1 accept_memory= [MM] !! 1 acpi= [HW,ACPI,X86,ARM64,RISCV64]
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,riscv64]
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 and RISCV64, ONLY "acpi=off", "acpi=on" or
25 default _seria !! 14 "acpi=force" are available
26 For ARM64, ONLY "acpi= <<
27 "acpi=nospcr" are avai <<
28 For RISCV64, ONLY "acp <<
29 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/arch/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 326 irtcachedis - Disable Interrupt Remapping Table (IRT) caching.
342 327
343 amd_iommu_dump= [HW,X86-64] 328 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 329 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 330 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 331 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 332 IOMMU initialization.
348 333
349 amd_iommu_intr= [HW,X86-64] 334 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 335 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 336 remapping modes:
352 legacy - Use legac 337 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 338 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 339 to inject interrupts directly into guest.
355 This mode 340 This mode requires kvm-amd.avic=1.
356 (Default 341 (Default when IOMMU HW support is present.)
357 342
358 amd_pstate= [X86,EARLY] !! 343 amd_pstate= [X86]
359 disable 344 disable
360 Do not enable amd_ps 345 Do not enable amd_pstate as the default
361 scaling driver for t 346 scaling driver for the supported processors
362 passive 347 passive
363 Use amd_pstate with 348 Use amd_pstate with passive mode as a scaling driver.
364 In this mode autonom 349 In this mode autonomous selection is disabled.
365 Driver requests a de 350 Driver requests a desired performance level and platform
366 tries to match the s 351 tries to match the same performance level if it is
367 satisfied by guarant 352 satisfied by guaranteed performance level.
368 active 353 active
369 Use amd_pstate_epp d 354 Use amd_pstate_epp driver instance as the scaling driver,
370 driver provides a hi 355 driver provides a hint to the hardware if software wants
371 to bias toward perfo 356 to bias toward performance (0x0) or energy efficiency (0xff)
372 to the CPPC firmware 357 to the CPPC firmware. then CPPC power algorithm will
373 calculate the runtim 358 calculate the runtime workload and adjust the realtime cores
374 frequency. 359 frequency.
375 guided 360 guided
376 Activate guided auto 361 Activate guided autonomous mode. Driver requests minimum and
377 maximum performance 362 maximum performance level and the platform autonomously
378 selects a performanc 363 selects a performance level in this range and appropriate
379 to the current workl 364 to the current workload.
380 365
381 amd_prefcore= <<
382 [X86] <<
383 disable <<
384 Disable amd-pstate p <<
385 <<
386 amijoy.map= [HW,JOY] Amiga joystic 366 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 367 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 368 Format: <a>,<b>
389 See also Documentation 369 See also Documentation/input/joydev/joystick.rst
390 370
391 analog.map= [HW,JOY] Analog joysti 371 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 372 Specifies type or capabilities of an analog joystick
393 connected to one of 16 373 connected to one of 16 gameports
394 Format: <type1>,<type2 374 Format: <type1>,<type2>,..<type16>
395 375
396 apc= [HW,SPARC] 376 apc= [HW,SPARC]
397 Power management funct 377 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 378 Format: noidle
399 Disable APC CPU standb 379 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 380 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 381 APC and your system crashes randomly.
402 382
403 apic= [APIC,X86,EARLY] Advan !! 383 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 384 Change the output verbosity while booting
405 Format: { quiet (defau 385 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 386 Change the amount of debugging information output
407 when initialising the 387 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 388 For X86-32, this can also be used to specify an APIC
409 driver name. 389 driver name.
410 Format: apic=driver_na 390 Format: apic=driver_name
411 Examples: apic=bigsmp 391 Examples: apic=bigsmp
412 392
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 393 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 394 Format: { bsp (default) | all | none }
415 bsp: External NMI is 395 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 396 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 397 backup of CPU 0
418 none: External NMI is 398 none: External NMI is masked for all CPUs. This is
419 useful so that a 399 useful so that a dump capture kernel won't be
420 shot down by NMI 400 shot down by NMI
421 401
422 autoconf= [IPV6] 402 autoconf= [IPV6]
423 See Documentation/netw 403 See Documentation/networking/ipv6.rst.
424 404
425 apm= [APM] Advanced Power M 405 apm= [APM] Advanced Power Management
426 See header of arch/x86 406 See header of arch/x86/kernel/apm_32.c.
427 407
428 apparmor= [APPARMOR] Disable or 408 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
429 Format: { "0" | "1" } 409 Format: { "0" | "1" }
430 See security/apparmor/ 410 See security/apparmor/Kconfig help text
431 0 -- disable. 411 0 -- disable.
432 1 -- enable. 412 1 -- enable.
433 Default value is set v 413 Default value is set via kernel config option.
434 414
435 arcrimi= [HW,NET] ARCnet - "RIM 415 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 416 Format: <io>,<irq>,<nodeID>
437 417
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall 418 arm64.nobti [ARM64] Unconditionally disable Branch Target
442 Identification support 419 Identification support
443 420
444 arm64.nomops [ARM64] Unconditionall !! 421 arm64.nopauth [ARM64] Unconditionally disable Pointer Authentication
445 Set instructions suppo !! 422 support
446 423
447 arm64.nomte [ARM64] Unconditionall 424 arm64.nomte [ARM64] Unconditionally disable Memory Tagging Extension
448 support 425 support
449 426
450 arm64.nopauth [ARM64] Unconditionall !! 427 arm64.nosve [ARM64] Unconditionally disable Scalable Vector
451 support !! 428 Extension support
452 429
453 arm64.nosme [ARM64] Unconditionall 430 arm64.nosme [ARM64] Unconditionally disable Scalable Matrix
454 Extension support 431 Extension support
455 432
456 arm64.nosve [ARM64] Unconditionall !! 433 arm64.nomops [ARM64] Unconditionally disable Memory Copy and Memory
457 Extension support !! 434 Set instructions support
458 435
459 ataflop= [HW,M68k] 436 ataflop= [HW,M68k]
460 437
461 atarimouse= [HW,MOUSE] Atari Mouse 438 atarimouse= [HW,MOUSE] Atari Mouse
462 439
463 atkbd.extra= [HW] Enable extra LEDs 440 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 441 EzKey and similar keyboards
465 442
466 atkbd.reset= [HW] Reset keyboard du 443 atkbd.reset= [HW] Reset keyboard during initialization
467 444
468 atkbd.set= [HW] Select keyboard c 445 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 446 Format: <int> (2 = AT (default), 3 = PS/2)
470 447
471 atkbd.scroll= [HW] Enable scroll whe 448 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 449 keyboards
473 450
474 atkbd.softraw= [HW] Choose between sy 451 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 452 Format: <bool> (0 = real, 1 = synthetic (default))
476 453
477 atkbd.softrepeat= [HW] 454 atkbd.softrepeat= [HW]
478 Use software keyboard 455 Use software keyboard repeat
479 456
480 audit= [KNL] Enable the audit 457 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 458 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 459 0 | off - kernel audit is disabled and can not be
483 enabled until the 460 enabled until the next reboot
484 unset - kernel audit i 461 unset - kernel audit is initialized but disabled and
485 will be fully enab 462 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 463 1 | on - kernel audit is initialized and partially
487 enabled, storing a 464 enabled, storing at most audit_backlog_limit
488 messages in RAM un 465 messages in RAM until it is fully enabled by the
489 userspace auditd. 466 userspace auditd.
490 Default: unset 467 Default: unset
491 468
492 audit_backlog_limit= [KNL] Set the aud 469 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 470 Format: <int> (must be >=0)
494 Default: 64 471 Default: 64
495 472
496 bau= [X86_UV] Enable the BA 473 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 474 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 475 Format: { "0" | "1" }
499 0 - Disable the BAU. 476 0 - Disable the BAU.
500 1 - Enable the BAU. 477 1 - Enable the BAU.
501 unset - Disable the BA 478 unset - Disable the BAU.
502 479
503 baycom_epp= [HW,AX25] 480 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 481 Format: <io>,<mode>
505 482
506 baycom_par= [HW,AX25] BayCom Paral 483 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 484 Format: <io>,<mode>
508 See header of drivers/ 485 See header of drivers/net/hamradio/baycom_par.c.
509 486
510 baycom_ser_fdx= [HW,AX25] 487 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 488 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 489 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 490 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 491
515 baycom_ser_hdx= [HW,AX25] 492 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 493 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 494 Format: <io>,<irq>,<mode>
518 See header of drivers/ 495 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 496
520 bert_disable [ACPI] 497 bert_disable [ACPI]
521 Disable BERT OS suppor 498 Disable BERT OS support on buggy BIOSes.
522 499
523 bgrt_disable [ACPI,X86,EARLY] !! 500 bgrt_disable [ACPI][X86]
524 Disable BGRT to avoid 501 Disable BGRT to avoid flickering OEM logo.
525 502
526 blkdevparts= Manual partition parsi 503 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 504 embedded devices based on command line input.
528 See Documentation/bloc 505 See Documentation/block/cmdline-partition.rst
529 506
530 boot_delay= [KNL,EARLY] !! 507 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay <<
532 Only works if CONFIG_B 508 Only works if CONFIG_BOOT_PRINTK_DELAY is enabled,
533 and you may also have 509 and you may also have to specify "lpj=". Boot_delay
534 values larger than 10 510 values larger than 10 seconds (10000) are assumed
535 erroneous and ignored. 511 erroneous and ignored.
536 Format: integer 512 Format: integer
537 513
538 bootconfig [KNL,EARLY] !! 514 bootconfig [KNL]
539 Extended command line 515 Extended command line options can be added to an initrd
540 and this will cause th 516 and this will cause the kernel to look for it.
541 517
542 See Documentation/admi 518 See Documentation/admin-guide/bootconfig.rst
543 519
544 bttv.card= [HW,V4L] bttv (bt848 + 520 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 521 bttv.radio= Most important insmod options are available as
546 kernel args too. 522 kernel args too.
547 bttv.pll= See Documentation/admi 523 bttv.pll= See Documentation/admin-guide/media/bttv.rst
548 bttv.tuner= 524 bttv.tuner=
549 525
550 bulk_remove=off [PPC] This parameter 526 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 527 firmware feature for flushing multiple hpte entries
552 at a time. 528 at a time.
553 529
554 c101= [NET] Moxa C101 synchr 530 c101= [NET] Moxa C101 synchronous serial card
555 531
556 cachesize= [BUGS=X86-32] Override 532 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 533 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 534 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 535 to fix known problems, but for some CPUs it is not
560 possible to determine 536 possible to determine what the correct size should be.
561 This option provides a 537 This option provides an override for these situations.
562 538
563 carrier_timeout= 539 carrier_timeout=
564 [NET] Specifies amount 540 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 541 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 542 it waits 120 seconds.
567 543
568 ca_keys= [KEYS] This parameter 544 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 545 the system trusted keyring to be used for certificate
570 trust validation. 546 trust validation.
571 format: { id:<keyid> | 547 format: { id:<keyid> | builtin }
572 548
573 cca= [MIPS,EARLY] Override !! 549 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 550 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 551 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 552 for platform specific values (SB1, Loongson3 and
577 others). 553 others).
578 554
579 ccw_timeout_log [S390] 555 ccw_timeout_log [S390]
580 See Documentation/arch !! 556 See Documentation/s390/common_io.rst for details.
581 557
582 cgroup_disable= [KNL] Disable a partic 558 cgroup_disable= [KNL] Disable a particular controller or optional feature
583 Format: {name of the c 559 Format: {name of the controller(s) or feature(s) to disable}
584 The effects of cgroup_ 560 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 561 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 562 a single hierarchy
587 - foo isn't visible as 563 - foo isn't visible as an individually mountable
588 subsystem 564 subsystem
589 - if foo is an optiona 565 - if foo is an optional feature then the feature is
590 disabled and corresp 566 disabled and corresponding cgroup files are not
591 created 567 created
592 {Currently only "memor 568 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 569 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 570 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" 571 Specifying "pressure" disables per-cgroup pressure
596 stall information acco 572 stall information accounting feature
597 573
598 cgroup_no_v1= [KNL] Disable cgroup c 574 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 575 Format: { { controller | "all" | "named" }
600 [,{ controll 576 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 577 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 578 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 579 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 580 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 581 all v1 hierarchies.
606 582
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 583 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 584 Format: <string>
613 nosocket -- Disable so 585 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 586 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m 587 nobpf -- Disable BPF memory accounting.
616 588
617 checkreqprot= [SELINUX] Set initial 589 checkreqprot= [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 590 Format: { "0" | "1" }
619 See security/selinux/K 591 See security/selinux/Kconfig help text.
620 0 -- check protection 592 0 -- check protection applied by kernel (includes
621 any implied ex 593 any implied execute protection).
622 1 -- check protection 594 1 -- check protection requested by application.
623 Default value is set v 595 Default value is set via a kernel config option.
624 Value can be changed a 596 Value can be changed at runtime via
625 /sys/fs/selinu 597 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 598 Setting checkreqprot to 1 is deprecated.
627 599
628 cio_ignore= [S390] 600 cio_ignore= [S390]
629 See Documentation/arch !! 601 See Documentation/s390/common_io.rst for details.
630 602
631 clearcpuid=X[,X...] [X86] 603 clearcpuid=X[,X...] [X86]
632 Disable CPUID feature 604 Disable CPUID feature X for the kernel. See
633 arch/x86/include/asm/c 605 arch/x86/include/asm/cpufeatures.h for the valid bit
634 numbers X. Note the Li 606 numbers X. Note the Linux-specific bits are not necessarily
635 stable over kernel opt 607 stable over kernel options, but the vendor-specific
636 ones should be. 608 ones should be.
637 X can also be a string 609 X can also be a string as appearing in the flags: line
638 in /proc/cpuinfo which 610 in /proc/cpuinfo which does not have the above
639 instability issue. How 611 instability issue. However, not all features have names
640 in /proc/cpuinfo. 612 in /proc/cpuinfo.
641 Note that using this o 613 Note that using this option will taint your kernel.
642 Also note that user pr 614 Also note that user programs calling CPUID directly
643 or using the feature w 615 or using the feature without checking anything
644 will still see it. Thi 616 will still see it. This just prevents it from
645 being used by the kern 617 being used by the kernel or shown in /proc/cpuinfo.
646 Also note the kernel m 618 Also note the kernel might malfunction if you disable
647 some critical bits. 619 some critical bits.
648 620
649 clk_ignore_unused 621 clk_ignore_unused
650 [CLK] 622 [CLK]
651 Prevents the clock fra 623 Prevents the clock framework from automatically gating
652 clocks that have not b 624 clocks that have not been explicitly enabled by a Linux
653 device driver but are 625 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 626 by the bootloader/firmware. Note that this does not
655 force such clocks to b 627 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 628 those clocks in any way. This parameter is useful for
657 debug and development, 629 debug and development, but should not be needed on a
658 platform with proper d 630 platform with proper driver support. For more
659 information, see Docum 631 information, see Documentation/driver-api/clk.rst.
660 632
661 clock= [BUGS=X86-32, HW] gett 633 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 634 [Deprecated]
663 Forces specified clock 635 Forces specified clocksource (if available) to be used
664 when calculating getti 636 when calculating gettimeofday(). If specified
665 clocksource is not ava 637 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 638 Format: { pit | tsc | cyclone | pmtmr }
667 639
668 clocksource= Override the default c 640 clocksource= Override the default clocksource
669 Format: <string> 641 Format: <string>
670 Override the default c 642 Override the default clocksource and use the clocksource
671 with the name specifie 643 with the name specified.
672 Some clocksource names 644 Some clocksource names to choose from, depending on
673 the platform: 645 the platform:
674 [all] jiffies (this is 646 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 647 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 648 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 649 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 650 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 651 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 652 [MIPS] MIPS
681 [PARISC] cr16 653 [PARISC] cr16
682 [S390] tod 654 [S390] tod
683 [SH] SuperH 655 [SH] SuperH
684 [SPARC64] tick 656 [SPARC64] tick
685 [X86-64] hpet,tsc 657 [X86-64] hpet,tsc
686 658
687 clocksource.arm_arch_timer.evtstrm= 659 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 660 [ARM,ARM64]
689 Format: <bool> 661 Format: <bool>
690 Enable/disable the eve 662 Enable/disable the eventstream feature of the ARM
691 architected timer so t 663 architected timer so that code using WFE-based polling
692 loops can be debugged 664 loops can be debugged more effectively on production
693 systems. 665 systems.
694 666
>> 667 clocksource.max_cswd_read_retries= [KNL]
>> 668 Number of clocksource_watchdog() retries due to
>> 669 external delays before the clock will be marked
>> 670 unstable. Defaults to two retries, that is,
>> 671 three attempts to read the clock under test.
>> 672
695 clocksource.verify_n_cpus= [KNL] 673 clocksource.verify_n_cpus= [KNL]
696 Limit the number of CP 674 Limit the number of CPUs checked for clocksources
697 marked with CLOCK_SOUR 675 marked with CLOCK_SOURCE_VERIFY_PERCPU that
698 are marked unstable du 676 are marked unstable due to excessive skew.
699 A negative value says 677 A negative value says to check all CPUs, while
700 zero says not to check 678 zero says not to check any. Values larger than
701 nr_cpu_ids are silentl 679 nr_cpu_ids are silently truncated to nr_cpu_ids.
702 The actual CPUs are ch 680 The actual CPUs are chosen randomly, with
703 no replacement if the 681 no replacement if the same CPU is chosen twice.
704 682
705 clocksource-wdtest.holdoff= [KNL] 683 clocksource-wdtest.holdoff= [KNL]
706 Set the time in second 684 Set the time in seconds that the clocksource
707 watchdog test waits be 685 watchdog test waits before commencing its tests.
708 Defaults to zero when 686 Defaults to zero when built as a module and to
709 10 seconds when built 687 10 seconds when built into the kernel.
710 688
711 cma=nn[MG]@[start[MG][-end[MG]]] 689 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 690 [KNL,CMA]
713 Sets the size of kerne 691 Sets the size of kernel global memory area for
714 contiguous memory allo 692 contiguous memory allocations and optionally the
715 placement constraint b 693 placement constraint by the physical address range of
716 memory allocations. A 694 memory allocations. A value of 0 disables CMA
717 altogether. For more i 695 altogether. For more information, see
718 kernel/dma/contiguous. 696 kernel/dma/contiguous.c
719 697
720 cma_pernuma=nn[MG] 698 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 699 [ARM64,KNL,CMA]
722 Sets the size of kerne 700 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 701 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 702 per-numa CMA altogether. And If this option is not
725 specified, the default 703 specified, the default value is 0.
726 With per-numa CMA enab 704 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 705 first try to allocate buffer from the pernuma area
728 which is located in no 706 which is located in node nid, if the allocation fails,
729 they will fallback to 707 they will fallback to the global default memory area.
730 708
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 | 709 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 710 Specify whether pages are marked as being inactive
744 when they are freed. 711 when they are freed. This is used in CMO environments
745 to determine OS memory 712 to determine OS memory pressure for page stealing by
746 a hypervisor. 713 a hypervisor.
747 Default: yes 714 Default: yes
748 715
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 716 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 717 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 718 allocations, by default set to 256K.
752 719
753 com20020= [HW,NET] ARCnet - COM2 720 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 721 Format:
755 <io>[,<irq>[,<nodeID>[ 722 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 723
757 com90io= [HW,NET] ARCnet - COM9 724 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 725 Format: <io>[,<irq>]
759 726
760 com90xx= [HW,NET] 727 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 728 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 729 Format: <io>[,<irq>[,<memstart>]]
763 730
764 condev= [HW,S390] console devi 731 condev= [HW,S390] console device
765 conmode= 732 conmode=
766 733
767 con3215_drop= [S390,EARLY] 3215 cons !! 734 con3215_drop= [S390] 3215 console drop mode.
768 Format: y|n|Y|N|1|0 735 Format: y|n|Y|N|1|0
769 When set to true, drop 736 When set to true, drop data on the 3215 console when
770 the console buffer is 737 the console buffer is full. In this case the
771 operator using a 3270 738 operator using a 3270 terminal emulator (for example
772 x3270) does not have t 739 x3270) does not have to enter the clear key for the
773 console output to adva 740 console output to advance and the kernel to continue.
774 This leads to a much f 741 This leads to a much faster boot time when a 3270
775 terminal emulator is a 742 terminal emulator is active. If no 3270 terminal
776 emulator is used, this 743 emulator is used, this parameter has no effect.
777 744
778 console= [KNL] Output console d 745 console= [KNL] Output console device and options.
779 746
780 tty<n> Use the virtual consol 747 tty<n> Use the virtual console device <n>.
781 748
782 ttyS<n>[,options] 749 ttyS<n>[,options]
783 ttyUSB0[,options] 750 ttyUSB0[,options]
784 Use the specified seri 751 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 752 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 753 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 754 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 755 omit it). Default is "9600n8".
789 756
790 See Documentation/admi 757 See Documentation/admin-guide/serial-console.rst for more
791 information. See 758 information. See
792 Documentation/networki 759 Documentation/networking/netconsole.rst for an
793 alternative. 760 alternative.
794 761
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] 762 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 763 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 764 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 765 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 766 uart[8250],0x<addr>[,options]
819 Start an early, polled 767 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 768 UART at the specified I/O port or MMIO address,
821 switching to the match 769 switching to the matching ttyS device later.
822 MMIO inter-register ad 770 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 771 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 772 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 773 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 774 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 775 the h/w is not re-initialized.
828 776
829 hvc<n> Use the hypervisor con 777 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 778 both Xen and PowerPC hypervisors.
831 779
832 { null | "" } 780 { null | "" }
833 Use to disable console 781 Use to disable console output, i.e., to have kernel
834 console messages disca 782 console messages discarded.
835 This must be the only 783 This must be the only console= parameter used on the
836 kernel command line. 784 kernel command line.
837 785
838 If the device connected to the 786 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 787 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 788 console=brl,ttyS0
841 For now, only VisioBraille is 789 For now, only VisioBraille is supported.
842 790
843 console_msg_format= 791 console_msg_format=
844 [KNL] Change console m 792 [KNL] Change console messages format
845 default 793 default
846 By default we print me 794 By default we print messages on consoles in
847 "[time stamp] text\n" 795 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 796 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 797 `printk_time' param).
850 syslog 798 syslog
851 Switch to syslog forma 799 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 800 IOW, each message will have a facility and loglevel
853 prefix. The format is 801 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 802 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 803 from /proc/kmsg.
856 804
857 consoleblank= [KNL] The console blan 805 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 806 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 807 Defaults to 0.
860 808
861 coredump_filter= 809 coredump_filter=
862 [KNL] Change the defau 810 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 811 /proc/<pid>/coredump_filter.
864 See also Documentation 812 See also Documentation/filesystems/proc.rst.
865 813
866 coresight_cpu_debug.enable 814 coresight_cpu_debug.enable
867 [ARM,ARM64] 815 [ARM,ARM64]
868 Format: <bool> 816 Format: <bool>
869 Enable/disable the CPU 817 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 818 0: default value, disable debugging
871 1: enable debugging at 819 1: enable debugging at boot time
872 820
873 cpcihp_generic= [HW,PCI] Generic port 821 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
874 Format: 822 Format:
875 <first_slot>,<last_slo 823 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
876 824
877 cpuidle.off=1 [CPU_IDLE] 825 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 826 disable the cpuidle sub-system
879 827
880 cpuidle.governor= 828 cpuidle.governor=
881 [CPU_IDLE] Name of the 829 [CPU_IDLE] Name of the cpuidle governor to use.
882 830
883 cpufreq.off=1 [CPU_FREQ] 831 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 832 disable the cpufreq sub-system
885 833
886 cpufreq.default_governor= 834 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 835 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 836 policy to use. This governor must be registered in the
889 kernel before the cpuf 837 kernel before the cpufreq driver probes.
890 838
891 cpu_init_udelay=N 839 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 840 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 841 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 842 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 843 Default: 10000
896 844
897 cpuhp.parallel= 845 cpuhp.parallel=
898 [SMP] Enable/disable p 846 [SMP] Enable/disable parallel bringup of secondary CPUs
899 Format: <bool> 847 Format: <bool>
900 Default is enabled if 848 Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
901 the parameter has no e 849 the parameter has no effect.
902 850
903 crash_kexec_post_notifiers 851 crash_kexec_post_notifiers
904 Run kdump after runnin 852 Run kdump after running panic-notifiers and dumping
905 kmsg. This only for th 853 kmsg. This only for the users who doubt kdump always
906 succeeds in any situat 854 succeeds in any situation.
907 Note that this also in 855 Note that this also increases risks of kdump failure,
908 because some panic not 856 because some panic notifiers can make the crashed
909 kernel more unstable. 857 kernel more unstable.
910 858
911 crashkernel=size[KMG][@offset[KMG]] 859 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 860 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 861 upon panic. This parameter reserves the physical
914 memory region [offset, 862 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 863 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 864 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 865 [KNL, X86-64, ARM64] Select a region under 4G first, and
918 under 4G first, and fa !! 866 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 867 hasn't been specified.
920 See Documentation/admi 868 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 869
922 crashkernel=range1:size1[,range2:size2 870 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 871 [KNL] Same as above, but depends on the memory
924 in the running system. 872 in the running system. The syntax of range is
925 start-[end] where star 873 start-[end] where start and end are both
926 a memory unit (amount[ 874 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 875 Documentation/admin-guide/kdump/kdump.rst for an example.
928 876
929 crashkernel=size[KMG],high 877 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 878 [KNL, X86-64, ARM64] range could be above 4G. Allow kernel
931 above 4G. !! 879 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 880 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 881 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 882 available.
935 below 4G, if available <<
936 It will be ignored if 883 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 884 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 885 [KNL, X86-64, ARM64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 886 is passed, kernel could allocate physical memory region
940 physical memory region !! 887 above 4G, that cause second kernel crash on system
941 crash on system that r !! 888 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 889 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 890 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 891 devices won't run out. Kernel would try to allocate
945 default size of memory 892 default size of memory below 4G automatically. The default
946 size is platform depen 893 size is platform dependent.
947 --> x86: max(swiotlb 894 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
948 --> arm64: 128MiB 895 --> arm64: 128MiB
949 --> riscv: 128MiB <<
950 --> loongarch: 128Mi <<
951 This one lets the user 896 This one lets the user specify own low range under 4G
952 for second kernel inst 897 for second kernel instead.
953 0: to disable low allo 898 0: to disable low allocation.
954 It will be ignored whe 899 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 900 or memory reserved is below 4G.
956 901
957 cryptomgr.notests 902 cryptomgr.notests
958 [KNL] Disable crypto s 903 [KNL] Disable crypto self-tests
959 904
960 cs89x0_dma= [HW,NET] 905 cs89x0_dma= [HW,NET]
961 Format: <dma> 906 Format: <dma>
962 907
963 cs89x0_media= [HW,NET] 908 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 909 Format: { rj45 | aui | bnc }
965 910
966 csdlock_debug= [KNL] Enable or disabl 911 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
967 function call handling 912 function call handling. When switched on,
968 additional debug data 913 additional debug data is printed to the console
969 in case a hanging CPU 914 in case a hanging CPU is detected, and that
970 CPU is pinged again in 915 CPU is pinged again in order to try to resolve
971 the hang situation. T 916 the hang situation. The default value of this
972 option depends on the 917 option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
973 Kconfig option. 918 Kconfig option.
974 919
975 dasd= [HW,NET] 920 dasd= [HW,NET]
976 See header of drivers/ 921 See header of drivers/s390/block/dasd_devmap.c.
977 922
978 db9.dev[2|3]= [HW,JOY] Multisystem j 923 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 924 (one device per port)
980 Format: <port#>,<type> 925 Format: <port#>,<type>
981 See also Documentation 926 See also Documentation/input/devices/joystick-parport.rst
982 927
983 debug [KNL,EARLY] Enable ker !! 928 debug [KNL] Enable kernel debugging (events log level).
984 929
985 debug_boot_weak_hash 930 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 931 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 932 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 933 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 934 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 935 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 936 insecure, please do not use on production kernels.
992 937
993 debug_locks_verbose= 938 debug_locks_verbose=
994 [KNL] verbose locking 939 [KNL] verbose locking self-tests
995 Format: <int> 940 Format: <int>
996 Print debugging info w 941 Print debugging info while doing the locking API
997 self-tests. 942 self-tests.
998 Bitmask for the variou 943 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 944 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 945 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 946 useful to lockdep developers.
1002 947
1003 debug_objects [KNL,EARLY] Enable ob !! 948 debug_objects [KNL] Enable object debugging
1004 949
1005 debug_guardpage_minorder= 950 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 951 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 952 parameter allows control of the order of pages that will
1008 be intentionally kept 953 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 954 buddy allocator. Bigger value increase the probability
1010 of catching random me 955 of catching random memory corruption, but reduce the
1011 amount of memory for 956 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 957 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 958 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 959 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 960 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 961 random memory location. Note that there exists a class
1017 a class of memory cor !! 962 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 963 F/W or by drivers badly programming DMA (basically when
1019 (basically when memor !! 964 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 965 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 966 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 967 tracking down these problems.
1023 968
1024 debug_pagealloc= 969 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 970 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 971 enables the feature at boot time. By default, it is
1027 disabled and the syst 972 disabled and the system will work mostly the same as a
1028 kernel built without 973 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 974 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 975 useful to also enable the page_owner functionality.
1031 on: enable the featur 976 on: enable the feature
1032 977
1033 debugfs= [KNL,EARLY] This para !! 978 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 979 and debugfs internal clients.
1035 Format: { on, no-moun 980 Format: { on, no-mount, off }
1036 on: All functions 981 on: All functions are enabled.
1037 no-mount: 982 no-mount:
1038 Filesystem is 983 Filesystem is not registered but kernel clients can
1039 access APIs a 984 access APIs and a crashkernel can be used to read
1040 its content. 985 its content. There is nothing to mount.
1041 off: Filesystem is 986 off: Filesystem is not registered and clients
1042 get a -EPERM 987 get a -EPERM as result when trying to register files
1043 or directorie 988 or directories within debugfs.
1044 This is equiv 989 This is equivalent of the runtime functionality if
1045 debugfs was n 990 debugfs was not enabled in the kernel at all.
1046 Default value is set 991 Default value is set in build-time with a kernel configuration.
1047 992
1048 debugpat [X86] Enable PAT debu 993 debugpat [X86] Enable PAT debugging
1049 994
1050 default_hugepagesz= 995 default_hugepagesz=
1051 [HW] The size of the 996 [HW] The size of the default HugeTLB page. This is
1052 the size represented 997 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 998 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 999 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 1000 filesystems. If not specified, defaults to the
1056 architecture's defaul 1001 architecture's default huge page size. Huge page
1057 sizes are architectur 1002 sizes are architecture dependent. See also
1058 Documentation/admin-g 1003 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 1004 Format: size[KMG]
1060 1005
1061 deferred_probe_timeout= 1006 deferred_probe_timeout=
1062 [KNL] Debugging optio 1007 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 1008 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 1009 probe. Only specific dependencies (subsystems or
1065 drivers) that have op 1010 drivers) that have opted in will be ignored. A timeout
1066 of 0 will timeout at 1011 of 0 will timeout at the end of initcalls. If the time
1067 out hasn't expired, i 1012 out hasn't expired, it'll be restarted by each
1068 successful driver reg 1013 successful driver registration. This option will also
1069 dump out devices stil 1014 dump out devices still on the deferred probe list after
1070 retrying. 1015 retrying.
1071 1016
1072 delayacct [KNL] Enable per-task 1017 delayacct [KNL] Enable per-task delay accounting
1073 1018
1074 dell_smm_hwmon.ignore_dmi= 1019 dell_smm_hwmon.ignore_dmi=
1075 [HW] Continue probing 1020 [HW] Continue probing hardware even if DMI data
1076 indicates that the dr 1021 indicates that the driver is running on unsupported
1077 hardware. 1022 hardware.
1078 1023
1079 dell_smm_hwmon.force= 1024 dell_smm_hwmon.force=
1080 [HW] Activate driver 1025 [HW] Activate driver even if SMM BIOS signature does
1081 not match list of sup 1026 not match list of supported models and enable otherwise
1082 blacklisted features. 1027 blacklisted features.
1083 1028
1084 dell_smm_hwmon.power_status= 1029 dell_smm_hwmon.power_status=
1085 [HW] Report power sta 1030 [HW] Report power status in /proc/i8k
1086 (disabled by default) 1031 (disabled by default).
1087 1032
1088 dell_smm_hwmon.restricted= 1033 dell_smm_hwmon.restricted=
1089 [HW] Allow controllin 1034 [HW] Allow controlling fans only if SYS_ADMIN
1090 capability is set. 1035 capability is set.
1091 1036
1092 dell_smm_hwmon.fan_mult= 1037 dell_smm_hwmon.fan_mult=
1093 [HW] Factor to multip 1038 [HW] Factor to multiply fan speed with.
1094 1039
1095 dell_smm_hwmon.fan_max= 1040 dell_smm_hwmon.fan_max=
1096 [HW] Maximum configur 1041 [HW] Maximum configurable fan speed.
1097 1042
1098 dfltcc= [HW,S390] 1043 dfltcc= [HW,S390]
1099 Format: { on | off | 1044 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 1045 on: s390 zlib hardware support for compression on
1101 level 1 and 1046 level 1 and decompression (default)
1102 off: No s390 zli 1047 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 1048 def_only: s390 zlib hardware support for deflate
1104 only (compr 1049 only (compression on level 1)
1105 inf_only: s390 zlib h 1050 inf_only: s390 zlib hardware support for inflate
1106 only (decom 1051 only (decompression)
1107 always: Same as 'on 1052 always: Same as 'on' but ignores the selected compression
1108 level alway 1053 level always using hardware support (used for debugging)
1109 1054
1110 dhash_entries= [KNL] 1055 dhash_entries= [KNL]
1111 Set number of hash bu 1056 Set number of hash buckets for dentry cache.
1112 1057
1113 disable_1tb_segments [PPC,EARLY] !! 1058 disable_1tb_segments [PPC]
1114 Disables the use of 1 1059 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 1060 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 1061 can be useful when debugging issues that require an SLB
1117 miss to occur. 1062 miss to occur.
1118 1063
1119 disable= [IPV6] 1064 disable= [IPV6]
1120 See Documentation/net 1065 See Documentation/networking/ipv6.rst.
1121 1066
1122 disable_radix [PPC,EARLY] !! 1067 disable_radix [PPC]
1123 Disable RADIX MMU mod 1068 Disable RADIX MMU mode on POWER9
1124 1069
1125 disable_tlbie [PPC] 1070 disable_tlbie [PPC]
1126 Disable TLBIE instruc 1071 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 1072 with KVM, with HASH MMU, or with coherent accelerators.
1128 1073
1129 disable_ddw [PPC/PSERIES,EARLY] !! 1074 disable_cpu_apicid= [X86,APIC,SMP]
>> 1075 Format: <int>
>> 1076 The number of initial APIC ID for the
>> 1077 corresponding CPU to be disabled at boot,
>> 1078 mostly used for the kdump 2nd kernel to
>> 1079 disable BSP to wake up multiple CPUs without
>> 1080 causing system reset or hang due to sending
>> 1081 INIT from AP to BSP.
>> 1082
>> 1083 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 1084 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 1085 to workaround buggy firmware.
1132 1086
1133 disable_ipv6= [IPV6] 1087 disable_ipv6= [IPV6]
1134 See Documentation/net 1088 See Documentation/networking/ipv6.rst.
1135 1089
1136 disable_mtrr_cleanup [X86,EARLY] !! 1090 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 1091 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 1092 to discrete, to make X server driver able to add WB
1139 entry later. This par 1093 entry later. This parameter disables that.
1140 1094
1141 disable_mtrr_trim [X86, Intel and AMD !! 1095 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 1096 By default the kernel will trim any uncacheable
1143 memory out of your av 1097 memory out of your available memory pool based on
1144 MTRR settings. This 1098 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 1099 possibly causing your machine to run very slowly.
1146 1100
1147 disable_timer_pin_1 [X86,EARLY] !! 1101 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 1102 Disable PIN 1 of APIC timer
1149 Can be useful to work 1103 Can be useful to work around chipset bugs.
1150 1104
1151 dis_ucode_ldr [X86] Disable the mic 1105 dis_ucode_ldr [X86] Disable the microcode loader.
1152 1106
1153 dma_debug=off If the kernel is comp 1107 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 1108 this option disables the debugging code at boot.
1155 1109
1156 dma_debug_entries=<number> 1110 dma_debug_entries=<number>
1157 This option allows to 1111 This option allows to tune the number of preallocated
1158 entries for DMA-API d 1112 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 1113 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 1114 DMA-API debugging code disables itself because the
1161 architectural default 1115 architectural default is too low.
1162 1116
1163 dma_debug_driver=<driver_name> 1117 dma_debug_driver=<driver_name>
1164 With this option the 1118 With this option the DMA-API debugging driver
1165 filter feature can be 1119 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1120 pass the driver to filter for as the parameter.
1167 The filter can be dis 1121 The filter can be disabled or changed to another
1168 driver later using sy 1122 driver later using sysfs.
1169 1123
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] 1124 driver_async_probe= [KNL]
1191 List of driver names 1125 List of driver names to be probed asynchronously. *
1192 matches with all driv 1126 matches with all driver names. If * is specified, the
1193 rest of the listed dr 1127 rest of the listed driver names are those that will NOT
1194 match the *. 1128 match the *.
1195 Format: <driver_name1 1129 Format: <driver_name1>,<driver_name2>...
1196 1130
1197 drm.edid_firmware=[<connector>:]<file 1131 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1132 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1133 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1134 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1135 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1136 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1137 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1138 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1139 and no file with the same name exists. Details and
>> 1140 instructions how to build your own EDID data are
>> 1141 available in Documentation/admin-guide/edid.rst. An EDID
>> 1142 data set will only be used for a particular connector,
>> 1143 if its name and a colon are prepended to the EDID
>> 1144 name. Each connector may use a unique EDID data
>> 1145 set by separating the files with a comma. An EDID
1206 data set with no conn 1146 data set with no connector name will be used for
1207 any connectors not ex 1147 any connectors not explicitly specified.
1208 1148
1209 dscc4.setup= [NET] 1149 dscc4.setup= [NET]
1210 1150
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1151 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1152 Format: {"off" | "known"}
1213 Control how the dt_cp 1153 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1154 used for CPU feature discovery and setup (if it
1215 exists). 1155 exists).
1216 off: Do not use it, f 1156 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1157 known: Do not pass through unknown features to guests
1218 or userspace, only th 1158 or userspace, only those that the kernel is aware of.
1219 1159
1220 dump_apple_properties [X86] 1160 dump_apple_properties [X86]
1221 Dump name and content 1161 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1162 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1163 what data is available or for reverse-engineering.
1224 1164
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1165 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1166 <module>.dyndbg[="val"]
1227 Enable debug messages 1167 Enable debug messages at boot time. See
1228 Documentation/admin-g 1168 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1169 for details.
1230 1170
1231 early_ioremap_debug [KNL,EARLY] !! 1171 early_ioremap_debug [KNL]
1232 Enable debug messages 1172 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1173 is useful for tracking down temporary early mappings
1234 which are not unmappe 1174 which are not unmapped.
