1 accept_memory= [MM] !! 1 acpi= [HW,ACPI,X86,ARM64]
2 Format: { eager | lazy <<
3 default: lazy <<
4 By default, unaccepted <<
5 avoid prolonged boot t <<
6 some runtime overhead <<
7 accepted. In most case <<
8 For some workloads or <<
9 accept_memory=eager ca <<
10 at once during boot. <<
11 <<
12 acpi= [HW,ACPI,X86,ARM64,RIS <<
13 Advanced Configuration 2 Advanced Configuration and Power Interface
14 Format: { force | on | 3 Format: { force | on | off | strict | noirq | rsdt |
15 copy_dsdt | !! 4 copy_dsdt }
16 force -- enable ACPI i 5 force -- enable ACPI if default was off
17 on -- enable ACPI but !! 6 on -- enable ACPI but allow fallback to DT [arm64]
18 off -- disable ACPI if 7 off -- disable ACPI if default was on
19 noirq -- do not use AC 8 noirq -- do not use ACPI for IRQ routing
20 strict -- Be less tole 9 strict -- Be less tolerant of platforms that are not
21 strictly ACPI 10 strictly ACPI specification compliant.
22 rsdt -- prefer RSDT ov 11 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT 12 copy_dsdt -- copy DSDT to memory
24 nospcr -- disable cons !! 13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
25 default _seria <<
26 For ARM64, ONLY "acpi= <<
27 "acpi=nospcr" are avai <<
28 For RISCV64, ONLY "acp <<
29 are available 14 are available
30 15
31 See also Documentation 16 See also Documentation/power/runtime_pm.rst, pci=noacpi
32 17
33 acpi_apic_instance= [ACPI,IOAPIC,E !! 18 acpi_apic_instance= [ACPI, IOAPIC]
34 Format: <int> 19 Format: <int>
35 2: use 2nd APIC table, 20 2: use 2nd APIC table, if available
36 1,0: use 1st APIC tabl 21 1,0: use 1st APIC table
37 default: 0 22 default: 0
38 23
39 acpi_backlight= [HW,ACPI] 24 acpi_backlight= [HW,ACPI]
40 { vendor | video | nat 25 { vendor | video | native | none }
41 If set to vendor, pref 26 If set to vendor, prefer vendor-specific driver
42 (e.g. thinkpad_acpi, s 27 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
43 of the ACPI video.ko d 28 of the ACPI video.ko driver.
44 If set to video, use t 29 If set to video, use the ACPI video.ko driver.
45 If set to native, use 30 If set to native, use the device's native backlight mode.
46 If set to none, disabl 31 If set to none, disable the ACPI backlight interface.
47 32
48 acpi_force_32bit_fadt_addr [ACPI,EARLY !! 33 acpi_force_32bit_fadt_addr
49 force FADT to use 32 b 34 force FADT to use 32 bit addresses rather than the
50 64 bit X_* addresses. 35 64 bit X_* addresses. Some firmware have broken 64
51 bit addresses for forc 36 bit addresses for force ACPI ignore these and use
52 the older legacy 32 bi 37 the older legacy 32 bit addresses.
53 38
54 acpica_no_return_repair [HW, ACPI] 39 acpica_no_return_repair [HW, ACPI]
55 Disable AML predefined 40 Disable AML predefined validation mechanism
56 This mechanism can rep 41 This mechanism can repair the evaluation result to make
57 the return objects mor 42 the return objects more ACPI specification compliant.
58 This option is useful 43 This option is useful for developers to identify the
59 root cause of an AML i 44 root cause of an AML interpreter issue when the issue
60 has something to do wi 45 has something to do with the repair mechanism.
61 46
62 acpi.debug_layer= [HW,ACPI,ACPI_ 47 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
63 acpi.debug_level= [HW,ACPI,ACPI_ 48 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
64 Format: <int> 49 Format: <int>
65 CONFIG_ACPI_DEBUG must 50 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
66 debug output. Bits in 51 debug output. Bits in debug_layer correspond to a
67 _COMPONENT in an ACPI 52 _COMPONENT in an ACPI source file, e.g.,
68 #define _COMPONENT 53 #define _COMPONENT ACPI_EVENTS
69 Bits in debug_level co 54 Bits in debug_level correspond to a level in
70 ACPI_DEBUG_PRINT state 55 ACPI_DEBUG_PRINT statements, e.g.,
71 ACPI_DEBUG_PRINT(( 56 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
72 The debug_level mask d 57 The debug_level mask defaults to "info". See
73 Documentation/firmware 58 Documentation/firmware-guide/acpi/debug.rst for more information about
74 debug layers and level 59 debug layers and levels.
75 60
76 Enable processor drive 61 Enable processor driver info messages:
77 acpi.debug_layer=0 62 acpi.debug_layer=0x20000000
78 Enable AML "Debug" out 63 Enable AML "Debug" output, i.e., stores to the Debug
79 object while interpret 64 object while interpreting AML:
80 acpi.debug_layer=0 65 acpi.debug_layer=0xffffffff acpi.debug_level=0x2
81 Enable all messages re 66 Enable all messages related to ACPI hardware:
82 acpi.debug_layer=0 67 acpi.debug_layer=0x2 acpi.debug_level=0xffffffff
83 68
84 Some values produce so 69 Some values produce so much output that the system is
85 unusable. The "log_bu 70 unusable. The "log_buf_len" parameter may be useful
86 if you need to capture 71 if you need to capture more output.
87 72
88 acpi_enforce_resources= [ACPI] 73 acpi_enforce_resources= [ACPI]
89 { strict | lax | no } 74 { strict | lax | no }
90 Check for resource con 75 Check for resource conflicts between native drivers
91 and ACPI OperationRegi 76 and ACPI OperationRegions (SystemIO and SystemMemory
92 only). IO ports and me 77 only). IO ports and memory declared in ACPI might be
93 used by the ACPI subsy 78 used by the ACPI subsystem in arbitrary AML code and
94 can interfere with leg 79 can interfere with legacy drivers.
95 strict (default): acce 80 strict (default): access to resources claimed by ACPI
96 is denied; legacy driv 81 is denied; legacy drivers trying to access reserved
97 resources will fail to 82 resources will fail to bind to device using them.
98 lax: access to resourc 83 lax: access to resources claimed by ACPI is allowed;
99 legacy drivers trying 84 legacy drivers trying to access reserved resources
100 will bind successfully 85 will bind successfully but a warning message is logged.
101 no: ACPI OperationRegi 86 no: ACPI OperationRegions are not marked as reserved,
102 no further checks are 87 no further checks are performed.
103 88
104 acpi_force_table_verification [HW,AC !! 89 acpi_force_table_verification [HW,ACPI]
105 Enable table checksum 90 Enable table checksum verification during early stage.
106 By default, this is di 91 By default, this is disabled due to x86 early mapping
107 size limitation. 92 size limitation.
108 93
109 acpi_irq_balance [HW,ACPI] 94 acpi_irq_balance [HW,ACPI]
110 ACPI will balance acti 95 ACPI will balance active IRQs
111 default in APIC mode 96 default in APIC mode
112 97
113 acpi_irq_nobalance [HW,ACPI] 98 acpi_irq_nobalance [HW,ACPI]
114 ACPI will not move act 99 ACPI will not move active IRQs (default)
115 default in PIC mode 100 default in PIC mode
116 101
117 acpi_irq_isa= [HW,ACPI] If irq_balan 102 acpi_irq_isa= [HW,ACPI] If irq_balance, mark listed IRQs used by ISA
118 Format: <irq>,<irq>... 103 Format: <irq>,<irq>...
119 104
120 acpi_irq_pci= [HW,ACPI] If irq_balan 105 acpi_irq_pci= [HW,ACPI] If irq_balance, clear listed IRQs for
121 use by PCI 106 use by PCI
122 Format: <irq>,<irq>... 107 Format: <irq>,<irq>...
123 108
124 acpi_mask_gpe= [HW,ACPI] 109 acpi_mask_gpe= [HW,ACPI]
125 Due to the existence o 110 Due to the existence of _Lxx/_Exx, some GPEs triggered
126 by unsupported hardwar 111 by unsupported hardware/firmware features can result in
127 GPE floodings that can 112 GPE floodings that cannot be automatically disabled by
128 the GPE dispatcher. 113 the GPE dispatcher.
129 This facility can be u 114 This facility can be used to prevent such uncontrolled
130 GPE floodings. 115 GPE floodings.
131 Format: <byte> or <bit 116 Format: <byte> or <bitmap-list>
132 117
133 acpi_no_auto_serialize [HW,ACPI] 118 acpi_no_auto_serialize [HW,ACPI]
134 Disable auto-serializa 119 Disable auto-serialization of AML methods
135 AML control methods th 120 AML control methods that contain the opcodes to create
136 named objects will be 121 named objects will be marked as "Serialized" by the
137 auto-serialization fea 122 auto-serialization feature.
138 This feature is enable 123 This feature is enabled by default.
139 This option allows to 124 This option allows to turn off the feature.
140 125
141 acpi_no_memhotplug [ACPI] Disable memo 126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
142 kernels. 127 kernels.
143 128
144 acpi_no_static_ssdt [HW,ACPI,EARLY !! 129 acpi_no_static_ssdt [HW,ACPI]
145 Disable installation o 130 Disable installation of static SSDTs at early boot time
146 By default, SSDTs cont 131 By default, SSDTs contained in the RSDT/XSDT will be
147 installed automaticall 132 installed automatically and they will appear under
148 /sys/firmware/acpi/tab 133 /sys/firmware/acpi/tables.
149 This option turns off 134 This option turns off this feature.
150 Note that specifying t 135 Note that specifying this option does not affect
151 dynamic table installa 136 dynamic table installation which will install SSDT
152 tables to /sys/firmwar 137 tables to /sys/firmware/acpi/tables/dynamic.
153 138
154 acpi_no_watchdog [HW,ACPI,WDT] 139 acpi_no_watchdog [HW,ACPI,WDT]
155 Ignore the ACPI-based 140 Ignore the ACPI-based watchdog interface (WDAT) and let
156 a native driver contro 141 a native driver control the watchdog device instead.
157 142
158 acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] !! 143 acpi_rsdp= [ACPI,EFI,KEXEC]
159 Pass the RSDP address 144 Pass the RSDP address to the kernel, mostly used
160 on machines running EF 145 on machines running EFI runtime service to boot the
161 second kernel for kdum 146 second kernel for kdump.
162 147
163 acpi_os_name= [HW,ACPI] Tell ACPI BI 148 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
164 Format: To spoof as Wi 149 Format: To spoof as Windows 98: ="Microsoft Windows"
165 150
166 acpi_rev_override [ACPI] Override the 151 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167 of 2 which is mandated 152 of 2 which is mandated by ACPI 6) as the supported ACPI
168 specification revision 153 specification revision (when using this switch, it may
169 be necessary to carry 154 be necessary to carry out a cold reboot _twice_ in a
170 row to make it take ef 155 row to make it take effect on the platform firmware).
171 156
172 acpi_osi= [HW,ACPI] Modify list 157 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" 158 acpi_osi="string1" # add string1
174 acpi_osi="!string2" 159 acpi_osi="!string2" # remove string2
175 acpi_osi=!* 160 acpi_osi=!* # remove all strings
176 acpi_osi=! 161 acpi_osi=! # disable all built-in OS vendor
177 162 strings
178 acpi_osi=!! 163 acpi_osi=!! # enable all built-in OS vendor
179 164 strings
180 acpi_osi= 165 acpi_osi= # disable all strings
181 166
182 'acpi_osi=!' can be us 167 'acpi_osi=!' can be used in combination with single or
183 multiple 'acpi_osi="st 168 multiple 'acpi_osi="string1"' to support specific OS
184 vendor string(s). Not 169 vendor string(s). Note that such command can only
185 affect the default sta 170 affect the default state of the OS vendor strings, thus
186 it cannot affect the d 171 it cannot affect the default state of the feature group
187 strings and the curren 172 strings and the current state of the OS vendor strings,
188 specifying it multiple 173 specifying it multiple times through kernel command line
189 is meaningless. This 174 is meaningless. This command is useful when one do not
190 care about the state o 175 care about the state of the feature group strings which
191 should be controlled b 176 should be controlled by the OSPM.
192 Examples: 177 Examples:
193 1. 'acpi_osi=! acpi_ 178 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194 to 'acpi_osi="Win 179 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 can make '_OSI("W 180 can make '_OSI("Windows 2000")' TRUE.
196 181
197 'acpi_osi=' cannot be 182 'acpi_osi=' cannot be used in combination with other
198 'acpi_osi=' command li 183 'acpi_osi=' command lines, the _OSI method will not
199 exist in the ACPI name 184 exist in the ACPI namespace. NOTE that such command can
200 only affect the _OSI s 185 only affect the _OSI support state, thus specifying it
201 multiple times through 186 multiple times through kernel command line is also
202 meaningless. 187 meaningless.
203 Examples: 188 Examples:
204 1. 'acpi_osi=' can m 189 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205 FALSE. 190 FALSE.
206 191
207 'acpi_osi=!*' can be u 192 'acpi_osi=!*' can be used in combination with single or
208 multiple 'acpi_osi="st 193 multiple 'acpi_osi="string1"' to support specific
209 string(s). Note that 194 string(s). Note that such command can affect the
210 current state of both 195 current state of both the OS vendor strings and the
211 feature group strings, 196 feature group strings, thus specifying it multiple times
212 through kernel command 197 through kernel command line is meaningful. But it may
213 still not able to affe 198 still not able to affect the final state of a string if
214 there are quirks relat 199 there are quirks related to this string. This command
215 is useful when one wan 200 is useful when one want to control the state of the
216 feature group strings 201 feature group strings to debug BIOS issues related to
217 the OSPM features. 202 the OSPM features.
218 Examples: 203 Examples:
219 1. 'acpi_osi="Module 204 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220 '_OSI("Module Dev 205 '_OSI("Module Device")' FALSE.
221 2. 'acpi_osi=!* acpi 206 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222 '_OSI("Module Dev 207 '_OSI("Module Device")' TRUE.
223 3. 'acpi_osi=! acpi_ 208 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224 equivalent to 209 equivalent to
225 'acpi_osi=!* acpi 210 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226 and 211 and
227 'acpi_osi=!* acpi 212 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228 they all will mak 213 they all will make '_OSI("Windows 2000")' TRUE.
229 214
230 acpi_pm_good [X86] 215 acpi_pm_good [X86]
231 Override the pmtimer b 216 Override the pmtimer bug detection: force the kernel
232 to assume that this ma 217 to assume that this machine's pmtimer latches its value
233 and always returns goo 218 and always returns good values.
234 219
235 acpi_sci= [HW,ACPI,EARLY] ACPI S !! 220 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge 221 Format: { level | edge | high | low }
237 222
238 acpi_skip_timer_override [HW,ACPI,EARL !! 223 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore I 224 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIO 225 For broken nForce2 BIOS resulting in XT-PIC timer.
241 226
242 acpi_sleep= [HW,ACPI] Sleep option 227 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_ 228 Format: { s3_bios, s3_mode, s3_beep, s4_hwsig,
244 s4_nohwsig, 229 s4_nohwsig, old_ordering, nonvs,
245 sci_force_en 230 sci_force_enable, nobl }
246 See Documentation/powe 231 See Documentation/power/video.rst for information on
247 s3_bios and s3_mode. 232 s3_bios and s3_mode.
248 s3_beep is for debuggi 233 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel' 234 as soon as the kernel's real-mode entry point is called.
250 s4_hwsig causes the ke 235 s4_hwsig causes the kernel to check the ACPI hardware
251 signature during resum 236 signature during resume from hibernation, and gracefully
252 refuse to resume if it 237 refuse to resume if it has changed. This complies with
253 the ACPI specification 238 the ACPI specification but not with reality, since
254 Windows does not do th 239 Windows does not do this and many laptops do change it
255 on docking. So the def 240 on docking. So the default behaviour is to allow resume
256 and simply warn when t 241 and simply warn when the signature changes, unless the
257 s4_hwsig option is ena 242 s4_hwsig option is enabled.
258 s4_nohwsig prevents AC 243 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a 244 used (or even warned about) during resume.
260 old_ordering causes th 245 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 246 control method, with respect to putting devices into
262 low power states, to b 247 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 248 of _PTS is used by default).
264 nonvs prevents the ker 249 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 250 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 251 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 252 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 253 but some broken systems don't work without it).
269 nobl causes the intern 254 nobl causes the internal blacklist of systems known to
270 behave incorrectly in 255 behave incorrectly in some ways with respect to system
271 suspend and resume to 256 suspend and resume to be ignored (use wisely).
272 257
273 acpi_use_timer_override [HW,ACPI,EARLY !! 258 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 259 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 260 that require a timer override, but don't have HPET
276 261
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 262 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 263 kernel's map of available physical RAM.
279 264
280 agp= [AGP] 265 agp= [AGP]
281 { off | try_unsupporte 266 { off | try_unsupported }
282 off: disable AGP suppo 267 off: disable AGP support
283 try_unsupported: try t 268 try_unsupported: try to drive unsupported chipsets
284 (may crash com 269 (may crash computer or cause data corruption)
285 270
286 ALSA [HW,ALSA] 271 ALSA [HW,ALSA]
287 See Documentation/soun 272 See Documentation/sound/alsa-configuration.rst
288 273
289 alignment= [KNL,ARM] 274 alignment= [KNL,ARM]
290 Allow the default user 275 Allow the default userspace alignment fault handler
291 behaviour to be specif 276 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 277 bit 1 enables fixups, and bit 2 sends a segfault.
293 278
294 align_va_addr= [X86-64] 279 align_va_addr= [X86-64]
295 Align virtual addresse 280 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 281 allocating a VMA at process creation time. This option
297 gives you up to 3% per 282 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 283 machines (where it is enabled by default) for a
299 CPU-intensive style be 284 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 285 a microbenchmark depending on workload and compiler.
301 286
302 32: only for 32-bit pr 287 32: only for 32-bit processes
303 64: only for 64-bit pr 288 64: only for 64-bit processes
304 on: enable for both 32 289 on: enable for both 32- and 64-bit processes
305 off: disable for both 290 off: disable for both 32- and 64-bit processes
306 291
307 alloc_snapshot [FTRACE] 292 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 293 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 294 main buffer is allocated. This is handy if debugging
310 and you need to use tr 295 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 296 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 297 to be done where GFP_KERNEL allocations are allowed.
313 298
314 allow_mismatched_32bit_el0 [ARM64,EARL !! 299 allow_mismatched_32bit_el0 [ARM64]
315 Allow execve() of 32-b 300 Allow execve() of 32-bit applications and setting of the
316 PER_LINUX32 personalit 301 PER_LINUX32 personality on systems where only a strict
317 subset of the CPUs sup 302 subset of the CPUs support 32-bit EL0. When this
318 parameter is present, 303 parameter is present, the set of CPUs supporting 32-bit
319 EL0 is indicated by /s 304 EL0 is indicated by /sys/devices/system/cpu/aarch32_el0
320 and hot-unplug operati 305 and hot-unplug operations may be restricted.
321 306
322 See Documentation/arch !! 307 See Documentation/arm64/asymmetric-32bit.rst for more
323 information. 308 information.
324 309
325 amd_iommu= [HW,X86-64] 310 amd_iommu= [HW,X86-64]
326 Pass parameters to the 311 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 312 Possible values are:
328 fullflush - Deprecated 313 fullflush - Deprecated, equivalent to iommu.strict=1
329 off - do not ini 314 off - do not initialize any AMD IOMMU found in
330 the system 315 the system
331 force_isolation - Forc 316 force_isolation - Force device isolation for all
332 devi 317 devices. The IOMMU driver is not
333 allo 318 allowed anymore to lift isolation
334 requ 319 requirements as needed. This option
335 does 320 does not override iommu=pt
336 force_enable - Force e 321 force_enable - Force enable the IOMMU on platforms known
337 to be b 322 to be buggy with IOMMU enabled. Use this
338 option 323 option with care.
339 pgtbl_v1 - Use v1 324 pgtbl_v1 - Use v1 page table for DMA-API (Default).
340 pgtbl_v2 - Use v2 325 pgtbl_v2 - Use v2 page table for DMA-API.
341 irtcachedis - Disable <<
342 326
343 amd_iommu_dump= [HW,X86-64] 327 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 328 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 329 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 330 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 331 IOMMU initialization.
348 332
349 amd_iommu_intr= [HW,X86-64] 333 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 334 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 335 remapping modes:
352 legacy - Use legac 336 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 337 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 338 to inject interrupts directly into guest.
355 This mode 339 This mode requires kvm-amd.avic=1.
356 (Default 340 (Default when IOMMU HW support is present.)
357 341
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 342 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 343 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 344 Format: <a>,<b>
389 See also Documentation 345 See also Documentation/input/joydev/joystick.rst
390 346
391 analog.map= [HW,JOY] Analog joysti 347 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 348 Specifies type or capabilities of an analog joystick
393 connected to one of 16 349 connected to one of 16 gameports
394 Format: <type1>,<type2 350 Format: <type1>,<type2>,..<type16>
395 351
396 apc= [HW,SPARC] 352 apc= [HW,SPARC]
397 Power management funct 353 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 354 Format: noidle
399 Disable APC CPU standb 355 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 356 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 357 APC and your system crashes randomly.
402 358
403 apic= [APIC,X86,EARLY] Advan !! 359 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 360 Change the output verbosity while booting
405 Format: { quiet (defau 361 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 362 Change the amount of debugging information output
407 when initialising the 363 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 364 For X86-32, this can also be used to specify an APIC
409 driver name. 365 driver name.
410 Format: apic=driver_na 366 Format: apic=driver_name
411 Examples: apic=bigsmp 367 Examples: apic=bigsmp
412 368
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 369 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 370 Format: { bsp (default) | all | none }
415 bsp: External NMI is 371 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 372 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 373 backup of CPU 0
418 none: External NMI is 374 none: External NMI is masked for all CPUs. This is
419 useful so that a 375 useful so that a dump capture kernel won't be
420 shot down by NMI 376 shot down by NMI
421 377
422 autoconf= [IPV6] 378 autoconf= [IPV6]
423 See Documentation/netw 379 See Documentation/networking/ipv6.rst.
424 380
>> 381 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 382 Limit apic dumping. The parameter defines the maximal
>> 383 number of local apics being dumped. Also it is possible
>> 384 to set it to "all" by meaning -- no limit here.
>> 385 Format: { 1 (default) | 2 | ... | all }.
>> 386 The parameter valid if only apic=debug or
>> 387 apic=verbose is specified.
>> 388 Example: apic=debug show_lapic=all
>> 389
425 apm= [APM] Advanced Power M 390 apm= [APM] Advanced Power Management
426 See header of arch/x86 391 See header of arch/x86/kernel/apm_32.c.
427 392
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 393 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 394 Format: <io>,<irq>,<nodeID>
437 395
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall 396 arm64.nobti [ARM64] Unconditionally disable Branch Target
442 Identification support 397 Identification support
443 398
444 arm64.nomops [ARM64] Unconditionall !! 399 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support 400 support
449 401
450 arm64.nopauth [ARM64] Unconditionall !! 402 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
451 support 403 support
452 404
453 arm64.nosme [ARM64] Unconditionall !! 405 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
454 Extension support 406 Extension support
455 407
456 arm64.nosve [ARM64] Unconditionall !! 408 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
457 Extension support 409 Extension support
458 410
459 ataflop= [HW,M68k] 411 ataflop= [HW,M68k]
460 412
461 atarimouse= [HW,MOUSE] Atari Mouse 413 atarimouse= [HW,MOUSE] Atari Mouse
462 414
463 atkbd.extra= [HW] Enable extra LEDs 415 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 416 EzKey and similar keyboards
465 417
466 atkbd.reset= [HW] Reset keyboard du 418 atkbd.reset= [HW] Reset keyboard during initialization
467 419
468 atkbd.set= [HW] Select keyboard c 420 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 421 Format: <int> (2 = AT (default), 3 = PS/2)
470 422
471 atkbd.scroll= [HW] Enable scroll whe 423 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 424 keyboards
473 425
474 atkbd.softraw= [HW] Choose between sy 426 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 427 Format: <bool> (0 = real, 1 = synthetic (default))
476 428
477 atkbd.softrepeat= [HW] 429 atkbd.softrepeat= [HW]
478 Use software keyboard 430 Use software keyboard repeat
479 431
480 audit= [KNL] Enable the audit 432 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 433 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 434 0 | off - kernel audit is disabled and can not be
483 enabled until the 435 enabled until the next reboot
484 unset - kernel audit i 436 unset - kernel audit is initialized but disabled and
485 will be fully enab 437 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 438 1 | on - kernel audit is initialized and partially
487 enabled, storing a 439 enabled, storing at most audit_backlog_limit
488 messages in RAM un 440 messages in RAM until it is fully enabled by the
489 userspace auditd. 441 userspace auditd.
490 Default: unset 442 Default: unset
491 443
492 audit_backlog_limit= [KNL] Set the aud 444 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 445 Format: <int> (must be >=0)
494 Default: 64 446 Default: 64
495 447
496 bau= [X86_UV] Enable the BA 448 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 449 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 450 Format: { "0" | "1" }
499 0 - Disable the BAU. 451 0 - Disable the BAU.
500 1 - Enable the BAU. 452 1 - Enable the BAU.
501 unset - Disable the BA 453 unset - Disable the BAU.
502 454
503 baycom_epp= [HW,AX25] 455 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 456 Format: <io>,<mode>
505 457
506 baycom_par= [HW,AX25] BayCom Paral 458 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 459 Format: <io>,<mode>
508 See header of drivers/ 460 See header of drivers/net/hamradio/baycom_par.c.
509 461
510 baycom_ser_fdx= [HW,AX25] 462 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 463 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 464 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 465 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 466
515 baycom_ser_hdx= [HW,AX25] 467 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 468 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 469 Format: <io>,<irq>,<mode>
518 See header of drivers/ 470 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 471
520 bert_disable [ACPI] 472 bert_disable [ACPI]
521 Disable BERT OS suppor 473 Disable BERT OS support on buggy BIOSes.
522 474
523 bgrt_disable [ACPI,X86,EARLY] !! 475 bgrt_disable [ACPI][X86]
524 Disable BGRT to avoid 476 Disable BGRT to avoid flickering OEM logo.
525 477
526 blkdevparts= Manual partition parsi 478 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 479 embedded devices based on command line input.
528 See Documentation/bloc 480 See Documentation/block/cmdline-partition.rst
529 481
530 boot_delay= [KNL,EARLY] !! 482 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 483 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 484 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 485 Format: integer
537 486
538 bootconfig [KNL,EARLY] !! 487 bootconfig [KNL]
539 Extended command line 488 Extended command line options can be added to an initrd
540 and this will cause th 489 and this will cause the kernel to look for it.
541 490
542 See Documentation/admi 491 See Documentation/admin-guide/bootconfig.rst
543 492
544 bttv.card= [HW,V4L] bttv (bt848 + 493 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 494 bttv.radio= Most important insmod options are available as
546 kernel args too. 495 kernel args too.
547 bttv.pll= See Documentation/admi 496 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 497 bttv.tuner=
549 498
550 bulk_remove=off [PPC] This parameter 499 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 500 firmware feature for flushing multiple hpte entries
552 at a time. 501 at a time.
553 502
554 c101= [NET] Moxa C101 synchr 503 c101= [NET] Moxa C101 synchronous serial card
555 504
556 cachesize= [BUGS=X86-32] Override 505 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 506 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 507 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 508 to fix known problems, but for some CPUs it is not
560 possible to determine 509 possible to determine what the correct size should be.
561 This option provides a 510 This option provides an override for these situations.
562 511
563 carrier_timeout= 512 carrier_timeout=
564 [NET] Specifies amount 513 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 514 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 515 it waits 120 seconds.
567 516
568 ca_keys= [KEYS] This parameter 517 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 518 the system trusted keyring to be used for certificate
570 trust validation. 519 trust validation.
571 format: { id:<keyid> | 520 format: { id:<keyid> | builtin }
572 521
573 cca= [MIPS,EARLY] Override !! 522 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 523 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 524 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 525 for platform specific values (SB1, Loongson3 and
577 others). 526 others).
578 527
579 ccw_timeout_log [S390] 528 ccw_timeout_log [S390]
580 See Documentation/arch !! 529 See Documentation/s390/common_io.rst for details.
581 530
582 cgroup_disable= [KNL] Disable a partic 531 cgroup_disable= [KNL] Disable a particular controller or optional feature
583 Format: {name of the c 532 Format: {name of the controller(s) or feature(s) to disable}
584 The effects of cgroup_ 533 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 534 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 535 a single hierarchy
587 - foo isn't visible as 536 - foo isn't visible as an individually mountable
588 subsystem 537 subsystem
589 - if foo is an optiona 538 - if foo is an optional feature then the feature is
590 disabled and corresp 539 disabled and corresponding cgroup files are not
591 created 540 created
592 {Currently only "memor 541 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 542 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 543 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" 544 Specifying "pressure" disables per-cgroup pressure
596 stall information acco 545 stall information accounting feature
597 546
598 cgroup_no_v1= [KNL] Disable cgroup c 547 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 548 Format: { { controller | "all" | "named" }
600 [,{ controll 549 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 550 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 551 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 552 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 553 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 554 all v1 hierarchies.
606 555
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 556 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 557 Format: <string>
613 nosocket -- Disable so 558 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 559 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 560
617 checkreqprot= [SELINUX] Set initial 561 checkreqprot= [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 562 Format: { "0" | "1" }
619 See security/selinux/K 563 See security/selinux/Kconfig help text.
620 0 -- check protection 564 0 -- check protection applied by kernel (includes
621 any implied ex 565 any implied execute protection).
622 1 -- check protection 566 1 -- check protection requested by application.
623 Default value is set v 567 Default value is set via a kernel config option.
624 Value can be changed a 568 Value can be changed at runtime via
625 /sys/fs/selinu 569 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 570 Setting checkreqprot to 1 is deprecated.
627 571
628 cio_ignore= [S390] 572 cio_ignore= [S390]
629 See Documentation/arch !! 573 See Documentation/s390/common_io.rst for details.
630 574
631 clearcpuid=X[,X...] [X86] 575 clearcpuid=X[,X...] [X86]
632 Disable CPUID feature 576 Disable CPUID feature X for the kernel. See
633 arch/x86/include/asm/c 577 arch/x86/include/asm/cpufeatures.h for the valid bit
634 numbers X. Note the Li 578 numbers X. Note the Linux-specific bits are not necessarily
635 stable over kernel opt 579 stable over kernel options, but the vendor-specific
636 ones should be. 580 ones should be.
637 X can also be a string 581 X can also be a string as appearing in the flags: line
638 in /proc/cpuinfo which 582 in /proc/cpuinfo which does not have the above
639 instability issue. How 583 instability issue. However, not all features have names
640 in /proc/cpuinfo. 584 in /proc/cpuinfo.
641 Note that using this o 585 Note that using this option will taint your kernel.
642 Also note that user pr 586 Also note that user programs calling CPUID directly
643 or using the feature w 587 or using the feature without checking anything
644 will still see it. Thi 588 will still see it. This just prevents it from
645 being used by the kern 589 being used by the kernel or shown in /proc/cpuinfo.
646 Also note the kernel m 590 Also note the kernel might malfunction if you disable
647 some critical bits. 591 some critical bits.
648 592
649 clk_ignore_unused 593 clk_ignore_unused
650 [CLK] 594 [CLK]
651 Prevents the clock fra 595 Prevents the clock framework from automatically gating
652 clocks that have not b 596 clocks that have not been explicitly enabled by a Linux
653 device driver but are 597 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 598 by the bootloader/firmware. Note that this does not
655 force such clocks to b 599 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 600 those clocks in any way. This parameter is useful for
657 debug and development, 601 debug and development, but should not be needed on a
658 platform with proper d 602 platform with proper driver support. For more
659 information, see Docum 603 information, see Documentation/driver-api/clk.rst.
660 604
661 clock= [BUGS=X86-32, HW] gett 605 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 606 [Deprecated]
663 Forces specified clock 607 Forces specified clocksource (if available) to be used
664 when calculating getti 608 when calculating gettimeofday(). If specified
665 clocksource is not ava 609 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 610 Format: { pit | tsc | cyclone | pmtmr }
667 611
668 clocksource= Override the default c 612 clocksource= Override the default clocksource
669 Format: <string> 613 Format: <string>
670 Override the default c 614 Override the default clocksource and use the clocksource
671 with the name specifie 615 with the name specified.
672 Some clocksource names 616 Some clocksource names to choose from, depending on
673 the platform: 617 the platform:
674 [all] jiffies (this is 618 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 619 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 620 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 621 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 622 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 623 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 624 [MIPS] MIPS
681 [PARISC] cr16 625 [PARISC] cr16
682 [S390] tod 626 [S390] tod
683 [SH] SuperH 627 [SH] SuperH
684 [SPARC64] tick 628 [SPARC64] tick
685 [X86-64] hpet,tsc 629 [X86-64] hpet,tsc
686 630
687 clocksource.arm_arch_timer.evtstrm= 631 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 632 [ARM,ARM64]
689 Format: <bool> 633 Format: <bool>
690 Enable/disable the eve 634 Enable/disable the eventstream feature of the ARM
691 architected timer so t 635 architected timer so that code using WFE-based polling
692 loops can be debugged 636 loops can be debugged more effectively on production
693 systems. 637 systems.
694 638
>> 639 clocksource.max_cswd_read_retries= [KNL]
>> 640 Number of clocksource_watchdog() retries due to
>> 641 external delays before the clock will be marked
>> 642 unstable. Defaults to two retries, that is,
>> 643 three attempts to read the clock under test.
>> 644
695 clocksource.verify_n_cpus= [KNL] 645 clocksource.verify_n_cpus= [KNL]
696 Limit the number of CP 646 Limit the number of CPUs checked for clocksources
697 marked with CLOCK_SOUR 647 marked with CLOCK_SOURCE_VERIFY_PERCPU that
698 are marked unstable du 648 are marked unstable due to excessive skew.
699 A negative value says 649 A negative value says to check all CPUs, while
700 zero says not to check 650 zero says not to check any. Values larger than
701 nr_cpu_ids are silentl 651 nr_cpu_ids are silently truncated to nr_cpu_ids.
702 The actual CPUs are ch 652 The actual CPUs are chosen randomly, with
703 no replacement if the 653 no replacement if the same CPU is chosen twice.
704 654
705 clocksource-wdtest.holdoff= [KNL] 655 clocksource-wdtest.holdoff= [KNL]
706 Set the time in second 656 Set the time in seconds that the clocksource
707 watchdog test waits be 657 watchdog test waits before commencing its tests.
708 Defaults to zero when 658 Defaults to zero when built as a module and to
709 10 seconds when built 659 10 seconds when built into the kernel.
710 660
711 cma=nn[MG]@[start[MG][-end[MG]]] 661 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 662 [KNL,CMA]
713 Sets the size of kerne 663 Sets the size of kernel global memory area for
714 contiguous memory allo 664 contiguous memory allocations and optionally the
715 placement constraint b 665 placement constraint by the physical address range of
716 memory allocations. A 666 memory allocations. A value of 0 disables CMA
717 altogether. For more i 667 altogether. For more information, see
718 kernel/dma/contiguous. 668 kernel/dma/contiguous.c
719 669
720 cma_pernuma=nn[MG] 670 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 671 [ARM64,KNL,CMA]
722 Sets the size of kerne 672 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 673 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 674 per-numa CMA altogether. And If this option is not
725 specified, the default !! 675 specificed, the default value is 0.
726 With per-numa CMA enab 676 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 677 first try to allocate buffer from the pernuma area
728 which is located in no 678 which is located in node nid, if the allocation fails,
729 they will fallback to 679 they will fallback to the global default memory area.
730 680
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 | 681 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 682 Specify whether pages are marked as being inactive
744 when they are freed. 683 when they are freed. This is used in CMO environments
745 to determine OS memory 684 to determine OS memory pressure for page stealing by
746 a hypervisor. 685 a hypervisor.
747 Default: yes 686 Default: yes
748 687
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 688 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 689 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 690 allocations, by default set to 256K.
752 691
753 com20020= [HW,NET] ARCnet - COM2 692 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 693 Format:
755 <io>[,<irq>[,<nodeID>[ 694 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 695
757 com90io= [HW,NET] ARCnet - COM9 696 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 697 Format: <io>[,<irq>]
759 698
760 com90xx= [HW,NET] 699 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 700 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 701 Format: <io>[,<irq>[,<memstart>]]
763 702
764 condev= [HW,S390] console devi 703 condev= [HW,S390] console device
765 conmode= 704 conmode=
766 705
767 con3215_drop= [S390,EARLY] 3215 cons !! 706 con3215_drop= [S390] 3215 console drop mode.
768 Format: y|n|Y|N|1|0 707 Format: y|n|Y|N|1|0
769 When set to true, drop 708 When set to true, drop data on the 3215 console when
770 the console buffer is 709 the console buffer is full. In this case the
771 operator using a 3270 710 operator using a 3270 terminal emulator (for example
772 x3270) does not have t 711 x3270) does not have to enter the clear key for the
773 console output to adva 712 console output to advance and the kernel to continue.
774 This leads to a much f 713 This leads to a much faster boot time when a 3270
775 terminal emulator is a 714 terminal emulator is active. If no 3270 terminal
776 emulator is used, this 715 emulator is used, this parameter has no effect.
777 716
778 console= [KNL] Output console d 717 console= [KNL] Output console device and options.
779 718
780 tty<n> Use the virtual consol 719 tty<n> Use the virtual console device <n>.
781 720
782 ttyS<n>[,options] 721 ttyS<n>[,options]
783 ttyUSB0[,options] 722 ttyUSB0[,options]
784 Use the specified seri 723 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 724 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 725 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 726 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 727 omit it). Default is "9600n8".
789 728
790 See Documentation/admi 729 See Documentation/admin-guide/serial-console.rst for more
791 information. See 730 information. See
792 Documentation/networki 731 Documentation/networking/netconsole.rst for an
793 alternative. 732 alternative.
794 733
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] 734 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 735 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 736 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 737 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 738 uart[8250],0x<addr>[,options]
819 Start an early, polled 739 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 740 UART at the specified I/O port or MMIO address,
821 switching to the match 741 switching to the matching ttyS device later.
822 MMIO inter-register ad 742 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 743 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 744 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 745 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 746 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 747 the h/w is not re-initialized.
828 748
829 hvc<n> Use the hypervisor con 749 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 750 both Xen and PowerPC hypervisors.
831 751
832 { null | "" } 752 { null | "" }
833 Use to disable console 753 Use to disable console output, i.e., to have kernel
834 console messages disca 754 console messages discarded.
835 This must be the only 755 This must be the only console= parameter used on the
836 kernel command line. 756 kernel command line.
837 757
838 If the device connected to the 758 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 759 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 760 console=brl,ttyS0
841 For now, only VisioBraille is 761 For now, only VisioBraille is supported.
842 762
843 console_msg_format= 763 console_msg_format=
844 [KNL] Change console m 764 [KNL] Change console messages format
845 default 765 default
846 By default we print me 766 By default we print messages on consoles in
847 "[time stamp] text\n" 767 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 768 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 769 `printk_time' param).
850 syslog 770 syslog
851 Switch to syslog forma 771 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 772 IOW, each message will have a facility and loglevel
853 prefix. The format is 773 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 774 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 775 from /proc/kmsg.
856 776
857 consoleblank= [KNL] The console blan 777 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 778 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 779 Defaults to 0.
