ptrace': only allo << 
4798                         - 'never':  never all << 
4799                         If not specified, def << 
4800                                               << 
4801         processor.max_cstate=   [HW,ACPI]        4731         processor.max_cstate=   [HW,ACPI]
4802                         Limit processor to ma    4732                         Limit processor to maximum C-state
4803                         max_cstate=9 override    4733                         max_cstate=9 overrides any DMI blacklist limit.
4804                                                  4734 
4805         processor.nocst [HW,ACPI]                4735         processor.nocst [HW,ACPI]
4806                         Ignore the _CST metho    4736                         Ignore the _CST method to determine C-states,
4807                         instead using the leg    4737                         instead using the legacy FADT method
4808                                                  4738 
4809         profile=        [KNL] Enable kernel p    4739         profile=        [KNL] Enable kernel profiling via /proc/profile
4810                         Format: [<profiletype    4740                         Format: [<profiletype>,]<number>
4811                         Param: <profiletype>: !! 4741                         Param: <profiletype>: "schedule", "sleep", or "kvm"
4812                                 [defaults to     4742                                 [defaults to kernel profiling]
4813                         Param: "schedule" - p    4743                         Param: "schedule" - profile schedule points.
                                                   >> 4744                         Param: "sleep" - profile D-state sleeping (millisecs).
                                                   >> 4745                                 Requires CONFIG_SCHEDSTATS
4814                         Param: "kvm" - profil    4746                         Param: "kvm" - profile VM exits.
4815                         Param: <number> - ste    4747                         Param: <number> - step/bucket size as a power of 2 for
4816                                 statistical t    4748                                 statistical time based profiling.
4817                                                  4749 
4818         prompt_ramdisk= [RAM] [Deprecated]       4750         prompt_ramdisk= [RAM] [Deprecated]
4819                                                  4751 
4820         prot_virt=      [S390] enable hosting    4752         prot_virt=      [S390] enable hosting protected virtual machines
4821                         isolated from the hyp    4753                         isolated from the hypervisor (if hardware supports
4822                         that). If enabled, th !! 4754                         that).
4823                         might be overridden e << 
4824                         Layout Randomization  << 
4825                         Format: <bool>           4755                         Format: <bool>
4826                                                  4756 
4827         psi=            [KNL] Enable or disab    4757         psi=            [KNL] Enable or disable pressure stall information
4828                         tracking.                4758                         tracking.
4829                         Format: <bool>           4759                         Format: <bool>
4830                                                  4760 
4831         psmouse.proto=  [HW,MOUSE] Highest PS    4761         psmouse.proto=  [HW,MOUSE] Highest PS2 mouse protocol extension to
4832                         probe for; one of (ba    4762                         probe for; one of (bare|imps|exps|lifebook|any).
4833         psmouse.rate=   [HW,MOUSE] Set desire    4763         psmouse.rate=   [HW,MOUSE] Set desired mouse report rate, in reports
4834                         per second.              4764                         per second.
4835         psmouse.resetafter=     [HW,MOUSE]       4765         psmouse.resetafter=     [HW,MOUSE]
4836                         Try to reset the devi    4766                         Try to reset the device after so many bad packets
4837                         (0 = never).             4767                         (0 = never).
4838         psmouse.resolution=                      4768         psmouse.resolution=
4839                         [HW,MOUSE] Set desire    4769                         [HW,MOUSE] Set desired mouse resolution, in dpi.
4840         psmouse.smartscroll=                     4770         psmouse.smartscroll=
4841                         [HW,MOUSE] Controls L    4771                         [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842                         0 = disabled, 1 = ena    4772                         0 = disabled, 1 = enabled (default).
4843                                                  4773 
4844         pstore.backend= Specify the name of t    4774         pstore.backend= Specify the name of the pstore backend to use
4845                                                  4775 
4846         pti=            [X86-64] Control Page    4776         pti=            [X86-64] Control Page Table Isolation of user and
4847                         kernel address spaces    4777                         kernel address spaces.  Disabling this feature
4848                         removes hardening, bu    4778                         removes hardening, but improves performance of
4849                         system calls and inte    4779                         system calls and interrupts.
4850                                                  4780 
4851                         on   - unconditionall    4781                         on   - unconditionally enable
4852                         off  - unconditionall    4782                         off  - unconditionally disable
4853                         auto - kernel detects    4783                         auto - kernel detects whether your CPU model is
4854                                vulnerable to     4784                                vulnerable to issues that PTI mitigates
4855                                                  4785 
4856                         Not specifying this o    4786                         Not specifying this option is equivalent to pti=auto.
4857                                                  4787 
4858         pty.legacy_count=                        4788         pty.legacy_count=
4859                         [KNL] Number of legac    4789                         [KNL] Number of legacy pty's. Overwrites compiled-in
4860                         default number.          4790                         default number.
4861                                                  4791 
4862         quiet           [KNL,EARLY] Disable m !! 4792         quiet           [KNL] Disable most log messages
4863                                                  4793 
4864         r128=           [HW,DRM]                 4794         r128=           [HW,DRM]
4865                                                  4795 
4866         radix_hcall_invalidate=on  [PPC/PSERI    4796         radix_hcall_invalidate=on  [PPC/PSERIES]
4867                         Disable RADIX GTSE fe    4797                         Disable RADIX GTSE feature and use hcall for TLB
4868                         invalidate.              4798                         invalidate.
4869                                                  4799 
4870         raid=           [HW,RAID]                4800         raid=           [HW,RAID]
4871                         See Documentation/adm    4801                         See Documentation/admin-guide/md.rst.
4872                                                  4802 
4873         ramdisk_size=   [RAM] Sizes of RAM di    4803         ramdisk_size=   [RAM] Sizes of RAM disks in kilobytes
4874                         See Documentation/adm    4804                         See Documentation/admin-guide/blockdev/ramdisk.rst.
4875                                                  4805 
4876         ramdisk_start=  [RAM] RAM disk image     4806         ramdisk_start=  [RAM] RAM disk image start address
4877                                                  4807 
4878         random.trust_cpu=off                     4808         random.trust_cpu=off
4879                         [KNL,EARLY] Disable t !! 4809                         [KNL] Disable trusting the use of the CPU's
4880                         random number generat    4810                         random number generator (if available) to
4881                         initialize the kernel    4811                         initialize the kernel's RNG.
4882                                                  4812 
4883         random.trust_bootloader=off              4813         random.trust_bootloader=off
4884                         [KNL,EARLY] Disable t !! 4814                         [KNL] Disable trusting the use of the a seed
4885                         passed by the bootloa    4815                         passed by the bootloader (if available) to
4886                         initialize the kernel    4816                         initialize the kernel's RNG.
4887                                                  4817 
4888         randomize_kstack_offset=                 4818         randomize_kstack_offset=
4889                         [KNL,EARLY] Enable or !! 4819                         [KNL] Enable or disable kernel stack offset
4890                         randomization, which     4820                         randomization, which provides roughly 5 bits of
4891                         entropy, frustrating     4821                         entropy, frustrating memory corruption attacks
4892                         that depend on stack     4822                         that depend on stack address determinism or
4893                         cross-syscall address    4823                         cross-syscall address exposures. This is only
4894                         available on architec    4824                         available on architectures that have defined
4895                         CONFIG_HAVE_ARCH_RAND    4825                         CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896                         Format: <bool>  (1/Y/    4826                         Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
4897                         Default is CONFIG_RAN    4827                         Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898                                                  4828 
4899         ras=option[,option,...] [KNL] RAS-spe    4829         ras=option[,option,...] [KNL] RAS-specific options
4900                                                  4830 
4901                 cec_disable     [X86]            4831                 cec_disable     [X86]
4902                                 Disable the C    4832                                 Disable the Correctable Errors Collector,
4903                                 see CONFIG_RA    4833                                 see CONFIG_RAS_CEC help text.
4904                                                  4834 
4905         rcu_nocbs[=cpu-list]                     4835         rcu_nocbs[=cpu-list]
4906                         [KNL] The optional ar    4836                         [KNL] The optional argument is a cpu list,
4907                         as described above.      4837                         as described above.
4908                                                  4838 
4909                         In kernels built with    4839                         In kernels built with CONFIG_RCU_NOCB_CPU=y,
4910                         enable the no-callbac    4840                         enable the no-callback CPU mode, which prevents
4911                         such CPUs' callbacks     4841                         such CPUs' callbacks from being invoked in
4912                         softirq context.  Inv    4842                         softirq context.  Invocation of such CPUs' RCU
4913                         callbacks will instea    4843                         callbacks will instead be offloaded to "rcuox/N"
4914                         kthreads created for     4844                         kthreads created for that purpose, where "x" is
4915                         "p" for RCU-preempt,     4845                         "p" for RCU-preempt, "s" for RCU-sched, and "g"
4916                         for the kthreads that    4846                         for the kthreads that mediate grace periods; and
4917                         "N" is the CPU number    4847                         "N" is the CPU number. This reduces OS jitter on
4918                         the offloaded CPUs, w    4848                         the offloaded CPUs, which can be useful for HPC
4919                         and real-time workloa    4849                         and real-time workloads.  It can also improve
4920                         energy efficiency for    4850                         energy efficiency for asymmetric multiprocessors.
4921                                                  4851 
4922                         If a cpulist is passe    4852                         If a cpulist is passed as an argument, the specified
4923                         list of CPUs is set t    4853                         list of CPUs is set to no-callback mode from boot.
4924                                                  4854 
4925                         Otherwise, if the '='    4855                         Otherwise, if the '=' sign and the cpulist
4926                         arguments are omitted    4856                         arguments are omitted, no CPU will be set to
4927                         no-callback mode from    4857                         no-callback mode from boot but the mode may be
4928                         toggled at runtime vi    4858                         toggled at runtime via cpusets.
4929                                                  4859 
4930                         Note that this argume    4860                         Note that this argument takes precedence over
4931                         the CONFIG_RCU_NOCB_C    4861                         the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4932                                                  4862 
4933         rcu_nocb_poll   [KNL]                    4863         rcu_nocb_poll   [KNL]
4934                         Rather than requiring    4864                         Rather than requiring that offloaded CPUs
4935                         (specified by rcu_noc    4865                         (specified by rcu_nocbs= above) explicitly
4936                         awaken the correspond    4866                         awaken the corresponding "rcuoN" kthreads,
4937                         make these kthreads p    4867                         make these kthreads poll for callbacks.
4938                         This improves the rea    4868                         This improves the real-time response for the
4939                         offloaded CPUs by rel    4869                         offloaded CPUs by relieving them of the need to
4940                         wake up the correspon    4870                         wake up the corresponding kthread, but degrades
4941                         energy efficiency by     4871                         energy efficiency by requiring that the kthreads
4942                         periodically wake up     4872                         periodically wake up to do the polling.
4943                                                  4873 
4944         rcutree.blimit= [KNL]                    4874         rcutree.blimit= [KNL]
4945                         Set maximum number of    4875                         Set maximum number of finished RCU callbacks to
4946                         process in one batch.    4876                         process in one batch.
4947                                                  4877 
4948         rcutree.do_rcu_barrier= [KNL]            4878         rcutree.do_rcu_barrier= [KNL]
4949                         Request a call to rcu    4879                         Request a call to rcu_barrier().  This is
4950                         throttled so that use    4880                         throttled so that userspace tests can safely
4951                         hammer on the sysfs v    4881                         hammer on the sysfs variable if they so choose.
4952                         If triggered before t    4882                         If triggered before the RCU grace-period machinery
4953                         is fully active, this    4883                         is fully active, this will error out with EAGAIN.
4954                                                  4884 
4955         rcutree.dump_tree=      [KNL]            4885         rcutree.dump_tree=      [KNL]
4956                         Dump the structure of    4886                         Dump the structure of the rcu_node combining tree
4957                         out at early boot.  T    4887                         out at early boot.  This is used for diagnostic
4958                         purposes, to verify c    4888                         purposes, to verify correct tree setup.
4959                                                  4889 
4960         rcutree.gp_cleanup_delay=       [KNL]    4890         rcutree.gp_cleanup_delay=       [KNL]
4961                         Set the number of jif    4891                         Set the number of jiffies to delay each step of
4962                         RCU grace-period clea    4892                         RCU grace-period cleanup.
4963                                                  4893 
4964         rcutree.gp_init_delay=  [KNL]            4894         rcutree.gp_init_delay=  [KNL]
4965                         Set the number of jif    4895                         Set the number of jiffies to delay each step of
4966                         RCU grace-period init    4896                         RCU grace-period initialization.
4967                                                  4897 
4968         rcutree.gp_preinit_delay=       [KNL]    4898         rcutree.gp_preinit_delay=       [KNL]
4969                         Set the number of jif    4899                         Set the number of jiffies to delay each step of
4970                         RCU grace-period pre-    4900                         RCU grace-period pre-initialization, that is,
4971                         the propagation of re    4901                         the propagation of recent CPU-hotplug changes up
4972                         the rcu_node combinin    4902                         the rcu_node combining tree.
4973                                                  4903 
4974         rcutree.jiffies_till_first_fqs= [KNL]    4904         rcutree.jiffies_till_first_fqs= [KNL]
4975                         Set delay from grace-    4905                         Set delay from grace-period initialization to
4976                         first attempt to forc    4906                         first attempt to force quiescent states.
4977                         Units are jiffies, mi    4907                         Units are jiffies, minimum value is zero,
4978                         and maximum value is     4908                         and maximum value is HZ.
4979                                                  4909 
4980         rcutree.jiffies_till_next_fqs= [KNL]     4910         rcutree.jiffies_till_next_fqs= [KNL]
4981                         Set delay between sub    4911                         Set delay between subsequent attempts to force
4982                         quiescent states.  Un    4912                         quiescent states.  Units are jiffies, minimum
4983                         value is one, and max    4913                         value is one, and maximum value is HZ.
4984                                                  4914 
4985         rcutree.jiffies_till_sched_qs= [KNL]     4915         rcutree.jiffies_till_sched_qs= [KNL]
4986                         Set required age in j    4916                         Set required age in jiffies for a
4987                         given grace period be    4917                         given grace period before RCU starts
4988                         soliciting quiescent-    4918                         soliciting quiescent-state help from
4989                         rcu_note_context_swit    4919                         rcu_note_context_switch() and cond_resched().
4990                         If not specified, the    4920                         If not specified, the kernel will calculate
4991                         a value based on the     4921                         a value based on the most recent settings
4992                         of rcutree.jiffies_ti    4922                         of rcutree.jiffies_till_first_fqs
4993                         and rcutree.jiffies_t    4923                         and rcutree.jiffies_till_next_fqs.
4994                         This calculated value    4924                         This calculated value may be viewed in
4995                         rcutree.jiffies_to_sc    4925                         rcutree.jiffies_to_sched_qs.  Any attempt to set
4996                         rcutree.jiffies_to_sc    4926                         rcutree.jiffies_to_sched_qs will be cheerfully
4997                         overwritten.             4927                         overwritten.
4998                                                  4928 
4999         rcutree.kthread_prio=    [KNL,BOOT]      4929         rcutree.kthread_prio=    [KNL,BOOT]
5000                         Set the SCHED_FIFO pr    4930                         Set the SCHED_FIFO priority of the RCU per-CPU
5001                         kthreads (rcuc/N). Th    4931                         kthreads (rcuc/N). This value is also used for
5002                         the priority of the R    4932                         the priority of the RCU boost threads (rcub/N)
5003                         and for the RCU grace    4933                         and for the RCU grace-period kthreads (rcu_bh,
5004                         rcu_preempt, and rcu_    4934                         rcu_preempt, and rcu_sched). If RCU_BOOST is
5005                         set, valid values are    4935                         set, valid values are 1-99 and the default is 1
5006                         (the least-favored pr    4936                         (the least-favored priority).  Otherwise, when
5007                         RCU_BOOST is not set,    4937                         RCU_BOOST is not set, valid values are 0-99 and
5008                         the default is zero (    4938                         the default is zero (non-realtime operation).
5009                         When RCU_NOCB_CPU is     4939                         When RCU_NOCB_CPU is set, also adjust the
5010                         priority of NOCB call    4940                         priority of NOCB callback kthreads.
5011                                                  4941 
5012         rcutree.nocb_nobypass_lim_per_jiffy=     4942         rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5013                         On callback-offloaded    4943                         On callback-offloaded (rcu_nocbs) CPUs,
5014                         RCU reduces the lock     4944                         RCU reduces the lock contention that would
5015                         otherwise be caused b    4945                         otherwise be caused by callback floods through
5016                         use of the ->nocb_byp    4946                         use of the ->nocb_bypass list.  However, in the
5017                         common non-flooded ca    4947                         common non-flooded case, RCU queues directly to
5018                         the main ->cblist in     4948                         the main ->cblist in order to avoid the extra
5019                         overhead of the ->noc    4949                         overhead of the ->nocb_bypass list and its lock.
5020                         But if there are too     4950                         But if there are too many callbacks queued during
5021                         a single jiffy, RCU p    4951                         a single jiffy, RCU pre-queues the callbacks into
5022                         the ->nocb_bypass que    4952                         the ->nocb_bypass queue.  The definition of "too
5023                         many" is supplied by     4953                         many" is supplied by this kernel boot parameter.
5024                                                  4954 
5025         rcutree.nohz_full_patience_delay= [KN << 
5026                         On callback-offloaded << 
5027                         disturbing RCU unless << 
5028                         reached the specified << 
5029                         Defaults to zero.  La << 
5030                         at five seconds.  All << 
5031                         to the nearest value  << 
5032                                               << 
5033         rcutree.qhimark= [KNL]                   4955         rcutree.qhimark= [KNL]
5034                         Set threshold of queu    4956                         Set threshold of queued RCU callbacks beyond which
5035                         batch limiting is dis    4957                         batch limiting is disabled.
5036                                                  4958 
5037         rcutree.qlowmark= [KNL]                  4959         rcutree.qlowmark= [KNL]
5038                         Set threshold of queu    4960                         Set threshold of queued RCU callbacks below which
5039                         batch limiting is re-    4961                         batch limiting is re-enabled.
5040                                                  4962 
5041         rcutree.qovld= [KNL]                     4963         rcutree.qovld= [KNL]
5042                         Set threshold of queu    4964                         Set threshold of queued RCU callbacks beyond which
5043                         RCU's force-quiescent    4965                         RCU's force-quiescent-state scan will aggressively
5044                         enlist help from cond    4966                         enlist help from cond_resched() and sched IPIs to
5045                         help CPUs more quickl    4967                         help CPUs more quickly reach quiescent states.
5046                         Set to less than zero    4968                         Set to less than zero to make this be set based
5047                         on rcutree.qhimark at    4969                         on rcutree.qhimark at boot time and to zero to
5048                         disable more aggressi    4970                         disable more aggressive help enlistment.
5049                                                  4971 
5050         rcutree.rcu_delay_page_cache_fill_mse    4972         rcutree.rcu_delay_page_cache_fill_msec= [KNL]
5051                         Set the page-cache re    4973                         Set the page-cache refill delay (in milliseconds)
5052                         in response to low-me    4974                         in response to low-memory conditions.  The range
5053                         of permitted values i    4975                         of permitted values is in the range 0:100000.
5054                                                  4976 
5055         rcutree.rcu_divisor= [KNL]               4977         rcutree.rcu_divisor= [KNL]
5056                         Set the shift-right c    4978                         Set the shift-right count to use to compute
5057                         the callback-invocati    4979                         the callback-invocation batch limit bl from
5058                         the number of callbac    4980                         the number of callbacks queued on this CPU.
5059                         The result will be bo    4981                         The result will be bounded below by the value of
5060                         the rcutree.blimit ke    4982                         the rcutree.blimit kernel parameter.  Every bl
5061                         callbacks, the softir    4983                         callbacks, the softirq handler will exit in
5062                         order to allow the CP    4984                         order to allow the CPU to do other work.
5063                                                  4985 
5064                         Please note that this    4986                         Please note that this callback-invocation batch
5065                         limit applies only to    4987                         limit applies only to non-offloaded callback
5066                         invocation.  Offloade    4988                         invocation.  Offloaded callbacks are instead
5067                         invoked in the contex    4989                         invoked in the context of an rcuoc kthread, which
5068                         scheduler will preemp    4990                         scheduler will preempt as it does any other task.
5069                                                  4991 
5070         rcutree.rcu_fanout_exact= [KNL]          4992         rcutree.rcu_fanout_exact= [KNL]
5071                         Disable autobalancing    4993                         Disable autobalancing of the rcu_node combining
5072                         tree.  This is used b    4994                         tree.  This is used by rcutorture, and might
5073                         possibly be useful fo    4995                         possibly be useful for architectures having high
5074                         cache-to-cache transf    4996                         cache-to-cache transfer latencies.
5075                                                  4997 
5076         rcutree.rcu_fanout_leaf= [KNL]           4998         rcutree.rcu_fanout_leaf= [KNL]
5077                         Change the number of     4999                         Change the number of CPUs assigned to each
5078                         leaf rcu_node structu    5000                         leaf rcu_node structure.  Useful for very
5079                         large systems, which     5001                         large systems, which will choose the value 64,
5080                         and for NUMA systems     5002                         and for NUMA systems with large remote-access
5081                         latencies, which will    5003                         latencies, which will choose a value aligned
5082                         with the appropriate     5004                         with the appropriate hardware boundaries.
5083                                                  5005 
5084         rcutree.rcu_min_cached_objs= [KNL]       5006         rcutree.rcu_min_cached_objs= [KNL]
5085                         Minimum number of obj    5007                         Minimum number of objects which are cached and
5086                         maintained per one CP    5008                         maintained per one CPU. Object size is equal
5087                         to PAGE_SIZE. The cac    5009                         to PAGE_SIZE. The cache allows to reduce the
5088                         pressure to page allo    5010                         pressure to page allocator, also it makes the
5089                         whole algorithm to be    5011                         whole algorithm to behave better in low memory
5090                         condition.               5012                         condition.
5091                                                  5013 
5092         rcutree.rcu_nocb_gp_stride= [KNL]        5014         rcutree.rcu_nocb_gp_stride= [KNL]
5093                         Set the number of NOC    5015                         Set the number of NOCB callback kthreads in
5094                         each group, which def    5016                         each group, which defaults to the square root
5095                         of the number of CPUs    5017                         of the number of CPUs.  Larger numbers reduce
5096                         the wakeup overhead o    5018                         the wakeup overhead on the global grace-period
5097                         kthread, but increase    5019                         kthread, but increases that same overhead on
5098                         each group's NOCB gra    5020                         each group's NOCB grace-period kthread.
5099                                                  5021 
5100         rcutree.rcu_kick_kthreads= [KNL]         5022         rcutree.rcu_kick_kthreads= [KNL]
5101                         Cause the grace-perio    5023                         Cause the grace-period kthread to get an extra
5102                         wake_up() if it sleep    5024                         wake_up() if it sleeps three times longer than
5103                         it should at force-qu    5025                         it should at force-quiescent-state time.
5104                         This wake_up() will b    5026                         This wake_up() will be accompanied by a
5105                         WARN_ONCE() splat and    5027                         WARN_ONCE() splat and an ftrace_dump().
5106                                                  5028 
5107         rcutree.rcu_resched_ns= [KNL]            5029         rcutree.rcu_resched_ns= [KNL]
5108                         Limit the time spend     5030                         Limit the time spend invoking a batch of RCU
5109                         callbacks to the spec    5031                         callbacks to the specified number of nanoseconds.
5110                         By default, this limi    5032                         By default, this limit is checked only once
5111                         every 32 callbacks in    5033                         every 32 callbacks in order to limit the pain
5112                         inflicted by local_cl    5034                         inflicted by local_clock() overhead.
5113                                                  5035 
5114         rcutree.rcu_unlock_delay= [KNL]          5036         rcutree.rcu_unlock_delay= [KNL]
5115                         In CONFIG_RCU_STRICT_    5037                         In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116                         this specifies an rcu    5038                         this specifies an rcu_read_unlock()-time delay
5117                         in microseconds.  Thi    5039                         in microseconds.  This defaults to zero.
5118                         Larger delays increas    5040                         Larger delays increase the probability of
5119                         catching RCU pointer     5041                         catching RCU pointer leaks, that is, buggy use
5120                         of RCU-protected poin    5042                         of RCU-protected pointers after the relevant
5121                         rcu_read_unlock() has    5043                         rcu_read_unlock() has completed.
5122                                                  5044 
5123         rcutree.sysrq_rcu= [KNL]                 5045         rcutree.sysrq_rcu= [KNL]
5124                         Commandeer a sysrq ke    5046                         Commandeer a sysrq key to dump out Tree RCU's
5125                         rcu_node tree with an    5047                         rcu_node tree with an eye towards determining
5126                         why a new grace perio    5048                         why a new grace period has not yet started.
