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 !! 397 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support 398 support
449 399
450 arm64.nopauth [ARM64] Unconditionall !! 400 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
451 support 401 support
452 402
453 arm64.nosme [ARM64] Unconditionall !! 403 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
454 Extension support 404 Extension support
455 405
456 arm64.nosve [ARM64] Unconditionall !! 406 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
457 Extension support 407 Extension support
458 408
459 ataflop= [HW,M68k] 409 ataflop= [HW,M68k]
460 410
461 atarimouse= [HW,MOUSE] Atari Mouse 411 atarimouse= [HW,MOUSE] Atari Mouse
462 412
463 atkbd.extra= [HW] Enable extra LEDs 413 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 414 EzKey and similar keyboards
465 415
466 atkbd.reset= [HW] Reset keyboard du 416 atkbd.reset= [HW] Reset keyboard during initialization
467 417
468 atkbd.set= [HW] Select keyboard c 418 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 419 Format: <int> (2 = AT (default), 3 = PS/2)
470 420
471 atkbd.scroll= [HW] Enable scroll whe 421 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 422 keyboards
473 423
474 atkbd.softraw= [HW] Choose between sy 424 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 425 Format: <bool> (0 = real, 1 = synthetic (default))
476 426
477 atkbd.softrepeat= [HW] 427 atkbd.softrepeat= [HW]
478 Use software keyboard 428 Use software keyboard repeat
479 429
480 audit= [KNL] Enable the audit 430 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 431 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 432 0 | off - kernel audit is disabled and can not be
483 enabled until the 433 enabled until the next reboot
484 unset - kernel audit i 434 unset - kernel audit is initialized but disabled and
485 will be fully enab 435 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 436 1 | on - kernel audit is initialized and partially
487 enabled, storing a 437 enabled, storing at most audit_backlog_limit
488 messages in RAM un 438 messages in RAM until it is fully enabled by the
489 userspace auditd. 439 userspace auditd.
490 Default: unset 440 Default: unset
491 441
492 audit_backlog_limit= [KNL] Set the aud 442 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 443 Format: <int> (must be >=0)
494 Default: 64 444 Default: 64
495 445
496 bau= [X86_UV] Enable the BA 446 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 447 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 448 Format: { "0" | "1" }
499 0 - Disable the BAU. 449 0 - Disable the BAU.
500 1 - Enable the BAU. 450 1 - Enable the BAU.
501 unset - Disable the BA 451 unset - Disable the BAU.
502 452
503 baycom_epp= [HW,AX25] 453 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 454 Format: <io>,<mode>
505 455
506 baycom_par= [HW,AX25] BayCom Paral 456 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 457 Format: <io>,<mode>
508 See header of drivers/ 458 See header of drivers/net/hamradio/baycom_par.c.
509 459
510 baycom_ser_fdx= [HW,AX25] 460 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 461 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 462 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 463 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 464
515 baycom_ser_hdx= [HW,AX25] 465 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 466 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 467 Format: <io>,<irq>,<mode>
518 See header of drivers/ 468 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 469
520 bert_disable [ACPI] 470 bert_disable [ACPI]
521 Disable BERT OS suppor 471 Disable BERT OS support on buggy BIOSes.
522 472
523 bgrt_disable [ACPI,X86,EARLY] !! 473 bgrt_disable [ACPI][X86]
524 Disable BGRT to avoid 474 Disable BGRT to avoid flickering OEM logo.
525 475
526 blkdevparts= Manual partition parsi 476 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 477 embedded devices based on command line input.
528 See Documentation/bloc 478 See Documentation/block/cmdline-partition.rst
529 479
530 boot_delay= [KNL,EARLY] !! 480 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 481 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 482 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 483 Format: integer
537 484
538 bootconfig [KNL,EARLY] !! 485 bootconfig [KNL]
539 Extended command line 486 Extended command line options can be added to an initrd
540 and this will cause th 487 and this will cause the kernel to look for it.
541 488
542 See Documentation/admi 489 See Documentation/admin-guide/bootconfig.rst
543 490
544 bttv.card= [HW,V4L] bttv (bt848 + 491 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 492 bttv.radio= Most important insmod options are available as
546 kernel args too. 493 kernel args too.
547 bttv.pll= See Documentation/admi 494 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 495 bttv.tuner=
549 496
550 bulk_remove=off [PPC] This parameter 497 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 498 firmware feature for flushing multiple hpte entries
552 at a time. 499 at a time.
553 500
554 c101= [NET] Moxa C101 synchr 501 c101= [NET] Moxa C101 synchronous serial card
555 502
556 cachesize= [BUGS=X86-32] Override 503 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 504 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 505 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 506 to fix known problems, but for some CPUs it is not
560 possible to determine 507 possible to determine what the correct size should be.
561 This option provides a 508 This option provides an override for these situations.
562 509
563 carrier_timeout= 510 carrier_timeout=
564 [NET] Specifies amount 511 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 512 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 513 it waits 120 seconds.
567 514
568 ca_keys= [KEYS] This parameter 515 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 516 the system trusted keyring to be used for certificate
570 trust validation. 517 trust validation.
571 format: { id:<keyid> | 518 format: { id:<keyid> | builtin }
572 519
573 cca= [MIPS,EARLY] Override !! 520 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 521 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 522 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 523 for platform specific values (SB1, Loongson3 and
577 others). 524 others).
578 525
579 ccw_timeout_log [S390] 526 ccw_timeout_log [S390]
580 See Documentation/arch !! 527 See Documentation/s390/common_io.rst for details.
581 528
582 cgroup_disable= [KNL] Disable a partic 529 cgroup_disable= [KNL] Disable a particular controller or optional feature
583 Format: {name of the c 530 Format: {name of the controller(s) or feature(s) to disable}
584 The effects of cgroup_ 531 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 532 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 533 a single hierarchy
587 - foo isn't visible as 534 - foo isn't visible as an individually mountable
588 subsystem 535 subsystem
589 - if foo is an optiona 536 - if foo is an optional feature then the feature is
590 disabled and corresp 537 disabled and corresponding cgroup files are not
591 created 538 created
592 {Currently only "memor 539 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 540 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 541 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" 542 Specifying "pressure" disables per-cgroup pressure
596 stall information acco 543 stall information accounting feature
597 544
598 cgroup_no_v1= [KNL] Disable cgroup c 545 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 546 Format: { { controller | "all" | "named" }
600 [,{ controll 547 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 548 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 549 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 550 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 551 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 552 all v1 hierarchies.
606 553
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 554 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 555 Format: <string>
613 nosocket -- Disable so 556 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 557 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 558
617 checkreqprot= [SELINUX] Set initial 559 checkreqprot= [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 560 Format: { "0" | "1" }
619 See security/selinux/K 561 See security/selinux/Kconfig help text.
620 0 -- check protection 562 0 -- check protection applied by kernel (includes
621 any implied ex 563 any implied execute protection).
622 1 -- check protection 564 1 -- check protection requested by application.
623 Default value is set v 565 Default value is set via a kernel config option.
624 Value can be changed a 566 Value can be changed at runtime via
625 /sys/fs/selinu 567 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 568 Setting checkreqprot to 1 is deprecated.
627 569
628 cio_ignore= [S390] 570 cio_ignore= [S390]
629 See Documentation/arch !! 571 See Documentation/s390/common_io.rst for details.
630 572
631 clearcpuid=X[,X...] [X86] 573 clearcpuid=X[,X...] [X86]
632 Disable CPUID feature 574 Disable CPUID feature X for the kernel. See
633 arch/x86/include/asm/c 575 arch/x86/include/asm/cpufeatures.h for the valid bit
634 numbers X. Note the Li 576 numbers X. Note the Linux-specific bits are not necessarily
635 stable over kernel opt 577 stable over kernel options, but the vendor-specific
636 ones should be. 578 ones should be.
637 X can also be a string 579 X can also be a string as appearing in the flags: line
638 in /proc/cpuinfo which 580 in /proc/cpuinfo which does not have the above
639 instability issue. How 581 instability issue. However, not all features have names
640 in /proc/cpuinfo. 582 in /proc/cpuinfo.
641 Note that using this o 583 Note that using this option will taint your kernel.
642 Also note that user pr 584 Also note that user programs calling CPUID directly
643 or using the feature w 585 or using the feature without checking anything
644 will still see it. Thi 586 will still see it. This just prevents it from
645 being used by the kern 587 being used by the kernel or shown in /proc/cpuinfo.
646 Also note the kernel m 588 Also note the kernel might malfunction if you disable
647 some critical bits. 589 some critical bits.
648 590
649 clk_ignore_unused 591 clk_ignore_unused
650 [CLK] 592 [CLK]
651 Prevents the clock fra 593 Prevents the clock framework from automatically gating
652 clocks that have not b 594 clocks that have not been explicitly enabled by a Linux
653 device driver but are 595 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 596 by the bootloader/firmware. Note that this does not
655 force such clocks to b 597 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 598 those clocks in any way. This parameter is useful for
657 debug and development, 599 debug and development, but should not be needed on a
658 platform with proper d 600 platform with proper driver support. For more
659 information, see Docum 601 information, see Documentation/driver-api/clk.rst.
660 602
661 clock= [BUGS=X86-32, HW] gett 603 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 604 [Deprecated]
663 Forces specified clock 605 Forces specified clocksource (if available) to be used
664 when calculating getti 606 when calculating gettimeofday(). If specified
665 clocksource is not ava 607 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 608 Format: { pit | tsc | cyclone | pmtmr }
667 609
668 clocksource= Override the default c 610 clocksource= Override the default clocksource
669 Format: <string> 611 Format: <string>
670 Override the default c 612 Override the default clocksource and use the clocksource
671 with the name specifie 613 with the name specified.
672 Some clocksource names 614 Some clocksource names to choose from, depending on
673 the platform: 615 the platform:
674 [all] jiffies (this is 616 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 617 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 618 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 619 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 620 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 621 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 622 [MIPS] MIPS
681 [PARISC] cr16 623 [PARISC] cr16
682 [S390] tod 624 [S390] tod
683 [SH] SuperH 625 [SH] SuperH
684 [SPARC64] tick 626 [SPARC64] tick
685 [X86-64] hpet,tsc 627 [X86-64] hpet,tsc
686 628
687 clocksource.arm_arch_timer.evtstrm= 629 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 630 [ARM,ARM64]
689 Format: <bool> 631 Format: <bool>
690 Enable/disable the eve 632 Enable/disable the eventstream feature of the ARM
691 architected timer so t 633 architected timer so that code using WFE-based polling
692 loops can be debugged 634 loops can be debugged more effectively on production
693 systems. 635 systems.
694 636
>> 637 clocksource.max_cswd_read_retries= [KNL]
>> 638 Number of clocksource_watchdog() retries due to
>> 639 external delays before the clock will be marked
>> 640 unstable. Defaults to two retries, that is,
>> 641 three attempts to read the clock under test.
>> 642
695 clocksource.verify_n_cpus= [KNL] 643 clocksource.verify_n_cpus= [KNL]
696 Limit the number of CP 644 Limit the number of CPUs checked for clocksources
697 marked with CLOCK_SOUR 645 marked with CLOCK_SOURCE_VERIFY_PERCPU that
698 are marked unstable du 646 are marked unstable due to excessive skew.
699 A negative value says 647 A negative value says to check all CPUs, while
700 zero says not to check 648 zero says not to check any. Values larger than
701 nr_cpu_ids are silentl 649 nr_cpu_ids are silently truncated to nr_cpu_ids.
702 The actual CPUs are ch 650 The actual CPUs are chosen randomly, with
703 no replacement if the 651 no replacement if the same CPU is chosen twice.
704 652
705 clocksource-wdtest.holdoff= [KNL] 653 clocksource-wdtest.holdoff= [KNL]
706 Set the time in second 654 Set the time in seconds that the clocksource
707 watchdog test waits be 655 watchdog test waits before commencing its tests.
708 Defaults to zero when 656 Defaults to zero when built as a module and to
709 10 seconds when built 657 10 seconds when built into the kernel.
710 658
711 cma=nn[MG]@[start[MG][-end[MG]]] 659 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 660 [KNL,CMA]
713 Sets the size of kerne 661 Sets the size of kernel global memory area for
714 contiguous memory allo 662 contiguous memory allocations and optionally the
715 placement constraint b 663 placement constraint by the physical address range of
716 memory allocations. A 664 memory allocations. A value of 0 disables CMA
717 altogether. For more i 665 altogether. For more information, see
718 kernel/dma/contiguous. 666 kernel/dma/contiguous.c
719 667
720 cma_pernuma=nn[MG] 668 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 669 [ARM64,KNL,CMA]
722 Sets the size of kerne 670 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 671 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 672 per-numa CMA altogether. And If this option is not
725 specified, the default !! 673 specificed, the default value is 0.
726 With per-numa CMA enab 674 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 675 first try to allocate buffer from the pernuma area
728 which is located in no 676 which is located in node nid, if the allocation fails,
729 they will fallback to 677 they will fallback to the global default memory area.
730 678
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 | 679 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 680 Specify whether pages are marked as being inactive
744 when they are freed. 681 when they are freed. This is used in CMO environments
745 to determine OS memory 682 to determine OS memory pressure for page stealing by
746 a hypervisor. 683 a hypervisor.
747 Default: yes 684 Default: yes
748 685
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 686 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 687 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 688 allocations, by default set to 256K.
752 689
753 com20020= [HW,NET] ARCnet - COM2 690 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 691 Format:
755 <io>[,<irq>[,<nodeID>[ 692 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 693
757 com90io= [HW,NET] ARCnet - COM9 694 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 695 Format: <io>[,<irq>]
759 696
760 com90xx= [HW,NET] 697 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 698 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 699 Format: <io>[,<irq>[,<memstart>]]
763 700
764 condev= [HW,S390] console devi 701 condev= [HW,S390] console device
765 conmode= 702 conmode=
766 703
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 704 console= [KNL] Output console device and options.
779 705
780 tty<n> Use the virtual consol 706 tty<n> Use the virtual console device <n>.
781 707
782 ttyS<n>[,options] 708 ttyS<n>[,options]
783 ttyUSB0[,options] 709 ttyUSB0[,options]
784 Use the specified seri 710 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 711 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 712 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 713 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 714 omit it). Default is "9600n8".
789 715
790 See Documentation/admi 716 See Documentation/admin-guide/serial-console.rst for more
791 information. See 717 information. See
792 Documentation/networki 718 Documentation/networking/netconsole.rst for an
793 alternative. 719 alternative.
794 720
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] 721 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 722 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 723 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 724 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 725 uart[8250],0x<addr>[,options]
819 Start an early, polled 726 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 727 UART at the specified I/O port or MMIO address,
821 switching to the match 728 switching to the matching ttyS device later.
822 MMIO inter-register ad 729 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 730 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 731 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 732 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 733 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 734 the h/w is not re-initialized.
828 735
829 hvc<n> Use the hypervisor con 736 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 737 both Xen and PowerPC hypervisors.
831 738
832 { null | "" } 739 { null | "" }
833 Use to disable console 740 Use to disable console output, i.e., to have kernel
834 console messages disca 741 console messages discarded.
835 This must be the only 742 This must be the only console= parameter used on the
836 kernel command line. 743 kernel command line.
837 744
838 If the device connected to the 745 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 746 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 747 console=brl,ttyS0
841 For now, only VisioBraille is 748 For now, only VisioBraille is supported.
842 749
843 console_msg_format= 750 console_msg_format=
844 [KNL] Change console m 751 [KNL] Change console messages format
845 default 752 default
846 By default we print me 753 By default we print messages on consoles in
847 "[time stamp] text\n" 754 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 755 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 756 `printk_time' param).
850 syslog 757 syslog
851 Switch to syslog forma 758 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 759 IOW, each message will have a facility and loglevel
853 prefix. The format is 760 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 761 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 762 from /proc/kmsg.
856 763
857 consoleblank= [KNL] The console blan 764 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 765 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 766 Defaults to 0.
860 767
861 coredump_filter= 768 coredump_filter=
862 [KNL] Change the defau 769 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 770 /proc/<pid>/coredump_filter.
864 See also Documentation 771 See also Documentation/filesystems/proc.rst.
865 772
866 coresight_cpu_debug.enable 773 coresight_cpu_debug.enable
867 [ARM,ARM64] 774 [ARM,ARM64]
868 Format: <bool> 775 Format: <bool>
869 Enable/disable the CPU 776 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 777 0: default value, disable debugging
871 1: enable debugging at 778 1: enable debugging at boot time
872 779
873 cpcihp_generic= [HW,PCI] Generic port 780 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
874 Format: 781 Format:
875 <first_slot>,<last_slo 782 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
876 783
>> 784 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
>> 785 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
>> 786 Some features depend on CPU0. Known dependencies are:
>> 787 1. Resume from suspend/hibernate depends on CPU0.
>> 788 Suspend/hibernate will fail if CPU0 is offline and you
>> 789 need to online CPU0 before suspend/hibernate.
>> 790 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 791 removed if a PIC interrupt is detected.
>> 792 It's said poweroff/reboot may depend on CPU0 on some
>> 793 machines although I haven't seen such issues so far
>> 794 after CPU0 is offline on a few tested machines.
>> 795 If the dependencies are under your control, you can
>> 796 turn on cpu0_hotplug.
>> 797
877 cpuidle.off=1 [CPU_IDLE] 798 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 799 disable the cpuidle sub-system
879 800
880 cpuidle.governor= 801 cpuidle.governor=
881 [CPU_IDLE] Name of the 802 [CPU_IDLE] Name of the cpuidle governor to use.
882 803
883 cpufreq.off=1 [CPU_FREQ] 804 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 805 disable the cpufreq sub-system
885 806
886 cpufreq.default_governor= 807 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 808 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 809 policy to use. This governor must be registered in the
889 kernel before the cpuf 810 kernel before the cpufreq driver probes.
890 811
891 cpu_init_udelay=N 812 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 813 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 814 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 815 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 816 Default: 10000
896 817
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 818 crash_kexec_post_notifiers
904 Run kdump after runnin 819 Run kdump after running panic-notifiers and dumping
905 kmsg. This only for th 820 kmsg. This only for the users who doubt kdump always
906 succeeds in any situat 821 succeeds in any situation.
907 Note that this also in 822 Note that this also increases risks of kdump failure,
908 because some panic not 823 because some panic notifiers can make the crashed
909 kernel more unstable. 824 kernel more unstable.
910 825
911 crashkernel=size[KMG][@offset[KMG]] 826 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 827 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 828 upon panic. This parameter reserves the physical
914 memory region [offset, 829 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 830 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 831 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 832 [KNL, X86-64] Select a region under 4G first, and
918 under 4G first, and fa !! 833 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 834 hasn't been specified.
920 See Documentation/admi 835 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 836
922 crashkernel=range1:size1[,range2:size2 837 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 838 [KNL] Same as above, but depends on the memory
924 in the running system. 839 in the running system. The syntax of range is
925 start-[end] where star 840 start-[end] where start and end are both
926 a memory unit (amount[ 841 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 842 Documentation/admin-guide/kdump/kdump.rst for an example.
928 843
929 crashkernel=size[KMG],high 844 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 845 [KNL, X86-64, ARM64] range could be above 4G. Allow kernel
931 above 4G. !! 846 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 847 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 848 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 849 available.
935 below 4G, if available <<
936 It will be ignored if 850 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 851 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 852 [KNL, X86-64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 853 is passed, kernel could allocate physical memory region
940 physical memory region !! 854 above 4G, that cause second kernel crash on system
941 crash on system that r !! 855 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 856 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 857 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 858 devices won't run out. Kernel would try to allocate
945 default size of memory !! 859 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 860 This one lets the user specify own low range under 4G
952 for second kernel inst 861 for second kernel instead.
953 0: to disable low allo 862 0: to disable low allocation.
954 It will be ignored whe 863 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 864 or memory reserved is below 4G.
956 865
>> 866 [KNL, ARM64] range in low memory.
>> 867 This one lets the user specify a low range in the
>> 868 DMA zone for the crash dump kernel.
>> 869 It will be ignored when crashkernel=X,high is not used
>> 870 or memory reserved is located in the DMA zones.
>> 871
957 cryptomgr.notests 872 cryptomgr.notests
958 [KNL] Disable crypto s 873 [KNL] Disable crypto self-tests
959 874
960 cs89x0_dma= [HW,NET] 875 cs89x0_dma= [HW,NET]
961 Format: <dma> 876 Format: <dma>
962 877
963 cs89x0_media= [HW,NET] 878 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 879 Format: { rj45 | aui | bnc }
965 880
966 csdlock_debug= [KNL] Enable or disabl !! 881 csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
967 function call handling !! 882 handling. When switched on, additional debug data is
968 additional debug data !! 883 printed to the console in case a hanging CPU is
969 in case a hanging CPU !! 884 detected, and that CPU is pinged again in order to try
970 CPU is pinged again in !! 885 to resolve the hang situation.
971 the hang situation. T !! 886 0: disable csdlock debugging (default)
972 option depends on the !! 887 1: enable basic csdlock debugging (minor impact)
973 Kconfig option. !! 888 ext: enable extended csdlock debugging (more impact,
>> 889 but more data)
974 890
975 dasd= [HW,NET] 891 dasd= [HW,NET]
976 See header of drivers/ 892 See header of drivers/s390/block/dasd_devmap.c.
977 893
978 db9.dev[2|3]= [HW,JOY] Multisystem j 894 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 895 (one device per port)
980 Format: <port#>,<type> 896 Format: <port#>,<type>
981 See also Documentation 897 See also Documentation/input/devices/joystick-parport.rst
982 898
983 debug [KNL,EARLY] Enable ker !! 899 debug [KNL] Enable kernel debugging (events log level).
984 900
985 debug_boot_weak_hash 901 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 902 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 903 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 904 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 905 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 906 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 907 insecure, please do not use on production kernels.
992 908
993 debug_locks_verbose= 909 debug_locks_verbose=
994 [KNL] verbose locking 910 [KNL] verbose locking self-tests
995 Format: <int> 911 Format: <int>
996 Print debugging info w 912 Print debugging info while doing the locking API
997 self-tests. 913 self-tests.
998 Bitmask for the variou 914 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 915 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 916 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 917 useful to lockdep developers.
1002 918
1003 debug_objects [KNL,EARLY] Enable ob !! 919 debug_objects [KNL] Enable object debugging
>> 920
>> 921 no_debug_objects
>> 922 [KNL] Disable object debugging
1004 923
1005 debug_guardpage_minorder= 924 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 925 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 926 parameter allows control of the order of pages that will
1008 be intentionally kept 927 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 928 buddy allocator. Bigger value increase the probability
1010 of catching random me 929 of catching random memory corruption, but reduce the
1011 amount of memory for 930 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 931 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 932 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 933 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 934 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 935 random memory location. Note that there exists a class
1017 a class of memory cor !! 936 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 937 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 938 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 939 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 940 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 941 tracking down these problems.
1023 942
1024 debug_pagealloc= 943 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 944 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 945 enables the feature at boot time. By default, it is
1027 disabled and the syst 946 disabled and the system will work mostly the same as a
1028 kernel built without 947 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 948 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 949 useful to also enable the page_owner functionality.
1031 on: enable the featur 950 on: enable the feature
1032 951
1033 debugfs= [KNL,EARLY] This para !! 952 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 953 and debugfs internal clients.
1035 Format: { on, no-moun 954 Format: { on, no-mount, off }
1036 on: All functions 955 on: All functions are enabled.
1037 no-mount: 956 no-mount:
1038 Filesystem is 957 Filesystem is not registered but kernel clients can
1039 access APIs a 958 access APIs and a crashkernel can be used to read
1040 its content. 959 its content. There is nothing to mount.
1041 off: Filesystem is 960 off: Filesystem is not registered and clients
1042 get a -EPERM 961 get a -EPERM as result when trying to register files
1043 or directorie 962 or directories within debugfs.
1044 This is equiv 963 This is equivalent of the runtime functionality if
1045 debugfs was n 964 debugfs was not enabled in the kernel at all.
1046 Default value is set 965 Default value is set in build-time with a kernel configuration.
1047 966
1048 debugpat [X86] Enable PAT debu 967 debugpat [X86] Enable PAT debugging
1049 968
>> 969 decnet.addr= [HW,NET]
>> 970 Format: <area>[,<node>]
>> 971 See also Documentation/networking/decnet.rst.
>> 972
1050 default_hugepagesz= 973 default_hugepagesz=
1051 [HW] The size of the 974 [HW] The size of the default HugeTLB page. This is
1052 the size represented 975 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 976 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 977 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 978 filesystems. If not specified, defaults to the
1056 architecture's defaul 979 architecture's default huge page size. Huge page
1057 sizes are architectur 980 sizes are architecture dependent. See also
1058 Documentation/admin-g 981 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 982 Format: size[KMG]
1060 983
1061 deferred_probe_timeout= 984 deferred_probe_timeout=
1062 [KNL] Debugging optio 985 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 986 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 987 probe. Only specific dependencies (subsystems or
1065 drivers) that have op 988 drivers) that have opted in will be ignored. A timeout
1066 of 0 will timeout at 989 of 0 will timeout at the end of initcalls. If the time
1067 out hasn't expired, i 990 out hasn't expired, it'll be restarted by each
1068 successful driver reg 991 successful driver registration. This option will also
1069 dump out devices stil 992 dump out devices still on the deferred probe list after
1070 retrying. 993 retrying.
1071 994
1072 delayacct [KNL] Enable per-task 995 delayacct [KNL] Enable per-task delay accounting
1073 996
1074 dell_smm_hwmon.ignore_dmi= 997 dell_smm_hwmon.ignore_dmi=
1075 [HW] Continue probing 998 [HW] Continue probing hardware even if DMI data
1076 indicates that the dr 999 indicates that the driver is running on unsupported
1077 hardware. 1000 hardware.
1078 1001
1079 dell_smm_hwmon.force= 1002 dell_smm_hwmon.force=
1080 [HW] Activate driver 1003 [HW] Activate driver even if SMM BIOS signature does
1081 not match list of sup 1004 not match list of supported models and enable otherwise
1082 blacklisted features. 1005 blacklisted features.
1083 1006
1084 dell_smm_hwmon.power_status= 1007 dell_smm_hwmon.power_status=
1085 [HW] Report power sta 1008 [HW] Report power status in /proc/i8k
1086 (disabled by default) 1009 (disabled by default).
1087 1010
1088 dell_smm_hwmon.restricted= 1011 dell_smm_hwmon.restricted=
1089 [HW] Allow controllin 1012 [HW] Allow controlling fans only if SYS_ADMIN
1090 capability is set. 1013 capability is set.
1091 1014
1092 dell_smm_hwmon.fan_mult= 1015 dell_smm_hwmon.fan_mult=
1093 [HW] Factor to multip 1016 [HW] Factor to multiply fan speed with.
1094 1017
1095 dell_smm_hwmon.fan_max= 1018 dell_smm_hwmon.fan_max=
1096 [HW] Maximum configur 1019 [HW] Maximum configurable fan speed.
1097 1020
1098 dfltcc= [HW,S390] 1021 dfltcc= [HW,S390]
1099 Format: { on | off | 1022 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 1023 on: s390 zlib hardware support for compression on
1101 level 1 and 1024 level 1 and decompression (default)
1102 off: No s390 zli 1025 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 1026 def_only: s390 zlib hardware support for deflate
1104 only (compr 1027 only (compression on level 1)
1105 inf_only: s390 zlib h 1028 inf_only: s390 zlib hardware support for inflate
1106 only (decom 1029 only (decompression)
1107 always: Same as 'on 1030 always: Same as 'on' but ignores the selected compression
1108 level alway 1031 level always using hardware support (used for debugging)
1109 1032
1110 dhash_entries= [KNL] 1033 dhash_entries= [KNL]
1111 Set number of hash bu 1034 Set number of hash buckets for dentry cache.
1112 1035
1113 disable_1tb_segments [PPC,EARLY] !! 1036 disable_1tb_segments [PPC]
1114 Disables the use of 1 1037 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 1038 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 1039 can be useful when debugging issues that require an SLB
1117 miss to occur. 1040 miss to occur.
1118 1041
>> 1042 stress_slb [PPC]
>> 1043 Limits the number of kernel SLB entries, and flushes
>> 1044 them frequently to increase the rate of SLB faults
>> 1045 on kernel addresses.
>> 1046
1119 disable= [IPV6] 1047 disable= [IPV6]
1120 See Documentation/net 1048 See Documentation/networking/ipv6.rst.
1121 1049
1122 disable_radix [PPC,EARLY] !! 1050 disable_radix [PPC]
1123 Disable RADIX MMU mod 1051 Disable RADIX MMU mode on POWER9
1124 1052
>> 1053 radix_hcall_invalidate=on [PPC/PSERIES]
>> 1054 Disable RADIX GTSE feature and use hcall for TLB
>> 1055 invalidate.
>> 1056
1125 disable_tlbie [PPC] 1057 disable_tlbie [PPC]
1126 Disable TLBIE instruc 1058 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 1059 with KVM, with HASH MMU, or with coherent accelerators.
1128 1060
1129 disable_ddw [PPC/PSERIES,EARLY] !! 1061 disable_cpu_apicid= [X86,APIC,SMP]
>> 1062 Format: <int>
>> 1063 The number of initial APIC ID for the
>> 1064 corresponding CPU to be disabled at boot,
>> 1065 mostly used for the kdump 2nd kernel to
>> 1066 disable BSP to wake up multiple CPUs without
>> 1067 causing system reset or hang due to sending
>> 1068 INIT from AP to BSP.
>> 1069
>> 1070 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 1071 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 1072 to workaround buggy firmware.
1132 1073
1133 disable_ipv6= [IPV6] 1074 disable_ipv6= [IPV6]
1134 See Documentation/net 1075 See Documentation/networking/ipv6.rst.
1135 1076
1136 disable_mtrr_cleanup [X86,EARLY] !! 1077 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 1078 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 1079 to discrete, to make X server driver able to add WB
1139 entry later. This par 1080 entry later. This parameter disables that.
1140 1081
1141 disable_mtrr_trim [X86, Intel and AMD !! 1082 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 1083 By default the kernel will trim any uncacheable
1143 memory out of your av 1084 memory out of your available memory pool based on
1144 MTRR settings. This 1085 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 1086 possibly causing your machine to run very slowly.
1146 1087
1147 disable_timer_pin_1 [X86,EARLY] !! 1088 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 1089 Disable PIN 1 of APIC timer
1149 Can be useful to work 1090 Can be useful to work around chipset bugs.
1150 1091
1151 dis_ucode_ldr [X86] Disable the mic 1092 dis_ucode_ldr [X86] Disable the microcode loader.
1152 1093
1153 dma_debug=off If the kernel is comp 1094 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 1095 this option disables the debugging code at boot.
1155 1096
1156 dma_debug_entries=<number> 1097 dma_debug_entries=<number>
1157 This option allows to 1098 This option allows to tune the number of preallocated
1158 entries for DMA-API d 1099 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 1100 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 1101 DMA-API debugging code disables itself because the
1161 architectural default 1102 architectural default is too low.
1162 1103
1163 dma_debug_driver=<driver_name> 1104 dma_debug_driver=<driver_name>
1164 With this option the 1105 With this option the DMA-API debugging driver
1165 filter feature can be 1106 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1107 pass the driver to filter for as the parameter.
1167 The filter can be dis 1108 The filter can be disabled or changed to another
1168 driver later using sy 1109 driver later using sysfs.
1169 1110
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] 1111 driver_async_probe= [KNL]
1191 List of driver names 1112 List of driver names to be probed asynchronously. *
1192 matches with all driv 1113 matches with all driver names. If * is specified, the
1193 rest of the listed dr 1114 rest of the listed driver names are those that will NOT
1194 match the *. 1115 match the *.
1195 Format: <driver_name1 1116 Format: <driver_name1>,<driver_name2>...
1196 1117
1197 drm.edid_firmware=[<connector>:]<file 1118 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1119 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1120 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1121 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1122 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1123 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1124 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1125 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1126 and no file with the same name exists. Details and
>> 1127 instructions how to build your own EDID data are
>> 1128 available in Documentation/admin-guide/edid.rst. An EDID
>> 1129 data set will only be used for a particular connector,
>> 1130 if its name and a colon are prepended to the EDID
>> 1131 name. Each connector may use a unique EDID data
>> 1132 set by separating the files with a comma. An EDID
1206 data set with no conn 1133 data set with no connector name will be used for
1207 any connectors not ex 1134 any connectors not explicitly specified.
1208 1135
1209 dscc4.setup= [NET] 1136 dscc4.setup= [NET]
1210 1137
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1138 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1139 Format: {"off" | "known"}
1213 Control how the dt_cp 1140 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1141 used for CPU feature discovery and setup (if it
1215 exists). 1142 exists).
1216 off: Do not use it, f 1143 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1144 known: Do not pass through unknown features to guests
1218 or userspace, only th 1145 or userspace, only those that the kernel is aware of.
1219 1146
1220 dump_apple_properties [X86] 1147 dump_apple_properties [X86]
1221 Dump name and content 1148 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1149 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1150 what data is available or for reverse-engineering.
1224 1151
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1152 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1153 <module>.dyndbg[="val"]
1227 Enable debug messages 1154 Enable debug messages at boot time. See
1228 Documentation/admin-g 1155 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1156 for details.
1230 1157
1231 early_ioremap_debug [KNL,EARLY] !! 1158 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1159 in some Intel CPUs.
>> 1160
>> 1161 <module>.async_probe[=<bool>] [KNL]
>> 1162 If no <bool> value is specified or if the value
>> 1163 specified is not a valid <bool>, enable asynchronous
>> 1164 probe on this module. Otherwise, enable/disable
>> 1165 asynchronous probe on this module as indicated by the
>> 1166 <bool> value. See also: module.async_probe
>> 1167
>> 1168 early_ioremap_debug [KNL]
1232 Enable debug messages 1169 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1170 is useful for tracking down temporary early mappings
1234 which are not unmappe 1171 which are not unmapped.
1235 1172
1236 earlycon= [KNL,EARLY] Output ea !! 1173 earlycon= [KNL] Output early console device and options.
1237 1174
1238 When used with no opt 1175 When used with no options, the early console is
1239 determined by stdout- 1176 determined by stdout-path property in device tree's
1240 chosen node or the AC 1177 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1178 the platform.
1242 1179
1243 cdns,<addr>[,options] 1180 cdns,<addr>[,options]
1244 Start an early, polle 1181 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1182 (xuartps) serial port at the specified address. Only
1246 supported option is b 1183 supported option is baud rate. If baud rate is not
1247 specified, the serial 1184 specified, the serial port must already be setup and
1248 configured. 1185 configured.
1249 1186
1250 uart[8250],io,<addr>[,options !! 1187 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1188 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1189 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1190 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1191 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1192 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1193 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1194 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1195 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1196 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1197 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1198 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1199 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1200
1266 pl011,<addr> 1201 pl011,<addr>
1267 pl011,mmio32,<addr> 1202 pl011,mmio32,<addr>
1268 Start an early, polle 1203 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1204 port at the specified address. The pl011 serial port
1270 must already be setup 1205 must already be setup and configured. Options are not
1271 yet supported. If 'm 1206 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1207 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1208 the device registers.
