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 376 arm64.nobti [ARM64] Unconditionally disable Branch Target
442 Identification support 377 Identification support
443 378
444 arm64.nomops [ARM64] Unconditionall <<
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support <<
449 <<
450 arm64.nopauth [ARM64] Unconditionall 379 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
451 support 380 support
452 381
453 arm64.nosme [ARM64] Unconditionall <<
454 Extension support <<
455 <<
456 arm64.nosve [ARM64] Unconditionall <<
457 Extension support <<
458 <<
459 ataflop= [HW,M68k] 382 ataflop= [HW,M68k]
460 383
461 atarimouse= [HW,MOUSE] Atari Mouse 384 atarimouse= [HW,MOUSE] Atari Mouse
462 385
463 atkbd.extra= [HW] Enable extra LEDs 386 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 387 EzKey and similar keyboards
465 388
466 atkbd.reset= [HW] Reset keyboard du 389 atkbd.reset= [HW] Reset keyboard during initialization
467 390
468 atkbd.set= [HW] Select keyboard c 391 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 392 Format: <int> (2 = AT (default), 3 = PS/2)
470 393
471 atkbd.scroll= [HW] Enable scroll whe 394 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 395 keyboards
473 396
474 atkbd.softraw= [HW] Choose between sy 397 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 398 Format: <bool> (0 = real, 1 = synthetic (default))
476 399
477 atkbd.softrepeat= [HW] 400 atkbd.softrepeat= [HW]
478 Use software keyboard 401 Use software keyboard repeat
479 402
480 audit= [KNL] Enable the audit 403 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 404 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 405 0 | off - kernel audit is disabled and can not be
483 enabled until the 406 enabled until the next reboot
484 unset - kernel audit i 407 unset - kernel audit is initialized but disabled and
485 will be fully enab 408 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 409 1 | on - kernel audit is initialized and partially
487 enabled, storing a 410 enabled, storing at most audit_backlog_limit
488 messages in RAM un 411 messages in RAM until it is fully enabled by the
489 userspace auditd. 412 userspace auditd.
490 Default: unset 413 Default: unset
491 414
492 audit_backlog_limit= [KNL] Set the aud 415 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 416 Format: <int> (must be >=0)
494 Default: 64 417 Default: 64
495 418
496 bau= [X86_UV] Enable the BA 419 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 420 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 421 Format: { "0" | "1" }
499 0 - Disable the BAU. 422 0 - Disable the BAU.
500 1 - Enable the BAU. 423 1 - Enable the BAU.
501 unset - Disable the BA 424 unset - Disable the BAU.
502 425
503 baycom_epp= [HW,AX25] 426 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 427 Format: <io>,<mode>
505 428
506 baycom_par= [HW,AX25] BayCom Paral 429 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 430 Format: <io>,<mode>
508 See header of drivers/ 431 See header of drivers/net/hamradio/baycom_par.c.
509 432
510 baycom_ser_fdx= [HW,AX25] 433 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 434 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 435 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 436 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 437
515 baycom_ser_hdx= [HW,AX25] 438 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 439 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 440 Format: <io>,<irq>,<mode>
518 See header of drivers/ 441 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 442
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 443 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 444 embedded devices based on command line input.
528 See Documentation/bloc 445 See Documentation/block/cmdline-partition.rst
529 446
530 boot_delay= [KNL,EARLY] !! 447 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 448 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 449 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 450 Format: integer
537 451
538 bootconfig [KNL,EARLY] !! 452 bootconfig [KNL]
539 Extended command line 453 Extended command line options can be added to an initrd
540 and this will cause th 454 and this will cause the kernel to look for it.
541 455
542 See Documentation/admi 456 See Documentation/admin-guide/bootconfig.rst
543 457
>> 458 bert_disable [ACPI]
>> 459 Disable BERT OS support on buggy BIOSes.
>> 460
>> 461 bgrt_disable [ACPI][X86]
>> 462 Disable BGRT to avoid flickering OEM logo.
>> 463
544 bttv.card= [HW,V4L] bttv (bt848 + 464 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 465 bttv.radio= Most important insmod options are available as
546 kernel args too. 466 kernel args too.
547 bttv.pll= See Documentation/admi 467 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 468 bttv.tuner=
549 469
550 bulk_remove=off [PPC] This parameter 470 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 471 firmware feature for flushing multiple hpte entries
552 at a time. 472 at a time.
553 473
554 c101= [NET] Moxa C101 synchr 474 c101= [NET] Moxa C101 synchronous serial card
555 475
556 cachesize= [BUGS=X86-32] Override 476 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 477 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 478 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 479 to fix known problems, but for some CPUs it is not
560 possible to determine 480 possible to determine what the correct size should be.
561 This option provides a 481 This option provides an override for these situations.
562 482
563 carrier_timeout= 483 carrier_timeout=
564 [NET] Specifies amount 484 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 485 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 486 it waits 120 seconds.
567 487
568 ca_keys= [KEYS] This parameter 488 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 489 the system trusted keyring to be used for certificate
570 trust validation. 490 trust validation.
571 format: { id:<keyid> | 491 format: { id:<keyid> | builtin }
572 492
573 cca= [MIPS,EARLY] Override !! 493 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 494 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 495 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 496 for platform specific values (SB1, Loongson3 and
577 others). 497 others).
578 498
579 ccw_timeout_log [S390] 499 ccw_timeout_log [S390]
580 See Documentation/arch !! 500 See Documentation/s390/common_io.rst for details.
581 501
582 cgroup_disable= [KNL] Disable a partic !! 502 cgroup_disable= [KNL] Disable a particular controller
583 Format: {name of the c !! 503 Format: {name of the controller(s) to disable}
584 The effects of cgroup_ 504 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 505 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 506 a single hierarchy
587 - foo isn't visible as 507 - foo isn't visible as an individually mountable
588 subsystem 508 subsystem
589 - if foo is an optiona <<
590 disabled and corresp <<
591 created <<
592 {Currently only "memor 509 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 510 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 511 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" <<
596 stall information acco <<
597 512
598 cgroup_no_v1= [KNL] Disable cgroup c 513 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 514 Format: { { controller | "all" | "named" }
600 [,{ controll 515 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 516 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 517 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 518 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 519 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 520 all v1 hierarchies.
606 521
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 522 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 523 Format: <string>
613 nosocket -- Disable so 524 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 525 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 526
617 checkreqprot= [SELINUX] Set initial !! 527 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 528 Format: { "0" | "1" }
619 See security/selinux/K 529 See security/selinux/Kconfig help text.
620 0 -- check protection 530 0 -- check protection applied by kernel (includes
621 any implied ex 531 any implied execute protection).
622 1 -- check protection 532 1 -- check protection requested by application.
623 Default value is set v 533 Default value is set via a kernel config option.
624 Value can be changed a 534 Value can be changed at runtime via
625 /sys/fs/selinu 535 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 536 Setting checkreqprot to 1 is deprecated.
627 537
628 cio_ignore= [S390] 538 cio_ignore= [S390]
629 See Documentation/arch !! 539 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 540 clk_ignore_unused
650 [CLK] 541 [CLK]
651 Prevents the clock fra 542 Prevents the clock framework from automatically gating
652 clocks that have not b 543 clocks that have not been explicitly enabled by a Linux
653 device driver but are 544 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 545 by the bootloader/firmware. Note that this does not
655 force such clocks to b 546 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 547 those clocks in any way. This parameter is useful for
657 debug and development, 548 debug and development, but should not be needed on a
658 platform with proper d 549 platform with proper driver support. For more
659 information, see Docum 550 information, see Documentation/driver-api/clk.rst.
660 551
661 clock= [BUGS=X86-32, HW] gett 552 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 553 [Deprecated]
663 Forces specified clock 554 Forces specified clocksource (if available) to be used
664 when calculating getti 555 when calculating gettimeofday(). If specified
665 clocksource is not ava 556 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 557 Format: { pit | tsc | cyclone | pmtmr }
667 558
668 clocksource= Override the default c 559 clocksource= Override the default clocksource
669 Format: <string> 560 Format: <string>
670 Override the default c 561 Override the default clocksource and use the clocksource
671 with the name specifie 562 with the name specified.
672 Some clocksource names 563 Some clocksource names to choose from, depending on
673 the platform: 564 the platform:
674 [all] jiffies (this is 565 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 566 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 567 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 568 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 569 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 570 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 571 [MIPS] MIPS
681 [PARISC] cr16 572 [PARISC] cr16
682 [S390] tod 573 [S390] tod
683 [SH] SuperH 574 [SH] SuperH
684 [SPARC64] tick 575 [SPARC64] tick
685 [X86-64] hpet,tsc 576 [X86-64] hpet,tsc
686 577
687 clocksource.arm_arch_timer.evtstrm= 578 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 579 [ARM,ARM64]
689 Format: <bool> 580 Format: <bool>
690 Enable/disable the eve 581 Enable/disable the eventstream feature of the ARM
691 architected timer so t 582 architected timer so that code using WFE-based polling
692 loops can be debugged 583 loops can be debugged more effectively on production
693 systems. 584 systems.
694 585
695 clocksource.verify_n_cpus= [KNL] !! 586 clocksource.max_cswd_read_retries= [KNL]
696 Limit the number of CP !! 587 Number of clocksource_watchdog() retries due to
697 marked with CLOCK_SOUR !! 588 external delays before the clock will be marked
698 are marked unstable du !! 589 unstable. Defaults to three retries, that is,
699 A negative value says !! 590 four attempts to read the clock under test.
700 zero says not to check !! 591
701 nr_cpu_ids are silentl !! 592 clearcpuid=BITNUM[,BITNUM...] [X86]
702 The actual CPUs are ch !! 593 Disable CPUID feature X for the kernel. See
703 no replacement if the !! 594 arch/x86/include/asm/cpufeatures.h for the valid bit
704 !! 595 numbers. Note the Linux specific bits are not necessarily
705 clocksource-wdtest.holdoff= [KNL] !! 596 stable over kernel options, but the vendor specific
706 Set the time in second !! 597 ones should be.
707 watchdog test waits be !! 598 Also note that user programs calling CPUID directly
708 Defaults to zero when !! 599 or using the feature without checking anything
709 10 seconds when built !! 600 will still see it. This just prevents it from
>> 601 being used by the kernel or shown in /proc/cpuinfo.
>> 602 Also note the kernel might malfunction if you disable
>> 603 some critical bits.
710 604
711 cma=nn[MG]@[start[MG][-end[MG]]] 605 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 606 [KNL,CMA]
713 Sets the size of kerne 607 Sets the size of kernel global memory area for
714 contiguous memory allo 608 contiguous memory allocations and optionally the
715 placement constraint b 609 placement constraint by the physical address range of
716 memory allocations. A 610 memory allocations. A value of 0 disables CMA
717 altogether. For more i 611 altogether. For more information, see
718 kernel/dma/contiguous. 612 kernel/dma/contiguous.c
719 613
720 cma_pernuma=nn[MG] 614 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 615 [ARM64,KNL,CMA]
722 Sets the size of kerne 616 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 617 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 618 per-numa CMA altogether. And If this option is not
725 specified, the default !! 619 specificed, the default value is 0.
726 With per-numa CMA enab 620 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 621 first try to allocate buffer from the pernuma area
728 which is located in no 622 which is located in node nid, if the allocation fails,
729 they will fallback to 623 they will fallback to the global default memory area.
730 624
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 | 625 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 626 Specify whether pages are marked as being inactive
744 when they are freed. 627 when they are freed. This is used in CMO environments
745 to determine OS memory 628 to determine OS memory pressure for page stealing by
746 a hypervisor. 629 a hypervisor.
747 Default: yes 630 Default: yes
748 631
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 632 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 633 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 634 allocations, by default set to 256K.
752 635
753 com20020= [HW,NET] ARCnet - COM2 636 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 637 Format:
755 <io>[,<irq>[,<nodeID>[ 638 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 639
757 com90io= [HW,NET] ARCnet - COM9 640 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 641 Format: <io>[,<irq>]
759 642
760 com90xx= [HW,NET] 643 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 644 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 645 Format: <io>[,<irq>[,<memstart>]]
763 646
764 condev= [HW,S390] console devi 647 condev= [HW,S390] console device
765 conmode= 648 conmode=
766 649
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 650 console= [KNL] Output console device and options.
779 651
780 tty<n> Use the virtual consol 652 tty<n> Use the virtual console device <n>.
781 653
782 ttyS<n>[,options] 654 ttyS<n>[,options]
783 ttyUSB0[,options] 655 ttyUSB0[,options]
784 Use the specified seri 656 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 657 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 658 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 659 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 660 omit it). Default is "9600n8".
789 661
790 See Documentation/admi 662 See Documentation/admin-guide/serial-console.rst for more
791 information. See 663 information. See
792 Documentation/networki 664 Documentation/networking/netconsole.rst for an
793 alternative. 665 alternative.
794 666
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] 667 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 668 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 669 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 670 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 671 uart[8250],0x<addr>[,options]
819 Start an early, polled 672 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 673 UART at the specified I/O port or MMIO address,
821 switching to the match 674 switching to the matching ttyS device later.
822 MMIO inter-register ad 675 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 676 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 677 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 678 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 679 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 680 the h/w is not re-initialized.
828 681
829 hvc<n> Use the hypervisor con 682 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 683 both Xen and PowerPC hypervisors.
831 684
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 685 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 686 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 687 console=brl,ttyS0
841 For now, only VisioBraille is 688 For now, only VisioBraille is supported.
842 689
843 console_msg_format= 690 console_msg_format=
844 [KNL] Change console m 691 [KNL] Change console messages format
845 default 692 default
846 By default we print me 693 By default we print messages on consoles in
847 "[time stamp] text\n" 694 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 695 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 696 `printk_time' param).
850 syslog 697 syslog
851 Switch to syslog forma 698 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 699 IOW, each message will have a facility and loglevel
853 prefix. The format is 700 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 701 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 702 from /proc/kmsg.
856 703
857 consoleblank= [KNL] The console blan 704 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 705 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 706 Defaults to 0.
860 707
861 coredump_filter= 708 coredump_filter=
862 [KNL] Change the defau 709 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 710 /proc/<pid>/coredump_filter.
864 See also Documentation 711 See also Documentation/filesystems/proc.rst.
865 712
866 coresight_cpu_debug.enable 713 coresight_cpu_debug.enable
867 [ARM,ARM64] 714 [ARM,ARM64]
868 Format: <bool> 715 Format: <bool>
869 Enable/disable the CPU 716 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 717 0: default value, disable debugging
871 1: enable debugging at 718 1: enable debugging at boot time
872 719
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 720 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 721 disable the cpuidle sub-system
879 722
880 cpuidle.governor= 723 cpuidle.governor=
881 [CPU_IDLE] Name of the 724 [CPU_IDLE] Name of the cpuidle governor to use.
882 725
883 cpufreq.off=1 [CPU_FREQ] 726 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 727 disable the cpufreq sub-system
885 728
886 cpufreq.default_governor= 729 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 730 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 731 policy to use. This governor must be registered in the
889 kernel before the cpuf 732 kernel before the cpufreq driver probes.
890 733
891 cpu_init_udelay=N 734 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 735 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 736 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 737 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 738 Default: 10000
896 739
897 cpuhp.parallel= !! 740 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 741 Format:
899 Format: <bool> !! 742 <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. <<
910 743
911 crashkernel=size[KMG][@offset[KMG]] 744 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 745 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 746 upon panic. This parameter reserves the physical
914 memory region [offset, 747 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 748 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 749 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 750 [KNL, X86-64] Select a region under 4G first, and
918 under 4G first, and fa !! 751 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 752 hasn't been specified.
920 See Documentation/admi 753 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 754
922 crashkernel=range1:size1[,range2:size2 755 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 756 [KNL] Same as above, but depends on the memory
924 in the running system. 757 in the running system. The syntax of range is
925 start-[end] where star 758 start-[end] where start and end are both
926 a memory unit (amount[ 759 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 760 Documentation/admin-guide/kdump/kdump.rst for an example.
928 761
929 crashkernel=size[KMG],high 762 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 763 [KNL, X86-64] range could be above 4G. Allow kernel
931 above 4G. !! 764 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 765 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 766 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 767 available.
935 below 4G, if available <<
936 It will be ignored if 768 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 769 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 770 [KNL, X86-64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 771 is passed, kernel could allocate physical memory region
940 physical memory region !! 772 above 4G, that cause second kernel crash on system
941 crash on system that r !! 773 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 774 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 775 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 776 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 777 at least 256M below 4G automatically.
946 size is platform depen !! 778 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 779 for second kernel instead.
953 0: to disable low allo 780 0: to disable low allocation.
954 It will be ignored whe 781 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 782 or memory reserved is below 4G.
956 783
957 cryptomgr.notests 784 cryptomgr.notests
958 [KNL] Disable crypto s 785 [KNL] Disable crypto self-tests
959 786
960 cs89x0_dma= [HW,NET] 787 cs89x0_dma= [HW,NET]
961 Format: <dma> 788 Format: <dma>
962 789
963 cs89x0_media= [HW,NET] 790 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 791 Format: { rj45 | aui | bnc }
965 792
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] 793 dasd= [HW,NET]
976 See header of drivers/ 794 See header of drivers/s390/block/dasd_devmap.c.
977 795
978 db9.dev[2|3]= [HW,JOY] Multisystem j 796 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 797 (one device per port)
980 Format: <port#>,<type> 798 Format: <port#>,<type>
981 See also Documentation 799 See also Documentation/input/devices/joystick-parport.rst
982 800
983 debug [KNL,EARLY] Enable ker !! 801 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 802 time. See
>> 803 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 804 details. Deprecated, see dyndbg.
>> 805
>> 806 debug [KNL] Enable kernel debugging (events log level).
984 807
985 debug_boot_weak_hash 808 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 809 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 810 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 811 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 812 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 813 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 814 insecure, please do not use on production kernels.
992 815
993 debug_locks_verbose= 816 debug_locks_verbose=
994 [KNL] verbose locking 817 [KNL] verbose locking self-tests
995 Format: <int> 818 Format: <int>
996 Print debugging info w 819 Print debugging info while doing the locking API
997 self-tests. 820 self-tests.
998 Bitmask for the variou 821 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 822 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 823 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 824 useful to lockdep developers.
1002 825
1003 debug_objects [KNL,EARLY] Enable ob !! 826 debug_objects [KNL] Enable object debugging
>> 827
>> 828 no_debug_objects
>> 829 [KNL] Disable object debugging
1004 830
1005 debug_guardpage_minorder= 831 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 832 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 833 parameter allows control of the order of pages that will
1008 be intentionally kept 834 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 835 buddy allocator. Bigger value increase the probability
1010 of catching random me 836 of catching random memory corruption, but reduce the
1011 amount of memory for 837 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 838 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 839 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 840 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 841 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 842 random memory location. Note that there exists a class
1017 a class of memory cor !! 843 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 844 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 845 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 846 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 847 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 848 tracking down these problems.
1023 849
1024 debug_pagealloc= 850 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 851 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 852 enables the feature at boot time. By default, it is
1027 disabled and the syst 853 disabled and the system will work mostly the same as a
1028 kernel built without 854 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 855 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 856 useful to also enable the page_owner functionality.
1031 on: enable the featur 857 on: enable the feature
1032 858
1033 debugfs= [KNL,EARLY] This para !! 859 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 860 and debugfs internal clients.
1035 Format: { on, no-moun 861 Format: { on, no-mount, off }
1036 on: All functions 862 on: All functions are enabled.
1037 no-mount: 863 no-mount:
1038 Filesystem is 864 Filesystem is not registered but kernel clients can
1039 access APIs a 865 access APIs and a crashkernel can be used to read
1040 its content. 866 its content. There is nothing to mount.
1041 off: Filesystem is 867 off: Filesystem is not registered and clients
1042 get a -EPERM 868 get a -EPERM as result when trying to register files
1043 or directorie 869 or directories within debugfs.
1044 This is equiv 870 This is equivalent of the runtime functionality if
1045 debugfs was n 871 debugfs was not enabled in the kernel at all.
1046 Default value is set 872 Default value is set in build-time with a kernel configuration.
1047 873
1048 debugpat [X86] Enable PAT debu 874 debugpat [X86] Enable PAT debugging
1049 875
>> 876 decnet.addr= [HW,NET]
>> 877 Format: <area>[,<node>]
>> 878 See also Documentation/networking/decnet.rst.
>> 879
1050 default_hugepagesz= 880 default_hugepagesz=
1051 [HW] The size of the 881 [HW] The size of the default HugeTLB page. This is
1052 the size represented 882 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 883 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 884 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 885 filesystems. If not specified, defaults to the
1056 architecture's defaul 886 architecture's default huge page size. Huge page
1057 sizes are architectur 887 sizes are architecture dependent. See also
1058 Documentation/admin-g 888 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 889 Format: size[KMG]
1060 890
1061 deferred_probe_timeout= 891 deferred_probe_timeout=
1062 [KNL] Debugging optio 892 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 893 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 894 probe. Only specific dependencies (subsystems or
1065 drivers) that have op !! 895 drivers) that have opted in will be ignored. A timeout of 0
1066 of 0 will timeout at !! 896 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 897 dump out devices still on the deferred probe list after
1070 retrying. 898 retrying.
1071 899
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] 900 dfltcc= [HW,S390]
1099 Format: { on | off | 901 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 902 on: s390 zlib hardware support for compression on
1101 level 1 and 903 level 1 and decompression (default)
1102 off: No s390 zli 904 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 905 def_only: s390 zlib hardware support for deflate
1104 only (compr 906 only (compression on level 1)
1105 inf_only: s390 zlib h 907 inf_only: s390 zlib hardware support for inflate
1106 only (decom 908 only (decompression)
1107 always: Same as 'on 909 always: Same as 'on' but ignores the selected compression
1108 level alway 910 level always using hardware support (used for debugging)
1109 911
1110 dhash_entries= [KNL] 912 dhash_entries= [KNL]
1111 Set number of hash bu 913 Set number of hash buckets for dentry cache.
1112 914
1113 disable_1tb_segments [PPC,EARLY] !! 915 disable_1tb_segments [PPC]
1114 Disables the use of 1 916 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 917 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 918 can be useful when debugging issues that require an SLB
1117 miss to occur. 919 miss to occur.
1118 920
>> 921 stress_slb [PPC]
>> 922 Limits the number of kernel SLB entries, and flushes
>> 923 them frequently to increase the rate of SLB faults
>> 924 on kernel addresses.
>> 925
1119 disable= [IPV6] 926 disable= [IPV6]
1120 See Documentation/net 927 See Documentation/networking/ipv6.rst.
1121 928
1122 disable_radix [PPC,EARLY] !! 929 hardened_usercopy=
>> 930 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
>> 931 hardening is enabled for this boot. Hardened
>> 932 usercopy checking is used to protect the kernel
>> 933 from reading or writing beyond known memory
>> 934 allocation boundaries as a proactive defense
>> 935 against bounds-checking flaws in the kernel's
>> 936 copy_to_user()/copy_from_user() interface.
>> 937 on Perform hardened usercopy checks (default).
>> 938 off Disable hardened usercopy checks.
>> 939
>> 940 disable_radix [PPC]
1123 Disable RADIX MMU mod 941 Disable RADIX MMU mode on POWER9
1124 942
>> 943 radix_hcall_invalidate=on [PPC/PSERIES]
>> 944 Disable RADIX GTSE feature and use hcall for TLB
>> 945 invalidate.
>> 946
1125 disable_tlbie [PPC] 947 disable_tlbie [PPC]
1126 Disable TLBIE instruc 948 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 949 with KVM, with HASH MMU, or with coherent accelerators.
1128 950
1129 disable_ddw [PPC/PSERIES,EARLY] !! 951 disable_cpu_apicid= [X86,APIC,SMP]
>> 952 Format: <int>
>> 953 The number of initial APIC ID for the
>> 954 corresponding CPU to be disabled at boot,
>> 955 mostly used for the kdump 2nd kernel to
>> 956 disable BSP to wake up multiple CPUs without
>> 957 causing system reset or hang due to sending
>> 958 INIT from AP to BSP.
>> 959
>> 960 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 961 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 962 to workaround buggy firmware.
1132 963
1133 disable_ipv6= [IPV6] 964 disable_ipv6= [IPV6]
1134 See Documentation/net 965 See Documentation/networking/ipv6.rst.
1135 966
1136 disable_mtrr_cleanup [X86,EARLY] !! 967 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 968 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 969 to discrete, to make X server driver able to add WB
1139 entry later. This par 970 entry later. This parameter disables that.
1140 971
1141 disable_mtrr_trim [X86, Intel and AMD !! 972 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 973 By default the kernel will trim any uncacheable
1143 memory out of your av 974 memory out of your available memory pool based on
1144 MTRR settings. This 975 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 976 possibly causing your machine to run very slowly.
1146 977
1147 disable_timer_pin_1 [X86,EARLY] !! 978 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 979 Disable PIN 1 of APIC timer
1149 Can be useful to work 980 Can be useful to work around chipset bugs.
1150 981
1151 dis_ucode_ldr [X86] Disable the mic 982 dis_ucode_ldr [X86] Disable the microcode loader.
1152 983
1153 dma_debug=off If the kernel is comp 984 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 985 this option disables the debugging code at boot.
1155 986
1156 dma_debug_entries=<number> 987 dma_debug_entries=<number>
1157 This option allows to 988 This option allows to tune the number of preallocated
1158 entries for DMA-API d 989 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 990 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 991 DMA-API debugging code disables itself because the
1161 architectural default 992 architectural default is too low.
1162 993
1163 dma_debug_driver=<driver_name> 994 dma_debug_driver=<driver_name>
1164 With this option the 995 With this option the DMA-API debugging driver
1165 filter feature can be 996 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 997 pass the driver to filter for as the parameter.
1167 The filter can be dis 998 The filter can be disabled or changed to another
1168 driver later using sy 999 driver later using sysfs.
1169 1000
1170 reg_file_data_sampling= <<
1171 [X86] Controls mitiga <<
1172 Sampling (RFDS) vulne <<
1173 vulnerability which m <<
1174 kernel data values pr <<
1175 registers, vector reg <<
1176 RFDS only affects Int <<
1177 <<
1178 on: Turns ON the <<
1179 off: Turns OFF the <<
1180 <<
1181 This parameter overri <<
1182 by CONFIG_MITIGATION_ <<
1183 disabled when other V <<
1184 are enabled. In order <<
1185 VERW based mitigation <<
1186 <<
1187 For details see: <<
1188 Documentation/admin-g <<
1189 <<
1190 driver_async_probe= [KNL] 1001 driver_async_probe= [KNL]
1191 List of driver names !! 1002 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 1003 Format: <driver_name1>,<driver_name2>...
1196 1004
1197 drm.edid_firmware=[<connector>:]<file 1005 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1006 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1007 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1008 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1009 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1010 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1011 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1012 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1013 and no file with the same name exists. Details and
>> 1014 instructions how to build your own EDID data are
>> 1015 available in Documentation/admin-guide/edid.rst. An EDID
>> 1016 data set will only be used for a particular connector,
>> 1017 if its name and a colon are prepended to the EDID
>> 1018 name. Each connector may use a unique EDID data
>> 1019 set by separating the files with a comma. An EDID
1206 data set with no conn 1020 data set with no connector name will be used for
1207 any connectors not ex 1021 any connectors not explicitly specified.
1208 1022
1209 dscc4.setup= [NET] 1023 dscc4.setup= [NET]
1210 1024
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1025 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1026 Format: {"off" | "known"}
1213 Control how the dt_cp 1027 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1028 used for CPU feature discovery and setup (if it
1215 exists). 1029 exists).
1216 off: Do not use it, f 1030 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1031 known: Do not pass through unknown features to guests
1218 or userspace, only th 1032 or userspace, only those that the kernel is aware of.
1219 1033
1220 dump_apple_properties [X86] 1034 dump_apple_properties [X86]
1221 Dump name and content 1035 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1036 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1037 what data is available or for reverse-engineering.
1224 1038
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1039 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1040 <module>.dyndbg[="val"]
1227 Enable debug messages 1041 Enable debug messages at boot time. See
1228 Documentation/admin-g 1042 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1043 for details.
1230 1044
1231 early_ioremap_debug [KNL,EARLY] !! 1045 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1046 in some Intel CPUs.
>> 1047
>> 1048 <module>.async_probe [KNL]
>> 1049 Enable asynchronous probe on this module.
>> 1050
>> 1051 early_ioremap_debug [KNL]
1232 Enable debug messages 1052 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1053 is useful for tracking down temporary early mappings
1234 which are not unmappe 1054 which are not unmapped.
1235 1055
1236 earlycon= [KNL,EARLY] Output ea !! 1056 earlycon= [KNL] Output early console device and options.
1237 1057
1238 When used with no opt 1058 When used with no options, the early console is
1239 determined by stdout- 1059 determined by stdout-path property in device tree's
1240 chosen node or the AC 1060 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1061 the platform.
1242 1062
1243 cdns,<addr>[,options] 1063 cdns,<addr>[,options]
1244 Start an early, polle 1064 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1065 (xuartps) serial port at the specified address. Only
1246 supported option is b 1066 supported option is baud rate. If baud rate is not
1247 specified, the serial 1067 specified, the serial port must already be setup and
1248 configured. 1068 configured.
