1 accept_memory= [MM] !! 1 acpi= [HW,ACPI,X86,ARM64]
2 Format: { eager | lazy <<
3 default: lazy <<
4 By default, unaccepted <<
5 avoid prolonged boot t <<
6 some runtime overhead <<
7 accepted. In most case <<
8 For some workloads or <<
9 accept_memory=eager ca <<
10 at once during boot. <<
11 <<
12 acpi= [HW,ACPI,X86,ARM64,RIS <<
13 Advanced Configuration 2 Advanced Configuration and Power Interface
14 Format: { force | on | 3 Format: { force | on | off | strict | noirq | rsdt |
15 copy_dsdt | !! 4 copy_dsdt }
16 force -- enable ACPI i 5 force -- enable ACPI if default was off
17 on -- enable ACPI but !! 6 on -- enable ACPI but allow fallback to DT [arm64]
18 off -- disable ACPI if 7 off -- disable ACPI if default was on
19 noirq -- do not use AC 8 noirq -- do not use ACPI for IRQ routing
20 strict -- Be less tole 9 strict -- Be less tolerant of platforms that are not
21 strictly ACPI 10 strictly ACPI specification compliant.
22 rsdt -- prefer RSDT ov 11 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT 12 copy_dsdt -- copy DSDT to memory
24 nospcr -- disable cons !! 13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
25 default _seria <<
26 For ARM64, ONLY "acpi= <<
27 "acpi=nospcr" are avai <<
28 For RISCV64, ONLY "acp <<
29 are available 14 are available
30 15
31 See also Documentation 16 See also Documentation/power/runtime_pm.rst, pci=noacpi
32 17
33 acpi_apic_instance= [ACPI,IOAPIC,E !! 18 acpi_apic_instance= [ACPI, IOAPIC]
34 Format: <int> 19 Format: <int>
35 2: use 2nd APIC table, 20 2: use 2nd APIC table, if available
36 1,0: use 1st APIC tabl 21 1,0: use 1st APIC table
37 default: 0 22 default: 0
38 23
39 acpi_backlight= [HW,ACPI] 24 acpi_backlight= [HW,ACPI]
40 { vendor | video | nat 25 { vendor | video | native | none }
41 If set to vendor, pref 26 If set to vendor, prefer vendor-specific driver
42 (e.g. thinkpad_acpi, s 27 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
43 of the ACPI video.ko d 28 of the ACPI video.ko driver.
44 If set to video, use t 29 If set to video, use the ACPI video.ko driver.
45 If set to native, use 30 If set to native, use the device's native backlight mode.
46 If set to none, disabl 31 If set to none, disable the ACPI backlight interface.
47 32
48 acpi_force_32bit_fadt_addr [ACPI,EARLY !! 33 acpi_force_32bit_fadt_addr
49 force FADT to use 32 b 34 force FADT to use 32 bit addresses rather than the
50 64 bit X_* addresses. 35 64 bit X_* addresses. Some firmware have broken 64
51 bit addresses for forc 36 bit addresses for force ACPI ignore these and use
52 the older legacy 32 bi 37 the older legacy 32 bit addresses.
53 38
54 acpica_no_return_repair [HW, ACPI] 39 acpica_no_return_repair [HW, ACPI]
55 Disable AML predefined 40 Disable AML predefined validation mechanism
56 This mechanism can rep 41 This mechanism can repair the evaluation result to make
57 the return objects mor 42 the return objects more ACPI specification compliant.
58 This option is useful 43 This option is useful for developers to identify the
59 root cause of an AML i 44 root cause of an AML interpreter issue when the issue
60 has something to do wi 45 has something to do with the repair mechanism.
61 46
62 acpi.debug_layer= [HW,ACPI,ACPI_ 47 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
63 acpi.debug_level= [HW,ACPI,ACPI_ 48 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
64 Format: <int> 49 Format: <int>
65 CONFIG_ACPI_DEBUG must 50 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
66 debug output. Bits in 51 debug output. Bits in debug_layer correspond to a
67 _COMPONENT in an ACPI 52 _COMPONENT in an ACPI source file, e.g.,
68 #define _COMPONENT 53 #define _COMPONENT ACPI_EVENTS
69 Bits in debug_level co 54 Bits in debug_level correspond to a level in
70 ACPI_DEBUG_PRINT state 55 ACPI_DEBUG_PRINT statements, e.g.,
71 ACPI_DEBUG_PRINT(( 56 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
72 The debug_level mask d 57 The debug_level mask defaults to "info". See
73 Documentation/firmware 58 Documentation/firmware-guide/acpi/debug.rst for more information about
74 debug layers and level 59 debug layers and levels.
75 60
76 Enable processor drive 61 Enable processor driver info messages:
77 acpi.debug_layer=0 62 acpi.debug_layer=0x20000000
78 Enable AML "Debug" out 63 Enable AML "Debug" output, i.e., stores to the Debug
79 object while interpret 64 object while interpreting AML:
80 acpi.debug_layer=0 65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
81 Enable all messages re 66 Enable all messages related to ACPI hardware:
82 acpi.debug_layer=0 67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
83 68
84 Some values produce so 69 Some values produce so much output that the system is
85 unusable. The "log_bu 70 unusable. The "log_buf_len" parameter may be useful
86 if you need to capture 71 if you need to capture more output.
87 72
88 acpi_enforce_resources= [ACPI] 73 acpi_enforce_resources= [ACPI]
89 { strict | lax | no } 74 { strict | lax | no }
90 Check for resource con 75 Check for resource conflicts between native drivers
91 and ACPI OperationRegi 76 and ACPI OperationRegions (SystemIO and SystemMemory
92 only). IO ports and me 77 only). IO ports and memory declared in ACPI might be
93 used by the ACPI subsy 78 used by the ACPI subsystem in arbitrary AML code and
94 can interfere with leg 79 can interfere with legacy drivers.
95 strict (default): acce 80 strict (default): access to resources claimed by ACPI
96 is denied; legacy driv 81 is denied; legacy drivers trying to access reserved
97 resources will fail to 82 resources will fail to bind to device using them.
98 lax: access to resourc 83 lax: access to resources claimed by ACPI is allowed;
99 legacy drivers trying 84 legacy drivers trying to access reserved resources
100 will bind successfully 85 will bind successfully but a warning message is logged.
101 no: ACPI OperationRegi 86 no: ACPI OperationRegions are not marked as reserved,
102 no further checks are 87 no further checks are performed.
103 88
104 acpi_force_table_verification [HW,AC !! 89 acpi_force_table_verification [HW,ACPI]
105 Enable table checksum 90 Enable table checksum verification during early stage.
106 By default, this is di 91 By default, this is disabled due to x86 early mapping
107 size limitation. 92 size limitation.
108 93
109 acpi_irq_balance [HW,ACPI] 94 acpi_irq_balance [HW,ACPI]
110 ACPI will balance acti 95 ACPI will balance active IRQs
111 default in APIC mode 96 default in APIC mode
112 97
113 acpi_irq_nobalance [HW,ACPI] 98 acpi_irq_nobalance [HW,ACPI]
114 ACPI will not move act 99 ACPI will not move active IRQs (default)
115 default in PIC mode 100 default in PIC mode
116 101
117 acpi_irq_isa= [HW,ACPI] If irq_balan 102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
118 Format: <irq>,<irq>... 103 Format: <irq>,<irq>...
119 104
120 acpi_irq_pci= [HW,ACPI] If irq_balan 105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
121 use by PCI 106 use by PCI
122 Format: <irq>,<irq>... 107 Format: <irq>,<irq>...
123 108
124 acpi_mask_gpe= [HW,ACPI] 109 acpi_mask_gpe= [HW,ACPI]
125 Due to the existence o 110 Due to the existence of _Lxx/_Exx, some GPEs triggered
126 by unsupported hardwar 111 by unsupported hardware/firmware features can result in
127 GPE floodings that can 112 GPE floodings that cannot be automatically disabled by
128 the GPE dispatcher. 113 the GPE dispatcher.
129 This facility can be u 114 This facility can be used to prevent such uncontrolled
130 GPE floodings. 115 GPE floodings.
131 Format: <byte> or <bit !! 116 Format: <byte>
132 117
133 acpi_no_auto_serialize [HW,ACPI] 118 acpi_no_auto_serialize [HW,ACPI]
134 Disable auto-serializa 119 Disable auto-serialization of AML methods
135 AML control methods th 120 AML control methods that contain the opcodes to create
136 named objects will be 121 named objects will be marked as "Serialized" by the
137 auto-serialization fea 122 auto-serialization feature.
138 This feature is enable 123 This feature is enabled by default.
139 This option allows to 124 This option allows to turn off the feature.
140 125
141 acpi_no_memhotplug [ACPI] Disable memo 126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
142 kernels. 127 kernels.
143 128
144 acpi_no_static_ssdt [HW,ACPI,EARLY !! 129 acpi_no_static_ssdt [HW,ACPI]
145 Disable installation o 130 Disable installation of static SSDTs at early boot time
146 By default, SSDTs cont 131 By default, SSDTs contained in the RSDT/XSDT will be
147 installed automaticall 132 installed automatically and they will appear under
148 /sys/firmware/acpi/tab 133 /sys/firmware/acpi/tables.
149 This option turns off 134 This option turns off this feature.
150 Note that specifying t 135 Note that specifying this option does not affect
151 dynamic table installa 136 dynamic table installation which will install SSDT
152 tables to /sys/firmwar 137 tables to /sys/firmware/acpi/tables/dynamic.
153 138
154 acpi_no_watchdog [HW,ACPI,WDT] 139 acpi_no_watchdog [HW,ACPI,WDT]
155 Ignore the ACPI-based 140 Ignore the ACPI-based watchdog interface (WDAT) and let
156 a native driver contro 141 a native driver control the watchdog device instead.
157 142
158 acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] !! 143 acpi_rsdp= [ACPI,EFI,KEXEC]
159 Pass the RSDP address 144 Pass the RSDP address to the kernel, mostly used
160 on machines running EF 145 on machines running EFI runtime service to boot the
161 second kernel for kdum 146 second kernel for kdump.
162 147
163 acpi_os_name= [HW,ACPI] Tell ACPI BI 148 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
164 Format: To spoof as Wi 149 Format: To spoof as Windows 98: ="Microsoft Windows"
165 150
166 acpi_rev_override [ACPI] Override the 151 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167 of 2 which is mandated 152 of 2 which is mandated by ACPI 6) as the supported ACPI
168 specification revision 153 specification revision (when using this switch, it may
169 be necessary to carry 154 be necessary to carry out a cold reboot _twice_ in a
170 row to make it take ef 155 row to make it take effect on the platform firmware).
171 156
172 acpi_osi= [HW,ACPI] Modify list 157 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" 158 acpi_osi="string1" # add string1
174 acpi_osi="!string2" 159 acpi_osi="!string2" # remove string2
175 acpi_osi=!* 160 acpi_osi=!* # remove all strings
176 acpi_osi=! 161 acpi_osi=! # disable all built-in OS vendor
177 162 strings
178 acpi_osi=!! 163 acpi_osi=!! # enable all built-in OS vendor
179 164 strings
180 acpi_osi= 165 acpi_osi= # disable all strings
181 166
182 'acpi_osi=!' can be us 167 'acpi_osi=!' can be used in combination with single or
183 multiple 'acpi_osi="st 168 multiple 'acpi_osi="string1"' to support specific OS
184 vendor string(s). Not 169 vendor string(s). Note that such command can only
185 affect the default sta 170 affect the default state of the OS vendor strings, thus
186 it cannot affect the d 171 it cannot affect the default state of the feature group
187 strings and the curren 172 strings and the current state of the OS vendor strings,
188 specifying it multiple 173 specifying it multiple times through kernel command line
189 is meaningless. This 174 is meaningless. This command is useful when one do not
190 care about the state o 175 care about the state of the feature group strings which
191 should be controlled b 176 should be controlled by the OSPM.
192 Examples: 177 Examples:
193 1. 'acpi_osi=! acpi_ 178 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194 to 'acpi_osi="Win 179 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 can make '_OSI("W 180 can make '_OSI("Windows 2000")' TRUE.
196 181
197 'acpi_osi=' cannot be 182 'acpi_osi=' cannot be used in combination with other
198 'acpi_osi=' command li 183 'acpi_osi=' command lines, the _OSI method will not
199 exist in the ACPI name 184 exist in the ACPI namespace. NOTE that such command can
200 only affect the _OSI s 185 only affect the _OSI support state, thus specifying it
201 multiple times through 186 multiple times through kernel command line is also
202 meaningless. 187 meaningless.
203 Examples: 188 Examples:
204 1. 'acpi_osi=' can m 189 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205 FALSE. 190 FALSE.
206 191
207 'acpi_osi=!*' can be u 192 'acpi_osi=!*' can be used in combination with single or
208 multiple 'acpi_osi="st 193 multiple 'acpi_osi="string1"' to support specific
209 string(s). Note that 194 string(s). Note that such command can affect the
210 current state of both 195 current state of both the OS vendor strings and the
211 feature group strings, 196 feature group strings, thus specifying it multiple times
212 through kernel command 197 through kernel command line is meaningful. But it may
213 still not able to affe 198 still not able to affect the final state of a string if
214 there are quirks relat 199 there are quirks related to this string. This command
215 is useful when one wan 200 is useful when one want to control the state of the
216 feature group strings 201 feature group strings to debug BIOS issues related to
217 the OSPM features. 202 the OSPM features.
218 Examples: 203 Examples:
219 1. 'acpi_osi="Module 204 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220 '_OSI("Module Dev 205 '_OSI("Module Device")' FALSE.
221 2. 'acpi_osi=!* acpi 206 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222 '_OSI("Module Dev 207 '_OSI("Module Device")' TRUE.
223 3. 'acpi_osi=! acpi_ 208 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224 equivalent to 209 equivalent to
225 'acpi_osi=!* acpi 210 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226 and 211 and
227 'acpi_osi=!* acpi 212 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228 they all will mak 213 they all will make '_OSI("Windows 2000")' TRUE.
229 214
230 acpi_pm_good [X86] 215 acpi_pm_good [X86]
231 Override the pmtimer b 216 Override the pmtimer bug detection: force the kernel
232 to assume that this ma 217 to assume that this machine's pmtimer latches its value
233 and always returns goo 218 and always returns good values.
234 219
235 acpi_sci= [HW,ACPI,EARLY] ACPI S !! 220 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge 221 Format: { level | edge | high | low }
237 222
238 acpi_skip_timer_override [HW,ACPI,EARL !! 223 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore I 224 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIO 225 For broken nForce2 BIOS resulting in XT-PIC timer.
241 226
242 acpi_sleep= [HW,ACPI] Sleep option 227 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_ !! 228 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 s4_nohwsig, !! 229 old_ordering, nonvs, sci_force_enable, nobl }
245 sci_force_en <<
246 See Documentation/powe 230 See Documentation/power/video.rst for information on
247 s3_bios and s3_mode. 231 s3_bios and s3_mode.
248 s3_beep is for debuggi 232 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel' 233 as soon as the kernel's real-mode entry point is called.
250 s4_hwsig causes the ke <<
251 signature during resum <<
252 refuse to resume if it <<
253 the ACPI specification <<
254 Windows does not do th <<
255 on docking. So the def <<
256 and simply warn when t <<
257 s4_hwsig option is ena <<
258 s4_nohwsig prevents AC 234 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a !! 235 used during resume from hibernation.
260 old_ordering causes th 236 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 237 control method, with respect to putting devices into
262 low power states, to b 238 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 239 of _PTS is used by default).
264 nonvs prevents the ker 240 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 241 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 242 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 243 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 244 but some broken systems don't work without it).
269 nobl causes the intern 245 nobl causes the internal blacklist of systems known to
270 behave incorrectly in 246 behave incorrectly in some ways with respect to system
271 suspend and resume to 247 suspend and resume to be ignored (use wisely).
272 248
273 acpi_use_timer_override [HW,ACPI,EARLY !! 249 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 250 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 251 that require a timer override, but don't have HPET
276 252
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 253 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 254 kernel's map of available physical RAM.
279 255
280 agp= [AGP] 256 agp= [AGP]
281 { off | try_unsupporte 257 { off | try_unsupported }
282 off: disable AGP suppo 258 off: disable AGP support
283 try_unsupported: try t 259 try_unsupported: try to drive unsupported chipsets
284 (may crash com 260 (may crash computer or cause data corruption)
285 261
286 ALSA [HW,ALSA] 262 ALSA [HW,ALSA]
287 See Documentation/soun 263 See Documentation/sound/alsa-configuration.rst
288 264
289 alignment= [KNL,ARM] 265 alignment= [KNL,ARM]
290 Allow the default user 266 Allow the default userspace alignment fault handler
291 behaviour to be specif 267 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 268 bit 1 enables fixups, and bit 2 sends a segfault.
293 269
294 align_va_addr= [X86-64] 270 align_va_addr= [X86-64]
295 Align virtual addresse 271 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 272 allocating a VMA at process creation time. This option
297 gives you up to 3% per 273 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 274 machines (where it is enabled by default) for a
299 CPU-intensive style be 275 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 276 a microbenchmark depending on workload and compiler.
301 277
302 32: only for 32-bit pr 278 32: only for 32-bit processes
303 64: only for 64-bit pr 279 64: only for 64-bit processes
304 on: enable for both 32 280 on: enable for both 32- and 64-bit processes
305 off: disable for both 281 off: disable for both 32- and 64-bit processes
306 282
307 alloc_snapshot [FTRACE] 283 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 284 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 285 main buffer is allocated. This is handy if debugging
310 and you need to use tr 286 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 287 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 288 to be done where GFP_KERNEL allocations are allowed.
313 289
314 allow_mismatched_32bit_el0 [ARM64,EARL <<
315 Allow execve() of 32-b <<
316 PER_LINUX32 personalit <<
317 subset of the CPUs sup <<
318 parameter is present, <<
319 EL0 is indicated by /s <<
320 and hot-unplug operati <<
321 <<
322 See Documentation/arch <<
323 information. <<
324 <<
325 amd_iommu= [HW,X86-64] 290 amd_iommu= [HW,X86-64]
326 Pass parameters to the 291 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 292 Possible values are:
328 fullflush - Deprecated !! 293 fullflush - enable flushing of IO/TLB entries when
>> 294 they are unmapped. Otherwise they are
>> 295 flushed before they will be reused, which
>> 296 is a lot of faster
329 off - do not ini 297 off - do not initialize any AMD IOMMU found in
330 the system 298 the system
331 force_isolation - Forc 299 force_isolation - Force device isolation for all
332 devi 300 devices. The IOMMU driver is not
333 allo 301 allowed anymore to lift isolation
334 requ 302 requirements as needed. This option
335 does 303 does not override iommu=pt
336 force_enable - Force e <<
337 to be b <<
338 option <<
339 pgtbl_v1 - Use v1 <<
340 pgtbl_v2 - Use v2 <<
341 irtcachedis - Disable <<
342 304
343 amd_iommu_dump= [HW,X86-64] 305 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 306 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 307 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 308 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 309 IOMMU initialization.
348 310
349 amd_iommu_intr= [HW,X86-64] 311 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 312 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 313 remapping modes:
352 legacy - Use legac 314 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 315 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 316 to inject interrupts directly into guest.
355 This mode 317 This mode requires kvm-amd.avic=1.
356 (Default 318 (Default when IOMMU HW support is present.)
357 319
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 320 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 321 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 322 Format: <a>,<b>
389 See also Documentation 323 See also Documentation/input/joydev/joystick.rst
390 324
391 analog.map= [HW,JOY] Analog joysti 325 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 326 Specifies type or capabilities of an analog joystick
393 connected to one of 16 327 connected to one of 16 gameports
394 Format: <type1>,<type2 328 Format: <type1>,<type2>,..<type16>
395 329
396 apc= [HW,SPARC] 330 apc= [HW,SPARC]
397 Power management funct 331 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 332 Format: noidle
399 Disable APC CPU standb 333 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 334 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 335 APC and your system crashes randomly.
402 336
403 apic= [APIC,X86,EARLY] Advan !! 337 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 338 Change the output verbosity while booting
405 Format: { quiet (defau 339 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 340 Change the amount of debugging information output
407 when initialising the 341 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 342 For X86-32, this can also be used to specify an APIC
409 driver name. 343 driver name.
410 Format: apic=driver_na 344 Format: apic=driver_name
411 Examples: apic=bigsmp 345 Examples: apic=bigsmp
412 346
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 347 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 348 Format: { bsp (default) | all | none }
415 bsp: External NMI is 349 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 350 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 351 backup of CPU 0
418 none: External NMI is 352 none: External NMI is masked for all CPUs. This is
419 useful so that a 353 useful so that a dump capture kernel won't be
420 shot down by NMI 354 shot down by NMI
421 355
422 autoconf= [IPV6] 356 autoconf= [IPV6]
423 See Documentation/netw 357 See Documentation/networking/ipv6.rst.
424 358
>> 359 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 360 Limit apic dumping. The parameter defines the maximal
>> 361 number of local apics being dumped. Also it is possible
>> 362 to set it to "all" by meaning -- no limit here.
>> 363 Format: { 1 (default) | 2 | ... | all }.
>> 364 The parameter valid if only apic=debug or
>> 365 apic=verbose is specified.
>> 366 Example: apic=debug show_lapic=all
>> 367
425 apm= [APM] Advanced Power M 368 apm= [APM] Advanced Power Management
426 See header of arch/x86 369 See header of arch/x86/kernel/apm_32.c.
427 370
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 371 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 372 Format: <io>,<irq>,<nodeID>
437 373
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall 374 arm64.nobti [ARM64] Unconditionally disable Branch Target
442 Identification support 375 Identification support
443 376
444 arm64.nomops [ARM64] Unconditionall <<
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support <<
449 <<
450 arm64.nopauth [ARM64] Unconditionall 377 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
451 support 378 support
452 379
453 arm64.nosme [ARM64] Unconditionall <<
454 Extension support <<
455 <<
456 arm64.nosve [ARM64] Unconditionall <<
457 Extension support <<
458 <<
459 ataflop= [HW,M68k] 380 ataflop= [HW,M68k]
460 381
461 atarimouse= [HW,MOUSE] Atari Mouse 382 atarimouse= [HW,MOUSE] Atari Mouse
462 383
463 atkbd.extra= [HW] Enable extra LEDs 384 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 385 EzKey and similar keyboards
465 386
466 atkbd.reset= [HW] Reset keyboard du 387 atkbd.reset= [HW] Reset keyboard during initialization
467 388
468 atkbd.set= [HW] Select keyboard c 389 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 390 Format: <int> (2 = AT (default), 3 = PS/2)
470 391
471 atkbd.scroll= [HW] Enable scroll whe 392 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 393 keyboards
473 394
474 atkbd.softraw= [HW] Choose between sy 395 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 396 Format: <bool> (0 = real, 1 = synthetic (default))
476 397
477 atkbd.softrepeat= [HW] 398 atkbd.softrepeat= [HW]
478 Use software keyboard 399 Use software keyboard repeat
479 400
480 audit= [KNL] Enable the audit 401 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 402 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 403 0 | off - kernel audit is disabled and can not be
483 enabled until the 404 enabled until the next reboot
484 unset - kernel audit i 405 unset - kernel audit is initialized but disabled and
485 will be fully enab 406 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 407 1 | on - kernel audit is initialized and partially
487 enabled, storing a 408 enabled, storing at most audit_backlog_limit
488 messages in RAM un 409 messages in RAM until it is fully enabled by the
489 userspace auditd. 410 userspace auditd.
490 Default: unset 411 Default: unset
491 412
492 audit_backlog_limit= [KNL] Set the aud 413 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 414 Format: <int> (must be >=0)
494 Default: 64 415 Default: 64
495 416
496 bau= [X86_UV] Enable the BA 417 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 418 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 419 Format: { "0" | "1" }
499 0 - Disable the BAU. 420 0 - Disable the BAU.
500 1 - Enable the BAU. 421 1 - Enable the BAU.
501 unset - Disable the BA 422 unset - Disable the BAU.
502 423
503 baycom_epp= [HW,AX25] 424 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 425 Format: <io>,<mode>
505 426
506 baycom_par= [HW,AX25] BayCom Paral 427 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 428 Format: <io>,<mode>
508 See header of drivers/ 429 See header of drivers/net/hamradio/baycom_par.c.
509 430
510 baycom_ser_fdx= [HW,AX25] 431 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 432 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 433 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 434 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 435
515 baycom_ser_hdx= [HW,AX25] 436 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 437 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 438 Format: <io>,<irq>,<mode>
518 See header of drivers/ 439 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 440
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 441 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 442 embedded devices based on command line input.
528 See Documentation/bloc 443 See Documentation/block/cmdline-partition.rst
529 444
530 boot_delay= [KNL,EARLY] !! 445 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 446 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 447 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 448 Format: integer
537 449
538 bootconfig [KNL,EARLY] !! 450 bootconfig [KNL]
539 Extended command line 451 Extended command line options can be added to an initrd
540 and this will cause th 452 and this will cause the kernel to look for it.
541 453
542 See Documentation/admi 454 See Documentation/admin-guide/bootconfig.rst
543 455
>> 456 bert_disable [ACPI]
>> 457 Disable BERT OS support on buggy BIOSes.
>> 458
>> 459 bgrt_disable [ACPI][X86]
>> 460 Disable BGRT to avoid flickering OEM logo.
>> 461
544 bttv.card= [HW,V4L] bttv (bt848 + 462 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 463 bttv.radio= Most important insmod options are available as
546 kernel args too. 464 kernel args too.
547 bttv.pll= See Documentation/admi 465 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 466 bttv.tuner=
549 467
550 bulk_remove=off [PPC] This parameter 468 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 469 firmware feature for flushing multiple hpte entries
552 at a time. 470 at a time.
553 471
554 c101= [NET] Moxa C101 synchr 472 c101= [NET] Moxa C101 synchronous serial card
555 473
556 cachesize= [BUGS=X86-32] Override 474 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 475 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 476 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 477 to fix known problems, but for some CPUs it is not
560 possible to determine 478 possible to determine what the correct size should be.
561 This option provides a 479 This option provides an override for these situations.
562 480
563 carrier_timeout= 481 carrier_timeout=
564 [NET] Specifies amount 482 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 483 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 484 it waits 120 seconds.
567 485
568 ca_keys= [KEYS] This parameter 486 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 487 the system trusted keyring to be used for certificate
570 trust validation. 488 trust validation.
571 format: { id:<keyid> | 489 format: { id:<keyid> | builtin }
572 490
573 cca= [MIPS,EARLY] Override !! 491 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 492 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 493 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 494 for platform specific values (SB1, Loongson3 and
577 others). 495 others).
578 496
579 ccw_timeout_log [S390] 497 ccw_timeout_log [S390]
580 See Documentation/arch !! 498 See Documentation/s390/common_io.rst for details.
581 499
582 cgroup_disable= [KNL] Disable a partic !! 500 cgroup_disable= [KNL] Disable a particular controller
583 Format: {name of the c !! 501 Format: {name of the controller(s) to disable}
584 The effects of cgroup_ 502 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 503 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 504 a single hierarchy
587 - foo isn't visible as 505 - foo isn't visible as an individually mountable
588 subsystem 506 subsystem
589 - if foo is an optiona <<
590 disabled and corresp <<
591 created <<
592 {Currently only "memor 507 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 508 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 509 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" <<
596 stall information acco <<
597 510
598 cgroup_no_v1= [KNL] Disable cgroup c 511 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 512 Format: { { controller | "all" | "named" }
600 [,{ controll 513 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 514 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 515 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 516 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 517 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 518 all v1 hierarchies.
606 519
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 520 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 521 Format: <string>
613 nosocket -- Disable so 522 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 523 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 524
617 checkreqprot= [SELINUX] Set initial !! 525 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 526 Format: { "0" | "1" }
619 See security/selinux/K 527 See security/selinux/Kconfig help text.
620 0 -- check protection 528 0 -- check protection applied by kernel (includes
621 any implied ex 529 any implied execute protection).
622 1 -- check protection 530 1 -- check protection requested by application.
623 Default value is set v 531 Default value is set via a kernel config option.
624 Value can be changed a 532 Value can be changed at runtime via
625 /sys/fs/selinu 533 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 534 Setting checkreqprot to 1 is deprecated.
627 535
628 cio_ignore= [S390] 536 cio_ignore= [S390]
629 See Documentation/arch !! 537 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 538 clk_ignore_unused
650 [CLK] 539 [CLK]
651 Prevents the clock fra 540 Prevents the clock framework from automatically gating
652 clocks that have not b 541 clocks that have not been explicitly enabled by a Linux
653 device driver but are 542 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 543 by the bootloader/firmware. Note that this does not
655 force such clocks to b 544 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 545 those clocks in any way. This parameter is useful for
657 debug and development, 546 debug and development, but should not be needed on a
658 platform with proper d 547 platform with proper driver support. For more
659 information, see Docum 548 information, see Documentation/driver-api/clk.rst.
660 549
661 clock= [BUGS=X86-32, HW] gett 550 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 551 [Deprecated]
663 Forces specified clock 552 Forces specified clocksource (if available) to be used
664 when calculating getti 553 when calculating gettimeofday(). If specified
665 clocksource is not ava 554 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 555 Format: { pit | tsc | cyclone | pmtmr }
667 556
668 clocksource= Override the default c 557 clocksource= Override the default clocksource
669 Format: <string> 558 Format: <string>
670 Override the default c 559 Override the default clocksource and use the clocksource
671 with the name specifie 560 with the name specified.
672 Some clocksource names 561 Some clocksource names to choose from, depending on
673 the platform: 562 the platform:
674 [all] jiffies (this is 563 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 564 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 565 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 566 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 567 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 568 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 569 [MIPS] MIPS
681 [PARISC] cr16 570 [PARISC] cr16
682 [S390] tod 571 [S390] tod
683 [SH] SuperH 572 [SH] SuperH
684 [SPARC64] tick 573 [SPARC64] tick
685 [X86-64] hpet,tsc 574 [X86-64] hpet,tsc
686 575
687 clocksource.arm_arch_timer.evtstrm= 576 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 577 [ARM,ARM64]
689 Format: <bool> 578 Format: <bool>
690 Enable/disable the eve 579 Enable/disable the eventstream feature of the ARM
691 architected timer so t 580 architected timer so that code using WFE-based polling
692 loops can be debugged 581 loops can be debugged more effectively on production
693 systems. 582 systems.
694 583
695 clocksource.verify_n_cpus= [KNL] !! 584 clocksource.max_cswd_read_retries= [KNL]
696 Limit the number of CP !! 585 Number of clocksource_watchdog() retries due to
697 marked with CLOCK_SOUR !! 586 external delays before the clock will be marked
698 are marked unstable du !! 587 unstable. Defaults to three retries, that is,
699 A negative value says !! 588 four attempts to read the clock under test.
700 zero says not to check !! 589
701 nr_cpu_ids are silentl !! 590 clearcpuid=BITNUM[,BITNUM...] [X86]
702 The actual CPUs are ch !! 591 Disable CPUID feature X for the kernel. See
703 no replacement if the !! 592 arch/x86/include/asm/cpufeatures.h for the valid bit
704 !! 593 numbers. Note the Linux specific bits are not necessarily
705 clocksource-wdtest.holdoff= [KNL] !! 594 stable over kernel options, but the vendor specific
706 Set the time in second !! 595 ones should be.
707 watchdog test waits be !! 596 Also note that user programs calling CPUID directly
708 Defaults to zero when !! 597 or using the feature without checking anything
709 10 seconds when built !! 598 will still see it. This just prevents it from
>> 599 being used by the kernel or shown in /proc/cpuinfo.
>> 600 Also note the kernel might malfunction if you disable
>> 601 some critical bits.
710 602
711 cma=nn[MG]@[start[MG][-end[MG]]] 603 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 604 [KNL,CMA]
713 Sets the size of kerne 605 Sets the size of kernel global memory area for
714 contiguous memory allo 606 contiguous memory allocations and optionally the
715 placement constraint b 607 placement constraint by the physical address range of
716 memory allocations. A 608 memory allocations. A value of 0 disables CMA
717 altogether. For more i 609 altogether. For more information, see
718 kernel/dma/contiguous. 610 kernel/dma/contiguous.c
719 611
720 cma_pernuma=nn[MG] 612 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 613 [ARM64,KNL,CMA]
722 Sets the size of kerne 614 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 615 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 616 per-numa CMA altogether. And If this option is not
725 specified, the default !! 617 specificed, the default value is 0.
726 With per-numa CMA enab 618 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 619 first try to allocate buffer from the pernuma area
728 which is located in no 620 which is located in node nid, if the allocation fails,
729 they will fallback to 621 they will fallback to the global default memory area.
730 622
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 | 623 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 624 Specify whether pages are marked as being inactive
744 when they are freed. 625 when they are freed. This is used in CMO environments
745 to determine OS memory 626 to determine OS memory pressure for page stealing by
746 a hypervisor. 627 a hypervisor.