1274 1209
1275 liteuart,<addr> 1210 liteuart,<addr>
1276 Start an early consol 1211 Start an early console on a litex serial port at the
1277 specified address. Th 1212 specified address. The serial port must already be
1278 setup and configured. 1213 setup and configured. Options are not yet supported.
1279 1214
1280 meson,<addr> 1215 meson,<addr>
1281 Start an early, polle 1216 Start an early, polled-mode console on a meson serial
1282 port at the specified 1217 port at the specified address. The serial port must
1283 already be setup and 1218 already be setup and configured. Options are not yet
1284 supported. 1219 supported.
1285 1220
1286 msm_serial,<addr> 1221 msm_serial,<addr>
1287 Start an early, polle 1222 Start an early, polled-mode console on an msm serial
1288 port at the specified 1223 port at the specified address. The serial port
1289 must already be setup 1224 must already be setup and configured. Options are not
1290 yet supported. 1225 yet supported.
1291 1226
1292 msm_serial_dm,<addr> 1227 msm_serial_dm,<addr>
1293 Start an early, polle 1228 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1229 dm port at the specified address. The serial port
1295 must already be setup 1230 must already be setup and configured. Options are not
1296 yet supported. 1231 yet supported.
1297 1232
1298 owl,<addr> 1233 owl,<addr>
1299 Start an early, polle 1234 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1235 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1236 specified address. The serial port must already be
1302 setup and configured. 1237 setup and configured. Options are not yet supported.
1303 1238
1304 rda,<addr> 1239 rda,<addr>
1305 Start an early, polle 1240 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1241 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1242 specified address. The serial port must already be
1308 setup and configured. 1243 setup and configured. Options are not yet supported.
1309 1244
1310 sbi 1245 sbi
1311 Use RISC-V SBI (Super 1246 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1247 console.
1313 1248
1314 smh Use ARM semihosting c 1249 smh Use ARM semihosting calls for early console.
1315 1250
1316 s3c2410,<addr> 1251 s3c2410,<addr>
1317 s3c2412,<addr> 1252 s3c2412,<addr>
1318 s3c2440,<addr> 1253 s3c2440,<addr>
1319 s3c6400,<addr> 1254 s3c6400,<addr>
1320 s5pv210,<addr> 1255 s5pv210,<addr>
1321 exynos4210,<addr> 1256 exynos4210,<addr>
1322 Use early console pro 1257 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1258 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1259 a correct base address of the selected UART port. The
1325 serial port must alre 1260 serial port must already be setup and configured.
1326 Options are not yet s 1261 Options are not yet supported.
1327 1262
1328 lantiq,<addr> 1263 lantiq,<addr>
1329 Start an early, polle 1264 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1265 (lqasc) port at the specified address. The serial port
1331 must already be setup 1266 must already be setup and configured. Options are not
1332 yet supported. 1267 yet supported.
1333 1268
1334 lpuart,<addr> 1269 lpuart,<addr>
1335 lpuart32,<addr> 1270 lpuart32,<addr>
1336 Use early console pro 1271 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1272 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1273 A valid base address must be provided, and the serial
1339 port must already be 1274 port must already be setup and configured.
1340 1275
1341 ec_imx21,<addr> 1276 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1277 ec_imx6q,<addr>
1343 Start an early, polle 1278 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1279 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1280 must already be setup and configured.
1346 1281
1347 ar3700_uart,<addr> 1282 ar3700_uart,<addr>
1348 Start an early, polle 1283 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1284 Armada 3700 serial port at the specified
1350 address. The serial p 1285 address. The serial port must already be setup
1351 and configured. Optio 1286 and configured. Options are not yet supported.
1352 1287
1353 qcom_geni,<addr> 1288 qcom_geni,<addr>
1354 Start an early, polle 1289 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1290 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1291 specified address. The serial port must already be
1357 setup and configured. 1292 setup and configured. Options are not yet supported.
1358 1293
1359 efifb,[options] 1294 efifb,[options]
1360 Start an early, unacc 1295 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1296 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1297 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1298 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1299 mapped with the correct attributes.
1365 1300
1366 linflex,<addr> 1301 linflex,<addr>
1367 Use early console pro 1302 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1303 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1304 address must be provided, and the serial port must
1370 already be setup and 1305 already be setup and configured.
1371 1306
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1307 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1308 earlyprintk=vga
1374 earlyprintk=sclp 1309 earlyprintk=sclp
1375 earlyprintk=xen 1310 earlyprintk=xen
1376 earlyprintk=serial[,t 1311 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1312 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1313 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1314 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1315 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1316 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1317
1384 earlyprintk is useful 1318 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1319 the normal console is initialized. It is not enabled by
1386 default because it ha 1320 default because it has some cosmetic problems.
1387 1321
1388 Append ",keep" to not 1322 Append ",keep" to not disable it when the real console
1389 takes over. 1323 takes over.
1390 1324
1391 Only one of vga, seri 1325 Only one of vga, serial, or usb debug port can
1392 be used at a time. 1326 be used at a time.
1393 1327
1394 Currently only ttyS0 1328 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1329 name. Other I/O ports may be explicitly specified
1396 on some architectures 1330 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1331 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1332 earlyprintk=serial,0x1008,115200
1399 You can find the port 1333 You can find the port for a given device in
1400 /proc/tty/driver/seri 1334 /proc/tty/driver/serial:
1401 2: uart:ST166 1335 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1336
1403 Interaction with the 1337 Interaction with the standard serial driver is not
1404 very good. 1338 very good.
1405 1339
1406 The VGA output is eve 1340 The VGA output is eventually overwritten by
1407 the real console. 1341 the real console.
1408 1342
1409 The xen option can on 1343 The xen option can only be used in Xen domains.
1410 1344
1411 The sclp output can o 1345 The sclp output can only be used on s390.
1412 1346
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1347 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1348 PCI device even when its classcode is not of the
1417 UART class. 1349 UART class.
1418 1350
1419 edac_report= [HW,EDAC] Control how 1351 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1352 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1353 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1354 by other higher priority error reporting module.
1423 off: disable H/W even 1355 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1356 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1357 default: on.
1426 1358
1427 edd= [EDD] 1359 edd= [EDD]
1428 Format: {"off" | "on" 1360 Format: {"off" | "on" | "skip[mbr]"}
1429 1361
1430 efi= [EFI,EARLY] !! 1362 efi= [EFI]
1431 Format: { "debug", "d 1363 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1364 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1365 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1366 debug: enable misc debug output.
1435 disable_early_pci_dma 1367 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1368 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1369 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1370 boot stub, as chunking can cause problems with some
1439 firmware implementati 1371 firmware implementations.
1440 noruntime : disable E 1372 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1373 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1374 attribute may cause the kernel to reserve the
1443 memory range for a me 1375 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1376 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1377 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1378 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1379 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1380 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1381 on all PCI bridges while in the EFI boot stub
1450 1382
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1383 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1384 Using this parameter you can use more than 50% of
1453 your efi variable sto 1385 your efi variable storage. Use this parameter only if
1454 you are really sure t 1386 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1387 fulfills the spec otherwise your board may brick.
1456 1388
>> 1389 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1390 Add arbitrary attribute to specific memory range by
>> 1391 updating original EFI memory map.
>> 1392 Region of memory which aa attribute is added to is
>> 1393 from ss to ss+nn.
>> 1394
>> 1395 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1396 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1397 attribute is added to range 0x100000000-0x180000000 and
>> 1398 0x10a0000000-0x1120000000.
>> 1399
>> 1400 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1401 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1402 range 0x240000000-0x43fffffff.
>> 1403
>> 1404 Using this parameter you can do debugging of EFI memmap
>> 1405 related features. For example, you can do debugging of
>> 1406 Address Range Mirroring feature even if your box
>> 1407 doesn't support it, or mark specific memory as
>> 1408 "soft reserved".
>> 1409
1457 efivar_ssdt= [EFI; X86] Name of an 1410 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1411 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1412 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1413 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1414 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1415
1463 1416
1464 eisa_irq_edge= [PARISC,HW] 1417 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1418 See header of drivers/parisc/eisa.c.
1466 1419
1467 ekgdboc= [X86,KGDB,EARLY] Allo !! 1420 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1468 Format: ekgdboc=kbd 1421 Format: ekgdboc=kbd
1469 1422
1470 This is designed to b 1423 This is designed to be used in conjunction with
1471 the boot argument: ea 1424 the boot argument: earlyprintk=vga
1472 1425
1473 This parameter works 1426 This parameter works in place of the kgdboc parameter
1474 but can only be used 1427 but can only be used if the backing tty is available
1475 very early in the boo 1428 very early in the boot process. For early debugging
1476 via a serial port see 1429 via a serial port see kgdboc_earlycon instead.
1477 1430
1478 elanfreq= [X86-32] 1431 elanfreq= [X86-32]
1479 See comment before fu 1432 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1433 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1434
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1435 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1436 Specifies physical address of start of kernel core
1484 image elf header and 1437 image elf header and optionally the size. Generally
1485 kexec loader will pas 1438 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1439 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1440
1488 enable_mtrr_cleanup [X86,EARLY] !! 1441 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1442 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1443 to discrete, to make X server driver able to add WB
1491 entry later. This par 1444 entry later. This parameter enables that.
1492 1445
1493 enable_timer_pin_1 [X86] 1446 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1447 Enable PIN 1 of APIC timer
1495 Can be useful to work 1448 Can be useful to work around chipset bugs
1496 (in particular on som 1449 (in particular on some ATI chipsets).
1497 The kernel tries to s 1450 The kernel tries to set a reasonable default.
1498 1451
1499 enforcing= [SELINUX] Set initial 1452 enforcing= [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1453 Format: {"0" | "1"}
1501 See security/selinux/ 1454 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1455 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1456 1 -- enforcing (deny and log).
1504 Default value is 0. 1457 Default value is 0.
1505 Value can be changed 1458 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1459 /sys/fs/selinux/enforce.
1507 1460
1508 erst_disable [ACPI] 1461 erst_disable [ACPI]
1509 Disable Error Record 1462 Disable Error Record Serialization Table (ERST)
1510 support. 1463 support.
1511 1464
1512 ether= [HW,NET] Ethernet car 1465 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1466 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1467 has equivalent usage. See its documentation for details.
1515 1468
1516 evm= [EVM] 1469 evm= [EVM]
1517 Format: { "fix" } 1470 Format: { "fix" }
1518 Permit 'security.evm' 1471 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1472 current integrity status.
1520 1473
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= 1474 failslab=
1530 fail_usercopy= 1475 fail_usercopy=
1531 fail_page_alloc= 1476 fail_page_alloc=
1532 fail_make_request=[KNL] 1477 fail_make_request=[KNL]
1533 General fault injecti 1478 General fault injection mechanism.
1534 Format: <interval>,<p 1479 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1480 See also Documentation/fault-injection/.
1536 1481
1537 fb_tunnels= [NET] 1482 fb_tunnels= [NET]
1538 Format: { initns | no 1483 Format: { initns | none }
1539 See Documentation/adm 1484 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1485 fb_tunnels_only_for_init_ns
1541 1486
1542 floppy= [HW] 1487 floppy= [HW]
1543 See Documentation/adm 1488 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1489
>> 1490 force_pal_cache_flush
>> 1491 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1492 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1493 parameter will force ia64_sal_cache_flush to call
>> 1494 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1495
1545 forcepae [X86-32] 1496 forcepae [X86-32]
1546 Forcefully enable Phy 1497 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1498 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1499 functionally usable PAE implementation.
1549 Warning: use of this 1500 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1501 and may cause unknown problems.
1551 1502
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] 1503 ftrace=[tracer]
1559 [FTRACE] will set and 1504 [FTRACE] will set and start the specified tracer
1560 as early as possible 1505 as early as possible in order to facilitate early
1561 boot debugging. 1506 boot debugging.
1562 1507
1563 ftrace_boot_snapshot 1508 ftrace_boot_snapshot
1564 [FTRACE] On boot up, 1509 [FTRACE] On boot up, a snapshot will be taken of the
1565 ftrace ring buffer th 1510 ftrace ring buffer that can be read at:
1566 /sys/kernel/tracing/s 1511 /sys/kernel/tracing/snapshot.
1567 This is useful if you 1512 This is useful if you need tracing information from kernel
1568 boot up that is likel 1513 boot up that is likely to be overridden by user space
1569 start up functionalit 1514 start up functionality.
1570 1515
1571 Optionally, the snaps !! 1516 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 1517 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1518 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1519 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1520 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1521 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 1522
1603 ftrace_filter=[function-list] 1523 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1524 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1525 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1526 list of functions. This list can be changed at run
1607 time by the set_ftrac 1527 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1528 tracing directory.
1609 1529
1610 ftrace_notrace=[function-list] 1530 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1531 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1532 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1533 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1534 tracing directory.
1615 1535
1616 ftrace_graph_filter=[function-list] 1536 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1537 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1538 by the function graph tracer at boot up.
1619 function-list is a co 1539 function-list is a comma-separated list of functions
1620 that can be changed a 1540 that can be changed at run time by the
1621 set_graph_function fi 1541 set_graph_function file in the debugfs tracing directory.
1622 1542
1623 ftrace_graph_notrace=[function-list] 1543 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1544 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1545 function-list. This list is a comma-separated list of
1626 functions that can be 1546 functions that can be changed at run time by the
1627 set_graph_notrace fil 1547 set_graph_notrace file in the debugfs tracing directory.
1628 1548
1629 ftrace_graph_max_depth=<uint> 1549 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1550 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1551 the max depth it will trace into a function. This value
1632 can be changed at run 1552 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1553 in the tracefs tracing directory. default: 0 (no limit)
1634 1554
1635 fw_devlink= [KNL,EARLY] Create de !! 1555 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1556 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1557 consumer/supplier relationships. This feature is
1638 especially useful whe 1558 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1559 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1560 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1561 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1562 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1563 suppliers).
1644 Format: { off | permi 1564 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1565 off -- Don't create device links from firmware info.
1646 permissive -- Create 1566 permissive -- Create device links from firmware info
1647 but use it on 1567 but use it only for ordering boot state clean
1648 up (sync_stat 1568 up (sync_state() calls).
1649 on -- Create device 1569 on -- Create device links from firmware info and use it
1650 to enforce pr 1570 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1571 rpm -- Like "on", but also use to order runtime PM.
1652 1572
1653 fw_devlink.strict=<bool> 1573 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1574 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1575 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1576 Format: <bool>
1657 1577
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]= 1578 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1579 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1580 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1581 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1582 See also Documentation/input/devices/joystick-parport.rst
1677 1583
1678 gamma= [HW,DRM] 1584 gamma= [HW,DRM]
1679 1585
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1586 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1587 Format: off | on
1682 default: on 1588 default: on
1683 1589
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 1590 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1591 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1592 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1593 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1594 debugfs files are removed at module unload time.
1709 1595
1710 goldfish [X86] Enable the gold 1596 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1597 Don't use this when you are not running on the
1712 android emulator 1598 android emulator
1713 1599
1714 gpio-mockup.gpio_mockup_ranges 1600 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1601 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1602 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1603 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1604 [HW] Let the driver know GPIO lines should be named.
1719 1605
1720 gpt [EFI] Forces disk wit 1606 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1607 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1608 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1609 GPT to be used instead.
1724 1610
1725 grcan.enable0= [HW] Configuration of 1611 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1612 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1613 Format: 0 | 1
1728 Default: 0 1614 Default: 0
1729 grcan.enable1= [HW] Configuration of 1615 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1616 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1617 Format: 0 | 1
1732 Default: 0 1618 Default: 0
1733 grcan.select= [HW] Select which phy 1619 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1620 Format: 0 | 1
1735 Default: 0 1621 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1622 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1623 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1624 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1625 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1626 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1627 Default: 1024
1742 1628
1743 hardened_usercopy= 1629 hardened_usercopy=
1744 [KNL] Under CONFIG_HA 1630 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
1745 hardening is enabled 1631 hardening is enabled for this boot. Hardened
1746 usercopy checking is 1632 usercopy checking is used to protect the kernel
1747 from reading or writi 1633 from reading or writing beyond known memory
1748 allocation boundaries 1634 allocation boundaries as a proactive defense
1749 against bounds-checki 1635 against bounds-checking flaws in the kernel's
1750 copy_to_user()/copy_f 1636 copy_to_user()/copy_from_user() interface.
1751 on Perform hardened user 1637 on Perform hardened usercopy checks (default).
1752 off Disable hardened user 1638 off Disable hardened usercopy checks.
1753 1639
1754 hardlockup_all_cpu_backtrace= 1640 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1641 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1642 backtraces on all cpus.
1757 Format: 0 | 1 1643 Format: 0 | 1
1758 1644
1759 hashdist= [KNL,NUMA] Large hash 1645 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1646 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1647 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1648 Format: 0 | 1 (for off | on)
1763 1649
>> 1650 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1651
1764 hd= [EIDE] (E)IDE hard dr 1652 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1653 Format: <cyl>,<head>,<sect>
1766 1654
1767 hest_disable [ACPI] 1655 hest_disable [ACPI]
1768 Disable Hardware Erro 1656 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1657 corresponding firmware-first mode error processing
1770 logic will be disable 1658 logic will be disabled.
1771 1659
1772 hibernate= [HIBERNATION] 1660 hibernate= [HIBERNATION]
1773 noresume Don't check i 1661 noresume Don't check if there's a hibernation image
1774 present durin 1662 present during boot.
1775 nocompress Don't compres 1663 nocompress Don't compress/decompress hibernation images.
1776 no Disable hiber 1664 no Disable hibernation and resume.
1777 protect_image Turn on image 1665 protect_image Turn on image protection during restoration
1778 (that will se 1666 (that will set all pages holding image data
1779 during restor 1667 during restoration read-only).
1780 1668
1781 hibernate.compressor= [HIBERNATION] !! 1669 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 1670 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1671 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1672 size on bigger boxes.
1796 1673
1797 highres= [KNL] Enable/disable 1674 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1675 Valid parameters: "on", "off"
1799 Default: "on" 1676 Default: "on"
1800 1677
1801 hlt [BUGS=ARM,SH] 1678 hlt [BUGS=ARM,SH]
1802 1679
1803 hostname= [KNL,EARLY] Set the h !! 1680 hostname= [KNL] Set the hostname (aka UTS nodename).
1804 Format: <string> 1681 Format: <string>
1805 This allows setting t 1682 This allows setting the system's hostname during early
1806 startup. This sets th 1683 startup. This sets the name returned by gethostname.
1807 Using this parameter 1684 Using this parameter to set the hostname makes it
1808 possible to ensure th 1685 possible to ensure the hostname is correctly set before
1809 any userspace process 1686 any userspace processes run, avoiding the possibility
1810 that a process may ca 1687 that a process may call gethostname before the hostname
1811 has been explicitly s 1688 has been explicitly set, resulting in the calling
1812 process getting an in 1689 process getting an incorrect result. The string must
1813 not exceed the maximu 1690 not exceed the maximum allowed hostname length (usually
1814 64 characters) and wi 1691 64 characters) and will be truncated otherwise.
1815 1692
1816 hpet= [X86-32,HPET] option 1693 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1694 Format: { enable (default) | disable | force |
1818 verbose } 1695 verbose }
1819 disable: disable HPET 1696 disable: disable HPET and use PIT instead
1820 force: allow force en 1697 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1698 VIA, nVidia)
1822 verbose: show content 1699 verbose: show contents of HPET registers during setup
1823 1700
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1701 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1702 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1703
1827 hugepages= [HW] Number of HugeTL 1704 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1705 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1706 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1707 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1708 line, it specifies the number of pages to allocate for
1832 the default huge page 1709 the default huge page size. If using node format, the
1833 number of pages to al 1710 number of pages to allocate per-node can be specified.
1834 See also Documentatio 1711 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1835 Format: <integer> or 1712 Format: <integer> or (node format)
1836 <node>:<integ 1713 <node>:<integer>[,<node>:<integer>]
1837 1714
1838 hugepagesz= 1715 hugepagesz=
1839 [HW] The size of the 1716 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1717 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1718 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1719 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1720 each supported huge page size. Huge page sizes are
1844 architecture dependen 1721 architecture dependent. See also
1845 Documentation/admin-g 1722 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1723 Format: size[KMG]
1847 1724
1848 hugetlb_cma= [HW,CMA,EARLY] The si !! 1725 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
1849 of gigantic hugepages 1726 of gigantic hugepages. Or using node format, the size
1850 of a CMA area per nod 1727 of a CMA area per node can be specified.
1851 Format: nn[KMGTPE] or 1728 Format: nn[KMGTPE] or (node format)
1852 <node>:nn[KMG 1729 <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1853 1730
1854 Reserve a CMA area of 1731 Reserve a CMA area of given size and allocate gigantic
1855 hugepages using the C 1732 hugepages using the CMA allocator. If enabled, the
1856 boot-time allocation 1733 boot-time allocation of gigantic hugepages is skipped.
1857 1734
1858 hugetlb_free_vmemmap= 1735 hugetlb_free_vmemmap=
1859 [KNL] Requires CONFIG !! 1736 [KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1860 enabled. 1737 enabled.
1861 Control if HugeTLB Vm 1738 Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1862 Allows heavy hugetlb 1739 Allows heavy hugetlb users to free up some more
1863 memory (7 * PAGE_SIZE 1740 memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1864 Format: { on | off (d 1741 Format: { on | off (default) }
1865 1742
1866 on: enable HVO 1743 on: enable HVO
1867 off: disable HVO 1744 off: disable HVO
1868 1745
1869 Built with CONFIG_HUG 1746 Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1870 the default is on. 1747 the default is on.
1871 1748
1872 Note that the vmemmap 1749 Note that the vmemmap pages may be allocated from the added
1873 memory block itself w 1750 memory block itself when memory_hotplug.memmap_on_memory is
1874 enabled, those vmemma 1751 enabled, those vmemmap pages cannot be optimized even if this
1875 feature is enabled. 1752 feature is enabled. Other vmemmap pages not allocated from
1876 the added memory bloc 1753 the added memory block itself do not be affected.
1877 1754
1878 hung_task_panic= 1755 hung_task_panic=
1879 [KNL] Should the hung 1756 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1757 Format: 0 | 1
1881 1758
1882 A value of 1 instruct 1759 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1760 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1761 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1762 option. The value selected by this boot parameter can
1886 be changed later by t 1763 be changed later by the kernel.hung_task_panic sysctl.
1887 1764
1888 hvc_iucv= [S390] Number of z/V 1765 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1766 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1767 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1768 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1769 from listed z/VM user IDs only.
1893 1770
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1771 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1772 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1773 guest on lock contention.
1897 on lock contention. !! 1774
>> 1775 keep_bootcon [KNL]
>> 1776 Do not unregister boot console at start. This is only
>> 1777 useful for debugging when something happens in the window
>> 1778 between unregistering the boot console and initializing
>> 1779 the real console.
1898 1780
1899 i2c_bus= [HW] Override the 1781 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1782 or register an additional I2C bus that is not
1901 registered fr 1783 registered from board initialization code.
1902 Format: 1784 Format:
1903 <bus_id>,<clk 1785 <bus_id>,<clkrate>
1904 1786
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 1787 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1788 i8042.unmask_kbd_data
1929 [HW] Enable printing 1789 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1790 (disabled by default, and as a pre-condition
1931 requires that i8 1791 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1792 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1793 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1794 keyboard and cannot control its state
1935 (Don't attempt t 1795 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1796 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1797 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1798 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1799 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1800 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1801 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1802 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1803 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1804 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1805 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1806 suspend-to-ram transitions, only during s2r
1947 transitions, or 1807 transitions, or never reset
1948 Format: { 1 | Y | y | 1808 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1809 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1810 0, N, n: don't ever reset controller
1951 Default: only on s2r 1811 Default: only on s2r transitions on x86; most other
1952 architectures force r 1812 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1813 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1814 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer 1815 i8042.probe_defer
1956 [HW] Allow deferred p 1816 [HW] Allow deferred probing upon i8042 probe errors
1957 1817
1958 i810= [HW,DRM] 1818 i810= [HW,DRM]
1959 1819
1960 i915.invert_brightness= 1820 i915.invert_brightness=
1961 [DRM] Invert the sens 1821 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1822 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1823 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1824 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1825 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1826 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1827 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1828 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1829 value switches the backlight off.
1970 -1 -- never invert br 1830 -1 -- never invert brightness
1971 0 -- machine default 1831 0 -- machine default
1972 1 -- force brightnes 1832 1 -- force brightness inversion
1973 1833
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] 1834 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1835 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1836
1983 1837
1984 idle= [X86,EARLY] !! 1838 idle= [X86]
1985 Format: idle=poll, id 1839 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1840 Poll forces a polling idle loop that can slightly
1987 improve the performan 1841 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1842 will use a lot of power and make the system run hot.
1989 Not recommended. 1843 Not recommended.
1990 idle=halt: Halt is fo 1844 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1845 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1846 idle=nomwait: Disable mwait for CPU C-states
1993 1847
1994 idxd.sva= [HW] 1848 idxd.sva= [HW]
1995 Format: <bool> 1849 Format: <bool>
1996 Allow force disabling 1850 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1851 support for the idxd driver. By default it is set to
1998 true (1). 1852 true (1).
1999 1853
2000 idxd.tc_override= [HW] 1854 idxd.tc_override= [HW]
2001 Format: <bool> 1855 Format: <bool>
2002 Allow override of def 1856 Allow override of default traffic class configuration
2003 for the device. By de 1857 for the device. By default it is set to false (0).
2004 1858
2005 ieee754= [MIPS] Select IEEE St 1859 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1860 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1861 Default: strict
2008 1862
2009 Choose which programs 1863 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1864 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1865 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1866 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1867 binary. Hardware implementations are permitted to
2014 support either or bot 1868 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1869 encoding mode.
2016 1870
2017 Available settings ar 1871 Available settings are as follows:
2018 strict accept binari 1872 strict accept binaries that request a NaN encoding
2019 supported by 1873 supported by the FPU
2020 legacy only accept l 1874 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1875 by the FPU
2022 2008 only accept 2 1876 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1877 by the FPU
2024 relaxed accept any bi 1878 relaxed accept any binaries regardless of whether
2025 supported by 1879 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1880
2029 The FPU emulator is a 1881 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1882 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1883 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1884 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1885 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1886 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1887 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1888 MIPS64 CPUs.
2037 1889
2038 The setting for ABS.f 1890 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1891 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1892 except where unsupported by hardware.
2041 1893
2042 ignore_loglevel [KNL,EARLY] !! 1894 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1895 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1896 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1897 We also add it as printk module parameter, so users
2046 could change it dynam 1898 could change it dynamically, usually by
2047 /sys/module/printk/pa 1899 /sys/module/printk/parameters/ignore_loglevel.
2048 1900
2049 ignore_rlimit_data 1901 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1902 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1903 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1904 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1905
2054 ihash_entries= [KNL] 1906 ihash_entries= [KNL]
2055 Set number of hash bu 1907 Set number of hash buckets for inode cache.
2056 1908
2057 ima_appraise= [IMA] appraise integr 1909 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1910 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1911 default: "enforce"
2060 1912
2061 ima_appraise_tcb [IMA] Deprecated. U 1913 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1914 The builtin appraise policy appraises all files
2063 owned by uid=0. 1915 owned by uid=0.
2064 1916
2065 ima_canonical_fmt [IMA] 1917 ima_canonical_fmt [IMA]
2066 Use the canonical for 1918 Use the canonical format for the binary runtime
2067 measurements, instead 1919 measurements, instead of host native format.
2068 1920
2069 ima_hash= [IMA] 1921 ima_hash= [IMA]
2070 Format: { md5 | sha1 1922 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1923 | sha512 | ... }
2072 default: "sha1" 1924 default: "sha1"
2073 1925
2074 The list of supported 1926 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1927 in crypto/hash_info.h.
2076 1928
2077 ima_policy= [IMA] 1929 ima_policy= [IMA]
2078 The builtin policies 1930 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1931 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1932 fail_securely | critical_data"
2081 1933
2082 The "tcb" policy meas 1934 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1935 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1936 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1937 uid=0.
2086 1938
2087 The "appraise_tcb" po 1939 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1940 all files owned by root.
2089 1941
2090 The "secure_boot" pol 1942 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1943 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1944 firmware, policy, etc) based on file signatures.
2093 1945
2094 The "fail_securely" p 1946 The "fail_securely" policy forces file signature
2095 verification failure 1947 verification failure also on privileged mounted
2096 filesystems with the 1948 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1949 flag.
2098 1950
2099 The "critical_data" p 1951 The "critical_data" policy measures kernel integrity
2100 critical data. 1952 critical data.
2101 1953
2102 ima_tcb [IMA] Deprecated. Us 1954 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1955 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1956 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1957 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1958 opened for read by uid=0.
2107 1959
2108 ima_template= [IMA] 1960 ima_template= [IMA]
2109 Select one of defined 1961 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i 1962 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2111 "ima-sigv2 1963 "ima-sigv2" }
2112 Default: "ima-ng" 1964 Default: "ima-ng"
2113 1965
2114 ima_template_fmt= 1966 ima_template_fmt=
2115 [IMA] Define a custom 1967 [IMA] Define a custom template format.
2116 Format: { "field1|... 1968 Format: { "field1|...|fieldN" }
2117 1969
2118 ima.ahash_minsize= [IMA] Minimum file 1970 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1971 Format: <min_file_size>
2120 Set the minimal file 1972 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1973 If left unspecified, ahash usage is disabled.
2122 1974
2123 ahash performance var 1975 ahash performance varies for different data sizes on
2124 different crypto acce 1976 different crypto accelerators. This option can be used
2125 to achieve the best p 1977 to achieve the best performance for a particular HW.
2126 1978
2127 ima.ahash_bufsize= [IMA] Asynchronous 1979 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1980 Format: <bufsize>
2129 Set hashing buffer si 1981 Set hashing buffer size. Default: 4k.
2130 1982
2131 ahash performance var 1983 ahash performance varies for different chunk sizes on
2132 different crypto acce 1984 different crypto accelerators. This option can be used
2133 to achieve best perfo 1985 to achieve best performance for particular HW.
2134 1986
2135 init= [KNL] 1987 init= [KNL]
2136 Format: <full_path> 1988 Format: <full_path>
2137 Run specified binary 1989 Run specified binary instead of /sbin/init as init
2138 process. 1990 process.
2139 1991
2140 initcall_debug [KNL] Trace initcalls 1992 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1993 for working out where the kernel is dying during
2142 startup. 1994 startup.
2143 1995
2144 initcall_blacklist= [KNL] Do not exe 1996 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1997 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1998 modules and initcalls.
2147 1999
2148 initramfs_async= [KNL] 2000 initramfs_async= [KNL]
2149 Format: <bool> 2001 Format: <bool>
2150 Default: 1 2002 Default: 1
2151 This parameter contro 2003 This parameter controls whether the initramfs
2152 image is unpacked asy 2004 image is unpacked asynchronously, concurrently
2153 with devices being pr 2005 with devices being probed and
2154 initialized. This sho 2006 initialized. This should normally just work,
2155 but as a debugging ai 2007 but as a debugging aid, one can get the
2156 historical behaviour 2008 historical behaviour of the initramfs
2157 unpacking being compl 2009 unpacking being completed before device_ and
2158 late_ initcalls. 2010 late_ initcalls.
2159 2011
2160 initrd= [BOOT,EARLY] Specify !! 2012 initrd= [BOOT] Specify the location of the initial ramdisk
2161 2013
2162 initrdmem= [KNL,EARLY] Specify a !! 2014 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 2015 load the initrd. If an initrd is compiled in or
2164 specified in the boot 2016 specified in the bootparams, it takes priority over this
2165 setting. 2017 setting.
2166 Format: ss[KMG],nn[KM 2018 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 2019 Default is 0, 0
2168 2020
2169 init_on_alloc= [MM,EARLY] Fill newly !! 2021 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 2022 zeroes.
2171 Format: 0 | 1 2023 Format: 0 | 1
2172 Default set by CONFIG 2024 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 2025
2174 init_on_free= [MM,EARLY] Fill freed !! 2026 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 2027 Format: 0 | 1
2176 Default set by CONFIG 2028 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 2029
2178 init_pkru= [X86] Specify the def 2030 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 2031 register contents for all processes. 0x55555554 by
2180 default (disallow acc 2032 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 2033 override in debugfs after boot.
2182 2034
2183 inport.irq= [HW] Inport (ATI XL a 2035 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 2036 Format: <irq>
2185 2037
2186 int_pln_enable [X86] Enable power li 2038 int_pln_enable [X86] Enable power limit notification interrupt
2187 2039
2188 integrity_audit=[IMA] 2040 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 2041 Format: { "0" | "1" }
2190 0 -- basic integrity 2042 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 2043 1 -- additional integrity auditing messages.
2192 2044
2193 intel_iommu= [DMAR] Intel IOMMU dr 2045 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 2046 on
2195 Enable intel iommu dr 2047 Enable intel iommu driver.
2196 off 2048 off
2197 Disable intel iommu d 2049 Disable intel iommu driver.
2198 igfx_off [Default Off] 2050 igfx_off [Default Off]
2199 By default, gfx is ma 2051 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 2052 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 2053 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 2054 this case, gfx device will use physical address for
2203 DMA. 2055 DMA.
2204 strict [Default Off] 2056 strict [Default Off]
2205 Deprecated, equivalen 2057 Deprecated, equivalent to iommu.strict=1.
2206 sp_off [Default Off] 2058 sp_off [Default Off]
2207 By default, super pag 2059 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 2060 has the capability. With this option, super page will
2209 not be supported. 2061 not be supported.
2210 sm_on 2062 sm_on
2211 Enable the Intel IOMM 2063 Enable the Intel IOMMU scalable mode if the hardware
2212 advertises that it ha 2064 advertises that it has support for the scalable mode
2213 translation. 2065 translation.
2214 sm_off 2066 sm_off
2215 Disallow use of the I 2067 Disallow use of the Intel IOMMU scalable mode.
2216 tboot_noforce [Default Off] 2068 tboot_noforce [Default Off]
2217 Do not force the Inte 2069 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 2070 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 2071 could harm performance of some high-throughput
2220 devices like 40GBit n 2072 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 2073 mapping is enabled.
2222 Note that using this 2074 Note that using this option lowers the security
2223 provided by tboot bec 2075 provided by tboot because it makes the system
2224 vulnerable to DMA att 2076 vulnerable to DMA attacks.
2225 2077
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 2078 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 2079 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 2080 1 to 9 specify maximum depth of C-state.
2229 2081
2230 intel_pstate= [X86,EARLY] !! 2082 intel_pstate= [X86]
2231 disable 2083 disable
2232 Do not enable intel 2084 Do not enable intel_pstate as the default
2233 scaling driver for 2085 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 2086 passive
2245 Use intel_pstate as 2087 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 2088 to work with generic cpufreq governors (instead of
2247 enabling its intern 2089 enabling its internal governor). This mode cannot be
2248 used along with the 2090 used along with the hardware-managed P-states (HWP)
2249 feature. 2091 feature.
2250 force 2092 force
2251 Enable intel_pstate 2093 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 2094 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 2095 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 2096 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 2097 P-States information being indicated to OSPM and therefore
2256 should be used with 2098 should be used with caution. This option does not work with
2257 processors that are 2099 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 2100 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 2101 no_hwp
2260 Do not enable hardw 2102 Do not enable hardware P state control (HWP)
2261 if available. 2103 if available.
