1 accept_memory= [MM] !! 1 acpi= [HW,ACPI,X86,ARM64]
2 Format: { eager | lazy <<
3 default: lazy <<
4 By default, unaccepted <<
5 avoid prolonged boot t <<
6 some runtime overhead <<
7 accepted. In most case <<
8 For some workloads or <<
9 accept_memory=eager ca <<
10 at once during boot. <<
11 <<
12 acpi= [HW,ACPI,X86,ARM64,RIS <<
13 Advanced Configuration 2 Advanced Configuration and Power Interface
14 Format: { force | on | 3 Format: { force | on | off | strict | noirq | rsdt |
15 copy_dsdt | !! 4 copy_dsdt }
16 force -- enable ACPI i 5 force -- enable ACPI if default was off
17 on -- enable ACPI but !! 6 on -- enable ACPI but allow fallback to DT [arm64]
18 off -- disable ACPI if 7 off -- disable ACPI if default was on
19 noirq -- do not use AC 8 noirq -- do not use ACPI for IRQ routing
20 strict -- Be less tole 9 strict -- Be less tolerant of platforms that are not
21 strictly ACPI 10 strictly ACPI specification compliant.
22 rsdt -- prefer RSDT ov 11 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT 12 copy_dsdt -- copy DSDT to memory
24 nospcr -- disable cons !! 13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
25 default _seria <<
26 For ARM64, ONLY "acpi= <<
27 "acpi=nospcr" are avai <<
28 For RISCV64, ONLY "acp <<
29 are available 14 are available
30 15
31 See also Documentation 16 See also Documentation/power/runtime_pm.rst, pci=noacpi
32 17
33 acpi_apic_instance= [ACPI,IOAPIC,E !! 18 acpi_apic_instance= [ACPI, IOAPIC]
34 Format: <int> 19 Format: <int>
35 2: use 2nd APIC table, 20 2: use 2nd APIC table, if available
36 1,0: use 1st APIC tabl 21 1,0: use 1st APIC table
37 default: 0 22 default: 0
38 23
39 acpi_backlight= [HW,ACPI] 24 acpi_backlight= [HW,ACPI]
40 { vendor | video | nat 25 { vendor | video | native | none }
41 If set to vendor, pref 26 If set to vendor, prefer vendor-specific driver
42 (e.g. thinkpad_acpi, s 27 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
43 of the ACPI video.ko d 28 of the ACPI video.ko driver.
44 If set to video, use t 29 If set to video, use the ACPI video.ko driver.
45 If set to native, use 30 If set to native, use the device's native backlight mode.
46 If set to none, disabl 31 If set to none, disable the ACPI backlight interface.
47 32
48 acpi_force_32bit_fadt_addr [ACPI,EARLY !! 33 acpi_force_32bit_fadt_addr
49 force FADT to use 32 b 34 force FADT to use 32 bit addresses rather than the
50 64 bit X_* addresses. 35 64 bit X_* addresses. Some firmware have broken 64
51 bit addresses for forc 36 bit addresses for force ACPI ignore these and use
52 the older legacy 32 bi 37 the older legacy 32 bit addresses.
53 38
54 acpica_no_return_repair [HW, ACPI] 39 acpica_no_return_repair [HW, ACPI]
55 Disable AML predefined 40 Disable AML predefined validation mechanism
56 This mechanism can rep 41 This mechanism can repair the evaluation result to make
57 the return objects mor 42 the return objects more ACPI specification compliant.
58 This option is useful 43 This option is useful for developers to identify the
59 root cause of an AML i 44 root cause of an AML interpreter issue when the issue
60 has something to do wi 45 has something to do with the repair mechanism.
61 46
62 acpi.debug_layer= [HW,ACPI,ACPI_ 47 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
63 acpi.debug_level= [HW,ACPI,ACPI_ 48 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
64 Format: <int> 49 Format: <int>
65 CONFIG_ACPI_DEBUG must 50 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
66 debug output. Bits in 51 debug output. Bits in debug_layer correspond to a
67 _COMPONENT in an ACPI 52 _COMPONENT in an ACPI source file, e.g.,
68 #define _COMPONENT !! 53 #define _COMPONENT ACPI_PCI_COMPONENT
69 Bits in debug_level co 54 Bits in debug_level correspond to a level in
70 ACPI_DEBUG_PRINT state 55 ACPI_DEBUG_PRINT statements, e.g.,
71 ACPI_DEBUG_PRINT(( 56 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
72 The debug_level mask d 57 The debug_level mask defaults to "info". See
73 Documentation/firmware 58 Documentation/firmware-guide/acpi/debug.rst for more information about
74 debug layers and level 59 debug layers and levels.
75 60
76 Enable processor drive 61 Enable processor driver info messages:
77 acpi.debug_layer=0 62 acpi.debug_layer=0x20000000
>> 63 Enable PCI/PCI interrupt routing info messages:
>> 64 acpi.debug_layer=0x400000
78 Enable AML "Debug" out 65 Enable AML "Debug" output, i.e., stores to the Debug
79 object while interpret 66 object while interpreting AML:
80 acpi.debug_layer=0 67 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
81 Enable all messages re 68 Enable all messages related to ACPI hardware:
82 acpi.debug_layer=0 69 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
83 70
84 Some values produce so 71 Some values produce so much output that the system is
85 unusable. The "log_bu 72 unusable. The "log_buf_len" parameter may be useful
86 if you need to capture 73 if you need to capture more output.
87 74
88 acpi_enforce_resources= [ACPI] 75 acpi_enforce_resources= [ACPI]
89 { strict | lax | no } 76 { strict | lax | no }
90 Check for resource con 77 Check for resource conflicts between native drivers
91 and ACPI OperationRegi 78 and ACPI OperationRegions (SystemIO and SystemMemory
92 only). IO ports and me 79 only). IO ports and memory declared in ACPI might be
93 used by the ACPI subsy 80 used by the ACPI subsystem in arbitrary AML code and
94 can interfere with leg 81 can interfere with legacy drivers.
95 strict (default): acce 82 strict (default): access to resources claimed by ACPI
96 is denied; legacy driv 83 is denied; legacy drivers trying to access reserved
97 resources will fail to 84 resources will fail to bind to device using them.
98 lax: access to resourc 85 lax: access to resources claimed by ACPI is allowed;
99 legacy drivers trying 86 legacy drivers trying to access reserved resources
100 will bind successfully 87 will bind successfully but a warning message is logged.
101 no: ACPI OperationRegi 88 no: ACPI OperationRegions are not marked as reserved,
102 no further checks are 89 no further checks are performed.
103 90
104 acpi_force_table_verification [HW,AC !! 91 acpi_force_table_verification [HW,ACPI]
105 Enable table checksum 92 Enable table checksum verification during early stage.
106 By default, this is di 93 By default, this is disabled due to x86 early mapping
107 size limitation. 94 size limitation.
108 95
109 acpi_irq_balance [HW,ACPI] 96 acpi_irq_balance [HW,ACPI]
110 ACPI will balance acti 97 ACPI will balance active IRQs
111 default in APIC mode 98 default in APIC mode
112 99
113 acpi_irq_nobalance [HW,ACPI] 100 acpi_irq_nobalance [HW,ACPI]
114 ACPI will not move act 101 ACPI will not move active IRQs (default)
115 default in PIC mode 102 default in PIC mode
116 103
117 acpi_irq_isa= [HW,ACPI] If irq_balan 104 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
118 Format: <irq>,<irq>... 105 Format: <irq>,<irq>...
119 106
120 acpi_irq_pci= [HW,ACPI] If irq_balan 107 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
121 use by PCI 108 use by PCI
122 Format: <irq>,<irq>... 109 Format: <irq>,<irq>...
123 110
124 acpi_mask_gpe= [HW,ACPI] 111 acpi_mask_gpe= [HW,ACPI]
125 Due to the existence o 112 Due to the existence of _Lxx/_Exx, some GPEs triggered
126 by unsupported hardwar 113 by unsupported hardware/firmware features can result in
127 GPE floodings that can 114 GPE floodings that cannot be automatically disabled by
128 the GPE dispatcher. 115 the GPE dispatcher.
129 This facility can be u 116 This facility can be used to prevent such uncontrolled
130 GPE floodings. 117 GPE floodings.
131 Format: <byte> or <bit !! 118 Format: <byte>
132 119
133 acpi_no_auto_serialize [HW,ACPI] 120 acpi_no_auto_serialize [HW,ACPI]
134 Disable auto-serializa 121 Disable auto-serialization of AML methods
135 AML control methods th 122 AML control methods that contain the opcodes to create
136 named objects will be 123 named objects will be marked as "Serialized" by the
137 auto-serialization fea 124 auto-serialization feature.
138 This feature is enable 125 This feature is enabled by default.
139 This option allows to 126 This option allows to turn off the feature.
140 127
141 acpi_no_memhotplug [ACPI] Disable memo 128 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
142 kernels. 129 kernels.
143 130
144 acpi_no_static_ssdt [HW,ACPI,EARLY !! 131 acpi_no_static_ssdt [HW,ACPI]
145 Disable installation o 132 Disable installation of static SSDTs at early boot time
146 By default, SSDTs cont 133 By default, SSDTs contained in the RSDT/XSDT will be
147 installed automaticall 134 installed automatically and they will appear under
148 /sys/firmware/acpi/tab 135 /sys/firmware/acpi/tables.
149 This option turns off 136 This option turns off this feature.
150 Note that specifying t 137 Note that specifying this option does not affect
151 dynamic table installa 138 dynamic table installation which will install SSDT
152 tables to /sys/firmwar 139 tables to /sys/firmware/acpi/tables/dynamic.
153 140
154 acpi_no_watchdog [HW,ACPI,WDT] 141 acpi_no_watchdog [HW,ACPI,WDT]
155 Ignore the ACPI-based 142 Ignore the ACPI-based watchdog interface (WDAT) and let
156 a native driver contro 143 a native driver control the watchdog device instead.
157 144
158 acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] !! 145 acpi_rsdp= [ACPI,EFI,KEXEC]
159 Pass the RSDP address 146 Pass the RSDP address to the kernel, mostly used
160 on machines running EF 147 on machines running EFI runtime service to boot the
161 second kernel for kdum 148 second kernel for kdump.
162 149
163 acpi_os_name= [HW,ACPI] Tell ACPI BI 150 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
164 Format: To spoof as Wi 151 Format: To spoof as Windows 98: ="Microsoft Windows"
165 152
166 acpi_rev_override [ACPI] Override the 153 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167 of 2 which is mandated 154 of 2 which is mandated by ACPI 6) as the supported ACPI
168 specification revision 155 specification revision (when using this switch, it may
169 be necessary to carry 156 be necessary to carry out a cold reboot _twice_ in a
170 row to make it take ef 157 row to make it take effect on the platform firmware).
171 158
172 acpi_osi= [HW,ACPI] Modify list 159 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" 160 acpi_osi="string1" # add string1
174 acpi_osi="!string2" 161 acpi_osi="!string2" # remove string2
175 acpi_osi=!* 162 acpi_osi=!* # remove all strings
176 acpi_osi=! 163 acpi_osi=! # disable all built-in OS vendor
177 164 strings
178 acpi_osi=!! 165 acpi_osi=!! # enable all built-in OS vendor
179 166 strings
180 acpi_osi= 167 acpi_osi= # disable all strings
181 168
182 'acpi_osi=!' can be us 169 'acpi_osi=!' can be used in combination with single or
183 multiple 'acpi_osi="st 170 multiple 'acpi_osi="string1"' to support specific OS
184 vendor string(s). Not 171 vendor string(s). Note that such command can only
185 affect the default sta 172 affect the default state of the OS vendor strings, thus
186 it cannot affect the d 173 it cannot affect the default state of the feature group
187 strings and the curren 174 strings and the current state of the OS vendor strings,
188 specifying it multiple 175 specifying it multiple times through kernel command line
189 is meaningless. This 176 is meaningless. This command is useful when one do not
190 care about the state o 177 care about the state of the feature group strings which
191 should be controlled b 178 should be controlled by the OSPM.
192 Examples: 179 Examples:
193 1. 'acpi_osi=! acpi_ 180 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194 to 'acpi_osi="Win 181 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 can make '_OSI("W 182 can make '_OSI("Windows 2000")' TRUE.
196 183
197 'acpi_osi=' cannot be 184 'acpi_osi=' cannot be used in combination with other
198 'acpi_osi=' command li 185 'acpi_osi=' command lines, the _OSI method will not
199 exist in the ACPI name 186 exist in the ACPI namespace. NOTE that such command can
200 only affect the _OSI s 187 only affect the _OSI support state, thus specifying it
201 multiple times through 188 multiple times through kernel command line is also
202 meaningless. 189 meaningless.
203 Examples: 190 Examples:
204 1. 'acpi_osi=' can m 191 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205 FALSE. 192 FALSE.
206 193
207 'acpi_osi=!*' can be u 194 'acpi_osi=!*' can be used in combination with single or
208 multiple 'acpi_osi="st 195 multiple 'acpi_osi="string1"' to support specific
209 string(s). Note that 196 string(s). Note that such command can affect the
210 current state of both 197 current state of both the OS vendor strings and the
211 feature group strings, 198 feature group strings, thus specifying it multiple times
212 through kernel command 199 through kernel command line is meaningful. But it may
213 still not able to affe 200 still not able to affect the final state of a string if
214 there are quirks relat 201 there are quirks related to this string. This command
215 is useful when one wan 202 is useful when one want to control the state of the
216 feature group strings 203 feature group strings to debug BIOS issues related to
217 the OSPM features. 204 the OSPM features.
218 Examples: 205 Examples:
219 1. 'acpi_osi="Module 206 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220 '_OSI("Module Dev 207 '_OSI("Module Device")' FALSE.
221 2. 'acpi_osi=!* acpi 208 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222 '_OSI("Module Dev 209 '_OSI("Module Device")' TRUE.
223 3. 'acpi_osi=! acpi_ 210 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224 equivalent to 211 equivalent to
225 'acpi_osi=!* acpi 212 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226 and 213 and
227 'acpi_osi=!* acpi 214 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228 they all will mak 215 they all will make '_OSI("Windows 2000")' TRUE.
229 216
230 acpi_pm_good [X86] 217 acpi_pm_good [X86]
231 Override the pmtimer b 218 Override the pmtimer bug detection: force the kernel
232 to assume that this ma 219 to assume that this machine's pmtimer latches its value
233 and always returns goo 220 and always returns good values.
234 221
235 acpi_sci= [HW,ACPI,EARLY] ACPI S !! 222 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge 223 Format: { level | edge | high | low }
237 224
238 acpi_skip_timer_override [HW,ACPI,EARL !! 225 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore I 226 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIO 227 For broken nForce2 BIOS resulting in XT-PIC timer.
241 228
242 acpi_sleep= [HW,ACPI] Sleep option 229 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_ !! 230 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 s4_nohwsig, !! 231 old_ordering, nonvs, sci_force_enable, nobl }
245 sci_force_en <<
246 See Documentation/powe 232 See Documentation/power/video.rst for information on
247 s3_bios and s3_mode. 233 s3_bios and s3_mode.
248 s3_beep is for debuggi 234 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel' 235 as soon as the kernel's real-mode entry point is called.
250 s4_hwsig causes the ke <<
251 signature during resum <<
252 refuse to resume if it <<
253 the ACPI specification <<
254 Windows does not do th <<
255 on docking. So the def <<
256 and simply warn when t <<
257 s4_hwsig option is ena <<
258 s4_nohwsig prevents AC 236 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a !! 237 used during resume from hibernation.
260 old_ordering causes th 238 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 239 control method, with respect to putting devices into
262 low power states, to b 240 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 241 of _PTS is used by default).
264 nonvs prevents the ker 242 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 243 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 244 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 245 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 246 but some broken systems don't work without it).
269 nobl causes the intern 247 nobl causes the internal blacklist of systems known to
270 behave incorrectly in 248 behave incorrectly in some ways with respect to system
271 suspend and resume to 249 suspend and resume to be ignored (use wisely).
272 250
273 acpi_use_timer_override [HW,ACPI,EARLY !! 251 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 252 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 253 that require a timer override, but don't have HPET
276 254
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 255 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 256 kernel's map of available physical RAM.
279 257
280 agp= [AGP] 258 agp= [AGP]
281 { off | try_unsupporte 259 { off | try_unsupported }
282 off: disable AGP suppo 260 off: disable AGP support
283 try_unsupported: try t 261 try_unsupported: try to drive unsupported chipsets
284 (may crash com 262 (may crash computer or cause data corruption)
285 263
286 ALSA [HW,ALSA] 264 ALSA [HW,ALSA]
287 See Documentation/soun 265 See Documentation/sound/alsa-configuration.rst
288 266
289 alignment= [KNL,ARM] 267 alignment= [KNL,ARM]
290 Allow the default user 268 Allow the default userspace alignment fault handler
291 behaviour to be specif 269 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 270 bit 1 enables fixups, and bit 2 sends a segfault.
293 271
294 align_va_addr= [X86-64] 272 align_va_addr= [X86-64]
295 Align virtual addresse 273 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 274 allocating a VMA at process creation time. This option
297 gives you up to 3% per 275 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 276 machines (where it is enabled by default) for a
299 CPU-intensive style be 277 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 278 a microbenchmark depending on workload and compiler.
301 279
302 32: only for 32-bit pr 280 32: only for 32-bit processes
303 64: only for 64-bit pr 281 64: only for 64-bit processes
304 on: enable for both 32 282 on: enable for both 32- and 64-bit processes
305 off: disable for both 283 off: disable for both 32- and 64-bit processes
306 284
307 alloc_snapshot [FTRACE] 285 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 286 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 287 main buffer is allocated. This is handy if debugging
310 and you need to use tr 288 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 289 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 290 to be done where GFP_KERNEL allocations are allowed.
313 291
314 allow_mismatched_32bit_el0 [ARM64,EARL <<
315 Allow execve() of 32-b <<
316 PER_LINUX32 personalit <<
317 subset of the CPUs sup <<
318 parameter is present, <<
319 EL0 is indicated by /s <<
320 and hot-unplug operati <<
321 <<
322 See Documentation/arch <<
323 information. <<
324 <<
325 amd_iommu= [HW,X86-64] 292 amd_iommu= [HW,X86-64]
326 Pass parameters to the 293 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 294 Possible values are:
328 fullflush - Deprecated !! 295 fullflush - enable flushing of IO/TLB entries when
>> 296 they are unmapped. Otherwise they are
>> 297 flushed before they will be reused, which
>> 298 is a lot of faster
329 off - do not ini 299 off - do not initialize any AMD IOMMU found in
330 the system 300 the system
331 force_isolation - Forc 301 force_isolation - Force device isolation for all
332 devi 302 devices. The IOMMU driver is not
333 allo 303 allowed anymore to lift isolation
334 requ 304 requirements as needed. This option
335 does 305 does not override iommu=pt
336 force_enable - Force e <<
337 to be b <<
338 option <<
339 pgtbl_v1 - Use v1 <<
340 pgtbl_v2 - Use v2 <<
341 irtcachedis - Disable <<
342 306
343 amd_iommu_dump= [HW,X86-64] 307 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 308 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 309 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 310 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 311 IOMMU initialization.
348 312
349 amd_iommu_intr= [HW,X86-64] 313 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 314 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 315 remapping modes:
352 legacy - Use legac 316 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 317 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 318 to inject interrupts directly into guest.
355 This mode 319 This mode requires kvm-amd.avic=1.
356 (Default 320 (Default when IOMMU HW support is present.)
357 321
358 amd_pstate= [X86,EARLY] <<
359 disable <<
360 Do not enable amd_ps <<
361 scaling driver for t <<
362 passive <<
363 Use amd_pstate with <<
364 In this mode autonom <<
365 Driver requests a de <<
366 tries to match the s <<
367 satisfied by guarant <<
368 active <<
369 Use amd_pstate_epp d <<
370 driver provides a hi <<
371 to bias toward perfo <<
372 to the CPPC firmware <<
373 calculate the runtim <<
374 frequency. <<
375 guided <<
376 Activate guided auto <<
377 maximum performance <<
378 selects a performanc <<
379 to the current workl <<
380 <<
381 amd_prefcore= <<
382 [X86] <<
383 disable <<
384 Disable amd-pstate p <<
385 <<
386 amijoy.map= [HW,JOY] Amiga joystic 322 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 323 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 324 Format: <a>,<b>
389 See also Documentation 325 See also Documentation/input/joydev/joystick.rst
390 326
391 analog.map= [HW,JOY] Analog joysti 327 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 328 Specifies type or capabilities of an analog joystick
393 connected to one of 16 329 connected to one of 16 gameports
394 Format: <type1>,<type2 330 Format: <type1>,<type2>,..<type16>
395 331
396 apc= [HW,SPARC] 332 apc= [HW,SPARC]
397 Power management funct 333 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 334 Format: noidle
399 Disable APC CPU standb 335 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 336 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 337 APC and your system crashes randomly.
402 338
403 apic= [APIC,X86,EARLY] Advan !! 339 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 340 Change the output verbosity while booting
405 Format: { quiet (defau 341 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 342 Change the amount of debugging information output
407 when initialising the 343 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 344 For X86-32, this can also be used to specify an APIC
409 driver name. 345 driver name.
410 Format: apic=driver_na 346 Format: apic=driver_name
411 Examples: apic=bigsmp 347 Examples: apic=bigsmp
412 348
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 349 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 350 Format: { bsp (default) | all | none }
415 bsp: External NMI is 351 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 352 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 353 backup of CPU 0
418 none: External NMI is 354 none: External NMI is masked for all CPUs. This is
419 useful so that a 355 useful so that a dump capture kernel won't be
420 shot down by NMI 356 shot down by NMI
421 357
422 autoconf= [IPV6] 358 autoconf= [IPV6]
423 See Documentation/netw 359 See Documentation/networking/ipv6.rst.
424 360
>> 361 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 362 Limit apic dumping. The parameter defines the maximal
>> 363 number of local apics being dumped. Also it is possible
>> 364 to set it to "all" by meaning -- no limit here.
>> 365 Format: { 1 (default) | 2 | ... | all }.
>> 366 The parameter valid if only apic=debug or
>> 367 apic=verbose is specified.
>> 368 Example: apic=debug show_lapic=all
>> 369
425 apm= [APM] Advanced Power M 370 apm= [APM] Advanced Power Management
426 See header of arch/x86 371 See header of arch/x86/kernel/apm_32.c.
427 372
428 apparmor= [APPARMOR] Disable or <<
429 Format: { "0" | "1" } <<
430 See security/apparmor/ <<
431 0 -- disable. <<
432 1 -- enable. <<
433 Default value is set v <<
434 <<
435 arcrimi= [HW,NET] ARCnet - "RIM 373 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 374 Format: <io>,<irq>,<nodeID>
437 375
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall <<
442 Identification support <<
443 <<
444 arm64.nomops [ARM64] Unconditionall <<
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support <<
449 <<
450 arm64.nopauth [ARM64] Unconditionall <<
451 support <<
452 <<
453 arm64.nosme [ARM64] Unconditionall <<
454 Extension support <<
455 <<
456 arm64.nosve [ARM64] Unconditionall <<
457 Extension support <<
458 <<
459 ataflop= [HW,M68k] 376 ataflop= [HW,M68k]
460 377
461 atarimouse= [HW,MOUSE] Atari Mouse 378 atarimouse= [HW,MOUSE] Atari Mouse
462 379
463 atkbd.extra= [HW] Enable extra LEDs 380 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 381 EzKey and similar keyboards
465 382
466 atkbd.reset= [HW] Reset keyboard du 383 atkbd.reset= [HW] Reset keyboard during initialization
467 384
468 atkbd.set= [HW] Select keyboard c 385 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 386 Format: <int> (2 = AT (default), 3 = PS/2)
470 387
471 atkbd.scroll= [HW] Enable scroll whe 388 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 389 keyboards
473 390
474 atkbd.softraw= [HW] Choose between sy 391 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 392 Format: <bool> (0 = real, 1 = synthetic (default))
476 393
477 atkbd.softrepeat= [HW] 394 atkbd.softrepeat= [HW]
478 Use software keyboard 395 Use software keyboard repeat
479 396
480 audit= [KNL] Enable the audit 397 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 398 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 399 0 | off - kernel audit is disabled and can not be
483 enabled until the 400 enabled until the next reboot
484 unset - kernel audit i 401 unset - kernel audit is initialized but disabled and
485 will be fully enab 402 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 403 1 | on - kernel audit is initialized and partially
487 enabled, storing a 404 enabled, storing at most audit_backlog_limit
488 messages in RAM un 405 messages in RAM until it is fully enabled by the
489 userspace auditd. 406 userspace auditd.
490 Default: unset 407 Default: unset
491 408
492 audit_backlog_limit= [KNL] Set the aud 409 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 410 Format: <int> (must be >=0)
494 Default: 64 411 Default: 64
495 412
496 bau= [X86_UV] Enable the BA 413 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 414 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 415 Format: { "0" | "1" }
499 0 - Disable the BAU. 416 0 - Disable the BAU.
500 1 - Enable the BAU. 417 1 - Enable the BAU.
501 unset - Disable the BA 418 unset - Disable the BAU.
502 419
503 baycom_epp= [HW,AX25] 420 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 421 Format: <io>,<mode>
505 422
506 baycom_par= [HW,AX25] BayCom Paral 423 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 424 Format: <io>,<mode>
508 See header of drivers/ 425 See header of drivers/net/hamradio/baycom_par.c.
509 426
510 baycom_ser_fdx= [HW,AX25] 427 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 428 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 429 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 430 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 431
515 baycom_ser_hdx= [HW,AX25] 432 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 433 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 434 Format: <io>,<irq>,<mode>
518 See header of drivers/ 435 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 436
520 bert_disable [ACPI] <<
521 Disable BERT OS suppor <<
522 <<
523 bgrt_disable [ACPI,X86,EARLY] <<
524 Disable BGRT to avoid <<
525 <<
526 blkdevparts= Manual partition parsi 437 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 438 embedded devices based on command line input.
528 See Documentation/bloc 439 See Documentation/block/cmdline-partition.rst
529 440
530 boot_delay= [KNL,EARLY] !! 441 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 442 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 443 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 444 Format: integer
537 445
538 bootconfig [KNL,EARLY] !! 446 bootconfig [KNL]
539 Extended command line 447 Extended command line options can be added to an initrd
540 and this will cause th 448 and this will cause the kernel to look for it.
541 449
542 See Documentation/admi 450 See Documentation/admin-guide/bootconfig.rst
543 451
>> 452 bert_disable [ACPI]
>> 453 Disable BERT OS support on buggy BIOSes.
>> 454
>> 455 bgrt_disable [ACPI][X86]
>> 456 Disable BGRT to avoid flickering OEM logo.
>> 457
544 bttv.card= [HW,V4L] bttv (bt848 + 458 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 459 bttv.radio= Most important insmod options are available as
546 kernel args too. 460 kernel args too.
547 bttv.pll= See Documentation/admi 461 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 462 bttv.tuner=
549 463
550 bulk_remove=off [PPC] This parameter 464 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 465 firmware feature for flushing multiple hpte entries
552 at a time. 466 at a time.
553 467
554 c101= [NET] Moxa C101 synchr 468 c101= [NET] Moxa C101 synchronous serial card
555 469
556 cachesize= [BUGS=X86-32] Override 470 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 471 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 472 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 473 to fix known problems, but for some CPUs it is not
560 possible to determine 474 possible to determine what the correct size should be.
561 This option provides a 475 This option provides an override for these situations.
562 476
563 carrier_timeout= 477 carrier_timeout=
564 [NET] Specifies amount 478 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 479 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 480 it waits 120 seconds.
567 481
568 ca_keys= [KEYS] This parameter 482 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 483 the system trusted keyring to be used for certificate
570 trust validation. 484 trust validation.
571 format: { id:<keyid> | 485 format: { id:<keyid> | builtin }
572 486
573 cca= [MIPS,EARLY] Override !! 487 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 488 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 489 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 490 for platform specific values (SB1, Loongson3 and
577 others). 491 others).
578 492
579 ccw_timeout_log [S390] 493 ccw_timeout_log [S390]
580 See Documentation/arch !! 494 See Documentation/s390/common_io.rst for details.
581 495
582 cgroup_disable= [KNL] Disable a partic !! 496 cgroup_disable= [KNL] Disable a particular controller
583 Format: {name of the c !! 497 Format: {name of the controller(s) to disable}
584 The effects of cgroup_ 498 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 499 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 500 a single hierarchy
587 - foo isn't visible as 501 - foo isn't visible as an individually mountable
588 subsystem 502 subsystem
589 - if foo is an optiona <<
590 disabled and corresp <<
591 created <<
592 {Currently only "memor 503 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 504 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 505 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" <<
596 stall information acco <<
597 506
598 cgroup_no_v1= [KNL] Disable cgroup c 507 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 508 Format: { { controller | "all" | "named" }
600 [,{ controll 509 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 510 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 511 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 512 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 513 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 514 all v1 hierarchies.
606 515
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 516 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 517 Format: <string>
613 nosocket -- Disable so 518 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 519 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 520
617 checkreqprot= [SELINUX] Set initial !! 521 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 522 Format: { "0" | "1" }
619 See security/selinux/K 523 See security/selinux/Kconfig help text.
620 0 -- check protection 524 0 -- check protection applied by kernel (includes
621 any implied ex 525 any implied execute protection).
622 1 -- check protection 526 1 -- check protection requested by application.
623 Default value is set v 527 Default value is set via a kernel config option.
624 Value can be changed a 528 Value can be changed at runtime via
625 /sys/fs/selinu 529 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 530 Setting checkreqprot to 1 is deprecated.
627 531
628 cio_ignore= [S390] 532 cio_ignore= [S390]
629 See Documentation/arch !! 533 See Documentation/s390/common_io.rst for details.
630 <<
631 clearcpuid=X[,X...] [X86] <<
632 Disable CPUID feature <<
633 arch/x86/include/asm/c <<
634 numbers X. Note the Li <<
635 stable over kernel opt <<
636 ones should be. <<
637 X can also be a string <<
638 in /proc/cpuinfo which <<
639 instability issue. How <<
640 in /proc/cpuinfo. <<
641 Note that using this o <<
642 Also note that user pr <<
643 or using the feature w <<
644 will still see it. Thi <<
645 being used by the kern <<
646 Also note the kernel m <<
647 some critical bits. <<
648 <<
649 clk_ignore_unused 534 clk_ignore_unused
650 [CLK] 535 [CLK]
651 Prevents the clock fra 536 Prevents the clock framework from automatically gating
652 clocks that have not b 537 clocks that have not been explicitly enabled by a Linux
653 device driver but are 538 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 539 by the bootloader/firmware. Note that this does not
655 force such clocks to b 540 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 541 those clocks in any way. This parameter is useful for
657 debug and development, 542 debug and development, but should not be needed on a
658 platform with proper d 543 platform with proper driver support. For more
659 information, see Docum 544 information, see Documentation/driver-api/clk.rst.
660 545
661 clock= [BUGS=X86-32, HW] gett 546 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 547 [Deprecated]
663 Forces specified clock 548 Forces specified clocksource (if available) to be used
664 when calculating getti 549 when calculating gettimeofday(). If specified
665 clocksource is not ava 550 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 551 Format: { pit | tsc | cyclone | pmtmr }
667 552
668 clocksource= Override the default c 553 clocksource= Override the default clocksource
669 Format: <string> 554 Format: <string>
670 Override the default c 555 Override the default clocksource and use the clocksource
671 with the name specifie 556 with the name specified.
672 Some clocksource names 557 Some clocksource names to choose from, depending on
673 the platform: 558 the platform:
674 [all] jiffies (this is 559 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 560 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 561 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 562 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 563 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 564 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 565 [MIPS] MIPS
681 [PARISC] cr16 566 [PARISC] cr16
682 [S390] tod 567 [S390] tod
683 [SH] SuperH 568 [SH] SuperH
684 [SPARC64] tick 569 [SPARC64] tick
685 [X86-64] hpet,tsc 570 [X86-64] hpet,tsc
686 571
687 clocksource.arm_arch_timer.evtstrm= 572 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 573 [ARM,ARM64]
689 Format: <bool> 574 Format: <bool>
690 Enable/disable the eve 575 Enable/disable the eventstream feature of the ARM
691 architected timer so t 576 architected timer so that code using WFE-based polling
692 loops can be debugged 577 loops can be debugged more effectively on production
693 systems. 578 systems.
694 579
695 clocksource.verify_n_cpus= [KNL] !! 580 clearcpuid=BITNUM[,BITNUM...] [X86]
696 Limit the number of CP !! 581 Disable CPUID feature X for the kernel. See
697 marked with CLOCK_SOUR !! 582 arch/x86/include/asm/cpufeatures.h for the valid bit
698 are marked unstable du !! 583 numbers. Note the Linux specific bits are not necessarily
699 A negative value says !! 584 stable over kernel options, but the vendor specific
700 zero says not to check !! 585 ones should be.
701 nr_cpu_ids are silentl !! 586 Also note that user programs calling CPUID directly
702 The actual CPUs are ch !! 587 or using the feature without checking anything
703 no replacement if the !! 588 will still see it. This just prevents it from
704 !! 589 being used by the kernel or shown in /proc/cpuinfo.
705 clocksource-wdtest.holdoff= [KNL] !! 590 Also note the kernel might malfunction if you disable
706 Set the time in second !! 591 some critical bits.
707 watchdog test waits be <<
708 Defaults to zero when <<
709 10 seconds when built <<
710 592
711 cma=nn[MG]@[start[MG][-end[MG]]] 593 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 594 [KNL,CMA]
713 Sets the size of kerne 595 Sets the size of kernel global memory area for
714 contiguous memory allo 596 contiguous memory allocations and optionally the
715 placement constraint b 597 placement constraint by the physical address range of
716 memory allocations. A 598 memory allocations. A value of 0 disables CMA
717 altogether. For more i 599 altogether. For more information, see
718 kernel/dma/contiguous. 600 kernel/dma/contiguous.c
719 601
720 cma_pernuma=nn[MG] 602 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 603 [ARM64,KNL]
722 Sets the size of kerne 604 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 605 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 606 per-numa CMA altogether. And If this option is not
725 specified, the default !! 607 specificed, the default value is 0.
726 With per-numa CMA enab 608 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 609 first try to allocate buffer from the pernuma area
728 which is located in no 610 which is located in node nid, if the allocation fails,
729 they will fallback to 611 they will fallback to the global default memory area.
730 612
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 | 613 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 614 Specify whether pages are marked as being inactive
744 when they are freed. 615 when they are freed. This is used in CMO environments
745 to determine OS memory 616 to determine OS memory pressure for page stealing by
746 a hypervisor. 617 a hypervisor.
747 Default: yes 618 Default: yes
748 619
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 620 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 621 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 622 allocations, by default set to 256K.
752 623
753 com20020= [HW,NET] ARCnet - COM2 624 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 625 Format:
755 <io>[,<irq>[,<nodeID>[ 626 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 627
757 com90io= [HW,NET] ARCnet - COM9 628 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 629 Format: <io>[,<irq>]
759 630
760 com90xx= [HW,NET] 631 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 632 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 633 Format: <io>[,<irq>[,<memstart>]]
763 634
764 condev= [HW,S390] console devi 635 condev= [HW,S390] console device
765 conmode= 636 conmode=
766 637
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 638 console= [KNL] Output console device and options.
779 639
780 tty<n> Use the virtual consol 640 tty<n> Use the virtual console device <n>.
781 641
782 ttyS<n>[,options] 642 ttyS<n>[,options]
783 ttyUSB0[,options] 643 ttyUSB0[,options]
784 Use the specified seri 644 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 645 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 646 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 647 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 648 omit it). Default is "9600n8".
789 649
790 See Documentation/admi 650 See Documentation/admin-guide/serial-console.rst for more
791 information. See 651 information. See
792 Documentation/networki 652 Documentation/networking/netconsole.rst for an
793 alternative. 653 alternative.
794 654
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] 655 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 656 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 657 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 658 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 659 uart[8250],0x<addr>[,options]
819 Start an early, polled 660 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 661 UART at the specified I/O port or MMIO address,
821 switching to the match 662 switching to the matching ttyS device later.
822 MMIO inter-register ad 663 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 664 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 665 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 666 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 667 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 668 the h/w is not re-initialized.
828 669
829 hvc<n> Use the hypervisor con 670 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 671 both Xen and PowerPC hypervisors.