5127                                                  5049 
5128         rcutree.use_softirq=    [KNL]            5050         rcutree.use_softirq=    [KNL]
5129                         If set to zero, move     5051                         If set to zero, move all RCU_SOFTIRQ processing to
5130                         per-CPU rcuc kthreads    5052                         per-CPU rcuc kthreads.  Defaults to a non-zero
5131                         value, meaning that R    5053                         value, meaning that RCU_SOFTIRQ is used by default.
5132                         Specify rcutree.use_s    5054                         Specify rcutree.use_softirq=0 to use rcuc kthreads.
5133                                                  5055 
5134                         But note that CONFIG_    5056                         But note that CONFIG_PREEMPT_RT=y kernels disable
5135                         this kernel boot para    5057                         this kernel boot parameter, forcibly setting it
5136                         to zero.                 5058                         to zero.
5137                                                  5059 
5138         rcutree.enable_rcu_lazy= [KNL]        << 
5139                         To save power, batch  << 
5140                         delay, memory pressur << 
5141                         big.                  << 
5142                                               << 
5143         rcutree.rcu_normal_wake_from_gp= [KNL << 
5144                         Reduces a latency of  << 
5145                         maintains its own tra << 
5146                         does not interact wit << 
5147                         use a call_rcu[_hurry << 
5148                         normal grace period.  << 
5149                                               << 
5150                         How to enable it:     << 
5151                                               << 
5152                         echo 1 > /sys/module/ << 
5153                         or pass a boot parame << 
5154                                               << 
5155                         Default is 0.         << 
5156                                               << 
5157         rcuscale.gp_async= [KNL]                 5060         rcuscale.gp_async= [KNL]
5158                         Measure performance o    5061                         Measure performance of asynchronous
5159                         grace-period primitiv    5062                         grace-period primitives such as call_rcu().
5160                                                  5063 
5161         rcuscale.gp_async_max= [KNL]             5064         rcuscale.gp_async_max= [KNL]
5162                         Specify the maximum n    5065                         Specify the maximum number of outstanding
5163                         callbacks per writer     5066                         callbacks per writer thread.  When a writer
5164                         thread exceeds this l    5067                         thread exceeds this limit, it invokes the
5165                         corresponding flavor     5068                         corresponding flavor of rcu_barrier() to allow
5166                         previously posted cal    5069                         previously posted callbacks to drain.
5167                                                  5070 
5168         rcuscale.gp_exp= [KNL]                   5071         rcuscale.gp_exp= [KNL]
5169                         Measure performance o    5072                         Measure performance of expedited synchronous
5170                         grace-period primitiv    5073                         grace-period primitives.
5171                                                  5074 
5172         rcuscale.holdoff= [KNL]                  5075         rcuscale.holdoff= [KNL]
5173                         Set test-start holdof    5076                         Set test-start holdoff period.  The purpose of
5174                         this parameter is to     5077                         this parameter is to delay the start of the
5175                         test until boot compl    5078                         test until boot completes in order to avoid
5176                         interference.            5079                         interference.
5177                                                  5080 
5178         rcuscale.kfree_by_call_rcu= [KNL]        5081         rcuscale.kfree_by_call_rcu= [KNL]
5179                         In kernels built with    5082                         In kernels built with CONFIG_RCU_LAZY=y, test
5180                         call_rcu() instead of    5083                         call_rcu() instead of kfree_rcu().
5181                                                  5084 
5182         rcuscale.kfree_mult= [KNL]               5085         rcuscale.kfree_mult= [KNL]
5183                         Instead of allocating    5086                         Instead of allocating an object of size kfree_obj,
5184                         allocate one of kfree    5087                         allocate one of kfree_mult * sizeof(kfree_obj).
5185                         Defaults to 1.           5088                         Defaults to 1.
5186                                                  5089 
5187         rcuscale.kfree_rcu_test= [KNL]           5090         rcuscale.kfree_rcu_test= [KNL]
5188                         Set to measure perfor    5091                         Set to measure performance of kfree_rcu() flooding.
5189                                                  5092 
5190         rcuscale.kfree_rcu_test_double= [KNL]    5093         rcuscale.kfree_rcu_test_double= [KNL]
5191                         Test the double-argum    5094                         Test the double-argument variant of kfree_rcu().
5192                         If this parameter has    5095                         If this parameter has the same value as
5193                         rcuscale.kfree_rcu_te    5096                         rcuscale.kfree_rcu_test_single, both the single-
5194                         and double-argument v    5097                         and double-argument variants are tested.
5195                                                  5098 
5196         rcuscale.kfree_rcu_test_single= [KNL]    5099         rcuscale.kfree_rcu_test_single= [KNL]
5197                         Test the single-argum    5100                         Test the single-argument variant of kfree_rcu().
5198                         If this parameter has    5101                         If this parameter has the same value as
5199                         rcuscale.kfree_rcu_te    5102                         rcuscale.kfree_rcu_test_double, both the single-
5200                         and double-argument v    5103                         and double-argument variants are tested.
5201                                                  5104 
5202         rcuscale.kfree_nthreads= [KNL]           5105         rcuscale.kfree_nthreads= [KNL]
5203                         The number of threads    5106                         The number of threads running loops of kfree_rcu().
5204                                                  5107 
5205         rcuscale.kfree_alloc_num= [KNL]          5108         rcuscale.kfree_alloc_num= [KNL]
5206                         Number of allocations    5109                         Number of allocations and frees done in an iteration.
5207                                                  5110 
5208         rcuscale.kfree_loops= [KNL]              5111         rcuscale.kfree_loops= [KNL]
5209                         Number of loops doing    5112                         Number of loops doing rcuscale.kfree_alloc_num number
5210                         of allocations and fr    5113                         of allocations and frees.
5211                                                  5114 
5212         rcuscale.minruntime= [KNL]               5115         rcuscale.minruntime= [KNL]
5213                         Set the minimum test     5116                         Set the minimum test run time in seconds.  This
5214                         does not affect the d    5117                         does not affect the data-collection interval,
5215                         but instead allows be    5118                         but instead allows better measurement of things
5216                         like CPU consumption.    5119                         like CPU consumption.
5217                                                  5120 
5218         rcuscale.nreaders= [KNL]                 5121         rcuscale.nreaders= [KNL]
5219                         Set number of RCU rea    5122                         Set number of RCU readers.  The value -1 selects
5220                         N, where N is the num    5123                         N, where N is the number of CPUs.  A value
5221                         "n" less than -1 sele    5124                         "n" less than -1 selects N-n+1, where N is again
5222                         the number of CPUs.      5125                         the number of CPUs.  For example, -2 selects N
5223                         (the number of CPUs),    5126                         (the number of CPUs), -3 selects N+1, and so on.
5224                         A value of "n" less t    5127                         A value of "n" less than or equal to -N selects
5225                         a single reader.         5128                         a single reader.
5226                                                  5129 
5227         rcuscale.nwriters= [KNL]                 5130         rcuscale.nwriters= [KNL]
5228                         Set number of RCU wri    5131                         Set number of RCU writers.  The values operate
5229                         the same as for rcusc    5132                         the same as for rcuscale.nreaders.
5230                         N, where N is the num    5133                         N, where N is the number of CPUs
5231                                                  5134 
5232         rcuscale.scale_type= [KNL]               5135         rcuscale.scale_type= [KNL]
5233                         Specify the RCU imple    5136                         Specify the RCU implementation to test.
5234                                                  5137 
5235         rcuscale.shutdown= [KNL]                 5138         rcuscale.shutdown= [KNL]
5236                         Shut the system down     5139                         Shut the system down after performance tests
5237                         complete.  This is us    5140                         complete.  This is useful for hands-off automated
5238                         testing.                 5141                         testing.
5239                                                  5142 
5240         rcuscale.verbose= [KNL]                  5143         rcuscale.verbose= [KNL]
5241                         Enable additional pri    5144                         Enable additional printk() statements.
5242                                                  5145 
5243         rcuscale.writer_holdoff= [KNL]           5146         rcuscale.writer_holdoff= [KNL]
5244                         Write-side holdoff be    5147                         Write-side holdoff between grace periods,
5245                         in microseconds.  The    5148                         in microseconds.  The default of zero says
5246                         no holdoff.              5149                         no holdoff.
5247                                                  5150 
5248         rcuscale.writer_holdoff_jiffies= [KNL    5151         rcuscale.writer_holdoff_jiffies= [KNL]
5249                         Additional write-side    5152                         Additional write-side holdoff between grace
5250                         periods, but in jiffi    5153                         periods, but in jiffies.  The default of zero
5251                         says no holdoff.         5154                         says no holdoff.
5252                                                  5155 
5253         rcutorture.fqs_duration= [KNL]           5156         rcutorture.fqs_duration= [KNL]
5254                         Set duration of force    5157                         Set duration of force_quiescent_state bursts
5255                         in microseconds.         5158                         in microseconds.
5256                                                  5159 
5257         rcutorture.fqs_holdoff= [KNL]            5160         rcutorture.fqs_holdoff= [KNL]
5258                         Set holdoff time with    5161                         Set holdoff time within force_quiescent_state bursts
5259                         in microseconds.         5162                         in microseconds.
5260                                                  5163 
5261         rcutorture.fqs_stutter= [KNL]            5164         rcutorture.fqs_stutter= [KNL]
5262                         Set wait time between    5165                         Set wait time between force_quiescent_state bursts
5263                         in seconds.              5166                         in seconds.
5264                                                  5167 
5265         rcutorture.fwd_progress= [KNL]           5168         rcutorture.fwd_progress= [KNL]
5266                         Specifies the number     5169                         Specifies the number of kthreads to be used
5267                         for  RCU grace-period    5170                         for  RCU grace-period forward-progress testing
5268                         for the types of RCU     5171                         for the types of RCU supporting this notion.
5269                         Defaults to 1 kthread    5172                         Defaults to 1 kthread, values less than zero or
5270                         greater than the numb    5173                         greater than the number of CPUs cause the number
5271                         of CPUs to be used.      5174                         of CPUs to be used.
5272                                                  5175 
5273         rcutorture.fwd_progress_div= [KNL]       5176         rcutorture.fwd_progress_div= [KNL]
5274                         Specify the fraction     5177                         Specify the fraction of a CPU-stall-warning
5275                         period to do tight-lo    5178                         period to do tight-loop forward-progress testing.
5276                                                  5179 
5277         rcutorture.fwd_progress_holdoff= [KNL    5180         rcutorture.fwd_progress_holdoff= [KNL]
5278                         Number of seconds to     5181                         Number of seconds to wait between successive
5279                         forward-progress test    5182                         forward-progress tests.
5280                                                  5183 
5281         rcutorture.fwd_progress_need_resched=    5184         rcutorture.fwd_progress_need_resched= [KNL]
5282                         Enclose cond_resched(    5185                         Enclose cond_resched() calls within checks for
5283                         need_resched() during    5186                         need_resched() during tight-loop forward-progress
5284                         testing.                 5187                         testing.
5285                                                  5188 
5286         rcutorture.gp_cond= [KNL]                5189         rcutorture.gp_cond= [KNL]
5287                         Use conditional/async    5190                         Use conditional/asynchronous update-side
5288                         primitives, if availa    5191                         primitives, if available.
5289                                                  5192 
5290         rcutorture.gp_exp= [KNL]                 5193         rcutorture.gp_exp= [KNL]
5291                         Use expedited update-    5194                         Use expedited update-side primitives, if available.
5292                                                  5195 
5293         rcutorture.gp_normal= [KNL]              5196         rcutorture.gp_normal= [KNL]
5294                         Use normal (non-exped    5197                         Use normal (non-expedited) asynchronous
5295                         update-side primitive    5198                         update-side primitives, if available.
5296                                                  5199 
5297         rcutorture.gp_sync= [KNL]                5200         rcutorture.gp_sync= [KNL]
5298                         Use normal (non-exped    5201                         Use normal (non-expedited) synchronous
5299                         update-side primitive    5202                         update-side primitives, if available.  If all
5300                         of rcutorture.gp_cond    5203                         of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301                         rcutorture.gp_normal=    5204                         rcutorture.gp_normal=, and rcutorture.gp_sync=
5302                         are zero, rcutorture     5205                         are zero, rcutorture acts as if is interpreted
5303                         they are all non-zero    5206                         they are all non-zero.
5304                                                  5207 
5305         rcutorture.irqreader= [KNL]              5208         rcutorture.irqreader= [KNL]
5306                         Run RCU readers from     5209                         Run RCU readers from irq handlers, or, more
5307                         accurately, from a ti    5210                         accurately, from a timer handler.  Not all RCU
5308                         flavors take kindly t    5211                         flavors take kindly to this sort of thing.
5309                                                  5212 
5310         rcutorture.leakpointer= [KNL]            5213         rcutorture.leakpointer= [KNL]
5311                         Leak an RCU-protected    5214                         Leak an RCU-protected pointer out of the reader.
5312                         This can of course re    5215                         This can of course result in splats, and is
5313                         intended to test the     5216                         intended to test the ability of things like
5314                         CONFIG_RCU_STRICT_GRA    5217                         CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315                         such leaks.              5218                         such leaks.
5316                                                  5219 
5317         rcutorture.n_barrier_cbs= [KNL]          5220         rcutorture.n_barrier_cbs= [KNL]
5318                         Set callbacks/threads    5221                         Set callbacks/threads for rcu_barrier() testing.
5319                                                  5222 
5320         rcutorture.nfakewriters= [KNL]           5223         rcutorture.nfakewriters= [KNL]
5321                         Set number of concurr    5224                         Set number of concurrent RCU writers.  These just
5322                         stress RCU, they don'    5225                         stress RCU, they don't participate in the actual
5323                         test, hence the "fake    5226                         test, hence the "fake".
5324                                                  5227 
5325         rcutorture.nocbs_nthreads= [KNL]         5228         rcutorture.nocbs_nthreads= [KNL]
5326                         Set number of RCU cal    5229                         Set number of RCU callback-offload togglers.
5327                         Zero (the default) di    5230                         Zero (the default) disables toggling.
5328                                                  5231 
5329         rcutorture.nocbs_toggle= [KNL]           5232         rcutorture.nocbs_toggle= [KNL]
5330                         Set the delay in mill    5233                         Set the delay in milliseconds between successive
5331                         callback-offload togg    5234                         callback-offload toggling attempts.
5332                                                  5235 
5333         rcutorture.nreaders= [KNL]               5236         rcutorture.nreaders= [KNL]
5334                         Set number of RCU rea    5237                         Set number of RCU readers.  The value -1 selects
5335                         N-1, where N is the n    5238                         N-1, where N is the number of CPUs.  A value
5336                         "n" less than -1 sele    5239                         "n" less than -1 selects N-n-2, where N is again
5337                         the number of CPUs.      5240                         the number of CPUs.  For example, -2 selects N
5338                         (the number of CPUs),    5241                         (the number of CPUs), -3 selects N+1, and so on.
5339                                                  5242 
5340         rcutorture.object_debug= [KNL]           5243         rcutorture.object_debug= [KNL]
5341                         Enable debug-object d    5244                         Enable debug-object double-call_rcu() testing.
5342                                                  5245 
5343         rcutorture.onoff_holdoff= [KNL]          5246         rcutorture.onoff_holdoff= [KNL]
5344                         Set time (s) after bo    5247                         Set time (s) after boot for CPU-hotplug testing.
5345                                                  5248 
5346         rcutorture.onoff_interval= [KNL]         5249         rcutorture.onoff_interval= [KNL]
5347                         Set time (jiffies) be    5250                         Set time (jiffies) between CPU-hotplug operations,
5348                         or zero to disable CP    5251                         or zero to disable CPU-hotplug testing.
5349                                                  5252 
5350         rcutorture.read_exit= [KNL]              5253         rcutorture.read_exit= [KNL]
5351                         Set the number of rea    5254                         Set the number of read-then-exit kthreads used
5352                         to test the interacti    5255                         to test the interaction of RCU updaters and
5353                         task-exit processing.    5256                         task-exit processing.
5354                                                  5257 
5355         rcutorture.read_exit_burst= [KNL]        5258         rcutorture.read_exit_burst= [KNL]
5356                         The number of times i    5259                         The number of times in a given read-then-exit
5357                         episode that a set of    5260                         episode that a set of read-then-exit kthreads
5358                         is spawned.              5261                         is spawned.
5359                                                  5262 
5360         rcutorture.read_exit_delay= [KNL]        5263         rcutorture.read_exit_delay= [KNL]
5361                         The delay, in seconds    5264                         The delay, in seconds, between successive
5362                         read-then-exit testin    5265                         read-then-exit testing episodes.
5363                                                  5266 
5364         rcutorture.shuffle_interval= [KNL]       5267         rcutorture.shuffle_interval= [KNL]
5365                         Set task-shuffle inte    5268                         Set task-shuffle interval (s).  Shuffling tasks
5366                         allows some CPUs to g    5269                         allows some CPUs to go into dyntick-idle mode
5367                         during the rcutorture    5270                         during the rcutorture test.
5368                                                  5271 
5369         rcutorture.shutdown_secs= [KNL]          5272         rcutorture.shutdown_secs= [KNL]
5370                         Set time (s) after bo    5273                         Set time (s) after boot system shutdown.  This
5371                         is useful for hands-o    5274                         is useful for hands-off automated testing.
5372                                                  5275 
5373         rcutorture.stall_cpu= [KNL]              5276         rcutorture.stall_cpu= [KNL]
5374                         Duration of CPU stall    5277                         Duration of CPU stall (s) to test RCU CPU stall
5375                         warnings, zero to dis    5278                         warnings, zero to disable.
5376                                                  5279 
5377         rcutorture.stall_cpu_block= [KNL]        5280         rcutorture.stall_cpu_block= [KNL]
5378                         Sleep while stalling     5281                         Sleep while stalling if set.  This will result
5379                         in warnings from pree    5282                         in warnings from preemptible RCU in addition to
5380                         any other stall-relat    5283                         any other stall-related activity.  Note that
5381                         in kernels built with    5284                         in kernels built with CONFIG_PREEMPTION=n and
5382                         CONFIG_PREEMPT_COUNT=    5285                         CONFIG_PREEMPT_COUNT=y, this parameter will
5383                         cause the CPU to pass    5286                         cause the CPU to pass through a quiescent state.
5384                         Given CONFIG_PREEMPTI    5287                         Given CONFIG_PREEMPTION=n, this will suppress
5385                         RCU CPU stall warning    5288                         RCU CPU stall warnings, but will instead result
5386                         in scheduling-while-a    5289                         in scheduling-while-atomic splats.
5387                                                  5290 
5388                         Use of this module pa    5291                         Use of this module parameter results in splats.
5389                                                  5292 
5390                                                  5293 
5391         rcutorture.stall_cpu_holdoff= [KNL]      5294         rcutorture.stall_cpu_holdoff= [KNL]
5392                         Time to wait (s) afte    5295                         Time to wait (s) after boot before inducing stall.
5393                                                  5296 
5394         rcutorture.stall_cpu_irqsoff= [KNL]      5297         rcutorture.stall_cpu_irqsoff= [KNL]
5395                         Disable interrupts wh    5298                         Disable interrupts while stalling if set.
5396                                                  5299 
5397         rcutorture.stall_gp_kthread= [KNL]       5300         rcutorture.stall_gp_kthread= [KNL]
5398                         Duration (s) of force    5301                         Duration (s) of forced sleep within RCU
5399                         grace-period kthread     5302                         grace-period kthread to test RCU CPU stall
5400                         warnings, zero to dis    5303                         warnings, zero to disable.  If both stall_cpu
5401                         and stall_gp_kthread     5304                         and stall_gp_kthread are specified, the
5402                         kthread is starved fi    5305                         kthread is starved first, then the CPU.
5403                                                  5306 
5404         rcutorture.stat_interval= [KNL]          5307         rcutorture.stat_interval= [KNL]
5405                         Time (s) between stat    5308                         Time (s) between statistics printk()s.
5406                                                  5309 
5407         rcutorture.stutter= [KNL]                5310         rcutorture.stutter= [KNL]
5408                         Time (s) to stutter t    5311                         Time (s) to stutter testing, for example, specifying
5409                         five seconds causes t    5312                         five seconds causes the test to run for five seconds,
5410                         wait for five seconds    5313                         wait for five seconds, and so on.  This tests RCU's
5411                         ability to transition    5314                         ability to transition abruptly to and from idle.
5412                                                  5315 
5413         rcutorture.test_boost= [KNL]             5316         rcutorture.test_boost= [KNL]
5414                         Test RCU priority boo    5317                         Test RCU priority boosting?  0=no, 1=maybe, 2=yes.
5415                         "Maybe" means test if    5318                         "Maybe" means test if the RCU implementation
5416                         under test support RC    5319                         under test support RCU priority boosting.
5417                                                  5320 
5418         rcutorture.test_boost_duration= [KNL]    5321         rcutorture.test_boost_duration= [KNL]
5419                         Duration (s) of each     5322                         Duration (s) of each individual boost test.
5420                                                  5323 
5421         rcutorture.test_boost_interval= [KNL]    5324         rcutorture.test_boost_interval= [KNL]
5422                         Interval (s) between     5325                         Interval (s) between each boost test.
5423                                                  5326 
5424         rcutorture.test_no_idle_hz= [KNL]        5327         rcutorture.test_no_idle_hz= [KNL]
5425                         Test RCU's dyntick-id    5328                         Test RCU's dyntick-idle handling.  See also the
5426                         rcutorture.shuffle_in    5329                         rcutorture.shuffle_interval parameter.
5427                                                  5330 
5428         rcutorture.torture_type= [KNL]           5331         rcutorture.torture_type= [KNL]
5429                         Specify the RCU imple    5332                         Specify the RCU implementation to test.
5430                                                  5333 
5431         rcutorture.verbose= [KNL]                5334         rcutorture.verbose= [KNL]
5432                         Enable additional pri    5335                         Enable additional printk() statements.
5433                                                  5336 
5434         rcupdate.rcu_cpu_stall_ftrace_dump= [    5337         rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435                         Dump ftrace buffer af    5338                         Dump ftrace buffer after reporting RCU CPU
5436                         stall warning.           5339                         stall warning.
5437                                                  5340 
5438         rcupdate.rcu_cpu_stall_notifiers= [KN    5341         rcupdate.rcu_cpu_stall_notifiers= [KNL]
5439                         Provide RCU CPU stall    5342                         Provide RCU CPU stall notifiers, but see the
5440                         warnings in the RCU_C    5343                         warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
5441                         option's help text.      5344                         option's help text.  TL;DR:  You almost certainly
5442                         do not want rcupdate.    5345                         do not want rcupdate.rcu_cpu_stall_notifiers.
5443                                                  5346 
5444         rcupdate.rcu_cpu_stall_suppress= [KNL    5347         rcupdate.rcu_cpu_stall_suppress= [KNL]
5445                         Suppress RCU CPU stal    5348                         Suppress RCU CPU stall warning messages.
5446                                                  5349 
5447         rcupdate.rcu_cpu_stall_suppress_at_bo    5350         rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448                         Suppress RCU CPU stal    5351                         Suppress RCU CPU stall warning messages and
5449                         rcutorture writer sta    5352                         rcutorture writer stall warnings that occur
5450                         during early boot, th    5353                         during early boot, that is, during the time
5451                         before the init task     5354                         before the init task is spawned.
5452                                                  5355 
5453         rcupdate.rcu_cpu_stall_timeout= [KNL]    5356         rcupdate.rcu_cpu_stall_timeout= [KNL]
5454                         Set timeout for RCU C    5357                         Set timeout for RCU CPU stall warning messages.
5455                         The value is in secon    5358                         The value is in seconds and the maximum allowed
5456                         value is 300 seconds.    5359                         value is 300 seconds.
5457                                                  5360 
5458         rcupdate.rcu_exp_cpu_stall_timeout= [    5361         rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5459                         Set timeout for exped    5362                         Set timeout for expedited RCU CPU stall warning
5460                         messages.  The value     5363                         messages.  The value is in milliseconds
5461                         and the maximum allow    5364                         and the maximum allowed value is 21000
5462                         milliseconds. Please     5365                         milliseconds. Please note that this value is
5463                         adjusted to an arch t    5366                         adjusted to an arch timer tick resolution.
5464                         Setting this to zero     5367                         Setting this to zero causes the value from
5465                         rcupdate.rcu_cpu_stal    5368                         rcupdate.rcu_cpu_stall_timeout to be used (after
5466                         conversion from secon    5369                         conversion from seconds to milliseconds).