1235 1175
1236 earlycon= [KNL,EARLY] Output ea !! 1176 earlycon= [KNL] Output early console device and options.
1237 1177
1238 When used with no opt 1178 When used with no options, the early console is
1239 determined by stdout- 1179 determined by stdout-path property in device tree's
1240 chosen node or the AC 1180 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1181 the platform.
1242 1182
1243 cdns,<addr>[,options] 1183 cdns,<addr>[,options]
1244 Start an early, polle 1184 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1185 (xuartps) serial port at the specified address. Only
1246 supported option is b 1186 supported option is baud rate. If baud rate is not
1247 specified, the serial 1187 specified, the serial port must already be setup and
1248 configured. 1188 configured.
1249 1189
1250 uart[8250],io,<addr>[,options 1190 uart[8250],io,<addr>[,options[,uartclk]]
1251 uart[8250],mmio,<addr>[,optio 1191 uart[8250],mmio,<addr>[,options[,uartclk]]
1252 uart[8250],mmio32,<addr>[,opt 1192 uart[8250],mmio32,<addr>[,options[,uartclk]]
1253 uart[8250],mmio32be,<addr>[,o 1193 uart[8250],mmio32be,<addr>[,options[,uartclk]]
1254 uart[8250],0x<addr>[,options] 1194 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1195 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1196 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1197 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1198 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1199 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1200 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1201 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w 1202 unspecified, the h/w is not initialized. 'uartclk' is
1263 the uart clock freque 1203 the uart clock frequency; if unspecified, it is set
1264 to 'BASE_BAUD' * 16. 1204 to 'BASE_BAUD' * 16.
1265 1205
1266 pl011,<addr> 1206 pl011,<addr>
1267 pl011,mmio32,<addr> 1207 pl011,mmio32,<addr>
1268 Start an early, polle 1208 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1209 port at the specified address. The pl011 serial port
1270 must already be setup 1210 must already be setup and configured. Options are not
1271 yet supported. If 'm 1211 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1212 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1213 the device registers.
1274 1214
1275 liteuart,<addr> 1215 liteuart,<addr>
1276 Start an early consol 1216 Start an early console on a litex serial port at the
1277 specified address. Th 1217 specified address. The serial port must already be
1278 setup and configured. 1218 setup and configured. Options are not yet supported.
1279 1219
1280 meson,<addr> 1220 meson,<addr>
1281 Start an early, polle 1221 Start an early, polled-mode console on a meson serial
1282 port at the specified 1222 port at the specified address. The serial port must
1283 already be setup and 1223 already be setup and configured. Options are not yet
1284 supported. 1224 supported.
1285 1225
1286 msm_serial,<addr> 1226 msm_serial,<addr>
1287 Start an early, polle 1227 Start an early, polled-mode console on an msm serial
1288 port at the specified 1228 port at the specified address. The serial port
1289 must already be setup 1229 must already be setup and configured. Options are not
1290 yet supported. 1230 yet supported.
1291 1231
1292 msm_serial_dm,<addr> 1232 msm_serial_dm,<addr>
1293 Start an early, polle 1233 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1234 dm port at the specified address. The serial port
1295 must already be setup 1235 must already be setup and configured. Options are not
1296 yet supported. 1236 yet supported.
1297 1237
1298 owl,<addr> 1238 owl,<addr>
1299 Start an early, polle 1239 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1240 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1241 specified address. The serial port must already be
1302 setup and configured. 1242 setup and configured. Options are not yet supported.
1303 1243
1304 rda,<addr> 1244 rda,<addr>
1305 Start an early, polle 1245 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1246 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1247 specified address. The serial port must already be
1308 setup and configured. 1248 setup and configured. Options are not yet supported.
1309 1249
1310 sbi 1250 sbi
1311 Use RISC-V SBI (Super 1251 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1252 console.
1313 1253
1314 smh Use ARM semihosting c 1254 smh Use ARM semihosting calls for early console.
1315 1255
1316 s3c2410,<addr> 1256 s3c2410,<addr>
1317 s3c2412,<addr> 1257 s3c2412,<addr>
1318 s3c2440,<addr> 1258 s3c2440,<addr>
1319 s3c6400,<addr> 1259 s3c6400,<addr>
1320 s5pv210,<addr> 1260 s5pv210,<addr>
1321 exynos4210,<addr> 1261 exynos4210,<addr>
1322 Use early console pro 1262 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1263 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1264 a correct base address of the selected UART port. The
1325 serial port must alre 1265 serial port must already be setup and configured.
1326 Options are not yet s 1266 Options are not yet supported.
1327 1267
1328 lantiq,<addr> 1268 lantiq,<addr>
1329 Start an early, polle 1269 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1270 (lqasc) port at the specified address. The serial port
1331 must already be setup 1271 must already be setup and configured. Options are not
1332 yet supported. 1272 yet supported.
1333 1273
1334 lpuart,<addr> 1274 lpuart,<addr>
1335 lpuart32,<addr> 1275 lpuart32,<addr>
1336 Use early console pro 1276 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1277 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1278 A valid base address must be provided, and the serial
1339 port must already be 1279 port must already be setup and configured.
1340 1280
1341 ec_imx21,<addr> 1281 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1282 ec_imx6q,<addr>
1343 Start an early, polle 1283 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1284 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1285 must already be setup and configured.
1346 1286
1347 ar3700_uart,<addr> 1287 ar3700_uart,<addr>
1348 Start an early, polle 1288 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1289 Armada 3700 serial port at the specified
1350 address. The serial p 1290 address. The serial port must already be setup
1351 and configured. Optio 1291 and configured. Options are not yet supported.
1352 1292
1353 qcom_geni,<addr> 1293 qcom_geni,<addr>
1354 Start an early, polle 1294 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1295 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1296 specified address. The serial port must already be
1357 setup and configured. 1297 setup and configured. Options are not yet supported.
1358 1298
1359 efifb,[options] 1299 efifb,[options]
1360 Start an early, unacc 1300 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1301 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1302 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1303 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1304 mapped with the correct attributes.
1365 1305
1366 linflex,<addr> 1306 linflex,<addr>
1367 Use early console pro 1307 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1308 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1309 address must be provided, and the serial port must
1370 already be setup and 1310 already be setup and configured.
1371 1311
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1312 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1313 earlyprintk=vga
1374 earlyprintk=sclp 1314 earlyprintk=sclp
1375 earlyprintk=xen 1315 earlyprintk=xen
1376 earlyprintk=serial[,t 1316 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1317 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1318 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1319 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1320 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1321 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1322
1384 earlyprintk is useful 1323 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1324 the normal console is initialized. It is not enabled by
1386 default because it ha 1325 default because it has some cosmetic problems.
1387 1326
1388 Append ",keep" to not 1327 Append ",keep" to not disable it when the real console
1389 takes over. 1328 takes over.
1390 1329
1391 Only one of vga, seri 1330 Only one of vga, serial, or usb debug port can
1392 be used at a time. 1331 be used at a time.
1393 1332
1394 Currently only ttyS0 1333 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1334 name. Other I/O ports may be explicitly specified
1396 on some architectures 1335 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1336 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1337 earlyprintk=serial,0x1008,115200
1399 You can find the port 1338 You can find the port for a given device in
1400 /proc/tty/driver/seri 1339 /proc/tty/driver/serial:
1401 2: uart:ST166 1340 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1341
1403 Interaction with the 1342 Interaction with the standard serial driver is not
1404 very good. 1343 very good.
1405 1344
1406 The VGA output is eve 1345 The VGA output is eventually overwritten by
1407 the real console. 1346 the real console.
1408 1347
1409 The xen option can on 1348 The xen option can only be used in Xen domains.
1410 1349
1411 The sclp output can o 1350 The sclp output can only be used on s390.
1412 1351
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1352 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1353 PCI device even when its classcode is not of the
1417 UART class. 1354 UART class.
1418 1355
1419 edac_report= [HW,EDAC] Control how 1356 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1357 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1358 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1359 by other higher priority error reporting module.
1423 off: disable H/W even 1360 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1361 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1362 default: on.
1426 1363
1427 edd= [EDD] 1364 edd= [EDD]
1428 Format: {"off" | "on" 1365 Format: {"off" | "on" | "skip[mbr]"}
1429 1366
1430 efi= [EFI,EARLY] !! 1367 efi= [EFI]
1431 Format: { "debug", "d 1368 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1369 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1370 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1371 debug: enable misc debug output.
1435 disable_early_pci_dma 1372 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1373 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1374 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1375 boot stub, as chunking can cause problems with some
1439 firmware implementati 1376 firmware implementations.
1440 noruntime : disable E 1377 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1378 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1379 attribute may cause the kernel to reserve the
1443 memory range for a me 1380 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1381 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1382 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1383 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1384 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1385 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1386 on all PCI bridges while in the EFI boot stub
1450 1387
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1388 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1389 Using this parameter you can use more than 50% of
1453 your efi variable sto 1390 your efi variable storage. Use this parameter only if
1454 you are really sure t 1391 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1392 fulfills the spec otherwise your board may brick.
1456 1393
>> 1394 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1395 Add arbitrary attribute to specific memory range by
>> 1396 updating original EFI memory map.
>> 1397 Region of memory which aa attribute is added to is
>> 1398 from ss to ss+nn.
>> 1399
>> 1400 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1401 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1402 attribute is added to range 0x100000000-0x180000000 and
>> 1403 0x10a0000000-0x1120000000.
>> 1404
>> 1405 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1406 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1407 range 0x240000000-0x43fffffff.
>> 1408
>> 1409 Using this parameter you can do debugging of EFI memmap
>> 1410 related features. For example, you can do debugging of
>> 1411 Address Range Mirroring feature even if your box
>> 1412 doesn't support it, or mark specific memory as
>> 1413 "soft reserved".
>> 1414
1457 efivar_ssdt= [EFI; X86] Name of an 1415 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1416 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1417 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1418 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1419 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1420
1463 1421
1464 eisa_irq_edge= [PARISC,HW] 1422 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1423 See header of drivers/parisc/eisa.c.
1466 1424
1467 ekgdboc= [X86,KGDB,EARLY] Allo !! 1425 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1468 Format: ekgdboc=kbd 1426 Format: ekgdboc=kbd
1469 1427
1470 This is designed to b 1428 This is designed to be used in conjunction with
1471 the boot argument: ea 1429 the boot argument: earlyprintk=vga
1472 1430
1473 This parameter works 1431 This parameter works in place of the kgdboc parameter
1474 but can only be used 1432 but can only be used if the backing tty is available
1475 very early in the boo 1433 very early in the boot process. For early debugging
1476 via a serial port see 1434 via a serial port see kgdboc_earlycon instead.
1477 1435
1478 elanfreq= [X86-32] 1436 elanfreq= [X86-32]
1479 See comment before fu 1437 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1438 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1439
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1440 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1441 Specifies physical address of start of kernel core
1484 image elf header and 1442 image elf header and optionally the size. Generally
1485 kexec loader will pas 1443 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1444 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1445
1488 enable_mtrr_cleanup [X86,EARLY] !! 1446 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1447 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1448 to discrete, to make X server driver able to add WB
1491 entry later. This par 1449 entry later. This parameter enables that.
1492 1450
1493 enable_timer_pin_1 [X86] 1451 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1452 Enable PIN 1 of APIC timer
1495 Can be useful to work 1453 Can be useful to work around chipset bugs
1496 (in particular on som 1454 (in particular on some ATI chipsets).
1497 The kernel tries to s 1455 The kernel tries to set a reasonable default.
1498 1456
1499 enforcing= [SELINUX] Set initial 1457 enforcing= [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1458 Format: {"0" | "1"}
1501 See security/selinux/ 1459 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1460 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1461 1 -- enforcing (deny and log).
1504 Default value is 0. 1462 Default value is 0.
1505 Value can be changed 1463 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1464 /sys/fs/selinux/enforce.
1507 1465
1508 erst_disable [ACPI] 1466 erst_disable [ACPI]
1509 Disable Error Record 1467 Disable Error Record Serialization Table (ERST)
1510 support. 1468 support.
1511 1469
1512 ether= [HW,NET] Ethernet car 1470 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1471 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1472 has equivalent usage. See its documentation for details.
1515 1473
1516 evm= [EVM] 1474 evm= [EVM]
1517 Format: { "fix" } 1475 Format: { "fix" }
1518 Permit 'security.evm' 1476 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1477 current integrity status.
1520 1478
1521 early_page_ext [KNL,EARLY] Enforces p !! 1479 early_page_ext [KNL] Enforces page_ext initialization to earlier
1522 stages so cover more 1480 stages so cover more early boot allocations.
1523 Please note that as s 1481 Please note that as side effect some optimizations
1524 might be disabled to 1482 might be disabled to achieve that (e.g. parallelized
1525 memory initialization 1483 memory initialization is disabled) so the boot process
1526 might take longer, es 1484 might take longer, especially on systems with a lot of
1527 memory. Available wit 1485 memory. Available with CONFIG_PAGE_EXTENSION=y.
1528 1486
1529 failslab= 1487 failslab=
1530 fail_usercopy= 1488 fail_usercopy=
1531 fail_page_alloc= 1489 fail_page_alloc=
1532 fail_make_request=[KNL] 1490 fail_make_request=[KNL]
1533 General fault injecti 1491 General fault injection mechanism.
1534 Format: <interval>,<p 1492 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1493 See also Documentation/fault-injection/.
1536 1494
1537 fb_tunnels= [NET] 1495 fb_tunnels= [NET]
1538 Format: { initns | no 1496 Format: { initns | none }
1539 See Documentation/adm 1497 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1498 fb_tunnels_only_for_init_ns
1541 1499
1542 floppy= [HW] 1500 floppy= [HW]
1543 See Documentation/adm 1501 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1502
>> 1503 force_pal_cache_flush
>> 1504 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1505 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1506 parameter will force ia64_sal_cache_flush to call
>> 1507 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
>> 1508
1545 forcepae [X86-32] 1509 forcepae [X86-32]
1546 Forcefully enable Phy 1510 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1511 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1512 functionally usable PAE implementation.
1549 Warning: use of this 1513 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1514 and may cause unknown problems.
1551 1515
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] 1516 ftrace=[tracer]
1559 [FTRACE] will set and 1517 [FTRACE] will set and start the specified tracer
1560 as early as possible 1518 as early as possible in order to facilitate early
1561 boot debugging. 1519 boot debugging.
1562 1520
1563 ftrace_boot_snapshot 1521 ftrace_boot_snapshot
1564 [FTRACE] On boot up, 1522 [FTRACE] On boot up, a snapshot will be taken of the
1565 ftrace ring buffer th 1523 ftrace ring buffer that can be read at:
1566 /sys/kernel/tracing/s 1524 /sys/kernel/tracing/snapshot.
1567 This is useful if you 1525 This is useful if you need tracing information from kernel
1568 boot up that is likel 1526 boot up that is likely to be overridden by user space
1569 start up functionalit 1527 start up functionality.
1570 1528
1571 Optionally, the snaps 1529 Optionally, the snapshot can also be defined for a tracing
1572 instance that was cre 1530 instance that was created by the trace_instance= command
1573 line parameter. 1531 line parameter.
1574 1532
1575 trace_instance=foo,sc 1533 trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1576 1534
1577 The above will cause 1535 The above will cause the "foo" tracing instance to trigger
1578 a snapshot at the end 1536 a snapshot at the end of boot up.
1579 1537
1580 ftrace_dump_on_oops[=2(orig_cpu) | =< !! 1538 ftrace_dump_on_oops[=orig_cpu]
1581 ,<instance>=2(orig_ <<
1582 [FTRACE] will dump th 1539 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1540 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1541 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1542 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1543 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 1544
1603 ftrace_filter=[function-list] 1545 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1546 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1547 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1548 list of functions. This list can be changed at run
1607 time by the set_ftrac 1549 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1550 tracing directory.
1609 1551
1610 ftrace_notrace=[function-list] 1552 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1553 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1554 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1555 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1556 tracing directory.
1615 1557
1616 ftrace_graph_filter=[function-list] 1558 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1559 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1560 by the function graph tracer at boot up.
1619 function-list is a co 1561 function-list is a comma-separated list of functions
1620 that can be changed a 1562 that can be changed at run time by the
1621 set_graph_function fi 1563 set_graph_function file in the debugfs tracing directory.
1622 1564
1623 ftrace_graph_notrace=[function-list] 1565 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1566 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1567 function-list. This list is a comma-separated list of
1626 functions that can be 1568 functions that can be changed at run time by the
1627 set_graph_notrace fil 1569 set_graph_notrace file in the debugfs tracing directory.
1628 1570
1629 ftrace_graph_max_depth=<uint> 1571 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1572 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1573 the max depth it will trace into a function. This value
1632 can be changed at run 1574 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1575 in the tracefs tracing directory. default: 0 (no limit)
1634 1576
1635 fw_devlink= [KNL,EARLY] Create de !! 1577 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1578 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1579 consumer/supplier relationships. This feature is
1638 especially useful whe 1580 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1581 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1582 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1583 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1584 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1585 suppliers).
1644 Format: { off | permi 1586 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1587 off -- Don't create device links from firmware info.
1646 permissive -- Create 1588 permissive -- Create device links from firmware info
1647 but use it on 1589 but use it only for ordering boot state clean
1648 up (sync_stat 1590 up (sync_state() calls).
1649 on -- Create device 1591 on -- Create device links from firmware info and use it
1650 to enforce pr 1592 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1593 rpm -- Like "on", but also use to order runtime PM.
1652 1594
1653 fw_devlink.strict=<bool> 1595 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1596 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1597 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1598 Format: <bool>
1657 1599
1658 fw_devlink.sync_state = 1600 fw_devlink.sync_state =
1659 [KNL,EARLY] When all !! 1601 [KNL] When all devices that could probe have finished
1660 probing, this paramet 1602 probing, this parameter controls what to do with
1661 devices that haven't 1603 devices that haven't yet received their sync_state()
1662 calls. 1604 calls.
1663 Format: { strict | ti 1605 Format: { strict | timeout }
1664 strict -- Default. Co 1606 strict -- Default. Continue waiting on consumers to
1665 probe success 1607 probe successfully.
1666 timeout -- Give up wa 1608 timeout -- Give up waiting on consumers and call
1667 sync_state() 1609 sync_state() on any devices that haven't yet
1668 received thei 1610 received their sync_state() calls after
1669 deferred_prob 1611 deferred_probe_timeout has expired or by
1670 late_initcall 1612 late_initcall() if !CONFIG_MODULES.
1671 1613
1672 gamecon.map[2|3]= 1614 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1615 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1616 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1617 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1618 See also Documentation/input/devices/joystick-parport.rst
1677 1619
1678 gamma= [HW,DRM] 1620 gamma= [HW,DRM]
1679 1621
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1622 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1623 Format: off | on
1682 default: on 1624 default: on
1683 1625
1684 gather_data_sampling= 1626 gather_data_sampling=
1685 [X86,INTEL,EARLY] Con !! 1627 [X86,INTEL] Control the Gather Data Sampling (GDS)
1686 mitigation. 1628 mitigation.
1687 1629
1688 Gather Data Sampling 1630 Gather Data Sampling is a hardware vulnerability which
1689 allows unprivileged s 1631 allows unprivileged speculative access to data which was
1690 previously stored in 1632 previously stored in vector registers.
1691 1633
1692 This issue is mitigat 1634 This issue is mitigated by default in updated microcode.
1693 The mitigation may ha 1635 The mitigation may have a performance impact but can be
1694 disabled. On systems 1636 disabled. On systems without the microcode mitigation
1695 disabling AVX serves 1637 disabling AVX serves as a mitigation.
1696 1638
1697 force: Disable AVX t 1639 force: Disable AVX to mitigate systems without
1698 microcode mit 1640 microcode mitigation. No effect if the microcode
1699 mitigation is 1641 mitigation is present. Known to cause crashes in
1700 userspace wit 1642 userspace with buggy AVX enumeration.
1701 1643
1702 off: Disable GDS m 1644 off: Disable GDS mitigation.
1703 1645
1704 gcov_persist= [GCOV] When non-zero 1646 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1647 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1648 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1649 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1650 debugfs files are removed at module unload time.
1709 1651
1710 goldfish [X86] Enable the gold 1652 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1653 Don't use this when you are not running on the
1712 android emulator 1654 android emulator
1713 1655
1714 gpio-mockup.gpio_mockup_ranges 1656 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1657 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1658 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1659 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1660 [HW] Let the driver know GPIO lines should be named.
1719 1661
1720 gpt [EFI] Forces disk wit 1662 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1663 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1664 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1665 GPT to be used instead.
1724 1666
1725 grcan.enable0= [HW] Configuration of 1667 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1668 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1669 Format: 0 | 1
1728 Default: 0 1670 Default: 0
1729 grcan.enable1= [HW] Configuration of 1671 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1672 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1673 Format: 0 | 1
1732 Default: 0 1674 Default: 0
1733 grcan.select= [HW] Select which phy 1675 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1676 Format: 0 | 1
1735 Default: 0 1677 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1678 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1679 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1680 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1681 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1682 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1683 Default: 1024
1742 1684
1743 hardened_usercopy= 1685 hardened_usercopy=
1744 [KNL] Under CONFIG_HA 1686 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
1745 hardening is enabled 1687 hardening is enabled for this boot. Hardened
1746 usercopy checking is 1688 usercopy checking is used to protect the kernel
1747 from reading or writi 1689 from reading or writing beyond known memory
1748 allocation boundaries 1690 allocation boundaries as a proactive defense
1749 against bounds-checki 1691 against bounds-checking flaws in the kernel's
1750 copy_to_user()/copy_f 1692 copy_to_user()/copy_from_user() interface.
1751 on Perform hardened user 1693 on Perform hardened usercopy checks (default).
1752 off Disable hardened user 1694 off Disable hardened usercopy checks.
1753 1695
1754 hardlockup_all_cpu_backtrace= 1696 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1697 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1698 backtraces on all cpus.
1757 Format: 0 | 1 1699 Format: 0 | 1
1758 1700
1759 hashdist= [KNL,NUMA] Large hash 1701 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1702 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1703 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1704 Format: 0 | 1 (for off | on)
1763 1705
>> 1706 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1707
1764 hd= [EIDE] (E)IDE hard dr 1708 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1709 Format: <cyl>,<head>,<sect>
1766 1710
1767 hest_disable [ACPI] 1711 hest_disable [ACPI]
1768 Disable Hardware Erro 1712 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1713 corresponding firmware-first mode error processing
1770 logic will be disable 1714 logic will be disabled.
1771 1715
1772 hibernate= [HIBERNATION] 1716 hibernate= [HIBERNATION]
1773 noresume Don't check i 1717 noresume Don't check if there's a hibernation image
1774 present durin 1718 present during boot.
1775 nocompress Don't compres 1719 nocompress Don't compress/decompress hibernation images.
1776 no Disable hiber 1720 no Disable hibernation and resume.
1777 protect_image Turn on image 1721 protect_image Turn on image protection during restoration
1778 (that will se 1722 (that will set all pages holding image data
1779 during restor 1723 during restoration read-only).
1780 1724
1781 hibernate.compressor= [HIBERNATION] !! 1725 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 1726 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1727 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1728 size on bigger boxes.
1796 1729
1797 highres= [KNL] Enable/disable 1730 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1731 Valid parameters: "on", "off"
1799 Default: "on" 1732 Default: "on"
1800 1733
1801 hlt [BUGS=ARM,SH] 1734 hlt [BUGS=ARM,SH]
1802 1735
1803 hostname= [KNL,EARLY] Set the h !! 1736 hostname= [KNL] Set the hostname (aka UTS nodename).
1804 Format: <string> 1737 Format: <string>
1805 This allows setting t 1738 This allows setting the system's hostname during early
1806 startup. This sets th 1739 startup. This sets the name returned by gethostname.
1807 Using this parameter 1740 Using this parameter to set the hostname makes it
1808 possible to ensure th 1741 possible to ensure the hostname is correctly set before
1809 any userspace process 1742 any userspace processes run, avoiding the possibility
1810 that a process may ca 1743 that a process may call gethostname before the hostname
1811 has been explicitly s 1744 has been explicitly set, resulting in the calling
1812 process getting an in 1745 process getting an incorrect result. The string must
1813 not exceed the maximu 1746 not exceed the maximum allowed hostname length (usually
1814 64 characters) and wi 1747 64 characters) and will be truncated otherwise.
1815 1748
1816 hpet= [X86-32,HPET] option 1749 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1750 Format: { enable (default) | disable | force |
1818 verbose } 1751 verbose }
1819 disable: disable HPET 1752 disable: disable HPET and use PIT instead
1820 force: allow force en 1753 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1754 VIA, nVidia)
1822 verbose: show content 1755 verbose: show contents of HPET registers during setup
1823 1756
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1757 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1758 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1759
1827 hugepages= [HW] Number of HugeTL 1760 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1761 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1762 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1763 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1764 line, it specifies the number of pages to allocate for
1832 the default huge page 1765 the default huge page size. If using node format, the
1833 number of pages to al 1766 number of pages to allocate per-node can be specified.
1834 See also Documentatio 1767 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1835 Format: <integer> or 1768 Format: <integer> or (node format)
1836 <node>:<integ 1769 <node>:<integer>[,<node>:<integer>]
1837 1770
1838 hugepagesz= 1771 hugepagesz=
1839 [HW] The size of the 1772 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1773 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1774 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1775 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1776 each supported huge page size. Huge page sizes are
1844 architecture dependen 1777 architecture dependent. See also
1845 Documentation/admin-g 1778 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1779 Format: size[KMG]
1847 1780
1848 hugetlb_cma= [HW,CMA,EARLY] The si !! 1781 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
1849 of gigantic hugepages 1782 of gigantic hugepages. Or using node format, the size
1850 of a CMA area per nod 1783 of a CMA area per node can be specified.
1851 Format: nn[KMGTPE] or 1784 Format: nn[KMGTPE] or (node format)
1852 <node>:nn[KMG 1785 <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1853 1786
1854 Reserve a CMA area of 1787 Reserve a CMA area of given size and allocate gigantic
1855 hugepages using the C 1788 hugepages using the CMA allocator. If enabled, the
1856 boot-time allocation 1789 boot-time allocation of gigantic hugepages is skipped.
1857 1790
1858 hugetlb_free_vmemmap= 1791 hugetlb_free_vmemmap=
1859 [KNL] Requires CONFIG 1792 [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1860 enabled. 1793 enabled.
1861 Control if HugeTLB Vm 1794 Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1862 Allows heavy hugetlb 1795 Allows heavy hugetlb users to free up some more
1863 memory (7 * PAGE_SIZE 1796 memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1864 Format: { on | off (d 1797 Format: { on | off (default) }
1865 1798
1866 on: enable HVO 1799 on: enable HVO
1867 off: disable HVO 1800 off: disable HVO
1868 1801
1869 Built with CONFIG_HUG 1802 Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1870 the default is on. 1803 the default is on.
1871 1804
1872 Note that the vmemmap 1805 Note that the vmemmap pages may be allocated from the added
1873 memory block itself w 1806 memory block itself when memory_hotplug.memmap_on_memory is
1874 enabled, those vmemma 1807 enabled, those vmemmap pages cannot be optimized even if this
1875 feature is enabled. 1808 feature is enabled. Other vmemmap pages not allocated from
1876 the added memory bloc 1809 the added memory block itself do not be affected.
1877 1810
1878 hung_task_panic= 1811 hung_task_panic=
1879 [KNL] Should the hung 1812 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1813 Format: 0 | 1
1881 1814
1882 A value of 1 instruct 1815 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1816 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1817 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1818 option. The value selected by this boot parameter can
1886 be changed later by t 1819 be changed later by the kernel.hung_task_panic sysctl.
1887 1820
1888 hvc_iucv= [S390] Number of z/V 1821 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1822 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1823 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1824 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1825 from listed z/VM user IDs only.
1893 1826
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1827 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1828 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1829 guest on lock contention.
1897 on lock contention. <<
1898 1830
1899 i2c_bus= [HW] Override the 1831 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1832 or register an additional I2C bus that is not
1901 registered fr 1833 registered from board initialization code.
1902 Format: 1834 Format:
1903 <bus_id>,<clk 1835 <bus_id>,<clkrate>
1904 1836
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 1837 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1838 i8042.unmask_kbd_data
1929 [HW] Enable printing 1839 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1840 (disabled by default, and as a pre-condition
1931 requires that i8 1841 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1842 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1843 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1844 keyboard and cannot control its state
1935 (Don't attempt t 1845 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1846 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1847 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1848 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1849 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1850 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1851 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1852 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1853 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1854 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1855 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1856 suspend-to-ram transitions, only during s2r
1947 transitions, or 1857 transitions, or never reset
1948 Format: { 1 | Y | y | 1858 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1859 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1860 0, N, n: don't ever reset controller
1951 Default: only on s2r 1861 Default: only on s2r transitions on x86; most other
1952 architectures force r 1862 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1863 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1864 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer 1865 i8042.probe_defer
1956 [HW] Allow deferred p 1866 [HW] Allow deferred probing upon i8042 probe errors
1957 1867
1958 i810= [HW,DRM] 1868 i810= [HW,DRM]
1959 1869
1960 i915.invert_brightness= 1870 i915.invert_brightness=
1961 [DRM] Invert the sens 1871 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1872 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1873 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1874 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1875 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1876 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1877 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1878 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1879 value switches the backlight off.
1970 -1 -- never invert br 1880 -1 -- never invert brightness
1971 0 -- machine default 1881 0 -- machine default
1972 1 -- force brightnes 1882 1 -- force brightness inversion
1973 1883
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] 1884 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1885 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1886
1983 1887
1984 idle= [X86,EARLY] !! 1888 idle= [X86]
1985 Format: idle=poll, id 1889 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1890 Poll forces a polling idle loop that can slightly
1987 improve the performan 1891 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1892 will use a lot of power and make the system run hot.
1989 Not recommended. 1893 Not recommended.
1990 idle=halt: Halt is fo 1894 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1895 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1896 idle=nomwait: Disable mwait for CPU C-states
1993 1897
1994 idxd.sva= [HW] 1898 idxd.sva= [HW]
1995 Format: <bool> 1899 Format: <bool>
1996 Allow force disabling 1900 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1901 support for the idxd driver. By default it is set to
1998 true (1). 1902 true (1).
1999 1903
2000 idxd.tc_override= [HW] 1904 idxd.tc_override= [HW]
2001 Format: <bool> 1905 Format: <bool>
2002 Allow override of def 1906 Allow override of default traffic class configuration
2003 for the device. By de 1907 for the device. By default it is set to false (0).
2004 1908
2005 ieee754= [MIPS] Select IEEE St 1909 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1910 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1911 Default: strict
2008 1912
2009 Choose which programs 1913 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1914 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1915 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1916 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1917 binary. Hardware implementations are permitted to
2014 support either or bot 1918 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1919 encoding mode.
2016 1920
2017 Available settings ar 1921 Available settings are as follows:
2018 strict accept binari 1922 strict accept binaries that request a NaN encoding
2019 supported by 1923 supported by the FPU
2020 legacy only accept l 1924 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1925 by the FPU
2022 2008 only accept 2 1926 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1927 by the FPU
2024 relaxed accept any bi 1928 relaxed accept any binaries regardless of whether
2025 supported by 1929 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1930
2029 The FPU emulator is a 1931 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1932 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1933 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1934 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1935 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1936 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1937 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1938 MIPS64 CPUs.
2037 1939
2038 The setting for ABS.f 1940 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1941 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1942 except where unsupported by hardware.
2041 1943
2042 ignore_loglevel [KNL,EARLY] !! 1944 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1945 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1946 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1947 We also add it as printk module parameter, so users
2046 could change it dynam 1948 could change it dynamically, usually by
2047 /sys/module/printk/pa 1949 /sys/module/printk/parameters/ignore_loglevel.
2048 1950
2049 ignore_rlimit_data 1951 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1952 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1953 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1954 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1955
2054 ihash_entries= [KNL] 1956 ihash_entries= [KNL]
2055 Set number of hash bu 1957 Set number of hash buckets for inode cache.
2056 1958
2057 ima_appraise= [IMA] appraise integr 1959 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1960 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1961 default: "enforce"
2060 1962
2061 ima_appraise_tcb [IMA] Deprecated. U 1963 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1964 The builtin appraise policy appraises all files
2063 owned by uid=0. 1965 owned by uid=0.
2064 1966
2065 ima_canonical_fmt [IMA] 1967 ima_canonical_fmt [IMA]
2066 Use the canonical for 1968 Use the canonical format for the binary runtime
2067 measurements, instead 1969 measurements, instead of host native format.
2068 1970
2069 ima_hash= [IMA] 1971 ima_hash= [IMA]
2070 Format: { md5 | sha1 1972 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1973 | sha512 | ... }
2072 default: "sha1" 1974 default: "sha1"
2073 1975
2074 The list of supported 1976 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1977 in crypto/hash_info.h.
2076 1978
2077 ima_policy= [IMA] 1979 ima_policy= [IMA]
2078 The builtin policies 1980 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1981 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 1982 fail_securely | critical_data"
2081 1983
2082 The "tcb" policy meas 1984 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1985 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1986 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1987 uid=0.
2086 1988
2087 The "appraise_tcb" po 1989 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1990 all files owned by root.
2089 1991
2090 The "secure_boot" pol 1992 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1993 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1994 firmware, policy, etc) based on file signatures.
2093 1995
2094 The "fail_securely" p 1996 The "fail_securely" policy forces file signature
2095 verification failure 1997 verification failure also on privileged mounted
2096 filesystems with the 1998 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1999 flag.
2098 2000
2099 The "critical_data" p 2001 The "critical_data" policy measures kernel integrity
2100 critical data. 2002 critical data.
2101 2003
2102 ima_tcb [IMA] Deprecated. Us 2004 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 2005 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 2006 Computing Base. This means IMA will measure all
2105 programs exec'd, file 2007 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 2008 opened for read by uid=0.
2107 2009
2108 ima_template= [IMA] 2010 ima_template= [IMA]
2109 Select one of defined 2011 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i 2012 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2111 "ima-sigv2 2013 "ima-sigv2" }
2112 Default: "ima-ng" 2014 Default: "ima-ng"
2113 2015
2114 ima_template_fmt= 2016 ima_template_fmt=
2115 [IMA] Define a custom 2017 [IMA] Define a custom template format.
2116 Format: { "field1|... 2018 Format: { "field1|...|fieldN" }
2117 2019
2118 ima.ahash_minsize= [IMA] Minimum file 2020 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 2021 Format: <min_file_size>
2120 Set the minimal file 2022 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 2023 If left unspecified, ahash usage is disabled.
2122 2024
2123 ahash performance var 2025 ahash performance varies for different data sizes on
2124 different crypto acce 2026 different crypto accelerators. This option can be used
2125 to achieve the best p 2027 to achieve the best performance for a particular HW.
2126 2028
2127 ima.ahash_bufsize= [IMA] Asynchronous 2029 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 2030 Format: <bufsize>
2129 Set hashing buffer si 2031 Set hashing buffer size. Default: 4k.
2130 2032
2131 ahash performance var 2033 ahash performance varies for different chunk sizes on
2132 different crypto acce 2034 different crypto accelerators. This option can be used
2133 to achieve best perfo 2035 to achieve best performance for particular HW.
2134 2036
2135 init= [KNL] 2037 init= [KNL]
2136 Format: <full_path> 2038 Format: <full_path>
2137 Run specified binary 2039 Run specified binary instead of /sbin/init as init
2138 process. 2040 process.
2139 2041
2140 initcall_debug [KNL] Trace initcalls 2042 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 2043 for working out where the kernel is dying during
2142 startup. 2044 startup.
2143 2045
2144 initcall_blacklist= [KNL] Do not exe 2046 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 2047 initcall functions. Useful for debugging built-in
2146 modules and initcalls 2048 modules and initcalls.
2147 2049
2148 initramfs_async= [KNL] 2050 initramfs_async= [KNL]
2149 Format: <bool> 2051 Format: <bool>
2150 Default: 1 2052 Default: 1
2151 This parameter contro 2053 This parameter controls whether the initramfs
2152 image is unpacked asy 2054 image is unpacked asynchronously, concurrently
2153 with devices being pr 2055 with devices being probed and
2154 initialized. This sho 2056 initialized. This should normally just work,
2155 but as a debugging ai 2057 but as a debugging aid, one can get the
2156 historical behaviour 2058 historical behaviour of the initramfs
2157 unpacking being compl 2059 unpacking being completed before device_ and
2158 late_ initcalls. 2060 late_ initcalls.
2159 2061
2160 initrd= [BOOT,EARLY] Specify !! 2062 initrd= [BOOT] Specify the location of the initial ramdisk
2161 2063
2162 initrdmem= [KNL,EARLY] Specify a !! 2064 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 2065 load the initrd. If an initrd is compiled in or
2164 specified in the boot 2066 specified in the bootparams, it takes priority over this
2165 setting. 2067 setting.
2166 Format: ss[KMG],nn[KM 2068 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 2069 Default is 0, 0
2168 2070
2169 init_on_alloc= [MM,EARLY] Fill newly !! 2071 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 2072 zeroes.
2171 Format: 0 | 1 2073 Format: 0 | 1
2172 Default set by CONFIG 2074 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 2075
2174 init_on_free= [MM,EARLY] Fill freed !! 2076 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 2077 Format: 0 | 1
2176 Default set by CONFIG 2078 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 2079
2178 init_pkru= [X86] Specify the def 2080 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 2081 register contents for all processes. 0x55555554 by
2180 default (disallow acc 2082 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 2083 override in debugfs after boot.
2182 2084
2183 inport.irq= [HW] Inport (ATI XL a 2085 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 2086 Format: <irq>
2185 2087
2186 int_pln_enable [X86] Enable power li 2088 int_pln_enable [X86] Enable power limit notification interrupt
2187 2089
2188 integrity_audit=[IMA] 2090 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 2091 Format: { "0" | "1" }
2190 0 -- basic integrity 2092 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 2093 1 -- additional integrity auditing messages.
2192 2094
2193 intel_iommu= [DMAR] Intel IOMMU dr 2095 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 2096 on
2195 Enable intel iommu dr 2097 Enable intel iommu driver.
2196 off 2098 off
2197 Disable intel iommu d 2099 Disable intel iommu driver.
2198 igfx_off [Default Off] 2100 igfx_off [Default Off]
2199 By default, gfx is ma 2101 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 2102 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 2103 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 2104 this case, gfx device will use physical address for
2203 DMA. 2105 DMA.
2204 strict [Default Off] 2106 strict [Default Off]
2205 Deprecated, equivalen 2107 Deprecated, equivalent to iommu.strict=1.
2206 sp_off [Default Off] 2108 sp_off [Default Off]
2207 By default, super pag 2109 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 2110 has the capability. With this option, super page will
2209 not be supported. 2111 not be supported.
2210 sm_on 2112 sm_on
2211 Enable the Intel IOMM 2113 Enable the Intel IOMMU scalable mode if the hardware
2212 advertises that it ha 2114 advertises that it has support for the scalable mode
2213 translation. 2115 translation.
2214 sm_off 2116 sm_off
2215 Disallow use of the I 2117 Disallow use of the Intel IOMMU scalable mode.
2216 tboot_noforce [Default Off] 2118 tboot_noforce [Default Off]
2217 Do not force the Inte 2119 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 2120 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 2121 could harm performance of some high-throughput
2220 devices like 40GBit n 2122 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 2123 mapping is enabled.
