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_EVENTS
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
78 Enable AML "Debug" out 63 Enable AML "Debug" output, i.e., stores to the Debug
79 object while interpret 64 object while interpreting AML:
80 acpi.debug_layer=0 65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
81 Enable all messages re 66 Enable all messages related to ACPI hardware:
82 acpi.debug_layer=0 67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
83 68
84 Some values produce so 69 Some values produce so much output that the system is
85 unusable. The "log_bu 70 unusable. The "log_buf_len" parameter may be useful
86 if you need to capture 71 if you need to capture more output.
87 72
88 acpi_enforce_resources= [ACPI] 73 acpi_enforce_resources= [ACPI]
89 { strict | lax | no } 74 { strict | lax | no }
90 Check for resource con 75 Check for resource conflicts between native drivers
91 and ACPI OperationRegi 76 and ACPI OperationRegions (SystemIO and SystemMemory
92 only). IO ports and me 77 only). IO ports and memory declared in ACPI might be
93 used by the ACPI subsy 78 used by the ACPI subsystem in arbitrary AML code and
94 can interfere with leg 79 can interfere with legacy drivers.
95 strict (default): acce 80 strict (default): access to resources claimed by ACPI
96 is denied; legacy driv 81 is denied; legacy drivers trying to access reserved
97 resources will fail to 82 resources will fail to bind to device using them.
98 lax: access to resourc 83 lax: access to resources claimed by ACPI is allowed;
99 legacy drivers trying 84 legacy drivers trying to access reserved resources
100 will bind successfully 85 will bind successfully but a warning message is logged.
101 no: ACPI OperationRegi 86 no: ACPI OperationRegions are not marked as reserved,
102 no further checks are 87 no further checks are performed.
103 88
104 acpi_force_table_verification [HW,AC !! 89 acpi_force_table_verification [HW,ACPI]
105 Enable table checksum 90 Enable table checksum verification during early stage.
106 By default, this is di 91 By default, this is disabled due to x86 early mapping
107 size limitation. 92 size limitation.
108 93
109 acpi_irq_balance [HW,ACPI] 94 acpi_irq_balance [HW,ACPI]
110 ACPI will balance acti 95 ACPI will balance active IRQs
111 default in APIC mode 96 default in APIC mode
112 97
113 acpi_irq_nobalance [HW,ACPI] 98 acpi_irq_nobalance [HW,ACPI]
114 ACPI will not move act 99 ACPI will not move active IRQs (default)
115 default in PIC mode 100 default in PIC mode
116 101
117 acpi_irq_isa= [HW,ACPI] If irq_balan 102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
118 Format: <irq>,<irq>... 103 Format: <irq>,<irq>...
119 104
120 acpi_irq_pci= [HW,ACPI] If irq_balan 105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
121 use by PCI 106 use by PCI
122 Format: <irq>,<irq>... 107 Format: <irq>,<irq>...
123 108
124 acpi_mask_gpe= [HW,ACPI] 109 acpi_mask_gpe= [HW,ACPI]
125 Due to the existence o 110 Due to the existence of _Lxx/_Exx, some GPEs triggered
126 by unsupported hardwar 111 by unsupported hardware/firmware features can result in
127 GPE floodings that can 112 GPE floodings that cannot be automatically disabled by
128 the GPE dispatcher. 113 the GPE dispatcher.
129 This facility can be u 114 This facility can be used to prevent such uncontrolled
130 GPE floodings. 115 GPE floodings.
131 Format: <byte> or <bit 116 Format: <byte> or <bitmap-list>
132 117
133 acpi_no_auto_serialize [HW,ACPI] 118 acpi_no_auto_serialize [HW,ACPI]
134 Disable auto-serializa 119 Disable auto-serialization of AML methods
135 AML control methods th 120 AML control methods that contain the opcodes to create
136 named objects will be 121 named objects will be marked as "Serialized" by the
137 auto-serialization fea 122 auto-serialization feature.
138 This feature is enable 123 This feature is enabled by default.
139 This option allows to 124 This option allows to turn off the feature.
140 125
141 acpi_no_memhotplug [ACPI] Disable memo 126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
142 kernels. 127 kernels.
143 128
144 acpi_no_static_ssdt [HW,ACPI,EARLY !! 129 acpi_no_static_ssdt [HW,ACPI]
145 Disable installation o 130 Disable installation of static SSDTs at early boot time
146 By default, SSDTs cont 131 By default, SSDTs contained in the RSDT/XSDT will be
147 installed automaticall 132 installed automatically and they will appear under
148 /sys/firmware/acpi/tab 133 /sys/firmware/acpi/tables.
149 This option turns off 134 This option turns off this feature.
150 Note that specifying t 135 Note that specifying this option does not affect
151 dynamic table installa 136 dynamic table installation which will install SSDT
152 tables to /sys/firmwar 137 tables to /sys/firmware/acpi/tables/dynamic.
153 138
154 acpi_no_watchdog [HW,ACPI,WDT] 139 acpi_no_watchdog [HW,ACPI,WDT]
155 Ignore the ACPI-based 140 Ignore the ACPI-based watchdog interface (WDAT) and let
156 a native driver contro 141 a native driver control the watchdog device instead.
157 142
158 acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] !! 143 acpi_rsdp= [ACPI,EFI,KEXEC]
159 Pass the RSDP address 144 Pass the RSDP address to the kernel, mostly used
160 on machines running EF 145 on machines running EFI runtime service to boot the
161 second kernel for kdum 146 second kernel for kdump.
162 147
163 acpi_os_name= [HW,ACPI] Tell ACPI BI 148 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
164 Format: To spoof as Wi 149 Format: To spoof as Windows 98: ="Microsoft Windows"
165 150
166 acpi_rev_override [ACPI] Override the 151 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167 of 2 which is mandated 152 of 2 which is mandated by ACPI 6) as the supported ACPI
168 specification revision 153 specification revision (when using this switch, it may
169 be necessary to carry 154 be necessary to carry out a cold reboot _twice_ in a
170 row to make it take ef 155 row to make it take effect on the platform firmware).
171 156
172 acpi_osi= [HW,ACPI] Modify list 157 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" 158 acpi_osi="string1" # add string1
174 acpi_osi="!string2" 159 acpi_osi="!string2" # remove string2
175 acpi_osi=!* 160 acpi_osi=!* # remove all strings
176 acpi_osi=! 161 acpi_osi=! # disable all built-in OS vendor
177 162 strings
178 acpi_osi=!! 163 acpi_osi=!! # enable all built-in OS vendor
179 164 strings
180 acpi_osi= 165 acpi_osi= # disable all strings
181 166
182 'acpi_osi=!' can be us 167 'acpi_osi=!' can be used in combination with single or
183 multiple 'acpi_osi="st 168 multiple 'acpi_osi="string1"' to support specific OS
184 vendor string(s). Not 169 vendor string(s). Note that such command can only
185 affect the default sta 170 affect the default state of the OS vendor strings, thus
186 it cannot affect the d 171 it cannot affect the default state of the feature group
187 strings and the curren 172 strings and the current state of the OS vendor strings,
188 specifying it multiple 173 specifying it multiple times through kernel command line
189 is meaningless. This 174 is meaningless. This command is useful when one do not
190 care about the state o 175 care about the state of the feature group strings which
191 should be controlled b 176 should be controlled by the OSPM.
192 Examples: 177 Examples:
193 1. 'acpi_osi=! acpi_ 178 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194 to 'acpi_osi="Win 179 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 can make '_OSI("W 180 can make '_OSI("Windows 2000")' TRUE.
196 181
197 'acpi_osi=' cannot be 182 'acpi_osi=' cannot be used in combination with other
198 'acpi_osi=' command li 183 'acpi_osi=' command lines, the _OSI method will not
199 exist in the ACPI name 184 exist in the ACPI namespace. NOTE that such command can
200 only affect the _OSI s 185 only affect the _OSI support state, thus specifying it
201 multiple times through 186 multiple times through kernel command line is also
202 meaningless. 187 meaningless.
203 Examples: 188 Examples:
204 1. 'acpi_osi=' can m 189 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205 FALSE. 190 FALSE.
206 191
207 'acpi_osi=!*' can be u 192 'acpi_osi=!*' can be used in combination with single or
208 multiple 'acpi_osi="st 193 multiple 'acpi_osi="string1"' to support specific
209 string(s). Note that 194 string(s). Note that such command can affect the
210 current state of both 195 current state of both the OS vendor strings and the
211 feature group strings, 196 feature group strings, thus specifying it multiple times
212 through kernel command 197 through kernel command line is meaningful. But it may
213 still not able to affe 198 still not able to affect the final state of a string if
214 there are quirks relat 199 there are quirks related to this string. This command
215 is useful when one wan 200 is useful when one want to control the state of the
216 feature group strings 201 feature group strings to debug BIOS issues related to
217 the OSPM features. 202 the OSPM features.
218 Examples: 203 Examples:
219 1. 'acpi_osi="Module 204 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220 '_OSI("Module Dev 205 '_OSI("Module Device")' FALSE.
221 2. 'acpi_osi=!* acpi 206 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222 '_OSI("Module Dev 207 '_OSI("Module Device")' TRUE.
223 3. 'acpi_osi=! acpi_ 208 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224 equivalent to 209 equivalent to
225 'acpi_osi=!* acpi 210 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226 and 211 and
227 'acpi_osi=!* acpi 212 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228 they all will mak 213 they all will make '_OSI("Windows 2000")' TRUE.
229 214
230 acpi_pm_good [X86] 215 acpi_pm_good [X86]
231 Override the pmtimer b 216 Override the pmtimer bug detection: force the kernel
232 to assume that this ma 217 to assume that this machine's pmtimer latches its value
233 and always returns goo 218 and always returns good values.
234 219
235 acpi_sci= [HW,ACPI,EARLY] ACPI S !! 220 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge 221 Format: { level | edge | high | low }
237 222
238 acpi_skip_timer_override [HW,ACPI,EARL !! 223 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore I 224 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIO 225 For broken nForce2 BIOS resulting in XT-PIC timer.
241 226
242 acpi_sleep= [HW,ACPI] Sleep option 227 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_ !! 228 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 s4_nohwsig, !! 229 old_ordering, nonvs, sci_force_enable, nobl }
245 sci_force_en <<
246 See Documentation/powe 230 See Documentation/power/video.rst for information on
247 s3_bios and s3_mode. 231 s3_bios and s3_mode.
248 s3_beep is for debuggi 232 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel' 233 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 234 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a !! 235 used during resume from hibernation.
260 old_ordering causes th 236 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 237 control method, with respect to putting devices into
262 low power states, to b 238 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 239 of _PTS is used by default).
264 nonvs prevents the ker 240 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 241 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 242 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 243 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 244 but some broken systems don't work without it).
269 nobl causes the intern 245 nobl causes the internal blacklist of systems known to
270 behave incorrectly in 246 behave incorrectly in some ways with respect to system
271 suspend and resume to 247 suspend and resume to be ignored (use wisely).
272 248
273 acpi_use_timer_override [HW,ACPI,EARLY !! 249 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 250 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 251 that require a timer override, but don't have HPET
276 252
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 253 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 254 kernel's map of available physical RAM.
279 255
280 agp= [AGP] 256 agp= [AGP]
281 { off | try_unsupporte 257 { off | try_unsupported }
282 off: disable AGP suppo 258 off: disable AGP support
283 try_unsupported: try t 259 try_unsupported: try to drive unsupported chipsets
284 (may crash com 260 (may crash computer or cause data corruption)
285 261
286 ALSA [HW,ALSA] 262 ALSA [HW,ALSA]
287 See Documentation/soun 263 See Documentation/sound/alsa-configuration.rst
288 264
289 alignment= [KNL,ARM] 265 alignment= [KNL,ARM]
290 Allow the default user 266 Allow the default userspace alignment fault handler
291 behaviour to be specif 267 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 268 bit 1 enables fixups, and bit 2 sends a segfault.
293 269
294 align_va_addr= [X86-64] 270 align_va_addr= [X86-64]
295 Align virtual addresse 271 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 272 allocating a VMA at process creation time. This option
297 gives you up to 3% per 273 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 274 machines (where it is enabled by default) for a
299 CPU-intensive style be 275 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 276 a microbenchmark depending on workload and compiler.
301 277
302 32: only for 32-bit pr 278 32: only for 32-bit processes
303 64: only for 64-bit pr 279 64: only for 64-bit processes
304 on: enable for both 32 280 on: enable for both 32- and 64-bit processes
305 off: disable for both 281 off: disable for both 32- and 64-bit processes
306 282
307 alloc_snapshot [FTRACE] 283 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 284 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 285 main buffer is allocated. This is handy if debugging
310 and you need to use tr 286 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 287 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 288 to be done where GFP_KERNEL allocations are allowed.
313 289
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] 290 amd_iommu= [HW,X86-64]
326 Pass parameters to the 291 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 292 Possible values are:
328 fullflush - Deprecated !! 293 fullflush - enable flushing of IO/TLB entries when
>> 294 they are unmapped. Otherwise they are
>> 295 flushed before they will be reused, which
>> 296 is a lot of faster
329 off - do not ini 297 off - do not initialize any AMD IOMMU found in
330 the system 298 the system
331 force_isolation - Forc 299 force_isolation - Force device isolation for all
332 devi 300 devices. The IOMMU driver is not
333 allo 301 allowed anymore to lift isolation
334 requ 302 requirements as needed. This option
335 does 303 does not override iommu=pt
336 force_enable - Force e 304 force_enable - Force enable the IOMMU on platforms known
337 to be b 305 to be buggy with IOMMU enabled. Use this
338 option 306 option with care.
339 pgtbl_v1 - Use v1 <<
340 pgtbl_v2 - Use v2 <<
341 irtcachedis - Disable <<
342 307
343 amd_iommu_dump= [HW,X86-64] 308 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 309 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 310 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 311 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 312 IOMMU initialization.
348 313
349 amd_iommu_intr= [HW,X86-64] 314 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 315 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 316 remapping modes:
352 legacy - Use legac 317 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 318 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 319 to inject interrupts directly into guest.
355 This mode 320 This mode requires kvm-amd.avic=1.
356 (Default 321 (Default when IOMMU HW support is present.)
357 322
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 323 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 324 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 325 Format: <a>,<b>
389 See also Documentation 326 See also Documentation/input/joydev/joystick.rst
390 327
391 analog.map= [HW,JOY] Analog joysti 328 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 329 Specifies type or capabilities of an analog joystick
393 connected to one of 16 330 connected to one of 16 gameports
394 Format: <type1>,<type2 331 Format: <type1>,<type2>,..<type16>
395 332
396 apc= [HW,SPARC] 333 apc= [HW,SPARC]
397 Power management funct 334 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 335 Format: noidle
399 Disable APC CPU standb 336 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 337 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 338 APC and your system crashes randomly.
402 339
403 apic= [APIC,X86,EARLY] Advan !! 340 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 341 Change the output verbosity while booting
405 Format: { quiet (defau 342 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 343 Change the amount of debugging information output
407 when initialising the 344 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 345 For X86-32, this can also be used to specify an APIC
409 driver name. 346 driver name.
410 Format: apic=driver_na 347 Format: apic=driver_name
411 Examples: apic=bigsmp 348 Examples: apic=bigsmp
412 349
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 350 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 351 Format: { bsp (default) | all | none }
415 bsp: External NMI is 352 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 353 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 354 backup of CPU 0
418 none: External NMI is 355 none: External NMI is masked for all CPUs. This is
419 useful so that a 356 useful so that a dump capture kernel won't be
420 shot down by NMI 357 shot down by NMI
421 358
422 autoconf= [IPV6] 359 autoconf= [IPV6]
423 See Documentation/netw 360 See Documentation/networking/ipv6.rst.
424 361
>> 362 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 363 Limit apic dumping. The parameter defines the maximal
>> 364 number of local apics being dumped. Also it is possible
>> 365 to set it to "all" by meaning -- no limit here.
>> 366 Format: { 1 (default) | 2 | ... | all }.
>> 367 The parameter valid if only apic=debug or
>> 368 apic=verbose is specified.
>> 369 Example: apic=debug show_lapic=all
>> 370
425 apm= [APM] Advanced Power M 371 apm= [APM] Advanced Power Management
426 See header of arch/x86 372 See header of arch/x86/kernel/apm_32.c.
427 373
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 374 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 375 Format: <io>,<irq>,<nodeID>
437 376
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall 377 arm64.nobti [ARM64] Unconditionally disable Branch Target
442 Identification support 378 Identification support
443 379
444 arm64.nomops [ARM64] Unconditionall <<
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support <<
449 <<
450 arm64.nopauth [ARM64] Unconditionall 380 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
451 support 381 support
452 382
453 arm64.nosme [ARM64] Unconditionall <<
454 Extension support <<
455 <<
456 arm64.nosve [ARM64] Unconditionall <<
457 Extension support <<
458 <<
459 ataflop= [HW,M68k] 383 ataflop= [HW,M68k]
460 384
461 atarimouse= [HW,MOUSE] Atari Mouse 385 atarimouse= [HW,MOUSE] Atari Mouse
462 386
463 atkbd.extra= [HW] Enable extra LEDs 387 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 388 EzKey and similar keyboards
465 389
466 atkbd.reset= [HW] Reset keyboard du 390 atkbd.reset= [HW] Reset keyboard during initialization
467 391
468 atkbd.set= [HW] Select keyboard c 392 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 393 Format: <int> (2 = AT (default), 3 = PS/2)
470 394
471 atkbd.scroll= [HW] Enable scroll whe 395 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 396 keyboards
473 397
474 atkbd.softraw= [HW] Choose between sy 398 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 399 Format: <bool> (0 = real, 1 = synthetic (default))
476 400
477 atkbd.softrepeat= [HW] 401 atkbd.softrepeat= [HW]
478 Use software keyboard 402 Use software keyboard repeat
479 403
480 audit= [KNL] Enable the audit 404 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 405 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 406 0 | off - kernel audit is disabled and can not be
483 enabled until the 407 enabled until the next reboot
484 unset - kernel audit i 408 unset - kernel audit is initialized but disabled and
485 will be fully enab 409 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 410 1 | on - kernel audit is initialized and partially
487 enabled, storing a 411 enabled, storing at most audit_backlog_limit
488 messages in RAM un 412 messages in RAM until it is fully enabled by the
489 userspace auditd. 413 userspace auditd.
490 Default: unset 414 Default: unset
491 415
492 audit_backlog_limit= [KNL] Set the aud 416 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 417 Format: <int> (must be >=0)
494 Default: 64 418 Default: 64
495 419
496 bau= [X86_UV] Enable the BA 420 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 421 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 422 Format: { "0" | "1" }
499 0 - Disable the BAU. 423 0 - Disable the BAU.
500 1 - Enable the BAU. 424 1 - Enable the BAU.
501 unset - Disable the BA 425 unset - Disable the BAU.
502 426
503 baycom_epp= [HW,AX25] 427 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 428 Format: <io>,<mode>
505 429
506 baycom_par= [HW,AX25] BayCom Paral 430 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 431 Format: <io>,<mode>
508 See header of drivers/ 432 See header of drivers/net/hamradio/baycom_par.c.
509 433
510 baycom_ser_fdx= [HW,AX25] 434 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 435 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 436 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 437 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 438
515 baycom_ser_hdx= [HW,AX25] 439 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 440 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 441 Format: <io>,<irq>,<mode>
518 See header of drivers/ 442 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 443
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 444 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 445 embedded devices based on command line input.
528 See Documentation/bloc 446 See Documentation/block/cmdline-partition.rst
529 447
530 boot_delay= [KNL,EARLY] !! 448 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 449 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 450 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 451 Format: integer
537 452
538 bootconfig [KNL,EARLY] !! 453 bootconfig [KNL]
539 Extended command line 454 Extended command line options can be added to an initrd
540 and this will cause th 455 and this will cause the kernel to look for it.
541 456
542 See Documentation/admi 457 See Documentation/admin-guide/bootconfig.rst
543 458
>> 459 bert_disable [ACPI]
>> 460 Disable BERT OS support on buggy BIOSes.
>> 461
>> 462 bgrt_disable [ACPI][X86]
>> 463 Disable BGRT to avoid flickering OEM logo.
>> 464
544 bttv.card= [HW,V4L] bttv (bt848 + 465 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 466 bttv.radio= Most important insmod options are available as
546 kernel args too. 467 kernel args too.
547 bttv.pll= See Documentation/admi 468 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 469 bttv.tuner=
549 470
550 bulk_remove=off [PPC] This parameter 471 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 472 firmware feature for flushing multiple hpte entries
552 at a time. 473 at a time.
553 474
554 c101= [NET] Moxa C101 synchr 475 c101= [NET] Moxa C101 synchronous serial card
555 476
556 cachesize= [BUGS=X86-32] Override 477 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 478 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 479 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 480 to fix known problems, but for some CPUs it is not
560 possible to determine 481 possible to determine what the correct size should be.
561 This option provides a 482 This option provides an override for these situations.
562 483
563 carrier_timeout= 484 carrier_timeout=
564 [NET] Specifies amount 485 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 486 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 487 it waits 120 seconds.
567 488
568 ca_keys= [KEYS] This parameter 489 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 490 the system trusted keyring to be used for certificate
570 trust validation. 491 trust validation.
571 format: { id:<keyid> | 492 format: { id:<keyid> | builtin }
572 493
573 cca= [MIPS,EARLY] Override !! 494 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 495 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 496 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 497 for platform specific values (SB1, Loongson3 and
577 others). 498 others).
578 499
579 ccw_timeout_log [S390] 500 ccw_timeout_log [S390]
580 See Documentation/arch !! 501 See Documentation/s390/common_io.rst for details.
581 502
582 cgroup_disable= [KNL] Disable a partic 503 cgroup_disable= [KNL] Disable a particular controller or optional feature
583 Format: {name of the c 504 Format: {name of the controller(s) or feature(s) to disable}
584 The effects of cgroup_ 505 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 506 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 507 a single hierarchy
587 - foo isn't visible as 508 - foo isn't visible as an individually mountable
588 subsystem 509 subsystem
589 - if foo is an optiona 510 - if foo is an optional feature then the feature is
590 disabled and corresp 511 disabled and corresponding cgroup files are not
591 created 512 created
592 {Currently only "memor 513 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 514 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 515 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" 516 Specifying "pressure" disables per-cgroup pressure
596 stall information acco 517 stall information accounting feature
597 518
598 cgroup_no_v1= [KNL] Disable cgroup c 519 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 520 Format: { { controller | "all" | "named" }
600 [,{ controll 521 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 522 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 523 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 524 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 525 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 526 all v1 hierarchies.
606 527
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 528 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 529 Format: <string>
613 nosocket -- Disable so 530 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 531 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 532
617 checkreqprot= [SELINUX] Set initial !! 533 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 534 Format: { "0" | "1" }
619 See security/selinux/K 535 See security/selinux/Kconfig help text.
620 0 -- check protection 536 0 -- check protection applied by kernel (includes
621 any implied ex 537 any implied execute protection).
622 1 -- check protection 538 1 -- check protection requested by application.
623 Default value is set v 539 Default value is set via a kernel config option.
624 Value can be changed a 540 Value can be changed at runtime via
625 /sys/fs/selinu 541 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 542 Setting checkreqprot to 1 is deprecated.
627 543
628 cio_ignore= [S390] 544 cio_ignore= [S390]
629 See Documentation/arch !! 545 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 546 clk_ignore_unused
650 [CLK] 547 [CLK]
651 Prevents the clock fra 548 Prevents the clock framework from automatically gating
652 clocks that have not b 549 clocks that have not been explicitly enabled by a Linux
653 device driver but are 550 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 551 by the bootloader/firmware. Note that this does not
655 force such clocks to b 552 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 553 those clocks in any way. This parameter is useful for
657 debug and development, 554 debug and development, but should not be needed on a
658 platform with proper d 555 platform with proper driver support. For more
659 information, see Docum 556 information, see Documentation/driver-api/clk.rst.
660 557
661 clock= [BUGS=X86-32, HW] gett 558 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 559 [Deprecated]
663 Forces specified clock 560 Forces specified clocksource (if available) to be used
664 when calculating getti 561 when calculating gettimeofday(). If specified
665 clocksource is not ava 562 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 563 Format: { pit | tsc | cyclone | pmtmr }
667 564
668 clocksource= Override the default c 565 clocksource= Override the default clocksource
669 Format: <string> 566 Format: <string>
670 Override the default c 567 Override the default clocksource and use the clocksource
671 with the name specifie 568 with the name specified.
672 Some clocksource names 569 Some clocksource names to choose from, depending on
673 the platform: 570 the platform:
674 [all] jiffies (this is 571 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 572 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 573 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 574 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 575 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 576 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 577 [MIPS] MIPS
681 [PARISC] cr16 578 [PARISC] cr16
682 [S390] tod 579 [S390] tod
683 [SH] SuperH 580 [SH] SuperH
684 [SPARC64] tick 581 [SPARC64] tick
685 [X86-64] hpet,tsc 582 [X86-64] hpet,tsc
686 583
687 clocksource.arm_arch_timer.evtstrm= 584 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 585 [ARM,ARM64]
689 Format: <bool> 586 Format: <bool>
690 Enable/disable the eve 587 Enable/disable the eventstream feature of the ARM
691 architected timer so t 588 architected timer so that code using WFE-based polling
692 loops can be debugged 589 loops can be debugged more effectively on production
693 systems. 590 systems.
694 591
>> 592 clocksource.max_cswd_read_retries= [KNL]
>> 593 Number of clocksource_watchdog() retries due to
>> 594 external delays before the clock will be marked
>> 595 unstable. Defaults to three retries, that is,
>> 596 four attempts to read the clock under test.
>> 597
695 clocksource.verify_n_cpus= [KNL] 598 clocksource.verify_n_cpus= [KNL]
696 Limit the number of CP 599 Limit the number of CPUs checked for clocksources
697 marked with CLOCK_SOUR 600 marked with CLOCK_SOURCE_VERIFY_PERCPU that
698 are marked unstable du 601 are marked unstable due to excessive skew.
699 A negative value says 602 A negative value says to check all CPUs, while
700 zero says not to check 603 zero says not to check any. Values larger than
701 nr_cpu_ids are silentl 604 nr_cpu_ids are silently truncated to nr_cpu_ids.
702 The actual CPUs are ch 605 The actual CPUs are chosen randomly, with
703 no replacement if the 606 no replacement if the same CPU is chosen twice.
704 607
705 clocksource-wdtest.holdoff= [KNL] 608 clocksource-wdtest.holdoff= [KNL]
706 Set the time in second 609 Set the time in seconds that the clocksource
707 watchdog test waits be 610 watchdog test waits before commencing its tests.
708 Defaults to zero when 611 Defaults to zero when built as a module and to
709 10 seconds when built 612 10 seconds when built into the kernel.
710 613
>> 614 clearcpuid=BITNUM[,BITNUM...] [X86]
>> 615 Disable CPUID feature X for the kernel. See
>> 616 arch/x86/include/asm/cpufeatures.h for the valid bit
>> 617 numbers. Note the Linux specific bits are not necessarily
>> 618 stable over kernel options, but the vendor specific
>> 619 ones should be.
>> 620 Also note that user programs calling CPUID directly
>> 621 or using the feature without checking anything
>> 622 will still see it. This just prevents it from
>> 623 being used by the kernel or shown in /proc/cpuinfo.
>> 624 Also note the kernel might malfunction if you disable
>> 625 some critical bits.
>> 626
711 cma=nn[MG]@[start[MG][-end[MG]]] 627 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 628 [KNL,CMA]
713 Sets the size of kerne 629 Sets the size of kernel global memory area for
714 contiguous memory allo 630 contiguous memory allocations and optionally the
715 placement constraint b 631 placement constraint by the physical address range of
716 memory allocations. A 632 memory allocations. A value of 0 disables CMA
717 altogether. For more i 633 altogether. For more information, see
718 kernel/dma/contiguous. 634 kernel/dma/contiguous.c
719 635
720 cma_pernuma=nn[MG] 636 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 637 [ARM64,KNL,CMA]
722 Sets the size of kerne 638 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 639 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 640 per-numa CMA altogether. And If this option is not
725 specified, the default !! 641 specificed, the default value is 0.
726 With per-numa CMA enab 642 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 643 first try to allocate buffer from the pernuma area
728 which is located in no 644 which is located in node nid, if the allocation fails,
729 they will fallback to 645 they will fallback to the global default memory area.
730 646
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 | 647 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 648 Specify whether pages are marked as being inactive
744 when they are freed. 649 when they are freed. This is used in CMO environments
745 to determine OS memory 650 to determine OS memory pressure for page stealing by
746 a hypervisor. 651 a hypervisor.
747 Default: yes 652 Default: yes
748 653
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 654 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 655 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 656 allocations, by default set to 256K.
752 657
753 com20020= [HW,NET] ARCnet - COM2 658 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 659 Format:
755 <io>[,<irq>[,<nodeID>[ 660 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 661
757 com90io= [HW,NET] ARCnet - COM9 662 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 663 Format: <io>[,<irq>]
759 664
760 com90xx= [HW,NET] 665 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 666 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 667 Format: <io>[,<irq>[,<memstart>]]
763 668
764 condev= [HW,S390] console devi 669 condev= [HW,S390] console device
765 conmode= 670 conmode=
766 671
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 672 console= [KNL] Output console device and options.
779 673
780 tty<n> Use the virtual consol 674 tty<n> Use the virtual console device <n>.
781 675
782 ttyS<n>[,options] 676 ttyS<n>[,options]
783 ttyUSB0[,options] 677 ttyUSB0[,options]
784 Use the specified seri 678 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 679 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 680 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 681 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 682 omit it). Default is "9600n8".
789 683
790 See Documentation/admi 684 See Documentation/admin-guide/serial-console.rst for more
791 information. See 685 information. See
792 Documentation/networki 686 Documentation/networking/netconsole.rst for an
793 alternative. 687 alternative.
794 688
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] 689 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 690 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 691 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 692 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 693 uart[8250],0x<addr>[,options]
819 Start an early, polled 694 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 695 UART at the specified I/O port or MMIO address,
821 switching to the match 696 switching to the matching ttyS device later.
822 MMIO inter-register ad 697 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 698 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 699 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 700 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 701 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 702 the h/w is not re-initialized.
828 703
829 hvc<n> Use the hypervisor con 704 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 705 both Xen and PowerPC hypervisors.
831 706
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 707 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 708 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 709 console=brl,ttyS0
841 For now, only VisioBraille is 710 For now, only VisioBraille is supported.
842 711
843 console_msg_format= 712 console_msg_format=
844 [KNL] Change console m 713 [KNL] Change console messages format
845 default 714 default
846 By default we print me 715 By default we print messages on consoles in
847 "[time stamp] text\n" 716 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 717 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 718 `printk_time' param).
850 syslog 719 syslog
851 Switch to syslog forma 720 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 721 IOW, each message will have a facility and loglevel
853 prefix. The format is 722 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 723 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 724 from /proc/kmsg.
856 725
857 consoleblank= [KNL] The console blan 726 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 727 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 728 Defaults to 0.
860 729
861 coredump_filter= 730 coredump_filter=
862 [KNL] Change the defau 731 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 732 /proc/<pid>/coredump_filter.
864 See also Documentation 733 See also Documentation/filesystems/proc.rst.
865 734
866 coresight_cpu_debug.enable 735 coresight_cpu_debug.enable
867 [ARM,ARM64] 736 [ARM,ARM64]
868 Format: <bool> 737 Format: <bool>
869 Enable/disable the CPU 738 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 739 0: default value, disable debugging
871 1: enable debugging at 740 1: enable debugging at boot time
872 741
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 742 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 743 disable the cpuidle sub-system
879 744
880 cpuidle.governor= 745 cpuidle.governor=
881 [CPU_IDLE] Name of the 746 [CPU_IDLE] Name of the cpuidle governor to use.
882 747
883 cpufreq.off=1 [CPU_FREQ] 748 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 749 disable the cpufreq sub-system
885 750
886 cpufreq.default_governor= 751 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 752 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 753 policy to use. This governor must be registered in the
889 kernel before the cpuf 754 kernel before the cpufreq driver probes.