860 780
861 coredump_filter= 781 coredump_filter=
862 [KNL] Change the defau 782 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 783 /proc/<pid>/coredump_filter.
864 See also Documentation 784 See also Documentation/filesystems/proc.rst.
865 785
866 coresight_cpu_debug.enable 786 coresight_cpu_debug.enable
867 [ARM,ARM64] 787 [ARM,ARM64]
868 Format: <bool> 788 Format: <bool>
869 Enable/disable the CPU 789 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 790 0: default value, disable debugging
871 1: enable debugging at 791 1: enable debugging at boot time
872 792
873 cpcihp_generic= [HW,PCI] Generic port 793 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
874 Format: 794 Format:
875 <first_slot>,<last_slo 795 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
876 796
>> 797 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
>> 798 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
>> 799 Some features depend on CPU0. Known dependencies are:
>> 800 1. Resume from suspend/hibernate depends on CPU0.
>> 801 Suspend/hibernate will fail if CPU0 is offline and you
>> 802 need to online CPU0 before suspend/hibernate.
>> 803 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 804 removed if a PIC interrupt is detected.
>> 805 It's said poweroff/reboot may depend on CPU0 on some
>> 806 machines although I haven't seen such issues so far
>> 807 after CPU0 is offline on a few tested machines.
>> 808 If the dependencies are under your control, you can
>> 809 turn on cpu0_hotplug.
>> 810
877 cpuidle.off=1 [CPU_IDLE] 811 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 812 disable the cpuidle sub-system
879 813
880 cpuidle.governor= 814 cpuidle.governor=
881 [CPU_IDLE] Name of the 815 [CPU_IDLE] Name of the cpuidle governor to use.
882 816
883 cpufreq.off=1 [CPU_FREQ] 817 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 818 disable the cpufreq sub-system
885 819
886 cpufreq.default_governor= 820 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 821 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 822 policy to use. This governor must be registered in the
889 kernel before the cpuf 823 kernel before the cpufreq driver probes.
890 824
891 cpu_init_udelay=N 825 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 826 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 827 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 828 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 829 Default: 10000
896 830
897 cpuhp.parallel= <<
898 [SMP] Enable/disable p <<
899 Format: <bool> <<
900 Default is enabled if <<
901 the parameter has no e <<
902 <<
903 crash_kexec_post_notifiers 831 crash_kexec_post_notifiers
904 Run kdump after runnin 832 Run kdump after running panic-notifiers and dumping
905 kmsg. This only for th 833 kmsg. This only for the users who doubt kdump always
906 succeeds in any situat 834 succeeds in any situation.
907 Note that this also in 835 Note that this also increases risks of kdump failure,
908 because some panic not 836 because some panic notifiers can make the crashed
909 kernel more unstable. 837 kernel more unstable.
910 838
911 crashkernel=size[KMG][@offset[KMG]] 839 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 840 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 841 upon panic. This parameter reserves the physical
914 memory region [offset, 842 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 843 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 844 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 845 [KNL, X86-64, ARM64] Select a region under 4G first, and
918 under 4G first, and fa !! 846 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 847 hasn't been specified.
920 See Documentation/admi 848 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 849
922 crashkernel=range1:size1[,range2:size2 850 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 851 [KNL] Same as above, but depends on the memory
924 in the running system. 852 in the running system. The syntax of range is
925 start-[end] where star 853 start-[end] where start and end are both
926 a memory unit (amount[ 854 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 855 Documentation/admin-guide/kdump/kdump.rst for an example.
928 856
929 crashkernel=size[KMG],high 857 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 858 [KNL, X86-64, ARM64] range could be above 4G. Allow kernel
931 above 4G. !! 859 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 860 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 861 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 862 available.
935 below 4G, if available <<
936 It will be ignored if 863 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 864 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 865 [KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 866 is passed, kernel could allocate physical memory region
940 physical memory region !! 867 above 4G, that cause second kernel crash on system
941 crash on system that r !! 868 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 869 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 870 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 871 devices won't run out. Kernel would try to allocate
945 default size of memory 872 default size of memory below 4G automatically. The default
946 size is platform depen 873 size is platform dependent.
947 --> x86: max(swiotlb 874 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
948 --> arm64: 128MiB 875 --> arm64: 128MiB
949 --> riscv: 128MiB <<
950 --> loongarch: 128Mi <<
951 This one lets the user 876 This one lets the user specify own low range under 4G
952 for second kernel inst 877 for second kernel instead.
953 0: to disable low allo 878 0: to disable low allocation.
954 It will be ignored whe 879 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 880 or memory reserved is below 4G.
956 881
957 cryptomgr.notests 882 cryptomgr.notests
958 [KNL] Disable crypto s 883 [KNL] Disable crypto self-tests
959 884
960 cs89x0_dma= [HW,NET] 885 cs89x0_dma= [HW,NET]
961 Format: <dma> 886 Format: <dma>
962 887
963 cs89x0_media= [HW,NET] 888 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 889 Format: { rj45 | aui | bnc }
965 890
966 csdlock_debug= [KNL] Enable or disabl !! 891 csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
967 function call handling !! 892 handling. When switched on, additional debug data is
968 additional debug data !! 893 printed to the console in case a hanging CPU is
969 in case a hanging CPU !! 894 detected, and that CPU is pinged again in order to try
970 CPU is pinged again in !! 895 to resolve the hang situation.
971 the hang situation. T !! 896 0: disable csdlock debugging (default)
972 option depends on the !! 897 1: enable basic csdlock debugging (minor impact)
973 Kconfig option. !! 898 ext: enable extended csdlock debugging (more impact,
>> 899 but more data)
974 900
975 dasd= [HW,NET] 901 dasd= [HW,NET]
976 See header of drivers/ 902 See header of drivers/s390/block/dasd_devmap.c.
977 903
978 db9.dev[2|3]= [HW,JOY] Multisystem j 904 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 905 (one device per port)
980 Format: <port#>,<type> 906 Format: <port#>,<type>
981 See also Documentation 907 See also Documentation/input/devices/joystick-parport.rst
982 908
983 debug [KNL,EARLY] Enable ker !! 909 debug [KNL] Enable kernel debugging (events log level).
984 910
985 debug_boot_weak_hash 911 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 912 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 913 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 914 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 915 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 916 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 917 insecure, please do not use on production kernels.
992 918
993 debug_locks_verbose= 919 debug_locks_verbose=
994 [KNL] verbose locking 920 [KNL] verbose locking self-tests
995 Format: <int> 921 Format: <int>
996 Print debugging info w 922 Print debugging info while doing the locking API
997 self-tests. 923 self-tests.
998 Bitmask for the variou 924 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 925 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 926 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 927 useful to lockdep developers.
1002 928
1003 debug_objects [KNL,EARLY] Enable ob !! 929 debug_objects [KNL] Enable object debugging
>> 930
>> 931 no_debug_objects
>> 932 [KNL] Disable object debugging
1004 933
1005 debug_guardpage_minorder= 934 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 935 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 936 parameter allows control of the order of pages that will
1008 be intentionally kept 937 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 938 buddy allocator. Bigger value increase the probability
1010 of catching random me 939 of catching random memory corruption, but reduce the
1011 amount of memory for 940 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 941 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 942 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 943 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 944 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 945 random memory location. Note that there exists a class
1017 a class of memory cor !! 946 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 947 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 948 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 949 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 950 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 951 tracking down these problems.
1023 952
1024 debug_pagealloc= 953 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 954 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 955 enables the feature at boot time. By default, it is
1027 disabled and the syst 956 disabled and the system will work mostly the same as a
1028 kernel built without 957 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 958 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 959 useful to also enable the page_owner functionality.
1031 on: enable the featur 960 on: enable the feature
1032 961
1033 debugfs= [KNL,EARLY] This para !! 962 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 963 and debugfs internal clients.
1035 Format: { on, no-moun 964 Format: { on, no-mount, off }
1036 on: All functions 965 on: All functions are enabled.
1037 no-mount: 966 no-mount:
1038 Filesystem is 967 Filesystem is not registered but kernel clients can
1039 access APIs a 968 access APIs and a crashkernel can be used to read
1040 its content. 969 its content. There is nothing to mount.
1041 off: Filesystem is 970 off: Filesystem is not registered and clients
1042 get a -EPERM 971 get a -EPERM as result when trying to register files
1043 or directorie 972 or directories within debugfs.
1044 This is equiv 973 This is equivalent of the runtime functionality if
1045 debugfs was n 974 debugfs was not enabled in the kernel at all.
1046 Default value is set 975 Default value is set in build-time with a kernel configuration.
1047 976
1048 debugpat [X86] Enable PAT debu 977 debugpat [X86] Enable PAT debugging
1049 978
1050 default_hugepagesz= 979 default_hugepagesz=
1051 [HW] The size of the 980 [HW] The size of the default HugeTLB page. This is
1052 the size represented 981 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 982 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 983 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 984 filesystems. If not specified, defaults to the
1056 architecture's defaul 985 architecture's default huge page size. Huge page
1057 sizes are architectur 986 sizes are architecture dependent. See also
1058 Documentation/admin-g 987 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 988 Format: size[KMG]
1060 989
1061 deferred_probe_timeout= 990 deferred_probe_timeout=
1062 [KNL] Debugging optio 991 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 992 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 993 probe. Only specific dependencies (subsystems or
1065 drivers) that have op 994 drivers) that have opted in will be ignored. A timeout
1066 of 0 will timeout at 995 of 0 will timeout at the end of initcalls. If the time
1067 out hasn't expired, i 996 out hasn't expired, it'll be restarted by each
1068 successful driver reg 997 successful driver registration. This option will also
1069 dump out devices stil 998 dump out devices still on the deferred probe list after
1070 retrying. 999 retrying.
1071 1000
1072 delayacct [KNL] Enable per-task 1001 delayacct [KNL] Enable per-task delay accounting
1073 1002
1074 dell_smm_hwmon.ignore_dmi= 1003 dell_smm_hwmon.ignore_dmi=
1075 [HW] Continue probing 1004 [HW] Continue probing hardware even if DMI data
1076 indicates that the dr 1005 indicates that the driver is running on unsupported
1077 hardware. 1006 hardware.
1078 1007
1079 dell_smm_hwmon.force= 1008 dell_smm_hwmon.force=
1080 [HW] Activate driver 1009 [HW] Activate driver even if SMM BIOS signature does
1081 not match list of sup 1010 not match list of supported models and enable otherwise
1082 blacklisted features. 1011 blacklisted features.
1083 1012
1084 dell_smm_hwmon.power_status= 1013 dell_smm_hwmon.power_status=
1085 [HW] Report power sta 1014 [HW] Report power status in /proc/i8k
1086 (disabled by default) 1015 (disabled by default).
1087 1016
1088 dell_smm_hwmon.restricted= 1017 dell_smm_hwmon.restricted=
1089 [HW] Allow controllin 1018 [HW] Allow controlling fans only if SYS_ADMIN
1090 capability is set. 1019 capability is set.
1091 1020
1092 dell_smm_hwmon.fan_mult= 1021 dell_smm_hwmon.fan_mult=
1093 [HW] Factor to multip 1022 [HW] Factor to multiply fan speed with.
1094 1023
1095 dell_smm_hwmon.fan_max= 1024 dell_smm_hwmon.fan_max=
1096 [HW] Maximum configur 1025 [HW] Maximum configurable fan speed.
1097 1026
1098 dfltcc= [HW,S390] 1027 dfltcc= [HW,S390]
1099 Format: { on | off | 1028 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 1029 on: s390 zlib hardware support for compression on
1101 level 1 and 1030 level 1 and decompression (default)
1102 off: No s390 zli 1031 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 1032 def_only: s390 zlib hardware support for deflate
1104 only (compr 1033 only (compression on level 1)
1105 inf_only: s390 zlib h 1034 inf_only: s390 zlib hardware support for inflate
1106 only (decom 1035 only (decompression)
1107 always: Same as 'on 1036 always: Same as 'on' but ignores the selected compression
1108 level alway 1037 level always using hardware support (used for debugging)
1109 1038
1110 dhash_entries= [KNL] 1039 dhash_entries= [KNL]
1111 Set number of hash bu 1040 Set number of hash buckets for dentry cache.
1112 1041
1113 disable_1tb_segments [PPC,EARLY] !! 1042 disable_1tb_segments [PPC]
1114 Disables the use of 1 1043 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 1044 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 1045 can be useful when debugging issues that require an SLB
1117 miss to occur. 1046 miss to occur.
1118 1047
>> 1048 stress_slb [PPC]
>> 1049 Limits the number of kernel SLB entries, and flushes
>> 1050 them frequently to increase the rate of SLB faults
>> 1051 on kernel addresses.
>> 1052
>> 1053 stress_hpt [PPC]
>> 1054 Limits the number of kernel HPT entries in the hash
>> 1055 page table to increase the rate of hash page table
>> 1056 faults on kernel addresses.
>> 1057
1119 disable= [IPV6] 1058 disable= [IPV6]
1120 See Documentation/net 1059 See Documentation/networking/ipv6.rst.
1121 1060
1122 disable_radix [PPC,EARLY] !! 1061 disable_radix [PPC]
1123 Disable RADIX MMU mod 1062 Disable RADIX MMU mode on POWER9
1124 1063
>> 1064 radix_hcall_invalidate=on [PPC/PSERIES]
>> 1065 Disable RADIX GTSE feature and use hcall for TLB
>> 1066 invalidate.
>> 1067
1125 disable_tlbie [PPC] 1068 disable_tlbie [PPC]
1126 Disable TLBIE instruc 1069 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 1070 with KVM, with HASH MMU, or with coherent accelerators.
1128 1071
1129 disable_ddw [PPC/PSERIES,EARLY] !! 1072 disable_cpu_apicid= [X86,APIC,SMP]
>> 1073 Format: <int>
>> 1074 The number of initial APIC ID for the
>> 1075 corresponding CPU to be disabled at boot,
>> 1076 mostly used for the kdump 2nd kernel to
>> 1077 disable BSP to wake up multiple CPUs without
>> 1078 causing system reset or hang due to sending
>> 1079 INIT from AP to BSP.
>> 1080
>> 1081 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 1082 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 1083 to workaround buggy firmware.
1132 1084
1133 disable_ipv6= [IPV6] 1085 disable_ipv6= [IPV6]
1134 See Documentation/net 1086 See Documentation/networking/ipv6.rst.
1135 1087
1136 disable_mtrr_cleanup [X86,EARLY] !! 1088 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 1089 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 1090 to discrete, to make X server driver able to add WB
1139 entry later. This par 1091 entry later. This parameter disables that.
1140 1092
1141 disable_mtrr_trim [X86, Intel and AMD !! 1093 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 1094 By default the kernel will trim any uncacheable
1143 memory out of your av 1095 memory out of your available memory pool based on
1144 MTRR settings. This 1096 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 1097 possibly causing your machine to run very slowly.
1146 1098
1147 disable_timer_pin_1 [X86,EARLY] !! 1099 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 1100 Disable PIN 1 of APIC timer
1149 Can be useful to work 1101 Can be useful to work around chipset bugs.
1150 1102
1151 dis_ucode_ldr [X86] Disable the mic 1103 dis_ucode_ldr [X86] Disable the microcode loader.
1152 1104
1153 dma_debug=off If the kernel is comp 1105 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 1106 this option disables the debugging code at boot.
1155 1107
1156 dma_debug_entries=<number> 1108 dma_debug_entries=<number>
1157 This option allows to 1109 This option allows to tune the number of preallocated
1158 entries for DMA-API d 1110 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 1111 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 1112 DMA-API debugging code disables itself because the
1161 architectural default 1113 architectural default is too low.
1162 1114
1163 dma_debug_driver=<driver_name> 1115 dma_debug_driver=<driver_name>
1164 With this option the 1116 With this option the DMA-API debugging driver
1165 filter feature can be 1117 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1118 pass the driver to filter for as the parameter.
1167 The filter can be dis 1119 The filter can be disabled or changed to another
1168 driver later using sy 1120 driver later using sysfs.
1169 1121
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] 1122 driver_async_probe= [KNL]
1191 List of driver names 1123 List of driver names to be probed asynchronously. *
1192 matches with all driv 1124 matches with all driver names. If * is specified, the
1193 rest of the listed dr 1125 rest of the listed driver names are those that will NOT
1194 match the *. 1126 match the *.
1195 Format: <driver_name1 1127 Format: <driver_name1>,<driver_name2>...
1196 1128
1197 drm.edid_firmware=[<connector>:]<file 1129 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1130 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1131 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1132 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1133 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1134 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1135 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1136 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1137 and no file with the same name exists. Details and
>> 1138 instructions how to build your own EDID data are
>> 1139 available in Documentation/admin-guide/edid.rst. An EDID
>> 1140 data set will only be used for a particular connector,
>> 1141 if its name and a colon are prepended to the EDID
>> 1142 name. Each connector may use a unique EDID data
>> 1143 set by separating the files with a comma. An EDID
1206 data set with no conn 1144 data set with no connector name will be used for
1207 any connectors not ex 1145 any connectors not explicitly specified.
1208 1146
1209 dscc4.setup= [NET] 1147 dscc4.setup= [NET]
1210 1148
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1149 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1150 Format: {"off" | "known"}
1213 Control how the dt_cp 1151 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1152 used for CPU feature discovery and setup (if it
1215 exists). 1153 exists).
1216 off: Do not use it, f 1154 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1155 known: Do not pass through unknown features to guests
1218 or userspace, only th 1156 or userspace, only those that the kernel is aware of.
1219 1157
1220 dump_apple_properties [X86] 1158 dump_apple_properties [X86]
1221 Dump name and content 1159 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1160 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1161 what data is available or for reverse-engineering.
1224 1162
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1163 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1164 <module>.dyndbg[="val"]
1227 Enable debug messages 1165 Enable debug messages at boot time. See
1228 Documentation/admin-g 1166 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1167 for details.
1230 1168
1231 early_ioremap_debug [KNL,EARLY] !! 1169 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 1170 in some Intel CPUs.
>> 1171
>> 1172 <module>.async_probe[=<bool>] [KNL]
>> 1173 If no <bool> value is specified or if the value
>> 1174 specified is not a valid <bool>, enable asynchronous
>> 1175 probe on this module. Otherwise, enable/disable
>> 1176 asynchronous probe on this module as indicated by the
>> 1177 <bool> value. See also: module.async_probe
>> 1178
>> 1179 early_ioremap_debug [KNL]
1232 Enable debug messages 1180 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1181 is useful for tracking down temporary early mappings
1234 which are not unmappe 1182 which are not unmapped.
1235 1183
1236 earlycon= [KNL,EARLY] Output ea !! 1184 earlycon= [KNL] Output early console device and options.
1237 1185
1238 When used with no opt 1186 When used with no options, the early console is
1239 determined by stdout- 1187 determined by stdout-path property in device tree's
1240 chosen node or the AC 1188 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1189 the platform.
1242 1190
1243 cdns,<addr>[,options] 1191 cdns,<addr>[,options]
1244 Start an early, polle 1192 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1193 (xuartps) serial port at the specified address. Only
1246 supported option is b 1194 supported option is baud rate. If baud rate is not
1247 specified, the serial 1195 specified, the serial port must already be setup and
1248 configured. 1196 configured.
1249 1197
1250 uart[8250],io,<addr>[,options !! 1198 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 1199 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 1200 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 1201 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1202 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1203 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1204 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1205 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1206 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1207 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1208 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1209 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1210 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1211
1266 pl011,<addr> 1212 pl011,<addr>
1267 pl011,mmio32,<addr> 1213 pl011,mmio32,<addr>
1268 Start an early, polle 1214 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1215 port at the specified address. The pl011 serial port
1270 must already be setup 1216 must already be setup and configured. Options are not
1271 yet supported. If 'm 1217 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1218 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1219 the device registers.
1274 1220
1275 liteuart,<addr> 1221 liteuart,<addr>
1276 Start an early consol 1222 Start an early console on a litex serial port at the
1277 specified address. Th 1223 specified address. The serial port must already be
1278 setup and configured. 1224 setup and configured. Options are not yet supported.
1279 1225
1280 meson,<addr> 1226 meson,<addr>
1281 Start an early, polle 1227 Start an early, polled-mode console on a meson serial
1282 port at the specified 1228 port at the specified address. The serial port must
1283 already be setup and 1229 already be setup and configured. Options are not yet
1284 supported. 1230 supported.
1285 1231
1286 msm_serial,<addr> 1232 msm_serial,<addr>
1287 Start an early, polle 1233 Start an early, polled-mode console on an msm serial
1288 port at the specified 1234 port at the specified address. The serial port
1289 must already be setup 1235 must already be setup and configured. Options are not
1290 yet supported. 1236 yet supported.
1291 1237
1292 msm_serial_dm,<addr> 1238 msm_serial_dm,<addr>
1293 Start an early, polle 1239 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1240 dm port at the specified address. The serial port
1295 must already be setup 1241 must already be setup and configured. Options are not
1296 yet supported. 1242 yet supported.
1297 1243
1298 owl,<addr> 1244 owl,<addr>
1299 Start an early, polle 1245 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1246 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1247 specified address. The serial port must already be
1302 setup and configured. 1248 setup and configured. Options are not yet supported.
1303 1249
1304 rda,<addr> 1250 rda,<addr>
1305 Start an early, polle 1251 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1252 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1253 specified address. The serial port must already be
1308 setup and configured. 1254 setup and configured. Options are not yet supported.
1309 1255
1310 sbi 1256 sbi
1311 Use RISC-V SBI (Super 1257 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1258 console.
1313 1259
1314 smh Use ARM semihosting c 1260 smh Use ARM semihosting calls for early console.
1315 1261
1316 s3c2410,<addr> 1262 s3c2410,<addr>
1317 s3c2412,<addr> 1263 s3c2412,<addr>
1318 s3c2440,<addr> 1264 s3c2440,<addr>
1319 s3c6400,<addr> 1265 s3c6400,<addr>
1320 s5pv210,<addr> 1266 s5pv210,<addr>
1321 exynos4210,<addr> 1267 exynos4210,<addr>
1322 Use early console pro 1268 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1269 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1270 a correct base address of the selected UART port. The
1325 serial port must alre 1271 serial port must already be setup and configured.
1326 Options are not yet s 1272 Options are not yet supported.
1327 1273
1328 lantiq,<addr> 1274 lantiq,<addr>
1329 Start an early, polle 1275 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1276 (lqasc) port at the specified address. The serial port
1331 must already be setup 1277 must already be setup and configured. Options are not
1332 yet supported. 1278 yet supported.
1333 1279
1334 lpuart,<addr> 1280 lpuart,<addr>
1335 lpuart32,<addr> 1281 lpuart32,<addr>
1336 Use early console pro 1282 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1283 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1284 A valid base address must be provided, and the serial
1339 port must already be 1285 port must already be setup and configured.
1340 1286
1341 ec_imx21,<addr> 1287 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1288 ec_imx6q,<addr>
1343 Start an early, polle 1289 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1290 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1291 must already be setup and configured.
1346 1292
1347 ar3700_uart,<addr> 1293 ar3700_uart,<addr>
1348 Start an early, polle 1294 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1295 Armada 3700 serial port at the specified
1350 address. The serial p 1296 address. The serial port must already be setup
1351 and configured. Optio 1297 and configured. Options are not yet supported.
1352 1298
1353 qcom_geni,<addr> 1299 qcom_geni,<addr>
1354 Start an early, polle 1300 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1301 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1302 specified address. The serial port must already be
1357 setup and configured. 1303 setup and configured. Options are not yet supported.
1358 1304
1359 efifb,[options] 1305 efifb,[options]
1360 Start an early, unacc 1306 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1307 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1308 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1309 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1310 mapped with the correct attributes.
1365 1311
1366 linflex,<addr> 1312 linflex,<addr>
1367 Use early console pro 1313 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1314 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1315 address must be provided, and the serial port must
1370 already be setup and 1316 already be setup and configured.
1371 1317
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1318 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1319 earlyprintk=vga
1374 earlyprintk=sclp 1320 earlyprintk=sclp
1375 earlyprintk=xen 1321 earlyprintk=xen
1376 earlyprintk=serial[,t 1322 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1323 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1324 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1325 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1326 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1327 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1328
1384 earlyprintk is useful 1329 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1330 the normal console is initialized. It is not enabled by
1386 default because it ha 1331 default because it has some cosmetic problems.
1387 1332
1388 Append ",keep" to not 1333 Append ",keep" to not disable it when the real console
1389 takes over. 1334 takes over.
1390 1335
1391 Only one of vga, seri 1336 Only one of vga, serial, or usb debug port can
1392 be used at a time. 1337 be used at a time.
1393 1338
1394 Currently only ttyS0 1339 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1340 name. Other I/O ports may be explicitly specified
1396 on some architectures 1341 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1342 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1343 earlyprintk=serial,0x1008,115200
1399 You can find the port 1344 You can find the port for a given device in
1400 /proc/tty/driver/seri 1345 /proc/tty/driver/serial:
1401 2: uart:ST166 1346 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1347
1403 Interaction with the 1348 Interaction with the standard serial driver is not
1404 very good. 1349 very good.
1405 1350
1406 The VGA output is eve 1351 The VGA output is eventually overwritten by
1407 the real console. 1352 the real console.
1408 1353
1409 The xen option can on 1354 The xen option can only be used in Xen domains.
1410 1355
1411 The sclp output can o 1356 The sclp output can only be used on s390.
1412 1357
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1358 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1359 PCI device even when its classcode is not of the
1417 UART class. 1360 UART class.
1418 1361
1419 edac_report= [HW,EDAC] Control how 1362 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1363 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1364 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1365 by other higher priority error reporting module.
1423 off: disable H/W even 1366 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1367 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1368 default: on.
1426 1369
1427 edd= [EDD] 1370 edd= [EDD]
1428 Format: {"off" | "on" 1371 Format: {"off" | "on" | "skip[mbr]"}
1429 1372
1430 efi= [EFI,EARLY] !! 1373 efi= [EFI]
1431 Format: { "debug", "d 1374 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1375 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1376 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1377 debug: enable misc debug output.
1435 disable_early_pci_dma 1378 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1379 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1380 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1381 boot stub, as chunking can cause problems with some
1439 firmware implementati 1382 firmware implementations.
1440 noruntime : disable E 1383 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1384 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1385 attribute may cause the kernel to reserve the
1443 memory range for a me 1386 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1387 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1388 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1389 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1390 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1391 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1392 on all PCI bridges while in the EFI boot stub
1450 1393
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1394 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1395 Using this parameter you can use more than 50% of
1453 your efi variable sto 1396 your efi variable storage. Use this parameter only if
1454 you are really sure t 1397 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1398 fulfills the spec otherwise your board may brick.
1456 1399
>> 1400 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1401 Add arbitrary attribute to specific memory range by
>> 1402 updating original EFI memory map.
>> 1403 Region of memory which aa attribute is added to is
>> 1404 from ss to ss+nn.
>> 1405
>> 1406 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1407 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1408 attribute is added to range 0x100000000-0x180000000 and
>> 1409 0x10a0000000-0x1120000000.
>> 1410
>> 1411 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1412 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1413 range 0x240000000-0x43fffffff.
>> 1414
>> 1415 Using this parameter you can do debugging of EFI memmap
>> 1416 related features. For example, you can do debugging of
>> 1417 Address Range Mirroring feature even if your box
>> 1418 doesn't support it, or mark specific memory as
>> 1419 "soft reserved".
>> 1420
1457 efivar_ssdt= [EFI; X86] Name of an 1421 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1422 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1423 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1424 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1425 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1426
1463 1427
1464 eisa_irq_edge= [PARISC,HW] 1428 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1429 See header of drivers/parisc/eisa.c.
1466 1430
1467 ekgdboc= [X86,KGDB,EARLY] Allo !! 1431 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1468 Format: ekgdboc=kbd 1432 Format: ekgdboc=kbd
1469 1433
1470 This is designed to b 1434 This is designed to be used in conjunction with
1471 the boot argument: ea 1435 the boot argument: earlyprintk=vga
1472 1436
1473 This parameter works 1437 This parameter works in place of the kgdboc parameter
1474 but can only be used 1438 but can only be used if the backing tty is available
1475 very early in the boo 1439 very early in the boot process. For early debugging
1476 via a serial port see 1440 via a serial port see kgdboc_earlycon instead.
1477 1441
1478 elanfreq= [X86-32] 1442 elanfreq= [X86-32]
1479 See comment before fu 1443 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1444 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1445
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1446 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1447 Specifies physical address of start of kernel core
1484 image elf header and 1448 image elf header and optionally the size. Generally
1485 kexec loader will pas 1449 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1450 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1451
1488 enable_mtrr_cleanup [X86,EARLY] !! 1452 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1453 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1454 to discrete, to make X server driver able to add WB
1491 entry later. This par 1455 entry later. This parameter enables that.
1492 1456
1493 enable_timer_pin_1 [X86] 1457 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1458 Enable PIN 1 of APIC timer
1495 Can be useful to work 1459 Can be useful to work around chipset bugs
1496 (in particular on som 1460 (in particular on some ATI chipsets).
1497 The kernel tries to s 1461 The kernel tries to set a reasonable default.
1498 1462
1499 enforcing= [SELINUX] Set initial 1463 enforcing= [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1464 Format: {"0" | "1"}
1501 See security/selinux/ 1465 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1466 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1467 1 -- enforcing (deny and log).
1504 Default value is 0. 1468 Default value is 0.
1505 Value can be changed 1469 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1470 /sys/fs/selinux/enforce.
1507 1471
1508 erst_disable [ACPI] 1472 erst_disable [ACPI]
1509 Disable Error Record 1473 Disable Error Record Serialization Table (ERST)
1510 support. 1474 support.
1511 1475
1512 ether= [HW,NET] Ethernet car 1476 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1477 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1478 has equivalent usage. See its documentation for details.
1515 1479
1516 evm= [EVM] 1480 evm= [EVM]
1517 Format: { "fix" } 1481 Format: { "fix" }
1518 Permit 'security.evm' 1482 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1483 current integrity status.
1520 1484
1521 early_page_ext [KNL,EARLY] Enforces p !! 1485 early_page_ext [KNL] Enforces page_ext initialization to earlier
1522 stages so cover more 1486 stages so cover more early boot allocations.
1523 Please note that as s 1487 Please note that as side effect some optimizations
1524 might be disabled to 1488 might be disabled to achieve that (e.g. parallelized
1525 memory initialization 1489 memory initialization is disabled) so the boot process
1526 might take longer, es 1490 might take longer, especially on systems with a lot of
1527 memory. Available wit 1491 memory. Available with CONFIG_PAGE_EXTENSION=y.
1528 1492
1529 failslab= 1493 failslab=
1530 fail_usercopy= 1494 fail_usercopy=
1531 fail_page_alloc= 1495 fail_page_alloc=
1532 fail_make_request=[KNL] 1496 fail_make_request=[KNL]
1533 General fault injecti 1497 General fault injection mechanism.
1534 Format: <interval>,<p 1498 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1499 See also Documentation/fault-injection/.
1536 1500
1537 fb_tunnels= [NET] 1501 fb_tunnels= [NET]
1538 Format: { initns | no 1502 Format: { initns | none }
1539 See Documentation/adm 1503 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1504 fb_tunnels_only_for_init_ns
1541 1505
1542 floppy= [HW] 1506 floppy= [HW]
1543 See Documentation/adm 1507 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1508
>> 1509 force_pal_cache_flush
>> 1510 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1511 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1512 parameter will force ia64_sal_cache_flush to call
>> 1513 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1514
1545 forcepae [X86-32] 1515 forcepae [X86-32]
1546 Forcefully enable Phy 1516 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1517 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1518 functionally usable PAE implementation.
1549 Warning: use of this 1519 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1520 and may cause unknown problems.
1551 1521
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] 1522 ftrace=[tracer]
1559 [FTRACE] will set and 1523 [FTRACE] will set and start the specified tracer
1560 as early as possible 1524 as early as possible in order to facilitate early
1561 boot debugging. 1525 boot debugging.
1562 1526
1563 ftrace_boot_snapshot 1527 ftrace_boot_snapshot
1564 [FTRACE] On boot up, 1528 [FTRACE] On boot up, a snapshot will be taken of the
1565 ftrace ring buffer th 1529 ftrace ring buffer that can be read at:
1566 /sys/kernel/tracing/s 1530 /sys/kernel/tracing/snapshot.
1567 This is useful if you 1531 This is useful if you need tracing information from kernel
1568 boot up that is likel 1532 boot up that is likely to be overridden by user space
1569 start up functionalit 1533 start up functionality.
1570 1534
1571 Optionally, the snaps !! 1535 ftrace_dump_on_oops[=orig_cpu]
1572 instance that was cre <<
1573 line parameter. <<
1574 <<
1575 trace_instance=foo,sc <<
1576 <<
1577 The above will cause <<
1578 a snapshot at the end <<
1579 <<
1580 ftrace_dump_on_oops[=2(orig_cpu) | =< <<
1581 ,<instance>=2(orig_ <<
1582 [FTRACE] will dump th 1536 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1537 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1538 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1539 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1540 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 1541
1603 ftrace_filter=[function-list] 1542 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1543 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1544 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1545 list of functions. This list can be changed at run
1607 time by the set_ftrac 1546 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1547 tracing directory.
1609 1548
1610 ftrace_notrace=[function-list] 1549 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1550 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1551 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1552 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1553 tracing directory.
1615 1554
1616 ftrace_graph_filter=[function-list] 1555 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1556 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1557 by the function graph tracer at boot up.
1619 function-list is a co 1558 function-list is a comma-separated list of functions
1620 that can be changed a 1559 that can be changed at run time by the
1621 set_graph_function fi 1560 set_graph_function file in the debugfs tracing directory.
1622 1561
1623 ftrace_graph_notrace=[function-list] 1562 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1563 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1564 function-list. This list is a comma-separated list of
1626 functions that can be 1565 functions that can be changed at run time by the
1627 set_graph_notrace fil 1566 set_graph_notrace file in the debugfs tracing directory.
1628 1567
1629 ftrace_graph_max_depth=<uint> 1568 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1569 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1570 the max depth it will trace into a function. This value
1632 can be changed at run 1571 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1572 in the tracefs tracing directory. default: 0 (no limit)
1634 1573
1635 fw_devlink= [KNL,EARLY] Create de !! 1574 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1575 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1576 consumer/supplier relationships. This feature is
1638 especially useful whe 1577 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1578 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1579 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1580 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1581 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1582 suppliers).
1644 Format: { off | permi 1583 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1584 off -- Don't create device links from firmware info.
1646 permissive -- Create 1585 permissive -- Create device links from firmware info
1647 but use it on 1586 but use it only for ordering boot state clean
1648 up (sync_stat 1587 up (sync_state() calls).
1649 on -- Create device 1588 on -- Create device links from firmware info and use it
1650 to enforce pr 1589 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1590 rpm -- Like "on", but also use to order runtime PM.
1652 1591
1653 fw_devlink.strict=<bool> 1592 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1593 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1594 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1595 Format: <bool>
1657 1596
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]= 1597 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1598 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1599 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1600 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1601 See also Documentation/input/devices/joystick-parport.rst
1677 1602
1678 gamma= [HW,DRM] 1603 gamma= [HW,DRM]
1679 1604
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1605 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1606 Format: off | on
1682 default: on 1607 default: on
1683 1608
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 1609 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1610 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1611 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1612 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1613 debugfs files are removed at module unload time.
1709 1614
1710 goldfish [X86] Enable the gold 1615 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1616 Don't use this when you are not running on the
1712 android emulator 1617 android emulator
1713 1618
1714 gpio-mockup.gpio_mockup_ranges 1619 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1620 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1621 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1622 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1623 [HW] Let the driver know GPIO lines should be named.
1719 1624
1720 gpt [EFI] Forces disk wit 1625 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1626 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1627 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1628 GPT to be used instead.
1724 1629
1725 grcan.enable0= [HW] Configuration of 1630 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1631 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1632 Format: 0 | 1
1728 Default: 0 1633 Default: 0
1729 grcan.enable1= [HW] Configuration of 1634 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1635 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1636 Format: 0 | 1
1732 Default: 0 1637 Default: 0
1733 grcan.select= [HW] Select which phy 1638 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1639 Format: 0 | 1
1735 Default: 0 1640 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1641 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1642 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1643 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1644 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1645 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1646 Default: 1024
1742 1647
1743 hardened_usercopy= 1648 hardened_usercopy=
1744 [KNL] Under CONFIG_HA 1649 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
1745 hardening is enabled 1650 hardening is enabled for this boot. Hardened
1746 usercopy checking is 1651 usercopy checking is used to protect the kernel
1747 from reading or writi 1652 from reading or writing beyond known memory
1748 allocation boundaries 1653 allocation boundaries as a proactive defense
1749 against bounds-checki 1654 against bounds-checking flaws in the kernel's
1750 copy_to_user()/copy_f 1655 copy_to_user()/copy_from_user() interface.
1751 on Perform hardened user 1656 on Perform hardened usercopy checks (default).
1752 off Disable hardened user 1657 off Disable hardened usercopy checks.
1753 1658
1754 hardlockup_all_cpu_backtrace= 1659 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1660 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1661 backtraces on all cpus.
1757 Format: 0 | 1 1662 Format: 0 | 1
1758 1663
1759 hashdist= [KNL,NUMA] Large hash 1664 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1665 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1666 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1667 Format: 0 | 1 (for off | on)
1763 1668
>> 1669 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1670
1764 hd= [EIDE] (E)IDE hard dr 1671 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1672 Format: <cyl>,<head>,<sect>
1766 1673
1767 hest_disable [ACPI] 1674 hest_disable [ACPI]
1768 Disable Hardware Erro 1675 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1676 corresponding firmware-first mode error processing
1770 logic will be disable 1677 logic will be disabled.
1771 1678
1772 hibernate= [HIBERNATION] 1679 hibernate= [HIBERNATION]
1773 noresume Don't check i 1680 noresume Don't check if there's a hibernation image
1774 present durin 1681 present during boot.
1775 nocompress Don't compres 1682 nocompress Don't compress/decompress hibernation images.
1776 no Disable hiber 1683 no Disable hibernation and resume.
1777 protect_image Turn on image 1684 protect_image Turn on image protection during restoration
1778 (that will se 1685 (that will set all pages holding image data
1779 during restor 1686 during restoration read-only).
1780 1687
1781 hibernate.compressor= [HIBERNATION] !! 1688 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1782 used with hib <<
1783 Format: { lzo <<
1784 Default: lzo <<
1785 <<
1786 lzo: Select L <<
1787 compress/deco <<
1788 <<
1789 lz4: Select L <<
1790 compress/deco <<
1791 <<
1792 highmem=nn[KMG] [KNL,BOOT,EARLY] forc <<
1793 size of <nn>. This wo 1689 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1690 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1691 size on bigger boxes.
1796 1692
1797 highres= [KNL] Enable/disable 1693 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1694 Valid parameters: "on", "off"
1799 Default: "on" 1695 Default: "on"
1800 1696
1801 hlt [BUGS=ARM,SH] 1697 hlt [BUGS=ARM,SH]
1802 1698
1803 hostname= [KNL,EARLY] Set the h !! 1699 hostname= [KNL] Set the hostname (aka UTS nodename).
1804 Format: <string> 1700 Format: <string>
1805 This allows setting t 1701 This allows setting the system's hostname during early
1806 startup. This sets th 1702 startup. This sets the name returned by gethostname.