2222 Note that using this 2124 Note that using this option lowers the security
2223 provided by tboot bec 2125 provided by tboot because it makes the system
2224 vulnerable to DMA att 2126 vulnerable to DMA attacks.
2225 2127
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 2128 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 2129 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 2130 1 to 9 specify maximum depth of C-state.
2229 2131
2230 intel_pstate= [X86,EARLY] !! 2132 intel_pstate= [X86]
2231 disable 2133 disable
2232 Do not enable intel 2134 Do not enable intel_pstate as the default
2233 scaling driver for 2135 scaling driver for the supported processors
2234 active 2136 active
2235 Use intel_pstate dr 2137 Use intel_pstate driver to bypass the scaling
2236 governors layer of 2138 governors layer of cpufreq and provides it own
2237 algorithms for p-st 2139 algorithms for p-state selection. There are two
2238 P-state selection a 2140 P-state selection algorithms provided by
2239 intel_pstate in the 2141 intel_pstate in the active mode: powersave and
2240 performance. The w 2142 performance. The way they both operate depends
2241 on whether or not t 2143 on whether or not the hardware managed P-states
2242 (HWP) feature has b 2144 (HWP) feature has been enabled in the processor
2243 and possibly on the 2145 and possibly on the processor model.
2244 passive 2146 passive
2245 Use intel_pstate as 2147 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 2148 to work with generic cpufreq governors (instead of
2247 enabling its intern 2149 enabling its internal governor). This mode cannot be
2248 used along with the 2150 used along with the hardware-managed P-states (HWP)
2249 feature. 2151 feature.
2250 force 2152 force
2251 Enable intel_pstate 2153 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 2154 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 2155 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 2156 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 2157 P-States information being indicated to OSPM and therefore
2256 should be used with 2158 should be used with caution. This option does not work with
2257 processors that are 2159 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 2160 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 2161 no_hwp
2260 Do not enable hardw 2162 Do not enable hardware P state control (HWP)
2261 if available. 2163 if available.
2262 hwp_only 2164 hwp_only
2263 Only load intel_pst 2165 Only load intel_pstate on systems which support
2264 hardware P state co 2166 hardware P state control (HWP) if available.
2265 support_acpi_ppc 2167 support_acpi_ppc
2266 Enforce ACPI _PPC p 2168 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 2169 Description Table, specifies preferred power management
2268 profile as "Enterpr 2170 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 2171 then this feature is turned on by default.
2270 per_cpu_perf_limits 2172 per_cpu_perf_limits
2271 Allow per-logical-C 2173 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 2174 cpufreq sysfs interface
2273 2175
2274 intremap= [X86-64,Intel-IOMMU,E !! 2176 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 2177 on enable Interrupt Remapping (default)
2276 off disable Inter 2178 off disable Interrupt Remapping
2277 nosid disable Sourc 2179 nosid disable Source ID checking
2278 no_x2apic_optout 2180 no_x2apic_optout
2279 BIOS x2APIC o 2181 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 2182 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 2183
2284 iomem= Disable strict checki 2184 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 2185 strict regions from userspace.
2286 relaxed 2186 relaxed
2287 2187
2288 iommu= [X86,EARLY] !! 2188 iommu= [X86]
2289 off 2189 off
2290 force 2190 force
2291 noforce 2191 noforce
2292 biomerge 2192 biomerge
2293 panic 2193 panic
2294 nopanic 2194 nopanic
2295 merge 2195 merge
2296 nomerge 2196 nomerge
2297 soft 2197 soft
2298 pt [X86] 2198 pt [X86]
2299 nopt [X86] 2199 nopt [X86]
2300 nobypass [PPC/POWERNV] 2200 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 2201 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2202
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2203 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 2204 Format: { "0" | "1" }
2305 0 - Try to allocate a 2205 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 2206 falling back to the full range if needed.
2307 1 - Allocate directly 2207 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 2208 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 2209 greater than 32-bit addressing.
2310 2210
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 2211 iommu.strict= [ARM64, X86] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 2212 Format: { "0" | "1" }
2313 0 - Lazy mode. 2213 0 - Lazy mode.
2314 Request that DMA un 2214 Request that DMA unmap operations use deferred
2315 invalidation of har 2215 invalidation of hardware TLBs, for increased
2316 throughput at the c 2216 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2217 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2218 the relevant IOMMU driver.
2319 1 - Strict mode. 2219 1 - Strict mode.
2320 DMA unmap operation 2220 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2221 synchronously.
2322 unset - Use value of 2222 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2323 Note: on x86, strict 2223 Note: on x86, strict mode specified via one of the
2324 legacy driver-specifi 2224 legacy driver-specific options takes precedence.
2325 2225
2326 iommu.passthrough= 2226 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2227 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2228 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2229 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2230 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2231 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2232
2333 io7= [HW] IO7 for Marvel-b 2233 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2234 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2235 arch/alpha/kernel/core_marvel.c.
2336 2236
2337 io_delay= [X86,EARLY] I/O delay !! 2237 io_delay= [X86] I/O delay method
2338 0x80 2238 0x80
2339 Standard port 0x80 ba 2239 Standard port 0x80 based delay
2340 0xed 2240 0xed
2341 Alternate port 0xed b 2241 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2242 udelay
2343 Simple two microsecon 2243 Simple two microseconds delay
2344 none 2244 none
2345 No delay 2245 No delay
2346 2246
2347 ip= [IP_PNP] 2247 ip= [IP_PNP]
2348 See Documentation/adm 2248 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2249
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2250 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2251 IPC identifiers from 32,768 to 16,777,216.
2352 2252
2353 irqaffinity= [SMP] Set the default 2253 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2254 The argument is a cpu list, as described above.
2355 2255
2356 irqchip.gicv2_force_probe= 2256 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2257 [ARM, ARM64]
2358 Format: <bool> 2258 Format: <bool>
2359 Force the kernel to l 2259 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2260 of a GICv2 controller even if the memory range
2361 exposed by the device 2261 exposed by the device tree is too small.
2362 2262
2363 irqchip.gicv3_nolpi= 2263 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2264 [ARM, ARM64]
2365 Force the kernel to i 2265 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2266 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2267 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2268 to let secondary kernels in charge of setting up
2369 LPIs. 2269 LPIs.
2370 2270
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2271 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2272 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2273 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2274 CONFIG_ARM64_PSEUDO_NMI.
2375 2275
2376 irqfixup [HW] 2276 irqfixup [HW]
2377 When an interrupt is 2277 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2278 for it. Intended to get systems with badly broken
2379 firmware running. 2279 firmware running.
2380 2280
2381 irqpoll [HW] 2281 irqpoll [HW]
2382 When an interrupt is 2282 When an interrupt is not handled search all handlers
2383 for it. Also check al 2283 for it. Also check all handlers each timer
2384 interrupt. Intended t 2284 interrupt. Intended to get systems with badly broken
2385 firmware running. 2285 firmware running.
2386 2286
2387 isapnp= [ISAPNP] 2287 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2288 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2289
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2290 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2291 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2292 Format: [flag-list,]<cpu-list>
2393 2293
2394 Specify one or more C 2294 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2295 specified in the flag list (default: domain):
2396 2296
2397 nohz 2297 nohz
2398 Disable the tick wh 2298 Disable the tick when a single task runs.
2399 2299
2400 A residual 1Hz tick 2300 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2301 need to affine to housekeeping through the global
2402 workqueue's affinit 2302 workqueue's affinity configured via the
2403 /sys/devices/virtua 2303 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2304 by using the 'domain' flag described below.
2405 2305
2406 NOTE: by default th 2306 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2307 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2308 be configured manually after bootup.
2409 2309
2410 domain 2310 domain
2411 Isolate from the ge 2311 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2312 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2313 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2314 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2315 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2316 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2317 It offers a much more flexible interface where CPUs can
2418 move in and out of 2318 move in and out of an isolated set anytime.
2419 2319
2420 You can move a proc 2320 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2321 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2322 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2323 "number of CPUs in system - 1".
2424 2324
2425 managed_irq 2325 managed_irq
2426 2326
2427 Isolate from being 2327 Isolate from being targeted by managed interrupts
2428 which have an inter 2328 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2329 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2330 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2331 the /proc/irq/* interfaces.
2432 2332
2433 This isolation is b 2333 This isolation is best effort and only effective
2434 if the automaticall 2334 if the automatically assigned interrupt mask of a
2435 device queue contai 2335 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2336 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2337 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2338 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2339 cannot disturb the isolated CPU.
2440 2340
2441 If a queue's affini 2341 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2342 CPUs then this parameter has no effect on the
2443 interrupt routing d 2343 interrupt routing decision, though interrupts are
2444 only delivered when 2344 only delivered when tasks running on those
2445 isolated CPUs submi 2345 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2346 housekeeping CPUs has no influence on those
2447 queues. 2347 queues.
2448 2348
2449 The format of <cpu-li 2349 The format of <cpu-list> is described above.
2450 2350
2451 iucv= [HW,NET] 2351 iucv= [HW,NET]
2452 2352
2453 ivrs_ioapic [HW,X86-64] 2353 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2354 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t 2355 mapping provided in the IVRS ACPI table.
2456 By default, PCI segme 2356 By default, PCI segment is 0, and can be omitted.
2457 2357
2458 For example, to map I 2358 For example, to map IOAPIC-ID decimal 10 to
2459 PCI segment 0x1 and P 2359 PCI segment 0x1 and PCI device 00:14.0,
2460 write the parameter a 2360 write the parameter as:
2461 ivrs_ioapic=1 2361 ivrs_ioapic=10@0001:00:14.0
2462 2362
2463 Deprecated formats: 2363 Deprecated formats:
2464 * To map IOAPIC-ID de 2364 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2465 write the parameter 2365 write the parameter as:
2466 ivrs_ioapic[1 2366 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de 2367 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2468 PCI device 00:14.0 2368 PCI device 00:14.0 write the parameter as:
2469 ivrs_ioapic[1 2369 ivrs_ioapic[10]=0001:00:14.0
2470 2370
2471 ivrs_hpet [HW,X86-64] 2371 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2372 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t 2373 mapping provided in the IVRS ACPI table.
2474 By default, PCI segme 2374 By default, PCI segment is 0, and can be omitted.
2475 2375
2476 For example, to map H 2376 For example, to map HPET-ID decimal 10 to
2477 PCI segment 0x1 and P 2377 PCI segment 0x1 and PCI device 00:14.0,
2478 write the parameter a 2378 write the parameter as:
2479 ivrs_hpet=10@ 2379 ivrs_hpet=10@0001:00:14.0
2480 2380
2481 Deprecated formats: 2381 Deprecated formats:
2482 * To map HPET-ID deci 2382 * To map HPET-ID decimal 0 to PCI device 00:14.0
2483 write the parameter 2383 write the parameter as:
2484 ivrs_hpet[0]= 2384 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci 2385 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2486 PCI device 00:14.0 2386 PCI device 00:14.0 write the parameter as:
2487 ivrs_ioapic[1 2387 ivrs_ioapic[10]=0001:00:14.0
2488 2388
2489 ivrs_acpihid [HW,X86-64] 2389 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2390 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t 2391 mapping provided in the IVRS ACPI table.
2492 By default, PCI segme 2392 By default, PCI segment is 0, and can be omitted.
2493 2393
2494 For example, to map U 2394 For example, to map UART-HID:UID AMD0020:0 to
2495 PCI segment 0x1 and P 2395 PCI segment 0x1 and PCI device ID 00:14.5,
2496 write the parameter a 2396 write the parameter as:
2497 ivrs_acpihid= 2397 ivrs_acpihid=AMD0020:0@0001:00:14.5
2498 2398
2499 Deprecated formats: 2399 Deprecated formats:
2500 * To map UART-HID:UID 2400 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2501 PCI device ID 00:14 2401 PCI device ID 00:14.5, write the parameter as:
2502 ivrs_acpihid[ 2402 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID 2403 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2504 PCI device ID 00:14 2404 PCI device ID 00:14.5, write the parameter as:
2505 ivrs_acpihid[ 2405 ivrs_acpihid[0001:00:14.5]=AMD0020:0
2506 2406
2507 js= [HW,JOY] Analog joyst 2407 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2408 See Documentation/input/joydev/joystick.rst.
2509 2409
2510 kasan_multi_shot 2410 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2411 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2412 report on every invalid memory access. Without this
2513 parameter KASAN will 2413 parameter KASAN will print report only for the first
2514 invalid access. 2414 invalid access.
2515 2415
2516 keep_bootcon [KNL,EARLY] !! 2416 keep_bootcon [KNL]
2517 Do not unregister boo 2417 Do not unregister boot console at start. This is only
2518 useful for debugging 2418 useful for debugging when something happens in the window
2519 between unregistering 2419 between unregistering the boot console and initializing
2520 the real console. 2420 the real console.
2521 2421
2522 keepinitrd [HW,ARM] See retain_i !! 2422 keepinitrd [HW,ARM]
2523 2423
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2424 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2425 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2426 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2427 the kernel for non-movable allocations. The requested
2528 amount is spread even 2428 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2429 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2430 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2431 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2432 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2433 other nodes will have a larger ZONE_MOVABLE.
2534 2434
2535 ZONE_MOVABLE is used 2435 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2436 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2437 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2438 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2439 zone if it does not.
2540 2440
2541 It is possible to spe 2441 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2442 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2443 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2444 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2445 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2446 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2447 are exclusive, so you cannot specify multiple forms.
2548 2448
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2449 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2450 Format: <Controller#>[,poll interval]
2551 The controller # is t 2451 The controller # is the number of the ehci usb debug
2552 port as it is probed 2452 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2453 optional and is the number seconds in between
2554 each poll cycle to th 2454 each poll cycle to the debug port in case you need
2555 the functionality for 2455 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2456 gdb or control-c on the dbgp connection. When
2557 not using this parame 2457 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2458 the kernel debugger.
2559 2459
2560 kgdboc= [KGDB,HW] kgdb over c 2460 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2461 Requires a tty driver that supports console polling,
2562 or a supported pollin 2462 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2463 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2464 keyboard only format: kbd
2565 keyboard and serial 2465 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2466 Optional Kernel mode setting:
2567 kms, kbd format: kms 2467 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2468 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2469
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2470 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2471 If the boot console provides the ability to read
2572 characters and can wo 2472 characters and can work in polling mode, you can use
2573 this parameter to tel 2473 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2474 until the normal console is registered. Intended to
2575 be used together with 2475 be used together with the kgdboc parameter which
2576 specifies the normal 2476 specifies the normal console to transition to.
2577 2477
2578 The name of the early 2478 The name of the early console should be specified
2579 as the value of this 2479 as the value of this parameter. Note that the name of
2580 the early console mig 2480 the early console might be different than the tty
2581 name passed to kgdboc 2481 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2482 blank and the first boot console that implements
2583 read() will be picked 2483 read() will be picked.
2584 2484
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2485 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2486 kernel debugger at the earliest opportunity.
2587 2487
2588 kmac= [MIPS] Korina etherne 2488 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2489 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2490 Ethernet adapter MAC address.
2591 2491
2592 kmemleak= [KNL,EARLY] Boot-time !! 2492 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2493 Valid arguments: on, off
2594 Default: on 2494 Default: on
2595 Built with CONFIG_DEB 2495 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2496 the default is off.
2597 2497
2598 kprobe_event=[probe-list] 2498 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2499 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2500 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2501 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2502 interface, but the parameters are comma delimited.
2603 For example, to add a 2503 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2504 arg1 and arg2, add to the command line;
2605 2505
2606 kprobe_event=p, 2506 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2507
2608 See also Documentatio 2508 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2509 Boot Parameter" section.
2610 2510
2611 kpti= [ARM64,EARLY] Control !! 2511 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2512 and kernel address spaces.
2613 Default: enabled on c 2513 Default: enabled on cores which need mitigation.
2614 0: force disabled 2514 0: force disabled
2615 1: force enabled 2515 1: force enabled
2616 2516
2617 kunit.enable= [KUNIT] Enable execut 2517 kunit.enable= [KUNIT] Enable executing KUnit tests. Requires
2618 CONFIG_KUNIT to be se 2518 CONFIG_KUNIT to be set to be fully enabled. The
2619 default value can be 2519 default value can be overridden via
2620 KUNIT_DEFAULT_ENABLED 2520 KUNIT_DEFAULT_ENABLED.
2621 Default is 1 (enabled 2521 Default is 1 (enabled)
2622 2522
2623 kvm.ignore_msrs=[KVM] Ignore guest ac 2523 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2524 Default is 0 (don't ignore, but inject #GP)
2625 2525
2626 kvm.eager_page_split= 2526 kvm.eager_page_split=
2627 [KVM,X86] Controls wh 2527 [KVM,X86] Controls whether or not KVM will try to
2628 proactively split all 2528 proactively split all huge pages during dirty logging.
2629 Eager page splitting 2529 Eager page splitting reduces interruptions to vCPU
2630 execution by eliminat 2530 execution by eliminating the write-protection faults
2631 and MMU lock contenti 2531 and MMU lock contention that would otherwise be
2632 required to split hug 2532 required to split huge pages lazily.
2633 2533
2634 VM workloads that rar 2534 VM workloads that rarely perform writes or that write
2635 only to a small regio 2535 only to a small region of VM memory may benefit from
2636 disabling eager page 2536 disabling eager page splitting to allow huge pages to
2637 still be used for rea 2537 still be used for reads.
2638 2538
2639 The behavior of eager 2539 The behavior of eager page splitting depends on whether
2640 KVM_DIRTY_LOG_INITIAL 2540 KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2641 disabled, all huge pa 2541 disabled, all huge pages in a memslot will be eagerly
2642 split when dirty logg 2542 split when dirty logging is enabled on that memslot. If
2643 enabled, eager page s 2543 enabled, eager page splitting will be performed during
2644 the KVM_CLEAR_DIRTY i 2544 the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2645 cleared. 2545 cleared.
2646 2546
2647 Eager page splitting 2547 Eager page splitting is only supported when kvm.tdp_mmu=Y.
2648 2548
2649 Default is Y (on). 2549 Default is Y (on).
2650 2550
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2551 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2552 Default is false (don't support).
2653 2553
2654 kvm.nx_huge_pages= 2554 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2555 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2556 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2557 force : Always deploy workaround.
2658 off : Never deplo 2558 off : Never deploy workaround.
2659 auto : Deploy work 2559 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2560 X86_BUG_ITLB_MULTIHIT.
2661 2561
2662 Default is 'auto'. 2562 Default is 'auto'.
2663 2563
2664 If the software worka 2564 If the software workaround is enabled for the host,
2665 guests do need not to 2565 guests do need not to enable it for nested guests.
2666 2566
2667 kvm.nx_huge_pages_recovery_ratio= 2567 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2568 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2569 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2570 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). 2571 period (see below). The default is 60.
2672 2572
2673 kvm.nx_huge_pages_recovery_period_ms= 2573 kvm.nx_huge_pages_recovery_period_ms=
2674 [KVM] Controls the ti 2574 [KVM] Controls the time period at which KVM zaps 4KiB pages
2675 back to huge pages. I 2575 back to huge pages. If the value is a non-zero N, KVM will
2676 zap a portion (see ra 2576 zap a portion (see ratio above) of the pages every N msecs.
2677 If the value is 0 (th 2577 If the value is 0 (the default), KVM will pick a period based
2678 on the ratio, such th 2578 on the ratio, such that a page is zapped after 1 hour on average.
2679 2579
2680 kvm-amd.nested= [KVM,AMD] Control nes 2580 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2681 KVM/SVM. Default is 1 2581 KVM/SVM. Default is 1 (enabled).
2682 2582
2683 kvm-amd.npt= [KVM,AMD] Control KVM 2583 kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
2684 a.k.a. Two-Dimensiona 2584 a.k.a. Two-Dimensional Page Tables. Default is 1
2685 (enabled). Disable by 2585 (enabled). Disable by KVM if hardware lacks support
2686 for NPT. 2586 for NPT.
2687 2587
2688 kvm-arm.mode= 2588 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2589 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 2590
2692 none: Forcefully disa 2591 none: Forcefully disable KVM.
2693 2592
2694 nvhe: Standard nVHE-b 2593 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2594 protected guests.
2696 2595
2697 protected: nVHE-based 2596 protected: nVHE-based mode with support for guests whose
2698 state is k 2597 state is kept private from the host.
2699 2598
2700 nested: VHE-based mod 2599 nested: VHE-based mode with support for nested
2701 virtualizatio 2600 virtualization. Requires at least ARMv8.3
2702 hardware. 2601 hardware.
2703 2602
2704 Defaults to VHE/nVHE 2603 Defaults to VHE/nVHE based on hardware support. Setting
2705 mode to "protected" w 2604 mode to "protected" will disable kexec and hibernation
2706 for the host. "nested 2605 for the host. "nested" is experimental and should be
2707 used with extreme cau 2606 used with extreme caution.
2708 2607
2709 kvm-arm.vgic_v3_group0_trap= 2608 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2609 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2610 system registers
2712 2611
2713 kvm-arm.vgic_v3_group1_trap= 2612 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2613 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2614 system registers
2716 2615
2717 kvm-arm.vgic_v3_common_trap= 2616 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2617 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2618 system registers
2720 2619
2721 kvm-arm.vgic_v4_enable= 2620 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2621 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2622 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 2623
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2624 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2625 Reserves given percentage from system memory area for
2745 contiguous memory all 2626 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2627 allocation.
2747 By default it reserve 2628 By default it reserves 5% of total system memory.
2748 Format: <integer> 2629 Format: <integer>
2749 Default: 5 2630 Default: 5
2750 2631
2751 kvm-intel.ept= [KVM,Intel] Control K 2632 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
2752 a.k.a. Two-Dimensiona 2633 a.k.a. Two-Dimensional Page Tables. Default is 1
2753 (enabled). Disable by 2634 (enabled). Disable by KVM if hardware lacks support
2754 for EPT. 2635 for EPT.
2755 2636
2756 kvm-intel.emulate_invalid_guest_state 2637 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w 2638 [KVM,Intel] Control whether to emulate invalid guest
2758 state. Ignored if kvm 2639 state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2759 as guest state is nev 2640 as guest state is never invalid for unrestricted
2760 guests. This param do 2641 guests. This param doesn't apply to nested guests (L2),
2761 as KVM never emulates 2642 as KVM never emulates invalid L2 guest state.
2762 Default is 1 (enabled 2643 Default is 1 (enabled).
2763 2644
2764 kvm-intel.flexpriority= 2645 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K 2646 [KVM,Intel] Control KVM's use of FlexPriority feature
2766 (TPR shadow). Default !! 2647 (TPR shadow). Default is 1 (enabled). Disalbe by KVM if
2767 hardware lacks suppor 2648 hardware lacks support for it.
2768 2649
2769 kvm-intel.nested= 2650 kvm-intel.nested=
2770 [KVM,Intel] Control n 2651 [KVM,Intel] Control nested virtualization feature in
2771 KVM/VMX. Default is 1 2652 KVM/VMX. Default is 1 (enabled).
2772 2653
2773 kvm-intel.unrestricted_guest= 2654 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K 2655 [KVM,Intel] Control KVM's use of unrestricted guest
2775 feature (virtualized 2656 feature (virtualized real and unpaged mode). Default
2776 is 1 (enabled). Disab 2657 is 1 (enabled). Disable by KVM if EPT is disabled or
2777 hardware lacks suppor 2658 hardware lacks support for it.
2778 2659
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2660 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2661 CVE-2018-3620.
2781 2662
2782 Valid arguments: neve 2663 Valid arguments: never, cond, always
2783 2664
2784 always: L1D cache flu 2665 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2666 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2667 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2668 never: Disables the mitigation
2788 2669
2789 Default is cond (do L 2670 Default is cond (do L1 cache flush in specific instances)
2790 2671
2791 kvm-intel.vpid= [KVM,Intel] Control K 2672 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2792 Identification featur 2673 Identification feature (tagged TLBs). Default is 1
2793 (enabled). Disable by 2674 (enabled). Disable by KVM if hardware lacks support
2794 for it. 2675 for it.
2795 2676
2796 l1d_flush= [X86,INTEL,EARLY] !! 2677 l1d_flush= [X86,INTEL]
2797 Control mitigation fo 2678 Control mitigation for L1D based snooping vulnerability.
2798 2679
2799 Certain CPUs are vuln 2680 Certain CPUs are vulnerable to an exploit against CPU
2800 internal buffers whic 2681 internal buffers which can forward information to a
2801 disclosure gadget und 2682 disclosure gadget under certain conditions.
2802 2683
2803 In vulnerable process 2684 In vulnerable processors, the speculatively
2804 forwarded data can be 2685 forwarded data can be used in a cache side channel
2805 attack, to access dat 2686 attack, to access data to which the attacker does
2806 not have direct acces 2687 not have direct access.
2807 2688
2808 This parameter contro 2689 This parameter controls the mitigation. The
2809 options are: 2690 options are:
2810 2691
2811 on - enable t 2692 on - enable the interface for the mitigation
2812 2693
2813 l1tf= [X86,EARLY] Control m !! 2694 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2695 affected CPUs
2815 2696
2816 The kernel PTE invers 2697 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2698 enabled and cannot be disabled.
2818 2699
2819 full 2700 full
2820 Provides all 2701 Provides all available mitigations for the
2821 L1TF vulnerab 2702 L1TF vulnerability. Disables SMT and
2822 enables all m 2703 enables all mitigations in the
2823 hypervisors, 2704 hypervisors, i.e. unconditional L1D flush.
2824 2705
2825 SMT control a 2706 SMT control and L1D flush control via the
2826 sysfs interfa 2707 sysfs interface is still possible after
2827 boot. Hyperv 2708 boot. Hypervisors will issue a warning
2828 when the firs 2709 when the first VM is started in a
2829 potentially i 2710 potentially insecure configuration,
2830 i.e. SMT enab 2711 i.e. SMT enabled or L1D flush disabled.
2831 2712
2832 full,force 2713 full,force
2833 Same as 'full 2714 Same as 'full', but disables SMT and L1D
2834 flush runtime 2715 flush runtime control. Implies the
2835 'nosmt=force' 2716 'nosmt=force' command line option.
2836 (i.e. sysfs c 2717 (i.e. sysfs control of SMT is disabled.)
2837 2718
2838 flush 2719 flush
2839 Leaves SMT en 2720 Leaves SMT enabled and enables the default
2840 hypervisor mi 2721 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2722 L1D flush.
2842 2723
2843 SMT control a 2724 SMT control and L1D flush control via the
2844 sysfs interfa 2725 sysfs interface is still possible after
2845 boot. Hyperv 2726 boot. Hypervisors will issue a warning
2846 when the firs 2727 when the first VM is started in a
2847 potentially i 2728 potentially insecure configuration,
2848 i.e. SMT enab 2729 i.e. SMT enabled or L1D flush disabled.
2849 2730
2850 flush,nosmt 2731 flush,nosmt
2851 2732
2852 Disables SMT 2733 Disables SMT and enables the default
2853 hypervisor mi 2734 hypervisor mitigation.
2854 2735
2855 SMT control a 2736 SMT control and L1D flush control via the
2856 sysfs interfa 2737 sysfs interface is still possible after
2857 boot. Hyperv 2738 boot. Hypervisors will issue a warning
2858 when the firs 2739 when the first VM is started in a
2859 potentially i 2740 potentially insecure configuration,
2860 i.e. SMT enab 2741 i.e. SMT enabled or L1D flush disabled.
2861 2742
2862 flush,nowarn 2743 flush,nowarn
2863 Same as 'flus 2744 Same as 'flush', but hypervisors will not
2864 warn when a V 2745 warn when a VM is started in a potentially
2865 insecure conf 2746 insecure configuration.
2866 2747
2867 off 2748 off
2868 Disables hype 2749 Disables hypervisor mitigations and doesn't
2869 emit any warn 2750 emit any warnings.
2870 It also drops 2751 It also drops the swap size and available
2871 RAM limit res 2752 RAM limit restriction on both hypervisor and
2872 bare metal. 2753 bare metal.
2873 2754
2874 Default is 'flush'. 2755 Default is 'flush'.
2875 2756
2876 For details see: Docu 2757 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2758
2878 l2cr= [PPC] 2759 l2cr= [PPC]
2879 2760
2880 l3cr= [PPC] 2761 l3cr= [PPC]
2881 2762
2882 lapic [X86-32,APIC,EARLY] E !! 2763 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2764 disabled it.
2884 2765
2885 lapic= [X86,APIC] Do not use 2766 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2767 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2768 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2769 Format: notscdeadline
2889 2770
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2771 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2772 in C2 power state.
2892 2773
2893 libata.dma= [LIBATA] DMA control 2774 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2775 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2776 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2777 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2778 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2779 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2780 for disks and CDROMs, but not CFs.
2900 2781
2901 libata.ignore_hpa= [LIBATA] Igno 2782 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2783 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2784 libata.ignore_hpa=1 ignore limits, using full disk
2904 2785
2905 libata.noacpi [LIBATA] Disables use 2786 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2787 when set.
2907 Format: <int> 2788 Format: <int>
2908 2789
2909 libata.force= [LIBATA] Force config 2790 libata.force= [LIBATA] Force configurations. The format is a comma-
2910 separated list of "[I 2791 separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2911 PORT and DEVICE are d 2792 PORT and DEVICE are decimal numbers matching port, link
2912 or device. Basically 2793 or device. Basically, it matches the ATA ID string
2913 printed on console by 2794 printed on console by libata. If the whole ID part is
2914 omitted, the last POR 2795 omitted, the last PORT and DEVICE values are used. If
2915 ID hasn't been specif 2796 ID hasn't been specified yet, the configuration applies
2916 to all ports, links a 2797 to all ports, links and devices.
2917 2798
2918 If only DEVICE is omi 2799 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2800 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2801 number of 0 either selects the first device or the
2921 first fan-out link be 2802 first fan-out link behind PMP device. It does not
2922 select the host link. 2803 select the host link. DEVICE number of 15 selects the
2923 host link and device 2804 host link and device attached to it.
2924 2805
2925 The VAL specifies the 2806 The VAL specifies the configuration to force. As long
2926 as there is no ambigu 2807 as there is no ambiguity, shortcut notation is allowed.
2927 For example, both 1.5 2808 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2809 The following configurations can be forced.
2929 2810
2930 * Cable type: 40c, 80 2811 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2812 Any ID with matching PORT is used.
2932 2813
2933 * SATA link speed lim 2814 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2815
2935 * Transfer mode: pio[ 2816 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2817 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2818 allowed.
2938 2819
2939 * nohrst, nosrst, nor 2820 * nohrst, nosrst, norst: suppress hard, soft and both
2940 resets. 2821 resets.
2941 2822
2942 * rstonce: only attem 2823 * rstonce: only attempt one reset during hot-unplug
2943 link recovery. 2824 link recovery.
2944 2825
2945 * [no]dbdelay: Enable 2826 * [no]dbdelay: Enable or disable the extra 200ms delay
2946 before debouncing a 2827 before debouncing a link PHY and device presence
2947 detection. 2828 detection.
2948 2829
2949 * [no]ncq: Turn on or 2830 * [no]ncq: Turn on or off NCQ.
2950 2831
2951 * [no]ncqtrim: Enable 2832 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2952 2833
2953 * [no]ncqati: Enable 2834 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2954 2835
2955 * [no]trim: Enable or 2836 * [no]trim: Enable or disable (unqueued) TRIM.
2956 2837
2957 * trim_zero: Indicate 2838 * trim_zero: Indicate that TRIM command zeroes data.
2958 2839
2959 * max_trim_128m: Set 2840 * max_trim_128m: Set 128M maximum trim size limit.
2960 2841
2961 * [no]dma: Turn on or 2842 * [no]dma: Turn on or off DMA transfers.
2962 2843
2963 * atapi_dmadir: Enabl 2844 * atapi_dmadir: Enable ATAPI DMADIR bridge support.
2964 2845
2965 * atapi_mod16_dma: En 2846 * atapi_mod16_dma: Enable the use of ATAPI DMA for
2966 commands that are n 2847 commands that are not a multiple of 16 bytes.
2967 2848
2968 * [no]dmalog: Enable 2849 * [no]dmalog: Enable or disable the use of the
2969 READ LOG DMA EXT co 2850 READ LOG DMA EXT command to access logs.
2970 2851
2971 * [no]iddevlog: Enabl 2852 * [no]iddevlog: Enable or disable access to the
2972 identify device dat 2853 identify device data log.
2973 2854
2974 * [no]logdir: Enable 2855 * [no]logdir: Enable or disable access to the general
2975 purpose log directo 2856 purpose log directory.
2976 2857
2977 * max_sec_128: Set tr 2858 * max_sec_128: Set transfer size limit to 128 sectors.
2978 2859
2979 * max_sec_1024: Set o 2860 * max_sec_1024: Set or clear transfer size limit to
2980 1024 sectors. 2861 1024 sectors.
2981 2862
2982 * max_sec_lba48: Set 2863 * max_sec_lba48: Set or clear transfer size limit to
2983 65535 sectors. 2864 65535 sectors.
2984 2865
2985 * [no]lpm: Enable or 2866 * [no]lpm: Enable or disable link power management.
2986 2867
2987 * [no]setxfer: Indica 2868 * [no]setxfer: Indicate if transfer speed mode setting
2988 should be skipped. 2869 should be skipped.
2989 2870
2990 * [no]fua: Disable or 2871 * [no]fua: Disable or enable FUA (Force Unit Access)
2991 support for devices 2872 support for devices supporting this feature.
2992 2873
2993 * dump_id: Dump IDENT 2874 * dump_id: Dump IDENTIFY data.
2994 2875
2995 * disable: Disable th 2876 * disable: Disable this device.
2996 2877
2997 If there are multiple 2878 If there are multiple matching configurations changing
2998 the same attribute, t 2879 the same attribute, the last one is used.
2999 2880
3000 load_ramdisk= [RAM] [Deprecated] 2881 load_ramdisk= [RAM] [Deprecated]
3001 2882
3002 lockd.nlm_grace_period=P [NFS] Assig 2883 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2884 Format: <integer>
3004 2885
3005 lockd.nlm_tcpport=N [NFS] Assign 2886 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2887 Format: <integer>
3007 2888
3008 lockd.nlm_timeout=T [NFS] Assign 2889 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2890 Format: <integer>
3010 2891
3011 lockd.nlm_udpport=M [NFS] Assign 2892 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2893 Format: <integer>
3013 2894
3014 lockdown= [SECURITY,EARLY] !! 2895 lockdown= [SECURITY]
3015 { integrity | confide 2896 { integrity | confidentiality }
3016 Enable the kernel loc 2897 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2898 integrity, kernel features that allow userland to
3018 modify the running ke 2899 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2900 confidentiality, kernel features that allow userland
3020 to extract confidenti 2901 to extract confidential information from the kernel
3021 are also disabled. 2902 are also disabled.
3022 2903
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] 2904 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2905 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2906 Defaults to being automatically set based on the
3058 number of online CPUs 2907 number of online CPUs.
3059 2908
3060 locktorture.nwriters_stress= [KNL] 2909 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2910 Set the number of locking write-acquisition kthreads.
3062 2911
3063 locktorture.onoff_holdoff= [KNL] 2912 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2913 Set time (s) after boot for CPU-hotplug testing.
3065 2914
3066 locktorture.onoff_interval= [KNL] 2915 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2916 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2917 zero to disable CPU-hotplug testing.
3069 2918
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] 2919 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2920 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2921 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2922 mode during the locktorture test.
3093 2923
3094 locktorture.shutdown_secs= [KNL] 2924 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2925 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2926 is useful for hands-off automated testing.
3097 2927
3098 locktorture.stat_interval= [KNL] 2928 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2929 Time (s) between statistics printk()s.
3100 2930
3101 locktorture.stutter= [KNL] 2931 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2932 Time (s) to stutter testing, for example,
3103 specifying five secon 2933 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2934 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2935 This tests the locking primitive's ability to
3106 transition abruptly t 2936 transition abruptly to and from idle.
3107 2937
3108 locktorture.torture_type= [KNL] 2938 locktorture.torture_type= [KNL]
3109 Specify the locking i 2939 Specify the locking implementation to test.
3110 2940
3111 locktorture.verbose= [KNL] <<
3112 Enable additional pri <<
3113 <<
3114 locktorture.writer_fifo= [KNL] 2941 locktorture.writer_fifo= [KNL]
3115 Run the write-side lo 2942 Run the write-side locktorture kthreads at
3116 sched_set_fifo() real 2943 sched_set_fifo() real-time priority.
3117 2944
>> 2945 locktorture.verbose= [KNL]
>> 2946 Enable additional printk() statements.
>> 2947
3118 logibm.irq= [HW,MOUSE] Logitech B 2948 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2949 Format: <irq>
3120 2950
3121 loglevel= [KNL,EARLY] !! 2951 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2952 console loglevel will be printed to the console. It can
3124 also be changed with 2953 also be changed with klogd or other programs. The
3125 loglevels are defined 2954 loglevels are defined as follows:
3126 2955
3127 0 (KERN_EMERG) 2956 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2957 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2958 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2959 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2960 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2961 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2962 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2963 7 (KERN_DEBUG) debug-level messages
3135 2964
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2965 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2966 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2967 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2968 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2969 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2970 that allows to increase the default size depending on
3142 parameter that allows !! 2971 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2972
3146 logo.nologo [FB] Disables display 2973 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2974 This may be used to provide more screen space for
3148 kernel log messages a 2975 kernel log messages and is useful when debugging
3149 kernel boot problems. 2976 kernel boot problems.
3150 2977
3151 lp=0 [LP] Specify paral 2978 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2979 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2980 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2981 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2982 specified in addition to the ports) causes
3156 attached prin 2983 attached printers to be reset. Using
3157 lp=port1,port 2984 lp=port1,port2,... specifies the parallel ports
3158 to associate 2985 to associate lp devices with, starting with
3159 lp0. A port s 2986 lp0. A port specification may be 'none' to skip
3160 that lp devic 2987 that lp device, or a parport name such as
3161 'parport0'. S 2988 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2989 port specification list means that device IDs
3163 from each por 2990 from each port should be examined, to see if
3164 an IEEE 1284- 2991 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2992 so, the driver will manage that printer.
3166 See also head 2993 See also header of drivers/char/lp.c.
3167 2994
3168 lpj=n [KNL] 2995 lpj=n [KNL]
3169 Sets loops_per_jiffy 2996 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2997 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2998 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2999 the correct value for your kernel, boot with normal
3173 autodetection and see 3000 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 3001 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 3002 which is likely to cause problems if your CPUs need
3176 significantly diverge 3003 significantly divergent settings. An incorrect value
3177 will cause delays in 3004 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 3005 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 3006 unlikely, in the extreme case this might damage your
3180 hardware. 3007 hardware.
3181 3008
>> 3009 ltpc= [NET]
>> 3010 Format: <io>,<irq>,<dma>
>> 3011
3182 lsm.debug [SECURITY] Enable LSM 3012 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 3013
3184 lsm=lsm1,...,lsmN 3014 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 3015 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 3016 overrides CONFIG_LSM, and the "security=" parameter.
3187 3017
>> 3018 machvec= [IA-64] Force the use of a particular machine-vector
>> 3019 (machvec) in a generic kernel.