890 755
891 cpu_init_udelay=N 756 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 757 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 758 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 759 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 760 Default: 10000
896 761
897 cpuhp.parallel= !! 762 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 763 Format:
899 Format: <bool> !! 764 <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. <<
910 765
911 crashkernel=size[KMG][@offset[KMG]] 766 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 767 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 768 upon panic. This parameter reserves the physical
914 memory region [offset, 769 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 770 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 771 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 772 [KNL, X86-64] Select a region under 4G first, and
918 under 4G first, and fa !! 773 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 774 hasn't been specified.
920 See Documentation/admi 775 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 776
922 crashkernel=range1:size1[,range2:size2 777 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 778 [KNL] Same as above, but depends on the memory
924 in the running system. 779 in the running system. The syntax of range is
925 start-[end] where star 780 start-[end] where start and end are both
926 a memory unit (amount[ 781 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 782 Documentation/admin-guide/kdump/kdump.rst for an example.
928 783
929 crashkernel=size[KMG],high 784 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 785 [KNL, X86-64] range could be above 4G. Allow kernel
931 above 4G. !! 786 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 787 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 788 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 789 available.
935 below 4G, if available <<
936 It will be ignored if 790 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 791 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 792 [KNL, X86-64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 793 is passed, kernel could allocate physical memory region
940 physical memory region !! 794 above 4G, that cause second kernel crash on system
941 crash on system that r !! 795 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 796 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 797 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 798 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 799 at least 256M below 4G automatically.
946 size is platform depen !! 800 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 801 for second kernel instead.
953 0: to disable low allo 802 0: to disable low allocation.
954 It will be ignored whe 803 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 804 or memory reserved is below 4G.
956 805
957 cryptomgr.notests 806 cryptomgr.notests
958 [KNL] Disable crypto s 807 [KNL] Disable crypto self-tests
959 808
960 cs89x0_dma= [HW,NET] 809 cs89x0_dma= [HW,NET]
961 Format: <dma> 810 Format: <dma>
962 811
963 cs89x0_media= [HW,NET] 812 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 813 Format: { rj45 | aui | bnc }
965 814
966 csdlock_debug= [KNL] Enable or disabl !! 815 csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
967 function call handling !! 816 handling. When switched on, additional debug data is
968 additional debug data !! 817 printed to the console in case a hanging CPU is
969 in case a hanging CPU !! 818 detected, and that CPU is pinged again in order to try
970 CPU is pinged again in !! 819 to resolve the hang situation.
971 the hang situation. T !! 820 0: disable csdlock debugging (default)
972 option depends on the !! 821 1: enable basic csdlock debugging (minor impact)
973 Kconfig option. !! 822 ext: enable extended csdlock debugging (more impact,
>> 823 but more data)
974 824
975 dasd= [HW,NET] 825 dasd= [HW,NET]
976 See header of drivers/ 826 See header of drivers/s390/block/dasd_devmap.c.
977 827
978 db9.dev[2|3]= [HW,JOY] Multisystem j 828 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 829 (one device per port)
980 Format: <port#>,<type> 830 Format: <port#>,<type>
981 See also Documentation 831 See also Documentation/input/devices/joystick-parport.rst
982 832
983 debug [KNL,EARLY] Enable ker !! 833 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 834 time. See
>> 835 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 836 details. Deprecated, see dyndbg.
>> 837
>> 838 debug [KNL] Enable kernel debugging (events log level).
984 839
985 debug_boot_weak_hash 840 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 841 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 842 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 843 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 844 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 845 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 846 insecure, please do not use on production kernels.
992 847
993 debug_locks_verbose= 848 debug_locks_verbose=
994 [KNL] verbose locking 849 [KNL] verbose locking self-tests
995 Format: <int> 850 Format: <int>
996 Print debugging info w 851 Print debugging info while doing the locking API
997 self-tests. 852 self-tests.
998 Bitmask for the variou 853 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 854 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 855 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 856 useful to lockdep developers.
1002 857
1003 debug_objects [KNL,EARLY] Enable ob !! 858 debug_objects [KNL] Enable object debugging
>> 859
>> 860 no_debug_objects
>> 861 [KNL] Disable object debugging
1004 862
1005 debug_guardpage_minorder= 863 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 864 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 865 parameter allows control of the order of pages that will
1008 be intentionally kept 866 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 867 buddy allocator. Bigger value increase the probability
1010 of catching random me 868 of catching random memory corruption, but reduce the
1011 amount of memory for 869 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 870 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 871 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 872 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 873 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 874 random memory location. Note that there exists a class
1017 a class of memory cor !! 875 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 876 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 877 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 878 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 879 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 880 tracking down these problems.
1023 881
1024 debug_pagealloc= 882 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 883 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 884 enables the feature at boot time. By default, it is
1027 disabled and the syst 885 disabled and the system will work mostly the same as a
1028 kernel built without 886 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 887 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 888 useful to also enable the page_owner functionality.
1031 on: enable the featur 889 on: enable the feature
1032 890
1033 debugfs= [KNL,EARLY] This para !! 891 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 892 and debugfs internal clients.
1035 Format: { on, no-moun 893 Format: { on, no-mount, off }
1036 on: All functions 894 on: All functions are enabled.
1037 no-mount: 895 no-mount:
1038 Filesystem is 896 Filesystem is not registered but kernel clients can
1039 access APIs a 897 access APIs and a crashkernel can be used to read
1040 its content. 898 its content. There is nothing to mount.
1041 off: Filesystem is 899 off: Filesystem is not registered and clients
1042 get a -EPERM 900 get a -EPERM as result when trying to register files
1043 or directorie 901 or directories within debugfs.
1044 This is equiv 902 This is equivalent of the runtime functionality if
1045 debugfs was n 903 debugfs was not enabled in the kernel at all.
1046 Default value is set 904 Default value is set in build-time with a kernel configuration.
1047 905
1048 debugpat [X86] Enable PAT debu 906 debugpat [X86] Enable PAT debugging
1049 907
>> 908 decnet.addr= [HW,NET]
>> 909 Format: <area>[,<node>]
>> 910 See also Documentation/networking/decnet.rst.
>> 911
1050 default_hugepagesz= 912 default_hugepagesz=
1051 [HW] The size of the 913 [HW] The size of the default HugeTLB page. This is
1052 the size represented 914 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 915 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 916 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 917 filesystems. If not specified, defaults to the
1056 architecture's defaul 918 architecture's default huge page size. Huge page
1057 sizes are architectur 919 sizes are architecture dependent. See also
1058 Documentation/admin-g 920 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 921 Format: size[KMG]
1060 922
1061 deferred_probe_timeout= 923 deferred_probe_timeout=
1062 [KNL] Debugging optio 924 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 925 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 926 probe. Only specific dependencies (subsystems or
1065 drivers) that have op !! 927 drivers) that have opted in will be ignored. A timeout of 0
1066 of 0 will timeout at !! 928 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 929 dump out devices still on the deferred probe list after
1070 retrying. 930 retrying.
1071 931
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] 932 dfltcc= [HW,S390]
1099 Format: { on | off | 933 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 934 on: s390 zlib hardware support for compression on
1101 level 1 and 935 level 1 and decompression (default)
1102 off: No s390 zli 936 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 937 def_only: s390 zlib hardware support for deflate
1104 only (compr 938 only (compression on level 1)
1105 inf_only: s390 zlib h 939 inf_only: s390 zlib hardware support for inflate
1106 only (decom 940 only (decompression)
1107 always: Same as 'on 941 always: Same as 'on' but ignores the selected compression
1108 level alway 942 level always using hardware support (used for debugging)
1109 943
1110 dhash_entries= [KNL] 944 dhash_entries= [KNL]
1111 Set number of hash bu 945 Set number of hash buckets for dentry cache.
1112 946
1113 disable_1tb_segments [PPC,EARLY] !! 947 disable_1tb_segments [PPC]
1114 Disables the use of 1 948 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 949 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 950 can be useful when debugging issues that require an SLB
1117 miss to occur. 951 miss to occur.
1118 952
>> 953 stress_slb [PPC]
>> 954 Limits the number of kernel SLB entries, and flushes
>> 955 them frequently to increase the rate of SLB faults
>> 956 on kernel addresses.
>> 957
1119 disable= [IPV6] 958 disable= [IPV6]
1120 See Documentation/net 959 See Documentation/networking/ipv6.rst.
1121 960
1122 disable_radix [PPC,EARLY] !! 961 hardened_usercopy=
>> 962 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
>> 963 hardening is enabled for this boot. Hardened
>> 964 usercopy checking is used to protect the kernel
>> 965 from reading or writing beyond known memory
>> 966 allocation boundaries as a proactive defense
>> 967 against bounds-checking flaws in the kernel's
>> 968 copy_to_user()/copy_from_user() interface.
>> 969 on Perform hardened usercopy checks (default).
>> 970 off Disable hardened usercopy checks.
>> 971
>> 972 disable_radix [PPC]
1123 Disable RADIX MMU mod 973 Disable RADIX MMU mode on POWER9
1124 974
>> 975 radix_hcall_invalidate=on [PPC/PSERIES]
>> 976 Disable RADIX GTSE feature and use hcall for TLB
>> 977 invalidate.
>> 978
1125 disable_tlbie [PPC] 979 disable_tlbie [PPC]
1126 Disable TLBIE instruc 980 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 981 with KVM, with HASH MMU, or with coherent accelerators.
1128 982
1129 disable_ddw [PPC/PSERIES,EARLY] !! 983 disable_cpu_apicid= [X86,APIC,SMP]
>> 984 Format: <int>
>> 985 The number of initial APIC ID for the
>> 986 corresponding CPU to be disabled at boot,
>> 987 mostly used for the kdump 2nd kernel to
>> 988 disable BSP to wake up multiple CPUs without
>> 989 causing system reset or hang due to sending
>> 990 INIT from AP to BSP.
>> 991
>> 992 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 993 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 994 to workaround buggy firmware.
1132 995
1133 disable_ipv6= [IPV6] 996 disable_ipv6= [IPV6]
1134 See Documentation/net 997 See Documentation/networking/ipv6.rst.
1135 998
1136 disable_mtrr_cleanup [X86,EARLY] !! 999 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 1000 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 1001 to discrete, to make X server driver able to add WB
1139 entry later. This par 1002 entry later. This parameter disables that.
1140 1003
1141 disable_mtrr_trim [X86, Intel and AMD !! 1004 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 1005 By default the kernel will trim any uncacheable
1143 memory out of your av 1006 memory out of your available memory pool based on
1144 MTRR settings. This 1007 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 1008 possibly causing your machine to run very slowly.
1146 1009
1147 disable_timer_pin_1 [X86,EARLY] !! 1010 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 1011 Disable PIN 1 of APIC timer
1149 Can be useful to work 1012 Can be useful to work around chipset bugs.
1150 1013
1151 dis_ucode_ldr [X86] Disable the mic 1014 dis_ucode_ldr [X86] Disable the microcode loader.
1152 1015
1153 dma_debug=off If the kernel is comp 1016 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 1017 this option disables the debugging code at boot.
1155 1018
1156 dma_debug_entries=<number> 1019 dma_debug_entries=<number>
1157 This option allows to 1020 This option allows to tune the number of preallocated
1158 entries for DMA-API d 1021 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 1022 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 1023 DMA-API debugging code disables itself because the
1161 architectural default 1024 architectural default is too low.
1162 1025
1163 dma_debug_driver=<driver_name> 1026 dma_debug_driver=<driver_name>
1164 With this option the 1027 With this option the DMA-API debugging driver
1165 filter feature can be 1028 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1029 pass the driver to filter for as the parameter.
1167 The filter can be dis 1030 The filter can be disabled or changed to another
1168 driver later using sy 1031 driver later using sysfs.
1169 1032
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] 1033 driver_async_probe= [KNL]
1191 List of driver names !! 1034 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 1035 Format: <driver_name1>,<driver_name2>...
1196 1036
1197 drm.edid_firmware=[<connector>:]<file 1037 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1038 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1039 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1040 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1041 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1042 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1043 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1044 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1045 and no file with the same name exists. Details and
>> 1046 instructions how to build your own EDID data are
>> 1047 available in Documentation/admin-guide/edid.rst. An EDID
>> 1048 data set will only be used for a particular connector,
>> 1049 if its name and a colon are prepended to the EDID
>> 1050 name. Each connector may use a unique EDID data
>> 1051 set by separating the files with a comma. An EDID
1206 data set with no conn 1052 data set with no connector name will be used for
1207 any connectors not ex 1053 any connectors not explicitly specified.
1208 1054
1209 dscc4.setup= [NET] 1055 dscc4.setup= [NET]
1210 1056
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1057 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1058 Format: {"off" | "known"}
1213 Control how the dt_cp 1059 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1060 used for CPU feature discovery and setup (if it
1215 exists). 1061 exists).
1216 off: Do not use it, f 1062 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1063 known: Do not pass through unknown features to guests
1218 or userspace, only th 1064 or userspace, only those that the kernel is aware of.
1219 1065
1220 dump_apple_properties [X86] 1066 dump_apple_properties [X86]
1221 Dump name and content 1067 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1068 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1069 what data is available or for reverse-engineering.
1224 1070
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1071 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1072 <module>.dyndbg[="val"]
1227 Enable debug messages 1073 Enable debug messages at boot time. See
1228 Documentation/admin-g 1074 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1075 for details.
1230 1076
1231 early_ioremap_debug [KNL,EARLY] !! 1077 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1078 in some Intel CPUs.
>> 1079
>> 1080 <module>.async_probe [KNL]
>> 1081 Enable asynchronous probe on this module.
>> 1082
>> 1083 early_ioremap_debug [KNL]
1232 Enable debug messages 1084 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1085 is useful for tracking down temporary early mappings
1234 which are not unmappe 1086 which are not unmapped.
1235 1087
1236 earlycon= [KNL,EARLY] Output ea !! 1088 earlycon= [KNL] Output early console device and options.
1237 1089
1238 When used with no opt 1090 When used with no options, the early console is
1239 determined by stdout- 1091 determined by stdout-path property in device tree's
1240 chosen node or the AC 1092 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1093 the platform.
1242 1094
1243 cdns,<addr>[,options] 1095 cdns,<addr>[,options]
1244 Start an early, polle 1096 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1097 (xuartps) serial port at the specified address. Only
1246 supported option is b 1098 supported option is baud rate. If baud rate is not
1247 specified, the serial 1099 specified, the serial port must already be setup and
1248 configured. 1100 configured.
1249 1101
1250 uart[8250],io,<addr>[,options !! 1102 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1103 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1104 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1105 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1106 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1107 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1108 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1109 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1110 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1111 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1112 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1113 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1114 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1115
1266 pl011,<addr> 1116 pl011,<addr>
1267 pl011,mmio32,<addr> 1117 pl011,mmio32,<addr>
1268 Start an early, polle 1118 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1119 port at the specified address. The pl011 serial port
1270 must already be setup 1120 must already be setup and configured. Options are not
1271 yet supported. If 'm 1121 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1122 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1123 the device registers.
1274 1124
1275 liteuart,<addr> 1125 liteuart,<addr>
1276 Start an early consol 1126 Start an early console on a litex serial port at the
1277 specified address. Th 1127 specified address. The serial port must already be
1278 setup and configured. 1128 setup and configured. Options are not yet supported.
1279 1129
1280 meson,<addr> 1130 meson,<addr>
1281 Start an early, polle 1131 Start an early, polled-mode console on a meson serial
1282 port at the specified 1132 port at the specified address. The serial port must
1283 already be setup and 1133 already be setup and configured. Options are not yet
1284 supported. 1134 supported.
1285 1135
1286 msm_serial,<addr> 1136 msm_serial,<addr>
1287 Start an early, polle 1137 Start an early, polled-mode console on an msm serial
1288 port at the specified 1138 port at the specified address. The serial port
1289 must already be setup 1139 must already be setup and configured. Options are not
1290 yet supported. 1140 yet supported.
1291 1141
1292 msm_serial_dm,<addr> 1142 msm_serial_dm,<addr>
1293 Start an early, polle 1143 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1144 dm port at the specified address. The serial port
1295 must already be setup 1145 must already be setup and configured. Options are not
1296 yet supported. 1146 yet supported.
1297 1147
1298 owl,<addr> 1148 owl,<addr>
1299 Start an early, polle 1149 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1150 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1151 specified address. The serial port must already be
1302 setup and configured. 1152 setup and configured. Options are not yet supported.
1303 1153
1304 rda,<addr> 1154 rda,<addr>
1305 Start an early, polle 1155 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1156 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1157 specified address. The serial port must already be
1308 setup and configured. 1158 setup and configured. Options are not yet supported.
1309 1159
1310 sbi 1160 sbi
1311 Use RISC-V SBI (Super 1161 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1162 console.
1313 1163
1314 smh Use ARM semihosting c 1164 smh Use ARM semihosting calls for early console.
1315 1165
1316 s3c2410,<addr> 1166 s3c2410,<addr>
1317 s3c2412,<addr> 1167 s3c2412,<addr>
1318 s3c2440,<addr> 1168 s3c2440,<addr>
1319 s3c6400,<addr> 1169 s3c6400,<addr>
1320 s5pv210,<addr> 1170 s5pv210,<addr>
1321 exynos4210,<addr> 1171 exynos4210,<addr>
1322 Use early console pro 1172 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1173 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1174 a correct base address of the selected UART port. The
1325 serial port must alre 1175 serial port must already be setup and configured.
1326 Options are not yet s 1176 Options are not yet supported.
1327 1177
1328 lantiq,<addr> 1178 lantiq,<addr>
1329 Start an early, polle 1179 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1180 (lqasc) port at the specified address. The serial port
1331 must already be setup 1181 must already be setup and configured. Options are not
1332 yet supported. 1182 yet supported.
1333 1183
1334 lpuart,<addr> 1184 lpuart,<addr>
1335 lpuart32,<addr> 1185 lpuart32,<addr>
1336 Use early console pro 1186 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1187 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1188 A valid base address must be provided, and the serial
1339 port must already be 1189 port must already be setup and configured.
1340 1190
1341 ec_imx21,<addr> 1191 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1192 ec_imx6q,<addr>
1343 Start an early, polle 1193 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1194 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1195 must already be setup and configured.
1346 1196
1347 ar3700_uart,<addr> 1197 ar3700_uart,<addr>
1348 Start an early, polle 1198 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1199 Armada 3700 serial port at the specified
1350 address. The serial p 1200 address. The serial port must already be setup
1351 and configured. Optio 1201 and configured. Options are not yet supported.
1352 1202
1353 qcom_geni,<addr> 1203 qcom_geni,<addr>
1354 Start an early, polle 1204 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1205 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1206 specified address. The serial port must already be
1357 setup and configured. 1207 setup and configured. Options are not yet supported.
1358 1208
1359 efifb,[options] 1209 efifb,[options]
1360 Start an early, unacc 1210 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1211 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1212 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1213 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1214 mapped with the correct attributes.
1365 1215
1366 linflex,<addr> 1216 linflex,<addr>
1367 Use early console pro 1217 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1218 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1219 address must be provided, and the serial port must
1370 already be setup and 1220 already be setup and configured.
1371 1221
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1222 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1223 earlyprintk=vga
1374 earlyprintk=sclp 1224 earlyprintk=sclp
1375 earlyprintk=xen 1225 earlyprintk=xen
1376 earlyprintk=serial[,t 1226 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1227 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1228 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1229 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1230 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1231 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1232
1384 earlyprintk is useful 1233 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1234 the normal console is initialized. It is not enabled by
1386 default because it ha 1235 default because it has some cosmetic problems.
1387 1236
1388 Append ",keep" to not 1237 Append ",keep" to not disable it when the real console
1389 takes over. 1238 takes over.
1390 1239
1391 Only one of vga, seri !! 1240 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1241 be used at a time.
1393 1242
1394 Currently only ttyS0 1243 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1244 name. Other I/O ports may be explicitly specified
1396 on some architectures 1245 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1246 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1247 earlyprintk=serial,0x1008,115200
1399 You can find the port 1248 You can find the port for a given device in
1400 /proc/tty/driver/seri 1249 /proc/tty/driver/serial:
1401 2: uart:ST166 1250 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1251
1403 Interaction with the 1252 Interaction with the standard serial driver is not
1404 very good. 1253 very good.
1405 1254
1406 The VGA output is eve !! 1255 The VGA and EFI output is eventually overwritten by
1407 the real console. 1256 the real console.
1408 1257
1409 The xen option can on !! 1258 The xen output can only be used by Xen PV guests.
1410 1259
1411 The sclp output can o 1260 The sclp output can only be used on s390.
1412 1261
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1262 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1263 PCI device even when its classcode is not of the
1417 UART class. 1264 UART class.
1418 1265
1419 edac_report= [HW,EDAC] Control how 1266 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1267 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1268 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1269 by other higher priority error reporting module.
1423 off: disable H/W even 1270 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1271 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1272 default: on.
1426 1273
>> 1274 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1275 ekgdboc=kbd
>> 1276
>> 1277 This is designed to be used in conjunction with
>> 1278 the boot argument: earlyprintk=vga
>> 1279
>> 1280 This parameter works in place of the kgdboc parameter
>> 1281 but can only be used if the backing tty is available
>> 1282 very early in the boot process. For early debugging
>> 1283 via a serial port see kgdboc_earlycon instead.
>> 1284
1427 edd= [EDD] 1285 edd= [EDD]
1428 Format: {"off" | "on" 1286 Format: {"off" | "on" | "skip[mbr]"}
1429 1287
1430 efi= [EFI,EARLY] !! 1288 efi= [EFI]
1431 Format: { "debug", "d 1289 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1290 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1291 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1292 debug: enable misc debug output.
1435 disable_early_pci_dma 1293 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1294 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1295 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1296 boot stub, as chunking can cause problems with some
1439 firmware implementati 1297 firmware implementations.
1440 noruntime : disable E 1298 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1299 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1300 attribute may cause the kernel to reserve the
1443 memory range for a me 1301 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1302 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1303 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1304 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1305 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1306 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1307 on all PCI bridges while in the EFI boot stub
1450 1308
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1309 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1310 Using this parameter you can use more than 50% of
1453 your efi variable sto 1311 your efi variable storage. Use this parameter only if
1454 you are really sure t 1312 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1313 fulfills the spec otherwise your board may brick.
1456 1314
>> 1315 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1316 Add arbitrary attribute to specific memory range by
>> 1317 updating original EFI memory map.
>> 1318 Region of memory which aa attribute is added to is
>> 1319 from ss to ss+nn.
>> 1320
>> 1321 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1322 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1323 attribute is added to range 0x100000000-0x180000000 and
>> 1324 0x10a0000000-0x1120000000.
>> 1325
>> 1326 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1327 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1328 range 0x240000000-0x43fffffff.
>> 1329
>> 1330 Using this parameter you can do debugging of EFI memmap
>> 1331 related features. For example, you can do debugging of
>> 1332 Address Range Mirroring feature even if your box
>> 1333 doesn't support it, or mark specific memory as
>> 1334 "soft reserved".
>> 1335
1457 efivar_ssdt= [EFI; X86] Name of an 1336 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1337 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1338 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1339 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1340 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1341
1463 1342
1464 eisa_irq_edge= [PARISC,HW] 1343 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1344 See header of drivers/parisc/eisa.c.
1466 1345
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] 1346 elanfreq= [X86-32]
1479 See comment before fu 1347 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1348 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1349
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1350 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1351 Specifies physical address of start of kernel core
1484 image elf header and 1352 image elf header and optionally the size. Generally
1485 kexec loader will pas 1353 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1354 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1355
1488 enable_mtrr_cleanup [X86,EARLY] !! 1356 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1357 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1358 to discrete, to make X server driver able to add WB
1491 entry later. This par 1359 entry later. This parameter enables that.
1492 1360
1493 enable_timer_pin_1 [X86] 1361 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1362 Enable PIN 1 of APIC timer
1495 Can be useful to work 1363 Can be useful to work around chipset bugs
1496 (in particular on som 1364 (in particular on some ATI chipsets).
1497 The kernel tries to s 1365 The kernel tries to set a reasonable default.
1498 1366
1499 enforcing= [SELINUX] Set initial !! 1367 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1368 Format: {"0" | "1"}
1501 See security/selinux/ 1369 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1370 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1371 1 -- enforcing (deny and log).
1504 Default value is 0. 1372 Default value is 0.
1505 Value can be changed 1373 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1374 /sys/fs/selinux/enforce.
1507 1375
1508 erst_disable [ACPI] 1376 erst_disable [ACPI]
1509 Disable Error Record 1377 Disable Error Record Serialization Table (ERST)
1510 support. 1378 support.
1511 1379
1512 ether= [HW,NET] Ethernet car 1380 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1381 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1382 has equivalent usage. See its documentation for details.
1515 1383
1516 evm= [EVM] 1384 evm= [EVM]
1517 Format: { "fix" } 1385 Format: { "fix" }
1518 Permit 'security.evm' 1386 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1387 current integrity status.
1520 1388
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= 1389 failslab=
1530 fail_usercopy= 1390 fail_usercopy=
1531 fail_page_alloc= 1391 fail_page_alloc=
1532 fail_make_request=[KNL] 1392 fail_make_request=[KNL]
1533 General fault injecti 1393 General fault injection mechanism.
1534 Format: <interval>,<p 1394 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1395 See also Documentation/fault-injection/.
1536 1396
1537 fb_tunnels= [NET] 1397 fb_tunnels= [NET]
1538 Format: { initns | no 1398 Format: { initns | none }
1539 See Documentation/adm 1399 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1400 fb_tunnels_only_for_init_ns
1541 1401
1542 floppy= [HW] 1402 floppy= [HW]
1543 See Documentation/adm 1403 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1404
>> 1405 force_pal_cache_flush
>> 1406 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1407 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1408 parameter will force ia64_sal_cache_flush to call
>> 1409 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1410
1545 forcepae [X86-32] 1411 forcepae [X86-32]
1546 Forcefully enable Phy 1412 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1413 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1414 functionally usable PAE implementation.
1549 Warning: use of this 1415 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1416 and may cause unknown problems.
1551 1417
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] 1418 ftrace=[tracer]
1559 [FTRACE] will set and 1419 [FTRACE] will set and start the specified tracer
1560 as early as possible 1420 as early as possible in order to facilitate early
1561 boot debugging. 1421 boot debugging.
1562 1422
1563 ftrace_boot_snapshot !! 1423 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 1424 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1425 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1426 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1427 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1428 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 1429
1603 ftrace_filter=[function-list] 1430 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1431 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1432 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1433 list of functions. This list can be changed at run
1607 time by the set_ftrac 1434 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1435 tracing directory.
1609 1436
1610 ftrace_notrace=[function-list] 1437 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1438 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1439 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1440 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1441 tracing directory.
1615 1442
1616 ftrace_graph_filter=[function-list] 1443 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1444 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1445 by the function graph tracer at boot up.
1619 function-list is a co 1446 function-list is a comma-separated list of functions
1620 that can be changed a 1447 that can be changed at run time by the
1621 set_graph_function fi 1448 set_graph_function file in the debugfs tracing directory.
1622 1449
1623 ftrace_graph_notrace=[function-list] 1450 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1451 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1452 function-list. This list is a comma-separated list of
1626 functions that can be 1453 functions that can be changed at run time by the
1627 set_graph_notrace fil 1454 set_graph_notrace file in the debugfs tracing directory.
1628 1455
1629 ftrace_graph_max_depth=<uint> 1456 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1457 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1458 the max depth it will trace into a function. This value
1632 can be changed at run 1459 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1460 in the tracefs tracing directory. default: 0 (no limit)
1634 1461
1635 fw_devlink= [KNL,EARLY] Create de !! 1462 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1463 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1464 consumer/supplier relationships. This feature is
1638 especially useful whe 1465 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1466 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1467 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1468 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1469 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1470 suppliers).
1644 Format: { off | permi 1471 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1472 off -- Don't create device links from firmware info.
1646 permissive -- Create 1473 permissive -- Create device links from firmware info
1647 but use it on 1474 but use it only for ordering boot state clean
1648 up (sync_stat 1475 up (sync_state() calls).
1649 on -- Create device 1476 on -- Create device links from firmware info and use it
1650 to enforce pr 1477 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1478 rpm -- Like "on", but also use to order runtime PM.
1652 1479
1653 fw_devlink.strict=<bool> 1480 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1481 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1482 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1483 Format: <bool>
1657 1484
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]= 1485 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1486 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1487 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1488 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1489 See also Documentation/input/devices/joystick-parport.rst
1677 1490
1678 gamma= [HW,DRM] 1491 gamma= [HW,DRM]
1679 1492
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1493 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1494 Format: off | on
1682 default: on 1495 default: on
1683 1496
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 1497 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1498 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1499 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1500 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1501 debugfs files are removed at module unload time.
1709 1502
1710 goldfish [X86] Enable the gold 1503 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1504 Don't use this when you are not running on the
1712 android emulator 1505 android emulator
1713 1506
1714 gpio-mockup.gpio_mockup_ranges 1507 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1508 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1509 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1510 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1511 [HW] Let the driver know GPIO lines should be named.
1719 1512
1720 gpt [EFI] Forces disk wit 1513 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1514 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1515 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1516 GPT to be used instead.
1724 1517
1725 grcan.enable0= [HW] Configuration of 1518 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1519 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1520 Format: 0 | 1
1728 Default: 0 1521 Default: 0
1729 grcan.enable1= [HW] Configuration of 1522 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1523 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1524 Format: 0 | 1
1732 Default: 0 1525 Default: 0
1733 grcan.select= [HW] Select which phy 1526 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1527 Format: 0 | 1
1735 Default: 0 1528 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1529 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1530 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1531 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1532 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1533 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1534 Default: 1024
1742 1535
1743 hardened_usercopy= <<
1744 [KNL] Under CONFIG_HA <<
1745 hardening is enabled <<
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 <<
1754 hardlockup_all_cpu_backtrace= 1536 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1537 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1538 backtraces on all cpus.
1757 Format: 0 | 1 1539 Format: 0 | 1
1758 1540
1759 hashdist= [KNL,NUMA] Large hash 1541 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1542 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1543 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1544 Format: 0 | 1 (for off | on)
1763 1545
>> 1546 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1547
1764 hd= [EIDE] (E)IDE hard dr 1548 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1549 Format: <cyl>,<head>,<sect>
1766 1550
1767 hest_disable [ACPI] 1551 hest_disable [ACPI]
1768 Disable Hardware Erro 1552 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1553 corresponding firmware-first mode error processing
1770 logic will be disable 1554 logic will be disabled.
1771 1555
1772 hibernate= [HIBERNATION] !! 1556 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 1557 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1558 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1559 size on bigger boxes.
1796 1560
1797 highres= [KNL] Enable/disable 1561 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1562 Valid parameters: "on", "off"
1799 Default: "on" 1563 Default: "on"
1800 1564
1801 hlt [BUGS=ARM,SH] 1565 hlt [BUGS=ARM,SH]
1802 1566
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 1567 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1568 Format: { enable (default) | disable | force |
1818 verbose } 1569 verbose }
1819 disable: disable HPET 1570 disable: disable HPET and use PIT instead
1820 force: allow force en 1571 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1572 VIA, nVidia)
1822 verbose: show content 1573 verbose: show contents of HPET registers during setup
1823 1574
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1575 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1576 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1577
>> 1578 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
>> 1579 of gigantic hugepages.
>> 1580 Format: nn[KMGTPE]
>> 1581
>> 1582 Reserve a CMA area of given size and allocate gigantic
>> 1583 hugepages using the CMA allocator. If enabled, the
>> 1584 boot-time allocation of gigantic hugepages is skipped.
>> 1585
1827 hugepages= [HW] Number of HugeTL 1586 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1587 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1588 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1589 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1590 line, it specifies the number of pages to allocate for
1832 the default huge page !! 1591 the default huge page size. See also
1833 number of pages to al !! 1592 Documentation/admin-guide/mm/hugetlbpage.rst.
1834 See also Documentatio !! 1593 Format: <integer>
1835 Format: <integer> or <<
1836 <node>:<integ <<
1837 1594
1838 hugepagesz= 1595 hugepagesz=
1839 [HW] The size of the 1596 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1597 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1598 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1599 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1600 each supported huge page size. Huge page sizes are
1844 architecture dependen 1601 architecture dependent. See also
1845 Documentation/admin-g 1602 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1603 Format: size[KMG]
1847 1604
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= 1605 hugetlb_free_vmemmap=
1859 [KNL] Requires CONFIG !! 1606 [KNL] Reguires CONFIG_HUGETLB_PAGE_FREE_VMEMMAP
1860 enabled. 1607 enabled.
