1 accept_memory= [MM] !! 1 acpi= [HW,ACPI,X86,ARM64]
2 Format: { eager | lazy <<
3 default: lazy <<
4 By default, unaccepted <<
5 avoid prolonged boot t <<
6 some runtime overhead <<
7 accepted. In most case <<
8 For some workloads or <<
9 accept_memory=eager ca <<
10 at once during boot. <<
11 <<
12 acpi= [HW,ACPI,X86,ARM64,RIS <<
13 Advanced Configuration 2 Advanced Configuration and Power Interface
14 Format: { force | on | 3 Format: { force | on | off | strict | noirq | rsdt |
15 copy_dsdt | !! 4 copy_dsdt }
16 force -- enable ACPI i 5 force -- enable ACPI if default was off
17 on -- enable ACPI but !! 6 on -- enable ACPI but allow fallback to DT [arm64]
18 off -- disable ACPI if 7 off -- disable ACPI if default was on
19 noirq -- do not use AC 8 noirq -- do not use ACPI for IRQ routing
20 strict -- Be less tole 9 strict -- Be less tolerant of platforms that are not
21 strictly ACPI 10 strictly ACPI specification compliant.
22 rsdt -- prefer RSDT ov 11 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT 12 copy_dsdt -- copy DSDT to memory
24 nospcr -- disable cons !! 13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
25 default _seria <<
26 For ARM64, ONLY "acpi= <<
27 "acpi=nospcr" are avai <<
28 For RISCV64, ONLY "acp <<
29 are available 14 are available
30 15
31 See also Documentation 16 See also Documentation/power/runtime_pm.rst, pci=noacpi
32 17
33 acpi_apic_instance= [ACPI,IOAPIC,E !! 18 acpi_apic_instance= [ACPI, IOAPIC]
34 Format: <int> 19 Format: <int>
35 2: use 2nd APIC table, 20 2: use 2nd APIC table, if available
36 1,0: use 1st APIC tabl 21 1,0: use 1st APIC table
37 default: 0 22 default: 0
38 23
39 acpi_backlight= [HW,ACPI] 24 acpi_backlight= [HW,ACPI]
40 { vendor | video | nat 25 { vendor | video | native | none }
41 If set to vendor, pref 26 If set to vendor, prefer vendor-specific driver
42 (e.g. thinkpad_acpi, s 27 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
43 of the ACPI video.ko d 28 of the ACPI video.ko driver.
44 If set to video, use t 29 If set to video, use the ACPI video.ko driver.
45 If set to native, use 30 If set to native, use the device's native backlight mode.
46 If set to none, disabl 31 If set to none, disable the ACPI backlight interface.
47 32
48 acpi_force_32bit_fadt_addr [ACPI,EARLY !! 33 acpi_force_32bit_fadt_addr
49 force FADT to use 32 b 34 force FADT to use 32 bit addresses rather than the
50 64 bit X_* addresses. 35 64 bit X_* addresses. Some firmware have broken 64
51 bit addresses for forc 36 bit addresses for force ACPI ignore these and use
52 the older legacy 32 bi 37 the older legacy 32 bit addresses.
53 38
54 acpica_no_return_repair [HW, ACPI] 39 acpica_no_return_repair [HW, ACPI]
55 Disable AML predefined 40 Disable AML predefined validation mechanism
56 This mechanism can rep 41 This mechanism can repair the evaluation result to make
57 the return objects mor 42 the return objects more ACPI specification compliant.
58 This option is useful 43 This option is useful for developers to identify the
59 root cause of an AML i 44 root cause of an AML interpreter issue when the issue
60 has something to do wi 45 has something to do with the repair mechanism.
61 46
62 acpi.debug_layer= [HW,ACPI,ACPI_ 47 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
63 acpi.debug_level= [HW,ACPI,ACPI_ 48 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
64 Format: <int> 49 Format: <int>
65 CONFIG_ACPI_DEBUG must 50 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
66 debug output. Bits in 51 debug output. Bits in debug_layer correspond to a
67 _COMPONENT in an ACPI 52 _COMPONENT in an ACPI source file, e.g.,
68 #define _COMPONENT !! 53 #define _COMPONENT ACPI_PCI_COMPONENT
69 Bits in debug_level co 54 Bits in debug_level correspond to a level in
70 ACPI_DEBUG_PRINT state 55 ACPI_DEBUG_PRINT statements, e.g.,
71 ACPI_DEBUG_PRINT(( 56 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
72 The debug_level mask d 57 The debug_level mask defaults to "info". See
73 Documentation/firmware 58 Documentation/firmware-guide/acpi/debug.rst for more information about
74 debug layers and level 59 debug layers and levels.
75 60
76 Enable processor drive 61 Enable processor driver info messages:
77 acpi.debug_layer=0 62 acpi.debug_layer=0x20000000
>> 63 Enable PCI/PCI interrupt routing info messages:
>> 64 acpi.debug_layer=0x400000
78 Enable AML "Debug" out 65 Enable AML "Debug" output, i.e., stores to the Debug
79 object while interpret 66 object while interpreting AML:
80 acpi.debug_layer=0 67 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
81 Enable all messages re 68 Enable all messages related to ACPI hardware:
82 acpi.debug_layer=0 69 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
83 70
84 Some values produce so 71 Some values produce so much output that the system is
85 unusable. The "log_bu 72 unusable. The "log_buf_len" parameter may be useful
86 if you need to capture 73 if you need to capture more output.
87 74
88 acpi_enforce_resources= [ACPI] 75 acpi_enforce_resources= [ACPI]
89 { strict | lax | no } 76 { strict | lax | no }
90 Check for resource con 77 Check for resource conflicts between native drivers
91 and ACPI OperationRegi 78 and ACPI OperationRegions (SystemIO and SystemMemory
92 only). IO ports and me 79 only). IO ports and memory declared in ACPI might be
93 used by the ACPI subsy 80 used by the ACPI subsystem in arbitrary AML code and
94 can interfere with leg 81 can interfere with legacy drivers.
95 strict (default): acce 82 strict (default): access to resources claimed by ACPI
96 is denied; legacy driv 83 is denied; legacy drivers trying to access reserved
97 resources will fail to 84 resources will fail to bind to device using them.
98 lax: access to resourc 85 lax: access to resources claimed by ACPI is allowed;
99 legacy drivers trying 86 legacy drivers trying to access reserved resources
100 will bind successfully 87 will bind successfully but a warning message is logged.
101 no: ACPI OperationRegi 88 no: ACPI OperationRegions are not marked as reserved,
102 no further checks are 89 no further checks are performed.
103 90
104 acpi_force_table_verification [HW,AC !! 91 acpi_force_table_verification [HW,ACPI]
105 Enable table checksum 92 Enable table checksum verification during early stage.
106 By default, this is di 93 By default, this is disabled due to x86 early mapping
107 size limitation. 94 size limitation.
108 95
109 acpi_irq_balance [HW,ACPI] 96 acpi_irq_balance [HW,ACPI]
110 ACPI will balance acti 97 ACPI will balance active IRQs
111 default in APIC mode 98 default in APIC mode
112 99
113 acpi_irq_nobalance [HW,ACPI] 100 acpi_irq_nobalance [HW,ACPI]
114 ACPI will not move act 101 ACPI will not move active IRQs (default)
115 default in PIC mode 102 default in PIC mode
116 103
117 acpi_irq_isa= [HW,ACPI] If irq_balan 104 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
118 Format: <irq>,<irq>... 105 Format: <irq>,<irq>...
119 106
120 acpi_irq_pci= [HW,ACPI] If irq_balan 107 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
121 use by PCI 108 use by PCI
122 Format: <irq>,<irq>... 109 Format: <irq>,<irq>...
123 110
124 acpi_mask_gpe= [HW,ACPI] 111 acpi_mask_gpe= [HW,ACPI]
125 Due to the existence o 112 Due to the existence of _Lxx/_Exx, some GPEs triggered
126 by unsupported hardwar 113 by unsupported hardware/firmware features can result in
127 GPE floodings that can 114 GPE floodings that cannot be automatically disabled by
128 the GPE dispatcher. 115 the GPE dispatcher.
129 This facility can be u 116 This facility can be used to prevent such uncontrolled
130 GPE floodings. 117 GPE floodings.
131 Format: <byte> or <bit !! 118 Format: <byte>
132 119
133 acpi_no_auto_serialize [HW,ACPI] 120 acpi_no_auto_serialize [HW,ACPI]
134 Disable auto-serializa 121 Disable auto-serialization of AML methods
135 AML control methods th 122 AML control methods that contain the opcodes to create
136 named objects will be 123 named objects will be marked as "Serialized" by the
137 auto-serialization fea 124 auto-serialization feature.
138 This feature is enable 125 This feature is enabled by default.
139 This option allows to 126 This option allows to turn off the feature.
140 127
141 acpi_no_memhotplug [ACPI] Disable memo 128 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
142 kernels. 129 kernels.
143 130
144 acpi_no_static_ssdt [HW,ACPI,EARLY !! 131 acpi_no_static_ssdt [HW,ACPI]
145 Disable installation o 132 Disable installation of static SSDTs at early boot time
146 By default, SSDTs cont 133 By default, SSDTs contained in the RSDT/XSDT will be
147 installed automaticall 134 installed automatically and they will appear under
148 /sys/firmware/acpi/tab 135 /sys/firmware/acpi/tables.
149 This option turns off 136 This option turns off this feature.
150 Note that specifying t 137 Note that specifying this option does not affect
151 dynamic table installa 138 dynamic table installation which will install SSDT
152 tables to /sys/firmwar 139 tables to /sys/firmware/acpi/tables/dynamic.
153 140
154 acpi_no_watchdog [HW,ACPI,WDT] 141 acpi_no_watchdog [HW,ACPI,WDT]
155 Ignore the ACPI-based 142 Ignore the ACPI-based watchdog interface (WDAT) and let
156 a native driver contro 143 a native driver control the watchdog device instead.
157 144
158 acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] !! 145 acpi_rsdp= [ACPI,EFI,KEXEC]
159 Pass the RSDP address 146 Pass the RSDP address to the kernel, mostly used
160 on machines running EF 147 on machines running EFI runtime service to boot the
161 second kernel for kdum 148 second kernel for kdump.
162 149
163 acpi_os_name= [HW,ACPI] Tell ACPI BI 150 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
164 Format: To spoof as Wi 151 Format: To spoof as Windows 98: ="Microsoft Windows"
165 152
166 acpi_rev_override [ACPI] Override the 153 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167 of 2 which is mandated 154 of 2 which is mandated by ACPI 6) as the supported ACPI
168 specification revision 155 specification revision (when using this switch, it may
169 be necessary to carry 156 be necessary to carry out a cold reboot _twice_ in a
170 row to make it take ef 157 row to make it take effect on the platform firmware).
171 158
172 acpi_osi= [HW,ACPI] Modify list 159 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" 160 acpi_osi="string1" # add string1
174 acpi_osi="!string2" 161 acpi_osi="!string2" # remove string2
175 acpi_osi=!* 162 acpi_osi=!* # remove all strings
176 acpi_osi=! 163 acpi_osi=! # disable all built-in OS vendor
177 164 strings
178 acpi_osi=!! 165 acpi_osi=!! # enable all built-in OS vendor
179 166 strings
180 acpi_osi= 167 acpi_osi= # disable all strings
181 168
182 'acpi_osi=!' can be us 169 'acpi_osi=!' can be used in combination with single or
183 multiple 'acpi_osi="st 170 multiple 'acpi_osi="string1"' to support specific OS
184 vendor string(s). Not 171 vendor string(s). Note that such command can only
185 affect the default sta 172 affect the default state of the OS vendor strings, thus
186 it cannot affect the d 173 it cannot affect the default state of the feature group
187 strings and the curren 174 strings and the current state of the OS vendor strings,
188 specifying it multiple 175 specifying it multiple times through kernel command line
189 is meaningless. This 176 is meaningless. This command is useful when one do not
190 care about the state o 177 care about the state of the feature group strings which
191 should be controlled b 178 should be controlled by the OSPM.
192 Examples: 179 Examples:
193 1. 'acpi_osi=! acpi_ 180 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194 to 'acpi_osi="Win 181 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 can make '_OSI("W 182 can make '_OSI("Windows 2000")' TRUE.
196 183
197 'acpi_osi=' cannot be 184 'acpi_osi=' cannot be used in combination with other
198 'acpi_osi=' command li 185 'acpi_osi=' command lines, the _OSI method will not
199 exist in the ACPI name 186 exist in the ACPI namespace. NOTE that such command can
200 only affect the _OSI s 187 only affect the _OSI support state, thus specifying it
201 multiple times through 188 multiple times through kernel command line is also
202 meaningless. 189 meaningless.
203 Examples: 190 Examples:
204 1. 'acpi_osi=' can m 191 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205 FALSE. 192 FALSE.
206 193
207 'acpi_osi=!*' can be u 194 'acpi_osi=!*' can be used in combination with single or
208 multiple 'acpi_osi="st 195 multiple 'acpi_osi="string1"' to support specific
209 string(s). Note that 196 string(s). Note that such command can affect the
210 current state of both 197 current state of both the OS vendor strings and the
211 feature group strings, 198 feature group strings, thus specifying it multiple times
212 through kernel command 199 through kernel command line is meaningful. But it may
213 still not able to affe 200 still not able to affect the final state of a string if
214 there are quirks relat 201 there are quirks related to this string. This command
215 is useful when one wan 202 is useful when one want to control the state of the
216 feature group strings 203 feature group strings to debug BIOS issues related to
217 the OSPM features. 204 the OSPM features.
218 Examples: 205 Examples:
219 1. 'acpi_osi="Module 206 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220 '_OSI("Module Dev 207 '_OSI("Module Device")' FALSE.
221 2. 'acpi_osi=!* acpi 208 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222 '_OSI("Module Dev 209 '_OSI("Module Device")' TRUE.
223 3. 'acpi_osi=! acpi_ 210 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224 equivalent to 211 equivalent to
225 'acpi_osi=!* acpi 212 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226 and 213 and
227 'acpi_osi=!* acpi 214 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228 they all will mak 215 they all will make '_OSI("Windows 2000")' TRUE.
229 216
230 acpi_pm_good [X86] 217 acpi_pm_good [X86]
231 Override the pmtimer b 218 Override the pmtimer bug detection: force the kernel
232 to assume that this ma 219 to assume that this machine's pmtimer latches its value
233 and always returns goo 220 and always returns good values.
234 221
235 acpi_sci= [HW,ACPI,EARLY] ACPI S !! 222 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge 223 Format: { level | edge | high | low }
237 224
238 acpi_skip_timer_override [HW,ACPI,EARL !! 225 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore I 226 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIO 227 For broken nForce2 BIOS resulting in XT-PIC timer.
241 228
242 acpi_sleep= [HW,ACPI] Sleep option 229 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_ !! 230 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 s4_nohwsig, !! 231 old_ordering, nonvs, sci_force_enable, nobl }
245 sci_force_en <<
246 See Documentation/powe 232 See Documentation/power/video.rst for information on
247 s3_bios and s3_mode. 233 s3_bios and s3_mode.
248 s3_beep is for debuggi 234 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel' 235 as soon as the kernel's real-mode entry point is called.
250 s4_hwsig causes the ke <<
251 signature during resum <<
252 refuse to resume if it <<
253 the ACPI specification <<
254 Windows does not do th <<
255 on docking. So the def <<
256 and simply warn when t <<
257 s4_hwsig option is ena <<
258 s4_nohwsig prevents AC 236 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a !! 237 used during resume from hibernation.
260 old_ordering causes th 238 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 239 control method, with respect to putting devices into
262 low power states, to b 240 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 241 of _PTS is used by default).
264 nonvs prevents the ker 242 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 243 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 244 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 245 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 246 but some broken systems don't work without it).
269 nobl causes the intern 247 nobl causes the internal blacklist of systems known to
270 behave incorrectly in 248 behave incorrectly in some ways with respect to system
271 suspend and resume to 249 suspend and resume to be ignored (use wisely).
272 250
273 acpi_use_timer_override [HW,ACPI,EARLY !! 251 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 252 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 253 that require a timer override, but don't have HPET
276 254
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 255 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 256 kernel's map of available physical RAM.
279 257
280 agp= [AGP] 258 agp= [AGP]
281 { off | try_unsupporte 259 { off | try_unsupported }
282 off: disable AGP suppo 260 off: disable AGP support
283 try_unsupported: try t 261 try_unsupported: try to drive unsupported chipsets
284 (may crash com 262 (may crash computer or cause data corruption)
285 263
286 ALSA [HW,ALSA] 264 ALSA [HW,ALSA]
287 See Documentation/soun 265 See Documentation/sound/alsa-configuration.rst
288 266
289 alignment= [KNL,ARM] 267 alignment= [KNL,ARM]
290 Allow the default user 268 Allow the default userspace alignment fault handler
291 behaviour to be specif 269 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 270 bit 1 enables fixups, and bit 2 sends a segfault.
293 271
294 align_va_addr= [X86-64] 272 align_va_addr= [X86-64]
295 Align virtual addresse 273 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 274 allocating a VMA at process creation time. This option
297 gives you up to 3% per 275 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 276 machines (where it is enabled by default) for a
299 CPU-intensive style be 277 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 278 a microbenchmark depending on workload and compiler.
301 279
302 32: only for 32-bit pr 280 32: only for 32-bit processes
303 64: only for 64-bit pr 281 64: only for 64-bit processes
304 on: enable for both 32 282 on: enable for both 32- and 64-bit processes
305 off: disable for both 283 off: disable for both 32- and 64-bit processes
306 284
307 alloc_snapshot [FTRACE] 285 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 286 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 287 main buffer is allocated. This is handy if debugging
310 and you need to use tr 288 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 289 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 290 to be done where GFP_KERNEL allocations are allowed.
313 291
314 allow_mismatched_32bit_el0 [ARM64,EARL <<
315 Allow execve() of 32-b <<
316 PER_LINUX32 personalit <<
317 subset of the CPUs sup <<
318 parameter is present, <<
319 EL0 is indicated by /s <<
320 and hot-unplug operati <<
321 <<
322 See Documentation/arch <<
323 information. <<
324 <<
325 amd_iommu= [HW,X86-64] 292 amd_iommu= [HW,X86-64]
326 Pass parameters to the 293 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 294 Possible values are:
328 fullflush - Deprecated !! 295 fullflush - enable flushing of IO/TLB entries when
>> 296 they are unmapped. Otherwise they are
>> 297 flushed before they will be reused, which
>> 298 is a lot of faster
329 off - do not ini 299 off - do not initialize any AMD IOMMU found in
330 the system 300 the system
331 force_isolation - Forc 301 force_isolation - Force device isolation for all
332 devi 302 devices. The IOMMU driver is not
333 allo 303 allowed anymore to lift isolation
334 requ 304 requirements as needed. This option
335 does 305 does not override iommu=pt
336 force_enable - Force e <<
337 to be b <<
338 option <<
339 pgtbl_v1 - Use v1 <<
340 pgtbl_v2 - Use v2 <<
341 irtcachedis - Disable <<
342 306
343 amd_iommu_dump= [HW,X86-64] 307 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 308 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 309 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 310 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 311 IOMMU initialization.
348 312
349 amd_iommu_intr= [HW,X86-64] 313 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 314 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 315 remapping modes:
352 legacy - Use legac 316 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 317 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 318 to inject interrupts directly into guest.
355 This mode 319 This mode requires kvm-amd.avic=1.
356 (Default 320 (Default when IOMMU HW support is present.)
357 321
358 amd_pstate= [X86,EARLY] <<
359 disable <<
360 Do not enable amd_ps <<
361 scaling driver for t <<
362 passive <<
363 Use amd_pstate with <<
364 In this mode autonom <<
365 Driver requests a de <<
366 tries to match the s <<
367 satisfied by guarant <<
368 active <<
369 Use amd_pstate_epp d <<
370 driver provides a hi <<
371 to bias toward perfo <<
372 to the CPPC firmware <<
373 calculate the runtim <<
374 frequency. <<
375 guided <<
376 Activate guided auto <<
377 maximum performance <<
378 selects a performanc <<
379 to the current workl <<
380 <<
381 amd_prefcore= <<
382 [X86] <<
383 disable <<
384 Disable amd-pstate p <<
385 <<
386 amijoy.map= [HW,JOY] Amiga joystic 322 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 323 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 324 Format: <a>,<b>
389 See also Documentation 325 See also Documentation/input/joydev/joystick.rst
390 326
391 analog.map= [HW,JOY] Analog joysti 327 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 328 Specifies type or capabilities of an analog joystick
393 connected to one of 16 329 connected to one of 16 gameports
394 Format: <type1>,<type2 330 Format: <type1>,<type2>,..<type16>
395 331
396 apc= [HW,SPARC] 332 apc= [HW,SPARC]
397 Power management funct 333 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 334 Format: noidle
399 Disable APC CPU standb 335 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 336 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 337 APC and your system crashes randomly.
402 338
403 apic= [APIC,X86,EARLY] Advan !! 339 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 340 Change the output verbosity while booting
405 Format: { quiet (defau 341 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 342 Change the amount of debugging information output
407 when initialising the 343 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 344 For X86-32, this can also be used to specify an APIC
409 driver name. 345 driver name.
410 Format: apic=driver_na 346 Format: apic=driver_name
411 Examples: apic=bigsmp 347 Examples: apic=bigsmp
412 348
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 349 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 350 Format: { bsp (default) | all | none }
415 bsp: External NMI is 351 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 352 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 353 backup of CPU 0
418 none: External NMI is 354 none: External NMI is masked for all CPUs. This is
419 useful so that a 355 useful so that a dump capture kernel won't be
420 shot down by NMI 356 shot down by NMI
421 357
422 autoconf= [IPV6] 358 autoconf= [IPV6]
423 See Documentation/netw 359 See Documentation/networking/ipv6.rst.
424 360
>> 361 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 362 Limit apic dumping. The parameter defines the maximal
>> 363 number of local apics being dumped. Also it is possible
>> 364 to set it to "all" by meaning -- no limit here.
>> 365 Format: { 1 (default) | 2 | ... | all }.
>> 366 The parameter valid if only apic=debug or
>> 367 apic=verbose is specified.
>> 368 Example: apic=debug show_lapic=all
>> 369
425 apm= [APM] Advanced Power M 370 apm= [APM] Advanced Power Management
426 See header of arch/x86 371 See header of arch/x86/kernel/apm_32.c.
427 372
428 apparmor= [APPARMOR] Disable or <<
429 Format: { "0" | "1" } <<
430 See security/apparmor/ <<
431 0 -- disable. <<
432 1 -- enable. <<
433 Default value is set v <<
434 <<
435 arcrimi= [HW,NET] ARCnet - "RIM 373 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 374 Format: <io>,<irq>,<nodeID>
437 375
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall <<
442 Identification support <<
443 <<
444 arm64.nomops [ARM64] Unconditionall <<
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support <<
449 <<
450 arm64.nopauth [ARM64] Unconditionall <<
451 support <<
452 <<
453 arm64.nosme [ARM64] Unconditionall <<
454 Extension support <<
455 <<
456 arm64.nosve [ARM64] Unconditionall <<
457 Extension support <<
458 <<
459 ataflop= [HW,M68k] 376 ataflop= [HW,M68k]
460 377
461 atarimouse= [HW,MOUSE] Atari Mouse 378 atarimouse= [HW,MOUSE] Atari Mouse
462 379
463 atkbd.extra= [HW] Enable extra LEDs 380 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 381 EzKey and similar keyboards
465 382
466 atkbd.reset= [HW] Reset keyboard du 383 atkbd.reset= [HW] Reset keyboard during initialization
467 384
468 atkbd.set= [HW] Select keyboard c 385 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 386 Format: <int> (2 = AT (default), 3 = PS/2)
470 387
471 atkbd.scroll= [HW] Enable scroll whe 388 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 389 keyboards
473 390
474 atkbd.softraw= [HW] Choose between sy 391 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 392 Format: <bool> (0 = real, 1 = synthetic (default))
476 393
477 atkbd.softrepeat= [HW] 394 atkbd.softrepeat= [HW]
478 Use software keyboard 395 Use software keyboard repeat
479 396
480 audit= [KNL] Enable the audit 397 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 398 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 399 0 | off - kernel audit is disabled and can not be
483 enabled until the 400 enabled until the next reboot
484 unset - kernel audit i 401 unset - kernel audit is initialized but disabled and
485 will be fully enab 402 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 403 1 | on - kernel audit is initialized and partially
487 enabled, storing a 404 enabled, storing at most audit_backlog_limit
488 messages in RAM un 405 messages in RAM until it is fully enabled by the
489 userspace auditd. 406 userspace auditd.
490 Default: unset 407 Default: unset
491 408
492 audit_backlog_limit= [KNL] Set the aud 409 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 410 Format: <int> (must be >=0)
494 Default: 64 411 Default: 64
495 412
496 bau= [X86_UV] Enable the BA 413 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 414 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 415 Format: { "0" | "1" }
499 0 - Disable the BAU. 416 0 - Disable the BAU.
500 1 - Enable the BAU. 417 1 - Enable the BAU.
501 unset - Disable the BA 418 unset - Disable the BAU.
502 419
503 baycom_epp= [HW,AX25] 420 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 421 Format: <io>,<mode>
505 422
506 baycom_par= [HW,AX25] BayCom Paral 423 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 424 Format: <io>,<mode>
508 See header of drivers/ 425 See header of drivers/net/hamradio/baycom_par.c.
509 426
510 baycom_ser_fdx= [HW,AX25] 427 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 428 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 429 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 430 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 431
515 baycom_ser_hdx= [HW,AX25] 432 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 433 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 434 Format: <io>,<irq>,<mode>
518 See header of drivers/ 435 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 436
520 bert_disable [ACPI] <<
521 Disable BERT OS suppor <<
522 <<
523 bgrt_disable [ACPI,X86,EARLY] <<
524 Disable BGRT to avoid <<
525 <<
526 blkdevparts= Manual partition parsi 437 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 438 embedded devices based on command line input.
528 See Documentation/bloc 439 See Documentation/block/cmdline-partition.rst
529 440
530 boot_delay= [KNL,EARLY] !! 441 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 442 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 443 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 444 Format: integer
537 445
538 bootconfig [KNL,EARLY] !! 446 bootconfig [KNL]
539 Extended command line 447 Extended command line options can be added to an initrd
540 and this will cause th 448 and this will cause the kernel to look for it.
541 449
542 See Documentation/admi 450 See Documentation/admin-guide/bootconfig.rst
543 451
>> 452 bert_disable [ACPI]
>> 453 Disable BERT OS support on buggy BIOSes.
>> 454
>> 455 bgrt_disable [ACPI][X86]
>> 456 Disable BGRT to avoid flickering OEM logo.
>> 457
544 bttv.card= [HW,V4L] bttv (bt848 + 458 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 459 bttv.radio= Most important insmod options are available as
546 kernel args too. 460 kernel args too.
547 bttv.pll= See Documentation/admi 461 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 462 bttv.tuner=
549 463
550 bulk_remove=off [PPC] This parameter 464 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 465 firmware feature for flushing multiple hpte entries
552 at a time. 466 at a time.
553 467
554 c101= [NET] Moxa C101 synchr 468 c101= [NET] Moxa C101 synchronous serial card
555 469
556 cachesize= [BUGS=X86-32] Override 470 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 471 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 472 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 473 to fix known problems, but for some CPUs it is not
560 possible to determine 474 possible to determine what the correct size should be.
561 This option provides a 475 This option provides an override for these situations.
562 476
563 carrier_timeout= 477 carrier_timeout=
564 [NET] Specifies amount 478 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 479 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 480 it waits 120 seconds.
567 481
568 ca_keys= [KEYS] This parameter 482 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 483 the system trusted keyring to be used for certificate
570 trust validation. 484 trust validation.
571 format: { id:<keyid> | 485 format: { id:<keyid> | builtin }
572 486
573 cca= [MIPS,EARLY] Override !! 487 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 488 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 489 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 490 for platform specific values (SB1, Loongson3 and
577 others). 491 others).
578 492
579 ccw_timeout_log [S390] 493 ccw_timeout_log [S390]
580 See Documentation/arch !! 494 See Documentation/s390/common_io.rst for details.
581 495
582 cgroup_disable= [KNL] Disable a partic !! 496 cgroup_disable= [KNL] Disable a particular controller
583 Format: {name of the c !! 497 Format: {name of the controller(s) to disable}
584 The effects of cgroup_ 498 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 499 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 500 a single hierarchy
587 - foo isn't visible as 501 - foo isn't visible as an individually mountable
588 subsystem 502 subsystem
589 - if foo is an optiona <<
590 disabled and corresp <<
591 created <<
592 {Currently only "memor 503 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 504 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 505 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" <<
596 stall information acco <<
597 506
598 cgroup_no_v1= [KNL] Disable cgroup c 507 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 508 Format: { { controller | "all" | "named" }
600 [,{ controll 509 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 510 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 511 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 512 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 513 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 514 all v1 hierarchies.
606 515
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 516 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 517 Format: <string>
613 nosocket -- Disable so 518 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 519 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 520
617 checkreqprot= [SELINUX] Set initial !! 521 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 522 Format: { "0" | "1" }
619 See security/selinux/K 523 See security/selinux/Kconfig help text.
620 0 -- check protection 524 0 -- check protection applied by kernel (includes
621 any implied ex 525 any implied execute protection).
622 1 -- check protection 526 1 -- check protection requested by application.
623 Default value is set v 527 Default value is set via a kernel config option.
624 Value can be changed a 528 Value can be changed at runtime via
625 /sys/fs/selinu 529 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 530 Setting checkreqprot to 1 is deprecated.
627 531
628 cio_ignore= [S390] 532 cio_ignore= [S390]
629 See Documentation/arch !! 533 See Documentation/s390/common_io.rst for details.
630 <<
631 clearcpuid=X[,X...] [X86] <<
632 Disable CPUID feature <<
633 arch/x86/include/asm/c <<
634 numbers X. Note the Li <<
635 stable over kernel opt <<
636 ones should be. <<
637 X can also be a string <<
638 in /proc/cpuinfo which <<
639 instability issue. How <<
640 in /proc/cpuinfo. <<
641 Note that using this o <<
642 Also note that user pr <<
643 or using the feature w <<
644 will still see it. Thi <<
645 being used by the kern <<
646 Also note the kernel m <<
647 some critical bits. <<
648 <<
649 clk_ignore_unused 534 clk_ignore_unused
650 [CLK] 535 [CLK]
651 Prevents the clock fra 536 Prevents the clock framework from automatically gating
652 clocks that have not b 537 clocks that have not been explicitly enabled by a Linux
653 device driver but are 538 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 539 by the bootloader/firmware. Note that this does not
655 force such clocks to b 540 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 541 those clocks in any way. This parameter is useful for
657 debug and development, 542 debug and development, but should not be needed on a
658 platform with proper d 543 platform with proper driver support. For more
659 information, see Docum 544 information, see Documentation/driver-api/clk.rst.
660 545
661 clock= [BUGS=X86-32, HW] gett 546 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 547 [Deprecated]
663 Forces specified clock 548 Forces specified clocksource (if available) to be used
664 when calculating getti 549 when calculating gettimeofday(). If specified
665 clocksource is not ava 550 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 551 Format: { pit | tsc | cyclone | pmtmr }
667 552
668 clocksource= Override the default c 553 clocksource= Override the default clocksource
669 Format: <string> 554 Format: <string>
670 Override the default c 555 Override the default clocksource and use the clocksource
671 with the name specifie 556 with the name specified.
672 Some clocksource names 557 Some clocksource names to choose from, depending on
673 the platform: 558 the platform:
674 [all] jiffies (this is 559 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 560 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 561 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 562 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 563 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 564 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 565 [MIPS] MIPS
681 [PARISC] cr16 566 [PARISC] cr16
682 [S390] tod 567 [S390] tod
683 [SH] SuperH 568 [SH] SuperH
684 [SPARC64] tick 569 [SPARC64] tick
685 [X86-64] hpet,tsc 570 [X86-64] hpet,tsc
686 571
687 clocksource.arm_arch_timer.evtstrm= 572 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 573 [ARM,ARM64]
689 Format: <bool> 574 Format: <bool>
690 Enable/disable the eve 575 Enable/disable the eventstream feature of the ARM
691 architected timer so t 576 architected timer so that code using WFE-based polling
692 loops can be debugged 577 loops can be debugged more effectively on production
693 systems. 578 systems.
694 579
695 clocksource.verify_n_cpus= [KNL] !! 580 clocksource.max_cswd_read_retries= [KNL]
696 Limit the number of CP !! 581 Number of clocksource_watchdog() retries due to
697 marked with CLOCK_SOUR !! 582 external delays before the clock will be marked
698 are marked unstable du !! 583 unstable. Defaults to three retries, that is,
699 A negative value says !! 584 four attempts to read the clock under test.
700 zero says not to check !! 585
701 nr_cpu_ids are silentl !! 586 clearcpuid=BITNUM[,BITNUM...] [X86]
702 The actual CPUs are ch !! 587 Disable CPUID feature X for the kernel. See
703 no replacement if the !! 588 arch/x86/include/asm/cpufeatures.h for the valid bit
704 !! 589 numbers. Note the Linux specific bits are not necessarily
705 clocksource-wdtest.holdoff= [KNL] !! 590 stable over kernel options, but the vendor specific
706 Set the time in second !! 591 ones should be.
707 watchdog test waits be !! 592 Also note that user programs calling CPUID directly
708 Defaults to zero when !! 593 or using the feature without checking anything
709 10 seconds when built !! 594 will still see it. This just prevents it from
>> 595 being used by the kernel or shown in /proc/cpuinfo.
>> 596 Also note the kernel might malfunction if you disable
>> 597 some critical bits.
710 598
711 cma=nn[MG]@[start[MG][-end[MG]]] 599 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 600 [KNL,CMA]
713 Sets the size of kerne 601 Sets the size of kernel global memory area for
714 contiguous memory allo 602 contiguous memory allocations and optionally the
715 placement constraint b 603 placement constraint by the physical address range of
716 memory allocations. A 604 memory allocations. A value of 0 disables CMA
717 altogether. For more i 605 altogether. For more information, see
718 kernel/dma/contiguous. 606 kernel/dma/contiguous.c
719 607
720 cma_pernuma=nn[MG] 608 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 609 [ARM64,KNL]
722 Sets the size of kerne 610 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 611 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 612 per-numa CMA altogether. And If this option is not
725 specified, the default !! 613 specificed, the default value is 0.
726 With per-numa CMA enab 614 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 615 first try to allocate buffer from the pernuma area
728 which is located in no 616 which is located in node nid, if the allocation fails,
729 they will fallback to 617 they will fallback to the global default memory area.
730 618
731 numa_cma=<node>:nn[MG][,<node>:nn[MG]] <<
732 [KNL,CMA,EARLY] <<
733 Sets the size of kerne <<
734 contiguous memory allo <<
735 area for the specified <<
736 <<
737 With numa CMA enabled, <<
738 first try to allocate <<
739 which is located in no <<
740 they will fallback to <<
741 <<
742 cmo_free_hint= [PPC] Format: { yes | 619 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 620 Specify whether pages are marked as being inactive
744 when they are freed. 621 when they are freed. This is used in CMO environments
745 to determine OS memory 622 to determine OS memory pressure for page stealing by
746 a hypervisor. 623 a hypervisor.
747 Default: yes 624 Default: yes
748 625
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 626 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 627 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 628 allocations, by default set to 256K.
752 629
753 com20020= [HW,NET] ARCnet - COM2 630 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 631 Format:
755 <io>[,<irq>[,<nodeID>[ 632 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 633
757 com90io= [HW,NET] ARCnet - COM9 634 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 635 Format: <io>[,<irq>]
759 636
760 com90xx= [HW,NET] 637 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 638 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 639 Format: <io>[,<irq>[,<memstart>]]
763 640
764 condev= [HW,S390] console devi 641 condev= [HW,S390] console device
765 conmode= 642 conmode=
766 643
767 con3215_drop= [S390,EARLY] 3215 cons <<
768 Format: y|n|Y|N|1|0 <<
769 When set to true, drop <<
770 the console buffer is <<
771 operator using a 3270 <<
772 x3270) does not have t <<
773 console output to adva <<
774 This leads to a much f <<
775 terminal emulator is a <<
776 emulator is used, this <<
777 <<
778 console= [KNL] Output console d 644 console= [KNL] Output console device and options.
779 645
780 tty<n> Use the virtual consol 646 tty<n> Use the virtual console device <n>.
781 647
782 ttyS<n>[,options] 648 ttyS<n>[,options]
783 ttyUSB0[,options] 649 ttyUSB0[,options]
784 Use the specified seri 650 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 651 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 652 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 653 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 654 omit it). Default is "9600n8".
789 655
790 See Documentation/admi 656 See Documentation/admin-guide/serial-console.rst for more
791 information. See 657 information. See
792 Documentation/networki 658 Documentation/networking/netconsole.rst for an
793 alternative. 659 alternative.
794 660
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] 661 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 662 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 663 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 664 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 665 uart[8250],0x<addr>[,options]
819 Start an early, polled 666 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 667 UART at the specified I/O port or MMIO address,
821 switching to the match 668 switching to the matching ttyS device later.
822 MMIO inter-register ad 669 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 670 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 671 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 672 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 673 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 674 the h/w is not re-initialized.
828 675
829 hvc<n> Use the hypervisor con 676 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 677 both Xen and PowerPC hypervisors.
831 678
832 { null | "" } <<
833 Use to disable console <<
834 console messages disca <<
835 This must be the only <<
836 kernel command line. <<
837 <<
838 If the device connected to the 679 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 680 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 681 console=brl,ttyS0
841 For now, only VisioBraille is 682 For now, only VisioBraille is supported.
842 683
843 console_msg_format= 684 console_msg_format=
844 [KNL] Change console m 685 [KNL] Change console messages format
845 default 686 default
846 By default we print me 687 By default we print messages on consoles in
847 "[time stamp] text\n" 688 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 689 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 690 `printk_time' param).
850 syslog 691 syslog
851 Switch to syslog forma 692 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 693 IOW, each message will have a facility and loglevel
853 prefix. The format is 694 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 695 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 696 from /proc/kmsg.
856 697
857 consoleblank= [KNL] The console blan 698 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 699 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 700 Defaults to 0.
860 701
861 coredump_filter= 702 coredump_filter=
862 [KNL] Change the defau 703 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 704 /proc/<pid>/coredump_filter.
864 See also Documentation 705 See also Documentation/filesystems/proc.rst.
865 706
866 coresight_cpu_debug.enable 707 coresight_cpu_debug.enable
867 [ARM,ARM64] 708 [ARM,ARM64]
868 Format: <bool> 709 Format: <bool>
869 Enable/disable the CPU 710 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 711 0: default value, disable debugging
871 1: enable debugging at 712 1: enable debugging at boot time
872 713
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 714 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 715 disable the cpuidle sub-system
879 716
880 cpuidle.governor= 717 cpuidle.governor=
881 [CPU_IDLE] Name of the 718 [CPU_IDLE] Name of the cpuidle governor to use.