1249 1069
1250 uart[8250],io,<addr>[,options !! 1070 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1071 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1072 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1073 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1074 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1075 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1076 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1077 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1078 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1079 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1080 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1081 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1082 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1083
1266 pl011,<addr> 1084 pl011,<addr>
1267 pl011,mmio32,<addr> 1085 pl011,mmio32,<addr>
1268 Start an early, polle 1086 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1087 port at the specified address. The pl011 serial port
1270 must already be setup 1088 must already be setup and configured. Options are not
1271 yet supported. If 'm 1089 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1090 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1091 the device registers.
1274 1092
1275 liteuart,<addr> <<
1276 Start an early consol <<
1277 specified address. Th <<
1278 setup and configured. <<
1279 <<
1280 meson,<addr> 1093 meson,<addr>
1281 Start an early, polle 1094 Start an early, polled-mode console on a meson serial
1282 port at the specified 1095 port at the specified address. The serial port must
1283 already be setup and 1096 already be setup and configured. Options are not yet
1284 supported. 1097 supported.
1285 1098
1286 msm_serial,<addr> 1099 msm_serial,<addr>
1287 Start an early, polle 1100 Start an early, polled-mode console on an msm serial
1288 port at the specified 1101 port at the specified address. The serial port
1289 must already be setup 1102 must already be setup and configured. Options are not
1290 yet supported. 1103 yet supported.
1291 1104
1292 msm_serial_dm,<addr> 1105 msm_serial_dm,<addr>
1293 Start an early, polle 1106 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1107 dm port at the specified address. The serial port
1295 must already be setup 1108 must already be setup and configured. Options are not
1296 yet supported. 1109 yet supported.
1297 1110
1298 owl,<addr> 1111 owl,<addr>
1299 Start an early, polle 1112 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1113 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1114 specified address. The serial port must already be
1302 setup and configured. 1115 setup and configured. Options are not yet supported.
1303 1116
1304 rda,<addr> 1117 rda,<addr>
1305 Start an early, polle 1118 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1119 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1120 specified address. The serial port must already be
1308 setup and configured. 1121 setup and configured. Options are not yet supported.
1309 1122
1310 sbi 1123 sbi
1311 Use RISC-V SBI (Super 1124 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1125 console.
1313 1126
1314 smh Use ARM semihosting c 1127 smh Use ARM semihosting calls for early console.
1315 1128
1316 s3c2410,<addr> 1129 s3c2410,<addr>
1317 s3c2412,<addr> 1130 s3c2412,<addr>
1318 s3c2440,<addr> 1131 s3c2440,<addr>
1319 s3c6400,<addr> 1132 s3c6400,<addr>
1320 s5pv210,<addr> 1133 s5pv210,<addr>
1321 exynos4210,<addr> 1134 exynos4210,<addr>
1322 Use early console pro 1135 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1136 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1137 a correct base address of the selected UART port. The
1325 serial port must alre 1138 serial port must already be setup and configured.
1326 Options are not yet s 1139 Options are not yet supported.
1327 1140
1328 lantiq,<addr> 1141 lantiq,<addr>
1329 Start an early, polle 1142 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1143 (lqasc) port at the specified address. The serial port
1331 must already be setup 1144 must already be setup and configured. Options are not
1332 yet supported. 1145 yet supported.
1333 1146
1334 lpuart,<addr> 1147 lpuart,<addr>
1335 lpuart32,<addr> 1148 lpuart32,<addr>
1336 Use early console pro 1149 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1150 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1151 A valid base address must be provided, and the serial
1339 port must already be 1152 port must already be setup and configured.
1340 1153
1341 ec_imx21,<addr> 1154 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1155 ec_imx6q,<addr>
1343 Start an early, polle 1156 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1157 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1158 must already be setup and configured.
1346 1159
1347 ar3700_uart,<addr> 1160 ar3700_uart,<addr>
1348 Start an early, polle 1161 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1162 Armada 3700 serial port at the specified
1350 address. The serial p 1163 address. The serial port must already be setup
1351 and configured. Optio 1164 and configured. Options are not yet supported.
1352 1165
1353 qcom_geni,<addr> 1166 qcom_geni,<addr>
1354 Start an early, polle 1167 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1168 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1169 specified address. The serial port must already be
1357 setup and configured. 1170 setup and configured. Options are not yet supported.
1358 1171
1359 efifb,[options] 1172 efifb,[options]
1360 Start an early, unacc 1173 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1174 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1175 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1176 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1177 mapped with the correct attributes.
1365 1178
1366 linflex,<addr> 1179 linflex,<addr>
1367 Use early console pro 1180 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1181 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1182 address must be provided, and the serial port must
1370 already be setup and 1183 already be setup and configured.
1371 1184
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1185 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1186 earlyprintk=vga
1374 earlyprintk=sclp 1187 earlyprintk=sclp
1375 earlyprintk=xen 1188 earlyprintk=xen
1376 earlyprintk=serial[,t 1189 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1190 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1191 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1192 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1193 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1194 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1195
1384 earlyprintk is useful 1196 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1197 the normal console is initialized. It is not enabled by
1386 default because it ha 1198 default because it has some cosmetic problems.
1387 1199
1388 Append ",keep" to not 1200 Append ",keep" to not disable it when the real console
1389 takes over. 1201 takes over.
1390 1202
1391 Only one of vga, seri !! 1203 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1204 be used at a time.
1393 1205
1394 Currently only ttyS0 1206 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1207 name. Other I/O ports may be explicitly specified
1396 on some architectures 1208 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1209 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1210 earlyprintk=serial,0x1008,115200
1399 You can find the port 1211 You can find the port for a given device in
1400 /proc/tty/driver/seri 1212 /proc/tty/driver/serial:
1401 2: uart:ST166 1213 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1214
1403 Interaction with the 1215 Interaction with the standard serial driver is not
1404 very good. 1216 very good.
1405 1217
1406 The VGA output is eve !! 1218 The VGA and EFI output is eventually overwritten by
1407 the real console. 1219 the real console.
1408 1220
1409 The xen option can on !! 1221 The xen output can only be used by Xen PV guests.
1410 1222
1411 The sclp output can o 1223 The sclp output can only be used on s390.
1412 1224
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1225 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1226 PCI device even when its classcode is not of the
1417 UART class. 1227 UART class.
1418 1228
1419 edac_report= [HW,EDAC] Control how 1229 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1230 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1231 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1232 by other higher priority error reporting module.
1423 off: disable H/W even 1233 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1234 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1235 default: on.
1426 1236
>> 1237 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1238 ekgdboc=kbd
>> 1239
>> 1240 This is designed to be used in conjunction with
>> 1241 the boot argument: earlyprintk=vga
>> 1242
>> 1243 This parameter works in place of the kgdboc parameter
>> 1244 but can only be used if the backing tty is available
>> 1245 very early in the boot process. For early debugging
>> 1246 via a serial port see kgdboc_earlycon instead.
>> 1247
1427 edd= [EDD] 1248 edd= [EDD]
1428 Format: {"off" | "on" 1249 Format: {"off" | "on" | "skip[mbr]"}
1429 1250
1430 efi= [EFI,EARLY] !! 1251 efi= [EFI]
1431 Format: { "debug", "d 1252 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1253 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1254 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1255 debug: enable misc debug output.
1435 disable_early_pci_dma 1256 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1257 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1258 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1259 boot stub, as chunking can cause problems with some
1439 firmware implementati 1260 firmware implementations.
1440 noruntime : disable E 1261 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1262 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1263 attribute may cause the kernel to reserve the
1443 memory range for a me 1264 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1265 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1266 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1267 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1268 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1269 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1270 on all PCI bridges while in the EFI boot stub
1450 1271
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1272 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1273 Using this parameter you can use more than 50% of
1453 your efi variable sto 1274 your efi variable storage. Use this parameter only if
1454 you are really sure t 1275 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1276 fulfills the spec otherwise your board may brick.
1456 1277
>> 1278 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1279 Add arbitrary attribute to specific memory range by
>> 1280 updating original EFI memory map.
>> 1281 Region of memory which aa attribute is added to is
>> 1282 from ss to ss+nn.
>> 1283
>> 1284 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1285 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1286 attribute is added to range 0x100000000-0x180000000 and
>> 1287 0x10a0000000-0x1120000000.
>> 1288
>> 1289 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1290 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1291 range 0x240000000-0x43fffffff.
>> 1292
>> 1293 Using this parameter you can do debugging of EFI memmap
>> 1294 related features. For example, you can do debugging of
>> 1295 Address Range Mirroring feature even if your box
>> 1296 doesn't support it, or mark specific memory as
>> 1297 "soft reserved".
>> 1298
1457 efivar_ssdt= [EFI; X86] Name of an 1299 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1300 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1301 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1302 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1303 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1304
1463 1305
1464 eisa_irq_edge= [PARISC,HW] 1306 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1307 See header of drivers/parisc/eisa.c.
1466 1308
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] 1309 elanfreq= [X86-32]
1479 See comment before fu 1310 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1311 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1312
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1313 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1314 Specifies physical address of start of kernel core
1484 image elf header and 1315 image elf header and optionally the size. Generally
1485 kexec loader will pas 1316 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1317 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1318
1488 enable_mtrr_cleanup [X86,EARLY] !! 1319 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1320 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1321 to discrete, to make X server driver able to add WB
1491 entry later. This par 1322 entry later. This parameter enables that.
1492 1323
1493 enable_timer_pin_1 [X86] 1324 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1325 Enable PIN 1 of APIC timer
1495 Can be useful to work 1326 Can be useful to work around chipset bugs
1496 (in particular on som 1327 (in particular on some ATI chipsets).
1497 The kernel tries to s 1328 The kernel tries to set a reasonable default.
1498 1329
1499 enforcing= [SELINUX] Set initial !! 1330 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1331 Format: {"0" | "1"}
1501 See security/selinux/ 1332 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1333 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1334 1 -- enforcing (deny and log).
1504 Default value is 0. 1335 Default value is 0.
1505 Value can be changed 1336 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1337 /sys/fs/selinux/enforce.
1507 1338
1508 erst_disable [ACPI] 1339 erst_disable [ACPI]
1509 Disable Error Record 1340 Disable Error Record Serialization Table (ERST)
1510 support. 1341 support.
1511 1342
1512 ether= [HW,NET] Ethernet car 1343 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1344 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1345 has equivalent usage. See its documentation for details.
1515 1346
1516 evm= [EVM] 1347 evm= [EVM]
1517 Format: { "fix" } 1348 Format: { "fix" }
1518 Permit 'security.evm' 1349 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1350 current integrity status.
1520 1351
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= 1352 failslab=
1530 fail_usercopy= 1353 fail_usercopy=
1531 fail_page_alloc= 1354 fail_page_alloc=
1532 fail_make_request=[KNL] 1355 fail_make_request=[KNL]
1533 General fault injecti 1356 General fault injection mechanism.
1534 Format: <interval>,<p 1357 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1358 See also Documentation/fault-injection/.
1536 1359
1537 fb_tunnels= [NET] 1360 fb_tunnels= [NET]
1538 Format: { initns | no 1361 Format: { initns | none }
1539 See Documentation/adm 1362 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1363 fb_tunnels_only_for_init_ns
1541 1364
1542 floppy= [HW] 1365 floppy= [HW]
1543 See Documentation/adm 1366 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1367
>> 1368 force_pal_cache_flush
>> 1369 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1370 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1371 parameter will force ia64_sal_cache_flush to call
>> 1372 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1373
1545 forcepae [X86-32] 1374 forcepae [X86-32]
1546 Forcefully enable Phy 1375 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1376 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1377 functionally usable PAE implementation.
1549 Warning: use of this 1378 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1379 and may cause unknown problems.
1551 1380
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] 1381 ftrace=[tracer]
1559 [FTRACE] will set and 1382 [FTRACE] will set and start the specified tracer
1560 as early as possible 1383 as early as possible in order to facilitate early
1561 boot debugging. 1384 boot debugging.
1562 1385
1563 ftrace_boot_snapshot !! 1386 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 1387 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1388 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1389 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1390 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1391 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 1392
1603 ftrace_filter=[function-list] 1393 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1394 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1395 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1396 list of functions. This list can be changed at run
1607 time by the set_ftrac 1397 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1398 tracing directory.
1609 1399
1610 ftrace_notrace=[function-list] 1400 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1401 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1402 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1403 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1404 tracing directory.
1615 1405
1616 ftrace_graph_filter=[function-list] 1406 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1407 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1408 by the function graph tracer at boot up.
1619 function-list is a co 1409 function-list is a comma-separated list of functions
1620 that can be changed a 1410 that can be changed at run time by the
1621 set_graph_function fi 1411 set_graph_function file in the debugfs tracing directory.
1622 1412
1623 ftrace_graph_notrace=[function-list] 1413 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1414 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1415 function-list. This list is a comma-separated list of
1626 functions that can be 1416 functions that can be changed at run time by the
1627 set_graph_notrace fil 1417 set_graph_notrace file in the debugfs tracing directory.
1628 1418
1629 ftrace_graph_max_depth=<uint> 1419 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1420 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1421 the max depth it will trace into a function. This value
1632 can be changed at run 1422 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1423 in the tracefs tracing directory. default: 0 (no limit)
1634 1424
1635 fw_devlink= [KNL,EARLY] Create de !! 1425 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1426 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1427 consumer/supplier relationships. This feature is
1638 especially useful whe 1428 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1429 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1430 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1431 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1432 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1433 suppliers).
1644 Format: { off | permi 1434 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1435 off -- Don't create device links from firmware info.
1646 permissive -- Create 1436 permissive -- Create device links from firmware info
1647 but use it on 1437 but use it only for ordering boot state clean
1648 up (sync_stat 1438 up (sync_state() calls).
1649 on -- Create device 1439 on -- Create device links from firmware info and use it
1650 to enforce pr 1440 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1441 rpm -- Like "on", but also use to order runtime PM.
1652 1442
1653 fw_devlink.strict=<bool> 1443 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1444 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1445 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1446 Format: <bool>
1657 1447
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]= 1448 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1449 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1450 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1451 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1452 See also Documentation/input/devices/joystick-parport.rst
1677 1453
1678 gamma= [HW,DRM] 1454 gamma= [HW,DRM]
1679 1455
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1456 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1457 Format: off | on
1682 default: on 1458 default: on
1683 1459
1684 gather_data_sampling= <<
1685 [X86,INTEL,EARLY] Con <<
1686 mitigation. <<
1687 <<
1688 Gather Data Sampling <<
1689 allows unprivileged s <<
1690 previously stored in <<
1691 <<
1692 This issue is mitigat <<
1693 The mitigation may ha <<
1694 disabled. On systems <<
1695 disabling AVX serves <<
1696 <<
1697 force: Disable AVX t <<
1698 microcode mit <<
1699 mitigation is <<
1700 userspace wit <<
1701 <<
1702 off: Disable GDS m <<
1703 <<
1704 gcov_persist= [GCOV] When non-zero 1460 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1461 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1462 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1463 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1464 debugfs files are removed at module unload time.
1709 1465
1710 goldfish [X86] Enable the gold 1466 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1467 Don't use this when you are not running on the
1712 android emulator 1468 android emulator
1713 1469
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 1470 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1471 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1472 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1473 GPT to be used instead.
1724 1474
1725 grcan.enable0= [HW] Configuration of 1475 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1476 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1477 Format: 0 | 1
1728 Default: 0 1478 Default: 0
1729 grcan.enable1= [HW] Configuration of 1479 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1480 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1481 Format: 0 | 1
1732 Default: 0 1482 Default: 0
1733 grcan.select= [HW] Select which phy 1483 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1484 Format: 0 | 1
1735 Default: 0 1485 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1486 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1487 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1488 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1489 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1490 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1491 Default: 1024
1742 1492
1743 hardened_usercopy= !! 1493 gpio-mockup.gpio_mockup_ranges
1744 [KNL] Under CONFIG_HA !! 1494 [HW] Sets the ranges of gpiochip of for this device.
1745 hardening is enabled !! 1495 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 1496
1754 hardlockup_all_cpu_backtrace= 1497 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1498 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1499 backtraces on all cpus.
1757 Format: 0 | 1 1500 Format: 0 | 1
1758 1501
1759 hashdist= [KNL,NUMA] Large hash 1502 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1503 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1504 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1505 Format: 0 | 1 (for off | on)
1763 1506
>> 1507 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1508
1764 hd= [EIDE] (E)IDE hard dr 1509 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1510 Format: <cyl>,<head>,<sect>
1766 1511
1767 hest_disable [ACPI] 1512 hest_disable [ACPI]
1768 Disable Hardware Erro 1513 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1514 corresponding firmware-first mode error processing
1770 logic will be disable 1515 logic will be disabled.
1771 1516
1772 hibernate= [HIBERNATION] !! 1517 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 1518 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1519 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1520 size on bigger boxes.
1796 1521
1797 highres= [KNL] Enable/disable 1522 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1523 Valid parameters: "on", "off"
1799 Default: "on" 1524 Default: "on"
1800 1525
1801 hlt [BUGS=ARM,SH] 1526 hlt [BUGS=ARM,SH]
1802 1527
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 1528 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1529 Format: { enable (default) | disable | force |
1818 verbose } 1530 verbose }
1819 disable: disable HPET 1531 disable: disable HPET and use PIT instead
1820 force: allow force en 1532 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1533 VIA, nVidia)
1822 verbose: show content 1534 verbose: show contents of HPET registers during setup
1823 1535
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1536 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1537 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1538
>> 1539 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
>> 1540 of gigantic hugepages.
>> 1541 Format: nn[KMGTPE]
>> 1542
>> 1543 Reserve a CMA area of given size and allocate gigantic
>> 1544 hugepages using the CMA allocator. If enabled, the
>> 1545 boot-time allocation of gigantic hugepages is skipped.
>> 1546
1827 hugepages= [HW] Number of HugeTL 1547 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1548 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1549 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1550 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1551 line, it specifies the number of pages to allocate for
1832 the default huge page !! 1552 the default huge page size. See also
1833 number of pages to al !! 1553 Documentation/admin-guide/mm/hugetlbpage.rst.
1834 See also Documentatio !! 1554 Format: <integer>
1835 Format: <integer> or <<
1836 <node>:<integ <<
1837 1555
1838 hugepagesz= 1556 hugepagesz=
1839 [HW] The size of the 1557 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1558 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1559 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1560 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1561 each supported huge page size. Huge page sizes are
1844 architecture dependen 1562 architecture dependent. See also
1845 Documentation/admin-g 1563 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1564 Format: size[KMG]
1847 1565
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= 1566 hung_task_panic=
1879 [KNL] Should the hung 1567 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1568 Format: 0 | 1
1881 1569
1882 A value of 1 instruct 1570 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1571 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1572 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1573 option. The value selected by this boot parameter can
1886 be changed later by t 1574 be changed later by the kernel.hung_task_panic sysctl.
1887 1575
1888 hvc_iucv= [S390] Number of z/V 1576 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1577 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1578 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1579 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1580 from listed z/VM user IDs only.
1893 1581
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1582 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1583 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1584 guest on lock contention.
1897 on lock contention. !! 1585
>> 1586 keep_bootcon [KNL]
>> 1587 Do not unregister boot console at start. This is only
>> 1588 useful for debugging when something happens in the window
>> 1589 between unregistering the boot console and initializing
>> 1590 the real console.
1898 1591
1899 i2c_bus= [HW] Override the 1592 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1593 or register an additional I2C bus that is not
1901 registered fr 1594 registered from board initialization code.
1902 Format: 1595 Format:
1903 <bus_id>,<clk 1596 <bus_id>,<clkrate>
1904 1597
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 1598 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1599 i8042.unmask_kbd_data
1929 [HW] Enable printing 1600 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1601 (disabled by default, and as a pre-condition
1931 requires that i8 1602 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1603 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1604 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1605 keyboard and cannot control its state
1935 (Don't attempt t 1606 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1607 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1608 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1609 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1610 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1611 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1612 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1613 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1614 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1615 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1616 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1617 suspend-to-ram transitions, only during s2r
1947 transitions, or 1618 transitions, or never reset
1948 Format: { 1 | Y | y | 1619 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1620 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1621 0, N, n: don't ever reset controller
1951 Default: only on s2r 1622 Default: only on s2r transitions on x86; most other
1952 architectures force r 1623 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1624 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1625 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer <<
1956 [HW] Allow deferred p <<
1957 1626
1958 i810= [HW,DRM] 1627 i810= [HW,DRM]
1959 1628
>> 1629 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1630 indicates that the driver is running on unsupported
>> 1631 hardware.
>> 1632 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1633 does not match list of supported models.
>> 1634 i8k.power_status
>> 1635 [HW] Report power status in /proc/i8k
>> 1636 (disabled by default)
>> 1637 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1638 capability is set.
>> 1639
1960 i915.invert_brightness= 1640 i915.invert_brightness=
1961 [DRM] Invert the sens 1641 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1642 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1643 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1644 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1645 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1646 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1647 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1648 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1649 value switches the backlight off.
1970 -1 -- never invert br 1650 -1 -- never invert brightness
1971 0 -- machine default 1651 0 -- machine default
1972 1 -- force brightnes 1652 1 -- force brightness inversion
1973 1653
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] 1654 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1655 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1656
>> 1657 ide-core.nodma= [HW] (E)IDE subsystem
>> 1658 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1659 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1660 .cdrom .chs .ignore_cable are additional options
>> 1661 See Documentation/ide/ide.rst.
>> 1662
>> 1663 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1664 Format: <int>
>> 1665 Probe mask for legacy ISA IDE ports. Depending on
>> 1666 platform up to 6 ports are supported, enabled by
>> 1667 setting corresponding bits in the mask to 1. The
>> 1668 default value is 0x0, which has a special meaning.
>> 1669 On systems that have PCI, it triggers scanning the
>> 1670 PCI bus for the first and the second port, which
>> 1671 are then probed. On systems without PCI the value
>> 1672 of 0x0 enables probing the two first ports as if it
>> 1673 was 0x3.
>> 1674
>> 1675 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1676 Claim all unknown PCI IDE storage controllers.
1983 1677
1984 idle= [X86,EARLY] !! 1678 idle= [X86]
1985 Format: idle=poll, id 1679 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1680 Poll forces a polling idle loop that can slightly
1987 improve the performan 1681 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1682 will use a lot of power and make the system run hot.
1989 Not recommended. 1683 Not recommended.
1990 idle=halt: Halt is fo 1684 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1685 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1686 idle=nomwait: Disable mwait for CPU C-states
1993 1687
1994 idxd.sva= [HW] 1688 idxd.sva= [HW]
1995 Format: <bool> 1689 Format: <bool>
1996 Allow force disabling 1690 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1691 support for the idxd driver. By default it is set to
1998 true (1). 1692 true (1).
1999 1693
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 1694 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1695 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1696 Default: strict
2008 1697
2009 Choose which programs 1698 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1699 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1700 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1701 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1702 binary. Hardware implementations are permitted to
2014 support either or bot 1703 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1704 encoding mode.
2016 1705
2017 Available settings ar 1706 Available settings are as follows:
2018 strict accept binari 1707 strict accept binaries that request a NaN encoding
2019 supported by 1708 supported by the FPU
2020 legacy only accept l 1709 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1710 by the FPU
2022 2008 only accept 2 1711 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1712 by the FPU
2024 relaxed accept any bi 1713 relaxed accept any binaries regardless of whether
2025 supported by 1714 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1715
2029 The FPU emulator is a 1716 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1717 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1718 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1719 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1720 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1721 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1722 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1723 MIPS64 CPUs.
2037 1724
2038 The setting for ABS.f 1725 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1726 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1727 except where unsupported by hardware.
2041 1728
2042 ignore_loglevel [KNL,EARLY] !! 1729 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1730 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1731 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1732 We also add it as printk module parameter, so users
2046 could change it dynam 1733 could change it dynamically, usually by
2047 /sys/module/printk/pa 1734 /sys/module/printk/parameters/ignore_loglevel.
2048 1735
2049 ignore_rlimit_data 1736 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1737 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1738 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1739 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1740
2054 ihash_entries= [KNL] 1741 ihash_entries= [KNL]
2055 Set number of hash bu 1742 Set number of hash buckets for inode cache.
2056 1743
2057 ima_appraise= [IMA] appraise integr 1744 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1745 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1746 default: "enforce"
2060 1747
2061 ima_appraise_tcb [IMA] Deprecated. U 1748 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1749 The builtin appraise policy appraises all files
2063 owned by uid=0. 1750 owned by uid=0.
2064 1751
2065 ima_canonical_fmt [IMA] 1752 ima_canonical_fmt [IMA]
2066 Use the canonical for 1753 Use the canonical format for the binary runtime
2067 measurements, instead 1754 measurements, instead of host native format.
2068 1755
2069 ima_hash= [IMA] 1756 ima_hash= [IMA]
2070 Format: { md5 | sha1 1757 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1758 | sha512 | ... }
2072 default: "sha1" 1759 default: "sha1"
2073 1760
2074 The list of supported 1761 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1762 in crypto/hash_info.h.
2076 1763
2077 ima_policy= [IMA] 1764 ima_policy= [IMA]
2078 The builtin policies 1765 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1766 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1767 fail_securely | critical_data"
2081 1768
2082 The "tcb" policy meas 1769 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1770 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1771 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1772 uid=0.
2086 1773
2087 The "appraise_tcb" po 1774 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1775 all files owned by root.
2089 1776
2090 The "secure_boot" pol 1777 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1778 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1779 firmware, policy, etc) based on file signatures.
2093 1780
2094 The "fail_securely" p 1781 The "fail_securely" policy forces file signature
2095 verification failure 1782 verification failure also on privileged mounted
2096 filesystems with the 1783 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1784 flag.
2098 1785
2099 The "critical_data" p 1786 The "critical_data" policy measures kernel integrity
2100 critical data. 1787 critical data.
2101 1788
2102 ima_tcb [IMA] Deprecated. Us 1789 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1790 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1791 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1792 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1793 opened for read by uid=0.
2107 1794
2108 ima_template= [IMA] 1795 ima_template= [IMA]
2109 Select one of defined 1796 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1797 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1798 Default: "ima-ng"
2113 1799
2114 ima_template_fmt= 1800 ima_template_fmt=
2115 [IMA] Define a custom 1801 [IMA] Define a custom template format.
2116 Format: { "field1|... 1802 Format: { "field1|...|fieldN" }
2117 1803
2118 ima.ahash_minsize= [IMA] Minimum file 1804 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1805 Format: <min_file_size>
2120 Set the minimal file 1806 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1807 If left unspecified, ahash usage is disabled.
2122 1808
2123 ahash performance var 1809 ahash performance varies for different data sizes on
2124 different crypto acce 1810 different crypto accelerators. This option can be used
2125 to achieve the best p 1811 to achieve the best performance for a particular HW.
2126 1812
2127 ima.ahash_bufsize= [IMA] Asynchronous 1813 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1814 Format: <bufsize>
2129 Set hashing buffer si 1815 Set hashing buffer size. Default: 4k.
2130 1816
2131 ahash performance var 1817 ahash performance varies for different chunk sizes on
2132 different crypto acce 1818 different crypto accelerators. This option can be used
2133 to achieve best perfo 1819 to achieve best performance for particular HW.
2134 1820
2135 init= [KNL] 1821 init= [KNL]
2136 Format: <full_path> 1822 Format: <full_path>
2137 Run specified binary 1823 Run specified binary instead of /sbin/init as init
2138 process. 1824 process.
2139 1825
2140 initcall_debug [KNL] Trace initcalls 1826 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1827 for working out where the kernel is dying during
2142 startup. 1828 startup.
2143 1829
2144 initcall_blacklist= [KNL] Do not exe 1830 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1831 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1832 modules and initcalls.
2147 1833
2148 initramfs_async= [KNL] !! 1834 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 1835
2162 initrdmem= [KNL,EARLY] Specify a !! 1836 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 1837 load the initrd. If an initrd is compiled in or
2164 specified in the boot 1838 specified in the bootparams, it takes priority over this
2165 setting. 1839 setting.
2166 Format: ss[KMG],nn[KM 1840 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 1841 Default is 0, 0
2168 1842
2169 init_on_alloc= [MM,EARLY] Fill newly !! 1843 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 1844 zeroes.
2171 Format: 0 | 1 1845 Format: 0 | 1
2172 Default set by CONFIG 1846 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 1847
2174 init_on_free= [MM,EARLY] Fill freed !! 1848 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 1849 Format: 0 | 1
2176 Default set by CONFIG 1850 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 1851
2178 init_pkru= [X86] Specify the def 1852 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 1853 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1854 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1855 override in debugfs after boot.
2182 1856
2183 inport.irq= [HW] Inport (ATI XL a 1857 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1858 Format: <irq>
2185 1859
2186 int_pln_enable [X86] Enable power li 1860 int_pln_enable [X86] Enable power limit notification interrupt
2187 1861
2188 integrity_audit=[IMA] 1862 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1863 Format: { "0" | "1" }
2190 0 -- basic integrity 1864 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1865 1 -- additional integrity auditing messages.
2192 1866
2193 intel_iommu= [DMAR] Intel IOMMU dr 1867 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1868 on
2195 Enable intel iommu dr 1869 Enable intel iommu driver.
2196 off 1870 off
2197 Disable intel iommu d 1871 Disable intel iommu driver.
2198 igfx_off [Default Off] 1872 igfx_off [Default Off]
2199 By default, gfx is ma 1873 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1874 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1875 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1876 this case, gfx device will use physical address for
2203 DMA. 1877 DMA.
2204 strict [Default Off] 1878 strict [Default Off]
2205 Deprecated, equivalen !! 1879 With this option on every unmap_single operation will
>> 1880 result in a hardware IOTLB flush operation as opposed
>> 1881 to batching them for performance.
