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_hwsig,
244 s4_nohwsig, 229 s4_nohwsig, old_ordering, nonvs,
245 sci_force_en 230 sci_force_enable, nobl }
246 See Documentation/powe 231 See Documentation/power/video.rst for information on
247 s3_bios and s3_mode. 232 s3_bios and s3_mode.
248 s3_beep is for debuggi 233 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel' 234 as soon as the kernel's real-mode entry point is called.
250 s4_hwsig causes the ke 235 s4_hwsig causes the kernel to check the ACPI hardware
251 signature during resum 236 signature during resume from hibernation, and gracefully
252 refuse to resume if it 237 refuse to resume if it has changed. This complies with
253 the ACPI specification 238 the ACPI specification but not with reality, since
254 Windows does not do th 239 Windows does not do this and many laptops do change it
255 on docking. So the def 240 on docking. So the default behaviour is to allow resume
256 and simply warn when t 241 and simply warn when the signature changes, unless the
257 s4_hwsig option is ena 242 s4_hwsig option is enabled.
258 s4_nohwsig prevents AC 243 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a 244 used (or even warned about) during resume.
260 old_ordering causes th 245 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 246 control method, with respect to putting devices into
262 low power states, to b 247 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 248 of _PTS is used by default).
264 nonvs prevents the ker 249 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 250 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 251 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 252 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 253 but some broken systems don't work without it).
269 nobl causes the intern 254 nobl causes the internal blacklist of systems known to
270 behave incorrectly in 255 behave incorrectly in some ways with respect to system
271 suspend and resume to 256 suspend and resume to be ignored (use wisely).
272 257
273 acpi_use_timer_override [HW,ACPI,EARLY !! 258 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 259 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 260 that require a timer override, but don't have HPET
276 261
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 262 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 263 kernel's map of available physical RAM.
279 264
280 agp= [AGP] 265 agp= [AGP]
281 { off | try_unsupporte 266 { off | try_unsupported }
282 off: disable AGP suppo 267 off: disable AGP support
283 try_unsupported: try t 268 try_unsupported: try to drive unsupported chipsets
284 (may crash com 269 (may crash computer or cause data corruption)
285 270
286 ALSA [HW,ALSA] 271 ALSA [HW,ALSA]
287 See Documentation/soun 272 See Documentation/sound/alsa-configuration.rst
288 273
289 alignment= [KNL,ARM] 274 alignment= [KNL,ARM]
290 Allow the default user 275 Allow the default userspace alignment fault handler
291 behaviour to be specif 276 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 277 bit 1 enables fixups, and bit 2 sends a segfault.
293 278
294 align_va_addr= [X86-64] 279 align_va_addr= [X86-64]
295 Align virtual addresse 280 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 281 allocating a VMA at process creation time. This option
297 gives you up to 3% per 282 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 283 machines (where it is enabled by default) for a
299 CPU-intensive style be 284 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 285 a microbenchmark depending on workload and compiler.
301 286
302 32: only for 32-bit pr 287 32: only for 32-bit processes
303 64: only for 64-bit pr 288 64: only for 64-bit processes
304 on: enable for both 32 289 on: enable for both 32- and 64-bit processes
305 off: disable for both 290 off: disable for both 32- and 64-bit processes
306 291
307 alloc_snapshot [FTRACE] 292 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 293 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 294 main buffer is allocated. This is handy if debugging
310 and you need to use tr 295 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 296 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 297 to be done where GFP_KERNEL allocations are allowed.
313 298
314 allow_mismatched_32bit_el0 [ARM64,EARL !! 299 allow_mismatched_32bit_el0 [ARM64]
315 Allow execve() of 32-b 300 Allow execve() of 32-bit applications and setting of the
316 PER_LINUX32 personalit 301 PER_LINUX32 personality on systems where only a strict
317 subset of the CPUs sup 302 subset of the CPUs support 32-bit EL0. When this
318 parameter is present, 303 parameter is present, the set of CPUs supporting 32-bit
319 EL0 is indicated by /s 304 EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
320 and hot-unplug operati 305 and hot-unplug operations may be restricted.
321 306
322 See Documentation/arch !! 307 See Documentation/arm64/asymmetric-32bit.rst for more
323 information. 308 information.
324 309
325 amd_iommu= [HW,X86-64] 310 amd_iommu= [HW,X86-64]
326 Pass parameters to the 311 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 312 Possible values are:
328 fullflush - Deprecated 313 fullflush - Deprecated, equivalent to iommu.strict=1
329 off - do not ini 314 off - do not initialize any AMD IOMMU found in
330 the system 315 the system
331 force_isolation - Forc 316 force_isolation - Force device isolation for all
332 devi 317 devices. The IOMMU driver is not
333 allo 318 allowed anymore to lift isolation
334 requ 319 requirements as needed. This option
335 does 320 does not override iommu=pt
336 force_enable - Force e 321 force_enable - Force enable the IOMMU on platforms known
337 to be b 322 to be buggy with IOMMU enabled. Use this
338 option 323 option with care.
339 pgtbl_v1 - Use v1 <<
340 pgtbl_v2 - Use v2 <<
341 irtcachedis - Disable <<
342 324
343 amd_iommu_dump= [HW,X86-64] 325 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 326 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 327 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 328 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 329 IOMMU initialization.
348 330
349 amd_iommu_intr= [HW,X86-64] 331 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 332 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 333 remapping modes:
352 legacy - Use legac 334 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 335 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 336 to inject interrupts directly into guest.
355 This mode 337 This mode requires kvm-amd.avic=1.
356 (Default 338 (Default when IOMMU HW support is present.)
357 339
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 340 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 341 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 342 Format: <a>,<b>
389 See also Documentation 343 See also Documentation/input/joydev/joystick.rst
390 344
391 analog.map= [HW,JOY] Analog joysti 345 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 346 Specifies type or capabilities of an analog joystick
393 connected to one of 16 347 connected to one of 16 gameports
394 Format: <type1>,<type2 348 Format: <type1>,<type2>,..<type16>
395 349
396 apc= [HW,SPARC] 350 apc= [HW,SPARC]
397 Power management funct 351 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 352 Format: noidle
399 Disable APC CPU standb 353 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 354 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 355 APC and your system crashes randomly.
402 356
403 apic= [APIC,X86,EARLY] Advan !! 357 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 358 Change the output verbosity while booting
405 Format: { quiet (defau 359 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 360 Change the amount of debugging information output
407 when initialising the 361 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 362 For X86-32, this can also be used to specify an APIC
409 driver name. 363 driver name.
410 Format: apic=driver_na 364 Format: apic=driver_name
411 Examples: apic=bigsmp 365 Examples: apic=bigsmp
412 366
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 367 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 368 Format: { bsp (default) | all | none }
415 bsp: External NMI is 369 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 370 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 371 backup of CPU 0
418 none: External NMI is 372 none: External NMI is masked for all CPUs. This is
419 useful so that a 373 useful so that a dump capture kernel won't be
420 shot down by NMI 374 shot down by NMI
421 375
422 autoconf= [IPV6] 376 autoconf= [IPV6]
423 See Documentation/netw 377 See Documentation/networking/ipv6.rst.
424 378
>> 379 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 380 Limit apic dumping. The parameter defines the maximal
>> 381 number of local apics being dumped. Also it is possible
>> 382 to set it to "all" by meaning -- no limit here.
>> 383 Format: { 1 (default) | 2 | ... | all }.
>> 384 The parameter valid if only apic=debug or
>> 385 apic=verbose is specified.
>> 386 Example: apic=debug show_lapic=all
>> 387
425 apm= [APM] Advanced Power M 388 apm= [APM] Advanced Power Management
426 See header of arch/x86 389 See header of arch/x86/kernel/apm_32.c.
427 390
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 391 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 392 Format: <io>,<irq>,<nodeID>
437 393
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall 394 arm64.nobti [ARM64] Unconditionally disable Branch Target
442 Identification support 395 Identification support
443 396
444 arm64.nomops [ARM64] Unconditionall <<
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support <<
449 <<
450 arm64.nopauth [ARM64] Unconditionall 397 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
451 support 398 support
452 399
453 arm64.nosme [ARM64] Unconditionall !! 400 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
454 Extension support !! 401 support
455 <<
456 arm64.nosve [ARM64] Unconditionall <<
457 Extension support <<
458 402
459 ataflop= [HW,M68k] 403 ataflop= [HW,M68k]
460 404
461 atarimouse= [HW,MOUSE] Atari Mouse 405 atarimouse= [HW,MOUSE] Atari Mouse
462 406
463 atkbd.extra= [HW] Enable extra LEDs 407 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 408 EzKey and similar keyboards
465 409
466 atkbd.reset= [HW] Reset keyboard du 410 atkbd.reset= [HW] Reset keyboard during initialization
467 411
468 atkbd.set= [HW] Select keyboard c 412 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 413 Format: <int> (2 = AT (default), 3 = PS/2)
470 414
471 atkbd.scroll= [HW] Enable scroll whe 415 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 416 keyboards
473 417
474 atkbd.softraw= [HW] Choose between sy 418 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 419 Format: <bool> (0 = real, 1 = synthetic (default))
476 420
477 atkbd.softrepeat= [HW] 421 atkbd.softrepeat= [HW]
478 Use software keyboard 422 Use software keyboard repeat
479 423
480 audit= [KNL] Enable the audit 424 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 425 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 426 0 | off - kernel audit is disabled and can not be
483 enabled until the 427 enabled until the next reboot
484 unset - kernel audit i 428 unset - kernel audit is initialized but disabled and
485 will be fully enab 429 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 430 1 | on - kernel audit is initialized and partially
487 enabled, storing a 431 enabled, storing at most audit_backlog_limit
488 messages in RAM un 432 messages in RAM until it is fully enabled by the
489 userspace auditd. 433 userspace auditd.
490 Default: unset 434 Default: unset
491 435
492 audit_backlog_limit= [KNL] Set the aud 436 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 437 Format: <int> (must be >=0)
494 Default: 64 438 Default: 64
495 439
496 bau= [X86_UV] Enable the BA 440 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 441 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 442 Format: { "0" | "1" }
499 0 - Disable the BAU. 443 0 - Disable the BAU.
500 1 - Enable the BAU. 444 1 - Enable the BAU.
501 unset - Disable the BA 445 unset - Disable the BAU.
502 446
503 baycom_epp= [HW,AX25] 447 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 448 Format: <io>,<mode>
505 449
506 baycom_par= [HW,AX25] BayCom Paral 450 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 451 Format: <io>,<mode>
508 See header of drivers/ 452 See header of drivers/net/hamradio/baycom_par.c.
509 453
510 baycom_ser_fdx= [HW,AX25] 454 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 455 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 456 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 457 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 458
515 baycom_ser_hdx= [HW,AX25] 459 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 460 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 461 Format: <io>,<irq>,<mode>
518 See header of drivers/ 462 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 463
520 bert_disable [ACPI] 464 bert_disable [ACPI]
521 Disable BERT OS suppor 465 Disable BERT OS support on buggy BIOSes.
522 466
523 bgrt_disable [ACPI,X86,EARLY] !! 467 bgrt_disable [ACPI][X86]
524 Disable BGRT to avoid 468 Disable BGRT to avoid flickering OEM logo.
525 469
526 blkdevparts= Manual partition parsi 470 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 471 embedded devices based on command line input.
528 See Documentation/bloc 472 See Documentation/block/cmdline-partition.rst
529 473
530 boot_delay= [KNL,EARLY] !! 474 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 475 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 476 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 477 Format: integer
537 478
538 bootconfig [KNL,EARLY] !! 479 bootconfig [KNL]
539 Extended command line 480 Extended command line options can be added to an initrd
540 and this will cause th 481 and this will cause the kernel to look for it.
541 482
542 See Documentation/admi 483 See Documentation/admin-guide/bootconfig.rst
543 484
544 bttv.card= [HW,V4L] bttv (bt848 + 485 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 486 bttv.radio= Most important insmod options are available as
546 kernel args too. 487 kernel args too.
547 bttv.pll= See Documentation/admi 488 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 489 bttv.tuner=
549 490
550 bulk_remove=off [PPC] This parameter 491 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 492 firmware feature for flushing multiple hpte entries
552 at a time. 493 at a time.
553 494
554 c101= [NET] Moxa C101 synchr 495 c101= [NET] Moxa C101 synchronous serial card
555 496
556 cachesize= [BUGS=X86-32] Override 497 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 498 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 499 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 500 to fix known problems, but for some CPUs it is not
560 possible to determine 501 possible to determine what the correct size should be.
561 This option provides a 502 This option provides an override for these situations.
562 503
563 carrier_timeout= 504 carrier_timeout=
564 [NET] Specifies amount 505 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 506 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 507 it waits 120 seconds.
567 508
568 ca_keys= [KEYS] This parameter 509 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 510 the system trusted keyring to be used for certificate
570 trust validation. 511 trust validation.
571 format: { id:<keyid> | 512 format: { id:<keyid> | builtin }
572 513
573 cca= [MIPS,EARLY] Override !! 514 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 515 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 516 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 517 for platform specific values (SB1, Loongson3 and
577 others). 518 others).
578 519
579 ccw_timeout_log [S390] 520 ccw_timeout_log [S390]
580 See Documentation/arch !! 521 See Documentation/s390/common_io.rst for details.
581 522
582 cgroup_disable= [KNL] Disable a partic 523 cgroup_disable= [KNL] Disable a particular controller or optional feature
583 Format: {name of the c 524 Format: {name of the controller(s) or feature(s) to disable}
584 The effects of cgroup_ 525 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 526 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 527 a single hierarchy
587 - foo isn't visible as 528 - foo isn't visible as an individually mountable
588 subsystem 529 subsystem
589 - if foo is an optiona 530 - if foo is an optional feature then the feature is
590 disabled and corresp 531 disabled and corresponding cgroup files are not
591 created 532 created
592 {Currently only "memor 533 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 534 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 535 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" 536 Specifying "pressure" disables per-cgroup pressure
596 stall information acco 537 stall information accounting feature
597 538
598 cgroup_no_v1= [KNL] Disable cgroup c 539 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 540 Format: { { controller | "all" | "named" }
600 [,{ controll 541 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 542 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 543 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 544 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 545 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 546 all v1 hierarchies.
606 547
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 548 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 549 Format: <string>
613 nosocket -- Disable so 550 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 551 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 552
617 checkreqprot= [SELINUX] Set initial !! 553 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 554 Format: { "0" | "1" }
619 See security/selinux/K 555 See security/selinux/Kconfig help text.
620 0 -- check protection 556 0 -- check protection applied by kernel (includes
621 any implied ex 557 any implied execute protection).
622 1 -- check protection 558 1 -- check protection requested by application.
623 Default value is set v 559 Default value is set via a kernel config option.
624 Value can be changed a 560 Value can be changed at runtime via
625 /sys/fs/selinu 561 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 562 Setting checkreqprot to 1 is deprecated.
627 563
628 cio_ignore= [S390] 564 cio_ignore= [S390]
629 See Documentation/arch !! 565 See Documentation/s390/common_io.rst for details.
630 566
631 clearcpuid=X[,X...] [X86] 567 clearcpuid=X[,X...] [X86]
632 Disable CPUID feature 568 Disable CPUID feature X for the kernel. See
633 arch/x86/include/asm/c 569 arch/x86/include/asm/cpufeatures.h for the valid bit
634 numbers X. Note the Li 570 numbers X. Note the Linux-specific bits are not necessarily
635 stable over kernel opt 571 stable over kernel options, but the vendor-specific
636 ones should be. 572 ones should be.
637 X can also be a string 573 X can also be a string as appearing in the flags: line
638 in /proc/cpuinfo which 574 in /proc/cpuinfo which does not have the above
639 instability issue. How 575 instability issue. However, not all features have names
640 in /proc/cpuinfo. 576 in /proc/cpuinfo.
641 Note that using this o 577 Note that using this option will taint your kernel.
642 Also note that user pr 578 Also note that user programs calling CPUID directly
643 or using the feature w 579 or using the feature without checking anything
644 will still see it. Thi 580 will still see it. This just prevents it from
645 being used by the kern 581 being used by the kernel or shown in /proc/cpuinfo.
646 Also note the kernel m 582 Also note the kernel might malfunction if you disable
647 some critical bits. 583 some critical bits.
648 584
649 clk_ignore_unused 585 clk_ignore_unused
650 [CLK] 586 [CLK]
651 Prevents the clock fra 587 Prevents the clock framework from automatically gating
652 clocks that have not b 588 clocks that have not been explicitly enabled by a Linux
653 device driver but are 589 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 590 by the bootloader/firmware. Note that this does not
655 force such clocks to b 591 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 592 those clocks in any way. This parameter is useful for
657 debug and development, 593 debug and development, but should not be needed on a
658 platform with proper d 594 platform with proper driver support. For more
659 information, see Docum 595 information, see Documentation/driver-api/clk.rst.
660 596
661 clock= [BUGS=X86-32, HW] gett 597 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 598 [Deprecated]
663 Forces specified clock 599 Forces specified clocksource (if available) to be used
664 when calculating getti 600 when calculating gettimeofday(). If specified
665 clocksource is not ava 601 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 602 Format: { pit | tsc | cyclone | pmtmr }
667 603
668 clocksource= Override the default c 604 clocksource= Override the default clocksource
669 Format: <string> 605 Format: <string>
670 Override the default c 606 Override the default clocksource and use the clocksource
671 with the name specifie 607 with the name specified.
672 Some clocksource names 608 Some clocksource names to choose from, depending on
673 the platform: 609 the platform:
674 [all] jiffies (this is 610 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 611 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 612 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 613 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 614 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 615 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 616 [MIPS] MIPS
681 [PARISC] cr16 617 [PARISC] cr16
682 [S390] tod 618 [S390] tod
683 [SH] SuperH 619 [SH] SuperH
684 [SPARC64] tick 620 [SPARC64] tick
685 [X86-64] hpet,tsc 621 [X86-64] hpet,tsc
686 622
687 clocksource.arm_arch_timer.evtstrm= 623 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 624 [ARM,ARM64]
689 Format: <bool> 625 Format: <bool>
690 Enable/disable the eve 626 Enable/disable the eventstream feature of the ARM
691 architected timer so t 627 architected timer so that code using WFE-based polling
692 loops can be debugged 628 loops can be debugged more effectively on production
693 systems. 629 systems.
694 630
>> 631 clocksource.max_cswd_read_retries= [KNL]
>> 632 Number of clocksource_watchdog() retries due to
>> 633 external delays before the clock will be marked
>> 634 unstable. Defaults to two retries, that is,
>> 635 three attempts to read the clock under test.
>> 636
695 clocksource.verify_n_cpus= [KNL] 637 clocksource.verify_n_cpus= [KNL]
696 Limit the number of CP 638 Limit the number of CPUs checked for clocksources
697 marked with CLOCK_SOUR 639 marked with CLOCK_SOURCE_VERIFY_PERCPU that
698 are marked unstable du 640 are marked unstable due to excessive skew.
699 A negative value says 641 A negative value says to check all CPUs, while
700 zero says not to check 642 zero says not to check any. Values larger than
701 nr_cpu_ids are silentl 643 nr_cpu_ids are silently truncated to nr_cpu_ids.
702 The actual CPUs are ch 644 The actual CPUs are chosen randomly, with
703 no replacement if the 645 no replacement if the same CPU is chosen twice.
704 646
705 clocksource-wdtest.holdoff= [KNL] 647 clocksource-wdtest.holdoff= [KNL]
706 Set the time in second 648 Set the time in seconds that the clocksource
707 watchdog test waits be 649 watchdog test waits before commencing its tests.
708 Defaults to zero when 650 Defaults to zero when built as a module and to
709 10 seconds when built 651 10 seconds when built into the kernel.
710 652
711 cma=nn[MG]@[start[MG][-end[MG]]] 653 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 654 [KNL,CMA]
713 Sets the size of kerne 655 Sets the size of kernel global memory area for
714 contiguous memory allo 656 contiguous memory allocations and optionally the
715 placement constraint b 657 placement constraint by the physical address range of
716 memory allocations. A 658 memory allocations. A value of 0 disables CMA
717 altogether. For more i 659 altogether. For more information, see
718 kernel/dma/contiguous. 660 kernel/dma/contiguous.c
719 661
720 cma_pernuma=nn[MG] 662 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 663 [ARM64,KNL,CMA]
722 Sets the size of kerne 664 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 665 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 666 per-numa CMA altogether. And If this option is not
725 specified, the default !! 667 specificed, the default value is 0.
726 With per-numa CMA enab 668 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 669 first try to allocate buffer from the pernuma area
728 which is located in no 670 which is located in node nid, if the allocation fails,
729 they will fallback to 671 they will fallback to the global default memory area.
730 672
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 | 673 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 674 Specify whether pages are marked as being inactive
744 when they are freed. 675 when they are freed. This is used in CMO environments
745 to determine OS memory 676 to determine OS memory pressure for page stealing by
746 a hypervisor. 677 a hypervisor.
747 Default: yes 678 Default: yes
748 679
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 680 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 681 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 682 allocations, by default set to 256K.
752 683
753 com20020= [HW,NET] ARCnet - COM2 684 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 685 Format:
755 <io>[,<irq>[,<nodeID>[ 686 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 687
757 com90io= [HW,NET] ARCnet - COM9 688 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 689 Format: <io>[,<irq>]
759 690
760 com90xx= [HW,NET] 691 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 692 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 693 Format: <io>[,<irq>[,<memstart>]]
763 694
764 condev= [HW,S390] console devi 695 condev= [HW,S390] console device
765 conmode= 696 conmode=
766 697
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 698 console= [KNL] Output console device and options.
779 699
780 tty<n> Use the virtual consol 700 tty<n> Use the virtual console device <n>.
781 701
782 ttyS<n>[,options] 702 ttyS<n>[,options]
783 ttyUSB0[,options] 703 ttyUSB0[,options]
784 Use the specified seri 704 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 705 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 706 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 707 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 708 omit it). Default is "9600n8".
789 709
790 See Documentation/admi 710 See Documentation/admin-guide/serial-console.rst for more
791 information. See 711 information. See
792 Documentation/networki 712 Documentation/networking/netconsole.rst for an
793 alternative. 713 alternative.
794 714
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] 715 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 716 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 717 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 718 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 719 uart[8250],0x<addr>[,options]
819 Start an early, polled 720 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 721 UART at the specified I/O port or MMIO address,
821 switching to the match 722 switching to the matching ttyS device later.
822 MMIO inter-register ad 723 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 724 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 725 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 726 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 727 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 728 the h/w is not re-initialized.
828 729
829 hvc<n> Use the hypervisor con 730 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 731 both Xen and PowerPC hypervisors.
831 732
832 { null | "" } 733 { null | "" }
833 Use to disable console 734 Use to disable console output, i.e., to have kernel
834 console messages disca 735 console messages discarded.
835 This must be the only 736 This must be the only console= parameter used on the
836 kernel command line. 737 kernel command line.
837 738
838 If the device connected to the 739 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 740 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 741 console=brl,ttyS0
841 For now, only VisioBraille is 742 For now, only VisioBraille is supported.
842 743
843 console_msg_format= 744 console_msg_format=
844 [KNL] Change console m 745 [KNL] Change console messages format
845 default 746 default
846 By default we print me 747 By default we print messages on consoles in
847 "[time stamp] text\n" 748 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 749 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 750 `printk_time' param).
850 syslog 751 syslog
851 Switch to syslog forma 752 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 753 IOW, each message will have a facility and loglevel
853 prefix. The format is 754 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 755 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 756 from /proc/kmsg.
856 757
857 consoleblank= [KNL] The console blan 758 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 759 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 760 Defaults to 0.
860 761
861 coredump_filter= 762 coredump_filter=
862 [KNL] Change the defau 763 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 764 /proc/<pid>/coredump_filter.
864 See also Documentation 765 See also Documentation/filesystems/proc.rst.
865 766
866 coresight_cpu_debug.enable 767 coresight_cpu_debug.enable
867 [ARM,ARM64] 768 [ARM,ARM64]
868 Format: <bool> 769 Format: <bool>
869 Enable/disable the CPU 770 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 771 0: default value, disable debugging
871 1: enable debugging at 772 1: enable debugging at boot time
872 773
873 cpcihp_generic= [HW,PCI] Generic port 774 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
874 Format: 775 Format:
875 <first_slot>,<last_slo 776 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
876 777
>> 778 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
>> 779 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
>> 780 Some features depend on CPU0. Known dependencies are:
>> 781 1. Resume from suspend/hibernate depends on CPU0.
>> 782 Suspend/hibernate will fail if CPU0 is offline and you
>> 783 need to online CPU0 before suspend/hibernate.
>> 784 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 785 removed if a PIC interrupt is detected.
>> 786 It's said poweroff/reboot may depend on CPU0 on some
>> 787 machines although I haven't seen such issues so far
>> 788 after CPU0 is offline on a few tested machines.
>> 789 If the dependencies are under your control, you can
>> 790 turn on cpu0_hotplug.
>> 791
877 cpuidle.off=1 [CPU_IDLE] 792 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 793 disable the cpuidle sub-system
879 794
880 cpuidle.governor= 795 cpuidle.governor=
881 [CPU_IDLE] Name of the 796 [CPU_IDLE] Name of the cpuidle governor to use.
882 797
883 cpufreq.off=1 [CPU_FREQ] 798 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 799 disable the cpufreq sub-system
885 800
886 cpufreq.default_governor= 801 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 802 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 803 policy to use. This governor must be registered in the
889 kernel before the cpuf 804 kernel before the cpufreq driver probes.
890 805
891 cpu_init_udelay=N 806 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 807 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 808 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 809 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 810 Default: 10000
896 811
897 cpuhp.parallel= <<
898 [SMP] Enable/disable p <<
899 Format: <bool> <<
900 Default is enabled if <<
901 the parameter has no e <<
902 <<
903 crash_kexec_post_notifiers 812 crash_kexec_post_notifiers
904 Run kdump after runnin 813 Run kdump after running panic-notifiers and dumping
905 kmsg. This only for th 814 kmsg. This only for the users who doubt kdump always
906 succeeds in any situat 815 succeeds in any situation.
907 Note that this also in 816 Note that this also increases risks of kdump failure,
908 because some panic not 817 because some panic notifiers can make the crashed
909 kernel more unstable. 818 kernel more unstable.
910 819
911 crashkernel=size[KMG][@offset[KMG]] 820 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 821 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 822 upon panic. This parameter reserves the physical
914 memory region [offset, 823 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 824 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 825 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 826 [KNL, X86-64] Select a region under 4G first, and
918 under 4G first, and fa !! 827 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 828 hasn't been specified.
920 See Documentation/admi 829 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 830
922 crashkernel=range1:size1[,range2:size2 831 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 832 [KNL] Same as above, but depends on the memory
924 in the running system. 833 in the running system. The syntax of range is
925 start-[end] where star 834 start-[end] where start and end are both
926 a memory unit (amount[ 835 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 836 Documentation/admin-guide/kdump/kdump.rst for an example.
928 837
929 crashkernel=size[KMG],high 838 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 839 [KNL, X86-64, ARM64] range could be above 4G. Allow kernel
931 above 4G. !! 840 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 841 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 842 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 843 available.
935 below 4G, if available <<
936 It will be ignored if 844 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 845 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 846 [KNL, X86-64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 847 is passed, kernel could allocate physical memory region
940 physical memory region !! 848 above 4G, that cause second kernel crash on system
941 crash on system that r !! 849 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 850 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 851 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 852 devices won't run out. Kernel would try to allocate
945 default size of memory !! 853 at least 256M below 4G automatically.
946 size is platform depen <<
947 --> x86: max(swiotlb <<
948 --> arm64: 128MiB <<
949 --> riscv: 128MiB <<
950 --> loongarch: 128Mi <<
951 This one lets the user 854 This one lets the user specify own low range under 4G
952 for second kernel inst 855 for second kernel instead.
953 0: to disable low allo 856 0: to disable low allocation.
954 It will be ignored whe 857 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 858 or memory reserved is below 4G.
956 859
>> 860 [KNL, ARM64] range in low memory.
>> 861 This one lets the user specify a low range in the
>> 862 DMA zone for the crash dump kernel.
>> 863 It will be ignored when crashkernel=X,high is not used
>> 864 or memory reserved is located in the DMA zones.
>> 865
957 cryptomgr.notests 866 cryptomgr.notests
958 [KNL] Disable crypto s 867 [KNL] Disable crypto self-tests
959 868
960 cs89x0_dma= [HW,NET] 869 cs89x0_dma= [HW,NET]
961 Format: <dma> 870 Format: <dma>
962 871
963 cs89x0_media= [HW,NET] 872 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 873 Format: { rj45 | aui | bnc }
965 874
966 csdlock_debug= [KNL] Enable or disabl !! 875 csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
967 function call handling !! 876 handling. When switched on, additional debug data is
968 additional debug data !! 877 printed to the console in case a hanging CPU is
969 in case a hanging CPU !! 878 detected, and that CPU is pinged again in order to try
970 CPU is pinged again in !! 879 to resolve the hang situation.
971 the hang situation. T !! 880 0: disable csdlock debugging (default)
972 option depends on the !! 881 1: enable basic csdlock debugging (minor impact)
973 Kconfig option. !! 882 ext: enable extended csdlock debugging (more impact,
>> 883 but more data)
974 884
975 dasd= [HW,NET] 885 dasd= [HW,NET]
976 See header of drivers/ 886 See header of drivers/s390/block/dasd_devmap.c.
977 887
978 db9.dev[2|3]= [HW,JOY] Multisystem j 888 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 889 (one device per port)
980 Format: <port#>,<type> 890 Format: <port#>,<type>
981 See also Documentation 891 See also Documentation/input/devices/joystick-parport.rst
982 892
983 debug [KNL,EARLY] Enable ker !! 893 debug [KNL] Enable kernel debugging (events log level).
984 894
985 debug_boot_weak_hash 895 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 896 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 897 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 898 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 899 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 900 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 901 insecure, please do not use on production kernels.
992 902
993 debug_locks_verbose= 903 debug_locks_verbose=
994 [KNL] verbose locking 904 [KNL] verbose locking self-tests
995 Format: <int> 905 Format: <int>
996 Print debugging info w 906 Print debugging info while doing the locking API
997 self-tests. 907 self-tests.
998 Bitmask for the variou 908 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 909 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 910 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 911 useful to lockdep developers.
1002 912
1003 debug_objects [KNL,EARLY] Enable ob !! 913 debug_objects [KNL] Enable object debugging
>> 914
>> 915 no_debug_objects
>> 916 [KNL] Disable object debugging
1004 917
1005 debug_guardpage_minorder= 918 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 919 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 920 parameter allows control of the order of pages that will
1008 be intentionally kept 921 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 922 buddy allocator. Bigger value increase the probability
1010 of catching random me 923 of catching random memory corruption, but reduce the
1011 amount of memory for 924 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 925 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 926 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 927 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 928 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 929 random memory location. Note that there exists a class
1017 a class of memory cor !! 930 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 931 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 932 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 933 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 934 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 935 tracking down these problems.
1023 936
1024 debug_pagealloc= 937 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 938 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 939 enables the feature at boot time. By default, it is
1027 disabled and the syst 940 disabled and the system will work mostly the same as a
1028 kernel built without 941 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 942 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 943 useful to also enable the page_owner functionality.
1031 on: enable the featur 944 on: enable the feature
1032 945
1033 debugfs= [KNL,EARLY] This para !! 946 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 947 and debugfs internal clients.
1035 Format: { on, no-moun 948 Format: { on, no-mount, off }
1036 on: All functions 949 on: All functions are enabled.
1037 no-mount: 950 no-mount:
1038 Filesystem is 951 Filesystem is not registered but kernel clients can
1039 access APIs a 952 access APIs and a crashkernel can be used to read
1040 its content. 953 its content. There is nothing to mount.
1041 off: Filesystem is 954 off: Filesystem is not registered and clients
1042 get a -EPERM 955 get a -EPERM as result when trying to register files
1043 or directorie 956 or directories within debugfs.
1044 This is equiv 957 This is equivalent of the runtime functionality if
1045 debugfs was n 958 debugfs was not enabled in the kernel at all.
1046 Default value is set 959 Default value is set in build-time with a kernel configuration.
1047 960
1048 debugpat [X86] Enable PAT debu 961 debugpat [X86] Enable PAT debugging
1049 962
>> 963 decnet.addr= [HW,NET]
>> 964 Format: <area>[,<node>]
>> 965 See also Documentation/networking/decnet.rst.
>> 966
1050 default_hugepagesz= 967 default_hugepagesz=
1051 [HW] The size of the 968 [HW] The size of the default HugeTLB page. This is
1052 the size represented 969 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 970 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 971 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 972 filesystems. If not specified, defaults to the
1056 architecture's defaul 973 architecture's default huge page size. Huge page
1057 sizes are architectur 974 sizes are architecture dependent. See also
1058 Documentation/admin-g 975 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 976 Format: size[KMG]
1060 977
1061 deferred_probe_timeout= 978 deferred_probe_timeout=
1062 [KNL] Debugging optio 979 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 980 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 981 probe. Only specific dependencies (subsystems or
1065 drivers) that have op 982 drivers) that have opted in will be ignored. A timeout
1066 of 0 will timeout at 983 of 0 will timeout at the end of initcalls. If the time
1067 out hasn't expired, i 984 out hasn't expired, it'll be restarted by each
1068 successful driver reg 985 successful driver registration. This option will also
1069 dump out devices stil 986 dump out devices still on the deferred probe list after
1070 retrying. 987 retrying.
1071 988
1072 delayacct [KNL] Enable per-task 989 delayacct [KNL] Enable per-task delay accounting
1073 990
1074 dell_smm_hwmon.ignore_dmi= 991 dell_smm_hwmon.ignore_dmi=
1075 [HW] Continue probing 992 [HW] Continue probing hardware even if DMI data
1076 indicates that the dr 993 indicates that the driver is running on unsupported
1077 hardware. 994 hardware.
1078 995
1079 dell_smm_hwmon.force= 996 dell_smm_hwmon.force=
1080 [HW] Activate driver 997 [HW] Activate driver even if SMM BIOS signature does
1081 not match list of sup 998 not match list of supported models and enable otherwise
1082 blacklisted features. 999 blacklisted features.
1083 1000
1084 dell_smm_hwmon.power_status= 1001 dell_smm_hwmon.power_status=
1085 [HW] Report power sta 1002 [HW] Report power status in /proc/i8k
1086 (disabled by default) 1003 (disabled by default).
1087 1004
1088 dell_smm_hwmon.restricted= 1005 dell_smm_hwmon.restricted=
1089 [HW] Allow controllin 1006 [HW] Allow controlling fans only if SYS_ADMIN
1090 capability is set. 1007 capability is set.
1091 1008
1092 dell_smm_hwmon.fan_mult= 1009 dell_smm_hwmon.fan_mult=
1093 [HW] Factor to multip 1010 [HW] Factor to multiply fan speed with.
1094 1011
1095 dell_smm_hwmon.fan_max= 1012 dell_smm_hwmon.fan_max=
1096 [HW] Maximum configur 1013 [HW] Maximum configurable fan speed.
1097 1014
1098 dfltcc= [HW,S390] 1015 dfltcc= [HW,S390]
1099 Format: { on | off | 1016 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 1017 on: s390 zlib hardware support for compression on
1101 level 1 and 1018 level 1 and decompression (default)
1102 off: No s390 zli 1019 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 1020 def_only: s390 zlib hardware support for deflate
1104 only (compr 1021 only (compression on level 1)
1105 inf_only: s390 zlib h 1022 inf_only: s390 zlib hardware support for inflate
1106 only (decom 1023 only (decompression)
1107 always: Same as 'on 1024 always: Same as 'on' but ignores the selected compression
1108 level alway 1025 level always using hardware support (used for debugging)
1109 1026
1110 dhash_entries= [KNL] 1027 dhash_entries= [KNL]
1111 Set number of hash bu 1028 Set number of hash buckets for dentry cache.
1112 1029
1113 disable_1tb_segments [PPC,EARLY] !! 1030 disable_1tb_segments [PPC]
1114 Disables the use of 1 1031 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 1032 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 1033 can be useful when debugging issues that require an SLB
1117 miss to occur. 1034 miss to occur.