831 672
832 { null | "" } <<
833 Use to disable console <<
834 console messages disca <<
835 This must be the only <<
836 kernel command line. <<
837 <<
838 If the device connected to the 673 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 674 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 675 console=brl,ttyS0
841 For now, only VisioBraille is 676 For now, only VisioBraille is supported.
842 677
843 console_msg_format= 678 console_msg_format=
844 [KNL] Change console m 679 [KNL] Change console messages format
845 default 680 default
846 By default we print me 681 By default we print messages on consoles in
847 "[time stamp] text\n" 682 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 683 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 684 `printk_time' param).
850 syslog 685 syslog
851 Switch to syslog forma 686 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 687 IOW, each message will have a facility and loglevel
853 prefix. The format is 688 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 689 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 690 from /proc/kmsg.
856 691
857 consoleblank= [KNL] The console blan 692 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 693 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 694 Defaults to 0.
860 695
861 coredump_filter= 696 coredump_filter=
862 [KNL] Change the defau 697 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 698 /proc/<pid>/coredump_filter.
864 See also Documentation 699 See also Documentation/filesystems/proc.rst.
865 700
866 coresight_cpu_debug.enable 701 coresight_cpu_debug.enable
867 [ARM,ARM64] 702 [ARM,ARM64]
868 Format: <bool> 703 Format: <bool>
869 Enable/disable the CPU 704 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 705 0: default value, disable debugging
871 1: enable debugging at 706 1: enable debugging at boot time
872 707
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 708 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 709 disable the cpuidle sub-system
879 710
880 cpuidle.governor= 711 cpuidle.governor=
881 [CPU_IDLE] Name of the 712 [CPU_IDLE] Name of the cpuidle governor to use.
882 713
883 cpufreq.off=1 [CPU_FREQ] 714 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 715 disable the cpufreq sub-system
885 716
886 cpufreq.default_governor= 717 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 718 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 719 policy to use. This governor must be registered in the
889 kernel before the cpuf 720 kernel before the cpufreq driver probes.
890 721
891 cpu_init_udelay=N 722 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 723 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 724 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 725 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 726 Default: 10000
896 727
897 cpuhp.parallel= !! 728 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 729 Format:
899 Format: <bool> !! 730 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
900 Default is enabled if <<
901 the parameter has no e <<
902 <<
903 crash_kexec_post_notifiers <<
904 Run kdump after runnin <<
905 kmsg. This only for th <<
906 succeeds in any situat <<
907 Note that this also in <<
908 because some panic not <<
909 kernel more unstable. <<
910 731
911 crashkernel=size[KMG][@offset[KMG]] 732 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 733 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 734 upon panic. This parameter reserves the physical
914 memory region [offset, 735 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 736 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 737 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 738 [KNL, X86-64] Select a region under 4G first, and
918 under 4G first, and fa !! 739 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 740 hasn't been specified.
920 See Documentation/admi 741 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 742
922 crashkernel=range1:size1[,range2:size2 743 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 744 [KNL] Same as above, but depends on the memory
924 in the running system. 745 in the running system. The syntax of range is
925 start-[end] where star 746 start-[end] where start and end are both
926 a memory unit (amount[ 747 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 748 Documentation/admin-guide/kdump/kdump.rst for an example.
928 749
929 crashkernel=size[KMG],high 750 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 751 [KNL, X86-64] range could be above 4G. Allow kernel
931 above 4G. !! 752 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 753 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 754 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 755 available.
935 below 4G, if available <<
936 It will be ignored if 756 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 757 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 758 [KNL, X86-64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 759 is passed, kernel could allocate physical memory region
940 physical memory region !! 760 above 4G, that cause second kernel crash on system
941 crash on system that r !! 761 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 762 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 763 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 764 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 765 at least 256M below 4G automatically.
946 size is platform depen !! 766 This one let user to specify own low range under 4G
947 --> x86: max(swiotlb <<
948 --> arm64: 128MiB <<
949 --> riscv: 128MiB <<
950 --> loongarch: 128Mi <<
951 This one lets the user <<
952 for second kernel inst 767 for second kernel instead.
953 0: to disable low allo 768 0: to disable low allocation.
954 It will be ignored whe 769 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 770 or memory reserved is below 4G.
956 771
957 cryptomgr.notests 772 cryptomgr.notests
958 [KNL] Disable crypto s 773 [KNL] Disable crypto self-tests
959 774
960 cs89x0_dma= [HW,NET] 775 cs89x0_dma= [HW,NET]
961 Format: <dma> 776 Format: <dma>
962 777
963 cs89x0_media= [HW,NET] 778 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 779 Format: { rj45 | aui | bnc }
965 780
966 csdlock_debug= [KNL] Enable or disabl <<
967 function call handling <<
968 additional debug data <<
969 in case a hanging CPU <<
970 CPU is pinged again in <<
971 the hang situation. T <<
972 option depends on the <<
973 Kconfig option. <<
974 <<
975 dasd= [HW,NET] 781 dasd= [HW,NET]
976 See header of drivers/ 782 See header of drivers/s390/block/dasd_devmap.c.
977 783
978 db9.dev[2|3]= [HW,JOY] Multisystem j 784 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 785 (one device per port)
980 Format: <port#>,<type> 786 Format: <port#>,<type>
981 See also Documentation 787 See also Documentation/input/devices/joystick-parport.rst
982 788
983 debug [KNL,EARLY] Enable ker !! 789 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 790 time. See
>> 791 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 792 details. Deprecated, see dyndbg.
>> 793
>> 794 debug [KNL] Enable kernel debugging (events log level).
984 795
985 debug_boot_weak_hash 796 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 797 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 798 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 799 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 800 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 801 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 802 insecure, please do not use on production kernels.
992 803
993 debug_locks_verbose= 804 debug_locks_verbose=
994 [KNL] verbose locking !! 805 [KNL] verbose self-tests
995 Format: <int> !! 806 Format=<0|1>
996 Print debugging info w 807 Print debugging info while doing the locking API
997 self-tests. 808 self-tests.
998 Bitmask for the variou !! 809 We default to 0 (no extra messages), setting it to
999 (no extra messages), s !! 810 1 will print _a lot_ more information - normally
1000 will print _a_lot_ mo !! 811 only useful to kernel developers.
1001 useful to lockdep dev !! 812
>> 813 debug_objects [KNL] Enable object debugging
1002 814
1003 debug_objects [KNL,EARLY] Enable ob !! 815 no_debug_objects
>> 816 [KNL] Disable object debugging
1004 817
1005 debug_guardpage_minorder= 818 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 819 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 820 parameter allows control of the order of pages that will
1008 be intentionally kept 821 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 822 buddy allocator. Bigger value increase the probability
1010 of catching random me 823 of catching random memory corruption, but reduce the
1011 amount of memory for 824 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 825 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 826 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 827 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 828 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 829 random memory location. Note that there exists a class
1017 a class of memory cor !! 830 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 831 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 832 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 833 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 834 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 835 tracking down these problems.
1023 836
1024 debug_pagealloc= 837 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 838 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 839 enables the feature at boot time. By default, it is
1027 disabled and the syst 840 disabled and the system will work mostly the same as a
1028 kernel built without 841 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 842 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 843 useful to also enable the page_owner functionality.
1031 on: enable the featur 844 on: enable the feature
1032 845
1033 debugfs= [KNL,EARLY] This para !! 846 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 847 and debugfs internal clients.
1035 Format: { on, no-moun 848 Format: { on, no-mount, off }
1036 on: All functions 849 on: All functions are enabled.
1037 no-mount: 850 no-mount:
1038 Filesystem is 851 Filesystem is not registered but kernel clients can
1039 access APIs a 852 access APIs and a crashkernel can be used to read
1040 its content. 853 its content. There is nothing to mount.
1041 off: Filesystem is 854 off: Filesystem is not registered and clients
1042 get a -EPERM 855 get a -EPERM as result when trying to register files
1043 or directorie 856 or directories within debugfs.
1044 This is equiv 857 This is equivalent of the runtime functionality if
1045 debugfs was n 858 debugfs was not enabled in the kernel at all.
1046 Default value is set 859 Default value is set in build-time with a kernel configuration.
1047 860
1048 debugpat [X86] Enable PAT debu 861 debugpat [X86] Enable PAT debugging
1049 862
>> 863 decnet.addr= [HW,NET]
>> 864 Format: <area>[,<node>]
>> 865 See also Documentation/networking/decnet.rst.
>> 866
1050 default_hugepagesz= 867 default_hugepagesz=
1051 [HW] The size of the 868 [HW] The size of the default HugeTLB page. This is
1052 the size represented 869 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 870 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 871 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 872 filesystems. If not specified, defaults to the
1056 architecture's defaul 873 architecture's default huge page size. Huge page
1057 sizes are architectur 874 sizes are architecture dependent. See also
1058 Documentation/admin-g 875 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 876 Format: size[KMG]
1060 877
1061 deferred_probe_timeout= 878 deferred_probe_timeout=
1062 [KNL] Debugging optio 879 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 880 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 881 probe. Only specific dependencies (subsystems or
1065 drivers) that have op !! 882 drivers) that have opted in will be ignored. A timeout of 0
1066 of 0 will timeout at !! 883 will timeout at the end of initcalls. This option will also
1067 out hasn't expired, i <<
1068 successful driver reg <<
1069 dump out devices stil 884 dump out devices still on the deferred probe list after
1070 retrying. 885 retrying.
1071 886
1072 delayacct [KNL] Enable per-task <<
1073 <<
1074 dell_smm_hwmon.ignore_dmi= <<
1075 [HW] Continue probing <<
1076 indicates that the dr <<
1077 hardware. <<
1078 <<
1079 dell_smm_hwmon.force= <<
1080 [HW] Activate driver <<
1081 not match list of sup <<
1082 blacklisted features. <<
1083 <<
1084 dell_smm_hwmon.power_status= <<
1085 [HW] Report power sta <<
1086 (disabled by default) <<
1087 <<
1088 dell_smm_hwmon.restricted= <<
1089 [HW] Allow controllin <<
1090 capability is set. <<
1091 <<
1092 dell_smm_hwmon.fan_mult= <<
1093 [HW] Factor to multip <<
1094 <<
1095 dell_smm_hwmon.fan_max= <<
1096 [HW] Maximum configur <<
1097 <<
1098 dfltcc= [HW,S390] 887 dfltcc= [HW,S390]
1099 Format: { on | off | 888 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 889 on: s390 zlib hardware support for compression on
1101 level 1 and 890 level 1 and decompression (default)
1102 off: No s390 zli 891 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 892 def_only: s390 zlib hardware support for deflate
1104 only (compr 893 only (compression on level 1)
1105 inf_only: s390 zlib h 894 inf_only: s390 zlib hardware support for inflate
1106 only (decom 895 only (decompression)
1107 always: Same as 'on 896 always: Same as 'on' but ignores the selected compression
1108 level alway 897 level always using hardware support (used for debugging)
1109 898
1110 dhash_entries= [KNL] 899 dhash_entries= [KNL]
1111 Set number of hash bu 900 Set number of hash buckets for dentry cache.
1112 901
1113 disable_1tb_segments [PPC,EARLY] !! 902 disable_1tb_segments [PPC]
1114 Disables the use of 1 903 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 904 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 905 can be useful when debugging issues that require an SLB
1117 miss to occur. 906 miss to occur.
1118 907
>> 908 stress_slb [PPC]
>> 909 Limits the number of kernel SLB entries, and flushes
>> 910 them frequently to increase the rate of SLB faults
>> 911 on kernel addresses.
>> 912
1119 disable= [IPV6] 913 disable= [IPV6]
1120 See Documentation/net 914 See Documentation/networking/ipv6.rst.
1121 915
1122 disable_radix [PPC,EARLY] !! 916 hardened_usercopy=
>> 917 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
>> 918 hardening is enabled for this boot. Hardened
>> 919 usercopy checking is used to protect the kernel
>> 920 from reading or writing beyond known memory
>> 921 allocation boundaries as a proactive defense
>> 922 against bounds-checking flaws in the kernel's
>> 923 copy_to_user()/copy_from_user() interface.
>> 924 on Perform hardened usercopy checks (default).
>> 925 off Disable hardened usercopy checks.
>> 926
>> 927 disable_radix [PPC]
1123 Disable RADIX MMU mod 928 Disable RADIX MMU mode on POWER9
1124 929
>> 930 radix_hcall_invalidate=on [PPC/PSERIES]
>> 931 Disable RADIX GTSE feature and use hcall for TLB
>> 932 invalidate.
>> 933
1125 disable_tlbie [PPC] 934 disable_tlbie [PPC]
1126 Disable TLBIE instruc 935 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 936 with KVM, with HASH MMU, or with coherent accelerators.
1128 937
1129 disable_ddw [PPC/PSERIES,EARLY] !! 938 disable_cpu_apicid= [X86,APIC,SMP]
>> 939 Format: <int>
>> 940 The number of initial APIC ID for the
>> 941 corresponding CPU to be disabled at boot,
>> 942 mostly used for the kdump 2nd kernel to
>> 943 disable BSP to wake up multiple CPUs without
>> 944 causing system reset or hang due to sending
>> 945 INIT from AP to BSP.
>> 946
>> 947 perf_v4_pmi= [X86,INTEL]
>> 948 Format: <bool>
>> 949 Disable Intel PMU counter freezing feature.
>> 950 The feature only exists starting from
>> 951 Arch Perfmon v4 (Skylake and newer).
>> 952
>> 953 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 954 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 955 to workaround buggy firmware.
1132 956
1133 disable_ipv6= [IPV6] 957 disable_ipv6= [IPV6]
1134 See Documentation/net 958 See Documentation/networking/ipv6.rst.
1135 959
1136 disable_mtrr_cleanup [X86,EARLY] !! 960 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 961 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 962 to discrete, to make X server driver able to add WB
1139 entry later. This par 963 entry later. This parameter disables that.
1140 964
1141 disable_mtrr_trim [X86, Intel and AMD !! 965 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 966 By default the kernel will trim any uncacheable
1143 memory out of your av 967 memory out of your available memory pool based on
1144 MTRR settings. This 968 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 969 possibly causing your machine to run very slowly.
1146 970
1147 disable_timer_pin_1 [X86,EARLY] !! 971 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 972 Disable PIN 1 of APIC timer
1149 Can be useful to work 973 Can be useful to work around chipset bugs.
1150 974
1151 dis_ucode_ldr [X86] Disable the mic 975 dis_ucode_ldr [X86] Disable the microcode loader.
1152 976
1153 dma_debug=off If the kernel is comp 977 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 978 this option disables the debugging code at boot.
1155 979
1156 dma_debug_entries=<number> 980 dma_debug_entries=<number>
1157 This option allows to 981 This option allows to tune the number of preallocated
1158 entries for DMA-API d 982 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 983 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 984 DMA-API debugging code disables itself because the
1161 architectural default 985 architectural default is too low.
1162 986
1163 dma_debug_driver=<driver_name> 987 dma_debug_driver=<driver_name>
1164 With this option the 988 With this option the DMA-API debugging driver
1165 filter feature can be 989 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 990 pass the driver to filter for as the parameter.
1167 The filter can be dis 991 The filter can be disabled or changed to another
1168 driver later using sy 992 driver later using sysfs.
1169 993
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] 994 driver_async_probe= [KNL]
1191 List of driver names !! 995 List of driver names to be probed asynchronously.
1192 matches with all driv <<
1193 rest of the listed dr <<
1194 match the *. <<
1195 Format: <driver_name1 996 Format: <driver_name1>,<driver_name2>...
1196 997
1197 drm.edid_firmware=[<connector>:]<file 998 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 999 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1000 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1001 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1002 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1003 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1004 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1005 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1006 and no file with the same name exists. Details and
>> 1007 instructions how to build your own EDID data are
>> 1008 available in Documentation/admin-guide/edid.rst. An EDID
>> 1009 data set will only be used for a particular connector,
>> 1010 if its name and a colon are prepended to the EDID
>> 1011 name. Each connector may use a unique EDID data
>> 1012 set by separating the files with a comma. An EDID
1206 data set with no conn 1013 data set with no connector name will be used for
1207 any connectors not ex 1014 any connectors not explicitly specified.
1208 1015
1209 dscc4.setup= [NET] 1016 dscc4.setup= [NET]
1210 1017
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1018 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1019 Format: {"off" | "known"}
1213 Control how the dt_cp 1020 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1021 used for CPU feature discovery and setup (if it
1215 exists). 1022 exists).
1216 off: Do not use it, f 1023 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1024 known: Do not pass through unknown features to guests
1218 or userspace, only th 1025 or userspace, only those that the kernel is aware of.
1219 1026
1220 dump_apple_properties [X86] 1027 dump_apple_properties [X86]
1221 Dump name and content 1028 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1029 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1030 what data is available or for reverse-engineering.
1224 1031
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1032 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1033 <module>.dyndbg[="val"]
1227 Enable debug messages 1034 Enable debug messages at boot time. See
1228 Documentation/admin-g 1035 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1036 for details.
1230 1037
1231 early_ioremap_debug [KNL,EARLY] !! 1038 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1039 in some Intel CPUs.
>> 1040
>> 1041 <module>.async_probe [KNL]
>> 1042 Enable asynchronous probe on this module.
>> 1043
>> 1044 early_ioremap_debug [KNL]
1232 Enable debug messages 1045 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1046 is useful for tracking down temporary early mappings
1234 which are not unmappe 1047 which are not unmapped.
1235 1048
1236 earlycon= [KNL,EARLY] Output ea !! 1049 earlycon= [KNL] Output early console device and options.
1237 1050
1238 When used with no opt 1051 When used with no options, the early console is
1239 determined by stdout- 1052 determined by stdout-path property in device tree's
1240 chosen node or the AC 1053 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1054 the platform.
1242 1055
1243 cdns,<addr>[,options] 1056 cdns,<addr>[,options]
1244 Start an early, polle 1057 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1058 (xuartps) serial port at the specified address. Only
1246 supported option is b 1059 supported option is baud rate. If baud rate is not
1247 specified, the serial 1060 specified, the serial port must already be setup and
1248 configured. 1061 configured.
1249 1062
1250 uart[8250],io,<addr>[,options !! 1063 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1064 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1065 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1066 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1067 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1068 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1069 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1070 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1071 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1072 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1073 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1074 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1075 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1076
1266 pl011,<addr> 1077 pl011,<addr>
1267 pl011,mmio32,<addr> 1078 pl011,mmio32,<addr>
1268 Start an early, polle 1079 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1080 port at the specified address. The pl011 serial port
1270 must already be setup 1081 must already be setup and configured. Options are not
1271 yet supported. If 'm 1082 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1083 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1084 the device registers.
1274 1085
1275 liteuart,<addr> <<
1276 Start an early consol <<
1277 specified address. Th <<
1278 setup and configured. <<
1279 <<
1280 meson,<addr> 1086 meson,<addr>
1281 Start an early, polle 1087 Start an early, polled-mode console on a meson serial
1282 port at the specified 1088 port at the specified address. The serial port must
1283 already be setup and 1089 already be setup and configured. Options are not yet
1284 supported. 1090 supported.
1285 1091
1286 msm_serial,<addr> 1092 msm_serial,<addr>
1287 Start an early, polle 1093 Start an early, polled-mode console on an msm serial
1288 port at the specified 1094 port at the specified address. The serial port
1289 must already be setup 1095 must already be setup and configured. Options are not
1290 yet supported. 1096 yet supported.
1291 1097
1292 msm_serial_dm,<addr> 1098 msm_serial_dm,<addr>
1293 Start an early, polle 1099 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1100 dm port at the specified address. The serial port
1295 must already be setup 1101 must already be setup and configured. Options are not
1296 yet supported. 1102 yet supported.
1297 1103
1298 owl,<addr> 1104 owl,<addr>
1299 Start an early, polle 1105 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1106 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1107 specified address. The serial port must already be
1302 setup and configured. 1108 setup and configured. Options are not yet supported.
1303 1109
1304 rda,<addr> 1110 rda,<addr>
1305 Start an early, polle 1111 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1112 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1113 specified address. The serial port must already be
1308 setup and configured. 1114 setup and configured. Options are not yet supported.
1309 1115
1310 sbi 1116 sbi
1311 Use RISC-V SBI (Super 1117 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1118 console.
1313 1119
1314 smh Use ARM semihosting c 1120 smh Use ARM semihosting calls for early console.
1315 1121
1316 s3c2410,<addr> 1122 s3c2410,<addr>
1317 s3c2412,<addr> 1123 s3c2412,<addr>
1318 s3c2440,<addr> 1124 s3c2440,<addr>
1319 s3c6400,<addr> 1125 s3c6400,<addr>
1320 s5pv210,<addr> 1126 s5pv210,<addr>
1321 exynos4210,<addr> 1127 exynos4210,<addr>
1322 Use early console pro 1128 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1129 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1130 a correct base address of the selected UART port. The
1325 serial port must alre 1131 serial port must already be setup and configured.
1326 Options are not yet s 1132 Options are not yet supported.
1327 1133
1328 lantiq,<addr> 1134 lantiq,<addr>
1329 Start an early, polle 1135 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1136 (lqasc) port at the specified address. The serial port
1331 must already be setup 1137 must already be setup and configured. Options are not
1332 yet supported. 1138 yet supported.
1333 1139
1334 lpuart,<addr> 1140 lpuart,<addr>
1335 lpuart32,<addr> 1141 lpuart32,<addr>
1336 Use early console pro 1142 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1143 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1144 A valid base address must be provided, and the serial
1339 port must already be 1145 port must already be setup and configured.
1340 1146
1341 ec_imx21,<addr> 1147 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1148 ec_imx6q,<addr>
1343 Start an early, polle 1149 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1150 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1151 must already be setup and configured.
1346 1152
1347 ar3700_uart,<addr> 1153 ar3700_uart,<addr>
1348 Start an early, polle 1154 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1155 Armada 3700 serial port at the specified
1350 address. The serial p 1156 address. The serial port must already be setup
1351 and configured. Optio 1157 and configured. Options are not yet supported.
1352 1158
1353 qcom_geni,<addr> 1159 qcom_geni,<addr>
1354 Start an early, polle 1160 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1161 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1162 specified address. The serial port must already be
1357 setup and configured. 1163 setup and configured. Options are not yet supported.
1358 1164
1359 efifb,[options] 1165 efifb,[options]
1360 Start an early, unacc 1166 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1167 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1168 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1169 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1170 mapped with the correct attributes.
1365 1171
1366 linflex,<addr> 1172 linflex,<addr>
1367 Use early console pro 1173 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1174 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1175 address must be provided, and the serial port must
1370 already be setup and 1176 already be setup and configured.
1371 1177
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1178 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1179 earlyprintk=vga
1374 earlyprintk=sclp 1180 earlyprintk=sclp
1375 earlyprintk=xen 1181 earlyprintk=xen
1376 earlyprintk=serial[,t 1182 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1183 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1184 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1185 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1186 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1187 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1188
1384 earlyprintk is useful 1189 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1190 the normal console is initialized. It is not enabled by
1386 default because it ha 1191 default because it has some cosmetic problems.
1387 1192
1388 Append ",keep" to not 1193 Append ",keep" to not disable it when the real console
1389 takes over. 1194 takes over.
1390 1195
1391 Only one of vga, seri !! 1196 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1197 be used at a time.
1393 1198
1394 Currently only ttyS0 1199 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1200 name. Other I/O ports may be explicitly specified
1396 on some architectures 1201 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1202 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1203 earlyprintk=serial,0x1008,115200
1399 You can find the port 1204 You can find the port for a given device in
1400 /proc/tty/driver/seri 1205 /proc/tty/driver/serial:
1401 2: uart:ST166 1206 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1207
1403 Interaction with the 1208 Interaction with the standard serial driver is not
1404 very good. 1209 very good.
1405 1210
1406 The VGA output is eve !! 1211 The VGA and EFI output is eventually overwritten by
1407 the real console. 1212 the real console.
1408 1213
1409 The xen option can on !! 1214 The xen output can only be used by Xen PV guests.
1410 1215
1411 The sclp output can o 1216 The sclp output can only be used on s390.
1412 1217
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1218 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1219 PCI device even when its classcode is not of the
1417 UART class. 1220 UART class.
1418 1221
1419 edac_report= [HW,EDAC] Control how 1222 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1223 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1224 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1225 by other higher priority error reporting module.
1423 off: disable H/W even 1226 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1227 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1228 default: on.
1426 1229
>> 1230 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1231 ekgdboc=kbd
>> 1232
>> 1233 This is designed to be used in conjunction with
>> 1234 the boot argument: earlyprintk=vga
>> 1235
>> 1236 This parameter works in place of the kgdboc parameter
>> 1237 but can only be used if the backing tty is available
>> 1238 very early in the boot process. For early debugging
>> 1239 via a serial port see kgdboc_earlycon instead.
>> 1240
1427 edd= [EDD] 1241 edd= [EDD]
1428 Format: {"off" | "on" 1242 Format: {"off" | "on" | "skip[mbr]"}
1429 1243
1430 efi= [EFI,EARLY] !! 1244 efi= [EFI]
1431 Format: { "debug", "d 1245 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1246 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1247 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1248 debug: enable misc debug output.
1435 disable_early_pci_dma 1249 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1250 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1251 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1252 boot stub, as chunking can cause problems with some
1439 firmware implementati 1253 firmware implementations.
1440 noruntime : disable E 1254 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1255 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1256 attribute may cause the kernel to reserve the
1443 memory range for a me 1257 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1258 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1259 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1260 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1261 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1262 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1263 on all PCI bridges while in the EFI boot stub
1450 1264
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1265 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1266 Using this parameter you can use more than 50% of
1453 your efi variable sto 1267 your efi variable storage. Use this parameter only if
1454 you are really sure t 1268 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1269 fulfills the spec otherwise your board may brick.
1456 1270
>> 1271 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1272 Add arbitrary attribute to specific memory range by
>> 1273 updating original EFI memory map.
>> 1274 Region of memory which aa attribute is added to is
>> 1275 from ss to ss+nn.
>> 1276
>> 1277 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1278 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1279 attribute is added to range 0x100000000-0x180000000 and
>> 1280 0x10a0000000-0x1120000000.
>> 1281
>> 1282 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1283 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1284 range 0x240000000-0x43fffffff.
>> 1285
>> 1286 Using this parameter you can do debugging of EFI memmap
>> 1287 related features. For example, you can do debugging of
>> 1288 Address Range Mirroring feature even if your box
>> 1289 doesn't support it, or mark specific memory as
>> 1290 "soft reserved".
>> 1291
1457 efivar_ssdt= [EFI; X86] Name of an 1292 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1293 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1294 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1295 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1296 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1297
1463 1298
1464 eisa_irq_edge= [PARISC,HW] 1299 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1300 See header of drivers/parisc/eisa.c.
1466 1301
1467 ekgdboc= [X86,KGDB,EARLY] Allo <<
1468 Format: ekgdboc=kbd <<
1469 <<
1470 This is designed to b <<
1471 the boot argument: ea <<
1472 <<
1473 This parameter works <<
1474 but can only be used <<
1475 very early in the boo <<
1476 via a serial port see <<
1477 <<
1478 elanfreq= [X86-32] 1302 elanfreq= [X86-32]
1479 See comment before fu 1303 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1304 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1305
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1306 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1307 Specifies physical address of start of kernel core
1484 image elf header and 1308 image elf header and optionally the size. Generally
1485 kexec loader will pas 1309 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1310 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1311
1488 enable_mtrr_cleanup [X86,EARLY] !! 1312 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1313 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1314 to discrete, to make X server driver able to add WB
1491 entry later. This par 1315 entry later. This parameter enables that.
1492 1316
1493 enable_timer_pin_1 [X86] 1317 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1318 Enable PIN 1 of APIC timer
1495 Can be useful to work 1319 Can be useful to work around chipset bugs
1496 (in particular on som 1320 (in particular on some ATI chipsets).
1497 The kernel tries to s 1321 The kernel tries to set a reasonable default.
1498 1322
1499 enforcing= [SELINUX] Set initial !! 1323 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1324 Format: {"0" | "1"}
1501 See security/selinux/ 1325 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1326 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1327 1 -- enforcing (deny and log).
1504 Default value is 0. 1328 Default value is 0.
1505 Value can be changed 1329 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1330 /sys/fs/selinux/enforce.
1507 1331
1508 erst_disable [ACPI] 1332 erst_disable [ACPI]
1509 Disable Error Record 1333 Disable Error Record Serialization Table (ERST)
1510 support. 1334 support.
1511 1335
1512 ether= [HW,NET] Ethernet car 1336 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1337 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1338 has equivalent usage. See its documentation for details.
1515 1339
1516 evm= [EVM] 1340 evm= [EVM]
1517 Format: { "fix" } 1341 Format: { "fix" }
1518 Permit 'security.evm' 1342 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1343 current integrity status.
1520 1344
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= 1345 failslab=
1530 fail_usercopy= 1346 fail_usercopy=
1531 fail_page_alloc= 1347 fail_page_alloc=
1532 fail_make_request=[KNL] 1348 fail_make_request=[KNL]
1533 General fault injecti 1349 General fault injection mechanism.
1534 Format: <interval>,<p 1350 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1351 See also Documentation/fault-injection/.
1536 1352
1537 fb_tunnels= [NET] 1353 fb_tunnels= [NET]
1538 Format: { initns | no 1354 Format: { initns | none }
1539 See Documentation/adm 1355 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1356 fb_tunnels_only_for_init_ns
1541 1357
1542 floppy= [HW] 1358 floppy= [HW]
1543 See Documentation/adm 1359 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1360
>> 1361 force_pal_cache_flush
>> 1362 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1363 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1364 parameter will force ia64_sal_cache_flush to call
>> 1365 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1366
1545 forcepae [X86-32] 1367 forcepae [X86-32]
1546 Forcefully enable Phy 1368 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1369 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1370 functionally usable PAE implementation.
1549 Warning: use of this 1371 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1372 and may cause unknown problems.
1551 1373
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] 1374 ftrace=[tracer]
1559 [FTRACE] will set and 1375 [FTRACE] will set and start the specified tracer
1560 as early as possible 1376 as early as possible in order to facilitate early
1561 boot debugging. 1377 boot debugging.
1562 1378
1563 ftrace_boot_snapshot !! 1379 ftrace_dump_on_oops[=orig_cpu]
1564 [FTRACE] On boot up, <<
1565 ftrace ring buffer th <<
1566 /sys/kernel/tracing/s <<
1567 This is useful if you <<
1568 boot up that is likel <<
1569 start up functionalit <<
1570 <<
1571 Optionally, the snaps <<
1572 instance that was cre <<
1573 line parameter. <<
1574 <<
1575 trace_instance=foo,sc <<
1576 <<
1577 The above will cause <<
1578 a snapshot at the end <<
1579 <<
1580 ftrace_dump_on_oops[=2(orig_cpu) | =< <<
1581 ,<instance>=2(orig_ <<
1582 [FTRACE] will dump th 1380 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1381 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1382 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1383 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1384 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 1385
1603 ftrace_filter=[function-list] 1386 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1387 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1388 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1389 list of functions. This list can be changed at run
1607 time by the set_ftrac 1390 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1391 tracing directory.
1609 1392
1610 ftrace_notrace=[function-list] 1393 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1394 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1395 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1396 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1397 tracing directory.
1615 1398
1616 ftrace_graph_filter=[function-list] 1399 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1400 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1401 by the function graph tracer at boot up.
1619 function-list is a co 1402 function-list is a comma-separated list of functions
1620 that can be changed a 1403 that can be changed at run time by the
1621 set_graph_function fi 1404 set_graph_function file in the debugfs tracing directory.
1622 1405
1623 ftrace_graph_notrace=[function-list] 1406 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1407 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1408 function-list. This list is a comma-separated list of
1626 functions that can be 1409 functions that can be changed at run time by the
1627 set_graph_notrace fil 1410 set_graph_notrace file in the debugfs tracing directory.
1628 1411
1629 ftrace_graph_max_depth=<uint> 1412 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1413 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1414 the max depth it will trace into a function. This value
1632 can be changed at run 1415 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1416 in the tracefs tracing directory. default: 0 (no limit)
1634 1417
1635 fw_devlink= [KNL,EARLY] Create de !! 1418 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1419 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1420 consumer/supplier relationships. This feature is
1638 especially useful whe 1421 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1422 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1423 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1424 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1425 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1426 suppliers).
1644 Format: { off | permi 1427 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1428 off -- Don't create device links from firmware info.
1646 permissive -- Create 1429 permissive -- Create device links from firmware info
1647 but use it on 1430 but use it only for ordering boot state clean
1648 up (sync_stat 1431 up (sync_state() calls).
1649 on -- Create device 1432 on -- Create device links from firmware info and use it
1650 to enforce pr 1433 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1434 rpm -- Like "on", but also use to order runtime PM.
1652 1435
1653 fw_devlink.strict=<bool> <<
1654 [KNL,EARLY] Treat all <<
1655 dependencies. This on <<
1656 Format: <bool> <<
1657 <<
1658 fw_devlink.sync_state = <<
1659 [KNL,EARLY] When all <<
1660 probing, this paramet <<
1661 devices that haven't <<
1662 calls. <<
1663 Format: { strict | ti <<
1664 strict -- Default. Co <<
1665 probe success <<
1666 timeout -- Give up wa <<
1667 sync_state() <<
1668 received thei <<
1669 deferred_prob <<
1670 late_initcall <<
1671 <<
1672 gamecon.map[2|3]= 1436 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1437 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1438 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1439 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1440 See also Documentation/input/devices/joystick-parport.rst
1677 1441
1678 gamma= [HW,DRM] 1442 gamma= [HW,DRM]
1679 1443
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1444 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1445 Format: off | on
1682 default: on 1446 default: on
1683 1447
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 1448 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1449 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1450 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1451 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1452 debugfs files are removed at module unload time.
1709 1453
1710 goldfish [X86] Enable the gold 1454 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1455 Don't use this when you are not running on the
1712 android emulator 1456 android emulator
1713 1457
1714 gpio-mockup.gpio_mockup_ranges <<
1715 [HW] Sets the ranges <<
1716 Format: <start1>,<end <<
1717 gpio-mockup.gpio_mockup_named_lines <<
1718 [HW] Let the driver k <<
1719 <<
1720 gpt [EFI] Forces disk wit 1458 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1459 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1460 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1461 GPT to be used instead.
1724 1462
1725 grcan.enable0= [HW] Configuration of 1463 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1464 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1465 Format: 0 | 1
1728 Default: 0 1466 Default: 0
1729 grcan.enable1= [HW] Configuration of 1467 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1468 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1469 Format: 0 | 1
1732 Default: 0 1470 Default: 0
1733 grcan.select= [HW] Select which phy 1471 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1472 Format: 0 | 1
1735 Default: 0 1473 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1474 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1475 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1476 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1477 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1478 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1479 Default: 1024
1742 1480
1743 hardened_usercopy= !! 1481 gpio-mockup.gpio_mockup_ranges
1744 [KNL] Under CONFIG_HA !! 1482 [HW] Sets the ranges of gpiochip of for this device.
1745 hardening is enabled !! 1483 Format: <start1>,<end1>,<start2>,<end2>...
1746 usercopy checking is <<
1747 from reading or writi <<
1748 allocation boundaries <<
1749 against bounds-checki <<
1750 copy_to_user()/copy_f <<
1751 on Perform hardened user <<
1752 off Disable hardened user <<
1753 1484
1754 hardlockup_all_cpu_backtrace= 1485 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1486 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1487 backtraces on all cpus.
1757 Format: 0 | 1 1488 Format: 0 | 1
1758 1489
1759 hashdist= [KNL,NUMA] Large hash 1490 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1491 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1492 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1493 Format: 0 | 1 (for off | on)
1763 1494
>> 1495 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1496
1764 hd= [EIDE] (E)IDE hard dr 1497 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1498 Format: <cyl>,<head>,<sect>
1766 1499
1767 hest_disable [ACPI] 1500 hest_disable [ACPI]
1768 Disable Hardware Erro 1501 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1502 corresponding firmware-first mode error processing
1770 logic will be disable 1503 logic will be disabled.
1771 1504
1772 hibernate= [HIBERNATION] !! 1505 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1773 noresume Don't check i <<
1774 present durin <<
1775 nocompress Don't compres <<
1776 no Disable hiber <<
1777 protect_image Turn on image <<
1778 (that will se <<
1779 during restor <<
1780 <<
1781 hibernate.compressor= [HIBERNATION] <<
1782 used with hib <<
1783 Format: { lzo <<
1784 Default: lzo <<
1785 <<
1786 lzo: Select L <<
1787 compress/deco <<
1788 <<
1789 lz4: Select L <<
1790 compress/deco <<
1791 <<
1792 highmem=nn[KMG] [KNL,BOOT,EARLY] forc <<
1793 size of <nn>. This wo 1506 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1507 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1508 size on bigger boxes.