882 719
883 cpufreq.off=1 [CPU_FREQ] 720 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 721 disable the cpufreq sub-system
885 722
886 cpufreq.default_governor= 723 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 724 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 725 policy to use. This governor must be registered in the
889 kernel before the cpuf 726 kernel before the cpufreq driver probes.
890 727
891 cpu_init_udelay=N 728 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 729 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 730 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 731 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 732 Default: 10000
896 733
897 cpuhp.parallel= !! 734 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 735 Format:
899 Format: <bool> !! 736 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
900 Default is enabled if <<
901 the parameter has no e <<
902 <<
903 crash_kexec_post_notifiers <<
904 Run kdump after runnin <<
905 kmsg. This only for th <<
906 succeeds in any situat <<
907 Note that this also in <<
908 because some panic not <<
909 kernel more unstable. <<
910 737
911 crashkernel=size[KMG][@offset[KMG]] 738 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 739 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 740 upon panic. This parameter reserves the physical
914 memory region [offset, 741 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 742 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 743 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 744 [KNL, X86-64] Select a region under 4G first, and
918 under 4G first, and fa !! 745 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 746 hasn't been specified.
920 See Documentation/admi 747 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 748
922 crashkernel=range1:size1[,range2:size2 749 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 750 [KNL] Same as above, but depends on the memory
924 in the running system. 751 in the running system. The syntax of range is
925 start-[end] where star 752 start-[end] where start and end are both
926 a memory unit (amount[ 753 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 754 Documentation/admin-guide/kdump/kdump.rst for an example.
928 755
929 crashkernel=size[KMG],high 756 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 757 [KNL, X86-64] range could be above 4G. Allow kernel
931 above 4G. !! 758 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 759 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 760 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 761 available.
935 below 4G, if available <<
936 It will be ignored if 762 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 763 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 764 [KNL, X86-64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 765 is passed, kernel could allocate physical memory region
940 physical memory region !! 766 above 4G, that cause second kernel crash on system
941 crash on system that r !! 767 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 768 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 769 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 770 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 771 at least 256M below 4G automatically.
946 size is platform depen !! 772 This one let user to specify own low range under 4G
947 --> x86: max(swiotlb <<
948 --> arm64: 128MiB <<
949 --> riscv: 128MiB <<
950 --> loongarch: 128Mi <<
951 This one lets the user <<
952 for second kernel inst 773 for second kernel instead.
953 0: to disable low allo 774 0: to disable low allocation.
954 It will be ignored whe 775 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 776 or memory reserved is below 4G.
956 777
957 cryptomgr.notests 778 cryptomgr.notests
958 [KNL] Disable crypto s 779 [KNL] Disable crypto self-tests
959 780
960 cs89x0_dma= [HW,NET] 781 cs89x0_dma= [HW,NET]
961 Format: <dma> 782 Format: <dma>
962 783
963 cs89x0_media= [HW,NET] 784 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 785 Format: { rj45 | aui | bnc }
965 786
966 csdlock_debug= [KNL] Enable or disabl <<
967 function call handling <<
968 additional debug data <<
969 in case a hanging CPU <<
970 CPU is pinged again in <<
971 the hang situation. T <<
972 option depends on the <<
973 Kconfig option. <<
974 <<
975 dasd= [HW,NET] 787 dasd= [HW,NET]
976 See header of drivers/ 788 See header of drivers/s390/block/dasd_devmap.c.
977 789
978 db9.dev[2|3]= [HW,JOY] Multisystem j 790 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 791 (one device per port)
980 Format: <port#>,<type> 792 Format: <port#>,<type>
981 See also Documentation 793 See also Documentation/input/devices/joystick-parport.rst
982 794
983 debug [KNL,EARLY] Enable ker !! 795 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 796 time. See
>> 797 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 798 details. Deprecated, see dyndbg.
>> 799
>> 800 debug [KNL] Enable kernel debugging (events log level).
984 801
985 debug_boot_weak_hash 802 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 803 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 804 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 805 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 806 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 807 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 808 insecure, please do not use on production kernels.
992 809
993 debug_locks_verbose= 810 debug_locks_verbose=
994 [KNL] verbose locking !! 811 [KNL] verbose self-tests
995 Format: <int> !! 812 Format=<0|1>
996 Print debugging info w 813 Print debugging info while doing the locking API
997 self-tests. 814 self-tests.
998 Bitmask for the variou !! 815 We default to 0 (no extra messages), setting it to
999 (no extra messages), s !! 816 1 will print _a lot_ more information - normally
1000 will print _a_lot_ mo !! 817 only useful to kernel developers.
1001 useful to lockdep dev <<
1002 818
1003 debug_objects [KNL,EARLY] Enable ob !! 819 debug_objects [KNL] Enable object debugging
>> 820
>> 821 no_debug_objects
>> 822 [KNL] Disable object debugging
1004 823
1005 debug_guardpage_minorder= 824 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 825 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 826 parameter allows control of the order of pages that will
1008 be intentionally kept 827 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 828 buddy allocator. Bigger value increase the probability
1010 of catching random me 829 of catching random memory corruption, but reduce the
1011 amount of memory for 830 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 831 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 832 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 833 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 834 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 835 random memory location. Note that there exists a class
1017 a class of memory cor !! 836 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 837 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 838 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 839 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 840 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 841 tracking down these problems.
1023 842
1024 debug_pagealloc= 843 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 844 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 845 enables the feature at boot time. By default, it is
1027 disabled and the syst 846 disabled and the system will work mostly the same as a
1028 kernel built without 847 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 848 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 849 useful to also enable the page_owner functionality.
1031 on: enable the featur 850 on: enable the feature
1032 851
1033 debugfs= [KNL,EARLY] This para !! 852 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 853 and debugfs internal clients.
1035 Format: { on, no-moun 854 Format: { on, no-mount, off }
1036 on: All functions 855 on: All functions are enabled.
1037 no-mount: 856 no-mount:
1038 Filesystem is 857 Filesystem is not registered but kernel clients can
1039 access APIs a 858 access APIs and a crashkernel can be used to read
1040 its content. 859 its content. There is nothing to mount.
1041 off: Filesystem is 860 off: Filesystem is not registered and clients
1042 get a -EPERM 861 get a -EPERM as result when trying to register files
1043 or directorie 862 or directories within debugfs.
1044 This is equiv 863 This is equivalent of the runtime functionality if
1045 debugfs was n 864 debugfs was not enabled in the kernel at all.
1046 Default value is set 865 Default value is set in build-time with a kernel configuration.
1047 866
1048 debugpat [X86] Enable PAT debu 867 debugpat [X86] Enable PAT debugging
1049 868
1050 default_hugepagesz= 869 default_hugepagesz=
1051 [HW] The size of the 870 [HW] The size of the default HugeTLB page. This is
1052 the size represented 871 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 872 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 873 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 874 filesystems. If not specified, defaults to the
1056 architecture's defaul 875 architecture's default huge page size. Huge page
1057 sizes are architectur 876 sizes are architecture dependent. See also
1058 Documentation/admin-g 877 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 878 Format: size[KMG]
1060 879
1061 deferred_probe_timeout= 880 deferred_probe_timeout=
1062 [KNL] Debugging optio 881 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 882 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 883 probe. Only specific dependencies (subsystems or
1065 drivers) that have op !! 884 drivers) that have opted in will be ignored. A timeout of 0
1066 of 0 will timeout at !! 885 will timeout at the end of initcalls. This option will also
1067 out hasn't expired, i <<
1068 successful driver reg <<
1069 dump out devices stil 886 dump out devices still on the deferred probe list after
1070 retrying. 887 retrying.
1071 888
1072 delayacct [KNL] Enable per-task <<
1073 <<
1074 dell_smm_hwmon.ignore_dmi= <<
1075 [HW] Continue probing <<
1076 indicates that the dr <<
1077 hardware. <<
1078 <<
1079 dell_smm_hwmon.force= <<
1080 [HW] Activate driver <<
1081 not match list of sup <<
1082 blacklisted features. <<
1083 <<
1084 dell_smm_hwmon.power_status= <<
1085 [HW] Report power sta <<
1086 (disabled by default) <<
1087 <<
1088 dell_smm_hwmon.restricted= <<
1089 [HW] Allow controllin <<
1090 capability is set. <<
1091 <<
1092 dell_smm_hwmon.fan_mult= <<
1093 [HW] Factor to multip <<
1094 <<
1095 dell_smm_hwmon.fan_max= <<
1096 [HW] Maximum configur <<
1097 <<
1098 dfltcc= [HW,S390] 889 dfltcc= [HW,S390]
1099 Format: { on | off | 890 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 891 on: s390 zlib hardware support for compression on
1101 level 1 and 892 level 1 and decompression (default)
1102 off: No s390 zli 893 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 894 def_only: s390 zlib hardware support for deflate
1104 only (compr 895 only (compression on level 1)
1105 inf_only: s390 zlib h 896 inf_only: s390 zlib hardware support for inflate
1106 only (decom 897 only (decompression)
1107 always: Same as 'on 898 always: Same as 'on' but ignores the selected compression
1108 level alway 899 level always using hardware support (used for debugging)
1109 900
1110 dhash_entries= [KNL] 901 dhash_entries= [KNL]
1111 Set number of hash bu 902 Set number of hash buckets for dentry cache.
1112 903
1113 disable_1tb_segments [PPC,EARLY] !! 904 disable_1tb_segments [PPC]
1114 Disables the use of 1 905 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 906 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 907 can be useful when debugging issues that require an SLB
1117 miss to occur. 908 miss to occur.
1118 909
>> 910 stress_slb [PPC]
>> 911 Limits the number of kernel SLB entries, and flushes
>> 912 them frequently to increase the rate of SLB faults
>> 913 on kernel addresses.
>> 914
1119 disable= [IPV6] 915 disable= [IPV6]
1120 See Documentation/net 916 See Documentation/networking/ipv6.rst.
1121 917
1122 disable_radix [PPC,EARLY] !! 918 hardened_usercopy=
>> 919 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
>> 920 hardening is enabled for this boot. Hardened
>> 921 usercopy checking is used to protect the kernel
>> 922 from reading or writing beyond known memory
>> 923 allocation boundaries as a proactive defense
>> 924 against bounds-checking flaws in the kernel's
>> 925 copy_to_user()/copy_from_user() interface.
>> 926 on Perform hardened usercopy checks (default).
>> 927 off Disable hardened usercopy checks.
>> 928
>> 929 disable_radix [PPC]
1123 Disable RADIX MMU mod 930 Disable RADIX MMU mode on POWER9
1124 931
>> 932 radix_hcall_invalidate=on [PPC/PSERIES]
>> 933 Disable RADIX GTSE feature and use hcall for TLB
>> 934 invalidate.
>> 935
1125 disable_tlbie [PPC] 936 disable_tlbie [PPC]
1126 Disable TLBIE instruc 937 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 938 with KVM, with HASH MMU, or with coherent accelerators.
1128 939
1129 disable_ddw [PPC/PSERIES,EARLY] !! 940 disable_cpu_apicid= [X86,APIC,SMP]
>> 941 Format: <int>
>> 942 The number of initial APIC ID for the
>> 943 corresponding CPU to be disabled at boot,
>> 944 mostly used for the kdump 2nd kernel to
>> 945 disable BSP to wake up multiple CPUs without
>> 946 causing system reset or hang due to sending
>> 947 INIT from AP to BSP.
>> 948
>> 949 perf_v4_pmi= [X86,INTEL]
>> 950 Format: <bool>
>> 951 Disable Intel PMU counter freezing feature.
>> 952 The feature only exists starting from
>> 953 Arch Perfmon v4 (Skylake and newer).
>> 954
>> 955 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 956 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 957 to workaround buggy firmware.
1132 958
1133 disable_ipv6= [IPV6] 959 disable_ipv6= [IPV6]
1134 See Documentation/net 960 See Documentation/networking/ipv6.rst.
1135 961
1136 disable_mtrr_cleanup [X86,EARLY] !! 962 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 963 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 964 to discrete, to make X server driver able to add WB
1139 entry later. This par 965 entry later. This parameter disables that.
1140 966
1141 disable_mtrr_trim [X86, Intel and AMD !! 967 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 968 By default the kernel will trim any uncacheable
1143 memory out of your av 969 memory out of your available memory pool based on
1144 MTRR settings. This 970 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 971 possibly causing your machine to run very slowly.
1146 972
1147 disable_timer_pin_1 [X86,EARLY] !! 973 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 974 Disable PIN 1 of APIC timer
1149 Can be useful to work 975 Can be useful to work around chipset bugs.
1150 976
1151 dis_ucode_ldr [X86] Disable the mic 977 dis_ucode_ldr [X86] Disable the microcode loader.
1152 978
1153 dma_debug=off If the kernel is comp 979 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 980 this option disables the debugging code at boot.
1155 981
1156 dma_debug_entries=<number> 982 dma_debug_entries=<number>
1157 This option allows to 983 This option allows to tune the number of preallocated
1158 entries for DMA-API d 984 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 985 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 986 DMA-API debugging code disables itself because the
1161 architectural default 987 architectural default is too low.
1162 988
1163 dma_debug_driver=<driver_name> 989 dma_debug_driver=<driver_name>
1164 With this option the 990 With this option the DMA-API debugging driver
1165 filter feature can be 991 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 992 pass the driver to filter for as the parameter.
1167 The filter can be dis 993 The filter can be disabled or changed to another
1168 driver later using sy 994 driver later using sysfs.
1169 995
1170 reg_file_data_sampling= 996 reg_file_data_sampling=
1171 [X86] Controls mitiga 997 [X86] Controls mitigation for Register File Data
1172 Sampling (RFDS) vulne 998 Sampling (RFDS) vulnerability. RFDS is a CPU
1173 vulnerability which m 999 vulnerability which may allow userspace to infer
1174 kernel data values pr 1000 kernel data values previously stored in floating point
1175 registers, vector reg 1001 registers, vector registers, or integer registers.
1176 RFDS only affects Int 1002 RFDS only affects Intel Atom processors.
1177 1003
1178 on: Turns ON the 1004 on: Turns ON the mitigation.
1179 off: Turns OFF the 1005 off: Turns OFF the mitigation.
1180 1006
1181 This parameter overri 1007 This parameter overrides the compile time default set
1182 by CONFIG_MITIGATION_ 1008 by CONFIG_MITIGATION_RFDS. Mitigation cannot be
1183 disabled when other V 1009 disabled when other VERW based mitigations (like MDS)
1184 are enabled. In order 1010 are enabled. In order to disable RFDS mitigation all
1185 VERW based mitigation 1011 VERW based mitigations need to be disabled.
1186 1012
1187 For details see: 1013 For details see:
1188 Documentation/admin-g 1014 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1189 1015
1190 driver_async_probe= [KNL] 1016 driver_async_probe= [KNL]
1191 List of driver names !! 1017 List of driver names to be probed asynchronously.
1192 matches with all driv <<
1193 rest of the listed dr <<
1194 match the *. <<
1195 Format: <driver_name1 1018 Format: <driver_name1>,<driver_name2>...
1196 1019
1197 drm.edid_firmware=[<connector>:]<file 1020 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1021 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1022 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1023 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1024 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1025 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1026 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1027 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1028 and no file with the same name exists. Details and
>> 1029 instructions how to build your own EDID data are
>> 1030 available in Documentation/admin-guide/edid.rst. An EDID
>> 1031 data set will only be used for a particular connector,
>> 1032 if its name and a colon are prepended to the EDID
>> 1033 name. Each connector may use a unique EDID data
>> 1034 set by separating the files with a comma. An EDID
1206 data set with no conn 1035 data set with no connector name will be used for
1207 any connectors not ex 1036 any connectors not explicitly specified.
1208 1037
1209 dscc4.setup= [NET] 1038 dscc4.setup= [NET]
1210 1039
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1040 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1041 Format: {"off" | "known"}
1213 Control how the dt_cp 1042 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1043 used for CPU feature discovery and setup (if it
1215 exists). 1044 exists).
1216 off: Do not use it, f 1045 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1046 known: Do not pass through unknown features to guests
1218 or userspace, only th 1047 or userspace, only those that the kernel is aware of.
1219 1048
1220 dump_apple_properties [X86] 1049 dump_apple_properties [X86]
1221 Dump name and content 1050 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1051 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1052 what data is available or for reverse-engineering.
1224 1053
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1054 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1055 <module>.dyndbg[="val"]
1227 Enable debug messages 1056 Enable debug messages at boot time. See
1228 Documentation/admin-g 1057 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1058 for details.
1230 1059
1231 early_ioremap_debug [KNL,EARLY] !! 1060 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1061 in some Intel CPUs.
>> 1062
>> 1063 <module>.async_probe [KNL]
>> 1064 Enable asynchronous probe on this module.
>> 1065
>> 1066 early_ioremap_debug [KNL]
1232 Enable debug messages 1067 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1068 is useful for tracking down temporary early mappings
1234 which are not unmappe 1069 which are not unmapped.
1235 1070
1236 earlycon= [KNL,EARLY] Output ea !! 1071 earlycon= [KNL] Output early console device and options.
1237 1072
1238 When used with no opt 1073 When used with no options, the early console is
1239 determined by stdout- 1074 determined by stdout-path property in device tree's
1240 chosen node or the AC 1075 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1076 the platform.
1242 1077
1243 cdns,<addr>[,options] 1078 cdns,<addr>[,options]
1244 Start an early, polle 1079 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1080 (xuartps) serial port at the specified address. Only
1246 supported option is b 1081 supported option is baud rate. If baud rate is not
1247 specified, the serial 1082 specified, the serial port must already be setup and
1248 configured. 1083 configured.
1249 1084
1250 uart[8250],io,<addr>[,options !! 1085 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1086 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1087 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1088 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1089 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1090 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1091 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1092 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1093 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1094 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1095 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1096 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1097 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1098
1266 pl011,<addr> 1099 pl011,<addr>
1267 pl011,mmio32,<addr> 1100 pl011,mmio32,<addr>
1268 Start an early, polle 1101 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1102 port at the specified address. The pl011 serial port
1270 must already be setup 1103 must already be setup and configured. Options are not
1271 yet supported. If 'm 1104 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1105 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1106 the device registers.
1274 1107
1275 liteuart,<addr> <<
1276 Start an early consol <<
1277 specified address. Th <<
1278 setup and configured. <<
1279 <<
1280 meson,<addr> 1108 meson,<addr>
1281 Start an early, polle 1109 Start an early, polled-mode console on a meson serial
1282 port at the specified 1110 port at the specified address. The serial port must
1283 already be setup and 1111 already be setup and configured. Options are not yet
1284 supported. 1112 supported.
1285 1113
1286 msm_serial,<addr> 1114 msm_serial,<addr>
1287 Start an early, polle 1115 Start an early, polled-mode console on an msm serial
1288 port at the specified 1116 port at the specified address. The serial port
1289 must already be setup 1117 must already be setup and configured. Options are not
1290 yet supported. 1118 yet supported.
1291 1119
1292 msm_serial_dm,<addr> 1120 msm_serial_dm,<addr>
1293 Start an early, polle 1121 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1122 dm port at the specified address. The serial port
1295 must already be setup 1123 must already be setup and configured. Options are not
1296 yet supported. 1124 yet supported.
1297 1125
1298 owl,<addr> 1126 owl,<addr>
1299 Start an early, polle 1127 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1128 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1129 specified address. The serial port must already be
1302 setup and configured. 1130 setup and configured. Options are not yet supported.
1303 1131
1304 rda,<addr> 1132 rda,<addr>
1305 Start an early, polle 1133 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1134 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1135 specified address. The serial port must already be
1308 setup and configured. 1136 setup and configured. Options are not yet supported.
1309 1137
1310 sbi 1138 sbi
1311 Use RISC-V SBI (Super 1139 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1140 console.
1313 1141
1314 smh Use ARM semihosting c 1142 smh Use ARM semihosting calls for early console.
1315 1143
1316 s3c2410,<addr> 1144 s3c2410,<addr>
1317 s3c2412,<addr> 1145 s3c2412,<addr>
1318 s3c2440,<addr> 1146 s3c2440,<addr>
1319 s3c6400,<addr> 1147 s3c6400,<addr>
1320 s5pv210,<addr> 1148 s5pv210,<addr>
1321 exynos4210,<addr> 1149 exynos4210,<addr>
1322 Use early console pro 1150 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1151 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1152 a correct base address of the selected UART port. The
1325 serial port must alre 1153 serial port must already be setup and configured.
1326 Options are not yet s 1154 Options are not yet supported.
1327 1155
1328 lantiq,<addr> 1156 lantiq,<addr>
1329 Start an early, polle 1157 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1158 (lqasc) port at the specified address. The serial port
1331 must already be setup 1159 must already be setup and configured. Options are not
1332 yet supported. 1160 yet supported.
1333 1161
1334 lpuart,<addr> 1162 lpuart,<addr>
1335 lpuart32,<addr> 1163 lpuart32,<addr>
1336 Use early console pro 1164 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1165 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1166 A valid base address must be provided, and the serial
1339 port must already be 1167 port must already be setup and configured.
1340 1168
1341 ec_imx21,<addr> 1169 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1170 ec_imx6q,<addr>
1343 Start an early, polle 1171 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1172 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1173 must already be setup and configured.
1346 1174
1347 ar3700_uart,<addr> 1175 ar3700_uart,<addr>
1348 Start an early, polle 1176 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1177 Armada 3700 serial port at the specified
1350 address. The serial p 1178 address. The serial port must already be setup
1351 and configured. Optio 1179 and configured. Options are not yet supported.
1352 1180
1353 qcom_geni,<addr> 1181 qcom_geni,<addr>
1354 Start an early, polle 1182 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1183 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1184 specified address. The serial port must already be
1357 setup and configured. 1185 setup and configured. Options are not yet supported.
1358 1186
1359 efifb,[options] 1187 efifb,[options]
1360 Start an early, unacc 1188 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1189 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1190 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1191 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1192 mapped with the correct attributes.
1365 1193
1366 linflex,<addr> 1194 linflex,<addr>
1367 Use early console pro 1195 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1196 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1197 address must be provided, and the serial port must
1370 already be setup and 1198 already be setup and configured.
1371 1199
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1200 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1201 earlyprintk=vga
1374 earlyprintk=sclp 1202 earlyprintk=sclp
1375 earlyprintk=xen 1203 earlyprintk=xen
1376 earlyprintk=serial[,t 1204 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1205 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1206 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1207 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1208 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1209 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1210
1384 earlyprintk is useful 1211 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1212 the normal console is initialized. It is not enabled by
1386 default because it ha 1213 default because it has some cosmetic problems.
1387 1214
1388 Append ",keep" to not 1215 Append ",keep" to not disable it when the real console
1389 takes over. 1216 takes over.
1390 1217
1391 Only one of vga, seri !! 1218 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1219 be used at a time.
1393 1220
1394 Currently only ttyS0 1221 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1222 name. Other I/O ports may be explicitly specified
1396 on some architectures 1223 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1224 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1225 earlyprintk=serial,0x1008,115200
1399 You can find the port 1226 You can find the port for a given device in
1400 /proc/tty/driver/seri 1227 /proc/tty/driver/serial:
1401 2: uart:ST166 1228 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1229
1403 Interaction with the 1230 Interaction with the standard serial driver is not
1404 very good. 1231 very good.
1405 1232
1406 The VGA output is eve !! 1233 The VGA and EFI output is eventually overwritten by
1407 the real console. 1234 the real console.
1408 1235
1409 The xen option can on !! 1236 The xen output can only be used by Xen PV guests.
1410 1237
1411 The sclp output can o 1238 The sclp output can only be used on s390.
1412 1239
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1240 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1241 PCI device even when its classcode is not of the
1417 UART class. 1242 UART class.
1418 1243
1419 edac_report= [HW,EDAC] Control how 1244 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1245 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1246 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1247 by other higher priority error reporting module.
1423 off: disable H/W even 1248 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1249 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1250 default: on.
1426 1251
>> 1252 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1253 ekgdboc=kbd
>> 1254
>> 1255 This is designed to be used in conjunction with
>> 1256 the boot argument: earlyprintk=vga
>> 1257
>> 1258 This parameter works in place of the kgdboc parameter
>> 1259 but can only be used if the backing tty is available
>> 1260 very early in the boot process. For early debugging
>> 1261 via a serial port see kgdboc_earlycon instead.
>> 1262
1427 edd= [EDD] 1263 edd= [EDD]
1428 Format: {"off" | "on" 1264 Format: {"off" | "on" | "skip[mbr]"}
1429 1265
1430 efi= [EFI,EARLY] !! 1266 efi= [EFI]
1431 Format: { "debug", "d 1267 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1268 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1269 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1270 debug: enable misc debug output.
1435 disable_early_pci_dma 1271 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1272 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1273 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1274 boot stub, as chunking can cause problems with some
1439 firmware implementati 1275 firmware implementations.
1440 noruntime : disable E 1276 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1277 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1278 attribute may cause the kernel to reserve the
1443 memory range for a me 1279 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1280 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1281 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1282 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1283 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1284 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1285 on all PCI bridges while in the EFI boot stub
1450 1286
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1287 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1288 Using this parameter you can use more than 50% of
1453 your efi variable sto 1289 your efi variable storage. Use this parameter only if
1454 you are really sure t 1290 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1291 fulfills the spec otherwise your board may brick.
1456 1292
>> 1293 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1294 Add arbitrary attribute to specific memory range by
>> 1295 updating original EFI memory map.
>> 1296 Region of memory which aa attribute is added to is
>> 1297 from ss to ss+nn.
>> 1298
>> 1299 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1300 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1301 attribute is added to range 0x100000000-0x180000000 and
>> 1302 0x10a0000000-0x1120000000.
>> 1303
>> 1304 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1305 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1306 range 0x240000000-0x43fffffff.
>> 1307
>> 1308 Using this parameter you can do debugging of EFI memmap
>> 1309 related features. For example, you can do debugging of
>> 1310 Address Range Mirroring feature even if your box
>> 1311 doesn't support it, or mark specific memory as
>> 1312 "soft reserved".
>> 1313
1457 efivar_ssdt= [EFI; X86] Name of an 1314 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1315 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1316 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1317 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1318 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1319
1463 1320
1464 eisa_irq_edge= [PARISC,HW] 1321 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1322 See header of drivers/parisc/eisa.c.
1466 1323
1467 ekgdboc= [X86,KGDB,EARLY] Allo <<
1468 Format: ekgdboc=kbd <<
1469 <<
1470 This is designed to b <<
1471 the boot argument: ea <<
1472 <<
1473 This parameter works <<
1474 but can only be used <<
1475 very early in the boo <<
1476 via a serial port see <<
1477 <<
1478 elanfreq= [X86-32] 1324 elanfreq= [X86-32]
1479 See comment before fu 1325 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1326 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1327
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1328 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1329 Specifies physical address of start of kernel core
1484 image elf header and 1330 image elf header and optionally the size. Generally
1485 kexec loader will pas 1331 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1332 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1333
1488 enable_mtrr_cleanup [X86,EARLY] !! 1334 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1335 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1336 to discrete, to make X server driver able to add WB
1491 entry later. This par 1337 entry later. This parameter enables that.
1492 1338
1493 enable_timer_pin_1 [X86] 1339 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1340 Enable PIN 1 of APIC timer
1495 Can be useful to work 1341 Can be useful to work around chipset bugs
1496 (in particular on som 1342 (in particular on some ATI chipsets).
1497 The kernel tries to s 1343 The kernel tries to set a reasonable default.
1498 1344
1499 enforcing= [SELINUX] Set initial !! 1345 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1346 Format: {"0" | "1"}
1501 See security/selinux/ 1347 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1348 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1349 1 -- enforcing (deny and log).
1504 Default value is 0. 1350 Default value is 0.
1505 Value can be changed 1351 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1352 /sys/fs/selinux/enforce.
1507 1353
1508 erst_disable [ACPI] 1354 erst_disable [ACPI]
1509 Disable Error Record 1355 Disable Error Record Serialization Table (ERST)
1510 support. 1356 support.
1511 1357
1512 ether= [HW,NET] Ethernet car 1358 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1359 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1360 has equivalent usage. See its documentation for details.
1515 1361
1516 evm= [EVM] 1362 evm= [EVM]
1517 Format: { "fix" } 1363 Format: { "fix" }
1518 Permit 'security.evm' 1364 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1365 current integrity status.
1520 1366
1521 early_page_ext [KNL,EARLY] Enforces p <<
1522 stages so cover more <<
1523 Please note that as s <<
1524 might be disabled to <<
1525 memory initialization <<
1526 might take longer, es <<
1527 memory. Available wit <<
1528 <<
1529 failslab= 1367 failslab=
1530 fail_usercopy= 1368 fail_usercopy=
1531 fail_page_alloc= 1369 fail_page_alloc=
1532 fail_make_request=[KNL] 1370 fail_make_request=[KNL]
1533 General fault injecti 1371 General fault injection mechanism.
1534 Format: <interval>,<p 1372 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1373 See also Documentation/fault-injection/.
1536 1374
1537 fb_tunnels= [NET] 1375 fb_tunnels= [NET]
1538 Format: { initns | no 1376 Format: { initns | none }
1539 See Documentation/adm 1377 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1378 fb_tunnels_only_for_init_ns
1541 1379
1542 floppy= [HW] 1380 floppy= [HW]
1543 See Documentation/adm 1381 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1382
>> 1383 force_pal_cache_flush
>> 1384 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1385 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1386 parameter will force ia64_sal_cache_flush to call
>> 1387 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1388
1545 forcepae [X86-32] 1389 forcepae [X86-32]
1546 Forcefully enable Phy 1390 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1391 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1392 functionally usable PAE implementation.
1549 Warning: use of this 1393 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1394 and may cause unknown problems.
1551 1395
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] 1396 ftrace=[tracer]
1559 [FTRACE] will set and 1397 [FTRACE] will set and start the specified tracer
1560 as early as possible 1398 as early as possible in order to facilitate early
1561 boot debugging. 1399 boot debugging.
1562 1400
1563 ftrace_boot_snapshot !! 1401 ftrace_dump_on_oops[=orig_cpu]
1564 [FTRACE] On boot up, <<
1565 ftrace ring buffer th <<
1566 /sys/kernel/tracing/s <<
1567 This is useful if you <<
1568 boot up that is likel <<
1569 start up functionalit <<
1570 <<
1571 Optionally, the snaps <<
1572 instance that was cre <<
1573 line parameter. <<
1574 <<
1575 trace_instance=foo,sc <<
1576 <<
1577 The above will cause <<
1578 a snapshot at the end <<
1579 <<
1580 ftrace_dump_on_oops[=2(orig_cpu) | =< <<
1581 ,<instance>=2(orig_ <<
1582 [FTRACE] will dump th 1402 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1403 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1404 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1405 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1406 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 1407
1603 ftrace_filter=[function-list] 1408 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1409 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu !! 1410 tracer at boot up. function-list is a comma separated
1606 list of functions. Th 1411 list of functions. This list can be changed at run
1607 time by the set_ftrac 1412 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1413 tracing directory.
1609 1414
1610 ftrace_notrace=[function-list] 1415 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1416 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1417 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1418 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1419 tracing directory.
1615 1420
1616 ftrace_graph_filter=[function-list] 1421 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1422 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1423 by the function graph tracer at boot up.
1619 function-list is a co !! 1424 function-list is a comma separated list of functions
1620 that can be changed a 1425 that can be changed at run time by the
1621 set_graph_function fi 1426 set_graph_function file in the debugfs tracing directory.
1622 1427
1623 ftrace_graph_notrace=[function-list] 1428 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1429 [FTRACE] Do not trace from the functions specified in
1625 function-list. This !! 1430 function-list. This list is a comma separated list of
1626 functions that can be 1431 functions that can be changed at run time by the
1627 set_graph_notrace fil 1432 set_graph_notrace file in the debugfs tracing directory.
1628 1433
1629 ftrace_graph_max_depth=<uint> 1434 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1435 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1436 the max depth it will trace into a function. This value
1632 can be changed at run 1437 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1438 in the tracefs tracing directory. default: 0 (no limit)
1634 1439
1635 fw_devlink= [KNL,EARLY] Create de !! 1440 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1441 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1442 consumer/supplier relationships. This feature is
1638 especially useful whe 1443 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1444 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1445 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1446 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1447 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1448 suppliers).
1644 Format: { off | permi 1449 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1450 off -- Don't create device links from firmware info.
1646 permissive -- Create 1451 permissive -- Create device links from firmware info
1647 but use it on 1452 but use it only for ordering boot state clean
1648 up (sync_stat 1453 up (sync_state() calls).
1649 on -- Create device 1454 on -- Create device links from firmware info and use it
1650 to enforce pr 1455 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1456 rpm -- Like "on", but also use to order runtime PM.
1652 1457
1653 fw_devlink.strict=<bool> <<
1654 [KNL,EARLY] Treat all <<
1655 dependencies. This on <<
1656 Format: <bool> <<
1657 <<
1658 fw_devlink.sync_state = <<
1659 [KNL,EARLY] When all <<
1660 probing, this paramet <<
1661 devices that haven't <<
1662 calls. <<
1663 Format: { strict | ti <<
1664 strict -- Default. Co <<
1665 probe success <<
1666 timeout -- Give up wa <<
1667 sync_state() <<
1668 received thei <<
1669 deferred_prob <<
1670 late_initcall <<
1671 <<
1672 gamecon.map[2|3]= 1458 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1459 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1460 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1461 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1462 See also Documentation/input/devices/joystick-parport.rst
1677 1463
1678 gamma= [HW,DRM] 1464 gamma= [HW,DRM]
1679 1465
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1466 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1467 Format: off | on
1682 default: on 1468 default: on
1683 1469
1684 gather_data_sampling= 1470 gather_data_sampling=
1685 [X86,INTEL,EARLY] Con !! 1471 [X86,INTEL] Control the Gather Data Sampling (GDS)
1686 mitigation. 1472 mitigation.
1687 1473
1688 Gather Data Sampling 1474 Gather Data Sampling is a hardware vulnerability which
1689 allows unprivileged s 1475 allows unprivileged speculative access to data which was
1690 previously stored in 1476 previously stored in vector registers.
1691 1477
1692 This issue is mitigat 1478 This issue is mitigated by default in updated microcode.
1693 The mitigation may ha 1479 The mitigation may have a performance impact but can be
1694 disabled. On systems 1480 disabled. On systems without the microcode mitigation
1695 disabling AVX serves 1481 disabling AVX serves as a mitigation.
1696 1482
1697 force: Disable AVX t 1483 force: Disable AVX to mitigate systems without
1698 microcode mit 1484 microcode mitigation. No effect if the microcode
1699 mitigation is 1485 mitigation is present. Known to cause crashes in
1700 userspace wit 1486 userspace with buggy AVX enumeration.
1701 1487
1702 off: Disable GDS m !! 1488 off: Disable GDS mitigation.
1703 1489
1704 gcov_persist= [GCOV] When non-zero 1490 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1491 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1492 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1493 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1494 debugfs files are removed at module unload time.
1709 1495
1710 goldfish [X86] Enable the gold 1496 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1497 Don't use this when you are not running on the
1712 android emulator 1498 android emulator
1713 1499
1714 gpio-mockup.gpio_mockup_ranges <<
1715 [HW] Sets the ranges <<
1716 Format: <start1>,<end <<
1717 gpio-mockup.gpio_mockup_named_lines <<
1718 [HW] Let the driver k <<
1719 <<
1720 gpt [EFI] Forces disk wit 1500 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1501 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1502 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1503 GPT to be used instead.
1724 1504
1725 grcan.enable0= [HW] Configuration of 1505 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1506 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1507 Format: 0 | 1
1728 Default: 0 1508 Default: 0
1729 grcan.enable1= [HW] Configuration of 1509 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1510 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1511 Format: 0 | 1
1732 Default: 0 1512 Default: 0
1733 grcan.select= [HW] Select which phy 1513 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1514 Format: 0 | 1
1735 Default: 0 1515 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1516 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1517 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1518 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1519 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1520 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1521 Default: 1024
1742 1522
1743 hardened_usercopy= !! 1523 gpio-mockup.gpio_mockup_ranges
1744 [KNL] Under CONFIG_HA !! 1524 [HW] Sets the ranges of gpiochip of for this device.
1745 hardening is enabled !! 1525 Format: <start1>,<end1>,<start2>,<end2>...
1746 usercopy checking is <<
1747 from reading or writi <<
1748 allocation boundaries <<
1749 against bounds-checki <<
1750 copy_to_user()/copy_f <<
1751 on Perform hardened user <<
1752 off Disable hardened user <<
1753 1526
1754 hardlockup_all_cpu_backtrace= 1527 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1528 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1529 backtraces on all cpus.
1757 Format: 0 | 1 1530 Format: 0 | 1
1758 1531
1759 hashdist= [KNL,NUMA] Large hash 1532 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1533 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1534 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1535 Format: 0 | 1 (for off | on)
1763 1536
>> 1537 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1538
1764 hd= [EIDE] (E)IDE hard dr 1539 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1540 Format: <cyl>,<head>,<sect>
1766 1541
1767 hest_disable [ACPI] 1542 hest_disable [ACPI]
1768 Disable Hardware Erro 1543 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1544 corresponding firmware-first mode error processing
1770 logic will be disable 1545 logic will be disabled.
1771 1546
1772 hibernate= [HIBERNATION] !! 1547 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1773 noresume Don't check i <<
1774 present durin <<
1775 nocompress Don't compres <<
1776 no Disable hiber <<
1777 protect_image Turn on image <<
1778 (that will se <<
1779 during restor <<
1780 <<
1781 hibernate.compressor= [HIBERNATION] <<
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 1548 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1549 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1550 size on bigger boxes.
1796 1551
1797 highres= [KNL] Enable/disable 1552 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1553 Valid parameters: "on", "off"
1799 Default: "on" 1554 Default: "on"
1800 1555
1801 hlt [BUGS=ARM,SH] 1556 hlt [BUGS=ARM,SH]
1802 1557
1803 hostname= [KNL,EARLY] Set the h <<
1804 Format: <string> <<
1805 This allows setting t <<
1806 startup. This sets th <<
1807 Using this parameter <<
1808 possible to ensure th <<
1809 any userspace process <<
1810 that a process may ca <<
1811 has been explicitly s <<
1812 process getting an in <<
1813 not exceed the maximu <<
1814 64 characters) and wi <<
1815 <<
1816 hpet= [X86-32,HPET] option 1558 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1559 Format: { enable (default) | disable | force |
1818 verbose } 1560 verbose }
1819 disable: disable HPET 1561 disable: disable HPET and use PIT instead
1820 force: allow force en 1562 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1563 VIA, nVidia)
1822 verbose: show content 1564 verbose: show contents of HPET registers during setup
1823 1565
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1566 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1567 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1568
>> 1569 hugetlb_cma= [HW] The size of a cma area used for allocation
>> 1570 of gigantic hugepages.