747 Default: yes 628 Default: yes
748 629
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 630 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 631 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 632 allocations, by default set to 256K.
752 633
753 com20020= [HW,NET] ARCnet - COM2 634 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 635 Format:
755 <io>[,<irq>[,<nodeID>[ 636 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 637
757 com90io= [HW,NET] ARCnet - COM9 638 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 639 Format: <io>[,<irq>]
759 640
760 com90xx= [HW,NET] 641 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 642 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 643 Format: <io>[,<irq>[,<memstart>]]
763 644
764 condev= [HW,S390] console devi 645 condev= [HW,S390] console device
765 conmode= 646 conmode=
766 647
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 648 console= [KNL] Output console device and options.
779 649
780 tty<n> Use the virtual consol 650 tty<n> Use the virtual console device <n>.
781 651
782 ttyS<n>[,options] 652 ttyS<n>[,options]
783 ttyUSB0[,options] 653 ttyUSB0[,options]
784 Use the specified seri 654 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 655 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 656 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 657 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 658 omit it). Default is "9600n8".
789 659
790 See Documentation/admi 660 See Documentation/admin-guide/serial-console.rst for more
791 information. See 661 information. See
792 Documentation/networki 662 Documentation/networking/netconsole.rst for an
793 alternative. 663 alternative.
794 664
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] 665 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 666 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 667 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 668 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 669 uart[8250],0x<addr>[,options]
819 Start an early, polled 670 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 671 UART at the specified I/O port or MMIO address,
821 switching to the match 672 switching to the matching ttyS device later.
822 MMIO inter-register ad 673 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 674 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 675 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 676 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 677 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 678 the h/w is not re-initialized.
828 679
829 hvc<n> Use the hypervisor con 680 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 681 both Xen and PowerPC hypervisors.
831 682
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 683 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 684 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 685 console=brl,ttyS0
841 For now, only VisioBraille is 686 For now, only VisioBraille is supported.
842 687
843 console_msg_format= 688 console_msg_format=
844 [KNL] Change console m 689 [KNL] Change console messages format
845 default 690 default
846 By default we print me 691 By default we print messages on consoles in
847 "[time stamp] text\n" 692 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 693 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 694 `printk_time' param).
850 syslog 695 syslog
851 Switch to syslog forma 696 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 697 IOW, each message will have a facility and loglevel
853 prefix. The format is 698 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 699 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 700 from /proc/kmsg.
856 701
857 consoleblank= [KNL] The console blan 702 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 703 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 704 Defaults to 0.
860 705
861 coredump_filter= 706 coredump_filter=
862 [KNL] Change the defau 707 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 708 /proc/<pid>/coredump_filter.
864 See also Documentation 709 See also Documentation/filesystems/proc.rst.
865 710
866 coresight_cpu_debug.enable 711 coresight_cpu_debug.enable
867 [ARM,ARM64] 712 [ARM,ARM64]
868 Format: <bool> 713 Format: <bool>
869 Enable/disable the CPU 714 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 715 0: default value, disable debugging
871 1: enable debugging at 716 1: enable debugging at boot time
872 717
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 718 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 719 disable the cpuidle sub-system
879 720
880 cpuidle.governor= 721 cpuidle.governor=
881 [CPU_IDLE] Name of the 722 [CPU_IDLE] Name of the cpuidle governor to use.
882 723
883 cpufreq.off=1 [CPU_FREQ] 724 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 725 disable the cpufreq sub-system
885 726
886 cpufreq.default_governor= 727 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 728 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 729 policy to use. This governor must be registered in the
889 kernel before the cpuf 730 kernel before the cpufreq driver probes.
890 731
891 cpu_init_udelay=N 732 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 733 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 734 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 735 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 736 Default: 10000
896 737
897 cpuhp.parallel= !! 738 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 739 Format:
899 Format: <bool> !! 740 <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. <<
910 741
911 crashkernel=size[KMG][@offset[KMG]] 742 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 743 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 744 upon panic. This parameter reserves the physical
914 memory region [offset, 745 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 746 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 747 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 748 [KNL, X86-64] Select a region under 4G first, and
918 under 4G first, and fa !! 749 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 750 hasn't been specified.
920 See Documentation/admi 751 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 752
922 crashkernel=range1:size1[,range2:size2 753 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 754 [KNL] Same as above, but depends on the memory
924 in the running system. 755 in the running system. The syntax of range is
925 start-[end] where star 756 start-[end] where start and end are both
926 a memory unit (amount[ 757 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 758 Documentation/admin-guide/kdump/kdump.rst for an example.
928 759
929 crashkernel=size[KMG],high 760 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 761 [KNL, X86-64] range could be above 4G. Allow kernel
931 above 4G. !! 762 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 763 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 764 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 765 available.
935 below 4G, if available <<
936 It will be ignored if 766 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 767 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 768 [KNL, X86-64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 769 is passed, kernel could allocate physical memory region
940 physical memory region !! 770 above 4G, that cause second kernel crash on system
941 crash on system that r !! 771 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 772 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 773 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 774 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 775 at least 256M below 4G automatically.
946 size is platform depen !! 776 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 777 for second kernel instead.
953 0: to disable low allo 778 0: to disable low allocation.
954 It will be ignored whe 779 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 780 or memory reserved is below 4G.
956 781
957 cryptomgr.notests 782 cryptomgr.notests
958 [KNL] Disable crypto s 783 [KNL] Disable crypto self-tests
959 784
960 cs89x0_dma= [HW,NET] 785 cs89x0_dma= [HW,NET]
961 Format: <dma> 786 Format: <dma>
962 787
963 cs89x0_media= [HW,NET] 788 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 789 Format: { rj45 | aui | bnc }
965 790
966 csdlock_debug= [KNL] Enable or disabl !! 791 csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
967 function call handling !! 792 handling. When switched on, additional debug data is
968 additional debug data !! 793 printed to the console in case a hanging CPU is
969 in case a hanging CPU !! 794 detected, and that CPU is pinged again in order to try
970 CPU is pinged again in !! 795 to resolve the hang situation.
971 the hang situation. T !! 796 0: disable csdlock debugging (default)
972 option depends on the !! 797 1: enable basic csdlock debugging (minor impact)
973 Kconfig option. !! 798 ext: enable extended csdlock debugging (more impact,
>> 799 but more data)
974 800
975 dasd= [HW,NET] 801 dasd= [HW,NET]
976 See header of drivers/ 802 See header of drivers/s390/block/dasd_devmap.c.
977 803
978 db9.dev[2|3]= [HW,JOY] Multisystem j 804 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 805 (one device per port)
980 Format: <port#>,<type> 806 Format: <port#>,<type>
981 See also Documentation 807 See also Documentation/input/devices/joystick-parport.rst
982 808
983 debug [KNL,EARLY] Enable ker !! 809 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 810 time. See
>> 811 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 812 details. Deprecated, see dyndbg.
>> 813
>> 814 debug [KNL] Enable kernel debugging (events log level).
984 815
985 debug_boot_weak_hash 816 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 817 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 818 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 819 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 820 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 821 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 822 insecure, please do not use on production kernels.
992 823
993 debug_locks_verbose= 824 debug_locks_verbose=
994 [KNL] verbose locking 825 [KNL] verbose locking self-tests
995 Format: <int> 826 Format: <int>
996 Print debugging info w 827 Print debugging info while doing the locking API
997 self-tests. 828 self-tests.
998 Bitmask for the variou 829 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 830 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 831 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 832 useful to lockdep developers.
1002 833
1003 debug_objects [KNL,EARLY] Enable ob !! 834 debug_objects [KNL] Enable object debugging
>> 835
>> 836 no_debug_objects
>> 837 [KNL] Disable object debugging
1004 838
1005 debug_guardpage_minorder= 839 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 840 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 841 parameter allows control of the order of pages that will
1008 be intentionally kept 842 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 843 buddy allocator. Bigger value increase the probability
1010 of catching random me 844 of catching random memory corruption, but reduce the
1011 amount of memory for 845 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 846 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 847 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 848 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 849 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 850 random memory location. Note that there exists a class
1017 a class of memory cor !! 851 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 852 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 853 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 854 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 855 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 856 tracking down these problems.
1023 857
1024 debug_pagealloc= 858 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 859 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 860 enables the feature at boot time. By default, it is
1027 disabled and the syst 861 disabled and the system will work mostly the same as a
1028 kernel built without 862 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 863 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 864 useful to also enable the page_owner functionality.
1031 on: enable the featur 865 on: enable the feature
1032 866
1033 debugfs= [KNL,EARLY] This para !! 867 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 868 and debugfs internal clients.
1035 Format: { on, no-moun 869 Format: { on, no-mount, off }
1036 on: All functions 870 on: All functions are enabled.
1037 no-mount: 871 no-mount:
1038 Filesystem is 872 Filesystem is not registered but kernel clients can
1039 access APIs a 873 access APIs and a crashkernel can be used to read
1040 its content. 874 its content. There is nothing to mount.
1041 off: Filesystem is 875 off: Filesystem is not registered and clients
1042 get a -EPERM 876 get a -EPERM as result when trying to register files
1043 or directorie 877 or directories within debugfs.
1044 This is equiv 878 This is equivalent of the runtime functionality if
1045 debugfs was n 879 debugfs was not enabled in the kernel at all.
1046 Default value is set 880 Default value is set in build-time with a kernel configuration.
1047 881
1048 debugpat [X86] Enable PAT debu 882 debugpat [X86] Enable PAT debugging
1049 883
>> 884 decnet.addr= [HW,NET]
>> 885 Format: <area>[,<node>]
>> 886 See also Documentation/networking/decnet.rst.
>> 887
1050 default_hugepagesz= 888 default_hugepagesz=
1051 [HW] The size of the 889 [HW] The size of the default HugeTLB page. This is
1052 the size represented 890 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 891 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 892 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 893 filesystems. If not specified, defaults to the
1056 architecture's defaul 894 architecture's default huge page size. Huge page
1057 sizes are architectur 895 sizes are architecture dependent. See also
1058 Documentation/admin-g 896 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 897 Format: size[KMG]
1060 898
1061 deferred_probe_timeout= 899 deferred_probe_timeout=
1062 [KNL] Debugging optio 900 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 901 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 902 probe. Only specific dependencies (subsystems or
1065 drivers) that have op !! 903 drivers) that have opted in will be ignored. A timeout of 0
1066 of 0 will timeout at !! 904 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 905 dump out devices still on the deferred probe list after
1070 retrying. 906 retrying.
1071 907
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] 908 dfltcc= [HW,S390]
1099 Format: { on | off | 909 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 910 on: s390 zlib hardware support for compression on
1101 level 1 and 911 level 1 and decompression (default)
1102 off: No s390 zli 912 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 913 def_only: s390 zlib hardware support for deflate
1104 only (compr 914 only (compression on level 1)
1105 inf_only: s390 zlib h 915 inf_only: s390 zlib hardware support for inflate
1106 only (decom 916 only (decompression)
1107 always: Same as 'on 917 always: Same as 'on' but ignores the selected compression
1108 level alway 918 level always using hardware support (used for debugging)
1109 919
1110 dhash_entries= [KNL] 920 dhash_entries= [KNL]
1111 Set number of hash bu 921 Set number of hash buckets for dentry cache.
1112 922
1113 disable_1tb_segments [PPC,EARLY] !! 923 disable_1tb_segments [PPC]
1114 Disables the use of 1 924 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 925 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 926 can be useful when debugging issues that require an SLB
1117 miss to occur. 927 miss to occur.
1118 928
>> 929 stress_slb [PPC]
>> 930 Limits the number of kernel SLB entries, and flushes
>> 931 them frequently to increase the rate of SLB faults
>> 932 on kernel addresses.
>> 933
1119 disable= [IPV6] 934 disable= [IPV6]
1120 See Documentation/net 935 See Documentation/networking/ipv6.rst.
1121 936
1122 disable_radix [PPC,EARLY] !! 937 hardened_usercopy=
>> 938 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
>> 939 hardening is enabled for this boot. Hardened
>> 940 usercopy checking is used to protect the kernel
>> 941 from reading or writing beyond known memory
>> 942 allocation boundaries as a proactive defense
>> 943 against bounds-checking flaws in the kernel's
>> 944 copy_to_user()/copy_from_user() interface.
>> 945 on Perform hardened usercopy checks (default).
>> 946 off Disable hardened usercopy checks.
>> 947
>> 948 disable_radix [PPC]
1123 Disable RADIX MMU mod 949 Disable RADIX MMU mode on POWER9
1124 950
>> 951 radix_hcall_invalidate=on [PPC/PSERIES]
>> 952 Disable RADIX GTSE feature and use hcall for TLB
>> 953 invalidate.
>> 954
1125 disable_tlbie [PPC] 955 disable_tlbie [PPC]
1126 Disable TLBIE instruc 956 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 957 with KVM, with HASH MMU, or with coherent accelerators.
1128 958
1129 disable_ddw [PPC/PSERIES,EARLY] !! 959 disable_cpu_apicid= [X86,APIC,SMP]
>> 960 Format: <int>
>> 961 The number of initial APIC ID for the
>> 962 corresponding CPU to be disabled at boot,
>> 963 mostly used for the kdump 2nd kernel to
>> 964 disable BSP to wake up multiple CPUs without
>> 965 causing system reset or hang due to sending
>> 966 INIT from AP to BSP.
>> 967
>> 968 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 969 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 970 to workaround buggy firmware.
1132 971
1133 disable_ipv6= [IPV6] 972 disable_ipv6= [IPV6]
1134 See Documentation/net 973 See Documentation/networking/ipv6.rst.
1135 974
1136 disable_mtrr_cleanup [X86,EARLY] !! 975 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 976 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 977 to discrete, to make X server driver able to add WB
1139 entry later. This par 978 entry later. This parameter disables that.
1140 979
1141 disable_mtrr_trim [X86, Intel and AMD !! 980 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 981 By default the kernel will trim any uncacheable
1143 memory out of your av 982 memory out of your available memory pool based on
1144 MTRR settings. This 983 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 984 possibly causing your machine to run very slowly.
1146 985
1147 disable_timer_pin_1 [X86,EARLY] !! 986 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 987 Disable PIN 1 of APIC timer
1149 Can be useful to work 988 Can be useful to work around chipset bugs.
1150 989
1151 dis_ucode_ldr [X86] Disable the mic 990 dis_ucode_ldr [X86] Disable the microcode loader.
1152 991
1153 dma_debug=off If the kernel is comp 992 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 993 this option disables the debugging code at boot.
1155 994
1156 dma_debug_entries=<number> 995 dma_debug_entries=<number>
1157 This option allows to 996 This option allows to tune the number of preallocated
1158 entries for DMA-API d 997 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 998 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 999 DMA-API debugging code disables itself because the
1161 architectural default 1000 architectural default is too low.
1162 1001
1163 dma_debug_driver=<driver_name> 1002 dma_debug_driver=<driver_name>
1164 With this option the 1003 With this option the DMA-API debugging driver
1165 filter feature can be 1004 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1005 pass the driver to filter for as the parameter.
1167 The filter can be dis 1006 The filter can be disabled or changed to another
1168 driver later using sy 1007 driver later using sysfs.
1169 1008
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] 1009 driver_async_probe= [KNL]
1191 List of driver names !! 1010 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 1011 Format: <driver_name1>,<driver_name2>...
1196 1012
1197 drm.edid_firmware=[<connector>:]<file 1013 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1014 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1015 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1016 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1017 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1018 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1019 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1020 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1021 and no file with the same name exists. Details and
>> 1022 instructions how to build your own EDID data are
>> 1023 available in Documentation/admin-guide/edid.rst. An EDID
>> 1024 data set will only be used for a particular connector,
>> 1025 if its name and a colon are prepended to the EDID
>> 1026 name. Each connector may use a unique EDID data
>> 1027 set by separating the files with a comma. An EDID
1206 data set with no conn 1028 data set with no connector name will be used for
1207 any connectors not ex 1029 any connectors not explicitly specified.
1208 1030
1209 dscc4.setup= [NET] 1031 dscc4.setup= [NET]
1210 1032
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1033 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1034 Format: {"off" | "known"}
1213 Control how the dt_cp 1035 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1036 used for CPU feature discovery and setup (if it
1215 exists). 1037 exists).
1216 off: Do not use it, f 1038 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1039 known: Do not pass through unknown features to guests
1218 or userspace, only th 1040 or userspace, only those that the kernel is aware of.
1219 1041
1220 dump_apple_properties [X86] 1042 dump_apple_properties [X86]
1221 Dump name and content 1043 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1044 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1045 what data is available or for reverse-engineering.
1224 1046
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1047 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1048 <module>.dyndbg[="val"]
1227 Enable debug messages 1049 Enable debug messages at boot time. See
1228 Documentation/admin-g 1050 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1051 for details.
1230 1052
1231 early_ioremap_debug [KNL,EARLY] !! 1053 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1054 in some Intel CPUs.
>> 1055
>> 1056 <module>.async_probe [KNL]
>> 1057 Enable asynchronous probe on this module.
>> 1058
>> 1059 early_ioremap_debug [KNL]
1232 Enable debug messages 1060 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1061 is useful for tracking down temporary early mappings
1234 which are not unmappe 1062 which are not unmapped.
1235 1063
1236 earlycon= [KNL,EARLY] Output ea !! 1064 earlycon= [KNL] Output early console device and options.
1237 1065
1238 When used with no opt 1066 When used with no options, the early console is
1239 determined by stdout- 1067 determined by stdout-path property in device tree's
1240 chosen node or the AC 1068 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1069 the platform.
1242 1070
1243 cdns,<addr>[,options] 1071 cdns,<addr>[,options]
1244 Start an early, polle 1072 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1073 (xuartps) serial port at the specified address. Only
1246 supported option is b 1074 supported option is baud rate. If baud rate is not
1247 specified, the serial 1075 specified, the serial port must already be setup and
1248 configured. 1076 configured.
1249 1077
1250 uart[8250],io,<addr>[,options !! 1078 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1079 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1080 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1081 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1082 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1083 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1084 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1085 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1086 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1087 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1088 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1089 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1090 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1091
1266 pl011,<addr> 1092 pl011,<addr>
1267 pl011,mmio32,<addr> 1093 pl011,mmio32,<addr>
1268 Start an early, polle 1094 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1095 port at the specified address. The pl011 serial port
1270 must already be setup 1096 must already be setup and configured. Options are not
1271 yet supported. If 'm 1097 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1098 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1099 the device registers.
1274 1100
1275 liteuart,<addr> <<
1276 Start an early consol <<
1277 specified address. Th <<
1278 setup and configured. <<
1279 <<
1280 meson,<addr> 1101 meson,<addr>
1281 Start an early, polle 1102 Start an early, polled-mode console on a meson serial
1282 port at the specified 1103 port at the specified address. The serial port must
1283 already be setup and 1104 already be setup and configured. Options are not yet
1284 supported. 1105 supported.
1285 1106
1286 msm_serial,<addr> 1107 msm_serial,<addr>
1287 Start an early, polle 1108 Start an early, polled-mode console on an msm serial
1288 port at the specified 1109 port at the specified address. The serial port
1289 must already be setup 1110 must already be setup and configured. Options are not
1290 yet supported. 1111 yet supported.
1291 1112
1292 msm_serial_dm,<addr> 1113 msm_serial_dm,<addr>
1293 Start an early, polle 1114 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1115 dm port at the specified address. The serial port
1295 must already be setup 1116 must already be setup and configured. Options are not
1296 yet supported. 1117 yet supported.
1297 1118
1298 owl,<addr> 1119 owl,<addr>
1299 Start an early, polle 1120 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1121 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1122 specified address. The serial port must already be
1302 setup and configured. 1123 setup and configured. Options are not yet supported.
1303 1124
1304 rda,<addr> 1125 rda,<addr>
1305 Start an early, polle 1126 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1127 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1128 specified address. The serial port must already be
1308 setup and configured. 1129 setup and configured. Options are not yet supported.
1309 1130
1310 sbi 1131 sbi
1311 Use RISC-V SBI (Super 1132 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1133 console.
1313 1134
1314 smh Use ARM semihosting c 1135 smh Use ARM semihosting calls for early console.
1315 1136
1316 s3c2410,<addr> 1137 s3c2410,<addr>
1317 s3c2412,<addr> 1138 s3c2412,<addr>
1318 s3c2440,<addr> 1139 s3c2440,<addr>
1319 s3c6400,<addr> 1140 s3c6400,<addr>
1320 s5pv210,<addr> 1141 s5pv210,<addr>
1321 exynos4210,<addr> 1142 exynos4210,<addr>
1322 Use early console pro 1143 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1144 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1145 a correct base address of the selected UART port. The
1325 serial port must alre 1146 serial port must already be setup and configured.
1326 Options are not yet s 1147 Options are not yet supported.
1327 1148
1328 lantiq,<addr> 1149 lantiq,<addr>
1329 Start an early, polle 1150 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1151 (lqasc) port at the specified address. The serial port
1331 must already be setup 1152 must already be setup and configured. Options are not
1332 yet supported. 1153 yet supported.
1333 1154
1334 lpuart,<addr> 1155 lpuart,<addr>
1335 lpuart32,<addr> 1156 lpuart32,<addr>
1336 Use early console pro 1157 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1158 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1159 A valid base address must be provided, and the serial
1339 port must already be 1160 port must already be setup and configured.
1340 1161
1341 ec_imx21,<addr> 1162 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1163 ec_imx6q,<addr>
1343 Start an early, polle 1164 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1165 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1166 must already be setup and configured.
1346 1167
1347 ar3700_uart,<addr> 1168 ar3700_uart,<addr>
1348 Start an early, polle 1169 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1170 Armada 3700 serial port at the specified
1350 address. The serial p 1171 address. The serial port must already be setup
1351 and configured. Optio 1172 and configured. Options are not yet supported.
1352 1173
1353 qcom_geni,<addr> 1174 qcom_geni,<addr>
1354 Start an early, polle 1175 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1176 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1177 specified address. The serial port must already be
1357 setup and configured. 1178 setup and configured. Options are not yet supported.
1358 1179
1359 efifb,[options] 1180 efifb,[options]
1360 Start an early, unacc 1181 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1182 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1183 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1184 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1185 mapped with the correct attributes.
1365 1186
1366 linflex,<addr> 1187 linflex,<addr>
1367 Use early console pro 1188 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1189 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1190 address must be provided, and the serial port must
1370 already be setup and 1191 already be setup and configured.
1371 1192
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1193 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1194 earlyprintk=vga
1374 earlyprintk=sclp 1195 earlyprintk=sclp
1375 earlyprintk=xen 1196 earlyprintk=xen
1376 earlyprintk=serial[,t 1197 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1198 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1199 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1200 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1201 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1202 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1203
1384 earlyprintk is useful 1204 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1205 the normal console is initialized. It is not enabled by
1386 default because it ha 1206 default because it has some cosmetic problems.
1387 1207
1388 Append ",keep" to not 1208 Append ",keep" to not disable it when the real console
1389 takes over. 1209 takes over.
1390 1210
1391 Only one of vga, seri !! 1211 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1212 be used at a time.
1393 1213
1394 Currently only ttyS0 1214 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1215 name. Other I/O ports may be explicitly specified
1396 on some architectures 1216 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1217 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1218 earlyprintk=serial,0x1008,115200
1399 You can find the port 1219 You can find the port for a given device in
1400 /proc/tty/driver/seri 1220 /proc/tty/driver/serial:
1401 2: uart:ST166 1221 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1222
1403 Interaction with the 1223 Interaction with the standard serial driver is not
1404 very good. 1224 very good.
1405 1225
1406 The VGA output is eve !! 1226 The VGA and EFI output is eventually overwritten by
1407 the real console. 1227 the real console.
1408 1228
1409 The xen option can on !! 1229 The xen output can only be used by Xen PV guests.
1410 1230
1411 The sclp output can o 1231 The sclp output can only be used on s390.
1412 1232
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1233 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1234 PCI device even when its classcode is not of the
1417 UART class. 1235 UART class.
1418 1236
1419 edac_report= [HW,EDAC] Control how 1237 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1238 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1239 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1240 by other higher priority error reporting module.
1423 off: disable H/W even 1241 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1242 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1243 default: on.
1426 1244
>> 1245 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1246 ekgdboc=kbd
>> 1247
>> 1248 This is designed to be used in conjunction with
>> 1249 the boot argument: earlyprintk=vga
>> 1250
>> 1251 This parameter works in place of the kgdboc parameter
>> 1252 but can only be used if the backing tty is available
>> 1253 very early in the boot process. For early debugging
>> 1254 via a serial port see kgdboc_earlycon instead.
>> 1255
1427 edd= [EDD] 1256 edd= [EDD]
1428 Format: {"off" | "on" 1257 Format: {"off" | "on" | "skip[mbr]"}
1429 1258
1430 efi= [EFI,EARLY] !! 1259 efi= [EFI]
1431 Format: { "debug", "d 1260 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1261 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1262 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1263 debug: enable misc debug output.
1435 disable_early_pci_dma 1264 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1265 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1266 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1267 boot stub, as chunking can cause problems with some
1439 firmware implementati 1268 firmware implementations.
1440 noruntime : disable E 1269 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1270 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1271 attribute may cause the kernel to reserve the
1443 memory range for a me 1272 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1273 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1274 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1275 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1276 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1277 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1278 on all PCI bridges while in the EFI boot stub
1450 1279
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1280 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1281 Using this parameter you can use more than 50% of
1453 your efi variable sto 1282 your efi variable storage. Use this parameter only if
1454 you are really sure t 1283 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1284 fulfills the spec otherwise your board may brick.
1456 1285
>> 1286 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1287 Add arbitrary attribute to specific memory range by
>> 1288 updating original EFI memory map.
>> 1289 Region of memory which aa attribute is added to is
>> 1290 from ss to ss+nn.
>> 1291
>> 1292 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1293 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1294 attribute is added to range 0x100000000-0x180000000 and
>> 1295 0x10a0000000-0x1120000000.
>> 1296
>> 1297 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1298 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1299 range 0x240000000-0x43fffffff.
>> 1300
>> 1301 Using this parameter you can do debugging of EFI memmap
>> 1302 related features. For example, you can do debugging of
>> 1303 Address Range Mirroring feature even if your box
>> 1304 doesn't support it, or mark specific memory as
>> 1305 "soft reserved".
>> 1306
1457 efivar_ssdt= [EFI; X86] Name of an 1307 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1308 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1309 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1310 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1311 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1312
1463 1313
1464 eisa_irq_edge= [PARISC,HW] 1314 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1315 See header of drivers/parisc/eisa.c.
1466 1316
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] 1317 elanfreq= [X86-32]
1479 See comment before fu 1318 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1319 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1320
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1321 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1322 Specifies physical address of start of kernel core
1484 image elf header and 1323 image elf header and optionally the size. Generally
1485 kexec loader will pas 1324 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1325 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1326
1488 enable_mtrr_cleanup [X86,EARLY] !! 1327 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1328 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1329 to discrete, to make X server driver able to add WB
1491 entry later. This par 1330 entry later. This parameter enables that.
1492 1331
1493 enable_timer_pin_1 [X86] 1332 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1333 Enable PIN 1 of APIC timer
1495 Can be useful to work 1334 Can be useful to work around chipset bugs
1496 (in particular on som 1335 (in particular on some ATI chipsets).
1497 The kernel tries to s 1336 The kernel tries to set a reasonable default.
1498 1337
1499 enforcing= [SELINUX] Set initial !! 1338 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1339 Format: {"0" | "1"}
1501 See security/selinux/ 1340 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1341 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1342 1 -- enforcing (deny and log).
1504 Default value is 0. 1343 Default value is 0.
1505 Value can be changed 1344 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1345 /sys/fs/selinux/enforce.
1507 1346
1508 erst_disable [ACPI] 1347 erst_disable [ACPI]
1509 Disable Error Record 1348 Disable Error Record Serialization Table (ERST)
1510 support. 1349 support.
1511 1350
1512 ether= [HW,NET] Ethernet car 1351 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1352 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1353 has equivalent usage. See its documentation for details.
1515 1354
1516 evm= [EVM] 1355 evm= [EVM]
1517 Format: { "fix" } 1356 Format: { "fix" }
1518 Permit 'security.evm' 1357 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1358 current integrity status.
1520 1359
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= 1360 failslab=
1530 fail_usercopy= 1361 fail_usercopy=
1531 fail_page_alloc= 1362 fail_page_alloc=
1532 fail_make_request=[KNL] 1363 fail_make_request=[KNL]
1533 General fault injecti 1364 General fault injection mechanism.
1534 Format: <interval>,<p 1365 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1366 See also Documentation/fault-injection/.
1536 1367
1537 fb_tunnels= [NET] 1368 fb_tunnels= [NET]
1538 Format: { initns | no 1369 Format: { initns | none }
1539 See Documentation/adm 1370 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1371 fb_tunnels_only_for_init_ns
1541 1372
1542 floppy= [HW] 1373 floppy= [HW]
1543 See Documentation/adm 1374 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1375
>> 1376 force_pal_cache_flush
>> 1377 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1378 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1379 parameter will force ia64_sal_cache_flush to call
>> 1380 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1381
1545 forcepae [X86-32] 1382 forcepae [X86-32]
1546 Forcefully enable Phy 1383 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1384 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1385 functionally usable PAE implementation.
1549 Warning: use of this 1386 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1387 and may cause unknown problems.
1551 1388
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] 1389 ftrace=[tracer]
1559 [FTRACE] will set and 1390 [FTRACE] will set and start the specified tracer
1560 as early as possible 1391 as early as possible in order to facilitate early
1561 boot debugging. 1392 boot debugging.
1562 1393
1563 ftrace_boot_snapshot !! 1394 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 1395 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1396 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1397 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1398 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1399 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 1400
1603 ftrace_filter=[function-list] 1401 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1402 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1403 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1404 list of functions. This list can be changed at run
1607 time by the set_ftrac 1405 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1406 tracing directory.
1609 1407
1610 ftrace_notrace=[function-list] 1408 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1409 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1410 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1411 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1412 tracing directory.
1615 1413
1616 ftrace_graph_filter=[function-list] 1414 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1415 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1416 by the function graph tracer at boot up.
1619 function-list is a co 1417 function-list is a comma-separated list of functions
1620 that can be changed a 1418 that can be changed at run time by the
1621 set_graph_function fi 1419 set_graph_function file in the debugfs tracing directory.
1622 1420
1623 ftrace_graph_notrace=[function-list] 1421 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1422 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1423 function-list. This list is a comma-separated list of
1626 functions that can be 1424 functions that can be changed at run time by the
1627 set_graph_notrace fil 1425 set_graph_notrace file in the debugfs tracing directory.
1628 1426
1629 ftrace_graph_max_depth=<uint> 1427 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1428 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1429 the max depth it will trace into a function. This value
1632 can be changed at run 1430 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1431 in the tracefs tracing directory. default: 0 (no limit)
1634 1432
1635 fw_devlink= [KNL,EARLY] Create de !! 1433 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1434 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1435 consumer/supplier relationships. This feature is
1638 especially useful whe 1436 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1437 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1438 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1439 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1440 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1441 suppliers).
1644 Format: { off | permi 1442 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1443 off -- Don't create device links from firmware info.
1646 permissive -- Create 1444 permissive -- Create device links from firmware info
1647 but use it on 1445 but use it only for ordering boot state clean
1648 up (sync_stat 1446 up (sync_state() calls).
1649 on -- Create device 1447 on -- Create device links from firmware info and use it
1650 to enforce pr 1448 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1449 rpm -- Like "on", but also use to order runtime PM.
1652 1450
1653 fw_devlink.strict=<bool> 1451 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1452 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1453 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1454 Format: <bool>
1657 1455
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]= 1456 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1457 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1458 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1459 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1460 See also Documentation/input/devices/joystick-parport.rst
1677 1461
1678 gamma= [HW,DRM] 1462 gamma= [HW,DRM]
1679 1463
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1464 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1465 Format: off | on
1682 default: on 1466 default: on
1683 1467
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 1468 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1469 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1470 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1471 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1472 debugfs files are removed at module unload time.
1709 1473
1710 goldfish [X86] Enable the gold 1474 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1475 Don't use this when you are not running on the
1712 android emulator 1476 android emulator
1713 1477
1714 gpio-mockup.gpio_mockup_ranges 1478 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1479 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1480 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1481 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1482 [HW] Let the driver know GPIO lines should be named.
1719 1483
1720 gpt [EFI] Forces disk wit 1484 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1485 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1486 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1487 GPT to be used instead.