1796 1509
1797 highres= [KNL] Enable/disable 1510 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1511 Valid parameters: "on", "off"
1799 Default: "on" 1512 Default: "on"
1800 1513
1801 hlt [BUGS=ARM,SH] 1514 hlt [BUGS=ARM,SH]
1802 1515
1803 hostname= [KNL,EARLY] Set the h <<
1804 Format: <string> <<
1805 This allows setting t <<
1806 startup. This sets th <<
1807 Using this parameter <<
1808 possible to ensure th <<
1809 any userspace process <<
1810 that a process may ca <<
1811 has been explicitly s <<
1812 process getting an in <<
1813 not exceed the maximu <<
1814 64 characters) and wi <<
1815 <<
1816 hpet= [X86-32,HPET] option 1516 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1517 Format: { enable (default) | disable | force |
1818 verbose } 1518 verbose }
1819 disable: disable HPET 1519 disable: disable HPET and use PIT instead
1820 force: allow force en 1520 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1521 VIA, nVidia)
1822 verbose: show content 1522 verbose: show contents of HPET registers during setup
1823 1523
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1524 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1525 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1526
>> 1527 hugetlb_cma= [HW] The size of a cma area used for allocation
>> 1528 of gigantic hugepages.
>> 1529 Format: nn[KMGTPE]
>> 1530
>> 1531 Reserve a cma area of given size and allocate gigantic
>> 1532 hugepages using the cma allocator. If enabled, the
>> 1533 boot-time allocation of gigantic hugepages is skipped.
>> 1534
1827 hugepages= [HW] Number of HugeTL 1535 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1536 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1537 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1538 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1539 line, it specifies the number of pages to allocate for
1832 the default huge page !! 1540 the default huge page size. See also
1833 number of pages to al !! 1541 Documentation/admin-guide/mm/hugetlbpage.rst.
1834 See also Documentatio !! 1542 Format: <integer>
1835 Format: <integer> or <<
1836 <node>:<integ <<
1837 1543
1838 hugepagesz= 1544 hugepagesz=
1839 [HW] The size of the 1545 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1546 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1547 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1548 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1549 each supported huge page size. Huge page sizes are
1844 architecture dependen 1550 architecture dependent. See also
1845 Documentation/admin-g 1551 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1552 Format: size[KMG]
1847 1553
1848 hugetlb_cma= [HW,CMA,EARLY] The si <<
1849 of gigantic hugepages <<
1850 of a CMA area per nod <<
1851 Format: nn[KMGTPE] or <<
1852 <node>:nn[KMG <<
1853 <<
1854 Reserve a CMA area of <<
1855 hugepages using the C <<
1856 boot-time allocation <<
1857 <<
1858 hugetlb_free_vmemmap= <<
1859 [KNL] Requires CONFIG <<
1860 enabled. <<
1861 Control if HugeTLB Vm <<
1862 Allows heavy hugetlb <<
1863 memory (7 * PAGE_SIZE <<
1864 Format: { on | off (d <<
1865 <<
1866 on: enable HVO <<
1867 off: disable HVO <<
1868 <<
1869 Built with CONFIG_HUG <<
1870 the default is on. <<
1871 <<
1872 Note that the vmemmap <<
1873 memory block itself w <<
1874 enabled, those vmemma <<
1875 feature is enabled. <<
1876 the added memory bloc <<
1877 <<
1878 hung_task_panic= 1554 hung_task_panic=
1879 [KNL] Should the hung 1555 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1556 Format: 0 | 1
1881 1557
1882 A value of 1 instruct 1558 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1559 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1560 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1561 option. The value selected by this boot parameter can
1886 be changed later by t 1562 be changed later by the kernel.hung_task_panic sysctl.
1887 1563
1888 hvc_iucv= [S390] Number of z/V 1564 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1565 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1566 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1567 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1568 from listed z/VM user IDs only.
1893 1569
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1570 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1571 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1572 guest on lock contention.
1897 on lock contention. !! 1573
>> 1574 keep_bootcon [KNL]
>> 1575 Do not unregister boot console at start. This is only
>> 1576 useful for debugging when something happens in the window
>> 1577 between unregistering the boot console and initializing
>> 1578 the real console.
1898 1579
1899 i2c_bus= [HW] Override the 1580 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1581 or register an additional I2C bus that is not
1901 registered fr 1582 registered from board initialization code.
1902 Format: 1583 Format:
1903 <bus_id>,<clk 1584 <bus_id>,<clkrate>
1904 1585
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 1586 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1587 i8042.unmask_kbd_data
1929 [HW] Enable printing 1588 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1589 (disabled by default, and as a pre-condition
1931 requires that i8 1590 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1591 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1592 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1593 keyboard and cannot control its state
1935 (Don't attempt t 1594 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1595 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1596 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1597 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1598 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1599 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1600 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1601 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1602 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1603 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1604 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1605 suspend-to-ram transitions, only during s2r
1947 transitions, or 1606 transitions, or never reset
1948 Format: { 1 | Y | y | 1607 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1608 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1609 0, N, n: don't ever reset controller
1951 Default: only on s2r 1610 Default: only on s2r transitions on x86; most other
1952 architectures force r 1611 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1612 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1613 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer <<
1956 [HW] Allow deferred p <<
1957 1614
1958 i810= [HW,DRM] 1615 i810= [HW,DRM]
1959 1616
>> 1617 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1618 indicates that the driver is running on unsupported
>> 1619 hardware.
>> 1620 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1621 does not match list of supported models.
>> 1622 i8k.power_status
>> 1623 [HW] Report power status in /proc/i8k
>> 1624 (disabled by default)
>> 1625 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1626 capability is set.
>> 1627
1960 i915.invert_brightness= 1628 i915.invert_brightness=
1961 [DRM] Invert the sens 1629 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1630 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1631 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1632 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1633 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1634 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1635 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1636 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1637 value switches the backlight off.
1970 -1 -- never invert br 1638 -1 -- never invert brightness
1971 0 -- machine default 1639 0 -- machine default
1972 1 -- force brightnes 1640 1 -- force brightness inversion
1973 1641
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] 1642 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1643 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1644
>> 1645 ide-core.nodma= [HW] (E)IDE subsystem
>> 1646 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1647 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1648 .cdrom .chs .ignore_cable are additional options
>> 1649 See Documentation/ide/ide.rst.
>> 1650
>> 1651 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1652 Format: <int>
>> 1653 Probe mask for legacy ISA IDE ports. Depending on
>> 1654 platform up to 6 ports are supported, enabled by
>> 1655 setting corresponding bits in the mask to 1. The
>> 1656 default value is 0x0, which has a special meaning.
>> 1657 On systems that have PCI, it triggers scanning the
>> 1658 PCI bus for the first and the second port, which
>> 1659 are then probed. On systems without PCI the value
>> 1660 of 0x0 enables probing the two first ports as if it
>> 1661 was 0x3.
1983 1662
1984 idle= [X86,EARLY] !! 1663 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1664 Claim all unknown PCI IDE storage controllers.
>> 1665
>> 1666 idle= [X86]
1985 Format: idle=poll, id 1667 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1668 Poll forces a polling idle loop that can slightly
1987 improve the performan 1669 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1670 will use a lot of power and make the system run hot.
1989 Not recommended. 1671 Not recommended.
1990 idle=halt: Halt is fo 1672 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1673 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1674 idle=nomwait: Disable mwait for CPU C-states
1993 1675
1994 idxd.sva= [HW] <<
1995 Format: <bool> <<
1996 Allow force disabling <<
1997 support for the idxd <<
1998 true (1). <<
1999 <<
2000 idxd.tc_override= [HW] <<
2001 Format: <bool> <<
2002 Allow override of def <<
2003 for the device. By de <<
2004 <<
2005 ieee754= [MIPS] Select IEEE St 1676 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1677 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1678 Default: strict
2008 1679
2009 Choose which programs 1680 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1681 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1682 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1683 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1684 binary. Hardware implementations are permitted to
2014 support either or bot 1685 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1686 encoding mode.
2016 1687
2017 Available settings ar 1688 Available settings are as follows:
2018 strict accept binari 1689 strict accept binaries that request a NaN encoding
2019 supported by 1690 supported by the FPU
2020 legacy only accept l 1691 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1692 by the FPU
2022 2008 only accept 2 1693 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1694 by the FPU
2024 relaxed accept any bi 1695 relaxed accept any binaries regardless of whether
2025 supported by 1696 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1697
2029 The FPU emulator is a 1698 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1699 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1700 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1701 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1702 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1703 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1704 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1705 MIPS64 CPUs.
2037 1706
2038 The setting for ABS.f 1707 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1708 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1709 except where unsupported by hardware.
2041 1710
2042 ignore_loglevel [KNL,EARLY] !! 1711 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1712 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1713 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1714 We also add it as printk module parameter, so users
2046 could change it dynam 1715 could change it dynamically, usually by
2047 /sys/module/printk/pa 1716 /sys/module/printk/parameters/ignore_loglevel.
2048 1717
2049 ignore_rlimit_data 1718 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1719 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1720 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1721 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1722
2054 ihash_entries= [KNL] 1723 ihash_entries= [KNL]
2055 Set number of hash bu 1724 Set number of hash buckets for inode cache.
2056 1725
2057 ima_appraise= [IMA] appraise integr 1726 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1727 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1728 default: "enforce"
2060 1729
2061 ima_appraise_tcb [IMA] Deprecated. U 1730 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1731 The builtin appraise policy appraises all files
2063 owned by uid=0. 1732 owned by uid=0.
2064 1733
2065 ima_canonical_fmt [IMA] 1734 ima_canonical_fmt [IMA]
2066 Use the canonical for 1735 Use the canonical format for the binary runtime
2067 measurements, instead 1736 measurements, instead of host native format.
2068 1737
2069 ima_hash= [IMA] 1738 ima_hash= [IMA]
2070 Format: { md5 | sha1 1739 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1740 | sha512 | ... }
2072 default: "sha1" 1741 default: "sha1"
2073 1742
2074 The list of supported 1743 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1744 in crypto/hash_info.h.
2076 1745
2077 ima_policy= [IMA] 1746 ima_policy= [IMA]
2078 The builtin policies 1747 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1748 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel !! 1749 fail_securely"
2081 1750
2082 The "tcb" policy meas 1751 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1752 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1753 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1754 uid=0.
2086 1755
2087 The "appraise_tcb" po 1756 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1757 all files owned by root.
2089 1758
2090 The "secure_boot" pol 1759 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1760 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1761 firmware, policy, etc) based on file signatures.
2093 1762
2094 The "fail_securely" p 1763 The "fail_securely" policy forces file signature
2095 verification failure 1764 verification failure also on privileged mounted
2096 filesystems with the 1765 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1766 flag.
2098 1767
2099 The "critical_data" p <<
2100 critical data. <<
2101 <<
2102 ima_tcb [IMA] Deprecated. Us 1768 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1769 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1770 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1771 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1772 opened for read by uid=0.
2107 1773
2108 ima_template= [IMA] 1774 ima_template= [IMA]
2109 Select one of defined 1775 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1776 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1777 Default: "ima-ng"
2113 1778
2114 ima_template_fmt= 1779 ima_template_fmt=
2115 [IMA] Define a custom 1780 [IMA] Define a custom template format.
2116 Format: { "field1|... 1781 Format: { "field1|...|fieldN" }
2117 1782
2118 ima.ahash_minsize= [IMA] Minimum file 1783 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1784 Format: <min_file_size>
2120 Set the minimal file 1785 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1786 If left unspecified, ahash usage is disabled.
2122 1787
2123 ahash performance var 1788 ahash performance varies for different data sizes on
2124 different crypto acce 1789 different crypto accelerators. This option can be used
2125 to achieve the best p 1790 to achieve the best performance for a particular HW.
2126 1791
2127 ima.ahash_bufsize= [IMA] Asynchronous 1792 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1793 Format: <bufsize>
2129 Set hashing buffer si 1794 Set hashing buffer size. Default: 4k.
2130 1795
2131 ahash performance var 1796 ahash performance varies for different chunk sizes on
2132 different crypto acce 1797 different crypto accelerators. This option can be used
2133 to achieve best perfo 1798 to achieve best performance for particular HW.
2134 1799
2135 init= [KNL] 1800 init= [KNL]
2136 Format: <full_path> 1801 Format: <full_path>
2137 Run specified binary 1802 Run specified binary instead of /sbin/init as init
2138 process. 1803 process.
2139 1804
2140 initcall_debug [KNL] Trace initcalls 1805 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1806 for working out where the kernel is dying during
2142 startup. 1807 startup.
2143 1808
2144 initcall_blacklist= [KNL] Do not exe 1809 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1810 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1811 modules and initcalls.
2147 1812
2148 initramfs_async= [KNL] !! 1813 initrd= [BOOT] Specify the location of the initial ramdisk
2149 Format: <bool> <<
2150 Default: 1 <<
2151 This parameter contro <<
2152 image is unpacked asy <<
2153 with devices being pr <<
2154 initialized. This sho <<
2155 but as a debugging ai <<
2156 historical behaviour <<
2157 unpacking being compl <<
2158 late_ initcalls. <<
2159 1814
2160 initrd= [BOOT,EARLY] Specify !! 1815 initrdmem= [KNL] Specify a physical address and size from which to
2161 <<
2162 initrdmem= [KNL,EARLY] Specify a <<
2163 load the initrd. If a 1816 load the initrd. If an initrd is compiled in or
2164 specified in the boot 1817 specified in the bootparams, it takes priority over this
2165 setting. 1818 setting.
2166 Format: ss[KMG],nn[KM 1819 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 1820 Default is 0, 0
2168 1821
2169 init_on_alloc= [MM,EARLY] Fill newly !! 1822 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 1823 zeroes.
2171 Format: 0 | 1 1824 Format: 0 | 1
2172 Default set by CONFIG 1825 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 1826
2174 init_on_free= [MM,EARLY] Fill freed !! 1827 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 1828 Format: 0 | 1
2176 Default set by CONFIG 1829 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 1830
2178 init_pkru= [X86] Specify the def 1831 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 1832 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1833 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1834 override in debugfs after boot.
2182 1835
2183 inport.irq= [HW] Inport (ATI XL a 1836 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1837 Format: <irq>
2185 1838
2186 int_pln_enable [X86] Enable power li 1839 int_pln_enable [X86] Enable power limit notification interrupt
2187 1840
2188 integrity_audit=[IMA] 1841 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1842 Format: { "0" | "1" }
2190 0 -- basic integrity 1843 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1844 1 -- additional integrity auditing messages.
2192 1845
2193 intel_iommu= [DMAR] Intel IOMMU dr 1846 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1847 on
2195 Enable intel iommu dr 1848 Enable intel iommu driver.
2196 off 1849 off
2197 Disable intel iommu d 1850 Disable intel iommu driver.
2198 igfx_off [Default Off] 1851 igfx_off [Default Off]
2199 By default, gfx is ma 1852 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1853 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1854 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1855 this case, gfx device will use physical address for
2203 DMA. 1856 DMA.
2204 strict [Default Off] 1857 strict [Default Off]
2205 Deprecated, equivalen !! 1858 With this option on every unmap_single operation will
>> 1859 result in a hardware IOTLB flush operation as opposed
>> 1860 to batching them for performance.
2206 sp_off [Default Off] 1861 sp_off [Default Off]
2207 By default, super pag 1862 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1863 has the capability. With this option, super page will
2209 not be supported. 1864 not be supported.
2210 sm_on !! 1865 sm_on [Default Off]
2211 Enable the Intel IOMM !! 1866 By default, scalable mode will be disabled even if the
2212 advertises that it ha !! 1867 hardware advertises that it has support for the scalable
2213 translation. !! 1868 mode translation. With this option set, scalable mode
2214 sm_off !! 1869 will be used on hardware which claims to support it.
2215 Disallow use of the I <<
2216 tboot_noforce [Default Off] 1870 tboot_noforce [Default Off]
2217 Do not force the Inte 1871 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1872 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1873 could harm performance of some high-throughput
2220 devices like 40GBit n 1874 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1875 mapping is enabled.
2222 Note that using this 1876 Note that using this option lowers the security
2223 provided by tboot bec 1877 provided by tboot because it makes the system
2224 vulnerable to DMA att 1878 vulnerable to DMA attacks.
2225 1879
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1880 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1881 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1882 1 to 9 specify maximum depth of C-state.
2229 1883
2230 intel_pstate= [X86,EARLY] !! 1884 intel_pstate= [X86]
2231 disable 1885 disable
2232 Do not enable intel 1886 Do not enable intel_pstate as the default
2233 scaling driver for 1887 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 1888 passive
2245 Use intel_pstate as 1889 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 1890 to work with generic cpufreq governors (instead of
2247 enabling its intern 1891 enabling its internal governor). This mode cannot be
2248 used along with the 1892 used along with the hardware-managed P-states (HWP)
2249 feature. 1893 feature.
2250 force 1894 force
2251 Enable intel_pstate 1895 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 1896 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 1897 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 1898 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 1899 P-States information being indicated to OSPM and therefore
2256 should be used with 1900 should be used with caution. This option does not work with
2257 processors that are 1901 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 1902 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 1903 no_hwp
2260 Do not enable hardw 1904 Do not enable hardware P state control (HWP)
2261 if available. 1905 if available.
2262 hwp_only 1906 hwp_only
2263 Only load intel_pst 1907 Only load intel_pstate on systems which support
2264 hardware P state co 1908 hardware P state control (HWP) if available.
2265 support_acpi_ppc 1909 support_acpi_ppc
2266 Enforce ACPI _PPC p 1910 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 1911 Description Table, specifies preferred power management
2268 profile as "Enterpr 1912 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 1913 then this feature is turned on by default.
2270 per_cpu_perf_limits 1914 per_cpu_perf_limits
2271 Allow per-logical-C 1915 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 1916 cpufreq sysfs interface
2273 1917
2274 intremap= [X86-64,Intel-IOMMU,E !! 1918 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 1919 on enable Interrupt Remapping (default)
2276 off disable Inter 1920 off disable Interrupt Remapping
2277 nosid disable Sourc 1921 nosid disable Source ID checking
2278 no_x2apic_optout 1922 no_x2apic_optout
2279 BIOS x2APIC o 1923 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 1924 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 1925
2284 iomem= Disable strict checki 1926 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 1927 strict regions from userspace.
2286 relaxed 1928 relaxed
2287 1929
2288 iommu= [X86,EARLY] !! 1930 iommu= [X86]
2289 off 1931 off
2290 force 1932 force
2291 noforce 1933 noforce
2292 biomerge 1934 biomerge
2293 panic 1935 panic
2294 nopanic 1936 nopanic
2295 merge 1937 merge
2296 nomerge 1938 nomerge
2297 soft 1939 soft
2298 pt [X86] 1940 pt [X86]
2299 nopt [X86] 1941 nopt [X86]
2300 nobypass [PPC/POWERNV] 1942 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 1943 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 1944
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 1945 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 1946 Format: { "0" | "1" }
2305 0 - Try to allocate a 1947 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 1948 falling back to the full range if needed.
2307 1 - Allocate directly 1949 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 1950 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 1951 greater than 32-bit addressing.
2310 1952
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 1953 iommu.strict= [ARM64] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 1954 Format: { "0" | "1" }
2313 0 - Lazy mode. 1955 0 - Lazy mode.
2314 Request that DMA un 1956 Request that DMA unmap operations use deferred
2315 invalidation of har 1957 invalidation of hardware TLBs, for increased
2316 throughput at the c 1958 throughput at the cost of reduced device isolation.
2317 Will fall back to s 1959 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 1960 the relevant IOMMU driver.
2319 1 - Strict mode. !! 1961 1 - Strict mode (default).
2320 DMA unmap operation 1962 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 1963 synchronously.
2322 unset - Use value of <<
2323 Note: on x86, strict <<
2324 legacy driver-specifi <<
2325 1964
2326 iommu.passthrough= 1965 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 1966 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 1967 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 1968 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 1969 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 1970 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 1971
2333 io7= [HW] IO7 for Marvel-b 1972 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 1973 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 1974 arch/alpha/kernel/core_marvel.c.
2336 1975
2337 io_delay= [X86,EARLY] I/O delay !! 1976 io_delay= [X86] I/O delay method
2338 0x80 1977 0x80
2339 Standard port 0x80 ba 1978 Standard port 0x80 based delay
2340 0xed 1979 0xed
2341 Alternate port 0xed b 1980 Alternate port 0xed based delay (needed on some systems)
2342 udelay 1981 udelay
2343 Simple two microsecon 1982 Simple two microseconds delay
2344 none 1983 none
2345 No delay 1984 No delay
2346 1985
2347 ip= [IP_PNP] 1986 ip= [IP_PNP]
2348 See Documentation/adm 1987 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 1988
2350 ipcmni_extend [KNL,EARLY] Extend th !! 1989 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 1990 IPC identifiers from 32,768 to 16,777,216.
2352 1991
2353 irqaffinity= [SMP] Set the default 1992 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 1993 The argument is a cpu list, as described above.
2355 1994
2356 irqchip.gicv2_force_probe= 1995 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 1996 [ARM, ARM64]
2358 Format: <bool> 1997 Format: <bool>
2359 Force the kernel to l 1998 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 1999 of a GICv2 controller even if the memory range
2361 exposed by the device 2000 exposed by the device tree is too small.
2362 2001
2363 irqchip.gicv3_nolpi= 2002 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2003 [ARM, ARM64]
2365 Force the kernel to i 2004 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2005 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2006 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2007 to let secondary kernels in charge of setting up
2369 LPIs. 2008 LPIs.
2370 2009
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2010 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2011 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2012 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2013 CONFIG_ARM64_PSEUDO_NMI.
2375 2014
2376 irqfixup [HW] 2015 irqfixup [HW]
2377 When an interrupt is 2016 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2017 for it. Intended to get systems with badly broken
2379 firmware running. 2018 firmware running.
2380 2019
2381 irqpoll [HW] 2020 irqpoll [HW]
2382 When an interrupt is 2021 When an interrupt is not handled search all handlers
2383 for it. Also check al 2022 for it. Also check all handlers each timer
2384 interrupt. Intended t 2023 interrupt. Intended to get systems with badly broken
2385 firmware running. 2024 firmware running.
2386 2025
2387 isapnp= [ISAPNP] 2026 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2027 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2028
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2029 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2030 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2031 Format: [flag-list,]<cpu-list>
2393 2032
2394 Specify one or more C 2033 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2034 specified in the flag list (default: domain):
2396 2035
2397 nohz 2036 nohz
2398 Disable the tick wh 2037 Disable the tick when a single task runs.
2399 2038
2400 A residual 1Hz tick 2039 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2040 need to affine to housekeeping through the global
2402 workqueue's affinit 2041 workqueue's affinity configured via the
2403 /sys/devices/virtua 2042 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2043 by using the 'domain' flag described below.
2405 2044
2406 NOTE: by default th 2045 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2046 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2047 be configured manually after bootup.
2409 2048
2410 domain 2049 domain
2411 Isolate from the ge 2050 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2051 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2052 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2053 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2054 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2055 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2056 It offers a much more flexible interface where CPUs can
2418 move in and out of 2057 move in and out of an isolated set anytime.
2419 2058
2420 You can move a proc 2059 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2060 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2061 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2062 "number of CPUs in system - 1".
2424 2063
2425 managed_irq 2064 managed_irq
2426 2065
2427 Isolate from being 2066 Isolate from being targeted by managed interrupts
2428 which have an inter 2067 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2068 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2069 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2070 the /proc/irq/* interfaces.
2432 2071
2433 This isolation is b 2072 This isolation is best effort and only effective
2434 if the automaticall 2073 if the automatically assigned interrupt mask of a
2435 device queue contai 2074 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2075 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2076 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2077 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2078 cannot disturb the isolated CPU.
2440 2079
2441 If a queue's affini 2080 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2081 CPUs then this parameter has no effect on the
2443 interrupt routing d 2082 interrupt routing decision, though interrupts are
2444 only delivered when 2083 only delivered when tasks running on those
2445 isolated CPUs submi 2084 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2085 housekeeping CPUs has no influence on those
2447 queues. 2086 queues.
2448 2087
2449 The format of <cpu-li 2088 The format of <cpu-list> is described above.
2450 2089
2451 iucv= [HW,NET] 2090 iucv= [HW,NET]
2452 2091
2453 ivrs_ioapic [HW,X86-64] 2092 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2093 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 2094 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 2095 example, to map IOAPIC-ID decimal 10 to
2457 !! 2096 PCI device 00:14.0 write the parameter as:
2458 For example, to map I <<
2459 PCI segment 0x1 and P <<
2460 write the parameter a <<
2461 ivrs_ioapic=1 <<
2462 <<
2463 Deprecated formats: <<
2464 * To map IOAPIC-ID de <<
2465 write the parameter <<
2466 ivrs_ioapic[1 2097 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 2098
2471 ivrs_hpet [HW,X86-64] 2099 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2100 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 2101 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 2102 example, to map HPET-ID decimal 0 to
2475 !! 2103 PCI device 00:14.0 write the parameter as:
2476 For example, to map H <<
2477 PCI segment 0x1 and P <<
2478 write the parameter a <<
2479 ivrs_hpet=10@ <<
2480 <<
2481 Deprecated formats: <<
2482 * To map HPET-ID deci <<
2483 write the parameter <<
2484 ivrs_hpet[0]= 2104 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 2105
2489 ivrs_acpihid [HW,X86-64] 2106 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2107 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 2108 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 2109 example, to map UART-HID:UID AMD0020:0 to
2493 !! 2110 PCI device 00:14.5 write the parameter as:
2494 For example, to map U <<
2495 PCI segment 0x1 and P <<
2496 write the parameter a <<
2497 ivrs_acpihid= <<
2498 <<
2499 Deprecated formats: <<
2500 * To map UART-HID:UID <<
2501 PCI device ID 00:14 <<
2502 ivrs_acpihid[ 2111 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 2112
2507 js= [HW,JOY] Analog joyst 2113 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2114 See Documentation/input/joydev/joystick.rst.
2509 2115
>> 2116 nokaslr [KNL]
>> 2117 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2118 kernel and module base offset ASLR (Address Space
>> 2119 Layout Randomization).
>> 2120
2510 kasan_multi_shot 2121 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2122 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2123 report on every invalid memory access. Without this
2513 parameter KASAN will 2124 parameter KASAN will print report only for the first
2514 invalid access. 2125 invalid access.
2515 2126
2516 keep_bootcon [KNL,EARLY] !! 2127 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 2128
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2129 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2130 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2131 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2132 the kernel for non-movable allocations. The requested
2528 amount is spread even 2133 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2134 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2135 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2136 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2137 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2138 other nodes will have a larger ZONE_MOVABLE.
2534 2139
2535 ZONE_MOVABLE is used 2140 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2141 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2142 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2143 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2144 zone if it does not.
2540 2145
2541 It is possible to spe 2146 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2147 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2148 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2149 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2150 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2151 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2152 are exclusive, so you cannot specify multiple forms.
2548 2153
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2154 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2155 Format: <Controller#>[,poll interval]
2551 The controller # is t 2156 The controller # is the number of the ehci usb debug
2552 port as it is probed 2157 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2158 optional and is the number seconds in between
2554 each poll cycle to th 2159 each poll cycle to the debug port in case you need
2555 the functionality for 2160 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2161 gdb or control-c on the dbgp connection. When
2557 not using this parame 2162 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2163 the kernel debugger.
2559 2164
2560 kgdboc= [KGDB,HW] kgdb over c 2165 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2166 Requires a tty driver that supports console polling,
2562 or a supported pollin 2167 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2168 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2169 keyboard only format: kbd
2565 keyboard and serial 2170 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2171 Optional Kernel mode setting:
2567 kms, kbd format: kms 2172 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2173 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2174
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2175 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2176 If the boot console provides the ability to read
2572 characters and can wo 2177 characters and can work in polling mode, you can use
2573 this parameter to tel 2178 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2179 until the normal console is registered. Intended to
2575 be used together with 2180 be used together with the kgdboc parameter which
2576 specifies the normal 2181 specifies the normal console to transition to.
2577 2182
2578 The name of the early 2183 The name of the early console should be specified
2579 as the value of this 2184 as the value of this parameter. Note that the name of
2580 the early console mig 2185 the early console might be different than the tty
2581 name passed to kgdboc 2186 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2187 blank and the first boot console that implements
2583 read() will be picked 2188 read() will be picked.
2584 2189
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2190 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2191 kernel debugger at the earliest opportunity.
2587 2192
2588 kmac= [MIPS] Korina etherne 2193 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2194 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2195 Ethernet adapter MAC address.
2591 2196
2592 kmemleak= [KNL,EARLY] Boot-time !! 2197 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2198 Valid arguments: on, off
2594 Default: on 2199 Default: on
2595 Built with CONFIG_DEB 2200 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2201 the default is off.
2597 2202
2598 kprobe_event=[probe-list] 2203 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2204 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2205 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2206 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2207 interface, but the parameters are comma delimited.
2603 For example, to add a 2208 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2209 arg1 and arg2, add to the command line;
2605 2210
2606 kprobe_event=p, 2211 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2212
2608 See also Documentatio 2213 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2214 Boot Parameter" section.
2610 2215
2611 kpti= [ARM64,EARLY] Control !! 2216 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2217 and kernel address spaces.
2613 Default: enabled on c 2218 Default: enabled on cores which need mitigation.
2614 0: force disabled 2219 0: force disabled
2615 1: force enabled 2220 1: force enabled
2616 2221
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 2222 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2223 Default is 0 (don't ignore, but inject #GP)
2625 2224
2626 kvm.eager_page_split= <<
2627 [KVM,X86] Controls wh <<
2628 proactively split all <<
2629 Eager page splitting <<
2630 execution by eliminat <<
2631 and MMU lock contenti <<
2632 required to split hug <<
2633 <<
2634 VM workloads that rar <<
2635 only to a small regio <<
2636 disabling eager page <<
2637 still be used for rea <<
2638 <<
2639 The behavior of eager <<
2640 KVM_DIRTY_LOG_INITIAL <<
2641 disabled, all huge pa <<
2642 split when dirty logg <<
2643 enabled, eager page s <<
2644 the KVM_CLEAR_DIRTY i <<
2645 cleared. <<
2646 <<
2647 Eager page splitting <<
2648 <<
2649 Default is Y (on). <<
2650 <<
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2225 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2226 Default is false (don't support).
2653 2227
>> 2228 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
>> 2229 KVM MMU at runtime.
>> 2230 Default is 0 (off)
>> 2231
2654 kvm.nx_huge_pages= 2232 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2233 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2234 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2235 force : Always deploy workaround.
2658 off : Never deplo 2236 off : Never deploy workaround.
2659 auto : Deploy work 2237 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2238 X86_BUG_ITLB_MULTIHIT.
2661 2239
2662 Default is 'auto'. 2240 Default is 'auto'.
2663 2241
2664 If the software worka 2242 If the software workaround is enabled for the host,
2665 guests do need not to 2243 guests do need not to enable it for nested guests.
2666 2244
2667 kvm.nx_huge_pages_recovery_ratio= 2245 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2246 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2247 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2248 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). !! 2249 minute. The default is 60.
2672 <<
2673 kvm.nx_huge_pages_recovery_period_ms= <<
2674 [KVM] Controls the ti <<
2675 back to huge pages. I <<
2676 zap a portion (see ra <<
2677 If the value is 0 (th <<
2678 on the ratio, such th <<
2679 <<
2680 kvm-amd.nested= [KVM,AMD] Control nes <<
2681 KVM/SVM. Default is 1 <<
2682 <<
2683 kvm-amd.npt= [KVM,AMD] Control KVM <<
2684 a.k.a. Two-Dimensiona <<
2685 (enabled). Disable by <<
2686 for NPT. <<
2687 2250
2688 kvm-arm.mode= !! 2251 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2689 [KVM,ARM,EARLY] Selec !! 2252 Default is 1 (enabled)
2690 operation. <<
2691 2253
2692 none: Forcefully disa !! 2254 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
>> 2255 for all guests.
>> 2256 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2693 2257
2694 nvhe: Standard nVHE-b !! 2258 kvm-arm.mode=
2695 protected guest !! 2259 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2696 2260
2697 protected: nVHE-based 2261 protected: nVHE-based mode with support for guests whose
2698 state is k 2262 state is kept private from the host.
>> 2263 Not valid if the kernel is running in EL2.
2699 2264
2700 nested: VHE-based mod !! 2265 Defaults to VHE/nVHE based on hardware support and
2701 virtualizatio !! 2266 the value of CONFIG_ARM64_VHE.
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE <<
2705 mode to "protected" w <<
2706 for the host. "nested <<
2707 used with extreme cau <<
2708 2267
2709 kvm-arm.vgic_v3_group0_trap= 2268 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2269 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2270 system registers
2712 2271
2713 kvm-arm.vgic_v3_group1_trap= 2272 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2273 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2274 system registers
2716 2275
2717 kvm-arm.vgic_v3_common_trap= 2276 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2277 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2278 system registers
2720 2279
2721 kvm-arm.vgic_v4_enable= 2280 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2281 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2282 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 2283
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2284 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2285 Reserves given percentage from system memory area for
2745 contiguous memory all 2286 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2287 allocation.
2747 By default it reserve 2288 By default it reserves 5% of total system memory.
2748 Format: <integer> 2289 Format: <integer>
2749 Default: 5 2290 Default: 5
2750 2291
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2292 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2293 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2294 Default is 1 (enabled)
2754 for EPT. <<
2755 2295
2756 kvm-intel.emulate_invalid_guest_state 2296 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2297 [KVM,Intel] Enable emulation of invalid guest states
2758 state. Ignored if kvm !! 2298 Default is 0 (disabled)
2759 as guest state is nev <<
2760 guests. This param do <<
2761 as KVM never emulates <<
2762 Default is 1 (enabled <<
2763 2299
2764 kvm-intel.flexpriority= 2300 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2301 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2302 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2303
2769 kvm-intel.nested= 2304 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2305 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2306 Default is 0 (disabled)
2772 2307
2773 kvm-intel.unrestricted_guest= 2308 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2309 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2310 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2311 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2312
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2313 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2314 CVE-2018-3620.
2781 2315
2782 Valid arguments: neve 2316 Valid arguments: never, cond, always
2783 2317
2784 always: L1D cache flu 2318 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2319 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2320 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2321 never: Disables the mitigation
2788 2322
2789 Default is cond (do L 2323 Default is cond (do L1 cache flush in specific instances)
2790 2324
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2325 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2326 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2327 Default is 1 (enabled)
2794 for it. <<
2795 <<
2796 l1d_flush= [X86,INTEL,EARLY] <<
2797 Control mitigation fo <<
2798 <<
2799 Certain CPUs are vuln <<
2800 internal buffers whic <<
2801 disclosure gadget und <<
2802 <<
2803 In vulnerable process <<
2804 forwarded data can be <<
2805 attack, to access dat <<
2806 not have direct acces <<
2807 <<
2808 This parameter contro <<
2809 options are: <<
2810 <<
2811 on - enable t <<
2812 2328
2813 l1tf= [X86,EARLY] Control m !! 2329 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2330 affected CPUs
2815 2331
2816 The kernel PTE invers 2332 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2333 enabled and cannot be disabled.
2818 2334
2819 full 2335 full
2820 Provides all 2336 Provides all available mitigations for the
2821 L1TF vulnerab 2337 L1TF vulnerability. Disables SMT and
2822 enables all m 2338 enables all mitigations in the
2823 hypervisors, 2339 hypervisors, i.e. unconditional L1D flush.
2824 2340
2825 SMT control a 2341 SMT control and L1D flush control via the
2826 sysfs interfa 2342 sysfs interface is still possible after
2827 boot. Hyperv 2343 boot. Hypervisors will issue a warning
2828 when the firs 2344 when the first VM is started in a
2829 potentially i 2345 potentially insecure configuration,
2830 i.e. SMT enab 2346 i.e. SMT enabled or L1D flush disabled.
2831 2347
2832 full,force 2348 full,force
2833 Same as 'full 2349 Same as 'full', but disables SMT and L1D
2834 flush runtime 2350 flush runtime control. Implies the
2835 'nosmt=force' 2351 'nosmt=force' command line option.
