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.nomops [ARM64] Unconditionally disable Memory Copy and Memory
445 Set instructions suppo 422 Set instructions 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.nopauth [ARM64] Unconditionally disable Pointer Authentication
451 support 428 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.nosve [ARM64] Unconditionally disable Scalable Vector
457 Extension support 434 Extension 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/arch/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 583 cgroup_favordynmods= [KNL] Enable or Disable favordynmods.
608 Format: { "true" | "fa 584 Format: { "true" | "false" }
609 Defaults to the value 585 Defaults to the value of CONFIG_CGROUP_FAVOR_DYNMODS.
610 586
611 cgroup.memory= [KNL] Pass options to 587 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 588 Format: <string>
613 nosocket -- Disable so 589 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 590 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m 591 nobpf -- Disable BPF memory accounting.
616 592
617 checkreqprot= [SELINUX] Set initial 593 checkreqprot= [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 594 Format: { "0" | "1" }
619 See security/selinux/K 595 See security/selinux/Kconfig help text.
620 0 -- check protection 596 0 -- check protection applied by kernel (includes
621 any implied ex 597 any implied execute protection).
622 1 -- check protection 598 1 -- check protection requested by application.
623 Default value is set v 599 Default value is set via a kernel config option.
624 Value can be changed a 600 Value can be changed at runtime via
625 /sys/fs/selinu 601 /sys/fs/selinux/checkreqprot.
626 Setting checkreqprot t 602 Setting checkreqprot to 1 is deprecated.
627 603
628 cio_ignore= [S390] 604 cio_ignore= [S390]
629 See Documentation/arch 605 See Documentation/arch/s390/common_io.rst for details.
630 606
631 clearcpuid=X[,X...] [X86] 607 clearcpuid=X[,X...] [X86]
632 Disable CPUID feature 608 Disable CPUID feature X for the kernel. See
633 arch/x86/include/asm/c 609 arch/x86/include/asm/cpufeatures.h for the valid bit
634 numbers X. Note the Li 610 numbers X. Note the Linux-specific bits are not necessarily
635 stable over kernel opt 611 stable over kernel options, but the vendor-specific
636 ones should be. 612 ones should be.
637 X can also be a string 613 X can also be a string as appearing in the flags: line
638 in /proc/cpuinfo which 614 in /proc/cpuinfo which does not have the above
639 instability issue. How 615 instability issue. However, not all features have names
640 in /proc/cpuinfo. 616 in /proc/cpuinfo.
641 Note that using this o 617 Note that using this option will taint your kernel.
642 Also note that user pr 618 Also note that user programs calling CPUID directly
643 or using the feature w 619 or using the feature without checking anything
644 will still see it. Thi 620 will still see it. This just prevents it from
645 being used by the kern 621 being used by the kernel or shown in /proc/cpuinfo.
646 Also note the kernel m 622 Also note the kernel might malfunction if you disable
647 some critical bits. 623 some critical bits.
648 624
649 clk_ignore_unused 625 clk_ignore_unused
650 [CLK] 626 [CLK]
651 Prevents the clock fra 627 Prevents the clock framework from automatically gating
652 clocks that have not b 628 clocks that have not been explicitly enabled by a Linux
653 device driver but are 629 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 630 by the bootloader/firmware. Note that this does not
655 force such clocks to b 631 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 632 those clocks in any way. This parameter is useful for
657 debug and development, 633 debug and development, but should not be needed on a
658 platform with proper d 634 platform with proper driver support. For more
659 information, see Docum 635 information, see Documentation/driver-api/clk.rst.
660 636
661 clock= [BUGS=X86-32, HW] gett 637 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 638 [Deprecated]
663 Forces specified clock 639 Forces specified clocksource (if available) to be used
664 when calculating getti 640 when calculating gettimeofday(). If specified
665 clocksource is not ava 641 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 642 Format: { pit | tsc | cyclone | pmtmr }
667 643
668 clocksource= Override the default c 644 clocksource= Override the default clocksource
669 Format: <string> 645 Format: <string>
670 Override the default c 646 Override the default clocksource and use the clocksource
671 with the name specifie 647 with the name specified.
672 Some clocksource names 648 Some clocksource names to choose from, depending on
673 the platform: 649 the platform:
674 [all] jiffies (this is 650 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 651 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 652 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 653 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 654 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 655 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 656 [MIPS] MIPS
681 [PARISC] cr16 657 [PARISC] cr16
682 [S390] tod 658 [S390] tod
683 [SH] SuperH 659 [SH] SuperH
684 [SPARC64] tick 660 [SPARC64] tick
685 [X86-64] hpet,tsc 661 [X86-64] hpet,tsc
686 662
687 clocksource.arm_arch_timer.evtstrm= 663 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 664 [ARM,ARM64]
689 Format: <bool> 665 Format: <bool>
690 Enable/disable the eve 666 Enable/disable the eventstream feature of the ARM
691 architected timer so t 667 architected timer so that code using WFE-based polling
692 loops can be debugged 668 loops can be debugged more effectively on production
693 systems. 669 systems.
694 670
>> 671 clocksource.max_cswd_read_retries= [KNL]
>> 672 Number of clocksource_watchdog() retries due to
>> 673 external delays before the clock will be marked
>> 674 unstable. Defaults to two retries, that is,
>> 675 three attempts to read the clock under test.
>> 676
695 clocksource.verify_n_cpus= [KNL] 677 clocksource.verify_n_cpus= [KNL]
696 Limit the number of CP 678 Limit the number of CPUs checked for clocksources
697 marked with CLOCK_SOUR 679 marked with CLOCK_SOURCE_VERIFY_PERCPU that
698 are marked unstable du 680 are marked unstable due to excessive skew.
699 A negative value says 681 A negative value says to check all CPUs, while
700 zero says not to check 682 zero says not to check any. Values larger than
701 nr_cpu_ids are silentl 683 nr_cpu_ids are silently truncated to nr_cpu_ids.
702 The actual CPUs are ch 684 The actual CPUs are chosen randomly, with
703 no replacement if the 685 no replacement if the same CPU is chosen twice.
704 686
705 clocksource-wdtest.holdoff= [KNL] 687 clocksource-wdtest.holdoff= [KNL]
706 Set the time in second 688 Set the time in seconds that the clocksource
707 watchdog test waits be 689 watchdog test waits before commencing its tests.
708 Defaults to zero when 690 Defaults to zero when built as a module and to
709 10 seconds when built 691 10 seconds when built into the kernel.
710 692
711 cma=nn[MG]@[start[MG][-end[MG]]] 693 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 694 [KNL,CMA]
713 Sets the size of kerne 695 Sets the size of kernel global memory area for
714 contiguous memory allo 696 contiguous memory allocations and optionally the
715 placement constraint b 697 placement constraint by the physical address range of
716 memory allocations. A 698 memory allocations. A value of 0 disables CMA
717 altogether. For more i 699 altogether. For more information, see
718 kernel/dma/contiguous. 700 kernel/dma/contiguous.c
719 701
720 cma_pernuma=nn[MG] 702 cma_pernuma=nn[MG]
721 [KNL,CMA,EARLY] !! 703 [KNL,CMA]
722 Sets the size of kerne 704 Sets the size of kernel per-numa memory area for
723 contiguous memory allo 705 contiguous memory allocations. A value of 0 disables
724 per-numa CMA altogethe 706 per-numa CMA altogether. And If this option is not
725 specified, the default 707 specified, the default value is 0.
726 With per-numa CMA enab 708 With per-numa CMA enabled, DMA users on node nid will
727 first try to allocate 709 first try to allocate buffer from the pernuma area
728 which is located in no 710 which is located in node nid, if the allocation fails,
729 they will fallback to 711 they will fallback to the global default memory area.
730 712
731 numa_cma=<node>:nn[MG][,<node>:nn[MG]] 713 numa_cma=<node>:nn[MG][,<node>:nn[MG]]
732 [KNL,CMA,EARLY] !! 714 [KNL,CMA]
733 Sets the size of kerne 715 Sets the size of kernel numa memory area for
734 contiguous memory allo 716 contiguous memory allocations. It will reserve CMA
735 area for the specified 717 area for the specified node.
736 718
737 With numa CMA enabled, 719 With numa CMA enabled, DMA users on node nid will
738 first try to allocate 720 first try to allocate buffer from the numa area
739 which is located in no 721 which is located in node nid, if the allocation fails,
740 they will fallback to 722 they will fallback to the global default memory area.
741 723
742 cmo_free_hint= [PPC] Format: { yes | 724 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 725 Specify whether pages are marked as being inactive
744 when they are freed. 726 when they are freed. This is used in CMO environments
745 to determine OS memory 727 to determine OS memory pressure for page stealing by
746 a hypervisor. 728 a hypervisor.
747 Default: yes 729 Default: yes
748 730
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 731 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 732 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 733 allocations, by default set to 256K.
752 734
753 com20020= [HW,NET] ARCnet - COM2 735 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 736 Format:
755 <io>[,<irq>[,<nodeID>[ 737 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 738
757 com90io= [HW,NET] ARCnet - COM9 739 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 740 Format: <io>[,<irq>]
759 741
760 com90xx= [HW,NET] 742 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 743 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 744 Format: <io>[,<irq>[,<memstart>]]
763 745
764 condev= [HW,S390] console devi 746 condev= [HW,S390] console device
765 conmode= 747 conmode=
766 748
767 con3215_drop= [S390,EARLY] 3215 cons !! 749 con3215_drop= [S390] 3215 console drop mode.
768 Format: y|n|Y|N|1|0 750 Format: y|n|Y|N|1|0
769 When set to true, drop 751 When set to true, drop data on the 3215 console when
770 the console buffer is 752 the console buffer is full. In this case the
771 operator using a 3270 753 operator using a 3270 terminal emulator (for example
772 x3270) does not have t 754 x3270) does not have to enter the clear key for the
773 console output to adva 755 console output to advance and the kernel to continue.
774 This leads to a much f 756 This leads to a much faster boot time when a 3270
775 terminal emulator is a 757 terminal emulator is active. If no 3270 terminal
776 emulator is used, this 758 emulator is used, this parameter has no effect.
777 759
778 console= [KNL] Output console d 760 console= [KNL] Output console device and options.
779 761
780 tty<n> Use the virtual consol 762 tty<n> Use the virtual console device <n>.
781 763
782 ttyS<n>[,options] 764 ttyS<n>[,options]
783 ttyUSB0[,options] 765 ttyUSB0[,options]
784 Use the specified seri 766 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 767 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 768 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 769 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 770 omit it). Default is "9600n8".
789 771
790 See Documentation/admi 772 See Documentation/admin-guide/serial-console.rst for more
791 information. See 773 information. See
792 Documentation/networki 774 Documentation/networking/netconsole.rst for an
793 alternative. 775 alternative.
794 776
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] 777 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 778 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 779 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 780 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 781 uart[8250],0x<addr>[,options]
819 Start an early, polled 782 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 783 UART at the specified I/O port or MMIO address,
821 switching to the match 784 switching to the matching ttyS device later.
822 MMIO inter-register ad 785 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 786 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 787 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 788 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 789 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 790 the h/w is not re-initialized.
828 791
829 hvc<n> Use the hypervisor con 792 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 793 both Xen and PowerPC hypervisors.
831 794
832 { null | "" } 795 { null | "" }
833 Use to disable console 796 Use to disable console output, i.e., to have kernel
834 console messages disca 797 console messages discarded.
835 This must be the only 798 This must be the only console= parameter used on the
836 kernel command line. 799 kernel command line.
837 800
838 If the device connected to the 801 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 802 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 803 console=brl,ttyS0
841 For now, only VisioBraille is 804 For now, only VisioBraille is supported.
842 805
843 console_msg_format= 806 console_msg_format=
844 [KNL] Change console m 807 [KNL] Change console messages format
845 default 808 default
846 By default we print me 809 By default we print messages on consoles in
847 "[time stamp] text\n" 810 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 811 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 812 `printk_time' param).
850 syslog 813 syslog
851 Switch to syslog forma 814 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 815 IOW, each message will have a facility and loglevel
853 prefix. The format is 816 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 817 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 818 from /proc/kmsg.
856 819
857 consoleblank= [KNL] The console blan 820 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 821 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 822 Defaults to 0.
860 823
861 coredump_filter= 824 coredump_filter=
862 [KNL] Change the defau 825 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 826 /proc/<pid>/coredump_filter.
864 See also Documentation 827 See also Documentation/filesystems/proc.rst.
865 828
866 coresight_cpu_debug.enable 829 coresight_cpu_debug.enable
867 [ARM,ARM64] 830 [ARM,ARM64]
868 Format: <bool> 831 Format: <bool>
869 Enable/disable the CPU 832 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 833 0: default value, disable debugging
871 1: enable debugging at 834 1: enable debugging at boot time
872 835
873 cpcihp_generic= [HW,PCI] Generic port 836 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
874 Format: 837 Format:
875 <first_slot>,<last_slo 838 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
876 839
877 cpuidle.off=1 [CPU_IDLE] 840 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 841 disable the cpuidle sub-system
879 842
880 cpuidle.governor= 843 cpuidle.governor=
881 [CPU_IDLE] Name of the 844 [CPU_IDLE] Name of the cpuidle governor to use.
882 845
883 cpufreq.off=1 [CPU_FREQ] 846 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 847 disable the cpufreq sub-system
885 848
886 cpufreq.default_governor= 849 cpufreq.default_governor=
887 [CPU_FREQ] Name of the 850 [CPU_FREQ] Name of the default cpufreq governor or
888 policy to use. This go 851 policy to use. This governor must be registered in the
889 kernel before the cpuf 852 kernel before the cpufreq driver probes.
890 853
891 cpu_init_udelay=N 854 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 855 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 856 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 857 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 858 Default: 10000
896 859
897 cpuhp.parallel= 860 cpuhp.parallel=
898 [SMP] Enable/disable p 861 [SMP] Enable/disable parallel bringup of secondary CPUs
899 Format: <bool> 862 Format: <bool>
900 Default is enabled if 863 Default is enabled if CONFIG_HOTPLUG_PARALLEL=y. Otherwise
901 the parameter has no e 864 the parameter has no effect.
902 865
903 crash_kexec_post_notifiers 866 crash_kexec_post_notifiers
904 Run kdump after runnin 867 Run kdump after running panic-notifiers and dumping
905 kmsg. This only for th 868 kmsg. This only for the users who doubt kdump always
906 succeeds in any situat 869 succeeds in any situation.
907 Note that this also in 870 Note that this also increases risks of kdump failure,
908 because some panic not 871 because some panic notifiers can make the crashed
909 kernel more unstable. 872 kernel more unstable.
910 873
911 crashkernel=size[KMG][@offset[KMG]] 874 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 875 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 876 upon panic. This parameter reserves the physical
914 memory region [offset, 877 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 878 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 879 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 880 [KNL, X86-64, ARM64, RISCV] Select a region under 4G first, and
918 under 4G first, and fa !! 881 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 882 hasn't been specified.
920 See Documentation/admi 883 See Documentation/admin-guide/kdump/kdump.rst for further details.
921 884
922 crashkernel=range1:size1[,range2:size2 885 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 886 [KNL] Same as above, but depends on the memory
924 in the running system. 887 in the running system. The syntax of range is
925 start-[end] where star 888 start-[end] where start and end are both
926 a memory unit (amount[ 889 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu 890 Documentation/admin-guide/kdump/kdump.rst for an example.
928 891
929 crashkernel=size[KMG],high 892 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 893 [KNL, X86-64, ARM64, RISCV] range could be above 4G.
931 above 4G. <<
932 Allow kernel to alloca 894 Allow kernel to allocate physical memory region from top,
933 so could be above 4G i 895 so could be above 4G if system have more than 4G ram
934 installed. Otherwise m 896 installed. Otherwise memory region will be allocated
935 below 4G, if available 897 below 4G, if available.
936 It will be ignored if 898 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 899 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 900 [KNL, X86-64, ARM64, RISCV] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 901 is passed, kernel could allocate physical memory region
940 physical memory region !! 902 above 4G, that cause second kernel crash on system
941 crash on system that r !! 903 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 904 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 905 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 906 devices won't run out. Kernel would try to allocate
945 default size of memory 907 default size of memory below 4G automatically. The default
946 size is platform depen 908 size is platform dependent.
947 --> x86: max(swiotlb 909 --> x86: max(swiotlb_size_or_default() + 8MiB, 256MiB)
948 --> arm64: 128MiB 910 --> arm64: 128MiB
949 --> riscv: 128MiB 911 --> riscv: 128MiB
950 --> loongarch: 128Mi <<
951 This one lets the user 912 This one lets the user specify own low range under 4G
952 for second kernel inst 913 for second kernel instead.
953 0: to disable low allo 914 0: to disable low allocation.
954 It will be ignored whe 915 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 916 or memory reserved is below 4G.
956 917
957 cryptomgr.notests 918 cryptomgr.notests
958 [KNL] Disable crypto s 919 [KNL] Disable crypto self-tests
959 920
960 cs89x0_dma= [HW,NET] 921 cs89x0_dma= [HW,NET]
961 Format: <dma> 922 Format: <dma>
962 923
963 cs89x0_media= [HW,NET] 924 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 925 Format: { rj45 | aui | bnc }
965 926
966 csdlock_debug= [KNL] Enable or disabl 927 csdlock_debug= [KNL] Enable or disable debug add-ons of cross-CPU
967 function call handling 928 function call handling. When switched on,
968 additional debug data 929 additional debug data is printed to the console
969 in case a hanging CPU 930 in case a hanging CPU is detected, and that
970 CPU is pinged again in 931 CPU is pinged again in order to try to resolve
971 the hang situation. T 932 the hang situation. The default value of this
972 option depends on the 933 option depends on the CSD_LOCK_WAIT_DEBUG_DEFAULT
973 Kconfig option. 934 Kconfig option.
974 935
975 dasd= [HW,NET] 936 dasd= [HW,NET]
976 See header of drivers/ 937 See header of drivers/s390/block/dasd_devmap.c.
977 938
978 db9.dev[2|3]= [HW,JOY] Multisystem j 939 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 940 (one device per port)
980 Format: <port#>,<type> 941 Format: <port#>,<type>
981 See also Documentation 942 See also Documentation/input/devices/joystick-parport.rst
982 943
983 debug [KNL,EARLY] Enable ker !! 944 debug [KNL] Enable kernel debugging (events log level).
984 945
985 debug_boot_weak_hash 946 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 947 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 948 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 949 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 950 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 951 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 952 insecure, please do not use on production kernels.
992 953
993 debug_locks_verbose= 954 debug_locks_verbose=
994 [KNL] verbose locking 955 [KNL] verbose locking self-tests
995 Format: <int> 956 Format: <int>
996 Print debugging info w 957 Print debugging info while doing the locking API
997 self-tests. 958 self-tests.
998 Bitmask for the variou 959 Bitmask for the various LOCKTYPE_ tests. Defaults to 0
999 (no extra messages), s 960 (no extra messages), setting it to -1 (all bits set)
1000 will print _a_lot_ mo 961 will print _a_lot_ more information - normally only
1001 useful to lockdep dev 962 useful to lockdep developers.
1002 963
1003 debug_objects [KNL,EARLY] Enable ob !! 964 debug_objects [KNL] Enable object debugging
1004 965
1005 debug_guardpage_minorder= 966 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 967 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 968 parameter allows control of the order of pages that will
1008 be intentionally kept 969 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 970 buddy allocator. Bigger value increase the probability
1010 of catching random me 971 of catching random memory corruption, but reduce the
1011 amount of memory for 972 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 973 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 974 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 975 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 976 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 977 random memory location. Note that there exists a class
1017 a class of memory cor !! 978 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 979 F/W or by drivers badly programming DMA (basically when
1019 (basically when memor !! 980 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 981 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 982 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 983 tracking down these problems.
1023 984
1024 debug_pagealloc= 985 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 986 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this parameter
1026 enables the feature a 987 enables the feature at boot time. By default, it is
1027 disabled and the syst 988 disabled and the system will work mostly the same as a
1028 kernel built without 989 kernel built without CONFIG_DEBUG_PAGEALLOC.
1029 Note: to get most of 990 Note: to get most of debug_pagealloc error reports, it's
1030 useful to also enable 991 useful to also enable the page_owner functionality.
1031 on: enable the featur 992 on: enable the feature
1032 993
1033 debugfs= [KNL,EARLY] This para !! 994 debugfs= [KNL] This parameter enables what is exposed to userspace
1034 userspace and debugfs !! 995 and debugfs internal clients.
1035 Format: { on, no-moun 996 Format: { on, no-mount, off }
1036 on: All functions 997 on: All functions are enabled.
1037 no-mount: 998 no-mount:
1038 Filesystem is 999 Filesystem is not registered but kernel clients can
1039 access APIs a 1000 access APIs and a crashkernel can be used to read
1040 its content. 1001 its content. There is nothing to mount.
1041 off: Filesystem is 1002 off: Filesystem is not registered and clients
1042 get a -EPERM 1003 get a -EPERM as result when trying to register files
1043 or directorie 1004 or directories within debugfs.
1044 This is equiv 1005 This is equivalent of the runtime functionality if
1045 debugfs was n 1006 debugfs was not enabled in the kernel at all.
1046 Default value is set 1007 Default value is set in build-time with a kernel configuration.
1047 1008
1048 debugpat [X86] Enable PAT debu 1009 debugpat [X86] Enable PAT debugging
1049 1010
1050 default_hugepagesz= 1011 default_hugepagesz=
1051 [HW] The size of the 1012 [HW] The size of the default HugeTLB page. This is
1052 the size represented 1013 the size represented by the legacy /proc/ hugepages
1053 APIs. In addition, t 1014 APIs. In addition, this is the default hugetlb size
1054 used for shmget(), mm 1015 used for shmget(), mmap() and mounting hugetlbfs
1055 filesystems. If not 1016 filesystems. If not specified, defaults to the
1056 architecture's defaul 1017 architecture's default huge page size. Huge page
1057 sizes are architectur 1018 sizes are architecture dependent. See also
1058 Documentation/admin-g 1019 Documentation/admin-guide/mm/hugetlbpage.rst.
1059 Format: size[KMG] 1020 Format: size[KMG]
1060 1021
1061 deferred_probe_timeout= 1022 deferred_probe_timeout=
1062 [KNL] Debugging optio 1023 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 1024 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 1025 probe. Only specific dependencies (subsystems or
1065 drivers) that have op 1026 drivers) that have opted in will be ignored. A timeout
1066 of 0 will timeout at 1027 of 0 will timeout at the end of initcalls. If the time
1067 out hasn't expired, i 1028 out hasn't expired, it'll be restarted by each
1068 successful driver reg 1029 successful driver registration. This option will also
1069 dump out devices stil 1030 dump out devices still on the deferred probe list after
1070 retrying. 1031 retrying.
1071 1032
1072 delayacct [KNL] Enable per-task 1033 delayacct [KNL] Enable per-task delay accounting
1073 1034
1074 dell_smm_hwmon.ignore_dmi= 1035 dell_smm_hwmon.ignore_dmi=
1075 [HW] Continue probing 1036 [HW] Continue probing hardware even if DMI data
1076 indicates that the dr 1037 indicates that the driver is running on unsupported
1077 hardware. 1038 hardware.
1078 1039
1079 dell_smm_hwmon.force= 1040 dell_smm_hwmon.force=
1080 [HW] Activate driver 1041 [HW] Activate driver even if SMM BIOS signature does
1081 not match list of sup 1042 not match list of supported models and enable otherwise
1082 blacklisted features. 1043 blacklisted features.
1083 1044
1084 dell_smm_hwmon.power_status= 1045 dell_smm_hwmon.power_status=
1085 [HW] Report power sta 1046 [HW] Report power status in /proc/i8k
1086 (disabled by default) 1047 (disabled by default).
1087 1048
1088 dell_smm_hwmon.restricted= 1049 dell_smm_hwmon.restricted=
1089 [HW] Allow controllin 1050 [HW] Allow controlling fans only if SYS_ADMIN
1090 capability is set. 1051 capability is set.
1091 1052
1092 dell_smm_hwmon.fan_mult= 1053 dell_smm_hwmon.fan_mult=
1093 [HW] Factor to multip 1054 [HW] Factor to multiply fan speed with.
1094 1055
1095 dell_smm_hwmon.fan_max= 1056 dell_smm_hwmon.fan_max=
1096 [HW] Maximum configur 1057 [HW] Maximum configurable fan speed.
1097 1058
1098 dfltcc= [HW,S390] 1059 dfltcc= [HW,S390]
1099 Format: { on | off | 1060 Format: { on | off | def_only | inf_only | always }
1100 on: s390 zlib h 1061 on: s390 zlib hardware support for compression on
1101 level 1 and 1062 level 1 and decompression (default)
1102 off: No s390 zli 1063 off: No s390 zlib hardware support
1103 def_only: s390 zlib h 1064 def_only: s390 zlib hardware support for deflate
1104 only (compr 1065 only (compression on level 1)
1105 inf_only: s390 zlib h 1066 inf_only: s390 zlib hardware support for inflate
1106 only (decom 1067 only (decompression)
1107 always: Same as 'on 1068 always: Same as 'on' but ignores the selected compression
1108 level alway 1069 level always using hardware support (used for debugging)
1109 1070
1110 dhash_entries= [KNL] 1071 dhash_entries= [KNL]
1111 Set number of hash bu 1072 Set number of hash buckets for dentry cache.
1112 1073
1113 disable_1tb_segments [PPC,EARLY] !! 1074 disable_1tb_segments [PPC]
1114 Disables the use of 1 1075 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 1076 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 1077 can be useful when debugging issues that require an SLB
1117 miss to occur. 1078 miss to occur.
1118 1079
1119 disable= [IPV6] 1080 disable= [IPV6]
1120 See Documentation/net 1081 See Documentation/networking/ipv6.rst.
1121 1082
1122 disable_radix [PPC,EARLY] !! 1083 disable_radix [PPC]
1123 Disable RADIX MMU mod 1084 Disable RADIX MMU mode on POWER9
1124 1085
1125 disable_tlbie [PPC] 1086 disable_tlbie [PPC]
1126 Disable TLBIE instruc 1087 Disable TLBIE instruction. Currently does not work
1127 with KVM, with HASH M 1088 with KVM, with HASH MMU, or with coherent accelerators.
1128 1089
1129 disable_ddw [PPC/PSERIES,EARLY] !! 1090 disable_cpu_apicid= [X86,APIC,SMP]
>> 1091 Format: <int>
>> 1092 The number of initial APIC ID for the
>> 1093 corresponding CPU to be disabled at boot,
>> 1094 mostly used for the kdump 2nd kernel to
>> 1095 disable BSP to wake up multiple CPUs without
>> 1096 causing system reset or hang due to sending
>> 1097 INIT from AP to BSP.
>> 1098
>> 1099 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W 1100 Disable Dynamic DMA Window support. Use this
1131 to workaround buggy f 1101 to workaround buggy firmware.
1132 1102
1133 disable_ipv6= [IPV6] 1103 disable_ipv6= [IPV6]
1134 See Documentation/net 1104 See Documentation/networking/ipv6.rst.
1135 1105
1136 disable_mtrr_cleanup [X86,EARLY] !! 1106 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 1107 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 1108 to discrete, to make X server driver able to add WB
1139 entry later. This par 1109 entry later. This parameter disables that.
1140 1110
1141 disable_mtrr_trim [X86, Intel and AMD !! 1111 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 1112 By default the kernel will trim any uncacheable
1143 memory out of your av 1113 memory out of your available memory pool based on
1144 MTRR settings. This 1114 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 1115 possibly causing your machine to run very slowly.
1146 1116
1147 disable_timer_pin_1 [X86,EARLY] !! 1117 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 1118 Disable PIN 1 of APIC timer
1149 Can be useful to work 1119 Can be useful to work around chipset bugs.
1150 1120
1151 dis_ucode_ldr [X86] Disable the mic 1121 dis_ucode_ldr [X86] Disable the microcode loader.
1152 1122
1153 dma_debug=off If the kernel is comp 1123 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 1124 this option disables the debugging code at boot.
1155 1125
1156 dma_debug_entries=<number> 1126 dma_debug_entries=<number>
1157 This option allows to 1127 This option allows to tune the number of preallocated
1158 entries for DMA-API d 1128 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 1129 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 1130 DMA-API debugging code disables itself because the
1161 architectural default 1131 architectural default is too low.
1162 1132
1163 dma_debug_driver=<driver_name> 1133 dma_debug_driver=<driver_name>
1164 With this option the 1134 With this option the DMA-API debugging driver
1165 filter feature can be 1135 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 1136 pass the driver to filter for as the parameter.
1167 The filter can be dis 1137 The filter can be disabled or changed to another
1168 driver later using sy 1138 driver later using sysfs.
1169 1139
1170 reg_file_data_sampling= 1140 reg_file_data_sampling=
1171 [X86] Controls mitiga 1141 [X86] Controls mitigation for Register File Data
1172 Sampling (RFDS) vulne 1142 Sampling (RFDS) vulnerability. RFDS is a CPU
1173 vulnerability which m 1143 vulnerability which may allow userspace to infer
1174 kernel data values pr 1144 kernel data values previously stored in floating point
1175 registers, vector reg 1145 registers, vector registers, or integer registers.
1176 RFDS only affects Int 1146 RFDS only affects Intel Atom processors.
1177 1147
1178 on: Turns ON the 1148 on: Turns ON the mitigation.
1179 off: Turns OFF the 1149 off: Turns OFF the mitigation.
1180 1150
1181 This parameter overri 1151 This parameter overrides the compile time default set
1182 by CONFIG_MITIGATION_ 1152 by CONFIG_MITIGATION_RFDS. Mitigation cannot be
1183 disabled when other V 1153 disabled when other VERW based mitigations (like MDS)
1184 are enabled. In order 1154 are enabled. In order to disable RFDS mitigation all
1185 VERW based mitigation 1155 VERW based mitigations need to be disabled.
1186 1156
1187 For details see: 1157 For details see:
1188 Documentation/admin-g 1158 Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst
1189 1159
1190 driver_async_probe= [KNL] 1160 driver_async_probe= [KNL]
1191 List of driver names 1161 List of driver names to be probed asynchronously. *
1192 matches with all driv 1162 matches with all driver names. If * is specified, the
1193 rest of the listed dr 1163 rest of the listed driver names are those that will NOT
1194 match the *. 1164 match the *.
1195 Format: <driver_name1 1165 Format: <driver_name1>,<driver_name2>...
1196 1166
1197 drm.edid_firmware=[<connector>:]<file 1167 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 1168 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 1169 panels may send no or incorrect EDID data sets.
1200 This parameter allows 1170 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 1171 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 1172 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 1173 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 1174 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 1175 and no file with the same name exists. Details and
>> 1176 instructions how to build your own EDID data are
>> 1177 available in Documentation/admin-guide/edid.rst. An EDID
>> 1178 data set will only be used for a particular connector,
>> 1179 if its name and a colon are prepended to the EDID
>> 1180 name. Each connector may use a unique EDID data
>> 1181 set by separating the files with a comma. An EDID
1206 data set with no conn 1182 data set with no connector name will be used for
1207 any connectors not ex 1183 any connectors not explicitly specified.
1208 1184
1209 dscc4.setup= [NET] 1185 dscc4.setup= [NET]
1210 1186
1211 dt_cpu_ftrs= [PPC,EARLY] !! 1187 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 1188 Format: {"off" | "known"}
1213 Control how the dt_cp 1189 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 1190 used for CPU feature discovery and setup (if it
1215 exists). 1191 exists).
1216 off: Do not use it, f 1192 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 1193 known: Do not pass through unknown features to guests
1218 or userspace, only th 1194 or userspace, only those that the kernel is aware of.
1219 1195
1220 dump_apple_properties [X86] 1196 dump_apple_properties [X86]
1221 Dump name and content 1197 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 1198 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 1199 what data is available or for reverse-engineering.
1224 1200
1225 dyndbg[="val"] [KNL,DYNAMIC_ 1201 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] 1202 <module>.dyndbg[="val"]
1227 Enable debug messages 1203 Enable debug messages at boot time. See
1228 Documentation/admin-g 1204 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 1205 for details.
1230 1206
1231 early_ioremap_debug [KNL,EARLY] !! 1207 early_ioremap_debug [KNL]
1232 Enable debug messages 1208 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 1209 is useful for tracking down temporary early mappings
1234 which are not unmappe 1210 which are not unmapped.
1235 1211
1236 earlycon= [KNL,EARLY] Output ea !! 1212 earlycon= [KNL] Output early console device and options.
1237 1213
1238 When used with no opt 1214 When used with no options, the early console is
1239 determined by stdout- 1215 determined by stdout-path property in device tree's
1240 chosen node or the AC 1216 chosen node or the ACPI SPCR table if supported by
1241 the platform. 1217 the platform.
1242 1218
1243 cdns,<addr>[,options] 1219 cdns,<addr>[,options]
1244 Start an early, polle 1220 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 1221 (xuartps) serial port at the specified address. Only
1246 supported option is b 1222 supported option is baud rate. If baud rate is not
1247 specified, the serial 1223 specified, the serial port must already be setup and
1248 configured. 1224 configured.
1249 1225
1250 uart[8250],io,<addr>[,options 1226 uart[8250],io,<addr>[,options[,uartclk]]
1251 uart[8250],mmio,<addr>[,optio 1227 uart[8250],mmio,<addr>[,options[,uartclk]]
1252 uart[8250],mmio32,<addr>[,opt 1228 uart[8250],mmio32,<addr>[,options[,uartclk]]
1253 uart[8250],mmio32be,<addr>[,o 1229 uart[8250],mmio32be,<addr>[,options[,uartclk]]
1254 uart[8250],0x<addr>[,options] 1230 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1231 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1232 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1233 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1234 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1235 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1236 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1237 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w 1238 unspecified, the h/w is not initialized. 'uartclk' is
1263 the uart clock freque 1239 the uart clock frequency; if unspecified, it is set
1264 to 'BASE_BAUD' * 16. 1240 to 'BASE_BAUD' * 16.
1265 1241
1266 pl011,<addr> 1242 pl011,<addr>
1267 pl011,mmio32,<addr> 1243 pl011,mmio32,<addr>
1268 Start an early, polle 1244 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1245 port at the specified address. The pl011 serial port
1270 must already be setup 1246 must already be setup and configured. Options are not
1271 yet supported. If 'm 1247 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1248 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1249 the device registers.
1274 1250
1275 liteuart,<addr> 1251 liteuart,<addr>
1276 Start an early consol 1252 Start an early console on a litex serial port at the
1277 specified address. Th 1253 specified address. The serial port must already be
1278 setup and configured. 1254 setup and configured. Options are not yet supported.
1279 1255
1280 meson,<addr> 1256 meson,<addr>
1281 Start an early, polle 1257 Start an early, polled-mode console on a meson serial
1282 port at the specified 1258 port at the specified address. The serial port must
1283 already be setup and 1259 already be setup and configured. Options are not yet
1284 supported. 1260 supported.
1285 1261
1286 msm_serial,<addr> 1262 msm_serial,<addr>
1287 Start an early, polle 1263 Start an early, polled-mode console on an msm serial
1288 port at the specified 1264 port at the specified address. The serial port
1289 must already be setup 1265 must already be setup and configured. Options are not
1290 yet supported. 1266 yet supported.
1291 1267
1292 msm_serial_dm,<addr> 1268 msm_serial_dm,<addr>
1293 Start an early, polle 1269 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1270 dm port at the specified address. The serial port
1295 must already be setup 1271 must already be setup and configured. Options are not
1296 yet supported. 1272 yet supported.
1297 1273
1298 owl,<addr> 1274 owl,<addr>
1299 Start an early, polle 1275 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1276 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1277 specified address. The serial port must already be
1302 setup and configured. 1278 setup and configured. Options are not yet supported.
1303 1279
1304 rda,<addr> 1280 rda,<addr>
1305 Start an early, polle 1281 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1282 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1283 specified address. The serial port must already be
1308 setup and configured. 1284 setup and configured. Options are not yet supported.
1309 1285
1310 sbi 1286 sbi
1311 Use RISC-V SBI (Super 1287 Use RISC-V SBI (Supervisor Binary Interface) for early
1312 console. 1288 console.
1313 1289
1314 smh Use ARM semihosting c 1290 smh Use ARM semihosting calls for early console.
1315 1291
1316 s3c2410,<addr> 1292 s3c2410,<addr>
1317 s3c2412,<addr> 1293 s3c2412,<addr>
1318 s3c2440,<addr> 1294 s3c2440,<addr>
1319 s3c6400,<addr> 1295 s3c6400,<addr>
1320 s5pv210,<addr> 1296 s5pv210,<addr>
1321 exynos4210,<addr> 1297 exynos4210,<addr>
1322 Use early console pro 1298 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1299 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1300 a correct base address of the selected UART port. The
1325 serial port must alre 1301 serial port must already be setup and configured.
1326 Options are not yet s 1302 Options are not yet supported.
1327 1303
1328 lantiq,<addr> 1304 lantiq,<addr>
1329 Start an early, polle 1305 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1306 (lqasc) port at the specified address. The serial port
1331 must already be setup 1307 must already be setup and configured. Options are not
1332 yet supported. 1308 yet supported.
1333 1309
1334 lpuart,<addr> 1310 lpuart,<addr>
1335 lpuart32,<addr> 1311 lpuart32,<addr>
1336 Use early console pro 1312 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1313 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1314 A valid base address must be provided, and the serial
1339 port must already be 1315 port must already be setup and configured.
1340 1316
1341 ec_imx21,<addr> 1317 ec_imx21,<addr>
1342 ec_imx6q,<addr> 1318 ec_imx6q,<addr>
1343 Start an early, polle 1319 Start an early, polled-mode, output-only console on the
1344 Freescale i.MX UART a 1320 Freescale i.MX UART at the specified address. The UART
1345 must already be setup 1321 must already be setup and configured.
1346 1322
1347 ar3700_uart,<addr> 1323 ar3700_uart,<addr>
1348 Start an early, polle 1324 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1325 Armada 3700 serial port at the specified
1350 address. The serial p 1326 address. The serial port must already be setup
1351 and configured. Optio 1327 and configured. Options are not yet supported.
1352 1328
1353 qcom_geni,<addr> 1329 qcom_geni,<addr>
1354 Start an early, polle 1330 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1331 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1332 specified address. The serial port must already be
1357 setup and configured. 1333 setup and configured. Options are not yet supported.
1358 1334
1359 efifb,[options] 1335 efifb,[options]
1360 Start an early, unacc 1336 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1337 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1338 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1339 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1340 mapped with the correct attributes.
1365 1341
1366 linflex,<addr> 1342 linflex,<addr>
1367 Use early console pro 1343 Use early console provided by Freescale LINFlexD UART
1368 serial driver for NXP 1344 serial driver for NXP S32V234 SoCs. A valid base
1369 address must be provi 1345 address must be provided, and the serial port must
1370 already be setup and 1346 already be setup and configured.
1371 1347
1372 earlyprintk= [X86,SH,ARM,M68k,S390 !! 1348 earlyprintk= [X86,SH,ARM,M68k,S390]
1373 earlyprintk=vga 1349 earlyprintk=vga
1374 earlyprintk=sclp 1350 earlyprintk=sclp
1375 earlyprintk=xen 1351 earlyprintk=xen
1376 earlyprintk=serial[,t 1352 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1353 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1354 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1355 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1356 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1357 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios 1358 earlyprintk=bios
1383 1359
1384 earlyprintk is useful 1360 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1361 the normal console is initialized. It is not enabled by
1386 default because it ha 1362 default because it has some cosmetic problems.
1387 1363
1388 Append ",keep" to not 1364 Append ",keep" to not disable it when the real console
1389 takes over. 1365 takes over.
1390 1366
1391 Only one of vga, seri 1367 Only one of vga, serial, or usb debug port can
1392 be used at a time. 1368 be used at a time.
1393 1369
1394 Currently only ttyS0 1370 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1371 name. Other I/O ports may be explicitly specified
1396 on some architectures 1372 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1373 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1374 earlyprintk=serial,0x1008,115200
1399 You can find the port 1375 You can find the port for a given device in
1400 /proc/tty/driver/seri 1376 /proc/tty/driver/serial:
1401 2: uart:ST166 1377 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1378
1403 Interaction with the 1379 Interaction with the standard serial driver is not
1404 very good. 1380 very good.
1405 1381
1406 The VGA output is eve 1382 The VGA output is eventually overwritten by
1407 the real console. 1383 the real console.
1408 1384
1409 The xen option can on 1385 The xen option can only be used in Xen domains.
1410 1386
1411 The sclp output can o 1387 The sclp output can only be used on s390.
1412 1388
1413 The bios output can o 1389 The bios output can only be used on SuperH.
1414 1390
1415 The optional "force" 1391 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1392 PCI device even when its classcode is not of the
1417 UART class. 1393 UART class.
1418 1394
1419 edac_report= [HW,EDAC] Control how 1395 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1396 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1397 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1398 by other higher priority error reporting module.
1423 off: disable H/W even 1399 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1400 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1401 default: on.
1426 1402
1427 edd= [EDD] 1403 edd= [EDD]
1428 Format: {"off" | "on" 1404 Format: {"off" | "on" | "skip[mbr]"}
1429 1405
1430 efi= [EFI,EARLY] !! 1406 efi= [EFI]
1431 Format: { "debug", "d 1407 Format: { "debug", "disable_early_pci_dma",
1432 "nochunk", 1408 "nochunk", "noruntime", "nosoftreserve",
1433 "novamap", 1409 "novamap", "no_disable_early_pci_dma" }
1434 debug: enable misc de 1410 debug: enable misc debug output.
1435 disable_early_pci_dma 1411 disable_early_pci_dma: disable the busmaster bit on all
1436 PCI bridges while in 1412 PCI bridges while in the EFI boot stub.
1437 nochunk: disable read 1413 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1414 boot stub, as chunking can cause problems with some
1439 firmware implementati 1415 firmware implementations.
1440 noruntime : disable E 1416 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF 1417 nosoftreserve: The EFI_MEMORY_SP (Specific Purpose)
1442 attribute may cause t 1418 attribute may cause the kernel to reserve the
1443 memory range for a me 1419 memory range for a memory mapping driver to
1444 claim. Specify efi=no 1420 claim. Specify efi=nosoftreserve to disable this
1445 reservation and treat 1421 reservation and treat the memory by its base type
1446 (i.e. EFI_CONVENTIONA 1422 (i.e. EFI_CONVENTIONAL_MEMORY / "System RAM").
1447 novamap: do not call 1423 novamap: do not call SetVirtualAddressMap().