5467                                                  5370 
5468         rcupdate.rcu_cpu_stall_cputime= [KNL]    5371         rcupdate.rcu_cpu_stall_cputime= [KNL]
5469                         Provide statistics on    5372                         Provide statistics on the cputime and count of
5470                         interrupts and tasks     5373                         interrupts and tasks during the sampling period. For
5471                         multiple continuous R    5374                         multiple continuous RCU stalls, all sampling periods
5472                         begin at half of the     5375                         begin at half of the first RCU stall timeout.
5473                                                  5376 
5474         rcupdate.rcu_exp_stall_task_details=     5377         rcupdate.rcu_exp_stall_task_details= [KNL]
5475                         Print stack dumps of     5378                         Print stack dumps of any tasks blocking the
5476                         current expedited RCU    5379                         current expedited RCU grace period during an
5477                         expedited RCU CPU sta    5380                         expedited RCU CPU stall warning.
5478                                                  5381 
5479         rcupdate.rcu_expedited= [KNL]            5382         rcupdate.rcu_expedited= [KNL]
5480                         Use expedited grace-p    5383                         Use expedited grace-period primitives, for
5481                         example, synchronize_    5384                         example, synchronize_rcu_expedited() instead
5482                         of synchronize_rcu().    5385                         of synchronize_rcu().  This reduces latency,
5483                         but can increase CPU     5386                         but can increase CPU utilization, degrade
5484                         real-time latency, an    5387                         real-time latency, and degrade energy efficiency.
5485                         No effect on CONFIG_T    5388                         No effect on CONFIG_TINY_RCU kernels.
5486                                                  5389 
5487         rcupdate.rcu_normal= [KNL]               5390         rcupdate.rcu_normal= [KNL]
5488                         Use only normal grace    5391                         Use only normal grace-period primitives,
5489                         for example, synchron    5392                         for example, synchronize_rcu() instead of
5490                         synchronize_rcu_exped    5393                         synchronize_rcu_expedited().  This improves
5491                         real-time latency, CP    5394                         real-time latency, CPU utilization, and
5492                         energy efficiency, bu    5395                         energy efficiency, but can expose users to
5493                         increased grace-perio    5396                         increased grace-period latency.  This parameter
5494                         overrides rcupdate.rc    5397                         overrides rcupdate.rcu_expedited.  No effect on
5495                         CONFIG_TINY_RCU kerne    5398                         CONFIG_TINY_RCU kernels.
5496                                                  5399 
5497         rcupdate.rcu_normal_after_boot= [KNL]    5400         rcupdate.rcu_normal_after_boot= [KNL]
5498                         Once boot has complet    5401                         Once boot has completed (that is, after
5499                         rcu_end_inkernel_boot    5402                         rcu_end_inkernel_boot() has been invoked), use
5500                         only normal grace-per    5403                         only normal grace-period primitives.  No effect
5501                         on CONFIG_TINY_RCU ke    5404                         on CONFIG_TINY_RCU kernels.
5502                                                  5405 
5503                         But note that CONFIG_    5406                         But note that CONFIG_PREEMPT_RT=y kernels enables
5504                         this kernel boot para    5407                         this kernel boot parameter, forcibly setting
5505                         it to the value one,     5408                         it to the value one, that is, converting any
5506                         post-boot attempt at     5409                         post-boot attempt at an expedited RCU grace
5507                         period to instead use    5410                         period to instead use normal non-expedited
5508                         grace-period processi    5411                         grace-period processing.
5509                                                  5412 
5510         rcupdate.rcu_task_collapse_lim= [KNL]    5413         rcupdate.rcu_task_collapse_lim= [KNL]
5511                         Set the maximum numbe    5414                         Set the maximum number of callbacks present
5512                         at the beginning of a    5415                         at the beginning of a grace period that allows
5513                         the RCU Tasks flavors    5416                         the RCU Tasks flavors to collapse back to using
5514                         a single callback que    5417                         a single callback queue.  This switching only
5515                         occurs when rcupdate.    5418                         occurs when rcupdate.rcu_task_enqueue_lim is
5516                         set to the default va    5419                         set to the default value of -1.
5517                                                  5420 
5518         rcupdate.rcu_task_contend_lim= [KNL]     5421         rcupdate.rcu_task_contend_lim= [KNL]
5519                         Set the minimum numbe    5422                         Set the minimum number of callback-queuing-time
5520                         lock-contention event    5423                         lock-contention events per jiffy required to
5521                         cause the RCU Tasks f    5424                         cause the RCU Tasks flavors to switch to per-CPU
5522                         callback queuing.  Th    5425                         callback queuing.  This switching only occurs
5523                         when rcupdate.rcu_tas    5426                         when rcupdate.rcu_task_enqueue_lim is set to
5524                         the default value of     5427                         the default value of -1.
5525                                                  5428 
5526         rcupdate.rcu_task_enqueue_lim= [KNL]     5429         rcupdate.rcu_task_enqueue_lim= [KNL]
5527                         Set the number of cal    5430                         Set the number of callback queues to use for the
5528                         RCU Tasks family of R    5431                         RCU Tasks family of RCU flavors.  The default
5529                         of -1 allows this to     5432                         of -1 allows this to be automatically (and
5530                         dynamically) adjusted    5433                         dynamically) adjusted.  This parameter is intended
5531                         for use in testing.      5434                         for use in testing.
5532                                                  5435 
5533         rcupdate.rcu_task_ipi_delay= [KNL]       5436         rcupdate.rcu_task_ipi_delay= [KNL]
5534                         Set time in jiffies d    5437                         Set time in jiffies during which RCU tasks will
5535                         avoid sending IPIs, s    5438                         avoid sending IPIs, starting with the beginning
5536                         of a given grace peri    5439                         of a given grace period.  Setting a large
5537                         number avoids disturb    5440                         number avoids disturbing real-time workloads,
5538                         but lengthens grace p    5441                         but lengthens grace periods.
5539                                                  5442 
5540         rcupdate.rcu_task_lazy_lim= [KNL]        5443         rcupdate.rcu_task_lazy_lim= [KNL]
5541                         Number of callbacks o    5444                         Number of callbacks on a given CPU that will
5542                         cancel laziness on th    5445                         cancel laziness on that CPU.  Use -1 to disable
5543                         cancellation of lazin    5446                         cancellation of laziness, but be advised that
5544                         doing so increases th    5447                         doing so increases the danger of OOM due to
5545                         callback flooding.       5448                         callback flooding.
5546                                                  5449 
5547         rcupdate.rcu_task_stall_info= [KNL]      5450         rcupdate.rcu_task_stall_info= [KNL]
5548                         Set initial timeout i    5451                         Set initial timeout in jiffies for RCU task stall
5549                         informational message    5452                         informational messages, which give some indication
5550                         of the problem for th    5453                         of the problem for those not patient enough to
5551                         wait for ten minutes.    5454                         wait for ten minutes.  Informational messages are
5552                         only printed prior to    5455                         only printed prior to the stall-warning message
5553                         for a given grace per    5456                         for a given grace period. Disable with a value
5554                         less than or equal to    5457                         less than or equal to zero.  Defaults to ten
5555                         seconds.  A change in    5458                         seconds.  A change in value does not take effect
5556                         until the beginning o    5459                         until the beginning of the next grace period.
5557                                                  5460 
5558         rcupdate.rcu_task_stall_info_mult= [K    5461         rcupdate.rcu_task_stall_info_mult= [KNL]
5559                         Multiplier for time i    5462                         Multiplier for time interval between successive
5560                         RCU task stall inform    5463                         RCU task stall informational messages for a given
5561                         RCU tasks grace perio    5464                         RCU tasks grace period.  This value is clamped
5562                         to one through ten, i    5465                         to one through ten, inclusive.  It defaults to
5563                         the value three, so t    5466                         the value three, so that the first informational
5564                         message is printed 10    5467                         message is printed 10 seconds into the grace
5565                         period, the second at    5468                         period, the second at 40 seconds, the third at
5566                         160 seconds, and then    5469                         160 seconds, and then the stall warning at 600
5567                         seconds would prevent    5470                         seconds would prevent a fourth at 640 seconds.
5568                                                  5471 
5569         rcupdate.rcu_task_stall_timeout= [KNL    5472         rcupdate.rcu_task_stall_timeout= [KNL]
5570                         Set timeout in jiffie    5473                         Set timeout in jiffies for RCU task stall
5571                         warning messages.  Di    5474                         warning messages.  Disable with a value less
5572                         than or equal to zero    5475                         than or equal to zero.  Defaults to ten minutes.
5573                         A change in value doe    5476                         A change in value does not take effect until
5574                         the beginning of the     5477                         the beginning of the next grace period.
5575                                                  5478 
5576         rcupdate.rcu_tasks_lazy_ms= [KNL]        5479         rcupdate.rcu_tasks_lazy_ms= [KNL]
5577                         Set timeout in millis    5480                         Set timeout in milliseconds RCU Tasks asynchronous
5578                         callback batching for    5481                         callback batching for call_rcu_tasks().
5579                         A negative value will    5482                         A negative value will take the default.  A value
5580                         of zero will disable     5483                         of zero will disable batching.  Batching is
5581                         always disabled for s    5484                         always disabled for synchronize_rcu_tasks().
5582                                                  5485 
5583         rcupdate.rcu_tasks_rude_lazy_ms= [KNL    5486         rcupdate.rcu_tasks_rude_lazy_ms= [KNL]
5584                         Set timeout in millis    5487                         Set timeout in milliseconds RCU Tasks
5585                         Rude asynchronous cal    5488                         Rude asynchronous callback batching for
5586                         call_rcu_tasks_rude()    5489                         call_rcu_tasks_rude().  A negative value
5587                         will take the default    5490                         will take the default.  A value of zero will
5588                         disable batching.  Ba    5491                         disable batching.  Batching is always disabled
5589                         for synchronize_rcu_t    5492                         for synchronize_rcu_tasks_rude().
5590                                                  5493 
5591         rcupdate.rcu_tasks_trace_lazy_ms= [KN    5494         rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
5592                         Set timeout in millis    5495                         Set timeout in milliseconds RCU Tasks
5593                         Trace asynchronous ca    5496                         Trace asynchronous callback batching for
5594                         call_rcu_tasks_trace(    5497                         call_rcu_tasks_trace().  A negative value
5595                         will take the default    5498                         will take the default.  A value of zero will
5596                         disable batching.  Ba    5499                         disable batching.  Batching is always disabled
5597                         for synchronize_rcu_t    5500                         for synchronize_rcu_tasks_trace().
5598                                                  5501 
5599         rcupdate.rcu_self_test= [KNL]            5502         rcupdate.rcu_self_test= [KNL]
5600                         Run the RCU early boo    5503                         Run the RCU early boot self tests
5601                                                  5504 
5602         rdinit=         [KNL]                    5505         rdinit=         [KNL]
5603                         Format: <full_path>      5506                         Format: <full_path>
5604                         Run specified binary     5507                         Run specified binary instead of /init from the ramdisk,
5605                         used for early usersp    5508                         used for early userspace startup. See initrd.
5606                                                  5509 
5607         rdrand=         [X86,EARLY]           !! 5510         rdrand=         [X86]
5608                         force - Override the     5511                         force - Override the decision by the kernel to hide the
5609                                 advertisement    5512                                 advertisement of RDRAND support (this affects
5610                                 certain AMD p    5513                                 certain AMD processors because of buggy BIOS
5611                                 support, spec    5514                                 support, specifically around the suspend/resume
5612                                 path).           5515                                 path).
5613                                                  5516 
5614         rdt=            [HW,X86,RDT]             5517         rdt=            [HW,X86,RDT]
5615                         Turn on/off individua    5518                         Turn on/off individual RDT features. List is:
5616                         cmt, mbmtotal, mbmloc    5519                         cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617                         mba, smba, bmec.         5520                         mba, smba, bmec.
5618                         E.g. to turn on cmt a    5521                         E.g. to turn on cmt and turn off mba use:
5619                                 rdt=cmt,!mba     5522                                 rdt=cmt,!mba
5620                                                  5523 
5621         reboot=         [KNL]                    5524         reboot=         [KNL]
5622                         Format (x86 or x86_64    5525                         Format (x86 or x86_64):
5623                                 [w[arm] | c[o    5526                                 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5624                                 [[,]s[mp]####    5527                                 [[,]s[mp]#### \
5625                                 [[,]b[ios] |     5528                                 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626                                 [[,]f[orce]      5529                                 [[,]f[orce]
5627                         Where reboot_mode is     5530                         Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628                                         (pref    5531                                         (prefix with 'panic_' to set mode for panic
5629                                         reboo    5532                                         reboot only),
5630                               reboot_type is     5533                               reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631                               reboot_force is    5534                               reboot_force is either force or not specified,
5632                               reboot_cpu is s    5535                               reboot_cpu is s[mp]#### with #### being the processor
5633                                         to be    5536                                         to be used for rebooting.
5634                                                  5537 
5635         refscale.holdoff= [KNL]                  5538         refscale.holdoff= [KNL]
5636                         Set test-start holdof    5539                         Set test-start holdoff period.  The purpose of
5637                         this parameter is to     5540                         this parameter is to delay the start of the
5638                         test until boot compl    5541                         test until boot completes in order to avoid
5639                         interference.            5542                         interference.
5640                                                  5543 
5641         refscale.lookup_instances= [KNL]         5544         refscale.lookup_instances= [KNL]
5642                         Number of data elemen    5545                         Number of data elements to use for the forms of
5643                         SLAB_TYPESAFE_BY_RCU     5546                         SLAB_TYPESAFE_BY_RCU testing.  A negative number
5644                         is negated and multip    5547                         is negated and multiplied by nr_cpu_ids, while
5645                         zero specifies nr_cpu    5548                         zero specifies nr_cpu_ids.
5646                                                  5549 
5647         refscale.loops= [KNL]                    5550         refscale.loops= [KNL]
5648                         Set the number of loo    5551                         Set the number of loops over the synchronization
5649                         primitive under test.    5552                         primitive under test.  Increasing this number
5650                         reduces noise due to     5553                         reduces noise due to loop start/end overhead,
5651                         but the default has a    5554                         but the default has already reduced the per-pass
5652                         noise to a handful of    5555                         noise to a handful of picoseconds on ca. 2020
5653                         x86 laptops.             5556                         x86 laptops.
5654                                                  5557 
5655         refscale.nreaders= [KNL]                 5558         refscale.nreaders= [KNL]
5656                         Set number of readers    5559                         Set number of readers.  The default value of -1
5657                         selects N, where N is    5560                         selects N, where N is roughly 75% of the number
5658                         of CPUs.  A value of     5561                         of CPUs.  A value of zero is an interesting choice.
5659                                                  5562 
5660         refscale.nruns= [KNL]                    5563         refscale.nruns= [KNL]
5661                         Set number of runs, e    5564                         Set number of runs, each of which is dumped onto
5662                         the console log.         5565                         the console log.
5663                                                  5566 
5664         refscale.readdelay= [KNL]                5567         refscale.readdelay= [KNL]
5665                         Set the read-side cri    5568                         Set the read-side critical-section duration,
5666                         measured in microseco    5569                         measured in microseconds.
5667                                                  5570 
5668         refscale.scale_type= [KNL]               5571         refscale.scale_type= [KNL]
5669                         Specify the read-prot    5572                         Specify the read-protection implementation to test.
5670                                                  5573 
5671         refscale.shutdown= [KNL]                 5574         refscale.shutdown= [KNL]
5672                         Shut down the system     5575                         Shut down the system at the end of the performance
5673                         test.  This defaults     5576                         test.  This defaults to 1 (shut it down) when
5674                         refscale is built int    5577                         refscale is built into the kernel and to 0 (leave
5675                         it running) when refs    5578                         it running) when refscale is built as a module.
5676                                                  5579 
5677         refscale.verbose= [KNL]                  5580         refscale.verbose= [KNL]
5678                         Enable additional pri    5581                         Enable additional printk() statements.
5679                                                  5582 
5680         refscale.verbose_batched= [KNL]          5583         refscale.verbose_batched= [KNL]
5681                         Batch the additional     5584                         Batch the additional printk() statements.  If zero
5682                         (the default) or nega    5585                         (the default) or negative, print everything.  Otherwise,
5683                         print every Nth verbo    5586                         print every Nth verbose statement, where N is the value
5684                         specified.               5587                         specified.
5685                                                  5588 
5686         regulator_ignore_unused                  5589         regulator_ignore_unused
5687                         [REGULATOR]              5590                         [REGULATOR]
5688                         Prevents regulator fr    5591                         Prevents regulator framework from disabling regulators
5689                         that are unused, due     5592                         that are unused, due no driver claiming them. This may
5690                         be useful for debug a    5593                         be useful for debug and development, but should not be
5691                         needed on a platform     5594                         needed on a platform with proper driver support.
5692                                                  5595 
5693         relax_domain_level=                      5596         relax_domain_level=
5694                         [KNL, SMP] Set schedu    5597                         [KNL, SMP] Set scheduler's default relax_domain_level.
5695                         See Documentation/adm    5598                         See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696                                                  5599 
5697         reserve=        [KNL,BUGS] Force kern    5600         reserve=        [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698                         Format: <base1>,<size    5601                         Format: <base1>,<size1>[,<base2>,<size2>,...]
5699                         Reserve I/O ports or     5602                         Reserve I/O ports or memory so the kernel won't use
5700                         them.  If <base> is l    5603                         them.  If <base> is less than 0x10000, the region
5701                         is assumed to be I/O     5604                         is assumed to be I/O ports; otherwise it is memory.
5702                                                  5605 
5703         reserve_mem=    [RAM]                 !! 5606         reservetop=     [X86-32]
5704                         Format: nn[KNG]:<alig << 
5705                         Reserve physical memo << 
5706                         other subsystems can  << 
5707                         used for systems that << 
5708                         line will try to rese << 
5709                         soft reboots. Note, i << 
5710                         location. For example << 
5711                         or if booting a diffe << 
5712                         places the kernel at  << 
5713                         was from a previous b << 
5714                         different location.   << 
5715                         Any subsystem using t << 
5716                         that the contents of  << 
5717                         boot, as there may be << 
5718                         located at the same l << 
5719                                               << 
5720                         The format is size:al << 
5721                         12 megabytes of 4096  << 
5722                                               << 
5723                         reserve_mem=12M:4096: << 
5724                                               << 
5725         reservetop=     [X86-32,EARLY]        << 
5726                         Format: nn[KMG]          5607                         Format: nn[KMG]
5727                         Reserves a hole at th    5608                         Reserves a hole at the top of the kernel virtual
5728                         address space.           5609                         address space.
5729                                                  5610 
5730         reset_devices   [KNL] Force drivers t    5611         reset_devices   [KNL] Force drivers to reset the underlying device
5731                         during initialization    5612                         during initialization.
5732                                                  5613 
5733         resume=         [SWSUSP]                 5614         resume=         [SWSUSP]
5734                         Specify the partition    5615                         Specify the partition device for software suspend
5735                         Format:                  5616                         Format:
5736                         {/dev/<dev> | PARTUUI    5617                         {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737                                                  5618 
5738         resume_offset=  [SWSUSP]                 5619         resume_offset=  [SWSUSP]
5739                         Specify the offset fr    5620                         Specify the offset from the beginning of the partition
5740                         given by "resume=" at    5621                         given by "resume=" at which the swap header is located,
5741                         in <PAGE_SIZE> units     5622                         in <PAGE_SIZE> units (needed only for swap files).
5742                         See  Documentation/po    5623                         See  Documentation/power/swsusp-and-swap-files.rst
5743                                                  5624 
5744         resumedelay=    [HIBERNATION] Delay (    5625         resumedelay=    [HIBERNATION] Delay (in seconds) to pause before attempting to
5745                         read the resume files    5626                         read the resume files
5746                                                  5627 
5747         resumewait      [HIBERNATION] Wait (i    5628         resumewait      [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748                         Useful for devices th    5629                         Useful for devices that are detected asynchronously
5749                         (e.g. USB and MMC dev    5630                         (e.g. USB and MMC devices).
5750                                                  5631 
5751         retain_initrd   [RAM] Keep initrd mem    5632         retain_initrd   [RAM] Keep initrd memory after extraction. After boot, it will
5752                         be accessible via /sy    5633                         be accessible via /sys/firmware/initrd.
5753                                                  5634 
5754         retbleed=       [X86] Control mitigat    5635         retbleed=       [X86] Control mitigation of RETBleed (Arbitrary
5755                         Speculative Code Exec    5636                         Speculative Code Execution with Return Instructions)
5756                         vulnerability.           5637                         vulnerability.
5757                                                  5638 
5758                         AMD-based UNRET and I    5639                         AMD-based UNRET and IBPB mitigations alone do not stop
5759                         sibling threads from     5640                         sibling threads from influencing the predictions of other
5760                         sibling threads. For     5641                         sibling threads. For that reason, STIBP is used on pro-
5761                         cessors that support     5642                         cessors that support it, and mitigate SMT on processors
5762                         that don't.              5643                         that don't.
5763                                                  5644 
5764                         off          - no mit    5645                         off          - no mitigation
5765                         auto         - automa    5646                         auto         - automatically select a migitation
5766                         auto,nosmt   - automa    5647                         auto,nosmt   - automatically select a mitigation,
5767                                        disabl    5648                                        disabling SMT if necessary for
5768                                        the fu    5649                                        the full mitigation (only on Zen1
5769                                        and ol    5650                                        and older without STIBP).
5770                         ibpb         - On AMD    5651                         ibpb         - On AMD, mitigate short speculation
5771                                        window    5652                                        windows on basic block boundaries too.
5772                                        Safe,     5653                                        Safe, highest perf impact. It also
5773                                        enable    5654                                        enables STIBP if present. Not suitable
5774                                        on Int    5655                                        on Intel.
5775                         ibpb,nosmt   - Like "    5656                         ibpb,nosmt   - Like "ibpb" above but will disable SMT
5776                                        when S    5657                                        when STIBP is not available. This is
5777                                        the al    5658                                        the alternative for systems which do not
5778                                        have S    5659                                        have STIBP.
5779                         unret        - Force     5660                         unret        - Force enable untrained return thunks,
5780                                        only e    5661                                        only effective on AMD f15h-f17h based
5781                                        system    5662                                        systems.
5782                         unret,nosmt  - Like u    5663                         unret,nosmt  - Like unret, but will disable SMT when STIBP
5783                                        is not    5664                                        is not available. This is the alternative for
5784                                        system    5665                                        systems which do not have STIBP.
5785                                                  5666 
5786                         Selecting 'auto' will    5667                         Selecting 'auto' will choose a mitigation method at run
5787                         time according to the    5668                         time according to the CPU.
5788                                                  5669 
5789                         Not specifying this o    5670                         Not specifying this option is equivalent to retbleed=auto.
5790                                                  5671 
5791         rfkill.default_state=                    5672         rfkill.default_state=
5792                 0       "airplane mode".  All    5673                 0       "airplane mode".  All wifi, bluetooth, wimax, gps, fm,
5793                         etc. communication is    5674                         etc. communication is blocked by default.
5794                 1       Unblocked.               5675                 1       Unblocked.
5795                                                  5676 
5796         rfkill.master_switch_mode=               5677         rfkill.master_switch_mode=
5797                 0       The "airplane mode" b    5678                 0       The "airplane mode" button does nothing.
5798                 1       The "airplane mode" b    5679                 1       The "airplane mode" button toggles between everything
5799                         blocked and the previ    5680                         blocked and the previous configuration.
5800                 2       The "airplane mode" b    5681                 2       The "airplane mode" button toggles between everything
5801                         blocked and everythin    5682                         blocked and everything unblocked.
5802                                                  5683 
                                                   >> 5684         rhash_entries=  [KNL,NET]
                                                   >> 5685                         Set number of hash buckets for route cache
                                                   >> 5686 
5803         ring3mwait=disable                       5687         ring3mwait=disable
5804                         [KNL] Disable ring 3     5688                         [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805                         CPUs.                    5689                         CPUs.
5806                                                  5690 
5807         riscv_isa_fallback [RISCV,EARLY]      !! 5691         riscv_isa_fallback [RISCV]
5808                         When CONFIG_RISCV_ISA    5692                         When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
5809                         falling back to detec    5693                         falling back to detecting extension support by parsing
5810                         "riscv,isa" property     5694                         "riscv,isa" property on devicetree systems when the
5811                         replacement propertie    5695                         replacement properties are not found. See the Kconfig
5812                         entry for RISCV_ISA_F    5696                         entry for RISCV_ISA_FALLBACK.
5813                                                  5697 
5814         ro              [KNL] Mount root devi    5698         ro              [KNL] Mount root device read-only on boot
5815                                                  5699 
5816         rodata=         [KNL,EARLY]           !! 5700         rodata=         [KNL]
5817                 on      Mark read-only kernel    5701                 on      Mark read-only kernel memory as read-only (default).