2206 sp_off [Default Off] 1882 sp_off [Default Off]
2207 By default, super pag 1883 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1884 has the capability. With this option, super page will
2209 not be supported. 1885 not be supported.
2210 sm_on !! 1886 sm_on [Default Off]
2211 Enable the Intel IOMM !! 1887 By default, scalable mode will be disabled even if the
2212 advertises that it ha !! 1888 hardware advertises that it has support for the scalable
2213 translation. !! 1889 mode translation. With this option set, scalable mode
2214 sm_off !! 1890 will be used on hardware which claims to support it.
2215 Disallow use of the I <<
2216 tboot_noforce [Default Off] 1891 tboot_noforce [Default Off]
2217 Do not force the Inte 1892 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1893 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1894 could harm performance of some high-throughput
2220 devices like 40GBit n 1895 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1896 mapping is enabled.
2222 Note that using this 1897 Note that using this option lowers the security
2223 provided by tboot bec 1898 provided by tboot because it makes the system
2224 vulnerable to DMA att 1899 vulnerable to DMA attacks.
2225 1900
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1901 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1902 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1903 1 to 9 specify maximum depth of C-state.
2229 1904
2230 intel_pstate= [X86,EARLY] !! 1905 intel_pstate= [X86]
2231 disable 1906 disable
2232 Do not enable intel 1907 Do not enable intel_pstate as the default
2233 scaling driver for 1908 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 1909 passive
2245 Use intel_pstate as 1910 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 1911 to work with generic cpufreq governors (instead of
2247 enabling its intern 1912 enabling its internal governor). This mode cannot be
2248 used along with the 1913 used along with the hardware-managed P-states (HWP)
2249 feature. 1914 feature.
2250 force 1915 force
2251 Enable intel_pstate 1916 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 1917 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 1918 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 1919 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 1920 P-States information being indicated to OSPM and therefore
2256 should be used with 1921 should be used with caution. This option does not work with
2257 processors that are 1922 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 1923 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 1924 no_hwp
2260 Do not enable hardw 1925 Do not enable hardware P state control (HWP)
2261 if available. 1926 if available.
2262 hwp_only 1927 hwp_only
2263 Only load intel_pst 1928 Only load intel_pstate on systems which support
2264 hardware P state co 1929 hardware P state control (HWP) if available.
2265 support_acpi_ppc 1930 support_acpi_ppc
2266 Enforce ACPI _PPC p 1931 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 1932 Description Table, specifies preferred power management
2268 profile as "Enterpr 1933 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 1934 then this feature is turned on by default.
2270 per_cpu_perf_limits 1935 per_cpu_perf_limits
2271 Allow per-logical-C 1936 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 1937 cpufreq sysfs interface
2273 1938
2274 intremap= [X86-64,Intel-IOMMU,E !! 1939 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 1940 on enable Interrupt Remapping (default)
2276 off disable Inter 1941 off disable Interrupt Remapping
2277 nosid disable Sourc 1942 nosid disable Source ID checking
2278 no_x2apic_optout 1943 no_x2apic_optout
2279 BIOS x2APIC o 1944 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 1945 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 1946
2284 iomem= Disable strict checki 1947 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 1948 strict regions from userspace.
2286 relaxed 1949 relaxed
2287 1950
2288 iommu= [X86,EARLY] !! 1951 iommu= [X86]
2289 off 1952 off
2290 force 1953 force
2291 noforce 1954 noforce
2292 biomerge 1955 biomerge
2293 panic 1956 panic
2294 nopanic 1957 nopanic
2295 merge 1958 merge
2296 nomerge 1959 nomerge
2297 soft 1960 soft
2298 pt [X86] 1961 pt [X86]
2299 nopt [X86] 1962 nopt [X86]
2300 nobypass [PPC/POWERNV] 1963 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 1964 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 1965
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 1966 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 1967 Format: { "0" | "1" }
2305 0 - Try to allocate a 1968 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 1969 falling back to the full range if needed.
2307 1 - Allocate directly 1970 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 1971 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 1972 greater than 32-bit addressing.
2310 1973
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 1974 iommu.strict= [ARM64] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 1975 Format: { "0" | "1" }
2313 0 - Lazy mode. 1976 0 - Lazy mode.
2314 Request that DMA un 1977 Request that DMA unmap operations use deferred
2315 invalidation of har 1978 invalidation of hardware TLBs, for increased
2316 throughput at the c 1979 throughput at the cost of reduced device isolation.
2317 Will fall back to s 1980 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 1981 the relevant IOMMU driver.
2319 1 - Strict mode. !! 1982 1 - Strict mode (default).
2320 DMA unmap operation 1983 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 1984 synchronously.
2322 unset - Use value of <<
2323 Note: on x86, strict <<
2324 legacy driver-specifi <<
2325 1985
2326 iommu.passthrough= 1986 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 1987 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 1988 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 1989 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 1990 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 1991 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 1992
2333 io7= [HW] IO7 for Marvel-b 1993 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 1994 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 1995 arch/alpha/kernel/core_marvel.c.
2336 1996
2337 io_delay= [X86,EARLY] I/O delay !! 1997 io_delay= [X86] I/O delay method
2338 0x80 1998 0x80
2339 Standard port 0x80 ba 1999 Standard port 0x80 based delay
2340 0xed 2000 0xed
2341 Alternate port 0xed b 2001 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2002 udelay
2343 Simple two microsecon 2003 Simple two microseconds delay
2344 none 2004 none
2345 No delay 2005 No delay
2346 2006
2347 ip= [IP_PNP] 2007 ip= [IP_PNP]
2348 See Documentation/adm 2008 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2009
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2010 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2011 IPC identifiers from 32,768 to 16,777,216.
2352 2012
2353 irqaffinity= [SMP] Set the default 2013 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2014 The argument is a cpu list, as described above.
2355 2015
2356 irqchip.gicv2_force_probe= 2016 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2017 [ARM, ARM64]
2358 Format: <bool> 2018 Format: <bool>
2359 Force the kernel to l 2019 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2020 of a GICv2 controller even if the memory range
2361 exposed by the device 2021 exposed by the device tree is too small.
2362 2022
2363 irqchip.gicv3_nolpi= 2023 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2024 [ARM, ARM64]
2365 Force the kernel to i 2025 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2026 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2027 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2028 to let secondary kernels in charge of setting up
2369 LPIs. 2029 LPIs.
2370 2030
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2031 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2032 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2033 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2034 CONFIG_ARM64_PSEUDO_NMI.
2375 2035
2376 irqfixup [HW] 2036 irqfixup [HW]
2377 When an interrupt is 2037 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2038 for it. Intended to get systems with badly broken
2379 firmware running. 2039 firmware running.
2380 2040
2381 irqpoll [HW] 2041 irqpoll [HW]
2382 When an interrupt is 2042 When an interrupt is not handled search all handlers
2383 for it. Also check al 2043 for it. Also check all handlers each timer
2384 interrupt. Intended t 2044 interrupt. Intended to get systems with badly broken
2385 firmware running. 2045 firmware running.
2386 2046
2387 isapnp= [ISAPNP] 2047 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2048 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2049
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2050 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2051 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2052 Format: [flag-list,]<cpu-list>
2393 2053
2394 Specify one or more C 2054 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2055 specified in the flag list (default: domain):
2396 2056
2397 nohz 2057 nohz
2398 Disable the tick wh 2058 Disable the tick when a single task runs.
2399 2059
2400 A residual 1Hz tick 2060 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2061 need to affine to housekeeping through the global
2402 workqueue's affinit 2062 workqueue's affinity configured via the
2403 /sys/devices/virtua 2063 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2064 by using the 'domain' flag described below.
2405 2065
2406 NOTE: by default th 2066 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2067 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2068 be configured manually after bootup.
2409 2069
2410 domain 2070 domain
2411 Isolate from the ge 2071 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2072 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2073 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2074 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2075 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2076 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2077 It offers a much more flexible interface where CPUs can
2418 move in and out of 2078 move in and out of an isolated set anytime.
2419 2079
2420 You can move a proc 2080 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2081 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2082 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2083 "number of CPUs in system - 1".
2424 2084
2425 managed_irq 2085 managed_irq
2426 2086
2427 Isolate from being 2087 Isolate from being targeted by managed interrupts
2428 which have an inter 2088 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2089 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2090 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2091 the /proc/irq/* interfaces.
2432 2092
2433 This isolation is b 2093 This isolation is best effort and only effective
2434 if the automaticall 2094 if the automatically assigned interrupt mask of a
2435 device queue contai 2095 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2096 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2097 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2098 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2099 cannot disturb the isolated CPU.
2440 2100
2441 If a queue's affini 2101 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2102 CPUs then this parameter has no effect on the
2443 interrupt routing d 2103 interrupt routing decision, though interrupts are
2444 only delivered when 2104 only delivered when tasks running on those
2445 isolated CPUs submi 2105 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2106 housekeeping CPUs has no influence on those
2447 queues. 2107 queues.
2448 2108
2449 The format of <cpu-li 2109 The format of <cpu-list> is described above.
2450 2110
2451 iucv= [HW,NET] 2111 iucv= [HW,NET]
2452 2112
2453 ivrs_ioapic [HW,X86-64] 2113 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2114 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 2115 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 2116 example, to map IOAPIC-ID decimal 10 to
2457 !! 2117 PCI device 00:14.0 write the parameter as:
2458 For example, to map I <<
2459 PCI segment 0x1 and P <<
2460 write the parameter a <<
2461 ivrs_ioapic=1 <<
2462 <<
2463 Deprecated formats: <<
2464 * To map IOAPIC-ID de <<
2465 write the parameter <<
2466 ivrs_ioapic[1 2118 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 2119
2471 ivrs_hpet [HW,X86-64] 2120 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2121 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 2122 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 2123 example, to map HPET-ID decimal 0 to
2475 !! 2124 PCI device 00:14.0 write the parameter as:
2476 For example, to map H <<
2477 PCI segment 0x1 and P <<
2478 write the parameter a <<
2479 ivrs_hpet=10@ <<
2480 <<
2481 Deprecated formats: <<
2482 * To map HPET-ID deci <<
2483 write the parameter <<
2484 ivrs_hpet[0]= 2125 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 2126
2489 ivrs_acpihid [HW,X86-64] 2127 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2128 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 2129 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 2130 example, to map UART-HID:UID AMD0020:0 to
2493 !! 2131 PCI device 00:14.5 write the parameter as:
2494 For example, to map U <<
2495 PCI segment 0x1 and P <<
2496 write the parameter a <<
2497 ivrs_acpihid= <<
2498 <<
2499 Deprecated formats: <<
2500 * To map UART-HID:UID <<
2501 PCI device ID 00:14 <<
2502 ivrs_acpihid[ 2132 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 2133
2507 js= [HW,JOY] Analog joyst 2134 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2135 See Documentation/input/joydev/joystick.rst.
2509 2136
>> 2137 nokaslr [KNL]
>> 2138 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2139 kernel and module base offset ASLR (Address Space
>> 2140 Layout Randomization).
>> 2141
2510 kasan_multi_shot 2142 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2143 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2144 report on every invalid memory access. Without this
2513 parameter KASAN will 2145 parameter KASAN will print report only for the first
2514 invalid access. 2146 invalid access.
2515 2147
2516 keep_bootcon [KNL,EARLY] !! 2148 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 2149
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2150 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2151 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2152 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2153 the kernel for non-movable allocations. The requested
2528 amount is spread even 2154 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2155 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2156 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2157 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2158 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2159 other nodes will have a larger ZONE_MOVABLE.
2534 2160
2535 ZONE_MOVABLE is used 2161 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2162 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2163 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2164 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2165 zone if it does not.
2540 2166
2541 It is possible to spe 2167 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2168 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2169 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2170 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2171 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2172 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2173 are exclusive, so you cannot specify multiple forms.
2548 2174
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2175 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2176 Format: <Controller#>[,poll interval]
2551 The controller # is t 2177 The controller # is the number of the ehci usb debug
2552 port as it is probed 2178 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2179 optional and is the number seconds in between
2554 each poll cycle to th 2180 each poll cycle to the debug port in case you need
2555 the functionality for 2181 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2182 gdb or control-c on the dbgp connection. When
2557 not using this parame 2183 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2184 the kernel debugger.
2559 2185
2560 kgdboc= [KGDB,HW] kgdb over c 2186 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2187 Requires a tty driver that supports console polling,
2562 or a supported pollin 2188 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2189 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2190 keyboard only format: kbd
2565 keyboard and serial 2191 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2192 Optional Kernel mode setting:
2567 kms, kbd format: kms 2193 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2194 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2195
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2196 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2197 If the boot console provides the ability to read
2572 characters and can wo 2198 characters and can work in polling mode, you can use
2573 this parameter to tel 2199 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2200 until the normal console is registered. Intended to
2575 be used together with 2201 be used together with the kgdboc parameter which
2576 specifies the normal 2202 specifies the normal console to transition to.
2577 2203
2578 The name of the early 2204 The name of the early console should be specified
2579 as the value of this 2205 as the value of this parameter. Note that the name of
2580 the early console mig 2206 the early console might be different than the tty
2581 name passed to kgdboc 2207 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2208 blank and the first boot console that implements
2583 read() will be picked 2209 read() will be picked.
2584 2210
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2211 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2212 kernel debugger at the earliest opportunity.
2587 2213
2588 kmac= [MIPS] Korina etherne 2214 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2215 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2216 Ethernet adapter MAC address.
2591 2217
2592 kmemleak= [KNL,EARLY] Boot-time !! 2218 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2219 Valid arguments: on, off
2594 Default: on 2220 Default: on
2595 Built with CONFIG_DEB 2221 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2222 the default is off.
2597 2223
2598 kprobe_event=[probe-list] 2224 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2225 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2226 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2227 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2228 interface, but the parameters are comma delimited.
2603 For example, to add a 2229 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2230 arg1 and arg2, add to the command line;
2605 2231
2606 kprobe_event=p, 2232 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2233
2608 See also Documentatio 2234 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2235 Boot Parameter" section.
2610 2236
2611 kpti= [ARM64,EARLY] Control !! 2237 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2238 and kernel address spaces.
2613 Default: enabled on c 2239 Default: enabled on cores which need mitigation.
2614 0: force disabled 2240 0: force disabled
2615 1: force enabled 2241 1: force enabled
2616 2242
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 2243 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2244 Default is 0 (don't ignore, but inject #GP)
2625 2245
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 2246 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2247 Default is false (don't support).
2653 2248
>> 2249 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
>> 2250 KVM MMU at runtime.
>> 2251 Default is 0 (off)
>> 2252
2654 kvm.nx_huge_pages= 2253 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2254 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2255 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2256 force : Always deploy workaround.
2658 off : Never deplo 2257 off : Never deploy workaround.
2659 auto : Deploy work 2258 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2259 X86_BUG_ITLB_MULTIHIT.
2661 2260
2662 Default is 'auto'. 2261 Default is 'auto'.
2663 2262
2664 If the software worka 2263 If the software workaround is enabled for the host,
2665 guests do need not to 2264 guests do need not to enable it for nested guests.
2666 2265
2667 kvm.nx_huge_pages_recovery_ratio= 2266 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2267 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2268 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2269 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). !! 2270 minute. The default is 60.
>> 2271
>> 2272 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
>> 2273 Default is 1 (enabled)
2672 2274
2673 kvm.nx_huge_pages_recovery_period_ms= !! 2275 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2674 [KVM] Controls the ti !! 2276 for all guests.
2675 back to huge pages. I !! 2277 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2676 zap a portion (see ra <<
2677 If the value is 0 (th <<
2678 on the ratio, such th <<
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 2278
2688 kvm-arm.mode= 2279 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2280 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 <<
2692 none: Forcefully disa <<
2693 2281
2694 nvhe: Standard nVHE-b 2282 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2283 protected guests.
2696 2284
2697 protected: nVHE-based 2285 protected: nVHE-based mode with support for guests whose
2698 state is k 2286 state is kept private from the host.
>> 2287 Not valid if the kernel is running in EL2.
2699 2288
2700 nested: VHE-based mod !! 2289 Defaults to VHE/nVHE based on hardware support and
2701 virtualizatio !! 2290 the value of CONFIG_ARM64_VHE.
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE <<
2705 mode to "protected" w <<
2706 for the host. "nested <<
2707 used with extreme cau <<
2708 2291
2709 kvm-arm.vgic_v3_group0_trap= 2292 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2293 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2294 system registers
2712 2295
2713 kvm-arm.vgic_v3_group1_trap= 2296 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2297 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2298 system registers
2716 2299
2717 kvm-arm.vgic_v3_common_trap= 2300 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2301 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2302 system registers
2720 2303
2721 kvm-arm.vgic_v4_enable= 2304 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2305 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2306 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 2307
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2308 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2309 Reserves given percentage from system memory area for
2745 contiguous memory all 2310 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2311 allocation.
2747 By default it reserve 2312 By default it reserves 5% of total system memory.
2748 Format: <integer> 2313 Format: <integer>
2749 Default: 5 2314 Default: 5
2750 2315
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2316 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2317 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2318 Default is 1 (enabled)
2754 for EPT. <<
2755 2319
2756 kvm-intel.emulate_invalid_guest_state 2320 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2321 [KVM,Intel] Enable emulation of invalid guest states
2758 state. Ignored if kvm !! 2322 Default is 0 (disabled)
2759 as guest state is nev <<
2760 guests. This param do <<
2761 as KVM never emulates <<
2762 Default is 1 (enabled <<
2763 2323
2764 kvm-intel.flexpriority= 2324 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2325 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2326 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2327
2769 kvm-intel.nested= 2328 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2329 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2330 Default is 0 (disabled)
2772 2331
2773 kvm-intel.unrestricted_guest= 2332 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2333 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2334 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2335 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2336
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2337 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2338 CVE-2018-3620.
2781 2339
2782 Valid arguments: neve 2340 Valid arguments: never, cond, always
2783 2341
2784 always: L1D cache flu 2342 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2343 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2344 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2345 never: Disables the mitigation
2788 2346
2789 Default is cond (do L 2347 Default is cond (do L1 cache flush in specific instances)
2790 2348
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2349 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2350 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2351 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 2352
2813 l1tf= [X86,EARLY] Control m !! 2353 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2354 affected CPUs
2815 2355
2816 The kernel PTE invers 2356 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2357 enabled and cannot be disabled.
2818 2358
2819 full 2359 full
2820 Provides all 2360 Provides all available mitigations for the
2821 L1TF vulnerab 2361 L1TF vulnerability. Disables SMT and
2822 enables all m 2362 enables all mitigations in the
2823 hypervisors, 2363 hypervisors, i.e. unconditional L1D flush.
2824 2364
2825 SMT control a 2365 SMT control and L1D flush control via the
2826 sysfs interfa 2366 sysfs interface is still possible after
2827 boot. Hyperv 2367 boot. Hypervisors will issue a warning
2828 when the firs 2368 when the first VM is started in a
2829 potentially i 2369 potentially insecure configuration,
2830 i.e. SMT enab 2370 i.e. SMT enabled or L1D flush disabled.
2831 2371
2832 full,force 2372 full,force
2833 Same as 'full 2373 Same as 'full', but disables SMT and L1D
2834 flush runtime 2374 flush runtime control. Implies the
2835 'nosmt=force' 2375 'nosmt=force' command line option.
2836 (i.e. sysfs c 2376 (i.e. sysfs control of SMT is disabled.)
2837 2377
2838 flush 2378 flush
2839 Leaves SMT en 2379 Leaves SMT enabled and enables the default
2840 hypervisor mi 2380 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2381 L1D flush.
2842 2382
2843 SMT control a 2383 SMT control and L1D flush control via the
2844 sysfs interfa 2384 sysfs interface is still possible after
2845 boot. Hyperv 2385 boot. Hypervisors will issue a warning
2846 when the firs 2386 when the first VM is started in a
2847 potentially i 2387 potentially insecure configuration,
2848 i.e. SMT enab 2388 i.e. SMT enabled or L1D flush disabled.
2849 2389
2850 flush,nosmt 2390 flush,nosmt
2851 2391
2852 Disables SMT 2392 Disables SMT and enables the default
2853 hypervisor mi 2393 hypervisor mitigation.
2854 2394
2855 SMT control a 2395 SMT control and L1D flush control via the
2856 sysfs interfa 2396 sysfs interface is still possible after
2857 boot. Hyperv 2397 boot. Hypervisors will issue a warning
2858 when the firs 2398 when the first VM is started in a
2859 potentially i 2399 potentially insecure configuration,
2860 i.e. SMT enab 2400 i.e. SMT enabled or L1D flush disabled.
2861 2401
2862 flush,nowarn 2402 flush,nowarn
2863 Same as 'flus 2403 Same as 'flush', but hypervisors will not
2864 warn when a V 2404 warn when a VM is started in a potentially
2865 insecure conf 2405 insecure configuration.
2866 2406
2867 off 2407 off
2868 Disables hype 2408 Disables hypervisor mitigations and doesn't
2869 emit any warn 2409 emit any warnings.
2870 It also drops 2410 It also drops the swap size and available
2871 RAM limit res 2411 RAM limit restriction on both hypervisor and
2872 bare metal. 2412 bare metal.
2873 2413
2874 Default is 'flush'. 2414 Default is 'flush'.
2875 2415
2876 For details see: Docu 2416 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2417
2878 l2cr= [PPC] 2418 l2cr= [PPC]
2879 2419
2880 l3cr= [PPC] 2420 l3cr= [PPC]
2881 2421
2882 lapic [X86-32,APIC,EARLY] E !! 2422 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2423 disabled it.
2884 2424
2885 lapic= [X86,APIC] Do not use 2425 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2426 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2427 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2428 Format: notscdeadline
2889 2429
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2430 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2431 in C2 power state.
2892 2432
2893 libata.dma= [LIBATA] DMA control 2433 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2434 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2435 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2436 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2437 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2438 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2439 for disks and CDROMs, but not CFs.
2900 2440
2901 libata.ignore_hpa= [LIBATA] Igno 2441 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2442 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2443 libata.ignore_hpa=1 ignore limits, using full disk
2904 2444
2905 libata.noacpi [LIBATA] Disables use 2445 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2446 when set.
2907 Format: <int> 2447 Format: <int>
2908 2448
2909 libata.force= [LIBATA] Force config !! 2449 libata.force= [LIBATA] Force configurations. The format is comma-
2910 separated list of "[I !! 2450 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2451 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2452 matching port, link or device. Basically, it matches
2913 printed on console by !! 2453 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2454 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2455 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2456 configuration applies to all ports, links and devices.
2917 2457
2918 If only DEVICE is omi 2458 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2459 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2460 number of 0 either selects the first device or the
2921 first fan-out link be 2461 first fan-out link behind PMP device. It does not
2922 select the host link. 2462 select the host link. DEVICE number of 15 selects the
2923 host link and device 2463 host link and device attached to it.
2924 2464
2925 The VAL specifies the 2465 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2466 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2467 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2468 The following configurations can be forced.
2929 2469
2930 * Cable type: 40c, 80 2470 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2471 Any ID with matching PORT is used.
2932 2472
2933 * SATA link speed lim 2473 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2474
2935 * Transfer mode: pio[ 2475 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2476 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2477 allowed.
2938 2478
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 2479 * [no]ncq: Turn on or off NCQ.
2950 2480
2951 * [no]ncqtrim: Enable !! 2481 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 2482
2953 * [no]ncqati: Enable !! 2483 * nohrst, nosrst, norst: suppress hard, soft
>> 2484 and both resets.
2954 2485
2955 * [no]trim: Enable or !! 2486 * rstonce: only attempt one reset during
>> 2487 hot-unplug link recovery
2956 2488
2957 * trim_zero: Indicate !! 2489 * dump_id: dump IDENTIFY data.
2958 2490
2959 * max_trim_128m: Set !! 2491 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2960 <<
2961 * [no]dma: Turn on or <<
2962 <<
2963 * atapi_dmadir: Enabl <<
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 2492
2995 * disable: Disable th 2493 * disable: Disable this device.
2996 2494
2997 If there are multiple 2495 If there are multiple matching configurations changing
2998 the same attribute, t 2496 the same attribute, the last one is used.
2999 2497
>> 2498 memblock=debug [KNL] Enable memblock debug messages.
>> 2499
3000 load_ramdisk= [RAM] [Deprecated] 2500 load_ramdisk= [RAM] [Deprecated]
3001 2501
3002 lockd.nlm_grace_period=P [NFS] Assig 2502 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2503 Format: <integer>
3004 2504
3005 lockd.nlm_tcpport=N [NFS] Assign 2505 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2506 Format: <integer>
3007 2507
3008 lockd.nlm_timeout=T [NFS] Assign 2508 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2509 Format: <integer>
3010 2510
3011 lockd.nlm_udpport=M [NFS] Assign 2511 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2512 Format: <integer>
3013 2513
3014 lockdown= [SECURITY,EARLY] !! 2514 lockdown= [SECURITY]
3015 { integrity | confide 2515 { integrity | confidentiality }
3016 Enable the kernel loc 2516 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2517 integrity, kernel features that allow userland to
3018 modify the running ke 2518 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2519 confidentiality, kernel features that allow userland
3020 to extract confidenti 2520 to extract confidential information from the kernel
3021 are also disabled. 2521 are also disabled.
3022 2522
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] 2523 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2524 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2525 Defaults to being automatically set based on the
3058 number of online CPUs 2526 number of online CPUs.
3059 2527
3060 locktorture.nwriters_stress= [KNL] 2528 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2529 Set the number of locking write-acquisition kthreads.
3062 2530
3063 locktorture.onoff_holdoff= [KNL] 2531 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2532 Set time (s) after boot for CPU-hotplug testing.
3065 2533
3066 locktorture.onoff_interval= [KNL] 2534 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2535 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2536 zero to disable CPU-hotplug testing.
3069 2537
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] 2538 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2539 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2540 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2541 mode during the locktorture test.
3093 2542
3094 locktorture.shutdown_secs= [KNL] 2543 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2544 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2545 is useful for hands-off automated testing.
3097 2546
3098 locktorture.stat_interval= [KNL] 2547 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2548 Time (s) between statistics printk()s.
3100 2549
3101 locktorture.stutter= [KNL] 2550 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2551 Time (s) to stutter testing, for example,
3103 specifying five secon 2552 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2553 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2554 This tests the locking primitive's ability to
3106 transition abruptly t 2555 transition abruptly to and from idle.
3107 2556
3108 locktorture.torture_type= [KNL] 2557 locktorture.torture_type= [KNL]
3109 Specify the locking i 2558 Specify the locking implementation to test.
3110 2559
3111 locktorture.verbose= [KNL] 2560 locktorture.verbose= [KNL]
3112 Enable additional pri 2561 Enable additional printk() statements.
3113 2562
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2563 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2564 Format: <irq>
3120 2565
3121 loglevel= [KNL,EARLY] !! 2566 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2567 console loglevel will be printed to the console. It can
3124 also be changed with 2568 also be changed with klogd or other programs. The
3125 loglevels are defined 2569 loglevels are defined as follows:
3126 2570
3127 0 (KERN_EMERG) 2571 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2572 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2573 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2574 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2575 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2576 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2577 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2578 7 (KERN_DEBUG) debug-level messages
3135 2579
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2580 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2581 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2582 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2583 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2584 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2585 that allows to increase the default size depending on
3142 parameter that allows !! 2586 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2587
3146 logo.nologo [FB] Disables display 2588 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2589 This may be used to provide more screen space for
3148 kernel log messages a 2590 kernel log messages and is useful when debugging
3149 kernel boot problems. 2591 kernel boot problems.
3150 2592
3151 lp=0 [LP] Specify paral 2593 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2594 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2595 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2596 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2597 specified in addition to the ports) causes
3156 attached prin 2598 attached printers to be reset. Using
3157 lp=port1,port 2599 lp=port1,port2,... specifies the parallel ports
3158 to associate 2600 to associate lp devices with, starting with
3159 lp0. A port s 2601 lp0. A port specification may be 'none' to skip
3160 that lp devic 2602 that lp device, or a parport name such as
3161 'parport0'. S 2603 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2604 port specification list means that device IDs
3163 from each por 2605 from each port should be examined, to see if
3164 an IEEE 1284- 2606 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2607 so, the driver will manage that printer.
3166 See also head 2608 See also header of drivers/char/lp.c.
3167 2609
3168 lpj=n [KNL] 2610 lpj=n [KNL]
3169 Sets loops_per_jiffy 2611 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2612 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2613 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2614 the correct value for your kernel, boot with normal
3173 autodetection and see 2615 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2616 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2617 which is likely to cause problems if your CPUs need
3176 significantly diverge 2618 significantly divergent settings. An incorrect value
3177 will cause delays in 2619 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2620 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2621 unlikely, in the extreme case this might damage your
3180 hardware. 2622 hardware.
3181 2623
>> 2624 ltpc= [NET]
>> 2625 Format: <io>,<irq>,<dma>
>> 2626
3182 lsm.debug [SECURITY] Enable LSM 2627 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2628
3184 lsm=lsm1,...,lsmN 2629 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2630 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2631 overrides CONFIG_LSM, and the "security=" parameter.
3187 2632
>> 2633 machvec= [IA-64] Force the use of a particular machine-vector
>> 2634 (machvec) in a generic kernel.
>> 2635 Example: machvec=hpzx1
>> 2636
3188 machtype= [Loongson] Share the 2637 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2638 different yeeloong laptops.