>> 1571 Format: nn[KMGTPE]
>> 1572
>> 1573 Reserve a cma area of given size and allocate gigantic
>> 1574 hugepages using the cma allocator. If enabled, the
>> 1575 boot-time allocation of gigantic hugepages is skipped.
>> 1576
1827 hugepages= [HW] Number of HugeTL 1577 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1578 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1579 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1580 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1581 line, it specifies the number of pages to allocate for
1832 the default huge page !! 1582 the default huge page size. See also
1833 number of pages to al !! 1583 Documentation/admin-guide/mm/hugetlbpage.rst.
1834 See also Documentatio !! 1584 Format: <integer>
1835 Format: <integer> or <<
1836 <node>:<integ <<
1837 1585
1838 hugepagesz= 1586 hugepagesz=
1839 [HW] The size of the 1587 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1588 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1589 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1590 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1591 each supported huge page size. Huge page sizes are
1844 architecture dependen 1592 architecture dependent. See also
1845 Documentation/admin-g 1593 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1594 Format: size[KMG]
1847 1595
1848 hugetlb_cma= [HW,CMA,EARLY] The si <<
1849 of gigantic hugepages <<
1850 of a CMA area per nod <<
1851 Format: nn[KMGTPE] or <<
1852 <node>:nn[KMG <<
1853 <<
1854 Reserve a CMA area of <<
1855 hugepages using the C <<
1856 boot-time allocation <<
1857 <<
1858 hugetlb_free_vmemmap= <<
1859 [KNL] Requires CONFIG <<
1860 enabled. <<
1861 Control if HugeTLB Vm <<
1862 Allows heavy hugetlb <<
1863 memory (7 * PAGE_SIZE <<
1864 Format: { on | off (d <<
1865 <<
1866 on: enable HVO <<
1867 off: disable HVO <<
1868 <<
1869 Built with CONFIG_HUG <<
1870 the default is on. <<
1871 <<
1872 Note that the vmemmap <<
1873 memory block itself w <<
1874 enabled, those vmemma <<
1875 feature is enabled. <<
1876 the added memory bloc <<
1877 <<
1878 hung_task_panic= 1596 hung_task_panic=
1879 [KNL] Should the hung 1597 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1598 Format: 0 | 1
1881 1599
1882 A value of 1 instruct 1600 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1601 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1602 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1603 option. The value selected by this boot parameter can
1886 be changed later by t 1604 be changed later by the kernel.hung_task_panic sysctl.
1887 1605
1888 hvc_iucv= [S390] Number of z/V 1606 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1607 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1608 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1609 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1610 from listed z/VM user IDs only.
1893 1611
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1612 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1613 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1614 guest on lock contention.
1897 on lock contention. !! 1615
>> 1616 keep_bootcon [KNL]
>> 1617 Do not unregister boot console at start. This is only
>> 1618 useful for debugging when something happens in the window
>> 1619 between unregistering the boot console and initializing
>> 1620 the real console.
1898 1621
1899 i2c_bus= [HW] Override the 1622 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1623 or register an additional I2C bus that is not
1901 registered fr 1624 registered from board initialization code.
1902 Format: 1625 Format:
1903 <bus_id>,<clk 1626 <bus_id>,<clkrate>
1904 1627
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 1628 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1629 i8042.unmask_kbd_data
1929 [HW] Enable printing 1630 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1631 (disabled by default, and as a pre-condition
1931 requires that i8 1632 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1633 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1634 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1635 keyboard and cannot control its state
1935 (Don't attempt t 1636 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1637 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1638 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1639 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1640 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1641 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1642 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1643 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1644 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1645 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1646 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1647 suspend-to-ram transitions, only during s2r
1947 transitions, or 1648 transitions, or never reset
1948 Format: { 1 | Y | y | 1649 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1650 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1651 0, N, n: don't ever reset controller
1951 Default: only on s2r 1652 Default: only on s2r transitions on x86; most other
1952 architectures force r 1653 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1654 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1655 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer 1656 i8042.probe_defer
1956 [HW] Allow deferred p 1657 [HW] Allow deferred probing upon i8042 probe errors
1957 1658
1958 i810= [HW,DRM] 1659 i810= [HW,DRM]
1959 1660
>> 1661 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1662 indicates that the driver is running on unsupported
>> 1663 hardware.
>> 1664 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1665 does not match list of supported models.
>> 1666 i8k.power_status
>> 1667 [HW] Report power status in /proc/i8k
>> 1668 (disabled by default)
>> 1669 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1670 capability is set.
>> 1671
1960 i915.invert_brightness= 1672 i915.invert_brightness=
1961 [DRM] Invert the sens 1673 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1674 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1675 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1676 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1677 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1678 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1679 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1680 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1681 value switches the backlight off.
1970 -1 -- never invert br 1682 -1 -- never invert brightness
1971 0 -- machine default 1683 0 -- machine default
1972 1 -- force brightnes 1684 1 -- force brightness inversion
1973 1685
1974 ia32_emulation= [X86-64] <<
1975 Format: <bool> <<
1976 When true, allows loa <<
1977 syscalls, essentially <<
1978 boot time. When false <<
1979 <<
1980 icn= [HW,ISDN] 1686 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1687 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1688
>> 1689 ide-core.nodma= [HW] (E)IDE subsystem
>> 1690 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1691 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1692 .cdrom .chs .ignore_cable are additional options
>> 1693 See Documentation/ide/ide.rst.
1983 1694
1984 idle= [X86,EARLY] !! 1695 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1696 Format: <int>
>> 1697 Probe mask for legacy ISA IDE ports. Depending on
>> 1698 platform up to 6 ports are supported, enabled by
>> 1699 setting corresponding bits in the mask to 1. The
>> 1700 default value is 0x0, which has a special meaning.
>> 1701 On systems that have PCI, it triggers scanning the
>> 1702 PCI bus for the first and the second port, which
>> 1703 are then probed. On systems without PCI the value
>> 1704 of 0x0 enables probing the two first ports as if it
>> 1705 was 0x3.
>> 1706
>> 1707 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1708 Claim all unknown PCI IDE storage controllers.
>> 1709
>> 1710 idle= [X86]
1985 Format: idle=poll, id 1711 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1712 Poll forces a polling idle loop that can slightly
1987 improve the performan 1713 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1714 will use a lot of power and make the system run hot.
1989 Not recommended. 1715 Not recommended.
1990 idle=halt: Halt is fo 1716 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1717 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1718 idle=nomwait: Disable mwait for CPU C-states
1993 1719
1994 idxd.sva= [HW] <<
1995 Format: <bool> <<
1996 Allow force disabling <<
1997 support for the idxd <<
1998 true (1). <<
1999 <<
2000 idxd.tc_override= [HW] <<
2001 Format: <bool> <<
2002 Allow override of def <<
2003 for the device. By de <<
2004 <<
2005 ieee754= [MIPS] Select IEEE St 1720 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1721 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1722 Default: strict
2008 1723
2009 Choose which programs 1724 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1725 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1726 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1727 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1728 binary. Hardware implementations are permitted to
2014 support either or bot 1729 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1730 encoding mode.
2016 1731
2017 Available settings ar 1732 Available settings are as follows:
2018 strict accept binari 1733 strict accept binaries that request a NaN encoding
2019 supported by 1734 supported by the FPU
2020 legacy only accept l 1735 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1736 by the FPU
2022 2008 only accept 2 1737 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1738 by the FPU
2024 relaxed accept any bi 1739 relaxed accept any binaries regardless of whether
2025 supported by 1740 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1741
2029 The FPU emulator is a 1742 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1743 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1744 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1745 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1746 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1747 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1748 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1749 MIPS64 CPUs.
2037 1750
2038 The setting for ABS.f 1751 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1752 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1753 except where unsupported by hardware.
2041 1754
2042 ignore_loglevel [KNL,EARLY] !! 1755 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1756 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1757 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1758 We also add it as printk module parameter, so users
2046 could change it dynam 1759 could change it dynamically, usually by
2047 /sys/module/printk/pa 1760 /sys/module/printk/parameters/ignore_loglevel.
2048 1761
2049 ignore_rlimit_data 1762 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1763 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1764 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1765 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1766
2054 ihash_entries= [KNL] 1767 ihash_entries= [KNL]
2055 Set number of hash bu 1768 Set number of hash buckets for inode cache.
2056 1769
2057 ima_appraise= [IMA] appraise integr 1770 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1771 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1772 default: "enforce"
2060 1773
2061 ima_appraise_tcb [IMA] Deprecated. U 1774 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1775 The builtin appraise policy appraises all files
2063 owned by uid=0. 1776 owned by uid=0.
2064 1777
2065 ima_canonical_fmt [IMA] 1778 ima_canonical_fmt [IMA]
2066 Use the canonical for 1779 Use the canonical format for the binary runtime
2067 measurements, instead 1780 measurements, instead of host native format.
2068 1781
2069 ima_hash= [IMA] 1782 ima_hash= [IMA]
2070 Format: { md5 | sha1 1783 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1784 | sha512 | ... }
2072 default: "sha1" 1785 default: "sha1"
2073 1786
2074 The list of supported 1787 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1788 in crypto/hash_info.h.
2076 1789
2077 ima_policy= [IMA] 1790 ima_policy= [IMA]
2078 The builtin policies 1791 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1792 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel !! 1793 fail_securely"
2081 1794
2082 The "tcb" policy meas 1795 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1796 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1797 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1798 uid=0.
2086 1799
2087 The "appraise_tcb" po 1800 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1801 all files owned by root.
2089 1802
2090 The "secure_boot" pol 1803 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1804 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1805 firmware, policy, etc) based on file signatures.
2093 1806
2094 The "fail_securely" p 1807 The "fail_securely" policy forces file signature
2095 verification failure 1808 verification failure also on privileged mounted
2096 filesystems with the 1809 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1810 flag.
2098 1811
2099 The "critical_data" p <<
2100 critical data. <<
2101 <<
2102 ima_tcb [IMA] Deprecated. Us 1812 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1813 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1814 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1815 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1816 opened for read by uid=0.
2107 1817
2108 ima_template= [IMA] 1818 ima_template= [IMA]
2109 Select one of defined 1819 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1820 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1821 Default: "ima-ng"
2113 1822
2114 ima_template_fmt= 1823 ima_template_fmt=
2115 [IMA] Define a custom 1824 [IMA] Define a custom template format.
2116 Format: { "field1|... 1825 Format: { "field1|...|fieldN" }
2117 1826
2118 ima.ahash_minsize= [IMA] Minimum file 1827 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1828 Format: <min_file_size>
2120 Set the minimal file 1829 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1830 If left unspecified, ahash usage is disabled.
2122 1831
2123 ahash performance var 1832 ahash performance varies for different data sizes on
2124 different crypto acce 1833 different crypto accelerators. This option can be used
2125 to achieve the best p 1834 to achieve the best performance for a particular HW.
2126 1835
2127 ima.ahash_bufsize= [IMA] Asynchronous 1836 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1837 Format: <bufsize>
2129 Set hashing buffer si 1838 Set hashing buffer size. Default: 4k.
2130 1839
2131 ahash performance var 1840 ahash performance varies for different chunk sizes on
2132 different crypto acce 1841 different crypto accelerators. This option can be used
2133 to achieve best perfo 1842 to achieve best performance for particular HW.
2134 1843
2135 init= [KNL] 1844 init= [KNL]
2136 Format: <full_path> 1845 Format: <full_path>
2137 Run specified binary 1846 Run specified binary instead of /sbin/init as init
2138 process. 1847 process.
2139 1848
2140 initcall_debug [KNL] Trace initcalls 1849 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1850 for working out where the kernel is dying during
2142 startup. 1851 startup.
2143 1852
2144 initcall_blacklist= [KNL] Do not exe 1853 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1854 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1855 modules and initcalls.
2147 1856
2148 initramfs_async= [KNL] !! 1857 initrd= [BOOT] Specify the location of the initial ramdisk
2149 Format: <bool> <<
2150 Default: 1 <<
2151 This parameter contro <<
2152 image is unpacked asy <<
2153 with devices being pr <<
2154 initialized. This sho <<
2155 but as a debugging ai <<
2156 historical behaviour <<
2157 unpacking being compl <<
2158 late_ initcalls. <<
2159 <<
2160 initrd= [BOOT,EARLY] Specify <<
2161 1858
2162 initrdmem= [KNL,EARLY] Specify a !! 1859 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 1860 load the initrd. If an initrd is compiled in or
2164 specified in the boot 1861 specified in the bootparams, it takes priority over this
2165 setting. 1862 setting.
2166 Format: ss[KMG],nn[KM 1863 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 1864 Default is 0, 0
2168 1865
2169 init_on_alloc= [MM,EARLY] Fill newly !! 1866 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 1867 zeroes.
2171 Format: 0 | 1 1868 Format: 0 | 1
2172 Default set by CONFIG 1869 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 1870
2174 init_on_free= [MM,EARLY] Fill freed !! 1871 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 1872 Format: 0 | 1
2176 Default set by CONFIG 1873 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 1874
2178 init_pkru= [X86] Specify the def 1875 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 1876 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1877 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1878 override in debugfs after boot.
2182 1879
2183 inport.irq= [HW] Inport (ATI XL a 1880 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1881 Format: <irq>
2185 1882
2186 int_pln_enable [X86] Enable power li 1883 int_pln_enable [X86] Enable power limit notification interrupt
2187 1884
2188 integrity_audit=[IMA] 1885 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1886 Format: { "0" | "1" }
2190 0 -- basic integrity 1887 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1888 1 -- additional integrity auditing messages.
2192 1889
2193 intel_iommu= [DMAR] Intel IOMMU dr 1890 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1891 on
2195 Enable intel iommu dr 1892 Enable intel iommu driver.
2196 off 1893 off
2197 Disable intel iommu d 1894 Disable intel iommu driver.
2198 igfx_off [Default Off] 1895 igfx_off [Default Off]
2199 By default, gfx is ma 1896 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1897 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1898 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1899 this case, gfx device will use physical address for
2203 DMA. 1900 DMA.
>> 1901 forcedac [X86-64]
>> 1902 With this option iommu will not optimize to look
>> 1903 for io virtual address below 32-bit forcing dual
>> 1904 address cycle on pci bus for cards supporting greater
>> 1905 than 32-bit addressing. The default is to look
>> 1906 for translation below 32-bit and if not available
>> 1907 then look in the higher range.
2204 strict [Default Off] 1908 strict [Default Off]
2205 Deprecated, equivalen !! 1909 With this option on every unmap_single operation will
>> 1910 result in a hardware IOTLB flush operation as opposed
>> 1911 to batching them for performance.
2206 sp_off [Default Off] 1912 sp_off [Default Off]
2207 By default, super pag 1913 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1914 has the capability. With this option, super page will
2209 not be supported. 1915 not be supported.
2210 sm_on !! 1916 sm_on [Default Off]
2211 Enable the Intel IOMM !! 1917 By default, scalable mode will be disabled even if the
2212 advertises that it ha !! 1918 hardware advertises that it has support for the scalable
2213 translation. !! 1919 mode translation. With this option set, scalable mode
2214 sm_off !! 1920 will be used on hardware which claims to support it.
2215 Disallow use of the I <<
2216 tboot_noforce [Default Off] 1921 tboot_noforce [Default Off]
2217 Do not force the Inte 1922 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1923 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1924 could harm performance of some high-throughput
2220 devices like 40GBit n 1925 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1926 mapping is enabled.
2222 Note that using this 1927 Note that using this option lowers the security
2223 provided by tboot bec 1928 provided by tboot because it makes the system
2224 vulnerable to DMA att 1929 vulnerable to DMA attacks.
>> 1930 nobounce [Default off]
>> 1931 Disable bounce buffer for untrusted devices such as
>> 1932 the Thunderbolt devices. This will treat the untrusted
>> 1933 devices as the trusted ones, hence might expose security
>> 1934 risks of DMA attacks.
2225 1935
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1936 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1937 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1938 1 to 9 specify maximum depth of C-state.
2229 1939
2230 intel_pstate= [X86,EARLY] !! 1940 intel_pstate= [X86]
2231 disable 1941 disable
2232 Do not enable intel 1942 Do not enable intel_pstate as the default
2233 scaling driver for 1943 scaling driver for the supported processors
2234 active <<
2235 Use intel_pstate dr <<
2236 governors layer of <<
2237 algorithms for p-st <<
2238 P-state selection a <<
2239 intel_pstate in the <<
2240 performance. The w <<
2241 on whether or not t <<
2242 (HWP) feature has b <<
2243 and possibly on the <<
2244 passive 1944 passive
2245 Use intel_pstate as 1945 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 1946 to work with generic cpufreq governors (instead of
2247 enabling its intern 1947 enabling its internal governor). This mode cannot be
2248 used along with the 1948 used along with the hardware-managed P-states (HWP)
2249 feature. 1949 feature.
2250 force 1950 force
2251 Enable intel_pstate 1951 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 1952 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 1953 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 1954 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 1955 P-States information being indicated to OSPM and therefore
2256 should be used with 1956 should be used with caution. This option does not work with
2257 processors that are 1957 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 1958 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 1959 no_hwp
2260 Do not enable hardw 1960 Do not enable hardware P state control (HWP)
2261 if available. 1961 if available.
2262 hwp_only 1962 hwp_only
2263 Only load intel_pst 1963 Only load intel_pstate on systems which support
2264 hardware P state co 1964 hardware P state control (HWP) if available.
2265 support_acpi_ppc 1965 support_acpi_ppc
2266 Enforce ACPI _PPC p 1966 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 1967 Description Table, specifies preferred power management
2268 profile as "Enterpr 1968 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 1969 then this feature is turned on by default.
2270 per_cpu_perf_limits 1970 per_cpu_perf_limits
2271 Allow per-logical-C 1971 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 1972 cpufreq sysfs interface
2273 1973
2274 intremap= [X86-64,Intel-IOMMU,E !! 1974 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 1975 on enable Interrupt Remapping (default)
2276 off disable Inter 1976 off disable Interrupt Remapping
2277 nosid disable Sourc 1977 nosid disable Source ID checking
2278 no_x2apic_optout 1978 no_x2apic_optout
2279 BIOS x2APIC o 1979 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 1980 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 1981
2284 iomem= Disable strict checki 1982 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 1983 strict regions from userspace.
2286 relaxed 1984 relaxed
2287 1985
2288 iommu= [X86,EARLY] !! 1986 iommu= [X86]
2289 off 1987 off
2290 force 1988 force
2291 noforce 1989 noforce
2292 biomerge 1990 biomerge
2293 panic 1991 panic
2294 nopanic 1992 nopanic
2295 merge 1993 merge
2296 nomerge 1994 nomerge
2297 soft 1995 soft
2298 pt [X86] 1996 pt [X86]
2299 nopt [X86] 1997 nopt [X86]
2300 nobypass [PPC/POWERNV] 1998 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 1999 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2000
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2001 iommu.strict= [ARM64] Configure TLB invalidation behaviour
2304 Format: { "0" | "1" } <<
2305 0 - Try to allocate a <<
2306 falling back to the <<
2307 1 - Allocate directly <<
2308 forcing Dual Addres <<
2309 greater than 32-bit <<
2310 <<
2311 iommu.strict= [ARM64,X86,S390,EARLY <<
2312 Format: { "0" | "1" } 2002 Format: { "0" | "1" }
2313 0 - Lazy mode. 2003 0 - Lazy mode.
2314 Request that DMA un 2004 Request that DMA unmap operations use deferred
2315 invalidation of har 2005 invalidation of hardware TLBs, for increased
2316 throughput at the c 2006 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2007 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2008 the relevant IOMMU driver.
2319 1 - Strict mode. !! 2009 1 - Strict mode (default).
2320 DMA unmap operation 2010 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2011 synchronously.
2322 unset - Use value of <<
2323 Note: on x86, strict <<
2324 legacy driver-specifi <<
2325 2012
2326 iommu.passthrough= 2013 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2014 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2015 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2016 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2017 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2018 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2019
2333 io7= [HW] IO7 for Marvel-b 2020 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2021 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2022 arch/alpha/kernel/core_marvel.c.
2336 2023
2337 io_delay= [X86,EARLY] I/O delay !! 2024 io_delay= [X86] I/O delay method
2338 0x80 2025 0x80
2339 Standard port 0x80 ba 2026 Standard port 0x80 based delay
2340 0xed 2027 0xed
2341 Alternate port 0xed b 2028 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2029 udelay
2343 Simple two microsecon 2030 Simple two microseconds delay
2344 none 2031 none
2345 No delay 2032 No delay
2346 2033
2347 ip= [IP_PNP] 2034 ip= [IP_PNP]
2348 See Documentation/adm 2035 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2036
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2037 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2038 IPC identifiers from 32,768 to 16,777,216.
2352 2039
2353 irqaffinity= [SMP] Set the default 2040 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2041 The argument is a cpu list, as described above.
2355 2042
2356 irqchip.gicv2_force_probe= 2043 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2044 [ARM, ARM64]
2358 Format: <bool> 2045 Format: <bool>
2359 Force the kernel to l 2046 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2047 of a GICv2 controller even if the memory range
2361 exposed by the device 2048 exposed by the device tree is too small.
2362 2049
2363 irqchip.gicv3_nolpi= 2050 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2051 [ARM, ARM64]
2365 Force the kernel to i 2052 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2053 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2054 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2055 to let secondary kernels in charge of setting up
2369 LPIs. 2056 LPIs.
2370 2057
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2058 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2059 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2060 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2061 CONFIG_ARM64_PSEUDO_NMI.
2375 2062
2376 irqfixup [HW] 2063 irqfixup [HW]
2377 When an interrupt is 2064 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2065 for it. Intended to get systems with badly broken
2379 firmware running. 2066 firmware running.
2380 2067
2381 irqpoll [HW] 2068 irqpoll [HW]
2382 When an interrupt is 2069 When an interrupt is not handled search all handlers
2383 for it. Also check al 2070 for it. Also check all handlers each timer
2384 interrupt. Intended t 2071 interrupt. Intended to get systems with badly broken
2385 firmware running. 2072 firmware running.
2386 2073
2387 isapnp= [ISAPNP] 2074 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2075 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2076
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2077 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2078 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2079 Format: [flag-list,]<cpu-list>
2393 2080
2394 Specify one or more C 2081 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2082 specified in the flag list (default: domain):
2396 2083
2397 nohz 2084 nohz
2398 Disable the tick wh 2085 Disable the tick when a single task runs.
2399 2086
2400 A residual 1Hz tick 2087 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2088 need to affine to housekeeping through the global
2402 workqueue's affinit 2089 workqueue's affinity configured via the
2403 /sys/devices/virtua 2090 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2091 by using the 'domain' flag described below.
2405 2092
2406 NOTE: by default th 2093 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2094 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2095 be configured manually after bootup.
2409 2096
2410 domain 2097 domain
2411 Isolate from the ge 2098 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2099 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2100 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2101 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2102 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2103 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2104 It offers a much more flexible interface where CPUs can
2418 move in and out of 2105 move in and out of an isolated set anytime.
2419 2106
2420 You can move a proc 2107 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2108 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2109 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2110 "number of CPUs in system - 1".
2424 2111
2425 managed_irq 2112 managed_irq
2426 2113
2427 Isolate from being 2114 Isolate from being targeted by managed interrupts
2428 which have an inter 2115 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2116 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2117 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2118 the /proc/irq/* interfaces.
2432 2119
2433 This isolation is b 2120 This isolation is best effort and only effective
2434 if the automaticall 2121 if the automatically assigned interrupt mask of a
2435 device queue contai 2122 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2123 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2124 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2125 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2126 cannot disturb the isolated CPU.
2440 2127
2441 If a queue's affini 2128 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2129 CPUs then this parameter has no effect on the
2443 interrupt routing d 2130 interrupt routing decision, though interrupts are
2444 only delivered when 2131 only delivered when tasks running on those
2445 isolated CPUs submi 2132 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2133 housekeeping CPUs has no influence on those
2447 queues. 2134 queues.
2448 2135
2449 The format of <cpu-li 2136 The format of <cpu-list> is described above.
2450 2137
2451 iucv= [HW,NET] 2138 iucv= [HW,NET]
2452 2139
2453 ivrs_ioapic [HW,X86-64] 2140 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2141 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t 2142 mapping provided in the IVRS ACPI table.
2456 By default, PCI segme 2143 By default, PCI segment is 0, and can be omitted.
2457 2144
2458 For example, to map I 2145 For example, to map IOAPIC-ID decimal 10 to
2459 PCI segment 0x1 and P 2146 PCI segment 0x1 and PCI device 00:14.0,
2460 write the parameter a 2147 write the parameter as:
2461 ivrs_ioapic=1 2148 ivrs_ioapic=10@0001:00:14.0
2462 2149
2463 Deprecated formats: 2150 Deprecated formats:
2464 * To map IOAPIC-ID de 2151 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2465 write the parameter 2152 write the parameter as:
2466 ivrs_ioapic[1 2153 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de 2154 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2468 PCI device 00:14.0 2155 PCI device 00:14.0 write the parameter as:
2469 ivrs_ioapic[1 2156 ivrs_ioapic[10]=0001:00:14.0
2470 2157
2471 ivrs_hpet [HW,X86-64] 2158 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2159 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t 2160 mapping provided in the IVRS ACPI table.
2474 By default, PCI segme 2161 By default, PCI segment is 0, and can be omitted.
2475 2162
2476 For example, to map H 2163 For example, to map HPET-ID decimal 10 to
2477 PCI segment 0x1 and P 2164 PCI segment 0x1 and PCI device 00:14.0,
2478 write the parameter a 2165 write the parameter as:
2479 ivrs_hpet=10@ 2166 ivrs_hpet=10@0001:00:14.0
2480 2167
2481 Deprecated formats: 2168 Deprecated formats:
2482 * To map HPET-ID deci 2169 * To map HPET-ID decimal 0 to PCI device 00:14.0
2483 write the parameter 2170 write the parameter as:
2484 ivrs_hpet[0]= 2171 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci 2172 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2486 PCI device 00:14.0 2173 PCI device 00:14.0 write the parameter as:
2487 ivrs_ioapic[1 2174 ivrs_ioapic[10]=0001:00:14.0
2488 2175
2489 ivrs_acpihid [HW,X86-64] 2176 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2177 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t 2178 mapping provided in the IVRS ACPI table.
2492 By default, PCI segme 2179 By default, PCI segment is 0, and can be omitted.
2493 2180
2494 For example, to map U 2181 For example, to map UART-HID:UID AMD0020:0 to
2495 PCI segment 0x1 and P 2182 PCI segment 0x1 and PCI device ID 00:14.5,
2496 write the parameter a 2183 write the parameter as:
2497 ivrs_acpihid= 2184 ivrs_acpihid=AMD0020:0@0001:00:14.5
2498 2185
2499 Deprecated formats: 2186 Deprecated formats:
2500 * To map UART-HID:UID 2187 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2501 PCI device ID 00:14 2188 PCI device ID 00:14.5, write the parameter as:
2502 ivrs_acpihid[ 2189 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID 2190 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2504 PCI device ID 00:14 2191 PCI device ID 00:14.5, write the parameter as:
2505 ivrs_acpihid[ 2192 ivrs_acpihid[0001:00:14.5]=AMD0020:0
2506 2193
2507 js= [HW,JOY] Analog joyst 2194 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2195 See Documentation/input/joydev/joystick.rst.
2509 2196
>> 2197 nokaslr [KNL]
>> 2198 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2199 kernel and module base offset ASLR (Address Space
>> 2200 Layout Randomization).
>> 2201
2510 kasan_multi_shot 2202 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2203 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2204 report on every invalid memory access. Without this
2513 parameter KASAN will 2205 parameter KASAN will print report only for the first
2514 invalid access. 2206 invalid access.
2515 2207
2516 keep_bootcon [KNL,EARLY] !! 2208 keepinitrd [HW,ARM]
2517 Do not unregister boo <<
2518 useful for debugging <<
2519 between unregistering <<
2520 the real console. <<
2521 <<
2522 keepinitrd [HW,ARM] See retain_i <<
2523 2209
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2210 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2211 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2212 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2213 the kernel for non-movable allocations. The requested
2528 amount is spread even 2214 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2215 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2216 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2217 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2218 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2219 other nodes will have a larger ZONE_MOVABLE.
2534 2220
2535 ZONE_MOVABLE is used 2221 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2222 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2223 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2224 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2225 zone if it does not.
2540 2226
2541 It is possible to spe 2227 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2228 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2229 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2230 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2231 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2232 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2233 are exclusive, so you cannot specify multiple forms.
2548 2234
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2235 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2236 Format: <Controller#>[,poll interval]
2551 The controller # is t 2237 The controller # is the number of the ehci usb debug
2552 port as it is probed 2238 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2239 optional and is the number seconds in between
2554 each poll cycle to th 2240 each poll cycle to the debug port in case you need
2555 the functionality for 2241 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2242 gdb or control-c on the dbgp connection. When
2557 not using this parame 2243 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2244 the kernel debugger.
2559 2245
2560 kgdboc= [KGDB,HW] kgdb over c 2246 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2247 Requires a tty driver that supports console polling,
2562 or a supported pollin 2248 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2249 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2250 keyboard only format: kbd
2565 keyboard and serial 2251 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2252 Optional Kernel mode setting:
2567 kms, kbd format: kms 2253 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2254 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2255
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2256 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2257 If the boot console provides the ability to read
2572 characters and can wo 2258 characters and can work in polling mode, you can use
2573 this parameter to tel 2259 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2260 until the normal console is registered. Intended to
2575 be used together with 2261 be used together with the kgdboc parameter which
2576 specifies the normal 2262 specifies the normal console to transition to.
2577 2263
2578 The name of the early 2264 The name of the early console should be specified
2579 as the value of this 2265 as the value of this parameter. Note that the name of
2580 the early console mig 2266 the early console might be different than the tty
2581 name passed to kgdboc 2267 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2268 blank and the first boot console that implements
2583 read() will be picked 2269 read() will be picked.
2584 2270
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2271 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2272 kernel debugger at the earliest opportunity.
2587 2273
2588 kmac= [MIPS] Korina etherne 2274 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2275 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2276 Ethernet adapter MAC address.
2591 2277
2592 kmemleak= [KNL,EARLY] Boot-time !! 2278 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2279 Valid arguments: on, off
2594 Default: on 2280 Default: on
2595 Built with CONFIG_DEB 2281 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2282 the default is off.
2597 2283
2598 kprobe_event=[probe-list] 2284 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2285 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2286 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2287 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2288 interface, but the parameters are comma delimited.
2603 For example, to add a 2289 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2290 arg1 and arg2, add to the command line;
2605 2291
2606 kprobe_event=p, 2292 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2293
2608 See also Documentatio 2294 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2295 Boot Parameter" section.
2610 2296
2611 kpti= [ARM64,EARLY] Control !! 2297 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2298 and kernel address spaces.
2613 Default: enabled on c 2299 Default: enabled on cores which need mitigation.
2614 0: force disabled 2300 0: force disabled
2615 1: force enabled 2301 1: force enabled
2616 2302
2617 kunit.enable= [KUNIT] Enable execut <<
2618 CONFIG_KUNIT to be se <<
2619 default value can be <<
2620 KUNIT_DEFAULT_ENABLED <<
2621 Default is 1 (enabled <<
2622 <<
2623 kvm.ignore_msrs=[KVM] Ignore guest ac 2303 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2304 Default is 0 (don't ignore, but inject #GP)
2625 2305
2626 kvm.eager_page_split= <<
2627 [KVM,X86] Controls wh <<
2628 proactively split all <<
2629 Eager page splitting <<
2630 execution by eliminat <<
2631 and MMU lock contenti <<
2632 required to split hug <<
2633 <<
2634 VM workloads that rar <<
2635 only to a small regio <<
2636 disabling eager page <<
2637 still be used for rea <<
2638 <<
2639 The behavior of eager <<
2640 KVM_DIRTY_LOG_INITIAL <<
2641 disabled, all huge pa <<
2642 split when dirty logg <<
2643 enabled, eager page s <<
2644 the KVM_CLEAR_DIRTY i <<
2645 cleared. <<
2646 <<
2647 Eager page splitting <<
2648 <<
2649 Default is Y (on). <<
2650 <<
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2306 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2307 Default is false (don't support).
2653 2308
>> 2309 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
>> 2310 KVM MMU at runtime.
>> 2311 Default is 0 (off)
>> 2312
2654 kvm.nx_huge_pages= 2313 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2314 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2315 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2316 force : Always deploy workaround.
2658 off : Never deplo 2317 off : Never deploy workaround.
2659 auto : Deploy work 2318 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2319 X86_BUG_ITLB_MULTIHIT.
2661 2320
2662 Default is 'auto'. 2321 Default is 'auto'.
2663 2322
2664 If the software worka 2323 If the software workaround is enabled for the host,
2665 guests do need not to 2324 guests do need not to enable it for nested guests.
2666 2325
2667 kvm.nx_huge_pages_recovery_ratio= 2326 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2327 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2328 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2329 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). !! 2330 minute. The default is 60.
2672 2331
2673 kvm.nx_huge_pages_recovery_period_ms= !! 2332 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2674 [KVM] Controls the ti !! 2333 Default is 1 (enabled)
2675 back to huge pages. I !! 2334
2676 zap a portion (see ra !! 2335 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2677 If the value is 0 (th !! 2336 for all guests.
2678 on the ratio, such th !! 2337 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2679 <<
2680 kvm-amd.nested= [KVM,AMD] Control nes <<
2681 KVM/SVM. Default is 1 <<
2682 <<
2683 kvm-amd.npt= [KVM,AMD] Control KVM <<
2684 a.k.a. Two-Dimensiona <<
2685 (enabled). Disable by <<
2686 for NPT. <<
2687 <<
2688 kvm-arm.mode= <<
2689 [KVM,ARM,EARLY] Selec <<
2690 operation. <<
2691 <<
2692 none: Forcefully disa <<
2693 <<
2694 nvhe: Standard nVHE-b <<
2695 protected guest <<
2696 <<
2697 protected: nVHE-based <<
2698 state is k <<
2699 <<
2700 nested: VHE-based mod <<
2701 virtualizatio <<
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE <<
2705 mode to "protected" w <<
2706 for the host. "nested <<
2707 used with extreme cau <<
2708 2338
2709 kvm-arm.vgic_v3_group0_trap= 2339 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2340 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2341 system registers
2712 2342
2713 kvm-arm.vgic_v3_group1_trap= 2343 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2344 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2345 system registers
2716 2346
2717 kvm-arm.vgic_v3_common_trap= 2347 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2348 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2349 system registers
2720 2350
2721 kvm-arm.vgic_v4_enable= 2351 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2352 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2353 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 2354
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2355 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2356 Reserves given percentage from system memory area for
2745 contiguous memory all 2357 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2358 allocation.
2747 By default it reserve 2359 By default it reserves 5% of total system memory.
2748 Format: <integer> 2360 Format: <integer>
2749 Default: 5 2361 Default: 5
2750 2362
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2363 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2364 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2365 Default is 1 (enabled)
2754 for EPT. <<
2755 2366
2756 kvm-intel.emulate_invalid_guest_state 2367 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2368 [KVM,Intel] Disable emulation of invalid guest state.
2758 state. Ignored if kvm !! 2369 Ignored if kvm-intel.enable_unrestricted_guest=1, as
2759 as guest state is nev !! 2370 guest state is never invalid for unrestricted guests.
2760 guests. This param do !! 2371 This param doesn't apply to nested guests (L2), as KVM
2761 as KVM never emulates !! 2372 never emulates invalid L2 guest state.
2762 Default is 1 (enabled !! 2373 Default is 1 (enabled)
2763 2374
2764 kvm-intel.flexpriority= 2375 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2376 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2377 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2378
2769 kvm-intel.nested= 2379 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2380 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2381 Default is 0 (disabled)
2772 2382
2773 kvm-intel.unrestricted_guest= 2383 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2384 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2385 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2386 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2387
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2388 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2389 CVE-2018-3620.
2781 2390
2782 Valid arguments: neve 2391 Valid arguments: never, cond, always
2783 2392
2784 always: L1D cache flu 2393 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2394 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2395 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2396 never: Disables the mitigation
2788 2397
2789 Default is cond (do L 2398 Default is cond (do L1 cache flush in specific instances)
2790 2399
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2400 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2401 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2402 Default is 1 (enabled)
2794 for it. <<
2795 <<
2796 l1d_flush= [X86,INTEL,EARLY] <<
2797 Control mitigation fo <<
2798 <<
2799 Certain CPUs are vuln <<
2800 internal buffers whic <<
2801 disclosure gadget und <<
2802 <<
2803 In vulnerable process <<
2804 forwarded data can be <<
2805 attack, to access dat <<
2806 not have direct acces <<
2807 <<
2808 This parameter contro <<
2809 options are: <<
2810 <<
2811 on - enable t <<
2812 2403
2813 l1tf= [X86,EARLY] Control m !! 2404 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2405 affected CPUs
2815 2406
2816 The kernel PTE invers 2407 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2408 enabled and cannot be disabled.
2818 2409
2819 full 2410 full
2820 Provides all 2411 Provides all available mitigations for the
2821 L1TF vulnerab 2412 L1TF vulnerability. Disables SMT and
2822 enables all m 2413 enables all mitigations in the
2823 hypervisors, 2414 hypervisors, i.e. unconditional L1D flush.
2824 2415
2825 SMT control a 2416 SMT control and L1D flush control via the
2826 sysfs interfa 2417 sysfs interface is still possible after
2827 boot. Hyperv 2418 boot. Hypervisors will issue a warning
2828 when the firs 2419 when the first VM is started in a
2829 potentially i 2420 potentially insecure configuration,
2830 i.e. SMT enab 2421 i.e. SMT enabled or L1D flush disabled.
2831 2422
2832 full,force 2423 full,force
2833 Same as 'full 2424 Same as 'full', but disables SMT and L1D
2834 flush runtime 2425 flush runtime control. Implies the
2835 'nosmt=force' 2426 'nosmt=force' command line option.
2836 (i.e. sysfs c 2427 (i.e. sysfs control of SMT is disabled.)
2837 2428
2838 flush 2429 flush
2839 Leaves SMT en 2430 Leaves SMT enabled and enables the default
2840 hypervisor mi 2431 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2432 L1D flush.
2842 2433
2843 SMT control a 2434 SMT control and L1D flush control via the
2844 sysfs interfa 2435 sysfs interface is still possible after
2845 boot. Hyperv 2436 boot. Hypervisors will issue a warning
2846 when the firs 2437 when the first VM is started in a
2847 potentially i 2438 potentially insecure configuration,
2848 i.e. SMT enab 2439 i.e. SMT enabled or L1D flush disabled.
