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
425 apm= [APM] Advanced Power M 381 apm= [APM] Advanced Power Management
426 See header of arch/x86 382 See header of arch/x86/kernel/apm_32.c.
427 383
428 apparmor= [APPARMOR] Disable or 384 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
429 Format: { "0" | "1" } 385 Format: { "0" | "1" }
430 See security/apparmor/ 386 See security/apparmor/Kconfig help text
431 0 -- disable. 387 0 -- disable.
432 1 -- enable. 388 1 -- enable.
433 Default value is set v 389 Default value is set via kernel config option.
434 390
435 arcrimi= [HW,NET] ARCnet - "RIM 391 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 392 Format: <io>,<irq>,<nodeID>
437 393
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall 394 arm64.nobti [ARM64] Unconditionally disable Branch Target
442 Identification support 395 Identification support
443 396
444 arm64.nomops [ARM64] Unconditionall !! 397 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support 398 support
449 399
450 arm64.nopauth [ARM64] Unconditionall !! 400 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
451 support 401 support
452 402
453 arm64.nosme [ARM64] Unconditionall !! 403 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
454 Extension support 404 Extension support
455 405
456 arm64.nosve [ARM64] Unconditionall !! 406 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
457 Extension support 407 Extension support
458 408
459 ataflop= [HW,M68k] 409 ataflop= [HW,M68k]
460 410
461 atarimouse= [HW,MOUSE] Atari Mouse 411 atarimouse= [HW,MOUSE] Atari Mouse
462 412
463 atkbd.extra= [HW] Enable extra LEDs 413 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 414 EzKey and similar keyboards
465 415
466 atkbd.reset= [HW] Reset keyboard du 416 atkbd.reset= [HW] Reset keyboard during initialization
467 417
468 atkbd.set= [HW] Select keyboard c 418 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 419 Format: <int> (2 = AT (default), 3 = PS/2)
470 420
471 atkbd.scroll= [HW] Enable scroll whe 421 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 422 keyboards
473 423
474 atkbd.softraw= [HW] Choose between sy 424 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 425 Format: <bool> (0 = real, 1 = synthetic (default))
476 426
477 atkbd.softrepeat= [HW] 427 atkbd.softrepeat= [HW]
478 Use software keyboard 428 Use software keyboard repeat
479 429
480 audit= [KNL] Enable the audit 430 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 431 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 432 0 | off - kernel audit is disabled and can not be
483 enabled until the 433 enabled until the next reboot
484 unset - kernel audit i 434 unset - kernel audit is initialized but disabled and
485 will be fully enab 435 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 436 1 | on - kernel audit is initialized and partially
487 enabled, storing a 437 enabled, storing at most audit_backlog_limit
488 messages in RAM un 438 messages in RAM until it is fully enabled by the
489 userspace auditd. 439 userspace auditd.
490 Default: unset 440 Default: unset
491 441
492 audit_backlog_limit= [KNL] Set the aud 442 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 443 Format: <int> (must be >=0)
494 Default: 64 444 Default: 64
495 445
496 bau= [X86_UV] Enable the BA 446 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 447 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 448 Format: { "0" | "1" }
499 0 - Disable the BAU. 449 0 - Disable the BAU.
500 1 - Enable the BAU. 450 1 - Enable the BAU.
501 unset - Disable the BA 451 unset - Disable the BAU.
502 452
503 baycom_epp= [HW,AX25] 453 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 454 Format: <io>,<mode>
505 455
506 baycom_par= [HW,AX25] BayCom Paral 456 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 457 Format: <io>,<mode>
508 See header of drivers/ 458 See header of drivers/net/hamradio/baycom_par.c.
509 459
510 baycom_ser_fdx= [HW,AX25] 460 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 461 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 462 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 463 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 464
515 baycom_ser_hdx= [HW,AX25] 465 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 466 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 467 Format: <io>,<irq>,<mode>
518 See header of drivers/ 468 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 469
520 bert_disable [ACPI] 470 bert_disable [ACPI]
521 Disable BERT OS suppor 471 Disable BERT OS support on buggy BIOSes.
522 472
523 bgrt_disable [ACPI,X86,EARLY] !! 473 bgrt_disable [ACPI][X86]
524 Disable BGRT to avoid 474 Disable BGRT to avoid flickering OEM logo.
525 475
526 blkdevparts= Manual partition parsi 476 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 477 embedded devices based on command line input.
528 See Documentation/bloc 478 See Documentation/block/cmdline-partition.rst
529 479
530 boot_delay= [KNL,EARLY] !! 480 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay <<
532 Only works if CONFIG_B 481 Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
533 and you may also have 482 and you may also have to specify "lpj=". Boot_delay
534 values larger than 10 483 values larger than 10 seconds (10000) are assumed
535 erroneous and ignored. 484 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 560 nobpf -- Disable BPF memory accounting.
616 561
617 checkreqprot= [SELINUX] Set initial 562 checkreqprot= [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 563 Format: { "0" | "1" }
619 See security/selinux/K 564 See security/selinux/Kconfig help text.
620 0 -- check protection 565 0 -- check protection applied by kernel (includes
621 any implied ex 566 any implied execute protection).
622 1 -- check protection 567 1 -- check protection requested by application.
623 Default value is set v 568 Default value is set via a kernel config option.
624 Value can be changed a 569 Value can be changed at runtime via
625 /sys/fs/selinu 570 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 571 Setting checkreqprot to 1 is deprecated.
627 572
628 cio_ignore= [S390] 573 cio_ignore= [S390]
629 See Documentation/arch !! 574 See Documentation/s390/common_io.rst for details.
630 575
631 clearcpuid=X[,X...] [X86] 576 clearcpuid=X[,X...] [X86]
632 Disable CPUID feature 577 Disable CPUID feature X for the kernel. See
633 arch/x86/include/asm/c 578 arch/x86/include/asm/cpufeatures.h for the valid bit
634 numbers X. Note the Li 579 numbers X. Note the Linux-specific bits are not necessarily
635 stable over kernel opt 580 stable over kernel options, but the vendor-specific
636 ones should be. 581 ones should be.
637 X can also be a string 582 X can also be a string as appearing in the flags: line
638 in /proc/cpuinfo which 583 in /proc/cpuinfo which does not have the above
639 instability issue. How 584 instability issue. However, not all features have names
640 in /proc/cpuinfo. 585 in /proc/cpuinfo.
641 Note that using this o 586 Note that using this option will taint your kernel.
642 Also note that user pr 587 Also note that user programs calling CPUID directly
643 or using the feature w 588 or using the feature without checking anything
644 will still see it. Thi 589 will still see it. This just prevents it from
645 being used by the kern 590 being used by the kernel or shown in /proc/cpuinfo.
646 Also note the kernel m 591 Also note the kernel might malfunction if you disable
647 some critical bits. 592 some critical bits.
648 593
649 clk_ignore_unused 594 clk_ignore_unused
650 [CLK] 595 [CLK]
651 Prevents the clock fra 596 Prevents the clock framework from automatically gating
652 clocks that have not b 597 clocks that have not been explicitly enabled by a Linux
653 device driver but are 598 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 599 by the bootloader/firmware. Note that this does not
655 force such clocks to b 600 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 601 those clocks in any way. This parameter is useful for
657 debug and development, 602 debug and development, but should not be needed on a
658 platform with proper d 603 platform with proper driver support. For more
659 information, see Docum 604 information, see Documentation/driver-api/clk.rst.
660 605
661 clock= [BUGS=X86-32, HW] gett 606 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 607 [Deprecated]
663 Forces specified clock 608 Forces specified clocksource (if available) to be used
664 when calculating getti 609 when calculating gettimeofday(). If specified
665 clocksource is not ava 610 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 611 Format: { pit | tsc | cyclone | pmtmr }
667 612
668 clocksource= Override the default c 613 clocksource= Override the default clocksource
669 Format: <string> 614 Format: <string>
670 Override the default c 615 Override the default clocksource and use the clocksource
671 with the name specifie 616 with the name specified.
672 Some clocksource names 617 Some clocksource names to choose from, depending on
673 the platform: 618 the platform:
674 [all] jiffies (this is 619 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 620 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 621 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 622 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 623 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 624 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 625 [MIPS] MIPS
681 [PARISC] cr16 626 [PARISC] cr16
682 [S390] tod 627 [S390] tod
683 [SH] SuperH 628 [SH] SuperH
684 [SPARC64] tick 629 [SPARC64] tick
685 [X86-64] hpet,tsc 630 [X86-64] hpet,tsc
686 631
687 clocksource.arm_arch_timer.evtstrm= 632 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 633 [ARM,ARM64]
689 Format: <bool> 634 Format: <bool>
690 Enable/disable the eve 635 Enable/disable the eventstream feature of the ARM
691 architected timer so t 636 architected timer so that code using WFE-based polling
692 loops can be debugged 637 loops can be debugged more effectively on production
693 systems. 638 systems.
694 639
>> 640 clocksource.max_cswd_read_retries= [KNL]
>> 641 Number of clocksource_watchdog() retries due to
>> 642 external delays before the clock will be marked
>> 643 unstable. Defaults to two retries, that is,
>> 644 three attempts to read the clock under test.
>> 645
695 clocksource.verify_n_cpus= [KNL] 646 clocksource.verify_n_cpus= [KNL]
696 Limit the number of CP 647 Limit the number of CPUs checked for clocksources
697 marked with CLOCK_SOUR 648 marked with CLOCK_SOURCE_VERIFY_PERCPU that
698 are marked unstable du 649 are marked unstable due to excessive skew.
699 A negative value says 650 A negative value says to check all CPUs, while
700 zero says not to check 651 zero says not to check any. Values larger than
701 nr_cpu_ids are silentl 652 nr_cpu_ids are silently truncated to nr_cpu_ids.
702 The actual CPUs are ch 653 The actual CPUs are chosen randomly, with
703 no replacement if the 654 no replacement if the same CPU is chosen twice.
704 655
705 clocksource-wdtest.holdoff= [KNL] 656 clocksource-wdtest.holdoff= [KNL]
706 Set the time in second 657 Set the time in seconds that the clocksource
707 watchdog test waits be 658 watchdog test waits before commencing its tests.
708 Defaults to zero when 659 Defaults to zero when built as a module and to
709 10 seconds when built 660 10 seconds when built into the kernel.
710 661
711 cma=nn[MG]@[start[MG][-end[MG]]] 662 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 663 [KNL,CMA]
713 Sets the size of kerne 664 Sets the size of kernel global memory area for
714 contiguous memory allo 665 contiguous memory allocations and optionally the
715 placement constraint b 666 placement constraint by the physical address range of
716 memory allocations. A 667 memory allocations. A value of 0 disables CMA
717 altogether. For more i 668 altogether. For more information, see
718 kernel/dma/contiguous. 669 kernel/dma/contiguous.c
719 670
720 cma_pernuma=nn[MG] 671 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 672 [ARM64,KNL,CMA]
722 Sets the size of kerne 673 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 674 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 675 per-numa CMA altogether. And If this option is not
725 specified, the default 676 specified, the default value is 0.
726 With per-numa CMA enab 677 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 678 first try to allocate buffer from the pernuma area
728 which is located in no 679 which is located in node nid, if the allocation fails,
729 they will fallback to 680 they will fallback to the global default memory area.
730 681
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 | 682 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 683 Specify whether pages are marked as being inactive
744 when they are freed. 684 when they are freed. This is used in CMO environments
745 to determine OS memory 685 to determine OS memory pressure for page stealing by
746 a hypervisor. 686 a hypervisor.
747 Default: yes 687 Default: yes
748 688
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 689 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 690 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 691 allocations, by default set to 256K.
752 692
753 com20020= [HW,NET] ARCnet - COM2 693 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 694 Format:
755 <io>[,<irq>[,<nodeID>[ 695 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 696
757 com90io= [HW,NET] ARCnet - COM9 697 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 698 Format: <io>[,<irq>]
759 699
760 com90xx= [HW,NET] 700 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 701 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 702 Format: <io>[,<irq>[,<memstart>]]
763 703
764 condev= [HW,S390] console devi 704 condev= [HW,S390] console device
765 conmode= 705 conmode=
766 706
767 con3215_drop= [S390,EARLY] 3215 cons !! 707 con3215_drop= [S390] 3215 console drop mode.
768 Format: y|n|Y|N|1|0 708 Format: y|n|Y|N|1|0
769 When set to true, drop 709 When set to true, drop data on the 3215 console when
770 the console buffer is 710 the console buffer is full. In this case the
771 operator using a 3270 711 operator using a 3270 terminal emulator (for example
772 x3270) does not have t 712 x3270) does not have to enter the clear key for the
773 console output to adva 713 console output to advance and the kernel to continue.
774 This leads to a much f 714 This leads to a much faster boot time when a 3270
775 terminal emulator is a 715 terminal emulator is active. If no 3270 terminal
776 emulator is used, this 716 emulator is used, this parameter has no effect.
777 717
778 console= [KNL] Output console d 718 console= [KNL] Output console device and options.
779 719
780 tty<n> Use the virtual consol 720 tty<n> Use the virtual console device <n>.
781 721
782 ttyS<n>[,options] 722 ttyS<n>[,options]
783 ttyUSB0[,options] 723 ttyUSB0[,options]
784 Use the specified seri 724 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 725 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 726 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 727 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 728 omit it). Default is "9600n8".
789 729
790 See Documentation/admi 730 See Documentation/admin-guide/serial-console.rst for more
791 information. See 731 information. See
792 Documentation/networki 732 Documentation/networking/netconsole.rst for an
793 alternative. 733 alternative.
794 734
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] 735 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 736 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 737 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 738 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 739 uart[8250],0x<addr>[,options]
819 Start an early, polled 740 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 741 UART at the specified I/O port or MMIO address,
821 switching to the match 742 switching to the matching ttyS device later.
822 MMIO inter-register ad 743 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 744 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 745 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 746 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 747 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 748 the h/w is not re-initialized.
828 749
829 hvc<n> Use the hypervisor con 750 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 751 both Xen and PowerPC hypervisors.
831 752
832 { null | "" } 753 { null | "" }
833 Use to disable console 754 Use to disable console output, i.e., to have kernel
834 console messages disca 755 console messages discarded.
835 This must be the only 756 This must be the only console= parameter used on the
836 kernel command line. 757 kernel command line.
837 758
838 If the device connected to the 759 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 760 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 761 console=brl,ttyS0
841 For now, only VisioBraille is 762 For now, only VisioBraille is supported.
842 763
843 console_msg_format= 764 console_msg_format=
844 [KNL] Change console m 765 [KNL] Change console messages format
845 default 766 default
846 By default we print me 767 By default we print messages on consoles in
847 "[time stamp] text\n" 768 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 769 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 770 `printk_time' param).
850 syslog 771 syslog
851 Switch to syslog forma 772 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 773 IOW, each message will have a facility and loglevel
853 prefix. The format is 774 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 775 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 776 from /proc/kmsg.
856 777
857 consoleblank= [KNL] The console blan 778 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 779 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 780 Defaults to 0.
860 781
861 coredump_filter= 782 coredump_filter=
862 [KNL] Change the defau 783 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 784 /proc/<pid>/coredump_filter.
864 See also Documentation 785 See also Documentation/filesystems/proc.rst.
865 786
866 coresight_cpu_debug.enable 787 coresight_cpu_debug.enable
867 [ARM,ARM64] 788 [ARM,ARM64]
868 Format: <bool> 789 Format: <bool>
869 Enable/disable the CPU 790 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 791 0: default value, disable debugging
871 1: enable debugging at 792 1: enable debugging at boot time
872 793
873 cpcihp_generic= [HW,PCI] Generic port 794 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
874 Format: 795 Format:
875 <first_slot>,<last_slo 796 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
876 797
>> 798 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
>> 799 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
>> 800 Some features depend on CPU0. Known dependencies are:
>> 801 1. Resume from suspend/hibernate depends on CPU0.
>> 802 Suspend/hibernate will fail if CPU0 is offline and you
>> 803 need to online CPU0 before suspend/hibernate.
>> 804 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 805 removed if a PIC interrupt is detected.
>> 806 It's said poweroff/reboot may depend on CPU0 on some
>> 807 machines although I haven't seen such issues so far
>> 808 after CPU0 is offline on a few tested machines.
>> 809 If the dependencies are under your control, you can
>> 810 turn on cpu0_hotplug.
>> 811
877 cpuidle.off=1 [CPU_IDLE] 812 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 813 disable the cpuidle sub-system
879 814
880 cpuidle.governor= 815 cpuidle.governor=
881 [CPU_IDLE] Name of the 816 [CPU_IDLE] Name of the cpuidle governor to use.
882 817
883 cpufreq.off=1 [CPU_FREQ] 818 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 819 disable the cpufreq sub-system
885 820
886 cpufreq.default_governor= 821 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 822 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 823 policy to use. This governor must be registered in the
889 kernel before the cpuf 824 kernel before the cpufreq driver probes.
890 825
891 cpu_init_udelay=N 826 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 827 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 828 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 829 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 830 Default: 10000
896 831
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 832 crash_kexec_post_notifiers
904 Run kdump after runnin 833 Run kdump after running panic-notifiers and dumping
905 kmsg. This only for th 834 kmsg. This only for the users who doubt kdump always
906 succeeds in any situat 835 succeeds in any situation.
907 Note that this also in 836 Note that this also increases risks of kdump failure,
908 because some panic not 837 because some panic notifiers can make the crashed
909 kernel more unstable. 838 kernel more unstable.
910 839
911 crashkernel=size[KMG][@offset[KMG]] 840 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 841 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 842 upon panic. This parameter reserves the physical
914 memory region [offset, 843 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 844 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 845 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 846 [KNL, X86-64, ARM64] Select a region under 4G first, and
918 under 4G first, and fa !! 847 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 848 hasn't been specified.
920 See Documentation/admi 849 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 850
922 crashkernel=range1:size1[,range2:size2 851 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 852 [KNL] Same as above, but depends on the memory
924 in the running system. 853 in the running system. The syntax of range is
925 start-[end] where star 854 start-[end] where start and end are both
926 a memory unit (amount[ 855 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 856 Documentation/admin-guide/kdump/kdump.rst for an example.
928 857
929 crashkernel=size[KMG],high 858 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 859 [KNL, X86-64, ARM64] range could be above 4G. Allow kernel
931 above 4G. !! 860 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 861 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 862 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 863 available.
935 below 4G, if available <<
936 It will be ignored if 864 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 865 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 866 [KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 867 is passed, kernel could allocate physical memory region
940 physical memory region !! 868 above 4G, that cause second kernel crash on system
941 crash on system that r !! 869 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 870 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 871 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 872 devices won't run out. Kernel would try to allocate
945 default size of memory 873 default size of memory below 4G automatically. The default
946 size is platform depen 874 size is platform dependent.
947 --> x86: max(swiotlb 875 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
948 --> arm64: 128MiB 876 --> arm64: 128MiB
949 --> riscv: 128MiB <<
950 --> loongarch: 128Mi <<
951 This one lets the user 877 This one lets the user specify own low range under 4G
952 for second kernel inst 878 for second kernel instead.
953 0: to disable low allo 879 0: to disable low allocation.
954 It will be ignored whe 880 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 881 or memory reserved is below 4G.
956 882
957 cryptomgr.notests 883 cryptomgr.notests
958 [KNL] Disable crypto s 884 [KNL] Disable crypto self-tests
959 885
960 cs89x0_dma= [HW,NET] 886 cs89x0_dma= [HW,NET]
961 Format: <dma> 887 Format: <dma>
962 888
963 cs89x0_media= [HW,NET] 889 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 890 Format: { rj45 | aui | bnc }
965 891
966 csdlock_debug= [KNL] Enable or disabl !! 892 csdlock_debug= [KNL] Enable debug add-ons of cross-CPU function call
967 function call handling !! 893 handling. When switched on, additional debug data is
968 additional debug data !! 894 printed to the console in case a hanging CPU is
969 in case a hanging CPU !! 895 detected, and that CPU is pinged again in order to try
970 CPU is pinged again in !! 896 to resolve the hang situation.
971 the hang situation. T !! 897 0: disable csdlock debugging (default)
972 option depends on the !! 898 1: enable basic csdlock debugging (minor impact)
973 Kconfig option. !! 899 ext: enable extended csdlock debugging (more impact,
>> 900 but more data)
974 901
975 dasd= [HW,NET] 902 dasd= [HW,NET]
976 See header of drivers/ 903 See header of drivers/s390/block/dasd_devmap.c.
977 904
978 db9.dev[2|3]= [HW,JOY] Multisystem j 905 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 906 (one device per port)
980 Format: <port#>,<type> 907 Format: <port#>,<type>
981 See also Documentation 908 See also Documentation/input/devices/joystick-parport.rst
982 909
983 debug [KNL,EARLY] Enable ker !! 910 debug [KNL] Enable kernel debugging (events log level).
984 911
985 debug_boot_weak_hash 912 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 913 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 914 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 915 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 916 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 917 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 918 insecure, please do not use on production kernels.
992 919
993 debug_locks_verbose= 920 debug_locks_verbose=
994 [KNL] verbose locking 921 [KNL] verbose locking self-tests
995 Format: <int> 922 Format: <int>
996 Print debugging info w 923 Print debugging info while doing the locking API
997 self-tests. 924 self-tests.
998 Bitmask for the variou 925 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 926 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 927 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 928 useful to lockdep developers.
1002 929
1003 debug_objects [KNL,EARLY] Enable ob !! 930 debug_objects [KNL] Enable object debugging
>> 931
>> 932 no_debug_objects
>> 933 [KNL] Disable object debugging
1004 934
1005 debug_guardpage_minorder= 935 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 936 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 937 parameter allows control of the order of pages that will
1008 be intentionally kept 938 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 939 buddy allocator. Bigger value increase the probability
1010 of catching random me 940 of catching random memory corruption, but reduce the
1011 amount of memory for 941 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 942 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 943 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 944 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 945 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 946 random memory location. Note that there exists a class
1017 a class of memory cor !! 947 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 948 F/W or by drivers badly programming DMA (basically when
1019 (basically when memor !! 949 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 950 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 951 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 952 tracking down these problems.
1023 953
1024 debug_pagealloc= 954 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 955 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 956 enables the feature at boot time. By default, it is
1027 disabled and the syst 957 disabled and the system will work mostly the same as a
1028 kernel built without 958 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 959 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 960 useful to also enable the page_owner functionality.
1031 on: enable the featur 961 on: enable the feature
1032 962
1033 debugfs= [KNL,EARLY] This para !! 963 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 964 and debugfs internal clients.
1035 Format: { on, no-moun 965 Format: { on, no-mount, off }
1036 on: All functions 966 on: All functions are enabled.
1037 no-mount: 967 no-mount:
1038 Filesystem is 968 Filesystem is not registered but kernel clients can
1039 access APIs a 969 access APIs and a crashkernel can be used to read
1040 its content. 970 its content. There is nothing to mount.
1041 off: Filesystem is 971 off: Filesystem is not registered and clients
1042 get a -EPERM 972 get a -EPERM as result when trying to register files
1043 or directorie 973 or directories within debugfs.
1044 This is equiv 974 This is equivalent of the runtime functionality if
1045 debugfs was n 975 debugfs was not enabled in the kernel at all.
1046 Default value is set 976 Default value is set in build-time with a kernel configuration.
1047 977
1048 debugpat [X86] Enable PAT debu 978 debugpat [X86] Enable PAT debugging
1049 979
1050 default_hugepagesz= 980 default_hugepagesz=
1051 [HW] The size of the 981 [HW] The size of the default HugeTLB page. This is
1052 the size represented 982 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 983 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 984 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 985 filesystems. If not specified, defaults to the
1056 architecture's defaul 986 architecture's default huge page size. Huge page
1057 sizes are architectur 987 sizes are architecture dependent. See also
1058 Documentation/admin-g 988 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 989 Format: size[KMG]
1060 990
1061 deferred_probe_timeout= 991 deferred_probe_timeout=
1062 [KNL] Debugging optio 992 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 993 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 994 probe. Only specific dependencies (subsystems or
1065 drivers) that have op 995 drivers) that have opted in will be ignored. A timeout
1066 of 0 will timeout at 996 of 0 will timeout at the end of initcalls. If the time
1067 out hasn't expired, i 997 out hasn't expired, it'll be restarted by each
1068 successful driver reg 998 successful driver registration. This option will also
1069 dump out devices stil 999 dump out devices still on the deferred probe list after
1070 retrying. 1000 retrying.
1071 1001
1072 delayacct [KNL] Enable per-task 1002 delayacct [KNL] Enable per-task delay accounting
1073 1003
1074 dell_smm_hwmon.ignore_dmi= 1004 dell_smm_hwmon.ignore_dmi=
1075 [HW] Continue probing 1005 [HW] Continue probing hardware even if DMI data
1076 indicates that the dr 1006 indicates that the driver is running on unsupported
1077 hardware. 1007 hardware.
1078 1008
1079 dell_smm_hwmon.force= 1009 dell_smm_hwmon.force=
1080 [HW] Activate driver 1010 [HW] Activate driver even if SMM BIOS signature does
1081 not match list of sup 1011 not match list of supported models and enable otherwise
1082 blacklisted features. 1012 blacklisted features.
1083 1013
1084 dell_smm_hwmon.power_status= 1014 dell_smm_hwmon.power_status=
1085 [HW] Report power sta 1015 [HW] Report power status in /proc/i8k
1086 (disabled by default) 1016 (disabled by default).
1087 1017
1088 dell_smm_hwmon.restricted= 1018 dell_smm_hwmon.restricted=
1089 [HW] Allow controllin 1019 [HW] Allow controlling fans only if SYS_ADMIN
1090 capability is set. 1020 capability is set.
1091 1021
1092 dell_smm_hwmon.fan_mult= 1022 dell_smm_hwmon.fan_mult=
1093 [HW] Factor to multip 1023 [HW] Factor to multiply fan speed with.
1094 1024
1095 dell_smm_hwmon.fan_max= 1025 dell_smm_hwmon.fan_max=
1096 [HW] Maximum configur 1026 [HW] Maximum configurable fan speed.
1097 1027
1098 dfltcc= [HW,S390] 1028 dfltcc= [HW,S390]
1099 Format: { on | off | 1029 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 1030 on: s390 zlib hardware support for compression on
1101 level 1 and 1031 level 1 and decompression (default)
1102 off: No s390 zli 1032 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 1033 def_only: s390 zlib hardware support for deflate
1104 only (compr 1034 only (compression on level 1)
1105 inf_only: s390 zlib h 1035 inf_only: s390 zlib hardware support for inflate
1106 only (decom 1036 only (decompression)
1107 always: Same as 'on 1037 always: Same as 'on' but ignores the selected compression
1108 level alway 1038 level always using hardware support (used for debugging)
1109 1039
1110 dhash_entries= [KNL] 1040 dhash_entries= [KNL]
1111 Set number of hash bu 1041 Set number of hash buckets for dentry cache.
1112 1042
1113 disable_1tb_segments [PPC,EARLY] !! 1043 disable_1tb_segments [PPC]
1114 Disables the use of 1 1044 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 1045 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 1046 can be useful when debugging issues that require an SLB
1117 miss to occur. 1047 miss to occur.
1118 1048
1119 disable= [IPV6] 1049 disable= [IPV6]
1120 See Documentation/net 1050 See Documentation/networking/ipv6.rst.
1121 1051
1122 disable_radix [PPC,EARLY] !! 1052 disable_radix [PPC]
1123 Disable RADIX MMU mod 1053 Disable RADIX MMU mode on POWER9
1124 1054
1125 disable_tlbie [PPC] 1055 disable_tlbie [PPC]
1126 Disable TLBIE instruc 1056 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 1057 with KVM, with HASH MMU, or with coherent accelerators.
1128 1058
1129 disable_ddw [PPC/PSERIES,EARLY] !! 1059 disable_cpu_apicid= [X86,APIC,SMP]
>> 1060 Format: <int>
>> 1061 The number of initial APIC ID for the
>> 1062 corresponding CPU to be disabled at boot,
>> 1063 mostly used for the kdump 2nd kernel to
>> 1064 disable BSP to wake up multiple CPUs without
>> 1065 causing system reset or hang due to sending
>> 1066 INIT from AP to BSP.
>> 1067
>> 1068 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 1069 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 1070 to workaround buggy firmware.
1132 1071
1133 disable_ipv6= [IPV6] 1072 disable_ipv6= [IPV6]
1134 See Documentation/net 1073 See Documentation/networking/ipv6.rst.
1135 1074
1136 disable_mtrr_cleanup [X86,EARLY] !! 1075 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 1076 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 1077 to discrete, to make X server driver able to add WB
1139 entry later. This par 1078 entry later. This parameter disables that.
1140 1079
1141 disable_mtrr_trim [X86, Intel and AMD !! 1080 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 1081 By default the kernel will trim any uncacheable
1143 memory out of your av 1082 memory out of your available memory pool based on
1144 MTRR settings. This 1083 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 1084 possibly causing your machine to run very slowly.
1146 1085
1147 disable_timer_pin_1 [X86,EARLY] !! 1086 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 1087 Disable PIN 1 of APIC timer
1149 Can be useful to work 1088 Can be useful to work around chipset bugs.
1150 1089
1151 dis_ucode_ldr [X86] Disable the mic 1090 dis_ucode_ldr [X86] Disable the microcode loader.
1152 1091
1153 dma_debug=off If the kernel is comp 1092 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 1093 this option disables the debugging code at boot.
1155 1094
1156 dma_debug_entries=<number> 1095 dma_debug_entries=<number>
1157 This option allows to 1096 This option allows to tune the number of preallocated
1158 entries for DMA-API d 1097 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 1098 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 1099 DMA-API debugging code disables itself because the
1161 architectural default 1100 architectural default is too low.
1162 1101
1163 dma_debug_driver=<driver_name> 1102 dma_debug_driver=<driver_name>
1164 With this option the 1103 With this option the DMA-API debugging driver
1165 filter feature can be 1104 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1105 pass the driver to filter for as the parameter.
1167 The filter can be dis 1106 The filter can be disabled or changed to another
1168 driver later using sy 1107 driver later using sysfs.
1169 1108
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] 1109 driver_async_probe= [KNL]
1191 List of driver names 1110 List of driver names to be probed asynchronously. *
1192 matches with all driv 1111 matches with all driver names. If * is specified, the
1193 rest of the listed dr 1112 rest of the listed driver names are those that will NOT
1194 match the *. 1113 match the *.
1195 Format: <driver_name1 1114 Format: <driver_name1>,<driver_name2>...
1196 1115
1197 drm.edid_firmware=[<connector>:]<file 1116 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1117 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1118 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1119 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1120 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1121 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1122 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1123 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1124 and no file with the same name exists. Details and
>> 1125 instructions how to build your own EDID data are
>> 1126 available in Documentation/admin-guide/edid.rst. An EDID
>> 1127 data set will only be used for a particular connector,
>> 1128 if its name and a colon are prepended to the EDID
>> 1129 name. Each connector may use a unique EDID data
>> 1130 set by separating the files with a comma. An EDID
1206 data set with no conn 1131 data set with no connector name will be used for
1207 any connectors not ex 1132 any connectors not explicitly specified.
1208 1133
1209 dscc4.setup= [NET] 1134 dscc4.setup= [NET]
1210 1135
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1136 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1137 Format: {"off" | "known"}
1213 Control how the dt_cp 1138 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1139 used for CPU feature discovery and setup (if it
1215 exists). 1140 exists).
1216 off: Do not use it, f 1141 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1142 known: Do not pass through unknown features to guests
1218 or userspace, only th 1143 or userspace, only those that the kernel is aware of.
1219 1144
1220 dump_apple_properties [X86] 1145 dump_apple_properties [X86]
1221 Dump name and content 1146 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1147 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1148 what data is available or for reverse-engineering.
1224 1149
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1150 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1151 <module>.dyndbg[="val"]
1227 Enable debug messages 1152 Enable debug messages at boot time. See
1228 Documentation/admin-g 1153 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1154 for details.
1230 1155
1231 early_ioremap_debug [KNL,EARLY] !! 1156 early_ioremap_debug [KNL]
1232 Enable debug messages 1157 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1158 is useful for tracking down temporary early mappings
1234 which are not unmappe 1159 which are not unmapped.
1235 1160
1236 earlycon= [KNL,EARLY] Output ea !! 1161 earlycon= [KNL] Output early console device and options.
1237 1162
1238 When used with no opt 1163 When used with no options, the early console is
1239 determined by stdout- 1164 determined by stdout-path property in device tree's
1240 chosen node or the AC 1165 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1166 the platform.
1242 1167
1243 cdns,<addr>[,options] 1168 cdns,<addr>[,options]
1244 Start an early, polle 1169 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1170 (xuartps) serial port at the specified address. Only
1246 supported option is b 1171 supported option is baud rate. If baud rate is not
1247 specified, the serial 1172 specified, the serial port must already be setup and
1248 configured. 1173 configured.
1249 1174
1250 uart[8250],io,<addr>[,options 1175 uart[8250],io,<addr>[,options[,uartclk]]
1251 uart[8250],mmio,<addr>[,optio 1176 uart[8250],mmio,<addr>[,options[,uartclk]]
1252 uart[8250],mmio32,<addr>[,opt 1177 uart[8250],mmio32,<addr>[,options[,uartclk]]
1253 uart[8250],mmio32be,<addr>[,o 1178 uart[8250],mmio32be,<addr>[,options[,uartclk]]
1254 uart[8250],0x<addr>[,options] 1179 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1180 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1181 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1182 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1183 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1184 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1185 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1186 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w 1187 unspecified, the h/w is not initialized. 'uartclk' is
1263 the uart clock freque 1188 the uart clock frequency; if unspecified, it is set
1264 to 'BASE_BAUD' * 16. 1189 to 'BASE_BAUD' * 16.
1265 1190
1266 pl011,<addr> 1191 pl011,<addr>
1267 pl011,mmio32,<addr> 1192 pl011,mmio32,<addr>
1268 Start an early, polle 1193 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1194 port at the specified address. The pl011 serial port
1270 must already be setup 1195 must already be setup and configured. Options are not
1271 yet supported. If 'm 1196 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1197 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1198 the device registers.
1274 1199
1275 liteuart,<addr> 1200 liteuart,<addr>
1276 Start an early consol 1201 Start an early console on a litex serial port at the
1277 specified address. Th 1202 specified address. The serial port must already be
1278 setup and configured. 1203 setup and configured. Options are not yet supported.
1279 1204
1280 meson,<addr> 1205 meson,<addr>
1281 Start an early, polle 1206 Start an early, polled-mode console on a meson serial
1282 port at the specified 1207 port at the specified address. The serial port must
1283 already be setup and 1208 already be setup and configured. Options are not yet
1284 supported. 1209 supported.
1285 1210
1286 msm_serial,<addr> 1211 msm_serial,<addr>
1287 Start an early, polle 1212 Start an early, polled-mode console on an msm serial
1288 port at the specified 1213 port at the specified address. The serial port
1289 must already be setup 1214 must already be setup and configured. Options are not
1290 yet supported. 1215 yet supported.
1291 1216
1292 msm_serial_dm,<addr> 1217 msm_serial_dm,<addr>
1293 Start an early, polle 1218 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1219 dm port at the specified address. The serial port
1295 must already be setup 1220 must already be setup and configured. Options are not
1296 yet supported. 1221 yet supported.
1297 1222
1298 owl,<addr> 1223 owl,<addr>
1299 Start an early, polle 1224 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1225 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1226 specified address. The serial port must already be
1302 setup and configured. 1227 setup and configured. Options are not yet supported.
1303 1228
1304 rda,<addr> 1229 rda,<addr>
1305 Start an early, polle 1230 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1231 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1232 specified address. The serial port must already be
1308 setup and configured. 1233 setup and configured. Options are not yet supported.
1309 1234
1310 sbi 1235 sbi
1311 Use RISC-V SBI (Super 1236 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1237 console.
1313 1238
1314 smh Use ARM semihosting c 1239 smh Use ARM semihosting calls for early console.
1315 1240
1316 s3c2410,<addr> 1241 s3c2410,<addr>
1317 s3c2412,<addr> 1242 s3c2412,<addr>
1318 s3c2440,<addr> 1243 s3c2440,<addr>
1319 s3c6400,<addr> 1244 s3c6400,<addr>
1320 s5pv210,<addr> 1245 s5pv210,<addr>
1321 exynos4210,<addr> 1246 exynos4210,<addr>
1322 Use early console pro 1247 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1248 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1249 a correct base address of the selected UART port. The
1325 serial port must alre 1250 serial port must already be setup and configured.