3190 Example: machtype=lem 2639 Example: machtype=lemote-yeeloong-2f-7inch
3191 2640
3192 maxcpus= [SMP,EARLY] Maximum n !! 2641 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2642 than or equal to this physical address is ignored.
>> 2643
>> 2644 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2645 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2646 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2647 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2648 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2649 only takes effect during system bootup.
3198 While n=0 is a specia 2650 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2651 which also disables the IO APIC.
3200 2652
3201 max_loop= [LOOP] The number of 2653 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2654 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2655 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2656 of statically allocating a predefined number, loop
3205 devices can be reques 2657 devices can be requested on-demand with the
3206 /dev/loop-control int 2658 /dev/loop-control interface.
3207 2659
3208 mce [X86-32] Machine Chec 2660 mce [X86-32] Machine Check Exception
3209 2661
3210 mce=option [X86-64] See Document !! 2662 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2663
3212 md= [HW] RAID subsystems 2664 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2665 See Documentation/admin-guide/md.rst.
3214 2666
3215 mdacon= [MDA] 2667 mdacon= [MDA]
3216 Format: <first>,<last 2668 Format: <first>,<last>
3217 Specifies range of co 2669 Specifies range of consoles to be captured by the MDA.
3218 2670
3219 mds= [X86,INTEL,EARLY] !! 2671 mds= [X86,INTEL]
3220 Control mitigation fo 2672 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2673 Sampling (MDS) vulnerability.
3222 2674
3223 Certain CPUs are vuln 2675 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2676 internal buffers which can forward information to a
3225 disclosure gadget und 2677 disclosure gadget under certain conditions.
3226 2678
3227 In vulnerable process 2679 In vulnerable processors, the speculatively
3228 forwarded data can be 2680 forwarded data can be used in a cache side channel
3229 attack, to access dat 2681 attack, to access data to which the attacker does
3230 not have direct acces 2682 not have direct access.
3231 2683
3232 This parameter contro 2684 This parameter controls the MDS mitigation. The
3233 options are: 2685 options are:
3234 2686
3235 full - Enable M 2687 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2688 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2689 SMT on vulnerable CPUs
3238 off - Uncondit 2690 off - Unconditionally disable MDS mitigation
3239 2691
3240 On TAA-affected machi 2692 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2693 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2694 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2695 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2696 too.
3245 2697
3246 Not specifying this o 2698 Not specifying this option is equivalent to
3247 mds=full. 2699 mds=full.
3248 2700
3249 For details see: Docu 2701 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2702
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2703 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3252 Must be specified, ot !! 2704 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 2705
3258 1 for test; 2706 1 for test;
3259 2 when the kernel is 2707 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 2708 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 2709 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 2710
3270 [X86] Work as limitin 2711 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2712 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2713 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2714 belonging to unused RAM.
3274 2715
3275 Note that this only t 2716 Note that this only takes effects during boot time since
3276 in above case 3, memo 2717 in above case 3, memory may need be hot added after boot
3277 if system memory of h 2718 if system memory of hypervisor is not sufficient.
3278 2719
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 2720 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2721 memory.
3289 2722
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2723 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2724 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2725 per-device physically contiguous DMA buffers.
3295 2726
3296 memhp_default_state=online/offline/on !! 2727 memhp_default_state=online/offline
3297 [KNL] Set the initial 2728 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2729 onlining policy. If not specified, the default value is
3299 set according to the 2730 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2731 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2732 option.
3302 See Documentation/adm 2733 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 2734
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2735 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2736 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2737 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2738 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2739 option description.
3309 2740
3310 memmap=nn[KMG]@ss[KMG] 2741 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2742 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 2743 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2744 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2745 which limits max address to nn[KMG].
3315 Multiple different re 2746 Multiple different regions can be specified,
3316 comma delimited. 2747 comma delimited.
3317 Example: 2748 Example:
3318 memmap=100M@2 2749 memmap=100M@2G,100M#3G,1G!1024G
3319 2750
3320 memmap=nn[KMG]#ss[KMG] 2751 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2752 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2753 Region of memory to be marked is from ss to ss+nn.
3323 2754
3324 memmap=nn[KMG]$ss[KMG] 2755 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2756 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2757 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2758 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2759 memmap=64K$0x18690000
3329 or 2760 or
3330 memmap=0x100 2761 memmap=0x10000$0x18690000
3331 Some bootloaders may 2762 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2763 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2764 will be eaten.
3334 2765
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2766 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2767 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2768 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2769 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2770 and is NVDIMM or ADR memory.
3340 2771
3341 memmap=<size>%<offset>-<oldtype>+<new 2772 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 2773 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 2774 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 2775 out, the whole region will be marked as <newtype>,
3345 even if previously un 2776 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 2777 out, matching memory will be removed. Types are
3347 specified as e820 typ 2778 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 2779 3 = ACPI, 12 = PRAM.
3349 2780
3350 memory_corruption_check=0/1 [X86,EARL !! 2781 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 2782 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2783 memory when doing things like suspend/resume.
3353 Setting this option w 2784 Setting this option will scan the memory
3354 looking for corruptio 2785 looking for corruption. Enabling this will
3355 both detect corruptio 2786 both detect corruption and prevent the kernel
3356 from using the memory 2787 from using the memory being corrupted.
3357 However, its intended 2788 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2789 repeatable BIOS-originated corruption always
3359 affects the same memo 2790 affects the same memory, you can use memmap=
3360 to prevent the kernel 2791 to prevent the kernel from using that memory.
3361 2792
3362 memory_corruption_check_size=size [X8 !! 2793 memory_corruption_check_size=size [X86]
3363 By default it checks 2794 By default it checks for corruption in the low
3364 64k, making this memo 2795 64k, making this memory unavailable for normal
3365 use. Use this parame 2796 use. Use this parameter to scan for
3366 corruption in more or 2797 corruption in more or less memory.
3367 2798
3368 memory_corruption_check_period=second !! 2799 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2800 By default it checks for corruption every 60
3370 seconds. Use this pa 2801 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2802 other rate. 0 disables periodic checking.
3372 2803
3373 memory_hotplug.memmap_on_memory !! 2804 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> 2805 Format: <integer>
3394 default : 0 <disable> 2806 default : 0 <disable>
3395 Specifies the number 2807 Specifies the number of memtest passes to be
3396 performed. Each pass 2808 performed. Each pass selects another test
3397 pattern from a given 2809 pattern from a given set of patterns. Memtest
3398 fills the memory with 2810 fills the memory with this pattern, validates
3399 memory contents and r 2811 memory contents and reserves bad memory
3400 regions that are dete 2812 regions that are detected.
3401 2813
3402 mem_encrypt= [X86-64] AMD Secure M 2814 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2815 Valid arguments: on, off
3404 Default: off !! 2816 Default (depends on kernel configuration option):
>> 2817 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2818 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2819 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2820 mem_encrypt=off: Do not activate SME
3407 2821
3408 Refer to Documentatio !! 2822 Refer to Documentation/virt/kvm/amd-memory-encryption.rst
3409 for details on when m 2823 for details on when memory encryption can be activated.
3410 2824
3411 mem_sleep_default= [SUSPEND] Def 2825 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2826 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2827 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2828 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 2829 See Documentation/admin-guide/pm/sleep-states.rst.
3416 2830
>> 2831 meye.*= [HW] Set MotionEye Camera parameters
>> 2832 See Documentation/admin-guide/media/meye.rst.
>> 2833
>> 2834 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2835 Multi-Function General Purpose Timers on AMD Geode
>> 2836 platforms.
>> 2837
3417 mfgptfix [X86-32] Fix MFGPT ti 2838 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2839 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2840 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2841 problem by letting the user disable the workaround.
3421 2842
3422 mga= [HW,DRM] 2843 mga= [HW,DRM]
3423 2844
3424 microcode.force_minrev= [X86] !! 2845 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2846 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2847
3429 mini2440= [ARM,HW,KNL] 2848 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2849 Format:[0..2][b][c][t]
3431 Default: "0tb" 2850 Default: "0tb"
3432 MINI2440 configuratio 2851 MINI2440 configuration specification:
3433 0 - The attached scre 2852 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2853 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2854 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2855 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2856 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2857 unconfigured.
3439 b - Enable backlight. 2858 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2859 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2860 LED. This parameter is not necessary when using the
3442 VGA shield. 2861 VGA shield.
3443 c - Enable the s3c ca 2862 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2863 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2864 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2865 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2866 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 2867 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 2868
3450 mitigations= 2869 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 2870 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 2871 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 2872 arch-independent options, each of which is an
3454 aggregation of existi 2873 aggregation of existing arch-specific options.
3455 2874
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 2875 off
3460 Disable all o 2876 Disable all optional CPU mitigations. This
3461 improves syst 2877 improves system performance, but it may also
3462 expose users 2878 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 2879 Equivalent to: nopti [X86,PPC]
3464 !! 2880 kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 2881 nospectre_v1 [X86,PPC]
>> 2882 nobp=0 [S390]
3475 2883 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 2884 spectre_v2_user=off [X86]
3482 !! 2885 spec_store_bypass_disable=off [X86,PPC]
3483 2886 ssbd=force-off [ARM64]
>> 2887 l1tf=off [X86]
>> 2888 mds=off [X86]
3484 2889 tsx_async_abort=off [X86]
>> 2890 kvm.nx_huge_pages=off [X86]
>> 2891 no_entry_flush [PPC]
>> 2892 no_uaccess_flush [PPC]
3485 2893
3486 Exceptions: 2894 Exceptions:
3487 2895 This does not have any effect on
3488 2896 kvm.nx_huge_pages when
3489 2897 kvm.nx_huge_pages=force.
3490 2898
3491 auto (default) 2899 auto (default)
3492 Mitigate all 2900 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 2901 enabled, even if it's vulnerable. This is for
3494 users who don 2902 users who don't want to be surprised by SMT
3495 getting disab 2903 getting disabled across kernel upgrades, or who
3496 have other wa 2904 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 2905 Equivalent to: (default behavior)
3498 2906
3499 auto,nosmt 2907 auto,nosmt
3500 Mitigate all 2908 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 2909 if needed. This is for users who always want to
3502 be fully miti 2910 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 2911 Equivalent to: l1tf=flush,nosmt [X86]
3504 2912 mds=full,nosmt [X86]
3505 2913 tsx_async_abort=full,nosmt [X86]
3506 <<
3507 <<
3508 2914
3509 mminit_loglevel= 2915 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 2916 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 2917 parameter allows control of the logging verbosity for
3512 the additional memory 2918 the additional memory initialisation checks. A value
3513 of 0 disables mminit 2919 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 2920 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 2921 so loglevel=8 may also need to be specified.
3516 2922
3517 mmio_stale_data= <<
3518 [X86,INTEL,EARLY] Con <<
3519 MMIO Stale Data vulne <<
3520 <<
3521 Processor MMIO Stale <<
3522 vulnerabilities that <<
3523 operation. Exposed da <<
3524 the same CPU buffers <<
3525 Therefore, similar to <<
3526 is to clear the affec <<
3527 <<
3528 This parameter contro <<
3529 options are: <<
3530 <<
3531 full - Enable m <<
3532 <<
3533 full,nosmt - Enable m <<
3534 vulnerab <<
3535 <<
3536 off - Uncondit <<
3537 <<
3538 On MDS or TAA affecte <<
3539 mmio_stale_data=off c <<
3540 MDS or TAA mitigation <<
3541 mitigated with the sa <<
3542 disable this mitigati <<
3543 mds=off and tsx_async <<
3544 <<
3545 Not specifying this o <<
3546 mmio_stale_data=full. <<
3547 <<
3548 For details see: <<
3549 Documentation/admin-g <<
3550 <<
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 2923 module.sig_enforce
3574 [KNL] When CONFIG_MOD 2924 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 2925 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 2926 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 2927 is always true, so this option does nothing.
3578 2928
3579 module_blacklist= [KNL] Do not load 2929 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 2930 modules. Useful for debugging problem modules.
3581 2931
3582 mousedev.tap_time= 2932 mousedev.tap_time=
3583 [MOUSE] Maximum time 2933 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 2934 leaving touchpad surface for touch to be considered
3585 a tap and be reported 2935 a tap and be reported as a left button click (for
3586 touchpads working in 2936 touchpads working in absolute mode only).
3587 Format: <msecs> 2937 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 2938 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 2939 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 2940 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 2941 reporting absolute coordinates, such as tablets
3592 2942
3593 movablecore= [KNL,X86,PPC,EARLY] !! 2943 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 2944 Format: nn[KMGTPE] | nn%
3595 This parameter is the 2945 This parameter is the complement to kernelcore=, it
3596 specifies the amount 2946 specifies the amount of memory used for migratable
3597 allocations. If both 2947 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 2948 specified, then kernelcore will be at *least* the
3599 specified value but m 2949 specified value but may be more. If movablecore on its
3600 own is specified, the 2950 own is specified, the administrator must be careful
3601 that the amount of me 2951 that the amount of memory usable for all allocations
3602 is not too small. 2952 is not too small.
3603 2953
3604 movable_node [KNL,EARLY] Boot-time !! 2954 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 2955 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 2956 of such nodes will be usable only for movable
3607 allocations which rul 2957 allocations which rules out almost all kernel
3608 allocations. Use with 2958 allocations. Use with caution!
3609 2959
3610 MTD_Partition= [MTD] 2960 MTD_Partition= [MTD]
3611 Format: <name>,<regio 2961 Format: <name>,<region-number>,<size>,<offset>
3612 2962
3613 MTD_Region= [MTD] Format: 2963 MTD_Region= [MTD] Format:
3614 <name>,<region-number 2964 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 2965
3616 mtdparts= [MTD] 2966 mtdparts= [MTD]
3617 See drivers/mtd/parse 2967 See drivers/mtd/parsers/cmdlinepart.c
3618 2968
>> 2969 multitce=off [PPC] This parameter disables the use of the pSeries
>> 2970 firmware feature for updating multiple TCE entries
>> 2971 at a time.
>> 2972
>> 2973 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 2974
>> 2975 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 2976
>> 2977 boundary - index of last SLC block on Flex-OneNAND.
>> 2978 The remaining blocks are configured as MLC blocks.
>> 2979 lock - Configure if Flex-OneNAND boundary should be locked.
>> 2980 Once locked, the boundary cannot be changed.
>> 2981 1 indicates lock status, 0 indicates unlock status.
>> 2982
>> 2983 mtdset= [ARM]
>> 2984 ARM/S3C2412 JIVE boot control
>> 2985
>> 2986 See arch/arm/mach-s3c/mach-jive.c
>> 2987
3619 mtouchusb.raw_coordinates= 2988 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 2989 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 2990 ('y', default) or cooked coordinates ('n')
3622 2991
3623 mtrr=debug [X86,EARLY] !! 2992 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 2993 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 2994 that could hold holes aka. UC entries.
3630 2995
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 2996 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 2997 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 2998 Default is 1.
3634 Large value could pre 2999 Large value could prevent small alignment from
3635 using up MTRRs. 3000 using up MTRRs.
3636 3001
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3002 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3003 Format: <integer>
3639 Range: 0,7 : spare re 3004 Range: 0,7 : spare reg number
3640 Default : 1 3005 Default : 1
3641 Used for mtrr cleanup 3006 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3007 Set to 2 or more if your graphical card needs more.
3643 3008
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 3009 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3010
3650 netdev= [NET] Network devices 3011 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3012 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3013 Note that mem_start is often overloaded to mean
3653 something different a 3014 something different and driver-specific.
3654 This usage is only do 3015 This usage is only documented in each driver source
3655 file if at all. 3016 file if at all.
3656 3017
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 3018 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3019 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3020 0 to disable accounting
3665 1 to enable accountin 3021 1 to enable accounting
3666 Default value is 0. 3022 Default value is 0.
3667 3023
3668 nfs.cache_getent= !! 3024 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3025 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3026
3672 nfs.cache_getent_timeout= !! 3027 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3028 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3029
>> 3030 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3031 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3032
3676 nfs.callback_nr_threads= 3033 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3034 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3035 NFS client will assign to service NFSv4 callback
3679 requests. 3036 requests.
3680 3037
3681 nfs.callback_tcpport= 3038 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3039 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3040 channel should listen.
3684 3041
3685 nfs.delay_retrans= !! 3042 nfs.cache_getent=
3686 [NFS] specifies the n !! 3043 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3044 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3045
3689 Only applies if the s !! 3046 nfs.cache_getent_timeout=
3690 and the specified val !! 3047 [NFS] sets the timeout after which an attempt to
>> 3048 update a cache entry is deemed to have failed.
>> 3049
>> 3050 nfs.idmap_cache_timeout=
>> 3051 [NFS] set the maximum lifetime for idmapper cache
>> 3052 entries.
3691 3053
3692 nfs.enable_ino64= 3054 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3055 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3056 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3057 number for the readdir() and stat() syscalls instead
3696 of returning the full 3058 of returning the full 64-bit number.
3697 The default is to ret 3059 The default is to return 64-bit inode numbers.
3698 3060
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3061 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3062 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3063 slots the client will assign to the callback
3706 channel. This determi 3064 channel. This determines the maximum number of
3707 callbacks the client 3065 callbacks the client will process in parallel for
3708 a particular server. 3066 a particular server.
3709 3067
3710 nfs.max_session_slots= 3068 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3069 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3070 the client will attempt to negotiate with the server.
3713 This limits the numbe 3071 This limits the number of simultaneous RPC requests
3714 that the client can s 3072 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3073 Note that there is little point in setting this
3716 value higher than the 3074 value higher than the max_tcp_slot_table_limit.
3717 3075
3718 nfs.nfs4_disable_idmapping= 3076 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3077 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3078 ensures that both the RPC level authentication
3721 scheme and the NFS le 3079 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3080 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3081 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3082 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3083 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3084 Servers that do not support this mode of operation
3727 will be autodetected 3085 will be autodetected by the client, and it will fall
3728 back to using the idm 3086 back to using the idmapper.
3729 To turn off this beha 3087 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3088 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3089 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3090 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3091 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3092 UUID that is generated at system install time.
3736 3093
3737 nfs.recover_lost_locks= !! 3094 nfs.send_implementation_id =
>> 3095 [NFSv4.1] Send client implementation identification
>> 3096 information in exchange_id requests.
>> 3097 If zero, no implementation identification information
>> 3098 will be sent.
>> 3099 The default is to send the implementation identification
>> 3100 information.
>> 3101
>> 3102 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3103 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3104 to a lease timeout on the server. Please note that
3740 doing this risks data 3105 doing this risks data corruption, since there are
3741 no guarantees that th 3106 no guarantees that the file will remain unchanged
3742 after the locks are l 3107 after the locks are lost.
3743 If you want to enable 3108 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3109 attempting to recover these locks, then set this
3745 parameter to '1'. 3110 parameter to '1'.
3746 The default parameter 3111 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3112 not to attempt recovery of lost locks.
3748 3113
3749 nfs.send_implementation_id= !! 3114 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 3115 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3116 layoutstats to the pNFS metadata server.
3760 3117
3761 Setting this to value 3118 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3119 whatever value is the default set by the layout
3763 driver. A non-zero va 3120 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3121 in seconds between layoutstats transmissions.
3765 3122
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= 3123 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 3124 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 3125 server will return only numeric uids and gids to
3774 clients using auth_sy 3126 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 3127 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 3128 migration from NFSv2/v3.
3777 3129
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] 3130 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3131 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3132 NMI stack-backtrace request.
3798 3133
3799 nmi_debug= [KNL,SH] Specify one 3134 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3135 when a NMI is triggered.
3801 Format: [state][,regs 3136 Format: [state][,regs][,debounce][,die]
3802 3137
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3138 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3139 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3140 Valid num: 0 or 1
3806 0 - turn hardlockup d 3141 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3142 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3143 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3144 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3145 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3146 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3147 please see 'nowatchdog'.
3815 This is useful when y 3148 This is useful when you use a panic=... timeout and
3816 need the box quickly 3149 need the box quickly up again.
3817 3150
3818 These settings can be 3151 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3152 the nmi_watchdog and hardlockup_panic sysctls.
3820 3153
>> 3154 netpoll.carrier_timeout=
>> 3155 [NET] Specifies amount of time (in seconds) that
>> 3156 netpoll should wait for a carrier. By default netpoll
>> 3157 waits 4 seconds.
>> 3158
3821 no387 [BUGS=X86-32] Tells t 3159 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3160 emulation library even if a 387 maths coprocessor
3823 is present. 3161 is present.
3824 3162
3825 no4lvl [RISCV,EARLY] Disable !! 3163 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 3164 kernel to use 4-level paging instead.
3830 3165
3831 noalign [KNL,ARM] !! 3166 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 3167
3840 no_console_suspend 3168 no_console_suspend
3841 [HW] Never suspend th 3169 [HW] Never suspend the console
3842 Disable suspending of 3170 Disable suspending of consoles during suspend and
3843 hibernate operations. 3171 hibernate operations. Once disabled, debugging
3844 messages can reach va 3172 messages can reach various consoles while the rest
3845 of the system is bein 3173 of the system is being put to sleep (ie, while
3846 debugging driver susp 3174 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3175 not work reliably with all consoles, but is known
3848 to work with serial a 3176 to work with serial and VGA consoles.
3849 To facilitate more fl 3177 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3178 console_suspend, a printk module parameter to control
3851 it. Users could use c 3179 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3180 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3181 turn on/off it dynamically.
3854 3182
3855 no_debug_objects !! 3183 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3184 Disable device dump. Device dump allows drivers to
>> 3185 append dump data to vmcore so you can collect driver
>> 3186 specified debug info. Drivers can append the data
>> 3187 without any limit and this data is stored in memory,
>> 3188 so this may cause significant memory stress. Disabling
>> 3189 device dump can help save memory but the driver debug
>> 3190 data will be no longer available. This parameter
>> 3191 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3192 is set.
>> 3193
>> 3194 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3195 caches in the slab allocator. Saves per-node memory,
>> 3196 but will impact performance.
>> 3197
>> 3198 noalign [KNL,ARM]
>> 3199
>> 3200 noaltinstr [S390] Disables alternative instructions patching
>> 3201 (CPU alternatives feature).
>> 3202
>> 3203 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3204 IOAPICs that may be present in the system.
>> 3205
>> 3206 noautogroup Disable scheduler automatic task group creation.
>> 3207
>> 3208 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 3209 on "Classic" PPC cores.
>> 3210
>> 3211 nocache [ARM]
>> 3212
>> 3213 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 3214
>> 3215 nodelayacct [KNL] Disable per-task delay accounting
3857 3216
3858 nodsp [SH] Disable hardware 3217 nodsp [SH] Disable hardware DSP at boot time.
3859 3218
3860 noefi [EFI,EARLY] Disable E !! 3219 noefi Disable EFI runtime services support.
>> 3220
>> 3221 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
>> 3222
>> 3223 noexec [IA-64]
>> 3224
>> 3225 noexec [X86]
>> 3226 On X86-32 available only on PAE configured kernels.
>> 3227 noexec=on: enable non-executable mappings (default)
>> 3228 noexec=off: disable non-executable mappings
3861 3229
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3230 nosmap [X86,PPC]
>> 3231 Disable SMAP (Supervisor Mode Access Prevention)
>> 3232 even if it is supported by processor.
>> 3233
>> 3234 nosmep [X86,PPC]
>> 3235 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3236 even if it is supported by processor.
3863 3237
3864 noexec32 [X86-64] 3238 noexec32 [X86-64]
3865 This affects only 32- 3239 This affects only 32-bit executables.
3866 noexec32=on: enable n 3240 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3241 read doesn't imply executable mappings
3868 noexec32=off: disable 3242 noexec32=off: disable non-executable mappings
3869 read implies 3243 read implies executable mappings
3870 3244
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 3245 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3246
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3247 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3248 register save and restore. The kernel will only save
3881 legacy floating-point 3249 legacy floating-point registers on task switch.
3882 3250
>> 3251 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
>> 3252
>> 3253 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3254 Equivalent to smt=1.
>> 3255
>> 3256 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3257 nosmt=force: Force disable SMT, cannot be undone
>> 3258 via the sysfs control file.
>> 3259
>> 3260 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3261 (bounds check bypass). With this option data leaks are
>> 3262 possible in the system.
>> 3263
>> 3264 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 3265 the Spectre variant 2 (indirect branch prediction)
>> 3266 vulnerability. System may allow data leaks with this
>> 3267 option.
>> 3268
>> 3269 nospec_store_bypass_disable
>> 3270 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3271
>> 3272 no_uaccess_flush
>> 3273 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3274
>> 3275 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3276 and restore using xsave. The kernel will fallback to
>> 3277 enabling legacy floating-point and sse state.
>> 3278
>> 3279 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3280 register states. The kernel will fall back to use
>> 3281 xsave to save the states. By using this parameter,
>> 3282 performance of saving the states is degraded because
>> 3283 xsave doesn't support modified optimization while
>> 3284 xsaveopt supports it on xsaveopt enabled systems.
>> 3285
>> 3286 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3287 restoring x86 extended register state in compacted
>> 3288 form of xsave area. The kernel will fall back to use
>> 3289 xsaveopt and xrstor to save and restore the states
>> 3290 in standard form of xsave area. By using this
>> 3291 parameter, xsave area per process might occupy more
>> 3292 memory on xsaves enabled systems.
>> 3293
>> 3294 nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
>> 3295 in do_idle() and not use the arch_cpu_idle()
>> 3296 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
>> 3297 to be effective. This is useful on platforms where the
>> 3298 sleep(SH) or wfi(ARM,ARM64) instructions do not work
>> 3299 correctly or when doing power measurements to evalute
>> 3300 the impact of the sleep instructions. This is also
>> 3301 useful when using JTAG debugger.
>> 3302
>> 3303 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3304 only way then for a file to be executed with privilege
>> 3305 is to be setuid root or executed by root.
>> 3306
>> 3307 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3308 function PAL_HALT_LIGHT when idle. This increases
>> 3309 power-consumption. On the positive side, it reduces
>> 3310 interrupt wake-up latency, which may improve performance
>> 3311 in certain environments such as networked servers or
>> 3312 real-time systems.
>> 3313
3883 no_hash_pointers 3314 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3315 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3316 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3317 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3318 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3319 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3320 users, but it also makes debugging the kernel more
3891 difficult since unequ 3321 difficult since unequal pointers can no longer be
3892 compared. However, i 3322 compared. However, if this command-line option is
3893 specified, then all n 3323 specified, then all normal pointers will have their true
3894 value printed. This o !! 3324 value printed. Pointers printed via %pK may still be
>> 3325 hashed. This option should only be specified when
3895 debugging the kernel. 3326 debugging the kernel. Please do not use on production
3896 kernels. 3327 kernels.
3897 3328
3898 nohibernate [HIBERNATION] Disable 3329 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3330
3900 nohlt [ARM,ARM64,MICROBLAZE <<
3901 busy wait in do_idle( <<
3902 implementation; requi <<
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 <<
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA <<
3910 <<
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA <<
3912 <<
3913 nohz= [KNL] Boottime enable 3331 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3332 Valid arguments: on, off
3915 Default: on 3333 Default: on
3916 3334
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3335 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3336 The argument is a cpu list, as described above.
3919 In kernels built with 3337 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3338 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3339 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3340 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3341 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3342 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3343 rcu_nocbs= boot parameter.
3926 3344
3927 Note that this argume !! 3345 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 3346
>> 3347 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3348 disable unhandled interrupt sources.
>> 3349
>> 3350 no_timer_check [X86,APIC] Disables the code which tests for
>> 3351 broken timer IRQ sources.
>> 3352
>> 3353 noisapnp [ISAPNP] Disables ISA PnP code.
3929 3354
3930 noinitrd [RAM] Tells the kerne 3355 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3356 initial RAM disk.
3932 3357
3933 nointremap [X86-64,Intel-IOMMU,E !! 3358 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3359 remapping.
3935 [Deprecated - use int 3360 [Deprecated - use intremap=off]
3936 3361
3937 noinvpcid [X86,EARLY] Disable t !! 3362 nointroute [IA-64]
3938 3363
3939 noiotrap [SH] Disables trapped !! 3364 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 3365
3941 noirqdebug [X86-32] Disables the !! 3366 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 <<
3944 noisapnp [ISAPNP] Disables ISA <<
3945 3367
3946 nokaslr [KNL,EARLY] !! 3368 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 3369
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3370 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3371 fault handling.
3953 3372
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3373 no-vmw-sched-clock
>> 3374 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3375 clock and use the default one.
3955 3376
3956 nolapic [X86-32,APIC,EARLY] D !! 3377 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
>> 3378 accounting. steal time is computed, but won't
>> 3379 influence scheduler behaviour
3957 3380
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3381 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3959 3382
3960 nomce [X86-32] Disable Mach !! 3383 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3961 3384
3962 nomfgpt [X86-32] Disable Mult !! 3385 noltlbs [PPC] Do not use large page/tlb entries for kernel
3963 Timer usage (for AMD !! 3386 lowmem mapping on PPC40x and PPC8xx
3964 3387
3965 nomodeset Disable kernel modese !! 3388 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 3389
3973 Useful as error fallb !! 3390 nomce [X86-32] Disable Machine Check Exception
3974 3391
3975 nomodule Disable module load !! 3392 nomfgpt [X86-32] Disable Multi-Function General Purpose
>> 3393 Timer usage (for AMD Geode machines).
3976 3394
3977 nonmi_ipi [X86] Disable using N 3395 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3396 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3397 irq.