1448 no_disable_early_pci_ 1424 no_disable_early_pci_dma: Leave the busmaster bit set
1449 on all PCI bridges wh 1425 on all PCI bridges while in the EFI boot stub
1450 1426
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1427 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1428 Using this parameter you can use more than 50% of
1453 your efi variable sto 1429 your efi variable storage. Use this parameter only if
1454 you are really sure t 1430 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1431 fulfills the spec otherwise your board may brick.
1456 1432
>> 1433 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1434 Add arbitrary attribute to specific memory range by
>> 1435 updating original EFI memory map.
>> 1436 Region of memory which aa attribute is added to is
>> 1437 from ss to ss+nn.
>> 1438
>> 1439 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1440 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1441 attribute is added to range 0x100000000-0x180000000 and
>> 1442 0x10a0000000-0x1120000000.
>> 1443
>> 1444 If efi_fake_mem=8G@9G:0x40000 is specified, the
>> 1445 EFI_MEMORY_SP(0x40000) attribute is added to
>> 1446 range 0x240000000-0x43fffffff.
>> 1447
>> 1448 Using this parameter you can do debugging of EFI memmap
>> 1449 related features. For example, you can do debugging of
>> 1450 Address Range Mirroring feature even if your box
>> 1451 doesn't support it, or mark specific memory as
>> 1452 "soft reserved".
>> 1453
1457 efivar_ssdt= [EFI; X86] Name of an 1454 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1455 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1456 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1457 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g 1458 Documentation/admin-guide/acpi/ssdt-overlays.rst for details.
1462 1459
1463 1460
1464 eisa_irq_edge= [PARISC,HW] 1461 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1462 See header of drivers/parisc/eisa.c.
1466 1463
1467 ekgdboc= [X86,KGDB,EARLY] Allo !! 1464 ekgdboc= [X86,KGDB] Allow early kernel console debugging
1468 Format: ekgdboc=kbd 1465 Format: ekgdboc=kbd
1469 1466
1470 This is designed to b 1467 This is designed to be used in conjunction with
1471 the boot argument: ea 1468 the boot argument: earlyprintk=vga
1472 1469
1473 This parameter works 1470 This parameter works in place of the kgdboc parameter
1474 but can only be used 1471 but can only be used if the backing tty is available
1475 very early in the boo 1472 very early in the boot process. For early debugging
1476 via a serial port see 1473 via a serial port see kgdboc_earlycon instead.
1477 1474
1478 elanfreq= [X86-32] 1475 elanfreq= [X86-32]
1479 See comment before fu 1476 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1477 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1478
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1479 elfcorehdr=[size[KMG]@]offset[KMG] [PPC,SH,X86,S390]
1483 Specifies physical ad 1480 Specifies physical address of start of kernel core
1484 image elf header and 1481 image elf header and optionally the size. Generally
1485 kexec loader will pas 1482 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm 1483 See Documentation/admin-guide/kdump/kdump.rst for details.
1487 1484
1488 enable_mtrr_cleanup [X86,EARLY] !! 1485 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1486 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1487 to discrete, to make X server driver able to add WB
1491 entry later. This par 1488 entry later. This parameter enables that.
1492 1489
1493 enable_timer_pin_1 [X86] 1490 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1491 Enable PIN 1 of APIC timer
1495 Can be useful to work 1492 Can be useful to work around chipset bugs
1496 (in particular on som 1493 (in particular on some ATI chipsets).
1497 The kernel tries to s 1494 The kernel tries to set a reasonable default.
1498 1495
1499 enforcing= [SELINUX] Set initial 1496 enforcing= [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1497 Format: {"0" | "1"}
1501 See security/selinux/ 1498 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1499 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1500 1 -- enforcing (deny and log).
1504 Default value is 0. 1501 Default value is 0.
1505 Value can be changed 1502 Value can be changed at runtime via
1506 /sys/fs/selinux/enfor 1503 /sys/fs/selinux/enforce.
1507 1504
1508 erst_disable [ACPI] 1505 erst_disable [ACPI]
1509 Disable Error Record 1506 Disable Error Record Serialization Table (ERST)
1510 support. 1507 support.
1511 1508
1512 ether= [HW,NET] Ethernet car 1509 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1510 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1511 has equivalent usage. See its documentation for details.
1515 1512
1516 evm= [EVM] 1513 evm= [EVM]
1517 Format: { "fix" } 1514 Format: { "fix" }
1518 Permit 'security.evm' 1515 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1516 current integrity status.
1520 1517
1521 early_page_ext [KNL,EARLY] Enforces p !! 1518 early_page_ext [KNL] Enforces page_ext initialization to earlier
1522 stages so cover more 1519 stages so cover more early boot allocations.
1523 Please note that as s 1520 Please note that as side effect some optimizations
1524 might be disabled to 1521 might be disabled to achieve that (e.g. parallelized
1525 memory initialization 1522 memory initialization is disabled) so the boot process
1526 might take longer, es 1523 might take longer, especially on systems with a lot of
1527 memory. Available wit 1524 memory. Available with CONFIG_PAGE_EXTENSION=y.
1528 1525
1529 failslab= 1526 failslab=
1530 fail_usercopy= 1527 fail_usercopy=
1531 fail_page_alloc= 1528 fail_page_alloc=
1532 fail_make_request=[KNL] 1529 fail_make_request=[KNL]
1533 General fault injecti 1530 General fault injection mechanism.
1534 Format: <interval>,<p 1531 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1532 See also Documentation/fault-injection/.
1536 1533
1537 fb_tunnels= [NET] 1534 fb_tunnels= [NET]
1538 Format: { initns | no 1535 Format: { initns | none }
1539 See Documentation/adm 1536 See Documentation/admin-guide/sysctl/net.rst for
1540 fb_tunnels_only_for_i 1537 fb_tunnels_only_for_init_ns
1541 1538
1542 floppy= [HW] 1539 floppy= [HW]
1543 See Documentation/adm 1540 See Documentation/admin-guide/blockdev/floppy.rst.
1544 1541
1545 forcepae [X86-32] 1542 forcepae [X86-32]
1546 Forcefully enable Phy 1543 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1544 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1545 functionally usable PAE implementation.
1549 Warning: use of this 1546 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1547 and may cause unknown problems.
1551 1548
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] 1549 ftrace=[tracer]
1559 [FTRACE] will set and 1550 [FTRACE] will set and start the specified tracer
1560 as early as possible 1551 as early as possible in order to facilitate early
1561 boot debugging. 1552 boot debugging.
1562 1553
1563 ftrace_boot_snapshot 1554 ftrace_boot_snapshot
1564 [FTRACE] On boot up, 1555 [FTRACE] On boot up, a snapshot will be taken of the
1565 ftrace ring buffer th 1556 ftrace ring buffer that can be read at:
1566 /sys/kernel/tracing/s 1557 /sys/kernel/tracing/snapshot.
1567 This is useful if you 1558 This is useful if you need tracing information from kernel
1568 boot up that is likel 1559 boot up that is likely to be overridden by user space
1569 start up functionalit 1560 start up functionality.
1570 1561
1571 Optionally, the snaps 1562 Optionally, the snapshot can also be defined for a tracing
1572 instance that was cre 1563 instance that was created by the trace_instance= command
1573 line parameter. 1564 line parameter.
1574 1565
1575 trace_instance=foo,sc 1566 trace_instance=foo,sched_switch ftrace_boot_snapshot=foo
1576 1567
1577 The above will cause 1568 The above will cause the "foo" tracing instance to trigger
1578 a snapshot at the end 1569 a snapshot at the end of boot up.
1579 1570
1580 ftrace_dump_on_oops[=2(orig_cpu) | =< !! 1571 ftrace_dump_on_oops[=orig_cpu]
1581 ,<instance>=2(orig_ <<
1582 [FTRACE] will dump th 1572 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1573 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1574 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1575 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1576 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 1577
1603 ftrace_filter=[function-list] 1578 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1579 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu 1580 tracer at boot up. function-list is a comma-separated
1606 list of functions. Th 1581 list of functions. This list can be changed at run
1607 time by the set_ftrac 1582 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1583 tracing directory.
1609 1584
1610 ftrace_notrace=[function-list] 1585 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1586 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1587 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1588 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1589 tracing directory.
1615 1590
1616 ftrace_graph_filter=[function-list] 1591 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1592 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1593 by the function graph tracer at boot up.
1619 function-list is a co 1594 function-list is a comma-separated list of functions
1620 that can be changed a 1595 that can be changed at run time by the
1621 set_graph_function fi 1596 set_graph_function file in the debugfs tracing directory.
1622 1597
1623 ftrace_graph_notrace=[function-list] 1598 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1599 [FTRACE] Do not trace from the functions specified in
1625 function-list. This 1600 function-list. This list is a comma-separated list of
1626 functions that can be 1601 functions that can be changed at run time by the
1627 set_graph_notrace fil 1602 set_graph_notrace file in the debugfs tracing directory.
1628 1603
1629 ftrace_graph_max_depth=<uint> 1604 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1605 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1606 the max depth it will trace into a function. This value
1632 can be changed at run 1607 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1608 in the tracefs tracing directory. default: 0 (no limit)
1634 1609
1635 fw_devlink= [KNL,EARLY] Create de !! 1610 fw_devlink= [KNL] Create device links between consumer and supplier
1636 devices by scanning t 1611 devices by scanning the firmware to infer the
1637 consumer/supplier rel 1612 consumer/supplier relationships. This feature is
1638 especially useful whe 1613 especially useful when drivers are loaded as modules as
1639 it ensures proper ord 1614 it ensures proper ordering of tasks like device probing
1640 (suppliers first, the 1615 (suppliers first, then consumers), supplier boot state
1641 clean up (only after 1616 clean up (only after all consumers have probed),
1642 suspend/resume & runt 1617 suspend/resume & runtime PM (consumers first, then
1643 suppliers). 1618 suppliers).
1644 Format: { off | permi 1619 Format: { off | permissive | on | rpm }
1645 off -- Don't create 1620 off -- Don't create device links from firmware info.
1646 permissive -- Create 1621 permissive -- Create device links from firmware info
1647 but use it on 1622 but use it only for ordering boot state clean
1648 up (sync_stat 1623 up (sync_state() calls).
1649 on -- Create device 1624 on -- Create device links from firmware info and use it
1650 to enforce pr 1625 to enforce probe and suspend/resume ordering.
1651 rpm -- Like "on", bu 1626 rpm -- Like "on", but also use to order runtime PM.
1652 1627
1653 fw_devlink.strict=<bool> 1628 fw_devlink.strict=<bool>
1654 [KNL,EARLY] Treat all !! 1629 [KNL] Treat all inferred dependencies as mandatory
1655 dependencies. This on 1630 dependencies. This only applies for fw_devlink=on|rpm.
1656 Format: <bool> 1631 Format: <bool>
1657 1632
1658 fw_devlink.sync_state = 1633 fw_devlink.sync_state =
1659 [KNL,EARLY] When all !! 1634 [KNL] When all devices that could probe have finished
1660 probing, this paramet 1635 probing, this parameter controls what to do with
1661 devices that haven't 1636 devices that haven't yet received their sync_state()
1662 calls. 1637 calls.
1663 Format: { strict | ti 1638 Format: { strict | timeout }
1664 strict -- Default. Co 1639 strict -- Default. Continue waiting on consumers to
1665 probe success 1640 probe successfully.
1666 timeout -- Give up wa 1641 timeout -- Give up waiting on consumers and call
1667 sync_state() 1642 sync_state() on any devices that haven't yet
1668 received thei 1643 received their sync_state() calls after
1669 deferred_prob 1644 deferred_probe_timeout has expired or by
1670 late_initcall 1645 late_initcall() if !CONFIG_MODULES.
1671 1646
1672 gamecon.map[2|3]= 1647 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1648 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1649 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1650 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1651 See also Documentation/input/devices/joystick-parport.rst
1677 1652
1678 gamma= [HW,DRM] 1653 gamma= [HW,DRM]
1679 1654
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1655 gart_fix_e820= [X86-64] disable the fix e820 for K8 GART
1681 Format: off | on 1656 Format: off | on
1682 default: on 1657 default: on
1683 1658
1684 gather_data_sampling= 1659 gather_data_sampling=
1685 [X86,INTEL,EARLY] Con !! 1660 [X86,INTEL] Control the Gather Data Sampling (GDS)
1686 mitigation. 1661 mitigation.
1687 1662
1688 Gather Data Sampling 1663 Gather Data Sampling is a hardware vulnerability which
1689 allows unprivileged s 1664 allows unprivileged speculative access to data which was
1690 previously stored in 1665 previously stored in vector registers.
1691 1666
1692 This issue is mitigat 1667 This issue is mitigated by default in updated microcode.
1693 The mitigation may ha 1668 The mitigation may have a performance impact but can be
1694 disabled. On systems 1669 disabled. On systems without the microcode mitigation
1695 disabling AVX serves 1670 disabling AVX serves as a mitigation.
1696 1671
1697 force: Disable AVX t 1672 force: Disable AVX to mitigate systems without
1698 microcode mit 1673 microcode mitigation. No effect if the microcode
1699 mitigation is 1674 mitigation is present. Known to cause crashes in
1700 userspace wit 1675 userspace with buggy AVX enumeration.
1701 1676
1702 off: Disable GDS m 1677 off: Disable GDS mitigation.
1703 1678
1704 gcov_persist= [GCOV] When non-zero 1679 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1680 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1681 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1682 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1683 debugfs files are removed at module unload time.
1709 1684
1710 goldfish [X86] Enable the gold 1685 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1686 Don't use this when you are not running on the
1712 android emulator 1687 android emulator
1713 1688
1714 gpio-mockup.gpio_mockup_ranges 1689 gpio-mockup.gpio_mockup_ranges
1715 [HW] Sets the ranges 1690 [HW] Sets the ranges of gpiochip of for this device.
1716 Format: <start1>,<end 1691 Format: <start1>,<end1>,<start2>,<end2>...
1717 gpio-mockup.gpio_mockup_named_lines 1692 gpio-mockup.gpio_mockup_named_lines
1718 [HW] Let the driver k 1693 [HW] Let the driver know GPIO lines should be named.
1719 1694
1720 gpt [EFI] Forces disk wit 1695 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1696 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1697 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1698 GPT to be used instead.
1724 1699
1725 grcan.enable0= [HW] Configuration of 1700 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1701 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1702 Format: 0 | 1
1728 Default: 0 1703 Default: 0
1729 grcan.enable1= [HW] Configuration of 1704 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1705 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1706 Format: 0 | 1
1732 Default: 0 1707 Default: 0
1733 grcan.select= [HW] Select which phy 1708 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1709 Format: 0 | 1
1735 Default: 0 1710 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1711 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1712 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1713 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1714 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1715 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1716 Default: 1024
1742 1717
1743 hardened_usercopy= 1718 hardened_usercopy=
1744 [KNL] Under CONFIG_HA 1719 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
1745 hardening is enabled 1720 hardening is enabled for this boot. Hardened
1746 usercopy checking is 1721 usercopy checking is used to protect the kernel
1747 from reading or writi 1722 from reading or writing beyond known memory
1748 allocation boundaries 1723 allocation boundaries as a proactive defense
1749 against bounds-checki 1724 against bounds-checking flaws in the kernel's
1750 copy_to_user()/copy_f 1725 copy_to_user()/copy_from_user() interface.
1751 on Perform hardened user 1726 on Perform hardened usercopy checks (default).
1752 off Disable hardened user 1727 off Disable hardened usercopy checks.
1753 1728
1754 hardlockup_all_cpu_backtrace= 1729 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1730 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1731 backtraces on all cpus.
1757 Format: 0 | 1 1732 Format: 0 | 1
1758 1733
1759 hashdist= [KNL,NUMA] Large hash 1734 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1735 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1736 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1737 Format: 0 | 1 (for off | on)
1763 1738
>> 1739 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1740
1764 hd= [EIDE] (E)IDE hard dr 1741 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1742 Format: <cyl>,<head>,<sect>
1766 1743
1767 hest_disable [ACPI] 1744 hest_disable [ACPI]
1768 Disable Hardware Erro 1745 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1746 corresponding firmware-first mode error processing
1770 logic will be disable 1747 logic will be disabled.
1771 1748
1772 hibernate= [HIBERNATION] 1749 hibernate= [HIBERNATION]
1773 noresume Don't check i 1750 noresume Don't check if there's a hibernation image
1774 present durin 1751 present during boot.
1775 nocompress Don't compres 1752 nocompress Don't compress/decompress hibernation images.
1776 no Disable hiber 1753 no Disable hibernation and resume.
1777 protect_image Turn on image 1754 protect_image Turn on image protection during restoration
1778 (that will se 1755 (that will set all pages holding image data
1779 during restor 1756 during restoration read-only).
1780 1757
1781 hibernate.compressor= [HIBERNATION] !! 1758 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 1759 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1760 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1761 size on bigger boxes.
1796 1762
1797 highres= [KNL] Enable/disable 1763 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1764 Valid parameters: "on", "off"
1799 Default: "on" 1765 Default: "on"
1800 1766
1801 hlt [BUGS=ARM,SH] 1767 hlt [BUGS=ARM,SH]
1802 1768
1803 hostname= [KNL,EARLY] Set the h !! 1769 hostname= [KNL] Set the hostname (aka UTS nodename).
1804 Format: <string> 1770 Format: <string>
1805 This allows setting t 1771 This allows setting the system's hostname during early
1806 startup. This sets th 1772 startup. This sets the name returned by gethostname.
1807 Using this parameter 1773 Using this parameter to set the hostname makes it
1808 possible to ensure th 1774 possible to ensure the hostname is correctly set before
1809 any userspace process 1775 any userspace processes run, avoiding the possibility
1810 that a process may ca 1776 that a process may call gethostname before the hostname
1811 has been explicitly s 1777 has been explicitly set, resulting in the calling
1812 process getting an in 1778 process getting an incorrect result. The string must
1813 not exceed the maximu 1779 not exceed the maximum allowed hostname length (usually
1814 64 characters) and wi 1780 64 characters) and will be truncated otherwise.
1815 1781
1816 hpet= [X86-32,HPET] option 1782 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1783 Format: { enable (default) | disable | force |
1818 verbose } 1784 verbose }
1819 disable: disable HPET 1785 disable: disable HPET and use PIT instead
1820 force: allow force en 1786 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1787 VIA, nVidia)
1822 verbose: show content 1788 verbose: show contents of HPET registers during setup
1823 1789
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1790 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1791 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1792
1827 hugepages= [HW] Number of HugeTL 1793 hugepages= [HW] Number of HugeTLB pages to allocate at boot.
1828 If this follows hugep 1794 If this follows hugepagesz (below), it specifies
1829 the number of pages o 1795 the number of pages of hugepagesz to be allocated.
1830 If this is the first 1796 If this is the first HugeTLB parameter on the command
1831 line, it specifies th 1797 line, it specifies the number of pages to allocate for
1832 the default huge page 1798 the default huge page size. If using node format, the
1833 number of pages to al 1799 number of pages to allocate per-node can be specified.
1834 See also Documentatio 1800 See also Documentation/admin-guide/mm/hugetlbpage.rst.
1835 Format: <integer> or 1801 Format: <integer> or (node format)
1836 <node>:<integ 1802 <node>:<integer>[,<node>:<integer>]
1837 1803
1838 hugepagesz= 1804 hugepagesz=
1839 [HW] The size of the 1805 [HW] The size of the HugeTLB pages. This is used in
1840 conjunction with huge 1806 conjunction with hugepages (above) to allocate huge
1841 pages of a specific s 1807 pages of a specific size at boot. The pair
1842 hugepagesz=X hugepage 1808 hugepagesz=X hugepages=Y can be specified once for
1843 each supported huge p 1809 each supported huge page size. Huge page sizes are
1844 architecture dependen 1810 architecture dependent. See also
1845 Documentation/admin-g 1811 Documentation/admin-guide/mm/hugetlbpage.rst.
1846 Format: size[KMG] 1812 Format: size[KMG]
1847 1813
1848 hugetlb_cma= [HW,CMA,EARLY] The si !! 1814 hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
1849 of gigantic hugepages 1815 of gigantic hugepages. Or using node format, the size
1850 of a CMA area per nod 1816 of a CMA area per node can be specified.
1851 Format: nn[KMGTPE] or 1817 Format: nn[KMGTPE] or (node format)
1852 <node>:nn[KMG 1818 <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
1853 1819
1854 Reserve a CMA area of 1820 Reserve a CMA area of given size and allocate gigantic
1855 hugepages using the C 1821 hugepages using the CMA allocator. If enabled, the
1856 boot-time allocation 1822 boot-time allocation of gigantic hugepages is skipped.
1857 1823
1858 hugetlb_free_vmemmap= 1824 hugetlb_free_vmemmap=
1859 [KNL] Requires CONFIG 1825 [KNL] Requires CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP
1860 enabled. 1826 enabled.
1861 Control if HugeTLB Vm 1827 Control if HugeTLB Vmemmap Optimization (HVO) is enabled.
1862 Allows heavy hugetlb 1828 Allows heavy hugetlb users to free up some more
1863 memory (7 * PAGE_SIZE 1829 memory (7 * PAGE_SIZE for each 2MB hugetlb page).
1864 Format: { on | off (d 1830 Format: { on | off (default) }
1865 1831
1866 on: enable HVO 1832 on: enable HVO
1867 off: disable HVO 1833 off: disable HVO
1868 1834
1869 Built with CONFIG_HUG 1835 Built with CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP_DEFAULT_ON=y,
1870 the default is on. 1836 the default is on.
1871 1837
1872 Note that the vmemmap 1838 Note that the vmemmap pages may be allocated from the added
1873 memory block itself w 1839 memory block itself when memory_hotplug.memmap_on_memory is
1874 enabled, those vmemma 1840 enabled, those vmemmap pages cannot be optimized even if this
1875 feature is enabled. 1841 feature is enabled. Other vmemmap pages not allocated from
1876 the added memory bloc 1842 the added memory block itself do not be affected.
1877 1843
1878 hung_task_panic= 1844 hung_task_panic=
1879 [KNL] Should the hung 1845 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 1846 Format: 0 | 1
1881 1847
1882 A value of 1 instruct 1848 A value of 1 instructs the kernel to panic when a
1883 hung task is detected 1849 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1850 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1851 option. The value selected by this boot parameter can
1886 be changed later by t 1852 be changed later by the kernel.hung_task_panic sysctl.
1887 1853
1888 hvc_iucv= [S390] Number of z/V 1854 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1855 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1856 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1857 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1858 from listed z/VM user IDs only.
1893 1859
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1860 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1861 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1862 guest on lock contention.
1897 on lock contention. <<
1898 1863
1899 i2c_bus= [HW] Override the 1864 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1865 or register an additional I2C bus that is not
1901 registered fr 1866 registered from board initialization code.
1902 Format: 1867 Format:
1903 <bus_id>,<clk 1868 <bus_id>,<clkrate>
1904 1869
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 1870 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1871 i8042.unmask_kbd_data
1929 [HW] Enable printing 1872 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1873 (disabled by default, and as a pre-condition
1931 requires that i8 1874 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1875 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1876 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1877 keyboard and cannot control its state
1935 (Don't attempt t 1878 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1879 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1880 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1881 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1882 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1883 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1884 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1885 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1886 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1887 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1888 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1889 suspend-to-ram transitions, only during s2r
1947 transitions, or 1890 transitions, or never reset
1948 Format: { 1 | Y | y | 1891 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1892 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1893 0, N, n: don't ever reset controller
1951 Default: only on s2r 1894 Default: only on s2r transitions on x86; most other
1952 architectures force r 1895 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1896 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1897 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer 1898 i8042.probe_defer
1956 [HW] Allow deferred p 1899 [HW] Allow deferred probing upon i8042 probe errors
1957 1900
1958 i810= [HW,DRM] 1901 i810= [HW,DRM]
1959 1902
1960 i915.invert_brightness= 1903 i915.invert_brightness=
1961 [DRM] Invert the sens 1904 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1905 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1906 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1907 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1908 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1909 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1910 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1911 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1912 value switches the backlight off.
1970 -1 -- never invert br 1913 -1 -- never invert brightness
1971 0 -- machine default 1914 0 -- machine default
1972 1 -- force brightnes 1915 1 -- force brightness inversion
1973 1916
1974 ia32_emulation= [X86-64] 1917 ia32_emulation= [X86-64]
1975 Format: <bool> 1918 Format: <bool>
1976 When true, allows loa 1919 When true, allows loading 32-bit programs and executing 32-bit
1977 syscalls, essentially 1920 syscalls, essentially overriding IA32_EMULATION_DEFAULT_DISABLED at
1978 boot time. When false 1921 boot time. When false, unconditionally disables IA32 emulation.
1979 1922
1980 icn= [HW,ISDN] 1923 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1924 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1925
1983 1926
1984 idle= [X86,EARLY] !! 1927 idle= [X86]
1985 Format: idle=poll, id 1928 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1929 Poll forces a polling idle loop that can slightly
1987 improve the performan 1930 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1931 will use a lot of power and make the system run hot.
1989 Not recommended. 1932 Not recommended.
1990 idle=halt: Halt is fo 1933 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1934 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1935 idle=nomwait: Disable mwait for CPU C-states
1993 1936
1994 idxd.sva= [HW] 1937 idxd.sva= [HW]
1995 Format: <bool> 1938 Format: <bool>
1996 Allow force disabling 1939 Allow force disabling of Shared Virtual Memory (SVA)
1997 support for the idxd 1940 support for the idxd driver. By default it is set to
1998 true (1). 1941 true (1).
1999 1942
2000 idxd.tc_override= [HW] 1943 idxd.tc_override= [HW]
2001 Format: <bool> 1944 Format: <bool>
2002 Allow override of def 1945 Allow override of default traffic class configuration
2003 for the device. By de 1946 for the device. By default it is set to false (0).
2004 1947
2005 ieee754= [MIPS] Select IEEE St 1948 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1949 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1950 Default: strict
2008 1951
2009 Choose which programs 1952 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1953 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1954 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1955 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1956 binary. Hardware implementations are permitted to
2014 support either or bot 1957 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1958 encoding mode.
2016 1959
2017 Available settings ar 1960 Available settings are as follows:
2018 strict accept binari 1961 strict accept binaries that request a NaN encoding
2019 supported by 1962 supported by the FPU
2020 legacy only accept l 1963 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1964 by the FPU
2022 2008 only accept 2 1965 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1966 by the FPU
2024 relaxed accept any bi 1967 relaxed accept any binaries regardless of whether
2025 supported by 1968 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1969
2029 The FPU emulator is a 1970 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1971 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1972 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1973 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1974 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1975 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1976 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1977 MIPS64 CPUs.
2037 1978
2038 The setting for ABS.f 1979 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1980 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1981 except where unsupported by hardware.
2041 1982
2042 ignore_loglevel [KNL,EARLY] !! 1983 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1984 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1985 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1986 We also add it as printk module parameter, so users
2046 could change it dynam 1987 could change it dynamically, usually by
2047 /sys/module/printk/pa 1988 /sys/module/printk/parameters/ignore_loglevel.
2048 1989
2049 ignore_rlimit_data 1990 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1991 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1992 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1993 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1994
2054 ihash_entries= [KNL] 1995 ihash_entries= [KNL]
2055 Set number of hash bu 1996 Set number of hash buckets for inode cache.
2056 1997
2057 ima_appraise= [IMA] appraise integr 1998 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1999 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 2000 default: "enforce"
2060 2001
2061 ima_appraise_tcb [IMA] Deprecated. U 2002 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 2003 The builtin appraise policy appraises all files
2063 owned by uid=0. 2004 owned by uid=0.
2064 2005
2065 ima_canonical_fmt [IMA] 2006 ima_canonical_fmt [IMA]
2066 Use the canonical for 2007 Use the canonical format for the binary runtime
2067 measurements, instead 2008 measurements, instead of host native format.
2068 2009
2069 ima_hash= [IMA] 2010 ima_hash= [IMA]
2070 Format: { md5 | sha1 2011 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 2012 | sha512 | ... }
2072 default: "sha1" 2013 default: "sha1"
2073 2014
2074 The list of supported 2015 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 2016 in crypto/hash_info.h.
2076 2017
2077 ima_policy= [IMA] 2018 ima_policy= [IMA]
2078 The builtin policies 2019 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 2020 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel 2021 fail_securely | critical_data"
2081 2022
2082 The "tcb" policy meas 2023 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 2024 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 2025 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 2026 uid=0.
2086 2027
2087 The "appraise_tcb" po 2028 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 2029 all files owned by root.
2089 2030
2090 The "secure_boot" pol 2031 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 2032 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 2033 firmware, policy, etc) based on file signatures.
2093 2034
2094 The "fail_securely" p 2035 The "fail_securely" policy forces file signature
2095 verification failure 2036 verification failure also on privileged mounted
2096 filesystems with the 2037 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 2038 flag.
2098 2039
2099 The "critical_data" p 2040 The "critical_data" policy measures kernel integrity
2100 critical data. 2041 critical data.
2101 2042
2102 ima_tcb [IMA] Deprecated. Us 2043 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 2044 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 2045 Computing Base. This means IMA will measure all
2105 programs exec'd, file 2046 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 2047 opened for read by uid=0.
2107 2048
2108 ima_template= [IMA] 2049 ima_template= [IMA]
2109 Select one of defined 2050 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i 2051 Formats: { "ima" | "ima-ng" | "ima-ngv2" | "ima-sig" |
2111 "ima-sigv2 2052 "ima-sigv2" }
2112 Default: "ima-ng" 2053 Default: "ima-ng"
2113 2054
2114 ima_template_fmt= 2055 ima_template_fmt=
2115 [IMA] Define a custom 2056 [IMA] Define a custom template format.
2116 Format: { "field1|... 2057 Format: { "field1|...|fieldN" }
2117 2058
2118 ima.ahash_minsize= [IMA] Minimum file 2059 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 2060 Format: <min_file_size>
2120 Set the minimal file 2061 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 2062 If left unspecified, ahash usage is disabled.
2122 2063
2123 ahash performance var 2064 ahash performance varies for different data sizes on
2124 different crypto acce 2065 different crypto accelerators. This option can be used
2125 to achieve the best p 2066 to achieve the best performance for a particular HW.
2126 2067
2127 ima.ahash_bufsize= [IMA] Asynchronous 2068 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 2069 Format: <bufsize>
2129 Set hashing buffer si 2070 Set hashing buffer size. Default: 4k.
2130 2071
2131 ahash performance var 2072 ahash performance varies for different chunk sizes on
2132 different crypto acce 2073 different crypto accelerators. This option can be used
2133 to achieve best perfo 2074 to achieve best performance for particular HW.
2134 2075
2135 init= [KNL] 2076 init= [KNL]
2136 Format: <full_path> 2077 Format: <full_path>
2137 Run specified binary 2078 Run specified binary instead of /sbin/init as init
2138 process. 2079 process.
2139 2080
2140 initcall_debug [KNL] Trace initcalls 2081 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 2082 for working out where the kernel is dying during
2142 startup. 2083 startup.
2143 2084
2144 initcall_blacklist= [KNL] Do not exe 2085 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 2086 initcall functions. Useful for debugging built-in
2146 modules and initcalls 2087 modules and initcalls.
2147 2088
2148 initramfs_async= [KNL] 2089 initramfs_async= [KNL]
2149 Format: <bool> 2090 Format: <bool>
2150 Default: 1 2091 Default: 1
2151 This parameter contro 2092 This parameter controls whether the initramfs
2152 image is unpacked asy 2093 image is unpacked asynchronously, concurrently
2153 with devices being pr 2094 with devices being probed and
2154 initialized. This sho 2095 initialized. This should normally just work,
2155 but as a debugging ai 2096 but as a debugging aid, one can get the
2156 historical behaviour 2097 historical behaviour of the initramfs
2157 unpacking being compl 2098 unpacking being completed before device_ and
2158 late_ initcalls. 2099 late_ initcalls.
2159 2100
2160 initrd= [BOOT,EARLY] Specify !! 2101 initrd= [BOOT] Specify the location of the initial ramdisk
2161 2102
2162 initrdmem= [KNL,EARLY] Specify a !! 2103 initrdmem= [KNL] Specify a physical address and size from which to
2163 load the initrd. If a 2104 load the initrd. If an initrd is compiled in or
2164 specified in the boot 2105 specified in the bootparams, it takes priority over this
2165 setting. 2106 setting.
2166 Format: ss[KMG],nn[KM 2107 Format: ss[KMG],nn[KMG]
2167 Default is 0, 0 2108 Default is 0, 0
2168 2109
2169 init_on_alloc= [MM,EARLY] Fill newly !! 2110 init_on_alloc= [MM] Fill newly allocated pages and heap objects with
2170 zeroes. 2111 zeroes.
2171 Format: 0 | 1 2112 Format: 0 | 1
2172 Default set by CONFIG 2113 Default set by CONFIG_INIT_ON_ALLOC_DEFAULT_ON.
2173 2114
2174 init_on_free= [MM,EARLY] Fill freed !! 2115 init_on_free= [MM] Fill freed pages and heap objects with zeroes.
2175 Format: 0 | 1 2116 Format: 0 | 1
2176 Default set by CONFIG 2117 Default set by CONFIG_INIT_ON_FREE_DEFAULT_ON.
2177 2118
2178 init_pkru= [X86] Specify the def 2119 init_pkru= [X86] Specify the default memory protection keys rights
2179 register contents for 2120 register contents for all processes. 0x55555554 by
2180 default (disallow acc 2121 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 2122 override in debugfs after boot.
2182 2123
2183 inport.irq= [HW] Inport (ATI XL a 2124 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 2125 Format: <irq>
2185 2126
2186 int_pln_enable [X86] Enable power li 2127 int_pln_enable [X86] Enable power limit notification interrupt
2187 2128
2188 integrity_audit=[IMA] 2129 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 2130 Format: { "0" | "1" }
2190 0 -- basic integrity 2131 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 2132 1 -- additional integrity auditing messages.
2192 2133
2193 intel_iommu= [DMAR] Intel IOMMU dr 2134 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 2135 on
2195 Enable intel iommu dr 2136 Enable intel iommu driver.
2196 off 2137 off
2197 Disable intel iommu d 2138 Disable intel iommu driver.
2198 igfx_off [Default Off] 2139 igfx_off [Default Off]
2199 By default, gfx is ma 2140 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 2141 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 2142 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 2143 this case, gfx device will use physical address for
2203 DMA. 2144 DMA.
2204 strict [Default Off] 2145 strict [Default Off]
2205 Deprecated, equivalen 2146 Deprecated, equivalent to iommu.strict=1.
2206 sp_off [Default Off] 2147 sp_off [Default Off]
2207 By default, super pag 2148 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 2149 has the capability. With this option, super page will
2209 not be supported. 2150 not be supported.
2210 sm_on 2151 sm_on
2211 Enable the Intel IOMM 2152 Enable the Intel IOMMU scalable mode if the hardware
2212 advertises that it ha 2153 advertises that it has support for the scalable mode
2213 translation. 2154 translation.
2214 sm_off 2155 sm_off
2215 Disallow use of the I 2156 Disallow use of the Intel IOMMU scalable mode.
2216 tboot_noforce [Default Off] 2157 tboot_noforce [Default Off]
2217 Do not force the Inte 2158 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 2159 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 2160 could harm performance of some high-throughput
2220 devices like 40GBit n 2161 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 2162 mapping is enabled.
2222 Note that using this 2163 Note that using this option lowers the security
2223 provided by tboot bec 2164 provided by tboot because it makes the system
2224 vulnerable to DMA att 2165 vulnerable to DMA attacks.
2225 2166
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 2167 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 2168 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 2169 1 to 9 specify maximum depth of C-state.
2229 2170
2230 intel_pstate= [X86,EARLY] !! 2171 intel_pstate= [X86]
2231 disable 2172 disable
2232 Do not enable intel 2173 Do not enable intel_pstate as the default
2233 scaling driver for 2174 scaling driver for the supported processors
2234 active 2175 active
2235 Use intel_pstate dr 2176 Use intel_pstate driver to bypass the scaling
2236 governors layer of 2177 governors layer of cpufreq and provides it own
2237 algorithms for p-st 2178 algorithms for p-state selection. There are two
2238 P-state selection a 2179 P-state selection algorithms provided by
2239 intel_pstate in the 2180 intel_pstate in the active mode: powersave and
2240 performance. The w 2181 performance. The way they both operate depends
2241 on whether or not t 2182 on whether or not the hardware managed P-states
2242 (HWP) feature has b 2183 (HWP) feature has been enabled in the processor
2243 and possibly on the 2184 and possibly on the processor model.
2244 passive 2185 passive
2245 Use intel_pstate as 2186 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 2187 to work with generic cpufreq governors (instead of
2247 enabling its intern 2188 enabling its internal governor). This mode cannot be
2248 used along with the 2189 used along with the hardware-managed P-states (HWP)
2249 feature. 2190 feature.
2250 force 2191 force
2251 Enable intel_pstate 2192 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 2193 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 2194 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 2195 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 2196 P-States information being indicated to OSPM and therefore
2256 should be used with 2197 should be used with caution. This option does not work with
2257 processors that are 2198 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 2199 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 2200 no_hwp
2260 Do not enable hardw 2201 Do not enable hardware P state control (HWP)
2261 if available. 2202 if available.
2262 hwp_only 2203 hwp_only
2263 Only load intel_pst 2204 Only load intel_pstate on systems which support
2264 hardware P state co 2205 hardware P state control (HWP) if available.
2265 support_acpi_ppc 2206 support_acpi_ppc
2266 Enforce ACPI _PPC p 2207 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 2208 Description Table, specifies preferred power management
2268 profile as "Enterpr 2209 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 2210 then this feature is turned on by default.
2270 per_cpu_perf_limits 2211 per_cpu_perf_limits
2271 Allow per-logical-C 2212 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 2213 cpufreq sysfs interface
2273 2214
2274 intremap= [X86-64,Intel-IOMMU,E !! 2215 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 2216 on enable Interrupt Remapping (default)
2276 off disable Inter 2217 off disable Interrupt Remapping
2277 nosid disable Sourc 2218 nosid disable Source ID checking
2278 no_x2apic_optout 2219 no_x2apic_optout
2279 BIOS x2APIC o 2220 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 2221 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 2222
2284 iomem= Disable strict checki 2223 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 2224 strict regions from userspace.
2286 relaxed 2225 relaxed
2287 2226
2288 iommu= [X86,EARLY] !! 2227 iommu= [X86]
2289 off 2228 off
2290 force 2229 force
2291 noforce 2230 noforce
2292 biomerge 2231 biomerge
2293 panic 2232 panic
2294 nopanic 2233 nopanic
2295 merge 2234 merge
2296 nomerge 2235 nomerge
2297 soft 2236 soft
2298 pt [X86] 2237 pt [X86]
2299 nopt [X86] 2238 nopt [X86]
2300 nobypass [PPC/POWERNV] 2239 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 2240 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 2241
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 2242 iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices.
2304 Format: { "0" | "1" } 2243 Format: { "0" | "1" }
2305 0 - Try to allocate a 2244 0 - Try to allocate a 32-bit DMA address first, before
2306 falling back to the 2245 falling back to the full range if needed.
2307 1 - Allocate directly 2246 1 - Allocate directly from the full usable range,
2308 forcing Dual Addres 2247 forcing Dual Address Cycle for PCI cards supporting
2309 greater than 32-bit 2248 greater than 32-bit addressing.
2310 2249
2311 iommu.strict= [ARM64,X86,S390,EARLY !! 2250 iommu.strict= [ARM64, X86, S390] Configure TLB invalidation behaviour
2312 Format: { "0" | "1" } 2251 Format: { "0" | "1" }
2313 0 - Lazy mode. 2252 0 - Lazy mode.
2314 Request that DMA un 2253 Request that DMA unmap operations use deferred
2315 invalidation of har 2254 invalidation of hardware TLBs, for increased
2316 throughput at the c 2255 throughput at the cost of reduced device isolation.
2317 Will fall back to s 2256 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 2257 the relevant IOMMU driver.
2319 1 - Strict mode. 2258 1 - Strict mode.
2320 DMA unmap operation 2259 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 2260 synchronously.
2322 unset - Use value of 2261 unset - Use value of CONFIG_IOMMU_DEFAULT_DMA_{LAZY,STRICT}.
2323 Note: on x86, strict 2262 Note: on x86, strict mode specified via one of the
2324 legacy driver-specifi 2263 legacy driver-specific options takes precedence.
2325 2264
2326 iommu.passthrough= 2265 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 2266 [ARM64, X86] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 2267 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 2268 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 2269 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 2270 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 2271
2333 io7= [HW] IO7 for Marvel-b 2272 io7= [HW] IO7 for Marvel-based Alpha systems
2334 See comment before ma 2273 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 2274 arch/alpha/kernel/core_marvel.c.
2336 2275
2337 io_delay= [X86,EARLY] I/O delay !! 2276 io_delay= [X86] I/O delay method
2338 0x80 2277 0x80
2339 Standard port 0x80 ba 2278 Standard port 0x80 based delay
2340 0xed 2279 0xed
2341 Alternate port 0xed b 2280 Alternate port 0xed based delay (needed on some systems)
2342 udelay 2281 udelay
2343 Simple two microsecon 2282 Simple two microseconds delay
2344 none 2283 none
2345 No delay 2284 No delay
2346 2285
2347 ip= [IP_PNP] 2286 ip= [IP_PNP]
2348 See Documentation/adm 2287 See Documentation/admin-guide/nfs/nfsroot.rst.
2349 2288
2350 ipcmni_extend [KNL,EARLY] Extend th !! 2289 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 2290 IPC identifiers from 32,768 to 16,777,216.
2352 2291
2353 irqaffinity= [SMP] Set the default 2292 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 2293 The argument is a cpu list, as described above.
2355 2294
2356 irqchip.gicv2_force_probe= 2295 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 2296 [ARM, ARM64]
2358 Format: <bool> 2297 Format: <bool>
2359 Force the kernel to l 2298 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 2299 of a GICv2 controller even if the memory range
2361 exposed by the device 2300 exposed by the device tree is too small.
2362 2301
2363 irqchip.gicv3_nolpi= 2302 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 2303 [ARM, ARM64]
2365 Force the kernel to i 2304 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 2305 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 2306 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 2307 to let secondary kernels in charge of setting up
2369 LPIs. 2308 LPIs.
2370 2309
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 2310 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 2311 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 2312 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 2313 CONFIG_ARM64_PSEUDO_NMI.
2375 2314
2376 irqfixup [HW] 2315 irqfixup [HW]
2377 When an interrupt is 2316 When an interrupt is not handled search all handlers
2378 for it. Intended to g 2317 for it. Intended to get systems with badly broken
2379 firmware running. 2318 firmware running.