2836 (i.e. sysfs c 2352 (i.e. sysfs control of SMT is disabled.)
2837 2353
2838 flush 2354 flush
2839 Leaves SMT en 2355 Leaves SMT enabled and enables the default
2840 hypervisor mi 2356 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2357 L1D flush.
2842 2358
2843 SMT control a 2359 SMT control and L1D flush control via the
2844 sysfs interfa 2360 sysfs interface is still possible after
2845 boot. Hyperv 2361 boot. Hypervisors will issue a warning
2846 when the firs 2362 when the first VM is started in a
2847 potentially i 2363 potentially insecure configuration,
2848 i.e. SMT enab 2364 i.e. SMT enabled or L1D flush disabled.
2849 2365
2850 flush,nosmt 2366 flush,nosmt
2851 2367
2852 Disables SMT 2368 Disables SMT and enables the default
2853 hypervisor mi 2369 hypervisor mitigation.
2854 2370
2855 SMT control a 2371 SMT control and L1D flush control via the
2856 sysfs interfa 2372 sysfs interface is still possible after
2857 boot. Hyperv 2373 boot. Hypervisors will issue a warning
2858 when the firs 2374 when the first VM is started in a
2859 potentially i 2375 potentially insecure configuration,
2860 i.e. SMT enab 2376 i.e. SMT enabled or L1D flush disabled.
2861 2377
2862 flush,nowarn 2378 flush,nowarn
2863 Same as 'flus 2379 Same as 'flush', but hypervisors will not
2864 warn when a V 2380 warn when a VM is started in a potentially
2865 insecure conf 2381 insecure configuration.
2866 2382
2867 off 2383 off
2868 Disables hype 2384 Disables hypervisor mitigations and doesn't
2869 emit any warn 2385 emit any warnings.
2870 It also drops 2386 It also drops the swap size and available
2871 RAM limit res 2387 RAM limit restriction on both hypervisor and
2872 bare metal. 2388 bare metal.
2873 2389
2874 Default is 'flush'. 2390 Default is 'flush'.
2875 2391
2876 For details see: Docu 2392 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2393
2878 l2cr= [PPC] 2394 l2cr= [PPC]
2879 2395
2880 l3cr= [PPC] 2396 l3cr= [PPC]
2881 2397
2882 lapic [X86-32,APIC,EARLY] E !! 2398 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2399 disabled it.
2884 2400
2885 lapic= [X86,APIC] Do not use 2401 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2402 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2403 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2404 Format: notscdeadline
2889 2405
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2406 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2407 in C2 power state.
2892 2408
2893 libata.dma= [LIBATA] DMA control 2409 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2410 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2411 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2412 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2413 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2414 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2415 for disks and CDROMs, but not CFs.
2900 2416
2901 libata.ignore_hpa= [LIBATA] Igno 2417 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2418 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2419 libata.ignore_hpa=1 ignore limits, using full disk
2904 2420
2905 libata.noacpi [LIBATA] Disables use 2421 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2422 when set.
2907 Format: <int> 2423 Format: <int>
2908 2424
2909 libata.force= [LIBATA] Force config !! 2425 libata.force= [LIBATA] Force configurations. The format is comma-
2910 separated list of "[I !! 2426 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2427 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2428 matching port, link or device. Basically, it matches
2913 printed on console by !! 2429 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2430 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2431 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2432 configuration applies to all ports, links and devices.
2917 2433
2918 If only DEVICE is omi 2434 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2435 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2436 number of 0 either selects the first device or the
2921 first fan-out link be 2437 first fan-out link behind PMP device. It does not
2922 select the host link. 2438 select the host link. DEVICE number of 15 selects the
2923 host link and device 2439 host link and device attached to it.
2924 2440
2925 The VAL specifies the 2441 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2442 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2443 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2444 The following configurations can be forced.
2929 2445
2930 * Cable type: 40c, 80 2446 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2447 Any ID with matching PORT is used.
2932 2448
2933 * SATA link speed lim 2449 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2450
2935 * Transfer mode: pio[ 2451 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2452 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2453 allowed.
2938 2454
2939 * nohrst, nosrst, nor <<
2940 resets. <<
2941 <<
2942 * rstonce: only attem <<
2943 link recovery. <<
2944 <<
2945 * [no]dbdelay: Enable <<
2946 before debouncing a <<
2947 detection. <<
2948 <<
2949 * [no]ncq: Turn on or 2455 * [no]ncq: Turn on or off NCQ.
2950 2456
2951 * [no]ncqtrim: Enable !! 2457 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 <<
2953 * [no]ncqati: Enable <<
2954 <<
2955 * [no]trim: Enable or <<
2956 <<
2957 * trim_zero: Indicate <<
2958 <<
2959 * max_trim_128m: Set <<
2960 <<
2961 * [no]dma: Turn on or <<
2962 2458
2963 * atapi_dmadir: Enabl !! 2459 * nohrst, nosrst, norst: suppress hard, soft
>> 2460 and both resets.
2964 2461
2965 * atapi_mod16_dma: En !! 2462 * rstonce: only attempt one reset during
2966 commands that are n !! 2463 hot-unplug link recovery
2967 2464
2968 * [no]dmalog: Enable !! 2465 * dump_id: dump IDENTIFY data.
2969 READ LOG DMA EXT co <<
2970 2466
2971 * [no]iddevlog: Enabl !! 2467 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2972 identify device dat <<
2973 <<
2974 * [no]logdir: Enable <<
2975 purpose log directo <<
2976 <<
2977 * max_sec_128: Set tr <<
2978 <<
2979 * max_sec_1024: Set o <<
2980 1024 sectors. <<
2981 <<
2982 * max_sec_lba48: Set <<
2983 65535 sectors. <<
2984 <<
2985 * [no]lpm: Enable or <<
2986 <<
2987 * [no]setxfer: Indica <<
2988 should be skipped. <<
2989 <<
2990 * [no]fua: Disable or <<
2991 support for devices <<
2992 <<
2993 * dump_id: Dump IDENT <<
2994 2468
2995 * disable: Disable th 2469 * disable: Disable this device.
2996 2470
2997 If there are multiple 2471 If there are multiple matching configurations changing
2998 the same attribute, t 2472 the same attribute, the last one is used.
2999 2473
>> 2474 memblock=debug [KNL] Enable memblock debug messages.
>> 2475
3000 load_ramdisk= [RAM] [Deprecated] 2476 load_ramdisk= [RAM] [Deprecated]
3001 2477
3002 lockd.nlm_grace_period=P [NFS] Assig 2478 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2479 Format: <integer>
3004 2480
3005 lockd.nlm_tcpport=N [NFS] Assign 2481 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2482 Format: <integer>
3007 2483
3008 lockd.nlm_timeout=T [NFS] Assign 2484 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2485 Format: <integer>
3010 2486
3011 lockd.nlm_udpport=M [NFS] Assign 2487 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2488 Format: <integer>
3013 2489
3014 lockdown= [SECURITY,EARLY] !! 2490 lockdown= [SECURITY]
3015 { integrity | confide 2491 { integrity | confidentiality }
3016 Enable the kernel loc 2492 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2493 integrity, kernel features that allow userland to
3018 modify the running ke 2494 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2495 confidentiality, kernel features that allow userland
3020 to extract confidenti 2496 to extract confidential information from the kernel
3021 are also disabled. 2497 are also disabled.
3022 2498
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] 2499 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2500 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2501 Defaults to being automatically set based on the
3058 number of online CPUs 2502 number of online CPUs.
3059 2503
3060 locktorture.nwriters_stress= [KNL] 2504 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2505 Set the number of locking write-acquisition kthreads.
3062 2506
3063 locktorture.onoff_holdoff= [KNL] 2507 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2508 Set time (s) after boot for CPU-hotplug testing.
3065 2509
3066 locktorture.onoff_interval= [KNL] 2510 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2511 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2512 zero to disable CPU-hotplug testing.
3069 2513
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] 2514 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2515 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2516 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2517 mode during the locktorture test.
3093 2518
3094 locktorture.shutdown_secs= [KNL] 2519 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2520 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2521 is useful for hands-off automated testing.
3097 2522
3098 locktorture.stat_interval= [KNL] 2523 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2524 Time (s) between statistics printk()s.
3100 2525
3101 locktorture.stutter= [KNL] 2526 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2527 Time (s) to stutter testing, for example,
3103 specifying five secon 2528 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2529 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2530 This tests the locking primitive's ability to
3106 transition abruptly t 2531 transition abruptly to and from idle.
3107 2532
3108 locktorture.torture_type= [KNL] 2533 locktorture.torture_type= [KNL]
3109 Specify the locking i 2534 Specify the locking implementation to test.
3110 2535
3111 locktorture.verbose= [KNL] 2536 locktorture.verbose= [KNL]
3112 Enable additional pri 2537 Enable additional printk() statements.
3113 2538
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2539 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2540 Format: <irq>
3120 2541
3121 loglevel= [KNL,EARLY] !! 2542 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2543 console loglevel will be printed to the console. It can
3124 also be changed with 2544 also be changed with klogd or other programs. The
3125 loglevels are defined 2545 loglevels are defined as follows:
3126 2546
3127 0 (KERN_EMERG) 2547 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2548 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2549 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2550 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2551 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2552 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2553 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2554 7 (KERN_DEBUG) debug-level messages
3135 2555
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2556 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2557 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2558 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2559 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2560 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2561 that allows to increase the default size depending on
3142 parameter that allows !! 2562 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2563
3146 logo.nologo [FB] Disables display 2564 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2565 This may be used to provide more screen space for
3148 kernel log messages a 2566 kernel log messages and is useful when debugging
3149 kernel boot problems. 2567 kernel boot problems.
3150 2568
3151 lp=0 [LP] Specify paral 2569 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2570 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2571 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2572 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2573 specified in addition to the ports) causes
3156 attached prin 2574 attached printers to be reset. Using
3157 lp=port1,port 2575 lp=port1,port2,... specifies the parallel ports
3158 to associate 2576 to associate lp devices with, starting with
3159 lp0. A port s 2577 lp0. A port specification may be 'none' to skip
3160 that lp devic 2578 that lp device, or a parport name such as
3161 'parport0'. S 2579 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2580 port specification list means that device IDs
3163 from each por 2581 from each port should be examined, to see if
3164 an IEEE 1284- 2582 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2583 so, the driver will manage that printer.
3166 See also head 2584 See also header of drivers/char/lp.c.
3167 2585
3168 lpj=n [KNL] 2586 lpj=n [KNL]
3169 Sets loops_per_jiffy 2587 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2588 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2589 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2590 the correct value for your kernel, boot with normal
3173 autodetection and see 2591 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2592 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2593 which is likely to cause problems if your CPUs need
3176 significantly diverge 2594 significantly divergent settings. An incorrect value
3177 will cause delays in 2595 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2596 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2597 unlikely, in the extreme case this might damage your
3180 hardware. 2598 hardware.
3181 2599
>> 2600 ltpc= [NET]
>> 2601 Format: <io>,<irq>,<dma>
>> 2602
3182 lsm.debug [SECURITY] Enable LSM 2603 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2604
3184 lsm=lsm1,...,lsmN 2605 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2606 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2607 overrides CONFIG_LSM, and the "security=" parameter.
3187 2608
>> 2609 machvec= [IA-64] Force the use of a particular machine-vector
>> 2610 (machvec) in a generic kernel.
>> 2611 Example: machvec=hpzx1
>> 2612
3188 machtype= [Loongson] Share the 2613 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2614 different yeeloong laptops.
3190 Example: machtype=lem 2615 Example: machtype=lemote-yeeloong-2f-7inch
3191 2616
3192 maxcpus= [SMP,EARLY] Maximum n !! 2617 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2618 than or equal to this physical address is ignored.
>> 2619
>> 2620 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2621 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2622 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2623 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2624 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2625 only takes effect during system bootup.
3198 While n=0 is a specia 2626 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2627 which also disables the IO APIC.
3200 2628
3201 max_loop= [LOOP] The number of 2629 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2630 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2631 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2632 of statically allocating a predefined number, loop
3205 devices can be reques 2633 devices can be requested on-demand with the
3206 /dev/loop-control int 2634 /dev/loop-control interface.
3207 2635
3208 mce [X86-32] Machine Chec 2636 mce [X86-32] Machine Check Exception
3209 2637
3210 mce=option [X86-64] See Document !! 2638 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2639
3212 md= [HW] RAID subsystems 2640 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2641 See Documentation/admin-guide/md.rst.
3214 2642
3215 mdacon= [MDA] 2643 mdacon= [MDA]
3216 Format: <first>,<last 2644 Format: <first>,<last>
3217 Specifies range of co 2645 Specifies range of consoles to be captured by the MDA.
3218 2646
3219 mds= [X86,INTEL,EARLY] !! 2647 mds= [X86,INTEL]
3220 Control mitigation fo 2648 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2649 Sampling (MDS) vulnerability.
3222 2650
3223 Certain CPUs are vuln 2651 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2652 internal buffers which can forward information to a
3225 disclosure gadget und 2653 disclosure gadget under certain conditions.
3226 2654
3227 In vulnerable process 2655 In vulnerable processors, the speculatively
3228 forwarded data can be 2656 forwarded data can be used in a cache side channel
3229 attack, to access dat 2657 attack, to access data to which the attacker does
3230 not have direct acces 2658 not have direct access.
3231 2659
3232 This parameter contro 2660 This parameter controls the MDS mitigation. The
3233 options are: 2661 options are:
3234 2662
3235 full - Enable M 2663 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2664 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2665 SMT on vulnerable CPUs
3238 off - Uncondit 2666 off - Unconditionally disable MDS mitigation
3239 2667
3240 On TAA-affected machi 2668 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2669 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2670 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2671 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2672 too.
3245 2673
3246 Not specifying this o 2674 Not specifying this option is equivalent to
3247 mds=full. 2675 mds=full.
3248 2676
3249 For details see: Docu 2677 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2678
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2679 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3252 Must be specified, ot !! 2680 Amount of memory to be used in cases as follows:
3253 <<
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc <<
3255 of memory Amount of m <<
3256 as follows: <<
3257 2681
3258 1 for test; 2682 1 for test;
3259 2 when the kernel is 2683 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 2684 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 2685 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory <<
3263 <<
3264 [ARC,MICROBLAZE] - th <<
3265 high memory is not af <<
3266 <<
3267 [ARM64] - only limits <<
3268 mapping. The NOMAP re <<
3269 2686
3270 [X86] Work as limitin 2687 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2688 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2689 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2690 belonging to unused RAM.
3274 2691
3275 Note that this only t 2692 Note that this only takes effects during boot time since
3276 in above case 3, memo 2693 in above case 3, memory may need be hot added after boot
3277 if system memory of h 2694 if system memory of hypervisor is not sufficient.
3278 2695
3279 mem=nn[KMG]@ss[KMG] <<
3280 [ARM,MIPS,EARLY] - ov <<
3281 reported by firmware. <<
3282 Define a memory regio <<
3283 ss[KMG]. <<
3284 Multiple different re <<
3285 multiple mem= paramet <<
3286 <<
3287 mem=nopentium [BUGS=X86-32] Disable 2696 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2697 memory.
3289 2698
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2699 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2700 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2701 per-device physically contiguous DMA buffers.
3295 2702
3296 memhp_default_state=online/offline/on !! 2703 memhp_default_state=online/offline
3297 [KNL] Set the initial 2704 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2705 onlining policy. If not specified, the default value is
3299 set according to the 2706 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2707 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2708 option.
3302 See Documentation/adm 2709 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 2710
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2711 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2712 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2713 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2714 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2715 option description.
3309 2716
3310 memmap=nn[KMG]@ss[KMG] 2717 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2718 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 2719 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2720 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2721 which limits max address to nn[KMG].
3315 Multiple different re 2722 Multiple different regions can be specified,
3316 comma delimited. 2723 comma delimited.
3317 Example: 2724 Example:
3318 memmap=100M@2 2725 memmap=100M@2G,100M#3G,1G!1024G
3319 2726
3320 memmap=nn[KMG]#ss[KMG] 2727 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2728 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2729 Region of memory to be marked is from ss to ss+nn.
3323 2730
3324 memmap=nn[KMG]$ss[KMG] 2731 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2732 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2733 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2734 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2735 memmap=64K$0x18690000
3329 or 2736 or
3330 memmap=0x100 2737 memmap=0x10000$0x18690000
3331 Some bootloaders may 2738 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2739 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2740 will be eaten.
3334 2741
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2742 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2743 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2744 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2745 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2746 and is NVDIMM or ADR memory.
3340 2747
3341 memmap=<size>%<offset>-<oldtype>+<new 2748 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 2749 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 2750 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 2751 out, the whole region will be marked as <newtype>,
3345 even if previously un 2752 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 2753 out, matching memory will be removed. Types are
3347 specified as e820 typ 2754 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 2755 3 = ACPI, 12 = PRAM.
3349 2756
3350 memory_corruption_check=0/1 [X86,EARL !! 2757 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 2758 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2759 memory when doing things like suspend/resume.
3353 Setting this option w 2760 Setting this option will scan the memory
3354 looking for corruptio 2761 looking for corruption. Enabling this will
3355 both detect corruptio 2762 both detect corruption and prevent the kernel
3356 from using the memory 2763 from using the memory being corrupted.
3357 However, its intended 2764 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2765 repeatable BIOS-originated corruption always
3359 affects the same memo 2766 affects the same memory, you can use memmap=
3360 to prevent the kernel 2767 to prevent the kernel from using that memory.
3361 2768
3362 memory_corruption_check_size=size [X8 !! 2769 memory_corruption_check_size=size [X86]
3363 By default it checks 2770 By default it checks for corruption in the low
3364 64k, making this memo 2771 64k, making this memory unavailable for normal
3365 use. Use this parame 2772 use. Use this parameter to scan for
3366 corruption in more or 2773 corruption in more or less memory.
3367 2774
3368 memory_corruption_check_period=second !! 2775 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2776 By default it checks for corruption every 60
3370 seconds. Use this pa 2777 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2778 other rate. 0 disables periodic checking.
3372 2779
3373 memory_hotplug.memmap_on_memory !! 2780 memtest= [KNL,X86,ARM,PPC] Enable memtest
3374 [KNL,X86,ARM] Boolean <<
3375 Format: {on | off (de <<
3376 When enabled, runtime <<
3377 allocate its internal <<
3378 those vmemmap pages c <<
3379 if hugetlb_free_vmemm <<
3380 hotadded memory which <<
3381 lot of memory without <<
3382 memory to do so. <<
3383 This feature is disab <<
3384 has some implication <<
3385 allocations in some c <<
3386 memory blocks). <<
3387 The state of the flag <<
3388 /sys/module/memory_ho <<
3389 Note that even when e <<
3390 the feature is not ef <<
3391 <<
3392 memtest= [KNL,X86,ARM,M68K,PPC <<
3393 Format: <integer> 2781 Format: <integer>
3394 default : 0 <disable> 2782 default : 0 <disable>
3395 Specifies the number 2783 Specifies the number of memtest passes to be
3396 performed. Each pass 2784 performed. Each pass selects another test
3397 pattern from a given 2785 pattern from a given set of patterns. Memtest
3398 fills the memory with 2786 fills the memory with this pattern, validates
3399 memory contents and r 2787 memory contents and reserves bad memory
3400 regions that are dete 2788 regions that are detected.
3401 2789
3402 mem_encrypt= [X86-64] AMD Secure M 2790 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2791 Valid arguments: on, off
3404 Default: off !! 2792 Default (depends on kernel configuration option):
>> 2793 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2794 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2795 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2796 mem_encrypt=off: Do not activate SME
3407 2797
3408 Refer to Documentatio !! 2798 Refer to Documentation/virt/kvm/amd-memory-encryption.rst
3409 for details on when m 2799 for details on when memory encryption can be activated.
3410 2800
3411 mem_sleep_default= [SUSPEND] Def 2801 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2802 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2803 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2804 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 2805 See Documentation/admin-guide/pm/sleep-states.rst.
3416 2806
>> 2807 meye.*= [HW] Set MotionEye Camera parameters
>> 2808 See Documentation/admin-guide/media/meye.rst.
>> 2809
>> 2810 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2811 Multi-Function General Purpose Timers on AMD Geode
>> 2812 platforms.
>> 2813
3417 mfgptfix [X86-32] Fix MFGPT ti 2814 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2815 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2816 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2817 problem by letting the user disable the workaround.
3421 2818
3422 mga= [HW,DRM] 2819 mga= [HW,DRM]
3423 2820
3424 microcode.force_minrev= [X86] !! 2821 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2822 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2823
3429 mini2440= [ARM,HW,KNL] 2824 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2825 Format:[0..2][b][c][t]
3431 Default: "0tb" 2826 Default: "0tb"
3432 MINI2440 configuratio 2827 MINI2440 configuration specification:
3433 0 - The attached scre 2828 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2829 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2830 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2831 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2832 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2833 unconfigured.
3439 b - Enable backlight. 2834 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2835 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2836 LED. This parameter is not necessary when using the
3442 VGA shield. 2837 VGA shield.
3443 c - Enable the s3c ca 2838 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2839 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2840 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2841 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2842 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 2843 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 2844
3450 mitigations= 2845 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 2846 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 2847 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 2848 arch-independent options, each of which is an
3454 aggregation of existi 2849 aggregation of existing arch-specific options.
3455 2850
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 2851 off
3460 Disable all o 2852 Disable all optional CPU mitigations. This
3461 improves syst 2853 improves system performance, but it may also
3462 expose users 2854 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 2855 Equivalent to: nopti [X86,PPC]
3464 !! 2856 kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 2857 nospectre_v1 [X86,PPC]
>> 2858 nobp=0 [S390]
3475 2859 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 2860 spectre_v2_user=off [X86]
3482 !! 2861 spec_store_bypass_disable=off [X86,PPC]
3483 2862 ssbd=force-off [ARM64]
>> 2863 l1tf=off [X86]
>> 2864 mds=off [X86]
3484 2865 tsx_async_abort=off [X86]
>> 2866 kvm.nx_huge_pages=off [X86]
>> 2867 no_entry_flush [PPC]
>> 2868 no_uaccess_flush [PPC]
3485 2869
3486 Exceptions: 2870 Exceptions:
3487 2871 This does not have any effect on
3488 2872 kvm.nx_huge_pages when
3489 2873 kvm.nx_huge_pages=force.
3490 2874
3491 auto (default) 2875 auto (default)
3492 Mitigate all 2876 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 2877 enabled, even if it's vulnerable. This is for
3494 users who don 2878 users who don't want to be surprised by SMT
3495 getting disab 2879 getting disabled across kernel upgrades, or who
3496 have other wa 2880 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 2881 Equivalent to: (default behavior)
3498 2882
3499 auto,nosmt 2883 auto,nosmt
3500 Mitigate all 2884 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 2885 if needed. This is for users who always want to
3502 be fully miti 2886 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 2887 Equivalent to: l1tf=flush,nosmt [X86]
3504 2888 mds=full,nosmt [X86]
3505 2889 tsx_async_abort=full,nosmt [X86]
3506 <<
3507 <<
3508 2890
3509 mminit_loglevel= 2891 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 2892 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 2893 parameter allows control of the logging verbosity for
3512 the additional memory 2894 the additional memory initialisation checks. A value
3513 of 0 disables mminit 2895 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 2896 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 2897 so loglevel=8 may also need to be specified.
3516 2898
3517 mmio_stale_data= <<
3518 [X86,INTEL,EARLY] Con <<
3519 MMIO Stale Data vulne <<
3520 <<
3521 Processor MMIO Stale <<
3522 vulnerabilities that <<
3523 operation. Exposed da <<
3524 the same CPU buffers <<
3525 Therefore, similar to <<
3526 is to clear the affec <<
3527 <<
3528 This parameter contro <<
3529 options are: <<
3530 <<
3531 full - Enable m <<
3532 <<
3533 full,nosmt - Enable m <<
3534 vulnerab <<
3535 <<
3536 off - Uncondit <<
3537 <<
3538 On MDS or TAA affecte <<
3539 mmio_stale_data=off c <<
3540 MDS or TAA mitigation <<
3541 mitigated with the sa <<
3542 disable this mitigati <<
3543 mds=off and tsx_async <<
3544 <<
3545 Not specifying this o <<
3546 mmio_stale_data=full. <<
3547 <<
3548 For details see: <<
3549 Documentation/admin-g <<
3550 <<
3551 <module>.async_probe[=<bool>] [KNL] <<
3552 If no <bool> value is <<
3553 specified is not a va <<
3554 probe on this module. <<
3555 asynchronous probe on <<
3556 <bool> value. See als <<
3557 <<
3558 module.async_probe=<bool> <<
3559 [KNL] When set to tru <<
3560 by default. To enable <<
3561 specific module, use <<
3562 is documented under < <<
3563 module.async_probe an <<
3564 specified, <module>.a <<
3565 the specific module. <<
3566 <<
3567 module.enable_dups_trace <<
3568 [KNL] When CONFIG_MOD <<
3569 this means that dupli <<
3570 trigger a WARN_ON() i <<
3571 if MODULE_DEBUG_AUTOL <<
3572 will always be issued <<
3573 module.sig_enforce 2899 module.sig_enforce
3574 [KNL] When CONFIG_MOD 2900 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 2901 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 2902 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 2903 is always true, so this option does nothing.
3578 2904
3579 module_blacklist= [KNL] Do not load 2905 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 2906 modules. Useful for debugging problem modules.
3581 2907
3582 mousedev.tap_time= 2908 mousedev.tap_time=
3583 [MOUSE] Maximum time 2909 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 2910 leaving touchpad surface for touch to be considered
3585 a tap and be reported 2911 a tap and be reported as a left button click (for
3586 touchpads working in 2912 touchpads working in absolute mode only).
3587 Format: <msecs> 2913 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 2914 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 2915 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 2916 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 2917 reporting absolute coordinates, such as tablets
3592 2918
3593 movablecore= [KNL,X86,PPC,EARLY] !! 2919 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 2920 Format: nn[KMGTPE] | nn%
3595 This parameter is the 2921 This parameter is the complement to kernelcore=, it
3596 specifies the amount 2922 specifies the amount of memory used for migratable
3597 allocations. If both 2923 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 2924 specified, then kernelcore will be at *least* the
3599 specified value but m 2925 specified value but may be more. If movablecore on its
3600 own is specified, the 2926 own is specified, the administrator must be careful
3601 that the amount of me 2927 that the amount of memory usable for all allocations
3602 is not too small. 2928 is not too small.
3603 2929
3604 movable_node [KNL,EARLY] Boot-time !! 2930 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 2931 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 2932 of such nodes will be usable only for movable
3607 allocations which rul 2933 allocations which rules out almost all kernel
3608 allocations. Use with 2934 allocations. Use with caution!
3609 2935
3610 MTD_Partition= [MTD] 2936 MTD_Partition= [MTD]
3611 Format: <name>,<regio 2937 Format: <name>,<region-number>,<size>,<offset>
3612 2938
3613 MTD_Region= [MTD] Format: 2939 MTD_Region= [MTD] Format:
3614 <name>,<region-number 2940 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 2941
3616 mtdparts= [MTD] 2942 mtdparts= [MTD]
3617 See drivers/mtd/parse 2943 See drivers/mtd/parsers/cmdlinepart.c
3618 2944
>> 2945 multitce=off [PPC] This parameter disables the use of the pSeries
>> 2946 firmware feature for updating multiple TCE entries
>> 2947 at a time.
>> 2948
>> 2949 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 2950
>> 2951 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 2952
>> 2953 boundary - index of last SLC block on Flex-OneNAND.
>> 2954 The remaining blocks are configured as MLC blocks.
>> 2955 lock - Configure if Flex-OneNAND boundary should be locked.
>> 2956 Once locked, the boundary cannot be changed.
>> 2957 1 indicates lock status, 0 indicates unlock status.
>> 2958
>> 2959 mtdset= [ARM]
>> 2960 ARM/S3C2412 JIVE boot control
>> 2961
>> 2962 See arch/arm/mach-s3c/mach-jive.c
>> 2963
3619 mtouchusb.raw_coordinates= 2964 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 2965 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 2966 ('y', default) or cooked coordinates ('n')
3622 2967
3623 mtrr=debug [X86,EARLY] !! 2968 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 2969 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 2970 that could hold holes aka. UC entries.
3630 2971
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 2972 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 2973 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 2974 Default is 1.
3634 Large value could pre 2975 Large value could prevent small alignment from
3635 using up MTRRs. 2976 using up MTRRs.
3636 2977
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 2978 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 2979 Format: <integer>
3639 Range: 0,7 : spare re 2980 Range: 0,7 : spare reg number
3640 Default : 1 2981 Default : 1
3641 Used for mtrr cleanup 2982 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 2983 Set to 2 or more if your graphical card needs more.
3643 2984
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 2985 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 2986
3650 netdev= [NET] Network devices 2987 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 2988 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 2989 Note that mem_start is often overloaded to mean
3653 something different a 2990 something different and driver-specific.
3654 This usage is only do 2991 This usage is only documented in each driver source
3655 file if at all. 2992 file if at all.
3656 2993
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 2994 nf_conntrack.acct=
3663 [NETFILTER] Enable co 2995 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 2996 0 to disable accounting
3665 1 to enable accountin 2997 1 to enable accounting
3666 Default value is 0. 2998 Default value is 0.
3667 2999
3668 nfs.cache_getent= !! 3000 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3001 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3002
3672 nfs.cache_getent_timeout= !! 3003 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3004 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3005
>> 3006 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3007 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3008
3676 nfs.callback_nr_threads= 3009 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3010 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3011 NFS client will assign to service NFSv4 callback
3679 requests. 3012 requests.
3680 3013
3681 nfs.callback_tcpport= 3014 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3015 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3016 channel should listen.
3684 3017
3685 nfs.delay_retrans= !! 3018 nfs.cache_getent=
3686 [NFS] specifies the n !! 3019 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3020 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3021
3689 Only applies if the s !! 3022 nfs.cache_getent_timeout=
3690 and the specified val !! 3023 [NFS] sets the timeout after which an attempt to
>> 3024 update a cache entry is deemed to have failed.
>> 3025
>> 3026 nfs.idmap_cache_timeout=
>> 3027 [NFS] set the maximum lifetime for idmapper cache
>> 3028 entries.
3691 3029
3692 nfs.enable_ino64= 3030 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3031 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3032 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3033 number for the readdir() and stat() syscalls instead
3696 of returning the full 3034 of returning the full 64-bit number.
3697 The default is to ret 3035 The default is to return 64-bit inode numbers.
3698 3036
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3037 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3038 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3039 slots the client will assign to the callback
3706 channel. This determi 3040 channel. This determines the maximum number of
3707 callbacks the client 3041 callbacks the client will process in parallel for
3708 a particular server. 3042 a particular server.
3709 3043
3710 nfs.max_session_slots= 3044 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3045 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3046 the client will attempt to negotiate with the server.
3713 This limits the numbe 3047 This limits the number of simultaneous RPC requests
3714 that the client can s 3048 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3049 Note that there is little point in setting this
3716 value higher than the 3050 value higher than the max_tcp_slot_table_limit.
3717 3051
3718 nfs.nfs4_disable_idmapping= 3052 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3053 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3054 ensures that both the RPC level authentication
3721 scheme and the NFS le 3055 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3056 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3057 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3058 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3059 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3060 Servers that do not support this mode of operation
3727 will be autodetected 3061 will be autodetected by the client, and it will fall
3728 back to using the idm 3062 back to using the idmapper.
3729 To turn off this beha 3063 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3064 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3065 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3066 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3067 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3068 UUID that is generated at system install time.
3736 3069
3737 nfs.recover_lost_locks= !! 3070 nfs.send_implementation_id =
>> 3071 [NFSv4.1] Send client implementation identification
>> 3072 information in exchange_id requests.
>> 3073 If zero, no implementation identification information
>> 3074 will be sent.
>> 3075 The default is to send the implementation identification
>> 3076 information.
>> 3077
>> 3078 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3079 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3080 to a lease timeout on the server. Please note that
3740 doing this risks data 3081 doing this risks data corruption, since there are
3741 no guarantees that th 3082 no guarantees that the file will remain unchanged
3742 after the locks are l 3083 after the locks are lost.
3743 If you want to enable 3084 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3085 attempting to recover these locks, then set this
3745 parameter to '1'. 3086 parameter to '1'.
3746 The default parameter 3087 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3088 not to attempt recovery of lost locks.
3748 3089
3749 nfs.send_implementation_id= !! 3090 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 3091 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3092 layoutstats to the pNFS metadata server.
3760 3093
3761 Setting this to value 3094 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3095 whatever value is the default set by the layout
3763 driver. A non-zero va 3096 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3097 in seconds between layoutstats transmissions.
3765 3098
3766 nfsd.inter_copy_offload_enable= <<
3767 [NFSv4.2] When set to <<
3768 server-to-server copi <<
3769 the destination of th <<
3770 <<
3771 nfsd.nfs4_disable_idmapping= 3099 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 3100 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 3101 server will return only numeric uids and gids to
3774 clients using auth_sy 3102 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 3103 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 3104 migration from NFSv2/v3.
3777 3105
3778 nfsd.nfsd4_ssc_umount_timeout= <<
3779 [NFSv4.2] When used a <<
3780 server-to-server copy <<
3781 the source server. I <<
3782 it will be needed aga <<
3783 used for the number o <<
3784 this parameter. <<
3785 <<
3786 nfsaddrs= [NFS] Deprecated. Us <<
3787 See Documentation/adm <<
3788 <<
3789 nfsroot= [NFS] nfs root filesy <<
3790 See Documentation/adm <<
3791 <<
3792 nfsrootdebug [NFS] enable nfsroot <<
3793 See Documentation/adm <<
3794 <<
3795 nmi_backtrace.backtrace_idle [KNL] 3106 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3107 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3108 NMI stack-backtrace request.
3798 3109
3799 nmi_debug= [KNL,SH] Specify one 3110 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3111 when a NMI is triggered.
3801 Format: [state][,regs 3112 Format: [state][,regs][,debounce][,die]
3802 3113
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3114 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3115 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3116 Valid num: 0 or 1
3806 0 - turn hardlockup d 3117 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3118 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3119 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3120 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3121 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3122 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3123 please see 'nowatchdog'.
3815 This is useful when y 3124 This is useful when you use a panic=... timeout and
3816 need the box quickly 3125 need the box quickly up again.
3817 3126
3818 These settings can be 3127 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3128 the nmi_watchdog and hardlockup_panic sysctls.
3820 3129
>> 3130 netpoll.carrier_timeout=
>> 3131 [NET] Specifies amount of time (in seconds) that
>> 3132 netpoll should wait for a carrier. By default netpoll
>> 3133 waits 4 seconds.
>> 3134
3821 no387 [BUGS=X86-32] Tells t 3135 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3136 emulation library even if a 387 maths coprocessor
3823 is present. 3137 is present.
3824 3138
3825 no4lvl [RISCV,EARLY] Disable !! 3139 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 3140 kernel to use 4-level paging instead.
3830 3141
3831 noalign [KNL,ARM] !! 3142 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 3143
3840 no_console_suspend 3144 no_console_suspend
3841 [HW] Never suspend th 3145 [HW] Never suspend the console
3842 Disable suspending of 3146 Disable suspending of consoles during suspend and
3843 hibernate operations. 3147 hibernate operations. Once disabled, debugging
3844 messages can reach va 3148 messages can reach various consoles while the rest
3845 of the system is bein 3149 of the system is being put to sleep (ie, while
3846 debugging driver susp 3150 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3151 not work reliably with all consoles, but is known
3848 to work with serial a 3152 to work with serial and VGA consoles.
3849 To facilitate more fl 3153 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3154 console_suspend, a printk module parameter to control
3851 it. Users could use c 3155 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3156 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3157 turn on/off it dynamically.
3854 3158
3855 no_debug_objects !! 3159 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3160 Disable device dump. Device dump allows drivers to
>> 3161 append dump data to vmcore so you can collect driver
>> 3162 specified debug info. Drivers can append the data
>> 3163 without any limit and this data is stored in memory,
>> 3164 so this may cause significant memory stress. Disabling
>> 3165 device dump can help save memory but the driver debug
>> 3166 data will be no longer available. This parameter
>> 3167 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3168 is set.
>> 3169
>> 3170 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3171 caches in the slab allocator. Saves per-node memory,
>> 3172 but will impact performance.