1326 Options are not yet s 1251 Options are not yet supported.
1327 1252
1328 lantiq,<addr> 1253 lantiq,<addr>
1329 Start an early, polle 1254 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1255 (lqasc) port at the specified address. The serial port
1331 must already be setup 1256 must already be setup and configured. Options are not
1332 yet supported. 1257 yet supported.
1333 1258
1334 lpuart,<addr> 1259 lpuart,<addr>
1335 lpuart32,<addr> 1260 lpuart32,<addr>
1336 Use early console pro 1261 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1262 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1263 A valid base address must be provided, and the serial
1339 port must already be 1264 port must already be setup and configured.
1340 1265
1341 ec_imx21,<addr> 1266 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1267 ec_imx6q,<addr>
1343 Start an early, polle 1268 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1269 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1270 must already be setup and configured.
1346 1271
1347 ar3700_uart,<addr> 1272 ar3700_uart,<addr>
1348 Start an early, polle 1273 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1274 Armada 3700 serial port at the specified
1350 address. The serial p 1275 address. The serial port must already be setup
1351 and configured. Optio 1276 and configured. Options are not yet supported.
1352 1277
1353 qcom_geni,<addr> 1278 qcom_geni,<addr>
1354 Start an early, polle 1279 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1280 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1281 specified address. The serial port must already be
1357 setup and configured. 1282 setup and configured. Options are not yet supported.
1358 1283
1359 efifb,[options] 1284 efifb,[options]
1360 Start an early, unacc 1285 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1286 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1287 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1288 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1289 mapped with the correct attributes.
1365 1290
1366 linflex,<addr> 1291 linflex,<addr>
1367 Use early console pro 1292 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1293 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1294 address must be provided, and the serial port must
1370 already be setup and 1295 already be setup and configured.
1371 1296
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1297 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1298 earlyprintk=vga
1374 earlyprintk=sclp 1299 earlyprintk=sclp
1375 earlyprintk=xen 1300 earlyprintk=xen
1376 earlyprintk=serial[,t 1301 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1302 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1303 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1304 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1305 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1306 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1307
1384 earlyprintk is useful 1308 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1309 the normal console is initialized. It is not enabled by
1386 default because it ha 1310 default because it has some cosmetic problems.
1387 1311
1388 Append ",keep" to not 1312 Append ",keep" to not disable it when the real console
1389 takes over. 1313 takes over.
1390 1314
1391 Only one of vga, seri 1315 Only one of vga, serial, or usb debug port can
1392 be used at a time. 1316 be used at a time.
1393 1317
1394 Currently only ttyS0 1318 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1319 name. Other I/O ports may be explicitly specified
1396 on some architectures 1320 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1321 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1322 earlyprintk=serial,0x1008,115200
1399 You can find the port 1323 You can find the port for a given device in
1400 /proc/tty/driver/seri 1324 /proc/tty/driver/serial:
1401 2: uart:ST166 1325 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1326
1403 Interaction with the 1327 Interaction with the standard serial driver is not
1404 very good. 1328 very good.
1405 1329
1406 The VGA output is eve 1330 The VGA output is eventually overwritten by
1407 the real console. 1331 the real console.
1408 1332
1409 The xen option can on 1333 The xen option can only be used in Xen domains.
1410 1334
1411 The sclp output can o 1335 The sclp output can only be used on s390.
1412 1336
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1337 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1338 PCI device even when its classcode is not of the
1417 UART class. 1339 UART class.
1418 1340
1419 edac_report= [HW,EDAC] Control how 1341 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1342 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1343 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1344 by other higher priority error reporting module.
1423 off: disable H/W even 1345 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1346 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1347 default: on.
1426 1348
1427 edd= [EDD] 1349 edd= [EDD]
1428 Format: {"off" | "on" 1350 Format: {"off" | "on" | "skip[mbr]"}
1429 1351
1430 efi= [EFI,EARLY] !! 1352 efi= [EFI]
1431 Format: { "debug", "d 1353 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1354 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1355 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1356 debug: enable misc debug output.
1435 disable_early_pci_dma 1357 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1358 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1359 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1360 boot stub, as chunking can cause problems with some
1439 firmware implementati 1361 firmware implementations.
1440 noruntime : disable E 1362 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1363 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1364 attribute may cause the kernel to reserve the
1443 memory range for a me 1365 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1366 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1367 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1368 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1369 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1370 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1371 on all PCI bridges while in the EFI boot stub
1450 1372
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1373 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1374 Using this parameter you can use more than 50% of
1453 your efi variable sto 1375 your efi variable storage. Use this parameter only if
1454 you are really sure t 1376 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1377 fulfills the spec otherwise your board may brick.
1456 1378
>> 1379 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1380 Add arbitrary attribute to specific memory range by
>> 1381 updating original EFI memory map.
>> 1382 Region of memory which aa attribute is added to is
>> 1383 from ss to ss+nn.
>> 1384
>> 1385 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1386 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1387 attribute is added to range 0x100000000-0x180000000 and
>> 1388 0x10a0000000-0x1120000000.
>> 1389
>> 1390 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1391 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1392 range 0x240000000-0x43fffffff.
>> 1393
>> 1394 Using this parameter you can do debugging of EFI memmap
>> 1395 related features. For example, you can do debugging of
>> 1396 Address Range Mirroring feature even if your box
>> 1397 doesn't support it, or mark specific memory as
>> 1398 "soft reserved".
>> 1399
1457 efivar_ssdt= [EFI; X86] Name of an 1400 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1401 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1402 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1403 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1404 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1405
1463 1406
1464 eisa_irq_edge= [PARISC,HW] 1407 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1408 See header of drivers/parisc/eisa.c.
1466 1409
1467 ekgdboc= [X86,KGDB,EARLY] Allo !! 1410 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1468 Format: ekgdboc=kbd 1411 Format: ekgdboc=kbd
1469 1412
1470 This is designed to b 1413 This is designed to be used in conjunction with
1471 the boot argument: ea 1414 the boot argument: earlyprintk=vga
1472 1415
1473 This parameter works 1416 This parameter works in place of the kgdboc parameter
1474 but can only be used 1417 but can only be used if the backing tty is available
1475 very early in the boo 1418 very early in the boot process. For early debugging
1476 via a serial port see 1419 via a serial port see kgdboc_earlycon instead.
1477 1420
1478 elanfreq= [X86-32] 1421 elanfreq= [X86-32]
1479 See comment before fu 1422 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1423 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1424
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1425 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1426 Specifies physical address of start of kernel core
1484 image elf header and 1427 image elf header and optionally the size. Generally
1485 kexec loader will pas 1428 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1429 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1430
1488 enable_mtrr_cleanup [X86,EARLY] !! 1431 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1432 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1433 to discrete, to make X server driver able to add WB
1491 entry later. This par 1434 entry later. This parameter enables that.
1492 1435
1493 enable_timer_pin_1 [X86] 1436 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1437 Enable PIN 1 of APIC timer
1495 Can be useful to work 1438 Can be useful to work around chipset bugs
1496 (in particular on som 1439 (in particular on some ATI chipsets).
1497 The kernel tries to s 1440 The kernel tries to set a reasonable default.
1498 1441
1499 enforcing= [SELINUX] Set initial 1442 enforcing= [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1443 Format: {"0" | "1"}
1501 See security/selinux/ 1444 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1445 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1446 1 -- enforcing (deny and log).
1504 Default value is 0. 1447 Default value is 0.
1505 Value can be changed 1448 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1449 /sys/fs/selinux/enforce.
1507 1450
1508 erst_disable [ACPI] 1451 erst_disable [ACPI]
1509 Disable Error Record 1452 Disable Error Record Serialization Table (ERST)
1510 support. 1453 support.
1511 1454
1512 ether= [HW,NET] Ethernet car 1455 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1456 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1457 has equivalent usage. See its documentation for details.
1515 1458
1516 evm= [EVM] 1459 evm= [EVM]
1517 Format: { "fix" } 1460 Format: { "fix" }
1518 Permit 'security.evm' 1461 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1462 current integrity status.
1520 1463
1521 early_page_ext [KNL,EARLY] Enforces p !! 1464 early_page_ext [KNL] Enforces page_ext initialization to earlier
1522 stages so cover more 1465 stages so cover more early boot allocations.
1523 Please note that as s 1466 Please note that as side effect some optimizations
1524 might be disabled to 1467 might be disabled to achieve that (e.g. parallelized
1525 memory initialization 1468 memory initialization is disabled) so the boot process
1526 might take longer, es 1469 might take longer, especially on systems with a lot of
1527 memory. Available wit 1470 memory. Available with CONFIG_PAGE_EXTENSION=y.
1528 1471
1529 failslab= 1472 failslab=
1530 fail_usercopy= 1473 fail_usercopy=
1531 fail_page_alloc= 1474 fail_page_alloc=
1532 fail_make_request=[KNL] 1475 fail_make_request=[KNL]
1533 General fault injecti 1476 General fault injection mechanism.
1534 Format: <interval>,<p 1477 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1478 See also Documentation/fault-injection/.
1536 1479
1537 fb_tunnels= [NET] 1480 fb_tunnels= [NET]
1538 Format: { initns | no 1481 Format: { initns | none }
1539 See Documentation/adm 1482 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1483 fb_tunnels_only_for_init_ns
1541 1484
1542 floppy= [HW] 1485 floppy= [HW]
1543 See Documentation/adm 1486 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1487
>> 1488 force_pal_cache_flush
>> 1489 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1490 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1491 parameter will force ia64_sal_cache_flush to call
>> 1492 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1493
1545 forcepae [X86-32] 1494 forcepae [X86-32]
1546 Forcefully enable Phy 1495 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1496 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1497 functionally usable PAE implementation.
1549 Warning: use of this 1498 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1499 and may cause unknown problems.
1551 1500
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] 1501 ftrace=[tracer]
1559 [FTRACE] will set and 1502 [FTRACE] will set and start the specified tracer
1560 as early as possible 1503 as early as possible in order to facilitate early
1561 boot debugging. 1504 boot debugging.
1562 1505
1563 ftrace_boot_snapshot 1506 ftrace_boot_snapshot
1564 [FTRACE] On boot up, 1507 [FTRACE] On boot up, a snapshot will be taken of the
1565 ftrace ring buffer th 1508 ftrace ring buffer that can be read at:
1566 /sys/kernel/tracing/s 1509 /sys/kernel/tracing/snapshot.
1567 This is useful if you 1510 This is useful if you need tracing information from kernel
1568 boot up that is likel 1511 boot up that is likely to be overridden by user space
1569 start up functionalit 1512 start up functionality.
1570 1513
1571 Optionally, the snaps 1514 Optionally, the snapshot can also be defined for a tracing
1572 instance that was cre 1515 instance that was created by the trace_instance= command
1573 line parameter. 1516 line parameter.
1574 1517
1575 trace_instance=foo,sc 1518 trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1576 1519
1577 The above will cause 1520 The above will cause the "foo" tracing instance to trigger
1578 a snapshot at the end 1521 a snapshot at the end of boot up.
1579 1522
1580 ftrace_dump_on_oops[=2(orig_cpu) | =< !! 1523 ftrace_dump_on_oops[=orig_cpu]
1581 ,<instance>=2(orig_ <<
1582 [FTRACE] will dump th 1524 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1525 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1526 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1527 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1528 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 1529
1603 ftrace_filter=[function-list] 1530 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1531 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1532 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1533 list of functions. This list can be changed at run
1607 time by the set_ftrac 1534 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1535 tracing directory.
1609 1536
1610 ftrace_notrace=[function-list] 1537 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1538 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1539 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1540 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1541 tracing directory.
1615 1542
1616 ftrace_graph_filter=[function-list] 1543 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1544 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1545 by the function graph tracer at boot up.
1619 function-list is a co 1546 function-list is a comma-separated list of functions
1620 that can be changed a 1547 that can be changed at run time by the
1621 set_graph_function fi 1548 set_graph_function file in the debugfs tracing directory.
1622 1549
1623 ftrace_graph_notrace=[function-list] 1550 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1551 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1552 function-list. This list is a comma-separated list of
1626 functions that can be 1553 functions that can be changed at run time by the
1627 set_graph_notrace fil 1554 set_graph_notrace file in the debugfs tracing directory.
1628 1555
1629 ftrace_graph_max_depth=<uint> 1556 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1557 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1558 the max depth it will trace into a function. This value
1632 can be changed at run 1559 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1560 in the tracefs tracing directory. default: 0 (no limit)
1634 1561
1635 fw_devlink= [KNL,EARLY] Create de !! 1562 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1563 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1564 consumer/supplier relationships. This feature is
1638 especially useful whe 1565 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1566 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1567 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1568 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1569 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1570 suppliers).
1644 Format: { off | permi 1571 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1572 off -- Don't create device links from firmware info.
1646 permissive -- Create 1573 permissive -- Create device links from firmware info
1647 but use it on 1574 but use it only for ordering boot state clean
1648 up (sync_stat 1575 up (sync_state() calls).
1649 on -- Create device 1576 on -- Create device links from firmware info and use it
1650 to enforce pr 1577 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1578 rpm -- Like "on", but also use to order runtime PM.
1652 1579
1653 fw_devlink.strict=<bool> 1580 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1581 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1582 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1583 Format: <bool>
1657 1584
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]= 1585 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1586 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1587 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1588 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1589 See also Documentation/input/devices/joystick-parport.rst
1677 1590
1678 gamma= [HW,DRM] 1591 gamma= [HW,DRM]
1679 1592
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1593 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1594 Format: off | on
1682 default: on 1595 default: on
1683 1596
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 1597 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1598 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1599 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1600 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1601 debugfs files are removed at module unload time.
1709 1602
1710 goldfish [X86] Enable the gold 1603 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1604 Don't use this when you are not running on the
1712 android emulator 1605 android emulator
1713 1606
1714 gpio-mockup.gpio_mockup_ranges 1607 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1608 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1609 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1610 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1611 [HW] Let the driver know GPIO lines should be named.
1719 1612
1720 gpt [EFI] Forces disk wit 1613 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1614 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1615 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1616 GPT to be used instead.
1724 1617
1725 grcan.enable0= [HW] Configuration of 1618 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1619 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1620 Format: 0 | 1
1728 Default: 0 1621 Default: 0
1729 grcan.enable1= [HW] Configuration of 1622 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1623 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1624 Format: 0 | 1
1732 Default: 0 1625 Default: 0
1733 grcan.select= [HW] Select which phy 1626 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1627 Format: 0 | 1
1735 Default: 0 1628 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1629 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1630 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1631 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1632 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1633 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1634 Default: 1024
1742 1635
1743 hardened_usercopy= 1636 hardened_usercopy=
1744 [KNL] Under CONFIG_HA 1637 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
1745 hardening is enabled 1638 hardening is enabled for this boot. Hardened
1746 usercopy checking is 1639 usercopy checking is used to protect the kernel
1747 from reading or writi 1640 from reading or writing beyond known memory
1748 allocation boundaries 1641 allocation boundaries as a proactive defense
1749 against bounds-checki 1642 against bounds-checking flaws in the kernel's
1750 copy_to_user()/copy_f 1643 copy_to_user()/copy_from_user() interface.
1751 on Perform hardened user 1644 on Perform hardened usercopy checks (default).
1752 off Disable hardened user 1645 off Disable hardened usercopy checks.
1753 1646
1754 hardlockup_all_cpu_backtrace= 1647 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1648 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1649 backtraces on all cpus.
1757 Format: 0 | 1 1650 Format: 0 | 1
1758 1651
1759 hashdist= [KNL,NUMA] Large hash 1652 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1653 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1654 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1655 Format: 0 | 1 (for off | on)
1763 1656
>> 1657 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1658
1764 hd= [EIDE] (E)IDE hard dr 1659 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1660 Format: <cyl>,<head>,<sect>
1766 1661
1767 hest_disable [ACPI] 1662 hest_disable [ACPI]
1768 Disable Hardware Erro 1663 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1664 corresponding firmware-first mode error processing
1770 logic will be disable 1665 logic will be disabled.
1771 1666
1772 hibernate= [HIBERNATION] 1667 hibernate= [HIBERNATION]
1773 noresume Don't check i 1668 noresume Don't check if there's a hibernation image
1774 present durin 1669 present during boot.
1775 nocompress Don't compres 1670 nocompress Don't compress/decompress hibernation images.
1776 no Disable hiber 1671 no Disable hibernation and resume.
1777 protect_image Turn on image 1672 protect_image Turn on image protection during restoration
1778 (that will se 1673 (that will set all pages holding image data
1779 during restor 1674 during restoration read-only).
1780 1675
1781 hibernate.compressor= [HIBERNATION] !! 1676 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 1677 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1678 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1679 size on bigger boxes.
1796 1680
1797 highres= [KNL] Enable/disable 1681 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1682 Valid parameters: "on", "off"
1799 Default: "on" 1683 Default: "on"
1800 1684
1801 hlt [BUGS=ARM,SH] 1685 hlt [BUGS=ARM,SH]
1802 1686
1803 hostname= [KNL,EARLY] Set the h !! 1687 hostname= [KNL] Set the hostname (aka UTS nodename).
1804 Format: <string> 1688 Format: <string>
1805 This allows setting t 1689 This allows setting the system's hostname during early
1806 startup. This sets th 1690 startup. This sets the name returned by gethostname.
1807 Using this parameter 1691 Using this parameter to set the hostname makes it
1808 possible to ensure th 1692 possible to ensure the hostname is correctly set before
1809 any userspace process 1693 any userspace processes run, avoiding the possibility
1810 that a process may ca 1694 that a process may call gethostname before the hostname
1811 has been explicitly s 1695 has been explicitly set, resulting in the calling
1812 process getting an in 1696 process getting an incorrect result. The string must
1813 not exceed the maximu 1697 not exceed the maximum allowed hostname length (usually
1814 64 characters) and wi 1698 64 characters) and will be truncated otherwise.
1815 1699
1816 hpet= [X86-32,HPET] option 1700 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1701 Format: { enable (default) | disable | force |
1818 verbose } 1702 verbose }
1819 disable: disable HPET 1703 disable: disable HPET and use PIT instead
1820 force: allow force en 1704 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1705 VIA, nVidia)
1822 verbose: show content 1706 verbose: show contents of HPET registers during setup
1823 1707
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1708 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1709 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1710
1827 hugepages= [HW] Number of HugeTL 1711 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1712 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1713 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1714 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1715 line, it specifies the number of pages to allocate for
1832 the default huge page 1716 the default huge page size. If using node format, the
1833 number of pages to al 1717 number of pages to allocate per-node can be specified.
1834 See also Documentatio 1718 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1835 Format: <integer> or 1719 Format: <integer> or (node format)
1836 <node>:<integ 1720 <node>:<integer>[,<node>:<integer>]
1837 1721
1838 hugepagesz= 1722 hugepagesz=
1839 [HW] The size of the 1723 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1724 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1725 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1726 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1727 each supported huge page size. Huge page sizes are
1844 architecture dependen 1728 architecture dependent. See also
1845 Documentation/admin-g 1729 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1730 Format: size[KMG]
1847 1731
1848 hugetlb_cma= [HW,CMA,EARLY] The si !! 1732 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
1849 of gigantic hugepages 1733 of gigantic hugepages. Or using node format, the size
1850 of a CMA area per nod 1734 of a CMA area per node can be specified.
1851 Format: nn[KMGTPE] or 1735 Format: nn[KMGTPE] or (node format)
1852 <node>:nn[KMG 1736 <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1853 1737
1854 Reserve a CMA area of 1738 Reserve a CMA area of given size and allocate gigantic
1855 hugepages using the C 1739 hugepages using the CMA allocator. If enabled, the
1856 boot-time allocation 1740 boot-time allocation of gigantic hugepages is skipped.
1857 1741
1858 hugetlb_free_vmemmap= 1742 hugetlb_free_vmemmap=
1859 [KNL] Requires CONFIG 1743 [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1860 enabled. 1744 enabled.
1861 Control if HugeTLB Vm 1745 Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1862 Allows heavy hugetlb 1746 Allows heavy hugetlb users to free up some more
1863 memory (7 * PAGE_SIZE 1747 memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1864 Format: { on | off (d 1748 Format: { on | off (default) }
1865 1749
1866 on: enable HVO 1750 on: enable HVO
1867 off: disable HVO 1751 off: disable HVO
1868 1752
1869 Built with CONFIG_HUG 1753 Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1870 the default is on. 1754 the default is on.
1871 1755
1872 Note that the vmemmap 1756 Note that the vmemmap pages may be allocated from the added
1873 memory block itself w 1757 memory block itself when memory_hotplug.memmap_on_memory is
1874 enabled, those vmemma 1758 enabled, those vmemmap pages cannot be optimized even if this
1875 feature is enabled. 1759 feature is enabled. Other vmemmap pages not allocated from
1876 the added memory bloc 1760 the added memory block itself do not be affected.
1877 1761
1878 hung_task_panic= 1762 hung_task_panic=
1879 [KNL] Should the hung 1763 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1764 Format: 0 | 1
1881 1765
1882 A value of 1 instruct 1766 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1767 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1768 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1769 option. The value selected by this boot parameter can
1886 be changed later by t 1770 be changed later by the kernel.hung_task_panic sysctl.
1887 1771
1888 hvc_iucv= [S390] Number of z/V 1772 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1773 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1774 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1775 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1776 from listed z/VM user IDs only.
1893 1777
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1778 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1779 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1780 guest on lock contention.
1897 on lock contention. <<
1898 1781
1899 i2c_bus= [HW] Override the 1782 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1783 or register an additional I2C bus that is not
1901 registered fr 1784 registered from board initialization code.
1902 Format: 1785 Format:
1903 <bus_id>,<clk 1786 <bus_id>,<clkrate>
1904 1787
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 1788 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1789 i8042.unmask_kbd_data
1929 [HW] Enable printing 1790 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1791 (disabled by default, and as a pre-condition
1931 requires that i8 1792 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1793 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1794 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1795 keyboard and cannot control its state
1935 (Don't attempt t 1796 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1797 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1798 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1799 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1800 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1801 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1802 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1803 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1804 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1805 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1806 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1807 suspend-to-ram transitions, only during s2r
1947 transitions, or 1808 transitions, or never reset
1948 Format: { 1 | Y | y | 1809 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1810 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1811 0, N, n: don't ever reset controller
1951 Default: only on s2r 1812 Default: only on s2r transitions on x86; most other
1952 architectures force r 1813 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1814 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1815 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer 1816 i8042.probe_defer
1956 [HW] Allow deferred p 1817 [HW] Allow deferred probing upon i8042 probe errors
1957 1818
1958 i810= [HW,DRM] 1819 i810= [HW,DRM]
1959 1820
1960 i915.invert_brightness= 1821 i915.invert_brightness=
1961 [DRM] Invert the sens 1822 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1823 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1824 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1825 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1826 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1827 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1828 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1829 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1830 value switches the backlight off.
1970 -1 -- never invert br 1831 -1 -- never invert brightness
1971 0 -- machine default 1832 0 -- machine default
1972 1 -- force brightnes 1833 1 -- force brightness inversion
1973 1834
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] 1835 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1836 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1837
1983 1838
1984 idle= [X86,EARLY] !! 1839 idle= [X86]
1985 Format: idle=poll, id 1840 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1841 Poll forces a polling idle loop that can slightly
1987 improve the performan 1842 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1843 will use a lot of power and make the system run hot.
1989 Not recommended. 1844 Not recommended.
1990 idle=halt: Halt is fo 1845 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1846 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1847 idle=nomwait: Disable mwait for CPU C-states
1993 1848
1994 idxd.sva= [HW] 1849 idxd.sva= [HW]
1995 Format: <bool> 1850 Format: <bool>
1996 Allow force disabling 1851 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1852 support for the idxd driver. By default it is set to
1998 true (1). 1853 true (1).
1999 1854
2000 idxd.tc_override= [HW] 1855 idxd.tc_override= [HW]
2001 Format: <bool> 1856 Format: <bool>
2002 Allow override of def 1857 Allow override of default traffic class configuration
2003 for the device. By de 1858 for the device. By default it is set to false (0).
2004 1859
2005 ieee754= [MIPS] Select IEEE St 1860 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1861 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1862 Default: strict
2008 1863
2009 Choose which programs 1864 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1865 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1866 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1867 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1868 binary. Hardware implementations are permitted to
2014 support either or bot 1869 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1870 encoding mode.
2016 1871
2017 Available settings ar 1872 Available settings are as follows:
2018 strict accept binari 1873 strict accept binaries that request a NaN encoding
2019 supported by 1874 supported by the FPU
2020 legacy only accept l 1875 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1876 by the FPU
2022 2008 only accept 2 1877 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1878 by the FPU
2024 relaxed accept any bi 1879 relaxed accept any binaries regardless of whether
2025 supported by 1880 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1881
2029 The FPU emulator is a 1882 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1883 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1884 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1885 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1886 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1887 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1888 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1889 MIPS64 CPUs.
2037 1890
2038 The setting for ABS.f 1891 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1892 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1893 except where unsupported by hardware.
2041 1894
2042 ignore_loglevel [KNL,EARLY] !! 1895 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1896 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1897 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1898 We also add it as printk module parameter, so users
2046 could change it dynam 1899 could change it dynamically, usually by
2047 /sys/module/printk/pa 1900 /sys/module/printk/parameters/ignore_loglevel.
2048 1901
2049 ignore_rlimit_data 1902 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1903 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1904 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1905 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1906
2054 ihash_entries= [KNL] 1907 ihash_entries= [KNL]
2055 Set number of hash bu 1908 Set number of hash buckets for inode cache.
2056 1909
2057 ima_appraise= [IMA] appraise integr 1910 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1911 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1912 default: "enforce"
2060 1913
2061 ima_appraise_tcb [IMA] Deprecated. U 1914 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1915 The builtin appraise policy appraises all files
2063 owned by uid=0. 1916 owned by uid=0.
2064 1917
2065 ima_canonical_fmt [IMA] 1918 ima_canonical_fmt [IMA]
2066 Use the canonical for 1919 Use the canonical format for the binary runtime
2067 measurements, instead 1920 measurements, instead of host native format.
2068 1921
2069 ima_hash= [IMA] 1922 ima_hash= [IMA]
2070 Format: { md5 | sha1 1923 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1924 | sha512 | ... }
2072 default: "sha1" 1925 default: "sha1"
2073 1926
2074 The list of supported 1927 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1928 in crypto/hash_info.h.
2076 1929
2077 ima_policy= [IMA] 1930 ima_policy= [IMA]
2078 The builtin policies 1931 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1932 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1933 fail_securely | critical_data"
2081 1934
2082 The "tcb" policy meas 1935 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1936 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1937 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1938 uid=0.
2086 1939
2087 The "appraise_tcb" po 1940 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1941 all files owned by root.
2089 1942
2090 The "secure_boot" pol 1943 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1944 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1945 firmware, policy, etc) based on file signatures.
2093 1946
2094 The "fail_securely" p 1947 The "fail_securely" policy forces file signature
2095 verification failure 1948 verification failure also on privileged mounted
2096 filesystems with the 1949 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1950 flag.
2098 1951
2099 The "critical_data" p 1952 The "critical_data" policy measures kernel integrity
2100 critical data. 1953 critical data.
2101 1954
2102 ima_tcb [IMA] Deprecated. Us 1955 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1956 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1957 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1958 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1959 opened for read by uid=0.
2107 1960
2108 ima_template= [IMA] 1961 ima_template= [IMA]
2109 Select one of defined 1962 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i 1963 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2111 "ima-sigv2 1964 "ima-sigv2" }
2112 Default: "ima-ng" 1965 Default: "ima-ng"
2113 1966
2114 ima_template_fmt= 1967 ima_template_fmt=
2115 [IMA] Define a custom 1968 [IMA] Define a custom template format.
2116 Format: { "field1|... 1969 Format: { "field1|...|fieldN" }
2117 1970
2118 ima.ahash_minsize= [IMA] Minimum file 1971 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1972 Format: <min_file_size>
2120 Set the minimal file 1973 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1974 If left unspecified, ahash usage is disabled.
2122 1975
2123 ahash performance var 1976 ahash performance varies for different data sizes on
2124 different crypto acce 1977 different crypto accelerators. This option can be used
2125 to achieve the best p 1978 to achieve the best performance for a particular HW.
2126 1979
2127 ima.ahash_bufsize= [IMA] Asynchronous 1980 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1981 Format: <bufsize>
2129 Set hashing buffer si 1982 Set hashing buffer size. Default: 4k.
2130 1983
2131 ahash performance var 1984 ahash performance varies for different chunk sizes on
2132 different crypto acce 1985 different crypto accelerators. This option can be used
2133 to achieve best perfo 1986 to achieve best performance for particular HW.
2134 1987
2135 init= [KNL] 1988 init= [KNL]
2136 Format: <full_path> 1989 Format: <full_path>
2137 Run specified binary 1990 Run specified binary instead of /sbin/init as init
2138 process. 1991 process.
2139 1992
2140 initcall_debug [KNL] Trace initcalls 1993 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1994 for working out where the kernel is dying during
2142 startup. 1995 startup.
2143 1996
2144 initcall_blacklist= [KNL] Do not exe 1997 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1998 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1999 modules and initcalls.
2147 2000
2148 initramfs_async= [KNL] 2001 initramfs_async= [KNL]
2149 Format: <bool> 2002 Format: <bool>
2150 Default: 1 2003 Default: 1
2151 This parameter contro 2004 This parameter controls whether the initramfs
2152 image is unpacked asy 2005 image is unpacked asynchronously, concurrently
2153 with devices being pr 2006 with devices being probed and
2154 initialized. This sho 2007 initialized. This should normally just work,
2155 but as a debugging ai 2008 but as a debugging aid, one can get the
2156 historical behaviour 2009 historical behaviour of the initramfs
2157 unpacking being compl 2010 unpacking being completed before device_ and
2158 late_ initcalls. 2011 late_ initcalls.
2159 2012
2160 initrd= [BOOT,EARLY] Specify !! 2013 initrd= [BOOT] Specify the location of the initial ramdisk
2161 2014
2162 initrdmem= [KNL,EARLY] Specify a !! 2015 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 2016 load the initrd. If an initrd is compiled in or
2164 specified in the boot 2017 specified in the bootparams, it takes priority over this
2165 setting. 2018 setting.
2166 Format: ss[KMG],nn[KM 2019 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 2020 Default is 0, 0
2168 2021
2169 init_on_alloc= [MM,EARLY] Fill newly !! 2022 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 2023 zeroes.
2171 Format: 0 | 1 2024 Format: 0 | 1
2172 Default set by CONFIG 2025 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 2026
2174 init_on_free= [MM,EARLY] Fill freed !! 2027 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 2028 Format: 0 | 1
2176 Default set by CONFIG 2029 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 2030
2178 init_pkru= [X86] Specify the def 2031 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 2032 register contents for all processes. 0x55555554 by
2180 default (disallow acc 2033 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 2034 override in debugfs after boot.
2182 2035
2183 inport.irq= [HW] Inport (ATI XL a 2036 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 2037 Format: <irq>
2185 2038
2186 int_pln_enable [X86] Enable power li 2039 int_pln_enable [X86] Enable power limit notification interrupt
2187 2040
2188 integrity_audit=[IMA] 2041 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 2042 Format: { "0" | "1" }
2190 0 -- basic integrity 2043 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 2044 1 -- additional integrity auditing messages.
2192 2045
2193 intel_iommu= [DMAR] Intel IOMMU dr 2046 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 2047 on
2195 Enable intel iommu dr 2048 Enable intel iommu driver.
2196 off 2049 off
2197 Disable intel iommu d 2050 Disable intel iommu driver.
2198 igfx_off [Default Off] 2051 igfx_off [Default Off]
2199 By default, gfx is ma 2052 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 2053 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 2054 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 2055 this case, gfx device will use physical address for
2203 DMA. 2056 DMA.
2204 strict [Default Off] 2057 strict [Default Off]
2205 Deprecated, equivalen 2058 Deprecated, equivalent to iommu.strict=1.
2206 sp_off [Default Off] 2059 sp_off [Default Off]
2207 By default, super pag 2060 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 2061 has the capability. With this option, super page will
2209 not be supported. 2062 not be supported.
2210 sm_on 2063 sm_on
2211 Enable the Intel IOMM 2064 Enable the Intel IOMMU scalable mode if the hardware
2212 advertises that it ha 2065 advertises that it has support for the scalable mode
2213 translation. 2066 translation.
2214 sm_off 2067 sm_off
2215 Disallow use of the I 2068 Disallow use of the Intel IOMMU scalable mode.
2216 tboot_noforce [Default Off] 2069 tboot_noforce [Default Off]
2217 Do not force the Inte 2070 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 2071 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 2072 could harm performance of some high-throughput
2220 devices like 40GBit n 2073 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 2074 mapping is enabled.
2222 Note that using this 2075 Note that using this option lowers the security
2223 provided by tboot bec 2076 provided by tboot because it makes the system
2224 vulnerable to DMA att 2077 vulnerable to DMA attacks.
2225 2078
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 2079 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 2080 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 2081 1 to 9 specify maximum depth of C-state.
2229 2082
2230 intel_pstate= [X86,EARLY] !! 2083 intel_pstate= [X86]
2231 disable 2084 disable
2232 Do not enable intel 2085 Do not enable intel_pstate as the default
2233 scaling driver for 2086 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 2087 passive
2245 Use intel_pstate as 2088 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 2089 to work with generic cpufreq governors (instead of
2247 enabling its intern 2090 enabling its internal governor). This mode cannot be
2248 used along with the 2091 used along with the hardware-managed P-states (HWP)
2249 feature. 2092 feature.
2250 force 2093 force
2251 Enable intel_pstate 2094 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 2095 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 2096 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 2097 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 2098 P-States information being indicated to OSPM and therefore
2256 should be used with 2099 should be used with caution. This option does not work with
2257 processors that are 2100 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 2101 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 2102 no_hwp
2260 Do not enable hardw 2103 Do not enable hardware P state control (HWP)
2261 if available. 2104 if available.
2262 hwp_only 2105 hwp_only
2263 Only load intel_pst 2106 Only load intel_pstate on systems which support
2264 hardware P state co 2107 hardware P state control (HWP) if available.
2265 support_acpi_ppc 2108 support_acpi_ppc
2266 Enforce ACPI _PPC p 2109 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 2110 Description Table, specifies preferred power management
2268 profile as "Enterpr 2111 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 2112 then this feature is turned on by default.
2270 per_cpu_perf_limits 2113 per_cpu_perf_limits
2271 Allow per-logical-C 2114 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 2115 cpufreq sysfs interface
2273 2116
2274 intremap= [X86-64,Intel-IOMMU,E !! 2117 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 2118 on enable Interrupt Remapping (default)
2276 off disable Inter 2119 off disable Interrupt Remapping
2277 nosid disable Sourc 2120 nosid disable Source ID checking
2278 no_x2apic_optout 2121 no_x2apic_optout
2279 BIOS x2APIC o 2122 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 2123 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 2124
2284 iomem= Disable strict checki 2125 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 2126 strict regions from userspace.
2286 relaxed 2127 relaxed
2287 2128
2288 iommu= [X86,EARLY] !! 2129 iommu= [X86]
2289 off 2130 off
2290 force 2131 force
2291 noforce 2132 noforce
2292 biomerge 2133 biomerge
2293 panic 2134 panic
2294 nopanic 2135 nopanic
2295 merge 2136 merge
2296 nomerge 2137 nomerge
2297 soft 2138 soft
2298 pt [X86] 2139 pt [X86]
2299 nopt [X86] 2140 nopt [X86]
2300 nobypass [PPC/POWERNV] 2141 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 2142 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2143
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2144 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 2145 Format: { "0" | "1" }
2305 0 - Try to allocate a 2146 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 2147 falling back to the full range if needed.
2307 1 - Allocate directly 2148 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 2149 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 2150 greater than 32-bit addressing.
2310 2151
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 2152 iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 2153 Format: { "0" | "1" }
2313 0 - Lazy mode. 2154 0 - Lazy mode.
2314 Request that DMA un 2155 Request that DMA unmap operations use deferred
2315 invalidation of har 2156 invalidation of hardware TLBs, for increased
2316 throughput at the c 2157 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2158 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2159 the relevant IOMMU driver.
2319 1 - Strict mode. 2160 1 - Strict mode.