2380 2319
2381 irqpoll [HW] 2320 irqpoll [HW]
2382 When an interrupt is 2321 When an interrupt is not handled search all handlers
2383 for it. Also check al 2322 for it. Also check all handlers each timer
2384 interrupt. Intended t 2323 interrupt. Intended to get systems with badly broken
2385 firmware running. 2324 firmware running.
2386 2325
2387 isapnp= [ISAPNP] 2326 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 2327 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 2328
2390 isolcpus= [KNL,SMP,ISOL] Isolat 2329 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 2330 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 2331 Format: [flag-list,]<cpu-list>
2393 2332
2394 Specify one or more C 2333 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 2334 specified in the flag list (default: domain):
2396 2335
2397 nohz 2336 nohz
2398 Disable the tick wh 2337 Disable the tick when a single task runs.
2399 2338
2400 A residual 1Hz tick 2339 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 2340 need to affine to housekeeping through the global
2402 workqueue's affinit 2341 workqueue's affinity configured via the
2403 /sys/devices/virtua 2342 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 2343 by using the 'domain' flag described below.
2405 2344
2406 NOTE: by default th 2345 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 2346 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 2347 be configured manually after bootup.
2409 2348
2410 domain 2349 domain
2411 Isolate from the ge 2350 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 2351 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 2352 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 2353 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 2354 advised to use cpusets instead to disable scheduler load
2416 balancing through t 2355 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 2356 It offers a much more flexible interface where CPUs can
2418 move in and out of 2357 move in and out of an isolated set anytime.
2419 2358
2420 You can move a proc 2359 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 2360 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 2361 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 2362 "number of CPUs in system - 1".
2424 2363
2425 managed_irq 2364 managed_irq
2426 2365
2427 Isolate from being 2366 Isolate from being targeted by managed interrupts
2428 which have an inter 2367 which have an interrupt mask containing isolated
2429 CPUs. The affinity 2368 CPUs. The affinity of managed interrupts is
2430 handled by the kern 2369 handled by the kernel and cannot be changed via
2431 the /proc/irq/* int 2370 the /proc/irq/* interfaces.
2432 2371
2433 This isolation is b 2372 This isolation is best effort and only effective
2434 if the automaticall 2373 if the automatically assigned interrupt mask of a
2435 device queue contai 2374 device queue contains isolated and housekeeping
2436 CPUs. If housekeepi 2375 CPUs. If housekeeping CPUs are online then such
2437 interrupts are dire 2376 interrupts are directed to the housekeeping CPU
2438 so that IO submitte 2377 so that IO submitted on the housekeeping CPU
2439 cannot disturb the 2378 cannot disturb the isolated CPU.
2440 2379
2441 If a queue's affini 2380 If a queue's affinity mask contains only isolated
2442 CPUs then this para 2381 CPUs then this parameter has no effect on the
2443 interrupt routing d 2382 interrupt routing decision, though interrupts are
2444 only delivered when 2383 only delivered when tasks running on those
2445 isolated CPUs submi 2384 isolated CPUs submit IO. IO submitted on
2446 housekeeping CPUs h 2385 housekeeping CPUs has no influence on those
2447 queues. 2386 queues.
2448 2387
2449 The format of <cpu-li 2388 The format of <cpu-list> is described above.
2450 2389
2451 iucv= [HW,NET] 2390 iucv= [HW,NET]
2452 2391
2453 ivrs_ioapic [HW,X86-64] 2392 ivrs_ioapic [HW,X86-64]
2454 Provide an override t 2393 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t 2394 mapping provided in the IVRS ACPI table.
2456 By default, PCI segme 2395 By default, PCI segment is 0, and can be omitted.
2457 2396
2458 For example, to map I 2397 For example, to map IOAPIC-ID decimal 10 to
2459 PCI segment 0x1 and P 2398 PCI segment 0x1 and PCI device 00:14.0,
2460 write the parameter a 2399 write the parameter as:
2461 ivrs_ioapic=1 2400 ivrs_ioapic=10@0001:00:14.0
2462 2401
2463 Deprecated formats: 2402 Deprecated formats:
2464 * To map IOAPIC-ID de 2403 * To map IOAPIC-ID decimal 10 to PCI device 00:14.0
2465 write the parameter 2404 write the parameter as:
2466 ivrs_ioapic[1 2405 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de 2406 * To map IOAPIC-ID decimal 10 to PCI segment 0x1 and
2468 PCI device 00:14.0 2407 PCI device 00:14.0 write the parameter as:
2469 ivrs_ioapic[1 2408 ivrs_ioapic[10]=0001:00:14.0
2470 2409
2471 ivrs_hpet [HW,X86-64] 2410 ivrs_hpet [HW,X86-64]
2472 Provide an override t 2411 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t 2412 mapping provided in the IVRS ACPI table.
2474 By default, PCI segme 2413 By default, PCI segment is 0, and can be omitted.
2475 2414
2476 For example, to map H 2415 For example, to map HPET-ID decimal 10 to
2477 PCI segment 0x1 and P 2416 PCI segment 0x1 and PCI device 00:14.0,
2478 write the parameter a 2417 write the parameter as:
2479 ivrs_hpet=10@ 2418 ivrs_hpet=10@0001:00:14.0
2480 2419
2481 Deprecated formats: 2420 Deprecated formats:
2482 * To map HPET-ID deci 2421 * To map HPET-ID decimal 0 to PCI device 00:14.0
2483 write the parameter 2422 write the parameter as:
2484 ivrs_hpet[0]= 2423 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci 2424 * To map HPET-ID decimal 10 to PCI segment 0x1 and
2486 PCI device 00:14.0 2425 PCI device 00:14.0 write the parameter as:
2487 ivrs_ioapic[1 2426 ivrs_ioapic[10]=0001:00:14.0
2488 2427
2489 ivrs_acpihid [HW,X86-64] 2428 ivrs_acpihid [HW,X86-64]
2490 Provide an override t 2429 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t 2430 mapping provided in the IVRS ACPI table.
2492 By default, PCI segme 2431 By default, PCI segment is 0, and can be omitted.
2493 2432
2494 For example, to map U 2433 For example, to map UART-HID:UID AMD0020:0 to
2495 PCI segment 0x1 and P 2434 PCI segment 0x1 and PCI device ID 00:14.5,
2496 write the parameter a 2435 write the parameter as:
2497 ivrs_acpihid= 2436 ivrs_acpihid=AMD0020:0@0001:00:14.5
2498 2437
2499 Deprecated formats: 2438 Deprecated formats:
2500 * To map UART-HID:UID 2439 * To map UART-HID:UID AMD0020:0 to PCI segment is 0,
2501 PCI device ID 00:14 2440 PCI device ID 00:14.5, write the parameter as:
2502 ivrs_acpihid[ 2441 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID 2442 * To map UART-HID:UID AMD0020:0 to PCI segment 0x1 and
2504 PCI device ID 00:14 2443 PCI device ID 00:14.5, write the parameter as:
2505 ivrs_acpihid[ 2444 ivrs_acpihid[0001:00:14.5]=AMD0020:0
2506 2445
2507 js= [HW,JOY] Analog joyst 2446 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 2447 See Documentation/input/joydev/joystick.rst.
2509 2448
2510 kasan_multi_shot 2449 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 2450 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 2451 report on every invalid memory access. Without this
2513 parameter KASAN will 2452 parameter KASAN will print report only for the first
2514 invalid access. 2453 invalid access.
2515 2454
2516 keep_bootcon [KNL,EARLY] !! 2455 keep_bootcon [KNL]
2517 Do not unregister boo 2456 Do not unregister boot console at start. This is only
2518 useful for debugging 2457 useful for debugging when something happens in the window
2519 between unregistering 2458 between unregistering the boot console and initializing
2520 the real console. 2459 the real console.
2521 2460
2522 keepinitrd [HW,ARM] See retain_i !! 2461 keepinitrd [HW,ARM]
2523 2462
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 2463 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 2464 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 2465 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 2466 the kernel for non-movable allocations. The requested
2528 amount is spread even 2467 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 2468 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 2469 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 2470 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 2471 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 2472 other nodes will have a larger ZONE_MOVABLE.
2534 2473
2535 ZONE_MOVABLE is used 2474 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 2475 may be reclaimed or moved by the page migration
2537 subsystem. Note that 2476 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 2477 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 2478 zone if it does not.
2540 2479
2541 It is possible to spe 2480 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 2481 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 2482 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 2483 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 2484 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 2485 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 2486 are exclusive, so you cannot specify multiple forms.
2548 2487
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 2488 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 2489 Format: <Controller#>[,poll interval]
2551 The controller # is t 2490 The controller # is the number of the ehci usb debug
2552 port as it is probed 2491 port as it is probed via PCI. The poll interval is
2553 optional and is the n 2492 optional and is the number seconds in between
2554 each poll cycle to th 2493 each poll cycle to the debug port in case you need
2555 the functionality for 2494 the functionality for interrupting the kernel with
2556 gdb or control-c on t 2495 gdb or control-c on the dbgp connection. When
2557 not using this parame 2496 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 2497 the kernel debugger.
2559 2498
2560 kgdboc= [KGDB,HW] kgdb over c 2499 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 2500 Requires a tty driver that supports console polling,
2562 or a supported pollin 2501 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 2502 Serial only format: <serial_device>[,baud]
2564 keyboard only format 2503 keyboard only format: kbd
2565 keyboard and serial 2504 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 2505 Optional Kernel mode setting:
2567 kms, kbd format: kms 2506 kms, kbd format: kms,kbd
2568 kms, kbd and serial 2507 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 2508
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 2509 kgdboc_earlycon= [KGDB,HW]
2571 If the boot console p 2510 If the boot console provides the ability to read
2572 characters and can wo 2511 characters and can work in polling mode, you can use
2573 this parameter to tel 2512 this parameter to tell kgdb to use it as a backend
2574 until the normal cons 2513 until the normal console is registered. Intended to
2575 be used together with 2514 be used together with the kgdboc parameter which
2576 specifies the normal 2515 specifies the normal console to transition to.
2577 2516
2578 The name of the early 2517 The name of the early console should be specified
2579 as the value of this 2518 as the value of this parameter. Note that the name of
2580 the early console mig 2519 the early console might be different than the tty
2581 name passed to kgdboc 2520 name passed to kgdboc. It's OK to leave the value
2582 blank and the first b 2521 blank and the first boot console that implements
2583 read() will be picked 2522 read() will be picked.
2584 2523
2585 kgdbwait [KGDB,EARLY] Stop ker !! 2524 kgdbwait [KGDB] Stop kernel execution and enter the
2586 kernel debugger at th 2525 kernel debugger at the earliest opportunity.
2587 2526
2588 kmac= [MIPS] Korina etherne 2527 kmac= [MIPS] Korina ethernet MAC address.
2589 Configure the RouterB 2528 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2529 Ethernet adapter MAC address.
2591 2530
2592 kmemleak= [KNL,EARLY] Boot-time !! 2531 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2532 Valid arguments: on, off
2594 Default: on 2533 Default: on
2595 Built with CONFIG_DEB 2534 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2535 the default is off.
2597 2536
2598 kprobe_event=[probe-list] 2537 kprobe_event=[probe-list]
2599 [FTRACE] Add kprobe e 2538 [FTRACE] Add kprobe events and enable at boot time.
2600 The probe-list is a s 2539 The probe-list is a semicolon delimited list of probe
2601 definitions. Each def 2540 definitions. Each definition is same as kprobe_events
2602 interface, but the pa 2541 interface, but the parameters are comma delimited.
2603 For example, to add a 2542 For example, to add a kprobe event on vfs_read with
2604 arg1 and arg2, add to 2543 arg1 and arg2, add to the command line;
2605 2544
2606 kprobe_event=p, 2545 kprobe_event=p,vfs_read,$arg1,$arg2
2607 2546
2608 See also Documentatio 2547 See also Documentation/trace/kprobetrace.rst "Kernel
2609 Boot Parameter" secti 2548 Boot Parameter" section.
2610 2549
2611 kpti= [ARM64,EARLY] Control !! 2550 kpti= [ARM64] Control page table isolation of user
2612 user and kernel addre !! 2551 and kernel address spaces.
2613 Default: enabled on c 2552 Default: enabled on cores which need mitigation.
2614 0: force disabled 2553 0: force disabled
2615 1: force enabled 2554 1: force enabled
2616 2555
2617 kunit.enable= [KUNIT] Enable execut 2556 kunit.enable= [KUNIT] Enable executing KUnit tests. Requires
2618 CONFIG_KUNIT to be se 2557 CONFIG_KUNIT to be set to be fully enabled. The
2619 default value can be 2558 default value can be overridden via
2620 KUNIT_DEFAULT_ENABLED 2559 KUNIT_DEFAULT_ENABLED.
2621 Default is 1 (enabled 2560 Default is 1 (enabled)
2622 2561
2623 kvm.ignore_msrs=[KVM] Ignore guest ac 2562 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2563 Default is 0 (don't ignore, but inject #GP)
2625 2564
2626 kvm.eager_page_split= 2565 kvm.eager_page_split=
2627 [KVM,X86] Controls wh 2566 [KVM,X86] Controls whether or not KVM will try to
2628 proactively split all 2567 proactively split all huge pages during dirty logging.
2629 Eager page splitting 2568 Eager page splitting reduces interruptions to vCPU
2630 execution by eliminat 2569 execution by eliminating the write-protection faults
2631 and MMU lock contenti 2570 and MMU lock contention that would otherwise be
2632 required to split hug 2571 required to split huge pages lazily.
2633 2572
2634 VM workloads that rar 2573 VM workloads that rarely perform writes or that write
2635 only to a small regio 2574 only to a small region of VM memory may benefit from
2636 disabling eager page 2575 disabling eager page splitting to allow huge pages to
2637 still be used for rea 2576 still be used for reads.
2638 2577
2639 The behavior of eager 2578 The behavior of eager page splitting depends on whether
2640 KVM_DIRTY_LOG_INITIAL 2579 KVM_DIRTY_LOG_INITIALLY_SET is enabled or disabled. If
2641 disabled, all huge pa 2580 disabled, all huge pages in a memslot will be eagerly
2642 split when dirty logg 2581 split when dirty logging is enabled on that memslot. If
2643 enabled, eager page s 2582 enabled, eager page splitting will be performed during
2644 the KVM_CLEAR_DIRTY i 2583 the KVM_CLEAR_DIRTY ioctl, and only for the pages being
2645 cleared. 2584 cleared.
2646 2585
2647 Eager page splitting 2586 Eager page splitting is only supported when kvm.tdp_mmu=Y.
2648 2587
2649 Default is Y (on). 2588 Default is Y (on).
2650 2589
2651 kvm.enable_vmware_backdoor=[KVM] Supp 2590 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2591 Default is false (don't support).
2653 2592
2654 kvm.nx_huge_pages= 2593 kvm.nx_huge_pages=
2655 [KVM] Controls the so 2594 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 2595 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 2596 force : Always deploy workaround.
2658 off : Never deplo 2597 off : Never deploy workaround.
2659 auto : Deploy work 2598 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 2599 X86_BUG_ITLB_MULTIHIT.
2661 2600
2662 Default is 'auto'. 2601 Default is 'auto'.
2663 2602
2664 If the software worka 2603 If the software workaround is enabled for the host,
2665 guests do need not to 2604 guests do need not to enable it for nested guests.
2666 2605
2667 kvm.nx_huge_pages_recovery_ratio= 2606 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 2607 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 2608 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 2609 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). 2610 period (see below). The default is 60.
2672 2611
2673 kvm.nx_huge_pages_recovery_period_ms= 2612 kvm.nx_huge_pages_recovery_period_ms=
2674 [KVM] Controls the ti 2613 [KVM] Controls the time period at which KVM zaps 4KiB pages
2675 back to huge pages. I 2614 back to huge pages. If the value is a non-zero N, KVM will
2676 zap a portion (see ra 2615 zap a portion (see ratio above) of the pages every N msecs.
2677 If the value is 0 (th 2616 If the value is 0 (the default), KVM will pick a period based
2678 on the ratio, such th 2617 on the ratio, such that a page is zapped after 1 hour on average.
2679 2618
2680 kvm-amd.nested= [KVM,AMD] Control nes 2619 kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in
2681 KVM/SVM. Default is 1 2620 KVM/SVM. Default is 1 (enabled).
2682 2621
2683 kvm-amd.npt= [KVM,AMD] Control KVM 2622 kvm-amd.npt= [KVM,AMD] Control KVM's use of Nested Page Tables,
2684 a.k.a. Two-Dimensiona 2623 a.k.a. Two-Dimensional Page Tables. Default is 1
2685 (enabled). Disable by 2624 (enabled). Disable by KVM if hardware lacks support
2686 for NPT. 2625 for NPT.
2687 2626
2688 kvm-arm.mode= 2627 kvm-arm.mode=
2689 [KVM,ARM,EARLY] Selec !! 2628 [KVM,ARM] Select one of KVM/arm64's modes of operation.
2690 operation. <<
2691 2629
2692 none: Forcefully disa 2630 none: Forcefully disable KVM.
2693 2631
2694 nvhe: Standard nVHE-b 2632 nvhe: Standard nVHE-based mode, without support for
2695 protected guest 2633 protected guests.
2696 2634
2697 protected: nVHE-based 2635 protected: nVHE-based mode with support for guests whose
2698 state is k 2636 state is kept private from the host.
2699 2637
2700 nested: VHE-based mod 2638 nested: VHE-based mode with support for nested
2701 virtualizatio 2639 virtualization. Requires at least ARMv8.3
2702 hardware. 2640 hardware.
2703 2641
2704 Defaults to VHE/nVHE 2642 Defaults to VHE/nVHE based on hardware support. Setting
2705 mode to "protected" w 2643 mode to "protected" will disable kexec and hibernation
2706 for the host. "nested 2644 for the host. "nested" is experimental and should be
2707 used with extreme cau 2645 used with extreme caution.
2708 2646
2709 kvm-arm.vgic_v3_group0_trap= 2647 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2648 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2649 system registers
2712 2650
2713 kvm-arm.vgic_v3_group1_trap= 2651 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2652 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2653 system registers
2716 2654
2717 kvm-arm.vgic_v3_common_trap= 2655 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2656 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2657 system registers
2720 2658
2721 kvm-arm.vgic_v4_enable= 2659 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2660 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2661 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 2662
2743 kvm_cma_resv_ratio=n [PPC,EARLY] !! 2663 kvm_cma_resv_ratio=n [PPC]
2744 Reserves given percen 2664 Reserves given percentage from system memory area for
2745 contiguous memory all 2665 contiguous memory allocation for KVM hash pagetable
2746 allocation. 2666 allocation.
2747 By default it reserve 2667 By default it reserves 5% of total system memory.
2748 Format: <integer> 2668 Format: <integer>
2749 Default: 5 2669 Default: 5
2750 2670
2751 kvm-intel.ept= [KVM,Intel] Control K 2671 kvm-intel.ept= [KVM,Intel] Control KVM's use of Extended Page Tables,
2752 a.k.a. Two-Dimensiona 2672 a.k.a. Two-Dimensional Page Tables. Default is 1
2753 (enabled). Disable by 2673 (enabled). Disable by KVM if hardware lacks support
2754 for EPT. 2674 for EPT.
2755 2675
2756 kvm-intel.emulate_invalid_guest_state 2676 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w 2677 [KVM,Intel] Control whether to emulate invalid guest
2758 state. Ignored if kvm 2678 state. Ignored if kvm-intel.enable_unrestricted_guest=1,
2759 as guest state is nev 2679 as guest state is never invalid for unrestricted
2760 guests. This param do 2680 guests. This param doesn't apply to nested guests (L2),
2761 as KVM never emulates 2681 as KVM never emulates invalid L2 guest state.
2762 Default is 1 (enabled 2682 Default is 1 (enabled).
2763 2683
2764 kvm-intel.flexpriority= 2684 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K 2685 [KVM,Intel] Control KVM's use of FlexPriority feature
2766 (TPR shadow). Default 2686 (TPR shadow). Default is 1 (enabled). Disable by KVM if
2767 hardware lacks suppor 2687 hardware lacks support for it.
2768 2688
2769 kvm-intel.nested= 2689 kvm-intel.nested=
2770 [KVM,Intel] Control n 2690 [KVM,Intel] Control nested virtualization feature in
2771 KVM/VMX. Default is 1 2691 KVM/VMX. Default is 1 (enabled).
2772 2692
2773 kvm-intel.unrestricted_guest= 2693 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K 2694 [KVM,Intel] Control KVM's use of unrestricted guest
2775 feature (virtualized 2695 feature (virtualized real and unpaged mode). Default
2776 is 1 (enabled). Disab 2696 is 1 (enabled). Disable by KVM if EPT is disabled or
2777 hardware lacks suppor 2697 hardware lacks support for it.
2778 2698
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2699 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2700 CVE-2018-3620.
2781 2701
2782 Valid arguments: neve 2702 Valid arguments: never, cond, always
2783 2703
2784 always: L1D cache flu 2704 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2705 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2706 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2707 never: Disables the mitigation
2788 2708
2789 Default is cond (do L 2709 Default is cond (do L1 cache flush in specific instances)
2790 2710
2791 kvm-intel.vpid= [KVM,Intel] Control K 2711 kvm-intel.vpid= [KVM,Intel] Control KVM's use of Virtual Processor
2792 Identification featur 2712 Identification feature (tagged TLBs). Default is 1
2793 (enabled). Disable by 2713 (enabled). Disable by KVM if hardware lacks support
2794 for it. 2714 for it.
2795 2715
2796 l1d_flush= [X86,INTEL,EARLY] !! 2716 l1d_flush= [X86,INTEL]
2797 Control mitigation fo 2717 Control mitigation for L1D based snooping vulnerability.
2798 2718
2799 Certain CPUs are vuln 2719 Certain CPUs are vulnerable to an exploit against CPU
2800 internal buffers whic 2720 internal buffers which can forward information to a
2801 disclosure gadget und 2721 disclosure gadget under certain conditions.
2802 2722
2803 In vulnerable process 2723 In vulnerable processors, the speculatively
2804 forwarded data can be 2724 forwarded data can be used in a cache side channel
2805 attack, to access dat 2725 attack, to access data to which the attacker does
2806 not have direct acces 2726 not have direct access.
2807 2727
2808 This parameter contro 2728 This parameter controls the mitigation. The
2809 options are: 2729 options are:
2810 2730
2811 on - enable t 2731 on - enable the interface for the mitigation
2812 2732
2813 l1tf= [X86,EARLY] Control m !! 2733 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2734 affected CPUs
2815 2735
2816 The kernel PTE invers 2736 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2737 enabled and cannot be disabled.
2818 2738
2819 full 2739 full
2820 Provides all 2740 Provides all available mitigations for the
2821 L1TF vulnerab 2741 L1TF vulnerability. Disables SMT and
2822 enables all m 2742 enables all mitigations in the
2823 hypervisors, 2743 hypervisors, i.e. unconditional L1D flush.
2824 2744
2825 SMT control a 2745 SMT control and L1D flush control via the
2826 sysfs interfa 2746 sysfs interface is still possible after
2827 boot. Hyperv 2747 boot. Hypervisors will issue a warning
2828 when the firs 2748 when the first VM is started in a
2829 potentially i 2749 potentially insecure configuration,
2830 i.e. SMT enab 2750 i.e. SMT enabled or L1D flush disabled.
2831 2751
2832 full,force 2752 full,force
2833 Same as 'full 2753 Same as 'full', but disables SMT and L1D
2834 flush runtime 2754 flush runtime control. Implies the
2835 'nosmt=force' 2755 'nosmt=force' command line option.
2836 (i.e. sysfs c 2756 (i.e. sysfs control of SMT is disabled.)
2837 2757
2838 flush 2758 flush
2839 Leaves SMT en 2759 Leaves SMT enabled and enables the default
2840 hypervisor mi 2760 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2761 L1D flush.
2842 2762
2843 SMT control a 2763 SMT control and L1D flush control via the
2844 sysfs interfa 2764 sysfs interface is still possible after
2845 boot. Hyperv 2765 boot. Hypervisors will issue a warning
2846 when the firs 2766 when the first VM is started in a
2847 potentially i 2767 potentially insecure configuration,
2848 i.e. SMT enab 2768 i.e. SMT enabled or L1D flush disabled.
2849 2769
2850 flush,nosmt 2770 flush,nosmt
2851 2771
2852 Disables SMT 2772 Disables SMT and enables the default
2853 hypervisor mi 2773 hypervisor mitigation.
2854 2774
2855 SMT control a 2775 SMT control and L1D flush control via the
2856 sysfs interfa 2776 sysfs interface is still possible after
2857 boot. Hyperv 2777 boot. Hypervisors will issue a warning
2858 when the firs 2778 when the first VM is started in a
2859 potentially i 2779 potentially insecure configuration,
2860 i.e. SMT enab 2780 i.e. SMT enabled or L1D flush disabled.
2861 2781
2862 flush,nowarn 2782 flush,nowarn
2863 Same as 'flus 2783 Same as 'flush', but hypervisors will not
2864 warn when a V 2784 warn when a VM is started in a potentially
2865 insecure conf 2785 insecure configuration.
2866 2786
2867 off 2787 off
2868 Disables hype 2788 Disables hypervisor mitigations and doesn't
2869 emit any warn 2789 emit any warnings.
2870 It also drops 2790 It also drops the swap size and available
2871 RAM limit res 2791 RAM limit restriction on both hypervisor and
2872 bare metal. 2792 bare metal.
2873 2793
2874 Default is 'flush'. 2794 Default is 'flush'.
2875 2795
2876 For details see: Docu 2796 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2797
2878 l2cr= [PPC] 2798 l2cr= [PPC]
2879 2799
2880 l3cr= [PPC] 2800 l3cr= [PPC]
2881 2801
2882 lapic [X86-32,APIC,EARLY] E !! 2802 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2803 disabled it.
2884 2804
2885 lapic= [X86,APIC] Do not use 2805 lapic= [X86,APIC] Do not use TSC deadline
2886 value for LAPIC timer 2806 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2807 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline 2808 Format: notscdeadline
2889 2809
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2810 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2811 in C2 power state.
2892 2812
2893 libata.dma= [LIBATA] DMA control 2813 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2814 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2815 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2816 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2817 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2818 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2819 for disks and CDROMs, but not CFs.
2900 2820
2901 libata.ignore_hpa= [LIBATA] Igno 2821 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2822 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2823 libata.ignore_hpa=1 ignore limits, using full disk
2904 2824
2905 libata.noacpi [LIBATA] Disables use 2825 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2826 when set.
2907 Format: <int> 2827 Format: <int>
2908 2828
2909 libata.force= [LIBATA] Force config 2829 libata.force= [LIBATA] Force configurations. The format is a comma-
2910 separated list of "[I 2830 separated list of "[ID:]VAL" where ID is PORT[.DEVICE].
2911 PORT and DEVICE are d 2831 PORT and DEVICE are decimal numbers matching port, link
2912 or device. Basically 2832 or device. Basically, it matches the ATA ID string
2913 printed on console by 2833 printed on console by libata. If the whole ID part is
2914 omitted, the last POR 2834 omitted, the last PORT and DEVICE values are used. If
2915 ID hasn't been specif 2835 ID hasn't been specified yet, the configuration applies
2916 to all ports, links a 2836 to all ports, links and devices.
2917 2837
2918 If only DEVICE is omi 2838 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2839 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2840 number of 0 either selects the first device or the
2921 first fan-out link be 2841 first fan-out link behind PMP device. It does not
2922 select the host link. 2842 select the host link. DEVICE number of 15 selects the
2923 host link and device 2843 host link and device attached to it.
2924 2844
2925 The VAL specifies the 2845 The VAL specifies the configuration to force. As long
2926 as there is no ambigu 2846 as there is no ambiguity, shortcut notation is allowed.
2927 For example, both 1.5 2847 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2848 The following configurations can be forced.
2929 2849
2930 * Cable type: 40c, 80 2850 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2851 Any ID with matching PORT is used.
2932 2852
2933 * SATA link speed lim 2853 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2854
2935 * Transfer mode: pio[ 2855 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2856 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2857 allowed.
2938 2858
2939 * nohrst, nosrst, nor 2859 * nohrst, nosrst, norst: suppress hard, soft and both
2940 resets. 2860 resets.
2941 2861
2942 * rstonce: only attem 2862 * rstonce: only attempt one reset during hot-unplug
2943 link recovery. 2863 link recovery.
2944 2864
2945 * [no]dbdelay: Enable 2865 * [no]dbdelay: Enable or disable the extra 200ms delay
2946 before debouncing a 2866 before debouncing a link PHY and device presence
2947 detection. 2867 detection.
2948 2868
2949 * [no]ncq: Turn on or 2869 * [no]ncq: Turn on or off NCQ.
2950 2870
2951 * [no]ncqtrim: Enable 2871 * [no]ncqtrim: Enable or disable queued DSM TRIM.
2952 2872
2953 * [no]ncqati: Enable 2873 * [no]ncqati: Enable or disable NCQ trim on ATI chipset.
2954 2874
2955 * [no]trim: Enable or 2875 * [no]trim: Enable or disable (unqueued) TRIM.
2956 2876
2957 * trim_zero: Indicate 2877 * trim_zero: Indicate that TRIM command zeroes data.
2958 2878
2959 * max_trim_128m: Set 2879 * max_trim_128m: Set 128M maximum trim size limit.
2960 2880
2961 * [no]dma: Turn on or 2881 * [no]dma: Turn on or off DMA transfers.
2962 2882
2963 * atapi_dmadir: Enabl 2883 * atapi_dmadir: Enable ATAPI DMADIR bridge support.
2964 2884
2965 * atapi_mod16_dma: En 2885 * atapi_mod16_dma: Enable the use of ATAPI DMA for
2966 commands that are n 2886 commands that are not a multiple of 16 bytes.
2967 2887
2968 * [no]dmalog: Enable 2888 * [no]dmalog: Enable or disable the use of the
2969 READ LOG DMA EXT co 2889 READ LOG DMA EXT command to access logs.
2970 2890
2971 * [no]iddevlog: Enabl 2891 * [no]iddevlog: Enable or disable access to the
2972 identify device dat 2892 identify device data log.
2973 2893
2974 * [no]logdir: Enable 2894 * [no]logdir: Enable or disable access to the general
2975 purpose log directo 2895 purpose log directory.
2976 2896
2977 * max_sec_128: Set tr 2897 * max_sec_128: Set transfer size limit to 128 sectors.
2978 2898
2979 * max_sec_1024: Set o 2899 * max_sec_1024: Set or clear transfer size limit to
2980 1024 sectors. 2900 1024 sectors.
2981 2901
2982 * max_sec_lba48: Set 2902 * max_sec_lba48: Set or clear transfer size limit to
2983 65535 sectors. 2903 65535 sectors.
2984 2904
2985 * [no]lpm: Enable or 2905 * [no]lpm: Enable or disable link power management.
2986 2906
2987 * [no]setxfer: Indica 2907 * [no]setxfer: Indicate if transfer speed mode setting
2988 should be skipped. 2908 should be skipped.
2989 2909
2990 * [no]fua: Disable or 2910 * [no]fua: Disable or enable FUA (Force Unit Access)
2991 support for devices 2911 support for devices supporting this feature.
2992 2912
2993 * dump_id: Dump IDENT 2913 * dump_id: Dump IDENTIFY data.
2994 2914
2995 * disable: Disable th 2915 * disable: Disable this device.
2996 2916
2997 If there are multiple 2917 If there are multiple matching configurations changing
2998 the same attribute, t 2918 the same attribute, the last one is used.
2999 2919
3000 load_ramdisk= [RAM] [Deprecated] 2920 load_ramdisk= [RAM] [Deprecated]
3001 2921
3002 lockd.nlm_grace_period=P [NFS] Assig 2922 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2923 Format: <integer>
3004 2924
3005 lockd.nlm_tcpport=N [NFS] Assign 2925 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2926 Format: <integer>
3007 2927
3008 lockd.nlm_timeout=T [NFS] Assign 2928 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2929 Format: <integer>
3010 2930
3011 lockd.nlm_udpport=M [NFS] Assign 2931 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2932 Format: <integer>
3013 2933
3014 lockdown= [SECURITY,EARLY] !! 2934 lockdown= [SECURITY]
3015 { integrity | confide 2935 { integrity | confidentiality }
3016 Enable the kernel loc 2936 Enable the kernel lockdown feature. If set to
3017 integrity, kernel fea 2937 integrity, kernel features that allow userland to
3018 modify the running ke 2938 modify the running kernel are disabled. If set to
3019 confidentiality, kern 2939 confidentiality, kernel features that allow userland
3020 to extract confidenti 2940 to extract confidential information from the kernel
3021 are also disabled. 2941 are also disabled.
3022 2942
3023 locktorture.acq_writer_lim= [KNL] 2943 locktorture.acq_writer_lim= [KNL]
3024 Set the time limit in 2944 Set the time limit in jiffies for a lock
3025 acquisition. Acquisi 2945 acquisition. Acquisitions exceeding this limit
3026 will result in a spla 2946 will result in a splat once they do complete.
3027 2947
3028 locktorture.bind_readers= [KNL] 2948 locktorture.bind_readers= [KNL]
3029 Specify the list of C 2949 Specify the list of CPUs to which the readers are
3030 to be bound. 2950 to be bound.
3031 2951
3032 locktorture.bind_writers= [KNL] 2952 locktorture.bind_writers= [KNL]
3033 Specify the list of C 2953 Specify the list of CPUs to which the writers are
3034 to be bound. 2954 to be bound.
3035 2955
3036 locktorture.call_rcu_chains= [KNL] 2956 locktorture.call_rcu_chains= [KNL]
3037 Specify the number of 2957 Specify the number of self-propagating call_rcu()
3038 chains to set up. Th 2958 chains to set up. These are used to ensure that
3039 there is a high proba 2959 there is a high probability of an RCU grace period
3040 in progress at any gi 2960 in progress at any given time. Defaults to 0,
3041 which disables these 2961 which disables these call_rcu() chains.
3042 2962
3043 locktorture.long_hold= [KNL] 2963 locktorture.long_hold= [KNL]
3044 Specify the duration 2964 Specify the duration in milliseconds for the
3045 occasional long-durat 2965 occasional long-duration lock hold time. Defaults
3046 to 100 milliseconds. 2966 to 100 milliseconds. Select 0 to disable.
3047 2967
3048 locktorture.nested_locks= [KNL] 2968 locktorture.nested_locks= [KNL]
3049 Specify the maximum l 2969 Specify the maximum lock nesting depth that
3050 locktorture is to exe 2970 locktorture is to exercise, up to a limit of 8
3051 (MAX_NESTED_LOCKS). 2971 (MAX_NESTED_LOCKS). Specify zero to disable.
3052 Note that this parame 2972 Note that this parameter is ineffective on types
3053 of locks that do not 2973 of locks that do not support nested acquisition.
3054 2974
3055 locktorture.nreaders_stress= [KNL] 2975 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2976 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2977 Defaults to being automatically set based on the
3058 number of online CPUs 2978 number of online CPUs.
3059 2979
3060 locktorture.nwriters_stress= [KNL] 2980 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2981 Set the number of locking write-acquisition kthreads.
3062 2982
3063 locktorture.onoff_holdoff= [KNL] 2983 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2984 Set time (s) after boot for CPU-hotplug testing.
3065 2985
3066 locktorture.onoff_interval= [KNL] 2986 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2987 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2988 zero to disable CPU-hotplug testing.
3069 2989
3070 locktorture.rt_boost= [KNL] 2990 locktorture.rt_boost= [KNL]
3071 Do periodic testing o 2991 Do periodic testing of real-time lock priority
3072 boosting. Select 0 t 2992 boosting. Select 0 to disable, 1 to boost
3073 only rt_mutex, and 2 2993 only rt_mutex, and 2 to boost unconditionally.
3074 Defaults to 2, which 2994 Defaults to 2, which might seem to be an
3075 odd choice, but which 2995 odd choice, but which should be harmless for
3076 non-real-time spinloc 2996 non-real-time spinlocks, due to their disabling
3077 of preemption. Note 2997 of preemption. Note that non-realtime mutexes
3078 disable boosting. 2998 disable boosting.
3079 2999
3080 locktorture.rt_boost_factor= [KNL] 3000 locktorture.rt_boost_factor= [KNL]
3081 Number that determine 3001 Number that determines how often and for how
3082 long priority boostin 3002 long priority boosting is exercised. This is
3083 scaled down by the nu 3003 scaled down by the number of writers, so that the
3084 number of boosts per 3004 number of boosts per unit time remains roughly
3085 constant as the numbe 3005 constant as the number of writers increases.
3086 On the other hand, th 3006 On the other hand, the duration of each boost
3087 increases with the nu 3007 increases with the number of writers.
3088 3008
3089 locktorture.shuffle_interval= [KNL] 3009 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 3010 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 3011 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 3012 mode during the locktorture test.
3093 3013
3094 locktorture.shutdown_secs= [KNL] 3014 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 3015 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 3016 is useful for hands-off automated testing.
3097 3017
3098 locktorture.stat_interval= [KNL] 3018 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 3019 Time (s) between statistics printk()s.
3100 3020
3101 locktorture.stutter= [KNL] 3021 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 3022 Time (s) to stutter testing, for example,
3103 specifying five secon 3023 specifying five seconds causes the test to run for
3104 five seconds, wait fo 3024 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 3025 This tests the locking primitive's ability to
3106 transition abruptly t 3026 transition abruptly to and from idle.
3107 3027
3108 locktorture.torture_type= [KNL] 3028 locktorture.torture_type= [KNL]
3109 Specify the locking i 3029 Specify the locking implementation to test.
3110 3030
3111 locktorture.verbose= [KNL] 3031 locktorture.verbose= [KNL]
3112 Enable additional pri 3032 Enable additional printk() statements.
3113 3033
3114 locktorture.writer_fifo= [KNL] 3034 locktorture.writer_fifo= [KNL]
3115 Run the write-side lo 3035 Run the write-side locktorture kthreads at
3116 sched_set_fifo() real 3036 sched_set_fifo() real-time priority.
3117 3037
3118 logibm.irq= [HW,MOUSE] Logitech B 3038 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 3039 Format: <irq>
3120 3040
3121 loglevel= [KNL,EARLY] !! 3041 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 3042 console loglevel will be printed to the console. It can
3124 also be changed with 3043 also be changed with klogd or other programs. The
3125 loglevels are defined 3044 loglevels are defined as follows:
3126 3045
3127 0 (KERN_EMERG) 3046 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 3047 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 3048 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 3049 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 3050 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 3051 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 3052 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 3053 7 (KERN_DEBUG) debug-level messages
3135 3054
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 3055 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 3056 in bytes. n must be a power of two and greater
3138 n must be a power of !! 3057 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 3058 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 3059 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 3060 that allows to increase the default size depending on
3142 parameter that allows !! 3061 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 3062
3146 logo.nologo [FB] Disables display 3063 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 3064 This may be used to provide more screen space for
3148 kernel log messages a 3065 kernel log messages and is useful when debugging
3149 kernel boot problems. 3066 kernel boot problems.
3150 3067
3151 lp=0 [LP] Specify paral 3068 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 3069 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 3070 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 3071 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 3072 specified in addition to the ports) causes
3156 attached prin 3073 attached printers to be reset. Using
3157 lp=port1,port 3074 lp=port1,port2,... specifies the parallel ports
3158 to associate 3075 to associate lp devices with, starting with
3159 lp0. A port s 3076 lp0. A port specification may be 'none' to skip
3160 that lp devic 3077 that lp device, or a parport name such as
3161 'parport0'. S 3078 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 3079 port specification list means that device IDs
3163 from each por 3080 from each port should be examined, to see if
3164 an IEEE 1284- 3081 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 3082 so, the driver will manage that printer.
3166 See also head 3083 See also header of drivers/char/lp.c.
3167 3084
3168 lpj=n [KNL] 3085 lpj=n [KNL]
3169 Sets loops_per_jiffy 3086 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 3087 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 3088 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 3089 the correct value for your kernel, boot with normal
3173 autodetection and see 3090 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 3091 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 3092 which is likely to cause problems if your CPUs need
3176 significantly diverge 3093 significantly divergent settings. An incorrect value
3177 will cause delays in 3094 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 3095 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 3096 unlikely, in the extreme case this might damage your
3180 hardware. 3097 hardware.
3181 3098
>> 3099 ltpc= [NET]
>> 3100 Format: <io>,<irq>,<dma>
>> 3101
3182 lsm.debug [SECURITY] Enable LSM 3102 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 3103
3184 lsm=lsm1,...,lsmN 3104 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 3105 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 3106 overrides CONFIG_LSM, and the "security=" parameter.
3187 3107
>> 3108 machvec= [IA-64] Force the use of a particular machine-vector
>> 3109 (machvec) in a generic kernel.
>> 3110 Example: machvec=hpzx1
>> 3111
3188 machtype= [Loongson] Share the 3112 machtype= [Loongson] Share the same kernel image file between
3189 different yeeloong la 3113 different yeeloong laptops.
3190 Example: machtype=lem 3114 Example: machtype=lemote-yeeloong-2f-7inch
3191 3115
3192 maxcpus= [SMP,EARLY] Maximum n !! 3116 max_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory greater
>> 3117 than or equal to this physical address is ignored.
>> 3118
>> 3119 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 3120 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 3121 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 3122 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 3123 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 3124 only takes effect during system bootup.
3198 While n=0 is a specia 3125 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 3126 which also disables the IO APIC.
3200 3127
3201 max_loop= [LOOP] The number of 3128 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 3129 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 3130 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 3131 of statically allocating a predefined number, loop
3205 devices can be reques 3132 devices can be requested on-demand with the
3206 /dev/loop-control int 3133 /dev/loop-control interface.
3207 3134
3208 mce [X86-32] Machine Chec 3135 mce [X86-32] Machine Check Exception
3209 3136
3210 mce=option [X86-64] See Document 3137 mce=option [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
3211 3138
3212 md= [HW] RAID subsystems 3139 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 3140 See Documentation/admin-guide/md.rst.
3214 3141
3215 mdacon= [MDA] 3142 mdacon= [MDA]
3216 Format: <first>,<last 3143 Format: <first>,<last>
3217 Specifies range of co 3144 Specifies range of consoles to be captured by the MDA.
3218 3145
3219 mds= [X86,INTEL,EARLY] !! 3146 mds= [X86,INTEL]
3220 Control mitigation fo 3147 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 3148 Sampling (MDS) vulnerability.
3222 3149
3223 Certain CPUs are vuln 3150 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 3151 internal buffers which can forward information to a
3225 disclosure gadget und 3152 disclosure gadget under certain conditions.