>> 3173
>> 3174 noalign [KNL,ARM]
>> 3175
>> 3176 noaltinstr [S390] Disables alternative instructions patching
>> 3177 (CPU alternatives feature).
>> 3178
>> 3179 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3180 IOAPICs that may be present in the system.
>> 3181
>> 3182 noautogroup Disable scheduler automatic task group creation.
>> 3183
>> 3184 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 3185 on "Classic" PPC cores.
>> 3186
>> 3187 nocache [ARM]
>> 3188
>> 3189 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 3190
>> 3191 nodelayacct [KNL] Disable per-task delay accounting
3857 3192
3858 nodsp [SH] Disable hardware 3193 nodsp [SH] Disable hardware DSP at boot time.
3859 3194
3860 noefi [EFI,EARLY] Disable E !! 3195 noefi Disable EFI runtime services support.
>> 3196
>> 3197 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3861 3198
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3199 noexec [IA-64]
>> 3200
>> 3201 noexec [X86]
>> 3202 On X86-32 available only on PAE configured kernels.
>> 3203 noexec=on: enable non-executable mappings (default)
>> 3204 noexec=off: disable non-executable mappings
>> 3205
>> 3206 nosmap [X86,PPC]
>> 3207 Disable SMAP (Supervisor Mode Access Prevention)
>> 3208 even if it is supported by processor.
>> 3209
>> 3210 nosmep [X86,PPC]
>> 3211 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3212 even if it is supported by processor.
3863 3213
3864 noexec32 [X86-64] 3214 noexec32 [X86-64]
3865 This affects only 32- 3215 This affects only 32-bit executables.
3866 noexec32=on: enable n 3216 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3217 read doesn't imply executable mappings
3868 noexec32=off: disable 3218 noexec32=off: disable non-executable mappings
3869 read implies 3219 read implies executable mappings
3870 3220
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 3221 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3222
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3223 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3224 register save and restore. The kernel will only save
3881 legacy floating-point 3225 legacy floating-point registers on task switch.
3882 3226
3883 no_hash_pointers !! 3227 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3884 [KNL,EARLY] <<
3885 Force pointers printe <<
3886 unhashed. By default <<
3887 format string, that p <<
3888 by hashing the pointe <<
3889 that hides actual ker <<
3890 users, but it also ma <<
3891 difficult since unequ <<
3892 compared. However, i <<
3893 specified, then all n <<
3894 value printed. This o <<
3895 debugging the kernel. <<
3896 kernels. <<
3897 3228
3898 nohibernate [HIBERNATION] Disable !! 3229 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3230 Equivalent to smt=1.
3899 3231
3900 nohlt [ARM,ARM64,MICROBLAZE !! 3232 [KNL,X86] Disable symmetric multithreading (SMT).
3901 busy wait in do_idle( !! 3233 nosmt=force: Force disable SMT, cannot be undone
3902 implementation; requi !! 3234 via the sysfs control file.
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 3235
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA !! 3236 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3237 (bounds check bypass). With this option data leaks are
>> 3238 possible in the system.
3910 3239
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA !! 3240 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 3241 the Spectre variant 2 (indirect branch prediction)
>> 3242 vulnerability. System may allow data leaks with this
>> 3243 option.
>> 3244
>> 3245 nospec_store_bypass_disable
>> 3246 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3247
>> 3248 no_uaccess_flush
>> 3249 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3250
>> 3251 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3252 and restore using xsave. The kernel will fallback to
>> 3253 enabling legacy floating-point and sse state.
>> 3254
>> 3255 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3256 register states. The kernel will fall back to use
>> 3257 xsave to save the states. By using this parameter,
>> 3258 performance of saving the states is degraded because
>> 3259 xsave doesn't support modified optimization while
>> 3260 xsaveopt supports it on xsaveopt enabled systems.
>> 3261
>> 3262 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3263 restoring x86 extended register state in compacted
>> 3264 form of xsave area. The kernel will fall back to use
>> 3265 xsaveopt and xrstor to save and restore the states
>> 3266 in standard form of xsave area. By using this
>> 3267 parameter, xsave area per process might occupy more
>> 3268 memory on xsaves enabled systems.
>> 3269
>> 3270 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
>> 3271 wfi(ARM) instruction doesn't work correctly and not to
>> 3272 use it. This is also useful when using JTAG debugger.
>> 3273
>> 3274 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3275 only way then for a file to be executed with privilege
>> 3276 is to be setuid root or executed by root.
>> 3277
>> 3278 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3279 function PAL_HALT_LIGHT when idle. This increases
>> 3280 power-consumption. On the positive side, it reduces
>> 3281 interrupt wake-up latency, which may improve performance
>> 3282 in certain environments such as networked servers or
>> 3283 real-time systems.
>> 3284
>> 3285 nohibernate [HIBERNATION] Disable hibernation and resume.
3912 3286
3913 nohz= [KNL] Boottime enable 3287 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3288 Valid arguments: on, off
3915 Default: on 3289 Default: on
3916 3290
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3291 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3292 The argument is a cpu list, as described above.
3919 In kernels built with 3293 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3294 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3295 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3296 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3297 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3298 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3299 rcu_nocbs= boot parameter.
3926 3300
3927 Note that this argume !! 3301 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 3302
>> 3303 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3304 disable unhandled interrupt sources.
>> 3305
>> 3306 no_timer_check [X86,APIC] Disables the code which tests for
>> 3307 broken timer IRQ sources.
>> 3308
>> 3309 noisapnp [ISAPNP] Disables ISA PnP code.
3929 3310
3930 noinitrd [RAM] Tells the kerne 3311 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3312 initial RAM disk.
3932 3313
3933 nointremap [X86-64,Intel-IOMMU,E !! 3314 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3315 remapping.
3935 [Deprecated - use int 3316 [Deprecated - use intremap=off]
3936 3317
3937 noinvpcid [X86,EARLY] Disable t !! 3318 nointroute [IA-64]
3938 3319
3939 noiotrap [SH] Disables trapped !! 3320 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 3321
3941 noirqdebug [X86-32] Disables the !! 3322 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 3323
3944 noisapnp [ISAPNP] Disables ISA !! 3324 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3945 3325
3946 nokaslr [KNL,EARLY] !! 3326 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. 3327 fault handling.
3953 3328
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3329 no-vmw-sched-clock
>> 3330 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3331 clock and use the default one.
3955 3332
3956 nolapic [X86-32,APIC,EARLY] D !! 3333 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
>> 3334 accounting. steal time is computed, but won't
>> 3335 influence scheduler behaviour
3957 3336
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3337 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3959 3338
3960 nomce [X86-32] Disable Mach !! 3339 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3961 3340
3962 nomfgpt [X86-32] Disable Mult !! 3341 noltlbs [PPC] Do not use large page/tlb entries for kernel
3963 Timer usage (for AMD !! 3342 lowmem mapping on PPC40x and PPC8xx
3964 3343
3965 nomodeset Disable kernel modese !! 3344 nomca [IA-64] Disable machine check abort handling
3966 sets up a display mod <<
3967 for output. With nomo <<
3968 not load if they coul <<
3969 initialized output. O <<
3970 be available for use. <<
3971 perform display-mode <<
3972 3345
3973 Useful as error fallb !! 3346 nomce [X86-32] Disable Machine Check Exception
3974 3347
3975 nomodule Disable module load !! 3348 nomfgpt [X86-32] Disable Multi-Function General Purpose
>> 3349 Timer usage (for AMD Geode machines).
3976 3350
3977 nonmi_ipi [X86] Disable using N 3351 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3352 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3353 irq.
3980 3354
3981 nopat [X86,EARLY] Disable P !! 3355 nomodule Disable module load
3982 pagetables) support. <<
3983 <<
3984 nopcid [X86-64,EARLY] Disabl <<
3985 <<
3986 nopku [X86] Disable Memory <<
3987 in some Intel CPUs. <<
3988 <<
3989 nopti [X86-64,EARLY] <<
3990 Equivalent to pti=off <<
3991 3356
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3357 nopat [X86] Disable PAT (page attribute table extension of
3993 Disables the PV optim !! 3358 pagetables) support.
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 3359
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3360 nopcid [X86-64] Disable the PCID cpu feature.
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3361
4002 norandmaps Don't use address spa 3362 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3363 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3364
4005 noreplace-smp [X86-32,SMP] Don't re 3365 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3366 with UP alternatives
4007 3367
>> 3368 nordrand [X86] Disable kernel use of the RDRAND and
>> 3369 RDSEED instructions even if they are supported
>> 3370 by the processor. RDRAND and RDSEED are still
>> 3371 available to user space applications.
>> 3372
4008 noresume [SWSUSP] Disables res 3373 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3374 space.
4010 3375
4011 no-scroll [VGA] Disables scroll 3376 no-scroll [VGA] Disables scrollback.
4012 This is required for 3377 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3378 reader made by F.H. Papenmeier (Germany).
4014 3379
4015 nosgx [X86-64,SGX,EARLY] Di !! 3380 nosbagart [IA-64]
4016 3381
4017 nosmap [PPC,EARLY] !! 3382 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 3383
4021 nosmep [PPC64s,EARLY] !! 3384 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 3385
4025 nosmp [SMP,EARLY] Tells an !! 3386 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3387 and disable the IO APIC. legacy for "maxcpus=0".
4027 3388
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 3389 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3390
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 3391 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3392
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 3393 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3394 soft-lockup and NMI watchdog (hard-lockup).
4083 3395
4084 nowb [ARM,EARLY] !! 3396 nowb [ARM]
4085 <<
4086 nox2apic [X86-64,APIC,EARLY] D <<
4087 <<
4088 NOTE: this parameter <<
4089 LEGACY_XAPIC_DISABLED <<
4090 IA32_XAPIC_DISABLE_ST <<
4091 3397
4092 noxsave [BUGS=X86] Disables x !! 3398 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4093 and restore using xsa <<
4094 enabling legacy float <<
4095 <<
4096 noxsaveopt [X86] Disables xsaveo <<
4097 register states. The <<
4098 xsave to save the sta <<
4099 performance of saving <<
4100 xsave doesn't support <<
4101 xsaveopt supports it <<
4102 3399
4103 noxsaves [X86] Disables xsaves !! 3400 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4104 restoring x86 extende !! 3401 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4105 form of xsave area. T !! 3402 Some features depend on CPU0. Known dependencies are:
4106 xsaveopt and xrstor t !! 3403 1. Resume from suspend/hibernate depends on CPU0.
4107 in standard form of x !! 3404 Suspend/hibernate will fail if CPU0 is offline and you
4108 parameter, xsave area !! 3405 need to online CPU0 before suspend/hibernate.
4109 memory on xsaves enab !! 3406 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 3407 removed if a PIC interrupt is detected.
>> 3408 It's said poweroff/reboot may depend on CPU0 on some
>> 3409 machines although I haven't seen such issues so far
>> 3410 after CPU0 is offline on a few tested machines.
>> 3411 If the dependencies are under your control, you can
>> 3412 turn on cpu0_hotplug.
>> 3413
>> 3414 nps_mtm_hs_ctr= [KNL,ARC]
>> 3415 This parameter sets the maximum duration, in
>> 3416 cycles, each HW thread of the CTOP can run
>> 3417 without interruptions, before HW switches it.
>> 3418 The actual maximum duration is 16 times this
>> 3419 parameter's value.
>> 3420 Format: integer between 1 and 255
>> 3421 Default: 255
>> 3422
>> 3423 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3424 purges which is reported from either PAL_VM_SUMMARY or
>> 3425 SAL PALO.
4110 3426
4111 nr_cpus= [SMP,EARLY] Maximum n !! 3427 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4112 could support. nr_cp 3428 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3429 support 'n' processors. It could be larger than the
4114 number of already plu 3430 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3431 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3432 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3433 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3434 hot plugging.
4119 3435
4120 nr_uarts= [SERIAL] maximum numb 3436 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3437
4122 numa=off [KNL, ARM64, PPC, RIS !! 3438 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
4123 Disable NUMA, Only se <<
4124 spanning all memory. <<
4125 <<
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, <<
4127 NUMA balancing. <<
4128 Allowed values are en 3439 Allowed values are enable and disable
4129 3440
4130 numa_zonelist_order= [KNL, BOOT] Sele 3441 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3442 'node', 'default' can be specified
4132 This can be set from 3443 This can be set from sysctl after boot.
4133 See Documentation/adm 3444 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3445
4135 ohci1394_dma=early [HW,EARLY] en !! 3446 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3447 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3448 info.
4138 3449
4139 olpc_ec_timeout= [OLPC] ms delay when 3450 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3451 Rather than timing out after 20 ms if an EC
4141 command is not proper 3452 command is not properly ACKed, override the length
4142 of the timeout. We h 3453 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3454 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3455 interrupts *may* be lost!
4145 3456
4146 omap_mux= [OMAP] Override bootl 3457 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3458 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3459 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3460 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3461
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 3462 oprofile.timer= [HW]
>> 3463 Use timer interrupt instead of performance counters
4152 3464
4153 Format: [die0_boundar !! 3465 oprofile.cpu_type= Force an oprofile cpu type
>> 3466 This might be useful if you have an older oprofile
>> 3467 userland or if you want common events.
>> 3468 Format: { arch_perfmon }
>> 3469 arch_perfmon: [X86] Force use of architectural
>> 3470 perfmon on Intel CPUs instead of the
>> 3471 CPU specific event set.
>> 3472 timer: [X86] Force use of architectural NMI
>> 3473 timer mode (see also oprofile.timer
>> 3474 for generic hr timer mode)
4154 3475
4155 boundary - index of l !! 3476 oops=panic Always panic on oopses. Default is to just kill the
4156 The remain <<
4157 lock - Configure <<
4158 Once locke <<
4159 1 indicate <<
4160 <<
4161 oops=panic [KNL,EARLY] <<
4162 Always panic on oopse <<
4163 process, but there is 3477 process, but there is a small probability of
4164 deadlocking the machi 3478 deadlocking the machine.
4165 This will also cause 3479 This will also cause panics on machine check exceptions.
4166 Useful together with 3480 Useful together with panic=30 to trigger a reboot.
4167 3481
4168 page_alloc.shuffle= 3482 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3483 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3484 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3485 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3486 running on a platform with a direct-mapped memory-side
>> 3487 cache, and this parameter can be used to
>> 3488 override/disable that behavior. The state of the flag
>> 3489 can be read from sysfs at:
4173 /sys/module/page_allo 3490 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3491
4176 page_owner= [KNL,EARLY] Boot-time !! 3492 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3493 Storage of the information about who allocated
4178 each page is disabled 3494 each page is disabled in default. With this switch,
4179 we can turn it on. 3495 we can turn it on.
4180 on: enable the featur 3496 on: enable the feature
4181 3497
4182 page_poison= [KNL,EARLY] Boot-time !! 3498 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3499 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3500 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3501 off: turn off poisoning (default)
4186 on: turn on poisoning 3502 on: turn on poisoning
4187 3503
4188 page_reporting.page_reporting_order= <<
4189 [KNL] Minimal page re <<
4190 Format: <integer> <<
4191 Adjust the minimal pa <<
4192 reporting is disabled <<
4193 <<
4194 panic= [KNL] Kernel behaviou 3504 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3505 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3506 timeout = 0: wait forever
4197 timeout < 0: reboot i 3507 timeout < 0: reboot immediately
4198 Format: <timeout> 3508 Format: <timeout>
4199 3509
4200 panic_on_taint= [KNL,EARLY] !! 3510 panic_print= Bitmask for printing system info when panic happens.
4201 Bitmask for condition !! 3511 User can chose combination of the following bits:
>> 3512 bit 0: print all tasks info
>> 3513 bit 1: print system memory info
>> 3514 bit 2: print timer info
>> 3515 bit 3: print locks info if CONFIG_LOCKDEP is on
>> 3516 bit 4: print ftrace buffer
>> 3517 bit 5: print all printk messages in buffer
>> 3518
>> 3519 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4202 Format: <hex>[,nouser 3520 Format: <hex>[,nousertaint]
4203 Hexadecimal bitmask r 3521 Hexadecimal bitmask representing the set of TAINT flags
4204 that will cause the k 3522 that will cause the kernel to panic when add_taint() is
4205 called with any of th 3523 called with any of the flags in this set.
4206 The optional switch " 3524 The optional switch "nousertaint" can be utilized to
4207 prevent userspace for 3525 prevent userspace forced crashes by writing to sysctl
4208 /proc/sys/kernel/tain 3526 /proc/sys/kernel/tainted any flagset matching with the
4209 bitmask set on panic_ 3527 bitmask set on panic_on_taint.
4210 See Documentation/adm 3528 See Documentation/admin-guide/tainted-kernels.rst for
4211 extra details on the 3529 extra details on the taint flags that users can pick
4212 to compose the bitmas 3530 to compose the bitmask to assign to panic_on_taint.
4213 3531
4214 panic_on_warn=1 panic() instead of WA !! 3532 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4215 on a WARN(). 3533 on a WARN().
4216 3534
4217 panic_print= Bitmask for printing !! 3535 crash_kexec_post_notifiers
4218 User can chose combin !! 3536 Run kdump after running panic-notifiers and dumping
4219 bit 0: print all task !! 3537 kmsg. This only for the users who doubt kdump always
4220 bit 1: print system m !! 3538 succeeds in any situation.
4221 bit 2: print timer in !! 3539 Note that this also increases risks of kdump failure,
4222 bit 3: print locks in !! 3540 because some panic notifiers can make the crashed
4223 bit 4: print ftrace b !! 3541 kernel more unstable.
4224 bit 5: print all prin <<
4225 bit 6: print all CPUs <<
4226 bit 7: print only tas <<
4227 *Be aware* that this <<
4228 so there are risks of <<
4229 Use this option caref <<
4230 bigger log buffer wit <<
4231 3542
4232 parkbd.port= [HW] Parallel port nu 3543 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3544 connected to, default is 0.
4234 Format: <parport#> 3545 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3546 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3547 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3548 Format: <mode>
4238 3549
4239 parport= [HW,PPT] Specify para 3550 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3551 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3552 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3553 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3554 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3555 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3556 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3557 should be numbers, or 'auto' (for using detected
4247 settings on that part 3558 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3559 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3560 Parallel ports are assigned in the order they
4250 are specified on the 3561 are specified on the command line, starting
4251 with parport0. 3562 with parport0.
4252 3563
4253 parport_init_mode= [HW,PPT] 3564 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3565 Configure VIA parallel port to operate in
4255 a specific mode. This 3566 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3567 computer where firmware has no options for setting
4257 up parallel port mode 3568 up parallel port mode and sets it to spp.
4258 Currently this functi 3569 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3570 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3571
4261 pata_legacy.all= [HW,LIBATA] !! 3572 pause_on_oops=
4262 Format: <int> <<
4263 Set to non-zero to pr <<
4264 port ranges on PCI sy <<
4265 has been found at eit <<
4266 <<
4267 pata_legacy.autospeed= [HW,LIBATA] <<
4268 Format: <int> <<
4269 Set to non-zero if a <<
4270 changes. Disabled by <<
4271 <<
4272 pata_legacy.ht6560a= [HW,LIBATA] <<
4273 Format: <int> <<
4274 Set to 1, 2, or 3 for <<
4275 the secondary channel <<
4276 Disabled by default. <<
4277 <<
4278 pata_legacy.ht6560b= [HW,LIBATA] <<
4279 Format: <int> <<
4280 Set to 1, 2, or 3 for <<
4281 the secondary channel <<
4282 Disabled by default. <<
4283 <<
4284 pata_legacy.iordy_mask= [HW,LIBATA] <<
4285 Format: <int> <<
4286 IORDY enable mask. S <<
4287 for the respective ch <<
4288 legacy channel handle <<
4289 the second channel, a <<
4290 correspond to the pri <<
4291 legacy channel, and s <<
4292 bus and the use of ot <<
4293 with the sequence. B <<
4294 all channels. <<
4295 <<
4296 pata_legacy.opti82c46x= [HW,LIBATA] <<
4297 Format: <int> <<
4298 Set to 1, 2, or 3 for <<
4299 channel, the secondar <<
4300 respectively. Disabl <<
4301 <<
4302 pata_legacy.opti82c611a= [HW,L <<
4303 Format: <int> <<
4304 Set to 1, 2, or 3 for <<
4305 channel, the secondar <<
4306 respectively. Disabl <<
4307 <<
4308 pata_legacy.pio_mask= [HW,LIBATA] <<
4309 Format: <int> <<
4310 PIO mode mask for aut <<
4311 bits to allow the use <<
4312 Bit 0 is for mode 0, <<
4313 All modes allowed by <<
4314 <<
4315 pata_legacy.probe_all= [HW,LIBATA] <<
4316 Format: <int> <<
4317 Set to non-zero to pr <<
4318 port ranges on PCI sy <<
4319 <<
4320 pata_legacy.probe_mask= [HW,LIBATA] <<
4321 Format: <int> <<
4322 Probe mask for legacy <<
4323 platform configuratio <<
4324 options up to 6 legac <<
4325 0x170, 0x1e8, 0x168, <<
4326 of individual ports c <<
4327 corresponding bits in <<
4328 the first port in the <<
4329 By default all suppor <<
4330 <<
4331 pata_legacy.qdi= [HW,LIBATA] <<
4332 Format: <int> <<
4333 Set to non-zero to pr <<
4334 set to 1 if CONFIG_PA <<
4335 <<
4336 pata_legacy.winbond= [HW,LIBATA] <<
4337 Format: <int> <<
4338 Set to non-zero to pr <<
4339 the standard I/O port <<
4340 value given is the I/ <<
4341 By default set to 1 i <<
4342 0 otherwise. <<
4343 <<
4344 pata_platform.pio_mask= [HW,LIBATA] <<
4345 Format: <int> <<
4346 Supported PIO mode ma <<
4347 the use of the respec <<
4348 mode 0, bit 1 is for <<
4349 allowed by default. <<
4350 <<
4351 pause_on_oops=<int> <<
4352 Halt all CPUs after t 3573 Halt all CPUs after the first oops has been printed for
4353 the specified number 3574 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3575 your oopses keep scrolling off the screen.
4355 3576
4356 pcbit= [HW,ISDN] 3577 pcbit= [HW,ISDN]
4357 3578
4358 pci=option[,option...] [PCI,EARLY] v !! 3579 pcd. [PARIDE]
>> 3580 See header of drivers/block/paride/pcd.c.
>> 3581 See also Documentation/admin-guide/blockdev/paride.rst.
>> 3582
>> 3583 pci=option[,option...] [PCI] various PCI subsystem options.
4359 3584
4360 Some options 3585 Some options herein operate on a specific device
4361 or a set of d 3586 or a set of devices (<pci_dev>). These are
4362 specified in 3587 specified in one of the following formats:
4363 3588
4364 [<domain>:]<b 3589 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 3590 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 3591
4367 Note: the fir 3592 Note: the first format specifies a PCI
4368 bus/device/fu 3593 bus/device/function address which may change
4369 if new hardwa 3594 if new hardware is inserted, if motherboard
4370 firmware chan 3595 firmware changes, or due to changes caused
4371 by other kern 3596 by other kernel parameters. If the
4372 domain is lef 3597 domain is left unspecified, it is
4373 taken to be z 3598 taken to be zero. Optionally, a path
4374 to a device t 3599 to a device through multiple device/function
4375 addresses can 3600 addresses can be specified after the base
4376 address (this 3601 address (this is more robust against
4377 renumbering i 3602 renumbering issues). The second format
4378 selects devic 3603 selects devices using IDs from the
4379 configuration 3604 configuration space which may match multiple
4380 devices in th 3605 devices in the system.
4381 3606
4382 earlydump dump PCI conf 3607 earlydump dump PCI config space before the kernel
4383 changes anyth 3608 changes anything
4384 off [X86] don't p 3609 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3610 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3611 the hardware directly. Use this if your machine
4387 has a non-sta 3612 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3613 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3614 hardware access methods are allowed. Use this
4390 if you experi 3615 if you experience crashes upon bootup and you
4391 suspect they 3616 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3617 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3618 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3619 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3620 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3621 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3622 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3623 bus number. The config space is then accessed
4399 through ports 3624 through ports 0xC000-0xCFFF).
4400 See http://wi 3625 See http://wiki.osdev.org/PCI for more info
4401 on the config 3626 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3627 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3628 enabled, this kernel boot option can be used to
4404 disable the u 3629 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3630 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3631 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3632 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3633 Configuration
4409 check_enable_amd_mmconf [X86] 3634 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3635 properly configured MMIO access to PCI
4411 config space 3636 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3637 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3638 enabled, this kernel boot option can be used to
4414 disable the u 3639 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3640 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3641 Safety option to keep boot IRQs enabled. This
4417 should never 3642 should never be necessary.
4418 ioapicreroute [APIC] Enable 3643 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3644 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3645 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3646 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3647 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3648 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3649 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3650 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3651 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3652 routing table. These calls are known to be buggy
4428 on several ma 3653 on several machines and they hang the machine
4429 when used, bu 3654 when used, but on other computers it's the only
4430 way to get th 3655 way to get the interrupt routing table. Try
4431 this option i 3656 this option if the kernel is unable to allocate
4432 IRQs or disco 3657 IRQs or discover secondary PCI buses on your
4433 motherboard. 3658 motherboard.
4434 rom [X86] Assign 3659 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3660 Use with caution as certain devices share
4436 address decod 3661 address decoders between ROMs and other
4437 resources. 3662 resources.
4438 norom [X86] Do not 3663 norom [X86] Do not assign address space to
4439 expansion ROM 3664 expansion ROMs that do not already have
4440 BIOS assigned 3665 BIOS assigned address ranges.
4441 nobar [X86] Do not 3666 nobar [X86] Do not assign address space to the
4442 BARs that wer 3667 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3668 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3669 assigned automatically to PCI devices. You can
4445 make the kern 3670 make the kernel exclude IRQs of your ISA cards
4446 this way. 3671 this way.
4447 pirqaddr=0xAAAAA [X86] 3672 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3673 of the PIRQ table (normally generated
4449 by the BIOS) 3674 by the BIOS) if it is outside the
4450 F0000h-100000 3675 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3676 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3677 useful if the kernel is unable to find your
4453 secondary bus 3678 secondary buses and you want to tell it
4454 explicitly wh 3679 explicitly which ones they are.
4455 assign-busses [X86] Always 3680 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3681 numbers ourselves, overriding
4457 whatever the 3682 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3683 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3684 in the BIOS $PIR table. This is needed on
4460 some systems 3685 some systems with broken BIOSes, notably
4461 some HP Pavil 3686 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3687 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3688 IRQ routing is enabled.
4464 noacpi [X86] Do not 3689 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3690 or for PCI scanning.
4466 use_crs [X86] Use PCI 3691 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3692 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3693 is enabled by default. If you need to use this,
4469 please report 3694 please report a bug.
4470 nocrs [X86] Ignore 3695 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 3696 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 <<
4473 PCI host brid <<
4474 for BIOS defe <<
4475 If you need t <<
4476 <linux-pci@vge <<
4477 no_e820 [X86] Ignore <<
4478 bridge window <<
4479 hardware. If <<
4480 a bug to <linu <<
4481 routeirq Do IRQ routin 3697 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3698 This is normally done in pci_enable_device(),
4483 so this optio 3699 so this option is a temporary workaround
4484 for broken dr 3700 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3701 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3702 handle more pci cards
4487 noearly [X86] Don't d 3703 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3704 This might help on some broken boards which
4489 machine check 3705 machine check when some devices' config space
4490 is read. But 3706 is read. But various workarounds are disabled
4491 and some IOMM 3707 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3708 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3709 This sorting is done to get a device
4494 order compati 3710 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3711 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3712 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3713 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3714 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3715 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3716 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3717 based on its parent bus. Also set MRRS (Max
4502 Read Request 3718 Read Request Size) to the largest supported
4503 value (no lar 3719 value (no larger than the MPS that the device
4504 or bus can su 3720 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3721 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3722 every device is guaranteed to support. This
4507 configuration 3723 configuration allows peer-to-peer DMA between
4508 any pair of d 3724 any pair of devices, possibly at the cost of
4509 reduced perfo 3725 reduced performance. This also guarantees
4510 that hot-adde 3726 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3727 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3728 reserved for the CardBus bridge's IO window.
4513 The default v 3729 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3730 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3731 reserved for the CardBus bridge's memory
4516 window. The d 3732 window. The default value is 64 megabytes.
4517 resource_alignment= 3733 resource_alignment=
4518 Format: 3734 Format:
4519 [<order of ali 3735 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 3736 Specifies alignment and device to reassign
4521 aligned memor 3737 aligned memory resources. How to
4522 specify the d 3738 specify the device is described above.
4523 If <order of 3739 If <order of align> is not specified,
4524 PAGE_SIZE is 3740 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 3741 A PCI-PCI bridge can be specified if resource
4526 windows need 3742 windows need to be expanded.
4527 To specify th 3743 To specify the alignment for several
4528 instances of 3744 instances of a device, the PCI vendor,
4529 device, subve 3745 device, subvendor, and subdevice may be
4530 specified, e. 3746 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 3747 for 4096-byte alignment.
4532 ecrc= Enable/disabl 3748 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3749 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3750 bios: Use BIOS/firmware settings. This is the
4537 the default. 3751 the default.
4538 off: Turn ECR 3752 off: Turn ECRC off
4539 on: Turn ECRC 3753 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3754 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3755 reserved for hotplug bridge's IO window.
4542 Default size 3756 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 3757 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 3758 reserved for hotplug bridge's MMIO window.
4545 Default size 3759 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 3760 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 3761 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 3762 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 3763 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 3764 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 3765 MMIO_PREF window.
4552 Default size 3766 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3767 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3768 reserved for buses below a hotplug bridge.
4555 Default is 1. 3769 Default is 1.
4556 realloc= Enable/disabl 3770 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3771 if allocations done by BIOS are too small to
4558 accommodate r 3772 accommodate resources required by all child
4559 devices. 3773 devices.
4560 off: Turn rea 3774 off: Turn realloc off
4561 on: Turn real 3775 on: Turn realloc on
4562 realloc same as reall 3776 realloc same as realloc=on
4563 noari do not use PC 3777 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 3778 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 3779 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 3780 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 3781 only look for one device below a PCIe downstream
4568 port. 3782 port.
4569 big_root_window Try to add a 3783 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 3784 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 3785 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 3786 Adding the window is slightly risky (it may
4573 conflict with 3787 conflict with unreported devices), so this
4574 taints the ke 3788 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 3789 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 3790 Specify one or more PCI devices (in the format
4577 specified abo 3791 specified above) separated by semicolons.
4578 Each device s 3792 Each device specified will have the PCI ACS
4579 redirect capa 3793 redirect capabilities forced off which will
4580 allow P2P tra 3794 allow P2P traffic between devices through
4581 bridges witho 3795 bridges without forcing it upstream. Note:
4582 this removes 3796 this removes isolation between devices and
4583 may put more 3797 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 3798 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 3799 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 3800 norid [S390] ignore the RID field and force use of
4619 one PCI domai 3801 one PCI domain per PCI function
4620 3802
4621 pcie_aspm= [PCIE] Forcibly enabl !! 3803 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 3804 Management.
4623 off Don't touch ASPM conf !! 3805 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 3806 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 3807 WARNING: Forcing ASPM on may cause system lockups.
4627 3808
4628 pcie_ports= [PCIE] PCIe port serv 3809 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 3810 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 3811 even if the platform doesn't give the OS permission to
4631 use them. This may c 3812 use them. This may cause conflicts if the platform
4632 also tries to use the 3813 also tries to use these services.
4633 dpc-native Use native PC 3814 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 3815 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 3816 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 3817 hotplug).
4637 3818
4638 pcie_port_pm= [PCIE] PCIe port powe 3819 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 3820 off Disable power management of all PCIe ports
4640 force Forcibly enable power 3821 force Forcibly enable power management of all PCIe ports
4641 3822
4642 pcie_pme= [PCIE,PM] Native PCIe 3823 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 3824 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 3825 all PCIe root ports use INTx for all services).
4645 3826
4646 pcmv= [HW,PCMCIA] BadgePAD 3827 pcmv= [HW,PCMCIA] BadgePAD 4
4647 3828
4648 pd_ignore_unused 3829 pd_ignore_unused
4649 [PM] 3830 [PM]
4650 Keep all power-domain 3831 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 3832 even if no driver has claimed them. This is useful
4652 for debug and develop 3833 for debug and development, but should not be
4653 needed on a platform 3834 needed on a platform with proper driver support.
4654 3835
>> 3836 pd. [PARIDE]
>> 3837 See Documentation/admin-guide/blockdev/paride.rst.
>> 3838
4655 pdcchassis= [PARISC,HW] Disable/E 3839 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 3840 boot time.
4657 Format: { 0 | 1 } 3841 Format: { 0 | 1 }
4658 See arch/parisc/kerne 3842 See arch/parisc/kernel/pdc_chassis.c
4659 3843
4660 percpu_alloc= [MM,EARLY] !! 3844 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 3845 Currently supported values are "embed" and "page".
4663 Archs may support sub 3846 Archs may support subset or none of the selections.
4664 See comments in mm/pe 3847 See comments in mm/percpu.c for details on each
4665 allocator. This para 3848 allocator. This parameter is primarily for debugging
4666 and performance compa 3849 and performance comparison.
4667 3850
>> 3851 pf. [PARIDE]
>> 3852 See Documentation/admin-guide/blockdev/paride.rst.
>> 3853
>> 3854 pg. [PARIDE]
>> 3855 See Documentation/admin-guide/blockdev/paride.rst.
>> 3856
4668 pirq= [SMP,APIC] Manual mp- 3857 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 3858 See Documentation/x86/i386/IO-APIC.rst.
4670 3859
4671 plip= [PPT,NET] Parallel po 3860 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 3861 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 3862 See also Documentation/admin-guide/parport.rst.
4674 3863
4675 pmtmr= [X86] Manual setup of 3864 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 3865 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 3866 e.g. pmtmr=0x508
4678 3867
4679 pmu_override= [PPC] Override the PM <<
4680 This option takes ove <<
4681 longer usable by perf <<
4682 PMU counters by setti <<
4683 cleared). If a number <<
4684 that number, otherwis <<
4685 remains 0. <<
4686 <<
4687 pm_debug_messages [SUSPEND,KNL] 3868 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 3869 Enable suspend/resume debug messages during boot up.
4689 3870
4690 pnp.debug=1 [PNP] 3871 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 3872 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 3873 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 3874 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 3875 current resource usage; turning this on also shows
4695 possible settings and 3876 possible settings and some assignment information.
4696 3877
4697 pnpacpi= [ACPI] 3878 pnpacpi= [ACPI]
4698 { off } 3879 { off }
4699 3880
4700 pnpbios= [ISAPNP] 3881 pnpbios= [ISAPNP]
4701 { on | off | curr | r 3882 { on | off | curr | res | no-curr | no-res }
4702 3883
4703 pnp_reserve_irq= 3884 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 3885 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 3886
4706 pnp_reserve_dma= 3887 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 3888 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 3889
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 3890 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 3891 Ranges are in pairs (I/O port base and size).
4711 3892
4712 pnp_reserve_mem= 3893 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 3894 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 3895 autoconfiguration.
4715 Ranges are in pairs ( 3896 Ranges are in pairs (memory base and size).
4716 3897
4717 ports= [IP_VS_FTP] IPVS ftp 3898 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 3899 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 3900 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 3901 may be specified.
4721 Format: <port>,<port> 3902 Format: <port>,<port>....
4722 3903
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 3904 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 3905 It specifically disables cpuidle and sets the
4730 platform machine desc 3906 platform machine description specific power_save
4731 function to NULL. On 3907 function to NULL. On Idle the CPU just reduces
4732 execution priority. 3908 execution priority.
4733 3909
4734 ppc_strict_facility_enable 3910 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 3911 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 3912 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 3913 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 3914 There is some performance impact when enabling this.
4739 3915
4740 ppc_tm= [PPC,EARLY] !! 3916 ppc_tm= [PPC]
4741 Format: {"off"} 3917 Format: {"off"}
4742 Disable Hardware Tran 3918 Disable Hardware Transactional Memory
4743 3919
4744 preempt= [KNL] <<
4745 Select preemption mod <<
4746 none - Limited to con <<
4747 voluntary - Limited t <<
4748 full - Any section th <<
4749 can be preempt <<
4750 contended spin <<
4751 explicitly pre <<
4752 <<
4753 print-fatal-signals= 3920 print-fatal-signals=
4754 [KNL] debug: print fa 3921 [KNL] debug: print fatal signals
4755 3922
4756 If enabled, warn abou 3923 If enabled, warn about various signal handling
4757 related application a 3924 related application anomalies: too many signals,
4758 too many POSIX.1 time 3925 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 3926 coredump - etc.