2262 hwp_only 2104 hwp_only
2263 Only load intel_pst 2105 Only load intel_pstate on systems which support
2264 hardware P state co 2106 hardware P state control (HWP) if available.
2265 support_acpi_ppc 2107 support_acpi_ppc
2266 Enforce ACPI _PPC p 2108 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 2109 Description Table, specifies preferred power management
2268 profile as "Enterpr 2110 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 2111 then this feature is turned on by default.
2270 per_cpu_perf_limits 2112 per_cpu_perf_limits
2271 Allow per-logical-C 2113 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 2114 cpufreq sysfs interface
2273 2115
2274 intremap= [X86-64,Intel-IOMMU,E !! 2116 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 2117 on enable Interrupt Remapping (default)
2276 off disable Inter 2118 off disable Interrupt Remapping
2277 nosid disable Sourc 2119 nosid disable Source ID checking
2278 no_x2apic_optout 2120 no_x2apic_optout
2279 BIOS x2APIC o 2121 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 2122 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 2123
2284 iomem= Disable strict checki 2124 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 2125 strict regions from userspace.
2286 relaxed 2126 relaxed
2287 2127
2288 iommu= [X86,EARLY] !! 2128 iommu= [X86]
2289 off 2129 off
2290 force 2130 force
2291 noforce 2131 noforce
2292 biomerge 2132 biomerge
2293 panic 2133 panic
2294 nopanic 2134 nopanic
2295 merge 2135 merge
2296 nomerge 2136 nomerge
2297 soft 2137 soft
2298 pt [X86] 2138 pt [X86]
2299 nopt [X86] 2139 nopt [X86]
2300 nobypass [PPC/POWERNV] 2140 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 2141 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2142
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2143 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 2144 Format: { "0" | "1" }
2305 0 - Try to allocate a 2145 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 2146 falling back to the full range if needed.
2307 1 - Allocate directly 2147 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 2148 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 2149 greater than 32-bit addressing.
2310 2150
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 2151 iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 2152 Format: { "0" | "1" }
2313 0 - Lazy mode. 2153 0 - Lazy mode.
2314 Request that DMA un 2154 Request that DMA unmap operations use deferred
2315 invalidation of har 2155 invalidation of hardware TLBs, for increased
2316 throughput at the c 2156 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2157 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2158 the relevant IOMMU driver.
2319 1 - Strict mode. 2159 1 - Strict mode.
2320 DMA unmap operation 2160 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2161 synchronously.
2322 unset - Use value of 2162 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2323 Note: on x86, strict 2163 Note: on x86, strict mode specified via one of the
2324 legacy driver-specifi 2164 legacy driver-specific options takes precedence.
2325 2165
2326 iommu.passthrough= 2166 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2167 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2168 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2169 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2170 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2171 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2172
2333 io7= [HW] IO7 for Marvel-b 2173 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2174 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2175 arch/alpha/kernel/core_marvel.c.
2336 2176
2337 io_delay= [X86,EARLY] I/O delay !! 2177 io_delay= [X86] I/O delay method
2338 0x80 2178 0x80
2339 Standard port 0x80 ba 2179 Standard port 0x80 based delay
2340 0xed 2180 0xed
2341 Alternate port 0xed b 2181 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2182 udelay
2343 Simple two microsecon 2183 Simple two microseconds delay
2344 none 2184 none
2345 No delay 2185 No delay
2346 2186
2347 ip= [IP_PNP] 2187 ip= [IP_PNP]
2348 See Documentation/adm 2188 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2189
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2190 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2191 IPC identifiers from 32,768 to 16,777,216.
2352 2192
2353 irqaffinity= [SMP] Set the default 2193 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2194 The argument is a cpu list, as described above.
2355 2195
2356 irqchip.gicv2_force_probe= 2196 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2197 [ARM, ARM64]
2358 Format: <bool> 2198 Format: <bool>
2359 Force the kernel to l 2199 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2200 of a GICv2 controller even if the memory range
2361 exposed by the device 2201 exposed by the device tree is too small.
2362 2202
2363 irqchip.gicv3_nolpi= 2203 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2204 [ARM, ARM64]
2365 Force the kernel to i 2205 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2206 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2207 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2208 to let secondary kernels in charge of setting up
2369 LPIs. 2209 LPIs.
2370 2210
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2211 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2212 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2213 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2214 CONFIG_ARM64_PSEUDO_NMI.
2375 2215
2376 irqfixup [HW] 2216 irqfixup [HW]
2377 When an interrupt is 2217 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2218 for it. Intended to get systems with badly broken
2379 firmware running. 2219 firmware running.
2380 2220
2381 irqpoll [HW] 2221 irqpoll [HW]
2382 When an interrupt is 2222 When an interrupt is not handled search all handlers
2383 for it. Also check al 2223 for it. Also check all handlers each timer
2384 interrupt. Intended t 2224 interrupt. Intended to get systems with badly broken
2385 firmware running. 2225 firmware running.
2386 2226
2387 isapnp= [ISAPNP] 2227 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2228 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2229
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2230 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2231 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2232 Format: [flag-list,]<cpu-list>
2393 2233
2394 Specify one or more C 2234 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2235 specified in the flag list (default: domain):
2396 2236
2397 nohz 2237 nohz
2398 Disable the tick wh 2238 Disable the tick when a single task runs.
2399 2239
2400 A residual 1Hz tick 2240 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2241 need to affine to housekeeping through the global
2402 workqueue's affinit 2242 workqueue's affinity configured via the
2403 /sys/devices/virtua 2243 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2244 by using the 'domain' flag described below.
2405 2245
2406 NOTE: by default th 2246 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2247 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2248 be configured manually after bootup.
2409 2249
2410 domain 2250 domain
2411 Isolate from the ge 2251 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2252 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2253 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2254 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2255 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2256 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2257 It offers a much more flexible interface where CPUs can
2418 move in and out of 2258 move in and out of an isolated set anytime.
2419 2259
2420 You can move a proc 2260 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2261 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2262 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2263 "number of CPUs in system - 1".
2424 2264
2425 managed_irq 2265 managed_irq
2426 2266
2427 Isolate from being 2267 Isolate from being targeted by managed interrupts
2428 which have an inter 2268 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2269 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2270 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2271 the /proc/irq/* interfaces.
2432 2272
2433 This isolation is b 2273 This isolation is best effort and only effective
2434 if the automaticall 2274 if the automatically assigned interrupt mask of a
2435 device queue contai 2275 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2276 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2277 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2278 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2279 cannot disturb the isolated CPU.
2440 2280
2441 If a queue's affini 2281 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2282 CPUs then this parameter has no effect on the
2443 interrupt routing d 2283 interrupt routing decision, though interrupts are
2444 only delivered when 2284 only delivered when tasks running on those
2445 isolated CPUs submi 2285 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2286 housekeeping CPUs has no influence on those
2447 queues. 2287 queues.
2448 2288
2449 The format of <cpu-li 2289 The format of <cpu-list> is described above.
2450 2290
2451 iucv= [HW,NET] 2291 iucv= [HW,NET]
2452 2292
2453 ivrs_ioapic [HW,X86-64] 2293 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2294 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t 2295 mapping provided in the IVRS ACPI table.
2456 By default, PCI segme 2296 By default, PCI segment is 0, and can be omitted.
2457 2297
2458 For example, to map I 2298 For example, to map IOAPIC-ID decimal 10 to
2459 PCI segment 0x1 and P 2299 PCI segment 0x1 and PCI device 00:14.0,
2460 write the parameter a 2300 write the parameter as:
2461 ivrs_ioapic=1 2301 ivrs_ioapic=10@0001:00:14.0
2462 2302
2463 Deprecated formats: 2303 Deprecated formats:
2464 * To map IOAPIC-ID de 2304 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2465 write the parameter 2305 write the parameter as:
2466 ivrs_ioapic[1 2306 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de 2307 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2468 PCI device 00:14.0 2308 PCI device 00:14.0 write the parameter as:
2469 ivrs_ioapic[1 2309 ivrs_ioapic[10]=0001:00:14.0
2470 2310
2471 ivrs_hpet [HW,X86-64] 2311 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2312 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t 2313 mapping provided in the IVRS ACPI table.
2474 By default, PCI segme 2314 By default, PCI segment is 0, and can be omitted.
2475 2315
2476 For example, to map H 2316 For example, to map HPET-ID decimal 10 to
2477 PCI segment 0x1 and P 2317 PCI segment 0x1 and PCI device 00:14.0,
2478 write the parameter a 2318 write the parameter as:
2479 ivrs_hpet=10@ 2319 ivrs_hpet=10@0001:00:14.0
2480 2320
2481 Deprecated formats: 2321 Deprecated formats:
2482 * To map HPET-ID deci 2322 * To map HPET-ID decimal 0 to PCI device 00:14.0
2483 write the parameter 2323 write the parameter as:
2484 ivrs_hpet[0]= 2324 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci 2325 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2486 PCI device 00:14.0 2326 PCI device 00:14.0 write the parameter as:
2487 ivrs_ioapic[1 2327 ivrs_ioapic[10]=0001:00:14.0
2488 2328
2489 ivrs_acpihid [HW,X86-64] 2329 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2330 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t 2331 mapping provided in the IVRS ACPI table.
2492 By default, PCI segme 2332 By default, PCI segment is 0, and can be omitted.
2493 2333
2494 For example, to map U 2334 For example, to map UART-HID:UID AMD0020:0 to
2495 PCI segment 0x1 and P 2335 PCI segment 0x1 and PCI device ID 00:14.5,
2496 write the parameter a 2336 write the parameter as:
2497 ivrs_acpihid= 2337 ivrs_acpihid=AMD0020:0@0001:00:14.5
2498 2338
2499 Deprecated formats: 2339 Deprecated formats:
2500 * To map UART-HID:UID 2340 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2501 PCI device ID 00:14 2341 PCI device ID 00:14.5, write the parameter as:
2502 ivrs_acpihid[ 2342 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID 2343 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2504 PCI device ID 00:14 2344 PCI device ID 00:14.5, write the parameter as:
2505 ivrs_acpihid[ 2345 ivrs_acpihid[0001:00:14.5]=AMD0020:0
2506 2346
2507 js= [HW,JOY] Analog joyst 2347 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2348 See Documentation/input/joydev/joystick.rst.
2509 2349
>> 2350 nokaslr [KNL]
>> 2351 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2352 kernel and module base offset ASLR (Address Space
>> 2353 Layout Randomization).
>> 2354
2510 kasan_multi_shot 2355 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2356 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2357 report on every invalid memory access. Without this
2513 parameter KASAN will 2358 parameter KASAN will print report only for the first
2514 invalid access. 2359 invalid access.
2515 2360
2516 keep_bootcon [KNL,EARLY] !! 2361 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 2362
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2363 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2364 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2365 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2366 the kernel for non-movable allocations. The requested
2528 amount is spread even 2367 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2368 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2369 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2370 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2371 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2372 other nodes will have a larger ZONE_MOVABLE.
2534 2373
2535 ZONE_MOVABLE is used 2374 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2375 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2376 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2377 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2378 zone if it does not.
2540 2379
2541 It is possible to spe 2380 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2381 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2382 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2383 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2384 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2385 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2386 are exclusive, so you cannot specify multiple forms.
2548 2387
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2388 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2389 Format: <Controller#>[,poll interval]
2551 The controller # is t 2390 The controller # is the number of the ehci usb debug
2552 port as it is probed 2391 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2392 optional and is the number seconds in between
2554 each poll cycle to th 2393 each poll cycle to the debug port in case you need
2555 the functionality for 2394 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2395 gdb or control-c on the dbgp connection. When
2557 not using this parame 2396 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2397 the kernel debugger.
2559 2398
2560 kgdboc= [KGDB,HW] kgdb over c 2399 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2400 Requires a tty driver that supports console polling,
2562 or a supported pollin 2401 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2402 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2403 keyboard only format: kbd
2565 keyboard and serial 2404 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2405 Optional Kernel mode setting:
2567 kms, kbd format: kms 2406 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2407 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2408
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2409 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2410 If the boot console provides the ability to read
2572 characters and can wo 2411 characters and can work in polling mode, you can use
2573 this parameter to tel 2412 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2413 until the normal console is registered. Intended to
2575 be used together with 2414 be used together with the kgdboc parameter which
2576 specifies the normal 2415 specifies the normal console to transition to.
2577 2416
2578 The name of the early 2417 The name of the early console should be specified
2579 as the value of this 2418 as the value of this parameter. Note that the name of
2580 the early console mig 2419 the early console might be different than the tty
2581 name passed to kgdboc 2420 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2421 blank and the first boot console that implements
2583 read() will be picked 2422 read() will be picked.
2584 2423
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2424 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2425 kernel debugger at the earliest opportunity.
2587 2426
2588 kmac= [MIPS] Korina etherne 2427 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2428 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2429 Ethernet adapter MAC address.
2591 2430
2592 kmemleak= [KNL,EARLY] Boot-time !! 2431 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2432 Valid arguments: on, off
2594 Default: on 2433 Default: on
2595 Built with CONFIG_DEB 2434 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2435 the default is off.
2597 2436
2598 kprobe_event=[probe-list] 2437 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2438 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2439 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2440 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2441 interface, but the parameters are comma delimited.
2603 For example, to add a 2442 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2443 arg1 and arg2, add to the command line;
2605 2444
2606 kprobe_event=p, 2445 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2446
2608 See also Documentatio 2447 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2448 Boot Parameter" section.
2610 2449
2611 kpti= [ARM64,EARLY] Control !! 2450 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2451 and kernel address spaces.
2613 Default: enabled on c 2452 Default: enabled on cores which need mitigation.
2614 0: force disabled 2453 0: force disabled
2615 1: force enabled 2454 1: force enabled
2616 2455
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 2456 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2457 Default is 0 (don't ignore, but inject #GP)
2625 2458
2626 kvm.eager_page_split= 2459 kvm.eager_page_split=
2627 [KVM,X86] Controls wh 2460 [KVM,X86] Controls whether or not KVM will try to
2628 proactively split all 2461 proactively split all huge pages during dirty logging.
2629 Eager page splitting 2462 Eager page splitting reduces interruptions to vCPU
2630 execution by eliminat 2463 execution by eliminating the write-protection faults
2631 and MMU lock contenti 2464 and MMU lock contention that would otherwise be
2632 required to split hug 2465 required to split huge pages lazily.
2633 2466
2634 VM workloads that rar 2467 VM workloads that rarely perform writes or that write
2635 only to a small regio 2468 only to a small region of VM memory may benefit from
2636 disabling eager page 2469 disabling eager page splitting to allow huge pages to
2637 still be used for rea 2470 still be used for reads.
2638 2471
2639 The behavior of eager 2472 The behavior of eager page splitting depends on whether
2640 KVM_DIRTY_LOG_INITIAL 2473 KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2641 disabled, all huge pa 2474 disabled, all huge pages in a memslot will be eagerly
2642 split when dirty logg 2475 split when dirty logging is enabled on that memslot. If
2643 enabled, eager page s 2476 enabled, eager page splitting will be performed during
2644 the KVM_CLEAR_DIRTY i 2477 the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2645 cleared. 2478 cleared.
2646 2479
2647 Eager page splitting 2480 Eager page splitting is only supported when kvm.tdp_mmu=Y.
2648 2481
2649 Default is Y (on). 2482 Default is Y (on).
2650 2483
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2484 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2485 Default is false (don't support).
2653 2486
2654 kvm.nx_huge_pages= 2487 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2488 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2489 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2490 force : Always deploy workaround.
2658 off : Never deplo 2491 off : Never deploy workaround.
2659 auto : Deploy work 2492 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2493 X86_BUG_ITLB_MULTIHIT.
2661 2494
2662 Default is 'auto'. 2495 Default is 'auto'.
2663 2496
2664 If the software worka 2497 If the software workaround is enabled for the host,
2665 guests do need not to 2498 guests do need not to enable it for nested guests.
2666 2499
2667 kvm.nx_huge_pages_recovery_ratio= 2500 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2501 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2502 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2503 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). 2504 period (see below). The default is 60.
2672 2505
2673 kvm.nx_huge_pages_recovery_period_ms= 2506 kvm.nx_huge_pages_recovery_period_ms=
2674 [KVM] Controls the ti 2507 [KVM] Controls the time period at which KVM zaps 4KiB pages
2675 back to huge pages. I 2508 back to huge pages. If the value is a non-zero N, KVM will
2676 zap a portion (see ra 2509 zap a portion (see ratio above) of the pages every N msecs.
2677 If the value is 0 (th 2510 If the value is 0 (the default), KVM will pick a period based
2678 on the ratio, such th 2511 on the ratio, such that a page is zapped after 1 hour on average.
2679 2512
2680 kvm-amd.nested= [KVM,AMD] Control nes !! 2513 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2681 KVM/SVM. Default is 1 !! 2514 Default is 1 (enabled)
2682 2515
2683 kvm-amd.npt= [KVM,AMD] Control KVM !! 2516 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2684 a.k.a. Two-Dimensiona !! 2517 for all guests.
2685 (enabled). Disable by !! 2518 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2686 for NPT. <<
2687 2519
2688 kvm-arm.mode= 2520 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2521 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 2522
2692 none: Forcefully disa 2523 none: Forcefully disable KVM.
2693 2524
2694 nvhe: Standard nVHE-b 2525 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2526 protected guests.
2696 2527
2697 protected: nVHE-based 2528 protected: nVHE-based mode with support for guests whose
2698 state is k 2529 state is kept private from the host.
2699 2530
2700 nested: VHE-based mod <<
2701 virtualizatio <<
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE 2531 Defaults to VHE/nVHE based on hardware support. Setting
2705 mode to "protected" w 2532 mode to "protected" will disable kexec and hibernation
2706 for the host. "nested !! 2533 for the host.
2707 used with extreme cau <<
2708 2534
2709 kvm-arm.vgic_v3_group0_trap= 2535 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2536 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2537 system registers
2712 2538
2713 kvm-arm.vgic_v3_group1_trap= 2539 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2540 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2541 system registers
2716 2542
2717 kvm-arm.vgic_v3_common_trap= 2543 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2544 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2545 system registers
2720 2546
2721 kvm-arm.vgic_v4_enable= 2547 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2548 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2549 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 2550
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2551 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2552 Reserves given percentage from system memory area for
2745 contiguous memory all 2553 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2554 allocation.
2747 By default it reserve 2555 By default it reserves 5% of total system memory.
2748 Format: <integer> 2556 Format: <integer>
2749 Default: 5 2557 Default: 5
2750 2558
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2559 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2560 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2561 Default is 1 (enabled)
2754 for EPT. <<
2755 2562
2756 kvm-intel.emulate_invalid_guest_state 2563 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2564 [KVM,Intel] Disable emulation of invalid guest state.
2758 state. Ignored if kvm !! 2565 Ignored if kvm-intel.enable_unrestricted_guest=1, as
2759 as guest state is nev !! 2566 guest state is never invalid for unrestricted guests.
2760 guests. This param do !! 2567 This param doesn't apply to nested guests (L2), as KVM
2761 as KVM never emulates !! 2568 never emulates invalid L2 guest state.
2762 Default is 1 (enabled !! 2569 Default is 1 (enabled)
2763 2570
2764 kvm-intel.flexpriority= 2571 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2572 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2573 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2574
2769 kvm-intel.nested= 2575 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2576 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2577 Default is 0 (disabled)
2772 2578
2773 kvm-intel.unrestricted_guest= 2579 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2580 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2581 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2582 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2583
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2584 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2585 CVE-2018-3620.
2781 2586
2782 Valid arguments: neve 2587 Valid arguments: never, cond, always
2783 2588
2784 always: L1D cache flu 2589 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2590 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2591 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2592 never: Disables the mitigation
2788 2593
2789 Default is cond (do L 2594 Default is cond (do L1 cache flush in specific instances)
2790 2595
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2596 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2597 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2598 Default is 1 (enabled)
2794 for it. <<
2795 2599
2796 l1d_flush= [X86,INTEL,EARLY] !! 2600 l1d_flush= [X86,INTEL]
2797 Control mitigation fo 2601 Control mitigation for L1D based snooping vulnerability.
2798 2602
2799 Certain CPUs are vuln 2603 Certain CPUs are vulnerable to an exploit against CPU
2800 internal buffers whic 2604 internal buffers which can forward information to a
2801 disclosure gadget und 2605 disclosure gadget under certain conditions.
2802 2606
2803 In vulnerable process 2607 In vulnerable processors, the speculatively
2804 forwarded data can be 2608 forwarded data can be used in a cache side channel
2805 attack, to access dat 2609 attack, to access data to which the attacker does
2806 not have direct acces 2610 not have direct access.
2807 2611
2808 This parameter contro 2612 This parameter controls the mitigation. The
2809 options are: 2613 options are:
2810 2614
2811 on - enable t 2615 on - enable the interface for the mitigation
2812 2616
2813 l1tf= [X86,EARLY] Control m !! 2617 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2618 affected CPUs
2815 2619
2816 The kernel PTE invers 2620 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2621 enabled and cannot be disabled.
2818 2622
2819 full 2623 full
2820 Provides all 2624 Provides all available mitigations for the
2821 L1TF vulnerab 2625 L1TF vulnerability. Disables SMT and
2822 enables all m 2626 enables all mitigations in the
2823 hypervisors, 2627 hypervisors, i.e. unconditional L1D flush.
2824 2628
2825 SMT control a 2629 SMT control and L1D flush control via the
2826 sysfs interfa 2630 sysfs interface is still possible after
2827 boot. Hyperv 2631 boot. Hypervisors will issue a warning
2828 when the firs 2632 when the first VM is started in a
2829 potentially i 2633 potentially insecure configuration,
2830 i.e. SMT enab 2634 i.e. SMT enabled or L1D flush disabled.
2831 2635
2832 full,force 2636 full,force
2833 Same as 'full 2637 Same as 'full', but disables SMT and L1D
2834 flush runtime 2638 flush runtime control. Implies the
2835 'nosmt=force' 2639 'nosmt=force' command line option.
2836 (i.e. sysfs c 2640 (i.e. sysfs control of SMT is disabled.)
2837 2641
2838 flush 2642 flush
2839 Leaves SMT en 2643 Leaves SMT enabled and enables the default
2840 hypervisor mi 2644 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2645 L1D flush.
2842 2646
2843 SMT control a 2647 SMT control and L1D flush control via the
2844 sysfs interfa 2648 sysfs interface is still possible after
2845 boot. Hyperv 2649 boot. Hypervisors will issue a warning
2846 when the firs 2650 when the first VM is started in a
2847 potentially i 2651 potentially insecure configuration,
2848 i.e. SMT enab 2652 i.e. SMT enabled or L1D flush disabled.
2849 2653
2850 flush,nosmt 2654 flush,nosmt
2851 2655
2852 Disables SMT 2656 Disables SMT and enables the default
2853 hypervisor mi 2657 hypervisor mitigation.
2854 2658
2855 SMT control a 2659 SMT control and L1D flush control via the
2856 sysfs interfa 2660 sysfs interface is still possible after
2857 boot. Hyperv 2661 boot. Hypervisors will issue a warning
2858 when the firs 2662 when the first VM is started in a
2859 potentially i 2663 potentially insecure configuration,
2860 i.e. SMT enab 2664 i.e. SMT enabled or L1D flush disabled.
2861 2665
2862 flush,nowarn 2666 flush,nowarn
2863 Same as 'flus 2667 Same as 'flush', but hypervisors will not
2864 warn when a V 2668 warn when a VM is started in a potentially
2865 insecure conf 2669 insecure configuration.
2866 2670
2867 off 2671 off
2868 Disables hype 2672 Disables hypervisor mitigations and doesn't
2869 emit any warn 2673 emit any warnings.
2870 It also drops 2674 It also drops the swap size and available
2871 RAM limit res 2675 RAM limit restriction on both hypervisor and
2872 bare metal. 2676 bare metal.
2873 2677
2874 Default is 'flush'. 2678 Default is 'flush'.
2875 2679
2876 For details see: Docu 2680 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2681
2878 l2cr= [PPC] 2682 l2cr= [PPC]
2879 2683
2880 l3cr= [PPC] 2684 l3cr= [PPC]
2881 2685
2882 lapic [X86-32,APIC,EARLY] E !! 2686 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2687 disabled it.
2884 2688
2885 lapic= [X86,APIC] Do not use 2689 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2690 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2691 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2692 Format: notscdeadline
2889 2693
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2694 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2695 in C2 power state.
2892 2696
2893 libata.dma= [LIBATA] DMA control 2697 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2698 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2699 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2700 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2701 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2702 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2703 for disks and CDROMs, but not CFs.
2900 2704
2901 libata.ignore_hpa= [LIBATA] Igno 2705 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2706 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2707 libata.ignore_hpa=1 ignore limits, using full disk
2904 2708
2905 libata.noacpi [LIBATA] Disables use 2709 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2710 when set.
2907 Format: <int> 2711 Format: <int>
2908 2712
2909 libata.force= [LIBATA] Force config 2713 libata.force= [LIBATA] Force configurations. The format is a comma-
2910 separated list of "[I 2714 separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2911 PORT and DEVICE are d 2715 PORT and DEVICE are decimal numbers matching port, link
2912 or device. Basically 2716 or device. Basically, it matches the ATA ID string
2913 printed on console by 2717 printed on console by libata. If the whole ID part is
2914 omitted, the last POR 2718 omitted, the last PORT and DEVICE values are used. If
2915 ID hasn't been specif 2719 ID hasn't been specified yet, the configuration applies
2916 to all ports, links a 2720 to all ports, links and devices.
2917 2721
2918 If only DEVICE is omi 2722 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2723 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2724 number of 0 either selects the first device or the
2921 first fan-out link be 2725 first fan-out link behind PMP device. It does not
2922 select the host link. 2726 select the host link. DEVICE number of 15 selects the
2923 host link and device 2727 host link and device attached to it.
2924 2728
2925 The VAL specifies the 2729 The VAL specifies the configuration to force. As long
2926 as there is no ambigu 2730 as there is no ambiguity, shortcut notation is allowed.
2927 For example, both 1.5 2731 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2732 The following configurations can be forced.
2929 2733
2930 * Cable type: 40c, 80 2734 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2735 Any ID with matching PORT is used.
2932 2736
2933 * SATA link speed lim 2737 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2738
2935 * Transfer mode: pio[ 2739 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2740 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2741 allowed.
2938 2742
2939 * nohrst, nosrst, nor 2743 * nohrst, nosrst, norst: suppress hard, soft and both
2940 resets. 2744 resets.
2941 2745
2942 * rstonce: only attem 2746 * rstonce: only attempt one reset during hot-unplug
2943 link recovery. 2747 link recovery.
2944 2748
2945 * [no]dbdelay: Enable 2749 * [no]dbdelay: Enable or disable the extra 200ms delay
2946 before debouncing a 2750 before debouncing a link PHY and device presence
2947 detection. 2751 detection.
2948 2752
2949 * [no]ncq: Turn on or 2753 * [no]ncq: Turn on or off NCQ.
2950 2754
2951 * [no]ncqtrim: Enable 2755 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2952 2756
2953 * [no]ncqati: Enable 2757 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2954 2758
2955 * [no]trim: Enable or 2759 * [no]trim: Enable or disable (unqueued) TRIM.
2956 2760
2957 * trim_zero: Indicate 2761 * trim_zero: Indicate that TRIM command zeroes data.
2958 2762
2959 * max_trim_128m: Set 2763 * max_trim_128m: Set 128M maximum trim size limit.
2960 2764
2961 * [no]dma: Turn on or 2765 * [no]dma: Turn on or off DMA transfers.
2962 2766
2963 * atapi_dmadir: Enabl 2767 * atapi_dmadir: Enable ATAPI DMADIR bridge support.
2964 2768
2965 * atapi_mod16_dma: En 2769 * atapi_mod16_dma: Enable the use of ATAPI DMA for
2966 commands that are n 2770 commands that are not a multiple of 16 bytes.
2967 2771
2968 * [no]dmalog: Enable 2772 * [no]dmalog: Enable or disable the use of the
2969 READ LOG DMA EXT co 2773 READ LOG DMA EXT command to access logs.
2970 2774
2971 * [no]iddevlog: Enabl 2775 * [no]iddevlog: Enable or disable access to the
2972 identify device dat 2776 identify device data log.
2973 2777
2974 * [no]logdir: Enable 2778 * [no]logdir: Enable or disable access to the general
2975 purpose log directo 2779 purpose log directory.
2976 2780
2977 * max_sec_128: Set tr 2781 * max_sec_128: Set transfer size limit to 128 sectors.
2978 2782
2979 * max_sec_1024: Set o 2783 * max_sec_1024: Set or clear transfer size limit to
2980 1024 sectors. 2784 1024 sectors.
2981 2785
2982 * max_sec_lba48: Set 2786 * max_sec_lba48: Set or clear transfer size limit to
2983 65535 sectors. 2787 65535 sectors.
2984 2788
2985 * [no]lpm: Enable or 2789 * [no]lpm: Enable or disable link power management.
2986 2790
2987 * [no]setxfer: Indica 2791 * [no]setxfer: Indicate if transfer speed mode setting
2988 should be skipped. 2792 should be skipped.
2989 2793
2990 * [no]fua: Disable or <<
2991 support for devices <<
2992 <<
2993 * dump_id: Dump IDENT 2794 * dump_id: Dump IDENTIFY data.
2994 2795
2995 * disable: Disable th 2796 * disable: Disable this device.
2996 2797
2997 If there are multiple 2798 If there are multiple matching configurations changing
2998 the same attribute, t 2799 the same attribute, the last one is used.
2999 2800
3000 load_ramdisk= [RAM] [Deprecated] 2801 load_ramdisk= [RAM] [Deprecated]
3001 2802
3002 lockd.nlm_grace_period=P [NFS] Assig 2803 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2804 Format: <integer>
3004 2805
3005 lockd.nlm_tcpport=N [NFS] Assign 2806 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2807 Format: <integer>
3007 2808
3008 lockd.nlm_timeout=T [NFS] Assign 2809 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2810 Format: <integer>
3010 2811
3011 lockd.nlm_udpport=M [NFS] Assign 2812 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2813 Format: <integer>
3013 2814
3014 lockdown= [SECURITY,EARLY] !! 2815 lockdown= [SECURITY]
3015 { integrity | confide 2816 { integrity | confidentiality }
3016 Enable the kernel loc 2817 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2818 integrity, kernel features that allow userland to
3018 modify the running ke 2819 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2820 confidentiality, kernel features that allow userland
3020 to extract confidenti 2821 to extract confidential information from the kernel
3021 are also disabled. 2822 are also disabled.
3022 2823
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] 2824 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2825 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2826 Defaults to being automatically set based on the
3058 number of online CPUs 2827 number of online CPUs.
3059 2828
3060 locktorture.nwriters_stress= [KNL] 2829 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2830 Set the number of locking write-acquisition kthreads.
3062 2831
3063 locktorture.onoff_holdoff= [KNL] 2832 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2833 Set time (s) after boot for CPU-hotplug testing.
3065 2834
3066 locktorture.onoff_interval= [KNL] 2835 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2836 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2837 zero to disable CPU-hotplug testing.
3069 2838
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] 2839 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2840 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2841 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2842 mode during the locktorture test.
3093 2843
3094 locktorture.shutdown_secs= [KNL] 2844 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2845 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2846 is useful for hands-off automated testing.
3097 2847
3098 locktorture.stat_interval= [KNL] 2848 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2849 Time (s) between statistics printk()s.
3100 2850
3101 locktorture.stutter= [KNL] 2851 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2852 Time (s) to stutter testing, for example,
3103 specifying five secon 2853 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2854 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2855 This tests the locking primitive's ability to
3106 transition abruptly t 2856 transition abruptly to and from idle.
3107 2857
3108 locktorture.torture_type= [KNL] 2858 locktorture.torture_type= [KNL]
3109 Specify the locking i 2859 Specify the locking implementation to test.
3110 2860
3111 locktorture.verbose= [KNL] 2861 locktorture.verbose= [KNL]
3112 Enable additional pri 2862 Enable additional printk() statements.
3113 2863
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2864 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2865 Format: <irq>
3120 2866
3121 loglevel= [KNL,EARLY] !! 2867 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2868 console loglevel will be printed to the console. It can
3124 also be changed with 2869 also be changed with klogd or other programs. The
3125 loglevels are defined 2870 loglevels are defined as follows:
3126 2871
3127 0 (KERN_EMERG) 2872 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2873 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2874 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2875 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2876 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2877 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2878 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2879 7 (KERN_DEBUG) debug-level messages
3135 2880
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2881 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2882 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2883 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2884 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2885 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2886 that allows to increase the default size depending on
3142 parameter that allows !! 2887 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2888
3146 logo.nologo [FB] Disables display 2889 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2890 This may be used to provide more screen space for
3148 kernel log messages a 2891 kernel log messages and is useful when debugging
3149 kernel boot problems. 2892 kernel boot problems.
3150 2893
3151 lp=0 [LP] Specify paral 2894 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2895 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2896 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2897 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2898 specified in addition to the ports) causes
3156 attached prin 2899 attached printers to be reset. Using
3157 lp=port1,port 2900 lp=port1,port2,... specifies the parallel ports
3158 to associate 2901 to associate lp devices with, starting with
3159 lp0. A port s 2902 lp0. A port specification may be 'none' to skip
3160 that lp devic 2903 that lp device, or a parport name such as
3161 'parport0'. S 2904 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2905 port specification list means that device IDs
3163 from each por 2906 from each port should be examined, to see if
3164 an IEEE 1284- 2907 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2908 so, the driver will manage that printer.
3166 See also head 2909 See also header of drivers/char/lp.c.
3167 2910
3168 lpj=n [KNL] 2911 lpj=n [KNL]
3169 Sets loops_per_jiffy 2912 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2913 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2914 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2915 the correct value for your kernel, boot with normal
3173 autodetection and see 2916 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2917 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2918 which is likely to cause problems if your CPUs need
3176 significantly diverge 2919 significantly divergent settings. An incorrect value
3177 will cause delays in 2920 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2921 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2922 unlikely, in the extreme case this might damage your
3180 hardware. 2923 hardware.
3181 2924
>> 2925 ltpc= [NET]
>> 2926 Format: <io>,<irq>,<dma>
>> 2927
3182 lsm.debug [SECURITY] Enable LSM 2928 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2929
3184 lsm=lsm1,...,lsmN 2930 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2931 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2932 overrides CONFIG_LSM, and the "security=" parameter.
3187 2933
>> 2934 machvec= [IA-64] Force the use of a particular machine-vector
>> 2935 (machvec) in a generic kernel.
>> 2936 Example: machvec=hpzx1
>> 2937
3188 machtype= [Loongson] Share the 2938 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2939 different yeeloong laptops.
3190 Example: machtype=lem 2940 Example: machtype=lemote-yeeloong-2f-7inch
3191 2941
3192 maxcpus= [SMP,EARLY] Maximum n !! 2942 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
>> 2943 than or equal to this physical address is ignored.
>> 2944
>> 2945 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2946 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2947 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2948 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2949 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2950 only takes effect during system bootup.
3198 While n=0 is a specia 2951 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2952 which also disables the IO APIC.