2320 DMA unmap operation 2161 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2162 synchronously.
2322 unset - Use value of 2163 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2323 Note: on x86, strict 2164 Note: on x86, strict mode specified via one of the
2324 legacy driver-specifi 2165 legacy driver-specific options takes precedence.
2325 2166
2326 iommu.passthrough= 2167 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2168 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2169 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2170 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2171 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2172 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2173
2333 io7= [HW] IO7 for Marvel-b 2174 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2175 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2176 arch/alpha/kernel/core_marvel.c.
2336 2177
2337 io_delay= [X86,EARLY] I/O delay !! 2178 io_delay= [X86] I/O delay method
2338 0x80 2179 0x80
2339 Standard port 0x80 ba 2180 Standard port 0x80 based delay
2340 0xed 2181 0xed
2341 Alternate port 0xed b 2182 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2183 udelay
2343 Simple two microsecon 2184 Simple two microseconds delay
2344 none 2185 none
2345 No delay 2186 No delay
2346 2187
2347 ip= [IP_PNP] 2188 ip= [IP_PNP]
2348 See Documentation/adm 2189 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2190
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2191 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2192 IPC identifiers from 32,768 to 16,777,216.
2352 2193
2353 irqaffinity= [SMP] Set the default 2194 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2195 The argument is a cpu list, as described above.
2355 2196
2356 irqchip.gicv2_force_probe= 2197 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2198 [ARM, ARM64]
2358 Format: <bool> 2199 Format: <bool>
2359 Force the kernel to l 2200 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2201 of a GICv2 controller even if the memory range
2361 exposed by the device 2202 exposed by the device tree is too small.
2362 2203
2363 irqchip.gicv3_nolpi= 2204 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2205 [ARM, ARM64]
2365 Force the kernel to i 2206 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2207 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2208 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2209 to let secondary kernels in charge of setting up
2369 LPIs. 2210 LPIs.
2370 2211
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2212 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2213 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2214 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2215 CONFIG_ARM64_PSEUDO_NMI.
2375 2216
2376 irqfixup [HW] 2217 irqfixup [HW]
2377 When an interrupt is 2218 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2219 for it. Intended to get systems with badly broken
2379 firmware running. 2220 firmware running.
2380 2221
2381 irqpoll [HW] 2222 irqpoll [HW]
2382 When an interrupt is 2223 When an interrupt is not handled search all handlers
2383 for it. Also check al 2224 for it. Also check all handlers each timer
2384 interrupt. Intended t 2225 interrupt. Intended to get systems with badly broken
2385 firmware running. 2226 firmware running.
2386 2227
2387 isapnp= [ISAPNP] 2228 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2229 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2230
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2231 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2232 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2233 Format: [flag-list,]<cpu-list>
2393 2234
2394 Specify one or more C 2235 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2236 specified in the flag list (default: domain):
2396 2237
2397 nohz 2238 nohz
2398 Disable the tick wh 2239 Disable the tick when a single task runs.
2399 2240
2400 A residual 1Hz tick 2241 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2242 need to affine to housekeeping through the global
2402 workqueue's affinit 2243 workqueue's affinity configured via the
2403 /sys/devices/virtua 2244 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2245 by using the 'domain' flag described below.
2405 2246
2406 NOTE: by default th 2247 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2248 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2249 be configured manually after bootup.
2409 2250
2410 domain 2251 domain
2411 Isolate from the ge 2252 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2253 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2254 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2255 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2256 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2257 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2258 It offers a much more flexible interface where CPUs can
2418 move in and out of 2259 move in and out of an isolated set anytime.
2419 2260
2420 You can move a proc 2261 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2262 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2263 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2264 "number of CPUs in system - 1".
2424 2265
2425 managed_irq 2266 managed_irq
2426 2267
2427 Isolate from being 2268 Isolate from being targeted by managed interrupts
2428 which have an inter 2269 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2270 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2271 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2272 the /proc/irq/* interfaces.
2432 2273
2433 This isolation is b 2274 This isolation is best effort and only effective
2434 if the automaticall 2275 if the automatically assigned interrupt mask of a
2435 device queue contai 2276 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2277 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2278 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2279 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2280 cannot disturb the isolated CPU.
2440 2281
2441 If a queue's affini 2282 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2283 CPUs then this parameter has no effect on the
2443 interrupt routing d 2284 interrupt routing decision, though interrupts are
2444 only delivered when 2285 only delivered when tasks running on those
2445 isolated CPUs submi 2286 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2287 housekeeping CPUs has no influence on those
2447 queues. 2288 queues.
2448 2289
2449 The format of <cpu-li 2290 The format of <cpu-list> is described above.
2450 2291
2451 iucv= [HW,NET] 2292 iucv= [HW,NET]
2452 2293
2453 ivrs_ioapic [HW,X86-64] 2294 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2295 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t 2296 mapping provided in the IVRS ACPI table.
2456 By default, PCI segme 2297 By default, PCI segment is 0, and can be omitted.
2457 2298
2458 For example, to map I 2299 For example, to map IOAPIC-ID decimal 10 to
2459 PCI segment 0x1 and P 2300 PCI segment 0x1 and PCI device 00:14.0,
2460 write the parameter a 2301 write the parameter as:
2461 ivrs_ioapic=1 2302 ivrs_ioapic=10@0001:00:14.0
2462 2303
2463 Deprecated formats: 2304 Deprecated formats:
2464 * To map IOAPIC-ID de 2305 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2465 write the parameter 2306 write the parameter as:
2466 ivrs_ioapic[1 2307 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de 2308 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2468 PCI device 00:14.0 2309 PCI device 00:14.0 write the parameter as:
2469 ivrs_ioapic[1 2310 ivrs_ioapic[10]=0001:00:14.0
2470 2311
2471 ivrs_hpet [HW,X86-64] 2312 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2313 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t 2314 mapping provided in the IVRS ACPI table.
2474 By default, PCI segme 2315 By default, PCI segment is 0, and can be omitted.
2475 2316
2476 For example, to map H 2317 For example, to map HPET-ID decimal 10 to
2477 PCI segment 0x1 and P 2318 PCI segment 0x1 and PCI device 00:14.0,
2478 write the parameter a 2319 write the parameter as:
2479 ivrs_hpet=10@ 2320 ivrs_hpet=10@0001:00:14.0
2480 2321
2481 Deprecated formats: 2322 Deprecated formats:
2482 * To map HPET-ID deci 2323 * To map HPET-ID decimal 0 to PCI device 00:14.0
2483 write the parameter 2324 write the parameter as:
2484 ivrs_hpet[0]= 2325 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci 2326 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2486 PCI device 00:14.0 2327 PCI device 00:14.0 write the parameter as:
2487 ivrs_ioapic[1 2328 ivrs_ioapic[10]=0001:00:14.0
2488 2329
2489 ivrs_acpihid [HW,X86-64] 2330 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2331 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t 2332 mapping provided in the IVRS ACPI table.
2492 By default, PCI segme 2333 By default, PCI segment is 0, and can be omitted.
2493 2334
2494 For example, to map U 2335 For example, to map UART-HID:UID AMD0020:0 to
2495 PCI segment 0x1 and P 2336 PCI segment 0x1 and PCI device ID 00:14.5,
2496 write the parameter a 2337 write the parameter as:
2497 ivrs_acpihid= 2338 ivrs_acpihid=AMD0020:0@0001:00:14.5
2498 2339
2499 Deprecated formats: 2340 Deprecated formats:
2500 * To map UART-HID:UID 2341 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2501 PCI device ID 00:14 2342 PCI device ID 00:14.5, write the parameter as:
2502 ivrs_acpihid[ 2343 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID 2344 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2504 PCI device ID 00:14 2345 PCI device ID 00:14.5, write the parameter as:
2505 ivrs_acpihid[ 2346 ivrs_acpihid[0001:00:14.5]=AMD0020:0
2506 2347
2507 js= [HW,JOY] Analog joyst 2348 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2349 See Documentation/input/joydev/joystick.rst.
2509 2350
2510 kasan_multi_shot 2351 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2352 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2353 report on every invalid memory access. Without this
2513 parameter KASAN will 2354 parameter KASAN will print report only for the first
2514 invalid access. 2355 invalid access.
2515 2356
2516 keep_bootcon [KNL,EARLY] !! 2357 keep_bootcon [KNL]
2517 Do not unregister boo 2358 Do not unregister boot console at start. This is only
2518 useful for debugging 2359 useful for debugging when something happens in the window
2519 between unregistering 2360 between unregistering the boot console and initializing
2520 the real console. 2361 the real console.
2521 2362
2522 keepinitrd [HW,ARM] See retain_i !! 2363 keepinitrd [HW,ARM]
2523 2364
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2365 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2366 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2367 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2368 the kernel for non-movable allocations. The requested
2528 amount is spread even 2369 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2370 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2371 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2372 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2373 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2374 other nodes will have a larger ZONE_MOVABLE.
2534 2375
2535 ZONE_MOVABLE is used 2376 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2377 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2378 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2379 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2380 zone if it does not.
2540 2381
2541 It is possible to spe 2382 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2383 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2384 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2385 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2386 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2387 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2388 are exclusive, so you cannot specify multiple forms.
2548 2389
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2390 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2391 Format: <Controller#>[,poll interval]
2551 The controller # is t 2392 The controller # is the number of the ehci usb debug
2552 port as it is probed 2393 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2394 optional and is the number seconds in between
2554 each poll cycle to th 2395 each poll cycle to the debug port in case you need
2555 the functionality for 2396 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2397 gdb or control-c on the dbgp connection. When
2557 not using this parame 2398 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2399 the kernel debugger.
2559 2400
2560 kgdboc= [KGDB,HW] kgdb over c 2401 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2402 Requires a tty driver that supports console polling,
2562 or a supported pollin 2403 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2404 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2405 keyboard only format: kbd
2565 keyboard and serial 2406 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2407 Optional Kernel mode setting:
2567 kms, kbd format: kms 2408 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2409 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2410
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2411 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2412 If the boot console provides the ability to read
2572 characters and can wo 2413 characters and can work in polling mode, you can use
2573 this parameter to tel 2414 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2415 until the normal console is registered. Intended to
2575 be used together with 2416 be used together with the kgdboc parameter which
2576 specifies the normal 2417 specifies the normal console to transition to.
2577 2418
2578 The name of the early 2419 The name of the early console should be specified
2579 as the value of this 2420 as the value of this parameter. Note that the name of
2580 the early console mig 2421 the early console might be different than the tty
2581 name passed to kgdboc 2422 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2423 blank and the first boot console that implements
2583 read() will be picked 2424 read() will be picked.
2584 2425
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2426 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2427 kernel debugger at the earliest opportunity.
2587 2428
2588 kmac= [MIPS] Korina etherne 2429 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2430 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2431 Ethernet adapter MAC address.
2591 2432
2592 kmemleak= [KNL,EARLY] Boot-time !! 2433 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2434 Valid arguments: on, off
2594 Default: on 2435 Default: on
2595 Built with CONFIG_DEB 2436 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2437 the default is off.
2597 2438
2598 kprobe_event=[probe-list] 2439 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2440 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2441 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2442 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2443 interface, but the parameters are comma delimited.
2603 For example, to add a 2444 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2445 arg1 and arg2, add to the command line;
2605 2446
2606 kprobe_event=p, 2447 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2448
2608 See also Documentatio 2449 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2450 Boot Parameter" section.
2610 2451
2611 kpti= [ARM64,EARLY] Control !! 2452 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2453 and kernel address spaces.
2613 Default: enabled on c 2454 Default: enabled on cores which need mitigation.
2614 0: force disabled 2455 0: force disabled
2615 1: force enabled 2456 1: force enabled
2616 2457
2617 kunit.enable= [KUNIT] Enable execut 2458 kunit.enable= [KUNIT] Enable executing KUnit tests. Requires
2618 CONFIG_KUNIT to be se 2459 CONFIG_KUNIT to be set to be fully enabled. The
2619 default value can be 2460 default value can be overridden via
2620 KUNIT_DEFAULT_ENABLED 2461 KUNIT_DEFAULT_ENABLED.
2621 Default is 1 (enabled 2462 Default is 1 (enabled)
2622 2463
2623 kvm.ignore_msrs=[KVM] Ignore guest ac 2464 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2465 Default is 0 (don't ignore, but inject #GP)
2625 2466
2626 kvm.eager_page_split= 2467 kvm.eager_page_split=
2627 [KVM,X86] Controls wh 2468 [KVM,X86] Controls whether or not KVM will try to
2628 proactively split all 2469 proactively split all huge pages during dirty logging.
2629 Eager page splitting 2470 Eager page splitting reduces interruptions to vCPU
2630 execution by eliminat 2471 execution by eliminating the write-protection faults
2631 and MMU lock contenti 2472 and MMU lock contention that would otherwise be
2632 required to split hug 2473 required to split huge pages lazily.
2633 2474
2634 VM workloads that rar 2475 VM workloads that rarely perform writes or that write
2635 only to a small regio 2476 only to a small region of VM memory may benefit from
2636 disabling eager page 2477 disabling eager page splitting to allow huge pages to
2637 still be used for rea 2478 still be used for reads.
2638 2479
2639 The behavior of eager 2480 The behavior of eager page splitting depends on whether
2640 KVM_DIRTY_LOG_INITIAL 2481 KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2641 disabled, all huge pa 2482 disabled, all huge pages in a memslot will be eagerly
2642 split when dirty logg 2483 split when dirty logging is enabled on that memslot. If
2643 enabled, eager page s 2484 enabled, eager page splitting will be performed during
2644 the KVM_CLEAR_DIRTY i 2485 the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2645 cleared. 2486 cleared.
2646 2487
2647 Eager page splitting 2488 Eager page splitting is only supported when kvm.tdp_mmu=Y.
2648 2489
2649 Default is Y (on). 2490 Default is Y (on).
2650 2491
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2492 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2493 Default is false (don't support).
2653 2494
2654 kvm.nx_huge_pages= 2495 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2496 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2497 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2498 force : Always deploy workaround.
2658 off : Never deplo 2499 off : Never deploy workaround.
2659 auto : Deploy work 2500 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2501 X86_BUG_ITLB_MULTIHIT.
2661 2502
2662 Default is 'auto'. 2503 Default is 'auto'.
2663 2504
2664 If the software worka 2505 If the software workaround is enabled for the host,
2665 guests do need not to 2506 guests do need not to enable it for nested guests.
2666 2507
2667 kvm.nx_huge_pages_recovery_ratio= 2508 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2509 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2510 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2511 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). 2512 period (see below). The default is 60.
2672 2513
2673 kvm.nx_huge_pages_recovery_period_ms= 2514 kvm.nx_huge_pages_recovery_period_ms=
2674 [KVM] Controls the ti 2515 [KVM] Controls the time period at which KVM zaps 4KiB pages
2675 back to huge pages. I 2516 back to huge pages. If the value is a non-zero N, KVM will
2676 zap a portion (see ra 2517 zap a portion (see ratio above) of the pages every N msecs.
2677 If the value is 0 (th 2518 If the value is 0 (the default), KVM will pick a period based
2678 on the ratio, such th 2519 on the ratio, such that a page is zapped after 1 hour on average.
2679 2520
2680 kvm-amd.nested= [KVM,AMD] Control nes !! 2521 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2681 KVM/SVM. Default is 1 !! 2522 Default is 1 (enabled)
2682 2523
2683 kvm-amd.npt= [KVM,AMD] Control KVM !! 2524 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2684 a.k.a. Two-Dimensiona !! 2525 for all guests.
2685 (enabled). Disable by !! 2526 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2686 for NPT. <<
2687 2527
2688 kvm-arm.mode= 2528 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2529 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 2530
2692 none: Forcefully disa 2531 none: Forcefully disable KVM.
2693 2532
2694 nvhe: Standard nVHE-b 2533 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2534 protected guests.
2696 2535
2697 protected: nVHE-based 2536 protected: nVHE-based mode with support for guests whose
2698 state is k 2537 state is kept private from the host.
2699 2538
2700 nested: VHE-based mod 2539 nested: VHE-based mode with support for nested
2701 virtualizatio 2540 virtualization. Requires at least ARMv8.3
2702 hardware. 2541 hardware.
2703 2542
2704 Defaults to VHE/nVHE 2543 Defaults to VHE/nVHE based on hardware support. Setting
2705 mode to "protected" w 2544 mode to "protected" will disable kexec and hibernation
2706 for the host. "nested 2545 for the host. "nested" is experimental and should be
2707 used with extreme cau 2546 used with extreme caution.
2708 2547
2709 kvm-arm.vgic_v3_group0_trap= 2548 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2549 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2550 system registers
2712 2551
2713 kvm-arm.vgic_v3_group1_trap= 2552 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2553 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2554 system registers
2716 2555
2717 kvm-arm.vgic_v3_common_trap= 2556 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2557 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2558 system registers
2720 2559
2721 kvm-arm.vgic_v4_enable= 2560 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2561 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2562 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 2563
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2564 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2565 Reserves given percentage from system memory area for
2745 contiguous memory all 2566 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2567 allocation.
2747 By default it reserve 2568 By default it reserves 5% of total system memory.
2748 Format: <integer> 2569 Format: <integer>
2749 Default: 5 2570 Default: 5
2750 2571
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2572 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2573 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2574 Default is 1 (enabled)
2754 for EPT. <<
2755 2575
2756 kvm-intel.emulate_invalid_guest_state 2576 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2577 [KVM,Intel] Disable emulation of invalid guest state.
2758 state. Ignored if kvm !! 2578 Ignored if kvm-intel.enable_unrestricted_guest=1, as
2759 as guest state is nev !! 2579 guest state is never invalid for unrestricted guests.
2760 guests. This param do !! 2580 This param doesn't apply to nested guests (L2), as KVM
2761 as KVM never emulates !! 2581 never emulates invalid L2 guest state.
2762 Default is 1 (enabled !! 2582 Default is 1 (enabled)
2763 2583
2764 kvm-intel.flexpriority= 2584 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2585 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2586 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2587
2769 kvm-intel.nested= 2588 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2589 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2590 Default is 0 (disabled)
2772 2591
2773 kvm-intel.unrestricted_guest= 2592 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2593 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2594 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2595 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2596
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2597 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2598 CVE-2018-3620.
2781 2599
2782 Valid arguments: neve 2600 Valid arguments: never, cond, always
2783 2601
2784 always: L1D cache flu 2602 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2603 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2604 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2605 never: Disables the mitigation
2788 2606
2789 Default is cond (do L 2607 Default is cond (do L1 cache flush in specific instances)
2790 2608
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2609 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2610 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2611 Default is 1 (enabled)
2794 for it. <<
2795 2612
2796 l1d_flush= [X86,INTEL,EARLY] !! 2613 l1d_flush= [X86,INTEL]
2797 Control mitigation fo 2614 Control mitigation for L1D based snooping vulnerability.
2798 2615
2799 Certain CPUs are vuln 2616 Certain CPUs are vulnerable to an exploit against CPU
2800 internal buffers whic 2617 internal buffers which can forward information to a
2801 disclosure gadget und 2618 disclosure gadget under certain conditions.
2802 2619
2803 In vulnerable process 2620 In vulnerable processors, the speculatively
2804 forwarded data can be 2621 forwarded data can be used in a cache side channel
2805 attack, to access dat 2622 attack, to access data to which the attacker does
2806 not have direct acces 2623 not have direct access.
2807 2624
2808 This parameter contro 2625 This parameter controls the mitigation. The
2809 options are: 2626 options are:
2810 2627
2811 on - enable t 2628 on - enable the interface for the mitigation
2812 2629
2813 l1tf= [X86,EARLY] Control m !! 2630 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2631 affected CPUs
2815 2632
2816 The kernel PTE invers 2633 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2634 enabled and cannot be disabled.
2818 2635
2819 full 2636 full
2820 Provides all 2637 Provides all available mitigations for the
2821 L1TF vulnerab 2638 L1TF vulnerability. Disables SMT and
2822 enables all m 2639 enables all mitigations in the
2823 hypervisors, 2640 hypervisors, i.e. unconditional L1D flush.
2824 2641
2825 SMT control a 2642 SMT control and L1D flush control via the
2826 sysfs interfa 2643 sysfs interface is still possible after
2827 boot. Hyperv 2644 boot. Hypervisors will issue a warning
2828 when the firs 2645 when the first VM is started in a
2829 potentially i 2646 potentially insecure configuration,
2830 i.e. SMT enab 2647 i.e. SMT enabled or L1D flush disabled.
2831 2648
2832 full,force 2649 full,force
2833 Same as 'full 2650 Same as 'full', but disables SMT and L1D
2834 flush runtime 2651 flush runtime control. Implies the
2835 'nosmt=force' 2652 'nosmt=force' command line option.
2836 (i.e. sysfs c 2653 (i.e. sysfs control of SMT is disabled.)
2837 2654
2838 flush 2655 flush
2839 Leaves SMT en 2656 Leaves SMT enabled and enables the default
2840 hypervisor mi 2657 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2658 L1D flush.
2842 2659
2843 SMT control a 2660 SMT control and L1D flush control via the
2844 sysfs interfa 2661 sysfs interface is still possible after
2845 boot. Hyperv 2662 boot. Hypervisors will issue a warning
2846 when the firs 2663 when the first VM is started in a
2847 potentially i 2664 potentially insecure configuration,
2848 i.e. SMT enab 2665 i.e. SMT enabled or L1D flush disabled.
2849 2666
2850 flush,nosmt 2667 flush,nosmt
2851 2668
2852 Disables SMT 2669 Disables SMT and enables the default
2853 hypervisor mi 2670 hypervisor mitigation.
2854 2671
2855 SMT control a 2672 SMT control and L1D flush control via the
2856 sysfs interfa 2673 sysfs interface is still possible after
2857 boot. Hyperv 2674 boot. Hypervisors will issue a warning
2858 when the firs 2675 when the first VM is started in a
2859 potentially i 2676 potentially insecure configuration,
2860 i.e. SMT enab 2677 i.e. SMT enabled or L1D flush disabled.
2861 2678
2862 flush,nowarn 2679 flush,nowarn
2863 Same as 'flus 2680 Same as 'flush', but hypervisors will not
2864 warn when a V 2681 warn when a VM is started in a potentially
2865 insecure conf 2682 insecure configuration.
2866 2683
2867 off 2684 off
2868 Disables hype 2685 Disables hypervisor mitigations and doesn't
2869 emit any warn 2686 emit any warnings.
2870 It also drops 2687 It also drops the swap size and available
2871 RAM limit res 2688 RAM limit restriction on both hypervisor and
2872 bare metal. 2689 bare metal.
2873 2690
2874 Default is 'flush'. 2691 Default is 'flush'.
2875 2692
2876 For details see: Docu 2693 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2694
2878 l2cr= [PPC] 2695 l2cr= [PPC]
2879 2696
2880 l3cr= [PPC] 2697 l3cr= [PPC]
2881 2698
2882 lapic [X86-32,APIC,EARLY] E !! 2699 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2700 disabled it.
2884 2701
2885 lapic= [X86,APIC] Do not use 2702 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2703 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2704 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2705 Format: notscdeadline
2889 2706
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2707 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2708 in C2 power state.
2892 2709
2893 libata.dma= [LIBATA] DMA control 2710 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2711 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2712 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2713 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2714 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2715 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2716 for disks and CDROMs, but not CFs.
2900 2717
2901 libata.ignore_hpa= [LIBATA] Igno 2718 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2719 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2720 libata.ignore_hpa=1 ignore limits, using full disk
2904 2721
2905 libata.noacpi [LIBATA] Disables use 2722 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2723 when set.
2907 Format: <int> 2724 Format: <int>
2908 2725
2909 libata.force= [LIBATA] Force config 2726 libata.force= [LIBATA] Force configurations. The format is a comma-
2910 separated list of "[I 2727 separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2911 PORT and DEVICE are d 2728 PORT and DEVICE are decimal numbers matching port, link
2912 or device. Basically 2729 or device. Basically, it matches the ATA ID string
2913 printed on console by 2730 printed on console by libata. If the whole ID part is
2914 omitted, the last POR 2731 omitted, the last PORT and DEVICE values are used. If
2915 ID hasn't been specif 2732 ID hasn't been specified yet, the configuration applies
2916 to all ports, links a 2733 to all ports, links and devices.
2917 2734
2918 If only DEVICE is omi 2735 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2736 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2737 number of 0 either selects the first device or the
2921 first fan-out link be 2738 first fan-out link behind PMP device. It does not
2922 select the host link. 2739 select the host link. DEVICE number of 15 selects the
2923 host link and device 2740 host link and device attached to it.
2924 2741
2925 The VAL specifies the 2742 The VAL specifies the configuration to force. As long
2926 as there is no ambigu 2743 as there is no ambiguity, shortcut notation is allowed.
2927 For example, both 1.5 2744 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2745 The following configurations can be forced.
2929 2746
2930 * Cable type: 40c, 80 2747 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2748 Any ID with matching PORT is used.
2932 2749
2933 * SATA link speed lim 2750 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2751
2935 * Transfer mode: pio[ 2752 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2753 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2754 allowed.
2938 2755
2939 * nohrst, nosrst, nor 2756 * nohrst, nosrst, norst: suppress hard, soft and both
2940 resets. 2757 resets.
2941 2758
2942 * rstonce: only attem 2759 * rstonce: only attempt one reset during hot-unplug
2943 link recovery. 2760 link recovery.
2944 2761
2945 * [no]dbdelay: Enable 2762 * [no]dbdelay: Enable or disable the extra 200ms delay
2946 before debouncing a 2763 before debouncing a link PHY and device presence
2947 detection. 2764 detection.
2948 2765
2949 * [no]ncq: Turn on or 2766 * [no]ncq: Turn on or off NCQ.
2950 2767
2951 * [no]ncqtrim: Enable 2768 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2952 2769
2953 * [no]ncqati: Enable 2770 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2954 2771
2955 * [no]trim: Enable or 2772 * [no]trim: Enable or disable (unqueued) TRIM.
2956 2773
2957 * trim_zero: Indicate 2774 * trim_zero: Indicate that TRIM command zeroes data.
2958 2775
2959 * max_trim_128m: Set 2776 * max_trim_128m: Set 128M maximum trim size limit.
2960 2777
2961 * [no]dma: Turn on or 2778 * [no]dma: Turn on or off DMA transfers.
2962 2779
2963 * atapi_dmadir: Enabl 2780 * atapi_dmadir: Enable ATAPI DMADIR bridge support.
2964 2781
2965 * atapi_mod16_dma: En 2782 * atapi_mod16_dma: Enable the use of ATAPI DMA for
2966 commands that are n 2783 commands that are not a multiple of 16 bytes.
2967 2784
2968 * [no]dmalog: Enable 2785 * [no]dmalog: Enable or disable the use of the
2969 READ LOG DMA EXT co 2786 READ LOG DMA EXT command to access logs.
2970 2787
2971 * [no]iddevlog: Enabl 2788 * [no]iddevlog: Enable or disable access to the
2972 identify device dat 2789 identify device data log.
2973 2790
2974 * [no]logdir: Enable 2791 * [no]logdir: Enable or disable access to the general
2975 purpose log directo 2792 purpose log directory.
2976 2793
2977 * max_sec_128: Set tr 2794 * max_sec_128: Set transfer size limit to 128 sectors.
2978 2795
2979 * max_sec_1024: Set o 2796 * max_sec_1024: Set or clear transfer size limit to
2980 1024 sectors. 2797 1024 sectors.
2981 2798
2982 * max_sec_lba48: Set 2799 * max_sec_lba48: Set or clear transfer size limit to
2983 65535 sectors. 2800 65535 sectors.
2984 2801
2985 * [no]lpm: Enable or 2802 * [no]lpm: Enable or disable link power management.
2986 2803
2987 * [no]setxfer: Indica 2804 * [no]setxfer: Indicate if transfer speed mode setting
2988 should be skipped. 2805 should be skipped.
2989 2806
2990 * [no]fua: Disable or 2807 * [no]fua: Disable or enable FUA (Force Unit Access)
2991 support for devices 2808 support for devices supporting this feature.
2992 2809
2993 * dump_id: Dump IDENT 2810 * dump_id: Dump IDENTIFY data.
2994 2811
2995 * disable: Disable th 2812 * disable: Disable this device.
2996 2813
2997 If there are multiple 2814 If there are multiple matching configurations changing
2998 the same attribute, t 2815 the same attribute, the last one is used.
2999 2816
3000 load_ramdisk= [RAM] [Deprecated] 2817 load_ramdisk= [RAM] [Deprecated]
3001 2818
3002 lockd.nlm_grace_period=P [NFS] Assig 2819 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2820 Format: <integer>
3004 2821
3005 lockd.nlm_tcpport=N [NFS] Assign 2822 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2823 Format: <integer>
3007 2824
3008 lockd.nlm_timeout=T [NFS] Assign 2825 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2826 Format: <integer>
3010 2827
3011 lockd.nlm_udpport=M [NFS] Assign 2828 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2829 Format: <integer>
3013 2830
3014 lockdown= [SECURITY,EARLY] !! 2831 lockdown= [SECURITY]
3015 { integrity | confide 2832 { integrity | confidentiality }
3016 Enable the kernel loc 2833 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2834 integrity, kernel features that allow userland to
3018 modify the running ke 2835 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2836 confidentiality, kernel features that allow userland
3020 to extract confidenti 2837 to extract confidential information from the kernel
3021 are also disabled. 2838 are also disabled.
3022 2839
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] 2840 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2841 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2842 Defaults to being automatically set based on the
3058 number of online CPUs 2843 number of online CPUs.
3059 2844
3060 locktorture.nwriters_stress= [KNL] 2845 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2846 Set the number of locking write-acquisition kthreads.
3062 2847
3063 locktorture.onoff_holdoff= [KNL] 2848 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2849 Set time (s) after boot for CPU-hotplug testing.
3065 2850
3066 locktorture.onoff_interval= [KNL] 2851 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2852 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2853 zero to disable CPU-hotplug testing.
3069 2854
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] 2855 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2856 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2857 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2858 mode during the locktorture test.
3093 2859
3094 locktorture.shutdown_secs= [KNL] 2860 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2861 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2862 is useful for hands-off automated testing.
3097 2863
3098 locktorture.stat_interval= [KNL] 2864 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2865 Time (s) between statistics printk()s.
3100 2866
3101 locktorture.stutter= [KNL] 2867 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2868 Time (s) to stutter testing, for example,
3103 specifying five secon 2869 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2870 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2871 This tests the locking primitive's ability to
3106 transition abruptly t 2872 transition abruptly to and from idle.
3107 2873
3108 locktorture.torture_type= [KNL] 2874 locktorture.torture_type= [KNL]
3109 Specify the locking i 2875 Specify the locking implementation to test.
3110 2876
3111 locktorture.verbose= [KNL] 2877 locktorture.verbose= [KNL]
3112 Enable additional pri 2878 Enable additional printk() statements.
3113 2879
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2880 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2881 Format: <irq>
3120 2882
3121 loglevel= [KNL,EARLY] !! 2883 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2884 console loglevel will be printed to the console. It can
3124 also be changed with 2885 also be changed with klogd or other programs. The
3125 loglevels are defined 2886 loglevels are defined as follows:
3126 2887
3127 0 (KERN_EMERG) 2888 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2889 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2890 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2891 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2892 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2893 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2894 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2895 7 (KERN_DEBUG) debug-level messages
3135 2896
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2897 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2898 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2899 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2900 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2901 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2902 that allows to increase the default size depending on
3142 parameter that allows !! 2903 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2904
3146 logo.nologo [FB] Disables display 2905 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2906 This may be used to provide more screen space for
3148 kernel log messages a 2907 kernel log messages and is useful when debugging
3149 kernel boot problems. 2908 kernel boot problems.
3150 2909
3151 lp=0 [LP] Specify paral 2910 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2911 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2912 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2913 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2914 specified in addition to the ports) causes
3156 attached prin 2915 attached printers to be reset. Using
3157 lp=port1,port 2916 lp=port1,port2,... specifies the parallel ports
3158 to associate 2917 to associate lp devices with, starting with
3159 lp0. A port s 2918 lp0. A port specification may be 'none' to skip
3160 that lp devic 2919 that lp device, or a parport name such as
3161 'parport0'. S 2920 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2921 port specification list means that device IDs
3163 from each por 2922 from each port should be examined, to see if
3164 an IEEE 1284- 2923 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2924 so, the driver will manage that printer.
3166 See also head 2925 See also header of drivers/char/lp.c.
3167 2926
3168 lpj=n [KNL] 2927 lpj=n [KNL]
3169 Sets loops_per_jiffy 2928 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2929 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2930 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2931 the correct value for your kernel, boot with normal
3173 autodetection and see 2932 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2933 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2934 which is likely to cause problems if your CPUs need
3176 significantly diverge 2935 significantly divergent settings. An incorrect value
3177 will cause delays in 2936 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2937 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2938 unlikely, in the extreme case this might damage your
3180 hardware. 2939 hardware.
3181 2940
>> 2941 ltpc= [NET]
>> 2942 Format: <io>,<irq>,<dma>
>> 2943
3182 lsm.debug [SECURITY] Enable LSM 2944 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2945
3184 lsm=lsm1,...,lsmN 2946 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2947 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2948 overrides CONFIG_LSM, and the "security=" parameter.
3187 2949
>> 2950 machvec= [IA-64] Force the use of a particular machine-vector
>> 2951 (machvec) in a generic kernel.
>> 2952 Example: machvec=hpzx1
>> 2953
3188 machtype= [Loongson] Share the 2954 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 2955 different yeeloong laptops.
3190 Example: machtype=lem 2956 Example: machtype=lemote-yeeloong-2f-7inch
3191 2957
3192 maxcpus= [SMP,EARLY] Maximum n !! 2958 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
>> 2959 than or equal to this physical address is ignored.
>> 2960
>> 2961 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2962 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2963 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2964 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2965 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2966 only takes effect during system bootup.
3198 While n=0 is a specia 2967 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2968 which also disables the IO APIC.
3200 2969
3201 max_loop= [LOOP] The number of 2970 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2971 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2972 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2973 of statically allocating a predefined number, loop
3205 devices can be reques 2974 devices can be requested on-demand with the
3206 /dev/loop-control int 2975 /dev/loop-control interface.
3207 2976
3208 mce [X86-32] Machine Chec 2977 mce [X86-32] Machine Check Exception
3209 2978
3210 mce=option [X86-64] See Document !! 2979 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.rst
3211 2980
3212 md= [HW] RAID subsystems 2981 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2982 See Documentation/admin-guide/md.rst.
3214 2983
3215 mdacon= [MDA] 2984 mdacon= [MDA]
3216 Format: <first>,<last 2985 Format: <first>,<last>
3217 Specifies range of co 2986 Specifies range of consoles to be captured by the MDA.
3218 2987
3219 mds= [X86,INTEL,EARLY] !! 2988 mds= [X86,INTEL]
3220 Control mitigation fo 2989 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2990 Sampling (MDS) vulnerability.
3222 2991
3223 Certain CPUs are vuln 2992 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2993 internal buffers which can forward information to a
3225 disclosure gadget und 2994 disclosure gadget under certain conditions.
3226 2995
3227 In vulnerable process 2996 In vulnerable processors, the speculatively
3228 forwarded data can be 2997 forwarded data can be used in a cache side channel
3229 attack, to access dat 2998 attack, to access data to which the attacker does
3230 not have direct acces 2999 not have direct access.
3231 3000
3232 This parameter contro 3001 This parameter controls the MDS mitigation. The
3233 options are: 3002 options are:
3234 3003
3235 full - Enable M 3004 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 3005 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 3006 SMT on vulnerable CPUs
3238 off - Uncondit 3007 off - Unconditionally disable MDS mitigation
3239 3008
3240 On TAA-affected machi 3009 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 3010 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 3011 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 3012 this mitigation, you need to specify tsx_async_abort=off
3244 too. 3013 too.
3245 3014
3246 Not specifying this o 3015 Not specifying this option is equivalent to
3247 mds=full. 3016 mds=full.
3248 3017
3249 For details see: Docu 3018 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 3019
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 3020 mem=nn[KMG] [HEXAGON] Set the memory size.
3252 Must be specified, ot 3021 Must be specified, otherwise memory size will be 0.
3253 3022
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc !! 3023 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3255 of memory Amount of m !! 3024 Amount of memory to be used in cases as follows:
3256 as follows: <<
3257 3025
3258 1 for test; 3026 1 for test;
3259 2 when the kernel is 3027 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 3028 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 3029 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory 3030 4 to limit the memory available for kdump kernel.