4760 3927
4761 If you hit the warnin 3928 If you hit the warning due to signal overflow,
4762 you might want to try 3929 you might want to try "ulimit -i unlimited".
4763 3930
4764 default: off. 3931 default: off.
4765 3932
4766 printk.always_kmsg_dump= 3933 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 3934 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 3935 panics
4769 Format: <bool> (1/Y/ 3936 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 3937 default: disabled
4771 3938
4772 printk.console_no_auto_verbose= <<
4773 Disable console logle <<
4774 or lockdep-detected i <<
4775 With an exception to <<
4776 serial console, keepi <<
4777 in order to provide m <<
4778 Format: <bool> <<
4779 default: 0 (auto_verb <<
4780 <<
4781 printk.devkmsg={on,off,ratelimit} 3939 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 3940 Control writing to /dev/kmsg.
4783 on - unlimited loggin 3941 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 3942 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 3943 ratelimit - ratelimit the logging
4786 Default: ratelimit 3944 Default: ratelimit
4787 3945
4788 printk.time= Show timing data pref 3946 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 3947 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 3948
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] 3949 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 3950 Limit processor to maximum C-state
4803 max_cstate=9 override 3951 max_cstate=9 overrides any DMI blacklist limit.
4804 3952
4805 processor.nocst [HW,ACPI] 3953 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 3954 Ignore the _CST method to determine C-states,
4807 instead using the leg 3955 instead using the legacy FADT method
4808 3956
4809 profile= [KNL] Enable kernel p 3957 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 3958 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 3959 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 3960 [defaults to kernel profiling]
4813 Param: "schedule" - p 3961 Param: "schedule" - profile schedule points.
>> 3962 Param: "sleep" - profile D-state sleeping (millisecs).
>> 3963 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 3964 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 3965 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 3966 statistical time based profiling.
4817 3967
4818 prompt_ramdisk= [RAM] [Deprecated] 3968 prompt_ramdisk= [RAM] [Deprecated]
4819 3969
4820 prot_virt= [S390] enable hosting 3970 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 3971 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 3972 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 3973 Format: <bool>
4826 3974
4827 psi= [KNL] Enable or disab 3975 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 3976 tracking.
4829 Format: <bool> 3977 Format: <bool>
4830 3978
4831 psmouse.proto= [HW,MOUSE] Highest PS 3979 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 3980 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 3981 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 3982 per second.
4835 psmouse.resetafter= [HW,MOUSE] 3983 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 3984 Try to reset the device after so many bad packets
4837 (0 = never). 3985 (0 = never).
4838 psmouse.resolution= 3986 psmouse.resolution=
4839 [HW,MOUSE] Set desire 3987 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 3988 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 3989 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 3990 0 = disabled, 1 = enabled (default).
4843 3991
4844 pstore.backend= Specify the name of t 3992 pstore.backend= Specify the name of the pstore backend to use
4845 3993
>> 3994 pt. [PARIDE]
>> 3995 See Documentation/admin-guide/blockdev/paride.rst.
>> 3996
4846 pti= [X86-64] Control Page 3997 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 3998 kernel address spaces. Disabling this feature
4848 removes hardening, bu 3999 removes hardening, but improves performance of
4849 system calls and inte 4000 system calls and interrupts.
4850 4001
4851 on - unconditionall 4002 on - unconditionally enable
4852 off - unconditionall 4003 off - unconditionally disable
4853 auto - kernel detects 4004 auto - kernel detects whether your CPU model is
4854 vulnerable to 4005 vulnerable to issues that PTI mitigates
4855 4006
4856 Not specifying this o 4007 Not specifying this option is equivalent to pti=auto.
4857 4008
>> 4009 nopti [X86-64]
>> 4010 Equivalent to pti=off
>> 4011
4858 pty.legacy_count= 4012 pty.legacy_count=
4859 [KNL] Number of legac 4013 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4014 default number.
4861 4015
4862 quiet [KNL,EARLY] Disable m !! 4016 quiet [KNL] Disable most log messages
4863 4017
4864 r128= [HW,DRM] 4018 r128= [HW,DRM]
4865 4019
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4020 raid= [HW,RAID]
4871 See Documentation/adm 4021 See Documentation/admin-guide/md.rst.
4872 4022
4873 ramdisk_size= [RAM] Sizes of RAM di 4023 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4024 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4025
4876 ramdisk_start= [RAM] RAM disk image 4026 ramdisk_start= [RAM] RAM disk image start address
4877 4027
4878 random.trust_cpu=off !! 4028 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 4029 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 4030 CPU's random number generator (if available) to
4881 initialize the kernel !! 4031 fully seed the kernel's CRNG. Default is controlled
4882 !! 4032 by CONFIG_RANDOM_TRUST_CPU.
4883 random.trust_bootloader=off <<
4884 [KNL,EARLY] Disable t <<
4885 passed by the bootloa <<
4886 initialize the kernel <<
4887 <<
4888 randomize_kstack_offset= <<
4889 [KNL,EARLY] Enable or <<
4890 randomization, which <<
4891 entropy, frustrating <<
4892 that depend on stack <<
4893 cross-syscall address <<
4894 available on architec <<
4895 CONFIG_HAVE_ARCH_RAND <<
4896 Format: <bool> (1/Y/ <<
4897 Default is CONFIG_RAN <<
4898 4033
4899 ras=option[,option,...] [KNL] RAS-spe 4034 ras=option[,option,...] [KNL] RAS-specific options
4900 4035
4901 cec_disable [X86] 4036 cec_disable [X86]
4902 Disable the C 4037 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4038 see CONFIG_RAS_CEC help text.
4904 4039
4905 rcu_nocbs[=cpu-list] !! 4040 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 4041 The argument is a cpu list, as described above,
4907 as described above. !! 4042 except that the string "all" can be used to
4908 !! 4043 specify every CPU on the system.
4909 In kernels built with !! 4044
4910 enable the no-callbac !! 4045 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4911 such CPUs' callbacks !! 4046 the specified list of CPUs to be no-callback CPUs.
4912 softirq context. Inv !! 4047 Invocation of these CPUs' RCU callbacks will be
4913 callbacks will instea !! 4048 offloaded to "rcuox/N" kthreads created for that
4914 kthreads created for !! 4049 purpose, where "x" is "p" for RCU-preempt, and
4915 "p" for RCU-preempt, !! 4050 "s" for RCU-sched, and "N" is the CPU number.
4916 for the kthreads that !! 4051 This reduces OS jitter on the offloaded CPUs,
4917 "N" is the CPU number !! 4052 which can be useful for HPC and real-time
4918 the offloaded CPUs, w !! 4053 workloads. It can also improve energy efficiency
4919 and real-time workloa !! 4054 for asymmetric multiprocessors.
4920 energy efficiency for <<
4921 <<
4922 If a cpulist is passe <<
4923 list of CPUs is set t <<
4924 <<
4925 Otherwise, if the '=' <<
4926 arguments are omitted <<
4927 no-callback mode from <<
4928 toggled at runtime vi <<
4929 <<
4930 Note that this argume <<
4931 the CONFIG_RCU_NOCB_C <<
4932 4055
4933 rcu_nocb_poll [KNL] 4056 rcu_nocb_poll [KNL]
4934 Rather than requiring 4057 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4058 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4059 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4060 make these kthreads poll for callbacks.
4938 This improves the rea 4061 This improves the real-time response for the
4939 offloaded CPUs by rel 4062 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4063 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4064 energy efficiency by requiring that the kthreads
4942 periodically wake up 4065 periodically wake up to do the polling.
4943 4066
4944 rcutree.blimit= [KNL] 4067 rcutree.blimit= [KNL]
4945 Set maximum number of 4068 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4069 process in one batch.
4947 4070
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] 4071 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4072 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4073 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4074 purposes, to verify correct tree setup.
4959 4075
4960 rcutree.gp_cleanup_delay= [KNL] 4076 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4077 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4078 RCU grace-period cleanup.
4963 4079
4964 rcutree.gp_init_delay= [KNL] 4080 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4081 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4082 RCU grace-period initialization.
4967 4083
4968 rcutree.gp_preinit_delay= [KNL] 4084 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4085 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4086 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4087 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4088 the rcu_node combining tree.
4973 4089
>> 4090 rcutree.use_softirq= [KNL]
>> 4091 If set to zero, move all RCU_SOFTIRQ processing to
>> 4092 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4093 value, meaning that RCU_SOFTIRQ is used by default.
>> 4094 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4095
>> 4096 rcutree.rcu_fanout_exact= [KNL]
>> 4097 Disable autobalancing of the rcu_node combining
>> 4098 tree. This is used by rcutorture, and might
>> 4099 possibly be useful for architectures having high
>> 4100 cache-to-cache transfer latencies.
>> 4101
>> 4102 rcutree.rcu_fanout_leaf= [KNL]
>> 4103 Change the number of CPUs assigned to each
>> 4104 leaf rcu_node structure. Useful for very
>> 4105 large systems, which will choose the value 64,
>> 4106 and for NUMA systems with large remote-access
>> 4107 latencies, which will choose a value aligned
>> 4108 with the appropriate hardware boundaries.
>> 4109
>> 4110 rcutree.rcu_min_cached_objs= [KNL]
>> 4111 Minimum number of objects which are cached and
>> 4112 maintained per one CPU. Object size is equal
>> 4113 to PAGE_SIZE. The cache allows to reduce the
>> 4114 pressure to page allocator, also it makes the
>> 4115 whole algorithm to behave better in low memory
>> 4116 condition.
>> 4117
4974 rcutree.jiffies_till_first_fqs= [KNL] 4118 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4119 Set delay from grace-period initialization to
4976 first attempt to forc 4120 first attempt to force quiescent states.
4977 Units are jiffies, mi 4121 Units are jiffies, minimum value is zero,
4978 and maximum value is 4122 and maximum value is HZ.
4979 4123
4980 rcutree.jiffies_till_next_fqs= [KNL] 4124 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4125 Set delay between subsequent attempts to force
4982 quiescent states. Un 4126 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4127 value is one, and maximum value is HZ.
4984 4128
4985 rcutree.jiffies_till_sched_qs= [KNL] 4129 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4130 Set required age in jiffies for a
4987 given grace period be 4131 given grace period before RCU starts
4988 soliciting quiescent- 4132 soliciting quiescent-state help from
4989 rcu_note_context_swit 4133 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4134 If not specified, the kernel will calculate
4991 a value based on the 4135 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4136 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4137 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4138 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4139 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4140 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4141 overwritten.
4998 4142
4999 rcutree.kthread_prio= [KNL,BOOT] 4143 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4144 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4145 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4146 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4147 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4148 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4149 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4150 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4151 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4152 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 4153
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 4154 rcutree.rcu_nocb_gp_stride= [KNL]
5013 On callback-offloaded !! 4155 Set the number of NOCB callback kthreads in
5014 RCU reduces the lock !! 4156 each group, which defaults to the square root
5015 otherwise be caused b !! 4157 of the number of CPUs. Larger numbers reduce
5016 use of the ->nocb_byp !! 4158 the wakeup overhead on the global grace-period
5017 common non-flooded ca !! 4159 kthread, but increases that same overhead on
5018 the main ->cblist in !! 4160 each group's NOCB grace-period kthread.
5019 overhead of the ->noc <<
5020 But if there are too <<
5021 a single jiffy, RCU p <<
5022 the ->nocb_bypass que <<
5023 many" is supplied by <<
5024 <<
5025 rcutree.nohz_full_patience_delay= [KN <<
5026 On callback-offloaded <<
5027 disturbing RCU unless <<
5028 reached the specified <<
5029 Defaults to zero. La <<
5030 at five seconds. All <<
5031 to the nearest value <<
5032 4161
5033 rcutree.qhimark= [KNL] 4162 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4163 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4164 batch limiting is disabled.
5036 4165
5037 rcutree.qlowmark= [KNL] 4166 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4167 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4168 batch limiting is re-enabled.
5040 4169
5041 rcutree.qovld= [KNL] 4170 rcutree.qovld= [KNL]
5042 Set threshold of queu 4171 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4172 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4173 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4174 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4175 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4176 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4177 disable more aggressive help enlistment.
5049 4178
5050 rcutree.rcu_delay_page_cache_fill_mse !! 4179 rcutree.rcu_idle_gp_delay= [KNL]
5051 Set the page-cache re !! 4180 Set wakeup interval for idle CPUs that have
5052 in response to low-me !! 4181 RCU callbacks (RCU_FAST_NO_HZ=y).
5053 of permitted values i !! 4182
5054 !! 4183 rcutree.rcu_idle_lazy_gp_delay= [KNL]
5055 rcutree.rcu_divisor= [KNL] !! 4184 Set wakeup interval for idle CPUs that have
5056 Set the shift-right c !! 4185 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
5057 the callback-invocati !! 4186 Lazy RCU callbacks are those which RCU can
5058 the number of callbac !! 4187 prove do nothing more than free memory.
5059 The result will be bo <<
5060 the rcutree.blimit ke <<
5061 callbacks, the softir <<
5062 order to allow the CP <<
5063 <<
5064 Please note that this <<
5065 limit applies only to <<
5066 invocation. Offloade <<
5067 invoked in the contex <<
5068 scheduler will preemp <<
5069 <<
5070 rcutree.rcu_fanout_exact= [KNL] <<
5071 Disable autobalancing <<
5072 tree. This is used b <<
5073 possibly be useful fo <<
5074 cache-to-cache transf <<
5075 <<
5076 rcutree.rcu_fanout_leaf= [KNL] <<
5077 Change the number of <<
5078 leaf rcu_node structu <<
5079 large systems, which <<
5080 and for NUMA systems <<
5081 latencies, which will <<
5082 with the appropriate <<
5083 <<
5084 rcutree.rcu_min_cached_objs= [KNL] <<
5085 Minimum number of obj <<
5086 maintained per one CP <<
5087 to PAGE_SIZE. The cac <<
5088 pressure to page allo <<
5089 whole algorithm to be <<
5090 condition. <<
5091 <<
5092 rcutree.rcu_nocb_gp_stride= [KNL] <<
5093 Set the number of NOC <<
5094 each group, which def <<
5095 of the number of CPUs <<
5096 the wakeup overhead o <<
5097 kthread, but increase <<
5098 each group's NOCB gra <<
5099 4188
5100 rcutree.rcu_kick_kthreads= [KNL] 4189 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4190 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4191 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4192 it should at force-quiescent-state time.
5104 This wake_up() will b 4193 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4194 WARN_ONCE() splat and an ftrace_dump().
5106 4195
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] 4196 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4197 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4198 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4199 in microseconds. This defaults to zero.
5118 Larger delays increas 4200 Larger delays increase the probability of
5119 catching RCU pointer 4201 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4202 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4203 rcu_read_unlock() has completed.
5122 4204
5123 rcutree.sysrq_rcu= [KNL] 4205 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4206 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4207 rcu_node tree with an eye towards determining
5126 why a new grace perio 4208 why a new grace period has not yet started.
5127 4209
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] 4210 rcuscale.gp_async= [KNL]
5158 Measure performance o 4211 Measure performance of asynchronous
5159 grace-period primitiv 4212 grace-period primitives such as call_rcu().
5160 4213
5161 rcuscale.gp_async_max= [KNL] 4214 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4215 Specify the maximum number of outstanding
5163 callbacks per writer 4216 callbacks per writer thread. When a writer
5164 thread exceeds this l 4217 thread exceeds this limit, it invokes the
5165 corresponding flavor 4218 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4219 previously posted callbacks to drain.
5167 4220
5168 rcuscale.gp_exp= [KNL] 4221 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4222 Measure performance of expedited synchronous
5170 grace-period primitiv 4223 grace-period primitives.
5171 4224
5172 rcuscale.holdoff= [KNL] 4225 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4226 Set test-start holdoff period. The purpose of
5174 this parameter is to 4227 this parameter is to delay the start of the
5175 test until boot compl 4228 test until boot completes in order to avoid
5176 interference. 4229 interference.
5177 4230
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] 4231 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4232 Set to measure performance of kfree_rcu() flooding.
5189 4233
5190 rcuscale.kfree_rcu_test_double= [KNL] <<
5191 Test the double-argum <<
5192 If this parameter has <<
5193 rcuscale.kfree_rcu_te <<
5194 and double-argument v <<
5195 <<
5196 rcuscale.kfree_rcu_test_single= [KNL] <<
5197 Test the single-argum <<
5198 If this parameter has <<
5199 rcuscale.kfree_rcu_te <<
5200 and double-argument v <<
5201 <<
5202 rcuscale.kfree_nthreads= [KNL] 4234 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4235 The number of threads running loops of kfree_rcu().
5204 4236
5205 rcuscale.kfree_alloc_num= [KNL] 4237 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4238 Number of allocations and frees done in an iteration.
5207 4239
5208 rcuscale.kfree_loops= [KNL] 4240 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4241 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4242 of allocations and frees.
5211 4243
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] 4244 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4245 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4246 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4247 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4248 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4249 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4250 A value of "n" less than or equal to -N selects
5225 a single reader. 4251 a single reader.
5226 4252
5227 rcuscale.nwriters= [KNL] 4253 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4254 Set number of RCU writers. The values operate
5229 the same as for rcusc 4255 the same as for rcuscale.nreaders.
5230 N, where N is the num 4256 N, where N is the number of CPUs
5231 4257
5232 rcuscale.scale_type= [KNL] !! 4258 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4259 Specify the RCU implementation to test.
5234 4260
5235 rcuscale.shutdown= [KNL] 4261 rcuscale.shutdown= [KNL]
5236 Shut the system down 4262 Shut the system down after performance tests
5237 complete. This is us 4263 complete. This is useful for hands-off automated
5238 testing. 4264 testing.
5239 4265
5240 rcuscale.verbose= [KNL] 4266 rcuscale.verbose= [KNL]
5241 Enable additional pri 4267 Enable additional printk() statements.
5242 4268
5243 rcuscale.writer_holdoff= [KNL] 4269 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4270 Write-side holdoff between grace periods,
5245 in microseconds. The 4271 in microseconds. The default of zero says
5246 no holdoff. 4272 no holdoff.
5247 4273
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] 4274 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4275 Set duration of force_quiescent_state bursts
5255 in microseconds. 4276 in microseconds.
5256 4277
5257 rcutorture.fqs_holdoff= [KNL] 4278 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4279 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4280 in microseconds.
5260 4281
5261 rcutorture.fqs_stutter= [KNL] 4282 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4283 Set wait time between force_quiescent_state bursts
5263 in seconds. 4284 in seconds.
5264 4285
5265 rcutorture.fwd_progress= [KNL] 4286 rcutorture.fwd_progress= [KNL]
5266 Specifies the number !! 4287 Enable RCU grace-period forward-progress testing
5267 for RCU grace-period <<
5268 for the types of RCU 4288 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread <<
5270 greater than the numb <<
5271 of CPUs to be used. <<
5272 4289
5273 rcutorture.fwd_progress_div= [KNL] 4290 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4291 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4292 period to do tight-loop forward-progress testing.
5276 4293
5277 rcutorture.fwd_progress_holdoff= [KNL 4294 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4295 Number of seconds to wait between successive
5279 forward-progress test 4296 forward-progress tests.
5280 4297
5281 rcutorture.fwd_progress_need_resched= 4298 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4299 Enclose cond_resched() calls within checks for
5283 need_resched() during 4300 need_resched() during tight-loop forward-progress
5284 testing. 4301 testing.
5285 4302
5286 rcutorture.gp_cond= [KNL] 4303 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4304 Use conditional/asynchronous update-side
5288 primitives, if availa 4305 primitives, if available.
5289 4306
5290 rcutorture.gp_exp= [KNL] 4307 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4308 Use expedited update-side primitives, if available.
5292 4309
5293 rcutorture.gp_normal= [KNL] 4310 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4311 Use normal (non-expedited) asynchronous
5295 update-side primitive 4312 update-side primitives, if available.
5296 4313
5297 rcutorture.gp_sync= [KNL] 4314 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4315 Use normal (non-expedited) synchronous
5299 update-side primitive 4316 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4317 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4318 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4319 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4320 they are all non-zero.
5304 4321
5305 rcutorture.irqreader= [KNL] 4322 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4323 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4324 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4325 flavors take kindly to this sort of thing.
5309 4326
5310 rcutorture.leakpointer= [KNL] 4327 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4328 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4329 This can of course result in splats, and is
5313 intended to test the 4330 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4331 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4332 such leaks.
5316 4333
5317 rcutorture.n_barrier_cbs= [KNL] 4334 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4335 Set callbacks/threads for rcu_barrier() testing.
5319 4336
5320 rcutorture.nfakewriters= [KNL] 4337 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4338 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4339 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4340 test, hence the "fake".
5324 4341
5325 rcutorture.nocbs_nthreads= [KNL] <<
5326 Set number of RCU cal <<
5327 Zero (the default) di <<
5328 <<
5329 rcutorture.nocbs_toggle= [KNL] <<
5330 Set the delay in mill <<
5331 callback-offload togg <<
5332 <<
5333 rcutorture.nreaders= [KNL] 4342 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4343 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4344 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4345 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 4346 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 4347 (the number of CPUs), -3 selects N+1, and so on.
5339 4348
5340 rcutorture.object_debug= [KNL] 4349 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 4350 Enable debug-object double-call_rcu() testing.
5342 4351
5343 rcutorture.onoff_holdoff= [KNL] 4352 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 4353 Set time (s) after boot for CPU-hotplug testing.
5345 4354
5346 rcutorture.onoff_interval= [KNL] 4355 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 4356 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 4357 or zero to disable CPU-hotplug testing.
5349 4358
5350 rcutorture.read_exit= [KNL] 4359 rcutorture.read_exit= [KNL]
5351 Set the number of rea 4360 Set the number of read-then-exit kthreads used
5352 to test the interacti 4361 to test the interaction of RCU updaters and
5353 task-exit processing. 4362 task-exit processing.
5354 4363
5355 rcutorture.read_exit_burst= [KNL] 4364 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 4365 The number of times in a given read-then-exit
5357 episode that a set of 4366 episode that a set of read-then-exit kthreads
5358 is spawned. 4367 is spawned.
5359 4368
5360 rcutorture.read_exit_delay= [KNL] 4369 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 4370 The delay, in seconds, between successive
5362 read-then-exit testin 4371 read-then-exit testing episodes.
5363 4372
5364 rcutorture.shuffle_interval= [KNL] 4373 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 4374 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 4375 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 4376 during the rcutorture test.
5368 4377
5369 rcutorture.shutdown_secs= [KNL] 4378 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 4379 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 4380 is useful for hands-off automated testing.
5372 4381
5373 rcutorture.stall_cpu= [KNL] 4382 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 4383 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 4384 warnings, zero to disable.
5376 4385
5377 rcutorture.stall_cpu_block= [KNL] 4386 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 4387 Sleep while stalling if set. This will result
5379 in warnings from pree !! 4388 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 4389 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 4390
5391 rcutorture.stall_cpu_holdoff= [KNL] 4391 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 4392 Time to wait (s) after boot before inducing stall.
5393 4393
5394 rcutorture.stall_cpu_irqsoff= [KNL] 4394 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 4395 Disable interrupts while stalling if set.
5396 4396
5397 rcutorture.stall_gp_kthread= [KNL] 4397 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 4398 Duration (s) of forced sleep within RCU
5399 grace-period kthread 4399 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 4400 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 4401 and stall_gp_kthread are specified, the
5402 kthread is starved fi 4402 kthread is starved first, then the CPU.
5403 4403
5404 rcutorture.stat_interval= [KNL] 4404 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 4405 Time (s) between statistics printk()s.
5406 4406
5407 rcutorture.stutter= [KNL] 4407 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 4408 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 4409 five seconds causes the test to run for five seconds,
5410 wait for five seconds 4410 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 4411 ability to transition abruptly to and from idle.
5412 4412
5413 rcutorture.test_boost= [KNL] 4413 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 4414 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 4415 "Maybe" means test if the RCU implementation
5416 under test support RC 4416 under test support RCU priority boosting.
5417 4417
5418 rcutorture.test_boost_duration= [KNL] 4418 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 4419 Duration (s) of each individual boost test.
5420 4420
5421 rcutorture.test_boost_interval= [KNL] 4421 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 4422 Interval (s) between each boost test.
5423 4423
5424 rcutorture.test_no_idle_hz= [KNL] 4424 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 4425 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 4426 rcutorture.shuffle_interval parameter.
5427 4427
5428 rcutorture.torture_type= [KNL] 4428 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 4429 Specify the RCU implementation to test.
5430 4430
5431 rcutorture.verbose= [KNL] 4431 rcutorture.verbose= [KNL]
5432 Enable additional pri 4432 Enable additional printk() statements.
5433 4433
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 4434 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 4435 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 4436 stall warning.
5437 4437
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 4438 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 4439 Suppress RCU CPU stall warning messages.
5446 4440
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 4441 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 4442 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 4443 rcutorture writer stall warnings that occur
5450 during early boot, th 4444 during early boot, that is, during the time
5451 before the init task 4445 before the init task is spawned.
5452 4446
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 4447 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 4448 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon <<
5456 value is 300 seconds. <<
5457 <<
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ <<
5459 Set timeout for exped <<
5460 messages. The value <<
5461 and the maximum allow <<
5462 milliseconds. Please <<
5463 adjusted to an arch t <<
5464 Setting this to zero <<
5465 rcupdate.rcu_cpu_stal <<
5466 conversion from secon <<
5467 <<
5468 rcupdate.rcu_cpu_stall_cputime= [KNL] <<
5469 Provide statistics on <<
5470 interrupts and tasks <<
5471 multiple continuous R <<
5472 begin at half of the <<
5473 <<
5474 rcupdate.rcu_exp_stall_task_details= <<
5475 Print stack dumps of <<
5476 current expedited RCU <<
5477 expedited RCU CPU sta <<
5478 4449
5479 rcupdate.rcu_expedited= [KNL] 4450 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 4451 Use expedited grace-period primitives, for
5481 example, synchronize_ 4452 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 4453 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 4454 but can increase CPU utilization, degrade
5484 real-time latency, an 4455 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 4456 No effect on CONFIG_TINY_RCU kernels.
5486 4457
5487 rcupdate.rcu_normal= [KNL] 4458 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 4459 Use only normal grace-period primitives,
5489 for example, synchron 4460 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 4461 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 4462 real-time latency, CPU utilization, and
5492 energy efficiency, bu 4463 energy efficiency, but can expose users to
5493 increased grace-perio 4464 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 4465 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 4466 CONFIG_TINY_RCU kernels.
5496 4467
5497 rcupdate.rcu_normal_after_boot= [KNL] 4468 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 4469 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 4470 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 4471 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 4472 on CONFIG_TINY_RCU kernels.
5502 4473
5503 But note that CONFIG_ <<
5504 this kernel boot para <<
5505 it to the value one, <<
5506 post-boot attempt at <<
5507 period to instead use <<
5508 grace-period processi <<
5509 <<
5510 rcupdate.rcu_task_collapse_lim= [KNL] <<
5511 Set the maximum numbe <<
5512 at the beginning of a <<
5513 the RCU Tasks flavors <<
5514 a single callback que <<
5515 occurs when rcupdate. <<
5516 set to the default va <<
5517 <<
5518 rcupdate.rcu_task_contend_lim= [KNL] <<
5519 Set the minimum numbe <<
5520 lock-contention event <<
5521 cause the RCU Tasks f <<
5522 callback queuing. Th <<
5523 when rcupdate.rcu_tas <<
5524 the default value of <<
5525 <<
5526 rcupdate.rcu_task_enqueue_lim= [KNL] <<
5527 Set the number of cal <<
5528 RCU Tasks family of R <<
5529 of -1 allows this to <<
5530 dynamically) adjusted <<
5531 for use in testing. <<
5532 <<
5533 rcupdate.rcu_task_ipi_delay= [KNL] 4474 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 4475 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 4476 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 4477 of a given grace period. Setting a large
5537 number avoids disturb 4478 number avoids disturbing real-time workloads,
5538 but lengthens grace p 4479 but lengthens grace periods.
5539 4480
5540 rcupdate.rcu_task_lazy_lim= [KNL] <<
5541 Number of callbacks o <<
5542 cancel laziness on th <<
5543 cancellation of lazin <<
5544 doing so increases th <<
5545 callback flooding. <<
5546 <<
5547 rcupdate.rcu_task_stall_info= [KNL] <<
5548 Set initial timeout i <<
5549 informational message <<
5550 of the problem for th <<
5551 wait for ten minutes. <<
5552 only printed prior to <<
5553 for a given grace per <<
5554 less than or equal to <<
5555 seconds. A change in <<
5556 until the beginning o <<
5557 <<
5558 rcupdate.rcu_task_stall_info_mult= [K <<
5559 Multiplier for time i <<
5560 RCU task stall inform <<
5561 RCU tasks grace perio <<
5562 to one through ten, i <<
5563 the value three, so t <<
5564 message is printed 10 <<
5565 period, the second at <<
5566 160 seconds, and then <<
5567 seconds would prevent <<
5568 <<
5569 rcupdate.rcu_task_stall_timeout= [KNL 4481 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 4482 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 4483 messages. Disable with a value less than or equal
5572 than or equal to zero !! 4484 to zero.
5573 A change in value doe <<
5574 the beginning of the <<
5575 <<
5576 rcupdate.rcu_tasks_lazy_ms= [KNL] <<
5577 Set timeout in millis <<
5578 callback batching for <<
5579 A negative value will <<
5580 of zero will disable <<
5581 always disabled for s <<
5582 <<
5583 rcupdate.rcu_tasks_rude_lazy_ms= [KNL <<
5584 Set timeout in millis <<
5585 Rude asynchronous cal <<
5586 call_rcu_tasks_rude() <<
5587 will take the default <<
5588 disable batching. Ba <<
5589 for synchronize_rcu_t <<
5590 <<
5591 rcupdate.rcu_tasks_trace_lazy_ms= [KN <<
5592 Set timeout in millis <<
5593 Trace asynchronous ca <<
5594 call_rcu_tasks_trace( <<
5595 will take the default <<
5596 disable batching. Ba <<
5597 for synchronize_rcu_t <<
5598 4485
5599 rcupdate.rcu_self_test= [KNL] 4486 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 4487 Run the RCU early boot self tests
5601 4488
5602 rdinit= [KNL] 4489 rdinit= [KNL]
5603 Format: <full_path> 4490 Format: <full_path>
5604 Run specified binary 4491 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 4492 used for early userspace startup. See initrd.
5606 4493
5607 rdrand= [X86,EARLY] !! 4494 rdrand= [X86]
5608 force - Override the 4495 force - Override the decision by the kernel to hide the
5609 advertisement 4496 advertisement of RDRAND support (this affects
5610 certain AMD p 4497 certain AMD processors because of buggy BIOS
5611 support, spec 4498 support, specifically around the suspend/resume
5612 path). 4499 path).
5613 4500
5614 rdt= [HW,X86,RDT] 4501 rdt= [HW,X86,RDT]
5615 Turn on/off individua 4502 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 4503 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 4504 mba.
5618 E.g. to turn on cmt a 4505 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 4506 rdt=cmt,!mba
5620 4507
5621 reboot= [KNL] 4508 reboot= [KNL]
5622 Format (x86 or x86_64 4509 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 4510 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 4511 [[,]s[mp]#### \
5625 [[,]b[ios] | 4512 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 4513 [[,]f[orce]
5627 Where reboot_mode is 4514 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 4515 (prefix with 'panic_' to set mode for panic
5629 reboo 4516 reboot only),
5630 reboot_type is 4517 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 4518 reboot_force is either force or not specified,
5632 reboot_cpu is s 4519 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 4520 to be used for rebooting.
5634 4521
5635 refscale.holdoff= [KNL] 4522 refscale.holdoff= [KNL]
5636 Set test-start holdof 4523 Set test-start holdoff period. The purpose of
5637 this parameter is to 4524 this parameter is to delay the start of the
5638 test until boot compl 4525 test until boot completes in order to avoid
5639 interference. 4526 interference.
5640 4527
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] 4528 refscale.loops= [KNL]
5648 Set the number of loo 4529 Set the number of loops over the synchronization
5649 primitive under test. 4530 primitive under test. Increasing this number
5650 reduces noise due to 4531 reduces noise due to loop start/end overhead,
5651 but the default has a 4532 but the default has already reduced the per-pass
5652 noise to a handful of 4533 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 4534 x86 laptops.
5654 4535
5655 refscale.nreaders= [KNL] 4536 refscale.nreaders= [KNL]
5656 Set number of readers 4537 Set number of readers. The default value of -1
5657 selects N, where N is 4538 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 4539 of CPUs. A value of zero is an interesting choice.
5659 4540
5660 refscale.nruns= [KNL] 4541 refscale.nruns= [KNL]
5661 Set number of runs, e 4542 Set number of runs, each of which is dumped onto
5662 the console log. 4543 the console log.
5663 4544
5664 refscale.readdelay= [KNL] 4545 refscale.readdelay= [KNL]
5665 Set the read-side cri 4546 Set the read-side critical-section duration,
5666 measured in microseco 4547 measured in microseconds.
5667 4548
5668 refscale.scale_type= [KNL] 4549 refscale.scale_type= [KNL]
5669 Specify the read-prot 4550 Specify the read-protection implementation to test.
5670 4551
5671 refscale.shutdown= [KNL] 4552 refscale.shutdown= [KNL]
5672 Shut down the system 4553 Shut down the system at the end of the performance
5673 test. This defaults 4554 test. This defaults to 1 (shut it down) when
5674 refscale is built int 4555 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 4556 it running) when refscale is built as a module.
5676 4557
5677 refscale.verbose= [KNL] 4558 refscale.verbose= [KNL]
5678 Enable additional pri 4559 Enable additional printk() statements.
5679 4560
5680 refscale.verbose_batched= [KNL] <<
5681 Batch the additional <<
5682 (the default) or nega <<
5683 print every Nth verbo <<
5684 specified. <<
5685 <<
5686 regulator_ignore_unused <<
5687 [REGULATOR] <<
5688 Prevents regulator fr <<
5689 that are unused, due <<
5690 be useful for debug a <<
5691 needed on a platform <<
5692 <<
5693 relax_domain_level= 4561 relax_domain_level=
5694 [KNL, SMP] Set schedu 4562 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 4563 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 4564
5697 reserve= [KNL,BUGS] Force kern 4565 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 4566 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 4567 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 4568 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 4569 is assumed to be I/O ports; otherwise it is memory.
5702 4570
5703 reserve_mem= [RAM] !! 4571 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] 4572 Format: nn[KMG]
5727 Reserves a hole at th 4573 Reserves a hole at the top of the kernel virtual
5728 address space. 4574 address space.
5729 4575
>> 4576 reservelow= [X86]
>> 4577 Format: nn[K]
>> 4578 Set the amount of memory to reserve for BIOS at
>> 4579 the bottom of the address space.
>> 4580
5730 reset_devices [KNL] Force drivers t 4581 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 4582 during initialization.
5732 4583
5733 resume= [SWSUSP] 4584 resume= [SWSUSP]
5734 Specify the partition 4585 Specify the partition device for software suspend
5735 Format: 4586 Format:
5736 {/dev/<dev> | PARTUUI 4587 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 4588
5738 resume_offset= [SWSUSP] 4589 resume_offset= [SWSUSP]
5739 Specify the offset fr 4590 Specify the offset from the beginning of the partition
5740 given by "resume=" at 4591 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 4592 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 4593 See Documentation/power/swsusp-and-swap-files.rst
5743 4594
5744 resumedelay= [HIBERNATION] Delay ( 4595 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 4596 read the resume files
5746 4597
5747 resumewait [HIBERNATION] Wait (i 4598 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 4599 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 4600 (e.g. USB and MMC devices).
5750 4601
5751 retain_initrd [RAM] Keep initrd mem !! 4602 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 4603 noresume Don't check if there's a hibernation image
5753 !! 4604 present during boot.
5754 retbleed= [X86] Control mitigat !! 4605 nocompress Don't compress/decompress hibernation images.