1118 1035
>> 1036 stress_slb [PPC]
>> 1037 Limits the number of kernel SLB entries, and flushes
>> 1038 them frequently to increase the rate of SLB faults
>> 1039 on kernel addresses.
>> 1040
1119 disable= [IPV6] 1041 disable= [IPV6]
1120 See Documentation/net 1042 See Documentation/networking/ipv6.rst.
1121 1043
1122 disable_radix [PPC,EARLY] !! 1044 disable_radix [PPC]
1123 Disable RADIX MMU mod 1045 Disable RADIX MMU mode on POWER9
1124 1046
>> 1047 radix_hcall_invalidate=on [PPC/PSERIES]
>> 1048 Disable RADIX GTSE feature and use hcall for TLB
>> 1049 invalidate.
>> 1050
1125 disable_tlbie [PPC] 1051 disable_tlbie [PPC]
1126 Disable TLBIE instruc 1052 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 1053 with KVM, with HASH MMU, or with coherent accelerators.
1128 1054
1129 disable_ddw [PPC/PSERIES,EARLY] !! 1055 disable_cpu_apicid= [X86,APIC,SMP]
>> 1056 Format: <int>
>> 1057 The number of initial APIC ID for the
>> 1058 corresponding CPU to be disabled at boot,
>> 1059 mostly used for the kdump 2nd kernel to
>> 1060 disable BSP to wake up multiple CPUs without
>> 1061 causing system reset or hang due to sending
>> 1062 INIT from AP to BSP.
>> 1063
>> 1064 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 1065 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 1066 to workaround buggy firmware.
1132 1067
1133 disable_ipv6= [IPV6] 1068 disable_ipv6= [IPV6]
1134 See Documentation/net 1069 See Documentation/networking/ipv6.rst.
1135 1070
1136 disable_mtrr_cleanup [X86,EARLY] !! 1071 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 1072 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 1073 to discrete, to make X server driver able to add WB
1139 entry later. This par 1074 entry later. This parameter disables that.
1140 1075
1141 disable_mtrr_trim [X86, Intel and AMD !! 1076 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 1077 By default the kernel will trim any uncacheable
1143 memory out of your av 1078 memory out of your available memory pool based on
1144 MTRR settings. This 1079 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 1080 possibly causing your machine to run very slowly.
1146 1081
1147 disable_timer_pin_1 [X86,EARLY] !! 1082 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 1083 Disable PIN 1 of APIC timer
1149 Can be useful to work 1084 Can be useful to work around chipset bugs.
1150 1085
1151 dis_ucode_ldr [X86] Disable the mic 1086 dis_ucode_ldr [X86] Disable the microcode loader.
1152 1087
1153 dma_debug=off If the kernel is comp 1088 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 1089 this option disables the debugging code at boot.
1155 1090
1156 dma_debug_entries=<number> 1091 dma_debug_entries=<number>
1157 This option allows to 1092 This option allows to tune the number of preallocated
1158 entries for DMA-API d 1093 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 1094 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 1095 DMA-API debugging code disables itself because the
1161 architectural default 1096 architectural default is too low.
1162 1097
1163 dma_debug_driver=<driver_name> 1098 dma_debug_driver=<driver_name>
1164 With this option the 1099 With this option the DMA-API debugging driver
1165 filter feature can be 1100 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1101 pass the driver to filter for as the parameter.
1167 The filter can be dis 1102 The filter can be disabled or changed to another
1168 driver later using sy 1103 driver later using sysfs.
1169 1104
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] 1105 driver_async_probe= [KNL]
1191 List of driver names 1106 List of driver names to be probed asynchronously. *
1192 matches with all driv 1107 matches with all driver names. If * is specified, the
1193 rest of the listed dr 1108 rest of the listed driver names are those that will NOT
1194 match the *. 1109 match the *.
1195 Format: <driver_name1 1110 Format: <driver_name1>,<driver_name2>...
1196 1111
1197 drm.edid_firmware=[<connector>:]<file 1112 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1113 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1114 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1115 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1116 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1117 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1118 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1119 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1120 and no file with the same name exists. Details and
>> 1121 instructions how to build your own EDID data are
>> 1122 available in Documentation/admin-guide/edid.rst. An EDID
>> 1123 data set will only be used for a particular connector,
>> 1124 if its name and a colon are prepended to the EDID
>> 1125 name. Each connector may use a unique EDID data
>> 1126 set by separating the files with a comma. An EDID
1206 data set with no conn 1127 data set with no connector name will be used for
1207 any connectors not ex 1128 any connectors not explicitly specified.
1208 1129
1209 dscc4.setup= [NET] 1130 dscc4.setup= [NET]
1210 1131
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1132 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1133 Format: {"off" | "known"}
1213 Control how the dt_cp 1134 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1135 used for CPU feature discovery and setup (if it
1215 exists). 1136 exists).
1216 off: Do not use it, f 1137 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1138 known: Do not pass through unknown features to guests
1218 or userspace, only th 1139 or userspace, only those that the kernel is aware of.
1219 1140
1220 dump_apple_properties [X86] 1141 dump_apple_properties [X86]
1221 Dump name and content 1142 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1143 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1144 what data is available or for reverse-engineering.
1224 1145
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1146 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1147 <module>.dyndbg[="val"]
1227 Enable debug messages 1148 Enable debug messages at boot time. See
1228 Documentation/admin-g 1149 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1150 for details.
1230 1151
1231 early_ioremap_debug [KNL,EARLY] !! 1152 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1153 in some Intel CPUs.
>> 1154
>> 1155 <module>.async_probe [KNL]
>> 1156 Enable asynchronous probe on this module.
>> 1157
>> 1158 early_ioremap_debug [KNL]
1232 Enable debug messages 1159 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1160 is useful for tracking down temporary early mappings
1234 which are not unmappe 1161 which are not unmapped.
1235 1162
1236 earlycon= [KNL,EARLY] Output ea !! 1163 earlycon= [KNL] Output early console device and options.
1237 1164
1238 When used with no opt 1165 When used with no options, the early console is
1239 determined by stdout- 1166 determined by stdout-path property in device tree's
1240 chosen node or the AC 1167 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1168 the platform.
1242 1169
1243 cdns,<addr>[,options] 1170 cdns,<addr>[,options]
1244 Start an early, polle 1171 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1172 (xuartps) serial port at the specified address. Only
1246 supported option is b 1173 supported option is baud rate. If baud rate is not
1247 specified, the serial 1174 specified, the serial port must already be setup and
1248 configured. 1175 configured.
1249 1176
1250 uart[8250],io,<addr>[,options !! 1177 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1178 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1179 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1180 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1181 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1182 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1183 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1184 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1185 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1186 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1187 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1188 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1189 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1190
1266 pl011,<addr> 1191 pl011,<addr>
1267 pl011,mmio32,<addr> 1192 pl011,mmio32,<addr>
1268 Start an early, polle 1193 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1194 port at the specified address. The pl011 serial port
1270 must already be setup 1195 must already be setup and configured. Options are not
1271 yet supported. If 'm 1196 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1197 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1198 the device registers.
1274 1199
1275 liteuart,<addr> 1200 liteuart,<addr>
1276 Start an early consol 1201 Start an early console on a litex serial port at the
1277 specified address. Th 1202 specified address. The serial port must already be
1278 setup and configured. 1203 setup and configured. Options are not yet supported.
1279 1204
1280 meson,<addr> 1205 meson,<addr>
1281 Start an early, polle 1206 Start an early, polled-mode console on a meson serial
1282 port at the specified 1207 port at the specified address. The serial port must
1283 already be setup and 1208 already be setup and configured. Options are not yet
1284 supported. 1209 supported.
1285 1210
1286 msm_serial,<addr> 1211 msm_serial,<addr>
1287 Start an early, polle 1212 Start an early, polled-mode console on an msm serial
1288 port at the specified 1213 port at the specified address. The serial port
1289 must already be setup 1214 must already be setup and configured. Options are not
1290 yet supported. 1215 yet supported.
1291 1216
1292 msm_serial_dm,<addr> 1217 msm_serial_dm,<addr>
1293 Start an early, polle 1218 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1219 dm port at the specified address. The serial port
1295 must already be setup 1220 must already be setup and configured. Options are not
1296 yet supported. 1221 yet supported.
1297 1222
1298 owl,<addr> 1223 owl,<addr>
1299 Start an early, polle 1224 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1225 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1226 specified address. The serial port must already be
1302 setup and configured. 1227 setup and configured. Options are not yet supported.
1303 1228
1304 rda,<addr> 1229 rda,<addr>
1305 Start an early, polle 1230 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1231 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1232 specified address. The serial port must already be
1308 setup and configured. 1233 setup and configured. Options are not yet supported.
1309 1234
1310 sbi 1235 sbi
1311 Use RISC-V SBI (Super 1236 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1237 console.
1313 1238
1314 smh Use ARM semihosting c 1239 smh Use ARM semihosting calls for early console.
1315 1240
1316 s3c2410,<addr> 1241 s3c2410,<addr>
1317 s3c2412,<addr> 1242 s3c2412,<addr>
1318 s3c2440,<addr> 1243 s3c2440,<addr>
1319 s3c6400,<addr> 1244 s3c6400,<addr>
1320 s5pv210,<addr> 1245 s5pv210,<addr>
1321 exynos4210,<addr> 1246 exynos4210,<addr>
1322 Use early console pro 1247 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1248 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1249 a correct base address of the selected UART port. The
1325 serial port must alre 1250 serial port must already be setup and configured.
1326 Options are not yet s 1251 Options are not yet supported.
1327 1252
1328 lantiq,<addr> 1253 lantiq,<addr>
1329 Start an early, polle 1254 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1255 (lqasc) port at the specified address. The serial port
1331 must already be setup 1256 must already be setup and configured. Options are not
1332 yet supported. 1257 yet supported.
1333 1258
1334 lpuart,<addr> 1259 lpuart,<addr>
1335 lpuart32,<addr> 1260 lpuart32,<addr>
1336 Use early console pro 1261 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1262 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1263 A valid base address must be provided, and the serial
1339 port must already be 1264 port must already be setup and configured.
1340 1265
1341 ec_imx21,<addr> 1266 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1267 ec_imx6q,<addr>
1343 Start an early, polle 1268 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1269 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1270 must already be setup and configured.
1346 1271
1347 ar3700_uart,<addr> 1272 ar3700_uart,<addr>
1348 Start an early, polle 1273 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1274 Armada 3700 serial port at the specified
1350 address. The serial p 1275 address. The serial port must already be setup
1351 and configured. Optio 1276 and configured. Options are not yet supported.
1352 1277
1353 qcom_geni,<addr> 1278 qcom_geni,<addr>
1354 Start an early, polle 1279 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1280 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1281 specified address. The serial port must already be
1357 setup and configured. 1282 setup and configured. Options are not yet supported.
1358 1283
1359 efifb,[options] 1284 efifb,[options]
1360 Start an early, unacc 1285 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1286 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1287 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1288 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1289 mapped with the correct attributes.
1365 1290
1366 linflex,<addr> 1291 linflex,<addr>
1367 Use early console pro 1292 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1293 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1294 address must be provided, and the serial port must
1370 already be setup and 1295 already be setup and configured.
1371 1296
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1297 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1298 earlyprintk=vga
1374 earlyprintk=sclp 1299 earlyprintk=sclp
1375 earlyprintk=xen 1300 earlyprintk=xen
1376 earlyprintk=serial[,t 1301 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1302 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1303 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1304 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1305 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1306 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1307
1384 earlyprintk is useful 1308 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1309 the normal console is initialized. It is not enabled by
1386 default because it ha 1310 default because it has some cosmetic problems.
1387 1311
1388 Append ",keep" to not 1312 Append ",keep" to not disable it when the real console
1389 takes over. 1313 takes over.
1390 1314
1391 Only one of vga, seri 1315 Only one of vga, serial, or usb debug port can
1392 be used at a time. 1316 be used at a time.
1393 1317
1394 Currently only ttyS0 1318 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1319 name. Other I/O ports may be explicitly specified
1396 on some architectures 1320 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1321 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1322 earlyprintk=serial,0x1008,115200
1399 You can find the port 1323 You can find the port for a given device in
1400 /proc/tty/driver/seri 1324 /proc/tty/driver/serial:
1401 2: uart:ST166 1325 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1326
1403 Interaction with the 1327 Interaction with the standard serial driver is not
1404 very good. 1328 very good.
1405 1329
1406 The VGA output is eve 1330 The VGA output is eventually overwritten by
1407 the real console. 1331 the real console.
1408 1332
1409 The xen option can on 1333 The xen option can only be used in Xen domains.
1410 1334
1411 The sclp output can o 1335 The sclp output can only be used on s390.
1412 1336
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1337 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1338 PCI device even when its classcode is not of the
1417 UART class. 1339 UART class.
1418 1340
1419 edac_report= [HW,EDAC] Control how 1341 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1342 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1343 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1344 by other higher priority error reporting module.
1423 off: disable H/W even 1345 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1346 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1347 default: on.
1426 1348
1427 edd= [EDD] 1349 edd= [EDD]
1428 Format: {"off" | "on" 1350 Format: {"off" | "on" | "skip[mbr]"}
1429 1351
1430 efi= [EFI,EARLY] !! 1352 efi= [EFI]
1431 Format: { "debug", "d 1353 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1354 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1355 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1356 debug: enable misc debug output.
1435 disable_early_pci_dma 1357 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1358 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1359 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1360 boot stub, as chunking can cause problems with some
1439 firmware implementati 1361 firmware implementations.
1440 noruntime : disable E 1362 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1363 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1364 attribute may cause the kernel to reserve the
1443 memory range for a me 1365 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1366 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1367 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1368 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1369 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1370 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1371 on all PCI bridges while in the EFI boot stub
1450 1372
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1373 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1374 Using this parameter you can use more than 50% of
1453 your efi variable sto 1375 your efi variable storage. Use this parameter only if
1454 you are really sure t 1376 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1377 fulfills the spec otherwise your board may brick.
1456 1378
>> 1379 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1380 Add arbitrary attribute to specific memory range by
>> 1381 updating original EFI memory map.
>> 1382 Region of memory which aa attribute is added to is
>> 1383 from ss to ss+nn.
>> 1384
>> 1385 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1386 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1387 attribute is added to range 0x100000000-0x180000000 and
>> 1388 0x10a0000000-0x1120000000.
>> 1389
>> 1390 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1391 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1392 range 0x240000000-0x43fffffff.
>> 1393
>> 1394 Using this parameter you can do debugging of EFI memmap
>> 1395 related features. For example, you can do debugging of
>> 1396 Address Range Mirroring feature even if your box
>> 1397 doesn't support it, or mark specific memory as
>> 1398 "soft reserved".
>> 1399
1457 efivar_ssdt= [EFI; X86] Name of an 1400 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1401 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1402 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1403 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1404 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1405
1463 1406
1464 eisa_irq_edge= [PARISC,HW] 1407 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1408 See header of drivers/parisc/eisa.c.
1466 1409
1467 ekgdboc= [X86,KGDB,EARLY] Allo !! 1410 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1468 Format: ekgdboc=kbd 1411 Format: ekgdboc=kbd
1469 1412
1470 This is designed to b 1413 This is designed to be used in conjunction with
1471 the boot argument: ea 1414 the boot argument: earlyprintk=vga
1472 1415
1473 This parameter works 1416 This parameter works in place of the kgdboc parameter
1474 but can only be used 1417 but can only be used if the backing tty is available
1475 very early in the boo 1418 very early in the boot process. For early debugging
1476 via a serial port see 1419 via a serial port see kgdboc_earlycon instead.
1477 1420
1478 elanfreq= [X86-32] 1421 elanfreq= [X86-32]
1479 See comment before fu 1422 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1423 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1424
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1425 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1426 Specifies physical address of start of kernel core
1484 image elf header and 1427 image elf header and optionally the size. Generally
1485 kexec loader will pas 1428 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1429 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1430
1488 enable_mtrr_cleanup [X86,EARLY] !! 1431 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1432 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1433 to discrete, to make X server driver able to add WB
1491 entry later. This par 1434 entry later. This parameter enables that.
1492 1435
1493 enable_timer_pin_1 [X86] 1436 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1437 Enable PIN 1 of APIC timer
1495 Can be useful to work 1438 Can be useful to work around chipset bugs
1496 (in particular on som 1439 (in particular on some ATI chipsets).
1497 The kernel tries to s 1440 The kernel tries to set a reasonable default.
1498 1441
1499 enforcing= [SELINUX] Set initial !! 1442 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1443 Format: {"0" | "1"}
1501 See security/selinux/ 1444 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1445 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1446 1 -- enforcing (deny and log).
1504 Default value is 0. 1447 Default value is 0.
1505 Value can be changed 1448 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1449 /sys/fs/selinux/enforce.
1507 1450
1508 erst_disable [ACPI] 1451 erst_disable [ACPI]
1509 Disable Error Record 1452 Disable Error Record Serialization Table (ERST)
1510 support. 1453 support.
1511 1454
1512 ether= [HW,NET] Ethernet car 1455 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1456 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1457 has equivalent usage. See its documentation for details.
1515 1458
1516 evm= [EVM] 1459 evm= [EVM]
1517 Format: { "fix" } 1460 Format: { "fix" }
1518 Permit 'security.evm' 1461 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1462 current integrity status.
1520 1463
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= 1464 failslab=
1530 fail_usercopy= 1465 fail_usercopy=
1531 fail_page_alloc= 1466 fail_page_alloc=
1532 fail_make_request=[KNL] 1467 fail_make_request=[KNL]
1533 General fault injecti 1468 General fault injection mechanism.
1534 Format: <interval>,<p 1469 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1470 See also Documentation/fault-injection/.
1536 1471
1537 fb_tunnels= [NET] 1472 fb_tunnels= [NET]
1538 Format: { initns | no 1473 Format: { initns | none }
1539 See Documentation/adm 1474 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1475 fb_tunnels_only_for_init_ns
1541 1476
1542 floppy= [HW] 1477 floppy= [HW]
1543 See Documentation/adm 1478 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1479
>> 1480 force_pal_cache_flush
>> 1481 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1482 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1483 parameter will force ia64_sal_cache_flush to call
>> 1484 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1485
1545 forcepae [X86-32] 1486 forcepae [X86-32]
1546 Forcefully enable Phy 1487 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1488 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1489 functionally usable PAE implementation.
1549 Warning: use of this 1490 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1491 and may cause unknown problems.
1551 1492
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] 1493 ftrace=[tracer]
1559 [FTRACE] will set and 1494 [FTRACE] will set and start the specified tracer
1560 as early as possible 1495 as early as possible in order to facilitate early
1561 boot debugging. 1496 boot debugging.
1562 1497
1563 ftrace_boot_snapshot 1498 ftrace_boot_snapshot
1564 [FTRACE] On boot up, 1499 [FTRACE] On boot up, a snapshot will be taken of the
1565 ftrace ring buffer th 1500 ftrace ring buffer that can be read at:
1566 /sys/kernel/tracing/s 1501 /sys/kernel/tracing/snapshot.
1567 This is useful if you 1502 This is useful if you need tracing information from kernel
1568 boot up that is likel 1503 boot up that is likely to be overridden by user space
1569 start up functionalit 1504 start up functionality.
1570 1505
1571 Optionally, the snaps !! 1506 ftrace_dump_on_oops[=orig_cpu]
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 1507 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1508 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1509 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1510 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1511 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 1512
1603 ftrace_filter=[function-list] 1513 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1514 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1515 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1516 list of functions. This list can be changed at run
1607 time by the set_ftrac 1517 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1518 tracing directory.
1609 1519
1610 ftrace_notrace=[function-list] 1520 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1521 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1522 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1523 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1524 tracing directory.
1615 1525
1616 ftrace_graph_filter=[function-list] 1526 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1527 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1528 by the function graph tracer at boot up.
1619 function-list is a co 1529 function-list is a comma-separated list of functions
1620 that can be changed a 1530 that can be changed at run time by the
1621 set_graph_function fi 1531 set_graph_function file in the debugfs tracing directory.
1622 1532
1623 ftrace_graph_notrace=[function-list] 1533 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1534 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1535 function-list. This list is a comma-separated list of
1626 functions that can be 1536 functions that can be changed at run time by the
1627 set_graph_notrace fil 1537 set_graph_notrace file in the debugfs tracing directory.
1628 1538
1629 ftrace_graph_max_depth=<uint> 1539 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1540 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1541 the max depth it will trace into a function. This value
1632 can be changed at run 1542 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1543 in the tracefs tracing directory. default: 0 (no limit)
1634 1544
1635 fw_devlink= [KNL,EARLY] Create de !! 1545 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1546 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1547 consumer/supplier relationships. This feature is
1638 especially useful whe 1548 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1549 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1550 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1551 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1552 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1553 suppliers).
1644 Format: { off | permi 1554 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1555 off -- Don't create device links from firmware info.
1646 permissive -- Create 1556 permissive -- Create device links from firmware info
1647 but use it on 1557 but use it only for ordering boot state clean
1648 up (sync_stat 1558 up (sync_state() calls).
1649 on -- Create device 1559 on -- Create device links from firmware info and use it
1650 to enforce pr 1560 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1561 rpm -- Like "on", but also use to order runtime PM.
1652 1562
1653 fw_devlink.strict=<bool> 1563 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1564 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1565 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1566 Format: <bool>
1657 1567
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]= 1568 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1569 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1570 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1571 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1572 See also Documentation/input/devices/joystick-parport.rst
1677 1573
1678 gamma= [HW,DRM] 1574 gamma= [HW,DRM]
1679 1575
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1576 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1577 Format: off | on
1682 default: on 1578 default: on
1683 1579
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 1580 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1581 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1582 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1583 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1584 debugfs files are removed at module unload time.
1709 1585
1710 goldfish [X86] Enable the gold 1586 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1587 Don't use this when you are not running on the
1712 android emulator 1588 android emulator
1713 1589
1714 gpio-mockup.gpio_mockup_ranges 1590 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1591 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1592 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1593 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1594 [HW] Let the driver know GPIO lines should be named.
1719 1595
1720 gpt [EFI] Forces disk wit 1596 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1597 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1598 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1599 GPT to be used instead.
1724 1600
1725 grcan.enable0= [HW] Configuration of 1601 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1602 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1603 Format: 0 | 1
1728 Default: 0 1604 Default: 0
1729 grcan.enable1= [HW] Configuration of 1605 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1606 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1607 Format: 0 | 1
1732 Default: 0 1608 Default: 0
1733 grcan.select= [HW] Select which phy 1609 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1610 Format: 0 | 1
1735 Default: 0 1611 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1612 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1613 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1614 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1615 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1616 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1617 Default: 1024
1742 1618
1743 hardened_usercopy= 1619 hardened_usercopy=
1744 [KNL] Under CONFIG_HA 1620 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
1745 hardening is enabled 1621 hardening is enabled for this boot. Hardened
1746 usercopy checking is 1622 usercopy checking is used to protect the kernel
1747 from reading or writi 1623 from reading or writing beyond known memory
1748 allocation boundaries 1624 allocation boundaries as a proactive defense
1749 against bounds-checki 1625 against bounds-checking flaws in the kernel's
1750 copy_to_user()/copy_f 1626 copy_to_user()/copy_from_user() interface.
1751 on Perform hardened user 1627 on Perform hardened usercopy checks (default).
1752 off Disable hardened user 1628 off Disable hardened usercopy checks.
1753 1629
1754 hardlockup_all_cpu_backtrace= 1630 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1631 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1632 backtraces on all cpus.
1757 Format: 0 | 1 1633 Format: 0 | 1
1758 1634
1759 hashdist= [KNL,NUMA] Large hash 1635 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1636 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1637 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1638 Format: 0 | 1 (for off | on)
1763 1639
>> 1640 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1641
1764 hd= [EIDE] (E)IDE hard dr 1642 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1643 Format: <cyl>,<head>,<sect>
1766 1644
1767 hest_disable [ACPI] 1645 hest_disable [ACPI]
1768 Disable Hardware Erro 1646 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1647 corresponding firmware-first mode error processing
1770 logic will be disable 1648 logic will be disabled.
1771 1649
1772 hibernate= [HIBERNATION] 1650 hibernate= [HIBERNATION]
1773 noresume Don't check i 1651 noresume Don't check if there's a hibernation image
1774 present durin 1652 present during boot.
1775 nocompress Don't compres 1653 nocompress Don't compress/decompress hibernation images.
1776 no Disable hiber 1654 no Disable hibernation and resume.
1777 protect_image Turn on image 1655 protect_image Turn on image protection during restoration
1778 (that will se 1656 (that will set all pages holding image data
1779 during restor 1657 during restoration read-only).
1780 1658
1781 hibernate.compressor= [HIBERNATION] !! 1659 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1782 used with hib <<
1783 Format: { lzo <<
1784 Default: lzo <<
1785 <<
1786 lzo: Select L <<
1787 compress/deco <<
1788 <<
1789 lz4: Select L <<
1790 compress/deco <<
1791 <<
1792 highmem=nn[KMG] [KNL,BOOT,EARLY] forc <<
1793 size of <nn>. This wo 1660 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1661 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1662 size on bigger boxes.
1796 1663
1797 highres= [KNL] Enable/disable 1664 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1665 Valid parameters: "on", "off"
1799 Default: "on" 1666 Default: "on"
1800 1667
1801 hlt [BUGS=ARM,SH] 1668 hlt [BUGS=ARM,SH]
1802 1669
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 1670 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1671 Format: { enable (default) | disable | force |
1818 verbose } 1672 verbose }
1819 disable: disable HPET 1673 disable: disable HPET and use PIT instead
1820 force: allow force en 1674 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1675 VIA, nVidia)
1822 verbose: show content 1676 verbose: show contents of HPET registers during setup
1823 1677
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1678 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1679 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1680
1827 hugepages= [HW] Number of HugeTL 1681 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1682 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1683 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1684 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1685 line, it specifies the number of pages to allocate for
1832 the default huge page 1686 the default huge page size. If using node format, the
1833 number of pages to al 1687 number of pages to allocate per-node can be specified.
1834 See also Documentatio 1688 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1835 Format: <integer> or 1689 Format: <integer> or (node format)
1836 <node>:<integ 1690 <node>:<integer>[,<node>:<integer>]
1837 1691
1838 hugepagesz= 1692 hugepagesz=
1839 [HW] The size of the 1693 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1694 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1695 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1696 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1697 each supported huge page size. Huge page sizes are
1844 architecture dependen 1698 architecture dependent. See also
1845 Documentation/admin-g 1699 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1700 Format: size[KMG]
1847 1701
1848 hugetlb_cma= [HW,CMA,EARLY] The si !! 1702 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
1849 of gigantic hugepages 1703 of gigantic hugepages. Or using node format, the size
1850 of a CMA area per nod 1704 of a CMA area per node can be specified.
1851 Format: nn[KMGTPE] or 1705 Format: nn[KMGTPE] or (node format)
1852 <node>:nn[KMG 1706 <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1853 1707
1854 Reserve a CMA area of 1708 Reserve a CMA area of given size and allocate gigantic
1855 hugepages using the C 1709 hugepages using the CMA allocator. If enabled, the
1856 boot-time allocation 1710 boot-time allocation of gigantic hugepages is skipped.
1857 1711
1858 hugetlb_free_vmemmap= 1712 hugetlb_free_vmemmap=
1859 [KNL] Requires CONFIG !! 1713 [KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1860 enabled. 1714 enabled.
1861 Control if HugeTLB Vm <<
1862 Allows heavy hugetlb 1715 Allows heavy hugetlb users to free up some more
1863 memory (7 * PAGE_SIZE 1716 memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1864 Format: { on | off (d !! 1717 Format: { [oO][Nn]/Y/y/1 | [oO][Ff]/N/n/0 (default) }
1865 1718
1866 on: enable HVO !! 1719 [oO][Nn]/Y/y/1: enable the feature
1867 off: disable HVO !! 1720 [oO][Ff]/N/n/0: disable the feature
1868 1721
1869 Built with CONFIG_HUG 1722 Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1870 the default is on. 1723 the default is on.
1871 1724
1872 Note that the vmemmap !! 1725 This is not compatible with memory_hotplug.memmap_on_memory.
1873 memory block itself w !! 1726 If both parameters are enabled, hugetlb_free_vmemmap takes
1874 enabled, those vmemma !! 1727 precedence over memory_hotplug.memmap_on_memory.
1875 feature is enabled. <<
1876 the added memory bloc <<
1877 1728
1878 hung_task_panic= 1729 hung_task_panic=
1879 [KNL] Should the hung 1730 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1731 Format: 0 | 1
1881 1732
1882 A value of 1 instruct 1733 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1734 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1735 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1736 option. The value selected by this boot parameter can
1886 be changed later by t 1737 be changed later by the kernel.hung_task_panic sysctl.
1887 1738
1888 hvc_iucv= [S390] Number of z/V 1739 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1740 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1741 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1742 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1743 from listed z/VM user IDs only.
1893 1744
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1745 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1746 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1747 guest on lock contention.
1897 on lock contention. !! 1748
>> 1749 keep_bootcon [KNL]
>> 1750 Do not unregister boot console at start. This is only
>> 1751 useful for debugging when something happens in the window
>> 1752 between unregistering the boot console and initializing
>> 1753 the real console.
1898 1754
1899 i2c_bus= [HW] Override the 1755 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1756 or register an additional I2C bus that is not
1901 registered fr 1757 registered from board initialization code.
1902 Format: 1758 Format:
1903 <bus_id>,<clk 1759 <bus_id>,<clkrate>
1904 1760
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 1761 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1762 i8042.unmask_kbd_data
1929 [HW] Enable printing 1763 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1764 (disabled by default, and as a pre-condition
1931 requires that i8 1765 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1766 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1767 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1768 keyboard and cannot control its state
1935 (Don't attempt t 1769 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1770 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1771 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1772 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1773 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1774 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1775 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1776 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1777 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1778 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1779 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1780 suspend-to-ram transitions, only during s2r
1947 transitions, or 1781 transitions, or never reset
1948 Format: { 1 | Y | y | 1782 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1783 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1784 0, N, n: don't ever reset controller
1951 Default: only on s2r 1785 Default: only on s2r transitions on x86; most other
1952 architectures force r 1786 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1787 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1788 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer 1789 i8042.probe_defer
1956 [HW] Allow deferred p 1790 [HW] Allow deferred probing upon i8042 probe errors
1957 1791
1958 i810= [HW,DRM] 1792 i810= [HW,DRM]
1959 1793
1960 i915.invert_brightness= 1794 i915.invert_brightness=
1961 [DRM] Invert the sens 1795 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1796 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1797 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1798 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1799 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1800 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1801 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1802 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1803 value switches the backlight off.
1970 -1 -- never invert br 1804 -1 -- never invert brightness
1971 0 -- machine default 1805 0 -- machine default
1972 1 -- force brightnes 1806 1 -- force brightness inversion
1973 1807
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] 1808 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1809 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1810
1983 1811
1984 idle= [X86,EARLY] !! 1812 idle= [X86]
1985 Format: idle=poll, id 1813 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1814 Poll forces a polling idle loop that can slightly
1987 improve the performan 1815 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1816 will use a lot of power and make the system run hot.
1989 Not recommended. 1817 Not recommended.
1990 idle=halt: Halt is fo 1818 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1819 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1820 idle=nomwait: Disable mwait for CPU C-states
1993 1821
1994 idxd.sva= [HW] 1822 idxd.sva= [HW]
1995 Format: <bool> 1823 Format: <bool>
1996 Allow force disabling 1824 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1825 support for the idxd driver. By default it is set to
1998 true (1). 1826 true (1).
1999 1827
2000 idxd.tc_override= [HW] 1828 idxd.tc_override= [HW]
2001 Format: <bool> 1829 Format: <bool>
2002 Allow override of def 1830 Allow override of default traffic class configuration
2003 for the device. By de 1831 for the device. By default it is set to false (0).
2004 1832
2005 ieee754= [MIPS] Select IEEE St 1833 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1834 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1835 Default: strict
2008 1836
2009 Choose which programs 1837 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1838 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1839 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1840 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1841 binary. Hardware implementations are permitted to
2014 support either or bot 1842 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1843 encoding mode.
2016 1844
2017 Available settings ar 1845 Available settings are as follows:
2018 strict accept binari 1846 strict accept binaries that request a NaN encoding
2019 supported by 1847 supported by the FPU
2020 legacy only accept l 1848 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1849 by the FPU
2022 2008 only accept 2 1850 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1851 by the FPU
2024 relaxed accept any bi 1852 relaxed accept any binaries regardless of whether
2025 supported by 1853 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1854
2029 The FPU emulator is a 1855 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1856 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1857 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1858 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1859 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1860 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1861 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1862 MIPS64 CPUs.
2037 1863
2038 The setting for ABS.f 1864 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1865 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1866 except where unsupported by hardware.
2041 1867
2042 ignore_loglevel [KNL,EARLY] !! 1868 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1869 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1870 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1871 We also add it as printk module parameter, so users
2046 could change it dynam 1872 could change it dynamically, usually by
2047 /sys/module/printk/pa 1873 /sys/module/printk/parameters/ignore_loglevel.
2048 1874
2049 ignore_rlimit_data 1875 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1876 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1877 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1878 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1879
2054 ihash_entries= [KNL] 1880 ihash_entries= [KNL]
2055 Set number of hash bu 1881 Set number of hash buckets for inode cache.
2056 1882
2057 ima_appraise= [IMA] appraise integr 1883 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1884 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1885 default: "enforce"
2060 1886
2061 ima_appraise_tcb [IMA] Deprecated. U 1887 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1888 The builtin appraise policy appraises all files
2063 owned by uid=0. 1889 owned by uid=0.
2064 1890
2065 ima_canonical_fmt [IMA] 1891 ima_canonical_fmt [IMA]
2066 Use the canonical for 1892 Use the canonical format for the binary runtime
2067 measurements, instead 1893 measurements, instead of host native format.
2068 1894
2069 ima_hash= [IMA] 1895 ima_hash= [IMA]
2070 Format: { md5 | sha1 1896 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1897 | sha512 | ... }
2072 default: "sha1" 1898 default: "sha1"
2073 1899
2074 The list of supported 1900 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1901 in crypto/hash_info.h.
2076 1902
2077 ima_policy= [IMA] 1903 ima_policy= [IMA]
2078 The builtin policies 1904 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1905 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1906 fail_securely | critical_data"
2081 1907
2082 The "tcb" policy meas 1908 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1909 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1910 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1911 uid=0.
2086 1912
2087 The "appraise_tcb" po 1913 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1914 all files owned by root.
2089 1915
2090 The "secure_boot" pol 1916 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1917 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1918 firmware, policy, etc) based on file signatures.
2093 1919
2094 The "fail_securely" p 1920 The "fail_securely" policy forces file signature
2095 verification failure 1921 verification failure also on privileged mounted
2096 filesystems with the 1922 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1923 flag.
2098 1924
2099 The "critical_data" p 1925 The "critical_data" policy measures kernel integrity
2100 critical data. 1926 critical data.
2101 1927
2102 ima_tcb [IMA] Deprecated. Us 1928 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1929 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1930 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1931 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1932 opened for read by uid=0.