1724 1488
1725 grcan.enable0= [HW] Configuration of 1489 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1490 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1491 Format: 0 | 1
1728 Default: 0 1492 Default: 0
1729 grcan.enable1= [HW] Configuration of 1493 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1494 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1495 Format: 0 | 1
1732 Default: 0 1496 Default: 0
1733 grcan.select= [HW] Select which phy 1497 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1498 Format: 0 | 1
1735 Default: 0 1499 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1500 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1501 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1502 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1503 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1504 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1505 Default: 1024
1742 1506
1743 hardened_usercopy= <<
1744 [KNL] Under CONFIG_HA <<
1745 hardening is enabled <<
1746 usercopy checking is <<
1747 from reading or writi <<
1748 allocation boundaries <<
1749 against bounds-checki <<
1750 copy_to_user()/copy_f <<
1751 on Perform hardened user <<
1752 off Disable hardened user <<
1753 <<
1754 hardlockup_all_cpu_backtrace= 1507 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1508 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1509 backtraces on all cpus.
1757 Format: 0 | 1 1510 Format: 0 | 1
1758 1511
1759 hashdist= [KNL,NUMA] Large hash 1512 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1513 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1514 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1515 Format: 0 | 1 (for off | on)
1763 1516
>> 1517 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1518
1764 hd= [EIDE] (E)IDE hard dr 1519 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1520 Format: <cyl>,<head>,<sect>
1766 1521
1767 hest_disable [ACPI] 1522 hest_disable [ACPI]
1768 Disable Hardware Erro 1523 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1524 corresponding firmware-first mode error processing
1770 logic will be disable 1525 logic will be disabled.
1771 1526
1772 hibernate= [HIBERNATION] !! 1527 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 1528 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1529 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1530 size on bigger boxes.
1796 1531
1797 highres= [KNL] Enable/disable 1532 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1533 Valid parameters: "on", "off"
1799 Default: "on" 1534 Default: "on"
1800 1535
1801 hlt [BUGS=ARM,SH] 1536 hlt [BUGS=ARM,SH]
1802 1537
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 1538 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1539 Format: { enable (default) | disable | force |
1818 verbose } 1540 verbose }
1819 disable: disable HPET 1541 disable: disable HPET and use PIT instead
1820 force: allow force en 1542 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1543 VIA, nVidia)
1822 verbose: show content 1544 verbose: show contents of HPET registers during setup
1823 1545
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1546 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1547 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1548
>> 1549 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
>> 1550 of gigantic hugepages.
>> 1551 Format: nn[KMGTPE]
>> 1552
>> 1553 Reserve a CMA area of given size and allocate gigantic
>> 1554 hugepages using the CMA allocator. If enabled, the
>> 1555 boot-time allocation of gigantic hugepages is skipped.
>> 1556
1827 hugepages= [HW] Number of HugeTL 1557 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1558 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1559 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1560 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1561 line, it specifies the number of pages to allocate for
1832 the default huge page !! 1562 the default huge page size. See also
1833 number of pages to al !! 1563 Documentation/admin-guide/mm/hugetlbpage.rst.
1834 See also Documentatio !! 1564 Format: <integer>
1835 Format: <integer> or <<
1836 <node>:<integ <<
1837 1565
1838 hugepagesz= 1566 hugepagesz=
1839 [HW] The size of the 1567 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1568 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1569 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1570 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1571 each supported huge page size. Huge page sizes are
1844 architecture dependen 1572 architecture dependent. See also
1845 Documentation/admin-g 1573 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1574 Format: size[KMG]
1847 1575
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= 1576 hung_task_panic=
1879 [KNL] Should the hung 1577 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1578 Format: 0 | 1
1881 1579
1882 A value of 1 instruct 1580 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1581 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1582 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1583 option. The value selected by this boot parameter can
1886 be changed later by t 1584 be changed later by the kernel.hung_task_panic sysctl.
1887 1585
1888 hvc_iucv= [S390] Number of z/V 1586 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1587 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1588 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1589 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1590 from listed z/VM user IDs only.
1893 1591
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1592 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1593 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1594 guest on lock contention.
1897 on lock contention. !! 1595
>> 1596 keep_bootcon [KNL]
>> 1597 Do not unregister boot console at start. This is only
>> 1598 useful for debugging when something happens in the window
>> 1599 between unregistering the boot console and initializing
>> 1600 the real console.
1898 1601
1899 i2c_bus= [HW] Override the 1602 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1603 or register an additional I2C bus that is not
1901 registered fr 1604 registered from board initialization code.
1902 Format: 1605 Format:
1903 <bus_id>,<clk 1606 <bus_id>,<clkrate>
1904 1607
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 1608 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1609 i8042.unmask_kbd_data
1929 [HW] Enable printing 1610 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1611 (disabled by default, and as a pre-condition
1931 requires that i8 1612 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1613 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1614 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1615 keyboard and cannot control its state
1935 (Don't attempt t 1616 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1617 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1618 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1619 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1620 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1621 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1622 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1623 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1624 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1625 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1626 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1627 suspend-to-ram transitions, only during s2r
1947 transitions, or 1628 transitions, or never reset
1948 Format: { 1 | Y | y | 1629 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1630 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1631 0, N, n: don't ever reset controller
1951 Default: only on s2r 1632 Default: only on s2r transitions on x86; most other
1952 architectures force r 1633 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1634 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1635 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer <<
1956 [HW] Allow deferred p <<
1957 1636
1958 i810= [HW,DRM] 1637 i810= [HW,DRM]
1959 1638
>> 1639 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1640 indicates that the driver is running on unsupported
>> 1641 hardware.
>> 1642 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1643 does not match list of supported models.
>> 1644 i8k.power_status
>> 1645 [HW] Report power status in /proc/i8k
>> 1646 (disabled by default)
>> 1647 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1648 capability is set.
>> 1649
1960 i915.invert_brightness= 1650 i915.invert_brightness=
1961 [DRM] Invert the sens 1651 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1652 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1653 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1654 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1655 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1656 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1657 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1658 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1659 value switches the backlight off.
1970 -1 -- never invert br 1660 -1 -- never invert brightness
1971 0 -- machine default 1661 0 -- machine default
1972 1 -- force brightnes 1662 1 -- force brightness inversion
1973 1663
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] 1664 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1665 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1666
>> 1667 ide-core.nodma= [HW] (E)IDE subsystem
>> 1668 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1669 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1670 .cdrom .chs .ignore_cable are additional options
>> 1671 See Documentation/ide/ide.rst.
>> 1672
>> 1673 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1674 Format: <int>
>> 1675 Probe mask for legacy ISA IDE ports. Depending on
>> 1676 platform up to 6 ports are supported, enabled by
>> 1677 setting corresponding bits in the mask to 1. The
>> 1678 default value is 0x0, which has a special meaning.
>> 1679 On systems that have PCI, it triggers scanning the
>> 1680 PCI bus for the first and the second port, which
>> 1681 are then probed. On systems without PCI the value
>> 1682 of 0x0 enables probing the two first ports as if it
>> 1683 was 0x3.
>> 1684
>> 1685 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1686 Claim all unknown PCI IDE storage controllers.
1983 1687
1984 idle= [X86,EARLY] !! 1688 idle= [X86]
1985 Format: idle=poll, id 1689 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1690 Poll forces a polling idle loop that can slightly
1987 improve the performan 1691 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1692 will use a lot of power and make the system run hot.
1989 Not recommended. 1693 Not recommended.
1990 idle=halt: Halt is fo 1694 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1695 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1696 idle=nomwait: Disable mwait for CPU C-states
1993 1697
1994 idxd.sva= [HW] 1698 idxd.sva= [HW]
1995 Format: <bool> 1699 Format: <bool>
1996 Allow force disabling 1700 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1701 support for the idxd driver. By default it is set to
1998 true (1). 1702 true (1).
1999 1703
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 1704 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1705 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1706 Default: strict
2008 1707
2009 Choose which programs 1708 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1709 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1710 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1711 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1712 binary. Hardware implementations are permitted to
2014 support either or bot 1713 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1714 encoding mode.
2016 1715
2017 Available settings ar 1716 Available settings are as follows:
2018 strict accept binari 1717 strict accept binaries that request a NaN encoding
2019 supported by 1718 supported by the FPU
2020 legacy only accept l 1719 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1720 by the FPU
2022 2008 only accept 2 1721 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1722 by the FPU
2024 relaxed accept any bi 1723 relaxed accept any binaries regardless of whether
2025 supported by 1724 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1725
2029 The FPU emulator is a 1726 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1727 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1728 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1729 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1730 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1731 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1732 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1733 MIPS64 CPUs.
2037 1734
2038 The setting for ABS.f 1735 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1736 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1737 except where unsupported by hardware.
2041 1738
2042 ignore_loglevel [KNL,EARLY] !! 1739 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1740 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1741 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1742 We also add it as printk module parameter, so users
2046 could change it dynam 1743 could change it dynamically, usually by
2047 /sys/module/printk/pa 1744 /sys/module/printk/parameters/ignore_loglevel.
2048 1745
2049 ignore_rlimit_data 1746 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1747 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1748 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1749 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1750
2054 ihash_entries= [KNL] 1751 ihash_entries= [KNL]
2055 Set number of hash bu 1752 Set number of hash buckets for inode cache.
2056 1753
2057 ima_appraise= [IMA] appraise integr 1754 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1755 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1756 default: "enforce"
2060 1757
2061 ima_appraise_tcb [IMA] Deprecated. U 1758 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1759 The builtin appraise policy appraises all files
2063 owned by uid=0. 1760 owned by uid=0.
2064 1761
2065 ima_canonical_fmt [IMA] 1762 ima_canonical_fmt [IMA]
2066 Use the canonical for 1763 Use the canonical format for the binary runtime
2067 measurements, instead 1764 measurements, instead of host native format.
2068 1765
2069 ima_hash= [IMA] 1766 ima_hash= [IMA]
2070 Format: { md5 | sha1 1767 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1768 | sha512 | ... }
2072 default: "sha1" 1769 default: "sha1"
2073 1770
2074 The list of supported 1771 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1772 in crypto/hash_info.h.
2076 1773
2077 ima_policy= [IMA] 1774 ima_policy= [IMA]
2078 The builtin policies 1775 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1776 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1777 fail_securely | critical_data"
2081 1778
2082 The "tcb" policy meas 1779 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1780 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1781 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1782 uid=0.
2086 1783
2087 The "appraise_tcb" po 1784 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1785 all files owned by root.
2089 1786
2090 The "secure_boot" pol 1787 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1788 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1789 firmware, policy, etc) based on file signatures.
2093 1790
2094 The "fail_securely" p 1791 The "fail_securely" policy forces file signature
2095 verification failure 1792 verification failure also on privileged mounted
2096 filesystems with the 1793 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1794 flag.
2098 1795
2099 The "critical_data" p 1796 The "critical_data" policy measures kernel integrity
2100 critical data. 1797 critical data.
2101 1798
2102 ima_tcb [IMA] Deprecated. Us 1799 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1800 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1801 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1802 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1803 opened for read by uid=0.
2107 1804
2108 ima_template= [IMA] 1805 ima_template= [IMA]
2109 Select one of defined 1806 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1807 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1808 Default: "ima-ng"
2113 1809
2114 ima_template_fmt= 1810 ima_template_fmt=
2115 [IMA] Define a custom 1811 [IMA] Define a custom template format.
2116 Format: { "field1|... 1812 Format: { "field1|...|fieldN" }
2117 1813
2118 ima.ahash_minsize= [IMA] Minimum file 1814 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1815 Format: <min_file_size>
2120 Set the minimal file 1816 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1817 If left unspecified, ahash usage is disabled.
2122 1818
2123 ahash performance var 1819 ahash performance varies for different data sizes on
2124 different crypto acce 1820 different crypto accelerators. This option can be used
2125 to achieve the best p 1821 to achieve the best performance for a particular HW.
2126 1822
2127 ima.ahash_bufsize= [IMA] Asynchronous 1823 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1824 Format: <bufsize>
2129 Set hashing buffer si 1825 Set hashing buffer size. Default: 4k.
2130 1826
2131 ahash performance var 1827 ahash performance varies for different chunk sizes on
2132 different crypto acce 1828 different crypto accelerators. This option can be used
2133 to achieve best perfo 1829 to achieve best performance for particular HW.
2134 1830
2135 init= [KNL] 1831 init= [KNL]
2136 Format: <full_path> 1832 Format: <full_path>
2137 Run specified binary 1833 Run specified binary instead of /sbin/init as init
2138 process. 1834 process.
2139 1835
2140 initcall_debug [KNL] Trace initcalls 1836 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1837 for working out where the kernel is dying during
2142 startup. 1838 startup.
2143 1839
2144 initcall_blacklist= [KNL] Do not exe 1840 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1841 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1842 modules and initcalls.
2147 1843
2148 initramfs_async= [KNL] 1844 initramfs_async= [KNL]
2149 Format: <bool> 1845 Format: <bool>
2150 Default: 1 1846 Default: 1
2151 This parameter contro 1847 This parameter controls whether the initramfs
2152 image is unpacked asy 1848 image is unpacked asynchronously, concurrently
2153 with devices being pr 1849 with devices being probed and
2154 initialized. This sho 1850 initialized. This should normally just work,
2155 but as a debugging ai 1851 but as a debugging aid, one can get the
2156 historical behaviour 1852 historical behaviour of the initramfs
2157 unpacking being compl 1853 unpacking being completed before device_ and
2158 late_ initcalls. 1854 late_ initcalls.
2159 1855
2160 initrd= [BOOT,EARLY] Specify !! 1856 initrd= [BOOT] Specify the location of the initial ramdisk
2161 1857
2162 initrdmem= [KNL,EARLY] Specify a !! 1858 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 1859 load the initrd. If an initrd is compiled in or
2164 specified in the boot 1860 specified in the bootparams, it takes priority over this
2165 setting. 1861 setting.
2166 Format: ss[KMG],nn[KM 1862 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 1863 Default is 0, 0
2168 1864
2169 init_on_alloc= [MM,EARLY] Fill newly !! 1865 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 1866 zeroes.
2171 Format: 0 | 1 1867 Format: 0 | 1
2172 Default set by CONFIG 1868 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 1869
2174 init_on_free= [MM,EARLY] Fill freed !! 1870 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 1871 Format: 0 | 1
2176 Default set by CONFIG 1872 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 1873
2178 init_pkru= [X86] Specify the def 1874 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 1875 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1876 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1877 override in debugfs after boot.
2182 1878
2183 inport.irq= [HW] Inport (ATI XL a 1879 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1880 Format: <irq>
2185 1881
2186 int_pln_enable [X86] Enable power li 1882 int_pln_enable [X86] Enable power limit notification interrupt
2187 1883
2188 integrity_audit=[IMA] 1884 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1885 Format: { "0" | "1" }
2190 0 -- basic integrity 1886 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1887 1 -- additional integrity auditing messages.
2192 1888
2193 intel_iommu= [DMAR] Intel IOMMU dr 1889 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1890 on
2195 Enable intel iommu dr 1891 Enable intel iommu driver.
2196 off 1892 off
2197 Disable intel iommu d 1893 Disable intel iommu driver.
2198 igfx_off [Default Off] 1894 igfx_off [Default Off]
2199 By default, gfx is ma 1895 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1896 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1897 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1898 this case, gfx device will use physical address for
2203 DMA. 1899 DMA.
2204 strict [Default Off] 1900 strict [Default Off]
2205 Deprecated, equivalen !! 1901 With this option on every unmap_single operation will
>> 1902 result in a hardware IOTLB flush operation as opposed
>> 1903 to batching them for performance.
2206 sp_off [Default Off] 1904 sp_off [Default Off]
2207 By default, super pag 1905 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1906 has the capability. With this option, super page will
2209 not be supported. 1907 not be supported.
2210 sm_on !! 1908 sm_on [Default Off]
2211 Enable the Intel IOMM !! 1909 By default, scalable mode will be disabled even if the
2212 advertises that it ha !! 1910 hardware advertises that it has support for the scalable
2213 translation. !! 1911 mode translation. With this option set, scalable mode
2214 sm_off !! 1912 will be used on hardware which claims to support it.
2215 Disallow use of the I <<
2216 tboot_noforce [Default Off] 1913 tboot_noforce [Default Off]
2217 Do not force the Inte 1914 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1915 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1916 could harm performance of some high-throughput
2220 devices like 40GBit n 1917 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1918 mapping is enabled.
2222 Note that using this 1919 Note that using this option lowers the security
2223 provided by tboot bec 1920 provided by tboot because it makes the system
2224 vulnerable to DMA att 1921 vulnerable to DMA attacks.
2225 1922
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1923 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1924 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1925 1 to 9 specify maximum depth of C-state.
2229 1926
2230 intel_pstate= [X86,EARLY] !! 1927 intel_pstate= [X86]
2231 disable 1928 disable
2232 Do not enable intel 1929 Do not enable intel_pstate as the default
2233 scaling driver for 1930 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 1931 passive
2245 Use intel_pstate as 1932 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 1933 to work with generic cpufreq governors (instead of
2247 enabling its intern 1934 enabling its internal governor). This mode cannot be
2248 used along with the 1935 used along with the hardware-managed P-states (HWP)
2249 feature. 1936 feature.
2250 force 1937 force
2251 Enable intel_pstate 1938 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 1939 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 1940 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 1941 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 1942 P-States information being indicated to OSPM and therefore
2256 should be used with 1943 should be used with caution. This option does not work with
2257 processors that are 1944 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 1945 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 1946 no_hwp
2260 Do not enable hardw 1947 Do not enable hardware P state control (HWP)
2261 if available. 1948 if available.
2262 hwp_only 1949 hwp_only
2263 Only load intel_pst 1950 Only load intel_pstate on systems which support
2264 hardware P state co 1951 hardware P state control (HWP) if available.
2265 support_acpi_ppc 1952 support_acpi_ppc
2266 Enforce ACPI _PPC p 1953 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 1954 Description Table, specifies preferred power management
2268 profile as "Enterpr 1955 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 1956 then this feature is turned on by default.
2270 per_cpu_perf_limits 1957 per_cpu_perf_limits
2271 Allow per-logical-C 1958 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 1959 cpufreq sysfs interface
2273 1960
2274 intremap= [X86-64,Intel-IOMMU,E !! 1961 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 1962 on enable Interrupt Remapping (default)
2276 off disable Inter 1963 off disable Interrupt Remapping
2277 nosid disable Sourc 1964 nosid disable Source ID checking
2278 no_x2apic_optout 1965 no_x2apic_optout
2279 BIOS x2APIC o 1966 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 1967 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 1968
2284 iomem= Disable strict checki 1969 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 1970 strict regions from userspace.
2286 relaxed 1971 relaxed
2287 1972
2288 iommu= [X86,EARLY] !! 1973 iommu= [X86]
2289 off 1974 off
2290 force 1975 force
2291 noforce 1976 noforce
2292 biomerge 1977 biomerge
2293 panic 1978 panic
2294 nopanic 1979 nopanic
2295 merge 1980 merge
2296 nomerge 1981 nomerge
2297 soft 1982 soft
2298 pt [X86] 1983 pt [X86]
2299 nopt [X86] 1984 nopt [X86]
2300 nobypass [PPC/POWERNV] 1985 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 1986 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 1987
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 1988 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 1989 Format: { "0" | "1" }
2305 0 - Try to allocate a 1990 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 1991 falling back to the full range if needed.
2307 1 - Allocate directly 1992 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 1993 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 1994 greater than 32-bit addressing.
2310 1995
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 1996 iommu.strict= [ARM64] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 1997 Format: { "0" | "1" }
2313 0 - Lazy mode. 1998 0 - Lazy mode.
2314 Request that DMA un 1999 Request that DMA unmap operations use deferred
2315 invalidation of har 2000 invalidation of hardware TLBs, for increased
2316 throughput at the c 2001 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2002 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2003 the relevant IOMMU driver.
2319 1 - Strict mode. !! 2004 1 - Strict mode (default).
2320 DMA unmap operation 2005 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2006 synchronously.
2322 unset - Use value of <<
2323 Note: on x86, strict <<
2324 legacy driver-specifi <<
2325 2007
2326 iommu.passthrough= 2008 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2009 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2010 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2011 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2012 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2013 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2014
2333 io7= [HW] IO7 for Marvel-b 2015 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2016 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2017 arch/alpha/kernel/core_marvel.c.
2336 2018
2337 io_delay= [X86,EARLY] I/O delay !! 2019 io_delay= [X86] I/O delay method
2338 0x80 2020 0x80
2339 Standard port 0x80 ba 2021 Standard port 0x80 based delay
2340 0xed 2022 0xed
2341 Alternate port 0xed b 2023 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2024 udelay
2343 Simple two microsecon 2025 Simple two microseconds delay
2344 none 2026 none
2345 No delay 2027 No delay
2346 2028
2347 ip= [IP_PNP] 2029 ip= [IP_PNP]
2348 See Documentation/adm 2030 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2031
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2032 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2033 IPC identifiers from 32,768 to 16,777,216.
2352 2034
2353 irqaffinity= [SMP] Set the default 2035 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2036 The argument is a cpu list, as described above.
2355 2037
2356 irqchip.gicv2_force_probe= 2038 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2039 [ARM, ARM64]
2358 Format: <bool> 2040 Format: <bool>
2359 Force the kernel to l 2041 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2042 of a GICv2 controller even if the memory range
2361 exposed by the device 2043 exposed by the device tree is too small.
2362 2044
2363 irqchip.gicv3_nolpi= 2045 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2046 [ARM, ARM64]
2365 Force the kernel to i 2047 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2048 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2049 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2050 to let secondary kernels in charge of setting up
2369 LPIs. 2051 LPIs.
2370 2052
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2053 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2054 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2055 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2056 CONFIG_ARM64_PSEUDO_NMI.
2375 2057
2376 irqfixup [HW] 2058 irqfixup [HW]
2377 When an interrupt is 2059 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2060 for it. Intended to get systems with badly broken
2379 firmware running. 2061 firmware running.
2380 2062
2381 irqpoll [HW] 2063 irqpoll [HW]
2382 When an interrupt is 2064 When an interrupt is not handled search all handlers
2383 for it. Also check al 2065 for it. Also check all handlers each timer
2384 interrupt. Intended t 2066 interrupt. Intended to get systems with badly broken
2385 firmware running. 2067 firmware running.
2386 2068
2387 isapnp= [ISAPNP] 2069 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2070 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2071
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2072 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2073 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2074 Format: [flag-list,]<cpu-list>
2393 2075
2394 Specify one or more C 2076 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2077 specified in the flag list (default: domain):
2396 2078
2397 nohz 2079 nohz
2398 Disable the tick wh 2080 Disable the tick when a single task runs.
2399 2081
2400 A residual 1Hz tick 2082 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2083 need to affine to housekeeping through the global
2402 workqueue's affinit 2084 workqueue's affinity configured via the
2403 /sys/devices/virtua 2085 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2086 by using the 'domain' flag described below.
2405 2087
2406 NOTE: by default th 2088 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2089 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2090 be configured manually after bootup.
2409 2091
2410 domain 2092 domain
2411 Isolate from the ge 2093 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2094 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2095 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2096 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2097 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2098 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2099 It offers a much more flexible interface where CPUs can
2418 move in and out of 2100 move in and out of an isolated set anytime.
2419 2101
2420 You can move a proc 2102 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2103 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2104 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2105 "number of CPUs in system - 1".
2424 2106
2425 managed_irq 2107 managed_irq
2426 2108
2427 Isolate from being 2109 Isolate from being targeted by managed interrupts
2428 which have an inter 2110 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2111 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2112 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2113 the /proc/irq/* interfaces.
2432 2114
2433 This isolation is b 2115 This isolation is best effort and only effective
2434 if the automaticall 2116 if the automatically assigned interrupt mask of a
2435 device queue contai 2117 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2118 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2119 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2120 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2121 cannot disturb the isolated CPU.
2440 2122
2441 If a queue's affini 2123 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2124 CPUs then this parameter has no effect on the
2443 interrupt routing d 2125 interrupt routing decision, though interrupts are
2444 only delivered when 2126 only delivered when tasks running on those
2445 isolated CPUs submi 2127 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2128 housekeeping CPUs has no influence on those
2447 queues. 2129 queues.
2448 2130
2449 The format of <cpu-li 2131 The format of <cpu-list> is described above.
2450 2132
2451 iucv= [HW,NET] 2133 iucv= [HW,NET]
2452 2134
2453 ivrs_ioapic [HW,X86-64] 2135 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2136 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 2137 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 2138 example, to map IOAPIC-ID decimal 10 to
2457 !! 2139 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 2140 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 2141
2471 ivrs_hpet [HW,X86-64] 2142 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2143 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 2144 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 2145 example, to map HPET-ID decimal 0 to
2475 !! 2146 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]= 2147 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 2148
2489 ivrs_acpihid [HW,X86-64] 2149 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2150 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 2151 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 2152 example, to map UART-HID:UID AMD0020:0 to
2493 !! 2153 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[ 2154 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 2155
2507 js= [HW,JOY] Analog joyst 2156 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2157 See Documentation/input/joydev/joystick.rst.
2509 2158
>> 2159 nokaslr [KNL]
>> 2160 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2161 kernel and module base offset ASLR (Address Space
>> 2162 Layout Randomization).
>> 2163
2510 kasan_multi_shot 2164 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2165 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2166 report on every invalid memory access. Without this
2513 parameter KASAN will 2167 parameter KASAN will print report only for the first
2514 invalid access. 2168 invalid access.
2515 2169
2516 keep_bootcon [KNL,EARLY] !! 2170 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 2171
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2172 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2173 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2174 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2175 the kernel for non-movable allocations. The requested
2528 amount is spread even 2176 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2177 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2178 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2179 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2180 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2181 other nodes will have a larger ZONE_MOVABLE.
2534 2182
2535 ZONE_MOVABLE is used 2183 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2184 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2185 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2186 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2187 zone if it does not.
2540 2188
2541 It is possible to spe 2189 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2190 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2191 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2192 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2193 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2194 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2195 are exclusive, so you cannot specify multiple forms.
2548 2196
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2197 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2198 Format: <Controller#>[,poll interval]
2551 The controller # is t 2199 The controller # is the number of the ehci usb debug
2552 port as it is probed 2200 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2201 optional and is the number seconds in between
2554 each poll cycle to th 2202 each poll cycle to the debug port in case you need
2555 the functionality for 2203 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2204 gdb or control-c on the dbgp connection. When
2557 not using this parame 2205 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2206 the kernel debugger.
2559 2207
2560 kgdboc= [KGDB,HW] kgdb over c 2208 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2209 Requires a tty driver that supports console polling,
2562 or a supported pollin 2210 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2211 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2212 keyboard only format: kbd
2565 keyboard and serial 2213 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2214 Optional Kernel mode setting:
2567 kms, kbd format: kms 2215 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2216 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2217
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2218 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2219 If the boot console provides the ability to read
2572 characters and can wo 2220 characters and can work in polling mode, you can use
2573 this parameter to tel 2221 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2222 until the normal console is registered. Intended to
2575 be used together with 2223 be used together with the kgdboc parameter which
2576 specifies the normal 2224 specifies the normal console to transition to.
2577 2225
2578 The name of the early 2226 The name of the early console should be specified
2579 as the value of this 2227 as the value of this parameter. Note that the name of
2580 the early console mig 2228 the early console might be different than the tty
2581 name passed to kgdboc 2229 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2230 blank and the first boot console that implements
2583 read() will be picked 2231 read() will be picked.
2584 2232
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2233 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2234 kernel debugger at the earliest opportunity.
2587 2235
2588 kmac= [MIPS] Korina etherne 2236 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2237 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2238 Ethernet adapter MAC address.
2591 2239
2592 kmemleak= [KNL,EARLY] Boot-time !! 2240 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2241 Valid arguments: on, off
2594 Default: on 2242 Default: on
2595 Built with CONFIG_DEB 2243 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2244 the default is off.
2597 2245
2598 kprobe_event=[probe-list] 2246 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2247 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2248 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2249 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2250 interface, but the parameters are comma delimited.
2603 For example, to add a 2251 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2252 arg1 and arg2, add to the command line;
2605 2253
2606 kprobe_event=p, 2254 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2255
2608 See also Documentatio 2256 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2257 Boot Parameter" section.
2610 2258
2611 kpti= [ARM64,EARLY] Control !! 2259 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2260 and kernel address spaces.
2613 Default: enabled on c 2261 Default: enabled on cores which need mitigation.
2614 0: force disabled 2262 0: force disabled
2615 1: force enabled 2263 1: force enabled
2616 2264
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 2265 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2266 Default is 0 (don't ignore, but inject #GP)
2625 2267
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 2268 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2269 Default is false (don't support).
2653 2270
>> 2271 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
>> 2272 KVM MMU at runtime.
>> 2273 Default is 0 (off)
>> 2274
2654 kvm.nx_huge_pages= 2275 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2276 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2277 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2278 force : Always deploy workaround.
2658 off : Never deplo 2279 off : Never deploy workaround.
2659 auto : Deploy work 2280 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2281 X86_BUG_ITLB_MULTIHIT.
2661 2282
2662 Default is 'auto'. 2283 Default is 'auto'.
2663 2284
2664 If the software worka 2285 If the software workaround is enabled for the host,
2665 guests do need not to 2286 guests do need not to enable it for nested guests.
2666 2287
2667 kvm.nx_huge_pages_recovery_ratio= 2288 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2289 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2290 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2291 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). !! 2292 minute. The default is 60.
2672 2293
2673 kvm.nx_huge_pages_recovery_period_ms= !! 2294 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2674 [KVM] Controls the ti !! 2295 Default is 1 (enabled)
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 2296
2688 kvm-arm.mode= !! 2297 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2689 [KVM,ARM,EARLY] Selec !! 2298 for all guests.
2690 operation. !! 2299 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2691 2300
2692 none: Forcefully disa !! 2301 kvm-arm.mode=
>> 2302 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2693 2303
2694 nvhe: Standard nVHE-b 2304 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2305 protected guests.
2696 2306
2697 protected: nVHE-based 2307 protected: nVHE-based mode with support for guests whose
2698 state is k 2308 state is kept private from the host.
>> 2309 Not valid if the kernel is running in EL2.
2699 2310
2700 nested: VHE-based mod !! 2311 Defaults to VHE/nVHE based on hardware support.
2701 virtualizatio <<
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE <<
2705 mode to "protected" w <<
2706 for the host. "nested <<
2707 used with extreme cau <<
2708 2312
2709 kvm-arm.vgic_v3_group0_trap= 2313 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2314 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2315 system registers
2712 2316
2713 kvm-arm.vgic_v3_group1_trap= 2317 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2318 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2319 system registers
2716 2320
2717 kvm-arm.vgic_v3_common_trap= 2321 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2322 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2323 system registers
2720 2324
2721 kvm-arm.vgic_v4_enable= 2325 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2326 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2327 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 2328
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2329 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2330 Reserves given percentage from system memory area for
2745 contiguous memory all 2331 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2332 allocation.
2747 By default it reserve 2333 By default it reserves 5% of total system memory.
2748 Format: <integer> 2334 Format: <integer>
2749 Default: 5 2335 Default: 5
2750 2336
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2337 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2338 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2339 Default is 1 (enabled)
2754 for EPT. <<
2755 2340
2756 kvm-intel.emulate_invalid_guest_state 2341 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2342 [KVM,Intel] Enable emulation of invalid guest states
2758 state. Ignored if kvm !! 2343 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 2344
2764 kvm-intel.flexpriority= 2345 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2346 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2347 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2348
2769 kvm-intel.nested= 2349 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2350 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2351 Default is 0 (disabled)
2772 2352
2773 kvm-intel.unrestricted_guest= 2353 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2354 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2355 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2356 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2357
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2358 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2359 CVE-2018-3620.
2781 2360
2782 Valid arguments: neve 2361 Valid arguments: never, cond, always
2783 2362
2784 always: L1D cache flu 2363 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2364 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2365 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2366 never: Disables the mitigation
2788 2367
2789 Default is cond (do L 2368 Default is cond (do L1 cache flush in specific instances)
2790 2369
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2370 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2371 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2372 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 2373
2813 l1tf= [X86,EARLY] Control m !! 2374 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2375 affected CPUs
2815 2376
2816 The kernel PTE invers 2377 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2378 enabled and cannot be disabled.
2818 2379
2819 full 2380 full
2820 Provides all 2381 Provides all available mitigations for the
2821 L1TF vulnerab 2382 L1TF vulnerability. Disables SMT and
2822 enables all m 2383 enables all mitigations in the
2823 hypervisors, 2384 hypervisors, i.e. unconditional L1D flush.
2824 2385
2825 SMT control a 2386 SMT control and L1D flush control via the
2826 sysfs interfa 2387 sysfs interface is still possible after
2827 boot. Hyperv 2388 boot. Hypervisors will issue a warning
2828 when the firs 2389 when the first VM is started in a
2829 potentially i 2390 potentially insecure configuration,
2830 i.e. SMT enab 2391 i.e. SMT enabled or L1D flush disabled.