2849 2440
2850 flush,nosmt 2441 flush,nosmt
2851 2442
2852 Disables SMT 2443 Disables SMT and enables the default
2853 hypervisor mi 2444 hypervisor mitigation.
2854 2445
2855 SMT control a 2446 SMT control and L1D flush control via the
2856 sysfs interfa 2447 sysfs interface is still possible after
2857 boot. Hyperv 2448 boot. Hypervisors will issue a warning
2858 when the firs 2449 when the first VM is started in a
2859 potentially i 2450 potentially insecure configuration,
2860 i.e. SMT enab 2451 i.e. SMT enabled or L1D flush disabled.
2861 2452
2862 flush,nowarn 2453 flush,nowarn
2863 Same as 'flus 2454 Same as 'flush', but hypervisors will not
2864 warn when a V 2455 warn when a VM is started in a potentially
2865 insecure conf 2456 insecure configuration.
2866 2457
2867 off 2458 off
2868 Disables hype 2459 Disables hypervisor mitigations and doesn't
2869 emit any warn 2460 emit any warnings.
2870 It also drops 2461 It also drops the swap size and available
2871 RAM limit res 2462 RAM limit restriction on both hypervisor and
2872 bare metal. 2463 bare metal.
2873 2464
2874 Default is 'flush'. 2465 Default is 'flush'.
2875 2466
2876 For details see: Docu 2467 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2468
2878 l2cr= [PPC] 2469 l2cr= [PPC]
2879 2470
2880 l3cr= [PPC] 2471 l3cr= [PPC]
2881 2472
2882 lapic [X86-32,APIC,EARLY] E !! 2473 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2474 disabled it.
2884 2475
2885 lapic= [X86,APIC] Do not use 2476 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2477 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2478 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2479 Format: notscdeadline
2889 2480
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2481 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2482 in C2 power state.
2892 2483
2893 libata.dma= [LIBATA] DMA control 2484 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2485 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2486 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2487 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2488 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2489 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2490 for disks and CDROMs, but not CFs.
2900 2491
2901 libata.ignore_hpa= [LIBATA] Igno 2492 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2493 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2494 libata.ignore_hpa=1 ignore limits, using full disk
2904 2495
2905 libata.noacpi [LIBATA] Disables use 2496 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2497 when set.
2907 Format: <int> 2498 Format: <int>
2908 2499
2909 libata.force= [LIBATA] Force config !! 2500 libata.force= [LIBATA] Force configurations. The format is comma
2910 separated list of "[I !! 2501 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2502 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2503 matching port, link or device. Basically, it matches
2913 printed on console by !! 2504 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2505 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2506 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2507 configuration applies to all ports, links and devices.
2917 2508
2918 If only DEVICE is omi 2509 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2510 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2511 number of 0 either selects the first device or the
2921 first fan-out link be 2512 first fan-out link behind PMP device. It does not
2922 select the host link. 2513 select the host link. DEVICE number of 15 selects the
2923 host link and device 2514 host link and device attached to it.
2924 2515
2925 The VAL specifies the 2516 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2517 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2518 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2519 The following configurations can be forced.
2929 2520
2930 * Cable type: 40c, 80 2521 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2522 Any ID with matching PORT is used.
2932 2523
2933 * SATA link speed lim 2524 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2525
2935 * Transfer mode: pio[ 2526 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2527 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2528 allowed.
2938 2529
2939 * nohrst, nosrst, nor <<
2940 resets. <<
2941 <<
2942 * rstonce: only attem <<
2943 link recovery. <<
2944 <<
2945 * [no]dbdelay: Enable <<
2946 before debouncing a <<
2947 detection. <<
2948 <<
2949 * [no]ncq: Turn on or 2530 * [no]ncq: Turn on or off NCQ.
2950 2531
2951 * [no]ncqtrim: Enable !! 2532 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 <<
2953 * [no]ncqati: Enable <<
2954 <<
2955 * [no]trim: Enable or <<
2956 2533
2957 * trim_zero: Indicate !! 2534 * nohrst, nosrst, norst: suppress hard, soft
>> 2535 and both resets.
2958 2536
2959 * max_trim_128m: Set !! 2537 * rstonce: only attempt one reset during
>> 2538 hot-unplug link recovery
2960 2539
2961 * [no]dma: Turn on or !! 2540 * dump_id: dump IDENTIFY data.
2962 2541
2963 * atapi_dmadir: Enabl !! 2542 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2964 <<
2965 * atapi_mod16_dma: En <<
2966 commands that are n <<
2967 <<
2968 * [no]dmalog: Enable <<
2969 READ LOG DMA EXT co <<
2970 <<
2971 * [no]iddevlog: Enabl <<
2972 identify device dat <<
2973 <<
2974 * [no]logdir: Enable <<
2975 purpose log directo <<
2976 <<
2977 * max_sec_128: Set tr <<
2978 <<
2979 * max_sec_1024: Set o <<
2980 1024 sectors. <<
2981 <<
2982 * max_sec_lba48: Set <<
2983 65535 sectors. <<
2984 <<
2985 * [no]lpm: Enable or <<
2986 <<
2987 * [no]setxfer: Indica <<
2988 should be skipped. <<
2989 <<
2990 * [no]fua: Disable or <<
2991 support for devices <<
2992 <<
2993 * dump_id: Dump IDENT <<
2994 2543
2995 * disable: Disable th 2544 * disable: Disable this device.
2996 2545
2997 If there are multiple 2546 If there are multiple matching configurations changing
2998 the same attribute, t 2547 the same attribute, the last one is used.
2999 2548
>> 2549 memblock=debug [KNL] Enable memblock debug messages.
>> 2550
3000 load_ramdisk= [RAM] [Deprecated] 2551 load_ramdisk= [RAM] [Deprecated]
3001 2552
3002 lockd.nlm_grace_period=P [NFS] Assig 2553 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2554 Format: <integer>
3004 2555
3005 lockd.nlm_tcpport=N [NFS] Assign 2556 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2557 Format: <integer>
3007 2558
3008 lockd.nlm_timeout=T [NFS] Assign 2559 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2560 Format: <integer>
3010 2561
3011 lockd.nlm_udpport=M [NFS] Assign 2562 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2563 Format: <integer>
3013 2564
3014 lockdown= [SECURITY,EARLY] !! 2565 lockdown= [SECURITY]
3015 { integrity | confide 2566 { integrity | confidentiality }
3016 Enable the kernel loc 2567 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2568 integrity, kernel features that allow userland to
3018 modify the running ke 2569 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2570 confidentiality, kernel features that allow userland
3020 to extract confidenti 2571 to extract confidential information from the kernel
3021 are also disabled. 2572 are also disabled.
3022 2573
3023 locktorture.acq_writer_lim= [KNL] <<
3024 Set the time limit in <<
3025 acquisition. Acquisi <<
3026 will result in a spla <<
3027 <<
3028 locktorture.bind_readers= [KNL] <<
3029 Specify the list of C <<
3030 to be bound. <<
3031 <<
3032 locktorture.bind_writers= [KNL] <<
3033 Specify the list of C <<
3034 to be bound. <<
3035 <<
3036 locktorture.call_rcu_chains= [KNL] <<
3037 Specify the number of <<
3038 chains to set up. Th <<
3039 there is a high proba <<
3040 in progress at any gi <<
3041 which disables these <<
3042 <<
3043 locktorture.long_hold= [KNL] <<
3044 Specify the duration <<
3045 occasional long-durat <<
3046 to 100 milliseconds. <<
3047 <<
3048 locktorture.nested_locks= [KNL] <<
3049 Specify the maximum l <<
3050 locktorture is to exe <<
3051 (MAX_NESTED_LOCKS). <<
3052 Note that this parame <<
3053 of locks that do not <<
3054 <<
3055 locktorture.nreaders_stress= [KNL] 2574 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2575 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2576 Defaults to being automatically set based on the
3058 number of online CPUs 2577 number of online CPUs.
3059 2578
3060 locktorture.nwriters_stress= [KNL] 2579 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2580 Set the number of locking write-acquisition kthreads.
3062 2581
3063 locktorture.onoff_holdoff= [KNL] 2582 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2583 Set time (s) after boot for CPU-hotplug testing.
3065 2584
3066 locktorture.onoff_interval= [KNL] 2585 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2586 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2587 zero to disable CPU-hotplug testing.
3069 2588
3070 locktorture.rt_boost= [KNL] <<
3071 Do periodic testing o <<
3072 boosting. Select 0 t <<
3073 only rt_mutex, and 2 <<
3074 Defaults to 2, which <<
3075 odd choice, but which <<
3076 non-real-time spinloc <<
3077 of preemption. Note <<
3078 disable boosting. <<
3079 <<
3080 locktorture.rt_boost_factor= [KNL] <<
3081 Number that determine <<
3082 long priority boostin <<
3083 scaled down by the nu <<
3084 number of boosts per <<
3085 constant as the numbe <<
3086 On the other hand, th <<
3087 increases with the nu <<
3088 <<
3089 locktorture.shuffle_interval= [KNL] 2589 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2590 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2591 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2592 mode during the locktorture test.
3093 2593
3094 locktorture.shutdown_secs= [KNL] 2594 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2595 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2596 is useful for hands-off automated testing.
3097 2597
3098 locktorture.stat_interval= [KNL] 2598 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2599 Time (s) between statistics printk()s.
3100 2600
3101 locktorture.stutter= [KNL] 2601 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2602 Time (s) to stutter testing, for example,
3103 specifying five secon 2603 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2604 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2605 This tests the locking primitive's ability to
3106 transition abruptly t 2606 transition abruptly to and from idle.
3107 2607
3108 locktorture.torture_type= [KNL] 2608 locktorture.torture_type= [KNL]
3109 Specify the locking i 2609 Specify the locking implementation to test.
3110 2610
3111 locktorture.verbose= [KNL] 2611 locktorture.verbose= [KNL]
3112 Enable additional pri 2612 Enable additional printk() statements.
3113 2613
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2614 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2615 Format: <irq>
3120 2616
3121 loglevel= [KNL,EARLY] !! 2617 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2618 console loglevel will be printed to the console. It can
3124 also be changed with 2619 also be changed with klogd or other programs. The
3125 loglevels are defined 2620 loglevels are defined as follows:
3126 2621
3127 0 (KERN_EMERG) 2622 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2623 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2624 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2625 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2626 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2627 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2628 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2629 7 (KERN_DEBUG) debug-level messages
3135 2630
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2631 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2632 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2633 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2634 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2635 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2636 that allows to increase the default size depending on
3142 parameter that allows !! 2637 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2638
3146 logo.nologo [FB] Disables display 2639 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2640 This may be used to provide more screen space for
3148 kernel log messages a 2641 kernel log messages and is useful when debugging
3149 kernel boot problems. 2642 kernel boot problems.
3150 2643
3151 lp=0 [LP] Specify paral 2644 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2645 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2646 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2647 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2648 specified in addition to the ports) causes
3156 attached prin 2649 attached printers to be reset. Using
3157 lp=port1,port 2650 lp=port1,port2,... specifies the parallel ports
3158 to associate 2651 to associate lp devices with, starting with
3159 lp0. A port s 2652 lp0. A port specification may be 'none' to skip
3160 that lp devic 2653 that lp device, or a parport name such as
3161 'parport0'. S 2654 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2655 port specification list means that device IDs
3163 from each por 2656 from each port should be examined, to see if
3164 an IEEE 1284- 2657 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2658 so, the driver will manage that printer.
3166 See also head 2659 See also header of drivers/char/lp.c.
3167 2660
3168 lpj=n [KNL] 2661 lpj=n [KNL]
3169 Sets loops_per_jiffy 2662 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2663 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2664 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2665 the correct value for your kernel, boot with normal
3173 autodetection and see 2666 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2667 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2668 which is likely to cause problems if your CPUs need
3176 significantly diverge 2669 significantly divergent settings. An incorrect value
3177 will cause delays in 2670 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2671 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2672 unlikely, in the extreme case this might damage your
3180 hardware. 2673 hardware.
3181 2674
>> 2675 ltpc= [NET]
>> 2676 Format: <io>,<irq>,<dma>
>> 2677
3182 lsm.debug [SECURITY] Enable LSM 2678 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2679
3184 lsm=lsm1,...,lsmN 2680 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2681 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2682 overrides CONFIG_LSM, and the "security=" parameter.
3187 2683
>> 2684 machvec= [IA-64] Force the use of a particular machine-vector
>> 2685 (machvec) in a generic kernel.
>> 2686 Example: machvec=hpzx1
>> 2687
3188 machtype= [Loongson] Share the 2688 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2689 different yeeloong laptops.
3190 Example: machtype=lem 2690 Example: machtype=lemote-yeeloong-2f-7inch
3191 2691
3192 maxcpus= [SMP,EARLY] Maximum n !! 2692 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2693 than or equal to this physical address is ignored.
>> 2694
>> 2695 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2696 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2697 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2698 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2699 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2700 only takes effect during system bootup.
3198 While n=0 is a specia 2701 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2702 which also disables the IO APIC.
3200 2703
3201 max_loop= [LOOP] The number of 2704 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2705 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2706 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2707 of statically allocating a predefined number, loop
3205 devices can be reques 2708 devices can be requested on-demand with the
3206 /dev/loop-control int 2709 /dev/loop-control interface.
3207 2710
3208 mce [X86-32] Machine Chec 2711 mce [X86-32] Machine Check Exception
3209 2712
3210 mce=option [X86-64] See Document !! 2713 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2714
3212 md= [HW] RAID subsystems 2715 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2716 See Documentation/admin-guide/md.rst.
3214 2717
3215 mdacon= [MDA] 2718 mdacon= [MDA]
3216 Format: <first>,<last 2719 Format: <first>,<last>
3217 Specifies range of co 2720 Specifies range of consoles to be captured by the MDA.
3218 2721
3219 mds= [X86,INTEL,EARLY] !! 2722 mds= [X86,INTEL]
3220 Control mitigation fo 2723 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2724 Sampling (MDS) vulnerability.
3222 2725
3223 Certain CPUs are vuln 2726 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2727 internal buffers which can forward information to a
3225 disclosure gadget und 2728 disclosure gadget under certain conditions.
3226 2729
3227 In vulnerable process 2730 In vulnerable processors, the speculatively
3228 forwarded data can be 2731 forwarded data can be used in a cache side channel
3229 attack, to access dat 2732 attack, to access data to which the attacker does
3230 not have direct acces 2733 not have direct access.
3231 2734
3232 This parameter contro 2735 This parameter controls the MDS mitigation. The
3233 options are: 2736 options are:
3234 2737
3235 full - Enable M 2738 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2739 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2740 SMT on vulnerable CPUs
3238 off - Uncondit 2741 off - Unconditionally disable MDS mitigation
3239 2742
3240 On TAA-affected machi 2743 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2744 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2745 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2746 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2747 too.
3245 2748
3246 Not specifying this o 2749 Not specifying this option is equivalent to
3247 mds=full. 2750 mds=full.
3248 2751
3249 For details see: Docu 2752 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2753
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2754 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3252 Must be specified, ot !! 2755 Amount of memory to be used in cases as follows:
3253 <<
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc <<
3255 of memory Amount of m <<
3256 as follows: <<
3257 2756
3258 1 for test; 2757 1 for test;
3259 2 when the kernel is 2758 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 2759 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 2760 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory <<
3263 <<
3264 [ARC,MICROBLAZE] - th <<
3265 high memory is not af <<
3266 <<
3267 [ARM64] - only limits <<
3268 mapping. The NOMAP re <<
3269 2761
3270 [X86] Work as limitin 2762 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2763 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2764 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2765 belonging to unused RAM.
3274 2766
3275 Note that this only t 2767 Note that this only takes effects during boot time since
3276 in above case 3, memo 2768 in above case 3, memory may need be hot added after boot
3277 if system memory of h 2769 if system memory of hypervisor is not sufficient.
3278 2770
3279 mem=nn[KMG]@ss[KMG] <<
3280 [ARM,MIPS,EARLY] - ov <<
3281 reported by firmware. <<
3282 Define a memory regio <<
3283 ss[KMG]. <<
3284 Multiple different re <<
3285 multiple mem= paramet <<
3286 <<
3287 mem=nopentium [BUGS=X86-32] Disable 2771 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2772 memory.
3289 2773
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2774 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2775 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2776 per-device physically contiguous DMA buffers.
3295 2777
3296 memhp_default_state=online/offline/on !! 2778 memhp_default_state=online/offline
3297 [KNL] Set the initial 2779 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2780 onlining policy. If not specified, the default value is
3299 set according to the 2781 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2782 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2783 option.
3302 See Documentation/adm 2784 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 2785
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2786 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2787 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2788 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2789 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2790 option description.
3309 2791
3310 memmap=nn[KMG]@ss[KMG] 2792 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2793 [KNL] Force usage of a specific region of memory.
3312 Region of memory to b 2794 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2795 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2796 which limits max address to nn[KMG].
3315 Multiple different re 2797 Multiple different regions can be specified,
3316 comma delimited. 2798 comma delimited.
3317 Example: 2799 Example:
3318 memmap=100M@2 2800 memmap=100M@2G,100M#3G,1G!1024G
3319 2801
3320 memmap=nn[KMG]#ss[KMG] 2802 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2803 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2804 Region of memory to be marked is from ss to ss+nn.
3323 2805
3324 memmap=nn[KMG]$ss[KMG] 2806 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2807 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2808 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2809 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2810 memmap=64K$0x18690000
3329 or 2811 or
3330 memmap=0x100 2812 memmap=0x10000$0x18690000
3331 Some bootloaders may 2813 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2814 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2815 will be eaten.
3334 2816
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2817 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2818 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2819 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2820 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2821 and is NVDIMM or ADR memory.
3340 2822
3341 memmap=<size>%<offset>-<oldtype>+<new 2823 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 2824 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 2825 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 2826 out, the whole region will be marked as <newtype>,
3345 even if previously un 2827 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 2828 out, matching memory will be removed. Types are
3347 specified as e820 typ 2829 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 2830 3 = ACPI, 12 = PRAM.
3349 2831
3350 memory_corruption_check=0/1 [X86,EARL !! 2832 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 2833 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2834 memory when doing things like suspend/resume.
3353 Setting this option w 2835 Setting this option will scan the memory
3354 looking for corruptio 2836 looking for corruption. Enabling this will
3355 both detect corruptio 2837 both detect corruption and prevent the kernel
3356 from using the memory 2838 from using the memory being corrupted.
3357 However, its intended 2839 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2840 repeatable BIOS-originated corruption always
3359 affects the same memo 2841 affects the same memory, you can use memmap=
3360 to prevent the kernel 2842 to prevent the kernel from using that memory.
3361 2843
3362 memory_corruption_check_size=size [X8 !! 2844 memory_corruption_check_size=size [X86]
3363 By default it checks 2845 By default it checks for corruption in the low
3364 64k, making this memo 2846 64k, making this memory unavailable for normal
3365 use. Use this parame 2847 use. Use this parameter to scan for
3366 corruption in more or 2848 corruption in more or less memory.
3367 2849
3368 memory_corruption_check_period=second !! 2850 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2851 By default it checks for corruption every 60
3370 seconds. Use this pa 2852 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2853 other rate. 0 disables periodic checking.
3372 2854
3373 memory_hotplug.memmap_on_memory !! 2855 memtest= [KNL,X86,ARM,PPC] Enable memtest
3374 [KNL,X86,ARM] Boolean <<
3375 Format: {on | off (de <<
3376 When enabled, runtime <<
3377 allocate its internal <<
3378 those vmemmap pages c <<
3379 if hugetlb_free_vmemm <<
3380 hotadded memory which <<
3381 lot of memory without <<
3382 memory to do so. <<
3383 This feature is disab <<
3384 has some implication <<
3385 allocations in some c <<
3386 memory blocks). <<
3387 The state of the flag <<
3388 /sys/module/memory_ho <<
3389 Note that even when e <<
3390 the feature is not ef <<
3391 <<
3392 memtest= [KNL,X86,ARM,M68K,PPC <<
3393 Format: <integer> 2856 Format: <integer>
3394 default : 0 <disable> 2857 default : 0 <disable>
3395 Specifies the number 2858 Specifies the number of memtest passes to be
3396 performed. Each pass 2859 performed. Each pass selects another test
3397 pattern from a given 2860 pattern from a given set of patterns. Memtest
3398 fills the memory with 2861 fills the memory with this pattern, validates
3399 memory contents and r 2862 memory contents and reserves bad memory
3400 regions that are dete 2863 regions that are detected.
3401 2864
3402 mem_encrypt= [X86-64] AMD Secure M 2865 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2866 Valid arguments: on, off
3404 Default: off !! 2867 Default (depends on kernel configuration option):
>> 2868 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2869 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2870 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2871 mem_encrypt=off: Do not activate SME
3407 2872
3408 Refer to Documentatio !! 2873 Refer to Documentation/virt/kvm/amd-memory-encryption.rst
3409 for details on when m 2874 for details on when memory encryption can be activated.
3410 2875
3411 mem_sleep_default= [SUSPEND] Def 2876 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2877 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2878 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2879 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 2880 See Documentation/admin-guide/pm/sleep-states.rst.
3416 2881
>> 2882 meye.*= [HW] Set MotionEye Camera parameters
>> 2883 See Documentation/admin-guide/media/meye.rst.
>> 2884
>> 2885 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2886 Multi-Function General Purpose Timers on AMD Geode
>> 2887 platforms.
>> 2888
3417 mfgptfix [X86-32] Fix MFGPT ti 2889 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2890 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2891 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2892 problem by letting the user disable the workaround.
3421 2893
3422 mga= [HW,DRM] 2894 mga= [HW,DRM]
3423 2895
3424 microcode.force_minrev= [X86] !! 2896 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2897 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2898
3429 mini2440= [ARM,HW,KNL] 2899 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2900 Format:[0..2][b][c][t]
3431 Default: "0tb" 2901 Default: "0tb"
3432 MINI2440 configuratio 2902 MINI2440 configuration specification:
3433 0 - The attached scre 2903 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2904 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2905 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2906 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2907 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2908 unconfigured.
3439 b - Enable backlight. 2909 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2910 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2911 LED. This parameter is not necessary when using the
3442 VGA shield. 2912 VGA shield.
3443 c - Enable the s3c ca 2913 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2914 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2915 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2916 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2917 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 2918 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 2919
3450 mitigations= 2920 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 2921 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 2922 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 2923 arch-independent options, each of which is an
3454 aggregation of existi 2924 aggregation of existing arch-specific options.
3455 2925
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 2926 off
3460 Disable all o 2927 Disable all optional CPU mitigations. This
3461 improves syst 2928 improves system performance, but it may also
3462 expose users 2929 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 2930 Equivalent to: gather_data_sampling=off [X86]
3464 !! 2931 kpti=0 [ARM64]
3465 2932 kvm.nx_huge_pages=off [X86]
3466 2933 l1tf=off [X86]
3467 2934 mds=off [X86]
3468 2935 mmio_stale_data=off [X86]
3469 2936 no_entry_flush [PPC]
3470 2937 no_uaccess_flush [PPC]
3471 2938 nobp=0 [S390]
3472 2939 nopti [X86,PPC]
3473 <<
3474 2940 nospectre_v1 [X86,PPC]
3475 2941 nospectre_v2 [X86,PPC,S390,ARM64]
3476 2942 reg_file_data_sampling=off [X86]
3477 2943 retbleed=off [X86]
3478 <<
3479 2944 spec_store_bypass_disable=off [X86,PPC]
3480 <<
3481 2945 spectre_v2_user=off [X86]
3482 <<
3483 2946 ssbd=force-off [ARM64]
3484 2947 tsx_async_abort=off [X86]
3485 2948
3486 Exceptions: 2949 Exceptions:
3487 2950 This does not have any effect on
3488 2951 kvm.nx_huge_pages when
3489 2952 kvm.nx_huge_pages=force.
3490 2953
3491 auto (default) 2954 auto (default)
3492 Mitigate all 2955 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 2956 enabled, even if it's vulnerable. This is for
3494 users who don 2957 users who don't want to be surprised by SMT
3495 getting disab 2958 getting disabled across kernel upgrades, or who
3496 have other wa 2959 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 2960 Equivalent to: (default behavior)
3498 2961
3499 auto,nosmt 2962 auto,nosmt
3500 Mitigate all 2963 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 2964 if needed. This is for users who always want to
3502 be fully miti 2965 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 2966 Equivalent to: l1tf=flush,nosmt [X86]
3504 2967 mds=full,nosmt [X86]
3505 2968 tsx_async_abort=full,nosmt [X86]
3506 2969 mmio_stale_data=full,nosmt [X86]
3507 2970 retbleed=auto,nosmt [X86]
3508 2971
3509 mminit_loglevel= 2972 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 2973 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 2974 parameter allows control of the logging verbosity for
3512 the additional memory 2975 the additional memory initialisation checks. A value
3513 of 0 disables mminit 2976 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 2977 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 2978 so loglevel=8 may also need to be specified.
3516 2979
3517 mmio_stale_data= 2980 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 2981 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 2982 MMIO Stale Data vulnerabilities.
3520 2983
3521 Processor MMIO Stale 2984 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 2985 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 2986 operation. Exposed data could originate or end in
3524 the same CPU buffers 2987 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 2988 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 2989 is to clear the affected CPU buffers.
3527 2990
3528 This parameter contro 2991 This parameter controls the mitigation. The
3529 options are: 2992 options are:
3530 2993
3531 full - Enable m 2994 full - Enable mitigation on vulnerable CPUs
3532 2995
3533 full,nosmt - Enable m 2996 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 2997 vulnerable CPUs.
3535 2998
3536 off - Uncondit 2999 off - Unconditionally disable mitigation
3537 3000
3538 On MDS or TAA affecte 3001 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 3002 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 3003 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 3004 mitigated with the same mechanism so in order to
3542 disable this mitigati 3005 disable this mitigation, you need to specify
3543 mds=off and tsx_async 3006 mds=off and tsx_async_abort=off too.
3544 3007
3545 Not specifying this o 3008 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 3009 mmio_stale_data=full.
3547 3010
3548 For details see: 3011 For details see:
3549 Documentation/admin-g 3012 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 3013
3551 <module>.async_probe[=<bool>] [KNL] <<
3552 If no <bool> value is <<
3553 specified is not a va <<
3554 probe on this module. <<
3555 asynchronous probe on <<
3556 <bool> value. See als <<
3557 <<
3558 module.async_probe=<bool> <<
3559 [KNL] When set to tru <<
3560 by default. To enable <<
3561 specific module, use <<
3562 is documented under < <<
3563 module.async_probe an <<
3564 specified, <module>.a <<
3565 the specific module. <<
3566 <<
3567 module.enable_dups_trace <<
3568 [KNL] When CONFIG_MOD <<
3569 this means that dupli <<
3570 trigger a WARN_ON() i <<
3571 if MODULE_DEBUG_AUTOL <<
3572 will always be issued <<
3573 module.sig_enforce 3014 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3015 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3016 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3017 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3018 is always true, so this option does nothing.
3578 3019
3579 module_blacklist= [KNL] Do not load 3020 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3021 modules. Useful for debugging problem modules.
3581 3022
3582 mousedev.tap_time= 3023 mousedev.tap_time=
3583 [MOUSE] Maximum time 3024 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3025 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3026 a tap and be reported as a left button click (for
3586 touchpads working in 3027 touchpads working in absolute mode only).
3587 Format: <msecs> 3028 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3029 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3030 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3031 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3032 reporting absolute coordinates, such as tablets
3592 3033
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3034 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3035 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3036 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3037 specifies the amount of memory used for migratable
3597 allocations. If both 3038 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3039 specified, then kernelcore will be at *least* the
3599 specified value but m 3040 specified value but may be more. If movablecore on its
3600 own is specified, the 3041 own is specified, the administrator must be careful
3601 that the amount of me 3042 that the amount of memory usable for all allocations
3602 is not too small. 3043 is not too small.
3603 3044
3604 movable_node [KNL,EARLY] Boot-time !! 3045 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3046 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3047 of such nodes will be usable only for movable
3607 allocations which rul 3048 allocations which rules out almost all kernel
3608 allocations. Use with 3049 allocations. Use with caution!
3609 3050
3610 MTD_Partition= [MTD] 3051 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3052 Format: <name>,<region-number>,<size>,<offset>
3612 3053
3613 MTD_Region= [MTD] Format: 3054 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3055 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3056
3616 mtdparts= [MTD] 3057 mtdparts= [MTD]
3617 See drivers/mtd/parse 3058 See drivers/mtd/parsers/cmdlinepart.c
3618 3059
>> 3060 multitce=off [PPC] This parameter disables the use of the pSeries
>> 3061 firmware feature for updating multiple TCE entries
>> 3062 at a time.
>> 3063
>> 3064 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 3065
>> 3066 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 3067
>> 3068 boundary - index of last SLC block on Flex-OneNAND.
>> 3069 The remaining blocks are configured as MLC blocks.
>> 3070 lock - Configure if Flex-OneNAND boundary should be locked.
>> 3071 Once locked, the boundary cannot be changed.
>> 3072 1 indicates lock status, 0 indicates unlock status.
>> 3073
>> 3074 mtdset= [ARM]
>> 3075 ARM/S3C2412 JIVE boot control
>> 3076
>> 3077 See arch/arm/mach-s3c2412/mach-jive.c
>> 3078
3619 mtouchusb.raw_coordinates= 3079 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3080 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3081 ('y', default) or cooked coordinates ('n')
3622 3082
3623 mtrr=debug [X86,EARLY] !! 3083 mtrr_chunk_size=nn[KMG] [X86]
3624 Enable printing debug <<
3625 registers at boot tim <<
3626 <<
3627 mtrr_chunk_size=nn[KMG,X86,EARLY] <<
3628 used for mtrr cleanup 3084 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3085 that could hold holes aka. UC entries.
3630 3086
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3087 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3088 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3089 Default is 1.
3634 Large value could pre 3090 Large value could prevent small alignment from
3635 using up MTRRs. 3091 using up MTRRs.
3636 3092
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3093 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3094 Format: <integer>
3639 Range: 0,7 : spare re 3095 Range: 0,7 : spare reg number
3640 Default : 1 3096 Default : 1
3641 Used for mtrr cleanup 3097 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3098 Set to 2 or more if your graphical card needs more.
3643 3099
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 3100 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3101
3650 netdev= [NET] Network devices 3102 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3103 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3104 Note that mem_start is often overloaded to mean
3653 something different a 3105 something different and driver-specific.
3654 This usage is only do 3106 This usage is only documented in each driver source
3655 file if at all. 3107 file if at all.
3656 3108
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 3109 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3110 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3111 0 to disable accounting
3665 1 to enable accountin 3112 1 to enable accounting
3666 Default value is 0. 3113 Default value is 0.
3667 3114
3668 nfs.cache_getent= !! 3115 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3116 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3117
3672 nfs.cache_getent_timeout= !! 3118 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3119 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3120
>> 3121 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3122 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3123
3676 nfs.callback_nr_threads= 3124 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3125 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3126 NFS client will assign to service NFSv4 callback
3679 requests. 3127 requests.
3680 3128
3681 nfs.callback_tcpport= 3129 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3130 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3131 channel should listen.
3684 3132
3685 nfs.delay_retrans= !! 3133 nfs.cache_getent=
3686 [NFS] specifies the n !! 3134 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3135 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3136
3689 Only applies if the s !! 3137 nfs.cache_getent_timeout=
3690 and the specified val !! 3138 [NFS] sets the timeout after which an attempt to
>> 3139 update a cache entry is deemed to have failed.
>> 3140
>> 3141 nfs.idmap_cache_timeout=
>> 3142 [NFS] set the maximum lifetime for idmapper cache
>> 3143 entries.
3691 3144
3692 nfs.enable_ino64= 3145 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3146 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3147 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3148 number for the readdir() and stat() syscalls instead
3696 of returning the full 3149 of returning the full 64-bit number.
3697 The default is to ret 3150 The default is to return 64-bit inode numbers.
3698 3151
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3152 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3153 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3154 slots the client will assign to the callback
3706 channel. This determi 3155 channel. This determines the maximum number of
3707 callbacks the client 3156 callbacks the client will process in parallel for
3708 a particular server. 3157 a particular server.
3709 3158
3710 nfs.max_session_slots= 3159 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3160 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3161 the client will attempt to negotiate with the server.
3713 This limits the numbe 3162 This limits the number of simultaneous RPC requests
3714 that the client can s 3163 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3164 Note that there is little point in setting this
3716 value higher than the 3165 value higher than the max_tcp_slot_table_limit.
3717 3166
3718 nfs.nfs4_disable_idmapping= 3167 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3168 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3169 ensures that both the RPC level authentication
3721 scheme and the NFS le 3170 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3171 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3172 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3173 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3174 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3175 Servers that do not support this mode of operation
3727 will be autodetected 3176 will be autodetected by the client, and it will fall
3728 back to using the idm 3177 back to using the idmapper.
3729 To turn off this beha 3178 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3179 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3180 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3181 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3182 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3183 UUID that is generated at system install time.
3736 3184
3737 nfs.recover_lost_locks= !! 3185 nfs.send_implementation_id =
>> 3186 [NFSv4.1] Send client implementation identification
>> 3187 information in exchange_id requests.
>> 3188 If zero, no implementation identification information
>> 3189 will be sent.
>> 3190 The default is to send the implementation identification
>> 3191 information.
>> 3192
>> 3193 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3194 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3195 to a lease timeout on the server. Please note that
3740 doing this risks data 3196 doing this risks data corruption, since there are
3741 no guarantees that th 3197 no guarantees that the file will remain unchanged
3742 after the locks are l 3198 after the locks are lost.
3743 If you want to enable 3199 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3200 attempting to recover these locks, then set this
3745 parameter to '1'. 3201 parameter to '1'.
3746 The default parameter 3202 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3203 not to attempt recovery of lost locks.
3748 3204
3749 nfs.send_implementation_id= !! 3205 nfs4.layoutstats_timer =
3750 [NFSv4.1] Send client <<
3751 information in exchan <<
3752 If zero, no implement <<
3753 will be sent. <<
3754 The default is to sen <<
3755 information. <<
3756 <<
3757 nfs4.layoutstats_timer= <<
3758 [NFSv4.2] Change the 3206 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3207 layoutstats to the pNFS metadata server.
3760 3208
3761 Setting this to value 3209 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3210 whatever value is the default set by the layout
3763 driver. A non-zero va 3211 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3212 in seconds between layoutstats transmissions.
3765 3213
3766 nfsd.inter_copy_offload_enable= <<
3767 [NFSv4.2] When set to <<
3768 server-to-server copi <<
3769 the destination of th <<
3770 <<
3771 nfsd.nfs4_disable_idmapping= 3214 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 3215 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 3216 server will return only numeric uids and gids to
3774 clients using auth_sy 3217 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 3218 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 3219 migration from NFSv2/v3.
3777 3220
3778 nfsd.nfsd4_ssc_umount_timeout= <<
3779 [NFSv4.2] When used a <<
3780 server-to-server copy <<
3781 the source server. I <<
3782 it will be needed aga <<
3783 used for the number o <<
3784 this parameter. <<
3785 <<
3786 nfsaddrs= [NFS] Deprecated. Us <<
3787 See Documentation/adm <<
3788 <<
3789 nfsroot= [NFS] nfs root filesy <<
3790 See Documentation/adm <<
3791 <<
3792 nfsrootdebug [NFS] enable nfsroot <<
3793 See Documentation/adm <<
3794 <<
3795 nmi_backtrace.backtrace_idle [KNL] 3221 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3222 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3223 NMI stack-backtrace request.
3798 3224
3799 nmi_debug= [KNL,SH] Specify one 3225 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3226 when a NMI is triggered.
3801 Format: [state][,regs 3227 Format: [state][,regs][,debounce][,die]
3802 3228
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3229 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3230 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3231 Valid num: 0 or 1
3806 0 - turn hardlockup d 3232 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3233 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3234 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3235 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3236 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3237 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3238 please see 'nowatchdog'.
3815 This is useful when y 3239 This is useful when you use a panic=... timeout and
3816 need the box quickly 3240 need the box quickly up again.
3817 3241
3818 These settings can be 3242 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3243 the nmi_watchdog and hardlockup_panic sysctls.
3820 3244
>> 3245 netpoll.carrier_timeout=
>> 3246 [NET] Specifies amount of time (in seconds) that
>> 3247 netpoll should wait for a carrier. By default netpoll
>> 3248 waits 4 seconds.
>> 3249
3821 no387 [BUGS=X86-32] Tells t 3250 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3251 emulation library even if a 387 maths coprocessor
3823 is present. 3252 is present.
3824 3253
3825 no4lvl [RISCV,EARLY] Disable !! 3254 no5lvl [X86-64] Disable 5-level paging mode. Forces
3826 Forces kernel to use <<
3827 <<
3828 no5lvl [X86-64,RISCV,EARLY] <<
3829 kernel to use 4-level 3255 kernel to use 4-level paging instead.
3830 3256
3831 noalign [KNL,ARM] !! 3257 nofsgsbase [X86] Disables FSGSBASE instructions.
3832 <<
3833 noapic [SMP,APIC,EARLY] Tell <<
3834 IOAPICs that may be p <<
3835 <<
3836 noautogroup Disable scheduler aut <<
3837 <<
3838 nocache [ARM,EARLY] <<
3839 3258
3840 no_console_suspend 3259 no_console_suspend
3841 [HW] Never suspend th 3260 [HW] Never suspend the console
3842 Disable suspending of 3261 Disable suspending of consoles during suspend and
3843 hibernate operations. 3262 hibernate operations. Once disabled, debugging
3844 messages can reach va 3263 messages can reach various consoles while the rest
3845 of the system is bein 3264 of the system is being put to sleep (ie, while
3846 debugging driver susp 3265 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3266 not work reliably with all consoles, but is known
3848 to work with serial a 3267 to work with serial and VGA consoles.
3849 To facilitate more fl 3268 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3269 console_suspend, a printk module parameter to control
3851 it. Users could use c 3270 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3271 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3272 turn on/off it dynamically.
3854 3273
3855 no_debug_objects !! 3274 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3275 Disable device dump. Device dump allows drivers to
>> 3276 append dump data to vmcore so you can collect driver
>> 3277 specified debug info. Drivers can append the data
>> 3278 without any limit and this data is stored in memory,
>> 3279 so this may cause significant memory stress. Disabling
>> 3280 device dump can help save memory but the driver debug
>> 3281 data will be no longer available. This parameter
>> 3282 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3283 is set.
>> 3284
>> 3285 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3286 caches in the slab allocator. Saves per-node memory,
>> 3287 but will impact performance.