3226 3153
3227 In vulnerable process 3154 In vulnerable processors, the speculatively
3228 forwarded data can be 3155 forwarded data can be used in a cache side channel
3229 attack, to access dat 3156 attack, to access data to which the attacker does
3230 not have direct acces 3157 not have direct access.
3231 3158
3232 This parameter contro 3159 This parameter controls the MDS mitigation. The
3233 options are: 3160 options are:
3234 3161
3235 full - Enable M 3162 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 3163 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 3164 SMT on vulnerable CPUs
3238 off - Uncondit 3165 off - Unconditionally disable MDS mitigation
3239 3166
3240 On TAA-affected machi 3167 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 3168 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 3169 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 3170 this mitigation, you need to specify tsx_async_abort=off
3244 too. 3171 too.
3245 3172
3246 Not specifying this o 3173 Not specifying this option is equivalent to
3247 mds=full. 3174 mds=full.
3248 3175
3249 For details see: Docu 3176 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 3177
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 3178 mem=nn[KMG] [HEXAGON] Set the memory size.
3252 Must be specified, ot 3179 Must be specified, otherwise memory size will be 0.
3253 3180
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc !! 3181 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3255 of memory Amount of m !! 3182 Amount of memory to be used in cases as follows:
3256 as follows: <<
3257 3183
3258 1 for test; 3184 1 for test;
3259 2 when the kernel is 3185 2 when the kernel is not able to see the whole system memory;
3260 3 memory that lies af 3186 3 memory that lies after 'mem=' boundary is excluded from
3261 the hypervisor, then 3187 the hypervisor, then assigned to KVM guests.
3262 4 to limit the memory 3188 4 to limit the memory available for kdump kernel.
3263 3189
3264 [ARC,MICROBLAZE] - th 3190 [ARC,MICROBLAZE] - the limit applies only to low memory,
3265 high memory is not af 3191 high memory is not affected.
3266 3192
3267 [ARM64] - only limits 3193 [ARM64] - only limits memory covered by the linear
3268 mapping. The NOMAP re 3194 mapping. The NOMAP regions are not affected.
3269 3195
3270 [X86] Work as limitin 3196 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 3197 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 3198 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 3199 belonging to unused RAM.
3274 3200
3275 Note that this only t 3201 Note that this only takes effects during boot time since
3276 in above case 3, memo 3202 in above case 3, memory may need be hot added after boot
3277 if system memory of h 3203 if system memory of hypervisor is not sufficient.
3278 3204
3279 mem=nn[KMG]@ss[KMG] 3205 mem=nn[KMG]@ss[KMG]
3280 [ARM,MIPS,EARLY] - ov !! 3206 [ARM,MIPS] - override the memory layout reported by
3281 reported by firmware. !! 3207 firmware.
3282 Define a memory regio 3208 Define a memory region of size nn[KMG] starting at
3283 ss[KMG]. 3209 ss[KMG].
3284 Multiple different re 3210 Multiple different regions can be specified with
3285 multiple mem= paramet 3211 multiple mem= parameters on the command line.
3286 3212
3287 mem=nopentium [BUGS=X86-32] Disable 3213 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 3214 memory.
3289 3215
3290 memblock=debug [KNL,EARLY] Enable me !! 3216 memblock=debug [KNL] Enable memblock debug messages.
3291 3217
3292 memchunk=nn[KMG] 3218 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 3219 [KNL,SH] Allow user to override the default size for
3294 per-device physically 3220 per-device physically contiguous DMA buffers.
3295 3221
3296 memhp_default_state=online/offline/on 3222 memhp_default_state=online/offline/online_kernel/online_movable
3297 [KNL] Set the initial 3223 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 3224 onlining policy. If not specified, the default value is
3299 set according to the 3225 set according to the
3300 CONFIG_MEMORY_HOTPLUG 3226 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 3227 option.
3302 See Documentation/adm 3228 See Documentation/admin-guide/mm/memory-hotplug.rst.
3303 3229
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 3230 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 3231 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 3232 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 3233 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 3234 option description.
3309 3235
3310 memmap=nn[KMG]@ss[KMG] 3236 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 3237 [KNL, X86, MIPS, XTENSA] Force usage of a specific region of memory.
3312 Region of memory to b 3238 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 3239 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 3240 which limits max address to nn[KMG].
3315 Multiple different re 3241 Multiple different regions can be specified,
3316 comma delimited. 3242 comma delimited.
3317 Example: 3243 Example:
3318 memmap=100M@2 3244 memmap=100M@2G,100M#3G,1G!1024G
3319 3245
3320 memmap=nn[KMG]#ss[KMG] 3246 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 3247 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 3248 Region of memory to be marked is from ss to ss+nn.
3323 3249
3324 memmap=nn[KMG]$ss[KMG] 3250 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 3251 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 3252 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 3253 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 3254 memmap=64K$0x18690000
3329 or 3255 or
3330 memmap=0x100 3256 memmap=0x10000$0x18690000
3331 Some bootloaders may 3257 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 3258 like Grub2, otherwise '$' and the following number
3333 will be eaten. 3259 will be eaten.
3334 3260
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 3261 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 3262 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 3263 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 3264 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 3265 and is NVDIMM or ADR memory.
3340 3266
3341 memmap=<size>%<offset>-<oldtype>+<new 3267 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 3268 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 3269 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 3270 out, the whole region will be marked as <newtype>,
3345 even if previously un 3271 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 3272 out, matching memory will be removed. Types are
3347 specified as e820 typ 3273 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 3274 3 = ACPI, 12 = PRAM.
3349 3275
3350 memory_corruption_check=0/1 [X86,EARL !! 3276 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 3277 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 3278 memory when doing things like suspend/resume.
3353 Setting this option w 3279 Setting this option will scan the memory
3354 looking for corruptio 3280 looking for corruption. Enabling this will
3355 both detect corruptio 3281 both detect corruption and prevent the kernel
3356 from using the memory 3282 from using the memory being corrupted.
3357 However, its intended 3283 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 3284 repeatable BIOS-originated corruption always
3359 affects the same memo 3285 affects the same memory, you can use memmap=
3360 to prevent the kernel 3286 to prevent the kernel from using that memory.
3361 3287
3362 memory_corruption_check_size=size [X8 !! 3288 memory_corruption_check_size=size [X86]
3363 By default it checks 3289 By default it checks for corruption in the low
3364 64k, making this memo 3290 64k, making this memory unavailable for normal
3365 use. Use this parame 3291 use. Use this parameter to scan for
3366 corruption in more or 3292 corruption in more or less memory.
3367 3293
3368 memory_corruption_check_period=second !! 3294 memory_corruption_check_period=seconds [X86]
3369 By default it checks 3295 By default it checks for corruption every 60
3370 seconds. Use this pa 3296 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 3297 other rate. 0 disables periodic checking.
3372 3298
3373 memory_hotplug.memmap_on_memory 3299 memory_hotplug.memmap_on_memory
3374 [KNL,X86,ARM] Boolean 3300 [KNL,X86,ARM] Boolean flag to enable this feature.
3375 Format: {on | off (de 3301 Format: {on | off (default)}
3376 When enabled, runtime 3302 When enabled, runtime hotplugged memory will
3377 allocate its internal 3303 allocate its internal metadata (struct pages,
3378 those vmemmap pages c 3304 those vmemmap pages cannot be optimized even
3379 if hugetlb_free_vmemm 3305 if hugetlb_free_vmemmap is enabled) from the
3380 hotadded memory which 3306 hotadded memory which will allow to hotadd a
3381 lot of memory without 3307 lot of memory without requiring additional
3382 memory to do so. 3308 memory to do so.
3383 This feature is disab 3309 This feature is disabled by default because it
3384 has some implication 3310 has some implication on large (e.g. GB)
3385 allocations in some c 3311 allocations in some configurations (e.g. small
3386 memory blocks). 3312 memory blocks).
3387 The state of the flag 3313 The state of the flag can be read in
3388 /sys/module/memory_ho 3314 /sys/module/memory_hotplug/parameters/memmap_on_memory.
3389 Note that even when e 3315 Note that even when enabled, there are a few cases where
3390 the feature is not ef 3316 the feature is not effective.
3391 3317
3392 memtest= [KNL,X86,ARM,M68K,PPC !! 3318 memtest= [KNL,X86,ARM,M68K,PPC,RISCV] Enable memtest
3393 Format: <integer> 3319 Format: <integer>
3394 default : 0 <disable> 3320 default : 0 <disable>
3395 Specifies the number 3321 Specifies the number of memtest passes to be
3396 performed. Each pass 3322 performed. Each pass selects another test
3397 pattern from a given 3323 pattern from a given set of patterns. Memtest
3398 fills the memory with 3324 fills the memory with this pattern, validates
3399 memory contents and r 3325 memory contents and reserves bad memory
3400 regions that are dete 3326 regions that are detected.
3401 3327
3402 mem_encrypt= [X86-64] AMD Secure M 3328 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 3329 Valid arguments: on, off
3404 Default: off 3330 Default: off
3405 mem_encrypt=on: 3331 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 3332 mem_encrypt=off: Do not activate SME
3407 3333
3408 Refer to Documentatio 3334 Refer to Documentation/virt/kvm/x86/amd-memory-encryption.rst
3409 for details on when m 3335 for details on when memory encryption can be activated.
3410 3336
3411 mem_sleep_default= [SUSPEND] Def 3337 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 3338 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 3339 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 3340 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 3341 See Documentation/admin-guide/pm/sleep-states.rst.
3416 3342
>> 3343 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 3344 Multi-Function General Purpose Timers on AMD Geode
>> 3345 platforms.
>> 3346
3417 mfgptfix [X86-32] Fix MFGPT ti 3347 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 3348 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 3349 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 3350 problem by letting the user disable the workaround.
3421 3351
3422 mga= [HW,DRM] 3352 mga= [HW,DRM]
3423 3353
3424 microcode.force_minrev= [X86] 3354 microcode.force_minrev= [X86]
3425 Format: <bool> 3355 Format: <bool>
3426 Enable or disable the 3356 Enable or disable the microcode minimal revision
3427 enforcement for the r 3357 enforcement for the runtime microcode loader.
3428 3358
>> 3359 min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this
>> 3360 physical address is ignored.
>> 3361
3429 mini2440= [ARM,HW,KNL] 3362 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 3363 Format:[0..2][b][c][t]
3431 Default: "0tb" 3364 Default: "0tb"
3432 MINI2440 configuratio 3365 MINI2440 configuration specification:
3433 0 - The attached scre 3366 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 3367 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 3368 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 3369 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 3370 the TFT driver, and the framebuffer will be left
3438 unconfigured. 3371 unconfigured.
3439 b - Enable backlight. 3372 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 3373 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 3374 LED. This parameter is not necessary when using the
3442 VGA shield. 3375 VGA shield.
3443 c - Enable the s3c ca 3376 c - Enable the s3c camera interface.
3444 t - Reserved for enab 3377 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 3378 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 3379 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 3380 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ 3381 https://repo.or.cz/w/linux-2.6/mini2440.git
3449 3382
3450 mitigations= 3383 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 3384 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 3385 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 3386 arch-independent options, each of which is an
3454 aggregation of existi 3387 aggregation of existing arch-specific options.
3455 3388
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 3389 off
3460 Disable all o 3390 Disable all optional CPU mitigations. This
3461 improves syst 3391 improves system performance, but it may also
3462 expose users 3392 expose users to several CPU vulnerabilities.
3463 Equivalent to 3393 Equivalent to: if nokaslr then kpti=0 [ARM64]
3464 3394 gather_data_sampling=off [X86]
3465 3395 kvm.nx_huge_pages=off [X86]
3466 3396 l1tf=off [X86]
3467 3397 mds=off [X86]
3468 3398 mmio_stale_data=off [X86]
3469 3399 no_entry_flush [PPC]
3470 3400 no_uaccess_flush [PPC]
3471 3401 nobp=0 [S390]
3472 3402 nopti [X86,PPC]
3473 3403 nospectre_bhb [ARM64]
3474 3404 nospectre_v1 [X86,PPC]
3475 3405 nospectre_v2 [X86,PPC,S390,ARM64]
3476 3406 reg_file_data_sampling=off [X86]
3477 3407 retbleed=off [X86]
3478 <<
3479 3408 spec_store_bypass_disable=off [X86,PPC]
3480 <<
3481 3409 spectre_v2_user=off [X86]
3482 3410 srbds=off [X86,INTEL]
3483 3411 ssbd=force-off [ARM64]
3484 3412 tsx_async_abort=off [X86]
3485 3413
3486 Exceptions: 3414 Exceptions:
3487 3415 This does not have any effect on
3488 3416 kvm.nx_huge_pages when
3489 3417 kvm.nx_huge_pages=force.
3490 3418
3491 auto (default) 3419 auto (default)
3492 Mitigate all 3420 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 3421 enabled, even if it's vulnerable. This is for
3494 users who don 3422 users who don't want to be surprised by SMT
3495 getting disab 3423 getting disabled across kernel upgrades, or who
3496 have other wa 3424 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 3425 Equivalent to: (default behavior)
3498 3426
3499 auto,nosmt 3427 auto,nosmt
3500 Mitigate all 3428 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 3429 if needed. This is for users who always want to
3502 be fully miti 3430 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 3431 Equivalent to: l1tf=flush,nosmt [X86]
3504 3432 mds=full,nosmt [X86]
3505 3433 tsx_async_abort=full,nosmt [X86]
3506 3434 mmio_stale_data=full,nosmt [X86]
3507 3435 retbleed=auto,nosmt [X86]
3508 3436
3509 mminit_loglevel= 3437 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 3438 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 3439 parameter allows control of the logging verbosity for
3512 the additional memory 3440 the additional memory initialisation checks. A value
3513 of 0 disables mminit 3441 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 3442 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 3443 so loglevel=8 may also need to be specified.
3516 3444
3517 mmio_stale_data= 3445 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 3446 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 3447 MMIO Stale Data vulnerabilities.
3520 3448
3521 Processor MMIO Stale 3449 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 3450 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 3451 operation. Exposed data could originate or end in
3524 the same CPU buffers 3452 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 3453 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 3454 is to clear the affected CPU buffers.
3527 3455
3528 This parameter contro 3456 This parameter controls the mitigation. The
3529 options are: 3457 options are:
3530 3458
3531 full - Enable m 3459 full - Enable mitigation on vulnerable CPUs
3532 3460
3533 full,nosmt - Enable m 3461 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 3462 vulnerable CPUs.
3535 3463
3536 off - Uncondit 3464 off - Unconditionally disable mitigation
3537 3465
3538 On MDS or TAA affecte 3466 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 3467 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 3468 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 3469 mitigated with the same mechanism so in order to
3542 disable this mitigati 3470 disable this mitigation, you need to specify
3543 mds=off and tsx_async 3471 mds=off and tsx_async_abort=off too.
3544 3472
3545 Not specifying this o 3473 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 3474 mmio_stale_data=full.
3547 3475
3548 For details see: 3476 For details see:
3549 Documentation/admin-g 3477 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 3478
3551 <module>.async_probe[=<bool>] [KNL] 3479 <module>.async_probe[=<bool>] [KNL]
3552 If no <bool> value is 3480 If no <bool> value is specified or if the value
3553 specified is not a va 3481 specified is not a valid <bool>, enable asynchronous
3554 probe on this module. 3482 probe on this module. Otherwise, enable/disable
3555 asynchronous probe on 3483 asynchronous probe on this module as indicated by the
3556 <bool> value. See als 3484 <bool> value. See also: module.async_probe
3557 3485
3558 module.async_probe=<bool> 3486 module.async_probe=<bool>
3559 [KNL] When set to tru 3487 [KNL] When set to true, modules will use async probing
3560 by default. To enable 3488 by default. To enable/disable async probing for a
3561 specific module, use 3489 specific module, use the module specific control that
3562 is documented under < 3490 is documented under <module>.async_probe. When both
3563 module.async_probe an 3491 module.async_probe and <module>.async_probe are
3564 specified, <module>.a 3492 specified, <module>.async_probe takes precedence for
3565 the specific module. 3493 the specific module.
3566 3494
3567 module.enable_dups_trace 3495 module.enable_dups_trace
3568 [KNL] When CONFIG_MOD 3496 [KNL] When CONFIG_MODULE_DEBUG_AUTOLOAD_DUPS is set,
3569 this means that dupli 3497 this means that duplicate request_module() calls will
3570 trigger a WARN_ON() i 3498 trigger a WARN_ON() instead of a pr_warn(). Note that
3571 if MODULE_DEBUG_AUTOL 3499 if MODULE_DEBUG_AUTOLOAD_DUPS_TRACE is set, WARN_ON()s
3572 will always be issued 3500 will always be issued and this option does nothing.
3573 module.sig_enforce 3501 module.sig_enforce
3574 [KNL] When CONFIG_MOD 3502 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 3503 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 3504 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 3505 is always true, so this option does nothing.
3578 3506
3579 module_blacklist= [KNL] Do not load 3507 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 3508 modules. Useful for debugging problem modules.
3581 3509
3582 mousedev.tap_time= 3510 mousedev.tap_time=
3583 [MOUSE] Maximum time 3511 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 3512 leaving touchpad surface for touch to be considered
3585 a tap and be reported 3513 a tap and be reported as a left button click (for
3586 touchpads working in 3514 touchpads working in absolute mode only).
3587 Format: <msecs> 3515 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 3516 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 3517 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 3518 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 3519 reporting absolute coordinates, such as tablets
3592 3520
3593 movablecore= [KNL,X86,PPC,EARLY] !! 3521 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 3522 Format: nn[KMGTPE] | nn%
3595 This parameter is the 3523 This parameter is the complement to kernelcore=, it
3596 specifies the amount 3524 specifies the amount of memory used for migratable
3597 allocations. If both 3525 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 3526 specified, then kernelcore will be at *least* the
3599 specified value but m 3527 specified value but may be more. If movablecore on its
3600 own is specified, the 3528 own is specified, the administrator must be careful
3601 that the amount of me 3529 that the amount of memory usable for all allocations
3602 is not too small. 3530 is not too small.
3603 3531
3604 movable_node [KNL,EARLY] Boot-time !! 3532 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 3533 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 3534 of such nodes will be usable only for movable
3607 allocations which rul 3535 allocations which rules out almost all kernel
3608 allocations. Use with 3536 allocations. Use with caution!
3609 3537
3610 MTD_Partition= [MTD] 3538 MTD_Partition= [MTD]
3611 Format: <name>,<regio 3539 Format: <name>,<region-number>,<size>,<offset>
3612 3540
3613 MTD_Region= [MTD] Format: 3541 MTD_Region= [MTD] Format:
3614 <name>,<region-number 3542 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 3543
3616 mtdparts= [MTD] 3544 mtdparts= [MTD]
3617 See drivers/mtd/parse 3545 See drivers/mtd/parsers/cmdlinepart.c
3618 3546
>> 3547 mtdset= [ARM]
>> 3548 ARM/S3C2412 JIVE boot control
>> 3549
>> 3550 See arch/arm/mach-s3c/mach-jive.c
>> 3551
3619 mtouchusb.raw_coordinates= 3552 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 3553 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 3554 ('y', default) or cooked coordinates ('n')
3622 3555
3623 mtrr=debug [X86,EARLY] !! 3556 mtrr=debug [X86]
3624 Enable printing debug 3557 Enable printing debug information related to MTRR
3625 registers at boot tim 3558 registers at boot time.
3626 3559
3627 mtrr_chunk_size=nn[KMG,X86,EARLY] !! 3560 mtrr_chunk_size=nn[KMG] [X86]
3628 used for mtrr cleanup 3561 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 3562 that could hold holes aka. UC entries.
3630 3563
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 3564 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 3565 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 3566 Default is 1.
3634 Large value could pre 3567 Large value could prevent small alignment from
3635 using up MTRRs. 3568 using up MTRRs.
3636 3569
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 3570 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 3571 Format: <integer>
3639 Range: 0,7 : spare re 3572 Range: 0,7 : spare reg number
3640 Default : 1 3573 Default : 1
3641 Used for mtrr cleanup 3574 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 3575 Set to 2 or more if your graphical card needs more.
3643 3576
3644 multitce=off [PPC] This parameter 3577 multitce=off [PPC] This parameter disables the use of the pSeries
3645 firmware feature for 3578 firmware feature for updating multiple TCE entries
3646 at a time. 3579 at a time.
3647 3580
3648 n2= [NET] SDL Inc. RISCom 3581 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 3582
3650 netdev= [NET] Network devices 3583 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 3584 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 3585 Note that mem_start is often overloaded to mean
3653 something different a 3586 something different and driver-specific.
3654 This usage is only do 3587 This usage is only documented in each driver source
3655 file if at all. 3588 file if at all.
3656 3589
3657 netpoll.carrier_timeout= 3590 netpoll.carrier_timeout=
3658 [NET] Specifies amoun 3591 [NET] Specifies amount of time (in seconds) that
3659 netpoll should wait f 3592 netpoll should wait for a carrier. By default netpoll
3660 waits 4 seconds. 3593 waits 4 seconds.
3661 3594
3662 nf_conntrack.acct= 3595 nf_conntrack.acct=
3663 [NETFILTER] Enable co 3596 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 3597 0 to disable accounting
3665 1 to enable accountin 3598 1 to enable accounting
3666 Default value is 0. 3599 Default value is 0.
3667 3600
3668 nfs.cache_getent= 3601 nfs.cache_getent=
3669 [NFS] sets the pathna 3602 [NFS] sets the pathname to the program which is used
3670 to update the NFS cli 3603 to update the NFS client cache entries.
3671 3604
3672 nfs.cache_getent_timeout= 3605 nfs.cache_getent_timeout=
3673 [NFS] sets the timeou 3606 [NFS] sets the timeout after which an attempt to
3674 update a cache entry 3607 update a cache entry is deemed to have failed.
3675 3608
3676 nfs.callback_nr_threads= 3609 nfs.callback_nr_threads=
3677 [NFSv4] set the total 3610 [NFSv4] set the total number of threads that the
3678 NFS client will assig 3611 NFS client will assign to service NFSv4 callback
3679 requests. 3612 requests.
3680 3613
3681 nfs.callback_tcpport= 3614 nfs.callback_tcpport=
3682 [NFS] set the TCP por 3615 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 3616 channel should listen.
3684 3617
3685 nfs.delay_retrans= 3618 nfs.delay_retrans=
3686 [NFS] specifies the n 3619 [NFS] specifies the number of times the NFSv4 client
3687 retries the request b 3620 retries the request before returning an EAGAIN error,
3688 after a reply of NFS4 3621 after a reply of NFS4ERR_DELAY from the server.
3689 Only applies if the s 3622 Only applies if the softerr mount option is enabled,
3690 and the specified val 3623 and the specified value is >= 0.
3691 3624
3692 nfs.enable_ino64= 3625 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 3626 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 3627 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 3628 number for the readdir() and stat() syscalls instead
3696 of returning the full 3629 of returning the full 64-bit number.
3697 The default is to ret 3630 The default is to return 64-bit inode numbers.
3698 3631
3699 nfs.idmap_cache_timeout= 3632 nfs.idmap_cache_timeout=
3700 [NFS] set the maximum 3633 [NFS] set the maximum lifetime for idmapper cache
3701 entries. 3634 entries.
3702 3635
3703 nfs.max_session_cb_slots= 3636 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 3637 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 3638 slots the client will assign to the callback
3706 channel. This determi 3639 channel. This determines the maximum number of
3707 callbacks the client 3640 callbacks the client will process in parallel for
3708 a particular server. 3641 a particular server.
3709 3642
3710 nfs.max_session_slots= 3643 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 3644 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 3645 the client will attempt to negotiate with the server.
3713 This limits the numbe 3646 This limits the number of simultaneous RPC requests
3714 that the client can s 3647 that the client can send to the NFSv4.1 server.
3715 Note that there is li 3648 Note that there is little point in setting this
3716 value higher than the 3649 value higher than the max_tcp_slot_table_limit.
3717 3650
3718 nfs.nfs4_disable_idmapping= 3651 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 3652 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 3653 ensures that both the RPC level authentication
3721 scheme and the NFS le 3654 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 3655 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 3656 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 3657 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 3658 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 3659 Servers that do not support this mode of operation
3727 will be autodetected 3660 will be autodetected by the client, and it will fall
3728 back to using the idm 3661 back to using the idmapper.
3729 To turn off this beha 3662 To turn off this behaviour, set the value to '0'.
3730 3663
3731 nfs.nfs4_unique_id= 3664 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 3665 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 3666 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 3667 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 3668 UUID that is generated at system install time.
3736 3669
3737 nfs.recover_lost_locks= 3670 nfs.recover_lost_locks=
3738 [NFSv4] Attempt to re 3671 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 3672 to a lease timeout on the server. Please note that
3740 doing this risks data 3673 doing this risks data corruption, since there are
3741 no guarantees that th 3674 no guarantees that the file will remain unchanged
3742 after the locks are l 3675 after the locks are lost.
3743 If you want to enable 3676 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 3677 attempting to recover these locks, then set this
3745 parameter to '1'. 3678 parameter to '1'.
3746 The default parameter 3679 The default parameter value of '0' causes the kernel
3747 not to attempt recove 3680 not to attempt recovery of lost locks.
3748 3681
3749 nfs.send_implementation_id= 3682 nfs.send_implementation_id=
3750 [NFSv4.1] Send client 3683 [NFSv4.1] Send client implementation identification
3751 information in exchan 3684 information in exchange_id requests.
3752 If zero, no implement 3685 If zero, no implementation identification information
3753 will be sent. 3686 will be sent.
3754 The default is to sen 3687 The default is to send the implementation identification
3755 information. 3688 information.
3756 3689
3757 nfs4.layoutstats_timer= 3690 nfs4.layoutstats_timer=
3758 [NFSv4.2] Change the 3691 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 3692 layoutstats to the pNFS metadata server.
3760 3693
3761 Setting this to value 3694 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 3695 whatever value is the default set by the layout
3763 driver. A non-zero va 3696 driver. A non-zero value sets the minimum interval
3764 in seconds between la 3697 in seconds between layoutstats transmissions.
3765 3698
3766 nfsd.inter_copy_offload_enable= 3699 nfsd.inter_copy_offload_enable=
3767 [NFSv4.2] When set to 3700 [NFSv4.2] When set to 1, the server will support
3768 server-to-server copi 3701 server-to-server copies for which this server is
3769 the destination of th 3702 the destination of the copy.
3770 3703
3771 nfsd.nfs4_disable_idmapping= 3704 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 3705 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 3706 server will return only numeric uids and gids to
3774 clients using auth_sy 3707 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 3708 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 3709 migration from NFSv2/v3.
3777 3710
3778 nfsd.nfsd4_ssc_umount_timeout= 3711 nfsd.nfsd4_ssc_umount_timeout=
3779 [NFSv4.2] When used a 3712 [NFSv4.2] When used as the destination of a
3780 server-to-server copy 3713 server-to-server copy, knfsd temporarily mounts
3781 the source server. I 3714 the source server. It caches the mount in case
3782 it will be needed aga 3715 it will be needed again, and discards it if not
3783 used for the number o 3716 used for the number of milliseconds specified by
3784 this parameter. 3717 this parameter.
3785 3718
3786 nfsaddrs= [NFS] Deprecated. Us 3719 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3787 See Documentation/adm 3720 See Documentation/admin-guide/nfs/nfsroot.rst.
3788 3721
3789 nfsroot= [NFS] nfs root filesy 3722 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3790 See Documentation/adm 3723 See Documentation/admin-guide/nfs/nfsroot.rst.
3791 3724
3792 nfsrootdebug [NFS] enable nfsroot 3725 nfsrootdebug [NFS] enable nfsroot debugging messages.
3793 See Documentation/adm 3726 See Documentation/admin-guide/nfs/nfsroot.rst.
3794 3727
3795 nmi_backtrace.backtrace_idle [KNL] 3728 nmi_backtrace.backtrace_idle [KNL]
3796 Dump stacks even of i 3729 Dump stacks even of idle CPUs in response to an
3797 NMI stack-backtrace r 3730 NMI stack-backtrace request.
3798 3731
3799 nmi_debug= [KNL,SH] Specify one 3732 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 3733 when a NMI is triggered.
3801 Format: [state][,regs 3734 Format: [state][,regs][,debounce][,die]
3802 3735
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 3736 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 3737 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 3738 Valid num: 0 or 1
3806 0 - turn hardlockup d 3739 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 3740 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 3741 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n 3742 timeout occurs (or 'nopanic' to not panic on an NMI
3812 watchdog, if CONFIG_B 3743 watchdog, if CONFIG_BOOTPARAM_HARDLOCKUP_PANIC is set)
3813 To disable both hard 3744 To disable both hard and soft lockup detectors,
3814 please see 'nowatchdo 3745 please see 'nowatchdog'.
3815 This is useful when y 3746 This is useful when you use a panic=... timeout and
3816 need the box quickly 3747 need the box quickly up again.
3817 3748
3818 These settings can be 3749 These settings can be accessed at runtime via
3819 the nmi_watchdog and 3750 the nmi_watchdog and hardlockup_panic sysctls.
3820 3751
3821 no387 [BUGS=X86-32] Tells t 3752 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 3753 emulation library even if a 387 maths coprocessor
3823 is present. 3754 is present.
3824 3755
3825 no4lvl [RISCV,EARLY] Disable !! 3756 no4lvl [RISCV] Disable 4-level and 5-level paging modes. Forces
3826 Forces kernel to use !! 3757 kernel to use 3-level paging instead.
3827 3758
3828 no5lvl [X86-64,RISCV,EARLY] !! 3759 no5lvl [X86-64,RISCV] Disable 5-level paging mode. Forces
3829 kernel to use 4-level 3760 kernel to use 4-level paging instead.
3830 3761
>> 3762 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
>> 3763 caches in the slab allocator. Saves per-node memory,
>> 3764 but will impact performance.
>> 3765
3831 noalign [KNL,ARM] 3766 noalign [KNL,ARM]
3832 3767
3833 noapic [SMP,APIC,EARLY] Tell !! 3768 noaltinstr [S390] Disables alternative instructions patching
>> 3769 (CPU alternatives feature).
>> 3770
>> 3771 noapic [SMP,APIC] Tells the kernel to not make use of any
3834 IOAPICs that may be p 3772 IOAPICs that may be present in the system.
3835 3773
3836 noautogroup Disable scheduler aut 3774 noautogroup Disable scheduler automatic task group creation.
3837 3775
3838 nocache [ARM,EARLY] !! 3776 nocache [ARM]
3839 3777
3840 no_console_suspend 3778 no_console_suspend
3841 [HW] Never suspend th 3779 [HW] Never suspend the console
3842 Disable suspending of 3780 Disable suspending of consoles during suspend and
3843 hibernate operations. 3781 hibernate operations. Once disabled, debugging
3844 messages can reach va 3782 messages can reach various consoles while the rest
3845 of the system is bein 3783 of the system is being put to sleep (ie, while
3846 debugging driver susp 3784 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 3785 not work reliably with all consoles, but is known
3848 to work with serial a 3786 to work with serial and VGA consoles.
3849 To facilitate more fl 3787 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 3788 console_suspend, a printk module parameter to control
3851 it. Users could use c 3789 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 3790 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 3791 turn on/off it dynamically.
3854 3792
3855 no_debug_objects 3793 no_debug_objects
3856 [KNL,EARLY] Disable o !! 3794 [KNL] Disable object debugging
3857 3795
3858 nodsp [SH] Disable hardware 3796 nodsp [SH] Disable hardware DSP at boot time.
3859 3797
3860 noefi [EFI,EARLY] Disable E !! 3798 noefi Disable EFI runtime services support.
>> 3799
>> 3800 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
3861 3801
3862 no_entry_flush [PPC,EARLY] Don't flu !! 3802 noexec [IA-64]
3863 3803
3864 noexec32 [X86-64] 3804 noexec32 [X86-64]
3865 This affects only 32- 3805 This affects only 32-bit executables.
3866 noexec32=on: enable n 3806 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 3807 read doesn't imply executable mappings
3868 noexec32=off: disable 3808 noexec32=off: disable non-executable mappings
3869 read implies 3809 read implies executable mappings
3870 3810
3871 no_file_caps Tells the kernel not 3811 no_file_caps Tells the kernel not to honor file capabilities. The
3872 only way then for a f 3812 only way then for a file to be executed with privilege
3873 is to be setuid root 3813 is to be setuid root or executed by root.
3874 3814
3875 nofpu [MIPS,SH] Disable har 3815 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 3816
3877 nofsgsbase [X86] Disables FSGSBA 3817 nofsgsbase [X86] Disables FSGSBASE instructions.
3878 3818
3879 nofxsr [BUGS=X86-32] Disable 3819 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 3820 register save and restore. The kernel will only save
3881 legacy floating-point 3821 legacy floating-point registers on task switch.
3882 3822
>> 3823 nohalt [IA-64] Tells the kernel not to use the power saving
>> 3824 function PAL_HALT_LIGHT when idle. This increases
>> 3825 power-consumption. On the positive side, it reduces
>> 3826 interrupt wake-up latency, which may improve performance
>> 3827 in certain environments such as networked servers or
>> 3828 real-time systems.
>> 3829
3883 no_hash_pointers 3830 no_hash_pointers
3884 [KNL,EARLY] <<
3885 Force pointers printe 3831 Force pointers printed to the console or buffers to be
3886 unhashed. By default 3832 unhashed. By default, when a pointer is printed via %p
3887 format string, that p 3833 format string, that pointer is "hashed", i.e. obscured
3888 by hashing the pointe 3834 by hashing the pointer value. This is a security feature
3889 that hides actual ker 3835 that hides actual kernel addresses from unprivileged
3890 users, but it also ma 3836 users, but it also makes debugging the kernel more
3891 difficult since unequ 3837 difficult since unequal pointers can no longer be
3892 compared. However, i 3838 compared. However, if this command-line option is
3893 specified, then all n 3839 specified, then all normal pointers will have their true
3894 value printed. This o 3840 value printed. This option should only be specified when
3895 debugging the kernel. 3841 debugging the kernel. Please do not use on production
3896 kernels. 3842 kernels.
3897 3843
3898 nohibernate [HIBERNATION] Disable 3844 nohibernate [HIBERNATION] Disable hibernation and resume.
3899 3845
3900 nohlt [ARM,ARM64,MICROBLAZE !! 3846 nohlt [ARM,ARM64,MICROBLAZE,MIPS,PPC,SH] Forces the kernel to
3901 busy wait in do_idle( 3847 busy wait in do_idle() and not use the arch_cpu_idle()
3902 implementation; requi 3848 implementation; requires CONFIG_GENERIC_IDLE_POLL_SETUP
3903 to be effective. This 3849 to be effective. This is useful on platforms where the
3904 sleep(SH) or wfi(ARM, 3850 sleep(SH) or wfi(ARM,ARM64) instructions do not work
3905 correctly or when doi 3851 correctly or when doing power measurements to evaluate
3906 the impact of the sle 3852 the impact of the sleep instructions. This is also
3907 useful when using JTA 3853 useful when using JTAG debugger.
3908 3854
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA !! 3855 nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings.
3910 3856
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA !! 3857 nohugevmalloc [KNL,X86,PPC,ARM64] Disable kernel huge vmalloc mappings.
3912 3858
3913 nohz= [KNL] Boottime enable 3859 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 3860 Valid arguments: on, off
3915 Default: on 3861 Default: on
3916 3862
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 3863 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 3864 The argument is a cpu list, as described above.
3919 In kernels built with 3865 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 3866 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 3867 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 3868 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 3869 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 3870 just as if they had also been called out in the
3925 rcu_nocbs= boot param 3871 rcu_nocbs= boot parameter.
3926 3872
3927 Note that this argume 3873 Note that this argument takes precedence over
3928 the CONFIG_RCU_NOCB_C 3874 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
3929 3875
3930 noinitrd [RAM] Tells the kerne 3876 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3877 initial RAM disk.
3932 3878
3933 nointremap [X86-64,Intel-IOMMU,E !! 3879 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3880 remapping.
3935 [Deprecated - use int 3881 [Deprecated - use intremap=off]
3936 3882
3937 noinvpcid [X86,EARLY] Disable t !! 3883 nointroute [IA-64]
>> 3884
>> 3885 noinvpcid [X86] Disable the INVPCID cpu feature.
3938 3886
3939 noiotrap [SH] Disables trapped 3887 noiotrap [SH] Disables trapped I/O port accesses.
3940 3888
3941 noirqdebug [X86-32] Disables the 3889 noirqdebug [X86-32] Disables the code which attempts to detect and
3942 disable unhandled int 3890 disable unhandled interrupt sources.
3943 3891
3944 noisapnp [ISAPNP] Disables ISA 3892 noisapnp [ISAPNP] Disables ISA PnP code.
3945 3893
3946 nokaslr [KNL,EARLY] !! 3894 nojitter [IA-64] Disables jitter checking for ITC timers.
>> 3895
>> 3896 nokaslr [KNL]
3947 When CONFIG_RANDOMIZE 3897 When CONFIG_RANDOMIZE_BASE is set, this disables
3948 kernel and module bas 3898 kernel and module base offset ASLR (Address Space
3949 Layout Randomization) 3899 Layout Randomization).
3950 3900
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3901 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3902 fault handling.
3953 3903
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3904 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
>> 3905
>> 3906 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3955 3907
3956 nolapic [X86-32,APIC,EARLY] D !! 3908 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3957 3909
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3910 nomca [IA-64] Disable machine check abort handling
3959 3911
3960 nomce [X86-32] Disable Mach 3912 nomce [X86-32] Disable Machine Check Exception
3961 3913
3962 nomfgpt [X86-32] Disable Mult 3914 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 3915 Timer usage (for AMD Geode machines).
3964 3916
3965 nomodeset Disable kernel modese 3917 nomodeset Disable kernel modesetting. Most systems' firmware
3966 sets up a display mod 3918 sets up a display mode and provides framebuffer memory
3967 for output. With nomo 3919 for output. With nomodeset, DRM and fbdev drivers will
3968 not load if they coul 3920 not load if they could possibly displace the pre-
3969 initialized output. O 3921 initialized output. Only the system framebuffer will
3970 be available for use. 3922 be available for use. The respective drivers will not
3971 perform display-mode 3923 perform display-mode changes or accelerated rendering.
3972 3924
3973 Useful as error fallb 3925 Useful as error fallback, or for testing and debugging.
3974 3926
3975 nomodule Disable module load 3927 nomodule Disable module load
3976 3928
3977 nonmi_ipi [X86] Disable using N 3929 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3930 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3931 irq.
3980 3932
3981 nopat [X86,EARLY] Disable P !! 3933 nopat [X86] Disable PAT (page attribute table extension of
3982 pagetables) support. 3934 pagetables) support.
3983 3935
3984 nopcid [X86-64,EARLY] Disabl !! 3936 nopcid [X86-64] Disable the PCID cpu feature.
3985 3937
3986 nopku [X86] Disable Memory 3938 nopku [X86] Disable Memory Protection Keys CPU feature found
3987 in some Intel CPUs. 3939 in some Intel CPUs.
3988 3940
3989 nopti [X86-64,EARLY] !! 3941 nopti [X86-64]
3990 Equivalent to pti=off 3942 Equivalent to pti=off
3991 3943
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3944 nopv= [X86,XEN,KVM,HYPER_V,VMWARE]
3993 Disables the PV optim 3945 Disables the PV optimizations forcing the guest to run
3994 as generic guest with 3946 as generic guest with no PV drivers. Currently support
3995 XEN HVM, KVM, HYPER_V 3947 XEN HVM, KVM, HYPER_V and VMWARE guest.
3996 3948
3997 nopvspin [X86,XEN,KVM,EARLY] !! 3949 nopvspin [X86,XEN,KVM]
3998 Disables the qspinloc 3950 Disables the qspinlock slow path using PV optimizations
3999 which allow the hyper 3951 which allow the hypervisor to 'idle' the guest on lock
4000 contention. 3952 contention.
4001 3953
4002 norandmaps Don't use address spa 3954 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3955 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3956
4005 noreplace-smp [X86-32,SMP] Don't re 3957 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3958 with UP alternatives
4007 3959
4008 noresume [SWSUSP] Disables res 3960 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3961 space.
4010 3962
>> 3963 nosbagart [IA-64]
>> 3964
4011 no-scroll [VGA] Disables scroll 3965 no-scroll [VGA] Disables scrollback.
4012 This is required for 3966 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3967 reader made by F.H. Papenmeier (Germany).
4014 3968
4015 nosgx [X86-64,SGX,EARLY] Di !! 3969 nosgx [X86-64,SGX] Disables Intel SGX kernel support.
4016 3970
4017 nosmap [PPC,EARLY] !! 3971 nosmap [PPC]
4018 Disable SMAP (Supervi 3972 Disable SMAP (Supervisor Mode Access Prevention)
4019 even if it is support 3973 even if it is supported by processor.
4020 3974
4021 nosmep [PPC64s,EARLY] !! 3975 nosmep [PPC64s]
4022 Disable SMEP (Supervi 3976 Disable SMEP (Supervisor Mode Execution Prevention)
4023 even if it is support 3977 even if it is supported by processor.
4024 3978
4025 nosmp [SMP,EARLY] Tells an !! 3979 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 3980 and disable the IO APIC. legacy for "maxcpus=0".
4027 3981
4028 nosmt [KNL,MIPS,PPC,S390,EA !! 3982 nosmt [KNL,MIPS,PPC,S390] Disable symmetric multithreading (SMT).
4029 Equivalent to smt=1. 3983 Equivalent to smt=1.
4030 3984
4031 [KNL,X86,PPC] Disable 3985 [KNL,X86,PPC] Disable symmetric multithreading (SMT).
4032 nosmt=force: Force di 3986 nosmt=force: Force disable SMT, cannot be undone
4033 via the 3987 via the sysfs control file.
4034 3988
4035 nosoftlockup [KNL] Disable the sof 3989 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3990
4037 nospec_store_bypass_disable 3991 nospec_store_bypass_disable
4038 [HW,EARLY] Disable al !! 3992 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
4039 Store Bypass vulnerab <<
4040 3993
4041 nospectre_bhb [ARM64,EARLY] Disable !! 3994 nospectre_bhb [ARM64] Disable all mitigations for Spectre-BHB (branch
4042 history injection) vu 3995 history injection) vulnerability. System may allow data leaks
4043 with this option. 3996 with this option.
4044 3997
4045 nospectre_v1 [X86,PPC,EARLY] Disab !! 3998 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
4046 (bounds check bypass) 3999 (bounds check bypass). With this option data leaks are
4047 possible in the syste 4000 possible in the system.