2831 2392
2832 full,force 2393 full,force
2833 Same as 'full 2394 Same as 'full', but disables SMT and L1D
2834 flush runtime 2395 flush runtime control. Implies the
2835 'nosmt=force' 2396 'nosmt=force' command line option.
2836 (i.e. sysfs c 2397 (i.e. sysfs control of SMT is disabled.)
2837 2398
2838 flush 2399 flush
2839 Leaves SMT en 2400 Leaves SMT enabled and enables the default
2840 hypervisor mi 2401 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2402 L1D flush.
2842 2403
2843 SMT control a 2404 SMT control and L1D flush control via the
2844 sysfs interfa 2405 sysfs interface is still possible after
2845 boot. Hyperv 2406 boot. Hypervisors will issue a warning
2846 when the firs 2407 when the first VM is started in a
2847 potentially i 2408 potentially insecure configuration,
2848 i.e. SMT enab 2409 i.e. SMT enabled or L1D flush disabled.
2849 2410
2850 flush,nosmt 2411 flush,nosmt
2851 2412
2852 Disables SMT 2413 Disables SMT and enables the default
2853 hypervisor mi 2414 hypervisor mitigation.
2854 2415
2855 SMT control a 2416 SMT control and L1D flush control via the
2856 sysfs interfa 2417 sysfs interface is still possible after
2857 boot. Hyperv 2418 boot. Hypervisors will issue a warning
2858 when the firs 2419 when the first VM is started in a
2859 potentially i 2420 potentially insecure configuration,
2860 i.e. SMT enab 2421 i.e. SMT enabled or L1D flush disabled.
2861 2422
2862 flush,nowarn 2423 flush,nowarn
2863 Same as 'flus 2424 Same as 'flush', but hypervisors will not
2864 warn when a V 2425 warn when a VM is started in a potentially
2865 insecure conf 2426 insecure configuration.
2866 2427
2867 off 2428 off
2868 Disables hype 2429 Disables hypervisor mitigations and doesn't
2869 emit any warn 2430 emit any warnings.
2870 It also drops 2431 It also drops the swap size and available
2871 RAM limit res 2432 RAM limit restriction on both hypervisor and
2872 bare metal. 2433 bare metal.
2873 2434
2874 Default is 'flush'. 2435 Default is 'flush'.
2875 2436
2876 For details see: Docu 2437 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2438
2878 l2cr= [PPC] 2439 l2cr= [PPC]
2879 2440
2880 l3cr= [PPC] 2441 l3cr= [PPC]
2881 2442
2882 lapic [X86-32,APIC,EARLY] E !! 2443 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2444 disabled it.
2884 2445
2885 lapic= [X86,APIC] Do not use 2446 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2447 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2448 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2449 Format: notscdeadline
2889 2450
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2451 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2452 in C2 power state.
2892 2453
2893 libata.dma= [LIBATA] DMA control 2454 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2455 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2456 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2457 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2458 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2459 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2460 for disks and CDROMs, but not CFs.
2900 2461
2901 libata.ignore_hpa= [LIBATA] Igno 2462 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2463 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2464 libata.ignore_hpa=1 ignore limits, using full disk
2904 2465
2905 libata.noacpi [LIBATA] Disables use 2466 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2467 when set.
2907 Format: <int> 2468 Format: <int>
2908 2469
2909 libata.force= [LIBATA] Force config !! 2470 libata.force= [LIBATA] Force configurations. The format is comma-
2910 separated list of "[I !! 2471 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2472 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2473 matching port, link or device. Basically, it matches
2913 printed on console by !! 2474 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2475 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2476 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2477 configuration applies to all ports, links and devices.
2917 2478
2918 If only DEVICE is omi 2479 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2480 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2481 number of 0 either selects the first device or the
2921 first fan-out link be 2482 first fan-out link behind PMP device. It does not
2922 select the host link. 2483 select the host link. DEVICE number of 15 selects the
2923 host link and device 2484 host link and device attached to it.
2924 2485
2925 The VAL specifies the 2486 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2487 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2488 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2489 The following configurations can be forced.
2929 2490
2930 * Cable type: 40c, 80 2491 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2492 Any ID with matching PORT is used.
2932 2493
2933 * SATA link speed lim 2494 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2495
2935 * Transfer mode: pio[ 2496 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2497 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2498 allowed.
2938 2499
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 2500 * [no]ncq: Turn on or off NCQ.
2950 2501
2951 * [no]ncqtrim: Enable !! 2502 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 2503
2953 * [no]ncqati: Enable !! 2504 * nohrst, nosrst, norst: suppress hard, soft
>> 2505 and both resets.
2954 2506
2955 * [no]trim: Enable or !! 2507 * rstonce: only attempt one reset during
>> 2508 hot-unplug link recovery
2956 2509
2957 * trim_zero: Indicate !! 2510 * dump_id: dump IDENTIFY data.
2958 2511
2959 * max_trim_128m: Set !! 2512 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2960 <<
2961 * [no]dma: Turn on or <<
2962 <<
2963 * atapi_dmadir: Enabl <<
2964 <<
2965 * atapi_mod16_dma: En <<
2966 commands that are n <<
2967 <<
2968 * [no]dmalog: Enable <<
2969 READ LOG DMA EXT co <<
2970 <<
2971 * [no]iddevlog: Enabl <<
2972 identify device dat <<
2973 <<
2974 * [no]logdir: Enable <<
2975 purpose log directo <<
2976 <<
2977 * max_sec_128: Set tr <<
2978 <<
2979 * max_sec_1024: Set o <<
2980 1024 sectors. <<
2981 <<
2982 * max_sec_lba48: Set <<
2983 65535 sectors. <<
2984 <<
2985 * [no]lpm: Enable or <<
2986 <<
2987 * [no]setxfer: Indica <<
2988 should be skipped. <<
2989 <<
2990 * [no]fua: Disable or <<
2991 support for devices <<
2992 <<
2993 * dump_id: Dump IDENT <<
2994 2513
2995 * disable: Disable th 2514 * disable: Disable this device.
2996 2515
2997 If there are multiple 2516 If there are multiple matching configurations changing
2998 the same attribute, t 2517 the same attribute, the last one is used.
2999 2518
>> 2519 memblock=debug [KNL] Enable memblock debug messages.
>> 2520
3000 load_ramdisk= [RAM] [Deprecated] 2521 load_ramdisk= [RAM] [Deprecated]
3001 2522
3002 lockd.nlm_grace_period=P [NFS] Assig 2523 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2524 Format: <integer>
3004 2525
3005 lockd.nlm_tcpport=N [NFS] Assign 2526 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2527 Format: <integer>
3007 2528
3008 lockd.nlm_timeout=T [NFS] Assign 2529 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2530 Format: <integer>
3010 2531
3011 lockd.nlm_udpport=M [NFS] Assign 2532 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2533 Format: <integer>
3013 2534
3014 lockdown= [SECURITY,EARLY] !! 2535 lockdown= [SECURITY]
3015 { integrity | confide 2536 { integrity | confidentiality }
3016 Enable the kernel loc 2537 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2538 integrity, kernel features that allow userland to
3018 modify the running ke 2539 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2540 confidentiality, kernel features that allow userland
3020 to extract confidenti 2541 to extract confidential information from the kernel
3021 are also disabled. 2542 are also disabled.
3022 2543
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] 2544 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2545 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2546 Defaults to being automatically set based on the
3058 number of online CPUs 2547 number of online CPUs.
3059 2548
3060 locktorture.nwriters_stress= [KNL] 2549 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2550 Set the number of locking write-acquisition kthreads.
3062 2551
3063 locktorture.onoff_holdoff= [KNL] 2552 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2553 Set time (s) after boot for CPU-hotplug testing.
3065 2554
3066 locktorture.onoff_interval= [KNL] 2555 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2556 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2557 zero to disable CPU-hotplug testing.
3069 2558
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] 2559 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2560 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2561 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2562 mode during the locktorture test.
3093 2563
3094 locktorture.shutdown_secs= [KNL] 2564 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2565 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2566 is useful for hands-off automated testing.
3097 2567
3098 locktorture.stat_interval= [KNL] 2568 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2569 Time (s) between statistics printk()s.
3100 2570
3101 locktorture.stutter= [KNL] 2571 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2572 Time (s) to stutter testing, for example,
3103 specifying five secon 2573 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2574 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2575 This tests the locking primitive's ability to
3106 transition abruptly t 2576 transition abruptly to and from idle.
3107 2577
3108 locktorture.torture_type= [KNL] 2578 locktorture.torture_type= [KNL]
3109 Specify the locking i 2579 Specify the locking implementation to test.
3110 2580
3111 locktorture.verbose= [KNL] 2581 locktorture.verbose= [KNL]
3112 Enable additional pri 2582 Enable additional printk() statements.
3113 2583
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2584 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2585 Format: <irq>
3120 2586
3121 loglevel= [KNL,EARLY] !! 2587 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2588 console loglevel will be printed to the console. It can
3124 also be changed with 2589 also be changed with klogd or other programs. The
3125 loglevels are defined 2590 loglevels are defined as follows:
3126 2591
3127 0 (KERN_EMERG) 2592 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2593 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2594 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2595 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2596 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2597 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2598 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2599 7 (KERN_DEBUG) debug-level messages
3135 2600
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2601 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2602 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2603 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2604 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2605 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2606 that allows to increase the default size depending on
3142 parameter that allows !! 2607 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2608
3146 logo.nologo [FB] Disables display 2609 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2610 This may be used to provide more screen space for
3148 kernel log messages a 2611 kernel log messages and is useful when debugging
3149 kernel boot problems. 2612 kernel boot problems.
3150 2613
3151 lp=0 [LP] Specify paral 2614 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2615 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2616 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2617 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2618 specified in addition to the ports) causes
3156 attached prin 2619 attached printers to be reset. Using
3157 lp=port1,port 2620 lp=port1,port2,... specifies the parallel ports
3158 to associate 2621 to associate lp devices with, starting with
3159 lp0. A port s 2622 lp0. A port specification may be 'none' to skip
3160 that lp devic 2623 that lp device, or a parport name such as
3161 'parport0'. S 2624 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2625 port specification list means that device IDs
3163 from each por 2626 from each port should be examined, to see if
3164 an IEEE 1284- 2627 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2628 so, the driver will manage that printer.
3166 See also head 2629 See also header of drivers/char/lp.c.
3167 2630
3168 lpj=n [KNL] 2631 lpj=n [KNL]
3169 Sets loops_per_jiffy 2632 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2633 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2634 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2635 the correct value for your kernel, boot with normal
3173 autodetection and see 2636 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2637 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2638 which is likely to cause problems if your CPUs need
3176 significantly diverge 2639 significantly divergent settings. An incorrect value
3177 will cause delays in 2640 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2641 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2642 unlikely, in the extreme case this might damage your
3180 hardware. 2643 hardware.
3181 2644
>> 2645 ltpc= [NET]
>> 2646 Format: <io>,<irq>,<dma>
>> 2647
3182 lsm.debug [SECURITY] Enable LSM 2648 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2649
3184 lsm=lsm1,...,lsmN 2650 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2651 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2652 overrides CONFIG_LSM, and the "security=" parameter.
3187 2653
>> 2654 machvec= [IA-64] Force the use of a particular machine-vector
>> 2655 (machvec) in a generic kernel.
>> 2656 Example: machvec=hpzx1
>> 2657
3188 machtype= [Loongson] Share the 2658 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2659 different yeeloong laptops.
3190 Example: machtype=lem 2660 Example: machtype=lemote-yeeloong-2f-7inch
3191 2661
3192 maxcpus= [SMP,EARLY] Maximum n !! 2662 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2663 than or equal to this physical address is ignored.
>> 2664
>> 2665 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2666 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2667 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2668 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2669 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2670 only takes effect during system bootup.
3198 While n=0 is a specia 2671 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2672 which also disables the IO APIC.
3200 2673
3201 max_loop= [LOOP] The number of 2674 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2675 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2676 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2677 of statically allocating a predefined number, loop
3205 devices can be reques 2678 devices can be requested on-demand with the
3206 /dev/loop-control int 2679 /dev/loop-control interface.
3207 2680
3208 mce [X86-32] Machine Chec 2681 mce [X86-32] Machine Check Exception
3209 2682
3210 mce=option [X86-64] See Document !! 2683 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2684
3212 md= [HW] RAID subsystems 2685 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2686 See Documentation/admin-guide/md.rst.
3214 2687
3215 mdacon= [MDA] 2688 mdacon= [MDA]
3216 Format: <first>,<last 2689 Format: <first>,<last>
3217 Specifies range of co 2690 Specifies range of consoles to be captured by the MDA.
3218 2691
3219 mds= [X86,INTEL,EARLY] !! 2692 mds= [X86,INTEL]
3220 Control mitigation fo 2693 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2694 Sampling (MDS) vulnerability.
3222 2695
3223 Certain CPUs are vuln 2696 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2697 internal buffers which can forward information to a
3225 disclosure gadget und 2698 disclosure gadget under certain conditions.
3226 2699
3227 In vulnerable process 2700 In vulnerable processors, the speculatively
3228 forwarded data can be 2701 forwarded data can be used in a cache side channel
3229 attack, to access dat 2702 attack, to access data to which the attacker does
3230 not have direct acces 2703 not have direct access.
3231 2704
3232 This parameter contro 2705 This parameter controls the MDS mitigation. The
3233 options are: 2706 options are:
3234 2707
3235 full - Enable M 2708 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2709 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2710 SMT on vulnerable CPUs
3238 off - Uncondit 2711 off - Unconditionally disable MDS mitigation
3239 2712
3240 On TAA-affected machi 2713 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2714 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2715 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2716 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2717 too.
3245 2718
3246 Not specifying this o 2719 Not specifying this option is equivalent to
3247 mds=full. 2720 mds=full.
3248 2721
3249 For details see: Docu 2722 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2723
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2724 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3252 Must be specified, ot !! 2725 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 2726
3258 1 for test; 2727 1 for test;
3259 2 when the kernel is 2728 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 2729 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 2730 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 2731
3270 [X86] Work as limitin 2732 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2733 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2734 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2735 belonging to unused RAM.
3274 2736
3275 Note that this only t 2737 Note that this only takes effects during boot time since
3276 in above case 3, memo 2738 in above case 3, memory may need be hot added after boot
3277 if system memory of h 2739 if system memory of hypervisor is not sufficient.
3278 2740
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 2741 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2742 memory.
3289 2743
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2744 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2745 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2746 per-device physically contiguous DMA buffers.
3295 2747
3296 memhp_default_state=online/offline/on !! 2748 memhp_default_state=online/offline
3297 [KNL] Set the initial 2749 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2750 onlining policy. If not specified, the default value is
3299 set according to the 2751 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2752 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2753 option.
3302 See Documentation/adm 2754 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 2755
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2756 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2757 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2758 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2759 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2760 option description.
3309 2761
3310 memmap=nn[KMG]@ss[KMG] 2762 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2763 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 2764 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2765 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2766 which limits max address to nn[KMG].
3315 Multiple different re 2767 Multiple different regions can be specified,
3316 comma delimited. 2768 comma delimited.
3317 Example: 2769 Example:
3318 memmap=100M@2 2770 memmap=100M@2G,100M#3G,1G!1024G
3319 2771
3320 memmap=nn[KMG]#ss[KMG] 2772 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2773 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2774 Region of memory to be marked is from ss to ss+nn.
3323 2775
3324 memmap=nn[KMG]$ss[KMG] 2776 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2777 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2778 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2779 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2780 memmap=64K$0x18690000
3329 or 2781 or
3330 memmap=0x100 2782 memmap=0x10000$0x18690000
3331 Some bootloaders may 2783 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2784 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2785 will be eaten.
3334 2786
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2787 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2788 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2789 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2790 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2791 and is NVDIMM or ADR memory.
3340 2792
3341 memmap=<size>%<offset>-<oldtype>+<new 2793 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 2794 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 2795 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 2796 out, the whole region will be marked as <newtype>,
3345 even if previously un 2797 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 2798 out, matching memory will be removed. Types are
3347 specified as e820 typ 2799 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 2800 3 = ACPI, 12 = PRAM.
3349 2801
3350 memory_corruption_check=0/1 [X86,EARL !! 2802 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 2803 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2804 memory when doing things like suspend/resume.
3353 Setting this option w 2805 Setting this option will scan the memory
3354 looking for corruptio 2806 looking for corruption. Enabling this will
3355 both detect corruptio 2807 both detect corruption and prevent the kernel
3356 from using the memory 2808 from using the memory being corrupted.
3357 However, its intended 2809 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2810 repeatable BIOS-originated corruption always
3359 affects the same memo 2811 affects the same memory, you can use memmap=
3360 to prevent the kernel 2812 to prevent the kernel from using that memory.
3361 2813
3362 memory_corruption_check_size=size [X8 !! 2814 memory_corruption_check_size=size [X86]
3363 By default it checks 2815 By default it checks for corruption in the low
3364 64k, making this memo 2816 64k, making this memory unavailable for normal
3365 use. Use this parame 2817 use. Use this parameter to scan for
3366 corruption in more or 2818 corruption in more or less memory.
3367 2819
3368 memory_corruption_check_period=second !! 2820 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2821 By default it checks for corruption every 60
3370 seconds. Use this pa 2822 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2823 other rate. 0 disables periodic checking.
3372 2824
3373 memory_hotplug.memmap_on_memory 2825 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 2826 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 2827 Format: {on | off (default)}
3376 When enabled, runtime 2828 When enabled, runtime hotplugged memory will
3377 allocate its internal !! 2829 allocate its internal metadata (struct pages)
3378 those vmemmap pages c !! 2830 from the hotadded memory which will allow to
3379 if hugetlb_free_vmemm !! 2831 hotadd a lot of memory without requiring
3380 hotadded memory which !! 2832 additional memory to do so.
3381 lot of memory without <<
3382 memory to do so. <<
3383 This feature is disab 2833 This feature is disabled by default because it
3384 has some implication 2834 has some implication on large (e.g. GB)
3385 allocations in some c 2835 allocations in some configurations (e.g. small
3386 memory blocks). 2836 memory blocks).
3387 The state of the flag 2837 The state of the flag can be read in
3388 /sys/module/memory_ho 2838 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 2839 Note that even when enabled, there are a few cases where
3390 the feature is not ef 2840 the feature is not effective.
3391 2841
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 2842 memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest
3393 Format: <integer> 2843 Format: <integer>
3394 default : 0 <disable> 2844 default : 0 <disable>
3395 Specifies the number 2845 Specifies the number of memtest passes to be
3396 performed. Each pass 2846 performed. Each pass selects another test
3397 pattern from a given 2847 pattern from a given set of patterns. Memtest
3398 fills the memory with 2848 fills the memory with this pattern, validates
3399 memory contents and r 2849 memory contents and reserves bad memory
3400 regions that are dete 2850 regions that are detected.
3401 2851
3402 mem_encrypt= [X86-64] AMD Secure M 2852 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2853 Valid arguments: on, off
3404 Default: off !! 2854 Default (depends on kernel configuration option):
>> 2855 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2856 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2857 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2858 mem_encrypt=off: Do not activate SME
3407 2859
3408 Refer to Documentatio !! 2860 Refer to Documentation/virt/kvm/amd-memory-encryption.rst
3409 for details on when m 2861 for details on when memory encryption can be activated.
3410 2862
3411 mem_sleep_default= [SUSPEND] Def 2863 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2864 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2865 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2866 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 2867 See Documentation/admin-guide/pm/sleep-states.rst.
3416 2868
>> 2869 meye.*= [HW] Set MotionEye Camera parameters
>> 2870 See Documentation/admin-guide/media/meye.rst.
>> 2871
>> 2872 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2873 Multi-Function General Purpose Timers on AMD Geode
>> 2874 platforms.
>> 2875
3417 mfgptfix [X86-32] Fix MFGPT ti 2876 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2877 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2878 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2879 problem by letting the user disable the workaround.
3421 2880
3422 mga= [HW,DRM] 2881 mga= [HW,DRM]
3423 2882
3424 microcode.force_minrev= [X86] !! 2883 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2884 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2885
3429 mini2440= [ARM,HW,KNL] 2886 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2887 Format:[0..2][b][c][t]
3431 Default: "0tb" 2888 Default: "0tb"
3432 MINI2440 configuratio 2889 MINI2440 configuration specification:
3433 0 - The attached scre 2890 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2891 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2892 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2893 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2894 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2895 unconfigured.
3439 b - Enable backlight. 2896 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2897 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2898 LED. This parameter is not necessary when using the
3442 VGA shield. 2899 VGA shield.
3443 c - Enable the s3c ca 2900 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2901 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2902 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2903 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2904 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 2905 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 2906
3450 mitigations= 2907 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 2908 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 2909 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 2910 arch-independent options, each of which is an
3454 aggregation of existi 2911 aggregation of existing arch-specific options.
3455 2912
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 2913 off
3460 Disable all o 2914 Disable all optional CPU mitigations. This
3461 improves syst 2915 improves system performance, but it may also
3462 expose users 2916 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 2917 Equivalent to: nopti [X86,PPC]
3464 !! 2918 kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 2919 nospectre_v1 [X86,PPC]
>> 2920 nobp=0 [S390]
3475 2921 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 2922 spectre_v2_user=off [X86]
3482 !! 2923 spec_store_bypass_disable=off [X86,PPC]
3483 2924 ssbd=force-off [ARM64]
>> 2925 l1tf=off [X86]
>> 2926 mds=off [X86]
3484 2927 tsx_async_abort=off [X86]
>> 2928 kvm.nx_huge_pages=off [X86]
>> 2929 no_entry_flush [PPC]
>> 2930 no_uaccess_flush [PPC]
3485 2931
3486 Exceptions: 2932 Exceptions:
3487 2933 This does not have any effect on
3488 2934 kvm.nx_huge_pages when
3489 2935 kvm.nx_huge_pages=force.
3490 2936
3491 auto (default) 2937 auto (default)
3492 Mitigate all 2938 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 2939 enabled, even if it's vulnerable. This is for
3494 users who don 2940 users who don't want to be surprised by SMT
3495 getting disab 2941 getting disabled across kernel upgrades, or who
3496 have other wa 2942 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 2943 Equivalent to: (default behavior)
3498 2944
3499 auto,nosmt 2945 auto,nosmt
3500 Mitigate all 2946 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 2947 if needed. This is for users who always want to
3502 be fully miti 2948 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 2949 Equivalent to: l1tf=flush,nosmt [X86]
3504 2950 mds=full,nosmt [X86]
3505 2951 tsx_async_abort=full,nosmt [X86]
3506 <<
3507 <<
3508 2952
3509 mminit_loglevel= 2953 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 2954 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 2955 parameter allows control of the logging verbosity for
3512 the additional memory 2956 the additional memory initialisation checks. A value
3513 of 0 disables mminit 2957 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 2958 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 2959 so loglevel=8 may also need to be specified.
3516 2960
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 2961 module.sig_enforce
3574 [KNL] When CONFIG_MOD 2962 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 2963 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 2964 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 2965 is always true, so this option does nothing.
3578 2966
3579 module_blacklist= [KNL] Do not load 2967 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 2968 modules. Useful for debugging problem modules.
3581 2969
3582 mousedev.tap_time= 2970 mousedev.tap_time=
3583 [MOUSE] Maximum time 2971 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 2972 leaving touchpad surface for touch to be considered
3585 a tap and be reported 2973 a tap and be reported as a left button click (for
3586 touchpads working in 2974 touchpads working in absolute mode only).
3587 Format: <msecs> 2975 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 2976 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 2977 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 2978 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 2979 reporting absolute coordinates, such as tablets
3592 2980
3593 movablecore= [KNL,X86,PPC,EARLY] !! 2981 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 2982 Format: nn[KMGTPE] | nn%
3595 This parameter is the 2983 This parameter is the complement to kernelcore=, it
3596 specifies the amount 2984 specifies the amount of memory used for migratable
3597 allocations. If both 2985 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 2986 specified, then kernelcore will be at *least* the
3599 specified value but m 2987 specified value but may be more. If movablecore on its
3600 own is specified, the 2988 own is specified, the administrator must be careful
3601 that the amount of me 2989 that the amount of memory usable for all allocations
3602 is not too small. 2990 is not too small.
3603 2991
3604 movable_node [KNL,EARLY] Boot-time !! 2992 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 2993 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 2994 of such nodes will be usable only for movable
3607 allocations which rul 2995 allocations which rules out almost all kernel
3608 allocations. Use with 2996 allocations. Use with caution!
3609 2997
3610 MTD_Partition= [MTD] 2998 MTD_Partition= [MTD]
3611 Format: <name>,<regio 2999 Format: <name>,<region-number>,<size>,<offset>
3612 3000
3613 MTD_Region= [MTD] Format: 3001 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3002 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3003
3616 mtdparts= [MTD] 3004 mtdparts= [MTD]
3617 See drivers/mtd/parse 3005 See drivers/mtd/parsers/cmdlinepart.c
3618 3006
>> 3007 multitce=off [PPC] This parameter disables the use of the pSeries
>> 3008 firmware feature for updating multiple TCE entries
>> 3009 at a time.
>> 3010
>> 3011 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 3012
>> 3013 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 3014
>> 3015 boundary - index of last SLC block on Flex-OneNAND.
>> 3016 The remaining blocks are configured as MLC blocks.
>> 3017 lock - Configure if Flex-OneNAND boundary should be locked.
>> 3018 Once locked, the boundary cannot be changed.
>> 3019 1 indicates lock status, 0 indicates unlock status.
>> 3020
>> 3021 mtdset= [ARM]
>> 3022 ARM/S3C2412 JIVE boot control
>> 3023
>> 3024 See arch/arm/mach-s3c/mach-jive.c
>> 3025
3619 mtouchusb.raw_coordinates= 3026 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3027 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3028 ('y', default) or cooked coordinates ('n')
3622 3029
3623 mtrr=debug [X86,EARLY] !! 3030 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 3031 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3032 that could hold holes aka. UC entries.
3630 3033
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3034 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3035 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3036 Default is 1.
3634 Large value could pre 3037 Large value could prevent small alignment from
3635 using up MTRRs. 3038 using up MTRRs.
3636 3039
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3040 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3041 Format: <integer>
3639 Range: 0,7 : spare re 3042 Range: 0,7 : spare reg number
3640 Default : 1 3043 Default : 1
3641 Used for mtrr cleanup 3044 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3045 Set to 2 or more if your graphical card needs more.
3643 3046
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 3047 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3048
3650 netdev= [NET] Network devices 3049 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3050 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3051 Note that mem_start is often overloaded to mean
3653 something different a 3052 something different and driver-specific.
3654 This usage is only do 3053 This usage is only documented in each driver source
3655 file if at all. 3054 file if at all.
3656 3055
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 3056 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3057 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3058 0 to disable accounting
3665 1 to enable accountin 3059 1 to enable accounting
3666 Default value is 0. 3060 Default value is 0.
3667 3061
3668 nfs.cache_getent= !! 3062 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3063 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3064
3672 nfs.cache_getent_timeout= !! 3065 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3066 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3067
>> 3068 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3069 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3070
3676 nfs.callback_nr_threads= 3071 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3072 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3073 NFS client will assign to service NFSv4 callback
3679 requests. 3074 requests.
3680 3075
3681 nfs.callback_tcpport= 3076 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3077 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3078 channel should listen.
3684 3079
3685 nfs.delay_retrans= !! 3080 nfs.cache_getent=
3686 [NFS] specifies the n !! 3081 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3082 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3083
3689 Only applies if the s !! 3084 nfs.cache_getent_timeout=
3690 and the specified val !! 3085 [NFS] sets the timeout after which an attempt to
>> 3086 update a cache entry is deemed to have failed.
>> 3087
>> 3088 nfs.idmap_cache_timeout=
>> 3089 [NFS] set the maximum lifetime for idmapper cache
>> 3090 entries.
3691 3091
3692 nfs.enable_ino64= 3092 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3093 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3094 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3095 number for the readdir() and stat() syscalls instead
3696 of returning the full 3096 of returning the full 64-bit number.
3697 The default is to ret 3097 The default is to return 64-bit inode numbers.
3698 3098
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3099 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3100 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3101 slots the client will assign to the callback
3706 channel. This determi 3102 channel. This determines the maximum number of
3707 callbacks the client 3103 callbacks the client will process in parallel for
3708 a particular server. 3104 a particular server.
3709 3105
3710 nfs.max_session_slots= 3106 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3107 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3108 the client will attempt to negotiate with the server.
3713 This limits the numbe 3109 This limits the number of simultaneous RPC requests
3714 that the client can s 3110 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3111 Note that there is little point in setting this
3716 value higher than the 3112 value higher than the max_tcp_slot_table_limit.
3717 3113
3718 nfs.nfs4_disable_idmapping= 3114 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3115 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3116 ensures that both the RPC level authentication
3721 scheme and the NFS le 3117 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3118 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3119 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3120 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3121 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3122 Servers that do not support this mode of operation
3727 will be autodetected 3123 will be autodetected by the client, and it will fall
3728 back to using the idm 3124 back to using the idmapper.
3729 To turn off this beha 3125 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3126 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3127 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3128 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3129 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3130 UUID that is generated at system install time.
3736 3131
3737 nfs.recover_lost_locks= !! 3132 nfs.send_implementation_id =
>> 3133 [NFSv4.1] Send client implementation identification
>> 3134 information in exchange_id requests.
>> 3135 If zero, no implementation identification information
>> 3136 will be sent.
>> 3137 The default is to send the implementation identification
>> 3138 information.
>> 3139
>> 3140 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3141 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3142 to a lease timeout on the server. Please note that
3740 doing this risks data 3143 doing this risks data corruption, since there are
3741 no guarantees that th 3144 no guarantees that the file will remain unchanged
3742 after the locks are l 3145 after the locks are lost.
3743 If you want to enable 3146 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3147 attempting to recover these locks, then set this
3745 parameter to '1'. 3148 parameter to '1'.
3746 The default parameter 3149 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3150 not to attempt recovery of lost locks.
3748 3151
3749 nfs.send_implementation_id= !! 3152 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 3153 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3154 layoutstats to the pNFS metadata server.
3760 3155
3761 Setting this to value 3156 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3157 whatever value is the default set by the layout
3763 driver. A non-zero va 3158 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3159 in seconds between layoutstats transmissions.
3765 3160
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= 3161 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 3162 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 3163 server will return only numeric uids and gids to
3774 clients using auth_sy 3164 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 3165 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 3166 migration from NFSv2/v3.
3777 3167
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] 3168 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3169 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3170 NMI stack-backtrace request.
3798 3171
3799 nmi_debug= [KNL,SH] Specify one 3172 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3173 when a NMI is triggered.
3801 Format: [state][,regs 3174 Format: [state][,regs][,debounce][,die]
3802 3175
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3176 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3177 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3178 Valid num: 0 or 1
3806 0 - turn hardlockup d 3179 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3180 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3181 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3182 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3183 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3184 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3185 please see 'nowatchdog'.
3815 This is useful when y 3186 This is useful when you use a panic=... timeout and
3816 need the box quickly 3187 need the box quickly up again.
3817 3188
3818 These settings can be 3189 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3190 the nmi_watchdog and hardlockup_panic sysctls.
3820 3191
>> 3192 netpoll.carrier_timeout=
>> 3193 [NET] Specifies amount of time (in seconds) that
>> 3194 netpoll should wait for a carrier. By default netpoll
>> 3195 waits 4 seconds.
>> 3196
3821 no387 [BUGS=X86-32] Tells t 3197 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3198 emulation library even if a 387 maths coprocessor
3823 is present. 3199 is present.
3824 3200
3825 no4lvl [RISCV,EARLY] Disable !! 3201 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 3202 kernel to use 4-level paging instead.
3830 3203
3831 noalign [KNL,ARM] !! 3204 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 3205
3840 no_console_suspend 3206 no_console_suspend
3841 [HW] Never suspend th 3207 [HW] Never suspend the console
3842 Disable suspending of 3208 Disable suspending of consoles during suspend and
3843 hibernate operations. 3209 hibernate operations. Once disabled, debugging
3844 messages can reach va 3210 messages can reach various consoles while the rest
3845 of the system is bein 3211 of the system is being put to sleep (ie, while
3846 debugging driver susp 3212 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3213 not work reliably with all consoles, but is known
3848 to work with serial a 3214 to work with serial and VGA consoles.
3849 To facilitate more fl 3215 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3216 console_suspend, a printk module parameter to control
3851 it. Users could use c 3217 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3218 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3219 turn on/off it dynamically.
3854 3220
3855 no_debug_objects !! 3221 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3222 Disable device dump. Device dump allows drivers to
>> 3223 append dump data to vmcore so you can collect driver
>> 3224 specified debug info. Drivers can append the data
>> 3225 without any limit and this data is stored in memory,
>> 3226 so this may cause significant memory stress. Disabling
>> 3227 device dump can help save memory but the driver debug
>> 3228 data will be no longer available. This parameter
>> 3229 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3230 is set.