5818                 off     Leave read-only kerne    5702                 off     Leave read-only kernel memory writable for debugging.
5819                 full    Mark read-only kernel    5703                 full    Mark read-only kernel memory and aliases as read-only
5820                         [arm64]                  5704                         [arm64]
5821                                                  5705 
5822         rockchip.usb_uart                        5706         rockchip.usb_uart
5823                         [EARLY]               << 
5824                         Enable the uart passt    5707                         Enable the uart passthrough on the designated usb port
5825                         on Rockchip SoCs. Whe    5708                         on Rockchip SoCs. When active, the signals of the
5826                         debug-uart get routed    5709                         debug-uart get routed to the D+ and D- pins of the usb
5827                         port and the regular     5710                         port and the regular usb controller gets disabled.
5828                                                  5711 
5829         root=           [KNL] Root filesystem    5712         root=           [KNL] Root filesystem
5830                         Usually this a a bloc    5713                         Usually this a a block device specifier of some kind,
5831                         see the early_lookup_    5714                         see the early_lookup_bdev comment in
5832                         block/early-lookup.c     5715                         block/early-lookup.c for details.
5833                         Alternatively this ca    5716                         Alternatively this can be "ram" for the legacy initial
5834                         ramdisk, "nfs" and "c    5717                         ramdisk, "nfs" and "cifs" for root on a network file
5835                         system, or "mtd" and     5718                         system, or "mtd" and "ubi" for mounting from raw flash.
5836                                                  5719 
5837         rootdelay=      [KNL] Delay (in secon    5720         rootdelay=      [KNL] Delay (in seconds) to pause before attempting to
5838                         mount the root filesy    5721                         mount the root filesystem
5839                                                  5722 
5840         rootflags=      [KNL] Set root filesy    5723         rootflags=      [KNL] Set root filesystem mount option string
5841                                                  5724 
5842         rootfstype=     [KNL] Set root filesy    5725         rootfstype=     [KNL] Set root filesystem type
5843                                                  5726 
5844         rootwait        [KNL] Wait (indefinit    5727         rootwait        [KNL] Wait (indefinitely) for root device to show up.
5845                         Useful for devices th    5728                         Useful for devices that are detected asynchronously
5846                         (e.g. USB and MMC dev    5729                         (e.g. USB and MMC devices).
5847                                                  5730 
5848         rootwait=       [KNL] Maximum time (i    5731         rootwait=       [KNL] Maximum time (in seconds) to wait for root device
5849                         to show up before att    5732                         to show up before attempting to mount the root
5850                         filesystem.              5733                         filesystem.
5851                                                  5734 
5852         rproc_mem=nn[KMG][@address]              5735         rproc_mem=nn[KMG][@address]
5853                         [KNL,ARM,CMA] Remotep    5736                         [KNL,ARM,CMA] Remoteproc physical memory block.
5854                         Memory area to be use    5737                         Memory area to be used by remote processor image,
5855                         managed by CMA.          5738                         managed by CMA.
5856                                                  5739 
5857         rw              [KNL] Mount root devi    5740         rw              [KNL] Mount root device read-write on boot
5858                                                  5741 
5859         S               [KNL] Run init in sin    5742         S               [KNL] Run init in single mode
5860                                                  5743 
5861         s390_iommu=     [HW,S390]                5744         s390_iommu=     [HW,S390]
5862                         Set s390 IOTLB flushi    5745                         Set s390 IOTLB flushing mode
5863                 strict                           5746                 strict
5864                         With strict flushing     5747                         With strict flushing every unmap operation will result
5865                         in an IOTLB flush. De    5748                         in an IOTLB flush. Default is lazy flushing before
5866                         reuse, which is faste    5749                         reuse, which is faster. Deprecated, equivalent to
5867                         iommu.strict=1.          5750                         iommu.strict=1.
5868                                                  5751 
5869         s390_iommu_aperture=    [KNL,S390]       5752         s390_iommu_aperture=    [KNL,S390]
5870                         Specifies the size of    5753                         Specifies the size of the per device DMA address space
5871                         accessible through th    5754                         accessible through the DMA and IOMMU APIs as a decimal
5872                         factor of the size of    5755                         factor of the size of main memory.
5873                         The default is 1 mean    5756                         The default is 1 meaning that one can concurrently use
5874                         as many DMA addresses    5757                         as many DMA addresses as physical memory is installed,
5875                         if supported by hardw    5758                         if supported by hardware, and thus map all of memory
5876                         once. With a value of    5759                         once. With a value of 2 one can map all of memory twice
5877                         and so on. As a speci    5760                         and so on. As a special case a factor of 0 imposes no
5878                         restrictions other th    5761                         restrictions other than those given by hardware at the
5879                         cost of significant a    5762                         cost of significant additional memory use for tables.
5880                                                  5763 
5881         sa1100ir        [NET]                    5764         sa1100ir        [NET]
5882                         See drivers/net/irda/    5765                         See drivers/net/irda/sa1100_ir.c.
5883                                                  5766 
5884         sched_verbose   [KNL,EARLY] Enables v !! 5767         sched_verbose   [KNL] Enables verbose scheduler debug messages.
5885                                                  5768 
5886         schedstats=     [KNL,X86] Enable or d    5769         schedstats=     [KNL,X86] Enable or disable scheduled statistics.
5887                         Allowed values are en    5770                         Allowed values are enable and disable. This feature
5888                         incurs a small amount    5771                         incurs a small amount of overhead in the scheduler
5889                         but is useful for deb    5772                         but is useful for debugging and performance tuning.
5890                                                  5773 
5891         sched_thermal_decay_shift=               5774         sched_thermal_decay_shift=
5892                         [Deprecated]          << 
5893                         [KNL, SMP] Set a deca    5775                         [KNL, SMP] Set a decay shift for scheduler thermal
5894                         pressure signal. Ther    5776                         pressure signal. Thermal pressure signal follows the
5895                         default decay period     5777                         default decay period of other scheduler pelt
5896                         signals(usually 32 ms    5778                         signals(usually 32 ms but configurable). Setting
5897                         sched_thermal_decay_s    5779                         sched_thermal_decay_shift will left shift the decay
5898                         period for the therma    5780                         period for the thermal pressure signal by the shift
5899                         value.                   5781                         value.
5900                         i.e. with the default    5782                         i.e. with the default pelt decay period of 32 ms
5901                         sched_thermal_decay_s    5783                         sched_thermal_decay_shift   thermal pressure decay pr
5902                                 1                5784                                 1                       64 ms
5903                                 2                5785                                 2                       128 ms
5904                         and so on.               5786                         and so on.
5905                         Format: integer betwe    5787                         Format: integer between 0 and 10
5906                         Default is 0.            5788                         Default is 0.
5907                                                  5789 
5908         scftorture.holdoff= [KNL]                5790         scftorture.holdoff= [KNL]
5909                         Number of seconds to     5791                         Number of seconds to hold off before starting
5910                         test.  Defaults to ze    5792                         test.  Defaults to zero for module insertion and
5911                         to 10 seconds for bui    5793                         to 10 seconds for built-in smp_call_function()
5912                         tests.                   5794                         tests.
5913                                                  5795 
5914         scftorture.longwait= [KNL]               5796         scftorture.longwait= [KNL]
5915                         Request ridiculously     5797                         Request ridiculously long waits randomly selected
5916                         up to the chosen limi    5798                         up to the chosen limit in seconds.  Zero (the
5917                         default) disables thi    5799                         default) disables this feature.  Please note
5918                         that requesting even     5800                         that requesting even small non-zero numbers of
5919                         seconds can result in    5801                         seconds can result in RCU CPU stall warnings,
5920                         softlockup complaints    5802                         softlockup complaints, and so on.
5921                                                  5803 
5922         scftorture.nthreads= [KNL]               5804         scftorture.nthreads= [KNL]
5923                         Number of kthreads to    5805                         Number of kthreads to spawn to invoke the
5924                         smp_call_function() f    5806                         smp_call_function() family of functions.
5925                         The default of -1 spe    5807                         The default of -1 specifies a number of kthreads
5926                         equal to the number o    5808                         equal to the number of CPUs.
5927                                                  5809 
5928         scftorture.onoff_holdoff= [KNL]          5810         scftorture.onoff_holdoff= [KNL]
5929                         Number seconds to wai    5811                         Number seconds to wait after the start of the
5930                         test before initiatin    5812                         test before initiating CPU-hotplug operations.
5931                                                  5813 
5932         scftorture.onoff_interval= [KNL]         5814         scftorture.onoff_interval= [KNL]
5933                         Number seconds to wai    5815                         Number seconds to wait between successive
5934                         CPU-hotplug operation    5816                         CPU-hotplug operations.  Specifying zero (which
5935                         is the default) disab    5817                         is the default) disables CPU-hotplug operations.
5936                                                  5818 
5937         scftorture.shutdown_secs= [KNL]          5819         scftorture.shutdown_secs= [KNL]
5938                         The number of seconds    5820                         The number of seconds following the start of the
5939                         test after which to s    5821                         test after which to shut down the system.  The
5940                         default of zero avoid    5822                         default of zero avoids shutting down the system.
5941                         Non-zero values are u    5823                         Non-zero values are useful for automated tests.
5942                                                  5824 
5943         scftorture.stat_interval= [KNL]          5825         scftorture.stat_interval= [KNL]
5944                         The number of seconds    5826                         The number of seconds between outputting the
5945                         current test statisti    5827                         current test statistics to the console.  A value
5946                         of zero disables stat    5828                         of zero disables statistics output.
5947                                                  5829 
5948         scftorture.stutter_cpus= [KNL]           5830         scftorture.stutter_cpus= [KNL]
5949                         The number of jiffies    5831                         The number of jiffies to wait between each change
5950                         to the set of CPUs un    5832                         to the set of CPUs under test.
5951                                                  5833 
5952         scftorture.use_cpus_read_lock= [KNL]     5834         scftorture.use_cpus_read_lock= [KNL]
5953                         Use use_cpus_read_loc    5835                         Use use_cpus_read_lock() instead of the default
5954                         preempt_disable() to     5836                         preempt_disable() to disable CPU hotplug
5955                         while invoking one of    5837                         while invoking one of the smp_call_function*()
5956                         functions.               5838                         functions.
5957                                                  5839 
5958         scftorture.verbose= [KNL]                5840         scftorture.verbose= [KNL]
5959                         Enable additional pri    5841                         Enable additional printk() statements.
5960                                                  5842 
5961         scftorture.weight_single= [KNL]          5843         scftorture.weight_single= [KNL]
5962                         The probability weigh    5844                         The probability weighting to use for the
5963                         smp_call_function_sin    5845                         smp_call_function_single() function with a zero
5964                         "wait" parameter.  A     5846                         "wait" parameter.  A value of -1 selects the
5965                         default if all other     5847                         default if all other weights are -1.  However,
5966                         if at least one weigh    5848                         if at least one weight has some other value, a
5967                         value of -1 will inst    5849                         value of -1 will instead select a weight of zero.
5968                                                  5850 
5969         scftorture.weight_single_wait= [KNL]     5851         scftorture.weight_single_wait= [KNL]
5970                         The probability weigh    5852                         The probability weighting to use for the
5971                         smp_call_function_sin    5853                         smp_call_function_single() function with a
5972                         non-zero "wait" param    5854                         non-zero "wait" parameter.  See weight_single.
5973                                                  5855 
5974         scftorture.weight_many= [KNL]            5856         scftorture.weight_many= [KNL]
5975                         The probability weigh    5857                         The probability weighting to use for the
5976                         smp_call_function_man    5858                         smp_call_function_many() function with a zero
5977                         "wait" parameter.  Se    5859                         "wait" parameter.  See weight_single.
5978                         Note well that settin    5860                         Note well that setting a high probability for
5979                         this weighting can pl    5861                         this weighting can place serious IPI load
5980                         on the system.           5862                         on the system.
5981                                                  5863 
5982         scftorture.weight_many_wait= [KNL]       5864         scftorture.weight_many_wait= [KNL]
5983                         The probability weigh    5865                         The probability weighting to use for the
5984                         smp_call_function_man    5866                         smp_call_function_many() function with a
5985                         non-zero "wait" param    5867                         non-zero "wait" parameter.  See weight_single
5986                         and weight_many.         5868                         and weight_many.
5987                                                  5869 
5988         scftorture.weight_all= [KNL]             5870         scftorture.weight_all= [KNL]
5989                         The probability weigh    5871                         The probability weighting to use for the
5990                         smp_call_function_all    5872                         smp_call_function_all() function with a zero
5991                         "wait" parameter.  Se    5873                         "wait" parameter.  See weight_single and
5992                         weight_many.             5874                         weight_many.
5993                                                  5875 
5994         scftorture.weight_all_wait= [KNL]        5876         scftorture.weight_all_wait= [KNL]
5995                         The probability weigh    5877                         The probability weighting to use for the
5996                         smp_call_function_all    5878                         smp_call_function_all() function with a
5997                         non-zero "wait" param    5879                         non-zero "wait" parameter.  See weight_single
5998                         and weight_many.         5880                         and weight_many.
5999                                                  5881 
6000         skew_tick=      [KNL,EARLY] Offset th !! 5882         skew_tick=      [KNL] Offset the periodic timer tick per cpu to mitigate
6001                         xtime_lock contention    5883                         xtime_lock contention on larger systems, and/or RCU lock
6002                         contention on all sys    5884                         contention on all systems with CONFIG_MAXSMP set.
6003                         Format: { "0" | "1" }    5885                         Format: { "0" | "1" }
6004                         0 -- disable. (may be    5886                         0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005                         1 -- enable.             5887                         1 -- enable.
6006                         Note: increases power    5888                         Note: increases power consumption, thus should only be
6007                         enabled if running ji    5889                         enabled if running jitter sensitive (HPC/RT) workloads.
6008                                                  5890 
6009         security=       [SECURITY] Choose a l    5891         security=       [SECURITY] Choose a legacy "major" security module to
6010                         enable at boot. This     5892                         enable at boot. This has been deprecated by the
6011                         "lsm=" parameter.        5893                         "lsm=" parameter.
6012                                                  5894 
6013         selinux=        [SELINUX] Disable or     5895         selinux=        [SELINUX] Disable or enable SELinux at boot time.
6014                         Format: { "0" | "1" }    5896                         Format: { "0" | "1" }
6015                         See security/selinux/    5897                         See security/selinux/Kconfig help text.
6016                         0 -- disable.            5898                         0 -- disable.
6017                         1 -- enable.             5899                         1 -- enable.
6018                         Default value is 1.      5900                         Default value is 1.
6019                                                  5901 
6020         serialnumber    [BUGS=X86-32]            5902         serialnumber    [BUGS=X86-32]
6021                                                  5903 
6022         sev=option[,option...] [X86-64] See D    5904         sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
6023                                                  5905 
6024         shapers=        [NET]                    5906         shapers=        [NET]
6025                         Maximal number of sha    5907                         Maximal number of shapers.
6026                                                  5908 
6027         show_lapic=     [APIC,X86] Advanced P    5909         show_lapic=     [APIC,X86] Advanced Programmable Interrupt Controller
6028                         Limit apic dumping. T    5910                         Limit apic dumping. The parameter defines the maximal
6029                         number of local apics    5911                         number of local apics being dumped. Also it is possible
6030                         to set it to "all" by    5912                         to set it to "all" by meaning -- no limit here.
6031                         Format: { 1 (default)    5913                         Format: { 1 (default) | 2 | ... | all }.
6032                         The parameter valid i    5914                         The parameter valid if only apic=debug or
6033                         apic=verbose is speci    5915                         apic=verbose is specified.
6034                         Example: apic=debug s    5916                         Example: apic=debug show_lapic=all
6035                                                  5917 
6036         slab_debug[=options[,slabs][;[options !! 5918         simeth=         [IA-64]
6037                         Enabling slab_debug a !! 5919         simscsi=
                                                   >> 5920 
                                                   >> 5921         slram=          [HW,MTD]
                                                   >> 5922 
                                                   >> 5923         slab_merge      [MM]
                                                   >> 5924                         Enable merging of slabs with similar size when the
                                                   >> 5925                         kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
                                                   >> 5926 
                                                   >> 5927         slab_nomerge    [MM]
                                                   >> 5928                         Disable merging of slabs with similar size. May be
                                                   >> 5929                         necessary if there is some reason to distinguish
                                                   >> 5930                         allocs to different slabs, especially in hardened
                                                   >> 5931                         environments where the risk of heap overflows and
                                                   >> 5932                         layout control by attackers can usually be
                                                   >> 5933                         frustrated by disabling merging. This will reduce
                                                   >> 5934                         most of the exposure of a heap attack to a single
                                                   >> 5935                         cache (risks via metadata attacks are mostly
                                                   >> 5936                         unchanged). Debug options disable merging on their
                                                   >> 5937                         own.
                                                   >> 5938                         For more information see Documentation/mm/slub.rst.
                                                   >> 5939 
                                                   >> 5940         slab_max_order= [MM, SLAB]
                                                   >> 5941                         Determines the maximum allowed order for slabs.
                                                   >> 5942                         A high setting may cause OOMs due to memory
                                                   >> 5943                         fragmentation.  Defaults to 1 for systems with
                                                   >> 5944                         more than 32MB of RAM, 0 otherwise.
                                                   >> 5945 
                                                   >> 5946         slub_debug[=options[,slabs][;[options[,slabs]]...]      [MM, SLUB]
                                                   >> 5947                         Enabling slub_debug allows one to determine the
6038                         culprit if slab objec    5948                         culprit if slab objects become corrupted. Enabling
6039                         slab_debug can create !! 5949                         slub_debug can create guard zones around objects and
6040                         may poison objects wh    5950                         may poison objects when not in use. Also tracks the
6041                         last alloc / free. Fo    5951                         last alloc / free. For more information see
6042                         Documentation/mm/slub    5952                         Documentation/mm/slub.rst.
6043                         (slub_debug legacy na << 
6044                                                  5953 
6045         slab_max_order= [MM]                  !! 5954         slub_max_order= [MM, SLUB]
6046                         Determines the maximu    5955                         Determines the maximum allowed order for slabs.
6047                         A high setting may ca    5956                         A high setting may cause OOMs due to memory
6048                         fragmentation. For mo    5957                         fragmentation. For more information see
6049                         Documentation/mm/slub    5958                         Documentation/mm/slub.rst.
6050                         (slub_max_order legac << 
6051                                               << 
6052         slab_merge      [MM]                  << 
6053                         Enable merging of sla << 
6054                         kernel is built witho << 
6055                         (slub_merge legacy na << 
6056                                                  5959 
6057         slab_min_objects=       [MM]          !! 5960         slub_min_objects=       [MM, SLUB]
6058                         The minimum number of    5961                         The minimum number of objects per slab. SLUB will
6059                         increase the slab ord !! 5962                         increase the slab order up to slub_max_order to
6060                         generate a sufficient    5963                         generate a sufficiently large slab able to contain
6061                         the number of objects    5964                         the number of objects indicated. The higher the number
6062                         of objects the smalle    5965                         of objects the smaller the overhead of tracking slabs
6063                         and the less frequent    5966                         and the less frequently locks need to be acquired.
6064                         For more information     5967                         For more information see Documentation/mm/slub.rst.
6065                         (slub_min_objects leg << 
6066                                                  5968 
6067         slab_min_order= [MM]                  !! 5969         slub_min_order= [MM, SLUB]
6068                         Determines the minimu    5970                         Determines the minimum page order for slabs. Must be
6069                         lower or equal to sla !! 5971                         lower than slub_max_order.
6070                         Documentation/mm/slub << 
6071                         (slub_min_order legac << 
6072                                               << 
6073         slab_nomerge    [MM]                  << 
6074                         Disable merging of sl << 
6075                         necessary if there is << 
6076                         allocs to different s << 
6077                         environments where th << 
6078                         layout control by att << 
6079                         frustrated by disabli << 
6080                         most of the exposure  << 
6081                         cache (risks via meta << 
6082                         unchanged). Debug opt << 
6083                         own.                  << 
6084                         For more information     5972                         For more information see Documentation/mm/slub.rst.
6085                         (slub_nomerge legacy  << 
6086                                                  5973 
6087         slram=          [HW,MTD]              !! 5974         slub_merge      [MM, SLUB]
                                                   >> 5975                         Same with slab_merge.
                                                   >> 5976 
                                                   >> 5977         slub_nomerge    [MM, SLUB]
                                                   >> 5978                         Same with slab_nomerge. This is supported for legacy.
                                                   >> 5979                         See slab_nomerge for more information.
6088                                                  5980 
6089         smart2=         [HW]                     5981         smart2=         [HW]
6090                         Format: <io1>[,<io2>[    5982                         Format: <io1>[,<io2>[,...,<io8>]]
6091                                                  5983 
6092         smp.csd_lock_timeout= [KNL]              5984         smp.csd_lock_timeout= [KNL]
6093                         Specify the period of    5985                         Specify the period of time in milliseconds
6094                         that smp_call_functio    5986                         that smp_call_function() and friends will wait
6095                         for a CPU to release     5987                         for a CPU to release the CSD lock.  This is
6096                         useful when diagnosin    5988                         useful when diagnosing bugs involving CPUs
6097                         disabling interrupts     5989                         disabling interrupts for extended periods
6098                         of time.  Defaults to    5990                         of time.  Defaults to 5,000 milliseconds, and
6099                         setting a value of ze    5991                         setting a value of zero disables this feature.
6100                         This feature may be m    5992                         This feature may be more efficiently disabled
6101                         using the csdlock_deb    5993                         using the csdlock_debug- kernel parameter.
6102                                                  5994 
6103         smp.panic_on_ipistall= [KNL]             5995         smp.panic_on_ipistall= [KNL]
6104                         If a csd_lock_timeout    5996                         If a csd_lock_timeout extends for more than
6105                         the specified number     5997                         the specified number of milliseconds, panic the
6106                         system.  By default,     5998                         system.  By default, let CSD-lock acquisition
6107                         take as long as they     5999                         take as long as they take.  Specifying 300,000
6108                         for this value provid    6000                         for this value provides a 5-minute timeout.
6109                                                  6001 
6110         smsc-ircc2.nopnp        [HW] Don't us    6002         smsc-ircc2.nopnp        [HW] Don't use PNP to discover SMC devices
6111         smsc-ircc2.ircc_cfg=    [HW] Device c    6003         smsc-ircc2.ircc_cfg=    [HW] Device configuration I/O port
6112         smsc-ircc2.ircc_sir=    [HW] SIR base    6004         smsc-ircc2.ircc_sir=    [HW] SIR base I/O port
6113         smsc-ircc2.ircc_fir=    [HW] FIR base    6005         smsc-ircc2.ircc_fir=    [HW] FIR base I/O port
6114         smsc-ircc2.ircc_irq=    [HW] IRQ line    6006         smsc-ircc2.ircc_irq=    [HW] IRQ line
6115         smsc-ircc2.ircc_dma=    [HW] DMA chan    6007         smsc-ircc2.ircc_dma=    [HW] DMA channel
6116         smsc-ircc2.ircc_transceiver= [HW] Tra    6008         smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117                                 0: Toshiba Sa    6009                                 0: Toshiba Satellite 1800 (GP data pin select)
6118                                 1: Fast pin s    6010                                 1: Fast pin select (default)
6119                                 2: ATC IRMode    6011                                 2: ATC IRMode
6120                                                  6012 
6121         smt=            [KNL,MIPS,S390,EARLY] !! 6013         smt=            [KNL,MIPS,S390] Set the maximum number of threads (logical
6122                         (logical CPUs) to use !! 6014                         CPUs) to use per physical CPU on systems capable of
6123                         capable of symmetric  !! 6015                         symmetric multithreading (SMT). Will be capped to the
6124                         be capped to the actu !! 6016                         actual hardware limit.
6125                         Format: <integer>        6017                         Format: <integer>
6126                         Default: -1 (no limit    6018                         Default: -1 (no limit)
6127                                                  6019 
6128         softlockup_panic=                        6020         softlockup_panic=
6129                         [KNL] Should the soft    6021                         [KNL] Should the soft-lockup detector generate panics.
6130                         Format: 0 | 1            6022                         Format: 0 | 1
6131                                                  6023 
6132                         A value of 1 instruct    6024                         A value of 1 instructs the soft-lockup detector
6133                         to panic the machine     6025                         to panic the machine when a soft-lockup occurs. It is
6134                         also controlled by th    6026                         also controlled by the kernel.softlockup_panic sysctl
6135                         and CONFIG_BOOTPARAM_    6027                         and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136                         respective build-time    6028                         respective build-time switch to that functionality.