>> 3020 Example: machvec=hpzx1
>> 3021
3188 machtype= [Loongson] Share the 3022 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 3023 different yeeloong laptops.
3190 Example: machtype=lem 3024 Example: machtype=lemote-yeeloong-2f-7inch
3191 3025
3192 maxcpus= [SMP,EARLY] Maximum n !! 3026 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
>> 3027 than or equal to this physical address is ignored.
>> 3028
>> 3029 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 3030 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 3031 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 3032 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 3033 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 3034 only takes effect during system bootup.
3198 While n=0 is a specia 3035 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 3036 which also disables the IO APIC.
3200 3037
3201 max_loop= [LOOP] The number of 3038 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 3039 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 3040 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 3041 of statically allocating a predefined number, loop
3205 devices can be reques 3042 devices can be requested on-demand with the
3206 /dev/loop-control int 3043 /dev/loop-control interface.
3207 3044
3208 mce [X86-32] Machine Chec 3045 mce [X86-32] Machine Check Exception
3209 3046
3210 mce=option [X86-64] See Document 3047 mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
3211 3048
3212 md= [HW] RAID subsystems 3049 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 3050 See Documentation/admin-guide/md.rst.
3214 3051
3215 mdacon= [MDA] 3052 mdacon= [MDA]
3216 Format: <first>,<last 3053 Format: <first>,<last>
3217 Specifies range of co 3054 Specifies range of consoles to be captured by the MDA.
3218 3055
3219 mds= [X86,INTEL,EARLY] !! 3056 mds= [X86,INTEL]
3220 Control mitigation fo 3057 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 3058 Sampling (MDS) vulnerability.
3222 3059
3223 Certain CPUs are vuln 3060 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 3061 internal buffers which can forward information to a
3225 disclosure gadget und 3062 disclosure gadget under certain conditions.
3226 3063
3227 In vulnerable process 3064 In vulnerable processors, the speculatively
3228 forwarded data can be 3065 forwarded data can be used in a cache side channel
3229 attack, to access dat 3066 attack, to access data to which the attacker does
3230 not have direct acces 3067 not have direct access.
3231 3068
3232 This parameter contro 3069 This parameter controls the MDS mitigation. The
3233 options are: 3070 options are:
3234 3071
3235 full - Enable M 3072 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 3073 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 3074 SMT on vulnerable CPUs
3238 off - Uncondit 3075 off - Unconditionally disable MDS mitigation
3239 3076
3240 On TAA-affected machi 3077 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 3078 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 3079 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 3080 this mitigation, you need to specify tsx_async_abort=off
3244 too. 3081 too.
3245 3082
3246 Not specifying this o 3083 Not specifying this option is equivalent to
3247 mds=full. 3084 mds=full.
3248 3085
3249 For details see: Docu 3086 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 3087
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 3088 mem=nn[KMG] [HEXAGON] Set the memory size.
3252 Must be specified, ot 3089 Must be specified, otherwise memory size will be 0.
3253 3090
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc !! 3091 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3255 of memory Amount of m !! 3092 Amount of memory to be used in cases as follows:
3256 as follows: <<
3257 3093
3258 1 for test; 3094 1 for test;
3259 2 when the kernel is 3095 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 3096 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 3097 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory 3098 4 to limit the memory available for kdump kernel.
3263 3099
3264 [ARC,MICROBLAZE] - th 3100 [ARC,MICROBLAZE] - the limit applies only to low memory,
3265 high memory is not af 3101 high memory is not affected.
3266 3102
3267 [ARM64] - only limits 3103 [ARM64] - only limits memory covered by the linear
3268 mapping. The NOMAP re 3104 mapping. The NOMAP regions are not affected.
3269 3105
3270 [X86] Work as limitin 3106 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 3107 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 3108 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 3109 belonging to unused RAM.
3274 3110
3275 Note that this only t 3111 Note that this only takes effects during boot time since
3276 in above case 3, memo 3112 in above case 3, memory may need be hot added after boot
3277 if system memory of h 3113 if system memory of hypervisor is not sufficient.
3278 3114
3279 mem=nn[KMG]@ss[KMG] 3115 mem=nn[KMG]@ss[KMG]
3280 [ARM,MIPS,EARLY] - ov !! 3116 [ARM,MIPS] - override the memory layout reported by
3281 reported by firmware. !! 3117 firmware.
3282 Define a memory regio 3118 Define a memory region of size nn[KMG] starting at
3283 ss[KMG]. 3119 ss[KMG].
3284 Multiple different re 3120 Multiple different regions can be specified with
3285 multiple mem= paramet 3121 multiple mem= parameters on the command line.
3286 3122
3287 mem=nopentium [BUGS=X86-32] Disable 3123 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 3124 memory.
3289 3125
3290 memblock=debug [KNL,EARLY] Enable me !! 3126 memblock=debug [KNL] Enable memblock debug messages.
3291 3127
3292 memchunk=nn[KMG] 3128 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 3129 [KNL,SH] Allow user to override the default size for
3294 per-device physically 3130 per-device physically contiguous DMA buffers.
3295 3131
3296 memhp_default_state=online/offline/on !! 3132 memhp_default_state=online/offline
3297 [KNL] Set the initial 3133 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 3134 onlining policy. If not specified, the default value is
3299 set according to the 3135 set according to the
3300 CONFIG_MEMORY_HOTPLUG 3136 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 3137 option.
3302 See Documentation/adm 3138 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 3139
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 3140 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 3141 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 3142 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 3143 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 3144 option description.
3309 3145
3310 memmap=nn[KMG]@ss[KMG] 3146 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 3147 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 3148 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 3149 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 3150 which limits max address to nn[KMG].
3315 Multiple different re 3151 Multiple different regions can be specified,
3316 comma delimited. 3152 comma delimited.
3317 Example: 3153 Example:
3318 memmap=100M@2 3154 memmap=100M@2G,100M#3G,1G!1024G
3319 3155
3320 memmap=nn[KMG]#ss[KMG] 3156 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 3157 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 3158 Region of memory to be marked is from ss to ss+nn.
3323 3159
3324 memmap=nn[KMG]$ss[KMG] 3160 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 3161 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 3162 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 3163 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 3164 memmap=64K$0x18690000
3329 or 3165 or
3330 memmap=0x100 3166 memmap=0x10000$0x18690000
3331 Some bootloaders may 3167 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 3168 like Grub2, otherwise '$' and the following number
3333 will be eaten. 3169 will be eaten.
3334 3170
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 3171 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 3172 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 3173 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 3174 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 3175 and is NVDIMM or ADR memory.
3340 3176
3341 memmap=<size>%<offset>-<oldtype>+<new 3177 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 3178 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 3179 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 3180 out, the whole region will be marked as <newtype>,
3345 even if previously un 3181 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 3182 out, matching memory will be removed. Types are
3347 specified as e820 typ 3183 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 3184 3 = ACPI, 12 = PRAM.
3349 3185
3350 memory_corruption_check=0/1 [X86,EARL !! 3186 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 3187 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 3188 memory when doing things like suspend/resume.
3353 Setting this option w 3189 Setting this option will scan the memory
3354 looking for corruptio 3190 looking for corruption. Enabling this will
3355 both detect corruptio 3191 both detect corruption and prevent the kernel
3356 from using the memory 3192 from using the memory being corrupted.
3357 However, its intended 3193 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 3194 repeatable BIOS-originated corruption always
3359 affects the same memo 3195 affects the same memory, you can use memmap=
3360 to prevent the kernel 3196 to prevent the kernel from using that memory.
3361 3197
3362 memory_corruption_check_size=size [X8 !! 3198 memory_corruption_check_size=size [X86]
3363 By default it checks 3199 By default it checks for corruption in the low
3364 64k, making this memo 3200 64k, making this memory unavailable for normal
3365 use. Use this parame 3201 use. Use this parameter to scan for
3366 corruption in more or 3202 corruption in more or less memory.
3367 3203
3368 memory_corruption_check_period=second !! 3204 memory_corruption_check_period=seconds [X86]
3369 By default it checks 3205 By default it checks for corruption every 60
3370 seconds. Use this pa 3206 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 3207 other rate. 0 disables periodic checking.
3372 3208
3373 memory_hotplug.memmap_on_memory 3209 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 3210 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 3211 Format: {on | off (default)}
3376 When enabled, runtime 3212 When enabled, runtime hotplugged memory will
3377 allocate its internal 3213 allocate its internal metadata (struct pages,
3378 those vmemmap pages c 3214 those vmemmap pages cannot be optimized even
3379 if hugetlb_free_vmemm 3215 if hugetlb_free_vmemmap is enabled) from the
3380 hotadded memory which 3216 hotadded memory which will allow to hotadd a
3381 lot of memory without 3217 lot of memory without requiring additional
3382 memory to do so. 3218 memory to do so.
3383 This feature is disab 3219 This feature is disabled by default because it
3384 has some implication 3220 has some implication on large (e.g. GB)
3385 allocations in some c 3221 allocations in some configurations (e.g. small
3386 memory blocks). 3222 memory blocks).
3387 The state of the flag 3223 The state of the flag can be read in
3388 /sys/module/memory_ho 3224 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 3225 Note that even when enabled, there are a few cases where
3390 the feature is not ef 3226 the feature is not effective.
3391 3227
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 3228 memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
3393 Format: <integer> 3229 Format: <integer>
3394 default : 0 <disable> 3230 default : 0 <disable>
3395 Specifies the number 3231 Specifies the number of memtest passes to be
3396 performed. Each pass 3232 performed. Each pass selects another test
3397 pattern from a given 3233 pattern from a given set of patterns. Memtest
3398 fills the memory with 3234 fills the memory with this pattern, validates
3399 memory contents and r 3235 memory contents and reserves bad memory
3400 regions that are dete 3236 regions that are detected.
3401 3237
3402 mem_encrypt= [X86-64] AMD Secure M 3238 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 3239 Valid arguments: on, off
3404 Default: off !! 3240 Default (depends on kernel configuration option):
>> 3241 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 3242 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 3243 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 3244 mem_encrypt=off: Do not activate SME
3407 3245
3408 Refer to Documentatio 3246 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3409 for details on when m 3247 for details on when memory encryption can be activated.
3410 3248
3411 mem_sleep_default= [SUSPEND] Def 3249 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 3250 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 3251 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 3252 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 3253 See Documentation/admin-guide/pm/sleep-states.rst.
3416 3254
>> 3255 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 3256 Multi-Function General Purpose Timers on AMD Geode
>> 3257 platforms.
>> 3258
3417 mfgptfix [X86-32] Fix MFGPT ti 3259 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 3260 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 3261 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 3262 problem by letting the user disable the workaround.
3421 3263
3422 mga= [HW,DRM] 3264 mga= [HW,DRM]
3423 3265
3424 microcode.force_minrev= [X86] !! 3266 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
3425 Format: <bool> !! 3267 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 3268
3429 mini2440= [ARM,HW,KNL] 3269 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 3270 Format:[0..2][b][c][t]
3431 Default: "0tb" 3271 Default: "0tb"
3432 MINI2440 configuratio 3272 MINI2440 configuration specification:
3433 0 - The attached scre 3273 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 3274 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 3275 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 3276 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 3277 the TFT driver, and the framebuffer will be left
3438 unconfigured. 3278 unconfigured.
3439 b - Enable backlight. 3279 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 3280 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 3281 LED. This parameter is not necessary when using the
3442 VGA shield. 3282 VGA shield.
3443 c - Enable the s3c ca 3283 c - Enable the s3c camera interface.
3444 t - Reserved for enab 3284 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 3285 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 3286 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 3287 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 3288 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 3289
3450 mitigations= 3290 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 3291 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 3292 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 3293 arch-independent options, each of which is an
3454 aggregation of existi 3294 aggregation of existing arch-specific options.
3455 3295
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 3296 off
3460 Disable all o 3297 Disable all optional CPU mitigations. This
3461 improves syst 3298 improves system performance, but it may also
3462 expose users 3299 expose users to several CPU vulnerabilities.
3463 Equivalent to 3300 Equivalent to: if nokaslr then kpti=0 [ARM64]
3464 3301 gather_data_sampling=off [X86]
3465 3302 kvm.nx_huge_pages=off [X86]
3466 3303 l1tf=off [X86]
3467 3304 mds=off [X86]
3468 3305 mmio_stale_data=off [X86]
3469 3306 no_entry_flush [PPC]
3470 3307 no_uaccess_flush [PPC]
3471 3308 nobp=0 [S390]
3472 3309 nopti [X86,PPC]
3473 3310 nospectre_bhb [ARM64]
3474 3311 nospectre_v1 [X86,PPC]
3475 3312 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 3313 retbleed=off [X86]
3478 <<
3479 3314 spec_store_bypass_disable=off [X86,PPC]
3480 <<
3481 3315 spectre_v2_user=off [X86]
3482 3316 srbds=off [X86,INTEL]
3483 3317 ssbd=force-off [ARM64]
3484 3318 tsx_async_abort=off [X86]
3485 3319
3486 Exceptions: 3320 Exceptions:
3487 3321 This does not have any effect on
3488 3322 kvm.nx_huge_pages when
3489 3323 kvm.nx_huge_pages=force.
3490 3324
3491 auto (default) 3325 auto (default)
3492 Mitigate all 3326 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 3327 enabled, even if it's vulnerable. This is for
3494 users who don 3328 users who don't want to be surprised by SMT
3495 getting disab 3329 getting disabled across kernel upgrades, or who
3496 have other wa 3330 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 3331 Equivalent to: (default behavior)
3498 3332
3499 auto,nosmt 3333 auto,nosmt
3500 Mitigate all 3334 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 3335 if needed. This is for users who always want to
3502 be fully miti 3336 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 3337 Equivalent to: l1tf=flush,nosmt [X86]
3504 3338 mds=full,nosmt [X86]
3505 3339 tsx_async_abort=full,nosmt [X86]
3506 3340 mmio_stale_data=full,nosmt [X86]
3507 3341 retbleed=auto,nosmt [X86]
3508 3342
3509 mminit_loglevel= 3343 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 3344 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 3345 parameter allows control of the logging verbosity for
3512 the additional memory 3346 the additional memory initialisation checks. A value
3513 of 0 disables mminit 3347 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 3348 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 3349 so loglevel=8 may also need to be specified.
3516 3350
3517 mmio_stale_data= 3351 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 3352 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 3353 MMIO Stale Data vulnerabilities.
3520 3354
3521 Processor MMIO Stale 3355 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 3356 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 3357 operation. Exposed data could originate or end in
3524 the same CPU buffers 3358 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 3359 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 3360 is to clear the affected CPU buffers.
3527 3361
3528 This parameter contro 3362 This parameter controls the mitigation. The
3529 options are: 3363 options are:
3530 3364
3531 full - Enable m 3365 full - Enable mitigation on vulnerable CPUs
3532 3366
3533 full,nosmt - Enable m 3367 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 3368 vulnerable CPUs.
3535 3369
3536 off - Uncondit 3370 off - Unconditionally disable mitigation
3537 3371
3538 On MDS or TAA affecte 3372 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 3373 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 3374 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 3375 mitigated with the same mechanism so in order to
3542 disable this mitigati 3376 disable this mitigation, you need to specify
3543 mds=off and tsx_async 3377 mds=off and tsx_async_abort=off too.
3544 3378
3545 Not specifying this o 3379 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 3380 mmio_stale_data=full.
3547 3381
3548 For details see: 3382 For details see:
3549 Documentation/admin-g 3383 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 3384
3551 <module>.async_probe[=<bool>] [KNL] 3385 <module>.async_probe[=<bool>] [KNL]
3552 If no <bool> value is 3386 If no <bool> value is specified or if the value
3553 specified is not a va 3387 specified is not a valid <bool>, enable asynchronous
3554 probe on this module. 3388 probe on this module. Otherwise, enable/disable
3555 asynchronous probe on 3389 asynchronous probe on this module as indicated by the
3556 <bool> value. See als 3390 <bool> value. See also: module.async_probe
3557 3391
3558 module.async_probe=<bool> 3392 module.async_probe=<bool>
3559 [KNL] When set to tru 3393 [KNL] When set to true, modules will use async probing
3560 by default. To enable 3394 by default. To enable/disable async probing for a
3561 specific module, use 3395 specific module, use the module specific control that
3562 is documented under < 3396 is documented under <module>.async_probe. When both
3563 module.async_probe an 3397 module.async_probe and <module>.async_probe are
3564 specified, <module>.a 3398 specified, <module>.async_probe takes precedence for
3565 the specific module. 3399 the specific module.
3566 3400
3567 module.enable_dups_trace 3401 module.enable_dups_trace
3568 [KNL] When CONFIG_MOD 3402 [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
3569 this means that dupli 3403 this means that duplicate request_module() calls will
3570 trigger a WARN_ON() i 3404 trigger a WARN_ON() instead of a pr_warn(). Note that
3571 if MODULE_DEBUG_AUTOL 3405 if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
3572 will always be issued 3406 will always be issued and this option does nothing.
3573 module.sig_enforce 3407 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3408 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3409 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3410 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3411 is always true, so this option does nothing.
3578 3412
3579 module_blacklist= [KNL] Do not load 3413 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3414 modules. Useful for debugging problem modules.
3581 3415
3582 mousedev.tap_time= 3416 mousedev.tap_time=
3583 [MOUSE] Maximum time 3417 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3418 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3419 a tap and be reported as a left button click (for
3586 touchpads working in 3420 touchpads working in absolute mode only).
3587 Format: <msecs> 3421 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3422 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3423 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3424 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3425 reporting absolute coordinates, such as tablets
3592 3426
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3427 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3428 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3429 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3430 specifies the amount of memory used for migratable
3597 allocations. If both 3431 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3432 specified, then kernelcore will be at *least* the
3599 specified value but m 3433 specified value but may be more. If movablecore on its
3600 own is specified, the 3434 own is specified, the administrator must be careful
3601 that the amount of me 3435 that the amount of memory usable for all allocations
3602 is not too small. 3436 is not too small.
3603 3437
3604 movable_node [KNL,EARLY] Boot-time !! 3438 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3439 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3440 of such nodes will be usable only for movable
3607 allocations which rul 3441 allocations which rules out almost all kernel
3608 allocations. Use with 3442 allocations. Use with caution!
3609 3443
3610 MTD_Partition= [MTD] 3444 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3445 Format: <name>,<region-number>,<size>,<offset>
3612 3446
3613 MTD_Region= [MTD] Format: 3447 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3448 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3449
3616 mtdparts= [MTD] 3450 mtdparts= [MTD]
3617 See drivers/mtd/parse 3451 See drivers/mtd/parsers/cmdlinepart.c
3618 3452
>> 3453 mtdset= [ARM]
>> 3454 ARM/S3C2412 JIVE boot control
>> 3455
>> 3456 See arch/arm/mach-s3c/mach-jive.c
>> 3457
3619 mtouchusb.raw_coordinates= 3458 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3459 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3460 ('y', default) or cooked coordinates ('n')
3622 3461
3623 mtrr=debug [X86,EARLY] !! 3462 mtrr=debug [X86]
3624 Enable printing debug 3463 Enable printing debug information related to MTRR
3625 registers at boot tim 3464 registers at boot time.
3626 3465
3627 mtrr_chunk_size=nn[KMG,X86,EARLY] !! 3466 mtrr_chunk_size=nn[KMG] [X86]
3628 used for mtrr cleanup 3467 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3468 that could hold holes aka. UC entries.
3630 3469
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3470 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3471 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3472 Default is 1.
3634 Large value could pre 3473 Large value could prevent small alignment from
3635 using up MTRRs. 3474 using up MTRRs.
3636 3475
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3476 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3477 Format: <integer>
3639 Range: 0,7 : spare re 3478 Range: 0,7 : spare reg number
3640 Default : 1 3479 Default : 1
3641 Used for mtrr cleanup 3480 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3481 Set to 2 or more if your graphical card needs more.
3643 3482
3644 multitce=off [PPC] This parameter 3483 multitce=off [PPC] This parameter disables the use of the pSeries
3645 firmware feature for 3484 firmware feature for updating multiple TCE entries
3646 at a time. 3485 at a time.
3647 3486
3648 n2= [NET] SDL Inc. RISCom 3487 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3488
3650 netdev= [NET] Network devices 3489 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3490 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3491 Note that mem_start is often overloaded to mean
3653 something different a 3492 something different and driver-specific.
3654 This usage is only do 3493 This usage is only documented in each driver source
3655 file if at all. 3494 file if at all.
3656 3495
3657 netpoll.carrier_timeout= 3496 netpoll.carrier_timeout=
3658 [NET] Specifies amoun 3497 [NET] Specifies amount of time (in seconds) that
3659 netpoll should wait f 3498 netpoll should wait for a carrier. By default netpoll
3660 waits 4 seconds. 3499 waits 4 seconds.
3661 3500
3662 nf_conntrack.acct= 3501 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3502 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3503 0 to disable accounting
3665 1 to enable accountin 3504 1 to enable accounting
3666 Default value is 0. 3505 Default value is 0.
3667 3506
3668 nfs.cache_getent= 3507 nfs.cache_getent=
3669 [NFS] sets the pathna 3508 [NFS] sets the pathname to the program which is used
3670 to update the NFS cli 3509 to update the NFS client cache entries.
3671 3510
3672 nfs.cache_getent_timeout= 3511 nfs.cache_getent_timeout=
3673 [NFS] sets the timeou 3512 [NFS] sets the timeout after which an attempt to
3674 update a cache entry 3513 update a cache entry is deemed to have failed.
3675 3514
3676 nfs.callback_nr_threads= 3515 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3516 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3517 NFS client will assign to service NFSv4 callback
3679 requests. 3518 requests.
3680 3519
3681 nfs.callback_tcpport= 3520 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3521 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3522 channel should listen.
3684 3523
3685 nfs.delay_retrans= <<
3686 [NFS] specifies the n <<
3687 retries the request b <<
3688 after a reply of NFS4 <<
3689 Only applies if the s <<
3690 and the specified val <<
3691 <<
3692 nfs.enable_ino64= 3524 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3525 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3526 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3527 number for the readdir() and stat() syscalls instead
3696 of returning the full 3528 of returning the full 64-bit number.
3697 The default is to ret 3529 The default is to return 64-bit inode numbers.
3698 3530
3699 nfs.idmap_cache_timeout= 3531 nfs.idmap_cache_timeout=
3700 [NFS] set the maximum 3532 [NFS] set the maximum lifetime for idmapper cache
3701 entries. 3533 entries.
3702 3534
3703 nfs.max_session_cb_slots= 3535 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3536 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3537 slots the client will assign to the callback
3706 channel. This determi 3538 channel. This determines the maximum number of
3707 callbacks the client 3539 callbacks the client will process in parallel for
3708 a particular server. 3540 a particular server.
3709 3541
3710 nfs.max_session_slots= 3542 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3543 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3544 the client will attempt to negotiate with the server.
3713 This limits the numbe 3545 This limits the number of simultaneous RPC requests
3714 that the client can s 3546 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3547 Note that there is little point in setting this
3716 value higher than the 3548 value higher than the max_tcp_slot_table_limit.
3717 3549
3718 nfs.nfs4_disable_idmapping= 3550 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3551 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3552 ensures that both the RPC level authentication
3721 scheme and the NFS le 3553 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3554 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3555 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3556 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3557 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3558 Servers that do not support this mode of operation
3727 will be autodetected 3559 will be autodetected by the client, and it will fall
3728 back to using the idm 3560 back to using the idmapper.
3729 To turn off this beha 3561 To turn off this behaviour, set the value to '0'.
3730 3562
3731 nfs.nfs4_unique_id= 3563 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3564 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3565 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3566 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3567 UUID that is generated at system install time.
3736 3568
3737 nfs.recover_lost_locks= 3569 nfs.recover_lost_locks=
3738 [NFSv4] Attempt to re 3570 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3571 to a lease timeout on the server. Please note that
3740 doing this risks data 3572 doing this risks data corruption, since there are
3741 no guarantees that th 3573 no guarantees that the file will remain unchanged
3742 after the locks are l 3574 after the locks are lost.
3743 If you want to enable 3575 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3576 attempting to recover these locks, then set this
3745 parameter to '1'. 3577 parameter to '1'.
3746 The default parameter 3578 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3579 not to attempt recovery of lost locks.
3748 3580
3749 nfs.send_implementation_id= 3581 nfs.send_implementation_id=
3750 [NFSv4.1] Send client 3582 [NFSv4.1] Send client implementation identification
3751 information in exchan 3583 information in exchange_id requests.
3752 If zero, no implement 3584 If zero, no implementation identification information
3753 will be sent. 3585 will be sent.
3754 The default is to sen 3586 The default is to send the implementation identification
3755 information. 3587 information.
3756 3588
3757 nfs4.layoutstats_timer= 3589 nfs4.layoutstats_timer=
3758 [NFSv4.2] Change the 3590 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3591 layoutstats to the pNFS metadata server.
3760 3592
3761 Setting this to value 3593 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3594 whatever value is the default set by the layout
3763 driver. A non-zero va 3595 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3596 in seconds between layoutstats transmissions.
3765 3597
3766 nfsd.inter_copy_offload_enable= 3598 nfsd.inter_copy_offload_enable=
3767 [NFSv4.2] When set to 3599 [NFSv4.2] When set to 1, the server will support
3768 server-to-server copi 3600 server-to-server copies for which this server is
3769 the destination of th 3601 the destination of the copy.
3770 3602
3771 nfsd.nfs4_disable_idmapping= 3603 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 3604 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 3605 server will return only numeric uids and gids to
3774 clients using auth_sy 3606 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 3607 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 3608 migration from NFSv2/v3.
3777 3609
3778 nfsd.nfsd4_ssc_umount_timeout= 3610 nfsd.nfsd4_ssc_umount_timeout=
3779 [NFSv4.2] When used a 3611 [NFSv4.2] When used as the destination of a
3780 server-to-server copy 3612 server-to-server copy, knfsd temporarily mounts
3781 the source server. I 3613 the source server. It caches the mount in case
3782 it will be needed aga 3614 it will be needed again, and discards it if not
3783 used for the number o 3615 used for the number of milliseconds specified by
3784 this parameter. 3616 this parameter.
3785 3617
3786 nfsaddrs= [NFS] Deprecated. Us 3618 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3787 See Documentation/adm 3619 See Documentation/admin-guide/nfs/nfsroot.rst.
3788 3620
3789 nfsroot= [NFS] nfs root filesy 3621 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3790 See Documentation/adm 3622 See Documentation/admin-guide/nfs/nfsroot.rst.
3791 3623
3792 nfsrootdebug [NFS] enable nfsroot 3624 nfsrootdebug [NFS] enable nfsroot debugging messages.
3793 See Documentation/adm 3625 See Documentation/admin-guide/nfs/nfsroot.rst.
3794 3626
3795 nmi_backtrace.backtrace_idle [KNL] 3627 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3628 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3629 NMI stack-backtrace request.
3798 3630
3799 nmi_debug= [KNL,SH] Specify one 3631 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3632 when a NMI is triggered.
3801 Format: [state][,regs 3633 Format: [state][,regs][,debounce][,die]
3802 3634
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3635 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3636 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3637 Valid num: 0 or 1
3806 0 - turn hardlockup d 3638 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3639 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3640 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3641 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3642 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3643 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3644 please see 'nowatchdog'.
3815 This is useful when y 3645 This is useful when you use a panic=... timeout and
3816 need the box quickly 3646 need the box quickly up again.
3817 3647
3818 These settings can be 3648 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3649 the nmi_watchdog and hardlockup_panic sysctls.
3820 3650
3821 no387 [BUGS=X86-32] Tells t 3651 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3652 emulation library even if a 387 maths coprocessor
3823 is present. 3653 is present.
3824 3654
3825 no4lvl [RISCV,EARLY] Disable !! 3655 no4lvl [RISCV] Disable 4-level and 5-level paging modes. Forces
3826 Forces kernel to use !! 3656 kernel to use 3-level paging instead.
3827 3657
3828 no5lvl [X86-64,RISCV,EARLY] !! 3658 no5lvl [X86-64,RISCV] Disable 5-level paging mode. Forces
3829 kernel to use 4-level 3659 kernel to use 4-level paging instead.
3830 3660
>> 3661 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3662 caches in the slab allocator. Saves per-node memory,
>> 3663 but will impact performance.
>> 3664
3831 noalign [KNL,ARM] 3665 noalign [KNL,ARM]
3832 3666
3833 noapic [SMP,APIC,EARLY] Tell !! 3667 noaltinstr [S390] Disables alternative instructions patching
>> 3668 (CPU alternatives feature).
>> 3669
>> 3670 noapic [SMP,APIC] Tells the kernel to not make use of any
3834 IOAPICs that may be p 3671 IOAPICs that may be present in the system.
3835 3672
3836 noautogroup Disable scheduler aut 3673 noautogroup Disable scheduler automatic task group creation.
3837 3674
3838 nocache [ARM,EARLY] !! 3675 nocache [ARM]
3839 3676
3840 no_console_suspend 3677 no_console_suspend
3841 [HW] Never suspend th 3678 [HW] Never suspend the console
3842 Disable suspending of 3679 Disable suspending of consoles during suspend and
3843 hibernate operations. 3680 hibernate operations. Once disabled, debugging
3844 messages can reach va 3681 messages can reach various consoles while the rest
3845 of the system is bein 3682 of the system is being put to sleep (ie, while
3846 debugging driver susp 3683 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3684 not work reliably with all consoles, but is known
3848 to work with serial a 3685 to work with serial and VGA consoles.
3849 To facilitate more fl 3686 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3687 console_suspend, a printk module parameter to control
3851 it. Users could use c 3688 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3689 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3690 turn on/off it dynamically.
3854 3691
3855 no_debug_objects 3692 no_debug_objects
3856 [KNL,EARLY] Disable o !! 3693 [KNL] Disable object debugging
3857 3694
3858 nodsp [SH] Disable hardware 3695 nodsp [SH] Disable hardware DSP at boot time.
3859 3696
3860 noefi [EFI,EARLY] Disable E !! 3697 noefi Disable EFI runtime services support.
>> 3698
>> 3699 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3861 3700
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3701 noexec [IA-64]
3863 3702
3864 noexec32 [X86-64] 3703 noexec32 [X86-64]
3865 This affects only 32- 3704 This affects only 32-bit executables.
3866 noexec32=on: enable n 3705 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3706 read doesn't imply executable mappings
3868 noexec32=off: disable 3707 noexec32=off: disable non-executable mappings
3869 read implies 3708 read implies executable mappings
3870 3709
3871 no_file_caps Tells the kernel not 3710 no_file_caps Tells the kernel not to honor file capabilities. The
3872 only way then for a f 3711 only way then for a file to be executed with privilege
3873 is to be setuid root 3712 is to be setuid root or executed by root.
3874 3713
3875 nofpu [MIPS,SH] Disable har 3714 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3715
3877 nofsgsbase [X86] Disables FSGSBA 3716 nofsgsbase [X86] Disables FSGSBASE instructions.
3878 3717
3879 nofxsr [BUGS=X86-32] Disable 3718 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3719 register save and restore. The kernel will only save
3881 legacy floating-point 3720 legacy floating-point registers on task switch.
3882 3721
>> 3722 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3723 function PAL_HALT_LIGHT when idle. This increases
>> 3724 power-consumption. On the positive side, it reduces
>> 3725 interrupt wake-up latency, which may improve performance
>> 3726 in certain environments such as networked servers or
>> 3727 real-time systems.
>> 3728
3883 no_hash_pointers 3729 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3730 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3731 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3732 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3733 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3734 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3735 users, but it also makes debugging the kernel more
3891 difficult since unequ 3736 difficult since unequal pointers can no longer be
3892 compared. However, i 3737 compared. However, if this command-line option is
3893 specified, then all n 3738 specified, then all normal pointers will have their true
3894 value printed. This o 3739 value printed. This option should only be specified when
3895 debugging the kernel. 3740 debugging the kernel. Please do not use on production
3896 kernels. 3741 kernels.
3897 3742
3898 nohibernate [HIBERNATION] Disable 3743 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3744
3900 nohlt [ARM,ARM64,MICROBLAZE !! 3745 nohlt [ARM,ARM64,MICROBLAZE,MIPS,SH] Forces the kernel to
3901 busy wait in do_idle( 3746 busy wait in do_idle() and not use the arch_cpu_idle()
3902 implementation; requi 3747 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
3903 to be effective. This 3748 to be effective. This is useful on platforms where the
3904 sleep(SH) or wfi(ARM, 3749 sleep(SH) or wfi(ARM,ARM64) instructions do not work
3905 correctly or when doi 3750 correctly or when doing power measurements to evaluate
3906 the impact of the sle 3751 the impact of the sleep instructions. This is also
3907 useful when using JTA 3752 useful when using JTAG debugger.
3908 3753
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA !! 3754 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3910 3755
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA !! 3756 nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
3912 3757
3913 nohz= [KNL] Boottime enable 3758 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3759 Valid arguments: on, off
3915 Default: on 3760 Default: on
3916 3761
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3762 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3763 The argument is a cpu list, as described above.
3919 In kernels built with 3764 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3765 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3766 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3767 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3768 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3769 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3770 rcu_nocbs= boot parameter.
3926 3771
3927 Note that this argume 3772 Note that this argument takes precedence over
3928 the CONFIG_RCU_NOCB_C 3773 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
3929 3774
3930 noinitrd [RAM] Tells the kerne 3775 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3776 initial RAM disk.
3932 3777
3933 nointremap [X86-64,Intel-IOMMU,E !! 3778 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3779 remapping.
3935 [Deprecated - use int 3780 [Deprecated - use intremap=off]
3936 3781
3937 noinvpcid [X86,EARLY] Disable t !! 3782 nointroute [IA-64]
>> 3783
>> 3784 noinvpcid [X86] Disable the INVPCID cpu feature.
3938 3785
3939 noiotrap [SH] Disables trapped 3786 noiotrap [SH] Disables trapped I/O port accesses.
3940 3787
3941 noirqdebug [X86-32] Disables the 3788 noirqdebug [X86-32] Disables the code which attempts to detect and
3942 disable unhandled int 3789 disable unhandled interrupt sources.
3943 3790
3944 noisapnp [ISAPNP] Disables ISA 3791 noisapnp [ISAPNP] Disables ISA PnP code.
3945 3792
3946 nokaslr [KNL,EARLY] !! 3793 nojitter [IA-64] Disables jitter checking for ITC timers.
>> 3794
>> 3795 nokaslr [KNL]
3947 When CONFIG_RANDOMIZE 3796 When CONFIG_RANDOMIZE_BASE is set, this disables
3948 kernel and module bas 3797 kernel and module base offset ASLR (Address Space
3949 Layout Randomization) 3798 Layout Randomization).
3950 3799
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3800 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3801 fault handling.
3953 3802
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3803 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
>> 3804
>> 3805 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3955 3806
3956 nolapic [X86-32,APIC,EARLY] D !! 3807 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3957 3808
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3809 nomca [IA-64] Disable machine check abort handling
3959 3810
3960 nomce [X86-32] Disable Mach 3811 nomce [X86-32] Disable Machine Check Exception
3961 3812
3962 nomfgpt [X86-32] Disable Mult 3813 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 3814 Timer usage (for AMD Geode machines).
3964 3815
3965 nomodeset Disable kernel modese 3816 nomodeset Disable kernel modesetting. Most systems' firmware
3966 sets up a display mod 3817 sets up a display mode and provides framebuffer memory
3967 for output. With nomo 3818 for output. With nomodeset, DRM and fbdev drivers will
3968 not load if they coul 3819 not load if they could possibly displace the pre-
3969 initialized output. O 3820 initialized output. Only the system framebuffer will
3970 be available for use. 3821 be available for use. The respective drivers will not
3971 perform display-mode 3822 perform display-mode changes or accelerated rendering.
3972 3823
3973 Useful as error fallb 3824 Useful as error fallback, or for testing and debugging.
3974 3825
3975 nomodule Disable module load 3826 nomodule Disable module load
3976 3827
3977 nonmi_ipi [X86] Disable using N 3828 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3829 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3830 irq.
3980 3831
3981 nopat [X86,EARLY] Disable P !! 3832 nopat [X86] Disable PAT (page attribute table extension of
3982 pagetables) support. 3833 pagetables) support.
3983 3834
3984 nopcid [X86-64,EARLY] Disabl !! 3835 nopcid [X86-64] Disable the PCID cpu feature.
3985 3836
3986 nopku [X86] Disable Memory 3837 nopku [X86] Disable Memory Protection Keys CPU feature found
3987 in some Intel CPUs. 3838 in some Intel CPUs.
3988 3839
3989 nopti [X86-64,EARLY] !! 3840 nopti [X86-64]
3990 Equivalent to pti=off 3841 Equivalent to pti=off
3991 3842
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3843 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
3993 Disables the PV optim 3844 Disables the PV optimizations forcing the guest to run
3994 as generic guest with 3845 as generic guest with no PV drivers. Currently support
3995 XEN HVM, KVM, HYPER_V 3846 XEN HVM, KVM, HYPER_V and VMWARE guest.
3996 3847
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3848 nopvspin [X86,XEN,KVM]
3998 Disables the qspinloc 3849 Disables the qspinlock slow path using PV optimizations
3999 which allow the hyper 3850 which allow the hypervisor to 'idle' the guest on lock
4000 contention. 3851 contention.
4001 3852
4002 norandmaps Don't use address spa 3853 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3854 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3855
4005 noreplace-smp [X86-32,SMP] Don't re 3856 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3857 with UP alternatives
4007 3858
4008 noresume [SWSUSP] Disables res 3859 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3860 space.
4010 3861
>> 3862 nosbagart [IA-64]
>> 3863
4011 no-scroll [VGA] Disables scroll 3864 no-scroll [VGA] Disables scrollback.
4012 This is required for 3865 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3866 reader made by F.H. Papenmeier (Germany).
4014 3867
4015 nosgx [X86-64,SGX,EARLY] Di !! 3868 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4016 3869
4017 nosmap [PPC,EARLY] !! 3870 nosmap [PPC]
4018 Disable SMAP (Supervi 3871 Disable SMAP (Supervisor Mode Access Prevention)
4019 even if it is support 3872 even if it is supported by processor.
4020 3873
4021 nosmep [PPC64s,EARLY] !! 3874 nosmep [PPC64s]
4022 Disable SMEP (Supervi 3875 Disable SMEP (Supervisor Mode Execution Prevention)
4023 even if it is support 3876 even if it is supported by processor.
4024 3877
4025 nosmp [SMP,EARLY] Tells an !! 3878 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3879 and disable the IO APIC. legacy for "maxcpus=0".
4027 3880
4028 nosmt [KNL,MIPS,PPC,S390,EA !! 3881 nosmt [KNL,MIPS,S390] Disable symmetric multithreading (SMT).
4029 Equivalent to smt=1. 3882 Equivalent to smt=1.
4030 3883
4031 [KNL,X86,PPC] Disable !! 3884 [KNL,X86] Disable symmetric multithreading (SMT).
4032 nosmt=force: Force di 3885 nosmt=force: Force disable SMT, cannot be undone
4033 via the 3886 via the sysfs control file.