>> 3231
>> 3232 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3233 caches in the slab allocator. Saves per-node memory,
>> 3234 but will impact performance.
>> 3235
>> 3236 noalign [KNL,ARM]
>> 3237
>> 3238 noaltinstr [S390] Disables alternative instructions patching
>> 3239 (CPU alternatives feature).
>> 3240
>> 3241 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3242 IOAPICs that may be present in the system.
>> 3243
>> 3244 noautogroup Disable scheduler automatic task group creation.
>> 3245
>> 3246 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 3247 on "Classic" PPC cores.
>> 3248
>> 3249 nocache [ARM]
>> 3250
>> 3251 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 3252
>> 3253 nodelayacct [KNL] Disable per-task delay accounting
3857 3254
3858 nodsp [SH] Disable hardware 3255 nodsp [SH] Disable hardware DSP at boot time.
3859 3256
3860 noefi [EFI,EARLY] Disable E !! 3257 noefi Disable EFI runtime services support.
>> 3258
>> 3259 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
>> 3260
>> 3261 noexec [IA-64]
>> 3262
>> 3263 noexec [X86]
>> 3264 On X86-32 available only on PAE configured kernels.
>> 3265 noexec=on: enable non-executable mappings (default)
>> 3266 noexec=off: disable non-executable mappings
>> 3267
>> 3268 nosmap [X86,PPC]
>> 3269 Disable SMAP (Supervisor Mode Access Prevention)
>> 3270 even if it is supported by processor.
3861 3271
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3272 nosmep [X86,PPC]
>> 3273 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3274 even if it is supported by processor.
3863 3275
3864 noexec32 [X86-64] 3276 noexec32 [X86-64]
3865 This affects only 32- 3277 This affects only 32-bit executables.
3866 noexec32=on: enable n 3278 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3279 read doesn't imply executable mappings
3868 noexec32=off: disable 3280 noexec32=off: disable non-executable mappings
3869 read implies 3281 read implies executable mappings
3870 3282
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 3283 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3284
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3285 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3286 register save and restore. The kernel will only save
3881 legacy floating-point 3287 legacy floating-point registers on task switch.
3882 3288
>> 3289 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
>> 3290
>> 3291 nohugevmalloc [PPC] Disable kernel huge vmalloc mappings.
>> 3292
>> 3293 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3294 Equivalent to smt=1.
>> 3295
>> 3296 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3297 nosmt=force: Force disable SMT, cannot be undone
>> 3298 via the sysfs control file.
>> 3299
>> 3300 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3301 (bounds check bypass). With this option data leaks are
>> 3302 possible in the system.
>> 3303
>> 3304 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 3305 the Spectre variant 2 (indirect branch prediction)
>> 3306 vulnerability. System may allow data leaks with this
>> 3307 option.
>> 3308
>> 3309 nospec_store_bypass_disable
>> 3310 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3311
>> 3312 no_uaccess_flush
>> 3313 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3314
>> 3315 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3316 and restore using xsave. The kernel will fallback to
>> 3317 enabling legacy floating-point and sse state.
>> 3318
>> 3319 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3320 register states. The kernel will fall back to use
>> 3321 xsave to save the states. By using this parameter,
>> 3322 performance of saving the states is degraded because
>> 3323 xsave doesn't support modified optimization while
>> 3324 xsaveopt supports it on xsaveopt enabled systems.
>> 3325
>> 3326 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3327 restoring x86 extended register state in compacted
>> 3328 form of xsave area. The kernel will fall back to use
>> 3329 xsaveopt and xrstor to save and restore the states
>> 3330 in standard form of xsave area. By using this
>> 3331 parameter, xsave area per process might occupy more
>> 3332 memory on xsaves enabled systems.
>> 3333
>> 3334 nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
>> 3335 in do_idle() and not use the arch_cpu_idle()
>> 3336 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
>> 3337 to be effective. This is useful on platforms where the
>> 3338 sleep(SH) or wfi(ARM,ARM64) instructions do not work
>> 3339 correctly or when doing power measurements to evalute
>> 3340 the impact of the sleep instructions. This is also
>> 3341 useful when using JTAG debugger.
>> 3342
>> 3343 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3344 only way then for a file to be executed with privilege
>> 3345 is to be setuid root or executed by root.
>> 3346
>> 3347 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3348 function PAL_HALT_LIGHT when idle. This increases
>> 3349 power-consumption. On the positive side, it reduces
>> 3350 interrupt wake-up latency, which may improve performance
>> 3351 in certain environments such as networked servers or
>> 3352 real-time systems.
>> 3353
3883 no_hash_pointers 3354 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3355 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3356 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3357 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3358 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3359 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3360 users, but it also makes debugging the kernel more
3891 difficult since unequ 3361 difficult since unequal pointers can no longer be
3892 compared. However, i 3362 compared. However, if this command-line option is
3893 specified, then all n 3363 specified, then all normal pointers will have their true
3894 value printed. This o !! 3364 value printed. Pointers printed via %pK may still be
>> 3365 hashed. This option should only be specified when
3895 debugging the kernel. 3366 debugging the kernel. Please do not use on production
3896 kernels. 3367 kernels.
3897 3368
3898 nohibernate [HIBERNATION] Disable 3369 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3370
3900 nohlt [ARM,ARM64,MICROBLAZE <<
3901 busy wait in do_idle( <<
3902 implementation; requi <<
3903 to be effective. This <<
3904 sleep(SH) or wfi(ARM, <<
3905 correctly or when doi <<
3906 the impact of the sle <<
3907 useful when using JTA <<
3908 <<
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA <<
3910 <<
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA <<
3912 <<
3913 nohz= [KNL] Boottime enable 3371 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3372 Valid arguments: on, off
3915 Default: on 3373 Default: on
3916 3374
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3375 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3376 The argument is a cpu list, as described above.
3919 In kernels built with 3377 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3378 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3379 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3380 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3381 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3382 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3383 rcu_nocbs= boot parameter.
3926 3384
3927 Note that this argume !! 3385 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 3386
>> 3387 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3388 disable unhandled interrupt sources.
>> 3389
>> 3390 no_timer_check [X86,APIC] Disables the code which tests for
>> 3391 broken timer IRQ sources.
>> 3392
>> 3393 noisapnp [ISAPNP] Disables ISA PnP code.
3929 3394
3930 noinitrd [RAM] Tells the kerne 3395 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3396 initial RAM disk.
3932 3397
3933 nointremap [X86-64,Intel-IOMMU,E !! 3398 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3399 remapping.
3935 [Deprecated - use int 3400 [Deprecated - use intremap=off]
3936 3401
3937 noinvpcid [X86,EARLY] Disable t !! 3402 nointroute [IA-64]
3938 3403
3939 noiotrap [SH] Disables trapped !! 3404 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 3405
3941 noirqdebug [X86-32] Disables the !! 3406 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 <<
3944 noisapnp [ISAPNP] Disables ISA <<
3945 3407
3946 nokaslr [KNL,EARLY] !! 3408 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 3409
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3410 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3411 fault handling.
3953 3412
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3413 no-vmw-sched-clock
>> 3414 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3415 clock and use the default one.
3955 3416
3956 nolapic [X86-32,APIC,EARLY] D !! 3417 no-steal-acc [X86,PV_OPS,ARM64] Disable paravirtualized steal time
>> 3418 accounting. steal time is computed, but won't
>> 3419 influence scheduler behaviour
3957 3420
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3421 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3959 3422
3960 nomce [X86-32] Disable Mach !! 3423 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3961 3424
3962 nomfgpt [X86-32] Disable Mult !! 3425 noltlbs [PPC] Do not use large page/tlb entries for kernel
3963 Timer usage (for AMD !! 3426 lowmem mapping on PPC40x and PPC8xx
3964 3427
3965 nomodeset Disable kernel modese !! 3428 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 3429
3973 Useful as error fallb !! 3430 nomce [X86-32] Disable Machine Check Exception
3974 3431
3975 nomodule Disable module load !! 3432 nomfgpt [X86-32] Disable Multi-Function General Purpose
>> 3433 Timer usage (for AMD Geode machines).
3976 3434
3977 nonmi_ipi [X86] Disable using N 3435 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3436 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3437 irq.
3980 3438
3981 nopat [X86,EARLY] Disable P !! 3439 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 3440
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3441 nopat [X86] Disable PAT (page attribute table extension of
3993 Disables the PV optim !! 3442 pagetables) support.
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 3443
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3444 nopcid [X86-64] Disable the PCID cpu feature.
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3445
4002 norandmaps Don't use address spa 3446 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3447 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3448
4005 noreplace-smp [X86-32,SMP] Don't re 3449 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3450 with UP alternatives
4007 3451
>> 3452 nordrand [X86] Disable kernel use of the RDRAND and
>> 3453 RDSEED instructions even if they are supported
>> 3454 by the processor. RDRAND and RDSEED are still
>> 3455 available to user space applications.
>> 3456
4008 noresume [SWSUSP] Disables res 3457 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3458 space.
4010 3459
4011 no-scroll [VGA] Disables scroll 3460 no-scroll [VGA] Disables scrollback.
4012 This is required for 3461 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3462 reader made by F.H. Papenmeier (Germany).
4014 3463
4015 nosgx [X86-64,SGX,EARLY] Di !! 3464 nosbagart [IA-64]
4016 3465
4017 nosmap [PPC,EARLY] !! 3466 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 3467
4021 nosmep [PPC64s,EARLY] !! 3468 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 3469
4025 nosmp [SMP,EARLY] Tells an !! 3470 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3471 and disable the IO APIC. legacy for "maxcpus=0".
4027 3472
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 3473 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3474
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 3475 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3476
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 3477 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3478 soft-lockup and NMI watchdog (hard-lockup).
4083 3479
4084 nowb [ARM,EARLY] !! 3480 nowb [ARM]
4085 3481
4086 nox2apic [X86-64,APIC,EARLY] D !! 3482 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3483
4088 NOTE: this parameter !! 3484 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4089 LEGACY_XAPIC_DISABLED !! 3485 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4090 IA32_XAPIC_DISABLE_ST !! 3486 Some features depend on CPU0. Known dependencies are:
4091 !! 3487 1. Resume from suspend/hibernate depends on CPU0.
4092 noxsave [BUGS=X86] Disables x !! 3488 Suspend/hibernate will fail if CPU0 is offline and you
4093 and restore using xsa !! 3489 need to online CPU0 before suspend/hibernate.
4094 enabling legacy float !! 3490 2. PIC interrupts also depend on CPU0. CPU0 can't be
4095 !! 3491 removed if a PIC interrupt is detected.
4096 noxsaveopt [X86] Disables xsaveo !! 3492 It's said poweroff/reboot may depend on CPU0 on some
4097 register states. The !! 3493 machines although I haven't seen such issues so far
4098 xsave to save the sta !! 3494 after CPU0 is offline on a few tested machines.
4099 performance of saving !! 3495 If the dependencies are under your control, you can
4100 xsave doesn't support !! 3496 turn on cpu0_hotplug.
4101 xsaveopt supports it !! 3497
>> 3498 nps_mtm_hs_ctr= [KNL,ARC]
>> 3499 This parameter sets the maximum duration, in
>> 3500 cycles, each HW thread of the CTOP can run
>> 3501 without interruptions, before HW switches it.
>> 3502 The actual maximum duration is 16 times this
>> 3503 parameter's value.
>> 3504 Format: integer between 1 and 255
>> 3505 Default: 255
>> 3506
>> 3507 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3508 purges which is reported from either PAL_VM_SUMMARY or
>> 3509 SAL PALO.
4102 3510
4103 noxsaves [X86] Disables xsaves !! 3511 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4104 restoring x86 extende <<
4105 form of xsave area. T <<
4106 xsaveopt and xrstor t <<
4107 in standard form of x <<
4108 parameter, xsave area <<
4109 memory on xsaves enab <<
4110 <<
4111 nr_cpus= [SMP,EARLY] Maximum n <<
4112 could support. nr_cp 3512 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3513 support 'n' processors. It could be larger than the
4114 number of already plu 3514 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3515 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3516 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3517 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3518 hot plugging.
4119 3519
4120 nr_uarts= [SERIAL] maximum numb 3520 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3521
4122 numa=off [KNL, ARM64, PPC, RIS <<
4123 Disable NUMA, Only se <<
4124 spanning all memory. <<
4125 <<
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 3522 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 3523 NUMA balancing.
4128 Allowed values are en 3524 Allowed values are enable and disable
4129 3525
4130 numa_zonelist_order= [KNL, BOOT] Sele 3526 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3527 'node', 'default' can be specified
4132 This can be set from 3528 This can be set from sysctl after boot.
4133 See Documentation/adm 3529 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3530
4135 ohci1394_dma=early [HW,EARLY] en !! 3531 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3532 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3533 info.
4138 3534
4139 olpc_ec_timeout= [OLPC] ms delay when 3535 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3536 Rather than timing out after 20 ms if an EC
4141 command is not proper 3537 command is not properly ACKed, override the length
4142 of the timeout. We h 3538 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3539 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3540 interrupts *may* be lost!
4145 3541
4146 omap_mux= [OMAP] Override bootl 3542 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3543 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3544 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3545 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3546
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 3547 oops=panic Always panic on oopses. Default is to just kill the
4152 <<
4153 Format: [die0_boundar <<
4154 <<
4155 boundary - index of l <<
4156 The remain <<
4157 lock - Configure <<
4158 Once locke <<
4159 1 indicate <<
4160 <<
4161 oops=panic [KNL,EARLY] <<
4162 Always panic on oopse <<
4163 process, but there is 3548 process, but there is a small probability of
4164 deadlocking the machi 3549 deadlocking the machine.
4165 This will also cause 3550 This will also cause panics on machine check exceptions.
4166 Useful together with 3551 Useful together with panic=30 to trigger a reboot.
4167 3552
4168 page_alloc.shuffle= 3553 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3554 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3555 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3556 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3557 running on a platform with a direct-mapped memory-side
>> 3558 cache, and this parameter can be used to
>> 3559 override/disable that behavior. The state of the flag
>> 3560 can be read from sysfs at:
4173 /sys/module/page_allo 3561 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3562
4176 page_owner= [KNL,EARLY] Boot-time !! 3563 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3564 Storage of the information about who allocated
4178 each page is disabled 3565 each page is disabled in default. With this switch,
4179 we can turn it on. 3566 we can turn it on.
4180 on: enable the featur 3567 on: enable the feature
4181 3568
4182 page_poison= [KNL,EARLY] Boot-time !! 3569 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3570 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3571 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3572 off: turn off poisoning (default)
4186 on: turn on poisoning 3573 on: turn on poisoning
4187 3574
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 3575 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3576 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3577 timeout = 0: wait forever
4197 timeout < 0: reboot i 3578 timeout < 0: reboot immediately
4198 Format: <timeout> 3579 Format: <timeout>
4199 3580
4200 panic_on_taint= [KNL,EARLY] !! 3581 panic_print= Bitmask for printing system info when panic happens.
4201 Bitmask for condition !! 3582 User can chose combination of the following bits:
>> 3583 bit 0: print all tasks info
>> 3584 bit 1: print system memory info
>> 3585 bit 2: print timer info
>> 3586 bit 3: print locks info if CONFIG_LOCKDEP is on
>> 3587 bit 4: print ftrace buffer
>> 3588 bit 5: print all printk messages in buffer
>> 3589
>> 3590 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4202 Format: <hex>[,nouser 3591 Format: <hex>[,nousertaint]
4203 Hexadecimal bitmask r 3592 Hexadecimal bitmask representing the set of TAINT flags
4204 that will cause the k 3593 that will cause the kernel to panic when add_taint() is
4205 called with any of th 3594 called with any of the flags in this set.
4206 The optional switch " 3595 The optional switch "nousertaint" can be utilized to
4207 prevent userspace for 3596 prevent userspace forced crashes by writing to sysctl
4208 /proc/sys/kernel/tain 3597 /proc/sys/kernel/tainted any flagset matching with the
4209 bitmask set on panic_ 3598 bitmask set on panic_on_taint.
4210 See Documentation/adm 3599 See Documentation/admin-guide/tainted-kernels.rst for
4211 extra details on the 3600 extra details on the taint flags that users can pick
4212 to compose the bitmas 3601 to compose the bitmask to assign to panic_on_taint.
4213 3602
4214 panic_on_warn=1 panic() instead of WA !! 3603 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4215 on a WARN(). 3604 on a WARN().
4216 3605
4217 panic_print= Bitmask for printing !! 3606 crash_kexec_post_notifiers
4218 User can chose combin !! 3607 Run kdump after running panic-notifiers and dumping
4219 bit 0: print all task !! 3608 kmsg. This only for the users who doubt kdump always
4220 bit 1: print system m !! 3609 succeeds in any situation.
4221 bit 2: print timer in !! 3610 Note that this also increases risks of kdump failure,
4222 bit 3: print locks in !! 3611 because some panic notifiers can make the crashed
4223 bit 4: print ftrace b !! 3612 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 3613
4232 parkbd.port= [HW] Parallel port nu 3614 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3615 connected to, default is 0.
4234 Format: <parport#> 3616 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3617 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3618 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3619 Format: <mode>
4238 3620
4239 parport= [HW,PPT] Specify para 3621 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3622 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3623 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3624 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3625 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3626 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3627 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3628 should be numbers, or 'auto' (for using detected
4247 settings on that part 3629 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3630 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3631 Parallel ports are assigned in the order they
4250 are specified on the 3632 are specified on the command line, starting
4251 with parport0. 3633 with parport0.
4252 3634
4253 parport_init_mode= [HW,PPT] 3635 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3636 Configure VIA parallel port to operate in
4255 a specific mode. This 3637 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3638 computer where firmware has no options for setting
4257 up parallel port mode 3639 up parallel port mode and sets it to spp.
4258 Currently this functi 3640 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3641 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3642
4261 pata_legacy.all= [HW,LIBATA] 3643 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 3644 Format: <int>
4263 Set to non-zero to pr 3645 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 3646 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 3647 has been found at either range. Disabled by default.
4266 3648
4267 pata_legacy.autospeed= [HW,LIBATA] 3649 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 3650 Format: <int>
4269 Set to non-zero if a 3651 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 3652 changes. Disabled by default.
4271 3653
4272 pata_legacy.ht6560a= [HW,LIBATA] 3654 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 3655 Format: <int>
4274 Set to 1, 2, or 3 for 3656 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 3657 the secondary channel, or both channels respectively.
4276 Disabled by default. 3658 Disabled by default.
4277 3659
4278 pata_legacy.ht6560b= [HW,LIBATA] 3660 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 3661 Format: <int>
4280 Set to 1, 2, or 3 for 3662 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 3663 the secondary channel, or both channels respectively.
4282 Disabled by default. 3664 Disabled by default.
4283 3665
4284 pata_legacy.iordy_mask= [HW,LIBATA] 3666 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 3667 Format: <int>
4286 IORDY enable mask. S 3668 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 3669 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 3670 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 3671 the second channel, and so on. The sequence will often
4290 correspond to the pri 3672 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 3673 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 3674 bus and the use of other driver options may interfere
4293 with the sequence. B 3675 with the sequence. By default IORDY is allowed across
4294 all channels. 3676 all channels.
4295 3677
4296 pata_legacy.opti82c46x= [HW,LIBATA] 3678 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 3679 Format: <int>
4298 Set to 1, 2, or 3 for 3680 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 3681 channel, the secondary channel, or both channels
4300 respectively. Disabl 3682 respectively. Disabled by default.
4301 3683
4302 pata_legacy.opti82c611a= [HW,L 3684 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 3685 Format: <int>
4304 Set to 1, 2, or 3 for 3686 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 3687 channel, the secondary channel, or both channels
4306 respectively. Disabl 3688 respectively. Disabled by default.
4307 3689
4308 pata_legacy.pio_mask= [HW,LIBATA] 3690 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 3691 Format: <int>
4310 PIO mode mask for aut 3692 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 3693 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 3694 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 3695 All modes allowed by default.
4314 3696
4315 pata_legacy.probe_all= [HW,LIBATA] 3697 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 3698 Format: <int>
4317 Set to non-zero to pr 3699 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 3700 port ranges on PCI systems. Disabled by default.
4319 3701
4320 pata_legacy.probe_mask= [HW,LIBATA] 3702 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 3703 Format: <int>
4322 Probe mask for legacy 3704 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 3705 platform configuration and the use of other driver
4324 options up to 6 legac 3706 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 3707 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 3708 of individual ports can be disabled by setting the
4327 corresponding bits in 3709 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 3710 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 3711 By default all supported ports are probed.
4330 3712
4331 pata_legacy.qdi= [HW,LIBATA] 3713 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 3714 Format: <int>
4333 Set to non-zero to pr 3715 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 3716 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 3717
4336 pata_legacy.winbond= [HW,LIBATA] 3718 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 3719 Format: <int>
4338 Set to non-zero to pr 3720 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 3721 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 3722 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 3723 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 3724 0 otherwise.
4343 3725
4344 pata_platform.pio_mask= [HW,LIBATA] 3726 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 3727 Format: <int>
4346 Supported PIO mode ma 3728 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 3729 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 3730 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 3731 allowed by default.
4350 3732
4351 pause_on_oops=<int> !! 3733 pause_on_oops=
4352 Halt all CPUs after t 3734 Halt all CPUs after the first oops has been printed for
4353 the specified number 3735 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3736 your oopses keep scrolling off the screen.
4355 3737
4356 pcbit= [HW,ISDN] 3738 pcbit= [HW,ISDN]
4357 3739
4358 pci=option[,option...] [PCI,EARLY] v !! 3740 pcd. [PARIDE]
>> 3741 See header of drivers/block/paride/pcd.c.
>> 3742 See also Documentation/admin-guide/blockdev/paride.rst.
>> 3743
>> 3744 pci=option[,option...] [PCI] various PCI subsystem options.
4359 3745
4360 Some options 3746 Some options herein operate on a specific device
4361 or a set of d 3747 or a set of devices (<pci_dev>). These are
4362 specified in 3748 specified in one of the following formats:
4363 3749
4364 [<domain>:]<b 3750 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 3751 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 3752
4367 Note: the fir 3753 Note: the first format specifies a PCI
4368 bus/device/fu 3754 bus/device/function address which may change
4369 if new hardwa 3755 if new hardware is inserted, if motherboard
4370 firmware chan 3756 firmware changes, or due to changes caused
4371 by other kern 3757 by other kernel parameters. If the
4372 domain is lef 3758 domain is left unspecified, it is
4373 taken to be z 3759 taken to be zero. Optionally, a path
4374 to a device t 3760 to a device through multiple device/function
4375 addresses can 3761 addresses can be specified after the base
4376 address (this 3762 address (this is more robust against
4377 renumbering i 3763 renumbering issues). The second format
4378 selects devic 3764 selects devices using IDs from the
4379 configuration 3765 configuration space which may match multiple
4380 devices in th 3766 devices in the system.
4381 3767
4382 earlydump dump PCI conf 3768 earlydump dump PCI config space before the kernel
4383 changes anyth 3769 changes anything
4384 off [X86] don't p 3770 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3771 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3772 the hardware directly. Use this if your machine
4387 has a non-sta 3773 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3774 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3775 hardware access methods are allowed. Use this
4390 if you experi 3776 if you experience crashes upon bootup and you
4391 suspect they 3777 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3778 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3779 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3780 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3781 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3782 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3783 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3784 bus number. The config space is then accessed
4399 through ports 3785 through ports 0xC000-0xCFFF).
4400 See http://wi 3786 See http://wiki.osdev.org/PCI for more info
4401 on the config 3787 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3788 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3789 enabled, this kernel boot option can be used to
4404 disable the u 3790 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3791 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3792 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3793 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3794 Configuration
4409 check_enable_amd_mmconf [X86] 3795 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3796 properly configured MMIO access to PCI
4411 config space 3797 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3798 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3799 enabled, this kernel boot option can be used to
4414 disable the u 3800 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3801 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3802 Safety option to keep boot IRQs enabled. This
4417 should never 3803 should never be necessary.
4418 ioapicreroute [APIC] Enable 3804 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3805 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3806 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3807 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3808 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3809 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3810 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3811 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3812 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3813 routing table. These calls are known to be buggy
4428 on several ma 3814 on several machines and they hang the machine
4429 when used, bu 3815 when used, but on other computers it's the only
4430 way to get th 3816 way to get the interrupt routing table. Try
4431 this option i 3817 this option if the kernel is unable to allocate
4432 IRQs or disco 3818 IRQs or discover secondary PCI buses on your
4433 motherboard. 3819 motherboard.
4434 rom [X86] Assign 3820 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3821 Use with caution as certain devices share
4436 address decod 3822 address decoders between ROMs and other
4437 resources. 3823 resources.
4438 norom [X86] Do not 3824 norom [X86] Do not assign address space to
4439 expansion ROM 3825 expansion ROMs that do not already have
4440 BIOS assigned 3826 BIOS assigned address ranges.
4441 nobar [X86] Do not 3827 nobar [X86] Do not assign address space to the
4442 BARs that wer 3828 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3829 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3830 assigned automatically to PCI devices. You can
4445 make the kern 3831 make the kernel exclude IRQs of your ISA cards
4446 this way. 3832 this way.
4447 pirqaddr=0xAAAAA [X86] 3833 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3834 of the PIRQ table (normally generated
4449 by the BIOS) 3835 by the BIOS) if it is outside the
4450 F0000h-100000 3836 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3837 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3838 useful if the kernel is unable to find your
4453 secondary bus 3839 secondary buses and you want to tell it
4454 explicitly wh 3840 explicitly which ones they are.
4455 assign-busses [X86] Always 3841 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3842 numbers ourselves, overriding
4457 whatever the 3843 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3844 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3845 in the BIOS $PIR table. This is needed on
4460 some systems 3846 some systems with broken BIOSes, notably
4461 some HP Pavil 3847 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3848 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3849 IRQ routing is enabled.
4464 noacpi [X86] Do not 3850 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3851 or for PCI scanning.
4466 use_crs [X86] Use PCI 3852 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3853 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3854 is enabled by default. If you need to use this,
4469 please report 3855 please report a bug.
4470 nocrs [X86] Ignore 3856 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 3857 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 3858 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3859 This is normally done in pci_enable_device(),
4483 so this optio 3860 so this option is a temporary workaround
4484 for broken dr 3861 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3862 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3863 handle more pci cards
4487 noearly [X86] Don't d 3864 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3865 This might help on some broken boards which
4489 machine check 3866 machine check when some devices' config space
4490 is read. But 3867 is read. But various workarounds are disabled
4491 and some IOMM 3868 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3869 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3870 This sorting is done to get a device
4494 order compati 3871 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3872 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3873 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3874 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3875 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3876 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3877 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3878 based on its parent bus. Also set MRRS (Max
4502 Read Request 3879 Read Request Size) to the largest supported
4503 value (no lar 3880 value (no larger than the MPS that the device
4504 or bus can su 3881 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3882 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3883 every device is guaranteed to support. This
4507 configuration 3884 configuration allows peer-to-peer DMA between
4508 any pair of d 3885 any pair of devices, possibly at the cost of
4509 reduced perfo 3886 reduced performance. This also guarantees
4510 that hot-adde 3887 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3888 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3889 reserved for the CardBus bridge's IO window.
4513 The default v 3890 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3891 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3892 reserved for the CardBus bridge's memory
4516 window. The d 3893 window. The default value is 64 megabytes.
4517 resource_alignment= 3894 resource_alignment=
4518 Format: 3895 Format:
4519 [<order of ali 3896 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 3897 Specifies alignment and device to reassign
4521 aligned memor 3898 aligned memory resources. How to
4522 specify the d 3899 specify the device is described above.
4523 If <order of 3900 If <order of align> is not specified,
4524 PAGE_SIZE is 3901 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 3902 A PCI-PCI bridge can be specified if resource
4526 windows need 3903 windows need to be expanded.
4527 To specify th 3904 To specify the alignment for several
4528 instances of 3905 instances of a device, the PCI vendor,
4529 device, subve 3906 device, subvendor, and subdevice may be
4530 specified, e. 3907 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 3908 for 4096-byte alignment.
4532 ecrc= Enable/disabl 3909 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3910 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3911 bios: Use BIOS/firmware settings. This is the
4537 the default. 3912 the default.
4538 off: Turn ECR 3913 off: Turn ECRC off
4539 on: Turn ECRC 3914 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3915 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3916 reserved for hotplug bridge's IO window.
4542 Default size 3917 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 3918 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 3919 reserved for hotplug bridge's MMIO window.
4545 Default size 3920 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 3921 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 3922 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 3923 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 3924 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 3925 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 3926 MMIO_PREF window.
4552 Default size 3927 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3928 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3929 reserved for buses below a hotplug bridge.
4555 Default is 1. 3930 Default is 1.
4556 realloc= Enable/disabl 3931 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3932 if allocations done by BIOS are too small to
4558 accommodate r 3933 accommodate resources required by all child
4559 devices. 3934 devices.
4560 off: Turn rea 3935 off: Turn realloc off
4561 on: Turn real 3936 on: Turn realloc on
4562 realloc same as reall 3937 realloc same as realloc=on
4563 noari do not use PC 3938 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 3939 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 3940 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 3941 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 3942 only look for one device below a PCIe downstream
4568 port. 3943 port.
4569 big_root_window Try to add a 3944 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 3945 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 3946 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 3947 Adding the window is slightly risky (it may
4573 conflict with 3948 conflict with unreported devices), so this
4574 taints the ke 3949 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 3950 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 3951 Specify one or more PCI devices (in the format
4577 specified abo 3952 specified above) separated by semicolons.
4578 Each device s 3953 Each device specified will have the PCI ACS
4579 redirect capa 3954 redirect capabilities forced off which will
4580 allow P2P tra 3955 allow P2P traffic between devices through
4581 bridges witho 3956 bridges without forcing it upstream. Note:
4582 this removes 3957 this removes isolation between devices and
4583 may put more 3958 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 3959 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 3960 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 3961 norid [S390] ignore the RID field and force use of
4619 one PCI domai 3962 one PCI domain per PCI function
4620 3963
4621 pcie_aspm= [PCIE] Forcibly enabl !! 3964 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 3965 Management.
4623 off Don't touch ASPM conf !! 3966 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 3967 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 3968 WARNING: Forcing ASPM on may cause system lockups.
4627 3969
4628 pcie_ports= [PCIE] PCIe port serv 3970 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 3971 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 3972 even if the platform doesn't give the OS permission to
4631 use them. This may c 3973 use them. This may cause conflicts if the platform
4632 also tries to use the 3974 also tries to use these services.
4633 dpc-native Use native PC 3975 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 3976 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 3977 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 3978 hotplug).
4637 3979
4638 pcie_port_pm= [PCIE] PCIe port powe 3980 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 3981 off Disable power management of all PCIe ports
4640 force Forcibly enable power 3982 force Forcibly enable power management of all PCIe ports
4641 3983
4642 pcie_pme= [PCIE,PM] Native PCIe 3984 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 3985 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 3986 all PCIe root ports use INTx for all services).
4645 3987
4646 pcmv= [HW,PCMCIA] BadgePAD 3988 pcmv= [HW,PCMCIA] BadgePAD 4
4647 3989
4648 pd_ignore_unused 3990 pd_ignore_unused
4649 [PM] 3991 [PM]
4650 Keep all power-domain 3992 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 3993 even if no driver has claimed them. This is useful
4652 for debug and develop 3994 for debug and development, but should not be
4653 needed on a platform 3995 needed on a platform with proper driver support.
4654 3996
>> 3997 pd. [PARIDE]
>> 3998 See Documentation/admin-guide/blockdev/paride.rst.
>> 3999
4655 pdcchassis= [PARISC,HW] Disable/E 4000 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4001 boot time.
4657 Format: { 0 | 1 } 4002 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4003 See arch/parisc/kernel/pdc_chassis.c
4659 4004
4660 percpu_alloc= [MM,EARLY] !! 4005 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4006 Currently supported values are "embed" and "page".
4663 Archs may support sub 4007 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4008 See comments in mm/percpu.c for details on each
4665 allocator. This para 4009 allocator. This parameter is primarily for debugging
4666 and performance compa 4010 and performance comparison.
4667 4011
>> 4012 pf. [PARIDE]
>> 4013 See Documentation/admin-guide/blockdev/paride.rst.
>> 4014
>> 4015 pg. [PARIDE]
>> 4016 See Documentation/admin-guide/blockdev/paride.rst.
>> 4017
4668 pirq= [SMP,APIC] Manual mp- 4018 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 4019 See Documentation/x86/i386/IO-APIC.rst.
4670 4020
4671 plip= [PPT,NET] Parallel po 4021 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4022 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4023 See also Documentation/admin-guide/parport.rst.
4674 4024
4675 pmtmr= [X86] Manual setup of 4025 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4026 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4027 e.g. pmtmr=0x508
4678 4028
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] 4029 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4030 Enable suspend/resume debug messages during boot up.