3980 3398
3981 nopat [X86,EARLY] Disable P !! 3399 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 3400
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3401 nopat [X86] Disable PAT (page attribute table extension of
3993 Disables the PV optim !! 3402 pagetables) support.
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 3403
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3404 nopcid [X86-64] Disable the PCID cpu feature.
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3405
4002 norandmaps Don't use address spa 3406 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3407 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3408
4005 noreplace-smp [X86-32,SMP] Don't re 3409 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3410 with UP alternatives
4007 3411
>> 3412 nordrand [X86] Disable kernel use of the RDRAND and
>> 3413 RDSEED instructions even if they are supported
>> 3414 by the processor. RDRAND and RDSEED are still
>> 3415 available to user space applications.
>> 3416
4008 noresume [SWSUSP] Disables res 3417 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3418 space.
4010 3419
4011 no-scroll [VGA] Disables scroll 3420 no-scroll [VGA] Disables scrollback.
4012 This is required for 3421 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3422 reader made by F.H. Papenmeier (Germany).
4014 3423
4015 nosgx [X86-64,SGX,EARLY] Di !! 3424 nosbagart [IA-64]
4016 3425
4017 nosmap [PPC,EARLY] !! 3426 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 3427
4021 nosmep [PPC64s,EARLY] !! 3428 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 3429
4025 nosmp [SMP,EARLY] Tells an !! 3430 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3431 and disable the IO APIC. legacy for "maxcpus=0".
4027 3432
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 3433 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3434
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 3435 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3436
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 3437 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3438 soft-lockup and NMI watchdog (hard-lockup).
4083 3439
4084 nowb [ARM,EARLY] !! 3440 nowb [ARM]
4085 <<
4086 nox2apic [X86-64,APIC,EARLY] D <<
4087 3441
4088 NOTE: this parameter !! 3442 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4089 LEGACY_XAPIC_DISABLED <<
4090 IA32_XAPIC_DISABLE_ST <<
4091 3443
4092 noxsave [BUGS=X86] Disables x !! 3444 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4093 and restore using xsa !! 3445 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4094 enabling legacy float !! 3446 Some features depend on CPU0. Known dependencies are:
>> 3447 1. Resume from suspend/hibernate depends on CPU0.
>> 3448 Suspend/hibernate will fail if CPU0 is offline and you
>> 3449 need to online CPU0 before suspend/hibernate.
>> 3450 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 3451 removed if a PIC interrupt is detected.
>> 3452 It's said poweroff/reboot may depend on CPU0 on some
>> 3453 machines although I haven't seen such issues so far
>> 3454 after CPU0 is offline on a few tested machines.
>> 3455 If the dependencies are under your control, you can
>> 3456 turn on cpu0_hotplug.
>> 3457
>> 3458 nps_mtm_hs_ctr= [KNL,ARC]
>> 3459 This parameter sets the maximum duration, in
>> 3460 cycles, each HW thread of the CTOP can run
>> 3461 without interruptions, before HW switches it.
>> 3462 The actual maximum duration is 16 times this
>> 3463 parameter's value.
>> 3464 Format: integer between 1 and 255
>> 3465 Default: 255
>> 3466
>> 3467 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3468 purges which is reported from either PAL_VM_SUMMARY or
>> 3469 SAL PALO.
4095 3470
4096 noxsaveopt [X86] Disables xsaveo !! 3471 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4097 register states. The <<
4098 xsave to save the sta <<
4099 performance of saving <<
4100 xsave doesn't support <<
4101 xsaveopt supports it <<
4102 <<
4103 noxsaves [X86] Disables xsaves <<
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 3472 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3473 support 'n' processors. It could be larger than the
4114 number of already plu 3474 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3475 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3476 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3477 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3478 hot plugging.
4119 3479
4120 nr_uarts= [SERIAL] maximum numb 3480 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3481
4122 numa=off [KNL, ARM64, PPC, RIS !! 3482 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 3483 Allowed values are enable and disable
4129 3484
4130 numa_zonelist_order= [KNL, BOOT] Sele 3485 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3486 'node', 'default' can be specified
4132 This can be set from 3487 This can be set from sysctl after boot.
4133 See Documentation/adm 3488 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3489
4135 ohci1394_dma=early [HW,EARLY] en !! 3490 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3491 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3492 info.
4138 3493
4139 olpc_ec_timeout= [OLPC] ms delay when 3494 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3495 Rather than timing out after 20 ms if an EC
4141 command is not proper 3496 command is not properly ACKed, override the length
4142 of the timeout. We h 3497 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3498 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3499 interrupts *may* be lost!
4145 3500
4146 omap_mux= [OMAP] Override bootl 3501 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3502 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3503 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3504 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3505
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 3506 oops=panic Always panic on oopses. Default is to just kill the
4152 <<
4153 Format: [die0_boundar <<
4154 <<
4155 boundary - index of l <<
4156 The remain <<
4157 lock - Configure <<
4158 Once locke <<
4159 1 indicate <<
4160 <<
4161 oops=panic [KNL,EARLY] <<
4162 Always panic on oopse <<
4163 process, but there is 3507 process, but there is a small probability of
4164 deadlocking the machi 3508 deadlocking the machine.
4165 This will also cause 3509 This will also cause panics on machine check exceptions.
4166 Useful together with 3510 Useful together with panic=30 to trigger a reboot.
4167 3511
4168 page_alloc.shuffle= 3512 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3513 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3514 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3515 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3516 running on a platform with a direct-mapped memory-side
>> 3517 cache, and this parameter can be used to
>> 3518 override/disable that behavior. The state of the flag
>> 3519 can be read from sysfs at:
4173 /sys/module/page_allo 3520 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3521
4176 page_owner= [KNL,EARLY] Boot-time !! 3522 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3523 Storage of the information about who allocated
4178 each page is disabled 3524 each page is disabled in default. With this switch,
4179 we can turn it on. 3525 we can turn it on.
4180 on: enable the featur 3526 on: enable the feature
4181 3527
4182 page_poison= [KNL,EARLY] Boot-time !! 3528 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3529 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3530 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3531 off: turn off poisoning (default)
4186 on: turn on poisoning 3532 on: turn on poisoning
4187 3533
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 3534 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3535 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3536 timeout = 0: wait forever
4197 timeout < 0: reboot i 3537 timeout < 0: reboot immediately
4198 Format: <timeout> 3538 Format: <timeout>
4199 3539
4200 panic_on_taint= [KNL,EARLY] !! 3540 panic_print= Bitmask for printing system info when panic happens.
4201 Bitmask for condition !! 3541 User can chose combination of the following bits:
>> 3542 bit 0: print all tasks info
>> 3543 bit 1: print system memory info
>> 3544 bit 2: print timer info
>> 3545 bit 3: print locks info if CONFIG_LOCKDEP is on
>> 3546 bit 4: print ftrace buffer
>> 3547 bit 5: print all printk messages in buffer
>> 3548
>> 3549 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4202 Format: <hex>[,nouser 3550 Format: <hex>[,nousertaint]
4203 Hexadecimal bitmask r 3551 Hexadecimal bitmask representing the set of TAINT flags
4204 that will cause the k 3552 that will cause the kernel to panic when add_taint() is
4205 called with any of th 3553 called with any of the flags in this set.
4206 The optional switch " 3554 The optional switch "nousertaint" can be utilized to
4207 prevent userspace for 3555 prevent userspace forced crashes by writing to sysctl
4208 /proc/sys/kernel/tain 3556 /proc/sys/kernel/tainted any flagset matching with the
4209 bitmask set on panic_ 3557 bitmask set on panic_on_taint.
4210 See Documentation/adm 3558 See Documentation/admin-guide/tainted-kernels.rst for
4211 extra details on the 3559 extra details on the taint flags that users can pick
4212 to compose the bitmas 3560 to compose the bitmask to assign to panic_on_taint.
4213 3561
4214 panic_on_warn=1 panic() instead of WA !! 3562 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4215 on a WARN(). 3563 on a WARN().
4216 3564
4217 panic_print= Bitmask for printing !! 3565 crash_kexec_post_notifiers
4218 User can chose combin !! 3566 Run kdump after running panic-notifiers and dumping
4219 bit 0: print all task !! 3567 kmsg. This only for the users who doubt kdump always
4220 bit 1: print system m !! 3568 succeeds in any situation.
4221 bit 2: print timer in !! 3569 Note that this also increases risks of kdump failure,
4222 bit 3: print locks in !! 3570 because some panic notifiers can make the crashed
4223 bit 4: print ftrace b !! 3571 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 3572
4232 parkbd.port= [HW] Parallel port nu 3573 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3574 connected to, default is 0.
4234 Format: <parport#> 3575 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3576 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3577 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3578 Format: <mode>
4238 3579
4239 parport= [HW,PPT] Specify para 3580 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3581 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3582 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3583 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3584 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3585 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3586 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3587 should be numbers, or 'auto' (for using detected
4247 settings on that part 3588 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3589 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3590 Parallel ports are assigned in the order they
4250 are specified on the 3591 are specified on the command line, starting
4251 with parport0. 3592 with parport0.
4252 3593
4253 parport_init_mode= [HW,PPT] 3594 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3595 Configure VIA parallel port to operate in
4255 a specific mode. This 3596 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3597 computer where firmware has no options for setting
4257 up parallel port mode 3598 up parallel port mode and sets it to spp.
4258 Currently this functi 3599 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3600 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3601
4261 pata_legacy.all= [HW,LIBATA] !! 3602 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 3603 Halt all CPUs after the first oops has been printed for
4353 the specified number 3604 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3605 your oopses keep scrolling off the screen.
4355 3606
4356 pcbit= [HW,ISDN] 3607 pcbit= [HW,ISDN]
4357 3608
4358 pci=option[,option...] [PCI,EARLY] v !! 3609 pcd. [PARIDE]
>> 3610 See header of drivers/block/paride/pcd.c.
>> 3611 See also Documentation/admin-guide/blockdev/paride.rst.
>> 3612
>> 3613 pci=option[,option...] [PCI] various PCI subsystem options.
4359 3614
4360 Some options 3615 Some options herein operate on a specific device
4361 or a set of d 3616 or a set of devices (<pci_dev>). These are
4362 specified in 3617 specified in one of the following formats:
4363 3618
4364 [<domain>:]<b 3619 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 3620 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 3621
4367 Note: the fir 3622 Note: the first format specifies a PCI
4368 bus/device/fu 3623 bus/device/function address which may change
4369 if new hardwa 3624 if new hardware is inserted, if motherboard
4370 firmware chan 3625 firmware changes, or due to changes caused
4371 by other kern 3626 by other kernel parameters. If the
4372 domain is lef 3627 domain is left unspecified, it is
4373 taken to be z 3628 taken to be zero. Optionally, a path
4374 to a device t 3629 to a device through multiple device/function
4375 addresses can 3630 addresses can be specified after the base
4376 address (this 3631 address (this is more robust against
4377 renumbering i 3632 renumbering issues). The second format
4378 selects devic 3633 selects devices using IDs from the
4379 configuration 3634 configuration space which may match multiple
4380 devices in th 3635 devices in the system.
4381 3636
4382 earlydump dump PCI conf 3637 earlydump dump PCI config space before the kernel
4383 changes anyth 3638 changes anything
4384 off [X86] don't p 3639 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3640 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3641 the hardware directly. Use this if your machine
4387 has a non-sta 3642 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3643 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3644 hardware access methods are allowed. Use this
4390 if you experi 3645 if you experience crashes upon bootup and you
4391 suspect they 3646 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3647 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3648 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3649 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3650 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3651 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3652 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3653 bus number. The config space is then accessed
4399 through ports 3654 through ports 0xC000-0xCFFF).
4400 See http://wi 3655 See http://wiki.osdev.org/PCI for more info
4401 on the config 3656 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3657 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3658 enabled, this kernel boot option can be used to
4404 disable the u 3659 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3660 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3661 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3662 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3663 Configuration
4409 check_enable_amd_mmconf [X86] 3664 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3665 properly configured MMIO access to PCI
4411 config space 3666 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3667 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3668 enabled, this kernel boot option can be used to
4414 disable the u 3669 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3670 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3671 Safety option to keep boot IRQs enabled. This
4417 should never 3672 should never be necessary.
4418 ioapicreroute [APIC] Enable 3673 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3674 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3675 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3676 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3677 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3678 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3679 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3680 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3681 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3682 routing table. These calls are known to be buggy
4428 on several ma 3683 on several machines and they hang the machine
4429 when used, bu 3684 when used, but on other computers it's the only
4430 way to get th 3685 way to get the interrupt routing table. Try
4431 this option i 3686 this option if the kernel is unable to allocate
4432 IRQs or disco 3687 IRQs or discover secondary PCI buses on your
4433 motherboard. 3688 motherboard.
4434 rom [X86] Assign 3689 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3690 Use with caution as certain devices share
4436 address decod 3691 address decoders between ROMs and other
4437 resources. 3692 resources.
4438 norom [X86] Do not 3693 norom [X86] Do not assign address space to
4439 expansion ROM 3694 expansion ROMs that do not already have
4440 BIOS assigned 3695 BIOS assigned address ranges.
4441 nobar [X86] Do not 3696 nobar [X86] Do not assign address space to the
4442 BARs that wer 3697 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3698 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3699 assigned automatically to PCI devices. You can
4445 make the kern 3700 make the kernel exclude IRQs of your ISA cards
4446 this way. 3701 this way.
4447 pirqaddr=0xAAAAA [X86] 3702 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3703 of the PIRQ table (normally generated
4449 by the BIOS) 3704 by the BIOS) if it is outside the
4450 F0000h-100000 3705 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3706 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3707 useful if the kernel is unable to find your
4453 secondary bus 3708 secondary buses and you want to tell it
4454 explicitly wh 3709 explicitly which ones they are.
4455 assign-busses [X86] Always 3710 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3711 numbers ourselves, overriding
4457 whatever the 3712 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3713 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3714 in the BIOS $PIR table. This is needed on
4460 some systems 3715 some systems with broken BIOSes, notably
4461 some HP Pavil 3716 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3717 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3718 IRQ routing is enabled.
4464 noacpi [X86] Do not 3719 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3720 or for PCI scanning.
4466 use_crs [X86] Use PCI 3721 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3722 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3723 is enabled by default. If you need to use this,
4469 please report 3724 please report a bug.
4470 nocrs [X86] Ignore 3725 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 3726 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 3727 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3728 This is normally done in pci_enable_device(),
4483 so this optio 3729 so this option is a temporary workaround
4484 for broken dr 3730 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3731 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3732 handle more pci cards
4487 noearly [X86] Don't d 3733 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3734 This might help on some broken boards which
4489 machine check 3735 machine check when some devices' config space
4490 is read. But 3736 is read. But various workarounds are disabled
4491 and some IOMM 3737 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3738 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3739 This sorting is done to get a device
4494 order compati 3740 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3741 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3742 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3743 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3744 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3745 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3746 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3747 based on its parent bus. Also set MRRS (Max
4502 Read Request 3748 Read Request Size) to the largest supported
4503 value (no lar 3749 value (no larger than the MPS that the device
4504 or bus can su 3750 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3751 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3752 every device is guaranteed to support. This
4507 configuration 3753 configuration allows peer-to-peer DMA between
4508 any pair of d 3754 any pair of devices, possibly at the cost of
4509 reduced perfo 3755 reduced performance. This also guarantees
4510 that hot-adde 3756 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3757 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3758 reserved for the CardBus bridge's IO window.
4513 The default v 3759 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3760 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3761 reserved for the CardBus bridge's memory
4516 window. The d 3762 window. The default value is 64 megabytes.
4517 resource_alignment= 3763 resource_alignment=
4518 Format: 3764 Format:
4519 [<order of ali 3765 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 3766 Specifies alignment and device to reassign
4521 aligned memor 3767 aligned memory resources. How to
4522 specify the d 3768 specify the device is described above.
4523 If <order of 3769 If <order of align> is not specified,
4524 PAGE_SIZE is 3770 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 3771 A PCI-PCI bridge can be specified if resource
4526 windows need 3772 windows need to be expanded.
4527 To specify th 3773 To specify the alignment for several
4528 instances of 3774 instances of a device, the PCI vendor,
4529 device, subve 3775 device, subvendor, and subdevice may be
4530 specified, e. 3776 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 3777 for 4096-byte alignment.
4532 ecrc= Enable/disabl 3778 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3779 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3780 bios: Use BIOS/firmware settings. This is the
4537 the default. 3781 the default.
4538 off: Turn ECR 3782 off: Turn ECRC off
4539 on: Turn ECRC 3783 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3784 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3785 reserved for hotplug bridge's IO window.
4542 Default size 3786 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 3787 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 3788 reserved for hotplug bridge's MMIO window.
4545 Default size 3789 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 3790 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 3791 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 3792 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 3793 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 3794 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 3795 MMIO_PREF window.
4552 Default size 3796 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3797 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3798 reserved for buses below a hotplug bridge.
4555 Default is 1. 3799 Default is 1.
4556 realloc= Enable/disabl 3800 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3801 if allocations done by BIOS are too small to
4558 accommodate r 3802 accommodate resources required by all child
4559 devices. 3803 devices.
4560 off: Turn rea 3804 off: Turn realloc off
4561 on: Turn real 3805 on: Turn realloc on
4562 realloc same as reall 3806 realloc same as realloc=on
4563 noari do not use PC 3807 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 3808 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 3809 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 3810 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 3811 only look for one device below a PCIe downstream
4568 port. 3812 port.
4569 big_root_window Try to add a 3813 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 3814 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 3815 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 3816 Adding the window is slightly risky (it may
4573 conflict with 3817 conflict with unreported devices), so this
4574 taints the ke 3818 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 3819 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 3820 Specify one or more PCI devices (in the format
4577 specified abo 3821 specified above) separated by semicolons.
4578 Each device s 3822 Each device specified will have the PCI ACS
4579 redirect capa 3823 redirect capabilities forced off which will
4580 allow P2P tra 3824 allow P2P traffic between devices through
4581 bridges witho 3825 bridges without forcing it upstream. Note:
4582 this removes 3826 this removes isolation between devices and
4583 may put more 3827 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 3828 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 3829 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 3830 norid [S390] ignore the RID field and force use of
4619 one PCI domai 3831 one PCI domain per PCI function
4620 3832
4621 pcie_aspm= [PCIE] Forcibly enabl !! 3833 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 3834 Management.
4623 off Don't touch ASPM conf !! 3835 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 3836 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 3837 WARNING: Forcing ASPM on may cause system lockups.
4627 3838
4628 pcie_ports= [PCIE] PCIe port serv 3839 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 3840 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 3841 even if the platform doesn't give the OS permission to
4631 use them. This may c 3842 use them. This may cause conflicts if the platform
4632 also tries to use the 3843 also tries to use these services.
4633 dpc-native Use native PC 3844 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 3845 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 3846 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 3847 hotplug).
4637 3848
4638 pcie_port_pm= [PCIE] PCIe port powe 3849 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 3850 off Disable power management of all PCIe ports
4640 force Forcibly enable power 3851 force Forcibly enable power management of all PCIe ports
4641 3852
4642 pcie_pme= [PCIE,PM] Native PCIe 3853 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 3854 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 3855 all PCIe root ports use INTx for all services).
4645 3856
4646 pcmv= [HW,PCMCIA] BadgePAD 3857 pcmv= [HW,PCMCIA] BadgePAD 4
4647 3858
4648 pd_ignore_unused 3859 pd_ignore_unused
4649 [PM] 3860 [PM]
4650 Keep all power-domain 3861 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 3862 even if no driver has claimed them. This is useful
4652 for debug and develop 3863 for debug and development, but should not be
4653 needed on a platform 3864 needed on a platform with proper driver support.
4654 3865
>> 3866 pd. [PARIDE]
>> 3867 See Documentation/admin-guide/blockdev/paride.rst.
>> 3868
4655 pdcchassis= [PARISC,HW] Disable/E 3869 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 3870 boot time.
4657 Format: { 0 | 1 } 3871 Format: { 0 | 1 }
4658 See arch/parisc/kerne 3872 See arch/parisc/kernel/pdc_chassis.c
4659 3873
4660 percpu_alloc= [MM,EARLY] !! 3874 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 3875 Currently supported values are "embed" and "page".
4663 Archs may support sub 3876 Archs may support subset or none of the selections.
4664 See comments in mm/pe 3877 See comments in mm/percpu.c for details on each
4665 allocator. This para 3878 allocator. This parameter is primarily for debugging
4666 and performance compa 3879 and performance comparison.
4667 3880
>> 3881 pf. [PARIDE]
>> 3882 See Documentation/admin-guide/blockdev/paride.rst.
>> 3883
>> 3884 pg. [PARIDE]
>> 3885 See Documentation/admin-guide/blockdev/paride.rst.
>> 3886
4668 pirq= [SMP,APIC] Manual mp- 3887 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 3888 See Documentation/x86/i386/IO-APIC.rst.
4670 3889
4671 plip= [PPT,NET] Parallel po 3890 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 3891 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 3892 See also Documentation/admin-guide/parport.rst.
4674 3893
4675 pmtmr= [X86] Manual setup of 3894 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 3895 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 3896 e.g. pmtmr=0x508
4678 3897
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] 3898 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 3899 Enable suspend/resume debug messages during boot up.
4689 3900
4690 pnp.debug=1 [PNP] 3901 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 3902 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 3903 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 3904 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 3905 current resource usage; turning this on also shows
4695 possible settings and 3906 possible settings and some assignment information.
4696 3907
4697 pnpacpi= [ACPI] 3908 pnpacpi= [ACPI]
4698 { off } 3909 { off }
4699 3910
4700 pnpbios= [ISAPNP] 3911 pnpbios= [ISAPNP]
4701 { on | off | curr | r 3912 { on | off | curr | res | no-curr | no-res }
4702 3913
4703 pnp_reserve_irq= 3914 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 3915 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 3916
4706 pnp_reserve_dma= 3917 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 3918 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 3919
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 3920 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 3921 Ranges are in pairs (I/O port base and size).
4711 3922
4712 pnp_reserve_mem= 3923 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 3924 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 3925 autoconfiguration.
4715 Ranges are in pairs ( 3926 Ranges are in pairs (memory base and size).
4716 3927
4717 ports= [IP_VS_FTP] IPVS ftp 3928 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 3929 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 3930 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 3931 may be specified.
4721 Format: <port>,<port> 3932 Format: <port>,<port>....
4722 3933
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 3934 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 3935 It specifically disables cpuidle and sets the
4730 platform machine desc 3936 platform machine description specific power_save
4731 function to NULL. On 3937 function to NULL. On Idle the CPU just reduces
4732 execution priority. 3938 execution priority.
4733 3939
4734 ppc_strict_facility_enable 3940 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 3941 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 3942 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 3943 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 3944 There is some performance impact when enabling this.
4739 3945
4740 ppc_tm= [PPC,EARLY] !! 3946 ppc_tm= [PPC]
4741 Format: {"off"} 3947 Format: {"off"}
4742 Disable Hardware Tran 3948 Disable Hardware Transactional Memory
4743 3949
4744 preempt= [KNL] 3950 preempt= [KNL]
4745 Select preemption mod 3951 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 3952 none - Limited to cond_resched() calls
4747 voluntary - Limited t 3953 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 3954 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 3955 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 3956
4753 print-fatal-signals= 3957 print-fatal-signals=
4754 [KNL] debug: print fa 3958 [KNL] debug: print fatal signals
4755 3959
4756 If enabled, warn abou 3960 If enabled, warn about various signal handling
4757 related application a 3961 related application anomalies: too many signals,
4758 too many POSIX.1 time 3962 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 3963 coredump - etc.
4760 3964
4761 If you hit the warnin 3965 If you hit the warning due to signal overflow,
4762 you might want to try 3966 you might want to try "ulimit -i unlimited".
4763 3967
4764 default: off. 3968 default: off.
4765 3969
4766 printk.always_kmsg_dump= 3970 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 3971 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 3972 panics
4769 Format: <bool> (1/Y/ 3973 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 3974 default: disabled
4771 3975
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} 3976 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 3977 Control writing to /dev/kmsg.
4783 on - unlimited loggin 3978 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 3979 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 3980 ratelimit - ratelimit the logging
4786 Default: ratelimit 3981 Default: ratelimit
4787 3982
4788 printk.time= Show timing data pref 3983 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 3984 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 3985
4791 proc_mem.force_override= [KNL] <<
4792 Format: {always | ptr <<
4793 Traditionally /proc/p <<
4794 overridden without re <<
4795 restrict that. Can be <<
4796 - 'always': tradition <<
4797 - 'ptrace': only allo <<
4798 - 'never': never all <<
4799 If not specified, def <<
4800 <<
4801 processor.max_cstate= [HW,ACPI] 3986 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 3987 Limit processor to maximum C-state
4803 max_cstate=9 override 3988 max_cstate=9 overrides any DMI blacklist limit.
4804 3989
4805 processor.nocst [HW,ACPI] 3990 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 3991 Ignore the _CST method to determine C-states,
4807 instead using the leg 3992 instead using the legacy FADT method
4808 3993
4809 profile= [KNL] Enable kernel p 3994 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 3995 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 3996 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 3997 [defaults to kernel profiling]
4813 Param: "schedule" - p 3998 Param: "schedule" - profile schedule points.
>> 3999 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4000 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4001 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4002 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4003 statistical time based profiling.
4817 4004
4818 prompt_ramdisk= [RAM] [Deprecated] 4005 prompt_ramdisk= [RAM] [Deprecated]
4819 4006
4820 prot_virt= [S390] enable hosting 4007 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4008 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4009 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4010 Format: <bool>
4826 4011
4827 psi= [KNL] Enable or disab 4012 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4013 tracking.
4829 Format: <bool> 4014 Format: <bool>
4830 4015
4831 psmouse.proto= [HW,MOUSE] Highest PS 4016 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4017 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4018 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4019 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4020 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4021 Try to reset the device after so many bad packets
4837 (0 = never). 4022 (0 = never).
4838 psmouse.resolution= 4023 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4024 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4025 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4026 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4027 0 = disabled, 1 = enabled (default).
4843 4028
4844 pstore.backend= Specify the name of t 4029 pstore.backend= Specify the name of the pstore backend to use
4845 4030
>> 4031 pt. [PARIDE]
>> 4032 See Documentation/admin-guide/blockdev/paride.rst.
>> 4033
4846 pti= [X86-64] Control Page 4034 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4035 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4036 removes hardening, but improves performance of
4849 system calls and inte 4037 system calls and interrupts.
4850 4038
4851 on - unconditionall 4039 on - unconditionally enable
4852 off - unconditionall 4040 off - unconditionally disable
4853 auto - kernel detects 4041 auto - kernel detects whether your CPU model is
4854 vulnerable to 4042 vulnerable to issues that PTI mitigates
4855 4043
4856 Not specifying this o 4044 Not specifying this option is equivalent to pti=auto.
4857 4045
>> 4046 nopti [X86-64]
>> 4047 Equivalent to pti=off
>> 4048
4858 pty.legacy_count= 4049 pty.legacy_count=
4859 [KNL] Number of legac 4050 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4051 default number.
4861 4052
4862 quiet [KNL,EARLY] Disable m !! 4053 quiet [KNL] Disable most log messages
4863 4054
4864 r128= [HW,DRM] 4055 r128= [HW,DRM]
4865 4056
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4057 raid= [HW,RAID]
4871 See Documentation/adm 4058 See Documentation/admin-guide/md.rst.
4872 4059
4873 ramdisk_size= [RAM] Sizes of RAM di 4060 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4061 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4062
4876 ramdisk_start= [RAM] RAM disk image 4063 ramdisk_start= [RAM] RAM disk image start address
4877 4064
4878 random.trust_cpu=off !! 4065 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 4066 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 4067 CPU's random number generator (if available) to
4881 initialize the kernel !! 4068 fully seed the kernel's CRNG. Default is controlled
4882 !! 4069 by CONFIG_RANDOM_TRUST_CPU.
4883 random.trust_bootloader=off <<
4884 [KNL,EARLY] Disable t <<
4885 passed by the bootloa <<
4886 initialize the kernel <<
4887 <<
4888 randomize_kstack_offset= <<
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 4070
4899 ras=option[,option,...] [KNL] RAS-spe 4071 ras=option[,option,...] [KNL] RAS-specific options
4900 4072
4901 cec_disable [X86] 4073 cec_disable [X86]
4902 Disable the C 4074 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4075 see CONFIG_RAS_CEC help text.
4904 4076
4905 rcu_nocbs[=cpu-list] !! 4077 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 4078 The argument is a cpu list, as described above,
4907 as described above. !! 4079 except that the string "all" can be used to
4908 !! 4080 specify every CPU on the system.
4909 In kernels built with !! 4081
4910 enable the no-callbac !! 4082 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4911 such CPUs' callbacks !! 4083 the specified list of CPUs to be no-callback CPUs.
4912 softirq context. Inv !! 4084 Invocation of these CPUs' RCU callbacks will be
4913 callbacks will instea !! 4085 offloaded to "rcuox/N" kthreads created for that
4914 kthreads created for !! 4086 purpose, where "x" is "p" for RCU-preempt, and
4915 "p" for RCU-preempt, !! 4087 "s" for RCU-sched, and "N" is the CPU number.
4916 for the kthreads that !! 4088 This reduces OS jitter on the offloaded CPUs,
4917 "N" is the CPU number !! 4089 which can be useful for HPC and real-time
4918 the offloaded CPUs, w !! 4090 workloads. It can also improve energy efficiency
4919 and real-time workloa !! 4091 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 4092
4933 rcu_nocb_poll [KNL] 4093 rcu_nocb_poll [KNL]
4934 Rather than requiring 4094 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4095 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4096 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4097 make these kthreads poll for callbacks.