1861 Control if HugeTLB Vm <<
1862 Allows heavy hugetlb 1608 Allows heavy hugetlb users to free up some more
1863 memory (7 * PAGE_SIZE !! 1609 memory (6 * PAGE_SIZE for each 2MB hugetlb page).
1864 Format: { on | off (d 1610 Format: { on | off (default) }
1865 1611
1866 on: enable HVO !! 1612 on: enable the feature
1867 off: disable HVO !! 1613 off: disable the feature
1868 1614
1869 Built with CONFIG_HUG !! 1615 Built with CONFIG_HUGETLB_PAGE_FREE_VMEMMAP_DEFAULT_ON=y,
1870 the default is on. 1616 the default is on.
1871 1617
1872 Note that the vmemmap !! 1618 This is not compatible with memory_hotplug.memmap_on_memory.
1873 memory block itself w !! 1619 If both parameters are enabled, hugetlb_free_vmemmap takes
1874 enabled, those vmemma !! 1620 precedence over memory_hotplug.memmap_on_memory.
1875 feature is enabled. <<
1876 the added memory bloc <<
1877 1621
1878 hung_task_panic= 1622 hung_task_panic=
1879 [KNL] Should the hung 1623 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1624 Format: 0 | 1
1881 1625
1882 A value of 1 instruct 1626 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1627 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1628 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1629 option. The value selected by this boot parameter can
1886 be changed later by t 1630 be changed later by the kernel.hung_task_panic sysctl.
1887 1631
1888 hvc_iucv= [S390] Number of z/V 1632 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1633 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1634 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1635 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1636 from listed z/VM user IDs only.
1893 1637
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1638 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1639 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1640 guest on lock contention.
1897 on lock contention. !! 1641
>> 1642 keep_bootcon [KNL]
>> 1643 Do not unregister boot console at start. This is only
>> 1644 useful for debugging when something happens in the window
>> 1645 between unregistering the boot console and initializing
>> 1646 the real console.
1898 1647
1899 i2c_bus= [HW] Override the 1648 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1649 or register an additional I2C bus that is not
1901 registered fr 1650 registered from board initialization code.
1902 Format: 1651 Format:
1903 <bus_id>,<clk 1652 <bus_id>,<clkrate>
1904 1653
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 1654 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1655 i8042.unmask_kbd_data
1929 [HW] Enable printing 1656 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1657 (disabled by default, and as a pre-condition
1931 requires that i8 1658 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1659 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1660 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1661 keyboard and cannot control its state
1935 (Don't attempt t 1662 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1663 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1664 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1665 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1666 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1667 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1668 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1669 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1670 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1671 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1672 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1673 suspend-to-ram transitions, only during s2r
1947 transitions, or 1674 transitions, or never reset
1948 Format: { 1 | Y | y | 1675 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1676 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1677 0, N, n: don't ever reset controller
1951 Default: only on s2r 1678 Default: only on s2r transitions on x86; most other
1952 architectures force r 1679 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1680 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1681 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer <<
1956 [HW] Allow deferred p <<
1957 1682
1958 i810= [HW,DRM] 1683 i810= [HW,DRM]
1959 1684
>> 1685 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1686 indicates that the driver is running on unsupported
>> 1687 hardware.
>> 1688 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1689 does not match list of supported models.
>> 1690 i8k.power_status
>> 1691 [HW] Report power status in /proc/i8k
>> 1692 (disabled by default)
>> 1693 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1694 capability is set.
>> 1695
1960 i915.invert_brightness= 1696 i915.invert_brightness=
1961 [DRM] Invert the sens 1697 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1698 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1699 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1700 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1701 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1702 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1703 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1704 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1705 value switches the backlight off.
1970 -1 -- never invert br 1706 -1 -- never invert brightness
1971 0 -- machine default 1707 0 -- machine default
1972 1 -- force brightnes 1708 1 -- force brightness inversion
1973 1709
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] 1710 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1711 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1712
>> 1713 ide-core.nodma= [HW] (E)IDE subsystem
>> 1714 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1715 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1716 .cdrom .chs .ignore_cable are additional options
>> 1717 See Documentation/ide/ide.rst.
1983 1718
1984 idle= [X86,EARLY] !! 1719 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1720 Format: <int>
>> 1721 Probe mask for legacy ISA IDE ports. Depending on
>> 1722 platform up to 6 ports are supported, enabled by
>> 1723 setting corresponding bits in the mask to 1. The
>> 1724 default value is 0x0, which has a special meaning.
>> 1725 On systems that have PCI, it triggers scanning the
>> 1726 PCI bus for the first and the second port, which
>> 1727 are then probed. On systems without PCI the value
>> 1728 of 0x0 enables probing the two first ports as if it
>> 1729 was 0x3.
>> 1730
>> 1731 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1732 Claim all unknown PCI IDE storage controllers.
>> 1733
>> 1734 idle= [X86]
1985 Format: idle=poll, id 1735 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1736 Poll forces a polling idle loop that can slightly
1987 improve the performan 1737 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1738 will use a lot of power and make the system run hot.
1989 Not recommended. 1739 Not recommended.
1990 idle=halt: Halt is fo 1740 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1741 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1742 idle=nomwait: Disable mwait for CPU C-states
1993 1743
1994 idxd.sva= [HW] 1744 idxd.sva= [HW]
1995 Format: <bool> 1745 Format: <bool>
1996 Allow force disabling 1746 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1747 support for the idxd driver. By default it is set to
1998 true (1). 1748 true (1).
1999 1749
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 1750 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1751 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1752 Default: strict
2008 1753
2009 Choose which programs 1754 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1755 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1756 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1757 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1758 binary. Hardware implementations are permitted to
2014 support either or bot 1759 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1760 encoding mode.
2016 1761
2017 Available settings ar 1762 Available settings are as follows:
2018 strict accept binari 1763 strict accept binaries that request a NaN encoding
2019 supported by 1764 supported by the FPU
2020 legacy only accept l 1765 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1766 by the FPU
2022 2008 only accept 2 1767 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1768 by the FPU
2024 relaxed accept any bi 1769 relaxed accept any binaries regardless of whether
2025 supported by 1770 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1771
2029 The FPU emulator is a 1772 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1773 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1774 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1775 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1776 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1777 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1778 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1779 MIPS64 CPUs.
2037 1780
2038 The setting for ABS.f 1781 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1782 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1783 except where unsupported by hardware.
2041 1784
2042 ignore_loglevel [KNL,EARLY] !! 1785 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1786 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1787 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1788 We also add it as printk module parameter, so users
2046 could change it dynam 1789 could change it dynamically, usually by
2047 /sys/module/printk/pa 1790 /sys/module/printk/parameters/ignore_loglevel.
2048 1791
2049 ignore_rlimit_data 1792 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1793 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1794 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1795 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1796
2054 ihash_entries= [KNL] 1797 ihash_entries= [KNL]
2055 Set number of hash bu 1798 Set number of hash buckets for inode cache.
2056 1799
2057 ima_appraise= [IMA] appraise integr 1800 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1801 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1802 default: "enforce"
2060 1803
2061 ima_appraise_tcb [IMA] Deprecated. U 1804 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1805 The builtin appraise policy appraises all files
2063 owned by uid=0. 1806 owned by uid=0.
2064 1807
2065 ima_canonical_fmt [IMA] 1808 ima_canonical_fmt [IMA]
2066 Use the canonical for 1809 Use the canonical format for the binary runtime
2067 measurements, instead 1810 measurements, instead of host native format.
2068 1811
2069 ima_hash= [IMA] 1812 ima_hash= [IMA]
2070 Format: { md5 | sha1 1813 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1814 | sha512 | ... }
2072 default: "sha1" 1815 default: "sha1"
2073 1816
2074 The list of supported 1817 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1818 in crypto/hash_info.h.
2076 1819
2077 ima_policy= [IMA] 1820 ima_policy= [IMA]
2078 The builtin policies 1821 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1822 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1823 fail_securely | critical_data"
2081 1824
2082 The "tcb" policy meas 1825 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1826 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1827 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1828 uid=0.
2086 1829
2087 The "appraise_tcb" po 1830 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1831 all files owned by root.
2089 1832
2090 The "secure_boot" pol 1833 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1834 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1835 firmware, policy, etc) based on file signatures.
2093 1836
2094 The "fail_securely" p 1837 The "fail_securely" policy forces file signature
2095 verification failure 1838 verification failure also on privileged mounted
2096 filesystems with the 1839 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1840 flag.
2098 1841
2099 The "critical_data" p 1842 The "critical_data" policy measures kernel integrity
2100 critical data. 1843 critical data.
2101 1844
2102 ima_tcb [IMA] Deprecated. Us 1845 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1846 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1847 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1848 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1849 opened for read by uid=0.
2107 1850
2108 ima_template= [IMA] 1851 ima_template= [IMA]
2109 Select one of defined 1852 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1853 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1854 Default: "ima-ng"
2113 1855
2114 ima_template_fmt= 1856 ima_template_fmt=
2115 [IMA] Define a custom 1857 [IMA] Define a custom template format.
2116 Format: { "field1|... 1858 Format: { "field1|...|fieldN" }
2117 1859
2118 ima.ahash_minsize= [IMA] Minimum file 1860 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1861 Format: <min_file_size>
2120 Set the minimal file 1862 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1863 If left unspecified, ahash usage is disabled.
2122 1864
2123 ahash performance var 1865 ahash performance varies for different data sizes on
2124 different crypto acce 1866 different crypto accelerators. This option can be used
2125 to achieve the best p 1867 to achieve the best performance for a particular HW.
2126 1868
2127 ima.ahash_bufsize= [IMA] Asynchronous 1869 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1870 Format: <bufsize>
2129 Set hashing buffer si 1871 Set hashing buffer size. Default: 4k.
2130 1872
2131 ahash performance var 1873 ahash performance varies for different chunk sizes on
2132 different crypto acce 1874 different crypto accelerators. This option can be used
2133 to achieve best perfo 1875 to achieve best performance for particular HW.
2134 1876
2135 init= [KNL] 1877 init= [KNL]
2136 Format: <full_path> 1878 Format: <full_path>
2137 Run specified binary 1879 Run specified binary instead of /sbin/init as init
2138 process. 1880 process.
2139 1881
2140 initcall_debug [KNL] Trace initcalls 1882 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1883 for working out where the kernel is dying during
2142 startup. 1884 startup.
2143 1885
2144 initcall_blacklist= [KNL] Do not exe 1886 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1887 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1888 modules and initcalls.
2147 1889
2148 initramfs_async= [KNL] 1890 initramfs_async= [KNL]
2149 Format: <bool> 1891 Format: <bool>
2150 Default: 1 1892 Default: 1
2151 This parameter contro 1893 This parameter controls whether the initramfs
2152 image is unpacked asy 1894 image is unpacked asynchronously, concurrently
2153 with devices being pr 1895 with devices being probed and
2154 initialized. This sho 1896 initialized. This should normally just work,
2155 but as a debugging ai 1897 but as a debugging aid, one can get the
2156 historical behaviour 1898 historical behaviour of the initramfs
2157 unpacking being compl 1899 unpacking being completed before device_ and
2158 late_ initcalls. 1900 late_ initcalls.
2159 1901
2160 initrd= [BOOT,EARLY] Specify !! 1902 initrd= [BOOT] Specify the location of the initial ramdisk
2161 1903
2162 initrdmem= [KNL,EARLY] Specify a !! 1904 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 1905 load the initrd. If an initrd is compiled in or
2164 specified in the boot 1906 specified in the bootparams, it takes priority over this
2165 setting. 1907 setting.
2166 Format: ss[KMG],nn[KM 1908 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 1909 Default is 0, 0
2168 1910
2169 init_on_alloc= [MM,EARLY] Fill newly !! 1911 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 1912 zeroes.
2171 Format: 0 | 1 1913 Format: 0 | 1
2172 Default set by CONFIG 1914 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 1915
2174 init_on_free= [MM,EARLY] Fill freed !! 1916 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 1917 Format: 0 | 1
2176 Default set by CONFIG 1918 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 1919
2178 init_pkru= [X86] Specify the def 1920 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 1921 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1922 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1923 override in debugfs after boot.
2182 1924
2183 inport.irq= [HW] Inport (ATI XL a 1925 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1926 Format: <irq>
2185 1927
2186 int_pln_enable [X86] Enable power li 1928 int_pln_enable [X86] Enable power limit notification interrupt
2187 1929
2188 integrity_audit=[IMA] 1930 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1931 Format: { "0" | "1" }
2190 0 -- basic integrity 1932 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1933 1 -- additional integrity auditing messages.
2192 1934
2193 intel_iommu= [DMAR] Intel IOMMU dr 1935 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1936 on
2195 Enable intel iommu dr 1937 Enable intel iommu driver.
2196 off 1938 off
2197 Disable intel iommu d 1939 Disable intel iommu driver.
2198 igfx_off [Default Off] 1940 igfx_off [Default Off]
2199 By default, gfx is ma 1941 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1942 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1943 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1944 this case, gfx device will use physical address for
2203 DMA. 1945 DMA.
2204 strict [Default Off] 1946 strict [Default Off]
2205 Deprecated, equivalen !! 1947 With this option on every unmap_single operation will
>> 1948 result in a hardware IOTLB flush operation as opposed
>> 1949 to batching them for performance.
2206 sp_off [Default Off] 1950 sp_off [Default Off]
2207 By default, super pag 1951 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1952 has the capability. With this option, super page will
2209 not be supported. 1953 not be supported.
2210 sm_on !! 1954 sm_on [Default Off]
2211 Enable the Intel IOMM !! 1955 By default, scalable mode will be disabled even if the
2212 advertises that it ha !! 1956 hardware advertises that it has support for the scalable
2213 translation. !! 1957 mode translation. With this option set, scalable mode
2214 sm_off !! 1958 will be used on hardware which claims to support it.
2215 Disallow use of the I <<
2216 tboot_noforce [Default Off] 1959 tboot_noforce [Default Off]
2217 Do not force the Inte 1960 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1961 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1962 could harm performance of some high-throughput
2220 devices like 40GBit n 1963 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1964 mapping is enabled.
2222 Note that using this 1965 Note that using this option lowers the security
2223 provided by tboot bec 1966 provided by tboot because it makes the system
2224 vulnerable to DMA att 1967 vulnerable to DMA attacks.
2225 1968
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1969 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1970 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1971 1 to 9 specify maximum depth of C-state.
2229 1972
2230 intel_pstate= [X86,EARLY] !! 1973 intel_pstate= [X86]
2231 disable 1974 disable
2232 Do not enable intel 1975 Do not enable intel_pstate as the default
2233 scaling driver for 1976 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 1977 passive
2245 Use intel_pstate as 1978 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 1979 to work with generic cpufreq governors (instead of
2247 enabling its intern 1980 enabling its internal governor). This mode cannot be
2248 used along with the 1981 used along with the hardware-managed P-states (HWP)
2249 feature. 1982 feature.
2250 force 1983 force
2251 Enable intel_pstate 1984 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 1985 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 1986 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 1987 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 1988 P-States information being indicated to OSPM and therefore
2256 should be used with 1989 should be used with caution. This option does not work with
2257 processors that are 1990 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 1991 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 1992 no_hwp
2260 Do not enable hardw 1993 Do not enable hardware P state control (HWP)
2261 if available. 1994 if available.
2262 hwp_only 1995 hwp_only
2263 Only load intel_pst 1996 Only load intel_pstate on systems which support
2264 hardware P state co 1997 hardware P state control (HWP) if available.
2265 support_acpi_ppc 1998 support_acpi_ppc
2266 Enforce ACPI _PPC p 1999 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 2000 Description Table, specifies preferred power management
2268 profile as "Enterpr 2001 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 2002 then this feature is turned on by default.
2270 per_cpu_perf_limits 2003 per_cpu_perf_limits
2271 Allow per-logical-C 2004 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 2005 cpufreq sysfs interface
2273 2006
2274 intremap= [X86-64,Intel-IOMMU,E !! 2007 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 2008 on enable Interrupt Remapping (default)
2276 off disable Inter 2009 off disable Interrupt Remapping
2277 nosid disable Sourc 2010 nosid disable Source ID checking
2278 no_x2apic_optout 2011 no_x2apic_optout
2279 BIOS x2APIC o 2012 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 2013 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 2014
2284 iomem= Disable strict checki 2015 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 2016 strict regions from userspace.
2286 relaxed 2017 relaxed
2287 2018
2288 iommu= [X86,EARLY] !! 2019 iommu= [X86]
2289 off 2020 off
2290 force 2021 force
2291 noforce 2022 noforce
2292 biomerge 2023 biomerge
2293 panic 2024 panic
2294 nopanic 2025 nopanic
2295 merge 2026 merge
2296 nomerge 2027 nomerge
2297 soft 2028 soft
2298 pt [X86] 2029 pt [X86]
2299 nopt [X86] 2030 nopt [X86]
2300 nobypass [PPC/POWERNV] 2031 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 2032 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2033
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2034 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 2035 Format: { "0" | "1" }
2305 0 - Try to allocate a 2036 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 2037 falling back to the full range if needed.
2307 1 - Allocate directly 2038 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 2039 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 2040 greater than 32-bit addressing.
2310 2041
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 2042 iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 2043 Format: { "0" | "1" }
2313 0 - Lazy mode. 2044 0 - Lazy mode.
2314 Request that DMA un 2045 Request that DMA unmap operations use deferred
2315 invalidation of har 2046 invalidation of hardware TLBs, for increased
2316 throughput at the c 2047 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2048 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2049 the relevant IOMMU driver.
2319 1 - Strict mode. !! 2050 1 - Strict mode (default).
2320 DMA unmap operation 2051 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2052 synchronously.
2322 unset - Use value of !! 2053 Note: on x86, the default behaviour depends on the
2323 Note: on x86, strict !! 2054 equivalent driver-specific parameters, but a strict
2324 legacy driver-specifi !! 2055 mode explicitly specified by either method takes
>> 2056 precedence.
2325 2057
2326 iommu.passthrough= 2058 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2059 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2060 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2061 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2062 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2063 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2064
2333 io7= [HW] IO7 for Marvel-b 2065 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2066 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2067 arch/alpha/kernel/core_marvel.c.
2336 2068
2337 io_delay= [X86,EARLY] I/O delay !! 2069 io_delay= [X86] I/O delay method
2338 0x80 2070 0x80
2339 Standard port 0x80 ba 2071 Standard port 0x80 based delay
2340 0xed 2072 0xed
2341 Alternate port 0xed b 2073 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2074 udelay
2343 Simple two microsecon 2075 Simple two microseconds delay
2344 none 2076 none
2345 No delay 2077 No delay
2346 2078
2347 ip= [IP_PNP] 2079 ip= [IP_PNP]
2348 See Documentation/adm 2080 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2081
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2082 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2083 IPC identifiers from 32,768 to 16,777,216.
2352 2084
2353 irqaffinity= [SMP] Set the default 2085 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2086 The argument is a cpu list, as described above.
2355 2087
2356 irqchip.gicv2_force_probe= 2088 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2089 [ARM, ARM64]
2358 Format: <bool> 2090 Format: <bool>
2359 Force the kernel to l 2091 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2092 of a GICv2 controller even if the memory range
2361 exposed by the device 2093 exposed by the device tree is too small.
2362 2094
2363 irqchip.gicv3_nolpi= 2095 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2096 [ARM, ARM64]
2365 Force the kernel to i 2097 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2098 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2099 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2100 to let secondary kernels in charge of setting up
2369 LPIs. 2101 LPIs.
2370 2102
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2103 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2104 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2105 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2106 CONFIG_ARM64_PSEUDO_NMI.
2375 2107
2376 irqfixup [HW] 2108 irqfixup [HW]
2377 When an interrupt is 2109 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2110 for it. Intended to get systems with badly broken
2379 firmware running. 2111 firmware running.
2380 2112
2381 irqpoll [HW] 2113 irqpoll [HW]
2382 When an interrupt is 2114 When an interrupt is not handled search all handlers
2383 for it. Also check al 2115 for it. Also check all handlers each timer
2384 interrupt. Intended t 2116 interrupt. Intended to get systems with badly broken
2385 firmware running. 2117 firmware running.
2386 2118
2387 isapnp= [ISAPNP] 2119 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2120 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2121
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2122 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2123 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2124 Format: [flag-list,]<cpu-list>
2393 2125
2394 Specify one or more C 2126 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2127 specified in the flag list (default: domain):
2396 2128
2397 nohz 2129 nohz
2398 Disable the tick wh 2130 Disable the tick when a single task runs.
2399 2131
2400 A residual 1Hz tick 2132 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2133 need to affine to housekeeping through the global
2402 workqueue's affinit 2134 workqueue's affinity configured via the
2403 /sys/devices/virtua 2135 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2136 by using the 'domain' flag described below.
2405 2137
2406 NOTE: by default th 2138 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2139 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2140 be configured manually after bootup.
2409 2141
2410 domain 2142 domain
2411 Isolate from the ge 2143 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2144 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2145 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2146 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2147 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2148 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2149 It offers a much more flexible interface where CPUs can
2418 move in and out of 2150 move in and out of an isolated set anytime.
2419 2151
2420 You can move a proc 2152 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2153 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2154 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2155 "number of CPUs in system - 1".
2424 2156
2425 managed_irq 2157 managed_irq
2426 2158
2427 Isolate from being 2159 Isolate from being targeted by managed interrupts
2428 which have an inter 2160 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2161 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2162 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2163 the /proc/irq/* interfaces.
2432 2164
2433 This isolation is b 2165 This isolation is best effort and only effective
2434 if the automaticall 2166 if the automatically assigned interrupt mask of a
2435 device queue contai 2167 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2168 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2169 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2170 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2171 cannot disturb the isolated CPU.
2440 2172
2441 If a queue's affini 2173 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2174 CPUs then this parameter has no effect on the
2443 interrupt routing d 2175 interrupt routing decision, though interrupts are
2444 only delivered when 2176 only delivered when tasks running on those
2445 isolated CPUs submi 2177 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2178 housekeeping CPUs has no influence on those
2447 queues. 2179 queues.
2448 2180
2449 The format of <cpu-li 2181 The format of <cpu-list> is described above.
2450 2182
2451 iucv= [HW,NET] 2183 iucv= [HW,NET]
2452 2184
2453 ivrs_ioapic [HW,X86-64] 2185 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2186 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 2187 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 2188 example, to map IOAPIC-ID decimal 10 to
2457 !! 2189 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 2190 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 2191
2471 ivrs_hpet [HW,X86-64] 2192 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2193 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 2194 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 2195 example, to map HPET-ID decimal 0 to
2475 !! 2196 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]= 2197 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 2198
2489 ivrs_acpihid [HW,X86-64] 2199 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2200 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 2201 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 2202 example, to map UART-HID:UID AMD0020:0 to
2493 !! 2203 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[ 2204 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 2205
2507 js= [HW,JOY] Analog joyst 2206 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2207 See Documentation/input/joydev/joystick.rst.
2509 2208
>> 2209 nokaslr [KNL]
>> 2210 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2211 kernel and module base offset ASLR (Address Space
>> 2212 Layout Randomization).
>> 2213
2510 kasan_multi_shot 2214 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2215 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2216 report on every invalid memory access. Without this
2513 parameter KASAN will 2217 parameter KASAN will print report only for the first
2514 invalid access. 2218 invalid access.
2515 2219
2516 keep_bootcon [KNL,EARLY] !! 2220 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 2221
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2222 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2223 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2224 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2225 the kernel for non-movable allocations. The requested
2528 amount is spread even 2226 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2227 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2228 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2229 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2230 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2231 other nodes will have a larger ZONE_MOVABLE.
2534 2232
2535 ZONE_MOVABLE is used 2233 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2234 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2235 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2236 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2237 zone if it does not.
2540 2238
2541 It is possible to spe 2239 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2240 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2241 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2242 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2243 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2244 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2245 are exclusive, so you cannot specify multiple forms.
2548 2246
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2247 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2248 Format: <Controller#>[,poll interval]
2551 The controller # is t 2249 The controller # is the number of the ehci usb debug
2552 port as it is probed 2250 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2251 optional and is the number seconds in between
2554 each poll cycle to th 2252 each poll cycle to the debug port in case you need
2555 the functionality for 2253 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2254 gdb or control-c on the dbgp connection. When
2557 not using this parame 2255 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2256 the kernel debugger.
2559 2257
2560 kgdboc= [KGDB,HW] kgdb over c 2258 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2259 Requires a tty driver that supports console polling,
2562 or a supported pollin 2260 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2261 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2262 keyboard only format: kbd
2565 keyboard and serial 2263 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2264 Optional Kernel mode setting:
2567 kms, kbd format: kms 2265 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2266 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2267
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2268 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2269 If the boot console provides the ability to read
2572 characters and can wo 2270 characters and can work in polling mode, you can use
2573 this parameter to tel 2271 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2272 until the normal console is registered. Intended to
2575 be used together with 2273 be used together with the kgdboc parameter which
2576 specifies the normal 2274 specifies the normal console to transition to.
2577 2275
2578 The name of the early 2276 The name of the early console should be specified
2579 as the value of this 2277 as the value of this parameter. Note that the name of
2580 the early console mig 2278 the early console might be different than the tty
2581 name passed to kgdboc 2279 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2280 blank and the first boot console that implements
2583 read() will be picked 2281 read() will be picked.
2584 2282
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2283 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2284 kernel debugger at the earliest opportunity.
2587 2285
2588 kmac= [MIPS] Korina etherne 2286 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2287 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2288 Ethernet adapter MAC address.
2591 2289
2592 kmemleak= [KNL,EARLY] Boot-time !! 2290 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2291 Valid arguments: on, off
2594 Default: on 2292 Default: on
2595 Built with CONFIG_DEB 2293 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2294 the default is off.
2597 2295
2598 kprobe_event=[probe-list] 2296 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2297 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2298 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2299 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2300 interface, but the parameters are comma delimited.
2603 For example, to add a 2301 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2302 arg1 and arg2, add to the command line;
2605 2303
2606 kprobe_event=p, 2304 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2305
2608 See also Documentatio 2306 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2307 Boot Parameter" section.
2610 2308
2611 kpti= [ARM64,EARLY] Control !! 2309 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2310 and kernel address spaces.
2613 Default: enabled on c 2311 Default: enabled on cores which need mitigation.
2614 0: force disabled 2312 0: force disabled
2615 1: force enabled 2313 1: force enabled
2616 2314
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 2315 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2316 Default is 0 (don't ignore, but inject #GP)
2625 2317
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 2318 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2319 Default is false (don't support).
2653 2320
>> 2321 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
>> 2322 KVM MMU at runtime.
>> 2323 Default is 0 (off)
>> 2324
2654 kvm.nx_huge_pages= 2325 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2326 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2327 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2328 force : Always deploy workaround.
2658 off : Never deplo 2329 off : Never deploy workaround.
2659 auto : Deploy work 2330 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2331 X86_BUG_ITLB_MULTIHIT.
2661 2332
2662 Default is 'auto'. 2333 Default is 'auto'.
2663 2334
2664 If the software worka 2335 If the software workaround is enabled for the host,
2665 guests do need not to 2336 guests do need not to enable it for nested guests.
2666 2337
2667 kvm.nx_huge_pages_recovery_ratio= 2338 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2339 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2340 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2341 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). !! 2342 minute. The default is 60.
>> 2343
>> 2344 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
>> 2345 Default is 1 (enabled)
2672 2346
2673 kvm.nx_huge_pages_recovery_period_ms= !! 2347 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2674 [KVM] Controls the ti !! 2348 for all guests.
2675 back to huge pages. I !! 2349 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 2350
2688 kvm-arm.mode= 2351 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2352 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 <<
2692 none: Forcefully disa <<
2693 2353
2694 nvhe: Standard nVHE-b 2354 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2355 protected guests.
2696 2356
2697 protected: nVHE-based 2357 protected: nVHE-based mode with support for guests whose
2698 state is k 2358 state is kept private from the host.
>> 2359 Not valid if the kernel is running in EL2.
2699 2360
2700 nested: VHE-based mod !! 2361 Defaults to VHE/nVHE based on hardware support.
2701 virtualizatio <<
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE <<
2705 mode to "protected" w <<
2706 for the host. "nested <<
2707 used with extreme cau <<
2708 2362
2709 kvm-arm.vgic_v3_group0_trap= 2363 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2364 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2365 system registers
2712 2366
2713 kvm-arm.vgic_v3_group1_trap= 2367 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2368 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2369 system registers
2716 2370
2717 kvm-arm.vgic_v3_common_trap= 2371 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2372 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2373 system registers
2720 2374
2721 kvm-arm.vgic_v4_enable= 2375 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2376 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2377 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 2378
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2379 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2380 Reserves given percentage from system memory area for
2745 contiguous memory all 2381 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2382 allocation.
2747 By default it reserve 2383 By default it reserves 5% of total system memory.
2748 Format: <integer> 2384 Format: <integer>
2749 Default: 5 2385 Default: 5
2750 2386
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2387 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2388 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2389 Default is 1 (enabled)
2754 for EPT. <<
2755 2390
2756 kvm-intel.emulate_invalid_guest_state 2391 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2392 [KVM,Intel] Enable emulation of invalid guest states
2758 state. Ignored if kvm !! 2393 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 2394
2764 kvm-intel.flexpriority= 2395 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2396 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2397 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2398
2769 kvm-intel.nested= 2399 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2400 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2401 Default is 0 (disabled)
2772 2402
2773 kvm-intel.unrestricted_guest= 2403 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2404 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2405 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2406 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2407
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2408 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2409 CVE-2018-3620.
2781 2410
2782 Valid arguments: neve 2411 Valid arguments: never, cond, always
2783 2412
2784 always: L1D cache flu 2413 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2414 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2415 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2416 never: Disables the mitigation
2788 2417
2789 Default is cond (do L 2418 Default is cond (do L1 cache flush in specific instances)
2790 2419
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2420 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2421 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2422 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 2423
2813 l1tf= [X86,EARLY] Control m !! 2424 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2425 affected CPUs
2815 2426
2816 The kernel PTE invers 2427 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2428 enabled and cannot be disabled.
2818 2429
2819 full 2430 full
2820 Provides all 2431 Provides all available mitigations for the
2821 L1TF vulnerab 2432 L1TF vulnerability. Disables SMT and
2822 enables all m 2433 enables all mitigations in the
2823 hypervisors, 2434 hypervisors, i.e. unconditional L1D flush.
2824 2435
2825 SMT control a 2436 SMT control and L1D flush control via the
2826 sysfs interfa 2437 sysfs interface is still possible after
2827 boot. Hyperv 2438 boot. Hypervisors will issue a warning
2828 when the firs 2439 when the first VM is started in a
2829 potentially i 2440 potentially insecure configuration,
2830 i.e. SMT enab 2441 i.e. SMT enabled or L1D flush disabled.
2831 2442
2832 full,force 2443 full,force
2833 Same as 'full 2444 Same as 'full', but disables SMT and L1D
2834 flush runtime 2445 flush runtime control. Implies the
2835 'nosmt=force' 2446 'nosmt=force' command line option.
2836 (i.e. sysfs c 2447 (i.e. sysfs control of SMT is disabled.)
2837 2448
2838 flush 2449 flush
2839 Leaves SMT en 2450 Leaves SMT enabled and enables the default
2840 hypervisor mi 2451 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2452 L1D flush.
2842 2453
2843 SMT control a 2454 SMT control and L1D flush control via the
2844 sysfs interfa 2455 sysfs interface is still possible after
2845 boot. Hyperv 2456 boot. Hypervisors will issue a warning
2846 when the firs 2457 when the first VM is started in a
2847 potentially i 2458 potentially insecure configuration,
2848 i.e. SMT enab 2459 i.e. SMT enabled or L1D flush disabled.
2849 2460
2850 flush,nosmt 2461 flush,nosmt
2851 2462
2852 Disables SMT 2463 Disables SMT and enables the default
2853 hypervisor mi 2464 hypervisor mitigation.