4689 4031
4690 pnp.debug=1 [PNP] 4032 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4033 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4034 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4035 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4036 current resource usage; turning this on also shows
4695 possible settings and 4037 possible settings and some assignment information.
4696 4038
4697 pnpacpi= [ACPI] 4039 pnpacpi= [ACPI]
4698 { off } 4040 { off }
4699 4041
4700 pnpbios= [ISAPNP] 4042 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4043 { on | off | curr | res | no-curr | no-res }
4702 4044
4703 pnp_reserve_irq= 4045 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4046 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4047
4706 pnp_reserve_dma= 4048 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4049 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4050
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4051 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4052 Ranges are in pairs (I/O port base and size).
4711 4053
4712 pnp_reserve_mem= 4054 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4055 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4056 autoconfiguration.
4715 Ranges are in pairs ( 4057 Ranges are in pairs (memory base and size).
4716 4058
4717 ports= [IP_VS_FTP] IPVS ftp 4059 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4060 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4061 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4062 may be specified.
4721 Format: <port>,<port> 4063 Format: <port>,<port>....
4722 4064
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 4065 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4066 It specifically disables cpuidle and sets the
4730 platform machine desc 4067 platform machine description specific power_save
4731 function to NULL. On 4068 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4069 execution priority.
4733 4070
4734 ppc_strict_facility_enable 4071 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4072 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4073 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4074 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4075 There is some performance impact when enabling this.
4739 4076
4740 ppc_tm= [PPC,EARLY] !! 4077 ppc_tm= [PPC]
4741 Format: {"off"} 4078 Format: {"off"}
4742 Disable Hardware Tran 4079 Disable Hardware Transactional Memory
4743 4080
4744 preempt= [KNL] 4081 preempt= [KNL]
4745 Select preemption mod 4082 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4083 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4084 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4085 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4086 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4087
4753 print-fatal-signals= 4088 print-fatal-signals=
4754 [KNL] debug: print fa 4089 [KNL] debug: print fatal signals
4755 4090
4756 If enabled, warn abou 4091 If enabled, warn about various signal handling
4757 related application a 4092 related application anomalies: too many signals,
4758 too many POSIX.1 time 4093 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4094 coredump - etc.
4760 4095
4761 If you hit the warnin 4096 If you hit the warning due to signal overflow,
4762 you might want to try 4097 you might want to try "ulimit -i unlimited".
4763 4098
4764 default: off. 4099 default: off.
4765 4100
4766 printk.always_kmsg_dump= 4101 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4102 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4103 panics
4769 Format: <bool> (1/Y/ 4104 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4105 default: disabled
4771 4106
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} 4107 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4108 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4109 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4110 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4111 ratelimit - ratelimit the logging
4786 Default: ratelimit 4112 Default: ratelimit
4787 4113
4788 printk.time= Show timing data pref 4114 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4115 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4116
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] 4117 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4118 Limit processor to maximum C-state
4803 max_cstate=9 override 4119 max_cstate=9 overrides any DMI blacklist limit.
4804 4120
4805 processor.nocst [HW,ACPI] 4121 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4122 Ignore the _CST method to determine C-states,
4807 instead using the leg 4123 instead using the legacy FADT method
4808 4124
4809 profile= [KNL] Enable kernel p 4125 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4126 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4127 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4128 [defaults to kernel profiling]
4813 Param: "schedule" - p 4129 Param: "schedule" - profile schedule points.
>> 4130 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4131 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4132 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4133 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4134 statistical time based profiling.
4817 4135
4818 prompt_ramdisk= [RAM] [Deprecated] 4136 prompt_ramdisk= [RAM] [Deprecated]
4819 4137
4820 prot_virt= [S390] enable hosting 4138 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4139 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4140 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4141 Format: <bool>
4826 4142
4827 psi= [KNL] Enable or disab 4143 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4144 tracking.
4829 Format: <bool> 4145 Format: <bool>
4830 4146
4831 psmouse.proto= [HW,MOUSE] Highest PS 4147 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4148 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4149 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4150 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4151 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4152 Try to reset the device after so many bad packets
4837 (0 = never). 4153 (0 = never).
4838 psmouse.resolution= 4154 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4155 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4156 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4157 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4158 0 = disabled, 1 = enabled (default).
4843 4159
4844 pstore.backend= Specify the name of t 4160 pstore.backend= Specify the name of the pstore backend to use
4845 4161
>> 4162 pt. [PARIDE]
>> 4163 See Documentation/admin-guide/blockdev/paride.rst.
>> 4164
4846 pti= [X86-64] Control Page 4165 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4166 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4167 removes hardening, but improves performance of
4849 system calls and inte 4168 system calls and interrupts.
4850 4169
4851 on - unconditionall 4170 on - unconditionally enable
4852 off - unconditionall 4171 off - unconditionally disable
4853 auto - kernel detects 4172 auto - kernel detects whether your CPU model is
4854 vulnerable to 4173 vulnerable to issues that PTI mitigates
4855 4174
4856 Not specifying this o 4175 Not specifying this option is equivalent to pti=auto.
4857 4176
>> 4177 nopti [X86-64]
>> 4178 Equivalent to pti=off
>> 4179
4858 pty.legacy_count= 4180 pty.legacy_count=
4859 [KNL] Number of legac 4181 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4182 default number.
4861 4183
4862 quiet [KNL,EARLY] Disable m !! 4184 quiet [KNL] Disable most log messages
4863 4185
4864 r128= [HW,DRM] 4186 r128= [HW,DRM]
4865 4187
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4188 raid= [HW,RAID]
4871 See Documentation/adm 4189 See Documentation/admin-guide/md.rst.
4872 4190
4873 ramdisk_size= [RAM] Sizes of RAM di 4191 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4192 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4193
4876 ramdisk_start= [RAM] RAM disk image 4194 ramdisk_start= [RAM] RAM disk image start address
4877 4195
4878 random.trust_cpu=off !! 4196 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 4197 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 4198 CPU's random number generator (if available) to
4881 initialize the kernel !! 4199 fully seed the kernel's CRNG. Default is controlled
4882 !! 4200 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 4201
4888 randomize_kstack_offset= 4202 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4203 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4204 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4205 entropy, frustrating memory corruption attacks
4892 that depend on stack 4206 that depend on stack address determinism or
4893 cross-syscall address 4207 cross-syscall address exposures. This is only
4894 available on architec 4208 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4209 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4210 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4211 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4212
4899 ras=option[,option,...] [KNL] RAS-spe 4213 ras=option[,option,...] [KNL] RAS-specific options
4900 4214
4901 cec_disable [X86] 4215 cec_disable [X86]
4902 Disable the C 4216 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4217 see CONFIG_RAS_CEC help text.
4904 4218
4905 rcu_nocbs[=cpu-list] !! 4219 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 4220 The argument is a cpu list, as described above.
4907 as described above. <<
4908 <<
4909 In kernels built with <<
4910 enable the no-callbac <<
4911 such CPUs' callbacks <<
4912 softirq context. Inv <<
4913 callbacks will instea <<
4914 kthreads created for <<
4915 "p" for RCU-preempt, <<
4916 for the kthreads that <<
4917 "N" is the CPU number <<
4918 the offloaded CPUs, w <<
4919 and real-time workloa <<
4920 energy efficiency for <<
4921 <<
4922 If a cpulist is passe <<
4923 list of CPUs is set t <<
4924 <<
4925 Otherwise, if the '=' <<
4926 arguments are omitted <<
4927 no-callback mode from <<
4928 toggled at runtime vi <<
4929 4221
4930 Note that this argume !! 4222 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4931 the CONFIG_RCU_NOCB_C !! 4223 the specified list of CPUs to be no-callback CPUs.
>> 4224 Invocation of these CPUs' RCU callbacks will be
>> 4225 offloaded to "rcuox/N" kthreads created for that
>> 4226 purpose, where "x" is "p" for RCU-preempt, and
>> 4227 "s" for RCU-sched, and "N" is the CPU number.
>> 4228 This reduces OS jitter on the offloaded CPUs,
>> 4229 which can be useful for HPC and real-time
>> 4230 workloads. It can also improve energy efficiency
>> 4231 for asymmetric multiprocessors.
4932 4232
4933 rcu_nocb_poll [KNL] 4233 rcu_nocb_poll [KNL]
4934 Rather than requiring 4234 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4235 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4236 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4237 make these kthreads poll for callbacks.
4938 This improves the rea 4238 This improves the real-time response for the
4939 offloaded CPUs by rel 4239 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4240 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4241 energy efficiency by requiring that the kthreads
4942 periodically wake up 4242 periodically wake up to do the polling.
4943 4243
4944 rcutree.blimit= [KNL] 4244 rcutree.blimit= [KNL]
4945 Set maximum number of 4245 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4246 process in one batch.
4947 4247
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] 4248 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4249 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4250 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4251 purposes, to verify correct tree setup.
4959 4252
4960 rcutree.gp_cleanup_delay= [KNL] 4253 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4254 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4255 RCU grace-period cleanup.
4963 4256
4964 rcutree.gp_init_delay= [KNL] 4257 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4258 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4259 RCU grace-period initialization.
4967 4260
4968 rcutree.gp_preinit_delay= [KNL] 4261 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4262 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4263 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4264 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4265 the rcu_node combining tree.
4973 4266
>> 4267 rcutree.use_softirq= [KNL]
>> 4268 If set to zero, move all RCU_SOFTIRQ processing to
>> 4269 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4270 value, meaning that RCU_SOFTIRQ is used by default.
>> 4271 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4272
>> 4273 But note that CONFIG_PREEMPT_RT=y kernels disable
>> 4274 this kernel boot parameter, forcibly setting it
>> 4275 to zero.
>> 4276
>> 4277 rcutree.rcu_fanout_exact= [KNL]
>> 4278 Disable autobalancing of the rcu_node combining
>> 4279 tree. This is used by rcutorture, and might
>> 4280 possibly be useful for architectures having high
>> 4281 cache-to-cache transfer latencies.
>> 4282
>> 4283 rcutree.rcu_fanout_leaf= [KNL]
>> 4284 Change the number of CPUs assigned to each
>> 4285 leaf rcu_node structure. Useful for very
>> 4286 large systems, which will choose the value 64,
>> 4287 and for NUMA systems with large remote-access
>> 4288 latencies, which will choose a value aligned
>> 4289 with the appropriate hardware boundaries.
>> 4290
>> 4291 rcutree.rcu_min_cached_objs= [KNL]
>> 4292 Minimum number of objects which are cached and
>> 4293 maintained per one CPU. Object size is equal
>> 4294 to PAGE_SIZE. The cache allows to reduce the
>> 4295 pressure to page allocator, also it makes the
>> 4296 whole algorithm to behave better in low memory
>> 4297 condition.
>> 4298
4974 rcutree.jiffies_till_first_fqs= [KNL] 4299 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4300 Set delay from grace-period initialization to
4976 first attempt to forc 4301 first attempt to force quiescent states.
4977 Units are jiffies, mi 4302 Units are jiffies, minimum value is zero,
4978 and maximum value is 4303 and maximum value is HZ.
4979 4304
4980 rcutree.jiffies_till_next_fqs= [KNL] 4305 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4306 Set delay between subsequent attempts to force
4982 quiescent states. Un 4307 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4308 value is one, and maximum value is HZ.
4984 4309
4985 rcutree.jiffies_till_sched_qs= [KNL] 4310 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4311 Set required age in jiffies for a
4987 given grace period be 4312 given grace period before RCU starts
4988 soliciting quiescent- 4313 soliciting quiescent-state help from
4989 rcu_note_context_swit 4314 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4315 If not specified, the kernel will calculate
4991 a value based on the 4316 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4317 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4318 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4319 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4320 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4321 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4322 overwritten.
4998 4323
4999 rcutree.kthread_prio= [KNL,BOOT] 4324 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4325 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4326 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4327 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4328 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4329 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4330 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4331 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4332 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4333 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 4334
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 4335 rcutree.rcu_nocb_gp_stride= [KNL]
5013 On callback-offloaded !! 4336 Set the number of NOCB callback kthreads in
5014 RCU reduces the lock !! 4337 each group, which defaults to the square root
5015 otherwise be caused b !! 4338 of the number of CPUs. Larger numbers reduce
5016 use of the ->nocb_byp !! 4339 the wakeup overhead on the global grace-period
5017 common non-flooded ca !! 4340 kthread, but increases that same overhead on
5018 the main ->cblist in !! 4341 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 4342
5033 rcutree.qhimark= [KNL] 4343 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4344 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4345 batch limiting is disabled.
5036 4346
5037 rcutree.qlowmark= [KNL] 4347 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4348 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4349 batch limiting is re-enabled.
5040 4350
5041 rcutree.qovld= [KNL] 4351 rcutree.qovld= [KNL]
5042 Set threshold of queu 4352 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4353 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4354 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4355 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4356 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4357 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4358 disable more aggressive help enlistment.
5049 4359
5050 rcutree.rcu_delay_page_cache_fill_mse !! 4360 rcutree.rcu_idle_gp_delay= [KNL]
5051 Set the page-cache re !! 4361 Set wakeup interval for idle CPUs that have
5052 in response to low-me !! 4362 RCU callbacks (RCU_FAST_NO_HZ=y).
5053 of permitted values i <<
5054 <<
5055 rcutree.rcu_divisor= [KNL] <<
5056 Set the shift-right c <<
5057 the callback-invocati <<
5058 the number of callbac <<
5059 The result will be bo <<
5060 the rcutree.blimit ke <<
5061 callbacks, the softir <<
5062 order to allow the CP <<
5063 <<
5064 Please note that this <<
5065 limit applies only to <<
5066 invocation. Offloade <<
5067 invoked in the contex <<
5068 scheduler will preemp <<
5069 <<
5070 rcutree.rcu_fanout_exact= [KNL] <<
5071 Disable autobalancing <<
5072 tree. This is used b <<
5073 possibly be useful fo <<
5074 cache-to-cache transf <<
5075 <<
5076 rcutree.rcu_fanout_leaf= [KNL] <<
5077 Change the number of <<
5078 leaf rcu_node structu <<
5079 large systems, which <<
5080 and for NUMA systems <<
5081 latencies, which will <<
5082 with the appropriate <<
5083 <<
5084 rcutree.rcu_min_cached_objs= [KNL] <<
5085 Minimum number of obj <<
5086 maintained per one CP <<
5087 to PAGE_SIZE. The cac <<
5088 pressure to page allo <<
5089 whole algorithm to be <<
5090 condition. <<
5091 <<
5092 rcutree.rcu_nocb_gp_stride= [KNL] <<
5093 Set the number of NOC <<
5094 each group, which def <<
5095 of the number of CPUs <<
5096 the wakeup overhead o <<
5097 kthread, but increase <<
5098 each group's NOCB gra <<
5099 4363
5100 rcutree.rcu_kick_kthreads= [KNL] 4364 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4365 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4366 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4367 it should at force-quiescent-state time.
5104 This wake_up() will b 4368 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4369 WARN_ONCE() splat and an ftrace_dump().
5106 4370
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] 4371 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4372 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4373 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4374 in microseconds. This defaults to zero.
5118 Larger delays increas 4375 Larger delays increase the probability of
5119 catching RCU pointer 4376 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4377 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4378 rcu_read_unlock() has completed.
5122 4379
5123 rcutree.sysrq_rcu= [KNL] 4380 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4381 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4382 rcu_node tree with an eye towards determining
5126 why a new grace perio 4383 why a new grace period has not yet started.
5127 4384
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] 4385 rcuscale.gp_async= [KNL]
5158 Measure performance o 4386 Measure performance of asynchronous
5159 grace-period primitiv 4387 grace-period primitives such as call_rcu().
5160 4388
5161 rcuscale.gp_async_max= [KNL] 4389 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4390 Specify the maximum number of outstanding
5163 callbacks per writer 4391 callbacks per writer thread. When a writer
5164 thread exceeds this l 4392 thread exceeds this limit, it invokes the
5165 corresponding flavor 4393 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4394 previously posted callbacks to drain.
5167 4395
5168 rcuscale.gp_exp= [KNL] 4396 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4397 Measure performance of expedited synchronous
5170 grace-period primitiv 4398 grace-period primitives.
5171 4399
5172 rcuscale.holdoff= [KNL] 4400 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4401 Set test-start holdoff period. The purpose of
5174 this parameter is to 4402 this parameter is to delay the start of the
5175 test until boot compl 4403 test until boot completes in order to avoid
5176 interference. 4404 interference.
5177 4405
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] 4406 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4407 Set to measure performance of kfree_rcu() flooding.
5189 4408
5190 rcuscale.kfree_rcu_test_double= [KNL] 4409 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 4410 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 4411 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 4412 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 4413 and double-argument variants are tested.
5195 4414
5196 rcuscale.kfree_rcu_test_single= [KNL] 4415 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 4416 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 4417 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 4418 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 4419 and double-argument variants are tested.
5201 4420
5202 rcuscale.kfree_nthreads= [KNL] 4421 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4422 The number of threads running loops of kfree_rcu().
5204 4423
5205 rcuscale.kfree_alloc_num= [KNL] 4424 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4425 Number of allocations and frees done in an iteration.
5207 4426
5208 rcuscale.kfree_loops= [KNL] 4427 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4428 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4429 of allocations and frees.
5211 4430
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] 4431 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4432 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4433 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4434 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4435 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4436 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4437 A value of "n" less than or equal to -N selects
5225 a single reader. 4438 a single reader.
5226 4439
5227 rcuscale.nwriters= [KNL] 4440 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4441 Set number of RCU writers. The values operate
5229 the same as for rcusc 4442 the same as for rcuscale.nreaders.
5230 N, where N is the num 4443 N, where N is the number of CPUs
5231 4444
5232 rcuscale.scale_type= [KNL] !! 4445 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4446 Specify the RCU implementation to test.
5234 4447
5235 rcuscale.shutdown= [KNL] 4448 rcuscale.shutdown= [KNL]
5236 Shut the system down 4449 Shut the system down after performance tests
5237 complete. This is us 4450 complete. This is useful for hands-off automated
5238 testing. 4451 testing.
5239 4452
5240 rcuscale.verbose= [KNL] 4453 rcuscale.verbose= [KNL]
5241 Enable additional pri 4454 Enable additional printk() statements.
5242 4455
5243 rcuscale.writer_holdoff= [KNL] 4456 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4457 Write-side holdoff between grace periods,
5245 in microseconds. The 4458 in microseconds. The default of zero says
5246 no holdoff. 4459 no holdoff.
5247 4460
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] 4461 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4462 Set duration of force_quiescent_state bursts
5255 in microseconds. 4463 in microseconds.
5256 4464
5257 rcutorture.fqs_holdoff= [KNL] 4465 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4466 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4467 in microseconds.
5260 4468
5261 rcutorture.fqs_stutter= [KNL] 4469 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4470 Set wait time between force_quiescent_state bursts
5263 in seconds. 4471 in seconds.
5264 4472
5265 rcutorture.fwd_progress= [KNL] 4473 rcutorture.fwd_progress= [KNL]
5266 Specifies the number !! 4474 Enable RCU grace-period forward-progress testing
5267 for RCU grace-period <<
5268 for the types of RCU 4475 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 4476
5273 rcutorture.fwd_progress_div= [KNL] 4477 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4478 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4479 period to do tight-loop forward-progress testing.
5276 4480
5277 rcutorture.fwd_progress_holdoff= [KNL 4481 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4482 Number of seconds to wait between successive
5279 forward-progress test 4483 forward-progress tests.
5280 4484
5281 rcutorture.fwd_progress_need_resched= 4485 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4486 Enclose cond_resched() calls within checks for
5283 need_resched() during 4487 need_resched() during tight-loop forward-progress
5284 testing. 4488 testing.
5285 4489
5286 rcutorture.gp_cond= [KNL] 4490 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4491 Use conditional/asynchronous update-side
5288 primitives, if availa 4492 primitives, if available.
5289 4493
5290 rcutorture.gp_exp= [KNL] 4494 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4495 Use expedited update-side primitives, if available.
5292 4496
5293 rcutorture.gp_normal= [KNL] 4497 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4498 Use normal (non-expedited) asynchronous
5295 update-side primitive 4499 update-side primitives, if available.
5296 4500
5297 rcutorture.gp_sync= [KNL] 4501 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4502 Use normal (non-expedited) synchronous
5299 update-side primitive 4503 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4504 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4505 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4506 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4507 they are all non-zero.
5304 4508
5305 rcutorture.irqreader= [KNL] 4509 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4510 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4511 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4512 flavors take kindly to this sort of thing.
5309 4513
5310 rcutorture.leakpointer= [KNL] 4514 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4515 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4516 This can of course result in splats, and is
5313 intended to test the 4517 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4518 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4519 such leaks.
5316 4520
5317 rcutorture.n_barrier_cbs= [KNL] 4521 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4522 Set callbacks/threads for rcu_barrier() testing.
5319 4523
5320 rcutorture.nfakewriters= [KNL] 4524 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4525 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4526 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4527 test, hence the "fake".
5324 4528
5325 rcutorture.nocbs_nthreads= [KNL] 4529 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 4530 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 4531 Zero (the default) disables toggling.
5328 4532
5329 rcutorture.nocbs_toggle= [KNL] 4533 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 4534 Set the delay in milliseconds between successive
5331 callback-offload togg 4535 callback-offload toggling attempts.
5332 4536
5333 rcutorture.nreaders= [KNL] 4537 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4538 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4539 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4540 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 4541 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 4542 (the number of CPUs), -3 selects N+1, and so on.
5339 4543
5340 rcutorture.object_debug= [KNL] 4544 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 4545 Enable debug-object double-call_rcu() testing.
5342 4546
5343 rcutorture.onoff_holdoff= [KNL] 4547 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 4548 Set time (s) after boot for CPU-hotplug testing.
5345 4549
5346 rcutorture.onoff_interval= [KNL] 4550 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 4551 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 4552 or zero to disable CPU-hotplug testing.
5349 4553
5350 rcutorture.read_exit= [KNL] 4554 rcutorture.read_exit= [KNL]
5351 Set the number of rea 4555 Set the number of read-then-exit kthreads used
5352 to test the interacti 4556 to test the interaction of RCU updaters and
5353 task-exit processing. 4557 task-exit processing.
5354 4558
5355 rcutorture.read_exit_burst= [KNL] 4559 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 4560 The number of times in a given read-then-exit
5357 episode that a set of 4561 episode that a set of read-then-exit kthreads
5358 is spawned. 4562 is spawned.
5359 4563
5360 rcutorture.read_exit_delay= [KNL] 4564 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 4565 The delay, in seconds, between successive
5362 read-then-exit testin 4566 read-then-exit testing episodes.
5363 4567
5364 rcutorture.shuffle_interval= [KNL] 4568 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 4569 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 4570 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 4571 during the rcutorture test.
5368 4572
5369 rcutorture.shutdown_secs= [KNL] 4573 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 4574 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 4575 is useful for hands-off automated testing.
5372 4576
5373 rcutorture.stall_cpu= [KNL] 4577 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 4578 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 4579 warnings, zero to disable.
5376 4580
5377 rcutorture.stall_cpu_block= [KNL] 4581 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 4582 Sleep while stalling if set. This will result
5379 in warnings from pree !! 4583 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 4584 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 4585
5391 rcutorture.stall_cpu_holdoff= [KNL] 4586 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 4587 Time to wait (s) after boot before inducing stall.
5393 4588
5394 rcutorture.stall_cpu_irqsoff= [KNL] 4589 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 4590 Disable interrupts while stalling if set.
5396 4591
5397 rcutorture.stall_gp_kthread= [KNL] 4592 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 4593 Duration (s) of forced sleep within RCU
5399 grace-period kthread 4594 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 4595 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 4596 and stall_gp_kthread are specified, the
5402 kthread is starved fi 4597 kthread is starved first, then the CPU.
5403 4598
5404 rcutorture.stat_interval= [KNL] 4599 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 4600 Time (s) between statistics printk()s.
5406 4601
5407 rcutorture.stutter= [KNL] 4602 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 4603 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 4604 five seconds causes the test to run for five seconds,
5410 wait for five seconds 4605 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 4606 ability to transition abruptly to and from idle.
5412 4607
5413 rcutorture.test_boost= [KNL] 4608 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 4609 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 4610 "Maybe" means test if the RCU implementation
5416 under test support RC 4611 under test support RCU priority boosting.
5417 4612
5418 rcutorture.test_boost_duration= [KNL] 4613 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 4614 Duration (s) of each individual boost test.
5420 4615
5421 rcutorture.test_boost_interval= [KNL] 4616 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 4617 Interval (s) between each boost test.
5423 4618
5424 rcutorture.test_no_idle_hz= [KNL] 4619 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 4620 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 4621 rcutorture.shuffle_interval parameter.
5427 4622
5428 rcutorture.torture_type= [KNL] 4623 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 4624 Specify the RCU implementation to test.
5430 4625
5431 rcutorture.verbose= [KNL] 4626 rcutorture.verbose= [KNL]
5432 Enable additional pri 4627 Enable additional printk() statements.
5433 4628
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 4629 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 4630 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 4631 stall warning.
5437 4632
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 4633 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 4634 Suppress RCU CPU stall warning messages.
5446 4635
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 4636 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 4637 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 4638 rcutorture writer stall warnings that occur
5450 during early boot, th 4639 during early boot, that is, during the time
5451 before the init task 4640 before the init task is spawned.
5452 4641
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 4642 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 4643 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 4644
5479 rcupdate.rcu_expedited= [KNL] 4645 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 4646 Use expedited grace-period primitives, for
5481 example, synchronize_ 4647 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 4648 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 4649 but can increase CPU utilization, degrade
5484 real-time latency, an 4650 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 4651 No effect on CONFIG_TINY_RCU kernels.
5486 4652
5487 rcupdate.rcu_normal= [KNL] 4653 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 4654 Use only normal grace-period primitives,
5489 for example, synchron 4655 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 4656 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 4657 real-time latency, CPU utilization, and
5492 energy efficiency, bu 4658 energy efficiency, but can expose users to
5493 increased grace-perio 4659 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 4660 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 4661 CONFIG_TINY_RCU kernels.
5496 4662
5497 rcupdate.rcu_normal_after_boot= [KNL] 4663 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 4664 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 4665 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 4666 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 4667 on CONFIG_TINY_RCU kernels.
5502 4668
5503 But note that CONFIG_ 4669 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 4670 this kernel boot parameter, forcibly setting
5505 it to the value one, 4671 it to the value one, that is, converting any
5506 post-boot attempt at 4672 post-boot attempt at an expedited RCU grace
5507 period to instead use 4673 period to instead use normal non-expedited
5508 grace-period processi 4674 grace-period processing.
5509 4675
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] 4676 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 4677 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 4678 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 4679 of a given grace period. Setting a large
5537 number avoids disturb 4680 number avoids disturbing real-time workloads,
5538 but lengthens grace p 4681 but lengthens grace periods.
5539 4682
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 4683 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 4684 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 4685 messages. Disable with a value less than or equal
5572 than or equal to zero !! 4686 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 4687
5599 rcupdate.rcu_self_test= [KNL] 4688 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 4689 Run the RCU early boot self tests
5601 4690
5602 rdinit= [KNL] 4691 rdinit= [KNL]
5603 Format: <full_path> 4692 Format: <full_path>
5604 Run specified binary 4693 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 4694 used for early userspace startup. See initrd.
5606 4695
5607 rdrand= [X86,EARLY] !! 4696 rdrand= [X86]
5608 force - Override the 4697 force - Override the decision by the kernel to hide the
5609 advertisement 4698 advertisement of RDRAND support (this affects
5610 certain AMD p 4699 certain AMD processors because of buggy BIOS
5611 support, spec 4700 support, specifically around the suspend/resume
5612 path). 4701 path).
5613 4702
5614 rdt= [HW,X86,RDT] 4703 rdt= [HW,X86,RDT]
5615 Turn on/off individua 4704 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 4705 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 4706 mba.
5618 E.g. to turn on cmt a 4707 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 4708 rdt=cmt,!mba
5620 4709
5621 reboot= [KNL] 4710 reboot= [KNL]
5622 Format (x86 or x86_64 4711 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 4712 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 4713 [[,]s[mp]#### \
5625 [[,]b[ios] | 4714 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 4715 [[,]f[orce]
5627 Where reboot_mode is 4716 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 4717 (prefix with 'panic_' to set mode for panic
5629 reboo 4718 reboot only),
5630 reboot_type is 4719 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 4720 reboot_force is either force or not specified,
5632 reboot_cpu is s 4721 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 4722 to be used for rebooting.
5634 4723
5635 refscale.holdoff= [KNL] 4724 refscale.holdoff= [KNL]
5636 Set test-start holdof 4725 Set test-start holdoff period. The purpose of
5637 this parameter is to 4726 this parameter is to delay the start of the
5638 test until boot compl 4727 test until boot completes in order to avoid
5639 interference. 4728 interference.
5640 4729
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] 4730 refscale.loops= [KNL]
5648 Set the number of loo 4731 Set the number of loops over the synchronization
5649 primitive under test. 4732 primitive under test. Increasing this number
5650 reduces noise due to 4733 reduces noise due to loop start/end overhead,
5651 but the default has a 4734 but the default has already reduced the per-pass
5652 noise to a handful of 4735 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 4736 x86 laptops.
5654 4737
5655 refscale.nreaders= [KNL] 4738 refscale.nreaders= [KNL]
5656 Set number of readers 4739 Set number of readers. The default value of -1
5657 selects N, where N is 4740 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 4741 of CPUs. A value of zero is an interesting choice.
5659 4742
5660 refscale.nruns= [KNL] 4743 refscale.nruns= [KNL]
5661 Set number of runs, e 4744 Set number of runs, each of which is dumped onto
5662 the console log. 4745 the console log.
5663 4746
5664 refscale.readdelay= [KNL] 4747 refscale.readdelay= [KNL]
5665 Set the read-side cri 4748 Set the read-side critical-section duration,
5666 measured in microseco 4749 measured in microseconds.
5667 4750
5668 refscale.scale_type= [KNL] 4751 refscale.scale_type= [KNL]
5669 Specify the read-prot 4752 Specify the read-protection implementation to test.
5670 4753
5671 refscale.shutdown= [KNL] 4754 refscale.shutdown= [KNL]
5672 Shut down the system 4755 Shut down the system at the end of the performance
5673 test. This defaults 4756 test. This defaults to 1 (shut it down) when
5674 refscale is built int 4757 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 4758 it running) when refscale is built as a module.
5676 4759
5677 refscale.verbose= [KNL] 4760 refscale.verbose= [KNL]
5678 Enable additional pri 4761 Enable additional printk() statements.
5679 4762
5680 refscale.verbose_batched= [KNL] 4763 refscale.verbose_batched= [KNL]
5681 Batch the additional 4764 Batch the additional printk() statements. If zero
5682 (the default) or nega 4765 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 4766 print every Nth verbose statement, where N is the value
5684 specified. 4767 specified.
5685 4768
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= 4769 relax_domain_level=
5694 [KNL, SMP] Set schedu 4770 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 4771 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 4772
5697 reserve= [KNL,BUGS] Force kern 4773 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 4774 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 4775 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 4776 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 4777 is assumed to be I/O ports; otherwise it is memory.
5702 4778
5703 reserve_mem= [RAM] !! 4779 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] 4780 Format: nn[KMG]
5727 Reserves a hole at th 4781 Reserves a hole at the top of the kernel virtual
5728 address space. 4782 address space.
5729 4783
>> 4784 reservelow= [X86]
>> 4785 Format: nn[K]
>> 4786 Set the amount of memory to reserve for BIOS at
>> 4787 the bottom of the address space.
>> 4788
5730 reset_devices [KNL] Force drivers t 4789 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 4790 during initialization.
5732 4791
5733 resume= [SWSUSP] 4792 resume= [SWSUSP]
5734 Specify the partition 4793 Specify the partition device for software suspend
5735 Format: 4794 Format:
5736 {/dev/<dev> | PARTUUI 4795 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 4796
5738 resume_offset= [SWSUSP] 4797 resume_offset= [SWSUSP]
5739 Specify the offset fr 4798 Specify the offset from the beginning of the partition
5740 given by "resume=" at 4799 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 4800 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 4801 See Documentation/power/swsusp-and-swap-files.rst
5743 4802
5744 resumedelay= [HIBERNATION] Delay ( 4803 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 4804 read the resume files
5746 4805
5747 resumewait [HIBERNATION] Wait (i 4806 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 4807 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 4808 (e.g. USB and MMC devices).
5750 4809
5751 retain_initrd [RAM] Keep initrd mem !! 4810 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 4811 noresume Don't check if there's a hibernation image
5753 !! 4812 present during boot.
5754 retbleed= [X86] Control mitigat !! 4813 nocompress Don't compress/decompress hibernation images.