3263 3031
3264 [ARC,MICROBLAZE] - th 3032 [ARC,MICROBLAZE] - the limit applies only to low memory,
3265 high memory is not af 3033 high memory is not affected.
3266 3034
3267 [ARM64] - only limits 3035 [ARM64] - only limits memory covered by the linear
3268 mapping. The NOMAP re 3036 mapping. The NOMAP regions are not affected.
3269 3037
3270 [X86] Work as limitin 3038 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 3039 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 3040 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 3041 belonging to unused RAM.
3274 3042
3275 Note that this only t 3043 Note that this only takes effects during boot time since
3276 in above case 3, memo 3044 in above case 3, memory may need be hot added after boot
3277 if system memory of h 3045 if system memory of hypervisor is not sufficient.
3278 3046
3279 mem=nn[KMG]@ss[KMG] 3047 mem=nn[KMG]@ss[KMG]
3280 [ARM,MIPS,EARLY] - ov !! 3048 [ARM,MIPS] - override the memory layout reported by
3281 reported by firmware. !! 3049 firmware.
3282 Define a memory regio 3050 Define a memory region of size nn[KMG] starting at
3283 ss[KMG]. 3051 ss[KMG].
3284 Multiple different re 3052 Multiple different regions can be specified with
3285 multiple mem= paramet 3053 multiple mem= parameters on the command line.
3286 3054
3287 mem=nopentium [BUGS=X86-32] Disable 3055 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 3056 memory.
3289 3057
3290 memblock=debug [KNL,EARLY] Enable me !! 3058 memblock=debug [KNL] Enable memblock debug messages.
3291 3059
3292 memchunk=nn[KMG] 3060 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 3061 [KNL,SH] Allow user to override the default size for
3294 per-device physically 3062 per-device physically contiguous DMA buffers.
3295 3063
3296 memhp_default_state=online/offline/on !! 3064 memhp_default_state=online/offline
3297 [KNL] Set the initial 3065 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 3066 onlining policy. If not specified, the default value is
3299 set according to the 3067 set according to the
3300 CONFIG_MEMORY_HOTPLUG 3068 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 3069 option.
3302 See Documentation/adm 3070 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 3071
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 3072 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 3073 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 3074 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 3075 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 3076 option description.
3309 3077
3310 memmap=nn[KMG]@ss[KMG] 3078 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 3079 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 3080 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 3081 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 3082 which limits max address to nn[KMG].
3315 Multiple different re 3083 Multiple different regions can be specified,
3316 comma delimited. 3084 comma delimited.
3317 Example: 3085 Example:
3318 memmap=100M@2 3086 memmap=100M@2G,100M#3G,1G!1024G
3319 3087
3320 memmap=nn[KMG]#ss[KMG] 3088 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 3089 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 3090 Region of memory to be marked is from ss to ss+nn.
3323 3091
3324 memmap=nn[KMG]$ss[KMG] 3092 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 3093 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 3094 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 3095 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 3096 memmap=64K$0x18690000
3329 or 3097 or
3330 memmap=0x100 3098 memmap=0x10000$0x18690000
3331 Some bootloaders may 3099 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 3100 like Grub2, otherwise '$' and the following number
3333 will be eaten. 3101 will be eaten.
3334 3102
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 3103 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 3104 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 3105 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 3106 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 3107 and is NVDIMM or ADR memory.
3340 3108
3341 memmap=<size>%<offset>-<oldtype>+<new 3109 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 3110 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 3111 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 3112 out, the whole region will be marked as <newtype>,
3345 even if previously un 3113 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 3114 out, matching memory will be removed. Types are
3347 specified as e820 typ 3115 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 3116 3 = ACPI, 12 = PRAM.
3349 3117
3350 memory_corruption_check=0/1 [X86,EARL !! 3118 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 3119 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 3120 memory when doing things like suspend/resume.
3353 Setting this option w 3121 Setting this option will scan the memory
3354 looking for corruptio 3122 looking for corruption. Enabling this will
3355 both detect corruptio 3123 both detect corruption and prevent the kernel
3356 from using the memory 3124 from using the memory being corrupted.
3357 However, its intended 3125 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 3126 repeatable BIOS-originated corruption always
3359 affects the same memo 3127 affects the same memory, you can use memmap=
3360 to prevent the kernel 3128 to prevent the kernel from using that memory.
3361 3129
3362 memory_corruption_check_size=size [X8 !! 3130 memory_corruption_check_size=size [X86]
3363 By default it checks 3131 By default it checks for corruption in the low
3364 64k, making this memo 3132 64k, making this memory unavailable for normal
3365 use. Use this parame 3133 use. Use this parameter to scan for
3366 corruption in more or 3134 corruption in more or less memory.
3367 3135
3368 memory_corruption_check_period=second !! 3136 memory_corruption_check_period=seconds [X86]
3369 By default it checks 3137 By default it checks for corruption every 60
3370 seconds. Use this pa 3138 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 3139 other rate. 0 disables periodic checking.
3372 3140
3373 memory_hotplug.memmap_on_memory 3141 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 3142 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 3143 Format: {on | off (default)}
3376 When enabled, runtime 3144 When enabled, runtime hotplugged memory will
3377 allocate its internal 3145 allocate its internal metadata (struct pages,
3378 those vmemmap pages c 3146 those vmemmap pages cannot be optimized even
3379 if hugetlb_free_vmemm 3147 if hugetlb_free_vmemmap is enabled) from the
3380 hotadded memory which 3148 hotadded memory which will allow to hotadd a
3381 lot of memory without 3149 lot of memory without requiring additional
3382 memory to do so. 3150 memory to do so.
3383 This feature is disab 3151 This feature is disabled by default because it
3384 has some implication 3152 has some implication on large (e.g. GB)
3385 allocations in some c 3153 allocations in some configurations (e.g. small
3386 memory blocks). 3154 memory blocks).
3387 The state of the flag 3155 The state of the flag can be read in
3388 /sys/module/memory_ho 3156 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 3157 Note that even when enabled, there are a few cases where
3390 the feature is not ef 3158 the feature is not effective.
3391 3159
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 3160 memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
3393 Format: <integer> 3161 Format: <integer>
3394 default : 0 <disable> 3162 default : 0 <disable>
3395 Specifies the number 3163 Specifies the number of memtest passes to be
3396 performed. Each pass 3164 performed. Each pass selects another test
3397 pattern from a given 3165 pattern from a given set of patterns. Memtest
3398 fills the memory with 3166 fills the memory with this pattern, validates
3399 memory contents and r 3167 memory contents and reserves bad memory
3400 regions that are dete 3168 regions that are detected.
3401 3169
3402 mem_encrypt= [X86-64] AMD Secure M 3170 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 3171 Valid arguments: on, off
3404 Default: off !! 3172 Default (depends on kernel configuration option):
>> 3173 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 3174 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 3175 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 3176 mem_encrypt=off: Do not activate SME
3407 3177
3408 Refer to Documentatio 3178 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3409 for details on when m 3179 for details on when memory encryption can be activated.
3410 3180
3411 mem_sleep_default= [SUSPEND] Def 3181 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 3182 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 3183 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 3184 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 3185 See Documentation/admin-guide/pm/sleep-states.rst.
3416 3186
>> 3187 meye.*= [HW] Set MotionEye Camera parameters
>> 3188 See Documentation/admin-guide/media/meye.rst.
>> 3189
>> 3190 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 3191 Multi-Function General Purpose Timers on AMD Geode
>> 3192 platforms.
>> 3193
3417 mfgptfix [X86-32] Fix MFGPT ti 3194 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 3195 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 3196 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 3197 problem by letting the user disable the workaround.
3421 3198
3422 mga= [HW,DRM] 3199 mga= [HW,DRM]
3423 3200
3424 microcode.force_minrev= [X86] !! 3201 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
3425 Format: <bool> !! 3202 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 3203
3429 mini2440= [ARM,HW,KNL] 3204 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 3205 Format:[0..2][b][c][t]
3431 Default: "0tb" 3206 Default: "0tb"
3432 MINI2440 configuratio 3207 MINI2440 configuration specification:
3433 0 - The attached scre 3208 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 3209 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 3210 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 3211 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 3212 the TFT driver, and the framebuffer will be left
3438 unconfigured. 3213 unconfigured.
3439 b - Enable backlight. 3214 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 3215 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 3216 LED. This parameter is not necessary when using the
3442 VGA shield. 3217 VGA shield.
3443 c - Enable the s3c ca 3218 c - Enable the s3c camera interface.
3444 t - Reserved for enab 3219 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 3220 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 3221 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 3222 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 3223 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 3224
3450 mitigations= 3225 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 3226 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 3227 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 3228 arch-independent options, each of which is an
3454 aggregation of existi 3229 aggregation of existing arch-specific options.
3455 3230
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 3231 off
3460 Disable all o 3232 Disable all optional CPU mitigations. This
3461 improves syst 3233 improves system performance, but it may also
3462 expose users 3234 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 3235 Equivalent to: nopti [X86,PPC]
3464 !! 3236 if nokaslr then kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 3237 nospectre_v1 [X86,PPC]
>> 3238 nobp=0 [S390]
3475 3239 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 3240 spectre_v2_user=off [X86]
3482 !! 3241 spec_store_bypass_disable=off [X86,PPC]
3483 3242 ssbd=force-off [ARM64]
>> 3243 nospectre_bhb [ARM64]
>> 3244 l1tf=off [X86]
>> 3245 mds=off [X86]
3484 3246 tsx_async_abort=off [X86]
>> 3247 kvm.nx_huge_pages=off [X86]
>> 3248 srbds=off [X86,INTEL]
>> 3249 no_entry_flush [PPC]
>> 3250 no_uaccess_flush [PPC]
>> 3251 mmio_stale_data=off [X86]
>> 3252 retbleed=off [X86]
3485 3253
3486 Exceptions: 3254 Exceptions:
3487 3255 This does not have any effect on
3488 3256 kvm.nx_huge_pages when
3489 3257 kvm.nx_huge_pages=force.
3490 3258
3491 auto (default) 3259 auto (default)
3492 Mitigate all 3260 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 3261 enabled, even if it's vulnerable. This is for
3494 users who don 3262 users who don't want to be surprised by SMT
3495 getting disab 3263 getting disabled across kernel upgrades, or who
3496 have other wa 3264 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 3265 Equivalent to: (default behavior)
3498 3266
3499 auto,nosmt 3267 auto,nosmt
3500 Mitigate all 3268 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 3269 if needed. This is for users who always want to
3502 be fully miti 3270 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 3271 Equivalent to: l1tf=flush,nosmt [X86]
3504 3272 mds=full,nosmt [X86]
3505 3273 tsx_async_abort=full,nosmt [X86]
3506 3274 mmio_stale_data=full,nosmt [X86]
3507 3275 retbleed=auto,nosmt [X86]
3508 3276
3509 mminit_loglevel= 3277 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 3278 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 3279 parameter allows control of the logging verbosity for
3512 the additional memory 3280 the additional memory initialisation checks. A value
3513 of 0 disables mminit 3281 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 3282 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 3283 so loglevel=8 may also need to be specified.
3516 3284
3517 mmio_stale_data= 3285 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 3286 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 3287 MMIO Stale Data vulnerabilities.
3520 3288
3521 Processor MMIO Stale 3289 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 3290 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 3291 operation. Exposed data could originate or end in
3524 the same CPU buffers 3292 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 3293 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 3294 is to clear the affected CPU buffers.
3527 3295
3528 This parameter contro 3296 This parameter controls the mitigation. The
3529 options are: 3297 options are:
3530 3298
3531 full - Enable m 3299 full - Enable mitigation on vulnerable CPUs
3532 3300
3533 full,nosmt - Enable m 3301 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 3302 vulnerable CPUs.
3535 3303
3536 off - Uncondit 3304 off - Unconditionally disable mitigation
3537 3305
3538 On MDS or TAA affecte 3306 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 3307 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 3308 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 3309 mitigated with the same mechanism so in order to
3542 disable this mitigati 3310 disable this mitigation, you need to specify
3543 mds=off and tsx_async 3311 mds=off and tsx_async_abort=off too.
3544 3312
3545 Not specifying this o 3313 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 3314 mmio_stale_data=full.
3547 3315
3548 For details see: 3316 For details see:
3549 Documentation/admin-g 3317 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 3318
3551 <module>.async_probe[=<bool>] [KNL] 3319 <module>.async_probe[=<bool>] [KNL]
3552 If no <bool> value is 3320 If no <bool> value is specified or if the value
3553 specified is not a va 3321 specified is not a valid <bool>, enable asynchronous
3554 probe on this module. 3322 probe on this module. Otherwise, enable/disable
3555 asynchronous probe on 3323 asynchronous probe on this module as indicated by the
3556 <bool> value. See als 3324 <bool> value. See also: module.async_probe
3557 3325
3558 module.async_probe=<bool> 3326 module.async_probe=<bool>
3559 [KNL] When set to tru 3327 [KNL] When set to true, modules will use async probing
3560 by default. To enable 3328 by default. To enable/disable async probing for a
3561 specific module, use 3329 specific module, use the module specific control that
3562 is documented under < 3330 is documented under <module>.async_probe. When both
3563 module.async_probe an 3331 module.async_probe and <module>.async_probe are
3564 specified, <module>.a 3332 specified, <module>.async_probe takes precedence for
3565 the specific module. 3333 the specific module.
3566 3334
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 3335 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3336 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3337 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3338 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3339 is always true, so this option does nothing.
3578 3340
3579 module_blacklist= [KNL] Do not load 3341 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3342 modules. Useful for debugging problem modules.
3581 3343
3582 mousedev.tap_time= 3344 mousedev.tap_time=
3583 [MOUSE] Maximum time 3345 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3346 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3347 a tap and be reported as a left button click (for
3586 touchpads working in 3348 touchpads working in absolute mode only).
3587 Format: <msecs> 3349 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3350 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3351 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3352 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3353 reporting absolute coordinates, such as tablets
3592 3354
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3355 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3356 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3357 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3358 specifies the amount of memory used for migratable
3597 allocations. If both 3359 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3360 specified, then kernelcore will be at *least* the
3599 specified value but m 3361 specified value but may be more. If movablecore on its
3600 own is specified, the 3362 own is specified, the administrator must be careful
3601 that the amount of me 3363 that the amount of memory usable for all allocations
3602 is not too small. 3364 is not too small.
3603 3365
3604 movable_node [KNL,EARLY] Boot-time !! 3366 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3367 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3368 of such nodes will be usable only for movable
3607 allocations which rul 3369 allocations which rules out almost all kernel
3608 allocations. Use with 3370 allocations. Use with caution!
3609 3371
3610 MTD_Partition= [MTD] 3372 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3373 Format: <name>,<region-number>,<size>,<offset>
3612 3374
3613 MTD_Region= [MTD] Format: 3375 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3376 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3377
3616 mtdparts= [MTD] 3378 mtdparts= [MTD]
3617 See drivers/mtd/parse 3379 See drivers/mtd/parsers/cmdlinepart.c
3618 3380
>> 3381 mtdset= [ARM]
>> 3382 ARM/S3C2412 JIVE boot control
>> 3383
>> 3384 See arch/arm/mach-s3c/mach-jive.c
>> 3385
3619 mtouchusb.raw_coordinates= 3386 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3387 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3388 ('y', default) or cooked coordinates ('n')
3622 3389
3623 mtrr=debug [X86,EARLY] !! 3390 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 3391 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3392 that could hold holes aka. UC entries.
3630 3393
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3394 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3395 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3396 Default is 1.
3634 Large value could pre 3397 Large value could prevent small alignment from
3635 using up MTRRs. 3398 using up MTRRs.
3636 3399
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3400 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3401 Format: <integer>
3639 Range: 0,7 : spare re 3402 Range: 0,7 : spare reg number
3640 Default : 1 3403 Default : 1
3641 Used for mtrr cleanup 3404 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3405 Set to 2 or more if your graphical card needs more.
3643 3406
3644 multitce=off [PPC] This parameter 3407 multitce=off [PPC] This parameter disables the use of the pSeries
3645 firmware feature for 3408 firmware feature for updating multiple TCE entries
3646 at a time. 3409 at a time.
3647 3410
3648 n2= [NET] SDL Inc. RISCom 3411 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3412
3650 netdev= [NET] Network devices 3413 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3414 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3415 Note that mem_start is often overloaded to mean
3653 something different a 3416 something different and driver-specific.
3654 This usage is only do 3417 This usage is only documented in each driver source
3655 file if at all. 3418 file if at all.
3656 3419
3657 netpoll.carrier_timeout= 3420 netpoll.carrier_timeout=
3658 [NET] Specifies amoun 3421 [NET] Specifies amount of time (in seconds) that
3659 netpoll should wait f 3422 netpoll should wait for a carrier. By default netpoll
3660 waits 4 seconds. 3423 waits 4 seconds.
3661 3424
3662 nf_conntrack.acct= 3425 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3426 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3427 0 to disable accounting
3665 1 to enable accountin 3428 1 to enable accounting
3666 Default value is 0. 3429 Default value is 0.
3667 3430
3668 nfs.cache_getent= !! 3431 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 3432 See Documentation/admin-guide/nfs/nfsroot.rst.
3670 to update the NFS cli <<
3671 3433
3672 nfs.cache_getent_timeout= !! 3434 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 3435 See Documentation/admin-guide/nfs/nfsroot.rst.
3674 update a cache entry !! 3436
>> 3437 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 3438 See Documentation/admin-guide/nfs/nfsroot.rst.
3675 3439
3676 nfs.callback_nr_threads= 3440 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3441 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3442 NFS client will assign to service NFSv4 callback
3679 requests. 3443 requests.
3680 3444
3681 nfs.callback_tcpport= 3445 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3446 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3447 channel should listen.
3684 3448
3685 nfs.delay_retrans= !! 3449 nfs.cache_getent=
3686 [NFS] specifies the n !! 3450 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 3451 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 3452
3689 Only applies if the s !! 3453 nfs.cache_getent_timeout=
3690 and the specified val !! 3454 [NFS] sets the timeout after which an attempt to
>> 3455 update a cache entry is deemed to have failed.
>> 3456
>> 3457 nfs.idmap_cache_timeout=
>> 3458 [NFS] set the maximum lifetime for idmapper cache
>> 3459 entries.
3691 3460
3692 nfs.enable_ino64= 3461 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3462 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3463 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3464 number for the readdir() and stat() syscalls instead
3696 of returning the full 3465 of returning the full 64-bit number.
3697 The default is to ret 3466 The default is to return 64-bit inode numbers.
3698 3467
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 3468 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3469 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3470 slots the client will assign to the callback
3706 channel. This determi 3471 channel. This determines the maximum number of
3707 callbacks the client 3472 callbacks the client will process in parallel for
3708 a particular server. 3473 a particular server.
3709 3474
3710 nfs.max_session_slots= 3475 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3476 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3477 the client will attempt to negotiate with the server.
3713 This limits the numbe 3478 This limits the number of simultaneous RPC requests
3714 that the client can s 3479 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3480 Note that there is little point in setting this
3716 value higher than the 3481 value higher than the max_tcp_slot_table_limit.
3717 3482
3718 nfs.nfs4_disable_idmapping= 3483 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3484 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3485 ensures that both the RPC level authentication
3721 scheme and the NFS le 3486 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3487 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3488 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3489 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3490 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3491 Servers that do not support this mode of operation
3727 will be autodetected 3492 will be autodetected by the client, and it will fall
3728 back to using the idm 3493 back to using the idmapper.
3729 To turn off this beha 3494 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 3495 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3496 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3497 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3498 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3499 UUID that is generated at system install time.
3736 3500
3737 nfs.recover_lost_locks= !! 3501 nfs.send_implementation_id =
>> 3502 [NFSv4.1] Send client implementation identification
>> 3503 information in exchange_id requests.
>> 3504 If zero, no implementation identification information
>> 3505 will be sent.
>> 3506 The default is to send the implementation identification
>> 3507 information.
>> 3508
>> 3509 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 3510 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3511 to a lease timeout on the server. Please note that
3740 doing this risks data 3512 doing this risks data corruption, since there are
3741 no guarantees that th 3513 no guarantees that the file will remain unchanged
3742 after the locks are l 3514 after the locks are lost.
3743 If you want to enable 3515 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3516 attempting to recover these locks, then set this
3745 parameter to '1'. 3517 parameter to '1'.
3746 The default parameter 3518 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3519 not to attempt recovery of lost locks.
3748 3520
3749 nfs.send_implementation_id= !! 3521 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 3522 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3523 layoutstats to the pNFS metadata server.
3760 3524
3761 Setting this to value 3525 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3526 whatever value is the default set by the layout
3763 driver. A non-zero va 3527 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3528 in seconds between layoutstats transmissions.
3765 3529
3766 nfsd.inter_copy_offload_enable= !! 3530 nfsd.inter_copy_offload_enable =
3767 [NFSv4.2] When set to 3531 [NFSv4.2] When set to 1, the server will support
3768 server-to-server copi 3532 server-to-server copies for which this server is
3769 the destination of th 3533 the destination of the copy.
3770 3534
3771 nfsd.nfs4_disable_idmapping= !! 3535 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 3536 [NFSv4.2] When used as the destination of a
3780 server-to-server copy 3537 server-to-server copy, knfsd temporarily mounts
3781 the source server. I 3538 the source server. It caches the mount in case
3782 it will be needed aga 3539 it will be needed again, and discards it if not
3783 used for the number o 3540 used for the number of milliseconds specified by
3784 this parameter. 3541 this parameter.
3785 3542
3786 nfsaddrs= [NFS] Deprecated. Us !! 3543 nfsd.nfs4_disable_idmapping=
3787 See Documentation/adm !! 3544 [NFSv4] When set to the default of '1', the NFSv4
3788 !! 3545 server will return only numeric uids and gids to
3789 nfsroot= [NFS] nfs root filesy !! 3546 clients using auth_sys, and will accept numeric uids
3790 See Documentation/adm !! 3547 and gids from such clients. This is intended to ease
>> 3548 migration from NFSv2/v3.
3791 3549
3792 nfsrootdebug [NFS] enable nfsroot <<
3793 See Documentation/adm <<
3794 3550
3795 nmi_backtrace.backtrace_idle [KNL] 3551 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3552 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3553 NMI stack-backtrace request.
3798 3554
3799 nmi_debug= [KNL,SH] Specify one 3555 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3556 when a NMI is triggered.
3801 Format: [state][,regs 3557 Format: [state][,regs][,debounce][,die]
3802 3558
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3559 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3560 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3561 Valid num: 0 or 1
3806 0 - turn hardlockup d 3562 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3563 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3564 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3565 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3566 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3567 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3568 please see 'nowatchdog'.
3815 This is useful when y 3569 This is useful when you use a panic=... timeout and
3816 need the box quickly 3570 need the box quickly up again.
3817 3571
3818 These settings can be 3572 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3573 the nmi_watchdog and hardlockup_panic sysctls.
3820 3574
3821 no387 [BUGS=X86-32] Tells t 3575 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3576 emulation library even if a 387 maths coprocessor
3823 is present. 3577 is present.
3824 3578
3825 no4lvl [RISCV,EARLY] Disable !! 3579 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 3580 kernel to use 4-level paging instead.
3830 3581
3831 noalign [KNL,ARM] !! 3582 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 3583
3840 no_console_suspend 3584 no_console_suspend
3841 [HW] Never suspend th 3585 [HW] Never suspend the console
3842 Disable suspending of 3586 Disable suspending of consoles during suspend and
3843 hibernate operations. 3587 hibernate operations. Once disabled, debugging
3844 messages can reach va 3588 messages can reach various consoles while the rest
3845 of the system is bein 3589 of the system is being put to sleep (ie, while
3846 debugging driver susp 3590 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3591 not work reliably with all consoles, but is known
3848 to work with serial a 3592 to work with serial and VGA consoles.
3849 To facilitate more fl 3593 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3594 console_suspend, a printk module parameter to control
3851 it. Users could use c 3595 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3596 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3597 turn on/off it dynamically.
3854 3598
3855 no_debug_objects !! 3599 novmcoredd [KNL,KDUMP]
3856 [KNL,EARLY] Disable o !! 3600 Disable device dump. Device dump allows drivers to
>> 3601 append dump data to vmcore so you can collect driver
>> 3602 specified debug info. Drivers can append the data
>> 3603 without any limit and this data is stored in memory,
>> 3604 so this may cause significant memory stress. Disabling
>> 3605 device dump can help save memory but the driver debug
>> 3606 data will be no longer available. This parameter
>> 3607 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
>> 3608 is set.
>> 3609
>> 3610 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3611 caches in the slab allocator. Saves per-node memory,
>> 3612 but will impact performance.
>> 3613
>> 3614 noalign [KNL,ARM]
>> 3615
>> 3616 noaltinstr [S390] Disables alternative instructions patching
>> 3617 (CPU alternatives feature).
>> 3618
>> 3619 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 3620 IOAPICs that may be present in the system.
>> 3621
>> 3622 noautogroup Disable scheduler automatic task group creation.
>> 3623
>> 3624 nocache [ARM]
3857 3625
3858 nodsp [SH] Disable hardware 3626 nodsp [SH] Disable hardware DSP at boot time.
3859 3627
3860 noefi [EFI,EARLY] Disable E !! 3628 noefi Disable EFI runtime services support.
3861 3629
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3630 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
>> 3631
>> 3632 noexec [IA-64]
>> 3633
>> 3634 nosmap [PPC]
>> 3635 Disable SMAP (Supervisor Mode Access Prevention)
>> 3636 even if it is supported by processor.
>> 3637
>> 3638 nosmep [PPC64s]
>> 3639 Disable SMEP (Supervisor Mode Execution Prevention)
>> 3640 even if it is supported by processor.
3863 3641
3864 noexec32 [X86-64] 3642 noexec32 [X86-64]
3865 This affects only 32- 3643 This affects only 32-bit executables.
3866 noexec32=on: enable n 3644 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3645 read doesn't imply executable mappings
3868 noexec32=off: disable 3646 noexec32=off: disable non-executable mappings
3869 read implies 3647 read implies executable mappings
3870 3648
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 3649 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3650
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 3651 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3652 register save and restore. The kernel will only save
3881 legacy floating-point 3653 legacy floating-point registers on task switch.
3882 3654
>> 3655 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
>> 3656
>> 3657 nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
>> 3658
>> 3659 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 3660 Equivalent to smt=1.
>> 3661
>> 3662 [KNL,X86] Disable symmetric multithreading (SMT).
>> 3663 nosmt=force: Force disable SMT, cannot be undone
>> 3664 via the sysfs control file.
>> 3665
>> 3666 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 3667 (bounds check bypass). With this option data leaks are
>> 3668 possible in the system.
>> 3669
>> 3670 nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for
>> 3671 the Spectre variant 2 (indirect branch prediction)
>> 3672 vulnerability. System may allow data leaks with this
>> 3673 option.
>> 3674
>> 3675 nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch
>> 3676 history injection) vulnerability. System may allow data leaks
>> 3677 with this option.
>> 3678
>> 3679 nospec_store_bypass_disable
>> 3680 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 3681
>> 3682 no_uaccess_flush
>> 3683 [PPC] Don't flush the L1-D cache after accessing user data.
>> 3684
>> 3685 noxsave [BUGS=X86] Disables x86 extended register state save
>> 3686 and restore using xsave. The kernel will fallback to
>> 3687 enabling legacy floating-point and sse state.
>> 3688
>> 3689 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 3690 register states. The kernel will fall back to use
>> 3691 xsave to save the states. By using this parameter,
>> 3692 performance of saving the states is degraded because
>> 3693 xsave doesn't support modified optimization while
>> 3694 xsaveopt supports it on xsaveopt enabled systems.
>> 3695
>> 3696 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 3697 restoring x86 extended register state in compacted
>> 3698 form of xsave area. The kernel will fall back to use
>> 3699 xsaveopt and xrstor to save and restore the states
>> 3700 in standard form of xsave area. By using this
>> 3701 parameter, xsave area per process might occupy more
>> 3702 memory on xsaves enabled systems.
>> 3703
>> 3704 nohlt [ARM,ARM64,MICROBLAZE,SH] Forces the kernel to busy wait
>> 3705 in do_idle() and not use the arch_cpu_idle()
>> 3706 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
>> 3707 to be effective. This is useful on platforms where the
>> 3708 sleep(SH) or wfi(ARM,ARM64) instructions do not work
>> 3709 correctly or when doing power measurements to evaluate
>> 3710 the impact of the sleep instructions. This is also
>> 3711 useful when using JTAG debugger.
>> 3712
>> 3713 no_file_caps Tells the kernel not to honor file capabilities. The
>> 3714 only way then for a file to be executed with privilege
>> 3715 is to be setuid root or executed by root.
>> 3716
>> 3717 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3718 function PAL_HALT_LIGHT when idle. This increases
>> 3719 power-consumption. On the positive side, it reduces
>> 3720 interrupt wake-up latency, which may improve performance
>> 3721 in certain environments such as networked servers or
>> 3722 real-time systems.
>> 3723
3883 no_hash_pointers 3724 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3725 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3726 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3727 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3728 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3729 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3730 users, but it also makes debugging the kernel more
3891 difficult since unequ 3731 difficult since unequal pointers can no longer be
3892 compared. However, i 3732 compared. However, if this command-line option is
3893 specified, then all n 3733 specified, then all normal pointers will have their true
3894 value printed. This o 3734 value printed. This option should only be specified when
3895 debugging the kernel. 3735 debugging the kernel. Please do not use on production
3896 kernels. 3736 kernels.
3897 3737
3898 nohibernate [HIBERNATION] Disable 3738 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3739
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 3740 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3741 Valid arguments: on, off
3915 Default: on 3742 Default: on
3916 3743
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3744 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3745 The argument is a cpu list, as described above.
3919 In kernels built with 3746 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3747 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3748 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3749 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3750 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3751 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3752 rcu_nocbs= boot parameter.
3926 3753
3927 Note that this argume 3754 Note that this argument takes precedence over
3928 the CONFIG_RCU_NOCB_C 3755 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
3929 3756
>> 3757 noiotrap [SH] Disables trapped I/O port accesses.
>> 3758
>> 3759 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3760 disable unhandled interrupt sources.
>> 3761
>> 3762 no_timer_check [X86,APIC] Disables the code which tests for
>> 3763 broken timer IRQ sources.
>> 3764
>> 3765 noisapnp [ISAPNP] Disables ISA PnP code.
>> 3766
3930 noinitrd [RAM] Tells the kerne 3767 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3768 initial RAM disk.
3932 3769
3933 nointremap [X86-64,Intel-IOMMU,E !! 3770 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3771 remapping.
3935 [Deprecated - use int 3772 [Deprecated - use intremap=off]
3936 3773
3937 noinvpcid [X86,EARLY] Disable t !! 3774 nointroute [IA-64]
3938 <<
3939 noiotrap [SH] Disables trapped <<
3940 3775
3941 noirqdebug [X86-32] Disables the !! 3776 noinvpcid [X86] Disable the INVPCID cpu feature.
3942 disable unhandled int <<
3943 3777
3944 noisapnp [ISAPNP] Disables ISA !! 3778 nojitter [IA-64] Disables jitter checking for ITC timers.
3945 3779
3946 nokaslr [KNL,EARLY] !! 3780 nokaslr [KNL]
3947 When CONFIG_RANDOMIZE 3781 When CONFIG_RANDOMIZE_BASE is set, this disables
3948 kernel and module bas 3782 kernel and module base offset ASLR (Address Space
3949 Layout Randomization) 3783 Layout Randomization).
3950 3784
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3785 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
>> 3786
>> 3787 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3788 fault handling.
3953 3789
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3790 no-vmw-sched-clock
>> 3791 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3792 clock and use the default one.
>> 3793
>> 3794 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
>> 3795 steal time accounting. steal time is computed, but
>> 3796 won't influence scheduler behaviour
3955 3797
3956 nolapic [X86-32,APIC,EARLY] D !! 3798 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3957 3799
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3800 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
>> 3801
>> 3802 nomca [IA-64] Disable machine check abort handling
3959 3803
3960 nomce [X86-32] Disable Mach 3804 nomce [X86-32] Disable Machine Check Exception
3961 3805
3962 nomfgpt [X86-32] Disable Mult 3806 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 3807 Timer usage (for AMD Geode machines).
3964 3808
>> 3809 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
>> 3810 shutdown the other cpus. Instead use the REBOOT_VECTOR
>> 3811 irq.
>> 3812
3965 nomodeset Disable kernel modese 3813 nomodeset Disable kernel modesetting. Most systems' firmware
3966 sets up a display mod 3814 sets up a display mode and provides framebuffer memory
3967 for output. With nomo 3815 for output. With nomodeset, DRM and fbdev drivers will
3968 not load if they coul 3816 not load if they could possibly displace the pre-
3969 initialized output. O 3817 initialized output. Only the system framebuffer will
3970 be available for use. 3818 be available for use. The respective drivers will not
3971 perform display-mode 3819 perform display-mode changes or accelerated rendering.
3972 3820
3973 Useful as error fallb 3821 Useful as error fallback, or for testing and debugging.
3974 3822
3975 nomodule Disable module load 3823 nomodule Disable module load
3976 3824
3977 nonmi_ipi [X86] Disable using N !! 3825 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. 3826 pagetables) support.
3983 3827
3984 nopcid [X86-64,EARLY] Disabl !! 3828 nopcid [X86-64] Disable the PCID cpu feature.
3985 3829
3986 nopku [X86] Disable Memory 3830 nopku [X86] Disable Memory Protection Keys CPU feature found
3987 in some Intel CPUs. 3831 in some Intel CPUs.
3988 3832
3989 nopti [X86-64,EARLY] !! 3833 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
3990 Equivalent to pti=off <<
3991 <<
3992 nopv= [X86,XEN,KVM,HYPER_V, <<
3993 Disables the PV optim 3834 Disables the PV optimizations forcing the guest to run
3994 as generic guest with 3835 as generic guest with no PV drivers. Currently support
3995 XEN HVM, KVM, HYPER_V 3836 XEN HVM, KVM, HYPER_V and VMWARE guest.
3996 3837
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3838 nopvspin [X86,XEN,KVM]
3998 Disables the qspinloc 3839 Disables the qspinlock slow path using PV optimizations
3999 which allow the hyper 3840 which allow the hypervisor to 'idle' the guest on lock
4000 contention. 3841 contention.
4001 3842
4002 norandmaps Don't use address spa 3843 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3844 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3845
4005 noreplace-smp [X86-32,SMP] Don't re 3846 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3847 with UP alternatives
4007 3848
4008 noresume [SWSUSP] Disables res 3849 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3850 space.
4010 3851
4011 no-scroll [VGA] Disables scroll 3852 no-scroll [VGA] Disables scrollback.
4012 This is required for 3853 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3854 reader made by F.H. Papenmeier (Germany).
4014 3855
4015 nosgx [X86-64,SGX,EARLY] Di !! 3856 nosbagart [IA-64]
4016 3857
4017 nosmap [PPC,EARLY] !! 3858 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 3859
4021 nosmep [PPC64s,EARLY] !! 3860 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 <<
4025 nosmp [SMP,EARLY] Tells an <<
4026 and disable the IO AP 3861 and disable the IO APIC. legacy for "maxcpus=0".
4027 3862
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 3863 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3864
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 3865 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3866
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 3867 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3868 soft-lockup and NMI watchdog (hard-lockup).
4083 3869
4084 nowb [ARM,EARLY] !! 3870 nowb [ARM]
4085 3871
4086 nox2apic [X86-64,APIC,EARLY] D !! 3872 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3873
4088 NOTE: this parameter 3874 NOTE: this parameter will be ignored on systems with the
4089 LEGACY_XAPIC_DISABLED 3875 LEGACY_XAPIC_DISABLED bit set in the
4090 IA32_XAPIC_DISABLE_ST 3876 IA32_XAPIC_DISABLE_STATUS MSR.
4091 3877
4092 noxsave [BUGS=X86] Disables x !! 3878 nps_mtm_hs_ctr= [KNL,ARC]
4093 and restore using xsa !! 3879 This parameter sets the maximum duration, in
4094 enabling legacy float !! 3880 cycles, each HW thread of the CTOP can run
>> 3881 without interruptions, before HW switches it.
>> 3882 The actual maximum duration is 16 times this
>> 3883 parameter's value.
>> 3884 Format: integer between 1 and 255
>> 3885 Default: 255
>> 3886
>> 3887 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3888 purges which is reported from either PAL_VM_SUMMARY or
>> 3889 SAL PALO.