2107 1933
2108 ima_template= [IMA] 1934 ima_template= [IMA]
2109 Select one of defined 1935 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i 1936 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2111 "ima-sigv2 1937 "ima-sigv2" }
2112 Default: "ima-ng" 1938 Default: "ima-ng"
2113 1939
2114 ima_template_fmt= 1940 ima_template_fmt=
2115 [IMA] Define a custom 1941 [IMA] Define a custom template format.
2116 Format: { "field1|... 1942 Format: { "field1|...|fieldN" }
2117 1943
2118 ima.ahash_minsize= [IMA] Minimum file 1944 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1945 Format: <min_file_size>
2120 Set the minimal file 1946 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1947 If left unspecified, ahash usage is disabled.
2122 1948
2123 ahash performance var 1949 ahash performance varies for different data sizes on
2124 different crypto acce 1950 different crypto accelerators. This option can be used
2125 to achieve the best p 1951 to achieve the best performance for a particular HW.
2126 1952
2127 ima.ahash_bufsize= [IMA] Asynchronous 1953 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1954 Format: <bufsize>
2129 Set hashing buffer si 1955 Set hashing buffer size. Default: 4k.
2130 1956
2131 ahash performance var 1957 ahash performance varies for different chunk sizes on
2132 different crypto acce 1958 different crypto accelerators. This option can be used
2133 to achieve best perfo 1959 to achieve best performance for particular HW.
2134 1960
2135 init= [KNL] 1961 init= [KNL]
2136 Format: <full_path> 1962 Format: <full_path>
2137 Run specified binary 1963 Run specified binary instead of /sbin/init as init
2138 process. 1964 process.
2139 1965
2140 initcall_debug [KNL] Trace initcalls 1966 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1967 for working out where the kernel is dying during
2142 startup. 1968 startup.
2143 1969
2144 initcall_blacklist= [KNL] Do not exe 1970 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1971 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1972 modules and initcalls.
2147 1973
2148 initramfs_async= [KNL] 1974 initramfs_async= [KNL]
2149 Format: <bool> 1975 Format: <bool>
2150 Default: 1 1976 Default: 1
2151 This parameter contro 1977 This parameter controls whether the initramfs
2152 image is unpacked asy 1978 image is unpacked asynchronously, concurrently
2153 with devices being pr 1979 with devices being probed and
2154 initialized. This sho 1980 initialized. This should normally just work,
2155 but as a debugging ai 1981 but as a debugging aid, one can get the
2156 historical behaviour 1982 historical behaviour of the initramfs
2157 unpacking being compl 1983 unpacking being completed before device_ and
2158 late_ initcalls. 1984 late_ initcalls.
2159 1985
2160 initrd= [BOOT,EARLY] Specify !! 1986 initrd= [BOOT] Specify the location of the initial ramdisk
2161 1987
2162 initrdmem= [KNL,EARLY] Specify a !! 1988 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 1989 load the initrd. If an initrd is compiled in or
2164 specified in the boot 1990 specified in the bootparams, it takes priority over this
2165 setting. 1991 setting.
2166 Format: ss[KMG],nn[KM 1992 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 1993 Default is 0, 0
2168 1994
2169 init_on_alloc= [MM,EARLY] Fill newly !! 1995 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 1996 zeroes.
2171 Format: 0 | 1 1997 Format: 0 | 1
2172 Default set by CONFIG 1998 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 1999
2174 init_on_free= [MM,EARLY] Fill freed !! 2000 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 2001 Format: 0 | 1
2176 Default set by CONFIG 2002 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 2003
2178 init_pkru= [X86] Specify the def 2004 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 2005 register contents for all processes. 0x55555554 by
2180 default (disallow acc 2006 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 2007 override in debugfs after boot.
2182 2008
2183 inport.irq= [HW] Inport (ATI XL a 2009 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 2010 Format: <irq>
2185 2011
2186 int_pln_enable [X86] Enable power li 2012 int_pln_enable [X86] Enable power limit notification interrupt
2187 2013
2188 integrity_audit=[IMA] 2014 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 2015 Format: { "0" | "1" }
2190 0 -- basic integrity 2016 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 2017 1 -- additional integrity auditing messages.
2192 2018
2193 intel_iommu= [DMAR] Intel IOMMU dr 2019 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 2020 on
2195 Enable intel iommu dr 2021 Enable intel iommu driver.
2196 off 2022 off
2197 Disable intel iommu d 2023 Disable intel iommu driver.
2198 igfx_off [Default Off] 2024 igfx_off [Default Off]
2199 By default, gfx is ma 2025 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 2026 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 2027 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 2028 this case, gfx device will use physical address for
2203 DMA. 2029 DMA.
2204 strict [Default Off] 2030 strict [Default Off]
2205 Deprecated, equivalen 2031 Deprecated, equivalent to iommu.strict=1.
2206 sp_off [Default Off] 2032 sp_off [Default Off]
2207 By default, super pag 2033 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 2034 has the capability. With this option, super page will
2209 not be supported. 2035 not be supported.
2210 sm_on 2036 sm_on
2211 Enable the Intel IOMM 2037 Enable the Intel IOMMU scalable mode if the hardware
2212 advertises that it ha 2038 advertises that it has support for the scalable mode
2213 translation. 2039 translation.
2214 sm_off 2040 sm_off
2215 Disallow use of the I 2041 Disallow use of the Intel IOMMU scalable mode.
2216 tboot_noforce [Default Off] 2042 tboot_noforce [Default Off]
2217 Do not force the Inte 2043 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 2044 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 2045 could harm performance of some high-throughput
2220 devices like 40GBit n 2046 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 2047 mapping is enabled.
2222 Note that using this 2048 Note that using this option lowers the security
2223 provided by tboot bec 2049 provided by tboot because it makes the system
2224 vulnerable to DMA att 2050 vulnerable to DMA attacks.
2225 2051
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 2052 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 2053 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 2054 1 to 9 specify maximum depth of C-state.
2229 2055
2230 intel_pstate= [X86,EARLY] !! 2056 intel_pstate= [X86]
2231 disable 2057 disable
2232 Do not enable intel 2058 Do not enable intel_pstate as the default
2233 scaling driver for 2059 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 2060 passive
2245 Use intel_pstate as 2061 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 2062 to work with generic cpufreq governors (instead of
2247 enabling its intern 2063 enabling its internal governor). This mode cannot be
2248 used along with the 2064 used along with the hardware-managed P-states (HWP)
2249 feature. 2065 feature.
2250 force 2066 force
2251 Enable intel_pstate 2067 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 2068 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 2069 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 2070 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 2071 P-States information being indicated to OSPM and therefore
2256 should be used with 2072 should be used with caution. This option does not work with
2257 processors that are 2073 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 2074 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 2075 no_hwp
2260 Do not enable hardw 2076 Do not enable hardware P state control (HWP)
2261 if available. 2077 if available.
2262 hwp_only 2078 hwp_only
2263 Only load intel_pst 2079 Only load intel_pstate on systems which support
2264 hardware P state co 2080 hardware P state control (HWP) if available.
2265 support_acpi_ppc 2081 support_acpi_ppc
2266 Enforce ACPI _PPC p 2082 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 2083 Description Table, specifies preferred power management
2268 profile as "Enterpr 2084 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 2085 then this feature is turned on by default.
2270 per_cpu_perf_limits 2086 per_cpu_perf_limits
2271 Allow per-logical-C 2087 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 2088 cpufreq sysfs interface
2273 2089
2274 intremap= [X86-64,Intel-IOMMU,E !! 2090 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 2091 on enable Interrupt Remapping (default)
2276 off disable Inter 2092 off disable Interrupt Remapping
2277 nosid disable Sourc 2093 nosid disable Source ID checking
2278 no_x2apic_optout 2094 no_x2apic_optout
2279 BIOS x2APIC o 2095 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 2096 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 2097
2284 iomem= Disable strict checki 2098 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 2099 strict regions from userspace.
2286 relaxed 2100 relaxed
2287 2101
2288 iommu= [X86,EARLY] !! 2102 iommu= [X86]
2289 off 2103 off
2290 force 2104 force
2291 noforce 2105 noforce
2292 biomerge 2106 biomerge
2293 panic 2107 panic
2294 nopanic 2108 nopanic
2295 merge 2109 merge
2296 nomerge 2110 nomerge
2297 soft 2111 soft
2298 pt [X86] 2112 pt [X86]
2299 nopt [X86] 2113 nopt [X86]
2300 nobypass [PPC/POWERNV] 2114 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 2115 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2116
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2117 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 2118 Format: { "0" | "1" }
2305 0 - Try to allocate a 2119 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 2120 falling back to the full range if needed.
2307 1 - Allocate directly 2121 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 2122 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 2123 greater than 32-bit addressing.
2310 2124
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 2125 iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 2126 Format: { "0" | "1" }
2313 0 - Lazy mode. 2127 0 - Lazy mode.
2314 Request that DMA un 2128 Request that DMA unmap operations use deferred
2315 invalidation of har 2129 invalidation of hardware TLBs, for increased
2316 throughput at the c 2130 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2131 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2132 the relevant IOMMU driver.
2319 1 - Strict mode. 2133 1 - Strict mode.
2320 DMA unmap operation 2134 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2135 synchronously.
2322 unset - Use value of 2136 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2323 Note: on x86, strict 2137 Note: on x86, strict mode specified via one of the
2324 legacy driver-specifi 2138 legacy driver-specific options takes precedence.
2325 2139
2326 iommu.passthrough= 2140 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2141 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2142 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2143 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2144 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2145 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2146
2333 io7= [HW] IO7 for Marvel-b 2147 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2148 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2149 arch/alpha/kernel/core_marvel.c.
2336 2150
2337 io_delay= [X86,EARLY] I/O delay !! 2151 io_delay= [X86] I/O delay method
2338 0x80 2152 0x80
2339 Standard port 0x80 ba 2153 Standard port 0x80 based delay
2340 0xed 2154 0xed
2341 Alternate port 0xed b 2155 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2156 udelay
2343 Simple two microsecon 2157 Simple two microseconds delay
2344 none 2158 none
2345 No delay 2159 No delay
2346 2160
2347 ip= [IP_PNP] 2161 ip= [IP_PNP]
2348 See Documentation/adm 2162 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2163
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2164 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2165 IPC identifiers from 32,768 to 16,777,216.
2352 2166
2353 irqaffinity= [SMP] Set the default 2167 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2168 The argument is a cpu list, as described above.
2355 2169
2356 irqchip.gicv2_force_probe= 2170 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2171 [ARM, ARM64]
2358 Format: <bool> 2172 Format: <bool>
2359 Force the kernel to l 2173 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2174 of a GICv2 controller even if the memory range
2361 exposed by the device 2175 exposed by the device tree is too small.
2362 2176
2363 irqchip.gicv3_nolpi= 2177 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2178 [ARM, ARM64]
2365 Force the kernel to i 2179 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2180 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2181 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2182 to let secondary kernels in charge of setting up
2369 LPIs. 2183 LPIs.
2370 2184
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2185 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2186 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2187 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2188 CONFIG_ARM64_PSEUDO_NMI.
2375 2189
2376 irqfixup [HW] 2190 irqfixup [HW]
2377 When an interrupt is 2191 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2192 for it. Intended to get systems with badly broken
2379 firmware running. 2193 firmware running.
2380 2194
2381 irqpoll [HW] 2195 irqpoll [HW]
2382 When an interrupt is 2196 When an interrupt is not handled search all handlers
2383 for it. Also check al 2197 for it. Also check all handlers each timer
2384 interrupt. Intended t 2198 interrupt. Intended to get systems with badly broken
2385 firmware running. 2199 firmware running.
2386 2200
2387 isapnp= [ISAPNP] 2201 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2202 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2203
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2204 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2205 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2206 Format: [flag-list,]<cpu-list>
2393 2207
2394 Specify one or more C 2208 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2209 specified in the flag list (default: domain):
2396 2210
2397 nohz 2211 nohz
2398 Disable the tick wh 2212 Disable the tick when a single task runs.
2399 2213
2400 A residual 1Hz tick 2214 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2215 need to affine to housekeeping through the global
2402 workqueue's affinit 2216 workqueue's affinity configured via the
2403 /sys/devices/virtua 2217 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2218 by using the 'domain' flag described below.
2405 2219
2406 NOTE: by default th 2220 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2221 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2222 be configured manually after bootup.
2409 2223
2410 domain 2224 domain
2411 Isolate from the ge 2225 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2226 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2227 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2228 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2229 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2230 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2231 It offers a much more flexible interface where CPUs can
2418 move in and out of 2232 move in and out of an isolated set anytime.
2419 2233
2420 You can move a proc 2234 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2235 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2236 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2237 "number of CPUs in system - 1".
2424 2238
2425 managed_irq 2239 managed_irq
2426 2240
2427 Isolate from being 2241 Isolate from being targeted by managed interrupts
2428 which have an inter 2242 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2243 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2244 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2245 the /proc/irq/* interfaces.
2432 2246
2433 This isolation is b 2247 This isolation is best effort and only effective
2434 if the automaticall 2248 if the automatically assigned interrupt mask of a
2435 device queue contai 2249 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2250 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2251 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2252 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2253 cannot disturb the isolated CPU.
2440 2254
2441 If a queue's affini 2255 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2256 CPUs then this parameter has no effect on the
2443 interrupt routing d 2257 interrupt routing decision, though interrupts are
2444 only delivered when 2258 only delivered when tasks running on those
2445 isolated CPUs submi 2259 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2260 housekeeping CPUs has no influence on those
2447 queues. 2261 queues.
2448 2262
2449 The format of <cpu-li 2263 The format of <cpu-list> is described above.
2450 2264
2451 iucv= [HW,NET] 2265 iucv= [HW,NET]
2452 2266
2453 ivrs_ioapic [HW,X86-64] 2267 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2268 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 2269 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 2270 example, to map IOAPIC-ID decimal 10 to
2457 !! 2271 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 2272 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 2273
2471 ivrs_hpet [HW,X86-64] 2274 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2275 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 2276 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 2277 example, to map HPET-ID decimal 0 to
2475 !! 2278 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]= 2279 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 2280
2489 ivrs_acpihid [HW,X86-64] 2281 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2282 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 2283 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 2284 example, to map UART-HID:UID AMD0020:0 to
2493 !! 2285 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[ 2286 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 2287
2507 js= [HW,JOY] Analog joyst 2288 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2289 See Documentation/input/joydev/joystick.rst.
2509 2290
>> 2291 nokaslr [KNL]
>> 2292 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2293 kernel and module base offset ASLR (Address Space
>> 2294 Layout Randomization).
>> 2295
2510 kasan_multi_shot 2296 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2297 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2298 report on every invalid memory access. Without this
2513 parameter KASAN will 2299 parameter KASAN will print report only for the first
2514 invalid access. 2300 invalid access.
2515 2301
2516 keep_bootcon [KNL,EARLY] !! 2302 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 2303
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2304 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2305 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2306 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2307 the kernel for non-movable allocations. The requested
2528 amount is spread even 2308 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2309 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2310 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2311 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2312 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2313 other nodes will have a larger ZONE_MOVABLE.
2534 2314
2535 ZONE_MOVABLE is used 2315 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2316 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2317 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2318 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2319 zone if it does not.
2540 2320
2541 It is possible to spe 2321 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2322 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2323 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2324 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2325 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2326 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2327 are exclusive, so you cannot specify multiple forms.
2548 2328
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2329 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2330 Format: <Controller#>[,poll interval]
2551 The controller # is t 2331 The controller # is the number of the ehci usb debug
2552 port as it is probed 2332 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2333 optional and is the number seconds in between
2554 each poll cycle to th 2334 each poll cycle to the debug port in case you need
2555 the functionality for 2335 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2336 gdb or control-c on the dbgp connection. When
2557 not using this parame 2337 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2338 the kernel debugger.
2559 2339
2560 kgdboc= [KGDB,HW] kgdb over c 2340 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2341 Requires a tty driver that supports console polling,
2562 or a supported pollin 2342 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2343 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2344 keyboard only format: kbd
2565 keyboard and serial 2345 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2346 Optional Kernel mode setting:
2567 kms, kbd format: kms 2347 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2348 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2349
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2350 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2351 If the boot console provides the ability to read
2572 characters and can wo 2352 characters and can work in polling mode, you can use
2573 this parameter to tel 2353 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2354 until the normal console is registered. Intended to
2575 be used together with 2355 be used together with the kgdboc parameter which
2576 specifies the normal 2356 specifies the normal console to transition to.
2577 2357
2578 The name of the early 2358 The name of the early console should be specified
2579 as the value of this 2359 as the value of this parameter. Note that the name of
2580 the early console mig 2360 the early console might be different than the tty
2581 name passed to kgdboc 2361 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2362 blank and the first boot console that implements
2583 read() will be picked 2363 read() will be picked.
2584 2364
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2365 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2366 kernel debugger at the earliest opportunity.
2587 2367
2588 kmac= [MIPS] Korina etherne 2368 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2369 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2370 Ethernet adapter MAC address.
2591 2371
2592 kmemleak= [KNL,EARLY] Boot-time !! 2372 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2373 Valid arguments: on, off
2594 Default: on 2374 Default: on
2595 Built with CONFIG_DEB 2375 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2376 the default is off.
2597 2377
2598 kprobe_event=[probe-list] 2378 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2379 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2380 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2381 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2382 interface, but the parameters are comma delimited.
2603 For example, to add a 2383 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2384 arg1 and arg2, add to the command line;
2605 2385
2606 kprobe_event=p, 2386 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2387
2608 See also Documentatio 2388 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2389 Boot Parameter" section.
2610 2390
2611 kpti= [ARM64,EARLY] Control !! 2391 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2392 and kernel address spaces.
2613 Default: enabled on c 2393 Default: enabled on cores which need mitigation.
2614 0: force disabled 2394 0: force disabled
2615 1: force enabled 2395 1: force enabled
2616 2396
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 2397 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2398 Default is 0 (don't ignore, but inject #GP)
2625 2399
2626 kvm.eager_page_split= 2400 kvm.eager_page_split=
2627 [KVM,X86] Controls wh 2401 [KVM,X86] Controls whether or not KVM will try to
2628 proactively split all 2402 proactively split all huge pages during dirty logging.
2629 Eager page splitting 2403 Eager page splitting reduces interruptions to vCPU
2630 execution by eliminat 2404 execution by eliminating the write-protection faults
2631 and MMU lock contenti 2405 and MMU lock contention that would otherwise be
2632 required to split hug 2406 required to split huge pages lazily.
2633 2407
2634 VM workloads that rar 2408 VM workloads that rarely perform writes or that write
2635 only to a small regio 2409 only to a small region of VM memory may benefit from
2636 disabling eager page 2410 disabling eager page splitting to allow huge pages to
2637 still be used for rea 2411 still be used for reads.
2638 2412
2639 The behavior of eager 2413 The behavior of eager page splitting depends on whether
2640 KVM_DIRTY_LOG_INITIAL 2414 KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2641 disabled, all huge pa 2415 disabled, all huge pages in a memslot will be eagerly
2642 split when dirty logg 2416 split when dirty logging is enabled on that memslot. If
2643 enabled, eager page s 2417 enabled, eager page splitting will be performed during
2644 the KVM_CLEAR_DIRTY i 2418 the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2645 cleared. 2419 cleared.
2646 2420
2647 Eager page splitting !! 2421 Eager page splitting currently only supports splitting
>> 2422 huge pages mapped by the TDP MMU.
2648 2423
2649 Default is Y (on). 2424 Default is Y (on).
2650 2425
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2426 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2427 Default is false (don't support).
2653 2428
2654 kvm.nx_huge_pages= 2429 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2430 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2431 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2432 force : Always deploy workaround.
2658 off : Never deplo 2433 off : Never deploy workaround.
2659 auto : Deploy work 2434 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2435 X86_BUG_ITLB_MULTIHIT.
2661 2436
2662 Default is 'auto'. 2437 Default is 'auto'.
2663 2438
2664 If the software worka 2439 If the software workaround is enabled for the host,
2665 guests do need not to 2440 guests do need not to enable it for nested guests.
2666 2441
2667 kvm.nx_huge_pages_recovery_ratio= 2442 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2443 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2444 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2445 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). 2446 period (see below). The default is 60.
2672 2447
2673 kvm.nx_huge_pages_recovery_period_ms= 2448 kvm.nx_huge_pages_recovery_period_ms=
2674 [KVM] Controls the ti 2449 [KVM] Controls the time period at which KVM zaps 4KiB pages
2675 back to huge pages. I 2450 back to huge pages. If the value is a non-zero N, KVM will
2676 zap a portion (see ra 2451 zap a portion (see ratio above) of the pages every N msecs.
2677 If the value is 0 (th 2452 If the value is 0 (the default), KVM will pick a period based
2678 on the ratio, such th 2453 on the ratio, such that a page is zapped after 1 hour on average.
2679 2454
2680 kvm-amd.nested= [KVM,AMD] Control nes !! 2455 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2681 KVM/SVM. Default is 1 !! 2456 Default is 1 (enabled)
2682 2457
2683 kvm-amd.npt= [KVM,AMD] Control KVM !! 2458 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2684 a.k.a. Two-Dimensiona !! 2459 for all guests.
2685 (enabled). Disable by !! 2460 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2686 for NPT. <<
2687 2461
2688 kvm-arm.mode= 2462 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2463 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 2464
2692 none: Forcefully disa 2465 none: Forcefully disable KVM.
2693 2466
2694 nvhe: Standard nVHE-b 2467 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2468 protected guests.
2696 2469
2697 protected: nVHE-based 2470 protected: nVHE-based mode with support for guests whose
2698 state is k 2471 state is kept private from the host.
2699 2472
2700 nested: VHE-based mod <<
2701 virtualizatio <<
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE 2473 Defaults to VHE/nVHE based on hardware support. Setting
2705 mode to "protected" w 2474 mode to "protected" will disable kexec and hibernation
2706 for the host. "nested !! 2475 for the host.
2707 used with extreme cau <<
2708 2476
2709 kvm-arm.vgic_v3_group0_trap= 2477 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2478 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2479 system registers
2712 2480
2713 kvm-arm.vgic_v3_group1_trap= 2481 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2482 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2483 system registers
2716 2484
2717 kvm-arm.vgic_v3_common_trap= 2485 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2486 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2487 system registers
2720 2488
2721 kvm-arm.vgic_v4_enable= 2489 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2490 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2491 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 2492
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2493 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2494 Reserves given percentage from system memory area for
2745 contiguous memory all 2495 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2496 allocation.
2747 By default it reserve 2497 By default it reserves 5% of total system memory.
2748 Format: <integer> 2498 Format: <integer>
2749 Default: 5 2499 Default: 5
2750 2500
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2501 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2502 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2503 Default is 1 (enabled)
2754 for EPT. <<
2755 2504
2756 kvm-intel.emulate_invalid_guest_state 2505 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2506 [KVM,Intel] Disable emulation of invalid guest state.
2758 state. Ignored if kvm !! 2507 Ignored if kvm-intel.enable_unrestricted_guest=1, as
2759 as guest state is nev !! 2508 guest state is never invalid for unrestricted guests.
2760 guests. This param do !! 2509 This param doesn't apply to nested guests (L2), as KVM
2761 as KVM never emulates !! 2510 never emulates invalid L2 guest state.
2762 Default is 1 (enabled !! 2511 Default is 1 (enabled)
2763 2512
2764 kvm-intel.flexpriority= 2513 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2514 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2515 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2516
2769 kvm-intel.nested= 2517 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2518 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2519 Default is 0 (disabled)
2772 2520
2773 kvm-intel.unrestricted_guest= 2521 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2522 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2523 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2524 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2525
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2526 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2527 CVE-2018-3620.
2781 2528
2782 Valid arguments: neve 2529 Valid arguments: never, cond, always
2783 2530
2784 always: L1D cache flu 2531 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2532 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2533 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2534 never: Disables the mitigation
2788 2535
2789 Default is cond (do L 2536 Default is cond (do L1 cache flush in specific instances)
2790 2537
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2538 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2539 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2540 Default is 1 (enabled)
2794 for it. <<
2795 2541
2796 l1d_flush= [X86,INTEL,EARLY] !! 2542 l1d_flush= [X86,INTEL]
2797 Control mitigation fo 2543 Control mitigation for L1D based snooping vulnerability.
2798 2544
2799 Certain CPUs are vuln 2545 Certain CPUs are vulnerable to an exploit against CPU
2800 internal buffers whic 2546 internal buffers which can forward information to a
2801 disclosure gadget und 2547 disclosure gadget under certain conditions.
2802 2548
2803 In vulnerable process 2549 In vulnerable processors, the speculatively
2804 forwarded data can be 2550 forwarded data can be used in a cache side channel
2805 attack, to access dat 2551 attack, to access data to which the attacker does
2806 not have direct acces 2552 not have direct access.
2807 2553
2808 This parameter contro 2554 This parameter controls the mitigation. The
2809 options are: 2555 options are:
2810 2556
2811 on - enable t 2557 on - enable the interface for the mitigation
2812 2558
2813 l1tf= [X86,EARLY] Control m !! 2559 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2560 affected CPUs
2815 2561
2816 The kernel PTE invers 2562 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2563 enabled and cannot be disabled.
2818 2564
2819 full 2565 full
2820 Provides all 2566 Provides all available mitigations for the
2821 L1TF vulnerab 2567 L1TF vulnerability. Disables SMT and
2822 enables all m 2568 enables all mitigations in the
2823 hypervisors, 2569 hypervisors, i.e. unconditional L1D flush.
2824 2570
2825 SMT control a 2571 SMT control and L1D flush control via the
2826 sysfs interfa 2572 sysfs interface is still possible after
2827 boot. Hyperv 2573 boot. Hypervisors will issue a warning
2828 when the firs 2574 when the first VM is started in a
2829 potentially i 2575 potentially insecure configuration,
2830 i.e. SMT enab 2576 i.e. SMT enabled or L1D flush disabled.
2831 2577
2832 full,force 2578 full,force
2833 Same as 'full 2579 Same as 'full', but disables SMT and L1D
2834 flush runtime 2580 flush runtime control. Implies the
2835 'nosmt=force' 2581 'nosmt=force' command line option.
2836 (i.e. sysfs c 2582 (i.e. sysfs control of SMT is disabled.)
2837 2583
2838 flush 2584 flush
2839 Leaves SMT en 2585 Leaves SMT enabled and enables the default
2840 hypervisor mi 2586 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2587 L1D flush.
2842 2588
2843 SMT control a 2589 SMT control and L1D flush control via the
2844 sysfs interfa 2590 sysfs interface is still possible after
2845 boot. Hyperv 2591 boot. Hypervisors will issue a warning
2846 when the firs 2592 when the first VM is started in a
2847 potentially i 2593 potentially insecure configuration,
2848 i.e. SMT enab 2594 i.e. SMT enabled or L1D flush disabled.
2849 2595
2850 flush,nosmt 2596 flush,nosmt
2851 2597
2852 Disables SMT 2598 Disables SMT and enables the default
2853 hypervisor mi 2599 hypervisor mitigation.
2854 2600
2855 SMT control a 2601 SMT control and L1D flush control via the
2856 sysfs interfa 2602 sysfs interface is still possible after
2857 boot. Hyperv 2603 boot. Hypervisors will issue a warning
2858 when the firs 2604 when the first VM is started in a
2859 potentially i 2605 potentially insecure configuration,
2860 i.e. SMT enab 2606 i.e. SMT enabled or L1D flush disabled.
2861 2607
2862 flush,nowarn 2608 flush,nowarn
2863 Same as 'flus 2609 Same as 'flush', but hypervisors will not
2864 warn when a V 2610 warn when a VM is started in a potentially
2865 insecure conf 2611 insecure configuration.
2866 2612
2867 off 2613 off
2868 Disables hype 2614 Disables hypervisor mitigations and doesn't
2869 emit any warn 2615 emit any warnings.
2870 It also drops 2616 It also drops the swap size and available
2871 RAM limit res 2617 RAM limit restriction on both hypervisor and
2872 bare metal. 2618 bare metal.
2873 2619
2874 Default is 'flush'. 2620 Default is 'flush'.
2875 2621
2876 For details see: Docu 2622 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2623
2878 l2cr= [PPC] 2624 l2cr= [PPC]
2879 2625
2880 l3cr= [PPC] 2626 l3cr= [PPC]
2881 2627
2882 lapic [X86-32,APIC,EARLY] E !! 2628 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2629 disabled it.
2884 2630
2885 lapic= [X86,APIC] Do not use 2631 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2632 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2633 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2634 Format: notscdeadline
2889 2635
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2636 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2637 in C2 power state.
2892 2638
2893 libata.dma= [LIBATA] DMA control 2639 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2640 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2641 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2642 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2643 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2644 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2645 for disks and CDROMs, but not CFs.
2900 2646
2901 libata.ignore_hpa= [LIBATA] Igno 2647 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2648 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2649 libata.ignore_hpa=1 ignore limits, using full disk
2904 2650
2905 libata.noacpi [LIBATA] Disables use 2651 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2652 when set.
2907 Format: <int> 2653 Format: <int>
2908 2654
2909 libata.force= [LIBATA] Force config 2655 libata.force= [LIBATA] Force configurations. The format is a comma-
2910 separated list of "[I 2656 separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2911 PORT and DEVICE are d 2657 PORT and DEVICE are decimal numbers matching port, link
2912 or device. Basically 2658 or device. Basically, it matches the ATA ID string
2913 printed on console by 2659 printed on console by libata. If the whole ID part is
2914 omitted, the last POR 2660 omitted, the last PORT and DEVICE values are used. If
2915 ID hasn't been specif 2661 ID hasn't been specified yet, the configuration applies
2916 to all ports, links a 2662 to all ports, links and devices.
2917 2663
2918 If only DEVICE is omi 2664 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2665 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2666 number of 0 either selects the first device or the
2921 first fan-out link be 2667 first fan-out link behind PMP device. It does not
2922 select the host link. 2668 select the host link. DEVICE number of 15 selects the
2923 host link and device 2669 host link and device attached to it.
2924 2670
2925 The VAL specifies the 2671 The VAL specifies the configuration to force. As long
2926 as there is no ambigu 2672 as there is no ambiguity, shortcut notation is allowed.
2927 For example, both 1.5 2673 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2674 The following configurations can be forced.
2929 2675
2930 * Cable type: 40c, 80 2676 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2677 Any ID with matching PORT is used.
2932 2678
2933 * SATA link speed lim 2679 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2680
2935 * Transfer mode: pio[ 2681 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2682 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2683 allowed.
2938 2684
2939 * nohrst, nosrst, nor 2685 * nohrst, nosrst, norst: suppress hard, soft and both
2940 resets. 2686 resets.
2941 2687
2942 * rstonce: only attem 2688 * rstonce: only attempt one reset during hot-unplug
2943 link recovery. 2689 link recovery.
2944 2690
2945 * [no]dbdelay: Enable 2691 * [no]dbdelay: Enable or disable the extra 200ms delay
2946 before debouncing a 2692 before debouncing a link PHY and device presence
2947 detection. 2693 detection.
2948 2694
2949 * [no]ncq: Turn on or 2695 * [no]ncq: Turn on or off NCQ.
2950 2696
2951 * [no]ncqtrim: Enable 2697 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2952 2698
2953 * [no]ncqati: Enable 2699 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2954 2700
2955 * [no]trim: Enable or 2701 * [no]trim: Enable or disable (unqueued) TRIM.
2956 2702
2957 * trim_zero: Indicate 2703 * trim_zero: Indicate that TRIM command zeroes data.
2958 2704
2959 * max_trim_128m: Set 2705 * max_trim_128m: Set 128M maximum trim size limit.
2960 2706
2961 * [no]dma: Turn on or 2707 * [no]dma: Turn on or off DMA transfers.
2962 2708
2963 * atapi_dmadir: Enabl 2709 * atapi_dmadir: Enable ATAPI DMADIR bridge support.
2964 2710
2965 * atapi_mod16_dma: En 2711 * atapi_mod16_dma: Enable the use of ATAPI DMA for
2966 commands that are n 2712 commands that are not a multiple of 16 bytes.
2967 2713
2968 * [no]dmalog: Enable 2714 * [no]dmalog: Enable or disable the use of the
2969 READ LOG DMA EXT co 2715 READ LOG DMA EXT command to access logs.
2970 2716
2971 * [no]iddevlog: Enabl 2717 * [no]iddevlog: Enable or disable access to the
2972 identify device dat 2718 identify device data log.
2973 2719
2974 * [no]logdir: Enable 2720 * [no]logdir: Enable or disable access to the general
2975 purpose log directo 2721 purpose log directory.
2976 2722
2977 * max_sec_128: Set tr 2723 * max_sec_128: Set transfer size limit to 128 sectors.
2978 2724
2979 * max_sec_1024: Set o 2725 * max_sec_1024: Set or clear transfer size limit to
2980 1024 sectors. 2726 1024 sectors.
2981 2727
2982 * max_sec_lba48: Set 2728 * max_sec_lba48: Set or clear transfer size limit to
2983 65535 sectors. 2729 65535 sectors.
2984 2730
2985 * [no]lpm: Enable or 2731 * [no]lpm: Enable or disable link power management.
2986 2732
2987 * [no]setxfer: Indica 2733 * [no]setxfer: Indicate if transfer speed mode setting
2988 should be skipped. 2734 should be skipped.
2989 2735
2990 * [no]fua: Disable or <<
2991 support for devices <<
2992 <<
2993 * dump_id: Dump IDENT 2736 * dump_id: Dump IDENTIFY data.
2994 2737
2995 * disable: Disable th 2738 * disable: Disable this device.
2996 2739
2997 If there are multiple 2740 If there are multiple matching configurations changing
2998 the same attribute, t 2741 the same attribute, the last one is used.
2999 2742
3000 load_ramdisk= [RAM] [Deprecated] 2743 load_ramdisk= [RAM] [Deprecated]
3001 2744
3002 lockd.nlm_grace_period=P [NFS] Assig 2745 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2746 Format: <integer>
3004 2747
3005 lockd.nlm_tcpport=N [NFS] Assign 2748 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2749 Format: <integer>
3007 2750
3008 lockd.nlm_timeout=T [NFS] Assign 2751 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2752 Format: <integer>
3010 2753
3011 lockd.nlm_udpport=M [NFS] Assign 2754 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2755 Format: <integer>
3013 2756
3014 lockdown= [SECURITY,EARLY] !! 2757 lockdown= [SECURITY]
3015 { integrity | confide 2758 { integrity | confidentiality }
3016 Enable the kernel loc 2759 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2760 integrity, kernel features that allow userland to
3018 modify the running ke 2761 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2762 confidentiality, kernel features that allow userland
3020 to extract confidenti 2763 to extract confidential information from the kernel
3021 are also disabled. 2764 are also disabled.
3022 2765
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] 2766 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2767 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2768 Defaults to being automatically set based on the
3058 number of online CPUs 2769 number of online CPUs.
3059 2770
3060 locktorture.nwriters_stress= [KNL] 2771 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2772 Set the number of locking write-acquisition kthreads.
3062 2773
3063 locktorture.onoff_holdoff= [KNL] 2774 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2775 Set time (s) after boot for CPU-hotplug testing.
3065 2776
3066 locktorture.onoff_interval= [KNL] 2777 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2778 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2779 zero to disable CPU-hotplug testing.
3069 2780
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] 2781 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2782 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2783 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2784 mode during the locktorture test.
3093 2785
3094 locktorture.shutdown_secs= [KNL] 2786 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2787 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2788 is useful for hands-off automated testing.
3097 2789
3098 locktorture.stat_interval= [KNL] 2790 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2791 Time (s) between statistics printk()s.
3100 2792
3101 locktorture.stutter= [KNL] 2793 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2794 Time (s) to stutter testing, for example,
3103 specifying five secon 2795 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2796 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2797 This tests the locking primitive's ability to
3106 transition abruptly t 2798 transition abruptly to and from idle.