6137                                                  6029 
6138         softlockup_all_cpu_backtrace=            6030         softlockup_all_cpu_backtrace=
6139                         [KNL] Should the soft    6031                         [KNL] Should the soft-lockup detector generate
6140                         backtraces on all cpu    6032                         backtraces on all cpus.
6141                         Format: 0 | 1            6033                         Format: 0 | 1
6142                                                  6034 
6143         sonypi.*=       [HW] Sony Programmabl    6035         sonypi.*=       [HW] Sony Programmable I/O Control Device driver
6144                         See Documentation/adm    6036                         See Documentation/admin-guide/laptops/sonypi.rst
6145                                                  6037 
6146         spectre_bhi=    [X86] Control mitigat    6038         spectre_bhi=    [X86] Control mitigation of Branch History Injection
6147                         (BHI) vulnerability.     6039                         (BHI) vulnerability.  This setting affects the
6148                         deployment of the HW     6040                         deployment of the HW BHI control and the SW BHB
6149                         clearing sequence.       6041                         clearing sequence.
6150                                                  6042 
6151                         on     - (default) En !! 6043                         on   - (default) Enable the HW or SW mitigation
6152                                  needed.  Thi !! 6044                                as needed.
6153                                  both syscall !! 6045                         off  - Disable the mitigation.
6154                         vmexit - On systems w << 
6155                                  available, e << 
6156                                  ONLY.  On su << 
6157                                  protected fr << 
6158                                  may still be << 
6159                         off    - Disable the  << 
6160                                                  6046 
6161         spectre_v2=     [X86,EARLY] Control m !! 6047         spectre_v2=     [X86] Control mitigation of Spectre variant 2
6162                         (indirect branch spec    6048                         (indirect branch speculation) vulnerability.
6163                         The default operation    6049                         The default operation protects the kernel from
6164                         user space attacks.      6050                         user space attacks.
6165                                                  6051 
6166                         on   - unconditionall    6052                         on   - unconditionally enable, implies
6167                                spectre_v2_use    6053                                spectre_v2_user=on
6168                         off  - unconditionall    6054                         off  - unconditionally disable, implies
6169                                spectre_v2_use    6055                                spectre_v2_user=off
6170                         auto - kernel detects    6056                         auto - kernel detects whether your CPU model is
6171                                vulnerable        6057                                vulnerable
6172                                                  6058 
6173                         Selecting 'on' will,     6059                         Selecting 'on' will, and 'auto' may, choose a
6174                         mitigation method at     6060                         mitigation method at run time according to the
6175                         CPU, the available mi    6061                         CPU, the available microcode, the setting of the
6176                         CONFIG_MITIGATION_RET !! 6062                         CONFIG_RETPOLINE configuration option, and the
6177                         and the compiler with !! 6063                         compiler with which the kernel was built.
6178                                                  6064 
6179                         Selecting 'on' will a    6065                         Selecting 'on' will also enable the mitigation
6180                         against user space to    6066                         against user space to user space task attacks.
6181                                                  6067 
6182                         Selecting 'off' will     6068                         Selecting 'off' will disable both the kernel and
6183                         the user space protec    6069                         the user space protections.
6184                                                  6070 
6185                         Specific mitigations     6071                         Specific mitigations can also be selected manually:
6186                                                  6072 
6187                         retpoline         - r    6073                         retpoline         - replace indirect branches
6188                         retpoline,generic - R    6074                         retpoline,generic - Retpolines
6189                         retpoline,lfence  - L    6075                         retpoline,lfence  - LFENCE; indirect branch
6190                         retpoline,amd     - a    6076                         retpoline,amd     - alias for retpoline,lfence
6191                         eibrs             - E    6077                         eibrs             - Enhanced/Auto IBRS
6192                         eibrs,retpoline   - E    6078                         eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
6193                         eibrs,lfence      - E    6079                         eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
6194                         ibrs              - u    6080                         ibrs              - use IBRS to protect kernel
6195                                                  6081 
6196                         Not specifying this o    6082                         Not specifying this option is equivalent to
6197                         spectre_v2=auto.         6083                         spectre_v2=auto.
6198                                                  6084 
6199         spectre_v2_user=                         6085         spectre_v2_user=
6200                         [X86] Control mitigat    6086                         [X86] Control mitigation of Spectre variant 2
6201                         (indirect branch spec    6087                         (indirect branch speculation) vulnerability between
6202                         user space tasks         6088                         user space tasks
6203                                                  6089 
6204                         on      - Uncondition    6090                         on      - Unconditionally enable mitigations. Is
6205                                   enforced by    6091                                   enforced by spectre_v2=on
6206                                                  6092 
6207                         off     - Uncondition    6093                         off     - Unconditionally disable mitigations. Is
6208                                   enforced by    6094                                   enforced by spectre_v2=off
6209                                                  6095 
6210                         prctl   - Indirect br    6096                         prctl   - Indirect branch speculation is enabled,
6211                                   but mitigat    6097                                   but mitigation can be enabled via prctl
6212                                   per thread.    6098                                   per thread.  The mitigation control state
6213                                   is inherite    6099                                   is inherited on fork.
6214                                                  6100 
6215                         prctl,ibpb               6101                         prctl,ibpb
6216                                 - Like "prctl    6102                                 - Like "prctl" above, but only STIBP is
6217                                   controlled     6103                                   controlled per thread. IBPB is issued
6218                                   always when    6104                                   always when switching between different user
6219                                   space proce    6105                                   space processes.
6220                                                  6106 
6221                         seccomp                  6107                         seccomp
6222                                 - Same as "pr    6108                                 - Same as "prctl" above, but all seccomp
6223                                   threads wil    6109                                   threads will enable the mitigation unless
6224                                   they explic    6110                                   they explicitly opt out.
6225                                                  6111 
6226                         seccomp,ibpb             6112                         seccomp,ibpb
6227                                 - Like "secco    6113                                 - Like "seccomp" above, but only STIBP is
6228                                   controlled     6114                                   controlled per thread. IBPB is issued
6229                                   always when    6115                                   always when switching between different
6230                                   user space     6116                                   user space processes.
6231                                                  6117 
6232                         auto    - Kernel sele    6118                         auto    - Kernel selects the mitigation depending on
6233                                   the availab    6119                                   the available CPU features and vulnerability.
6234                                                  6120 
6235                         Default mitigation: "    6121                         Default mitigation: "prctl"
6236                                                  6122 
6237                         Not specifying this o    6123                         Not specifying this option is equivalent to
6238                         spectre_v2_user=auto.    6124                         spectre_v2_user=auto.
6239                                                  6125 
6240         spec_rstack_overflow=                    6126         spec_rstack_overflow=
6241                         [X86,EARLY] Control R !! 6127                         [X86] Control RAS overflow mitigation on AMD Zen CPUs
6242                                                  6128 
6243                         off             - Dis    6129                         off             - Disable mitigation
6244                         microcode       - Ena    6130                         microcode       - Enable microcode mitigation only
6245                         safe-ret        - Ena    6131                         safe-ret        - Enable sw-only safe RET mitigation (default)
6246                         ibpb            - Ena    6132                         ibpb            - Enable mitigation by issuing IBPB on
6247                                           ker    6133                                           kernel entry
6248                         ibpb-vmexit     - Iss    6134                         ibpb-vmexit     - Issue IBPB only on VMEXIT
6249                                           (cl    6135                                           (cloud-specific mitigation)
6250                                                  6136 
6251         spec_store_bypass_disable=               6137         spec_store_bypass_disable=
6252                         [HW,EARLY] Control Sp !! 6138                         [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253                         (Speculative Store By    6139                         (Speculative Store Bypass vulnerability)
6254                                                  6140 
6255                         Certain CPUs are vuln    6141                         Certain CPUs are vulnerable to an exploit against a
6256                         a common industry wid    6142                         a common industry wide performance optimization known
6257                         as "Speculative Store    6143                         as "Speculative Store Bypass" in which recent stores
6258                         to the same memory lo    6144                         to the same memory location may not be observed by
6259                         later loads during sp    6145                         later loads during speculative execution. The idea
6260                         is that such stores a    6146                         is that such stores are unlikely and that they can
6261                         be detected prior to     6147                         be detected prior to instruction retirement at the
6262                         end of a particular s    6148                         end of a particular speculation execution window.
6263                                                  6149 
6264                         In vulnerable process    6150                         In vulnerable processors, the speculatively forwarded
6265                         store can be used in     6151                         store can be used in a cache side channel attack, for
6266                         example to read memor    6152                         example to read memory to which the attacker does not
6267                         directly have access     6153                         directly have access (e.g. inside sandboxed code).
6268                                                  6154 
6269                         This parameter contro    6155                         This parameter controls whether the Speculative Store
6270                         Bypass optimization i    6156                         Bypass optimization is used.
6271                                                  6157 
6272                         On x86 the options ar    6158                         On x86 the options are:
6273                                                  6159 
6274                         on      - Uncondition    6160                         on      - Unconditionally disable Speculative Store Bypass
6275                         off     - Uncondition    6161                         off     - Unconditionally enable Speculative Store Bypass
6276                         auto    - Kernel dete    6162                         auto    - Kernel detects whether the CPU model contains an
6277                                   implementat    6163                                   implementation of Speculative Store Bypass and
6278                                   picks the m    6164                                   picks the most appropriate mitigation. If the
6279                                   CPU is not     6165                                   CPU is not vulnerable, "off" is selected. If the
6280                                   CPU is vuln    6166                                   CPU is vulnerable the default mitigation is
6281                                   architectur    6167                                   architecture and Kconfig dependent. See below.
6282                         prctl   - Control Spe    6168                         prctl   - Control Speculative Store Bypass per thread
6283                                   via prctl.     6169                                   via prctl. Speculative Store Bypass is enabled
6284                                   for a proce    6170                                   for a process by default. The state of the control
6285                                   is inherite    6171                                   is inherited on fork.
6286                         seccomp - Same as "pr    6172                         seccomp - Same as "prctl" above, but all seccomp threads
6287                                   will disabl    6173                                   will disable SSB unless they explicitly opt out.
6288                                                  6174 
6289                         Default mitigations:     6175                         Default mitigations:
6290                         X86:    "prctl"          6176                         X86:    "prctl"
6291                                                  6177 
6292                         On powerpc the option    6178                         On powerpc the options are:
6293                                                  6179 
6294                         on,auto - On Power8 a    6180                         on,auto - On Power8 and Power9 insert a store-forwarding
6295                                   barrier on     6181                                   barrier on kernel entry and exit. On Power7
6296                                   perform a s    6182                                   perform a software flush on kernel entry and
6297                                   exit.          6183                                   exit.
6298                         off     - No action.     6184                         off     - No action.
6299                                                  6185 
6300                         Not specifying this o    6186                         Not specifying this option is equivalent to
6301                         spec_store_bypass_dis    6187                         spec_store_bypass_disable=auto.
6302                                                  6188 
                                                   >> 6189         spia_io_base=   [HW,MTD]
                                                   >> 6190         spia_fio_base=
                                                   >> 6191         spia_pedr=
                                                   >> 6192         spia_peddr=
                                                   >> 6193 
6303         split_lock_detect=                       6194         split_lock_detect=
6304                         [X86] Enable split lo    6195                         [X86] Enable split lock detection or bus lock detection
6305                                                  6196 
6306                         When enabled (and if     6197                         When enabled (and if hardware support is present), atomic
6307                         instructions that acc    6198                         instructions that access data across cache line
6308                         boundaries will resul    6199                         boundaries will result in an alignment check exception
6309                         for split lock detect    6200                         for split lock detection or a debug exception for
6310                         bus lock detection.      6201                         bus lock detection.
6311                                                  6202 
6312                         off     - not enabled    6203                         off     - not enabled
6313                                                  6204 
6314                         warn    - the kernel     6205                         warn    - the kernel will emit rate-limited warnings
6315                                   about appli    6206                                   about applications triggering the #AC
6316                                   exception o    6207                                   exception or the #DB exception. This mode is
6317                                   the default    6208                                   the default on CPUs that support split lock
6318                                   detection o    6209                                   detection or bus lock detection. Default
6319                                   behavior is    6210                                   behavior is by #AC if both features are
6320                                   enabled in     6211                                   enabled in hardware.
6321                                                  6212 
6322                         fatal   - the kernel     6213                         fatal   - the kernel will send SIGBUS to applications
6323                                   that trigge    6214                                   that trigger the #AC exception or the #DB
6324                                   exception.     6215                                   exception. Default behavior is by #AC if
6325                                   both featur    6216                                   both features are enabled in hardware.
6326                                                  6217 
6327                         ratelimit:N -            6218                         ratelimit:N -
6328                                   Set system     6219                                   Set system wide rate limit to N bus locks
6329                                   per second     6220                                   per second for bus lock detection.
6330                                   0 < N <= 10    6221                                   0 < N <= 1000.
6331                                                  6222 
6332                                   N/A for spl    6223                                   N/A for split lock detection.
6333                                                  6224 
6334                                                  6225 
6335                         If an #AC exception i    6226                         If an #AC exception is hit in the kernel or in
6336                         firmware (i.e. not wh    6227                         firmware (i.e. not while executing in user mode)
6337                         the kernel will oops     6228                         the kernel will oops in either "warn" or "fatal"
6338                         mode.                    6229                         mode.
6339                                                  6230 
6340                         #DB exception for bus    6231                         #DB exception for bus lock is triggered only when
6341                         CPL > 0.                 6232                         CPL > 0.
6342                                                  6233 
6343         srbds=          [X86,INTEL,EARLY]     !! 6234         srbds=          [X86,INTEL]
6344                         Control the Special R    6235                         Control the Special Register Buffer Data Sampling
6345                         (SRBDS) mitigation.      6236                         (SRBDS) mitigation.
6346                                                  6237 
6347                         Certain CPUs are vuln    6238                         Certain CPUs are vulnerable to an MDS-like
6348                         exploit which can lea    6239                         exploit which can leak bits from the random
6349                         number generator.        6240                         number generator.
6350                                                  6241 
6351                         By default, this issu    6242                         By default, this issue is mitigated by
6352                         microcode.  However,     6243                         microcode.  However, the microcode fix can cause
6353                         the RDRAND and RDSEED    6244                         the RDRAND and RDSEED instructions to become
6354                         much slower.  Among o    6245                         much slower.  Among other effects, this will
6355                         result in reduced thr    6246                         result in reduced throughput from /dev/urandom.
6356                                                  6247 
6357                         The microcode mitigat    6248                         The microcode mitigation can be disabled with
6358                         the following option:    6249                         the following option:
6359                                                  6250 
6360                         off:    Disable mitig    6251                         off:    Disable mitigation and remove
6361                                 performance i    6252                                 performance impact to RDRAND and RDSEED
6362                                                  6253 
6363         srcutree.big_cpu_lim [KNL]               6254         srcutree.big_cpu_lim [KNL]
6364                         Specifies the number     6255                         Specifies the number of CPUs constituting a
6365                         large system, such th    6256                         large system, such that srcu_struct structures
6366                         should immediately al    6257                         should immediately allocate an srcu_node array.
6367                         This kernel-boot para    6258                         This kernel-boot parameter defaults to 128,
6368                         but takes effect only    6259                         but takes effect only when the low-order four
6369                         bits of srcutree.conv    6260                         bits of srcutree.convert_to_big is equal to 3
6370                         (decide at boot).        6261                         (decide at boot).
6371                                                  6262 
6372         srcutree.convert_to_big [KNL]            6263         srcutree.convert_to_big [KNL]
6373                         Specifies under what     6264                         Specifies under what conditions an SRCU tree
6374                         srcu_struct structure    6265                         srcu_struct structure will be converted to big
6375                         form, that is, with a    6266                         form, that is, with an rcu_node tree:
6376                                                  6267 
6377                                    0:  Never.    6268                                    0:  Never.
6378                                    1:  At ini    6269                                    1:  At init_srcu_struct() time.
6379                                    2:  When r    6270                                    2:  When rcutorture decides to.
6380                                    3:  Decide    6271                                    3:  Decide at boot time (default).
6381                                 0x1X:  Above     6272                                 0x1X:  Above plus if high contention.
6382                                                  6273 
6383                         Either way, the srcu_    6274                         Either way, the srcu_node tree will be sized based
6384                         on the actual runtime    6275                         on the actual runtime number of CPUs (nr_cpu_ids)
6385                         instead of the compil    6276                         instead of the compile-time CONFIG_NR_CPUS.
6386                                                  6277 
6387         srcutree.counter_wrap_check [KNL]        6278         srcutree.counter_wrap_check [KNL]
6388                         Specifies how frequen    6279                         Specifies how frequently to check for
6389                         grace-period sequence    6280                         grace-period sequence counter wrap for the
6390                         srcu_data structure's    6281                         srcu_data structure's ->srcu_gp_seq_needed field.
6391                         The greater the numbe    6282                         The greater the number of bits set in this kernel
6392                         parameter, the less f    6283                         parameter, the less frequently counter wrap will
6393                         be checked for.  Note    6284                         be checked for.  Note that the bottom two bits
6394                         are ignored.             6285                         are ignored.
6395                                                  6286 
6396         srcutree.exp_holdoff [KNL]               6287         srcutree.exp_holdoff [KNL]
6397                         Specifies how many na    6288                         Specifies how many nanoseconds must elapse
6398                         since the end of the     6289                         since the end of the last SRCU grace period for
6399                         a given srcu_struct u    6290                         a given srcu_struct until the next normal SRCU
6400                         grace period will be     6291                         grace period will be considered for automatic
6401                         expediting.  Set to z    6292                         expediting.  Set to zero to disable automatic
6402                         expediting.              6293                         expediting.
6403                                                  6294 
6404         srcutree.srcu_max_nodelay [KNL]          6295         srcutree.srcu_max_nodelay [KNL]
6405                         Specifies the number     6296                         Specifies the number of no-delay instances
6406                         per jiffy for which t    6297                         per jiffy for which the SRCU grace period
6407                         worker thread will be    6298                         worker thread will be rescheduled with zero
6408                         delay. Beyond this li    6299                         delay. Beyond this limit, worker thread will
6409                         be rescheduled with a    6300                         be rescheduled with a sleep delay of one jiffy.
6410                                                  6301 
6411         srcutree.srcu_max_nodelay_phase [KNL]    6302         srcutree.srcu_max_nodelay_phase [KNL]
6412                         Specifies the per-gra    6303                         Specifies the per-grace-period phase, number of
6413                         non-sleeping polls of    6304                         non-sleeping polls of readers. Beyond this limit,
6414                         grace period worker t    6305                         grace period worker thread will be rescheduled
6415                         with a sleep delay of    6306                         with a sleep delay of one jiffy, between each
6416                         rescan of the readers    6307                         rescan of the readers, for a grace period phase.
6417                                                  6308 
6418         srcutree.srcu_retry_check_delay [KNL]    6309         srcutree.srcu_retry_check_delay [KNL]
6419                         Specifies number of m    6310                         Specifies number of microseconds of non-sleeping
6420                         delay between each no    6311                         delay between each non-sleeping poll of readers.
6421                                                  6312 
6422         srcutree.small_contention_lim [KNL]      6313         srcutree.small_contention_lim [KNL]
6423                         Specifies the number     6314                         Specifies the number of update-side contention
6424                         events per jiffy will    6315                         events per jiffy will be tolerated before
6425                         initiating a conversi    6316                         initiating a conversion of an srcu_struct
6426                         structure to big form    6317                         structure to big form.  Note that the value of
6427                         srcutree.convert_to_b    6318                         srcutree.convert_to_big must have the 0x10 bit
6428                         set for contention-ba    6319                         set for contention-based conversions to occur.
6429                                                  6320 
6430         ssbd=           [ARM64,HW,EARLY]      !! 6321         ssbd=           [ARM64,HW]
6431                         Speculative Store Byp    6322                         Speculative Store Bypass Disable control
6432                                                  6323 
6433                         On CPUs that are vuln    6324                         On CPUs that are vulnerable to the Speculative
6434                         Store Bypass vulnerab    6325                         Store Bypass vulnerability and offer a
6435                         firmware based mitiga    6326                         firmware based mitigation, this parameter
6436                         indicates how the mit    6327                         indicates how the mitigation should be used:
6437                                                  6328 
6438                         force-on:  Unconditio    6329                         force-on:  Unconditionally enable mitigation for
6439                                    for both k    6330                                    for both kernel and userspace
6440                         force-off: Unconditio    6331                         force-off: Unconditionally disable mitigation for
6441                                    for both k    6332                                    for both kernel and userspace
6442                         kernel:    Always ena    6333                         kernel:    Always enable mitigation in the
6443                                    kernel, an    6334                                    kernel, and offer a prctl interface
6444                                    to allow u    6335                                    to allow userspace to register its
6445                                    interest i    6336                                    interest in being mitigated too.
6446                                                  6337 
6447         stack_guard_gap=        [MM]             6338         stack_guard_gap=        [MM]
6448                         override the default     6339                         override the default stack gap protection. The value
6449                         is in page units and     6340                         is in page units and it defines how many pages prior
6450                         to (for stacks growin    6341                         to (for stacks growing down) resp. after (for stacks
6451                         growing up) the main     6342                         growing up) the main stack are reserved for no other
6452                         mapping. Default valu    6343                         mapping. Default value is 256 pages.
6453                                                  6344 
6454         stack_depot_disable= [KNL,EARLY]      !! 6345         stack_depot_disable= [KNL]
6455                         Setting this to true     6346                         Setting this to true through kernel command line will
6456                         disable the stack dep    6347                         disable the stack depot thereby saving the static memory
6457                         consumed by the stack    6348                         consumed by the stack hash table. By default this is set
6458                         to false.                6349                         to false.
6459                                                  6350 
6460         stacktrace      [FTRACE]                 6351         stacktrace      [FTRACE]
6461                         Enabled the stack tra    6352                         Enabled the stack tracer on boot up.
6462                                                  6353 
6463         stacktrace_filter=[function-list]        6354         stacktrace_filter=[function-list]
6464                         [FTRACE] Limit the fu    6355                         [FTRACE] Limit the functions that the stack tracer
6465                         will trace at boot up    6356                         will trace at boot up. function-list is a comma-separated
6466                         list of functions. Th    6357                         list of functions. This list can be changed at run
6467                         time by the stack_tra    6358                         time by the stack_trace_filter file in the debugfs
6468                         tracing directory. No    6359                         tracing directory. Note, this enables stack tracing
6469                         and the stacktrace ab    6360                         and the stacktrace above is not needed.
6470                                                  6361 
6471         sti=            [PARISC,HW]              6362         sti=            [PARISC,HW]
6472                         Format: <num>            6363                         Format: <num>
6473                         Set the STI (builtin     6364                         Set the STI (builtin display/keyboard on the HP-PARISC
6474                         machines) console (gr    6365                         machines) console (graphic card) which should be used
6475                         as the initial boot-c    6366                         as the initial boot-console.
6476                         See also comment in d    6367                         See also comment in drivers/video/console/sticore.c.
6477                                                  6368 
6478         sti_font=       [HW]                     6369         sti_font=       [HW]
6479                         See comment in driver    6370                         See comment in drivers/video/console/sticore.c.
6480                                                  6371 
6481         stifb=          [HW]                     6372         stifb=          [HW]
6482                         Format: bpp:<bpp1>[:<    6373                         Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483                                                  6374 
6484         strict_sas_size=                         6375         strict_sas_size=
6485                         [X86]                    6376                         [X86]
6486                         Format: <bool>           6377                         Format: <bool>
6487                         Enable or disable str    6378                         Enable or disable strict sigaltstack size checks
6488                         against the required     6379                         against the required signal frame size which
6489                         depends on the suppor    6380                         depends on the supported FPU features. This can
6490                         be used to filter out    6381                         be used to filter out binaries which have
6491                         not yet been made awa    6382                         not yet been made aware of AT_MINSIGSTKSZ.
6492                                                  6383 
6493         stress_hpt      [PPC,EARLY]           !! 6384         stress_hpt      [PPC]
6494                         Limits the number of     6385                         Limits the number of kernel HPT entries in the hash
6495                         page table to increas    6386                         page table to increase the rate of hash page table
6496                         faults on kernel addr    6387                         faults on kernel addresses.
6497                                                  6388 
6498         stress_slb      [PPC,EARLY]           !! 6389         stress_slb      [PPC]
6499                         Limits the number of     6390                         Limits the number of kernel SLB entries, and flushes
6500                         them frequently to in    6391                         them frequently to increase the rate of SLB faults
6501                         on kernel addresses.     6392                         on kernel addresses.
6502                                                  6393 
6503         sunrpc.min_resvport=                     6394         sunrpc.min_resvport=
6504         sunrpc.max_resvport=                     6395         sunrpc.max_resvport=
6505                         [NFS,SUNRPC]             6396                         [NFS,SUNRPC]
6506                         SunRPC servers often     6397                         SunRPC servers often require that client requests
6507                         originate from a priv    6398                         originate from a privileged port (i.e. a port in the
6508                         range 0 < portnr < 10    6399                         range 0 < portnr < 1024).