3200 2953
3201 max_loop= [LOOP] The number of 2954 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2955 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2956 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2957 of statically allocating a predefined number, loop
3205 devices can be reques 2958 devices can be requested on-demand with the
3206 /dev/loop-control int 2959 /dev/loop-control interface.
3207 2960
3208 mce [X86-32] Machine Chec 2961 mce [X86-32] Machine Check Exception
3209 2962
3210 mce=option [X86-64] See Document !! 2963 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2964
3212 md= [HW] RAID subsystems 2965 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2966 See Documentation/admin-guide/md.rst.
3214 2967
3215 mdacon= [MDA] 2968 mdacon= [MDA]
3216 Format: <first>,<last 2969 Format: <first>,<last>
3217 Specifies range of co 2970 Specifies range of consoles to be captured by the MDA.
3218 2971
3219 mds= [X86,INTEL,EARLY] !! 2972 mds= [X86,INTEL]
3220 Control mitigation fo 2973 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2974 Sampling (MDS) vulnerability.
3222 2975
3223 Certain CPUs are vuln 2976 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2977 internal buffers which can forward information to a
3225 disclosure gadget und 2978 disclosure gadget under certain conditions.
3226 2979
3227 In vulnerable process 2980 In vulnerable processors, the speculatively
3228 forwarded data can be 2981 forwarded data can be used in a cache side channel
3229 attack, to access dat 2982 attack, to access data to which the attacker does
3230 not have direct acces 2983 not have direct access.
3231 2984
3232 This parameter contro 2985 This parameter controls the MDS mitigation. The
3233 options are: 2986 options are:
3234 2987
3235 full - Enable M 2988 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2989 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2990 SMT on vulnerable CPUs
3238 off - Uncondit 2991 off - Unconditionally disable MDS mitigation
3239 2992
3240 On TAA-affected machi 2993 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2994 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2995 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2996 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2997 too.
3245 2998
3246 Not specifying this o 2999 Not specifying this option is equivalent to
3247 mds=full. 3000 mds=full.
3248 3001
3249 For details see: Docu 3002 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 3003
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 3004 mem=nn[KMG] [HEXAGON] Set the memory size.
3252 Must be specified, ot 3005 Must be specified, otherwise memory size will be 0.
3253 3006
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc !! 3007 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3255 of memory Amount of m !! 3008 Amount of memory to be used in cases as follows:
3256 as follows: <<
3257 3009
3258 1 for test; 3010 1 for test;
3259 2 when the kernel is 3011 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 3012 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 3013 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory 3014 4 to limit the memory available for kdump kernel.
3263 3015
3264 [ARC,MICROBLAZE] - th 3016 [ARC,MICROBLAZE] - the limit applies only to low memory,
3265 high memory is not af 3017 high memory is not affected.
3266 3018
3267 [ARM64] - only limits 3019 [ARM64] - only limits memory covered by the linear
3268 mapping. The NOMAP re 3020 mapping. The NOMAP regions are not affected.
3269 3021
3270 [X86] Work as limitin 3022 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 3023 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 3024 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 3025 belonging to unused RAM.
3274 3026
3275 Note that this only t 3027 Note that this only takes effects during boot time since
3276 in above case 3, memo 3028 in above case 3, memory may need be hot added after boot
3277 if system memory of h 3029 if system memory of hypervisor is not sufficient.
3278 3030
3279 mem=nn[KMG]@ss[KMG] 3031 mem=nn[KMG]@ss[KMG]
3280 [ARM,MIPS,EARLY] - ov !! 3032 [ARM,MIPS] - override the memory layout reported by
3281 reported by firmware. !! 3033 firmware.
3282 Define a memory regio 3034 Define a memory region of size nn[KMG] starting at
3283 ss[KMG]. 3035 ss[KMG].
3284 Multiple different re 3036 Multiple different regions can be specified with
3285 multiple mem= paramet 3037 multiple mem= parameters on the command line.
3286 3038
3287 mem=nopentium [BUGS=X86-32] Disable 3039 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 3040 memory.
3289 3041
3290 memblock=debug [KNL,EARLY] Enable me !! 3042 memblock=debug [KNL] Enable memblock debug messages.
3291 3043
3292 memchunk=nn[KMG] 3044 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 3045 [KNL,SH] Allow user to override the default size for
3294 per-device physically 3046 per-device physically contiguous DMA buffers.
3295 3047
3296 memhp_default_state=online/offline/on !! 3048 memhp_default_state=online/offline
3297 [KNL] Set the initial 3049 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 3050 onlining policy. If not specified, the default value is
3299 set according to the 3051 set according to the
3300 CONFIG_MEMORY_HOTPLUG 3052 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 3053 option.
3302 See Documentation/adm 3054 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 3055
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 3056 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 3057 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 3058 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 3059 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 3060 option description.
3309 3061
3310 memmap=nn[KMG]@ss[KMG] 3062 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 3063 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 3064 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 3065 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 3066 which limits max address to nn[KMG].
3315 Multiple different re 3067 Multiple different regions can be specified,
3316 comma delimited. 3068 comma delimited.
3317 Example: 3069 Example:
3318 memmap=100M@2 3070 memmap=100M@2G,100M#3G,1G!1024G
3319 3071
3320 memmap=nn[KMG]#ss[KMG] 3072 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 3073 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 3074 Region of memory to be marked is from ss to ss+nn.
3323 3075
3324 memmap=nn[KMG]$ss[KMG] 3076 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 3077 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 3078 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 3079 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 3080 memmap=64K$0x18690000
3329 or 3081 or
3330 memmap=0x100 3082 memmap=0x10000$0x18690000
3331 Some bootloaders may 3083 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 3084 like Grub2, otherwise '$' and the following number
3333 will be eaten. 3085 will be eaten.
3334 3086
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 3087 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 3088 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 3089 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 3090 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 3091 and is NVDIMM or ADR memory.
3340 3092
3341 memmap=<size>%<offset>-<oldtype>+<new 3093 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 3094 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 3095 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 3096 out, the whole region will be marked as <newtype>,
3345 even if previously un 3097 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 3098 out, matching memory will be removed. Types are
3347 specified as e820 typ 3099 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 3100 3 = ACPI, 12 = PRAM.
3349 3101
3350 memory_corruption_check=0/1 [X86,EARL !! 3102 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 3103 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 3104 memory when doing things like suspend/resume.
3353 Setting this option w 3105 Setting this option will scan the memory
3354 looking for corruptio 3106 looking for corruption. Enabling this will
3355 both detect corruptio 3107 both detect corruption and prevent the kernel
3356 from using the memory 3108 from using the memory being corrupted.
3357 However, its intended 3109 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 3110 repeatable BIOS-originated corruption always
3359 affects the same memo 3111 affects the same memory, you can use memmap=
3360 to prevent the kernel 3112 to prevent the kernel from using that memory.
3361 3113
3362 memory_corruption_check_size=size [X8 !! 3114 memory_corruption_check_size=size [X86]
3363 By default it checks 3115 By default it checks for corruption in the low
3364 64k, making this memo 3116 64k, making this memory unavailable for normal
3365 use. Use this parame 3117 use. Use this parameter to scan for
3366 corruption in more or 3118 corruption in more or less memory.
3367 3119
3368 memory_corruption_check_period=second !! 3120 memory_corruption_check_period=seconds [X86]
3369 By default it checks 3121 By default it checks for corruption every 60
3370 seconds. Use this pa 3122 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 3123 other rate. 0 disables periodic checking.
3372 3124
3373 memory_hotplug.memmap_on_memory 3125 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 3126 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 3127 Format: {on | off (default)}
3376 When enabled, runtime 3128 When enabled, runtime hotplugged memory will
3377 allocate its internal 3129 allocate its internal metadata (struct pages,
3378 those vmemmap pages c 3130 those vmemmap pages cannot be optimized even
3379 if hugetlb_free_vmemm 3131 if hugetlb_free_vmemmap is enabled) from the
3380 hotadded memory which 3132 hotadded memory which will allow to hotadd a
3381 lot of memory without 3133 lot of memory without requiring additional
3382 memory to do so. 3134 memory to do so.
3383 This feature is disab 3135 This feature is disabled by default because it
3384 has some implication 3136 has some implication on large (e.g. GB)
3385 allocations in some c 3137 allocations in some configurations (e.g. small
3386 memory blocks). 3138 memory blocks).
3387 The state of the flag 3139 The state of the flag can be read in
3388 /sys/module/memory_ho 3140 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 3141 Note that even when enabled, there are a few cases where
3390 the feature is not ef 3142 the feature is not effective.
3391 3143
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 3144 memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
3393 Format: <integer> 3145 Format: <integer>
3394 default : 0 <disable> 3146 default : 0 <disable>
3395 Specifies the number 3147 Specifies the number of memtest passes to be
3396 performed. Each pass 3148 performed. Each pass selects another test
3397 pattern from a given 3149 pattern from a given set of patterns. Memtest
3398 fills the memory with 3150 fills the memory with this pattern, validates
3399 memory contents and r 3151 memory contents and reserves bad memory
3400 regions that are dete 3152 regions that are detected.
3401 3153
3402 mem_encrypt= [X86-64] AMD Secure M 3154 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 3155 Valid arguments: on, off
3404 Default: off !! 3156 Default (depends on kernel configuration option):
>> 3157 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 3158 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 3159 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 3160 mem_encrypt=off: Do not activate SME
3407 3161
3408 Refer to Documentatio 3162 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3409 for details on when m 3163 for details on when memory encryption can be activated.
3410 3164
3411 mem_sleep_default= [SUSPEND] Def 3165 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 3166 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 3167 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 3168 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 3169 See Documentation/admin-guide/pm/sleep-states.rst.
3416 3170
>> 3171 meye.*= [HW] Set MotionEye Camera parameters
>> 3172 See Documentation/admin-guide/media/meye.rst.
>> 3173
>> 3174 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 3175 Multi-Function General Purpose Timers on AMD Geode
>> 3176 platforms.
>> 3177
3417 mfgptfix [X86-32] Fix MFGPT ti 3178 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 3179 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 3180 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 3181 problem by letting the user disable the workaround.
3421 3182
3422 mga= [HW,DRM] 3183 mga= [HW,DRM]
3423 3184
3424 microcode.force_minrev= [X86] !! 3185 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
3425 Format: <bool> !! 3186 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 3187
3429 mini2440= [ARM,HW,KNL] 3188 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 3189 Format:[0..2][b][c][t]
3431 Default: "0tb" 3190 Default: "0tb"
3432 MINI2440 configuratio 3191 MINI2440 configuration specification:
3433 0 - The attached scre 3192 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 3193 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 3194 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 3195 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 3196 the TFT driver, and the framebuffer will be left
3438 unconfigured. 3197 unconfigured.
3439 b - Enable backlight. 3198 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 3199 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 3200 LED. This parameter is not necessary when using the
3442 VGA shield. 3201 VGA shield.
3443 c - Enable the s3c ca 3202 c - Enable the s3c camera interface.
3444 t - Reserved for enab 3203 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 3204 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 3205 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 3206 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 3207 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 3208
3450 mitigations= 3209 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 3210 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 3211 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 3212 arch-independent options, each of which is an
3454 aggregation of existi 3213 aggregation of existing arch-specific options.
3455 3214
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 3215 off
3460 Disable all o 3216 Disable all optional CPU mitigations. This
3461 improves syst 3217 improves system performance, but it may also
3462 expose users 3218 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 3219 Equivalent to: nopti [X86,PPC]
3464 !! 3220 if nokaslr then kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 3221 nospectre_v1 [X86,PPC]
>> 3222 nobp=0 [S390]
3475 3223 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 3224 spectre_v2_user=off [X86]
3482 !! 3225 spec_store_bypass_disable=off [X86,PPC]
3483 3226 ssbd=force-off [ARM64]
>> 3227 l1tf=off [X86]
>> 3228 mds=off [X86]
3484 3229 tsx_async_abort=off [X86]
>> 3230 kvm.nx_huge_pages=off [X86]
>> 3231 srbds=off [X86,INTEL]
>> 3232 no_entry_flush [PPC]
>> 3233 no_uaccess_flush [PPC]
>> 3234 mmio_stale_data=off [X86]
>> 3235 retbleed=off [X86]
3485 3236
3486 Exceptions: 3237 Exceptions:
3487 3238 This does not have any effect on
3488 3239 kvm.nx_huge_pages when
3489 3240 kvm.nx_huge_pages=force.
3490 3241
3491 auto (default) 3242 auto (default)
3492 Mitigate all 3243 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 3244 enabled, even if it's vulnerable. This is for
3494 users who don 3245 users who don't want to be surprised by SMT
3495 getting disab 3246 getting disabled across kernel upgrades, or who
3496 have other wa 3247 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 3248 Equivalent to: (default behavior)
3498 3249
3499 auto,nosmt 3250 auto,nosmt
3500 Mitigate all 3251 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 3252 if needed. This is for users who always want to
3502 be fully miti 3253 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 3254 Equivalent to: l1tf=flush,nosmt [X86]
3504 3255 mds=full,nosmt [X86]
3505 3256 tsx_async_abort=full,nosmt [X86]
3506 3257 mmio_stale_data=full,nosmt [X86]
3507 3258 retbleed=auto,nosmt [X86]
3508 3259
3509 mminit_loglevel= 3260 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 3261 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 3262 parameter allows control of the logging verbosity for
3512 the additional memory 3263 the additional memory initialisation checks. A value
3513 of 0 disables mminit 3264 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 3265 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 3266 so loglevel=8 may also need to be specified.
3516 3267
3517 mmio_stale_data= 3268 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 3269 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 3270 MMIO Stale Data vulnerabilities.
3520 3271
3521 Processor MMIO Stale 3272 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 3273 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 3274 operation. Exposed data could originate or end in
3524 the same CPU buffers 3275 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 3276 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 3277 is to clear the affected CPU buffers.
3527 3278
3528 This parameter contro 3279 This parameter controls the mitigation. The
3529 options are: 3280 options are:
3530 3281
3531 full - Enable m 3282 full - Enable mitigation on vulnerable CPUs
3532 3283
3533 full,nosmt - Enable m 3284 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 3285 vulnerable CPUs.
3535 3286
3536 off - Uncondit 3287 off - Unconditionally disable mitigation
3537 3288
3538 On MDS or TAA affecte 3289 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 3290 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 3291 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 3292 mitigated with the same mechanism so in order to
3542 disable this mitigati 3293 disable this mitigation, you need to specify
3543 mds=off and tsx_async 3294 mds=off and tsx_async_abort=off too.
3544 3295
3545 Not specifying this o 3296 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 3297 mmio_stale_data=full.
3547 3298
3548 For details see: 3299 For details see:
3549 Documentation/admin-g 3300 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 3301
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> 3302 module.async_probe=<bool>
3559 [KNL] When set to tru 3303 [KNL] When set to true, modules will use async probing
3560 by default. To enable 3304 by default. To enable/disable async probing for a
3561 specific module, use 3305 specific module, use the module specific control that
3562 is documented under < 3306 is documented under <module>.async_probe. When both
3563 module.async_probe an 3307 module.async_probe and <module>.async_probe are
3564 specified, <module>.a 3308 specified, <module>.async_probe takes precedence for
3565 the specific module. 3309 the specific module.
3566 3310
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 3311 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3312 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3313 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3314 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3315 is always true, so this option does nothing.
3578 3316
3579 module_blacklist= [KNL] Do not load 3317 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3318 modules. Useful for debugging problem modules.
3581 3319
3582 mousedev.tap_time= 3320 mousedev.tap_time=
3583 [MOUSE] Maximum time 3321 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3322 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3323 a tap and be reported as a left button click (for
3586 touchpads working in 3324 touchpads working in absolute mode only).
3587 Format: <msecs> 3325 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3326 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3327 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3328 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3329 reporting absolute coordinates, such as tablets
3592 3330
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3331 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3332 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3333 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3334 specifies the amount of memory used for migratable
3597 allocations. If both 3335 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3336 specified, then kernelcore will be at *least* the
3599 specified value but m 3337 specified value but may be more. If movablecore on its
3600 own is specified, the 3338 own is specified, the administrator must be careful
3601 that the amount of me 3339 that the amount of memory usable for all allocations
3602 is not too small. 3340 is not too small.
3603 3341
3604 movable_node [KNL,EARLY] Boot-time !! 3342 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3343 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3344 of such nodes will be usable only for movable
3607 allocations which rul 3345 allocations which rules out almost all kernel
3608 allocations. Use with 3346 allocations. Use with caution!
3609 3347
3610 MTD_Partition= [MTD] 3348 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3349 Format: <name>,<region-number>,<size>,<offset>
3612 3350
3613 MTD_Region= [MTD] Format: 3351 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3352 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3353
3616 mtdparts= [MTD] 3354 mtdparts= [MTD]
3617 See drivers/mtd/parse 3355 See drivers/mtd/parsers/cmdlinepart.c
3618 3356
>> 3357 mtdset= [ARM]
>> 3358 ARM/S3C2412 JIVE boot control
>> 3359
>> 3360 See arch/arm/mach-s3c/mach-jive.c
>> 3361
3619 mtouchusb.raw_coordinates= 3362 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3363 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3364 ('y', default) or cooked coordinates ('n')
3622 3365
3623 mtrr=debug [X86,EARLY] !! 3366 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 3367 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3368 that could hold holes aka. UC entries.
3630 3369
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3370 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3371 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3372 Default is 1.
3634 Large value could pre 3373 Large value could prevent small alignment from
3635 using up MTRRs. 3374 using up MTRRs.
3636 3375
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3376 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3377 Format: <integer>
3639 Range: 0,7 : spare re 3378 Range: 0,7 : spare reg number
3640 Default : 1 3379 Default : 1
3641 Used for mtrr cleanup 3380 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3381 Set to 2 or more if your graphical card needs more.
3643 3382
3644 multitce=off [PPC] This parameter 3383 multitce=off [PPC] This parameter disables the use of the pSeries
3645 firmware feature for 3384 firmware feature for updating multiple TCE entries
3646 at a time. 3385 at a time.
3647 3386
3648 n2= [NET] SDL Inc. RISCom 3387 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3388
3650 netdev= [NET] Network devices 3389 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3390 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3391 Note that mem_start is often overloaded to mean
3653 something different a 3392 something different and driver-specific.
3654 This usage is only do 3393 This usage is only documented in each driver source
3655 file if at all. 3394 file if at all.
3656 3395
3657 netpoll.carrier_timeout= 3396 netpoll.carrier_timeout=
3658 [NET] Specifies amoun 3397 [NET] Specifies amount of time (in seconds) that
3659 netpoll should wait f 3398 netpoll should wait for a carrier. By default netpoll
3660 waits 4 seconds. 3399 waits 4 seconds.
3661 3400
3662 nf_conntrack.acct= 3401 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3402 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3403 0 to disable accounting
3665 1 to enable accountin 3404 1 to enable accounting
3666 Default value is 0. 3405 Default value is 0.
3667 3406
3668 nfs.cache_getent= !! 3407 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3408 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3409
3672 nfs.cache_getent_timeout= !! 3410 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3411 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3412
>> 3413 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3414 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3415
3676 nfs.callback_nr_threads= 3416 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3417 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3418 NFS client will assign to service NFSv4 callback
3679 requests. 3419 requests.
3680 3420
3681 nfs.callback_tcpport= 3421 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3422 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3423 channel should listen.
3684 3424
3685 nfs.delay_retrans= !! 3425 nfs.cache_getent=
3686 [NFS] specifies the n !! 3426 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3427 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3428
3689 Only applies if the s !! 3429 nfs.cache_getent_timeout=
3690 and the specified val !! 3430 [NFS] sets the timeout after which an attempt to
>> 3431 update a cache entry is deemed to have failed.
>> 3432
>> 3433 nfs.idmap_cache_timeout=
>> 3434 [NFS] set the maximum lifetime for idmapper cache
>> 3435 entries.
3691 3436
3692 nfs.enable_ino64= 3437 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3438 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3439 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3440 number for the readdir() and stat() syscalls instead
3696 of returning the full 3441 of returning the full 64-bit number.
3697 The default is to ret 3442 The default is to return 64-bit inode numbers.
3698 3443
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3444 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3445 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3446 slots the client will assign to the callback
3706 channel. This determi 3447 channel. This determines the maximum number of
3707 callbacks the client 3448 callbacks the client will process in parallel for
3708 a particular server. 3449 a particular server.
3709 3450
3710 nfs.max_session_slots= 3451 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3452 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3453 the client will attempt to negotiate with the server.
3713 This limits the numbe 3454 This limits the number of simultaneous RPC requests
3714 that the client can s 3455 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3456 Note that there is little point in setting this
3716 value higher than the 3457 value higher than the max_tcp_slot_table_limit.
3717 3458
3718 nfs.nfs4_disable_idmapping= 3459 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3460 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3461 ensures that both the RPC level authentication
3721 scheme and the NFS le 3462 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3463 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3464 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3465 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3466 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3467 Servers that do not support this mode of operation
3727 will be autodetected 3468 will be autodetected by the client, and it will fall
3728 back to using the idm 3469 back to using the idmapper.
3729 To turn off this beha 3470 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3471 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3472 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3473 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3474 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3475 UUID that is generated at system install time.
3736 3476
3737 nfs.recover_lost_locks= !! 3477 nfs.send_implementation_id =
>> 3478 [NFSv4.1] Send client implementation identification
>> 3479 information in exchange_id requests.
>> 3480 If zero, no implementation identification information
>> 3481 will be sent.
>> 3482 The default is to send the implementation identification
>> 3483 information.
>> 3484
>> 3485 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3486 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3487 to a lease timeout on the server. Please note that
3740 doing this risks data 3488 doing this risks data corruption, since there are
3741 no guarantees that th 3489 no guarantees that the file will remain unchanged
3742 after the locks are l 3490 after the locks are lost.
3743 If you want to enable 3491 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3492 attempting to recover these locks, then set this
3745 parameter to '1'. 3493 parameter to '1'.
3746 The default parameter 3494 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3495 not to attempt recovery of lost locks.
3748 3496
3749 nfs.send_implementation_id= !! 3497 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 3498 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3499 layoutstats to the pNFS metadata server.
3760 3500
3761 Setting this to value 3501 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3502 whatever value is the default set by the layout
3763 driver. A non-zero va 3503 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3504 in seconds between layoutstats transmissions.
3765 3505
3766 nfsd.inter_copy_offload_enable= !! 3506 nfsd.inter_copy_offload_enable =
3767 [NFSv4.2] When set to 3507 [NFSv4.2] When set to 1, the server will support
3768 server-to-server copi 3508 server-to-server copies for which this server is
3769 the destination of th 3509 the destination of the copy.
3770 3510
3771 nfsd.nfs4_disable_idmapping= !! 3511 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 3512 [NFSv4.2] When used as the destination of a
3780 server-to-server copy 3513 server-to-server copy, knfsd temporarily mounts
3781 the source server. I 3514 the source server. It caches the mount in case
3782 it will be needed aga 3515 it will be needed again, and discards it if not
3783 used for the number o 3516 used for the number of milliseconds specified by
3784 this parameter. 3517 this parameter.
3785 3518
3786 nfsaddrs= [NFS] Deprecated. Us !! 3519 nfsd.nfs4_disable_idmapping=
3787 See Documentation/adm !! 3520 [NFSv4] When set to the default of '1', the NFSv4
3788 !! 3521 server will return only numeric uids and gids to
3789 nfsroot= [NFS] nfs root filesy !! 3522 clients using auth_sys, and will accept numeric uids
3790 See Documentation/adm !! 3523 and gids from such clients. This is intended to ease
>> 3524 migration from NFSv2/v3.
3791 3525
3792 nfsrootdebug [NFS] enable nfsroot <<
3793 See Documentation/adm <<
3794 3526
3795 nmi_backtrace.backtrace_idle [KNL] 3527 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3528 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3529 NMI stack-backtrace request.
3798 3530
3799 nmi_debug= [KNL,SH] Specify one 3531 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3532 when a NMI is triggered.
3801 Format: [state][,regs 3533 Format: [state][,regs][,debounce][,die]
3802 3534
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3535 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3536 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3537 Valid num: 0 or 1
3806 0 - turn hardlockup d 3538 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3539 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3540 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3541 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3542 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3543 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3544 please see 'nowatchdog'.
3815 This is useful when y 3545 This is useful when you use a panic=... timeout and
3816 need the box quickly 3546 need the box quickly up again.
3817 3547
3818 These settings can be 3548 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3549 the nmi_watchdog and hardlockup_panic sysctls.
3820 3550
3821 no387 [BUGS=X86-32] Tells t 3551 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3552 emulation library even if a 387 maths coprocessor
3823 is present. 3553 is present.
3824 3554
3825 no4lvl [RISCV,EARLY] Disable !! 3555 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 3556 kernel to use 4-level paging instead.
3830 3557
3831 noalign [KNL,ARM] !! 3558 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 3559
3840 no_console_suspend 3560 no_console_suspend
3841 [HW] Never suspend th 3561 [HW] Never suspend the console
3842 Disable suspending of 3562 Disable suspending of consoles during suspend and
3843 hibernate operations. 3563 hibernate operations. Once disabled, debugging
3844 messages can reach va 3564 messages can reach various consoles while the rest
3845 of the system is bein 3565 of the system is being put to sleep (ie, while
3846 debugging driver susp 3566 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3567 not work reliably with all consoles, but is known
3848 to work with serial a 3568 to work with serial and VGA consoles.
3849 To facilitate more fl 3569 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3570 console_suspend, a printk module parameter to control
3851 it. Users could use c 3571 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3572 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3573 turn on/off it dynamically.
3854 3574
3855 no_debug_objects !! 3575 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3576 Disable device dump. Device dump allows drivers to
>> 3577 append dump data to vmcore so you can collect driver
>> 3578 specified debug info. Drivers can append the data
>> 3579 without any limit and this data is stored in memory,
>> 3580 so this may cause significant memory stress. Disabling
>> 3581 device dump can help save memory but the driver debug
>> 3582 data will be no longer available. This parameter
>> 3583 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3584 is set.
>> 3585
>> 3586 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3587 caches in the slab allocator. Saves per-node memory,
>> 3588 but will impact performance.
>> 3589
>> 3590 noalign [KNL,ARM]
>> 3591
>> 3592 noaltinstr [S390] Disables alternative instructions patching
>> 3593 (CPU alternatives feature).
>> 3594
>> 3595 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3596 IOAPICs that may be present in the system.
>> 3597
>> 3598 noautogroup Disable scheduler automatic task group creation.
>> 3599
>> 3600 nocache [ARM]
3857 3601
3858 nodsp [SH] Disable hardware 3602 nodsp [SH] Disable hardware DSP at boot time.
3859 3603
3860 noefi [EFI,EARLY] Disable E !! 3604 noefi Disable EFI runtime services support.
3861 3605
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3606 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
>> 3607
>> 3608 noexec [IA-64]
>> 3609
>> 3610 nosmap [PPC]
>> 3611 Disable SMAP (Supervisor Mode Access Prevention)
>> 3612 even if it is supported by processor.
>> 3613
>> 3614 nosmep [PPC64s]
>> 3615 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3616 even if it is supported by processor.
3863 3617
3864 noexec32 [X86-64] 3618 noexec32 [X86-64]
3865 This affects only 32- 3619 This affects only 32-bit executables.
3866 noexec32=on: enable n 3620 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3621 read doesn't imply executable mappings
3868 noexec32=off: disable 3622 noexec32=off: disable non-executable mappings
3869 read implies 3623 read implies executable mappings
3870 3624
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 3625 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3626
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3627 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3628 register save and restore. The kernel will only save
3881 legacy floating-point 3629 legacy floating-point registers on task switch.
3882 3630
>> 3631 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
>> 3632
>> 3633 nohugevmalloc [PPC] Disable kernel huge vmalloc mappings.
>> 3634
>> 3635 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3636 Equivalent to smt=1.
>> 3637
>> 3638 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3639 nosmt=force: Force disable SMT, cannot be undone
>> 3640 via the sysfs control file.
>> 3641
>> 3642 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3643 (bounds check bypass). With this option data leaks are
>> 3644 possible in the system.
>> 3645
>> 3646 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 3647 the Spectre variant 2 (indirect branch prediction)
>> 3648 vulnerability. System may allow data leaks with this
>> 3649 option.
>> 3650
>> 3651 nospec_store_bypass_disable
>> 3652 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3653
>> 3654 no_uaccess_flush
>> 3655 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3656
>> 3657 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3658 and restore using xsave. The kernel will fallback to
>> 3659 enabling legacy floating-point and sse state.
>> 3660
>> 3661 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3662 register states. The kernel will fall back to use
>> 3663 xsave to save the states. By using this parameter,
>> 3664 performance of saving the states is degraded because
>> 3665 xsave doesn't support modified optimization while
>> 3666 xsaveopt supports it on xsaveopt enabled systems.
>> 3667
>> 3668 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3669 restoring x86 extended register state in compacted
>> 3670 form of xsave area. The kernel will fall back to use
>> 3671 xsaveopt and xrstor to save and restore the states
>> 3672 in standard form of xsave area. By using this
>> 3673 parameter, xsave area per process might occupy more
>> 3674 memory on xsaves enabled systems.
>> 3675
>> 3676 nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
>> 3677 in do_idle() and not use the arch_cpu_idle()
>> 3678 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
>> 3679 to be effective. This is useful on platforms where the
>> 3680 sleep(SH) or wfi(ARM,ARM64) instructions do not work
>> 3681 correctly or when doing power measurements to evalute
>> 3682 the impact of the sleep instructions. This is also
>> 3683 useful when using JTAG debugger.
>> 3684
>> 3685 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3686 only way then for a file to be executed with privilege
>> 3687 is to be setuid root or executed by root.
>> 3688
>> 3689 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3690 function PAL_HALT_LIGHT when idle. This increases
>> 3691 power-consumption. On the positive side, it reduces
>> 3692 interrupt wake-up latency, which may improve performance
>> 3693 in certain environments such as networked servers or
>> 3694 real-time systems.
>> 3695
3883 no_hash_pointers 3696 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3697 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3698 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3699 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3700 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3701 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3702 users, but it also makes debugging the kernel more
3891 difficult since unequ 3703 difficult since unequal pointers can no longer be
3892 compared. However, i 3704 compared. However, if this command-line option is
3893 specified, then all n 3705 specified, then all normal pointers will have their true
3894 value printed. This o 3706 value printed. This option should only be specified when
3895 debugging the kernel. 3707 debugging the kernel. Please do not use on production
3896 kernels. 3708 kernels.
3897 3709
3898 nohibernate [HIBERNATION] Disable 3710 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3711
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 3712 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3713 Valid arguments: on, off
3915 Default: on 3714 Default: on
3916 3715
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3716 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3717 The argument is a cpu list, as described above.
3919 In kernels built with 3718 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3719 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3720 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3721 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3722 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3723 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3724 rcu_nocbs= boot parameter.
3926 3725
3927 Note that this argume 3726 Note that this argument takes precedence over
3928 the CONFIG_RCU_NOCB_C 3727 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
3929 3728
>> 3729 noiotrap [SH] Disables trapped I/O port accesses.
>> 3730
>> 3731 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3732 disable unhandled interrupt sources.
>> 3733
>> 3734 no_timer_check [X86,APIC] Disables the code which tests for
>> 3735 broken timer IRQ sources.
>> 3736
>> 3737 noisapnp [ISAPNP] Disables ISA PnP code.
>> 3738
3930 noinitrd [RAM] Tells the kerne 3739 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3740 initial RAM disk.
3932 3741
3933 nointremap [X86-64,Intel-IOMMU,E !! 3742 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3743 remapping.
3935 [Deprecated - use int 3744 [Deprecated - use intremap=off]
3936 3745
3937 noinvpcid [X86,EARLY] Disable t !! 3746 nointroute [IA-64]
3938 3747
3939 noiotrap [SH] Disables trapped !! 3748 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 3749
3941 noirqdebug [X86-32] Disables the !! 3750 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 3751
3944 noisapnp [ISAPNP] Disables ISA !! 3752 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3945 3753
3946 nokaslr [KNL,EARLY] !! 3754 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 <<
3951 no-kvmapf [X86,KVM,EARLY] Disab <<
3952 fault handling. 3755 fault handling.
3953 3756
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3757 no-vmw-sched-clock
>> 3758 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3759 clock and use the default one.
>> 3760
>> 3761 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
>> 3762 accounting. steal time is computed, but won't
>> 3763 influence scheduler behaviour
>> 3764
>> 3765 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3955 3766
3956 nolapic [X86-32,APIC,EARLY] D !! 3767 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3957 3768
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3769 nomca [IA-64] Disable machine check abort handling
3959 3770
3960 nomce [X86-32] Disable Mach 3771 nomce [X86-32] Disable Machine Check Exception
3961 3772
3962 nomfgpt [X86-32] Disable Mult 3773 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 3774 Timer usage (for AMD Geode machines).
3964 3775
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 3776 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3777 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3778 irq.
3980 3779
3981 nopat [X86,EARLY] Disable P !! 3780 nomodeset Disable kernel modesetting. DRM drivers will not perform
3982 pagetables) support. !! 3781 display-mode changes or accelerated rendering. Only the
>> 3782 system framebuffer will be available for use if this was
>> 3783 set-up by the firmware or boot loader.
3983 3784
3984 nopcid [X86-64,EARLY] Disabl !! 3785 Useful as fallback, or for testing and debugging.
3985 3786
3986 nopku [X86] Disable Memory !! 3787 nomodule Disable module load
3987 in some Intel CPUs. <<
3988 <<
3989 nopti [X86-64,EARLY] <<
3990 Equivalent to pti=off <<
3991 3788
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3789 nopat [X86] Disable PAT (page attribute table extension of
3993 Disables the PV optim !! 3790 pagetables) support.
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 3791
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3792 nopcid [X86-64] Disable the PCID cpu feature.
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3793
4002 norandmaps Don't use address spa 3794 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3795 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3796
4005 noreplace-smp [X86-32,SMP] Don't re 3797 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3798 with UP alternatives
4007 3799
4008 noresume [SWSUSP] Disables res 3800 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3801 space.
4010 3802
4011 no-scroll [VGA] Disables scroll 3803 no-scroll [VGA] Disables scrollback.
4012 This is required for 3804 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3805 reader made by F.H. Papenmeier (Germany).
4014 3806
4015 nosgx [X86-64,SGX,EARLY] Di !! 3807 nosbagart [IA-64]
4016 3808
4017 nosmap [PPC,EARLY] !! 3809 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 3810
4021 nosmep [PPC64s,EARLY] !! 3811 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 <<
4025 nosmp [SMP,EARLY] Tells an <<
4026 and disable the IO AP 3812 and disable the IO APIC. legacy for "maxcpus=0".
4027 3813
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 3814 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3815
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 3816 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3817
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 3818 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3819 soft-lockup and NMI watchdog (hard-lockup).