4095 3890
4096 noxsaveopt [X86] Disables xsaveo !! 3891 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 3892 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3893 support 'n' processors. It could be larger than the
4114 number of already plu 3894 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3895 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3896 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3897 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3898 hot plugging.
4119 3899
4120 nr_uarts= [SERIAL] maximum numb 3900 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3901
4122 numa=off [KNL, ARM64, PPC, RIS !! 3902 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123 Disable NUMA, Only se !! 3903 set up a single NUMA node spanning all memory.
4124 spanning all memory. <<
4125 3904
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 3905 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 3906 NUMA balancing.
4128 Allowed values are en 3907 Allowed values are enable and disable
4129 3908
4130 numa_zonelist_order= [KNL, BOOT] Sele 3909 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3910 'node', 'default' can be specified
4132 This can be set from 3911 This can be set from sysctl after boot.
4133 See Documentation/adm 3912 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3913
4135 ohci1394_dma=early [HW,EARLY] en !! 3914 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 3915 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 3916 info.
4138 3917
4139 olpc_ec_timeout= [OLPC] ms delay when 3918 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3919 Rather than timing out after 20 ms if an EC
4141 command is not proper 3920 command is not properly ACKed, override the length
4142 of the timeout. We h 3921 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3922 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3923 interrupts *may* be lost!
4145 3924
4146 omap_mux= [OMAP] Override bootl 3925 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3926 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3927 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3928 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3929
4151 onenand.bdry= [HW,MTD] Flex-OneNAND 3930 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4152 3931
4153 Format: [die0_boundar 3932 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4154 3933
4155 boundary - index of l 3934 boundary - index of last SLC block on Flex-OneNAND.
4156 The remain 3935 The remaining blocks are configured as MLC blocks.
4157 lock - Configure 3936 lock - Configure if Flex-OneNAND boundary should be locked.
4158 Once locke 3937 Once locked, the boundary cannot be changed.
4159 1 indicate 3938 1 indicates lock status, 0 indicates unlock status.
4160 3939
4161 oops=panic [KNL,EARLY] !! 3940 oops=panic Always panic on oopses. Default is to just kill the
4162 Always panic on oopse <<
4163 process, but there is 3941 process, but there is a small probability of
4164 deadlocking the machi 3942 deadlocking the machine.
4165 This will also cause 3943 This will also cause panics on machine check exceptions.
4166 Useful together with 3944 Useful together with panic=30 to trigger a reboot.
4167 3945
4168 page_alloc.shuffle= 3946 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3947 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3948 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3949 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3950 running on a platform with a direct-mapped memory-side
>> 3951 cache, and this parameter can be used to
>> 3952 override/disable that behavior. The state of the flag
>> 3953 can be read from sysfs at:
4173 /sys/module/page_allo 3954 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3955
4176 page_owner= [KNL,EARLY] Boot-time !! 3956 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3957 Storage of the information about who allocated
4178 each page is disabled 3958 each page is disabled in default. With this switch,
4179 we can turn it on. 3959 we can turn it on.
4180 on: enable the featur 3960 on: enable the feature
4181 3961
4182 page_poison= [KNL,EARLY] Boot-time !! 3962 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3963 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3964 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3965 off: turn off poisoning (default)
4186 on: turn on poisoning 3966 on: turn on poisoning
4187 3967
4188 page_reporting.page_reporting_order= 3968 page_reporting.page_reporting_order=
4189 [KNL] Minimal page re 3969 [KNL] Minimal page reporting order
4190 Format: <integer> 3970 Format: <integer>
4191 Adjust the minimal pa 3971 Adjust the minimal page reporting order. The page
4192 reporting is disabled !! 3972 reporting is disabled when it exceeds (MAX_ORDER-1).
4193 3973
4194 panic= [KNL] Kernel behaviou 3974 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3975 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3976 timeout = 0: wait forever
4197 timeout < 0: reboot i 3977 timeout < 0: reboot immediately
4198 Format: <timeout> 3978 Format: <timeout>
4199 3979
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 3980 panic_print= Bitmask for printing system info when panic happens.
4218 User can chose combin 3981 User can chose combination of the following bits:
4219 bit 0: print all task 3982 bit 0: print all tasks info
4220 bit 1: print system m 3983 bit 1: print system memory info
4221 bit 2: print timer in 3984 bit 2: print timer info
4222 bit 3: print locks in 3985 bit 3: print locks info if CONFIG_LOCKDEP is on
4223 bit 4: print ftrace b 3986 bit 4: print ftrace buffer
4224 bit 5: print all prin 3987 bit 5: print all printk messages in buffer
4225 bit 6: print all CPUs 3988 bit 6: print all CPUs backtrace (if available in the arch)
4226 bit 7: print only tas <<
4227 *Be aware* that this 3989 *Be aware* that this option may print a _lot_ of lines,
4228 so there are risks of 3990 so there are risks of losing older messages in the log.
4229 Use this option caref 3991 Use this option carefully, maybe worth to setup a
4230 bigger log buffer wit 3992 bigger log buffer with "log_buf_len" along with this.
4231 3993
>> 3994 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
>> 3995 Format: <hex>[,nousertaint]
>> 3996 Hexadecimal bitmask representing the set of TAINT flags
>> 3997 that will cause the kernel to panic when add_taint() is
>> 3998 called with any of the flags in this set.
>> 3999 The optional switch "nousertaint" can be utilized to
>> 4000 prevent userspace forced crashes by writing to sysctl
>> 4001 /proc/sys/kernel/tainted any flagset matching with the
>> 4002 bitmask set on panic_on_taint.
>> 4003 See Documentation/admin-guide/tainted-kernels.rst for
>> 4004 extra details on the taint flags that users can pick
>> 4005 to compose the bitmask to assign to panic_on_taint.
>> 4006
>> 4007 panic_on_warn panic() instead of WARN(). Useful to cause kdump
>> 4008 on a WARN().
>> 4009
4232 parkbd.port= [HW] Parallel port nu 4010 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 4011 connected to, default is 0.
4234 Format: <parport#> 4012 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 4013 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 4014 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 4015 Format: <mode>
4238 4016
4239 parport= [HW,PPT] Specify para 4017 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 4018 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 4019 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 4020 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 4021 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 4022 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 4023 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 4024 should be numbers, or 'auto' (for using detected
4247 settings on that part 4025 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 4026 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 4027 Parallel ports are assigned in the order they
4250 are specified on the 4028 are specified on the command line, starting
4251 with parport0. 4029 with parport0.
4252 4030
4253 parport_init_mode= [HW,PPT] 4031 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 4032 Configure VIA parallel port to operate in
4255 a specific mode. This 4033 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 4034 computer where firmware has no options for setting
4257 up parallel port mode 4035 up parallel port mode and sets it to spp.
4258 Currently this functi 4036 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 4037 Format: [spp|ps2|epp|ecp|ecpepp]
4260 4038
4261 pata_legacy.all= [HW,LIBATA] 4039 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 4040 Format: <int>
4263 Set to non-zero to pr 4041 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 4042 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 4043 has been found at either range. Disabled by default.
4266 4044
4267 pata_legacy.autospeed= [HW,LIBATA] 4045 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 4046 Format: <int>
4269 Set to non-zero if a 4047 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 4048 changes. Disabled by default.
4271 4049
4272 pata_legacy.ht6560a= [HW,LIBATA] 4050 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 4051 Format: <int>
4274 Set to 1, 2, or 3 for 4052 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 4053 the secondary channel, or both channels respectively.
4276 Disabled by default. 4054 Disabled by default.
4277 4055
4278 pata_legacy.ht6560b= [HW,LIBATA] 4056 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 4057 Format: <int>
4280 Set to 1, 2, or 3 for 4058 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 4059 the secondary channel, or both channels respectively.
4282 Disabled by default. 4060 Disabled by default.
4283 4061
4284 pata_legacy.iordy_mask= [HW,LIBATA] 4062 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 4063 Format: <int>
4286 IORDY enable mask. S 4064 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 4065 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 4066 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 4067 the second channel, and so on. The sequence will often
4290 correspond to the pri 4068 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 4069 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 4070 bus and the use of other driver options may interfere
4293 with the sequence. B 4071 with the sequence. By default IORDY is allowed across
4294 all channels. 4072 all channels.
4295 4073
4296 pata_legacy.opti82c46x= [HW,LIBATA] 4074 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 4075 Format: <int>
4298 Set to 1, 2, or 3 for 4076 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 4077 channel, the secondary channel, or both channels
4300 respectively. Disabl 4078 respectively. Disabled by default.
4301 4079
4302 pata_legacy.opti82c611a= [HW,L 4080 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 4081 Format: <int>
4304 Set to 1, 2, or 3 for 4082 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 4083 channel, the secondary channel, or both channels
4306 respectively. Disabl 4084 respectively. Disabled by default.
4307 4085
4308 pata_legacy.pio_mask= [HW,LIBATA] 4086 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 4087 Format: <int>
4310 PIO mode mask for aut 4088 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 4089 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 4090 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 4091 All modes allowed by default.
4314 4092
4315 pata_legacy.probe_all= [HW,LIBATA] 4093 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 4094 Format: <int>
4317 Set to non-zero to pr 4095 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 4096 port ranges on PCI systems. Disabled by default.
4319 4097
4320 pata_legacy.probe_mask= [HW,LIBATA] 4098 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 4099 Format: <int>
4322 Probe mask for legacy 4100 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 4101 platform configuration and the use of other driver
4324 options up to 6 legac 4102 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 4103 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 4104 of individual ports can be disabled by setting the
4327 corresponding bits in 4105 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 4106 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 4107 By default all supported ports are probed.
4330 4108
4331 pata_legacy.qdi= [HW,LIBATA] 4109 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 4110 Format: <int>
4333 Set to non-zero to pr 4111 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 4112 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 4113
4336 pata_legacy.winbond= [HW,LIBATA] 4114 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 4115 Format: <int>
4338 Set to non-zero to pr 4116 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 4117 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 4118 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 4119 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 4120 0 otherwise.
4343 4121
4344 pata_platform.pio_mask= [HW,LIBATA] 4122 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 4123 Format: <int>
4346 Supported PIO mode ma 4124 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 4125 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 4126 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 4127 allowed by default.
4350 4128
4351 pause_on_oops=<int> !! 4129 pause_on_oops=
4352 Halt all CPUs after t 4130 Halt all CPUs after the first oops has been printed for
4353 the specified number 4131 the specified number of seconds. This is to be used if
4354 your oopses keep scro 4132 your oopses keep scrolling off the screen.
4355 4133
4356 pcbit= [HW,ISDN] 4134 pcbit= [HW,ISDN]
4357 4135
4358 pci=option[,option...] [PCI,EARLY] v !! 4136 pci=option[,option...] [PCI] various PCI subsystem options.
4359 4137
4360 Some options 4138 Some options herein operate on a specific device
4361 or a set of d 4139 or a set of devices (<pci_dev>). These are
4362 specified in 4140 specified in one of the following formats:
4363 4141
4364 [<domain>:]<b 4142 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 4143 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 4144
4367 Note: the fir 4145 Note: the first format specifies a PCI
4368 bus/device/fu 4146 bus/device/function address which may change
4369 if new hardwa 4147 if new hardware is inserted, if motherboard
4370 firmware chan 4148 firmware changes, or due to changes caused
4371 by other kern 4149 by other kernel parameters. If the
4372 domain is lef 4150 domain is left unspecified, it is
4373 taken to be z 4151 taken to be zero. Optionally, a path
4374 to a device t 4152 to a device through multiple device/function
4375 addresses can 4153 addresses can be specified after the base
4376 address (this 4154 address (this is more robust against
4377 renumbering i 4155 renumbering issues). The second format
4378 selects devic 4156 selects devices using IDs from the
4379 configuration 4157 configuration space which may match multiple
4380 devices in th 4158 devices in the system.
4381 4159
4382 earlydump dump PCI conf 4160 earlydump dump PCI config space before the kernel
4383 changes anyth 4161 changes anything
4384 off [X86] don't p 4162 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 4163 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 4164 the hardware directly. Use this if your machine
4387 has a non-sta 4165 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 4166 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 4167 hardware access methods are allowed. Use this
4390 if you experi 4168 if you experience crashes upon bootup and you
4391 suspect they 4169 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 4170 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 4171 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 4172 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 4173 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 4174 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 4175 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 4176 bus number. The config space is then accessed
4399 through ports 4177 through ports 0xC000-0xCFFF).
4400 See http://wi 4178 See http://wiki.osdev.org/PCI for more info
4401 on the config 4179 on the configuration access mechanisms.
4402 noaer [PCIE] If the 4180 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 4181 enabled, this kernel boot option can be used to
4404 disable the u 4182 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 4183 nodomains [PCI] Disable support for multiple PCI
4406 root domains 4184 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 4185 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 4186 Configuration
4409 check_enable_amd_mmconf [X86] 4187 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 4188 properly configured MMIO access to PCI
4411 config space 4189 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 4190 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 4191 enabled, this kernel boot option can be used to
4414 disable the u 4192 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 4193 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 4194 Safety option to keep boot IRQs enabled. This
4417 should never 4195 should never be necessary.
4418 ioapicreroute [APIC] Enable 4196 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 4197 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 4198 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 4199 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 4200 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 4201 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 4202 a chipset where boot IRQs cannot be disabled.
4425 The opposite 4203 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 4204 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 4205 routing table. These calls are known to be buggy
4428 on several ma 4206 on several machines and they hang the machine
4429 when used, bu 4207 when used, but on other computers it's the only
4430 way to get th 4208 way to get the interrupt routing table. Try
4431 this option i 4209 this option if the kernel is unable to allocate
4432 IRQs or disco 4210 IRQs or discover secondary PCI buses on your
4433 motherboard. 4211 motherboard.
4434 rom [X86] Assign 4212 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 4213 Use with caution as certain devices share
4436 address decod 4214 address decoders between ROMs and other
4437 resources. 4215 resources.
4438 norom [X86] Do not 4216 norom [X86] Do not assign address space to
4439 expansion ROM 4217 expansion ROMs that do not already have
4440 BIOS assigned 4218 BIOS assigned address ranges.
4441 nobar [X86] Do not 4219 nobar [X86] Do not assign address space to the
4442 BARs that wer 4220 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 4221 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 4222 assigned automatically to PCI devices. You can
4445 make the kern 4223 make the kernel exclude IRQs of your ISA cards
4446 this way. 4224 this way.
4447 pirqaddr=0xAAAAA [X86] 4225 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 4226 of the PIRQ table (normally generated
4449 by the BIOS) 4227 by the BIOS) if it is outside the
4450 F0000h-100000 4228 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 4229 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 4230 useful if the kernel is unable to find your
4453 secondary bus 4231 secondary buses and you want to tell it
4454 explicitly wh 4232 explicitly which ones they are.
4455 assign-busses [X86] Always 4233 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 4234 numbers ourselves, overriding
4457 whatever the 4235 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 4236 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 4237 in the BIOS $PIR table. This is needed on
4460 some systems 4238 some systems with broken BIOSes, notably
4461 some HP Pavil 4239 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 4240 notebooks. This will have no effect if ACPI
4463 IRQ routing i 4241 IRQ routing is enabled.
4464 noacpi [X86] Do not 4242 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 4243 or for PCI scanning.
4466 use_crs [X86] Use PCI 4244 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 4245 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 4246 is enabled by default. If you need to use this,
4469 please report 4247 please report a bug.
4470 nocrs [X86] Ignore 4248 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 4249 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 4250 use_e820 [X86] Use E820 reservations to exclude parts of
4473 PCI host brid 4251 PCI host bridge windows. This is a workaround
4474 for BIOS defe 4252 for BIOS defects in host bridge _CRS methods.
4475 If you need t 4253 If you need to use this, please report a bug to
4476 <linux-pci@vge 4254 <linux-pci@vger.kernel.org>.
4477 no_e820 [X86] Ignore 4255 no_e820 [X86] Ignore E820 reservations for PCI host
4478 bridge window 4256 bridge windows. This is the default on modern
4479 hardware. If 4257 hardware. If you need to use this, please report
4480 a bug to <linu 4258 a bug to <linux-pci@vger.kernel.org>.
4481 routeirq Do IRQ routin 4259 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 4260 This is normally done in pci_enable_device(),
4483 so this optio 4261 so this option is a temporary workaround
4484 for broken dr 4262 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 4263 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 4264 handle more pci cards
4487 noearly [X86] Don't d 4265 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 4266 This might help on some broken boards which
4489 machine check 4267 machine check when some devices' config space
4490 is read. But 4268 is read. But various workarounds are disabled
4491 and some IOMM 4269 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 4270 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 4271 This sorting is done to get a device
4494 order compati 4272 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 4273 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 4274 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 4275 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 4276 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 4277 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 4278 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 4279 based on its parent bus. Also set MRRS (Max
4502 Read Request 4280 Read Request Size) to the largest supported
4503 value (no lar 4281 value (no larger than the MPS that the device
4504 or bus can su 4282 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 4283 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 4284 every device is guaranteed to support. This
4507 configuration 4285 configuration allows peer-to-peer DMA between
4508 any pair of d 4286 any pair of devices, possibly at the cost of
4509 reduced perfo 4287 reduced performance. This also guarantees
4510 that hot-adde 4288 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 4289 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 4290 reserved for the CardBus bridge's IO window.
4513 The default v 4291 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 4292 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 4293 reserved for the CardBus bridge's memory
4516 window. The d 4294 window. The default value is 64 megabytes.
4517 resource_alignment= 4295 resource_alignment=
4518 Format: 4296 Format:
4519 [<order of ali 4297 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 4298 Specifies alignment and device to reassign
4521 aligned memor 4299 aligned memory resources. How to
4522 specify the d 4300 specify the device is described above.
4523 If <order of 4301 If <order of align> is not specified,
4524 PAGE_SIZE is 4302 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 4303 A PCI-PCI bridge can be specified if resource
4526 windows need 4304 windows need to be expanded.
4527 To specify th 4305 To specify the alignment for several
4528 instances of 4306 instances of a device, the PCI vendor,
4529 device, subve 4307 device, subvendor, and subdevice may be
4530 specified, e. 4308 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 4309 for 4096-byte alignment.
4532 ecrc= Enable/disabl 4310 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR 4311 end-to-end CRC checking). Only effective if
4534 OS has native 4312 OS has native AER control (either granted by
4535 ACPI _OSC or 4313 ACPI _OSC or forced via "pcie_ports=native")
4536 bios: Use BIO 4314 bios: Use BIOS/firmware settings. This is the
4537 the default. 4315 the default.
4538 off: Turn ECR 4316 off: Turn ECRC off
4539 on: Turn ECRC 4317 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 4318 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 4319 reserved for hotplug bridge's IO window.
4542 Default size 4320 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 4321 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 4322 reserved for hotplug bridge's MMIO window.
4545 Default size 4323 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 4324 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 4325 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 4326 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 4327 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 4328 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 4329 MMIO_PREF window.
4552 Default size 4330 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 4331 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 4332 reserved for buses below a hotplug bridge.
4555 Default is 1. 4333 Default is 1.
4556 realloc= Enable/disabl 4334 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 4335 if allocations done by BIOS are too small to
4558 accommodate r 4336 accommodate resources required by all child
4559 devices. 4337 devices.
4560 off: Turn rea 4338 off: Turn realloc off
4561 on: Turn real 4339 on: Turn realloc on
4562 realloc same as reall 4340 realloc same as realloc=on
4563 noari do not use PC 4341 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 4342 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 4343 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 4344 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 4345 only look for one device below a PCIe downstream
4568 port. 4346 port.
4569 big_root_window Try to add a 4347 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 4348 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 4349 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 4350 Adding the window is slightly risky (it may
4573 conflict with 4351 conflict with unreported devices), so this
4574 taints the ke 4352 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 4353 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 4354 Specify one or more PCI devices (in the format
4577 specified abo 4355 specified above) separated by semicolons.
4578 Each device s 4356 Each device specified will have the PCI ACS
4579 redirect capa 4357 redirect capabilities forced off which will
4580 allow P2P tra 4358 allow P2P traffic between devices through
4581 bridges witho 4359 bridges without forcing it upstream. Note:
4582 this removes 4360 this removes isolation between devices and
4583 may put more 4361 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 4362 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 4363 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 4364 norid [S390] ignore the RID field and force use of
4619 one PCI domai 4365 one PCI domain per PCI function
4620 4366
4621 pcie_aspm= [PCIE] Forcibly enabl !! 4367 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 4368 Management.
4623 off Don't touch ASPM conf !! 4369 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 4370 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 4371 WARNING: Forcing ASPM on may cause system lockups.
4627 4372
4628 pcie_ports= [PCIE] PCIe port serv 4373 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 4374 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 4375 even if the platform doesn't give the OS permission to
4631 use them. This may c 4376 use them. This may cause conflicts if the platform
4632 also tries to use the 4377 also tries to use these services.
4633 dpc-native Use native PC 4378 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 4379 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 4380 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 4381 hotplug).
4637 4382
4638 pcie_port_pm= [PCIE] PCIe port powe 4383 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 4384 off Disable power management of all PCIe ports
4640 force Forcibly enable power 4385 force Forcibly enable power management of all PCIe ports
4641 4386
4642 pcie_pme= [PCIE,PM] Native PCIe 4387 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 4388 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 4389 all PCIe root ports use INTx for all services).
4645 4390
4646 pcmv= [HW,PCMCIA] BadgePAD 4391 pcmv= [HW,PCMCIA] BadgePAD 4
4647 4392
4648 pd_ignore_unused 4393 pd_ignore_unused
4649 [PM] 4394 [PM]
4650 Keep all power-domain 4395 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 4396 even if no driver has claimed them. This is useful
4652 for debug and develop 4397 for debug and development, but should not be
4653 needed on a platform 4398 needed on a platform with proper driver support.
4654 4399
4655 pdcchassis= [PARISC,HW] Disable/E 4400 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4401 boot time.
4657 Format: { 0 | 1 } 4402 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4403 See arch/parisc/kernel/pdc_chassis.c
4659 4404
4660 percpu_alloc= [MM,EARLY] !! 4405 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4406 Currently supported values are "embed" and "page".
4663 Archs may support sub 4407 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4408 See comments in mm/percpu.c for details on each
4665 allocator. This para 4409 allocator. This parameter is primarily for debugging
4666 and performance compa 4410 and performance comparison.
4667 4411
4668 pirq= [SMP,APIC] Manual mp- 4412 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 4413 See Documentation/x86/i386/IO-APIC.rst.
4670 4414
4671 plip= [PPT,NET] Parallel po 4415 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4416 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4417 See also Documentation/admin-guide/parport.rst.
4674 4418
4675 pmtmr= [X86] Manual setup of 4419 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4420 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4421 e.g. pmtmr=0x508
4678 4422
4679 pmu_override= [PPC] Override the PM 4423 pmu_override= [PPC] Override the PMU.
4680 This option takes ove 4424 This option takes over the PMU facility, so it is no
4681 longer usable by perf 4425 longer usable by perf. Setting this option starts the
4682 PMU counters by setti 4426 PMU counters by setting MMCR0 to 0 (the FC bit is
4683 cleared). If a number 4427 cleared). If a number is given, then MMCR1 is set to
4684 that number, otherwis 4428 that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4685 remains 0. 4429 remains 0.
4686 4430
4687 pm_debug_messages [SUSPEND,KNL] 4431 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4432 Enable suspend/resume debug messages during boot up.
4689 4433
4690 pnp.debug=1 [PNP] 4434 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4435 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4436 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4437 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4438 current resource usage; turning this on also shows
4695 possible settings and 4439 possible settings and some assignment information.
4696 4440
4697 pnpacpi= [ACPI] 4441 pnpacpi= [ACPI]
4698 { off } 4442 { off }
4699 4443
4700 pnpbios= [ISAPNP] 4444 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4445 { on | off | curr | res | no-curr | no-res }
4702 4446
4703 pnp_reserve_irq= 4447 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4448 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4449
4706 pnp_reserve_dma= 4450 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4451 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4452
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4453 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4454 Ranges are in pairs (I/O port base and size).
4711 4455
4712 pnp_reserve_mem= 4456 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4457 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4458 autoconfiguration.
4715 Ranges are in pairs ( 4459 Ranges are in pairs (memory base and size).
4716 4460
4717 ports= [IP_VS_FTP] IPVS ftp 4461 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4462 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4463 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4464 may be specified.
4721 Format: <port>,<port> 4465 Format: <port>,<port>....
4722 4466
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 4467 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4468 It specifically disables cpuidle and sets the
4730 platform machine desc 4469 platform machine description specific power_save
4731 function to NULL. On 4470 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4471 execution priority.
4733 4472
4734 ppc_strict_facility_enable 4473 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4474 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4475 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4476 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4477 There is some performance impact when enabling this.
4739 4478
4740 ppc_tm= [PPC,EARLY] !! 4479 ppc_tm= [PPC]
4741 Format: {"off"} 4480 Format: {"off"}
4742 Disable Hardware Tran 4481 Disable Hardware Transactional Memory
4743 4482
4744 preempt= [KNL] 4483 preempt= [KNL]
4745 Select preemption mod 4484 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4485 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4486 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4487 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4488 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4489
4753 print-fatal-signals= 4490 print-fatal-signals=
4754 [KNL] debug: print fa 4491 [KNL] debug: print fatal signals
4755 4492
4756 If enabled, warn abou 4493 If enabled, warn about various signal handling
4757 related application a 4494 related application anomalies: too many signals,
4758 too many POSIX.1 time 4495 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4496 coredump - etc.
4760 4497
4761 If you hit the warnin 4498 If you hit the warning due to signal overflow,
4762 you might want to try 4499 you might want to try "ulimit -i unlimited".
4763 4500
4764 default: off. 4501 default: off.
4765 4502
4766 printk.always_kmsg_dump= 4503 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4504 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4505 panics
4769 Format: <bool> (1/Y/ 4506 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4507 default: disabled
4771 4508
4772 printk.console_no_auto_verbose= 4509 printk.console_no_auto_verbose=
4773 Disable console logle 4510 Disable console loglevel raise on oops, panic
4774 or lockdep-detected i 4511 or lockdep-detected issues (only if lock debug is on).
4775 With an exception to 4512 With an exception to setups with low baudrate on
4776 serial console, keepi 4513 serial console, keeping this 0 is a good choice
4777 in order to provide m 4514 in order to provide more debug information.
4778 Format: <bool> 4515 Format: <bool>
4779 default: 0 (auto_verb 4516 default: 0 (auto_verbose is enabled)
4780 4517
4781 printk.devkmsg={on,off,ratelimit} 4518 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4519 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4520 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4521 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4522 ratelimit - ratelimit the logging
4786 Default: ratelimit 4523 Default: ratelimit
4787 4524
4788 printk.time= Show timing data pref 4525 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4526 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4527
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] 4528 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4529 Limit processor to maximum C-state
4803 max_cstate=9 override 4530 max_cstate=9 overrides any DMI blacklist limit.
4804 4531
4805 processor.nocst [HW,ACPI] 4532 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4533 Ignore the _CST method to determine C-states,
4807 instead using the leg 4534 instead using the legacy FADT method
4808 4535
4809 profile= [KNL] Enable kernel p 4536 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4537 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4538 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4539 [defaults to kernel profiling]
4813 Param: "schedule" - p 4540 Param: "schedule" - profile schedule points.
>> 4541 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4542 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4543 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4544 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4545 statistical time based profiling.
4817 4546
4818 prompt_ramdisk= [RAM] [Deprecated] 4547 prompt_ramdisk= [RAM] [Deprecated]
4819 4548
4820 prot_virt= [S390] enable hosting 4549 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4550 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4551 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4552 Format: <bool>
4826 4553
4827 psi= [KNL] Enable or disab 4554 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4555 tracking.
4829 Format: <bool> 4556 Format: <bool>
4830 4557
4831 psmouse.proto= [HW,MOUSE] Highest PS 4558 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4559 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4560 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4561 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4562 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4563 Try to reset the device after so many bad packets
4837 (0 = never). 4564 (0 = never).
4838 psmouse.resolution= 4565 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4566 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4567 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4568 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4569 0 = disabled, 1 = enabled (default).
4843 4570
4844 pstore.backend= Specify the name of t 4571 pstore.backend= Specify the name of the pstore backend to use
4845 4572
4846 pti= [X86-64] Control Page 4573 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4574 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4575 removes hardening, but improves performance of
4849 system calls and inte 4576 system calls and interrupts.
4850 4577
4851 on - unconditionall 4578 on - unconditionally enable
4852 off - unconditionall 4579 off - unconditionally disable
4853 auto - kernel detects 4580 auto - kernel detects whether your CPU model is
4854 vulnerable to 4581 vulnerable to issues that PTI mitigates
4855 4582
4856 Not specifying this o 4583 Not specifying this option is equivalent to pti=auto.
4857 4584
>> 4585 nopti [X86-64]
>> 4586 Equivalent to pti=off
>> 4587
4858 pty.legacy_count= 4588 pty.legacy_count=
4859 [KNL] Number of legac 4589 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4590 default number.
4861 4591
4862 quiet [KNL,EARLY] Disable m !! 4592 quiet [KNL] Disable most log messages
4863 4593
4864 r128= [HW,DRM] 4594 r128= [HW,DRM]
4865 4595
4866 radix_hcall_invalidate=on [PPC/PSERI 4596 radix_hcall_invalidate=on [PPC/PSERIES]
4867 Disable RADIX GTSE fe 4597 Disable RADIX GTSE feature and use hcall for TLB
4868 invalidate. 4598 invalidate.
4869 4599
4870 raid= [HW,RAID] 4600 raid= [HW,RAID]
4871 See Documentation/adm 4601 See Documentation/admin-guide/md.rst.
4872 4602
4873 ramdisk_size= [RAM] Sizes of RAM di 4603 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4604 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4605
4876 ramdisk_start= [RAM] RAM disk image 4606 ramdisk_start= [RAM] RAM disk image start address
4877 4607
4878 random.trust_cpu=off 4608 random.trust_cpu=off
4879 [KNL,EARLY] Disable t !! 4609 [KNL] Disable trusting the use of the CPU's
4880 random number generat 4610 random number generator (if available) to
4881 initialize the kernel 4611 initialize the kernel's RNG.
4882 4612
4883 random.trust_bootloader=off 4613 random.trust_bootloader=off
4884 [KNL,EARLY] Disable t !! 4614 [KNL] Disable trusting the use of the a seed
4885 passed by the bootloa 4615 passed by the bootloader (if available) to
4886 initialize the kernel 4616 initialize the kernel's RNG.
4887 4617
4888 randomize_kstack_offset= 4618 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4619 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4620 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4621 entropy, frustrating memory corruption attacks
4892 that depend on stack 4622 that depend on stack address determinism or
4893 cross-syscall address 4623 cross-syscall address exposures. This is only
4894 available on architec 4624 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4625 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4626 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4627 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4628
4899 ras=option[,option,...] [KNL] RAS-spe 4629 ras=option[,option,...] [KNL] RAS-specific options
4900 4630
4901 cec_disable [X86] 4631 cec_disable [X86]
4902 Disable the C 4632 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4633 see CONFIG_RAS_CEC help text.
4904 4634
4905 rcu_nocbs[=cpu-list] 4635 rcu_nocbs[=cpu-list]
4906 [KNL] The optional ar 4636 [KNL] The optional argument is a cpu list,
4907 as described above. 4637 as described above.
4908 4638
4909 In kernels built with 4639 In kernels built with CONFIG_RCU_NOCB_CPU=y,
4910 enable the no-callbac 4640 enable the no-callback CPU mode, which prevents
4911 such CPUs' callbacks 4641 such CPUs' callbacks from being invoked in
4912 softirq context. Inv 4642 softirq context. Invocation of such CPUs' RCU
4913 callbacks will instea 4643 callbacks will instead be offloaded to "rcuox/N"
4914 kthreads created for 4644 kthreads created for that purpose, where "x" is
4915 "p" for RCU-preempt, 4645 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4916 for the kthreads that 4646 for the kthreads that mediate grace periods; and
4917 "N" is the CPU number 4647 "N" is the CPU number. This reduces OS jitter on
4918 the offloaded CPUs, w 4648 the offloaded CPUs, which can be useful for HPC
4919 and real-time workloa 4649 and real-time workloads. It can also improve
4920 energy efficiency for 4650 energy efficiency for asymmetric multiprocessors.
4921 4651
4922 If a cpulist is passe 4652 If a cpulist is passed as an argument, the specified
4923 list of CPUs is set t 4653 list of CPUs is set to no-callback mode from boot.
4924 4654
4925 Otherwise, if the '=' 4655 Otherwise, if the '=' sign and the cpulist
4926 arguments are omitted 4656 arguments are omitted, no CPU will be set to
4927 no-callback mode from 4657 no-callback mode from boot but the mode may be
4928 toggled at runtime vi 4658 toggled at runtime via cpusets.
4929 4659
4930 Note that this argume 4660 Note that this argument takes precedence over
4931 the CONFIG_RCU_NOCB_C 4661 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4932 4662
4933 rcu_nocb_poll [KNL] 4663 rcu_nocb_poll [KNL]
4934 Rather than requiring 4664 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4665 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4666 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4667 make these kthreads poll for callbacks.
4938 This improves the rea 4668 This improves the real-time response for the
4939 offloaded CPUs by rel 4669 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4670 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4671 energy efficiency by requiring that the kthreads
4942 periodically wake up 4672 periodically wake up to do the polling.
4943 4673
4944 rcutree.blimit= [KNL] 4674 rcutree.blimit= [KNL]
4945 Set maximum number of 4675 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4676 process in one batch.
4947 4677
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] 4678 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4679 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4680 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4681 purposes, to verify correct tree setup.
4959 4682
4960 rcutree.gp_cleanup_delay= [KNL] 4683 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4684 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4685 RCU grace-period cleanup.
4963 4686
4964 rcutree.gp_init_delay= [KNL] 4687 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4688 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4689 RCU grace-period initialization.
4967 4690
4968 rcutree.gp_preinit_delay= [KNL] 4691 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4692 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4693 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4694 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4695 the rcu_node combining tree.
4973 4696
>> 4697 rcutree.use_softirq= [KNL]
>> 4698 If set to zero, move all RCU_SOFTIRQ processing to
>> 4699 per-CPU rcuc kthreads. Defaults to a non-zero
>> 4700 value, meaning that RCU_SOFTIRQ is used by default.
>> 4701 Specify rcutree.use_softirq=0 to use rcuc kthreads.
>> 4702
>> 4703 But note that CONFIG_PREEMPT_RT=y kernels disable
>> 4704 this kernel boot parameter, forcibly setting it
>> 4705 to zero.
>> 4706
>> 4707 rcutree.rcu_fanout_exact= [KNL]
>> 4708 Disable autobalancing of the rcu_node combining
>> 4709 tree. This is used by rcutorture, and might
>> 4710 possibly be useful for architectures having high
>> 4711 cache-to-cache transfer latencies.
>> 4712
>> 4713 rcutree.rcu_fanout_leaf= [KNL]
>> 4714 Change the number of CPUs assigned to each
>> 4715 leaf rcu_node structure. Useful for very
>> 4716 large systems, which will choose the value 64,
>> 4717 and for NUMA systems with large remote-access
>> 4718 latencies, which will choose a value aligned
>> 4719 with the appropriate hardware boundaries.
>> 4720
>> 4721 rcutree.rcu_min_cached_objs= [KNL]
>> 4722 Minimum number of objects which are cached and
>> 4723 maintained per one CPU. Object size is equal
>> 4724 to PAGE_SIZE. The cache allows to reduce the
>> 4725 pressure to page allocator, also it makes the
>> 4726 whole algorithm to behave better in low memory
>> 4727 condition.
>> 4728
>> 4729 rcutree.rcu_delay_page_cache_fill_msec= [KNL]
>> 4730 Set the page-cache refill delay (in milliseconds)
>> 4731 in response to low-memory conditions. The range
>> 4732 of permitted values is in the range 0:100000.
>> 4733
4974 rcutree.jiffies_till_first_fqs= [KNL] 4734 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4735 Set delay from grace-period initialization to
4976 first attempt to forc 4736 first attempt to force quiescent states.
4977 Units are jiffies, mi 4737 Units are jiffies, minimum value is zero,
4978 and maximum value is 4738 and maximum value is HZ.