1807 Using this parameter 1703 Using this parameter to set the hostname makes it
1808 possible to ensure th 1704 possible to ensure the hostname is correctly set before
1809 any userspace process 1705 any userspace processes run, avoiding the possibility
1810 that a process may ca 1706 that a process may call gethostname before the hostname
1811 has been explicitly s 1707 has been explicitly set, resulting in the calling
1812 process getting an in 1708 process getting an incorrect result. The string must
1813 not exceed the maximu 1709 not exceed the maximum allowed hostname length (usually
1814 64 characters) and wi 1710 64 characters) and will be truncated otherwise.
1815 1711
1816 hpet= [X86-32,HPET] option 1712 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1713 Format: { enable (default) | disable | force |
1818 verbose } 1714 verbose }
1819 disable: disable HPET 1715 disable: disable HPET and use PIT instead
1820 force: allow force en 1716 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1717 VIA, nVidia)
1822 verbose: show content 1718 verbose: show contents of HPET registers during setup
1823 1719
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1720 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1721 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1722
1827 hugepages= [HW] Number of HugeTL 1723 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1724 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1725 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1726 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1727 line, it specifies the number of pages to allocate for
1832 the default huge page 1728 the default huge page size. If using node format, the
1833 number of pages to al 1729 number of pages to allocate per-node can be specified.
1834 See also Documentatio 1730 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1835 Format: <integer> or 1731 Format: <integer> or (node format)
1836 <node>:<integ 1732 <node>:<integer>[,<node>:<integer>]
1837 1733
1838 hugepagesz= 1734 hugepagesz=
1839 [HW] The size of the 1735 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1736 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1737 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1738 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1739 each supported huge page size. Huge page sizes are
1844 architecture dependen 1740 architecture dependent. See also
1845 Documentation/admin-g 1741 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1742 Format: size[KMG]
1847 1743
1848 hugetlb_cma= [HW,CMA,EARLY] The si !! 1744 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
1849 of gigantic hugepages 1745 of gigantic hugepages. Or using node format, the size
1850 of a CMA area per nod 1746 of a CMA area per node can be specified.
1851 Format: nn[KMGTPE] or 1747 Format: nn[KMGTPE] or (node format)
1852 <node>:nn[KMG 1748 <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1853 1749
1854 Reserve a CMA area of 1750 Reserve a CMA area of given size and allocate gigantic
1855 hugepages using the C 1751 hugepages using the CMA allocator. If enabled, the
1856 boot-time allocation 1752 boot-time allocation of gigantic hugepages is skipped.
1857 1753
1858 hugetlb_free_vmemmap= 1754 hugetlb_free_vmemmap=
1859 [KNL] Requires CONFIG !! 1755 [KNL] Reguires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1860 enabled. 1756 enabled.
1861 Control if HugeTLB Vm 1757 Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1862 Allows heavy hugetlb 1758 Allows heavy hugetlb users to free up some more
1863 memory (7 * PAGE_SIZE 1759 memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1864 Format: { on | off (d 1760 Format: { on | off (default) }
1865 1761
1866 on: enable HVO 1762 on: enable HVO
1867 off: disable HVO 1763 off: disable HVO
1868 1764
1869 Built with CONFIG_HUG 1765 Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1870 the default is on. 1766 the default is on.
1871 1767
1872 Note that the vmemmap 1768 Note that the vmemmap pages may be allocated from the added
1873 memory block itself w 1769 memory block itself when memory_hotplug.memmap_on_memory is
1874 enabled, those vmemma 1770 enabled, those vmemmap pages cannot be optimized even if this
1875 feature is enabled. 1771 feature is enabled. Other vmemmap pages not allocated from
1876 the added memory bloc 1772 the added memory block itself do not be affected.
1877 1773
1878 hung_task_panic= 1774 hung_task_panic=
1879 [KNL] Should the hung 1775 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1776 Format: 0 | 1
1881 1777
1882 A value of 1 instruct 1778 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1779 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1780 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1781 option. The value selected by this boot parameter can
1886 be changed later by t 1782 be changed later by the kernel.hung_task_panic sysctl.
1887 1783
1888 hvc_iucv= [S390] Number of z/V 1784 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1785 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1786 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1787 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1788 from listed z/VM user IDs only.
1893 1789
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1790 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1791 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1792 guest on lock contention.
1897 on lock contention. !! 1793
>> 1794 keep_bootcon [KNL]
>> 1795 Do not unregister boot console at start. This is only
>> 1796 useful for debugging when something happens in the window
>> 1797 between unregistering the boot console and initializing
>> 1798 the real console.
1898 1799
1899 i2c_bus= [HW] Override the 1800 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1801 or register an additional I2C bus that is not
1901 registered fr 1802 registered from board initialization code.
1902 Format: 1803 Format:
1903 <bus_id>,<clk 1804 <bus_id>,<clkrate>
1904 1805
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 1806 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1807 i8042.unmask_kbd_data
1929 [HW] Enable printing 1808 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1809 (disabled by default, and as a pre-condition
1931 requires that i8 1810 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1811 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1812 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1813 keyboard and cannot control its state
1935 (Don't attempt t 1814 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1815 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1816 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1817 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1818 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1819 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1820 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1821 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1822 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1823 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1824 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1825 suspend-to-ram transitions, only during s2r
1947 transitions, or 1826 transitions, or never reset
1948 Format: { 1 | Y | y | 1827 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1828 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1829 0, N, n: don't ever reset controller
1951 Default: only on s2r 1830 Default: only on s2r transitions on x86; most other
1952 architectures force r 1831 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1832 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1833 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer 1834 i8042.probe_defer
1956 [HW] Allow deferred p 1835 [HW] Allow deferred probing upon i8042 probe errors
1957 1836
1958 i810= [HW,DRM] 1837 i810= [HW,DRM]
1959 1838
1960 i915.invert_brightness= 1839 i915.invert_brightness=
1961 [DRM] Invert the sens 1840 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1841 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1842 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1843 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1844 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1845 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1846 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1847 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1848 value switches the backlight off.
1970 -1 -- never invert br 1849 -1 -- never invert brightness
1971 0 -- machine default 1850 0 -- machine default
1972 1 -- force brightnes 1851 1 -- force brightness inversion
1973 1852
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] 1853 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1854 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1855
1983 1856
1984 idle= [X86,EARLY] !! 1857 idle= [X86]
1985 Format: idle=poll, id 1858 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1859 Poll forces a polling idle loop that can slightly
1987 improve the performan 1860 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1861 will use a lot of power and make the system run hot.
1989 Not recommended. 1862 Not recommended.
1990 idle=halt: Halt is fo 1863 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1864 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1865 idle=nomwait: Disable mwait for CPU C-states
1993 1866
1994 idxd.sva= [HW] 1867 idxd.sva= [HW]
1995 Format: <bool> 1868 Format: <bool>
1996 Allow force disabling 1869 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1870 support for the idxd driver. By default it is set to
1998 true (1). 1871 true (1).
1999 1872
2000 idxd.tc_override= [HW] 1873 idxd.tc_override= [HW]
2001 Format: <bool> 1874 Format: <bool>
2002 Allow override of def 1875 Allow override of default traffic class configuration
2003 for the device. By de 1876 for the device. By default it is set to false (0).
2004 1877
2005 ieee754= [MIPS] Select IEEE St 1878 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1879 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1880 Default: strict
2008 1881
2009 Choose which programs 1882 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1883 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1884 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1885 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1886 binary. Hardware implementations are permitted to
2014 support either or bot 1887 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1888 encoding mode.
2016 1889
2017 Available settings ar 1890 Available settings are as follows:
2018 strict accept binari 1891 strict accept binaries that request a NaN encoding
2019 supported by 1892 supported by the FPU
2020 legacy only accept l 1893 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1894 by the FPU
2022 2008 only accept 2 1895 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1896 by the FPU
2024 relaxed accept any bi 1897 relaxed accept any binaries regardless of whether
2025 supported by 1898 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1899
2029 The FPU emulator is a 1900 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1901 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1902 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1903 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1904 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1905 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1906 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1907 MIPS64 CPUs.
2037 1908
2038 The setting for ABS.f 1909 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1910 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1911 except where unsupported by hardware.
2041 1912
2042 ignore_loglevel [KNL,EARLY] !! 1913 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1914 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1915 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1916 We also add it as printk module parameter, so users
2046 could change it dynam 1917 could change it dynamically, usually by
2047 /sys/module/printk/pa 1918 /sys/module/printk/parameters/ignore_loglevel.
2048 1919
2049 ignore_rlimit_data 1920 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1921 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1922 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1923 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1924
2054 ihash_entries= [KNL] 1925 ihash_entries= [KNL]
2055 Set number of hash bu 1926 Set number of hash buckets for inode cache.
2056 1927
2057 ima_appraise= [IMA] appraise integr 1928 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1929 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1930 default: "enforce"
2060 1931
2061 ima_appraise_tcb [IMA] Deprecated. U 1932 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1933 The builtin appraise policy appraises all files
2063 owned by uid=0. 1934 owned by uid=0.
2064 1935
2065 ima_canonical_fmt [IMA] 1936 ima_canonical_fmt [IMA]
2066 Use the canonical for 1937 Use the canonical format for the binary runtime
2067 measurements, instead 1938 measurements, instead of host native format.
2068 1939
2069 ima_hash= [IMA] 1940 ima_hash= [IMA]
2070 Format: { md5 | sha1 1941 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1942 | sha512 | ... }
2072 default: "sha1" 1943 default: "sha1"
2073 1944
2074 The list of supported 1945 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1946 in crypto/hash_info.h.
2076 1947
2077 ima_policy= [IMA] 1948 ima_policy= [IMA]
2078 The builtin policies 1949 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1950 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1951 fail_securely | critical_data"
2081 1952
2082 The "tcb" policy meas 1953 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1954 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1955 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1956 uid=0.
2086 1957
2087 The "appraise_tcb" po 1958 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1959 all files owned by root.
2089 1960
2090 The "secure_boot" pol 1961 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1962 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1963 firmware, policy, etc) based on file signatures.
2093 1964
2094 The "fail_securely" p 1965 The "fail_securely" policy forces file signature
2095 verification failure 1966 verification failure also on privileged mounted
2096 filesystems with the 1967 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1968 flag.
2098 1969
2099 The "critical_data" p 1970 The "critical_data" policy measures kernel integrity
2100 critical data. 1971 critical data.
2101 1972
2102 ima_tcb [IMA] Deprecated. Us 1973 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1974 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1975 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1976 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1977 opened for read by uid=0.
2107 1978
2108 ima_template= [IMA] 1979 ima_template= [IMA]
2109 Select one of defined 1980 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i 1981 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2111 "ima-sigv2 1982 "ima-sigv2" }
2112 Default: "ima-ng" 1983 Default: "ima-ng"
2113 1984
2114 ima_template_fmt= 1985 ima_template_fmt=
2115 [IMA] Define a custom 1986 [IMA] Define a custom template format.
2116 Format: { "field1|... 1987 Format: { "field1|...|fieldN" }
2117 1988
2118 ima.ahash_minsize= [IMA] Minimum file 1989 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1990 Format: <min_file_size>
2120 Set the minimal file 1991 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1992 If left unspecified, ahash usage is disabled.
2122 1993
2123 ahash performance var 1994 ahash performance varies for different data sizes on
2124 different crypto acce 1995 different crypto accelerators. This option can be used
2125 to achieve the best p 1996 to achieve the best performance for a particular HW.
2126 1997
2127 ima.ahash_bufsize= [IMA] Asynchronous 1998 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1999 Format: <bufsize>
2129 Set hashing buffer si 2000 Set hashing buffer size. Default: 4k.
2130 2001
2131 ahash performance var 2002 ahash performance varies for different chunk sizes on
2132 different crypto acce 2003 different crypto accelerators. This option can be used
2133 to achieve best perfo 2004 to achieve best performance for particular HW.
2134 2005
2135 init= [KNL] 2006 init= [KNL]
2136 Format: <full_path> 2007 Format: <full_path>
2137 Run specified binary 2008 Run specified binary instead of /sbin/init as init
2138 process. 2009 process.
2139 2010
2140 initcall_debug [KNL] Trace initcalls 2011 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 2012 for working out where the kernel is dying during
2142 startup. 2013 startup.
2143 2014
2144 initcall_blacklist= [KNL] Do not exe 2015 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 2016 initcall functions. Useful for debugging built-in
2146 modules and initcalls 2017 modules and initcalls.
2147 2018
2148 initramfs_async= [KNL] 2019 initramfs_async= [KNL]
2149 Format: <bool> 2020 Format: <bool>
2150 Default: 1 2021 Default: 1
2151 This parameter contro 2022 This parameter controls whether the initramfs
2152 image is unpacked asy 2023 image is unpacked asynchronously, concurrently
2153 with devices being pr 2024 with devices being probed and
2154 initialized. This sho 2025 initialized. This should normally just work,
2155 but as a debugging ai 2026 but as a debugging aid, one can get the
2156 historical behaviour 2027 historical behaviour of the initramfs
2157 unpacking being compl 2028 unpacking being completed before device_ and
2158 late_ initcalls. 2029 late_ initcalls.
2159 2030
2160 initrd= [BOOT,EARLY] Specify !! 2031 initrd= [BOOT] Specify the location of the initial ramdisk
2161 2032
2162 initrdmem= [KNL,EARLY] Specify a !! 2033 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 2034 load the initrd. If an initrd is compiled in or
2164 specified in the boot 2035 specified in the bootparams, it takes priority over this
2165 setting. 2036 setting.
2166 Format: ss[KMG],nn[KM 2037 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 2038 Default is 0, 0
2168 2039
2169 init_on_alloc= [MM,EARLY] Fill newly !! 2040 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 2041 zeroes.
2171 Format: 0 | 1 2042 Format: 0 | 1
2172 Default set by CONFIG 2043 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 2044
2174 init_on_free= [MM,EARLY] Fill freed !! 2045 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 2046 Format: 0 | 1
2176 Default set by CONFIG 2047 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 2048
2178 init_pkru= [X86] Specify the def 2049 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 2050 register contents for all processes. 0x55555554 by
2180 default (disallow acc 2051 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 2052 override in debugfs after boot.
2182 2053
2183 inport.irq= [HW] Inport (ATI XL a 2054 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 2055 Format: <irq>
2185 2056
2186 int_pln_enable [X86] Enable power li 2057 int_pln_enable [X86] Enable power limit notification interrupt
2187 2058
2188 integrity_audit=[IMA] 2059 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 2060 Format: { "0" | "1" }
2190 0 -- basic integrity 2061 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 2062 1 -- additional integrity auditing messages.
2192 2063
2193 intel_iommu= [DMAR] Intel IOMMU dr 2064 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 2065 on
2195 Enable intel iommu dr 2066 Enable intel iommu driver.
2196 off 2067 off
2197 Disable intel iommu d 2068 Disable intel iommu driver.
2198 igfx_off [Default Off] 2069 igfx_off [Default Off]
2199 By default, gfx is ma 2070 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 2071 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 2072 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 2073 this case, gfx device will use physical address for
2203 DMA. 2074 DMA.
2204 strict [Default Off] 2075 strict [Default Off]
2205 Deprecated, equivalen 2076 Deprecated, equivalent to iommu.strict=1.
2206 sp_off [Default Off] 2077 sp_off [Default Off]
2207 By default, super pag 2078 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 2079 has the capability. With this option, super page will
2209 not be supported. 2080 not be supported.
2210 sm_on 2081 sm_on
2211 Enable the Intel IOMM 2082 Enable the Intel IOMMU scalable mode if the hardware
2212 advertises that it ha 2083 advertises that it has support for the scalable mode
2213 translation. 2084 translation.
2214 sm_off 2085 sm_off
2215 Disallow use of the I 2086 Disallow use of the Intel IOMMU scalable mode.
2216 tboot_noforce [Default Off] 2087 tboot_noforce [Default Off]
2217 Do not force the Inte 2088 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 2089 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 2090 could harm performance of some high-throughput
2220 devices like 40GBit n 2091 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 2092 mapping is enabled.
2222 Note that using this 2093 Note that using this option lowers the security
2223 provided by tboot bec 2094 provided by tboot because it makes the system
2224 vulnerable to DMA att 2095 vulnerable to DMA attacks.
2225 2096
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 2097 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 2098 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 2099 1 to 9 specify maximum depth of C-state.
2229 2100
2230 intel_pstate= [X86,EARLY] !! 2101 intel_pstate= [X86]
2231 disable 2102 disable
2232 Do not enable intel 2103 Do not enable intel_pstate as the default
2233 scaling driver for 2104 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 2105 passive
2245 Use intel_pstate as 2106 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 2107 to work with generic cpufreq governors (instead of
2247 enabling its intern 2108 enabling its internal governor). This mode cannot be
2248 used along with the 2109 used along with the hardware-managed P-states (HWP)
2249 feature. 2110 feature.
2250 force 2111 force
2251 Enable intel_pstate 2112 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 2113 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 2114 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 2115 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 2116 P-States information being indicated to OSPM and therefore
2256 should be used with 2117 should be used with caution. This option does not work with
2257 processors that are 2118 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 2119 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 2120 no_hwp
2260 Do not enable hardw 2121 Do not enable hardware P state control (HWP)
2261 if available. 2122 if available.
2262 hwp_only 2123 hwp_only
2263 Only load intel_pst 2124 Only load intel_pstate on systems which support
2264 hardware P state co 2125 hardware P state control (HWP) if available.
2265 support_acpi_ppc 2126 support_acpi_ppc
2266 Enforce ACPI _PPC p 2127 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 2128 Description Table, specifies preferred power management
2268 profile as "Enterpr 2129 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 2130 then this feature is turned on by default.
2270 per_cpu_perf_limits 2131 per_cpu_perf_limits
2271 Allow per-logical-C 2132 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 2133 cpufreq sysfs interface
2273 2134
2274 intremap= [X86-64,Intel-IOMMU,E !! 2135 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 2136 on enable Interrupt Remapping (default)
2276 off disable Inter 2137 off disable Interrupt Remapping
2277 nosid disable Sourc 2138 nosid disable Source ID checking
2278 no_x2apic_optout 2139 no_x2apic_optout
2279 BIOS x2APIC o 2140 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 2141 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 2142
2284 iomem= Disable strict checki 2143 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 2144 strict regions from userspace.
2286 relaxed 2145 relaxed
2287 2146
2288 iommu= [X86,EARLY] !! 2147 iommu= [X86]
2289 off 2148 off
2290 force 2149 force
2291 noforce 2150 noforce
2292 biomerge 2151 biomerge
2293 panic 2152 panic
2294 nopanic 2153 nopanic
2295 merge 2154 merge
2296 nomerge 2155 nomerge
2297 soft 2156 soft
2298 pt [X86] 2157 pt [X86]
2299 nopt [X86] 2158 nopt [X86]
2300 nobypass [PPC/POWERNV] 2159 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 2160 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2161
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2162 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 2163 Format: { "0" | "1" }
2305 0 - Try to allocate a 2164 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 2165 falling back to the full range if needed.
2307 1 - Allocate directly 2166 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 2167 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 2168 greater than 32-bit addressing.
2310 2169
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 2170 iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 2171 Format: { "0" | "1" }
2313 0 - Lazy mode. 2172 0 - Lazy mode.
2314 Request that DMA un 2173 Request that DMA unmap operations use deferred
2315 invalidation of har 2174 invalidation of hardware TLBs, for increased
2316 throughput at the c 2175 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2176 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2177 the relevant IOMMU driver.
2319 1 - Strict mode. 2178 1 - Strict mode.
2320 DMA unmap operation 2179 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2180 synchronously.
2322 unset - Use value of 2181 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2323 Note: on x86, strict 2182 Note: on x86, strict mode specified via one of the
2324 legacy driver-specifi 2183 legacy driver-specific options takes precedence.
2325 2184
2326 iommu.passthrough= 2185 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2186 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2187 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2188 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2189 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2190 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2191
2333 io7= [HW] IO7 for Marvel-b 2192 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2193 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2194 arch/alpha/kernel/core_marvel.c.
2336 2195
2337 io_delay= [X86,EARLY] I/O delay !! 2196 io_delay= [X86] I/O delay method
2338 0x80 2197 0x80
2339 Standard port 0x80 ba 2198 Standard port 0x80 based delay
2340 0xed 2199 0xed
2341 Alternate port 0xed b 2200 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2201 udelay
2343 Simple two microsecon 2202 Simple two microseconds delay
2344 none 2203 none
2345 No delay 2204 No delay
2346 2205
2347 ip= [IP_PNP] 2206 ip= [IP_PNP]
2348 See Documentation/adm 2207 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2208
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2209 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2210 IPC identifiers from 32,768 to 16,777,216.
2352 2211
2353 irqaffinity= [SMP] Set the default 2212 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2213 The argument is a cpu list, as described above.
2355 2214
2356 irqchip.gicv2_force_probe= 2215 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2216 [ARM, ARM64]
2358 Format: <bool> 2217 Format: <bool>
2359 Force the kernel to l 2218 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2219 of a GICv2 controller even if the memory range
2361 exposed by the device 2220 exposed by the device tree is too small.
2362 2221
2363 irqchip.gicv3_nolpi= 2222 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2223 [ARM, ARM64]
2365 Force the kernel to i 2224 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2225 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2226 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2227 to let secondary kernels in charge of setting up
2369 LPIs. 2228 LPIs.
2370 2229
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2230 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2231 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2232 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2233 CONFIG_ARM64_PSEUDO_NMI.
2375 2234
2376 irqfixup [HW] 2235 irqfixup [HW]
2377 When an interrupt is 2236 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2237 for it. Intended to get systems with badly broken
2379 firmware running. 2238 firmware running.
2380 2239
2381 irqpoll [HW] 2240 irqpoll [HW]
2382 When an interrupt is 2241 When an interrupt is not handled search all handlers
2383 for it. Also check al 2242 for it. Also check all handlers each timer
2384 interrupt. Intended t 2243 interrupt. Intended to get systems with badly broken
2385 firmware running. 2244 firmware running.
2386 2245
2387 isapnp= [ISAPNP] 2246 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2247 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2248
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2249 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2250 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2251 Format: [flag-list,]<cpu-list>
2393 2252
2394 Specify one or more C 2253 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2254 specified in the flag list (default: domain):
2396 2255
2397 nohz 2256 nohz
2398 Disable the tick wh 2257 Disable the tick when a single task runs.
2399 2258
2400 A residual 1Hz tick 2259 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2260 need to affine to housekeeping through the global
2402 workqueue's affinit 2261 workqueue's affinity configured via the
2403 /sys/devices/virtua 2262 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2263 by using the 'domain' flag described below.
2405 2264
2406 NOTE: by default th 2265 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2266 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2267 be configured manually after bootup.
2409 2268
2410 domain 2269 domain
2411 Isolate from the ge 2270 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2271 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2272 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2273 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2274 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2275 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2276 It offers a much more flexible interface where CPUs can
2418 move in and out of 2277 move in and out of an isolated set anytime.
2419 2278
2420 You can move a proc 2279 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2280 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2281 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2282 "number of CPUs in system - 1".
2424 2283
2425 managed_irq 2284 managed_irq
2426 2285
2427 Isolate from being 2286 Isolate from being targeted by managed interrupts
2428 which have an inter 2287 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2288 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2289 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2290 the /proc/irq/* interfaces.
2432 2291
2433 This isolation is b 2292 This isolation is best effort and only effective
2434 if the automaticall 2293 if the automatically assigned interrupt mask of a
2435 device queue contai 2294 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2295 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2296 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2297 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2298 cannot disturb the isolated CPU.
2440 2299
2441 If a queue's affini 2300 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2301 CPUs then this parameter has no effect on the
2443 interrupt routing d 2302 interrupt routing decision, though interrupts are
2444 only delivered when 2303 only delivered when tasks running on those
2445 isolated CPUs submi 2304 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2305 housekeeping CPUs has no influence on those
2447 queues. 2306 queues.
2448 2307
2449 The format of <cpu-li 2308 The format of <cpu-list> is described above.
2450 2309
2451 iucv= [HW,NET] 2310 iucv= [HW,NET]
2452 2311
2453 ivrs_ioapic [HW,X86-64] 2312 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2313 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t 2314 mapping provided in the IVRS ACPI table.
2456 By default, PCI segme 2315 By default, PCI segment is 0, and can be omitted.
2457 2316
2458 For example, to map I 2317 For example, to map IOAPIC-ID decimal 10 to
2459 PCI segment 0x1 and P 2318 PCI segment 0x1 and PCI device 00:14.0,
2460 write the parameter a 2319 write the parameter as:
2461 ivrs_ioapic=1 2320 ivrs_ioapic=10@0001:00:14.0
2462 2321
2463 Deprecated formats: 2322 Deprecated formats:
2464 * To map IOAPIC-ID de 2323 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2465 write the parameter 2324 write the parameter as:
2466 ivrs_ioapic[1 2325 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de 2326 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2468 PCI device 00:14.0 2327 PCI device 00:14.0 write the parameter as:
2469 ivrs_ioapic[1 2328 ivrs_ioapic[10]=0001:00:14.0
2470 2329
2471 ivrs_hpet [HW,X86-64] 2330 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2331 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t 2332 mapping provided in the IVRS ACPI table.
2474 By default, PCI segme 2333 By default, PCI segment is 0, and can be omitted.
2475 2334
2476 For example, to map H 2335 For example, to map HPET-ID decimal 10 to
2477 PCI segment 0x1 and P 2336 PCI segment 0x1 and PCI device 00:14.0,
2478 write the parameter a 2337 write the parameter as:
2479 ivrs_hpet=10@ 2338 ivrs_hpet=10@0001:00:14.0
2480 2339
2481 Deprecated formats: 2340 Deprecated formats:
2482 * To map HPET-ID deci 2341 * To map HPET-ID decimal 0 to PCI device 00:14.0
2483 write the parameter 2342 write the parameter as:
2484 ivrs_hpet[0]= 2343 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci 2344 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2486 PCI device 00:14.0 2345 PCI device 00:14.0 write the parameter as:
2487 ivrs_ioapic[1 2346 ivrs_ioapic[10]=0001:00:14.0
2488 2347
2489 ivrs_acpihid [HW,X86-64] 2348 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2349 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t 2350 mapping provided in the IVRS ACPI table.
2492 By default, PCI segme 2351 By default, PCI segment is 0, and can be omitted.
2493 2352
2494 For example, to map U 2353 For example, to map UART-HID:UID AMD0020:0 to
2495 PCI segment 0x1 and P 2354 PCI segment 0x1 and PCI device ID 00:14.5,
2496 write the parameter a 2355 write the parameter as:
2497 ivrs_acpihid= 2356 ivrs_acpihid=AMD0020:0@0001:00:14.5
2498 2357
2499 Deprecated formats: 2358 Deprecated formats:
2500 * To map UART-HID:UID 2359 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2501 PCI device ID 00:14 2360 PCI device ID 00:14.5, write the parameter as:
2502 ivrs_acpihid[ 2361 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID 2362 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2504 PCI device ID 00:14 2363 PCI device ID 00:14.5, write the parameter as:
2505 ivrs_acpihid[ 2364 ivrs_acpihid[0001:00:14.5]=AMD0020:0
2506 2365
2507 js= [HW,JOY] Analog joyst 2366 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2367 See Documentation/input/joydev/joystick.rst.
2509 2368
>> 2369 nokaslr [KNL]
>> 2370 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 2371 kernel and module base offset ASLR (Address Space
>> 2372 Layout Randomization).
>> 2373
2510 kasan_multi_shot 2374 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2375 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2376 report on every invalid memory access. Without this
2513 parameter KASAN will 2377 parameter KASAN will print report only for the first
2514 invalid access. 2378 invalid access.
2515 2379
2516 keep_bootcon [KNL,EARLY] !! 2380 keepinitrd [HW,ARM]
2517 Do not unregister boo <<
2518 useful for debugging <<
2519 between unregistering <<
2520 the real console. <<
2521 2381
2522 keepinitrd [HW,ARM] See retain_i !! 2382 kernelcore= [KNL,X86,IA-64,PPC]
2523 <<
2524 kernelcore= [KNL,X86,PPC,EARLY] <<
2525 Format: nn[KMGTPE] | 2383 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2384 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2385 the kernel for non-movable allocations. The requested
2528 amount is spread even 2386 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2387 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2388 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2389 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2390 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2391 other nodes will have a larger ZONE_MOVABLE.
2534 2392
2535 ZONE_MOVABLE is used 2393 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2394 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2395 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2396 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2397 zone if it does not.
2540 2398
2541 It is possible to spe 2399 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2400 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2401 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2402 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2403 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2404 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2405 are exclusive, so you cannot specify multiple forms.
2548 2406
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2407 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2408 Format: <Controller#>[,poll interval]
2551 The controller # is t 2409 The controller # is the number of the ehci usb debug
2552 port as it is probed 2410 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2411 optional and is the number seconds in between
2554 each poll cycle to th 2412 each poll cycle to the debug port in case you need
2555 the functionality for 2413 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2414 gdb or control-c on the dbgp connection. When
2557 not using this parame 2415 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2416 the kernel debugger.
2559 2417
2560 kgdboc= [KGDB,HW] kgdb over c 2418 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2419 Requires a tty driver that supports console polling,
2562 or a supported pollin 2420 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2421 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2422 keyboard only format: kbd
2565 keyboard and serial 2423 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2424 Optional Kernel mode setting:
2567 kms, kbd format: kms 2425 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2426 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2427
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2428 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2429 If the boot console provides the ability to read
2572 characters and can wo 2430 characters and can work in polling mode, you can use
2573 this parameter to tel 2431 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2432 until the normal console is registered. Intended to
2575 be used together with 2433 be used together with the kgdboc parameter which
2576 specifies the normal 2434 specifies the normal console to transition to.
2577 2435
2578 The name of the early 2436 The name of the early console should be specified
2579 as the value of this 2437 as the value of this parameter. Note that the name of
2580 the early console mig 2438 the early console might be different than the tty
2581 name passed to kgdboc 2439 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2440 blank and the first boot console that implements
2583 read() will be picked 2441 read() will be picked.
2584 2442
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2443 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2444 kernel debugger at the earliest opportunity.
2587 2445
2588 kmac= [MIPS] Korina etherne 2446 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2447 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2448 Ethernet adapter MAC address.
2591 2449
2592 kmemleak= [KNL,EARLY] Boot-time !! 2450 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2451 Valid arguments: on, off
2594 Default: on 2452 Default: on
2595 Built with CONFIG_DEB 2453 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2454 the default is off.
2597 2455
2598 kprobe_event=[probe-list] 2456 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2457 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2458 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2459 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2460 interface, but the parameters are comma delimited.
2603 For example, to add a 2461 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2462 arg1 and arg2, add to the command line;
2605 2463
2606 kprobe_event=p, 2464 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2465
2608 See also Documentatio 2466 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2467 Boot Parameter" section.
2610 2468
2611 kpti= [ARM64,EARLY] Control !! 2469 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2470 and kernel address spaces.
2613 Default: enabled on c 2471 Default: enabled on cores which need mitigation.
2614 0: force disabled 2472 0: force disabled
2615 1: force enabled 2473 1: force enabled
2616 2474
2617 kunit.enable= [KUNIT] Enable execut 2475 kunit.enable= [KUNIT] Enable executing KUnit tests. Requires
2618 CONFIG_KUNIT to be se 2476 CONFIG_KUNIT to be set to be fully enabled. The
2619 default value can be 2477 default value can be overridden via
2620 KUNIT_DEFAULT_ENABLED 2478 KUNIT_DEFAULT_ENABLED.
2621 Default is 1 (enabled 2479 Default is 1 (enabled)
2622 2480
2623 kvm.ignore_msrs=[KVM] Ignore guest ac 2481 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2482 Default is 0 (don't ignore, but inject #GP)
2625 2483
2626 kvm.eager_page_split= 2484 kvm.eager_page_split=
2627 [KVM,X86] Controls wh 2485 [KVM,X86] Controls whether or not KVM will try to
2628 proactively split all 2486 proactively split all huge pages during dirty logging.
2629 Eager page splitting 2487 Eager page splitting reduces interruptions to vCPU
2630 execution by eliminat 2488 execution by eliminating the write-protection faults
2631 and MMU lock contenti 2489 and MMU lock contention that would otherwise be
2632 required to split hug 2490 required to split huge pages lazily.
2633 2491
2634 VM workloads that rar 2492 VM workloads that rarely perform writes or that write
2635 only to a small regio 2493 only to a small region of VM memory may benefit from
2636 disabling eager page 2494 disabling eager page splitting to allow huge pages to
2637 still be used for rea 2495 still be used for reads.
2638 2496
2639 The behavior of eager 2497 The behavior of eager page splitting depends on whether
2640 KVM_DIRTY_LOG_INITIAL 2498 KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2641 disabled, all huge pa 2499 disabled, all huge pages in a memslot will be eagerly
2642 split when dirty logg 2500 split when dirty logging is enabled on that memslot. If
2643 enabled, eager page s 2501 enabled, eager page splitting will be performed during
2644 the KVM_CLEAR_DIRTY i 2502 the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2645 cleared. 2503 cleared.
2646 2504
2647 Eager page splitting 2505 Eager page splitting is only supported when kvm.tdp_mmu=Y.
2648 2506
2649 Default is Y (on). 2507 Default is Y (on).
2650 2508
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2509 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2510 Default is false (don't support).
2653 2511
2654 kvm.nx_huge_pages= 2512 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2513 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2514 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2515 force : Always deploy workaround.
2658 off : Never deplo 2516 off : Never deploy workaround.
2659 auto : Deploy work 2517 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2518 X86_BUG_ITLB_MULTIHIT.
2661 2519
2662 Default is 'auto'. 2520 Default is 'auto'.
2663 2521
2664 If the software worka 2522 If the software workaround is enabled for the host,
2665 guests do need not to 2523 guests do need not to enable it for nested guests.
2666 2524
2667 kvm.nx_huge_pages_recovery_ratio= 2525 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2526 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2527 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2528 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). 2529 period (see below). The default is 60.
2672 2530
2673 kvm.nx_huge_pages_recovery_period_ms= 2531 kvm.nx_huge_pages_recovery_period_ms=
2674 [KVM] Controls the ti 2532 [KVM] Controls the time period at which KVM zaps 4KiB pages
2675 back to huge pages. I 2533 back to huge pages. If the value is a non-zero N, KVM will
2676 zap a portion (see ra 2534 zap a portion (see ratio above) of the pages every N msecs.
2677 If the value is 0 (th 2535 If the value is 0 (the default), KVM will pick a period based
2678 on the ratio, such th 2536 on the ratio, such that a page is zapped after 1 hour on average.
2679 2537
2680 kvm-amd.nested= [KVM,AMD] Control nes !! 2538 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2681 KVM/SVM. Default is 1 !! 2539 Default is 1 (enabled)
2682 2540
2683 kvm-amd.npt= [KVM,AMD] Control KVM !! 2541 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2684 a.k.a. Two-Dimensiona !! 2542 for all guests.
2685 (enabled). Disable by !! 2543 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2686 for NPT. <<
2687 2544
2688 kvm-arm.mode= 2545 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2546 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 2547
2692 none: Forcefully disa 2548 none: Forcefully disable KVM.
2693 2549
2694 nvhe: Standard nVHE-b 2550 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2551 protected guests.
2696 2552
2697 protected: nVHE-based 2553 protected: nVHE-based mode with support for guests whose
2698 state is k 2554 state is kept private from the host.
2699 2555
2700 nested: VHE-based mod <<
2701 virtualizatio <<
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE 2556 Defaults to VHE/nVHE based on hardware support. Setting
2705 mode to "protected" w 2557 mode to "protected" will disable kexec and hibernation
2706 for the host. "nested !! 2558 for the host.
2707 used with extreme cau <<
2708 2559
2709 kvm-arm.vgic_v3_group0_trap= 2560 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2561 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2562 system registers
2712 2563
2713 kvm-arm.vgic_v3_group1_trap= 2564 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2565 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2566 system registers
2716 2567
2717 kvm-arm.vgic_v3_common_trap= 2568 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2569 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2570 system registers
2720 2571
2721 kvm-arm.vgic_v4_enable= 2572 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2573 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2574 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 2575
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2576 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2577 Reserves given percentage from system memory area for
2745 contiguous memory all 2578 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2579 allocation.
2747 By default it reserve 2580 By default it reserves 5% of total system memory.
2748 Format: <integer> 2581 Format: <integer>
2749 Default: 5 2582 Default: 5
2750 2583
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2584 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2585 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2586 Default is 1 (enabled)
2754 for EPT. <<
2755 2587
2756 kvm-intel.emulate_invalid_guest_state 2588 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2589 [KVM,Intel] Disable emulation of invalid guest state.
2758 state. Ignored if kvm !! 2590 Ignored if kvm-intel.enable_unrestricted_guest=1, as
2759 as guest state is nev !! 2591 guest state is never invalid for unrestricted guests.
2760 guests. This param do !! 2592 This param doesn't apply to nested guests (L2), as KVM
2761 as KVM never emulates !! 2593 never emulates invalid L2 guest state.
2762 Default is 1 (enabled !! 2594 Default is 1 (enabled)
2763 2595
2764 kvm-intel.flexpriority= 2596 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2597 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2598 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2599
2769 kvm-intel.nested= 2600 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2601 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2602 Default is 0 (disabled)
2772 2603
2773 kvm-intel.unrestricted_guest= 2604 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2605 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2606 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2607 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2608
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2609 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2610 CVE-2018-3620.
2781 2611
2782 Valid arguments: neve 2612 Valid arguments: never, cond, always
2783 2613
2784 always: L1D cache flu 2614 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2615 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2616 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2617 never: Disables the mitigation
2788 2618
2789 Default is cond (do L 2619 Default is cond (do L1 cache flush in specific instances)
2790 2620
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2621 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2622 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2623 Default is 1 (enabled)
2794 for it. <<
2795 2624
2796 l1d_flush= [X86,INTEL,EARLY] !! 2625 l1d_flush= [X86,INTEL]
2797 Control mitigation fo 2626 Control mitigation for L1D based snooping vulnerability.
2798 2627
2799 Certain CPUs are vuln 2628 Certain CPUs are vulnerable to an exploit against CPU
2800 internal buffers whic 2629 internal buffers which can forward information to a
2801 disclosure gadget und 2630 disclosure gadget under certain conditions.
2802 2631
2803 In vulnerable process 2632 In vulnerable processors, the speculatively
2804 forwarded data can be 2633 forwarded data can be used in a cache side channel
2805 attack, to access dat 2634 attack, to access data to which the attacker does
2806 not have direct acces 2635 not have direct access.
2807 2636
2808 This parameter contro 2637 This parameter controls the mitigation. The
2809 options are: 2638 options are:
2810 2639
2811 on - enable t 2640 on - enable the interface for the mitigation
2812 2641
2813 l1tf= [X86,EARLY] Control m !! 2642 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2643 affected CPUs
2815 2644
2816 The kernel PTE invers 2645 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2646 enabled and cannot be disabled.
2818 2647
2819 full 2648 full
2820 Provides all 2649 Provides all available mitigations for the
2821 L1TF vulnerab 2650 L1TF vulnerability. Disables SMT and
2822 enables all m 2651 enables all mitigations in the
2823 hypervisors, 2652 hypervisors, i.e. unconditional L1D flush.
2824 2653
2825 SMT control a 2654 SMT control and L1D flush control via the
2826 sysfs interfa 2655 sysfs interface is still possible after
2827 boot. Hyperv 2656 boot. Hypervisors will issue a warning
2828 when the firs 2657 when the first VM is started in a
2829 potentially i 2658 potentially insecure configuration,
2830 i.e. SMT enab 2659 i.e. SMT enabled or L1D flush disabled.