2854 2465
2855 SMT control a 2466 SMT control and L1D flush control via the
2856 sysfs interfa 2467 sysfs interface is still possible after
2857 boot. Hyperv 2468 boot. Hypervisors will issue a warning
2858 when the firs 2469 when the first VM is started in a
2859 potentially i 2470 potentially insecure configuration,
2860 i.e. SMT enab 2471 i.e. SMT enabled or L1D flush disabled.
2861 2472
2862 flush,nowarn 2473 flush,nowarn
2863 Same as 'flus 2474 Same as 'flush', but hypervisors will not
2864 warn when a V 2475 warn when a VM is started in a potentially
2865 insecure conf 2476 insecure configuration.
2866 2477
2867 off 2478 off
2868 Disables hype 2479 Disables hypervisor mitigations and doesn't
2869 emit any warn 2480 emit any warnings.
2870 It also drops 2481 It also drops the swap size and available
2871 RAM limit res 2482 RAM limit restriction on both hypervisor and
2872 bare metal. 2483 bare metal.
2873 2484
2874 Default is 'flush'. 2485 Default is 'flush'.
2875 2486
2876 For details see: Docu 2487 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2488
2878 l2cr= [PPC] 2489 l2cr= [PPC]
2879 2490
2880 l3cr= [PPC] 2491 l3cr= [PPC]
2881 2492
2882 lapic [X86-32,APIC,EARLY] E !! 2493 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2494 disabled it.
2884 2495
2885 lapic= [X86,APIC] Do not use 2496 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2497 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2498 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2499 Format: notscdeadline
2889 2500
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2501 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2502 in C2 power state.
2892 2503
2893 libata.dma= [LIBATA] DMA control 2504 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2505 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2506 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2507 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2508 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2509 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2510 for disks and CDROMs, but not CFs.
2900 2511
2901 libata.ignore_hpa= [LIBATA] Igno 2512 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2513 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2514 libata.ignore_hpa=1 ignore limits, using full disk
2904 2515
2905 libata.noacpi [LIBATA] Disables use 2516 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2517 when set.
2907 Format: <int> 2518 Format: <int>
2908 2519
2909 libata.force= [LIBATA] Force config !! 2520 libata.force= [LIBATA] Force configurations. The format is comma-
2910 separated list of "[I !! 2521 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2522 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2523 matching port, link or device. Basically, it matches
2913 printed on console by !! 2524 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2525 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2526 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2527 configuration applies to all ports, links and devices.
2917 2528
2918 If only DEVICE is omi 2529 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2530 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2531 number of 0 either selects the first device or the
2921 first fan-out link be 2532 first fan-out link behind PMP device. It does not
2922 select the host link. 2533 select the host link. DEVICE number of 15 selects the
2923 host link and device 2534 host link and device attached to it.
2924 2535
2925 The VAL specifies the 2536 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2537 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2538 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2539 The following configurations can be forced.
2929 2540
2930 * Cable type: 40c, 80 2541 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2542 Any ID with matching PORT is used.
2932 2543
2933 * SATA link speed lim 2544 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2545
2935 * Transfer mode: pio[ 2546 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2547 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2548 allowed.
2938 2549
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 2550 * [no]ncq: Turn on or off NCQ.
2950 2551
2951 * [no]ncqtrim: Enable !! 2552 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 <<
2953 * [no]ncqati: Enable <<
2954 <<
2955 * [no]trim: Enable or <<
2956 <<
2957 * trim_zero: Indicate <<
2958 <<
2959 * max_trim_128m: Set <<
2960 <<
2961 * [no]dma: Turn on or <<
2962 <<
2963 * atapi_dmadir: Enabl <<
2964 2553
2965 * atapi_mod16_dma: En !! 2554 * nohrst, nosrst, norst: suppress hard, soft
2966 commands that are n !! 2555 and both resets.
2967 2556
2968 * [no]dmalog: Enable !! 2557 * rstonce: only attempt one reset during
2969 READ LOG DMA EXT co !! 2558 hot-unplug link recovery
2970 2559
2971 * [no]iddevlog: Enabl !! 2560 * dump_id: dump IDENTIFY data.
2972 identify device dat <<
2973 2561
2974 * [no]logdir: Enable !! 2562 * atapi_dmadir: Enable ATAPI DMADIR bridge support
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 2563
2995 * disable: Disable th 2564 * disable: Disable this device.
2996 2565
2997 If there are multiple 2566 If there are multiple matching configurations changing
2998 the same attribute, t 2567 the same attribute, the last one is used.
2999 2568
>> 2569 memblock=debug [KNL] Enable memblock debug messages.
>> 2570
3000 load_ramdisk= [RAM] [Deprecated] 2571 load_ramdisk= [RAM] [Deprecated]
3001 2572
3002 lockd.nlm_grace_period=P [NFS] Assig 2573 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2574 Format: <integer>
3004 2575
3005 lockd.nlm_tcpport=N [NFS] Assign 2576 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2577 Format: <integer>
3007 2578
3008 lockd.nlm_timeout=T [NFS] Assign 2579 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2580 Format: <integer>
3010 2581
3011 lockd.nlm_udpport=M [NFS] Assign 2582 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2583 Format: <integer>
3013 2584
3014 lockdown= [SECURITY,EARLY] !! 2585 lockdown= [SECURITY]
3015 { integrity | confide 2586 { integrity | confidentiality }
3016 Enable the kernel loc 2587 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2588 integrity, kernel features that allow userland to
3018 modify the running ke 2589 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2590 confidentiality, kernel features that allow userland
3020 to extract confidenti 2591 to extract confidential information from the kernel
3021 are also disabled. 2592 are also disabled.
3022 2593
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] 2594 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2595 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2596 Defaults to being automatically set based on the
3058 number of online CPUs 2597 number of online CPUs.
3059 2598
3060 locktorture.nwriters_stress= [KNL] 2599 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2600 Set the number of locking write-acquisition kthreads.
3062 2601
3063 locktorture.onoff_holdoff= [KNL] 2602 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2603 Set time (s) after boot for CPU-hotplug testing.
3065 2604
3066 locktorture.onoff_interval= [KNL] 2605 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2606 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2607 zero to disable CPU-hotplug testing.
3069 2608
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] 2609 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2610 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2611 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2612 mode during the locktorture test.
3093 2613
3094 locktorture.shutdown_secs= [KNL] 2614 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2615 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2616 is useful for hands-off automated testing.
3097 2617
3098 locktorture.stat_interval= [KNL] 2618 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2619 Time (s) between statistics printk()s.
3100 2620
3101 locktorture.stutter= [KNL] 2621 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2622 Time (s) to stutter testing, for example,
3103 specifying five secon 2623 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2624 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2625 This tests the locking primitive's ability to
3106 transition abruptly t 2626 transition abruptly to and from idle.
3107 2627
3108 locktorture.torture_type= [KNL] 2628 locktorture.torture_type= [KNL]
3109 Specify the locking i 2629 Specify the locking implementation to test.
3110 2630
3111 locktorture.verbose= [KNL] 2631 locktorture.verbose= [KNL]
3112 Enable additional pri 2632 Enable additional printk() statements.
3113 2633
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2634 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2635 Format: <irq>
3120 2636
3121 loglevel= [KNL,EARLY] !! 2637 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2638 console loglevel will be printed to the console. It can
3124 also be changed with 2639 also be changed with klogd or other programs. The
3125 loglevels are defined 2640 loglevels are defined as follows:
3126 2641
3127 0 (KERN_EMERG) 2642 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2643 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2644 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2645 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2646 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2647 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2648 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2649 7 (KERN_DEBUG) debug-level messages
3135 2650
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2651 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2652 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2653 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2654 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2655 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2656 that allows to increase the default size depending on
3142 parameter that allows !! 2657 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2658
3146 logo.nologo [FB] Disables display 2659 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2660 This may be used to provide more screen space for
3148 kernel log messages a 2661 kernel log messages and is useful when debugging
3149 kernel boot problems. 2662 kernel boot problems.
3150 2663
3151 lp=0 [LP] Specify paral 2664 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2665 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2666 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2667 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2668 specified in addition to the ports) causes
3156 attached prin 2669 attached printers to be reset. Using
3157 lp=port1,port 2670 lp=port1,port2,... specifies the parallel ports
3158 to associate 2671 to associate lp devices with, starting with
3159 lp0. A port s 2672 lp0. A port specification may be 'none' to skip
3160 that lp devic 2673 that lp device, or a parport name such as
3161 'parport0'. S 2674 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2675 port specification list means that device IDs
3163 from each por 2676 from each port should be examined, to see if
3164 an IEEE 1284- 2677 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2678 so, the driver will manage that printer.
3166 See also head 2679 See also header of drivers/char/lp.c.
3167 2680
3168 lpj=n [KNL] 2681 lpj=n [KNL]
3169 Sets loops_per_jiffy 2682 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2683 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2684 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2685 the correct value for your kernel, boot with normal
3173 autodetection and see 2686 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2687 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2688 which is likely to cause problems if your CPUs need
3176 significantly diverge 2689 significantly divergent settings. An incorrect value
3177 will cause delays in 2690 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2691 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2692 unlikely, in the extreme case this might damage your
3180 hardware. 2693 hardware.
3181 2694
>> 2695 ltpc= [NET]
>> 2696 Format: <io>,<irq>,<dma>
>> 2697
3182 lsm.debug [SECURITY] Enable LSM 2698 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2699
3184 lsm=lsm1,...,lsmN 2700 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2701 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2702 overrides CONFIG_LSM, and the "security=" parameter.
3187 2703
>> 2704 machvec= [IA-64] Force the use of a particular machine-vector
>> 2705 (machvec) in a generic kernel.
>> 2706 Example: machvec=hpzx1
>> 2707
3188 machtype= [Loongson] Share the 2708 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2709 different yeeloong laptops.
3190 Example: machtype=lem 2710 Example: machtype=lemote-yeeloong-2f-7inch
3191 2711
3192 maxcpus= [SMP,EARLY] Maximum n !! 2712 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2713 than or equal to this physical address is ignored.
>> 2714
>> 2715 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2716 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2717 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2718 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2719 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2720 only takes effect during system bootup.
3198 While n=0 is a specia 2721 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2722 which also disables the IO APIC.
3200 2723
3201 max_loop= [LOOP] The number of 2724 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2725 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2726 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2727 of statically allocating a predefined number, loop
3205 devices can be reques 2728 devices can be requested on-demand with the
3206 /dev/loop-control int 2729 /dev/loop-control interface.
3207 2730
3208 mce [X86-32] Machine Chec 2731 mce [X86-32] Machine Check Exception
3209 2732
3210 mce=option [X86-64] See Document !! 2733 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2734
3212 md= [HW] RAID subsystems 2735 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2736 See Documentation/admin-guide/md.rst.
3214 2737
3215 mdacon= [MDA] 2738 mdacon= [MDA]
3216 Format: <first>,<last 2739 Format: <first>,<last>
3217 Specifies range of co 2740 Specifies range of consoles to be captured by the MDA.
3218 2741
3219 mds= [X86,INTEL,EARLY] !! 2742 mds= [X86,INTEL]
3220 Control mitigation fo 2743 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2744 Sampling (MDS) vulnerability.
3222 2745
3223 Certain CPUs are vuln 2746 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2747 internal buffers which can forward information to a
3225 disclosure gadget und 2748 disclosure gadget under certain conditions.
3226 2749
3227 In vulnerable process 2750 In vulnerable processors, the speculatively
3228 forwarded data can be 2751 forwarded data can be used in a cache side channel
3229 attack, to access dat 2752 attack, to access data to which the attacker does
3230 not have direct acces 2753 not have direct access.
3231 2754
3232 This parameter contro 2755 This parameter controls the MDS mitigation. The
3233 options are: 2756 options are:
3234 2757
3235 full - Enable M 2758 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2759 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2760 SMT on vulnerable CPUs
3238 off - Uncondit 2761 off - Unconditionally disable MDS mitigation
3239 2762
3240 On TAA-affected machi 2763 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2764 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2765 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2766 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2767 too.
3245 2768
3246 Not specifying this o 2769 Not specifying this option is equivalent to
3247 mds=full. 2770 mds=full.
3248 2771
3249 For details see: Docu 2772 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2773
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2774 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3252 Must be specified, ot !! 2775 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 2776
3258 1 for test; 2777 1 for test;
3259 2 when the kernel is 2778 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 2779 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 2780 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 2781
3270 [X86] Work as limitin 2782 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2783 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2784 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2785 belonging to unused RAM.
3274 2786
3275 Note that this only t 2787 Note that this only takes effects during boot time since
3276 in above case 3, memo 2788 in above case 3, memory may need be hot added after boot
3277 if system memory of h 2789 if system memory of hypervisor is not sufficient.
3278 2790
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 2791 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2792 memory.
3289 2793
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2794 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2795 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2796 per-device physically contiguous DMA buffers.
3295 2797
3296 memhp_default_state=online/offline/on !! 2798 memhp_default_state=online/offline
3297 [KNL] Set the initial 2799 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2800 onlining policy. If not specified, the default value is
3299 set according to the 2801 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2802 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2803 option.
3302 See Documentation/adm 2804 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 2805
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2806 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2807 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2808 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2809 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2810 option description.
3309 2811
3310 memmap=nn[KMG]@ss[KMG] 2812 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2813 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 2814 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2815 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2816 which limits max address to nn[KMG].
3315 Multiple different re 2817 Multiple different regions can be specified,
3316 comma delimited. 2818 comma delimited.
3317 Example: 2819 Example:
3318 memmap=100M@2 2820 memmap=100M@2G,100M#3G,1G!1024G
3319 2821
3320 memmap=nn[KMG]#ss[KMG] 2822 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2823 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2824 Region of memory to be marked is from ss to ss+nn.
3323 2825
3324 memmap=nn[KMG]$ss[KMG] 2826 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2827 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2828 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2829 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2830 memmap=64K$0x18690000
3329 or 2831 or
3330 memmap=0x100 2832 memmap=0x10000$0x18690000
3331 Some bootloaders may 2833 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2834 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2835 will be eaten.
3334 2836
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2837 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2838 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2839 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2840 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2841 and is NVDIMM or ADR memory.
3340 2842
3341 memmap=<size>%<offset>-<oldtype>+<new 2843 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 2844 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 2845 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 2846 out, the whole region will be marked as <newtype>,
3345 even if previously un 2847 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 2848 out, matching memory will be removed. Types are
3347 specified as e820 typ 2849 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 2850 3 = ACPI, 12 = PRAM.
3349 2851
3350 memory_corruption_check=0/1 [X86,EARL !! 2852 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 2853 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2854 memory when doing things like suspend/resume.
3353 Setting this option w 2855 Setting this option will scan the memory
3354 looking for corruptio 2856 looking for corruption. Enabling this will
3355 both detect corruptio 2857 both detect corruption and prevent the kernel
3356 from using the memory 2858 from using the memory being corrupted.
3357 However, its intended 2859 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2860 repeatable BIOS-originated corruption always
3359 affects the same memo 2861 affects the same memory, you can use memmap=
3360 to prevent the kernel 2862 to prevent the kernel from using that memory.
3361 2863
3362 memory_corruption_check_size=size [X8 !! 2864 memory_corruption_check_size=size [X86]
3363 By default it checks 2865 By default it checks for corruption in the low
3364 64k, making this memo 2866 64k, making this memory unavailable for normal
3365 use. Use this parame 2867 use. Use this parameter to scan for
3366 corruption in more or 2868 corruption in more or less memory.
3367 2869
3368 memory_corruption_check_period=second !! 2870 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2871 By default it checks for corruption every 60
3370 seconds. Use this pa 2872 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2873 other rate. 0 disables periodic checking.
3372 2874
3373 memory_hotplug.memmap_on_memory 2875 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 2876 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 2877 Format: {on | off (default)}
3376 When enabled, runtime 2878 When enabled, runtime hotplugged memory will
3377 allocate its internal !! 2879 allocate its internal metadata (struct pages)
3378 those vmemmap pages c !! 2880 from the hotadded memory which will allow to
3379 if hugetlb_free_vmemm !! 2881 hotadd a lot of memory without requiring
3380 hotadded memory which !! 2882 additional memory to do so.
3381 lot of memory without <<
3382 memory to do so. <<
3383 This feature is disab 2883 This feature is disabled by default because it
3384 has some implication 2884 has some implication on large (e.g. GB)
3385 allocations in some c 2885 allocations in some configurations (e.g. small
3386 memory blocks). 2886 memory blocks).
3387 The state of the flag 2887 The state of the flag can be read in
3388 /sys/module/memory_ho 2888 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 2889 Note that even when enabled, there are a few cases where
3390 the feature is not ef 2890 the feature is not effective.
3391 2891
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 2892 This is not compatible with hugetlb_free_vmemmap. If
>> 2893 both parameters are enabled, hugetlb_free_vmemmap takes
>> 2894 precedence over memory_hotplug.memmap_on_memory.
>> 2895
>> 2896 memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest
3393 Format: <integer> 2897 Format: <integer>
3394 default : 0 <disable> 2898 default : 0 <disable>
3395 Specifies the number 2899 Specifies the number of memtest passes to be
3396 performed. Each pass 2900 performed. Each pass selects another test
3397 pattern from a given 2901 pattern from a given set of patterns. Memtest
3398 fills the memory with 2902 fills the memory with this pattern, validates
3399 memory contents and r 2903 memory contents and reserves bad memory
3400 regions that are dete 2904 regions that are detected.
3401 2905
3402 mem_encrypt= [X86-64] AMD Secure M 2906 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2907 Valid arguments: on, off
3404 Default: off !! 2908 Default (depends on kernel configuration option):
>> 2909 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2910 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2911 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2912 mem_encrypt=off: Do not activate SME
3407 2913
3408 Refer to Documentatio !! 2914 Refer to Documentation/virt/kvm/amd-memory-encryption.rst
3409 for details on when m 2915 for details on when memory encryption can be activated.
3410 2916
3411 mem_sleep_default= [SUSPEND] Def 2917 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2918 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2919 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2920 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 2921 See Documentation/admin-guide/pm/sleep-states.rst.
3416 2922
>> 2923 meye.*= [HW] Set MotionEye Camera parameters
>> 2924 See Documentation/admin-guide/media/meye.rst.
>> 2925
>> 2926 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2927 Multi-Function General Purpose Timers on AMD Geode
>> 2928 platforms.
>> 2929
3417 mfgptfix [X86-32] Fix MFGPT ti 2930 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2931 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2932 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2933 problem by letting the user disable the workaround.
3421 2934
3422 mga= [HW,DRM] 2935 mga= [HW,DRM]
3423 2936
3424 microcode.force_minrev= [X86] !! 2937 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2938 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2939
3429 mini2440= [ARM,HW,KNL] 2940 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2941 Format:[0..2][b][c][t]
3431 Default: "0tb" 2942 Default: "0tb"
3432 MINI2440 configuratio 2943 MINI2440 configuration specification:
3433 0 - The attached scre 2944 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2945 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2946 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2947 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2948 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2949 unconfigured.
3439 b - Enable backlight. 2950 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2951 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2952 LED. This parameter is not necessary when using the
3442 VGA shield. 2953 VGA shield.
3443 c - Enable the s3c ca 2954 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2955 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2956 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2957 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2958 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 2959 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 2960
3450 mitigations= 2961 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 2962 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 2963 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 2964 arch-independent options, each of which is an
3454 aggregation of existi 2965 aggregation of existing arch-specific options.
3455 2966
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 2967 off
3460 Disable all o 2968 Disable all optional CPU mitigations. This
3461 improves syst 2969 improves system performance, but it may also
3462 expose users 2970 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 2971 Equivalent to: nopti [X86,PPC]
3464 !! 2972 kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 2973 nospectre_v1 [X86,PPC]
>> 2974 nobp=0 [S390]
3475 2975 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 2976 spectre_v2_user=off [X86]
3482 !! 2977 spec_store_bypass_disable=off [X86,PPC]
3483 2978 ssbd=force-off [ARM64]
>> 2979 l1tf=off [X86]
>> 2980 mds=off [X86]
3484 2981 tsx_async_abort=off [X86]
>> 2982 kvm.nx_huge_pages=off [X86]
>> 2983 no_entry_flush [PPC]
>> 2984 no_uaccess_flush [PPC]
3485 2985
3486 Exceptions: 2986 Exceptions:
3487 2987 This does not have any effect on
3488 2988 kvm.nx_huge_pages when
3489 2989 kvm.nx_huge_pages=force.
3490 2990
3491 auto (default) 2991 auto (default)
3492 Mitigate all 2992 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 2993 enabled, even if it's vulnerable. This is for
3494 users who don 2994 users who don't want to be surprised by SMT
3495 getting disab 2995 getting disabled across kernel upgrades, or who
3496 have other wa 2996 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 2997 Equivalent to: (default behavior)
3498 2998
3499 auto,nosmt 2999 auto,nosmt
3500 Mitigate all 3000 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 3001 if needed. This is for users who always want to
3502 be fully miti 3002 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 3003 Equivalent to: l1tf=flush,nosmt [X86]
3504 3004 mds=full,nosmt [X86]
3505 3005 tsx_async_abort=full,nosmt [X86]
3506 <<
3507 <<
3508 3006
3509 mminit_loglevel= 3007 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 3008 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 3009 parameter allows control of the logging verbosity for
3512 the additional memory 3010 the additional memory initialisation checks. A value
3513 of 0 disables mminit 3011 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 3012 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 3013 so loglevel=8 may also need to be specified.
3516 3014
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 3015 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3016 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3017 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3018 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3019 is always true, so this option does nothing.
3578 3020
3579 module_blacklist= [KNL] Do not load 3021 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3022 modules. Useful for debugging problem modules.
3581 3023
3582 mousedev.tap_time= 3024 mousedev.tap_time=
3583 [MOUSE] Maximum time 3025 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3026 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3027 a tap and be reported as a left button click (for
3586 touchpads working in 3028 touchpads working in absolute mode only).
3587 Format: <msecs> 3029 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3030 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3031 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3032 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3033 reporting absolute coordinates, such as tablets
3592 3034
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3035 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3036 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3037 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3038 specifies the amount of memory used for migratable
3597 allocations. If both 3039 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3040 specified, then kernelcore will be at *least* the
3599 specified value but m 3041 specified value but may be more. If movablecore on its
3600 own is specified, the 3042 own is specified, the administrator must be careful
3601 that the amount of me 3043 that the amount of memory usable for all allocations
3602 is not too small. 3044 is not too small.
3603 3045
3604 movable_node [KNL,EARLY] Boot-time !! 3046 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3047 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3048 of such nodes will be usable only for movable
3607 allocations which rul 3049 allocations which rules out almost all kernel
3608 allocations. Use with 3050 allocations. Use with caution!
3609 3051
3610 MTD_Partition= [MTD] 3052 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3053 Format: <name>,<region-number>,<size>,<offset>
3612 3054
3613 MTD_Region= [MTD] Format: 3055 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3056 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3057
3616 mtdparts= [MTD] 3058 mtdparts= [MTD]
3617 See drivers/mtd/parse 3059 See drivers/mtd/parsers/cmdlinepart.c
3618 3060
>> 3061 multitce=off [PPC] This parameter disables the use of the pSeries
>> 3062 firmware feature for updating multiple TCE entries
>> 3063 at a time.
>> 3064
>> 3065 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 3066
>> 3067 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 3068
>> 3069 boundary - index of last SLC block on Flex-OneNAND.
>> 3070 The remaining blocks are configured as MLC blocks.
>> 3071 lock - Configure if Flex-OneNAND boundary should be locked.
>> 3072 Once locked, the boundary cannot be changed.
>> 3073 1 indicates lock status, 0 indicates unlock status.
>> 3074
>> 3075 mtdset= [ARM]
>> 3076 ARM/S3C2412 JIVE boot control
>> 3077
>> 3078 See arch/arm/mach-s3c/mach-jive.c
>> 3079
3619 mtouchusb.raw_coordinates= 3080 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3081 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3082 ('y', default) or cooked coordinates ('n')
3622 3083
3623 mtrr=debug [X86,EARLY] !! 3084 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 3085 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3086 that could hold holes aka. UC entries.
3630 3087
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3088 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3089 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3090 Default is 1.
3634 Large value could pre 3091 Large value could prevent small alignment from
3635 using up MTRRs. 3092 using up MTRRs.
3636 3093
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3094 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3095 Format: <integer>
3639 Range: 0,7 : spare re 3096 Range: 0,7 : spare reg number
3640 Default : 1 3097 Default : 1
3641 Used for mtrr cleanup 3098 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3099 Set to 2 or more if your graphical card needs more.
3643 3100
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 3101 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3102
3650 netdev= [NET] Network devices 3103 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3104 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3105 Note that mem_start is often overloaded to mean
3653 something different a 3106 something different and driver-specific.
3654 This usage is only do 3107 This usage is only documented in each driver source
3655 file if at all. 3108 file if at all.
3656 3109
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 3110 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3111 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3112 0 to disable accounting
3665 1 to enable accountin 3113 1 to enable accounting
3666 Default value is 0. 3114 Default value is 0.
3667 3115
3668 nfs.cache_getent= !! 3116 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3117 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3118
3672 nfs.cache_getent_timeout= !! 3119 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3120 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3121
>> 3122 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3123 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3124
3676 nfs.callback_nr_threads= 3125 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3126 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3127 NFS client will assign to service NFSv4 callback
3679 requests. 3128 requests.
3680 3129
3681 nfs.callback_tcpport= 3130 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3131 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3132 channel should listen.
3684 3133
3685 nfs.delay_retrans= !! 3134 nfs.cache_getent=
3686 [NFS] specifies the n !! 3135 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3136 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3137
3689 Only applies if the s !! 3138 nfs.cache_getent_timeout=
3690 and the specified val !! 3139 [NFS] sets the timeout after which an attempt to
>> 3140 update a cache entry is deemed to have failed.
>> 3141
>> 3142 nfs.idmap_cache_timeout=
>> 3143 [NFS] set the maximum lifetime for idmapper cache
>> 3144 entries.
3691 3145
3692 nfs.enable_ino64= 3146 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3147 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3148 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3149 number for the readdir() and stat() syscalls instead
3696 of returning the full 3150 of returning the full 64-bit number.
3697 The default is to ret 3151 The default is to return 64-bit inode numbers.
3698 3152
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3153 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3154 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3155 slots the client will assign to the callback
3706 channel. This determi 3156 channel. This determines the maximum number of
3707 callbacks the client 3157 callbacks the client will process in parallel for
3708 a particular server. 3158 a particular server.
3709 3159
3710 nfs.max_session_slots= 3160 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3161 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3162 the client will attempt to negotiate with the server.
3713 This limits the numbe 3163 This limits the number of simultaneous RPC requests
3714 that the client can s 3164 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3165 Note that there is little point in setting this
3716 value higher than the 3166 value higher than the max_tcp_slot_table_limit.
3717 3167
3718 nfs.nfs4_disable_idmapping= 3168 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3169 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3170 ensures that both the RPC level authentication
3721 scheme and the NFS le 3171 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3172 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3173 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3174 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3175 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3176 Servers that do not support this mode of operation
3727 will be autodetected 3177 will be autodetected by the client, and it will fall
3728 back to using the idm 3178 back to using the idmapper.
3729 To turn off this beha 3179 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3180 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3181 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3182 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3183 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3184 UUID that is generated at system install time.
3736 3185
3737 nfs.recover_lost_locks= !! 3186 nfs.send_implementation_id =
>> 3187 [NFSv4.1] Send client implementation identification
>> 3188 information in exchange_id requests.
>> 3189 If zero, no implementation identification information
>> 3190 will be sent.
>> 3191 The default is to send the implementation identification
>> 3192 information.
>> 3193
>> 3194 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3195 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3196 to a lease timeout on the server. Please note that
3740 doing this risks data 3197 doing this risks data corruption, since there are
3741 no guarantees that th 3198 no guarantees that the file will remain unchanged
3742 after the locks are l 3199 after the locks are lost.
3743 If you want to enable 3200 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3201 attempting to recover these locks, then set this
3745 parameter to '1'. 3202 parameter to '1'.
3746 The default parameter 3203 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3204 not to attempt recovery of lost locks.
3748 3205
3749 nfs.send_implementation_id= !! 3206 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 3207 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3208 layoutstats to the pNFS metadata server.
3760 3209
3761 Setting this to value 3210 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3211 whatever value is the default set by the layout
3763 driver. A non-zero va 3212 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3213 in seconds between layoutstats transmissions.
3765 3214
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= 3215 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 3216 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 3217 server will return only numeric uids and gids to
3774 clients using auth_sy 3218 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 3219 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 3220 migration from NFSv2/v3.
3777 3221
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] 3222 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3223 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3224 NMI stack-backtrace request.
3798 3225
3799 nmi_debug= [KNL,SH] Specify one 3226 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3227 when a NMI is triggered.
3801 Format: [state][,regs 3228 Format: [state][,regs][,debounce][,die]
3802 3229
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3230 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3231 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3232 Valid num: 0 or 1
3806 0 - turn hardlockup d 3233 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3234 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3235 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3236 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3237 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3238 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3239 please see 'nowatchdog'.
3815 This is useful when y 3240 This is useful when you use a panic=... timeout and
3816 need the box quickly 3241 need the box quickly up again.
3817 3242
3818 These settings can be 3243 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3244 the nmi_watchdog and hardlockup_panic sysctls.
3820 3245
>> 3246 netpoll.carrier_timeout=
>> 3247 [NET] Specifies amount of time (in seconds) that
>> 3248 netpoll should wait for a carrier. By default netpoll
>> 3249 waits 4 seconds.
>> 3250
3821 no387 [BUGS=X86-32] Tells t 3251 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3252 emulation library even if a 387 maths coprocessor
3823 is present. 3253 is present.
3824 3254
3825 no4lvl [RISCV,EARLY] Disable !! 3255 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 3256 kernel to use 4-level paging instead.
3830 3257
3831 noalign [KNL,ARM] !! 3258 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 3259
3840 no_console_suspend 3260 no_console_suspend
3841 [HW] Never suspend th 3261 [HW] Never suspend the console
3842 Disable suspending of 3262 Disable suspending of consoles during suspend and
3843 hibernate operations. 3263 hibernate operations. Once disabled, debugging
3844 messages can reach va 3264 messages can reach various consoles while the rest
3845 of the system is bein 3265 of the system is being put to sleep (ie, while
3846 debugging driver susp 3266 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3267 not work reliably with all consoles, but is known
3848 to work with serial a 3268 to work with serial and VGA consoles.
3849 To facilitate more fl 3269 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3270 console_suspend, a printk module parameter to control
3851 it. Users could use c 3271 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3272 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3273 turn on/off it dynamically.
3854 3274
3855 no_debug_objects !! 3275 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3276 Disable device dump. Device dump allows drivers to
>> 3277 append dump data to vmcore so you can collect driver
>> 3278 specified debug info. Drivers can append the data
>> 3279 without any limit and this data is stored in memory,
>> 3280 so this may cause significant memory stress. Disabling
>> 3281 device dump can help save memory but the driver debug
>> 3282 data will be no longer available. This parameter
>> 3283 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3284 is set.
>> 3285
>> 3286 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3287 caches in the slab allocator. Saves per-node memory,
>> 3288 but will impact performance.
>> 3289
>> 3290 noalign [KNL,ARM]
>> 3291
>> 3292 noaltinstr [S390] Disables alternative instructions patching
>> 3293 (CPU alternatives feature).
>> 3294
>> 3295 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3296 IOAPICs that may be present in the system.
>> 3297
>> 3298 noautogroup Disable scheduler automatic task group creation.
>> 3299
>> 3300 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 3301 on "Classic" PPC cores.
>> 3302
>> 3303 nocache [ARM]
>> 3304
>> 3305 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 3306
>> 3307 delayacct [KNL] Enable per-task delay accounting
3857 3308
3858 nodsp [SH] Disable hardware 3309 nodsp [SH] Disable hardware DSP at boot time.
3859 3310
3860 noefi [EFI,EARLY] Disable E !! 3311 noefi Disable EFI runtime services support.
>> 3312
>> 3313 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3861 3314
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3315 noexec [IA-64]
>> 3316
>> 3317 noexec [X86]
>> 3318 On X86-32 available only on PAE configured kernels.