5755 Speculative Code Exec !! 4814 no Disable hibernation and resume.
5756 vulnerability. !! 4815 protect_image Turn on image protection during restoration
5757 !! 4816 (that will set all pages holding image data
5758 AMD-based UNRET and I !! 4817 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 4818
5789 Not specifying this o !! 4819 retain_initrd [RAM] Keep initrd memory after extraction
5790 4820
5791 rfkill.default_state= 4821 rfkill.default_state=
5792 0 "airplane mode". All 4822 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 4823 etc. communication is blocked by default.
5794 1 Unblocked. 4824 1 Unblocked.
5795 4825
5796 rfkill.master_switch_mode= 4826 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 4827 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 4828 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 4829 blocked and the previous configuration.
5800 2 The "airplane mode" b 4830 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 4831 blocked and everything unblocked.
5802 4832
>> 4833 rhash_entries= [KNL,NET]
>> 4834 Set number of hash buckets for route cache
>> 4835
5803 ring3mwait=disable 4836 ring3mwait=disable
5804 [KNL] Disable ring 3 4837 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 4838 CPUs.
5806 4839
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 4840 ro [KNL] Mount root device read-only on boot
5815 4841
5816 rodata= [KNL,EARLY] !! 4842 rodata= [KNL]
5817 on Mark read-only kernel 4843 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 4844 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 4845
5822 rockchip.usb_uart 4846 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 4847 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 4848 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 4849 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 4850 port and the regular usb controller gets disabled.
5828 4851
5829 root= [KNL] Root filesystem 4852 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 4853 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 4854
5837 rootdelay= [KNL] Delay (in secon 4855 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 4856 mount the root filesystem
5839 4857
5840 rootflags= [KNL] Set root filesy 4858 rootflags= [KNL] Set root filesystem mount option string
5841 4859
5842 rootfstype= [KNL] Set root filesy 4860 rootfstype= [KNL] Set root filesystem type
5843 4861
5844 rootwait [KNL] Wait (indefinit 4862 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 4863 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 4864 (e.g. USB and MMC devices).
5847 4865
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 4866 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 4867 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 4868 Memory area to be used by remote processor image,
5855 managed by CMA. 4869 managed by CMA.
5856 4870
5857 rw [KNL] Mount root devi 4871 rw [KNL] Mount root device read-write on boot
5858 4872
5859 S [KNL] Run init in sin 4873 S [KNL] Run init in single mode
5860 4874
5861 s390_iommu= [HW,S390] 4875 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 4876 Set s390 IOTLB flushing mode
5863 strict 4877 strict
5864 With strict flushing !! 4878 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 4879 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 4880 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 4881
5881 sa1100ir [NET] 4882 sa1100ir [NET]
5882 See drivers/net/irda/ 4883 See drivers/net/irda/sa1100_ir.c.
5883 4884
5884 sched_verbose [KNL,EARLY] Enables v !! 4885 sbni= [NET] Granch SBNI12 leased line adapter
>> 4886
>> 4887 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 4888
5886 schedstats= [KNL,X86] Enable or d 4889 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 4890 Allowed values are enable and disable. This feature
5888 incurs a small amount 4891 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 4892 but is useful for debugging and performance tuning.
5890 4893
5891 sched_thermal_decay_shift= 4894 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 4895 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 4896 pressure signal. Thermal pressure signal follows the
5895 default decay period 4897 default decay period of other scheduler pelt
5896 signals(usually 32 ms 4898 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 4899 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 4900 period for the thermal pressure signal by the shift
5899 value. 4901 value.
5900 i.e. with the default 4902 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 4903 sched_thermal_decay_shift thermal pressure decay pr
5902 1 4904 1 64 ms
5903 2 4905 2 128 ms
5904 and so on. 4906 and so on.
5905 Format: integer betwe 4907 Format: integer between 0 and 10
5906 Default is 0. 4908 Default is 0.
5907 4909
5908 scftorture.holdoff= [KNL] 4910 scftorture.holdoff= [KNL]
5909 Number of seconds to 4911 Number of seconds to hold off before starting
5910 test. Defaults to ze 4912 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 4913 to 10 seconds for built-in smp_call_function()
5912 tests. 4914 tests.
5913 4915
5914 scftorture.longwait= [KNL] 4916 scftorture.longwait= [KNL]
5915 Request ridiculously 4917 Request ridiculously long waits randomly selected
5916 up to the chosen limi 4918 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 4919 default) disables this feature. Please note
5918 that requesting even 4920 that requesting even small non-zero numbers of
5919 seconds can result in 4921 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 4922 softlockup complaints, and so on.
5921 4923
5922 scftorture.nthreads= [KNL] 4924 scftorture.nthreads= [KNL]
5923 Number of kthreads to 4925 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 4926 smp_call_function() family of functions.
5925 The default of -1 spe 4927 The default of -1 specifies a number of kthreads
5926 equal to the number o 4928 equal to the number of CPUs.
5927 4929
5928 scftorture.onoff_holdoff= [KNL] 4930 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 4931 Number seconds to wait after the start of the
5930 test before initiatin 4932 test before initiating CPU-hotplug operations.
5931 4933
5932 scftorture.onoff_interval= [KNL] 4934 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 4935 Number seconds to wait between successive
5934 CPU-hotplug operation 4936 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 4937 is the default) disables CPU-hotplug operations.
5936 4938
5937 scftorture.shutdown_secs= [KNL] 4939 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 4940 The number of seconds following the start of the
5939 test after which to s 4941 test after which to shut down the system. The
5940 default of zero avoid 4942 default of zero avoids shutting down the system.
5941 Non-zero values are u 4943 Non-zero values are useful for automated tests.
5942 4944
5943 scftorture.stat_interval= [KNL] 4945 scftorture.stat_interval= [KNL]
5944 The number of seconds 4946 The number of seconds between outputting the
5945 current test statisti 4947 current test statistics to the console. A value
5946 of zero disables stat 4948 of zero disables statistics output.
5947 4949
5948 scftorture.stutter_cpus= [KNL] 4950 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 4951 The number of jiffies to wait between each change
5950 to the set of CPUs un 4952 to the set of CPUs under test.
5951 4953
5952 scftorture.use_cpus_read_lock= [KNL] 4954 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 4955 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 4956 preempt_disable() to disable CPU hotplug
5955 while invoking one of 4957 while invoking one of the smp_call_function*()
5956 functions. 4958 functions.
5957 4959
5958 scftorture.verbose= [KNL] 4960 scftorture.verbose= [KNL]
5959 Enable additional pri 4961 Enable additional printk() statements.
5960 4962
5961 scftorture.weight_single= [KNL] 4963 scftorture.weight_single= [KNL]
5962 The probability weigh 4964 The probability weighting to use for the
5963 smp_call_function_sin 4965 smp_call_function_single() function with a zero
5964 "wait" parameter. A 4966 "wait" parameter. A value of -1 selects the
5965 default if all other 4967 default if all other weights are -1. However,
5966 if at least one weigh 4968 if at least one weight has some other value, a
5967 value of -1 will inst 4969 value of -1 will instead select a weight of zero.
5968 4970
5969 scftorture.weight_single_wait= [KNL] 4971 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 4972 The probability weighting to use for the
5971 smp_call_function_sin 4973 smp_call_function_single() function with a
5972 non-zero "wait" param 4974 non-zero "wait" parameter. See weight_single.
5973 4975
5974 scftorture.weight_many= [KNL] 4976 scftorture.weight_many= [KNL]
5975 The probability weigh 4977 The probability weighting to use for the
5976 smp_call_function_man 4978 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 4979 "wait" parameter. See weight_single.
5978 Note well that settin 4980 Note well that setting a high probability for
5979 this weighting can pl 4981 this weighting can place serious IPI load
5980 on the system. 4982 on the system.
5981 4983
5982 scftorture.weight_many_wait= [KNL] 4984 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 4985 The probability weighting to use for the
5984 smp_call_function_man 4986 smp_call_function_many() function with a
5985 non-zero "wait" param 4987 non-zero "wait" parameter. See weight_single
5986 and weight_many. 4988 and weight_many.
5987 4989
5988 scftorture.weight_all= [KNL] 4990 scftorture.weight_all= [KNL]
5989 The probability weigh 4991 The probability weighting to use for the
5990 smp_call_function_all 4992 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 4993 "wait" parameter. See weight_single and
5992 weight_many. 4994 weight_many.
5993 4995
5994 scftorture.weight_all_wait= [KNL] 4996 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 4997 The probability weighting to use for the
5996 smp_call_function_all 4998 smp_call_function_all() function with a
5997 non-zero "wait" param 4999 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5000 and weight_many.
5999 5001
6000 skew_tick= [KNL,EARLY] Offset th !! 5002 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5003 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5004 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5005 Format: { "0" | "1" }
6004 0 -- disable. (may be 5006 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5007 1 -- enable.
6006 Note: increases power 5008 Note: increases power consumption, thus should only be
6007 enabled if running ji 5009 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5010
6009 security= [SECURITY] Choose a l 5011 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5012 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5013 "lsm=" parameter.
6012 5014
6013 selinux= [SELINUX] Disable or 5015 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5016 Format: { "0" | "1" }
6015 See security/selinux/ 5017 See security/selinux/Kconfig help text.
6016 0 -- disable. 5018 0 -- disable.
6017 1 -- enable. 5019 1 -- enable.
6018 Default value is 1. 5020 Default value is 1.
6019 5021
6020 serialnumber [BUGS=X86-32] !! 5022 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 5023 Format: { "0" | "1" }
>> 5024 See security/apparmor/Kconfig help text
>> 5025 0 -- disable.
>> 5026 1 -- enable.
>> 5027 Default value is set via kernel config option.
6021 5028
6022 sev=option[,option...] [X86-64] See D !! 5029 serialnumber [BUGS=X86-32]
6023 5030
6024 shapers= [NET] 5031 shapers= [NET]
6025 Maximal number of sha 5032 Maximal number of shapers.
6026 5033
6027 show_lapic= [APIC,X86] Advanced P !! 5034 simeth= [IA-64]
6028 Limit apic dumping. T !! 5035 simscsi=
6029 number of local apics <<
6030 to set it to "all" by <<
6031 Format: { 1 (default) <<
6032 The parameter valid i <<
6033 apic=verbose is speci <<
6034 Example: apic=debug s <<
6035 <<
6036 slab_debug[=options[,slabs][;[options <<
6037 Enabling slab_debug a <<
6038 culprit if slab objec <<
6039 slab_debug can create <<
6040 may poison objects wh <<
6041 last alloc / free. Fo <<
6042 Documentation/mm/slub <<
6043 (slub_debug legacy na <<
6044 5036
6045 slab_max_order= [MM] !! 5037 slram= [HW,MTD]
6046 Determines the maximu <<
6047 A high setting may ca <<
6048 fragmentation. For mo <<
6049 Documentation/mm/slub <<
6050 (slub_max_order legac <<
6051 5038
6052 slab_merge [MM] 5039 slab_merge [MM]
6053 Enable merging of sla 5040 Enable merging of slabs with similar size when the
6054 kernel is built witho 5041 kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
6055 (slub_merge legacy na <<
6056 <<
6057 slab_min_objects= [MM] <<
6058 The minimum number of <<
6059 increase the slab ord <<
6060 generate a sufficient <<
6061 the number of objects <<
6062 of objects the smalle <<
6063 and the less frequent <<
6064 For more information <<
6065 (slub_min_objects leg <<
6066 <<
6067 slab_min_order= [MM] <<
6068 Determines the minimu <<
6069 lower or equal to sla <<
6070 Documentation/mm/slub <<
6071 (slub_min_order legac <<
6072 5042
6073 slab_nomerge [MM] 5043 slab_nomerge [MM]
6074 Disable merging of sl 5044 Disable merging of slabs with similar size. May be
6075 necessary if there is 5045 necessary if there is some reason to distinguish
6076 allocs to different s 5046 allocs to different slabs, especially in hardened
6077 environments where th 5047 environments where the risk of heap overflows and
6078 layout control by att 5048 layout control by attackers can usually be
6079 frustrated by disabli 5049 frustrated by disabling merging. This will reduce
6080 most of the exposure 5050 most of the exposure of a heap attack to a single
6081 cache (risks via meta 5051 cache (risks via metadata attacks are mostly
6082 unchanged). Debug opt 5052 unchanged). Debug options disable merging on their
6083 own. 5053 own.
6084 For more information !! 5054 For more information see Documentation/vm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5055
6087 slram= [HW,MTD] !! 5056 slab_max_order= [MM, SLAB]
>> 5057 Determines the maximum allowed order for slabs.
>> 5058 A high setting may cause OOMs due to memory
>> 5059 fragmentation. Defaults to 1 for systems with
>> 5060 more than 32MB of RAM, 0 otherwise.
>> 5061
>> 5062 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 5063 Enabling slub_debug allows one to determine the
>> 5064 culprit if slab objects become corrupted. Enabling
>> 5065 slub_debug can create guard zones around objects and
>> 5066 may poison objects when not in use. Also tracks the
>> 5067 last alloc / free. For more information see
>> 5068 Documentation/vm/slub.rst.
>> 5069
>> 5070 slub_max_order= [MM, SLUB]
>> 5071 Determines the maximum allowed order for slabs.
>> 5072 A high setting may cause OOMs due to memory
>> 5073 fragmentation. For more information see
>> 5074 Documentation/vm/slub.rst.
>> 5075
>> 5076 slub_min_objects= [MM, SLUB]
>> 5077 The minimum number of objects per slab. SLUB will
>> 5078 increase the slab order up to slub_max_order to
>> 5079 generate a sufficiently large slab able to contain
>> 5080 the number of objects indicated. The higher the number
>> 5081 of objects the smaller the overhead of tracking slabs
>> 5082 and the less frequently locks need to be acquired.
>> 5083 For more information see Documentation/vm/slub.rst.
>> 5084
>> 5085 slub_min_order= [MM, SLUB]
>> 5086 Determines the minimum page order for slabs. Must be
>> 5087 lower than slub_max_order.
>> 5088 For more information see Documentation/vm/slub.rst.
>> 5089
>> 5090 slub_merge [MM, SLUB]
>> 5091 Same with slab_merge.
>> 5092
>> 5093 slub_nomerge [MM, SLUB]
>> 5094 Same with slab_nomerge. This is supported for legacy.
>> 5095 See slab_nomerge for more information.
6088 5096
6089 smart2= [HW] 5097 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5098 Format: <io1>[,<io2>[,...,<io8>]]
6091 5099
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 5100 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5101 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5102 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5103 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5104 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5105 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5106 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5107 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5108 1: Fast pin select (default)
6119 2: ATC IRMode 5109 2: ATC IRMode
6120 5110
6121 smt= [KNL,MIPS,S390,EARLY] !! 5111 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5112 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5113 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5114 actual hardware limit.
6125 Format: <integer> 5115 Format: <integer>
6126 Default: -1 (no limit 5116 Default: -1 (no limit)
6127 5117
6128 softlockup_panic= 5118 softlockup_panic=
6129 [KNL] Should the soft 5119 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5120 Format: 0 | 1
6131 5121
6132 A value of 1 instruct 5122 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5123 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5124 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5125 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5126 respective build-time switch to that functionality.
6137 5127
6138 softlockup_all_cpu_backtrace= 5128 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5129 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5130 backtraces on all cpus.
6141 Format: 0 | 1 5131 Format: 0 | 1
6142 5132
6143 sonypi.*= [HW] Sony Programmabl 5133 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5134 See Documentation/admin-guide/laptops/sonypi.rst
6145 5135
6146 spectre_bhi= [X86] Control mitigat !! 5136 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 5137 (indirect branch speculation) vulnerability.
6163 The default operation 5138 The default operation protects the kernel from
6164 user space attacks. 5139 user space attacks.
6165 5140
6166 on - unconditionall 5141 on - unconditionally enable, implies
6167 spectre_v2_use 5142 spectre_v2_user=on
6168 off - unconditionall 5143 off - unconditionally disable, implies
6169 spectre_v2_use 5144 spectre_v2_user=off
6170 auto - kernel detects 5145 auto - kernel detects whether your CPU model is
6171 vulnerable 5146 vulnerable
6172 5147
6173 Selecting 'on' will, 5148 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5149 mitigation method at run time according to the
6175 CPU, the available mi 5150 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5151 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5152 compiler with which the kernel was built.
6178 5153
6179 Selecting 'on' will a 5154 Selecting 'on' will also enable the mitigation
6180 against user space to 5155 against user space to user space task attacks.
6181 5156
6182 Selecting 'off' will 5157 Selecting 'off' will disable both the kernel and
6183 the user space protec 5158 the user space protections.
6184 5159
6185 Specific mitigations 5160 Specific mitigations can also be selected manually:
6186 5161
6187 retpoline - r 5162 retpoline - replace indirect branches
6188 retpoline,generic - R !! 5163 retpoline,generic - google's original retpoline
6189 retpoline,lfence - L !! 5164 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 5165
6196 Not specifying this o 5166 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5167 spectre_v2=auto.
6198 5168
6199 spectre_v2_user= 5169 spectre_v2_user=
6200 [X86] Control mitigat 5170 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5171 (indirect branch speculation) vulnerability between
6202 user space tasks 5172 user space tasks
6203 5173
6204 on - Uncondition 5174 on - Unconditionally enable mitigations. Is
6205 enforced by 5175 enforced by spectre_v2=on
6206 5176
6207 off - Uncondition 5177 off - Unconditionally disable mitigations. Is
6208 enforced by 5178 enforced by spectre_v2=off
6209 5179
6210 prctl - Indirect br 5180 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5181 but mitigation can be enabled via prctl
6212 per thread. 5182 per thread. The mitigation control state
6213 is inherite 5183 is inherited on fork.
6214 5184
6215 prctl,ibpb 5185 prctl,ibpb
6216 - Like "prctl 5186 - Like "prctl" above, but only STIBP is
6217 controlled 5187 controlled per thread. IBPB is issued
6218 always when 5188 always when switching between different user
6219 space proce 5189 space processes.
6220 5190
6221 seccomp 5191 seccomp
6222 - Same as "pr 5192 - Same as "prctl" above, but all seccomp
6223 threads wil 5193 threads will enable the mitigation unless
6224 they explic 5194 they explicitly opt out.
6225 5195
6226 seccomp,ibpb 5196 seccomp,ibpb
6227 - Like "secco 5197 - Like "seccomp" above, but only STIBP is
6228 controlled 5198 controlled per thread. IBPB is issued
6229 always when 5199 always when switching between different
6230 user space 5200 user space processes.
6231 5201
6232 auto - Kernel sele 5202 auto - Kernel selects the mitigation depending on
6233 the availab 5203 the available CPU features and vulnerability.
6234 5204
6235 Default mitigation: " !! 5205 Default mitigation:
>> 5206 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
6236 5207
6237 Not specifying this o 5208 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5209 spectre_v2_user=auto.
6239 5210
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= 5211 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5212 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5213 (Speculative Store Bypass vulnerability)
6254 5214
6255 Certain CPUs are vuln 5215 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5216 a common industry wide performance optimization known
6257 as "Speculative Store 5217 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5218 to the same memory location may not be observed by
6259 later loads during sp 5219 later loads during speculative execution. The idea
6260 is that such stores a 5220 is that such stores are unlikely and that they can
6261 be detected prior to 5221 be detected prior to instruction retirement at the
6262 end of a particular s 5222 end of a particular speculation execution window.
6263 5223
6264 In vulnerable process 5224 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5225 store can be used in a cache side channel attack, for
6266 example to read memor 5226 example to read memory to which the attacker does not
6267 directly have access 5227 directly have access (e.g. inside sandboxed code).
6268 5228
6269 This parameter contro 5229 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5230 Bypass optimization is used.
6271 5231
6272 On x86 the options ar 5232 On x86 the options are:
6273 5233
6274 on - Uncondition 5234 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5235 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5236 auto - Kernel detects whether the CPU model contains an
6277 implementat 5237 implementation of Speculative Store Bypass and
6278 picks the m 5238 picks the most appropriate mitigation. If the
6279 CPU is not 5239 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5240 CPU is vulnerable the default mitigation is
6281 architectur 5241 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5242 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5243 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5244 for a process by default. The state of the control
6285 is inherite 5245 is inherited on fork.
6286 seccomp - Same as "pr 5246 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5247 will disable SSB unless they explicitly opt out.
6288 5248
6289 Default mitigations: 5249 Default mitigations:
6290 X86: "prctl" !! 5250 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6291 5251
6292 On powerpc the option 5252 On powerpc the options are:
6293 5253
6294 on,auto - On Power8 a 5254 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5255 barrier on kernel entry and exit. On Power7
6296 perform a s 5256 perform a software flush on kernel entry and
6297 exit. 5257 exit.
6298 off - No action. 5258 off - No action.
6299 5259
6300 Not specifying this o 5260 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5261 spec_store_bypass_disable=auto.
6302 5262
>> 5263 spia_io_base= [HW,MTD]
>> 5264 spia_fio_base=
>> 5265 spia_pedr=
>> 5266 spia_peddr=
>> 5267
6303 split_lock_detect= 5268 split_lock_detect=
6304 [X86] Enable split lo 5269 [X86] Enable split lock detection or bus lock detection
6305 5270
6306 When enabled (and if 5271 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5272 instructions that access data across cache line
6308 boundaries will resul 5273 boundaries will result in an alignment check exception
6309 for split lock detect 5274 for split lock detection or a debug exception for
6310 bus lock detection. 5275 bus lock detection.
6311 5276
6312 off - not enabled 5277 off - not enabled
6313 5278
6314 warn - the kernel 5279 warn - the kernel will emit rate-limited warnings
6315 about appli 5280 about applications triggering the #AC
6316 exception o 5281 exception or the #DB exception. This mode is
6317 the default 5282 the default on CPUs that support split lock
6318 detection o 5283 detection or bus lock detection. Default
6319 behavior is 5284 behavior is by #AC if both features are
6320 enabled in 5285 enabled in hardware.
6321 5286
6322 fatal - the kernel 5287 fatal - the kernel will send SIGBUS to applications
6323 that trigge 5288 that trigger the #AC exception or the #DB
6324 exception. 5289 exception. Default behavior is by #AC if
6325 both featur 5290 both features are enabled in hardware.
6326 5291
6327 ratelimit:N - <<
6328 Set system <<
6329 per second <<
6330 0 < N <= 10 <<
6331 <<
6332 N/A for spl <<
6333 <<
6334 <<
6335 If an #AC exception i 5292 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5293 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5294 the kernel will oops in either "warn" or "fatal"
6338 mode. 5295 mode.
6339 5296
6340 #DB exception for bus 5297 #DB exception for bus lock is triggered only when
6341 CPL > 0. 5298 CPL > 0.
6342 5299
6343 srbds= [X86,INTEL,EARLY] !! 5300 srbds= [X86,INTEL]
6344 Control the Special R 5301 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5302 (SRBDS) mitigation.
6346 5303
6347 Certain CPUs are vuln 5304 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5305 exploit which can leak bits from the random
6349 number generator. 5306 number generator.
6350 5307
6351 By default, this issu 5308 By default, this issue is mitigated by
6352 microcode. However, 5309 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5310 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5311 much slower. Among other effects, this will
6355 result in reduced thr 5312 result in reduced throughput from /dev/urandom.
6356 5313
6357 The microcode mitigat 5314 The microcode mitigation can be disabled with
6358 the following option: 5315 the following option:
6359 5316
6360 off: Disable mitig 5317 off: Disable mitigation and remove
6361 performance i 5318 performance impact to RDRAND and RDSEED
6362 5319
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] 5320 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5321 Specifies how frequently to check for
6389 grace-period sequence 5322 grace-period sequence counter wrap for the
6390 srcu_data structure's 5323 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5324 The greater the number of bits set in this kernel
6392 parameter, the less f 5325 parameter, the less frequently counter wrap will
6393 be checked for. Note 5326 be checked for. Note that the bottom two bits
6394 are ignored. 5327 are ignored.
6395 5328
6396 srcutree.exp_holdoff [KNL] 5329 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5330 Specifies how many nanoseconds must elapse
6398 since the end of the 5331 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5332 a given srcu_struct until the next normal SRCU
6400 grace period will be 5333 grace period will be considered for automatic
6401 expediting. Set to z 5334 expediting. Set to zero to disable automatic
6402 expediting. 5335 expediting.
6403 5336
6404 srcutree.srcu_max_nodelay [KNL] !! 5337 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 5338 Speculative Store Bypass Disable control
6432 5339
6433 On CPUs that are vuln 5340 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5341 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5342 firmware based mitigation, this parameter
6436 indicates how the mit 5343 indicates how the mitigation should be used:
6437 5344
6438 force-on: Unconditio 5345 force-on: Unconditionally enable mitigation for
6439 for both k 5346 for both kernel and userspace
6440 force-off: Unconditio 5347 force-off: Unconditionally disable mitigation for
6441 for both k 5348 for both kernel and userspace
6442 kernel: Always ena 5349 kernel: Always enable mitigation in the
6443 kernel, an 5350 kernel, and offer a prctl interface
6444 to allow u 5351 to allow userspace to register its
6445 interest i 5352 interest in being mitigated too.
6446 5353
6447 stack_guard_gap= [MM] 5354 stack_guard_gap= [MM]
6448 override the default 5355 override the default stack gap protection. The value
6449 is in page units and 5356 is in page units and it defines how many pages prior
6450 to (for stacks growin 5357 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5358 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5359 mapping. Default value is 256 pages.
6453 5360
6454 stack_depot_disable= [KNL,EARLY] !! 5361 stack_depot_disable= [KNL]
6455 Setting this to true 5362 Setting this to true through kernel command line will
6456 disable the stack dep 5363 disable the stack depot thereby saving the static memory
6457 consumed by the stack 5364 consumed by the stack hash table. By default this is set
6458 to false. 5365 to false.
6459 5366
6460 stacktrace [FTRACE] 5367 stacktrace [FTRACE]
6461 Enabled the stack tra 5368 Enabled the stack tracer on boot up.
6462 5369
6463 stacktrace_filter=[function-list] 5370 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5371 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 5372 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 5373 list of functions. This list can be changed at run
6467 time by the stack_tra 5374 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 5375 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 5376 and the stacktrace above is not needed.
6470 5377
6471 sti= [PARISC,HW] 5378 sti= [PARISC,HW]
6472 Format: <num> 5379 Format: <num>
6473 Set the STI (builtin 5380 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 5381 machines) console (graphic card) which should be used
6475 as the initial boot-c 5382 as the initial boot-console.
6476 See also comment in d 5383 See also comment in drivers/video/console/sticore.c.
6477 5384
6478 sti_font= [HW] 5385 sti_font= [HW]
6479 See comment in driver 5386 See comment in drivers/video/console/sticore.c.
6480 5387
6481 stifb= [HW] 5388 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 5389 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 5390
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= 5391 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 5392 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 5393 [NFS,SUNRPC]
6506 SunRPC servers often 5394 SunRPC servers often require that client requests
6507 originate from a priv 5395 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 5396 range 0 < portnr < 1024).
6509 An administrator who 5397 An administrator who wishes to reserve some of these
6510 ports for other uses 5398 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 5399 kernel's sunrpc client considers to be privileged
6512 using these two param 5400 using these two parameters to set the minimum and
6513 maximum port values. 5401 maximum port values.
6514 5402
6515 sunrpc.svc_rpc_per_connection_limit= 5403 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 5404 [NFS,SUNRPC]
6517 Limit the number of r 5405 Limit the number of requests that the server will
6518 process in parallel f 5406 process in parallel from a single connection.
6519 The default value is 5407 The default value is 0 (no limit).
6520 5408
6521 sunrpc.pool_mode= 5409 sunrpc.pool_mode=
6522 [NFS] 5410 [NFS]
6523 Control how the NFS s 5411 Control how the NFS server code allocates CPUs to
6524 service thread pools. 5412 service thread pools. Depending on how many NICs
6525 you have and where th 5413 you have and where their interrupts are bound, this
6526 option will affect wh 5414 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 5415 Note: this parameter cannot be changed while the
6528 NFS server is running 5416 NFS server is running.
6529 5417
6530 auto the serve 5418 auto the server chooses an appropriate mode
6531 automatic 5419 automatically using heuristics
6532 global a single 5420 global a single global pool contains all CPUs
6533 percpu one pool 5421 percpu one pool for each CPU
6534 pernode one pool 5422 pernode one pool for each NUMA node (equivalent
6535 to global 5423 to global on non-NUMA machines)
6536 5424
6537 sunrpc.tcp_slot_table_entries= 5425 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 5426 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 5427 [NFS,SUNRPC]
6540 Sets the upper limit 5428 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 5429 RPC calls that can be sent from the client to a
6542 server. Increasing th 5430 server. Increasing these values may allow you to
6543 improve throughput, b 5431 improve throughput, but will also increase the
6544 amount of memory rese 5432 amount of memory reserved for use by the client.
6545 5433
6546 suspend.pm_test_delay= 5434 suspend.pm_test_delay=
6547 [SUSPEND] 5435 [SUSPEND]
6548 Sets the number of se 5436 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 5437 mode before resuming the system (see
6550 /sys/power/pm_test). 5438 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 5439 is set. Default value is 5.
6552 5440
6553 svm= [PPC] 5441 svm= [PPC]
6554 Format: { on | off | 5442 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 5443 This parameter controls use of the Protected
6556 Execution Facility on 5444 Execution Facility on pSeries.
6557 5445
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 5446 swapaccount=[0|1]
6559 Format: { <int> [,<in !! 5447 [KNL] Enable accounting of swap in memory resource
>> 5448 controller if no parameter or 1 is given or disable
>> 5449 it if 0 is given (See Documentation/admin-guide/cgroup-v1/memory.rst)
>> 5450
>> 5451 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
>> 5452 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 5453 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 5454 force -- force using of bounce buffers even if they
6565 wouldn't be 5455 wouldn't be automatically used by the kernel
6566 noforce -- Never use 5456 noforce -- Never use bounce buffers (for debugging)
6567 5457
6568 switches= [HW,M68k,EARLY] !! 5458 switches= [HW,M68k]
6569 5459
6570 sysctl.*= [KNL] 5460 sysctl.*= [KNL]
6571 Set a sysctl paramete 5461 Set a sysctl parameter, right before loading the init
6572 process, as if the va 5462 process, as if the value was written to the respective
6573 /proc/sys/... file. B 5463 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 5464 separators. Unrecognized parameters and invalid values
6575 are reported in the k 5465 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 5466 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 5467 Example: sysctl.vm.swappiness=40
6578 5468
>> 5469 sysfs.deprecated=0|1 [KNL]
>> 5470 Enable/disable old style sysfs layout for old udev
>> 5471 on older distributions. When this option is enabled
>> 5472 very new udev will not work anymore. When this option
>> 5473 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 5474 in older udev will not work anymore.
>> 5475 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 5476 the kernel configuration.
>> 5477
6579 sysrq_always_enabled 5478 sysrq_always_enabled
6580 [KNL] 5479 [KNL]
6581 Ignore sysrq setting 5480 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 5481 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 5482 Useful for debugging.
6584 5483
6585 tcpmhash_entries= [KNL,NET] 5484 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 5485 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 5486 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 5487 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 5488 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 5489 "tcp_no_metrics_save" section for more details.
6591 5490
6592 tdfx= [HW,DRM] 5491 tdfx= [HW,DRM]
6593 5492
6594 test_suspend= [SUSPEND] !! 5493 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 5494 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 5495 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 5496 as the system sleep state during system startup with
6599 the optional capabili 5497 the optional capability to repeat N number of times.
6600 The system is woken f 5498 The system is woken from this state using a
6601 wakeup-capable RTC al 5499 wakeup-capable RTC alarm.
6602 5500
6603 thash_entries= [KNL,NET] 5501 thash_entries= [KNL,NET]
6604 Set number of hash bu 5502 Set number of hash buckets for TCP connection
6605 5503
6606 thermal.act= [HW,ACPI] 5504 thermal.act= [HW,ACPI]
6607 -1: disable all activ 5505 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 5506 <degrees C>: override all lowest active trip points
6609 5507
6610 thermal.crt= [HW,ACPI] 5508 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 5509 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 5510 <degrees C>: override all critical trip points
6613 5511
>> 5512 thermal.nocrt= [HW,ACPI]
>> 5513 Set to disable actions on ACPI thermal zone
>> 5514 critical and hot trip points.
>> 5515
6614 thermal.off= [HW,ACPI] 5516 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 5517 1: disable ACPI thermal control
6616 5518
6617 thermal.psv= [HW,ACPI] 5519 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 5520 -1: disable all passive trip points
6619 <degrees C>: override 5521 <degrees C>: override all passive trip points to this
6620 value 5522 value
6621 5523
6622 thermal.tzp= [HW,ACPI] 5524 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 5525 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 5526 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 5527 0: no polling (default)
6626 5528
6627 threadirqs [KNL,EARLY] !! 5529 threadirqs [KNL]
6628 Force threading of al 5530 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 5531 marked explicitly IRQF_NO_THREAD.