5755 Speculative Code Exec !! 4606 no Disable hibernation and resume.
5756 vulnerability. !! 4607 protect_image Turn on image protection during restoration
5757 !! 4608 (that will set all pages holding image data
5758 AMD-based UNRET and I !! 4609 during restoration read-only).
5759 sibling threads from <<
5760 sibling threads. For <<
5761 cessors that support <<
5762 that don't. <<
5763 <<
5764 off - no mit <<
5765 auto - automa <<
5766 auto,nosmt - automa <<
5767 disabl <<
5768 the fu <<
5769 and ol <<
5770 ibpb - On AMD <<
5771 window <<
5772 Safe, <<
5773 enable <<
5774 on Int <<
5775 ibpb,nosmt - Like " <<
5776 when S <<
5777 the al <<
5778 have S <<
5779 unret - Force <<
5780 only e <<
5781 system <<
5782 unret,nosmt - Like u <<
5783 is not <<
5784 system <<
5785 <<
5786 Selecting 'auto' will <<
5787 time according to the <<
5788 4610
5789 Not specifying this o !! 4611 retain_initrd [RAM] Keep initrd memory after extraction
5790 4612
5791 rfkill.default_state= 4613 rfkill.default_state=
5792 0 "airplane mode". All 4614 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 4615 etc. communication is blocked by default.
5794 1 Unblocked. 4616 1 Unblocked.
5795 4617
5796 rfkill.master_switch_mode= 4618 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 4619 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 4620 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 4621 blocked and the previous configuration.
5800 2 The "airplane mode" b 4622 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 4623 blocked and everything unblocked.
5802 4624
>> 4625 rhash_entries= [KNL,NET]
>> 4626 Set number of hash buckets for route cache
>> 4627
5803 ring3mwait=disable 4628 ring3mwait=disable
5804 [KNL] Disable ring 3 4629 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 4630 CPUs.
5806 4631
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 4632 ro [KNL] Mount root device read-only on boot
5815 4633
5816 rodata= [KNL,EARLY] !! 4634 rodata= [KNL]
5817 on Mark read-only kernel 4635 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 4636 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 4637
5822 rockchip.usb_uart 4638 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 4639 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 4640 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 4641 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 4642 port and the regular usb controller gets disabled.
5828 4643
5829 root= [KNL] Root filesystem 4644 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 4645 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 4646
5837 rootdelay= [KNL] Delay (in secon 4647 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 4648 mount the root filesystem
5839 4649
5840 rootflags= [KNL] Set root filesy 4650 rootflags= [KNL] Set root filesystem mount option string
5841 4651
5842 rootfstype= [KNL] Set root filesy 4652 rootfstype= [KNL] Set root filesystem type
5843 4653
5844 rootwait [KNL] Wait (indefinit 4654 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 4655 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 4656 (e.g. USB and MMC devices).
5847 4657
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 4658 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 4659 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 4660 Memory area to be used by remote processor image,
5855 managed by CMA. 4661 managed by CMA.
5856 4662
5857 rw [KNL] Mount root devi 4663 rw [KNL] Mount root device read-write on boot
5858 4664
5859 S [KNL] Run init in sin 4665 S [KNL] Run init in single mode
5860 4666
5861 s390_iommu= [HW,S390] 4667 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 4668 Set s390 IOTLB flushing mode
5863 strict 4669 strict
5864 With strict flushing !! 4670 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 4671 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 4672 which is faster.
5867 iommu.strict=1. <<
5868 <<
5869 s390_iommu_aperture= [KNL,S390] <<
5870 Specifies the size of <<
5871 accessible through th <<
5872 factor of the size of <<
5873 The default is 1 mean <<
5874 as many DMA addresses <<
5875 if supported by hardw <<
5876 once. With a value of <<
5877 and so on. As a speci <<
5878 restrictions other th <<
5879 cost of significant a <<
5880 4673
5881 sa1100ir [NET] 4674 sa1100ir [NET]
5882 See drivers/net/irda/ 4675 See drivers/net/irda/sa1100_ir.c.
5883 4676
5884 sched_verbose [KNL,EARLY] Enables v !! 4677 sbni= [NET] Granch SBNI12 leased line adapter
>> 4678
>> 4679 sched_debug [KNL] Enables verbose scheduler debug messages.
5885 4680
5886 schedstats= [KNL,X86] Enable or d 4681 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 4682 Allowed values are enable and disable. This feature
5888 incurs a small amount 4683 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 4684 but is useful for debugging and performance tuning.
5890 4685
5891 sched_thermal_decay_shift= 4686 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 4687 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 4688 pressure signal. Thermal pressure signal follows the
5895 default decay period 4689 default decay period of other scheduler pelt
5896 signals(usually 32 ms 4690 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 4691 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 4692 period for the thermal pressure signal by the shift
5899 value. 4693 value.
5900 i.e. with the default 4694 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 4695 sched_thermal_decay_shift thermal pressure decay pr
5902 1 4696 1 64 ms
5903 2 4697 2 128 ms
5904 and so on. 4698 and so on.
5905 Format: integer betwe 4699 Format: integer between 0 and 10
5906 Default is 0. 4700 Default is 0.
5907 4701
5908 scftorture.holdoff= [KNL] 4702 scftorture.holdoff= [KNL]
5909 Number of seconds to 4703 Number of seconds to hold off before starting
5910 test. Defaults to ze 4704 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 4705 to 10 seconds for built-in smp_call_function()
5912 tests. 4706 tests.
5913 4707
5914 scftorture.longwait= [KNL] 4708 scftorture.longwait= [KNL]
5915 Request ridiculously 4709 Request ridiculously long waits randomly selected
5916 up to the chosen limi 4710 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 4711 default) disables this feature. Please note
5918 that requesting even 4712 that requesting even small non-zero numbers of
5919 seconds can result in 4713 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 4714 softlockup complaints, and so on.
5921 4715
5922 scftorture.nthreads= [KNL] 4716 scftorture.nthreads= [KNL]
5923 Number of kthreads to 4717 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 4718 smp_call_function() family of functions.
5925 The default of -1 spe 4719 The default of -1 specifies a number of kthreads
5926 equal to the number o 4720 equal to the number of CPUs.
5927 4721
5928 scftorture.onoff_holdoff= [KNL] 4722 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 4723 Number seconds to wait after the start of the
5930 test before initiatin 4724 test before initiating CPU-hotplug operations.
5931 4725
5932 scftorture.onoff_interval= [KNL] 4726 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 4727 Number seconds to wait between successive
5934 CPU-hotplug operation 4728 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 4729 is the default) disables CPU-hotplug operations.
5936 4730
5937 scftorture.shutdown_secs= [KNL] 4731 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 4732 The number of seconds following the start of the
5939 test after which to s 4733 test after which to shut down the system. The
5940 default of zero avoid 4734 default of zero avoids shutting down the system.
5941 Non-zero values are u 4735 Non-zero values are useful for automated tests.
5942 4736
5943 scftorture.stat_interval= [KNL] 4737 scftorture.stat_interval= [KNL]
5944 The number of seconds 4738 The number of seconds between outputting the
5945 current test statisti 4739 current test statistics to the console. A value
5946 of zero disables stat 4740 of zero disables statistics output.
5947 4741
5948 scftorture.stutter_cpus= [KNL] 4742 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 4743 The number of jiffies to wait between each change
5950 to the set of CPUs un 4744 to the set of CPUs under test.
5951 4745
5952 scftorture.use_cpus_read_lock= [KNL] 4746 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 4747 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 4748 preempt_disable() to disable CPU hotplug
5955 while invoking one of 4749 while invoking one of the smp_call_function*()
5956 functions. 4750 functions.
5957 4751
5958 scftorture.verbose= [KNL] 4752 scftorture.verbose= [KNL]
5959 Enable additional pri 4753 Enable additional printk() statements.
5960 4754
5961 scftorture.weight_single= [KNL] 4755 scftorture.weight_single= [KNL]
5962 The probability weigh 4756 The probability weighting to use for the
5963 smp_call_function_sin 4757 smp_call_function_single() function with a zero
5964 "wait" parameter. A 4758 "wait" parameter. A value of -1 selects the
5965 default if all other 4759 default if all other weights are -1. However,
5966 if at least one weigh 4760 if at least one weight has some other value, a
5967 value of -1 will inst 4761 value of -1 will instead select a weight of zero.
5968 4762
5969 scftorture.weight_single_wait= [KNL] 4763 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 4764 The probability weighting to use for the
5971 smp_call_function_sin 4765 smp_call_function_single() function with a
5972 non-zero "wait" param 4766 non-zero "wait" parameter. See weight_single.
5973 4767
5974 scftorture.weight_many= [KNL] 4768 scftorture.weight_many= [KNL]
5975 The probability weigh 4769 The probability weighting to use for the
5976 smp_call_function_man 4770 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 4771 "wait" parameter. See weight_single.
5978 Note well that settin 4772 Note well that setting a high probability for
5979 this weighting can pl 4773 this weighting can place serious IPI load
5980 on the system. 4774 on the system.
5981 4775
5982 scftorture.weight_many_wait= [KNL] 4776 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 4777 The probability weighting to use for the
5984 smp_call_function_man 4778 smp_call_function_many() function with a
5985 non-zero "wait" param 4779 non-zero "wait" parameter. See weight_single
5986 and weight_many. 4780 and weight_many.
5987 4781
5988 scftorture.weight_all= [KNL] 4782 scftorture.weight_all= [KNL]
5989 The probability weigh 4783 The probability weighting to use for the
5990 smp_call_function_all 4784 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 4785 "wait" parameter. See weight_single and
5992 weight_many. 4786 weight_many.
5993 4787
5994 scftorture.weight_all_wait= [KNL] 4788 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 4789 The probability weighting to use for the
5996 smp_call_function_all 4790 smp_call_function_all() function with a
5997 non-zero "wait" param 4791 non-zero "wait" parameter. See weight_single
5998 and weight_many. 4792 and weight_many.
5999 4793
6000 skew_tick= [KNL,EARLY] Offset th !! 4794 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 4795 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 4796 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 4797 Format: { "0" | "1" }
6004 0 -- disable. (may be 4798 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 4799 1 -- enable.
6006 Note: increases power 4800 Note: increases power consumption, thus should only be
6007 enabled if running ji 4801 enabled if running jitter sensitive (HPC/RT) workloads.
6008 4802
6009 security= [SECURITY] Choose a l 4803 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 4804 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 4805 "lsm=" parameter.
6012 4806
6013 selinux= [SELINUX] Disable or 4807 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 4808 Format: { "0" | "1" }
6015 See security/selinux/ 4809 See security/selinux/Kconfig help text.
6016 0 -- disable. 4810 0 -- disable.
6017 1 -- enable. 4811 1 -- enable.
6018 Default value is 1. 4812 Default value is 1.
6019 4813
6020 serialnumber [BUGS=X86-32] !! 4814 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 4815 Format: { "0" | "1" }
>> 4816 See security/apparmor/Kconfig help text
>> 4817 0 -- disable.
>> 4818 1 -- enable.
>> 4819 Default value is set via kernel config option.
6021 4820
6022 sev=option[,option...] [X86-64] See D !! 4821 serialnumber [BUGS=X86-32]
6023 4822
6024 shapers= [NET] 4823 shapers= [NET]
6025 Maximal number of sha 4824 Maximal number of shapers.
6026 4825
6027 show_lapic= [APIC,X86] Advanced P !! 4826 simeth= [IA-64]
6028 Limit apic dumping. T !! 4827 simscsi=
6029 number of local apics !! 4828
6030 to set it to "all" by !! 4829 slram= [HW,MTD]
6031 Format: { 1 (default) <<
6032 The parameter valid i <<
6033 apic=verbose is speci <<
6034 Example: apic=debug s <<
6035 4830
6036 slab_debug[=options[,slabs][;[options !! 4831 slab_nomerge [MM]
6037 Enabling slab_debug a !! 4832 Disable merging of slabs with similar size. May be
>> 4833 necessary if there is some reason to distinguish
>> 4834 allocs to different slabs, especially in hardened
>> 4835 environments where the risk of heap overflows and
>> 4836 layout control by attackers can usually be
>> 4837 frustrated by disabling merging. This will reduce
>> 4838 most of the exposure of a heap attack to a single
>> 4839 cache (risks via metadata attacks are mostly
>> 4840 unchanged). Debug options disable merging on their
>> 4841 own.
>> 4842 For more information see Documentation/vm/slub.rst.
>> 4843
>> 4844 slab_max_order= [MM, SLAB]
>> 4845 Determines the maximum allowed order for slabs.
>> 4846 A high setting may cause OOMs due to memory
>> 4847 fragmentation. Defaults to 1 for systems with
>> 4848 more than 32MB of RAM, 0 otherwise.
>> 4849
>> 4850 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 4851 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 4852 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 4853 slub_debug can create guard zones around objects and
6040 may poison objects wh 4854 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 4855 last alloc / free. For more information see
6042 Documentation/mm/slub !! 4856 Documentation/vm/slub.rst.
6043 (slub_debug legacy na !! 4857
>> 4858 slub_memcg_sysfs= [MM, SLUB]
>> 4859 Determines whether to enable sysfs directories for
>> 4860 memory cgroup sub-caches. 1 to enable, 0 to disable.
>> 4861 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
>> 4862 Enabling this can lead to a very high number of debug
>> 4863 directories and files being created under
>> 4864 /sys/kernel/slub.
6044 4865
6045 slab_max_order= [MM] !! 4866 slub_max_order= [MM, SLUB]
6046 Determines the maximu 4867 Determines the maximum allowed order for slabs.
6047 A high setting may ca 4868 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 4869 fragmentation. For more information see
6049 Documentation/mm/slub !! 4870 Documentation/vm/slub.rst.
6050 (slub_max_order legac <<
6051 4871
6052 slab_merge [MM] !! 4872 slub_min_objects= [MM, SLUB]
6053 Enable merging of sla <<
6054 kernel is built witho <<
6055 (slub_merge legacy na <<
6056 <<
6057 slab_min_objects= [MM] <<
6058 The minimum number of 4873 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 4874 increase the slab order up to slub_max_order to
6060 generate a sufficient 4875 generate a sufficiently large slab able to contain
6061 the number of objects 4876 the number of objects indicated. The higher the number
6062 of objects the smalle 4877 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 4878 and the less frequently locks need to be acquired.
6064 For more information !! 4879 For more information see Documentation/vm/slub.rst.
6065 (slub_min_objects leg <<
6066 4880
6067 slab_min_order= [MM] !! 4881 slub_min_order= [MM, SLUB]
6068 Determines the minimu 4882 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 4883 lower than slub_max_order.
6070 Documentation/mm/slub !! 4884 For more information see Documentation/vm/slub.rst.
6071 (slub_min_order legac <<
6072 4885
6073 slab_nomerge [MM] !! 4886 slub_nomerge [MM, SLUB]
6074 Disable merging of sl !! 4887 Same with slab_nomerge. This is supported for legacy.
6075 necessary if there is !! 4888 See slab_nomerge for more information.
6076 allocs to different s <<
6077 environments where th <<
6078 layout control by att <<
6079 frustrated by disabli <<
6080 most of the exposure <<
6081 cache (risks via meta <<
6082 unchanged). Debug opt <<
6083 own. <<
6084 For more information <<
6085 (slub_nomerge legacy <<
6086 <<
6087 slram= [HW,MTD] <<
6088 4889
6089 smart2= [HW] 4890 smart2= [HW]
6090 Format: <io1>[,<io2>[ 4891 Format: <io1>[,<io2>[,...,<io8>]]
6091 4892
6092 smp.csd_lock_timeout= [KNL] <<
6093 Specify the period of <<
6094 that smp_call_functio <<
6095 for a CPU to release <<
6096 useful when diagnosin <<
6097 disabling interrupts <<
6098 of time. Defaults to <<
6099 setting a value of ze <<
6100 This feature may be m <<
6101 using the csdlock_deb <<
6102 <<
6103 smp.panic_on_ipistall= [KNL] <<
6104 If a csd_lock_timeout <<
6105 the specified number <<
6106 system. By default, <<
6107 take as long as they <<
6108 for this value provid <<
6109 <<
6110 smsc-ircc2.nopnp [HW] Don't us 4893 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 4894 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 4895 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 4896 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 4897 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 4898 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 4899 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 4900 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 4901 1: Fast pin select (default)
6119 2: ATC IRMode 4902 2: ATC IRMode
6120 4903
6121 smt= [KNL,MIPS,S390,EARLY] !! 4904 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 4905 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 4906 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 4907 actual hardware limit.
6125 Format: <integer> 4908 Format: <integer>
6126 Default: -1 (no limit 4909 Default: -1 (no limit)
6127 4910
6128 softlockup_panic= 4911 softlockup_panic=
6129 [KNL] Should the soft 4912 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 4913 Format: 0 | 1
6131 4914
6132 A value of 1 instruct 4915 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 4916 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 4917 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 4918 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 4919 respective build-time switch to that functionality.
6137 4920
6138 softlockup_all_cpu_backtrace= 4921 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 4922 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 4923 backtraces on all cpus.
6141 Format: 0 | 1 4924 Format: 0 | 1
6142 4925
6143 sonypi.*= [HW] Sony Programmabl 4926 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 4927 See Documentation/admin-guide/laptops/sonypi.rst
6145 4928
6146 spectre_bhi= [X86] Control mitigat !! 4929 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 4930 (indirect branch speculation) vulnerability.
6163 The default operation 4931 The default operation protects the kernel from
6164 user space attacks. 4932 user space attacks.
6165 4933
6166 on - unconditionall 4934 on - unconditionally enable, implies
6167 spectre_v2_use 4935 spectre_v2_user=on
6168 off - unconditionall 4936 off - unconditionally disable, implies
6169 spectre_v2_use 4937 spectre_v2_user=off
6170 auto - kernel detects 4938 auto - kernel detects whether your CPU model is
6171 vulnerable 4939 vulnerable
6172 4940
6173 Selecting 'on' will, 4941 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 4942 mitigation method at run time according to the
6175 CPU, the available mi 4943 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 4944 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 4945 compiler with which the kernel was built.
6178 4946
6179 Selecting 'on' will a 4947 Selecting 'on' will also enable the mitigation
6180 against user space to 4948 against user space to user space task attacks.
6181 4949
6182 Selecting 'off' will 4950 Selecting 'off' will disable both the kernel and
6183 the user space protec 4951 the user space protections.
6184 4952
6185 Specific mitigations 4953 Specific mitigations can also be selected manually:
6186 4954
6187 retpoline - r 4955 retpoline - replace indirect branches
6188 retpoline,generic - R !! 4956 retpoline,generic - google's original retpoline
6189 retpoline,lfence - L !! 4957 retpoline,amd - AMD-specific minimal thunk
6190 retpoline,amd - a <<
6191 eibrs - E <<
6192 eibrs,retpoline - E <<
6193 eibrs,lfence - E <<
6194 ibrs - u <<
6195 4958
6196 Not specifying this o 4959 Not specifying this option is equivalent to
6197 spectre_v2=auto. 4960 spectre_v2=auto.
6198 4961
6199 spectre_v2_user= 4962 spectre_v2_user=
6200 [X86] Control mitigat 4963 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 4964 (indirect branch speculation) vulnerability between
6202 user space tasks 4965 user space tasks
6203 4966
6204 on - Uncondition 4967 on - Unconditionally enable mitigations. Is
6205 enforced by 4968 enforced by spectre_v2=on
6206 4969
6207 off - Uncondition 4970 off - Unconditionally disable mitigations. Is
6208 enforced by 4971 enforced by spectre_v2=off
6209 4972
6210 prctl - Indirect br 4973 prctl - Indirect branch speculation is enabled,
6211 but mitigat 4974 but mitigation can be enabled via prctl
6212 per thread. 4975 per thread. The mitigation control state
6213 is inherite 4976 is inherited on fork.
6214 4977
6215 prctl,ibpb 4978 prctl,ibpb
6216 - Like "prctl 4979 - Like "prctl" above, but only STIBP is
6217 controlled 4980 controlled per thread. IBPB is issued
6218 always when 4981 always when switching between different user
6219 space proce 4982 space processes.
6220 4983
6221 seccomp 4984 seccomp
6222 - Same as "pr 4985 - Same as "prctl" above, but all seccomp
6223 threads wil 4986 threads will enable the mitigation unless
6224 they explic 4987 they explicitly opt out.
6225 4988
6226 seccomp,ibpb 4989 seccomp,ibpb
6227 - Like "secco 4990 - Like "seccomp" above, but only STIBP is
6228 controlled 4991 controlled per thread. IBPB is issued
6229 always when 4992 always when switching between different
6230 user space 4993 user space processes.
6231 4994
6232 auto - Kernel sele 4995 auto - Kernel selects the mitigation depending on
6233 the availab 4996 the available CPU features and vulnerability.
6234 4997
6235 Default mitigation: " !! 4998 Default mitigation:
>> 4999 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
6236 5000
6237 Not specifying this o 5001 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5002 spectre_v2_user=auto.
6239 5003
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= 5004 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5005 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5006 (Speculative Store Bypass vulnerability)
6254 5007
6255 Certain CPUs are vuln 5008 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5009 a common industry wide performance optimization known
6257 as "Speculative Store 5010 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5011 to the same memory location may not be observed by
6259 later loads during sp 5012 later loads during speculative execution. The idea
6260 is that such stores a 5013 is that such stores are unlikely and that they can
6261 be detected prior to 5014 be detected prior to instruction retirement at the
6262 end of a particular s 5015 end of a particular speculation execution window.
6263 5016
6264 In vulnerable process 5017 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5018 store can be used in a cache side channel attack, for
6266 example to read memor 5019 example to read memory to which the attacker does not
6267 directly have access 5020 directly have access (e.g. inside sandboxed code).
6268 5021
6269 This parameter contro 5022 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5023 Bypass optimization is used.
6271 5024
6272 On x86 the options ar 5025 On x86 the options are:
6273 5026
6274 on - Uncondition 5027 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5028 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5029 auto - Kernel detects whether the CPU model contains an
6277 implementat 5030 implementation of Speculative Store Bypass and
6278 picks the m 5031 picks the most appropriate mitigation. If the
6279 CPU is not 5032 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5033 CPU is vulnerable the default mitigation is
6281 architectur 5034 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5035 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5036 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5037 for a process by default. The state of the control
6285 is inherite 5038 is inherited on fork.
6286 seccomp - Same as "pr 5039 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5040 will disable SSB unless they explicitly opt out.
6288 5041
6289 Default mitigations: 5042 Default mitigations:
6290 X86: "prctl" !! 5043 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6291 5044
6292 On powerpc the option 5045 On powerpc the options are:
6293 5046
6294 on,auto - On Power8 a 5047 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5048 barrier on kernel entry and exit. On Power7
6296 perform a s 5049 perform a software flush on kernel entry and
6297 exit. 5050 exit.
6298 off - No action. 5051 off - No action.
6299 5052
6300 Not specifying this o 5053 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5054 spec_store_bypass_disable=auto.
6302 5055
>> 5056 spia_io_base= [HW,MTD]
>> 5057 spia_fio_base=
>> 5058 spia_pedr=
>> 5059 spia_peddr=
>> 5060
6303 split_lock_detect= 5061 split_lock_detect=
6304 [X86] Enable split lo !! 5062 [X86] Enable split lock detection
6305 5063
6306 When enabled (and if 5064 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5065 instructions that access data across cache line
6308 boundaries will resul !! 5066 boundaries will result in an alignment check exception.
6309 for split lock detect <<
6310 bus lock detection. <<
6311 5067
6312 off - not enabled 5068 off - not enabled
6313 5069
6314 warn - the kernel !! 5070 warn - the kernel will emit rate limited warnings
6315 about appli 5071 about applications triggering the #AC
6316 exception o !! 5072 exception. This mode is the default on CPUs
6317 the default !! 5073 that supports split lock detection.
6318 detection o <<
6319 behavior is <<
6320 enabled in <<
6321 5074
6322 fatal - the kernel 5075 fatal - the kernel will send SIGBUS to applications
6323 that trigge !! 5076 that trigger the #AC exception.
6324 exception. <<
6325 both featur <<
6326 <<
6327 ratelimit:N - <<
6328 Set system <<
6329 per second <<
6330 0 < N <= 10 <<
6331 <<
6332 N/A for spl <<
6333 <<
6334 5077
6335 If an #AC exception i 5078 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5079 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5080 the kernel will oops in either "warn" or "fatal"
6338 mode. 5081 mode.
6339 5082
6340 #DB exception for bus !! 5083 srbds= [X86,INTEL]
6341 CPL > 0. <<
6342 <<
6343 srbds= [X86,INTEL,EARLY] <<
6344 Control the Special R 5084 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5085 (SRBDS) mitigation.
6346 5086
6347 Certain CPUs are vuln 5087 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5088 exploit which can leak bits from the random
6349 number generator. 5089 number generator.
6350 5090
6351 By default, this issu 5091 By default, this issue is mitigated by
6352 microcode. However, 5092 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5093 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5094 much slower. Among other effects, this will
6355 result in reduced thr 5095 result in reduced throughput from /dev/urandom.
6356 5096
6357 The microcode mitigat 5097 The microcode mitigation can be disabled with
6358 the following option: 5098 the following option:
6359 5099
6360 off: Disable mitig 5100 off: Disable mitigation and remove
6361 performance i 5101 performance impact to RDRAND and RDSEED
6362 5102
6363 srcutree.big_cpu_lim [KNL] <<
6364 Specifies the number <<
6365 large system, such th <<
6366 should immediately al <<
6367 This kernel-boot para <<
6368 but takes effect only <<
6369 bits of srcutree.conv <<
6370 (decide at boot). <<
6371 <<
6372 srcutree.convert_to_big [KNL] <<
6373 Specifies under what <<
6374 srcu_struct structure <<
6375 form, that is, with a <<
6376 <<
6377 0: Never. <<
6378 1: At ini <<
6379 2: When r <<
6380 3: Decide <<
6381 0x1X: Above <<
6382 <<
6383 Either way, the srcu_ <<
6384 on the actual runtime <<
6385 instead of the compil <<
6386 <<
6387 srcutree.counter_wrap_check [KNL] 5103 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5104 Specifies how frequently to check for
6389 grace-period sequence 5105 grace-period sequence counter wrap for the
6390 srcu_data structure's 5106 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5107 The greater the number of bits set in this kernel
6392 parameter, the less f 5108 parameter, the less frequently counter wrap will
6393 be checked for. Note 5109 be checked for. Note that the bottom two bits
6394 are ignored. 5110 are ignored.
6395 5111
6396 srcutree.exp_holdoff [KNL] 5112 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5113 Specifies how many nanoseconds must elapse
6398 since the end of the 5114 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5115 a given srcu_struct until the next normal SRCU
6400 grace period will be 5116 grace period will be considered for automatic
6401 expediting. Set to z 5117 expediting. Set to zero to disable automatic
6402 expediting. 5118 expediting.
6403 5119
6404 srcutree.srcu_max_nodelay [KNL] !! 5120 ssbd= [ARM64,HW]
6405 Specifies the number <<
6406 per jiffy for which t <<
6407 worker thread will be <<
6408 delay. Beyond this li <<
6409 be rescheduled with a <<
6410 <<
6411 srcutree.srcu_max_nodelay_phase [KNL] <<
6412 Specifies the per-gra <<
6413 non-sleeping polls of <<
6414 grace period worker t <<
6415 with a sleep delay of <<
6416 rescan of the readers <<
6417 <<
6418 srcutree.srcu_retry_check_delay [KNL] <<
6419 Specifies number of m <<
6420 delay between each no <<
6421 <<
6422 srcutree.small_contention_lim [KNL] <<
6423 Specifies the number <<
6424 events per jiffy will <<
6425 initiating a conversi <<
6426 structure to big form <<
6427 srcutree.convert_to_b <<
6428 set for contention-ba <<
6429 <<
6430 ssbd= [ARM64,HW,EARLY] <<
6431 Speculative Store Byp 5121 Speculative Store Bypass Disable control
6432 5122
6433 On CPUs that are vuln 5123 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5124 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5125 firmware based mitigation, this parameter
6436 indicates how the mit 5126 indicates how the mitigation should be used:
6437 5127
6438 force-on: Unconditio 5128 force-on: Unconditionally enable mitigation for
6439 for both k 5129 for both kernel and userspace
6440 force-off: Unconditio 5130 force-off: Unconditionally disable mitigation for
6441 for both k 5131 for both kernel and userspace
6442 kernel: Always ena 5132 kernel: Always enable mitigation in the
6443 kernel, an 5133 kernel, and offer a prctl interface
6444 to allow u 5134 to allow userspace to register its
6445 interest i 5135 interest in being mitigated too.
6446 5136
6447 stack_guard_gap= [MM] 5137 stack_guard_gap= [MM]
6448 override the default 5138 override the default stack gap protection. The value
6449 is in page units and 5139 is in page units and it defines how many pages prior
6450 to (for stacks growin 5140 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5141 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5142 mapping. Default value is 256 pages.
6453 5143
6454 stack_depot_disable= [KNL,EARLY] <<
6455 Setting this to true <<
6456 disable the stack dep <<
6457 consumed by the stack <<
6458 to false. <<
6459 <<
6460 stacktrace [FTRACE] 5144 stacktrace [FTRACE]
6461 Enabled the stack tra 5145 Enabled the stack tracer on boot up.
6462 5146
6463 stacktrace_filter=[function-list] 5147 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5148 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 5149 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 5150 list of functions. This list can be changed at run
6467 time by the stack_tra 5151 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 5152 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 5153 and the stacktrace above is not needed.
6470 5154
6471 sti= [PARISC,HW] 5155 sti= [PARISC,HW]
6472 Format: <num> 5156 Format: <num>
6473 Set the STI (builtin 5157 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 5158 machines) console (graphic card) which should be used
6475 as the initial boot-c 5159 as the initial boot-console.
6476 See also comment in d 5160 See also comment in drivers/video/console/sticore.c.
6477 5161
6478 sti_font= [HW] 5162 sti_font= [HW]
6479 See comment in driver 5163 See comment in drivers/video/console/sticore.c.
6480 5164
6481 stifb= [HW] 5165 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 5166 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 5167
6484 strict_sas_size= <<
6485 [X86] <<
6486 Format: <bool> <<
6487 Enable or disable str <<
6488 against the required <<
6489 depends on the suppor <<
6490 be used to filter out <<
6491 not yet been made awa <<
6492 <<
6493 stress_hpt [PPC,EARLY] <<
6494 Limits the number of <<
6495 page table to increas <<
6496 faults on kernel addr <<
6497 <<
6498 stress_slb [PPC,EARLY] <<
6499 Limits the number of <<
6500 them frequently to in <<
6501 on kernel addresses. <<
6502 <<
6503 sunrpc.min_resvport= 5168 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 5169 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 5170 [NFS,SUNRPC]
6506 SunRPC servers often 5171 SunRPC servers often require that client requests
6507 originate from a priv 5172 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 5173 range 0 < portnr < 1024).
6509 An administrator who 5174 An administrator who wishes to reserve some of these
6510 ports for other uses 5175 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 5176 kernel's sunrpc client considers to be privileged
6512 using these two param 5177 using these two parameters to set the minimum and
6513 maximum port values. 5178 maximum port values.
6514 5179
6515 sunrpc.svc_rpc_per_connection_limit= 5180 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 5181 [NFS,SUNRPC]
6517 Limit the number of r 5182 Limit the number of requests that the server will
6518 process in parallel f 5183 process in parallel from a single connection.
6519 The default value is 5184 The default value is 0 (no limit).
6520 5185
6521 sunrpc.pool_mode= 5186 sunrpc.pool_mode=
6522 [NFS] 5187 [NFS]
6523 Control how the NFS s 5188 Control how the NFS server code allocates CPUs to
6524 service thread pools. 5189 service thread pools. Depending on how many NICs
6525 you have and where th 5190 you have and where their interrupts are bound, this
6526 option will affect wh 5191 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 5192 Note: this parameter cannot be changed while the
6528 NFS server is running 5193 NFS server is running.
6529 5194
6530 auto the serve 5195 auto the server chooses an appropriate mode
6531 automatic 5196 automatically using heuristics
6532 global a single 5197 global a single global pool contains all CPUs
6533 percpu one pool 5198 percpu one pool for each CPU
6534 pernode one pool 5199 pernode one pool for each NUMA node (equivalent
6535 to global 5200 to global on non-NUMA machines)
6536 5201
6537 sunrpc.tcp_slot_table_entries= 5202 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 5203 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 5204 [NFS,SUNRPC]
6540 Sets the upper limit 5205 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 5206 RPC calls that can be sent from the client to a
6542 server. Increasing th 5207 server. Increasing these values may allow you to
6543 improve throughput, b 5208 improve throughput, but will also increase the
6544 amount of memory rese 5209 amount of memory reserved for use by the client.
6545 5210
6546 suspend.pm_test_delay= 5211 suspend.pm_test_delay=
6547 [SUSPEND] 5212 [SUSPEND]
6548 Sets the number of se 5213 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 5214 mode before resuming the system (see
6550 /sys/power/pm_test). 5215 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 5216 is set. Default value is 5.
6552 5217
6553 svm= [PPC] 5218 svm= [PPC]
6554 Format: { on | off | 5219 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 5220 This parameter controls use of the Protected
6556 Execution Facility on 5221 Execution Facility on pSeries.
6557 5222
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 5223 swapaccount=[0|1]
6559 Format: { <int> [,<in !! 5224 [KNL] Enable accounting of swap in memory resource
>> 5225 controller if no parameter or 1 is given or disable
>> 5226 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
>> 5227
>> 5228 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
>> 5229 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 5230 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 5231 force -- force using of bounce buffers even if they
6565 wouldn't be 5232 wouldn't be automatically used by the kernel
6566 noforce -- Never use 5233 noforce -- Never use bounce buffers (for debugging)
6567 5234
6568 switches= [HW,M68k,EARLY] !! 5235 switches= [HW,M68k]
6569 5236
6570 sysctl.*= [KNL] 5237 sysctl.*= [KNL]
6571 Set a sysctl paramete 5238 Set a sysctl parameter, right before loading the init
6572 process, as if the va 5239 process, as if the value was written to the respective
6573 /proc/sys/... file. B 5240 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 5241 separators. Unrecognized parameters and invalid values
6575 are reported in the k 5242 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 5243 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 5244 Example: sysctl.vm.swappiness=40
6578 5245
>> 5246 sysfs.deprecated=0|1 [KNL]
>> 5247 Enable/disable old style sysfs layout for old udev
>> 5248 on older distributions. When this option is enabled
>> 5249 very new udev will not work anymore. When this option
>> 5250 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 5251 in older udev will not work anymore.
>> 5252 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 5253 the kernel configuration.
>> 5254
6579 sysrq_always_enabled 5255 sysrq_always_enabled
6580 [KNL] 5256 [KNL]
6581 Ignore sysrq setting 5257 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 5258 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 5259 Useful for debugging.
6584 5260
6585 tcpmhash_entries= [KNL,NET] 5261 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 5262 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 5263 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 5264 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 5265 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 5266 "tcp_no_metrics_save" section for more details.
6591 5267
6592 tdfx= [HW,DRM] 5268 tdfx= [HW,DRM]
6593 5269
6594 test_suspend= [SUSPEND] !! 5270 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 5271 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 5272 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 5273 as the system sleep state during system startup with
6599 the optional capabili 5274 the optional capability to repeat N number of times.
6600 The system is woken f 5275 The system is woken from this state using a
6601 wakeup-capable RTC al 5276 wakeup-capable RTC alarm.
6602 5277
6603 thash_entries= [KNL,NET] 5278 thash_entries= [KNL,NET]
6604 Set number of hash bu 5279 Set number of hash buckets for TCP connection
6605 5280
6606 thermal.act= [HW,ACPI] 5281 thermal.act= [HW,ACPI]
6607 -1: disable all activ 5282 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 5283 <degrees C>: override all lowest active trip points
6609 5284
6610 thermal.crt= [HW,ACPI] 5285 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 5286 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 5287 <degrees C>: override all critical trip points
6613 5288
>> 5289 thermal.nocrt= [HW,ACPI]
>> 5290 Set to disable actions on ACPI thermal zone
>> 5291 critical and hot trip points.
>> 5292
6614 thermal.off= [HW,ACPI] 5293 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 5294 1: disable ACPI thermal control
6616 5295
6617 thermal.psv= [HW,ACPI] 5296 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 5297 -1: disable all passive trip points
6619 <degrees C>: override 5298 <degrees C>: override all passive trip points to this
6620 value 5299 value
6621 5300
6622 thermal.tzp= [HW,ACPI] 5301 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 5302 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 5303 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 5304 0: no polling (default)
6626 5305
6627 threadirqs [KNL,EARLY] !! 5306 threadirqs [KNL]
6628 Force threading of al 5307 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 5308 marked explicitly IRQF_NO_THREAD.