>> 3288
>> 3289 noalign [KNL,ARM]
>> 3290
>> 3291 noaltinstr [S390] Disables alternative instructions patching
>> 3292 (CPU alternatives feature).
>> 3293
>> 3294 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3295 IOAPICs that may be present in the system.
>> 3296
>> 3297 noautogroup Disable scheduler automatic task group creation.
>> 3298
>> 3299 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 3300 on "Classic" PPC cores.
>> 3301
>> 3302 nocache [ARM]
>> 3303
>> 3304 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 3305
>> 3306 nodelayacct [KNL] Disable per-task delay accounting
3857 3307
3858 nodsp [SH] Disable hardware 3308 nodsp [SH] Disable hardware DSP at boot time.
3859 3309
3860 noefi [EFI,EARLY] Disable E !! 3310 noefi Disable EFI runtime services support.
3861 3311
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3312 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
>> 3313
>> 3314 noexec [IA-64]
>> 3315
>> 3316 noexec [X86]
>> 3317 On X86-32 available only on PAE configured kernels.
>> 3318 noexec=on: enable non-executable mappings (default)
>> 3319 noexec=off: disable non-executable mappings
>> 3320
>> 3321 nosmap [X86,PPC]
>> 3322 Disable SMAP (Supervisor Mode Access Prevention)
>> 3323 even if it is supported by processor.
>> 3324
>> 3325 nosmep [X86,PPC]
>> 3326 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3327 even if it is supported by processor.
3863 3328
3864 noexec32 [X86-64] 3329 noexec32 [X86-64]
3865 This affects only 32- 3330 This affects only 32-bit executables.
3866 noexec32=on: enable n 3331 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3332 read doesn't imply executable mappings
3868 noexec32=off: disable 3333 noexec32=off: disable non-executable mappings
3869 read implies 3334 read implies executable mappings
3870 3335
3871 no_file_caps Tells the kernel not <<
3872 only way then for a f <<
3873 is to be setuid root <<
3874 <<
3875 nofpu [MIPS,SH] Disable har 3336 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3337
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3338 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3339 register save and restore. The kernel will only save
3881 legacy floating-point 3340 legacy floating-point registers on task switch.
3882 3341
3883 no_hash_pointers !! 3342 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3884 [KNL,EARLY] <<
3885 Force pointers printe <<
3886 unhashed. By default <<
3887 format string, that p <<
3888 by hashing the pointe <<
3889 that hides actual ker <<
3890 users, but it also ma <<
3891 difficult since unequ <<
3892 compared. However, i <<
3893 specified, then all n <<
3894 value printed. This o <<
3895 debugging the kernel. <<
3896 kernels. <<
3897 3343
3898 nohibernate [HIBERNATION] Disable !! 3344 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3345 Equivalent to smt=1.
>> 3346
>> 3347 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3348 nosmt=force: Force disable SMT, cannot be undone
>> 3349 via the sysfs control file.
>> 3350
>> 3351 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3352 (bounds check bypass). With this option data leaks are
>> 3353 possible in the system.
>> 3354
>> 3355 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 3356 the Spectre variant 2 (indirect branch prediction)
>> 3357 vulnerability. System may allow data leaks with this
>> 3358 option.
>> 3359
>> 3360 nospec_store_bypass_disable
>> 3361 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3362
>> 3363 no_uaccess_flush
>> 3364 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3365
>> 3366 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3367 and restore using xsave. The kernel will fallback to
>> 3368 enabling legacy floating-point and sse state.
>> 3369
>> 3370 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3371 register states. The kernel will fall back to use
>> 3372 xsave to save the states. By using this parameter,
>> 3373 performance of saving the states is degraded because
>> 3374 xsave doesn't support modified optimization while
>> 3375 xsaveopt supports it on xsaveopt enabled systems.
>> 3376
>> 3377 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3378 restoring x86 extended register state in compacted
>> 3379 form of xsave area. The kernel will fall back to use
>> 3380 xsaveopt and xrstor to save and restore the states
>> 3381 in standard form of xsave area. By using this
>> 3382 parameter, xsave area per process might occupy more
>> 3383 memory on xsaves enabled systems.
>> 3384
>> 3385 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
>> 3386 wfi(ARM) instruction doesn't work correctly and not to
>> 3387 use it. This is also useful when using JTAG debugger.
3899 3388
3900 nohlt [ARM,ARM64,MICROBLAZE !! 3389 no_file_caps Tells the kernel not to honor file capabilities. The
3901 busy wait in do_idle( !! 3390 only way then for a file to be executed with privilege
3902 implementation; requi !! 3391 is to be setuid root or executed by root.
3903 to be effective. This <<
3904 sleep(SH) or wfi(ARM, <<
3905 correctly or when doi <<
3906 the impact of the sle <<
3907 useful when using JTA <<
3908 3392
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA !! 3393 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3394 function PAL_HALT_LIGHT when idle. This increases
>> 3395 power-consumption. On the positive side, it reduces
>> 3396 interrupt wake-up latency, which may improve performance
>> 3397 in certain environments such as networked servers or
>> 3398 real-time systems.
3910 3399
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA !! 3400 nohibernate [HIBERNATION] Disable hibernation and resume.
3912 3401
3913 nohz= [KNL] Boottime enable 3402 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3403 Valid arguments: on, off
3915 Default: on 3404 Default: on
3916 3405
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3406 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3407 The argument is a cpu list, as described above.
3919 In kernels built with 3408 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3409 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3410 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3411 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3412 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3413 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3414 rcu_nocbs= boot parameter.
3926 3415
3927 Note that this argume !! 3416 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 3417
>> 3418 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3419 disable unhandled interrupt sources.
>> 3420
>> 3421 no_timer_check [X86,APIC] Disables the code which tests for
>> 3422 broken timer IRQ sources.
>> 3423
>> 3424 noisapnp [ISAPNP] Disables ISA PnP code.
3929 3425
3930 noinitrd [RAM] Tells the kerne 3426 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3427 initial RAM disk.
3932 3428
3933 nointremap [X86-64,Intel-IOMMU,E !! 3429 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3430 remapping.
3935 [Deprecated - use int 3431 [Deprecated - use intremap=off]
3936 3432
3937 noinvpcid [X86,EARLY] Disable t !! 3433 nointroute [IA-64]
3938 <<
3939 noiotrap [SH] Disables trapped <<
3940 3434
3941 noirqdebug [X86-32] Disables the !! 3435 noinvpcid [X86] Disable the INVPCID cpu feature.
3942 disable unhandled int <<
3943 3436
3944 noisapnp [ISAPNP] Disables ISA !! 3437 nojitter [IA-64] Disables jitter checking for ITC timers.
3945 3438
3946 nokaslr [KNL,EARLY] !! 3439 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 3440
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3441 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3442 fault handling.
3953 3443
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3444 no-vmw-sched-clock
>> 3445 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3446 clock and use the default one.
3955 3447
3956 nolapic [X86-32,APIC,EARLY] D !! 3448 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
>> 3449 accounting. steal time is computed, but won't
>> 3450 influence scheduler behaviour
3957 3451
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3452 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3959 3453
3960 nomce [X86-32] Disable Mach !! 3454 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3961 3455
3962 nomfgpt [X86-32] Disable Mult !! 3456 noltlbs [PPC] Do not use large page/tlb entries for kernel
3963 Timer usage (for AMD !! 3457 lowmem mapping on PPC40x and PPC8xx
3964 3458
3965 nomodeset Disable kernel modese !! 3459 nomca [IA-64] Disable machine check abort handling
3966 sets up a display mod <<
3967 for output. With nomo <<
3968 not load if they coul <<
3969 initialized output. O <<
3970 be available for use. <<
3971 perform display-mode <<
3972 3460
3973 Useful as error fallb !! 3461 nomce [X86-32] Disable Machine Check Exception
3974 3462
3975 nomodule Disable module load !! 3463 nomfgpt [X86-32] Disable Multi-Function General Purpose
>> 3464 Timer usage (for AMD Geode machines).
3976 3465
3977 nonmi_ipi [X86] Disable using N 3466 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3467 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3468 irq.
3980 3469
3981 nopat [X86,EARLY] Disable P !! 3470 nomodule Disable module load
3982 pagetables) support. <<
3983 <<
3984 nopcid [X86-64,EARLY] Disabl <<
3985 <<
3986 nopku [X86] Disable Memory <<
3987 in some Intel CPUs. <<
3988 <<
3989 nopti [X86-64,EARLY] <<
3990 Equivalent to pti=off <<
3991 3471
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3472 nopat [X86] Disable PAT (page attribute table extension of
3993 Disables the PV optim !! 3473 pagetables) support.
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 3474
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3475 nopcid [X86-64] Disable the PCID cpu feature.
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3476
4002 norandmaps Don't use address spa 3477 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3478 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3479
4005 noreplace-smp [X86-32,SMP] Don't re 3480 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3481 with UP alternatives
4007 3482
>> 3483 nordrand [X86] Disable kernel use of the RDRAND and
>> 3484 RDSEED instructions even if they are supported
>> 3485 by the processor. RDRAND and RDSEED are still
>> 3486 available to user space applications.
>> 3487
4008 noresume [SWSUSP] Disables res 3488 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3489 space.
4010 3490
4011 no-scroll [VGA] Disables scroll 3491 no-scroll [VGA] Disables scrollback.
4012 This is required for 3492 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3493 reader made by F.H. Papenmeier (Germany).
4014 3494
4015 nosgx [X86-64,SGX,EARLY] Di !! 3495 nosbagart [IA-64]
4016 3496
4017 nosmap [PPC,EARLY] !! 3497 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 <<
4021 nosmep [PPC64s,EARLY] <<
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 3498
4025 nosmp [SMP,EARLY] Tells an !! 3499 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3500 and disable the IO APIC. legacy for "maxcpus=0".
4027 3501
4028 nosmt [KNL,MIPS,PPC,S390,EA <<
4029 Equivalent to smt=1. <<
4030 <<
4031 [KNL,X86,PPC] Disable <<
4032 nosmt=force: Force di <<
4033 via the <<
4034 <<
4035 nosoftlockup [KNL] Disable the sof 3502 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3503
4037 nospec_store_bypass_disable <<
4038 [HW,EARLY] Disable al <<
4039 Store Bypass vulnerab <<
4040 <<
4041 nospectre_bhb [ARM64,EARLY] Disable <<
4042 history injection) vu <<
4043 with this option. <<
4044 <<
4045 nospectre_v1 [X86,PPC,EARLY] Disab <<
4046 (bounds check bypass) <<
4047 possible in the syste <<
4048 <<
4049 nospectre_v2 [X86,PPC_E500,ARM64,E <<
4050 for the Spectre varia <<
4051 prediction) vulnerabi <<
4052 leaks with this optio <<
4053 <<
4054 no-steal-acc [X86,PV_OPS,ARM64,PPC <<
4055 Disable paravirtualiz <<
4056 is computed, but won' <<
4057 <<
4058 nosync [HW,M68K] Disables sy 3504 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3505
4060 no_timer_check [X86,APIC] Disables t <<
4061 broken timer IRQ sour <<
4062 <<
4063 no_uaccess_flush <<
4064 [PPC,EARLY] Don't flu <<
4065 <<
4066 novmcoredd [KNL,KDUMP] <<
4067 Disable device dump. <<
4068 append dump data to v <<
4069 specified debug info. <<
4070 without any limit and <<
4071 so this may cause sig <<
4072 device dump can help <<
4073 data will be no longe <<
4074 is only available whe <<
4075 is set. <<
4076 <<
4077 no-vmw-sched-clock <<
4078 [X86,PV_OPS,EARLY] Di <<
4079 scheduler clock and u <<
4080 <<
4081 nowatchdog [KNL] Disable both lo 3506 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3507 soft-lockup and NMI watchdog (hard-lockup).
4083 3508
4084 nowb [ARM,EARLY] !! 3509 nowb [ARM]
4085 <<
4086 nox2apic [X86-64,APIC,EARLY] D <<
4087 3510
4088 NOTE: this parameter !! 3511 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4089 LEGACY_XAPIC_DISABLED <<
4090 IA32_XAPIC_DISABLE_ST <<
4091 <<
4092 noxsave [BUGS=X86] Disables x <<
4093 and restore using xsa <<
4094 enabling legacy float <<
4095 3512
4096 noxsaveopt [X86] Disables xsaveo !! 3513 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4097 register states. The !! 3514 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4098 xsave to save the sta !! 3515 Some features depend on CPU0. Known dependencies are:
4099 performance of saving !! 3516 1. Resume from suspend/hibernate depends on CPU0.
4100 xsave doesn't support !! 3517 Suspend/hibernate will fail if CPU0 is offline and you
4101 xsaveopt supports it !! 3518 need to online CPU0 before suspend/hibernate.
>> 3519 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 3520 removed if a PIC interrupt is detected.
>> 3521 It's said poweroff/reboot may depend on CPU0 on some
>> 3522 machines although I haven't seen such issues so far
>> 3523 after CPU0 is offline on a few tested machines.
>> 3524 If the dependencies are under your control, you can
>> 3525 turn on cpu0_hotplug.
>> 3526
>> 3527 nps_mtm_hs_ctr= [KNL,ARC]
>> 3528 This parameter sets the maximum duration, in
>> 3529 cycles, each HW thread of the CTOP can run
>> 3530 without interruptions, before HW switches it.
>> 3531 The actual maximum duration is 16 times this
>> 3532 parameter's value.
>> 3533 Format: integer between 1 and 255
>> 3534 Default: 255
>> 3535
>> 3536 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3537 purges which is reported from either PAL_VM_SUMMARY or
>> 3538 SAL PALO.
4102 3539
4103 noxsaves [X86] Disables xsaves !! 3540 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4104 restoring x86 extende <<
4105 form of xsave area. T <<
4106 xsaveopt and xrstor t <<
4107 in standard form of x <<
4108 parameter, xsave area <<
4109 memory on xsaves enab <<
4110 <<
4111 nr_cpus= [SMP,EARLY] Maximum n <<
4112 could support. nr_cp 3541 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3542 support 'n' processors. It could be larger than the
4114 number of already plu 3543 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3544 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3545 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3546 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3547 hot plugging.
4119 3548
4120 nr_uarts= [SERIAL] maximum numb 3549 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3550
4122 numa=off [KNL, ARM64, PPC, RIS !! 3551 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
4123 Disable NUMA, Only se <<
4124 spanning all memory. <<
4125 <<
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, <<
4127 NUMA balancing. <<
4128 Allowed values are en 3552 Allowed values are enable and disable
4129 3553
4130 numa_zonelist_order= [KNL, BOOT] Sele 3554 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3555 'node', 'default' can be specified
4132 This can be set from 3556 This can be set from sysctl after boot.
4133 See Documentation/adm 3557 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3558
4135 ohci1394_dma=early [HW,EARLY] en !! 3559 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3560 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3561 info.
4138 3562
4139 olpc_ec_timeout= [OLPC] ms delay when 3563 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3564 Rather than timing out after 20 ms if an EC
4141 command is not proper 3565 command is not properly ACKed, override the length
4142 of the timeout. We h 3566 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3567 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3568 interrupts *may* be lost!
4145 3569
4146 omap_mux= [OMAP] Override bootl 3570 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3571 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3572 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3573 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3574
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 3575 oprofile.timer= [HW]
>> 3576 Use timer interrupt instead of performance counters
4152 3577
4153 Format: [die0_boundar !! 3578 oprofile.cpu_type= Force an oprofile cpu type
4154 !! 3579 This might be useful if you have an older oprofile
4155 boundary - index of l !! 3580 userland or if you want common events.
4156 The remain !! 3581 Format: { arch_perfmon }
4157 lock - Configure !! 3582 arch_perfmon: [X86] Force use of architectural
4158 Once locke !! 3583 perfmon on Intel CPUs instead of the
4159 1 indicate !! 3584 CPU specific event set.
>> 3585 timer: [X86] Force use of architectural NMI
>> 3586 timer mode (see also oprofile.timer
>> 3587 for generic hr timer mode)
4160 3588
4161 oops=panic [KNL,EARLY] !! 3589 oops=panic Always panic on oopses. Default is to just kill the
4162 Always panic on oopse <<
4163 process, but there is 3590 process, but there is a small probability of
4164 deadlocking the machi 3591 deadlocking the machine.
4165 This will also cause 3592 This will also cause panics on machine check exceptions.
4166 Useful together with 3593 Useful together with panic=30 to trigger a reboot.
4167 3594
4168 page_alloc.shuffle= 3595 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3596 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3597 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3598 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3599 running on a platform with a direct-mapped memory-side
>> 3600 cache, and this parameter can be used to
>> 3601 override/disable that behavior. The state of the flag
>> 3602 can be read from sysfs at:
4173 /sys/module/page_allo 3603 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3604
4176 page_owner= [KNL,EARLY] Boot-time !! 3605 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3606 Storage of the information about who allocated
4178 each page is disabled 3607 each page is disabled in default. With this switch,
4179 we can turn it on. 3608 we can turn it on.
4180 on: enable the featur 3609 on: enable the feature
4181 3610
4182 page_poison= [KNL,EARLY] Boot-time !! 3611 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3612 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3613 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3614 off: turn off poisoning (default)
4186 on: turn on poisoning 3615 on: turn on poisoning
4187 3616
4188 page_reporting.page_reporting_order= <<
4189 [KNL] Minimal page re <<
4190 Format: <integer> <<
4191 Adjust the minimal pa <<
4192 reporting is disabled <<
4193 <<
4194 panic= [KNL] Kernel behaviou 3617 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3618 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3619 timeout = 0: wait forever
4197 timeout < 0: reboot i 3620 timeout < 0: reboot immediately
4198 Format: <timeout> 3621 Format: <timeout>
4199 3622
4200 panic_on_taint= [KNL,EARLY] !! 3623 panic_print= Bitmask for printing system info when panic happens.
4201 Bitmask for condition !! 3624 User can chose combination of the following bits:
>> 3625 bit 0: print all tasks info
>> 3626 bit 1: print system memory info
>> 3627 bit 2: print timer info
>> 3628 bit 3: print locks info if CONFIG_LOCKDEP is on
>> 3629 bit 4: print ftrace buffer
>> 3630 bit 5: print all printk messages in buffer
>> 3631
>> 3632 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4202 Format: <hex>[,nouser 3633 Format: <hex>[,nousertaint]
4203 Hexadecimal bitmask r 3634 Hexadecimal bitmask representing the set of TAINT flags
4204 that will cause the k 3635 that will cause the kernel to panic when add_taint() is
4205 called with any of th 3636 called with any of the flags in this set.
4206 The optional switch " 3637 The optional switch "nousertaint" can be utilized to
4207 prevent userspace for 3638 prevent userspace forced crashes by writing to sysctl
4208 /proc/sys/kernel/tain 3639 /proc/sys/kernel/tainted any flagset matching with the
4209 bitmask set on panic_ 3640 bitmask set on panic_on_taint.
4210 See Documentation/adm 3641 See Documentation/admin-guide/tainted-kernels.rst for
4211 extra details on the 3642 extra details on the taint flags that users can pick
4212 to compose the bitmas 3643 to compose the bitmask to assign to panic_on_taint.
4213 3644
4214 panic_on_warn=1 panic() instead of WA !! 3645 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4215 on a WARN(). 3646 on a WARN().
4216 3647
4217 panic_print= Bitmask for printing !! 3648 crash_kexec_post_notifiers
4218 User can chose combin !! 3649 Run kdump after running panic-notifiers and dumping
4219 bit 0: print all task !! 3650 kmsg. This only for the users who doubt kdump always
4220 bit 1: print system m !! 3651 succeeds in any situation.
4221 bit 2: print timer in !! 3652 Note that this also increases risks of kdump failure,
4222 bit 3: print locks in !! 3653 because some panic notifiers can make the crashed
4223 bit 4: print ftrace b !! 3654 kernel more unstable.
4224 bit 5: print all prin <<
4225 bit 6: print all CPUs <<
4226 bit 7: print only tas <<
4227 *Be aware* that this <<
4228 so there are risks of <<
4229 Use this option caref <<
4230 bigger log buffer wit <<
4231 3655
4232 parkbd.port= [HW] Parallel port nu 3656 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3657 connected to, default is 0.
4234 Format: <parport#> 3658 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3659 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3660 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3661 Format: <mode>
4238 3662
4239 parport= [HW,PPT] Specify para 3663 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3664 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3665 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3666 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3667 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3668 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3669 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3670 should be numbers, or 'auto' (for using detected
4247 settings on that part 3671 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3672 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3673 Parallel ports are assigned in the order they
4250 are specified on the 3674 are specified on the command line, starting
4251 with parport0. 3675 with parport0.
4252 3676
4253 parport_init_mode= [HW,PPT] 3677 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3678 Configure VIA parallel port to operate in
4255 a specific mode. This 3679 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3680 computer where firmware has no options for setting
4257 up parallel port mode 3681 up parallel port mode and sets it to spp.
4258 Currently this functi 3682 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3683 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3684
4261 pata_legacy.all= [HW,LIBATA] !! 3685 pause_on_oops=
4262 Format: <int> <<
4263 Set to non-zero to pr <<
4264 port ranges on PCI sy <<
4265 has been found at eit <<
4266 <<
4267 pata_legacy.autospeed= [HW,LIBATA] <<
4268 Format: <int> <<
4269 Set to non-zero if a <<
4270 changes. Disabled by <<
4271 <<
4272 pata_legacy.ht6560a= [HW,LIBATA] <<
4273 Format: <int> <<
4274 Set to 1, 2, or 3 for <<
4275 the secondary channel <<
4276 Disabled by default. <<
4277 <<
4278 pata_legacy.ht6560b= [HW,LIBATA] <<
4279 Format: <int> <<
4280 Set to 1, 2, or 3 for <<
4281 the secondary channel <<
4282 Disabled by default. <<
4283 <<
4284 pata_legacy.iordy_mask= [HW,LIBATA] <<
4285 Format: <int> <<
4286 IORDY enable mask. S <<
4287 for the respective ch <<
4288 legacy channel handle <<
4289 the second channel, a <<
4290 correspond to the pri <<
4291 legacy channel, and s <<
4292 bus and the use of ot <<
4293 with the sequence. B <<
4294 all channels. <<
4295 <<
4296 pata_legacy.opti82c46x= [HW,LIBATA] <<
4297 Format: <int> <<
4298 Set to 1, 2, or 3 for <<
4299 channel, the secondar <<
4300 respectively. Disabl <<
4301 <<
4302 pata_legacy.opti82c611a= [HW,L <<
4303 Format: <int> <<
4304 Set to 1, 2, or 3 for <<
4305 channel, the secondar <<
4306 respectively. Disabl <<
4307 <<
4308 pata_legacy.pio_mask= [HW,LIBATA] <<
4309 Format: <int> <<
4310 PIO mode mask for aut <<
4311 bits to allow the use <<
4312 Bit 0 is for mode 0, <<
4313 All modes allowed by <<
4314 <<
4315 pata_legacy.probe_all= [HW,LIBATA] <<
4316 Format: <int> <<
4317 Set to non-zero to pr <<
4318 port ranges on PCI sy <<
4319 <<
4320 pata_legacy.probe_mask= [HW,LIBATA] <<
4321 Format: <int> <<
4322 Probe mask for legacy <<
4323 platform configuratio <<
4324 options up to 6 legac <<
4325 0x170, 0x1e8, 0x168, <<
4326 of individual ports c <<
4327 corresponding bits in <<
4328 the first port in the <<
4329 By default all suppor <<
4330 <<
4331 pata_legacy.qdi= [HW,LIBATA] <<
4332 Format: <int> <<
4333 Set to non-zero to pr <<
4334 set to 1 if CONFIG_PA <<
4335 <<
4336 pata_legacy.winbond= [HW,LIBATA] <<
4337 Format: <int> <<
4338 Set to non-zero to pr <<
4339 the standard I/O port <<
4340 value given is the I/ <<
4341 By default set to 1 i <<
4342 0 otherwise. <<
4343 <<
4344 pata_platform.pio_mask= [HW,LIBATA] <<
4345 Format: <int> <<
4346 Supported PIO mode ma <<
4347 the use of the respec <<
4348 mode 0, bit 1 is for <<
4349 allowed by default. <<
4350 <<
4351 pause_on_oops=<int> <<
4352 Halt all CPUs after t 3686 Halt all CPUs after the first oops has been printed for
4353 the specified number 3687 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3688 your oopses keep scrolling off the screen.
4355 3689
4356 pcbit= [HW,ISDN] 3690 pcbit= [HW,ISDN]
4357 3691
4358 pci=option[,option...] [PCI,EARLY] v !! 3692 pcd. [PARIDE]
>> 3693 See header of drivers/block/paride/pcd.c.
>> 3694 See also Documentation/admin-guide/blockdev/paride.rst.
>> 3695
>> 3696 pci=option[,option...] [PCI] various PCI subsystem options.
4359 3697
4360 Some options 3698 Some options herein operate on a specific device
4361 or a set of d 3699 or a set of devices (<pci_dev>). These are
4362 specified in 3700 specified in one of the following formats:
4363 3701
4364 [<domain>:]<b 3702 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 3703 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 3704
4367 Note: the fir 3705 Note: the first format specifies a PCI
4368 bus/device/fu 3706 bus/device/function address which may change
4369 if new hardwa 3707 if new hardware is inserted, if motherboard
4370 firmware chan 3708 firmware changes, or due to changes caused
4371 by other kern 3709 by other kernel parameters. If the
4372 domain is lef 3710 domain is left unspecified, it is
4373 taken to be z 3711 taken to be zero. Optionally, a path
4374 to a device t 3712 to a device through multiple device/function
4375 addresses can 3713 addresses can be specified after the base
4376 address (this 3714 address (this is more robust against
4377 renumbering i 3715 renumbering issues). The second format
4378 selects devic 3716 selects devices using IDs from the
4379 configuration 3717 configuration space which may match multiple
4380 devices in th 3718 devices in the system.
4381 3719
4382 earlydump dump PCI conf 3720 earlydump dump PCI config space before the kernel
4383 changes anyth 3721 changes anything
4384 off [X86] don't p 3722 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3723 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3724 the hardware directly. Use this if your machine
4387 has a non-sta 3725 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3726 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3727 hardware access methods are allowed. Use this
4390 if you experi 3728 if you experience crashes upon bootup and you
4391 suspect they 3729 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3730 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3731 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3732 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3733 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3734 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3735 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3736 bus number. The config space is then accessed
4399 through ports 3737 through ports 0xC000-0xCFFF).
4400 See http://wi 3738 See http://wiki.osdev.org/PCI for more info
4401 on the config 3739 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3740 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3741 enabled, this kernel boot option can be used to
4404 disable the u 3742 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3743 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3744 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3745 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3746 Configuration
4409 check_enable_amd_mmconf [X86] 3747 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3748 properly configured MMIO access to PCI
4411 config space 3749 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3750 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3751 enabled, this kernel boot option can be used to
4414 disable the u 3752 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3753 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3754 Safety option to keep boot IRQs enabled. This
4417 should never 3755 should never be necessary.
4418 ioapicreroute [APIC] Enable 3756 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3757 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3758 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3759 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3760 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3761 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3762 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3763 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3764 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3765 routing table. These calls are known to be buggy
4428 on several ma 3766 on several machines and they hang the machine
4429 when used, bu 3767 when used, but on other computers it's the only
4430 way to get th 3768 way to get the interrupt routing table. Try
4431 this option i 3769 this option if the kernel is unable to allocate
4432 IRQs or disco 3770 IRQs or discover secondary PCI buses on your
4433 motherboard. 3771 motherboard.
4434 rom [X86] Assign 3772 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3773 Use with caution as certain devices share
4436 address decod 3774 address decoders between ROMs and other
4437 resources. 3775 resources.
4438 norom [X86] Do not 3776 norom [X86] Do not assign address space to
4439 expansion ROM 3777 expansion ROMs that do not already have
4440 BIOS assigned 3778 BIOS assigned address ranges.
4441 nobar [X86] Do not 3779 nobar [X86] Do not assign address space to the
4442 BARs that wer 3780 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3781 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3782 assigned automatically to PCI devices. You can
4445 make the kern 3783 make the kernel exclude IRQs of your ISA cards
4446 this way. 3784 this way.
4447 pirqaddr=0xAAAAA [X86] 3785 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3786 of the PIRQ table (normally generated
4449 by the BIOS) 3787 by the BIOS) if it is outside the
4450 F0000h-100000 3788 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3789 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3790 useful if the kernel is unable to find your
4453 secondary bus 3791 secondary buses and you want to tell it
4454 explicitly wh 3792 explicitly which ones they are.
4455 assign-busses [X86] Always 3793 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3794 numbers ourselves, overriding
4457 whatever the 3795 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3796 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3797 in the BIOS $PIR table. This is needed on
4460 some systems 3798 some systems with broken BIOSes, notably
4461 some HP Pavil 3799 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3800 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3801 IRQ routing is enabled.
4464 noacpi [X86] Do not 3802 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3803 or for PCI scanning.
4466 use_crs [X86] Use PCI 3804 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3805 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3806 is enabled by default. If you need to use this,
4469 please report 3807 please report a bug.
4470 nocrs [X86] Ignore 3808 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 3809 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 <<
4473 PCI host brid <<
4474 for BIOS defe <<
4475 If you need t <<
4476 <linux-pci@vge <<
4477 no_e820 [X86] Ignore <<
4478 bridge window <<
4479 hardware. If <<
4480 a bug to <linu <<
4481 routeirq Do IRQ routin 3810 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3811 This is normally done in pci_enable_device(),
4483 so this optio 3812 so this option is a temporary workaround
4484 for broken dr 3813 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3814 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3815 handle more pci cards
4487 noearly [X86] Don't d 3816 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3817 This might help on some broken boards which
4489 machine check 3818 machine check when some devices' config space
4490 is read. But 3819 is read. But various workarounds are disabled
4491 and some IOMM 3820 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3821 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3822 This sorting is done to get a device
4494 order compati 3823 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3824 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3825 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3826 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3827 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3828 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3829 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3830 based on its parent bus. Also set MRRS (Max
4502 Read Request 3831 Read Request Size) to the largest supported
4503 value (no lar 3832 value (no larger than the MPS that the device
4504 or bus can su 3833 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3834 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3835 every device is guaranteed to support. This
4507 configuration 3836 configuration allows peer-to-peer DMA between
4508 any pair of d 3837 any pair of devices, possibly at the cost of
4509 reduced perfo 3838 reduced performance. This also guarantees
4510 that hot-adde 3839 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3840 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3841 reserved for the CardBus bridge's IO window.
4513 The default v 3842 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3843 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3844 reserved for the CardBus bridge's memory
4516 window. The d 3845 window. The default value is 64 megabytes.
4517 resource_alignment= 3846 resource_alignment=
4518 Format: 3847 Format:
4519 [<order of ali 3848 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 3849 Specifies alignment and device to reassign
4521 aligned memor 3850 aligned memory resources. How to
4522 specify the d 3851 specify the device is described above.
4523 If <order of 3852 If <order of align> is not specified,
4524 PAGE_SIZE is 3853 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 3854 A PCI-PCI bridge can be specified if resource
4526 windows need 3855 windows need to be expanded.
4527 To specify th 3856 To specify the alignment for several
4528 instances of 3857 instances of a device, the PCI vendor,
4529 device, subve 3858 device, subvendor, and subdevice may be
4530 specified, e. 3859 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 3860 for 4096-byte alignment.
4532 ecrc= Enable/disabl 3861 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3862 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3863 bios: Use BIOS/firmware settings. This is the
4537 the default. 3864 the default.
4538 off: Turn ECR 3865 off: Turn ECRC off
4539 on: Turn ECRC 3866 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3867 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3868 reserved for hotplug bridge's IO window.
4542 Default size 3869 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 3870 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 3871 reserved for hotplug bridge's MMIO window.
4545 Default size 3872 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 3873 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 3874 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 3875 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 3876 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 3877 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 3878 MMIO_PREF window.
4552 Default size 3879 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3880 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3881 reserved for buses below a hotplug bridge.
4555 Default is 1. 3882 Default is 1.
4556 realloc= Enable/disabl 3883 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3884 if allocations done by BIOS are too small to
4558 accommodate r 3885 accommodate resources required by all child
4559 devices. 3886 devices.
4560 off: Turn rea 3887 off: Turn realloc off
4561 on: Turn real 3888 on: Turn realloc on
4562 realloc same as reall 3889 realloc same as realloc=on
4563 noari do not use PC 3890 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 3891 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 3892 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 3893 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 3894 only look for one device below a PCIe downstream
4568 port. 3895 port.
4569 big_root_window Try to add a 3896 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 3897 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 3898 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 3899 Adding the window is slightly risky (it may
4573 conflict with 3900 conflict with unreported devices), so this
4574 taints the ke 3901 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 3902 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 3903 Specify one or more PCI devices (in the format
4577 specified abo 3904 specified above) separated by semicolons.
4578 Each device s 3905 Each device specified will have the PCI ACS
4579 redirect capa 3906 redirect capabilities forced off which will
4580 allow P2P tra 3907 allow P2P traffic between devices through
4581 bridges witho 3908 bridges without forcing it upstream. Note:
4582 this removes 3909 this removes isolation between devices and
4583 may put more 3910 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 3911 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 3912 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 3913 norid [S390] ignore the RID field and force use of
4619 one PCI domai 3914 one PCI domain per PCI function
4620 3915
4621 pcie_aspm= [PCIE] Forcibly enabl !! 3916 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 3917 Management.
4623 off Don't touch ASPM conf !! 3918 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 3919 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 3920 WARNING: Forcing ASPM on may cause system lockups.
4627 3921
4628 pcie_ports= [PCIE] PCIe port serv 3922 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 3923 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 3924 even if the platform doesn't give the OS permission to
4631 use them. This may c 3925 use them. This may cause conflicts if the platform
4632 also tries to use the 3926 also tries to use these services.
4633 dpc-native Use native PC 3927 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 3928 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 3929 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 3930 hotplug).
4637 3931
4638 pcie_port_pm= [PCIE] PCIe port powe 3932 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 3933 off Disable power management of all PCIe ports
4640 force Forcibly enable power 3934 force Forcibly enable power management of all PCIe ports
4641 3935
4642 pcie_pme= [PCIE,PM] Native PCIe 3936 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 3937 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 3938 all PCIe root ports use INTx for all services).
4645 3939
4646 pcmv= [HW,PCMCIA] BadgePAD 3940 pcmv= [HW,PCMCIA] BadgePAD 4
4647 3941
4648 pd_ignore_unused 3942 pd_ignore_unused
4649 [PM] 3943 [PM]
4650 Keep all power-domain 3944 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 3945 even if no driver has claimed them. This is useful
4652 for debug and develop 3946 for debug and development, but should not be
4653 needed on a platform 3947 needed on a platform with proper driver support.
4654 3948
>> 3949 pd. [PARIDE]
>> 3950 See Documentation/admin-guide/blockdev/paride.rst.
>> 3951
4655 pdcchassis= [PARISC,HW] Disable/E 3952 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 3953 boot time.
4657 Format: { 0 | 1 } 3954 Format: { 0 | 1 }
4658 See arch/parisc/kerne 3955 See arch/parisc/kernel/pdc_chassis.c
4659 3956
4660 percpu_alloc= [MM,EARLY] !! 3957 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 3958 Currently supported values are "embed" and "page".
4663 Archs may support sub 3959 Archs may support subset or none of the selections.
4664 See comments in mm/pe 3960 See comments in mm/percpu.c for details on each
4665 allocator. This para 3961 allocator. This parameter is primarily for debugging
4666 and performance compa 3962 and performance comparison.
4667 3963
>> 3964 pf. [PARIDE]
>> 3965 See Documentation/admin-guide/blockdev/paride.rst.
>> 3966
>> 3967 pg. [PARIDE]
>> 3968 See Documentation/admin-guide/blockdev/paride.rst.
>> 3969
4668 pirq= [SMP,APIC] Manual mp- 3970 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 3971 See Documentation/x86/i386/IO-APIC.rst.
4670 3972
4671 plip= [PPT,NET] Parallel po 3973 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 3974 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 3975 See also Documentation/admin-guide/parport.rst.
4674 3976
4675 pmtmr= [X86] Manual setup of 3977 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 3978 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 3979 e.g. pmtmr=0x508
4678 3980
4679 pmu_override= [PPC] Override the PM <<
4680 This option takes ove <<
4681 longer usable by perf <<
4682 PMU counters by setti <<
4683 cleared). If a number <<
4684 that number, otherwis <<
4685 remains 0. <<
4686 <<
4687 pm_debug_messages [SUSPEND,KNL] 3981 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 3982 Enable suspend/resume debug messages during boot up.
4689 3983
4690 pnp.debug=1 [PNP] 3984 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 3985 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 3986 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 3987 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 3988 current resource usage; turning this on also shows
4695 possible settings and 3989 possible settings and some assignment information.
4696 3990
4697 pnpacpi= [ACPI] 3991 pnpacpi= [ACPI]
4698 { off } 3992 { off }
4699 3993
4700 pnpbios= [ISAPNP] 3994 pnpbios= [ISAPNP]
4701 { on | off | curr | r 3995 { on | off | curr | res | no-curr | no-res }
4702 3996
4703 pnp_reserve_irq= 3997 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 3998 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 3999
4706 pnp_reserve_dma= 4000 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4001 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4002
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4003 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4004 Ranges are in pairs (I/O port base and size).
4711 4005
4712 pnp_reserve_mem= 4006 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4007 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4008 autoconfiguration.
4715 Ranges are in pairs ( 4009 Ranges are in pairs (memory base and size).
4716 4010
4717 ports= [IP_VS_FTP] IPVS ftp 4011 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4012 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4013 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4014 may be specified.
4721 Format: <port>,<port> 4015 Format: <port>,<port>....
4722 4016
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 4017 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4018 It specifically disables cpuidle and sets the
4730 platform machine desc 4019 platform machine description specific power_save
4731 function to NULL. On 4020 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4021 execution priority.
4733 4022
4734 ppc_strict_facility_enable 4023 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4024 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4025 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4026 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4027 There is some performance impact when enabling this.
4739 4028
4740 ppc_tm= [PPC,EARLY] !! 4029 ppc_tm= [PPC]
4741 Format: {"off"} 4030 Format: {"off"}
4742 Disable Hardware Tran 4031 Disable Hardware Transactional Memory
4743 4032
4744 preempt= [KNL] <<
4745 Select preemption mod <<
4746 none - Limited to con <<
4747 voluntary - Limited t <<
4748 full - Any section th <<
4749 can be preempt <<
4750 contended spin <<
4751 explicitly pre <<
4752 <<
4753 print-fatal-signals= 4033 print-fatal-signals=
4754 [KNL] debug: print fa 4034 [KNL] debug: print fatal signals
4755 4035
4756 If enabled, warn abou 4036 If enabled, warn about various signal handling
4757 related application a 4037 related application anomalies: too many signals,
4758 too many POSIX.1 time 4038 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4039 coredump - etc.