>> 3319 noexec=on: enable non-executable mappings (default)
>> 3320 noexec=off: disable non-executable mappings
>> 3321
>> 3322 nosmap [X86,PPC]
>> 3323 Disable SMAP (Supervisor Mode Access Prevention)
>> 3324 even if it is supported by processor.
>> 3325
>> 3326 nosmep [X86,PPC]
>> 3327 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3328 even if it is supported by processor.
3863 3329
3864 noexec32 [X86-64] 3330 noexec32 [X86-64]
3865 This affects only 32- 3331 This affects only 32-bit executables.
3866 noexec32=on: enable n 3332 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3333 read doesn't imply executable mappings
3868 noexec32=off: disable 3334 noexec32=off: disable non-executable mappings
3869 read implies 3335 read implies executable mappings
3870 3336
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 3337 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3338
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3339 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3340 register save and restore. The kernel will only save
3881 legacy floating-point 3341 legacy floating-point registers on task switch.
3882 3342
>> 3343 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
>> 3344
>> 3345 nohugevmalloc [PPC] Disable kernel huge vmalloc mappings.
>> 3346
>> 3347 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3348 Equivalent to smt=1.
>> 3349
>> 3350 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3351 nosmt=force: Force disable SMT, cannot be undone
>> 3352 via the sysfs control file.
>> 3353
>> 3354 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3355 (bounds check bypass). With this option data leaks are
>> 3356 possible in the system.
>> 3357
>> 3358 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 3359 the Spectre variant 2 (indirect branch prediction)
>> 3360 vulnerability. System may allow data leaks with this
>> 3361 option.
>> 3362
>> 3363 nospec_store_bypass_disable
>> 3364 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3365
>> 3366 no_uaccess_flush
>> 3367 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3368
>> 3369 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3370 and restore using xsave. The kernel will fallback to
>> 3371 enabling legacy floating-point and sse state.
>> 3372
>> 3373 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3374 register states. The kernel will fall back to use
>> 3375 xsave to save the states. By using this parameter,
>> 3376 performance of saving the states is degraded because
>> 3377 xsave doesn't support modified optimization while
>> 3378 xsaveopt supports it on xsaveopt enabled systems.
>> 3379
>> 3380 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3381 restoring x86 extended register state in compacted
>> 3382 form of xsave area. The kernel will fall back to use
>> 3383 xsaveopt and xrstor to save and restore the states
>> 3384 in standard form of xsave area. By using this
>> 3385 parameter, xsave area per process might occupy more
>> 3386 memory on xsaves enabled systems.
>> 3387
>> 3388 nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
>> 3389 in do_idle() and not use the arch_cpu_idle()
>> 3390 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
>> 3391 to be effective. This is useful on platforms where the
>> 3392 sleep(SH) or wfi(ARM,ARM64) instructions do not work
>> 3393 correctly or when doing power measurements to evalute
>> 3394 the impact of the sleep instructions. This is also
>> 3395 useful when using JTAG debugger.
>> 3396
>> 3397 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3398 only way then for a file to be executed with privilege
>> 3399 is to be setuid root or executed by root.
>> 3400
>> 3401 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3402 function PAL_HALT_LIGHT when idle. This increases
>> 3403 power-consumption. On the positive side, it reduces
>> 3404 interrupt wake-up latency, which may improve performance
>> 3405 in certain environments such as networked servers or
>> 3406 real-time systems.
>> 3407
3883 no_hash_pointers 3408 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3409 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3410 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3411 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3412 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3413 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3414 users, but it also makes debugging the kernel more
3891 difficult since unequ 3415 difficult since unequal pointers can no longer be
3892 compared. However, i 3416 compared. However, if this command-line option is
3893 specified, then all n 3417 specified, then all normal pointers will have their true
3894 value printed. This o !! 3418 value printed. Pointers printed via %pK may still be
>> 3419 hashed. This option should only be specified when
3895 debugging the kernel. 3420 debugging the kernel. Please do not use on production
3896 kernels. 3421 kernels.
3897 3422
3898 nohibernate [HIBERNATION] Disable 3423 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3424
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 3425 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3426 Valid arguments: on, off
3915 Default: on 3427 Default: on
3916 3428
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3429 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3430 The argument is a cpu list, as described above.
3919 In kernels built with 3431 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3432 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3433 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3434 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3435 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3436 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3437 rcu_nocbs= boot parameter.
3926 3438
3927 Note that this argume !! 3439 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 3440
>> 3441 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3442 disable unhandled interrupt sources.
>> 3443
>> 3444 no_timer_check [X86,APIC] Disables the code which tests for
>> 3445 broken timer IRQ sources.
>> 3446
>> 3447 noisapnp [ISAPNP] Disables ISA PnP code.
3929 3448
3930 noinitrd [RAM] Tells the kerne 3449 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3450 initial RAM disk.
3932 3451
3933 nointremap [X86-64,Intel-IOMMU,E !! 3452 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3453 remapping.
3935 [Deprecated - use int 3454 [Deprecated - use intremap=off]
3936 3455
3937 noinvpcid [X86,EARLY] Disable t !! 3456 nointroute [IA-64]
3938 3457
3939 noiotrap [SH] Disables trapped !! 3458 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 3459
3941 noirqdebug [X86-32] Disables the !! 3460 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 <<
3944 noisapnp [ISAPNP] Disables ISA <<
3945 3461
3946 nokaslr [KNL,EARLY] !! 3462 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 3463
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3464 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3465 fault handling.
3953 3466
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3467 no-vmw-sched-clock
>> 3468 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3469 clock and use the default one.
3955 3470
3956 nolapic [X86-32,APIC,EARLY] D !! 3471 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
>> 3472 accounting. steal time is computed, but won't
>> 3473 influence scheduler behaviour
3957 3474
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3475 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3959 3476
3960 nomce [X86-32] Disable Mach !! 3477 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3961 3478
3962 nomfgpt [X86-32] Disable Mult !! 3479 noltlbs [PPC] Do not use large page/tlb entries for kernel
3963 Timer usage (for AMD !! 3480 lowmem mapping on PPC40x and PPC8xx
3964 3481
3965 nomodeset Disable kernel modese !! 3482 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 3483
3973 Useful as error fallb !! 3484 nomce [X86-32] Disable Machine Check Exception
3974 3485
3975 nomodule Disable module load !! 3486 nomfgpt [X86-32] Disable Multi-Function General Purpose
>> 3487 Timer usage (for AMD Geode machines).
3976 3488
3977 nonmi_ipi [X86] Disable using N 3489 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3490 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3491 irq.
3980 3492
3981 nopat [X86,EARLY] Disable P !! 3493 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 3494
3989 nopti [X86-64,EARLY] !! 3495 nopat [X86] Disable PAT (page attribute table extension of
3990 Equivalent to pti=off !! 3496 pagetables) support.
3991 3497
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3498 nopcid [X86-64] Disable the PCID cpu feature.
3993 Disables the PV optim <<
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 <<
3997 nopvspin [X86,XEN,KVM,EARLY] <<
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3499
4002 norandmaps Don't use address spa 3500 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3501 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3502
4005 noreplace-smp [X86-32,SMP] Don't re 3503 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3504 with UP alternatives
4007 3505
>> 3506 nordrand [X86] Disable kernel use of the RDRAND and
>> 3507 RDSEED instructions even if they are supported
>> 3508 by the processor. RDRAND and RDSEED are still
>> 3509 available to user space applications.
>> 3510
4008 noresume [SWSUSP] Disables res 3511 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3512 space.
4010 3513
4011 no-scroll [VGA] Disables scroll 3514 no-scroll [VGA] Disables scrollback.
4012 This is required for 3515 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3516 reader made by F.H. Papenmeier (Germany).
4014 3517
4015 nosgx [X86-64,SGX,EARLY] Di !! 3518 nosbagart [IA-64]
4016 3519
4017 nosmap [PPC,EARLY] !! 3520 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 3521
4021 nosmep [PPC64s,EARLY] !! 3522 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 3523
4025 nosmp [SMP,EARLY] Tells an !! 3524 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3525 and disable the IO APIC. legacy for "maxcpus=0".
4027 3526
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 3527 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3528
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 3529 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3530
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 3531 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3532 soft-lockup and NMI watchdog (hard-lockup).
4083 3533
4084 nowb [ARM,EARLY] !! 3534 nowb [ARM]
4085 3535
4086 nox2apic [X86-64,APIC,EARLY] D !! 3536 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3537
4088 NOTE: this parameter !! 3538 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4089 LEGACY_XAPIC_DISABLED !! 3539 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4090 IA32_XAPIC_DISABLE_ST !! 3540 Some features depend on CPU0. Known dependencies are:
>> 3541 1. Resume from suspend/hibernate depends on CPU0.
>> 3542 Suspend/hibernate will fail if CPU0 is offline and you
>> 3543 need to online CPU0 before suspend/hibernate.
>> 3544 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 3545 removed if a PIC interrupt is detected.
>> 3546 It's said poweroff/reboot may depend on CPU0 on some
>> 3547 machines although I haven't seen such issues so far
>> 3548 after CPU0 is offline on a few tested machines.
>> 3549 If the dependencies are under your control, you can
>> 3550 turn on cpu0_hotplug.
>> 3551
>> 3552 nps_mtm_hs_ctr= [KNL,ARC]
>> 3553 This parameter sets the maximum duration, in
>> 3554 cycles, each HW thread of the CTOP can run
>> 3555 without interruptions, before HW switches it.
>> 3556 The actual maximum duration is 16 times this
>> 3557 parameter's value.
>> 3558 Format: integer between 1 and 255
>> 3559 Default: 255
>> 3560
>> 3561 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3562 purges which is reported from either PAL_VM_SUMMARY or
>> 3563 SAL PALO.
4091 3564
4092 noxsave [BUGS=X86] Disables x !! 3565 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4093 and restore using xsa <<
4094 enabling legacy float <<
4095 <<
4096 noxsaveopt [X86] Disables xsaveo <<
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 3566 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3567 support 'n' processors. It could be larger than the
4114 number of already plu 3568 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3569 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3570 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3571 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3572 hot plugging.
4119 3573
4120 nr_uarts= [SERIAL] maximum numb 3574 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3575
4122 numa=off [KNL, ARM64, PPC, RIS !! 3576 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123 Disable NUMA, Only se !! 3577 set up a single NUMA node spanning all memory.
4124 spanning all memory. <<
4125 3578
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 3579 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 3580 NUMA balancing.
4128 Allowed values are en 3581 Allowed values are enable and disable
4129 3582
4130 numa_zonelist_order= [KNL, BOOT] Sele 3583 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3584 'node', 'default' can be specified
4132 This can be set from 3585 This can be set from sysctl after boot.
4133 See Documentation/adm 3586 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3587
4135 ohci1394_dma=early [HW,EARLY] en !! 3588 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3589 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3590 info.
4138 3591
4139 olpc_ec_timeout= [OLPC] ms delay when 3592 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3593 Rather than timing out after 20 ms if an EC
4141 command is not proper 3594 command is not properly ACKed, override the length
4142 of the timeout. We h 3595 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3596 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3597 interrupts *may* be lost!
4145 3598
4146 omap_mux= [OMAP] Override bootl 3599 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3600 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3601 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3602 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3603
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 3604 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 3605 process, but there is a small probability of
4164 deadlocking the machi 3606 deadlocking the machine.
4165 This will also cause 3607 This will also cause panics on machine check exceptions.
4166 Useful together with 3608 Useful together with panic=30 to trigger a reboot.
4167 3609
4168 page_alloc.shuffle= 3610 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3611 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3612 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3613 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3614 running on a platform with a direct-mapped memory-side
>> 3615 cache, and this parameter can be used to
>> 3616 override/disable that behavior. The state of the flag
>> 3617 can be read from sysfs at:
4173 /sys/module/page_allo 3618 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3619
4176 page_owner= [KNL,EARLY] Boot-time !! 3620 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3621 Storage of the information about who allocated
4178 each page is disabled 3622 each page is disabled in default. With this switch,
4179 we can turn it on. 3623 we can turn it on.
4180 on: enable the featur 3624 on: enable the feature
4181 3625
4182 page_poison= [KNL,EARLY] Boot-time !! 3626 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3627 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3628 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3629 off: turn off poisoning (default)
4186 on: turn on poisoning 3630 on: turn on poisoning
4187 3631
4188 page_reporting.page_reporting_order= 3632 page_reporting.page_reporting_order=
4189 [KNL] Minimal page re 3633 [KNL] Minimal page reporting order
4190 Format: <integer> 3634 Format: <integer>
4191 Adjust the minimal pa 3635 Adjust the minimal page reporting order. The page
4192 reporting is disabled !! 3636 reporting is disabled when it exceeds (MAX_ORDER-1).
4193 3637
4194 panic= [KNL] Kernel behaviou 3638 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3639 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3640 timeout = 0: wait forever
4197 timeout < 0: reboot i 3641 timeout < 0: reboot immediately
4198 Format: <timeout> 3642 Format: <timeout>
4199 3643
4200 panic_on_taint= [KNL,EARLY] !! 3644 panic_print= Bitmask for printing system info when panic happens.
4201 Bitmask for condition !! 3645 User can chose combination of the following bits:
>> 3646 bit 0: print all tasks info
>> 3647 bit 1: print system memory info
>> 3648 bit 2: print timer info
>> 3649 bit 3: print locks info if CONFIG_LOCKDEP is on
>> 3650 bit 4: print ftrace buffer
>> 3651 bit 5: print all printk messages in buffer
>> 3652
>> 3653 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4202 Format: <hex>[,nouser 3654 Format: <hex>[,nousertaint]
4203 Hexadecimal bitmask r 3655 Hexadecimal bitmask representing the set of TAINT flags
4204 that will cause the k 3656 that will cause the kernel to panic when add_taint() is
4205 called with any of th 3657 called with any of the flags in this set.
4206 The optional switch " 3658 The optional switch "nousertaint" can be utilized to
4207 prevent userspace for 3659 prevent userspace forced crashes by writing to sysctl
4208 /proc/sys/kernel/tain 3660 /proc/sys/kernel/tainted any flagset matching with the
4209 bitmask set on panic_ 3661 bitmask set on panic_on_taint.
4210 See Documentation/adm 3662 See Documentation/admin-guide/tainted-kernels.rst for
4211 extra details on the 3663 extra details on the taint flags that users can pick
4212 to compose the bitmas 3664 to compose the bitmask to assign to panic_on_taint.
4213 3665
4214 panic_on_warn=1 panic() instead of WA !! 3666 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4215 on a WARN(). 3667 on a WARN().
4216 3668
4217 panic_print= Bitmask for printing !! 3669 crash_kexec_post_notifiers
4218 User can chose combin !! 3670 Run kdump after running panic-notifiers and dumping
4219 bit 0: print all task !! 3671 kmsg. This only for the users who doubt kdump always
4220 bit 1: print system m !! 3672 succeeds in any situation.
4221 bit 2: print timer in !! 3673 Note that this also increases risks of kdump failure,
4222 bit 3: print locks in !! 3674 because some panic notifiers can make the crashed
4223 bit 4: print ftrace b !! 3675 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 3676
4232 parkbd.port= [HW] Parallel port nu 3677 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3678 connected to, default is 0.
4234 Format: <parport#> 3679 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3680 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3681 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3682 Format: <mode>
4238 3683
4239 parport= [HW,PPT] Specify para 3684 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3685 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3686 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3687 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3688 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3689 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3690 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3691 should be numbers, or 'auto' (for using detected
4247 settings on that part 3692 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3693 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3694 Parallel ports are assigned in the order they
4250 are specified on the 3695 are specified on the command line, starting
4251 with parport0. 3696 with parport0.
4252 3697
4253 parport_init_mode= [HW,PPT] 3698 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3699 Configure VIA parallel port to operate in
4255 a specific mode. This 3700 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3701 computer where firmware has no options for setting
4257 up parallel port mode 3702 up parallel port mode and sets it to spp.
4258 Currently this functi 3703 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3704 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3705
4261 pata_legacy.all= [HW,LIBATA] 3706 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 3707 Format: <int>
4263 Set to non-zero to pr 3708 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 3709 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 3710 has been found at either range. Disabled by default.
4266 3711
4267 pata_legacy.autospeed= [HW,LIBATA] 3712 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 3713 Format: <int>
4269 Set to non-zero if a 3714 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 3715 changes. Disabled by default.
4271 3716
4272 pata_legacy.ht6560a= [HW,LIBATA] 3717 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 3718 Format: <int>
4274 Set to 1, 2, or 3 for 3719 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 3720 the secondary channel, or both channels respectively.
4276 Disabled by default. 3721 Disabled by default.
4277 3722
4278 pata_legacy.ht6560b= [HW,LIBATA] 3723 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 3724 Format: <int>
4280 Set to 1, 2, or 3 for 3725 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 3726 the secondary channel, or both channels respectively.
4282 Disabled by default. 3727 Disabled by default.
4283 3728
4284 pata_legacy.iordy_mask= [HW,LIBATA] 3729 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 3730 Format: <int>
4286 IORDY enable mask. S 3731 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 3732 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 3733 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 3734 the second channel, and so on. The sequence will often
4290 correspond to the pri 3735 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 3736 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 3737 bus and the use of other driver options may interfere
4293 with the sequence. B 3738 with the sequence. By default IORDY is allowed across
4294 all channels. 3739 all channels.
4295 3740
4296 pata_legacy.opti82c46x= [HW,LIBATA] 3741 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 3742 Format: <int>
4298 Set to 1, 2, or 3 for 3743 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 3744 channel, the secondary channel, or both channels
4300 respectively. Disabl 3745 respectively. Disabled by default.
4301 3746
4302 pata_legacy.opti82c611a= [HW,L 3747 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 3748 Format: <int>
4304 Set to 1, 2, or 3 for 3749 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 3750 channel, the secondary channel, or both channels
4306 respectively. Disabl 3751 respectively. Disabled by default.
4307 3752
4308 pata_legacy.pio_mask= [HW,LIBATA] 3753 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 3754 Format: <int>
4310 PIO mode mask for aut 3755 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 3756 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 3757 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 3758 All modes allowed by default.
4314 3759
4315 pata_legacy.probe_all= [HW,LIBATA] 3760 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 3761 Format: <int>
4317 Set to non-zero to pr 3762 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 3763 port ranges on PCI systems. Disabled by default.
4319 3764
4320 pata_legacy.probe_mask= [HW,LIBATA] 3765 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 3766 Format: <int>
4322 Probe mask for legacy 3767 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 3768 platform configuration and the use of other driver
4324 options up to 6 legac 3769 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 3770 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 3771 of individual ports can be disabled by setting the
4327 corresponding bits in 3772 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 3773 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 3774 By default all supported ports are probed.
4330 3775
4331 pata_legacy.qdi= [HW,LIBATA] 3776 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 3777 Format: <int>
4333 Set to non-zero to pr 3778 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 3779 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 3780
4336 pata_legacy.winbond= [HW,LIBATA] 3781 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 3782 Format: <int>
4338 Set to non-zero to pr 3783 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 3784 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 3785 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 3786 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 3787 0 otherwise.
4343 3788
4344 pata_platform.pio_mask= [HW,LIBATA] 3789 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 3790 Format: <int>
4346 Supported PIO mode ma 3791 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 3792 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 3793 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 3794 allowed by default.
4350 3795
4351 pause_on_oops=<int> !! 3796 pause_on_oops=
4352 Halt all CPUs after t 3797 Halt all CPUs after the first oops has been printed for
4353 the specified number 3798 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3799 your oopses keep scrolling off the screen.
4355 3800
4356 pcbit= [HW,ISDN] 3801 pcbit= [HW,ISDN]
4357 3802
4358 pci=option[,option...] [PCI,EARLY] v !! 3803 pcd. [PARIDE]
>> 3804 See header of drivers/block/paride/pcd.c.
>> 3805 See also Documentation/admin-guide/blockdev/paride.rst.
>> 3806
>> 3807 pci=option[,option...] [PCI] various PCI subsystem options.
4359 3808
4360 Some options 3809 Some options herein operate on a specific device
4361 or a set of d 3810 or a set of devices (<pci_dev>). These are
4362 specified in 3811 specified in one of the following formats:
4363 3812
4364 [<domain>:]<b 3813 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 3814 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 3815
4367 Note: the fir 3816 Note: the first format specifies a PCI
4368 bus/device/fu 3817 bus/device/function address which may change
4369 if new hardwa 3818 if new hardware is inserted, if motherboard
4370 firmware chan 3819 firmware changes, or due to changes caused
4371 by other kern 3820 by other kernel parameters. If the
4372 domain is lef 3821 domain is left unspecified, it is
4373 taken to be z 3822 taken to be zero. Optionally, a path
4374 to a device t 3823 to a device through multiple device/function
4375 addresses can 3824 addresses can be specified after the base
4376 address (this 3825 address (this is more robust against
4377 renumbering i 3826 renumbering issues). The second format
4378 selects devic 3827 selects devices using IDs from the
4379 configuration 3828 configuration space which may match multiple
4380 devices in th 3829 devices in the system.
4381 3830
4382 earlydump dump PCI conf 3831 earlydump dump PCI config space before the kernel
4383 changes anyth 3832 changes anything
4384 off [X86] don't p 3833 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3834 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3835 the hardware directly. Use this if your machine
4387 has a non-sta 3836 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3837 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3838 hardware access methods are allowed. Use this
4390 if you experi 3839 if you experience crashes upon bootup and you
4391 suspect they 3840 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3841 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3842 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3843 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3844 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3845 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3846 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3847 bus number. The config space is then accessed
4399 through ports 3848 through ports 0xC000-0xCFFF).
4400 See http://wi 3849 See http://wiki.osdev.org/PCI for more info
4401 on the config 3850 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3851 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3852 enabled, this kernel boot option can be used to
4404 disable the u 3853 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3854 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3855 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3856 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3857 Configuration
4409 check_enable_amd_mmconf [X86] 3858 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3859 properly configured MMIO access to PCI
4411 config space 3860 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3861 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3862 enabled, this kernel boot option can be used to
4414 disable the u 3863 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3864 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3865 Safety option to keep boot IRQs enabled. This
4417 should never 3866 should never be necessary.
4418 ioapicreroute [APIC] Enable 3867 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3868 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3869 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3870 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3871 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3872 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3873 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3874 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3875 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3876 routing table. These calls are known to be buggy
4428 on several ma 3877 on several machines and they hang the machine
4429 when used, bu 3878 when used, but on other computers it's the only
4430 way to get th 3879 way to get the interrupt routing table. Try
4431 this option i 3880 this option if the kernel is unable to allocate
4432 IRQs or disco 3881 IRQs or discover secondary PCI buses on your
4433 motherboard. 3882 motherboard.
4434 rom [X86] Assign 3883 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3884 Use with caution as certain devices share
4436 address decod 3885 address decoders between ROMs and other
4437 resources. 3886 resources.
4438 norom [X86] Do not 3887 norom [X86] Do not assign address space to
4439 expansion ROM 3888 expansion ROMs that do not already have
4440 BIOS assigned 3889 BIOS assigned address ranges.
4441 nobar [X86] Do not 3890 nobar [X86] Do not assign address space to the
4442 BARs that wer 3891 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3892 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3893 assigned automatically to PCI devices. You can
4445 make the kern 3894 make the kernel exclude IRQs of your ISA cards
4446 this way. 3895 this way.
4447 pirqaddr=0xAAAAA [X86] 3896 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3897 of the PIRQ table (normally generated
4449 by the BIOS) 3898 by the BIOS) if it is outside the
4450 F0000h-100000 3899 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3900 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3901 useful if the kernel is unable to find your
4453 secondary bus 3902 secondary buses and you want to tell it
4454 explicitly wh 3903 explicitly which ones they are.
4455 assign-busses [X86] Always 3904 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3905 numbers ourselves, overriding
4457 whatever the 3906 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3907 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3908 in the BIOS $PIR table. This is needed on
4460 some systems 3909 some systems with broken BIOSes, notably
4461 some HP Pavil 3910 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3911 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3912 IRQ routing is enabled.
4464 noacpi [X86] Do not 3913 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3914 or for PCI scanning.
4466 use_crs [X86] Use PCI 3915 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3916 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3917 is enabled by default. If you need to use this,
4469 please report 3918 please report a bug.
4470 nocrs [X86] Ignore 3919 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 3920 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 3921 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3922 This is normally done in pci_enable_device(),
4483 so this optio 3923 so this option is a temporary workaround
4484 for broken dr 3924 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3925 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3926 handle more pci cards
4487 noearly [X86] Don't d 3927 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3928 This might help on some broken boards which
4489 machine check 3929 machine check when some devices' config space
4490 is read. But 3930 is read. But various workarounds are disabled
4491 and some IOMM 3931 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3932 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3933 This sorting is done to get a device
4494 order compati 3934 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3935 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3936 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3937 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3938 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3939 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3940 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3941 based on its parent bus. Also set MRRS (Max
4502 Read Request 3942 Read Request Size) to the largest supported
4503 value (no lar 3943 value (no larger than the MPS that the device
4504 or bus can su 3944 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3945 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3946 every device is guaranteed to support. This
4507 configuration 3947 configuration allows peer-to-peer DMA between
4508 any pair of d 3948 any pair of devices, possibly at the cost of
4509 reduced perfo 3949 reduced performance. This also guarantees
4510 that hot-adde 3950 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3951 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3952 reserved for the CardBus bridge's IO window.
4513 The default v 3953 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3954 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3955 reserved for the CardBus bridge's memory
4516 window. The d 3956 window. The default value is 64 megabytes.
4517 resource_alignment= 3957 resource_alignment=
4518 Format: 3958 Format:
4519 [<order of ali 3959 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 3960 Specifies alignment and device to reassign
4521 aligned memor 3961 aligned memory resources. How to
4522 specify the d 3962 specify the device is described above.
4523 If <order of 3963 If <order of align> is not specified,
4524 PAGE_SIZE is 3964 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 3965 A PCI-PCI bridge can be specified if resource
4526 windows need 3966 windows need to be expanded.
4527 To specify th 3967 To specify the alignment for several
4528 instances of 3968 instances of a device, the PCI vendor,
4529 device, subve 3969 device, subvendor, and subdevice may be
4530 specified, e. 3970 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 3971 for 4096-byte alignment.
4532 ecrc= Enable/disabl 3972 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3973 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3974 bios: Use BIOS/firmware settings. This is the
4537 the default. 3975 the default.
4538 off: Turn ECR 3976 off: Turn ECRC off
4539 on: Turn ECRC 3977 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3978 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3979 reserved for hotplug bridge's IO window.
4542 Default size 3980 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 3981 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 3982 reserved for hotplug bridge's MMIO window.
4545 Default size 3983 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 3984 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 3985 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 3986 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 3987 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 3988 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 3989 MMIO_PREF window.
4552 Default size 3990 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3991 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3992 reserved for buses below a hotplug bridge.
4555 Default is 1. 3993 Default is 1.
4556 realloc= Enable/disabl 3994 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3995 if allocations done by BIOS are too small to
4558 accommodate r 3996 accommodate resources required by all child
4559 devices. 3997 devices.
4560 off: Turn rea 3998 off: Turn realloc off
4561 on: Turn real 3999 on: Turn realloc on
4562 realloc same as reall 4000 realloc same as realloc=on
4563 noari do not use PC 4001 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 4002 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 4003 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 4004 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 4005 only look for one device below a PCIe downstream
4568 port. 4006 port.
4569 big_root_window Try to add a 4007 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 4008 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 4009 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 4010 Adding the window is slightly risky (it may
4573 conflict with 4011 conflict with unreported devices), so this
4574 taints the ke 4012 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 4013 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 4014 Specify one or more PCI devices (in the format
4577 specified abo 4015 specified above) separated by semicolons.
4578 Each device s 4016 Each device specified will have the PCI ACS
4579 redirect capa 4017 redirect capabilities forced off which will
4580 allow P2P tra 4018 allow P2P traffic between devices through
4581 bridges witho 4019 bridges without forcing it upstream. Note:
4582 this removes 4020 this removes isolation between devices and
4583 may put more 4021 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 4022 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 4023 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 4024 norid [S390] ignore the RID field and force use of
4619 one PCI domai 4025 one PCI domain per PCI function
4620 4026
4621 pcie_aspm= [PCIE] Forcibly enabl !! 4027 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 4028 Management.
4623 off Don't touch ASPM conf !! 4029 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 4030 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 4031 WARNING: Forcing ASPM on may cause system lockups.
4627 4032
4628 pcie_ports= [PCIE] PCIe port serv 4033 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 4034 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 4035 even if the platform doesn't give the OS permission to
4631 use them. This may c 4036 use them. This may cause conflicts if the platform
4632 also tries to use the 4037 also tries to use these services.
4633 dpc-native Use native PC 4038 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 4039 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 4040 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 4041 hotplug).
4637 4042
4638 pcie_port_pm= [PCIE] PCIe port powe 4043 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 4044 off Disable power management of all PCIe ports
4640 force Forcibly enable power 4045 force Forcibly enable power management of all PCIe ports
4641 4046
4642 pcie_pme= [PCIE,PM] Native PCIe 4047 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 4048 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 4049 all PCIe root ports use INTx for all services).
4645 4050
4646 pcmv= [HW,PCMCIA] BadgePAD 4051 pcmv= [HW,PCMCIA] BadgePAD 4
4647 4052
4648 pd_ignore_unused 4053 pd_ignore_unused
4649 [PM] 4054 [PM]
4650 Keep all power-domain 4055 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 4056 even if no driver has claimed them. This is useful
4652 for debug and develop 4057 for debug and development, but should not be
4653 needed on a platform 4058 needed on a platform with proper driver support.
4654 4059
>> 4060 pd. [PARIDE]
>> 4061 See Documentation/admin-guide/blockdev/paride.rst.
>> 4062
4655 pdcchassis= [PARISC,HW] Disable/E 4063 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4064 boot time.
4657 Format: { 0 | 1 } 4065 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4066 See arch/parisc/kernel/pdc_chassis.c
4659 4067
4660 percpu_alloc= [MM,EARLY] !! 4068 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4069 Currently supported values are "embed" and "page".
4663 Archs may support sub 4070 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4071 See comments in mm/percpu.c for details on each
4665 allocator. This para 4072 allocator. This parameter is primarily for debugging
4666 and performance compa 4073 and performance comparison.
4667 4074
>> 4075 pf. [PARIDE]
>> 4076 See Documentation/admin-guide/blockdev/paride.rst.
>> 4077
>> 4078 pg. [PARIDE]
>> 4079 See Documentation/admin-guide/blockdev/paride.rst.
>> 4080
4668 pirq= [SMP,APIC] Manual mp- 4081 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 4082 See Documentation/x86/i386/IO-APIC.rst.
4670 4083
4671 plip= [PPT,NET] Parallel po 4084 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4085 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4086 See also Documentation/admin-guide/parport.rst.
4674 4087
4675 pmtmr= [X86] Manual setup of 4088 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4089 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4090 e.g. pmtmr=0x508
4678 4091
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] 4092 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4093 Enable suspend/resume debug messages during boot up.
4689 4094
4690 pnp.debug=1 [PNP] 4095 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4096 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4097 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4098 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4099 current resource usage; turning this on also shows
4695 possible settings and 4100 possible settings and some assignment information.
4696 4101
4697 pnpacpi= [ACPI] 4102 pnpacpi= [ACPI]
4698 { off } 4103 { off }
4699 4104
4700 pnpbios= [ISAPNP] 4105 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4106 { on | off | curr | res | no-curr | no-res }
4702 4107
4703 pnp_reserve_irq= 4108 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4109 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4110
4706 pnp_reserve_dma= 4111 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4112 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4113
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4114 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4115 Ranges are in pairs (I/O port base and size).
4711 4116
4712 pnp_reserve_mem= 4117 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4118 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4119 autoconfiguration.
4715 Ranges are in pairs ( 4120 Ranges are in pairs (memory base and size).
4716 4121
4717 ports= [IP_VS_FTP] IPVS ftp 4122 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4123 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4124 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4125 may be specified.
4721 Format: <port>,<port> 4126 Format: <port>,<port>....
4722 4127
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 4128 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4129 It specifically disables cpuidle and sets the
4730 platform machine desc 4130 platform machine description specific power_save
4731 function to NULL. On 4131 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4132 execution priority.