4083 3820
4084 nowb [ARM,EARLY] !! 3821 nowb [ARM]
4085 3822
4086 nox2apic [X86-64,APIC,EARLY] D !! 3823 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3824
4088 NOTE: this parameter 3825 NOTE: this parameter will be ignored on systems with the
4089 LEGACY_XAPIC_DISABLED 3826 LEGACY_XAPIC_DISABLED bit set in the
4090 IA32_XAPIC_DISABLE_ST 3827 IA32_XAPIC_DISABLE_STATUS MSR.
4091 3828
4092 noxsave [BUGS=X86] Disables x !! 3829 nps_mtm_hs_ctr= [KNL,ARC]
4093 and restore using xsa !! 3830 This parameter sets the maximum duration, in
4094 enabling legacy float !! 3831 cycles, each HW thread of the CTOP can run
4095 !! 3832 without interruptions, before HW switches it.
4096 noxsaveopt [X86] Disables xsaveo !! 3833 The actual maximum duration is 16 times this
4097 register states. The !! 3834 parameter's value.
4098 xsave to save the sta !! 3835 Format: integer between 1 and 255
4099 performance of saving !! 3836 Default: 255
4100 xsave doesn't support !! 3837
4101 xsaveopt supports it !! 3838 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3839 purges which is reported from either PAL_VM_SUMMARY or
>> 3840 SAL PALO.
4102 3841
4103 noxsaves [X86] Disables xsaves !! 3842 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4104 restoring x86 extende <<
4105 form of xsave area. T <<
4106 xsaveopt and xrstor t <<
4107 in standard form of x <<
4108 parameter, xsave area <<
4109 memory on xsaves enab <<
4110 <<
4111 nr_cpus= [SMP,EARLY] Maximum n <<
4112 could support. nr_cp 3843 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3844 support 'n' processors. It could be larger than the
4114 number of already plu 3845 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3846 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3847 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3848 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3849 hot plugging.
4119 3850
4120 nr_uarts= [SERIAL] maximum numb 3851 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3852
4122 numa=off [KNL, ARM64, PPC, RIS !! 3853 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123 Disable NUMA, Only se !! 3854 set up a single NUMA node spanning all memory.
4124 spanning all memory. <<
4125 3855
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 3856 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 3857 NUMA balancing.
4128 Allowed values are en 3858 Allowed values are enable and disable
4129 3859
4130 numa_zonelist_order= [KNL, BOOT] Sele 3860 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3861 'node', 'default' can be specified
4132 This can be set from 3862 This can be set from sysctl after boot.
4133 See Documentation/adm 3863 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3864
4135 ohci1394_dma=early [HW,EARLY] en !! 3865 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3866 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3867 info.
4138 3868
4139 olpc_ec_timeout= [OLPC] ms delay when 3869 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3870 Rather than timing out after 20 ms if an EC
4141 command is not proper 3871 command is not properly ACKed, override the length
4142 of the timeout. We h 3872 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3873 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3874 interrupts *may* be lost!
4145 3875
4146 omap_mux= [OMAP] Override bootl 3876 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3877 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3878 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3879 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3880
4151 onenand.bdry= [HW,MTD] Flex-OneNAND 3881 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4152 3882
4153 Format: [die0_boundar 3883 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4154 3884
4155 boundary - index of l 3885 boundary - index of last SLC block on Flex-OneNAND.
4156 The remain 3886 The remaining blocks are configured as MLC blocks.
4157 lock - Configure 3887 lock - Configure if Flex-OneNAND boundary should be locked.
4158 Once locke 3888 Once locked, the boundary cannot be changed.
4159 1 indicate 3889 1 indicates lock status, 0 indicates unlock status.
4160 3890
4161 oops=panic [KNL,EARLY] !! 3891 oops=panic Always panic on oopses. Default is to just kill the
4162 Always panic on oopse <<
4163 process, but there is 3892 process, but there is a small probability of
4164 deadlocking the machi 3893 deadlocking the machine.
4165 This will also cause 3894 This will also cause panics on machine check exceptions.
4166 Useful together with 3895 Useful together with panic=30 to trigger a reboot.
4167 3896
4168 page_alloc.shuffle= 3897 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3898 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3899 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3900 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3901 running on a platform with a direct-mapped memory-side
>> 3902 cache, and this parameter can be used to
>> 3903 override/disable that behavior. The state of the flag
>> 3904 can be read from sysfs at:
4173 /sys/module/page_allo 3905 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3906
4176 page_owner= [KNL,EARLY] Boot-time !! 3907 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3908 Storage of the information about who allocated
4178 each page is disabled 3909 each page is disabled in default. With this switch,
4179 we can turn it on. 3910 we can turn it on.
4180 on: enable the featur 3911 on: enable the feature
4181 3912
4182 page_poison= [KNL,EARLY] Boot-time !! 3913 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3914 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3915 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3916 off: turn off poisoning (default)
4186 on: turn on poisoning 3917 on: turn on poisoning
4187 3918
4188 page_reporting.page_reporting_order= 3919 page_reporting.page_reporting_order=
4189 [KNL] Minimal page re 3920 [KNL] Minimal page reporting order
4190 Format: <integer> 3921 Format: <integer>
4191 Adjust the minimal pa 3922 Adjust the minimal page reporting order. The page
4192 reporting is disabled !! 3923 reporting is disabled when it exceeds (MAX_ORDER-1).
4193 3924
4194 panic= [KNL] Kernel behaviou 3925 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3926 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3927 timeout = 0: wait forever
4197 timeout < 0: reboot i 3928 timeout < 0: reboot immediately
4198 Format: <timeout> 3929 Format: <timeout>
4199 3930
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 3931 panic_print= Bitmask for printing system info when panic happens.
4218 User can chose combin 3932 User can chose combination of the following bits:
4219 bit 0: print all task 3933 bit 0: print all tasks info
4220 bit 1: print system m 3934 bit 1: print system memory info
4221 bit 2: print timer in 3935 bit 2: print timer info
4222 bit 3: print locks in 3936 bit 3: print locks info if CONFIG_LOCKDEP is on
4223 bit 4: print ftrace b 3937 bit 4: print ftrace buffer
4224 bit 5: print all prin 3938 bit 5: print all printk messages in buffer
4225 bit 6: print all CPUs 3939 bit 6: print all CPUs backtrace (if available in the arch)
4226 bit 7: print only tas <<
4227 *Be aware* that this 3940 *Be aware* that this option may print a _lot_ of lines,
4228 so there are risks of 3941 so there are risks of losing older messages in the log.
4229 Use this option caref 3942 Use this option carefully, maybe worth to setup a
4230 bigger log buffer wit 3943 bigger log buffer with "log_buf_len" along with this.
4231 3944
>> 3945 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
>> 3946 Format: <hex>[,nousertaint]
>> 3947 Hexadecimal bitmask representing the set of TAINT flags
>> 3948 that will cause the kernel to panic when add_taint() is
>> 3949 called with any of the flags in this set.
>> 3950 The optional switch "nousertaint" can be utilized to
>> 3951 prevent userspace forced crashes by writing to sysctl
>> 3952 /proc/sys/kernel/tainted any flagset matching with the
>> 3953 bitmask set on panic_on_taint.
>> 3954 See Documentation/admin-guide/tainted-kernels.rst for
>> 3955 extra details on the taint flags that users can pick
>> 3956 to compose the bitmask to assign to panic_on_taint.
>> 3957
>> 3958 panic_on_warn panic() instead of WARN(). Useful to cause kdump
>> 3959 on a WARN().
>> 3960
4232 parkbd.port= [HW] Parallel port nu 3961 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3962 connected to, default is 0.
4234 Format: <parport#> 3963 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3964 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3965 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3966 Format: <mode>
4238 3967
4239 parport= [HW,PPT] Specify para 3968 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3969 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3970 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3971 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3972 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3973 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3974 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3975 should be numbers, or 'auto' (for using detected
4247 settings on that part 3976 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3977 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3978 Parallel ports are assigned in the order they
4250 are specified on the 3979 are specified on the command line, starting
4251 with parport0. 3980 with parport0.
4252 3981
4253 parport_init_mode= [HW,PPT] 3982 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3983 Configure VIA parallel port to operate in
4255 a specific mode. This 3984 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3985 computer where firmware has no options for setting
4257 up parallel port mode 3986 up parallel port mode and sets it to spp.
4258 Currently this functi 3987 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3988 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3989
4261 pata_legacy.all= [HW,LIBATA] 3990 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 3991 Format: <int>
4263 Set to non-zero to pr 3992 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 3993 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 3994 has been found at either range. Disabled by default.
4266 3995
4267 pata_legacy.autospeed= [HW,LIBATA] 3996 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 3997 Format: <int>
4269 Set to non-zero if a 3998 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 3999 changes. Disabled by default.
4271 4000
4272 pata_legacy.ht6560a= [HW,LIBATA] 4001 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 4002 Format: <int>
4274 Set to 1, 2, or 3 for 4003 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 4004 the secondary channel, or both channels respectively.
4276 Disabled by default. 4005 Disabled by default.
4277 4006
4278 pata_legacy.ht6560b= [HW,LIBATA] 4007 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 4008 Format: <int>
4280 Set to 1, 2, or 3 for 4009 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 4010 the secondary channel, or both channels respectively.
4282 Disabled by default. 4011 Disabled by default.
4283 4012
4284 pata_legacy.iordy_mask= [HW,LIBATA] 4013 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 4014 Format: <int>
4286 IORDY enable mask. S 4015 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 4016 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 4017 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 4018 the second channel, and so on. The sequence will often
4290 correspond to the pri 4019 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 4020 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 4021 bus and the use of other driver options may interfere
4293 with the sequence. B 4022 with the sequence. By default IORDY is allowed across
4294 all channels. 4023 all channels.
4295 4024
4296 pata_legacy.opti82c46x= [HW,LIBATA] 4025 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 4026 Format: <int>
4298 Set to 1, 2, or 3 for 4027 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 4028 channel, the secondary channel, or both channels
4300 respectively. Disabl 4029 respectively. Disabled by default.
4301 4030
4302 pata_legacy.opti82c611a= [HW,L 4031 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 4032 Format: <int>
4304 Set to 1, 2, or 3 for 4033 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 4034 channel, the secondary channel, or both channels
4306 respectively. Disabl 4035 respectively. Disabled by default.
4307 4036
4308 pata_legacy.pio_mask= [HW,LIBATA] 4037 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 4038 Format: <int>
4310 PIO mode mask for aut 4039 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 4040 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 4041 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 4042 All modes allowed by default.
4314 4043
4315 pata_legacy.probe_all= [HW,LIBATA] 4044 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 4045 Format: <int>
4317 Set to non-zero to pr 4046 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 4047 port ranges on PCI systems. Disabled by default.
4319 4048
4320 pata_legacy.probe_mask= [HW,LIBATA] 4049 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 4050 Format: <int>
4322 Probe mask for legacy 4051 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 4052 platform configuration and the use of other driver
4324 options up to 6 legac 4053 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 4054 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 4055 of individual ports can be disabled by setting the
4327 corresponding bits in 4056 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 4057 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 4058 By default all supported ports are probed.
4330 4059
4331 pata_legacy.qdi= [HW,LIBATA] 4060 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 4061 Format: <int>
4333 Set to non-zero to pr 4062 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 4063 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 4064
4336 pata_legacy.winbond= [HW,LIBATA] 4065 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 4066 Format: <int>
4338 Set to non-zero to pr 4067 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 4068 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 4069 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 4070 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 4071 0 otherwise.
4343 4072
4344 pata_platform.pio_mask= [HW,LIBATA] 4073 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 4074 Format: <int>
4346 Supported PIO mode ma 4075 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 4076 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 4077 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 4078 allowed by default.
4350 4079
4351 pause_on_oops=<int> !! 4080 pause_on_oops=
4352 Halt all CPUs after t 4081 Halt all CPUs after the first oops has been printed for
4353 the specified number 4082 the specified number of seconds. This is to be used if
4354 your oopses keep scro 4083 your oopses keep scrolling off the screen.
4355 4084
4356 pcbit= [HW,ISDN] 4085 pcbit= [HW,ISDN]
4357 4086
4358 pci=option[,option...] [PCI,EARLY] v !! 4087 pcd. [PARIDE]
>> 4088 See header of drivers/block/paride/pcd.c.
>> 4089 See also Documentation/admin-guide/blockdev/paride.rst.
>> 4090
>> 4091 pci=option[,option...] [PCI] various PCI subsystem options.
4359 4092
4360 Some options 4093 Some options herein operate on a specific device
4361 or a set of d 4094 or a set of devices (<pci_dev>). These are
4362 specified in 4095 specified in one of the following formats:
4363 4096
4364 [<domain>:]<b 4097 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 4098 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 4099
4367 Note: the fir 4100 Note: the first format specifies a PCI
4368 bus/device/fu 4101 bus/device/function address which may change
4369 if new hardwa 4102 if new hardware is inserted, if motherboard
4370 firmware chan 4103 firmware changes, or due to changes caused
4371 by other kern 4104 by other kernel parameters. If the
4372 domain is lef 4105 domain is left unspecified, it is
4373 taken to be z 4106 taken to be zero. Optionally, a path
4374 to a device t 4107 to a device through multiple device/function
4375 addresses can 4108 addresses can be specified after the base
4376 address (this 4109 address (this is more robust against
4377 renumbering i 4110 renumbering issues). The second format
4378 selects devic 4111 selects devices using IDs from the
4379 configuration 4112 configuration space which may match multiple
4380 devices in th 4113 devices in the system.
4381 4114
4382 earlydump dump PCI conf 4115 earlydump dump PCI config space before the kernel
4383 changes anyth 4116 changes anything
4384 off [X86] don't p 4117 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 4118 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 4119 the hardware directly. Use this if your machine
4387 has a non-sta 4120 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 4121 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 4122 hardware access methods are allowed. Use this
4390 if you experi 4123 if you experience crashes upon bootup and you
4391 suspect they 4124 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 4125 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 4126 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 4127 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 4128 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 4129 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 4130 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 4131 bus number. The config space is then accessed
4399 through ports 4132 through ports 0xC000-0xCFFF).
4400 See http://wi 4133 See http://wiki.osdev.org/PCI for more info
4401 on the config 4134 on the configuration access mechanisms.
4402 noaer [PCIE] If the 4135 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 4136 enabled, this kernel boot option can be used to
4404 disable the u 4137 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 4138 nodomains [PCI] Disable support for multiple PCI
4406 root domains 4139 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 4140 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 4141 Configuration
4409 check_enable_amd_mmconf [X86] 4142 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 4143 properly configured MMIO access to PCI
4411 config space 4144 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 4145 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 4146 enabled, this kernel boot option can be used to
4414 disable the u 4147 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 4148 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 4149 Safety option to keep boot IRQs enabled. This
4417 should never 4150 should never be necessary.
4418 ioapicreroute [APIC] Enable 4151 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 4152 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 4153 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 4154 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 4155 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 4156 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 4157 a chipset where boot IRQs cannot be disabled.
4425 The opposite 4158 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 4159 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 4160 routing table. These calls are known to be buggy
4428 on several ma 4161 on several machines and they hang the machine
4429 when used, bu 4162 when used, but on other computers it's the only
4430 way to get th 4163 way to get the interrupt routing table. Try
4431 this option i 4164 this option if the kernel is unable to allocate
4432 IRQs or disco 4165 IRQs or discover secondary PCI buses on your
4433 motherboard. 4166 motherboard.
4434 rom [X86] Assign 4167 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 4168 Use with caution as certain devices share
4436 address decod 4169 address decoders between ROMs and other
4437 resources. 4170 resources.
4438 norom [X86] Do not 4171 norom [X86] Do not assign address space to
4439 expansion ROM 4172 expansion ROMs that do not already have
4440 BIOS assigned 4173 BIOS assigned address ranges.
4441 nobar [X86] Do not 4174 nobar [X86] Do not assign address space to the
4442 BARs that wer 4175 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 4176 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 4177 assigned automatically to PCI devices. You can
4445 make the kern 4178 make the kernel exclude IRQs of your ISA cards
4446 this way. 4179 this way.
4447 pirqaddr=0xAAAAA [X86] 4180 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 4181 of the PIRQ table (normally generated
4449 by the BIOS) 4182 by the BIOS) if it is outside the
4450 F0000h-100000 4183 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 4184 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 4185 useful if the kernel is unable to find your
4453 secondary bus 4186 secondary buses and you want to tell it
4454 explicitly wh 4187 explicitly which ones they are.
4455 assign-busses [X86] Always 4188 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 4189 numbers ourselves, overriding
4457 whatever the 4190 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 4191 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 4192 in the BIOS $PIR table. This is needed on
4460 some systems 4193 some systems with broken BIOSes, notably
4461 some HP Pavil 4194 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 4195 notebooks. This will have no effect if ACPI
4463 IRQ routing i 4196 IRQ routing is enabled.
4464 noacpi [X86] Do not 4197 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 4198 or for PCI scanning.
4466 use_crs [X86] Use PCI 4199 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 4200 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 4201 is enabled by default. If you need to use this,
4469 please report 4202 please report a bug.
4470 nocrs [X86] Ignore 4203 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 4204 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 4205 use_e820 [X86] Use E820 reservations to exclude parts of
4473 PCI host brid 4206 PCI host bridge windows. This is a workaround
4474 for BIOS defe 4207 for BIOS defects in host bridge _CRS methods.
4475 If you need t 4208 If you need to use this, please report a bug to
4476 <linux-pci@vge 4209 <linux-pci@vger.kernel.org>.
4477 no_e820 [X86] Ignore 4210 no_e820 [X86] Ignore E820 reservations for PCI host
4478 bridge window 4211 bridge windows. This is the default on modern
4479 hardware. If 4212 hardware. If you need to use this, please report
4480 a bug to <linu 4213 a bug to <linux-pci@vger.kernel.org>.
4481 routeirq Do IRQ routin 4214 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 4215 This is normally done in pci_enable_device(),
4483 so this optio 4216 so this option is a temporary workaround
4484 for broken dr 4217 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 4218 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 4219 handle more pci cards
4487 noearly [X86] Don't d 4220 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 4221 This might help on some broken boards which
4489 machine check 4222 machine check when some devices' config space
4490 is read. But 4223 is read. But various workarounds are disabled
4491 and some IOMM 4224 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 4225 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 4226 This sorting is done to get a device
4494 order compati 4227 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 4228 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 4229 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 4230 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 4231 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 4232 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 4233 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 4234 based on its parent bus. Also set MRRS (Max
4502 Read Request 4235 Read Request Size) to the largest supported
4503 value (no lar 4236 value (no larger than the MPS that the device
4504 or bus can su 4237 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 4238 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 4239 every device is guaranteed to support. This
4507 configuration 4240 configuration allows peer-to-peer DMA between
4508 any pair of d 4241 any pair of devices, possibly at the cost of
4509 reduced perfo 4242 reduced performance. This also guarantees
4510 that hot-adde 4243 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 4244 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 4245 reserved for the CardBus bridge's IO window.
4513 The default v 4246 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 4247 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 4248 reserved for the CardBus bridge's memory
4516 window. The d 4249 window. The default value is 64 megabytes.
4517 resource_alignment= 4250 resource_alignment=
4518 Format: 4251 Format:
4519 [<order of ali 4252 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 4253 Specifies alignment and device to reassign
4521 aligned memor 4254 aligned memory resources. How to
4522 specify the d 4255 specify the device is described above.
4523 If <order of 4256 If <order of align> is not specified,
4524 PAGE_SIZE is 4257 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 4258 A PCI-PCI bridge can be specified if resource
4526 windows need 4259 windows need to be expanded.
4527 To specify th 4260 To specify the alignment for several
4528 instances of 4261 instances of a device, the PCI vendor,
4529 device, subve 4262 device, subvendor, and subdevice may be
4530 specified, e. 4263 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 4264 for 4096-byte alignment.
4532 ecrc= Enable/disabl 4265 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 4266 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 4267 bios: Use BIOS/firmware settings. This is the
4537 the default. 4268 the default.
4538 off: Turn ECR 4269 off: Turn ECRC off
4539 on: Turn ECRC 4270 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 4271 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 4272 reserved for hotplug bridge's IO window.
4542 Default size 4273 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 4274 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 4275 reserved for hotplug bridge's MMIO window.
4545 Default size 4276 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 4277 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 4278 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 4279 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 4280 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 4281 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 4282 MMIO_PREF window.
4552 Default size 4283 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 4284 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 4285 reserved for buses below a hotplug bridge.
4555 Default is 1. 4286 Default is 1.
4556 realloc= Enable/disabl 4287 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 4288 if allocations done by BIOS are too small to
4558 accommodate r 4289 accommodate resources required by all child
4559 devices. 4290 devices.
4560 off: Turn rea 4291 off: Turn realloc off
4561 on: Turn real 4292 on: Turn realloc on
4562 realloc same as reall 4293 realloc same as realloc=on
4563 noari do not use PC 4294 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 4295 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 4296 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 4297 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 4298 only look for one device below a PCIe downstream
4568 port. 4299 port.
4569 big_root_window Try to add a 4300 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 4301 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 4302 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 4303 Adding the window is slightly risky (it may
4573 conflict with 4304 conflict with unreported devices), so this
4574 taints the ke 4305 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 4306 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 4307 Specify one or more PCI devices (in the format
4577 specified abo 4308 specified above) separated by semicolons.
4578 Each device s 4309 Each device specified will have the PCI ACS
4579 redirect capa 4310 redirect capabilities forced off which will
4580 allow P2P tra 4311 allow P2P traffic between devices through
4581 bridges witho 4312 bridges without forcing it upstream. Note:
4582 this removes 4313 this removes isolation between devices and
4583 may put more 4314 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 4315 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 4316 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 4317 norid [S390] ignore the RID field and force use of
4619 one PCI domai 4318 one PCI domain per PCI function
4620 4319
4621 pcie_aspm= [PCIE] Forcibly enabl !! 4320 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 4321 Management.
4623 off Don't touch ASPM conf !! 4322 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 4323 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 4324 WARNING: Forcing ASPM on may cause system lockups.
4627 4325
4628 pcie_ports= [PCIE] PCIe port serv 4326 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 4327 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 4328 even if the platform doesn't give the OS permission to
4631 use them. This may c 4329 use them. This may cause conflicts if the platform
4632 also tries to use the 4330 also tries to use these services.
4633 dpc-native Use native PC 4331 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 4332 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 4333 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 4334 hotplug).
4637 4335
4638 pcie_port_pm= [PCIE] PCIe port powe 4336 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 4337 off Disable power management of all PCIe ports
4640 force Forcibly enable power 4338 force Forcibly enable power management of all PCIe ports
4641 4339
4642 pcie_pme= [PCIE,PM] Native PCIe 4340 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 4341 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 4342 all PCIe root ports use INTx for all services).
4645 4343
4646 pcmv= [HW,PCMCIA] BadgePAD 4344 pcmv= [HW,PCMCIA] BadgePAD 4
4647 4345
4648 pd_ignore_unused 4346 pd_ignore_unused
4649 [PM] 4347 [PM]
4650 Keep all power-domain 4348 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 4349 even if no driver has claimed them. This is useful
4652 for debug and develop 4350 for debug and development, but should not be
4653 needed on a platform 4351 needed on a platform with proper driver support.
4654 4352
>> 4353 pd. [PARIDE]
>> 4354 See Documentation/admin-guide/blockdev/paride.rst.
>> 4355
4655 pdcchassis= [PARISC,HW] Disable/E 4356 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4357 boot time.
4657 Format: { 0 | 1 } 4358 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4359 See arch/parisc/kernel/pdc_chassis.c
4659 4360
4660 percpu_alloc= [MM,EARLY] !! 4361 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4362 Currently supported values are "embed" and "page".
4663 Archs may support sub 4363 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4364 See comments in mm/percpu.c for details on each
4665 allocator. This para 4365 allocator. This parameter is primarily for debugging
4666 and performance compa 4366 and performance comparison.
4667 4367
>> 4368 pf. [PARIDE]
>> 4369 See Documentation/admin-guide/blockdev/paride.rst.
>> 4370
>> 4371 pg. [PARIDE]
>> 4372 See Documentation/admin-guide/blockdev/paride.rst.
>> 4373
4668 pirq= [SMP,APIC] Manual mp- 4374 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 4375 See Documentation/x86/i386/IO-APIC.rst.
4670 4376
4671 plip= [PPT,NET] Parallel po 4377 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4378 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4379 See also Documentation/admin-guide/parport.rst.
4674 4380
4675 pmtmr= [X86] Manual setup of 4381 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4382 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4383 e.g. pmtmr=0x508
4678 4384
4679 pmu_override= [PPC] Override the PM 4385 pmu_override= [PPC] Override the PMU.
4680 This option takes ove 4386 This option takes over the PMU facility, so it is no
4681 longer usable by perf 4387 longer usable by perf. Setting this option starts the
4682 PMU counters by setti 4388 PMU counters by setting MMCR0 to 0 (the FC bit is
4683 cleared). If a number 4389 cleared). If a number is given, then MMCR1 is set to
4684 that number, otherwis 4390 that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4685 remains 0. 4391 remains 0.
4686 4392
4687 pm_debug_messages [SUSPEND,KNL] 4393 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4394 Enable suspend/resume debug messages during boot up.
4689 4395
4690 pnp.debug=1 [PNP] 4396 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4397 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4398 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4399 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4400 current resource usage; turning this on also shows
4695 possible settings and 4401 possible settings and some assignment information.
4696 4402
4697 pnpacpi= [ACPI] 4403 pnpacpi= [ACPI]
4698 { off } 4404 { off }
4699 4405
4700 pnpbios= [ISAPNP] 4406 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4407 { on | off | curr | res | no-curr | no-res }
4702 4408
4703 pnp_reserve_irq= 4409 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4410 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4411
4706 pnp_reserve_dma= 4412 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4413 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4414
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4415 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4416 Ranges are in pairs (I/O port base and size).
4711 4417
4712 pnp_reserve_mem= 4418 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4419 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4420 autoconfiguration.
4715 Ranges are in pairs ( 4421 Ranges are in pairs (memory base and size).
4716 4422
4717 ports= [IP_VS_FTP] IPVS ftp 4423 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4424 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4425 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4426 may be specified.
4721 Format: <port>,<port> 4427 Format: <port>,<port>....
4722 4428
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 4429 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4430 It specifically disables cpuidle and sets the
4730 platform machine desc 4431 platform machine description specific power_save
4731 function to NULL. On 4432 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4433 execution priority.
4733 4434
4734 ppc_strict_facility_enable 4435 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4436 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4437 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4438 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4439 There is some performance impact when enabling this.
4739 4440
4740 ppc_tm= [PPC,EARLY] !! 4441 ppc_tm= [PPC]
4741 Format: {"off"} 4442 Format: {"off"}
4742 Disable Hardware Tran 4443 Disable Hardware Transactional Memory
4743 4444
4744 preempt= [KNL] 4445 preempt= [KNL]
4745 Select preemption mod 4446 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4447 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4448 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4449 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4450 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4451
4753 print-fatal-signals= 4452 print-fatal-signals=
4754 [KNL] debug: print fa 4453 [KNL] debug: print fatal signals
4755 4454
4756 If enabled, warn abou 4455 If enabled, warn about various signal handling
4757 related application a 4456 related application anomalies: too many signals,
4758 too many POSIX.1 time 4457 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4458 coredump - etc.
4760 4459
4761 If you hit the warnin 4460 If you hit the warning due to signal overflow,
4762 you might want to try 4461 you might want to try "ulimit -i unlimited".
4763 4462
4764 default: off. 4463 default: off.
4765 4464
4766 printk.always_kmsg_dump= 4465 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4466 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4467 panics
4769 Format: <bool> (1/Y/ 4468 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4469 default: disabled
4771 4470
4772 printk.console_no_auto_verbose= 4471 printk.console_no_auto_verbose=
4773 Disable console logle 4472 Disable console loglevel raise on oops, panic
4774 or lockdep-detected i 4473 or lockdep-detected issues (only if lock debug is on).
4775 With an exception to 4474 With an exception to setups with low baudrate on
4776 serial console, keepi 4475 serial console, keeping this 0 is a good choice
4777 in order to provide m 4476 in order to provide more debug information.
4778 Format: <bool> 4477 Format: <bool>
4779 default: 0 (auto_verb 4478 default: 0 (auto_verbose is enabled)
4780 4479
4781 printk.devkmsg={on,off,ratelimit} 4480 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4481 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4482 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4483 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4484 ratelimit - ratelimit the logging
4786 Default: ratelimit 4485 Default: ratelimit
4787 4486
4788 printk.time= Show timing data pref 4487 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4488 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4489
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] 4490 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4491 Limit processor to maximum C-state
4803 max_cstate=9 override 4492 max_cstate=9 overrides any DMI blacklist limit.
4804 4493
4805 processor.nocst [HW,ACPI] 4494 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4495 Ignore the _CST method to determine C-states,
4807 instead using the leg 4496 instead using the legacy FADT method
4808 4497
4809 profile= [KNL] Enable kernel p 4498 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4499 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4500 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4501 [defaults to kernel profiling]
4813 Param: "schedule" - p 4502 Param: "schedule" - profile schedule points.
>> 4503 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4504 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4505 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4506 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4507 statistical time based profiling.
4817 4508
4818 prompt_ramdisk= [RAM] [Deprecated] 4509 prompt_ramdisk= [RAM] [Deprecated]
4819 4510
4820 prot_virt= [S390] enable hosting 4511 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4512 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4513 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4514 Format: <bool>
4826 4515
4827 psi= [KNL] Enable or disab 4516 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4517 tracking.
4829 Format: <bool> 4518 Format: <bool>
4830 4519
4831 psmouse.proto= [HW,MOUSE] Highest PS 4520 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4521 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4522 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4523 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4524 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4525 Try to reset the device after so many bad packets
4837 (0 = never). 4526 (0 = never).
4838 psmouse.resolution= 4527 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4528 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4529 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4530 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4531 0 = disabled, 1 = enabled (default).
4843 4532
4844 pstore.backend= Specify the name of t 4533 pstore.backend= Specify the name of the pstore backend to use
4845 4534
>> 4535 pt. [PARIDE]
>> 4536 See Documentation/admin-guide/blockdev/paride.rst.
>> 4537
4846 pti= [X86-64] Control Page 4538 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4539 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4540 removes hardening, but improves performance of
4849 system calls and inte 4541 system calls and interrupts.
4850 4542
4851 on - unconditionall 4543 on - unconditionally enable
4852 off - unconditionall 4544 off - unconditionally disable
4853 auto - kernel detects 4545 auto - kernel detects whether your CPU model is
4854 vulnerable to 4546 vulnerable to issues that PTI mitigates
4855 4547
4856 Not specifying this o 4548 Not specifying this option is equivalent to pti=auto.
4857 4549
>> 4550 nopti [X86-64]
>> 4551 Equivalent to pti=off
>> 4552
4858 pty.legacy_count= 4553 pty.legacy_count=
4859 [KNL] Number of legac 4554 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4555 default number.
4861 4556
4862 quiet [KNL,EARLY] Disable m !! 4557 quiet [KNL] Disable most log messages
4863 4558
4864 r128= [HW,DRM] 4559 r128= [HW,DRM]
4865 4560
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4561 raid= [HW,RAID]
4871 See Documentation/adm 4562 See Documentation/admin-guide/md.rst.
4872 4563
4873 ramdisk_size= [RAM] Sizes of RAM di 4564 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4565 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4566
4876 ramdisk_start= [RAM] RAM disk image 4567 ramdisk_start= [RAM] RAM disk image start address
4877 4568
4878 random.trust_cpu=off !! 4569 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 4570 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 4571 CPU's random number generator (if available) to
4881 initialize the kernel !! 4572 fully seed the kernel's CRNG. Default is controlled
4882 !! 4573 by CONFIG_RANDOM_TRUST_CPU.
4883 random.trust_bootloader=off !! 4574
4884 [KNL,EARLY] Disable t !! 4575 random.trust_bootloader={on,off}
4885 passed by the bootloa !! 4576 [KNL] Enable or disable trusting the use of a
4886 initialize the kernel !! 4577 seed passed by the bootloader (if available) to
>> 4578 fully seed the kernel's CRNG. Default is controlled
>> 4579 by CONFIG_RANDOM_TRUST_BOOTLOADER.
4887 4580
4888 randomize_kstack_offset= 4581 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4582 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4583 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4584 entropy, frustrating memory corruption attacks
4892 that depend on stack 4585 that depend on stack address determinism or
4893 cross-syscall address 4586 cross-syscall address exposures. This is only
4894 available on architec 4587 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4588 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4589 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4590 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4591
4899 ras=option[,option,...] [KNL] RAS-spe 4592 ras=option[,option,...] [KNL] RAS-specific options
4900 4593
4901 cec_disable [X86] 4594 cec_disable [X86]
4902 Disable the C 4595 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4596 see CONFIG_RAS_CEC help text.
4904 4597
4905 rcu_nocbs[=cpu-list] 4598 rcu_nocbs[=cpu-list]
4906 [KNL] The optional ar 4599 [KNL] The optional argument is a cpu list,
4907 as described above. 4600 as described above.
4908 4601
4909 In kernels built with 4602 In kernels built with CONFIG_RCU_NOCB_CPU=y,
4910 enable the no-callbac 4603 enable the no-callback CPU mode, which prevents
4911 such CPUs' callbacks 4604 such CPUs' callbacks from being invoked in
4912 softirq context. Inv 4605 softirq context. Invocation of such CPUs' RCU
4913 callbacks will instea 4606 callbacks will instead be offloaded to "rcuox/N"
4914 kthreads created for 4607 kthreads created for that purpose, where "x" is
4915 "p" for RCU-preempt, 4608 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4916 for the kthreads that 4609 for the kthreads that mediate grace periods; and
4917 "N" is the CPU number 4610 "N" is the CPU number. This reduces OS jitter on
4918 the offloaded CPUs, w 4611 the offloaded CPUs, which can be useful for HPC
4919 and real-time workloa 4612 and real-time workloads. It can also improve
4920 energy efficiency for 4613 energy efficiency for asymmetric multiprocessors.
4921 4614
4922 If a cpulist is passe 4615 If a cpulist is passed as an argument, the specified
4923 list of CPUs is set t 4616 list of CPUs is set to no-callback mode from boot.
4924 4617
4925 Otherwise, if the '=' 4618 Otherwise, if the '=' sign and the cpulist
4926 arguments are omitted 4619 arguments are omitted, no CPU will be set to
4927 no-callback mode from 4620 no-callback mode from boot but the mode may be
4928 toggled at runtime vi 4621 toggled at runtime via cpusets.
4929 4622
4930 Note that this argume 4623 Note that this argument takes precedence over
4931 the CONFIG_RCU_NOCB_C 4624 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4932 4625
4933 rcu_nocb_poll [KNL] 4626 rcu_nocb_poll [KNL]
4934 Rather than requiring 4627 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4628 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4629 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4630 make these kthreads poll for callbacks.
4938 This improves the rea 4631 This improves the real-time response for the
4939 offloaded CPUs by rel 4632 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4633 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4634 energy efficiency by requiring that the kthreads
4942 periodically wake up 4635 periodically wake up to do the polling.
4943 4636
4944 rcutree.blimit= [KNL] 4637 rcutree.blimit= [KNL]
4945 Set maximum number of 4638 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4639 process in one batch.
4947 4640
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] 4641 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4642 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4643 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4644 purposes, to verify correct tree setup.
4959 4645
4960 rcutree.gp_cleanup_delay= [KNL] 4646 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4647 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4648 RCU grace-period cleanup.
4963 4649
4964 rcutree.gp_init_delay= [KNL] 4650 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4651 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4652 RCU grace-period initialization.