4034 3887
4035 nosoftlockup [KNL] Disable the sof 3888 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3889
4037 nospec_store_bypass_disable 3890 nospec_store_bypass_disable
4038 [HW,EARLY] Disable al !! 3891 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
4039 Store Bypass vulnerab <<
4040 3892
4041 nospectre_bhb [ARM64,EARLY] Disable !! 3893 nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch
4042 history injection) vu 3894 history injection) vulnerability. System may allow data leaks
4043 with this option. 3895 with this option.
4044 3896
4045 nospectre_v1 [X86,PPC,EARLY] Disab !! 3897 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
4046 (bounds check bypass) 3898 (bounds check bypass). With this option data leaks are
4047 possible in the syste 3899 possible in the system.
4048 3900
4049 nospectre_v2 [X86,PPC_E500,ARM64,E !! 3901 nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for
4050 for the Spectre varia !! 3902 the Spectre variant 2 (indirect branch prediction)
4051 prediction) vulnerabi !! 3903 vulnerability. System may allow data leaks with this
4052 leaks with this optio !! 3904 option.
4053 !! 3905
4054 no-steal-acc [X86,PV_OPS,ARM64,PPC !! 3906 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
4055 Disable paravirtualiz !! 3907 steal time accounting. steal time is computed, but
4056 is computed, but won' !! 3908 won't influence scheduler behaviour
4057 3909
4058 nosync [HW,M68K] Disables sy 3910 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3911
4060 no_timer_check [X86,APIC] Disables t 3912 no_timer_check [X86,APIC] Disables the code which tests for
4061 broken timer IRQ sour 3913 broken timer IRQ sources.
4062 3914
4063 no_uaccess_flush 3915 no_uaccess_flush
4064 [PPC,EARLY] Don't flu !! 3916 [PPC] Don't flush the L1-D cache after accessing user data.
4065 3917
4066 novmcoredd [KNL,KDUMP] 3918 novmcoredd [KNL,KDUMP]
4067 Disable device dump. 3919 Disable device dump. Device dump allows drivers to
4068 append dump data to v 3920 append dump data to vmcore so you can collect driver
4069 specified debug info. 3921 specified debug info. Drivers can append the data
4070 without any limit and 3922 without any limit and this data is stored in memory,
4071 so this may cause sig 3923 so this may cause significant memory stress. Disabling
4072 device dump can help 3924 device dump can help save memory but the driver debug
4073 data will be no longe 3925 data will be no longer available. This parameter
4074 is only available whe 3926 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
4075 is set. 3927 is set.
4076 3928
4077 no-vmw-sched-clock 3929 no-vmw-sched-clock
4078 [X86,PV_OPS,EARLY] Di !! 3930 [X86,PV_OPS] Disable paravirtualized VMware scheduler
4079 scheduler clock and u !! 3931 clock and use the default one.
4080 3932
4081 nowatchdog [KNL] Disable both lo 3933 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3934 soft-lockup and NMI watchdog (hard-lockup).
4083 3935
4084 nowb [ARM,EARLY] !! 3936 nowb [ARM]
4085 3937
4086 nox2apic [X86-64,APIC,EARLY] D !! 3938 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3939
4088 NOTE: this parameter 3940 NOTE: this parameter will be ignored on systems with the
4089 LEGACY_XAPIC_DISABLED 3941 LEGACY_XAPIC_DISABLED bit set in the
4090 IA32_XAPIC_DISABLE_ST 3942 IA32_XAPIC_DISABLE_STATUS MSR.
4091 3943
4092 noxsave [BUGS=X86] Disables x 3944 noxsave [BUGS=X86] Disables x86 extended register state save
4093 and restore using xsa 3945 and restore using xsave. The kernel will fallback to
4094 enabling legacy float 3946 enabling legacy floating-point and sse state.
4095 3947
4096 noxsaveopt [X86] Disables xsaveo 3948 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
4097 register states. The 3949 register states. The kernel will fall back to use
4098 xsave to save the sta 3950 xsave to save the states. By using this parameter,
4099 performance of saving 3951 performance of saving the states is degraded because
4100 xsave doesn't support 3952 xsave doesn't support modified optimization while
4101 xsaveopt supports it 3953 xsaveopt supports it on xsaveopt enabled systems.
4102 3954
4103 noxsaves [X86] Disables xsaves 3955 noxsaves [X86] Disables xsaves and xrstors used in saving and
4104 restoring x86 extende 3956 restoring x86 extended register state in compacted
4105 form of xsave area. T 3957 form of xsave area. The kernel will fall back to use
4106 xsaveopt and xrstor t 3958 xsaveopt and xrstor to save and restore the states
4107 in standard form of x 3959 in standard form of xsave area. By using this
4108 parameter, xsave area 3960 parameter, xsave area per process might occupy more
4109 memory on xsaves enab 3961 memory on xsaves enabled systems.
4110 3962
4111 nr_cpus= [SMP,EARLY] Maximum n !! 3963 nps_mtm_hs_ctr= [KNL,ARC]
>> 3964 This parameter sets the maximum duration, in
>> 3965 cycles, each HW thread of the CTOP can run
>> 3966 without interruptions, before HW switches it.
>> 3967 The actual maximum duration is 16 times this
>> 3968 parameter's value.
>> 3969 Format: integer between 1 and 255
>> 3970 Default: 255
>> 3971
>> 3972 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3973 purges which is reported from either PAL_VM_SUMMARY or
>> 3974 SAL PALO.
>> 3975
>> 3976 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4112 could support. nr_cp 3977 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3978 support 'n' processors. It could be larger than the
4114 number of already plu 3979 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3980 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3981 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3982 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3983 hot plugging.
4119 3984
4120 nr_uarts= [SERIAL] maximum numb 3985 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3986
4122 numa=off [KNL, ARM64, PPC, RIS !! 3987 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123 Disable NUMA, Only se !! 3988 set up a single NUMA node spanning all memory.
4124 spanning all memory. <<
4125 3989
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 3990 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 3991 NUMA balancing.
4128 Allowed values are en 3992 Allowed values are enable and disable
4129 3993
4130 numa_zonelist_order= [KNL, BOOT] Sele 3994 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3995 'node', 'default' can be specified
4132 This can be set from 3996 This can be set from sysctl after boot.
4133 See Documentation/adm 3997 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 3998
4135 ohci1394_dma=early [HW,EARLY] en !! 3999 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 4000 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 4001 info.
4138 4002
4139 olpc_ec_timeout= [OLPC] ms delay when 4003 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 4004 Rather than timing out after 20 ms if an EC
4141 command is not proper 4005 command is not properly ACKed, override the length
4142 of the timeout. We h 4006 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 4007 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 4008 interrupts *may* be lost!
4145 4009
4146 omap_mux= [OMAP] Override bootl 4010 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 4011 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 4012 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 4013 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 4014
4151 onenand.bdry= [HW,MTD] Flex-OneNAND 4015 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4152 4016
4153 Format: [die0_boundar 4017 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4154 4018
4155 boundary - index of l 4019 boundary - index of last SLC block on Flex-OneNAND.
4156 The remain 4020 The remaining blocks are configured as MLC blocks.
4157 lock - Configure 4021 lock - Configure if Flex-OneNAND boundary should be locked.
4158 Once locke 4022 Once locked, the boundary cannot be changed.
4159 1 indicate 4023 1 indicates lock status, 0 indicates unlock status.
4160 4024
4161 oops=panic [KNL,EARLY] !! 4025 oops=panic Always panic on oopses. Default is to just kill the
4162 Always panic on oopse <<
4163 process, but there is 4026 process, but there is a small probability of
4164 deadlocking the machi 4027 deadlocking the machine.
4165 This will also cause 4028 This will also cause panics on machine check exceptions.
4166 Useful together with 4029 Useful together with panic=30 to trigger a reboot.
4167 4030
4168 page_alloc.shuffle= 4031 page_alloc.shuffle=
4169 [KNL] Boolean flag to 4032 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 4033 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 4034 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 4035 running on a platform with a direct-mapped memory-side
>> 4036 cache, and this parameter can be used to
>> 4037 override/disable that behavior. The state of the flag
>> 4038 can be read from sysfs at:
4173 /sys/module/page_allo 4039 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 4040
4176 page_owner= [KNL,EARLY] Boot-time !! 4041 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 4042 Storage of the information about who allocated
4178 each page is disabled 4043 each page is disabled in default. With this switch,
4179 we can turn it on. 4044 we can turn it on.
4180 on: enable the featur 4045 on: enable the feature
4181 4046
4182 page_poison= [KNL,EARLY] Boot-time !! 4047 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 4048 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 4049 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 4050 off: turn off poisoning (default)
4186 on: turn on poisoning 4051 on: turn on poisoning
4187 4052
4188 page_reporting.page_reporting_order= 4053 page_reporting.page_reporting_order=
4189 [KNL] Minimal page re 4054 [KNL] Minimal page reporting order
4190 Format: <integer> 4055 Format: <integer>
4191 Adjust the minimal pa 4056 Adjust the minimal page reporting order. The page
4192 reporting is disabled !! 4057 reporting is disabled when it exceeds MAX_ORDER.
4193 4058
4194 panic= [KNL] Kernel behaviou 4059 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 4060 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 4061 timeout = 0: wait forever
4197 timeout < 0: reboot i 4062 timeout < 0: reboot immediately
4198 Format: <timeout> 4063 Format: <timeout>
4199 4064
4200 panic_on_taint= [KNL,EARLY] !! 4065 panic_print= Bitmask for printing system info when panic happens.
4201 Bitmask for condition !! 4066 User can chose combination of the following bits:
>> 4067 bit 0: print all tasks info
>> 4068 bit 1: print system memory info
>> 4069 bit 2: print timer info
>> 4070 bit 3: print locks info if CONFIG_LOCKDEP is on
>> 4071 bit 4: print ftrace buffer
>> 4072 bit 5: print all printk messages in buffer
>> 4073 bit 6: print all CPUs backtrace (if available in the arch)
>> 4074 *Be aware* that this option may print a _lot_ of lines,
>> 4075 so there are risks of losing older messages in the log.
>> 4076 Use this option carefully, maybe worth to setup a
>> 4077 bigger log buffer with "log_buf_len" along with this.
>> 4078
>> 4079 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4202 Format: <hex>[,nouser 4080 Format: <hex>[,nousertaint]
4203 Hexadecimal bitmask r 4081 Hexadecimal bitmask representing the set of TAINT flags
4204 that will cause the k 4082 that will cause the kernel to panic when add_taint() is
4205 called with any of th 4083 called with any of the flags in this set.
4206 The optional switch " 4084 The optional switch "nousertaint" can be utilized to
4207 prevent userspace for 4085 prevent userspace forced crashes by writing to sysctl
4208 /proc/sys/kernel/tain 4086 /proc/sys/kernel/tainted any flagset matching with the
4209 bitmask set on panic_ 4087 bitmask set on panic_on_taint.
4210 See Documentation/adm 4088 See Documentation/admin-guide/tainted-kernels.rst for
4211 extra details on the 4089 extra details on the taint flags that users can pick
4212 to compose the bitmas 4090 to compose the bitmask to assign to panic_on_taint.
4213 4091
4214 panic_on_warn=1 panic() instead of WA 4092 panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump
4215 on a WARN(). 4093 on a WARN().
4216 4094
4217 panic_print= Bitmask for printing <<
4218 User can chose combin <<
4219 bit 0: print all task <<
4220 bit 1: print system m <<
4221 bit 2: print timer in <<
4222 bit 3: print locks in <<
4223 bit 4: print ftrace b <<
4224 bit 5: print all prin <<
4225 bit 6: print all CPUs <<
4226 bit 7: print only tas <<
4227 *Be aware* that this <<
4228 so there are risks of <<
4229 Use this option caref <<
4230 bigger log buffer wit <<
4231 <<
4232 parkbd.port= [HW] Parallel port nu 4095 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 4096 connected to, default is 0.
4234 Format: <parport#> 4097 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 4098 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 4099 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 4100 Format: <mode>
4238 4101
4239 parport= [HW,PPT] Specify para 4102 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 4103 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 4104 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 4105 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 4106 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 4107 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 4108 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 4109 should be numbers, or 'auto' (for using detected
4247 settings on that part 4110 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 4111 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 4112 Parallel ports are assigned in the order they
4250 are specified on the 4113 are specified on the command line, starting
4251 with parport0. 4114 with parport0.
4252 4115
4253 parport_init_mode= [HW,PPT] 4116 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 4117 Configure VIA parallel port to operate in
4255 a specific mode. This 4118 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 4119 computer where firmware has no options for setting
4257 up parallel port mode 4120 up parallel port mode and sets it to spp.
4258 Currently this functi 4121 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 4122 Format: [spp|ps2|epp|ecp|ecpepp]
4260 4123
4261 pata_legacy.all= [HW,LIBATA] 4124 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 4125 Format: <int>
4263 Set to non-zero to pr 4126 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 4127 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 4128 has been found at either range. Disabled by default.
4266 4129
4267 pata_legacy.autospeed= [HW,LIBATA] 4130 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 4131 Format: <int>
4269 Set to non-zero if a 4132 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 4133 changes. Disabled by default.
4271 4134
4272 pata_legacy.ht6560a= [HW,LIBATA] 4135 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 4136 Format: <int>
4274 Set to 1, 2, or 3 for 4137 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 4138 the secondary channel, or both channels respectively.
4276 Disabled by default. 4139 Disabled by default.
4277 4140
4278 pata_legacy.ht6560b= [HW,LIBATA] 4141 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 4142 Format: <int>
4280 Set to 1, 2, or 3 for 4143 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 4144 the secondary channel, or both channels respectively.
4282 Disabled by default. 4145 Disabled by default.
4283 4146
4284 pata_legacy.iordy_mask= [HW,LIBATA] 4147 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 4148 Format: <int>
4286 IORDY enable mask. S 4149 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 4150 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 4151 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 4152 the second channel, and so on. The sequence will often
4290 correspond to the pri 4153 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 4154 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 4155 bus and the use of other driver options may interfere
4293 with the sequence. B 4156 with the sequence. By default IORDY is allowed across
4294 all channels. 4157 all channels.
4295 4158
4296 pata_legacy.opti82c46x= [HW,LIBATA] 4159 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 4160 Format: <int>
4298 Set to 1, 2, or 3 for 4161 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 4162 channel, the secondary channel, or both channels
4300 respectively. Disabl 4163 respectively. Disabled by default.
4301 4164
4302 pata_legacy.opti82c611a= [HW,L 4165 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 4166 Format: <int>
4304 Set to 1, 2, or 3 for 4167 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 4168 channel, the secondary channel, or both channels
4306 respectively. Disabl 4169 respectively. Disabled by default.
4307 4170
4308 pata_legacy.pio_mask= [HW,LIBATA] 4171 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 4172 Format: <int>
4310 PIO mode mask for aut 4173 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 4174 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 4175 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 4176 All modes allowed by default.
4314 4177
4315 pata_legacy.probe_all= [HW,LIBATA] 4178 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 4179 Format: <int>
4317 Set to non-zero to pr 4180 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 4181 port ranges on PCI systems. Disabled by default.
4319 4182
4320 pata_legacy.probe_mask= [HW,LIBATA] 4183 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 4184 Format: <int>
4322 Probe mask for legacy 4185 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 4186 platform configuration and the use of other driver
4324 options up to 6 legac 4187 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 4188 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 4189 of individual ports can be disabled by setting the
4327 corresponding bits in 4190 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 4191 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 4192 By default all supported ports are probed.
4330 4193
4331 pata_legacy.qdi= [HW,LIBATA] 4194 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 4195 Format: <int>
4333 Set to non-zero to pr 4196 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 4197 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 4198
4336 pata_legacy.winbond= [HW,LIBATA] 4199 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 4200 Format: <int>
4338 Set to non-zero to pr 4201 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 4202 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 4203 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 4204 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 4205 0 otherwise.
4343 4206
4344 pata_platform.pio_mask= [HW,LIBATA] 4207 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 4208 Format: <int>
4346 Supported PIO mode ma 4209 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 4210 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 4211 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 4212 allowed by default.
4350 4213
4351 pause_on_oops=<int> !! 4214 pause_on_oops=
4352 Halt all CPUs after t 4215 Halt all CPUs after the first oops has been printed for
4353 the specified number 4216 the specified number of seconds. This is to be used if
4354 your oopses keep scro 4217 your oopses keep scrolling off the screen.
4355 4218
4356 pcbit= [HW,ISDN] 4219 pcbit= [HW,ISDN]
4357 4220
4358 pci=option[,option...] [PCI,EARLY] v !! 4221 pci=option[,option...] [PCI] various PCI subsystem options.
4359 4222
4360 Some options 4223 Some options herein operate on a specific device
4361 or a set of d 4224 or a set of devices (<pci_dev>). These are
4362 specified in 4225 specified in one of the following formats:
4363 4226
4364 [<domain>:]<b 4227 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 4228 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 4229
4367 Note: the fir 4230 Note: the first format specifies a PCI
4368 bus/device/fu 4231 bus/device/function address which may change
4369 if new hardwa 4232 if new hardware is inserted, if motherboard
4370 firmware chan 4233 firmware changes, or due to changes caused
4371 by other kern 4234 by other kernel parameters. If the
4372 domain is lef 4235 domain is left unspecified, it is
4373 taken to be z 4236 taken to be zero. Optionally, a path
4374 to a device t 4237 to a device through multiple device/function
4375 addresses can 4238 addresses can be specified after the base
4376 address (this 4239 address (this is more robust against
4377 renumbering i 4240 renumbering issues). The second format
4378 selects devic 4241 selects devices using IDs from the
4379 configuration 4242 configuration space which may match multiple
4380 devices in th 4243 devices in the system.
4381 4244
4382 earlydump dump PCI conf 4245 earlydump dump PCI config space before the kernel
4383 changes anyth 4246 changes anything
4384 off [X86] don't p 4247 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 4248 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 4249 the hardware directly. Use this if your machine
4387 has a non-sta 4250 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 4251 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 4252 hardware access methods are allowed. Use this
4390 if you experi 4253 if you experience crashes upon bootup and you
4391 suspect they 4254 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 4255 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 4256 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 4257 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 4258 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 4259 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 4260 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 4261 bus number. The config space is then accessed
4399 through ports 4262 through ports 0xC000-0xCFFF).
4400 See http://wi 4263 See http://wiki.osdev.org/PCI for more info
4401 on the config 4264 on the configuration access mechanisms.
4402 noaer [PCIE] If the 4265 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 4266 enabled, this kernel boot option can be used to
4404 disable the u 4267 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 4268 nodomains [PCI] Disable support for multiple PCI
4406 root domains 4269 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 4270 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 4271 Configuration
4409 check_enable_amd_mmconf [X86] 4272 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 4273 properly configured MMIO access to PCI
4411 config space 4274 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 4275 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 4276 enabled, this kernel boot option can be used to
4414 disable the u 4277 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 4278 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 4279 Safety option to keep boot IRQs enabled. This
4417 should never 4280 should never be necessary.
4418 ioapicreroute [APIC] Enable 4281 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 4282 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 4283 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 4284 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 4285 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 4286 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 4287 a chipset where boot IRQs cannot be disabled.
4425 The opposite 4288 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 4289 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 4290 routing table. These calls are known to be buggy
4428 on several ma 4291 on several machines and they hang the machine
4429 when used, bu 4292 when used, but on other computers it's the only
4430 way to get th 4293 way to get the interrupt routing table. Try
4431 this option i 4294 this option if the kernel is unable to allocate
4432 IRQs or disco 4295 IRQs or discover secondary PCI buses on your
4433 motherboard. 4296 motherboard.
4434 rom [X86] Assign 4297 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 4298 Use with caution as certain devices share
4436 address decod 4299 address decoders between ROMs and other
4437 resources. 4300 resources.
4438 norom [X86] Do not 4301 norom [X86] Do not assign address space to
4439 expansion ROM 4302 expansion ROMs that do not already have
4440 BIOS assigned 4303 BIOS assigned address ranges.
4441 nobar [X86] Do not 4304 nobar [X86] Do not assign address space to the
4442 BARs that wer 4305 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 4306 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 4307 assigned automatically to PCI devices. You can
4445 make the kern 4308 make the kernel exclude IRQs of your ISA cards
4446 this way. 4309 this way.
4447 pirqaddr=0xAAAAA [X86] 4310 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 4311 of the PIRQ table (normally generated
4449 by the BIOS) 4312 by the BIOS) if it is outside the
4450 F0000h-100000 4313 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 4314 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 4315 useful if the kernel is unable to find your
4453 secondary bus 4316 secondary buses and you want to tell it
4454 explicitly wh 4317 explicitly which ones they are.
4455 assign-busses [X86] Always 4318 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 4319 numbers ourselves, overriding
4457 whatever the 4320 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 4321 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 4322 in the BIOS $PIR table. This is needed on
4460 some systems 4323 some systems with broken BIOSes, notably
4461 some HP Pavil 4324 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 4325 notebooks. This will have no effect if ACPI
4463 IRQ routing i 4326 IRQ routing is enabled.
4464 noacpi [X86] Do not 4327 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 4328 or for PCI scanning.
4466 use_crs [X86] Use PCI 4329 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 4330 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 4331 is enabled by default. If you need to use this,
4469 please report 4332 please report a bug.
4470 nocrs [X86] Ignore 4333 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 4334 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 4335 use_e820 [X86] Use E820 reservations to exclude parts of
4473 PCI host brid 4336 PCI host bridge windows. This is a workaround
4474 for BIOS defe 4337 for BIOS defects in host bridge _CRS methods.
4475 If you need t 4338 If you need to use this, please report a bug to
4476 <linux-pci@vge 4339 <linux-pci@vger.kernel.org>.
4477 no_e820 [X86] Ignore 4340 no_e820 [X86] Ignore E820 reservations for PCI host
4478 bridge window 4341 bridge windows. This is the default on modern
4479 hardware. If 4342 hardware. If you need to use this, please report
4480 a bug to <linu 4343 a bug to <linux-pci@vger.kernel.org>.
4481 routeirq Do IRQ routin 4344 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 4345 This is normally done in pci_enable_device(),
4483 so this optio 4346 so this option is a temporary workaround
4484 for broken dr 4347 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 4348 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 4349 handle more pci cards
4487 noearly [X86] Don't d 4350 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 4351 This might help on some broken boards which
4489 machine check 4352 machine check when some devices' config space
4490 is read. But 4353 is read. But various workarounds are disabled
4491 and some IOMM 4354 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 4355 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 4356 This sorting is done to get a device
4494 order compati 4357 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 4358 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 4359 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 4360 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 4361 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 4362 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 4363 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 4364 based on its parent bus. Also set MRRS (Max
4502 Read Request 4365 Read Request Size) to the largest supported
4503 value (no lar 4366 value (no larger than the MPS that the device
4504 or bus can su 4367 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 4368 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 4369 every device is guaranteed to support. This
4507 configuration 4370 configuration allows peer-to-peer DMA between
4508 any pair of d 4371 any pair of devices, possibly at the cost of
4509 reduced perfo 4372 reduced performance. This also guarantees
4510 that hot-adde 4373 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 4374 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 4375 reserved for the CardBus bridge's IO window.
4513 The default v 4376 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 4377 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 4378 reserved for the CardBus bridge's memory
4516 window. The d 4379 window. The default value is 64 megabytes.
4517 resource_alignment= 4380 resource_alignment=
4518 Format: 4381 Format:
4519 [<order of ali 4382 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 4383 Specifies alignment and device to reassign
4521 aligned memor 4384 aligned memory resources. How to
4522 specify the d 4385 specify the device is described above.
4523 If <order of 4386 If <order of align> is not specified,
4524 PAGE_SIZE is 4387 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 4388 A PCI-PCI bridge can be specified if resource
4526 windows need 4389 windows need to be expanded.
4527 To specify th 4390 To specify the alignment for several
4528 instances of 4391 instances of a device, the PCI vendor,
4529 device, subve 4392 device, subvendor, and subdevice may be
4530 specified, e. 4393 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 4394 for 4096-byte alignment.
4532 ecrc= Enable/disabl 4395 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR 4396 end-to-end CRC checking). Only effective if
4534 OS has native 4397 OS has native AER control (either granted by
4535 ACPI _OSC or 4398 ACPI _OSC or forced via "pcie_ports=native")
4536 bios: Use BIO 4399 bios: Use BIOS/firmware settings. This is the
4537 the default. 4400 the default.
4538 off: Turn ECR 4401 off: Turn ECRC off
4539 on: Turn ECRC 4402 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 4403 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 4404 reserved for hotplug bridge's IO window.
4542 Default size 4405 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 4406 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 4407 reserved for hotplug bridge's MMIO window.
4545 Default size 4408 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 4409 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 4410 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 4411 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 4412 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 4413 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 4414 MMIO_PREF window.
4552 Default size 4415 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 4416 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 4417 reserved for buses below a hotplug bridge.
4555 Default is 1. 4418 Default is 1.
4556 realloc= Enable/disabl 4419 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 4420 if allocations done by BIOS are too small to
4558 accommodate r 4421 accommodate resources required by all child
4559 devices. 4422 devices.
4560 off: Turn rea 4423 off: Turn realloc off
4561 on: Turn real 4424 on: Turn realloc on
4562 realloc same as reall 4425 realloc same as realloc=on
4563 noari do not use PC 4426 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 4427 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 4428 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 4429 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 4430 only look for one device below a PCIe downstream
4568 port. 4431 port.
4569 big_root_window Try to add a 4432 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 4433 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 4434 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 4435 Adding the window is slightly risky (it may
4573 conflict with 4436 conflict with unreported devices), so this
4574 taints the ke 4437 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 4438 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 4439 Specify one or more PCI devices (in the format
4577 specified abo 4440 specified above) separated by semicolons.
4578 Each device s 4441 Each device specified will have the PCI ACS
4579 redirect capa 4442 redirect capabilities forced off which will
4580 allow P2P tra 4443 allow P2P traffic between devices through
4581 bridges witho 4444 bridges without forcing it upstream. Note:
4582 this removes 4445 this removes isolation between devices and
4583 may put more 4446 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 4447 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 4448 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 4449 norid [S390] ignore the RID field and force use of
4619 one PCI domai 4450 one PCI domain per PCI function
4620 4451
4621 pcie_aspm= [PCIE] Forcibly enabl !! 4452 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 4453 Management.
4623 off Don't touch ASPM conf !! 4454 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 4455 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 4456 WARNING: Forcing ASPM on may cause system lockups.
4627 4457
4628 pcie_ports= [PCIE] PCIe port serv 4458 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 4459 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 4460 even if the platform doesn't give the OS permission to
4631 use them. This may c 4461 use them. This may cause conflicts if the platform
4632 also tries to use the 4462 also tries to use these services.
4633 dpc-native Use native PC 4463 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 4464 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 4465 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 4466 hotplug).
4637 4467
4638 pcie_port_pm= [PCIE] PCIe port powe 4468 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 4469 off Disable power management of all PCIe ports
4640 force Forcibly enable power 4470 force Forcibly enable power management of all PCIe ports
4641 4471
4642 pcie_pme= [PCIE,PM] Native PCIe 4472 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 4473 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 4474 all PCIe root ports use INTx for all services).
4645 4475
4646 pcmv= [HW,PCMCIA] BadgePAD 4476 pcmv= [HW,PCMCIA] BadgePAD 4
4647 4477
4648 pd_ignore_unused 4478 pd_ignore_unused
4649 [PM] 4479 [PM]
4650 Keep all power-domain 4480 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 4481 even if no driver has claimed them. This is useful
4652 for debug and develop 4482 for debug and development, but should not be
4653 needed on a platform 4483 needed on a platform with proper driver support.
4654 4484
4655 pdcchassis= [PARISC,HW] Disable/E 4485 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4486 boot time.
4657 Format: { 0 | 1 } 4487 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4488 See arch/parisc/kernel/pdc_chassis.c
4659 4489
4660 percpu_alloc= [MM,EARLY] !! 4490 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4491 Currently supported values are "embed" and "page".
4663 Archs may support sub 4492 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4493 See comments in mm/percpu.c for details on each
4665 allocator. This para 4494 allocator. This parameter is primarily for debugging
4666 and performance compa 4495 and performance comparison.
4667 4496
4668 pirq= [SMP,APIC] Manual mp- 4497 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc 4498 See Documentation/arch/x86/i386/IO-APIC.rst.
4670 4499
4671 plip= [PPT,NET] Parallel po 4500 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4501 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4502 See also Documentation/admin-guide/parport.rst.
4674 4503
4675 pmtmr= [X86] Manual setup of 4504 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4505 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4506 e.g. pmtmr=0x508
4678 4507
4679 pmu_override= [PPC] Override the PM 4508 pmu_override= [PPC] Override the PMU.
4680 This option takes ove 4509 This option takes over the PMU facility, so it is no
4681 longer usable by perf 4510 longer usable by perf. Setting this option starts the
4682 PMU counters by setti 4511 PMU counters by setting MMCR0 to 0 (the FC bit is
4683 cleared). If a number 4512 cleared). If a number is given, then MMCR1 is set to
4684 that number, otherwis 4513 that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4685 remains 0. 4514 remains 0.
4686 4515
4687 pm_debug_messages [SUSPEND,KNL] 4516 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4517 Enable suspend/resume debug messages during boot up.
4689 4518
4690 pnp.debug=1 [PNP] 4519 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4520 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4521 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4522 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4523 current resource usage; turning this on also shows
4695 possible settings and 4524 possible settings and some assignment information.
4696 4525
4697 pnpacpi= [ACPI] 4526 pnpacpi= [ACPI]
4698 { off } 4527 { off }
4699 4528
4700 pnpbios= [ISAPNP] 4529 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4530 { on | off | curr | res | no-curr | no-res }
4702 4531
4703 pnp_reserve_irq= 4532 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4533 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4534
4706 pnp_reserve_dma= 4535 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4536 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4537
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4538 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4539 Ranges are in pairs (I/O port base and size).
4711 4540
4712 pnp_reserve_mem= 4541 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4542 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4543 autoconfiguration.
4715 Ranges are in pairs ( 4544 Ranges are in pairs (memory base and size).
4716 4545
4717 ports= [IP_VS_FTP] IPVS ftp 4546 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4547 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4548 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4549 may be specified.
4721 Format: <port>,<port> 4550 Format: <port>,<port>....
4722 4551
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 4552 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4553 It specifically disables cpuidle and sets the
4730 platform machine desc 4554 platform machine description specific power_save
4731 function to NULL. On 4555 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4556 execution priority.
4733 4557
4734 ppc_strict_facility_enable 4558 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4559 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4560 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4561 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4562 There is some performance impact when enabling this.
4739 4563
4740 ppc_tm= [PPC,EARLY] !! 4564 ppc_tm= [PPC]
4741 Format: {"off"} 4565 Format: {"off"}
4742 Disable Hardware Tran 4566 Disable Hardware Transactional Memory
4743 4567
4744 preempt= [KNL] 4568 preempt= [KNL]
4745 Select preemption mod 4569 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4570 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4571 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4572 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4573 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4574
4753 print-fatal-signals= 4575 print-fatal-signals=
4754 [KNL] debug: print fa 4576 [KNL] debug: print fatal signals
4755 4577
4756 If enabled, warn abou 4578 If enabled, warn about various signal handling
4757 related application a 4579 related application anomalies: too many signals,
4758 too many POSIX.1 time 4580 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4581 coredump - etc.
4760 4582
4761 If you hit the warnin 4583 If you hit the warning due to signal overflow,
4762 you might want to try 4584 you might want to try "ulimit -i unlimited".
4763 4585
4764 default: off. 4586 default: off.
4765 4587
4766 printk.always_kmsg_dump= 4588 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4589 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4590 panics
4769 Format: <bool> (1/Y/ 4591 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4592 default: disabled
4771 4593
4772 printk.console_no_auto_verbose= 4594 printk.console_no_auto_verbose=
4773 Disable console logle 4595 Disable console loglevel raise on oops, panic
4774 or lockdep-detected i 4596 or lockdep-detected issues (only if lock debug is on).
4775 With an exception to 4597 With an exception to setups with low baudrate on
4776 serial console, keepi 4598 serial console, keeping this 0 is a good choice
4777 in order to provide m 4599 in order to provide more debug information.
4778 Format: <bool> 4600 Format: <bool>
4779 default: 0 (auto_verb 4601 default: 0 (auto_verbose is enabled)
4780 4602
4781 printk.devkmsg={on,off,ratelimit} 4603 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4604 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4605 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4606 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4607 ratelimit - ratelimit the logging
4786 Default: ratelimit 4608 Default: ratelimit
4787 4609
4788 printk.time= Show timing data pref 4610 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4611 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4612
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] 4613 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4614 Limit processor to maximum C-state
4803 max_cstate=9 override 4615 max_cstate=9 overrides any DMI blacklist limit.
4804 4616
4805 processor.nocst [HW,ACPI] 4617 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4618 Ignore the _CST method to determine C-states,
4807 instead using the leg 4619 instead using the legacy FADT method
4808 4620
4809 profile= [KNL] Enable kernel p 4621 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4622 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4623 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4624 [defaults to kernel profiling]
4813 Param: "schedule" - p 4625 Param: "schedule" - profile schedule points.
>> 4626 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4627 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4628 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4629 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4630 statistical time based profiling.
4817 4631
4818 prompt_ramdisk= [RAM] [Deprecated] 4632 prompt_ramdisk= [RAM] [Deprecated]
4819 4633
4820 prot_virt= [S390] enable hosting 4634 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4635 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4636 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4637 Format: <bool>
4826 4638
4827 psi= [KNL] Enable or disab 4639 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4640 tracking.
4829 Format: <bool> 4641 Format: <bool>
4830 4642
4831 psmouse.proto= [HW,MOUSE] Highest PS 4643 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4644 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4645 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4646 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4647 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4648 Try to reset the device after so many bad packets
4837 (0 = never). 4649 (0 = never).
4838 psmouse.resolution= 4650 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4651 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4652 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4653 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4654 0 = disabled, 1 = enabled (default).
4843 4655
4844 pstore.backend= Specify the name of t 4656 pstore.backend= Specify the name of the pstore backend to use
4845 4657
4846 pti= [X86-64] Control Page 4658 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4659 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4660 removes hardening, but improves performance of
4849 system calls and inte 4661 system calls and interrupts.
4850 4662
4851 on - unconditionall 4663 on - unconditionally enable
4852 off - unconditionall 4664 off - unconditionally disable
4853 auto - kernel detects 4665 auto - kernel detects whether your CPU model is
4854 vulnerable to 4666 vulnerable to issues that PTI mitigates
4855 4667
4856 Not specifying this o 4668 Not specifying this option is equivalent to pti=auto.
4857 4669
4858 pty.legacy_count= 4670 pty.legacy_count=
4859 [KNL] Number of legac 4671 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4672 default number.
4861 4673
4862 quiet [KNL,EARLY] Disable m !! 4674 quiet [KNL] Disable most log messages
4863 4675
4864 r128= [HW,DRM] 4676 r128= [HW,DRM]
4865 4677
4866 radix_hcall_invalidate=on [PPC/PSERI 4678 radix_hcall_invalidate=on [PPC/PSERIES]
4867 Disable RADIX GTSE fe 4679 Disable RADIX GTSE feature and use hcall for TLB
4868 invalidate. 4680 invalidate.
4869 4681
4870 raid= [HW,RAID] 4682 raid= [HW,RAID]
4871 See Documentation/adm 4683 See Documentation/admin-guide/md.rst.
4872 4684
4873 ramdisk_size= [RAM] Sizes of RAM di 4685 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4686 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4687
4876 ramdisk_start= [RAM] RAM disk image 4688 ramdisk_start= [RAM] RAM disk image start address
4877 4689
4878 random.trust_cpu=off 4690 random.trust_cpu=off
4879 [KNL,EARLY] Disable t !! 4691 [KNL] Disable trusting the use of the CPU's
4880 random number generat 4692 random number generator (if available) to
4881 initialize the kernel 4693 initialize the kernel's RNG.
4882 4694
4883 random.trust_bootloader=off 4695 random.trust_bootloader=off
4884 [KNL,EARLY] Disable t !! 4696 [KNL] Disable trusting the use of the a seed
4885 passed by the bootloa 4697 passed by the bootloader (if available) to
4886 initialize the kernel 4698 initialize the kernel's RNG.
4887 4699
4888 randomize_kstack_offset= 4700 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4701 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4702 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4703 entropy, frustrating memory corruption attacks
4892 that depend on stack 4704 that depend on stack address determinism or
4893 cross-syscall address 4705 cross-syscall address exposures. This is only
4894 available on architec 4706 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4707 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4708 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4709 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4710
4899 ras=option[,option,...] [KNL] RAS-spe 4711 ras=option[,option,...] [KNL] RAS-specific options
4900 4712
4901 cec_disable [X86] 4713 cec_disable [X86]
4902 Disable the C 4714 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4715 see CONFIG_RAS_CEC help text.
4904 4716
4905 rcu_nocbs[=cpu-list] 4717 rcu_nocbs[=cpu-list]
4906 [KNL] The optional ar 4718 [KNL] The optional argument is a cpu list,
4907 as described above. 4719 as described above.
4908 4720
4909 In kernels built with 4721 In kernels built with CONFIG_RCU_NOCB_CPU=y,
4910 enable the no-callbac 4722 enable the no-callback CPU mode, which prevents
4911 such CPUs' callbacks 4723 such CPUs' callbacks from being invoked in
4912 softirq context. Inv 4724 softirq context. Invocation of such CPUs' RCU
4913 callbacks will instea 4725 callbacks will instead be offloaded to "rcuox/N"
4914 kthreads created for 4726 kthreads created for that purpose, where "x" is
4915 "p" for RCU-preempt, 4727 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4916 for the kthreads that 4728 for the kthreads that mediate grace periods; and
4917 "N" is the CPU number 4729 "N" is the CPU number. This reduces OS jitter on
4918 the offloaded CPUs, w 4730 the offloaded CPUs, which can be useful for HPC
4919 and real-time workloa 4731 and real-time workloads. It can also improve
4920 energy efficiency for 4732 energy efficiency for asymmetric multiprocessors.
4921 4733
4922 If a cpulist is passe 4734 If a cpulist is passed as an argument, the specified
4923 list of CPUs is set t 4735 list of CPUs is set to no-callback mode from boot.
4924 4736
4925 Otherwise, if the '=' 4737 Otherwise, if the '=' sign and the cpulist
4926 arguments are omitted 4738 arguments are omitted, no CPU will be set to
4927 no-callback mode from 4739 no-callback mode from boot but the mode may be
4928 toggled at runtime vi 4740 toggled at runtime via cpusets.
4929 4741
4930 Note that this argume 4742 Note that this argument takes precedence over
4931 the CONFIG_RCU_NOCB_C 4743 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4932 4744
4933 rcu_nocb_poll [KNL] 4745 rcu_nocb_poll [KNL]
4934 Rather than requiring 4746 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4747 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4748 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4749 make these kthreads poll for callbacks.
4938 This improves the rea 4750 This improves the real-time response for the
4939 offloaded CPUs by rel 4751 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4752 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4753 energy efficiency by requiring that the kthreads
4942 periodically wake up 4754 periodically wake up to do the polling.
4943 4755
4944 rcutree.blimit= [KNL] 4756 rcutree.blimit= [KNL]
4945 Set maximum number of 4757 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4758 process in one batch.
4947 4759
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] 4760 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4761 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4762 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4763 purposes, to verify correct tree setup.