4979 4739
4980 rcutree.jiffies_till_next_fqs= [KNL] 4740 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4741 Set delay between subsequent attempts to force
4982 quiescent states. Un 4742 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4743 value is one, and maximum value is HZ.
4984 4744
4985 rcutree.jiffies_till_sched_qs= [KNL] 4745 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4746 Set required age in jiffies for a
4987 given grace period be 4747 given grace period before RCU starts
4988 soliciting quiescent- 4748 soliciting quiescent-state help from
4989 rcu_note_context_swit 4749 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4750 If not specified, the kernel will calculate
4991 a value based on the 4751 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4752 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4753 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4754 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4755 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4756 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4757 overwritten.
4998 4758
4999 rcutree.kthread_prio= [KNL,BOOT] 4759 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4760 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4761 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4762 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4763 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4764 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4765 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4766 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4767 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4768 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is 4769 When RCU_NOCB_CPU is set, also adjust the
5010 priority of NOCB call 4770 priority of NOCB callback kthreads.
5011 4771
>> 4772 rcutree.rcu_divisor= [KNL]
>> 4773 Set the shift-right count to use to compute
>> 4774 the callback-invocation batch limit bl from
>> 4775 the number of callbacks queued on this CPU.
>> 4776 The result will be bounded below by the value of
>> 4777 the rcutree.blimit kernel parameter. Every bl
>> 4778 callbacks, the softirq handler will exit in
>> 4779 order to allow the CPU to do other work.
>> 4780
>> 4781 Please note that this callback-invocation batch
>> 4782 limit applies only to non-offloaded callback
>> 4783 invocation. Offloaded callbacks are instead
>> 4784 invoked in the context of an rcuoc kthread, which
>> 4785 scheduler will preempt as it does any other task.
>> 4786
5012 rcutree.nocb_nobypass_lim_per_jiffy= 4787 rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5013 On callback-offloaded 4788 On callback-offloaded (rcu_nocbs) CPUs,
5014 RCU reduces the lock 4789 RCU reduces the lock contention that would
5015 otherwise be caused b 4790 otherwise be caused by callback floods through
5016 use of the ->nocb_byp 4791 use of the ->nocb_bypass list. However, in the
5017 common non-flooded ca 4792 common non-flooded case, RCU queues directly to
5018 the main ->cblist in 4793 the main ->cblist in order to avoid the extra
5019 overhead of the ->noc 4794 overhead of the ->nocb_bypass list and its lock.
5020 But if there are too 4795 But if there are too many callbacks queued during
5021 a single jiffy, RCU p 4796 a single jiffy, RCU pre-queues the callbacks into
5022 the ->nocb_bypass que 4797 the ->nocb_bypass queue. The definition of "too
5023 many" is supplied by 4798 many" is supplied by this kernel boot parameter.
5024 4799
5025 rcutree.nohz_full_patience_delay= [KN !! 4800 rcutree.rcu_nocb_gp_stride= [KNL]
5026 On callback-offloaded !! 4801 Set the number of NOCB callback kthreads in
5027 disturbing RCU unless !! 4802 each group, which defaults to the square root
5028 reached the specified !! 4803 of the number of CPUs. Larger numbers reduce
5029 Defaults to zero. La !! 4804 the wakeup overhead on the global grace-period
5030 at five seconds. All !! 4805 kthread, but increases that same overhead on
5031 to the nearest value !! 4806 each group's NOCB grace-period kthread.
5032 4807
5033 rcutree.qhimark= [KNL] 4808 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4809 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4810 batch limiting is disabled.
5036 4811
5037 rcutree.qlowmark= [KNL] 4812 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4813 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4814 batch limiting is re-enabled.
5040 4815
5041 rcutree.qovld= [KNL] 4816 rcutree.qovld= [KNL]
5042 Set threshold of queu 4817 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4818 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4819 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4820 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4821 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4822 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4823 disable more aggressive help enlistment.
5049 4824
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] 4825 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4826 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4827 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4828 it should at force-quiescent-state time.
5104 This wake_up() will b 4829 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4830 WARN_ONCE() splat and an ftrace_dump().
5106 4831
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] 4832 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4833 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4834 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4835 in microseconds. This defaults to zero.
5118 Larger delays increas 4836 Larger delays increase the probability of
5119 catching RCU pointer 4837 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4838 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4839 rcu_read_unlock() has completed.
5122 4840
5123 rcutree.sysrq_rcu= [KNL] 4841 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4842 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4843 rcu_node tree with an eye towards determining
5126 why a new grace perio 4844 why a new grace period has not yet started.
5127 4845
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] 4846 rcuscale.gp_async= [KNL]
5158 Measure performance o 4847 Measure performance of asynchronous
5159 grace-period primitiv 4848 grace-period primitives such as call_rcu().
5160 4849
5161 rcuscale.gp_async_max= [KNL] 4850 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4851 Specify the maximum number of outstanding
5163 callbacks per writer 4852 callbacks per writer thread. When a writer
5164 thread exceeds this l 4853 thread exceeds this limit, it invokes the
5165 corresponding flavor 4854 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4855 previously posted callbacks to drain.
5167 4856
5168 rcuscale.gp_exp= [KNL] 4857 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4858 Measure performance of expedited synchronous
5170 grace-period primitiv 4859 grace-period primitives.
5171 4860
5172 rcuscale.holdoff= [KNL] 4861 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4862 Set test-start holdoff period. The purpose of
5174 this parameter is to 4863 this parameter is to delay the start of the
5175 test until boot compl 4864 test until boot completes in order to avoid
5176 interference. 4865 interference.
5177 4866
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] 4867 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4868 Set to measure performance of kfree_rcu() flooding.
5189 4869
5190 rcuscale.kfree_rcu_test_double= [KNL] 4870 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 4871 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 4872 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 4873 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 4874 and double-argument variants are tested.
5195 4875
5196 rcuscale.kfree_rcu_test_single= [KNL] 4876 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 4877 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 4878 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 4879 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 4880 and double-argument variants are tested.
5201 4881
5202 rcuscale.kfree_nthreads= [KNL] 4882 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4883 The number of threads running loops of kfree_rcu().
5204 4884
5205 rcuscale.kfree_alloc_num= [KNL] 4885 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4886 Number of allocations and frees done in an iteration.
5207 4887
5208 rcuscale.kfree_loops= [KNL] 4888 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4889 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4890 of allocations and frees.
5211 4891
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] 4892 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4893 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4894 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4895 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4896 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4897 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4898 A value of "n" less than or equal to -N selects
5225 a single reader. 4899 a single reader.
5226 4900
5227 rcuscale.nwriters= [KNL] 4901 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4902 Set number of RCU writers. The values operate
5229 the same as for rcusc 4903 the same as for rcuscale.nreaders.
5230 N, where N is the num 4904 N, where N is the number of CPUs
5231 4905
5232 rcuscale.scale_type= [KNL] !! 4906 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4907 Specify the RCU implementation to test.
5234 4908
5235 rcuscale.shutdown= [KNL] 4909 rcuscale.shutdown= [KNL]
5236 Shut the system down 4910 Shut the system down after performance tests
5237 complete. This is us 4911 complete. This is useful for hands-off automated
5238 testing. 4912 testing.
5239 4913
5240 rcuscale.verbose= [KNL] 4914 rcuscale.verbose= [KNL]
5241 Enable additional pri 4915 Enable additional printk() statements.
5242 4916
5243 rcuscale.writer_holdoff= [KNL] 4917 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 4918 Write-side holdoff between grace periods,
5245 in microseconds. The 4919 in microseconds. The default of zero says
5246 no holdoff. 4920 no holdoff.
5247 4921
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] 4922 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 4923 Set duration of force_quiescent_state bursts
5255 in microseconds. 4924 in microseconds.
5256 4925
5257 rcutorture.fqs_holdoff= [KNL] 4926 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 4927 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 4928 in microseconds.
5260 4929
5261 rcutorture.fqs_stutter= [KNL] 4930 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 4931 Set wait time between force_quiescent_state bursts
5263 in seconds. 4932 in seconds.
5264 4933
5265 rcutorture.fwd_progress= [KNL] 4934 rcutorture.fwd_progress= [KNL]
5266 Specifies the number 4935 Specifies the number of kthreads to be used
5267 for RCU grace-period 4936 for RCU grace-period forward-progress testing
5268 for the types of RCU 4937 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread 4938 Defaults to 1 kthread, values less than zero or
5270 greater than the numb 4939 greater than the number of CPUs cause the number
5271 of CPUs to be used. 4940 of CPUs to be used.
5272 4941
5273 rcutorture.fwd_progress_div= [KNL] 4942 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 4943 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 4944 period to do tight-loop forward-progress testing.
5276 4945
5277 rcutorture.fwd_progress_holdoff= [KNL 4946 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 4947 Number of seconds to wait between successive
5279 forward-progress test 4948 forward-progress tests.
5280 4949
5281 rcutorture.fwd_progress_need_resched= 4950 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 4951 Enclose cond_resched() calls within checks for
5283 need_resched() during 4952 need_resched() during tight-loop forward-progress
5284 testing. 4953 testing.
5285 4954
5286 rcutorture.gp_cond= [KNL] 4955 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 4956 Use conditional/asynchronous update-side
5288 primitives, if availa 4957 primitives, if available.
5289 4958
5290 rcutorture.gp_exp= [KNL] 4959 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 4960 Use expedited update-side primitives, if available.
5292 4961
5293 rcutorture.gp_normal= [KNL] 4962 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 4963 Use normal (non-expedited) asynchronous
5295 update-side primitive 4964 update-side primitives, if available.
5296 4965
5297 rcutorture.gp_sync= [KNL] 4966 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 4967 Use normal (non-expedited) synchronous
5299 update-side primitive 4968 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 4969 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 4970 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 4971 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 4972 they are all non-zero.
5304 4973
5305 rcutorture.irqreader= [KNL] 4974 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 4975 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 4976 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 4977 flavors take kindly to this sort of thing.
5309 4978
5310 rcutorture.leakpointer= [KNL] 4979 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 4980 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 4981 This can of course result in splats, and is
5313 intended to test the 4982 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 4983 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 4984 such leaks.
5316 4985
5317 rcutorture.n_barrier_cbs= [KNL] 4986 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 4987 Set callbacks/threads for rcu_barrier() testing.
5319 4988
5320 rcutorture.nfakewriters= [KNL] 4989 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 4990 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 4991 stress RCU, they don't participate in the actual
5323 test, hence the "fake 4992 test, hence the "fake".
5324 4993
5325 rcutorture.nocbs_nthreads= [KNL] 4994 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 4995 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 4996 Zero (the default) disables toggling.
5328 4997
5329 rcutorture.nocbs_toggle= [KNL] 4998 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 4999 Set the delay in milliseconds between successive
5331 callback-offload togg 5000 callback-offload toggling attempts.
5332 5001
5333 rcutorture.nreaders= [KNL] 5002 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 5003 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 5004 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 5005 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 5006 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 5007 (the number of CPUs), -3 selects N+1, and so on.
5339 5008
5340 rcutorture.object_debug= [KNL] 5009 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 5010 Enable debug-object double-call_rcu() testing.
5342 5011
5343 rcutorture.onoff_holdoff= [KNL] 5012 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 5013 Set time (s) after boot for CPU-hotplug testing.
5345 5014
5346 rcutorture.onoff_interval= [KNL] 5015 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 5016 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 5017 or zero to disable CPU-hotplug testing.
5349 5018
5350 rcutorture.read_exit= [KNL] 5019 rcutorture.read_exit= [KNL]
5351 Set the number of rea 5020 Set the number of read-then-exit kthreads used
5352 to test the interacti 5021 to test the interaction of RCU updaters and
5353 task-exit processing. 5022 task-exit processing.
5354 5023
5355 rcutorture.read_exit_burst= [KNL] 5024 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 5025 The number of times in a given read-then-exit
5357 episode that a set of 5026 episode that a set of read-then-exit kthreads
5358 is spawned. 5027 is spawned.
5359 5028
5360 rcutorture.read_exit_delay= [KNL] 5029 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 5030 The delay, in seconds, between successive
5362 read-then-exit testin 5031 read-then-exit testing episodes.
5363 5032
5364 rcutorture.shuffle_interval= [KNL] 5033 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 5034 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 5035 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 5036 during the rcutorture test.
5368 5037
5369 rcutorture.shutdown_secs= [KNL] 5038 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 5039 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 5040 is useful for hands-off automated testing.
5372 5041
5373 rcutorture.stall_cpu= [KNL] 5042 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 5043 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 5044 warnings, zero to disable.
5376 5045
5377 rcutorture.stall_cpu_block= [KNL] 5046 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 5047 Sleep while stalling if set. This will result
5379 in warnings from pree !! 5048 in warnings from preemptible RCU in addition
5380 any other stall-relat !! 5049 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 5050
5391 rcutorture.stall_cpu_holdoff= [KNL] 5051 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 5052 Time to wait (s) after boot before inducing stall.
5393 5053
5394 rcutorture.stall_cpu_irqsoff= [KNL] 5054 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 5055 Disable interrupts while stalling if set.
5396 5056
5397 rcutorture.stall_gp_kthread= [KNL] 5057 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 5058 Duration (s) of forced sleep within RCU
5399 grace-period kthread 5059 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 5060 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 5061 and stall_gp_kthread are specified, the
5402 kthread is starved fi 5062 kthread is starved first, then the CPU.
5403 5063
5404 rcutorture.stat_interval= [KNL] 5064 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 5065 Time (s) between statistics printk()s.
5406 5066
5407 rcutorture.stutter= [KNL] 5067 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 5068 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 5069 five seconds causes the test to run for five seconds,
5410 wait for five seconds 5070 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 5071 ability to transition abruptly to and from idle.
5412 5072
5413 rcutorture.test_boost= [KNL] 5073 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 5074 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 5075 "Maybe" means test if the RCU implementation
5416 under test support RC 5076 under test support RCU priority boosting.
5417 5077
5418 rcutorture.test_boost_duration= [KNL] 5078 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 5079 Duration (s) of each individual boost test.
5420 5080
5421 rcutorture.test_boost_interval= [KNL] 5081 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 5082 Interval (s) between each boost test.
5423 5083
5424 rcutorture.test_no_idle_hz= [KNL] 5084 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 5085 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 5086 rcutorture.shuffle_interval parameter.
5427 5087
5428 rcutorture.torture_type= [KNL] 5088 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 5089 Specify the RCU implementation to test.
5430 5090
5431 rcutorture.verbose= [KNL] 5091 rcutorture.verbose= [KNL]
5432 Enable additional pri 5092 Enable additional printk() statements.
5433 5093
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 5094 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 5095 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 5096 stall warning.
5437 5097
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 5098 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 5099 Suppress RCU CPU stall warning messages.
5446 5100
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 5101 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 5102 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 5103 rcutorture writer stall warnings that occur
5450 during early boot, th 5104 during early boot, that is, during the time
5451 before the init task 5105 before the init task is spawned.
5452 5106
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 5107 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 5108 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon 5109 The value is in seconds and the maximum allowed
5456 value is 300 seconds. 5110 value is 300 seconds.
5457 5111
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ 5112 rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5459 Set timeout for exped 5113 Set timeout for expedited RCU CPU stall warning
5460 messages. The value 5114 messages. The value is in milliseconds
5461 and the maximum allow 5115 and the maximum allowed value is 21000
5462 milliseconds. Please 5116 milliseconds. Please note that this value is
5463 adjusted to an arch t 5117 adjusted to an arch timer tick resolution.
5464 Setting this to zero 5118 Setting this to zero causes the value from
5465 rcupdate.rcu_cpu_stal 5119 rcupdate.rcu_cpu_stall_timeout to be used (after
5466 conversion from secon 5120 conversion from seconds to milliseconds).
5467 5121
5468 rcupdate.rcu_cpu_stall_cputime= [KNL] 5122 rcupdate.rcu_cpu_stall_cputime= [KNL]
5469 Provide statistics on 5123 Provide statistics on the cputime and count of
5470 interrupts and tasks 5124 interrupts and tasks during the sampling period. For
5471 multiple continuous R 5125 multiple continuous RCU stalls, all sampling periods
5472 begin at half of the 5126 begin at half of the first RCU stall timeout.
5473 5127
5474 rcupdate.rcu_exp_stall_task_details= 5128 rcupdate.rcu_exp_stall_task_details= [KNL]
5475 Print stack dumps of 5129 Print stack dumps of any tasks blocking the
5476 current expedited RCU 5130 current expedited RCU grace period during an
5477 expedited RCU CPU sta 5131 expedited RCU CPU stall warning.
5478 5132
5479 rcupdate.rcu_expedited= [KNL] 5133 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 5134 Use expedited grace-period primitives, for
5481 example, synchronize_ 5135 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 5136 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 5137 but can increase CPU utilization, degrade
5484 real-time latency, an 5138 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 5139 No effect on CONFIG_TINY_RCU kernels.
5486 5140
5487 rcupdate.rcu_normal= [KNL] 5141 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 5142 Use only normal grace-period primitives,
5489 for example, synchron 5143 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 5144 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 5145 real-time latency, CPU utilization, and
5492 energy efficiency, bu 5146 energy efficiency, but can expose users to
5493 increased grace-perio 5147 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 5148 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 5149 CONFIG_TINY_RCU kernels.
5496 5150
5497 rcupdate.rcu_normal_after_boot= [KNL] 5151 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 5152 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 5153 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 5154 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 5155 on CONFIG_TINY_RCU kernels.
5502 5156
5503 But note that CONFIG_ 5157 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 5158 this kernel boot parameter, forcibly setting
5505 it to the value one, 5159 it to the value one, that is, converting any
5506 post-boot attempt at 5160 post-boot attempt at an expedited RCU grace
5507 period to instead use 5161 period to instead use normal non-expedited
5508 grace-period processi 5162 grace-period processing.
5509 5163
5510 rcupdate.rcu_task_collapse_lim= [KNL] 5164 rcupdate.rcu_task_collapse_lim= [KNL]
5511 Set the maximum numbe 5165 Set the maximum number of callbacks present
5512 at the beginning of a 5166 at the beginning of a grace period that allows
5513 the RCU Tasks flavors 5167 the RCU Tasks flavors to collapse back to using
5514 a single callback que 5168 a single callback queue. This switching only
5515 occurs when rcupdate. 5169 occurs when rcupdate.rcu_task_enqueue_lim is
5516 set to the default va 5170 set to the default value of -1.
5517 5171
5518 rcupdate.rcu_task_contend_lim= [KNL] 5172 rcupdate.rcu_task_contend_lim= [KNL]
5519 Set the minimum numbe 5173 Set the minimum number of callback-queuing-time
5520 lock-contention event 5174 lock-contention events per jiffy required to
5521 cause the RCU Tasks f 5175 cause the RCU Tasks flavors to switch to per-CPU
5522 callback queuing. Th 5176 callback queuing. This switching only occurs
5523 when rcupdate.rcu_tas 5177 when rcupdate.rcu_task_enqueue_lim is set to
5524 the default value of 5178 the default value of -1.
5525 5179
5526 rcupdate.rcu_task_enqueue_lim= [KNL] 5180 rcupdate.rcu_task_enqueue_lim= [KNL]
5527 Set the number of cal 5181 Set the number of callback queues to use for the
5528 RCU Tasks family of R 5182 RCU Tasks family of RCU flavors. The default
5529 of -1 allows this to 5183 of -1 allows this to be automatically (and
5530 dynamically) adjusted 5184 dynamically) adjusted. This parameter is intended
5531 for use in testing. 5185 for use in testing.
5532 5186
5533 rcupdate.rcu_task_ipi_delay= [KNL] 5187 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 5188 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 5189 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 5190 of a given grace period. Setting a large
5537 number avoids disturb 5191 number avoids disturbing real-time workloads,
5538 but lengthens grace p 5192 but lengthens grace periods.
5539 5193
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] 5194 rcupdate.rcu_task_stall_info= [KNL]
5548 Set initial timeout i 5195 Set initial timeout in jiffies for RCU task stall
5549 informational message 5196 informational messages, which give some indication
5550 of the problem for th 5197 of the problem for those not patient enough to
5551 wait for ten minutes. 5198 wait for ten minutes. Informational messages are
5552 only printed prior to 5199 only printed prior to the stall-warning message
5553 for a given grace per 5200 for a given grace period. Disable with a value
5554 less than or equal to 5201 less than or equal to zero. Defaults to ten
5555 seconds. A change in 5202 seconds. A change in value does not take effect
5556 until the beginning o 5203 until the beginning of the next grace period.
5557 5204
5558 rcupdate.rcu_task_stall_info_mult= [K 5205 rcupdate.rcu_task_stall_info_mult= [KNL]
5559 Multiplier for time i 5206 Multiplier for time interval between successive
5560 RCU task stall inform 5207 RCU task stall informational messages for a given
5561 RCU tasks grace perio 5208 RCU tasks grace period. This value is clamped
5562 to one through ten, i 5209 to one through ten, inclusive. It defaults to
5563 the value three, so t 5210 the value three, so that the first informational
5564 message is printed 10 5211 message is printed 10 seconds into the grace
5565 period, the second at 5212 period, the second at 40 seconds, the third at
5566 160 seconds, and then 5213 160 seconds, and then the stall warning at 600
5567 seconds would prevent 5214 seconds would prevent a fourth at 640 seconds.
5568 5215
5569 rcupdate.rcu_task_stall_timeout= [KNL 5216 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie 5217 Set timeout in jiffies for RCU task stall
5571 warning messages. Di 5218 warning messages. Disable with a value less
5572 than or equal to zero 5219 than or equal to zero. Defaults to ten minutes.
5573 A change in value doe 5220 A change in value does not take effect until
5574 the beginning of the 5221 the beginning of the next grace period.
5575 5222
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] 5223 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 5224 Run the RCU early boot self tests
5601 5225
5602 rdinit= [KNL] 5226 rdinit= [KNL]
5603 Format: <full_path> 5227 Format: <full_path>
5604 Run specified binary 5228 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 5229 used for early userspace startup. See initrd.
5606 5230
5607 rdrand= [X86,EARLY] !! 5231 rdrand= [X86]
5608 force - Override the 5232 force - Override the decision by the kernel to hide the
5609 advertisement 5233 advertisement of RDRAND support (this affects
5610 certain AMD p 5234 certain AMD processors because of buggy BIOS
5611 support, spec 5235 support, specifically around the suspend/resume
5612 path). 5236 path).
5613 5237
5614 rdt= [HW,X86,RDT] 5238 rdt= [HW,X86,RDT]
5615 Turn on/off individua 5239 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 5240 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. 5241 mba, smba, bmec.
5618 E.g. to turn on cmt a 5242 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 5243 rdt=cmt,!mba
5620 5244
5621 reboot= [KNL] 5245 reboot= [KNL]
5622 Format (x86 or x86_64 5246 Format (x86 or x86_64):
5623 [w[arm] | c[o 5247 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5624 [[,]s[mp]#### 5248 [[,]s[mp]#### \
5625 [[,]b[ios] | 5249 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 5250 [[,]f[orce]
5627 Where reboot_mode is 5251 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 5252 (prefix with 'panic_' to set mode for panic
5629 reboo 5253 reboot only),
5630 reboot_type is 5254 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 5255 reboot_force is either force or not specified,
5632 reboot_cpu is s 5256 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 5257 to be used for rebooting.
5634 5258
5635 refscale.holdoff= [KNL] 5259 refscale.holdoff= [KNL]
5636 Set test-start holdof 5260 Set test-start holdoff period. The purpose of
5637 this parameter is to 5261 this parameter is to delay the start of the
5638 test until boot compl 5262 test until boot completes in order to avoid
5639 interference. 5263 interference.
5640 5264
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] 5265 refscale.loops= [KNL]
5648 Set the number of loo 5266 Set the number of loops over the synchronization
5649 primitive under test. 5267 primitive under test. Increasing this number
5650 reduces noise due to 5268 reduces noise due to loop start/end overhead,
5651 but the default has a 5269 but the default has already reduced the per-pass
5652 noise to a handful of 5270 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 5271 x86 laptops.
5654 5272
5655 refscale.nreaders= [KNL] 5273 refscale.nreaders= [KNL]
5656 Set number of readers 5274 Set number of readers. The default value of -1
5657 selects N, where N is 5275 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 5276 of CPUs. A value of zero is an interesting choice.
5659 5277
5660 refscale.nruns= [KNL] 5278 refscale.nruns= [KNL]
5661 Set number of runs, e 5279 Set number of runs, each of which is dumped onto
5662 the console log. 5280 the console log.
5663 5281
5664 refscale.readdelay= [KNL] 5282 refscale.readdelay= [KNL]
5665 Set the read-side cri 5283 Set the read-side critical-section duration,
5666 measured in microseco 5284 measured in microseconds.
5667 5285
5668 refscale.scale_type= [KNL] 5286 refscale.scale_type= [KNL]
5669 Specify the read-prot 5287 Specify the read-protection implementation to test.
5670 5288
5671 refscale.shutdown= [KNL] 5289 refscale.shutdown= [KNL]
5672 Shut down the system 5290 Shut down the system at the end of the performance
5673 test. This defaults 5291 test. This defaults to 1 (shut it down) when
5674 refscale is built int 5292 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 5293 it running) when refscale is built as a module.
5676 5294
5677 refscale.verbose= [KNL] 5295 refscale.verbose= [KNL]
5678 Enable additional pri 5296 Enable additional printk() statements.
5679 5297
5680 refscale.verbose_batched= [KNL] 5298 refscale.verbose_batched= [KNL]
5681 Batch the additional 5299 Batch the additional printk() statements. If zero
5682 (the default) or nega 5300 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 5301 print every Nth verbose statement, where N is the value
5684 specified. 5302 specified.
5685 5303
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= 5304 relax_domain_level=
5694 [KNL, SMP] Set schedu 5305 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 5306 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 5307
5697 reserve= [KNL,BUGS] Force kern 5308 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 5309 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 5310 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 5311 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 5312 is assumed to be I/O ports; otherwise it is memory.
5702 5313
5703 reserve_mem= [RAM] !! 5314 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] 5315 Format: nn[KMG]
5727 Reserves a hole at th 5316 Reserves a hole at the top of the kernel virtual
5728 address space. 5317 address space.
5729 5318
5730 reset_devices [KNL] Force drivers t 5319 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 5320 during initialization.
5732 5321
5733 resume= [SWSUSP] 5322 resume= [SWSUSP]
5734 Specify the partition 5323 Specify the partition device for software suspend
5735 Format: 5324 Format:
5736 {/dev/<dev> | PARTUUI 5325 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 5326
5738 resume_offset= [SWSUSP] 5327 resume_offset= [SWSUSP]
5739 Specify the offset fr 5328 Specify the offset from the beginning of the partition
5740 given by "resume=" at 5329 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 5330 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 5331 See Documentation/power/swsusp-and-swap-files.rst
5743 5332
5744 resumedelay= [HIBERNATION] Delay ( 5333 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 5334 read the resume files
5746 5335
5747 resumewait [HIBERNATION] Wait (i 5336 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 5337 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 5338 (e.g. USB and MMC devices).
5750 5339
5751 retain_initrd [RAM] Keep initrd mem !! 5340 retain_initrd [RAM] Keep initrd memory after extraction
5752 be accessible via /sy <<
5753 5341
5754 retbleed= [X86] Control mitigat 5342 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 5343 Speculative Code Execution with Return Instructions)
5756 vulnerability. 5344 vulnerability.
5757 5345
5758 AMD-based UNRET and I 5346 AMD-based UNRET and IBPB mitigations alone do not stop
5759 sibling threads from 5347 sibling threads from influencing the predictions of other
5760 sibling threads. For 5348 sibling threads. For that reason, STIBP is used on pro-
5761 cessors that support 5349 cessors that support it, and mitigate SMT on processors
5762 that don't. 5350 that don't.
5763 5351
5764 off - no mit 5352 off - no mitigation
5765 auto - automa 5353 auto - automatically select a migitation
5766 auto,nosmt - automa 5354 auto,nosmt - automatically select a mitigation,
5767 disabl 5355 disabling SMT if necessary for
5768 the fu 5356 the full mitigation (only on Zen1
5769 and ol 5357 and older without STIBP).
5770 ibpb - On AMD 5358 ibpb - On AMD, mitigate short speculation
5771 window 5359 windows on basic block boundaries too.
5772 Safe, 5360 Safe, highest perf impact. It also
5773 enable 5361 enables STIBP if present. Not suitable
5774 on Int 5362 on Intel.
5775 ibpb,nosmt - Like " 5363 ibpb,nosmt - Like "ibpb" above but will disable SMT
5776 when S 5364 when STIBP is not available. This is
5777 the al 5365 the alternative for systems which do not
5778 have S 5366 have STIBP.
5779 unret - Force 5367 unret - Force enable untrained return thunks,
5780 only e 5368 only effective on AMD f15h-f17h based
5781 system 5369 systems.
5782 unret,nosmt - Like u 5370 unret,nosmt - Like unret, but will disable SMT when STIBP
5783 is not 5371 is not available. This is the alternative for
5784 system 5372 systems which do not have STIBP.
5785 5373
5786 Selecting 'auto' will 5374 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 5375 time according to the CPU.
5788 5376
5789 Not specifying this o 5377 Not specifying this option is equivalent to retbleed=auto.
5790 5378
5791 rfkill.default_state= 5379 rfkill.default_state=
5792 0 "airplane mode". All 5380 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 5381 etc. communication is blocked by default.
5794 1 Unblocked. 5382 1 Unblocked.
5795 5383
5796 rfkill.master_switch_mode= 5384 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 5385 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 5386 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 5387 blocked and the previous configuration.
5800 2 The "airplane mode" b 5388 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 5389 blocked and everything unblocked.
5802 5390
>> 5391 rhash_entries= [KNL,NET]
>> 5392 Set number of hash buckets for route cache
>> 5393
5803 ring3mwait=disable 5394 ring3mwait=disable
5804 [KNL] Disable ring 3 5395 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 5396 CPUs.
5806 5397
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 5398 ro [KNL] Mount root device read-only on boot
5815 5399
5816 rodata= [KNL,EARLY] !! 5400 rodata= [KNL]
5817 on Mark read-only kernel 5401 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 5402 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel 5403 full Mark read-only kernel memory and aliases as read-only
5820 [arm64] 5404 [arm64]
5821 5405
5822 rockchip.usb_uart 5406 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 5407 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 5408 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 5409 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 5410 port and the regular usb controller gets disabled.
5828 5411
5829 root= [KNL] Root filesystem 5412 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 5413 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 5414
5837 rootdelay= [KNL] Delay (in secon 5415 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 5416 mount the root filesystem
5839 5417
5840 rootflags= [KNL] Set root filesy 5418 rootflags= [KNL] Set root filesystem mount option string
5841 5419
5842 rootfstype= [KNL] Set root filesy 5420 rootfstype= [KNL] Set root filesystem type
5843 5421
5844 rootwait [KNL] Wait (indefinit 5422 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 5423 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 5424 (e.g. USB and MMC devices).
5847 5425
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 5426 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 5427 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 5428 Memory area to be used by remote processor image,
5855 managed by CMA. 5429 managed by CMA.
5856 5430
5857 rw [KNL] Mount root devi 5431 rw [KNL] Mount root device read-write on boot
5858 5432
5859 S [KNL] Run init in sin 5433 S [KNL] Run init in single mode
5860 5434
5861 s390_iommu= [HW,S390] 5435 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 5436 Set s390 IOTLB flushing mode
5863 strict 5437 strict
5864 With strict flushing !! 5438 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 5439 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 5440 which is faster.
5867 iommu.strict=1. <<
5868 5441
5869 s390_iommu_aperture= [KNL,S390] 5442 s390_iommu_aperture= [KNL,S390]
5870 Specifies the size of 5443 Specifies the size of the per device DMA address space
5871 accessible through th 5444 accessible through the DMA and IOMMU APIs as a decimal
5872 factor of the size of 5445 factor of the size of main memory.
5873 The default is 1 mean 5446 The default is 1 meaning that one can concurrently use
5874 as many DMA addresses 5447 as many DMA addresses as physical memory is installed,
5875 if supported by hardw 5448 if supported by hardware, and thus map all of memory
5876 once. With a value of 5449 once. With a value of 2 one can map all of memory twice
5877 and so on. As a speci 5450 and so on. As a special case a factor of 0 imposes no
5878 restrictions other th 5451 restrictions other than those given by hardware at the
5879 cost of significant a 5452 cost of significant additional memory use for tables.
5880 5453
5881 sa1100ir [NET] 5454 sa1100ir [NET]
5882 See drivers/net/irda/ 5455 See drivers/net/irda/sa1100_ir.c.
5883 5456
5884 sched_verbose [KNL,EARLY] Enables v !! 5457 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 5458
5886 schedstats= [KNL,X86] Enable or d 5459 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 5460 Allowed values are enable and disable. This feature
5888 incurs a small amount 5461 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 5462 but is useful for debugging and performance tuning.
5890 5463
5891 sched_thermal_decay_shift= 5464 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 5465 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 5466 pressure signal. Thermal pressure signal follows the
5895 default decay period 5467 default decay period of other scheduler pelt
5896 signals(usually 32 ms 5468 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 5469 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 5470 period for the thermal pressure signal by the shift
5899 value. 5471 value.
5900 i.e. with the default 5472 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 5473 sched_thermal_decay_shift thermal pressure decay pr
5902 1 5474 1 64 ms
5903 2 5475 2 128 ms
5904 and so on. 5476 and so on.
5905 Format: integer betwe 5477 Format: integer between 0 and 10
5906 Default is 0. 5478 Default is 0.
5907 5479
5908 scftorture.holdoff= [KNL] 5480 scftorture.holdoff= [KNL]
5909 Number of seconds to 5481 Number of seconds to hold off before starting
5910 test. Defaults to ze 5482 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 5483 to 10 seconds for built-in smp_call_function()
5912 tests. 5484 tests.
5913 5485
5914 scftorture.longwait= [KNL] 5486 scftorture.longwait= [KNL]
5915 Request ridiculously 5487 Request ridiculously long waits randomly selected
5916 up to the chosen limi 5488 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 5489 default) disables this feature. Please note
5918 that requesting even 5490 that requesting even small non-zero numbers of
5919 seconds can result in 5491 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 5492 softlockup complaints, and so on.
5921 5493
5922 scftorture.nthreads= [KNL] 5494 scftorture.nthreads= [KNL]
5923 Number of kthreads to 5495 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 5496 smp_call_function() family of functions.
5925 The default of -1 spe 5497 The default of -1 specifies a number of kthreads
5926 equal to the number o 5498 equal to the number of CPUs.
5927 5499
5928 scftorture.onoff_holdoff= [KNL] 5500 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 5501 Number seconds to wait after the start of the
5930 test before initiatin 5502 test before initiating CPU-hotplug operations.
5931 5503
5932 scftorture.onoff_interval= [KNL] 5504 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 5505 Number seconds to wait between successive
5934 CPU-hotplug operation 5506 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 5507 is the default) disables CPU-hotplug operations.
5936 5508
5937 scftorture.shutdown_secs= [KNL] 5509 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 5510 The number of seconds following the start of the
5939 test after which to s 5511 test after which to shut down the system. The
5940 default of zero avoid 5512 default of zero avoids shutting down the system.
5941 Non-zero values are u 5513 Non-zero values are useful for automated tests.
5942 5514
5943 scftorture.stat_interval= [KNL] 5515 scftorture.stat_interval= [KNL]
5944 The number of seconds 5516 The number of seconds between outputting the
5945 current test statisti 5517 current test statistics to the console. A value
5946 of zero disables stat 5518 of zero disables statistics output.
5947 5519
5948 scftorture.stutter_cpus= [KNL] 5520 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 5521 The number of jiffies to wait between each change
5950 to the set of CPUs un 5522 to the set of CPUs under test.
5951 5523
5952 scftorture.use_cpus_read_lock= [KNL] 5524 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 5525 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 5526 preempt_disable() to disable CPU hotplug
5955 while invoking one of 5527 while invoking one of the smp_call_function*()
5956 functions. 5528 functions.
5957 5529
5958 scftorture.verbose= [KNL] 5530 scftorture.verbose= [KNL]
5959 Enable additional pri 5531 Enable additional printk() statements.
5960 5532
5961 scftorture.weight_single= [KNL] 5533 scftorture.weight_single= [KNL]
5962 The probability weigh 5534 The probability weighting to use for the
5963 smp_call_function_sin 5535 smp_call_function_single() function with a zero
5964 "wait" parameter. A 5536 "wait" parameter. A value of -1 selects the
5965 default if all other 5537 default if all other weights are -1. However,
5966 if at least one weigh 5538 if at least one weight has some other value, a
5967 value of -1 will inst 5539 value of -1 will instead select a weight of zero.