6630 5532
6631 topology= [S390,EARLY] !! 5533 topology= [S390]
6632 Format: {off | on} 5534 Format: {off | on}
6633 Specify if the kernel 5535 Specify if the kernel should make use of the cpu
6634 topology information 5536 topology information if the hardware supports this.
6635 The scheduler will ma 5537 The scheduler will make use of this information and
6636 e.g. base its process 5538 e.g. base its process migration decisions on it.
6637 Default is on. 5539 Default is on.
6638 5540
>> 5541 topology_updates= [KNL, PPC, NUMA]
>> 5542 Format: {off}
>> 5543 Specify if the kernel should ignore (off)
>> 5544 topology updates sent by the hypervisor to this
>> 5545 LPAR.
>> 5546
6639 torture.disable_onoff_at_boot= [KNL] 5547 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 5548 Prevent the CPU-hotplug component of torturing
6641 until after init has 5549 until after init has spawned.
6642 5550
6643 torture.ftrace_dump_at_shutdown= [KNL 5551 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 5552 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 5553 even if there were no errors. This can be a
6646 very costly operation 5554 very costly operation when many torture tests
6647 are running concurren 5555 are running concurrently, especially on systems
6648 with rotating-rust st 5556 with rotating-rust storage.
6649 5557
6650 torture.verbose_sleep_frequency= [KNL 5558 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 5559 Specifies how many verbose printk()s should be
6652 emitted between each 5560 emitted between each sleep. The default of zero
6653 disables verbose-prin 5561 disables verbose-printk() sleeping.
6654 5562
6655 torture.verbose_sleep_duration= [KNL] 5563 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 5564 Duration of each verbose-printk() sleep in jiffies.
6657 5565
>> 5566 tp720= [HW,PS2]
>> 5567
6658 tpm_suspend_pcr=[HW,TPM] 5568 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 5569 Format: integer pcr id
6660 Specify that at suspe 5570 Specify that at suspend time, the tpm driver
6661 should extend the spe 5571 should extend the specified pcr with zeros,
6662 as a workaround for s 5572 as a workaround for some chips which fail to
6663 flush the last writte 5573 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 5574 This will guarantee that all the other pcrs
6665 are saved. 5575 are saved.
6666 5576
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] 5577 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 5578 [FTRACE] will set tracing buffer size on each cpu.
6707 5579
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] 5580 trace_event=[event-list]
6731 [FTRACE] Set and star 5581 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 5582 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 5583 comma-separated list of trace events to enable. See
6734 also Documentation/tr 5584 also Documentation/trace/events.rst
6735 5585
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] 5586 trace_options=[option-list]
6757 [FTRACE] Enable or di 5587 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 5588 The option-list is a comma delimited list of options
6759 that can be enabled o 5589 that can be enabled or disabled just as if you were
6760 to echo the option na 5590 to echo the option name into
6761 5591
6762 /sys/kernel/traci !! 5592 /sys/kernel/debug/tracing/trace_options
6763 5593
6764 For example, to enabl 5594 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 5595 stack trace of each event), add to the command line:
6766 5596
6767 trace_options=s 5597 trace_options=stacktrace
6768 5598
6769 See also Documentatio 5599 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 5600 section.
6771 5601
6772 trace_trigger=[trigger-list] !! 5602 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 5603 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 5604 tracing ring buffer. This is useful for early boot up
6775 filter. !! 5605 where the system hangs or reboots and does not give the
6776 !! 5606 option for reading the tracing buffer or performing a
6777 The format is is "tra !! 5607 ftrace_dump_on_oops.
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 5608
6784 The above will enable !! 5609 To turn off having tracepoints sent to printk,
6785 event but only trigge !! 5610 echo 0 > /proc/sys/kernel/tracepoint_printk
6786 event is "2" (TASK_UN !! 5611 Note, echoing 1 into this file without the
>> 5612 tracepoint_printk kernel cmdline option has no effect.
6787 5613
6788 See also "Event trigg !! 5614 ** CAUTION **
6789 5615
>> 5616 Having tracepoints sent to printk() and activating high
>> 5617 frequency tracepoints such as irq or sched, can cause
>> 5618 the system to live lock.
6790 5619
6791 traceoff_on_warning 5620 traceoff_on_warning
6792 [FTRACE] enable this 5621 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 5622 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 5623 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 5624 file located in /sys/kernel/debug/tracing/
6796 5625
6797 This option is useful 5626 This option is useful, as it disables the trace before
6798 the WARNING dump is c 5627 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 5628 be filled with content caused by the warning output.
6800 5629
6801 This option can also 5630 This option can also be set at run time via the sysctl
6802 option: kernel/trace 5631 option: kernel/traceoff_on_warning
6803 5632
6804 transparent_hugepage= 5633 transparent_hugepage=
6805 [KNL] 5634 [KNL]
6806 Format: [always|madvi 5635 Format: [always|madvise|never]
6807 Can be used to contro 5636 Can be used to control the default behavior of the system
6808 with respect to trans 5637 with respect to transparent hugepages.
6809 See Documentation/adm 5638 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 5639 for more details.
6811 5640
6812 trusted.source= [KEYS] 5641 trusted.source= [KEYS]
6813 Format: <string> 5642 Format: <string>
6814 This parameter identi 5643 This parameter identifies the trust source as a backend
6815 for trusted keys impl 5644 for trusted keys implementation. Supported trust
6816 sources: 5645 sources:
6817 - "tpm" 5646 - "tpm"
6818 - "tee" 5647 - "tee"
6819 - "caam" <<
6820 - "dcp" <<
6821 If not specified then 5648 If not specified then it defaults to iterating through
6822 the trust source list 5649 the trust source list starting with TPM and assigns the
6823 first trust source as 5650 first trust source as a backend which is initialized
6824 successfully during i 5651 successfully during iteration.
6825 5652
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 5653 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 5654 Format: <string>
6850 [x86] reliable: mark 5655 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 5656 disables clocksource verification at runtime, as well
6852 as the stability chec 5657 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 5658 high-resolution timer mode on older hardware, and in
6854 virtualized environme 5659 virtualized environment.
6855 [x86] noirqtime: Do n 5660 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 5661 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 5662 platforms where RDTSC is slow and this accounting
6858 can add overhead. 5663 can add overhead.
6859 [x86] unstable: mark 5664 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 5665 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 5666 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 5667 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 5668 in situations with strict latency requirements (where
6864 interruptions from cl 5669 interruptions from clocksource watchdog are not
6865 acceptable). 5670 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 5671
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 5672 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 5673 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 5674 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 5675 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 5676 Format: <unsigned int>
6882 5677
6883 tsx= [X86] Control Transac 5678 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 5679 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 5680 support TSX control.
6886 5681
6887 This parameter contro 5682 This parameter controls the TSX feature. The options are:
6888 5683
6889 on - Enable TSX 5684 on - Enable TSX on the system. Although there are
6890 mitigations f 5685 mitigations for all known security vulnerabilities,
6891 TSX has been 5686 TSX has been known to be an accelerator for
6892 several previ 5687 several previous speculation-related CVEs, and
6893 so there may 5688 so there may be unknown security risks associated
6894 with leaving 5689 with leaving it enabled.
6895 5690
6896 off - Disable TSX 5691 off - Disable TSX on the system. (Note that this
6897 option takes 5692 option takes effect only on newer CPUs which are
6898 not vulnerabl 5693 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 5694 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 5695 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 5696 update. This new MSR allows for the reliable
6902 deactivation 5697 deactivation of the TSX functionality.)
6903 5698
6904 auto - Disable TSX 5699 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 5700 otherwise enable TSX on the system.
6906 5701
6907 Not specifying this o 5702 Not specifying this option is equivalent to tsx=off.
6908 5703
6909 See Documentation/adm 5704 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 5705 for more details.
6911 5706
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 5707 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 5708 Abort (TAA) vulnerability.
6914 5709
6915 Similar to Micro-arch 5710 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 5711 certain CPUs that support Transactional
6917 Synchronization Exten 5712 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 5713 exploit against CPU internal buffers which can forward
6919 information to a disc 5714 information to a disclosure gadget under certain
6920 conditions. 5715 conditions.
6921 5716
6922 In vulnerable process 5717 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 5718 data can be used in a cache side channel attack, to
6924 access data to which 5719 access data to which the attacker does not have direct
6925 access. 5720 access.
6926 5721
6927 This parameter contro 5722 This parameter controls the TAA mitigation. The
6928 options are: 5723 options are:
6929 5724
6930 full - Enable T 5725 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 5726 if TSX is enabled.
6932 5727
6933 full,nosmt - Enable T 5728 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 5729 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 5730 is not disabled because CPU is not
6936 vulnerab 5731 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 5732 off - Unconditionally disable TAA mitigation
6938 5733
6939 On MDS-affected machi 5734 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 5735 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 5736 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 5737 this mitigation, you need to specify mds=off too.
6943 5738
6944 Not specifying this o 5739 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 5740 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 5741 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 5742 required and doesn't provide any additional
6948 mitigation. 5743 mitigation.
6949 5744
6950 For details see: 5745 For details see:
6951 Documentation/admin-g 5746 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 5747
6953 turbografx.map[2|3]= [HW,JOY] 5748 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 5749 TurboGraFX parallel port interface
6955 Format: 5750 Format:
6956 <port#>,<js1>,<js2>,< 5751 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 5752 See also Documentation/input/devices/joystick-parport.rst
6958 5753
6959 udbg-immortal [PPC] When debugging 5754 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 5755 happen after console_init() and before a proper
6961 console driver takes 5756 console driver takes over, this boot options might
6962 help "seeing" what's 5757 help "seeing" what's going on.
6963 5758
6964 uhash_entries= [KNL,NET] 5759 uhash_entries= [KNL,NET]
6965 Set number of hash bu 5760 Set number of hash buckets for UDP/UDP-Lite connections
6966 5761
6967 uhci-hcd.ignore_oc= 5762 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 5763 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 5764 Some badly-designed motherboards generate lots of
6970 bogus events, for por 5765 bogus events, for ports that aren't wired to
6971 anything. Set this p 5766 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 5767 Note that genuine overcurrent events won't be
6973 reported either. 5768 reported either.
6974 5769
6975 unknown_nmi_panic 5770 unknown_nmi_panic
6976 [X86] Cause panic on 5771 [X86] Cause panic on unknown NMI.
6977 5772
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= 5773 usbcore.authorized_default=
6985 [USB] Default USB dev 5774 [USB] Default USB device authorization:
6986 (default -1 = authori !! 5775 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 5776 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 5777 if device connected to internal port)
6989 5778
6990 usbcore.autosuspend= 5779 usbcore.autosuspend=
6991 [USB] The autosuspend 5780 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 5781 for newly-detected USB devices (default 2). This
6993 is the time required 5782 is the time required before an idle device will be
6994 autosuspended. Devic 5783 autosuspended. Devices for which the delay is set
6995 to a negative value w 5784 to a negative value won't be autosuspended at all.
6996 5785
6997 usbcore.usbfs_snoop= 5786 usbcore.usbfs_snoop=
6998 [USB] Set to log all 5787 [USB] Set to log all usbfs traffic (default 0 = off).
6999 5788
7000 usbcore.usbfs_snoop_max= 5789 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 5790 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 5791 (default = 65536).
7003 5792
7004 usbcore.blinkenlights= 5793 usbcore.blinkenlights=
7005 [USB] Set to cycle le 5794 [USB] Set to cycle leds on hubs (default 0 = off).
7006 5795
7007 usbcore.old_scheme_first= 5796 usbcore.old_scheme_first=
7008 [USB] Start with the 5797 [USB] Start with the old device initialization
7009 scheme (default 0 = o 5798 scheme (default 0 = off).
7010 5799
7011 usbcore.usbfs_memory_mb= 5800 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 5801 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 5802 usbfs (default = 16, 0 = max = 2047).
7014 5803
7015 usbcore.use_both_schemes= 5804 usbcore.use_both_schemes=
7016 [USB] Try the other d 5805 [USB] Try the other device initialization scheme
7017 if the first one fail 5806 if the first one fails (default 1 = enabled).
7018 5807
7019 usbcore.initial_descriptor_timeout= 5808 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 5809 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 5810 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 5811 (default 5000 = 5.0 seconds).
7023 5812
7024 usbcore.nousb [USB] Disable the USB 5813 usbcore.nousb [USB] Disable the USB subsystem
7025 5814
7026 usbcore.quirks= 5815 usbcore.quirks=
7027 [USB] A list of quirk 5816 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 5817 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 5818 commas. Each entry has the form
7030 VendorID:ProductID:Fl 5819 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 5820 numbers and Flags is a set of letters. Each letter
7032 will change the built 5821 will change the built-in quirk; setting it if it is
7033 clear and clearing it 5822 clear and clearing it if it is set. The letters have
7034 the following meaning 5823 the following meanings:
7035 a = USB_QUIRK 5824 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 5825 descriptors must not be fetched using
7037 a 255 5826 a 255-byte read);
7038 b = USB_QUIRK 5827 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 5828 correctly so reset it instead);
7040 c = USB_QUIRK 5829 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 5830 Set-Interface requests);
7042 d = USB_QUIRK 5831 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 5832 handle its Configuration or Interface
7044 strin 5833 strings);
7045 e = USB_QUIRK 5834 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 5835 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 5836 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 5837 more interface descriptions than the
7049 bNumI 5838 bNumInterfaces count, and can't handle
7050 talki 5839 talking to these interfaces);
7051 g = USB_QUIRK 5840 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 5841 during initialization, after we read
7053 the d 5842 the device descriptor);
7054 h = USB_QUIRK 5843 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 5844 high speed and super speed interrupt
7056 endpo 5845 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 5846 require the interval in microframes (1
7058 micro 5847 microframe = 125 microseconds) to be
7059 calcu 5848 calculated as interval = 2 ^
7060 (bInt 5849 (bInterval-1).
7061 Devic 5850 Devices with this quirk report their
7062 bInte 5851 bInterval as the result of this
7063 calcu 5852 calculation instead of the exponent
7064 varia 5853 variable used in the calculation);
7065 i = USB_QUIRK 5854 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 5855 handle device_qualifier descriptor
7067 reque 5856 requests);
7068 j = USB_QUIRK 5857 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 5858 generates spurious wakeup, ignore
7070 remot 5859 remote wakeup capability);
7071 k = USB_QUIRK 5860 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 5861 Power Management);
7073 l = USB_QUIRK 5862 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 5863 (Device reports its bInterval as linear
7075 frame 5864 frames instead of the USB 2.0
7076 calcu 5865 calculation);
7077 m = USB_QUIRK 5866 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 5867 to be disconnected before suspend to
7079 preve 5868 prevent spurious wakeup);
7080 n = USB_QUIRK 5869 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 5870 pause after every control message);
7082 o = USB_QUIRK 5871 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 5872 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 5873 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 5874
7089 usbhid.mousepoll= 5875 usbhid.mousepoll=
7090 [USBHID] The interval 5876 [USBHID] The interval which mice are to be polled at.
7091 5877
7092 usbhid.jspoll= 5878 usbhid.jspoll=
7093 [USBHID] The interval 5879 [USBHID] The interval which joysticks are to be polled at.
7094 5880
7095 usbhid.kbpoll= 5881 usbhid.kbpoll=
7096 [USBHID] The interval 5882 [USBHID] The interval which keyboards are to be polled at.
7097 5883
7098 usb-storage.delay_use= 5884 usb-storage.delay_use=
7099 [UMS] The delay in se 5885 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 5886 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 5887
7105 usb-storage.quirks= 5888 usb-storage.quirks=
7106 [UMS] A list of quirk 5889 [UMS] A list of quirks entries to supplement or
7107 override the built-in 5890 override the built-in unusual_devs list. List
7108 entries are separated 5891 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 5892 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 5893 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 5894 Flags is a set of characters, each corresponding
7112 to a common usb-stora 5895 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 5896 a = SANE_SENSE (collect more than 18 bytes
7114 of se 5897 of sense data, not on uas);
7115 b = BAD_SENSE 5898 b = BAD_SENSE (don't collect more than 18
7116 bytes 5899 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 5900 c = FIX_CAPACITY (decrease the reported
7118 devic 5901 device capacity by one sector);
7119 d = NO_READ_D 5902 d = NO_READ_DISC_INFO (don't use
7120 READ_ 5903 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 5904 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 5905 READ_CAPACITY_16 command);
7123 f = NO_REPORT 5906 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 5907 command, uas only);
7125 g = MAX_SECTO 5908 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 5909 240 sectors at a time, uas only);
7127 h = CAPACITY_ 5910 h = CAPACITY_HEURISTICS (decrease the
7128 repor 5911 reported device capacity by one
7129 secto 5912 sector if the number is odd);
7130 i = IGNORE_DE 5913 i = IGNORE_DEVICE (don't bind to this
7131 devic 5914 device);
7132 j = NO_REPORT 5915 j = NO_REPORT_LUNS (don't use report luns
7133 comma 5916 command, uas only);
7134 k = NO_SAME ( 5917 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 5918 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 5919 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 5920 m = MAX_SECTORS_64 (don't transfer more
7138 than 5921 than 64 sectors = 32 KB at a time,
7139 not o 5922 not on uas);
7140 n = INITIAL_R 5923 n = INITIAL_READ10 (force a retry of the
7141 initi 5924 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 5925 o = CAPACITY_OK (accept the capacity
7143 repor 5926 reported by the device, not on uas);
7144 p = WRITE_CAC 5927 p = WRITE_CACHE (the device cache is ON
7145 by de 5928 by default, not on uas);
7146 r = IGNORE_RE 5929 r = IGNORE_RESIDUE (the device reports
7147 bogus 5930 bogus residue values, not on uas);
7148 s = SINGLE_LU 5931 s = SINGLE_LUN (the device has only one
7149 Logic 5932 Logical Unit);
7150 t = NO_ATA_1X 5933 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 5934 commands, uas only);
7152 u = IGNORE_UA 5935 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 5936 w = NO_WP_DETECT (don't test whether the
7154 mediu 5937 medium is write-protected).
7155 y = ALWAYS_SY 5938 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 5939 even if the device claims no cache,
7157 not o 5940 not on uas)
7158 Example: quirks=0419: 5941 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 5942
7160 user_debug= [KNL,ARM] 5943 user_debug= [KNL,ARM]
7161 Format: <int> 5944 Format: <int>
7162 See arch/arm/Kconfig. 5945 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 5946 1 - undefined instruction events
7164 2 - system c 5947 2 - system calls
7165 4 - invalid 5948 4 - invalid data aborts
7166 8 - SIGSEGV 5949 8 - SIGSEGV faults
7167 16 - SIGBUS f 5950 16 - SIGBUS faults
7168 Example: user_debug=3 5951 Example: user_debug=31
7169 5952
7170 userpte= 5953 userpte=
7171 [X86,EARLY] Flags con !! 5954 [X86] Flags controlling user PTE allocations.
7172 5955
7173 nohigh = do n 5956 nohigh = do not allocate PTE pages in
7174 HIGHM 5957 HIGHMEM regardless of setting
7175 of CO 5958 of CONFIG_HIGHPTE.
7176 5959
7177 vdso= [X86,SH,SPARC] !! 5960 vdso= [X86,SH]
7178 On X86_32, this is an 5961 On X86_32, this is an alias for vdso32=. Otherwise:
7179 5962
7180 vdso=1: enable VDSO ( 5963 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 5964 vdso=0: disable VDSO mapping
7182 5965
7183 vdso32= [X86] Control the 32- 5966 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 5967 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 5968 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 5969
7187 See the help text for 5970 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 5971 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 5972 vdso32=0; otherwise, the default is vdso32=1.
7190 5973
7191 For compatibility wit 5974 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 5975 alias for vdso32=0.
7193 5976
7194 Try vdso32=0 if you e 5977 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 5978 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 5979
7197 video= [FB,EARLY] Frame buff !! 5980 vector= [IA-64,SMP]
>> 5981 vector=percpu: enable percpu vector domain
>> 5982
>> 5983 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 5984 See Documentation/fb/modedb.rst.
7199 5985
7200 video.brightness_switch_enabled= [ACP !! 5986 video.brightness_switch_enabled= [0,1]
7201 Format: [0|1] <<
7202 If set to 1, on recei 5987 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 5988 generated by hotkey, video driver will adjust brightness
7204 level and then send o 5989 level and then send out the event to user space through
7205 the allocated input d !! 5990 the allocated input device; If set to 0, video driver
7206 will only send out th 5991 will only send out the event without touching backlight
7207 brightness level. 5992 brightness level.
7208 default: 1 5993 default: 1
7209 5994
7210 virtio_mmio.device= 5995 virtio_mmio.device=
7211 [VMMIO] Memory mapped 5996 [VMMIO] Memory mapped virtio (platform) device.
7212 5997
7213 <size>@<basead 5998 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 5999 where:
7215 <size> := 6000 <size> := size (can use standard suffixes
7216 6001 like K, M and G)
7217 <baseaddr> := 6002 <baseaddr> := physical base address
7218 <irq> := 6003 <irq> := interrupt number (as passed to
7219 6004 request_irq())
7220 <id> := 6005 <id> := (optional) platform device id
7221 example: 6006 example:
7222 virtio_mmio.d 6007 virtio_mmio.device=1K@0x100b0000:48:7
7223 6008
7224 Can be used multiple 6009 Can be used multiple times for multiple devices.
7225 6010
7226 vga= [BOOT,X86-32] Select 6011 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 6012 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 6013 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 6014 Use vga=ask for menu.
7230 This is actually a bo 6015 This is actually a boot loader parameter; the value is
7231 passed to the kernel 6016 passed to the kernel using a special protocol.
7232 6017
7233 vm_debug[=options] [KNL] Availab 6018 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 6019 May slow down system boot speed, especially when
7235 enabled on systems wi 6020 enabled on systems with a large amount of memory.
7236 All options are enabl 6021 All options are enabled by default, and this
7237 interface is meant to 6022 interface is meant to allow for selectively
7238 enabling or disabling 6023 enabling or disabling specific virtual memory
7239 debugging features. 6024 debugging features.
7240 6025
7241 Available options are 6026 Available options are:
7242 P Enable page s 6027 P Enable page structure init time poisoning
7243 - Disable all o 6028 - Disable all of the above options
7244 6029
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 6030 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 6031 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 6032 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 6033 decrease the size and leave more room for directly
7249 for directly mapped k !! 6034 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 6035
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 6036 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 6037 Sets the memory size reserved for contiguous memory
7256 allocations for the v 6038 allocations for the vmcp device driver.
7257 6039
7258 vmhalt= [KNL,S390] Perform z/ 6040 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 6041 Format: <command>
7260 6042
7261 vmpanic= [KNL,S390] Perform z/ 6043 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 6044 Format: <command>
7263 6045
7264 vmpoff= [KNL,S390] Perform z/ 6046 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 6047 Format: <command>
7266 6048
7267 vsyscall= [X86-64,EARLY] !! 6049 vsyscall= [X86-64]
7268 Controls the behavior 6050 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 6051 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 6052 code). Most statically-linked binaries and older
7271 versions of glibc use 6053 versions of glibc use these calls. Because these
7272 functions are at fixe 6054 functions are at fixed addresses, they make nice
7273 targets for exploits 6055 targets for exploits that can control RIP.
7274 6056
7275 emulate Vsyscalls !! 6057 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 6058 emulated reasonably safely. The vsyscall
7277 readable. !! 6059 page is readable.
7278 6060
7279 xonly [default] !! 6061 xonly Vsyscalls turn into traps and are
7280 emulated 6062 emulated reasonably safely. The vsyscall
7281 page is n 6063 page is not readable.
7282 6064
7283 none Vsyscalls 6065 none Vsyscalls don't work at all. This makes
7284 them quit 6066 them quite hard to use for exploits but
7285 might bre 6067 might break your system.
7286 6068
7287 vt.color= [VT] Default text col 6069 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6070 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6071 Default: 0x07 = light gray on black.
7290 6072
7291 vt.cur_default= [VT] Default cursor s 6073 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6074 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6075 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6076 see VGA-softcursor.txt. Default: 2 = underline.
7295 6077
7296 vt.default_blu= [VT] 6078 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6079 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6080 Change the default blue palette of the console.
7299 This is a 16-member a 6081 This is a 16-member array composed of values
7300 ranging from 0-255. 6082 ranging from 0-255.
7301 6083
7302 vt.default_grn= [VT] 6084 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6085 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6086 Change the default green palette of the console.
7305 This is a 16-member a 6087 This is a 16-member array composed of values
7306 ranging from 0-255. 6088 ranging from 0-255.
7307 6089
7308 vt.default_red= [VT] 6090 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6091 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6092 Change the default red palette of the console.
7311 This is a 16-member a 6093 This is a 16-member array composed of values
7312 ranging from 0-255. 6094 ranging from 0-255.
7313 6095
7314 vt.default_utf8= 6096 vt.default_utf8=
7315 [VT] 6097 [VT]
7316 Format=<0|1> 6098 Format=<0|1>
7317 Set system-wide defau 6099 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6100 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6101 newly opened terminals.
7320 6102
7321 vt.global_cursor_default= 6103 vt.global_cursor_default=
7322 [VT] 6104 [VT]
7323 Format=<-1|0|1> 6105 Format=<-1|0|1>
7324 Set system-wide defau 6106 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6107 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6108 i.e. cursors will be created by default unless
7327 overridden by individ 6109 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6110 cursors, 1 will display them.
7329 6111
7330 vt.italic= [VT] Default color fo 6112 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6113 Default: 2 = green.
7332 6114
7333 vt.underline= [VT] Default color fo 6115 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6116 Default: 3 = cyan.
7335 6117
7336 watchdog timers [HW,WDT] For informat 6118 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6119 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6120 or other driver-specific files in the
7339 Documentation/watchdo 6121 Documentation/watchdog/ directory.
7340 6122
7341 watchdog_thresh= 6123 watchdog_thresh=
7342 [KNL] 6124 [KNL]
7343 Set the hard lockup d 6125 Set the hard lockup detector stall duration
7344 threshold in seconds. 6126 threshold in seconds. The soft lockup detector
7345 threshold is set to t 6127 threshold is set to twice the value. A value of 0
7346 disables both lockup 6128 disables both lockup detectors. Default is 10
7347 seconds. 6129 seconds.
7348 6130
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= 6131 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 6132 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 6133 warn stall conditions and dump internal state to
7359 help debugging. 0 di 6134 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 6135 detection; otherwise, it's the stall threshold
7361 duration in seconds. 6136 duration in seconds. The default value is 30 and
7362 it can be updated at 6137 it can be updated at runtime by writing to the
7363 corresponding sysfs f 6138 corresponding sysfs file.
7364 6139
7365 workqueue.cpu_intensive_thresh_us= !! 6140 workqueue.disable_numa
7366 Per-cpu work items wh !! 6141 By default, all work items queued to unbound
7367 threshold are automat !! 6142 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 6143 issued on, which results in better behavior in
7369 them from noticeably !! 6144 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 6145 whatever reason, this option can be used. Note
7371 !! 6146 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 6147 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 6148
7386 workqueue.power_efficient 6149 workqueue.power_efficient
7387 Per-cpu workqueues ar 6150 Per-cpu workqueues are generally preferred because
7388 they show better perf 6151 they show better performance thanks to cache
7389 locality; unfortunate 6152 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 6153 be more power hungry than unbound workqueues.
7391 6154
7392 Enabling this makes t 6155 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 6156 were observed to contribute significantly to power
7394 consumption unbound, 6157 consumption unbound, leading to measurably lower
7395 power usage at the co 6158 power usage at the cost of small performance
7396 overhead. 6159 overhead.
7397 6160
7398 The default value of 6161 The default value of this parameter is determined by
7399 the config option CON 6162 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 6163
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 6164 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 6165 Workqueue used to implicitly guarantee that work
7415 items queued without 6166 items queued without explicit CPU specified are put
7416 on the local CPU. Th 6167 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 6168 and while local CPU is still preferred work items
7418 may be put on foreign 6169 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 6170 forces round-robin CPU selection to flush out
7420 usages which depend o 6171 usages which depend on the now broken guarantee.
7421 When enabled, memory 6172 When enabled, memory and cache locality will be
7422 impacted. 6173 impacted.
7423 6174
7424 writecombine= [LOONGARCH,EARLY] Con !! 6175 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 6176 default x2apic cluster mode on platforms
7432 supporting x2apic. 6177 supporting x2apic.
7433 6178
7434 xen_512gb_limit [KNL,X86-64,X 6179 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 6180 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6181 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6182 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6183 save/restore/migration must be enabled to handle larger
7439 domains. 6184 domains.
7440 6185
7441 xen_emul_unplug= [HW,X !! 6186 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6187 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6188 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6189 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6190 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6191 nics -- unplug network devices
7447 all -- unplug all emu 6192 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6193 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6194 unnecessary even if the host did not respond to
7450 the unplug pr 6195 the unplug protocol
7451 never -- do not unplu 6196 never -- do not unplug even if version check succeeds
7452 6197
7453 xen_legacy_crash [X86,XEN,EARL !! 6198 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6199 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6200 panic() code such as dumping handler.
7456 6201
7457 xen_mc_debug [X86,XEN,EARLY] !! 6202 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 6203 Disables the qspinlock slowpath using Xen PV optimizations.
7459 Enabling this feature !! 6204 This parameter is obsoleted by "nopvspin" parameter, which
7460 bit, so it should onl !! 6205 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 6206
7469 xen_nopv [X86] 6207 xen_nopv [X86]
7470 Disables the PV optim 6208 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6209 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6210 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6211 has equivalent effect for XEN platform.
7474 6212
7475 xen_no_vector_callback 6213 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6214 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6215 event channel interrupts.
7478 6216
7479 xen_scrub_pages= [XEN] 6217 xen_scrub_pages= [XEN]
7480 Boolean option to con 6218 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6219 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6220 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6221 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6222
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6223 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6224 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6225 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6226 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 6227 improve timer resolution at the expense of processing
7490 more timer interrupts 6228 more timer interrupts.
7491 6229
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] 6230 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 6231 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 6232 storms (jiffies). Default is 10.
7502 6233
7503 xen.event_loop_timeout= [XEN] 6234 xen.event_loop_timeout= [XEN]
7504 After which time (jif 6235 After which time (jiffies) the event handling loop
7505 should start to delay 6236 should start to delay EOI handling. Default is 2.
7506 6237
7507 xen.fifo_events= [XEN] 6238 xen.fifo_events= [XEN]
7508 Boolean parameter to 6239 Boolean parameter to disable using fifo event handling
7509 even if available. No 6240 even if available. Normally fifo event handling is
7510 preferred over the 2- 6241 preferred over the 2-level event handling, as it is
7511 fairer and the number 6242 fairer and the number of possible event channels is
7512 much higher. Default 6243 much higher. Default is on (use fifo events).
7513 6244
>> 6245 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6246 Disables the PV optimizations forcing the guest to run
>> 6247 as generic guest with no PV drivers. Currently support
>> 6248 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6249
>> 6250 nopvspin [X86,XEN,KVM]
>> 6251 Disables the qspinlock slow path using PV optimizations
>> 6252 which allow the hypervisor to 'idle' the guest on lock
>> 6253 contention.
>> 6254
7514 xirc2ps_cs= [NET,PCMCIA] 6255 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6256 Format:
7516 <irq>,<irq_mask>,<io> 6257 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6258
7518 xive= [PPC] 6259 xive= [PPC]
7519 By default on POWER9 6260 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6261 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6262 allows the fallback firmware mode to be used:
7522 6263
7523 off Fallback to 6264 off Fallback to firmware control of XIVE interrupt
7524 controller 6265 controller on both pseries and powernv
7525 platforms. 6266 platforms. Only useful on POWER9 and above.
7526 6267
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] 6268 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6269 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6270 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6271 consulted in header drivers/usb/host/xhci.h.
7537 6272
7538 xmon [PPC,EARLY] !! 6273 xmon [PPC]
7539 Format: { early | on 6274 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 6275 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 6276 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 6277 early Call xmon as early as possible on boot; xmon
7543 debugger is c 6278 debugger is called from setup_arch().
7544 on xmon debugger 6279 on xmon debugger hooks will be installed so xmon
7545 is only calle 6280 is only called on a kernel crash. Default mode,
7546 i.e. either " 6281 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 6282 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 6283 rw xmon debugger hooks will be installed so xmon
7549 is called onl 6284 is called only on a kernel crash, mode is write,
7550 meaning SPR r 6285 meaning SPR registers, memory and, other data
7551 can be writte 6286 can be written using xmon commands.
7552 ro same as "rw" 6287 ro same as "rw" option above but SPR registers,
7553 memory, and o 6288 memory, and other data can't be written using
7554 xmon commands 6289 xmon commands.
7555 off xmon is disab 6290 off xmon is disabled.
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