2831 2660
2832 full,force 2661 full,force
2833 Same as 'full 2662 Same as 'full', but disables SMT and L1D
2834 flush runtime 2663 flush runtime control. Implies the
2835 'nosmt=force' 2664 'nosmt=force' command line option.
2836 (i.e. sysfs c 2665 (i.e. sysfs control of SMT is disabled.)
2837 2666
2838 flush 2667 flush
2839 Leaves SMT en 2668 Leaves SMT enabled and enables the default
2840 hypervisor mi 2669 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2670 L1D flush.
2842 2671
2843 SMT control a 2672 SMT control and L1D flush control via the
2844 sysfs interfa 2673 sysfs interface is still possible after
2845 boot. Hyperv 2674 boot. Hypervisors will issue a warning
2846 when the firs 2675 when the first VM is started in a
2847 potentially i 2676 potentially insecure configuration,
2848 i.e. SMT enab 2677 i.e. SMT enabled or L1D flush disabled.
2849 2678
2850 flush,nosmt 2679 flush,nosmt
2851 2680
2852 Disables SMT 2681 Disables SMT and enables the default
2853 hypervisor mi 2682 hypervisor mitigation.
2854 2683
2855 SMT control a 2684 SMT control and L1D flush control via the
2856 sysfs interfa 2685 sysfs interface is still possible after
2857 boot. Hyperv 2686 boot. Hypervisors will issue a warning
2858 when the firs 2687 when the first VM is started in a
2859 potentially i 2688 potentially insecure configuration,
2860 i.e. SMT enab 2689 i.e. SMT enabled or L1D flush disabled.
2861 2690
2862 flush,nowarn 2691 flush,nowarn
2863 Same as 'flus 2692 Same as 'flush', but hypervisors will not
2864 warn when a V 2693 warn when a VM is started in a potentially
2865 insecure conf 2694 insecure configuration.
2866 2695
2867 off 2696 off
2868 Disables hype 2697 Disables hypervisor mitigations and doesn't
2869 emit any warn 2698 emit any warnings.
2870 It also drops 2699 It also drops the swap size and available
2871 RAM limit res 2700 RAM limit restriction on both hypervisor and
2872 bare metal. 2701 bare metal.
2873 2702
2874 Default is 'flush'. 2703 Default is 'flush'.
2875 2704
2876 For details see: Docu 2705 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2706
2878 l2cr= [PPC] 2707 l2cr= [PPC]
2879 2708
2880 l3cr= [PPC] 2709 l3cr= [PPC]
2881 2710
2882 lapic [X86-32,APIC,EARLY] E !! 2711 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2712 disabled it.
2884 2713
2885 lapic= [X86,APIC] Do not use 2714 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2715 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2716 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2717 Format: notscdeadline
2889 2718
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2719 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2720 in C2 power state.
2892 2721
2893 libata.dma= [LIBATA] DMA control 2722 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2723 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2724 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2725 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2726 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2727 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2728 for disks and CDROMs, but not CFs.
2900 2729
2901 libata.ignore_hpa= [LIBATA] Igno 2730 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2731 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2732 libata.ignore_hpa=1 ignore limits, using full disk
2904 2733
2905 libata.noacpi [LIBATA] Disables use 2734 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2735 when set.
2907 Format: <int> 2736 Format: <int>
2908 2737
2909 libata.force= [LIBATA] Force config 2738 libata.force= [LIBATA] Force configurations. The format is a comma-
2910 separated list of "[I 2739 separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2911 PORT and DEVICE are d 2740 PORT and DEVICE are decimal numbers matching port, link
2912 or device. Basically 2741 or device. Basically, it matches the ATA ID string
2913 printed on console by 2742 printed on console by libata. If the whole ID part is
2914 omitted, the last POR 2743 omitted, the last PORT and DEVICE values are used. If
2915 ID hasn't been specif 2744 ID hasn't been specified yet, the configuration applies
2916 to all ports, links a 2745 to all ports, links and devices.
2917 2746
2918 If only DEVICE is omi 2747 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2748 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2749 number of 0 either selects the first device or the
2921 first fan-out link be 2750 first fan-out link behind PMP device. It does not
2922 select the host link. 2751 select the host link. DEVICE number of 15 selects the
2923 host link and device 2752 host link and device attached to it.
2924 2753
2925 The VAL specifies the 2754 The VAL specifies the configuration to force. As long
2926 as there is no ambigu 2755 as there is no ambiguity, shortcut notation is allowed.
2927 For example, both 1.5 2756 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2757 The following configurations can be forced.
2929 2758
2930 * Cable type: 40c, 80 2759 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2760 Any ID with matching PORT is used.
2932 2761
2933 * SATA link speed lim 2762 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2763
2935 * Transfer mode: pio[ 2764 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2765 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2766 allowed.
2938 2767
2939 * nohrst, nosrst, nor 2768 * nohrst, nosrst, norst: suppress hard, soft and both
2940 resets. 2769 resets.
2941 2770
2942 * rstonce: only attem 2771 * rstonce: only attempt one reset during hot-unplug
2943 link recovery. 2772 link recovery.
2944 2773
2945 * [no]dbdelay: Enable 2774 * [no]dbdelay: Enable or disable the extra 200ms delay
2946 before debouncing a 2775 before debouncing a link PHY and device presence
2947 detection. 2776 detection.
2948 2777
2949 * [no]ncq: Turn on or 2778 * [no]ncq: Turn on or off NCQ.
2950 2779
2951 * [no]ncqtrim: Enable 2780 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2952 2781
2953 * [no]ncqati: Enable 2782 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2954 2783
2955 * [no]trim: Enable or 2784 * [no]trim: Enable or disable (unqueued) TRIM.
2956 2785
2957 * trim_zero: Indicate 2786 * trim_zero: Indicate that TRIM command zeroes data.
2958 2787
2959 * max_trim_128m: Set 2788 * max_trim_128m: Set 128M maximum trim size limit.
2960 2789
2961 * [no]dma: Turn on or 2790 * [no]dma: Turn on or off DMA transfers.
2962 2791
2963 * atapi_dmadir: Enabl 2792 * atapi_dmadir: Enable ATAPI DMADIR bridge support.
2964 2793
2965 * atapi_mod16_dma: En 2794 * atapi_mod16_dma: Enable the use of ATAPI DMA for
2966 commands that are n 2795 commands that are not a multiple of 16 bytes.
2967 2796
2968 * [no]dmalog: Enable 2797 * [no]dmalog: Enable or disable the use of the
2969 READ LOG DMA EXT co 2798 READ LOG DMA EXT command to access logs.
2970 2799
2971 * [no]iddevlog: Enabl 2800 * [no]iddevlog: Enable or disable access to the
2972 identify device dat 2801 identify device data log.
2973 2802
2974 * [no]logdir: Enable 2803 * [no]logdir: Enable or disable access to the general
2975 purpose log directo 2804 purpose log directory.
2976 2805
2977 * max_sec_128: Set tr 2806 * max_sec_128: Set transfer size limit to 128 sectors.
2978 2807
2979 * max_sec_1024: Set o 2808 * max_sec_1024: Set or clear transfer size limit to
2980 1024 sectors. 2809 1024 sectors.
2981 2810
2982 * max_sec_lba48: Set 2811 * max_sec_lba48: Set or clear transfer size limit to
2983 65535 sectors. 2812 65535 sectors.
2984 2813
2985 * [no]lpm: Enable or 2814 * [no]lpm: Enable or disable link power management.
2986 2815
2987 * [no]setxfer: Indica 2816 * [no]setxfer: Indicate if transfer speed mode setting
2988 should be skipped. 2817 should be skipped.
2989 2818
2990 * [no]fua: Disable or <<
2991 support for devices <<
2992 <<
2993 * dump_id: Dump IDENT 2819 * dump_id: Dump IDENTIFY data.
2994 2820
2995 * disable: Disable th 2821 * disable: Disable this device.
2996 2822
2997 If there are multiple 2823 If there are multiple matching configurations changing
2998 the same attribute, t 2824 the same attribute, the last one is used.
2999 2825
3000 load_ramdisk= [RAM] [Deprecated] 2826 load_ramdisk= [RAM] [Deprecated]
3001 2827
3002 lockd.nlm_grace_period=P [NFS] Assig 2828 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2829 Format: <integer>
3004 2830
3005 lockd.nlm_tcpport=N [NFS] Assign 2831 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2832 Format: <integer>
3007 2833
3008 lockd.nlm_timeout=T [NFS] Assign 2834 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2835 Format: <integer>
3010 2836
3011 lockd.nlm_udpport=M [NFS] Assign 2837 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2838 Format: <integer>
3013 2839
3014 lockdown= [SECURITY,EARLY] !! 2840 lockdown= [SECURITY]
3015 { integrity | confide 2841 { integrity | confidentiality }
3016 Enable the kernel loc 2842 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2843 integrity, kernel features that allow userland to
3018 modify the running ke 2844 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2845 confidentiality, kernel features that allow userland
3020 to extract confidenti 2846 to extract confidential information from the kernel
3021 are also disabled. 2847 are also disabled.
3022 2848
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] 2849 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2850 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2851 Defaults to being automatically set based on the
3058 number of online CPUs 2852 number of online CPUs.
3059 2853
3060 locktorture.nwriters_stress= [KNL] 2854 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2855 Set the number of locking write-acquisition kthreads.
3062 2856
3063 locktorture.onoff_holdoff= [KNL] 2857 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2858 Set time (s) after boot for CPU-hotplug testing.
3065 2859
3066 locktorture.onoff_interval= [KNL] 2860 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2861 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2862 zero to disable CPU-hotplug testing.
3069 2863
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] 2864 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2865 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2866 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2867 mode during the locktorture test.
3093 2868
3094 locktorture.shutdown_secs= [KNL] 2869 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2870 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2871 is useful for hands-off automated testing.
3097 2872
3098 locktorture.stat_interval= [KNL] 2873 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2874 Time (s) between statistics printk()s.
3100 2875
3101 locktorture.stutter= [KNL] 2876 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2877 Time (s) to stutter testing, for example,
3103 specifying five secon 2878 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2879 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2880 This tests the locking primitive's ability to
3106 transition abruptly t 2881 transition abruptly to and from idle.
3107 2882
3108 locktorture.torture_type= [KNL] 2883 locktorture.torture_type= [KNL]
3109 Specify the locking i 2884 Specify the locking implementation to test.
3110 2885
3111 locktorture.verbose= [KNL] 2886 locktorture.verbose= [KNL]
3112 Enable additional pri 2887 Enable additional printk() statements.
3113 2888
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2889 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2890 Format: <irq>
3120 2891
3121 loglevel= [KNL,EARLY] !! 2892 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2893 console loglevel will be printed to the console. It can
3124 also be changed with 2894 also be changed with klogd or other programs. The
3125 loglevels are defined 2895 loglevels are defined as follows:
3126 2896
3127 0 (KERN_EMERG) 2897 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2898 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2899 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2900 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2901 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2902 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2903 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2904 7 (KERN_DEBUG) debug-level messages
3135 2905
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2906 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2907 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2908 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2909 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2910 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2911 that allows to increase the default size depending on
3142 parameter that allows !! 2912 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2913
3146 logo.nologo [FB] Disables display 2914 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2915 This may be used to provide more screen space for
3148 kernel log messages a 2916 kernel log messages and is useful when debugging
3149 kernel boot problems. 2917 kernel boot problems.
3150 2918
3151 lp=0 [LP] Specify paral 2919 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2920 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2921 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2922 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2923 specified in addition to the ports) causes
3156 attached prin 2924 attached printers to be reset. Using
3157 lp=port1,port 2925 lp=port1,port2,... specifies the parallel ports
3158 to associate 2926 to associate lp devices with, starting with
3159 lp0. A port s 2927 lp0. A port specification may be 'none' to skip
3160 that lp devic 2928 that lp device, or a parport name such as
3161 'parport0'. S 2929 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2930 port specification list means that device IDs
3163 from each por 2931 from each port should be examined, to see if
3164 an IEEE 1284- 2932 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2933 so, the driver will manage that printer.
3166 See also head 2934 See also header of drivers/char/lp.c.
3167 2935
3168 lpj=n [KNL] 2936 lpj=n [KNL]
3169 Sets loops_per_jiffy 2937 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2938 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2939 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2940 the correct value for your kernel, boot with normal
3173 autodetection and see 2941 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2942 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2943 which is likely to cause problems if your CPUs need
3176 significantly diverge 2944 significantly divergent settings. An incorrect value
3177 will cause delays in 2945 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2946 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2947 unlikely, in the extreme case this might damage your
3180 hardware. 2948 hardware.
3181 2949
>> 2950 ltpc= [NET]
>> 2951 Format: <io>,<irq>,<dma>
>> 2952
3182 lsm.debug [SECURITY] Enable LSM 2953 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2954
3184 lsm=lsm1,...,lsmN 2955 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2956 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2957 overrides CONFIG_LSM, and the "security=" parameter.
3187 2958
>> 2959 machvec= [IA-64] Force the use of a particular machine-vector
>> 2960 (machvec) in a generic kernel.
>> 2961 Example: machvec=hpzx1
>> 2962
3188 machtype= [Loongson] Share the 2963 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2964 different yeeloong laptops.
3190 Example: machtype=lem 2965 Example: machtype=lemote-yeeloong-2f-7inch
3191 2966
3192 maxcpus= [SMP,EARLY] Maximum n !! 2967 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
>> 2968 than or equal to this physical address is ignored.
>> 2969
>> 2970 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2971 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2972 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2973 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2974 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2975 only takes effect during system bootup.
3198 While n=0 is a specia 2976 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2977 which also disables the IO APIC.
3200 2978
3201 max_loop= [LOOP] The number of 2979 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2980 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2981 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2982 of statically allocating a predefined number, loop
3205 devices can be reques 2983 devices can be requested on-demand with the
3206 /dev/loop-control int 2984 /dev/loop-control interface.
3207 2985
3208 mce [X86-32] Machine Chec 2986 mce [X86-32] Machine Check Exception
3209 2987
3210 mce=option [X86-64] See Document !! 2988 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2989
3212 md= [HW] RAID subsystems 2990 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2991 See Documentation/admin-guide/md.rst.
3214 2992
3215 mdacon= [MDA] 2993 mdacon= [MDA]
3216 Format: <first>,<last 2994 Format: <first>,<last>
3217 Specifies range of co 2995 Specifies range of consoles to be captured by the MDA.
3218 2996
3219 mds= [X86,INTEL,EARLY] !! 2997 mds= [X86,INTEL]
3220 Control mitigation fo 2998 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2999 Sampling (MDS) vulnerability.
3222 3000
3223 Certain CPUs are vuln 3001 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 3002 internal buffers which can forward information to a
3225 disclosure gadget und 3003 disclosure gadget under certain conditions.
3226 3004
3227 In vulnerable process 3005 In vulnerable processors, the speculatively
3228 forwarded data can be 3006 forwarded data can be used in a cache side channel
3229 attack, to access dat 3007 attack, to access data to which the attacker does
3230 not have direct acces 3008 not have direct access.
3231 3009
3232 This parameter contro 3010 This parameter controls the MDS mitigation. The
3233 options are: 3011 options are:
3234 3012
3235 full - Enable M 3013 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 3014 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 3015 SMT on vulnerable CPUs
3238 off - Uncondit 3016 off - Unconditionally disable MDS mitigation
3239 3017
3240 On TAA-affected machi 3018 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 3019 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 3020 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 3021 this mitigation, you need to specify tsx_async_abort=off
3244 too. 3022 too.
3245 3023
3246 Not specifying this o 3024 Not specifying this option is equivalent to
3247 mds=full. 3025 mds=full.
3248 3026
3249 For details see: Docu 3027 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 3028
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 3029 mem=nn[KMG] [HEXAGON] Set the memory size.
3252 Must be specified, ot 3030 Must be specified, otherwise memory size will be 0.
3253 3031
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc !! 3032 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3255 of memory Amount of m !! 3033 Amount of memory to be used in cases as follows:
3256 as follows: <<
3257 3034
3258 1 for test; 3035 1 for test;
3259 2 when the kernel is 3036 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 3037 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 3038 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory 3039 4 to limit the memory available for kdump kernel.
3263 3040
3264 [ARC,MICROBLAZE] - th 3041 [ARC,MICROBLAZE] - the limit applies only to low memory,
3265 high memory is not af 3042 high memory is not affected.
3266 3043
3267 [ARM64] - only limits 3044 [ARM64] - only limits memory covered by the linear
3268 mapping. The NOMAP re 3045 mapping. The NOMAP regions are not affected.
3269 3046
3270 [X86] Work as limitin 3047 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 3048 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 3049 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 3050 belonging to unused RAM.
3274 3051
3275 Note that this only t 3052 Note that this only takes effects during boot time since
3276 in above case 3, memo 3053 in above case 3, memory may need be hot added after boot
3277 if system memory of h 3054 if system memory of hypervisor is not sufficient.
3278 3055
3279 mem=nn[KMG]@ss[KMG] 3056 mem=nn[KMG]@ss[KMG]
3280 [ARM,MIPS,EARLY] - ov !! 3057 [ARM,MIPS] - override the memory layout reported by
3281 reported by firmware. !! 3058 firmware.
3282 Define a memory regio 3059 Define a memory region of size nn[KMG] starting at
3283 ss[KMG]. 3060 ss[KMG].
3284 Multiple different re 3061 Multiple different regions can be specified with
3285 multiple mem= paramet 3062 multiple mem= parameters on the command line.
3286 3063
3287 mem=nopentium [BUGS=X86-32] Disable 3064 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 3065 memory.
3289 3066
3290 memblock=debug [KNL,EARLY] Enable me !! 3067 memblock=debug [KNL] Enable memblock debug messages.
3291 3068
3292 memchunk=nn[KMG] 3069 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 3070 [KNL,SH] Allow user to override the default size for
3294 per-device physically 3071 per-device physically contiguous DMA buffers.
3295 3072
3296 memhp_default_state=online/offline/on !! 3073 memhp_default_state=online/offline
3297 [KNL] Set the initial 3074 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 3075 onlining policy. If not specified, the default value is
3299 set according to the 3076 set according to the
3300 CONFIG_MEMORY_HOTPLUG 3077 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 3078 option.
3302 See Documentation/adm 3079 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 3080
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 3081 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 3082 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 3083 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 3084 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 3085 option description.
3309 3086
3310 memmap=nn[KMG]@ss[KMG] 3087 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 3088 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 3089 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 3090 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 3091 which limits max address to nn[KMG].
3315 Multiple different re 3092 Multiple different regions can be specified,
3316 comma delimited. 3093 comma delimited.
3317 Example: 3094 Example:
3318 memmap=100M@2 3095 memmap=100M@2G,100M#3G,1G!1024G
3319 3096
3320 memmap=nn[KMG]#ss[KMG] 3097 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 3098 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 3099 Region of memory to be marked is from ss to ss+nn.
3323 3100
3324 memmap=nn[KMG]$ss[KMG] 3101 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 3102 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 3103 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 3104 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 3105 memmap=64K$0x18690000
3329 or 3106 or
3330 memmap=0x100 3107 memmap=0x10000$0x18690000
3331 Some bootloaders may 3108 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 3109 like Grub2, otherwise '$' and the following number
3333 will be eaten. 3110 will be eaten.
3334 3111
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 3112 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 3113 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 3114 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 3115 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 3116 and is NVDIMM or ADR memory.
3340 3117
3341 memmap=<size>%<offset>-<oldtype>+<new 3118 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 3119 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 3120 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 3121 out, the whole region will be marked as <newtype>,
3345 even if previously un 3122 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 3123 out, matching memory will be removed. Types are
3347 specified as e820 typ 3124 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 3125 3 = ACPI, 12 = PRAM.
3349 3126
3350 memory_corruption_check=0/1 [X86,EARL !! 3127 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 3128 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 3129 memory when doing things like suspend/resume.
3353 Setting this option w 3130 Setting this option will scan the memory
3354 looking for corruptio 3131 looking for corruption. Enabling this will
3355 both detect corruptio 3132 both detect corruption and prevent the kernel
3356 from using the memory 3133 from using the memory being corrupted.
3357 However, its intended 3134 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 3135 repeatable BIOS-originated corruption always
3359 affects the same memo 3136 affects the same memory, you can use memmap=
3360 to prevent the kernel 3137 to prevent the kernel from using that memory.
3361 3138
3362 memory_corruption_check_size=size [X8 !! 3139 memory_corruption_check_size=size [X86]
3363 By default it checks 3140 By default it checks for corruption in the low
3364 64k, making this memo 3141 64k, making this memory unavailable for normal
3365 use. Use this parame 3142 use. Use this parameter to scan for
3366 corruption in more or 3143 corruption in more or less memory.
3367 3144
3368 memory_corruption_check_period=second !! 3145 memory_corruption_check_period=seconds [X86]
3369 By default it checks 3146 By default it checks for corruption every 60
3370 seconds. Use this pa 3147 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 3148 other rate. 0 disables periodic checking.
3372 3149
3373 memory_hotplug.memmap_on_memory 3150 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 3151 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 3152 Format: {on | off (default)}
3376 When enabled, runtime 3153 When enabled, runtime hotplugged memory will
3377 allocate its internal 3154 allocate its internal metadata (struct pages,
3378 those vmemmap pages c 3155 those vmemmap pages cannot be optimized even
3379 if hugetlb_free_vmemm 3156 if hugetlb_free_vmemmap is enabled) from the
3380 hotadded memory which 3157 hotadded memory which will allow to hotadd a
3381 lot of memory without 3158 lot of memory without requiring additional
3382 memory to do so. 3159 memory to do so.
3383 This feature is disab 3160 This feature is disabled by default because it
3384 has some implication 3161 has some implication on large (e.g. GB)
3385 allocations in some c 3162 allocations in some configurations (e.g. small
3386 memory blocks). 3163 memory blocks).
3387 The state of the flag 3164 The state of the flag can be read in
3388 /sys/module/memory_ho 3165 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 3166 Note that even when enabled, there are a few cases where
3390 the feature is not ef 3167 the feature is not effective.
3391 3168
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 3169 memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
3393 Format: <integer> 3170 Format: <integer>
3394 default : 0 <disable> 3171 default : 0 <disable>
3395 Specifies the number 3172 Specifies the number of memtest passes to be
3396 performed. Each pass 3173 performed. Each pass selects another test
3397 pattern from a given 3174 pattern from a given set of patterns. Memtest
3398 fills the memory with 3175 fills the memory with this pattern, validates
3399 memory contents and r 3176 memory contents and reserves bad memory
3400 regions that are dete 3177 regions that are detected.
3401 3178
3402 mem_encrypt= [X86-64] AMD Secure M 3179 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 3180 Valid arguments: on, off
3404 Default: off !! 3181 Default (depends on kernel configuration option):
>> 3182 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 3183 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 3184 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 3185 mem_encrypt=off: Do not activate SME
3407 3186
3408 Refer to Documentatio 3187 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3409 for details on when m 3188 for details on when memory encryption can be activated.
3410 3189
3411 mem_sleep_default= [SUSPEND] Def 3190 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 3191 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 3192 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 3193 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 3194 See Documentation/admin-guide/pm/sleep-states.rst.
3416 3195
>> 3196 meye.*= [HW] Set MotionEye Camera parameters
>> 3197 See Documentation/admin-guide/media/meye.rst.
>> 3198
>> 3199 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 3200 Multi-Function General Purpose Timers on AMD Geode
>> 3201 platforms.
>> 3202
3417 mfgptfix [X86-32] Fix MFGPT ti 3203 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 3204 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 3205 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 3206 problem by letting the user disable the workaround.
3421 3207
3422 mga= [HW,DRM] 3208 mga= [HW,DRM]
3423 3209
3424 microcode.force_minrev= [X86] !! 3210 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
3425 Format: <bool> !! 3211 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 3212
3429 mini2440= [ARM,HW,KNL] 3213 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 3214 Format:[0..2][b][c][t]
3431 Default: "0tb" 3215 Default: "0tb"
3432 MINI2440 configuratio 3216 MINI2440 configuration specification:
3433 0 - The attached scre 3217 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 3218 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 3219 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 3220 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 3221 the TFT driver, and the framebuffer will be left
3438 unconfigured. 3222 unconfigured.
3439 b - Enable backlight. 3223 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 3224 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 3225 LED. This parameter is not necessary when using the
3442 VGA shield. 3226 VGA shield.
3443 c - Enable the s3c ca 3227 c - Enable the s3c camera interface.
3444 t - Reserved for enab 3228 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 3229 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 3230 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 3231 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 3232 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 3233
3450 mitigations= 3234 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 3235 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 3236 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 3237 arch-independent options, each of which is an
3454 aggregation of existi 3238 aggregation of existing arch-specific options.
3455 3239
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 3240 off
3460 Disable all o 3241 Disable all optional CPU mitigations. This
3461 improves syst 3242 improves system performance, but it may also
3462 expose users 3243 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 3244 Equivalent to: nopti [X86,PPC]
3464 !! 3245 if nokaslr then kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 3246 nospectre_v1 [X86,PPC]
>> 3247 nobp=0 [S390]
3475 3248 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 3249 spectre_v2_user=off [X86]
3482 !! 3250 spec_store_bypass_disable=off [X86,PPC]
3483 3251 ssbd=force-off [ARM64]
>> 3252 nospectre_bhb [ARM64]
>> 3253 l1tf=off [X86]
>> 3254 mds=off [X86]
3484 3255 tsx_async_abort=off [X86]
>> 3256 kvm.nx_huge_pages=off [X86]
>> 3257 srbds=off [X86,INTEL]
>> 3258 no_entry_flush [PPC]
>> 3259 no_uaccess_flush [PPC]
>> 3260 mmio_stale_data=off [X86]
>> 3261 retbleed=off [X86]
3485 3262
3486 Exceptions: 3263 Exceptions:
3487 3264 This does not have any effect on
3488 3265 kvm.nx_huge_pages when
3489 3266 kvm.nx_huge_pages=force.
3490 3267
3491 auto (default) 3268 auto (default)
3492 Mitigate all 3269 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 3270 enabled, even if it's vulnerable. This is for
3494 users who don 3271 users who don't want to be surprised by SMT
3495 getting disab 3272 getting disabled across kernel upgrades, or who
3496 have other wa 3273 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 3274 Equivalent to: (default behavior)
3498 3275
3499 auto,nosmt 3276 auto,nosmt
3500 Mitigate all 3277 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 3278 if needed. This is for users who always want to
3502 be fully miti 3279 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 3280 Equivalent to: l1tf=flush,nosmt [X86]
3504 3281 mds=full,nosmt [X86]
3505 3282 tsx_async_abort=full,nosmt [X86]
3506 3283 mmio_stale_data=full,nosmt [X86]
3507 3284 retbleed=auto,nosmt [X86]
3508 3285
3509 mminit_loglevel= 3286 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 3287 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 3288 parameter allows control of the logging verbosity for
3512 the additional memory 3289 the additional memory initialisation checks. A value
3513 of 0 disables mminit 3290 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 3291 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 3292 so loglevel=8 may also need to be specified.
3516 3293
3517 mmio_stale_data= 3294 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 3295 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 3296 MMIO Stale Data vulnerabilities.
3520 3297
3521 Processor MMIO Stale 3298 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 3299 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 3300 operation. Exposed data could originate or end in
3524 the same CPU buffers 3301 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 3302 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 3303 is to clear the affected CPU buffers.
3527 3304
3528 This parameter contro 3305 This parameter controls the mitigation. The
3529 options are: 3306 options are:
3530 3307
3531 full - Enable m 3308 full - Enable mitigation on vulnerable CPUs
3532 3309
3533 full,nosmt - Enable m 3310 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 3311 vulnerable CPUs.
3535 3312
3536 off - Uncondit 3313 off - Unconditionally disable mitigation
3537 3314
3538 On MDS or TAA affecte 3315 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 3316 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 3317 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 3318 mitigated with the same mechanism so in order to
3542 disable this mitigati 3319 disable this mitigation, you need to specify
3543 mds=off and tsx_async 3320 mds=off and tsx_async_abort=off too.
3544 3321
3545 Not specifying this o 3322 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 3323 mmio_stale_data=full.
3547 3324
3548 For details see: 3325 For details see:
3549 Documentation/admin-g 3326 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 3327
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> 3328 module.async_probe=<bool>
3559 [KNL] When set to tru 3329 [KNL] When set to true, modules will use async probing
3560 by default. To enable 3330 by default. To enable/disable async probing for a
3561 specific module, use 3331 specific module, use the module specific control that
3562 is documented under < 3332 is documented under <module>.async_probe. When both
3563 module.async_probe an 3333 module.async_probe and <module>.async_probe are
3564 specified, <module>.a 3334 specified, <module>.async_probe takes precedence for
3565 the specific module. 3335 the specific module.
3566 3336
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 3337 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3338 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3339 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3340 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3341 is always true, so this option does nothing.
3578 3342
3579 module_blacklist= [KNL] Do not load 3343 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3344 modules. Useful for debugging problem modules.
3581 3345
3582 mousedev.tap_time= 3346 mousedev.tap_time=
3583 [MOUSE] Maximum time 3347 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3348 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3349 a tap and be reported as a left button click (for
3586 touchpads working in 3350 touchpads working in absolute mode only).
3587 Format: <msecs> 3351 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3352 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3353 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3354 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3355 reporting absolute coordinates, such as tablets
3592 3356
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3357 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3358 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3359 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3360 specifies the amount of memory used for migratable
3597 allocations. If both 3361 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3362 specified, then kernelcore will be at *least* the
3599 specified value but m 3363 specified value but may be more. If movablecore on its
3600 own is specified, the 3364 own is specified, the administrator must be careful
3601 that the amount of me 3365 that the amount of memory usable for all allocations
3602 is not too small. 3366 is not too small.
3603 3367
3604 movable_node [KNL,EARLY] Boot-time !! 3368 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3369 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3370 of such nodes will be usable only for movable
3607 allocations which rul 3371 allocations which rules out almost all kernel
3608 allocations. Use with 3372 allocations. Use with caution!
3609 3373
3610 MTD_Partition= [MTD] 3374 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3375 Format: <name>,<region-number>,<size>,<offset>
3612 3376
3613 MTD_Region= [MTD] Format: 3377 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3378 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3379
3616 mtdparts= [MTD] 3380 mtdparts= [MTD]
3617 See drivers/mtd/parse 3381 See drivers/mtd/parsers/cmdlinepart.c
3618 3382
>> 3383 mtdset= [ARM]
>> 3384 ARM/S3C2412 JIVE boot control
>> 3385
>> 3386 See arch/arm/mach-s3c/mach-jive.c
>> 3387
3619 mtouchusb.raw_coordinates= 3388 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3389 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3390 ('y', default) or cooked coordinates ('n')
3622 3391
3623 mtrr=debug [X86,EARLY] !! 3392 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 3393 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3394 that could hold holes aka. UC entries.
3630 3395
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3396 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3397 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3398 Default is 1.
3634 Large value could pre 3399 Large value could prevent small alignment from
3635 using up MTRRs. 3400 using up MTRRs.
3636 3401
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3402 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3403 Format: <integer>
3639 Range: 0,7 : spare re 3404 Range: 0,7 : spare reg number
3640 Default : 1 3405 Default : 1
3641 Used for mtrr cleanup 3406 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3407 Set to 2 or more if your graphical card needs more.
3643 3408
3644 multitce=off [PPC] This parameter 3409 multitce=off [PPC] This parameter disables the use of the pSeries
3645 firmware feature for 3410 firmware feature for updating multiple TCE entries
3646 at a time. 3411 at a time.
3647 3412
3648 n2= [NET] SDL Inc. RISCom 3413 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3414
3650 netdev= [NET] Network devices 3415 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3416 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3417 Note that mem_start is often overloaded to mean
3653 something different a 3418 something different and driver-specific.
3654 This usage is only do 3419 This usage is only documented in each driver source
3655 file if at all. 3420 file if at all.
3656 3421
3657 netpoll.carrier_timeout= 3422 netpoll.carrier_timeout=
3658 [NET] Specifies amoun 3423 [NET] Specifies amount of time (in seconds) that
3659 netpoll should wait f 3424 netpoll should wait for a carrier. By default netpoll
3660 waits 4 seconds. 3425 waits 4 seconds.
3661 3426
3662 nf_conntrack.acct= 3427 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3428 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3429 0 to disable accounting
3665 1 to enable accountin 3430 1 to enable accounting
3666 Default value is 0. 3431 Default value is 0.
3667 3432
3668 nfs.cache_getent= !! 3433 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3434 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3435
3672 nfs.cache_getent_timeout= !! 3436 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3437 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3438
>> 3439 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3440 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3441
3676 nfs.callback_nr_threads= 3442 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3443 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3444 NFS client will assign to service NFSv4 callback
3679 requests. 3445 requests.
3680 3446
3681 nfs.callback_tcpport= 3447 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3448 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3449 channel should listen.
3684 3450
3685 nfs.delay_retrans= !! 3451 nfs.cache_getent=
3686 [NFS] specifies the n !! 3452 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3453 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3454
3689 Only applies if the s !! 3455 nfs.cache_getent_timeout=
3690 and the specified val !! 3456 [NFS] sets the timeout after which an attempt to
>> 3457 update a cache entry is deemed to have failed.
>> 3458
>> 3459 nfs.idmap_cache_timeout=
>> 3460 [NFS] set the maximum lifetime for idmapper cache
>> 3461 entries.
3691 3462
3692 nfs.enable_ino64= 3463 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3464 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3465 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3466 number for the readdir() and stat() syscalls instead
3696 of returning the full 3467 of returning the full 64-bit number.
3697 The default is to ret 3468 The default is to return 64-bit inode numbers.
3698 3469
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3470 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3471 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3472 slots the client will assign to the callback
3706 channel. This determi 3473 channel. This determines the maximum number of
3707 callbacks the client 3474 callbacks the client will process in parallel for
3708 a particular server. 3475 a particular server.
3709 3476
3710 nfs.max_session_slots= 3477 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3478 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3479 the client will attempt to negotiate with the server.
3713 This limits the numbe 3480 This limits the number of simultaneous RPC requests
3714 that the client can s 3481 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3482 Note that there is little point in setting this
3716 value higher than the 3483 value higher than the max_tcp_slot_table_limit.
3717 3484
3718 nfs.nfs4_disable_idmapping= 3485 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3486 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3487 ensures that both the RPC level authentication
3721 scheme and the NFS le 3488 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3489 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3490 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3491 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3492 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3493 Servers that do not support this mode of operation
3727 will be autodetected 3494 will be autodetected by the client, and it will fall
3728 back to using the idm 3495 back to using the idmapper.
3729 To turn off this beha 3496 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3497 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3498 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3499 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3500 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3501 UUID that is generated at system install time.
3736 3502
3737 nfs.recover_lost_locks= !! 3503 nfs.send_implementation_id =
>> 3504 [NFSv4.1] Send client implementation identification
>> 3505 information in exchange_id requests.
>> 3506 If zero, no implementation identification information
>> 3507 will be sent.
>> 3508 The default is to send the implementation identification
>> 3509 information.
>> 3510
>> 3511 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3512 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3513 to a lease timeout on the server. Please note that
3740 doing this risks data 3514 doing this risks data corruption, since there are
3741 no guarantees that th 3515 no guarantees that the file will remain unchanged
3742 after the locks are l 3516 after the locks are lost.
3743 If you want to enable 3517 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3518 attempting to recover these locks, then set this
3745 parameter to '1'. 3519 parameter to '1'.
3746 The default parameter 3520 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3521 not to attempt recovery of lost locks.
3748 3522
3749 nfs.send_implementation_id= !! 3523 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 3524 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3525 layoutstats to the pNFS metadata server.
3760 3526
3761 Setting this to value 3527 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3528 whatever value is the default set by the layout
3763 driver. A non-zero va 3529 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3530 in seconds between layoutstats transmissions.
3765 3531
3766 nfsd.inter_copy_offload_enable= !! 3532 nfsd.inter_copy_offload_enable =
3767 [NFSv4.2] When set to 3533 [NFSv4.2] When set to 1, the server will support
3768 server-to-server copi 3534 server-to-server copies for which this server is
3769 the destination of th 3535 the destination of the copy.
3770 3536
3771 nfsd.nfs4_disable_idmapping= !! 3537 nfsd.nfsd4_ssc_umount_timeout =
3772 [NFSv4] When set to t <<
3773 server will return on <<
3774 clients using auth_sy <<
3775 and gids from such cl <<
3776 migration from NFSv2/ <<
3777 <<
3778 nfsd.nfsd4_ssc_umount_timeout= <<
3779 [NFSv4.2] When used a 3538 [NFSv4.2] When used as the destination of a
3780 server-to-server copy 3539 server-to-server copy, knfsd temporarily mounts
3781 the source server. I 3540 the source server. It caches the mount in case
3782 it will be needed aga 3541 it will be needed again, and discards it if not
3783 used for the number o 3542 used for the number of milliseconds specified by
3784 this parameter. 3543 this parameter.
3785 3544
3786 nfsaddrs= [NFS] Deprecated. Us !! 3545 nfsd.nfs4_disable_idmapping=
3787 See Documentation/adm !! 3546 [NFSv4] When set to the default of '1', the NFSv4
3788 !! 3547 server will return only numeric uids and gids to
3789 nfsroot= [NFS] nfs root filesy !! 3548 clients using auth_sys, and will accept numeric uids
3790 See Documentation/adm !! 3549 and gids from such clients. This is intended to ease
>> 3550 migration from NFSv2/v3.
3791 3551
3792 nfsrootdebug [NFS] enable nfsroot <<
3793 See Documentation/adm <<
3794 3552
3795 nmi_backtrace.backtrace_idle [KNL] 3553 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3554 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3555 NMI stack-backtrace request.
3798 3556
3799 nmi_debug= [KNL,SH] Specify one 3557 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3558 when a NMI is triggered.
3801 Format: [state][,regs 3559 Format: [state][,regs][,debounce][,die]
3802 3560
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3561 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3562 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3563 Valid num: 0 or 1
3806 0 - turn hardlockup d 3564 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3565 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3566 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3567 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3568 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3569 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3570 please see 'nowatchdog'.
3815 This is useful when y 3571 This is useful when you use a panic=... timeout and
3816 need the box quickly 3572 need the box quickly up again.
3817 3573
3818 These settings can be 3574 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3575 the nmi_watchdog and hardlockup_panic sysctls.
3820 3576
3821 no387 [BUGS=X86-32] Tells t 3577 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3578 emulation library even if a 387 maths coprocessor
3823 is present. 3579 is present.
3824 3580
3825 no4lvl [RISCV,EARLY] Disable !! 3581 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 3582 kernel to use 4-level paging instead.
3830 3583
3831 noalign [KNL,ARM] !! 3584 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 3585
3840 no_console_suspend 3586 no_console_suspend
3841 [HW] Never suspend th 3587 [HW] Never suspend the console
3842 Disable suspending of 3588 Disable suspending of consoles during suspend and
3843 hibernate operations. 3589 hibernate operations. Once disabled, debugging
3844 messages can reach va 3590 messages can reach various consoles while the rest
3845 of the system is bein 3591 of the system is being put to sleep (ie, while
3846 debugging driver susp 3592 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3593 not work reliably with all consoles, but is known
3848 to work with serial a 3594 to work with serial and VGA consoles.
3849 To facilitate more fl 3595 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3596 console_suspend, a printk module parameter to control
3851 it. Users could use c 3597 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3598 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3599 turn on/off it dynamically.