4048 4001
4049 nospectre_v2 [X86,PPC_E500,ARM64,E !! 4002 nospectre_v2 [X86,PPC_E500,ARM64] Disable all mitigations for
4050 for the Spectre varia !! 4003 the Spectre variant 2 (indirect branch prediction)
4051 prediction) vulnerabi !! 4004 vulnerability. System may allow data leaks with this
4052 leaks with this optio !! 4005 option.
4053 !! 4006
4054 no-steal-acc [X86,PV_OPS,ARM64,PPC !! 4007 no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES] Disable paravirtualized
4055 Disable paravirtualiz !! 4008 steal time accounting. steal time is computed, but
4056 is computed, but won' !! 4009 won't influence scheduler behaviour
4057 4010
4058 nosync [HW,M68K] Disables sy 4011 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 4012
4060 no_timer_check [X86,APIC] Disables t 4013 no_timer_check [X86,APIC] Disables the code which tests for
4061 broken timer IRQ sour 4014 broken timer IRQ sources.
4062 4015
4063 no_uaccess_flush 4016 no_uaccess_flush
4064 [PPC,EARLY] Don't flu !! 4017 [PPC] Don't flush the L1-D cache after accessing user data.
4065 4018
4066 novmcoredd [KNL,KDUMP] 4019 novmcoredd [KNL,KDUMP]
4067 Disable device dump. 4020 Disable device dump. Device dump allows drivers to
4068 append dump data to v 4021 append dump data to vmcore so you can collect driver
4069 specified debug info. 4022 specified debug info. Drivers can append the data
4070 without any limit and 4023 without any limit and this data is stored in memory,
4071 so this may cause sig 4024 so this may cause significant memory stress. Disabling
4072 device dump can help 4025 device dump can help save memory but the driver debug
4073 data will be no longe 4026 data will be no longer available. This parameter
4074 is only available whe 4027 is only available when CONFIG_PROC_VMCORE_DEVICE_DUMP
4075 is set. 4028 is set.
4076 4029
4077 no-vmw-sched-clock 4030 no-vmw-sched-clock
4078 [X86,PV_OPS,EARLY] Di !! 4031 [X86,PV_OPS] Disable paravirtualized VMware scheduler
4079 scheduler clock and u !! 4032 clock and use the default one.
4080 4033
4081 nowatchdog [KNL] Disable both lo 4034 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 4035 soft-lockup and NMI watchdog (hard-lockup).
4083 4036
4084 nowb [ARM,EARLY] !! 4037 nowb [ARM]
4085 4038
4086 nox2apic [X86-64,APIC,EARLY] D !! 4039 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 4040
4088 NOTE: this parameter 4041 NOTE: this parameter will be ignored on systems with the
4089 LEGACY_XAPIC_DISABLED 4042 LEGACY_XAPIC_DISABLED bit set in the
4090 IA32_XAPIC_DISABLE_ST 4043 IA32_XAPIC_DISABLE_STATUS MSR.
4091 4044
4092 noxsave [BUGS=X86] Disables x 4045 noxsave [BUGS=X86] Disables x86 extended register state save
4093 and restore using xsa 4046 and restore using xsave. The kernel will fallback to
4094 enabling legacy float 4047 enabling legacy floating-point and sse state.
4095 4048
4096 noxsaveopt [X86] Disables xsaveo 4049 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
4097 register states. The 4050 register states. The kernel will fall back to use
4098 xsave to save the sta 4051 xsave to save the states. By using this parameter,
4099 performance of saving 4052 performance of saving the states is degraded because
4100 xsave doesn't support 4053 xsave doesn't support modified optimization while
4101 xsaveopt supports it 4054 xsaveopt supports it on xsaveopt enabled systems.
4102 4055
4103 noxsaves [X86] Disables xsaves 4056 noxsaves [X86] Disables xsaves and xrstors used in saving and
4104 restoring x86 extende 4057 restoring x86 extended register state in compacted
4105 form of xsave area. T 4058 form of xsave area. The kernel will fall back to use
4106 xsaveopt and xrstor t 4059 xsaveopt and xrstor to save and restore the states
4107 in standard form of x 4060 in standard form of xsave area. By using this
4108 parameter, xsave area 4061 parameter, xsave area per process might occupy more
4109 memory on xsaves enab 4062 memory on xsaves enabled systems.
4110 4063
4111 nr_cpus= [SMP,EARLY] Maximum n !! 4064 nps_mtm_hs_ctr= [KNL,ARC]
>> 4065 This parameter sets the maximum duration, in
>> 4066 cycles, each HW thread of the CTOP can run
>> 4067 without interruptions, before HW switches it.
>> 4068 The actual maximum duration is 16 times this
>> 4069 parameter's value.
>> 4070 Format: integer between 1 and 255
>> 4071 Default: 255
>> 4072
>> 4073 nptcg= [IA-64] Override max number of concurrent global TLB
>> 4074 purges which is reported from either PAL_VM_SUMMARY or
>> 4075 SAL PALO.
>> 4076
>> 4077 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4112 could support. nr_cp 4078 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 4079 support 'n' processors. It could be larger than the
4114 number of already plu 4080 number of already plugged CPU during bootup, later in
4115 runtime you can physi 4081 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 4082 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 4083 variables need be pre-allocated for later physical cpu
4118 hot plugging. 4084 hot plugging.
4119 4085
4120 nr_uarts= [SERIAL] maximum numb 4086 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 4087
4122 numa=off [KNL, ARM64, PPC, RIS !! 4088 numa=off [KNL, ARM64, PPC, RISCV, SPARC, X86] Disable NUMA, Only
4123 Disable NUMA, Only se !! 4089 set up a single NUMA node spanning all memory.
4124 spanning all memory. <<
4125 4090
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, 4091 numa_balancing= [KNL,ARM64,PPC,RISCV,S390,X86] Enable or disable automatic
4127 NUMA balancing. 4092 NUMA balancing.
4128 Allowed values are en 4093 Allowed values are enable and disable
4129 4094
4130 numa_zonelist_order= [KNL, BOOT] Sele 4095 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 4096 'node', 'default' can be specified
4132 This can be set from 4097 This can be set from sysctl after boot.
4133 See Documentation/adm 4098 See Documentation/admin-guide/sysctl/vm.rst for details.
4134 4099
4135 ohci1394_dma=early [HW,EARLY] en !! 4100 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor 4101 See Documentation/core-api/debugging-via-ohci1394.rst for more
4137 info. 4102 info.
4138 4103
4139 olpc_ec_timeout= [OLPC] ms delay when 4104 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 4105 Rather than timing out after 20 ms if an EC
4141 command is not proper 4106 command is not properly ACKed, override the length
4142 of the timeout. We h 4107 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 4108 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 4109 interrupts *may* be lost!
4145 4110
4146 omap_mux= [OMAP] Override bootl 4111 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 4112 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 4113 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 4114 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 4115
4151 onenand.bdry= [HW,MTD] Flex-OneNAND 4116 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
4152 4117
4153 Format: [die0_boundar 4118 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
4154 4119
4155 boundary - index of l 4120 boundary - index of last SLC block on Flex-OneNAND.
4156 The remain 4121 The remaining blocks are configured as MLC blocks.
4157 lock - Configure 4122 lock - Configure if Flex-OneNAND boundary should be locked.
4158 Once locke 4123 Once locked, the boundary cannot be changed.
4159 1 indicate 4124 1 indicates lock status, 0 indicates unlock status.
4160 4125
4161 oops=panic [KNL,EARLY] !! 4126 oops=panic Always panic on oopses. Default is to just kill the
4162 Always panic on oopse <<
4163 process, but there is 4127 process, but there is a small probability of
4164 deadlocking the machi 4128 deadlocking the machine.
4165 This will also cause 4129 This will also cause panics on machine check exceptions.
4166 Useful together with 4130 Useful together with panic=30 to trigger a reboot.
4167 4131
4168 page_alloc.shuffle= 4132 page_alloc.shuffle=
4169 [KNL] Boolean flag to 4133 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 4134 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 4135 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 4136 running on a platform with a direct-mapped memory-side
>> 4137 cache, and this parameter can be used to
>> 4138 override/disable that behavior. The state of the flag
>> 4139 can be read from sysfs at:
4173 /sys/module/page_allo 4140 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 4141
4176 page_owner= [KNL,EARLY] Boot-time !! 4142 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 4143 Storage of the information about who allocated
4178 each page is disabled 4144 each page is disabled in default. With this switch,
4179 we can turn it on. 4145 we can turn it on.
4180 on: enable the featur 4146 on: enable the feature
4181 4147
4182 page_poison= [KNL,EARLY] Boot-time !! 4148 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 4149 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 4150 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 4151 off: turn off poisoning (default)
4186 on: turn on poisoning 4152 on: turn on poisoning
4187 4153
4188 page_reporting.page_reporting_order= 4154 page_reporting.page_reporting_order=
4189 [KNL] Minimal page re 4155 [KNL] Minimal page reporting order
4190 Format: <integer> 4156 Format: <integer>
4191 Adjust the minimal pa 4157 Adjust the minimal page reporting order. The page
4192 reporting is disabled !! 4158 reporting is disabled when it exceeds MAX_ORDER.
4193 4159
4194 panic= [KNL] Kernel behaviou 4160 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 4161 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 4162 timeout = 0: wait forever
4197 timeout < 0: reboot i 4163 timeout < 0: reboot immediately
4198 Format: <timeout> 4164 Format: <timeout>
4199 4165
4200 panic_on_taint= [KNL,EARLY] !! 4166 panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
4201 Bitmask for condition <<
4202 Format: <hex>[,nouser 4167 Format: <hex>[,nousertaint]
4203 Hexadecimal bitmask r 4168 Hexadecimal bitmask representing the set of TAINT flags
4204 that will cause the k 4169 that will cause the kernel to panic when add_taint() is
4205 called with any of th 4170 called with any of the flags in this set.
4206 The optional switch " 4171 The optional switch "nousertaint" can be utilized to
4207 prevent userspace for 4172 prevent userspace forced crashes by writing to sysctl
4208 /proc/sys/kernel/tain 4173 /proc/sys/kernel/tainted any flagset matching with the
4209 bitmask set on panic_ 4174 bitmask set on panic_on_taint.
4210 See Documentation/adm 4175 See Documentation/admin-guide/tainted-kernels.rst for
4211 extra details on the 4176 extra details on the taint flags that users can pick
4212 to compose the bitmas 4177 to compose the bitmask to assign to panic_on_taint.
4213 4178
4214 panic_on_warn=1 panic() instead of WA 4179 panic_on_warn=1 panic() instead of WARN(). Useful to cause kdump
4215 on a WARN(). 4180 on a WARN().
4216 4181
4217 panic_print= Bitmask for printing 4182 panic_print= Bitmask for printing system info when panic happens.
4218 User can chose combin 4183 User can chose combination of the following bits:
4219 bit 0: print all task 4184 bit 0: print all tasks info
4220 bit 1: print system m 4185 bit 1: print system memory info
4221 bit 2: print timer in 4186 bit 2: print timer info
4222 bit 3: print locks in 4187 bit 3: print locks info if CONFIG_LOCKDEP is on
4223 bit 4: print ftrace b 4188 bit 4: print ftrace buffer
4224 bit 5: print all prin 4189 bit 5: print all printk messages in buffer
4225 bit 6: print all CPUs 4190 bit 6: print all CPUs backtrace (if available in the arch)
4226 bit 7: print only tas <<
4227 *Be aware* that this 4191 *Be aware* that this option may print a _lot_ of lines,
4228 so there are risks of 4192 so there are risks of losing older messages in the log.
4229 Use this option caref 4193 Use this option carefully, maybe worth to setup a
4230 bigger log buffer wit 4194 bigger log buffer with "log_buf_len" along with this.
4231 4195
4232 parkbd.port= [HW] Parallel port nu 4196 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 4197 connected to, default is 0.
4234 Format: <parport#> 4198 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 4199 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 4200 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 4201 Format: <mode>
4238 4202
4239 parport= [HW,PPT] Specify para 4203 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 4204 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 4205 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 4206 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 4207 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 4208 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 4209 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 4210 should be numbers, or 'auto' (for using detected
4247 settings on that part 4211 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 4212 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 4213 Parallel ports are assigned in the order they
4250 are specified on the 4214 are specified on the command line, starting
4251 with parport0. 4215 with parport0.
4252 4216
4253 parport_init_mode= [HW,PPT] 4217 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 4218 Configure VIA parallel port to operate in
4255 a specific mode. This 4219 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 4220 computer where firmware has no options for setting
4257 up parallel port mode 4221 up parallel port mode and sets it to spp.
4258 Currently this functi 4222 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 4223 Format: [spp|ps2|epp|ecp|ecpepp]
4260 4224
4261 pata_legacy.all= [HW,LIBATA] 4225 pata_legacy.all= [HW,LIBATA]
4262 Format: <int> 4226 Format: <int>
4263 Set to non-zero to pr 4227 Set to non-zero to probe primary and secondary ISA
4264 port ranges on PCI sy 4228 port ranges on PCI systems where no PCI PATA device
4265 has been found at eit 4229 has been found at either range. Disabled by default.
4266 4230
4267 pata_legacy.autospeed= [HW,LIBATA] 4231 pata_legacy.autospeed= [HW,LIBATA]
4268 Format: <int> 4232 Format: <int>
4269 Set to non-zero if a 4233 Set to non-zero if a chip is present that snoops speed
4270 changes. Disabled by 4234 changes. Disabled by default.
4271 4235
4272 pata_legacy.ht6560a= [HW,LIBATA] 4236 pata_legacy.ht6560a= [HW,LIBATA]
4273 Format: <int> 4237 Format: <int>
4274 Set to 1, 2, or 3 for 4238 Set to 1, 2, or 3 for HT 6560A on the primary channel,
4275 the secondary channel 4239 the secondary channel, or both channels respectively.
4276 Disabled by default. 4240 Disabled by default.
4277 4241
4278 pata_legacy.ht6560b= [HW,LIBATA] 4242 pata_legacy.ht6560b= [HW,LIBATA]
4279 Format: <int> 4243 Format: <int>
4280 Set to 1, 2, or 3 for 4244 Set to 1, 2, or 3 for HT 6560B on the primary channel,
4281 the secondary channel 4245 the secondary channel, or both channels respectively.
4282 Disabled by default. 4246 Disabled by default.
4283 4247
4284 pata_legacy.iordy_mask= [HW,LIBATA] 4248 pata_legacy.iordy_mask= [HW,LIBATA]
4285 Format: <int> 4249 Format: <int>
4286 IORDY enable mask. S 4250 IORDY enable mask. Set individual bits to allow IORDY
4287 for the respective ch 4251 for the respective channel. Bit 0 is for the first
4288 legacy channel handle 4252 legacy channel handled by this driver, bit 1 is for
4289 the second channel, a 4253 the second channel, and so on. The sequence will often
4290 correspond to the pri 4254 correspond to the primary legacy channel, the secondary
4291 legacy channel, and s 4255 legacy channel, and so on, but the handling of a PCI
4292 bus and the use of ot 4256 bus and the use of other driver options may interfere
4293 with the sequence. B 4257 with the sequence. By default IORDY is allowed across
4294 all channels. 4258 all channels.
4295 4259
4296 pata_legacy.opti82c46x= [HW,LIBATA] 4260 pata_legacy.opti82c46x= [HW,LIBATA]
4297 Format: <int> 4261 Format: <int>
4298 Set to 1, 2, or 3 for 4262 Set to 1, 2, or 3 for Opti 82c611A on the primary
4299 channel, the secondar 4263 channel, the secondary channel, or both channels
4300 respectively. Disabl 4264 respectively. Disabled by default.
4301 4265
4302 pata_legacy.opti82c611a= [HW,L 4266 pata_legacy.opti82c611a= [HW,LIBATA]
4303 Format: <int> 4267 Format: <int>
4304 Set to 1, 2, or 3 for 4268 Set to 1, 2, or 3 for Opti 82c465MV on the primary
4305 channel, the secondar 4269 channel, the secondary channel, or both channels
4306 respectively. Disabl 4270 respectively. Disabled by default.
4307 4271
4308 pata_legacy.pio_mask= [HW,LIBATA] 4272 pata_legacy.pio_mask= [HW,LIBATA]
4309 Format: <int> 4273 Format: <int>
4310 PIO mode mask for aut 4274 PIO mode mask for autospeed devices. Set individual
4311 bits to allow the use 4275 bits to allow the use of the respective PIO modes.
4312 Bit 0 is for mode 0, 4276 Bit 0 is for mode 0, bit 1 is for mode 1, and so on.
4313 All modes allowed by 4277 All modes allowed by default.
4314 4278
4315 pata_legacy.probe_all= [HW,LIBATA] 4279 pata_legacy.probe_all= [HW,LIBATA]
4316 Format: <int> 4280 Format: <int>
4317 Set to non-zero to pr 4281 Set to non-zero to probe tertiary and further ISA
4318 port ranges on PCI sy 4282 port ranges on PCI systems. Disabled by default.
4319 4283
4320 pata_legacy.probe_mask= [HW,LIBATA] 4284 pata_legacy.probe_mask= [HW,LIBATA]
4321 Format: <int> 4285 Format: <int>
4322 Probe mask for legacy 4286 Probe mask for legacy ISA PATA ports. Depending on
4323 platform configuratio 4287 platform configuration and the use of other driver
4324 options up to 6 legac 4288 options up to 6 legacy ports are supported: 0x1f0,
4325 0x170, 0x1e8, 0x168, 4289 0x170, 0x1e8, 0x168, 0x1e0, 0x160, however probing
4326 of individual ports c 4290 of individual ports can be disabled by setting the
4327 corresponding bits in 4291 corresponding bits in the mask to 1. Bit 0 is for
4328 the first port in the 4292 the first port in the list above (0x1f0), and so on.
4329 By default all suppor 4293 By default all supported ports are probed.
4330 4294
4331 pata_legacy.qdi= [HW,LIBATA] 4295 pata_legacy.qdi= [HW,LIBATA]
4332 Format: <int> 4296 Format: <int>
4333 Set to non-zero to pr 4297 Set to non-zero to probe QDI controllers. By default
4334 set to 1 if CONFIG_PA 4298 set to 1 if CONFIG_PATA_QDI_MODULE, 0 otherwise.
4335 4299
4336 pata_legacy.winbond= [HW,LIBATA] 4300 pata_legacy.winbond= [HW,LIBATA]
4337 Format: <int> 4301 Format: <int>
4338 Set to non-zero to pr 4302 Set to non-zero to probe Winbond controllers. Use
4339 the standard I/O port 4303 the standard I/O port (0x130) if 1, otherwise the
4340 value given is the I/ 4304 value given is the I/O port to use (typically 0x1b0).
4341 By default set to 1 i 4305 By default set to 1 if CONFIG_PATA_WINBOND_VLB_MODULE,
4342 0 otherwise. 4306 0 otherwise.
4343 4307
4344 pata_platform.pio_mask= [HW,LIBATA] 4308 pata_platform.pio_mask= [HW,LIBATA]
4345 Format: <int> 4309 Format: <int>
4346 Supported PIO mode ma 4310 Supported PIO mode mask. Set individual bits to allow
4347 the use of the respec 4311 the use of the respective PIO modes. Bit 0 is for
4348 mode 0, bit 1 is for 4312 mode 0, bit 1 is for mode 1, and so on. Mode 0 only
4349 allowed by default. 4313 allowed by default.
4350 4314
4351 pause_on_oops=<int> 4315 pause_on_oops=<int>
4352 Halt all CPUs after t 4316 Halt all CPUs after the first oops has been printed for
4353 the specified number 4317 the specified number of seconds. This is to be used if
4354 your oopses keep scro 4318 your oopses keep scrolling off the screen.
4355 4319
4356 pcbit= [HW,ISDN] 4320 pcbit= [HW,ISDN]
4357 4321
4358 pci=option[,option...] [PCI,EARLY] v !! 4322 pci=option[,option...] [PCI] various PCI subsystem options.
4359 4323
4360 Some options 4324 Some options herein operate on a specific device
4361 or a set of d 4325 or a set of devices (<pci_dev>). These are
4362 specified in 4326 specified in one of the following formats:
4363 4327
4364 [<domain>:]<b 4328 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 4329 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 4330
4367 Note: the fir 4331 Note: the first format specifies a PCI
4368 bus/device/fu 4332 bus/device/function address which may change
4369 if new hardwa 4333 if new hardware is inserted, if motherboard
4370 firmware chan 4334 firmware changes, or due to changes caused
4371 by other kern 4335 by other kernel parameters. If the
4372 domain is lef 4336 domain is left unspecified, it is
4373 taken to be z 4337 taken to be zero. Optionally, a path
4374 to a device t 4338 to a device through multiple device/function
4375 addresses can 4339 addresses can be specified after the base
4376 address (this 4340 address (this is more robust against
4377 renumbering i 4341 renumbering issues). The second format
4378 selects devic 4342 selects devices using IDs from the
4379 configuration 4343 configuration space which may match multiple
4380 devices in th 4344 devices in the system.
4381 4345
4382 earlydump dump PCI conf 4346 earlydump dump PCI config space before the kernel
4383 changes anyth 4347 changes anything
4384 off [X86] don't p 4348 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 4349 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 4350 the hardware directly. Use this if your machine
4387 has a non-sta 4351 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 4352 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 4353 hardware access methods are allowed. Use this
4390 if you experi 4354 if you experience crashes upon bootup and you
4391 suspect they 4355 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 4356 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 4357 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 4358 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 4359 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 4360 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 4361 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 4362 bus number. The config space is then accessed
4399 through ports 4363 through ports 0xC000-0xCFFF).
4400 See http://wi 4364 See http://wiki.osdev.org/PCI for more info
4401 on the config 4365 on the configuration access mechanisms.
4402 noaer [PCIE] If the 4366 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 4367 enabled, this kernel boot option can be used to
4404 disable the u 4368 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 4369 nodomains [PCI] Disable support for multiple PCI
4406 root domains 4370 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 4371 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 4372 Configuration
4409 check_enable_amd_mmconf [X86] 4373 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 4374 properly configured MMIO access to PCI
4411 config space 4375 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 4376 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 4377 enabled, this kernel boot option can be used to
4414 disable the u 4378 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 4379 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 4380 Safety option to keep boot IRQs enabled. This
4417 should never 4381 should never be necessary.
4418 ioapicreroute [APIC] Enable 4382 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 4383 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 4384 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 4385 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 4386 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 4387 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 4388 a chipset where boot IRQs cannot be disabled.
4425 The opposite 4389 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 4390 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 4391 routing table. These calls are known to be buggy
4428 on several ma 4392 on several machines and they hang the machine
4429 when used, bu 4393 when used, but on other computers it's the only
4430 way to get th 4394 way to get the interrupt routing table. Try
4431 this option i 4395 this option if the kernel is unable to allocate
4432 IRQs or disco 4396 IRQs or discover secondary PCI buses on your
4433 motherboard. 4397 motherboard.
4434 rom [X86] Assign 4398 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 4399 Use with caution as certain devices share
4436 address decod 4400 address decoders between ROMs and other
4437 resources. 4401 resources.
4438 norom [X86] Do not 4402 norom [X86] Do not assign address space to
4439 expansion ROM 4403 expansion ROMs that do not already have
4440 BIOS assigned 4404 BIOS assigned address ranges.
4441 nobar [X86] Do not 4405 nobar [X86] Do not assign address space to the
4442 BARs that wer 4406 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 4407 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 4408 assigned automatically to PCI devices. You can
4445 make the kern 4409 make the kernel exclude IRQs of your ISA cards
4446 this way. 4410 this way.
4447 pirqaddr=0xAAAAA [X86] 4411 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 4412 of the PIRQ table (normally generated
4449 by the BIOS) 4413 by the BIOS) if it is outside the
4450 F0000h-100000 4414 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 4415 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 4416 useful if the kernel is unable to find your
4453 secondary bus 4417 secondary buses and you want to tell it
4454 explicitly wh 4418 explicitly which ones they are.
4455 assign-busses [X86] Always 4419 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 4420 numbers ourselves, overriding
4457 whatever the 4421 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 4422 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 4423 in the BIOS $PIR table. This is needed on
4460 some systems 4424 some systems with broken BIOSes, notably
4461 some HP Pavil 4425 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 4426 notebooks. This will have no effect if ACPI
4463 IRQ routing i 4427 IRQ routing is enabled.
4464 noacpi [X86] Do not 4428 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 4429 or for PCI scanning.
4466 use_crs [X86] Use PCI 4430 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 4431 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 4432 is enabled by default. If you need to use this,
4469 please report 4433 please report a bug.
4470 nocrs [X86] Ignore 4434 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 4435 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 4436 use_e820 [X86] Use E820 reservations to exclude parts of
4473 PCI host brid 4437 PCI host bridge windows. This is a workaround
4474 for BIOS defe 4438 for BIOS defects in host bridge _CRS methods.
4475 If you need t 4439 If you need to use this, please report a bug to
4476 <linux-pci@vge 4440 <linux-pci@vger.kernel.org>.
4477 no_e820 [X86] Ignore 4441 no_e820 [X86] Ignore E820 reservations for PCI host
4478 bridge window 4442 bridge windows. This is the default on modern
4479 hardware. If 4443 hardware. If you need to use this, please report
4480 a bug to <linu 4444 a bug to <linux-pci@vger.kernel.org>.
4481 routeirq Do IRQ routin 4445 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 4446 This is normally done in pci_enable_device(),
4483 so this optio 4447 so this option is a temporary workaround
4484 for broken dr 4448 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 4449 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 4450 handle more pci cards
4487 noearly [X86] Don't d 4451 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 4452 This might help on some broken boards which
4489 machine check 4453 machine check when some devices' config space
4490 is read. But 4454 is read. But various workarounds are disabled
4491 and some IOMM 4455 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 4456 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 4457 This sorting is done to get a device
4494 order compati 4458 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 4459 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 4460 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 4461 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 4462 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 4463 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 4464 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 4465 based on its parent bus. Also set MRRS (Max
4502 Read Request 4466 Read Request Size) to the largest supported
4503 value (no lar 4467 value (no larger than the MPS that the device
4504 or bus can su 4468 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 4469 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 4470 every device is guaranteed to support. This
4507 configuration 4471 configuration allows peer-to-peer DMA between
4508 any pair of d 4472 any pair of devices, possibly at the cost of
4509 reduced perfo 4473 reduced performance. This also guarantees
4510 that hot-adde 4474 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 4475 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 4476 reserved for the CardBus bridge's IO window.
4513 The default v 4477 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 4478 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 4479 reserved for the CardBus bridge's memory
4516 window. The d 4480 window. The default value is 64 megabytes.
4517 resource_alignment= 4481 resource_alignment=
4518 Format: 4482 Format:
4519 [<order of ali 4483 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 4484 Specifies alignment and device to reassign
4521 aligned memor 4485 aligned memory resources. How to
4522 specify the d 4486 specify the device is described above.
4523 If <order of 4487 If <order of align> is not specified,
4524 PAGE_SIZE is 4488 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri 4489 A PCI-PCI bridge can be specified if resource
4526 windows need 4490 windows need to be expanded.
4527 To specify th 4491 To specify the alignment for several
4528 instances of 4492 instances of a device, the PCI vendor,
4529 device, subve 4493 device, subvendor, and subdevice may be
4530 specified, e. 4494 specified, e.g., 12@pci:8086:9c22:103c:198f
4531 for 4096-byte 4495 for 4096-byte alignment.
4532 ecrc= Enable/disabl 4496 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR 4497 end-to-end CRC checking). Only effective if
4534 OS has native 4498 OS has native AER control (either granted by
4535 ACPI _OSC or 4499 ACPI _OSC or forced via "pcie_ports=native")
4536 bios: Use BIO 4500 bios: Use BIOS/firmware settings. This is the
4537 the default. 4501 the default.
4538 off: Turn ECR 4502 off: Turn ECRC off
4539 on: Turn ECRC 4503 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 4504 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 4505 reserved for hotplug bridge's IO window.
4542 Default size 4506 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f 4507 hpmmiosize=nn[KMG] The fixed amount of bus space which is
4544 reserved for 4508 reserved for hotplug bridge's MMIO window.
4545 Default size 4509 Default size is 2 megabytes.
4546 hpmmioprefsize=nn[KMG] The f 4510 hpmmioprefsize=nn[KMG] The fixed amount of bus space which is
4547 reserved for 4511 reserved for hotplug bridge's MMIO_PREF window.
4548 Default size 4512 Default size is 2 megabytes.
4549 hpmemsize=nn[KMG] The f 4513 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for 4514 reserved for hotplug bridge's MMIO and
4551 MMIO_PREF win 4515 MMIO_PREF window.
4552 Default size 4516 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 4517 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 4518 reserved for buses below a hotplug bridge.
4555 Default is 1. 4519 Default is 1.
4556 realloc= Enable/disabl 4520 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 4521 if allocations done by BIOS are too small to
4558 accommodate r 4522 accommodate resources required by all child
4559 devices. 4523 devices.
4560 off: Turn rea 4524 off: Turn realloc off
4561 on: Turn real 4525 on: Turn realloc on
4562 realloc same as reall 4526 realloc same as realloc=on
4563 noari do not use PC 4527 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 4528 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 4529 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 4530 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 4531 only look for one device below a PCIe downstream
4568 port. 4532 port.
4569 big_root_window Try to add a 4533 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 4534 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 4535 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 4536 Adding the window is slightly risky (it may
4573 conflict with 4537 conflict with unreported devices), so this
4574 taints the ke 4538 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 4539 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 4540 Specify one or more PCI devices (in the format
4577 specified abo 4541 specified above) separated by semicolons.
4578 Each device s 4542 Each device specified will have the PCI ACS
4579 redirect capa 4543 redirect capabilities forced off which will
4580 allow P2P tra 4544 allow P2P traffic between devices through
4581 bridges witho 4545 bridges without forcing it upstream. Note:
4582 this removes 4546 this removes isolation between devices and
4583 may put more 4547 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 4548 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 4549 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore 4550 norid [S390] ignore the RID field and force use of
4619 one PCI domai 4551 one PCI domain per PCI function
4620 4552
4621 pcie_aspm= [PCIE] Forcibly enabl !! 4553 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 4554 Management.
4623 off Don't touch ASPM conf !! 4555 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 4556 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 4557 WARNING: Forcing ASPM on may cause system lockups.
4627 4558
4628 pcie_ports= [PCIE] PCIe port serv 4559 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 4560 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 4561 even if the platform doesn't give the OS permission to
4631 use them. This may c 4562 use them. This may cause conflicts if the platform
4632 also tries to use the 4563 also tries to use these services.
4633 dpc-native Use native PC 4564 dpc-native Use native PCIe service for DPC only. May
4634 cause conflic 4565 cause conflicts if firmware uses AER or DPC.
4635 compat Disable native PCIe s 4566 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 4567 hotplug).
4637 4568
4638 pcie_port_pm= [PCIE] PCIe port powe 4569 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 4570 off Disable power management of all PCIe ports
4640 force Forcibly enable power 4571 force Forcibly enable power management of all PCIe ports
4641 4572
4642 pcie_pme= [PCIE,PM] Native PCIe 4573 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 4574 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 4575 all PCIe root ports use INTx for all services).
4645 4576
4646 pcmv= [HW,PCMCIA] BadgePAD 4577 pcmv= [HW,PCMCIA] BadgePAD 4
4647 4578
4648 pd_ignore_unused 4579 pd_ignore_unused
4649 [PM] 4580 [PM]
4650 Keep all power-domain 4581 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 4582 even if no driver has claimed them. This is useful
4652 for debug and develop 4583 for debug and development, but should not be
4653 needed on a platform 4584 needed on a platform with proper driver support.
4654 4585
4655 pdcchassis= [PARISC,HW] Disable/E 4586 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 4587 boot time.
4657 Format: { 0 | 1 } 4588 Format: { 0 | 1 }
4658 See arch/parisc/kerne 4589 See arch/parisc/kernel/pdc_chassis.c
4659 4590
4660 percpu_alloc= [MM,EARLY] !! 4591 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 4592 Currently supported values are "embed" and "page".
4663 Archs may support sub 4593 Archs may support subset or none of the selections.
4664 See comments in mm/pe 4594 See comments in mm/percpu.c for details on each
4665 allocator. This para 4595 allocator. This parameter is primarily for debugging
4666 and performance compa 4596 and performance comparison.
4667 4597
4668 pirq= [SMP,APIC] Manual mp- 4598 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc 4599 See Documentation/arch/x86/i386/IO-APIC.rst.
4670 4600
4671 plip= [PPT,NET] Parallel po 4601 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 4602 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 4603 See also Documentation/admin-guide/parport.rst.
4674 4604
4675 pmtmr= [X86] Manual setup of 4605 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 4606 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 4607 e.g. pmtmr=0x508
4678 4608
4679 pmu_override= [PPC] Override the PM 4609 pmu_override= [PPC] Override the PMU.
4680 This option takes ove 4610 This option takes over the PMU facility, so it is no
4681 longer usable by perf 4611 longer usable by perf. Setting this option starts the
4682 PMU counters by setti 4612 PMU counters by setting MMCR0 to 0 (the FC bit is
4683 cleared). If a number 4613 cleared). If a number is given, then MMCR1 is set to
4684 that number, otherwis 4614 that number, otherwise (e.g., 'pmu_override=on'), MMCR1
4685 remains 0. 4615 remains 0.
4686 4616
4687 pm_debug_messages [SUSPEND,KNL] 4617 pm_debug_messages [SUSPEND,KNL]
4688 Enable suspend/resume 4618 Enable suspend/resume debug messages during boot up.
4689 4619
4690 pnp.debug=1 [PNP] 4620 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 4621 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 4622 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 4623 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 4624 current resource usage; turning this on also shows
4695 possible settings and 4625 possible settings and some assignment information.
4696 4626
4697 pnpacpi= [ACPI] 4627 pnpacpi= [ACPI]
4698 { off } 4628 { off }
4699 4629
4700 pnpbios= [ISAPNP] 4630 pnpbios= [ISAPNP]
4701 { on | off | curr | r 4631 { on | off | curr | res | no-curr | no-res }
4702 4632
4703 pnp_reserve_irq= 4633 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 4634 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 4635
4706 pnp_reserve_dma= 4636 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 4637 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 4638
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 4639 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 4640 Ranges are in pairs (I/O port base and size).
4711 4641
4712 pnp_reserve_mem= 4642 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 4643 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 4644 autoconfiguration.
4715 Ranges are in pairs ( 4645 Ranges are in pairs (memory base and size).
4716 4646
4717 ports= [IP_VS_FTP] IPVS ftp 4647 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 4648 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 4649 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 4650 may be specified.
4721 Format: <port>,<port> 4651 Format: <port>,<port>....
4722 4652
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 4653 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 4654 It specifically disables cpuidle and sets the
4730 platform machine desc 4655 platform machine description specific power_save
4731 function to NULL. On 4656 function to NULL. On Idle the CPU just reduces
4732 execution priority. 4657 execution priority.
4733 4658
4734 ppc_strict_facility_enable 4659 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 4660 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 4661 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 4662 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 4663 There is some performance impact when enabling this.
4739 4664
4740 ppc_tm= [PPC,EARLY] !! 4665 ppc_tm= [PPC]
4741 Format: {"off"} 4666 Format: {"off"}
4742 Disable Hardware Tran 4667 Disable Hardware Transactional Memory
4743 4668
4744 preempt= [KNL] 4669 preempt= [KNL]
4745 Select preemption mod 4670 Select preemption mode if you have CONFIG_PREEMPT_DYNAMIC
4746 none - Limited to con 4671 none - Limited to cond_resched() calls
4747 voluntary - Limited t 4672 voluntary - Limited to cond_resched() and might_sleep() calls
4748 full - Any section th 4673 full - Any section that isn't explicitly preempt disabled
4749 can be preempt !! 4674 can be preempted anytime.
4750 contended spin <<
4751 explicitly pre <<
4752 4675
4753 print-fatal-signals= 4676 print-fatal-signals=
4754 [KNL] debug: print fa 4677 [KNL] debug: print fatal signals
4755 4678
4756 If enabled, warn abou 4679 If enabled, warn about various signal handling
4757 related application a 4680 related application anomalies: too many signals,
4758 too many POSIX.1 time 4681 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 4682 coredump - etc.
4760 4683
4761 If you hit the warnin 4684 If you hit the warning due to signal overflow,
4762 you might want to try 4685 you might want to try "ulimit -i unlimited".
4763 4686
4764 default: off. 4687 default: off.
4765 4688
4766 printk.always_kmsg_dump= 4689 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 4690 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 4691 panics
4769 Format: <bool> (1/Y/ 4692 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 4693 default: disabled
4771 4694
4772 printk.console_no_auto_verbose= 4695 printk.console_no_auto_verbose=
4773 Disable console logle 4696 Disable console loglevel raise on oops, panic
4774 or lockdep-detected i 4697 or lockdep-detected issues (only if lock debug is on).
4775 With an exception to 4698 With an exception to setups with low baudrate on
4776 serial console, keepi 4699 serial console, keeping this 0 is a good choice
4777 in order to provide m 4700 in order to provide more debug information.
4778 Format: <bool> 4701 Format: <bool>
4779 default: 0 (auto_verb 4702 default: 0 (auto_verbose is enabled)
4780 4703
4781 printk.devkmsg={on,off,ratelimit} 4704 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 4705 Control writing to /dev/kmsg.
4783 on - unlimited loggin 4706 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 4707 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 4708 ratelimit - ratelimit the logging
4786 Default: ratelimit 4709 Default: ratelimit
4787 4710
4788 printk.time= Show timing data pref 4711 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 4712 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 4713
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] 4714 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 4715 Limit processor to maximum C-state
4803 max_cstate=9 override 4716 max_cstate=9 overrides any DMI blacklist limit.
4804 4717
4805 processor.nocst [HW,ACPI] 4718 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 4719 Ignore the _CST method to determine C-states,
4807 instead using the leg 4720 instead using the legacy FADT method
4808 4721
4809 profile= [KNL] Enable kernel p 4722 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 4723 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 4724 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 4725 [defaults to kernel profiling]
4813 Param: "schedule" - p 4726 Param: "schedule" - profile schedule points.
>> 4727 Param: "sleep" - profile D-state sleeping (millisecs).
>> 4728 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 4729 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 4730 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 4731 statistical time based profiling.
4817 4732
4818 prompt_ramdisk= [RAM] [Deprecated] 4733 prompt_ramdisk= [RAM] [Deprecated]
4819 4734
4820 prot_virt= [S390] enable hosting 4735 prot_virt= [S390] enable hosting protected virtual machines
4821 isolated from the hyp 4736 isolated from the hypervisor (if hardware supports
4822 that). If enabled, th !! 4737 that).
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> 4738 Format: <bool>
4826 4739
4827 psi= [KNL] Enable or disab 4740 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 4741 tracking.
4829 Format: <bool> 4742 Format: <bool>
4830 4743
4831 psmouse.proto= [HW,MOUSE] Highest PS 4744 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 4745 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 4746 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 4747 per second.
4835 psmouse.resetafter= [HW,MOUSE] 4748 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 4749 Try to reset the device after so many bad packets
4837 (0 = never). 4750 (0 = never).
4838 psmouse.resolution= 4751 psmouse.resolution=
4839 [HW,MOUSE] Set desire 4752 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 4753 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 4754 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 4755 0 = disabled, 1 = enabled (default).
4843 4756
4844 pstore.backend= Specify the name of t 4757 pstore.backend= Specify the name of the pstore backend to use
4845 4758
4846 pti= [X86-64] Control Page 4759 pti= [X86-64] Control Page Table Isolation of user and
4847 kernel address spaces 4760 kernel address spaces. Disabling this feature
4848 removes hardening, bu 4761 removes hardening, but improves performance of
4849 system calls and inte 4762 system calls and interrupts.
4850 4763
4851 on - unconditionall 4764 on - unconditionally enable
4852 off - unconditionall 4765 off - unconditionally disable
4853 auto - kernel detects 4766 auto - kernel detects whether your CPU model is
4854 vulnerable to 4767 vulnerable to issues that PTI mitigates
4855 4768
4856 Not specifying this o 4769 Not specifying this option is equivalent to pti=auto.
4857 4770
4858 pty.legacy_count= 4771 pty.legacy_count=
4859 [KNL] Number of legac 4772 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 4773 default number.
4861 4774
4862 quiet [KNL,EARLY] Disable m !! 4775 quiet [KNL] Disable most log messages
4863 4776
4864 r128= [HW,DRM] 4777 r128= [HW,DRM]
4865 4778
4866 radix_hcall_invalidate=on [PPC/PSERI 4779 radix_hcall_invalidate=on [PPC/PSERIES]
4867 Disable RADIX GTSE fe 4780 Disable RADIX GTSE feature and use hcall for TLB
4868 invalidate. 4781 invalidate.
4869 4782
4870 raid= [HW,RAID] 4783 raid= [HW,RAID]
4871 See Documentation/adm 4784 See Documentation/admin-guide/md.rst.
4872 4785
4873 ramdisk_size= [RAM] Sizes of RAM di 4786 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm 4787 See Documentation/admin-guide/blockdev/ramdisk.rst.
4875 4788
4876 ramdisk_start= [RAM] RAM disk image 4789 ramdisk_start= [RAM] RAM disk image start address
4877 4790
4878 random.trust_cpu=off 4791 random.trust_cpu=off
4879 [KNL,EARLY] Disable t !! 4792 [KNL] Disable trusting the use of the CPU's
4880 random number generat 4793 random number generator (if available) to
4881 initialize the kernel 4794 initialize the kernel's RNG.
4882 4795
4883 random.trust_bootloader=off 4796 random.trust_bootloader=off
4884 [KNL,EARLY] Disable t !! 4797 [KNL] Disable trusting the use of the a seed
4885 passed by the bootloa 4798 passed by the bootloader (if available) to
4886 initialize the kernel 4799 initialize the kernel's RNG.
4887 4800
4888 randomize_kstack_offset= 4801 randomize_kstack_offset=
4889 [KNL,EARLY] Enable or !! 4802 [KNL] Enable or disable kernel stack offset
4890 randomization, which 4803 randomization, which provides roughly 5 bits of
4891 entropy, frustrating 4804 entropy, frustrating memory corruption attacks
4892 that depend on stack 4805 that depend on stack address determinism or
4893 cross-syscall address 4806 cross-syscall address exposures. This is only
4894 available on architec 4807 available on architectures that have defined
4895 CONFIG_HAVE_ARCH_RAND 4808 CONFIG_HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET.
4896 Format: <bool> (1/Y/ 4809 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4897 Default is CONFIG_RAN 4810 Default is CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT.