3107 2799
3108 locktorture.torture_type= [KNL] 2800 locktorture.torture_type= [KNL]
3109 Specify the locking i 2801 Specify the locking implementation to test.
3110 2802
3111 locktorture.verbose= [KNL] 2803 locktorture.verbose= [KNL]
3112 Enable additional pri 2804 Enable additional printk() statements.
3113 2805
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2806 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2807 Format: <irq>
3120 2808
3121 loglevel= [KNL,EARLY] !! 2809 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2810 console loglevel will be printed to the console. It can
3124 also be changed with 2811 also be changed with klogd or other programs. The
3125 loglevels are defined 2812 loglevels are defined as follows:
3126 2813
3127 0 (KERN_EMERG) 2814 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2815 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2816 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2817 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2818 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2819 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2820 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2821 7 (KERN_DEBUG) debug-level messages
3135 2822
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2823 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2824 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2825 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2826 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2827 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2828 that allows to increase the default size depending on
3142 parameter that allows !! 2829 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2830
3146 logo.nologo [FB] Disables display 2831 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2832 This may be used to provide more screen space for
3148 kernel log messages a 2833 kernel log messages and is useful when debugging
3149 kernel boot problems. 2834 kernel boot problems.
3150 2835
3151 lp=0 [LP] Specify paral 2836 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2837 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2838 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2839 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2840 specified in addition to the ports) causes
3156 attached prin 2841 attached printers to be reset. Using
3157 lp=port1,port 2842 lp=port1,port2,... specifies the parallel ports
3158 to associate 2843 to associate lp devices with, starting with
3159 lp0. A port s 2844 lp0. A port specification may be 'none' to skip
3160 that lp devic 2845 that lp device, or a parport name such as
3161 'parport0'. S 2846 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2847 port specification list means that device IDs
3163 from each por 2848 from each port should be examined, to see if
3164 an IEEE 1284- 2849 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2850 so, the driver will manage that printer.
3166 See also head 2851 See also header of drivers/char/lp.c.
3167 2852
3168 lpj=n [KNL] 2853 lpj=n [KNL]
3169 Sets loops_per_jiffy 2854 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2855 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2856 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2857 the correct value for your kernel, boot with normal
3173 autodetection and see 2858 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2859 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2860 which is likely to cause problems if your CPUs need
3176 significantly diverge 2861 significantly divergent settings. An incorrect value
3177 will cause delays in 2862 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2863 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2864 unlikely, in the extreme case this might damage your
3180 hardware. 2865 hardware.
3181 2866
>> 2867 ltpc= [NET]
>> 2868 Format: <io>,<irq>,<dma>
>> 2869
3182 lsm.debug [SECURITY] Enable LSM 2870 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2871
3184 lsm=lsm1,...,lsmN 2872 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2873 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2874 overrides CONFIG_LSM, and the "security=" parameter.
3187 2875
>> 2876 machvec= [IA-64] Force the use of a particular machine-vector
>> 2877 (machvec) in a generic kernel.
>> 2878 Example: machvec=hpzx1
>> 2879
3188 machtype= [Loongson] Share the 2880 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2881 different yeeloong laptops.
3190 Example: machtype=lem 2882 Example: machtype=lemote-yeeloong-2f-7inch
3191 2883
3192 maxcpus= [SMP,EARLY] Maximum n !! 2884 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
>> 2885 than or equal to this physical address is ignored.
>> 2886
>> 2887 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2888 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2889 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2890 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2891 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2892 only takes effect during system bootup.
3198 While n=0 is a specia 2893 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2894 which also disables the IO APIC.
3200 2895
3201 max_loop= [LOOP] The number of 2896 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2897 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2898 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2899 of statically allocating a predefined number, loop
3205 devices can be reques 2900 devices can be requested on-demand with the
3206 /dev/loop-control int 2901 /dev/loop-control interface.
3207 2902
3208 mce [X86-32] Machine Chec 2903 mce [X86-32] Machine Check Exception
3209 2904
3210 mce=option [X86-64] See Document !! 2905 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2906
3212 md= [HW] RAID subsystems 2907 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2908 See Documentation/admin-guide/md.rst.
3214 2909
3215 mdacon= [MDA] 2910 mdacon= [MDA]
3216 Format: <first>,<last 2911 Format: <first>,<last>
3217 Specifies range of co 2912 Specifies range of consoles to be captured by the MDA.
3218 2913
3219 mds= [X86,INTEL,EARLY] !! 2914 mds= [X86,INTEL]
3220 Control mitigation fo 2915 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2916 Sampling (MDS) vulnerability.
3222 2917
3223 Certain CPUs are vuln 2918 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2919 internal buffers which can forward information to a
3225 disclosure gadget und 2920 disclosure gadget under certain conditions.
3226 2921
3227 In vulnerable process 2922 In vulnerable processors, the speculatively
3228 forwarded data can be 2923 forwarded data can be used in a cache side channel
3229 attack, to access dat 2924 attack, to access data to which the attacker does
3230 not have direct acces 2925 not have direct access.
3231 2926
3232 This parameter contro 2927 This parameter controls the MDS mitigation. The
3233 options are: 2928 options are:
3234 2929
3235 full - Enable M 2930 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2931 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2932 SMT on vulnerable CPUs
3238 off - Uncondit 2933 off - Unconditionally disable MDS mitigation
3239 2934
3240 On TAA-affected machi 2935 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2936 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2937 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2938 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2939 too.
3245 2940
3246 Not specifying this o 2941 Not specifying this option is equivalent to
3247 mds=full. 2942 mds=full.
3248 2943
3249 For details see: Docu 2944 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2945
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2946 mem=nn[KMG] [HEXAGON] Set the memory size.
3252 Must be specified, ot 2947 Must be specified, otherwise memory size will be 0.
3253 2948
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc !! 2949 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3255 of memory Amount of m !! 2950 Amount of memory to be used in cases as follows:
3256 as follows: <<
3257 2951
3258 1 for test; 2952 1 for test;
3259 2 when the kernel is 2953 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 2954 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 2955 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory 2956 4 to limit the memory available for kdump kernel.
3263 2957
3264 [ARC,MICROBLAZE] - th 2958 [ARC,MICROBLAZE] - the limit applies only to low memory,
3265 high memory is not af 2959 high memory is not affected.
3266 2960
3267 [ARM64] - only limits 2961 [ARM64] - only limits memory covered by the linear
3268 mapping. The NOMAP re 2962 mapping. The NOMAP regions are not affected.
3269 2963
3270 [X86] Work as limitin 2964 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2965 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2966 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2967 belonging to unused RAM.
3274 2968
3275 Note that this only t 2969 Note that this only takes effects during boot time since
3276 in above case 3, memo 2970 in above case 3, memory may need be hot added after boot
3277 if system memory of h 2971 if system memory of hypervisor is not sufficient.
3278 2972
3279 mem=nn[KMG]@ss[KMG] 2973 mem=nn[KMG]@ss[KMG]
3280 [ARM,MIPS,EARLY] - ov !! 2974 [ARM,MIPS] - override the memory layout reported by
3281 reported by firmware. !! 2975 firmware.
3282 Define a memory regio 2976 Define a memory region of size nn[KMG] starting at
3283 ss[KMG]. 2977 ss[KMG].
3284 Multiple different re 2978 Multiple different regions can be specified with
3285 multiple mem= paramet 2979 multiple mem= parameters on the command line.
3286 2980
3287 mem=nopentium [BUGS=X86-32] Disable 2981 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2982 memory.
3289 2983
3290 memblock=debug [KNL,EARLY] Enable me !! 2984 memblock=debug [KNL] Enable memblock debug messages.
3291 2985
3292 memchunk=nn[KMG] 2986 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2987 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2988 per-device physically contiguous DMA buffers.
3295 2989
3296 memhp_default_state=online/offline/on !! 2990 memhp_default_state=online/offline
3297 [KNL] Set the initial 2991 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2992 onlining policy. If not specified, the default value is
3299 set according to the 2993 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2994 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2995 option.
3302 See Documentation/adm 2996 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 2997
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2998 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2999 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 3000 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 3001 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 3002 option description.
3309 3003
3310 memmap=nn[KMG]@ss[KMG] 3004 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 3005 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 3006 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 3007 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 3008 which limits max address to nn[KMG].
3315 Multiple different re 3009 Multiple different regions can be specified,
3316 comma delimited. 3010 comma delimited.
3317 Example: 3011 Example:
3318 memmap=100M@2 3012 memmap=100M@2G,100M#3G,1G!1024G
3319 3013
3320 memmap=nn[KMG]#ss[KMG] 3014 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 3015 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 3016 Region of memory to be marked is from ss to ss+nn.
3323 3017
3324 memmap=nn[KMG]$ss[KMG] 3018 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 3019 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 3020 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 3021 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 3022 memmap=64K$0x18690000
3329 or 3023 or
3330 memmap=0x100 3024 memmap=0x10000$0x18690000
3331 Some bootloaders may 3025 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 3026 like Grub2, otherwise '$' and the following number
3333 will be eaten. 3027 will be eaten.
3334 3028
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 3029 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 3030 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 3031 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 3032 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 3033 and is NVDIMM or ADR memory.
3340 3034
3341 memmap=<size>%<offset>-<oldtype>+<new 3035 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 3036 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 3037 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 3038 out, the whole region will be marked as <newtype>,
3345 even if previously un 3039 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 3040 out, matching memory will be removed. Types are
3347 specified as e820 typ 3041 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 3042 3 = ACPI, 12 = PRAM.
3349 3043
3350 memory_corruption_check=0/1 [X86,EARL !! 3044 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 3045 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 3046 memory when doing things like suspend/resume.
3353 Setting this option w 3047 Setting this option will scan the memory
3354 looking for corruptio 3048 looking for corruption. Enabling this will
3355 both detect corruptio 3049 both detect corruption and prevent the kernel
3356 from using the memory 3050 from using the memory being corrupted.
3357 However, its intended 3051 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 3052 repeatable BIOS-originated corruption always
3359 affects the same memo 3053 affects the same memory, you can use memmap=
3360 to prevent the kernel 3054 to prevent the kernel from using that memory.
3361 3055
3362 memory_corruption_check_size=size [X8 !! 3056 memory_corruption_check_size=size [X86]
3363 By default it checks 3057 By default it checks for corruption in the low
3364 64k, making this memo 3058 64k, making this memory unavailable for normal
3365 use. Use this parame 3059 use. Use this parameter to scan for
3366 corruption in more or 3060 corruption in more or less memory.
3367 3061
3368 memory_corruption_check_period=second !! 3062 memory_corruption_check_period=seconds [X86]
3369 By default it checks 3063 By default it checks for corruption every 60
3370 seconds. Use this pa 3064 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 3065 other rate. 0 disables periodic checking.
3372 3066
3373 memory_hotplug.memmap_on_memory 3067 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 3068 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 3069 Format: {on | off (default)}
3376 When enabled, runtime 3070 When enabled, runtime hotplugged memory will
3377 allocate its internal !! 3071 allocate its internal metadata (struct pages)
3378 those vmemmap pages c !! 3072 from the hotadded memory which will allow to
3379 if hugetlb_free_vmemm !! 3073 hotadd a lot of memory without requiring
3380 hotadded memory which !! 3074 additional memory to do so.
3381 lot of memory without <<
3382 memory to do so. <<
3383 This feature is disab 3075 This feature is disabled by default because it
3384 has some implication 3076 has some implication on large (e.g. GB)
3385 allocations in some c 3077 allocations in some configurations (e.g. small
3386 memory blocks). 3078 memory blocks).
3387 The state of the flag 3079 The state of the flag can be read in
3388 /sys/module/memory_ho 3080 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 3081 Note that even when enabled, there are a few cases where
3390 the feature is not ef 3082 the feature is not effective.
3391 3083
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 3084 This is not compatible with hugetlb_free_vmemmap. If
>> 3085 both parameters are enabled, hugetlb_free_vmemmap takes
>> 3086 precedence over memory_hotplug.memmap_on_memory.
>> 3087
>> 3088 memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
3393 Format: <integer> 3089 Format: <integer>
3394 default : 0 <disable> 3090 default : 0 <disable>
3395 Specifies the number 3091 Specifies the number of memtest passes to be
3396 performed. Each pass 3092 performed. Each pass selects another test
3397 pattern from a given 3093 pattern from a given set of patterns. Memtest
3398 fills the memory with 3094 fills the memory with this pattern, validates
3399 memory contents and r 3095 memory contents and reserves bad memory
3400 regions that are dete 3096 regions that are detected.
3401 3097
3402 mem_encrypt= [X86-64] AMD Secure M 3098 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 3099 Valid arguments: on, off
3404 Default: off !! 3100 Default (depends on kernel configuration option):
>> 3101 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 3102 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 3103 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 3104 mem_encrypt=off: Do not activate SME
3407 3105
3408 Refer to Documentatio !! 3106 Refer to Documentation/virt/kvm/amd-memory-encryption.rst
3409 for details on when m 3107 for details on when memory encryption can be activated.
3410 3108
3411 mem_sleep_default= [SUSPEND] Def 3109 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 3110 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 3111 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 3112 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 3113 See Documentation/admin-guide/pm/sleep-states.rst.
3416 3114
>> 3115 meye.*= [HW] Set MotionEye Camera parameters
>> 3116 See Documentation/admin-guide/media/meye.rst.
>> 3117
>> 3118 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 3119 Multi-Function General Purpose Timers on AMD Geode
>> 3120 platforms.
>> 3121
3417 mfgptfix [X86-32] Fix MFGPT ti 3122 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 3123 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 3124 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 3125 problem by letting the user disable the workaround.
3421 3126
3422 mga= [HW,DRM] 3127 mga= [HW,DRM]
3423 3128
3424 microcode.force_minrev= [X86] !! 3129 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
3425 Format: <bool> !! 3130 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 3131
3429 mini2440= [ARM,HW,KNL] 3132 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 3133 Format:[0..2][b][c][t]
3431 Default: "0tb" 3134 Default: "0tb"
3432 MINI2440 configuratio 3135 MINI2440 configuration specification:
3433 0 - The attached scre 3136 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 3137 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 3138 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 3139 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 3140 the TFT driver, and the framebuffer will be left
3438 unconfigured. 3141 unconfigured.
3439 b - Enable backlight. 3142 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 3143 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 3144 LED. This parameter is not necessary when using the
3442 VGA shield. 3145 VGA shield.
3443 c - Enable the s3c ca 3146 c - Enable the s3c camera interface.
3444 t - Reserved for enab 3147 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 3148 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 3149 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 3150 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 3151 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 3152
3450 mitigations= 3153 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 3154 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 3155 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 3156 arch-independent options, each of which is an
3454 aggregation of existi 3157 aggregation of existing arch-specific options.
3455 3158
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 3159 off
3460 Disable all o 3160 Disable all optional CPU mitigations. This
3461 improves syst 3161 improves system performance, but it may also
3462 expose users 3162 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 3163 Equivalent to: nopti [X86,PPC]
3464 !! 3164 kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 3165 nospectre_v1 [X86,PPC]
>> 3166 nobp=0 [S390]
3475 3167 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 3168 spectre_v2_user=off [X86]
3482 !! 3169 spec_store_bypass_disable=off [X86,PPC]
3483 3170 ssbd=force-off [ARM64]
>> 3171 l1tf=off [X86]
>> 3172 mds=off [X86]
3484 3173 tsx_async_abort=off [X86]
>> 3174 kvm.nx_huge_pages=off [X86]
>> 3175 srbds=off [X86,INTEL]
>> 3176 no_entry_flush [PPC]
>> 3177 no_uaccess_flush [PPC]
>> 3178 mmio_stale_data=off [X86]
>> 3179 retbleed=off [X86]
3485 3180
3486 Exceptions: 3181 Exceptions:
3487 3182 This does not have any effect on
3488 3183 kvm.nx_huge_pages when
3489 3184 kvm.nx_huge_pages=force.
3490 3185
3491 auto (default) 3186 auto (default)
3492 Mitigate all 3187 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 3188 enabled, even if it's vulnerable. This is for
3494 users who don 3189 users who don't want to be surprised by SMT
3495 getting disab 3190 getting disabled across kernel upgrades, or who
3496 have other wa 3191 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 3192 Equivalent to: (default behavior)
3498 3193
3499 auto,nosmt 3194 auto,nosmt
3500 Mitigate all 3195 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 3196 if needed. This is for users who always want to
3502 be fully miti 3197 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 3198 Equivalent to: l1tf=flush,nosmt [X86]
3504 3199 mds=full,nosmt [X86]
3505 3200 tsx_async_abort=full,nosmt [X86]
3506 3201 mmio_stale_data=full,nosmt [X86]
3507 3202 retbleed=auto,nosmt [X86]
3508 3203
3509 mminit_loglevel= 3204 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 3205 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 3206 parameter allows control of the logging verbosity for
3512 the additional memory 3207 the additional memory initialisation checks. A value
3513 of 0 disables mminit 3208 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 3209 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 3210 so loglevel=8 may also need to be specified.
3516 3211
3517 mmio_stale_data= 3212 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 3213 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 3214 MMIO Stale Data vulnerabilities.
3520 3215
3521 Processor MMIO Stale 3216 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 3217 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 3218 operation. Exposed data could originate or end in
3524 the same CPU buffers 3219 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 3220 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 3221 is to clear the affected CPU buffers.
3527 3222
3528 This parameter contro 3223 This parameter controls the mitigation. The
3529 options are: 3224 options are:
3530 3225
3531 full - Enable m 3226 full - Enable mitigation on vulnerable CPUs
3532 3227
3533 full,nosmt - Enable m 3228 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 3229 vulnerable CPUs.
3535 3230
3536 off - Uncondit 3231 off - Unconditionally disable mitigation
3537 3232
3538 On MDS or TAA affecte 3233 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 3234 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 3235 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 3236 mitigated with the same mechanism so in order to
3542 disable this mitigati 3237 disable this mitigation, you need to specify
3543 mds=off and tsx_async 3238 mds=off and tsx_async_abort=off too.
3544 3239
3545 Not specifying this o 3240 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 3241 mmio_stale_data=full.
3547 3242
3548 For details see: 3243 For details see:
3549 Documentation/admin-g 3244 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 3245
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 3246 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3247 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3248 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3249 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3250 is always true, so this option does nothing.
3578 3251
3579 module_blacklist= [KNL] Do not load 3252 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3253 modules. Useful for debugging problem modules.
3581 3254
3582 mousedev.tap_time= 3255 mousedev.tap_time=
3583 [MOUSE] Maximum time 3256 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3257 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3258 a tap and be reported as a left button click (for
3586 touchpads working in 3259 touchpads working in absolute mode only).
3587 Format: <msecs> 3260 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3261 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3262 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3263 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3264 reporting absolute coordinates, such as tablets
3592 3265
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3266 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3267 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3268 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3269 specifies the amount of memory used for migratable
3597 allocations. If both 3270 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3271 specified, then kernelcore will be at *least* the
3599 specified value but m 3272 specified value but may be more. If movablecore on its
3600 own is specified, the 3273 own is specified, the administrator must be careful
3601 that the amount of me 3274 that the amount of memory usable for all allocations
3602 is not too small. 3275 is not too small.
3603 3276
3604 movable_node [KNL,EARLY] Boot-time !! 3277 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3278 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3279 of such nodes will be usable only for movable
3607 allocations which rul 3280 allocations which rules out almost all kernel
3608 allocations. Use with 3281 allocations. Use with caution!
3609 3282
3610 MTD_Partition= [MTD] 3283 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3284 Format: <name>,<region-number>,<size>,<offset>
3612 3285
3613 MTD_Region= [MTD] Format: 3286 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3287 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3288
3616 mtdparts= [MTD] 3289 mtdparts= [MTD]
3617 See drivers/mtd/parse 3290 See drivers/mtd/parsers/cmdlinepart.c
3618 3291
>> 3292 mtdset= [ARM]
>> 3293 ARM/S3C2412 JIVE boot control
>> 3294
>> 3295 See arch/arm/mach-s3c/mach-jive.c
>> 3296
3619 mtouchusb.raw_coordinates= 3297 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3298 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3299 ('y', default) or cooked coordinates ('n')
3622 3300
3623 mtrr=debug [X86,EARLY] !! 3301 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 3302 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3303 that could hold holes aka. UC entries.
3630 3304
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3305 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3306 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3307 Default is 1.
3634 Large value could pre 3308 Large value could prevent small alignment from
3635 using up MTRRs. 3309 using up MTRRs.
3636 3310
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3311 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3312 Format: <integer>
3639 Range: 0,7 : spare re 3313 Range: 0,7 : spare reg number
3640 Default : 1 3314 Default : 1
3641 Used for mtrr cleanup 3315 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3316 Set to 2 or more if your graphical card needs more.
3643 3317
3644 multitce=off [PPC] This parameter 3318 multitce=off [PPC] This parameter disables the use of the pSeries
3645 firmware feature for 3319 firmware feature for updating multiple TCE entries
3646 at a time. 3320 at a time.
3647 3321
3648 n2= [NET] SDL Inc. RISCom 3322 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3323
3650 netdev= [NET] Network devices 3324 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3325 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3326 Note that mem_start is often overloaded to mean
3653 something different a 3327 something different and driver-specific.
3654 This usage is only do 3328 This usage is only documented in each driver source
3655 file if at all. 3329 file if at all.
3656 3330
3657 netpoll.carrier_timeout= 3331 netpoll.carrier_timeout=
3658 [NET] Specifies amoun 3332 [NET] Specifies amount of time (in seconds) that
3659 netpoll should wait f 3333 netpoll should wait for a carrier. By default netpoll
3660 waits 4 seconds. 3334 waits 4 seconds.
3661 3335
3662 nf_conntrack.acct= 3336 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3337 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3338 0 to disable accounting
3665 1 to enable accountin 3339 1 to enable accounting
3666 Default value is 0. 3340 Default value is 0.
3667 3341
3668 nfs.cache_getent= !! 3342 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3343 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3344
3672 nfs.cache_getent_timeout= !! 3345 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3346 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3347
>> 3348 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3349 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3350
3676 nfs.callback_nr_threads= 3351 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3352 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3353 NFS client will assign to service NFSv4 callback
3679 requests. 3354 requests.
3680 3355
3681 nfs.callback_tcpport= 3356 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3357 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3358 channel should listen.
3684 3359
3685 nfs.delay_retrans= !! 3360 nfs.cache_getent=
3686 [NFS] specifies the n !! 3361 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3362 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3363
3689 Only applies if the s !! 3364 nfs.cache_getent_timeout=
3690 and the specified val !! 3365 [NFS] sets the timeout after which an attempt to
>> 3366 update a cache entry is deemed to have failed.
>> 3367
>> 3368 nfs.idmap_cache_timeout=
>> 3369 [NFS] set the maximum lifetime for idmapper cache
>> 3370 entries.
3691 3371
3692 nfs.enable_ino64= 3372 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3373 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3374 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3375 number for the readdir() and stat() syscalls instead
3696 of returning the full 3376 of returning the full 64-bit number.
3697 The default is to ret 3377 The default is to return 64-bit inode numbers.
3698 3378
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3379 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3380 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3381 slots the client will assign to the callback
3706 channel. This determi 3382 channel. This determines the maximum number of
3707 callbacks the client 3383 callbacks the client will process in parallel for
3708 a particular server. 3384 a particular server.
3709 3385
3710 nfs.max_session_slots= 3386 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3387 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3388 the client will attempt to negotiate with the server.
3713 This limits the numbe 3389 This limits the number of simultaneous RPC requests
3714 that the client can s 3390 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3391 Note that there is little point in setting this
3716 value higher than the 3392 value higher than the max_tcp_slot_table_limit.
3717 3393
3718 nfs.nfs4_disable_idmapping= 3394 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3395 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3396 ensures that both the RPC level authentication
3721 scheme and the NFS le 3397 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3398 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3399 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3400 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3401 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3402 Servers that do not support this mode of operation
3727 will be autodetected 3403 will be autodetected by the client, and it will fall
3728 back to using the idm 3404 back to using the idmapper.
3729 To turn off this beha 3405 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3406 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3407 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3408 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3409 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3410 UUID that is generated at system install time.
3736 3411
3737 nfs.recover_lost_locks= !! 3412 nfs.send_implementation_id =
>> 3413 [NFSv4.1] Send client implementation identification
>> 3414 information in exchange_id requests.
>> 3415 If zero, no implementation identification information
>> 3416 will be sent.
>> 3417 The default is to send the implementation identification
>> 3418 information.
>> 3419
>> 3420 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3421 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3422 to a lease timeout on the server. Please note that
3740 doing this risks data 3423 doing this risks data corruption, since there are
3741 no guarantees that th 3424 no guarantees that the file will remain unchanged
3742 after the locks are l 3425 after the locks are lost.
3743 If you want to enable 3426 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3427 attempting to recover these locks, then set this
3745 parameter to '1'. 3428 parameter to '1'.
3746 The default parameter 3429 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3430 not to attempt recovery of lost locks.
3748 3431
3749 nfs.send_implementation_id= !! 3432 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 3433 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3434 layoutstats to the pNFS metadata server.
3760 3435
3761 Setting this to value 3436 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3437 whatever value is the default set by the layout
3763 driver. A non-zero va 3438 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3439 in seconds between layoutstats transmissions.
3765 3440
3766 nfsd.inter_copy_offload_enable= !! 3441 nfsd.inter_copy_offload_enable =
3767 [NFSv4.2] When set to 3442 [NFSv4.2] When set to 1, the server will support
3768 server-to-server copi 3443 server-to-server copies for which this server is
3769 the destination of th 3444 the destination of the copy.
3770 3445
3771 nfsd.nfs4_disable_idmapping= !! 3446 nfsd.nfsd4_ssc_umount_timeout =
3772 [NFSv4] When set to t <<
3773 server will return on <<
3774 clients using auth_sy <<
3775 and gids from such cl <<
3776 migration from NFSv2/ <<
3777 <<
3778 nfsd.nfsd4_ssc_umount_timeout= <<
3779 [NFSv4.2] When used a 3447 [NFSv4.2] When used as the destination of a
3780 server-to-server copy 3448 server-to-server copy, knfsd temporarily mounts
3781 the source server. I 3449 the source server. It caches the mount in case
3782 it will be needed aga 3450 it will be needed again, and discards it if not
3783 used for the number o 3451 used for the number of milliseconds specified by
3784 this parameter. 3452 this parameter.
3785 3453
3786 nfsaddrs= [NFS] Deprecated. Us !! 3454 nfsd.nfs4_disable_idmapping=
3787 See Documentation/adm !! 3455 [NFSv4] When set to the default of '1', the NFSv4
3788 !! 3456 server will return only numeric uids and gids to
3789 nfsroot= [NFS] nfs root filesy !! 3457 clients using auth_sys, and will accept numeric uids
3790 See Documentation/adm !! 3458 and gids from such clients. This is intended to ease
>> 3459 migration from NFSv2/v3.
3791 3460
3792 nfsrootdebug [NFS] enable nfsroot <<
3793 See Documentation/adm <<
3794 3461
3795 nmi_backtrace.backtrace_idle [KNL] 3462 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3463 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3464 NMI stack-backtrace request.
3798 3465
3799 nmi_debug= [KNL,SH] Specify one 3466 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3467 when a NMI is triggered.
3801 Format: [state][,regs 3468 Format: [state][,regs][,debounce][,die]
3802 3469
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3470 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3471 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3472 Valid num: 0 or 1
3806 0 - turn hardlockup d 3473 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3474 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3475 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3476 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3477 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3478 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3479 please see 'nowatchdog'.
3815 This is useful when y 3480 This is useful when you use a panic=... timeout and
3816 need the box quickly 3481 need the box quickly up again.
3817 3482
3818 These settings can be 3483 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3484 the nmi_watchdog and hardlockup_panic sysctls.
3820 3485
3821 no387 [BUGS=X86-32] Tells t 3486 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3487 emulation library even if a 387 maths coprocessor
3823 is present. 3488 is present.
3824 3489
3825 no4lvl [RISCV,EARLY] Disable !! 3490 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 3491 kernel to use 4-level paging instead.
3830 3492
3831 noalign [KNL,ARM] !! 3493 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 3494
3840 no_console_suspend 3495 no_console_suspend
3841 [HW] Never suspend th 3496 [HW] Never suspend the console
3842 Disable suspending of 3497 Disable suspending of consoles during suspend and
3843 hibernate operations. 3498 hibernate operations. Once disabled, debugging
3844 messages can reach va 3499 messages can reach various consoles while the rest
3845 of the system is bein 3500 of the system is being put to sleep (ie, while
3846 debugging driver susp 3501 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3502 not work reliably with all consoles, but is known
3848 to work with serial a 3503 to work with serial and VGA consoles.
3849 To facilitate more fl 3504 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3505 console_suspend, a printk module parameter to control
3851 it. Users could use c 3506 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3507 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3508 turn on/off it dynamically.
3854 3509
3855 no_debug_objects !! 3510 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3511 Disable device dump. Device dump allows drivers to
>> 3512 append dump data to vmcore so you can collect driver
>> 3513 specified debug info. Drivers can append the data
>> 3514 without any limit and this data is stored in memory,
>> 3515 so this may cause significant memory stress. Disabling
>> 3516 device dump can help save memory but the driver debug
>> 3517 data will be no longer available. This parameter
>> 3518 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3519 is set.
>> 3520
>> 3521 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3522 caches in the slab allocator. Saves per-node memory,
>> 3523 but will impact performance.
>> 3524
>> 3525 noalign [KNL,ARM]
>> 3526
>> 3527 noaltinstr [S390] Disables alternative instructions patching
>> 3528 (CPU alternatives feature).
>> 3529
>> 3530 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3531 IOAPICs that may be present in the system.
>> 3532
>> 3533 noautogroup Disable scheduler automatic task group creation.
>> 3534
>> 3535 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 3536 on "Classic" PPC cores.
>> 3537
>> 3538 nocache [ARM]
3857 3539
3858 nodsp [SH] Disable hardware 3540 nodsp [SH] Disable hardware DSP at boot time.
3859 3541
3860 noefi [EFI,EARLY] Disable E !! 3542 noefi Disable EFI runtime services support.
>> 3543
>> 3544 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3861 3545
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3546 noexec [IA-64]
>> 3547
>> 3548 nosmap [PPC]
>> 3549 Disable SMAP (Supervisor Mode Access Prevention)
>> 3550 even if it is supported by processor.
>> 3551
>> 3552 nosmep [PPC64s]
>> 3553 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3554 even if it is supported by processor.
3863 3555
3864 noexec32 [X86-64] 3556 noexec32 [X86-64]
3865 This affects only 32- 3557 This affects only 32-bit executables.
3866 noexec32=on: enable n 3558 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3559 read doesn't imply executable mappings
3868 noexec32=off: disable 3560 noexec32=off: disable non-executable mappings
3869 read implies 3561 read implies executable mappings
3870 3562
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 3563 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3564
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3565 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3566 register save and restore. The kernel will only save
3881 legacy floating-point 3567 legacy floating-point registers on task switch.
3882 3568
>> 3569 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
>> 3570
>> 3571 nohugevmalloc [PPC] Disable kernel huge vmalloc mappings.
>> 3572
>> 3573 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3574 Equivalent to smt=1.
>> 3575
>> 3576 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3577 nosmt=force: Force disable SMT, cannot be undone
>> 3578 via the sysfs control file.
>> 3579
>> 3580 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3581 (bounds check bypass). With this option data leaks are
>> 3582 possible in the system.
>> 3583
>> 3584 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 3585 the Spectre variant 2 (indirect branch prediction)
>> 3586 vulnerability. System may allow data leaks with this
>> 3587 option.
>> 3588
>> 3589 nospec_store_bypass_disable
>> 3590 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3591
>> 3592 no_uaccess_flush
>> 3593 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3594
>> 3595 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3596 and restore using xsave. The kernel will fallback to
>> 3597 enabling legacy floating-point and sse state.
>> 3598
>> 3599 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3600 register states. The kernel will fall back to use
>> 3601 xsave to save the states. By using this parameter,
>> 3602 performance of saving the states is degraded because
>> 3603 xsave doesn't support modified optimization while
>> 3604 xsaveopt supports it on xsaveopt enabled systems.
>> 3605
>> 3606 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3607 restoring x86 extended register state in compacted
>> 3608 form of xsave area. The kernel will fall back to use
>> 3609 xsaveopt and xrstor to save and restore the states
>> 3610 in standard form of xsave area. By using this
>> 3611 parameter, xsave area per process might occupy more
>> 3612 memory on xsaves enabled systems.
>> 3613
>> 3614 nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
>> 3615 in do_idle() and not use the arch_cpu_idle()
>> 3616 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
>> 3617 to be effective. This is useful on platforms where the
>> 3618 sleep(SH) or wfi(ARM,ARM64) instructions do not work
>> 3619 correctly or when doing power measurements to evalute
>> 3620 the impact of the sleep instructions. This is also
>> 3621 useful when using JTAG debugger.
>> 3622
>> 3623 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3624 only way then for a file to be executed with privilege
>> 3625 is to be setuid root or executed by root.
>> 3626
>> 3627 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3628 function PAL_HALT_LIGHT when idle. This increases
>> 3629 power-consumption. On the positive side, it reduces
>> 3630 interrupt wake-up latency, which may improve performance
>> 3631 in certain environments such as networked servers or
>> 3632 real-time systems.
>> 3633
3883 no_hash_pointers 3634 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3635 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3636 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3637 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3638 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3639 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3640 users, but it also makes debugging the kernel more
3891 difficult since unequ 3641 difficult since unequal pointers can no longer be
3892 compared. However, i 3642 compared. However, if this command-line option is
3893 specified, then all n 3643 specified, then all normal pointers will have their true
3894 value printed. This o 3644 value printed. This option should only be specified when
3895 debugging the kernel. 3645 debugging the kernel. Please do not use on production
3896 kernels. 3646 kernels.
3897 3647
3898 nohibernate [HIBERNATION] Disable 3648 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3649
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 3650 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3651 Valid arguments: on, off
3915 Default: on 3652 Default: on
3916 3653
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3654 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3655 The argument is a cpu list, as described above.
3919 In kernels built with 3656 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3657 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3658 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3659 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3660 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3661 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3662 rcu_nocbs= boot parameter.
3926 3663
3927 Note that this argume !! 3664 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 3665
>> 3666 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3667 disable unhandled interrupt sources.
>> 3668
>> 3669 no_timer_check [X86,APIC] Disables the code which tests for
>> 3670 broken timer IRQ sources.
>> 3671
>> 3672 noisapnp [ISAPNP] Disables ISA PnP code.
3929 3673
3930 noinitrd [RAM] Tells the kerne 3674 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3675 initial RAM disk.
3932 3676
3933 nointremap [X86-64,Intel-IOMMU,E !! 3677 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3678 remapping.
3935 [Deprecated - use int 3679 [Deprecated - use intremap=off]
3936 3680
3937 noinvpcid [X86,EARLY] Disable t !! 3681 nointroute [IA-64]
3938 <<
3939 noiotrap [SH] Disables trapped <<
3940 3682
3941 noirqdebug [X86-32] Disables the !! 3683 noinvpcid [X86] Disable the INVPCID cpu feature.
3942 disable unhandled int <<
3943 3684
3944 noisapnp [ISAPNP] Disables ISA !! 3685 nojitter [IA-64] Disables jitter checking for ITC timers.
3945 3686
3946 nokaslr [KNL,EARLY] !! 3687 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 3688
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3689 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3690 fault handling.
3953 3691
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3692 no-vmw-sched-clock
>> 3693 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3694 clock and use the default one.
>> 3695
>> 3696 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
>> 3697 accounting. steal time is computed, but won't
>> 3698 influence scheduler behaviour
>> 3699
>> 3700 nolapic [X86-32,APIC] Do not enable or use the local APIC.