6509                         An administrator who     6400                         An administrator who wishes to reserve some of these
6510                         ports for other uses     6401                         ports for other uses may adjust the range that the
6511                         kernel's sunrpc clien    6402                         kernel's sunrpc client considers to be privileged
6512                         using these two param    6403                         using these two parameters to set the minimum and
6513                         maximum port values.     6404                         maximum port values.
6514                                                  6405 
6515         sunrpc.svc_rpc_per_connection_limit=     6406         sunrpc.svc_rpc_per_connection_limit=
6516                         [NFS,SUNRPC]             6407                         [NFS,SUNRPC]
6517                         Limit the number of r    6408                         Limit the number of requests that the server will
6518                         process in parallel f    6409                         process in parallel from a single connection.
6519                         The default value is     6410                         The default value is 0 (no limit).
6520                                                  6411 
6521         sunrpc.pool_mode=                        6412         sunrpc.pool_mode=
6522                         [NFS]                    6413                         [NFS]
6523                         Control how the NFS s    6414                         Control how the NFS server code allocates CPUs to
6524                         service thread pools.    6415                         service thread pools.  Depending on how many NICs
6525                         you have and where th    6416                         you have and where their interrupts are bound, this
6526                         option will affect wh    6417                         option will affect which CPUs will do NFS serving.
6527                         Note: this parameter     6418                         Note: this parameter cannot be changed while the
6528                         NFS server is running    6419                         NFS server is running.
6529                                                  6420 
6530                         auto        the serve    6421                         auto        the server chooses an appropriate mode
6531                                     automatic    6422                                     automatically using heuristics
6532                         global      a single     6423                         global      a single global pool contains all CPUs
6533                         percpu      one pool     6424                         percpu      one pool for each CPU
6534                         pernode     one pool     6425                         pernode     one pool for each NUMA node (equivalent
6535                                     to global    6426                                     to global on non-NUMA machines)
6536                                                  6427 
6537         sunrpc.tcp_slot_table_entries=           6428         sunrpc.tcp_slot_table_entries=
6538         sunrpc.udp_slot_table_entries=           6429         sunrpc.udp_slot_table_entries=
6539                         [NFS,SUNRPC]             6430                         [NFS,SUNRPC]
6540                         Sets the upper limit     6431                         Sets the upper limit on the number of simultaneous
6541                         RPC calls that can be    6432                         RPC calls that can be sent from the client to a
6542                         server. Increasing th    6433                         server. Increasing these values may allow you to
6543                         improve throughput, b    6434                         improve throughput, but will also increase the
6544                         amount of memory rese    6435                         amount of memory reserved for use by the client.
6545                                                  6436 
6546         suspend.pm_test_delay=                   6437         suspend.pm_test_delay=
6547                         [SUSPEND]                6438                         [SUSPEND]
6548                         Sets the number of se    6439                         Sets the number of seconds to remain in a suspend test
6549                         mode before resuming     6440                         mode before resuming the system (see
6550                         /sys/power/pm_test).     6441                         /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551                         is set. Default value    6442                         is set. Default value is 5.
6552                                                  6443 
6553         svm=            [PPC]                    6444         svm=            [PPC]
6554                         Format: { on | off |     6445                         Format: { on | off | y | n | 1 | 0 }
6555                         This parameter contro    6446                         This parameter controls use of the Protected
6556                         Execution Facility on    6447                         Execution Facility on pSeries.
6557                                                  6448 
6558         swiotlb=        [ARM,PPC,MIPS,X86,S39 !! 6449         swiotlb=        [ARM,IA-64,PPC,MIPS,X86]
6559                         Format: { <int> [,<in    6450                         Format: { <int> [,<int>] | force | noforce }
6560                         <int> -- Number of I/    6451                         <int> -- Number of I/O TLB slabs
6561                         <int> -- Second integ    6452                         <int> -- Second integer after comma. Number of swiotlb
6562                                  areas with t    6453                                  areas with their own lock. Will be rounded up
6563                                  to a power o    6454                                  to a power of 2.
6564                         force -- force using     6455                         force -- force using of bounce buffers even if they
6565                                  wouldn't be     6456                                  wouldn't be automatically used by the kernel
6566                         noforce -- Never use     6457                         noforce -- Never use bounce buffers (for debugging)
6567                                                  6458 
6568         switches=       [HW,M68k,EARLY]       !! 6459         switches=       [HW,M68k]
6569                                                  6460 
6570         sysctl.*=       [KNL]                    6461         sysctl.*=       [KNL]
6571                         Set a sysctl paramete    6462                         Set a sysctl parameter, right before loading the init
6572                         process, as if the va    6463                         process, as if the value was written to the respective
6573                         /proc/sys/... file. B    6464                         /proc/sys/... file. Both '.' and '/' are recognized as
6574                         separators. Unrecogni    6465                         separators. Unrecognized parameters and invalid values
6575                         are reported in the k    6466                         are reported in the kernel log. Sysctls registered
6576                         later by a loaded mod    6467                         later by a loaded module cannot be set this way.
6577                         Example: sysctl.vm.sw    6468                         Example: sysctl.vm.swappiness=40
6578                                                  6469 
6579         sysrq_always_enabled                     6470         sysrq_always_enabled
6580                         [KNL]                    6471                         [KNL]
6581                         Ignore sysrq setting     6472                         Ignore sysrq setting - this boot parameter will
6582                         neutralize any effect    6473                         neutralize any effect of /proc/sys/kernel/sysrq.
6583                         Useful for debugging.    6474                         Useful for debugging.
6584                                                  6475 
6585         tcpmhash_entries= [KNL,NET]              6476         tcpmhash_entries= [KNL,NET]
6586                         Set the number of tcp    6477                         Set the number of tcp_metrics_hash slots.
6587                         Default value is 8192    6478                         Default value is 8192 or 16384 depending on total
6588                         ram pages. This is us    6479                         ram pages. This is used to specify the TCP metrics
6589                         cache size. See Docum    6480                         cache size. See Documentation/networking/ip-sysctl.rst
6590                         "tcp_no_metrics_save"    6481                         "tcp_no_metrics_save" section for more details.
6591                                                  6482 
6592         tdfx=           [HW,DRM]                 6483         tdfx=           [HW,DRM]
6593                                                  6484 
6594         test_suspend=   [SUSPEND]                6485         test_suspend=   [SUSPEND]
6595                         Format: { "mem" | "st    6486                         Format: { "mem" | "standby" | "freeze" }[,N]
6596                         Specify "mem" (for Su    6487                         Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597                         standby suspend) or "    6488                         standby suspend) or "freeze" (for suspend type freeze)
6598                         as the system sleep s    6489                         as the system sleep state during system startup with
6599                         the optional capabili    6490                         the optional capability to repeat N number of times.
6600                         The system is woken f    6491                         The system is woken from this state using a
6601                         wakeup-capable RTC al    6492                         wakeup-capable RTC alarm.
6602                                                  6493 
6603         thash_entries=  [KNL,NET]                6494         thash_entries=  [KNL,NET]
6604                         Set number of hash bu    6495                         Set number of hash buckets for TCP connection
6605                                                  6496 
6606         thermal.act=    [HW,ACPI]                6497         thermal.act=    [HW,ACPI]
6607                         -1: disable all activ    6498                         -1: disable all active trip points in all thermal zones
6608                         <degrees C>: override    6499                         <degrees C>: override all lowest active trip points
6609                                                  6500 
6610         thermal.crt=    [HW,ACPI]                6501         thermal.crt=    [HW,ACPI]
6611                         -1: disable all criti    6502                         -1: disable all critical trip points in all thermal zones
6612                         <degrees C>: override    6503                         <degrees C>: override all critical trip points
6613                                                  6504 
6614         thermal.off=    [HW,ACPI]                6505         thermal.off=    [HW,ACPI]
6615                         1: disable ACPI therm    6506                         1: disable ACPI thermal control
6616                                                  6507 
6617         thermal.psv=    [HW,ACPI]                6508         thermal.psv=    [HW,ACPI]
6618                         -1: disable all passi    6509                         -1: disable all passive trip points
6619                         <degrees C>: override    6510                         <degrees C>: override all passive trip points to this
6620                         value                    6511                         value
6621                                                  6512 
6622         thermal.tzp=    [HW,ACPI]                6513         thermal.tzp=    [HW,ACPI]
6623                         Specify global defaul    6514                         Specify global default ACPI thermal zone polling rate
6624                         <deci-seconds>: poll     6515                         <deci-seconds>: poll all this frequency
6625                         0: no polling (defaul    6516                         0: no polling (default)
6626                                                  6517 
6627         threadirqs      [KNL,EARLY]           !! 6518         threadirqs      [KNL]
6628                         Force threading of al    6519                         Force threading of all interrupt handlers except those
6629                         marked explicitly IRQ    6520                         marked explicitly IRQF_NO_THREAD.
6630                                                  6521 
6631         topology=       [S390,EARLY]          !! 6522         topology=       [S390]
6632                         Format: {off | on}       6523                         Format: {off | on}
6633                         Specify if the kernel    6524                         Specify if the kernel should make use of the cpu
6634                         topology information     6525                         topology information if the hardware supports this.
6635                         The scheduler will ma    6526                         The scheduler will make use of this information and
6636                         e.g. base its process    6527                         e.g. base its process migration decisions on it.
6637                         Default is on.           6528                         Default is on.
6638                                                  6529 
                                                   >> 6530         topology_updates= [KNL, PPC, NUMA]
                                                   >> 6531                         Format: {off}
                                                   >> 6532                         Specify if the kernel should ignore (off)
                                                   >> 6533                         topology updates sent by the hypervisor to this
                                                   >> 6534                         LPAR.
                                                   >> 6535 
6639         torture.disable_onoff_at_boot= [KNL]     6536         torture.disable_onoff_at_boot= [KNL]
6640                         Prevent the CPU-hotpl    6537                         Prevent the CPU-hotplug component of torturing
6641                         until after init has     6538                         until after init has spawned.
6642                                                  6539 
6643         torture.ftrace_dump_at_shutdown= [KNL    6540         torture.ftrace_dump_at_shutdown= [KNL]
6644                         Dump the ftrace buffe    6541                         Dump the ftrace buffer at torture-test shutdown,
6645                         even if there were no    6542                         even if there were no errors.  This can be a
6646                         very costly operation    6543                         very costly operation when many torture tests
6647                         are running concurren    6544                         are running concurrently, especially on systems
6648                         with rotating-rust st    6545                         with rotating-rust storage.
6649                                                  6546 
6650         torture.verbose_sleep_frequency= [KNL    6547         torture.verbose_sleep_frequency= [KNL]
6651                         Specifies how many ve    6548                         Specifies how many verbose printk()s should be
6652                         emitted between each     6549                         emitted between each sleep.  The default of zero
6653                         disables verbose-prin    6550                         disables verbose-printk() sleeping.
6654                                                  6551 
6655         torture.verbose_sleep_duration= [KNL]    6552         torture.verbose_sleep_duration= [KNL]
6656                         Duration of each verb    6553                         Duration of each verbose-printk() sleep in jiffies.
6657                                                  6554 
                                                   >> 6555         tp720=          [HW,PS2]
                                                   >> 6556 
6658         tpm_suspend_pcr=[HW,TPM]                 6557         tpm_suspend_pcr=[HW,TPM]
6659                         Format: integer pcr i    6558                         Format: integer pcr id
6660                         Specify that at suspe    6559                         Specify that at suspend time, the tpm driver
6661                         should extend the spe    6560                         should extend the specified pcr with zeros,
6662                         as a workaround for s    6561                         as a workaround for some chips which fail to
6663                         flush the last writte    6562                         flush the last written pcr on TPM_SaveState.
6664                         This will guarantee t    6563                         This will guarantee that all the other pcrs
6665                         are saved.               6564                         are saved.
6666                                                  6565 
6667         tpm_tis.interrupts= [HW,TPM]             6566         tpm_tis.interrupts= [HW,TPM]
6668                         Enable interrupts for    6567                         Enable interrupts for the MMIO based physical layer
6669                         for the FIFO interfac    6568                         for the FIFO interface. By default it is set to false
6670                         (0). For more informa    6569                         (0). For more information about TPM hardware interfaces
6671                         defined by Trusted Co    6570                         defined by Trusted Computing Group (TCG) see
6672                         https://trustedcomput    6571                         https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
6673                                                  6572 
6674         tp_printk       [FTRACE]                 6573         tp_printk       [FTRACE]
6675                         Have the tracepoints     6574                         Have the tracepoints sent to printk as well as the
6676                         tracing ring buffer.     6575                         tracing ring buffer. This is useful for early boot up
6677                         where the system hang    6576                         where the system hangs or reboots and does not give the
6678                         option for reading th    6577                         option for reading the tracing buffer or performing a
6679                         ftrace_dump_on_oops.     6578                         ftrace_dump_on_oops.
6680                                                  6579 
6681                         To turn off having tr    6580                         To turn off having tracepoints sent to printk,
6682                          echo 0 > /proc/sys/k    6581                          echo 0 > /proc/sys/kernel/tracepoint_printk
6683                         Note, echoing 1 into     6582                         Note, echoing 1 into this file without the
6684                         tp_printk kernel cmdl !! 6583                         tracepoint_printk kernel cmdline option has no effect.
6685                                                  6584 
6686                         The tp_printk_stop_on    6585                         The tp_printk_stop_on_boot (see below) can also be used
6687                         to stop the printing     6586                         to stop the printing of events to console at
6688                         late_initcall_sync.      6587                         late_initcall_sync.
6689                                                  6588 
6690                         ** CAUTION **            6589                         ** CAUTION **
6691                                                  6590 
6692                         Having tracepoints se    6591                         Having tracepoints sent to printk() and activating high
6693                         frequency tracepoints    6592                         frequency tracepoints such as irq or sched, can cause
6694                         the system to live lo    6593                         the system to live lock.
6695                                                  6594 
6696         tp_printk_stop_on_boot [FTRACE]          6595         tp_printk_stop_on_boot [FTRACE]
6697                         When tp_printk (above    6596                         When tp_printk (above) is set, it can cause a lot of noise
6698                         on the console. It ma    6597                         on the console. It may be useful to only include the
6699                         printing of events du    6598                         printing of events during boot up, as user space may
6700                         make the system inope    6599                         make the system inoperable.
6701                                                  6600 
6702                         This command line opt    6601                         This command line option will stop the printing of events
6703                         to console at the lat    6602                         to console at the late_initcall_sync() time frame.
6704                                                  6603 
6705         trace_buf_size=nn[KMG]                   6604         trace_buf_size=nn[KMG]
6706                         [FTRACE] will set tra    6605                         [FTRACE] will set tracing buffer size on each cpu.
6707                                                  6606 
6708         trace_clock=    [FTRACE] Set the cloc    6607         trace_clock=    [FTRACE] Set the clock used for tracing events
6709                         at boot up.              6608                         at boot up.
6710                         local - Use the per C    6609                         local - Use the per CPU time stamp counter
6711                                 (converted in    6610                                 (converted into nanoseconds). Fast, but
6712                                 depending on     6611                                 depending on the architecture, may not be
6713                                 in sync betwe    6612                                 in sync between CPUs.
6714                         global - Event time s    6613                         global - Event time stamps are synchronize across
6715                                 CPUs. May be     6614                                 CPUs. May be slower than the local clock,
6716                                 but better fo    6615                                 but better for some race conditions.
6717                         counter - Simple coun    6616                         counter - Simple counting of events (1, 2, ..)
6718                                 note, some co    6617                                 note, some counts may be skipped due to the
6719                                 infrastructur    6618                                 infrastructure grabbing the clock more than
6720                                 once per even    6619                                 once per event.
6721                         uptime - Use jiffies     6620                         uptime - Use jiffies as the time stamp.
6722                         perf - Use the same c    6621                         perf - Use the same clock that perf uses.
6723                         mono - Use ktime_get_    6622                         mono - Use ktime_get_mono_fast_ns() for time stamps.
6724                         mono_raw - Use ktime_    6623                         mono_raw - Use ktime_get_raw_fast_ns() for time
6725                                 stamps.          6624                                 stamps.
6726                         boot - Use ktime_get_    6625                         boot - Use ktime_get_boot_fast_ns() for time stamps.
6727                         Architectures may add    6626                         Architectures may add more clocks. See
6728                         Documentation/trace/f    6627                         Documentation/trace/ftrace.rst for more details.
6729                                                  6628 
6730         trace_event=[event-list]                 6629         trace_event=[event-list]
6731                         [FTRACE] Set and star    6630                         [FTRACE] Set and start specified trace events in order
6732                         to facilitate early b    6631                         to facilitate early boot debugging. The event-list is a
6733                         comma-separated list     6632                         comma-separated list of trace events to enable. See
6734                         also Documentation/tr    6633                         also Documentation/trace/events.rst
6735                                                  6634 
6736         trace_instance=[instance-info]           6635         trace_instance=[instance-info]
6737                         [FTRACE] Create a rin    6636                         [FTRACE] Create a ring buffer instance early in boot up.
6738                         This will be listed i    6637                         This will be listed in:
6739                                                  6638 
6740                                 /sys/kernel/t    6639                                 /sys/kernel/tracing/instances
6741                                                  6640 
6742                         Events can be enabled    6641                         Events can be enabled at the time the instance is created
6743                         via:                     6642                         via:
6744                                                  6643 
6745                                 trace_instanc    6644                                 trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
6746                                                  6645 
6747                         Note, the "<system*>:    6646                         Note, the "<system*>:" portion is optional if the event is
6748                         unique.                  6647                         unique.
6749                                                  6648 
6750                                 trace_instanc    6649                                 trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
6751                                                  6650 
6752                         will enable the "sche    6651                         will enable the "sched_switch" event (note, the "sched:" is optional, and
6753                         the same thing would     6652                         the same thing would happen if it was left off). The irq_handler_entry
6754                         event, and all events    6653                         event, and all events under the "initcall" system.
6755                                                  6654 
6756         trace_options=[option-list]              6655         trace_options=[option-list]
6757                         [FTRACE] Enable or di    6656                         [FTRACE] Enable or disable tracer options at boot.
6758                         The option-list is a     6657                         The option-list is a comma delimited list of options
6759                         that can be enabled o    6658                         that can be enabled or disabled just as if you were
6760                         to echo the option na    6659                         to echo the option name into
6761                                                  6660 
6762                             /sys/kernel/traci    6661                             /sys/kernel/tracing/trace_options
6763                                                  6662 
6764                         For example, to enabl    6663                         For example, to enable stacktrace option (to dump the
6765                         stack trace of each e    6664                         stack trace of each event), add to the command line:
6766                                                  6665 
6767                               trace_options=s    6666                               trace_options=stacktrace
6768                                                  6667 
6769                         See also Documentatio    6668                         See also Documentation/trace/ftrace.rst "trace options"
6770                         section.                 6669                         section.
6771                                                  6670 
6772         trace_trigger=[trigger-list]             6671         trace_trigger=[trigger-list]
6773                         [FTRACE] Add a event     6672                         [FTRACE] Add a event trigger on specific events.
6774                         Set a trigger on top     6673                         Set a trigger on top of a specific event, with an optional
6775                         filter.                  6674                         filter.
6776                                                  6675 
6777                         The format is is "tra    6676                         The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
6778                         Where more than one t    6677                         Where more than one trigger may be specified that are comma deliminated.
6779                                                  6678 
6780                         For example:             6679                         For example:
6781                                                  6680 
6782                           trace_trigger="sche    6681                           trace_trigger="sched_switch.stacktrace if prev_state == 2"
6783                                                  6682 
6784                         The above will enable    6683                         The above will enable the "stacktrace" trigger on the "sched_switch"
6785                         event but only trigge    6684                         event but only trigger it if the "prev_state" of the "sched_switch"
6786                         event is "2" (TASK_UN    6685                         event is "2" (TASK_UNINTERUPTIBLE).
6787                                                  6686 
6788                         See also "Event trigg    6687                         See also "Event triggers" in Documentation/trace/events.rst
6789                                                  6688 
6790                                                  6689 
6791         traceoff_on_warning                      6690         traceoff_on_warning
6792                         [FTRACE] enable this     6691                         [FTRACE] enable this option to disable tracing when a
6793                         warning is hit. This     6692                         warning is hit. This turns off "tracing_on". Tracing can
6794                         be enabled again by e    6693                         be enabled again by echoing '1' into the "tracing_on"
6795                         file located in /sys/    6694                         file located in /sys/kernel/tracing/
6796                                                  6695 
6797                         This option is useful    6696                         This option is useful, as it disables the trace before
6798                         the WARNING dump is c    6697                         the WARNING dump is called, which prevents the trace to
6799                         be filled with conten    6698                         be filled with content caused by the warning output.
6800                                                  6699 
6801                         This option can also     6700                         This option can also be set at run time via the sysctl
6802                         option:  kernel/trace    6701                         option:  kernel/traceoff_on_warning
6803                                                  6702 
6804         transparent_hugepage=                    6703         transparent_hugepage=
6805                         [KNL]                    6704                         [KNL]
6806                         Format: [always|madvi    6705                         Format: [always|madvise|never]
6807                         Can be used to contro    6706                         Can be used to control the default behavior of the system
6808                         with respect to trans    6707                         with respect to transparent hugepages.
6809                         See Documentation/adm    6708                         See Documentation/admin-guide/mm/transhuge.rst
6810                         for more details.        6709                         for more details.
6811                                                  6710 
6812         trusted.source= [KEYS]                   6711         trusted.source= [KEYS]
6813                         Format: <string>         6712                         Format: <string>
6814                         This parameter identi    6713                         This parameter identifies the trust source as a backend
6815                         for trusted keys impl    6714                         for trusted keys implementation. Supported trust
6816                         sources:                 6715                         sources:
6817                         - "tpm"                  6716                         - "tpm"
6818                         - "tee"                  6717                         - "tee"
6819                         - "caam"                 6718                         - "caam"
6820                         - "dcp"               << 
6821                         If not specified then    6719                         If not specified then it defaults to iterating through
6822                         the trust source list    6720                         the trust source list starting with TPM and assigns the
6823                         first trust source as    6721                         first trust source as a backend which is initialized
6824                         successfully during i    6722                         successfully during iteration.
6825                                                  6723 
6826         trusted.rng=    [KEYS]                   6724         trusted.rng=    [KEYS]
6827                         Format: <string>         6725                         Format: <string>
6828                         The RNG used to gener    6726                         The RNG used to generate key material for trusted keys.
6829                         Can be one of:           6727                         Can be one of:
6830                         - "kernel"               6728                         - "kernel"
6831                         - the same value as t    6729                         - the same value as trusted.source: "tpm" or "tee"
6832                         - "default"              6730                         - "default"
6833                         If not specified, "de    6731                         If not specified, "default" is used. In this case,
6834                         the RNG's choice is l    6732                         the RNG's choice is left to each individual trust source.
6835                                                  6733 
6836         trusted.dcp_use_otp_key               << 
6837                         This is intended to b << 
6838                         trusted.source=dcp an << 
6839                         instead of the DCP UN << 
6840                                               << 
6841         trusted.dcp_skip_zk_test              << 
6842                         This is intended to b << 
6843                         trusted.source=dcp an << 
6844                         blob key is all zeros << 
6845                         having this key zero' << 
6846                         scenarios.            << 
6847                                               << 
6848         tsc=            Disable clocksource s    6734         tsc=            Disable clocksource stability checks for TSC.
6849                         Format: <string>         6735                         Format: <string>
6850                         [x86] reliable: mark     6736                         [x86] reliable: mark tsc clocksource as reliable, this
6851                         disables clocksource     6737                         disables clocksource verification at runtime, as well
6852                         as the stability chec    6738                         as the stability checks done at bootup. Used to enable
6853                         high-resolution timer    6739                         high-resolution timer mode on older hardware, and in
6854                         virtualized environme    6740                         virtualized environment.
6855                         [x86] noirqtime: Do n    6741                         [x86] noirqtime: Do not use TSC to do irq accounting.
6856                         Used to run time disa    6742                         Used to run time disable IRQ_TIME_ACCOUNTING on any
6857                         platforms where RDTSC    6743                         platforms where RDTSC is slow and this accounting
6858                         can add overhead.        6744                         can add overhead.
6859                         [x86] unstable: mark     6745                         [x86] unstable: mark the TSC clocksource as unstable, this
6860                         marks the TSC uncondi    6746                         marks the TSC unconditionally unstable at bootup and
6861                         avoids any further wo    6747                         avoids any further wobbles once the TSC watchdog notices.