4733 4133
4734 ppc_strict_facility_enable 4134 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4135 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4136 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4137 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4138 There is some performance impact when enabling this.
4739 4139
4740 ppc_tm= [PPC,EARLY] !! 4140 ppc_tm= [PPC]
4741 Format: {"off"} 4141 Format: {"off"}
4742 Disable Hardware Tran 4142 Disable Hardware Transactional Memory
4743 4143
4744 preempt= [KNL] 4144 preempt= [KNL]
4745 Select preemption mod 4145 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4146 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4147 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4148 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4149 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4150
4753 print-fatal-signals= 4151 print-fatal-signals=
4754 [KNL] debug: print fa 4152 [KNL] debug: print fatal signals
4755 4153
4756 If enabled, warn abou 4154 If enabled, warn about various signal handling
4757 related application a 4155 related application anomalies: too many signals,
4758 too many POSIX.1 time 4156 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4157 coredump - etc.
4760 4158
4761 If you hit the warnin 4159 If you hit the warning due to signal overflow,
4762 you might want to try 4160 you might want to try "ulimit -i unlimited".
4763 4161
4764 default: off. 4162 default: off.
4765 4163
4766 printk.always_kmsg_dump= 4164 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4165 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4166 panics
4769 Format: <bool> (1/Y/ 4167 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4168 default: disabled
4771 4169
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} 4170 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4171 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4172 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4173 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4174 ratelimit - ratelimit the logging
4786 Default: ratelimit 4175 Default: ratelimit
4787 4176
4788 printk.time= Show timing data pref 4177 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4178 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4179
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] 4180 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4181 Limit processor to maximum C-state
4803 max_cstate=9 override 4182 max_cstate=9 overrides any DMI blacklist limit.
4804 4183
4805 processor.nocst [HW,ACPI] 4184 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4185 Ignore the _CST method to determine C-states,
4807 instead using the leg 4186 instead using the legacy FADT method
4808 4187
4809 profile= [KNL] Enable kernel p 4188 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4189 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4190 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4191 [defaults to kernel profiling]
4813 Param: "schedule" - p 4192 Param: "schedule" - profile schedule points.
>> 4193 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4194 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4195 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4196 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4197 statistical time based profiling.
4817 4198
4818 prompt_ramdisk= [RAM] [Deprecated] 4199 prompt_ramdisk= [RAM] [Deprecated]
4819 4200
4820 prot_virt= [S390] enable hosting 4201 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4202 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4203 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4204 Format: <bool>
4826 4205
4827 psi= [KNL] Enable or disab 4206 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4207 tracking.
4829 Format: <bool> 4208 Format: <bool>
4830 4209
4831 psmouse.proto= [HW,MOUSE] Highest PS 4210 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4211 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4212 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4213 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4214 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4215 Try to reset the device after so many bad packets
4837 (0 = never). 4216 (0 = never).
4838 psmouse.resolution= 4217 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4218 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4219 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4220 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4221 0 = disabled, 1 = enabled (default).
4843 4222
4844 pstore.backend= Specify the name of t 4223 pstore.backend= Specify the name of the pstore backend to use
4845 4224
>> 4225 pt. [PARIDE]
>> 4226 See Documentation/admin-guide/blockdev/paride.rst.
>> 4227
4846 pti= [X86-64] Control Page 4228 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4229 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4230 removes hardening, but improves performance of
4849 system calls and inte 4231 system calls and interrupts.
4850 4232
4851 on - unconditionall 4233 on - unconditionally enable
4852 off - unconditionall 4234 off - unconditionally disable
4853 auto - kernel detects 4235 auto - kernel detects whether your CPU model is
4854 vulnerable to 4236 vulnerable to issues that PTI mitigates
4855 4237
4856 Not specifying this o 4238 Not specifying this option is equivalent to pti=auto.
4857 4239
>> 4240 nopti [X86-64]
>> 4241 Equivalent to pti=off
>> 4242
4858 pty.legacy_count= 4243 pty.legacy_count=
4859 [KNL] Number of legac 4244 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4245 default number.
4861 4246
4862 quiet [KNL,EARLY] Disable m !! 4247 quiet [KNL] Disable most log messages
4863 4248
4864 r128= [HW,DRM] 4249 r128= [HW,DRM]
4865 4250
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4251 raid= [HW,RAID]
4871 See Documentation/adm 4252 See Documentation/admin-guide/md.rst.
4872 4253
4873 ramdisk_size= [RAM] Sizes of RAM di 4254 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4255 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4256
4876 ramdisk_start= [RAM] RAM disk image 4257 ramdisk_start= [RAM] RAM disk image start address
4877 4258
4878 random.trust_cpu=off !! 4259 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 4260 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 4261 CPU's random number generator (if available) to
4881 initialize the kernel !! 4262 fully seed the kernel's CRNG. Default is controlled
4882 !! 4263 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 4264
4888 randomize_kstack_offset= 4265 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4266 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4267 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4268 entropy, frustrating memory corruption attacks
4892 that depend on stack 4269 that depend on stack address determinism or
4893 cross-syscall address 4270 cross-syscall address exposures. This is only
4894 available on architec 4271 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4272 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4273 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4274 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4275
4899 ras=option[,option,...] [KNL] RAS-spe 4276 ras=option[,option,...] [KNL] RAS-specific options
4900 4277
4901 cec_disable [X86] 4278 cec_disable [X86]
4902 Disable the C 4279 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4280 see CONFIG_RAS_CEC help text.
4904 4281
4905 rcu_nocbs[=cpu-list] !! 4282 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 4283 The argument is a cpu list, as described above.
4907 as described above. <<
4908 <<
4909 In kernels built with <<
4910 enable the no-callbac <<
4911 such CPUs' callbacks <<
4912 softirq context. Inv <<
4913 callbacks will instea <<
4914 kthreads created for <<
4915 "p" for RCU-preempt, <<
4916 for the kthreads that <<
4917 "N" is the CPU number <<
4918 the offloaded CPUs, w <<
4919 and real-time workloa <<
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 4284
4930 Note that this argume !! 4285 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4931 the CONFIG_RCU_NOCB_C !! 4286 the specified list of CPUs to be no-callback CPUs.
>> 4287 Invocation of these CPUs' RCU callbacks will be
>> 4288 offloaded to "rcuox/N" kthreads created for that
>> 4289 purpose, where "x" is "p" for RCU-preempt, and
>> 4290 "s" for RCU-sched, and "N" is the CPU number.
>> 4291 This reduces OS jitter on the offloaded CPUs,
>> 4292 which can be useful for HPC and real-time
>> 4293 workloads. It can also improve energy efficiency
>> 4294 for asymmetric multiprocessors.
4932 4295
4933 rcu_nocb_poll [KNL] 4296 rcu_nocb_poll [KNL]
4934 Rather than requiring 4297 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4298 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4299 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4300 make these kthreads poll for callbacks.
4938 This improves the rea 4301 This improves the real-time response for the
4939 offloaded CPUs by rel 4302 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4303 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4304 energy efficiency by requiring that the kthreads
4942 periodically wake up 4305 periodically wake up to do the polling.
4943 4306
4944 rcutree.blimit= [KNL] 4307 rcutree.blimit= [KNL]
4945 Set maximum number of 4308 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4309 process in one batch.
4947 4310
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] 4311 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4312 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4313 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4314 purposes, to verify correct tree setup.
4959 4315
4960 rcutree.gp_cleanup_delay= [KNL] 4316 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4317 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4318 RCU grace-period cleanup.
4963 4319
4964 rcutree.gp_init_delay= [KNL] 4320 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4321 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4322 RCU grace-period initialization.
4967 4323
4968 rcutree.gp_preinit_delay= [KNL] 4324 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4325 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4326 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4327 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4328 the rcu_node combining tree.
4973 4329
>> 4330 rcutree.use_softirq= [KNL]
>> 4331 If set to zero, move all RCU_SOFTIRQ processing to
>> 4332 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4333 value, meaning that RCU_SOFTIRQ is used by default.
>> 4334 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4335
>> 4336 But note that CONFIG_PREEMPT_RT=y kernels disable
>> 4337 this kernel boot parameter, forcibly setting it
>> 4338 to zero.
>> 4339
>> 4340 rcutree.rcu_fanout_exact= [KNL]
>> 4341 Disable autobalancing of the rcu_node combining
>> 4342 tree. This is used by rcutorture, and might
>> 4343 possibly be useful for architectures having high
>> 4344 cache-to-cache transfer latencies.
>> 4345
>> 4346 rcutree.rcu_fanout_leaf= [KNL]
>> 4347 Change the number of CPUs assigned to each
>> 4348 leaf rcu_node structure. Useful for very
>> 4349 large systems, which will choose the value 64,
>> 4350 and for NUMA systems with large remote-access
>> 4351 latencies, which will choose a value aligned
>> 4352 with the appropriate hardware boundaries.
>> 4353
>> 4354 rcutree.rcu_min_cached_objs= [KNL]
>> 4355 Minimum number of objects which are cached and
>> 4356 maintained per one CPU. Object size is equal
>> 4357 to PAGE_SIZE. The cache allows to reduce the
>> 4358 pressure to page allocator, also it makes the
>> 4359 whole algorithm to behave better in low memory
>> 4360 condition.
>> 4361
>> 4362 rcutree.rcu_delay_page_cache_fill_msec= [KNL]
>> 4363 Set the page-cache refill delay (in milliseconds)
>> 4364 in response to low-memory conditions. The range
>> 4365 of permitted values is in the range 0:100000.
>> 4366
4974 rcutree.jiffies_till_first_fqs= [KNL] 4367 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4368 Set delay from grace-period initialization to
4976 first attempt to forc 4369 first attempt to force quiescent states.
4977 Units are jiffies, mi 4370 Units are jiffies, minimum value is zero,
4978 and maximum value is 4371 and maximum value is HZ.
4979 4372
4980 rcutree.jiffies_till_next_fqs= [KNL] 4373 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4374 Set delay between subsequent attempts to force
4982 quiescent states. Un 4375 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4376 value is one, and maximum value is HZ.
4984 4377
4985 rcutree.jiffies_till_sched_qs= [KNL] 4378 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4379 Set required age in jiffies for a
4987 given grace period be 4380 given grace period before RCU starts
4988 soliciting quiescent- 4381 soliciting quiescent-state help from
4989 rcu_note_context_swit 4382 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4383 If not specified, the kernel will calculate
4991 a value based on the 4384 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4385 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4386 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4387 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4388 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4389 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4390 overwritten.
4998 4391
4999 rcutree.kthread_prio= [KNL,BOOT] 4392 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4393 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4394 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4395 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4396 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4397 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4398 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4399 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4400 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4401 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 4402
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 4403 rcutree.rcu_nocb_gp_stride= [KNL]
5013 On callback-offloaded !! 4404 Set the number of NOCB callback kthreads in
5014 RCU reduces the lock !! 4405 each group, which defaults to the square root
5015 otherwise be caused b !! 4406 of the number of CPUs. Larger numbers reduce
5016 use of the ->nocb_byp !! 4407 the wakeup overhead on the global grace-period
5017 common non-flooded ca !! 4408 kthread, but increases that same overhead on
5018 the main ->cblist in !! 4409 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 4410
5033 rcutree.qhimark= [KNL] 4411 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4412 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4413 batch limiting is disabled.
5036 4414
5037 rcutree.qlowmark= [KNL] 4415 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4416 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4417 batch limiting is re-enabled.
5040 4418
5041 rcutree.qovld= [KNL] 4419 rcutree.qovld= [KNL]
5042 Set threshold of queu 4420 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4421 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4422 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4423 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4424 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4425 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4426 disable more aggressive help enlistment.
5049 4427
5050 rcutree.rcu_delay_page_cache_fill_mse !! 4428 rcutree.rcu_idle_gp_delay= [KNL]
5051 Set the page-cache re !! 4429 Set wakeup interval for idle CPUs that have
5052 in response to low-me !! 4430 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 4431
5100 rcutree.rcu_kick_kthreads= [KNL] 4432 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4433 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4434 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4435 it should at force-quiescent-state time.
5104 This wake_up() will b 4436 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4437 WARN_ONCE() splat and an ftrace_dump().
5106 4438
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] 4439 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4440 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4441 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4442 in microseconds. This defaults to zero.
5118 Larger delays increas 4443 Larger delays increase the probability of
5119 catching RCU pointer 4444 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4445 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4446 rcu_read_unlock() has completed.
5122 4447
5123 rcutree.sysrq_rcu= [KNL] 4448 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4449 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4450 rcu_node tree with an eye towards determining
5126 why a new grace perio 4451 why a new grace period has not yet started.
5127 4452
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] 4453 rcuscale.gp_async= [KNL]
5158 Measure performance o 4454 Measure performance of asynchronous
5159 grace-period primitiv 4455 grace-period primitives such as call_rcu().
5160 4456
5161 rcuscale.gp_async_max= [KNL] 4457 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4458 Specify the maximum number of outstanding
5163 callbacks per writer 4459 callbacks per writer thread. When a writer
5164 thread exceeds this l 4460 thread exceeds this limit, it invokes the
5165 corresponding flavor 4461 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4462 previously posted callbacks to drain.
5167 4463
5168 rcuscale.gp_exp= [KNL] 4464 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4465 Measure performance of expedited synchronous
5170 grace-period primitiv 4466 grace-period primitives.
5171 4467
5172 rcuscale.holdoff= [KNL] 4468 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4469 Set test-start holdoff period. The purpose of
5174 this parameter is to 4470 this parameter is to delay the start of the
5175 test until boot compl 4471 test until boot completes in order to avoid
5176 interference. 4472 interference.
5177 4473
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] 4474 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4475 Set to measure performance of kfree_rcu() flooding.
5189 4476
5190 rcuscale.kfree_rcu_test_double= [KNL] 4477 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 4478 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 4479 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 4480 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 4481 and double-argument variants are tested.
5195 4482
5196 rcuscale.kfree_rcu_test_single= [KNL] 4483 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 4484 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 4485 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 4486 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 4487 and double-argument variants are tested.
5201 4488
5202 rcuscale.kfree_nthreads= [KNL] 4489 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4490 The number of threads running loops of kfree_rcu().
5204 4491
5205 rcuscale.kfree_alloc_num= [KNL] 4492 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4493 Number of allocations and frees done in an iteration.
5207 4494
5208 rcuscale.kfree_loops= [KNL] 4495 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4496 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4497 of allocations and frees.
5211 4498
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] 4499 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4500 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4501 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4502 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4503 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4504 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4505 A value of "n" less than or equal to -N selects
5225 a single reader. 4506 a single reader.
5226 4507
5227 rcuscale.nwriters= [KNL] 4508 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4509 Set number of RCU writers. The values operate
5229 the same as for rcusc 4510 the same as for rcuscale.nreaders.
5230 N, where N is the num 4511 N, where N is the number of CPUs
5231 4512
5232 rcuscale.scale_type= [KNL] !! 4513 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4514 Specify the RCU implementation to test.
5234 4515
5235 rcuscale.shutdown= [KNL] 4516 rcuscale.shutdown= [KNL]
5236 Shut the system down 4517 Shut the system down after performance tests
5237 complete. This is us 4518 complete. This is useful for hands-off automated
5238 testing. 4519 testing.
5239 4520
5240 rcuscale.verbose= [KNL] 4521 rcuscale.verbose= [KNL]
5241 Enable additional pri 4522 Enable additional printk() statements.
5242 4523
5243 rcuscale.writer_holdoff= [KNL] 4524 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4525 Write-side holdoff between grace periods,
5245 in microseconds. The 4526 in microseconds. The default of zero says
5246 no holdoff. 4527 no holdoff.
5247 4528
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] 4529 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4530 Set duration of force_quiescent_state bursts
5255 in microseconds. 4531 in microseconds.
5256 4532
5257 rcutorture.fqs_holdoff= [KNL] 4533 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4534 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4535 in microseconds.
5260 4536
5261 rcutorture.fqs_stutter= [KNL] 4537 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4538 Set wait time between force_quiescent_state bursts
5263 in seconds. 4539 in seconds.
5264 4540
5265 rcutorture.fwd_progress= [KNL] 4541 rcutorture.fwd_progress= [KNL]
5266 Specifies the number !! 4542 Enable RCU grace-period forward-progress testing
5267 for RCU grace-period <<
5268 for the types of RCU 4543 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 4544
5273 rcutorture.fwd_progress_div= [KNL] 4545 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4546 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4547 period to do tight-loop forward-progress testing.
5276 4548
5277 rcutorture.fwd_progress_holdoff= [KNL 4549 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4550 Number of seconds to wait between successive
5279 forward-progress test 4551 forward-progress tests.
5280 4552
5281 rcutorture.fwd_progress_need_resched= 4553 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4554 Enclose cond_resched() calls within checks for
5283 need_resched() during 4555 need_resched() during tight-loop forward-progress
5284 testing. 4556 testing.
5285 4557
5286 rcutorture.gp_cond= [KNL] 4558 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4559 Use conditional/asynchronous update-side
5288 primitives, if availa 4560 primitives, if available.
5289 4561
5290 rcutorture.gp_exp= [KNL] 4562 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4563 Use expedited update-side primitives, if available.
5292 4564
5293 rcutorture.gp_normal= [KNL] 4565 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4566 Use normal (non-expedited) asynchronous
5295 update-side primitive 4567 update-side primitives, if available.
5296 4568
5297 rcutorture.gp_sync= [KNL] 4569 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4570 Use normal (non-expedited) synchronous
5299 update-side primitive 4571 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4572 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4573 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4574 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4575 they are all non-zero.
5304 4576
5305 rcutorture.irqreader= [KNL] 4577 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4578 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4579 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4580 flavors take kindly to this sort of thing.
5309 4581
5310 rcutorture.leakpointer= [KNL] 4582 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4583 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4584 This can of course result in splats, and is
5313 intended to test the 4585 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4586 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4587 such leaks.
5316 4588
5317 rcutorture.n_barrier_cbs= [KNL] 4589 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4590 Set callbacks/threads for rcu_barrier() testing.
5319 4591
5320 rcutorture.nfakewriters= [KNL] 4592 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4593 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4594 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4595 test, hence the "fake".
5324 4596
5325 rcutorture.nocbs_nthreads= [KNL] 4597 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 4598 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 4599 Zero (the default) disables toggling.
5328 4600
5329 rcutorture.nocbs_toggle= [KNL] 4601 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 4602 Set the delay in milliseconds between successive
5331 callback-offload togg 4603 callback-offload toggling attempts.
5332 4604
5333 rcutorture.nreaders= [KNL] 4605 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4606 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4607 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4608 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 4609 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 4610 (the number of CPUs), -3 selects N+1, and so on.
5339 4611
5340 rcutorture.object_debug= [KNL] 4612 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 4613 Enable debug-object double-call_rcu() testing.
5342 4614
5343 rcutorture.onoff_holdoff= [KNL] 4615 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 4616 Set time (s) after boot for CPU-hotplug testing.
5345 4617
5346 rcutorture.onoff_interval= [KNL] 4618 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 4619 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 4620 or zero to disable CPU-hotplug testing.
5349 4621
5350 rcutorture.read_exit= [KNL] 4622 rcutorture.read_exit= [KNL]
5351 Set the number of rea 4623 Set the number of read-then-exit kthreads used
5352 to test the interacti 4624 to test the interaction of RCU updaters and
5353 task-exit processing. 4625 task-exit processing.
5354 4626
5355 rcutorture.read_exit_burst= [KNL] 4627 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 4628 The number of times in a given read-then-exit
5357 episode that a set of 4629 episode that a set of read-then-exit kthreads
5358 is spawned. 4630 is spawned.
5359 4631
5360 rcutorture.read_exit_delay= [KNL] 4632 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 4633 The delay, in seconds, between successive
5362 read-then-exit testin 4634 read-then-exit testing episodes.
5363 4635
5364 rcutorture.shuffle_interval= [KNL] 4636 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 4637 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 4638 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 4639 during the rcutorture test.
5368 4640
5369 rcutorture.shutdown_secs= [KNL] 4641 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 4642 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 4643 is useful for hands-off automated testing.
5372 4644
5373 rcutorture.stall_cpu= [KNL] 4645 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 4646 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 4647 warnings, zero to disable.
5376 4648
5377 rcutorture.stall_cpu_block= [KNL] 4649 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 4650 Sleep while stalling if set. This will result
5379 in warnings from pree !! 4651 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 4652 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 4653
5391 rcutorture.stall_cpu_holdoff= [KNL] 4654 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 4655 Time to wait (s) after boot before inducing stall.
5393 4656
5394 rcutorture.stall_cpu_irqsoff= [KNL] 4657 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 4658 Disable interrupts while stalling if set.
5396 4659
5397 rcutorture.stall_gp_kthread= [KNL] 4660 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 4661 Duration (s) of forced sleep within RCU
5399 grace-period kthread 4662 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 4663 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 4664 and stall_gp_kthread are specified, the
5402 kthread is starved fi 4665 kthread is starved first, then the CPU.
5403 4666
5404 rcutorture.stat_interval= [KNL] 4667 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 4668 Time (s) between statistics printk()s.
5406 4669
5407 rcutorture.stutter= [KNL] 4670 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 4671 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 4672 five seconds causes the test to run for five seconds,
5410 wait for five seconds 4673 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 4674 ability to transition abruptly to and from idle.
5412 4675
5413 rcutorture.test_boost= [KNL] 4676 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 4677 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 4678 "Maybe" means test if the RCU implementation
5416 under test support RC 4679 under test support RCU priority boosting.
5417 4680
5418 rcutorture.test_boost_duration= [KNL] 4681 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 4682 Duration (s) of each individual boost test.
5420 4683
5421 rcutorture.test_boost_interval= [KNL] 4684 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 4685 Interval (s) between each boost test.
5423 4686
5424 rcutorture.test_no_idle_hz= [KNL] 4687 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 4688 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 4689 rcutorture.shuffle_interval parameter.
5427 4690
5428 rcutorture.torture_type= [KNL] 4691 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 4692 Specify the RCU implementation to test.
5430 4693
5431 rcutorture.verbose= [KNL] 4694 rcutorture.verbose= [KNL]
5432 Enable additional pri 4695 Enable additional printk() statements.
5433 4696
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 4697 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 4698 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 4699 stall warning.
5437 4700
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 4701 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 4702 Suppress RCU CPU stall warning messages.
5446 4703
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 4704 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 4705 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 4706 rcutorture writer stall warnings that occur
5450 during early boot, th 4707 during early boot, that is, during the time
5451 before the init task 4708 before the init task is spawned.
5452 4709
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 4710 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 4711 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 4712
5479 rcupdate.rcu_expedited= [KNL] 4713 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 4714 Use expedited grace-period primitives, for
5481 example, synchronize_ 4715 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 4716 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 4717 but can increase CPU utilization, degrade
5484 real-time latency, an 4718 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 4719 No effect on CONFIG_TINY_RCU kernels.
5486 4720
5487 rcupdate.rcu_normal= [KNL] 4721 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 4722 Use only normal grace-period primitives,
5489 for example, synchron 4723 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 4724 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 4725 real-time latency, CPU utilization, and
5492 energy efficiency, bu 4726 energy efficiency, but can expose users to
5493 increased grace-perio 4727 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 4728 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 4729 CONFIG_TINY_RCU kernels.
5496 4730
5497 rcupdate.rcu_normal_after_boot= [KNL] 4731 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 4732 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 4733 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 4734 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 4735 on CONFIG_TINY_RCU kernels.
5502 4736
5503 But note that CONFIG_ 4737 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 4738 this kernel boot parameter, forcibly setting
5505 it to the value one, 4739 it to the value one, that is, converting any
5506 post-boot attempt at 4740 post-boot attempt at an expedited RCU grace
5507 period to instead use 4741 period to instead use normal non-expedited
5508 grace-period processi 4742 grace-period processing.
5509 4743
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] 4744 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 4745 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 4746 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 4747 of a given grace period. Setting a large
5537 number avoids disturb 4748 number avoids disturbing real-time workloads,
5538 but lengthens grace p 4749 but lengthens grace periods.
5539 4750
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 4751 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 4752 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 4753 messages. Disable with a value less than or equal
5572 than or equal to zero !! 4754 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 4755
5599 rcupdate.rcu_self_test= [KNL] 4756 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 4757 Run the RCU early boot self tests
5601 4758
5602 rdinit= [KNL] 4759 rdinit= [KNL]
5603 Format: <full_path> 4760 Format: <full_path>
5604 Run specified binary 4761 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 4762 used for early userspace startup. See initrd.
5606 4763
5607 rdrand= [X86,EARLY] !! 4764 rdrand= [X86]
5608 force - Override the 4765 force - Override the decision by the kernel to hide the
5609 advertisement 4766 advertisement of RDRAND support (this affects
5610 certain AMD p 4767 certain AMD processors because of buggy BIOS
5611 support, spec 4768 support, specifically around the suspend/resume
5612 path). 4769 path).
5613 4770
5614 rdt= [HW,X86,RDT] 4771 rdt= [HW,X86,RDT]
5615 Turn on/off individua 4772 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 4773 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 4774 mba.
5618 E.g. to turn on cmt a 4775 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 4776 rdt=cmt,!mba
5620 4777
5621 reboot= [KNL] 4778 reboot= [KNL]
5622 Format (x86 or x86_64 4779 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 4780 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 4781 [[,]s[mp]#### \
5625 [[,]b[ios] | 4782 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 4783 [[,]f[orce]
5627 Where reboot_mode is 4784 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 4785 (prefix with 'panic_' to set mode for panic
5629 reboo 4786 reboot only),
5630 reboot_type is 4787 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 4788 reboot_force is either force or not specified,
5632 reboot_cpu is s 4789 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 4790 to be used for rebooting.
5634 4791
5635 refscale.holdoff= [KNL] 4792 refscale.holdoff= [KNL]
5636 Set test-start holdof 4793 Set test-start holdoff period. The purpose of
5637 this parameter is to 4794 this parameter is to delay the start of the
5638 test until boot compl 4795 test until boot completes in order to avoid
5639 interference. 4796 interference.
5640 4797
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] 4798 refscale.loops= [KNL]
5648 Set the number of loo 4799 Set the number of loops over the synchronization
5649 primitive under test. 4800 primitive under test. Increasing this number
5650 reduces noise due to 4801 reduces noise due to loop start/end overhead,
5651 but the default has a 4802 but the default has already reduced the per-pass
5652 noise to a handful of 4803 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 4804 x86 laptops.
5654 4805
5655 refscale.nreaders= [KNL] 4806 refscale.nreaders= [KNL]
5656 Set number of readers 4807 Set number of readers. The default value of -1
5657 selects N, where N is 4808 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 4809 of CPUs. A value of zero is an interesting choice.
5659 4810
5660 refscale.nruns= [KNL] 4811 refscale.nruns= [KNL]
5661 Set number of runs, e 4812 Set number of runs, each of which is dumped onto
5662 the console log. 4813 the console log.
5663 4814
5664 refscale.readdelay= [KNL] 4815 refscale.readdelay= [KNL]
5665 Set the read-side cri 4816 Set the read-side critical-section duration,
5666 measured in microseco 4817 measured in microseconds.
5667 4818
5668 refscale.scale_type= [KNL] 4819 refscale.scale_type= [KNL]
5669 Specify the read-prot 4820 Specify the read-protection implementation to test.
5670 4821
5671 refscale.shutdown= [KNL] 4822 refscale.shutdown= [KNL]
5672 Shut down the system 4823 Shut down the system at the end of the performance
5673 test. This defaults 4824 test. This defaults to 1 (shut it down) when
5674 refscale is built int 4825 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 4826 it running) when refscale is built as a module.
5676 4827
5677 refscale.verbose= [KNL] 4828 refscale.verbose= [KNL]
5678 Enable additional pri 4829 Enable additional printk() statements.
5679 4830
5680 refscale.verbose_batched= [KNL] 4831 refscale.verbose_batched= [KNL]
5681 Batch the additional 4832 Batch the additional printk() statements. If zero
5682 (the default) or nega 4833 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 4834 print every Nth verbose statement, where N is the value
5684 specified. 4835 specified.
5685 4836
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= 4837 relax_domain_level=
5694 [KNL, SMP] Set schedu 4838 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 4839 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 4840
5697 reserve= [KNL,BUGS] Force kern 4841 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 4842 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 4843 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 4844 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 4845 is assumed to be I/O ports; otherwise it is memory.
5702 4846
5703 reserve_mem= [RAM] !! 4847 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] 4848 Format: nn[KMG]
5727 Reserves a hole at th 4849 Reserves a hole at the top of the kernel virtual
5728 address space. 4850 address space.
5729 4851
5730 reset_devices [KNL] Force drivers t 4852 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 4853 during initialization.
5732 4854
5733 resume= [SWSUSP] 4855 resume= [SWSUSP]
5734 Specify the partition 4856 Specify the partition device for software suspend
5735 Format: 4857 Format:
5736 {/dev/<dev> | PARTUUI 4858 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 4859
5738 resume_offset= [SWSUSP] 4860 resume_offset= [SWSUSP]
5739 Specify the offset fr 4861 Specify the offset from the beginning of the partition
5740 given by "resume=" at 4862 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 4863 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 4864 See Documentation/power/swsusp-and-swap-files.rst
5743 4865
5744 resumedelay= [HIBERNATION] Delay ( 4866 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 4867 read the resume files
5746 4868
5747 resumewait [HIBERNATION] Wait (i 4869 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 4870 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 4871 (e.g. USB and MMC devices).
5750 4872
5751 retain_initrd [RAM] Keep initrd mem !! 4873 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 4874 noresume Don't check if there's a hibernation image
5753 !! 4875 present during boot.
5754 retbleed= [X86] Control mitigat !! 4876 nocompress Don't compress/decompress hibernation images.
5755 Speculative Code Exec !! 4877 no Disable hibernation and resume.
5756 vulnerability. !! 4878 protect_image Turn on image protection during restoration
5757 !! 4879 (that will set all pages holding image data
5758 AMD-based UNRET and I !! 4880 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 4881
5789 Not specifying this o !! 4882 retain_initrd [RAM] Keep initrd memory after extraction
5790 4883
5791 rfkill.default_state= 4884 rfkill.default_state=
5792 0 "airplane mode". All 4885 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 4886 etc. communication is blocked by default.
5794 1 Unblocked. 4887 1 Unblocked.
5795 4888
5796 rfkill.master_switch_mode= 4889 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 4890 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 4891 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 4892 blocked and the previous configuration.
5800 2 The "airplane mode" b 4893 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 4894 blocked and everything unblocked.
5802 4895
>> 4896 rhash_entries= [KNL,NET]
>> 4897 Set number of hash buckets for route cache
>> 4898
5803 ring3mwait=disable 4899 ring3mwait=disable
5804 [KNL] Disable ring 3 4900 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 4901 CPUs.
5806 4902
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 4903 ro [KNL] Mount root device read-only on boot
5815 4904
5816 rodata= [KNL,EARLY] !! 4905 rodata= [KNL]
5817 on Mark read-only kernel 4906 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 4907 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 4908
5822 rockchip.usb_uart 4909 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 4910 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 4911 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 4912 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 4913 port and the regular usb controller gets disabled.
5828 4914
5829 root= [KNL] Root filesystem 4915 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 4916 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 4917
5837 rootdelay= [KNL] Delay (in secon 4918 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 4919 mount the root filesystem
5839 4920
5840 rootflags= [KNL] Set root filesy 4921 rootflags= [KNL] Set root filesystem mount option string
5841 4922
5842 rootfstype= [KNL] Set root filesy 4923 rootfstype= [KNL] Set root filesystem type
5843 4924
5844 rootwait [KNL] Wait (indefinit 4925 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 4926 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 4927 (e.g. USB and MMC devices).
5847 4928
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 4929 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 4930 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 4931 Memory area to be used by remote processor image,
5855 managed by CMA. 4932 managed by CMA.