3854 3600
3855 no_debug_objects !! 3601 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3602 Disable device dump. Device dump allows drivers to
>> 3603 append dump data to vmcore so you can collect driver
>> 3604 specified debug info. Drivers can append the data
>> 3605 without any limit and this data is stored in memory,
>> 3606 so this may cause significant memory stress. Disabling
>> 3607 device dump can help save memory but the driver debug
>> 3608 data will be no longer available. This parameter
>> 3609 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3610 is set.
>> 3611
>> 3612 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3613 caches in the slab allocator. Saves per-node memory,
>> 3614 but will impact performance.
>> 3615
>> 3616 noalign [KNL,ARM]
>> 3617
>> 3618 noaltinstr [S390] Disables alternative instructions patching
>> 3619 (CPU alternatives feature).
>> 3620
>> 3621 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3622 IOAPICs that may be present in the system.
>> 3623
>> 3624 noautogroup Disable scheduler automatic task group creation.
>> 3625
>> 3626 nocache [ARM]
3857 3627
3858 nodsp [SH] Disable hardware 3628 nodsp [SH] Disable hardware DSP at boot time.
3859 3629
3860 noefi [EFI,EARLY] Disable E !! 3630 noefi Disable EFI runtime services support.
>> 3631
>> 3632 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
>> 3633
>> 3634 noexec [IA-64]
3861 3635
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3636 nosmap [PPC]
>> 3637 Disable SMAP (Supervisor Mode Access Prevention)
>> 3638 even if it is supported by processor.
>> 3639
>> 3640 nosmep [PPC64s]
>> 3641 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3642 even if it is supported by processor.
3863 3643
3864 noexec32 [X86-64] 3644 noexec32 [X86-64]
3865 This affects only 32- 3645 This affects only 32-bit executables.
3866 noexec32=on: enable n 3646 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3647 read doesn't imply executable mappings
3868 noexec32=off: disable 3648 noexec32=off: disable non-executable mappings
3869 read implies 3649 read implies executable mappings
3870 3650
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 3651 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3652
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3653 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3654 register save and restore. The kernel will only save
3881 legacy floating-point 3655 legacy floating-point registers on task switch.
3882 3656
>> 3657 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
>> 3658
>> 3659 nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
>> 3660
>> 3661 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3662 Equivalent to smt=1.
>> 3663
>> 3664 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3665 nosmt=force: Force disable SMT, cannot be undone
>> 3666 via the sysfs control file.
>> 3667
>> 3668 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3669 (bounds check bypass). With this option data leaks are
>> 3670 possible in the system.
>> 3671
>> 3672 nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for
>> 3673 the Spectre variant 2 (indirect branch prediction)
>> 3674 vulnerability. System may allow data leaks with this
>> 3675 option.
>> 3676
>> 3677 nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch
>> 3678 history injection) vulnerability. System may allow data leaks
>> 3679 with this option.
>> 3680
>> 3681 nospec_store_bypass_disable
>> 3682 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3683
>> 3684 no_uaccess_flush
>> 3685 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3686
>> 3687 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3688 and restore using xsave. The kernel will fallback to
>> 3689 enabling legacy floating-point and sse state.
>> 3690
>> 3691 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3692 register states. The kernel will fall back to use
>> 3693 xsave to save the states. By using this parameter,
>> 3694 performance of saving the states is degraded because
>> 3695 xsave doesn't support modified optimization while
>> 3696 xsaveopt supports it on xsaveopt enabled systems.
>> 3697
>> 3698 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3699 restoring x86 extended register state in compacted
>> 3700 form of xsave area. The kernel will fall back to use
>> 3701 xsaveopt and xrstor to save and restore the states
>> 3702 in standard form of xsave area. By using this
>> 3703 parameter, xsave area per process might occupy more
>> 3704 memory on xsaves enabled systems.
>> 3705
>> 3706 nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
>> 3707 in do_idle() and not use the arch_cpu_idle()
>> 3708 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
>> 3709 to be effective. This is useful on platforms where the
>> 3710 sleep(SH) or wfi(ARM,ARM64) instructions do not work
>> 3711 correctly or when doing power measurements to evalute
>> 3712 the impact of the sleep instructions. This is also
>> 3713 useful when using JTAG debugger.
>> 3714
>> 3715 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3716 only way then for a file to be executed with privilege
>> 3717 is to be setuid root or executed by root.
>> 3718
>> 3719 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3720 function PAL_HALT_LIGHT when idle. This increases
>> 3721 power-consumption. On the positive side, it reduces
>> 3722 interrupt wake-up latency, which may improve performance
>> 3723 in certain environments such as networked servers or
>> 3724 real-time systems.
>> 3725
3883 no_hash_pointers 3726 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3727 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3728 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3729 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3730 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3731 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3732 users, but it also makes debugging the kernel more
3891 difficult since unequ 3733 difficult since unequal pointers can no longer be
3892 compared. However, i 3734 compared. However, if this command-line option is
3893 specified, then all n 3735 specified, then all normal pointers will have their true
3894 value printed. This o 3736 value printed. This option should only be specified when
3895 debugging the kernel. 3737 debugging the kernel. Please do not use on production
3896 kernels. 3738 kernels.
3897 3739
3898 nohibernate [HIBERNATION] Disable 3740 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3741
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 3742 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3743 Valid arguments: on, off
3915 Default: on 3744 Default: on
3916 3745
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3746 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3747 The argument is a cpu list, as described above.
3919 In kernels built with 3748 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3749 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3750 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3751 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3752 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3753 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3754 rcu_nocbs= boot parameter.
3926 3755
3927 Note that this argume 3756 Note that this argument takes precedence over
3928 the CONFIG_RCU_NOCB_C 3757 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
3929 3758
>> 3759 noiotrap [SH] Disables trapped I/O port accesses.
>> 3760
>> 3761 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3762 disable unhandled interrupt sources.
>> 3763
>> 3764 no_timer_check [X86,APIC] Disables the code which tests for
>> 3765 broken timer IRQ sources.
>> 3766
>> 3767 noisapnp [ISAPNP] Disables ISA PnP code.
>> 3768
3930 noinitrd [RAM] Tells the kerne 3769 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3770 initial RAM disk.
3932 3771
3933 nointremap [X86-64,Intel-IOMMU,E !! 3772 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3773 remapping.
3935 [Deprecated - use int 3774 [Deprecated - use intremap=off]
3936 3775
3937 noinvpcid [X86,EARLY] Disable t !! 3776 nointroute [IA-64]
3938 3777
3939 noiotrap [SH] Disables trapped !! 3778 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 3779
3941 noirqdebug [X86-32] Disables the !! 3780 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 3781
3944 noisapnp [ISAPNP] Disables ISA !! 3782 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3945 3783
3946 nokaslr [KNL,EARLY] !! 3784 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 <<
3951 no-kvmapf [X86,KVM,EARLY] Disab <<
3952 fault handling. 3785 fault handling.
3953 3786
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3787 no-vmw-sched-clock
>> 3788 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3789 clock and use the default one.
>> 3790
>> 3791 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
>> 3792 steal time accounting. steal time is computed, but
>> 3793 won't influence scheduler behaviour
>> 3794
>> 3795 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3955 3796
3956 nolapic [X86-32,APIC,EARLY] D !! 3797 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3957 3798
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3799 nomca [IA-64] Disable machine check abort handling
3959 3800
3960 nomce [X86-32] Disable Mach 3801 nomce [X86-32] Disable Machine Check Exception
3961 3802
3962 nomfgpt [X86-32] Disable Mult 3803 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 3804 Timer usage (for AMD Geode machines).
3964 3805
>> 3806 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
>> 3807 shutdown the other cpus. Instead use the REBOOT_VECTOR
>> 3808 irq.
>> 3809
3965 nomodeset Disable kernel modese 3810 nomodeset Disable kernel modesetting. Most systems' firmware
3966 sets up a display mod 3811 sets up a display mode and provides framebuffer memory
3967 for output. With nomo 3812 for output. With nomodeset, DRM and fbdev drivers will
3968 not load if they coul 3813 not load if they could possibly displace the pre-
3969 initialized output. O 3814 initialized output. Only the system framebuffer will
3970 be available for use. 3815 be available for use. The respective drivers will not
3971 perform display-mode 3816 perform display-mode changes or accelerated rendering.
3972 3817
3973 Useful as error fallb 3818 Useful as error fallback, or for testing and debugging.
3974 3819
3975 nomodule Disable module load 3820 nomodule Disable module load
3976 3821
3977 nonmi_ipi [X86] Disable using N !! 3822 nopat [X86] Disable PAT (page attribute table extension of
3978 shutdown the other cp <<
3979 irq. <<
3980 <<
3981 nopat [X86,EARLY] Disable P <<
3982 pagetables) support. 3823 pagetables) support.
3983 3824
3984 nopcid [X86-64,EARLY] Disabl !! 3825 nopcid [X86-64] Disable the PCID cpu feature.
3985 <<
3986 nopku [X86] Disable Memory <<
3987 in some Intel CPUs. <<
3988 <<
3989 nopti [X86-64,EARLY] <<
3990 Equivalent to pti=off <<
3991 <<
3992 nopv= [X86,XEN,KVM,HYPER_V, <<
3993 Disables the PV optim <<
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 <<
3997 nopvspin [X86,XEN,KVM,EARLY] <<
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 3826
4002 norandmaps Don't use address spa 3827 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3828 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3829
4005 noreplace-smp [X86-32,SMP] Don't re 3830 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3831 with UP alternatives
4007 3832
4008 noresume [SWSUSP] Disables res 3833 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3834 space.
4010 3835
4011 no-scroll [VGA] Disables scroll 3836 no-scroll [VGA] Disables scrollback.
4012 This is required for 3837 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3838 reader made by F.H. Papenmeier (Germany).
4014 3839
4015 nosgx [X86-64,SGX,EARLY] Di !! 3840 nosbagart [IA-64]
4016 3841
4017 nosmap [PPC,EARLY] !! 3842 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 <<
4021 nosmep [PPC64s,EARLY] <<
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 3843
4025 nosmp [SMP,EARLY] Tells an !! 3844 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3845 and disable the IO APIC. legacy for "maxcpus=0".
4027 3846
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 3847 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3848
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 3849 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3850
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 3851 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3852 soft-lockup and NMI watchdog (hard-lockup).
4083 3853
4084 nowb [ARM,EARLY] !! 3854 nowb [ARM]
4085 3855
4086 nox2apic [X86-64,APIC,EARLY] D !! 3856 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3857
4088 NOTE: this parameter 3858 NOTE: this parameter will be ignored on systems with the
4089 LEGACY_XAPIC_DISABLED 3859 LEGACY_XAPIC_DISABLED bit set in the
4090 IA32_XAPIC_DISABLE_ST 3860 IA32_XAPIC_DISABLE_STATUS MSR.
4091 3861
4092 noxsave [BUGS=X86] Disables x !! 3862 nps_mtm_hs_ctr= [KNL,ARC]
4093 and restore using xsa !! 3863 This parameter sets the maximum duration, in
4094 enabling legacy float !! 3864 cycles, each HW thread of the CTOP can run
>> 3865 without interruptions, before HW switches it.
>> 3866 The actual maximum duration is 16 times this
>> 3867 parameter's value.
>> 3868 Format: integer between 1 and 255
>> 3869 Default: 255
>> 3870
>> 3871 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3872 purges which is reported from either PAL_VM_SUMMARY or
>> 3873 SAL PALO.
4095 3874
4096 noxsaveopt [X86] Disables xsaveo !! 3875 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4097 register states. The <<
4098 xsave to save the sta <<
4099 performance of saving <<
4100 xsave doesn't support <<
4101 xsaveopt supports it <<
4102 <<
4103 noxsaves [X86] Disables xsaves <<
4104 restoring x86 extende <<
4105 form of xsave area. T <<
4106 xsaveopt and xrstor t <<
4107 in standard form of x <<
4108 parameter, xsave area <<
4109 memory on xsaves enab <<
4110 <<
4111 nr_cpus= [SMP,EARLY] Maximum n <<
4112 could support. nr_cp 3876 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3877 support 'n' processors. It could be larger than the
4114 number of already plu 3878 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3879 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3880 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3881 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3882 hot plugging.
4119 3883
4120 nr_uarts= [SERIAL] maximum numb 3884 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3885
4122 numa=off [KNL, ARM64, PPC, RIS !! 3886 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123 Disable NUMA, Only se !! 3887 set up a single NUMA node spanning all memory.
4124 spanning all memory. <<
4125 3888
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 3889 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 3890 NUMA balancing.
4128 Allowed values are en 3891 Allowed values are enable and disable
4129 3892
4130 numa_zonelist_order= [KNL, BOOT] Sele 3893 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3894 'node', 'default' can be specified
4132 This can be set from 3895 This can be set from sysctl after boot.
4133 See Documentation/adm 3896 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3897
4135 ohci1394_dma=early [HW,EARLY] en !! 3898 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3899 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3900 info.
4138 3901
4139 olpc_ec_timeout= [OLPC] ms delay when 3902 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3903 Rather than timing out after 20 ms if an EC
4141 command is not proper 3904 command is not properly ACKed, override the length
4142 of the timeout. We h 3905 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3906 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3907 interrupts *may* be lost!
4145 3908
4146 omap_mux= [OMAP] Override bootl 3909 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3910 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3911 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3912 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3913
4151 onenand.bdry= [HW,MTD] Flex-OneNAND 3914 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4152 3915
4153 Format: [die0_boundar 3916 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4154 3917
4155 boundary - index of l 3918 boundary - index of last SLC block on Flex-OneNAND.
4156 The remain 3919 The remaining blocks are configured as MLC blocks.
4157 lock - Configure 3920 lock - Configure if Flex-OneNAND boundary should be locked.
4158 Once locke 3921 Once locked, the boundary cannot be changed.
4159 1 indicate 3922 1 indicates lock status, 0 indicates unlock status.
4160 3923
4161 oops=panic [KNL,EARLY] !! 3924 oops=panic Always panic on oopses. Default is to just kill the
4162 Always panic on oopse <<
4163 process, but there is 3925 process, but there is a small probability of
4164 deadlocking the machi 3926 deadlocking the machine.
4165 This will also cause 3927 This will also cause panics on machine check exceptions.
4166 Useful together with 3928 Useful together with panic=30 to trigger a reboot.
4167 3929
4168 page_alloc.shuffle= 3930 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3931 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3932 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3933 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3934 running on a platform with a direct-mapped memory-side
>> 3935 cache, and this parameter can be used to
>> 3936 override/disable that behavior. The state of the flag
>> 3937 can be read from sysfs at:
4173 /sys/module/page_allo 3938 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3939
4176 page_owner= [KNL,EARLY] Boot-time !! 3940 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3941 Storage of the information about who allocated
4178 each page is disabled 3942 each page is disabled in default. With this switch,
4179 we can turn it on. 3943 we can turn it on.
4180 on: enable the featur 3944 on: enable the feature
4181 3945
4182 page_poison= [KNL,EARLY] Boot-time !! 3946 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3947 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3948 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3949 off: turn off poisoning (default)
4186 on: turn on poisoning 3950 on: turn on poisoning
4187 3951
4188 page_reporting.page_reporting_order= 3952 page_reporting.page_reporting_order=
4189 [KNL] Minimal page re 3953 [KNL] Minimal page reporting order
4190 Format: <integer> 3954 Format: <integer>
4191 Adjust the minimal pa 3955 Adjust the minimal page reporting order. The page
4192 reporting is disabled !! 3956 reporting is disabled when it exceeds (MAX_ORDER-1).
4193 3957
4194 panic= [KNL] Kernel behaviou 3958 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3959 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3960 timeout = 0: wait forever
4197 timeout < 0: reboot i 3961 timeout < 0: reboot immediately
4198 Format: <timeout> 3962 Format: <timeout>
4199 3963
4200 panic_on_taint= [KNL,EARLY] <<
4201 Bitmask for condition <<
4202 Format: <hex>[,nouser <<
4203 Hexadecimal bitmask r <<
4204 that will cause the k <<
4205 called with any of th <<
4206 The optional switch " <<
4207 prevent userspace for <<
4208 /proc/sys/kernel/tain <<
4209 bitmask set on panic_ <<
4210 See Documentation/adm <<
4211 extra details on the <<
4212 to compose the bitmas <<
4213 <<
4214 panic_on_warn=1 panic() instead of WA <<
4215 on a WARN(). <<
4216 <<
4217 panic_print= Bitmask for printing 3964 panic_print= Bitmask for printing system info when panic happens.
4218 User can chose combin 3965 User can chose combination of the following bits:
4219 bit 0: print all task 3966 bit 0: print all tasks info
4220 bit 1: print system m 3967 bit 1: print system memory info
4221 bit 2: print timer in 3968 bit 2: print timer info
4222 bit 3: print locks in 3969 bit 3: print locks info if CONFIG_LOCKDEP is on
4223 bit 4: print ftrace b 3970 bit 4: print ftrace buffer
4224 bit 5: print all prin 3971 bit 5: print all printk messages in buffer
4225 bit 6: print all CPUs 3972 bit 6: print all CPUs backtrace (if available in the arch)
4226 bit 7: print only tas <<
4227 *Be aware* that this 3973 *Be aware* that this option may print a _lot_ of lines,
4228 so there are risks of 3974 so there are risks of losing older messages in the log.
4229 Use this option caref 3975 Use this option carefully, maybe worth to setup a
4230 bigger log buffer wit 3976 bigger log buffer with "log_buf_len" along with this.
4231 3977
>> 3978 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
>> 3979 Format: <hex>[,nousertaint]
>> 3980 Hexadecimal bitmask representing the set of TAINT flags
>> 3981 that will cause the kernel to panic when add_taint() is
>> 3982 called with any of the flags in this set.
>> 3983 The optional switch "nousertaint" can be utilized to
>> 3984 prevent userspace forced crashes by writing to sysctl
>> 3985 /proc/sys/kernel/tainted any flagset matching with the
>> 3986 bitmask set on panic_on_taint.
>> 3987 See Documentation/admin-guide/tainted-kernels.rst for
>> 3988 extra details on the taint flags that users can pick
>> 3989 to compose the bitmask to assign to panic_on_taint.
>> 3990
>> 3991 panic_on_warn panic() instead of WARN(). Useful to cause kdump
>> 3992 on a WARN().
>> 3993
4232 parkbd.port= [HW] Parallel port nu 3994 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3995 connected to, default is 0.
4234 Format: <parport#> 3996 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3997 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3998 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3999 Format: <mode>
4238 4000
4239 parport= [HW,PPT] Specify para 4001 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 4002 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 4003 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 4004 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 4005 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 4006 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 4007 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 4008 should be numbers, or 'auto' (for using detected
4247 settings on that part 4009 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 4010 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 4011 Parallel ports are assigned in the order they
4250 are specified on the 4012 are specified on the command line, starting
4251 with parport0. 4013 with parport0.
4252 4014
4253 parport_init_mode= [HW,PPT] 4015 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 4016 Configure VIA parallel port to operate in
4255 a specific mode. This 4017 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 4018 computer where firmware has no options for setting
4257 up parallel port mode 4019 up parallel port mode and sets it to spp.
4258 Currently this functi 4020 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 4021 Format: [spp|ps2|epp|ecp|ecpepp]
4260 4022
4261 pata_legacy.all= [HW,LIBATA] 4023 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 4024 Format: <int>
4263 Set to non-zero to pr 4025 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 4026 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 4027 has been found at either range. Disabled by default.
4266 4028
4267 pata_legacy.autospeed= [HW,LIBATA] 4029 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 4030 Format: <int>
4269 Set to non-zero if a 4031 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 4032 changes. Disabled by default.
4271 4033
4272 pata_legacy.ht6560a= [HW,LIBATA] 4034 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 4035 Format: <int>
4274 Set to 1, 2, or 3 for 4036 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 4037 the secondary channel, or both channels respectively.
4276 Disabled by default. 4038 Disabled by default.
4277 4039
4278 pata_legacy.ht6560b= [HW,LIBATA] 4040 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 4041 Format: <int>
4280 Set to 1, 2, or 3 for 4042 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 4043 the secondary channel, or both channels respectively.
4282 Disabled by default. 4044 Disabled by default.
4283 4045
4284 pata_legacy.iordy_mask= [HW,LIBATA] 4046 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 4047 Format: <int>
4286 IORDY enable mask. S 4048 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 4049 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 4050 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 4051 the second channel, and so on. The sequence will often
4290 correspond to the pri 4052 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 4053 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 4054 bus and the use of other driver options may interfere
4293 with the sequence. B 4055 with the sequence. By default IORDY is allowed across
4294 all channels. 4056 all channels.
4295 4057
4296 pata_legacy.opti82c46x= [HW,LIBATA] 4058 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 4059 Format: <int>
4298 Set to 1, 2, or 3 for 4060 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 4061 channel, the secondary channel, or both channels
4300 respectively. Disabl 4062 respectively. Disabled by default.
4301 4063
4302 pata_legacy.opti82c611a= [HW,L 4064 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 4065 Format: <int>
4304 Set to 1, 2, or 3 for 4066 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 4067 channel, the secondary channel, or both channels
4306 respectively. Disabl 4068 respectively. Disabled by default.
4307 4069
4308 pata_legacy.pio_mask= [HW,LIBATA] 4070 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 4071 Format: <int>
4310 PIO mode mask for aut 4072 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 4073 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 4074 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 4075 All modes allowed by default.
4314 4076
4315 pata_legacy.probe_all= [HW,LIBATA] 4077 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 4078 Format: <int>
4317 Set to non-zero to pr 4079 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 4080 port ranges on PCI systems. Disabled by default.
4319 4081
4320 pata_legacy.probe_mask= [HW,LIBATA] 4082 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 4083 Format: <int>
4322 Probe mask for legacy 4084 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 4085 platform configuration and the use of other driver
4324 options up to 6 legac 4086 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 4087 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 4088 of individual ports can be disabled by setting the
4327 corresponding bits in 4089 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 4090 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 4091 By default all supported ports are probed.
4330 4092
4331 pata_legacy.qdi= [HW,LIBATA] 4093 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 4094 Format: <int>
4333 Set to non-zero to pr 4095 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 4096 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 4097
4336 pata_legacy.winbond= [HW,LIBATA] 4098 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 4099 Format: <int>
4338 Set to non-zero to pr 4100 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 4101 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 4102 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 4103 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 4104 0 otherwise.
4343 4105
4344 pata_platform.pio_mask= [HW,LIBATA] 4106 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 4107 Format: <int>
4346 Supported PIO mode ma 4108 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 4109 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 4110 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 4111 allowed by default.
4350 4112
4351 pause_on_oops=<int> !! 4113 pause_on_oops=
4352 Halt all CPUs after t 4114 Halt all CPUs after the first oops has been printed for
4353 the specified number 4115 the specified number of seconds. This is to be used if
4354 your oopses keep scro 4116 your oopses keep scrolling off the screen.
4355 4117
4356 pcbit= [HW,ISDN] 4118 pcbit= [HW,ISDN]
4357 4119
4358 pci=option[,option...] [PCI,EARLY] v !! 4120 pcd. [PARIDE]
>> 4121 See header of drivers/block/paride/pcd.c.
>> 4122 See also Documentation/admin-guide/blockdev/paride.rst.
>> 4123
>> 4124 pci=option[,option...] [PCI] various PCI subsystem options.
4359 4125
4360 Some options 4126 Some options herein operate on a specific device
4361 or a set of d 4127 or a set of devices (<pci_dev>). These are
4362 specified in 4128 specified in one of the following formats:
4363 4129
4364 [<domain>:]<b 4130 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 4131 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 4132
4367 Note: the fir 4133 Note: the first format specifies a PCI
4368 bus/device/fu 4134 bus/device/function address which may change
4369 if new hardwa 4135 if new hardware is inserted, if motherboard
4370 firmware chan 4136 firmware changes, or due to changes caused
4371 by other kern 4137 by other kernel parameters. If the
4372 domain is lef 4138 domain is left unspecified, it is
4373 taken to be z 4139 taken to be zero. Optionally, a path
4374 to a device t 4140 to a device through multiple device/function
4375 addresses can 4141 addresses can be specified after the base
4376 address (this 4142 address (this is more robust against
4377 renumbering i 4143 renumbering issues). The second format
4378 selects devic 4144 selects devices using IDs from the
4379 configuration 4145 configuration space which may match multiple
4380 devices in th 4146 devices in the system.
4381 4147
4382 earlydump dump PCI conf 4148 earlydump dump PCI config space before the kernel
4383 changes anyth 4149 changes anything
4384 off [X86] don't p 4150 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 4151 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 4152 the hardware directly. Use this if your machine
4387 has a non-sta 4153 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 4154 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 4155 hardware access methods are allowed. Use this
4390 if you experi 4156 if you experience crashes upon bootup and you
4391 suspect they 4157 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 4158 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 4159 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 4160 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 4161 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 4162 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 4163 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 4164 bus number. The config space is then accessed
4399 through ports 4165 through ports 0xC000-0xCFFF).
4400 See http://wi 4166 See http://wiki.osdev.org/PCI for more info
4401 on the config 4167 on the configuration access mechanisms.
4402 noaer [PCIE] If the 4168 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 4169 enabled, this kernel boot option can be used to
4404 disable the u 4170 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 4171 nodomains [PCI] Disable support for multiple PCI
4406 root domains 4172 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 4173 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 4174 Configuration
4409 check_enable_amd_mmconf [X86] 4175 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 4176 properly configured MMIO access to PCI
4411 config space 4177 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 4178 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 4179 enabled, this kernel boot option can be used to
4414 disable the u 4180 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 4181 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 4182 Safety option to keep boot IRQs enabled. This
4417 should never 4183 should never be necessary.
4418 ioapicreroute [APIC] Enable 4184 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 4185 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 4186 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 4187 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 4188 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 4189 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 4190 a chipset where boot IRQs cannot be disabled.
4425 The opposite 4191 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 4192 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 4193 routing table. These calls are known to be buggy
4428 on several ma 4194 on several machines and they hang the machine
4429 when used, bu 4195 when used, but on other computers it's the only
4430 way to get th 4196 way to get the interrupt routing table. Try
4431 this option i 4197 this option if the kernel is unable to allocate
4432 IRQs or disco 4198 IRQs or discover secondary PCI buses on your
4433 motherboard. 4199 motherboard.
4434 rom [X86] Assign 4200 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 4201 Use with caution as certain devices share
4436 address decod 4202 address decoders between ROMs and other
4437 resources. 4203 resources.
4438 norom [X86] Do not 4204 norom [X86] Do not assign address space to
4439 expansion ROM 4205 expansion ROMs that do not already have
4440 BIOS assigned 4206 BIOS assigned address ranges.
4441 nobar [X86] Do not 4207 nobar [X86] Do not assign address space to the
4442 BARs that wer 4208 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 4209 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 4210 assigned automatically to PCI devices. You can
4445 make the kern 4211 make the kernel exclude IRQs of your ISA cards
4446 this way. 4212 this way.
4447 pirqaddr=0xAAAAA [X86] 4213 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 4214 of the PIRQ table (normally generated
4449 by the BIOS) 4215 by the BIOS) if it is outside the
4450 F0000h-100000 4216 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 4217 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 4218 useful if the kernel is unable to find your
4453 secondary bus 4219 secondary buses and you want to tell it
4454 explicitly wh 4220 explicitly which ones they are.
4455 assign-busses [X86] Always 4221 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 4222 numbers ourselves, overriding
4457 whatever the 4223 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 4224 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 4225 in the BIOS $PIR table. This is needed on
4460 some systems 4226 some systems with broken BIOSes, notably
4461 some HP Pavil 4227 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 4228 notebooks. This will have no effect if ACPI
4463 IRQ routing i 4229 IRQ routing is enabled.
4464 noacpi [X86] Do not 4230 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 4231 or for PCI scanning.
4466 use_crs [X86] Use PCI 4232 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 4233 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 4234 is enabled by default. If you need to use this,
4469 please report 4235 please report a bug.
4470 nocrs [X86] Ignore 4236 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 4237 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 4238 use_e820 [X86] Use E820 reservations to exclude parts of
4473 PCI host brid 4239 PCI host bridge windows. This is a workaround
4474 for BIOS defe 4240 for BIOS defects in host bridge _CRS methods.
4475 If you need t 4241 If you need to use this, please report a bug to
4476 <linux-pci@vge 4242 <linux-pci@vger.kernel.org>.
4477 no_e820 [X86] Ignore 4243 no_e820 [X86] Ignore E820 reservations for PCI host
4478 bridge window 4244 bridge windows. This is the default on modern
4479 hardware. If 4245 hardware. If you need to use this, please report
4480 a bug to <linu 4246 a bug to <linux-pci@vger.kernel.org>.
4481 routeirq Do IRQ routin 4247 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 4248 This is normally done in pci_enable_device(),
4483 so this optio 4249 so this option is a temporary workaround
4484 for broken dr 4250 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 4251 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 4252 handle more pci cards
4487 noearly [X86] Don't d 4253 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 4254 This might help on some broken boards which
4489 machine check 4255 machine check when some devices' config space
4490 is read. But 4256 is read. But various workarounds are disabled
4491 and some IOMM 4257 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 4258 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 4259 This sorting is done to get a device
4494 order compati 4260 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 4261 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 4262 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 4263 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 4264 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 4265 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 4266 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 4267 based on its parent bus. Also set MRRS (Max
4502 Read Request 4268 Read Request Size) to the largest supported
4503 value (no lar 4269 value (no larger than the MPS that the device
4504 or bus can su 4270 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 4271 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 4272 every device is guaranteed to support. This
4507 configuration 4273 configuration allows peer-to-peer DMA between
4508 any pair of d 4274 any pair of devices, possibly at the cost of
4509 reduced perfo 4275 reduced performance. This also guarantees
4510 that hot-adde 4276 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 4277 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 4278 reserved for the CardBus bridge's IO window.
4513 The default v 4279 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 4280 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 4281 reserved for the CardBus bridge's memory
4516 window. The d 4282 window. The default value is 64 megabytes.
4517 resource_alignment= 4283 resource_alignment=
4518 Format: 4284 Format:
4519 [<order of ali 4285 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 4286 Specifies alignment and device to reassign
4521 aligned memor 4287 aligned memory resources. How to
4522 specify the d 4288 specify the device is described above.
4523 If <order of 4289 If <order of align> is not specified,
4524 PAGE_SIZE is 4290 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 4291 A PCI-PCI bridge can be specified if resource
4526 windows need 4292 windows need to be expanded.
4527 To specify th 4293 To specify the alignment for several
4528 instances of 4294 instances of a device, the PCI vendor,
4529 device, subve 4295 device, subvendor, and subdevice may be
4530 specified, e. 4296 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 4297 for 4096-byte alignment.
4532 ecrc= Enable/disabl 4298 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 4299 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 4300 bios: Use BIOS/firmware settings. This is the
4537 the default. 4301 the default.
4538 off: Turn ECR 4302 off: Turn ECRC off
4539 on: Turn ECRC 4303 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 4304 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 4305 reserved for hotplug bridge's IO window.
4542 Default size 4306 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 4307 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 4308 reserved for hotplug bridge's MMIO window.
4545 Default size 4309 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 4310 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 4311 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 4312 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 4313 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 4314 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 4315 MMIO_PREF window.
4552 Default size 4316 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 4317 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 4318 reserved for buses below a hotplug bridge.
4555 Default is 1. 4319 Default is 1.
4556 realloc= Enable/disabl 4320 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 4321 if allocations done by BIOS are too small to
4558 accommodate r 4322 accommodate resources required by all child
4559 devices. 4323 devices.
4560 off: Turn rea 4324 off: Turn realloc off
4561 on: Turn real 4325 on: Turn realloc on
4562 realloc same as reall 4326 realloc same as realloc=on
4563 noari do not use PC 4327 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 4328 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 4329 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 4330 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 4331 only look for one device below a PCIe downstream
4568 port. 4332 port.
4569 big_root_window Try to add a 4333 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 4334 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 4335 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 4336 Adding the window is slightly risky (it may
4573 conflict with 4337 conflict with unreported devices), so this
4574 taints the ke 4338 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 4339 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 4340 Specify one or more PCI devices (in the format
4577 specified abo 4341 specified above) separated by semicolons.
4578 Each device s 4342 Each device specified will have the PCI ACS
4579 redirect capa 4343 redirect capabilities forced off which will
4580 allow P2P tra 4344 allow P2P traffic between devices through
4581 bridges witho 4345 bridges without forcing it upstream. Note:
4582 this removes 4346 this removes isolation between devices and
4583 may put more 4347 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 4348 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 4349 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 4350 norid [S390] ignore the RID field and force use of
4619 one PCI domai 4351 one PCI domain per PCI function
4620 4352
4621 pcie_aspm= [PCIE] Forcibly enabl !! 4353 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 4354 Management.
4623 off Don't touch ASPM conf !! 4355 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 4356 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 4357 WARNING: Forcing ASPM on may cause system lockups.
4627 4358
4628 pcie_ports= [PCIE] PCIe port serv 4359 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 4360 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 4361 even if the platform doesn't give the OS permission to
4631 use them. This may c 4362 use them. This may cause conflicts if the platform
4632 also tries to use the 4363 also tries to use these services.
4633 dpc-native Use native PC 4364 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 4365 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 4366 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 4367 hotplug).
4637 4368
4638 pcie_port_pm= [PCIE] PCIe port powe 4369 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 4370 off Disable power management of all PCIe ports
4640 force Forcibly enable power 4371 force Forcibly enable power management of all PCIe ports
4641 4372
4642 pcie_pme= [PCIE,PM] Native PCIe 4373 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 4374 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 4375 all PCIe root ports use INTx for all services).
4645 4376
4646 pcmv= [HW,PCMCIA] BadgePAD 4377 pcmv= [HW,PCMCIA] BadgePAD 4
4647 4378
4648 pd_ignore_unused 4379 pd_ignore_unused
4649 [PM] 4380 [PM]
4650 Keep all power-domain 4381 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 4382 even if no driver has claimed them. This is useful
4652 for debug and develop 4383 for debug and development, but should not be
4653 needed on a platform 4384 needed on a platform with proper driver support.
4654 4385
>> 4386 pd. [PARIDE]
>> 4387 See Documentation/admin-guide/blockdev/paride.rst.
>> 4388
4655 pdcchassis= [PARISC,HW] Disable/E 4389 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4390 boot time.
4657 Format: { 0 | 1 } 4391 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4392 See arch/parisc/kernel/pdc_chassis.c
4659 4393
4660 percpu_alloc= [MM,EARLY] !! 4394 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4395 Currently supported values are "embed" and "page".
4663 Archs may support sub 4396 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4397 See comments in mm/percpu.c for details on each
4665 allocator. This para 4398 allocator. This parameter is primarily for debugging
4666 and performance compa 4399 and performance comparison.
4667 4400
>> 4401 pf. [PARIDE]
>> 4402 See Documentation/admin-guide/blockdev/paride.rst.
>> 4403
>> 4404 pg. [PARIDE]
>> 4405 See Documentation/admin-guide/blockdev/paride.rst.
>> 4406
4668 pirq= [SMP,APIC] Manual mp- 4407 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 4408 See Documentation/x86/i386/IO-APIC.rst.
4670 4409
4671 plip= [PPT,NET] Parallel po 4410 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4411 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4412 See also Documentation/admin-guide/parport.rst.
4674 4413
4675 pmtmr= [X86] Manual setup of 4414 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4415 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4416 e.g. pmtmr=0x508
4678 4417
4679 pmu_override= [PPC] Override the PM 4418 pmu_override= [PPC] Override the PMU.
4680 This option takes ove 4419 This option takes over the PMU facility, so it is no
4681 longer usable by perf 4420 longer usable by perf. Setting this option starts the
4682 PMU counters by setti 4421 PMU counters by setting MMCR0 to 0 (the FC bit is
4683 cleared). If a number 4422 cleared). If a number is given, then MMCR1 is set to
4684 that number, otherwis 4423 that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4685 remains 0. 4424 remains 0.
4686 4425
4687 pm_debug_messages [SUSPEND,KNL] 4426 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4427 Enable suspend/resume debug messages during boot up.
4689 4428
4690 pnp.debug=1 [PNP] 4429 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4430 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4431 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4432 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4433 current resource usage; turning this on also shows
4695 possible settings and 4434 possible settings and some assignment information.
4696 4435
4697 pnpacpi= [ACPI] 4436 pnpacpi= [ACPI]
4698 { off } 4437 { off }
4699 4438
4700 pnpbios= [ISAPNP] 4439 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4440 { on | off | curr | res | no-curr | no-res }
4702 4441
4703 pnp_reserve_irq= 4442 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4443 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4444
4706 pnp_reserve_dma= 4445 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4446 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4447
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4448 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4449 Ranges are in pairs (I/O port base and size).
4711 4450
4712 pnp_reserve_mem= 4451 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4452 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4453 autoconfiguration.
4715 Ranges are in pairs ( 4454 Ranges are in pairs (memory base and size).
4716 4455
4717 ports= [IP_VS_FTP] IPVS ftp 4456 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4457 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4458 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4459 may be specified.
4721 Format: <port>,<port> 4460 Format: <port>,<port>....
4722 4461
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 4462 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4463 It specifically disables cpuidle and sets the
4730 platform machine desc 4464 platform machine description specific power_save
4731 function to NULL. On 4465 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4466 execution priority.
4733 4467
4734 ppc_strict_facility_enable 4468 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4469 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4470 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4471 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4472 There is some performance impact when enabling this.
4739 4473
4740 ppc_tm= [PPC,EARLY] !! 4474 ppc_tm= [PPC]
4741 Format: {"off"} 4475 Format: {"off"}
4742 Disable Hardware Tran 4476 Disable Hardware Transactional Memory
4743 4477
4744 preempt= [KNL] 4478 preempt= [KNL]
4745 Select preemption mod 4479 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4480 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4481 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4482 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4483 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4484
4753 print-fatal-signals= 4485 print-fatal-signals=
4754 [KNL] debug: print fa 4486 [KNL] debug: print fatal signals
4755 4487
4756 If enabled, warn abou 4488 If enabled, warn about various signal handling
4757 related application a 4489 related application anomalies: too many signals,
4758 too many POSIX.1 time 4490 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4491 coredump - etc.
4760 4492
4761 If you hit the warnin 4493 If you hit the warning due to signal overflow,
4762 you might want to try 4494 you might want to try "ulimit -i unlimited".
4763 4495
4764 default: off. 4496 default: off.
4765 4497
4766 printk.always_kmsg_dump= 4498 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4499 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4500 panics
4769 Format: <bool> (1/Y/ 4501 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4502 default: disabled
4771 4503
4772 printk.console_no_auto_verbose= 4504 printk.console_no_auto_verbose=
4773 Disable console logle 4505 Disable console loglevel raise on oops, panic
4774 or lockdep-detected i 4506 or lockdep-detected issues (only if lock debug is on).
4775 With an exception to 4507 With an exception to setups with low baudrate on
4776 serial console, keepi 4508 serial console, keeping this 0 is a good choice
4777 in order to provide m 4509 in order to provide more debug information.
4778 Format: <bool> 4510 Format: <bool>
4779 default: 0 (auto_verb 4511 default: 0 (auto_verbose is enabled)
4780 4512
4781 printk.devkmsg={on,off,ratelimit} 4513 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4514 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4515 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4516 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4517 ratelimit - ratelimit the logging
4786 Default: ratelimit 4518 Default: ratelimit
4787 4519
4788 printk.time= Show timing data pref 4520 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4521 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4522
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] 4523 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4524 Limit processor to maximum C-state
4803 max_cstate=9 override 4525 max_cstate=9 overrides any DMI blacklist limit.