4938 This improves the rea 4098 This improves the real-time response for the
4939 offloaded CPUs by rel 4099 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4100 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4101 energy efficiency by requiring that the kthreads
4942 periodically wake up 4102 periodically wake up to do the polling.
4943 4103
4944 rcutree.blimit= [KNL] 4104 rcutree.blimit= [KNL]
4945 Set maximum number of 4105 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4106 process in one batch.
4947 4107
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] 4108 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4109 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4110 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4111 purposes, to verify correct tree setup.
4959 4112
4960 rcutree.gp_cleanup_delay= [KNL] 4113 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4114 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4115 RCU grace-period cleanup.
4963 4116
4964 rcutree.gp_init_delay= [KNL] 4117 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4118 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4119 RCU grace-period initialization.
4967 4120
4968 rcutree.gp_preinit_delay= [KNL] 4121 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4122 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4123 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4124 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4125 the rcu_node combining tree.
4973 4126
>> 4127 rcutree.use_softirq= [KNL]
>> 4128 If set to zero, move all RCU_SOFTIRQ processing to
>> 4129 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4130 value, meaning that RCU_SOFTIRQ is used by default.
>> 4131 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4132
>> 4133 But note that CONFIG_PREEMPT_RT=y kernels disable
>> 4134 this kernel boot parameter, forcibly setting it
>> 4135 to zero.
>> 4136
>> 4137 rcutree.rcu_fanout_exact= [KNL]
>> 4138 Disable autobalancing of the rcu_node combining
>> 4139 tree. This is used by rcutorture, and might
>> 4140 possibly be useful for architectures having high
>> 4141 cache-to-cache transfer latencies.
>> 4142
>> 4143 rcutree.rcu_fanout_leaf= [KNL]
>> 4144 Change the number of CPUs assigned to each
>> 4145 leaf rcu_node structure. Useful for very
>> 4146 large systems, which will choose the value 64,
>> 4147 and for NUMA systems with large remote-access
>> 4148 latencies, which will choose a value aligned
>> 4149 with the appropriate hardware boundaries.
>> 4150
>> 4151 rcutree.rcu_min_cached_objs= [KNL]
>> 4152 Minimum number of objects which are cached and
>> 4153 maintained per one CPU. Object size is equal
>> 4154 to PAGE_SIZE. The cache allows to reduce the
>> 4155 pressure to page allocator, also it makes the
>> 4156 whole algorithm to behave better in low memory
>> 4157 condition.
>> 4158
4974 rcutree.jiffies_till_first_fqs= [KNL] 4159 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4160 Set delay from grace-period initialization to
4976 first attempt to forc 4161 first attempt to force quiescent states.
4977 Units are jiffies, mi 4162 Units are jiffies, minimum value is zero,
4978 and maximum value is 4163 and maximum value is HZ.
4979 4164
4980 rcutree.jiffies_till_next_fqs= [KNL] 4165 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4166 Set delay between subsequent attempts to force
4982 quiescent states. Un 4167 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4168 value is one, and maximum value is HZ.
4984 4169
4985 rcutree.jiffies_till_sched_qs= [KNL] 4170 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4171 Set required age in jiffies for a
4987 given grace period be 4172 given grace period before RCU starts
4988 soliciting quiescent- 4173 soliciting quiescent-state help from
4989 rcu_note_context_swit 4174 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4175 If not specified, the kernel will calculate
4991 a value based on the 4176 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4177 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4178 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4179 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4180 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4181 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4182 overwritten.
4998 4183
4999 rcutree.kthread_prio= [KNL,BOOT] 4184 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4185 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4186 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4187 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4188 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4189 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4190 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4191 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4192 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4193 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 4194
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 4195 rcutree.rcu_nocb_gp_stride= [KNL]
5013 On callback-offloaded !! 4196 Set the number of NOCB callback kthreads in
5014 RCU reduces the lock !! 4197 each group, which defaults to the square root
5015 otherwise be caused b !! 4198 of the number of CPUs. Larger numbers reduce
5016 use of the ->nocb_byp !! 4199 the wakeup overhead on the global grace-period
5017 common non-flooded ca !! 4200 kthread, but increases that same overhead on
5018 the main ->cblist in !! 4201 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 4202
5033 rcutree.qhimark= [KNL] 4203 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4204 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4205 batch limiting is disabled.
5036 4206
5037 rcutree.qlowmark= [KNL] 4207 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4208 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4209 batch limiting is re-enabled.
5040 4210
5041 rcutree.qovld= [KNL] 4211 rcutree.qovld= [KNL]
5042 Set threshold of queu 4212 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4213 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4214 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4215 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4216 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4217 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4218 disable more aggressive help enlistment.
5049 4219
5050 rcutree.rcu_delay_page_cache_fill_mse !! 4220 rcutree.rcu_idle_gp_delay= [KNL]
5051 Set the page-cache re !! 4221 Set wakeup interval for idle CPUs that have
5052 in response to low-me !! 4222 RCU callbacks (RCU_FAST_NO_HZ=y).
5053 of permitted values i <<
5054 <<
5055 rcutree.rcu_divisor= [KNL] <<
5056 Set the shift-right c <<
5057 the callback-invocati <<
5058 the number of callbac <<
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 4223
5100 rcutree.rcu_kick_kthreads= [KNL] 4224 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4225 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4226 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4227 it should at force-quiescent-state time.
5104 This wake_up() will b 4228 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4229 WARN_ONCE() splat and an ftrace_dump().
5106 4230
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] 4231 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4232 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4233 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4234 in microseconds. This defaults to zero.
5118 Larger delays increas 4235 Larger delays increase the probability of
5119 catching RCU pointer 4236 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4237 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4238 rcu_read_unlock() has completed.
5122 4239
5123 rcutree.sysrq_rcu= [KNL] 4240 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4241 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4242 rcu_node tree with an eye towards determining
5126 why a new grace perio 4243 why a new grace period has not yet started.
5127 4244
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] 4245 rcuscale.gp_async= [KNL]
5158 Measure performance o 4246 Measure performance of asynchronous
5159 grace-period primitiv 4247 grace-period primitives such as call_rcu().
5160 4248
5161 rcuscale.gp_async_max= [KNL] 4249 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4250 Specify the maximum number of outstanding
5163 callbacks per writer 4251 callbacks per writer thread. When a writer
5164 thread exceeds this l 4252 thread exceeds this limit, it invokes the
5165 corresponding flavor 4253 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4254 previously posted callbacks to drain.
5167 4255
5168 rcuscale.gp_exp= [KNL] 4256 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4257 Measure performance of expedited synchronous
5170 grace-period primitiv 4258 grace-period primitives.
5171 4259
5172 rcuscale.holdoff= [KNL] 4260 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4261 Set test-start holdoff period. The purpose of
5174 this parameter is to 4262 this parameter is to delay the start of the
5175 test until boot compl 4263 test until boot completes in order to avoid
5176 interference. 4264 interference.
5177 4265
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] 4266 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4267 Set to measure performance of kfree_rcu() flooding.
5189 4268
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] 4269 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4270 The number of threads running loops of kfree_rcu().
5204 4271
5205 rcuscale.kfree_alloc_num= [KNL] 4272 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4273 Number of allocations and frees done in an iteration.
5207 4274
5208 rcuscale.kfree_loops= [KNL] 4275 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4276 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4277 of allocations and frees.
5211 4278
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] 4279 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4280 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4281 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4282 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4283 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4284 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4285 A value of "n" less than or equal to -N selects
5225 a single reader. 4286 a single reader.
5226 4287
5227 rcuscale.nwriters= [KNL] 4288 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4289 Set number of RCU writers. The values operate
5229 the same as for rcusc 4290 the same as for rcuscale.nreaders.
5230 N, where N is the num 4291 N, where N is the number of CPUs
5231 4292
5232 rcuscale.scale_type= [KNL] !! 4293 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4294 Specify the RCU implementation to test.
5234 4295
5235 rcuscale.shutdown= [KNL] 4296 rcuscale.shutdown= [KNL]
5236 Shut the system down 4297 Shut the system down after performance tests
5237 complete. This is us 4298 complete. This is useful for hands-off automated
5238 testing. 4299 testing.
5239 4300
5240 rcuscale.verbose= [KNL] 4301 rcuscale.verbose= [KNL]
5241 Enable additional pri 4302 Enable additional printk() statements.
5242 4303
5243 rcuscale.writer_holdoff= [KNL] 4304 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4305 Write-side holdoff between grace periods,
5245 in microseconds. The 4306 in microseconds. The default of zero says
5246 no holdoff. 4307 no holdoff.
5247 4308
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] 4309 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4310 Set duration of force_quiescent_state bursts
5255 in microseconds. 4311 in microseconds.
5256 4312
5257 rcutorture.fqs_holdoff= [KNL] 4313 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4314 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4315 in microseconds.
5260 4316
5261 rcutorture.fqs_stutter= [KNL] 4317 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4318 Set wait time between force_quiescent_state bursts
5263 in seconds. 4319 in seconds.
5264 4320
5265 rcutorture.fwd_progress= [KNL] 4321 rcutorture.fwd_progress= [KNL]
5266 Specifies the number !! 4322 Enable RCU grace-period forward-progress testing
5267 for RCU grace-period <<
5268 for the types of RCU 4323 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 4324
5273 rcutorture.fwd_progress_div= [KNL] 4325 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4326 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4327 period to do tight-loop forward-progress testing.
5276 4328
5277 rcutorture.fwd_progress_holdoff= [KNL 4329 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4330 Number of seconds to wait between successive
5279 forward-progress test 4331 forward-progress tests.
5280 4332
5281 rcutorture.fwd_progress_need_resched= 4333 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4334 Enclose cond_resched() calls within checks for
5283 need_resched() during 4335 need_resched() during tight-loop forward-progress
5284 testing. 4336 testing.
5285 4337
5286 rcutorture.gp_cond= [KNL] 4338 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4339 Use conditional/asynchronous update-side
5288 primitives, if availa 4340 primitives, if available.
5289 4341
5290 rcutorture.gp_exp= [KNL] 4342 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4343 Use expedited update-side primitives, if available.
5292 4344
5293 rcutorture.gp_normal= [KNL] 4345 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4346 Use normal (non-expedited) asynchronous
5295 update-side primitive 4347 update-side primitives, if available.
5296 4348
5297 rcutorture.gp_sync= [KNL] 4349 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4350 Use normal (non-expedited) synchronous
5299 update-side primitive 4351 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4352 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4353 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4354 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4355 they are all non-zero.
5304 4356
5305 rcutorture.irqreader= [KNL] 4357 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4358 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4359 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4360 flavors take kindly to this sort of thing.
5309 4361
5310 rcutorture.leakpointer= [KNL] 4362 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4363 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4364 This can of course result in splats, and is
5313 intended to test the 4365 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4366 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4367 such leaks.
5316 4368
5317 rcutorture.n_barrier_cbs= [KNL] 4369 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4370 Set callbacks/threads for rcu_barrier() testing.
5319 4371
5320 rcutorture.nfakewriters= [KNL] 4372 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4373 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4374 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4375 test, hence the "fake".
5324 4376
5325 rcutorture.nocbs_nthreads= [KNL] 4377 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 4378 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 4379 Zero (the default) disables toggling.
5328 4380
5329 rcutorture.nocbs_toggle= [KNL] 4381 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 4382 Set the delay in milliseconds between successive
5331 callback-offload togg 4383 callback-offload toggling attempts.
5332 4384
5333 rcutorture.nreaders= [KNL] 4385 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4386 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4387 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4388 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 4389 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 4390 (the number of CPUs), -3 selects N+1, and so on.
5339 4391
5340 rcutorture.object_debug= [KNL] 4392 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 4393 Enable debug-object double-call_rcu() testing.
5342 4394
5343 rcutorture.onoff_holdoff= [KNL] 4395 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 4396 Set time (s) after boot for CPU-hotplug testing.
5345 4397
5346 rcutorture.onoff_interval= [KNL] 4398 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 4399 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 4400 or zero to disable CPU-hotplug testing.
5349 4401
5350 rcutorture.read_exit= [KNL] 4402 rcutorture.read_exit= [KNL]
5351 Set the number of rea 4403 Set the number of read-then-exit kthreads used
5352 to test the interacti 4404 to test the interaction of RCU updaters and
5353 task-exit processing. 4405 task-exit processing.
5354 4406
5355 rcutorture.read_exit_burst= [KNL] 4407 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 4408 The number of times in a given read-then-exit
5357 episode that a set of 4409 episode that a set of read-then-exit kthreads
5358 is spawned. 4410 is spawned.
5359 4411
5360 rcutorture.read_exit_delay= [KNL] 4412 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 4413 The delay, in seconds, between successive
5362 read-then-exit testin 4414 read-then-exit testing episodes.
5363 4415
5364 rcutorture.shuffle_interval= [KNL] 4416 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 4417 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 4418 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 4419 during the rcutorture test.
5368 4420
5369 rcutorture.shutdown_secs= [KNL] 4421 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 4422 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 4423 is useful for hands-off automated testing.
5372 4424
5373 rcutorture.stall_cpu= [KNL] 4425 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 4426 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 4427 warnings, zero to disable.
5376 4428
5377 rcutorture.stall_cpu_block= [KNL] 4429 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 4430 Sleep while stalling if set. This will result
5379 in warnings from pree !! 4431 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 4432 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 4433
5391 rcutorture.stall_cpu_holdoff= [KNL] 4434 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 4435 Time to wait (s) after boot before inducing stall.
5393 4436
5394 rcutorture.stall_cpu_irqsoff= [KNL] 4437 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 4438 Disable interrupts while stalling if set.
5396 4439
5397 rcutorture.stall_gp_kthread= [KNL] 4440 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 4441 Duration (s) of forced sleep within RCU
5399 grace-period kthread 4442 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 4443 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 4444 and stall_gp_kthread are specified, the
5402 kthread is starved fi 4445 kthread is starved first, then the CPU.
5403 4446
5404 rcutorture.stat_interval= [KNL] 4447 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 4448 Time (s) between statistics printk()s.
5406 4449
5407 rcutorture.stutter= [KNL] 4450 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 4451 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 4452 five seconds causes the test to run for five seconds,
5410 wait for five seconds 4453 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 4454 ability to transition abruptly to and from idle.
5412 4455
5413 rcutorture.test_boost= [KNL] 4456 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 4457 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 4458 "Maybe" means test if the RCU implementation
5416 under test support RC 4459 under test support RCU priority boosting.
5417 4460
5418 rcutorture.test_boost_duration= [KNL] 4461 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 4462 Duration (s) of each individual boost test.
5420 4463
5421 rcutorture.test_boost_interval= [KNL] 4464 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 4465 Interval (s) between each boost test.
5423 4466
5424 rcutorture.test_no_idle_hz= [KNL] 4467 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 4468 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 4469 rcutorture.shuffle_interval parameter.
5427 4470
5428 rcutorture.torture_type= [KNL] 4471 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 4472 Specify the RCU implementation to test.
5430 4473
5431 rcutorture.verbose= [KNL] 4474 rcutorture.verbose= [KNL]
5432 Enable additional pri 4475 Enable additional printk() statements.
5433 4476
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 4477 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 4478 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 4479 stall warning.
5437 4480
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 4481 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 4482 Suppress RCU CPU stall warning messages.
5446 4483
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 4484 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 4485 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 4486 rcutorture writer stall warnings that occur
5450 during early boot, th 4487 during early boot, that is, during the time
5451 before the init task 4488 before the init task is spawned.
5452 4489
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 4490 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 4491 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 4492
5479 rcupdate.rcu_expedited= [KNL] 4493 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 4494 Use expedited grace-period primitives, for
5481 example, synchronize_ 4495 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 4496 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 4497 but can increase CPU utilization, degrade
5484 real-time latency, an 4498 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 4499 No effect on CONFIG_TINY_RCU kernels.
5486 4500
5487 rcupdate.rcu_normal= [KNL] 4501 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 4502 Use only normal grace-period primitives,
5489 for example, synchron 4503 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 4504 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 4505 real-time latency, CPU utilization, and
5492 energy efficiency, bu 4506 energy efficiency, but can expose users to
5493 increased grace-perio 4507 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 4508 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 4509 CONFIG_TINY_RCU kernels.
5496 4510
5497 rcupdate.rcu_normal_after_boot= [KNL] 4511 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 4512 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 4513 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 4514 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 4515 on CONFIG_TINY_RCU kernels.
5502 4516
5503 But note that CONFIG_ 4517 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 4518 this kernel boot parameter, forcibly setting
5505 it to the value one, 4519 it to the value one, that is, converting any
5506 post-boot attempt at 4520 post-boot attempt at an expedited RCU grace
5507 period to instead use 4521 period to instead use normal non-expedited
5508 grace-period processi 4522 grace-period processing.
5509 4523
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] 4524 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 4525 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 4526 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 4527 of a given grace period. Setting a large
5537 number avoids disturb 4528 number avoids disturbing real-time workloads,
5538 but lengthens grace p 4529 but lengthens grace periods.
5539 4530
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 4531 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 4532 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 4533 messages. Disable with a value less than or equal
5572 than or equal to zero !! 4534 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 4535
5599 rcupdate.rcu_self_test= [KNL] 4536 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 4537 Run the RCU early boot self tests
5601 4538
5602 rdinit= [KNL] 4539 rdinit= [KNL]
5603 Format: <full_path> 4540 Format: <full_path>
5604 Run specified binary 4541 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 4542 used for early userspace startup. See initrd.
5606 4543
5607 rdrand= [X86,EARLY] !! 4544 rdrand= [X86]
5608 force - Override the 4545 force - Override the decision by the kernel to hide the
5609 advertisement 4546 advertisement of RDRAND support (this affects
5610 certain AMD p 4547 certain AMD processors because of buggy BIOS
5611 support, spec 4548 support, specifically around the suspend/resume
5612 path). 4549 path).
5613 4550
5614 rdt= [HW,X86,RDT] 4551 rdt= [HW,X86,RDT]
5615 Turn on/off individua 4552 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 4553 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 4554 mba.
5618 E.g. to turn on cmt a 4555 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 4556 rdt=cmt,!mba
5620 4557
5621 reboot= [KNL] 4558 reboot= [KNL]
5622 Format (x86 or x86_64 4559 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 4560 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 4561 [[,]s[mp]#### \
5625 [[,]b[ios] | 4562 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 4563 [[,]f[orce]
5627 Where reboot_mode is 4564 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 4565 (prefix with 'panic_' to set mode for panic
5629 reboo 4566 reboot only),
5630 reboot_type is 4567 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 4568 reboot_force is either force or not specified,
5632 reboot_cpu is s 4569 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 4570 to be used for rebooting.
5634 4571
5635 refscale.holdoff= [KNL] 4572 refscale.holdoff= [KNL]
5636 Set test-start holdof 4573 Set test-start holdoff period. The purpose of
5637 this parameter is to 4574 this parameter is to delay the start of the
5638 test until boot compl 4575 test until boot completes in order to avoid
5639 interference. 4576 interference.
5640 4577
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] 4578 refscale.loops= [KNL]
5648 Set the number of loo 4579 Set the number of loops over the synchronization
5649 primitive under test. 4580 primitive under test. Increasing this number
5650 reduces noise due to 4581 reduces noise due to loop start/end overhead,
5651 but the default has a 4582 but the default has already reduced the per-pass
5652 noise to a handful of 4583 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 4584 x86 laptops.
5654 4585
5655 refscale.nreaders= [KNL] 4586 refscale.nreaders= [KNL]
5656 Set number of readers 4587 Set number of readers. The default value of -1
5657 selects N, where N is 4588 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 4589 of CPUs. A value of zero is an interesting choice.
5659 4590
5660 refscale.nruns= [KNL] 4591 refscale.nruns= [KNL]
5661 Set number of runs, e 4592 Set number of runs, each of which is dumped onto
5662 the console log. 4593 the console log.
5663 4594
5664 refscale.readdelay= [KNL] 4595 refscale.readdelay= [KNL]
5665 Set the read-side cri 4596 Set the read-side critical-section duration,
5666 measured in microseco 4597 measured in microseconds.
5667 4598
5668 refscale.scale_type= [KNL] 4599 refscale.scale_type= [KNL]
5669 Specify the read-prot 4600 Specify the read-protection implementation to test.
5670 4601
5671 refscale.shutdown= [KNL] 4602 refscale.shutdown= [KNL]
5672 Shut down the system 4603 Shut down the system at the end of the performance
5673 test. This defaults 4604 test. This defaults to 1 (shut it down) when
5674 refscale is built int 4605 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 4606 it running) when refscale is built as a module.
5676 4607
5677 refscale.verbose= [KNL] 4608 refscale.verbose= [KNL]
5678 Enable additional pri 4609 Enable additional printk() statements.
5679 4610
5680 refscale.verbose_batched= [KNL] 4611 refscale.verbose_batched= [KNL]
5681 Batch the additional 4612 Batch the additional printk() statements. If zero
5682 (the default) or nega 4613 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 4614 print every Nth verbose statement, where N is the value
5684 specified. 4615 specified.
5685 4616
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= 4617 relax_domain_level=
5694 [KNL, SMP] Set schedu 4618 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 4619 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 4620
5697 reserve= [KNL,BUGS] Force kern 4621 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 4622 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 4623 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 4624 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 4625 is assumed to be I/O ports; otherwise it is memory.
5702 4626
5703 reserve_mem= [RAM] !! 4627 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] 4628 Format: nn[KMG]
5727 Reserves a hole at th 4629 Reserves a hole at the top of the kernel virtual
5728 address space. 4630 address space.
5729 4631
>> 4632 reservelow= [X86]
>> 4633 Format: nn[K]
>> 4634 Set the amount of memory to reserve for BIOS at
>> 4635 the bottom of the address space.
>> 4636
5730 reset_devices [KNL] Force drivers t 4637 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 4638 during initialization.
5732 4639
5733 resume= [SWSUSP] 4640 resume= [SWSUSP]
5734 Specify the partition 4641 Specify the partition device for software suspend
5735 Format: 4642 Format:
5736 {/dev/<dev> | PARTUUI 4643 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 4644
5738 resume_offset= [SWSUSP] 4645 resume_offset= [SWSUSP]
5739 Specify the offset fr 4646 Specify the offset from the beginning of the partition
5740 given by "resume=" at 4647 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 4648 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 4649 See Documentation/power/swsusp-and-swap-files.rst
5743 4650
5744 resumedelay= [HIBERNATION] Delay ( 4651 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 4652 read the resume files
5746 4653
5747 resumewait [HIBERNATION] Wait (i 4654 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 4655 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 4656 (e.g. USB and MMC devices).
5750 4657
5751 retain_initrd [RAM] Keep initrd mem !! 4658 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 4659 noresume Don't check if there's a hibernation image
5753 !! 4660 present during boot.
5754 retbleed= [X86] Control mitigat !! 4661 nocompress Don't compress/decompress hibernation images.
5755 Speculative Code Exec !! 4662 no Disable hibernation and resume.
5756 vulnerability. !! 4663 protect_image Turn on image protection during restoration
5757 !! 4664 (that will set all pages holding image data
5758 AMD-based UNRET and I !! 4665 during restoration read-only).
5759 sibling threads from <<
5760 sibling threads. For <<
5761 cessors that support <<
5762 that don't. <<
5763 <<
5764 off - no mit <<
5765 auto - automa <<
5766 auto,nosmt - automa <<
5767 disabl <<
5768 the fu <<
5769 and ol <<
5770 ibpb - On AMD <<
5771 window <<
5772 Safe, <<
5773 enable <<
5774 on Int <<
5775 ibpb,nosmt - Like " <<
5776 when S <<
5777 the al <<
5778 have S <<
5779 unret - Force <<
5780 only e <<
5781 system <<
5782 unret,nosmt - Like u <<
5783 is not <<
5784 system <<
5785 <<
5786 Selecting 'auto' will <<
5787 time according to the <<
5788 4666
5789 Not specifying this o !! 4667 retain_initrd [RAM] Keep initrd memory after extraction
5790 4668
5791 rfkill.default_state= 4669 rfkill.default_state=
5792 0 "airplane mode". All 4670 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 4671 etc. communication is blocked by default.
5794 1 Unblocked. 4672 1 Unblocked.
5795 4673
5796 rfkill.master_switch_mode= 4674 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 4675 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 4676 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 4677 blocked and the previous configuration.
5800 2 The "airplane mode" b 4678 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 4679 blocked and everything unblocked.
5802 4680
>> 4681 rhash_entries= [KNL,NET]
>> 4682 Set number of hash buckets for route cache
>> 4683
5803 ring3mwait=disable 4684 ring3mwait=disable
5804 [KNL] Disable ring 3 4685 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 4686 CPUs.
5806 4687
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 4688 ro [KNL] Mount root device read-only on boot
5815 4689
5816 rodata= [KNL,EARLY] !! 4690 rodata= [KNL]
5817 on Mark read-only kernel 4691 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 4692 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 4693
5822 rockchip.usb_uart 4694 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 4695 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 4696 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 4697 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 4698 port and the regular usb controller gets disabled.
5828 4699
5829 root= [KNL] Root filesystem 4700 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 4701 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 4702
5837 rootdelay= [KNL] Delay (in secon 4703 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 4704 mount the root filesystem
5839 4705
5840 rootflags= [KNL] Set root filesy 4706 rootflags= [KNL] Set root filesystem mount option string
5841 4707
5842 rootfstype= [KNL] Set root filesy 4708 rootfstype= [KNL] Set root filesystem type
5843 4709
5844 rootwait [KNL] Wait (indefinit 4710 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 4711 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 4712 (e.g. USB and MMC devices).
5847 4713
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 4714 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 4715 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 4716 Memory area to be used by remote processor image,
5855 managed by CMA. 4717 managed by CMA.
5856 4718
5857 rw [KNL] Mount root devi 4719 rw [KNL] Mount root device read-write on boot
5858 4720
5859 S [KNL] Run init in sin 4721 S [KNL] Run init in single mode
5860 4722
5861 s390_iommu= [HW,S390] 4723 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 4724 Set s390 IOTLB flushing mode
5863 strict 4725 strict
5864 With strict flushing !! 4726 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 4727 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 4728 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 4729
5881 sa1100ir [NET] 4730 sa1100ir [NET]
5882 See drivers/net/irda/ 4731 See drivers/net/irda/sa1100_ir.c.
5883 4732
5884 sched_verbose [KNL,EARLY] Enables v !! 4733 sbni= [NET] Granch SBNI12 leased line adapter
>> 4734
>> 4735 sched_debug [KNL] Enables verbose scheduler debug messages.
5885 4736
5886 schedstats= [KNL,X86] Enable or d 4737 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 4738 Allowed values are enable and disable. This feature
5888 incurs a small amount 4739 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 4740 but is useful for debugging and performance tuning.
5890 4741
5891 sched_thermal_decay_shift= 4742 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 4743 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 4744 pressure signal. Thermal pressure signal follows the
5895 default decay period 4745 default decay period of other scheduler pelt
5896 signals(usually 32 ms 4746 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 4747 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 4748 period for the thermal pressure signal by the shift
5899 value. 4749 value.
5900 i.e. with the default 4750 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 4751 sched_thermal_decay_shift thermal pressure decay pr
5902 1 4752 1 64 ms
5903 2 4753 2 128 ms
5904 and so on. 4754 and so on.
5905 Format: integer betwe 4755 Format: integer between 0 and 10
5906 Default is 0. 4756 Default is 0.
5907 4757
5908 scftorture.holdoff= [KNL] 4758 scftorture.holdoff= [KNL]
5909 Number of seconds to 4759 Number of seconds to hold off before starting
5910 test. Defaults to ze 4760 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 4761 to 10 seconds for built-in smp_call_function()
5912 tests. 4762 tests.
5913 4763
5914 scftorture.longwait= [KNL] 4764 scftorture.longwait= [KNL]
5915 Request ridiculously 4765 Request ridiculously long waits randomly selected
5916 up to the chosen limi 4766 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 4767 default) disables this feature. Please note
5918 that requesting even 4768 that requesting even small non-zero numbers of
5919 seconds can result in 4769 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 4770 softlockup complaints, and so on.
5921 4771
5922 scftorture.nthreads= [KNL] 4772 scftorture.nthreads= [KNL]
5923 Number of kthreads to 4773 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 4774 smp_call_function() family of functions.
5925 The default of -1 spe 4775 The default of -1 specifies a number of kthreads
5926 equal to the number o 4776 equal to the number of CPUs.
5927 4777
5928 scftorture.onoff_holdoff= [KNL] 4778 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 4779 Number seconds to wait after the start of the
5930 test before initiatin 4780 test before initiating CPU-hotplug operations.
5931 4781
5932 scftorture.onoff_interval= [KNL] 4782 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 4783 Number seconds to wait between successive
5934 CPU-hotplug operation 4784 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 4785 is the default) disables CPU-hotplug operations.
5936 4786
5937 scftorture.shutdown_secs= [KNL] 4787 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 4788 The number of seconds following the start of the
5939 test after which to s 4789 test after which to shut down the system. The
5940 default of zero avoid 4790 default of zero avoids shutting down the system.
5941 Non-zero values are u 4791 Non-zero values are useful for automated tests.
5942 4792
5943 scftorture.stat_interval= [KNL] 4793 scftorture.stat_interval= [KNL]
5944 The number of seconds 4794 The number of seconds between outputting the
5945 current test statisti 4795 current test statistics to the console. A value
5946 of zero disables stat 4796 of zero disables statistics output.