>> 3701
>> 3702 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3955 3703
3956 nolapic [X86-32,APIC,EARLY] D !! 3704 noltlbs [PPC] Do not use large page/tlb entries for kernel
>> 3705 lowmem mapping on PPC40x and PPC8xx
3957 3706
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3707 nomca [IA-64] Disable machine check abort handling
3959 3708
3960 nomce [X86-32] Disable Mach 3709 nomce [X86-32] Disable Machine Check Exception
3961 3710
3962 nomfgpt [X86-32] Disable Mult 3711 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 3712 Timer usage (for AMD Geode machines).
3964 3713
3965 nomodeset Disable kernel modese <<
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 <<
3973 Useful as error fallb <<
3974 <<
3975 nomodule Disable module load <<
3976 <<
3977 nonmi_ipi [X86] Disable using N 3714 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3715 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3716 irq.
3980 3717
3981 nopat [X86,EARLY] Disable P !! 3718 nomodeset Disable kernel modesetting. DRM drivers will not perform
3982 pagetables) support. !! 3719 display-mode changes or accelerated rendering. Only the
3983 !! 3720 system framebuffer will be available for use if this was
3984 nopcid [X86-64,EARLY] Disabl !! 3721 set-up by the firmware or boot loader.
3985 3722
3986 nopku [X86] Disable Memory !! 3723 Useful as fallback, or for testing and debugging.
3987 in some Intel CPUs. <<
3988 3724
3989 nopti [X86-64,EARLY] !! 3725 nomodule Disable module load
3990 Equivalent to pti=off <<
3991 3726
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3727 nopat [X86] Disable PAT (page attribute table extension of
3993 Disables the PV optim !! 3728 pagetables) support.
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 3729
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3730 nopcid [X86-64] Disable the PCID cpu feature.
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3731
4002 norandmaps Don't use address spa 3732 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3733 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3734
4005 noreplace-smp [X86-32,SMP] Don't re 3735 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3736 with UP alternatives
4007 3737
>> 3738 nordrand [X86] Disable kernel use of the RDRAND and
>> 3739 RDSEED instructions even if they are supported
>> 3740 by the processor. RDRAND and RDSEED are still
>> 3741 available to user space applications.
>> 3742
4008 noresume [SWSUSP] Disables res 3743 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3744 space.
4010 3745
4011 no-scroll [VGA] Disables scroll 3746 no-scroll [VGA] Disables scrollback.
4012 This is required for 3747 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3748 reader made by F.H. Papenmeier (Germany).
4014 3749
4015 nosgx [X86-64,SGX,EARLY] Di !! 3750 nosbagart [IA-64]
4016 3751
4017 nosmap [PPC,EARLY] !! 3752 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 <<
4021 nosmep [PPC64s,EARLY] <<
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 3753
4025 nosmp [SMP,EARLY] Tells an !! 3754 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3755 and disable the IO APIC. legacy for "maxcpus=0".
4027 3756
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 3757 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3758
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 3759 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3760
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 3761 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3762 soft-lockup and NMI watchdog (hard-lockup).
4083 3763
4084 nowb [ARM,EARLY] !! 3764 nowb [ARM]
4085 3765
4086 nox2apic [X86-64,APIC,EARLY] D !! 3766 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3767
4088 NOTE: this parameter 3768 NOTE: this parameter will be ignored on systems with the
4089 LEGACY_XAPIC_DISABLED 3769 LEGACY_XAPIC_DISABLED bit set in the
4090 IA32_XAPIC_DISABLE_ST 3770 IA32_XAPIC_DISABLE_STATUS MSR.
4091 3771
4092 noxsave [BUGS=X86] Disables x !! 3772 nps_mtm_hs_ctr= [KNL,ARC]
4093 and restore using xsa !! 3773 This parameter sets the maximum duration, in
4094 enabling legacy float !! 3774 cycles, each HW thread of the CTOP can run
4095 !! 3775 without interruptions, before HW switches it.
4096 noxsaveopt [X86] Disables xsaveo !! 3776 The actual maximum duration is 16 times this
4097 register states. The !! 3777 parameter's value.
4098 xsave to save the sta !! 3778 Format: integer between 1 and 255
4099 performance of saving !! 3779 Default: 255
4100 xsave doesn't support !! 3780
4101 xsaveopt supports it !! 3781 nptcg= [IA-64] Override max number of concurrent global TLB
4102 !! 3782 purges which is reported from either PAL_VM_SUMMARY or
4103 noxsaves [X86] Disables xsaves !! 3783 SAL PALO.
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 3784
4111 nr_cpus= [SMP,EARLY] Maximum n !! 3785 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4112 could support. nr_cp 3786 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3787 support 'n' processors. It could be larger than the
4114 number of already plu 3788 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3789 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3790 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3791 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3792 hot plugging.
4119 3793
4120 nr_uarts= [SERIAL] maximum numb 3794 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3795
4122 numa=off [KNL, ARM64, PPC, RIS !! 3796 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123 Disable NUMA, Only se !! 3797 set up a single NUMA node spanning all memory.
4124 spanning all memory. <<
4125 3798
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 3799 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 3800 NUMA balancing.
4128 Allowed values are en 3801 Allowed values are enable and disable
4129 3802
4130 numa_zonelist_order= [KNL, BOOT] Sele 3803 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3804 'node', 'default' can be specified
4132 This can be set from 3805 This can be set from sysctl after boot.
4133 See Documentation/adm 3806 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3807
4135 ohci1394_dma=early [HW,EARLY] en !! 3808 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3809 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3810 info.
4138 3811
4139 olpc_ec_timeout= [OLPC] ms delay when 3812 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3813 Rather than timing out after 20 ms if an EC
4141 command is not proper 3814 command is not properly ACKed, override the length
4142 of the timeout. We h 3815 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3816 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3817 interrupts *may* be lost!
4145 3818
4146 omap_mux= [OMAP] Override bootl 3819 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3820 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3821 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3822 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3823
4151 onenand.bdry= [HW,MTD] Flex-OneNAND 3824 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4152 3825
4153 Format: [die0_boundar 3826 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4154 3827
4155 boundary - index of l 3828 boundary - index of last SLC block on Flex-OneNAND.
4156 The remain 3829 The remaining blocks are configured as MLC blocks.
4157 lock - Configure 3830 lock - Configure if Flex-OneNAND boundary should be locked.
4158 Once locke 3831 Once locked, the boundary cannot be changed.
4159 1 indicate 3832 1 indicates lock status, 0 indicates unlock status.
4160 3833
4161 oops=panic [KNL,EARLY] !! 3834 oops=panic Always panic on oopses. Default is to just kill the
4162 Always panic on oopse <<
4163 process, but there is 3835 process, but there is a small probability of
4164 deadlocking the machi 3836 deadlocking the machine.
4165 This will also cause 3837 This will also cause panics on machine check exceptions.
4166 Useful together with 3838 Useful together with panic=30 to trigger a reboot.
4167 3839
4168 page_alloc.shuffle= 3840 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3841 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3842 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3843 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3844 running on a platform with a direct-mapped memory-side
>> 3845 cache, and this parameter can be used to
>> 3846 override/disable that behavior. The state of the flag
>> 3847 can be read from sysfs at:
4173 /sys/module/page_allo 3848 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3849
4176 page_owner= [KNL,EARLY] Boot-time !! 3850 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3851 Storage of the information about who allocated
4178 each page is disabled 3852 each page is disabled in default. With this switch,
4179 we can turn it on. 3853 we can turn it on.
4180 on: enable the featur 3854 on: enable the feature
4181 3855
4182 page_poison= [KNL,EARLY] Boot-time !! 3856 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3857 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3858 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3859 off: turn off poisoning (default)
4186 on: turn on poisoning 3860 on: turn on poisoning
4187 3861
4188 page_reporting.page_reporting_order= 3862 page_reporting.page_reporting_order=
4189 [KNL] Minimal page re 3863 [KNL] Minimal page reporting order
4190 Format: <integer> 3864 Format: <integer>
4191 Adjust the minimal pa 3865 Adjust the minimal page reporting order. The page
4192 reporting is disabled !! 3866 reporting is disabled when it exceeds (MAX_ORDER-1).
4193 3867
4194 panic= [KNL] Kernel behaviou 3868 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3869 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3870 timeout = 0: wait forever
4197 timeout < 0: reboot i 3871 timeout < 0: reboot immediately
4198 Format: <timeout> 3872 Format: <timeout>
4199 3873
4200 panic_on_taint= [KNL,EARLY] <<
4201 Bitmask for condition <<
4202 Format: <hex>[,nouser <<
4203 Hexadecimal bitmask r <<
4204 that will cause the k <<
4205 called with any of th <<
4206 The optional switch " <<
4207 prevent userspace for <<
4208 /proc/sys/kernel/tain <<
4209 bitmask set on panic_ <<
4210 See Documentation/adm <<
4211 extra details on the <<
4212 to compose the bitmas <<
4213 <<
4214 panic_on_warn=1 panic() instead of WA <<
4215 on a WARN(). <<
4216 <<
4217 panic_print= Bitmask for printing 3874 panic_print= Bitmask for printing system info when panic happens.
4218 User can chose combin 3875 User can chose combination of the following bits:
4219 bit 0: print all task 3876 bit 0: print all tasks info
4220 bit 1: print system m 3877 bit 1: print system memory info
4221 bit 2: print timer in 3878 bit 2: print timer info
4222 bit 3: print locks in 3879 bit 3: print locks info if CONFIG_LOCKDEP is on
4223 bit 4: print ftrace b 3880 bit 4: print ftrace buffer
4224 bit 5: print all prin 3881 bit 5: print all printk messages in buffer
4225 bit 6: print all CPUs 3882 bit 6: print all CPUs backtrace (if available in the arch)
4226 bit 7: print only tas <<
4227 *Be aware* that this 3883 *Be aware* that this option may print a _lot_ of lines,
4228 so there are risks of 3884 so there are risks of losing older messages in the log.
4229 Use this option caref 3885 Use this option carefully, maybe worth to setup a
4230 bigger log buffer wit 3886 bigger log buffer with "log_buf_len" along with this.
4231 3887
>> 3888 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
>> 3889 Format: <hex>[,nousertaint]
>> 3890 Hexadecimal bitmask representing the set of TAINT flags
>> 3891 that will cause the kernel to panic when add_taint() is
>> 3892 called with any of the flags in this set.
>> 3893 The optional switch "nousertaint" can be utilized to
>> 3894 prevent userspace forced crashes by writing to sysctl
>> 3895 /proc/sys/kernel/tainted any flagset matching with the
>> 3896 bitmask set on panic_on_taint.
>> 3897 See Documentation/admin-guide/tainted-kernels.rst for
>> 3898 extra details on the taint flags that users can pick
>> 3899 to compose the bitmask to assign to panic_on_taint.
>> 3900
>> 3901 panic_on_warn panic() instead of WARN(). Useful to cause kdump
>> 3902 on a WARN().
>> 3903
4232 parkbd.port= [HW] Parallel port nu 3904 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3905 connected to, default is 0.
4234 Format: <parport#> 3906 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3907 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3908 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3909 Format: <mode>
4238 3910
4239 parport= [HW,PPT] Specify para 3911 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3912 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3913 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3914 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3915 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3916 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3917 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3918 should be numbers, or 'auto' (for using detected
4247 settings on that part 3919 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3920 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3921 Parallel ports are assigned in the order they
4250 are specified on the 3922 are specified on the command line, starting
4251 with parport0. 3923 with parport0.
4252 3924
4253 parport_init_mode= [HW,PPT] 3925 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3926 Configure VIA parallel port to operate in
4255 a specific mode. This 3927 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3928 computer where firmware has no options for setting
4257 up parallel port mode 3929 up parallel port mode and sets it to spp.
4258 Currently this functi 3930 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3931 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3932
4261 pata_legacy.all= [HW,LIBATA] 3933 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 3934 Format: <int>
4263 Set to non-zero to pr 3935 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 3936 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 3937 has been found at either range. Disabled by default.
4266 3938
4267 pata_legacy.autospeed= [HW,LIBATA] 3939 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 3940 Format: <int>
4269 Set to non-zero if a 3941 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 3942 changes. Disabled by default.
4271 3943
4272 pata_legacy.ht6560a= [HW,LIBATA] 3944 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 3945 Format: <int>
4274 Set to 1, 2, or 3 for 3946 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 3947 the secondary channel, or both channels respectively.
4276 Disabled by default. 3948 Disabled by default.
4277 3949
4278 pata_legacy.ht6560b= [HW,LIBATA] 3950 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 3951 Format: <int>
4280 Set to 1, 2, or 3 for 3952 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 3953 the secondary channel, or both channels respectively.
4282 Disabled by default. 3954 Disabled by default.
4283 3955
4284 pata_legacy.iordy_mask= [HW,LIBATA] 3956 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 3957 Format: <int>
4286 IORDY enable mask. S 3958 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 3959 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 3960 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 3961 the second channel, and so on. The sequence will often
4290 correspond to the pri 3962 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 3963 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 3964 bus and the use of other driver options may interfere
4293 with the sequence. B 3965 with the sequence. By default IORDY is allowed across
4294 all channels. 3966 all channels.
4295 3967
4296 pata_legacy.opti82c46x= [HW,LIBATA] 3968 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 3969 Format: <int>
4298 Set to 1, 2, or 3 for 3970 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 3971 channel, the secondary channel, or both channels
4300 respectively. Disabl 3972 respectively. Disabled by default.
4301 3973
4302 pata_legacy.opti82c611a= [HW,L 3974 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 3975 Format: <int>
4304 Set to 1, 2, or 3 for 3976 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 3977 channel, the secondary channel, or both channels
4306 respectively. Disabl 3978 respectively. Disabled by default.
4307 3979
4308 pata_legacy.pio_mask= [HW,LIBATA] 3980 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 3981 Format: <int>
4310 PIO mode mask for aut 3982 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 3983 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 3984 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 3985 All modes allowed by default.
4314 3986
4315 pata_legacy.probe_all= [HW,LIBATA] 3987 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 3988 Format: <int>
4317 Set to non-zero to pr 3989 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 3990 port ranges on PCI systems. Disabled by default.
4319 3991
4320 pata_legacy.probe_mask= [HW,LIBATA] 3992 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 3993 Format: <int>
4322 Probe mask for legacy 3994 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 3995 platform configuration and the use of other driver
4324 options up to 6 legac 3996 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 3997 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 3998 of individual ports can be disabled by setting the
4327 corresponding bits in 3999 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 4000 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 4001 By default all supported ports are probed.
4330 4002
4331 pata_legacy.qdi= [HW,LIBATA] 4003 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 4004 Format: <int>
4333 Set to non-zero to pr 4005 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 4006 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 4007
4336 pata_legacy.winbond= [HW,LIBATA] 4008 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 4009 Format: <int>
4338 Set to non-zero to pr 4010 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 4011 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 4012 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 4013 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 4014 0 otherwise.
4343 4015
4344 pata_platform.pio_mask= [HW,LIBATA] 4016 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 4017 Format: <int>
4346 Supported PIO mode ma 4018 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 4019 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 4020 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 4021 allowed by default.
4350 4022
4351 pause_on_oops=<int> !! 4023 pause_on_oops=
4352 Halt all CPUs after t 4024 Halt all CPUs after the first oops has been printed for
4353 the specified number 4025 the specified number of seconds. This is to be used if
4354 your oopses keep scro 4026 your oopses keep scrolling off the screen.
4355 4027
4356 pcbit= [HW,ISDN] 4028 pcbit= [HW,ISDN]
4357 4029
4358 pci=option[,option...] [PCI,EARLY] v !! 4030 pcd. [PARIDE]
>> 4031 See header of drivers/block/paride/pcd.c.
>> 4032 See also Documentation/admin-guide/blockdev/paride.rst.
>> 4033
>> 4034 pci=option[,option...] [PCI] various PCI subsystem options.
4359 4035
4360 Some options 4036 Some options herein operate on a specific device
4361 or a set of d 4037 or a set of devices (<pci_dev>). These are
4362 specified in 4038 specified in one of the following formats:
4363 4039
4364 [<domain>:]<b 4040 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 4041 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 4042
4367 Note: the fir 4043 Note: the first format specifies a PCI
4368 bus/device/fu 4044 bus/device/function address which may change
4369 if new hardwa 4045 if new hardware is inserted, if motherboard
4370 firmware chan 4046 firmware changes, or due to changes caused
4371 by other kern 4047 by other kernel parameters. If the
4372 domain is lef 4048 domain is left unspecified, it is
4373 taken to be z 4049 taken to be zero. Optionally, a path
4374 to a device t 4050 to a device through multiple device/function
4375 addresses can 4051 addresses can be specified after the base
4376 address (this 4052 address (this is more robust against
4377 renumbering i 4053 renumbering issues). The second format
4378 selects devic 4054 selects devices using IDs from the
4379 configuration 4055 configuration space which may match multiple
4380 devices in th 4056 devices in the system.
4381 4057
4382 earlydump dump PCI conf 4058 earlydump dump PCI config space before the kernel
4383 changes anyth 4059 changes anything
4384 off [X86] don't p 4060 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 4061 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 4062 the hardware directly. Use this if your machine
4387 has a non-sta 4063 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 4064 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 4065 hardware access methods are allowed. Use this
4390 if you experi 4066 if you experience crashes upon bootup and you
4391 suspect they 4067 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 4068 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 4069 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 4070 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 4071 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 4072 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 4073 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 4074 bus number. The config space is then accessed
4399 through ports 4075 through ports 0xC000-0xCFFF).
4400 See http://wi 4076 See http://wiki.osdev.org/PCI for more info
4401 on the config 4077 on the configuration access mechanisms.
4402 noaer [PCIE] If the 4078 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 4079 enabled, this kernel boot option can be used to
4404 disable the u 4080 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 4081 nodomains [PCI] Disable support for multiple PCI
4406 root domains 4082 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 4083 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 4084 Configuration
4409 check_enable_amd_mmconf [X86] 4085 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 4086 properly configured MMIO access to PCI
4411 config space 4087 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 4088 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 4089 enabled, this kernel boot option can be used to
4414 disable the u 4090 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 4091 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 4092 Safety option to keep boot IRQs enabled. This
4417 should never 4093 should never be necessary.
4418 ioapicreroute [APIC] Enable 4094 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 4095 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 4096 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 4097 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 4098 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 4099 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 4100 a chipset where boot IRQs cannot be disabled.
4425 The opposite 4101 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 4102 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 4103 routing table. These calls are known to be buggy
4428 on several ma 4104 on several machines and they hang the machine
4429 when used, bu 4105 when used, but on other computers it's the only
4430 way to get th 4106 way to get the interrupt routing table. Try
4431 this option i 4107 this option if the kernel is unable to allocate
4432 IRQs or disco 4108 IRQs or discover secondary PCI buses on your
4433 motherboard. 4109 motherboard.
4434 rom [X86] Assign 4110 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 4111 Use with caution as certain devices share
4436 address decod 4112 address decoders between ROMs and other
4437 resources. 4113 resources.
4438 norom [X86] Do not 4114 norom [X86] Do not assign address space to
4439 expansion ROM 4115 expansion ROMs that do not already have
4440 BIOS assigned 4116 BIOS assigned address ranges.
4441 nobar [X86] Do not 4117 nobar [X86] Do not assign address space to the
4442 BARs that wer 4118 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 4119 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 4120 assigned automatically to PCI devices. You can
4445 make the kern 4121 make the kernel exclude IRQs of your ISA cards
4446 this way. 4122 this way.
4447 pirqaddr=0xAAAAA [X86] 4123 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 4124 of the PIRQ table (normally generated
4449 by the BIOS) 4125 by the BIOS) if it is outside the
4450 F0000h-100000 4126 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 4127 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 4128 useful if the kernel is unable to find your
4453 secondary bus 4129 secondary buses and you want to tell it
4454 explicitly wh 4130 explicitly which ones they are.
4455 assign-busses [X86] Always 4131 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 4132 numbers ourselves, overriding
4457 whatever the 4133 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 4134 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 4135 in the BIOS $PIR table. This is needed on
4460 some systems 4136 some systems with broken BIOSes, notably
4461 some HP Pavil 4137 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 4138 notebooks. This will have no effect if ACPI
4463 IRQ routing i 4139 IRQ routing is enabled.
4464 noacpi [X86] Do not 4140 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 4141 or for PCI scanning.
4466 use_crs [X86] Use PCI 4142 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 4143 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 4144 is enabled by default. If you need to use this,
4469 please report 4145 please report a bug.
4470 nocrs [X86] Ignore 4146 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 4147 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 4148 use_e820 [X86] Use E820 reservations to exclude parts of
4473 PCI host brid 4149 PCI host bridge windows. This is a workaround
4474 for BIOS defe 4150 for BIOS defects in host bridge _CRS methods.
4475 If you need t 4151 If you need to use this, please report a bug to
4476 <linux-pci@vge 4152 <linux-pci@vger.kernel.org>.
4477 no_e820 [X86] Ignore 4153 no_e820 [X86] Ignore E820 reservations for PCI host
4478 bridge window 4154 bridge windows. This is the default on modern
4479 hardware. If 4155 hardware. If you need to use this, please report
4480 a bug to <linu 4156 a bug to <linux-pci@vger.kernel.org>.
4481 routeirq Do IRQ routin 4157 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 4158 This is normally done in pci_enable_device(),
4483 so this optio 4159 so this option is a temporary workaround
4484 for broken dr 4160 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 4161 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 4162 handle more pci cards
4487 noearly [X86] Don't d 4163 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 4164 This might help on some broken boards which
4489 machine check 4165 machine check when some devices' config space
4490 is read. But 4166 is read. But various workarounds are disabled
4491 and some IOMM 4167 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 4168 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 4169 This sorting is done to get a device
4494 order compati 4170 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 4171 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 4172 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 4173 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 4174 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 4175 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 4176 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 4177 based on its parent bus. Also set MRRS (Max
4502 Read Request 4178 Read Request Size) to the largest supported
4503 value (no lar 4179 value (no larger than the MPS that the device
4504 or bus can su 4180 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 4181 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 4182 every device is guaranteed to support. This
4507 configuration 4183 configuration allows peer-to-peer DMA between
4508 any pair of d 4184 any pair of devices, possibly at the cost of
4509 reduced perfo 4185 reduced performance. This also guarantees
4510 that hot-adde 4186 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 4187 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 4188 reserved for the CardBus bridge's IO window.
4513 The default v 4189 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 4190 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 4191 reserved for the CardBus bridge's memory
4516 window. The d 4192 window. The default value is 64 megabytes.
4517 resource_alignment= 4193 resource_alignment=
4518 Format: 4194 Format:
4519 [<order of ali 4195 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 4196 Specifies alignment and device to reassign
4521 aligned memor 4197 aligned memory resources. How to
4522 specify the d 4198 specify the device is described above.
4523 If <order of 4199 If <order of align> is not specified,
4524 PAGE_SIZE is 4200 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 4201 A PCI-PCI bridge can be specified if resource
4526 windows need 4202 windows need to be expanded.
4527 To specify th 4203 To specify the alignment for several
4528 instances of 4204 instances of a device, the PCI vendor,
4529 device, subve 4205 device, subvendor, and subdevice may be
4530 specified, e. 4206 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 4207 for 4096-byte alignment.
4532 ecrc= Enable/disabl 4208 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 4209 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 4210 bios: Use BIOS/firmware settings. This is the
4537 the default. 4211 the default.
4538 off: Turn ECR 4212 off: Turn ECRC off
4539 on: Turn ECRC 4213 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 4214 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 4215 reserved for hotplug bridge's IO window.
4542 Default size 4216 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 4217 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 4218 reserved for hotplug bridge's MMIO window.
4545 Default size 4219 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 4220 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 4221 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 4222 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 4223 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 4224 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 4225 MMIO_PREF window.
4552 Default size 4226 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 4227 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 4228 reserved for buses below a hotplug bridge.
4555 Default is 1. 4229 Default is 1.
4556 realloc= Enable/disabl 4230 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 4231 if allocations done by BIOS are too small to
4558 accommodate r 4232 accommodate resources required by all child
4559 devices. 4233 devices.
4560 off: Turn rea 4234 off: Turn realloc off
4561 on: Turn real 4235 on: Turn realloc on
4562 realloc same as reall 4236 realloc same as realloc=on
4563 noari do not use PC 4237 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 4238 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 4239 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 4240 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 4241 only look for one device below a PCIe downstream
4568 port. 4242 port.
4569 big_root_window Try to add a 4243 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 4244 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 4245 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 4246 Adding the window is slightly risky (it may
4573 conflict with 4247 conflict with unreported devices), so this
4574 taints the ke 4248 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 4249 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 4250 Specify one or more PCI devices (in the format
4577 specified abo 4251 specified above) separated by semicolons.
4578 Each device s 4252 Each device specified will have the PCI ACS
4579 redirect capa 4253 redirect capabilities forced off which will
4580 allow P2P tra 4254 allow P2P traffic between devices through
4581 bridges witho 4255 bridges without forcing it upstream. Note:
4582 this removes 4256 this removes isolation between devices and
4583 may put more 4257 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 4258 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 4259 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 4260 norid [S390] ignore the RID field and force use of
4619 one PCI domai 4261 one PCI domain per PCI function
4620 4262
4621 pcie_aspm= [PCIE] Forcibly enabl !! 4263 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 4264 Management.
4623 off Don't touch ASPM conf !! 4265 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 4266 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 4267 WARNING: Forcing ASPM on may cause system lockups.
4627 4268
4628 pcie_ports= [PCIE] PCIe port serv 4269 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 4270 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 4271 even if the platform doesn't give the OS permission to
4631 use them. This may c 4272 use them. This may cause conflicts if the platform
4632 also tries to use the 4273 also tries to use these services.
4633 dpc-native Use native PC 4274 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 4275 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 4276 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 4277 hotplug).
4637 4278
4638 pcie_port_pm= [PCIE] PCIe port powe 4279 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 4280 off Disable power management of all PCIe ports
4640 force Forcibly enable power 4281 force Forcibly enable power management of all PCIe ports
4641 4282
4642 pcie_pme= [PCIE,PM] Native PCIe 4283 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 4284 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 4285 all PCIe root ports use INTx for all services).
4645 4286
4646 pcmv= [HW,PCMCIA] BadgePAD 4287 pcmv= [HW,PCMCIA] BadgePAD 4
4647 4288
4648 pd_ignore_unused 4289 pd_ignore_unused
4649 [PM] 4290 [PM]
4650 Keep all power-domain 4291 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 4292 even if no driver has claimed them. This is useful
4652 for debug and develop 4293 for debug and development, but should not be
4653 needed on a platform 4294 needed on a platform with proper driver support.
4654 4295
>> 4296 pd. [PARIDE]
>> 4297 See Documentation/admin-guide/blockdev/paride.rst.
>> 4298
4655 pdcchassis= [PARISC,HW] Disable/E 4299 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4300 boot time.
4657 Format: { 0 | 1 } 4301 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4302 See arch/parisc/kernel/pdc_chassis.c
4659 4303
4660 percpu_alloc= [MM,EARLY] !! 4304 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4305 Currently supported values are "embed" and "page".
4663 Archs may support sub 4306 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4307 See comments in mm/percpu.c for details on each
4665 allocator. This para 4308 allocator. This parameter is primarily for debugging
4666 and performance compa 4309 and performance comparison.
4667 4310
>> 4311 pf. [PARIDE]
>> 4312 See Documentation/admin-guide/blockdev/paride.rst.
>> 4313
>> 4314 pg. [PARIDE]
>> 4315 See Documentation/admin-guide/blockdev/paride.rst.
>> 4316
4668 pirq= [SMP,APIC] Manual mp- 4317 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 4318 See Documentation/x86/i386/IO-APIC.rst.
4670 4319
4671 plip= [PPT,NET] Parallel po 4320 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4321 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4322 See also Documentation/admin-guide/parport.rst.
4674 4323
4675 pmtmr= [X86] Manual setup of 4324 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4325 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4326 e.g. pmtmr=0x508
4678 4327
4679 pmu_override= [PPC] Override the PM 4328 pmu_override= [PPC] Override the PMU.
4680 This option takes ove 4329 This option takes over the PMU facility, so it is no
4681 longer usable by perf 4330 longer usable by perf. Setting this option starts the
4682 PMU counters by setti 4331 PMU counters by setting MMCR0 to 0 (the FC bit is
4683 cleared). If a number 4332 cleared). If a number is given, then MMCR1 is set to
4684 that number, otherwis 4333 that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4685 remains 0. 4334 remains 0.
4686 4335
4687 pm_debug_messages [SUSPEND,KNL] 4336 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4337 Enable suspend/resume debug messages during boot up.
4689 4338
4690 pnp.debug=1 [PNP] 4339 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4340 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4341 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4342 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4343 current resource usage; turning this on also shows
4695 possible settings and 4344 possible settings and some assignment information.
4696 4345
4697 pnpacpi= [ACPI] 4346 pnpacpi= [ACPI]
4698 { off } 4347 { off }
4699 4348
4700 pnpbios= [ISAPNP] 4349 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4350 { on | off | curr | res | no-curr | no-res }
4702 4351
4703 pnp_reserve_irq= 4352 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4353 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4354
4706 pnp_reserve_dma= 4355 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4356 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4357
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4358 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4359 Ranges are in pairs (I/O port base and size).
4711 4360
4712 pnp_reserve_mem= 4361 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4362 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4363 autoconfiguration.
4715 Ranges are in pairs ( 4364 Ranges are in pairs (memory base and size).
4716 4365
4717 ports= [IP_VS_FTP] IPVS ftp 4366 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4367 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4368 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4369 may be specified.
4721 Format: <port>,<port> 4370 Format: <port>,<port>....
4722 4371
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 4372 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4373 It specifically disables cpuidle and sets the
4730 platform machine desc 4374 platform machine description specific power_save
4731 function to NULL. On 4375 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4376 execution priority.
4733 4377
4734 ppc_strict_facility_enable 4378 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4379 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4380 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4381 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4382 There is some performance impact when enabling this.
4739 4383
4740 ppc_tm= [PPC,EARLY] !! 4384 ppc_tm= [PPC]
4741 Format: {"off"} 4385 Format: {"off"}
4742 Disable Hardware Tran 4386 Disable Hardware Transactional Memory
4743 4387
4744 preempt= [KNL] 4388 preempt= [KNL]
4745 Select preemption mod 4389 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4390 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4391 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4392 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4393 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4394
4753 print-fatal-signals= 4395 print-fatal-signals=
4754 [KNL] debug: print fa 4396 [KNL] debug: print fatal signals
4755 4397
4756 If enabled, warn abou 4398 If enabled, warn about various signal handling
4757 related application a 4399 related application anomalies: too many signals,
4758 too many POSIX.1 time 4400 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4401 coredump - etc.
4760 4402
4761 If you hit the warnin 4403 If you hit the warning due to signal overflow,
4762 you might want to try 4404 you might want to try "ulimit -i unlimited".
4763 4405
4764 default: off. 4406 default: off.
4765 4407
4766 printk.always_kmsg_dump= 4408 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4409 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4410 panics
4769 Format: <bool> (1/Y/ 4411 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4412 default: disabled
4771 4413
4772 printk.console_no_auto_verbose= 4414 printk.console_no_auto_verbose=
4773 Disable console logle 4415 Disable console loglevel raise on oops, panic
4774 or lockdep-detected i 4416 or lockdep-detected issues (only if lock debug is on).
4775 With an exception to 4417 With an exception to setups with low baudrate on
4776 serial console, keepi 4418 serial console, keeping this 0 is a good choice
4777 in order to provide m 4419 in order to provide more debug information.
4778 Format: <bool> 4420 Format: <bool>
4779 default: 0 (auto_verb 4421 default: 0 (auto_verbose is enabled)
4780 4422
4781 printk.devkmsg={on,off,ratelimit} 4423 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4424 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4425 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4426 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4427 ratelimit - ratelimit the logging
4786 Default: ratelimit 4428 Default: ratelimit
4787 4429
4788 printk.time= Show timing data pref 4430 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4431 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4432
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] 4433 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4434 Limit processor to maximum C-state
4803 max_cstate=9 override 4435 max_cstate=9 overrides any DMI blacklist limit.
4804 4436
4805 processor.nocst [HW,ACPI] 4437 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4438 Ignore the _CST method to determine C-states,
4807 instead using the leg 4439 instead using the legacy FADT method
4808 4440
4809 profile= [KNL] Enable kernel p 4441 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4442 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4443 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4444 [defaults to kernel profiling]
4813 Param: "schedule" - p 4445 Param: "schedule" - profile schedule points.
>> 4446 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4447 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4448 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4449 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4450 statistical time based profiling.
4817 4451
4818 prompt_ramdisk= [RAM] [Deprecated] 4452 prompt_ramdisk= [RAM] [Deprecated]
4819 4453
4820 prot_virt= [S390] enable hosting 4454 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4455 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4456 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4457 Format: <bool>
4826 4458
4827 psi= [KNL] Enable or disab 4459 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4460 tracking.
4829 Format: <bool> 4461 Format: <bool>
4830 4462
4831 psmouse.proto= [HW,MOUSE] Highest PS 4463 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4464 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4465 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4466 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4467 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4468 Try to reset the device after so many bad packets
4837 (0 = never). 4469 (0 = never).
4838 psmouse.resolution= 4470 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4471 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4472 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4473 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4474 0 = disabled, 1 = enabled (default).
4843 4475
4844 pstore.backend= Specify the name of t 4476 pstore.backend= Specify the name of the pstore backend to use
4845 4477
>> 4478 pt. [PARIDE]
>> 4479 See Documentation/admin-guide/blockdev/paride.rst.
>> 4480
4846 pti= [X86-64] Control Page 4481 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4482 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4483 removes hardening, but improves performance of
4849 system calls and inte 4484 system calls and interrupts.
4850 4485
4851 on - unconditionall 4486 on - unconditionally enable
4852 off - unconditionall 4487 off - unconditionally disable
4853 auto - kernel detects 4488 auto - kernel detects whether your CPU model is
4854 vulnerable to 4489 vulnerable to issues that PTI mitigates
4855 4490
4856 Not specifying this o 4491 Not specifying this option is equivalent to pti=auto.
4857 4492
>> 4493 nopti [X86-64]
>> 4494 Equivalent to pti=off
>> 4495
4858 pty.legacy_count= 4496 pty.legacy_count=
4859 [KNL] Number of legac 4497 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4498 default number.
4861 4499
4862 quiet [KNL,EARLY] Disable m !! 4500 quiet [KNL] Disable most log messages
4863 4501
4864 r128= [HW,DRM] 4502 r128= [HW,DRM]
4865 4503
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4504 raid= [HW,RAID]
4871 See Documentation/adm 4505 See Documentation/admin-guide/md.rst.
4872 4506
4873 ramdisk_size= [RAM] Sizes of RAM di 4507 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4508 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4509
4876 ramdisk_start= [RAM] RAM disk image 4510 ramdisk_start= [RAM] RAM disk image start address
4877 4511
4878 random.trust_cpu=off !! 4512 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 4513 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 4514 CPU's random number generator (if available) to
4881 initialize the kernel !! 4515 fully seed the kernel's CRNG. Default is controlled
4882 !! 4516 by CONFIG_RANDOM_TRUST_CPU.
4883 random.trust_bootloader=off !! 4517
4884 [KNL,EARLY] Disable t !! 4518 random.trust_bootloader={on,off}
4885 passed by the bootloa !! 4519 [KNL] Enable or disable trusting the use of a
4886 initialize the kernel !! 4520 seed passed by the bootloader (if available) to
>> 4521 fully seed the kernel's CRNG. Default is controlled
>> 4522 by CONFIG_RANDOM_TRUST_BOOTLOADER.