6862                         [x86] nowatchdog: dis    6748                         [x86] nowatchdog: disable clocksource watchdog. Used
6863                         in situations with st    6749                         in situations with strict latency requirements (where
6864                         interruptions from cl    6750                         interruptions from clocksource watchdog are not
6865                         acceptable).             6751                         acceptable).
6866                         [x86] recalibrate: fo    6752                         [x86] recalibrate: force recalibration against a HW timer
6867                         (HPET or PM timer) on    6753                         (HPET or PM timer) on systems whose TSC frequency was
6868                         obtained from HW or F    6754                         obtained from HW or FW using either an MSR or CPUID(0x15).
6869                         Warn if the differenc    6755                         Warn if the difference is more than 500 ppm.
6870                         [x86] watchdog: Use T    6756                         [x86] watchdog: Use TSC as the watchdog clocksource with
6871                         which to check other     6757                         which to check other HW timers (HPET or PM timer), but
6872                         only on systems where    6758                         only on systems where TSC has been deemed trustworthy.
6873                         This will be suppress    6759                         This will be suppressed by an earlier tsc=nowatchdog and
6874                         can be overridden by     6760                         can be overridden by a later tsc=nowatchdog.  A console
6875                         message will flag any    6761                         message will flag any such suppression or overriding.
6876                                                  6762 
6877         tsc_early_khz=  [X86,EARLY] Skip earl !! 6763         tsc_early_khz=  [X86] Skip early TSC calibration and use the given
6878                         value instead. Useful    6764                         value instead. Useful when the early TSC frequency discovery
6879                         procedure is not reli    6765                         procedure is not reliable, such as on overclocked systems
6880                         with CPUID.16h suppor    6766                         with CPUID.16h support and partial CPUID.15h support.
6881                         Format: <unsigned int    6767                         Format: <unsigned int>
6882                                                  6768 
6883         tsx=            [X86] Control Transac    6769         tsx=            [X86] Control Transactional Synchronization
6884                         Extensions (TSX) feat    6770                         Extensions (TSX) feature in Intel processors that
6885                         support TSX control.     6771                         support TSX control.
6886                                                  6772 
6887                         This parameter contro    6773                         This parameter controls the TSX feature. The options are:
6888                                                  6774 
6889                         on      - Enable TSX     6775                         on      - Enable TSX on the system. Although there are
6890                                 mitigations f    6776                                 mitigations for all known security vulnerabilities,
6891                                 TSX has been     6777                                 TSX has been known to be an accelerator for
6892                                 several previ    6778                                 several previous speculation-related CVEs, and
6893                                 so there may     6779                                 so there may be unknown security risks associated
6894                                 with leaving     6780                                 with leaving it enabled.
6895                                                  6781 
6896                         off     - Disable TSX    6782                         off     - Disable TSX on the system. (Note that this
6897                                 option takes     6783                                 option takes effect only on newer CPUs which are
6898                                 not vulnerabl    6784                                 not vulnerable to MDS, i.e., have
6899                                 MSR_IA32_ARCH    6785                                 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900                                 the new IA32_    6786                                 the new IA32_TSX_CTRL MSR through a microcode
6901                                 update. This     6787                                 update. This new MSR allows for the reliable
6902                                 deactivation     6788                                 deactivation of the TSX functionality.)
6903                                                  6789 
6904                         auto    - Disable TSX    6790                         auto    - Disable TSX if X86_BUG_TAA is present,
6905                                   otherwise e    6791                                   otherwise enable TSX on the system.
6906                                                  6792 
6907                         Not specifying this o    6793                         Not specifying this option is equivalent to tsx=off.
6908                                                  6794 
6909                         See Documentation/adm    6795                         See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910                         for more details.        6796                         for more details.
6911                                                  6797 
6912         tsx_async_abort= [X86,INTEL,EARLY] Co !! 6798         tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913                         Abort (TAA) vulnerabi    6799                         Abort (TAA) vulnerability.
6914                                                  6800 
6915                         Similar to Micro-arch    6801                         Similar to Micro-architectural Data Sampling (MDS)
6916                         certain CPUs that sup    6802                         certain CPUs that support Transactional
6917                         Synchronization Exten    6803                         Synchronization Extensions (TSX) are vulnerable to an
6918                         exploit against CPU i    6804                         exploit against CPU internal buffers which can forward
6919                         information to a disc    6805                         information to a disclosure gadget under certain
6920                         conditions.              6806                         conditions.
6921                                                  6807 
6922                         In vulnerable process    6808                         In vulnerable processors, the speculatively forwarded
6923                         data can be used in a    6809                         data can be used in a cache side channel attack, to
6924                         access data to which     6810                         access data to which the attacker does not have direct
6925                         access.                  6811                         access.
6926                                                  6812 
6927                         This parameter contro    6813                         This parameter controls the TAA mitigation.  The
6928                         options are:             6814                         options are:
6929                                                  6815 
6930                         full       - Enable T    6816                         full       - Enable TAA mitigation on vulnerable CPUs
6931                                      if TSX i    6817                                      if TSX is enabled.
6932                                                  6818 
6933                         full,nosmt - Enable T    6819                         full,nosmt - Enable TAA mitigation and disable SMT on
6934                                      vulnerab    6820                                      vulnerable CPUs. If TSX is disabled, SMT
6935                                      is not d    6821                                      is not disabled because CPU is not
6936                                      vulnerab    6822                                      vulnerable to cross-thread TAA attacks.
6937                         off        - Uncondit    6823                         off        - Unconditionally disable TAA mitigation
6938                                                  6824 
6939                         On MDS-affected machi    6825                         On MDS-affected machines, tsx_async_abort=off can be
6940                         prevented by an activ    6826                         prevented by an active MDS mitigation as both vulnerabilities
6941                         are mitigated with th    6827                         are mitigated with the same mechanism so in order to disable
6942                         this mitigation, you     6828                         this mitigation, you need to specify mds=off too.
6943                                                  6829 
6944                         Not specifying this o    6830                         Not specifying this option is equivalent to
6945                         tsx_async_abort=full.    6831                         tsx_async_abort=full.  On CPUs which are MDS affected
6946                         and deploy MDS mitiga    6832                         and deploy MDS mitigation, TAA mitigation is not
6947                         required and doesn't     6833                         required and doesn't provide any additional
6948                         mitigation.              6834                         mitigation.
6949                                                  6835 
6950                         For details see:         6836                         For details see:
6951                         Documentation/admin-g    6837                         Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952                                                  6838 
6953         turbografx.map[2|3]=    [HW,JOY]         6839         turbografx.map[2|3]=    [HW,JOY]
6954                         TurboGraFX parallel p    6840                         TurboGraFX parallel port interface
6955                         Format:                  6841                         Format:
6956                         <port#>,<js1>,<js2>,<    6842                         <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957                         See also Documentatio    6843                         See also Documentation/input/devices/joystick-parport.rst
6958                                                  6844 
6959         udbg-immortal   [PPC] When debugging     6845         udbg-immortal   [PPC] When debugging early kernel crashes that
6960                         happen after console_    6846                         happen after console_init() and before a proper
6961                         console driver takes     6847                         console driver takes over, this boot options might
6962                         help "seeing" what's     6848                         help "seeing" what's going on.
6963                                                  6849 
6964         uhash_entries=  [KNL,NET]                6850         uhash_entries=  [KNL,NET]
6965                         Set number of hash bu    6851                         Set number of hash buckets for UDP/UDP-Lite connections
6966                                                  6852 
6967         uhci-hcd.ignore_oc=                      6853         uhci-hcd.ignore_oc=
6968                         [USB] Ignore overcurr    6854                         [USB] Ignore overcurrent events (default N).
6969                         Some badly-designed m    6855                         Some badly-designed motherboards generate lots of
6970                         bogus events, for por    6856                         bogus events, for ports that aren't wired to
6971                         anything.  Set this p    6857                         anything.  Set this parameter to avoid log spamming.
6972                         Note that genuine ove    6858                         Note that genuine overcurrent events won't be
6973                         reported either.         6859                         reported either.
6974                                                  6860 
6975         unknown_nmi_panic                        6861         unknown_nmi_panic
6976                         [X86] Cause panic on     6862                         [X86] Cause panic on unknown NMI.
6977                                                  6863 
6978         unwind_debug    [X86-64,EARLY]        !! 6864         unwind_debug    [X86-64]
6979                         Enable unwinder debug    6865                         Enable unwinder debug output.  This can be
6980                         useful for debugging     6866                         useful for debugging certain unwinder error
6981                         conditions, including    6867                         conditions, including corrupt stacks and
6982                         bad/missing unwinder     6868                         bad/missing unwinder metadata.
6983                                                  6869 
6984         usbcore.authorized_default=              6870         usbcore.authorized_default=
6985                         [USB] Default USB dev    6871                         [USB] Default USB device authorization:
6986                         (default -1 = authori    6872                         (default -1 = authorized (same as 1),
6987                         0 = not authorized, 1    6873                         0 = not authorized, 1 = authorized, 2 = authorized
6988                         if device connected t    6874                         if device connected to internal port)
6989                                                  6875 
6990         usbcore.autosuspend=                     6876         usbcore.autosuspend=
6991                         [USB] The autosuspend    6877                         [USB] The autosuspend time delay (in seconds) used
6992                         for newly-detected US    6878                         for newly-detected USB devices (default 2).  This
6993                         is the time required     6879                         is the time required before an idle device will be
6994                         autosuspended.  Devic    6880                         autosuspended.  Devices for which the delay is set
6995                         to a negative value w    6881                         to a negative value won't be autosuspended at all.
6996                                                  6882 
6997         usbcore.usbfs_snoop=                     6883         usbcore.usbfs_snoop=
6998                         [USB] Set to log all     6884                         [USB] Set to log all usbfs traffic (default 0 = off).
6999                                                  6885 
7000         usbcore.usbfs_snoop_max=                 6886         usbcore.usbfs_snoop_max=
7001                         [USB] Maximum number     6887                         [USB] Maximum number of bytes to snoop in each URB
7002                         (default = 65536).       6888                         (default = 65536).
7003                                                  6889 
7004         usbcore.blinkenlights=                   6890         usbcore.blinkenlights=
7005                         [USB] Set to cycle le    6891                         [USB] Set to cycle leds on hubs (default 0 = off).
7006                                                  6892 
7007         usbcore.old_scheme_first=                6893         usbcore.old_scheme_first=
7008                         [USB] Start with the     6894                         [USB] Start with the old device initialization
7009                         scheme (default 0 = o    6895                         scheme (default 0 = off).
7010                                                  6896 
7011         usbcore.usbfs_memory_mb=                 6897         usbcore.usbfs_memory_mb=
7012                         [USB] Memory limit (i    6898                         [USB] Memory limit (in MB) for buffers allocated by
7013                         usbfs (default = 16,     6899                         usbfs (default = 16, 0 = max = 2047).
7014                                                  6900 
7015         usbcore.use_both_schemes=                6901         usbcore.use_both_schemes=
7016                         [USB] Try the other d    6902                         [USB] Try the other device initialization scheme
7017                         if the first one fail    6903                         if the first one fails (default 1 = enabled).
7018                                                  6904 
7019         usbcore.initial_descriptor_timeout=      6905         usbcore.initial_descriptor_timeout=
7020                         [USB] Specifies timeo    6906                         [USB] Specifies timeout for the initial 64-byte
7021                         USB_REQ_GET_DESCRIPTO    6907                         USB_REQ_GET_DESCRIPTOR request in milliseconds
7022                         (default 5000 = 5.0 s    6908                         (default 5000 = 5.0 seconds).
7023                                                  6909 
7024         usbcore.nousb   [USB] Disable the USB    6910         usbcore.nousb   [USB] Disable the USB subsystem
7025                                                  6911 
7026         usbcore.quirks=                          6912         usbcore.quirks=
7027                         [USB] A list of quirk    6913                         [USB] A list of quirk entries to augment the built-in
7028                         usb core quirk list.     6914                         usb core quirk list. List entries are separated by
7029                         commas. Each entry ha    6915                         commas. Each entry has the form
7030                         VendorID:ProductID:Fl    6916                         VendorID:ProductID:Flags. The IDs are 4-digit hex
7031                         numbers and Flags is     6917                         numbers and Flags is a set of letters. Each letter
7032                         will change the built    6918                         will change the built-in quirk; setting it if it is
7033                         clear and clearing it    6919                         clear and clearing it if it is set. The letters have
7034                         the following meaning    6920                         the following meanings:
7035                                 a = USB_QUIRK    6921                                 a = USB_QUIRK_STRING_FETCH_255 (string
7036                                         descr    6922                                         descriptors must not be fetched using
7037                                         a 255    6923                                         a 255-byte read);
7038                                 b = USB_QUIRK    6924                                 b = USB_QUIRK_RESET_RESUME (device can't resume
7039                                         corre    6925                                         correctly so reset it instead);
7040                                 c = USB_QUIRK    6926                                 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041                                         Set-I    6927                                         Set-Interface requests);
7042                                 d = USB_QUIRK    6928                                 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043                                         handl    6929                                         handle its Configuration or Interface
7044                                         strin    6930                                         strings);
7045                                 e = USB_QUIRK    6931                                 e = USB_QUIRK_RESET (device can't be reset
7046                                         (e.g     6932                                         (e.g morph devices), don't use reset);
7047                                 f = USB_QUIRK    6933                                 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048                                         more     6934                                         more interface descriptions than the
7049                                         bNumI    6935                                         bNumInterfaces count, and can't handle
7050                                         talki    6936                                         talking to these interfaces);
7051                                 g = USB_QUIRK    6937                                 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052                                         durin    6938                                         during initialization, after we read
7053                                         the d    6939                                         the device descriptor);
7054                                 h = USB_QUIRK    6940                                 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055                                         high     6941                                         high speed and super speed interrupt
7056                                         endpo    6942                                         endpoints, the USB 2.0 and USB 3.0 spec
7057                                         requi    6943                                         require the interval in microframes (1
7058                                         micro    6944                                         microframe = 125 microseconds) to be
7059                                         calcu    6945                                         calculated as interval = 2 ^
7060                                         (bInt    6946                                         (bInterval-1).
7061                                         Devic    6947                                         Devices with this quirk report their
7062                                         bInte    6948                                         bInterval as the result of this
7063                                         calcu    6949                                         calculation instead of the exponent
7064                                         varia    6950                                         variable used in the calculation);
7065                                 i = USB_QUIRK    6951                                 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066                                         handl    6952                                         handle device_qualifier descriptor
7067                                         reque    6953                                         requests);
7068                                 j = USB_QUIRK    6954                                 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069                                         gener    6955                                         generates spurious wakeup, ignore
7070                                         remot    6956                                         remote wakeup capability);
7071                                 k = USB_QUIRK    6957                                 k = USB_QUIRK_NO_LPM (device can't handle Link
7072                                         Power    6958                                         Power Management);
7073                                 l = USB_QUIRK    6959                                 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074                                         (Devi    6960                                         (Device reports its bInterval as linear
7075                                         frame    6961                                         frames instead of the USB 2.0
7076                                         calcu    6962                                         calculation);
7077                                 m = USB_QUIRK    6963                                 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078                                         to be    6964                                         to be disconnected before suspend to
7079                                         preve    6965                                         prevent spurious wakeup);
7080                                 n = USB_QUIRK    6966                                 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081                                         pause    6967                                         pause after every control message);
7082                                 o = USB_QUIRK    6968                                 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083                                         delay    6969                                         delay after resetting its port);
7084                                 p = USB_QUIRK    6970                                 p = USB_QUIRK_SHORT_SET_ADDRESS_REQ_TIMEOUT
7085                                         (Redu    6971                                         (Reduce timeout of the SET_ADDRESS
7086                                         reque    6972                                         request from 5000 ms to 500 ms);
7087                         Example: quirks=0781:    6973                         Example: quirks=0781:5580:bk,0a5c:5834:gij
7088                                                  6974 
7089         usbhid.mousepoll=                        6975         usbhid.mousepoll=
7090                         [USBHID] The interval    6976                         [USBHID] The interval which mice are to be polled at.
7091                                                  6977 
7092         usbhid.jspoll=                           6978         usbhid.jspoll=
7093                         [USBHID] The interval    6979                         [USBHID] The interval which joysticks are to be polled at.
7094                                                  6980 
7095         usbhid.kbpoll=                           6981         usbhid.kbpoll=
7096                         [USBHID] The interval    6982                         [USBHID] The interval which keyboards are to be polled at.
7097                                                  6983 
7098         usb-storage.delay_use=                   6984         usb-storage.delay_use=
7099                         [UMS] The delay in se    6985                         [UMS] The delay in seconds before a new device is
7100                         scanned for Logical U    6986                         scanned for Logical Units (default 1).
7101                         Optionally the delay  << 
7102                         suffix with "ms".     << 
7103                         Example: delay_use=25 << 
7104                                                  6987 
7105         usb-storage.quirks=                      6988         usb-storage.quirks=
7106                         [UMS] A list of quirk    6989                         [UMS] A list of quirks entries to supplement or
7107                         override the built-in    6990                         override the built-in unusual_devs list.  List
7108                         entries are separated    6991                         entries are separated by commas.  Each entry has
7109                         the form VID:PID:Flag    6992                         the form VID:PID:Flags where VID and PID are Vendor
7110                         and Product ID values    6993                         and Product ID values (4-digit hex numbers) and
7111                         Flags is a set of cha    6994                         Flags is a set of characters, each corresponding
7112                         to a common usb-stora    6995                         to a common usb-storage quirk flag as follows:
7113                                 a = SANE_SENS    6996                                 a = SANE_SENSE (collect more than 18 bytes
7114                                         of se    6997                                         of sense data, not on uas);
7115                                 b = BAD_SENSE    6998                                 b = BAD_SENSE (don't collect more than 18
7116                                         bytes    6999                                         bytes of sense data, not on uas);
7117                                 c = FIX_CAPAC    7000                                 c = FIX_CAPACITY (decrease the reported
7118                                         devic    7001                                         device capacity by one sector);
7119                                 d = NO_READ_D    7002                                 d = NO_READ_DISC_INFO (don't use
7120                                         READ_    7003                                         READ_DISC_INFO command, not on uas);
7121                                 e = NO_READ_C    7004                                 e = NO_READ_CAPACITY_16 (don't use
7122                                         READ_    7005                                         READ_CAPACITY_16 command);
7123                                 f = NO_REPORT    7006                                 f = NO_REPORT_OPCODES (don't use report opcodes
7124                                         comma    7007                                         command, uas only);
7125                                 g = MAX_SECTO    7008                                 g = MAX_SECTORS_240 (don't transfer more than
7126                                         240 s    7009                                         240 sectors at a time, uas only);
7127                                 h = CAPACITY_    7010                                 h = CAPACITY_HEURISTICS (decrease the
7128                                         repor    7011                                         reported device capacity by one
7129                                         secto    7012                                         sector if the number is odd);
7130                                 i = IGNORE_DE    7013                                 i = IGNORE_DEVICE (don't bind to this
7131                                         devic    7014                                         device);
7132                                 j = NO_REPORT    7015                                 j = NO_REPORT_LUNS (don't use report luns
7133                                         comma    7016                                         command, uas only);
7134                                 k = NO_SAME (    7017                                 k = NO_SAME (do not use WRITE_SAME, uas only)
7135                                 l = NOT_LOCKA    7018                                 l = NOT_LOCKABLE (don't try to lock and
7136                                         unloc    7019                                         unlock ejectable media, not on uas);
7137                                 m = MAX_SECTO    7020                                 m = MAX_SECTORS_64 (don't transfer more
7138                                         than     7021                                         than 64 sectors = 32 KB at a time,
7139                                         not o    7022                                         not on uas);
7140                                 n = INITIAL_R    7023                                 n = INITIAL_READ10 (force a retry of the
7141                                         initi    7024                                         initial READ(10) command, not on uas);
7142                                 o = CAPACITY_    7025                                 o = CAPACITY_OK (accept the capacity
7143                                         repor    7026                                         reported by the device, not on uas);
7144                                 p = WRITE_CAC    7027                                 p = WRITE_CACHE (the device cache is ON
7145                                         by de    7028                                         by default, not on uas);
7146                                 r = IGNORE_RE    7029                                 r = IGNORE_RESIDUE (the device reports
7147                                         bogus    7030                                         bogus residue values, not on uas);
7148                                 s = SINGLE_LU    7031                                 s = SINGLE_LUN (the device has only one
7149                                         Logic    7032                                         Logical Unit);
7150                                 t = NO_ATA_1X    7033                                 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151                                         comma    7034                                         commands, uas only);
7152                                 u = IGNORE_UA    7035                                 u = IGNORE_UAS (don't bind to the uas driver);
7153                                 w = NO_WP_DET    7036                                 w = NO_WP_DETECT (don't test whether the
7154                                         mediu    7037                                         medium is write-protected).
7155                                 y = ALWAYS_SY    7038                                 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156                                         even     7039                                         even if the device claims no cache,
7157                                         not o    7040                                         not on uas)
7158                         Example: quirks=0419:    7041                         Example: quirks=0419:aaf5:rl,0421:0433:rc
7159                                                  7042 
7160         user_debug=     [KNL,ARM]                7043         user_debug=     [KNL,ARM]
7161                         Format: <int>            7044                         Format: <int>
7162                         See arch/arm/Kconfig.    7045                         See arch/arm/Kconfig.debug help text.
7163                                  1 - undefine    7046                                  1 - undefined instruction events
7164                                  2 - system c    7047                                  2 - system calls
7165                                  4 - invalid     7048                                  4 - invalid data aborts
7166                                  8 - SIGSEGV     7049                                  8 - SIGSEGV faults
7167                                 16 - SIGBUS f    7050                                 16 - SIGBUS faults
7168                         Example: user_debug=3    7051                         Example: user_debug=31
7169                                                  7052 
7170         userpte=                                 7053         userpte=
7171                         [X86,EARLY] Flags con !! 7054                         [X86] Flags controlling user PTE allocations.
7172                                                  7055 
7173                                 nohigh = do n    7056                                 nohigh = do not allocate PTE pages in
7174                                         HIGHM    7057                                         HIGHMEM regardless of setting
7175                                         of CO    7058                                         of CONFIG_HIGHPTE.
7176                                                  7059 
7177         vdso=           [X86,SH,SPARC]           7060         vdso=           [X86,SH,SPARC]
7178                         On X86_32, this is an    7061                         On X86_32, this is an alias for vdso32=.  Otherwise:
7179                                                  7062 
7180                         vdso=1: enable VDSO (    7063                         vdso=1: enable VDSO (the default)
7181                         vdso=0: disable VDSO     7064                         vdso=0: disable VDSO mapping
7182                                                  7065 
7183         vdso32=         [X86] Control the 32-    7066         vdso32=         [X86] Control the 32-bit vDSO
7184                         vdso32=1: enable 32-b    7067                         vdso32=1: enable 32-bit VDSO
7185                         vdso32=0 or vdso32=2:    7068                         vdso32=0 or vdso32=2: disable 32-bit VDSO
7186                                                  7069 
7187                         See the help text for    7070                         See the help text for CONFIG_COMPAT_VDSO for more
7188                         details.  If CONFIG_C    7071                         details.  If CONFIG_COMPAT_VDSO is set, the default is
7189                         vdso32=0; otherwise,     7072                         vdso32=0; otherwise, the default is vdso32=1.
7190                                                  7073 
7191                         For compatibility wit    7074                         For compatibility with older kernels, vdso32=2 is an
7192                         alias for vdso32=0.      7075                         alias for vdso32=0.
7193                                                  7076 
7194                         Try vdso32=0 if you e    7077                         Try vdso32=0 if you encounter an error that says:
7195                         dl_main: Assertion `(    7078                         dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196                                                  7079 
7197         video=          [FB,EARLY] Frame buff !! 7080         vector=         [IA-64,SMP]
                                                   >> 7081                         vector=percpu: enable percpu vector domain
                                                   >> 7082 
                                                   >> 7083         video=          [FB] Frame buffer configuration
7198                         See Documentation/fb/    7084                         See Documentation/fb/modedb.rst.
7199                                                  7085 
7200         video.brightness_switch_enabled= [ACP    7086         video.brightness_switch_enabled= [ACPI]
7201                         Format: [0|1]            7087                         Format: [0|1]
7202                         If set to 1, on recei    7088                         If set to 1, on receiving an ACPI notify event
7203                         generated by hotkey,     7089                         generated by hotkey, video driver will adjust brightness
7204                         level and then send o    7090                         level and then send out the event to user space through
7205                         the allocated input d    7091                         the allocated input device. If set to 0, video driver
7206                         will only send out th    7092                         will only send out the event without touching backlight
7207                         brightness level.        7093                         brightness level.