4760 4040
4761 If you hit the warnin 4041 If you hit the warning due to signal overflow,
4762 you might want to try 4042 you might want to try "ulimit -i unlimited".
4763 4043
4764 default: off. 4044 default: off.
4765 4045
4766 printk.always_kmsg_dump= 4046 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4047 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4048 panics
4769 Format: <bool> (1/Y/ 4049 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4050 default: disabled
4771 4051
4772 printk.console_no_auto_verbose= <<
4773 Disable console logle <<
4774 or lockdep-detected i <<
4775 With an exception to <<
4776 serial console, keepi <<
4777 in order to provide m <<
4778 Format: <bool> <<
4779 default: 0 (auto_verb <<
4780 <<
4781 printk.devkmsg={on,off,ratelimit} 4052 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4053 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4054 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4055 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4056 ratelimit - ratelimit the logging
4786 Default: ratelimit 4057 Default: ratelimit
4787 4058
4788 printk.time= Show timing data pref 4059 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4060 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4061
4791 proc_mem.force_override= [KNL] 4062 proc_mem.force_override= [KNL]
4792 Format: {always | ptr 4063 Format: {always | ptrace | never}
4793 Traditionally /proc/p 4064 Traditionally /proc/pid/mem allows memory permissions to be
4794 overridden without re 4065 overridden without restrictions. This option may be set to
4795 restrict that. Can be 4066 restrict that. Can be one of:
4796 - 'always': tradition 4067 - 'always': traditional behavior always allows mem overrides.
4797 - 'ptrace': only allo 4068 - 'ptrace': only allow mem overrides for active ptracers.
4798 - 'never': never all 4069 - 'never': never allow mem overrides.
4799 If not specified, def 4070 If not specified, default is the CONFIG_PROC_MEM_* choice.
4800 4071
4801 processor.max_cstate= [HW,ACPI] 4072 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4073 Limit processor to maximum C-state
4803 max_cstate=9 override 4074 max_cstate=9 overrides any DMI blacklist limit.
4804 4075
4805 processor.nocst [HW,ACPI] 4076 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4077 Ignore the _CST method to determine C-states,
4807 instead using the leg 4078 instead using the legacy FADT method
4808 4079
4809 profile= [KNL] Enable kernel p 4080 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4081 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4082 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4083 [defaults to kernel profiling]
4813 Param: "schedule" - p 4084 Param: "schedule" - profile schedule points.
>> 4085 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4086 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4087 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4088 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4089 statistical time based profiling.
4817 4090
4818 prompt_ramdisk= [RAM] [Deprecated] 4091 prompt_ramdisk= [RAM] [Deprecated]
4819 4092
4820 prot_virt= [S390] enable hosting 4093 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4094 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4095 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4096 Format: <bool>
4826 4097
4827 psi= [KNL] Enable or disab 4098 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4099 tracking.
4829 Format: <bool> 4100 Format: <bool>
4830 4101
4831 psmouse.proto= [HW,MOUSE] Highest PS 4102 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4103 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4104 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4105 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4106 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4107 Try to reset the device after so many bad packets
4837 (0 = never). 4108 (0 = never).
4838 psmouse.resolution= 4109 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4110 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4111 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4112 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4113 0 = disabled, 1 = enabled (default).
4843 4114
4844 pstore.backend= Specify the name of t 4115 pstore.backend= Specify the name of the pstore backend to use
4845 4116
>> 4117 pt. [PARIDE]
>> 4118 See Documentation/admin-guide/blockdev/paride.rst.
>> 4119
4846 pti= [X86-64] Control Page 4120 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4121 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4122 removes hardening, but improves performance of
4849 system calls and inte 4123 system calls and interrupts.
4850 4124
4851 on - unconditionall 4125 on - unconditionally enable
4852 off - unconditionall 4126 off - unconditionally disable
4853 auto - kernel detects 4127 auto - kernel detects whether your CPU model is
4854 vulnerable to 4128 vulnerable to issues that PTI mitigates
4855 4129
4856 Not specifying this o 4130 Not specifying this option is equivalent to pti=auto.
4857 4131
>> 4132 nopti [X86-64]
>> 4133 Equivalent to pti=off
>> 4134
4858 pty.legacy_count= 4135 pty.legacy_count=
4859 [KNL] Number of legac 4136 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4137 default number.
4861 4138
4862 quiet [KNL,EARLY] Disable m !! 4139 quiet [KNL] Disable most log messages
4863 4140
4864 r128= [HW,DRM] 4141 r128= [HW,DRM]
4865 4142
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4143 raid= [HW,RAID]
4871 See Documentation/adm 4144 See Documentation/admin-guide/md.rst.
4872 4145
4873 ramdisk_size= [RAM] Sizes of RAM di 4146 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4147 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4148
4876 ramdisk_start= [RAM] RAM disk image 4149 ramdisk_start= [RAM] RAM disk image start address
4877 4150
4878 random.trust_cpu=off !! 4151 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 4152 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 4153 CPU's random number generator (if available) to
4881 initialize the kernel !! 4154 fully seed the kernel's CRNG. Default is controlled
4882 !! 4155 by CONFIG_RANDOM_TRUST_CPU.
4883 random.trust_bootloader=off !! 4156
4884 [KNL,EARLY] Disable t !! 4157 random.trust_bootloader={on,off}
4885 passed by the bootloa !! 4158 [KNL] Enable or disable trusting the use of a
4886 initialize the kernel !! 4159 seed passed by the bootloader (if available) to
4887 !! 4160 fully seed the kernel's CRNG. Default is controlled
4888 randomize_kstack_offset= !! 4161 by CONFIG_RANDOM_TRUST_BOOTLOADER.
4889 [KNL,EARLY] Enable or <<
4890 randomization, which <<
4891 entropy, frustrating <<
4892 that depend on stack <<
4893 cross-syscall address <<
4894 available on architec <<
4895 CONFIG_HAVE_ARCH_RAND <<
4896 Format: <bool> (1/Y/ <<
4897 Default is CONFIG_RAN <<
4898 4162
4899 ras=option[,option,...] [KNL] RAS-spe 4163 ras=option[,option,...] [KNL] RAS-specific options
4900 4164
4901 cec_disable [X86] 4165 cec_disable [X86]
4902 Disable the C 4166 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4167 see CONFIG_RAS_CEC help text.
4904 4168
4905 rcu_nocbs[=cpu-list] !! 4169 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 4170 The argument is a cpu list, as described above,
4907 as described above. !! 4171 except that the string "all" can be used to
4908 !! 4172 specify every CPU on the system.
4909 In kernels built with !! 4173
4910 enable the no-callbac !! 4174 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4911 such CPUs' callbacks !! 4175 the specified list of CPUs to be no-callback CPUs.
4912 softirq context. Inv !! 4176 Invocation of these CPUs' RCU callbacks will be
4913 callbacks will instea !! 4177 offloaded to "rcuox/N" kthreads created for that
4914 kthreads created for !! 4178 purpose, where "x" is "p" for RCU-preempt, and
4915 "p" for RCU-preempt, !! 4179 "s" for RCU-sched, and "N" is the CPU number.
4916 for the kthreads that !! 4180 This reduces OS jitter on the offloaded CPUs,
4917 "N" is the CPU number !! 4181 which can be useful for HPC and real-time
4918 the offloaded CPUs, w !! 4182 workloads. It can also improve energy efficiency
4919 and real-time workloa !! 4183 for asymmetric multiprocessors.
4920 energy efficiency for <<
4921 <<
4922 If a cpulist is passe <<
4923 list of CPUs is set t <<
4924 <<
4925 Otherwise, if the '=' <<
4926 arguments are omitted <<
4927 no-callback mode from <<
4928 toggled at runtime vi <<
4929 <<
4930 Note that this argume <<
4931 the CONFIG_RCU_NOCB_C <<
4932 4184
4933 rcu_nocb_poll [KNL] 4185 rcu_nocb_poll [KNL]
4934 Rather than requiring 4186 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4187 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4188 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4189 make these kthreads poll for callbacks.
4938 This improves the rea 4190 This improves the real-time response for the
4939 offloaded CPUs by rel 4191 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4192 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4193 energy efficiency by requiring that the kthreads
4942 periodically wake up 4194 periodically wake up to do the polling.
4943 4195
4944 rcutree.blimit= [KNL] 4196 rcutree.blimit= [KNL]
4945 Set maximum number of 4197 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4198 process in one batch.
4947 4199
4948 rcutree.do_rcu_barrier= [KNL] <<
4949 Request a call to rcu <<
4950 throttled so that use <<
4951 hammer on the sysfs v <<
4952 If triggered before t <<
4953 is fully active, this <<
4954 <<
4955 rcutree.dump_tree= [KNL] 4200 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4201 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4202 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4203 purposes, to verify correct tree setup.
4959 4204
4960 rcutree.gp_cleanup_delay= [KNL] 4205 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4206 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4207 RCU grace-period cleanup.
4963 4208
4964 rcutree.gp_init_delay= [KNL] 4209 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4210 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4211 RCU grace-period initialization.
4967 4212
4968 rcutree.gp_preinit_delay= [KNL] 4213 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4214 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4215 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4216 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4217 the rcu_node combining tree.
4973 4218
>> 4219 rcutree.use_softirq= [KNL]
>> 4220 If set to zero, move all RCU_SOFTIRQ processing to
>> 4221 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4222 value, meaning that RCU_SOFTIRQ is used by default.
>> 4223 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4224
>> 4225 rcutree.rcu_fanout_exact= [KNL]
>> 4226 Disable autobalancing of the rcu_node combining
>> 4227 tree. This is used by rcutorture, and might
>> 4228 possibly be useful for architectures having high
>> 4229 cache-to-cache transfer latencies.
>> 4230
>> 4231 rcutree.rcu_fanout_leaf= [KNL]
>> 4232 Change the number of CPUs assigned to each
>> 4233 leaf rcu_node structure. Useful for very
>> 4234 large systems, which will choose the value 64,
>> 4235 and for NUMA systems with large remote-access
>> 4236 latencies, which will choose a value aligned
>> 4237 with the appropriate hardware boundaries.
>> 4238
>> 4239 rcutree.rcu_min_cached_objs= [KNL]
>> 4240 Minimum number of objects which are cached and
>> 4241 maintained per one CPU. Object size is equal
>> 4242 to PAGE_SIZE. The cache allows to reduce the
>> 4243 pressure to page allocator, also it makes the
>> 4244 whole algorithm to behave better in low memory
>> 4245 condition.
>> 4246
4974 rcutree.jiffies_till_first_fqs= [KNL] 4247 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4248 Set delay from grace-period initialization to
4976 first attempt to forc 4249 first attempt to force quiescent states.
4977 Units are jiffies, mi 4250 Units are jiffies, minimum value is zero,
4978 and maximum value is 4251 and maximum value is HZ.
4979 4252
4980 rcutree.jiffies_till_next_fqs= [KNL] 4253 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4254 Set delay between subsequent attempts to force
4982 quiescent states. Un 4255 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4256 value is one, and maximum value is HZ.
4984 4257
4985 rcutree.jiffies_till_sched_qs= [KNL] 4258 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4259 Set required age in jiffies for a
4987 given grace period be 4260 given grace period before RCU starts
4988 soliciting quiescent- 4261 soliciting quiescent-state help from
4989 rcu_note_context_swit 4262 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4263 If not specified, the kernel will calculate
4991 a value based on the 4264 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4265 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4266 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4267 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4268 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4269 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4270 overwritten.
4998 4271
4999 rcutree.kthread_prio= [KNL,BOOT] 4272 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4273 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4274 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4275 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4276 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4277 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4278 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4279 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4280 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4281 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 4282
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 4283 rcutree.rcu_nocb_gp_stride= [KNL]
5013 On callback-offloaded !! 4284 Set the number of NOCB callback kthreads in
5014 RCU reduces the lock !! 4285 each group, which defaults to the square root
5015 otherwise be caused b !! 4286 of the number of CPUs. Larger numbers reduce
5016 use of the ->nocb_byp !! 4287 the wakeup overhead on the global grace-period
5017 common non-flooded ca !! 4288 kthread, but increases that same overhead on
5018 the main ->cblist in !! 4289 each group's NOCB grace-period kthread.
5019 overhead of the ->noc <<
5020 But if there are too <<
5021 a single jiffy, RCU p <<
5022 the ->nocb_bypass que <<
5023 many" is supplied by <<
5024 <<
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 4290
5033 rcutree.qhimark= [KNL] 4291 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4292 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4293 batch limiting is disabled.
5036 4294
5037 rcutree.qlowmark= [KNL] 4295 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4296 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4297 batch limiting is re-enabled.
5040 4298
5041 rcutree.qovld= [KNL] 4299 rcutree.qovld= [KNL]
5042 Set threshold of queu 4300 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4301 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4302 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4303 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4304 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4305 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4306 disable more aggressive help enlistment.
5049 4307
5050 rcutree.rcu_delay_page_cache_fill_mse !! 4308 rcutree.rcu_idle_gp_delay= [KNL]
5051 Set the page-cache re !! 4309 Set wakeup interval for idle CPUs that have
5052 in response to low-me !! 4310 RCU callbacks (RCU_FAST_NO_HZ=y).
5053 of permitted values i !! 4311
5054 !! 4312 rcutree.rcu_idle_lazy_gp_delay= [KNL]
5055 rcutree.rcu_divisor= [KNL] !! 4313 Set wakeup interval for idle CPUs that have
5056 Set the shift-right c !! 4314 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
5057 the callback-invocati !! 4315 Lazy RCU callbacks are those which RCU can
5058 the number of callbac !! 4316 prove do nothing more than free memory.
5059 The result will be bo <<
5060 the rcutree.blimit ke <<
5061 callbacks, the softir <<
5062 order to allow the CP <<
5063 <<
5064 Please note that this <<
5065 limit applies only to <<
5066 invocation. Offloade <<
5067 invoked in the contex <<
5068 scheduler will preemp <<
5069 <<
5070 rcutree.rcu_fanout_exact= [KNL] <<
5071 Disable autobalancing <<
5072 tree. This is used b <<
5073 possibly be useful fo <<
5074 cache-to-cache transf <<
5075 <<
5076 rcutree.rcu_fanout_leaf= [KNL] <<
5077 Change the number of <<
5078 leaf rcu_node structu <<
5079 large systems, which <<
5080 and for NUMA systems <<
5081 latencies, which will <<
5082 with the appropriate <<
5083 <<
5084 rcutree.rcu_min_cached_objs= [KNL] <<
5085 Minimum number of obj <<
5086 maintained per one CP <<
5087 to PAGE_SIZE. The cac <<
5088 pressure to page allo <<
5089 whole algorithm to be <<
5090 condition. <<
5091 <<
5092 rcutree.rcu_nocb_gp_stride= [KNL] <<
5093 Set the number of NOC <<
5094 each group, which def <<
5095 of the number of CPUs <<
5096 the wakeup overhead o <<
5097 kthread, but increase <<
5098 each group's NOCB gra <<
5099 4317
5100 rcutree.rcu_kick_kthreads= [KNL] 4318 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4319 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4320 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4321 it should at force-quiescent-state time.
5104 This wake_up() will b 4322 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4323 WARN_ONCE() splat and an ftrace_dump().
5106 4324
5107 rcutree.rcu_resched_ns= [KNL] <<
5108 Limit the time spend <<
5109 callbacks to the spec <<
5110 By default, this limi <<
5111 every 32 callbacks in <<
5112 inflicted by local_cl <<
5113 <<
5114 rcutree.rcu_unlock_delay= [KNL] 4325 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4326 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4327 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4328 in microseconds. This defaults to zero.
5118 Larger delays increas 4329 Larger delays increase the probability of
5119 catching RCU pointer 4330 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4331 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4332 rcu_read_unlock() has completed.
5122 4333
5123 rcutree.sysrq_rcu= [KNL] 4334 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4335 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4336 rcu_node tree with an eye towards determining
5126 why a new grace perio 4337 why a new grace period has not yet started.
5127 4338
5128 rcutree.use_softirq= [KNL] <<
5129 If set to zero, move <<
5130 per-CPU rcuc kthreads <<
5131 value, meaning that R <<
5132 Specify rcutree.use_s <<
5133 <<
5134 But note that CONFIG_ <<
5135 this kernel boot para <<
5136 to zero. <<
5137 <<
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] 4339 rcuscale.gp_async= [KNL]
5158 Measure performance o 4340 Measure performance of asynchronous
5159 grace-period primitiv 4341 grace-period primitives such as call_rcu().
5160 4342
5161 rcuscale.gp_async_max= [KNL] 4343 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4344 Specify the maximum number of outstanding
5163 callbacks per writer 4345 callbacks per writer thread. When a writer
5164 thread exceeds this l 4346 thread exceeds this limit, it invokes the
5165 corresponding flavor 4347 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4348 previously posted callbacks to drain.
5167 4349
5168 rcuscale.gp_exp= [KNL] 4350 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4351 Measure performance of expedited synchronous
5170 grace-period primitiv 4352 grace-period primitives.
5171 4353
5172 rcuscale.holdoff= [KNL] 4354 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4355 Set test-start holdoff period. The purpose of
5174 this parameter is to 4356 this parameter is to delay the start of the
5175 test until boot compl 4357 test until boot completes in order to avoid
5176 interference. 4358 interference.
5177 4359
5178 rcuscale.kfree_by_call_rcu= [KNL] <<
5179 In kernels built with <<
5180 call_rcu() instead of <<
5181 <<
5182 rcuscale.kfree_mult= [KNL] <<
5183 Instead of allocating <<
5184 allocate one of kfree <<
5185 Defaults to 1. <<
5186 <<
5187 rcuscale.kfree_rcu_test= [KNL] 4360 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4361 Set to measure performance of kfree_rcu() flooding.
5189 4362
5190 rcuscale.kfree_rcu_test_double= [KNL] <<
5191 Test the double-argum <<
5192 If this parameter has <<
5193 rcuscale.kfree_rcu_te <<
5194 and double-argument v <<
5195 <<
5196 rcuscale.kfree_rcu_test_single= [KNL] <<
5197 Test the single-argum <<
5198 If this parameter has <<
5199 rcuscale.kfree_rcu_te <<
5200 and double-argument v <<
5201 <<
5202 rcuscale.kfree_nthreads= [KNL] 4363 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4364 The number of threads running loops of kfree_rcu().
5204 4365
5205 rcuscale.kfree_alloc_num= [KNL] 4366 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4367 Number of allocations and frees done in an iteration.
5207 4368
5208 rcuscale.kfree_loops= [KNL] 4369 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4370 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4371 of allocations and frees.
5211 4372
5212 rcuscale.minruntime= [KNL] <<
5213 Set the minimum test <<
5214 does not affect the d <<
5215 but instead allows be <<
5216 like CPU consumption. <<
5217 <<
5218 rcuscale.nreaders= [KNL] 4373 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4374 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4375 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4376 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4377 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4378 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4379 A value of "n" less than or equal to -N selects
5225 a single reader. 4380 a single reader.
5226 4381
5227 rcuscale.nwriters= [KNL] 4382 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4383 Set number of RCU writers. The values operate
5229 the same as for rcusc 4384 the same as for rcuscale.nreaders.
5230 N, where N is the num 4385 N, where N is the number of CPUs
5231 4386
5232 rcuscale.scale_type= [KNL] !! 4387 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4388 Specify the RCU implementation to test.
5234 4389
5235 rcuscale.shutdown= [KNL] 4390 rcuscale.shutdown= [KNL]
5236 Shut the system down 4391 Shut the system down after performance tests
5237 complete. This is us 4392 complete. This is useful for hands-off automated
5238 testing. 4393 testing.
5239 4394
5240 rcuscale.verbose= [KNL] 4395 rcuscale.verbose= [KNL]
5241 Enable additional pri 4396 Enable additional printk() statements.
5242 4397
5243 rcuscale.writer_holdoff= [KNL] 4398 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4399 Write-side holdoff between grace periods,
5245 in microseconds. The 4400 in microseconds. The default of zero says
5246 no holdoff. 4401 no holdoff.
5247 4402
5248 rcuscale.writer_holdoff_jiffies= [KNL <<
5249 Additional write-side <<
5250 periods, but in jiffi <<
5251 says no holdoff. <<
5252 <<
5253 rcutorture.fqs_duration= [KNL] 4403 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4404 Set duration of force_quiescent_state bursts
5255 in microseconds. 4405 in microseconds.
5256 4406
5257 rcutorture.fqs_holdoff= [KNL] 4407 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4408 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4409 in microseconds.
5260 4410
5261 rcutorture.fqs_stutter= [KNL] 4411 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4412 Set wait time between force_quiescent_state bursts
5263 in seconds. 4413 in seconds.
5264 4414
5265 rcutorture.fwd_progress= [KNL] 4415 rcutorture.fwd_progress= [KNL]
5266 Specifies the number !! 4416 Enable RCU grace-period forward-progress testing
5267 for RCU grace-period <<
5268 for the types of RCU 4417 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread <<
5270 greater than the numb <<
5271 of CPUs to be used. <<
5272 4418
5273 rcutorture.fwd_progress_div= [KNL] 4419 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4420 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4421 period to do tight-loop forward-progress testing.
5276 4422
5277 rcutorture.fwd_progress_holdoff= [KNL 4423 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4424 Number of seconds to wait between successive
5279 forward-progress test 4425 forward-progress tests.
5280 4426
5281 rcutorture.fwd_progress_need_resched= 4427 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4428 Enclose cond_resched() calls within checks for
5283 need_resched() during 4429 need_resched() during tight-loop forward-progress
5284 testing. 4430 testing.
5285 4431
5286 rcutorture.gp_cond= [KNL] 4432 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4433 Use conditional/asynchronous update-side
5288 primitives, if availa 4434 primitives, if available.
5289 4435
5290 rcutorture.gp_exp= [KNL] 4436 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4437 Use expedited update-side primitives, if available.
5292 4438
5293 rcutorture.gp_normal= [KNL] 4439 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4440 Use normal (non-expedited) asynchronous
5295 update-side primitive 4441 update-side primitives, if available.
5296 4442
5297 rcutorture.gp_sync= [KNL] 4443 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4444 Use normal (non-expedited) synchronous
5299 update-side primitive 4445 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4446 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4447 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4448 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4449 they are all non-zero.
5304 4450
5305 rcutorture.irqreader= [KNL] 4451 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4452 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4453 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4454 flavors take kindly to this sort of thing.
5309 4455
5310 rcutorture.leakpointer= [KNL] 4456 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4457 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4458 This can of course result in splats, and is
5313 intended to test the 4459 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4460 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4461 such leaks.
5316 4462
5317 rcutorture.n_barrier_cbs= [KNL] 4463 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4464 Set callbacks/threads for rcu_barrier() testing.
5319 4465
5320 rcutorture.nfakewriters= [KNL] 4466 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4467 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4468 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4469 test, hence the "fake".
5324 4470
5325 rcutorture.nocbs_nthreads= [KNL] <<
5326 Set number of RCU cal <<
5327 Zero (the default) di <<
5328 <<
5329 rcutorture.nocbs_toggle= [KNL] <<
5330 Set the delay in mill <<
5331 callback-offload togg <<
5332 <<
5333 rcutorture.nreaders= [KNL] 4471 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4472 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4473 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4474 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 4475 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 4476 (the number of CPUs), -3 selects N+1, and so on.
5339 4477
5340 rcutorture.object_debug= [KNL] 4478 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 4479 Enable debug-object double-call_rcu() testing.
5342 4480
5343 rcutorture.onoff_holdoff= [KNL] 4481 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 4482 Set time (s) after boot for CPU-hotplug testing.
5345 4483
5346 rcutorture.onoff_interval= [KNL] 4484 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 4485 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 4486 or zero to disable CPU-hotplug testing.
5349 4487
5350 rcutorture.read_exit= [KNL] 4488 rcutorture.read_exit= [KNL]
5351 Set the number of rea 4489 Set the number of read-then-exit kthreads used
5352 to test the interacti 4490 to test the interaction of RCU updaters and
5353 task-exit processing. 4491 task-exit processing.
5354 4492
5355 rcutorture.read_exit_burst= [KNL] 4493 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 4494 The number of times in a given read-then-exit
5357 episode that a set of 4495 episode that a set of read-then-exit kthreads
5358 is spawned. 4496 is spawned.
5359 4497
5360 rcutorture.read_exit_delay= [KNL] 4498 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 4499 The delay, in seconds, between successive
5362 read-then-exit testin 4500 read-then-exit testing episodes.
5363 4501
5364 rcutorture.shuffle_interval= [KNL] 4502 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 4503 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 4504 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 4505 during the rcutorture test.
5368 4506
5369 rcutorture.shutdown_secs= [KNL] 4507 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 4508 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 4509 is useful for hands-off automated testing.
5372 4510
5373 rcutorture.stall_cpu= [KNL] 4511 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 4512 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 4513 warnings, zero to disable.
5376 4514
5377 rcutorture.stall_cpu_block= [KNL] 4515 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 4516 Sleep while stalling if set. This will result
5379 in warnings from pree !! 4517 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 4518 to any other stall-related activity.
5381 in kernels built with <<
5382 CONFIG_PREEMPT_COUNT= <<
5383 cause the CPU to pass <<
5384 Given CONFIG_PREEMPTI <<
5385 RCU CPU stall warning <<
5386 in scheduling-while-a <<
5387 <<
5388 Use of this module pa <<
5389 <<
5390 4519
5391 rcutorture.stall_cpu_holdoff= [KNL] 4520 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 4521 Time to wait (s) after boot before inducing stall.
5393 4522
5394 rcutorture.stall_cpu_irqsoff= [KNL] 4523 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 4524 Disable interrupts while stalling if set.
5396 4525
5397 rcutorture.stall_gp_kthread= [KNL] 4526 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 4527 Duration (s) of forced sleep within RCU
5399 grace-period kthread 4528 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 4529 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 4530 and stall_gp_kthread are specified, the
5402 kthread is starved fi 4531 kthread is starved first, then the CPU.
5403 4532
5404 rcutorture.stat_interval= [KNL] 4533 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 4534 Time (s) between statistics printk()s.
5406 4535
5407 rcutorture.stutter= [KNL] 4536 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 4537 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 4538 five seconds causes the test to run for five seconds,
5410 wait for five seconds 4539 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 4540 ability to transition abruptly to and from idle.
5412 4541
5413 rcutorture.test_boost= [KNL] 4542 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 4543 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 4544 "Maybe" means test if the RCU implementation
5416 under test support RC 4545 under test support RCU priority boosting.
5417 4546
5418 rcutorture.test_boost_duration= [KNL] 4547 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 4548 Duration (s) of each individual boost test.
5420 4549
5421 rcutorture.test_boost_interval= [KNL] 4550 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 4551 Interval (s) between each boost test.
5423 4552
5424 rcutorture.test_no_idle_hz= [KNL] 4553 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 4554 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 4555 rcutorture.shuffle_interval parameter.
5427 4556
5428 rcutorture.torture_type= [KNL] 4557 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 4558 Specify the RCU implementation to test.
5430 4559
5431 rcutorture.verbose= [KNL] 4560 rcutorture.verbose= [KNL]
5432 Enable additional pri 4561 Enable additional printk() statements.
5433 4562
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 4563 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 4564 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 4565 stall warning.
5437 4566
5438 rcupdate.rcu_cpu_stall_notifiers= [KN <<
5439 Provide RCU CPU stall <<
5440 warnings in the RCU_C <<
5441 option's help text. <<
5442 do not want rcupdate. <<
5443 <<
5444 rcupdate.rcu_cpu_stall_suppress= [KNL 4567 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 4568 Suppress RCU CPU stall warning messages.
5446 4569
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 4570 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 4571 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 4572 rcutorture writer stall warnings that occur
5450 during early boot, th 4573 during early boot, that is, during the time
5451 before the init task 4574 before the init task is spawned.
5452 4575
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 4576 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 4577 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon <<
5456 value is 300 seconds. <<
5457 <<
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ <<
5459 Set timeout for exped <<
5460 messages. The value <<
5461 and the maximum allow <<
5462 milliseconds. Please <<
5463 adjusted to an arch t <<
5464 Setting this to zero <<
5465 rcupdate.rcu_cpu_stal <<
5466 conversion from secon <<
5467 <<
5468 rcupdate.rcu_cpu_stall_cputime= [KNL] <<
5469 Provide statistics on <<
5470 interrupts and tasks <<
5471 multiple continuous R <<
5472 begin at half of the <<
5473 <<
5474 rcupdate.rcu_exp_stall_task_details= <<
5475 Print stack dumps of <<
5476 current expedited RCU <<
5477 expedited RCU CPU sta <<
5478 4578
5479 rcupdate.rcu_expedited= [KNL] 4579 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 4580 Use expedited grace-period primitives, for
5481 example, synchronize_ 4581 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 4582 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 4583 but can increase CPU utilization, degrade
5484 real-time latency, an 4584 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 4585 No effect on CONFIG_TINY_RCU kernels.
5486 4586
5487 rcupdate.rcu_normal= [KNL] 4587 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 4588 Use only normal grace-period primitives,
5489 for example, synchron 4589 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 4590 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 4591 real-time latency, CPU utilization, and
5492 energy efficiency, bu 4592 energy efficiency, but can expose users to
5493 increased grace-perio 4593 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 4594 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 4595 CONFIG_TINY_RCU kernels.
5496 4596
5497 rcupdate.rcu_normal_after_boot= [KNL] 4597 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 4598 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 4599 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 4600 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 4601 on CONFIG_TINY_RCU kernels.
5502 4602
5503 But note that CONFIG_ <<
5504 this kernel boot para <<
5505 it to the value one, <<
5506 post-boot attempt at <<
5507 period to instead use <<
5508 grace-period processi <<
5509 <<
5510 rcupdate.rcu_task_collapse_lim= [KNL] <<
5511 Set the maximum numbe <<
5512 at the beginning of a <<
5513 the RCU Tasks flavors <<
5514 a single callback que <<
5515 occurs when rcupdate. <<
5516 set to the default va <<
5517 <<
5518 rcupdate.rcu_task_contend_lim= [KNL] <<
5519 Set the minimum numbe <<
5520 lock-contention event <<
5521 cause the RCU Tasks f <<
5522 callback queuing. Th <<
5523 when rcupdate.rcu_tas <<
5524 the default value of <<
5525 <<
5526 rcupdate.rcu_task_enqueue_lim= [KNL] <<
5527 Set the number of cal <<
5528 RCU Tasks family of R <<
5529 of -1 allows this to <<
5530 dynamically) adjusted <<
5531 for use in testing. <<
5532 <<
5533 rcupdate.rcu_task_ipi_delay= [KNL] 4603 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 4604 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 4605 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 4606 of a given grace period. Setting a large
5537 number avoids disturb 4607 number avoids disturbing real-time workloads,
5538 but lengthens grace p 4608 but lengthens grace periods.
5539 4609
5540 rcupdate.rcu_task_lazy_lim= [KNL] <<
5541 Number of callbacks o <<
5542 cancel laziness on th <<
5543 cancellation of lazin <<
5544 doing so increases th <<
5545 callback flooding. <<
5546 <<
5547 rcupdate.rcu_task_stall_info= [KNL] <<
5548 Set initial timeout i <<
5549 informational message <<
5550 of the problem for th <<
5551 wait for ten minutes. <<
5552 only printed prior to <<
5553 for a given grace per <<
5554 less than or equal to <<
5555 seconds. A change in <<
5556 until the beginning o <<
5557 <<
5558 rcupdate.rcu_task_stall_info_mult= [K <<
5559 Multiplier for time i <<
5560 RCU task stall inform <<
5561 RCU tasks grace perio <<
5562 to one through ten, i <<
5563 the value three, so t <<
5564 message is printed 10 <<
5565 period, the second at <<
5566 160 seconds, and then <<
5567 seconds would prevent <<
5568 <<
5569 rcupdate.rcu_task_stall_timeout= [KNL 4610 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 4611 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 4612 messages. Disable with a value less than or equal
5572 than or equal to zero !! 4613 to zero.
5573 A change in value doe <<
5574 the beginning of the <<
5575 <<
5576 rcupdate.rcu_tasks_lazy_ms= [KNL] <<
5577 Set timeout in millis <<
5578 callback batching for <<
5579 A negative value will <<
5580 of zero will disable <<
5581 always disabled for s <<
5582 <<
5583 rcupdate.rcu_tasks_rude_lazy_ms= [KNL <<
5584 Set timeout in millis <<
5585 Rude asynchronous cal <<
5586 call_rcu_tasks_rude() <<
5587 will take the default <<
5588 disable batching. Ba <<
5589 for synchronize_rcu_t <<
5590 <<
5591 rcupdate.rcu_tasks_trace_lazy_ms= [KN <<
5592 Set timeout in millis <<
5593 Trace asynchronous ca <<
5594 call_rcu_tasks_trace( <<
5595 will take the default <<
5596 disable batching. Ba <<
5597 for synchronize_rcu_t <<
5598 4614
5599 rcupdate.rcu_self_test= [KNL] 4615 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 4616 Run the RCU early boot self tests
5601 4617
5602 rdinit= [KNL] 4618 rdinit= [KNL]
5603 Format: <full_path> 4619 Format: <full_path>
5604 Run specified binary 4620 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 4621 used for early userspace startup. See initrd.
5606 4622
5607 rdrand= [X86,EARLY] !! 4623 rdrand= [X86]
5608 force - Override the 4624 force - Override the decision by the kernel to hide the
5609 advertisement 4625 advertisement of RDRAND support (this affects
5610 certain AMD p 4626 certain AMD processors because of buggy BIOS
5611 support, spec 4627 support, specifically around the suspend/resume
5612 path). 4628 path).
5613 4629
5614 rdt= [HW,X86,RDT] 4630 rdt= [HW,X86,RDT]
5615 Turn on/off individua 4631 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 4632 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 4633 mba.
5618 E.g. to turn on cmt a 4634 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 4635 rdt=cmt,!mba
5620 4636
5621 reboot= [KNL] 4637 reboot= [KNL]
5622 Format (x86 or x86_64 4638 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 4639 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 4640 [[,]s[mp]#### \
5625 [[,]b[ios] | 4641 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 4642 [[,]f[orce]
5627 Where reboot_mode is 4643 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 4644 (prefix with 'panic_' to set mode for panic
5629 reboo 4645 reboot only),
5630 reboot_type is 4646 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 4647 reboot_force is either force or not specified,
5632 reboot_cpu is s 4648 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 4649 to be used for rebooting.
5634 4650
5635 refscale.holdoff= [KNL] 4651 refscale.holdoff= [KNL]
5636 Set test-start holdof 4652 Set test-start holdoff period. The purpose of
5637 this parameter is to 4653 this parameter is to delay the start of the
5638 test until boot compl 4654 test until boot completes in order to avoid
5639 interference. 4655 interference.
5640 4656
5641 refscale.lookup_instances= [KNL] <<
5642 Number of data elemen <<
5643 SLAB_TYPESAFE_BY_RCU <<
5644 is negated and multip <<
5645 zero specifies nr_cpu <<
5646 <<
5647 refscale.loops= [KNL] 4657 refscale.loops= [KNL]
5648 Set the number of loo 4658 Set the number of loops over the synchronization
5649 primitive under test. 4659 primitive under test. Increasing this number
5650 reduces noise due to 4660 reduces noise due to loop start/end overhead,
5651 but the default has a 4661 but the default has already reduced the per-pass
5652 noise to a handful of 4662 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 4663 x86 laptops.
5654 4664
5655 refscale.nreaders= [KNL] 4665 refscale.nreaders= [KNL]
5656 Set number of readers 4666 Set number of readers. The default value of -1
5657 selects N, where N is 4667 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 4668 of CPUs. A value of zero is an interesting choice.
5659 4669
5660 refscale.nruns= [KNL] 4670 refscale.nruns= [KNL]
5661 Set number of runs, e 4671 Set number of runs, each of which is dumped onto
5662 the console log. 4672 the console log.
5663 4673
5664 refscale.readdelay= [KNL] 4674 refscale.readdelay= [KNL]
5665 Set the read-side cri 4675 Set the read-side critical-section duration,
5666 measured in microseco 4676 measured in microseconds.
5667 4677
5668 refscale.scale_type= [KNL] 4678 refscale.scale_type= [KNL]
5669 Specify the read-prot 4679 Specify the read-protection implementation to test.
5670 4680
5671 refscale.shutdown= [KNL] 4681 refscale.shutdown= [KNL]
5672 Shut down the system 4682 Shut down the system at the end of the performance
5673 test. This defaults 4683 test. This defaults to 1 (shut it down) when
5674 refscale is built int 4684 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 4685 it running) when refscale is built as a module.
5676 4686
5677 refscale.verbose= [KNL] 4687 refscale.verbose= [KNL]
5678 Enable additional pri 4688 Enable additional printk() statements.
5679 4689
5680 refscale.verbose_batched= [KNL] <<
5681 Batch the additional <<
5682 (the default) or nega <<
5683 print every Nth verbo <<
5684 specified. <<
5685 <<
5686 regulator_ignore_unused <<
5687 [REGULATOR] <<
5688 Prevents regulator fr <<
5689 that are unused, due <<
5690 be useful for debug a <<
5691 needed on a platform <<
5692 <<
5693 relax_domain_level= 4690 relax_domain_level=
5694 [KNL, SMP] Set schedu 4691 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 4692 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 4693
5697 reserve= [KNL,BUGS] Force kern 4694 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 4695 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 4696 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 4697 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 4698 is assumed to be I/O ports; otherwise it is memory.
5702 4699
5703 reserve_mem= [RAM] !! 4700 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] 4701 Format: nn[KMG]
5727 Reserves a hole at th 4702 Reserves a hole at the top of the kernel virtual
5728 address space. 4703 address space.
5729 4704
>> 4705 reservelow= [X86]
>> 4706 Format: nn[K]
>> 4707 Set the amount of memory to reserve for BIOS at
>> 4708 the bottom of the address space.
>> 4709
5730 reset_devices [KNL] Force drivers t 4710 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 4711 during initialization.
5732 4712
5733 resume= [SWSUSP] 4713 resume= [SWSUSP]
5734 Specify the partition 4714 Specify the partition device for software suspend
5735 Format: 4715 Format:
5736 {/dev/<dev> | PARTUUI 4716 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 4717
5738 resume_offset= [SWSUSP] 4718 resume_offset= [SWSUSP]
5739 Specify the offset fr 4719 Specify the offset from the beginning of the partition
5740 given by "resume=" at 4720 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 4721 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 4722 See Documentation/power/swsusp-and-swap-files.rst
5743 4723
5744 resumedelay= [HIBERNATION] Delay ( 4724 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 4725 read the resume files
5746 4726
5747 resumewait [HIBERNATION] Wait (i 4727 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 4728 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 4729 (e.g. USB and MMC devices).