6630 5309
6631 topology= [S390,EARLY] !! 5310 topology= [S390]
6632 Format: {off | on} 5311 Format: {off | on}
6633 Specify if the kernel 5312 Specify if the kernel should make use of the cpu
6634 topology information 5313 topology information if the hardware supports this.
6635 The scheduler will ma 5314 The scheduler will make use of this information and
6636 e.g. base its process 5315 e.g. base its process migration decisions on it.
6637 Default is on. 5316 Default is on.
6638 5317
>> 5318 topology_updates= [KNL, PPC, NUMA]
>> 5319 Format: {off}
>> 5320 Specify if the kernel should ignore (off)
>> 5321 topology updates sent by the hypervisor to this
>> 5322 LPAR.
>> 5323
6639 torture.disable_onoff_at_boot= [KNL] 5324 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 5325 Prevent the CPU-hotplug component of torturing
6641 until after init has 5326 until after init has spawned.
6642 5327
6643 torture.ftrace_dump_at_shutdown= [KNL 5328 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 5329 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 5330 even if there were no errors. This can be a
6646 very costly operation 5331 very costly operation when many torture tests
6647 are running concurren 5332 are running concurrently, especially on systems
6648 with rotating-rust st 5333 with rotating-rust storage.
6649 5334
6650 torture.verbose_sleep_frequency= [KNL !! 5335 tp720= [HW,PS2]
6651 Specifies how many ve <<
6652 emitted between each <<
6653 disables verbose-prin <<
6654 <<
6655 torture.verbose_sleep_duration= [KNL] <<
6656 Duration of each verb <<
6657 5336
6658 tpm_suspend_pcr=[HW,TPM] 5337 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 5338 Format: integer pcr id
6660 Specify that at suspe 5339 Specify that at suspend time, the tpm driver
6661 should extend the spe 5340 should extend the specified pcr with zeros,
6662 as a workaround for s 5341 as a workaround for some chips which fail to
6663 flush the last writte 5342 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 5343 This will guarantee that all the other pcrs
6665 are saved. 5344 are saved.
6666 5345
6667 tpm_tis.interrupts= [HW,TPM] <<
6668 Enable interrupts for <<
6669 for the FIFO interfac <<
6670 (0). For more informa <<
6671 defined by Trusted Co <<
6672 https://trustedcomput <<
6673 <<
6674 tp_printk [FTRACE] <<
6675 Have the tracepoints <<
6676 tracing ring buffer. <<
6677 where the system hang <<
6678 option for reading th <<
6679 ftrace_dump_on_oops. <<
6680 <<
6681 To turn off having tr <<
6682 echo 0 > /proc/sys/k <<
6683 Note, echoing 1 into <<
6684 tp_printk kernel cmdl <<
6685 <<
6686 The tp_printk_stop_on <<
6687 to stop the printing <<
6688 late_initcall_sync. <<
6689 <<
6690 ** CAUTION ** <<
6691 <<
6692 Having tracepoints se <<
6693 frequency tracepoints <<
6694 the system to live lo <<
6695 <<
6696 tp_printk_stop_on_boot [FTRACE] <<
6697 When tp_printk (above <<
6698 on the console. It ma <<
6699 printing of events du <<
6700 make the system inope <<
6701 <<
6702 This command line opt <<
6703 to console at the lat <<
6704 <<
6705 trace_buf_size=nn[KMG] 5346 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 5347 [FTRACE] will set tracing buffer size on each cpu.
6707 5348
6708 trace_clock= [FTRACE] Set the cloc <<
6709 at boot up. <<
6710 local - Use the per C <<
6711 (converted in <<
6712 depending on <<
6713 in sync betwe <<
6714 global - Event time s <<
6715 CPUs. May be <<
6716 but better fo <<
6717 counter - Simple coun <<
6718 note, some co <<
6719 infrastructur <<
6720 once per even <<
6721 uptime - Use jiffies <<
6722 perf - Use the same c <<
6723 mono - Use ktime_get_ <<
6724 mono_raw - Use ktime_ <<
6725 stamps. <<
6726 boot - Use ktime_get_ <<
6727 Architectures may add <<
6728 Documentation/trace/f <<
6729 <<
6730 trace_event=[event-list] 5349 trace_event=[event-list]
6731 [FTRACE] Set and star 5350 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 5351 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 5352 comma-separated list of trace events to enable. See
6734 also Documentation/tr 5353 also Documentation/trace/events.rst
6735 5354
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] 5355 trace_options=[option-list]
6757 [FTRACE] Enable or di 5356 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 5357 The option-list is a comma delimited list of options
6759 that can be enabled o 5358 that can be enabled or disabled just as if you were
6760 to echo the option na 5359 to echo the option name into
6761 5360
6762 /sys/kernel/traci !! 5361 /sys/kernel/debug/tracing/trace_options
6763 5362
6764 For example, to enabl 5363 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 5364 stack trace of each event), add to the command line:
6766 5365
6767 trace_options=s 5366 trace_options=stacktrace
6768 5367
6769 See also Documentatio 5368 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 5369 section.
6771 5370
6772 trace_trigger=[trigger-list] !! 5371 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 5372 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 5373 tracing ring buffer. This is useful for early boot up
6775 filter. !! 5374 where the system hangs or reboots and does not give the
6776 !! 5375 option for reading the tracing buffer or performing a
6777 The format is is "tra !! 5376 ftrace_dump_on_oops.
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 5377
6784 The above will enable !! 5378 To turn off having tracepoints sent to printk,
6785 event but only trigge !! 5379 echo 0 > /proc/sys/kernel/tracepoint_printk
6786 event is "2" (TASK_UN !! 5380 Note, echoing 1 into this file without the
>> 5381 tracepoint_printk kernel cmdline option has no effect.
6787 5382
6788 See also "Event trigg !! 5383 ** CAUTION **
6789 5384
>> 5385 Having tracepoints sent to printk() and activating high
>> 5386 frequency tracepoints such as irq or sched, can cause
>> 5387 the system to live lock.
6790 5388
6791 traceoff_on_warning 5389 traceoff_on_warning
6792 [FTRACE] enable this 5390 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 5391 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 5392 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 5393 file located in /sys/kernel/debug/tracing/
6796 5394
6797 This option is useful 5395 This option is useful, as it disables the trace before
6798 the WARNING dump is c 5396 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 5397 be filled with content caused by the warning output.
6800 5398
6801 This option can also 5399 This option can also be set at run time via the sysctl
6802 option: kernel/trace 5400 option: kernel/traceoff_on_warning
6803 5401
6804 transparent_hugepage= 5402 transparent_hugepage=
6805 [KNL] 5403 [KNL]
6806 Format: [always|madvi 5404 Format: [always|madvise|never]
6807 Can be used to contro 5405 Can be used to control the default behavior of the system
6808 with respect to trans 5406 with respect to transparent hugepages.
6809 See Documentation/adm 5407 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 5408 for more details.
6811 5409
6812 trusted.source= [KEYS] <<
6813 Format: <string> <<
6814 This parameter identi <<
6815 for trusted keys impl <<
6816 sources: <<
6817 - "tpm" <<
6818 - "tee" <<
6819 - "caam" <<
6820 - "dcp" <<
6821 If not specified then <<
6822 the trust source list <<
6823 first trust source as <<
6824 successfully during i <<
6825 <<
6826 trusted.rng= [KEYS] <<
6827 Format: <string> <<
6828 The RNG used to gener <<
6829 Can be one of: <<
6830 - "kernel" <<
6831 - the same value as t <<
6832 - "default" <<
6833 If not specified, "de <<
6834 the RNG's choice is l <<
6835 <<
6836 trusted.dcp_use_otp_key <<
6837 This is intended to b <<
6838 trusted.source=dcp an <<
6839 instead of the DCP UN <<
6840 <<
6841 trusted.dcp_skip_zk_test <<
6842 This is intended to b <<
6843 trusted.source=dcp an <<
6844 blob key is all zeros <<
6845 having this key zero' <<
6846 scenarios. <<
6847 <<
6848 tsc= Disable clocksource s 5410 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 5411 Format: <string>
6850 [x86] reliable: mark 5412 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 5413 disables clocksource verification at runtime, as well
6852 as the stability chec 5414 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 5415 high-resolution timer mode on older hardware, and in
6854 virtualized environme 5416 virtualized environment.
6855 [x86] noirqtime: Do n 5417 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 5418 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 5419 platforms where RDTSC is slow and this accounting
6858 can add overhead. 5420 can add overhead.
6859 [x86] unstable: mark 5421 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 5422 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 5423 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 5424 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 5425 in situations with strict latency requirements (where
6864 interruptions from cl 5426 interruptions from clocksource watchdog are not
6865 acceptable). 5427 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 5428
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 5429 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 5430 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 5431 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 5432 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 5433 Format: <unsigned int>
6882 5434
6883 tsx= [X86] Control Transac 5435 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 5436 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 5437 support TSX control.
6886 5438
6887 This parameter contro 5439 This parameter controls the TSX feature. The options are:
6888 5440
6889 on - Enable TSX 5441 on - Enable TSX on the system. Although there are
6890 mitigations f 5442 mitigations for all known security vulnerabilities,
6891 TSX has been 5443 TSX has been known to be an accelerator for
6892 several previ 5444 several previous speculation-related CVEs, and
6893 so there may 5445 so there may be unknown security risks associated
6894 with leaving 5446 with leaving it enabled.
6895 5447
6896 off - Disable TSX 5448 off - Disable TSX on the system. (Note that this
6897 option takes 5449 option takes effect only on newer CPUs which are
6898 not vulnerabl 5450 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 5451 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 5452 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 5453 update. This new MSR allows for the reliable
6902 deactivation 5454 deactivation of the TSX functionality.)
6903 5455
6904 auto - Disable TSX 5456 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 5457 otherwise enable TSX on the system.
6906 5458
6907 Not specifying this o 5459 Not specifying this option is equivalent to tsx=off.
6908 5460
6909 See Documentation/adm 5461 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 5462 for more details.
6911 5463
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 5464 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 5465 Abort (TAA) vulnerability.
6914 5466
6915 Similar to Micro-arch 5467 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 5468 certain CPUs that support Transactional
6917 Synchronization Exten 5469 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 5470 exploit against CPU internal buffers which can forward
6919 information to a disc 5471 information to a disclosure gadget under certain
6920 conditions. 5472 conditions.
6921 5473
6922 In vulnerable process 5474 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 5475 data can be used in a cache side channel attack, to
6924 access data to which 5476 access data to which the attacker does not have direct
6925 access. 5477 access.
6926 5478
6927 This parameter contro 5479 This parameter controls the TAA mitigation. The
6928 options are: 5480 options are:
6929 5481
6930 full - Enable T 5482 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 5483 if TSX is enabled.
6932 5484
6933 full,nosmt - Enable T 5485 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 5486 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 5487 is not disabled because CPU is not
6936 vulnerab 5488 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 5489 off - Unconditionally disable TAA mitigation
6938 5490
6939 On MDS-affected machi 5491 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 5492 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 5493 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 5494 this mitigation, you need to specify mds=off too.
6943 5495
6944 Not specifying this o 5496 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 5497 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 5498 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 5499 required and doesn't provide any additional
6948 mitigation. 5500 mitigation.
6949 5501
6950 For details see: 5502 For details see:
6951 Documentation/admin-g 5503 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 5504
6953 turbografx.map[2|3]= [HW,JOY] 5505 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 5506 TurboGraFX parallel port interface
6955 Format: 5507 Format:
6956 <port#>,<js1>,<js2>,< 5508 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 5509 See also Documentation/input/devices/joystick-parport.rst
6958 5510
6959 udbg-immortal [PPC] When debugging 5511 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 5512 happen after console_init() and before a proper
6961 console driver takes 5513 console driver takes over, this boot options might
6962 help "seeing" what's 5514 help "seeing" what's going on.
6963 5515
6964 uhash_entries= [KNL,NET] 5516 uhash_entries= [KNL,NET]
6965 Set number of hash bu 5517 Set number of hash buckets for UDP/UDP-Lite connections
6966 5518
6967 uhci-hcd.ignore_oc= 5519 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 5520 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 5521 Some badly-designed motherboards generate lots of
6970 bogus events, for por 5522 bogus events, for ports that aren't wired to
6971 anything. Set this p 5523 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 5524 Note that genuine overcurrent events won't be
6973 reported either. 5525 reported either.
6974 5526
6975 unknown_nmi_panic 5527 unknown_nmi_panic
6976 [X86] Cause panic on 5528 [X86] Cause panic on unknown NMI.
6977 5529
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= 5530 usbcore.authorized_default=
6985 [USB] Default USB dev 5531 [USB] Default USB device authorization:
6986 (default -1 = authori !! 5532 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 5533 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 5534 if device connected to internal port)
6989 5535
6990 usbcore.autosuspend= 5536 usbcore.autosuspend=
6991 [USB] The autosuspend 5537 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 5538 for newly-detected USB devices (default 2). This
6993 is the time required 5539 is the time required before an idle device will be
6994 autosuspended. Devic 5540 autosuspended. Devices for which the delay is set
6995 to a negative value w 5541 to a negative value won't be autosuspended at all.
6996 5542
6997 usbcore.usbfs_snoop= 5543 usbcore.usbfs_snoop=
6998 [USB] Set to log all 5544 [USB] Set to log all usbfs traffic (default 0 = off).
6999 5545
7000 usbcore.usbfs_snoop_max= 5546 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 5547 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 5548 (default = 65536).
7003 5549
7004 usbcore.blinkenlights= 5550 usbcore.blinkenlights=
7005 [USB] Set to cycle le 5551 [USB] Set to cycle leds on hubs (default 0 = off).
7006 5552
7007 usbcore.old_scheme_first= 5553 usbcore.old_scheme_first=
7008 [USB] Start with the 5554 [USB] Start with the old device initialization
7009 scheme (default 0 = o 5555 scheme (default 0 = off).
7010 5556
7011 usbcore.usbfs_memory_mb= 5557 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 5558 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 5559 usbfs (default = 16, 0 = max = 2047).
7014 5560
7015 usbcore.use_both_schemes= 5561 usbcore.use_both_schemes=
7016 [USB] Try the other d 5562 [USB] Try the other device initialization scheme
7017 if the first one fail 5563 if the first one fails (default 1 = enabled).
7018 5564
7019 usbcore.initial_descriptor_timeout= 5565 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 5566 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 5567 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 5568 (default 5000 = 5.0 seconds).
7023 5569
7024 usbcore.nousb [USB] Disable the USB 5570 usbcore.nousb [USB] Disable the USB subsystem
7025 5571
7026 usbcore.quirks= 5572 usbcore.quirks=
7027 [USB] A list of quirk 5573 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 5574 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 5575 commas. Each entry has the form
7030 VendorID:ProductID:Fl 5576 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 5577 numbers and Flags is a set of letters. Each letter
7032 will change the built 5578 will change the built-in quirk; setting it if it is
7033 clear and clearing it 5579 clear and clearing it if it is set. The letters have
7034 the following meaning 5580 the following meanings:
7035 a = USB_QUIRK 5581 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 5582 descriptors must not be fetched using
7037 a 255 5583 a 255-byte read);
7038 b = USB_QUIRK 5584 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 5585 correctly so reset it instead);
7040 c = USB_QUIRK 5586 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 5587 Set-Interface requests);
7042 d = USB_QUIRK 5588 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 5589 handle its Configuration or Interface
7044 strin 5590 strings);
7045 e = USB_QUIRK 5591 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 5592 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 5593 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 5594 more interface descriptions than the
7049 bNumI 5595 bNumInterfaces count, and can't handle
7050 talki 5596 talking to these interfaces);
7051 g = USB_QUIRK 5597 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 5598 during initialization, after we read
7053 the d 5599 the device descriptor);
7054 h = USB_QUIRK 5600 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 5601 high speed and super speed interrupt
7056 endpo 5602 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 5603 require the interval in microframes (1
7058 micro 5604 microframe = 125 microseconds) to be
7059 calcu 5605 calculated as interval = 2 ^
7060 (bInt 5606 (bInterval-1).
7061 Devic 5607 Devices with this quirk report their
7062 bInte 5608 bInterval as the result of this
7063 calcu 5609 calculation instead of the exponent
7064 varia 5610 variable used in the calculation);
7065 i = USB_QUIRK 5611 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 5612 handle device_qualifier descriptor
7067 reque 5613 requests);
7068 j = USB_QUIRK 5614 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 5615 generates spurious wakeup, ignore
7070 remot 5616 remote wakeup capability);
7071 k = USB_QUIRK 5617 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 5618 Power Management);
7073 l = USB_QUIRK 5619 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 5620 (Device reports its bInterval as linear
7075 frame 5621 frames instead of the USB 2.0
7076 calcu 5622 calculation);
7077 m = USB_QUIRK 5623 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 5624 to be disconnected before suspend to
7079 preve 5625 prevent spurious wakeup);
7080 n = USB_QUIRK 5626 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 5627 pause after every control message);
7082 o = USB_QUIRK 5628 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 5629 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 5630 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 5631
7089 usbhid.mousepoll= 5632 usbhid.mousepoll=
7090 [USBHID] The interval 5633 [USBHID] The interval which mice are to be polled at.
7091 5634
7092 usbhid.jspoll= 5635 usbhid.jspoll=
7093 [USBHID] The interval 5636 [USBHID] The interval which joysticks are to be polled at.
7094 5637
7095 usbhid.kbpoll= 5638 usbhid.kbpoll=
7096 [USBHID] The interval 5639 [USBHID] The interval which keyboards are to be polled at.
7097 5640
7098 usb-storage.delay_use= 5641 usb-storage.delay_use=
7099 [UMS] The delay in se 5642 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 5643 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 5644
7105 usb-storage.quirks= 5645 usb-storage.quirks=
7106 [UMS] A list of quirk 5646 [UMS] A list of quirks entries to supplement or
7107 override the built-in 5647 override the built-in unusual_devs list. List
7108 entries are separated 5648 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 5649 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 5650 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 5651 Flags is a set of characters, each corresponding
7112 to a common usb-stora 5652 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 5653 a = SANE_SENSE (collect more than 18 bytes
7114 of se 5654 of sense data, not on uas);
7115 b = BAD_SENSE 5655 b = BAD_SENSE (don't collect more than 18
7116 bytes 5656 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 5657 c = FIX_CAPACITY (decrease the reported
7118 devic 5658 device capacity by one sector);
7119 d = NO_READ_D 5659 d = NO_READ_DISC_INFO (don't use
7120 READ_ 5660 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 5661 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 5662 READ_CAPACITY_16 command);
7123 f = NO_REPORT 5663 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 5664 command, uas only);
7125 g = MAX_SECTO 5665 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 5666 240 sectors at a time, uas only);
7127 h = CAPACITY_ 5667 h = CAPACITY_HEURISTICS (decrease the
7128 repor 5668 reported device capacity by one
7129 secto 5669 sector if the number is odd);
7130 i = IGNORE_DE 5670 i = IGNORE_DEVICE (don't bind to this
7131 devic 5671 device);
7132 j = NO_REPORT 5672 j = NO_REPORT_LUNS (don't use report luns
7133 comma 5673 command, uas only);
7134 k = NO_SAME ( 5674 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 5675 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 5676 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 5677 m = MAX_SECTORS_64 (don't transfer more
7138 than 5678 than 64 sectors = 32 KB at a time,
7139 not o 5679 not on uas);
7140 n = INITIAL_R 5680 n = INITIAL_READ10 (force a retry of the
7141 initi 5681 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 5682 o = CAPACITY_OK (accept the capacity
7143 repor 5683 reported by the device, not on uas);
7144 p = WRITE_CAC 5684 p = WRITE_CACHE (the device cache is ON
7145 by de 5685 by default, not on uas);
7146 r = IGNORE_RE 5686 r = IGNORE_RESIDUE (the device reports
7147 bogus 5687 bogus residue values, not on uas);
7148 s = SINGLE_LU 5688 s = SINGLE_LUN (the device has only one
7149 Logic 5689 Logical Unit);
7150 t = NO_ATA_1X 5690 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 5691 commands, uas only);
7152 u = IGNORE_UA 5692 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 5693 w = NO_WP_DETECT (don't test whether the
7154 mediu 5694 medium is write-protected).
7155 y = ALWAYS_SY 5695 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 5696 even if the device claims no cache,
7157 not o 5697 not on uas)
7158 Example: quirks=0419: 5698 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 5699
7160 user_debug= [KNL,ARM] 5700 user_debug= [KNL,ARM]
7161 Format: <int> 5701 Format: <int>
7162 See arch/arm/Kconfig. 5702 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 5703 1 - undefined instruction events
7164 2 - system c 5704 2 - system calls
7165 4 - invalid 5705 4 - invalid data aborts
7166 8 - SIGSEGV 5706 8 - SIGSEGV faults
7167 16 - SIGBUS f 5707 16 - SIGBUS faults
7168 Example: user_debug=3 5708 Example: user_debug=31
7169 5709
7170 userpte= 5710 userpte=
7171 [X86,EARLY] Flags con !! 5711 [X86] Flags controlling user PTE allocations.
7172 5712
7173 nohigh = do n 5713 nohigh = do not allocate PTE pages in
7174 HIGHM 5714 HIGHMEM regardless of setting
7175 of CO 5715 of CONFIG_HIGHPTE.
7176 5716
7177 vdso= [X86,SH,SPARC] !! 5717 vdso= [X86,SH]
7178 On X86_32, this is an 5718 On X86_32, this is an alias for vdso32=. Otherwise:
7179 5719
7180 vdso=1: enable VDSO ( 5720 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 5721 vdso=0: disable VDSO mapping
7182 5722
7183 vdso32= [X86] Control the 32- 5723 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 5724 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 5725 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 5726
7187 See the help text for 5727 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 5728 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 5729 vdso32=0; otherwise, the default is vdso32=1.
7190 5730
7191 For compatibility wit 5731 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 5732 alias for vdso32=0.
7193 5733
7194 Try vdso32=0 if you e 5734 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 5735 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 5736
7197 video= [FB,EARLY] Frame buff !! 5737 vector= [IA-64,SMP]
>> 5738 vector=percpu: enable percpu vector domain
>> 5739
>> 5740 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 5741 See Documentation/fb/modedb.rst.
7199 5742
7200 video.brightness_switch_enabled= [ACP !! 5743 video.brightness_switch_enabled= [0,1]
7201 Format: [0|1] <<
7202 If set to 1, on recei 5744 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 5745 generated by hotkey, video driver will adjust brightness
7204 level and then send o 5746 level and then send out the event to user space through
7205 the allocated input d !! 5747 the allocated input device; If set to 0, video driver
7206 will only send out th 5748 will only send out the event without touching backlight
7207 brightness level. 5749 brightness level.
7208 default: 1 5750 default: 1
7209 5751
7210 virtio_mmio.device= 5752 virtio_mmio.device=
7211 [VMMIO] Memory mapped 5753 [VMMIO] Memory mapped virtio (platform) device.
7212 5754
7213 <size>@<basead 5755 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 5756 where:
7215 <size> := 5757 <size> := size (can use standard suffixes
7216 5758 like K, M and G)
7217 <baseaddr> := 5759 <baseaddr> := physical base address
7218 <irq> := 5760 <irq> := interrupt number (as passed to
7219 5761 request_irq())
7220 <id> := 5762 <id> := (optional) platform device id
7221 example: 5763 example:
7222 virtio_mmio.d 5764 virtio_mmio.device=1K@0x100b0000:48:7
7223 5765
7224 Can be used multiple 5766 Can be used multiple times for multiple devices.
7225 5767
7226 vga= [BOOT,X86-32] Select 5768 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 5769 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 5770 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 5771 Use vga=ask for menu.
7230 This is actually a bo 5772 This is actually a boot loader parameter; the value is
7231 passed to the kernel 5773 passed to the kernel using a special protocol.
7232 5774
7233 vm_debug[=options] [KNL] Availab 5775 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 5776 May slow down system boot speed, especially when
7235 enabled on systems wi 5777 enabled on systems with a large amount of memory.
7236 All options are enabl 5778 All options are enabled by default, and this
7237 interface is meant to 5779 interface is meant to allow for selectively
7238 enabling or disabling 5780 enabling or disabling specific virtual memory
7239 debugging features. 5781 debugging features.
7240 5782
7241 Available options are 5783 Available options are:
7242 P Enable page s 5784 P Enable page structure init time poisoning
7243 - Disable all o 5785 - Disable all of the above options
7244 5786
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 5787 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 5788 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 5789 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 5790 decrease the size and leave more room for directly
7249 for directly mapped k !! 5791 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 5792
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 5793 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 5794 Sets the memory size reserved for contiguous memory
7256 allocations for the v 5795 allocations for the vmcp device driver.
7257 5796
7258 vmhalt= [KNL,S390] Perform z/ 5797 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 5798 Format: <command>
7260 5799
7261 vmpanic= [KNL,S390] Perform z/ 5800 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 5801 Format: <command>
7263 5802
7264 vmpoff= [KNL,S390] Perform z/ 5803 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 5804 Format: <command>
7266 5805
7267 vsyscall= [X86-64,EARLY] !! 5806 vsyscall= [X86-64]
7268 Controls the behavior 5807 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 5808 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 5809 code). Most statically-linked binaries and older
7271 versions of glibc use 5810 versions of glibc use these calls. Because these
7272 functions are at fixe 5811 functions are at fixed addresses, they make nice
7273 targets for exploits 5812 targets for exploits that can control RIP.
7274 5813
7275 emulate Vsyscalls !! 5814 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 5815 emulated reasonably safely. The vsyscall
7277 readable. !! 5816 page is readable.
7278 5817
7279 xonly [default] !! 5818 xonly Vsyscalls turn into traps and are
7280 emulated 5819 emulated reasonably safely. The vsyscall
7281 page is n 5820 page is not readable.
7282 5821
7283 none Vsyscalls 5822 none Vsyscalls don't work at all. This makes
7284 them quit 5823 them quite hard to use for exploits but
7285 might bre 5824 might break your system.
7286 5825
7287 vt.color= [VT] Default text col 5826 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 5827 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 5828 Default: 0x07 = light gray on black.
7290 5829
7291 vt.cur_default= [VT] Default cursor s 5830 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 5831 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 5832 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 5833 see VGA-softcursor.txt. Default: 2 = underline.
7295 5834
7296 vt.default_blu= [VT] 5835 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 5836 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 5837 Change the default blue palette of the console.
7299 This is a 16-member a 5838 This is a 16-member array composed of values
7300 ranging from 0-255. 5839 ranging from 0-255.
7301 5840
7302 vt.default_grn= [VT] 5841 vt.default_grn= [VT]
7303 Format: <green0>,<gre 5842 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 5843 Change the default green palette of the console.
7305 This is a 16-member a 5844 This is a 16-member array composed of values
7306 ranging from 0-255. 5845 ranging from 0-255.
7307 5846
7308 vt.default_red= [VT] 5847 vt.default_red= [VT]
7309 Format: <red0>,<red1> 5848 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 5849 Change the default red palette of the console.
7311 This is a 16-member a 5850 This is a 16-member array composed of values
7312 ranging from 0-255. 5851 ranging from 0-255.
7313 5852
7314 vt.default_utf8= 5853 vt.default_utf8=
7315 [VT] 5854 [VT]
7316 Format=<0|1> 5855 Format=<0|1>
7317 Set system-wide defau 5856 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 5857 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 5858 newly opened terminals.
7320 5859
7321 vt.global_cursor_default= 5860 vt.global_cursor_default=
7322 [VT] 5861 [VT]
7323 Format=<-1|0|1> 5862 Format=<-1|0|1>
7324 Set system-wide defau 5863 Set system-wide default for whether a cursor
7325 is shown on new VTs. 5864 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 5865 i.e. cursors will be created by default unless
7327 overridden by individ 5866 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 5867 cursors, 1 will display them.
7329 5868
7330 vt.italic= [VT] Default color fo 5869 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 5870 Default: 2 = green.
7332 5871
7333 vt.underline= [VT] Default color fo 5872 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 5873 Default: 3 = cyan.
7335 5874
7336 watchdog timers [HW,WDT] For informat 5875 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 5876 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 5877 or other driver-specific files in the
7339 Documentation/watchdo 5878 Documentation/watchdog/ directory.
7340 5879
7341 watchdog_thresh= 5880 watchdog_thresh=
7342 [KNL] 5881 [KNL]
7343 Set the hard lockup d 5882 Set the hard lockup detector stall duration
7344 threshold in seconds. 5883 threshold in seconds. The soft lockup detector
7345 threshold is set to t 5884 threshold is set to twice the value. A value of 0
7346 disables both lockup 5885 disables both lockup detectors. Default is 10
7347 seconds. 5886 seconds.
7348 5887
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= 5888 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 5889 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 5890 warn stall conditions and dump internal state to
7359 help debugging. 0 di 5891 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 5892 detection; otherwise, it's the stall threshold
7361 duration in seconds. 5893 duration in seconds. The default value is 30 and
7362 it can be updated at 5894 it can be updated at runtime by writing to the
7363 corresponding sysfs f 5895 corresponding sysfs file.
7364 5896
7365 workqueue.cpu_intensive_thresh_us= !! 5897 workqueue.disable_numa
7366 Per-cpu work items wh !! 5898 By default, all work items queued to unbound
7367 threshold are automat !! 5899 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 5900 issued on, which results in better behavior in
7369 them from noticeably !! 5901 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 5902 whatever reason, this option can be used. Note
7371 !! 5903 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 5904 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 5905
7386 workqueue.power_efficient 5906 workqueue.power_efficient
7387 Per-cpu workqueues ar 5907 Per-cpu workqueues are generally preferred because
7388 they show better perf 5908 they show better performance thanks to cache
7389 locality; unfortunate 5909 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 5910 be more power hungry than unbound workqueues.
7391 5911
7392 Enabling this makes t 5912 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 5913 were observed to contribute significantly to power
7394 consumption unbound, 5914 consumption unbound, leading to measurably lower
7395 power usage at the co 5915 power usage at the cost of small performance
7396 overhead. 5916 overhead.
7397 5917
7398 The default value of 5918 The default value of this parameter is determined by
7399 the config option CON 5919 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 5920
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 5921 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 5922 Workqueue used to implicitly guarantee that work
7415 items queued without 5923 items queued without explicit CPU specified are put
7416 on the local CPU. Th 5924 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 5925 and while local CPU is still preferred work items
7418 may be put on foreign 5926 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 5927 forces round-robin CPU selection to flush out
7420 usages which depend o 5928 usages which depend on the now broken guarantee.
7421 When enabled, memory 5929 When enabled, memory and cache locality will be
7422 impacted. 5930 impacted.
7423 5931
7424 writecombine= [LOONGARCH,EARLY] Con !! 5932 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 5933 default x2apic cluster mode on platforms
7432 supporting x2apic. 5934 supporting x2apic.
7433 5935
>> 5936 x86_intel_mid_timer= [X86-32,APBT]
>> 5937 Choose timer option for x86 Intel MID platform.
>> 5938 Two valid options are apbt timer only and lapic timer
>> 5939 plus one apbt timer for broadcast timer.
>> 5940 x86_intel_mid_timer=apbt_only | lapic_and_apbt
>> 5941
7434 xen_512gb_limit [KNL,X86-64,X 5942 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 5943 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 5944 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 5945 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 5946 save/restore/migration must be enabled to handle larger
7439 domains. 5947 domains.
7440 5948
7441 xen_emul_unplug= [HW,X !! 5949 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 5950 Unplug Xen emulated devices
7443 Format: [unplug0,][un 5951 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 5952 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 5953 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 5954 nics -- unplug network devices
7447 all -- unplug all emu 5955 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 5956 unnecessary -- unplugging emulated devices is
7449 unnecessary e 5957 unnecessary even if the host did not respond to
7450 the unplug pr 5958 the unplug protocol
7451 never -- do not unplu 5959 never -- do not unplug even if version check succeeds
7452 5960
7453 xen_legacy_crash [X86,XEN,EARL !! 5961 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 5962 Crash from Xen panic notifier, without executing late
7455 panic() code such as 5963 panic() code such as dumping handler.
7456 5964
7457 xen_mc_debug [X86,XEN,EARLY] !! 5965 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 5966 Disables the qspinlock slowpath using Xen PV optimizations.
7459 Enabling this feature !! 5967 This parameter is obsoleted by "nopvspin" parameter, which
7460 bit, so it should onl !! 5968 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 5969
7469 xen_nopv [X86] 5970 xen_nopv [X86]
7470 Disables the PV optim 5971 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 5972 run as generic HVM guest with no PV drivers.
7472 This option is obsole 5973 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 5974 has equivalent effect for XEN platform.
7474 5975
7475 xen_no_vector_callback 5976 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 5977 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 5978 event channel interrupts.
7478 5979
7479 xen_scrub_pages= [XEN] 5980 xen_scrub_pages= [XEN]
7480 Boolean option to con 5981 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 5982 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 5983 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 5984 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 5985
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 5986 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 5987 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 5988 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 5989 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 5990 improve timer resolution at the expense of processing
7490 more timer interrupts 5991 more timer interrupts.
7491 5992
7492 xen.balloon_boot_timeout= [XEN] <<
7493 The time (in seconds) <<
7494 in case initial ballo <<
7495 Applies only when run <<
7496 started with less mem <<
7497 max. Default is 180. <<
7498 <<
7499 xen.event_eoi_delay= [XEN] 5993 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 5994 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 5995 storms (jiffies). Default is 10.
7502 5996
7503 xen.event_loop_timeout= [XEN] 5997 xen.event_loop_timeout= [XEN]
7504 After which time (jif 5998 After which time (jiffies) the event handling loop
7505 should start to delay 5999 should start to delay EOI handling. Default is 2.
7506 6000
7507 xen.fifo_events= [XEN] 6001 xen.fifo_events= [XEN]
7508 Boolean parameter to 6002 Boolean parameter to disable using fifo event handling
7509 even if available. No 6003 even if available. Normally fifo event handling is
7510 preferred over the 2- 6004 preferred over the 2-level event handling, as it is
7511 fairer and the number 6005 fairer and the number of possible event channels is
7512 much higher. Default 6006 much higher. Default is on (use fifo events).
7513 6007
>> 6008 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6009 Disables the PV optimizations forcing the guest to run
>> 6010 as generic guest with no PV drivers. Currently support
>> 6011 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6012
>> 6013 nopvspin [X86,XEN,KVM]
>> 6014 Disables the qspinlock slow path using PV optimizations
>> 6015 which allow the hypervisor to 'idle' the guest on lock
>> 6016 contention.
>> 6017
7514 xirc2ps_cs= [NET,PCMCIA] 6018 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6019 Format:
7516 <irq>,<irq_mask>,<io> 6020 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6021
7518 xive= [PPC] 6022 xive= [PPC]
7519 By default on POWER9 6023 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6024 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6025 allows the fallback firmware mode to be used:
7522 6026
7523 off Fallback to 6027 off Fallback to firmware control of XIVE interrupt
7524 controller 6028 controller on both pseries and powernv
7525 platforms. 6029 platforms. Only useful on POWER9 and above.
7526 6030
7527 xive.store-eoi=off [PPC] <<
7528 By default on POWER10 <<
7529 stores for EOI handli <<
7530 is active. This optio <<
7531 loads instead, as on <<
7532 <<
7533 xhci-hcd.quirks [USB,KNL] 6031 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6032 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6033 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6034 consulted in header drivers/usb/host/xhci.h.
7537 6035
7538 xmon [PPC,EARLY] !! 6036 xmon [PPC]
7539 Format: { early | on 6037 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 6038 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 6039 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 6040 early Call xmon as early as possible on boot; xmon
7543 debugger is c 6041 debugger is called from setup_arch().
7544 on xmon debugger 6042 on xmon debugger hooks will be installed so xmon
7545 is only calle 6043 is only called on a kernel crash. Default mode,
7546 i.e. either " 6044 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 6045 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 6046 rw xmon debugger hooks will be installed so xmon
7549 is called onl 6047 is called only on a kernel crash, mode is write,
7550 meaning SPR r 6048 meaning SPR registers, memory and, other data
7551 can be writte 6049 can be written using xmon commands.
7552 ro same as "rw" 6050 ro same as "rw" option above but SPR registers,
7553 memory, and o 6051 memory, and other data can't be written using
7554 xmon commands 6052 xmon commands.
7555 off xmon is disab 6053 off xmon is disabled.
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