5947 4797
5948 scftorture.stutter_cpus= [KNL] 4798 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 4799 The number of jiffies to wait between each change
5950 to the set of CPUs un 4800 to the set of CPUs under test.
5951 4801
5952 scftorture.use_cpus_read_lock= [KNL] 4802 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 4803 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 4804 preempt_disable() to disable CPU hotplug
5955 while invoking one of 4805 while invoking one of the smp_call_function*()
5956 functions. 4806 functions.
5957 4807
5958 scftorture.verbose= [KNL] 4808 scftorture.verbose= [KNL]
5959 Enable additional pri 4809 Enable additional printk() statements.
5960 4810
5961 scftorture.weight_single= [KNL] 4811 scftorture.weight_single= [KNL]
5962 The probability weigh 4812 The probability weighting to use for the
5963 smp_call_function_sin 4813 smp_call_function_single() function with a zero
5964 "wait" parameter. A 4814 "wait" parameter. A value of -1 selects the
5965 default if all other 4815 default if all other weights are -1. However,
5966 if at least one weigh 4816 if at least one weight has some other value, a
5967 value of -1 will inst 4817 value of -1 will instead select a weight of zero.
5968 4818
5969 scftorture.weight_single_wait= [KNL] 4819 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 4820 The probability weighting to use for the
5971 smp_call_function_sin 4821 smp_call_function_single() function with a
5972 non-zero "wait" param 4822 non-zero "wait" parameter. See weight_single.
5973 4823
5974 scftorture.weight_many= [KNL] 4824 scftorture.weight_many= [KNL]
5975 The probability weigh 4825 The probability weighting to use for the
5976 smp_call_function_man 4826 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 4827 "wait" parameter. See weight_single.
5978 Note well that settin 4828 Note well that setting a high probability for
5979 this weighting can pl 4829 this weighting can place serious IPI load
5980 on the system. 4830 on the system.
5981 4831
5982 scftorture.weight_many_wait= [KNL] 4832 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 4833 The probability weighting to use for the
5984 smp_call_function_man 4834 smp_call_function_many() function with a
5985 non-zero "wait" param 4835 non-zero "wait" parameter. See weight_single
5986 and weight_many. 4836 and weight_many.
5987 4837
5988 scftorture.weight_all= [KNL] 4838 scftorture.weight_all= [KNL]
5989 The probability weigh 4839 The probability weighting to use for the
5990 smp_call_function_all 4840 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 4841 "wait" parameter. See weight_single and
5992 weight_many. 4842 weight_many.
5993 4843
5994 scftorture.weight_all_wait= [KNL] 4844 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 4845 The probability weighting to use for the
5996 smp_call_function_all 4846 smp_call_function_all() function with a
5997 non-zero "wait" param 4847 non-zero "wait" parameter. See weight_single
5998 and weight_many. 4848 and weight_many.
5999 4849
6000 skew_tick= [KNL,EARLY] Offset th !! 4850 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 4851 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 4852 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 4853 Format: { "0" | "1" }
6004 0 -- disable. (may be 4854 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 4855 1 -- enable.
6006 Note: increases power 4856 Note: increases power consumption, thus should only be
6007 enabled if running ji 4857 enabled if running jitter sensitive (HPC/RT) workloads.
6008 4858
6009 security= [SECURITY] Choose a l 4859 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 4860 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 4861 "lsm=" parameter.
6012 4862
6013 selinux= [SELINUX] Disable or 4863 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 4864 Format: { "0" | "1" }
6015 See security/selinux/ 4865 See security/selinux/Kconfig help text.
6016 0 -- disable. 4866 0 -- disable.
6017 1 -- enable. 4867 1 -- enable.
6018 Default value is 1. 4868 Default value is 1.
6019 4869
6020 serialnumber [BUGS=X86-32] !! 4870 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 4871 Format: { "0" | "1" }
>> 4872 See security/apparmor/Kconfig help text
>> 4873 0 -- disable.
>> 4874 1 -- enable.
>> 4875 Default value is set via kernel config option.
6021 4876
6022 sev=option[,option...] [X86-64] See D !! 4877 serialnumber [BUGS=X86-32]
6023 4878
6024 shapers= [NET] 4879 shapers= [NET]
6025 Maximal number of sha 4880 Maximal number of shapers.
6026 4881
6027 show_lapic= [APIC,X86] Advanced P !! 4882 simeth= [IA-64]
6028 Limit apic dumping. T !! 4883 simscsi=
6029 number of local apics !! 4884
6030 to set it to "all" by !! 4885 slram= [HW,MTD]
6031 Format: { 1 (default) !! 4886
6032 The parameter valid i !! 4887 slab_nomerge [MM]
6033 apic=verbose is speci !! 4888 Disable merging of slabs with similar size. May be
6034 Example: apic=debug s !! 4889 necessary if there is some reason to distinguish
>> 4890 allocs to different slabs, especially in hardened
>> 4891 environments where the risk of heap overflows and
>> 4892 layout control by attackers can usually be
>> 4893 frustrated by disabling merging. This will reduce
>> 4894 most of the exposure of a heap attack to a single
>> 4895 cache (risks via metadata attacks are mostly
>> 4896 unchanged). Debug options disable merging on their
>> 4897 own.
>> 4898 For more information see Documentation/vm/slub.rst.
6035 4899
6036 slab_debug[=options[,slabs][;[options !! 4900 slab_max_order= [MM, SLAB]
6037 Enabling slab_debug a !! 4901 Determines the maximum allowed order for slabs.
>> 4902 A high setting may cause OOMs due to memory
>> 4903 fragmentation. Defaults to 1 for systems with
>> 4904 more than 32MB of RAM, 0 otherwise.
>> 4905
>> 4906 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 4907 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 4908 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 4909 slub_debug can create guard zones around objects and
6040 may poison objects wh 4910 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 4911 last alloc / free. For more information see
6042 Documentation/mm/slub !! 4912 Documentation/vm/slub.rst.
6043 (slub_debug legacy na <<
6044 4913
6045 slab_max_order= [MM] !! 4914 slub_max_order= [MM, SLUB]
6046 Determines the maximu 4915 Determines the maximum allowed order for slabs.
6047 A high setting may ca 4916 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 4917 fragmentation. For more information see
6049 Documentation/mm/slub !! 4918 Documentation/vm/slub.rst.
6050 (slub_max_order legac <<
6051 <<
6052 slab_merge [MM] <<
6053 Enable merging of sla <<
6054 kernel is built witho <<
6055 (slub_merge legacy na <<
6056 4919
6057 slab_min_objects= [MM] !! 4920 slub_min_objects= [MM, SLUB]
6058 The minimum number of 4921 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 4922 increase the slab order up to slub_max_order to
6060 generate a sufficient 4923 generate a sufficiently large slab able to contain
6061 the number of objects 4924 the number of objects indicated. The higher the number
6062 of objects the smalle 4925 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 4926 and the less frequently locks need to be acquired.
6064 For more information !! 4927 For more information see Documentation/vm/slub.rst.
6065 (slub_min_objects leg <<
6066 4928
6067 slab_min_order= [MM] !! 4929 slub_min_order= [MM, SLUB]
6068 Determines the minimu 4930 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 4931 lower than slub_max_order.
6070 Documentation/mm/slub !! 4932 For more information see Documentation/vm/slub.rst.
6071 (slub_min_order legac <<
6072 4933
6073 slab_nomerge [MM] !! 4934 slub_nomerge [MM, SLUB]
6074 Disable merging of sl !! 4935 Same with slab_nomerge. This is supported for legacy.
6075 necessary if there is !! 4936 See slab_nomerge for more information.
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 <<
6087 slram= [HW,MTD] <<
6088 4937
6089 smart2= [HW] 4938 smart2= [HW]
6090 Format: <io1>[,<io2>[ 4939 Format: <io1>[,<io2>[,...,<io8>]]
6091 4940
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 4941 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 4942 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 4943 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 4944 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 4945 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 4946 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 4947 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 4948 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 4949 1: Fast pin select (default)
6119 2: ATC IRMode 4950 2: ATC IRMode
6120 4951
6121 smt= [KNL,MIPS,S390,EARLY] !! 4952 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 4953 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 4954 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 4955 actual hardware limit.
6125 Format: <integer> 4956 Format: <integer>
6126 Default: -1 (no limit 4957 Default: -1 (no limit)
6127 4958
6128 softlockup_panic= 4959 softlockup_panic=
6129 [KNL] Should the soft 4960 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 4961 Format: 0 | 1
6131 4962
6132 A value of 1 instruct 4963 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 4964 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 4965 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 4966 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 4967 respective build-time switch to that functionality.
6137 4968
6138 softlockup_all_cpu_backtrace= 4969 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 4970 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 4971 backtraces on all cpus.
6141 Format: 0 | 1 4972 Format: 0 | 1
6142 4973
6143 sonypi.*= [HW] Sony Programmabl 4974 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 4975 See Documentation/admin-guide/laptops/sonypi.rst
6145 4976
6146 spectre_bhi= [X86] Control mitigat !! 4977 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 4978 (indirect branch speculation) vulnerability.
6163 The default operation 4979 The default operation protects the kernel from
6164 user space attacks. 4980 user space attacks.
6165 4981
6166 on - unconditionall 4982 on - unconditionally enable, implies
6167 spectre_v2_use 4983 spectre_v2_user=on
6168 off - unconditionall 4984 off - unconditionally disable, implies
6169 spectre_v2_use 4985 spectre_v2_user=off
6170 auto - kernel detects 4986 auto - kernel detects whether your CPU model is
6171 vulnerable 4987 vulnerable
6172 4988
6173 Selecting 'on' will, 4989 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 4990 mitigation method at run time according to the
6175 CPU, the available mi 4991 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 4992 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 4993 compiler with which the kernel was built.
6178 4994
6179 Selecting 'on' will a 4995 Selecting 'on' will also enable the mitigation
6180 against user space to 4996 against user space to user space task attacks.
6181 4997
6182 Selecting 'off' will 4998 Selecting 'off' will disable both the kernel and
6183 the user space protec 4999 the user space protections.
6184 5000
6185 Specific mitigations 5001 Specific mitigations can also be selected manually:
6186 5002
6187 retpoline - r 5003 retpoline - replace indirect branches
6188 retpoline,generic - R !! 5004 retpoline,generic - google's original retpoline
6189 retpoline,lfence - L !! 5005 retpoline,amd - AMD-specific minimal thunk
6190 retpoline,amd - a <<
6191 eibrs - E <<
6192 eibrs,retpoline - E <<
6193 eibrs,lfence - E <<
6194 ibrs - u <<
6195 5006
6196 Not specifying this o 5007 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5008 spectre_v2=auto.
6198 5009
6199 spectre_v2_user= 5010 spectre_v2_user=
6200 [X86] Control mitigat 5011 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5012 (indirect branch speculation) vulnerability between
6202 user space tasks 5013 user space tasks
6203 5014
6204 on - Uncondition 5015 on - Unconditionally enable mitigations. Is
6205 enforced by 5016 enforced by spectre_v2=on
6206 5017
6207 off - Uncondition 5018 off - Unconditionally disable mitigations. Is
6208 enforced by 5019 enforced by spectre_v2=off
6209 5020
6210 prctl - Indirect br 5021 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5022 but mitigation can be enabled via prctl
6212 per thread. 5023 per thread. The mitigation control state
6213 is inherite 5024 is inherited on fork.
6214 5025
6215 prctl,ibpb 5026 prctl,ibpb
6216 - Like "prctl 5027 - Like "prctl" above, but only STIBP is
6217 controlled 5028 controlled per thread. IBPB is issued
6218 always when 5029 always when switching between different user
6219 space proce 5030 space processes.
6220 5031
6221 seccomp 5032 seccomp
6222 - Same as "pr 5033 - Same as "prctl" above, but all seccomp
6223 threads wil 5034 threads will enable the mitigation unless
6224 they explic 5035 they explicitly opt out.
6225 5036
6226 seccomp,ibpb 5037 seccomp,ibpb
6227 - Like "secco 5038 - Like "seccomp" above, but only STIBP is
6228 controlled 5039 controlled per thread. IBPB is issued
6229 always when 5040 always when switching between different
6230 user space 5041 user space processes.
6231 5042
6232 auto - Kernel sele 5043 auto - Kernel selects the mitigation depending on
6233 the availab 5044 the available CPU features and vulnerability.
6234 5045
6235 Default mitigation: " !! 5046 Default mitigation:
>> 5047 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
6236 5048
6237 Not specifying this o 5049 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5050 spectre_v2_user=auto.
6239 5051
6240 spec_rstack_overflow= <<
6241 [X86,EARLY] Control R <<
6242 <<
6243 off - Dis <<
6244 microcode - Ena <<
6245 safe-ret - Ena <<
6246 ibpb - Ena <<
6247 ker <<
6248 ibpb-vmexit - Iss <<
6249 (cl <<
6250 <<
6251 spec_store_bypass_disable= 5052 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5053 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5054 (Speculative Store Bypass vulnerability)
6254 5055
6255 Certain CPUs are vuln 5056 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5057 a common industry wide performance optimization known
6257 as "Speculative Store 5058 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5059 to the same memory location may not be observed by
6259 later loads during sp 5060 later loads during speculative execution. The idea
6260 is that such stores a 5061 is that such stores are unlikely and that they can
6261 be detected prior to 5062 be detected prior to instruction retirement at the
6262 end of a particular s 5063 end of a particular speculation execution window.
6263 5064
6264 In vulnerable process 5065 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5066 store can be used in a cache side channel attack, for
6266 example to read memor 5067 example to read memory to which the attacker does not
6267 directly have access 5068 directly have access (e.g. inside sandboxed code).
6268 5069
6269 This parameter contro 5070 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5071 Bypass optimization is used.
6271 5072
6272 On x86 the options ar 5073 On x86 the options are:
6273 5074
6274 on - Uncondition 5075 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5076 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5077 auto - Kernel detects whether the CPU model contains an
6277 implementat 5078 implementation of Speculative Store Bypass and
6278 picks the m 5079 picks the most appropriate mitigation. If the
6279 CPU is not 5080 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5081 CPU is vulnerable the default mitigation is
6281 architectur 5082 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5083 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5084 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5085 for a process by default. The state of the control
6285 is inherite 5086 is inherited on fork.
6286 seccomp - Same as "pr 5087 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5088 will disable SSB unless they explicitly opt out.
6288 5089
6289 Default mitigations: 5090 Default mitigations:
6290 X86: "prctl" !! 5091 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6291 5092
6292 On powerpc the option 5093 On powerpc the options are:
6293 5094
6294 on,auto - On Power8 a 5095 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5096 barrier on kernel entry and exit. On Power7
6296 perform a s 5097 perform a software flush on kernel entry and
6297 exit. 5098 exit.
6298 off - No action. 5099 off - No action.
6299 5100
6300 Not specifying this o 5101 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5102 spec_store_bypass_disable=auto.
6302 5103
>> 5104 spia_io_base= [HW,MTD]
>> 5105 spia_fio_base=
>> 5106 spia_pedr=
>> 5107 spia_peddr=
>> 5108
6303 split_lock_detect= 5109 split_lock_detect=
6304 [X86] Enable split lo !! 5110 [X86] Enable split lock detection
6305 5111
6306 When enabled (and if 5112 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5113 instructions that access data across cache line
6308 boundaries will resul !! 5114 boundaries will result in an alignment check exception.
6309 for split lock detect <<
6310 bus lock detection. <<
6311 5115
6312 off - not enabled 5116 off - not enabled
6313 5117
6314 warn - the kernel !! 5118 warn - the kernel will emit rate limited warnings
6315 about appli 5119 about applications triggering the #AC
6316 exception o !! 5120 exception. This mode is the default on CPUs
6317 the default !! 5121 that supports split lock detection.
6318 detection o <<
6319 behavior is <<
6320 enabled in <<
6321 5122
6322 fatal - the kernel 5123 fatal - the kernel will send SIGBUS to applications
6323 that trigge !! 5124 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 5125
6335 If an #AC exception i 5126 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5127 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5128 the kernel will oops in either "warn" or "fatal"
6338 mode. 5129 mode.
6339 5130
6340 #DB exception for bus !! 5131 srbds= [X86,INTEL]
6341 CPL > 0. <<
6342 <<
6343 srbds= [X86,INTEL,EARLY] <<
6344 Control the Special R 5132 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5133 (SRBDS) mitigation.
6346 5134
6347 Certain CPUs are vuln 5135 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5136 exploit which can leak bits from the random
6349 number generator. 5137 number generator.
6350 5138
6351 By default, this issu 5139 By default, this issue is mitigated by
6352 microcode. However, 5140 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5141 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5142 much slower. Among other effects, this will
6355 result in reduced thr 5143 result in reduced throughput from /dev/urandom.
6356 5144
6357 The microcode mitigat 5145 The microcode mitigation can be disabled with
6358 the following option: 5146 the following option:
6359 5147
6360 off: Disable mitig 5148 off: Disable mitigation and remove
6361 performance i 5149 performance impact to RDRAND and RDSEED
6362 5150
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] 5151 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5152 Specifies how frequently to check for
6389 grace-period sequence 5153 grace-period sequence counter wrap for the
6390 srcu_data structure's 5154 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5155 The greater the number of bits set in this kernel
6392 parameter, the less f 5156 parameter, the less frequently counter wrap will
6393 be checked for. Note 5157 be checked for. Note that the bottom two bits
6394 are ignored. 5158 are ignored.
6395 5159
6396 srcutree.exp_holdoff [KNL] 5160 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5161 Specifies how many nanoseconds must elapse
6398 since the end of the 5162 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5163 a given srcu_struct until the next normal SRCU
6400 grace period will be 5164 grace period will be considered for automatic
6401 expediting. Set to z 5165 expediting. Set to zero to disable automatic
6402 expediting. 5166 expediting.
6403 5167
6404 srcutree.srcu_max_nodelay [KNL] !! 5168 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 5169 Speculative Store Bypass Disable control
6432 5170
6433 On CPUs that are vuln 5171 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5172 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5173 firmware based mitigation, this parameter
6436 indicates how the mit 5174 indicates how the mitigation should be used:
6437 5175
6438 force-on: Unconditio 5176 force-on: Unconditionally enable mitigation for
6439 for both k 5177 for both kernel and userspace
6440 force-off: Unconditio 5178 force-off: Unconditionally disable mitigation for
6441 for both k 5179 for both kernel and userspace
6442 kernel: Always ena 5180 kernel: Always enable mitigation in the
6443 kernel, an 5181 kernel, and offer a prctl interface
6444 to allow u 5182 to allow userspace to register its
6445 interest i 5183 interest in being mitigated too.
6446 5184
6447 stack_guard_gap= [MM] 5185 stack_guard_gap= [MM]
6448 override the default 5186 override the default stack gap protection. The value
6449 is in page units and 5187 is in page units and it defines how many pages prior
6450 to (for stacks growin 5188 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5189 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5190 mapping. Default value is 256 pages.
6453 5191
6454 stack_depot_disable= [KNL,EARLY] !! 5192 stack_depot_disable= [KNL]
6455 Setting this to true 5193 Setting this to true through kernel command line will
6456 disable the stack dep 5194 disable the stack depot thereby saving the static memory
6457 consumed by the stack 5195 consumed by the stack hash table. By default this is set
6458 to false. 5196 to false.
6459 5197
6460 stacktrace [FTRACE] 5198 stacktrace [FTRACE]
6461 Enabled the stack tra 5199 Enabled the stack tracer on boot up.
6462 5200
6463 stacktrace_filter=[function-list] 5201 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5202 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 5203 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 5204 list of functions. This list can be changed at run
6467 time by the stack_tra 5205 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 5206 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 5207 and the stacktrace above is not needed.
6470 5208
6471 sti= [PARISC,HW] 5209 sti= [PARISC,HW]
6472 Format: <num> 5210 Format: <num>
6473 Set the STI (builtin 5211 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 5212 machines) console (graphic card) which should be used
6475 as the initial boot-c 5213 as the initial boot-console.
6476 See also comment in d 5214 See also comment in drivers/video/console/sticore.c.
6477 5215
6478 sti_font= [HW] 5216 sti_font= [HW]
6479 See comment in driver 5217 See comment in drivers/video/console/sticore.c.
6480 5218
6481 stifb= [HW] 5219 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 5220 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 5221
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= 5222 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 5223 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 5224 [NFS,SUNRPC]
6506 SunRPC servers often 5225 SunRPC servers often require that client requests
6507 originate from a priv 5226 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 5227 range 0 < portnr < 1024).
6509 An administrator who 5228 An administrator who wishes to reserve some of these
6510 ports for other uses 5229 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 5230 kernel's sunrpc client considers to be privileged
6512 using these two param 5231 using these two parameters to set the minimum and
6513 maximum port values. 5232 maximum port values.
6514 5233
6515 sunrpc.svc_rpc_per_connection_limit= 5234 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 5235 [NFS,SUNRPC]
6517 Limit the number of r 5236 Limit the number of requests that the server will
6518 process in parallel f 5237 process in parallel from a single connection.
6519 The default value is 5238 The default value is 0 (no limit).
6520 5239
6521 sunrpc.pool_mode= 5240 sunrpc.pool_mode=
6522 [NFS] 5241 [NFS]
6523 Control how the NFS s 5242 Control how the NFS server code allocates CPUs to
6524 service thread pools. 5243 service thread pools. Depending on how many NICs
6525 you have and where th 5244 you have and where their interrupts are bound, this
6526 option will affect wh 5245 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 5246 Note: this parameter cannot be changed while the
6528 NFS server is running 5247 NFS server is running.
6529 5248
6530 auto the serve 5249 auto the server chooses an appropriate mode
6531 automatic 5250 automatically using heuristics
6532 global a single 5251 global a single global pool contains all CPUs
6533 percpu one pool 5252 percpu one pool for each CPU
6534 pernode one pool 5253 pernode one pool for each NUMA node (equivalent
6535 to global 5254 to global on non-NUMA machines)
6536 5255
6537 sunrpc.tcp_slot_table_entries= 5256 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 5257 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 5258 [NFS,SUNRPC]
6540 Sets the upper limit 5259 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 5260 RPC calls that can be sent from the client to a
6542 server. Increasing th 5261 server. Increasing these values may allow you to
6543 improve throughput, b 5262 improve throughput, but will also increase the
6544 amount of memory rese 5263 amount of memory reserved for use by the client.
6545 5264
6546 suspend.pm_test_delay= 5265 suspend.pm_test_delay=
6547 [SUSPEND] 5266 [SUSPEND]
6548 Sets the number of se 5267 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 5268 mode before resuming the system (see
6550 /sys/power/pm_test). 5269 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 5270 is set. Default value is 5.
6552 5271
6553 svm= [PPC] 5272 svm= [PPC]
6554 Format: { on | off | 5273 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 5274 This parameter controls use of the Protected
6556 Execution Facility on 5275 Execution Facility on pSeries.
6557 5276
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 5277 swapaccount=[0|1]
6559 Format: { <int> [,<in !! 5278 [KNL] Enable accounting of swap in memory resource
>> 5279 controller if no parameter or 1 is given or disable
>> 5280 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
>> 5281
>> 5282 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
>> 5283 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 5284 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 5285 force -- force using of bounce buffers even if they
6565 wouldn't be 5286 wouldn't be automatically used by the kernel
6566 noforce -- Never use 5287 noforce -- Never use bounce buffers (for debugging)
6567 5288
6568 switches= [HW,M68k,EARLY] !! 5289 switches= [HW,M68k]
6569 5290
6570 sysctl.*= [KNL] 5291 sysctl.*= [KNL]
6571 Set a sysctl paramete 5292 Set a sysctl parameter, right before loading the init
6572 process, as if the va 5293 process, as if the value was written to the respective
6573 /proc/sys/... file. B 5294 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 5295 separators. Unrecognized parameters and invalid values
6575 are reported in the k 5296 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 5297 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 5298 Example: sysctl.vm.swappiness=40
6578 5299
>> 5300 sysfs.deprecated=0|1 [KNL]
>> 5301 Enable/disable old style sysfs layout for old udev
>> 5302 on older distributions. When this option is enabled
>> 5303 very new udev will not work anymore. When this option
>> 5304 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 5305 in older udev will not work anymore.
>> 5306 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 5307 the kernel configuration.
>> 5308
6579 sysrq_always_enabled 5309 sysrq_always_enabled
6580 [KNL] 5310 [KNL]
6581 Ignore sysrq setting 5311 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 5312 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 5313 Useful for debugging.
6584 5314
6585 tcpmhash_entries= [KNL,NET] 5315 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 5316 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 5317 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 5318 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 5319 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 5320 "tcp_no_metrics_save" section for more details.
6591 5321
6592 tdfx= [HW,DRM] 5322 tdfx= [HW,DRM]
6593 5323
6594 test_suspend= [SUSPEND] !! 5324 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 5325 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 5326 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 5327 as the system sleep state during system startup with
6599 the optional capabili 5328 the optional capability to repeat N number of times.
6600 The system is woken f 5329 The system is woken from this state using a
6601 wakeup-capable RTC al 5330 wakeup-capable RTC alarm.
6602 5331
6603 thash_entries= [KNL,NET] 5332 thash_entries= [KNL,NET]
6604 Set number of hash bu 5333 Set number of hash buckets for TCP connection
6605 5334
6606 thermal.act= [HW,ACPI] 5335 thermal.act= [HW,ACPI]
6607 -1: disable all activ 5336 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 5337 <degrees C>: override all lowest active trip points
6609 5338
6610 thermal.crt= [HW,ACPI] 5339 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 5340 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 5341 <degrees C>: override all critical trip points
6613 5342
>> 5343 thermal.nocrt= [HW,ACPI]
>> 5344 Set to disable actions on ACPI thermal zone
>> 5345 critical and hot trip points.
>> 5346
6614 thermal.off= [HW,ACPI] 5347 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 5348 1: disable ACPI thermal control
6616 5349
6617 thermal.psv= [HW,ACPI] 5350 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 5351 -1: disable all passive trip points
6619 <degrees C>: override 5352 <degrees C>: override all passive trip points to this
6620 value 5353 value
6621 5354
6622 thermal.tzp= [HW,ACPI] 5355 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 5356 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 5357 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 5358 0: no polling (default)
6626 5359
6627 threadirqs [KNL,EARLY] !! 5360 threadirqs [KNL]
6628 Force threading of al 5361 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 5362 marked explicitly IRQF_NO_THREAD.
6630 5363
6631 topology= [S390,EARLY] !! 5364 topology= [S390]
6632 Format: {off | on} 5365 Format: {off | on}
6633 Specify if the kernel 5366 Specify if the kernel should make use of the cpu
6634 topology information 5367 topology information if the hardware supports this.
6635 The scheduler will ma 5368 The scheduler will make use of this information and
6636 e.g. base its process 5369 e.g. base its process migration decisions on it.
6637 Default is on. 5370 Default is on.
6638 5371
>> 5372 topology_updates= [KNL, PPC, NUMA]
>> 5373 Format: {off}
>> 5374 Specify if the kernel should ignore (off)
>> 5375 topology updates sent by the hypervisor to this
>> 5376 LPAR.
>> 5377
6639 torture.disable_onoff_at_boot= [KNL] 5378 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 5379 Prevent the CPU-hotplug component of torturing
6641 until after init has 5380 until after init has spawned.
6642 5381
6643 torture.ftrace_dump_at_shutdown= [KNL 5382 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 5383 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 5384 even if there were no errors. This can be a
6646 very costly operation 5385 very costly operation when many torture tests
6647 are running concurren 5386 are running concurrently, especially on systems
6648 with rotating-rust st 5387 with rotating-rust storage.
6649 5388
6650 torture.verbose_sleep_frequency= [KNL 5389 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 5390 Specifies how many verbose printk()s should be
6652 emitted between each 5391 emitted between each sleep. The default of zero
6653 disables verbose-prin 5392 disables verbose-printk() sleeping.
6654 5393
6655 torture.verbose_sleep_duration= [KNL] 5394 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 5395 Duration of each verbose-printk() sleep in jiffies.
6657 5396
>> 5397 tp720= [HW,PS2]
>> 5398
6658 tpm_suspend_pcr=[HW,TPM] 5399 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 5400 Format: integer pcr id
6660 Specify that at suspe 5401 Specify that at suspend time, the tpm driver
6661 should extend the spe 5402 should extend the specified pcr with zeros,
6662 as a workaround for s 5403 as a workaround for some chips which fail to
6663 flush the last writte 5404 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 5405 This will guarantee that all the other pcrs
6665 are saved. 5406 are saved.
6666 5407
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] 5408 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 5409 [FTRACE] will set tracing buffer size on each cpu.
6707 5410
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] 5411 trace_event=[event-list]
6731 [FTRACE] Set and star 5412 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 5413 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 5414 comma-separated list of trace events to enable. See
6734 also Documentation/tr 5415 also Documentation/trace/events.rst
6735 5416
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] 5417 trace_options=[option-list]
6757 [FTRACE] Enable or di 5418 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 5419 The option-list is a comma delimited list of options
6759 that can be enabled o 5420 that can be enabled or disabled just as if you were
6760 to echo the option na 5421 to echo the option name into
6761 5422
6762 /sys/kernel/traci !! 5423 /sys/kernel/debug/tracing/trace_options
6763 5424
6764 For example, to enabl 5425 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 5426 stack trace of each event), add to the command line:
6766 5427
6767 trace_options=s 5428 trace_options=stacktrace
6768 5429
6769 See also Documentatio 5430 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 5431 section.
6771 5432
6772 trace_trigger=[trigger-list] !! 5433 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 5434 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 5435 tracing ring buffer. This is useful for early boot up
6775 filter. !! 5436 where the system hangs or reboots and does not give the
6776 !! 5437 option for reading the tracing buffer or performing a
6777 The format is is "tra !! 5438 ftrace_dump_on_oops.
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 5439
6784 The above will enable !! 5440 To turn off having tracepoints sent to printk,
6785 event but only trigge !! 5441 echo 0 > /proc/sys/kernel/tracepoint_printk
6786 event is "2" (TASK_UN !! 5442 Note, echoing 1 into this file without the
>> 5443 tracepoint_printk kernel cmdline option has no effect.