4898 4811
4899 ras=option[,option,...] [KNL] RAS-spe 4812 ras=option[,option,...] [KNL] RAS-specific options
4900 4813
4901 cec_disable [X86] 4814 cec_disable [X86]
4902 Disable the C 4815 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 4816 see CONFIG_RAS_CEC help text.
4904 4817
4905 rcu_nocbs[=cpu-list] 4818 rcu_nocbs[=cpu-list]
4906 [KNL] The optional ar 4819 [KNL] The optional argument is a cpu list,
4907 as described above. 4820 as described above.
4908 4821
4909 In kernels built with 4822 In kernels built with CONFIG_RCU_NOCB_CPU=y,
4910 enable the no-callbac 4823 enable the no-callback CPU mode, which prevents
4911 such CPUs' callbacks 4824 such CPUs' callbacks from being invoked in
4912 softirq context. Inv 4825 softirq context. Invocation of such CPUs' RCU
4913 callbacks will instea 4826 callbacks will instead be offloaded to "rcuox/N"
4914 kthreads created for 4827 kthreads created for that purpose, where "x" is
4915 "p" for RCU-preempt, 4828 "p" for RCU-preempt, "s" for RCU-sched, and "g"
4916 for the kthreads that 4829 for the kthreads that mediate grace periods; and
4917 "N" is the CPU number 4830 "N" is the CPU number. This reduces OS jitter on
4918 the offloaded CPUs, w 4831 the offloaded CPUs, which can be useful for HPC
4919 and real-time workloa 4832 and real-time workloads. It can also improve
4920 energy efficiency for 4833 energy efficiency for asymmetric multiprocessors.
4921 4834
4922 If a cpulist is passe 4835 If a cpulist is passed as an argument, the specified
4923 list of CPUs is set t 4836 list of CPUs is set to no-callback mode from boot.
4924 4837
4925 Otherwise, if the '=' 4838 Otherwise, if the '=' sign and the cpulist
4926 arguments are omitted 4839 arguments are omitted, no CPU will be set to
4927 no-callback mode from 4840 no-callback mode from boot but the mode may be
4928 toggled at runtime vi 4841 toggled at runtime via cpusets.
4929 4842
4930 Note that this argume 4843 Note that this argument takes precedence over
4931 the CONFIG_RCU_NOCB_C 4844 the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
4932 4845
4933 rcu_nocb_poll [KNL] 4846 rcu_nocb_poll [KNL]
4934 Rather than requiring 4847 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 4848 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 4849 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 4850 make these kthreads poll for callbacks.
4938 This improves the rea 4851 This improves the real-time response for the
4939 offloaded CPUs by rel 4852 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 4853 wake up the corresponding kthread, but degrades
4941 energy efficiency by 4854 energy efficiency by requiring that the kthreads
4942 periodically wake up 4855 periodically wake up to do the polling.
4943 4856
4944 rcutree.blimit= [KNL] 4857 rcutree.blimit= [KNL]
4945 Set maximum number of 4858 Set maximum number of finished RCU callbacks to
4946 process in one batch. 4859 process in one batch.
4947 4860
4948 rcutree.do_rcu_barrier= [KNL] 4861 rcutree.do_rcu_barrier= [KNL]
4949 Request a call to rcu 4862 Request a call to rcu_barrier(). This is
4950 throttled so that use 4863 throttled so that userspace tests can safely
4951 hammer on the sysfs v 4864 hammer on the sysfs variable if they so choose.
4952 If triggered before t 4865 If triggered before the RCU grace-period machinery
4953 is fully active, this 4866 is fully active, this will error out with EAGAIN.
4954 4867
4955 rcutree.dump_tree= [KNL] 4868 rcutree.dump_tree= [KNL]
4956 Dump the structure of 4869 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 4870 out at early boot. This is used for diagnostic
4958 purposes, to verify c 4871 purposes, to verify correct tree setup.
4959 4872
4960 rcutree.gp_cleanup_delay= [KNL] 4873 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 4874 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 4875 RCU grace-period cleanup.
4963 4876
4964 rcutree.gp_init_delay= [KNL] 4877 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 4878 Set the number of jiffies to delay each step of
4966 RCU grace-period init 4879 RCU grace-period initialization.
4967 4880
4968 rcutree.gp_preinit_delay= [KNL] 4881 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 4882 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 4883 RCU grace-period pre-initialization, that is,
4971 the propagation of re 4884 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 4885 the rcu_node combining tree.
4973 4886
4974 rcutree.jiffies_till_first_fqs= [KNL] 4887 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 4888 Set delay from grace-period initialization to
4976 first attempt to forc 4889 first attempt to force quiescent states.
4977 Units are jiffies, mi 4890 Units are jiffies, minimum value is zero,
4978 and maximum value is 4891 and maximum value is HZ.
4979 4892
4980 rcutree.jiffies_till_next_fqs= [KNL] 4893 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 4894 Set delay between subsequent attempts to force
4982 quiescent states. Un 4895 quiescent states. Units are jiffies, minimum
4983 value is one, and max 4896 value is one, and maximum value is HZ.
4984 4897
4985 rcutree.jiffies_till_sched_qs= [KNL] 4898 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 4899 Set required age in jiffies for a
4987 given grace period be 4900 given grace period before RCU starts
4988 soliciting quiescent- 4901 soliciting quiescent-state help from
4989 rcu_note_context_swit 4902 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 4903 If not specified, the kernel will calculate
4991 a value based on the 4904 a value based on the most recent settings
4992 of rcutree.jiffies_ti 4905 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 4906 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 4907 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 4908 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 4909 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 4910 overwritten.
4998 4911
4999 rcutree.kthread_prio= [KNL,BOOT] 4912 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 4913 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 4914 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 4915 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 4916 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 4917 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 4918 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 4919 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 4920 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 4921 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is 4922 When RCU_NOCB_CPU is set, also adjust the
5010 priority of NOCB call 4923 priority of NOCB callback kthreads.
5011 4924
5012 rcutree.nocb_nobypass_lim_per_jiffy= 4925 rcutree.nocb_nobypass_lim_per_jiffy= [KNL]
5013 On callback-offloaded 4926 On callback-offloaded (rcu_nocbs) CPUs,
5014 RCU reduces the lock 4927 RCU reduces the lock contention that would
5015 otherwise be caused b 4928 otherwise be caused by callback floods through
5016 use of the ->nocb_byp 4929 use of the ->nocb_bypass list. However, in the
5017 common non-flooded ca 4930 common non-flooded case, RCU queues directly to
5018 the main ->cblist in 4931 the main ->cblist in order to avoid the extra
5019 overhead of the ->noc 4932 overhead of the ->nocb_bypass list and its lock.
5020 But if there are too 4933 But if there are too many callbacks queued during
5021 a single jiffy, RCU p 4934 a single jiffy, RCU pre-queues the callbacks into
5022 the ->nocb_bypass que 4935 the ->nocb_bypass queue. The definition of "too
5023 many" is supplied by 4936 many" is supplied by this kernel boot parameter.
5024 4937
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] 4938 rcutree.qhimark= [KNL]
5034 Set threshold of queu 4939 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 4940 batch limiting is disabled.
5036 4941
5037 rcutree.qlowmark= [KNL] 4942 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 4943 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 4944 batch limiting is re-enabled.
5040 4945
5041 rcutree.qovld= [KNL] 4946 rcutree.qovld= [KNL]
5042 Set threshold of queu 4947 Set threshold of queued RCU callbacks beyond which
5043 RCU's force-quiescent 4948 RCU's force-quiescent-state scan will aggressively
5044 enlist help from cond 4949 enlist help from cond_resched() and sched IPIs to
5045 help CPUs more quickl 4950 help CPUs more quickly reach quiescent states.
5046 Set to less than zero 4951 Set to less than zero to make this be set based
5047 on rcutree.qhimark at 4952 on rcutree.qhimark at boot time and to zero to
5048 disable more aggressi 4953 disable more aggressive help enlistment.
5049 4954
5050 rcutree.rcu_delay_page_cache_fill_mse 4955 rcutree.rcu_delay_page_cache_fill_msec= [KNL]
5051 Set the page-cache re 4956 Set the page-cache refill delay (in milliseconds)
5052 in response to low-me 4957 in response to low-memory conditions. The range
5053 of permitted values i 4958 of permitted values is in the range 0:100000.
5054 4959
5055 rcutree.rcu_divisor= [KNL] 4960 rcutree.rcu_divisor= [KNL]
5056 Set the shift-right c 4961 Set the shift-right count to use to compute
5057 the callback-invocati 4962 the callback-invocation batch limit bl from
5058 the number of callbac 4963 the number of callbacks queued on this CPU.
5059 The result will be bo 4964 The result will be bounded below by the value of
5060 the rcutree.blimit ke 4965 the rcutree.blimit kernel parameter. Every bl
5061 callbacks, the softir 4966 callbacks, the softirq handler will exit in
5062 order to allow the CP 4967 order to allow the CPU to do other work.
5063 4968
5064 Please note that this 4969 Please note that this callback-invocation batch
5065 limit applies only to 4970 limit applies only to non-offloaded callback
5066 invocation. Offloade 4971 invocation. Offloaded callbacks are instead
5067 invoked in the contex 4972 invoked in the context of an rcuoc kthread, which
5068 scheduler will preemp 4973 scheduler will preempt as it does any other task.
5069 4974
5070 rcutree.rcu_fanout_exact= [KNL] 4975 rcutree.rcu_fanout_exact= [KNL]
5071 Disable autobalancing 4976 Disable autobalancing of the rcu_node combining
5072 tree. This is used b 4977 tree. This is used by rcutorture, and might
5073 possibly be useful fo 4978 possibly be useful for architectures having high
5074 cache-to-cache transf 4979 cache-to-cache transfer latencies.
5075 4980
5076 rcutree.rcu_fanout_leaf= [KNL] 4981 rcutree.rcu_fanout_leaf= [KNL]
5077 Change the number of 4982 Change the number of CPUs assigned to each
5078 leaf rcu_node structu 4983 leaf rcu_node structure. Useful for very
5079 large systems, which 4984 large systems, which will choose the value 64,
5080 and for NUMA systems 4985 and for NUMA systems with large remote-access
5081 latencies, which will 4986 latencies, which will choose a value aligned
5082 with the appropriate 4987 with the appropriate hardware boundaries.
5083 4988
5084 rcutree.rcu_min_cached_objs= [KNL] 4989 rcutree.rcu_min_cached_objs= [KNL]
5085 Minimum number of obj 4990 Minimum number of objects which are cached and
5086 maintained per one CP 4991 maintained per one CPU. Object size is equal
5087 to PAGE_SIZE. The cac 4992 to PAGE_SIZE. The cache allows to reduce the
5088 pressure to page allo 4993 pressure to page allocator, also it makes the
5089 whole algorithm to be 4994 whole algorithm to behave better in low memory
5090 condition. 4995 condition.
5091 4996
5092 rcutree.rcu_nocb_gp_stride= [KNL] 4997 rcutree.rcu_nocb_gp_stride= [KNL]
5093 Set the number of NOC 4998 Set the number of NOCB callback kthreads in
5094 each group, which def 4999 each group, which defaults to the square root
5095 of the number of CPUs 5000 of the number of CPUs. Larger numbers reduce
5096 the wakeup overhead o 5001 the wakeup overhead on the global grace-period
5097 kthread, but increase 5002 kthread, but increases that same overhead on
5098 each group's NOCB gra 5003 each group's NOCB grace-period kthread.
5099 5004
5100 rcutree.rcu_kick_kthreads= [KNL] 5005 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 5006 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 5007 wake_up() if it sleeps three times longer than
5103 it should at force-qu 5008 it should at force-quiescent-state time.
5104 This wake_up() will b 5009 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 5010 WARN_ONCE() splat and an ftrace_dump().
5106 5011
5107 rcutree.rcu_resched_ns= [KNL] 5012 rcutree.rcu_resched_ns= [KNL]
5108 Limit the time spend 5013 Limit the time spend invoking a batch of RCU
5109 callbacks to the spec 5014 callbacks to the specified number of nanoseconds.
5110 By default, this limi 5015 By default, this limit is checked only once
5111 every 32 callbacks in 5016 every 32 callbacks in order to limit the pain
5112 inflicted by local_cl 5017 inflicted by local_clock() overhead.
5113 5018
5114 rcutree.rcu_unlock_delay= [KNL] 5019 rcutree.rcu_unlock_delay= [KNL]
5115 In CONFIG_RCU_STRICT_ 5020 In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels,
5116 this specifies an rcu 5021 this specifies an rcu_read_unlock()-time delay
5117 in microseconds. Thi 5022 in microseconds. This defaults to zero.
5118 Larger delays increas 5023 Larger delays increase the probability of
5119 catching RCU pointer 5024 catching RCU pointer leaks, that is, buggy use
5120 of RCU-protected poin 5025 of RCU-protected pointers after the relevant
5121 rcu_read_unlock() has 5026 rcu_read_unlock() has completed.
5122 5027
5123 rcutree.sysrq_rcu= [KNL] 5028 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 5029 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 5030 rcu_node tree with an eye towards determining
5126 why a new grace perio 5031 why a new grace period has not yet started.
5127 5032
5128 rcutree.use_softirq= [KNL] 5033 rcutree.use_softirq= [KNL]
5129 If set to zero, move 5034 If set to zero, move all RCU_SOFTIRQ processing to
5130 per-CPU rcuc kthreads 5035 per-CPU rcuc kthreads. Defaults to a non-zero
5131 value, meaning that R 5036 value, meaning that RCU_SOFTIRQ is used by default.
5132 Specify rcutree.use_s 5037 Specify rcutree.use_softirq=0 to use rcuc kthreads.
5133 5038
5134 But note that CONFIG_ 5039 But note that CONFIG_PREEMPT_RT=y kernels disable
5135 this kernel boot para 5040 this kernel boot parameter, forcibly setting it
5136 to zero. 5041 to zero.
5137 5042
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] 5043 rcuscale.gp_async= [KNL]
5158 Measure performance o 5044 Measure performance of asynchronous
5159 grace-period primitiv 5045 grace-period primitives such as call_rcu().
5160 5046
5161 rcuscale.gp_async_max= [KNL] 5047 rcuscale.gp_async_max= [KNL]
5162 Specify the maximum n 5048 Specify the maximum number of outstanding
5163 callbacks per writer 5049 callbacks per writer thread. When a writer
5164 thread exceeds this l 5050 thread exceeds this limit, it invokes the
5165 corresponding flavor 5051 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 5052 previously posted callbacks to drain.
5167 5053
5168 rcuscale.gp_exp= [KNL] 5054 rcuscale.gp_exp= [KNL]
5169 Measure performance o 5055 Measure performance of expedited synchronous
5170 grace-period primitiv 5056 grace-period primitives.
5171 5057
5172 rcuscale.holdoff= [KNL] 5058 rcuscale.holdoff= [KNL]
5173 Set test-start holdof 5059 Set test-start holdoff period. The purpose of
5174 this parameter is to 5060 this parameter is to delay the start of the
5175 test until boot compl 5061 test until boot completes in order to avoid
5176 interference. 5062 interference.
5177 5063
5178 rcuscale.kfree_by_call_rcu= [KNL] 5064 rcuscale.kfree_by_call_rcu= [KNL]
5179 In kernels built with 5065 In kernels built with CONFIG_RCU_LAZY=y, test
5180 call_rcu() instead of 5066 call_rcu() instead of kfree_rcu().
5181 5067
5182 rcuscale.kfree_mult= [KNL] 5068 rcuscale.kfree_mult= [KNL]
5183 Instead of allocating 5069 Instead of allocating an object of size kfree_obj,
5184 allocate one of kfree 5070 allocate one of kfree_mult * sizeof(kfree_obj).
5185 Defaults to 1. 5071 Defaults to 1.
5186 5072
5187 rcuscale.kfree_rcu_test= [KNL] 5073 rcuscale.kfree_rcu_test= [KNL]
5188 Set to measure perfor 5074 Set to measure performance of kfree_rcu() flooding.
5189 5075
5190 rcuscale.kfree_rcu_test_double= [KNL] 5076 rcuscale.kfree_rcu_test_double= [KNL]
5191 Test the double-argum 5077 Test the double-argument variant of kfree_rcu().
5192 If this parameter has 5078 If this parameter has the same value as
5193 rcuscale.kfree_rcu_te 5079 rcuscale.kfree_rcu_test_single, both the single-
5194 and double-argument v 5080 and double-argument variants are tested.
5195 5081
5196 rcuscale.kfree_rcu_test_single= [KNL] 5082 rcuscale.kfree_rcu_test_single= [KNL]
5197 Test the single-argum 5083 Test the single-argument variant of kfree_rcu().
5198 If this parameter has 5084 If this parameter has the same value as
5199 rcuscale.kfree_rcu_te 5085 rcuscale.kfree_rcu_test_double, both the single-
5200 and double-argument v 5086 and double-argument variants are tested.
5201 5087
5202 rcuscale.kfree_nthreads= [KNL] 5088 rcuscale.kfree_nthreads= [KNL]
5203 The number of threads 5089 The number of threads running loops of kfree_rcu().
5204 5090
5205 rcuscale.kfree_alloc_num= [KNL] 5091 rcuscale.kfree_alloc_num= [KNL]
5206 Number of allocations 5092 Number of allocations and frees done in an iteration.
5207 5093
5208 rcuscale.kfree_loops= [KNL] 5094 rcuscale.kfree_loops= [KNL]
5209 Number of loops doing 5095 Number of loops doing rcuscale.kfree_alloc_num number
5210 of allocations and fr 5096 of allocations and frees.
5211 5097
5212 rcuscale.minruntime= [KNL] 5098 rcuscale.minruntime= [KNL]
5213 Set the minimum test 5099 Set the minimum test run time in seconds. This
5214 does not affect the d 5100 does not affect the data-collection interval,
5215 but instead allows be 5101 but instead allows better measurement of things
5216 like CPU consumption. 5102 like CPU consumption.
5217 5103
5218 rcuscale.nreaders= [KNL] 5104 rcuscale.nreaders= [KNL]
5219 Set number of RCU rea 5105 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 5106 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 5107 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 5108 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 5109 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 5110 A value of "n" less than or equal to -N selects
5225 a single reader. 5111 a single reader.
5226 5112
5227 rcuscale.nwriters= [KNL] 5113 rcuscale.nwriters= [KNL]
5228 Set number of RCU wri 5114 Set number of RCU writers. The values operate
5229 the same as for rcusc 5115 the same as for rcuscale.nreaders.
5230 N, where N is the num 5116 N, where N is the number of CPUs
5231 5117
5232 rcuscale.scale_type= [KNL] 5118 rcuscale.scale_type= [KNL]
5233 Specify the RCU imple 5119 Specify the RCU implementation to test.
5234 5120
5235 rcuscale.shutdown= [KNL] 5121 rcuscale.shutdown= [KNL]
5236 Shut the system down 5122 Shut the system down after performance tests
5237 complete. This is us 5123 complete. This is useful for hands-off automated
5238 testing. 5124 testing.
5239 5125
5240 rcuscale.verbose= [KNL] 5126 rcuscale.verbose= [KNL]
5241 Enable additional pri 5127 Enable additional printk() statements.
5242 5128
5243 rcuscale.writer_holdoff= [KNL] 5129 rcuscale.writer_holdoff= [KNL]
5244 Write-side holdoff be 5130 Write-side holdoff between grace periods,
5245 in microseconds. The 5131 in microseconds. The default of zero says
5246 no holdoff. 5132 no holdoff.
5247 5133
5248 rcuscale.writer_holdoff_jiffies= [KNL 5134 rcuscale.writer_holdoff_jiffies= [KNL]
5249 Additional write-side 5135 Additional write-side holdoff between grace
5250 periods, but in jiffi 5136 periods, but in jiffies. The default of zero
5251 says no holdoff. 5137 says no holdoff.
5252 5138
5253 rcutorture.fqs_duration= [KNL] 5139 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 5140 Set duration of force_quiescent_state bursts
5255 in microseconds. 5141 in microseconds.
5256 5142
5257 rcutorture.fqs_holdoff= [KNL] 5143 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 5144 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 5145 in microseconds.
5260 5146
5261 rcutorture.fqs_stutter= [KNL] 5147 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 5148 Set wait time between force_quiescent_state bursts
5263 in seconds. 5149 in seconds.
5264 5150
5265 rcutorture.fwd_progress= [KNL] 5151 rcutorture.fwd_progress= [KNL]
5266 Specifies the number 5152 Specifies the number of kthreads to be used
5267 for RCU grace-period 5153 for RCU grace-period forward-progress testing
5268 for the types of RCU 5154 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread 5155 Defaults to 1 kthread, values less than zero or
5270 greater than the numb 5156 greater than the number of CPUs cause the number
5271 of CPUs to be used. 5157 of CPUs to be used.
5272 5158
5273 rcutorture.fwd_progress_div= [KNL] 5159 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 5160 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 5161 period to do tight-loop forward-progress testing.
5276 5162
5277 rcutorture.fwd_progress_holdoff= [KNL 5163 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 5164 Number of seconds to wait between successive
5279 forward-progress test 5165 forward-progress tests.
5280 5166
5281 rcutorture.fwd_progress_need_resched= 5167 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 5168 Enclose cond_resched() calls within checks for
5283 need_resched() during 5169 need_resched() during tight-loop forward-progress
5284 testing. 5170 testing.
5285 5171
5286 rcutorture.gp_cond= [KNL] 5172 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 5173 Use conditional/asynchronous update-side
5288 primitives, if availa 5174 primitives, if available.
5289 5175
5290 rcutorture.gp_exp= [KNL] 5176 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 5177 Use expedited update-side primitives, if available.
5292 5178
5293 rcutorture.gp_normal= [KNL] 5179 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 5180 Use normal (non-expedited) asynchronous
5295 update-side primitive 5181 update-side primitives, if available.
5296 5182
5297 rcutorture.gp_sync= [KNL] 5183 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 5184 Use normal (non-expedited) synchronous
5299 update-side primitive 5185 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 5186 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 5187 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 5188 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 5189 they are all non-zero.
5304 5190
5305 rcutorture.irqreader= [KNL] 5191 rcutorture.irqreader= [KNL]
5306 Run RCU readers from 5192 Run RCU readers from irq handlers, or, more
5307 accurately, from a ti 5193 accurately, from a timer handler. Not all RCU
5308 flavors take kindly t 5194 flavors take kindly to this sort of thing.
5309 5195
5310 rcutorture.leakpointer= [KNL] 5196 rcutorture.leakpointer= [KNL]
5311 Leak an RCU-protected 5197 Leak an RCU-protected pointer out of the reader.
5312 This can of course re 5198 This can of course result in splats, and is
5313 intended to test the 5199 intended to test the ability of things like
5314 CONFIG_RCU_STRICT_GRA 5200 CONFIG_RCU_STRICT_GRACE_PERIOD=y to detect
5315 such leaks. 5201 such leaks.
5316 5202
5317 rcutorture.n_barrier_cbs= [KNL] 5203 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 5204 Set callbacks/threads for rcu_barrier() testing.
5319 5205
5320 rcutorture.nfakewriters= [KNL] 5206 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 5207 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 5208 stress RCU, they don't participate in the actual
5323 test, hence the "fake 5209 test, hence the "fake".
5324 5210
5325 rcutorture.nocbs_nthreads= [KNL] 5211 rcutorture.nocbs_nthreads= [KNL]
5326 Set number of RCU cal 5212 Set number of RCU callback-offload togglers.
5327 Zero (the default) di 5213 Zero (the default) disables toggling.
5328 5214
5329 rcutorture.nocbs_toggle= [KNL] 5215 rcutorture.nocbs_toggle= [KNL]
5330 Set the delay in mill 5216 Set the delay in milliseconds between successive
5331 callback-offload togg 5217 callback-offload toggling attempts.
5332 5218
5333 rcutorture.nreaders= [KNL] 5219 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 5220 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 5221 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 5222 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 5223 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 5224 (the number of CPUs), -3 selects N+1, and so on.
5339 5225
5340 rcutorture.object_debug= [KNL] 5226 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 5227 Enable debug-object double-call_rcu() testing.
5342 5228
5343 rcutorture.onoff_holdoff= [KNL] 5229 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 5230 Set time (s) after boot for CPU-hotplug testing.
5345 5231
5346 rcutorture.onoff_interval= [KNL] 5232 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 5233 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 5234 or zero to disable CPU-hotplug testing.
5349 5235
5350 rcutorture.read_exit= [KNL] 5236 rcutorture.read_exit= [KNL]
5351 Set the number of rea 5237 Set the number of read-then-exit kthreads used
5352 to test the interacti 5238 to test the interaction of RCU updaters and
5353 task-exit processing. 5239 task-exit processing.
5354 5240
5355 rcutorture.read_exit_burst= [KNL] 5241 rcutorture.read_exit_burst= [KNL]
5356 The number of times i 5242 The number of times in a given read-then-exit
5357 episode that a set of 5243 episode that a set of read-then-exit kthreads
5358 is spawned. 5244 is spawned.
5359 5245
5360 rcutorture.read_exit_delay= [KNL] 5246 rcutorture.read_exit_delay= [KNL]
5361 The delay, in seconds 5247 The delay, in seconds, between successive
5362 read-then-exit testin 5248 read-then-exit testing episodes.
5363 5249
5364 rcutorture.shuffle_interval= [KNL] 5250 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 5251 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 5252 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 5253 during the rcutorture test.
5368 5254
5369 rcutorture.shutdown_secs= [KNL] 5255 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 5256 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 5257 is useful for hands-off automated testing.
5372 5258
5373 rcutorture.stall_cpu= [KNL] 5259 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 5260 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 5261 warnings, zero to disable.
5376 5262
5377 rcutorture.stall_cpu_block= [KNL] 5263 rcutorture.stall_cpu_block= [KNL]
5378 Sleep while stalling 5264 Sleep while stalling if set. This will result
5379 in warnings from pree 5265 in warnings from preemptible RCU in addition to
5380 any other stall-relat 5266 any other stall-related activity. Note that
5381 in kernels built with 5267 in kernels built with CONFIG_PREEMPTION=n and
5382 CONFIG_PREEMPT_COUNT= 5268 CONFIG_PREEMPT_COUNT=y, this parameter will
5383 cause the CPU to pass 5269 cause the CPU to pass through a quiescent state.
5384 Given CONFIG_PREEMPTI 5270 Given CONFIG_PREEMPTION=n, this will suppress
5385 RCU CPU stall warning 5271 RCU CPU stall warnings, but will instead result
5386 in scheduling-while-a 5272 in scheduling-while-atomic splats.
5387 5273
5388 Use of this module pa 5274 Use of this module parameter results in splats.
5389 5275
5390 5276
5391 rcutorture.stall_cpu_holdoff= [KNL] 5277 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 5278 Time to wait (s) after boot before inducing stall.
5393 5279
5394 rcutorture.stall_cpu_irqsoff= [KNL] 5280 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 5281 Disable interrupts while stalling if set.
5396 5282
5397 rcutorture.stall_gp_kthread= [KNL] 5283 rcutorture.stall_gp_kthread= [KNL]
5398 Duration (s) of force 5284 Duration (s) of forced sleep within RCU
5399 grace-period kthread 5285 grace-period kthread to test RCU CPU stall
5400 warnings, zero to dis 5286 warnings, zero to disable. If both stall_cpu
5401 and stall_gp_kthread 5287 and stall_gp_kthread are specified, the
5402 kthread is starved fi 5288 kthread is starved first, then the CPU.
5403 5289
5404 rcutorture.stat_interval= [KNL] 5290 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 5291 Time (s) between statistics printk()s.
5406 5292
5407 rcutorture.stutter= [KNL] 5293 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 5294 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 5295 five seconds causes the test to run for five seconds,
5410 wait for five seconds 5296 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 5297 ability to transition abruptly to and from idle.
5412 5298
5413 rcutorture.test_boost= [KNL] 5299 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 5300 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 5301 "Maybe" means test if the RCU implementation
5416 under test support RC 5302 under test support RCU priority boosting.
5417 5303
5418 rcutorture.test_boost_duration= [KNL] 5304 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 5305 Duration (s) of each individual boost test.
5420 5306
5421 rcutorture.test_boost_interval= [KNL] 5307 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 5308 Interval (s) between each boost test.
5423 5309
5424 rcutorture.test_no_idle_hz= [KNL] 5310 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 5311 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 5312 rcutorture.shuffle_interval parameter.
5427 5313
5428 rcutorture.torture_type= [KNL] 5314 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 5315 Specify the RCU implementation to test.
5430 5316
5431 rcutorture.verbose= [KNL] 5317 rcutorture.verbose= [KNL]
5432 Enable additional pri 5318 Enable additional printk() statements.
5433 5319
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ 5320 rcupdate.rcu_cpu_stall_ftrace_dump= [KNL]
5435 Dump ftrace buffer af 5321 Dump ftrace buffer after reporting RCU CPU
5436 stall warning. 5322 stall warning.
5437 5323
5438 rcupdate.rcu_cpu_stall_notifiers= [KN 5324 rcupdate.rcu_cpu_stall_notifiers= [KNL]
5439 Provide RCU CPU stall 5325 Provide RCU CPU stall notifiers, but see the
5440 warnings in the RCU_C 5326 warnings in the RCU_CPU_STALL_NOTIFIER Kconfig
5441 option's help text. 5327 option's help text. TL;DR: You almost certainly
5442 do not want rcupdate. 5328 do not want rcupdate.rcu_cpu_stall_notifiers.
5443 5329
5444 rcupdate.rcu_cpu_stall_suppress= [KNL 5330 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 5331 Suppress RCU CPU stall warning messages.
5446 5332
5447 rcupdate.rcu_cpu_stall_suppress_at_bo 5333 rcupdate.rcu_cpu_stall_suppress_at_boot= [KNL]
5448 Suppress RCU CPU stal 5334 Suppress RCU CPU stall warning messages and
5449 rcutorture writer sta 5335 rcutorture writer stall warnings that occur
5450 during early boot, th 5336 during early boot, that is, during the time
5451 before the init task 5337 before the init task is spawned.
5452 5338
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 5339 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 5340 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon 5341 The value is in seconds and the maximum allowed
5456 value is 300 seconds. 5342 value is 300 seconds.
5457 5343
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ 5344 rcupdate.rcu_exp_cpu_stall_timeout= [KNL]
5459 Set timeout for exped 5345 Set timeout for expedited RCU CPU stall warning
5460 messages. The value 5346 messages. The value is in milliseconds
5461 and the maximum allow 5347 and the maximum allowed value is 21000
5462 milliseconds. Please 5348 milliseconds. Please note that this value is
5463 adjusted to an arch t 5349 adjusted to an arch timer tick resolution.
5464 Setting this to zero 5350 Setting this to zero causes the value from
5465 rcupdate.rcu_cpu_stal 5351 rcupdate.rcu_cpu_stall_timeout to be used (after
5466 conversion from secon 5352 conversion from seconds to milliseconds).
5467 5353
5468 rcupdate.rcu_cpu_stall_cputime= [KNL] 5354 rcupdate.rcu_cpu_stall_cputime= [KNL]
5469 Provide statistics on 5355 Provide statistics on the cputime and count of
5470 interrupts and tasks 5356 interrupts and tasks during the sampling period. For
5471 multiple continuous R 5357 multiple continuous RCU stalls, all sampling periods
5472 begin at half of the 5358 begin at half of the first RCU stall timeout.
5473 5359
5474 rcupdate.rcu_exp_stall_task_details= 5360 rcupdate.rcu_exp_stall_task_details= [KNL]
5475 Print stack dumps of 5361 Print stack dumps of any tasks blocking the
5476 current expedited RCU 5362 current expedited RCU grace period during an
5477 expedited RCU CPU sta 5363 expedited RCU CPU stall warning.
5478 5364
5479 rcupdate.rcu_expedited= [KNL] 5365 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 5366 Use expedited grace-period primitives, for
5481 example, synchronize_ 5367 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 5368 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 5369 but can increase CPU utilization, degrade
5484 real-time latency, an 5370 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 5371 No effect on CONFIG_TINY_RCU kernels.
5486 5372
5487 rcupdate.rcu_normal= [KNL] 5373 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 5374 Use only normal grace-period primitives,
5489 for example, synchron 5375 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 5376 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 5377 real-time latency, CPU utilization, and
5492 energy efficiency, bu 5378 energy efficiency, but can expose users to
5493 increased grace-perio 5379 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 5380 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 5381 CONFIG_TINY_RCU kernels.
5496 5382
5497 rcupdate.rcu_normal_after_boot= [KNL] 5383 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 5384 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 5385 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 5386 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 5387 on CONFIG_TINY_RCU kernels.
5502 5388
5503 But note that CONFIG_ 5389 But note that CONFIG_PREEMPT_RT=y kernels enables
5504 this kernel boot para 5390 this kernel boot parameter, forcibly setting
5505 it to the value one, 5391 it to the value one, that is, converting any
5506 post-boot attempt at 5392 post-boot attempt at an expedited RCU grace
5507 period to instead use 5393 period to instead use normal non-expedited
5508 grace-period processi 5394 grace-period processing.
5509 5395
5510 rcupdate.rcu_task_collapse_lim= [KNL] 5396 rcupdate.rcu_task_collapse_lim= [KNL]
5511 Set the maximum numbe 5397 Set the maximum number of callbacks present
5512 at the beginning of a 5398 at the beginning of a grace period that allows
5513 the RCU Tasks flavors 5399 the RCU Tasks flavors to collapse back to using
5514 a single callback que 5400 a single callback queue. This switching only
5515 occurs when rcupdate. 5401 occurs when rcupdate.rcu_task_enqueue_lim is
5516 set to the default va 5402 set to the default value of -1.
5517 5403
5518 rcupdate.rcu_task_contend_lim= [KNL] 5404 rcupdate.rcu_task_contend_lim= [KNL]
5519 Set the minimum numbe 5405 Set the minimum number of callback-queuing-time
5520 lock-contention event 5406 lock-contention events per jiffy required to
5521 cause the RCU Tasks f 5407 cause the RCU Tasks flavors to switch to per-CPU
5522 callback queuing. Th 5408 callback queuing. This switching only occurs
5523 when rcupdate.rcu_tas 5409 when rcupdate.rcu_task_enqueue_lim is set to
5524 the default value of 5410 the default value of -1.
5525 5411
5526 rcupdate.rcu_task_enqueue_lim= [KNL] 5412 rcupdate.rcu_task_enqueue_lim= [KNL]
5527 Set the number of cal 5413 Set the number of callback queues to use for the
5528 RCU Tasks family of R 5414 RCU Tasks family of RCU flavors. The default
5529 of -1 allows this to 5415 of -1 allows this to be automatically (and
5530 dynamically) adjusted 5416 dynamically) adjusted. This parameter is intended
5531 for use in testing. 5417 for use in testing.
5532 5418
5533 rcupdate.rcu_task_ipi_delay= [KNL] 5419 rcupdate.rcu_task_ipi_delay= [KNL]
5534 Set time in jiffies d 5420 Set time in jiffies during which RCU tasks will
5535 avoid sending IPIs, s 5421 avoid sending IPIs, starting with the beginning
5536 of a given grace peri 5422 of a given grace period. Setting a large
5537 number avoids disturb 5423 number avoids disturbing real-time workloads,
5538 but lengthens grace p 5424 but lengthens grace periods.
5539 5425
5540 rcupdate.rcu_task_lazy_lim= [KNL] 5426 rcupdate.rcu_task_lazy_lim= [KNL]
5541 Number of callbacks o 5427 Number of callbacks on a given CPU that will
5542 cancel laziness on th 5428 cancel laziness on that CPU. Use -1 to disable
5543 cancellation of lazin 5429 cancellation of laziness, but be advised that
5544 doing so increases th 5430 doing so increases the danger of OOM due to
5545 callback flooding. 5431 callback flooding.
5546 5432
5547 rcupdate.rcu_task_stall_info= [KNL] 5433 rcupdate.rcu_task_stall_info= [KNL]
5548 Set initial timeout i 5434 Set initial timeout in jiffies for RCU task stall
5549 informational message 5435 informational messages, which give some indication
5550 of the problem for th 5436 of the problem for those not patient enough to
5551 wait for ten minutes. 5437 wait for ten minutes. Informational messages are
5552 only printed prior to 5438 only printed prior to the stall-warning message
5553 for a given grace per 5439 for a given grace period. Disable with a value
5554 less than or equal to 5440 less than or equal to zero. Defaults to ten
5555 seconds. A change in 5441 seconds. A change in value does not take effect
5556 until the beginning o 5442 until the beginning of the next grace period.
5557 5443
5558 rcupdate.rcu_task_stall_info_mult= [K 5444 rcupdate.rcu_task_stall_info_mult= [KNL]
5559 Multiplier for time i 5445 Multiplier for time interval between successive
5560 RCU task stall inform 5446 RCU task stall informational messages for a given
5561 RCU tasks grace perio 5447 RCU tasks grace period. This value is clamped
5562 to one through ten, i 5448 to one through ten, inclusive. It defaults to
5563 the value three, so t 5449 the value three, so that the first informational
5564 message is printed 10 5450 message is printed 10 seconds into the grace
5565 period, the second at 5451 period, the second at 40 seconds, the third at
5566 160 seconds, and then 5452 160 seconds, and then the stall warning at 600
5567 seconds would prevent 5453 seconds would prevent a fourth at 640 seconds.
5568 5454
5569 rcupdate.rcu_task_stall_timeout= [KNL 5455 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie 5456 Set timeout in jiffies for RCU task stall
5571 warning messages. Di 5457 warning messages. Disable with a value less
5572 than or equal to zero 5458 than or equal to zero. Defaults to ten minutes.
5573 A change in value doe 5459 A change in value does not take effect until
5574 the beginning of the 5460 the beginning of the next grace period.
5575 5461
5576 rcupdate.rcu_tasks_lazy_ms= [KNL] 5462 rcupdate.rcu_tasks_lazy_ms= [KNL]
5577 Set timeout in millis 5463 Set timeout in milliseconds RCU Tasks asynchronous
5578 callback batching for 5464 callback batching for call_rcu_tasks().
5579 A negative value will 5465 A negative value will take the default. A value
5580 of zero will disable 5466 of zero will disable batching. Batching is
5581 always disabled for s 5467 always disabled for synchronize_rcu_tasks().
5582 5468
5583 rcupdate.rcu_tasks_rude_lazy_ms= [KNL 5469 rcupdate.rcu_tasks_rude_lazy_ms= [KNL]
5584 Set timeout in millis 5470 Set timeout in milliseconds RCU Tasks
5585 Rude asynchronous cal 5471 Rude asynchronous callback batching for
5586 call_rcu_tasks_rude() 5472 call_rcu_tasks_rude(). A negative value
5587 will take the default 5473 will take the default. A value of zero will
5588 disable batching. Ba 5474 disable batching. Batching is always disabled
5589 for synchronize_rcu_t 5475 for synchronize_rcu_tasks_rude().
5590 5476
5591 rcupdate.rcu_tasks_trace_lazy_ms= [KN 5477 rcupdate.rcu_tasks_trace_lazy_ms= [KNL]
5592 Set timeout in millis 5478 Set timeout in milliseconds RCU Tasks
5593 Trace asynchronous ca 5479 Trace asynchronous callback batching for
5594 call_rcu_tasks_trace( 5480 call_rcu_tasks_trace(). A negative value
5595 will take the default 5481 will take the default. A value of zero will
5596 disable batching. Ba 5482 disable batching. Batching is always disabled
5597 for synchronize_rcu_t 5483 for synchronize_rcu_tasks_trace().
5598 5484
5599 rcupdate.rcu_self_test= [KNL] 5485 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 5486 Run the RCU early boot self tests
5601 5487
5602 rdinit= [KNL] 5488 rdinit= [KNL]
5603 Format: <full_path> 5489 Format: <full_path>
5604 Run specified binary 5490 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 5491 used for early userspace startup. See initrd.
5606 5492
5607 rdrand= [X86,EARLY] !! 5493 rdrand= [X86]
5608 force - Override the 5494 force - Override the decision by the kernel to hide the
5609 advertisement 5495 advertisement of RDRAND support (this affects
5610 certain AMD p 5496 certain AMD processors because of buggy BIOS
5611 support, spec 5497 support, specifically around the suspend/resume
5612 path). 5498 path).
5613 5499
5614 rdt= [HW,X86,RDT] 5500 rdt= [HW,X86,RDT]
5615 Turn on/off individua 5501 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 5502 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. 5503 mba, smba, bmec.
5618 E.g. to turn on cmt a 5504 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 5505 rdt=cmt,!mba
5620 5506
5621 reboot= [KNL] 5507 reboot= [KNL]
5622 Format (x86 or x86_64 5508 Format (x86 or x86_64):
5623 [w[arm] | c[o 5509 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \
5624 [[,]s[mp]#### 5510 [[,]s[mp]#### \
5625 [[,]b[ios] | 5511 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 5512 [[,]f[orce]
5627 Where reboot_mode is 5513 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 5514 (prefix with 'panic_' to set mode for panic
5629 reboo 5515 reboot only),
5630 reboot_type is 5516 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 5517 reboot_force is either force or not specified,
5632 reboot_cpu is s 5518 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 5519 to be used for rebooting.
5634 5520
5635 refscale.holdoff= [KNL] 5521 refscale.holdoff= [KNL]
5636 Set test-start holdof 5522 Set test-start holdoff period. The purpose of
5637 this parameter is to 5523 this parameter is to delay the start of the
5638 test until boot compl 5524 test until boot completes in order to avoid
5639 interference. 5525 interference.
5640 5526
5641 refscale.lookup_instances= [KNL] 5527 refscale.lookup_instances= [KNL]
5642 Number of data elemen 5528 Number of data elements to use for the forms of
5643 SLAB_TYPESAFE_BY_RCU 5529 SLAB_TYPESAFE_BY_RCU testing. A negative number
5644 is negated and multip 5530 is negated and multiplied by nr_cpu_ids, while
5645 zero specifies nr_cpu 5531 zero specifies nr_cpu_ids.
5646 5532
5647 refscale.loops= [KNL] 5533 refscale.loops= [KNL]
5648 Set the number of loo 5534 Set the number of loops over the synchronization
5649 primitive under test. 5535 primitive under test. Increasing this number
5650 reduces noise due to 5536 reduces noise due to loop start/end overhead,
5651 but the default has a 5537 but the default has already reduced the per-pass
5652 noise to a handful of 5538 noise to a handful of picoseconds on ca. 2020
5653 x86 laptops. 5539 x86 laptops.
5654 5540
5655 refscale.nreaders= [KNL] 5541 refscale.nreaders= [KNL]
5656 Set number of readers 5542 Set number of readers. The default value of -1
5657 selects N, where N is 5543 selects N, where N is roughly 75% of the number
5658 of CPUs. A value of 5544 of CPUs. A value of zero is an interesting choice.