4804 4526
4805 processor.nocst [HW,ACPI] 4527 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4528 Ignore the _CST method to determine C-states,
4807 instead using the leg 4529 instead using the legacy FADT method
4808 4530
4809 profile= [KNL] Enable kernel p 4531 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4532 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4533 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4534 [defaults to kernel profiling]
4813 Param: "schedule" - p 4535 Param: "schedule" - profile schedule points.
>> 4536 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4537 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4538 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4539 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4540 statistical time based profiling.
4817 4541
4818 prompt_ramdisk= [RAM] [Deprecated] 4542 prompt_ramdisk= [RAM] [Deprecated]
4819 4543
4820 prot_virt= [S390] enable hosting 4544 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4545 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4546 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4547 Format: <bool>
4826 4548
4827 psi= [KNL] Enable or disab 4549 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4550 tracking.
4829 Format: <bool> 4551 Format: <bool>
4830 4552
4831 psmouse.proto= [HW,MOUSE] Highest PS 4553 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4554 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4555 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4556 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4557 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4558 Try to reset the device after so many bad packets
4837 (0 = never). 4559 (0 = never).
4838 psmouse.resolution= 4560 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4561 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4562 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4563 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4564 0 = disabled, 1 = enabled (default).
4843 4565
4844 pstore.backend= Specify the name of t 4566 pstore.backend= Specify the name of the pstore backend to use
4845 4567
>> 4568 pt. [PARIDE]
>> 4569 See Documentation/admin-guide/blockdev/paride.rst.
>> 4570
4846 pti= [X86-64] Control Page 4571 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4572 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4573 removes hardening, but improves performance of
4849 system calls and inte 4574 system calls and interrupts.
4850 4575
4851 on - unconditionall 4576 on - unconditionally enable
4852 off - unconditionall 4577 off - unconditionally disable
4853 auto - kernel detects 4578 auto - kernel detects whether your CPU model is
4854 vulnerable to 4579 vulnerable to issues that PTI mitigates
4855 4580
4856 Not specifying this o 4581 Not specifying this option is equivalent to pti=auto.
4857 4582
>> 4583 nopti [X86-64]
>> 4584 Equivalent to pti=off
>> 4585
4858 pty.legacy_count= 4586 pty.legacy_count=
4859 [KNL] Number of legac 4587 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4588 default number.
4861 4589
4862 quiet [KNL,EARLY] Disable m !! 4590 quiet [KNL] Disable most log messages
4863 4591
4864 r128= [HW,DRM] 4592 r128= [HW,DRM]
4865 4593
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 4594 raid= [HW,RAID]
4871 See Documentation/adm 4595 See Documentation/admin-guide/md.rst.
4872 4596
4873 ramdisk_size= [RAM] Sizes of RAM di 4597 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4598 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4599
4876 ramdisk_start= [RAM] RAM disk image 4600 ramdisk_start= [RAM] RAM disk image start address
4877 4601
4878 random.trust_cpu=off 4602 random.trust_cpu=off
4879 [KNL,EARLY] Disable t !! 4603 [KNL] Disable trusting the use of the CPU's
4880 random number generat 4604 random number generator (if available) to
4881 initialize the kernel 4605 initialize the kernel's RNG.
4882 4606
4883 random.trust_bootloader=off 4607 random.trust_bootloader=off
4884 [KNL,EARLY] Disable t !! 4608 [KNL] Disable trusting the use of the a seed
4885 passed by the bootloa 4609 passed by the bootloader (if available) to
4886 initialize the kernel 4610 initialize the kernel's RNG.
4887 4611
4888 randomize_kstack_offset= 4612 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4613 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4614 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4615 entropy, frustrating memory corruption attacks
4892 that depend on stack 4616 that depend on stack address determinism or
4893 cross-syscall address 4617 cross-syscall address exposures. This is only
4894 available on architec 4618 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4619 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4620 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4621 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4622
4899 ras=option[,option,...] [KNL] RAS-spe 4623 ras=option[,option,...] [KNL] RAS-specific options
4900 4624
4901 cec_disable [X86] 4625 cec_disable [X86]
4902 Disable the C 4626 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4627 see CONFIG_RAS_CEC help text.
4904 4628
4905 rcu_nocbs[=cpu-list] 4629 rcu_nocbs[=cpu-list]
4906 [KNL] The optional ar 4630 [KNL] The optional argument is a cpu list,
4907 as described above. 4631 as described above.
4908 4632
4909 In kernels built with 4633 In kernels built with CONFIG_RCU_NOCB_CPU=y,
4910 enable the no-callbac 4634 enable the no-callback CPU mode, which prevents
4911 such CPUs' callbacks 4635 such CPUs' callbacks from being invoked in
4912 softirq context. Inv 4636 softirq context. Invocation of such CPUs' RCU
4913 callbacks will instea 4637 callbacks will instead be offloaded to "rcuox/N"
4914 kthreads created for 4638 kthreads created for that purpose, where "x" is
4915 "p" for RCU-preempt, 4639 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4916 for the kthreads that 4640 for the kthreads that mediate grace periods; and
4917 "N" is the CPU number 4641 "N" is the CPU number. This reduces OS jitter on
4918 the offloaded CPUs, w 4642 the offloaded CPUs, which can be useful for HPC
4919 and real-time workloa 4643 and real-time workloads. It can also improve
4920 energy efficiency for 4644 energy efficiency for asymmetric multiprocessors.
4921 4645
4922 If a cpulist is passe 4646 If a cpulist is passed as an argument, the specified
4923 list of CPUs is set t 4647 list of CPUs is set to no-callback mode from boot.
4924 4648
4925 Otherwise, if the '=' 4649 Otherwise, if the '=' sign and the cpulist
4926 arguments are omitted 4650 arguments are omitted, no CPU will be set to
4927 no-callback mode from 4651 no-callback mode from boot but the mode may be
4928 toggled at runtime vi 4652 toggled at runtime via cpusets.
4929 4653
4930 Note that this argume 4654 Note that this argument takes precedence over
4931 the CONFIG_RCU_NOCB_C 4655 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4932 4656
4933 rcu_nocb_poll [KNL] 4657 rcu_nocb_poll [KNL]
4934 Rather than requiring 4658 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4659 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4660 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4661 make these kthreads poll for callbacks.
4938 This improves the rea 4662 This improves the real-time response for the
4939 offloaded CPUs by rel 4663 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4664 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4665 energy efficiency by requiring that the kthreads
4942 periodically wake up 4666 periodically wake up to do the polling.
4943 4667
4944 rcutree.blimit= [KNL] 4668 rcutree.blimit= [KNL]
4945 Set maximum number of 4669 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4670 process in one batch.
4947 4671
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] 4672 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4673 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4674 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4675 purposes, to verify correct tree setup.
4959 4676
4960 rcutree.gp_cleanup_delay= [KNL] 4677 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4678 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4679 RCU grace-period cleanup.
4963 4680
4964 rcutree.gp_init_delay= [KNL] 4681 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4682 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4683 RCU grace-period initialization.
4967 4684
4968 rcutree.gp_preinit_delay= [KNL] 4685 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4686 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4687 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4688 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4689 the rcu_node combining tree.
4973 4690
>> 4691 rcutree.use_softirq= [KNL]
>> 4692 If set to zero, move all RCU_SOFTIRQ processing to
>> 4693 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4694 value, meaning that RCU_SOFTIRQ is used by default.
>> 4695 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4696
>> 4697 But note that CONFIG_PREEMPT_RT=y kernels disable
>> 4698 this kernel boot parameter, forcibly setting it
>> 4699 to zero.
>> 4700
>> 4701 rcutree.rcu_fanout_exact= [KNL]
>> 4702 Disable autobalancing of the rcu_node combining
>> 4703 tree. This is used by rcutorture, and might
>> 4704 possibly be useful for architectures having high
>> 4705 cache-to-cache transfer latencies.
>> 4706
>> 4707 rcutree.rcu_fanout_leaf= [KNL]
>> 4708 Change the number of CPUs assigned to each
>> 4709 leaf rcu_node structure. Useful for very
>> 4710 large systems, which will choose the value 64,
>> 4711 and for NUMA systems with large remote-access
>> 4712 latencies, which will choose a value aligned
>> 4713 with the appropriate hardware boundaries.
>> 4714
>> 4715 rcutree.rcu_min_cached_objs= [KNL]
>> 4716 Minimum number of objects which are cached and
>> 4717 maintained per one CPU. Object size is equal
>> 4718 to PAGE_SIZE. The cache allows to reduce the
>> 4719 pressure to page allocator, also it makes the
>> 4720 whole algorithm to behave better in low memory
>> 4721 condition.
>> 4722
>> 4723 rcutree.rcu_delay_page_cache_fill_msec= [KNL]
>> 4724 Set the page-cache refill delay (in milliseconds)
>> 4725 in response to low-memory conditions. The range
>> 4726 of permitted values is in the range 0:100000.
>> 4727
4974 rcutree.jiffies_till_first_fqs= [KNL] 4728 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4729 Set delay from grace-period initialization to
4976 first attempt to forc 4730 first attempt to force quiescent states.
4977 Units are jiffies, mi 4731 Units are jiffies, minimum value is zero,
4978 and maximum value is 4732 and maximum value is HZ.
4979 4733
4980 rcutree.jiffies_till_next_fqs= [KNL] 4734 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4735 Set delay between subsequent attempts to force
4982 quiescent states. Un 4736 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4737 value is one, and maximum value is HZ.
4984 4738
4985 rcutree.jiffies_till_sched_qs= [KNL] 4739 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4740 Set required age in jiffies for a
4987 given grace period be 4741 given grace period before RCU starts
4988 soliciting quiescent- 4742 soliciting quiescent-state help from
4989 rcu_note_context_swit 4743 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4744 If not specified, the kernel will calculate
4991 a value based on the 4745 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4746 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4747 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4748 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4749 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4750 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4751 overwritten.
4998 4752
4999 rcutree.kthread_prio= [KNL,BOOT] 4753 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4754 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4755 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4756 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4757 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4758 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4759 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4760 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4761 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4762 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is 4763 When RCU_NOCB_CPU is set, also adjust the
5010 priority of NOCB call 4764 priority of NOCB callback kthreads.
5011 4765
>> 4766 rcutree.rcu_divisor= [KNL]
>> 4767 Set the shift-right count to use to compute
>> 4768 the callback-invocation batch limit bl from
>> 4769 the number of callbacks queued on this CPU.
>> 4770 The result will be bounded below by the value of
>> 4771 the rcutree.blimit kernel parameter. Every bl
>> 4772 callbacks, the softirq handler will exit in
>> 4773 order to allow the CPU to do other work.
>> 4774
>> 4775 Please note that this callback-invocation batch
>> 4776 limit applies only to non-offloaded callback
>> 4777 invocation. Offloaded callbacks are instead
>> 4778 invoked in the context of an rcuoc kthread, which
>> 4779 scheduler will preempt as it does any other task.
>> 4780
5012 rcutree.nocb_nobypass_lim_per_jiffy= 4781 rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5013 On callback-offloaded 4782 On callback-offloaded (rcu_nocbs) CPUs,
5014 RCU reduces the lock 4783 RCU reduces the lock contention that would
5015 otherwise be caused b 4784 otherwise be caused by callback floods through
5016 use of the ->nocb_byp 4785 use of the ->nocb_bypass list. However, in the
5017 common non-flooded ca 4786 common non-flooded case, RCU queues directly to
5018 the main ->cblist in 4787 the main ->cblist in order to avoid the extra
5019 overhead of the ->noc 4788 overhead of the ->nocb_bypass list and its lock.
5020 But if there are too 4789 But if there are too many callbacks queued during
5021 a single jiffy, RCU p 4790 a single jiffy, RCU pre-queues the callbacks into
5022 the ->nocb_bypass que 4791 the ->nocb_bypass queue. The definition of "too
5023 many" is supplied by 4792 many" is supplied by this kernel boot parameter.
5024 4793
5025 rcutree.nohz_full_patience_delay= [KN !! 4794 rcutree.rcu_nocb_gp_stride= [KNL]
5026 On callback-offloaded !! 4795 Set the number of NOCB callback kthreads in
5027 disturbing RCU unless !! 4796 each group, which defaults to the square root
5028 reached the specified !! 4797 of the number of CPUs. Larger numbers reduce
5029 Defaults to zero. La !! 4798 the wakeup overhead on the global grace-period
5030 at five seconds. All !! 4799 kthread, but increases that same overhead on
5031 to the nearest value !! 4800 each group's NOCB grace-period kthread.
5032 4801
5033 rcutree.qhimark= [KNL] 4802 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4803 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4804 batch limiting is disabled.
5036 4805
5037 rcutree.qlowmark= [KNL] 4806 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4807 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4808 batch limiting is re-enabled.
5040 4809
5041 rcutree.qovld= [KNL] 4810 rcutree.qovld= [KNL]
5042 Set threshold of queu 4811 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4812 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4813 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4814 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4815 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4816 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4817 disable more aggressive help enlistment.
5049 4818
5050 rcutree.rcu_delay_page_cache_fill_mse <<
5051 Set the page-cache re <<
5052 in response to low-me <<
5053 of permitted values i <<
5054 <<
5055 rcutree.rcu_divisor= [KNL] <<
5056 Set the shift-right c <<
5057 the callback-invocati <<
5058 the number of callbac <<
5059 The result will be bo <<
5060 the rcutree.blimit ke <<
5061 callbacks, the softir <<
5062 order to allow the CP <<
5063 <<
5064 Please note that this <<
5065 limit applies only to <<
5066 invocation. Offloade <<
5067 invoked in the contex <<
5068 scheduler will preemp <<
5069 <<
5070 rcutree.rcu_fanout_exact= [KNL] <<
5071 Disable autobalancing <<
5072 tree. This is used b <<
5073 possibly be useful fo <<
5074 cache-to-cache transf <<
5075 <<
5076 rcutree.rcu_fanout_leaf= [KNL] <<
5077 Change the number of <<
5078 leaf rcu_node structu <<
5079 large systems, which <<
5080 and for NUMA systems <<
5081 latencies, which will <<
5082 with the appropriate <<
5083 <<
5084 rcutree.rcu_min_cached_objs= [KNL] <<
5085 Minimum number of obj <<
5086 maintained per one CP <<
5087 to PAGE_SIZE. The cac <<
5088 pressure to page allo <<
5089 whole algorithm to be <<
5090 condition. <<
5091 <<
5092 rcutree.rcu_nocb_gp_stride= [KNL] <<
5093 Set the number of NOC <<
5094 each group, which def <<
5095 of the number of CPUs <<
5096 the wakeup overhead o <<
5097 kthread, but increase <<
5098 each group's NOCB gra <<
5099 <<
5100 rcutree.rcu_kick_kthreads= [KNL] 4819 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4820 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4821 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4822 it should at force-quiescent-state time.
5104 This wake_up() will b 4823 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4824 WARN_ONCE() splat and an ftrace_dump().
5106 4825
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] 4826 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4827 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4828 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4829 in microseconds. This defaults to zero.
5118 Larger delays increas 4830 Larger delays increase the probability of
5119 catching RCU pointer 4831 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4832 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4833 rcu_read_unlock() has completed.
5122 4834
5123 rcutree.sysrq_rcu= [KNL] 4835 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4836 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4837 rcu_node tree with an eye towards determining
5126 why a new grace perio 4838 why a new grace period has not yet started.
5127 4839
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] 4840 rcuscale.gp_async= [KNL]
5158 Measure performance o 4841 Measure performance of asynchronous
5159 grace-period primitiv 4842 grace-period primitives such as call_rcu().
5160 4843
5161 rcuscale.gp_async_max= [KNL] 4844 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4845 Specify the maximum number of outstanding
5163 callbacks per writer 4846 callbacks per writer thread. When a writer
5164 thread exceeds this l 4847 thread exceeds this limit, it invokes the
5165 corresponding flavor 4848 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4849 previously posted callbacks to drain.
5167 4850
5168 rcuscale.gp_exp= [KNL] 4851 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4852 Measure performance of expedited synchronous
5170 grace-period primitiv 4853 grace-period primitives.
5171 4854
5172 rcuscale.holdoff= [KNL] 4855 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4856 Set test-start holdoff period. The purpose of
5174 this parameter is to 4857 this parameter is to delay the start of the
5175 test until boot compl 4858 test until boot completes in order to avoid
5176 interference. 4859 interference.
5177 4860
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] 4861 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4862 Set to measure performance of kfree_rcu() flooding.
5189 4863
5190 rcuscale.kfree_rcu_test_double= [KNL] 4864 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 4865 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 4866 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 4867 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 4868 and double-argument variants are tested.
5195 4869
5196 rcuscale.kfree_rcu_test_single= [KNL] 4870 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 4871 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 4872 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 4873 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 4874 and double-argument variants are tested.
5201 4875
5202 rcuscale.kfree_nthreads= [KNL] 4876 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4877 The number of threads running loops of kfree_rcu().
5204 4878
5205 rcuscale.kfree_alloc_num= [KNL] 4879 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4880 Number of allocations and frees done in an iteration.
5207 4881
5208 rcuscale.kfree_loops= [KNL] 4882 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4883 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4884 of allocations and frees.
5211 4885
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] 4886 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4887 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4888 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4889 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4890 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4891 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4892 A value of "n" less than or equal to -N selects
5225 a single reader. 4893 a single reader.
5226 4894
5227 rcuscale.nwriters= [KNL] 4895 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4896 Set number of RCU writers. The values operate
5229 the same as for rcusc 4897 the same as for rcuscale.nreaders.
5230 N, where N is the num 4898 N, where N is the number of CPUs
5231 4899
5232 rcuscale.scale_type= [KNL] !! 4900 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4901 Specify the RCU implementation to test.
5234 4902
5235 rcuscale.shutdown= [KNL] 4903 rcuscale.shutdown= [KNL]
5236 Shut the system down 4904 Shut the system down after performance tests
5237 complete. This is us 4905 complete. This is useful for hands-off automated
5238 testing. 4906 testing.
5239 4907
5240 rcuscale.verbose= [KNL] 4908 rcuscale.verbose= [KNL]
5241 Enable additional pri 4909 Enable additional printk() statements.
5242 4910
5243 rcuscale.writer_holdoff= [KNL] 4911 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4912 Write-side holdoff between grace periods,
5245 in microseconds. The 4913 in microseconds. The default of zero says
5246 no holdoff. 4914 no holdoff.
5247 4915
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] 4916 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4917 Set duration of force_quiescent_state bursts
5255 in microseconds. 4918 in microseconds.
5256 4919
5257 rcutorture.fqs_holdoff= [KNL] 4920 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4921 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4922 in microseconds.
5260 4923
5261 rcutorture.fqs_stutter= [KNL] 4924 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4925 Set wait time between force_quiescent_state bursts
5263 in seconds. 4926 in seconds.
5264 4927
5265 rcutorture.fwd_progress= [KNL] 4928 rcutorture.fwd_progress= [KNL]
5266 Specifies the number 4929 Specifies the number of kthreads to be used
5267 for RCU grace-period 4930 for RCU grace-period forward-progress testing
5268 for the types of RCU 4931 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread 4932 Defaults to 1 kthread, values less than zero or
5270 greater than the numb 4933 greater than the number of CPUs cause the number
5271 of CPUs to be used. 4934 of CPUs to be used.
5272 4935
5273 rcutorture.fwd_progress_div= [KNL] 4936 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4937 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4938 period to do tight-loop forward-progress testing.
5276 4939
5277 rcutorture.fwd_progress_holdoff= [KNL 4940 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4941 Number of seconds to wait between successive
5279 forward-progress test 4942 forward-progress tests.
5280 4943
5281 rcutorture.fwd_progress_need_resched= 4944 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4945 Enclose cond_resched() calls within checks for
5283 need_resched() during 4946 need_resched() during tight-loop forward-progress
5284 testing. 4947 testing.
5285 4948
5286 rcutorture.gp_cond= [KNL] 4949 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4950 Use conditional/asynchronous update-side
5288 primitives, if availa 4951 primitives, if available.
5289 4952
5290 rcutorture.gp_exp= [KNL] 4953 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4954 Use expedited update-side primitives, if available.
5292 4955
5293 rcutorture.gp_normal= [KNL] 4956 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4957 Use normal (non-expedited) asynchronous
5295 update-side primitive 4958 update-side primitives, if available.
5296 4959
5297 rcutorture.gp_sync= [KNL] 4960 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4961 Use normal (non-expedited) synchronous
5299 update-side primitive 4962 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4963 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4964 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4965 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4966 they are all non-zero.
5304 4967
5305 rcutorture.irqreader= [KNL] 4968 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4969 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4970 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4971 flavors take kindly to this sort of thing.
5309 4972
5310 rcutorture.leakpointer= [KNL] 4973 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4974 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4975 This can of course result in splats, and is
5313 intended to test the 4976 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4977 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4978 such leaks.
5316 4979
5317 rcutorture.n_barrier_cbs= [KNL] 4980 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4981 Set callbacks/threads for rcu_barrier() testing.
5319 4982
5320 rcutorture.nfakewriters= [KNL] 4983 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4984 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4985 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4986 test, hence the "fake".
5324 4987
5325 rcutorture.nocbs_nthreads= [KNL] 4988 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 4989 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 4990 Zero (the default) disables toggling.
5328 4991
5329 rcutorture.nocbs_toggle= [KNL] 4992 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 4993 Set the delay in milliseconds between successive
5331 callback-offload togg 4994 callback-offload toggling attempts.
5332 4995
5333 rcutorture.nreaders= [KNL] 4996 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 4997 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 4998 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 4999 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 5000 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 5001 (the number of CPUs), -3 selects N+1, and so on.
5339 5002
5340 rcutorture.object_debug= [KNL] 5003 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 5004 Enable debug-object double-call_rcu() testing.
5342 5005
5343 rcutorture.onoff_holdoff= [KNL] 5006 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 5007 Set time (s) after boot for CPU-hotplug testing.
5345 5008
5346 rcutorture.onoff_interval= [KNL] 5009 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 5010 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 5011 or zero to disable CPU-hotplug testing.
5349 5012
5350 rcutorture.read_exit= [KNL] 5013 rcutorture.read_exit= [KNL]
5351 Set the number of rea 5014 Set the number of read-then-exit kthreads used
5352 to test the interacti 5015 to test the interaction of RCU updaters and
5353 task-exit processing. 5016 task-exit processing.
5354 5017
5355 rcutorture.read_exit_burst= [KNL] 5018 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 5019 The number of times in a given read-then-exit
5357 episode that a set of 5020 episode that a set of read-then-exit kthreads
5358 is spawned. 5021 is spawned.
5359 5022
5360 rcutorture.read_exit_delay= [KNL] 5023 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 5024 The delay, in seconds, between successive
5362 read-then-exit testin 5025 read-then-exit testing episodes.
5363 5026
5364 rcutorture.shuffle_interval= [KNL] 5027 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 5028 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 5029 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 5030 during the rcutorture test.
5368 5031
5369 rcutorture.shutdown_secs= [KNL] 5032 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 5033 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 5034 is useful for hands-off automated testing.
5372 5035
5373 rcutorture.stall_cpu= [KNL] 5036 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 5037 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 5038 warnings, zero to disable.
5376 5039
5377 rcutorture.stall_cpu_block= [KNL] 5040 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 5041 Sleep while stalling if set. This will result
5379 in warnings from pree !! 5042 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 5043 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 5044
5391 rcutorture.stall_cpu_holdoff= [KNL] 5045 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 5046 Time to wait (s) after boot before inducing stall.
5393 5047
5394 rcutorture.stall_cpu_irqsoff= [KNL] 5048 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 5049 Disable interrupts while stalling if set.
5396 5050
5397 rcutorture.stall_gp_kthread= [KNL] 5051 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 5052 Duration (s) of forced sleep within RCU
5399 grace-period kthread 5053 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 5054 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 5055 and stall_gp_kthread are specified, the
5402 kthread is starved fi 5056 kthread is starved first, then the CPU.
5403 5057
5404 rcutorture.stat_interval= [KNL] 5058 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 5059 Time (s) between statistics printk()s.
5406 5060
5407 rcutorture.stutter= [KNL] 5061 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 5062 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 5063 five seconds causes the test to run for five seconds,
5410 wait for five seconds 5064 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 5065 ability to transition abruptly to and from idle.
5412 5066
5413 rcutorture.test_boost= [KNL] 5067 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 5068 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 5069 "Maybe" means test if the RCU implementation
5416 under test support RC 5070 under test support RCU priority boosting.
5417 5071
5418 rcutorture.test_boost_duration= [KNL] 5072 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 5073 Duration (s) of each individual boost test.
5420 5074
5421 rcutorture.test_boost_interval= [KNL] 5075 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 5076 Interval (s) between each boost test.
5423 5077
5424 rcutorture.test_no_idle_hz= [KNL] 5078 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 5079 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 5080 rcutorture.shuffle_interval parameter.
5427 5081
5428 rcutorture.torture_type= [KNL] 5082 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 5083 Specify the RCU implementation to test.
5430 5084
5431 rcutorture.verbose= [KNL] 5085 rcutorture.verbose= [KNL]
5432 Enable additional pri 5086 Enable additional printk() statements.
5433 5087
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 5088 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 5089 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 5090 stall warning.
5437 5091
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 5092 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 5093 Suppress RCU CPU stall warning messages.
5446 5094
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 5095 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 5096 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 5097 rcutorture writer stall warnings that occur
5450 during early boot, th 5098 during early boot, that is, during the time
5451 before the init task 5099 before the init task is spawned.
5452 5100
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 5101 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 5102 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon 5103 The value is in seconds and the maximum allowed
5456 value is 300 seconds. 5104 value is 300 seconds.
5457 5105
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ 5106 rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5459 Set timeout for exped 5107 Set timeout for expedited RCU CPU stall warning
5460 messages. The value 5108 messages. The value is in milliseconds
5461 and the maximum allow 5109 and the maximum allowed value is 21000
5462 milliseconds. Please 5110 milliseconds. Please note that this value is
5463 adjusted to an arch t 5111 adjusted to an arch timer tick resolution.
5464 Setting this to zero 5112 Setting this to zero causes the value from
5465 rcupdate.rcu_cpu_stal 5113 rcupdate.rcu_cpu_stall_timeout to be used (after
5466 conversion from secon 5114 conversion from seconds to milliseconds).
5467 5115
5468 rcupdate.rcu_cpu_stall_cputime= [KNL] <<
5469 Provide statistics on <<
5470 interrupts and tasks <<
5471 multiple continuous R <<
5472 begin at half of the <<
5473 <<
5474 rcupdate.rcu_exp_stall_task_details= <<
5475 Print stack dumps of <<
5476 current expedited RCU <<
5477 expedited RCU CPU sta <<
5478 <<
5479 rcupdate.rcu_expedited= [KNL] 5116 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 5117 Use expedited grace-period primitives, for
5481 example, synchronize_ 5118 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 5119 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 5120 but can increase CPU utilization, degrade
5484 real-time latency, an 5121 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 5122 No effect on CONFIG_TINY_RCU kernels.
5486 5123
5487 rcupdate.rcu_normal= [KNL] 5124 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 5125 Use only normal grace-period primitives,
5489 for example, synchron 5126 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 5127 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 5128 real-time latency, CPU utilization, and
5492 energy efficiency, bu 5129 energy efficiency, but can expose users to
5493 increased grace-perio 5130 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 5131 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 5132 CONFIG_TINY_RCU kernels.
5496 5133
5497 rcupdate.rcu_normal_after_boot= [KNL] 5134 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 5135 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 5136 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 5137 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 5138 on CONFIG_TINY_RCU kernels.
5502 5139
5503 But note that CONFIG_ 5140 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 5141 this kernel boot parameter, forcibly setting
5505 it to the value one, 5142 it to the value one, that is, converting any
5506 post-boot attempt at 5143 post-boot attempt at an expedited RCU grace
5507 period to instead use 5144 period to instead use normal non-expedited
5508 grace-period processi 5145 grace-period processing.
5509 5146
5510 rcupdate.rcu_task_collapse_lim= [KNL] 5147 rcupdate.rcu_task_collapse_lim= [KNL]
5511 Set the maximum numbe 5148 Set the maximum number of callbacks present
5512 at the beginning of a 5149 at the beginning of a grace period that allows
5513 the RCU Tasks flavors 5150 the RCU Tasks flavors to collapse back to using
5514 a single callback que 5151 a single callback queue. This switching only
5515 occurs when rcupdate. 5152 occurs when rcupdate.rcu_task_enqueue_lim is
5516 set to the default va 5153 set to the default value of -1.
5517 5154
5518 rcupdate.rcu_task_contend_lim= [KNL] 5155 rcupdate.rcu_task_contend_lim= [KNL]
5519 Set the minimum numbe 5156 Set the minimum number of callback-queuing-time
5520 lock-contention event 5157 lock-contention events per jiffy required to
5521 cause the RCU Tasks f 5158 cause the RCU Tasks flavors to switch to per-CPU
5522 callback queuing. Th 5159 callback queuing. This switching only occurs
5523 when rcupdate.rcu_tas 5160 when rcupdate.rcu_task_enqueue_lim is set to
5524 the default value of 5161 the default value of -1.
5525 5162
5526 rcupdate.rcu_task_enqueue_lim= [KNL] 5163 rcupdate.rcu_task_enqueue_lim= [KNL]
5527 Set the number of cal 5164 Set the number of callback queues to use for the
5528 RCU Tasks family of R 5165 RCU Tasks family of RCU flavors. The default
5529 of -1 allows this to 5166 of -1 allows this to be automatically (and
5530 dynamically) adjusted 5167 dynamically) adjusted. This parameter is intended
5531 for use in testing. 5168 for use in testing.
5532 5169
5533 rcupdate.rcu_task_ipi_delay= [KNL] 5170 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 5171 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 5172 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 5173 of a given grace period. Setting a large
5537 number avoids disturb 5174 number avoids disturbing real-time workloads,
5538 but lengthens grace p 5175 but lengthens grace periods.
5539 5176
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] 5177 rcupdate.rcu_task_stall_info= [KNL]
5548 Set initial timeout i 5178 Set initial timeout in jiffies for RCU task stall
5549 informational message 5179 informational messages, which give some indication
5550 of the problem for th 5180 of the problem for those not patient enough to
5551 wait for ten minutes. 5181 wait for ten minutes. Informational messages are
5552 only printed prior to 5182 only printed prior to the stall-warning message
5553 for a given grace per 5183 for a given grace period. Disable with a value
5554 less than or equal to 5184 less than or equal to zero. Defaults to ten
5555 seconds. A change in 5185 seconds. A change in value does not take effect
5556 until the beginning o 5186 until the beginning of the next grace period.
5557 5187
5558 rcupdate.rcu_task_stall_info_mult= [K 5188 rcupdate.rcu_task_stall_info_mult= [KNL]
5559 Multiplier for time i 5189 Multiplier for time interval between successive
5560 RCU task stall inform 5190 RCU task stall informational messages for a given
5561 RCU tasks grace perio 5191 RCU tasks grace period. This value is clamped
5562 to one through ten, i 5192 to one through ten, inclusive. It defaults to
5563 the value three, so t 5193 the value three, so that the first informational
5564 message is printed 10 5194 message is printed 10 seconds into the grace
5565 period, the second at 5195 period, the second at 40 seconds, the third at
5566 160 seconds, and then 5196 160 seconds, and then the stall warning at 600
5567 seconds would prevent 5197 seconds would prevent a fourth at 640 seconds.
5568 5198
5569 rcupdate.rcu_task_stall_timeout= [KNL 5199 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie 5200 Set timeout in jiffies for RCU task stall
5571 warning messages. Di 5201 warning messages. Disable with a value less
5572 than or equal to zero 5202 than or equal to zero. Defaults to ten minutes.
5573 A change in value doe 5203 A change in value does not take effect until
5574 the beginning of the 5204 the beginning of the next grace period.
5575 5205
5576 rcupdate.rcu_tasks_lazy_ms= [KNL] <<
5577 Set timeout in millis <<
5578 callback batching for <<
5579 A negative value will <<
5580 of zero will disable <<
5581 always disabled for s <<
5582 <<
5583 rcupdate.rcu_tasks_rude_lazy_ms= [KNL <<
5584 Set timeout in millis <<
5585 Rude asynchronous cal <<
5586 call_rcu_tasks_rude() <<
5587 will take the default <<
5588 disable batching. Ba <<
5589 for synchronize_rcu_t <<
5590 <<
5591 rcupdate.rcu_tasks_trace_lazy_ms= [KN <<
5592 Set timeout in millis <<
5593 Trace asynchronous ca <<
5594 call_rcu_tasks_trace( <<
5595 will take the default <<
5596 disable batching. Ba <<
5597 for synchronize_rcu_t <<
5598 <<
5599 rcupdate.rcu_self_test= [KNL] 5206 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 5207 Run the RCU early boot self tests
5601 5208
5602 rdinit= [KNL] 5209 rdinit= [KNL]
5603 Format: <full_path> 5210 Format: <full_path>
5604 Run specified binary 5211 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 5212 used for early userspace startup. See initrd.
5606 5213
5607 rdrand= [X86,EARLY] !! 5214 rdrand= [X86]
5608 force - Override the 5215 force - Override the decision by the kernel to hide the
5609 advertisement 5216 advertisement of RDRAND support (this affects
5610 certain AMD p 5217 certain AMD processors because of buggy BIOS
5611 support, spec 5218 support, specifically around the suspend/resume
5612 path). 5219 path).
5613 5220
5614 rdt= [HW,X86,RDT] 5221 rdt= [HW,X86,RDT]
5615 Turn on/off individua 5222 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 5223 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 5224 mba.
5618 E.g. to turn on cmt a 5225 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 5226 rdt=cmt,!mba
5620 5227
5621 reboot= [KNL] 5228 reboot= [KNL]
5622 Format (x86 or x86_64 5229 Format (x86 or x86_64):
5623 [w[arm] | c[o 5230 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5624 [[,]s[mp]#### 5231 [[,]s[mp]#### \
5625 [[,]b[ios] | 5232 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 5233 [[,]f[orce]
5627 Where reboot_mode is 5234 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 5235 (prefix with 'panic_' to set mode for panic
5629 reboo 5236 reboot only),
5630 reboot_type is 5237 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 5238 reboot_force is either force or not specified,
5632 reboot_cpu is s 5239 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 5240 to be used for rebooting.
5634 5241
5635 refscale.holdoff= [KNL] 5242 refscale.holdoff= [KNL]
5636 Set test-start holdof 5243 Set test-start holdoff period. The purpose of
5637 this parameter is to 5244 this parameter is to delay the start of the
5638 test until boot compl 5245 test until boot completes in order to avoid
5639 interference. 5246 interference.
5640 5247
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] 5248 refscale.loops= [KNL]
5648 Set the number of loo 5249 Set the number of loops over the synchronization
5649 primitive under test. 5250 primitive under test. Increasing this number
5650 reduces noise due to 5251 reduces noise due to loop start/end overhead,
5651 but the default has a 5252 but the default has already reduced the per-pass
5652 noise to a handful of 5253 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 5254 x86 laptops.
5654 5255
5655 refscale.nreaders= [KNL] 5256 refscale.nreaders= [KNL]
5656 Set number of readers 5257 Set number of readers. The default value of -1
5657 selects N, where N is 5258 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 5259 of CPUs. A value of zero is an interesting choice.
5659 5260
5660 refscale.nruns= [KNL] 5261 refscale.nruns= [KNL]
5661 Set number of runs, e 5262 Set number of runs, each of which is dumped onto
5662 the console log. 5263 the console log.
5663 5264
5664 refscale.readdelay= [KNL] 5265 refscale.readdelay= [KNL]
5665 Set the read-side cri 5266 Set the read-side critical-section duration,
5666 measured in microseco 5267 measured in microseconds.
5667 5268
5668 refscale.scale_type= [KNL] 5269 refscale.scale_type= [KNL]
5669 Specify the read-prot 5270 Specify the read-protection implementation to test.
5670 5271
5671 refscale.shutdown= [KNL] 5272 refscale.shutdown= [KNL]
5672 Shut down the system 5273 Shut down the system at the end of the performance
5673 test. This defaults 5274 test. This defaults to 1 (shut it down) when
5674 refscale is built int 5275 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 5276 it running) when refscale is built as a module.
5676 5277
5677 refscale.verbose= [KNL] 5278 refscale.verbose= [KNL]
5678 Enable additional pri 5279 Enable additional printk() statements.
5679 5280
5680 refscale.verbose_batched= [KNL] 5281 refscale.verbose_batched= [KNL]
5681 Batch the additional 5282 Batch the additional printk() statements. If zero
5682 (the default) or nega 5283 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 5284 print every Nth verbose statement, where N is the value
5684 specified. 5285 specified.
5685 5286
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= 5287 relax_domain_level=
5694 [KNL, SMP] Set schedu 5288 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 5289 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 5290
5697 reserve= [KNL,BUGS] Force kern 5291 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 5292 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 5293 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 5294 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 5295 is assumed to be I/O ports; otherwise it is memory.
5702 5296
5703 reserve_mem= [RAM] !! 5297 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] 5298 Format: nn[KMG]
5727 Reserves a hole at th 5299 Reserves a hole at the top of the kernel virtual
5728 address space. 5300 address space.
5729 5301
5730 reset_devices [KNL] Force drivers t 5302 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 5303 during initialization.
5732 5304
5733 resume= [SWSUSP] 5305 resume= [SWSUSP]
5734 Specify the partition 5306 Specify the partition device for software suspend
5735 Format: 5307 Format:
5736 {/dev/<dev> | PARTUUI 5308 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 5309
5738 resume_offset= [SWSUSP] 5310 resume_offset= [SWSUSP]
5739 Specify the offset fr 5311 Specify the offset from the beginning of the partition
5740 given by "resume=" at 5312 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 5313 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 5314 See Documentation/power/swsusp-and-swap-files.rst
5743 5315
5744 resumedelay= [HIBERNATION] Delay ( 5316 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 5317 read the resume files
5746 5318
5747 resumewait [HIBERNATION] Wait (i 5319 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 5320 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 5321 (e.g. USB and MMC devices).
5750 5322
5751 retain_initrd [RAM] Keep initrd mem !! 5323 retain_initrd [RAM] Keep initrd memory after extraction
5752 be accessible via /sy <<
5753 5324
5754 retbleed= [X86] Control mitigat 5325 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 5326 Speculative Code Execution with Return Instructions)
5756 vulnerability. 5327 vulnerability.
5757 5328
5758 AMD-based UNRET and I 5329 AMD-based UNRET and IBPB mitigations alone do not stop
5759 sibling threads from 5330 sibling threads from influencing the predictions of other
5760 sibling threads. For 5331 sibling threads. For that reason, STIBP is used on pro-
5761 cessors that support 5332 cessors that support it, and mitigate SMT on processors
5762 that don't. 5333 that don't.
5763 5334
5764 off - no mit 5335 off - no mitigation
5765 auto - automa 5336 auto - automatically select a migitation
5766 auto,nosmt - automa 5337 auto,nosmt - automatically select a mitigation,
5767 disabl 5338 disabling SMT if necessary for
5768 the fu 5339 the full mitigation (only on Zen1
5769 and ol 5340 and older without STIBP).
5770 ibpb - On AMD 5341 ibpb - On AMD, mitigate short speculation
5771 window 5342 windows on basic block boundaries too.