4887 4523
4888 randomize_kstack_offset= 4524 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4525 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4526 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4527 entropy, frustrating memory corruption attacks
4892 that depend on stack 4528 that depend on stack address determinism or
4893 cross-syscall address 4529 cross-syscall address exposures. This is only
4894 available on architec 4530 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4531 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4532 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4533 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4534
4899 ras=option[,option,...] [KNL] RAS-spe 4535 ras=option[,option,...] [KNL] RAS-specific options
4900 4536
4901 cec_disable [X86] 4537 cec_disable [X86]
4902 Disable the C 4538 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4539 see CONFIG_RAS_CEC help text.
4904 4540
4905 rcu_nocbs[=cpu-list] 4541 rcu_nocbs[=cpu-list]
4906 [KNL] The optional ar 4542 [KNL] The optional argument is a cpu list,
4907 as described above. 4543 as described above.
4908 4544
4909 In kernels built with 4545 In kernels built with CONFIG_RCU_NOCB_CPU=y,
4910 enable the no-callbac 4546 enable the no-callback CPU mode, which prevents
4911 such CPUs' callbacks 4547 such CPUs' callbacks from being invoked in
4912 softirq context. Inv 4548 softirq context. Invocation of such CPUs' RCU
4913 callbacks will instea 4549 callbacks will instead be offloaded to "rcuox/N"
4914 kthreads created for 4550 kthreads created for that purpose, where "x" is
4915 "p" for RCU-preempt, 4551 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4916 for the kthreads that 4552 for the kthreads that mediate grace periods; and
4917 "N" is the CPU number 4553 "N" is the CPU number. This reduces OS jitter on
4918 the offloaded CPUs, w 4554 the offloaded CPUs, which can be useful for HPC
4919 and real-time workloa 4555 and real-time workloads. It can also improve
4920 energy efficiency for 4556 energy efficiency for asymmetric multiprocessors.
4921 4557
4922 If a cpulist is passe 4558 If a cpulist is passed as an argument, the specified
4923 list of CPUs is set t 4559 list of CPUs is set to no-callback mode from boot.
4924 4560
4925 Otherwise, if the '=' 4561 Otherwise, if the '=' sign and the cpulist
4926 arguments are omitted 4562 arguments are omitted, no CPU will be set to
4927 no-callback mode from 4563 no-callback mode from boot but the mode may be
4928 toggled at runtime vi 4564 toggled at runtime via cpusets.
4929 4565
4930 Note that this argume <<
4931 the CONFIG_RCU_NOCB_C <<
4932 <<
4933 rcu_nocb_poll [KNL] 4566 rcu_nocb_poll [KNL]
4934 Rather than requiring 4567 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4568 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4569 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4570 make these kthreads poll for callbacks.
4938 This improves the rea 4571 This improves the real-time response for the
4939 offloaded CPUs by rel 4572 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4573 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4574 energy efficiency by requiring that the kthreads
4942 periodically wake up 4575 periodically wake up to do the polling.
4943 4576
4944 rcutree.blimit= [KNL] 4577 rcutree.blimit= [KNL]
4945 Set maximum number of 4578 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4579 process in one batch.
4947 4580
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] 4581 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4582 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4583 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4584 purposes, to verify correct tree setup.
4959 4585
4960 rcutree.gp_cleanup_delay= [KNL] 4586 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4587 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4588 RCU grace-period cleanup.
4963 4589
4964 rcutree.gp_init_delay= [KNL] 4590 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4591 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4592 RCU grace-period initialization.
4967 4593
4968 rcutree.gp_preinit_delay= [KNL] 4594 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4595 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4596 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4597 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4598 the rcu_node combining tree.
4973 4599
>> 4600 rcutree.use_softirq= [KNL]
>> 4601 If set to zero, move all RCU_SOFTIRQ processing to
>> 4602 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4603 value, meaning that RCU_SOFTIRQ is used by default.
>> 4604 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4605
>> 4606 But note that CONFIG_PREEMPT_RT=y kernels disable
>> 4607 this kernel boot parameter, forcibly setting it
>> 4608 to zero.
>> 4609
>> 4610 rcutree.rcu_fanout_exact= [KNL]
>> 4611 Disable autobalancing of the rcu_node combining
>> 4612 tree. This is used by rcutorture, and might
>> 4613 possibly be useful for architectures having high
>> 4614 cache-to-cache transfer latencies.
>> 4615
>> 4616 rcutree.rcu_fanout_leaf= [KNL]
>> 4617 Change the number of CPUs assigned to each
>> 4618 leaf rcu_node structure. Useful for very
>> 4619 large systems, which will choose the value 64,
>> 4620 and for NUMA systems with large remote-access
>> 4621 latencies, which will choose a value aligned
>> 4622 with the appropriate hardware boundaries.
>> 4623
>> 4624 rcutree.rcu_min_cached_objs= [KNL]
>> 4625 Minimum number of objects which are cached and
>> 4626 maintained per one CPU. Object size is equal
>> 4627 to PAGE_SIZE. The cache allows to reduce the
>> 4628 pressure to page allocator, also it makes the
>> 4629 whole algorithm to behave better in low memory
>> 4630 condition.
>> 4631
>> 4632 rcutree.rcu_delay_page_cache_fill_msec= [KNL]
>> 4633 Set the page-cache refill delay (in milliseconds)
>> 4634 in response to low-memory conditions. The range
>> 4635 of permitted values is in the range 0:100000.
>> 4636
4974 rcutree.jiffies_till_first_fqs= [KNL] 4637 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4638 Set delay from grace-period initialization to
4976 first attempt to forc 4639 first attempt to force quiescent states.
4977 Units are jiffies, mi 4640 Units are jiffies, minimum value is zero,
4978 and maximum value is 4641 and maximum value is HZ.
4979 4642
4980 rcutree.jiffies_till_next_fqs= [KNL] 4643 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4644 Set delay between subsequent attempts to force
4982 quiescent states. Un 4645 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4646 value is one, and maximum value is HZ.
4984 4647
4985 rcutree.jiffies_till_sched_qs= [KNL] 4648 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4649 Set required age in jiffies for a
4987 given grace period be 4650 given grace period before RCU starts
4988 soliciting quiescent- 4651 soliciting quiescent-state help from
4989 rcu_note_context_swit 4652 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4653 If not specified, the kernel will calculate
4991 a value based on the 4654 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4655 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4656 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4657 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4658 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4659 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4660 overwritten.
4998 4661
4999 rcutree.kthread_prio= [KNL,BOOT] 4662 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4663 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4664 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4665 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4666 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4667 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4668 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4669 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4670 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4671 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is 4672 When RCU_NOCB_CPU is set, also adjust the
5010 priority of NOCB call 4673 priority of NOCB callback kthreads.
5011 4674
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 4675 rcutree.rcu_nocb_gp_stride= [KNL]
5013 On callback-offloaded !! 4676 Set the number of NOCB callback kthreads in
5014 RCU reduces the lock !! 4677 each group, which defaults to the square root
5015 otherwise be caused b !! 4678 of the number of CPUs. Larger numbers reduce
5016 use of the ->nocb_byp !! 4679 the wakeup overhead on the global grace-period
5017 common non-flooded ca !! 4680 kthread, but increases that same overhead on
5018 the main ->cblist in !! 4681 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 4682
5033 rcutree.qhimark= [KNL] 4683 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4684 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4685 batch limiting is disabled.
5036 4686
5037 rcutree.qlowmark= [KNL] 4687 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4688 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4689 batch limiting is re-enabled.
5040 4690
5041 rcutree.qovld= [KNL] 4691 rcutree.qovld= [KNL]
5042 Set threshold of queu 4692 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4693 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4694 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4695 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4696 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4697 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4698 disable more aggressive help enlistment.
5049 4699
5050 rcutree.rcu_delay_page_cache_fill_mse <<
5051 Set the page-cache re <<
5052 in response to low-me <<
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 <<
5100 rcutree.rcu_kick_kthreads= [KNL] 4700 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4701 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4702 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4703 it should at force-quiescent-state time.
5104 This wake_up() will b 4704 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4705 WARN_ONCE() splat and an ftrace_dump().
5106 4706
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] 4707 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4708 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4709 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4710 in microseconds. This defaults to zero.
5118 Larger delays increas 4711 Larger delays increase the probability of
5119 catching RCU pointer 4712 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4713 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4714 rcu_read_unlock() has completed.
5122 4715
5123 rcutree.sysrq_rcu= [KNL] 4716 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4717 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4718 rcu_node tree with an eye towards determining
5126 why a new grace perio 4719 why a new grace period has not yet started.
5127 4720
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] 4721 rcuscale.gp_async= [KNL]
5158 Measure performance o 4722 Measure performance of asynchronous
5159 grace-period primitiv 4723 grace-period primitives such as call_rcu().
5160 4724
5161 rcuscale.gp_async_max= [KNL] 4725 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4726 Specify the maximum number of outstanding
5163 callbacks per writer 4727 callbacks per writer thread. When a writer
5164 thread exceeds this l 4728 thread exceeds this limit, it invokes the
5165 corresponding flavor 4729 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4730 previously posted callbacks to drain.
5167 4731
5168 rcuscale.gp_exp= [KNL] 4732 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4733 Measure performance of expedited synchronous
5170 grace-period primitiv 4734 grace-period primitives.
5171 4735
5172 rcuscale.holdoff= [KNL] 4736 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4737 Set test-start holdoff period. The purpose of
5174 this parameter is to 4738 this parameter is to delay the start of the
5175 test until boot compl 4739 test until boot completes in order to avoid
5176 interference. 4740 interference.
5177 4741
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] 4742 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4743 Set to measure performance of kfree_rcu() flooding.
5189 4744
5190 rcuscale.kfree_rcu_test_double= [KNL] 4745 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 4746 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 4747 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 4748 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 4749 and double-argument variants are tested.
5195 4750
5196 rcuscale.kfree_rcu_test_single= [KNL] 4751 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 4752 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 4753 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 4754 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 4755 and double-argument variants are tested.
5201 4756
5202 rcuscale.kfree_nthreads= [KNL] 4757 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4758 The number of threads running loops of kfree_rcu().
5204 4759
5205 rcuscale.kfree_alloc_num= [KNL] 4760 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4761 Number of allocations and frees done in an iteration.
5207 4762
5208 rcuscale.kfree_loops= [KNL] 4763 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4764 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4765 of allocations and frees.
5211 4766
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] 4767 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4768 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4769 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4770 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4771 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4772 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4773 A value of "n" less than or equal to -N selects
5225 a single reader. 4774 a single reader.
5226 4775
5227 rcuscale.nwriters= [KNL] 4776 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4777 Set number of RCU writers. The values operate
5229 the same as for rcusc 4778 the same as for rcuscale.nreaders.
5230 N, where N is the num 4779 N, where N is the number of CPUs
5231 4780
5232 rcuscale.scale_type= [KNL] !! 4781 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4782 Specify the RCU implementation to test.
5234 4783
5235 rcuscale.shutdown= [KNL] 4784 rcuscale.shutdown= [KNL]
5236 Shut the system down 4785 Shut the system down after performance tests
5237 complete. This is us 4786 complete. This is useful for hands-off automated
5238 testing. 4787 testing.
5239 4788
5240 rcuscale.verbose= [KNL] 4789 rcuscale.verbose= [KNL]
5241 Enable additional pri 4790 Enable additional printk() statements.
5242 4791
5243 rcuscale.writer_holdoff= [KNL] 4792 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4793 Write-side holdoff between grace periods,
5245 in microseconds. The 4794 in microseconds. The default of zero says
5246 no holdoff. 4795 no holdoff.
5247 4796
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] 4797 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4798 Set duration of force_quiescent_state bursts
5255 in microseconds. 4799 in microseconds.
5256 4800
5257 rcutorture.fqs_holdoff= [KNL] 4801 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4802 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4803 in microseconds.
5260 4804
5261 rcutorture.fqs_stutter= [KNL] 4805 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4806 Set wait time between force_quiescent_state bursts
5263 in seconds. 4807 in seconds.
5264 4808
5265 rcutorture.fwd_progress= [KNL] 4809 rcutorture.fwd_progress= [KNL]
5266 Specifies the number 4810 Specifies the number of kthreads to be used
5267 for RCU grace-period 4811 for RCU grace-period forward-progress testing
5268 for the types of RCU 4812 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread 4813 Defaults to 1 kthread, values less than zero or
5270 greater than the numb 4814 greater than the number of CPUs cause the number
5271 of CPUs to be used. 4815 of CPUs to be used.
5272 4816
5273 rcutorture.fwd_progress_div= [KNL] 4817 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4818 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4819 period to do tight-loop forward-progress testing.
5276 4820
5277 rcutorture.fwd_progress_holdoff= [KNL 4821 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4822 Number of seconds to wait between successive
5279 forward-progress test 4823 forward-progress tests.
5280 4824
5281 rcutorture.fwd_progress_need_resched= 4825 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4826 Enclose cond_resched() calls within checks for
5283 need_resched() during 4827 need_resched() during tight-loop forward-progress
5284 testing. 4828 testing.
5285 4829
5286 rcutorture.gp_cond= [KNL] 4830 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4831 Use conditional/asynchronous update-side
5288 primitives, if availa 4832 primitives, if available.
5289 4833
5290 rcutorture.gp_exp= [KNL] 4834 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4835 Use expedited update-side primitives, if available.
5292 4836
5293 rcutorture.gp_normal= [KNL] 4837 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4838 Use normal (non-expedited) asynchronous
5295 update-side primitive 4839 update-side primitives, if available.
5296 4840
5297 rcutorture.gp_sync= [KNL] 4841 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4842 Use normal (non-expedited) synchronous
5299 update-side primitive 4843 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4844 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4845 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4846 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4847 they are all non-zero.
5304 4848
5305 rcutorture.irqreader= [KNL] 4849 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4850 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4851 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4852 flavors take kindly to this sort of thing.
5309 4853
5310 rcutorture.leakpointer= [KNL] 4854 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4855 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4856 This can of course result in splats, and is
5313 intended to test the 4857 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4858 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4859 such leaks.
5316 4860
5317 rcutorture.n_barrier_cbs= [KNL] 4861 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4862 Set callbacks/threads for rcu_barrier() testing.
5319 4863
5320 rcutorture.nfakewriters= [KNL] 4864 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4865 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4866 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4867 test, hence the "fake".
5324 4868
5325 rcutorture.nocbs_nthreads= [KNL] 4869 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 4870 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 4871 Zero (the default) disables toggling.
5328 4872
5329 rcutorture.nocbs_toggle= [KNL] 4873 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 4874 Set the delay in milliseconds between successive
5331 callback-offload togg 4875 callback-offload toggling attempts.
5332 4876
5333 rcutorture.nreaders= [KNL] 4877 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4878 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4879 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4880 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 4881 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 4882 (the number of CPUs), -3 selects N+1, and so on.
5339 4883
5340 rcutorture.object_debug= [KNL] 4884 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 4885 Enable debug-object double-call_rcu() testing.
5342 4886
5343 rcutorture.onoff_holdoff= [KNL] 4887 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 4888 Set time (s) after boot for CPU-hotplug testing.
5345 4889
5346 rcutorture.onoff_interval= [KNL] 4890 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 4891 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 4892 or zero to disable CPU-hotplug testing.
5349 4893
5350 rcutorture.read_exit= [KNL] 4894 rcutorture.read_exit= [KNL]
5351 Set the number of rea 4895 Set the number of read-then-exit kthreads used
5352 to test the interacti 4896 to test the interaction of RCU updaters and
5353 task-exit processing. 4897 task-exit processing.
5354 4898
5355 rcutorture.read_exit_burst= [KNL] 4899 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 4900 The number of times in a given read-then-exit
5357 episode that a set of 4901 episode that a set of read-then-exit kthreads
5358 is spawned. 4902 is spawned.
5359 4903
5360 rcutorture.read_exit_delay= [KNL] 4904 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 4905 The delay, in seconds, between successive
5362 read-then-exit testin 4906 read-then-exit testing episodes.
5363 4907
5364 rcutorture.shuffle_interval= [KNL] 4908 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 4909 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 4910 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 4911 during the rcutorture test.
5368 4912
5369 rcutorture.shutdown_secs= [KNL] 4913 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 4914 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 4915 is useful for hands-off automated testing.
5372 4916
5373 rcutorture.stall_cpu= [KNL] 4917 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 4918 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 4919 warnings, zero to disable.
5376 4920
5377 rcutorture.stall_cpu_block= [KNL] 4921 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 4922 Sleep while stalling if set. This will result
5379 in warnings from pree !! 4923 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 4924 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 4925
5391 rcutorture.stall_cpu_holdoff= [KNL] 4926 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 4927 Time to wait (s) after boot before inducing stall.
5393 4928
5394 rcutorture.stall_cpu_irqsoff= [KNL] 4929 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 4930 Disable interrupts while stalling if set.
5396 4931
5397 rcutorture.stall_gp_kthread= [KNL] 4932 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 4933 Duration (s) of forced sleep within RCU
5399 grace-period kthread 4934 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 4935 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 4936 and stall_gp_kthread are specified, the
5402 kthread is starved fi 4937 kthread is starved first, then the CPU.
5403 4938
5404 rcutorture.stat_interval= [KNL] 4939 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 4940 Time (s) between statistics printk()s.
5406 4941
5407 rcutorture.stutter= [KNL] 4942 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 4943 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 4944 five seconds causes the test to run for five seconds,
5410 wait for five seconds 4945 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 4946 ability to transition abruptly to and from idle.
5412 4947
5413 rcutorture.test_boost= [KNL] 4948 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 4949 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 4950 "Maybe" means test if the RCU implementation
5416 under test support RC 4951 under test support RCU priority boosting.
5417 4952
5418 rcutorture.test_boost_duration= [KNL] 4953 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 4954 Duration (s) of each individual boost test.
5420 4955
5421 rcutorture.test_boost_interval= [KNL] 4956 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 4957 Interval (s) between each boost test.
5423 4958
5424 rcutorture.test_no_idle_hz= [KNL] 4959 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 4960 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 4961 rcutorture.shuffle_interval parameter.
5427 4962
5428 rcutorture.torture_type= [KNL] 4963 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 4964 Specify the RCU implementation to test.
5430 4965
5431 rcutorture.verbose= [KNL] 4966 rcutorture.verbose= [KNL]
5432 Enable additional pri 4967 Enable additional printk() statements.
5433 4968
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 4969 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 4970 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 4971 stall warning.
5437 4972
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 4973 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 4974 Suppress RCU CPU stall warning messages.
5446 4975
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 4976 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 4977 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 4978 rcutorture writer stall warnings that occur
5450 during early boot, th 4979 during early boot, that is, during the time
5451 before the init task 4980 before the init task is spawned.
5452 4981
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 4982 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 4983 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon 4984 The value is in seconds and the maximum allowed
5456 value is 300 seconds. 4985 value is 300 seconds.
5457 4986
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ 4987 rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5459 Set timeout for exped 4988 Set timeout for expedited RCU CPU stall warning
5460 messages. The value 4989 messages. The value is in milliseconds
5461 and the maximum allow 4990 and the maximum allowed value is 21000
5462 milliseconds. Please 4991 milliseconds. Please note that this value is
5463 adjusted to an arch t 4992 adjusted to an arch timer tick resolution.
5464 Setting this to zero 4993 Setting this to zero causes the value from
5465 rcupdate.rcu_cpu_stal 4994 rcupdate.rcu_cpu_stall_timeout to be used (after
5466 conversion from secon 4995 conversion from seconds to milliseconds).
5467 4996
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 <<
5479 rcupdate.rcu_expedited= [KNL] 4997 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 4998 Use expedited grace-period primitives, for
5481 example, synchronize_ 4999 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 5000 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 5001 but can increase CPU utilization, degrade
5484 real-time latency, an 5002 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 5003 No effect on CONFIG_TINY_RCU kernels.
5486 5004
5487 rcupdate.rcu_normal= [KNL] 5005 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 5006 Use only normal grace-period primitives,
5489 for example, synchron 5007 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 5008 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 5009 real-time latency, CPU utilization, and
5492 energy efficiency, bu 5010 energy efficiency, but can expose users to
5493 increased grace-perio 5011 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 5012 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 5013 CONFIG_TINY_RCU kernels.
5496 5014
5497 rcupdate.rcu_normal_after_boot= [KNL] 5015 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 5016 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 5017 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 5018 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 5019 on CONFIG_TINY_RCU kernels.
5502 5020
5503 But note that CONFIG_ 5021 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 5022 this kernel boot parameter, forcibly setting
5505 it to the value one, 5023 it to the value one, that is, converting any
5506 post-boot attempt at 5024 post-boot attempt at an expedited RCU grace
5507 period to instead use 5025 period to instead use normal non-expedited
5508 grace-period processi 5026 grace-period processing.
5509 5027
5510 rcupdate.rcu_task_collapse_lim= [KNL] 5028 rcupdate.rcu_task_collapse_lim= [KNL]
5511 Set the maximum numbe 5029 Set the maximum number of callbacks present
5512 at the beginning of a 5030 at the beginning of a grace period that allows
5513 the RCU Tasks flavors 5031 the RCU Tasks flavors to collapse back to using
5514 a single callback que 5032 a single callback queue. This switching only
5515 occurs when rcupdate. 5033 occurs when rcupdate.rcu_task_enqueue_lim is
5516 set to the default va 5034 set to the default value of -1.
5517 5035
5518 rcupdate.rcu_task_contend_lim= [KNL] 5036 rcupdate.rcu_task_contend_lim= [KNL]
5519 Set the minimum numbe 5037 Set the minimum number of callback-queuing-time
5520 lock-contention event 5038 lock-contention events per jiffy required to
5521 cause the RCU Tasks f 5039 cause the RCU Tasks flavors to switch to per-CPU
5522 callback queuing. Th 5040 callback queuing. This switching only occurs
5523 when rcupdate.rcu_tas 5041 when rcupdate.rcu_task_enqueue_lim is set to
5524 the default value of 5042 the default value of -1.
5525 5043
5526 rcupdate.rcu_task_enqueue_lim= [KNL] 5044 rcupdate.rcu_task_enqueue_lim= [KNL]
5527 Set the number of cal 5045 Set the number of callback queues to use for the
5528 RCU Tasks family of R 5046 RCU Tasks family of RCU flavors. The default
5529 of -1 allows this to 5047 of -1 allows this to be automatically (and
5530 dynamically) adjusted 5048 dynamically) adjusted. This parameter is intended
5531 for use in testing. 5049 for use in testing.
5532 5050
5533 rcupdate.rcu_task_ipi_delay= [KNL] 5051 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 5052 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 5053 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 5054 of a given grace period. Setting a large
5537 number avoids disturb 5055 number avoids disturbing real-time workloads,
5538 but lengthens grace p 5056 but lengthens grace periods.
5539 5057
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] 5058 rcupdate.rcu_task_stall_info= [KNL]
5548 Set initial timeout i 5059 Set initial timeout in jiffies for RCU task stall
5549 informational message 5060 informational messages, which give some indication
5550 of the problem for th 5061 of the problem for those not patient enough to
5551 wait for ten minutes. 5062 wait for ten minutes. Informational messages are
5552 only printed prior to 5063 only printed prior to the stall-warning message
5553 for a given grace per 5064 for a given grace period. Disable with a value
5554 less than or equal to 5065 less than or equal to zero. Defaults to ten
5555 seconds. A change in 5066 seconds. A change in value does not take effect
5556 until the beginning o 5067 until the beginning of the next grace period.
5557 5068
5558 rcupdate.rcu_task_stall_info_mult= [K 5069 rcupdate.rcu_task_stall_info_mult= [KNL]
5559 Multiplier for time i 5070 Multiplier for time interval between successive
5560 RCU task stall inform 5071 RCU task stall informational messages for a given
5561 RCU tasks grace perio 5072 RCU tasks grace period. This value is clamped
5562 to one through ten, i 5073 to one through ten, inclusive. It defaults to
5563 the value three, so t 5074 the value three, so that the first informational
5564 message is printed 10 5075 message is printed 10 seconds into the grace
5565 period, the second at 5076 period, the second at 40 seconds, the third at
5566 160 seconds, and then 5077 160 seconds, and then the stall warning at 600
5567 seconds would prevent 5078 seconds would prevent a fourth at 640 seconds.
5568 5079
5569 rcupdate.rcu_task_stall_timeout= [KNL 5080 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie 5081 Set timeout in jiffies for RCU task stall
5571 warning messages. Di 5082 warning messages. Disable with a value less
5572 than or equal to zero 5083 than or equal to zero. Defaults to ten minutes.
5573 A change in value doe 5084 A change in value does not take effect until
5574 the beginning of the 5085 the beginning of the next grace period.
5575 5086
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 <<
5599 rcupdate.rcu_self_test= [KNL] 5087 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 5088 Run the RCU early boot self tests
5601 5089
5602 rdinit= [KNL] 5090 rdinit= [KNL]
5603 Format: <full_path> 5091 Format: <full_path>
5604 Run specified binary 5092 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 5093 used for early userspace startup. See initrd.
5606 5094
5607 rdrand= [X86,EARLY] !! 5095 rdrand= [X86]
5608 force - Override the 5096 force - Override the decision by the kernel to hide the
5609 advertisement 5097 advertisement of RDRAND support (this affects
5610 certain AMD p 5098 certain AMD processors because of buggy BIOS
5611 support, spec 5099 support, specifically around the suspend/resume
5612 path). 5100 path).
5613 5101
5614 rdt= [HW,X86,RDT] 5102 rdt= [HW,X86,RDT]
5615 Turn on/off individua 5103 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 5104 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 5105 mba.
5618 E.g. to turn on cmt a 5106 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 5107 rdt=cmt,!mba
5620 5108
5621 reboot= [KNL] 5109 reboot= [KNL]
5622 Format (x86 or x86_64 5110 Format (x86 or x86_64):
5623 [w[arm] | c[o 5111 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5624 [[,]s[mp]#### 5112 [[,]s[mp]#### \
5625 [[,]b[ios] | 5113 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 5114 [[,]f[orce]
5627 Where reboot_mode is 5115 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 5116 (prefix with 'panic_' to set mode for panic
5629 reboo 5117 reboot only),
5630 reboot_type is 5118 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 5119 reboot_force is either force or not specified,
5632 reboot_cpu is s 5120 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 5121 to be used for rebooting.
5634 5122
5635 refscale.holdoff= [KNL] 5123 refscale.holdoff= [KNL]
5636 Set test-start holdof 5124 Set test-start holdoff period. The purpose of
5637 this parameter is to 5125 this parameter is to delay the start of the
5638 test until boot compl 5126 test until boot completes in order to avoid
5639 interference. 5127 interference.
5640 5128
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] 5129 refscale.loops= [KNL]
5648 Set the number of loo 5130 Set the number of loops over the synchronization
5649 primitive under test. 5131 primitive under test. Increasing this number
5650 reduces noise due to 5132 reduces noise due to loop start/end overhead,
5651 but the default has a 5133 but the default has already reduced the per-pass
5652 noise to a handful of 5134 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 5135 x86 laptops.
5654 5136
5655 refscale.nreaders= [KNL] 5137 refscale.nreaders= [KNL]
5656 Set number of readers 5138 Set number of readers. The default value of -1
5657 selects N, where N is 5139 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 5140 of CPUs. A value of zero is an interesting choice.
5659 5141
5660 refscale.nruns= [KNL] 5142 refscale.nruns= [KNL]
5661 Set number of runs, e 5143 Set number of runs, each of which is dumped onto
5662 the console log. 5144 the console log.
5663 5145
5664 refscale.readdelay= [KNL] 5146 refscale.readdelay= [KNL]
5665 Set the read-side cri 5147 Set the read-side critical-section duration,
5666 measured in microseco 5148 measured in microseconds.
5667 5149
5668 refscale.scale_type= [KNL] 5150 refscale.scale_type= [KNL]
5669 Specify the read-prot 5151 Specify the read-protection implementation to test.
5670 5152
5671 refscale.shutdown= [KNL] 5153 refscale.shutdown= [KNL]
5672 Shut down the system 5154 Shut down the system at the end of the performance
5673 test. This defaults 5155 test. This defaults to 1 (shut it down) when
5674 refscale is built int 5156 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 5157 it running) when refscale is built as a module.
5676 5158
5677 refscale.verbose= [KNL] 5159 refscale.verbose= [KNL]
5678 Enable additional pri 5160 Enable additional printk() statements.
5679 5161
5680 refscale.verbose_batched= [KNL] 5162 refscale.verbose_batched= [KNL]
5681 Batch the additional 5163 Batch the additional printk() statements. If zero
5682 (the default) or nega 5164 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 5165 print every Nth verbose statement, where N is the value
5684 specified. 5166 specified.
5685 5167
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= 5168 relax_domain_level=
5694 [KNL, SMP] Set schedu 5169 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 5170 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 5171
5697 reserve= [KNL,BUGS] Force kern 5172 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 5173 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 5174 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 5175 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 5176 is assumed to be I/O ports; otherwise it is memory.
5702 5177
5703 reserve_mem= [RAM] !! 5178 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] 5179 Format: nn[KMG]
5727 Reserves a hole at th 5180 Reserves a hole at the top of the kernel virtual
5728 address space. 5181 address space.
5729 5182
5730 reset_devices [KNL] Force drivers t 5183 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 5184 during initialization.
5732 5185
5733 resume= [SWSUSP] 5186 resume= [SWSUSP]
5734 Specify the partition 5187 Specify the partition device for software suspend
5735 Format: 5188 Format:
5736 {/dev/<dev> | PARTUUI 5189 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 5190
5738 resume_offset= [SWSUSP] 5191 resume_offset= [SWSUSP]
5739 Specify the offset fr 5192 Specify the offset from the beginning of the partition
5740 given by "resume=" at 5193 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 5194 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 5195 See Documentation/power/swsusp-and-swap-files.rst
5743 5196
5744 resumedelay= [HIBERNATION] Delay ( 5197 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 5198 read the resume files
5746 5199
5747 resumewait [HIBERNATION] Wait (i 5200 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 5201 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 5202 (e.g. USB and MMC devices).
5750 5203
5751 retain_initrd [RAM] Keep initrd mem !! 5204 retain_initrd [RAM] Keep initrd memory after extraction
5752 be accessible via /sy <<
5753 5205
5754 retbleed= [X86] Control mitigat 5206 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 5207 Speculative Code Execution with Return Instructions)
5756 vulnerability. 5208 vulnerability.
5757 5209
5758 AMD-based UNRET and I 5210 AMD-based UNRET and IBPB mitigations alone do not stop
5759 sibling threads from 5211 sibling threads from influencing the predictions of other
5760 sibling threads. For 5212 sibling threads. For that reason, STIBP is used on pro-
5761 cessors that support 5213 cessors that support it, and mitigate SMT on processors
5762 that don't. 5214 that don't.
5763 5215
5764 off - no mit 5216 off - no mitigation
5765 auto - automa 5217 auto - automatically select a migitation
5766 auto,nosmt - automa 5218 auto,nosmt - automatically select a mitigation,
5767 disabl 5219 disabling SMT if necessary for
5768 the fu 5220 the full mitigation (only on Zen1
5769 and ol 5221 and older without STIBP).
5770 ibpb - On AMD 5222 ibpb - On AMD, mitigate short speculation
5771 window 5223 windows on basic block boundaries too.
5772 Safe, 5224 Safe, highest perf impact. It also
5773 enable 5225 enables STIBP if present. Not suitable
5774 on Int 5226 on Intel.
5775 ibpb,nosmt - Like " 5227 ibpb,nosmt - Like "ibpb" above but will disable SMT
5776 when S 5228 when STIBP is not available. This is
5777 the al 5229 the alternative for systems which do not
5778 have S 5230 have STIBP.
5779 unret - Force 5231 unret - Force enable untrained return thunks,
5780 only e 5232 only effective on AMD f15h-f17h based
5781 system 5233 systems.
5782 unret,nosmt - Like u 5234 unret,nosmt - Like unret, but will disable SMT when STIBP
5783 is not 5235 is not available. This is the alternative for
5784 system 5236 systems which do not have STIBP.
5785 5237
5786 Selecting 'auto' will 5238 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 5239 time according to the CPU.
5788 5240
5789 Not specifying this o 5241 Not specifying this option is equivalent to retbleed=auto.
5790 5242
5791 rfkill.default_state= 5243 rfkill.default_state=
5792 0 "airplane mode". All 5244 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 5245 etc. communication is blocked by default.
5794 1 Unblocked. 5246 1 Unblocked.
5795 5247
5796 rfkill.master_switch_mode= 5248 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 5249 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 5250 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 5251 blocked and the previous configuration.
5800 2 The "airplane mode" b 5252 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 5253 blocked and everything unblocked.
5802 5254
>> 5255 rhash_entries= [KNL,NET]
>> 5256 Set number of hash buckets for route cache
>> 5257
5803 ring3mwait=disable 5258 ring3mwait=disable
5804 [KNL] Disable ring 3 5259 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 5260 CPUs.
5806 5261
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 5262 ro [KNL] Mount root device read-only on boot
5815 5263
5816 rodata= [KNL,EARLY] !! 5264 rodata= [KNL]
5817 on Mark read-only kernel 5265 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 5266 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel 5267 full Mark read-only kernel memory and aliases as read-only
5820 [arm64] 5268 [arm64]
5821 5269
5822 rockchip.usb_uart 5270 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 5271 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 5272 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 5273 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 5274 port and the regular usb controller gets disabled.
5828 5275
5829 root= [KNL] Root filesystem 5276 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 5277 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 5278
5837 rootdelay= [KNL] Delay (in secon 5279 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 5280 mount the root filesystem
5839 5281
5840 rootflags= [KNL] Set root filesy 5282 rootflags= [KNL] Set root filesystem mount option string
5841 5283
5842 rootfstype= [KNL] Set root filesy 5284 rootfstype= [KNL] Set root filesystem type
5843 5285
5844 rootwait [KNL] Wait (indefinit 5286 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 5287 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 5288 (e.g. USB and MMC devices).
5847 5289
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 5290 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 5291 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 5292 Memory area to be used by remote processor image,
5855 managed by CMA. 5293 managed by CMA.
5856 5294
5857 rw [KNL] Mount root devi 5295 rw [KNL] Mount root device read-write on boot
5858 5296
5859 S [KNL] Run init in sin 5297 S [KNL] Run init in single mode
5860 5298
5861 s390_iommu= [HW,S390] 5299 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 5300 Set s390 IOTLB flushing mode
5863 strict 5301 strict
5864 With strict flushing !! 5302 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 5303 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 5304 which is faster.
5867 iommu.strict=1. <<
5868 5305
5869 s390_iommu_aperture= [KNL,S390] 5306 s390_iommu_aperture= [KNL,S390]
5870 Specifies the size of 5307 Specifies the size of the per device DMA address space
5871 accessible through th 5308 accessible through the DMA and IOMMU APIs as a decimal
5872 factor of the size of 5309 factor of the size of main memory.
5873 The default is 1 mean 5310 The default is 1 meaning that one can concurrently use
5874 as many DMA addresses 5311 as many DMA addresses as physical memory is installed,
5875 if supported by hardw 5312 if supported by hardware, and thus map all of memory
5876 once. With a value of 5313 once. With a value of 2 one can map all of memory twice
5877 and so on. As a speci 5314 and so on. As a special case a factor of 0 imposes no
5878 restrictions other th 5315 restrictions other than those given by hardware at the
5879 cost of significant a 5316 cost of significant additional memory use for tables.
5880 5317
5881 sa1100ir [NET] 5318 sa1100ir [NET]
5882 See drivers/net/irda/ 5319 See drivers/net/irda/sa1100_ir.c.
5883 5320
5884 sched_verbose [KNL,EARLY] Enables v !! 5321 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 5322
5886 schedstats= [KNL,X86] Enable or d 5323 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 5324 Allowed values are enable and disable. This feature
5888 incurs a small amount 5325 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 5326 but is useful for debugging and performance tuning.