4967 4653
4968 rcutree.gp_preinit_delay= [KNL] 4654 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4655 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4656 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4657 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4658 the rcu_node combining tree.
4973 4659
>> 4660 rcutree.use_softirq= [KNL]
>> 4661 If set to zero, move all RCU_SOFTIRQ processing to
>> 4662 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4663 value, meaning that RCU_SOFTIRQ is used by default.
>> 4664 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4665
>> 4666 But note that CONFIG_PREEMPT_RT=y kernels disable
>> 4667 this kernel boot parameter, forcibly setting it
>> 4668 to zero.
>> 4669
>> 4670 rcutree.rcu_fanout_exact= [KNL]
>> 4671 Disable autobalancing of the rcu_node combining
>> 4672 tree. This is used by rcutorture, and might
>> 4673 possibly be useful for architectures having high
>> 4674 cache-to-cache transfer latencies.
>> 4675
>> 4676 rcutree.rcu_fanout_leaf= [KNL]
>> 4677 Change the number of CPUs assigned to each
>> 4678 leaf rcu_node structure. Useful for very
>> 4679 large systems, which will choose the value 64,
>> 4680 and for NUMA systems with large remote-access
>> 4681 latencies, which will choose a value aligned
>> 4682 with the appropriate hardware boundaries.
>> 4683
>> 4684 rcutree.rcu_min_cached_objs= [KNL]
>> 4685 Minimum number of objects which are cached and
>> 4686 maintained per one CPU. Object size is equal
>> 4687 to PAGE_SIZE. The cache allows to reduce the
>> 4688 pressure to page allocator, also it makes the
>> 4689 whole algorithm to behave better in low memory
>> 4690 condition.
>> 4691
>> 4692 rcutree.rcu_delay_page_cache_fill_msec= [KNL]
>> 4693 Set the page-cache refill delay (in milliseconds)
>> 4694 in response to low-memory conditions. The range
>> 4695 of permitted values is in the range 0:100000.
>> 4696
4974 rcutree.jiffies_till_first_fqs= [KNL] 4697 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4698 Set delay from grace-period initialization to
4976 first attempt to forc 4699 first attempt to force quiescent states.
4977 Units are jiffies, mi 4700 Units are jiffies, minimum value is zero,
4978 and maximum value is 4701 and maximum value is HZ.
4979 4702
4980 rcutree.jiffies_till_next_fqs= [KNL] 4703 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4704 Set delay between subsequent attempts to force
4982 quiescent states. Un 4705 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4706 value is one, and maximum value is HZ.
4984 4707
4985 rcutree.jiffies_till_sched_qs= [KNL] 4708 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4709 Set required age in jiffies for a
4987 given grace period be 4710 given grace period before RCU starts
4988 soliciting quiescent- 4711 soliciting quiescent-state help from
4989 rcu_note_context_swit 4712 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4713 If not specified, the kernel will calculate
4991 a value based on the 4714 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4715 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4716 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4717 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4718 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4719 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4720 overwritten.
4998 4721
4999 rcutree.kthread_prio= [KNL,BOOT] 4722 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4723 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4724 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4725 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4726 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4727 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4728 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4729 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4730 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4731 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is 4732 When RCU_NOCB_CPU is set, also adjust the
5010 priority of NOCB call 4733 priority of NOCB callback kthreads.
5011 4734
>> 4735 rcutree.rcu_divisor= [KNL]
>> 4736 Set the shift-right count to use to compute
>> 4737 the callback-invocation batch limit bl from
>> 4738 the number of callbacks queued on this CPU.
>> 4739 The result will be bounded below by the value of
>> 4740 the rcutree.blimit kernel parameter. Every bl
>> 4741 callbacks, the softirq handler will exit in
>> 4742 order to allow the CPU to do other work.
>> 4743
>> 4744 Please note that this callback-invocation batch
>> 4745 limit applies only to non-offloaded callback
>> 4746 invocation. Offloaded callbacks are instead
>> 4747 invoked in the context of an rcuoc kthread, which
>> 4748 scheduler will preempt as it does any other task.
>> 4749
5012 rcutree.nocb_nobypass_lim_per_jiffy= 4750 rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5013 On callback-offloaded 4751 On callback-offloaded (rcu_nocbs) CPUs,
5014 RCU reduces the lock 4752 RCU reduces the lock contention that would
5015 otherwise be caused b 4753 otherwise be caused by callback floods through
5016 use of the ->nocb_byp 4754 use of the ->nocb_bypass list. However, in the
5017 common non-flooded ca 4755 common non-flooded case, RCU queues directly to
5018 the main ->cblist in 4756 the main ->cblist in order to avoid the extra
5019 overhead of the ->noc 4757 overhead of the ->nocb_bypass list and its lock.
5020 But if there are too 4758 But if there are too many callbacks queued during
5021 a single jiffy, RCU p 4759 a single jiffy, RCU pre-queues the callbacks into
5022 the ->nocb_bypass que 4760 the ->nocb_bypass queue. The definition of "too
5023 many" is supplied by 4761 many" is supplied by this kernel boot parameter.
5024 4762
5025 rcutree.nohz_full_patience_delay= [KN !! 4763 rcutree.rcu_nocb_gp_stride= [KNL]
5026 On callback-offloaded !! 4764 Set the number of NOCB callback kthreads in
5027 disturbing RCU unless !! 4765 each group, which defaults to the square root
5028 reached the specified !! 4766 of the number of CPUs. Larger numbers reduce
5029 Defaults to zero. La !! 4767 the wakeup overhead on the global grace-period
5030 at five seconds. All !! 4768 kthread, but increases that same overhead on
5031 to the nearest value !! 4769 each group's NOCB grace-period kthread.
5032 4770
5033 rcutree.qhimark= [KNL] 4771 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4772 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4773 batch limiting is disabled.
5036 4774
5037 rcutree.qlowmark= [KNL] 4775 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4776 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4777 batch limiting is re-enabled.
5040 4778
5041 rcutree.qovld= [KNL] 4779 rcutree.qovld= [KNL]
5042 Set threshold of queu 4780 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4781 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4782 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4783 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4784 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4785 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4786 disable more aggressive help enlistment.
5049 4787
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] 4788 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4789 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4790 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4791 it should at force-quiescent-state time.
5104 This wake_up() will b 4792 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4793 WARN_ONCE() splat and an ftrace_dump().
5106 4794
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] 4795 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4796 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4797 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4798 in microseconds. This defaults to zero.
5118 Larger delays increas 4799 Larger delays increase the probability of
5119 catching RCU pointer 4800 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4801 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4802 rcu_read_unlock() has completed.
5122 4803
5123 rcutree.sysrq_rcu= [KNL] 4804 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4805 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4806 rcu_node tree with an eye towards determining
5126 why a new grace perio 4807 why a new grace period has not yet started.
5127 4808
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] 4809 rcuscale.gp_async= [KNL]
5158 Measure performance o 4810 Measure performance of asynchronous
5159 grace-period primitiv 4811 grace-period primitives such as call_rcu().
5160 4812
5161 rcuscale.gp_async_max= [KNL] 4813 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4814 Specify the maximum number of outstanding
5163 callbacks per writer 4815 callbacks per writer thread. When a writer
5164 thread exceeds this l 4816 thread exceeds this limit, it invokes the
5165 corresponding flavor 4817 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4818 previously posted callbacks to drain.
5167 4819
5168 rcuscale.gp_exp= [KNL] 4820 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4821 Measure performance of expedited synchronous
5170 grace-period primitiv 4822 grace-period primitives.
5171 4823
5172 rcuscale.holdoff= [KNL] 4824 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4825 Set test-start holdoff period. The purpose of
5174 this parameter is to 4826 this parameter is to delay the start of the
5175 test until boot compl 4827 test until boot completes in order to avoid
5176 interference. 4828 interference.
5177 4829
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] 4830 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4831 Set to measure performance of kfree_rcu() flooding.
5189 4832
5190 rcuscale.kfree_rcu_test_double= [KNL] 4833 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 4834 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 4835 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 4836 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 4837 and double-argument variants are tested.
5195 4838
5196 rcuscale.kfree_rcu_test_single= [KNL] 4839 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 4840 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 4841 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 4842 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 4843 and double-argument variants are tested.
5201 4844
5202 rcuscale.kfree_nthreads= [KNL] 4845 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4846 The number of threads running loops of kfree_rcu().
5204 4847
5205 rcuscale.kfree_alloc_num= [KNL] 4848 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4849 Number of allocations and frees done in an iteration.
5207 4850
5208 rcuscale.kfree_loops= [KNL] 4851 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4852 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4853 of allocations and frees.
5211 4854
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] 4855 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4856 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4857 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4858 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4859 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4860 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4861 A value of "n" less than or equal to -N selects
5225 a single reader. 4862 a single reader.
5226 4863
5227 rcuscale.nwriters= [KNL] 4864 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4865 Set number of RCU writers. The values operate
5229 the same as for rcusc 4866 the same as for rcuscale.nreaders.
5230 N, where N is the num 4867 N, where N is the number of CPUs
5231 4868
5232 rcuscale.scale_type= [KNL] !! 4869 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4870 Specify the RCU implementation to test.
5234 4871
5235 rcuscale.shutdown= [KNL] 4872 rcuscale.shutdown= [KNL]
5236 Shut the system down 4873 Shut the system down after performance tests
5237 complete. This is us 4874 complete. This is useful for hands-off automated
5238 testing. 4875 testing.
5239 4876
5240 rcuscale.verbose= [KNL] 4877 rcuscale.verbose= [KNL]
5241 Enable additional pri 4878 Enable additional printk() statements.
5242 4879
5243 rcuscale.writer_holdoff= [KNL] 4880 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4881 Write-side holdoff between grace periods,
5245 in microseconds. The 4882 in microseconds. The default of zero says
5246 no holdoff. 4883 no holdoff.
5247 4884
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] 4885 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4886 Set duration of force_quiescent_state bursts
5255 in microseconds. 4887 in microseconds.
5256 4888
5257 rcutorture.fqs_holdoff= [KNL] 4889 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4890 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4891 in microseconds.
5260 4892
5261 rcutorture.fqs_stutter= [KNL] 4893 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4894 Set wait time between force_quiescent_state bursts
5263 in seconds. 4895 in seconds.
5264 4896
5265 rcutorture.fwd_progress= [KNL] 4897 rcutorture.fwd_progress= [KNL]
5266 Specifies the number 4898 Specifies the number of kthreads to be used
5267 for RCU grace-period 4899 for RCU grace-period forward-progress testing
5268 for the types of RCU 4900 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread 4901 Defaults to 1 kthread, values less than zero or
5270 greater than the numb 4902 greater than the number of CPUs cause the number
5271 of CPUs to be used. 4903 of CPUs to be used.
5272 4904
5273 rcutorture.fwd_progress_div= [KNL] 4905 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4906 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4907 period to do tight-loop forward-progress testing.
5276 4908
5277 rcutorture.fwd_progress_holdoff= [KNL 4909 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4910 Number of seconds to wait between successive
5279 forward-progress test 4911 forward-progress tests.
5280 4912
5281 rcutorture.fwd_progress_need_resched= 4913 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4914 Enclose cond_resched() calls within checks for
5283 need_resched() during 4915 need_resched() during tight-loop forward-progress
5284 testing. 4916 testing.
5285 4917
5286 rcutorture.gp_cond= [KNL] 4918 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4919 Use conditional/asynchronous update-side
5288 primitives, if availa 4920 primitives, if available.
5289 4921
5290 rcutorture.gp_exp= [KNL] 4922 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4923 Use expedited update-side primitives, if available.
5292 4924
5293 rcutorture.gp_normal= [KNL] 4925 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4926 Use normal (non-expedited) asynchronous
5295 update-side primitive 4927 update-side primitives, if available.
5296 4928
5297 rcutorture.gp_sync= [KNL] 4929 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4930 Use normal (non-expedited) synchronous
5299 update-side primitive 4931 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4932 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4933 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4934 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4935 they are all non-zero.
5304 4936
5305 rcutorture.irqreader= [KNL] 4937 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4938 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4939 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4940 flavors take kindly to this sort of thing.
5309 4941
5310 rcutorture.leakpointer= [KNL] 4942 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4943 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4944 This can of course result in splats, and is
5313 intended to test the 4945 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4946 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4947 such leaks.
5316 4948
5317 rcutorture.n_barrier_cbs= [KNL] 4949 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4950 Set callbacks/threads for rcu_barrier() testing.
5319 4951
5320 rcutorture.nfakewriters= [KNL] 4952 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4953 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4954 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4955 test, hence the "fake".
5324 4956
5325 rcutorture.nocbs_nthreads= [KNL] 4957 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 4958 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 4959 Zero (the default) disables toggling.
5328 4960
5329 rcutorture.nocbs_toggle= [KNL] 4961 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 4962 Set the delay in milliseconds between successive
5331 callback-offload togg 4963 callback-offload toggling attempts.
5332 4964
5333 rcutorture.nreaders= [KNL] 4965 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4966 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4967 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4968 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 4969 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 4970 (the number of CPUs), -3 selects N+1, and so on.
5339 4971
5340 rcutorture.object_debug= [KNL] 4972 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 4973 Enable debug-object double-call_rcu() testing.
5342 4974
5343 rcutorture.onoff_holdoff= [KNL] 4975 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 4976 Set time (s) after boot for CPU-hotplug testing.
5345 4977
5346 rcutorture.onoff_interval= [KNL] 4978 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 4979 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 4980 or zero to disable CPU-hotplug testing.
5349 4981
5350 rcutorture.read_exit= [KNL] 4982 rcutorture.read_exit= [KNL]
5351 Set the number of rea 4983 Set the number of read-then-exit kthreads used
5352 to test the interacti 4984 to test the interaction of RCU updaters and
5353 task-exit processing. 4985 task-exit processing.
5354 4986
5355 rcutorture.read_exit_burst= [KNL] 4987 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 4988 The number of times in a given read-then-exit
5357 episode that a set of 4989 episode that a set of read-then-exit kthreads
5358 is spawned. 4990 is spawned.
5359 4991
5360 rcutorture.read_exit_delay= [KNL] 4992 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 4993 The delay, in seconds, between successive
5362 read-then-exit testin 4994 read-then-exit testing episodes.
5363 4995
5364 rcutorture.shuffle_interval= [KNL] 4996 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 4997 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 4998 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 4999 during the rcutorture test.
5368 5000
5369 rcutorture.shutdown_secs= [KNL] 5001 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 5002 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 5003 is useful for hands-off automated testing.
5372 5004
5373 rcutorture.stall_cpu= [KNL] 5005 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 5006 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 5007 warnings, zero to disable.
5376 5008
5377 rcutorture.stall_cpu_block= [KNL] 5009 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 5010 Sleep while stalling if set. This will result
5379 in warnings from pree !! 5011 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 5012 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 5013
5391 rcutorture.stall_cpu_holdoff= [KNL] 5014 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 5015 Time to wait (s) after boot before inducing stall.
5393 5016
5394 rcutorture.stall_cpu_irqsoff= [KNL] 5017 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 5018 Disable interrupts while stalling if set.
5396 5019
5397 rcutorture.stall_gp_kthread= [KNL] 5020 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 5021 Duration (s) of forced sleep within RCU
5399 grace-period kthread 5022 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 5023 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 5024 and stall_gp_kthread are specified, the
5402 kthread is starved fi 5025 kthread is starved first, then the CPU.
5403 5026
5404 rcutorture.stat_interval= [KNL] 5027 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 5028 Time (s) between statistics printk()s.
5406 5029
5407 rcutorture.stutter= [KNL] 5030 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 5031 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 5032 five seconds causes the test to run for five seconds,
5410 wait for five seconds 5033 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 5034 ability to transition abruptly to and from idle.
5412 5035
5413 rcutorture.test_boost= [KNL] 5036 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 5037 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 5038 "Maybe" means test if the RCU implementation
5416 under test support RC 5039 under test support RCU priority boosting.
5417 5040
5418 rcutorture.test_boost_duration= [KNL] 5041 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 5042 Duration (s) of each individual boost test.
5420 5043
5421 rcutorture.test_boost_interval= [KNL] 5044 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 5045 Interval (s) between each boost test.
5423 5046
5424 rcutorture.test_no_idle_hz= [KNL] 5047 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 5048 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 5049 rcutorture.shuffle_interval parameter.
5427 5050
5428 rcutorture.torture_type= [KNL] 5051 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 5052 Specify the RCU implementation to test.
5430 5053
5431 rcutorture.verbose= [KNL] 5054 rcutorture.verbose= [KNL]
5432 Enable additional pri 5055 Enable additional printk() statements.
5433 5056
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 5057 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 5058 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 5059 stall warning.
5437 5060
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 5061 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 5062 Suppress RCU CPU stall warning messages.
5446 5063
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 5064 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 5065 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 5066 rcutorture writer stall warnings that occur
5450 during early boot, th 5067 during early boot, that is, during the time
5451 before the init task 5068 before the init task is spawned.
5452 5069
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 5070 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 5071 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon 5072 The value is in seconds and the maximum allowed
5456 value is 300 seconds. 5073 value is 300 seconds.
5457 5074
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ 5075 rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5459 Set timeout for exped 5076 Set timeout for expedited RCU CPU stall warning
5460 messages. The value 5077 messages. The value is in milliseconds
5461 and the maximum allow 5078 and the maximum allowed value is 21000
5462 milliseconds. Please 5079 milliseconds. Please note that this value is
5463 adjusted to an arch t 5080 adjusted to an arch timer tick resolution.
5464 Setting this to zero 5081 Setting this to zero causes the value from
5465 rcupdate.rcu_cpu_stal 5082 rcupdate.rcu_cpu_stall_timeout to be used (after
5466 conversion from secon 5083 conversion from seconds to milliseconds).
5467 5084
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] 5085 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 5086 Use expedited grace-period primitives, for
5481 example, synchronize_ 5087 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 5088 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 5089 but can increase CPU utilization, degrade
5484 real-time latency, an 5090 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 5091 No effect on CONFIG_TINY_RCU kernels.
5486 5092
5487 rcupdate.rcu_normal= [KNL] 5093 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 5094 Use only normal grace-period primitives,
5489 for example, synchron 5095 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 5096 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 5097 real-time latency, CPU utilization, and
5492 energy efficiency, bu 5098 energy efficiency, but can expose users to
5493 increased grace-perio 5099 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 5100 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 5101 CONFIG_TINY_RCU kernels.
5496 5102
5497 rcupdate.rcu_normal_after_boot= [KNL] 5103 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 5104 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 5105 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 5106 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 5107 on CONFIG_TINY_RCU kernels.
5502 5108
5503 But note that CONFIG_ 5109 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 5110 this kernel boot parameter, forcibly setting
5505 it to the value one, 5111 it to the value one, that is, converting any
5506 post-boot attempt at 5112 post-boot attempt at an expedited RCU grace
5507 period to instead use 5113 period to instead use normal non-expedited
5508 grace-period processi 5114 grace-period processing.
5509 5115
5510 rcupdate.rcu_task_collapse_lim= [KNL] 5116 rcupdate.rcu_task_collapse_lim= [KNL]
5511 Set the maximum numbe 5117 Set the maximum number of callbacks present
5512 at the beginning of a 5118 at the beginning of a grace period that allows
5513 the RCU Tasks flavors 5119 the RCU Tasks flavors to collapse back to using
5514 a single callback que 5120 a single callback queue. This switching only
5515 occurs when rcupdate. 5121 occurs when rcupdate.rcu_task_enqueue_lim is
5516 set to the default va 5122 set to the default value of -1.
5517 5123
5518 rcupdate.rcu_task_contend_lim= [KNL] 5124 rcupdate.rcu_task_contend_lim= [KNL]
5519 Set the minimum numbe 5125 Set the minimum number of callback-queuing-time
5520 lock-contention event 5126 lock-contention events per jiffy required to
5521 cause the RCU Tasks f 5127 cause the RCU Tasks flavors to switch to per-CPU
5522 callback queuing. Th 5128 callback queuing. This switching only occurs
5523 when rcupdate.rcu_tas 5129 when rcupdate.rcu_task_enqueue_lim is set to
5524 the default value of 5130 the default value of -1.
5525 5131
5526 rcupdate.rcu_task_enqueue_lim= [KNL] 5132 rcupdate.rcu_task_enqueue_lim= [KNL]
5527 Set the number of cal 5133 Set the number of callback queues to use for the
5528 RCU Tasks family of R 5134 RCU Tasks family of RCU flavors. The default
5529 of -1 allows this to 5135 of -1 allows this to be automatically (and
5530 dynamically) adjusted 5136 dynamically) adjusted. This parameter is intended
5531 for use in testing. 5137 for use in testing.
5532 5138
5533 rcupdate.rcu_task_ipi_delay= [KNL] 5139 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 5140 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 5141 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 5142 of a given grace period. Setting a large
5537 number avoids disturb 5143 number avoids disturbing real-time workloads,
5538 but lengthens grace p 5144 but lengthens grace periods.
5539 5145
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] 5146 rcupdate.rcu_task_stall_info= [KNL]
5548 Set initial timeout i 5147 Set initial timeout in jiffies for RCU task stall
5549 informational message 5148 informational messages, which give some indication
5550 of the problem for th 5149 of the problem for those not patient enough to
5551 wait for ten minutes. 5150 wait for ten minutes. Informational messages are
5552 only printed prior to 5151 only printed prior to the stall-warning message
5553 for a given grace per 5152 for a given grace period. Disable with a value
5554 less than or equal to 5153 less than or equal to zero. Defaults to ten
5555 seconds. A change in 5154 seconds. A change in value does not take effect
5556 until the beginning o 5155 until the beginning of the next grace period.
5557 5156
5558 rcupdate.rcu_task_stall_info_mult= [K 5157 rcupdate.rcu_task_stall_info_mult= [KNL]
5559 Multiplier for time i 5158 Multiplier for time interval between successive
5560 RCU task stall inform 5159 RCU task stall informational messages for a given
5561 RCU tasks grace perio 5160 RCU tasks grace period. This value is clamped
5562 to one through ten, i 5161 to one through ten, inclusive. It defaults to
5563 the value three, so t 5162 the value three, so that the first informational
5564 message is printed 10 5163 message is printed 10 seconds into the grace
5565 period, the second at 5164 period, the second at 40 seconds, the third at
5566 160 seconds, and then 5165 160 seconds, and then the stall warning at 600
5567 seconds would prevent 5166 seconds would prevent a fourth at 640 seconds.
5568 5167
5569 rcupdate.rcu_task_stall_timeout= [KNL 5168 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie 5169 Set timeout in jiffies for RCU task stall
5571 warning messages. Di 5170 warning messages. Disable with a value less
5572 than or equal to zero 5171 than or equal to zero. Defaults to ten minutes.
5573 A change in value doe 5172 A change in value does not take effect until
5574 the beginning of the 5173 the beginning of the next grace period.
5575 5174
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] 5175 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 5176 Run the RCU early boot self tests
5601 5177
5602 rdinit= [KNL] 5178 rdinit= [KNL]
5603 Format: <full_path> 5179 Format: <full_path>
5604 Run specified binary 5180 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 5181 used for early userspace startup. See initrd.
5606 5182
5607 rdrand= [X86,EARLY] !! 5183 rdrand= [X86]
5608 force - Override the 5184 force - Override the decision by the kernel to hide the
5609 advertisement 5185 advertisement of RDRAND support (this affects
5610 certain AMD p 5186 certain AMD processors because of buggy BIOS
5611 support, spec 5187 support, specifically around the suspend/resume
5612 path). 5188 path).
5613 5189
5614 rdt= [HW,X86,RDT] 5190 rdt= [HW,X86,RDT]
5615 Turn on/off individua 5191 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 5192 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 5193 mba.
5618 E.g. to turn on cmt a 5194 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 5195 rdt=cmt,!mba
5620 5196
5621 reboot= [KNL] 5197 reboot= [KNL]
5622 Format (x86 or x86_64 5198 Format (x86 or x86_64):
5623 [w[arm] | c[o 5199 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5624 [[,]s[mp]#### 5200 [[,]s[mp]#### \
5625 [[,]b[ios] | 5201 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 5202 [[,]f[orce]
5627 Where reboot_mode is 5203 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 5204 (prefix with 'panic_' to set mode for panic
5629 reboo 5205 reboot only),
5630 reboot_type is 5206 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 5207 reboot_force is either force or not specified,
5632 reboot_cpu is s 5208 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 5209 to be used for rebooting.
5634 5210
5635 refscale.holdoff= [KNL] 5211 refscale.holdoff= [KNL]
5636 Set test-start holdof 5212 Set test-start holdoff period. The purpose of
5637 this parameter is to 5213 this parameter is to delay the start of the
5638 test until boot compl 5214 test until boot completes in order to avoid
5639 interference. 5215 interference.
5640 5216
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] 5217 refscale.loops= [KNL]
5648 Set the number of loo 5218 Set the number of loops over the synchronization
5649 primitive under test. 5219 primitive under test. Increasing this number
5650 reduces noise due to 5220 reduces noise due to loop start/end overhead,
5651 but the default has a 5221 but the default has already reduced the per-pass
5652 noise to a handful of 5222 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 5223 x86 laptops.
5654 5224
5655 refscale.nreaders= [KNL] 5225 refscale.nreaders= [KNL]
5656 Set number of readers 5226 Set number of readers. The default value of -1
5657 selects N, where N is 5227 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 5228 of CPUs. A value of zero is an interesting choice.
5659 5229
5660 refscale.nruns= [KNL] 5230 refscale.nruns= [KNL]
5661 Set number of runs, e 5231 Set number of runs, each of which is dumped onto
5662 the console log. 5232 the console log.
5663 5233
5664 refscale.readdelay= [KNL] 5234 refscale.readdelay= [KNL]
5665 Set the read-side cri 5235 Set the read-side critical-section duration,
5666 measured in microseco 5236 measured in microseconds.
5667 5237
5668 refscale.scale_type= [KNL] 5238 refscale.scale_type= [KNL]
5669 Specify the read-prot 5239 Specify the read-protection implementation to test.
5670 5240
5671 refscale.shutdown= [KNL] 5241 refscale.shutdown= [KNL]
5672 Shut down the system 5242 Shut down the system at the end of the performance
5673 test. This defaults 5243 test. This defaults to 1 (shut it down) when
5674 refscale is built int 5244 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 5245 it running) when refscale is built as a module.
5676 5246
5677 refscale.verbose= [KNL] 5247 refscale.verbose= [KNL]
5678 Enable additional pri 5248 Enable additional printk() statements.
5679 5249
5680 refscale.verbose_batched= [KNL] 5250 refscale.verbose_batched= [KNL]
5681 Batch the additional 5251 Batch the additional printk() statements. If zero
5682 (the default) or nega 5252 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 5253 print every Nth verbose statement, where N is the value
5684 specified. 5254 specified.
5685 5255
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= 5256 relax_domain_level=
5694 [KNL, SMP] Set schedu 5257 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 5258 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 5259
5697 reserve= [KNL,BUGS] Force kern 5260 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 5261 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 5262 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 5263 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 5264 is assumed to be I/O ports; otherwise it is memory.
5702 5265
5703 reserve_mem= [RAM] !! 5266 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] 5267 Format: nn[KMG]
5727 Reserves a hole at th 5268 Reserves a hole at the top of the kernel virtual
5728 address space. 5269 address space.
5729 5270
5730 reset_devices [KNL] Force drivers t 5271 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 5272 during initialization.
5732 5273
5733 resume= [SWSUSP] 5274 resume= [SWSUSP]
5734 Specify the partition 5275 Specify the partition device for software suspend
5735 Format: 5276 Format:
5736 {/dev/<dev> | PARTUUI 5277 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 5278
5738 resume_offset= [SWSUSP] 5279 resume_offset= [SWSUSP]
5739 Specify the offset fr 5280 Specify the offset from the beginning of the partition
5740 given by "resume=" at 5281 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 5282 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 5283 See Documentation/power/swsusp-and-swap-files.rst
5743 5284
5744 resumedelay= [HIBERNATION] Delay ( 5285 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 5286 read the resume files
5746 5287
5747 resumewait [HIBERNATION] Wait (i 5288 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 5289 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 5290 (e.g. USB and MMC devices).
5750 5291
5751 retain_initrd [RAM] Keep initrd mem !! 5292 retain_initrd [RAM] Keep initrd memory after extraction
5752 be accessible via /sy <<
5753 5293
5754 retbleed= [X86] Control mitigat 5294 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 5295 Speculative Code Execution with Return Instructions)
5756 vulnerability. 5296 vulnerability.
5757 5297
5758 AMD-based UNRET and I 5298 AMD-based UNRET and IBPB mitigations alone do not stop
5759 sibling threads from 5299 sibling threads from influencing the predictions of other
5760 sibling threads. For 5300 sibling threads. For that reason, STIBP is used on pro-
5761 cessors that support 5301 cessors that support it, and mitigate SMT on processors
5762 that don't. 5302 that don't.
5763 5303
5764 off - no mit 5304 off - no mitigation
5765 auto - automa 5305 auto - automatically select a migitation
5766 auto,nosmt - automa 5306 auto,nosmt - automatically select a mitigation,
5767 disabl 5307 disabling SMT if necessary for
5768 the fu 5308 the full mitigation (only on Zen1
5769 and ol 5309 and older without STIBP).
5770 ibpb - On AMD 5310 ibpb - On AMD, mitigate short speculation
5771 window 5311 windows on basic block boundaries too.
5772 Safe, 5312 Safe, highest perf impact. It also
5773 enable 5313 enables STIBP if present. Not suitable
5774 on Int 5314 on Intel.
5775 ibpb,nosmt - Like " 5315 ibpb,nosmt - Like "ibpb" above but will disable SMT
5776 when S 5316 when STIBP is not available. This is
5777 the al 5317 the alternative for systems which do not
5778 have S 5318 have STIBP.
5779 unret - Force 5319 unret - Force enable untrained return thunks,
5780 only e 5320 only effective on AMD f15h-f17h based
5781 system 5321 systems.
5782 unret,nosmt - Like u 5322 unret,nosmt - Like unret, but will disable SMT when STIBP
5783 is not 5323 is not available. This is the alternative for
5784 system 5324 systems which do not have STIBP.
5785 5325
5786 Selecting 'auto' will 5326 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 5327 time according to the CPU.
5788 5328
5789 Not specifying this o 5329 Not specifying this option is equivalent to retbleed=auto.
5790 5330
5791 rfkill.default_state= 5331 rfkill.default_state=
5792 0 "airplane mode". All 5332 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 5333 etc. communication is blocked by default.
5794 1 Unblocked. 5334 1 Unblocked.
5795 5335
5796 rfkill.master_switch_mode= 5336 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 5337 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 5338 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 5339 blocked and the previous configuration.
5800 2 The "airplane mode" b 5340 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 5341 blocked and everything unblocked.
5802 5342
>> 5343 rhash_entries= [KNL,NET]
>> 5344 Set number of hash buckets for route cache
>> 5345
5803 ring3mwait=disable 5346 ring3mwait=disable
5804 [KNL] Disable ring 3 5347 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 5348 CPUs.
5806 5349
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 5350 ro [KNL] Mount root device read-only on boot
5815 5351
5816 rodata= [KNL,EARLY] !! 5352 rodata= [KNL]
5817 on Mark read-only kernel 5353 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 5354 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel 5355 full Mark read-only kernel memory and aliases as read-only
5820 [arm64] 5356 [arm64]
5821 5357
5822 rockchip.usb_uart 5358 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 5359 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 5360 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 5361 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 5362 port and the regular usb controller gets disabled.
5828 5363
5829 root= [KNL] Root filesystem 5364 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 5365 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 5366
5837 rootdelay= [KNL] Delay (in secon 5367 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 5368 mount the root filesystem
5839 5369
5840 rootflags= [KNL] Set root filesy 5370 rootflags= [KNL] Set root filesystem mount option string
5841 5371
5842 rootfstype= [KNL] Set root filesy 5372 rootfstype= [KNL] Set root filesystem type
5843 5373
5844 rootwait [KNL] Wait (indefinit 5374 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 5375 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 5376 (e.g. USB and MMC devices).
5847 5377
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 5378 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 5379 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 5380 Memory area to be used by remote processor image,
5855 managed by CMA. 5381 managed by CMA.
5856 5382
5857 rw [KNL] Mount root devi 5383 rw [KNL] Mount root device read-write on boot
5858 5384
5859 S [KNL] Run init in sin 5385 S [KNL] Run init in single mode
5860 5386
5861 s390_iommu= [HW,S390] 5387 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 5388 Set s390 IOTLB flushing mode
5863 strict 5389 strict
5864 With strict flushing !! 5390 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 5391 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 5392 which is faster.
5867 iommu.strict=1. <<
5868 5393
5869 s390_iommu_aperture= [KNL,S390] 5394 s390_iommu_aperture= [KNL,S390]
5870 Specifies the size of 5395 Specifies the size of the per device DMA address space
5871 accessible through th 5396 accessible through the DMA and IOMMU APIs as a decimal
5872 factor of the size of 5397 factor of the size of main memory.
5873 The default is 1 mean 5398 The default is 1 meaning that one can concurrently use
5874 as many DMA addresses 5399 as many DMA addresses as physical memory is installed,
5875 if supported by hardw 5400 if supported by hardware, and thus map all of memory
5876 once. With a value of 5401 once. With a value of 2 one can map all of memory twice
5877 and so on. As a speci 5402 and so on. As a special case a factor of 0 imposes no
5878 restrictions other th 5403 restrictions other than those given by hardware at the
5879 cost of significant a 5404 cost of significant additional memory use for tables.
5880 5405
5881 sa1100ir [NET] 5406 sa1100ir [NET]
5882 See drivers/net/irda/ 5407 See drivers/net/irda/sa1100_ir.c.
5883 5408
5884 sched_verbose [KNL,EARLY] Enables v !! 5409 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 5410
5886 schedstats= [KNL,X86] Enable or d 5411 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 5412 Allowed values are enable and disable. This feature
5888 incurs a small amount 5413 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 5414 but is useful for debugging and performance tuning.
5890 5415
5891 sched_thermal_decay_shift= 5416 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 5417 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 5418 pressure signal. Thermal pressure signal follows the
5895 default decay period 5419 default decay period of other scheduler pelt
5896 signals(usually 32 ms 5420 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 5421 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 5422 period for the thermal pressure signal by the shift
5899 value. 5423 value.
5900 i.e. with the default 5424 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 5425 sched_thermal_decay_shift thermal pressure decay pr
5902 1 5426 1 64 ms
5903 2 5427 2 128 ms
5904 and so on. 5428 and so on.
5905 Format: integer betwe 5429 Format: integer between 0 and 10
5906 Default is 0. 5430 Default is 0.
5907 5431
5908 scftorture.holdoff= [KNL] 5432 scftorture.holdoff= [KNL]
5909 Number of seconds to 5433 Number of seconds to hold off before starting
5910 test. Defaults to ze 5434 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 5435 to 10 seconds for built-in smp_call_function()
5912 tests. 5436 tests.
5913 5437
5914 scftorture.longwait= [KNL] 5438 scftorture.longwait= [KNL]
5915 Request ridiculously 5439 Request ridiculously long waits randomly selected
5916 up to the chosen limi 5440 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 5441 default) disables this feature. Please note
5918 that requesting even 5442 that requesting even small non-zero numbers of
5919 seconds can result in 5443 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 5444 softlockup complaints, and so on.