5772 Safe, 5343 Safe, highest perf impact. It also
5773 enable 5344 enables STIBP if present. Not suitable
5774 on Int 5345 on Intel.
5775 ibpb,nosmt - Like " 5346 ibpb,nosmt - Like "ibpb" above but will disable SMT
5776 when S 5347 when STIBP is not available. This is
5777 the al 5348 the alternative for systems which do not
5778 have S 5349 have STIBP.
5779 unret - Force 5350 unret - Force enable untrained return thunks,
5780 only e 5351 only effective on AMD f15h-f17h based
5781 system 5352 systems.
5782 unret,nosmt - Like u 5353 unret,nosmt - Like unret, but will disable SMT when STIBP
5783 is not 5354 is not available. This is the alternative for
5784 system 5355 systems which do not have STIBP.
5785 5356
5786 Selecting 'auto' will 5357 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 5358 time according to the CPU.
5788 5359
5789 Not specifying this o 5360 Not specifying this option is equivalent to retbleed=auto.
5790 5361
5791 rfkill.default_state= 5362 rfkill.default_state=
5792 0 "airplane mode". All 5363 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 5364 etc. communication is blocked by default.
5794 1 Unblocked. 5365 1 Unblocked.
5795 5366
5796 rfkill.master_switch_mode= 5367 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 5368 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 5369 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 5370 blocked and the previous configuration.
5800 2 The "airplane mode" b 5371 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 5372 blocked and everything unblocked.
5802 5373
>> 5374 rhash_entries= [KNL,NET]
>> 5375 Set number of hash buckets for route cache
>> 5376
5803 ring3mwait=disable 5377 ring3mwait=disable
5804 [KNL] Disable ring 3 5378 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 5379 CPUs.
5806 5380
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 5381 ro [KNL] Mount root device read-only on boot
5815 5382
5816 rodata= [KNL,EARLY] !! 5383 rodata= [KNL]
5817 on Mark read-only kernel 5384 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 5385 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel 5386 full Mark read-only kernel memory and aliases as read-only
5820 [arm64] 5387 [arm64]
5821 5388
5822 rockchip.usb_uart 5389 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 5390 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 5391 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 5392 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 5393 port and the regular usb controller gets disabled.
5828 5394
5829 root= [KNL] Root filesystem 5395 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 5396 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 5397
5837 rootdelay= [KNL] Delay (in secon 5398 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 5399 mount the root filesystem
5839 5400
5840 rootflags= [KNL] Set root filesy 5401 rootflags= [KNL] Set root filesystem mount option string
5841 5402
5842 rootfstype= [KNL] Set root filesy 5403 rootfstype= [KNL] Set root filesystem type
5843 5404
5844 rootwait [KNL] Wait (indefinit 5405 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 5406 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 5407 (e.g. USB and MMC devices).
5847 5408
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 5409 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 5410 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 5411 Memory area to be used by remote processor image,
5855 managed by CMA. 5412 managed by CMA.
5856 5413
5857 rw [KNL] Mount root devi 5414 rw [KNL] Mount root device read-write on boot
5858 5415
5859 S [KNL] Run init in sin 5416 S [KNL] Run init in single mode
5860 5417
5861 s390_iommu= [HW,S390] 5418 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 5419 Set s390 IOTLB flushing mode
5863 strict 5420 strict
5864 With strict flushing !! 5421 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 5422 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 5423 which is faster.
5867 iommu.strict=1. <<
5868 5424
5869 s390_iommu_aperture= [KNL,S390] 5425 s390_iommu_aperture= [KNL,S390]
5870 Specifies the size of 5426 Specifies the size of the per device DMA address space
5871 accessible through th 5427 accessible through the DMA and IOMMU APIs as a decimal
5872 factor of the size of 5428 factor of the size of main memory.
5873 The default is 1 mean 5429 The default is 1 meaning that one can concurrently use
5874 as many DMA addresses 5430 as many DMA addresses as physical memory is installed,
5875 if supported by hardw 5431 if supported by hardware, and thus map all of memory
5876 once. With a value of 5432 once. With a value of 2 one can map all of memory twice
5877 and so on. As a speci 5433 and so on. As a special case a factor of 0 imposes no
5878 restrictions other th 5434 restrictions other than those given by hardware at the
5879 cost of significant a 5435 cost of significant additional memory use for tables.
5880 5436
5881 sa1100ir [NET] 5437 sa1100ir [NET]
5882 See drivers/net/irda/ 5438 See drivers/net/irda/sa1100_ir.c.
5883 5439
5884 sched_verbose [KNL,EARLY] Enables v !! 5440 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 5441
5886 schedstats= [KNL,X86] Enable or d 5442 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 5443 Allowed values are enable and disable. This feature
5888 incurs a small amount 5444 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 5445 but is useful for debugging and performance tuning.
5890 5446
5891 sched_thermal_decay_shift= 5447 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 5448 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 5449 pressure signal. Thermal pressure signal follows the
5895 default decay period 5450 default decay period of other scheduler pelt
5896 signals(usually 32 ms 5451 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 5452 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 5453 period for the thermal pressure signal by the shift
5899 value. 5454 value.
5900 i.e. with the default 5455 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 5456 sched_thermal_decay_shift thermal pressure decay pr
5902 1 5457 1 64 ms
5903 2 5458 2 128 ms
5904 and so on. 5459 and so on.
5905 Format: integer betwe 5460 Format: integer between 0 and 10
5906 Default is 0. 5461 Default is 0.
5907 5462
5908 scftorture.holdoff= [KNL] 5463 scftorture.holdoff= [KNL]
5909 Number of seconds to 5464 Number of seconds to hold off before starting
5910 test. Defaults to ze 5465 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 5466 to 10 seconds for built-in smp_call_function()
5912 tests. 5467 tests.
5913 5468
5914 scftorture.longwait= [KNL] 5469 scftorture.longwait= [KNL]
5915 Request ridiculously 5470 Request ridiculously long waits randomly selected
5916 up to the chosen limi 5471 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 5472 default) disables this feature. Please note
5918 that requesting even 5473 that requesting even small non-zero numbers of
5919 seconds can result in 5474 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 5475 softlockup complaints, and so on.
5921 5476
5922 scftorture.nthreads= [KNL] 5477 scftorture.nthreads= [KNL]
5923 Number of kthreads to 5478 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 5479 smp_call_function() family of functions.
5925 The default of -1 spe 5480 The default of -1 specifies a number of kthreads
5926 equal to the number o 5481 equal to the number of CPUs.
5927 5482
5928 scftorture.onoff_holdoff= [KNL] 5483 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 5484 Number seconds to wait after the start of the
5930 test before initiatin 5485 test before initiating CPU-hotplug operations.
5931 5486
5932 scftorture.onoff_interval= [KNL] 5487 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 5488 Number seconds to wait between successive
5934 CPU-hotplug operation 5489 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 5490 is the default) disables CPU-hotplug operations.
5936 5491
5937 scftorture.shutdown_secs= [KNL] 5492 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 5493 The number of seconds following the start of the
5939 test after which to s 5494 test after which to shut down the system. The
5940 default of zero avoid 5495 default of zero avoids shutting down the system.
5941 Non-zero values are u 5496 Non-zero values are useful for automated tests.
5942 5497
5943 scftorture.stat_interval= [KNL] 5498 scftorture.stat_interval= [KNL]
5944 The number of seconds 5499 The number of seconds between outputting the
5945 current test statisti 5500 current test statistics to the console. A value
5946 of zero disables stat 5501 of zero disables statistics output.
5947 5502
5948 scftorture.stutter_cpus= [KNL] 5503 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 5504 The number of jiffies to wait between each change
5950 to the set of CPUs un 5505 to the set of CPUs under test.
5951 5506
5952 scftorture.use_cpus_read_lock= [KNL] 5507 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 5508 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 5509 preempt_disable() to disable CPU hotplug
5955 while invoking one of 5510 while invoking one of the smp_call_function*()
5956 functions. 5511 functions.
5957 5512
5958 scftorture.verbose= [KNL] 5513 scftorture.verbose= [KNL]
5959 Enable additional pri 5514 Enable additional printk() statements.
5960 5515
5961 scftorture.weight_single= [KNL] 5516 scftorture.weight_single= [KNL]
5962 The probability weigh 5517 The probability weighting to use for the
5963 smp_call_function_sin 5518 smp_call_function_single() function with a zero
5964 "wait" parameter. A 5519 "wait" parameter. A value of -1 selects the
5965 default if all other 5520 default if all other weights are -1. However,
5966 if at least one weigh 5521 if at least one weight has some other value, a
5967 value of -1 will inst 5522 value of -1 will instead select a weight of zero.
5968 5523
5969 scftorture.weight_single_wait= [KNL] 5524 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 5525 The probability weighting to use for the
5971 smp_call_function_sin 5526 smp_call_function_single() function with a
5972 non-zero "wait" param 5527 non-zero "wait" parameter. See weight_single.
5973 5528
5974 scftorture.weight_many= [KNL] 5529 scftorture.weight_many= [KNL]
5975 The probability weigh 5530 The probability weighting to use for the
5976 smp_call_function_man 5531 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 5532 "wait" parameter. See weight_single.
5978 Note well that settin 5533 Note well that setting a high probability for
5979 this weighting can pl 5534 this weighting can place serious IPI load
5980 on the system. 5535 on the system.
5981 5536
5982 scftorture.weight_many_wait= [KNL] 5537 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 5538 The probability weighting to use for the
5984 smp_call_function_man 5539 smp_call_function_many() function with a
5985 non-zero "wait" param 5540 non-zero "wait" parameter. See weight_single
5986 and weight_many. 5541 and weight_many.
5987 5542
5988 scftorture.weight_all= [KNL] 5543 scftorture.weight_all= [KNL]
5989 The probability weigh 5544 The probability weighting to use for the
5990 smp_call_function_all 5545 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 5546 "wait" parameter. See weight_single and
5992 weight_many. 5547 weight_many.
5993 5548
5994 scftorture.weight_all_wait= [KNL] 5549 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 5550 The probability weighting to use for the
5996 smp_call_function_all 5551 smp_call_function_all() function with a
5997 non-zero "wait" param 5552 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5553 and weight_many.
5999 5554
6000 skew_tick= [KNL,EARLY] Offset th !! 5555 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5556 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5557 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5558 Format: { "0" | "1" }
6004 0 -- disable. (may be 5559 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5560 1 -- enable.
6006 Note: increases power 5561 Note: increases power consumption, thus should only be
6007 enabled if running ji 5562 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5563
6009 security= [SECURITY] Choose a l 5564 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5565 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5566 "lsm=" parameter.
6012 5567
6013 selinux= [SELINUX] Disable or 5568 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5569 Format: { "0" | "1" }
6015 See security/selinux/ 5570 See security/selinux/Kconfig help text.
6016 0 -- disable. 5571 0 -- disable.
6017 1 -- enable. 5572 1 -- enable.
6018 Default value is 1. 5573 Default value is 1.
6019 5574
>> 5575 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 5576 Format: { "0" | "1" }
>> 5577 See security/apparmor/Kconfig help text
>> 5578 0 -- disable.
>> 5579 1 -- enable.
>> 5580 Default value is set via kernel config option.
>> 5581
6020 serialnumber [BUGS=X86-32] 5582 serialnumber [BUGS=X86-32]
6021 5583
6022 sev=option[,option...] [X86-64] See D !! 5584 sev=option[,option...] [X86-64] See Documentation/x86/x86_64/boot-options.rst
6023 5585
6024 shapers= [NET] 5586 shapers= [NET]
6025 Maximal number of sha 5587 Maximal number of shapers.
6026 5588
6027 show_lapic= [APIC,X86] Advanced P !! 5589 simeth= [IA-64]
6028 Limit apic dumping. T !! 5590 simscsi=
6029 number of local apics !! 5591
6030 to set it to "all" by !! 5592 slram= [HW,MTD]
6031 Format: { 1 (default) !! 5593
6032 The parameter valid i !! 5594 slab_merge [MM]
6033 apic=verbose is speci !! 5595 Enable merging of slabs with similar size when the
6034 Example: apic=debug s !! 5596 kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
>> 5597
>> 5598 slab_nomerge [MM]
>> 5599 Disable merging of slabs with similar size. May be
>> 5600 necessary if there is some reason to distinguish
>> 5601 allocs to different slabs, especially in hardened
>> 5602 environments where the risk of heap overflows and
>> 5603 layout control by attackers can usually be
>> 5604 frustrated by disabling merging. This will reduce
>> 5605 most of the exposure of a heap attack to a single
>> 5606 cache (risks via metadata attacks are mostly
>> 5607 unchanged). Debug options disable merging on their
>> 5608 own.
>> 5609 For more information see Documentation/mm/slub.rst.
>> 5610
>> 5611 slab_max_order= [MM, SLAB]
>> 5612 Determines the maximum allowed order for slabs.
>> 5613 A high setting may cause OOMs due to memory
>> 5614 fragmentation. Defaults to 1 for systems with
>> 5615 more than 32MB of RAM, 0 otherwise.
6035 5616
6036 slab_debug[=options[,slabs][;[options !! 5617 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
6037 Enabling slab_debug a !! 5618 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 5619 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 5620 slub_debug can create guard zones around objects and
6040 may poison objects wh 5621 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 5622 last alloc / free. For more information see
6042 Documentation/mm/slub 5623 Documentation/mm/slub.rst.
6043 (slub_debug legacy na <<
6044 5624
6045 slab_max_order= [MM] !! 5625 slub_max_order= [MM, SLUB]
6046 Determines the maximu 5626 Determines the maximum allowed order for slabs.
6047 A high setting may ca 5627 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 5628 fragmentation. For more information see
6049 Documentation/mm/slub 5629 Documentation/mm/slub.rst.
6050 (slub_max_order legac <<
6051 5630
6052 slab_merge [MM] !! 5631 slub_min_objects= [MM, SLUB]
6053 Enable merging of sla <<
6054 kernel is built witho <<
6055 (slub_merge legacy na <<
6056 <<
6057 slab_min_objects= [MM] <<
6058 The minimum number of 5632 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 5633 increase the slab order up to slub_max_order to
6060 generate a sufficient 5634 generate a sufficiently large slab able to contain
6061 the number of objects 5635 the number of objects indicated. The higher the number
6062 of objects the smalle 5636 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 5637 and the less frequently locks need to be acquired.
6064 For more information 5638 For more information see Documentation/mm/slub.rst.
6065 (slub_min_objects leg <<
6066 5639
6067 slab_min_order= [MM] !! 5640 slub_min_order= [MM, SLUB]
6068 Determines the minimu 5641 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 5642 lower than slub_max_order.
6070 Documentation/mm/slub <<
6071 (slub_min_order legac <<
6072 <<
6073 slab_nomerge [MM] <<
6074 Disable merging of sl <<
6075 necessary if there is <<
6076 allocs to different s <<
6077 environments where th <<
6078 layout control by att <<
6079 frustrated by disabli <<
6080 most of the exposure <<
6081 cache (risks via meta <<
6082 unchanged). Debug opt <<
6083 own. <<
6084 For more information 5643 For more information see Documentation/mm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5644
6087 slram= [HW,MTD] !! 5645 slub_merge [MM, SLUB]
>> 5646 Same with slab_merge.
>> 5647
>> 5648 slub_nomerge [MM, SLUB]
>> 5649 Same with slab_nomerge. This is supported for legacy.
>> 5650 See slab_nomerge for more information.
6088 5651
6089 smart2= [HW] 5652 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5653 Format: <io1>[,<io2>[,...,<io8>]]
6091 5654
6092 smp.csd_lock_timeout= [KNL] 5655 smp.csd_lock_timeout= [KNL]
6093 Specify the period of 5656 Specify the period of time in milliseconds
6094 that smp_call_functio 5657 that smp_call_function() and friends will wait
6095 for a CPU to release 5658 for a CPU to release the CSD lock. This is
6096 useful when diagnosin 5659 useful when diagnosing bugs involving CPUs
6097 disabling interrupts 5660 disabling interrupts for extended periods
6098 of time. Defaults to 5661 of time. Defaults to 5,000 milliseconds, and
6099 setting a value of ze 5662 setting a value of zero disables this feature.
6100 This feature may be m 5663 This feature may be more efficiently disabled
6101 using the csdlock_deb 5664 using the csdlock_debug- kernel parameter.
6102 5665
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 5666 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5667 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5668 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5669 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5670 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5671 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5672 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5673 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5674 1: Fast pin select (default)
6119 2: ATC IRMode 5675 2: ATC IRMode
6120 5676
6121 smt= [KNL,MIPS,S390,EARLY] !! 5677 smt= [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5678 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5679 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5680 actual hardware limit.
6125 Format: <integer> 5681 Format: <integer>
6126 Default: -1 (no limit 5682 Default: -1 (no limit)
6127 5683
6128 softlockup_panic= 5684 softlockup_panic=
6129 [KNL] Should the soft 5685 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5686 Format: 0 | 1
6131 5687
6132 A value of 1 instruct 5688 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5689 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5690 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5691 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5692 respective build-time switch to that functionality.
6137 5693
6138 softlockup_all_cpu_backtrace= 5694 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5695 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5696 backtraces on all cpus.
6141 Format: 0 | 1 5697 Format: 0 | 1
6142 5698
6143 sonypi.*= [HW] Sony Programmabl 5699 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5700 See Documentation/admin-guide/laptops/sonypi.rst
6145 5701
6146 spectre_bhi= [X86] Control mitigat !! 5702 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 5703 (indirect branch speculation) vulnerability.
6163 The default operation 5704 The default operation protects the kernel from
6164 user space attacks. 5705 user space attacks.
6165 5706
6166 on - unconditionall 5707 on - unconditionally enable, implies
6167 spectre_v2_use 5708 spectre_v2_user=on
6168 off - unconditionall 5709 off - unconditionally disable, implies
6169 spectre_v2_use 5710 spectre_v2_user=off
6170 auto - kernel detects 5711 auto - kernel detects whether your CPU model is
6171 vulnerable 5712 vulnerable
6172 5713
6173 Selecting 'on' will, 5714 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5715 mitigation method at run time according to the
6175 CPU, the available mi 5716 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5717 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5718 compiler with which the kernel was built.
6178 5719
6179 Selecting 'on' will a 5720 Selecting 'on' will also enable the mitigation
6180 against user space to 5721 against user space to user space task attacks.
6181 5722
6182 Selecting 'off' will 5723 Selecting 'off' will disable both the kernel and
6183 the user space protec 5724 the user space protections.
6184 5725
6185 Specific mitigations 5726 Specific mitigations can also be selected manually:
6186 5727
6187 retpoline - r 5728 retpoline - replace indirect branches
6188 retpoline,generic - R 5729 retpoline,generic - Retpolines
6189 retpoline,lfence - L 5730 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 5731 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E !! 5732 eibrs - enhanced IBRS
6192 eibrs,retpoline - E !! 5733 eibrs,retpoline - enhanced IBRS + Retpolines
6193 eibrs,lfence - E !! 5734 eibrs,lfence - enhanced IBRS + LFENCE
6194 ibrs - u 5735 ibrs - use IBRS to protect kernel
6195 5736
6196 Not specifying this o 5737 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5738 spectre_v2=auto.
6198 5739
6199 spectre_v2_user= 5740 spectre_v2_user=
6200 [X86] Control mitigat 5741 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5742 (indirect branch speculation) vulnerability between
6202 user space tasks 5743 user space tasks
6203 5744
6204 on - Uncondition 5745 on - Unconditionally enable mitigations. Is
6205 enforced by 5746 enforced by spectre_v2=on
6206 5747
6207 off - Uncondition 5748 off - Unconditionally disable mitigations. Is
6208 enforced by 5749 enforced by spectre_v2=off
6209 5750
6210 prctl - Indirect br 5751 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5752 but mitigation can be enabled via prctl
6212 per thread. 5753 per thread. The mitigation control state
6213 is inherite 5754 is inherited on fork.
6214 5755
6215 prctl,ibpb 5756 prctl,ibpb
6216 - Like "prctl 5757 - Like "prctl" above, but only STIBP is
6217 controlled 5758 controlled per thread. IBPB is issued
6218 always when 5759 always when switching between different user
6219 space proce 5760 space processes.
6220 5761
6221 seccomp 5762 seccomp
6222 - Same as "pr 5763 - Same as "prctl" above, but all seccomp
6223 threads wil 5764 threads will enable the mitigation unless
6224 they explic 5765 they explicitly opt out.
6225 5766
6226 seccomp,ibpb 5767 seccomp,ibpb
6227 - Like "secco 5768 - Like "seccomp" above, but only STIBP is
6228 controlled 5769 controlled per thread. IBPB is issued
6229 always when 5770 always when switching between different
6230 user space 5771 user space processes.
6231 5772
6232 auto - Kernel sele 5773 auto - Kernel selects the mitigation depending on
6233 the availab 5774 the available CPU features and vulnerability.
6234 5775
6235 Default mitigation: " 5776 Default mitigation: "prctl"
6236 5777
6237 Not specifying this o 5778 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5779 spectre_v2_user=auto.
6239 5780
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= 5781 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5782 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5783 (Speculative Store Bypass vulnerability)
6254 5784
6255 Certain CPUs are vuln 5785 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5786 a common industry wide performance optimization known
6257 as "Speculative Store 5787 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5788 to the same memory location may not be observed by
6259 later loads during sp 5789 later loads during speculative execution. The idea
6260 is that such stores a 5790 is that such stores are unlikely and that they can
6261 be detected prior to 5791 be detected prior to instruction retirement at the
6262 end of a particular s 5792 end of a particular speculation execution window.
6263 5793
6264 In vulnerable process 5794 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5795 store can be used in a cache side channel attack, for
6266 example to read memor 5796 example to read memory to which the attacker does not
6267 directly have access 5797 directly have access (e.g. inside sandboxed code).
6268 5798
6269 This parameter contro 5799 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5800 Bypass optimization is used.
6271 5801
6272 On x86 the options ar 5802 On x86 the options are:
6273 5803
6274 on - Uncondition 5804 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5805 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5806 auto - Kernel detects whether the CPU model contains an
6277 implementat 5807 implementation of Speculative Store Bypass and
6278 picks the m 5808 picks the most appropriate mitigation. If the
6279 CPU is not 5809 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5810 CPU is vulnerable the default mitigation is
6281 architectur 5811 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5812 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5813 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5814 for a process by default. The state of the control
6285 is inherite 5815 is inherited on fork.
6286 seccomp - Same as "pr 5816 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5817 will disable SSB unless they explicitly opt out.
6288 5818
6289 Default mitigations: 5819 Default mitigations:
6290 X86: "prctl" 5820 X86: "prctl"
6291 5821
6292 On powerpc the option 5822 On powerpc the options are:
6293 5823
6294 on,auto - On Power8 a 5824 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5825 barrier on kernel entry and exit. On Power7
6296 perform a s 5826 perform a software flush on kernel entry and
6297 exit. 5827 exit.
6298 off - No action. 5828 off - No action.
6299 5829
6300 Not specifying this o 5830 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5831 spec_store_bypass_disable=auto.
6302 5832
>> 5833 spia_io_base= [HW,MTD]
>> 5834 spia_fio_base=
>> 5835 spia_pedr=
>> 5836 spia_peddr=
>> 5837
6303 split_lock_detect= 5838 split_lock_detect=
6304 [X86] Enable split lo 5839 [X86] Enable split lock detection or bus lock detection
6305 5840
6306 When enabled (and if 5841 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5842 instructions that access data across cache line
6308 boundaries will resul 5843 boundaries will result in an alignment check exception
6309 for split lock detect 5844 for split lock detection or a debug exception for
6310 bus lock detection. 5845 bus lock detection.
6311 5846
6312 off - not enabled 5847 off - not enabled
6313 5848
6314 warn - the kernel 5849 warn - the kernel will emit rate-limited warnings
6315 about appli 5850 about applications triggering the #AC
6316 exception o 5851 exception or the #DB exception. This mode is
6317 the default 5852 the default on CPUs that support split lock
6318 detection o 5853 detection or bus lock detection. Default
6319 behavior is 5854 behavior is by #AC if both features are
6320 enabled in 5855 enabled in hardware.
6321 5856
6322 fatal - the kernel 5857 fatal - the kernel will send SIGBUS to applications
6323 that trigge 5858 that trigger the #AC exception or the #DB
6324 exception. 5859 exception. Default behavior is by #AC if
6325 both featur 5860 both features are enabled in hardware.
6326 5861
6327 ratelimit:N - 5862 ratelimit:N -
6328 Set system 5863 Set system wide rate limit to N bus locks
6329 per second 5864 per second for bus lock detection.
6330 0 < N <= 10 5865 0 < N <= 1000.
6331 5866
6332 N/A for spl 5867 N/A for split lock detection.
6333 5868
6334 5869
6335 If an #AC exception i 5870 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5871 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5872 the kernel will oops in either "warn" or "fatal"
6338 mode. 5873 mode.
6339 5874
6340 #DB exception for bus 5875 #DB exception for bus lock is triggered only when
6341 CPL > 0. 5876 CPL > 0.
6342 5877
6343 srbds= [X86,INTEL,EARLY] !! 5878 srbds= [X86,INTEL]
6344 Control the Special R 5879 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5880 (SRBDS) mitigation.
6346 5881
6347 Certain CPUs are vuln 5882 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5883 exploit which can leak bits from the random
6349 number generator. 5884 number generator.
6350 5885
6351 By default, this issu 5886 By default, this issue is mitigated by
6352 microcode. However, 5887 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5888 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5889 much slower. Among other effects, this will
6355 result in reduced thr 5890 result in reduced throughput from /dev/urandom.
6356 5891
6357 The microcode mitigat 5892 The microcode mitigation can be disabled with
6358 the following option: 5893 the following option:
6359 5894
6360 off: Disable mitig 5895 off: Disable mitigation and remove
6361 performance i 5896 performance impact to RDRAND and RDSEED
6362 5897
6363 srcutree.big_cpu_lim [KNL] 5898 srcutree.big_cpu_lim [KNL]
6364 Specifies the number 5899 Specifies the number of CPUs constituting a
6365 large system, such th 5900 large system, such that srcu_struct structures
6366 should immediately al 5901 should immediately allocate an srcu_node array.
6367 This kernel-boot para 5902 This kernel-boot parameter defaults to 128,
6368 but takes effect only 5903 but takes effect only when the low-order four
6369 bits of srcutree.conv 5904 bits of srcutree.convert_to_big is equal to 3
6370 (decide at boot). 5905 (decide at boot).
6371 5906
6372 srcutree.convert_to_big [KNL] 5907 srcutree.convert_to_big [KNL]
6373 Specifies under what 5908 Specifies under what conditions an SRCU tree
6374 srcu_struct structure 5909 srcu_struct structure will be converted to big
6375 form, that is, with a 5910 form, that is, with an rcu_node tree:
6376 5911
6377 0: Never. 5912 0: Never.
6378 1: At ini 5913 1: At init_srcu_struct() time.
6379 2: When r 5914 2: When rcutorture decides to.
6380 3: Decide 5915 3: Decide at boot time (default).
6381 0x1X: Above 5916 0x1X: Above plus if high contention.
6382 5917
6383 Either way, the srcu_ 5918 Either way, the srcu_node tree will be sized based
6384 on the actual runtime 5919 on the actual runtime number of CPUs (nr_cpu_ids)
6385 instead of the compil 5920 instead of the compile-time CONFIG_NR_CPUS.
6386 5921
6387 srcutree.counter_wrap_check [KNL] 5922 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5923 Specifies how frequently to check for
6389 grace-period sequence 5924 grace-period sequence counter wrap for the
6390 srcu_data structure's 5925 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5926 The greater the number of bits set in this kernel
6392 parameter, the less f 5927 parameter, the less frequently counter wrap will
6393 be checked for. Note 5928 be checked for. Note that the bottom two bits
6394 are ignored. 5929 are ignored.
6395 5930
6396 srcutree.exp_holdoff [KNL] 5931 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5932 Specifies how many nanoseconds must elapse
6398 since the end of the 5933 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5934 a given srcu_struct until the next normal SRCU
6400 grace period will be 5935 grace period will be considered for automatic
6401 expediting. Set to z 5936 expediting. Set to zero to disable automatic
6402 expediting. 5937 expediting.
6403 5938
6404 srcutree.srcu_max_nodelay [KNL] 5939 srcutree.srcu_max_nodelay [KNL]
6405 Specifies the number 5940 Specifies the number of no-delay instances
6406 per jiffy for which t 5941 per jiffy for which the SRCU grace period
6407 worker thread will be 5942 worker thread will be rescheduled with zero
6408 delay. Beyond this li 5943 delay. Beyond this limit, worker thread will
6409 be rescheduled with a 5944 be rescheduled with a sleep delay of one jiffy.
6410 5945
6411 srcutree.srcu_max_nodelay_phase [KNL] 5946 srcutree.srcu_max_nodelay_phase [KNL]
6412 Specifies the per-gra 5947 Specifies the per-grace-period phase, number of
6413 non-sleeping polls of 5948 non-sleeping polls of readers. Beyond this limit,
6414 grace period worker t 5949 grace period worker thread will be rescheduled
6415 with a sleep delay of 5950 with a sleep delay of one jiffy, between each
6416 rescan of the readers 5951 rescan of the readers, for a grace period phase.
6417 5952
6418 srcutree.srcu_retry_check_delay [KNL] 5953 srcutree.srcu_retry_check_delay [KNL]
6419 Specifies number of m 5954 Specifies number of microseconds of non-sleeping
6420 delay between each no 5955 delay between each non-sleeping poll of readers.
6421 5956
6422 srcutree.small_contention_lim [KNL] 5957 srcutree.small_contention_lim [KNL]
6423 Specifies the number 5958 Specifies the number of update-side contention
6424 events per jiffy will 5959 events per jiffy will be tolerated before
6425 initiating a conversi 5960 initiating a conversion of an srcu_struct
6426 structure to big form 5961 structure to big form. Note that the value of
6427 srcutree.convert_to_b 5962 srcutree.convert_to_big must have the 0x10 bit
6428 set for contention-ba 5963 set for contention-based conversions to occur.
6429 5964
6430 ssbd= [ARM64,HW,EARLY] !! 5965 ssbd= [ARM64,HW]
6431 Speculative Store Byp 5966 Speculative Store Bypass Disable control
6432 5967
6433 On CPUs that are vuln 5968 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5969 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5970 firmware based mitigation, this parameter
6436 indicates how the mit 5971 indicates how the mitigation should be used:
6437 5972
6438 force-on: Unconditio 5973 force-on: Unconditionally enable mitigation for
6439 for both k 5974 for both kernel and userspace
6440 force-off: Unconditio 5975 force-off: Unconditionally disable mitigation for
6441 for both k 5976 for both kernel and userspace
6442 kernel: Always ena 5977 kernel: Always enable mitigation in the
6443 kernel, an 5978 kernel, and offer a prctl interface
6444 to allow u 5979 to allow userspace to register its
6445 interest i 5980 interest in being mitigated too.
6446 5981
6447 stack_guard_gap= [MM] 5982 stack_guard_gap= [MM]
6448 override the default 5983 override the default stack gap protection. The value
6449 is in page units and 5984 is in page units and it defines how many pages prior
6450 to (for stacks growin 5985 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 5986 growing up) the main stack are reserved for no other
6452 mapping. Default valu 5987 mapping. Default value is 256 pages.
6453 5988
6454 stack_depot_disable= [KNL,EARLY] !! 5989 stack_depot_disable= [KNL]
6455 Setting this to true 5990 Setting this to true through kernel command line will
6456 disable the stack dep 5991 disable the stack depot thereby saving the static memory
6457 consumed by the stack 5992 consumed by the stack hash table. By default this is set
6458 to false. 5993 to false.
6459 5994
6460 stacktrace [FTRACE] 5995 stacktrace [FTRACE]
6461 Enabled the stack tra 5996 Enabled the stack tracer on boot up.
6462 5997
6463 stacktrace_filter=[function-list] 5998 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 5999 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 6000 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 6001 list of functions. This list can be changed at run
6467 time by the stack_tra 6002 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 6003 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 6004 and the stacktrace above is not needed.
6470 6005
6471 sti= [PARISC,HW] 6006 sti= [PARISC,HW]
6472 Format: <num> 6007 Format: <num>
6473 Set the STI (builtin 6008 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 6009 machines) console (graphic card) which should be used
6475 as the initial boot-c 6010 as the initial boot-console.
6476 See also comment in d 6011 See also comment in drivers/video/console/sticore.c.
6477 6012
6478 sti_font= [HW] 6013 sti_font= [HW]
6479 See comment in driver 6014 See comment in drivers/video/console/sticore.c.
6480 6015
6481 stifb= [HW] 6016 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 6017 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 6018
6484 strict_sas_size= 6019 strict_sas_size=
6485 [X86] 6020 [X86]
6486 Format: <bool> 6021 Format: <bool>
6487 Enable or disable str 6022 Enable or disable strict sigaltstack size checks
6488 against the required 6023 against the required signal frame size which
6489 depends on the suppor 6024 depends on the supported FPU features. This can
6490 be used to filter out 6025 be used to filter out binaries which have
6491 not yet been made awa 6026 not yet been made aware of AT_MINSIGSTKSZ.
6492 6027
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= 6028 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 6029 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 6030 [NFS,SUNRPC]
6506 SunRPC servers often 6031 SunRPC servers often require that client requests
6507 originate from a priv 6032 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 6033 range 0 < portnr < 1024).
6509 An administrator who 6034 An administrator who wishes to reserve some of these
6510 ports for other uses 6035 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 6036 kernel's sunrpc client considers to be privileged
6512 using these two param 6037 using these two parameters to set the minimum and
6513 maximum port values. 6038 maximum port values.
6514 6039
6515 sunrpc.svc_rpc_per_connection_limit= 6040 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 6041 [NFS,SUNRPC]
6517 Limit the number of r 6042 Limit the number of requests that the server will
6518 process in parallel f 6043 process in parallel from a single connection.
6519 The default value is 6044 The default value is 0 (no limit).
6520 6045
6521 sunrpc.pool_mode= 6046 sunrpc.pool_mode=
6522 [NFS] 6047 [NFS]
6523 Control how the NFS s 6048 Control how the NFS server code allocates CPUs to
6524 service thread pools. 6049 service thread pools. Depending on how many NICs
6525 you have and where th 6050 you have and where their interrupts are bound, this
6526 option will affect wh 6051 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 6052 Note: this parameter cannot be changed while the
6528 NFS server is running 6053 NFS server is running.
6529 6054
6530 auto the serve 6055 auto the server chooses an appropriate mode
6531 automatic 6056 automatically using heuristics
6532 global a single 6057 global a single global pool contains all CPUs
6533 percpu one pool 6058 percpu one pool for each CPU
6534 pernode one pool 6059 pernode one pool for each NUMA node (equivalent
6535 to global 6060 to global on non-NUMA machines)
6536 6061
6537 sunrpc.tcp_slot_table_entries= 6062 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 6063 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 6064 [NFS,SUNRPC]
6540 Sets the upper limit 6065 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 6066 RPC calls that can be sent from the client to a
6542 server. Increasing th 6067 server. Increasing these values may allow you to
6543 improve throughput, b 6068 improve throughput, but will also increase the
6544 amount of memory rese 6069 amount of memory reserved for use by the client.
6545 6070
6546 suspend.pm_test_delay= 6071 suspend.pm_test_delay=
6547 [SUSPEND] 6072 [SUSPEND]
6548 Sets the number of se 6073 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 6074 mode before resuming the system (see
6550 /sys/power/pm_test). 6075 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 6076 is set. Default value is 5.
6552 6077
6553 svm= [PPC] 6078 svm= [PPC]
6554 Format: { on | off | 6079 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 6080 This parameter controls use of the Protected
6556 Execution Facility on 6081 Execution Facility on pSeries.
6557 6082
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 6083 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in 6084 Format: { <int> [,<int>] | force | noforce }
6560 <int> -- Number of I/ 6085 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ 6086 <int> -- Second integer after comma. Number of swiotlb
6562 areas with t 6087 areas with their own lock. Will be rounded up
6563 to a power o 6088 to a power of 2.
6564 force -- force using 6089 force -- force using of bounce buffers even if they
6565 wouldn't be 6090 wouldn't be automatically used by the kernel
6566 noforce -- Never use 6091 noforce -- Never use bounce buffers (for debugging)
6567 6092
6568 switches= [HW,M68k,EARLY] !! 6093 switches= [HW,M68k]
6569 6094
6570 sysctl.*= [KNL] 6095 sysctl.*= [KNL]
6571 Set a sysctl paramete 6096 Set a sysctl parameter, right before loading the init
6572 process, as if the va 6097 process, as if the value was written to the respective
6573 /proc/sys/... file. B 6098 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 6099 separators. Unrecognized parameters and invalid values
6575 are reported in the k 6100 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 6101 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 6102 Example: sysctl.vm.swappiness=40
6578 6103
>> 6104 sysfs.deprecated=0|1 [KNL]
>> 6105 Enable/disable old style sysfs layout for old udev
>> 6106 on older distributions. When this option is enabled
>> 6107 very new udev will not work anymore. When this option
>> 6108 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 6109 in older udev will not work anymore.
>> 6110 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 6111 the kernel configuration.
>> 6112
6579 sysrq_always_enabled 6113 sysrq_always_enabled
6580 [KNL] 6114 [KNL]
6581 Ignore sysrq setting 6115 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 6116 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 6117 Useful for debugging.
6584 6118
6585 tcpmhash_entries= [KNL,NET] 6119 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 6120 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 6121 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 6122 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 6123 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 6124 "tcp_no_metrics_save" section for more details.
6591 6125
6592 tdfx= [HW,DRM] 6126 tdfx= [HW,DRM]
6593 6127
6594 test_suspend= [SUSPEND] 6128 test_suspend= [SUSPEND]
6595 Format: { "mem" | "st 6129 Format: { "mem" | "standby" | "freeze" }[,N]
6596 Specify "mem" (for Su 6130 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 6131 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 6132 as the system sleep state during system startup with
6599 the optional capabili 6133 the optional capability to repeat N number of times.
6600 The system is woken f 6134 The system is woken from this state using a
6601 wakeup-capable RTC al 6135 wakeup-capable RTC alarm.
6602 6136
6603 thash_entries= [KNL,NET] 6137 thash_entries= [KNL,NET]
6604 Set number of hash bu 6138 Set number of hash buckets for TCP connection
6605 6139
6606 thermal.act= [HW,ACPI] 6140 thermal.act= [HW,ACPI]
6607 -1: disable all activ 6141 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 6142 <degrees C>: override all lowest active trip points
6609 6143
6610 thermal.crt= [HW,ACPI] 6144 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 6145 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 6146 <degrees C>: override all critical trip points
6613 6147
>> 6148 thermal.nocrt= [HW,ACPI]
>> 6149 Set to disable actions on ACPI thermal zone
>> 6150 critical and hot trip points.
>> 6151
6614 thermal.off= [HW,ACPI] 6152 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 6153 1: disable ACPI thermal control
6616 6154
6617 thermal.psv= [HW,ACPI] 6155 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 6156 -1: disable all passive trip points
6619 <degrees C>: override 6157 <degrees C>: override all passive trip points to this
6620 value 6158 value
6621 6159
6622 thermal.tzp= [HW,ACPI] 6160 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 6161 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 6162 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 6163 0: no polling (default)
6626 6164
6627 threadirqs [KNL,EARLY] !! 6165 threadirqs [KNL]
6628 Force threading of al 6166 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 6167 marked explicitly IRQF_NO_THREAD.