5890 5327
5891 sched_thermal_decay_shift= 5328 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 5329 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 5330 pressure signal. Thermal pressure signal follows the
5895 default decay period 5331 default decay period of other scheduler pelt
5896 signals(usually 32 ms 5332 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 5333 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 5334 period for the thermal pressure signal by the shift
5899 value. 5335 value.
5900 i.e. with the default 5336 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 5337 sched_thermal_decay_shift thermal pressure decay pr
5902 1 5338 1 64 ms
5903 2 5339 2 128 ms
5904 and so on. 5340 and so on.
5905 Format: integer betwe 5341 Format: integer between 0 and 10
5906 Default is 0. 5342 Default is 0.
5907 5343
5908 scftorture.holdoff= [KNL] 5344 scftorture.holdoff= [KNL]
5909 Number of seconds to 5345 Number of seconds to hold off before starting
5910 test. Defaults to ze 5346 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 5347 to 10 seconds for built-in smp_call_function()
5912 tests. 5348 tests.
5913 5349
5914 scftorture.longwait= [KNL] 5350 scftorture.longwait= [KNL]
5915 Request ridiculously 5351 Request ridiculously long waits randomly selected
5916 up to the chosen limi 5352 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 5353 default) disables this feature. Please note
5918 that requesting even 5354 that requesting even small non-zero numbers of
5919 seconds can result in 5355 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 5356 softlockup complaints, and so on.
5921 5357
5922 scftorture.nthreads= [KNL] 5358 scftorture.nthreads= [KNL]
5923 Number of kthreads to 5359 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 5360 smp_call_function() family of functions.
5925 The default of -1 spe 5361 The default of -1 specifies a number of kthreads
5926 equal to the number o 5362 equal to the number of CPUs.
5927 5363
5928 scftorture.onoff_holdoff= [KNL] 5364 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 5365 Number seconds to wait after the start of the
5930 test before initiatin 5366 test before initiating CPU-hotplug operations.
5931 5367
5932 scftorture.onoff_interval= [KNL] 5368 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 5369 Number seconds to wait between successive
5934 CPU-hotplug operation 5370 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 5371 is the default) disables CPU-hotplug operations.
5936 5372
5937 scftorture.shutdown_secs= [KNL] 5373 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 5374 The number of seconds following the start of the
5939 test after which to s 5375 test after which to shut down the system. The
5940 default of zero avoid 5376 default of zero avoids shutting down the system.
5941 Non-zero values are u 5377 Non-zero values are useful for automated tests.
5942 5378
5943 scftorture.stat_interval= [KNL] 5379 scftorture.stat_interval= [KNL]
5944 The number of seconds 5380 The number of seconds between outputting the
5945 current test statisti 5381 current test statistics to the console. A value
5946 of zero disables stat 5382 of zero disables statistics output.
5947 5383
5948 scftorture.stutter_cpus= [KNL] 5384 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 5385 The number of jiffies to wait between each change
5950 to the set of CPUs un 5386 to the set of CPUs under test.
5951 5387
5952 scftorture.use_cpus_read_lock= [KNL] 5388 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 5389 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 5390 preempt_disable() to disable CPU hotplug
5955 while invoking one of 5391 while invoking one of the smp_call_function*()
5956 functions. 5392 functions.
5957 5393
5958 scftorture.verbose= [KNL] 5394 scftorture.verbose= [KNL]
5959 Enable additional pri 5395 Enable additional printk() statements.
5960 5396
5961 scftorture.weight_single= [KNL] 5397 scftorture.weight_single= [KNL]
5962 The probability weigh 5398 The probability weighting to use for the
5963 smp_call_function_sin 5399 smp_call_function_single() function with a zero
5964 "wait" parameter. A 5400 "wait" parameter. A value of -1 selects the
5965 default if all other 5401 default if all other weights are -1. However,
5966 if at least one weigh 5402 if at least one weight has some other value, a
5967 value of -1 will inst 5403 value of -1 will instead select a weight of zero.
5968 5404
5969 scftorture.weight_single_wait= [KNL] 5405 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 5406 The probability weighting to use for the
5971 smp_call_function_sin 5407 smp_call_function_single() function with a
5972 non-zero "wait" param 5408 non-zero "wait" parameter. See weight_single.
5973 5409
5974 scftorture.weight_many= [KNL] 5410 scftorture.weight_many= [KNL]
5975 The probability weigh 5411 The probability weighting to use for the
5976 smp_call_function_man 5412 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 5413 "wait" parameter. See weight_single.
5978 Note well that settin 5414 Note well that setting a high probability for
5979 this weighting can pl 5415 this weighting can place serious IPI load
5980 on the system. 5416 on the system.
5981 5417
5982 scftorture.weight_many_wait= [KNL] 5418 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 5419 The probability weighting to use for the
5984 smp_call_function_man 5420 smp_call_function_many() function with a
5985 non-zero "wait" param 5421 non-zero "wait" parameter. See weight_single
5986 and weight_many. 5422 and weight_many.
5987 5423
5988 scftorture.weight_all= [KNL] 5424 scftorture.weight_all= [KNL]
5989 The probability weigh 5425 The probability weighting to use for the
5990 smp_call_function_all 5426 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 5427 "wait" parameter. See weight_single and
5992 weight_many. 5428 weight_many.
5993 5429
5994 scftorture.weight_all_wait= [KNL] 5430 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 5431 The probability weighting to use for the
5996 smp_call_function_all 5432 smp_call_function_all() function with a
5997 non-zero "wait" param 5433 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5434 and weight_many.
5999 5435
6000 skew_tick= [KNL,EARLY] Offset th !! 5436 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5437 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5438 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5439 Format: { "0" | "1" }
6004 0 -- disable. (may be 5440 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5441 1 -- enable.
6006 Note: increases power 5442 Note: increases power consumption, thus should only be
6007 enabled if running ji 5443 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5444
6009 security= [SECURITY] Choose a l 5445 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5446 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5447 "lsm=" parameter.
6012 5448
6013 selinux= [SELINUX] Disable or 5449 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5450 Format: { "0" | "1" }
6015 See security/selinux/ 5451 See security/selinux/Kconfig help text.
6016 0 -- disable. 5452 0 -- disable.
6017 1 -- enable. 5453 1 -- enable.
6018 Default value is 1. 5454 Default value is 1.
6019 5455
>> 5456 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 5457 Format: { "0" | "1" }
>> 5458 See security/apparmor/Kconfig help text
>> 5459 0 -- disable.
>> 5460 1 -- enable.
>> 5461 Default value is set via kernel config option.
>> 5462
6020 serialnumber [BUGS=X86-32] 5463 serialnumber [BUGS=X86-32]
6021 5464
6022 sev=option[,option...] [X86-64] See D !! 5465 sev=option[,option...] [X86-64] See Documentation/x86/x86_64/boot-options.rst
6023 5466
6024 shapers= [NET] 5467 shapers= [NET]
6025 Maximal number of sha 5468 Maximal number of shapers.
6026 5469
6027 show_lapic= [APIC,X86] Advanced P !! 5470 simeth= [IA-64]
6028 Limit apic dumping. T !! 5471 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 <<
6036 slab_debug[=options[,slabs][;[options <<
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 5472
6045 slab_max_order= [MM] !! 5473 slram= [HW,MTD]
6046 Determines the maximu <<
6047 A high setting may ca <<
6048 fragmentation. For mo <<
6049 Documentation/mm/slub <<
6050 (slub_max_order legac <<
6051 5474
6052 slab_merge [MM] 5475 slab_merge [MM]
6053 Enable merging of sla 5476 Enable merging of slabs with similar size when the
6054 kernel is built witho 5477 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 5478
6073 slab_nomerge [MM] 5479 slab_nomerge [MM]
6074 Disable merging of sl 5480 Disable merging of slabs with similar size. May be
6075 necessary if there is 5481 necessary if there is some reason to distinguish
6076 allocs to different s 5482 allocs to different slabs, especially in hardened
6077 environments where th 5483 environments where the risk of heap overflows and
6078 layout control by att 5484 layout control by attackers can usually be
6079 frustrated by disabli 5485 frustrated by disabling merging. This will reduce
6080 most of the exposure 5486 most of the exposure of a heap attack to a single
6081 cache (risks via meta 5487 cache (risks via metadata attacks are mostly
6082 unchanged). Debug opt 5488 unchanged). Debug options disable merging on their
6083 own. 5489 own.
6084 For more information !! 5490 For more information see Documentation/vm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5491
6087 slram= [HW,MTD] !! 5492 slab_max_order= [MM, SLAB]
>> 5493 Determines the maximum allowed order for slabs.
>> 5494 A high setting may cause OOMs due to memory
>> 5495 fragmentation. Defaults to 1 for systems with
>> 5496 more than 32MB of RAM, 0 otherwise.
>> 5497
>> 5498 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 5499 Enabling slub_debug allows one to determine the
>> 5500 culprit if slab objects become corrupted. Enabling
>> 5501 slub_debug can create guard zones around objects and
>> 5502 may poison objects when not in use. Also tracks the
>> 5503 last alloc / free. For more information see
>> 5504 Documentation/vm/slub.rst.
>> 5505
>> 5506 slub_max_order= [MM, SLUB]
>> 5507 Determines the maximum allowed order for slabs.
>> 5508 A high setting may cause OOMs due to memory
>> 5509 fragmentation. For more information see
>> 5510 Documentation/vm/slub.rst.
>> 5511
>> 5512 slub_min_objects= [MM, SLUB]
>> 5513 The minimum number of objects per slab. SLUB will
>> 5514 increase the slab order up to slub_max_order to
>> 5515 generate a sufficiently large slab able to contain
>> 5516 the number of objects indicated. The higher the number
>> 5517 of objects the smaller the overhead of tracking slabs
>> 5518 and the less frequently locks need to be acquired.
>> 5519 For more information see Documentation/vm/slub.rst.
>> 5520
>> 5521 slub_min_order= [MM, SLUB]
>> 5522 Determines the minimum page order for slabs. Must be
>> 5523 lower than slub_max_order.
>> 5524 For more information see Documentation/vm/slub.rst.
>> 5525
>> 5526 slub_merge [MM, SLUB]
>> 5527 Same with slab_merge.
>> 5528
>> 5529 slub_nomerge [MM, SLUB]
>> 5530 Same with slab_nomerge. This is supported for legacy.
>> 5531 See slab_nomerge for more information.
6088 5532
6089 smart2= [HW] 5533 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5534 Format: <io1>[,<io2>[,...,<io8>]]
6091 5535
6092 smp.csd_lock_timeout= [KNL] 5536 smp.csd_lock_timeout= [KNL]
6093 Specify the period of 5537 Specify the period of time in milliseconds
6094 that smp_call_functio 5538 that smp_call_function() and friends will wait
6095 for a CPU to release 5539 for a CPU to release the CSD lock. This is
6096 useful when diagnosin 5540 useful when diagnosing bugs involving CPUs
6097 disabling interrupts 5541 disabling interrupts for extended periods
6098 of time. Defaults to 5542 of time. Defaults to 5,000 milliseconds, and
6099 setting a value of ze 5543 setting a value of zero disables this feature.
6100 This feature may be m 5544 This feature may be more efficiently disabled
6101 using the csdlock_deb 5545 using the csdlock_debug- kernel parameter.
6102 5546
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 5547 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5548 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5549 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5550 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5551 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5552 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5553 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5554 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5555 1: Fast pin select (default)
6119 2: ATC IRMode 5556 2: ATC IRMode
6120 5557
6121 smt= [KNL,MIPS,S390,EARLY] !! 5558 smt= [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5559 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5560 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5561 actual hardware limit.
6125 Format: <integer> 5562 Format: <integer>
6126 Default: -1 (no limit 5563 Default: -1 (no limit)
6127 5564
6128 softlockup_panic= 5565 softlockup_panic=
6129 [KNL] Should the soft 5566 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5567 Format: 0 | 1
6131 5568
6132 A value of 1 instruct 5569 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5570 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5571 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5572 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5573 respective build-time switch to that functionality.
6137 5574
6138 softlockup_all_cpu_backtrace= 5575 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5576 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5577 backtraces on all cpus.
6141 Format: 0 | 1 5578 Format: 0 | 1
6142 5579
6143 sonypi.*= [HW] Sony Programmabl 5580 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5581 See Documentation/admin-guide/laptops/sonypi.rst
6145 5582
6146 spectre_bhi= [X86] Control mitigat !! 5583 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 5584 (indirect branch speculation) vulnerability.
6163 The default operation 5585 The default operation protects the kernel from
6164 user space attacks. 5586 user space attacks.
6165 5587
6166 on - unconditionall 5588 on - unconditionally enable, implies
6167 spectre_v2_use 5589 spectre_v2_user=on
6168 off - unconditionall 5590 off - unconditionally disable, implies
6169 spectre_v2_use 5591 spectre_v2_user=off
6170 auto - kernel detects 5592 auto - kernel detects whether your CPU model is
6171 vulnerable 5593 vulnerable
6172 5594
6173 Selecting 'on' will, 5595 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5596 mitigation method at run time according to the
6175 CPU, the available mi 5597 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5598 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5599 compiler with which the kernel was built.
6178 5600
6179 Selecting 'on' will a 5601 Selecting 'on' will also enable the mitigation
6180 against user space to 5602 against user space to user space task attacks.
6181 5603
6182 Selecting 'off' will 5604 Selecting 'off' will disable both the kernel and
6183 the user space protec 5605 the user space protections.
6184 5606
6185 Specific mitigations 5607 Specific mitigations can also be selected manually:
6186 5608
6187 retpoline - r 5609 retpoline - replace indirect branches
6188 retpoline,generic - R 5610 retpoline,generic - Retpolines
6189 retpoline,lfence - L 5611 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 5612 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E !! 5613 eibrs - enhanced IBRS
6192 eibrs,retpoline - E !! 5614 eibrs,retpoline - enhanced IBRS + Retpolines
6193 eibrs,lfence - E !! 5615 eibrs,lfence - enhanced IBRS + LFENCE
6194 ibrs - u 5616 ibrs - use IBRS to protect kernel
6195 5617
6196 Not specifying this o 5618 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5619 spectre_v2=auto.
6198 5620
6199 spectre_v2_user= 5621 spectre_v2_user=
6200 [X86] Control mitigat 5622 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5623 (indirect branch speculation) vulnerability between
6202 user space tasks 5624 user space tasks
6203 5625
6204 on - Uncondition 5626 on - Unconditionally enable mitigations. Is
6205 enforced by 5627 enforced by spectre_v2=on
6206 5628
6207 off - Uncondition 5629 off - Unconditionally disable mitigations. Is
6208 enforced by 5630 enforced by spectre_v2=off
6209 5631
6210 prctl - Indirect br 5632 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5633 but mitigation can be enabled via prctl
6212 per thread. 5634 per thread. The mitigation control state
6213 is inherite 5635 is inherited on fork.
6214 5636
6215 prctl,ibpb 5637 prctl,ibpb
6216 - Like "prctl 5638 - Like "prctl" above, but only STIBP is
6217 controlled 5639 controlled per thread. IBPB is issued
6218 always when 5640 always when switching between different user
6219 space proce 5641 space processes.
6220 5642
6221 seccomp 5643 seccomp
6222 - Same as "pr 5644 - Same as "prctl" above, but all seccomp
6223 threads wil 5645 threads will enable the mitigation unless
6224 they explic 5646 they explicitly opt out.
6225 5647
6226 seccomp,ibpb 5648 seccomp,ibpb
6227 - Like "secco 5649 - Like "seccomp" above, but only STIBP is
6228 controlled 5650 controlled per thread. IBPB is issued
6229 always when 5651 always when switching between different
6230 user space 5652 user space processes.
6231 5653
6232 auto - Kernel sele 5654 auto - Kernel selects the mitigation depending on
6233 the availab 5655 the available CPU features and vulnerability.
6234 5656
6235 Default mitigation: " 5657 Default mitigation: "prctl"
6236 5658
6237 Not specifying this o 5659 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5660 spectre_v2_user=auto.
6239 5661
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= 5662 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5663 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5664 (Speculative Store Bypass vulnerability)
6254 5665
6255 Certain CPUs are vuln 5666 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5667 a common industry wide performance optimization known
6257 as "Speculative Store 5668 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5669 to the same memory location may not be observed by
6259 later loads during sp 5670 later loads during speculative execution. The idea
6260 is that such stores a 5671 is that such stores are unlikely and that they can
6261 be detected prior to 5672 be detected prior to instruction retirement at the
6262 end of a particular s 5673 end of a particular speculation execution window.
6263 5674
6264 In vulnerable process 5675 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5676 store can be used in a cache side channel attack, for
6266 example to read memor 5677 example to read memory to which the attacker does not
6267 directly have access 5678 directly have access (e.g. inside sandboxed code).
6268 5679
6269 This parameter contro 5680 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5681 Bypass optimization is used.
6271 5682
6272 On x86 the options ar 5683 On x86 the options are:
6273 5684
6274 on - Uncondition 5685 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5686 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5687 auto - Kernel detects whether the CPU model contains an
6277 implementat 5688 implementation of Speculative Store Bypass and
6278 picks the m 5689 picks the most appropriate mitigation. If the
6279 CPU is not 5690 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5691 CPU is vulnerable the default mitigation is
6281 architectur 5692 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5693 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5694 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5695 for a process by default. The state of the control
6285 is inherite 5696 is inherited on fork.
6286 seccomp - Same as "pr 5697 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5698 will disable SSB unless they explicitly opt out.
6288 5699
6289 Default mitigations: 5700 Default mitigations:
6290 X86: "prctl" 5701 X86: "prctl"
6291 5702
6292 On powerpc the option 5703 On powerpc the options are:
6293 5704
6294 on,auto - On Power8 a 5705 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5706 barrier on kernel entry and exit. On Power7
6296 perform a s 5707 perform a software flush on kernel entry and
6297 exit. 5708 exit.
6298 off - No action. 5709 off - No action.
6299 5710
6300 Not specifying this o 5711 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5712 spec_store_bypass_disable=auto.
6302 5713
>> 5714 spia_io_base= [HW,MTD]
>> 5715 spia_fio_base=
>> 5716 spia_pedr=
>> 5717 spia_peddr=
>> 5718
6303 split_lock_detect= 5719 split_lock_detect=
6304 [X86] Enable split lo 5720 [X86] Enable split lock detection or bus lock detection
6305 5721
6306 When enabled (and if 5722 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5723 instructions that access data across cache line
6308 boundaries will resul 5724 boundaries will result in an alignment check exception
6309 for split lock detect 5725 for split lock detection or a debug exception for
6310 bus lock detection. 5726 bus lock detection.
6311 5727
6312 off - not enabled 5728 off - not enabled
6313 5729
6314 warn - the kernel 5730 warn - the kernel will emit rate-limited warnings
6315 about appli 5731 about applications triggering the #AC
6316 exception o 5732 exception or the #DB exception. This mode is
6317 the default 5733 the default on CPUs that support split lock
6318 detection o 5734 detection or bus lock detection. Default
6319 behavior is 5735 behavior is by #AC if both features are
6320 enabled in 5736 enabled in hardware.
6321 5737
6322 fatal - the kernel 5738 fatal - the kernel will send SIGBUS to applications
6323 that trigge 5739 that trigger the #AC exception or the #DB
6324 exception. 5740 exception. Default behavior is by #AC if
6325 both featur 5741 both features are enabled in hardware.
6326 5742
6327 ratelimit:N - 5743 ratelimit:N -
6328 Set system 5744 Set system wide rate limit to N bus locks
6329 per second 5745 per second for bus lock detection.
6330 0 < N <= 10 5746 0 < N <= 1000.
6331 5747
6332 N/A for spl 5748 N/A for split lock detection.
6333 5749
6334 5750
6335 If an #AC exception i 5751 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5752 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5753 the kernel will oops in either "warn" or "fatal"
6338 mode. 5754 mode.
6339 5755
6340 #DB exception for bus 5756 #DB exception for bus lock is triggered only when
6341 CPL > 0. 5757 CPL > 0.
6342 5758
6343 srbds= [X86,INTEL,EARLY] !! 5759 srbds= [X86,INTEL]
6344 Control the Special R 5760 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5761 (SRBDS) mitigation.
6346 5762
6347 Certain CPUs are vuln 5763 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5764 exploit which can leak bits from the random
6349 number generator. 5765 number generator.
6350 5766
6351 By default, this issu 5767 By default, this issue is mitigated by
6352 microcode. However, 5768 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5769 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5770 much slower. Among other effects, this will
6355 result in reduced thr 5771 result in reduced throughput from /dev/urandom.
6356 5772
6357 The microcode mitigat 5773 The microcode mitigation can be disabled with
6358 the following option: 5774 the following option:
6359 5775
6360 off: Disable mitig 5776 off: Disable mitigation and remove
6361 performance i 5777 performance impact to RDRAND and RDSEED
6362 5778
6363 srcutree.big_cpu_lim [KNL] 5779 srcutree.big_cpu_lim [KNL]
6364 Specifies the number 5780 Specifies the number of CPUs constituting a
6365 large system, such th 5781 large system, such that srcu_struct structures
6366 should immediately al 5782 should immediately allocate an srcu_node array.
6367 This kernel-boot para 5783 This kernel-boot parameter defaults to 128,
6368 but takes effect only 5784 but takes effect only when the low-order four
6369 bits of srcutree.conv 5785 bits of srcutree.convert_to_big is equal to 3
6370 (decide at boot). 5786 (decide at boot).
6371 5787
6372 srcutree.convert_to_big [KNL] 5788 srcutree.convert_to_big [KNL]
6373 Specifies under what 5789 Specifies under what conditions an SRCU tree
6374 srcu_struct structure 5790 srcu_struct structure will be converted to big
6375 form, that is, with a 5791 form, that is, with an rcu_node tree:
6376 5792
6377 0: Never. 5793 0: Never.
6378 1: At ini 5794 1: At init_srcu_struct() time.
6379 2: When r 5795 2: When rcutorture decides to.
6380 3: Decide 5796 3: Decide at boot time (default).
6381 0x1X: Above 5797 0x1X: Above plus if high contention.
6382 5798
6383 Either way, the srcu_ 5799 Either way, the srcu_node tree will be sized based
6384 on the actual runtime 5800 on the actual runtime number of CPUs (nr_cpu_ids)
6385 instead of the compil 5801 instead of the compile-time CONFIG_NR_CPUS.
6386 5802
6387 srcutree.counter_wrap_check [KNL] 5803 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5804 Specifies how frequently to check for
6389 grace-period sequence 5805 grace-period sequence counter wrap for the
6390 srcu_data structure's 5806 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5807 The greater the number of bits set in this kernel
6392 parameter, the less f 5808 parameter, the less frequently counter wrap will
6393 be checked for. Note 5809 be checked for. Note that the bottom two bits
6394 are ignored. 5810 are ignored.
6395 5811
6396 srcutree.exp_holdoff [KNL] 5812 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5813 Specifies how many nanoseconds must elapse
6398 since the end of the 5814 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5815 a given srcu_struct until the next normal SRCU
6400 grace period will be 5816 grace period will be considered for automatic
6401 expediting. Set to z 5817 expediting. Set to zero to disable automatic
6402 expediting. 5818 expediting.
6403 5819
6404 srcutree.srcu_max_nodelay [KNL] 5820 srcutree.srcu_max_nodelay [KNL]
6405 Specifies the number 5821 Specifies the number of no-delay instances
6406 per jiffy for which t 5822 per jiffy for which the SRCU grace period
6407 worker thread will be 5823 worker thread will be rescheduled with zero
6408 delay. Beyond this li 5824 delay. Beyond this limit, worker thread will
6409 be rescheduled with a 5825 be rescheduled with a sleep delay of one jiffy.
6410 5826
6411 srcutree.srcu_max_nodelay_phase [KNL] 5827 srcutree.srcu_max_nodelay_phase [KNL]
6412 Specifies the per-gra 5828 Specifies the per-grace-period phase, number of
6413 non-sleeping polls of 5829 non-sleeping polls of readers. Beyond this limit,
6414 grace period worker t 5830 grace period worker thread will be rescheduled
6415 with a sleep delay of 5831 with a sleep delay of one jiffy, between each
6416 rescan of the readers 5832 rescan of the readers, for a grace period phase.
6417 5833
6418 srcutree.srcu_retry_check_delay [KNL] 5834 srcutree.srcu_retry_check_delay [KNL]
6419 Specifies number of m 5835 Specifies number of microseconds of non-sleeping
6420 delay between each no 5836 delay between each non-sleeping poll of readers.
6421 5837
6422 srcutree.small_contention_lim [KNL] 5838 srcutree.small_contention_lim [KNL]
6423 Specifies the number 5839 Specifies the number of update-side contention
6424 events per jiffy will 5840 events per jiffy will be tolerated before
6425 initiating a conversi 5841 initiating a conversion of an srcu_struct
6426 structure to big form 5842 structure to big form. Note that the value of
6427 srcutree.convert_to_b 5843 srcutree.convert_to_big must have the 0x10 bit
6428 set for contention-ba 5844 set for contention-based conversions to occur.
6429 5845
6430 ssbd= [ARM64,HW,EARLY] !! 5846 ssbd= [ARM64,HW]
6431 Speculative Store Byp 5847 Speculative Store Bypass Disable control
6432 5848
6433 On CPUs that are vuln 5849 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5850 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5851 firmware based mitigation, this parameter
6436 indicates how the mit 5852 indicates how the mitigation should be used:
6437 5853
6438 force-on: Unconditio 5854 force-on: Unconditionally enable mitigation for
6439 for both k 5855 for both kernel and userspace
6440 force-off: Unconditio 5856 force-off: Unconditionally disable mitigation for
6441 for both k 5857 for both kernel and userspace
6442 kernel: Always ena 5858 kernel: Always enable mitigation in the
6443 kernel, an 5859 kernel, and offer a prctl interface
6444 to allow u 5860 to allow userspace to register its
6445 interest i 5861 interest in being mitigated too.
6446 5862
6447 stack_guard_gap= [MM] 5863 stack_guard_gap= [MM]
6448 override the default 5864 override the default stack gap protection. The value
6449 is in page units and 5865 is in page units and it defines how many pages prior
6450 to (for stacks growin 5866 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5867 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5868 mapping. Default value is 256 pages.
6453 5869
6454 stack_depot_disable= [KNL,EARLY] !! 5870 stack_depot_disable= [KNL]
6455 Setting this to true 5871 Setting this to true through kernel command line will
6456 disable the stack dep 5872 disable the stack depot thereby saving the static memory
6457 consumed by the stack 5873 consumed by the stack hash table. By default this is set
6458 to false. 5874 to false.
6459 5875
6460 stacktrace [FTRACE] 5876 stacktrace [FTRACE]
6461 Enabled the stack tra 5877 Enabled the stack tracer on boot up.
6462 5878
6463 stacktrace_filter=[function-list] 5879 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5880 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 5881 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 5882 list of functions. This list can be changed at run
6467 time by the stack_tra 5883 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 5884 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 5885 and the stacktrace above is not needed.
6470 5886
6471 sti= [PARISC,HW] 5887 sti= [PARISC,HW]
6472 Format: <num> 5888 Format: <num>
6473 Set the STI (builtin 5889 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 5890 machines) console (graphic card) which should be used
6475 as the initial boot-c 5891 as the initial boot-console.
6476 See also comment in d 5892 See also comment in drivers/video/console/sticore.c.
6477 5893
6478 sti_font= [HW] 5894 sti_font= [HW]
6479 See comment in driver 5895 See comment in drivers/video/console/sticore.c.
6480 5896
6481 stifb= [HW] 5897 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 5898 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 5899
6484 strict_sas_size= 5900 strict_sas_size=
6485 [X86] 5901 [X86]
6486 Format: <bool> 5902 Format: <bool>
6487 Enable or disable str 5903 Enable or disable strict sigaltstack size checks
6488 against the required 5904 against the required signal frame size which
6489 depends on the suppor 5905 depends on the supported FPU features. This can
6490 be used to filter out 5906 be used to filter out binaries which have
6491 not yet been made awa 5907 not yet been made aware of AT_MINSIGSTKSZ.
6492 5908
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= 5909 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 5910 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 5911 [NFS,SUNRPC]
6506 SunRPC servers often 5912 SunRPC servers often require that client requests
6507 originate from a priv 5913 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 5914 range 0 < portnr < 1024).
6509 An administrator who 5915 An administrator who wishes to reserve some of these
6510 ports for other uses 5916 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 5917 kernel's sunrpc client considers to be privileged
6512 using these two param 5918 using these two parameters to set the minimum and
6513 maximum port values. 5919 maximum port values.
6514 5920
6515 sunrpc.svc_rpc_per_connection_limit= 5921 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 5922 [NFS,SUNRPC]
6517 Limit the number of r 5923 Limit the number of requests that the server will
6518 process in parallel f 5924 process in parallel from a single connection.
6519 The default value is 5925 The default value is 0 (no limit).
6520 5926
6521 sunrpc.pool_mode= 5927 sunrpc.pool_mode=
6522 [NFS] 5928 [NFS]
6523 Control how the NFS s 5929 Control how the NFS server code allocates CPUs to
6524 service thread pools. 5930 service thread pools. Depending on how many NICs
6525 you have and where th 5931 you have and where their interrupts are bound, this
6526 option will affect wh 5932 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 5933 Note: this parameter cannot be changed while the
6528 NFS server is running 5934 NFS server is running.
6529 5935
6530 auto the serve 5936 auto the server chooses an appropriate mode
6531 automatic 5937 automatically using heuristics
6532 global a single 5938 global a single global pool contains all CPUs
6533 percpu one pool 5939 percpu one pool for each CPU
6534 pernode one pool 5940 pernode one pool for each NUMA node (equivalent
6535 to global 5941 to global on non-NUMA machines)
6536 5942
6537 sunrpc.tcp_slot_table_entries= 5943 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 5944 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 5945 [NFS,SUNRPC]
6540 Sets the upper limit 5946 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 5947 RPC calls that can be sent from the client to a
6542 server. Increasing th 5948 server. Increasing these values may allow you to
6543 improve throughput, b 5949 improve throughput, but will also increase the
6544 amount of memory rese 5950 amount of memory reserved for use by the client.
6545 5951
6546 suspend.pm_test_delay= 5952 suspend.pm_test_delay=
6547 [SUSPEND] 5953 [SUSPEND]
6548 Sets the number of se 5954 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 5955 mode before resuming the system (see
6550 /sys/power/pm_test). 5956 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 5957 is set. Default value is 5.
6552 5958
6553 svm= [PPC] 5959 svm= [PPC]
6554 Format: { on | off | 5960 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 5961 This parameter controls use of the Protected
6556 Execution Facility on 5962 Execution Facility on pSeries.
6557 5963
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 5964 swapaccount= [KNL]
6559 Format: { <int> [,<in !! 5965 Format: [0|1]
>> 5966 Enable accounting of swap in memory resource
>> 5967 controller if no parameter or 1 is given or disable
>> 5968 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
>> 5969
>> 5970 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
>> 5971 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 5972 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 5973 force -- force using of bounce buffers even if they
6565 wouldn't be 5974 wouldn't be automatically used by the kernel
6566 noforce -- Never use 5975 noforce -- Never use bounce buffers (for debugging)
6567 5976
6568 switches= [HW,M68k,EARLY] !! 5977 switches= [HW,M68k]
6569 5978
6570 sysctl.*= [KNL] 5979 sysctl.*= [KNL]
6571 Set a sysctl paramete 5980 Set a sysctl parameter, right before loading the init
6572 process, as if the va 5981 process, as if the value was written to the respective
6573 /proc/sys/... file. B 5982 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 5983 separators. Unrecognized parameters and invalid values
6575 are reported in the k 5984 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 5985 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 5986 Example: sysctl.vm.swappiness=40
6578 5987
>> 5988 sysfs.deprecated=0|1 [KNL]
>> 5989 Enable/disable old style sysfs layout for old udev
>> 5990 on older distributions. When this option is enabled
>> 5991 very new udev will not work anymore. When this option
>> 5992 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 5993 in older udev will not work anymore.
>> 5994 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 5995 the kernel configuration.
>> 5996
6579 sysrq_always_enabled 5997 sysrq_always_enabled
6580 [KNL] 5998 [KNL]
6581 Ignore sysrq setting 5999 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 6000 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 6001 Useful for debugging.
6584 6002
6585 tcpmhash_entries= [KNL,NET] 6003 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 6004 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 6005 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 6006 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 6007 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 6008 "tcp_no_metrics_save" section for more details.
6591 6009
6592 tdfx= [HW,DRM] 6010 tdfx= [HW,DRM]
6593 6011
6594 test_suspend= [SUSPEND] 6012 test_suspend= [SUSPEND]
6595 Format: { "mem" | "st 6013 Format: { "mem" | "standby" | "freeze" }[,N]
6596 Specify "mem" (for Su 6014 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 6015 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 6016 as the system sleep state during system startup with
6599 the optional capabili 6017 the optional capability to repeat N number of times.
6600 The system is woken f 6018 The system is woken from this state using a
6601 wakeup-capable RTC al 6019 wakeup-capable RTC alarm.
6602 6020
6603 thash_entries= [KNL,NET] 6021 thash_entries= [KNL,NET]
6604 Set number of hash bu 6022 Set number of hash buckets for TCP connection
6605 6023
6606 thermal.act= [HW,ACPI] 6024 thermal.act= [HW,ACPI]
6607 -1: disable all activ 6025 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 6026 <degrees C>: override all lowest active trip points
6609 6027
6610 thermal.crt= [HW,ACPI] 6028 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 6029 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 6030 <degrees C>: override all critical trip points
6613 6031
>> 6032 thermal.nocrt= [HW,ACPI]
>> 6033 Set to disable actions on ACPI thermal zone
>> 6034 critical and hot trip points.
>> 6035
6614 thermal.off= [HW,ACPI] 6036 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 6037 1: disable ACPI thermal control
6616 6038
6617 thermal.psv= [HW,ACPI] 6039 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 6040 -1: disable all passive trip points
6619 <degrees C>: override 6041 <degrees C>: override all passive trip points to this
6620 value 6042 value
6621 6043
6622 thermal.tzp= [HW,ACPI] 6044 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 6045 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 6046 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 6047 0: no polling (default)
6626 6048
6627 threadirqs [KNL,EARLY] !! 6049 threadirqs [KNL]
6628 Force threading of al 6050 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 6051 marked explicitly IRQF_NO_THREAD.
6630 6052
6631 topology= [S390,EARLY] !! 6053 topology= [S390]
6632 Format: {off | on} 6054 Format: {off | on}
6633 Specify if the kernel 6055 Specify if the kernel should make use of the cpu
6634 topology information 6056 topology information if the hardware supports this.
6635 The scheduler will ma 6057 The scheduler will make use of this information and
6636 e.g. base its process 6058 e.g. base its process migration decisions on it.
6637 Default is on. 6059 Default is on.
6638 6060
>> 6061 topology_updates= [KNL, PPC, NUMA]
>> 6062 Format: {off}
>> 6063 Specify if the kernel should ignore (off)
>> 6064 topology updates sent by the hypervisor to this
>> 6065 LPAR.
>> 6066
6639 torture.disable_onoff_at_boot= [KNL] 6067 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 6068 Prevent the CPU-hotplug component of torturing
6641 until after init has 6069 until after init has spawned.
6642 6070
6643 torture.ftrace_dump_at_shutdown= [KNL 6071 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 6072 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 6073 even if there were no errors. This can be a
6646 very costly operation 6074 very costly operation when many torture tests
6647 are running concurren 6075 are running concurrently, especially on systems
6648 with rotating-rust st 6076 with rotating-rust storage.
6649 6077
6650 torture.verbose_sleep_frequency= [KNL 6078 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 6079 Specifies how many verbose printk()s should be
6652 emitted between each 6080 emitted between each sleep. The default of zero
6653 disables verbose-prin 6081 disables verbose-printk() sleeping.