5968 5540
5969 scftorture.weight_single_wait= [KNL] 5541 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 5542 The probability weighting to use for the
5971 smp_call_function_sin 5543 smp_call_function_single() function with a
5972 non-zero "wait" param 5544 non-zero "wait" parameter. See weight_single.
5973 5545
5974 scftorture.weight_many= [KNL] 5546 scftorture.weight_many= [KNL]
5975 The probability weigh 5547 The probability weighting to use for the
5976 smp_call_function_man 5548 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 5549 "wait" parameter. See weight_single.
5978 Note well that settin 5550 Note well that setting a high probability for
5979 this weighting can pl 5551 this weighting can place serious IPI load
5980 on the system. 5552 on the system.
5981 5553
5982 scftorture.weight_many_wait= [KNL] 5554 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 5555 The probability weighting to use for the
5984 smp_call_function_man 5556 smp_call_function_many() function with a
5985 non-zero "wait" param 5557 non-zero "wait" parameter. See weight_single
5986 and weight_many. 5558 and weight_many.
5987 5559
5988 scftorture.weight_all= [KNL] 5560 scftorture.weight_all= [KNL]
5989 The probability weigh 5561 The probability weighting to use for the
5990 smp_call_function_all 5562 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 5563 "wait" parameter. See weight_single and
5992 weight_many. 5564 weight_many.
5993 5565
5994 scftorture.weight_all_wait= [KNL] 5566 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 5567 The probability weighting to use for the
5996 smp_call_function_all 5568 smp_call_function_all() function with a
5997 non-zero "wait" param 5569 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5570 and weight_many.
5999 5571
6000 skew_tick= [KNL,EARLY] Offset th !! 5572 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5573 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5574 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5575 Format: { "0" | "1" }
6004 0 -- disable. (may be 5576 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5577 1 -- enable.
6006 Note: increases power 5578 Note: increases power consumption, thus should only be
6007 enabled if running ji 5579 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5580
6009 security= [SECURITY] Choose a l 5581 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5582 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5583 "lsm=" parameter.
6012 5584
6013 selinux= [SELINUX] Disable or 5585 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5586 Format: { "0" | "1" }
6015 See security/selinux/ 5587 See security/selinux/Kconfig help text.
6016 0 -- disable. 5588 0 -- disable.
6017 1 -- enable. 5589 1 -- enable.
6018 Default value is 1. 5590 Default value is 1.
6019 5591
6020 serialnumber [BUGS=X86-32] 5592 serialnumber [BUGS=X86-32]
6021 5593
6022 sev=option[,option...] [X86-64] See D !! 5594 sev=option[,option...] [X86-64] See Documentation/x86/x86_64/boot-options.rst
6023 5595
6024 shapers= [NET] 5596 shapers= [NET]
6025 Maximal number of sha 5597 Maximal number of shapers.
6026 5598
6027 show_lapic= [APIC,X86] Advanced P 5599 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
6028 Limit apic dumping. T 5600 Limit apic dumping. The parameter defines the maximal
6029 number of local apics 5601 number of local apics being dumped. Also it is possible
6030 to set it to "all" by 5602 to set it to "all" by meaning -- no limit here.
6031 Format: { 1 (default) 5603 Format: { 1 (default) | 2 | ... | all }.
6032 The parameter valid i 5604 The parameter valid if only apic=debug or
6033 apic=verbose is speci 5605 apic=verbose is specified.
6034 Example: apic=debug s 5606 Example: apic=debug show_lapic=all
6035 5607
6036 slab_debug[=options[,slabs][;[options !! 5608 simeth= [IA-64]
6037 Enabling slab_debug a !! 5609 simscsi=
>> 5610
>> 5611 slram= [HW,MTD]
>> 5612
>> 5613 slab_merge [MM]
>> 5614 Enable merging of slabs with similar size when the
>> 5615 kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
>> 5616
>> 5617 slab_nomerge [MM]
>> 5618 Disable merging of slabs with similar size. May be
>> 5619 necessary if there is some reason to distinguish
>> 5620 allocs to different slabs, especially in hardened
>> 5621 environments where the risk of heap overflows and
>> 5622 layout control by attackers can usually be
>> 5623 frustrated by disabling merging. This will reduce
>> 5624 most of the exposure of a heap attack to a single
>> 5625 cache (risks via metadata attacks are mostly
>> 5626 unchanged). Debug options disable merging on their
>> 5627 own.
>> 5628 For more information see Documentation/mm/slub.rst.
>> 5629
>> 5630 slab_max_order= [MM, SLAB]
>> 5631 Determines the maximum allowed order for slabs.
>> 5632 A high setting may cause OOMs due to memory
>> 5633 fragmentation. Defaults to 1 for systems with
>> 5634 more than 32MB of RAM, 0 otherwise.
>> 5635
>> 5636 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 5637 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 5638 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 5639 slub_debug can create guard zones around objects and
6040 may poison objects wh 5640 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 5641 last alloc / free. For more information see
6042 Documentation/mm/slub 5642 Documentation/mm/slub.rst.
6043 (slub_debug legacy na <<
6044 5643
6045 slab_max_order= [MM] !! 5644 slub_max_order= [MM, SLUB]
6046 Determines the maximu 5645 Determines the maximum allowed order for slabs.
6047 A high setting may ca 5646 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 5647 fragmentation. For more information see
6049 Documentation/mm/slub 5648 Documentation/mm/slub.rst.
6050 (slub_max_order legac <<
6051 5649
6052 slab_merge [MM] !! 5650 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 5651 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 5652 increase the slab order up to slub_max_order to
6060 generate a sufficient 5653 generate a sufficiently large slab able to contain
6061 the number of objects 5654 the number of objects indicated. The higher the number
6062 of objects the smalle 5655 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 5656 and the less frequently locks need to be acquired.
6064 For more information 5657 For more information see Documentation/mm/slub.rst.
6065 (slub_min_objects leg <<
6066 5658
6067 slab_min_order= [MM] !! 5659 slub_min_order= [MM, SLUB]
6068 Determines the minimu 5660 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 5661 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 5662 For more information see Documentation/mm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5663
6087 slram= [HW,MTD] !! 5664 slub_merge [MM, SLUB]
>> 5665 Same with slab_merge.
>> 5666
>> 5667 slub_nomerge [MM, SLUB]
>> 5668 Same with slab_nomerge. This is supported for legacy.
>> 5669 See slab_nomerge for more information.
6088 5670
6089 smart2= [HW] 5671 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5672 Format: <io1>[,<io2>[,...,<io8>]]
6091 5673
6092 smp.csd_lock_timeout= [KNL] 5674 smp.csd_lock_timeout= [KNL]
6093 Specify the period of 5675 Specify the period of time in milliseconds
6094 that smp_call_functio 5676 that smp_call_function() and friends will wait
6095 for a CPU to release 5677 for a CPU to release the CSD lock. This is
6096 useful when diagnosin 5678 useful when diagnosing bugs involving CPUs
6097 disabling interrupts 5679 disabling interrupts for extended periods
6098 of time. Defaults to 5680 of time. Defaults to 5,000 milliseconds, and
6099 setting a value of ze 5681 setting a value of zero disables this feature.
6100 This feature may be m 5682 This feature may be more efficiently disabled
6101 using the csdlock_deb 5683 using the csdlock_debug- kernel parameter.
6102 5684
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 5685 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5686 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5687 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5688 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5689 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5690 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5691 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5692 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5693 1: Fast pin select (default)
6119 2: ATC IRMode 5694 2: ATC IRMode
6120 5695
6121 smt= [KNL,MIPS,S390,EARLY] !! 5696 smt= [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5697 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5698 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5699 actual hardware limit.
6125 Format: <integer> 5700 Format: <integer>
6126 Default: -1 (no limit 5701 Default: -1 (no limit)
6127 5702
6128 softlockup_panic= 5703 softlockup_panic=
6129 [KNL] Should the soft 5704 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5705 Format: 0 | 1
6131 5706
6132 A value of 1 instruct 5707 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5708 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5709 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5710 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5711 respective build-time switch to that functionality.
6137 5712
6138 softlockup_all_cpu_backtrace= 5713 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5714 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5715 backtraces on all cpus.
6141 Format: 0 | 1 5716 Format: 0 | 1
6142 5717
6143 sonypi.*= [HW] Sony Programmabl 5718 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5719 See Documentation/admin-guide/laptops/sonypi.rst
6145 5720
6146 spectre_bhi= [X86] Control mitigat !! 5721 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 5722 (indirect branch speculation) vulnerability.
6163 The default operation 5723 The default operation protects the kernel from
6164 user space attacks. 5724 user space attacks.
6165 5725
6166 on - unconditionall 5726 on - unconditionally enable, implies
6167 spectre_v2_use 5727 spectre_v2_user=on
6168 off - unconditionall 5728 off - unconditionally disable, implies
6169 spectre_v2_use 5729 spectre_v2_user=off
6170 auto - kernel detects 5730 auto - kernel detects whether your CPU model is
6171 vulnerable 5731 vulnerable
6172 5732
6173 Selecting 'on' will, 5733 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5734 mitigation method at run time according to the
6175 CPU, the available mi 5735 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5736 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5737 compiler with which the kernel was built.
6178 5738
6179 Selecting 'on' will a 5739 Selecting 'on' will also enable the mitigation
6180 against user space to 5740 against user space to user space task attacks.
6181 5741
6182 Selecting 'off' will 5742 Selecting 'off' will disable both the kernel and
6183 the user space protec 5743 the user space protections.
6184 5744
6185 Specific mitigations 5745 Specific mitigations can also be selected manually:
6186 5746
6187 retpoline - r 5747 retpoline - replace indirect branches
6188 retpoline,generic - R 5748 retpoline,generic - Retpolines
6189 retpoline,lfence - L 5749 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 5750 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E 5751 eibrs - Enhanced/Auto IBRS
6192 eibrs,retpoline - E 5752 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6193 eibrs,lfence - E 5753 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6194 ibrs - u 5754 ibrs - use IBRS to protect kernel
6195 5755
6196 Not specifying this o 5756 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5757 spectre_v2=auto.
6198 5758
6199 spectre_v2_user= 5759 spectre_v2_user=
6200 [X86] Control mitigat 5760 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5761 (indirect branch speculation) vulnerability between
6202 user space tasks 5762 user space tasks
6203 5763
6204 on - Uncondition 5764 on - Unconditionally enable mitigations. Is
6205 enforced by 5765 enforced by spectre_v2=on
6206 5766
6207 off - Uncondition 5767 off - Unconditionally disable mitigations. Is
6208 enforced by 5768 enforced by spectre_v2=off
6209 5769
6210 prctl - Indirect br 5770 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5771 but mitigation can be enabled via prctl
6212 per thread. 5772 per thread. The mitigation control state
6213 is inherite 5773 is inherited on fork.
6214 5774
6215 prctl,ibpb 5775 prctl,ibpb
6216 - Like "prctl 5776 - Like "prctl" above, but only STIBP is
6217 controlled 5777 controlled per thread. IBPB is issued
6218 always when 5778 always when switching between different user
6219 space proce 5779 space processes.
6220 5780
6221 seccomp 5781 seccomp
6222 - Same as "pr 5782 - Same as "prctl" above, but all seccomp
6223 threads wil 5783 threads will enable the mitigation unless
6224 they explic 5784 they explicitly opt out.
6225 5785
6226 seccomp,ibpb 5786 seccomp,ibpb
6227 - Like "secco 5787 - Like "seccomp" above, but only STIBP is
6228 controlled 5788 controlled per thread. IBPB is issued
6229 always when 5789 always when switching between different
6230 user space 5790 user space processes.
6231 5791
6232 auto - Kernel sele 5792 auto - Kernel selects the mitigation depending on
6233 the availab 5793 the available CPU features and vulnerability.
6234 5794
6235 Default mitigation: " 5795 Default mitigation: "prctl"
6236 5796
6237 Not specifying this o 5797 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5798 spectre_v2_user=auto.
6239 5799
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= 5800 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5801 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5802 (Speculative Store Bypass vulnerability)
6254 5803
6255 Certain CPUs are vuln 5804 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5805 a common industry wide performance optimization known
6257 as "Speculative Store 5806 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5807 to the same memory location may not be observed by
6259 later loads during sp 5808 later loads during speculative execution. The idea
6260 is that such stores a 5809 is that such stores are unlikely and that they can
6261 be detected prior to 5810 be detected prior to instruction retirement at the
6262 end of a particular s 5811 end of a particular speculation execution window.
6263 5812
6264 In vulnerable process 5813 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5814 store can be used in a cache side channel attack, for
6266 example to read memor 5815 example to read memory to which the attacker does not
6267 directly have access 5816 directly have access (e.g. inside sandboxed code).
6268 5817
6269 This parameter contro 5818 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5819 Bypass optimization is used.
6271 5820
6272 On x86 the options ar 5821 On x86 the options are:
6273 5822
6274 on - Uncondition 5823 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5824 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5825 auto - Kernel detects whether the CPU model contains an
6277 implementat 5826 implementation of Speculative Store Bypass and
6278 picks the m 5827 picks the most appropriate mitigation. If the
6279 CPU is not 5828 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5829 CPU is vulnerable the default mitigation is
6281 architectur 5830 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5831 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5832 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5833 for a process by default. The state of the control
6285 is inherite 5834 is inherited on fork.
6286 seccomp - Same as "pr 5835 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5836 will disable SSB unless they explicitly opt out.
6288 5837
6289 Default mitigations: 5838 Default mitigations:
6290 X86: "prctl" 5839 X86: "prctl"
6291 5840
6292 On powerpc the option 5841 On powerpc the options are:
6293 5842
6294 on,auto - On Power8 a 5843 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5844 barrier on kernel entry and exit. On Power7
6296 perform a s 5845 perform a software flush on kernel entry and
6297 exit. 5846 exit.
6298 off - No action. 5847 off - No action.
6299 5848
6300 Not specifying this o 5849 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5850 spec_store_bypass_disable=auto.
6302 5851
>> 5852 spia_io_base= [HW,MTD]
>> 5853 spia_fio_base=
>> 5854 spia_pedr=
>> 5855 spia_peddr=
>> 5856
6303 split_lock_detect= 5857 split_lock_detect=
6304 [X86] Enable split lo 5858 [X86] Enable split lock detection or bus lock detection
6305 5859
6306 When enabled (and if 5860 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5861 instructions that access data across cache line
6308 boundaries will resul 5862 boundaries will result in an alignment check exception
6309 for split lock detect 5863 for split lock detection or a debug exception for
6310 bus lock detection. 5864 bus lock detection.
6311 5865
6312 off - not enabled 5866 off - not enabled
6313 5867
6314 warn - the kernel 5868 warn - the kernel will emit rate-limited warnings
6315 about appli 5869 about applications triggering the #AC
6316 exception o 5870 exception or the #DB exception. This mode is
6317 the default 5871 the default on CPUs that support split lock
6318 detection o 5872 detection or bus lock detection. Default
6319 behavior is 5873 behavior is by #AC if both features are
6320 enabled in 5874 enabled in hardware.
6321 5875
6322 fatal - the kernel 5876 fatal - the kernel will send SIGBUS to applications
6323 that trigge 5877 that trigger the #AC exception or the #DB
6324 exception. 5878 exception. Default behavior is by #AC if
6325 both featur 5879 both features are enabled in hardware.
6326 5880
6327 ratelimit:N - 5881 ratelimit:N -
6328 Set system 5882 Set system wide rate limit to N bus locks
6329 per second 5883 per second for bus lock detection.
6330 0 < N <= 10 5884 0 < N <= 1000.
6331 5885
6332 N/A for spl 5886 N/A for split lock detection.
6333 5887
6334 5888
6335 If an #AC exception i 5889 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 5890 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 5891 the kernel will oops in either "warn" or "fatal"
6338 mode. 5892 mode.
6339 5893
6340 #DB exception for bus 5894 #DB exception for bus lock is triggered only when
6341 CPL > 0. 5895 CPL > 0.
6342 5896
6343 srbds= [X86,INTEL,EARLY] !! 5897 srbds= [X86,INTEL]
6344 Control the Special R 5898 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 5899 (SRBDS) mitigation.
6346 5900
6347 Certain CPUs are vuln 5901 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 5902 exploit which can leak bits from the random
6349 number generator. 5903 number generator.
6350 5904
6351 By default, this issu 5905 By default, this issue is mitigated by
6352 microcode. However, 5906 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 5907 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 5908 much slower. Among other effects, this will
6355 result in reduced thr 5909 result in reduced throughput from /dev/urandom.
6356 5910
6357 The microcode mitigat 5911 The microcode mitigation can be disabled with
6358 the following option: 5912 the following option:
6359 5913
6360 off: Disable mitig 5914 off: Disable mitigation and remove
6361 performance i 5915 performance impact to RDRAND and RDSEED
6362 5916
6363 srcutree.big_cpu_lim [KNL] 5917 srcutree.big_cpu_lim [KNL]
6364 Specifies the number 5918 Specifies the number of CPUs constituting a
6365 large system, such th 5919 large system, such that srcu_struct structures
6366 should immediately al 5920 should immediately allocate an srcu_node array.
6367 This kernel-boot para 5921 This kernel-boot parameter defaults to 128,
6368 but takes effect only 5922 but takes effect only when the low-order four
6369 bits of srcutree.conv 5923 bits of srcutree.convert_to_big is equal to 3
6370 (decide at boot). 5924 (decide at boot).
6371 5925
6372 srcutree.convert_to_big [KNL] 5926 srcutree.convert_to_big [KNL]
6373 Specifies under what 5927 Specifies under what conditions an SRCU tree
6374 srcu_struct structure 5928 srcu_struct structure will be converted to big
6375 form, that is, with a 5929 form, that is, with an rcu_node tree:
6376 5930
6377 0: Never. 5931 0: Never.
6378 1: At ini 5932 1: At init_srcu_struct() time.
6379 2: When r 5933 2: When rcutorture decides to.
6380 3: Decide 5934 3: Decide at boot time (default).
6381 0x1X: Above 5935 0x1X: Above plus if high contention.
6382 5936
6383 Either way, the srcu_ 5937 Either way, the srcu_node tree will be sized based
6384 on the actual runtime 5938 on the actual runtime number of CPUs (nr_cpu_ids)
6385 instead of the compil 5939 instead of the compile-time CONFIG_NR_CPUS.
6386 5940
6387 srcutree.counter_wrap_check [KNL] 5941 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 5942 Specifies how frequently to check for
6389 grace-period sequence 5943 grace-period sequence counter wrap for the
6390 srcu_data structure's 5944 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 5945 The greater the number of bits set in this kernel
6392 parameter, the less f 5946 parameter, the less frequently counter wrap will
6393 be checked for. Note 5947 be checked for. Note that the bottom two bits
6394 are ignored. 5948 are ignored.
6395 5949
6396 srcutree.exp_holdoff [KNL] 5950 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 5951 Specifies how many nanoseconds must elapse
6398 since the end of the 5952 since the end of the last SRCU grace period for
6399 a given srcu_struct u 5953 a given srcu_struct until the next normal SRCU
6400 grace period will be 5954 grace period will be considered for automatic
6401 expediting. Set to z 5955 expediting. Set to zero to disable automatic
6402 expediting. 5956 expediting.
6403 5957
6404 srcutree.srcu_max_nodelay [KNL] 5958 srcutree.srcu_max_nodelay [KNL]
6405 Specifies the number 5959 Specifies the number of no-delay instances
6406 per jiffy for which t 5960 per jiffy for which the SRCU grace period
6407 worker thread will be 5961 worker thread will be rescheduled with zero
6408 delay. Beyond this li 5962 delay. Beyond this limit, worker thread will
6409 be rescheduled with a 5963 be rescheduled with a sleep delay of one jiffy.
6410 5964
6411 srcutree.srcu_max_nodelay_phase [KNL] 5965 srcutree.srcu_max_nodelay_phase [KNL]
6412 Specifies the per-gra 5966 Specifies the per-grace-period phase, number of
6413 non-sleeping polls of 5967 non-sleeping polls of readers. Beyond this limit,
6414 grace period worker t 5968 grace period worker thread will be rescheduled
6415 with a sleep delay of 5969 with a sleep delay of one jiffy, between each
6416 rescan of the readers 5970 rescan of the readers, for a grace period phase.
6417 5971
6418 srcutree.srcu_retry_check_delay [KNL] 5972 srcutree.srcu_retry_check_delay [KNL]
6419 Specifies number of m 5973 Specifies number of microseconds of non-sleeping
6420 delay between each no 5974 delay between each non-sleeping poll of readers.
6421 5975
6422 srcutree.small_contention_lim [KNL] 5976 srcutree.small_contention_lim [KNL]
6423 Specifies the number 5977 Specifies the number of update-side contention
6424 events per jiffy will 5978 events per jiffy will be tolerated before
6425 initiating a conversi 5979 initiating a conversion of an srcu_struct
6426 structure to big form 5980 structure to big form. Note that the value of
6427 srcutree.convert_to_b 5981 srcutree.convert_to_big must have the 0x10 bit
6428 set for contention-ba 5982 set for contention-based conversions to occur.
6429 5983
6430 ssbd= [ARM64,HW,EARLY] !! 5984 ssbd= [ARM64,HW]
6431 Speculative Store Byp 5985 Speculative Store Bypass Disable control
6432 5986
6433 On CPUs that are vuln 5987 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 5988 Store Bypass vulnerability and offer a
6435 firmware based mitiga 5989 firmware based mitigation, this parameter
6436 indicates how the mit 5990 indicates how the mitigation should be used:
6437 5991
6438 force-on: Unconditio 5992 force-on: Unconditionally enable mitigation for
6439 for both k 5993 for both kernel and userspace
6440 force-off: Unconditio 5994 force-off: Unconditionally disable mitigation for
6441 for both k 5995 for both kernel and userspace
6442 kernel: Always ena 5996 kernel: Always enable mitigation in the
6443 kernel, an 5997 kernel, and offer a prctl interface
6444 to allow u 5998 to allow userspace to register its
6445 interest i 5999 interest in being mitigated too.
6446 6000
6447 stack_guard_gap= [MM] 6001 stack_guard_gap= [MM]
6448 override the default 6002 override the default stack gap protection. The value
6449 is in page units and 6003 is in page units and it defines how many pages prior
6450 to (for stacks growin 6004 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 6005 growing up) the main stack are reserved for no other
6452 mapping. Default valu 6006 mapping. Default value is 256 pages.
6453 6007
6454 stack_depot_disable= [KNL,EARLY] !! 6008 stack_depot_disable= [KNL]
6455 Setting this to true 6009 Setting this to true through kernel command line will
6456 disable the stack dep 6010 disable the stack depot thereby saving the static memory
6457 consumed by the stack 6011 consumed by the stack hash table. By default this is set
6458 to false. 6012 to false.
6459 6013
6460 stacktrace [FTRACE] 6014 stacktrace [FTRACE]
6461 Enabled the stack tra 6015 Enabled the stack tracer on boot up.
6462 6016
6463 stacktrace_filter=[function-list] 6017 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 6018 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 6019 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 6020 list of functions. This list can be changed at run
6467 time by the stack_tra 6021 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 6022 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 6023 and the stacktrace above is not needed.
6470 6024
6471 sti= [PARISC,HW] 6025 sti= [PARISC,HW]
6472 Format: <num> 6026 Format: <num>
6473 Set the STI (builtin 6027 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 6028 machines) console (graphic card) which should be used
6475 as the initial boot-c 6029 as the initial boot-console.
6476 See also comment in d 6030 See also comment in drivers/video/console/sticore.c.
6477 6031
6478 sti_font= [HW] 6032 sti_font= [HW]
6479 See comment in driver 6033 See comment in drivers/video/console/sticore.c.
6480 6034
6481 stifb= [HW] 6035 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 6036 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 6037
6484 strict_sas_size= 6038 strict_sas_size=
6485 [X86] 6039 [X86]
6486 Format: <bool> 6040 Format: <bool>
6487 Enable or disable str 6041 Enable or disable strict sigaltstack size checks
6488 against the required 6042 against the required signal frame size which
6489 depends on the suppor 6043 depends on the supported FPU features. This can
6490 be used to filter out 6044 be used to filter out binaries which have
6491 not yet been made awa 6045 not yet been made aware of AT_MINSIGSTKSZ.
6492 6046
6493 stress_hpt [PPC,EARLY] !! 6047 stress_hpt [PPC]
6494 Limits the number of 6048 Limits the number of kernel HPT entries in the hash
6495 page table to increas 6049 page table to increase the rate of hash page table
6496 faults on kernel addr 6050 faults on kernel addresses.
6497 6051
6498 stress_slb [PPC,EARLY] !! 6052 stress_slb [PPC]
6499 Limits the number of 6053 Limits the number of kernel SLB entries, and flushes
6500 them frequently to in 6054 them frequently to increase the rate of SLB faults
6501 on kernel addresses. 6055 on kernel addresses.
6502 6056
6503 sunrpc.min_resvport= 6057 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 6058 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 6059 [NFS,SUNRPC]
6506 SunRPC servers often 6060 SunRPC servers often require that client requests
6507 originate from a priv 6061 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 6062 range 0 < portnr < 1024).
6509 An administrator who 6063 An administrator who wishes to reserve some of these
6510 ports for other uses 6064 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 6065 kernel's sunrpc client considers to be privileged
6512 using these two param 6066 using these two parameters to set the minimum and
6513 maximum port values. 6067 maximum port values.
6514 6068
6515 sunrpc.svc_rpc_per_connection_limit= 6069 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 6070 [NFS,SUNRPC]
6517 Limit the number of r 6071 Limit the number of requests that the server will
6518 process in parallel f 6072 process in parallel from a single connection.
6519 The default value is 6073 The default value is 0 (no limit).
6520 6074
6521 sunrpc.pool_mode= 6075 sunrpc.pool_mode=
6522 [NFS] 6076 [NFS]
6523 Control how the NFS s 6077 Control how the NFS server code allocates CPUs to
6524 service thread pools. 6078 service thread pools. Depending on how many NICs
6525 you have and where th 6079 you have and where their interrupts are bound, this
6526 option will affect wh 6080 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 6081 Note: this parameter cannot be changed while the
6528 NFS server is running 6082 NFS server is running.
6529 6083
6530 auto the serve 6084 auto the server chooses an appropriate mode
6531 automatic 6085 automatically using heuristics
6532 global a single 6086 global a single global pool contains all CPUs
6533 percpu one pool 6087 percpu one pool for each CPU
6534 pernode one pool 6088 pernode one pool for each NUMA node (equivalent
6535 to global 6089 to global on non-NUMA machines)
6536 6090
6537 sunrpc.tcp_slot_table_entries= 6091 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 6092 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 6093 [NFS,SUNRPC]
6540 Sets the upper limit 6094 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 6095 RPC calls that can be sent from the client to a
6542 server. Increasing th 6096 server. Increasing these values may allow you to
6543 improve throughput, b 6097 improve throughput, but will also increase the
6544 amount of memory rese 6098 amount of memory reserved for use by the client.
6545 6099
6546 suspend.pm_test_delay= 6100 suspend.pm_test_delay=
6547 [SUSPEND] 6101 [SUSPEND]
6548 Sets the number of se 6102 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 6103 mode before resuming the system (see
6550 /sys/power/pm_test). 6104 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 6105 is set. Default value is 5.
6552 6106
6553 svm= [PPC] 6107 svm= [PPC]
6554 Format: { on | off | 6108 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 6109 This parameter controls use of the Protected
6556 Execution Facility on 6110 Execution Facility on pSeries.
6557 6111
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 6112 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in 6113 Format: { <int> [,<int>] | force | noforce }
6560 <int> -- Number of I/ 6114 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ 6115 <int> -- Second integer after comma. Number of swiotlb
6562 areas with t 6116 areas with their own lock. Will be rounded up
6563 to a power o 6117 to a power of 2.
6564 force -- force using 6118 force -- force using of bounce buffers even if they
6565 wouldn't be 6119 wouldn't be automatically used by the kernel
6566 noforce -- Never use 6120 noforce -- Never use bounce buffers (for debugging)
6567 6121
6568 switches= [HW,M68k,EARLY] !! 6122 switches= [HW,M68k]
6569 6123
6570 sysctl.*= [KNL] 6124 sysctl.*= [KNL]
6571 Set a sysctl paramete 6125 Set a sysctl parameter, right before loading the init
6572 process, as if the va 6126 process, as if the value was written to the respective
6573 /proc/sys/... file. B 6127 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 6128 separators. Unrecognized parameters and invalid values
6575 are reported in the k 6129 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 6130 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 6131 Example: sysctl.vm.swappiness=40
6578 6132
>> 6133 sysfs.deprecated=0|1 [KNL]
>> 6134 Enable/disable old style sysfs layout for old udev
>> 6135 on older distributions. When this option is enabled
>> 6136 very new udev will not work anymore. When this option
>> 6137 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
>> 6138 in older udev will not work anymore.
>> 6139 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
>> 6140 the kernel configuration.
>> 6141
6579 sysrq_always_enabled 6142 sysrq_always_enabled
6580 [KNL] 6143 [KNL]
6581 Ignore sysrq setting 6144 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 6145 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 6146 Useful for debugging.
6584 6147
6585 tcpmhash_entries= [KNL,NET] 6148 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 6149 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 6150 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 6151 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 6152 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 6153 "tcp_no_metrics_save" section for more details.
6591 6154
6592 tdfx= [HW,DRM] 6155 tdfx= [HW,DRM]
6593 6156
6594 test_suspend= [SUSPEND] 6157 test_suspend= [SUSPEND]
6595 Format: { "mem" | "st 6158 Format: { "mem" | "standby" | "freeze" }[,N]
6596 Specify "mem" (for Su 6159 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 6160 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 6161 as the system sleep state during system startup with
6599 the optional capabili 6162 the optional capability to repeat N number of times.
6600 The system is woken f 6163 The system is woken from this state using a
6601 wakeup-capable RTC al 6164 wakeup-capable RTC alarm.
6602 6165
6603 thash_entries= [KNL,NET] 6166 thash_entries= [KNL,NET]
6604 Set number of hash bu 6167 Set number of hash buckets for TCP connection
6605 6168
6606 thermal.act= [HW,ACPI] 6169 thermal.act= [HW,ACPI]
6607 -1: disable all activ 6170 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 6171 <degrees C>: override all lowest active trip points
6609 6172
6610 thermal.crt= [HW,ACPI] 6173 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 6174 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 6175 <degrees C>: override all critical trip points
6613 6176
>> 6177 thermal.nocrt= [HW,ACPI]
>> 6178 Set to disable actions on ACPI thermal zone
>> 6179 critical and hot trip points.
>> 6180
6614 thermal.off= [HW,ACPI] 6181 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 6182 1: disable ACPI thermal control
6616 6183
6617 thermal.psv= [HW,ACPI] 6184 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 6185 -1: disable all passive trip points
6619 <degrees C>: override 6186 <degrees C>: override all passive trip points to this
6620 value 6187 value
6621 6188
6622 thermal.tzp= [HW,ACPI] 6189 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 6190 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 6191 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 6192 0: no polling (default)
6626 6193
6627 threadirqs [KNL,EARLY] !! 6194 threadirqs [KNL]
6628 Force threading of al 6195 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 6196 marked explicitly IRQF_NO_THREAD.
6630 6197
6631 topology= [S390,EARLY] !! 6198 topology= [S390]
6632 Format: {off | on} 6199 Format: {off | on}
6633 Specify if the kernel 6200 Specify if the kernel should make use of the cpu
6634 topology information 6201 topology information if the hardware supports this.
6635 The scheduler will ma 6202 The scheduler will make use of this information and
6636 e.g. base its process 6203 e.g. base its process migration decisions on it.
6637 Default is on. 6204 Default is on.
6638 6205
>> 6206 topology_updates= [KNL, PPC, NUMA]
>> 6207 Format: {off}
>> 6208 Specify if the kernel should ignore (off)
>> 6209 topology updates sent by the hypervisor to this
>> 6210 LPAR.
>> 6211
6639 torture.disable_onoff_at_boot= [KNL] 6212 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 6213 Prevent the CPU-hotplug component of torturing
6641 until after init has 6214 until after init has spawned.
6642 6215
6643 torture.ftrace_dump_at_shutdown= [KNL 6216 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 6217 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 6218 even if there were no errors. This can be a
6646 very costly operation 6219 very costly operation when many torture tests
6647 are running concurren 6220 are running concurrently, especially on systems
6648 with rotating-rust st 6221 with rotating-rust storage.
6649 6222
6650 torture.verbose_sleep_frequency= [KNL 6223 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 6224 Specifies how many verbose printk()s should be
6652 emitted between each 6225 emitted between each sleep. The default of zero
6653 disables verbose-prin 6226 disables verbose-printk() sleeping.
6654 6227
6655 torture.verbose_sleep_duration= [KNL] 6228 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 6229 Duration of each verbose-printk() sleep in jiffies.
6657 6230
>> 6231 tp720= [HW,PS2]
>> 6232
6658 tpm_suspend_pcr=[HW,TPM] 6233 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 6234 Format: integer pcr id
6660 Specify that at suspe 6235 Specify that at suspend time, the tpm driver
6661 should extend the spe 6236 should extend the specified pcr with zeros,
6662 as a workaround for s 6237 as a workaround for some chips which fail to
6663 flush the last writte 6238 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 6239 This will guarantee that all the other pcrs
6665 are saved. 6240 are saved.
6666 6241
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] 6242 tp_printk [FTRACE]
6675 Have the tracepoints 6243 Have the tracepoints sent to printk as well as the
6676 tracing ring buffer. 6244 tracing ring buffer. This is useful for early boot up
6677 where the system hang 6245 where the system hangs or reboots and does not give the
6678 option for reading th 6246 option for reading the tracing buffer or performing a
6679 ftrace_dump_on_oops. 6247 ftrace_dump_on_oops.
6680 6248
6681 To turn off having tr 6249 To turn off having tracepoints sent to printk,
6682 echo 0 > /proc/sys/k 6250 echo 0 > /proc/sys/kernel/tracepoint_printk
6683 Note, echoing 1 into 6251 Note, echoing 1 into this file without the
6684 tp_printk kernel cmdl !! 6252 tracepoint_printk kernel cmdline option has no effect.
6685 6253
6686 The tp_printk_stop_on 6254 The tp_printk_stop_on_boot (see below) can also be used
6687 to stop the printing 6255 to stop the printing of events to console at
6688 late_initcall_sync. 6256 late_initcall_sync.
6689 6257
6690 ** CAUTION ** 6258 ** CAUTION **
6691 6259
6692 Having tracepoints se 6260 Having tracepoints sent to printk() and activating high
6693 frequency tracepoints 6261 frequency tracepoints such as irq or sched, can cause
6694 the system to live lo 6262 the system to live lock.
6695 6263
6696 tp_printk_stop_on_boot [FTRACE] 6264 tp_printk_stop_on_boot [FTRACE]
6697 When tp_printk (above 6265 When tp_printk (above) is set, it can cause a lot of noise
6698 on the console. It ma 6266 on the console. It may be useful to only include the
6699 printing of events du 6267 printing of events during boot up, as user space may
6700 make the system inope 6268 make the system inoperable.
6701 6269
6702 This command line opt 6270 This command line option will stop the printing of events
6703 to console at the lat 6271 to console at the late_initcall_sync() time frame.
6704 6272
6705 trace_buf_size=nn[KMG] 6273 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 6274 [FTRACE] will set tracing buffer size on each cpu.
6707 6275
6708 trace_clock= [FTRACE] Set the cloc 6276 trace_clock= [FTRACE] Set the clock used for tracing events
6709 at boot up. 6277 at boot up.
6710 local - Use the per C 6278 local - Use the per CPU time stamp counter
6711 (converted in 6279 (converted into nanoseconds). Fast, but
6712 depending on 6280 depending on the architecture, may not be
6713 in sync betwe 6281 in sync between CPUs.
6714 global - Event time s 6282 global - Event time stamps are synchronize across
6715 CPUs. May be 6283 CPUs. May be slower than the local clock,
6716 but better fo 6284 but better for some race conditions.
6717 counter - Simple coun 6285 counter - Simple counting of events (1, 2, ..)
6718 note, some co 6286 note, some counts may be skipped due to the
6719 infrastructur 6287 infrastructure grabbing the clock more than
6720 once per even 6288 once per event.