4959 4764
4960 rcutree.gp_cleanup_delay= [KNL] 4765 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4766 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4767 RCU grace-period cleanup.
4963 4768
4964 rcutree.gp_init_delay= [KNL] 4769 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4770 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4771 RCU grace-period initialization.
4967 4772
4968 rcutree.gp_preinit_delay= [KNL] 4773 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4774 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4775 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4776 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4777 the rcu_node combining tree.
4973 4778
4974 rcutree.jiffies_till_first_fqs= [KNL] 4779 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4780 Set delay from grace-period initialization to
4976 first attempt to forc 4781 first attempt to force quiescent states.
4977 Units are jiffies, mi 4782 Units are jiffies, minimum value is zero,
4978 and maximum value is 4783 and maximum value is HZ.
4979 4784
4980 rcutree.jiffies_till_next_fqs= [KNL] 4785 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4786 Set delay between subsequent attempts to force
4982 quiescent states. Un 4787 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4788 value is one, and maximum value is HZ.
4984 4789
4985 rcutree.jiffies_till_sched_qs= [KNL] 4790 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4791 Set required age in jiffies for a
4987 given grace period be 4792 given grace period before RCU starts
4988 soliciting quiescent- 4793 soliciting quiescent-state help from
4989 rcu_note_context_swit 4794 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4795 If not specified, the kernel will calculate
4991 a value based on the 4796 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4797 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4798 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4799 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4800 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4801 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4802 overwritten.
4998 4803
4999 rcutree.kthread_prio= [KNL,BOOT] 4804 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4805 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4806 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4807 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4808 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4809 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4810 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4811 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4812 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4813 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is 4814 When RCU_NOCB_CPU is set, also adjust the
5010 priority of NOCB call 4815 priority of NOCB callback kthreads.
5011 4816
5012 rcutree.nocb_nobypass_lim_per_jiffy= 4817 rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5013 On callback-offloaded 4818 On callback-offloaded (rcu_nocbs) CPUs,
5014 RCU reduces the lock 4819 RCU reduces the lock contention that would
5015 otherwise be caused b 4820 otherwise be caused by callback floods through
5016 use of the ->nocb_byp 4821 use of the ->nocb_bypass list. However, in the
5017 common non-flooded ca 4822 common non-flooded case, RCU queues directly to
5018 the main ->cblist in 4823 the main ->cblist in order to avoid the extra
5019 overhead of the ->noc 4824 overhead of the ->nocb_bypass list and its lock.
5020 But if there are too 4825 But if there are too many callbacks queued during
5021 a single jiffy, RCU p 4826 a single jiffy, RCU pre-queues the callbacks into
5022 the ->nocb_bypass que 4827 the ->nocb_bypass queue. The definition of "too
5023 many" is supplied by 4828 many" is supplied by this kernel boot parameter.
5024 4829
5025 rcutree.nohz_full_patience_delay= [KN <<
5026 On callback-offloaded <<
5027 disturbing RCU unless <<
5028 reached the specified <<
5029 Defaults to zero. La <<
5030 at five seconds. All <<
5031 to the nearest value <<
5032 <<
5033 rcutree.qhimark= [KNL] 4830 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4831 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4832 batch limiting is disabled.
5036 4833
5037 rcutree.qlowmark= [KNL] 4834 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4835 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4836 batch limiting is re-enabled.
5040 4837
5041 rcutree.qovld= [KNL] 4838 rcutree.qovld= [KNL]
5042 Set threshold of queu 4839 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4840 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4841 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4842 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4843 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4844 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4845 disable more aggressive help enlistment.
5049 4846
5050 rcutree.rcu_delay_page_cache_fill_mse 4847 rcutree.rcu_delay_page_cache_fill_msec= [KNL]
5051 Set the page-cache re 4848 Set the page-cache refill delay (in milliseconds)
5052 in response to low-me 4849 in response to low-memory conditions. The range
5053 of permitted values i 4850 of permitted values is in the range 0:100000.
5054 4851
5055 rcutree.rcu_divisor= [KNL] 4852 rcutree.rcu_divisor= [KNL]
5056 Set the shift-right c 4853 Set the shift-right count to use to compute
5057 the callback-invocati 4854 the callback-invocation batch limit bl from
5058 the number of callbac 4855 the number of callbacks queued on this CPU.
5059 The result will be bo 4856 The result will be bounded below by the value of
5060 the rcutree.blimit ke 4857 the rcutree.blimit kernel parameter. Every bl
5061 callbacks, the softir 4858 callbacks, the softirq handler will exit in
5062 order to allow the CP 4859 order to allow the CPU to do other work.
5063 4860
5064 Please note that this 4861 Please note that this callback-invocation batch
5065 limit applies only to 4862 limit applies only to non-offloaded callback
5066 invocation. Offloade 4863 invocation. Offloaded callbacks are instead
5067 invoked in the contex 4864 invoked in the context of an rcuoc kthread, which
5068 scheduler will preemp 4865 scheduler will preempt as it does any other task.
5069 4866
5070 rcutree.rcu_fanout_exact= [KNL] 4867 rcutree.rcu_fanout_exact= [KNL]
5071 Disable autobalancing 4868 Disable autobalancing of the rcu_node combining
5072 tree. This is used b 4869 tree. This is used by rcutorture, and might
5073 possibly be useful fo 4870 possibly be useful for architectures having high
5074 cache-to-cache transf 4871 cache-to-cache transfer latencies.
5075 4872
5076 rcutree.rcu_fanout_leaf= [KNL] 4873 rcutree.rcu_fanout_leaf= [KNL]
5077 Change the number of 4874 Change the number of CPUs assigned to each
5078 leaf rcu_node structu 4875 leaf rcu_node structure. Useful for very
5079 large systems, which 4876 large systems, which will choose the value 64,
5080 and for NUMA systems 4877 and for NUMA systems with large remote-access
5081 latencies, which will 4878 latencies, which will choose a value aligned
5082 with the appropriate 4879 with the appropriate hardware boundaries.
5083 4880
5084 rcutree.rcu_min_cached_objs= [KNL] 4881 rcutree.rcu_min_cached_objs= [KNL]
5085 Minimum number of obj 4882 Minimum number of objects which are cached and
5086 maintained per one CP 4883 maintained per one CPU. Object size is equal
5087 to PAGE_SIZE. The cac 4884 to PAGE_SIZE. The cache allows to reduce the
5088 pressure to page allo 4885 pressure to page allocator, also it makes the
5089 whole algorithm to be 4886 whole algorithm to behave better in low memory
5090 condition. 4887 condition.
5091 4888
5092 rcutree.rcu_nocb_gp_stride= [KNL] 4889 rcutree.rcu_nocb_gp_stride= [KNL]
5093 Set the number of NOC 4890 Set the number of NOCB callback kthreads in
5094 each group, which def 4891 each group, which defaults to the square root
5095 of the number of CPUs 4892 of the number of CPUs. Larger numbers reduce
5096 the wakeup overhead o 4893 the wakeup overhead on the global grace-period
5097 kthread, but increase 4894 kthread, but increases that same overhead on
5098 each group's NOCB gra 4895 each group's NOCB grace-period kthread.
5099 4896
5100 rcutree.rcu_kick_kthreads= [KNL] 4897 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 4898 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 4899 wake_up() if it sleeps three times longer than
5103 it should at force-qu 4900 it should at force-quiescent-state time.
5104 This wake_up() will b 4901 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 4902 WARN_ONCE() splat and an ftrace_dump().
5106 4903
5107 rcutree.rcu_resched_ns= [KNL] 4904 rcutree.rcu_resched_ns= [KNL]
5108 Limit the time spend 4905 Limit the time spend invoking a batch of RCU
5109 callbacks to the spec 4906 callbacks to the specified number of nanoseconds.
5110 By default, this limi 4907 By default, this limit is checked only once
5111 every 32 callbacks in 4908 every 32 callbacks in order to limit the pain
5112 inflicted by local_cl 4909 inflicted by local_clock() overhead.
5113 4910
5114 rcutree.rcu_unlock_delay= [KNL] 4911 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 4912 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 4913 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 4914 in microseconds. This defaults to zero.
5118 Larger delays increas 4915 Larger delays increase the probability of
5119 catching RCU pointer 4916 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 4917 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 4918 rcu_read_unlock() has completed.
5122 4919
5123 rcutree.sysrq_rcu= [KNL] 4920 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 4921 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 4922 rcu_node tree with an eye towards determining
5126 why a new grace perio 4923 why a new grace period has not yet started.
5127 4924
5128 rcutree.use_softirq= [KNL] 4925 rcutree.use_softirq= [KNL]
5129 If set to zero, move 4926 If set to zero, move all RCU_SOFTIRQ processing to
5130 per-CPU rcuc kthreads 4927 per-CPU rcuc kthreads. Defaults to a non-zero
5131 value, meaning that R 4928 value, meaning that RCU_SOFTIRQ is used by default.
5132 Specify rcutree.use_s 4929 Specify rcutree.use_softirq=0 to use rcuc kthreads.
5133 4930
5134 But note that CONFIG_ 4931 But note that CONFIG_PREEMPT_RT=y kernels disable
5135 this kernel boot para 4932 this kernel boot parameter, forcibly setting it
5136 to zero. 4933 to zero.
5137 4934
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] 4935 rcuscale.gp_async= [KNL]
5158 Measure performance o 4936 Measure performance of asynchronous
5159 grace-period primitiv 4937 grace-period primitives such as call_rcu().
5160 4938
5161 rcuscale.gp_async_max= [KNL] 4939 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 4940 Specify the maximum number of outstanding
5163 callbacks per writer 4941 callbacks per writer thread. When a writer
5164 thread exceeds this l 4942 thread exceeds this limit, it invokes the
5165 corresponding flavor 4943 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 4944 previously posted callbacks to drain.
5167 4945
5168 rcuscale.gp_exp= [KNL] 4946 rcuscale.gp_exp= [KNL]
5169 Measure performance o 4947 Measure performance of expedited synchronous
5170 grace-period primitiv 4948 grace-period primitives.
5171 4949
5172 rcuscale.holdoff= [KNL] 4950 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 4951 Set test-start holdoff period. The purpose of
5174 this parameter is to 4952 this parameter is to delay the start of the
5175 test until boot compl 4953 test until boot completes in order to avoid
5176 interference. 4954 interference.
5177 4955
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] 4956 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 4957 Set to measure performance of kfree_rcu() flooding.
5189 4958
5190 rcuscale.kfree_rcu_test_double= [KNL] 4959 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 4960 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 4961 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 4962 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 4963 and double-argument variants are tested.
5195 4964
5196 rcuscale.kfree_rcu_test_single= [KNL] 4965 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 4966 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 4967 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 4968 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 4969 and double-argument variants are tested.
5201 4970
5202 rcuscale.kfree_nthreads= [KNL] 4971 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 4972 The number of threads running loops of kfree_rcu().
5204 4973
5205 rcuscale.kfree_alloc_num= [KNL] 4974 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 4975 Number of allocations and frees done in an iteration.
5207 4976
5208 rcuscale.kfree_loops= [KNL] 4977 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 4978 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 4979 of allocations and frees.
5211 4980
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] 4981 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 4982 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 4983 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 4984 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 4985 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 4986 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 4987 A value of "n" less than or equal to -N selects
5225 a single reader. 4988 a single reader.
5226 4989
5227 rcuscale.nwriters= [KNL] 4990 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 4991 Set number of RCU writers. The values operate
5229 the same as for rcusc 4992 the same as for rcuscale.nreaders.
5230 N, where N is the num 4993 N, where N is the number of CPUs
5231 4994
5232 rcuscale.scale_type= [KNL] !! 4995 rcuscale.perf_type= [KNL]
5233 Specify the RCU imple 4996 Specify the RCU implementation to test.
5234 4997
5235 rcuscale.shutdown= [KNL] 4998 rcuscale.shutdown= [KNL]
5236 Shut the system down 4999 Shut the system down after performance tests
5237 complete. This is us 5000 complete. This is useful for hands-off automated
5238 testing. 5001 testing.
5239 5002
5240 rcuscale.verbose= [KNL] 5003 rcuscale.verbose= [KNL]
5241 Enable additional pri 5004 Enable additional printk() statements.
5242 5005
5243 rcuscale.writer_holdoff= [KNL] 5006 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 5007 Write-side holdoff between grace periods,
5245 in microseconds. The 5008 in microseconds. The default of zero says
5246 no holdoff. 5009 no holdoff.
5247 5010
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] 5011 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 5012 Set duration of force_quiescent_state bursts
5255 in microseconds. 5013 in microseconds.
5256 5014
5257 rcutorture.fqs_holdoff= [KNL] 5015 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 5016 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 5017 in microseconds.
5260 5018
5261 rcutorture.fqs_stutter= [KNL] 5019 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 5020 Set wait time between force_quiescent_state bursts
5263 in seconds. 5021 in seconds.
5264 5022
5265 rcutorture.fwd_progress= [KNL] 5023 rcutorture.fwd_progress= [KNL]
5266 Specifies the number 5024 Specifies the number of kthreads to be used
5267 for RCU grace-period 5025 for RCU grace-period forward-progress testing
5268 for the types of RCU 5026 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread 5027 Defaults to 1 kthread, values less than zero or
5270 greater than the numb 5028 greater than the number of CPUs cause the number
5271 of CPUs to be used. 5029 of CPUs to be used.
5272 5030
5273 rcutorture.fwd_progress_div= [KNL] 5031 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 5032 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 5033 period to do tight-loop forward-progress testing.
5276 5034
5277 rcutorture.fwd_progress_holdoff= [KNL 5035 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 5036 Number of seconds to wait between successive
5279 forward-progress test 5037 forward-progress tests.
5280 5038
5281 rcutorture.fwd_progress_need_resched= 5039 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 5040 Enclose cond_resched() calls within checks for
5283 need_resched() during 5041 need_resched() during tight-loop forward-progress
5284 testing. 5042 testing.
5285 5043
5286 rcutorture.gp_cond= [KNL] 5044 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 5045 Use conditional/asynchronous update-side
5288 primitives, if availa 5046 primitives, if available.
5289 5047
5290 rcutorture.gp_exp= [KNL] 5048 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 5049 Use expedited update-side primitives, if available.
5292 5050
5293 rcutorture.gp_normal= [KNL] 5051 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 5052 Use normal (non-expedited) asynchronous
5295 update-side primitive 5053 update-side primitives, if available.
5296 5054
5297 rcutorture.gp_sync= [KNL] 5055 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 5056 Use normal (non-expedited) synchronous
5299 update-side primitive 5057 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 5058 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 5059 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 5060 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 5061 they are all non-zero.
5304 5062
5305 rcutorture.irqreader= [KNL] 5063 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 5064 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 5065 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 5066 flavors take kindly to this sort of thing.
5309 5067
5310 rcutorture.leakpointer= [KNL] 5068 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 5069 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 5070 This can of course result in splats, and is
5313 intended to test the 5071 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 5072 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 5073 such leaks.
5316 5074
5317 rcutorture.n_barrier_cbs= [KNL] 5075 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 5076 Set callbacks/threads for rcu_barrier() testing.
5319 5077
5320 rcutorture.nfakewriters= [KNL] 5078 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 5079 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 5080 stress RCU, they don't participate in the actual
5323 test, hence the "fake 5081 test, hence the "fake".
5324 5082
5325 rcutorture.nocbs_nthreads= [KNL] 5083 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 5084 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 5085 Zero (the default) disables toggling.
5328 5086
5329 rcutorture.nocbs_toggle= [KNL] 5087 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 5088 Set the delay in milliseconds between successive
5331 callback-offload togg 5089 callback-offload toggling attempts.
5332 5090
5333 rcutorture.nreaders= [KNL] 5091 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 5092 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 5093 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 5094 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 5095 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 5096 (the number of CPUs), -3 selects N+1, and so on.
5339 5097
5340 rcutorture.object_debug= [KNL] 5098 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 5099 Enable debug-object double-call_rcu() testing.
5342 5100
5343 rcutorture.onoff_holdoff= [KNL] 5101 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 5102 Set time (s) after boot for CPU-hotplug testing.
5345 5103
5346 rcutorture.onoff_interval= [KNL] 5104 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 5105 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 5106 or zero to disable CPU-hotplug testing.
5349 5107
5350 rcutorture.read_exit= [KNL] 5108 rcutorture.read_exit= [KNL]
5351 Set the number of rea 5109 Set the number of read-then-exit kthreads used
5352 to test the interacti 5110 to test the interaction of RCU updaters and
5353 task-exit processing. 5111 task-exit processing.
5354 5112
5355 rcutorture.read_exit_burst= [KNL] 5113 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 5114 The number of times in a given read-then-exit
5357 episode that a set of 5115 episode that a set of read-then-exit kthreads
5358 is spawned. 5116 is spawned.
5359 5117
5360 rcutorture.read_exit_delay= [KNL] 5118 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 5119 The delay, in seconds, between successive
5362 read-then-exit testin 5120 read-then-exit testing episodes.
5363 5121
5364 rcutorture.shuffle_interval= [KNL] 5122 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 5123 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 5124 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 5125 during the rcutorture test.
5368 5126
5369 rcutorture.shutdown_secs= [KNL] 5127 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 5128 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 5129 is useful for hands-off automated testing.
5372 5130
5373 rcutorture.stall_cpu= [KNL] 5131 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 5132 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 5133 warnings, zero to disable.
5376 5134
5377 rcutorture.stall_cpu_block= [KNL] 5135 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 5136 Sleep while stalling if set. This will result
5379 in warnings from pree 5137 in warnings from preemptible RCU in addition to
5380 any other stall-relat 5138 any other stall-related activity. Note that
5381 in kernels built with 5139 in kernels built with CONFIG_PREEMPTION=n and
5382 CONFIG_PREEMPT_COUNT= 5140 CONFIG_PREEMPT_COUNT=y, this parameter will
5383 cause the CPU to pass 5141 cause the CPU to pass through a quiescent state.
5384 Given CONFIG_PREEMPTI 5142 Given CONFIG_PREEMPTION=n, this will suppress
5385 RCU CPU stall warning 5143 RCU CPU stall warnings, but will instead result
5386 in scheduling-while-a 5144 in scheduling-while-atomic splats.
5387 5145
5388 Use of this module pa 5146 Use of this module parameter results in splats.
5389 5147
5390 5148
5391 rcutorture.stall_cpu_holdoff= [KNL] 5149 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 5150 Time to wait (s) after boot before inducing stall.
5393 5151
5394 rcutorture.stall_cpu_irqsoff= [KNL] 5152 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 5153 Disable interrupts while stalling if set.
5396 5154
5397 rcutorture.stall_gp_kthread= [KNL] 5155 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 5156 Duration (s) of forced sleep within RCU
5399 grace-period kthread 5157 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 5158 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 5159 and stall_gp_kthread are specified, the
5402 kthread is starved fi 5160 kthread is starved first, then the CPU.
5403 5161
5404 rcutorture.stat_interval= [KNL] 5162 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 5163 Time (s) between statistics printk()s.
5406 5164
5407 rcutorture.stutter= [KNL] 5165 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 5166 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 5167 five seconds causes the test to run for five seconds,
5410 wait for five seconds 5168 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 5169 ability to transition abruptly to and from idle.
5412 5170
5413 rcutorture.test_boost= [KNL] 5171 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 5172 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 5173 "Maybe" means test if the RCU implementation
5416 under test support RC 5174 under test support RCU priority boosting.
5417 5175
5418 rcutorture.test_boost_duration= [KNL] 5176 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 5177 Duration (s) of each individual boost test.
5420 5178
5421 rcutorture.test_boost_interval= [KNL] 5179 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 5180 Interval (s) between each boost test.
5423 5181
5424 rcutorture.test_no_idle_hz= [KNL] 5182 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 5183 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 5184 rcutorture.shuffle_interval parameter.
5427 5185
5428 rcutorture.torture_type= [KNL] 5186 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 5187 Specify the RCU implementation to test.
5430 5188
5431 rcutorture.verbose= [KNL] 5189 rcutorture.verbose= [KNL]
5432 Enable additional pri 5190 Enable additional printk() statements.
5433 5191
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 5192 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 5193 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 5194 stall warning.
5437 5195
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 5196 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 5197 Suppress RCU CPU stall warning messages.
5446 5198
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 5199 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 5200 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 5201 rcutorture writer stall warnings that occur
5450 during early boot, th 5202 during early boot, that is, during the time
5451 before the init task 5203 before the init task is spawned.
5452 5204
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 5205 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 5206 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon 5207 The value is in seconds and the maximum allowed
5456 value is 300 seconds. 5208 value is 300 seconds.
5457 5209
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ 5210 rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5459 Set timeout for exped 5211 Set timeout for expedited RCU CPU stall warning
5460 messages. The value 5212 messages. The value is in milliseconds
5461 and the maximum allow 5213 and the maximum allowed value is 21000
5462 milliseconds. Please 5214 milliseconds. Please note that this value is
5463 adjusted to an arch t 5215 adjusted to an arch timer tick resolution.
5464 Setting this to zero 5216 Setting this to zero causes the value from
5465 rcupdate.rcu_cpu_stal 5217 rcupdate.rcu_cpu_stall_timeout to be used (after
5466 conversion from secon 5218 conversion from seconds to milliseconds).
5467 5219
5468 rcupdate.rcu_cpu_stall_cputime= [KNL] 5220 rcupdate.rcu_cpu_stall_cputime= [KNL]
5469 Provide statistics on 5221 Provide statistics on the cputime and count of
5470 interrupts and tasks 5222 interrupts and tasks during the sampling period. For
5471 multiple continuous R 5223 multiple continuous RCU stalls, all sampling periods
5472 begin at half of the 5224 begin at half of the first RCU stall timeout.
5473 5225
5474 rcupdate.rcu_exp_stall_task_details= 5226 rcupdate.rcu_exp_stall_task_details= [KNL]
5475 Print stack dumps of 5227 Print stack dumps of any tasks blocking the
5476 current expedited RCU 5228 current expedited RCU grace period during an
5477 expedited RCU CPU sta 5229 expedited RCU CPU stall warning.
5478 5230
5479 rcupdate.rcu_expedited= [KNL] 5231 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 5232 Use expedited grace-period primitives, for
5481 example, synchronize_ 5233 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 5234 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 5235 but can increase CPU utilization, degrade
5484 real-time latency, an 5236 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 5237 No effect on CONFIG_TINY_RCU kernels.
5486 5238
5487 rcupdate.rcu_normal= [KNL] 5239 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 5240 Use only normal grace-period primitives,
5489 for example, synchron 5241 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 5242 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 5243 real-time latency, CPU utilization, and
5492 energy efficiency, bu 5244 energy efficiency, but can expose users to
5493 increased grace-perio 5245 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 5246 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 5247 CONFIG_TINY_RCU kernels.
5496 5248
5497 rcupdate.rcu_normal_after_boot= [KNL] 5249 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 5250 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 5251 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 5252 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 5253 on CONFIG_TINY_RCU kernels.
5502 5254
5503 But note that CONFIG_ 5255 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 5256 this kernel boot parameter, forcibly setting
5505 it to the value one, 5257 it to the value one, that is, converting any
5506 post-boot attempt at 5258 post-boot attempt at an expedited RCU grace
5507 period to instead use 5259 period to instead use normal non-expedited
5508 grace-period processi 5260 grace-period processing.
5509 5261
5510 rcupdate.rcu_task_collapse_lim= [KNL] 5262 rcupdate.rcu_task_collapse_lim= [KNL]
5511 Set the maximum numbe 5263 Set the maximum number of callbacks present
5512 at the beginning of a 5264 at the beginning of a grace period that allows
5513 the RCU Tasks flavors 5265 the RCU Tasks flavors to collapse back to using
5514 a single callback que 5266 a single callback queue. This switching only
5515 occurs when rcupdate. 5267 occurs when rcupdate.rcu_task_enqueue_lim is
5516 set to the default va 5268 set to the default value of -1.
5517 5269
5518 rcupdate.rcu_task_contend_lim= [KNL] 5270 rcupdate.rcu_task_contend_lim= [KNL]
5519 Set the minimum numbe 5271 Set the minimum number of callback-queuing-time
5520 lock-contention event 5272 lock-contention events per jiffy required to
5521 cause the RCU Tasks f 5273 cause the RCU Tasks flavors to switch to per-CPU
5522 callback queuing. Th 5274 callback queuing. This switching only occurs
5523 when rcupdate.rcu_tas 5275 when rcupdate.rcu_task_enqueue_lim is set to
5524 the default value of 5276 the default value of -1.
5525 5277
5526 rcupdate.rcu_task_enqueue_lim= [KNL] 5278 rcupdate.rcu_task_enqueue_lim= [KNL]
5527 Set the number of cal 5279 Set the number of callback queues to use for the
5528 RCU Tasks family of R 5280 RCU Tasks family of RCU flavors. The default
5529 of -1 allows this to 5281 of -1 allows this to be automatically (and
5530 dynamically) adjusted 5282 dynamically) adjusted. This parameter is intended
5531 for use in testing. 5283 for use in testing.
5532 5284
5533 rcupdate.rcu_task_ipi_delay= [KNL] 5285 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 5286 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 5287 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 5288 of a given grace period. Setting a large
5537 number avoids disturb 5289 number avoids disturbing real-time workloads,
5538 but lengthens grace p 5290 but lengthens grace periods.
5539 5291
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] 5292 rcupdate.rcu_task_stall_info= [KNL]
5548 Set initial timeout i 5293 Set initial timeout in jiffies for RCU task stall
5549 informational message 5294 informational messages, which give some indication
5550 of the problem for th 5295 of the problem for those not patient enough to
5551 wait for ten minutes. 5296 wait for ten minutes. Informational messages are
5552 only printed prior to 5297 only printed prior to the stall-warning message
5553 for a given grace per 5298 for a given grace period. Disable with a value
5554 less than or equal to 5299 less than or equal to zero. Defaults to ten
5555 seconds. A change in 5300 seconds. A change in value does not take effect
5556 until the beginning o 5301 until the beginning of the next grace period.
5557 5302
5558 rcupdate.rcu_task_stall_info_mult= [K 5303 rcupdate.rcu_task_stall_info_mult= [KNL]
5559 Multiplier for time i 5304 Multiplier for time interval between successive
5560 RCU task stall inform 5305 RCU task stall informational messages for a given
5561 RCU tasks grace perio 5306 RCU tasks grace period. This value is clamped
5562 to one through ten, i 5307 to one through ten, inclusive. It defaults to
5563 the value three, so t 5308 the value three, so that the first informational
5564 message is printed 10 5309 message is printed 10 seconds into the grace
5565 period, the second at 5310 period, the second at 40 seconds, the third at
5566 160 seconds, and then 5311 160 seconds, and then the stall warning at 600
5567 seconds would prevent 5312 seconds would prevent a fourth at 640 seconds.
5568 5313
5569 rcupdate.rcu_task_stall_timeout= [KNL 5314 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie 5315 Set timeout in jiffies for RCU task stall
5571 warning messages. Di 5316 warning messages. Disable with a value less
5572 than or equal to zero 5317 than or equal to zero. Defaults to ten minutes.
5573 A change in value doe 5318 A change in value does not take effect until
5574 the beginning of the 5319 the beginning of the next grace period.
5575 5320
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] 5321 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 5322 Run the RCU early boot self tests
5601 5323
5602 rdinit= [KNL] 5324 rdinit= [KNL]
5603 Format: <full_path> 5325 Format: <full_path>
5604 Run specified binary 5326 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 5327 used for early userspace startup. See initrd.
5606 5328
5607 rdrand= [X86,EARLY] !! 5329 rdrand= [X86]
5608 force - Override the 5330 force - Override the decision by the kernel to hide the
5609 advertisement 5331 advertisement of RDRAND support (this affects
5610 certain AMD p 5332 certain AMD processors because of buggy BIOS
5611 support, spec 5333 support, specifically around the suspend/resume
5612 path). 5334 path).
5613 5335
5614 rdt= [HW,X86,RDT] 5336 rdt= [HW,X86,RDT]
5615 Turn on/off individua 5337 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 5338 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. 5339 mba, smba, bmec.
5618 E.g. to turn on cmt a 5340 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 5341 rdt=cmt,!mba
5620 5342
5621 reboot= [KNL] 5343 reboot= [KNL]
5622 Format (x86 or x86_64 5344 Format (x86 or x86_64):
5623 [w[arm] | c[o 5345 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5624 [[,]s[mp]#### 5346 [[,]s[mp]#### \
5625 [[,]b[ios] | 5347 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 5348 [[,]f[orce]
5627 Where reboot_mode is 5349 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 5350 (prefix with 'panic_' to set mode for panic
5629 reboo 5351 reboot only),
5630 reboot_type is 5352 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 5353 reboot_force is either force or not specified,
5632 reboot_cpu is s 5354 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 5355 to be used for rebooting.
5634 5356
5635 refscale.holdoff= [KNL] 5357 refscale.holdoff= [KNL]
5636 Set test-start holdof 5358 Set test-start holdoff period. The purpose of
5637 this parameter is to 5359 this parameter is to delay the start of the
5638 test until boot compl 5360 test until boot completes in order to avoid
5639 interference. 5361 interference.
5640 5362
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] 5363 refscale.loops= [KNL]
5648 Set the number of loo 5364 Set the number of loops over the synchronization
5649 primitive under test. 5365 primitive under test. Increasing this number
5650 reduces noise due to 5366 reduces noise due to loop start/end overhead,
5651 but the default has a 5367 but the default has already reduced the per-pass
5652 noise to a handful of 5368 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 5369 x86 laptops.
5654 5370
5655 refscale.nreaders= [KNL] 5371 refscale.nreaders= [KNL]
5656 Set number of readers 5372 Set number of readers. The default value of -1
5657 selects N, where N is 5373 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 5374 of CPUs. A value of zero is an interesting choice.
5659 5375
5660 refscale.nruns= [KNL] 5376 refscale.nruns= [KNL]
5661 Set number of runs, e 5377 Set number of runs, each of which is dumped onto
5662 the console log. 5378 the console log.
5663 5379
5664 refscale.readdelay= [KNL] 5380 refscale.readdelay= [KNL]
5665 Set the read-side cri 5381 Set the read-side critical-section duration,
5666 measured in microseco 5382 measured in microseconds.
5667 5383
5668 refscale.scale_type= [KNL] 5384 refscale.scale_type= [KNL]
5669 Specify the read-prot 5385 Specify the read-protection implementation to test.
5670 5386
5671 refscale.shutdown= [KNL] 5387 refscale.shutdown= [KNL]
5672 Shut down the system 5388 Shut down the system at the end of the performance
5673 test. This defaults 5389 test. This defaults to 1 (shut it down) when
5674 refscale is built int 5390 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 5391 it running) when refscale is built as a module.
5676 5392
5677 refscale.verbose= [KNL] 5393 refscale.verbose= [KNL]
5678 Enable additional pri 5394 Enable additional printk() statements.
5679 5395
5680 refscale.verbose_batched= [KNL] 5396 refscale.verbose_batched= [KNL]
5681 Batch the additional 5397 Batch the additional printk() statements. If zero
5682 (the default) or nega 5398 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 5399 print every Nth verbose statement, where N is the value
5684 specified. 5400 specified.
5685 5401
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= 5402 relax_domain_level=
5694 [KNL, SMP] Set schedu 5403 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 5404 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 5405
5697 reserve= [KNL,BUGS] Force kern 5406 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 5407 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 5408 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 5409 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 5410 is assumed to be I/O ports; otherwise it is memory.
5702 5411
5703 reserve_mem= [RAM] !! 5412 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] 5413 Format: nn[KMG]
5727 Reserves a hole at th 5414 Reserves a hole at the top of the kernel virtual
5728 address space. 5415 address space.
5729 5416
5730 reset_devices [KNL] Force drivers t 5417 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 5418 during initialization.
5732 5419
5733 resume= [SWSUSP] 5420 resume= [SWSUSP]
5734 Specify the partition 5421 Specify the partition device for software suspend
5735 Format: 5422 Format:
5736 {/dev/<dev> | PARTUUI 5423 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 5424
5738 resume_offset= [SWSUSP] 5425 resume_offset= [SWSUSP]
5739 Specify the offset fr 5426 Specify the offset from the beginning of the partition
5740 given by "resume=" at 5427 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 5428 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 5429 See Documentation/power/swsusp-and-swap-files.rst
5743 5430
5744 resumedelay= [HIBERNATION] Delay ( 5431 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 5432 read the resume files
5746 5433
5747 resumewait [HIBERNATION] Wait (i 5434 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 5435 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 5436 (e.g. USB and MMC devices).
5750 5437
5751 retain_initrd [RAM] Keep initrd mem !! 5438 retain_initrd [RAM] Keep initrd memory after extraction
5752 be accessible via /sy <<
5753 5439
5754 retbleed= [X86] Control mitigat 5440 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 5441 Speculative Code Execution with Return Instructions)
5756 vulnerability. 5442 vulnerability.
5757 5443
5758 AMD-based UNRET and I 5444 AMD-based UNRET and IBPB mitigations alone do not stop
5759 sibling threads from 5445 sibling threads from influencing the predictions of other
5760 sibling threads. For 5446 sibling threads. For that reason, STIBP is used on pro-
5761 cessors that support 5447 cessors that support it, and mitigate SMT on processors
5762 that don't. 5448 that don't.
5763 5449
5764 off - no mit 5450 off - no mitigation
5765 auto - automa 5451 auto - automatically select a migitation
5766 auto,nosmt - automa 5452 auto,nosmt - automatically select a mitigation,
5767 disabl 5453 disabling SMT if necessary for
5768 the fu 5454 the full mitigation (only on Zen1
5769 and ol 5455 and older without STIBP).
5770 ibpb - On AMD 5456 ibpb - On AMD, mitigate short speculation
5771 window 5457 windows on basic block boundaries too.
5772 Safe, 5458 Safe, highest perf impact. It also
5773 enable 5459 enables STIBP if present. Not suitable
5774 on Int 5460 on Intel.
5775 ibpb,nosmt - Like " 5461 ibpb,nosmt - Like "ibpb" above but will disable SMT
5776 when S 5462 when STIBP is not available. This is
5777 the al 5463 the alternative for systems which do not
5778 have S 5464 have STIBP.
5779 unret - Force 5465 unret - Force enable untrained return thunks,
5780 only e 5466 only effective on AMD f15h-f17h based
5781 system 5467 systems.
5782 unret,nosmt - Like u 5468 unret,nosmt - Like unret, but will disable SMT when STIBP
5783 is not 5469 is not available. This is the alternative for
5784 system 5470 systems which do not have STIBP.
5785 5471
5786 Selecting 'auto' will 5472 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 5473 time according to the CPU.
5788 5474
5789 Not specifying this o 5475 Not specifying this option is equivalent to retbleed=auto.
5790 5476
5791 rfkill.default_state= 5477 rfkill.default_state=
5792 0 "airplane mode". All 5478 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 5479 etc. communication is blocked by default.
5794 1 Unblocked. 5480 1 Unblocked.
5795 5481
5796 rfkill.master_switch_mode= 5482 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 5483 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 5484 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 5485 blocked and the previous configuration.
5800 2 The "airplane mode" b 5486 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 5487 blocked and everything unblocked.
5802 5488
>> 5489 rhash_entries= [KNL,NET]
>> 5490 Set number of hash buckets for route cache
>> 5491
5803 ring3mwait=disable 5492 ring3mwait=disable
5804 [KNL] Disable ring 3 5493 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 5494 CPUs.
5806 5495
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 5496 ro [KNL] Mount root device read-only on boot
5815 5497
5816 rodata= [KNL,EARLY] !! 5498 rodata= [KNL]
5817 on Mark read-only kernel 5499 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 5500 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel 5501 full Mark read-only kernel memory and aliases as read-only
5820 [arm64] 5502 [arm64]
5821 5503
5822 rockchip.usb_uart 5504 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 5505 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 5506 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 5507 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 5508 port and the regular usb controller gets disabled.
5828 5509
5829 root= [KNL] Root filesystem 5510 root= [KNL] Root filesystem
5830 Usually this a a bloc 5511 Usually this a a block device specifier of some kind,
5831 see the early_lookup_ 5512 see the early_lookup_bdev comment in
5832 block/early-lookup.c 5513 block/early-lookup.c for details.
5833 Alternatively this ca 5514 Alternatively this can be "ram" for the legacy initial
5834 ramdisk, "nfs" and "c 5515 ramdisk, "nfs" and "cifs" for root on a network file
5835 system, or "mtd" and 5516 system, or "mtd" and "ubi" for mounting from raw flash.
5836 5517
5837 rootdelay= [KNL] Delay (in secon 5518 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 5519 mount the root filesystem
5839 5520
5840 rootflags= [KNL] Set root filesy 5521 rootflags= [KNL] Set root filesystem mount option string
5841 5522
5842 rootfstype= [KNL] Set root filesy 5523 rootfstype= [KNL] Set root filesystem type
5843 5524
5844 rootwait [KNL] Wait (indefinit 5525 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 5526 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 5527 (e.g. USB and MMC devices).
5847 5528
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 5529 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 5530 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 5531 Memory area to be used by remote processor image,
5855 managed by CMA. 5532 managed by CMA.
5856 5533
5857 rw [KNL] Mount root devi 5534 rw [KNL] Mount root device read-write on boot
5858 5535
5859 S [KNL] Run init in sin 5536 S [KNL] Run init in single mode
5860 5537
5861 s390_iommu= [HW,S390] 5538 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 5539 Set s390 IOTLB flushing mode
5863 strict 5540 strict
5864 With strict flushing !! 5541 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 5542 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 5543 which is faster.
5867 iommu.strict=1. <<
5868 5544
5869 s390_iommu_aperture= [KNL,S390] 5545 s390_iommu_aperture= [KNL,S390]
5870 Specifies the size of 5546 Specifies the size of the per device DMA address space
5871 accessible through th 5547 accessible through the DMA and IOMMU APIs as a decimal
5872 factor of the size of 5548 factor of the size of main memory.
5873 The default is 1 mean 5549 The default is 1 meaning that one can concurrently use
5874 as many DMA addresses 5550 as many DMA addresses as physical memory is installed,
5875 if supported by hardw 5551 if supported by hardware, and thus map all of memory
5876 once. With a value of 5552 once. With a value of 2 one can map all of memory twice
5877 and so on. As a speci 5553 and so on. As a special case a factor of 0 imposes no
5878 restrictions other th 5554 restrictions other than those given by hardware at the
5879 cost of significant a 5555 cost of significant additional memory use for tables.
5880 5556
5881 sa1100ir [NET] 5557 sa1100ir [NET]
5882 See drivers/net/irda/ 5558 See drivers/net/irda/sa1100_ir.c.
5883 5559
5884 sched_verbose [KNL,EARLY] Enables v !! 5560 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 5561
5886 schedstats= [KNL,X86] Enable or d 5562 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 5563 Allowed values are enable and disable. This feature
5888 incurs a small amount 5564 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 5565 but is useful for debugging and performance tuning.
5890 5566
5891 sched_thermal_decay_shift= 5567 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 5568 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 5569 pressure signal. Thermal pressure signal follows the
5895 default decay period 5570 default decay period of other scheduler pelt
5896 signals(usually 32 ms 5571 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 5572 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 5573 period for the thermal pressure signal by the shift
5899 value. 5574 value.