5921 5445
5922 scftorture.nthreads= [KNL] 5446 scftorture.nthreads= [KNL]
5923 Number of kthreads to 5447 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 5448 smp_call_function() family of functions.
5925 The default of -1 spe 5449 The default of -1 specifies a number of kthreads
5926 equal to the number o 5450 equal to the number of CPUs.
5927 5451
5928 scftorture.onoff_holdoff= [KNL] 5452 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 5453 Number seconds to wait after the start of the
5930 test before initiatin 5454 test before initiating CPU-hotplug operations.
5931 5455
5932 scftorture.onoff_interval= [KNL] 5456 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 5457 Number seconds to wait between successive
5934 CPU-hotplug operation 5458 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 5459 is the default) disables CPU-hotplug operations.
5936 5460
5937 scftorture.shutdown_secs= [KNL] 5461 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 5462 The number of seconds following the start of the
5939 test after which to s 5463 test after which to shut down the system. The
5940 default of zero avoid 5464 default of zero avoids shutting down the system.
5941 Non-zero values are u 5465 Non-zero values are useful for automated tests.
5942 5466
5943 scftorture.stat_interval= [KNL] 5467 scftorture.stat_interval= [KNL]
5944 The number of seconds 5468 The number of seconds between outputting the
5945 current test statisti 5469 current test statistics to the console. A value
5946 of zero disables stat 5470 of zero disables statistics output.
5947 5471
5948 scftorture.stutter_cpus= [KNL] 5472 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 5473 The number of jiffies to wait between each change
5950 to the set of CPUs un 5474 to the set of CPUs under test.
5951 5475
5952 scftorture.use_cpus_read_lock= [KNL] 5476 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 5477 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 5478 preempt_disable() to disable CPU hotplug
5955 while invoking one of 5479 while invoking one of the smp_call_function*()
5956 functions. 5480 functions.
5957 5481
5958 scftorture.verbose= [KNL] 5482 scftorture.verbose= [KNL]
5959 Enable additional pri 5483 Enable additional printk() statements.
5960 5484
5961 scftorture.weight_single= [KNL] 5485 scftorture.weight_single= [KNL]
5962 The probability weigh 5486 The probability weighting to use for the
5963 smp_call_function_sin 5487 smp_call_function_single() function with a zero
5964 "wait" parameter. A 5488 "wait" parameter. A value of -1 selects the
5965 default if all other 5489 default if all other weights are -1. However,
5966 if at least one weigh 5490 if at least one weight has some other value, a
5967 value of -1 will inst 5491 value of -1 will instead select a weight of zero.
5968 5492
5969 scftorture.weight_single_wait= [KNL] 5493 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 5494 The probability weighting to use for the
5971 smp_call_function_sin 5495 smp_call_function_single() function with a
5972 non-zero "wait" param 5496 non-zero "wait" parameter. See weight_single.
5973 5497
5974 scftorture.weight_many= [KNL] 5498 scftorture.weight_many= [KNL]
5975 The probability weigh 5499 The probability weighting to use for the
5976 smp_call_function_man 5500 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 5501 "wait" parameter. See weight_single.
5978 Note well that settin 5502 Note well that setting a high probability for
5979 this weighting can pl 5503 this weighting can place serious IPI load
5980 on the system. 5504 on the system.
5981 5505
5982 scftorture.weight_many_wait= [KNL] 5506 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 5507 The probability weighting to use for the
5984 smp_call_function_man 5508 smp_call_function_many() function with a
5985 non-zero "wait" param 5509 non-zero "wait" parameter. See weight_single
5986 and weight_many. 5510 and weight_many.
5987 5511
5988 scftorture.weight_all= [KNL] 5512 scftorture.weight_all= [KNL]
5989 The probability weigh 5513 The probability weighting to use for the
5990 smp_call_function_all 5514 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 5515 "wait" parameter. See weight_single and
5992 weight_many. 5516 weight_many.
5993 5517
5994 scftorture.weight_all_wait= [KNL] 5518 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 5519 The probability weighting to use for the
5996 smp_call_function_all 5520 smp_call_function_all() function with a
5997 non-zero "wait" param 5521 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5522 and weight_many.
5999 5523
6000 skew_tick= [KNL,EARLY] Offset th !! 5524 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5525 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5526 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5527 Format: { "0" | "1" }
6004 0 -- disable. (may be 5528 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5529 1 -- enable.
6006 Note: increases power 5530 Note: increases power consumption, thus should only be
6007 enabled if running ji 5531 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5532
6009 security= [SECURITY] Choose a l 5533 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5534 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5535 "lsm=" parameter.
6012 5536
6013 selinux= [SELINUX] Disable or 5537 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5538 Format: { "0" | "1" }
6015 See security/selinux/ 5539 See security/selinux/Kconfig help text.
6016 0 -- disable. 5540 0 -- disable.
6017 1 -- enable. 5541 1 -- enable.
6018 Default value is 1. 5542 Default value is 1.
6019 5543
>> 5544 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 5545 Format: { "0" | "1" }
>> 5546 See security/apparmor/Kconfig help text
>> 5547 0 -- disable.
>> 5548 1 -- enable.
>> 5549 Default value is set via kernel config option.
>> 5550
6020 serialnumber [BUGS=X86-32] 5551 serialnumber [BUGS=X86-32]
6021 5552
6022 sev=option[,option...] [X86-64] See D !! 5553 sev=option[,option...] [X86-64] See Documentation/x86/x86_64/boot-options.rst
6023 5554
6024 shapers= [NET] 5555 shapers= [NET]
6025 Maximal number of sha 5556 Maximal number of shapers.
6026 5557
6027 show_lapic= [APIC,X86] Advanced P !! 5558 simeth= [IA-64]
6028 Limit apic dumping. T !! 5559 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 5560
6036 slab_debug[=options[,slabs][;[options !! 5561 slram= [HW,MTD]
6037 Enabling slab_debug a !! 5562
>> 5563 slab_merge [MM]
>> 5564 Enable merging of slabs with similar size when the
>> 5565 kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
>> 5566
>> 5567 slab_nomerge [MM]
>> 5568 Disable merging of slabs with similar size. May be
>> 5569 necessary if there is some reason to distinguish
>> 5570 allocs to different slabs, especially in hardened
>> 5571 environments where the risk of heap overflows and
>> 5572 layout control by attackers can usually be
>> 5573 frustrated by disabling merging. This will reduce
>> 5574 most of the exposure of a heap attack to a single
>> 5575 cache (risks via metadata attacks are mostly
>> 5576 unchanged). Debug options disable merging on their
>> 5577 own.
>> 5578 For more information see Documentation/mm/slub.rst.
>> 5579
>> 5580 slab_max_order= [MM, SLAB]
>> 5581 Determines the maximum allowed order for slabs.
>> 5582 A high setting may cause OOMs due to memory
>> 5583 fragmentation. Defaults to 1 for systems with
>> 5584 more than 32MB of RAM, 0 otherwise.
>> 5585
>> 5586 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 5587 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 5588 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 5589 slub_debug can create guard zones around objects and
6040 may poison objects wh 5590 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 5591 last alloc / free. For more information see
6042 Documentation/mm/slub 5592 Documentation/mm/slub.rst.
6043 (slub_debug legacy na <<
6044 5593
6045 slab_max_order= [MM] !! 5594 slub_max_order= [MM, SLUB]
6046 Determines the maximu 5595 Determines the maximum allowed order for slabs.
6047 A high setting may ca 5596 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 5597 fragmentation. For more information see
6049 Documentation/mm/slub 5598 Documentation/mm/slub.rst.
6050 (slub_max_order legac <<
6051 <<
6052 slab_merge [MM] <<
6053 Enable merging of sla <<
6054 kernel is built witho <<
6055 (slub_merge legacy na <<
6056 5599
6057 slab_min_objects= [MM] !! 5600 slub_min_objects= [MM, SLUB]
6058 The minimum number of 5601 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 5602 increase the slab order up to slub_max_order to
6060 generate a sufficient 5603 generate a sufficiently large slab able to contain
6061 the number of objects 5604 the number of objects indicated. The higher the number
6062 of objects the smalle 5605 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 5606 and the less frequently locks need to be acquired.
6064 For more information 5607 For more information see Documentation/mm/slub.rst.
6065 (slub_min_objects leg <<
6066 5608
6067 slab_min_order= [MM] !! 5609 slub_min_order= [MM, SLUB]
6068 Determines the minimu 5610 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 5611 lower than slub_max_order.
6070 Documentation/mm/slub <<
6071 (slub_min_order legac <<
6072 <<
6073 slab_nomerge [MM] <<
6074 Disable merging of sl <<
6075 necessary if there is <<
6076 allocs to different s <<
6077 environments where th <<
6078 layout control by att <<
6079 frustrated by disabli <<
6080 most of the exposure <<
6081 cache (risks via meta <<
6082 unchanged). Debug opt <<
6083 own. <<
6084 For more information 5612 For more information see Documentation/mm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5613
6087 slram= [HW,MTD] !! 5614 slub_merge [MM, SLUB]
>> 5615 Same with slab_merge.
>> 5616
>> 5617 slub_nomerge [MM, SLUB]
>> 5618 Same with slab_nomerge. This is supported for legacy.
>> 5619 See slab_nomerge for more information.
6088 5620
6089 smart2= [HW] 5621 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5622 Format: <io1>[,<io2>[,...,<io8>]]
6091 5623
6092 smp.csd_lock_timeout= [KNL] 5624 smp.csd_lock_timeout= [KNL]
6093 Specify the period of 5625 Specify the period of time in milliseconds
6094 that smp_call_functio 5626 that smp_call_function() and friends will wait
6095 for a CPU to release 5627 for a CPU to release the CSD lock. This is
6096 useful when diagnosin 5628 useful when diagnosing bugs involving CPUs
6097 disabling interrupts 5629 disabling interrupts for extended periods
6098 of time. Defaults to 5630 of time. Defaults to 5,000 milliseconds, and
6099 setting a value of ze 5631 setting a value of zero disables this feature.
6100 This feature may be m 5632 This feature may be more efficiently disabled
6101 using the csdlock_deb 5633 using the csdlock_debug- kernel parameter.
6102 5634
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 5635 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5636 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5637 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5638 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5639 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5640 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5641 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5642 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5643 1: Fast pin select (default)
6119 2: ATC IRMode 5644 2: ATC IRMode
6120 5645
6121 smt= [KNL,MIPS,S390,EARLY] !! 5646 smt= [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5647 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5648 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5649 actual hardware limit.
6125 Format: <integer> 5650 Format: <integer>
6126 Default: -1 (no limit 5651 Default: -1 (no limit)
6127 5652
6128 softlockup_panic= 5653 softlockup_panic=
6129 [KNL] Should the soft 5654 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5655 Format: 0 | 1
6131 5656
6132 A value of 1 instruct 5657 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5658 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5659 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5660 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5661 respective build-time switch to that functionality.
6137 5662
6138 softlockup_all_cpu_backtrace= 5663 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5664 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5665 backtraces on all cpus.
6141 Format: 0 | 1 5666 Format: 0 | 1
6142 5667
6143 sonypi.*= [HW] Sony Programmabl 5668 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5669 See Documentation/admin-guide/laptops/sonypi.rst
6145 5670
6146 spectre_bhi= [X86] Control mitigat !! 5671 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 5672 (indirect branch speculation) vulnerability.
6163 The default operation 5673 The default operation protects the kernel from
6164 user space attacks. 5674 user space attacks.
6165 5675
6166 on - unconditionall 5676 on - unconditionally enable, implies
6167 spectre_v2_use 5677 spectre_v2_user=on
6168 off - unconditionall 5678 off - unconditionally disable, implies
6169 spectre_v2_use 5679 spectre_v2_user=off
6170 auto - kernel detects 5680 auto - kernel detects whether your CPU model is
6171 vulnerable 5681 vulnerable
6172 5682
6173 Selecting 'on' will, 5683 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5684 mitigation method at run time according to the
6175 CPU, the available mi 5685 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5686 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5687 compiler with which the kernel was built.
6178 5688
6179 Selecting 'on' will a 5689 Selecting 'on' will also enable the mitigation
6180 against user space to 5690 against user space to user space task attacks.
6181 5691
6182 Selecting 'off' will 5692 Selecting 'off' will disable both the kernel and
6183 the user space protec 5693 the user space protections.
6184 5694
6185 Specific mitigations 5695 Specific mitigations can also be selected manually:
6186 5696
6187 retpoline - r 5697 retpoline - replace indirect branches
6188 retpoline,generic - R 5698 retpoline,generic - Retpolines
6189 retpoline,lfence - L 5699 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 5700 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E !! 5701 eibrs - enhanced IBRS
6192 eibrs,retpoline - E !! 5702 eibrs,retpoline - enhanced IBRS + Retpolines
6193 eibrs,lfence - E !! 5703 eibrs,lfence - enhanced IBRS + LFENCE
6194 ibrs - u 5704 ibrs - use IBRS to protect kernel
6195 5705
6196 Not specifying this o 5706 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5707 spectre_v2=auto.
6198 5708
6199 spectre_v2_user= 5709 spectre_v2_user=
6200 [X86] Control mitigat 5710 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5711 (indirect branch speculation) vulnerability between
6202 user space tasks 5712 user space tasks
6203 5713
6204 on - Uncondition 5714 on - Unconditionally enable mitigations. Is
6205 enforced by 5715 enforced by spectre_v2=on
6206 5716
6207 off - Uncondition 5717 off - Unconditionally disable mitigations. Is
6208 enforced by 5718 enforced by spectre_v2=off
6209 5719
6210 prctl - Indirect br 5720 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5721 but mitigation can be enabled via prctl
6212 per thread. 5722 per thread. The mitigation control state
6213 is inherite 5723 is inherited on fork.
6214 5724
6215 prctl,ibpb 5725 prctl,ibpb
6216 - Like "prctl 5726 - Like "prctl" above, but only STIBP is
6217 controlled 5727 controlled per thread. IBPB is issued
6218 always when 5728 always when switching between different user
6219 space proce 5729 space processes.
6220 5730
6221 seccomp 5731 seccomp
6222 - Same as "pr 5732 - Same as "prctl" above, but all seccomp
6223 threads wil 5733 threads will enable the mitigation unless
6224 they explic 5734 they explicitly opt out.
6225 5735
6226 seccomp,ibpb 5736 seccomp,ibpb
6227 - Like "secco 5737 - Like "seccomp" above, but only STIBP is
6228 controlled 5738 controlled per thread. IBPB is issued
6229 always when 5739 always when switching between different
6230 user space 5740 user space processes.
6231 5741
6232 auto - Kernel sele 5742 auto - Kernel selects the mitigation depending on
6233 the availab 5743 the available CPU features and vulnerability.
6234 5744
6235 Default mitigation: " 5745 Default mitigation: "prctl"
6236 5746
6237 Not specifying this o 5747 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5748 spectre_v2_user=auto.
6239 5749
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= 5750 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5751 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5752 (Speculative Store Bypass vulnerability)
6254 5753
6255 Certain CPUs are vuln 5754 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5755 a common industry wide performance optimization known
6257 as "Speculative Store 5756 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5757 to the same memory location may not be observed by
6259 later loads during sp 5758 later loads during speculative execution. The idea
6260 is that such stores a 5759 is that such stores are unlikely and that they can
6261 be detected prior to 5760 be detected prior to instruction retirement at the
6262 end of a particular s 5761 end of a particular speculation execution window.
6263 5762
6264 In vulnerable process 5763 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5764 store can be used in a cache side channel attack, for
6266 example to read memor 5765 example to read memory to which the attacker does not
6267 directly have access 5766 directly have access (e.g. inside sandboxed code).
6268 5767
6269 This parameter contro 5768 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5769 Bypass optimization is used.
6271 5770
6272 On x86 the options ar 5771 On x86 the options are:
6273 5772
6274 on - Uncondition 5773 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5774 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5775 auto - Kernel detects whether the CPU model contains an
6277 implementat 5776 implementation of Speculative Store Bypass and
6278 picks the m 5777 picks the most appropriate mitigation. If the
6279 CPU is not 5778 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5779 CPU is vulnerable the default mitigation is
6281 architectur 5780 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5781 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5782 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5783 for a process by default. The state of the control
6285 is inherite 5784 is inherited on fork.
6286 seccomp - Same as "pr 5785 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5786 will disable SSB unless they explicitly opt out.
6288 5787
6289 Default mitigations: 5788 Default mitigations:
6290 X86: "prctl" 5789 X86: "prctl"
6291 5790
6292 On powerpc the option 5791 On powerpc the options are:
6293 5792
6294 on,auto - On Power8 a 5793 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5794 barrier on kernel entry and exit. On Power7
6296 perform a s 5795 perform a software flush on kernel entry and
6297 exit. 5796 exit.
6298 off - No action. 5797 off - No action.
6299 5798
6300 Not specifying this o 5799 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5800 spec_store_bypass_disable=auto.
6302 5801
>> 5802 spia_io_base= [HW,MTD]
>> 5803 spia_fio_base=
>> 5804 spia_pedr=
>> 5805 spia_peddr=
>> 5806
6303 split_lock_detect= 5807 split_lock_detect=
6304 [X86] Enable split lo 5808 [X86] Enable split lock detection or bus lock detection
6305 5809
6306 When enabled (and if 5810 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5811 instructions that access data across cache line
6308 boundaries will resul 5812 boundaries will result in an alignment check exception
6309 for split lock detect 5813 for split lock detection or a debug exception for
6310 bus lock detection. 5814 bus lock detection.
6311 5815
6312 off - not enabled 5816 off - not enabled
6313 5817
6314 warn - the kernel 5818 warn - the kernel will emit rate-limited warnings
6315 about appli 5819 about applications triggering the #AC
6316 exception o 5820 exception or the #DB exception. This mode is
6317 the default 5821 the default on CPUs that support split lock
6318 detection o 5822 detection or bus lock detection. Default
6319 behavior is 5823 behavior is by #AC if both features are
6320 enabled in 5824 enabled in hardware.
6321 5825
6322 fatal - the kernel 5826 fatal - the kernel will send SIGBUS to applications
6323 that trigge 5827 that trigger the #AC exception or the #DB
6324 exception. 5828 exception. Default behavior is by #AC if
6325 both featur 5829 both features are enabled in hardware.
6326 5830
6327 ratelimit:N - 5831 ratelimit:N -
6328 Set system 5832 Set system wide rate limit to N bus locks
6329 per second 5833 per second for bus lock detection.
6330 0 < N <= 10 5834 0 < N <= 1000.
6331 5835
6332 N/A for spl 5836 N/A for split lock detection.
6333 5837
6334 5838
6335 If an #AC exception i 5839 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5840 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5841 the kernel will oops in either "warn" or "fatal"
6338 mode. 5842 mode.
6339 5843
6340 #DB exception for bus 5844 #DB exception for bus lock is triggered only when
6341 CPL > 0. 5845 CPL > 0.
6342 5846
6343 srbds= [X86,INTEL,EARLY] !! 5847 srbds= [X86,INTEL]
6344 Control the Special R 5848 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5849 (SRBDS) mitigation.
6346 5850
6347 Certain CPUs are vuln 5851 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5852 exploit which can leak bits from the random
6349 number generator. 5853 number generator.
6350 5854
6351 By default, this issu 5855 By default, this issue is mitigated by
6352 microcode. However, 5856 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5857 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5858 much slower. Among other effects, this will
6355 result in reduced thr 5859 result in reduced throughput from /dev/urandom.
6356 5860
6357 The microcode mitigat 5861 The microcode mitigation can be disabled with
6358 the following option: 5862 the following option:
6359 5863
6360 off: Disable mitig 5864 off: Disable mitigation and remove
6361 performance i 5865 performance impact to RDRAND and RDSEED
6362 5866
6363 srcutree.big_cpu_lim [KNL] 5867 srcutree.big_cpu_lim [KNL]
6364 Specifies the number 5868 Specifies the number of CPUs constituting a
6365 large system, such th 5869 large system, such that srcu_struct structures
6366 should immediately al 5870 should immediately allocate an srcu_node array.
6367 This kernel-boot para 5871 This kernel-boot parameter defaults to 128,
6368 but takes effect only 5872 but takes effect only when the low-order four
6369 bits of srcutree.conv 5873 bits of srcutree.convert_to_big is equal to 3
6370 (decide at boot). 5874 (decide at boot).
6371 5875
6372 srcutree.convert_to_big [KNL] 5876 srcutree.convert_to_big [KNL]
6373 Specifies under what 5877 Specifies under what conditions an SRCU tree
6374 srcu_struct structure 5878 srcu_struct structure will be converted to big
6375 form, that is, with a 5879 form, that is, with an rcu_node tree:
6376 5880
6377 0: Never. 5881 0: Never.
6378 1: At ini 5882 1: At init_srcu_struct() time.
6379 2: When r 5883 2: When rcutorture decides to.
6380 3: Decide 5884 3: Decide at boot time (default).
6381 0x1X: Above 5885 0x1X: Above plus if high contention.
6382 5886
6383 Either way, the srcu_ 5887 Either way, the srcu_node tree will be sized based
6384 on the actual runtime 5888 on the actual runtime number of CPUs (nr_cpu_ids)
6385 instead of the compil 5889 instead of the compile-time CONFIG_NR_CPUS.
6386 5890
6387 srcutree.counter_wrap_check [KNL] 5891 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5892 Specifies how frequently to check for
6389 grace-period sequence 5893 grace-period sequence counter wrap for the
6390 srcu_data structure's 5894 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5895 The greater the number of bits set in this kernel
6392 parameter, the less f 5896 parameter, the less frequently counter wrap will
6393 be checked for. Note 5897 be checked for. Note that the bottom two bits
6394 are ignored. 5898 are ignored.
6395 5899
6396 srcutree.exp_holdoff [KNL] 5900 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5901 Specifies how many nanoseconds must elapse
6398 since the end of the 5902 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5903 a given srcu_struct until the next normal SRCU
6400 grace period will be 5904 grace period will be considered for automatic
6401 expediting. Set to z 5905 expediting. Set to zero to disable automatic
6402 expediting. 5906 expediting.
6403 5907
6404 srcutree.srcu_max_nodelay [KNL] 5908 srcutree.srcu_max_nodelay [KNL]
6405 Specifies the number 5909 Specifies the number of no-delay instances
6406 per jiffy for which t 5910 per jiffy for which the SRCU grace period
6407 worker thread will be 5911 worker thread will be rescheduled with zero
6408 delay. Beyond this li 5912 delay. Beyond this limit, worker thread will
6409 be rescheduled with a 5913 be rescheduled with a sleep delay of one jiffy.
6410 5914
6411 srcutree.srcu_max_nodelay_phase [KNL] 5915 srcutree.srcu_max_nodelay_phase [KNL]
6412 Specifies the per-gra 5916 Specifies the per-grace-period phase, number of
6413 non-sleeping polls of 5917 non-sleeping polls of readers. Beyond this limit,
6414 grace period worker t 5918 grace period worker thread will be rescheduled
6415 with a sleep delay of 5919 with a sleep delay of one jiffy, between each
6416 rescan of the readers 5920 rescan of the readers, for a grace period phase.
6417 5921
6418 srcutree.srcu_retry_check_delay [KNL] 5922 srcutree.srcu_retry_check_delay [KNL]
6419 Specifies number of m 5923 Specifies number of microseconds of non-sleeping
6420 delay between each no 5924 delay between each non-sleeping poll of readers.
6421 5925
6422 srcutree.small_contention_lim [KNL] 5926 srcutree.small_contention_lim [KNL]
6423 Specifies the number 5927 Specifies the number of update-side contention
6424 events per jiffy will 5928 events per jiffy will be tolerated before
6425 initiating a conversi 5929 initiating a conversion of an srcu_struct
6426 structure to big form 5930 structure to big form. Note that the value of
6427 srcutree.convert_to_b 5931 srcutree.convert_to_big must have the 0x10 bit
6428 set for contention-ba 5932 set for contention-based conversions to occur.
6429 5933
6430 ssbd= [ARM64,HW,EARLY] !! 5934 ssbd= [ARM64,HW]
6431 Speculative Store Byp 5935 Speculative Store Bypass Disable control
6432 5936
6433 On CPUs that are vuln 5937 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5938 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5939 firmware based mitigation, this parameter
6436 indicates how the mit 5940 indicates how the mitigation should be used:
6437 5941
6438 force-on: Unconditio 5942 force-on: Unconditionally enable mitigation for
6439 for both k 5943 for both kernel and userspace
6440 force-off: Unconditio 5944 force-off: Unconditionally disable mitigation for
6441 for both k 5945 for both kernel and userspace
6442 kernel: Always ena 5946 kernel: Always enable mitigation in the
6443 kernel, an 5947 kernel, and offer a prctl interface
6444 to allow u 5948 to allow userspace to register its
6445 interest i 5949 interest in being mitigated too.
6446 5950
6447 stack_guard_gap= [MM] 5951 stack_guard_gap= [MM]
6448 override the default 5952 override the default stack gap protection. The value
6449 is in page units and 5953 is in page units and it defines how many pages prior
6450 to (for stacks growin 5954 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5955 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5956 mapping. Default value is 256 pages.
6453 5957
6454 stack_depot_disable= [KNL,EARLY] !! 5958 stack_depot_disable= [KNL]
6455 Setting this to true 5959 Setting this to true through kernel command line will
6456 disable the stack dep 5960 disable the stack depot thereby saving the static memory
6457 consumed by the stack 5961 consumed by the stack hash table. By default this is set
6458 to false. 5962 to false.
6459 5963
6460 stacktrace [FTRACE] 5964 stacktrace [FTRACE]
6461 Enabled the stack tra 5965 Enabled the stack tracer on boot up.
6462 5966
6463 stacktrace_filter=[function-list] 5967 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5968 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 5969 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 5970 list of functions. This list can be changed at run
6467 time by the stack_tra 5971 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 5972 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 5973 and the stacktrace above is not needed.
6470 5974
6471 sti= [PARISC,HW] 5975 sti= [PARISC,HW]
6472 Format: <num> 5976 Format: <num>
6473 Set the STI (builtin 5977 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 5978 machines) console (graphic card) which should be used
6475 as the initial boot-c 5979 as the initial boot-console.
6476 See also comment in d 5980 See also comment in drivers/video/console/sticore.c.
6477 5981
6478 sti_font= [HW] 5982 sti_font= [HW]
6479 See comment in driver 5983 See comment in drivers/video/console/sticore.c.
6480 5984
6481 stifb= [HW] 5985 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 5986 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 5987
6484 strict_sas_size= 5988 strict_sas_size=
6485 [X86] 5989 [X86]
6486 Format: <bool> 5990 Format: <bool>
6487 Enable or disable str 5991 Enable or disable strict sigaltstack size checks
6488 against the required 5992 against the required signal frame size which
6489 depends on the suppor 5993 depends on the supported FPU features. This can
6490 be used to filter out 5994 be used to filter out binaries which have
6491 not yet been made awa 5995 not yet been made aware of AT_MINSIGSTKSZ.
6492 5996
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= 5997 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 5998 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 5999 [NFS,SUNRPC]
6506 SunRPC servers often 6000 SunRPC servers often require that client requests
6507 originate from a priv 6001 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 6002 range 0 < portnr < 1024).
6509 An administrator who 6003 An administrator who wishes to reserve some of these
6510 ports for other uses 6004 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 6005 kernel's sunrpc client considers to be privileged
6512 using these two param 6006 using these two parameters to set the minimum and
6513 maximum port values. 6007 maximum port values.
6514 6008
6515 sunrpc.svc_rpc_per_connection_limit= 6009 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 6010 [NFS,SUNRPC]
6517 Limit the number of r 6011 Limit the number of requests that the server will
6518 process in parallel f 6012 process in parallel from a single connection.
6519 The default value is 6013 The default value is 0 (no limit).
6520 6014
6521 sunrpc.pool_mode= 6015 sunrpc.pool_mode=
6522 [NFS] 6016 [NFS]
6523 Control how the NFS s 6017 Control how the NFS server code allocates CPUs to
6524 service thread pools. 6018 service thread pools. Depending on how many NICs
6525 you have and where th 6019 you have and where their interrupts are bound, this
6526 option will affect wh 6020 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 6021 Note: this parameter cannot be changed while the
6528 NFS server is running 6022 NFS server is running.
6529 6023
6530 auto the serve 6024 auto the server chooses an appropriate mode
6531 automatic 6025 automatically using heuristics
6532 global a single 6026 global a single global pool contains all CPUs
6533 percpu one pool 6027 percpu one pool for each CPU
6534 pernode one pool 6028 pernode one pool for each NUMA node (equivalent
6535 to global 6029 to global on non-NUMA machines)
6536 6030
6537 sunrpc.tcp_slot_table_entries= 6031 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 6032 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 6033 [NFS,SUNRPC]
6540 Sets the upper limit 6034 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 6035 RPC calls that can be sent from the client to a
6542 server. Increasing th 6036 server. Increasing these values may allow you to
6543 improve throughput, b 6037 improve throughput, but will also increase the
6544 amount of memory rese 6038 amount of memory reserved for use by the client.
6545 6039
6546 suspend.pm_test_delay= 6040 suspend.pm_test_delay=
6547 [SUSPEND] 6041 [SUSPEND]
6548 Sets the number of se 6042 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 6043 mode before resuming the system (see
6550 /sys/power/pm_test). 6044 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 6045 is set. Default value is 5.
6552 6046
6553 svm= [PPC] 6047 svm= [PPC]
6554 Format: { on | off | 6048 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 6049 This parameter controls use of the Protected
6556 Execution Facility on 6050 Execution Facility on pSeries.
6557 6051
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 6052 swapaccount= [KNL]
>> 6053 Format: [0|1]
>> 6054 Enable accounting of swap in memory resource
>> 6055 controller if no parameter or 1 is given or disable
>> 6056 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
>> 6057
>> 6058 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in 6059 Format: { <int> [,<int>] | force | noforce }
6560 <int> -- Number of I/ 6060 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ 6061 <int> -- Second integer after comma. Number of swiotlb
6562 areas with t 6062 areas with their own lock. Will be rounded up
6563 to a power o 6063 to a power of 2.
6564 force -- force using 6064 force -- force using of bounce buffers even if they
6565 wouldn't be 6065 wouldn't be automatically used by the kernel
6566 noforce -- Never use 6066 noforce -- Never use bounce buffers (for debugging)
6567 6067
6568 switches= [HW,M68k,EARLY] !! 6068 switches= [HW,M68k]
6569 6069
6570 sysctl.*= [KNL] 6070 sysctl.*= [KNL]
6571 Set a sysctl paramete 6071 Set a sysctl parameter, right before loading the init
6572 process, as if the va 6072 process, as if the value was written to the respective
6573 /proc/sys/... file. B 6073 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 6074 separators. Unrecognized parameters and invalid values
6575 are reported in the k 6075 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 6076 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 6077 Example: sysctl.vm.swappiness=40
6578 6078
>> 6079 sysfs.deprecated=0|1 [KNL]
>> 6080 Enable/disable old style sysfs layout for old udev
>> 6081 on older distributions. When this option is enabled
>> 6082 very new udev will not work anymore. When this option
>> 6083 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 6084 in older udev will not work anymore.
>> 6085 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 6086 the kernel configuration.
>> 6087
6579 sysrq_always_enabled 6088 sysrq_always_enabled
6580 [KNL] 6089 [KNL]
6581 Ignore sysrq setting 6090 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 6091 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 6092 Useful for debugging.
6584 6093
6585 tcpmhash_entries= [KNL,NET] 6094 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 6095 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 6096 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 6097 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 6098 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 6099 "tcp_no_metrics_save" section for more details.
6591 6100
6592 tdfx= [HW,DRM] 6101 tdfx= [HW,DRM]
6593 6102
6594 test_suspend= [SUSPEND] 6103 test_suspend= [SUSPEND]
6595 Format: { "mem" | "st 6104 Format: { "mem" | "standby" | "freeze" }[,N]
6596 Specify "mem" (for Su 6105 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 6106 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 6107 as the system sleep state during system startup with
6599 the optional capabili 6108 the optional capability to repeat N number of times.
6600 The system is woken f 6109 The system is woken from this state using a
6601 wakeup-capable RTC al 6110 wakeup-capable RTC alarm.
6602 6111
6603 thash_entries= [KNL,NET] 6112 thash_entries= [KNL,NET]
6604 Set number of hash bu 6113 Set number of hash buckets for TCP connection
6605 6114
6606 thermal.act= [HW,ACPI] 6115 thermal.act= [HW,ACPI]
6607 -1: disable all activ 6116 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 6117 <degrees C>: override all lowest active trip points
6609 6118
6610 thermal.crt= [HW,ACPI] 6119 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 6120 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 6121 <degrees C>: override all critical trip points
6613 6122
>> 6123 thermal.nocrt= [HW,ACPI]
>> 6124 Set to disable actions on ACPI thermal zone
>> 6125 critical and hot trip points.
>> 6126
6614 thermal.off= [HW,ACPI] 6127 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 6128 1: disable ACPI thermal control
6616 6129
6617 thermal.psv= [HW,ACPI] 6130 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 6131 -1: disable all passive trip points
6619 <degrees C>: override 6132 <degrees C>: override all passive trip points to this
6620 value 6133 value
6621 6134
6622 thermal.tzp= [HW,ACPI] 6135 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 6136 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 6137 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 6138 0: no polling (default)
6626 6139
6627 threadirqs [KNL,EARLY] !! 6140 threadirqs [KNL]
6628 Force threading of al 6141 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 6142 marked explicitly IRQF_NO_THREAD.
6630 6143
6631 topology= [S390,EARLY] !! 6144 topology= [S390]
6632 Format: {off | on} 6145 Format: {off | on}
6633 Specify if the kernel 6146 Specify if the kernel should make use of the cpu
6634 topology information 6147 topology information if the hardware supports this.
6635 The scheduler will ma 6148 The scheduler will make use of this information and
6636 e.g. base its process 6149 e.g. base its process migration decisions on it.
6637 Default is on. 6150 Default is on.
6638 6151
>> 6152 topology_updates= [KNL, PPC, NUMA]
>> 6153 Format: {off}
>> 6154 Specify if the kernel should ignore (off)
>> 6155 topology updates sent by the hypervisor to this
>> 6156 LPAR.
>> 6157
6639 torture.disable_onoff_at_boot= [KNL] 6158 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 6159 Prevent the CPU-hotplug component of torturing
6641 until after init has 6160 until after init has spawned.
6642 6161
6643 torture.ftrace_dump_at_shutdown= [KNL 6162 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 6163 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 6164 even if there were no errors. This can be a
6646 very costly operation 6165 very costly operation when many torture tests
6647 are running concurren 6166 are running concurrently, especially on systems
6648 with rotating-rust st 6167 with rotating-rust storage.
6649 6168
6650 torture.verbose_sleep_frequency= [KNL 6169 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 6170 Specifies how many verbose printk()s should be
6652 emitted between each 6171 emitted between each sleep. The default of zero
6653 disables verbose-prin 6172 disables verbose-printk() sleeping.