5750 4730
5751 retain_initrd [RAM] Keep initrd mem !! 4731 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 4732 noresume Don't check if there's a hibernation image
>> 4733 present during boot.
>> 4734 nocompress Don't compress/decompress hibernation images.
>> 4735 no Disable hibernation and resume.
>> 4736 protect_image Turn on image protection during restoration
>> 4737 (that will set all pages holding image data
>> 4738 during restoration read-only).
>> 4739
>> 4740 retain_initrd [RAM] Keep initrd memory after extraction
5753 4741
5754 retbleed= [X86] Control mitigat 4742 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 4743 Speculative Code Execution with Return Instructions)
5756 vulnerability. 4744 vulnerability.
5757 4745
5758 AMD-based UNRET and I 4746 AMD-based UNRET and IBPB mitigations alone do not stop
5759 sibling threads from 4747 sibling threads from influencing the predictions of other
5760 sibling threads. For 4748 sibling threads. For that reason, STIBP is used on pro-
5761 cessors that support 4749 cessors that support it, and mitigate SMT on processors
5762 that don't. 4750 that don't.
5763 4751
5764 off - no mit 4752 off - no mitigation
5765 auto - automa 4753 auto - automatically select a migitation
5766 auto,nosmt - automa 4754 auto,nosmt - automatically select a mitigation,
5767 disabl 4755 disabling SMT if necessary for
5768 the fu 4756 the full mitigation (only on Zen1
5769 and ol 4757 and older without STIBP).
5770 ibpb - On AMD 4758 ibpb - On AMD, mitigate short speculation
5771 window 4759 windows on basic block boundaries too.
5772 Safe, 4760 Safe, highest perf impact. It also
5773 enable 4761 enables STIBP if present. Not suitable
5774 on Int 4762 on Intel.
5775 ibpb,nosmt - Like " 4763 ibpb,nosmt - Like "ibpb" above but will disable SMT
5776 when S 4764 when STIBP is not available. This is
5777 the al 4765 the alternative for systems which do not
5778 have S 4766 have STIBP.
5779 unret - Force 4767 unret - Force enable untrained return thunks,
5780 only e 4768 only effective on AMD f15h-f17h based
5781 system 4769 systems.
5782 unret,nosmt - Like u 4770 unret,nosmt - Like unret, but will disable SMT when STIBP
5783 is not 4771 is not available. This is the alternative for
5784 system 4772 systems which do not have STIBP.
5785 4773
5786 Selecting 'auto' will 4774 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 4775 time according to the CPU.
5788 4776
5789 Not specifying this o 4777 Not specifying this option is equivalent to retbleed=auto.
5790 4778
5791 rfkill.default_state= 4779 rfkill.default_state=
5792 0 "airplane mode". All 4780 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 4781 etc. communication is blocked by default.
5794 1 Unblocked. 4782 1 Unblocked.
5795 4783
5796 rfkill.master_switch_mode= 4784 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 4785 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 4786 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 4787 blocked and the previous configuration.
5800 2 The "airplane mode" b 4788 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 4789 blocked and everything unblocked.
5802 4790
>> 4791 rhash_entries= [KNL,NET]
>> 4792 Set number of hash buckets for route cache
>> 4793
5803 ring3mwait=disable 4794 ring3mwait=disable
5804 [KNL] Disable ring 3 4795 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 4796 CPUs.
5806 4797
5807 riscv_isa_fallback [RISCV,EARLY] <<
5808 When CONFIG_RISCV_ISA <<
5809 falling back to detec <<
5810 "riscv,isa" property <<
5811 replacement propertie <<
5812 entry for RISCV_ISA_F <<
5813 <<
5814 ro [KNL] Mount root devi 4798 ro [KNL] Mount root device read-only on boot
5815 4799
5816 rodata= [KNL,EARLY] !! 4800 rodata= [KNL]
5817 on Mark read-only kernel 4801 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 4802 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 4803
5822 rockchip.usb_uart 4804 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 4805 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 4806 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 4807 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 4808 port and the regular usb controller gets disabled.
5828 4809
5829 root= [KNL] Root filesystem 4810 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 4811 See name_to_dev_t comment in init/do_mounts.c.
5831 see the early_lookup_ <<
5832 block/early-lookup.c <<
5833 Alternatively this ca <<
5834 ramdisk, "nfs" and "c <<
5835 system, or "mtd" and <<
5836 4812
5837 rootdelay= [KNL] Delay (in secon 4813 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 4814 mount the root filesystem
5839 4815
5840 rootflags= [KNL] Set root filesy 4816 rootflags= [KNL] Set root filesystem mount option string
5841 4817
5842 rootfstype= [KNL] Set root filesy 4818 rootfstype= [KNL] Set root filesystem type
5843 4819
5844 rootwait [KNL] Wait (indefinit 4820 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 4821 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 4822 (e.g. USB and MMC devices).
5847 4823
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 4824 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 4825 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 4826 Memory area to be used by remote processor image,
5855 managed by CMA. 4827 managed by CMA.
5856 4828
5857 rw [KNL] Mount root devi 4829 rw [KNL] Mount root device read-write on boot
5858 4830
5859 S [KNL] Run init in sin 4831 S [KNL] Run init in single mode
5860 4832
5861 s390_iommu= [HW,S390] 4833 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 4834 Set s390 IOTLB flushing mode
5863 strict 4835 strict
5864 With strict flushing !! 4836 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 4837 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 4838 which is faster.
5867 iommu.strict=1. <<
5868 <<
5869 s390_iommu_aperture= [KNL,S390] <<
5870 Specifies the size of <<
5871 accessible through th <<
5872 factor of the size of <<
5873 The default is 1 mean <<
5874 as many DMA addresses <<
5875 if supported by hardw <<
5876 once. With a value of <<
5877 and so on. As a speci <<
5878 restrictions other th <<
5879 cost of significant a <<
5880 4839
5881 sa1100ir [NET] 4840 sa1100ir [NET]
5882 See drivers/net/irda/ 4841 See drivers/net/irda/sa1100_ir.c.
5883 4842
5884 sched_verbose [KNL,EARLY] Enables v !! 4843 sbni= [NET] Granch SBNI12 leased line adapter
>> 4844
>> 4845 sched_debug [KNL] Enables verbose scheduler debug messages.
5885 4846
5886 schedstats= [KNL,X86] Enable or d 4847 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 4848 Allowed values are enable and disable. This feature
5888 incurs a small amount 4849 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 4850 but is useful for debugging and performance tuning.
5890 4851
5891 sched_thermal_decay_shift= 4852 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 4853 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 4854 pressure signal. Thermal pressure signal follows the
5895 default decay period 4855 default decay period of other scheduler pelt
5896 signals(usually 32 ms 4856 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 4857 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 4858 period for the thermal pressure signal by the shift
5899 value. 4859 value.
5900 i.e. with the default 4860 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 4861 sched_thermal_decay_shift thermal pressure decay pr
5902 1 4862 1 64 ms
5903 2 4863 2 128 ms
5904 and so on. 4864 and so on.
5905 Format: integer betwe 4865 Format: integer between 0 and 10
5906 Default is 0. 4866 Default is 0.
5907 4867
5908 scftorture.holdoff= [KNL] 4868 scftorture.holdoff= [KNL]
5909 Number of seconds to 4869 Number of seconds to hold off before starting
5910 test. Defaults to ze 4870 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 4871 to 10 seconds for built-in smp_call_function()
5912 tests. 4872 tests.
5913 4873
5914 scftorture.longwait= [KNL] 4874 scftorture.longwait= [KNL]
5915 Request ridiculously 4875 Request ridiculously long waits randomly selected
5916 up to the chosen limi 4876 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 4877 default) disables this feature. Please note
5918 that requesting even 4878 that requesting even small non-zero numbers of
5919 seconds can result in 4879 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 4880 softlockup complaints, and so on.
5921 4881
5922 scftorture.nthreads= [KNL] 4882 scftorture.nthreads= [KNL]
5923 Number of kthreads to 4883 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 4884 smp_call_function() family of functions.
5925 The default of -1 spe 4885 The default of -1 specifies a number of kthreads
5926 equal to the number o 4886 equal to the number of CPUs.
5927 4887
5928 scftorture.onoff_holdoff= [KNL] 4888 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 4889 Number seconds to wait after the start of the
5930 test before initiatin 4890 test before initiating CPU-hotplug operations.
5931 4891
5932 scftorture.onoff_interval= [KNL] 4892 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 4893 Number seconds to wait between successive
5934 CPU-hotplug operation 4894 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 4895 is the default) disables CPU-hotplug operations.
5936 4896
5937 scftorture.shutdown_secs= [KNL] 4897 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 4898 The number of seconds following the start of the
5939 test after which to s 4899 test after which to shut down the system. The
5940 default of zero avoid 4900 default of zero avoids shutting down the system.
5941 Non-zero values are u 4901 Non-zero values are useful for automated tests.
5942 4902
5943 scftorture.stat_interval= [KNL] 4903 scftorture.stat_interval= [KNL]
5944 The number of seconds 4904 The number of seconds between outputting the
5945 current test statisti 4905 current test statistics to the console. A value
5946 of zero disables stat 4906 of zero disables statistics output.
5947 4907
5948 scftorture.stutter_cpus= [KNL] 4908 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 4909 The number of jiffies to wait between each change
5950 to the set of CPUs un 4910 to the set of CPUs under test.
5951 4911
5952 scftorture.use_cpus_read_lock= [KNL] 4912 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 4913 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 4914 preempt_disable() to disable CPU hotplug
5955 while invoking one of 4915 while invoking one of the smp_call_function*()
5956 functions. 4916 functions.
5957 4917
5958 scftorture.verbose= [KNL] 4918 scftorture.verbose= [KNL]
5959 Enable additional pri 4919 Enable additional printk() statements.
5960 4920
5961 scftorture.weight_single= [KNL] 4921 scftorture.weight_single= [KNL]
5962 The probability weigh 4922 The probability weighting to use for the
5963 smp_call_function_sin 4923 smp_call_function_single() function with a zero
5964 "wait" parameter. A 4924 "wait" parameter. A value of -1 selects the
5965 default if all other 4925 default if all other weights are -1. However,
5966 if at least one weigh 4926 if at least one weight has some other value, a
5967 value of -1 will inst 4927 value of -1 will instead select a weight of zero.
5968 4928
5969 scftorture.weight_single_wait= [KNL] 4929 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 4930 The probability weighting to use for the
5971 smp_call_function_sin 4931 smp_call_function_single() function with a
5972 non-zero "wait" param 4932 non-zero "wait" parameter. See weight_single.
5973 4933
5974 scftorture.weight_many= [KNL] 4934 scftorture.weight_many= [KNL]
5975 The probability weigh 4935 The probability weighting to use for the
5976 smp_call_function_man 4936 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 4937 "wait" parameter. See weight_single.
5978 Note well that settin 4938 Note well that setting a high probability for
5979 this weighting can pl 4939 this weighting can place serious IPI load
5980 on the system. 4940 on the system.
5981 4941
5982 scftorture.weight_many_wait= [KNL] 4942 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 4943 The probability weighting to use for the
5984 smp_call_function_man 4944 smp_call_function_many() function with a
5985 non-zero "wait" param 4945 non-zero "wait" parameter. See weight_single
5986 and weight_many. 4946 and weight_many.
5987 4947
5988 scftorture.weight_all= [KNL] 4948 scftorture.weight_all= [KNL]
5989 The probability weigh 4949 The probability weighting to use for the
5990 smp_call_function_all 4950 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 4951 "wait" parameter. See weight_single and
5992 weight_many. 4952 weight_many.
5993 4953
5994 scftorture.weight_all_wait= [KNL] 4954 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 4955 The probability weighting to use for the
5996 smp_call_function_all 4956 smp_call_function_all() function with a
5997 non-zero "wait" param 4957 non-zero "wait" parameter. See weight_single
5998 and weight_many. 4958 and weight_many.
5999 4959
6000 skew_tick= [KNL,EARLY] Offset th !! 4960 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 4961 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 4962 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 4963 Format: { "0" | "1" }
6004 0 -- disable. (may be 4964 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 4965 1 -- enable.
6006 Note: increases power 4966 Note: increases power consumption, thus should only be
6007 enabled if running ji 4967 enabled if running jitter sensitive (HPC/RT) workloads.
6008 4968
6009 security= [SECURITY] Choose a l 4969 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 4970 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 4971 "lsm=" parameter.
6012 4972
6013 selinux= [SELINUX] Disable or 4973 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 4974 Format: { "0" | "1" }
6015 See security/selinux/ 4975 See security/selinux/Kconfig help text.
6016 0 -- disable. 4976 0 -- disable.
6017 1 -- enable. 4977 1 -- enable.
6018 Default value is 1. 4978 Default value is 1.
6019 4979
6020 serialnumber [BUGS=X86-32] !! 4980 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 4981 Format: { "0" | "1" }
>> 4982 See security/apparmor/Kconfig help text
>> 4983 0 -- disable.
>> 4984 1 -- enable.
>> 4985 Default value is set via kernel config option.
6021 4986
6022 sev=option[,option...] [X86-64] See D !! 4987 serialnumber [BUGS=X86-32]
6023 4988
6024 shapers= [NET] 4989 shapers= [NET]
6025 Maximal number of sha 4990 Maximal number of shapers.
6026 4991
6027 show_lapic= [APIC,X86] Advanced P !! 4992 simeth= [IA-64]
6028 Limit apic dumping. T !! 4993 simscsi=
6029 number of local apics !! 4994
6030 to set it to "all" by !! 4995 slram= [HW,MTD]
6031 Format: { 1 (default) !! 4996
6032 The parameter valid i !! 4997 slab_nomerge [MM]
6033 apic=verbose is speci !! 4998 Disable merging of slabs with similar size. May be
6034 Example: apic=debug s !! 4999 necessary if there is some reason to distinguish
>> 5000 allocs to different slabs, especially in hardened
>> 5001 environments where the risk of heap overflows and
>> 5002 layout control by attackers can usually be
>> 5003 frustrated by disabling merging. This will reduce
>> 5004 most of the exposure of a heap attack to a single
>> 5005 cache (risks via metadata attacks are mostly
>> 5006 unchanged). Debug options disable merging on their
>> 5007 own.
>> 5008 For more information see Documentation/vm/slub.rst.
>> 5009
>> 5010 slab_max_order= [MM, SLAB]
>> 5011 Determines the maximum allowed order for slabs.
>> 5012 A high setting may cause OOMs due to memory
>> 5013 fragmentation. Defaults to 1 for systems with
>> 5014 more than 32MB of RAM, 0 otherwise.
6035 5015
6036 slab_debug[=options[,slabs][;[options !! 5016 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
6037 Enabling slab_debug a !! 5017 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 5018 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 5019 slub_debug can create guard zones around objects and
6040 may poison objects wh 5020 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 5021 last alloc / free. For more information see
6042 Documentation/mm/slub !! 5022 Documentation/vm/slub.rst.
6043 (slub_debug legacy na !! 5023
>> 5024 slub_memcg_sysfs= [MM, SLUB]
>> 5025 Determines whether to enable sysfs directories for
>> 5026 memory cgroup sub-caches. 1 to enable, 0 to disable.
>> 5027 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
>> 5028 Enabling this can lead to a very high number of debug
>> 5029 directories and files being created under
>> 5030 /sys/kernel/slub.
6044 5031
6045 slab_max_order= [MM] !! 5032 slub_max_order= [MM, SLUB]
6046 Determines the maximu 5033 Determines the maximum allowed order for slabs.
6047 A high setting may ca 5034 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 5035 fragmentation. For more information see
6049 Documentation/mm/slub !! 5036 Documentation/vm/slub.rst.
6050 (slub_max_order legac <<
6051 5037
6052 slab_merge [MM] !! 5038 slub_min_objects= [MM, SLUB]
6053 Enable merging of sla <<
6054 kernel is built witho <<
6055 (slub_merge legacy na <<
6056 <<
6057 slab_min_objects= [MM] <<
6058 The minimum number of 5039 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 5040 increase the slab order up to slub_max_order to
6060 generate a sufficient 5041 generate a sufficiently large slab able to contain
6061 the number of objects 5042 the number of objects indicated. The higher the number
6062 of objects the smalle 5043 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 5044 and the less frequently locks need to be acquired.
6064 For more information !! 5045 For more information see Documentation/vm/slub.rst.
6065 (slub_min_objects leg <<
6066 5046
6067 slab_min_order= [MM] !! 5047 slub_min_order= [MM, SLUB]
6068 Determines the minimu 5048 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 5049 lower than slub_max_order.
6070 Documentation/mm/slub !! 5050 For more information see Documentation/vm/slub.rst.
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 <<
6085 (slub_nomerge legacy <<
6086 5051
6087 slram= [HW,MTD] !! 5052 slub_nomerge [MM, SLUB]
>> 5053 Same with slab_nomerge. This is supported for legacy.
>> 5054 See slab_nomerge for more information.
6088 5055
6089 smart2= [HW] 5056 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5057 Format: <io1>[,<io2>[,...,<io8>]]
6091 5058
6092 smp.csd_lock_timeout= [KNL] <<
6093 Specify the period of <<
6094 that smp_call_functio <<
6095 for a CPU to release <<
6096 useful when diagnosin <<
6097 disabling interrupts <<
6098 of time. Defaults to <<
6099 setting a value of ze <<
6100 This feature may be m <<
6101 using the csdlock_deb <<
6102 <<
6103 smp.panic_on_ipistall= [KNL] <<
6104 If a csd_lock_timeout <<
6105 the specified number <<
6106 system. By default, <<
6107 take as long as they <<
6108 for this value provid <<
6109 <<
6110 smsc-ircc2.nopnp [HW] Don't us 5059 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5060 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5061 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5062 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5063 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5064 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5065 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5066 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5067 1: Fast pin select (default)
6119 2: ATC IRMode 5068 2: ATC IRMode
6120 5069
6121 smt= [KNL,MIPS,S390,EARLY] !! 5070 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5071 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5072 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5073 actual hardware limit.
6125 Format: <integer> 5074 Format: <integer>
6126 Default: -1 (no limit 5075 Default: -1 (no limit)
6127 5076
6128 softlockup_panic= 5077 softlockup_panic=
6129 [KNL] Should the soft 5078 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5079 Format: 0 | 1
6131 5080
6132 A value of 1 instruct 5081 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5082 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5083 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5084 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5085 respective build-time switch to that functionality.
6137 5086
6138 softlockup_all_cpu_backtrace= 5087 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5088 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5089 backtraces on all cpus.
6141 Format: 0 | 1 5090 Format: 0 | 1
6142 5091
6143 sonypi.*= [HW] Sony Programmabl 5092 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5093 See Documentation/admin-guide/laptops/sonypi.rst
6145 5094
6146 spectre_bhi= [X86] Control mitigat !! 5095 spectre_v2= [X86] Control mitigation of Spectre variant 2
6147 (BHI) vulnerability. <<
6148 deployment of the HW <<
6149 clearing sequence. <<
6150 <<
6151 on - (default) En <<
6152 needed. Thi <<
6153 both syscall <<
6154 vmexit - On systems w <<
6155 available, e <<
6156 ONLY. On su <<
6157 protected fr <<
6158 may still be <<
6159 off - Disable the <<
6160 <<
6161 spectre_v2= [X86,EARLY] Control m <<
6162 (indirect branch spec 5096 (indirect branch speculation) vulnerability.
6163 The default operation 5097 The default operation protects the kernel from
6164 user space attacks. 5098 user space attacks.
6165 5099
6166 on - unconditionall 5100 on - unconditionally enable, implies
6167 spectre_v2_use 5101 spectre_v2_user=on
6168 off - unconditionall 5102 off - unconditionally disable, implies
6169 spectre_v2_use 5103 spectre_v2_user=off
6170 auto - kernel detects 5104 auto - kernel detects whether your CPU model is
6171 vulnerable 5105 vulnerable
6172 5106
6173 Selecting 'on' will, 5107 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5108 mitigation method at run time according to the
6175 CPU, the available mi 5109 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5110 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5111 compiler with which the kernel was built.
6178 5112
6179 Selecting 'on' will a 5113 Selecting 'on' will also enable the mitigation
6180 against user space to 5114 against user space to user space task attacks.
6181 5115
6182 Selecting 'off' will 5116 Selecting 'off' will disable both the kernel and
6183 the user space protec 5117 the user space protections.
6184 5118
6185 Specific mitigations 5119 Specific mitigations can also be selected manually:
6186 5120
6187 retpoline - r 5121 retpoline - replace indirect branches
6188 retpoline,generic - R 5122 retpoline,generic - Retpolines
6189 retpoline,lfence - L 5123 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 5124 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E 5125 eibrs - Enhanced/Auto IBRS
6192 eibrs,retpoline - E 5126 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6193 eibrs,lfence - E 5127 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6194 ibrs - u 5128 ibrs - use IBRS to protect kernel
6195 5129
6196 Not specifying this o 5130 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5131 spectre_v2=auto.
6198 5132
6199 spectre_v2_user= 5133 spectre_v2_user=
6200 [X86] Control mitigat 5134 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5135 (indirect branch speculation) vulnerability between
6202 user space tasks 5136 user space tasks
6203 5137
6204 on - Uncondition 5138 on - Unconditionally enable mitigations. Is
6205 enforced by 5139 enforced by spectre_v2=on
6206 5140
6207 off - Uncondition 5141 off - Unconditionally disable mitigations. Is
6208 enforced by 5142 enforced by spectre_v2=off
6209 5143
6210 prctl - Indirect br 5144 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5145 but mitigation can be enabled via prctl
6212 per thread. 5146 per thread. The mitigation control state
6213 is inherite 5147 is inherited on fork.
6214 5148
6215 prctl,ibpb 5149 prctl,ibpb
6216 - Like "prctl 5150 - Like "prctl" above, but only STIBP is
6217 controlled 5151 controlled per thread. IBPB is issued
6218 always when 5152 always when switching between different user
6219 space proce 5153 space processes.
6220 5154
6221 seccomp 5155 seccomp
6222 - Same as "pr 5156 - Same as "prctl" above, but all seccomp
6223 threads wil 5157 threads will enable the mitigation unless
6224 they explic 5158 they explicitly opt out.
6225 5159
6226 seccomp,ibpb 5160 seccomp,ibpb
6227 - Like "secco 5161 - Like "seccomp" above, but only STIBP is
6228 controlled 5162 controlled per thread. IBPB is issued
6229 always when 5163 always when switching between different
6230 user space 5164 user space processes.
6231 5165
6232 auto - Kernel sele 5166 auto - Kernel selects the mitigation depending on
6233 the availab 5167 the available CPU features and vulnerability.
6234 5168
6235 Default mitigation: " !! 5169 Default mitigation:
>> 5170 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
6236 5171
6237 Not specifying this o 5172 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5173 spectre_v2_user=auto.
6239 5174
6240 spec_rstack_overflow= 5175 spec_rstack_overflow=
6241 [X86,EARLY] Control R !! 5176 [X86] Control RAS overflow mitigation on AMD Zen CPUs
6242 5177
6243 off - Dis 5178 off - Disable mitigation
6244 microcode - Ena 5179 microcode - Enable microcode mitigation only
6245 safe-ret - Ena 5180 safe-ret - Enable sw-only safe RET mitigation (default)
6246 ibpb - Ena 5181 ibpb - Enable mitigation by issuing IBPB on
6247 ker 5182 kernel entry
6248 ibpb-vmexit - Iss 5183 ibpb-vmexit - Issue IBPB only on VMEXIT
6249 (cl 5184 (cloud-specific mitigation)
6250 5185
6251 spec_store_bypass_disable= 5186 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5187 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5188 (Speculative Store Bypass vulnerability)
6254 5189
6255 Certain CPUs are vuln 5190 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5191 a common industry wide performance optimization known
6257 as "Speculative Store 5192 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5193 to the same memory location may not be observed by
6259 later loads during sp 5194 later loads during speculative execution. The idea
6260 is that such stores a 5195 is that such stores are unlikely and that they can
6261 be detected prior to 5196 be detected prior to instruction retirement at the
6262 end of a particular s 5197 end of a particular speculation execution window.
6263 5198
6264 In vulnerable process 5199 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5200 store can be used in a cache side channel attack, for
6266 example to read memor 5201 example to read memory to which the attacker does not
6267 directly have access 5202 directly have access (e.g. inside sandboxed code).
6268 5203
6269 This parameter contro 5204 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5205 Bypass optimization is used.
6271 5206
6272 On x86 the options ar 5207 On x86 the options are:
6273 5208
6274 on - Uncondition 5209 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5210 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5211 auto - Kernel detects whether the CPU model contains an
6277 implementat 5212 implementation of Speculative Store Bypass and
6278 picks the m 5213 picks the most appropriate mitigation. If the
6279 CPU is not 5214 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5215 CPU is vulnerable the default mitigation is
6281 architectur 5216 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5217 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5218 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5219 for a process by default. The state of the control
6285 is inherite 5220 is inherited on fork.
6286 seccomp - Same as "pr 5221 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5222 will disable SSB unless they explicitly opt out.
6288 5223
6289 Default mitigations: 5224 Default mitigations:
6290 X86: "prctl" !! 5225 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6291 5226
6292 On powerpc the option 5227 On powerpc the options are:
6293 5228
6294 on,auto - On Power8 a 5229 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5230 barrier on kernel entry and exit. On Power7
6296 perform a s 5231 perform a software flush on kernel entry and
6297 exit. 5232 exit.
6298 off - No action. 5233 off - No action.
6299 5234
6300 Not specifying this o 5235 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5236 spec_store_bypass_disable=auto.
6302 5237
>> 5238 spia_io_base= [HW,MTD]
>> 5239 spia_fio_base=
>> 5240 spia_pedr=
>> 5241 spia_peddr=
>> 5242
6303 split_lock_detect= 5243 split_lock_detect=
6304 [X86] Enable split lo !! 5244 [X86] Enable split lock detection
6305 5245
6306 When enabled (and if 5246 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5247 instructions that access data across cache line
6308 boundaries will resul !! 5248 boundaries will result in an alignment check exception.
6309 for split lock detect <<
6310 bus lock detection. <<
6311 5249
6312 off - not enabled 5250 off - not enabled
6313 5251
6314 warn - the kernel !! 5252 warn - the kernel will emit rate limited warnings
6315 about appli 5253 about applications triggering the #AC
6316 exception o !! 5254 exception. This mode is the default on CPUs
6317 the default !! 5255 that supports split lock detection.
6318 detection o <<
6319 behavior is <<
6320 enabled in <<
6321 5256
6322 fatal - the kernel 5257 fatal - the kernel will send SIGBUS to applications
6323 that trigge !! 5258 that trigger the #AC exception.
6324 exception. <<
6325 both featur <<
6326 <<
6327 ratelimit:N - <<
6328 Set system <<
6329 per second <<
6330 0 < N <= 10 <<
6331 <<
6332 N/A for spl <<
6333 <<
6334 5259
6335 If an #AC exception i 5260 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5261 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5262 the kernel will oops in either "warn" or "fatal"
6338 mode. 5263 mode.
6339 5264
6340 #DB exception for bus !! 5265 srbds= [X86,INTEL]
6341 CPL > 0. <<
6342 <<
6343 srbds= [X86,INTEL,EARLY] <<
6344 Control the Special R 5266 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5267 (SRBDS) mitigation.
6346 5268
6347 Certain CPUs are vuln 5269 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5270 exploit which can leak bits from the random
6349 number generator. 5271 number generator.
6350 5272
6351 By default, this issu 5273 By default, this issue is mitigated by
6352 microcode. However, 5274 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5275 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5276 much slower. Among other effects, this will
6355 result in reduced thr 5277 result in reduced throughput from /dev/urandom.
6356 5278
6357 The microcode mitigat 5279 The microcode mitigation can be disabled with
6358 the following option: 5280 the following option:
6359 5281
6360 off: Disable mitig 5282 off: Disable mitigation and remove
6361 performance i 5283 performance impact to RDRAND and RDSEED
6362 5284
6363 srcutree.big_cpu_lim [KNL] <<
6364 Specifies the number <<
6365 large system, such th <<
6366 should immediately al <<
6367 This kernel-boot para <<
6368 but takes effect only <<
6369 bits of srcutree.conv <<
6370 (decide at boot). <<
6371 <<
6372 srcutree.convert_to_big [KNL] <<
6373 Specifies under what <<
6374 srcu_struct structure <<
6375 form, that is, with a <<
6376 <<
6377 0: Never. <<
6378 1: At ini <<
6379 2: When r <<
6380 3: Decide <<
6381 0x1X: Above <<
6382 <<
6383 Either way, the srcu_ <<
6384 on the actual runtime <<
6385 instead of the compil <<
6386 <<
6387 srcutree.counter_wrap_check [KNL] 5285 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5286 Specifies how frequently to check for
6389 grace-period sequence 5287 grace-period sequence counter wrap for the
6390 srcu_data structure's 5288 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5289 The greater the number of bits set in this kernel
6392 parameter, the less f 5290 parameter, the less frequently counter wrap will
6393 be checked for. Note 5291 be checked for. Note that the bottom two bits
6394 are ignored. 5292 are ignored.
6395 5293
6396 srcutree.exp_holdoff [KNL] 5294 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5295 Specifies how many nanoseconds must elapse
6398 since the end of the 5296 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5297 a given srcu_struct until the next normal SRCU
6400 grace period will be 5298 grace period will be considered for automatic
6401 expediting. Set to z 5299 expediting. Set to zero to disable automatic
6402 expediting. 5300 expediting.
6403 5301
6404 srcutree.srcu_max_nodelay [KNL] !! 5302 ssbd= [ARM64,HW]
6405 Specifies the number <<
6406 per jiffy for which t <<
6407 worker thread will be <<
6408 delay. Beyond this li <<
6409 be rescheduled with a <<
6410 <<
6411 srcutree.srcu_max_nodelay_phase [KNL] <<
6412 Specifies the per-gra <<
6413 non-sleeping polls of <<
6414 grace period worker t <<
6415 with a sleep delay of <<
6416 rescan of the readers <<
6417 <<
6418 srcutree.srcu_retry_check_delay [KNL] <<
6419 Specifies number of m <<
6420 delay between each no <<
6421 <<
6422 srcutree.small_contention_lim [KNL] <<
6423 Specifies the number <<
6424 events per jiffy will <<
6425 initiating a conversi <<
6426 structure to big form <<
6427 srcutree.convert_to_b <<
6428 set for contention-ba <<
6429 <<
6430 ssbd= [ARM64,HW,EARLY] <<
6431 Speculative Store Byp 5303 Speculative Store Bypass Disable control
6432 5304
6433 On CPUs that are vuln 5305 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5306 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5307 firmware based mitigation, this parameter
6436 indicates how the mit 5308 indicates how the mitigation should be used:
6437 5309
6438 force-on: Unconditio 5310 force-on: Unconditionally enable mitigation for
6439 for both k 5311 for both kernel and userspace
6440 force-off: Unconditio 5312 force-off: Unconditionally disable mitigation for
6441 for both k 5313 for both kernel and userspace
6442 kernel: Always ena 5314 kernel: Always enable mitigation in the
6443 kernel, an 5315 kernel, and offer a prctl interface
6444 to allow u 5316 to allow userspace to register its
6445 interest i 5317 interest in being mitigated too.
6446 5318
6447 stack_guard_gap= [MM] 5319 stack_guard_gap= [MM]
6448 override the default 5320 override the default stack gap protection. The value
6449 is in page units and 5321 is in page units and it defines how many pages prior
6450 to (for stacks growin 5322 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5323 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5324 mapping. Default value is 256 pages.
6453 5325
6454 stack_depot_disable= [KNL,EARLY] <<
6455 Setting this to true <<
6456 disable the stack dep <<
6457 consumed by the stack <<
6458 to false. <<
6459 <<
6460 stacktrace [FTRACE] 5326 stacktrace [FTRACE]
6461 Enabled the stack tra 5327 Enabled the stack tracer on boot up.
6462 5328
6463 stacktrace_filter=[function-list] 5329 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5330 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up !! 5331 will trace at boot up. function-list is a comma separated
6466 list of functions. Th 5332 list of functions. This list can be changed at run
6467 time by the stack_tra 5333 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 5334 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 5335 and the stacktrace above is not needed.
6470 5336
6471 sti= [PARISC,HW] 5337 sti= [PARISC,HW]
6472 Format: <num> 5338 Format: <num>
6473 Set the STI (builtin 5339 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 5340 machines) console (graphic card) which should be used
6475 as the initial boot-c 5341 as the initial boot-console.
6476 See also comment in d 5342 See also comment in drivers/video/console/sticore.c.
6477 5343
6478 sti_font= [HW] 5344 sti_font= [HW]
6479 See comment in driver 5345 See comment in drivers/video/console/sticore.c.
6480 5346
6481 stifb= [HW] 5347 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 5348 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 5349
6484 strict_sas_size= <<
6485 [X86] <<
6486 Format: <bool> <<
6487 Enable or disable str <<
6488 against the required <<
6489 depends on the suppor <<
6490 be used to filter out <<
6491 not yet been made awa <<
6492 <<
6493 stress_hpt [PPC,EARLY] <<
6494 Limits the number of <<
6495 page table to increas <<
6496 faults on kernel addr <<
6497 <<
6498 stress_slb [PPC,EARLY] <<
6499 Limits the number of <<
6500 them frequently to in <<
6501 on kernel addresses. <<
6502 <<
6503 sunrpc.min_resvport= 5350 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 5351 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 5352 [NFS,SUNRPC]
6506 SunRPC servers often 5353 SunRPC servers often require that client requests
6507 originate from a priv 5354 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 5355 range 0 < portnr < 1024).
6509 An administrator who 5356 An administrator who wishes to reserve some of these
6510 ports for other uses 5357 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 5358 kernel's sunrpc client considers to be privileged
6512 using these two param 5359 using these two parameters to set the minimum and
6513 maximum port values. 5360 maximum port values.
6514 5361
6515 sunrpc.svc_rpc_per_connection_limit= 5362 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 5363 [NFS,SUNRPC]
6517 Limit the number of r 5364 Limit the number of requests that the server will
6518 process in parallel f 5365 process in parallel from a single connection.
6519 The default value is 5366 The default value is 0 (no limit).
6520 5367
6521 sunrpc.pool_mode= 5368 sunrpc.pool_mode=
6522 [NFS] 5369 [NFS]
6523 Control how the NFS s 5370 Control how the NFS server code allocates CPUs to
6524 service thread pools. 5371 service thread pools. Depending on how many NICs
6525 you have and where th 5372 you have and where their interrupts are bound, this
6526 option will affect wh 5373 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 5374 Note: this parameter cannot be changed while the
6528 NFS server is running 5375 NFS server is running.
6529 5376
6530 auto the serve 5377 auto the server chooses an appropriate mode
6531 automatic 5378 automatically using heuristics
6532 global a single 5379 global a single global pool contains all CPUs
6533 percpu one pool 5380 percpu one pool for each CPU
6534 pernode one pool 5381 pernode one pool for each NUMA node (equivalent
6535 to global 5382 to global on non-NUMA machines)
6536 5383
6537 sunrpc.tcp_slot_table_entries= 5384 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 5385 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 5386 [NFS,SUNRPC]
6540 Sets the upper limit 5387 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 5388 RPC calls that can be sent from the client to a
6542 server. Increasing th 5389 server. Increasing these values may allow you to
6543 improve throughput, b 5390 improve throughput, but will also increase the
6544 amount of memory rese 5391 amount of memory reserved for use by the client.
6545 5392
6546 suspend.pm_test_delay= 5393 suspend.pm_test_delay=
6547 [SUSPEND] 5394 [SUSPEND]
6548 Sets the number of se 5395 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 5396 mode before resuming the system (see
6550 /sys/power/pm_test). 5397 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 5398 is set. Default value is 5.
6552 5399
6553 svm= [PPC] 5400 svm= [PPC]
6554 Format: { on | off | 5401 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 5402 This parameter controls use of the Protected
6556 Execution Facility on 5403 Execution Facility on pSeries.
6557 5404
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 5405 swapaccount=[0|1]
6559 Format: { <int> [,<in !! 5406 [KNL] Enable accounting of swap in memory resource
>> 5407 controller if no parameter or 1 is given or disable
>> 5408 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
>> 5409
>> 5410 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
>> 5411 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 5412 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 5413 force -- force using of bounce buffers even if they
6565 wouldn't be 5414 wouldn't be automatically used by the kernel
6566 noforce -- Never use 5415 noforce -- Never use bounce buffers (for debugging)
6567 5416
6568 switches= [HW,M68k,EARLY] !! 5417 switches= [HW,M68k]
6569 5418
6570 sysctl.*= [KNL] 5419 sysctl.*= [KNL]
6571 Set a sysctl paramete 5420 Set a sysctl parameter, right before loading the init
6572 process, as if the va 5421 process, as if the value was written to the respective
6573 /proc/sys/... file. B 5422 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 5423 separators. Unrecognized parameters and invalid values
6575 are reported in the k 5424 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 5425 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 5426 Example: sysctl.vm.swappiness=40
6578 5427
>> 5428 sysfs.deprecated=0|1 [KNL]
>> 5429 Enable/disable old style sysfs layout for old udev
>> 5430 on older distributions. When this option is enabled
>> 5431 very new udev will not work anymore. When this option
>> 5432 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 5433 in older udev will not work anymore.
>> 5434 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 5435 the kernel configuration.
>> 5436
6579 sysrq_always_enabled 5437 sysrq_always_enabled
6580 [KNL] 5438 [KNL]
6581 Ignore sysrq setting 5439 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 5440 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 5441 Useful for debugging.
6584 5442
6585 tcpmhash_entries= [KNL,NET] 5443 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 5444 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 5445 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 5446 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 5447 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 5448 "tcp_no_metrics_save" section for more details.
6591 5449
6592 tdfx= [HW,DRM] 5450 tdfx= [HW,DRM]
6593 5451
6594 test_suspend= [SUSPEND] !! 5452 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 5453 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 5454 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 5455 as the system sleep state during system startup with
6599 the optional capabili 5456 the optional capability to repeat N number of times.
6600 The system is woken f 5457 The system is woken from this state using a
6601 wakeup-capable RTC al 5458 wakeup-capable RTC alarm.
6602 5459
6603 thash_entries= [KNL,NET] 5460 thash_entries= [KNL,NET]
6604 Set number of hash bu 5461 Set number of hash buckets for TCP connection
6605 5462
6606 thermal.act= [HW,ACPI] 5463 thermal.act= [HW,ACPI]
6607 -1: disable all activ 5464 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 5465 <degrees C>: override all lowest active trip points
6609 5466
6610 thermal.crt= [HW,ACPI] 5467 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 5468 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 5469 <degrees C>: override all critical trip points
6613 5470
>> 5471 thermal.nocrt= [HW,ACPI]
>> 5472 Set to disable actions on ACPI thermal zone
>> 5473 critical and hot trip points.