6787 5444
6788 See also "Event trigg !! 5445 ** CAUTION **
6789 5446
>> 5447 Having tracepoints sent to printk() and activating high
>> 5448 frequency tracepoints such as irq or sched, can cause
>> 5449 the system to live lock.
6790 5450
6791 traceoff_on_warning 5451 traceoff_on_warning
6792 [FTRACE] enable this 5452 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 5453 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 5454 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 5455 file located in /sys/kernel/debug/tracing/
6796 5456
6797 This option is useful 5457 This option is useful, as it disables the trace before
6798 the WARNING dump is c 5458 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 5459 be filled with content caused by the warning output.
6800 5460
6801 This option can also 5461 This option can also be set at run time via the sysctl
6802 option: kernel/trace 5462 option: kernel/traceoff_on_warning
6803 5463
6804 transparent_hugepage= 5464 transparent_hugepage=
6805 [KNL] 5465 [KNL]
6806 Format: [always|madvi 5466 Format: [always|madvise|never]
6807 Can be used to contro 5467 Can be used to control the default behavior of the system
6808 with respect to trans 5468 with respect to transparent hugepages.
6809 See Documentation/adm 5469 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 5470 for more details.
6811 5471
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 5472 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 5473 Format: <string>
6850 [x86] reliable: mark 5474 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 5475 disables clocksource verification at runtime, as well
6852 as the stability chec 5476 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 5477 high-resolution timer mode on older hardware, and in
6854 virtualized environme 5478 virtualized environment.
6855 [x86] noirqtime: Do n 5479 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 5480 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 5481 platforms where RDTSC is slow and this accounting
6858 can add overhead. 5482 can add overhead.
6859 [x86] unstable: mark 5483 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 5484 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 5485 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 5486 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 5487 in situations with strict latency requirements (where
6864 interruptions from cl 5488 interruptions from clocksource watchdog are not
6865 acceptable). 5489 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 5490
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 5491 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 5492 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 5493 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 5494 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 5495 Format: <unsigned int>
6882 5496
6883 tsx= [X86] Control Transac 5497 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 5498 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 5499 support TSX control.
6886 5500
6887 This parameter contro 5501 This parameter controls the TSX feature. The options are:
6888 5502
6889 on - Enable TSX 5503 on - Enable TSX on the system. Although there are
6890 mitigations f 5504 mitigations for all known security vulnerabilities,
6891 TSX has been 5505 TSX has been known to be an accelerator for
6892 several previ 5506 several previous speculation-related CVEs, and
6893 so there may 5507 so there may be unknown security risks associated
6894 with leaving 5508 with leaving it enabled.
6895 5509
6896 off - Disable TSX 5510 off - Disable TSX on the system. (Note that this
6897 option takes 5511 option takes effect only on newer CPUs which are
6898 not vulnerabl 5512 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 5513 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 5514 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 5515 update. This new MSR allows for the reliable
6902 deactivation 5516 deactivation of the TSX functionality.)
6903 5517
6904 auto - Disable TSX 5518 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 5519 otherwise enable TSX on the system.
6906 5520
6907 Not specifying this o 5521 Not specifying this option is equivalent to tsx=off.
6908 5522
6909 See Documentation/adm 5523 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 5524 for more details.
6911 5525
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 5526 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 5527 Abort (TAA) vulnerability.
6914 5528
6915 Similar to Micro-arch 5529 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 5530 certain CPUs that support Transactional
6917 Synchronization Exten 5531 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 5532 exploit against CPU internal buffers which can forward
6919 information to a disc 5533 information to a disclosure gadget under certain
6920 conditions. 5534 conditions.
6921 5535
6922 In vulnerable process 5536 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 5537 data can be used in a cache side channel attack, to
6924 access data to which 5538 access data to which the attacker does not have direct
6925 access. 5539 access.
6926 5540
6927 This parameter contro 5541 This parameter controls the TAA mitigation. The
6928 options are: 5542 options are:
6929 5543
6930 full - Enable T 5544 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 5545 if TSX is enabled.
6932 5546
6933 full,nosmt - Enable T 5547 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 5548 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 5549 is not disabled because CPU is not
6936 vulnerab 5550 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 5551 off - Unconditionally disable TAA mitigation
6938 5552
6939 On MDS-affected machi 5553 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 5554 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 5555 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 5556 this mitigation, you need to specify mds=off too.
6943 5557
6944 Not specifying this o 5558 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 5559 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 5560 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 5561 required and doesn't provide any additional
6948 mitigation. 5562 mitigation.
6949 5563
6950 For details see: 5564 For details see:
6951 Documentation/admin-g 5565 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 5566
6953 turbografx.map[2|3]= [HW,JOY] 5567 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 5568 TurboGraFX parallel port interface
6955 Format: 5569 Format:
6956 <port#>,<js1>,<js2>,< 5570 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 5571 See also Documentation/input/devices/joystick-parport.rst
6958 5572
6959 udbg-immortal [PPC] When debugging 5573 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 5574 happen after console_init() and before a proper
6961 console driver takes 5575 console driver takes over, this boot options might
6962 help "seeing" what's 5576 help "seeing" what's going on.
6963 5577
6964 uhash_entries= [KNL,NET] 5578 uhash_entries= [KNL,NET]
6965 Set number of hash bu 5579 Set number of hash buckets for UDP/UDP-Lite connections
6966 5580
6967 uhci-hcd.ignore_oc= 5581 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 5582 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 5583 Some badly-designed motherboards generate lots of
6970 bogus events, for por 5584 bogus events, for ports that aren't wired to
6971 anything. Set this p 5585 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 5586 Note that genuine overcurrent events won't be
6973 reported either. 5587 reported either.
6974 5588
6975 unknown_nmi_panic 5589 unknown_nmi_panic
6976 [X86] Cause panic on 5590 [X86] Cause panic on unknown NMI.
6977 5591
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= 5592 usbcore.authorized_default=
6985 [USB] Default USB dev 5593 [USB] Default USB device authorization:
6986 (default -1 = authori !! 5594 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 5595 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 5596 if device connected to internal port)
6989 5597
6990 usbcore.autosuspend= 5598 usbcore.autosuspend=
6991 [USB] The autosuspend 5599 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 5600 for newly-detected USB devices (default 2). This
6993 is the time required 5601 is the time required before an idle device will be
6994 autosuspended. Devic 5602 autosuspended. Devices for which the delay is set
6995 to a negative value w 5603 to a negative value won't be autosuspended at all.
6996 5604
6997 usbcore.usbfs_snoop= 5605 usbcore.usbfs_snoop=
6998 [USB] Set to log all 5606 [USB] Set to log all usbfs traffic (default 0 = off).
6999 5607
7000 usbcore.usbfs_snoop_max= 5608 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 5609 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 5610 (default = 65536).
7003 5611
7004 usbcore.blinkenlights= 5612 usbcore.blinkenlights=
7005 [USB] Set to cycle le 5613 [USB] Set to cycle leds on hubs (default 0 = off).
7006 5614
7007 usbcore.old_scheme_first= 5615 usbcore.old_scheme_first=
7008 [USB] Start with the 5616 [USB] Start with the old device initialization
7009 scheme (default 0 = o 5617 scheme (default 0 = off).
7010 5618
7011 usbcore.usbfs_memory_mb= 5619 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 5620 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 5621 usbfs (default = 16, 0 = max = 2047).
7014 5622
7015 usbcore.use_both_schemes= 5623 usbcore.use_both_schemes=
7016 [USB] Try the other d 5624 [USB] Try the other device initialization scheme
7017 if the first one fail 5625 if the first one fails (default 1 = enabled).
7018 5626
7019 usbcore.initial_descriptor_timeout= 5627 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 5628 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 5629 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 5630 (default 5000 = 5.0 seconds).
7023 5631
7024 usbcore.nousb [USB] Disable the USB 5632 usbcore.nousb [USB] Disable the USB subsystem
7025 5633
7026 usbcore.quirks= 5634 usbcore.quirks=
7027 [USB] A list of quirk 5635 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 5636 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 5637 commas. Each entry has the form
7030 VendorID:ProductID:Fl 5638 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 5639 numbers and Flags is a set of letters. Each letter
7032 will change the built 5640 will change the built-in quirk; setting it if it is
7033 clear and clearing it 5641 clear and clearing it if it is set. The letters have
7034 the following meaning 5642 the following meanings:
7035 a = USB_QUIRK 5643 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 5644 descriptors must not be fetched using
7037 a 255 5645 a 255-byte read);
7038 b = USB_QUIRK 5646 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 5647 correctly so reset it instead);
7040 c = USB_QUIRK 5648 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 5649 Set-Interface requests);
7042 d = USB_QUIRK 5650 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 5651 handle its Configuration or Interface
7044 strin 5652 strings);
7045 e = USB_QUIRK 5653 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 5654 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 5655 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 5656 more interface descriptions than the
7049 bNumI 5657 bNumInterfaces count, and can't handle
7050 talki 5658 talking to these interfaces);
7051 g = USB_QUIRK 5659 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 5660 during initialization, after we read
7053 the d 5661 the device descriptor);
7054 h = USB_QUIRK 5662 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 5663 high speed and super speed interrupt
7056 endpo 5664 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 5665 require the interval in microframes (1
7058 micro 5666 microframe = 125 microseconds) to be
7059 calcu 5667 calculated as interval = 2 ^
7060 (bInt 5668 (bInterval-1).
7061 Devic 5669 Devices with this quirk report their
7062 bInte 5670 bInterval as the result of this
7063 calcu 5671 calculation instead of the exponent
7064 varia 5672 variable used in the calculation);
7065 i = USB_QUIRK 5673 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 5674 handle device_qualifier descriptor
7067 reque 5675 requests);
7068 j = USB_QUIRK 5676 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 5677 generates spurious wakeup, ignore
7070 remot 5678 remote wakeup capability);
7071 k = USB_QUIRK 5679 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 5680 Power Management);
7073 l = USB_QUIRK 5681 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 5682 (Device reports its bInterval as linear
7075 frame 5683 frames instead of the USB 2.0
7076 calcu 5684 calculation);
7077 m = USB_QUIRK 5685 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 5686 to be disconnected before suspend to
7079 preve 5687 prevent spurious wakeup);
7080 n = USB_QUIRK 5688 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 5689 pause after every control message);
7082 o = USB_QUIRK 5690 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 5691 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 5692 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 5693
7089 usbhid.mousepoll= 5694 usbhid.mousepoll=
7090 [USBHID] The interval 5695 [USBHID] The interval which mice are to be polled at.
7091 5696
7092 usbhid.jspoll= 5697 usbhid.jspoll=
7093 [USBHID] The interval 5698 [USBHID] The interval which joysticks are to be polled at.
7094 5699
7095 usbhid.kbpoll= 5700 usbhid.kbpoll=
7096 [USBHID] The interval 5701 [USBHID] The interval which keyboards are to be polled at.
7097 5702
7098 usb-storage.delay_use= 5703 usb-storage.delay_use=
7099 [UMS] The delay in se 5704 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 5705 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 5706
7105 usb-storage.quirks= 5707 usb-storage.quirks=
7106 [UMS] A list of quirk 5708 [UMS] A list of quirks entries to supplement or
7107 override the built-in 5709 override the built-in unusual_devs list. List
7108 entries are separated 5710 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 5711 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 5712 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 5713 Flags is a set of characters, each corresponding
7112 to a common usb-stora 5714 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 5715 a = SANE_SENSE (collect more than 18 bytes
7114 of se 5716 of sense data, not on uas);
7115 b = BAD_SENSE 5717 b = BAD_SENSE (don't collect more than 18
7116 bytes 5718 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 5719 c = FIX_CAPACITY (decrease the reported
7118 devic 5720 device capacity by one sector);
7119 d = NO_READ_D 5721 d = NO_READ_DISC_INFO (don't use
7120 READ_ 5722 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 5723 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 5724 READ_CAPACITY_16 command);
7123 f = NO_REPORT 5725 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 5726 command, uas only);
7125 g = MAX_SECTO 5727 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 5728 240 sectors at a time, uas only);
7127 h = CAPACITY_ 5729 h = CAPACITY_HEURISTICS (decrease the
7128 repor 5730 reported device capacity by one
7129 secto 5731 sector if the number is odd);
7130 i = IGNORE_DE 5732 i = IGNORE_DEVICE (don't bind to this
7131 devic 5733 device);
7132 j = NO_REPORT 5734 j = NO_REPORT_LUNS (don't use report luns
7133 comma 5735 command, uas only);
7134 k = NO_SAME ( 5736 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 5737 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 5738 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 5739 m = MAX_SECTORS_64 (don't transfer more
7138 than 5740 than 64 sectors = 32 KB at a time,
7139 not o 5741 not on uas);
7140 n = INITIAL_R 5742 n = INITIAL_READ10 (force a retry of the
7141 initi 5743 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 5744 o = CAPACITY_OK (accept the capacity
7143 repor 5745 reported by the device, not on uas);
7144 p = WRITE_CAC 5746 p = WRITE_CACHE (the device cache is ON
7145 by de 5747 by default, not on uas);
7146 r = IGNORE_RE 5748 r = IGNORE_RESIDUE (the device reports
7147 bogus 5749 bogus residue values, not on uas);
7148 s = SINGLE_LU 5750 s = SINGLE_LUN (the device has only one
7149 Logic 5751 Logical Unit);
7150 t = NO_ATA_1X 5752 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 5753 commands, uas only);
7152 u = IGNORE_UA 5754 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 5755 w = NO_WP_DETECT (don't test whether the
7154 mediu 5756 medium is write-protected).
7155 y = ALWAYS_SY 5757 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 5758 even if the device claims no cache,
7157 not o 5759 not on uas)
7158 Example: quirks=0419: 5760 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 5761
7160 user_debug= [KNL,ARM] 5762 user_debug= [KNL,ARM]
7161 Format: <int> 5763 Format: <int>
7162 See arch/arm/Kconfig. 5764 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 5765 1 - undefined instruction events
7164 2 - system c 5766 2 - system calls
7165 4 - invalid 5767 4 - invalid data aborts
7166 8 - SIGSEGV 5768 8 - SIGSEGV faults
7167 16 - SIGBUS f 5769 16 - SIGBUS faults
7168 Example: user_debug=3 5770 Example: user_debug=31
7169 5771
7170 userpte= 5772 userpte=
7171 [X86,EARLY] Flags con !! 5773 [X86] Flags controlling user PTE allocations.
7172 5774
7173 nohigh = do n 5775 nohigh = do not allocate PTE pages in
7174 HIGHM 5776 HIGHMEM regardless of setting
7175 of CO 5777 of CONFIG_HIGHPTE.
7176 5778
7177 vdso= [X86,SH,SPARC] !! 5779 vdso= [X86,SH]
7178 On X86_32, this is an 5780 On X86_32, this is an alias for vdso32=. Otherwise:
7179 5781
7180 vdso=1: enable VDSO ( 5782 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 5783 vdso=0: disable VDSO mapping
7182 5784
7183 vdso32= [X86] Control the 32- 5785 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 5786 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 5787 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 5788
7187 See the help text for 5789 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 5790 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 5791 vdso32=0; otherwise, the default is vdso32=1.
7190 5792
7191 For compatibility wit 5793 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 5794 alias for vdso32=0.
7193 5795
7194 Try vdso32=0 if you e 5796 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 5797 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 5798
7197 video= [FB,EARLY] Frame buff !! 5799 vector= [IA-64,SMP]
>> 5800 vector=percpu: enable percpu vector domain
>> 5801
>> 5802 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 5803 See Documentation/fb/modedb.rst.
7199 5804
7200 video.brightness_switch_enabled= [ACP !! 5805 video.brightness_switch_enabled= [0,1]
7201 Format: [0|1] <<
7202 If set to 1, on recei 5806 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 5807 generated by hotkey, video driver will adjust brightness
7204 level and then send o 5808 level and then send out the event to user space through
7205 the allocated input d !! 5809 the allocated input device; If set to 0, video driver
7206 will only send out th 5810 will only send out the event without touching backlight
7207 brightness level. 5811 brightness level.
7208 default: 1 5812 default: 1
7209 5813
7210 virtio_mmio.device= 5814 virtio_mmio.device=
7211 [VMMIO] Memory mapped 5815 [VMMIO] Memory mapped virtio (platform) device.
7212 5816
7213 <size>@<basead 5817 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 5818 where:
7215 <size> := 5819 <size> := size (can use standard suffixes
7216 5820 like K, M and G)
7217 <baseaddr> := 5821 <baseaddr> := physical base address
7218 <irq> := 5822 <irq> := interrupt number (as passed to
7219 5823 request_irq())
7220 <id> := 5824 <id> := (optional) platform device id
7221 example: 5825 example:
7222 virtio_mmio.d 5826 virtio_mmio.device=1K@0x100b0000:48:7
7223 5827
7224 Can be used multiple 5828 Can be used multiple times for multiple devices.
7225 5829
7226 vga= [BOOT,X86-32] Select 5830 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 5831 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 5832 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 5833 Use vga=ask for menu.
7230 This is actually a bo 5834 This is actually a boot loader parameter; the value is
7231 passed to the kernel 5835 passed to the kernel using a special protocol.
7232 5836
7233 vm_debug[=options] [KNL] Availab 5837 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 5838 May slow down system boot speed, especially when
7235 enabled on systems wi 5839 enabled on systems with a large amount of memory.
7236 All options are enabl 5840 All options are enabled by default, and this
7237 interface is meant to 5841 interface is meant to allow for selectively
7238 enabling or disabling 5842 enabling or disabling specific virtual memory
7239 debugging features. 5843 debugging features.
7240 5844
7241 Available options are 5845 Available options are:
7242 P Enable page s 5846 P Enable page structure init time poisoning
7243 - Disable all o 5847 - Disable all of the above options
7244 5848
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 5849 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 5850 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 5851 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 5852 decrease the size and leave more room for directly
7249 for directly mapped k !! 5853 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 5854
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 5855 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 5856 Sets the memory size reserved for contiguous memory
7256 allocations for the v 5857 allocations for the vmcp device driver.
7257 5858
7258 vmhalt= [KNL,S390] Perform z/ 5859 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 5860 Format: <command>
7260 5861
7261 vmpanic= [KNL,S390] Perform z/ 5862 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 5863 Format: <command>
7263 5864
7264 vmpoff= [KNL,S390] Perform z/ 5865 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 5866 Format: <command>
7266 5867
7267 vsyscall= [X86-64,EARLY] !! 5868 vsyscall= [X86-64]
7268 Controls the behavior 5869 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 5870 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 5871 code). Most statically-linked binaries and older
7271 versions of glibc use 5872 versions of glibc use these calls. Because these
7272 functions are at fixe 5873 functions are at fixed addresses, they make nice
7273 targets for exploits 5874 targets for exploits that can control RIP.
7274 5875
7275 emulate Vsyscalls !! 5876 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 5877 emulated reasonably safely. The vsyscall
7277 readable. !! 5878 page is readable.
7278 5879
7279 xonly [default] !! 5880 xonly Vsyscalls turn into traps and are
7280 emulated 5881 emulated reasonably safely. The vsyscall
7281 page is n 5882 page is not readable.
7282 5883
7283 none Vsyscalls 5884 none Vsyscalls don't work at all. This makes
7284 them quit 5885 them quite hard to use for exploits but
7285 might bre 5886 might break your system.
7286 5887
7287 vt.color= [VT] Default text col 5888 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 5889 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 5890 Default: 0x07 = light gray on black.
7290 5891
7291 vt.cur_default= [VT] Default cursor s 5892 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 5893 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 5894 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 5895 see VGA-softcursor.txt. Default: 2 = underline.
7295 5896
7296 vt.default_blu= [VT] 5897 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 5898 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 5899 Change the default blue palette of the console.
7299 This is a 16-member a 5900 This is a 16-member array composed of values
7300 ranging from 0-255. 5901 ranging from 0-255.
7301 5902
7302 vt.default_grn= [VT] 5903 vt.default_grn= [VT]
7303 Format: <green0>,<gre 5904 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 5905 Change the default green palette of the console.
7305 This is a 16-member a 5906 This is a 16-member array composed of values
7306 ranging from 0-255. 5907 ranging from 0-255.
7307 5908
7308 vt.default_red= [VT] 5909 vt.default_red= [VT]
7309 Format: <red0>,<red1> 5910 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 5911 Change the default red palette of the console.
7311 This is a 16-member a 5912 This is a 16-member array composed of values
7312 ranging from 0-255. 5913 ranging from 0-255.
7313 5914
7314 vt.default_utf8= 5915 vt.default_utf8=
7315 [VT] 5916 [VT]
7316 Format=<0|1> 5917 Format=<0|1>
7317 Set system-wide defau 5918 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 5919 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 5920 newly opened terminals.
7320 5921
7321 vt.global_cursor_default= 5922 vt.global_cursor_default=
7322 [VT] 5923 [VT]
7323 Format=<-1|0|1> 5924 Format=<-1|0|1>
7324 Set system-wide defau 5925 Set system-wide default for whether a cursor
7325 is shown on new VTs. 5926 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 5927 i.e. cursors will be created by default unless
7327 overridden by individ 5928 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 5929 cursors, 1 will display them.
7329 5930
7330 vt.italic= [VT] Default color fo 5931 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 5932 Default: 2 = green.
7332 5933
7333 vt.underline= [VT] Default color fo 5934 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 5935 Default: 3 = cyan.
7335 5936
7336 watchdog timers [HW,WDT] For informat 5937 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 5938 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 5939 or other driver-specific files in the
7339 Documentation/watchdo 5940 Documentation/watchdog/ directory.
7340 5941
7341 watchdog_thresh= 5942 watchdog_thresh=
7342 [KNL] 5943 [KNL]
7343 Set the hard lockup d 5944 Set the hard lockup detector stall duration
7344 threshold in seconds. 5945 threshold in seconds. The soft lockup detector
7345 threshold is set to t 5946 threshold is set to twice the value. A value of 0
7346 disables both lockup 5947 disables both lockup detectors. Default is 10
7347 seconds. 5948 seconds.
7348 5949
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= 5950 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 5951 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 5952 warn stall conditions and dump internal state to
7359 help debugging. 0 di 5953 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 5954 detection; otherwise, it's the stall threshold
7361 duration in seconds. 5955 duration in seconds. The default value is 30 and
7362 it can be updated at 5956 it can be updated at runtime by writing to the
7363 corresponding sysfs f 5957 corresponding sysfs file.
7364 5958
7365 workqueue.cpu_intensive_thresh_us= !! 5959 workqueue.disable_numa
7366 Per-cpu work items wh !! 5960 By default, all work items queued to unbound
7367 threshold are automat !! 5961 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 5962 issued on, which results in better behavior in
7369 them from noticeably !! 5963 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 5964 whatever reason, this option can be used. Note
7371 !! 5965 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 5966 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 5967
7386 workqueue.power_efficient 5968 workqueue.power_efficient
7387 Per-cpu workqueues ar 5969 Per-cpu workqueues are generally preferred because
7388 they show better perf 5970 they show better performance thanks to cache
7389 locality; unfortunate 5971 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 5972 be more power hungry than unbound workqueues.
7391 5973
7392 Enabling this makes t 5974 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 5975 were observed to contribute significantly to power
7394 consumption unbound, 5976 consumption unbound, leading to measurably lower
7395 power usage at the co 5977 power usage at the cost of small performance
7396 overhead. 5978 overhead.
7397 5979
7398 The default value of 5980 The default value of this parameter is determined by
7399 the config option CON 5981 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 5982
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 5983 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 5984 Workqueue used to implicitly guarantee that work
7415 items queued without 5985 items queued without explicit CPU specified are put
7416 on the local CPU. Th 5986 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 5987 and while local CPU is still preferred work items
7418 may be put on foreign 5988 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 5989 forces round-robin CPU selection to flush out
7420 usages which depend o 5990 usages which depend on the now broken guarantee.
7421 When enabled, memory 5991 When enabled, memory and cache locality will be
7422 impacted. 5992 impacted.
7423 5993
7424 writecombine= [LOONGARCH,EARLY] Con !! 5994 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 5995 default x2apic cluster mode on platforms
7432 supporting x2apic. 5996 supporting x2apic.
7433 5997
7434 xen_512gb_limit [KNL,X86-64,X 5998 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 5999 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6000 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6001 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6002 save/restore/migration must be enabled to handle larger
7439 domains. 6003 domains.
7440 6004
7441 xen_emul_unplug= [HW,X !! 6005 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6006 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6007 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6008 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6009 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6010 nics -- unplug network devices
7447 all -- unplug all emu 6011 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6012 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6013 unnecessary even if the host did not respond to
7450 the unplug pr 6014 the unplug protocol
7451 never -- do not unplu 6015 never -- do not unplug even if version check succeeds
7452 6016
7453 xen_legacy_crash [X86,XEN,EARL !! 6017 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6018 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6019 panic() code such as dumping handler.
7456 6020
7457 xen_mc_debug [X86,XEN,EARLY] !! 6021 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 6022 Disables the qspinlock slowpath using Xen PV optimizations.
7459 Enabling this feature !! 6023 This parameter is obsoleted by "nopvspin" parameter, which
7460 bit, so it should onl !! 6024 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 6025
7469 xen_nopv [X86] 6026 xen_nopv [X86]
7470 Disables the PV optim 6027 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6028 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6029 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6030 has equivalent effect for XEN platform.
7474 6031
7475 xen_no_vector_callback 6032 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6033 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6034 event channel interrupts.
7478 6035
7479 xen_scrub_pages= [XEN] 6036 xen_scrub_pages= [XEN]
7480 Boolean option to con 6037 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6038 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6039 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6040 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6041
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6042 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6043 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6044 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6045 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 6046 improve timer resolution at the expense of processing
7490 more timer interrupts 6047 more timer interrupts.
7491 6048
7492 xen.balloon_boot_timeout= [XEN] <<
7493 The time (in seconds) <<
7494 in case initial ballo <<
7495 Applies only when run <<
7496 started with less mem <<
7497 max. Default is 180. <<
7498 <<
7499 xen.event_eoi_delay= [XEN] 6049 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 6050 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 6051 storms (jiffies). Default is 10.
7502 6052
7503 xen.event_loop_timeout= [XEN] 6053 xen.event_loop_timeout= [XEN]
7504 After which time (jif 6054 After which time (jiffies) the event handling loop
7505 should start to delay 6055 should start to delay EOI handling. Default is 2.
7506 6056
7507 xen.fifo_events= [XEN] 6057 xen.fifo_events= [XEN]
7508 Boolean parameter to 6058 Boolean parameter to disable using fifo event handling
7509 even if available. No 6059 even if available. Normally fifo event handling is
7510 preferred over the 2- 6060 preferred over the 2-level event handling, as it is
7511 fairer and the number 6061 fairer and the number of possible event channels is
7512 much higher. Default 6062 much higher. Default is on (use fifo events).
7513 6063
>> 6064 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6065 Disables the PV optimizations forcing the guest to run
>> 6066 as generic guest with no PV drivers. Currently support
>> 6067 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6068
>> 6069 nopvspin [X86,XEN,KVM]
>> 6070 Disables the qspinlock slow path using PV optimizations
>> 6071 which allow the hypervisor to 'idle' the guest on lock
>> 6072 contention.
>> 6073
7514 xirc2ps_cs= [NET,PCMCIA] 6074 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6075 Format:
7516 <irq>,<irq_mask>,<io> 6076 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6077
7518 xive= [PPC] 6078 xive= [PPC]
7519 By default on POWER9 6079 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6080 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6081 allows the fallback firmware mode to be used:
7522 6082
7523 off Fallback to 6083 off Fallback to firmware control of XIVE interrupt
7524 controller 6084 controller on both pseries and powernv
7525 platforms. 6085 platforms. Only useful on POWER9 and above.
7526 6086
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] 6087 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6088 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6089 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6090 consulted in header drivers/usb/host/xhci.h.
7537 6091
7538 xmon [PPC,EARLY] !! 6092 xmon [PPC]
7539 Format: { early | on 6093 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 6094 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 6095 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 6096 early Call xmon as early as possible on boot; xmon
7543 debugger is c 6097 debugger is called from setup_arch().
7544 on xmon debugger 6098 on xmon debugger hooks will be installed so xmon
7545 is only calle 6099 is only called on a kernel crash. Default mode,
7546 i.e. either " 6100 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 6101 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 6102 rw xmon debugger hooks will be installed so xmon
7549 is called onl 6103 is called only on a kernel crash, mode is write,
7550 meaning SPR r 6104 meaning SPR registers, memory and, other data
7551 can be writte 6105 can be written using xmon commands.
7552 ro same as "rw" 6106 ro same as "rw" option above but SPR registers,
7553 memory, and o 6107 memory, and other data can't be written using
7554 xmon commands 6108 xmon commands.
7555 off xmon is disab 6109 off xmon is disabled.
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