7208                         default: 1               7094                         default: 1
7209                                                  7095 
7210         virtio_mmio.device=                      7096         virtio_mmio.device=
7211                         [VMMIO] Memory mapped    7097                         [VMMIO] Memory mapped virtio (platform) device.
7212                                                  7098 
7213                                 <size>@<basead    7099                                 <size>@<baseaddr>:<irq>[:<id>]
7214                         where:                   7100                         where:
7215                                 <size>     :=    7101                                 <size>     := size (can use standard suffixes
7216                                                  7102                                                 like K, M and G)
7217                                 <baseaddr> :=    7103                                 <baseaddr> := physical base address
7218                                 <irq>      :=    7104                                 <irq>      := interrupt number (as passed to
7219                                                  7105                                                 request_irq())
7220                                 <id>       :=    7106                                 <id>       := (optional) platform device id
7221                         example:                 7107                         example:
7222                                 virtio_mmio.d    7108                                 virtio_mmio.device=1K@0x100b0000:48:7
7223                                                  7109 
7224                         Can be used multiple     7110                         Can be used multiple times for multiple devices.
7225                                                  7111 
7226         vga=            [BOOT,X86-32] Select     7112         vga=            [BOOT,X86-32] Select a particular video mode
7227                         See Documentation/arc    7113                         See Documentation/arch/x86/boot.rst and
7228                         Documentation/admin-g    7114                         Documentation/admin-guide/svga.rst.
7229                         Use vga=ask for menu.    7115                         Use vga=ask for menu.
7230                         This is actually a bo    7116                         This is actually a boot loader parameter; the value is
7231                         passed to the kernel     7117                         passed to the kernel using a special protocol.
7232                                                  7118 
7233         vm_debug[=options]      [KNL] Availab    7119         vm_debug[=options]      [KNL] Available with CONFIG_DEBUG_VM=y.
7234                         May slow down system     7120                         May slow down system boot speed, especially when
7235                         enabled on systems wi    7121                         enabled on systems with a large amount of memory.
7236                         All options are enabl    7122                         All options are enabled by default, and this
7237                         interface is meant to    7123                         interface is meant to allow for selectively
7238                         enabling or disabling    7124                         enabling or disabling specific virtual memory
7239                         debugging features.      7125                         debugging features.
7240                                                  7126 
7241                         Available options are    7127                         Available options are:
7242                           P     Enable page s    7128                           P     Enable page structure init time poisoning
7243                           -     Disable all o    7129                           -     Disable all of the above options
7244                                                  7130 
7245         vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 7131         vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246                         exact size of <nn>. T !! 7132                         size of <nn>. This can be used to increase the
7247                         the minimum size (128 !! 7133                         minimum size (128MB on x86). It can also be used to
7248                         It can also be used t !! 7134                         decrease the size and leave more room for directly
7249                         for directly mapped k !! 7135                         mapped kernel RAM.
7250                         not exist on many oth << 
7251                         loongarch, arc, csky, << 
7252                         parisc, m64k, powerpc << 
7253                                                  7136 
7254         vmcp_cma=nn[MG] [KNL,S390,EARLY]      !! 7137         vmcp_cma=nn[MG] [KNL,S390]
7255                         Sets the memory size     7138                         Sets the memory size reserved for contiguous memory
7256                         allocations for the v    7139                         allocations for the vmcp device driver.
7257                                                  7140 
7258         vmhalt=         [KNL,S390] Perform z/    7141         vmhalt=         [KNL,S390] Perform z/VM CP command after system halt.
7259                         Format: <command>        7142                         Format: <command>
7260                                                  7143 
7261         vmpanic=        [KNL,S390] Perform z/    7144         vmpanic=        [KNL,S390] Perform z/VM CP command after kernel panic.
7262                         Format: <command>        7145                         Format: <command>
7263                                                  7146 
7264         vmpoff=         [KNL,S390] Perform z/    7147         vmpoff=         [KNL,S390] Perform z/VM CP command after power off.
7265                         Format: <command>        7148                         Format: <command>
7266                                                  7149 
7267         vsyscall=       [X86-64,EARLY]        !! 7150         vsyscall=       [X86-64]
7268                         Controls the behavior    7151                         Controls the behavior of vsyscalls (i.e. calls to
7269                         fixed addresses of 0x    7152                         fixed addresses of 0xffffffffff600x00 from legacy
7270                         code).  Most statical    7153                         code).  Most statically-linked binaries and older
7271                         versions of glibc use    7154                         versions of glibc use these calls.  Because these
7272                         functions are at fixe    7155                         functions are at fixed addresses, they make nice
7273                         targets for exploits     7156                         targets for exploits that can control RIP.
7274                                                  7157 
7275                         emulate     Vsyscalls    7158                         emulate     Vsyscalls turn into traps and are emulated
7276                                     reasonabl    7159                                     reasonably safely.  The vsyscall page is
7277                                     readable.    7160                                     readable.
7278                                                  7161 
7279                         xonly       [default]    7162                         xonly       [default] Vsyscalls turn into traps and are
7280                                     emulated     7163                                     emulated reasonably safely.  The vsyscall
7281                                     page is n    7164                                     page is not readable.
7282                                                  7165 
7283                         none        Vsyscalls    7166                         none        Vsyscalls don't work at all.  This makes
7284                                     them quit    7167                                     them quite hard to use for exploits but
7285                                     might bre    7168                                     might break your system.
7286                                                  7169 
7287         vt.color=       [VT] Default text col    7170         vt.color=       [VT] Default text color.
7288                         Format: 0xYX, X = for    7171                         Format: 0xYX, X = foreground, Y = background.
7289                         Default: 0x07 = light    7172                         Default: 0x07 = light gray on black.
7290                                                  7173 
7291         vt.cur_default= [VT] Default cursor s    7174         vt.cur_default= [VT] Default cursor shape.
7292                         Format: 0xCCBBAA, whe    7175                         Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293                         the parameters of the    7176                         the parameters of the <Esc>[?A;B;Cc escape sequence;
7294                         see VGA-softcursor.tx    7177                         see VGA-softcursor.txt. Default: 2 = underline.
7295                                                  7178 
7296         vt.default_blu= [VT]                     7179         vt.default_blu= [VT]
7297                         Format: <blue0>,<blue    7180                         Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298                         Change the default bl    7181                         Change the default blue palette of the console.
7299                         This is a 16-member a    7182                         This is a 16-member array composed of values
7300                         ranging from 0-255.      7183                         ranging from 0-255.
7301                                                  7184 
7302         vt.default_grn= [VT]                     7185         vt.default_grn= [VT]
7303                         Format: <green0>,<gre    7186                         Format: <green0>,<green1>,<green2>,...,<green15>
7304                         Change the default gr    7187                         Change the default green palette of the console.
7305                         This is a 16-member a    7188                         This is a 16-member array composed of values
7306                         ranging from 0-255.      7189                         ranging from 0-255.
7307                                                  7190 
7308         vt.default_red= [VT]                     7191         vt.default_red= [VT]
7309                         Format: <red0>,<red1>    7192                         Format: <red0>,<red1>,<red2>,...,<red15>
7310                         Change the default re    7193                         Change the default red palette of the console.
7311                         This is a 16-member a    7194                         This is a 16-member array composed of values
7312                         ranging from 0-255.      7195                         ranging from 0-255.
7313                                                  7196 
7314         vt.default_utf8=                         7197         vt.default_utf8=
7315                         [VT]                     7198                         [VT]
7316                         Format=<0|1>             7199                         Format=<0|1>
7317                         Set system-wide defau    7200                         Set system-wide default UTF-8 mode for all tty's.
7318                         Default is 1, i.e. UT    7201                         Default is 1, i.e. UTF-8 mode is enabled for all
7319                         newly opened terminal    7202                         newly opened terminals.
7320                                                  7203 
7321         vt.global_cursor_default=                7204         vt.global_cursor_default=
7322                         [VT]                     7205                         [VT]
7323                         Format=<-1|0|1>          7206                         Format=<-1|0|1>
7324                         Set system-wide defau    7207                         Set system-wide default for whether a cursor
7325                         is shown on new VTs.     7208                         is shown on new VTs. Default is -1,
7326                         i.e. cursors will be     7209                         i.e. cursors will be created by default unless
7327                         overridden by individ    7210                         overridden by individual drivers. 0 will hide
7328                         cursors, 1 will displ    7211                         cursors, 1 will display them.
7329                                                  7212 
7330         vt.italic=      [VT] Default color fo    7213         vt.italic=      [VT] Default color for italic text; 0-15.
7331                         Default: 2 = green.      7214                         Default: 2 = green.
7332                                                  7215 
7333         vt.underline=   [VT] Default color fo    7216         vt.underline=   [VT] Default color for underlined text; 0-15.
7334                         Default: 3 = cyan.       7217                         Default: 3 = cyan.
7335                                                  7218 
7336         watchdog timers [HW,WDT] For informat    7219         watchdog timers [HW,WDT] For information on watchdog timers,
7337                         see Documentation/wat    7220                         see Documentation/watchdog/watchdog-parameters.rst
7338                         or other driver-speci    7221                         or other driver-specific files in the
7339                         Documentation/watchdo    7222                         Documentation/watchdog/ directory.
7340                                                  7223 
7341         watchdog_thresh=                         7224         watchdog_thresh=
7342                         [KNL]                    7225                         [KNL]
7343                         Set the hard lockup d    7226                         Set the hard lockup detector stall duration
7344                         threshold in seconds.    7227                         threshold in seconds. The soft lockup detector
7345                         threshold is set to t    7228                         threshold is set to twice the value. A value of 0
7346                         disables both lockup     7229                         disables both lockup detectors. Default is 10
7347                         seconds.                 7230                         seconds.
7348                                                  7231 
7349         workqueue.unbound_cpus=                  7232         workqueue.unbound_cpus=
7350                         [KNL,SMP] Specify to     7233                         [KNL,SMP] Specify to constrain one or some CPUs
7351                         to use in unbound wor    7234                         to use in unbound workqueues.
7352                         Format: <cpu-list>       7235                         Format: <cpu-list>
7353                         By default, all onlin    7236                         By default, all online CPUs are available for
7354                         unbound workqueues.      7237                         unbound workqueues.
7355                                                  7238 
7356         workqueue.watchdog_thresh=               7239         workqueue.watchdog_thresh=
7357                         If CONFIG_WQ_WATCHDOG    7240                         If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358                         warn stall conditions    7241                         warn stall conditions and dump internal state to
7359                         help debugging.  0 di    7242                         help debugging.  0 disables workqueue stall
7360                         detection; otherwise,    7243                         detection; otherwise, it's the stall threshold
7361                         duration in seconds.     7244                         duration in seconds.  The default value is 30 and
7362                         it can be updated at     7245                         it can be updated at runtime by writing to the
7363                         corresponding sysfs f    7246                         corresponding sysfs file.
7364                                                  7247 
7365         workqueue.cpu_intensive_thresh_us=       7248         workqueue.cpu_intensive_thresh_us=
7366                         Per-cpu work items wh    7249                         Per-cpu work items which run for longer than this
7367                         threshold are automat    7250                         threshold are automatically considered CPU intensive
7368                         and excluded from con    7251                         and excluded from concurrency management to prevent
7369                         them from noticeably     7252                         them from noticeably delaying other per-cpu work
7370                         items. Default is 100    7253                         items. Default is 10000 (10ms).
7371                                                  7254 
7372                         If CONFIG_WQ_CPU_INTE    7255                         If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7373                         will report the work     7256                         will report the work functions which violate this
7374                         threshold repeatedly.    7257                         threshold repeatedly. They are likely good
7375                         candidates for using     7258                         candidates for using WQ_UNBOUND workqueues instead.
7376                                                  7259 
7377         workqueue.cpu_intensive_warning_thres << 
7378                         If CONFIG_WQ_CPU_INTE << 
7379                         will report the work  << 
7380                         intensive_threshold_u << 
7381                         spurious warnings, st << 
7382                         function has violated << 
7383                                               << 
7384                         The default is 4 time << 
7385                                               << 
7386         workqueue.power_efficient                7260         workqueue.power_efficient
7387                         Per-cpu workqueues ar    7261                         Per-cpu workqueues are generally preferred because
7388                         they show better perf    7262                         they show better performance thanks to cache
7389                         locality; unfortunate    7263                         locality; unfortunately, per-cpu workqueues tend to
7390                         be more power hungry     7264                         be more power hungry than unbound workqueues.
7391                                                  7265 
7392                         Enabling this makes t    7266                         Enabling this makes the per-cpu workqueues which
7393                         were observed to cont    7267                         were observed to contribute significantly to power
7394                         consumption unbound,     7268                         consumption unbound, leading to measurably lower
7395                         power usage at the co    7269                         power usage at the cost of small performance
7396                         overhead.                7270                         overhead.
7397                                                  7271 
7398                         The default value of     7272                         The default value of this parameter is determined by
7399                         the config option CON    7273                         the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400                                                  7274 
7401         workqueue.default_affinity_scope=        7275         workqueue.default_affinity_scope=
7402                         Select the default af    7276                         Select the default affinity scope to use for unbound
7403                         workqueues. Can be on    7277                         workqueues. Can be one of "cpu", "smt", "cache",
7404                         "numa" and "system".     7278                         "numa" and "system". Default is "cache". For more
7405                         information, see the     7279                         information, see the Affinity Scopes section in
7406                         Documentation/core-ap    7280                         Documentation/core-api/workqueue.rst.
7407                                                  7281 
7408                         This can be changed a    7282                         This can be changed after boot by writing to the
7409                         matching /sys/module/    7283                         matching /sys/module/workqueue/parameters file. All
7410                         workqueues with the "    7284                         workqueues with the "default" affinity scope will be
7411                         updated accordingly.  !! 7285                         updated accordignly.
7412                                                  7286 
7413         workqueue.debug_force_rr_cpu             7287         workqueue.debug_force_rr_cpu
7414                         Workqueue used to imp    7288                         Workqueue used to implicitly guarantee that work
7415                         items queued without     7289                         items queued without explicit CPU specified are put
7416                         on the local CPU.  Th    7290                         on the local CPU.  This guarantee is no longer true
7417                         and while local CPU i    7291                         and while local CPU is still preferred work items
7418                         may be put on foreign    7292                         may be put on foreign CPUs.  This debug option
7419                         forces round-robin CP    7293                         forces round-robin CPU selection to flush out
7420                         usages which depend o    7294                         usages which depend on the now broken guarantee.
7421                         When enabled, memory     7295                         When enabled, memory and cache locality will be
7422                         impacted.                7296                         impacted.
7423                                                  7297 
7424         writecombine=   [LOONGARCH,EARLY] Con !! 7298         writecombine=   [LOONGARCH] Control the MAT (Memory Access Type) of
7425                         Type) of ioremap_wc() !! 7299                         ioremap_wc().
7426                                                  7300 
7427                         on   - Enable writeco    7301                         on   - Enable writecombine, use WUC for ioremap_wc()
7428                         off  - Disable writec    7302                         off  - Disable writecombine, use SUC for ioremap_wc()
7429                                                  7303 
7430         x2apic_phys     [X86-64,APIC,EARLY] U !! 7304         x2apic_phys     [X86-64,APIC] Use x2apic physical mode instead of
7431                         default x2apic cluste    7305                         default x2apic cluster mode on platforms
7432                         supporting x2apic.       7306                         supporting x2apic.
7433                                                  7307 
7434         xen_512gb_limit         [KNL,X86-64,X    7308         xen_512gb_limit         [KNL,X86-64,XEN]
7435                         Restricts the kernel     7309                         Restricts the kernel running paravirtualized under Xen
7436                         to use only up to 512    7310                         to use only up to 512 GB of RAM. The reason to do so is
7437                         crash analysis tools     7311                         crash analysis tools and Xen tools for doing domain
7438                         save/restore/migratio    7312                         save/restore/migration must be enabled to handle larger
7439                         domains.                 7313                         domains.
7440                                                  7314 
7441         xen_emul_unplug=                [HW,X !! 7315         xen_emul_unplug=                [HW,X86,XEN]
7442                         Unplug Xen emulated d    7316                         Unplug Xen emulated devices
7443                         Format: [unplug0,][un    7317                         Format: [unplug0,][unplug1]
7444                         ide-disks -- unplug p    7318                         ide-disks -- unplug primary master IDE devices
7445                         aux-ide-disks -- unpl    7319                         aux-ide-disks -- unplug non-primary-master IDE devices
7446                         nics -- unplug networ    7320                         nics -- unplug network devices
7447                         all -- unplug all emu    7321                         all -- unplug all emulated devices (NICs and IDE disks)
7448                         unnecessary -- unplug    7322                         unnecessary -- unplugging emulated devices is
7449                                 unnecessary e    7323                                 unnecessary even if the host did not respond to
7450                                 the unplug pr    7324                                 the unplug protocol
7451                         never -- do not unplu    7325                         never -- do not unplug even if version check succeeds
7452                                                  7326 
7453         xen_legacy_crash        [X86,XEN,EARL !! 7327         xen_legacy_crash        [X86,XEN]
7454                         Crash from Xen panic     7328                         Crash from Xen panic notifier, without executing late
7455                         panic() code such as     7329                         panic() code such as dumping handler.
7456                                                  7330 
7457         xen_mc_debug    [X86,XEN,EARLY]       !! 7331         xen_msr_safe=   [X86,XEN]
7458                         Enable multicall debu << 
7459                         Enabling this feature << 
7460                         bit, so it should onl << 
7461                         debug data in case of << 
7462                                               << 
7463         xen_msr_safe=   [X86,XEN,EARLY]       << 
7464                         Format: <bool>           7332                         Format: <bool>
7465                         Select whether to alw    7333                         Select whether to always use non-faulting (safe) MSR
7466                         access functions when    7334                         access functions when running as Xen PV guest. The
7467                         default value is cont    7335                         default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
7468                                                  7336 
                                                   >> 7337         xen_nopvspin    [X86,XEN]
                                                   >> 7338                         Disables the qspinlock slowpath using Xen PV optimizations.
                                                   >> 7339                         This parameter is obsoleted by "nopvspin" parameter, which
                                                   >> 7340                         has equivalent effect for XEN platform.
                                                   >> 7341 
7469         xen_nopv        [X86]                    7342         xen_nopv        [X86]
7470                         Disables the PV optim    7343                         Disables the PV optimizations forcing the HVM guest to
7471                         run as generic HVM gu    7344                         run as generic HVM guest with no PV drivers.
7472                         This option is obsole    7345                         This option is obsoleted by the "nopv" option, which
7473                         has equivalent effect    7346                         has equivalent effect for XEN platform.
7474                                                  7347 
7475         xen_no_vector_callback                   7348         xen_no_vector_callback
7476                         [KNL,X86,XEN,EARLY] D !! 7349                         [KNL,X86,XEN] Disable the vector callback for Xen
7477                         event channel interru    7350                         event channel interrupts.
7478                                                  7351 
7479         xen_scrub_pages=        [XEN]            7352         xen_scrub_pages=        [XEN]
7480                         Boolean option to con    7353                         Boolean option to control scrubbing pages before giving them back
7481                         to Xen, for use by ot    7354                         to Xen, for use by other domains. Can be also changed at runtime
7482                         with /sys/devices/sys    7355                         with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483                         Default value control    7356                         Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484                                                  7357 
7485         xen_timer_slop= [X86-64,XEN,EARLY]    !! 7358         xen_timer_slop= [X86-64,XEN]
7486                         Set the timer slop (i    7359                         Set the timer slop (in nanoseconds) for the virtual Xen
7487                         timers (default is 10    7360                         timers (default is 100000). This adjusts the minimum
7488                         delta of virtualized     7361                         delta of virtualized Xen timers, where lower values
7489                         improve timer resolut    7362                         improve timer resolution at the expense of processing
7490                         more timer interrupts    7363                         more timer interrupts.
7491                                                  7364 
7492         xen.balloon_boot_timeout= [XEN]          7365         xen.balloon_boot_timeout= [XEN]
7493                         The time (in seconds)    7366                         The time (in seconds) to wait before giving up to boot
7494                         in case initial ballo    7367                         in case initial ballooning fails to free enough memory.
7495                         Applies only when run    7368                         Applies only when running as HVM or PVH guest and
7496                         started with less mem    7369                         started with less memory configured than allowed at
7497                         max. Default is 180.     7370                         max. Default is 180.
7498                                                  7371 
7499         xen.event_eoi_delay=    [XEN]            7372         xen.event_eoi_delay=    [XEN]
7500                         How long to delay EOI    7373                         How long to delay EOI handling in case of event
7501                         storms (jiffies). Def    7374                         storms (jiffies). Default is 10.
7502                                                  7375 
7503         xen.event_loop_timeout= [XEN]            7376         xen.event_loop_timeout= [XEN]
7504                         After which time (jif    7377                         After which time (jiffies) the event handling loop
7505                         should start to delay    7378                         should start to delay EOI handling. Default is 2.
7506                                                  7379 
7507         xen.fifo_events=        [XEN]            7380         xen.fifo_events=        [XEN]
7508                         Boolean parameter to     7381                         Boolean parameter to disable using fifo event handling
7509                         even if available. No    7382                         even if available. Normally fifo event handling is
7510                         preferred over the 2-    7383                         preferred over the 2-level event handling, as it is
7511                         fairer and the number    7384                         fairer and the number of possible event channels is
7512                         much higher. Default     7385                         much higher. Default is on (use fifo events).
7513                                                  7386 
7514         xirc2ps_cs=     [NET,PCMCIA]             7387         xirc2ps_cs=     [NET,PCMCIA]
7515                         Format:                  7388                         Format:
7516                         <irq>,<irq_mask>,<io>    7389                         <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517                                                  7390 
7518         xive=           [PPC]                    7391         xive=           [PPC]
7519                         By default on POWER9     7392                         By default on POWER9 and above, the kernel will
7520                         natively use the XIVE    7393                         natively use the XIVE interrupt controller. This option
7521                         allows the fallback f    7394                         allows the fallback firmware mode to be used:
7522                                                  7395 
7523                         off       Fallback to    7396                         off       Fallback to firmware control of XIVE interrupt
7524                                   controller     7397                                   controller on both pseries and powernv
7525                                   platforms.     7398                                   platforms. Only useful on POWER9 and above.
7526                                                  7399 
7527         xive.store-eoi=off      [PPC]            7400         xive.store-eoi=off      [PPC]
7528                         By default on POWER10    7401                         By default on POWER10 and above, the kernel will use
7529                         stores for EOI handli    7402                         stores for EOI handling when the XIVE interrupt mode
7530                         is active. This optio    7403                         is active. This option allows the XIVE driver to use
7531                         loads instead, as on     7404                         loads instead, as on POWER9.
7532                                                  7405 
7533         xhci-hcd.quirks         [USB,KNL]        7406         xhci-hcd.quirks         [USB,KNL]
7534                         A hex value specifyin    7407                         A hex value specifying bitmask with supplemental xhci
7535                         host controller quirk    7408                         host controller quirks. Meaning of each bit can be
7536                         consulted in header d    7409                         consulted in header drivers/usb/host/xhci.h.
7537                                                  7410 
7538         xmon            [PPC,EARLY]           !! 7411         xmon            [PPC]
7539                         Format: { early | on     7412                         Format: { early | on | rw | ro | off }
7540                         Controls if xmon debu    7413                         Controls if xmon debugger is enabled. Default is off.
7541                         Passing only "xmon" i    7414                         Passing only "xmon" is equivalent to "xmon=early".
7542                         early   Call xmon as     7415                         early   Call xmon as early as possible on boot; xmon
7543                                 debugger is c    7416                                 debugger is called from setup_arch().
7544                         on      xmon debugger    7417                         on      xmon debugger hooks will be installed so xmon
7545                                 is only calle    7418                                 is only called on a kernel crash. Default mode,
7546                                 i.e. either "    7419                                 i.e. either "ro" or "rw" mode, is controlled
7547                                 with CONFIG_X    7420                                 with CONFIG_XMON_DEFAULT_RO_MODE.
7548                         rw      xmon debugger    7421                         rw      xmon debugger hooks will be installed so xmon
7549                                 is called onl    7422                                 is called only on a kernel crash, mode is write,
7550                                 meaning SPR r    7423                                 meaning SPR registers, memory and, other data
7551                                 can be writte    7424                                 can be written using xmon commands.
7552                         ro      same as "rw"     7425                         ro      same as "rw" option above but SPR registers,
7553                                 memory, and o    7426                                 memory, and other data can't be written using
7554                                 xmon commands    7427                                 xmon commands.
7555                         off     xmon is disab    7428                         off     xmon is disabled.
                                                   >> 7429 
                                                      

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