6721 uptime - Use jiffies 6289 uptime - Use jiffies as the time stamp.
6722 perf - Use the same c 6290 perf - Use the same clock that perf uses.
6723 mono - Use ktime_get_ 6291 mono - Use ktime_get_mono_fast_ns() for time stamps.
6724 mono_raw - Use ktime_ 6292 mono_raw - Use ktime_get_raw_fast_ns() for time
6725 stamps. 6293 stamps.
6726 boot - Use ktime_get_ 6294 boot - Use ktime_get_boot_fast_ns() for time stamps.
6727 Architectures may add 6295 Architectures may add more clocks. See
6728 Documentation/trace/f 6296 Documentation/trace/ftrace.rst for more details.
6729 6297
6730 trace_event=[event-list] 6298 trace_event=[event-list]
6731 [FTRACE] Set and star 6299 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 6300 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 6301 comma-separated list of trace events to enable. See
6734 also Documentation/tr 6302 also Documentation/trace/events.rst
6735 6303
6736 trace_instance=[instance-info] 6304 trace_instance=[instance-info]
6737 [FTRACE] Create a rin 6305 [FTRACE] Create a ring buffer instance early in boot up.
6738 This will be listed i 6306 This will be listed in:
6739 6307
6740 /sys/kernel/t 6308 /sys/kernel/tracing/instances
6741 6309
6742 Events can be enabled 6310 Events can be enabled at the time the instance is created
6743 via: 6311 via:
6744 6312
6745 trace_instanc 6313 trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
6746 6314
6747 Note, the "<system*>: 6315 Note, the "<system*>:" portion is optional if the event is
6748 unique. 6316 unique.
6749 6317
6750 trace_instanc 6318 trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
6751 6319
6752 will enable the "sche 6320 will enable the "sched_switch" event (note, the "sched:" is optional, and
6753 the same thing would 6321 the same thing would happen if it was left off). The irq_handler_entry
6754 event, and all events 6322 event, and all events under the "initcall" system.
6755 6323
6756 trace_options=[option-list] 6324 trace_options=[option-list]
6757 [FTRACE] Enable or di 6325 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 6326 The option-list is a comma delimited list of options
6759 that can be enabled o 6327 that can be enabled or disabled just as if you were
6760 to echo the option na 6328 to echo the option name into
6761 6329
6762 /sys/kernel/traci 6330 /sys/kernel/tracing/trace_options
6763 6331
6764 For example, to enabl 6332 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 6333 stack trace of each event), add to the command line:
6766 6334
6767 trace_options=s 6335 trace_options=stacktrace
6768 6336
6769 See also Documentatio 6337 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 6338 section.
6771 6339
6772 trace_trigger=[trigger-list] 6340 trace_trigger=[trigger-list]
6773 [FTRACE] Add a event 6341 [FTRACE] Add a event trigger on specific events.
6774 Set a trigger on top 6342 Set a trigger on top of a specific event, with an optional
6775 filter. 6343 filter.
6776 6344
6777 The format is is "tra 6345 The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
6778 Where more than one t 6346 Where more than one trigger may be specified that are comma deliminated.
6779 6347
6780 For example: 6348 For example:
6781 6349
6782 trace_trigger="sche 6350 trace_trigger="sched_switch.stacktrace if prev_state == 2"
6783 6351
6784 The above will enable 6352 The above will enable the "stacktrace" trigger on the "sched_switch"
6785 event but only trigge 6353 event but only trigger it if the "prev_state" of the "sched_switch"
6786 event is "2" (TASK_UN 6354 event is "2" (TASK_UNINTERUPTIBLE).
6787 6355
6788 See also "Event trigg 6356 See also "Event triggers" in Documentation/trace/events.rst
6789 6357
6790 6358
6791 traceoff_on_warning 6359 traceoff_on_warning
6792 [FTRACE] enable this 6360 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 6361 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 6362 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ 6363 file located in /sys/kernel/tracing/
6796 6364
6797 This option is useful 6365 This option is useful, as it disables the trace before
6798 the WARNING dump is c 6366 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 6367 be filled with content caused by the warning output.
6800 6368
6801 This option can also 6369 This option can also be set at run time via the sysctl
6802 option: kernel/trace 6370 option: kernel/traceoff_on_warning
6803 6371
6804 transparent_hugepage= 6372 transparent_hugepage=
6805 [KNL] 6373 [KNL]
6806 Format: [always|madvi 6374 Format: [always|madvise|never]
6807 Can be used to contro 6375 Can be used to control the default behavior of the system
6808 with respect to trans 6376 with respect to transparent hugepages.
6809 See Documentation/adm 6377 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 6378 for more details.
6811 6379
6812 trusted.source= [KEYS] 6380 trusted.source= [KEYS]
6813 Format: <string> 6381 Format: <string>
6814 This parameter identi 6382 This parameter identifies the trust source as a backend
6815 for trusted keys impl 6383 for trusted keys implementation. Supported trust
6816 sources: 6384 sources:
6817 - "tpm" 6385 - "tpm"
6818 - "tee" 6386 - "tee"
6819 - "caam" 6387 - "caam"
6820 - "dcp" <<
6821 If not specified then 6388 If not specified then it defaults to iterating through
6822 the trust source list 6389 the trust source list starting with TPM and assigns the
6823 first trust source as 6390 first trust source as a backend which is initialized
6824 successfully during i 6391 successfully during iteration.
6825 6392
6826 trusted.rng= [KEYS] 6393 trusted.rng= [KEYS]
6827 Format: <string> 6394 Format: <string>
6828 The RNG used to gener 6395 The RNG used to generate key material for trusted keys.
6829 Can be one of: 6396 Can be one of:
6830 - "kernel" 6397 - "kernel"
6831 - the same value as t 6398 - the same value as trusted.source: "tpm" or "tee"
6832 - "default" 6399 - "default"
6833 If not specified, "de 6400 If not specified, "default" is used. In this case,
6834 the RNG's choice is l 6401 the RNG's choice is left to each individual trust source.
6835 6402
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 6403 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 6404 Format: <string>
6850 [x86] reliable: mark 6405 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 6406 disables clocksource verification at runtime, as well
6852 as the stability chec 6407 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 6408 high-resolution timer mode on older hardware, and in
6854 virtualized environme 6409 virtualized environment.
6855 [x86] noirqtime: Do n 6410 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 6411 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 6412 platforms where RDTSC is slow and this accounting
6858 can add overhead. 6413 can add overhead.
6859 [x86] unstable: mark 6414 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 6415 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 6416 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 6417 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 6418 in situations with strict latency requirements (where
6864 interruptions from cl 6419 interruptions from clocksource watchdog are not
6865 acceptable). 6420 acceptable).
6866 [x86] recalibrate: fo 6421 [x86] recalibrate: force recalibration against a HW timer
6867 (HPET or PM timer) on 6422 (HPET or PM timer) on systems whose TSC frequency was
6868 obtained from HW or F 6423 obtained from HW or FW using either an MSR or CPUID(0x15).
6869 Warn if the differenc 6424 Warn if the difference is more than 500 ppm.
6870 [x86] watchdog: Use T 6425 [x86] watchdog: Use TSC as the watchdog clocksource with
6871 which to check other 6426 which to check other HW timers (HPET or PM timer), but
6872 only on systems where 6427 only on systems where TSC has been deemed trustworthy.
6873 This will be suppress 6428 This will be suppressed by an earlier tsc=nowatchdog and
6874 can be overridden by 6429 can be overridden by a later tsc=nowatchdog. A console
6875 message will flag any 6430 message will flag any such suppression or overriding.
6876 6431
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 6432 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 6433 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 6434 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 6435 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 6436 Format: <unsigned int>
6882 6437
6883 tsx= [X86] Control Transac 6438 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 6439 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 6440 support TSX control.
6886 6441
6887 This parameter contro 6442 This parameter controls the TSX feature. The options are:
6888 6443
6889 on - Enable TSX 6444 on - Enable TSX on the system. Although there are
6890 mitigations f 6445 mitigations for all known security vulnerabilities,
6891 TSX has been 6446 TSX has been known to be an accelerator for
6892 several previ 6447 several previous speculation-related CVEs, and
6893 so there may 6448 so there may be unknown security risks associated
6894 with leaving 6449 with leaving it enabled.
6895 6450
6896 off - Disable TSX 6451 off - Disable TSX on the system. (Note that this
6897 option takes 6452 option takes effect only on newer CPUs which are
6898 not vulnerabl 6453 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 6454 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 6455 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 6456 update. This new MSR allows for the reliable
6902 deactivation 6457 deactivation of the TSX functionality.)
6903 6458
6904 auto - Disable TSX 6459 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 6460 otherwise enable TSX on the system.
6906 6461
6907 Not specifying this o 6462 Not specifying this option is equivalent to tsx=off.
6908 6463
6909 See Documentation/adm 6464 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 6465 for more details.
6911 6466
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 6467 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 6468 Abort (TAA) vulnerability.
6914 6469
6915 Similar to Micro-arch 6470 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 6471 certain CPUs that support Transactional
6917 Synchronization Exten 6472 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 6473 exploit against CPU internal buffers which can forward
6919 information to a disc 6474 information to a disclosure gadget under certain
6920 conditions. 6475 conditions.
6921 6476
6922 In vulnerable process 6477 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 6478 data can be used in a cache side channel attack, to
6924 access data to which 6479 access data to which the attacker does not have direct
6925 access. 6480 access.
6926 6481
6927 This parameter contro 6482 This parameter controls the TAA mitigation. The
6928 options are: 6483 options are:
6929 6484
6930 full - Enable T 6485 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 6486 if TSX is enabled.
6932 6487
6933 full,nosmt - Enable T 6488 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 6489 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 6490 is not disabled because CPU is not
6936 vulnerab 6491 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 6492 off - Unconditionally disable TAA mitigation
6938 6493
6939 On MDS-affected machi 6494 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 6495 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 6496 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 6497 this mitigation, you need to specify mds=off too.
6943 6498
6944 Not specifying this o 6499 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 6500 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 6501 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 6502 required and doesn't provide any additional
6948 mitigation. 6503 mitigation.
6949 6504
6950 For details see: 6505 For details see:
6951 Documentation/admin-g 6506 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 6507
6953 turbografx.map[2|3]= [HW,JOY] 6508 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 6509 TurboGraFX parallel port interface
6955 Format: 6510 Format:
6956 <port#>,<js1>,<js2>,< 6511 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 6512 See also Documentation/input/devices/joystick-parport.rst
6958 6513
6959 udbg-immortal [PPC] When debugging 6514 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 6515 happen after console_init() and before a proper
6961 console driver takes 6516 console driver takes over, this boot options might
6962 help "seeing" what's 6517 help "seeing" what's going on.
6963 6518
6964 uhash_entries= [KNL,NET] 6519 uhash_entries= [KNL,NET]
6965 Set number of hash bu 6520 Set number of hash buckets for UDP/UDP-Lite connections
6966 6521
6967 uhci-hcd.ignore_oc= 6522 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 6523 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 6524 Some badly-designed motherboards generate lots of
6970 bogus events, for por 6525 bogus events, for ports that aren't wired to
6971 anything. Set this p 6526 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 6527 Note that genuine overcurrent events won't be
6973 reported either. 6528 reported either.
6974 6529
6975 unknown_nmi_panic 6530 unknown_nmi_panic
6976 [X86] Cause panic on 6531 [X86] Cause panic on unknown NMI.
6977 6532
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= 6533 usbcore.authorized_default=
6985 [USB] Default USB dev 6534 [USB] Default USB device authorization:
6986 (default -1 = authori !! 6535 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 6536 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 6537 if device connected to internal port)
6989 6538
6990 usbcore.autosuspend= 6539 usbcore.autosuspend=
6991 [USB] The autosuspend 6540 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 6541 for newly-detected USB devices (default 2). This
6993 is the time required 6542 is the time required before an idle device will be
6994 autosuspended. Devic 6543 autosuspended. Devices for which the delay is set
6995 to a negative value w 6544 to a negative value won't be autosuspended at all.
6996 6545
6997 usbcore.usbfs_snoop= 6546 usbcore.usbfs_snoop=
6998 [USB] Set to log all 6547 [USB] Set to log all usbfs traffic (default 0 = off).
6999 6548
7000 usbcore.usbfs_snoop_max= 6549 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 6550 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 6551 (default = 65536).
7003 6552
7004 usbcore.blinkenlights= 6553 usbcore.blinkenlights=
7005 [USB] Set to cycle le 6554 [USB] Set to cycle leds on hubs (default 0 = off).
7006 6555
7007 usbcore.old_scheme_first= 6556 usbcore.old_scheme_first=
7008 [USB] Start with the 6557 [USB] Start with the old device initialization
7009 scheme (default 0 = o 6558 scheme (default 0 = off).
7010 6559
7011 usbcore.usbfs_memory_mb= 6560 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 6561 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 6562 usbfs (default = 16, 0 = max = 2047).
7014 6563
7015 usbcore.use_both_schemes= 6564 usbcore.use_both_schemes=
7016 [USB] Try the other d 6565 [USB] Try the other device initialization scheme
7017 if the first one fail 6566 if the first one fails (default 1 = enabled).
7018 6567
7019 usbcore.initial_descriptor_timeout= 6568 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 6569 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 6570 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 6571 (default 5000 = 5.0 seconds).
7023 6572
7024 usbcore.nousb [USB] Disable the USB 6573 usbcore.nousb [USB] Disable the USB subsystem
7025 6574
7026 usbcore.quirks= 6575 usbcore.quirks=
7027 [USB] A list of quirk 6576 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 6577 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 6578 commas. Each entry has the form
7030 VendorID:ProductID:Fl 6579 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 6580 numbers and Flags is a set of letters. Each letter
7032 will change the built 6581 will change the built-in quirk; setting it if it is
7033 clear and clearing it 6582 clear and clearing it if it is set. The letters have
7034 the following meaning 6583 the following meanings:
7035 a = USB_QUIRK 6584 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 6585 descriptors must not be fetched using
7037 a 255 6586 a 255-byte read);
7038 b = USB_QUIRK 6587 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 6588 correctly so reset it instead);
7040 c = USB_QUIRK 6589 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 6590 Set-Interface requests);
7042 d = USB_QUIRK 6591 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 6592 handle its Configuration or Interface
7044 strin 6593 strings);
7045 e = USB_QUIRK 6594 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 6595 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 6596 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 6597 more interface descriptions than the
7049 bNumI 6598 bNumInterfaces count, and can't handle
7050 talki 6599 talking to these interfaces);
7051 g = USB_QUIRK 6600 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 6601 during initialization, after we read
7053 the d 6602 the device descriptor);
7054 h = USB_QUIRK 6603 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 6604 high speed and super speed interrupt
7056 endpo 6605 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 6606 require the interval in microframes (1
7058 micro 6607 microframe = 125 microseconds) to be
7059 calcu 6608 calculated as interval = 2 ^
7060 (bInt 6609 (bInterval-1).
7061 Devic 6610 Devices with this quirk report their
7062 bInte 6611 bInterval as the result of this
7063 calcu 6612 calculation instead of the exponent
7064 varia 6613 variable used in the calculation);
7065 i = USB_QUIRK 6614 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 6615 handle device_qualifier descriptor
7067 reque 6616 requests);
7068 j = USB_QUIRK 6617 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 6618 generates spurious wakeup, ignore
7070 remot 6619 remote wakeup capability);
7071 k = USB_QUIRK 6620 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 6621 Power Management);
7073 l = USB_QUIRK 6622 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 6623 (Device reports its bInterval as linear
7075 frame 6624 frames instead of the USB 2.0
7076 calcu 6625 calculation);
7077 m = USB_QUIRK 6626 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 6627 to be disconnected before suspend to
7079 preve 6628 prevent spurious wakeup);
7080 n = USB_QUIRK 6629 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 6630 pause after every control message);
7082 o = USB_QUIRK 6631 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 6632 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 6633 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 6634
7089 usbhid.mousepoll= 6635 usbhid.mousepoll=
7090 [USBHID] The interval 6636 [USBHID] The interval which mice are to be polled at.
7091 6637
7092 usbhid.jspoll= 6638 usbhid.jspoll=
7093 [USBHID] The interval 6639 [USBHID] The interval which joysticks are to be polled at.
7094 6640
7095 usbhid.kbpoll= 6641 usbhid.kbpoll=
7096 [USBHID] The interval 6642 [USBHID] The interval which keyboards are to be polled at.
7097 6643
7098 usb-storage.delay_use= 6644 usb-storage.delay_use=
7099 [UMS] The delay in se 6645 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 6646 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 6647
7105 usb-storage.quirks= 6648 usb-storage.quirks=
7106 [UMS] A list of quirk 6649 [UMS] A list of quirks entries to supplement or
7107 override the built-in 6650 override the built-in unusual_devs list. List
7108 entries are separated 6651 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 6652 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 6653 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 6654 Flags is a set of characters, each corresponding
7112 to a common usb-stora 6655 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 6656 a = SANE_SENSE (collect more than 18 bytes
7114 of se 6657 of sense data, not on uas);
7115 b = BAD_SENSE 6658 b = BAD_SENSE (don't collect more than 18
7116 bytes 6659 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 6660 c = FIX_CAPACITY (decrease the reported
7118 devic 6661 device capacity by one sector);
7119 d = NO_READ_D 6662 d = NO_READ_DISC_INFO (don't use
7120 READ_ 6663 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 6664 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 6665 READ_CAPACITY_16 command);
7123 f = NO_REPORT 6666 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 6667 command, uas only);
7125 g = MAX_SECTO 6668 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 6669 240 sectors at a time, uas only);
7127 h = CAPACITY_ 6670 h = CAPACITY_HEURISTICS (decrease the
7128 repor 6671 reported device capacity by one
7129 secto 6672 sector if the number is odd);
7130 i = IGNORE_DE 6673 i = IGNORE_DEVICE (don't bind to this
7131 devic 6674 device);
7132 j = NO_REPORT 6675 j = NO_REPORT_LUNS (don't use report luns
7133 comma 6676 command, uas only);
7134 k = NO_SAME ( 6677 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 6678 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 6679 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 6680 m = MAX_SECTORS_64 (don't transfer more
7138 than 6681 than 64 sectors = 32 KB at a time,
7139 not o 6682 not on uas);
7140 n = INITIAL_R 6683 n = INITIAL_READ10 (force a retry of the
7141 initi 6684 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 6685 o = CAPACITY_OK (accept the capacity
7143 repor 6686 reported by the device, not on uas);
7144 p = WRITE_CAC 6687 p = WRITE_CACHE (the device cache is ON
7145 by de 6688 by default, not on uas);
7146 r = IGNORE_RE 6689 r = IGNORE_RESIDUE (the device reports
7147 bogus 6690 bogus residue values, not on uas);
7148 s = SINGLE_LU 6691 s = SINGLE_LUN (the device has only one
7149 Logic 6692 Logical Unit);
7150 t = NO_ATA_1X 6693 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 6694 commands, uas only);
7152 u = IGNORE_UA 6695 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 6696 w = NO_WP_DETECT (don't test whether the
7154 mediu 6697 medium is write-protected).
7155 y = ALWAYS_SY 6698 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 6699 even if the device claims no cache,
7157 not o 6700 not on uas)
7158 Example: quirks=0419: 6701 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 6702
7160 user_debug= [KNL,ARM] 6703 user_debug= [KNL,ARM]
7161 Format: <int> 6704 Format: <int>
7162 See arch/arm/Kconfig. 6705 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 6706 1 - undefined instruction events
7164 2 - system c 6707 2 - system calls
7165 4 - invalid 6708 4 - invalid data aborts
7166 8 - SIGSEGV 6709 8 - SIGSEGV faults
7167 16 - SIGBUS f 6710 16 - SIGBUS faults
7168 Example: user_debug=3 6711 Example: user_debug=31
7169 6712
7170 userpte= 6713 userpte=
7171 [X86,EARLY] Flags con !! 6714 [X86] Flags controlling user PTE allocations.
7172 6715
7173 nohigh = do n 6716 nohigh = do not allocate PTE pages in
7174 HIGHM 6717 HIGHMEM regardless of setting
7175 of CO 6718 of CONFIG_HIGHPTE.
7176 6719
7177 vdso= [X86,SH,SPARC] 6720 vdso= [X86,SH,SPARC]
7178 On X86_32, this is an 6721 On X86_32, this is an alias for vdso32=. Otherwise:
7179 6722
7180 vdso=1: enable VDSO ( 6723 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 6724 vdso=0: disable VDSO mapping
7182 6725
7183 vdso32= [X86] Control the 32- 6726 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 6727 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 6728 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 6729
7187 See the help text for 6730 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 6731 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 6732 vdso32=0; otherwise, the default is vdso32=1.
7190 6733
7191 For compatibility wit 6734 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 6735 alias for vdso32=0.
7193 6736
7194 Try vdso32=0 if you e 6737 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 6738 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 6739
7197 video= [FB,EARLY] Frame buff !! 6740 vector= [IA-64,SMP]
>> 6741 vector=percpu: enable percpu vector domain
>> 6742
>> 6743 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 6744 See Documentation/fb/modedb.rst.
7199 6745
7200 video.brightness_switch_enabled= [ACP 6746 video.brightness_switch_enabled= [ACPI]
7201 Format: [0|1] 6747 Format: [0|1]
7202 If set to 1, on recei 6748 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 6749 generated by hotkey, video driver will adjust brightness
7204 level and then send o 6750 level and then send out the event to user space through
7205 the allocated input d 6751 the allocated input device. If set to 0, video driver
7206 will only send out th 6752 will only send out the event without touching backlight
7207 brightness level. 6753 brightness level.
7208 default: 1 6754 default: 1
7209 6755
7210 virtio_mmio.device= 6756 virtio_mmio.device=
7211 [VMMIO] Memory mapped 6757 [VMMIO] Memory mapped virtio (platform) device.
7212 6758
7213 <size>@<basead 6759 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 6760 where:
7215 <size> := 6761 <size> := size (can use standard suffixes
7216 6762 like K, M and G)
7217 <baseaddr> := 6763 <baseaddr> := physical base address
7218 <irq> := 6764 <irq> := interrupt number (as passed to
7219 6765 request_irq())
7220 <id> := 6766 <id> := (optional) platform device id
7221 example: 6767 example:
7222 virtio_mmio.d 6768 virtio_mmio.device=1K@0x100b0000:48:7
7223 6769
7224 Can be used multiple 6770 Can be used multiple times for multiple devices.
7225 6771
7226 vga= [BOOT,X86-32] Select 6772 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 6773 See Documentation/x86/boot.rst and
7228 Documentation/admin-g 6774 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 6775 Use vga=ask for menu.
7230 This is actually a bo 6776 This is actually a boot loader parameter; the value is
7231 passed to the kernel 6777 passed to the kernel using a special protocol.
7232 6778
7233 vm_debug[=options] [KNL] Availab 6779 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 6780 May slow down system boot speed, especially when
7235 enabled on systems wi 6781 enabled on systems with a large amount of memory.
7236 All options are enabl 6782 All options are enabled by default, and this
7237 interface is meant to 6783 interface is meant to allow for selectively
7238 enabling or disabling 6784 enabling or disabling specific virtual memory
7239 debugging features. 6785 debugging features.
7240 6786
7241 Available options are 6787 Available options are:
7242 P Enable page s 6788 P Enable page structure init time poisoning
7243 - Disable all o 6789 - Disable all of the above options
7244 6790
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 6791 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 6792 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 6793 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 6794 decrease the size and leave more room for directly
7249 for directly mapped k !! 6795 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 6796
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 6797 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 6798 Sets the memory size reserved for contiguous memory
7256 allocations for the v 6799 allocations for the vmcp device driver.
7257 6800
7258 vmhalt= [KNL,S390] Perform z/ 6801 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 6802 Format: <command>
7260 6803
7261 vmpanic= [KNL,S390] Perform z/ 6804 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 6805 Format: <command>
7263 6806
7264 vmpoff= [KNL,S390] Perform z/ 6807 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 6808 Format: <command>
7266 6809
7267 vsyscall= [X86-64,EARLY] !! 6810 vsyscall= [X86-64]
7268 Controls the behavior 6811 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 6812 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 6813 code). Most statically-linked binaries and older
7271 versions of glibc use 6814 versions of glibc use these calls. Because these
7272 functions are at fixe 6815 functions are at fixed addresses, they make nice
7273 targets for exploits 6816 targets for exploits that can control RIP.
7274 6817
7275 emulate Vsyscalls 6818 emulate Vsyscalls turn into traps and are emulated
7276 reasonabl 6819 reasonably safely. The vsyscall page is
7277 readable. 6820 readable.
7278 6821
7279 xonly [default] 6822 xonly [default] Vsyscalls turn into traps and are
7280 emulated 6823 emulated reasonably safely. The vsyscall
7281 page is n 6824 page is not readable.
7282 6825
7283 none Vsyscalls 6826 none Vsyscalls don't work at all. This makes
7284 them quit 6827 them quite hard to use for exploits but
7285 might bre 6828 might break your system.
7286 6829
7287 vt.color= [VT] Default text col 6830 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6831 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6832 Default: 0x07 = light gray on black.
7290 6833
7291 vt.cur_default= [VT] Default cursor s 6834 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6835 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6836 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6837 see VGA-softcursor.txt. Default: 2 = underline.
7295 6838
7296 vt.default_blu= [VT] 6839 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6840 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6841 Change the default blue palette of the console.
7299 This is a 16-member a 6842 This is a 16-member array composed of values
7300 ranging from 0-255. 6843 ranging from 0-255.
7301 6844
7302 vt.default_grn= [VT] 6845 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6846 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6847 Change the default green palette of the console.
7305 This is a 16-member a 6848 This is a 16-member array composed of values
7306 ranging from 0-255. 6849 ranging from 0-255.
7307 6850
7308 vt.default_red= [VT] 6851 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6852 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6853 Change the default red palette of the console.
7311 This is a 16-member a 6854 This is a 16-member array composed of values
7312 ranging from 0-255. 6855 ranging from 0-255.
7313 6856
7314 vt.default_utf8= 6857 vt.default_utf8=
7315 [VT] 6858 [VT]
7316 Format=<0|1> 6859 Format=<0|1>
7317 Set system-wide defau 6860 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6861 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6862 newly opened terminals.
7320 6863
7321 vt.global_cursor_default= 6864 vt.global_cursor_default=
7322 [VT] 6865 [VT]
7323 Format=<-1|0|1> 6866 Format=<-1|0|1>
7324 Set system-wide defau 6867 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6868 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6869 i.e. cursors will be created by default unless
7327 overridden by individ 6870 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6871 cursors, 1 will display them.
7329 6872
7330 vt.italic= [VT] Default color fo 6873 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6874 Default: 2 = green.
7332 6875
7333 vt.underline= [VT] Default color fo 6876 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6877 Default: 3 = cyan.
7335 6878
7336 watchdog timers [HW,WDT] For informat 6879 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6880 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6881 or other driver-specific files in the
7339 Documentation/watchdo 6882 Documentation/watchdog/ directory.
7340 6883
7341 watchdog_thresh= 6884 watchdog_thresh=
7342 [KNL] 6885 [KNL]
7343 Set the hard lockup d 6886 Set the hard lockup detector stall duration
7344 threshold in seconds. 6887 threshold in seconds. The soft lockup detector
7345 threshold is set to t 6888 threshold is set to twice the value. A value of 0
7346 disables both lockup 6889 disables both lockup detectors. Default is 10
7347 seconds. 6890 seconds.
7348 6891
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= 6892 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 6893 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 6894 warn stall conditions and dump internal state to
7359 help debugging. 0 di 6895 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 6896 detection; otherwise, it's the stall threshold
7361 duration in seconds. 6897 duration in seconds. The default value is 30 and
7362 it can be updated at 6898 it can be updated at runtime by writing to the
7363 corresponding sysfs f 6899 corresponding sysfs file.
7364 6900
7365 workqueue.cpu_intensive_thresh_us= !! 6901 workqueue.disable_numa
7366 Per-cpu work items wh !! 6902 By default, all work items queued to unbound
7367 threshold are automat !! 6903 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 6904 issued on, which results in better behavior in
7369 them from noticeably !! 6905 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 6906 whatever reason, this option can be used. Note
7371 !! 6907 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 6908 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 6909
7386 workqueue.power_efficient 6910 workqueue.power_efficient
7387 Per-cpu workqueues ar 6911 Per-cpu workqueues are generally preferred because
7388 they show better perf 6912 they show better performance thanks to cache
7389 locality; unfortunate 6913 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 6914 be more power hungry than unbound workqueues.
7391 6915
7392 Enabling this makes t 6916 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 6917 were observed to contribute significantly to power
7394 consumption unbound, 6918 consumption unbound, leading to measurably lower
7395 power usage at the co 6919 power usage at the cost of small performance
7396 overhead. 6920 overhead.
7397 6921
7398 The default value of 6922 The default value of this parameter is determined by
7399 the config option CON 6923 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 6924
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 6925 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 6926 Workqueue used to implicitly guarantee that work
7415 items queued without 6927 items queued without explicit CPU specified are put
7416 on the local CPU. Th 6928 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 6929 and while local CPU is still preferred work items
7418 may be put on foreign 6930 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 6931 forces round-robin CPU selection to flush out
7420 usages which depend o 6932 usages which depend on the now broken guarantee.
7421 When enabled, memory 6933 When enabled, memory and cache locality will be
7422 impacted. 6934 impacted.
7423 6935
7424 writecombine= [LOONGARCH,EARLY] Con !! 6936 writecombine= [LOONGARCH] Control the MAT (Memory Access Type) of
7425 Type) of ioremap_wc() !! 6937 ioremap_wc().
7426 6938
7427 on - Enable writeco 6939 on - Enable writecombine, use WUC for ioremap_wc()
7428 off - Disable writec 6940 off - Disable writecombine, use SUC for ioremap_wc()
7429 6941
7430 x2apic_phys [X86-64,APIC,EARLY] U !! 6942 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7431 default x2apic cluste 6943 default x2apic cluster mode on platforms
7432 supporting x2apic. 6944 supporting x2apic.
7433 6945
7434 xen_512gb_limit [KNL,X86-64,X 6946 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 6947 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 6948 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 6949 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 6950 save/restore/migration must be enabled to handle larger
7439 domains. 6951 domains.
7440 6952
7441 xen_emul_unplug= [HW,X !! 6953 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 6954 Unplug Xen emulated devices
7443 Format: [unplug0,][un 6955 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 6956 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 6957 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 6958 nics -- unplug network devices
7447 all -- unplug all emu 6959 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 6960 unnecessary -- unplugging emulated devices is
7449 unnecessary e 6961 unnecessary even if the host did not respond to
7450 the unplug pr 6962 the unplug protocol
7451 never -- do not unplu 6963 never -- do not unplug even if version check succeeds
7452 6964
7453 xen_legacy_crash [X86,XEN,EARL !! 6965 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 6966 Crash from Xen panic notifier, without executing late
7455 panic() code such as 6967 panic() code such as dumping handler.
7456 6968
7457 xen_mc_debug [X86,XEN,EARLY] !! 6969 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> 6970 Format: <bool>
7465 Select whether to alw 6971 Select whether to always use non-faulting (safe) MSR
7466 access functions when 6972 access functions when running as Xen PV guest. The
7467 default value is cont 6973 default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
7468 6974
>> 6975 xen_nopvspin [X86,XEN]
>> 6976 Disables the qspinlock slowpath using Xen PV optimizations.
>> 6977 This parameter is obsoleted by "nopvspin" parameter, which
>> 6978 has equivalent effect for XEN platform.
>> 6979
7469 xen_nopv [X86] 6980 xen_nopv [X86]
7470 Disables the PV optim 6981 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 6982 run as generic HVM guest with no PV drivers.
7472 This option is obsole 6983 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 6984 has equivalent effect for XEN platform.
7474 6985
7475 xen_no_vector_callback 6986 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 6987 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 6988 event channel interrupts.
7478 6989
7479 xen_scrub_pages= [XEN] 6990 xen_scrub_pages= [XEN]
7480 Boolean option to con 6991 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 6992 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 6993 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 6994 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 6995
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 6996 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 6997 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 6998 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 6999 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 7000 improve timer resolution at the expense of processing
7490 more timer interrupts 7001 more timer interrupts.
7491 7002
7492 xen.balloon_boot_timeout= [XEN] 7003 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 7004 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 7005 in case initial ballooning fails to free enough memory.
7495 Applies only when run 7006 Applies only when running as HVM or PVH guest and
7496 started with less mem 7007 started with less memory configured than allowed at
7497 max. Default is 180. 7008 max. Default is 180.
7498 7009
7499 xen.event_eoi_delay= [XEN] 7010 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 7011 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 7012 storms (jiffies). Default is 10.
7502 7013
7503 xen.event_loop_timeout= [XEN] 7014 xen.event_loop_timeout= [XEN]
7504 After which time (jif 7015 After which time (jiffies) the event handling loop
7505 should start to delay 7016 should start to delay EOI handling. Default is 2.
7506 7017
7507 xen.fifo_events= [XEN] 7018 xen.fifo_events= [XEN]
7508 Boolean parameter to 7019 Boolean parameter to disable using fifo event handling
7509 even if available. No 7020 even if available. Normally fifo event handling is
7510 preferred over the 2- 7021 preferred over the 2-level event handling, as it is
7511 fairer and the number 7022 fairer and the number of possible event channels is
7512 much higher. Default 7023 much higher. Default is on (use fifo events).
7513 7024
7514 xirc2ps_cs= [NET,PCMCIA] 7025 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 7026 Format:
7516 <irq>,<irq_mask>,<io> 7027 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 7028
7518 xive= [PPC] 7029 xive= [PPC]
7519 By default on POWER9 7030 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 7031 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 7032 allows the fallback firmware mode to be used:
7522 7033
7523 off Fallback to 7034 off Fallback to firmware control of XIVE interrupt
7524 controller 7035 controller on both pseries and powernv
7525 platforms. 7036 platforms. Only useful on POWER9 and above.
7526 7037
7527 xive.store-eoi=off [PPC] 7038 xive.store-eoi=off [PPC]
7528 By default on POWER10 7039 By default on POWER10 and above, the kernel will use
7529 stores for EOI handli 7040 stores for EOI handling when the XIVE interrupt mode
7530 is active. This optio 7041 is active. This option allows the XIVE driver to use
7531 loads instead, as on 7042 loads instead, as on POWER9.
7532 7043
7533 xhci-hcd.quirks [USB,KNL] 7044 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 7045 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 7046 host controller quirks. Meaning of each bit can be
7536 consulted in header d 7047 consulted in header drivers/usb/host/xhci.h.
7537 7048
7538 xmon [PPC,EARLY] !! 7049 xmon [PPC]
7539 Format: { early | on 7050 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 7051 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 7052 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 7053 early Call xmon as early as possible on boot; xmon
7543 debugger is c 7054 debugger is called from setup_arch().
7544 on xmon debugger 7055 on xmon debugger hooks will be installed so xmon
7545 is only calle 7056 is only called on a kernel crash. Default mode,
7546 i.e. either " 7057 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 7058 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 7059 rw xmon debugger hooks will be installed so xmon
7549 is called onl 7060 is called only on a kernel crash, mode is write,
7550 meaning SPR r 7061 meaning SPR registers, memory and, other data
7551 can be writte 7062 can be written using xmon commands.
7552 ro same as "rw" 7063 ro same as "rw" option above but SPR registers,
7553 memory, and o 7064 memory, and other data can't be written using
7554 xmon commands 7065 xmon commands.
7555 off xmon is disab 7066 off xmon is disabled.
>> 7067
>> 7068 amd_pstate= [X86]
>> 7069 disable
>> 7070 Do not enable amd_pstate as the default
>> 7071 scaling driver for the supported processors
>> 7072 passive
>> 7073 Use amd_pstate as a scaling driver, driver requests a
>> 7074 desired performance on this abstract scale and the power
>> 7075 management firmware translates the requests into actual
>> 7076 hardware states (core frequency, data fabric and memory
>> 7077 clocks etc.)
>> 7078 active
>> 7079 Use amd_pstate_epp driver instance as the scaling driver,
>> 7080 driver provides a hint to the hardware if software wants
>> 7081 to bias toward performance (0x0) or energy efficiency (0xff)
>> 7082 to the CPPC firmware. then CPPC power algorithm will
>> 7083 calculate the runtime workload and adjust the realtime cores
>> 7084 frequency.
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