5856 4933
5857 rw [KNL] Mount root devi 4934 rw [KNL] Mount root device read-write on boot
5858 4935
5859 S [KNL] Run init in sin 4936 S [KNL] Run init in single mode
5860 4937
5861 s390_iommu= [HW,S390] 4938 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 4939 Set s390 IOTLB flushing mode
5863 strict 4940 strict
5864 With strict flushing !! 4941 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 4942 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 4943 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 4944
5881 sa1100ir [NET] 4945 sa1100ir [NET]
5882 See drivers/net/irda/ 4946 See drivers/net/irda/sa1100_ir.c.
5883 4947
5884 sched_verbose [KNL,EARLY] Enables v !! 4948 sbni= [NET] Granch SBNI12 leased line adapter
>> 4949
>> 4950 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 4951
5886 schedstats= [KNL,X86] Enable or d 4952 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 4953 Allowed values are enable and disable. This feature
5888 incurs a small amount 4954 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 4955 but is useful for debugging and performance tuning.
5890 4956
5891 sched_thermal_decay_shift= 4957 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 4958 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 4959 pressure signal. Thermal pressure signal follows the
5895 default decay period 4960 default decay period of other scheduler pelt
5896 signals(usually 32 ms 4961 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 4962 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 4963 period for the thermal pressure signal by the shift
5899 value. 4964 value.
5900 i.e. with the default 4965 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 4966 sched_thermal_decay_shift thermal pressure decay pr
5902 1 4967 1 64 ms
5903 2 4968 2 128 ms
5904 and so on. 4969 and so on.
5905 Format: integer betwe 4970 Format: integer between 0 and 10
5906 Default is 0. 4971 Default is 0.
5907 4972
5908 scftorture.holdoff= [KNL] 4973 scftorture.holdoff= [KNL]
5909 Number of seconds to 4974 Number of seconds to hold off before starting
5910 test. Defaults to ze 4975 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 4976 to 10 seconds for built-in smp_call_function()
5912 tests. 4977 tests.
5913 4978
5914 scftorture.longwait= [KNL] 4979 scftorture.longwait= [KNL]
5915 Request ridiculously 4980 Request ridiculously long waits randomly selected
5916 up to the chosen limi 4981 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 4982 default) disables this feature. Please note
5918 that requesting even 4983 that requesting even small non-zero numbers of
5919 seconds can result in 4984 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 4985 softlockup complaints, and so on.
5921 4986
5922 scftorture.nthreads= [KNL] 4987 scftorture.nthreads= [KNL]
5923 Number of kthreads to 4988 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 4989 smp_call_function() family of functions.
5925 The default of -1 spe 4990 The default of -1 specifies a number of kthreads
5926 equal to the number o 4991 equal to the number of CPUs.
5927 4992
5928 scftorture.onoff_holdoff= [KNL] 4993 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 4994 Number seconds to wait after the start of the
5930 test before initiatin 4995 test before initiating CPU-hotplug operations.
5931 4996
5932 scftorture.onoff_interval= [KNL] 4997 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 4998 Number seconds to wait between successive
5934 CPU-hotplug operation 4999 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 5000 is the default) disables CPU-hotplug operations.
5936 5001
5937 scftorture.shutdown_secs= [KNL] 5002 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 5003 The number of seconds following the start of the
5939 test after which to s 5004 test after which to shut down the system. The
5940 default of zero avoid 5005 default of zero avoids shutting down the system.
5941 Non-zero values are u 5006 Non-zero values are useful for automated tests.
5942 5007
5943 scftorture.stat_interval= [KNL] 5008 scftorture.stat_interval= [KNL]
5944 The number of seconds 5009 The number of seconds between outputting the
5945 current test statisti 5010 current test statistics to the console. A value
5946 of zero disables stat 5011 of zero disables statistics output.
5947 5012
5948 scftorture.stutter_cpus= [KNL] 5013 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 5014 The number of jiffies to wait between each change
5950 to the set of CPUs un 5015 to the set of CPUs under test.
5951 5016
5952 scftorture.use_cpus_read_lock= [KNL] 5017 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 5018 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 5019 preempt_disable() to disable CPU hotplug
5955 while invoking one of 5020 while invoking one of the smp_call_function*()
5956 functions. 5021 functions.
5957 5022
5958 scftorture.verbose= [KNL] 5023 scftorture.verbose= [KNL]
5959 Enable additional pri 5024 Enable additional printk() statements.
5960 5025
5961 scftorture.weight_single= [KNL] 5026 scftorture.weight_single= [KNL]
5962 The probability weigh 5027 The probability weighting to use for the
5963 smp_call_function_sin 5028 smp_call_function_single() function with a zero
5964 "wait" parameter. A 5029 "wait" parameter. A value of -1 selects the
5965 default if all other 5030 default if all other weights are -1. However,
5966 if at least one weigh 5031 if at least one weight has some other value, a
5967 value of -1 will inst 5032 value of -1 will instead select a weight of zero.
5968 5033
5969 scftorture.weight_single_wait= [KNL] 5034 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 5035 The probability weighting to use for the
5971 smp_call_function_sin 5036 smp_call_function_single() function with a
5972 non-zero "wait" param 5037 non-zero "wait" parameter. See weight_single.
5973 5038
5974 scftorture.weight_many= [KNL] 5039 scftorture.weight_many= [KNL]
5975 The probability weigh 5040 The probability weighting to use for the
5976 smp_call_function_man 5041 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 5042 "wait" parameter. See weight_single.
5978 Note well that settin 5043 Note well that setting a high probability for
5979 this weighting can pl 5044 this weighting can place serious IPI load
5980 on the system. 5045 on the system.
5981 5046
5982 scftorture.weight_many_wait= [KNL] 5047 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 5048 The probability weighting to use for the
5984 smp_call_function_man 5049 smp_call_function_many() function with a
5985 non-zero "wait" param 5050 non-zero "wait" parameter. See weight_single
5986 and weight_many. 5051 and weight_many.
5987 5052
5988 scftorture.weight_all= [KNL] 5053 scftorture.weight_all= [KNL]
5989 The probability weigh 5054 The probability weighting to use for the
5990 smp_call_function_all 5055 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 5056 "wait" parameter. See weight_single and
5992 weight_many. 5057 weight_many.
5993 5058
5994 scftorture.weight_all_wait= [KNL] 5059 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 5060 The probability weighting to use for the
5996 smp_call_function_all 5061 smp_call_function_all() function with a
5997 non-zero "wait" param 5062 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5063 and weight_many.
5999 5064
6000 skew_tick= [KNL,EARLY] Offset th !! 5065 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5066 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5067 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5068 Format: { "0" | "1" }
6004 0 -- disable. (may be 5069 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5070 1 -- enable.
6006 Note: increases power 5071 Note: increases power consumption, thus should only be
6007 enabled if running ji 5072 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5073
6009 security= [SECURITY] Choose a l 5074 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5075 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5076 "lsm=" parameter.
6012 5077
6013 selinux= [SELINUX] Disable or 5078 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5079 Format: { "0" | "1" }
6015 See security/selinux/ 5080 See security/selinux/Kconfig help text.
6016 0 -- disable. 5081 0 -- disable.
6017 1 -- enable. 5082 1 -- enable.
6018 Default value is 1. 5083 Default value is 1.
6019 5084
6020 serialnumber [BUGS=X86-32] !! 5085 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 5086 Format: { "0" | "1" }
>> 5087 See security/apparmor/Kconfig help text
>> 5088 0 -- disable.
>> 5089 1 -- enable.
>> 5090 Default value is set via kernel config option.
6021 5091
6022 sev=option[,option...] [X86-64] See D !! 5092 serialnumber [BUGS=X86-32]
6023 5093
6024 shapers= [NET] 5094 shapers= [NET]
6025 Maximal number of sha 5095 Maximal number of shapers.
6026 5096
6027 show_lapic= [APIC,X86] Advanced P !! 5097 simeth= [IA-64]
6028 Limit apic dumping. T !! 5098 simscsi=
6029 number of local apics <<
6030 to set it to "all" by <<
6031 Format: { 1 (default) <<
6032 The parameter valid i <<
6033 apic=verbose is speci <<
6034 Example: apic=debug s <<
6035 5099
6036 slab_debug[=options[,slabs][;[options !! 5100 slram= [HW,MTD]
6037 Enabling slab_debug a <<
6038 culprit if slab objec <<
6039 slab_debug can create <<
6040 may poison objects wh <<
6041 last alloc / free. Fo <<
6042 Documentation/mm/slub <<
6043 (slub_debug legacy na <<
6044 <<
6045 slab_max_order= [MM] <<
6046 Determines the maximu <<
6047 A high setting may ca <<
6048 fragmentation. For mo <<
6049 Documentation/mm/slub <<
6050 (slub_max_order legac <<
6051 5101
6052 slab_merge [MM] 5102 slab_merge [MM]
6053 Enable merging of sla 5103 Enable merging of slabs with similar size when the
6054 kernel is built witho 5104 kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
6055 (slub_merge legacy na <<
6056 <<
6057 slab_min_objects= [MM] <<
6058 The minimum number of <<
6059 increase the slab ord <<
6060 generate a sufficient <<
6061 the number of objects <<
6062 of objects the smalle <<
6063 and the less frequent <<
6064 For more information <<
6065 (slub_min_objects leg <<
6066 <<
6067 slab_min_order= [MM] <<
6068 Determines the minimu <<
6069 lower or equal to sla <<
6070 Documentation/mm/slub <<
6071 (slub_min_order legac <<
6072 5105
6073 slab_nomerge [MM] 5106 slab_nomerge [MM]
6074 Disable merging of sl 5107 Disable merging of slabs with similar size. May be
6075 necessary if there is 5108 necessary if there is some reason to distinguish
6076 allocs to different s 5109 allocs to different slabs, especially in hardened
6077 environments where th 5110 environments where the risk of heap overflows and
6078 layout control by att 5111 layout control by attackers can usually be
6079 frustrated by disabli 5112 frustrated by disabling merging. This will reduce
6080 most of the exposure 5113 most of the exposure of a heap attack to a single
6081 cache (risks via meta 5114 cache (risks via metadata attacks are mostly
6082 unchanged). Debug opt 5115 unchanged). Debug options disable merging on their
6083 own. 5116 own.
6084 For more information !! 5117 For more information see Documentation/vm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5118
6087 slram= [HW,MTD] !! 5119 slab_max_order= [MM, SLAB]
>> 5120 Determines the maximum allowed order for slabs.
>> 5121 A high setting may cause OOMs due to memory
>> 5122 fragmentation. Defaults to 1 for systems with
>> 5123 more than 32MB of RAM, 0 otherwise.
>> 5124
>> 5125 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 5126 Enabling slub_debug allows one to determine the
>> 5127 culprit if slab objects become corrupted. Enabling
>> 5128 slub_debug can create guard zones around objects and
>> 5129 may poison objects when not in use. Also tracks the
>> 5130 last alloc / free. For more information see
>> 5131 Documentation/vm/slub.rst.
>> 5132
>> 5133 slub_max_order= [MM, SLUB]
>> 5134 Determines the maximum allowed order for slabs.
>> 5135 A high setting may cause OOMs due to memory
>> 5136 fragmentation. For more information see
>> 5137 Documentation/vm/slub.rst.
>> 5138
>> 5139 slub_min_objects= [MM, SLUB]
>> 5140 The minimum number of objects per slab. SLUB will
>> 5141 increase the slab order up to slub_max_order to
>> 5142 generate a sufficiently large slab able to contain
>> 5143 the number of objects indicated. The higher the number
>> 5144 of objects the smaller the overhead of tracking slabs
>> 5145 and the less frequently locks need to be acquired.
>> 5146 For more information see Documentation/vm/slub.rst.
>> 5147
>> 5148 slub_min_order= [MM, SLUB]
>> 5149 Determines the minimum page order for slabs. Must be
>> 5150 lower than slub_max_order.
>> 5151 For more information see Documentation/vm/slub.rst.
>> 5152
>> 5153 slub_merge [MM, SLUB]
>> 5154 Same with slab_merge.
>> 5155
>> 5156 slub_nomerge [MM, SLUB]
>> 5157 Same with slab_nomerge. This is supported for legacy.
>> 5158 See slab_nomerge for more information.
6088 5159
6089 smart2= [HW] 5160 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5161 Format: <io1>[,<io2>[,...,<io8>]]
6091 5162
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 5163 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5164 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5165 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5166 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5167 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5168 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5169 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5170 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5171 1: Fast pin select (default)
6119 2: ATC IRMode 5172 2: ATC IRMode
6120 5173
6121 smt= [KNL,MIPS,S390,EARLY] !! 5174 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5175 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5176 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5177 actual hardware limit.
6125 Format: <integer> 5178 Format: <integer>
6126 Default: -1 (no limit 5179 Default: -1 (no limit)
6127 5180
6128 softlockup_panic= 5181 softlockup_panic=
6129 [KNL] Should the soft 5182 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5183 Format: 0 | 1
6131 5184
6132 A value of 1 instruct 5185 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5186 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5187 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5188 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5189 respective build-time switch to that functionality.
6137 5190
6138 softlockup_all_cpu_backtrace= 5191 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5192 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5193 backtraces on all cpus.
6141 Format: 0 | 1 5194 Format: 0 | 1
6142 5195
6143 sonypi.*= [HW] Sony Programmabl 5196 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5197 See Documentation/admin-guide/laptops/sonypi.rst
6145 5198
6146 spectre_bhi= [X86] Control mitigat !! 5199 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 5200 (indirect branch speculation) vulnerability.
6163 The default operation 5201 The default operation protects the kernel from
6164 user space attacks. 5202 user space attacks.
6165 5203
6166 on - unconditionall 5204 on - unconditionally enable, implies
6167 spectre_v2_use 5205 spectre_v2_user=on
6168 off - unconditionall 5206 off - unconditionally disable, implies
6169 spectre_v2_use 5207 spectre_v2_user=off
6170 auto - kernel detects 5208 auto - kernel detects whether your CPU model is
6171 vulnerable 5209 vulnerable
6172 5210
6173 Selecting 'on' will, 5211 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5212 mitigation method at run time according to the
6175 CPU, the available mi 5213 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5214 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5215 compiler with which the kernel was built.
6178 5216
6179 Selecting 'on' will a 5217 Selecting 'on' will also enable the mitigation
6180 against user space to 5218 against user space to user space task attacks.
6181 5219
6182 Selecting 'off' will 5220 Selecting 'off' will disable both the kernel and
6183 the user space protec 5221 the user space protections.
6184 5222
6185 Specific mitigations 5223 Specific mitigations can also be selected manually:
6186 5224
6187 retpoline - r 5225 retpoline - replace indirect branches
6188 retpoline,generic - R !! 5226 retpoline,generic - google's original retpoline
6189 retpoline,lfence - L !! 5227 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 5228
6196 Not specifying this o 5229 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5230 spectre_v2=auto.
6198 5231
6199 spectre_v2_user= 5232 spectre_v2_user=
6200 [X86] Control mitigat 5233 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5234 (indirect branch speculation) vulnerability between
6202 user space tasks 5235 user space tasks
6203 5236
6204 on - Uncondition 5237 on - Unconditionally enable mitigations. Is
6205 enforced by 5238 enforced by spectre_v2=on
6206 5239
6207 off - Uncondition 5240 off - Unconditionally disable mitigations. Is
6208 enforced by 5241 enforced by spectre_v2=off
6209 5242
6210 prctl - Indirect br 5243 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5244 but mitigation can be enabled via prctl
6212 per thread. 5245 per thread. The mitigation control state
6213 is inherite 5246 is inherited on fork.
6214 5247
6215 prctl,ibpb 5248 prctl,ibpb
6216 - Like "prctl 5249 - Like "prctl" above, but only STIBP is
6217 controlled 5250 controlled per thread. IBPB is issued
6218 always when 5251 always when switching between different user
6219 space proce 5252 space processes.
6220 5253
6221 seccomp 5254 seccomp
6222 - Same as "pr 5255 - Same as "prctl" above, but all seccomp
6223 threads wil 5256 threads will enable the mitigation unless
6224 they explic 5257 they explicitly opt out.
6225 5258
6226 seccomp,ibpb 5259 seccomp,ibpb
6227 - Like "secco 5260 - Like "seccomp" above, but only STIBP is
6228 controlled 5261 controlled per thread. IBPB is issued
6229 always when 5262 always when switching between different
6230 user space 5263 user space processes.
6231 5264
6232 auto - Kernel sele 5265 auto - Kernel selects the mitigation depending on
6233 the availab 5266 the available CPU features and vulnerability.
6234 5267
6235 Default mitigation: " !! 5268 Default mitigation:
>> 5269 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
6236 5270
6237 Not specifying this o 5271 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5272 spectre_v2_user=auto.
6239 5273
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= 5274 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5275 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5276 (Speculative Store Bypass vulnerability)
6254 5277
6255 Certain CPUs are vuln 5278 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5279 a common industry wide performance optimization known
6257 as "Speculative Store 5280 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5281 to the same memory location may not be observed by
6259 later loads during sp 5282 later loads during speculative execution. The idea
6260 is that such stores a 5283 is that such stores are unlikely and that they can
6261 be detected prior to 5284 be detected prior to instruction retirement at the
6262 end of a particular s 5285 end of a particular speculation execution window.
6263 5286
6264 In vulnerable process 5287 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5288 store can be used in a cache side channel attack, for
6266 example to read memor 5289 example to read memory to which the attacker does not
6267 directly have access 5290 directly have access (e.g. inside sandboxed code).
6268 5291
6269 This parameter contro 5292 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5293 Bypass optimization is used.
6271 5294
6272 On x86 the options ar 5295 On x86 the options are:
6273 5296
6274 on - Uncondition 5297 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5298 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5299 auto - Kernel detects whether the CPU model contains an
6277 implementat 5300 implementation of Speculative Store Bypass and
6278 picks the m 5301 picks the most appropriate mitigation. If the
6279 CPU is not 5302 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5303 CPU is vulnerable the default mitigation is
6281 architectur 5304 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5305 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5306 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5307 for a process by default. The state of the control
6285 is inherite 5308 is inherited on fork.
6286 seccomp - Same as "pr 5309 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5310 will disable SSB unless they explicitly opt out.
6288 5311
6289 Default mitigations: 5312 Default mitigations:
6290 X86: "prctl" !! 5313 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6291 5314
6292 On powerpc the option 5315 On powerpc the options are:
6293 5316
6294 on,auto - On Power8 a 5317 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5318 barrier on kernel entry and exit. On Power7
6296 perform a s 5319 perform a software flush on kernel entry and
6297 exit. 5320 exit.
6298 off - No action. 5321 off - No action.
6299 5322
6300 Not specifying this o 5323 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5324 spec_store_bypass_disable=auto.
6302 5325
>> 5326 spia_io_base= [HW,MTD]
>> 5327 spia_fio_base=
>> 5328 spia_pedr=
>> 5329 spia_peddr=
>> 5330
6303 split_lock_detect= 5331 split_lock_detect=
6304 [X86] Enable split lo 5332 [X86] Enable split lock detection or bus lock detection
6305 5333
6306 When enabled (and if 5334 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5335 instructions that access data across cache line
6308 boundaries will resul 5336 boundaries will result in an alignment check exception
6309 for split lock detect 5337 for split lock detection or a debug exception for
6310 bus lock detection. 5338 bus lock detection.
6311 5339
6312 off - not enabled 5340 off - not enabled
6313 5341
6314 warn - the kernel 5342 warn - the kernel will emit rate-limited warnings
6315 about appli 5343 about applications triggering the #AC
6316 exception o 5344 exception or the #DB exception. This mode is
6317 the default 5345 the default on CPUs that support split lock
6318 detection o 5346 detection or bus lock detection. Default
6319 behavior is 5347 behavior is by #AC if both features are
6320 enabled in 5348 enabled in hardware.
6321 5349
6322 fatal - the kernel 5350 fatal - the kernel will send SIGBUS to applications
6323 that trigge 5351 that trigger the #AC exception or the #DB
6324 exception. 5352 exception. Default behavior is by #AC if
6325 both featur 5353 both features are enabled in hardware.
6326 5354
6327 ratelimit:N - 5355 ratelimit:N -
6328 Set system 5356 Set system wide rate limit to N bus locks
6329 per second 5357 per second for bus lock detection.
6330 0 < N <= 10 5358 0 < N <= 1000.
6331 5359
6332 N/A for spl 5360 N/A for split lock detection.
6333 5361
6334 5362
6335 If an #AC exception i 5363 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5364 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5365 the kernel will oops in either "warn" or "fatal"
6338 mode. 5366 mode.
6339 5367
6340 #DB exception for bus 5368 #DB exception for bus lock is triggered only when
6341 CPL > 0. 5369 CPL > 0.
6342 5370
6343 srbds= [X86,INTEL,EARLY] !! 5371 srbds= [X86,INTEL]
6344 Control the Special R 5372 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5373 (SRBDS) mitigation.
6346 5374
6347 Certain CPUs are vuln 5375 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5376 exploit which can leak bits from the random
6349 number generator. 5377 number generator.
6350 5378
6351 By default, this issu 5379 By default, this issue is mitigated by
6352 microcode. However, 5380 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5381 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5382 much slower. Among other effects, this will
6355 result in reduced thr 5383 result in reduced throughput from /dev/urandom.
6356 5384
6357 The microcode mitigat 5385 The microcode mitigation can be disabled with
6358 the following option: 5386 the following option:
6359 5387
6360 off: Disable mitig 5388 off: Disable mitigation and remove
6361 performance i 5389 performance impact to RDRAND and RDSEED
6362 5390
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] 5391 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5392 Specifies how frequently to check for
6389 grace-period sequence 5393 grace-period sequence counter wrap for the
6390 srcu_data structure's 5394 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5395 The greater the number of bits set in this kernel
6392 parameter, the less f 5396 parameter, the less frequently counter wrap will
6393 be checked for. Note 5397 be checked for. Note that the bottom two bits
6394 are ignored. 5398 are ignored.
6395 5399
6396 srcutree.exp_holdoff [KNL] 5400 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5401 Specifies how many nanoseconds must elapse
6398 since the end of the 5402 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5403 a given srcu_struct until the next normal SRCU
6400 grace period will be 5404 grace period will be considered for automatic
6401 expediting. Set to z 5405 expediting. Set to zero to disable automatic
6402 expediting. 5406 expediting.
6403 5407
6404 srcutree.srcu_max_nodelay [KNL] !! 5408 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 5409 Speculative Store Bypass Disable control
6432 5410
6433 On CPUs that are vuln 5411 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5412 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5413 firmware based mitigation, this parameter
6436 indicates how the mit 5414 indicates how the mitigation should be used:
6437 5415
6438 force-on: Unconditio 5416 force-on: Unconditionally enable mitigation for
6439 for both k 5417 for both kernel and userspace
6440 force-off: Unconditio 5418 force-off: Unconditionally disable mitigation for
6441 for both k 5419 for both kernel and userspace
6442 kernel: Always ena 5420 kernel: Always enable mitigation in the
6443 kernel, an 5421 kernel, and offer a prctl interface
6444 to allow u 5422 to allow userspace to register its
6445 interest i 5423 interest in being mitigated too.
6446 5424
6447 stack_guard_gap= [MM] 5425 stack_guard_gap= [MM]
6448 override the default 5426 override the default stack gap protection. The value
6449 is in page units and 5427 is in page units and it defines how many pages prior
6450 to (for stacks growin 5428 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5429 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5430 mapping. Default value is 256 pages.
6453 5431
6454 stack_depot_disable= [KNL,EARLY] !! 5432 stack_depot_disable= [KNL]
6455 Setting this to true 5433 Setting this to true through kernel command line will
6456 disable the stack dep 5434 disable the stack depot thereby saving the static memory
6457 consumed by the stack 5435 consumed by the stack hash table. By default this is set
6458 to false. 5436 to false.
6459 5437
6460 stacktrace [FTRACE] 5438 stacktrace [FTRACE]
6461 Enabled the stack tra 5439 Enabled the stack tracer on boot up.
6462 5440
6463 stacktrace_filter=[function-list] 5441 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5442 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 5443 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 5444 list of functions. This list can be changed at run
6467 time by the stack_tra 5445 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 5446 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 5447 and the stacktrace above is not needed.
6470 5448
6471 sti= [PARISC,HW] 5449 sti= [PARISC,HW]
6472 Format: <num> 5450 Format: <num>
6473 Set the STI (builtin 5451 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 5452 machines) console (graphic card) which should be used
6475 as the initial boot-c 5453 as the initial boot-console.
6476 See also comment in d 5454 See also comment in drivers/video/console/sticore.c.
6477 5455
6478 sti_font= [HW] 5456 sti_font= [HW]
6479 See comment in driver 5457 See comment in drivers/video/console/sticore.c.
6480 5458
6481 stifb= [HW] 5459 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 5460 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 5461
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= 5462 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 5463 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 5464 [NFS,SUNRPC]
6506 SunRPC servers often 5465 SunRPC servers often require that client requests
6507 originate from a priv 5466 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 5467 range 0 < portnr < 1024).
6509 An administrator who 5468 An administrator who wishes to reserve some of these
6510 ports for other uses 5469 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 5470 kernel's sunrpc client considers to be privileged
6512 using these two param 5471 using these two parameters to set the minimum and
6513 maximum port values. 5472 maximum port values.
6514 5473
6515 sunrpc.svc_rpc_per_connection_limit= 5474 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 5475 [NFS,SUNRPC]
6517 Limit the number of r 5476 Limit the number of requests that the server will
6518 process in parallel f 5477 process in parallel from a single connection.
6519 The default value is 5478 The default value is 0 (no limit).
6520 5479
6521 sunrpc.pool_mode= 5480 sunrpc.pool_mode=
6522 [NFS] 5481 [NFS]
6523 Control how the NFS s 5482 Control how the NFS server code allocates CPUs to
6524 service thread pools. 5483 service thread pools. Depending on how many NICs
6525 you have and where th 5484 you have and where their interrupts are bound, this
6526 option will affect wh 5485 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 5486 Note: this parameter cannot be changed while the
6528 NFS server is running 5487 NFS server is running.
6529 5488
6530 auto the serve 5489 auto the server chooses an appropriate mode
6531 automatic 5490 automatically using heuristics
6532 global a single 5491 global a single global pool contains all CPUs
6533 percpu one pool 5492 percpu one pool for each CPU
6534 pernode one pool 5493 pernode one pool for each NUMA node (equivalent
6535 to global 5494 to global on non-NUMA machines)
6536 5495
6537 sunrpc.tcp_slot_table_entries= 5496 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 5497 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 5498 [NFS,SUNRPC]
6540 Sets the upper limit 5499 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 5500 RPC calls that can be sent from the client to a
6542 server. Increasing th 5501 server. Increasing these values may allow you to
6543 improve throughput, b 5502 improve throughput, but will also increase the
6544 amount of memory rese 5503 amount of memory reserved for use by the client.
6545 5504
6546 suspend.pm_test_delay= 5505 suspend.pm_test_delay=
6547 [SUSPEND] 5506 [SUSPEND]
6548 Sets the number of se 5507 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 5508 mode before resuming the system (see
6550 /sys/power/pm_test). 5509 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 5510 is set. Default value is 5.
6552 5511
6553 svm= [PPC] 5512 svm= [PPC]
6554 Format: { on | off | 5513 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 5514 This parameter controls use of the Protected
6556 Execution Facility on 5515 Execution Facility on pSeries.
6557 5516
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 5517 swapaccount=[0|1]
6559 Format: { <int> [,<in !! 5518 [KNL] Enable accounting of swap in memory resource
>> 5519 controller if no parameter or 1 is given or disable
>> 5520 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
>> 5521
>> 5522 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
>> 5523 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 5524 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 5525 force -- force using of bounce buffers even if they
6565 wouldn't be 5526 wouldn't be automatically used by the kernel
6566 noforce -- Never use 5527 noforce -- Never use bounce buffers (for debugging)
6567 5528
6568 switches= [HW,M68k,EARLY] !! 5529 switches= [HW,M68k]
6569 5530
6570 sysctl.*= [KNL] 5531 sysctl.*= [KNL]
6571 Set a sysctl paramete 5532 Set a sysctl parameter, right before loading the init
6572 process, as if the va 5533 process, as if the value was written to the respective
6573 /proc/sys/... file. B 5534 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 5535 separators. Unrecognized parameters and invalid values
6575 are reported in the k 5536 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 5537 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 5538 Example: sysctl.vm.swappiness=40
6578 5539
>> 5540 sysfs.deprecated=0|1 [KNL]
>> 5541 Enable/disable old style sysfs layout for old udev
>> 5542 on older distributions. When this option is enabled
>> 5543 very new udev will not work anymore. When this option
>> 5544 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 5545 in older udev will not work anymore.
>> 5546 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 5547 the kernel configuration.
>> 5548
6579 sysrq_always_enabled 5549 sysrq_always_enabled
6580 [KNL] 5550 [KNL]
6581 Ignore sysrq setting 5551 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 5552 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 5553 Useful for debugging.
6584 5554
6585 tcpmhash_entries= [KNL,NET] 5555 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 5556 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 5557 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 5558 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 5559 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 5560 "tcp_no_metrics_save" section for more details.
6591 5561
6592 tdfx= [HW,DRM] 5562 tdfx= [HW,DRM]
6593 5563
6594 test_suspend= [SUSPEND] !! 5564 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 5565 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 5566 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 5567 as the system sleep state during system startup with
6599 the optional capabili 5568 the optional capability to repeat N number of times.
6600 The system is woken f 5569 The system is woken from this state using a
6601 wakeup-capable RTC al 5570 wakeup-capable RTC alarm.
6602 5571
6603 thash_entries= [KNL,NET] 5572 thash_entries= [KNL,NET]
6604 Set number of hash bu 5573 Set number of hash buckets for TCP connection
6605 5574
6606 thermal.act= [HW,ACPI] 5575 thermal.act= [HW,ACPI]
6607 -1: disable all activ 5576 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 5577 <degrees C>: override all lowest active trip points
6609 5578
6610 thermal.crt= [HW,ACPI] 5579 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 5580 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 5581 <degrees C>: override all critical trip points
6613 5582
>> 5583 thermal.nocrt= [HW,ACPI]
>> 5584 Set to disable actions on ACPI thermal zone
>> 5585 critical and hot trip points.
>> 5586
6614 thermal.off= [HW,ACPI] 5587 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 5588 1: disable ACPI thermal control
6616 5589
6617 thermal.psv= [HW,ACPI] 5590 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 5591 -1: disable all passive trip points
6619 <degrees C>: override 5592 <degrees C>: override all passive trip points to this
6620 value 5593 value
6621 5594
6622 thermal.tzp= [HW,ACPI] 5595 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 5596 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 5597 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 5598 0: no polling (default)
6626 5599
6627 threadirqs [KNL,EARLY] !! 5600 threadirqs [KNL]
6628 Force threading of al 5601 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 5602 marked explicitly IRQF_NO_THREAD.
6630 5603
6631 topology= [S390,EARLY] !! 5604 topology= [S390]
6632 Format: {off | on} 5605 Format: {off | on}
6633 Specify if the kernel 5606 Specify if the kernel should make use of the cpu
6634 topology information 5607 topology information if the hardware supports this.
6635 The scheduler will ma 5608 The scheduler will make use of this information and
6636 e.g. base its process 5609 e.g. base its process migration decisions on it.
6637 Default is on. 5610 Default is on.
6638 5611
>> 5612 topology_updates= [KNL, PPC, NUMA]
>> 5613 Format: {off}
>> 5614 Specify if the kernel should ignore (off)
>> 5615 topology updates sent by the hypervisor to this
>> 5616 LPAR.
>> 5617
6639 torture.disable_onoff_at_boot= [KNL] 5618 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 5619 Prevent the CPU-hotplug component of torturing
6641 until after init has 5620 until after init has spawned.
6642 5621
6643 torture.ftrace_dump_at_shutdown= [KNL 5622 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 5623 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 5624 even if there were no errors. This can be a
6646 very costly operation 5625 very costly operation when many torture tests
6647 are running concurren 5626 are running concurrently, especially on systems
6648 with rotating-rust st 5627 with rotating-rust storage.
6649 5628
6650 torture.verbose_sleep_frequency= [KNL 5629 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 5630 Specifies how many verbose printk()s should be
6652 emitted between each 5631 emitted between each sleep. The default of zero
6653 disables verbose-prin 5632 disables verbose-printk() sleeping.