5900 i.e. with the default 5575 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 5576 sched_thermal_decay_shift thermal pressure decay pr
5902 1 5577 1 64 ms
5903 2 5578 2 128 ms
5904 and so on. 5579 and so on.
5905 Format: integer betwe 5580 Format: integer between 0 and 10
5906 Default is 0. 5581 Default is 0.
5907 5582
5908 scftorture.holdoff= [KNL] 5583 scftorture.holdoff= [KNL]
5909 Number of seconds to 5584 Number of seconds to hold off before starting
5910 test. Defaults to ze 5585 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 5586 to 10 seconds for built-in smp_call_function()
5912 tests. 5587 tests.
5913 5588
5914 scftorture.longwait= [KNL] 5589 scftorture.longwait= [KNL]
5915 Request ridiculously 5590 Request ridiculously long waits randomly selected
5916 up to the chosen limi 5591 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 5592 default) disables this feature. Please note
5918 that requesting even 5593 that requesting even small non-zero numbers of
5919 seconds can result in 5594 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 5595 softlockup complaints, and so on.
5921 5596
5922 scftorture.nthreads= [KNL] 5597 scftorture.nthreads= [KNL]
5923 Number of kthreads to 5598 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 5599 smp_call_function() family of functions.
5925 The default of -1 spe 5600 The default of -1 specifies a number of kthreads
5926 equal to the number o 5601 equal to the number of CPUs.
5927 5602
5928 scftorture.onoff_holdoff= [KNL] 5603 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 5604 Number seconds to wait after the start of the
5930 test before initiatin 5605 test before initiating CPU-hotplug operations.
5931 5606
5932 scftorture.onoff_interval= [KNL] 5607 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 5608 Number seconds to wait between successive
5934 CPU-hotplug operation 5609 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 5610 is the default) disables CPU-hotplug operations.
5936 5611
5937 scftorture.shutdown_secs= [KNL] 5612 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 5613 The number of seconds following the start of the
5939 test after which to s 5614 test after which to shut down the system. The
5940 default of zero avoid 5615 default of zero avoids shutting down the system.
5941 Non-zero values are u 5616 Non-zero values are useful for automated tests.
5942 5617
5943 scftorture.stat_interval= [KNL] 5618 scftorture.stat_interval= [KNL]
5944 The number of seconds 5619 The number of seconds between outputting the
5945 current test statisti 5620 current test statistics to the console. A value
5946 of zero disables stat 5621 of zero disables statistics output.
5947 5622
5948 scftorture.stutter_cpus= [KNL] 5623 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 5624 The number of jiffies to wait between each change
5950 to the set of CPUs un 5625 to the set of CPUs under test.
5951 5626
5952 scftorture.use_cpus_read_lock= [KNL] 5627 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 5628 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 5629 preempt_disable() to disable CPU hotplug
5955 while invoking one of 5630 while invoking one of the smp_call_function*()
5956 functions. 5631 functions.
5957 5632
5958 scftorture.verbose= [KNL] 5633 scftorture.verbose= [KNL]
5959 Enable additional pri 5634 Enable additional printk() statements.
5960 5635
5961 scftorture.weight_single= [KNL] 5636 scftorture.weight_single= [KNL]
5962 The probability weigh 5637 The probability weighting to use for the
5963 smp_call_function_sin 5638 smp_call_function_single() function with a zero
5964 "wait" parameter. A 5639 "wait" parameter. A value of -1 selects the
5965 default if all other 5640 default if all other weights are -1. However,
5966 if at least one weigh 5641 if at least one weight has some other value, a
5967 value of -1 will inst 5642 value of -1 will instead select a weight of zero.
5968 5643
5969 scftorture.weight_single_wait= [KNL] 5644 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 5645 The probability weighting to use for the
5971 smp_call_function_sin 5646 smp_call_function_single() function with a
5972 non-zero "wait" param 5647 non-zero "wait" parameter. See weight_single.
5973 5648
5974 scftorture.weight_many= [KNL] 5649 scftorture.weight_many= [KNL]
5975 The probability weigh 5650 The probability weighting to use for the
5976 smp_call_function_man 5651 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 5652 "wait" parameter. See weight_single.
5978 Note well that settin 5653 Note well that setting a high probability for
5979 this weighting can pl 5654 this weighting can place serious IPI load
5980 on the system. 5655 on the system.
5981 5656
5982 scftorture.weight_many_wait= [KNL] 5657 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 5658 The probability weighting to use for the
5984 smp_call_function_man 5659 smp_call_function_many() function with a
5985 non-zero "wait" param 5660 non-zero "wait" parameter. See weight_single
5986 and weight_many. 5661 and weight_many.
5987 5662
5988 scftorture.weight_all= [KNL] 5663 scftorture.weight_all= [KNL]
5989 The probability weigh 5664 The probability weighting to use for the
5990 smp_call_function_all 5665 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 5666 "wait" parameter. See weight_single and
5992 weight_many. 5667 weight_many.
5993 5668
5994 scftorture.weight_all_wait= [KNL] 5669 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 5670 The probability weighting to use for the
5996 smp_call_function_all 5671 smp_call_function_all() function with a
5997 non-zero "wait" param 5672 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5673 and weight_many.
5999 5674
6000 skew_tick= [KNL,EARLY] Offset th !! 5675 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5676 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5677 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5678 Format: { "0" | "1" }
6004 0 -- disable. (may be 5679 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5680 1 -- enable.
6006 Note: increases power 5681 Note: increases power consumption, thus should only be
6007 enabled if running ji 5682 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5683
6009 security= [SECURITY] Choose a l 5684 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5685 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5686 "lsm=" parameter.
6012 5687
6013 selinux= [SELINUX] Disable or 5688 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5689 Format: { "0" | "1" }
6015 See security/selinux/ 5690 See security/selinux/Kconfig help text.
6016 0 -- disable. 5691 0 -- disable.
6017 1 -- enable. 5692 1 -- enable.
6018 Default value is 1. 5693 Default value is 1.
6019 5694
6020 serialnumber [BUGS=X86-32] 5695 serialnumber [BUGS=X86-32]
6021 5696
6022 sev=option[,option...] [X86-64] See D 5697 sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
6023 5698
6024 shapers= [NET] 5699 shapers= [NET]
6025 Maximal number of sha 5700 Maximal number of shapers.
6026 5701
6027 show_lapic= [APIC,X86] Advanced P 5702 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
6028 Limit apic dumping. T 5703 Limit apic dumping. The parameter defines the maximal
6029 number of local apics 5704 number of local apics being dumped. Also it is possible
6030 to set it to "all" by 5705 to set it to "all" by meaning -- no limit here.
6031 Format: { 1 (default) 5706 Format: { 1 (default) | 2 | ... | all }.
6032 The parameter valid i 5707 The parameter valid if only apic=debug or
6033 apic=verbose is speci 5708 apic=verbose is specified.
6034 Example: apic=debug s 5709 Example: apic=debug show_lapic=all
6035 5710
6036 slab_debug[=options[,slabs][;[options !! 5711 simeth= [IA-64]
6037 Enabling slab_debug a !! 5712 simscsi=
>> 5713
>> 5714 slram= [HW,MTD]
>> 5715
>> 5716 slab_merge [MM]
>> 5717 Enable merging of slabs with similar size when the
>> 5718 kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
>> 5719
>> 5720 slab_nomerge [MM]
>> 5721 Disable merging of slabs with similar size. May be
>> 5722 necessary if there is some reason to distinguish
>> 5723 allocs to different slabs, especially in hardened
>> 5724 environments where the risk of heap overflows and
>> 5725 layout control by attackers can usually be
>> 5726 frustrated by disabling merging. This will reduce
>> 5727 most of the exposure of a heap attack to a single
>> 5728 cache (risks via metadata attacks are mostly
>> 5729 unchanged). Debug options disable merging on their
>> 5730 own.
>> 5731 For more information see Documentation/mm/slub.rst.
>> 5732
>> 5733 slab_max_order= [MM, SLAB]
>> 5734 Determines the maximum allowed order for slabs.
>> 5735 A high setting may cause OOMs due to memory
>> 5736 fragmentation. Defaults to 1 for systems with
>> 5737 more than 32MB of RAM, 0 otherwise.
>> 5738
>> 5739 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 5740 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 5741 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 5742 slub_debug can create guard zones around objects and
6040 may poison objects wh 5743 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 5744 last alloc / free. For more information see
6042 Documentation/mm/slub 5745 Documentation/mm/slub.rst.
6043 (slub_debug legacy na <<
6044 5746
6045 slab_max_order= [MM] !! 5747 slub_max_order= [MM, SLUB]
6046 Determines the maximu 5748 Determines the maximum allowed order for slabs.
6047 A high setting may ca 5749 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 5750 fragmentation. For more information see
6049 Documentation/mm/slub 5751 Documentation/mm/slub.rst.
6050 (slub_max_order legac <<
6051 <<
6052 slab_merge [MM] <<
6053 Enable merging of sla <<
6054 kernel is built witho <<
6055 (slub_merge legacy na <<
6056 5752
6057 slab_min_objects= [MM] !! 5753 slub_min_objects= [MM, SLUB]
6058 The minimum number of 5754 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 5755 increase the slab order up to slub_max_order to
6060 generate a sufficient 5756 generate a sufficiently large slab able to contain
6061 the number of objects 5757 the number of objects indicated. The higher the number
6062 of objects the smalle 5758 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 5759 and the less frequently locks need to be acquired.
6064 For more information 5760 For more information see Documentation/mm/slub.rst.
6065 (slub_min_objects leg <<
6066 5761
6067 slab_min_order= [MM] !! 5762 slub_min_order= [MM, SLUB]
6068 Determines the minimu 5763 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 5764 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 5765 For more information see Documentation/mm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5766
6087 slram= [HW,MTD] !! 5767 slub_merge [MM, SLUB]
>> 5768 Same with slab_merge.
>> 5769
>> 5770 slub_nomerge [MM, SLUB]
>> 5771 Same with slab_nomerge. This is supported for legacy.
>> 5772 See slab_nomerge for more information.
6088 5773
6089 smart2= [HW] 5774 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5775 Format: <io1>[,<io2>[,...,<io8>]]
6091 5776
6092 smp.csd_lock_timeout= [KNL] 5777 smp.csd_lock_timeout= [KNL]
6093 Specify the period of 5778 Specify the period of time in milliseconds
6094 that smp_call_functio 5779 that smp_call_function() and friends will wait
6095 for a CPU to release 5780 for a CPU to release the CSD lock. This is
6096 useful when diagnosin 5781 useful when diagnosing bugs involving CPUs
6097 disabling interrupts 5782 disabling interrupts for extended periods
6098 of time. Defaults to 5783 of time. Defaults to 5,000 milliseconds, and
6099 setting a value of ze 5784 setting a value of zero disables this feature.
6100 This feature may be m 5785 This feature may be more efficiently disabled
6101 using the csdlock_deb 5786 using the csdlock_debug- kernel parameter.
6102 5787
6103 smp.panic_on_ipistall= [KNL] 5788 smp.panic_on_ipistall= [KNL]
6104 If a csd_lock_timeout 5789 If a csd_lock_timeout extends for more than
6105 the specified number 5790 the specified number of milliseconds, panic the
6106 system. By default, 5791 system. By default, let CSD-lock acquisition
6107 take as long as they 5792 take as long as they take. Specifying 300,000
6108 for this value provid 5793 for this value provides a 5-minute timeout.
6109 5794
6110 smsc-ircc2.nopnp [HW] Don't us 5795 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5796 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5797 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5798 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5799 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5800 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5801 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5802 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5803 1: Fast pin select (default)
6119 2: ATC IRMode 5804 2: ATC IRMode
6120 5805
6121 smt= [KNL,MIPS,S390,EARLY] !! 5806 smt= [KNL,MIPS,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5807 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5808 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5809 actual hardware limit.
6125 Format: <integer> 5810 Format: <integer>
6126 Default: -1 (no limit 5811 Default: -1 (no limit)
6127 5812
6128 softlockup_panic= 5813 softlockup_panic=
6129 [KNL] Should the soft 5814 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5815 Format: 0 | 1
6131 5816
6132 A value of 1 instruct 5817 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 5818 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 5819 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 5820 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 5821 respective build-time switch to that functionality.
6137 5822
6138 softlockup_all_cpu_backtrace= 5823 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 5824 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 5825 backtraces on all cpus.
6141 Format: 0 | 1 5826 Format: 0 | 1
6142 5827
6143 sonypi.*= [HW] Sony Programmabl 5828 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 5829 See Documentation/admin-guide/laptops/sonypi.rst
6145 5830
6146 spectre_bhi= [X86] Control mitigat !! 5831 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 5832 (indirect branch speculation) vulnerability.
6163 The default operation 5833 The default operation protects the kernel from
6164 user space attacks. 5834 user space attacks.
6165 5835
6166 on - unconditionall 5836 on - unconditionally enable, implies
6167 spectre_v2_use 5837 spectre_v2_user=on
6168 off - unconditionall 5838 off - unconditionally disable, implies
6169 spectre_v2_use 5839 spectre_v2_user=off
6170 auto - kernel detects 5840 auto - kernel detects whether your CPU model is
6171 vulnerable 5841 vulnerable
6172 5842
6173 Selecting 'on' will, 5843 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 5844 mitigation method at run time according to the
6175 CPU, the available mi 5845 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 5846 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 5847 compiler with which the kernel was built.
6178 5848
6179 Selecting 'on' will a 5849 Selecting 'on' will also enable the mitigation
6180 against user space to 5850 against user space to user space task attacks.
6181 5851
6182 Selecting 'off' will 5852 Selecting 'off' will disable both the kernel and
6183 the user space protec 5853 the user space protections.
6184 5854
6185 Specific mitigations 5855 Specific mitigations can also be selected manually:
6186 5856
6187 retpoline - r 5857 retpoline - replace indirect branches
6188 retpoline,generic - R 5858 retpoline,generic - Retpolines
6189 retpoline,lfence - L 5859 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 5860 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E 5861 eibrs - Enhanced/Auto IBRS
6192 eibrs,retpoline - E 5862 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6193 eibrs,lfence - E 5863 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6194 ibrs - u 5864 ibrs - use IBRS to protect kernel
6195 5865
6196 Not specifying this o 5866 Not specifying this option is equivalent to
6197 spectre_v2=auto. 5867 spectre_v2=auto.
6198 5868
6199 spectre_v2_user= 5869 spectre_v2_user=
6200 [X86] Control mitigat 5870 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 5871 (indirect branch speculation) vulnerability between
6202 user space tasks 5872 user space tasks
6203 5873
6204 on - Uncondition 5874 on - Unconditionally enable mitigations. Is
6205 enforced by 5875 enforced by spectre_v2=on
6206 5876
6207 off - Uncondition 5877 off - Unconditionally disable mitigations. Is
6208 enforced by 5878 enforced by spectre_v2=off
6209 5879
6210 prctl - Indirect br 5880 prctl - Indirect branch speculation is enabled,
6211 but mitigat 5881 but mitigation can be enabled via prctl
6212 per thread. 5882 per thread. The mitigation control state
6213 is inherite 5883 is inherited on fork.
6214 5884
6215 prctl,ibpb 5885 prctl,ibpb
6216 - Like "prctl 5886 - Like "prctl" above, but only STIBP is
6217 controlled 5887 controlled per thread. IBPB is issued
6218 always when 5888 always when switching between different user
6219 space proce 5889 space processes.
6220 5890
6221 seccomp 5891 seccomp
6222 - Same as "pr 5892 - Same as "prctl" above, but all seccomp
6223 threads wil 5893 threads will enable the mitigation unless
6224 they explic 5894 they explicitly opt out.
6225 5895
6226 seccomp,ibpb 5896 seccomp,ibpb
6227 - Like "secco 5897 - Like "seccomp" above, but only STIBP is
6228 controlled 5898 controlled per thread. IBPB is issued
6229 always when 5899 always when switching between different
6230 user space 5900 user space processes.
6231 5901
6232 auto - Kernel sele 5902 auto - Kernel selects the mitigation depending on
6233 the availab 5903 the available CPU features and vulnerability.
6234 5904
6235 Default mitigation: " 5905 Default mitigation: "prctl"
6236 5906
6237 Not specifying this o 5907 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 5908 spectre_v2_user=auto.
6239 5909
6240 spec_rstack_overflow= 5910 spec_rstack_overflow=
6241 [X86,EARLY] Control R !! 5911 [X86] Control RAS overflow mitigation on AMD Zen CPUs
6242 5912
6243 off - Dis 5913 off - Disable mitigation
6244 microcode - Ena 5914 microcode - Enable microcode mitigation only
6245 safe-ret - Ena 5915 safe-ret - Enable sw-only safe RET mitigation (default)
6246 ibpb - Ena 5916 ibpb - Enable mitigation by issuing IBPB on
6247 ker 5917 kernel entry
6248 ibpb-vmexit - Iss 5918 ibpb-vmexit - Issue IBPB only on VMEXIT
6249 (cl 5919 (cloud-specific mitigation)
6250 5920
6251 spec_store_bypass_disable= 5921 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 5922 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 5923 (Speculative Store Bypass vulnerability)
6254 5924
6255 Certain CPUs are vuln 5925 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 5926 a common industry wide performance optimization known
6257 as "Speculative Store 5927 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 5928 to the same memory location may not be observed by
6259 later loads during sp 5929 later loads during speculative execution. The idea
6260 is that such stores a 5930 is that such stores are unlikely and that they can
6261 be detected prior to 5931 be detected prior to instruction retirement at the
6262 end of a particular s 5932 end of a particular speculation execution window.
6263 5933
6264 In vulnerable process 5934 In vulnerable processors, the speculatively forwarded
6265 store can be used in 5935 store can be used in a cache side channel attack, for
6266 example to read memor 5936 example to read memory to which the attacker does not
6267 directly have access 5937 directly have access (e.g. inside sandboxed code).
6268 5938
6269 This parameter contro 5939 This parameter controls whether the Speculative Store
6270 Bypass optimization i 5940 Bypass optimization is used.
6271 5941
6272 On x86 the options ar 5942 On x86 the options are:
6273 5943
6274 on - Uncondition 5944 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 5945 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 5946 auto - Kernel detects whether the CPU model contains an
6277 implementat 5947 implementation of Speculative Store Bypass and
6278 picks the m 5948 picks the most appropriate mitigation. If the
6279 CPU is not 5949 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 5950 CPU is vulnerable the default mitigation is
6281 architectur 5951 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 5952 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 5953 via prctl. Speculative Store Bypass is enabled
6284 for a proce 5954 for a process by default. The state of the control
6285 is inherite 5955 is inherited on fork.
6286 seccomp - Same as "pr 5956 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 5957 will disable SSB unless they explicitly opt out.
6288 5958
6289 Default mitigations: 5959 Default mitigations:
6290 X86: "prctl" 5960 X86: "prctl"
6291 5961
6292 On powerpc the option 5962 On powerpc the options are:
6293 5963
6294 on,auto - On Power8 a 5964 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 5965 barrier on kernel entry and exit. On Power7
6296 perform a s 5966 perform a software flush on kernel entry and
6297 exit. 5967 exit.
6298 off - No action. 5968 off - No action.
6299 5969
6300 Not specifying this o 5970 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 5971 spec_store_bypass_disable=auto.
6302 5972
>> 5973 spia_io_base= [HW,MTD]
>> 5974 spia_fio_base=
>> 5975 spia_pedr=
>> 5976 spia_peddr=
>> 5977
6303 split_lock_detect= 5978 split_lock_detect=
6304 [X86] Enable split lo 5979 [X86] Enable split lock detection or bus lock detection
6305 5980
6306 When enabled (and if 5981 When enabled (and if hardware support is present), atomic
6307 instructions that acc 5982 instructions that access data across cache line
6308 boundaries will resul 5983 boundaries will result in an alignment check exception
6309 for split lock detect 5984 for split lock detection or a debug exception for
6310 bus lock detection. 5985 bus lock detection.
6311 5986
6312 off - not enabled 5987 off - not enabled
6313 5988
6314 warn - the kernel 5989 warn - the kernel will emit rate-limited warnings
6315 about appli 5990 about applications triggering the #AC
6316 exception o 5991 exception or the #DB exception. This mode is
6317 the default 5992 the default on CPUs that support split lock
6318 detection o 5993 detection or bus lock detection. Default
6319 behavior is 5994 behavior is by #AC if both features are
6320 enabled in 5995 enabled in hardware.
6321 5996
6322 fatal - the kernel 5997 fatal - the kernel will send SIGBUS to applications
6323 that trigge 5998 that trigger the #AC exception or the #DB
6324 exception. 5999 exception. Default behavior is by #AC if
6325 both featur 6000 both features are enabled in hardware.
6326 6001
6327 ratelimit:N - 6002 ratelimit:N -
6328 Set system 6003 Set system wide rate limit to N bus locks
6329 per second 6004 per second for bus lock detection.
6330 0 < N <= 10 6005 0 < N <= 1000.
6331 6006
6332 N/A for spl 6007 N/A for split lock detection.
6333 6008
6334 6009
6335 If an #AC exception i 6010 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 6011 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 6012 the kernel will oops in either "warn" or "fatal"
6338 mode. 6013 mode.
6339 6014
6340 #DB exception for bus 6015 #DB exception for bus lock is triggered only when
6341 CPL > 0. 6016 CPL > 0.
6342 6017
6343 srbds= [X86,INTEL,EARLY] !! 6018 srbds= [X86,INTEL]
6344 Control the Special R 6019 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 6020 (SRBDS) mitigation.
6346 6021
6347 Certain CPUs are vuln 6022 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 6023 exploit which can leak bits from the random
6349 number generator. 6024 number generator.
6350 6025
6351 By default, this issu 6026 By default, this issue is mitigated by
6352 microcode. However, 6027 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 6028 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 6029 much slower. Among other effects, this will
6355 result in reduced thr 6030 result in reduced throughput from /dev/urandom.
6356 6031
6357 The microcode mitigat 6032 The microcode mitigation can be disabled with
6358 the following option: 6033 the following option:
6359 6034
6360 off: Disable mitig 6035 off: Disable mitigation and remove
6361 performance i 6036 performance impact to RDRAND and RDSEED
6362 6037
6363 srcutree.big_cpu_lim [KNL] 6038 srcutree.big_cpu_lim [KNL]
6364 Specifies the number 6039 Specifies the number of CPUs constituting a
6365 large system, such th 6040 large system, such that srcu_struct structures
6366 should immediately al 6041 should immediately allocate an srcu_node array.
6367 This kernel-boot para 6042 This kernel-boot parameter defaults to 128,
6368 but takes effect only 6043 but takes effect only when the low-order four
6369 bits of srcutree.conv 6044 bits of srcutree.convert_to_big is equal to 3
6370 (decide at boot). 6045 (decide at boot).
6371 6046
6372 srcutree.convert_to_big [KNL] 6047 srcutree.convert_to_big [KNL]
6373 Specifies under what 6048 Specifies under what conditions an SRCU tree
6374 srcu_struct structure 6049 srcu_struct structure will be converted to big
6375 form, that is, with a 6050 form, that is, with an rcu_node tree:
6376 6051
6377 0: Never. 6052 0: Never.
6378 1: At ini 6053 1: At init_srcu_struct() time.
6379 2: When r 6054 2: When rcutorture decides to.
6380 3: Decide 6055 3: Decide at boot time (default).
6381 0x1X: Above 6056 0x1X: Above plus if high contention.
6382 6057
6383 Either way, the srcu_ 6058 Either way, the srcu_node tree will be sized based
6384 on the actual runtime 6059 on the actual runtime number of CPUs (nr_cpu_ids)
6385 instead of the compil 6060 instead of the compile-time CONFIG_NR_CPUS.
6386 6061
6387 srcutree.counter_wrap_check [KNL] 6062 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 6063 Specifies how frequently to check for
6389 grace-period sequence 6064 grace-period sequence counter wrap for the
6390 srcu_data structure's 6065 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 6066 The greater the number of bits set in this kernel
6392 parameter, the less f 6067 parameter, the less frequently counter wrap will
6393 be checked for. Note 6068 be checked for. Note that the bottom two bits
6394 are ignored. 6069 are ignored.
6395 6070
6396 srcutree.exp_holdoff [KNL] 6071 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 6072 Specifies how many nanoseconds must elapse
6398 since the end of the 6073 since the end of the last SRCU grace period for
6399 a given srcu_struct u 6074 a given srcu_struct until the next normal SRCU
6400 grace period will be 6075 grace period will be considered for automatic
6401 expediting. Set to z 6076 expediting. Set to zero to disable automatic
6402 expediting. 6077 expediting.
6403 6078
6404 srcutree.srcu_max_nodelay [KNL] 6079 srcutree.srcu_max_nodelay [KNL]
6405 Specifies the number 6080 Specifies the number of no-delay instances
6406 per jiffy for which t 6081 per jiffy for which the SRCU grace period
6407 worker thread will be 6082 worker thread will be rescheduled with zero
6408 delay. Beyond this li 6083 delay. Beyond this limit, worker thread will
6409 be rescheduled with a 6084 be rescheduled with a sleep delay of one jiffy.
6410 6085
6411 srcutree.srcu_max_nodelay_phase [KNL] 6086 srcutree.srcu_max_nodelay_phase [KNL]
6412 Specifies the per-gra 6087 Specifies the per-grace-period phase, number of
6413 non-sleeping polls of 6088 non-sleeping polls of readers. Beyond this limit,
6414 grace period worker t 6089 grace period worker thread will be rescheduled
6415 with a sleep delay of 6090 with a sleep delay of one jiffy, between each
6416 rescan of the readers 6091 rescan of the readers, for a grace period phase.
6417 6092
6418 srcutree.srcu_retry_check_delay [KNL] 6093 srcutree.srcu_retry_check_delay [KNL]
6419 Specifies number of m 6094 Specifies number of microseconds of non-sleeping
6420 delay between each no 6095 delay between each non-sleeping poll of readers.
6421 6096
6422 srcutree.small_contention_lim [KNL] 6097 srcutree.small_contention_lim [KNL]
6423 Specifies the number 6098 Specifies the number of update-side contention
6424 events per jiffy will 6099 events per jiffy will be tolerated before
6425 initiating a conversi 6100 initiating a conversion of an srcu_struct
6426 structure to big form 6101 structure to big form. Note that the value of
6427 srcutree.convert_to_b 6102 srcutree.convert_to_big must have the 0x10 bit
6428 set for contention-ba 6103 set for contention-based conversions to occur.
6429 6104
6430 ssbd= [ARM64,HW,EARLY] !! 6105 ssbd= [ARM64,HW]
6431 Speculative Store Byp 6106 Speculative Store Bypass Disable control
6432 6107
6433 On CPUs that are vuln 6108 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 6109 Store Bypass vulnerability and offer a
6435 firmware based mitiga 6110 firmware based mitigation, this parameter
6436 indicates how the mit 6111 indicates how the mitigation should be used:
6437 6112
6438 force-on: Unconditio 6113 force-on: Unconditionally enable mitigation for
6439 for both k 6114 for both kernel and userspace
6440 force-off: Unconditio 6115 force-off: Unconditionally disable mitigation for
6441 for both k 6116 for both kernel and userspace
6442 kernel: Always ena 6117 kernel: Always enable mitigation in the
6443 kernel, an 6118 kernel, and offer a prctl interface
6444 to allow u 6119 to allow userspace to register its
6445 interest i 6120 interest in being mitigated too.
6446 6121
6447 stack_guard_gap= [MM] 6122 stack_guard_gap= [MM]
6448 override the default 6123 override the default stack gap protection. The value
6449 is in page units and 6124 is in page units and it defines how many pages prior
6450 to (for stacks growin 6125 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 6126 growing up) the main stack are reserved for no other
6452 mapping. Default valu 6127 mapping. Default value is 256 pages.
6453 6128
6454 stack_depot_disable= [KNL,EARLY] !! 6129 stack_depot_disable= [KNL]
6455 Setting this to true 6130 Setting this to true through kernel command line will
6456 disable the stack dep 6131 disable the stack depot thereby saving the static memory
6457 consumed by the stack 6132 consumed by the stack hash table. By default this is set
6458 to false. 6133 to false.
6459 6134
6460 stacktrace [FTRACE] 6135 stacktrace [FTRACE]
6461 Enabled the stack tra 6136 Enabled the stack tracer on boot up.
6462 6137
6463 stacktrace_filter=[function-list] 6138 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 6139 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 6140 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 6141 list of functions. This list can be changed at run
6467 time by the stack_tra 6142 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 6143 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 6144 and the stacktrace above is not needed.
6470 6145
6471 sti= [PARISC,HW] 6146 sti= [PARISC,HW]
6472 Format: <num> 6147 Format: <num>
6473 Set the STI (builtin 6148 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 6149 machines) console (graphic card) which should be used
6475 as the initial boot-c 6150 as the initial boot-console.
6476 See also comment in d 6151 See also comment in drivers/video/console/sticore.c.
6477 6152
6478 sti_font= [HW] 6153 sti_font= [HW]
6479 See comment in driver 6154 See comment in drivers/video/console/sticore.c.
6480 6155
6481 stifb= [HW] 6156 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 6157 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 6158
6484 strict_sas_size= 6159 strict_sas_size=
6485 [X86] 6160 [X86]
6486 Format: <bool> 6161 Format: <bool>
6487 Enable or disable str 6162 Enable or disable strict sigaltstack size checks
6488 against the required 6163 against the required signal frame size which
6489 depends on the suppor 6164 depends on the supported FPU features. This can
6490 be used to filter out 6165 be used to filter out binaries which have
6491 not yet been made awa 6166 not yet been made aware of AT_MINSIGSTKSZ.
6492 6167
6493 stress_hpt [PPC,EARLY] !! 6168 stress_hpt [PPC]
6494 Limits the number of 6169 Limits the number of kernel HPT entries in the hash
6495 page table to increas 6170 page table to increase the rate of hash page table
6496 faults on kernel addr 6171 faults on kernel addresses.
6497 6172
6498 stress_slb [PPC,EARLY] !! 6173 stress_slb [PPC]
6499 Limits the number of 6174 Limits the number of kernel SLB entries, and flushes
6500 them frequently to in 6175 them frequently to increase the rate of SLB faults
6501 on kernel addresses. 6176 on kernel addresses.
6502 6177
6503 sunrpc.min_resvport= 6178 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 6179 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 6180 [NFS,SUNRPC]
6506 SunRPC servers often 6181 SunRPC servers often require that client requests
6507 originate from a priv 6182 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 6183 range 0 < portnr < 1024).
6509 An administrator who 6184 An administrator who wishes to reserve some of these
6510 ports for other uses 6185 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 6186 kernel's sunrpc client considers to be privileged
6512 using these two param 6187 using these two parameters to set the minimum and
6513 maximum port values. 6188 maximum port values.
6514 6189
6515 sunrpc.svc_rpc_per_connection_limit= 6190 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 6191 [NFS,SUNRPC]
6517 Limit the number of r 6192 Limit the number of requests that the server will
6518 process in parallel f 6193 process in parallel from a single connection.
6519 The default value is 6194 The default value is 0 (no limit).
6520 6195
6521 sunrpc.pool_mode= 6196 sunrpc.pool_mode=
6522 [NFS] 6197 [NFS]
6523 Control how the NFS s 6198 Control how the NFS server code allocates CPUs to
6524 service thread pools. 6199 service thread pools. Depending on how many NICs
6525 you have and where th 6200 you have and where their interrupts are bound, this
6526 option will affect wh 6201 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 6202 Note: this parameter cannot be changed while the
6528 NFS server is running 6203 NFS server is running.
6529 6204
6530 auto the serve 6205 auto the server chooses an appropriate mode
6531 automatic 6206 automatically using heuristics
6532 global a single 6207 global a single global pool contains all CPUs
6533 percpu one pool 6208 percpu one pool for each CPU
6534 pernode one pool 6209 pernode one pool for each NUMA node (equivalent
6535 to global 6210 to global on non-NUMA machines)
6536 6211
6537 sunrpc.tcp_slot_table_entries= 6212 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 6213 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 6214 [NFS,SUNRPC]
6540 Sets the upper limit 6215 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 6216 RPC calls that can be sent from the client to a
6542 server. Increasing th 6217 server. Increasing these values may allow you to
6543 improve throughput, b 6218 improve throughput, but will also increase the
6544 amount of memory rese 6219 amount of memory reserved for use by the client.
6545 6220
6546 suspend.pm_test_delay= 6221 suspend.pm_test_delay=
6547 [SUSPEND] 6222 [SUSPEND]
6548 Sets the number of se 6223 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 6224 mode before resuming the system (see
6550 /sys/power/pm_test). 6225 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 6226 is set. Default value is 5.
6552 6227
6553 svm= [PPC] 6228 svm= [PPC]
6554 Format: { on | off | 6229 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 6230 This parameter controls use of the Protected
6556 Execution Facility on 6231 Execution Facility on pSeries.
6557 6232
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 6233 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in 6234 Format: { <int> [,<int>] | force | noforce }
6560 <int> -- Number of I/ 6235 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ 6236 <int> -- Second integer after comma. Number of swiotlb
6562 areas with t 6237 areas with their own lock. Will be rounded up
6563 to a power o 6238 to a power of 2.
6564 force -- force using 6239 force -- force using of bounce buffers even if they
6565 wouldn't be 6240 wouldn't be automatically used by the kernel
6566 noforce -- Never use 6241 noforce -- Never use bounce buffers (for debugging)
6567 6242
6568 switches= [HW,M68k,EARLY] !! 6243 switches= [HW,M68k]
6569 6244
6570 sysctl.*= [KNL] 6245 sysctl.*= [KNL]
6571 Set a sysctl paramete 6246 Set a sysctl parameter, right before loading the init
6572 process, as if the va 6247 process, as if the value was written to the respective
6573 /proc/sys/... file. B 6248 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 6249 separators. Unrecognized parameters and invalid values
6575 are reported in the k 6250 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 6251 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 6252 Example: sysctl.vm.swappiness=40
6578 6253
6579 sysrq_always_enabled 6254 sysrq_always_enabled
6580 [KNL] 6255 [KNL]
6581 Ignore sysrq setting 6256 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 6257 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 6258 Useful for debugging.
6584 6259
6585 tcpmhash_entries= [KNL,NET] 6260 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 6261 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 6262 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 6263 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 6264 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 6265 "tcp_no_metrics_save" section for more details.
6591 6266
6592 tdfx= [HW,DRM] 6267 tdfx= [HW,DRM]
6593 6268
6594 test_suspend= [SUSPEND] 6269 test_suspend= [SUSPEND]
6595 Format: { "mem" | "st 6270 Format: { "mem" | "standby" | "freeze" }[,N]
6596 Specify "mem" (for Su 6271 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 6272 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 6273 as the system sleep state during system startup with
6599 the optional capabili 6274 the optional capability to repeat N number of times.
6600 The system is woken f 6275 The system is woken from this state using a
6601 wakeup-capable RTC al 6276 wakeup-capable RTC alarm.
6602 6277
6603 thash_entries= [KNL,NET] 6278 thash_entries= [KNL,NET]
6604 Set number of hash bu 6279 Set number of hash buckets for TCP connection
6605 6280
6606 thermal.act= [HW,ACPI] 6281 thermal.act= [HW,ACPI]
6607 -1: disable all activ 6282 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 6283 <degrees C>: override all lowest active trip points
6609 6284
6610 thermal.crt= [HW,ACPI] 6285 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 6286 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 6287 <degrees C>: override all critical trip points
6613 6288
6614 thermal.off= [HW,ACPI] 6289 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 6290 1: disable ACPI thermal control
6616 6291
6617 thermal.psv= [HW,ACPI] 6292 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 6293 -1: disable all passive trip points
6619 <degrees C>: override 6294 <degrees C>: override all passive trip points to this
6620 value 6295 value
6621 6296
6622 thermal.tzp= [HW,ACPI] 6297 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 6298 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 6299 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 6300 0: no polling (default)
6626 6301
6627 threadirqs [KNL,EARLY] !! 6302 threadirqs [KNL]
6628 Force threading of al 6303 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 6304 marked explicitly IRQF_NO_THREAD.
6630 6305
6631 topology= [S390,EARLY] !! 6306 topology= [S390]
6632 Format: {off | on} 6307 Format: {off | on}
6633 Specify if the kernel 6308 Specify if the kernel should make use of the cpu
6634 topology information 6309 topology information if the hardware supports this.
6635 The scheduler will ma 6310 The scheduler will make use of this information and
6636 e.g. base its process 6311 e.g. base its process migration decisions on it.
6637 Default is on. 6312 Default is on.
6638 6313
>> 6314 topology_updates= [KNL, PPC, NUMA]
>> 6315 Format: {off}
>> 6316 Specify if the kernel should ignore (off)
>> 6317 topology updates sent by the hypervisor to this
>> 6318 LPAR.
>> 6319
6639 torture.disable_onoff_at_boot= [KNL] 6320 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 6321 Prevent the CPU-hotplug component of torturing
6641 until after init has 6322 until after init has spawned.
6642 6323
6643 torture.ftrace_dump_at_shutdown= [KNL 6324 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 6325 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 6326 even if there were no errors. This can be a
6646 very costly operation 6327 very costly operation when many torture tests
6647 are running concurren 6328 are running concurrently, especially on systems
6648 with rotating-rust st 6329 with rotating-rust storage.
6649 6330
6650 torture.verbose_sleep_frequency= [KNL 6331 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 6332 Specifies how many verbose printk()s should be
6652 emitted between each 6333 emitted between each sleep. The default of zero
6653 disables verbose-prin 6334 disables verbose-printk() sleeping.
6654 6335
6655 torture.verbose_sleep_duration= [KNL] 6336 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 6337 Duration of each verbose-printk() sleep in jiffies.
6657 6338
>> 6339 tp720= [HW,PS2]
>> 6340
6658 tpm_suspend_pcr=[HW,TPM] 6341 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 6342 Format: integer pcr id
6660 Specify that at suspe 6343 Specify that at suspend time, the tpm driver
6661 should extend the spe 6344 should extend the specified pcr with zeros,
6662 as a workaround for s 6345 as a workaround for some chips which fail to
6663 flush the last writte 6346 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 6347 This will guarantee that all the other pcrs
6665 are saved. 6348 are saved.
6666 6349
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] 6350 tp_printk [FTRACE]
6675 Have the tracepoints 6351 Have the tracepoints sent to printk as well as the
6676 tracing ring buffer. 6352 tracing ring buffer. This is useful for early boot up
6677 where the system hang 6353 where the system hangs or reboots and does not give the
6678 option for reading th 6354 option for reading the tracing buffer or performing a
6679 ftrace_dump_on_oops. 6355 ftrace_dump_on_oops.
6680 6356
6681 To turn off having tr 6357 To turn off having tracepoints sent to printk,
6682 echo 0 > /proc/sys/k 6358 echo 0 > /proc/sys/kernel/tracepoint_printk
6683 Note, echoing 1 into 6359 Note, echoing 1 into this file without the
6684 tp_printk kernel cmdl !! 6360 tracepoint_printk kernel cmdline option has no effect.