6630 6168
6631 topology= [S390,EARLY] !! 6169 topology= [S390]
6632 Format: {off | on} 6170 Format: {off | on}
6633 Specify if the kernel 6171 Specify if the kernel should make use of the cpu
6634 topology information 6172 topology information if the hardware supports this.
6635 The scheduler will ma 6173 The scheduler will make use of this information and
6636 e.g. base its process 6174 e.g. base its process migration decisions on it.
6637 Default is on. 6175 Default is on.
6638 6176
>> 6177 topology_updates= [KNL, PPC, NUMA]
>> 6178 Format: {off}
>> 6179 Specify if the kernel should ignore (off)
>> 6180 topology updates sent by the hypervisor to this
>> 6181 LPAR.
>> 6182
6639 torture.disable_onoff_at_boot= [KNL] 6183 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 6184 Prevent the CPU-hotplug component of torturing
6641 until after init has 6185 until after init has spawned.
6642 6186
6643 torture.ftrace_dump_at_shutdown= [KNL 6187 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 6188 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 6189 even if there were no errors. This can be a
6646 very costly operation 6190 very costly operation when many torture tests
6647 are running concurren 6191 are running concurrently, especially on systems
6648 with rotating-rust st 6192 with rotating-rust storage.
6649 6193
6650 torture.verbose_sleep_frequency= [KNL 6194 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 6195 Specifies how many verbose printk()s should be
6652 emitted between each 6196 emitted between each sleep. The default of zero
6653 disables verbose-prin 6197 disables verbose-printk() sleeping.
6654 6198
6655 torture.verbose_sleep_duration= [KNL] 6199 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 6200 Duration of each verbose-printk() sleep in jiffies.
6657 6201
>> 6202 tp720= [HW,PS2]
>> 6203
6658 tpm_suspend_pcr=[HW,TPM] 6204 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 6205 Format: integer pcr id
6660 Specify that at suspe 6206 Specify that at suspend time, the tpm driver
6661 should extend the spe 6207 should extend the specified pcr with zeros,
6662 as a workaround for s 6208 as a workaround for some chips which fail to
6663 flush the last writte 6209 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 6210 This will guarantee that all the other pcrs
6665 are saved. 6211 are saved.
6666 6212
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] 6213 tp_printk [FTRACE]
6675 Have the tracepoints 6214 Have the tracepoints sent to printk as well as the
6676 tracing ring buffer. 6215 tracing ring buffer. This is useful for early boot up
6677 where the system hang 6216 where the system hangs or reboots and does not give the
6678 option for reading th 6217 option for reading the tracing buffer or performing a
6679 ftrace_dump_on_oops. 6218 ftrace_dump_on_oops.
6680 6219
6681 To turn off having tr 6220 To turn off having tracepoints sent to printk,
6682 echo 0 > /proc/sys/k 6221 echo 0 > /proc/sys/kernel/tracepoint_printk
6683 Note, echoing 1 into 6222 Note, echoing 1 into this file without the
6684 tp_printk kernel cmdl !! 6223 tracepoint_printk kernel cmdline option has no effect.
6685 6224
6686 The tp_printk_stop_on 6225 The tp_printk_stop_on_boot (see below) can also be used
6687 to stop the printing 6226 to stop the printing of events to console at
6688 late_initcall_sync. 6227 late_initcall_sync.
6689 6228
6690 ** CAUTION ** 6229 ** CAUTION **
6691 6230
6692 Having tracepoints se 6231 Having tracepoints sent to printk() and activating high
6693 frequency tracepoints 6232 frequency tracepoints such as irq or sched, can cause
6694 the system to live lo 6233 the system to live lock.
6695 6234
6696 tp_printk_stop_on_boot [FTRACE] 6235 tp_printk_stop_on_boot [FTRACE]
6697 When tp_printk (above 6236 When tp_printk (above) is set, it can cause a lot of noise
6698 on the console. It ma 6237 on the console. It may be useful to only include the
6699 printing of events du 6238 printing of events during boot up, as user space may
6700 make the system inope 6239 make the system inoperable.
6701 6240
6702 This command line opt 6241 This command line option will stop the printing of events
6703 to console at the lat 6242 to console at the late_initcall_sync() time frame.
6704 6243
6705 trace_buf_size=nn[KMG] 6244 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 6245 [FTRACE] will set tracing buffer size on each cpu.
6707 6246
6708 trace_clock= [FTRACE] Set the cloc 6247 trace_clock= [FTRACE] Set the clock used for tracing events
6709 at boot up. 6248 at boot up.
6710 local - Use the per C 6249 local - Use the per CPU time stamp counter
6711 (converted in 6250 (converted into nanoseconds). Fast, but
6712 depending on 6251 depending on the architecture, may not be
6713 in sync betwe 6252 in sync between CPUs.
6714 global - Event time s 6253 global - Event time stamps are synchronize across
6715 CPUs. May be 6254 CPUs. May be slower than the local clock,
6716 but better fo 6255 but better for some race conditions.
6717 counter - Simple coun 6256 counter - Simple counting of events (1, 2, ..)
6718 note, some co 6257 note, some counts may be skipped due to the
6719 infrastructur 6258 infrastructure grabbing the clock more than
6720 once per even 6259 once per event.
6721 uptime - Use jiffies 6260 uptime - Use jiffies as the time stamp.
6722 perf - Use the same c 6261 perf - Use the same clock that perf uses.
6723 mono - Use ktime_get_ 6262 mono - Use ktime_get_mono_fast_ns() for time stamps.
6724 mono_raw - Use ktime_ 6263 mono_raw - Use ktime_get_raw_fast_ns() for time
6725 stamps. 6264 stamps.
6726 boot - Use ktime_get_ 6265 boot - Use ktime_get_boot_fast_ns() for time stamps.
6727 Architectures may add 6266 Architectures may add more clocks. See
6728 Documentation/trace/f 6267 Documentation/trace/ftrace.rst for more details.
6729 6268
6730 trace_event=[event-list] 6269 trace_event=[event-list]
6731 [FTRACE] Set and star 6270 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 6271 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 6272 comma-separated list of trace events to enable. See
6734 also Documentation/tr 6273 also Documentation/trace/events.rst
6735 6274
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] 6275 trace_options=[option-list]
6757 [FTRACE] Enable or di 6276 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 6277 The option-list is a comma delimited list of options
6759 that can be enabled o 6278 that can be enabled or disabled just as if you were
6760 to echo the option na 6279 to echo the option name into
6761 6280
6762 /sys/kernel/traci !! 6281 /sys/kernel/debug/tracing/trace_options
6763 6282
6764 For example, to enabl 6283 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 6284 stack trace of each event), add to the command line:
6766 6285
6767 trace_options=s 6286 trace_options=stacktrace
6768 6287
6769 See also Documentatio 6288 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 6289 section.
6771 6290
6772 trace_trigger=[trigger-list] 6291 trace_trigger=[trigger-list]
6773 [FTRACE] Add a event 6292 [FTRACE] Add a event trigger on specific events.
6774 Set a trigger on top 6293 Set a trigger on top of a specific event, with an optional
6775 filter. 6294 filter.
6776 6295
6777 The format is is "tra 6296 The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
6778 Where more than one t 6297 Where more than one trigger may be specified that are comma deliminated.
6779 6298
6780 For example: 6299 For example:
6781 6300
6782 trace_trigger="sche 6301 trace_trigger="sched_switch.stacktrace if prev_state == 2"
6783 6302
6784 The above will enable 6303 The above will enable the "stacktrace" trigger on the "sched_switch"
6785 event but only trigge 6304 event but only trigger it if the "prev_state" of the "sched_switch"
6786 event is "2" (TASK_UN 6305 event is "2" (TASK_UNINTERUPTIBLE).
6787 6306
6788 See also "Event trigg 6307 See also "Event triggers" in Documentation/trace/events.rst
6789 6308
6790 6309
6791 traceoff_on_warning 6310 traceoff_on_warning
6792 [FTRACE] enable this 6311 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 6312 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 6313 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 6314 file located in /sys/kernel/debug/tracing/
6796 6315
6797 This option is useful 6316 This option is useful, as it disables the trace before
6798 the WARNING dump is c 6317 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 6318 be filled with content caused by the warning output.
6800 6319
6801 This option can also 6320 This option can also be set at run time via the sysctl
6802 option: kernel/trace 6321 option: kernel/traceoff_on_warning
6803 6322
6804 transparent_hugepage= 6323 transparent_hugepage=
6805 [KNL] 6324 [KNL]
6806 Format: [always|madvi 6325 Format: [always|madvise|never]
6807 Can be used to contro 6326 Can be used to control the default behavior of the system
6808 with respect to trans 6327 with respect to transparent hugepages.
6809 See Documentation/adm 6328 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 6329 for more details.
6811 6330
6812 trusted.source= [KEYS] 6331 trusted.source= [KEYS]
6813 Format: <string> 6332 Format: <string>
6814 This parameter identi 6333 This parameter identifies the trust source as a backend
6815 for trusted keys impl 6334 for trusted keys implementation. Supported trust
6816 sources: 6335 sources:
6817 - "tpm" 6336 - "tpm"
6818 - "tee" 6337 - "tee"
6819 - "caam" 6338 - "caam"
6820 - "dcp" <<
6821 If not specified then 6339 If not specified then it defaults to iterating through
6822 the trust source list 6340 the trust source list starting with TPM and assigns the
6823 first trust source as 6341 first trust source as a backend which is initialized
6824 successfully during i 6342 successfully during iteration.
6825 6343
6826 trusted.rng= [KEYS] 6344 trusted.rng= [KEYS]
6827 Format: <string> 6345 Format: <string>
6828 The RNG used to gener 6346 The RNG used to generate key material for trusted keys.
6829 Can be one of: 6347 Can be one of:
6830 - "kernel" 6348 - "kernel"
6831 - the same value as t 6349 - the same value as trusted.source: "tpm" or "tee"
6832 - "default" 6350 - "default"
6833 If not specified, "de 6351 If not specified, "default" is used. In this case,
6834 the RNG's choice is l 6352 the RNG's choice is left to each individual trust source.
6835 6353
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 6354 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 6355 Format: <string>
6850 [x86] reliable: mark 6356 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 6357 disables clocksource verification at runtime, as well
6852 as the stability chec 6358 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 6359 high-resolution timer mode on older hardware, and in
6854 virtualized environme 6360 virtualized environment.
6855 [x86] noirqtime: Do n 6361 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 6362 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 6363 platforms where RDTSC is slow and this accounting
6858 can add overhead. 6364 can add overhead.
6859 [x86] unstable: mark 6365 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 6366 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 6367 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 6368 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 6369 in situations with strict latency requirements (where
6864 interruptions from cl 6370 interruptions from clocksource watchdog are not
6865 acceptable). 6371 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 6372
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 6373 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 6374 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 6375 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 6376 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 6377 Format: <unsigned int>
6882 6378
6883 tsx= [X86] Control Transac 6379 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 6380 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 6381 support TSX control.
6886 6382
6887 This parameter contro 6383 This parameter controls the TSX feature. The options are:
6888 6384
6889 on - Enable TSX 6385 on - Enable TSX on the system. Although there are
6890 mitigations f 6386 mitigations for all known security vulnerabilities,
6891 TSX has been 6387 TSX has been known to be an accelerator for
6892 several previ 6388 several previous speculation-related CVEs, and
6893 so there may 6389 so there may be unknown security risks associated
6894 with leaving 6390 with leaving it enabled.
6895 6391
6896 off - Disable TSX 6392 off - Disable TSX on the system. (Note that this
6897 option takes 6393 option takes effect only on newer CPUs which are
6898 not vulnerabl 6394 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 6395 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 6396 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 6397 update. This new MSR allows for the reliable
6902 deactivation 6398 deactivation of the TSX functionality.)
6903 6399
6904 auto - Disable TSX 6400 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 6401 otherwise enable TSX on the system.
6906 6402
6907 Not specifying this o 6403 Not specifying this option is equivalent to tsx=off.
6908 6404
6909 See Documentation/adm 6405 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 6406 for more details.
6911 6407
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 6408 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 6409 Abort (TAA) vulnerability.
6914 6410
6915 Similar to Micro-arch 6411 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 6412 certain CPUs that support Transactional
6917 Synchronization Exten 6413 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 6414 exploit against CPU internal buffers which can forward
6919 information to a disc 6415 information to a disclosure gadget under certain
6920 conditions. 6416 conditions.
6921 6417
6922 In vulnerable process 6418 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 6419 data can be used in a cache side channel attack, to
6924 access data to which 6420 access data to which the attacker does not have direct
6925 access. 6421 access.
6926 6422
6927 This parameter contro 6423 This parameter controls the TAA mitigation. The
6928 options are: 6424 options are:
6929 6425
6930 full - Enable T 6426 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 6427 if TSX is enabled.
6932 6428
6933 full,nosmt - Enable T 6429 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 6430 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 6431 is not disabled because CPU is not
6936 vulnerab 6432 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 6433 off - Unconditionally disable TAA mitigation
6938 6434
6939 On MDS-affected machi 6435 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 6436 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 6437 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 6438 this mitigation, you need to specify mds=off too.
6943 6439
6944 Not specifying this o 6440 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 6441 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 6442 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 6443 required and doesn't provide any additional
6948 mitigation. 6444 mitigation.
6949 6445
6950 For details see: 6446 For details see:
6951 Documentation/admin-g 6447 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 6448
6953 turbografx.map[2|3]= [HW,JOY] 6449 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 6450 TurboGraFX parallel port interface
6955 Format: 6451 Format:
6956 <port#>,<js1>,<js2>,< 6452 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 6453 See also Documentation/input/devices/joystick-parport.rst
6958 6454
6959 udbg-immortal [PPC] When debugging 6455 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 6456 happen after console_init() and before a proper
6961 console driver takes 6457 console driver takes over, this boot options might
6962 help "seeing" what's 6458 help "seeing" what's going on.
6963 6459
6964 uhash_entries= [KNL,NET] 6460 uhash_entries= [KNL,NET]
6965 Set number of hash bu 6461 Set number of hash buckets for UDP/UDP-Lite connections
6966 6462
6967 uhci-hcd.ignore_oc= 6463 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 6464 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 6465 Some badly-designed motherboards generate lots of
6970 bogus events, for por 6466 bogus events, for ports that aren't wired to
6971 anything. Set this p 6467 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 6468 Note that genuine overcurrent events won't be
6973 reported either. 6469 reported either.
6974 6470
6975 unknown_nmi_panic 6471 unknown_nmi_panic
6976 [X86] Cause panic on 6472 [X86] Cause panic on unknown NMI.
6977 6473
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= 6474 usbcore.authorized_default=
6985 [USB] Default USB dev 6475 [USB] Default USB device authorization:
6986 (default -1 = authori !! 6476 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 6477 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 6478 if device connected to internal port)
6989 6479
6990 usbcore.autosuspend= 6480 usbcore.autosuspend=
6991 [USB] The autosuspend 6481 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 6482 for newly-detected USB devices (default 2). This
6993 is the time required 6483 is the time required before an idle device will be
6994 autosuspended. Devic 6484 autosuspended. Devices for which the delay is set
6995 to a negative value w 6485 to a negative value won't be autosuspended at all.
6996 6486
6997 usbcore.usbfs_snoop= 6487 usbcore.usbfs_snoop=
6998 [USB] Set to log all 6488 [USB] Set to log all usbfs traffic (default 0 = off).
6999 6489
7000 usbcore.usbfs_snoop_max= 6490 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 6491 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 6492 (default = 65536).
7003 6493
7004 usbcore.blinkenlights= 6494 usbcore.blinkenlights=
7005 [USB] Set to cycle le 6495 [USB] Set to cycle leds on hubs (default 0 = off).
7006 6496
7007 usbcore.old_scheme_first= 6497 usbcore.old_scheme_first=
7008 [USB] Start with the 6498 [USB] Start with the old device initialization
7009 scheme (default 0 = o 6499 scheme (default 0 = off).
7010 6500
7011 usbcore.usbfs_memory_mb= 6501 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 6502 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 6503 usbfs (default = 16, 0 = max = 2047).
7014 6504
7015 usbcore.use_both_schemes= 6505 usbcore.use_both_schemes=
7016 [USB] Try the other d 6506 [USB] Try the other device initialization scheme
7017 if the first one fail 6507 if the first one fails (default 1 = enabled).
7018 6508
7019 usbcore.initial_descriptor_timeout= 6509 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 6510 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 6511 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 6512 (default 5000 = 5.0 seconds).
7023 6513
7024 usbcore.nousb [USB] Disable the USB 6514 usbcore.nousb [USB] Disable the USB subsystem
7025 6515
7026 usbcore.quirks= 6516 usbcore.quirks=
7027 [USB] A list of quirk 6517 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 6518 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 6519 commas. Each entry has the form
7030 VendorID:ProductID:Fl 6520 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 6521 numbers and Flags is a set of letters. Each letter
7032 will change the built 6522 will change the built-in quirk; setting it if it is
7033 clear and clearing it 6523 clear and clearing it if it is set. The letters have
7034 the following meaning 6524 the following meanings:
7035 a = USB_QUIRK 6525 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 6526 descriptors must not be fetched using
7037 a 255 6527 a 255-byte read);
7038 b = USB_QUIRK 6528 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 6529 correctly so reset it instead);
7040 c = USB_QUIRK 6530 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 6531 Set-Interface requests);
7042 d = USB_QUIRK 6532 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 6533 handle its Configuration or Interface
7044 strin 6534 strings);
7045 e = USB_QUIRK 6535 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 6536 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 6537 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 6538 more interface descriptions than the
7049 bNumI 6539 bNumInterfaces count, and can't handle
7050 talki 6540 talking to these interfaces);
7051 g = USB_QUIRK 6541 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 6542 during initialization, after we read
7053 the d 6543 the device descriptor);
7054 h = USB_QUIRK 6544 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 6545 high speed and super speed interrupt
7056 endpo 6546 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 6547 require the interval in microframes (1
7058 micro 6548 microframe = 125 microseconds) to be
7059 calcu 6549 calculated as interval = 2 ^
7060 (bInt 6550 (bInterval-1).
7061 Devic 6551 Devices with this quirk report their
7062 bInte 6552 bInterval as the result of this
7063 calcu 6553 calculation instead of the exponent
7064 varia 6554 variable used in the calculation);
7065 i = USB_QUIRK 6555 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 6556 handle device_qualifier descriptor
7067 reque 6557 requests);
7068 j = USB_QUIRK 6558 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 6559 generates spurious wakeup, ignore
7070 remot 6560 remote wakeup capability);
7071 k = USB_QUIRK 6561 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 6562 Power Management);
7073 l = USB_QUIRK 6563 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 6564 (Device reports its bInterval as linear
7075 frame 6565 frames instead of the USB 2.0
7076 calcu 6566 calculation);
7077 m = USB_QUIRK 6567 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 6568 to be disconnected before suspend to
7079 preve 6569 prevent spurious wakeup);
7080 n = USB_QUIRK 6570 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 6571 pause after every control message);
7082 o = USB_QUIRK 6572 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 6573 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 6574 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 6575
7089 usbhid.mousepoll= 6576 usbhid.mousepoll=
7090 [USBHID] The interval 6577 [USBHID] The interval which mice are to be polled at.
7091 6578
7092 usbhid.jspoll= 6579 usbhid.jspoll=
7093 [USBHID] The interval 6580 [USBHID] The interval which joysticks are to be polled at.
7094 6581
7095 usbhid.kbpoll= 6582 usbhid.kbpoll=
7096 [USBHID] The interval 6583 [USBHID] The interval which keyboards are to be polled at.
7097 6584
7098 usb-storage.delay_use= 6585 usb-storage.delay_use=
7099 [UMS] The delay in se 6586 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 6587 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 6588
7105 usb-storage.quirks= 6589 usb-storage.quirks=
7106 [UMS] A list of quirk 6590 [UMS] A list of quirks entries to supplement or
7107 override the built-in 6591 override the built-in unusual_devs list. List
7108 entries are separated 6592 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 6593 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 6594 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 6595 Flags is a set of characters, each corresponding
7112 to a common usb-stora 6596 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 6597 a = SANE_SENSE (collect more than 18 bytes
7114 of se 6598 of sense data, not on uas);
7115 b = BAD_SENSE 6599 b = BAD_SENSE (don't collect more than 18
7116 bytes 6600 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 6601 c = FIX_CAPACITY (decrease the reported
7118 devic 6602 device capacity by one sector);
7119 d = NO_READ_D 6603 d = NO_READ_DISC_INFO (don't use
7120 READ_ 6604 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 6605 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 6606 READ_CAPACITY_16 command);
7123 f = NO_REPORT 6607 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 6608 command, uas only);
7125 g = MAX_SECTO 6609 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 6610 240 sectors at a time, uas only);
7127 h = CAPACITY_ 6611 h = CAPACITY_HEURISTICS (decrease the
7128 repor 6612 reported device capacity by one
7129 secto 6613 sector if the number is odd);
7130 i = IGNORE_DE 6614 i = IGNORE_DEVICE (don't bind to this
7131 devic 6615 device);
7132 j = NO_REPORT 6616 j = NO_REPORT_LUNS (don't use report luns
7133 comma 6617 command, uas only);
7134 k = NO_SAME ( 6618 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 6619 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 6620 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 6621 m = MAX_SECTORS_64 (don't transfer more
7138 than 6622 than 64 sectors = 32 KB at a time,
7139 not o 6623 not on uas);
7140 n = INITIAL_R 6624 n = INITIAL_READ10 (force a retry of the
7141 initi 6625 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 6626 o = CAPACITY_OK (accept the capacity
7143 repor 6627 reported by the device, not on uas);
7144 p = WRITE_CAC 6628 p = WRITE_CACHE (the device cache is ON
7145 by de 6629 by default, not on uas);
7146 r = IGNORE_RE 6630 r = IGNORE_RESIDUE (the device reports
7147 bogus 6631 bogus residue values, not on uas);
7148 s = SINGLE_LU 6632 s = SINGLE_LUN (the device has only one
7149 Logic 6633 Logical Unit);
7150 t = NO_ATA_1X 6634 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 6635 commands, uas only);
7152 u = IGNORE_UA 6636 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 6637 w = NO_WP_DETECT (don't test whether the
7154 mediu 6638 medium is write-protected).
7155 y = ALWAYS_SY 6639 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 6640 even if the device claims no cache,
7157 not o 6641 not on uas)
7158 Example: quirks=0419: 6642 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 6643
7160 user_debug= [KNL,ARM] 6644 user_debug= [KNL,ARM]
7161 Format: <int> 6645 Format: <int>
7162 See arch/arm/Kconfig. 6646 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 6647 1 - undefined instruction events
7164 2 - system c 6648 2 - system calls
7165 4 - invalid 6649 4 - invalid data aborts
7166 8 - SIGSEGV 6650 8 - SIGSEGV faults
7167 16 - SIGBUS f 6651 16 - SIGBUS faults
7168 Example: user_debug=3 6652 Example: user_debug=31
7169 6653
7170 userpte= 6654 userpte=
7171 [X86,EARLY] Flags con !! 6655 [X86] Flags controlling user PTE allocations.
7172 6656
7173 nohigh = do n 6657 nohigh = do not allocate PTE pages in
7174 HIGHM 6658 HIGHMEM regardless of setting
7175 of CO 6659 of CONFIG_HIGHPTE.
7176 6660
7177 vdso= [X86,SH,SPARC] 6661 vdso= [X86,SH,SPARC]
7178 On X86_32, this is an 6662 On X86_32, this is an alias for vdso32=. Otherwise:
7179 6663
7180 vdso=1: enable VDSO ( 6664 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 6665 vdso=0: disable VDSO mapping
7182 6666
7183 vdso32= [X86] Control the 32- 6667 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 6668 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 6669 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 6670
7187 See the help text for 6671 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 6672 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 6673 vdso32=0; otherwise, the default is vdso32=1.
7190 6674
7191 For compatibility wit 6675 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 6676 alias for vdso32=0.
7193 6677
7194 Try vdso32=0 if you e 6678 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 6679 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 6680
7197 video= [FB,EARLY] Frame buff !! 6681 vector= [IA-64,SMP]
>> 6682 vector=percpu: enable percpu vector domain
>> 6683
>> 6684 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 6685 See Documentation/fb/modedb.rst.
7199 6686
7200 video.brightness_switch_enabled= [ACP 6687 video.brightness_switch_enabled= [ACPI]
7201 Format: [0|1] 6688 Format: [0|1]
7202 If set to 1, on recei 6689 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 6690 generated by hotkey, video driver will adjust brightness
7204 level and then send o 6691 level and then send out the event to user space through
7205 the allocated input d 6692 the allocated input device. If set to 0, video driver
7206 will only send out th 6693 will only send out the event without touching backlight
7207 brightness level. 6694 brightness level.
7208 default: 1 6695 default: 1
7209 6696
7210 virtio_mmio.device= 6697 virtio_mmio.device=
7211 [VMMIO] Memory mapped 6698 [VMMIO] Memory mapped virtio (platform) device.
7212 6699
7213 <size>@<basead 6700 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 6701 where:
7215 <size> := 6702 <size> := size (can use standard suffixes
7216 6703 like K, M and G)
7217 <baseaddr> := 6704 <baseaddr> := physical base address
7218 <irq> := 6705 <irq> := interrupt number (as passed to
7219 6706 request_irq())
7220 <id> := 6707 <id> := (optional) platform device id
7221 example: 6708 example:
7222 virtio_mmio.d 6709 virtio_mmio.device=1K@0x100b0000:48:7
7223 6710
7224 Can be used multiple 6711 Can be used multiple times for multiple devices.
7225 6712
7226 vga= [BOOT,X86-32] Select 6713 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 6714 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 6715 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 6716 Use vga=ask for menu.
7230 This is actually a bo 6717 This is actually a boot loader parameter; the value is
7231 passed to the kernel 6718 passed to the kernel using a special protocol.
7232 6719
7233 vm_debug[=options] [KNL] Availab 6720 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 6721 May slow down system boot speed, especially when
7235 enabled on systems wi 6722 enabled on systems with a large amount of memory.
7236 All options are enabl 6723 All options are enabled by default, and this
7237 interface is meant to 6724 interface is meant to allow for selectively
7238 enabling or disabling 6725 enabling or disabling specific virtual memory
7239 debugging features. 6726 debugging features.
7240 6727
7241 Available options are 6728 Available options are:
7242 P Enable page s 6729 P Enable page structure init time poisoning
7243 - Disable all o 6730 - Disable all of the above options
7244 6731
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 6732 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 6733 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 6734 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 6735 decrease the size and leave more room for directly
7249 for directly mapped k !! 6736 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 6737
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 6738 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 6739 Sets the memory size reserved for contiguous memory
7256 allocations for the v 6740 allocations for the vmcp device driver.
7257 6741
7258 vmhalt= [KNL,S390] Perform z/ 6742 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 6743 Format: <command>
7260 6744
7261 vmpanic= [KNL,S390] Perform z/ 6745 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 6746 Format: <command>
7263 6747
7264 vmpoff= [KNL,S390] Perform z/ 6748 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 6749 Format: <command>
7266 6750
7267 vsyscall= [X86-64,EARLY] !! 6751 vsyscall= [X86-64]
7268 Controls the behavior 6752 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 6753 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 6754 code). Most statically-linked binaries and older
7271 versions of glibc use 6755 versions of glibc use these calls. Because these
7272 functions are at fixe 6756 functions are at fixed addresses, they make nice
7273 targets for exploits 6757 targets for exploits that can control RIP.
7274 6758
7275 emulate Vsyscalls !! 6759 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 6760 emulated reasonably safely. The vsyscall
7277 readable. !! 6761 page is readable.
7278 6762
7279 xonly [default] !! 6763 xonly Vsyscalls turn into traps and are
7280 emulated 6764 emulated reasonably safely. The vsyscall
7281 page is n 6765 page is not readable.
7282 6766
7283 none Vsyscalls 6767 none Vsyscalls don't work at all. This makes
7284 them quit 6768 them quite hard to use for exploits but
7285 might bre 6769 might break your system.
7286 6770
7287 vt.color= [VT] Default text col 6771 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6772 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6773 Default: 0x07 = light gray on black.
7290 6774
7291 vt.cur_default= [VT] Default cursor s 6775 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6776 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6777 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6778 see VGA-softcursor.txt. Default: 2 = underline.
7295 6779
7296 vt.default_blu= [VT] 6780 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6781 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6782 Change the default blue palette of the console.
7299 This is a 16-member a 6783 This is a 16-member array composed of values
7300 ranging from 0-255. 6784 ranging from 0-255.
7301 6785
7302 vt.default_grn= [VT] 6786 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6787 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6788 Change the default green palette of the console.
7305 This is a 16-member a 6789 This is a 16-member array composed of values
7306 ranging from 0-255. 6790 ranging from 0-255.
7307 6791
7308 vt.default_red= [VT] 6792 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6793 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6794 Change the default red palette of the console.
7311 This is a 16-member a 6795 This is a 16-member array composed of values
7312 ranging from 0-255. 6796 ranging from 0-255.
7313 6797
7314 vt.default_utf8= 6798 vt.default_utf8=
7315 [VT] 6799 [VT]
7316 Format=<0|1> 6800 Format=<0|1>
7317 Set system-wide defau 6801 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6802 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6803 newly opened terminals.
7320 6804
7321 vt.global_cursor_default= 6805 vt.global_cursor_default=
7322 [VT] 6806 [VT]
7323 Format=<-1|0|1> 6807 Format=<-1|0|1>
7324 Set system-wide defau 6808 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6809 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6810 i.e. cursors will be created by default unless
7327 overridden by individ 6811 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6812 cursors, 1 will display them.
7329 6813
7330 vt.italic= [VT] Default color fo 6814 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6815 Default: 2 = green.
7332 6816
7333 vt.underline= [VT] Default color fo 6817 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6818 Default: 3 = cyan.
7335 6819
7336 watchdog timers [HW,WDT] For informat 6820 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6821 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6822 or other driver-specific files in the
7339 Documentation/watchdo 6823 Documentation/watchdog/ directory.
7340 6824
7341 watchdog_thresh= 6825 watchdog_thresh=
7342 [KNL] 6826 [KNL]
7343 Set the hard lockup d 6827 Set the hard lockup detector stall duration
7344 threshold in seconds. 6828 threshold in seconds. The soft lockup detector
7345 threshold is set to t 6829 threshold is set to twice the value. A value of 0
7346 disables both lockup 6830 disables both lockup detectors. Default is 10
7347 seconds. 6831 seconds.
7348 6832
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= 6833 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 6834 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 6835 warn stall conditions and dump internal state to
7359 help debugging. 0 di 6836 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 6837 detection; otherwise, it's the stall threshold
7361 duration in seconds. 6838 duration in seconds. The default value is 30 and
7362 it can be updated at 6839 it can be updated at runtime by writing to the
7363 corresponding sysfs f 6840 corresponding sysfs file.
7364 6841
7365 workqueue.cpu_intensive_thresh_us= !! 6842 workqueue.disable_numa
7366 Per-cpu work items wh !! 6843 By default, all work items queued to unbound
7367 threshold are automat !! 6844 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 6845 issued on, which results in better behavior in
7369 them from noticeably !! 6846 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 6847 whatever reason, this option can be used. Note
7371 !! 6848 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 6849 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 6850
7386 workqueue.power_efficient 6851 workqueue.power_efficient
7387 Per-cpu workqueues ar 6852 Per-cpu workqueues are generally preferred because
7388 they show better perf 6853 they show better performance thanks to cache
7389 locality; unfortunate 6854 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 6855 be more power hungry than unbound workqueues.
7391 6856
7392 Enabling this makes t 6857 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 6858 were observed to contribute significantly to power
7394 consumption unbound, 6859 consumption unbound, leading to measurably lower
7395 power usage at the co 6860 power usage at the cost of small performance
7396 overhead. 6861 overhead.
7397 6862
7398 The default value of 6863 The default value of this parameter is determined by
7399 the config option CON 6864 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 6865
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 6866 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 6867 Workqueue used to implicitly guarantee that work
7415 items queued without 6868 items queued without explicit CPU specified are put
7416 on the local CPU. Th 6869 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 6870 and while local CPU is still preferred work items
7418 may be put on foreign 6871 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 6872 forces round-robin CPU selection to flush out
7420 usages which depend o 6873 usages which depend on the now broken guarantee.
7421 When enabled, memory 6874 When enabled, memory and cache locality will be
7422 impacted. 6875 impacted.
7423 6876
7424 writecombine= [LOONGARCH,EARLY] Con !! 6877 writecombine= [LOONGARCH] Control the MAT (Memory Access Type) of
7425 Type) of ioremap_wc() !! 6878 ioremap_wc().
7426 6879
7427 on - Enable writeco 6880 on - Enable writecombine, use WUC for ioremap_wc()
7428 off - Disable writec 6881 off - Disable writecombine, use SUC for ioremap_wc()
7429 6882
7430 x2apic_phys [X86-64,APIC,EARLY] U !! 6883 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7431 default x2apic cluste 6884 default x2apic cluster mode on platforms
7432 supporting x2apic. 6885 supporting x2apic.
7433 6886
7434 xen_512gb_limit [KNL,X86-64,X 6887 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 6888 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6889 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6890 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6891 save/restore/migration must be enabled to handle larger
7439 domains. 6892 domains.
7440 6893
7441 xen_emul_unplug= [HW,X !! 6894 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6895 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6896 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6897 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6898 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6899 nics -- unplug network devices
7447 all -- unplug all emu 6900 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6901 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6902 unnecessary even if the host did not respond to
7450 the unplug pr 6903 the unplug protocol
7451 never -- do not unplu 6904 never -- do not unplug even if version check succeeds
7452 6905
7453 xen_legacy_crash [X86,XEN,EARL !! 6906 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6907 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6908 panic() code such as dumping handler.
7456 6909
7457 xen_mc_debug [X86,XEN,EARLY] !! 6910 xen_msr_safe= [X86,XEN]
7458 Enable multicall debu <<
7459 Enabling this feature <<
7460 bit, so it should onl <<
7461 debug data in case of <<
7462 <<
7463 xen_msr_safe= [X86,XEN,EARLY] <<
7464 Format: <bool> 6911 Format: <bool>
7465 Select whether to alw 6912 Select whether to always use non-faulting (safe) MSR
7466 access functions when 6913 access functions when running as Xen PV guest. The
7467 default value is cont 6914 default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
7468 6915
>> 6916 xen_nopvspin [X86,XEN]
>> 6917 Disables the qspinlock slowpath using Xen PV optimizations.
>> 6918 This parameter is obsoleted by "nopvspin" parameter, which
>> 6919 has equivalent effect for XEN platform.
>> 6920
7469 xen_nopv [X86] 6921 xen_nopv [X86]
7470 Disables the PV optim 6922 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6923 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6924 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6925 has equivalent effect for XEN platform.
7474 6926
7475 xen_no_vector_callback 6927 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6928 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6929 event channel interrupts.
7478 6930
7479 xen_scrub_pages= [XEN] 6931 xen_scrub_pages= [XEN]
7480 Boolean option to con 6932 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6933 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6934 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6935 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6936
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6937 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6938 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6939 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6940 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 6941 improve timer resolution at the expense of processing
7490 more timer interrupts 6942 more timer interrupts.
7491 6943
7492 xen.balloon_boot_timeout= [XEN] 6944 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 6945 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 6946 in case initial ballooning fails to free enough memory.
7495 Applies only when run 6947 Applies only when running as HVM or PVH guest and
7496 started with less mem 6948 started with less memory configured than allowed at
7497 max. Default is 180. 6949 max. Default is 180.
7498 6950
7499 xen.event_eoi_delay= [XEN] 6951 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 6952 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 6953 storms (jiffies). Default is 10.
7502 6954
7503 xen.event_loop_timeout= [XEN] 6955 xen.event_loop_timeout= [XEN]
7504 After which time (jif 6956 After which time (jiffies) the event handling loop
7505 should start to delay 6957 should start to delay EOI handling. Default is 2.
7506 6958
7507 xen.fifo_events= [XEN] 6959 xen.fifo_events= [XEN]
7508 Boolean parameter to 6960 Boolean parameter to disable using fifo event handling
7509 even if available. No 6961 even if available. Normally fifo event handling is
7510 preferred over the 2- 6962 preferred over the 2-level event handling, as it is
7511 fairer and the number 6963 fairer and the number of possible event channels is
7512 much higher. Default 6964 much higher. Default is on (use fifo events).
7513 6965
>> 6966 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
>> 6967 Disables the PV optimizations forcing the guest to run
>> 6968 as generic guest with no PV drivers. Currently support
>> 6969 XEN HVM, KVM, HYPER_V and VMWARE guest.
>> 6970
>> 6971 nopvspin [X86,XEN,KVM]
>> 6972 Disables the qspinlock slow path using PV optimizations
>> 6973 which allow the hypervisor to 'idle' the guest on lock
>> 6974 contention.
>> 6975
7514 xirc2ps_cs= [NET,PCMCIA] 6976 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 6977 Format:
7516 <irq>,<irq_mask>,<io> 6978 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 6979
7518 xive= [PPC] 6980 xive= [PPC]
7519 By default on POWER9 6981 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 6982 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 6983 allows the fallback firmware mode to be used:
7522 6984
7523 off Fallback to 6985 off Fallback to firmware control of XIVE interrupt
7524 controller 6986 controller on both pseries and powernv
7525 platforms. 6987 platforms. Only useful on POWER9 and above.
7526 6988
7527 xive.store-eoi=off [PPC] 6989 xive.store-eoi=off [PPC]
7528 By default on POWER10 6990 By default on POWER10 and above, the kernel will use
7529 stores for EOI handli 6991 stores for EOI handling when the XIVE interrupt mode
7530 is active. This optio 6992 is active. This option allows the XIVE driver to use
7531 loads instead, as on 6993 loads instead, as on POWER9.
7532 6994
7533 xhci-hcd.quirks [USB,KNL] 6995 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 6996 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 6997 host controller quirks. Meaning of each bit can be
7536 consulted in header d 6998 consulted in header drivers/usb/host/xhci.h.
7537 6999
7538 xmon [PPC,EARLY] !! 7000 xmon [PPC]
7539 Format: { early | on 7001 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 7002 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 7003 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 7004 early Call xmon as early as possible on boot; xmon
7543 debugger is c 7005 debugger is called from setup_arch().
7544 on xmon debugger 7006 on xmon debugger hooks will be installed so xmon
7545 is only calle 7007 is only called on a kernel crash. Default mode,
7546 i.e. either " 7008 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 7009 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 7010 rw xmon debugger hooks will be installed so xmon
7549 is called onl 7011 is called only on a kernel crash, mode is write,
7550 meaning SPR r 7012 meaning SPR registers, memory and, other data
7551 can be writte 7013 can be written using xmon commands.
7552 ro same as "rw" 7014 ro same as "rw" option above but SPR registers,
7553 memory, and o 7015 memory, and other data can't be written using
7554 xmon commands 7016 xmon commands.
7555 off xmon is disab 7017 off xmon is disabled.
>> 7018
>> 7019 amd_pstate= [X86]
>> 7020 disable
>> 7021 Do not enable amd_pstate as the default
>> 7022 scaling driver for the supported processors
>> 7023 passive
>> 7024 Use amd_pstate as a scaling driver, driver requests a
>> 7025 desired performance on this abstract scale and the power
>> 7026 management firmware translates the requests into actual
>> 7027 hardware states (core frequency, data fabric and memory
>> 7028 clocks etc.)
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