6654 5633
6655 torture.verbose_sleep_duration= [KNL] 5634 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 5635 Duration of each verbose-printk() sleep in jiffies.
6657 5636
>> 5637 tp720= [HW,PS2]
>> 5638
6658 tpm_suspend_pcr=[HW,TPM] 5639 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 5640 Format: integer pcr id
6660 Specify that at suspe 5641 Specify that at suspend time, the tpm driver
6661 should extend the spe 5642 should extend the specified pcr with zeros,
6662 as a workaround for s 5643 as a workaround for some chips which fail to
6663 flush the last writte 5644 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 5645 This will guarantee that all the other pcrs
6665 are saved. 5646 are saved.
6666 5647
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] 5648 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 5649 [FTRACE] will set tracing buffer size on each cpu.
6707 5650
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] 5651 trace_event=[event-list]
6731 [FTRACE] Set and star 5652 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 5653 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 5654 comma-separated list of trace events to enable. See
6734 also Documentation/tr 5655 also Documentation/trace/events.rst
6735 5656
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] 5657 trace_options=[option-list]
6757 [FTRACE] Enable or di 5658 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 5659 The option-list is a comma delimited list of options
6759 that can be enabled o 5660 that can be enabled or disabled just as if you were
6760 to echo the option na 5661 to echo the option name into
6761 5662
6762 /sys/kernel/traci !! 5663 /sys/kernel/debug/tracing/trace_options
6763 5664
6764 For example, to enabl 5665 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 5666 stack trace of each event), add to the command line:
6766 5667
6767 trace_options=s 5668 trace_options=stacktrace
6768 5669
6769 See also Documentatio 5670 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 5671 section.
6771 5672
6772 trace_trigger=[trigger-list] !! 5673 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 5674 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 5675 tracing ring buffer. This is useful for early boot up
6775 filter. !! 5676 where the system hangs or reboots and does not give the
>> 5677 option for reading the tracing buffer or performing a
>> 5678 ftrace_dump_on_oops.
6776 5679
6777 The format is is "tra !! 5680 To turn off having tracepoints sent to printk,
6778 Where more than one t !! 5681 echo 0 > /proc/sys/kernel/tracepoint_printk
>> 5682 Note, echoing 1 into this file without the
>> 5683 tracepoint_printk kernel cmdline option has no effect.
6779 5684
6780 For example: !! 5685 The tp_printk_stop_on_boot (see below) can also be used
>> 5686 to stop the printing of events to console at
>> 5687 late_initcall_sync.
6781 5688
6782 trace_trigger="sche !! 5689 ** CAUTION **
6783 5690
6784 The above will enable !! 5691 Having tracepoints sent to printk() and activating high
6785 event but only trigge !! 5692 frequency tracepoints such as irq or sched, can cause
6786 event is "2" (TASK_UN !! 5693 the system to live lock.
6787 5694
6788 See also "Event trigg !! 5695 tp_printk_stop_on_boot[FTRACE]
>> 5696 When tp_printk (above) is set, it can cause a lot of noise
>> 5697 on the console. It may be useful to only include the
>> 5698 printing of events during boot up, as user space may
>> 5699 make the system inoperable.
6789 5700
>> 5701 This command line option will stop the printing of events
>> 5702 to console at the late_initcall_sync() time frame.
6790 5703
6791 traceoff_on_warning 5704 traceoff_on_warning
6792 [FTRACE] enable this 5705 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 5706 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 5707 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 5708 file located in /sys/kernel/debug/tracing/
6796 5709
6797 This option is useful 5710 This option is useful, as it disables the trace before
6798 the WARNING dump is c 5711 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 5712 be filled with content caused by the warning output.
6800 5713
6801 This option can also 5714 This option can also be set at run time via the sysctl
6802 option: kernel/trace 5715 option: kernel/traceoff_on_warning
6803 5716
6804 transparent_hugepage= 5717 transparent_hugepage=
6805 [KNL] 5718 [KNL]
6806 Format: [always|madvi 5719 Format: [always|madvise|never]
6807 Can be used to contro 5720 Can be used to control the default behavior of the system
6808 with respect to trans 5721 with respect to transparent hugepages.
6809 See Documentation/adm 5722 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 5723 for more details.
6811 5724
6812 trusted.source= [KEYS] 5725 trusted.source= [KEYS]
6813 Format: <string> 5726 Format: <string>
6814 This parameter identi 5727 This parameter identifies the trust source as a backend
6815 for trusted keys impl 5728 for trusted keys implementation. Supported trust
6816 sources: 5729 sources:
6817 - "tpm" 5730 - "tpm"
6818 - "tee" 5731 - "tee"
6819 - "caam" <<
6820 - "dcp" <<
6821 If not specified then 5732 If not specified then it defaults to iterating through
6822 the trust source list 5733 the trust source list starting with TPM and assigns the
6823 first trust source as 5734 first trust source as a backend which is initialized
6824 successfully during i 5735 successfully during iteration.
6825 5736
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 5737 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 5738 Format: <string>
6850 [x86] reliable: mark 5739 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 5740 disables clocksource verification at runtime, as well
6852 as the stability chec 5741 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 5742 high-resolution timer mode on older hardware, and in
6854 virtualized environme 5743 virtualized environment.
6855 [x86] noirqtime: Do n 5744 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 5745 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 5746 platforms where RDTSC is slow and this accounting
6858 can add overhead. 5747 can add overhead.
6859 [x86] unstable: mark 5748 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 5749 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 5750 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 5751 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 5752 in situations with strict latency requirements (where
6864 interruptions from cl 5753 interruptions from clocksource watchdog are not
6865 acceptable). 5754 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 5755
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 5756 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 5757 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 5758 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 5759 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 5760 Format: <unsigned int>
6882 5761
6883 tsx= [X86] Control Transac 5762 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 5763 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 5764 support TSX control.
6886 5765
6887 This parameter contro 5766 This parameter controls the TSX feature. The options are:
6888 5767
6889 on - Enable TSX 5768 on - Enable TSX on the system. Although there are
6890 mitigations f 5769 mitigations for all known security vulnerabilities,
6891 TSX has been 5770 TSX has been known to be an accelerator for
6892 several previ 5771 several previous speculation-related CVEs, and
6893 so there may 5772 so there may be unknown security risks associated
6894 with leaving 5773 with leaving it enabled.
6895 5774
6896 off - Disable TSX 5775 off - Disable TSX on the system. (Note that this
6897 option takes 5776 option takes effect only on newer CPUs which are
6898 not vulnerabl 5777 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 5778 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 5779 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 5780 update. This new MSR allows for the reliable
6902 deactivation 5781 deactivation of the TSX functionality.)
6903 5782
6904 auto - Disable TSX 5783 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 5784 otherwise enable TSX on the system.
6906 5785
6907 Not specifying this o 5786 Not specifying this option is equivalent to tsx=off.
6908 5787
6909 See Documentation/adm 5788 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 5789 for more details.
6911 5790
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 5791 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 5792 Abort (TAA) vulnerability.
6914 5793
6915 Similar to Micro-arch 5794 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 5795 certain CPUs that support Transactional
6917 Synchronization Exten 5796 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 5797 exploit against CPU internal buffers which can forward
6919 information to a disc 5798 information to a disclosure gadget under certain
6920 conditions. 5799 conditions.
6921 5800
6922 In vulnerable process 5801 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 5802 data can be used in a cache side channel attack, to
6924 access data to which 5803 access data to which the attacker does not have direct
6925 access. 5804 access.
6926 5805
6927 This parameter contro 5806 This parameter controls the TAA mitigation. The
6928 options are: 5807 options are:
6929 5808
6930 full - Enable T 5809 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 5810 if TSX is enabled.
6932 5811
6933 full,nosmt - Enable T 5812 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 5813 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 5814 is not disabled because CPU is not
6936 vulnerab 5815 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 5816 off - Unconditionally disable TAA mitigation
6938 5817
6939 On MDS-affected machi 5818 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 5819 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 5820 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 5821 this mitigation, you need to specify mds=off too.
6943 5822
6944 Not specifying this o 5823 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 5824 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 5825 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 5826 required and doesn't provide any additional
6948 mitigation. 5827 mitigation.
6949 5828
6950 For details see: 5829 For details see:
6951 Documentation/admin-g 5830 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 5831
6953 turbografx.map[2|3]= [HW,JOY] 5832 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 5833 TurboGraFX parallel port interface
6955 Format: 5834 Format:
6956 <port#>,<js1>,<js2>,< 5835 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 5836 See also Documentation/input/devices/joystick-parport.rst
6958 5837
6959 udbg-immortal [PPC] When debugging 5838 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 5839 happen after console_init() and before a proper
6961 console driver takes 5840 console driver takes over, this boot options might
6962 help "seeing" what's 5841 help "seeing" what's going on.
6963 5842
6964 uhash_entries= [KNL,NET] 5843 uhash_entries= [KNL,NET]
6965 Set number of hash bu 5844 Set number of hash buckets for UDP/UDP-Lite connections
6966 5845
6967 uhci-hcd.ignore_oc= 5846 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 5847 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 5848 Some badly-designed motherboards generate lots of
6970 bogus events, for por 5849 bogus events, for ports that aren't wired to
6971 anything. Set this p 5850 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 5851 Note that genuine overcurrent events won't be
6973 reported either. 5852 reported either.
6974 5853
6975 unknown_nmi_panic 5854 unknown_nmi_panic
6976 [X86] Cause panic on 5855 [X86] Cause panic on unknown NMI.
6977 5856
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= 5857 usbcore.authorized_default=
6985 [USB] Default USB dev 5858 [USB] Default USB device authorization:
6986 (default -1 = authori !! 5859 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 5860 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 5861 if device connected to internal port)
6989 5862
6990 usbcore.autosuspend= 5863 usbcore.autosuspend=
6991 [USB] The autosuspend 5864 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 5865 for newly-detected USB devices (default 2). This
6993 is the time required 5866 is the time required before an idle device will be
6994 autosuspended. Devic 5867 autosuspended. Devices for which the delay is set
6995 to a negative value w 5868 to a negative value won't be autosuspended at all.
6996 5869
6997 usbcore.usbfs_snoop= 5870 usbcore.usbfs_snoop=
6998 [USB] Set to log all 5871 [USB] Set to log all usbfs traffic (default 0 = off).
6999 5872
7000 usbcore.usbfs_snoop_max= 5873 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 5874 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 5875 (default = 65536).
7003 5876
7004 usbcore.blinkenlights= 5877 usbcore.blinkenlights=
7005 [USB] Set to cycle le 5878 [USB] Set to cycle leds on hubs (default 0 = off).
7006 5879
7007 usbcore.old_scheme_first= 5880 usbcore.old_scheme_first=
7008 [USB] Start with the 5881 [USB] Start with the old device initialization
7009 scheme (default 0 = o 5882 scheme (default 0 = off).
7010 5883
7011 usbcore.usbfs_memory_mb= 5884 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 5885 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 5886 usbfs (default = 16, 0 = max = 2047).
7014 5887
7015 usbcore.use_both_schemes= 5888 usbcore.use_both_schemes=
7016 [USB] Try the other d 5889 [USB] Try the other device initialization scheme
7017 if the first one fail 5890 if the first one fails (default 1 = enabled).
7018 5891
7019 usbcore.initial_descriptor_timeout= 5892 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 5893 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 5894 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 5895 (default 5000 = 5.0 seconds).
7023 5896
7024 usbcore.nousb [USB] Disable the USB 5897 usbcore.nousb [USB] Disable the USB subsystem
7025 5898
7026 usbcore.quirks= 5899 usbcore.quirks=
7027 [USB] A list of quirk 5900 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 5901 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 5902 commas. Each entry has the form
7030 VendorID:ProductID:Fl 5903 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 5904 numbers and Flags is a set of letters. Each letter
7032 will change the built 5905 will change the built-in quirk; setting it if it is
7033 clear and clearing it 5906 clear and clearing it if it is set. The letters have
7034 the following meaning 5907 the following meanings:
7035 a = USB_QUIRK 5908 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 5909 descriptors must not be fetched using
7037 a 255 5910 a 255-byte read);
7038 b = USB_QUIRK 5911 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 5912 correctly so reset it instead);
7040 c = USB_QUIRK 5913 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 5914 Set-Interface requests);
7042 d = USB_QUIRK 5915 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 5916 handle its Configuration or Interface
7044 strin 5917 strings);
7045 e = USB_QUIRK 5918 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 5919 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 5920 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 5921 more interface descriptions than the
7049 bNumI 5922 bNumInterfaces count, and can't handle
7050 talki 5923 talking to these interfaces);
7051 g = USB_QUIRK 5924 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 5925 during initialization, after we read
7053 the d 5926 the device descriptor);
7054 h = USB_QUIRK 5927 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 5928 high speed and super speed interrupt
7056 endpo 5929 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 5930 require the interval in microframes (1
7058 micro 5931 microframe = 125 microseconds) to be
7059 calcu 5932 calculated as interval = 2 ^
7060 (bInt 5933 (bInterval-1).
7061 Devic 5934 Devices with this quirk report their
7062 bInte 5935 bInterval as the result of this
7063 calcu 5936 calculation instead of the exponent
7064 varia 5937 variable used in the calculation);
7065 i = USB_QUIRK 5938 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 5939 handle device_qualifier descriptor
7067 reque 5940 requests);
7068 j = USB_QUIRK 5941 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 5942 generates spurious wakeup, ignore
7070 remot 5943 remote wakeup capability);
7071 k = USB_QUIRK 5944 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 5945 Power Management);
7073 l = USB_QUIRK 5946 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 5947 (Device reports its bInterval as linear
7075 frame 5948 frames instead of the USB 2.0
7076 calcu 5949 calculation);
7077 m = USB_QUIRK 5950 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 5951 to be disconnected before suspend to
7079 preve 5952 prevent spurious wakeup);
7080 n = USB_QUIRK 5953 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 5954 pause after every control message);
7082 o = USB_QUIRK 5955 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 5956 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 5957 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 5958
7089 usbhid.mousepoll= 5959 usbhid.mousepoll=
7090 [USBHID] The interval 5960 [USBHID] The interval which mice are to be polled at.
7091 5961
7092 usbhid.jspoll= 5962 usbhid.jspoll=
7093 [USBHID] The interval 5963 [USBHID] The interval which joysticks are to be polled at.
7094 5964
7095 usbhid.kbpoll= 5965 usbhid.kbpoll=
7096 [USBHID] The interval 5966 [USBHID] The interval which keyboards are to be polled at.
7097 5967
7098 usb-storage.delay_use= 5968 usb-storage.delay_use=
7099 [UMS] The delay in se 5969 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 5970 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 5971
7105 usb-storage.quirks= 5972 usb-storage.quirks=
7106 [UMS] A list of quirk 5973 [UMS] A list of quirks entries to supplement or
7107 override the built-in 5974 override the built-in unusual_devs list. List
7108 entries are separated 5975 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 5976 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 5977 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 5978 Flags is a set of characters, each corresponding
7112 to a common usb-stora 5979 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 5980 a = SANE_SENSE (collect more than 18 bytes
7114 of se 5981 of sense data, not on uas);
7115 b = BAD_SENSE 5982 b = BAD_SENSE (don't collect more than 18
7116 bytes 5983 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 5984 c = FIX_CAPACITY (decrease the reported
7118 devic 5985 device capacity by one sector);
7119 d = NO_READ_D 5986 d = NO_READ_DISC_INFO (don't use
7120 READ_ 5987 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 5988 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 5989 READ_CAPACITY_16 command);
7123 f = NO_REPORT 5990 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 5991 command, uas only);
7125 g = MAX_SECTO 5992 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 5993 240 sectors at a time, uas only);
7127 h = CAPACITY_ 5994 h = CAPACITY_HEURISTICS (decrease the
7128 repor 5995 reported device capacity by one
7129 secto 5996 sector if the number is odd);
7130 i = IGNORE_DE 5997 i = IGNORE_DEVICE (don't bind to this
7131 devic 5998 device);
7132 j = NO_REPORT 5999 j = NO_REPORT_LUNS (don't use report luns
7133 comma 6000 command, uas only);
7134 k = NO_SAME ( 6001 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 6002 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 6003 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 6004 m = MAX_SECTORS_64 (don't transfer more
7138 than 6005 than 64 sectors = 32 KB at a time,
7139 not o 6006 not on uas);
7140 n = INITIAL_R 6007 n = INITIAL_READ10 (force a retry of the
7141 initi 6008 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 6009 o = CAPACITY_OK (accept the capacity
7143 repor 6010 reported by the device, not on uas);
7144 p = WRITE_CAC 6011 p = WRITE_CACHE (the device cache is ON
7145 by de 6012 by default, not on uas);
7146 r = IGNORE_RE 6013 r = IGNORE_RESIDUE (the device reports
7147 bogus 6014 bogus residue values, not on uas);
7148 s = SINGLE_LU 6015 s = SINGLE_LUN (the device has only one
7149 Logic 6016 Logical Unit);
7150 t = NO_ATA_1X 6017 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 6018 commands, uas only);
7152 u = IGNORE_UA 6019 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 6020 w = NO_WP_DETECT (don't test whether the
7154 mediu 6021 medium is write-protected).
7155 y = ALWAYS_SY 6022 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 6023 even if the device claims no cache,
7157 not o 6024 not on uas)
7158 Example: quirks=0419: 6025 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 6026
7160 user_debug= [KNL,ARM] 6027 user_debug= [KNL,ARM]
7161 Format: <int> 6028 Format: <int>
7162 See arch/arm/Kconfig. 6029 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 6030 1 - undefined instruction events
7164 2 - system c 6031 2 - system calls
7165 4 - invalid 6032 4 - invalid data aborts
7166 8 - SIGSEGV 6033 8 - SIGSEGV faults
7167 16 - SIGBUS f 6034 16 - SIGBUS faults
7168 Example: user_debug=3 6035 Example: user_debug=31
7169 6036
7170 userpte= 6037 userpte=
7171 [X86,EARLY] Flags con !! 6038 [X86] Flags controlling user PTE allocations.
7172 6039
7173 nohigh = do n 6040 nohigh = do not allocate PTE pages in
7174 HIGHM 6041 HIGHMEM regardless of setting
7175 of CO 6042 of CONFIG_HIGHPTE.
7176 6043
7177 vdso= [X86,SH,SPARC] !! 6044 vdso= [X86,SH]
7178 On X86_32, this is an 6045 On X86_32, this is an alias for vdso32=. Otherwise:
7179 6046
7180 vdso=1: enable VDSO ( 6047 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 6048 vdso=0: disable VDSO mapping
7182 6049
7183 vdso32= [X86] Control the 32- 6050 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 6051 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 6052 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 6053
7187 See the help text for 6054 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 6055 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 6056 vdso32=0; otherwise, the default is vdso32=1.
7190 6057
7191 For compatibility wit 6058 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 6059 alias for vdso32=0.
7193 6060
7194 Try vdso32=0 if you e 6061 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 6062 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 6063
7197 video= [FB,EARLY] Frame buff !! 6064 vector= [IA-64,SMP]
>> 6065 vector=percpu: enable percpu vector domain
>> 6066
>> 6067 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 6068 See Documentation/fb/modedb.rst.
7199 6069
7200 video.brightness_switch_enabled= [ACP !! 6070 video.brightness_switch_enabled= [0,1]
7201 Format: [0|1] <<
7202 If set to 1, on recei 6071 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 6072 generated by hotkey, video driver will adjust brightness
7204 level and then send o 6073 level and then send out the event to user space through
7205 the allocated input d !! 6074 the allocated input device; If set to 0, video driver
7206 will only send out th 6075 will only send out the event without touching backlight
7207 brightness level. 6076 brightness level.
7208 default: 1 6077 default: 1
7209 6078
7210 virtio_mmio.device= 6079 virtio_mmio.device=
7211 [VMMIO] Memory mapped 6080 [VMMIO] Memory mapped virtio (platform) device.
7212 6081
7213 <size>@<basead 6082 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 6083 where:
7215 <size> := 6084 <size> := size (can use standard suffixes
7216 6085 like K, M and G)
7217 <baseaddr> := 6086 <baseaddr> := physical base address
7218 <irq> := 6087 <irq> := interrupt number (as passed to
7219 6088 request_irq())
7220 <id> := 6089 <id> := (optional) platform device id
7221 example: 6090 example:
7222 virtio_mmio.d 6091 virtio_mmio.device=1K@0x100b0000:48:7
7223 6092
7224 Can be used multiple 6093 Can be used multiple times for multiple devices.
7225 6094
7226 vga= [BOOT,X86-32] Select 6095 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 6096 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 6097 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 6098 Use vga=ask for menu.
7230 This is actually a bo 6099 This is actually a boot loader parameter; the value is
7231 passed to the kernel 6100 passed to the kernel using a special protocol.
7232 6101
7233 vm_debug[=options] [KNL] Availab 6102 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 6103 May slow down system boot speed, especially when
7235 enabled on systems wi 6104 enabled on systems with a large amount of memory.
7236 All options are enabl 6105 All options are enabled by default, and this
7237 interface is meant to 6106 interface is meant to allow for selectively
7238 enabling or disabling 6107 enabling or disabling specific virtual memory
7239 debugging features. 6108 debugging features.
7240 6109
7241 Available options are 6110 Available options are:
7242 P Enable page s 6111 P Enable page structure init time poisoning
7243 - Disable all o 6112 - Disable all of the above options
7244 6113
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 6114 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 6115 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 6116 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 6117 decrease the size and leave more room for directly
7249 for directly mapped k !! 6118 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 6119
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 6120 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 6121 Sets the memory size reserved for contiguous memory
7256 allocations for the v 6122 allocations for the vmcp device driver.
7257 6123
7258 vmhalt= [KNL,S390] Perform z/ 6124 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 6125 Format: <command>
7260 6126
7261 vmpanic= [KNL,S390] Perform z/ 6127 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 6128 Format: <command>
7263 6129
7264 vmpoff= [KNL,S390] Perform z/ 6130 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 6131 Format: <command>
7266 6132
7267 vsyscall= [X86-64,EARLY] !! 6133 vsyscall= [X86-64]
7268 Controls the behavior 6134 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 6135 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 6136 code). Most statically-linked binaries and older
7271 versions of glibc use 6137 versions of glibc use these calls. Because these
7272 functions are at fixe 6138 functions are at fixed addresses, they make nice
7273 targets for exploits 6139 targets for exploits that can control RIP.
7274 6140
7275 emulate Vsyscalls !! 6141 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 6142 emulated reasonably safely. The vsyscall
7277 readable. !! 6143 page is readable.
7278 6144
7279 xonly [default] !! 6145 xonly Vsyscalls turn into traps and are
7280 emulated 6146 emulated reasonably safely. The vsyscall
7281 page is n 6147 page is not readable.
7282 6148
7283 none Vsyscalls 6149 none Vsyscalls don't work at all. This makes
7284 them quit 6150 them quite hard to use for exploits but
7285 might bre 6151 might break your system.
7286 6152
7287 vt.color= [VT] Default text col 6153 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6154 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6155 Default: 0x07 = light gray on black.
7290 6156
7291 vt.cur_default= [VT] Default cursor s 6157 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6158 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6159 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6160 see VGA-softcursor.txt. Default: 2 = underline.
7295 6161
7296 vt.default_blu= [VT] 6162 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6163 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6164 Change the default blue palette of the console.
7299 This is a 16-member a 6165 This is a 16-member array composed of values
7300 ranging from 0-255. 6166 ranging from 0-255.
7301 6167
7302 vt.default_grn= [VT] 6168 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6169 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6170 Change the default green palette of the console.
7305 This is a 16-member a 6171 This is a 16-member array composed of values
7306 ranging from 0-255. 6172 ranging from 0-255.
7307 6173
7308 vt.default_red= [VT] 6174 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6175 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6176 Change the default red palette of the console.
7311 This is a 16-member a 6177 This is a 16-member array composed of values
7312 ranging from 0-255. 6178 ranging from 0-255.
7313 6179
7314 vt.default_utf8= 6180 vt.default_utf8=
7315 [VT] 6181 [VT]
7316 Format=<0|1> 6182 Format=<0|1>
7317 Set system-wide defau 6183 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6184 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6185 newly opened terminals.
7320 6186
7321 vt.global_cursor_default= 6187 vt.global_cursor_default=
7322 [VT] 6188 [VT]
7323 Format=<-1|0|1> 6189 Format=<-1|0|1>
7324 Set system-wide defau 6190 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6191 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6192 i.e. cursors will be created by default unless
7327 overridden by individ 6193 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6194 cursors, 1 will display them.
7329 6195
7330 vt.italic= [VT] Default color fo 6196 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6197 Default: 2 = green.
7332 6198
7333 vt.underline= [VT] Default color fo 6199 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6200 Default: 3 = cyan.
7335 6201
7336 watchdog timers [HW,WDT] For informat 6202 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6203 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6204 or other driver-specific files in the
7339 Documentation/watchdo 6205 Documentation/watchdog/ directory.
7340 6206
7341 watchdog_thresh= 6207 watchdog_thresh=
7342 [KNL] 6208 [KNL]
7343 Set the hard lockup d 6209 Set the hard lockup detector stall duration
7344 threshold in seconds. 6210 threshold in seconds. The soft lockup detector
7345 threshold is set to t 6211 threshold is set to twice the value. A value of 0
7346 disables both lockup 6212 disables both lockup detectors. Default is 10
7347 seconds. 6213 seconds.
7348 6214
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= 6215 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 6216 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 6217 warn stall conditions and dump internal state to
7359 help debugging. 0 di 6218 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 6219 detection; otherwise, it's the stall threshold
7361 duration in seconds. 6220 duration in seconds. The default value is 30 and
7362 it can be updated at 6221 it can be updated at runtime by writing to the
7363 corresponding sysfs f 6222 corresponding sysfs file.
7364 6223
7365 workqueue.cpu_intensive_thresh_us= !! 6224 workqueue.disable_numa
7366 Per-cpu work items wh !! 6225 By default, all work items queued to unbound
7367 threshold are automat !! 6226 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 6227 issued on, which results in better behavior in
7369 them from noticeably !! 6228 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 6229 whatever reason, this option can be used. Note
7371 !! 6230 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 6231 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 6232
7386 workqueue.power_efficient 6233 workqueue.power_efficient
7387 Per-cpu workqueues ar 6234 Per-cpu workqueues are generally preferred because
7388 they show better perf 6235 they show better performance thanks to cache
7389 locality; unfortunate 6236 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 6237 be more power hungry than unbound workqueues.
7391 6238
7392 Enabling this makes t 6239 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 6240 were observed to contribute significantly to power
7394 consumption unbound, 6241 consumption unbound, leading to measurably lower
7395 power usage at the co 6242 power usage at the cost of small performance
7396 overhead. 6243 overhead.
7397 6244
7398 The default value of 6245 The default value of this parameter is determined by
7399 the config option CON 6246 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 6247
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 6248 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 6249 Workqueue used to implicitly guarantee that work
7415 items queued without 6250 items queued without explicit CPU specified are put
7416 on the local CPU. Th 6251 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 6252 and while local CPU is still preferred work items
7418 may be put on foreign 6253 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 6254 forces round-robin CPU selection to flush out
7420 usages which depend o 6255 usages which depend on the now broken guarantee.
7421 When enabled, memory 6256 When enabled, memory and cache locality will be
7422 impacted. 6257 impacted.
7423 6258
7424 writecombine= [LOONGARCH,EARLY] Con !! 6259 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 6260 default x2apic cluster mode on platforms
7432 supporting x2apic. 6261 supporting x2apic.
7433 6262
7434 xen_512gb_limit [KNL,X86-64,X 6263 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 6264 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6265 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6266 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6267 save/restore/migration must be enabled to handle larger
7439 domains. 6268 domains.
7440 6269
7441 xen_emul_unplug= [HW,X !! 6270 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6271 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6272 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6273 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6274 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6275 nics -- unplug network devices
7447 all -- unplug all emu 6276 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6277 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6278 unnecessary even if the host did not respond to
7450 the unplug pr 6279 the unplug protocol
7451 never -- do not unplu 6280 never -- do not unplug even if version check succeeds
7452 6281
7453 xen_legacy_crash [X86,XEN,EARL !! 6282 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6283 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6284 panic() code such as dumping handler.
7456 6285
7457 xen_mc_debug [X86,XEN,EARLY] !! 6286 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 6287 Disables the qspinlock slowpath using Xen PV optimizations.
7459 Enabling this feature !! 6288 This parameter is obsoleted by "nopvspin" parameter, which
7460 bit, so it should onl !! 6289 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 6290
7469 xen_nopv [X86] 6291 xen_nopv [X86]
7470 Disables the PV optim 6292 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6293 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6294 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6295 has equivalent effect for XEN platform.
7474 6296
7475 xen_no_vector_callback 6297 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6298 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6299 event channel interrupts.
7478 6300
7479 xen_scrub_pages= [XEN] 6301 xen_scrub_pages= [XEN]
7480 Boolean option to con 6302 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6303 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6304 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6305 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6306
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6307 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6308 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6309 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6310 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 6311 improve timer resolution at the expense of processing
7490 more timer interrupts 6312 more timer interrupts.
7491 6313
7492 xen.balloon_boot_timeout= [XEN] 6314 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 6315 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 6316 in case initial ballooning fails to free enough memory.
7495 Applies only when run 6317 Applies only when running as HVM or PVH guest and
7496 started with less mem 6318 started with less memory configured than allowed at
7497 max. Default is 180. 6319 max. Default is 180.
7498 6320
7499 xen.event_eoi_delay= [XEN] 6321 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 6322 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 6323 storms (jiffies). Default is 10.
7502 6324
7503 xen.event_loop_timeout= [XEN] 6325 xen.event_loop_timeout= [XEN]
7504 After which time (jif 6326 After which time (jiffies) the event handling loop
7505 should start to delay 6327 should start to delay EOI handling. Default is 2.
7506 6328
7507 xen.fifo_events= [XEN] 6329 xen.fifo_events= [XEN]
7508 Boolean parameter to 6330 Boolean parameter to disable using fifo event handling
7509 even if available. No 6331 even if available. Normally fifo event handling is
7510 preferred over the 2- 6332 preferred over the 2-level event handling, as it is
7511 fairer and the number 6333 fairer and the number of possible event channels is
7512 much higher. Default 6334 much higher. Default is on (use fifo events).
7513 6335
>> 6336 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6337 Disables the PV optimizations forcing the guest to run
>> 6338 as generic guest with no PV drivers. Currently support
>> 6339 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6340
>> 6341 nopvspin [X86,XEN,KVM]
>> 6342 Disables the qspinlock slow path using PV optimizations
>> 6343 which allow the hypervisor to 'idle' the guest on lock
>> 6344 contention.
>> 6345
7514 xirc2ps_cs= [NET,PCMCIA] 6346 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6347 Format:
7516 <irq>,<irq_mask>,<io> 6348 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6349
7518 xive= [PPC] 6350 xive= [PPC]
7519 By default on POWER9 6351 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6352 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6353 allows the fallback firmware mode to be used:
7522 6354
7523 off Fallback to 6355 off Fallback to firmware control of XIVE interrupt
7524 controller 6356 controller on both pseries and powernv
7525 platforms. 6357 platforms. Only useful on POWER9 and above.
7526 6358
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] 6359 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6360 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6361 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6362 consulted in header drivers/usb/host/xhci.h.
7537 6363
7538 xmon [PPC,EARLY] !! 6364 xmon [PPC]
7539 Format: { early | on 6365 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 6366 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 6367 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 6368 early Call xmon as early as possible on boot; xmon
7543 debugger is c 6369 debugger is called from setup_arch().
7544 on xmon debugger 6370 on xmon debugger hooks will be installed so xmon
7545 is only calle 6371 is only called on a kernel crash. Default mode,
7546 i.e. either " 6372 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 6373 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 6374 rw xmon debugger hooks will be installed so xmon
7549 is called onl 6375 is called only on a kernel crash, mode is write,
7550 meaning SPR r 6376 meaning SPR registers, memory and, other data
7551 can be writte 6377 can be written using xmon commands.
7552 ro same as "rw" 6378 ro same as "rw" option above but SPR registers,
7553 memory, and o 6379 memory, and other data can't be written using
7554 xmon commands 6380 xmon commands.
7555 off xmon is disab 6381 off xmon is disabled.
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