5659 5545
5660 refscale.nruns= [KNL] 5546 refscale.nruns= [KNL]
5661 Set number of runs, e 5547 Set number of runs, each of which is dumped onto
5662 the console log. 5548 the console log.
5663 5549
5664 refscale.readdelay= [KNL] 5550 refscale.readdelay= [KNL]
5665 Set the read-side cri 5551 Set the read-side critical-section duration,
5666 measured in microseco 5552 measured in microseconds.
5667 5553
5668 refscale.scale_type= [KNL] 5554 refscale.scale_type= [KNL]
5669 Specify the read-prot 5555 Specify the read-protection implementation to test.
5670 5556
5671 refscale.shutdown= [KNL] 5557 refscale.shutdown= [KNL]
5672 Shut down the system 5558 Shut down the system at the end of the performance
5673 test. This defaults 5559 test. This defaults to 1 (shut it down) when
5674 refscale is built int 5560 refscale is built into the kernel and to 0 (leave
5675 it running) when refs 5561 it running) when refscale is built as a module.
5676 5562
5677 refscale.verbose= [KNL] 5563 refscale.verbose= [KNL]
5678 Enable additional pri 5564 Enable additional printk() statements.
5679 5565
5680 refscale.verbose_batched= [KNL] 5566 refscale.verbose_batched= [KNL]
5681 Batch the additional 5567 Batch the additional printk() statements. If zero
5682 (the default) or nega 5568 (the default) or negative, print everything. Otherwise,
5683 print every Nth verbo 5569 print every Nth verbose statement, where N is the value
5684 specified. 5570 specified.
5685 5571
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= 5572 relax_domain_level=
5694 [KNL, SMP] Set schedu 5573 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm 5574 See Documentation/admin-guide/cgroup-v1/cpusets.rst.
5696 5575
5697 reserve= [KNL,BUGS] Force kern 5576 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 5577 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 5578 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 5579 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 5580 is assumed to be I/O ports; otherwise it is memory.
5702 5581
5703 reserve_mem= [RAM] !! 5582 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] 5583 Format: nn[KMG]
5727 Reserves a hole at th 5584 Reserves a hole at the top of the kernel virtual
5728 address space. 5585 address space.
5729 5586
5730 reset_devices [KNL] Force drivers t 5587 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 5588 during initialization.
5732 5589
5733 resume= [SWSUSP] 5590 resume= [SWSUSP]
5734 Specify the partition 5591 Specify the partition device for software suspend
5735 Format: 5592 Format:
5736 {/dev/<dev> | PARTUUI 5593 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 5594
5738 resume_offset= [SWSUSP] 5595 resume_offset= [SWSUSP]
5739 Specify the offset fr 5596 Specify the offset from the beginning of the partition
5740 given by "resume=" at 5597 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 5598 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po 5599 See Documentation/power/swsusp-and-swap-files.rst
5743 5600
5744 resumedelay= [HIBERNATION] Delay ( 5601 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 5602 read the resume files
5746 5603
5747 resumewait [HIBERNATION] Wait (i 5604 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 5605 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 5606 (e.g. USB and MMC devices).
5750 5607
5751 retain_initrd [RAM] Keep initrd mem !! 5608 retain_initrd [RAM] Keep initrd memory after extraction
5752 be accessible via /sy <<
5753 5609
5754 retbleed= [X86] Control mitigat 5610 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 5611 Speculative Code Execution with Return Instructions)
5756 vulnerability. 5612 vulnerability.
5757 5613
5758 AMD-based UNRET and I 5614 AMD-based UNRET and IBPB mitigations alone do not stop
5759 sibling threads from 5615 sibling threads from influencing the predictions of other
5760 sibling threads. For 5616 sibling threads. For that reason, STIBP is used on pro-
5761 cessors that support 5617 cessors that support it, and mitigate SMT on processors
5762 that don't. 5618 that don't.
5763 5619
5764 off - no mit 5620 off - no mitigation
5765 auto - automa 5621 auto - automatically select a migitation
5766 auto,nosmt - automa 5622 auto,nosmt - automatically select a mitigation,
5767 disabl 5623 disabling SMT if necessary for
5768 the fu 5624 the full mitigation (only on Zen1
5769 and ol 5625 and older without STIBP).
5770 ibpb - On AMD 5626 ibpb - On AMD, mitigate short speculation
5771 window 5627 windows on basic block boundaries too.
5772 Safe, 5628 Safe, highest perf impact. It also
5773 enable 5629 enables STIBP if present. Not suitable
5774 on Int 5630 on Intel.
5775 ibpb,nosmt - Like " 5631 ibpb,nosmt - Like "ibpb" above but will disable SMT
5776 when S 5632 when STIBP is not available. This is
5777 the al 5633 the alternative for systems which do not
5778 have S 5634 have STIBP.
5779 unret - Force 5635 unret - Force enable untrained return thunks,
5780 only e 5636 only effective on AMD f15h-f17h based
5781 system 5637 systems.
5782 unret,nosmt - Like u 5638 unret,nosmt - Like unret, but will disable SMT when STIBP
5783 is not 5639 is not available. This is the alternative for
5784 system 5640 systems which do not have STIBP.
5785 5641
5786 Selecting 'auto' will 5642 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 5643 time according to the CPU.
5788 5644
5789 Not specifying this o 5645 Not specifying this option is equivalent to retbleed=auto.
5790 5646
5791 rfkill.default_state= 5647 rfkill.default_state=
5792 0 "airplane mode". All 5648 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 5649 etc. communication is blocked by default.
5794 1 Unblocked. 5650 1 Unblocked.
5795 5651
5796 rfkill.master_switch_mode= 5652 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 5653 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 5654 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 5655 blocked and the previous configuration.
5800 2 The "airplane mode" b 5656 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 5657 blocked and everything unblocked.
5802 5658
>> 5659 rhash_entries= [KNL,NET]
>> 5660 Set number of hash buckets for route cache
>> 5661
5803 ring3mwait=disable 5662 ring3mwait=disable
5804 [KNL] Disable ring 3 5663 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 5664 CPUs.
5806 5665
5807 riscv_isa_fallback [RISCV,EARLY] !! 5666 riscv_isa_fallback [RISCV]
5808 When CONFIG_RISCV_ISA 5667 When CONFIG_RISCV_ISA_FALLBACK is not enabled, permit
5809 falling back to detec 5668 falling back to detecting extension support by parsing
5810 "riscv,isa" property 5669 "riscv,isa" property on devicetree systems when the
5811 replacement propertie 5670 replacement properties are not found. See the Kconfig
5812 entry for RISCV_ISA_F 5671 entry for RISCV_ISA_FALLBACK.
5813 5672
5814 ro [KNL] Mount root devi 5673 ro [KNL] Mount root device read-only on boot
5815 5674
5816 rodata= [KNL,EARLY] !! 5675 rodata= [KNL]
5817 on Mark read-only kernel 5676 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 5677 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel 5678 full Mark read-only kernel memory and aliases as read-only
5820 [arm64] 5679 [arm64]
5821 5680
5822 rockchip.usb_uart 5681 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 5682 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 5683 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 5684 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 5685 port and the regular usb controller gets disabled.
5828 5686
5829 root= [KNL] Root filesystem 5687 root= [KNL] Root filesystem
5830 Usually this a a bloc 5688 Usually this a a block device specifier of some kind,
5831 see the early_lookup_ 5689 see the early_lookup_bdev comment in
5832 block/early-lookup.c 5690 block/early-lookup.c for details.
5833 Alternatively this ca 5691 Alternatively this can be "ram" for the legacy initial
5834 ramdisk, "nfs" and "c 5692 ramdisk, "nfs" and "cifs" for root on a network file
5835 system, or "mtd" and 5693 system, or "mtd" and "ubi" for mounting from raw flash.
5836 5694
5837 rootdelay= [KNL] Delay (in secon 5695 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 5696 mount the root filesystem
5839 5697
5840 rootflags= [KNL] Set root filesy 5698 rootflags= [KNL] Set root filesystem mount option string
5841 5699
5842 rootfstype= [KNL] Set root filesy 5700 rootfstype= [KNL] Set root filesystem type
5843 5701
5844 rootwait [KNL] Wait (indefinit 5702 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 5703 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 5704 (e.g. USB and MMC devices).
5847 5705
5848 rootwait= [KNL] Maximum time (i 5706 rootwait= [KNL] Maximum time (in seconds) to wait for root device
5849 to show up before att 5707 to show up before attempting to mount the root
5850 filesystem. 5708 filesystem.
5851 5709
5852 rproc_mem=nn[KMG][@address] 5710 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 5711 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 5712 Memory area to be used by remote processor image,
5855 managed by CMA. 5713 managed by CMA.
5856 5714
5857 rw [KNL] Mount root devi 5715 rw [KNL] Mount root device read-write on boot
5858 5716
5859 S [KNL] Run init in sin 5717 S [KNL] Run init in single mode
5860 5718
5861 s390_iommu= [HW,S390] 5719 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 5720 Set s390 IOTLB flushing mode
5863 strict 5721 strict
5864 With strict flushing 5722 With strict flushing every unmap operation will result
5865 in an IOTLB flush. De 5723 in an IOTLB flush. Default is lazy flushing before
5866 reuse, which is faste 5724 reuse, which is faster. Deprecated, equivalent to
5867 iommu.strict=1. 5725 iommu.strict=1.
5868 5726
5869 s390_iommu_aperture= [KNL,S390] 5727 s390_iommu_aperture= [KNL,S390]
5870 Specifies the size of 5728 Specifies the size of the per device DMA address space
5871 accessible through th 5729 accessible through the DMA and IOMMU APIs as a decimal
5872 factor of the size of 5730 factor of the size of main memory.
5873 The default is 1 mean 5731 The default is 1 meaning that one can concurrently use
5874 as many DMA addresses 5732 as many DMA addresses as physical memory is installed,
5875 if supported by hardw 5733 if supported by hardware, and thus map all of memory
5876 once. With a value of 5734 once. With a value of 2 one can map all of memory twice
5877 and so on. As a speci 5735 and so on. As a special case a factor of 0 imposes no
5878 restrictions other th 5736 restrictions other than those given by hardware at the
5879 cost of significant a 5737 cost of significant additional memory use for tables.
5880 5738
5881 sa1100ir [NET] 5739 sa1100ir [NET]
5882 See drivers/net/irda/ 5740 See drivers/net/irda/sa1100_ir.c.
5883 5741
5884 sched_verbose [KNL,EARLY] Enables v !! 5742 sched_verbose [KNL] Enables verbose scheduler debug messages.
5885 5743
5886 schedstats= [KNL,X86] Enable or d 5744 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 5745 Allowed values are enable and disable. This feature
5888 incurs a small amount 5746 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 5747 but is useful for debugging and performance tuning.
5890 5748
5891 sched_thermal_decay_shift= 5749 sched_thermal_decay_shift=
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca 5750 [KNL, SMP] Set a decay shift for scheduler thermal
5894 pressure signal. Ther 5751 pressure signal. Thermal pressure signal follows the
5895 default decay period 5752 default decay period of other scheduler pelt
5896 signals(usually 32 ms 5753 signals(usually 32 ms but configurable). Setting
5897 sched_thermal_decay_s 5754 sched_thermal_decay_shift will left shift the decay
5898 period for the therma 5755 period for the thermal pressure signal by the shift
5899 value. 5756 value.
5900 i.e. with the default 5757 i.e. with the default pelt decay period of 32 ms
5901 sched_thermal_decay_s 5758 sched_thermal_decay_shift thermal pressure decay pr
5902 1 5759 1 64 ms
5903 2 5760 2 128 ms
5904 and so on. 5761 and so on.
5905 Format: integer betwe 5762 Format: integer between 0 and 10
5906 Default is 0. 5763 Default is 0.
5907 5764
5908 scftorture.holdoff= [KNL] 5765 scftorture.holdoff= [KNL]
5909 Number of seconds to 5766 Number of seconds to hold off before starting
5910 test. Defaults to ze 5767 test. Defaults to zero for module insertion and
5911 to 10 seconds for bui 5768 to 10 seconds for built-in smp_call_function()
5912 tests. 5769 tests.
5913 5770
5914 scftorture.longwait= [KNL] 5771 scftorture.longwait= [KNL]
5915 Request ridiculously 5772 Request ridiculously long waits randomly selected
5916 up to the chosen limi 5773 up to the chosen limit in seconds. Zero (the
5917 default) disables thi 5774 default) disables this feature. Please note
5918 that requesting even 5775 that requesting even small non-zero numbers of
5919 seconds can result in 5776 seconds can result in RCU CPU stall warnings,
5920 softlockup complaints 5777 softlockup complaints, and so on.
5921 5778
5922 scftorture.nthreads= [KNL] 5779 scftorture.nthreads= [KNL]
5923 Number of kthreads to 5780 Number of kthreads to spawn to invoke the
5924 smp_call_function() f 5781 smp_call_function() family of functions.
5925 The default of -1 spe 5782 The default of -1 specifies a number of kthreads
5926 equal to the number o 5783 equal to the number of CPUs.
5927 5784
5928 scftorture.onoff_holdoff= [KNL] 5785 scftorture.onoff_holdoff= [KNL]
5929 Number seconds to wai 5786 Number seconds to wait after the start of the
5930 test before initiatin 5787 test before initiating CPU-hotplug operations.
5931 5788
5932 scftorture.onoff_interval= [KNL] 5789 scftorture.onoff_interval= [KNL]
5933 Number seconds to wai 5790 Number seconds to wait between successive
5934 CPU-hotplug operation 5791 CPU-hotplug operations. Specifying zero (which
5935 is the default) disab 5792 is the default) disables CPU-hotplug operations.
5936 5793
5937 scftorture.shutdown_secs= [KNL] 5794 scftorture.shutdown_secs= [KNL]
5938 The number of seconds 5795 The number of seconds following the start of the
5939 test after which to s 5796 test after which to shut down the system. The
5940 default of zero avoid 5797 default of zero avoids shutting down the system.
5941 Non-zero values are u 5798 Non-zero values are useful for automated tests.
5942 5799
5943 scftorture.stat_interval= [KNL] 5800 scftorture.stat_interval= [KNL]
5944 The number of seconds 5801 The number of seconds between outputting the
5945 current test statisti 5802 current test statistics to the console. A value
5946 of zero disables stat 5803 of zero disables statistics output.
5947 5804
5948 scftorture.stutter_cpus= [KNL] 5805 scftorture.stutter_cpus= [KNL]
5949 The number of jiffies 5806 The number of jiffies to wait between each change
5950 to the set of CPUs un 5807 to the set of CPUs under test.
5951 5808
5952 scftorture.use_cpus_read_lock= [KNL] 5809 scftorture.use_cpus_read_lock= [KNL]
5953 Use use_cpus_read_loc 5810 Use use_cpus_read_lock() instead of the default
5954 preempt_disable() to 5811 preempt_disable() to disable CPU hotplug
5955 while invoking one of 5812 while invoking one of the smp_call_function*()
5956 functions. 5813 functions.
5957 5814
5958 scftorture.verbose= [KNL] 5815 scftorture.verbose= [KNL]
5959 Enable additional pri 5816 Enable additional printk() statements.
5960 5817
5961 scftorture.weight_single= [KNL] 5818 scftorture.weight_single= [KNL]
5962 The probability weigh 5819 The probability weighting to use for the
5963 smp_call_function_sin 5820 smp_call_function_single() function with a zero
5964 "wait" parameter. A 5821 "wait" parameter. A value of -1 selects the
5965 default if all other 5822 default if all other weights are -1. However,
5966 if at least one weigh 5823 if at least one weight has some other value, a
5967 value of -1 will inst 5824 value of -1 will instead select a weight of zero.
5968 5825
5969 scftorture.weight_single_wait= [KNL] 5826 scftorture.weight_single_wait= [KNL]
5970 The probability weigh 5827 The probability weighting to use for the
5971 smp_call_function_sin 5828 smp_call_function_single() function with a
5972 non-zero "wait" param 5829 non-zero "wait" parameter. See weight_single.
5973 5830
5974 scftorture.weight_many= [KNL] 5831 scftorture.weight_many= [KNL]
5975 The probability weigh 5832 The probability weighting to use for the
5976 smp_call_function_man 5833 smp_call_function_many() function with a zero
5977 "wait" parameter. Se 5834 "wait" parameter. See weight_single.
5978 Note well that settin 5835 Note well that setting a high probability for
5979 this weighting can pl 5836 this weighting can place serious IPI load
5980 on the system. 5837 on the system.
5981 5838
5982 scftorture.weight_many_wait= [KNL] 5839 scftorture.weight_many_wait= [KNL]
5983 The probability weigh 5840 The probability weighting to use for the
5984 smp_call_function_man 5841 smp_call_function_many() function with a
5985 non-zero "wait" param 5842 non-zero "wait" parameter. See weight_single
5986 and weight_many. 5843 and weight_many.
5987 5844
5988 scftorture.weight_all= [KNL] 5845 scftorture.weight_all= [KNL]
5989 The probability weigh 5846 The probability weighting to use for the
5990 smp_call_function_all 5847 smp_call_function_all() function with a zero
5991 "wait" parameter. Se 5848 "wait" parameter. See weight_single and
5992 weight_many. 5849 weight_many.
5993 5850
5994 scftorture.weight_all_wait= [KNL] 5851 scftorture.weight_all_wait= [KNL]
5995 The probability weigh 5852 The probability weighting to use for the
5996 smp_call_function_all 5853 smp_call_function_all() function with a
5997 non-zero "wait" param 5854 non-zero "wait" parameter. See weight_single
5998 and weight_many. 5855 and weight_many.
5999 5856
6000 skew_tick= [KNL,EARLY] Offset th !! 5857 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
6001 xtime_lock contention 5858 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 5859 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 5860 Format: { "0" | "1" }
6004 0 -- disable. (may be 5861 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 5862 1 -- enable.
6006 Note: increases power 5863 Note: increases power consumption, thus should only be
6007 enabled if running ji 5864 enabled if running jitter sensitive (HPC/RT) workloads.
6008 5865
6009 security= [SECURITY] Choose a l 5866 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 5867 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 5868 "lsm=" parameter.
6012 5869
6013 selinux= [SELINUX] Disable or 5870 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 5871 Format: { "0" | "1" }
6015 See security/selinux/ 5872 See security/selinux/Kconfig help text.
6016 0 -- disable. 5873 0 -- disable.
6017 1 -- enable. 5874 1 -- enable.
6018 Default value is 1. 5875 Default value is 1.
6019 5876
6020 serialnumber [BUGS=X86-32] 5877 serialnumber [BUGS=X86-32]
6021 5878
6022 sev=option[,option...] [X86-64] See D 5879 sev=option[,option...] [X86-64] See Documentation/arch/x86/x86_64/boot-options.rst
6023 5880
6024 shapers= [NET] 5881 shapers= [NET]
6025 Maximal number of sha 5882 Maximal number of shapers.
6026 5883
6027 show_lapic= [APIC,X86] Advanced P 5884 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
6028 Limit apic dumping. T 5885 Limit apic dumping. The parameter defines the maximal
6029 number of local apics 5886 number of local apics being dumped. Also it is possible
6030 to set it to "all" by 5887 to set it to "all" by meaning -- no limit here.
6031 Format: { 1 (default) 5888 Format: { 1 (default) | 2 | ... | all }.
6032 The parameter valid i 5889 The parameter valid if only apic=debug or
6033 apic=verbose is speci 5890 apic=verbose is specified.
6034 Example: apic=debug s 5891 Example: apic=debug show_lapic=all
6035 5892
6036 slab_debug[=options[,slabs][;[options !! 5893 simeth= [IA-64]
6037 Enabling slab_debug a !! 5894 simscsi=
>> 5895
>> 5896 slram= [HW,MTD]
>> 5897
>> 5898 slab_merge [MM]
>> 5899 Enable merging of slabs with similar size when the
>> 5900 kernel is built without CONFIG_SLAB_MERGE_DEFAULT.
>> 5901
>> 5902 slab_nomerge [MM]
>> 5903 Disable merging of slabs with similar size. May be
>> 5904 necessary if there is some reason to distinguish
>> 5905 allocs to different slabs, especially in hardened
>> 5906 environments where the risk of heap overflows and
>> 5907 layout control by attackers can usually be
>> 5908 frustrated by disabling merging. This will reduce
>> 5909 most of the exposure of a heap attack to a single
>> 5910 cache (risks via metadata attacks are mostly
>> 5911 unchanged). Debug options disable merging on their
>> 5912 own.
>> 5913 For more information see Documentation/mm/slub.rst.
>> 5914
>> 5915 slab_max_order= [MM, SLAB]
>> 5916 Determines the maximum allowed order for slabs.
>> 5917 A high setting may cause OOMs due to memory
>> 5918 fragmentation. Defaults to 1 for systems with
>> 5919 more than 32MB of RAM, 0 otherwise.
>> 5920
>> 5921 slub_debug[=options[,slabs][;[options[,slabs]]...] [MM, SLUB]
>> 5922 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 5923 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 5924 slub_debug can create guard zones around objects and
6040 may poison objects wh 5925 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 5926 last alloc / free. For more information see
6042 Documentation/mm/slub 5927 Documentation/mm/slub.rst.
6043 (slub_debug legacy na <<
6044 5928
6045 slab_max_order= [MM] !! 5929 slub_max_order= [MM, SLUB]
6046 Determines the maximu 5930 Determines the maximum allowed order for slabs.
6047 A high setting may ca 5931 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 5932 fragmentation. For more information see
6049 Documentation/mm/slub 5933 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 5934
6057 slab_min_objects= [MM] !! 5935 slub_min_objects= [MM, SLUB]
6058 The minimum number of 5936 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 5937 increase the slab order up to slub_max_order to
6060 generate a sufficient 5938 generate a sufficiently large slab able to contain
6061 the number of objects 5939 the number of objects indicated. The higher the number
6062 of objects the smalle 5940 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 5941 and the less frequently locks need to be acquired.
6064 For more information 5942 For more information see Documentation/mm/slub.rst.
6065 (slub_min_objects leg <<
6066 5943
6067 slab_min_order= [MM] !! 5944 slub_min_order= [MM, SLUB]
6068 Determines the minimu 5945 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 5946 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 5947 For more information see Documentation/mm/slub.rst.
6085 (slub_nomerge legacy <<
6086 5948
6087 slram= [HW,MTD] !! 5949 slub_merge [MM, SLUB]
>> 5950 Same with slab_merge.
>> 5951
>> 5952 slub_nomerge [MM, SLUB]
>> 5953 Same with slab_nomerge. This is supported for legacy.
>> 5954 See slab_nomerge for more information.
6088 5955
6089 smart2= [HW] 5956 smart2= [HW]
6090 Format: <io1>[,<io2>[ 5957 Format: <io1>[,<io2>[,...,<io8>]]
6091 5958
6092 smp.csd_lock_timeout= [KNL] 5959 smp.csd_lock_timeout= [KNL]
6093 Specify the period of 5960 Specify the period of time in milliseconds
6094 that smp_call_functio 5961 that smp_call_function() and friends will wait
6095 for a CPU to release 5962 for a CPU to release the CSD lock. This is
6096 useful when diagnosin 5963 useful when diagnosing bugs involving CPUs
6097 disabling interrupts 5964 disabling interrupts for extended periods
6098 of time. Defaults to 5965 of time. Defaults to 5,000 milliseconds, and
6099 setting a value of ze 5966 setting a value of zero disables this feature.
6100 This feature may be m 5967 This feature may be more efficiently disabled
6101 using the csdlock_deb 5968 using the csdlock_debug- kernel parameter.
6102 5969
6103 smp.panic_on_ipistall= [KNL] 5970 smp.panic_on_ipistall= [KNL]
6104 If a csd_lock_timeout 5971 If a csd_lock_timeout extends for more than
6105 the specified number 5972 the specified number of milliseconds, panic the
6106 system. By default, 5973 system. By default, let CSD-lock acquisition
6107 take as long as they 5974 take as long as they take. Specifying 300,000
6108 for this value provid 5975 for this value provides a 5-minute timeout.
6109 5976
6110 smsc-ircc2.nopnp [HW] Don't us 5977 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 5978 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 5979 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 5980 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 5981 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 5982 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 5983 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 5984 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 5985 1: Fast pin select (default)
6119 2: ATC IRMode 5986 2: ATC IRMode
6120 5987
6121 smt= [KNL,MIPS,S390,EARLY] !! 5988 smt= [KNL,MIPS,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 5989 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 5990 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 5991 actual hardware limit.
6125 Format: <integer> 5992 Format: <integer>
6126 Default: -1 (no limit 5993 Default: -1 (no limit)
6127 5994
6128 softlockup_panic= 5995 softlockup_panic=
6129 [KNL] Should the soft 5996 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 5997 Format: 0 | 1
6131 5998
6132 A value of 1 instruct 5999 A value of 1 instructs the soft-lockup detector
6133 to panic the machine 6000 to panic the machine when a soft-lockup occurs. It is
6134 also controlled by th 6001 also controlled by the kernel.softlockup_panic sysctl
6135 and CONFIG_BOOTPARAM_ 6002 and CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC, which is the
6136 respective build-time 6003 respective build-time switch to that functionality.
6137 6004
6138 softlockup_all_cpu_backtrace= 6005 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 6006 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 6007 backtraces on all cpus.
6141 Format: 0 | 1 6008 Format: 0 | 1
6142 6009
6143 sonypi.*= [HW] Sony Programmabl 6010 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm 6011 See Documentation/admin-guide/laptops/sonypi.rst
6145 6012
6146 spectre_bhi= [X86] Control mitigat !! 6013 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 6014 (indirect branch speculation) vulnerability.
6163 The default operation 6015 The default operation protects the kernel from
6164 user space attacks. 6016 user space attacks.
6165 6017
6166 on - unconditionall 6018 on - unconditionally enable, implies
6167 spectre_v2_use 6019 spectre_v2_user=on
6168 off - unconditionall 6020 off - unconditionally disable, implies
6169 spectre_v2_use 6021 spectre_v2_user=off
6170 auto - kernel detects 6022 auto - kernel detects whether your CPU model is
6171 vulnerable 6023 vulnerable
6172 6024
6173 Selecting 'on' will, 6025 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 6026 mitigation method at run time according to the
6175 CPU, the available mi 6027 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 6028 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 6029 compiler with which the kernel was built.
6178 6030
6179 Selecting 'on' will a 6031 Selecting 'on' will also enable the mitigation
6180 against user space to 6032 against user space to user space task attacks.
6181 6033
6182 Selecting 'off' will 6034 Selecting 'off' will disable both the kernel and
6183 the user space protec 6035 the user space protections.
6184 6036
6185 Specific mitigations 6037 Specific mitigations can also be selected manually:
6186 6038
6187 retpoline - r 6039 retpoline - replace indirect branches
6188 retpoline,generic - R 6040 retpoline,generic - Retpolines
6189 retpoline,lfence - L 6041 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 6042 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E 6043 eibrs - Enhanced/Auto IBRS
6192 eibrs,retpoline - E 6044 eibrs,retpoline - Enhanced/Auto IBRS + Retpolines
6193 eibrs,lfence - E 6045 eibrs,lfence - Enhanced/Auto IBRS + LFENCE
6194 ibrs - u 6046 ibrs - use IBRS to protect kernel
6195 6047
6196 Not specifying this o 6048 Not specifying this option is equivalent to
6197 spectre_v2=auto. 6049 spectre_v2=auto.
6198 6050
6199 spectre_v2_user= 6051 spectre_v2_user=
6200 [X86] Control mitigat 6052 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 6053 (indirect branch speculation) vulnerability between
6202 user space tasks 6054 user space tasks
6203 6055
6204 on - Uncondition 6056 on - Unconditionally enable mitigations. Is
6205 enforced by 6057 enforced by spectre_v2=on
6206 6058
6207 off - Uncondition 6059 off - Unconditionally disable mitigations. Is
6208 enforced by 6060 enforced by spectre_v2=off
6209 6061
6210 prctl - Indirect br 6062 prctl - Indirect branch speculation is enabled,
6211 but mitigat 6063 but mitigation can be enabled via prctl
6212 per thread. 6064 per thread. The mitigation control state
6213 is inherite 6065 is inherited on fork.
6214 6066
6215 prctl,ibpb 6067 prctl,ibpb
6216 - Like "prctl 6068 - Like "prctl" above, but only STIBP is
6217 controlled 6069 controlled per thread. IBPB is issued
6218 always when 6070 always when switching between different user
6219 space proce 6071 space processes.
6220 6072
6221 seccomp 6073 seccomp
6222 - Same as "pr 6074 - Same as "prctl" above, but all seccomp
6223 threads wil 6075 threads will enable the mitigation unless
6224 they explic 6076 they explicitly opt out.
6225 6077
6226 seccomp,ibpb 6078 seccomp,ibpb
6227 - Like "secco 6079 - Like "seccomp" above, but only STIBP is
6228 controlled 6080 controlled per thread. IBPB is issued
6229 always when 6081 always when switching between different
6230 user space 6082 user space processes.
6231 6083
6232 auto - Kernel sele 6084 auto - Kernel selects the mitigation depending on
6233 the availab 6085 the available CPU features and vulnerability.
6234 6086
6235 Default mitigation: " 6087 Default mitigation: "prctl"
6236 6088
6237 Not specifying this o 6089 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 6090 spectre_v2_user=auto.
6239 6091
6240 spec_rstack_overflow= 6092 spec_rstack_overflow=
6241 [X86,EARLY] Control R !! 6093 [X86] Control RAS overflow mitigation on AMD Zen CPUs
6242 6094
6243 off - Dis 6095 off - Disable mitigation
6244 microcode - Ena 6096 microcode - Enable microcode mitigation only
6245 safe-ret - Ena 6097 safe-ret - Enable sw-only safe RET mitigation (default)
6246 ibpb - Ena 6098 ibpb - Enable mitigation by issuing IBPB on
6247 ker 6099 kernel entry
6248 ibpb-vmexit - Iss 6100 ibpb-vmexit - Issue IBPB only on VMEXIT
6249 (cl 6101 (cloud-specific mitigation)
6250 6102
6251 spec_store_bypass_disable= 6103 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 6104 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 6105 (Speculative Store Bypass vulnerability)
6254 6106
6255 Certain CPUs are vuln 6107 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 6108 a common industry wide performance optimization known
6257 as "Speculative Store 6109 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 6110 to the same memory location may not be observed by
6259 later loads during sp 6111 later loads during speculative execution. The idea
6260 is that such stores a 6112 is that such stores are unlikely and that they can
6261 be detected prior to 6113 be detected prior to instruction retirement at the
6262 end of a particular s 6114 end of a particular speculation execution window.
6263 6115
6264 In vulnerable process 6116 In vulnerable processors, the speculatively forwarded
6265 store can be used in 6117 store can be used in a cache side channel attack, for
6266 example to read memor 6118 example to read memory to which the attacker does not
6267 directly have access 6119 directly have access (e.g. inside sandboxed code).
6268 6120
6269 This parameter contro 6121 This parameter controls whether the Speculative Store
6270 Bypass optimization i 6122 Bypass optimization is used.
6271 6123
6272 On x86 the options ar 6124 On x86 the options are:
6273 6125
6274 on - Uncondition 6126 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 6127 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 6128 auto - Kernel detects whether the CPU model contains an
6277 implementat 6129 implementation of Speculative Store Bypass and
6278 picks the m 6130 picks the most appropriate mitigation. If the
6279 CPU is not 6131 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 6132 CPU is vulnerable the default mitigation is
6281 architectur 6133 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 6134 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 6135 via prctl. Speculative Store Bypass is enabled
6284 for a proce 6136 for a process by default. The state of the control
6285 is inherite 6137 is inherited on fork.
6286 seccomp - Same as "pr 6138 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 6139 will disable SSB unless they explicitly opt out.
6288 6140
6289 Default mitigations: 6141 Default mitigations:
6290 X86: "prctl" 6142 X86: "prctl"
6291 6143
6292 On powerpc the option 6144 On powerpc the options are:
6293 6145
6294 on,auto - On Power8 a 6146 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 6147 barrier on kernel entry and exit. On Power7
6296 perform a s 6148 perform a software flush on kernel entry and
6297 exit. 6149 exit.
6298 off - No action. 6150 off - No action.
6299 6151
6300 Not specifying this o 6152 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 6153 spec_store_bypass_disable=auto.
6302 6154
>> 6155 spia_io_base= [HW,MTD]
>> 6156 spia_fio_base=
>> 6157 spia_pedr=
>> 6158 spia_peddr=
>> 6159
6303 split_lock_detect= 6160 split_lock_detect=
6304 [X86] Enable split lo 6161 [X86] Enable split lock detection or bus lock detection
6305 6162
6306 When enabled (and if 6163 When enabled (and if hardware support is present), atomic
6307 instructions that acc 6164 instructions that access data across cache line
6308 boundaries will resul 6165 boundaries will result in an alignment check exception
6309 for split lock detect 6166 for split lock detection or a debug exception for
6310 bus lock detection. 6167 bus lock detection.
6311 6168
6312 off - not enabled 6169 off - not enabled
6313 6170
6314 warn - the kernel 6171 warn - the kernel will emit rate-limited warnings
6315 about appli 6172 about applications triggering the #AC
6316 exception o 6173 exception or the #DB exception. This mode is
6317 the default 6174 the default on CPUs that support split lock
6318 detection o 6175 detection or bus lock detection. Default
6319 behavior is 6176 behavior is by #AC if both features are
6320 enabled in 6177 enabled in hardware.
6321 6178
6322 fatal - the kernel 6179 fatal - the kernel will send SIGBUS to applications
6323 that trigge 6180 that trigger the #AC exception or the #DB
6324 exception. 6181 exception. Default behavior is by #AC if
6325 both featur 6182 both features are enabled in hardware.
6326 6183
6327 ratelimit:N - 6184 ratelimit:N -
6328 Set system 6185 Set system wide rate limit to N bus locks
6329 per second 6186 per second for bus lock detection.
6330 0 < N <= 10 6187 0 < N <= 1000.
6331 6188
6332 N/A for spl 6189 N/A for split lock detection.
6333 6190
6334 6191
6335 If an #AC exception i 6192 If an #AC exception is hit in the kernel or in
6336 firmware (i.e. not wh 6193 firmware (i.e. not while executing in user mode)
6337 the kernel will oops 6194 the kernel will oops in either "warn" or "fatal"
6338 mode. 6195 mode.
6339 6196
6340 #DB exception for bus 6197 #DB exception for bus lock is triggered only when
6341 CPL > 0. 6198 CPL > 0.
6342 6199
6343 srbds= [X86,INTEL,EARLY] !! 6200 srbds= [X86,INTEL]
6344 Control the Special R 6201 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 6202 (SRBDS) mitigation.
6346 6203
6347 Certain CPUs are vuln 6204 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 6205 exploit which can leak bits from the random
6349 number generator. 6206 number generator.
6350 6207
6351 By default, this issu 6208 By default, this issue is mitigated by
6352 microcode. However, 6209 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 6210 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 6211 much slower. Among other effects, this will
6355 result in reduced thr 6212 result in reduced throughput from /dev/urandom.
6356 6213
6357 The microcode mitigat 6214 The microcode mitigation can be disabled with
6358 the following option: 6215 the following option:
6359 6216
6360 off: Disable mitig 6217 off: Disable mitigation and remove
6361 performance i 6218 performance impact to RDRAND and RDSEED
6362 6219
6363 srcutree.big_cpu_lim [KNL] 6220 srcutree.big_cpu_lim [KNL]
6364 Specifies the number 6221 Specifies the number of CPUs constituting a
6365 large system, such th 6222 large system, such that srcu_struct structures
6366 should immediately al 6223 should immediately allocate an srcu_node array.
6367 This kernel-boot para 6224 This kernel-boot parameter defaults to 128,
6368 but takes effect only 6225 but takes effect only when the low-order four
6369 bits of srcutree.conv 6226 bits of srcutree.convert_to_big is equal to 3
6370 (decide at boot). 6227 (decide at boot).
6371 6228
6372 srcutree.convert_to_big [KNL] 6229 srcutree.convert_to_big [KNL]
6373 Specifies under what 6230 Specifies under what conditions an SRCU tree
6374 srcu_struct structure 6231 srcu_struct structure will be converted to big
6375 form, that is, with a 6232 form, that is, with an rcu_node tree:
6376 6233
6377 0: Never. 6234 0: Never.
6378 1: At ini 6235 1: At init_srcu_struct() time.
6379 2: When r 6236 2: When rcutorture decides to.
6380 3: Decide 6237 3: Decide at boot time (default).
6381 0x1X: Above 6238 0x1X: Above plus if high contention.
6382 6239
6383 Either way, the srcu_ 6240 Either way, the srcu_node tree will be sized based
6384 on the actual runtime 6241 on the actual runtime number of CPUs (nr_cpu_ids)
6385 instead of the compil 6242 instead of the compile-time CONFIG_NR_CPUS.
6386 6243
6387 srcutree.counter_wrap_check [KNL] 6244 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 6245 Specifies how frequently to check for
6389 grace-period sequence 6246 grace-period sequence counter wrap for the
6390 srcu_data structure's 6247 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 6248 The greater the number of bits set in this kernel
6392 parameter, the less f 6249 parameter, the less frequently counter wrap will
6393 be checked for. Note 6250 be checked for. Note that the bottom two bits
6394 are ignored. 6251 are ignored.
6395 6252
6396 srcutree.exp_holdoff [KNL] 6253 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 6254 Specifies how many nanoseconds must elapse
6398 since the end of the 6255 since the end of the last SRCU grace period for
6399 a given srcu_struct u 6256 a given srcu_struct until the next normal SRCU
6400 grace period will be 6257 grace period will be considered for automatic
6401 expediting. Set to z 6258 expediting. Set to zero to disable automatic
6402 expediting. 6259 expediting.
6403 6260
6404 srcutree.srcu_max_nodelay [KNL] 6261 srcutree.srcu_max_nodelay [KNL]
6405 Specifies the number 6262 Specifies the number of no-delay instances
6406 per jiffy for which t 6263 per jiffy for which the SRCU grace period
6407 worker thread will be 6264 worker thread will be rescheduled with zero
6408 delay. Beyond this li 6265 delay. Beyond this limit, worker thread will
6409 be rescheduled with a 6266 be rescheduled with a sleep delay of one jiffy.
6410 6267
6411 srcutree.srcu_max_nodelay_phase [KNL] 6268 srcutree.srcu_max_nodelay_phase [KNL]
6412 Specifies the per-gra 6269 Specifies the per-grace-period phase, number of
6413 non-sleeping polls of 6270 non-sleeping polls of readers. Beyond this limit,
6414 grace period worker t 6271 grace period worker thread will be rescheduled
6415 with a sleep delay of 6272 with a sleep delay of one jiffy, between each
6416 rescan of the readers 6273 rescan of the readers, for a grace period phase.
6417 6274
6418 srcutree.srcu_retry_check_delay [KNL] 6275 srcutree.srcu_retry_check_delay [KNL]
6419 Specifies number of m 6276 Specifies number of microseconds of non-sleeping
6420 delay between each no 6277 delay between each non-sleeping poll of readers.
6421 6278
6422 srcutree.small_contention_lim [KNL] 6279 srcutree.small_contention_lim [KNL]
6423 Specifies the number 6280 Specifies the number of update-side contention
6424 events per jiffy will 6281 events per jiffy will be tolerated before
6425 initiating a conversi 6282 initiating a conversion of an srcu_struct
6426 structure to big form 6283 structure to big form. Note that the value of
6427 srcutree.convert_to_b 6284 srcutree.convert_to_big must have the 0x10 bit
6428 set for contention-ba 6285 set for contention-based conversions to occur.
6429 6286
6430 ssbd= [ARM64,HW,EARLY] !! 6287 ssbd= [ARM64,HW]
6431 Speculative Store Byp 6288 Speculative Store Bypass Disable control
6432 6289
6433 On CPUs that are vuln 6290 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 6291 Store Bypass vulnerability and offer a
6435 firmware based mitiga 6292 firmware based mitigation, this parameter
6436 indicates how the mit 6293 indicates how the mitigation should be used:
6437 6294
6438 force-on: Unconditio 6295 force-on: Unconditionally enable mitigation for
6439 for both k 6296 for both kernel and userspace
6440 force-off: Unconditio 6297 force-off: Unconditionally disable mitigation for
6441 for both k 6298 for both kernel and userspace
6442 kernel: Always ena 6299 kernel: Always enable mitigation in the
6443 kernel, an 6300 kernel, and offer a prctl interface
6444 to allow u 6301 to allow userspace to register its
6445 interest i 6302 interest in being mitigated too.
6446 6303
6447 stack_guard_gap= [MM] 6304 stack_guard_gap= [MM]
6448 override the default 6305 override the default stack gap protection. The value
6449 is in page units and 6306 is in page units and it defines how many pages prior
6450 to (for stacks growin 6307 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 6308 growing up) the main stack are reserved for no other
6452 mapping. Default valu 6309 mapping. Default value is 256 pages.
6453 6310
6454 stack_depot_disable= [KNL,EARLY] !! 6311 stack_depot_disable= [KNL]
6455 Setting this to true 6312 Setting this to true through kernel command line will
6456 disable the stack dep 6313 disable the stack depot thereby saving the static memory
6457 consumed by the stack 6314 consumed by the stack hash table. By default this is set
6458 to false. 6315 to false.
6459 6316
6460 stacktrace [FTRACE] 6317 stacktrace [FTRACE]
6461 Enabled the stack tra 6318 Enabled the stack tracer on boot up.
6462 6319
6463 stacktrace_filter=[function-list] 6320 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 6321 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up 6322 will trace at boot up. function-list is a comma-separated
6466 list of functions. Th 6323 list of functions. This list can be changed at run
6467 time by the stack_tra 6324 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 6325 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 6326 and the stacktrace above is not needed.
6470 6327
6471 sti= [PARISC,HW] 6328 sti= [PARISC,HW]
6472 Format: <num> 6329 Format: <num>
6473 Set the STI (builtin 6330 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 6331 machines) console (graphic card) which should be used
6475 as the initial boot-c 6332 as the initial boot-console.
6476 See also comment in d 6333 See also comment in drivers/video/console/sticore.c.
6477 6334
6478 sti_font= [HW] 6335 sti_font= [HW]
6479 See comment in driver 6336 See comment in drivers/video/console/sticore.c.
6480 6337
6481 stifb= [HW] 6338 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 6339 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 6340
6484 strict_sas_size= 6341 strict_sas_size=
6485 [X86] 6342 [X86]
6486 Format: <bool> 6343 Format: <bool>
6487 Enable or disable str 6344 Enable or disable strict sigaltstack size checks
6488 against the required 6345 against the required signal frame size which
6489 depends on the suppor 6346 depends on the supported FPU features. This can
6490 be used to filter out 6347 be used to filter out binaries which have
6491 not yet been made awa 6348 not yet been made aware of AT_MINSIGSTKSZ.