6654 6082
6655 torture.verbose_sleep_duration= [KNL] 6083 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 6084 Duration of each verbose-printk() sleep in jiffies.
6657 6085
>> 6086 tp720= [HW,PS2]
>> 6087
6658 tpm_suspend_pcr=[HW,TPM] 6088 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 6089 Format: integer pcr id
6660 Specify that at suspe 6090 Specify that at suspend time, the tpm driver
6661 should extend the spe 6091 should extend the specified pcr with zeros,
6662 as a workaround for s 6092 as a workaround for some chips which fail to
6663 flush the last writte 6093 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 6094 This will guarantee that all the other pcrs
6665 are saved. 6095 are saved.
6666 6096
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] 6097 tp_printk [FTRACE]
6675 Have the tracepoints 6098 Have the tracepoints sent to printk as well as the
6676 tracing ring buffer. 6099 tracing ring buffer. This is useful for early boot up
6677 where the system hang 6100 where the system hangs or reboots and does not give the
6678 option for reading th 6101 option for reading the tracing buffer or performing a
6679 ftrace_dump_on_oops. 6102 ftrace_dump_on_oops.
6680 6103
6681 To turn off having tr 6104 To turn off having tracepoints sent to printk,
6682 echo 0 > /proc/sys/k 6105 echo 0 > /proc/sys/kernel/tracepoint_printk
6683 Note, echoing 1 into 6106 Note, echoing 1 into this file without the
6684 tp_printk kernel cmdl !! 6107 tracepoint_printk kernel cmdline option has no effect.
6685 6108
6686 The tp_printk_stop_on 6109 The tp_printk_stop_on_boot (see below) can also be used
6687 to stop the printing 6110 to stop the printing of events to console at
6688 late_initcall_sync. 6111 late_initcall_sync.
6689 6112
6690 ** CAUTION ** 6113 ** CAUTION **
6691 6114
6692 Having tracepoints se 6115 Having tracepoints sent to printk() and activating high
6693 frequency tracepoints 6116 frequency tracepoints such as irq or sched, can cause
6694 the system to live lo 6117 the system to live lock.
6695 6118
6696 tp_printk_stop_on_boot [FTRACE] 6119 tp_printk_stop_on_boot [FTRACE]
6697 When tp_printk (above 6120 When tp_printk (above) is set, it can cause a lot of noise
6698 on the console. It ma 6121 on the console. It may be useful to only include the
6699 printing of events du 6122 printing of events during boot up, as user space may
6700 make the system inope 6123 make the system inoperable.
6701 6124
6702 This command line opt 6125 This command line option will stop the printing of events
6703 to console at the lat 6126 to console at the late_initcall_sync() time frame.
6704 6127
6705 trace_buf_size=nn[KMG] 6128 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 6129 [FTRACE] will set tracing buffer size on each cpu.
6707 6130
6708 trace_clock= [FTRACE] Set the cloc 6131 trace_clock= [FTRACE] Set the clock used for tracing events
6709 at boot up. 6132 at boot up.
6710 local - Use the per C 6133 local - Use the per CPU time stamp counter
6711 (converted in 6134 (converted into nanoseconds). Fast, but
6712 depending on 6135 depending on the architecture, may not be
6713 in sync betwe 6136 in sync between CPUs.
6714 global - Event time s 6137 global - Event time stamps are synchronize across
6715 CPUs. May be 6138 CPUs. May be slower than the local clock,
6716 but better fo 6139 but better for some race conditions.
6717 counter - Simple coun 6140 counter - Simple counting of events (1, 2, ..)
6718 note, some co 6141 note, some counts may be skipped due to the
6719 infrastructur 6142 infrastructure grabbing the clock more than
6720 once per even 6143 once per event.
6721 uptime - Use jiffies 6144 uptime - Use jiffies as the time stamp.
6722 perf - Use the same c 6145 perf - Use the same clock that perf uses.
6723 mono - Use ktime_get_ 6146 mono - Use ktime_get_mono_fast_ns() for time stamps.
6724 mono_raw - Use ktime_ 6147 mono_raw - Use ktime_get_raw_fast_ns() for time
6725 stamps. 6148 stamps.
6726 boot - Use ktime_get_ 6149 boot - Use ktime_get_boot_fast_ns() for time stamps.
6727 Architectures may add 6150 Architectures may add more clocks. See
6728 Documentation/trace/f 6151 Documentation/trace/ftrace.rst for more details.
6729 6152
6730 trace_event=[event-list] 6153 trace_event=[event-list]
6731 [FTRACE] Set and star 6154 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 6155 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 6156 comma-separated list of trace events to enable. See
6734 also Documentation/tr 6157 also Documentation/trace/events.rst
6735 6158
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] 6159 trace_options=[option-list]
6757 [FTRACE] Enable or di 6160 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 6161 The option-list is a comma delimited list of options
6759 that can be enabled o 6162 that can be enabled or disabled just as if you were
6760 to echo the option na 6163 to echo the option name into
6761 6164
6762 /sys/kernel/traci !! 6165 /sys/kernel/debug/tracing/trace_options
6763 6166
6764 For example, to enabl 6167 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 6168 stack trace of each event), add to the command line:
6766 6169
6767 trace_options=s 6170 trace_options=stacktrace
6768 6171
6769 See also Documentatio 6172 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 6173 section.
6771 6174
6772 trace_trigger=[trigger-list] <<
6773 [FTRACE] Add a event <<
6774 Set a trigger on top <<
6775 filter. <<
6776 <<
6777 The format is is "tra <<
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 <<
6784 The above will enable <<
6785 event but only trigge <<
6786 event is "2" (TASK_UN <<
6787 <<
6788 See also "Event trigg <<
6789 <<
6790 <<
6791 traceoff_on_warning 6175 traceoff_on_warning
6792 [FTRACE] enable this 6176 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 6177 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 6178 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 6179 file located in /sys/kernel/debug/tracing/
6796 6180
6797 This option is useful 6181 This option is useful, as it disables the trace before
6798 the WARNING dump is c 6182 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 6183 be filled with content caused by the warning output.
6800 6184
6801 This option can also 6185 This option can also be set at run time via the sysctl
6802 option: kernel/trace 6186 option: kernel/traceoff_on_warning
6803 6187
6804 transparent_hugepage= 6188 transparent_hugepage=
6805 [KNL] 6189 [KNL]
6806 Format: [always|madvi 6190 Format: [always|madvise|never]
6807 Can be used to contro 6191 Can be used to control the default behavior of the system
6808 with respect to trans 6192 with respect to transparent hugepages.
6809 See Documentation/adm 6193 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 6194 for more details.
6811 6195
6812 trusted.source= [KEYS] 6196 trusted.source= [KEYS]
6813 Format: <string> 6197 Format: <string>
6814 This parameter identi 6198 This parameter identifies the trust source as a backend
6815 for trusted keys impl 6199 for trusted keys implementation. Supported trust
6816 sources: 6200 sources:
6817 - "tpm" 6201 - "tpm"
6818 - "tee" 6202 - "tee"
6819 - "caam" 6203 - "caam"
6820 - "dcp" <<
6821 If not specified then 6204 If not specified then it defaults to iterating through
6822 the trust source list 6205 the trust source list starting with TPM and assigns the
6823 first trust source as 6206 first trust source as a backend which is initialized
6824 successfully during i 6207 successfully during iteration.
6825 6208
6826 trusted.rng= [KEYS] 6209 trusted.rng= [KEYS]
6827 Format: <string> 6210 Format: <string>
6828 The RNG used to gener 6211 The RNG used to generate key material for trusted keys.
6829 Can be one of: 6212 Can be one of:
6830 - "kernel" 6213 - "kernel"
6831 - the same value as t 6214 - the same value as trusted.source: "tpm" or "tee"
6832 - "default" 6215 - "default"
6833 If not specified, "de 6216 If not specified, "default" is used. In this case,
6834 the RNG's choice is l 6217 the RNG's choice is left to each individual trust source.
6835 6218
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 6219 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 6220 Format: <string>
6850 [x86] reliable: mark 6221 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 6222 disables clocksource verification at runtime, as well
6852 as the stability chec 6223 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 6224 high-resolution timer mode on older hardware, and in
6854 virtualized environme 6225 virtualized environment.
6855 [x86] noirqtime: Do n 6226 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 6227 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 6228 platforms where RDTSC is slow and this accounting
6858 can add overhead. 6229 can add overhead.
6859 [x86] unstable: mark 6230 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 6231 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 6232 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 6233 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 6234 in situations with strict latency requirements (where
6864 interruptions from cl 6235 interruptions from clocksource watchdog are not
6865 acceptable). 6236 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 6237
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 6238 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 6239 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 6240 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 6241 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 6242 Format: <unsigned int>
6882 6243
6883 tsx= [X86] Control Transac 6244 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 6245 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 6246 support TSX control.
6886 6247
6887 This parameter contro 6248 This parameter controls the TSX feature. The options are:
6888 6249
6889 on - Enable TSX 6250 on - Enable TSX on the system. Although there are
6890 mitigations f 6251 mitigations for all known security vulnerabilities,
6891 TSX has been 6252 TSX has been known to be an accelerator for
6892 several previ 6253 several previous speculation-related CVEs, and
6893 so there may 6254 so there may be unknown security risks associated
6894 with leaving 6255 with leaving it enabled.
6895 6256
6896 off - Disable TSX 6257 off - Disable TSX on the system. (Note that this
6897 option takes 6258 option takes effect only on newer CPUs which are
6898 not vulnerabl 6259 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 6260 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 6261 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 6262 update. This new MSR allows for the reliable
6902 deactivation 6263 deactivation of the TSX functionality.)
6903 6264
6904 auto - Disable TSX 6265 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 6266 otherwise enable TSX on the system.
6906 6267
6907 Not specifying this o 6268 Not specifying this option is equivalent to tsx=off.
6908 6269
6909 See Documentation/adm 6270 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 6271 for more details.
6911 6272
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 6273 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 6274 Abort (TAA) vulnerability.
6914 6275
6915 Similar to Micro-arch 6276 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 6277 certain CPUs that support Transactional
6917 Synchronization Exten 6278 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 6279 exploit against CPU internal buffers which can forward
6919 information to a disc 6280 information to a disclosure gadget under certain
6920 conditions. 6281 conditions.
6921 6282
6922 In vulnerable process 6283 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 6284 data can be used in a cache side channel attack, to
6924 access data to which 6285 access data to which the attacker does not have direct
6925 access. 6286 access.
6926 6287
6927 This parameter contro 6288 This parameter controls the TAA mitigation. The
6928 options are: 6289 options are:
6929 6290
6930 full - Enable T 6291 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 6292 if TSX is enabled.
6932 6293
6933 full,nosmt - Enable T 6294 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 6295 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 6296 is not disabled because CPU is not
6936 vulnerab 6297 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 6298 off - Unconditionally disable TAA mitigation
6938 6299
6939 On MDS-affected machi 6300 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 6301 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 6302 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 6303 this mitigation, you need to specify mds=off too.
6943 6304
6944 Not specifying this o 6305 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 6306 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 6307 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 6308 required and doesn't provide any additional
6948 mitigation. 6309 mitigation.
6949 6310
6950 For details see: 6311 For details see:
6951 Documentation/admin-g 6312 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 6313
6953 turbografx.map[2|3]= [HW,JOY] 6314 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 6315 TurboGraFX parallel port interface
6955 Format: 6316 Format:
6956 <port#>,<js1>,<js2>,< 6317 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 6318 See also Documentation/input/devices/joystick-parport.rst
6958 6319
6959 udbg-immortal [PPC] When debugging 6320 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 6321 happen after console_init() and before a proper
6961 console driver takes 6322 console driver takes over, this boot options might
6962 help "seeing" what's 6323 help "seeing" what's going on.
6963 6324
6964 uhash_entries= [KNL,NET] 6325 uhash_entries= [KNL,NET]
6965 Set number of hash bu 6326 Set number of hash buckets for UDP/UDP-Lite connections
6966 6327
6967 uhci-hcd.ignore_oc= 6328 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 6329 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 6330 Some badly-designed motherboards generate lots of
6970 bogus events, for por 6331 bogus events, for ports that aren't wired to
6971 anything. Set this p 6332 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 6333 Note that genuine overcurrent events won't be
6973 reported either. 6334 reported either.
6974 6335
6975 unknown_nmi_panic 6336 unknown_nmi_panic
6976 [X86] Cause panic on 6337 [X86] Cause panic on unknown NMI.
6977 6338
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= 6339 usbcore.authorized_default=
6985 [USB] Default USB dev 6340 [USB] Default USB device authorization:
6986 (default -1 = authori !! 6341 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 6342 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 6343 if device connected to internal port)
6989 6344
6990 usbcore.autosuspend= 6345 usbcore.autosuspend=
6991 [USB] The autosuspend 6346 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 6347 for newly-detected USB devices (default 2). This
6993 is the time required 6348 is the time required before an idle device will be
6994 autosuspended. Devic 6349 autosuspended. Devices for which the delay is set
6995 to a negative value w 6350 to a negative value won't be autosuspended at all.
6996 6351
6997 usbcore.usbfs_snoop= 6352 usbcore.usbfs_snoop=
6998 [USB] Set to log all 6353 [USB] Set to log all usbfs traffic (default 0 = off).
6999 6354
7000 usbcore.usbfs_snoop_max= 6355 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 6356 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 6357 (default = 65536).
7003 6358
7004 usbcore.blinkenlights= 6359 usbcore.blinkenlights=
7005 [USB] Set to cycle le 6360 [USB] Set to cycle leds on hubs (default 0 = off).
7006 6361
7007 usbcore.old_scheme_first= 6362 usbcore.old_scheme_first=
7008 [USB] Start with the 6363 [USB] Start with the old device initialization
7009 scheme (default 0 = o 6364 scheme (default 0 = off).
7010 6365
7011 usbcore.usbfs_memory_mb= 6366 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 6367 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 6368 usbfs (default = 16, 0 = max = 2047).
7014 6369
7015 usbcore.use_both_schemes= 6370 usbcore.use_both_schemes=
7016 [USB] Try the other d 6371 [USB] Try the other device initialization scheme
7017 if the first one fail 6372 if the first one fails (default 1 = enabled).
7018 6373
7019 usbcore.initial_descriptor_timeout= 6374 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 6375 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 6376 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 6377 (default 5000 = 5.0 seconds).
7023 6378
7024 usbcore.nousb [USB] Disable the USB 6379 usbcore.nousb [USB] Disable the USB subsystem
7025 6380
7026 usbcore.quirks= 6381 usbcore.quirks=
7027 [USB] A list of quirk 6382 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 6383 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 6384 commas. Each entry has the form
7030 VendorID:ProductID:Fl 6385 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 6386 numbers and Flags is a set of letters. Each letter
7032 will change the built 6387 will change the built-in quirk; setting it if it is
7033 clear and clearing it 6388 clear and clearing it if it is set. The letters have
7034 the following meaning 6389 the following meanings:
7035 a = USB_QUIRK 6390 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 6391 descriptors must not be fetched using
7037 a 255 6392 a 255-byte read);
7038 b = USB_QUIRK 6393 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 6394 correctly so reset it instead);
7040 c = USB_QUIRK 6395 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 6396 Set-Interface requests);
7042 d = USB_QUIRK 6397 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 6398 handle its Configuration or Interface
7044 strin 6399 strings);
7045 e = USB_QUIRK 6400 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 6401 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 6402 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 6403 more interface descriptions than the
7049 bNumI 6404 bNumInterfaces count, and can't handle
7050 talki 6405 talking to these interfaces);
7051 g = USB_QUIRK 6406 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 6407 during initialization, after we read
7053 the d 6408 the device descriptor);
7054 h = USB_QUIRK 6409 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 6410 high speed and super speed interrupt
7056 endpo 6411 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 6412 require the interval in microframes (1
7058 micro 6413 microframe = 125 microseconds) to be
7059 calcu 6414 calculated as interval = 2 ^
7060 (bInt 6415 (bInterval-1).
7061 Devic 6416 Devices with this quirk report their
7062 bInte 6417 bInterval as the result of this
7063 calcu 6418 calculation instead of the exponent
7064 varia 6419 variable used in the calculation);
7065 i = USB_QUIRK 6420 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 6421 handle device_qualifier descriptor
7067 reque 6422 requests);
7068 j = USB_QUIRK 6423 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 6424 generates spurious wakeup, ignore
7070 remot 6425 remote wakeup capability);
7071 k = USB_QUIRK 6426 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 6427 Power Management);
7073 l = USB_QUIRK 6428 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 6429 (Device reports its bInterval as linear
7075 frame 6430 frames instead of the USB 2.0
7076 calcu 6431 calculation);
7077 m = USB_QUIRK 6432 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 6433 to be disconnected before suspend to
7079 preve 6434 prevent spurious wakeup);
7080 n = USB_QUIRK 6435 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 6436 pause after every control message);
7082 o = USB_QUIRK 6437 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 6438 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 6439 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 6440
7089 usbhid.mousepoll= 6441 usbhid.mousepoll=
7090 [USBHID] The interval 6442 [USBHID] The interval which mice are to be polled at.
7091 6443
7092 usbhid.jspoll= 6444 usbhid.jspoll=
7093 [USBHID] The interval 6445 [USBHID] The interval which joysticks are to be polled at.
7094 6446
7095 usbhid.kbpoll= 6447 usbhid.kbpoll=
7096 [USBHID] The interval 6448 [USBHID] The interval which keyboards are to be polled at.
7097 6449
7098 usb-storage.delay_use= 6450 usb-storage.delay_use=
7099 [UMS] The delay in se 6451 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 6452 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 6453
7105 usb-storage.quirks= 6454 usb-storage.quirks=
7106 [UMS] A list of quirk 6455 [UMS] A list of quirks entries to supplement or
7107 override the built-in 6456 override the built-in unusual_devs list. List
7108 entries are separated 6457 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 6458 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 6459 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 6460 Flags is a set of characters, each corresponding
7112 to a common usb-stora 6461 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 6462 a = SANE_SENSE (collect more than 18 bytes
7114 of se 6463 of sense data, not on uas);
7115 b = BAD_SENSE 6464 b = BAD_SENSE (don't collect more than 18
7116 bytes 6465 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 6466 c = FIX_CAPACITY (decrease the reported
7118 devic 6467 device capacity by one sector);
7119 d = NO_READ_D 6468 d = NO_READ_DISC_INFO (don't use
7120 READ_ 6469 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 6470 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 6471 READ_CAPACITY_16 command);
7123 f = NO_REPORT 6472 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 6473 command, uas only);
7125 g = MAX_SECTO 6474 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 6475 240 sectors at a time, uas only);
7127 h = CAPACITY_ 6476 h = CAPACITY_HEURISTICS (decrease the
7128 repor 6477 reported device capacity by one
7129 secto 6478 sector if the number is odd);
7130 i = IGNORE_DE 6479 i = IGNORE_DEVICE (don't bind to this
7131 devic 6480 device);
7132 j = NO_REPORT 6481 j = NO_REPORT_LUNS (don't use report luns
7133 comma 6482 command, uas only);
7134 k = NO_SAME ( 6483 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 6484 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 6485 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 6486 m = MAX_SECTORS_64 (don't transfer more
7138 than 6487 than 64 sectors = 32 KB at a time,
7139 not o 6488 not on uas);
7140 n = INITIAL_R 6489 n = INITIAL_READ10 (force a retry of the
7141 initi 6490 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 6491 o = CAPACITY_OK (accept the capacity
7143 repor 6492 reported by the device, not on uas);
7144 p = WRITE_CAC 6493 p = WRITE_CACHE (the device cache is ON
7145 by de 6494 by default, not on uas);
7146 r = IGNORE_RE 6495 r = IGNORE_RESIDUE (the device reports
7147 bogus 6496 bogus residue values, not on uas);
7148 s = SINGLE_LU 6497 s = SINGLE_LUN (the device has only one
7149 Logic 6498 Logical Unit);
7150 t = NO_ATA_1X 6499 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 6500 commands, uas only);
7152 u = IGNORE_UA 6501 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 6502 w = NO_WP_DETECT (don't test whether the
7154 mediu 6503 medium is write-protected).
7155 y = ALWAYS_SY 6504 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 6505 even if the device claims no cache,
7157 not o 6506 not on uas)
7158 Example: quirks=0419: 6507 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 6508
7160 user_debug= [KNL,ARM] 6509 user_debug= [KNL,ARM]
7161 Format: <int> 6510 Format: <int>
7162 See arch/arm/Kconfig. 6511 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 6512 1 - undefined instruction events
7164 2 - system c 6513 2 - system calls
7165 4 - invalid 6514 4 - invalid data aborts
7166 8 - SIGSEGV 6515 8 - SIGSEGV faults
7167 16 - SIGBUS f 6516 16 - SIGBUS faults
7168 Example: user_debug=3 6517 Example: user_debug=31
7169 6518
7170 userpte= 6519 userpte=
7171 [X86,EARLY] Flags con !! 6520 [X86] Flags controlling user PTE allocations.
7172 6521
7173 nohigh = do n 6522 nohigh = do not allocate PTE pages in
7174 HIGHM 6523 HIGHMEM regardless of setting
7175 of CO 6524 of CONFIG_HIGHPTE.
7176 6525
7177 vdso= [X86,SH,SPARC] 6526 vdso= [X86,SH,SPARC]
7178 On X86_32, this is an 6527 On X86_32, this is an alias for vdso32=. Otherwise:
7179 6528
7180 vdso=1: enable VDSO ( 6529 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 6530 vdso=0: disable VDSO mapping
7182 6531
7183 vdso32= [X86] Control the 32- 6532 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 6533 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 6534 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 6535
7187 See the help text for 6536 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 6537 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 6538 vdso32=0; otherwise, the default is vdso32=1.
7190 6539
7191 For compatibility wit 6540 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 6541 alias for vdso32=0.
7193 6542
7194 Try vdso32=0 if you e 6543 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 6544 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 6545
7197 video= [FB,EARLY] Frame buff !! 6546 vector= [IA-64,SMP]
>> 6547 vector=percpu: enable percpu vector domain
>> 6548
>> 6549 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 6550 See Documentation/fb/modedb.rst.
7199 6551
7200 video.brightness_switch_enabled= [ACP 6552 video.brightness_switch_enabled= [ACPI]
7201 Format: [0|1] 6553 Format: [0|1]
7202 If set to 1, on recei 6554 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 6555 generated by hotkey, video driver will adjust brightness
7204 level and then send o 6556 level and then send out the event to user space through
7205 the allocated input d 6557 the allocated input device. If set to 0, video driver
7206 will only send out th 6558 will only send out the event without touching backlight
7207 brightness level. 6559 brightness level.
7208 default: 1 6560 default: 1
7209 6561
7210 virtio_mmio.device= 6562 virtio_mmio.device=
7211 [VMMIO] Memory mapped 6563 [VMMIO] Memory mapped virtio (platform) device.
7212 6564
7213 <size>@<basead 6565 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 6566 where:
7215 <size> := 6567 <size> := size (can use standard suffixes
7216 6568 like K, M and G)
7217 <baseaddr> := 6569 <baseaddr> := physical base address
7218 <irq> := 6570 <irq> := interrupt number (as passed to
7219 6571 request_irq())
7220 <id> := 6572 <id> := (optional) platform device id
7221 example: 6573 example:
7222 virtio_mmio.d 6574 virtio_mmio.device=1K@0x100b0000:48:7
7223 6575
7224 Can be used multiple 6576 Can be used multiple times for multiple devices.
7225 6577
7226 vga= [BOOT,X86-32] Select 6578 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 6579 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 6580 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 6581 Use vga=ask for menu.
7230 This is actually a bo 6582 This is actually a boot loader parameter; the value is
7231 passed to the kernel 6583 passed to the kernel using a special protocol.
7232 6584
7233 vm_debug[=options] [KNL] Availab 6585 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 6586 May slow down system boot speed, especially when
7235 enabled on systems wi 6587 enabled on systems with a large amount of memory.
7236 All options are enabl 6588 All options are enabled by default, and this
7237 interface is meant to 6589 interface is meant to allow for selectively
7238 enabling or disabling 6590 enabling or disabling specific virtual memory
7239 debugging features. 6591 debugging features.
7240 6592
7241 Available options are 6593 Available options are:
7242 P Enable page s 6594 P Enable page structure init time poisoning
7243 - Disable all o 6595 - Disable all of the above options
7244 6596
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 6597 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 6598 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 6599 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 6600 decrease the size and leave more room for directly
7249 for directly mapped k !! 6601 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 6602
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 6603 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 6604 Sets the memory size reserved for contiguous memory
7256 allocations for the v 6605 allocations for the vmcp device driver.
7257 6606
7258 vmhalt= [KNL,S390] Perform z/ 6607 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 6608 Format: <command>
7260 6609
7261 vmpanic= [KNL,S390] Perform z/ 6610 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 6611 Format: <command>
7263 6612
7264 vmpoff= [KNL,S390] Perform z/ 6613 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 6614 Format: <command>
7266 6615
7267 vsyscall= [X86-64,EARLY] !! 6616 vsyscall= [X86-64]
7268 Controls the behavior 6617 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 6618 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 6619 code). Most statically-linked binaries and older
7271 versions of glibc use 6620 versions of glibc use these calls. Because these
7272 functions are at fixe 6621 functions are at fixed addresses, they make nice
7273 targets for exploits 6622 targets for exploits that can control RIP.
7274 6623
7275 emulate Vsyscalls !! 6624 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 6625 emulated reasonably safely. The vsyscall
7277 readable. !! 6626 page is readable.
7278 6627
7279 xonly [default] !! 6628 xonly Vsyscalls turn into traps and are
7280 emulated 6629 emulated reasonably safely. The vsyscall
7281 page is n 6630 page is not readable.
7282 6631
7283 none Vsyscalls 6632 none Vsyscalls don't work at all. This makes
7284 them quit 6633 them quite hard to use for exploits but
7285 might bre 6634 might break your system.
7286 6635
7287 vt.color= [VT] Default text col 6636 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6637 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6638 Default: 0x07 = light gray on black.
7290 6639
7291 vt.cur_default= [VT] Default cursor s 6640 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6641 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6642 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6643 see VGA-softcursor.txt. Default: 2 = underline.
7295 6644
7296 vt.default_blu= [VT] 6645 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6646 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6647 Change the default blue palette of the console.
7299 This is a 16-member a 6648 This is a 16-member array composed of values
7300 ranging from 0-255. 6649 ranging from 0-255.
7301 6650
7302 vt.default_grn= [VT] 6651 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6652 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6653 Change the default green palette of the console.
7305 This is a 16-member a 6654 This is a 16-member array composed of values
7306 ranging from 0-255. 6655 ranging from 0-255.
7307 6656
7308 vt.default_red= [VT] 6657 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6658 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6659 Change the default red palette of the console.
7311 This is a 16-member a 6660 This is a 16-member array composed of values
7312 ranging from 0-255. 6661 ranging from 0-255.
7313 6662
7314 vt.default_utf8= 6663 vt.default_utf8=
7315 [VT] 6664 [VT]
7316 Format=<0|1> 6665 Format=<0|1>
7317 Set system-wide defau 6666 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6667 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6668 newly opened terminals.
7320 6669
7321 vt.global_cursor_default= 6670 vt.global_cursor_default=
7322 [VT] 6671 [VT]
7323 Format=<-1|0|1> 6672 Format=<-1|0|1>
7324 Set system-wide defau 6673 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6674 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6675 i.e. cursors will be created by default unless
7327 overridden by individ 6676 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6677 cursors, 1 will display them.
7329 6678
7330 vt.italic= [VT] Default color fo 6679 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6680 Default: 2 = green.
7332 6681
7333 vt.underline= [VT] Default color fo 6682 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6683 Default: 3 = cyan.
7335 6684
7336 watchdog timers [HW,WDT] For informat 6685 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6686 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6687 or other driver-specific files in the
7339 Documentation/watchdo 6688 Documentation/watchdog/ directory.
7340 6689
7341 watchdog_thresh= 6690 watchdog_thresh=
7342 [KNL] 6691 [KNL]
7343 Set the hard lockup d 6692 Set the hard lockup detector stall duration
7344 threshold in seconds. 6693 threshold in seconds. The soft lockup detector
7345 threshold is set to t 6694 threshold is set to twice the value. A value of 0
7346 disables both lockup 6695 disables both lockup detectors. Default is 10
7347 seconds. 6696 seconds.
7348 6697
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= 6698 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 6699 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 6700 warn stall conditions and dump internal state to
7359 help debugging. 0 di 6701 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 6702 detection; otherwise, it's the stall threshold
7361 duration in seconds. 6703 duration in seconds. The default value is 30 and
7362 it can be updated at 6704 it can be updated at runtime by writing to the
7363 corresponding sysfs f 6705 corresponding sysfs file.
7364 6706
7365 workqueue.cpu_intensive_thresh_us= !! 6707 workqueue.disable_numa
7366 Per-cpu work items wh !! 6708 By default, all work items queued to unbound
7367 threshold are automat !! 6709 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 6710 issued on, which results in better behavior in
7369 them from noticeably !! 6711 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 6712 whatever reason, this option can be used. Note
7371 !! 6713 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 6714 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 6715
7386 workqueue.power_efficient 6716 workqueue.power_efficient
7387 Per-cpu workqueues ar 6717 Per-cpu workqueues are generally preferred because
7388 they show better perf 6718 they show better performance thanks to cache
7389 locality; unfortunate 6719 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 6720 be more power hungry than unbound workqueues.
7391 6721
7392 Enabling this makes t 6722 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 6723 were observed to contribute significantly to power
7394 consumption unbound, 6724 consumption unbound, leading to measurably lower
7395 power usage at the co 6725 power usage at the cost of small performance
7396 overhead. 6726 overhead.
7397 6727
7398 The default value of 6728 The default value of this parameter is determined by
7399 the config option CON 6729 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 6730
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 6731 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 6732 Workqueue used to implicitly guarantee that work
7415 items queued without 6733 items queued without explicit CPU specified are put
7416 on the local CPU. Th 6734 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 6735 and while local CPU is still preferred work items
7418 may be put on foreign 6736 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 6737 forces round-robin CPU selection to flush out
7420 usages which depend o 6738 usages which depend on the now broken guarantee.
7421 When enabled, memory 6739 When enabled, memory and cache locality will be
7422 impacted. 6740 impacted.
7423 6741
7424 writecombine= [LOONGARCH,EARLY] Con !! 6742 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 6743 default x2apic cluster mode on platforms
7432 supporting x2apic. 6744 supporting x2apic.
7433 6745
7434 xen_512gb_limit [KNL,X86-64,X 6746 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 6747 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6748 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6749 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6750 save/restore/migration must be enabled to handle larger
7439 domains. 6751 domains.
7440 6752
7441 xen_emul_unplug= [HW,X !! 6753 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6754 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6755 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6756 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6757 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6758 nics -- unplug network devices
7447 all -- unplug all emu 6759 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6760 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6761 unnecessary even if the host did not respond to
7450 the unplug pr 6762 the unplug protocol
7451 never -- do not unplu 6763 never -- do not unplug even if version check succeeds
7452 6764
7453 xen_legacy_crash [X86,XEN,EARL !! 6765 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6766 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6767 panic() code such as dumping handler.
7456 6768
7457 xen_mc_debug [X86,XEN,EARLY] !! 6769 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 6770 Disables the qspinlock slowpath using Xen PV optimizations.
7459 Enabling this feature !! 6771 This parameter is obsoleted by "nopvspin" parameter, which
7460 bit, so it should onl !! 6772 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 6773
7469 xen_nopv [X86] 6774 xen_nopv [X86]
7470 Disables the PV optim 6775 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6776 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6777 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6778 has equivalent effect for XEN platform.
7474 6779
7475 xen_no_vector_callback 6780 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6781 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6782 event channel interrupts.
7478 6783
7479 xen_scrub_pages= [XEN] 6784 xen_scrub_pages= [XEN]
7480 Boolean option to con 6785 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6786 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6787 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6788 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6789
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6790 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6791 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6792 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6793 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 6794 improve timer resolution at the expense of processing
7490 more timer interrupts 6795 more timer interrupts.
7491 6796
7492 xen.balloon_boot_timeout= [XEN] 6797 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 6798 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 6799 in case initial ballooning fails to free enough memory.
7495 Applies only when run 6800 Applies only when running as HVM or PVH guest and
7496 started with less mem 6801 started with less memory configured than allowed at
7497 max. Default is 180. 6802 max. Default is 180.
7498 6803
7499 xen.event_eoi_delay= [XEN] 6804 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 6805 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 6806 storms (jiffies). Default is 10.
7502 6807
7503 xen.event_loop_timeout= [XEN] 6808 xen.event_loop_timeout= [XEN]
7504 After which time (jif 6809 After which time (jiffies) the event handling loop
7505 should start to delay 6810 should start to delay EOI handling. Default is 2.
7506 6811
7507 xen.fifo_events= [XEN] 6812 xen.fifo_events= [XEN]
7508 Boolean parameter to 6813 Boolean parameter to disable using fifo event handling
7509 even if available. No 6814 even if available. Normally fifo event handling is
7510 preferred over the 2- 6815 preferred over the 2-level event handling, as it is
7511 fairer and the number 6816 fairer and the number of possible event channels is
7512 much higher. Default 6817 much higher. Default is on (use fifo events).
7513 6818
>> 6819 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6820 Disables the PV optimizations forcing the guest to run
>> 6821 as generic guest with no PV drivers. Currently support
>> 6822 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6823
>> 6824 nopvspin [X86,XEN,KVM]
>> 6825 Disables the qspinlock slow path using PV optimizations
>> 6826 which allow the hypervisor to 'idle' the guest on lock
>> 6827 contention.
>> 6828
7514 xirc2ps_cs= [NET,PCMCIA] 6829 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6830 Format:
7516 <irq>,<irq_mask>,<io> 6831 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6832
7518 xive= [PPC] 6833 xive= [PPC]
7519 By default on POWER9 6834 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6835 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6836 allows the fallback firmware mode to be used:
7522 6837
7523 off Fallback to 6838 off Fallback to firmware control of XIVE interrupt
7524 controller 6839 controller on both pseries and powernv
7525 platforms. 6840 platforms. Only useful on POWER9 and above.
7526 6841
7527 xive.store-eoi=off [PPC] 6842 xive.store-eoi=off [PPC]
7528 By default on POWER10 6843 By default on POWER10 and above, the kernel will use
7529 stores for EOI handli 6844 stores for EOI handling when the XIVE interrupt mode
7530 is active. This optio 6845 is active. This option allows the XIVE driver to use
7531 loads instead, as on 6846 loads instead, as on POWER9.
7532 6847
7533 xhci-hcd.quirks [USB,KNL] 6848 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6849 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6850 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6851 consulted in header drivers/usb/host/xhci.h.
7537 6852
7538 xmon [PPC,EARLY] !! 6853 xmon [PPC]
7539 Format: { early | on 6854 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 6855 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 6856 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 6857 early Call xmon as early as possible on boot; xmon
7543 debugger is c 6858 debugger is called from setup_arch().
7544 on xmon debugger 6859 on xmon debugger hooks will be installed so xmon
7545 is only calle 6860 is only called on a kernel crash. Default mode,
7546 i.e. either " 6861 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 6862 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 6863 rw xmon debugger hooks will be installed so xmon
7549 is called onl 6864 is called only on a kernel crash, mode is write,
7550 meaning SPR r 6865 meaning SPR registers, memory and, other data
7551 can be writte 6866 can be written using xmon commands.
7552 ro same as "rw" 6867 ro same as "rw" option above but SPR registers,
7553 memory, and o 6868 memory, and other data can't be written using
7554 xmon commands 6869 xmon commands.
7555 off xmon is disab 6870 off xmon is disabled.
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