>> 5474
6614 thermal.off= [HW,ACPI] 5475 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 5476 1: disable ACPI thermal control
6616 5477
6617 thermal.psv= [HW,ACPI] 5478 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 5479 -1: disable all passive trip points
6619 <degrees C>: override 5480 <degrees C>: override all passive trip points to this
6620 value 5481 value
6621 5482
6622 thermal.tzp= [HW,ACPI] 5483 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 5484 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 5485 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 5486 0: no polling (default)
6626 5487
6627 threadirqs [KNL,EARLY] !! 5488 threadirqs [KNL]
6628 Force threading of al 5489 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 5490 marked explicitly IRQF_NO_THREAD.
6630 5491
6631 topology= [S390,EARLY] !! 5492 topology= [S390]
6632 Format: {off | on} 5493 Format: {off | on}
6633 Specify if the kernel 5494 Specify if the kernel should make use of the cpu
6634 topology information 5495 topology information if the hardware supports this.
6635 The scheduler will ma 5496 The scheduler will make use of this information and
6636 e.g. base its process 5497 e.g. base its process migration decisions on it.
6637 Default is on. 5498 Default is on.
6638 5499
>> 5500 topology_updates= [KNL, PPC, NUMA]
>> 5501 Format: {off}
>> 5502 Specify if the kernel should ignore (off)
>> 5503 topology updates sent by the hypervisor to this
>> 5504 LPAR.
>> 5505
6639 torture.disable_onoff_at_boot= [KNL] 5506 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 5507 Prevent the CPU-hotplug component of torturing
6641 until after init has 5508 until after init has spawned.
6642 5509
6643 torture.ftrace_dump_at_shutdown= [KNL 5510 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 5511 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 5512 even if there were no errors. This can be a
6646 very costly operation 5513 very costly operation when many torture tests
6647 are running concurren 5514 are running concurrently, especially on systems
6648 with rotating-rust st 5515 with rotating-rust storage.
6649 5516
6650 torture.verbose_sleep_frequency= [KNL !! 5517 tp720= [HW,PS2]
6651 Specifies how many ve <<
6652 emitted between each <<
6653 disables verbose-prin <<
6654 <<
6655 torture.verbose_sleep_duration= [KNL] <<
6656 Duration of each verb <<
6657 5518
6658 tpm_suspend_pcr=[HW,TPM] 5519 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 5520 Format: integer pcr id
6660 Specify that at suspe 5521 Specify that at suspend time, the tpm driver
6661 should extend the spe 5522 should extend the specified pcr with zeros,
6662 as a workaround for s 5523 as a workaround for some chips which fail to
6663 flush the last writte 5524 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 5525 This will guarantee that all the other pcrs
6665 are saved. 5526 are saved.
6666 5527
6667 tpm_tis.interrupts= [HW,TPM] <<
6668 Enable interrupts for <<
6669 for the FIFO interfac <<
6670 (0). For more informa <<
6671 defined by Trusted Co <<
6672 https://trustedcomput <<
6673 <<
6674 tp_printk [FTRACE] <<
6675 Have the tracepoints <<
6676 tracing ring buffer. <<
6677 where the system hang <<
6678 option for reading th <<
6679 ftrace_dump_on_oops. <<
6680 <<
6681 To turn off having tr <<
6682 echo 0 > /proc/sys/k <<
6683 Note, echoing 1 into <<
6684 tp_printk kernel cmdl <<
6685 <<
6686 The tp_printk_stop_on <<
6687 to stop the printing <<
6688 late_initcall_sync. <<
6689 <<
6690 ** CAUTION ** <<
6691 <<
6692 Having tracepoints se <<
6693 frequency tracepoints <<
6694 the system to live lo <<
6695 <<
6696 tp_printk_stop_on_boot [FTRACE] <<
6697 When tp_printk (above <<
6698 on the console. It ma <<
6699 printing of events du <<
6700 make the system inope <<
6701 <<
6702 This command line opt <<
6703 to console at the lat <<
6704 <<
6705 trace_buf_size=nn[KMG] 5528 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 5529 [FTRACE] will set tracing buffer size on each cpu.
6707 5530
6708 trace_clock= [FTRACE] Set the cloc <<
6709 at boot up. <<
6710 local - Use the per C <<
6711 (converted in <<
6712 depending on <<
6713 in sync betwe <<
6714 global - Event time s <<
6715 CPUs. May be <<
6716 but better fo <<
6717 counter - Simple coun <<
6718 note, some co <<
6719 infrastructur <<
6720 once per even <<
6721 uptime - Use jiffies <<
6722 perf - Use the same c <<
6723 mono - Use ktime_get_ <<
6724 mono_raw - Use ktime_ <<
6725 stamps. <<
6726 boot - Use ktime_get_ <<
6727 Architectures may add <<
6728 Documentation/trace/f <<
6729 <<
6730 trace_event=[event-list] 5531 trace_event=[event-list]
6731 [FTRACE] Set and star 5532 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 5533 to facilitate early boot debugging. The event-list is a
6733 comma-separated list !! 5534 comma separated list of trace events to enable. See
6734 also Documentation/tr 5535 also Documentation/trace/events.rst
6735 5536
6736 trace_instance=[instance-info] <<
6737 [FTRACE] Create a rin <<
6738 This will be listed i <<
6739 <<
6740 /sys/kernel/t <<
6741 <<
6742 Events can be enabled <<
6743 via: <<
6744 <<
6745 trace_instanc <<
6746 <<
6747 Note, the "<system*>: <<
6748 unique. <<
6749 <<
6750 trace_instanc <<
6751 <<
6752 will enable the "sche <<
6753 the same thing would <<
6754 event, and all events <<
6755 <<
6756 trace_options=[option-list] 5537 trace_options=[option-list]
6757 [FTRACE] Enable or di 5538 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 5539 The option-list is a comma delimited list of options
6759 that can be enabled o 5540 that can be enabled or disabled just as if you were
6760 to echo the option na 5541 to echo the option name into
6761 5542
6762 /sys/kernel/traci !! 5543 /sys/kernel/debug/tracing/trace_options
6763 5544
6764 For example, to enabl 5545 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 5546 stack trace of each event), add to the command line:
6766 5547
6767 trace_options=s 5548 trace_options=stacktrace
6768 5549
6769 See also Documentatio 5550 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 5551 section.
6771 5552
6772 trace_trigger=[trigger-list] !! 5553 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 5554 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 5555 tracing ring buffer. This is useful for early boot up
6775 filter. !! 5556 where the system hangs or reboots and does not give the
6776 !! 5557 option for reading the tracing buffer or performing a
6777 The format is is "tra !! 5558 ftrace_dump_on_oops.
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 5559
6784 The above will enable !! 5560 To turn off having tracepoints sent to printk,
6785 event but only trigge !! 5561 echo 0 > /proc/sys/kernel/tracepoint_printk
6786 event is "2" (TASK_UN !! 5562 Note, echoing 1 into this file without the
>> 5563 tracepoint_printk kernel cmdline option has no effect.
6787 5564
6788 See also "Event trigg !! 5565 ** CAUTION **
6789 5566
>> 5567 Having tracepoints sent to printk() and activating high
>> 5568 frequency tracepoints such as irq or sched, can cause
>> 5569 the system to live lock.
6790 5570
6791 traceoff_on_warning 5571 traceoff_on_warning
6792 [FTRACE] enable this 5572 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 5573 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 5574 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 5575 file located in /sys/kernel/debug/tracing/
6796 5576
6797 This option is useful 5577 This option is useful, as it disables the trace before
6798 the WARNING dump is c 5578 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 5579 be filled with content caused by the warning output.
6800 5580
6801 This option can also 5581 This option can also be set at run time via the sysctl
6802 option: kernel/trace 5582 option: kernel/traceoff_on_warning
6803 5583
6804 transparent_hugepage= 5584 transparent_hugepage=
6805 [KNL] 5585 [KNL]
6806 Format: [always|madvi 5586 Format: [always|madvise|never]
6807 Can be used to contro 5587 Can be used to control the default behavior of the system
6808 with respect to trans 5588 with respect to transparent hugepages.
6809 See Documentation/adm 5589 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 5590 for more details.
6811 5591
6812 trusted.source= [KEYS] <<
6813 Format: <string> <<
6814 This parameter identi <<
6815 for trusted keys impl <<
6816 sources: <<
6817 - "tpm" <<
6818 - "tee" <<
6819 - "caam" <<
6820 - "dcp" <<
6821 If not specified then <<
6822 the trust source list <<
6823 first trust source as <<
6824 successfully during i <<
6825 <<
6826 trusted.rng= [KEYS] <<
6827 Format: <string> <<
6828 The RNG used to gener <<
6829 Can be one of: <<
6830 - "kernel" <<
6831 - the same value as t <<
6832 - "default" <<
6833 If not specified, "de <<
6834 the RNG's choice is l <<
6835 <<
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 5592 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 5593 Format: <string>
6850 [x86] reliable: mark 5594 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 5595 disables clocksource verification at runtime, as well
6852 as the stability chec 5596 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 5597 high-resolution timer mode on older hardware, and in
6854 virtualized environme 5598 virtualized environment.
6855 [x86] noirqtime: Do n 5599 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 5600 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 5601 platforms where RDTSC is slow and this accounting
6858 can add overhead. 5602 can add overhead.
6859 [x86] unstable: mark 5603 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 5604 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 5605 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 5606 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 5607 in situations with strict latency requirements (where
6864 interruptions from cl 5608 interruptions from clocksource watchdog are not
6865 acceptable). 5609 acceptable).
6866 [x86] recalibrate: fo <<
6867 (HPET or PM timer) on <<
6868 obtained from HW or F <<
6869 Warn if the differenc <<
6870 [x86] watchdog: Use T <<
6871 which to check other <<
6872 only on systems where <<
6873 This will be suppress <<
6874 can be overridden by <<
6875 message will flag any <<
6876 5610
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 5611 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 5612 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 5613 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 5614 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 5615 Format: <unsigned int>
6882 5616
6883 tsx= [X86] Control Transac 5617 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 5618 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 5619 support TSX control.
6886 5620
6887 This parameter contro 5621 This parameter controls the TSX feature. The options are:
6888 5622
6889 on - Enable TSX 5623 on - Enable TSX on the system. Although there are
6890 mitigations f 5624 mitigations for all known security vulnerabilities,
6891 TSX has been 5625 TSX has been known to be an accelerator for
6892 several previ 5626 several previous speculation-related CVEs, and
6893 so there may 5627 so there may be unknown security risks associated
6894 with leaving 5628 with leaving it enabled.
6895 5629
6896 off - Disable TSX 5630 off - Disable TSX on the system. (Note that this
6897 option takes 5631 option takes effect only on newer CPUs which are
6898 not vulnerabl 5632 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 5633 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 5634 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 5635 update. This new MSR allows for the reliable
6902 deactivation 5636 deactivation of the TSX functionality.)
6903 5637
6904 auto - Disable TSX 5638 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 5639 otherwise enable TSX on the system.
6906 5640
6907 Not specifying this o 5641 Not specifying this option is equivalent to tsx=off.
6908 5642
6909 See Documentation/adm 5643 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 5644 for more details.
6911 5645
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 5646 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 5647 Abort (TAA) vulnerability.
6914 5648
6915 Similar to Micro-arch 5649 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 5650 certain CPUs that support Transactional
6917 Synchronization Exten 5651 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 5652 exploit against CPU internal buffers which can forward
6919 information to a disc 5653 information to a disclosure gadget under certain
6920 conditions. 5654 conditions.
6921 5655
6922 In vulnerable process 5656 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 5657 data can be used in a cache side channel attack, to
6924 access data to which 5658 access data to which the attacker does not have direct
6925 access. 5659 access.
6926 5660
6927 This parameter contro 5661 This parameter controls the TAA mitigation. The
6928 options are: 5662 options are:
6929 5663
6930 full - Enable T 5664 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 5665 if TSX is enabled.
6932 5666
6933 full,nosmt - Enable T 5667 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 5668 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 5669 is not disabled because CPU is not
6936 vulnerab 5670 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 5671 off - Unconditionally disable TAA mitigation
6938 5672
6939 On MDS-affected machi 5673 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 5674 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 5675 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 5676 this mitigation, you need to specify mds=off too.
6943 5677
6944 Not specifying this o 5678 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 5679 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 5680 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 5681 required and doesn't provide any additional
6948 mitigation. 5682 mitigation.
6949 5683
6950 For details see: 5684 For details see:
6951 Documentation/admin-g 5685 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 5686
6953 turbografx.map[2|3]= [HW,JOY] 5687 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 5688 TurboGraFX parallel port interface
6955 Format: 5689 Format:
6956 <port#>,<js1>,<js2>,< 5690 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 5691 See also Documentation/input/devices/joystick-parport.rst
6958 5692
6959 udbg-immortal [PPC] When debugging 5693 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 5694 happen after console_init() and before a proper
6961 console driver takes 5695 console driver takes over, this boot options might
6962 help "seeing" what's 5696 help "seeing" what's going on.
6963 5697
6964 uhash_entries= [KNL,NET] 5698 uhash_entries= [KNL,NET]
6965 Set number of hash bu 5699 Set number of hash buckets for UDP/UDP-Lite connections
6966 5700
6967 uhci-hcd.ignore_oc= 5701 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 5702 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 5703 Some badly-designed motherboards generate lots of
6970 bogus events, for por 5704 bogus events, for ports that aren't wired to
6971 anything. Set this p 5705 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 5706 Note that genuine overcurrent events won't be
6973 reported either. 5707 reported either.
6974 5708
6975 unknown_nmi_panic 5709 unknown_nmi_panic
6976 [X86] Cause panic on 5710 [X86] Cause panic on unknown NMI.
6977 5711
6978 unwind_debug [X86-64,EARLY] <<
6979 Enable unwinder debug <<
6980 useful for debugging <<
6981 conditions, including <<
6982 bad/missing unwinder <<
6983 <<
6984 usbcore.authorized_default= 5712 usbcore.authorized_default=
6985 [USB] Default USB dev 5713 [USB] Default USB device authorization:
6986 (default -1 = authori !! 5714 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 5715 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 5716 if device connected to internal port)
6989 5717
6990 usbcore.autosuspend= 5718 usbcore.autosuspend=
6991 [USB] The autosuspend 5719 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 5720 for newly-detected USB devices (default 2). This
6993 is the time required 5721 is the time required before an idle device will be
6994 autosuspended. Devic 5722 autosuspended. Devices for which the delay is set
6995 to a negative value w 5723 to a negative value won't be autosuspended at all.
6996 5724
6997 usbcore.usbfs_snoop= 5725 usbcore.usbfs_snoop=
6998 [USB] Set to log all 5726 [USB] Set to log all usbfs traffic (default 0 = off).
6999 5727
7000 usbcore.usbfs_snoop_max= 5728 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 5729 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 5730 (default = 65536).
7003 5731
7004 usbcore.blinkenlights= 5732 usbcore.blinkenlights=
7005 [USB] Set to cycle le 5733 [USB] Set to cycle leds on hubs (default 0 = off).
7006 5734
7007 usbcore.old_scheme_first= 5735 usbcore.old_scheme_first=
7008 [USB] Start with the 5736 [USB] Start with the old device initialization
7009 scheme (default 0 = o 5737 scheme (default 0 = off).
7010 5738
7011 usbcore.usbfs_memory_mb= 5739 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 5740 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 5741 usbfs (default = 16, 0 = max = 2047).
7014 5742
7015 usbcore.use_both_schemes= 5743 usbcore.use_both_schemes=
7016 [USB] Try the other d 5744 [USB] Try the other device initialization scheme
7017 if the first one fail 5745 if the first one fails (default 1 = enabled).
7018 5746
7019 usbcore.initial_descriptor_timeout= 5747 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 5748 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 5749 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 5750 (default 5000 = 5.0 seconds).
7023 5751
7024 usbcore.nousb [USB] Disable the USB 5752 usbcore.nousb [USB] Disable the USB subsystem
7025 5753
7026 usbcore.quirks= 5754 usbcore.quirks=
7027 [USB] A list of quirk 5755 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 5756 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 5757 commas. Each entry has the form
7030 VendorID:ProductID:Fl 5758 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 5759 numbers and Flags is a set of letters. Each letter
7032 will change the built 5760 will change the built-in quirk; setting it if it is
7033 clear and clearing it 5761 clear and clearing it if it is set. The letters have
7034 the following meaning 5762 the following meanings:
7035 a = USB_QUIRK 5763 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 5764 descriptors must not be fetched using
7037 a 255 5765 a 255-byte read);
7038 b = USB_QUIRK 5766 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 5767 correctly so reset it instead);
7040 c = USB_QUIRK 5768 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 5769 Set-Interface requests);
7042 d = USB_QUIRK 5770 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 5771 handle its Configuration or Interface
7044 strin 5772 strings);
7045 e = USB_QUIRK 5773 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 5774 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 5775 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 5776 more interface descriptions than the
7049 bNumI 5777 bNumInterfaces count, and can't handle
7050 talki 5778 talking to these interfaces);
7051 g = USB_QUIRK 5779 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 5780 during initialization, after we read
7053 the d 5781 the device descriptor);
7054 h = USB_QUIRK 5782 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 5783 high speed and super speed interrupt
7056 endpo 5784 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 5785 require the interval in microframes (1
7058 micro 5786 microframe = 125 microseconds) to be
7059 calcu 5787 calculated as interval = 2 ^
7060 (bInt 5788 (bInterval-1).
7061 Devic 5789 Devices with this quirk report their
7062 bInte 5790 bInterval as the result of this
7063 calcu 5791 calculation instead of the exponent
7064 varia 5792 variable used in the calculation);
7065 i = USB_QUIRK 5793 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 5794 handle device_qualifier descriptor
7067 reque 5795 requests);
7068 j = USB_QUIRK 5796 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 5797 generates spurious wakeup, ignore
7070 remot 5798 remote wakeup capability);
7071 k = USB_QUIRK 5799 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 5800 Power Management);
7073 l = USB_QUIRK 5801 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 5802 (Device reports its bInterval as linear
7075 frame 5803 frames instead of the USB 2.0
7076 calcu 5804 calculation);
7077 m = USB_QUIRK 5805 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 5806 to be disconnected before suspend to
7079 preve 5807 prevent spurious wakeup);
7080 n = USB_QUIRK 5808 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 5809 pause after every control message);
7082 o = USB_QUIRK 5810 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 5811 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 5812 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 5813
7089 usbhid.mousepoll= 5814 usbhid.mousepoll=
7090 [USBHID] The interval 5815 [USBHID] The interval which mice are to be polled at.
7091 5816
7092 usbhid.jspoll= 5817 usbhid.jspoll=
7093 [USBHID] The interval 5818 [USBHID] The interval which joysticks are to be polled at.
7094 5819
7095 usbhid.kbpoll= 5820 usbhid.kbpoll=
7096 [USBHID] The interval 5821 [USBHID] The interval which keyboards are to be polled at.
7097 5822
7098 usb-storage.delay_use= 5823 usb-storage.delay_use=
7099 [UMS] The delay in se 5824 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 5825 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 5826
7105 usb-storage.quirks= 5827 usb-storage.quirks=
7106 [UMS] A list of quirk 5828 [UMS] A list of quirks entries to supplement or
7107 override the built-in 5829 override the built-in unusual_devs list. List
7108 entries are separated 5830 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 5831 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 5832 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 5833 Flags is a set of characters, each corresponding
7112 to a common usb-stora 5834 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 5835 a = SANE_SENSE (collect more than 18 bytes
7114 of se 5836 of sense data, not on uas);
7115 b = BAD_SENSE 5837 b = BAD_SENSE (don't collect more than 18
7116 bytes 5838 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 5839 c = FIX_CAPACITY (decrease the reported
7118 devic 5840 device capacity by one sector);
7119 d = NO_READ_D 5841 d = NO_READ_DISC_INFO (don't use
7120 READ_ 5842 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 5843 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 5844 READ_CAPACITY_16 command);
7123 f = NO_REPORT 5845 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 5846 command, uas only);
7125 g = MAX_SECTO 5847 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 5848 240 sectors at a time, uas only);
7127 h = CAPACITY_ 5849 h = CAPACITY_HEURISTICS (decrease the
7128 repor 5850 reported device capacity by one
7129 secto 5851 sector if the number is odd);
7130 i = IGNORE_DE 5852 i = IGNORE_DEVICE (don't bind to this
7131 devic 5853 device);
7132 j = NO_REPORT 5854 j = NO_REPORT_LUNS (don't use report luns
7133 comma 5855 command, uas only);
7134 k = NO_SAME ( 5856 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 5857 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 5858 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 5859 m = MAX_SECTORS_64 (don't transfer more
7138 than 5860 than 64 sectors = 32 KB at a time,
7139 not o 5861 not on uas);
7140 n = INITIAL_R 5862 n = INITIAL_READ10 (force a retry of the
7141 initi 5863 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 5864 o = CAPACITY_OK (accept the capacity
7143 repor 5865 reported by the device, not on uas);
7144 p = WRITE_CAC 5866 p = WRITE_CACHE (the device cache is ON
7145 by de 5867 by default, not on uas);
7146 r = IGNORE_RE 5868 r = IGNORE_RESIDUE (the device reports
7147 bogus 5869 bogus residue values, not on uas);
7148 s = SINGLE_LU 5870 s = SINGLE_LUN (the device has only one
7149 Logic 5871 Logical Unit);
7150 t = NO_ATA_1X 5872 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 5873 commands, uas only);
7152 u = IGNORE_UA 5874 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 5875 w = NO_WP_DETECT (don't test whether the
7154 mediu 5876 medium is write-protected).
7155 y = ALWAYS_SY 5877 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 5878 even if the device claims no cache,
7157 not o 5879 not on uas)
7158 Example: quirks=0419: 5880 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 5881
7160 user_debug= [KNL,ARM] 5882 user_debug= [KNL,ARM]
7161 Format: <int> 5883 Format: <int>
7162 See arch/arm/Kconfig. 5884 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 5885 1 - undefined instruction events
7164 2 - system c 5886 2 - system calls
7165 4 - invalid 5887 4 - invalid data aborts
7166 8 - SIGSEGV 5888 8 - SIGSEGV faults
7167 16 - SIGBUS f 5889 16 - SIGBUS faults
7168 Example: user_debug=3 5890 Example: user_debug=31
7169 5891
7170 userpte= 5892 userpte=
7171 [X86,EARLY] Flags con !! 5893 [X86] Flags controlling user PTE allocations.
7172 5894
7173 nohigh = do n 5895 nohigh = do not allocate PTE pages in
7174 HIGHM 5896 HIGHMEM regardless of setting
7175 of CO 5897 of CONFIG_HIGHPTE.
7176 5898
7177 vdso= [X86,SH,SPARC] !! 5899 vdso= [X86,SH]
7178 On X86_32, this is an 5900 On X86_32, this is an alias for vdso32=. Otherwise:
7179 5901
7180 vdso=1: enable VDSO ( 5902 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 5903 vdso=0: disable VDSO mapping
7182 5904
7183 vdso32= [X86] Control the 32- 5905 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 5906 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 5907 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 5908
7187 See the help text for 5909 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 5910 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 5911 vdso32=0; otherwise, the default is vdso32=1.
7190 5912
7191 For compatibility wit 5913 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 5914 alias for vdso32=0.
7193 5915
7194 Try vdso32=0 if you e 5916 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 5917 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 5918
7197 video= [FB,EARLY] Frame buff !! 5919 vector= [IA-64,SMP]
>> 5920 vector=percpu: enable percpu vector domain
>> 5921
>> 5922 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 5923 See Documentation/fb/modedb.rst.
7199 5924
7200 video.brightness_switch_enabled= [ACP !! 5925 video.brightness_switch_enabled= [0,1]
7201 Format: [0|1] <<
7202 If set to 1, on recei 5926 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 5927 generated by hotkey, video driver will adjust brightness
7204 level and then send o 5928 level and then send out the event to user space through
7205 the allocated input d !! 5929 the allocated input device; If set to 0, video driver
7206 will only send out th 5930 will only send out the event without touching backlight
7207 brightness level. 5931 brightness level.
7208 default: 1 5932 default: 1
7209 5933
7210 virtio_mmio.device= 5934 virtio_mmio.device=
7211 [VMMIO] Memory mapped 5935 [VMMIO] Memory mapped virtio (platform) device.
7212 5936
7213 <size>@<basead 5937 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 5938 where:
7215 <size> := 5939 <size> := size (can use standard suffixes
7216 5940 like K, M and G)
7217 <baseaddr> := 5941 <baseaddr> := physical base address
7218 <irq> := 5942 <irq> := interrupt number (as passed to
7219 5943 request_irq())
7220 <id> := 5944 <id> := (optional) platform device id
7221 example: 5945 example:
7222 virtio_mmio.d 5946 virtio_mmio.device=1K@0x100b0000:48:7
7223 5947
7224 Can be used multiple 5948 Can be used multiple times for multiple devices.
7225 5949
7226 vga= [BOOT,X86-32] Select 5950 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 5951 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 5952 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 5953 Use vga=ask for menu.
7230 This is actually a bo 5954 This is actually a boot loader parameter; the value is
7231 passed to the kernel 5955 passed to the kernel using a special protocol.
7232 5956
7233 vm_debug[=options] [KNL] Availab 5957 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 5958 May slow down system boot speed, especially when
7235 enabled on systems wi 5959 enabled on systems with a large amount of memory.
7236 All options are enabl 5960 All options are enabled by default, and this
7237 interface is meant to 5961 interface is meant to allow for selectively
7238 enabling or disabling 5962 enabling or disabling specific virtual memory
7239 debugging features. 5963 debugging features.
7240 5964
7241 Available options are 5965 Available options are:
7242 P Enable page s 5966 P Enable page structure init time poisoning
7243 - Disable all o 5967 - Disable all of the above options
7244 5968
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 5969 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 5970 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 5971 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 5972 decrease the size and leave more room for directly
7249 for directly mapped k !! 5973 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 5974
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 5975 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 5976 Sets the memory size reserved for contiguous memory
7256 allocations for the v 5977 allocations for the vmcp device driver.
7257 5978
7258 vmhalt= [KNL,S390] Perform z/ 5979 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 5980 Format: <command>
7260 5981
7261 vmpanic= [KNL,S390] Perform z/ 5982 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 5983 Format: <command>
7263 5984
7264 vmpoff= [KNL,S390] Perform z/ 5985 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 5986 Format: <command>
7266 5987
7267 vsyscall= [X86-64,EARLY] !! 5988 vsyscall= [X86-64]
7268 Controls the behavior 5989 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 5990 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 5991 code). Most statically-linked binaries and older
7271 versions of glibc use 5992 versions of glibc use these calls. Because these
7272 functions are at fixe 5993 functions are at fixed addresses, they make nice
7273 targets for exploits 5994 targets for exploits that can control RIP.
7274 5995
7275 emulate Vsyscalls !! 5996 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 5997 emulated reasonably safely. The vsyscall
7277 readable. !! 5998 page is readable.
7278 5999
7279 xonly [default] !! 6000 xonly Vsyscalls turn into traps and are
7280 emulated 6001 emulated reasonably safely. The vsyscall
7281 page is n 6002 page is not readable.
7282 6003
7283 none Vsyscalls 6004 none Vsyscalls don't work at all. This makes
7284 them quit 6005 them quite hard to use for exploits but
7285 might bre 6006 might break your system.
7286 6007
7287 vt.color= [VT] Default text col 6008 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6009 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6010 Default: 0x07 = light gray on black.
7290 6011
7291 vt.cur_default= [VT] Default cursor s 6012 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6013 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6014 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6015 see VGA-softcursor.txt. Default: 2 = underline.
7295 6016
7296 vt.default_blu= [VT] 6017 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6018 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6019 Change the default blue palette of the console.
7299 This is a 16-member a 6020 This is a 16-member array composed of values
7300 ranging from 0-255. 6021 ranging from 0-255.
7301 6022
7302 vt.default_grn= [VT] 6023 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6024 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6025 Change the default green palette of the console.
7305 This is a 16-member a 6026 This is a 16-member array composed of values
7306 ranging from 0-255. 6027 ranging from 0-255.
7307 6028
7308 vt.default_red= [VT] 6029 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6030 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6031 Change the default red palette of the console.
7311 This is a 16-member a 6032 This is a 16-member array composed of values
7312 ranging from 0-255. 6033 ranging from 0-255.
7313 6034
7314 vt.default_utf8= 6035 vt.default_utf8=
7315 [VT] 6036 [VT]
7316 Format=<0|1> 6037 Format=<0|1>
7317 Set system-wide defau 6038 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6039 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6040 newly opened terminals.
7320 6041
7321 vt.global_cursor_default= 6042 vt.global_cursor_default=
7322 [VT] 6043 [VT]
7323 Format=<-1|0|1> 6044 Format=<-1|0|1>
7324 Set system-wide defau 6045 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6046 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6047 i.e. cursors will be created by default unless
7327 overridden by individ 6048 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6049 cursors, 1 will display them.
7329 6050
7330 vt.italic= [VT] Default color fo 6051 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6052 Default: 2 = green.
7332 6053
7333 vt.underline= [VT] Default color fo 6054 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6055 Default: 3 = cyan.
7335 6056
7336 watchdog timers [HW,WDT] For informat 6057 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6058 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6059 or other driver-specific files in the
7339 Documentation/watchdo 6060 Documentation/watchdog/ directory.
7340 6061
7341 watchdog_thresh= 6062 watchdog_thresh=
7342 [KNL] 6063 [KNL]
7343 Set the hard lockup d 6064 Set the hard lockup detector stall duration
7344 threshold in seconds. 6065 threshold in seconds. The soft lockup detector
7345 threshold is set to t 6066 threshold is set to twice the value. A value of 0
7346 disables both lockup 6067 disables both lockup detectors. Default is 10
7347 seconds. 6068 seconds.
7348 6069
7349 workqueue.unbound_cpus= <<
7350 [KNL,SMP] Specify to <<
7351 to use in unbound wor <<
7352 Format: <cpu-list> <<
7353 By default, all onlin <<
7354 unbound workqueues. <<
7355 <<
7356 workqueue.watchdog_thresh= 6070 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 6071 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 6072 warn stall conditions and dump internal state to
7359 help debugging. 0 di 6073 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 6074 detection; otherwise, it's the stall threshold
7361 duration in seconds. 6075 duration in seconds. The default value is 30 and
7362 it can be updated at 6076 it can be updated at runtime by writing to the
7363 corresponding sysfs f 6077 corresponding sysfs file.
7364 6078
7365 workqueue.cpu_intensive_thresh_us= !! 6079 workqueue.disable_numa
7366 Per-cpu work items wh !! 6080 By default, all work items queued to unbound
7367 threshold are automat !! 6081 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 6082 issued on, which results in better behavior in
7369 them from noticeably !! 6083 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 6084 whatever reason, this option can be used. Note
7371 !! 6085 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 6086 workqueues visible under /sys/bus/workqueue/.
7373 will report the work <<
7374 threshold repeatedly. <<
7375 candidates for using <<
7376 <<
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 6087
7386 workqueue.power_efficient 6088 workqueue.power_efficient
7387 Per-cpu workqueues ar 6089 Per-cpu workqueues are generally preferred because
7388 they show better perf 6090 they show better performance thanks to cache
7389 locality; unfortunate 6091 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 6092 be more power hungry than unbound workqueues.
7391 6093
7392 Enabling this makes t 6094 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 6095 were observed to contribute significantly to power
7394 consumption unbound, 6096 consumption unbound, leading to measurably lower
7395 power usage at the co 6097 power usage at the cost of small performance
7396 overhead. 6098 overhead.
7397 6099
7398 The default value of 6100 The default value of this parameter is determined by
7399 the config option CON 6101 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 6102
7401 workqueue.default_affinity_scope= <<
7402 Select the default af <<
7403 workqueues. Can be on <<
7404 "numa" and "system". <<
7405 information, see the <<
7406 Documentation/core-ap <<
7407 <<
7408 This can be changed a <<
7409 matching /sys/module/ <<
7410 workqueues with the " <<
7411 updated accordingly. <<
7412 <<
7413 workqueue.debug_force_rr_cpu 6103 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 6104 Workqueue used to implicitly guarantee that work
7415 items queued without 6105 items queued without explicit CPU specified are put
7416 on the local CPU. Th 6106 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 6107 and while local CPU is still preferred work items
7418 may be put on foreign 6108 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 6109 forces round-robin CPU selection to flush out
7420 usages which depend o 6110 usages which depend on the now broken guarantee.
7421 When enabled, memory 6111 When enabled, memory and cache locality will be
7422 impacted. 6112 impacted.
7423 6113
7424 writecombine= [LOONGARCH,EARLY] Con !! 6114 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7425 Type) of ioremap_wc() <<
7426 <<
7427 on - Enable writeco <<
7428 off - Disable writec <<
7429 <<
7430 x2apic_phys [X86-64,APIC,EARLY] U <<
7431 default x2apic cluste 6115 default x2apic cluster mode on platforms
7432 supporting x2apic. 6116 supporting x2apic.
7433 6117
>> 6118 x86_intel_mid_timer= [X86-32,APBT]
>> 6119 Choose timer option for x86 Intel MID platform.
>> 6120 Two valid options are apbt timer only and lapic timer
>> 6121 plus one apbt timer for broadcast timer.
>> 6122 x86_intel_mid_timer=apbt_only | lapic_and_apbt
>> 6123
7434 xen_512gb_limit [KNL,X86-64,X 6124 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 6125 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6126 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6127 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6128 save/restore/migration must be enabled to handle larger
7439 domains. 6129 domains.
7440 6130
7441 xen_emul_unplug= [HW,X !! 6131 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6132 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6133 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6134 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6135 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6136 nics -- unplug network devices
7447 all -- unplug all emu 6137 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6138 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6139 unnecessary even if the host did not respond to
7450 the unplug pr 6140 the unplug protocol
7451 never -- do not unplu 6141 never -- do not unplug even if version check succeeds
7452 6142
7453 xen_legacy_crash [X86,XEN,EARL !! 6143 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6144 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6145 panic() code such as dumping handler.
7456 6146
7457 xen_mc_debug [X86,XEN,EARLY] !! 6147 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 6148 Disables the qspinlock slowpath using Xen PV optimizations.
7459 Enabling this feature !! 6149 This parameter is obsoleted by "nopvspin" parameter, which
7460 bit, so it should onl !! 6150 has equivalent effect for XEN platform.
7461 debug data in case of <<
7462 <<
7463 xen_msr_safe= [X86,XEN,EARLY] <<
7464 Format: <bool> <<
7465 Select whether to alw <<
7466 access functions when <<
7467 default value is cont <<
7468 6151
7469 xen_nopv [X86] 6152 xen_nopv [X86]
7470 Disables the PV optim 6153 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6154 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6155 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6156 has equivalent effect for XEN platform.
7474 6157
7475 xen_no_vector_callback 6158 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6159 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6160 event channel interrupts.
7478 6161
7479 xen_scrub_pages= [XEN] 6162 xen_scrub_pages= [XEN]
7480 Boolean option to con 6163 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6164 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6165 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6166 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6167
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6168 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6169 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6170 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6171 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 6172 improve timer resolution at the expense of processing
7490 more timer interrupts 6173 more timer interrupts.
7491 6174
7492 xen.balloon_boot_timeout= [XEN] 6175 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 6176 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 6177 in case initial ballooning fails to free enough memory.
7495 Applies only when run 6178 Applies only when running as HVM or PVH guest and
7496 started with less mem 6179 started with less memory configured than allowed at
7497 max. Default is 180. 6180 max. Default is 180.
7498 6181
7499 xen.event_eoi_delay= [XEN] 6182 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 6183 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 6184 storms (jiffies). Default is 10.
7502 6185
7503 xen.event_loop_timeout= [XEN] 6186 xen.event_loop_timeout= [XEN]
7504 After which time (jif 6187 After which time (jiffies) the event handling loop
7505 should start to delay 6188 should start to delay EOI handling. Default is 2.
7506 6189
7507 xen.fifo_events= [XEN] 6190 xen.fifo_events= [XEN]
7508 Boolean parameter to 6191 Boolean parameter to disable using fifo event handling
7509 even if available. No 6192 even if available. Normally fifo event handling is
7510 preferred over the 2- 6193 preferred over the 2-level event handling, as it is
7511 fairer and the number 6194 fairer and the number of possible event channels is
7512 much higher. Default 6195 much higher. Default is on (use fifo events).
7513 6196
>> 6197 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6198 Disables the PV optimizations forcing the guest to run
>> 6199 as generic guest with no PV drivers. Currently support
>> 6200 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6201
>> 6202 nopvspin [X86,XEN,KVM]
>> 6203 Disables the qspinlock slow path using PV optimizations
>> 6204 which allow the hypervisor to 'idle' the guest on lock
>> 6205 contention.
>> 6206
7514 xirc2ps_cs= [NET,PCMCIA] 6207 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6208 Format:
7516 <irq>,<irq_mask>,<io> 6209 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6210
7518 xive= [PPC] 6211 xive= [PPC]
7519 By default on POWER9 6212 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6213 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6214 allows the fallback firmware mode to be used:
7522 6215
7523 off Fallback to 6216 off Fallback to firmware control of XIVE interrupt
7524 controller 6217 controller on both pseries and powernv
7525 platforms. 6218 platforms. Only useful on POWER9 and above.
7526 6219
7527 xive.store-eoi=off [PPC] <<
7528 By default on POWER10 <<
7529 stores for EOI handli <<
7530 is active. This optio <<
7531 loads instead, as on <<
7532 <<
7533 xhci-hcd.quirks [USB,KNL] 6220 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6221 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6222 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6223 consulted in header drivers/usb/host/xhci.h.
7537 6224
7538 xmon [PPC,EARLY] !! 6225 xmon [PPC]
7539 Format: { early | on 6226 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 6227 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 6228 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 6229 early Call xmon as early as possible on boot; xmon
7543 debugger is c 6230 debugger is called from setup_arch().
7544 on xmon debugger 6231 on xmon debugger hooks will be installed so xmon
7545 is only calle 6232 is only called on a kernel crash. Default mode,
7546 i.e. either " 6233 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 6234 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 6235 rw xmon debugger hooks will be installed so xmon
7549 is called onl 6236 is called only on a kernel crash, mode is write,
7550 meaning SPR r 6237 meaning SPR registers, memory and, other data
7551 can be writte 6238 can be written using xmon commands.
7552 ro same as "rw" 6239 ro same as "rw" option above but SPR registers,
7553 memory, and o 6240 memory, and other data can't be written using
7554 xmon commands 6241 xmon commands.
7555 off xmon is disab 6242 off xmon is disabled.
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