6654 6173
6655 torture.verbose_sleep_duration= [KNL] 6174 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 6175 Duration of each verbose-printk() sleep in jiffies.
6657 6176
>> 6177 tp720= [HW,PS2]
>> 6178
6658 tpm_suspend_pcr=[HW,TPM] 6179 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 6180 Format: integer pcr id
6660 Specify that at suspe 6181 Specify that at suspend time, the tpm driver
6661 should extend the spe 6182 should extend the specified pcr with zeros,
6662 as a workaround for s 6183 as a workaround for some chips which fail to
6663 flush the last writte 6184 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 6185 This will guarantee that all the other pcrs
6665 are saved. 6186 are saved.
6666 6187
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] 6188 tp_printk [FTRACE]
6675 Have the tracepoints 6189 Have the tracepoints sent to printk as well as the
6676 tracing ring buffer. 6190 tracing ring buffer. This is useful for early boot up
6677 where the system hang 6191 where the system hangs or reboots and does not give the
6678 option for reading th 6192 option for reading the tracing buffer or performing a
6679 ftrace_dump_on_oops. 6193 ftrace_dump_on_oops.
6680 6194
6681 To turn off having tr 6195 To turn off having tracepoints sent to printk,
6682 echo 0 > /proc/sys/k 6196 echo 0 > /proc/sys/kernel/tracepoint_printk
6683 Note, echoing 1 into 6197 Note, echoing 1 into this file without the
6684 tp_printk kernel cmdl !! 6198 tracepoint_printk kernel cmdline option has no effect.
6685 6199
6686 The tp_printk_stop_on 6200 The tp_printk_stop_on_boot (see below) can also be used
6687 to stop the printing 6201 to stop the printing of events to console at
6688 late_initcall_sync. 6202 late_initcall_sync.
6689 6203
6690 ** CAUTION ** 6204 ** CAUTION **
6691 6205
6692 Having tracepoints se 6206 Having tracepoints sent to printk() and activating high
6693 frequency tracepoints 6207 frequency tracepoints such as irq or sched, can cause
6694 the system to live lo 6208 the system to live lock.
6695 6209
6696 tp_printk_stop_on_boot [FTRACE] 6210 tp_printk_stop_on_boot [FTRACE]
6697 When tp_printk (above 6211 When tp_printk (above) is set, it can cause a lot of noise
6698 on the console. It ma 6212 on the console. It may be useful to only include the
6699 printing of events du 6213 printing of events during boot up, as user space may
6700 make the system inope 6214 make the system inoperable.
6701 6215
6702 This command line opt 6216 This command line option will stop the printing of events
6703 to console at the lat 6217 to console at the late_initcall_sync() time frame.
6704 6218
6705 trace_buf_size=nn[KMG] 6219 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 6220 [FTRACE] will set tracing buffer size on each cpu.
6707 6221
6708 trace_clock= [FTRACE] Set the cloc 6222 trace_clock= [FTRACE] Set the clock used for tracing events
6709 at boot up. 6223 at boot up.
6710 local - Use the per C 6224 local - Use the per CPU time stamp counter
6711 (converted in 6225 (converted into nanoseconds). Fast, but
6712 depending on 6226 depending on the architecture, may not be
6713 in sync betwe 6227 in sync between CPUs.
6714 global - Event time s 6228 global - Event time stamps are synchronize across
6715 CPUs. May be 6229 CPUs. May be slower than the local clock,
6716 but better fo 6230 but better for some race conditions.
6717 counter - Simple coun 6231 counter - Simple counting of events (1, 2, ..)
6718 note, some co 6232 note, some counts may be skipped due to the
6719 infrastructur 6233 infrastructure grabbing the clock more than
6720 once per even 6234 once per event.
6721 uptime - Use jiffies 6235 uptime - Use jiffies as the time stamp.
6722 perf - Use the same c 6236 perf - Use the same clock that perf uses.
6723 mono - Use ktime_get_ 6237 mono - Use ktime_get_mono_fast_ns() for time stamps.
6724 mono_raw - Use ktime_ 6238 mono_raw - Use ktime_get_raw_fast_ns() for time
6725 stamps. 6239 stamps.
6726 boot - Use ktime_get_ 6240 boot - Use ktime_get_boot_fast_ns() for time stamps.
6727 Architectures may add 6241 Architectures may add more clocks. See
6728 Documentation/trace/f 6242 Documentation/trace/ftrace.rst for more details.
6729 6243
6730 trace_event=[event-list] 6244 trace_event=[event-list]
6731 [FTRACE] Set and star 6245 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 6246 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 6247 comma-separated list of trace events to enable. See
6734 also Documentation/tr 6248 also Documentation/trace/events.rst
6735 6249
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] 6250 trace_options=[option-list]
6757 [FTRACE] Enable or di 6251 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 6252 The option-list is a comma delimited list of options
6759 that can be enabled o 6253 that can be enabled or disabled just as if you were
6760 to echo the option na 6254 to echo the option name into
6761 6255
6762 /sys/kernel/traci !! 6256 /sys/kernel/debug/tracing/trace_options
6763 6257
6764 For example, to enabl 6258 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 6259 stack trace of each event), add to the command line:
6766 6260
6767 trace_options=s 6261 trace_options=stacktrace
6768 6262
6769 See also Documentatio 6263 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 6264 section.
6771 6265
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 6266 traceoff_on_warning
6792 [FTRACE] enable this 6267 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 6268 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 6269 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 6270 file located in /sys/kernel/debug/tracing/
6796 6271
6797 This option is useful 6272 This option is useful, as it disables the trace before
6798 the WARNING dump is c 6273 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 6274 be filled with content caused by the warning output.
6800 6275
6801 This option can also 6276 This option can also be set at run time via the sysctl
6802 option: kernel/trace 6277 option: kernel/traceoff_on_warning
6803 6278
6804 transparent_hugepage= 6279 transparent_hugepage=
6805 [KNL] 6280 [KNL]
6806 Format: [always|madvi 6281 Format: [always|madvise|never]
6807 Can be used to contro 6282 Can be used to control the default behavior of the system
6808 with respect to trans 6283 with respect to transparent hugepages.
6809 See Documentation/adm 6284 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 6285 for more details.
6811 6286
6812 trusted.source= [KEYS] 6287 trusted.source= [KEYS]
6813 Format: <string> 6288 Format: <string>
6814 This parameter identi 6289 This parameter identifies the trust source as a backend
6815 for trusted keys impl 6290 for trusted keys implementation. Supported trust
6816 sources: 6291 sources:
6817 - "tpm" 6292 - "tpm"
6818 - "tee" 6293 - "tee"
6819 - "caam" 6294 - "caam"
6820 - "dcp" <<
6821 If not specified then 6295 If not specified then it defaults to iterating through
6822 the trust source list 6296 the trust source list starting with TPM and assigns the
6823 first trust source as 6297 first trust source as a backend which is initialized
6824 successfully during i 6298 successfully during iteration.
6825 6299
6826 trusted.rng= [KEYS] 6300 trusted.rng= [KEYS]
6827 Format: <string> 6301 Format: <string>
6828 The RNG used to gener 6302 The RNG used to generate key material for trusted keys.
6829 Can be one of: 6303 Can be one of:
6830 - "kernel" 6304 - "kernel"
6831 - the same value as t 6305 - the same value as trusted.source: "tpm" or "tee"
6832 - "default" 6306 - "default"
6833 If not specified, "de 6307 If not specified, "default" is used. In this case,
6834 the RNG's choice is l 6308 the RNG's choice is left to each individual trust source.
6835 6309
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 6310 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 6311 Format: <string>
6850 [x86] reliable: mark 6312 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 6313 disables clocksource verification at runtime, as well
6852 as the stability chec 6314 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 6315 high-resolution timer mode on older hardware, and in
6854 virtualized environme 6316 virtualized environment.
6855 [x86] noirqtime: Do n 6317 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 6318 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 6319 platforms where RDTSC is slow and this accounting
6858 can add overhead. 6320 can add overhead.
6859 [x86] unstable: mark 6321 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 6322 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 6323 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 6324 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 6325 in situations with strict latency requirements (where
6864 interruptions from cl 6326 interruptions from clocksource watchdog are not
6865 acceptable). 6327 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 6328
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 6329 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 6330 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 6331 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 6332 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 6333 Format: <unsigned int>
6882 6334
6883 tsx= [X86] Control Transac 6335 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 6336 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 6337 support TSX control.
6886 6338
6887 This parameter contro 6339 This parameter controls the TSX feature. The options are:
6888 6340
6889 on - Enable TSX 6341 on - Enable TSX on the system. Although there are
6890 mitigations f 6342 mitigations for all known security vulnerabilities,
6891 TSX has been 6343 TSX has been known to be an accelerator for
6892 several previ 6344 several previous speculation-related CVEs, and
6893 so there may 6345 so there may be unknown security risks associated
6894 with leaving 6346 with leaving it enabled.
6895 6347
6896 off - Disable TSX 6348 off - Disable TSX on the system. (Note that this
6897 option takes 6349 option takes effect only on newer CPUs which are
6898 not vulnerabl 6350 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 6351 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 6352 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 6353 update. This new MSR allows for the reliable
6902 deactivation 6354 deactivation of the TSX functionality.)
6903 6355
6904 auto - Disable TSX 6356 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 6357 otherwise enable TSX on the system.
6906 6358
6907 Not specifying this o 6359 Not specifying this option is equivalent to tsx=off.
6908 6360
6909 See Documentation/adm 6361 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 6362 for more details.
6911 6363
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 6364 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 6365 Abort (TAA) vulnerability.
6914 6366
6915 Similar to Micro-arch 6367 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 6368 certain CPUs that support Transactional
6917 Synchronization Exten 6369 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 6370 exploit against CPU internal buffers which can forward
6919 information to a disc 6371 information to a disclosure gadget under certain
6920 conditions. 6372 conditions.
6921 6373
6922 In vulnerable process 6374 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 6375 data can be used in a cache side channel attack, to
6924 access data to which 6376 access data to which the attacker does not have direct
6925 access. 6377 access.
6926 6378
6927 This parameter contro 6379 This parameter controls the TAA mitigation. The
6928 options are: 6380 options are:
6929 6381
6930 full - Enable T 6382 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 6383 if TSX is enabled.
6932 6384
6933 full,nosmt - Enable T 6385 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 6386 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 6387 is not disabled because CPU is not
6936 vulnerab 6388 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 6389 off - Unconditionally disable TAA mitigation
6938 6390
6939 On MDS-affected machi 6391 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 6392 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 6393 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 6394 this mitigation, you need to specify mds=off too.
6943 6395
6944 Not specifying this o 6396 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 6397 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 6398 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 6399 required and doesn't provide any additional
6948 mitigation. 6400 mitigation.
6949 6401
6950 For details see: 6402 For details see:
6951 Documentation/admin-g 6403 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 6404
6953 turbografx.map[2|3]= [HW,JOY] 6405 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 6406 TurboGraFX parallel port interface
6955 Format: 6407 Format:
6956 <port#>,<js1>,<js2>,< 6408 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 6409 See also Documentation/input/devices/joystick-parport.rst
6958 6410
6959 udbg-immortal [PPC] When debugging 6411 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 6412 happen after console_init() and before a proper
6961 console driver takes 6413 console driver takes over, this boot options might
6962 help "seeing" what's 6414 help "seeing" what's going on.
6963 6415
6964 uhash_entries= [KNL,NET] 6416 uhash_entries= [KNL,NET]
6965 Set number of hash bu 6417 Set number of hash buckets for UDP/UDP-Lite connections
6966 6418
6967 uhci-hcd.ignore_oc= 6419 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 6420 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 6421 Some badly-designed motherboards generate lots of
6970 bogus events, for por 6422 bogus events, for ports that aren't wired to
6971 anything. Set this p 6423 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 6424 Note that genuine overcurrent events won't be
6973 reported either. 6425 reported either.
6974 6426
6975 unknown_nmi_panic 6427 unknown_nmi_panic
6976 [X86] Cause panic on 6428 [X86] Cause panic on unknown NMI.
6977 6429
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= 6430 usbcore.authorized_default=
6985 [USB] Default USB dev 6431 [USB] Default USB device authorization:
6986 (default -1 = authori !! 6432 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 6433 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 6434 if device connected to internal port)
6989 6435
6990 usbcore.autosuspend= 6436 usbcore.autosuspend=
6991 [USB] The autosuspend 6437 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 6438 for newly-detected USB devices (default 2). This
6993 is the time required 6439 is the time required before an idle device will be
6994 autosuspended. Devic 6440 autosuspended. Devices for which the delay is set
6995 to a negative value w 6441 to a negative value won't be autosuspended at all.
6996 6442
6997 usbcore.usbfs_snoop= 6443 usbcore.usbfs_snoop=
6998 [USB] Set to log all 6444 [USB] Set to log all usbfs traffic (default 0 = off).
6999 6445
7000 usbcore.usbfs_snoop_max= 6446 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 6447 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 6448 (default = 65536).
7003 6449
7004 usbcore.blinkenlights= 6450 usbcore.blinkenlights=
7005 [USB] Set to cycle le 6451 [USB] Set to cycle leds on hubs (default 0 = off).
7006 6452
7007 usbcore.old_scheme_first= 6453 usbcore.old_scheme_first=
7008 [USB] Start with the 6454 [USB] Start with the old device initialization
7009 scheme (default 0 = o 6455 scheme (default 0 = off).
7010 6456
7011 usbcore.usbfs_memory_mb= 6457 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 6458 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 6459 usbfs (default = 16, 0 = max = 2047).
7014 6460
7015 usbcore.use_both_schemes= 6461 usbcore.use_both_schemes=
7016 [USB] Try the other d 6462 [USB] Try the other device initialization scheme
7017 if the first one fail 6463 if the first one fails (default 1 = enabled).
7018 6464
7019 usbcore.initial_descriptor_timeout= 6465 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 6466 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 6467 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 6468 (default 5000 = 5.0 seconds).
7023 6469
7024 usbcore.nousb [USB] Disable the USB 6470 usbcore.nousb [USB] Disable the USB subsystem
7025 6471
7026 usbcore.quirks= 6472 usbcore.quirks=
7027 [USB] A list of quirk 6473 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 6474 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 6475 commas. Each entry has the form
7030 VendorID:ProductID:Fl 6476 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 6477 numbers and Flags is a set of letters. Each letter
7032 will change the built 6478 will change the built-in quirk; setting it if it is
7033 clear and clearing it 6479 clear and clearing it if it is set. The letters have
7034 the following meaning 6480 the following meanings:
7035 a = USB_QUIRK 6481 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 6482 descriptors must not be fetched using
7037 a 255 6483 a 255-byte read);
7038 b = USB_QUIRK 6484 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 6485 correctly so reset it instead);
7040 c = USB_QUIRK 6486 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 6487 Set-Interface requests);
7042 d = USB_QUIRK 6488 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 6489 handle its Configuration or Interface
7044 strin 6490 strings);
7045 e = USB_QUIRK 6491 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 6492 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 6493 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 6494 more interface descriptions than the
7049 bNumI 6495 bNumInterfaces count, and can't handle
7050 talki 6496 talking to these interfaces);
7051 g = USB_QUIRK 6497 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 6498 during initialization, after we read
7053 the d 6499 the device descriptor);
7054 h = USB_QUIRK 6500 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 6501 high speed and super speed interrupt
7056 endpo 6502 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 6503 require the interval in microframes (1
7058 micro 6504 microframe = 125 microseconds) to be
7059 calcu 6505 calculated as interval = 2 ^
7060 (bInt 6506 (bInterval-1).
7061 Devic 6507 Devices with this quirk report their
7062 bInte 6508 bInterval as the result of this
7063 calcu 6509 calculation instead of the exponent
7064 varia 6510 variable used in the calculation);
7065 i = USB_QUIRK 6511 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 6512 handle device_qualifier descriptor
7067 reque 6513 requests);
7068 j = USB_QUIRK 6514 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 6515 generates spurious wakeup, ignore
7070 remot 6516 remote wakeup capability);
7071 k = USB_QUIRK 6517 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 6518 Power Management);
7073 l = USB_QUIRK 6519 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 6520 (Device reports its bInterval as linear
7075 frame 6521 frames instead of the USB 2.0
7076 calcu 6522 calculation);
7077 m = USB_QUIRK 6523 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 6524 to be disconnected before suspend to
7079 preve 6525 prevent spurious wakeup);
7080 n = USB_QUIRK 6526 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 6527 pause after every control message);
7082 o = USB_QUIRK 6528 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 6529 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 6530 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 6531
7089 usbhid.mousepoll= 6532 usbhid.mousepoll=
7090 [USBHID] The interval 6533 [USBHID] The interval which mice are to be polled at.
7091 6534
7092 usbhid.jspoll= 6535 usbhid.jspoll=
7093 [USBHID] The interval 6536 [USBHID] The interval which joysticks are to be polled at.
7094 6537
7095 usbhid.kbpoll= 6538 usbhid.kbpoll=
7096 [USBHID] The interval 6539 [USBHID] The interval which keyboards are to be polled at.
7097 6540
7098 usb-storage.delay_use= 6541 usb-storage.delay_use=
7099 [UMS] The delay in se 6542 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 6543 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 6544
7105 usb-storage.quirks= 6545 usb-storage.quirks=
7106 [UMS] A list of quirk 6546 [UMS] A list of quirks entries to supplement or
7107 override the built-in 6547 override the built-in unusual_devs list. List
7108 entries are separated 6548 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 6549 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 6550 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 6551 Flags is a set of characters, each corresponding
7112 to a common usb-stora 6552 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 6553 a = SANE_SENSE (collect more than 18 bytes
7114 of se 6554 of sense data, not on uas);
7115 b = BAD_SENSE 6555 b = BAD_SENSE (don't collect more than 18
7116 bytes 6556 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 6557 c = FIX_CAPACITY (decrease the reported
7118 devic 6558 device capacity by one sector);
7119 d = NO_READ_D 6559 d = NO_READ_DISC_INFO (don't use
7120 READ_ 6560 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 6561 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 6562 READ_CAPACITY_16 command);
7123 f = NO_REPORT 6563 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 6564 command, uas only);
7125 g = MAX_SECTO 6565 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 6566 240 sectors at a time, uas only);
7127 h = CAPACITY_ 6567 h = CAPACITY_HEURISTICS (decrease the
7128 repor 6568 reported device capacity by one
7129 secto 6569 sector if the number is odd);
7130 i = IGNORE_DE 6570 i = IGNORE_DEVICE (don't bind to this
7131 devic 6571 device);
7132 j = NO_REPORT 6572 j = NO_REPORT_LUNS (don't use report luns
7133 comma 6573 command, uas only);
7134 k = NO_SAME ( 6574 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 6575 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 6576 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 6577 m = MAX_SECTORS_64 (don't transfer more
7138 than 6578 than 64 sectors = 32 KB at a time,
7139 not o 6579 not on uas);
7140 n = INITIAL_R 6580 n = INITIAL_READ10 (force a retry of the
7141 initi 6581 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 6582 o = CAPACITY_OK (accept the capacity
7143 repor 6583 reported by the device, not on uas);
7144 p = WRITE_CAC 6584 p = WRITE_CACHE (the device cache is ON
7145 by de 6585 by default, not on uas);
7146 r = IGNORE_RE 6586 r = IGNORE_RESIDUE (the device reports
7147 bogus 6587 bogus residue values, not on uas);
7148 s = SINGLE_LU 6588 s = SINGLE_LUN (the device has only one
7149 Logic 6589 Logical Unit);
7150 t = NO_ATA_1X 6590 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 6591 commands, uas only);
7152 u = IGNORE_UA 6592 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 6593 w = NO_WP_DETECT (don't test whether the
7154 mediu 6594 medium is write-protected).
7155 y = ALWAYS_SY 6595 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 6596 even if the device claims no cache,
7157 not o 6597 not on uas)
7158 Example: quirks=0419: 6598 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 6599
7160 user_debug= [KNL,ARM] 6600 user_debug= [KNL,ARM]
7161 Format: <int> 6601 Format: <int>
7162 See arch/arm/Kconfig. 6602 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 6603 1 - undefined instruction events
7164 2 - system c 6604 2 - system calls
7165 4 - invalid 6605 4 - invalid data aborts
7166 8 - SIGSEGV 6606 8 - SIGSEGV faults
7167 16 - SIGBUS f 6607 16 - SIGBUS faults
7168 Example: user_debug=3 6608 Example: user_debug=31
7169 6609
7170 userpte= 6610 userpte=
7171 [X86,EARLY] Flags con !! 6611 [X86] Flags controlling user PTE allocations.
7172 6612
7173 nohigh = do n 6613 nohigh = do not allocate PTE pages in
7174 HIGHM 6614 HIGHMEM regardless of setting
7175 of CO 6615 of CONFIG_HIGHPTE.
7176 6616
7177 vdso= [X86,SH,SPARC] 6617 vdso= [X86,SH,SPARC]
7178 On X86_32, this is an 6618 On X86_32, this is an alias for vdso32=. Otherwise:
7179 6619
7180 vdso=1: enable VDSO ( 6620 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 6621 vdso=0: disable VDSO mapping
7182 6622
7183 vdso32= [X86] Control the 32- 6623 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 6624 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 6625 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 6626
7187 See the help text for 6627 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 6628 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 6629 vdso32=0; otherwise, the default is vdso32=1.
7190 6630
7191 For compatibility wit 6631 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 6632 alias for vdso32=0.
7193 6633
7194 Try vdso32=0 if you e 6634 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 6635 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 6636
7197 video= [FB,EARLY] Frame buff !! 6637 vector= [IA-64,SMP]
>> 6638 vector=percpu: enable percpu vector domain
>> 6639
>> 6640 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 6641 See Documentation/fb/modedb.rst.
7199 6642
7200 video.brightness_switch_enabled= [ACP 6643 video.brightness_switch_enabled= [ACPI]
7201 Format: [0|1] 6644 Format: [0|1]
7202 If set to 1, on recei 6645 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 6646 generated by hotkey, video driver will adjust brightness
7204 level and then send o 6647 level and then send out the event to user space through
7205 the allocated input d 6648 the allocated input device. If set to 0, video driver
7206 will only send out th 6649 will only send out the event without touching backlight
7207 brightness level. 6650 brightness level.
7208 default: 1 6651 default: 1
7209 6652
7210 virtio_mmio.device= 6653 virtio_mmio.device=
7211 [VMMIO] Memory mapped 6654 [VMMIO] Memory mapped virtio (platform) device.
7212 6655
7213 <size>@<basead 6656 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 6657 where:
7215 <size> := 6658 <size> := size (can use standard suffixes
7216 6659 like K, M and G)
7217 <baseaddr> := 6660 <baseaddr> := physical base address
7218 <irq> := 6661 <irq> := interrupt number (as passed to
7219 6662 request_irq())
7220 <id> := 6663 <id> := (optional) platform device id
7221 example: 6664 example:
7222 virtio_mmio.d 6665 virtio_mmio.device=1K@0x100b0000:48:7
7223 6666
7224 Can be used multiple 6667 Can be used multiple times for multiple devices.
7225 6668
7226 vga= [BOOT,X86-32] Select 6669 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 6670 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 6671 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 6672 Use vga=ask for menu.
7230 This is actually a bo 6673 This is actually a boot loader parameter; the value is
7231 passed to the kernel 6674 passed to the kernel using a special protocol.
7232 6675
7233 vm_debug[=options] [KNL] Availab 6676 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 6677 May slow down system boot speed, especially when
7235 enabled on systems wi 6678 enabled on systems with a large amount of memory.
7236 All options are enabl 6679 All options are enabled by default, and this
7237 interface is meant to 6680 interface is meant to allow for selectively
7238 enabling or disabling 6681 enabling or disabling specific virtual memory
7239 debugging features. 6682 debugging features.
7240 6683
7241 Available options are 6684 Available options are:
7242 P Enable page s 6685 P Enable page structure init time poisoning
7243 - Disable all o 6686 - Disable all of the above options
7244 6687
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 6688 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 6689 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 6690 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 6691 decrease the size and leave more room for directly
7249 for directly mapped k !! 6692 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 6693
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 6694 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 6695 Sets the memory size reserved for contiguous memory
7256 allocations for the v 6696 allocations for the vmcp device driver.
7257 6697
7258 vmhalt= [KNL,S390] Perform z/ 6698 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 6699 Format: <command>
7260 6700
7261 vmpanic= [KNL,S390] Perform z/ 6701 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 6702 Format: <command>
7263 6703
7264 vmpoff= [KNL,S390] Perform z/ 6704 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 6705 Format: <command>
7266 6706
7267 vsyscall= [X86-64,EARLY] !! 6707 vsyscall= [X86-64]
7268 Controls the behavior 6708 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 6709 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 6710 code). Most statically-linked binaries and older
7271 versions of glibc use 6711 versions of glibc use these calls. Because these
7272 functions are at fixe 6712 functions are at fixed addresses, they make nice
7273 targets for exploits 6713 targets for exploits that can control RIP.
7274 6714
7275 emulate Vsyscalls !! 6715 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 6716 emulated reasonably safely. The vsyscall
7277 readable. !! 6717 page is readable.
7278 6718
7279 xonly [default] !! 6719 xonly Vsyscalls turn into traps and are
7280 emulated 6720 emulated reasonably safely. The vsyscall
7281 page is n 6721 page is not readable.
7282 6722
7283 none Vsyscalls 6723 none Vsyscalls don't work at all. This makes
7284 them quit 6724 them quite hard to use for exploits but
7285 might bre 6725 might break your system.
7286 6726
7287 vt.color= [VT] Default text col 6727 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6728 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6729 Default: 0x07 = light gray on black.
7290 6730
7291 vt.cur_default= [VT] Default cursor s 6731 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6732 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6733 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6734 see VGA-softcursor.txt. Default: 2 = underline.
7295 6735
7296 vt.default_blu= [VT] 6736 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6737 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6738 Change the default blue palette of the console.
7299 This is a 16-member a 6739 This is a 16-member array composed of values
7300 ranging from 0-255. 6740 ranging from 0-255.
7301 6741
7302 vt.default_grn= [VT] 6742 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6743 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6744 Change the default green palette of the console.
7305 This is a 16-member a 6745 This is a 16-member array composed of values
7306 ranging from 0-255. 6746 ranging from 0-255.
7307 6747
7308 vt.default_red= [VT] 6748 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6749 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6750 Change the default red palette of the console.
7311 This is a 16-member a 6751 This is a 16-member array composed of values
7312 ranging from 0-255. 6752 ranging from 0-255.
7313 6753
7314 vt.default_utf8= 6754 vt.default_utf8=
7315 [VT] 6755 [VT]
7316 Format=<0|1> 6756 Format=<0|1>
7317 Set system-wide defau 6757 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6758 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6759 newly opened terminals.
7320 6760
7321 vt.global_cursor_default= 6761 vt.global_cursor_default=
7322 [VT] 6762 [VT]
7323 Format=<-1|0|1> 6763 Format=<-1|0|1>
7324 Set system-wide defau 6764 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6765 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6766 i.e. cursors will be created by default unless
7327 overridden by individ 6767 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6768 cursors, 1 will display them.
7329 6769
7330 vt.italic= [VT] Default color fo 6770 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6771 Default: 2 = green.
7332 6772
7333 vt.underline= [VT] Default color fo 6773 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6774 Default: 3 = cyan.
7335 6775
7336 watchdog timers [HW,WDT] For informat 6776 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6777 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6778 or other driver-specific files in the
7339 Documentation/watchdo 6779 Documentation/watchdog/ directory.
7340 6780
7341 watchdog_thresh= 6781 watchdog_thresh=
7342 [KNL] 6782 [KNL]
7343 Set the hard lockup d 6783 Set the hard lockup detector stall duration
7344 threshold in seconds. 6784 threshold in seconds. The soft lockup detector
7345 threshold is set to t 6785 threshold is set to twice the value. A value of 0
7346 disables both lockup 6786 disables both lockup detectors. Default is 10
7347 seconds. 6787 seconds.
7348 6788
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= 6789 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 6790 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 6791 warn stall conditions and dump internal state to
7359 help debugging. 0 di 6792 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 6793 detection; otherwise, it's the stall threshold
7361 duration in seconds. 6794 duration in seconds. The default value is 30 and
7362 it can be updated at 6795 it can be updated at runtime by writing to the
7363 corresponding sysfs f 6796 corresponding sysfs file.
7364 6797
7365 workqueue.cpu_intensive_thresh_us= !! 6798 workqueue.disable_numa
7366 Per-cpu work items wh !! 6799 By default, all work items queued to unbound
7367 threshold are automat !! 6800 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 6801 issued on, which results in better behavior in
7369 them from noticeably !! 6802 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 6803 whatever reason, this option can be used. Note
7371 !! 6804 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 6805 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 6806
7386 workqueue.power_efficient 6807 workqueue.power_efficient
7387 Per-cpu workqueues ar 6808 Per-cpu workqueues are generally preferred because
7388 they show better perf 6809 they show better performance thanks to cache
7389 locality; unfortunate 6810 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 6811 be more power hungry than unbound workqueues.
7391 6812
7392 Enabling this makes t 6813 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 6814 were observed to contribute significantly to power
7394 consumption unbound, 6815 consumption unbound, leading to measurably lower
7395 power usage at the co 6816 power usage at the cost of small performance
7396 overhead. 6817 overhead.
7397 6818
7398 The default value of 6819 The default value of this parameter is determined by
7399 the config option CON 6820 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 6821
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 6822 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 6823 Workqueue used to implicitly guarantee that work
7415 items queued without 6824 items queued without explicit CPU specified are put
7416 on the local CPU. Th 6825 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 6826 and while local CPU is still preferred work items
7418 may be put on foreign 6827 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 6828 forces round-robin CPU selection to flush out
7420 usages which depend o 6829 usages which depend on the now broken guarantee.
7421 When enabled, memory 6830 When enabled, memory and cache locality will be
7422 impacted. 6831 impacted.
7423 6832
7424 writecombine= [LOONGARCH,EARLY] Con !! 6833 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 6834 default x2apic cluster mode on platforms
7432 supporting x2apic. 6835 supporting x2apic.
7433 6836
7434 xen_512gb_limit [KNL,X86-64,X 6837 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 6838 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6839 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6840 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6841 save/restore/migration must be enabled to handle larger
7439 domains. 6842 domains.
7440 6843
7441 xen_emul_unplug= [HW,X !! 6844 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6845 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6846 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6847 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6848 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6849 nics -- unplug network devices
7447 all -- unplug all emu 6850 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6851 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6852 unnecessary even if the host did not respond to
7450 the unplug pr 6853 the unplug protocol
7451 never -- do not unplu 6854 never -- do not unplug even if version check succeeds
7452 6855
7453 xen_legacy_crash [X86,XEN,EARL !! 6856 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6857 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6858 panic() code such as dumping handler.
7456 6859
7457 xen_mc_debug [X86,XEN,EARLY] !! 6860 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 6861 Disables the qspinlock slowpath using Xen PV optimizations.
7459 Enabling this feature !! 6862 This parameter is obsoleted by "nopvspin" parameter, which
7460 bit, so it should onl !! 6863 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 6864
7469 xen_nopv [X86] 6865 xen_nopv [X86]
7470 Disables the PV optim 6866 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6867 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6868 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6869 has equivalent effect for XEN platform.
7474 6870
7475 xen_no_vector_callback 6871 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6872 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6873 event channel interrupts.
7478 6874
7479 xen_scrub_pages= [XEN] 6875 xen_scrub_pages= [XEN]
7480 Boolean option to con 6876 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6877 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6878 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6879 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6880
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6881 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6882 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6883 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6884 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 6885 improve timer resolution at the expense of processing
7490 more timer interrupts 6886 more timer interrupts.
7491 6887
7492 xen.balloon_boot_timeout= [XEN] 6888 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 6889 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 6890 in case initial ballooning fails to free enough memory.
7495 Applies only when run 6891 Applies only when running as HVM or PVH guest and
7496 started with less mem 6892 started with less memory configured than allowed at
7497 max. Default is 180. 6893 max. Default is 180.
7498 6894
7499 xen.event_eoi_delay= [XEN] 6895 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 6896 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 6897 storms (jiffies). Default is 10.
7502 6898
7503 xen.event_loop_timeout= [XEN] 6899 xen.event_loop_timeout= [XEN]
7504 After which time (jif 6900 After which time (jiffies) the event handling loop
7505 should start to delay 6901 should start to delay EOI handling. Default is 2.
7506 6902
7507 xen.fifo_events= [XEN] 6903 xen.fifo_events= [XEN]
7508 Boolean parameter to 6904 Boolean parameter to disable using fifo event handling
7509 even if available. No 6905 even if available. Normally fifo event handling is
7510 preferred over the 2- 6906 preferred over the 2-level event handling, as it is
7511 fairer and the number 6907 fairer and the number of possible event channels is
7512 much higher. Default 6908 much higher. Default is on (use fifo events).
7513 6909
>> 6910 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6911 Disables the PV optimizations forcing the guest to run
>> 6912 as generic guest with no PV drivers. Currently support
>> 6913 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6914
>> 6915 nopvspin [X86,XEN,KVM]
>> 6916 Disables the qspinlock slow path using PV optimizations
>> 6917 which allow the hypervisor to 'idle' the guest on lock
>> 6918 contention.
>> 6919
7514 xirc2ps_cs= [NET,PCMCIA] 6920 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6921 Format:
7516 <irq>,<irq_mask>,<io> 6922 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6923
7518 xive= [PPC] 6924 xive= [PPC]
7519 By default on POWER9 6925 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6926 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6927 allows the fallback firmware mode to be used:
7522 6928
7523 off Fallback to 6929 off Fallback to firmware control of XIVE interrupt
7524 controller 6930 controller on both pseries and powernv
7525 platforms. 6931 platforms. Only useful on POWER9 and above.
7526 6932
7527 xive.store-eoi=off [PPC] 6933 xive.store-eoi=off [PPC]
7528 By default on POWER10 6934 By default on POWER10 and above, the kernel will use
7529 stores for EOI handli 6935 stores for EOI handling when the XIVE interrupt mode
7530 is active. This optio 6936 is active. This option allows the XIVE driver to use
7531 loads instead, as on 6937 loads instead, as on POWER9.
7532 6938
7533 xhci-hcd.quirks [USB,KNL] 6939 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6940 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6941 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6942 consulted in header drivers/usb/host/xhci.h.
7537 6943
7538 xmon [PPC,EARLY] !! 6944 xmon [PPC]
7539 Format: { early | on 6945 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 6946 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 6947 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 6948 early Call xmon as early as possible on boot; xmon
7543 debugger is c 6949 debugger is called from setup_arch().
7544 on xmon debugger 6950 on xmon debugger hooks will be installed so xmon
7545 is only calle 6951 is only called on a kernel crash. Default mode,
7546 i.e. either " 6952 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 6953 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 6954 rw xmon debugger hooks will be installed so xmon
7549 is called onl 6955 is called only on a kernel crash, mode is write,
7550 meaning SPR r 6956 meaning SPR registers, memory and, other data
7551 can be writte 6957 can be written using xmon commands.
7552 ro same as "rw" 6958 ro same as "rw" option above but SPR registers,
7553 memory, and o 6959 memory, and other data can't be written using
7554 xmon commands 6960 xmon commands.
7555 off xmon is disab 6961 off xmon is disabled.
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