6685 6361
6686 The tp_printk_stop_on 6362 The tp_printk_stop_on_boot (see below) can also be used
6687 to stop the printing 6363 to stop the printing of events to console at
6688 late_initcall_sync. 6364 late_initcall_sync.
6689 6365
6690 ** CAUTION ** 6366 ** CAUTION **
6691 6367
6692 Having tracepoints se 6368 Having tracepoints sent to printk() and activating high
6693 frequency tracepoints 6369 frequency tracepoints such as irq or sched, can cause
6694 the system to live lo 6370 the system to live lock.
6695 6371
6696 tp_printk_stop_on_boot [FTRACE] 6372 tp_printk_stop_on_boot [FTRACE]
6697 When tp_printk (above 6373 When tp_printk (above) is set, it can cause a lot of noise
6698 on the console. It ma 6374 on the console. It may be useful to only include the
6699 printing of events du 6375 printing of events during boot up, as user space may
6700 make the system inope 6376 make the system inoperable.
6701 6377
6702 This command line opt 6378 This command line option will stop the printing of events
6703 to console at the lat 6379 to console at the late_initcall_sync() time frame.
6704 6380
6705 trace_buf_size=nn[KMG] 6381 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 6382 [FTRACE] will set tracing buffer size on each cpu.
6707 6383
6708 trace_clock= [FTRACE] Set the cloc 6384 trace_clock= [FTRACE] Set the clock used for tracing events
6709 at boot up. 6385 at boot up.
6710 local - Use the per C 6386 local - Use the per CPU time stamp counter
6711 (converted in 6387 (converted into nanoseconds). Fast, but
6712 depending on 6388 depending on the architecture, may not be
6713 in sync betwe 6389 in sync between CPUs.
6714 global - Event time s 6390 global - Event time stamps are synchronize across
6715 CPUs. May be 6391 CPUs. May be slower than the local clock,
6716 but better fo 6392 but better for some race conditions.
6717 counter - Simple coun 6393 counter - Simple counting of events (1, 2, ..)
6718 note, some co 6394 note, some counts may be skipped due to the
6719 infrastructur 6395 infrastructure grabbing the clock more than
6720 once per even 6396 once per event.
6721 uptime - Use jiffies 6397 uptime - Use jiffies as the time stamp.
6722 perf - Use the same c 6398 perf - Use the same clock that perf uses.
6723 mono - Use ktime_get_ 6399 mono - Use ktime_get_mono_fast_ns() for time stamps.
6724 mono_raw - Use ktime_ 6400 mono_raw - Use ktime_get_raw_fast_ns() for time
6725 stamps. 6401 stamps.
6726 boot - Use ktime_get_ 6402 boot - Use ktime_get_boot_fast_ns() for time stamps.
6727 Architectures may add 6403 Architectures may add more clocks. See
6728 Documentation/trace/f 6404 Documentation/trace/ftrace.rst for more details.
6729 6405
6730 trace_event=[event-list] 6406 trace_event=[event-list]
6731 [FTRACE] Set and star 6407 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 6408 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 6409 comma-separated list of trace events to enable. See
6734 also Documentation/tr 6410 also Documentation/trace/events.rst
6735 6411
6736 trace_instance=[instance-info] 6412 trace_instance=[instance-info]
6737 [FTRACE] Create a rin 6413 [FTRACE] Create a ring buffer instance early in boot up.
6738 This will be listed i 6414 This will be listed in:
6739 6415
6740 /sys/kernel/t 6416 /sys/kernel/tracing/instances
6741 6417
6742 Events can be enabled 6418 Events can be enabled at the time the instance is created
6743 via: 6419 via:
6744 6420
6745 trace_instanc 6421 trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
6746 6422
6747 Note, the "<system*>: 6423 Note, the "<system*>:" portion is optional if the event is
6748 unique. 6424 unique.
6749 6425
6750 trace_instanc 6426 trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
6751 6427
6752 will enable the "sche 6428 will enable the "sched_switch" event (note, the "sched:" is optional, and
6753 the same thing would 6429 the same thing would happen if it was left off). The irq_handler_entry
6754 event, and all events 6430 event, and all events under the "initcall" system.
6755 6431
6756 trace_options=[option-list] 6432 trace_options=[option-list]
6757 [FTRACE] Enable or di 6433 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 6434 The option-list is a comma delimited list of options
6759 that can be enabled o 6435 that can be enabled or disabled just as if you were
6760 to echo the option na 6436 to echo the option name into
6761 6437
6762 /sys/kernel/traci 6438 /sys/kernel/tracing/trace_options
6763 6439
6764 For example, to enabl 6440 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 6441 stack trace of each event), add to the command line:
6766 6442
6767 trace_options=s 6443 trace_options=stacktrace
6768 6444
6769 See also Documentatio 6445 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 6446 section.
6771 6447
6772 trace_trigger=[trigger-list] 6448 trace_trigger=[trigger-list]
6773 [FTRACE] Add a event 6449 [FTRACE] Add a event trigger on specific events.
6774 Set a trigger on top 6450 Set a trigger on top of a specific event, with an optional
6775 filter. 6451 filter.
6776 6452
6777 The format is is "tra 6453 The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
6778 Where more than one t 6454 Where more than one trigger may be specified that are comma deliminated.
6779 6455
6780 For example: 6456 For example:
6781 6457
6782 trace_trigger="sche 6458 trace_trigger="sched_switch.stacktrace if prev_state == 2"
6783 6459
6784 The above will enable 6460 The above will enable the "stacktrace" trigger on the "sched_switch"
6785 event but only trigge 6461 event but only trigger it if the "prev_state" of the "sched_switch"
6786 event is "2" (TASK_UN 6462 event is "2" (TASK_UNINTERUPTIBLE).
6787 6463
6788 See also "Event trigg 6464 See also "Event triggers" in Documentation/trace/events.rst
6789 6465
6790 6466
6791 traceoff_on_warning 6467 traceoff_on_warning
6792 [FTRACE] enable this 6468 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 6469 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 6470 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ 6471 file located in /sys/kernel/tracing/
6796 6472
6797 This option is useful 6473 This option is useful, as it disables the trace before
6798 the WARNING dump is c 6474 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 6475 be filled with content caused by the warning output.
6800 6476
6801 This option can also 6477 This option can also be set at run time via the sysctl
6802 option: kernel/trace 6478 option: kernel/traceoff_on_warning
6803 6479
6804 transparent_hugepage= 6480 transparent_hugepage=
6805 [KNL] 6481 [KNL]
6806 Format: [always|madvi 6482 Format: [always|madvise|never]
6807 Can be used to contro 6483 Can be used to control the default behavior of the system
6808 with respect to trans 6484 with respect to transparent hugepages.
6809 See Documentation/adm 6485 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 6486 for more details.
6811 6487
6812 trusted.source= [KEYS] 6488 trusted.source= [KEYS]
6813 Format: <string> 6489 Format: <string>
6814 This parameter identi 6490 This parameter identifies the trust source as a backend
6815 for trusted keys impl 6491 for trusted keys implementation. Supported trust
6816 sources: 6492 sources:
6817 - "tpm" 6493 - "tpm"
6818 - "tee" 6494 - "tee"
6819 - "caam" 6495 - "caam"
6820 - "dcp" <<
6821 If not specified then 6496 If not specified then it defaults to iterating through
6822 the trust source list 6497 the trust source list starting with TPM and assigns the
6823 first trust source as 6498 first trust source as a backend which is initialized
6824 successfully during i 6499 successfully during iteration.
6825 6500
6826 trusted.rng= [KEYS] 6501 trusted.rng= [KEYS]
6827 Format: <string> 6502 Format: <string>
6828 The RNG used to gener 6503 The RNG used to generate key material for trusted keys.
6829 Can be one of: 6504 Can be one of:
6830 - "kernel" 6505 - "kernel"
6831 - the same value as t 6506 - the same value as trusted.source: "tpm" or "tee"
6832 - "default" 6507 - "default"
6833 If not specified, "de 6508 If not specified, "default" is used. In this case,
6834 the RNG's choice is l 6509 the RNG's choice is left to each individual trust source.
6835 6510
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 6511 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 6512 Format: <string>
6850 [x86] reliable: mark 6513 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 6514 disables clocksource verification at runtime, as well
6852 as the stability chec 6515 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 6516 high-resolution timer mode on older hardware, and in
6854 virtualized environme 6517 virtualized environment.
6855 [x86] noirqtime: Do n 6518 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 6519 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 6520 platforms where RDTSC is slow and this accounting
6858 can add overhead. 6521 can add overhead.
6859 [x86] unstable: mark 6522 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 6523 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 6524 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 6525 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 6526 in situations with strict latency requirements (where
6864 interruptions from cl 6527 interruptions from clocksource watchdog are not
6865 acceptable). 6528 acceptable).
6866 [x86] recalibrate: fo 6529 [x86] recalibrate: force recalibration against a HW timer
6867 (HPET or PM timer) on 6530 (HPET or PM timer) on systems whose TSC frequency was
6868 obtained from HW or F 6531 obtained from HW or FW using either an MSR or CPUID(0x15).
6869 Warn if the differenc 6532 Warn if the difference is more than 500 ppm.
6870 [x86] watchdog: Use T 6533 [x86] watchdog: Use TSC as the watchdog clocksource with
6871 which to check other 6534 which to check other HW timers (HPET or PM timer), but
6872 only on systems where 6535 only on systems where TSC has been deemed trustworthy.
6873 This will be suppress 6536 This will be suppressed by an earlier tsc=nowatchdog and
6874 can be overridden by 6537 can be overridden by a later tsc=nowatchdog. A console
6875 message will flag any 6538 message will flag any such suppression or overriding.
6876 6539
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 6540 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 6541 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 6542 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 6543 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 6544 Format: <unsigned int>
6882 6545
6883 tsx= [X86] Control Transac 6546 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 6547 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 6548 support TSX control.
6886 6549
6887 This parameter contro 6550 This parameter controls the TSX feature. The options are:
6888 6551
6889 on - Enable TSX 6552 on - Enable TSX on the system. Although there are
6890 mitigations f 6553 mitigations for all known security vulnerabilities,
6891 TSX has been 6554 TSX has been known to be an accelerator for
6892 several previ 6555 several previous speculation-related CVEs, and
6893 so there may 6556 so there may be unknown security risks associated
6894 with leaving 6557 with leaving it enabled.
6895 6558
6896 off - Disable TSX 6559 off - Disable TSX on the system. (Note that this
6897 option takes 6560 option takes effect only on newer CPUs which are
6898 not vulnerabl 6561 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 6562 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 6563 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 6564 update. This new MSR allows for the reliable
6902 deactivation 6565 deactivation of the TSX functionality.)
6903 6566
6904 auto - Disable TSX 6567 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 6568 otherwise enable TSX on the system.
6906 6569
6907 Not specifying this o 6570 Not specifying this option is equivalent to tsx=off.
6908 6571
6909 See Documentation/adm 6572 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 6573 for more details.
6911 6574
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 6575 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 6576 Abort (TAA) vulnerability.
6914 6577
6915 Similar to Micro-arch 6578 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 6579 certain CPUs that support Transactional
6917 Synchronization Exten 6580 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 6581 exploit against CPU internal buffers which can forward
6919 information to a disc 6582 information to a disclosure gadget under certain
6920 conditions. 6583 conditions.
6921 6584
6922 In vulnerable process 6585 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 6586 data can be used in a cache side channel attack, to
6924 access data to which 6587 access data to which the attacker does not have direct
6925 access. 6588 access.
6926 6589
6927 This parameter contro 6590 This parameter controls the TAA mitigation. The
6928 options are: 6591 options are:
6929 6592
6930 full - Enable T 6593 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 6594 if TSX is enabled.
6932 6595
6933 full,nosmt - Enable T 6596 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 6597 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 6598 is not disabled because CPU is not
6936 vulnerab 6599 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 6600 off - Unconditionally disable TAA mitigation
6938 6601
6939 On MDS-affected machi 6602 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 6603 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 6604 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 6605 this mitigation, you need to specify mds=off too.
6943 6606
6944 Not specifying this o 6607 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 6608 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 6609 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 6610 required and doesn't provide any additional
6948 mitigation. 6611 mitigation.
6949 6612
6950 For details see: 6613 For details see:
6951 Documentation/admin-g 6614 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 6615
6953 turbografx.map[2|3]= [HW,JOY] 6616 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 6617 TurboGraFX parallel port interface
6955 Format: 6618 Format:
6956 <port#>,<js1>,<js2>,< 6619 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 6620 See also Documentation/input/devices/joystick-parport.rst
6958 6621
6959 udbg-immortal [PPC] When debugging 6622 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 6623 happen after console_init() and before a proper
6961 console driver takes 6624 console driver takes over, this boot options might
6962 help "seeing" what's 6625 help "seeing" what's going on.
6963 6626
6964 uhash_entries= [KNL,NET] 6627 uhash_entries= [KNL,NET]
6965 Set number of hash bu 6628 Set number of hash buckets for UDP/UDP-Lite connections
6966 6629
6967 uhci-hcd.ignore_oc= 6630 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 6631 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 6632 Some badly-designed motherboards generate lots of
6970 bogus events, for por 6633 bogus events, for ports that aren't wired to
6971 anything. Set this p 6634 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 6635 Note that genuine overcurrent events won't be
6973 reported either. 6636 reported either.
6974 6637
6975 unknown_nmi_panic 6638 unknown_nmi_panic
6976 [X86] Cause panic on 6639 [X86] Cause panic on unknown NMI.
6977 6640
6978 unwind_debug [X86-64,EARLY] !! 6641 unwind_debug [X86-64]
6979 Enable unwinder debug 6642 Enable unwinder debug output. This can be
6980 useful for debugging 6643 useful for debugging certain unwinder error
6981 conditions, including 6644 conditions, including corrupt stacks and
6982 bad/missing unwinder 6645 bad/missing unwinder metadata.
6983 6646
6984 usbcore.authorized_default= 6647 usbcore.authorized_default=
6985 [USB] Default USB dev 6648 [USB] Default USB device authorization:
6986 (default -1 = authori !! 6649 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 6650 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 6651 if device connected to internal port)
6989 6652
6990 usbcore.autosuspend= 6653 usbcore.autosuspend=
6991 [USB] The autosuspend 6654 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 6655 for newly-detected USB devices (default 2). This
6993 is the time required 6656 is the time required before an idle device will be
6994 autosuspended. Devic 6657 autosuspended. Devices for which the delay is set
6995 to a negative value w 6658 to a negative value won't be autosuspended at all.
6996 6659
6997 usbcore.usbfs_snoop= 6660 usbcore.usbfs_snoop=
6998 [USB] Set to log all 6661 [USB] Set to log all usbfs traffic (default 0 = off).
6999 6662
7000 usbcore.usbfs_snoop_max= 6663 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 6664 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 6665 (default = 65536).
7003 6666
7004 usbcore.blinkenlights= 6667 usbcore.blinkenlights=
7005 [USB] Set to cycle le 6668 [USB] Set to cycle leds on hubs (default 0 = off).
7006 6669
7007 usbcore.old_scheme_first= 6670 usbcore.old_scheme_first=
7008 [USB] Start with the 6671 [USB] Start with the old device initialization
7009 scheme (default 0 = o 6672 scheme (default 0 = off).
7010 6673
7011 usbcore.usbfs_memory_mb= 6674 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 6675 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 6676 usbfs (default = 16, 0 = max = 2047).
7014 6677
7015 usbcore.use_both_schemes= 6678 usbcore.use_both_schemes=
7016 [USB] Try the other d 6679 [USB] Try the other device initialization scheme
7017 if the first one fail 6680 if the first one fails (default 1 = enabled).
7018 6681
7019 usbcore.initial_descriptor_timeout= 6682 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 6683 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 6684 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 6685 (default 5000 = 5.0 seconds).
7023 6686
7024 usbcore.nousb [USB] Disable the USB 6687 usbcore.nousb [USB] Disable the USB subsystem
7025 6688
7026 usbcore.quirks= 6689 usbcore.quirks=
7027 [USB] A list of quirk 6690 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 6691 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 6692 commas. Each entry has the form
7030 VendorID:ProductID:Fl 6693 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 6694 numbers and Flags is a set of letters. Each letter
7032 will change the built 6695 will change the built-in quirk; setting it if it is
7033 clear and clearing it 6696 clear and clearing it if it is set. The letters have
7034 the following meaning 6697 the following meanings:
7035 a = USB_QUIRK 6698 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 6699 descriptors must not be fetched using
7037 a 255 6700 a 255-byte read);
7038 b = USB_QUIRK 6701 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 6702 correctly so reset it instead);
7040 c = USB_QUIRK 6703 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 6704 Set-Interface requests);
7042 d = USB_QUIRK 6705 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 6706 handle its Configuration or Interface
7044 strin 6707 strings);
7045 e = USB_QUIRK 6708 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 6709 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 6710 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 6711 more interface descriptions than the
7049 bNumI 6712 bNumInterfaces count, and can't handle
7050 talki 6713 talking to these interfaces);
7051 g = USB_QUIRK 6714 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 6715 during initialization, after we read
7053 the d 6716 the device descriptor);
7054 h = USB_QUIRK 6717 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 6718 high speed and super speed interrupt
7056 endpo 6719 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 6720 require the interval in microframes (1
7058 micro 6721 microframe = 125 microseconds) to be
7059 calcu 6722 calculated as interval = 2 ^
7060 (bInt 6723 (bInterval-1).
7061 Devic 6724 Devices with this quirk report their
7062 bInte 6725 bInterval as the result of this
7063 calcu 6726 calculation instead of the exponent
7064 varia 6727 variable used in the calculation);
7065 i = USB_QUIRK 6728 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 6729 handle device_qualifier descriptor
7067 reque 6730 requests);
7068 j = USB_QUIRK 6731 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 6732 generates spurious wakeup, ignore
7070 remot 6733 remote wakeup capability);
7071 k = USB_QUIRK 6734 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 6735 Power Management);
7073 l = USB_QUIRK 6736 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 6737 (Device reports its bInterval as linear
7075 frame 6738 frames instead of the USB 2.0
7076 calcu 6739 calculation);
7077 m = USB_QUIRK 6740 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 6741 to be disconnected before suspend to
7079 preve 6742 prevent spurious wakeup);
7080 n = USB_QUIRK 6743 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 6744 pause after every control message);
7082 o = USB_QUIRK 6745 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 6746 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 6747 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 6748
7089 usbhid.mousepoll= 6749 usbhid.mousepoll=
7090 [USBHID] The interval 6750 [USBHID] The interval which mice are to be polled at.
7091 6751
7092 usbhid.jspoll= 6752 usbhid.jspoll=
7093 [USBHID] The interval 6753 [USBHID] The interval which joysticks are to be polled at.
7094 6754
7095 usbhid.kbpoll= 6755 usbhid.kbpoll=
7096 [USBHID] The interval 6756 [USBHID] The interval which keyboards are to be polled at.
7097 6757
7098 usb-storage.delay_use= 6758 usb-storage.delay_use=
7099 [UMS] The delay in se 6759 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 6760 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 6761
7105 usb-storage.quirks= 6762 usb-storage.quirks=
7106 [UMS] A list of quirk 6763 [UMS] A list of quirks entries to supplement or
7107 override the built-in 6764 override the built-in unusual_devs list. List
7108 entries are separated 6765 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 6766 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 6767 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 6768 Flags is a set of characters, each corresponding
7112 to a common usb-stora 6769 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 6770 a = SANE_SENSE (collect more than 18 bytes
7114 of se 6771 of sense data, not on uas);
7115 b = BAD_SENSE 6772 b = BAD_SENSE (don't collect more than 18
7116 bytes 6773 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 6774 c = FIX_CAPACITY (decrease the reported
7118 devic 6775 device capacity by one sector);
7119 d = NO_READ_D 6776 d = NO_READ_DISC_INFO (don't use
7120 READ_ 6777 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 6778 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 6779 READ_CAPACITY_16 command);
7123 f = NO_REPORT 6780 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 6781 command, uas only);
7125 g = MAX_SECTO 6782 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 6783 240 sectors at a time, uas only);
7127 h = CAPACITY_ 6784 h = CAPACITY_HEURISTICS (decrease the
7128 repor 6785 reported device capacity by one
7129 secto 6786 sector if the number is odd);
7130 i = IGNORE_DE 6787 i = IGNORE_DEVICE (don't bind to this
7131 devic 6788 device);
7132 j = NO_REPORT 6789 j = NO_REPORT_LUNS (don't use report luns
7133 comma 6790 command, uas only);
7134 k = NO_SAME ( 6791 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 6792 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 6793 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 6794 m = MAX_SECTORS_64 (don't transfer more
7138 than 6795 than 64 sectors = 32 KB at a time,
7139 not o 6796 not on uas);
7140 n = INITIAL_R 6797 n = INITIAL_READ10 (force a retry of the
7141 initi 6798 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 6799 o = CAPACITY_OK (accept the capacity
7143 repor 6800 reported by the device, not on uas);
7144 p = WRITE_CAC 6801 p = WRITE_CACHE (the device cache is ON
7145 by de 6802 by default, not on uas);
7146 r = IGNORE_RE 6803 r = IGNORE_RESIDUE (the device reports
7147 bogus 6804 bogus residue values, not on uas);
7148 s = SINGLE_LU 6805 s = SINGLE_LUN (the device has only one
7149 Logic 6806 Logical Unit);
7150 t = NO_ATA_1X 6807 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 6808 commands, uas only);
7152 u = IGNORE_UA 6809 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 6810 w = NO_WP_DETECT (don't test whether the
7154 mediu 6811 medium is write-protected).
7155 y = ALWAYS_SY 6812 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 6813 even if the device claims no cache,
7157 not o 6814 not on uas)
7158 Example: quirks=0419: 6815 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 6816
7160 user_debug= [KNL,ARM] 6817 user_debug= [KNL,ARM]
7161 Format: <int> 6818 Format: <int>
7162 See arch/arm/Kconfig. 6819 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 6820 1 - undefined instruction events
7164 2 - system c 6821 2 - system calls
7165 4 - invalid 6822 4 - invalid data aborts
7166 8 - SIGSEGV 6823 8 - SIGSEGV faults
7167 16 - SIGBUS f 6824 16 - SIGBUS faults
7168 Example: user_debug=3 6825 Example: user_debug=31
7169 6826
7170 userpte= 6827 userpte=
7171 [X86,EARLY] Flags con !! 6828 [X86] Flags controlling user PTE allocations.
7172 6829
7173 nohigh = do n 6830 nohigh = do not allocate PTE pages in
7174 HIGHM 6831 HIGHMEM regardless of setting
7175 of CO 6832 of CONFIG_HIGHPTE.
7176 6833
7177 vdso= [X86,SH,SPARC] 6834 vdso= [X86,SH,SPARC]
7178 On X86_32, this is an 6835 On X86_32, this is an alias for vdso32=. Otherwise:
7179 6836
7180 vdso=1: enable VDSO ( 6837 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 6838 vdso=0: disable VDSO mapping
7182 6839
7183 vdso32= [X86] Control the 32- 6840 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 6841 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 6842 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 6843
7187 See the help text for 6844 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 6845 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 6846 vdso32=0; otherwise, the default is vdso32=1.
7190 6847
7191 For compatibility wit 6848 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 6849 alias for vdso32=0.
7193 6850
7194 Try vdso32=0 if you e 6851 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 6852 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 6853
7197 video= [FB,EARLY] Frame buff !! 6854 vector= [IA-64,SMP]
>> 6855 vector=percpu: enable percpu vector domain
>> 6856
>> 6857 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 6858 See Documentation/fb/modedb.rst.
7199 6859
7200 video.brightness_switch_enabled= [ACP 6860 video.brightness_switch_enabled= [ACPI]
7201 Format: [0|1] 6861 Format: [0|1]
7202 If set to 1, on recei 6862 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 6863 generated by hotkey, video driver will adjust brightness
7204 level and then send o 6864 level and then send out the event to user space through
7205 the allocated input d 6865 the allocated input device. If set to 0, video driver
7206 will only send out th 6866 will only send out the event without touching backlight
7207 brightness level. 6867 brightness level.
7208 default: 1 6868 default: 1
7209 6869
7210 virtio_mmio.device= 6870 virtio_mmio.device=
7211 [VMMIO] Memory mapped 6871 [VMMIO] Memory mapped virtio (platform) device.
7212 6872
7213 <size>@<basead 6873 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 6874 where:
7215 <size> := 6875 <size> := size (can use standard suffixes
7216 6876 like K, M and G)
7217 <baseaddr> := 6877 <baseaddr> := physical base address
7218 <irq> := 6878 <irq> := interrupt number (as passed to
7219 6879 request_irq())
7220 <id> := 6880 <id> := (optional) platform device id
7221 example: 6881 example:
7222 virtio_mmio.d 6882 virtio_mmio.device=1K@0x100b0000:48:7
7223 6883
7224 Can be used multiple 6884 Can be used multiple times for multiple devices.
7225 6885
7226 vga= [BOOT,X86-32] Select 6886 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc 6887 See Documentation/arch/x86/boot.rst and
7228 Documentation/admin-g 6888 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 6889 Use vga=ask for menu.
7230 This is actually a bo 6890 This is actually a boot loader parameter; the value is
7231 passed to the kernel 6891 passed to the kernel using a special protocol.
7232 6892
7233 vm_debug[=options] [KNL] Availab 6893 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 6894 May slow down system boot speed, especially when
7235 enabled on systems wi 6895 enabled on systems with a large amount of memory.
7236 All options are enabl 6896 All options are enabled by default, and this
7237 interface is meant to 6897 interface is meant to allow for selectively
7238 enabling or disabling 6898 enabling or disabling specific virtual memory
7239 debugging features. 6899 debugging features.
7240 6900
7241 Available options are 6901 Available options are:
7242 P Enable page s 6902 P Enable page structure init time poisoning
7243 - Disable all o 6903 - Disable all of the above options
7244 6904
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 6905 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 6906 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 6907 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 6908 decrease the size and leave more room for directly
7249 for directly mapped k !! 6909 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 6910
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 6911 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 6912 Sets the memory size reserved for contiguous memory
7256 allocations for the v 6913 allocations for the vmcp device driver.
7257 6914
7258 vmhalt= [KNL,S390] Perform z/ 6915 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 6916 Format: <command>
7260 6917
7261 vmpanic= [KNL,S390] Perform z/ 6918 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 6919 Format: <command>
7263 6920
7264 vmpoff= [KNL,S390] Perform z/ 6921 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 6922 Format: <command>
7266 6923
7267 vsyscall= [X86-64,EARLY] !! 6924 vsyscall= [X86-64]
7268 Controls the behavior 6925 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 6926 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 6927 code). Most statically-linked binaries and older
7271 versions of glibc use 6928 versions of glibc use these calls. Because these
7272 functions are at fixe 6929 functions are at fixed addresses, they make nice
7273 targets for exploits 6930 targets for exploits that can control RIP.
7274 6931
7275 emulate Vsyscalls 6932 emulate Vsyscalls turn into traps and are emulated
7276 reasonabl 6933 reasonably safely. The vsyscall page is
7277 readable. 6934 readable.
7278 6935
7279 xonly [default] 6936 xonly [default] Vsyscalls turn into traps and are
7280 emulated 6937 emulated reasonably safely. The vsyscall
7281 page is n 6938 page is not readable.
7282 6939
7283 none Vsyscalls 6940 none Vsyscalls don't work at all. This makes
7284 them quit 6941 them quite hard to use for exploits but
7285 might bre 6942 might break your system.
7286 6943
7287 vt.color= [VT] Default text col 6944 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 6945 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 6946 Default: 0x07 = light gray on black.
7290 6947
7291 vt.cur_default= [VT] Default cursor s 6948 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 6949 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 6950 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 6951 see VGA-softcursor.txt. Default: 2 = underline.
7295 6952
7296 vt.default_blu= [VT] 6953 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 6954 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 6955 Change the default blue palette of the console.
7299 This is a 16-member a 6956 This is a 16-member array composed of values
7300 ranging from 0-255. 6957 ranging from 0-255.
7301 6958
7302 vt.default_grn= [VT] 6959 vt.default_grn= [VT]
7303 Format: <green0>,<gre 6960 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 6961 Change the default green palette of the console.
7305 This is a 16-member a 6962 This is a 16-member array composed of values
7306 ranging from 0-255. 6963 ranging from 0-255.
7307 6964
7308 vt.default_red= [VT] 6965 vt.default_red= [VT]
7309 Format: <red0>,<red1> 6966 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 6967 Change the default red palette of the console.
7311 This is a 16-member a 6968 This is a 16-member array composed of values
7312 ranging from 0-255. 6969 ranging from 0-255.
7313 6970
7314 vt.default_utf8= 6971 vt.default_utf8=
7315 [VT] 6972 [VT]
7316 Format=<0|1> 6973 Format=<0|1>
7317 Set system-wide defau 6974 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 6975 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 6976 newly opened terminals.
7320 6977
7321 vt.global_cursor_default= 6978 vt.global_cursor_default=
7322 [VT] 6979 [VT]
7323 Format=<-1|0|1> 6980 Format=<-1|0|1>
7324 Set system-wide defau 6981 Set system-wide default for whether a cursor
7325 is shown on new VTs. 6982 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 6983 i.e. cursors will be created by default unless
7327 overridden by individ 6984 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 6985 cursors, 1 will display them.
7329 6986
7330 vt.italic= [VT] Default color fo 6987 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 6988 Default: 2 = green.
7332 6989
7333 vt.underline= [VT] Default color fo 6990 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 6991 Default: 3 = cyan.
7335 6992
7336 watchdog timers [HW,WDT] For informat 6993 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 6994 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 6995 or other driver-specific files in the
7339 Documentation/watchdo 6996 Documentation/watchdog/ directory.
7340 6997
7341 watchdog_thresh= 6998 watchdog_thresh=
7342 [KNL] 6999 [KNL]
7343 Set the hard lockup d 7000 Set the hard lockup detector stall duration
7344 threshold in seconds. 7001 threshold in seconds. The soft lockup detector
7345 threshold is set to t 7002 threshold is set to twice the value. A value of 0
7346 disables both lockup 7003 disables both lockup detectors. Default is 10
7347 seconds. 7004 seconds.
7348 7005
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= 7006 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 7007 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 7008 warn stall conditions and dump internal state to
7359 help debugging. 0 di 7009 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 7010 detection; otherwise, it's the stall threshold
7361 duration in seconds. 7011 duration in seconds. The default value is 30 and
7362 it can be updated at 7012 it can be updated at runtime by writing to the
7363 corresponding sysfs f 7013 corresponding sysfs file.
7364 7014
7365 workqueue.cpu_intensive_thresh_us= 7015 workqueue.cpu_intensive_thresh_us=
7366 Per-cpu work items wh 7016 Per-cpu work items which run for longer than this
7367 threshold are automat 7017 threshold are automatically considered CPU intensive
7368 and excluded from con 7018 and excluded from concurrency management to prevent
7369 them from noticeably 7019 them from noticeably delaying other per-cpu work
7370 items. Default is 100 7020 items. Default is 10000 (10ms).
7371 7021
7372 If CONFIG_WQ_CPU_INTE 7022 If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7373 will report the work 7023 will report the work functions which violate this
7374 threshold repeatedly. 7024 threshold repeatedly. They are likely good
7375 candidates for using 7025 candidates for using WQ_UNBOUND workqueues instead.
7376 7026
7377 workqueue.cpu_intensive_warning_thres !! 7027 workqueue.disable_numa
7378 If CONFIG_WQ_CPU_INTE !! 7028 By default, all work items queued to unbound
7379 will report the work !! 7029 workqueues are affine to the NUMA nodes they're
7380 intensive_threshold_u !! 7030 issued on, which results in better behavior in
7381 spurious warnings, st !! 7031 general. If NUMA affinity needs to be disabled for
7382 function has violated !! 7032 whatever reason, this option can be used. Note
7383 !! 7033 that this also can be controlled per-workqueue for
7384 The default is 4 time !! 7034 workqueues visible under /sys/bus/workqueue/.
7385 7035
7386 workqueue.power_efficient 7036 workqueue.power_efficient
7387 Per-cpu workqueues ar 7037 Per-cpu workqueues are generally preferred because
7388 they show better perf 7038 they show better performance thanks to cache
7389 locality; unfortunate 7039 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 7040 be more power hungry than unbound workqueues.
7391 7041
7392 Enabling this makes t 7042 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 7043 were observed to contribute significantly to power
7394 consumption unbound, 7044 consumption unbound, leading to measurably lower
7395 power usage at the co 7045 power usage at the cost of small performance
7396 overhead. 7046 overhead.
7397 7047
7398 The default value of 7048 The default value of this parameter is determined by
7399 the config option CON 7049 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 7050
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 7051 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 7052 Workqueue used to implicitly guarantee that work
7415 items queued without 7053 items queued without explicit CPU specified are put
7416 on the local CPU. Th 7054 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 7055 and while local CPU is still preferred work items
7418 may be put on foreign 7056 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 7057 forces round-robin CPU selection to flush out
7420 usages which depend o 7058 usages which depend on the now broken guarantee.
7421 When enabled, memory 7059 When enabled, memory and cache locality will be
7422 impacted. 7060 impacted.
7423 7061
7424 writecombine= [LOONGARCH,EARLY] Con !! 7062 writecombine= [LOONGARCH] Control the MAT (Memory Access Type) of
7425 Type) of ioremap_wc() !! 7063 ioremap_wc().
7426 7064
7427 on - Enable writeco 7065 on - Enable writecombine, use WUC for ioremap_wc()
7428 off - Disable writec 7066 off - Disable writecombine, use SUC for ioremap_wc()
7429 7067
7430 x2apic_phys [X86-64,APIC,EARLY] U !! 7068 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7431 default x2apic cluste 7069 default x2apic cluster mode on platforms
7432 supporting x2apic. 7070 supporting x2apic.
7433 7071
7434 xen_512gb_limit [KNL,X86-64,X 7072 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 7073 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 7074 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 7075 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 7076 save/restore/migration must be enabled to handle larger
7439 domains. 7077 domains.
7440 7078
7441 xen_emul_unplug= [HW,X !! 7079 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 7080 Unplug Xen emulated devices
7443 Format: [unplug0,][un 7081 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 7082 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 7083 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 7084 nics -- unplug network devices
7447 all -- unplug all emu 7085 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 7086 unnecessary -- unplugging emulated devices is
7449 unnecessary e 7087 unnecessary even if the host did not respond to
7450 the unplug pr 7088 the unplug protocol
7451 never -- do not unplu 7089 never -- do not unplug even if version check succeeds
7452 7090
7453 xen_legacy_crash [X86,XEN,EARL !! 7091 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 7092 Crash from Xen panic notifier, without executing late
7455 panic() code such as 7093 panic() code such as dumping handler.
7456 7094
7457 xen_mc_debug [X86,XEN,EARLY] !! 7095 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> 7096 Format: <bool>
7465 Select whether to alw 7097 Select whether to always use non-faulting (safe) MSR
7466 access functions when 7098 access functions when running as Xen PV guest. The
7467 default value is cont 7099 default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
7468 7100
>> 7101 xen_nopvspin [X86,XEN]
>> 7102 Disables the qspinlock slowpath using Xen PV optimizations.
>> 7103 This parameter is obsoleted by "nopvspin" parameter, which
>> 7104 has equivalent effect for XEN platform.
>> 7105
7469 xen_nopv [X86] 7106 xen_nopv [X86]
7470 Disables the PV optim 7107 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 7108 run as generic HVM guest with no PV drivers.
7472 This option is obsole 7109 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 7110 has equivalent effect for XEN platform.
7474 7111
7475 xen_no_vector_callback 7112 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 7113 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 7114 event channel interrupts.
7478 7115
7479 xen_scrub_pages= [XEN] 7116 xen_scrub_pages= [XEN]
7480 Boolean option to con 7117 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 7118 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 7119 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 7120 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 7121
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 7122 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 7123 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 7124 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 7125 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 7126 improve timer resolution at the expense of processing
7490 more timer interrupts 7127 more timer interrupts.
7491 7128
7492 xen.balloon_boot_timeout= [XEN] 7129 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 7130 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 7131 in case initial ballooning fails to free enough memory.
7495 Applies only when run 7132 Applies only when running as HVM or PVH guest and
7496 started with less mem 7133 started with less memory configured than allowed at
7497 max. Default is 180. 7134 max. Default is 180.
7498 7135
7499 xen.event_eoi_delay= [XEN] 7136 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 7137 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 7138 storms (jiffies). Default is 10.
7502 7139
7503 xen.event_loop_timeout= [XEN] 7140 xen.event_loop_timeout= [XEN]
7504 After which time (jif 7141 After which time (jiffies) the event handling loop
7505 should start to delay 7142 should start to delay EOI handling. Default is 2.
7506 7143
7507 xen.fifo_events= [XEN] 7144 xen.fifo_events= [XEN]
7508 Boolean parameter to 7145 Boolean parameter to disable using fifo event handling
7509 even if available. No 7146 even if available. Normally fifo event handling is
7510 preferred over the 2- 7147 preferred over the 2-level event handling, as it is
7511 fairer and the number 7148 fairer and the number of possible event channels is
7512 much higher. Default 7149 much higher. Default is on (use fifo events).
7513 7150
7514 xirc2ps_cs= [NET,PCMCIA] 7151 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 7152 Format:
7516 <irq>,<irq_mask>,<io> 7153 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 7154
7518 xive= [PPC] 7155 xive= [PPC]
7519 By default on POWER9 7156 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 7157 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 7158 allows the fallback firmware mode to be used:
7522 7159
7523 off Fallback to 7160 off Fallback to firmware control of XIVE interrupt
7524 controller 7161 controller on both pseries and powernv
7525 platforms. 7162 platforms. Only useful on POWER9 and above.
7526 7163
7527 xive.store-eoi=off [PPC] 7164 xive.store-eoi=off [PPC]
7528 By default on POWER10 7165 By default on POWER10 and above, the kernel will use
7529 stores for EOI handli 7166 stores for EOI handling when the XIVE interrupt mode
7530 is active. This optio 7167 is active. This option allows the XIVE driver to use
7531 loads instead, as on 7168 loads instead, as on POWER9.
7532 7169
7533 xhci-hcd.quirks [USB,KNL] 7170 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 7171 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 7172 host controller quirks. Meaning of each bit can be
7536 consulted in header d 7173 consulted in header drivers/usb/host/xhci.h.
7537 7174
7538 xmon [PPC,EARLY] !! 7175 xmon [PPC]
7539 Format: { early | on 7176 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 7177 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 7178 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 7179 early Call xmon as early as possible on boot; xmon
7543 debugger is c 7180 debugger is called from setup_arch().
7544 on xmon debugger 7181 on xmon debugger hooks will be installed so xmon
7545 is only calle 7182 is only called on a kernel crash. Default mode,
7546 i.e. either " 7183 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 7184 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 7185 rw xmon debugger hooks will be installed so xmon
7549 is called onl 7186 is called only on a kernel crash, mode is write,
7550 meaning SPR r 7187 meaning SPR registers, memory and, other data
7551 can be writte 7188 can be written using xmon commands.
7552 ro same as "rw" 7189 ro same as "rw" option above but SPR registers,
7553 memory, and o 7190 memory, and other data can't be written using
7554 xmon commands 7191 xmon commands.
7555 off xmon is disab 7192 off xmon is disabled.
>> 7193
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