6492 6349
6493 stress_hpt [PPC,EARLY] !! 6350 stress_hpt [PPC]
6494 Limits the number of 6351 Limits the number of kernel HPT entries in the hash
6495 page table to increas 6352 page table to increase the rate of hash page table
6496 faults on kernel addr 6353 faults on kernel addresses.
6497 6354
6498 stress_slb [PPC,EARLY] !! 6355 stress_slb [PPC]
6499 Limits the number of 6356 Limits the number of kernel SLB entries, and flushes
6500 them frequently to in 6357 them frequently to increase the rate of SLB faults
6501 on kernel addresses. 6358 on kernel addresses.
6502 6359
6503 sunrpc.min_resvport= 6360 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 6361 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 6362 [NFS,SUNRPC]
6506 SunRPC servers often 6363 SunRPC servers often require that client requests
6507 originate from a priv 6364 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 6365 range 0 < portnr < 1024).
6509 An administrator who 6366 An administrator who wishes to reserve some of these
6510 ports for other uses 6367 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 6368 kernel's sunrpc client considers to be privileged
6512 using these two param 6369 using these two parameters to set the minimum and
6513 maximum port values. 6370 maximum port values.
6514 6371
6515 sunrpc.svc_rpc_per_connection_limit= 6372 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 6373 [NFS,SUNRPC]
6517 Limit the number of r 6374 Limit the number of requests that the server will
6518 process in parallel f 6375 process in parallel from a single connection.
6519 The default value is 6376 The default value is 0 (no limit).
6520 6377
6521 sunrpc.pool_mode= 6378 sunrpc.pool_mode=
6522 [NFS] 6379 [NFS]
6523 Control how the NFS s 6380 Control how the NFS server code allocates CPUs to
6524 service thread pools. 6381 service thread pools. Depending on how many NICs
6525 you have and where th 6382 you have and where their interrupts are bound, this
6526 option will affect wh 6383 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 6384 Note: this parameter cannot be changed while the
6528 NFS server is running 6385 NFS server is running.
6529 6386
6530 auto the serve 6387 auto the server chooses an appropriate mode
6531 automatic 6388 automatically using heuristics
6532 global a single 6389 global a single global pool contains all CPUs
6533 percpu one pool 6390 percpu one pool for each CPU
6534 pernode one pool 6391 pernode one pool for each NUMA node (equivalent
6535 to global 6392 to global on non-NUMA machines)
6536 6393
6537 sunrpc.tcp_slot_table_entries= 6394 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 6395 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 6396 [NFS,SUNRPC]
6540 Sets the upper limit 6397 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 6398 RPC calls that can be sent from the client to a
6542 server. Increasing th 6399 server. Increasing these values may allow you to
6543 improve throughput, b 6400 improve throughput, but will also increase the
6544 amount of memory rese 6401 amount of memory reserved for use by the client.
6545 6402
6546 suspend.pm_test_delay= 6403 suspend.pm_test_delay=
6547 [SUSPEND] 6404 [SUSPEND]
6548 Sets the number of se 6405 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 6406 mode before resuming the system (see
6550 /sys/power/pm_test). 6407 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 6408 is set. Default value is 5.
6552 6409
6553 svm= [PPC] 6410 svm= [PPC]
6554 Format: { on | off | 6411 Format: { on | off | y | n | 1 | 0 }
6555 This parameter contro 6412 This parameter controls use of the Protected
6556 Execution Facility on 6413 Execution Facility on pSeries.
6557 6414
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 6415 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in 6416 Format: { <int> [,<int>] | force | noforce }
6560 <int> -- Number of I/ 6417 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ 6418 <int> -- Second integer after comma. Number of swiotlb
6562 areas with t 6419 areas with their own lock. Will be rounded up
6563 to a power o 6420 to a power of 2.
6564 force -- force using 6421 force -- force using of bounce buffers even if they
6565 wouldn't be 6422 wouldn't be automatically used by the kernel
6566 noforce -- Never use 6423 noforce -- Never use bounce buffers (for debugging)
6567 6424
6568 switches= [HW,M68k,EARLY] !! 6425 switches= [HW,M68k]
6569 6426
6570 sysctl.*= [KNL] 6427 sysctl.*= [KNL]
6571 Set a sysctl paramete 6428 Set a sysctl parameter, right before loading the init
6572 process, as if the va 6429 process, as if the value was written to the respective
6573 /proc/sys/... file. B 6430 /proc/sys/... file. Both '.' and '/' are recognized as
6574 separators. Unrecogni 6431 separators. Unrecognized parameters and invalid values
6575 are reported in the k 6432 are reported in the kernel log. Sysctls registered
6576 later by a loaded mod 6433 later by a loaded module cannot be set this way.
6577 Example: sysctl.vm.sw 6434 Example: sysctl.vm.swappiness=40
6578 6435
6579 sysrq_always_enabled 6436 sysrq_always_enabled
6580 [KNL] 6437 [KNL]
6581 Ignore sysrq setting 6438 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 6439 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 6440 Useful for debugging.
6584 6441
6585 tcpmhash_entries= [KNL,NET] 6442 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 6443 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 6444 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 6445 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum 6446 cache size. See Documentation/networking/ip-sysctl.rst
6590 "tcp_no_metrics_save" 6447 "tcp_no_metrics_save" section for more details.
6591 6448
6592 tdfx= [HW,DRM] 6449 tdfx= [HW,DRM]
6593 6450
6594 test_suspend= [SUSPEND] 6451 test_suspend= [SUSPEND]
6595 Format: { "mem" | "st 6452 Format: { "mem" | "standby" | "freeze" }[,N]
6596 Specify "mem" (for Su 6453 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 6454 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 6455 as the system sleep state during system startup with
6599 the optional capabili 6456 the optional capability to repeat N number of times.
6600 The system is woken f 6457 The system is woken from this state using a
6601 wakeup-capable RTC al 6458 wakeup-capable RTC alarm.
6602 6459
6603 thash_entries= [KNL,NET] 6460 thash_entries= [KNL,NET]
6604 Set number of hash bu 6461 Set number of hash buckets for TCP connection
6605 6462
6606 thermal.act= [HW,ACPI] 6463 thermal.act= [HW,ACPI]
6607 -1: disable all activ 6464 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 6465 <degrees C>: override all lowest active trip points
6609 6466
6610 thermal.crt= [HW,ACPI] 6467 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 6468 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 6469 <degrees C>: override all critical trip points
6613 6470
6614 thermal.off= [HW,ACPI] 6471 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 6472 1: disable ACPI thermal control
6616 6473
6617 thermal.psv= [HW,ACPI] 6474 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 6475 -1: disable all passive trip points
6619 <degrees C>: override 6476 <degrees C>: override all passive trip points to this
6620 value 6477 value
6621 6478
6622 thermal.tzp= [HW,ACPI] 6479 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 6480 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 6481 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 6482 0: no polling (default)
6626 6483
6627 threadirqs [KNL,EARLY] !! 6484 threadirqs [KNL]
6628 Force threading of al 6485 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 6486 marked explicitly IRQF_NO_THREAD.
6630 6487
6631 topology= [S390,EARLY] !! 6488 topology= [S390]
6632 Format: {off | on} 6489 Format: {off | on}
6633 Specify if the kernel 6490 Specify if the kernel should make use of the cpu
6634 topology information 6491 topology information if the hardware supports this.
6635 The scheduler will ma 6492 The scheduler will make use of this information and
6636 e.g. base its process 6493 e.g. base its process migration decisions on it.
6637 Default is on. 6494 Default is on.
6638 6495
>> 6496 topology_updates= [KNL, PPC, NUMA]
>> 6497 Format: {off}
>> 6498 Specify if the kernel should ignore (off)
>> 6499 topology updates sent by the hypervisor to this
>> 6500 LPAR.
>> 6501
6639 torture.disable_onoff_at_boot= [KNL] 6502 torture.disable_onoff_at_boot= [KNL]
6640 Prevent the CPU-hotpl 6503 Prevent the CPU-hotplug component of torturing
6641 until after init has 6504 until after init has spawned.
6642 6505
6643 torture.ftrace_dump_at_shutdown= [KNL 6506 torture.ftrace_dump_at_shutdown= [KNL]
6644 Dump the ftrace buffe 6507 Dump the ftrace buffer at torture-test shutdown,
6645 even if there were no 6508 even if there were no errors. This can be a
6646 very costly operation 6509 very costly operation when many torture tests
6647 are running concurren 6510 are running concurrently, especially on systems
6648 with rotating-rust st 6511 with rotating-rust storage.
6649 6512
6650 torture.verbose_sleep_frequency= [KNL 6513 torture.verbose_sleep_frequency= [KNL]
6651 Specifies how many ve 6514 Specifies how many verbose printk()s should be
6652 emitted between each 6515 emitted between each sleep. The default of zero
6653 disables verbose-prin 6516 disables verbose-printk() sleeping.
6654 6517
6655 torture.verbose_sleep_duration= [KNL] 6518 torture.verbose_sleep_duration= [KNL]
6656 Duration of each verb 6519 Duration of each verbose-printk() sleep in jiffies.
6657 6520
>> 6521 tp720= [HW,PS2]
>> 6522
6658 tpm_suspend_pcr=[HW,TPM] 6523 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 6524 Format: integer pcr id
6660 Specify that at suspe 6525 Specify that at suspend time, the tpm driver
6661 should extend the spe 6526 should extend the specified pcr with zeros,
6662 as a workaround for s 6527 as a workaround for some chips which fail to
6663 flush the last writte 6528 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 6529 This will guarantee that all the other pcrs
6665 are saved. 6530 are saved.
6666 6531
6667 tpm_tis.interrupts= [HW,TPM] 6532 tpm_tis.interrupts= [HW,TPM]
6668 Enable interrupts for 6533 Enable interrupts for the MMIO based physical layer
6669 for the FIFO interfac 6534 for the FIFO interface. By default it is set to false
6670 (0). For more informa 6535 (0). For more information about TPM hardware interfaces
6671 defined by Trusted Co 6536 defined by Trusted Computing Group (TCG) see
6672 https://trustedcomput 6537 https://trustedcomputinggroup.org/resource/pc-client-platform-tpm-profile-ptp-specification/
6673 6538
6674 tp_printk [FTRACE] 6539 tp_printk [FTRACE]
6675 Have the tracepoints 6540 Have the tracepoints sent to printk as well as the
6676 tracing ring buffer. 6541 tracing ring buffer. This is useful for early boot up
6677 where the system hang 6542 where the system hangs or reboots and does not give the
6678 option for reading th 6543 option for reading the tracing buffer or performing a
6679 ftrace_dump_on_oops. 6544 ftrace_dump_on_oops.
6680 6545
6681 To turn off having tr 6546 To turn off having tracepoints sent to printk,
6682 echo 0 > /proc/sys/k 6547 echo 0 > /proc/sys/kernel/tracepoint_printk
6683 Note, echoing 1 into 6548 Note, echoing 1 into this file without the
6684 tp_printk kernel cmdl !! 6549 tracepoint_printk kernel cmdline option has no effect.
6685 6550
6686 The tp_printk_stop_on 6551 The tp_printk_stop_on_boot (see below) can also be used
6687 to stop the printing 6552 to stop the printing of events to console at
6688 late_initcall_sync. 6553 late_initcall_sync.
6689 6554
6690 ** CAUTION ** 6555 ** CAUTION **
6691 6556
6692 Having tracepoints se 6557 Having tracepoints sent to printk() and activating high
6693 frequency tracepoints 6558 frequency tracepoints such as irq or sched, can cause
6694 the system to live lo 6559 the system to live lock.
6695 6560
6696 tp_printk_stop_on_boot [FTRACE] 6561 tp_printk_stop_on_boot [FTRACE]
6697 When tp_printk (above 6562 When tp_printk (above) is set, it can cause a lot of noise
6698 on the console. It ma 6563 on the console. It may be useful to only include the
6699 printing of events du 6564 printing of events during boot up, as user space may
6700 make the system inope 6565 make the system inoperable.
6701 6566
6702 This command line opt 6567 This command line option will stop the printing of events
6703 to console at the lat 6568 to console at the late_initcall_sync() time frame.
6704 6569
6705 trace_buf_size=nn[KMG] 6570 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 6571 [FTRACE] will set tracing buffer size on each cpu.
6707 6572
6708 trace_clock= [FTRACE] Set the cloc 6573 trace_clock= [FTRACE] Set the clock used for tracing events
6709 at boot up. 6574 at boot up.
6710 local - Use the per C 6575 local - Use the per CPU time stamp counter
6711 (converted in 6576 (converted into nanoseconds). Fast, but
6712 depending on 6577 depending on the architecture, may not be
6713 in sync betwe 6578 in sync between CPUs.
6714 global - Event time s 6579 global - Event time stamps are synchronize across
6715 CPUs. May be 6580 CPUs. May be slower than the local clock,
6716 but better fo 6581 but better for some race conditions.
6717 counter - Simple coun 6582 counter - Simple counting of events (1, 2, ..)
6718 note, some co 6583 note, some counts may be skipped due to the
6719 infrastructur 6584 infrastructure grabbing the clock more than
6720 once per even 6585 once per event.
6721 uptime - Use jiffies 6586 uptime - Use jiffies as the time stamp.
6722 perf - Use the same c 6587 perf - Use the same clock that perf uses.
6723 mono - Use ktime_get_ 6588 mono - Use ktime_get_mono_fast_ns() for time stamps.
6724 mono_raw - Use ktime_ 6589 mono_raw - Use ktime_get_raw_fast_ns() for time
6725 stamps. 6590 stamps.
6726 boot - Use ktime_get_ 6591 boot - Use ktime_get_boot_fast_ns() for time stamps.
6727 Architectures may add 6592 Architectures may add more clocks. See
6728 Documentation/trace/f 6593 Documentation/trace/ftrace.rst for more details.
6729 6594
6730 trace_event=[event-list] 6595 trace_event=[event-list]
6731 [FTRACE] Set and star 6596 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 6597 to facilitate early boot debugging. The event-list is a
6733 comma-separated list 6598 comma-separated list of trace events to enable. See
6734 also Documentation/tr 6599 also Documentation/trace/events.rst
6735 6600
6736 trace_instance=[instance-info] 6601 trace_instance=[instance-info]
6737 [FTRACE] Create a rin 6602 [FTRACE] Create a ring buffer instance early in boot up.
6738 This will be listed i 6603 This will be listed in:
6739 6604
6740 /sys/kernel/t 6605 /sys/kernel/tracing/instances
6741 6606
6742 Events can be enabled 6607 Events can be enabled at the time the instance is created
6743 via: 6608 via:
6744 6609
6745 trace_instanc 6610 trace_instance=<name>,<system1>:<event1>,<system2>:<event2>
6746 6611
6747 Note, the "<system*>: 6612 Note, the "<system*>:" portion is optional if the event is
6748 unique. 6613 unique.
6749 6614
6750 trace_instanc 6615 trace_instance=foo,sched:sched_switch,irq_handler_entry,initcall
6751 6616
6752 will enable the "sche 6617 will enable the "sched_switch" event (note, the "sched:" is optional, and
6753 the same thing would 6618 the same thing would happen if it was left off). The irq_handler_entry
6754 event, and all events 6619 event, and all events under the "initcall" system.
6755 6620
6756 trace_options=[option-list] 6621 trace_options=[option-list]
6757 [FTRACE] Enable or di 6622 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 6623 The option-list is a comma delimited list of options
6759 that can be enabled o 6624 that can be enabled or disabled just as if you were
6760 to echo the option na 6625 to echo the option name into
6761 6626
6762 /sys/kernel/traci 6627 /sys/kernel/tracing/trace_options
6763 6628
6764 For example, to enabl 6629 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 6630 stack trace of each event), add to the command line:
6766 6631
6767 trace_options=s 6632 trace_options=stacktrace
6768 6633
6769 See also Documentatio 6634 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 6635 section.
6771 6636
6772 trace_trigger=[trigger-list] 6637 trace_trigger=[trigger-list]
6773 [FTRACE] Add a event 6638 [FTRACE] Add a event trigger on specific events.
6774 Set a trigger on top 6639 Set a trigger on top of a specific event, with an optional
6775 filter. 6640 filter.
6776 6641
6777 The format is is "tra 6642 The format is is "trace_trigger=<event>.<trigger>[ if <filter>],..."
6778 Where more than one t 6643 Where more than one trigger may be specified that are comma deliminated.
6779 6644
6780 For example: 6645 For example:
6781 6646
6782 trace_trigger="sche 6647 trace_trigger="sched_switch.stacktrace if prev_state == 2"
6783 6648
6784 The above will enable 6649 The above will enable the "stacktrace" trigger on the "sched_switch"
6785 event but only trigge 6650 event but only trigger it if the "prev_state" of the "sched_switch"
6786 event is "2" (TASK_UN 6651 event is "2" (TASK_UNINTERUPTIBLE).
6787 6652
6788 See also "Event trigg 6653 See also "Event triggers" in Documentation/trace/events.rst
6789 6654
6790 6655
6791 traceoff_on_warning 6656 traceoff_on_warning
6792 [FTRACE] enable this 6657 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 6658 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 6659 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ 6660 file located in /sys/kernel/tracing/
6796 6661
6797 This option is useful 6662 This option is useful, as it disables the trace before
6798 the WARNING dump is c 6663 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 6664 be filled with content caused by the warning output.
6800 6665
6801 This option can also 6666 This option can also be set at run time via the sysctl
6802 option: kernel/trace 6667 option: kernel/traceoff_on_warning
6803 6668
6804 transparent_hugepage= 6669 transparent_hugepage=
6805 [KNL] 6670 [KNL]
6806 Format: [always|madvi 6671 Format: [always|madvise|never]
6807 Can be used to contro 6672 Can be used to control the default behavior of the system
6808 with respect to trans 6673 with respect to transparent hugepages.
6809 See Documentation/adm 6674 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 6675 for more details.
6811 6676
6812 trusted.source= [KEYS] 6677 trusted.source= [KEYS]
6813 Format: <string> 6678 Format: <string>
6814 This parameter identi 6679 This parameter identifies the trust source as a backend
6815 for trusted keys impl 6680 for trusted keys implementation. Supported trust
6816 sources: 6681 sources:
6817 - "tpm" 6682 - "tpm"
6818 - "tee" 6683 - "tee"
6819 - "caam" 6684 - "caam"
6820 - "dcp" <<
6821 If not specified then 6685 If not specified then it defaults to iterating through
6822 the trust source list 6686 the trust source list starting with TPM and assigns the
6823 first trust source as 6687 first trust source as a backend which is initialized
6824 successfully during i 6688 successfully during iteration.
6825 6689
6826 trusted.rng= [KEYS] 6690 trusted.rng= [KEYS]
6827 Format: <string> 6691 Format: <string>
6828 The RNG used to gener 6692 The RNG used to generate key material for trusted keys.
6829 Can be one of: 6693 Can be one of:
6830 - "kernel" 6694 - "kernel"
6831 - the same value as t 6695 - the same value as trusted.source: "tpm" or "tee"
6832 - "default" 6696 - "default"
6833 If not specified, "de 6697 If not specified, "default" is used. In this case,
6834 the RNG's choice is l 6698 the RNG's choice is left to each individual trust source.
6835 6699
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 6700 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 6701 Format: <string>
6850 [x86] reliable: mark 6702 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 6703 disables clocksource verification at runtime, as well
6852 as the stability chec 6704 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 6705 high-resolution timer mode on older hardware, and in
6854 virtualized environme 6706 virtualized environment.
6855 [x86] noirqtime: Do n 6707 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 6708 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 6709 platforms where RDTSC is slow and this accounting
6858 can add overhead. 6710 can add overhead.
6859 [x86] unstable: mark 6711 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 6712 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 6713 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 6714 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 6715 in situations with strict latency requirements (where
6864 interruptions from cl 6716 interruptions from clocksource watchdog are not
6865 acceptable). 6717 acceptable).
6866 [x86] recalibrate: fo 6718 [x86] recalibrate: force recalibration against a HW timer
6867 (HPET or PM timer) on 6719 (HPET or PM timer) on systems whose TSC frequency was
6868 obtained from HW or F 6720 obtained from HW or FW using either an MSR or CPUID(0x15).
6869 Warn if the differenc 6721 Warn if the difference is more than 500 ppm.
6870 [x86] watchdog: Use T 6722 [x86] watchdog: Use TSC as the watchdog clocksource with
6871 which to check other 6723 which to check other HW timers (HPET or PM timer), but
6872 only on systems where 6724 only on systems where TSC has been deemed trustworthy.
6873 This will be suppress 6725 This will be suppressed by an earlier tsc=nowatchdog and
6874 can be overridden by 6726 can be overridden by a later tsc=nowatchdog. A console
6875 message will flag any 6727 message will flag any such suppression or overriding.
6876 6728
6877 tsc_early_khz= [X86,EARLY] Skip earl !! 6729 tsc_early_khz= [X86] Skip early TSC calibration and use the given
6878 value instead. Useful 6730 value instead. Useful when the early TSC frequency discovery
6879 procedure is not reli 6731 procedure is not reliable, such as on overclocked systems
6880 with CPUID.16h suppor 6732 with CPUID.16h support and partial CPUID.15h support.
6881 Format: <unsigned int 6733 Format: <unsigned int>
6882 6734
6883 tsx= [X86] Control Transac 6735 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 6736 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 6737 support TSX control.
6886 6738
6887 This parameter contro 6739 This parameter controls the TSX feature. The options are:
6888 6740
6889 on - Enable TSX 6741 on - Enable TSX on the system. Although there are
6890 mitigations f 6742 mitigations for all known security vulnerabilities,
6891 TSX has been 6743 TSX has been known to be an accelerator for
6892 several previ 6744 several previous speculation-related CVEs, and
6893 so there may 6745 so there may be unknown security risks associated
6894 with leaving 6746 with leaving it enabled.
6895 6747
6896 off - Disable TSX 6748 off - Disable TSX on the system. (Note that this
6897 option takes 6749 option takes effect only on newer CPUs which are
6898 not vulnerabl 6750 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 6751 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 6752 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 6753 update. This new MSR allows for the reliable
6902 deactivation 6754 deactivation of the TSX functionality.)
6903 6755
6904 auto - Disable TSX 6756 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 6757 otherwise enable TSX on the system.
6906 6758
6907 Not specifying this o 6759 Not specifying this option is equivalent to tsx=off.
6908 6760
6909 See Documentation/adm 6761 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 6762 for more details.
6911 6763
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 6764 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 6765 Abort (TAA) vulnerability.
6914 6766
6915 Similar to Micro-arch 6767 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 6768 certain CPUs that support Transactional
6917 Synchronization Exten 6769 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 6770 exploit against CPU internal buffers which can forward
6919 information to a disc 6771 information to a disclosure gadget under certain
6920 conditions. 6772 conditions.
6921 6773
6922 In vulnerable process 6774 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 6775 data can be used in a cache side channel attack, to
6924 access data to which 6776 access data to which the attacker does not have direct
6925 access. 6777 access.
6926 6778
6927 This parameter contro 6779 This parameter controls the TAA mitigation. The
6928 options are: 6780 options are:
6929 6781
6930 full - Enable T 6782 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 6783 if TSX is enabled.
6932 6784
6933 full,nosmt - Enable T 6785 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 6786 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 6787 is not disabled because CPU is not
6936 vulnerab 6788 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 6789 off - Unconditionally disable TAA mitigation
6938 6790
6939 On MDS-affected machi 6791 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 6792 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 6793 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 6794 this mitigation, you need to specify mds=off too.
6943 6795
6944 Not specifying this o 6796 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 6797 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 6798 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 6799 required and doesn't provide any additional
6948 mitigation. 6800 mitigation.
6949 6801
6950 For details see: 6802 For details see:
6951 Documentation/admin-g 6803 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 6804
6953 turbografx.map[2|3]= [HW,JOY] 6805 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 6806 TurboGraFX parallel port interface
6955 Format: 6807 Format:
6956 <port#>,<js1>,<js2>,< 6808 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 6809 See also Documentation/input/devices/joystick-parport.rst
6958 6810
6959 udbg-immortal [PPC] When debugging 6811 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 6812 happen after console_init() and before a proper
6961 console driver takes 6813 console driver takes over, this boot options might
6962 help "seeing" what's 6814 help "seeing" what's going on.
6963 6815
6964 uhash_entries= [KNL,NET] 6816 uhash_entries= [KNL,NET]
6965 Set number of hash bu 6817 Set number of hash buckets for UDP/UDP-Lite connections
6966 6818
6967 uhci-hcd.ignore_oc= 6819 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 6820 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 6821 Some badly-designed motherboards generate lots of
6970 bogus events, for por 6822 bogus events, for ports that aren't wired to
6971 anything. Set this p 6823 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 6824 Note that genuine overcurrent events won't be
6973 reported either. 6825 reported either.
6974 6826
6975 unknown_nmi_panic 6827 unknown_nmi_panic
6976 [X86] Cause panic on 6828 [X86] Cause panic on unknown NMI.
6977 6829
6978 unwind_debug [X86-64,EARLY] !! 6830 unwind_debug [X86-64]
6979 Enable unwinder debug 6831 Enable unwinder debug output. This can be
6980 useful for debugging 6832 useful for debugging certain unwinder error
6981 conditions, including 6833 conditions, including corrupt stacks and
6982 bad/missing unwinder 6834 bad/missing unwinder metadata.
6983 6835
6984 usbcore.authorized_default= 6836 usbcore.authorized_default=
6985 [USB] Default USB dev 6837 [USB] Default USB device authorization:
6986 (default -1 = authori 6838 (default -1 = authorized (same as 1),
6987 0 = not authorized, 1 6839 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 6840 if device connected to internal port)
6989 6841
6990 usbcore.autosuspend= 6842 usbcore.autosuspend=
6991 [USB] The autosuspend 6843 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 6844 for newly-detected USB devices (default 2). This
6993 is the time required 6845 is the time required before an idle device will be
6994 autosuspended. Devic 6846 autosuspended. Devices for which the delay is set
6995 to a negative value w 6847 to a negative value won't be autosuspended at all.
6996 6848
6997 usbcore.usbfs_snoop= 6849 usbcore.usbfs_snoop=
6998 [USB] Set to log all 6850 [USB] Set to log all usbfs traffic (default 0 = off).
6999 6851
7000 usbcore.usbfs_snoop_max= 6852 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 6853 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 6854 (default = 65536).
7003 6855
7004 usbcore.blinkenlights= 6856 usbcore.blinkenlights=
7005 [USB] Set to cycle le 6857 [USB] Set to cycle leds on hubs (default 0 = off).
7006 6858
7007 usbcore.old_scheme_first= 6859 usbcore.old_scheme_first=
7008 [USB] Start with the 6860 [USB] Start with the old device initialization
7009 scheme (default 0 = o 6861 scheme (default 0 = off).
7010 6862
7011 usbcore.usbfs_memory_mb= 6863 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 6864 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 6865 usbfs (default = 16, 0 = max = 2047).
7014 6866
7015 usbcore.use_both_schemes= 6867 usbcore.use_both_schemes=
7016 [USB] Try the other d 6868 [USB] Try the other device initialization scheme
7017 if the first one fail 6869 if the first one fails (default 1 = enabled).
7018 6870
7019 usbcore.initial_descriptor_timeout= 6871 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 6872 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 6873 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 6874 (default 5000 = 5.0 seconds).
7023 6875
7024 usbcore.nousb [USB] Disable the USB 6876 usbcore.nousb [USB] Disable the USB subsystem
7025 6877
7026 usbcore.quirks= 6878 usbcore.quirks=
7027 [USB] A list of quirk 6879 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 6880 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 6881 commas. Each entry has the form
7030 VendorID:ProductID:Fl 6882 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 6883 numbers and Flags is a set of letters. Each letter
7032 will change the built 6884 will change the built-in quirk; setting it if it is
7033 clear and clearing it 6885 clear and clearing it if it is set. The letters have
7034 the following meaning 6886 the following meanings:
7035 a = USB_QUIRK 6887 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 6888 descriptors must not be fetched using
7037 a 255 6889 a 255-byte read);
7038 b = USB_QUIRK 6890 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 6891 correctly so reset it instead);
7040 c = USB_QUIRK 6892 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 6893 Set-Interface requests);
7042 d = USB_QUIRK 6894 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 6895 handle its Configuration or Interface
7044 strin 6896 strings);
7045 e = USB_QUIRK 6897 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 6898 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 6899 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 6900 more interface descriptions than the
7049 bNumI 6901 bNumInterfaces count, and can't handle
7050 talki 6902 talking to these interfaces);
7051 g = USB_QUIRK 6903 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 6904 during initialization, after we read
7053 the d 6905 the device descriptor);
7054 h = USB_QUIRK 6906 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 6907 high speed and super speed interrupt
7056 endpo 6908 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 6909 require the interval in microframes (1
7058 micro 6910 microframe = 125 microseconds) to be
7059 calcu 6911 calculated as interval = 2 ^
7060 (bInt 6912 (bInterval-1).
7061 Devic 6913 Devices with this quirk report their
7062 bInte 6914 bInterval as the result of this
7063 calcu 6915 calculation instead of the exponent
7064 varia 6916 variable used in the calculation);
7065 i = USB_QUIRK 6917 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 6918 handle device_qualifier descriptor
7067 reque 6919 requests);
7068 j = USB_QUIRK 6920 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 6921 generates spurious wakeup, ignore
7070 remot 6922 remote wakeup capability);
7071 k = USB_QUIRK 6923 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 6924 Power Management);
7073 l = USB_QUIRK 6925 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 6926 (Device reports its bInterval as linear
7075 frame 6927 frames instead of the USB 2.0
7076 calcu 6928 calculation);
7077 m = USB_QUIRK 6929 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 6930 to be disconnected before suspend to
7079 preve 6931 prevent spurious wakeup);
7080 n = USB_QUIRK 6932 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 6933 pause after every control message);
7082 o = USB_QUIRK 6934 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 6935 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 6936 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 6937
7089 usbhid.mousepoll= 6938 usbhid.mousepoll=
7090 [USBHID] The interval 6939 [USBHID] The interval which mice are to be polled at.
7091 6940
7092 usbhid.jspoll= 6941 usbhid.jspoll=
7093 [USBHID] The interval 6942 [USBHID] The interval which joysticks are to be polled at.
7094 6943
7095 usbhid.kbpoll= 6944 usbhid.kbpoll=
7096 [USBHID] The interval 6945 [USBHID] The interval which keyboards are to be polled at.
7097 6946
7098 usb-storage.delay_use= 6947 usb-storage.delay_use=
7099 [UMS] The delay in se 6948 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 6949 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 6950
7105 usb-storage.quirks= 6951 usb-storage.quirks=
7106 [UMS] A list of quirk 6952 [UMS] A list of quirks entries to supplement or
7107 override the built-in 6953 override the built-in unusual_devs list. List
7108 entries are separated 6954 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 6955 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 6956 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 6957 Flags is a set of characters, each corresponding
7112 to a common usb-stora 6958 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 6959 a = SANE_SENSE (collect more than 18 bytes
7114 of se 6960 of sense data, not on uas);
7115 b = BAD_SENSE 6961 b = BAD_SENSE (don't collect more than 18
7116 bytes 6962 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 6963 c = FIX_CAPACITY (decrease the reported
7118 devic 6964 device capacity by one sector);
7119 d = NO_READ_D 6965 d = NO_READ_DISC_INFO (don't use
7120 READ_ 6966 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 6967 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 6968 READ_CAPACITY_16 command);
7123 f = NO_REPORT 6969 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 6970 command, uas only);
7125 g = MAX_SECTO 6971 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 6972 240 sectors at a time, uas only);
7127 h = CAPACITY_ 6973 h = CAPACITY_HEURISTICS (decrease the
7128 repor 6974 reported device capacity by one
7129 secto 6975 sector if the number is odd);
7130 i = IGNORE_DE 6976 i = IGNORE_DEVICE (don't bind to this
7131 devic 6977 device);
7132 j = NO_REPORT 6978 j = NO_REPORT_LUNS (don't use report luns
7133 comma 6979 command, uas only);
7134 k = NO_SAME ( 6980 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 6981 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 6982 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 6983 m = MAX_SECTORS_64 (don't transfer more
7138 than 6984 than 64 sectors = 32 KB at a time,
7139 not o 6985 not on uas);
7140 n = INITIAL_R 6986 n = INITIAL_READ10 (force a retry of the
7141 initi 6987 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 6988 o = CAPACITY_OK (accept the capacity
7143 repor 6989 reported by the device, not on uas);
7144 p = WRITE_CAC 6990 p = WRITE_CACHE (the device cache is ON
7145 by de 6991 by default, not on uas);
7146 r = IGNORE_RE 6992 r = IGNORE_RESIDUE (the device reports
7147 bogus 6993 bogus residue values, not on uas);
7148 s = SINGLE_LU 6994 s = SINGLE_LUN (the device has only one
7149 Logic 6995 Logical Unit);
7150 t = NO_ATA_1X 6996 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 6997 commands, uas only);
7152 u = IGNORE_UA 6998 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 6999 w = NO_WP_DETECT (don't test whether the
7154 mediu 7000 medium is write-protected).
7155 y = ALWAYS_SY 7001 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 7002 even if the device claims no cache,
7157 not o 7003 not on uas)
7158 Example: quirks=0419: 7004 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 7005
7160 user_debug= [KNL,ARM] 7006 user_debug= [KNL,ARM]
7161 Format: <int> 7007 Format: <int>
7162 See arch/arm/Kconfig. 7008 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 7009 1 - undefined instruction events
7164 2 - system c 7010 2 - system calls
7165 4 - invalid 7011 4 - invalid data aborts
7166 8 - SIGSEGV 7012 8 - SIGSEGV faults
7167 16 - SIGBUS f 7013 16 - SIGBUS faults
7168 Example: user_debug=3 7014 Example: user_debug=31
7169 7015
7170 userpte= 7016 userpte=
7171 [X86,EARLY] Flags con !! 7017 [X86] Flags controlling user PTE allocations.
7172 7018
7173 nohigh = do n 7019 nohigh = do not allocate PTE pages in
7174 HIGHM 7020 HIGHMEM regardless of setting
7175 of CO 7021 of CONFIG_HIGHPTE.
7176 7022
7177 vdso= [X86,SH,SPARC] 7023 vdso= [X86,SH,SPARC]
7178 On X86_32, this is an 7024 On X86_32, this is an alias for vdso32=. Otherwise:
7179 7025
7180 vdso=1: enable VDSO ( 7026 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 7027 vdso=0: disable VDSO mapping
7182 7028
7183 vdso32= [X86] Control the 32- 7029 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 7030 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 7031 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 7032
7187 See the help text for 7033 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 7034 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 7035 vdso32=0; otherwise, the default is vdso32=1.
7190 7036
7191 For compatibility wit 7037 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 7038 alias for vdso32=0.
7193 7039
7194 Try vdso32=0 if you e 7040 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 7041 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 7042
7197 video= [FB,EARLY] Frame buff !! 7043 vector= [IA-64,SMP]
>> 7044 vector=percpu: enable percpu vector domain
>> 7045
>> 7046 video= [FB] Frame buffer configuration
7198 See Documentation/fb/ 7047 See Documentation/fb/modedb.rst.
7199 7048
7200 video.brightness_switch_enabled= [ACP 7049 video.brightness_switch_enabled= [ACPI]
7201 Format: [0|1] 7050 Format: [0|1]
7202 If set to 1, on recei 7051 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 7052 generated by hotkey, video driver will adjust brightness
7204 level and then send o 7053 level and then send out the event to user space through
7205 the allocated input d 7054 the allocated input device. If set to 0, video driver
7206 will only send out th 7055 will only send out the event without touching backlight
7207 brightness level. 7056 brightness level.
7208 default: 1 7057 default: 1
7209 7058
7210 virtio_mmio.device= 7059 virtio_mmio.device=
7211 [VMMIO] Memory mapped 7060 [VMMIO] Memory mapped virtio (platform) device.
7212 7061
7213 <size>@<basead 7062 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 7063 where:
7215 <size> := 7064 <size> := size (can use standard suffixes
7216 7065 like K, M and G)
7217 <baseaddr> := 7066 <baseaddr> := physical base address
7218 <irq> := 7067 <irq> := interrupt number (as passed to
7219 7068 request_irq())
7220 <id> := 7069 <id> := (optional) platform device id
7221 example: 7070 example:
7222 virtio_mmio.d 7071 virtio_mmio.device=1K@0x100b0000:48:7
7223 7072
7224 Can be used multiple 7073 Can be used multiple times for multiple devices.
7225 7074
7226 vga= [BOOT,X86-32] Select 7075 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc 7076 See Documentation/arch/x86/boot.rst and
7228 Documentation/admin-g 7077 Documentation/admin-guide/svga.rst.
7229 Use vga=ask for menu. 7078 Use vga=ask for menu.
7230 This is actually a bo 7079 This is actually a boot loader parameter; the value is
7231 passed to the kernel 7080 passed to the kernel using a special protocol.
7232 7081
7233 vm_debug[=options] [KNL] Availab 7082 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 7083 May slow down system boot speed, especially when
7235 enabled on systems wi 7084 enabled on systems with a large amount of memory.
7236 All options are enabl 7085 All options are enabled by default, and this
7237 interface is meant to 7086 interface is meant to allow for selectively
7238 enabling or disabling 7087 enabling or disabling specific virtual memory
7239 debugging features. 7088 debugging features.
7240 7089
7241 Available options are 7090 Available options are:
7242 P Enable page s 7091 P Enable page structure init time poisoning
7243 - Disable all o 7092 - Disable all of the above options
7244 7093
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 7094 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 7095 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 7096 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 7097 decrease the size and leave more room for directly
7249 for directly mapped k !! 7098 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 7099
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 7100 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 7101 Sets the memory size reserved for contiguous memory
7256 allocations for the v 7102 allocations for the vmcp device driver.
7257 7103
7258 vmhalt= [KNL,S390] Perform z/ 7104 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 7105 Format: <command>
7260 7106
7261 vmpanic= [KNL,S390] Perform z/ 7107 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 7108 Format: <command>
7263 7109
7264 vmpoff= [KNL,S390] Perform z/ 7110 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 7111 Format: <command>
7266 7112
7267 vsyscall= [X86-64,EARLY] !! 7113 vsyscall= [X86-64]
7268 Controls the behavior 7114 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 7115 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 7116 code). Most statically-linked binaries and older
7271 versions of glibc use 7117 versions of glibc use these calls. Because these
7272 functions are at fixe 7118 functions are at fixed addresses, they make nice
7273 targets for exploits 7119 targets for exploits that can control RIP.
7274 7120
7275 emulate Vsyscalls 7121 emulate Vsyscalls turn into traps and are emulated
7276 reasonabl 7122 reasonably safely. The vsyscall page is
7277 readable. 7123 readable.
7278 7124
7279 xonly [default] 7125 xonly [default] Vsyscalls turn into traps and are
7280 emulated 7126 emulated reasonably safely. The vsyscall
7281 page is n 7127 page is not readable.
7282 7128
7283 none Vsyscalls 7129 none Vsyscalls don't work at all. This makes
7284 them quit 7130 them quite hard to use for exploits but
7285 might bre 7131 might break your system.
7286 7132
7287 vt.color= [VT] Default text col 7133 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 7134 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 7135 Default: 0x07 = light gray on black.
7290 7136
7291 vt.cur_default= [VT] Default cursor s 7137 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 7138 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 7139 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 7140 see VGA-softcursor.txt. Default: 2 = underline.
7295 7141
7296 vt.default_blu= [VT] 7142 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 7143 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 7144 Change the default blue palette of the console.
7299 This is a 16-member a 7145 This is a 16-member array composed of values
7300 ranging from 0-255. 7146 ranging from 0-255.
7301 7147
7302 vt.default_grn= [VT] 7148 vt.default_grn= [VT]
7303 Format: <green0>,<gre 7149 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 7150 Change the default green palette of the console.
7305 This is a 16-member a 7151 This is a 16-member array composed of values
7306 ranging from 0-255. 7152 ranging from 0-255.
7307 7153
7308 vt.default_red= [VT] 7154 vt.default_red= [VT]
7309 Format: <red0>,<red1> 7155 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 7156 Change the default red palette of the console.
7311 This is a 16-member a 7157 This is a 16-member array composed of values
7312 ranging from 0-255. 7158 ranging from 0-255.
7313 7159
7314 vt.default_utf8= 7160 vt.default_utf8=
7315 [VT] 7161 [VT]
7316 Format=<0|1> 7162 Format=<0|1>
7317 Set system-wide defau 7163 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 7164 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 7165 newly opened terminals.
7320 7166
7321 vt.global_cursor_default= 7167 vt.global_cursor_default=
7322 [VT] 7168 [VT]
7323 Format=<-1|0|1> 7169 Format=<-1|0|1>
7324 Set system-wide defau 7170 Set system-wide default for whether a cursor
7325 is shown on new VTs. 7171 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 7172 i.e. cursors will be created by default unless
7327 overridden by individ 7173 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 7174 cursors, 1 will display them.
7329 7175
7330 vt.italic= [VT] Default color fo 7176 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 7177 Default: 2 = green.
7332 7178
7333 vt.underline= [VT] Default color fo 7179 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 7180 Default: 3 = cyan.
7335 7181
7336 watchdog timers [HW,WDT] For informat 7182 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat 7183 see Documentation/watchdog/watchdog-parameters.rst
7338 or other driver-speci 7184 or other driver-specific files in the
7339 Documentation/watchdo 7185 Documentation/watchdog/ directory.
7340 7186
7341 watchdog_thresh= 7187 watchdog_thresh=
7342 [KNL] 7188 [KNL]
7343 Set the hard lockup d 7189 Set the hard lockup detector stall duration
7344 threshold in seconds. 7190 threshold in seconds. The soft lockup detector
7345 threshold is set to t 7191 threshold is set to twice the value. A value of 0
7346 disables both lockup 7192 disables both lockup detectors. Default is 10
7347 seconds. 7193 seconds.
7348 7194
7349 workqueue.unbound_cpus= 7195 workqueue.unbound_cpus=
7350 [KNL,SMP] Specify to 7196 [KNL,SMP] Specify to constrain one or some CPUs
7351 to use in unbound wor 7197 to use in unbound workqueues.
7352 Format: <cpu-list> 7198 Format: <cpu-list>
7353 By default, all onlin 7199 By default, all online CPUs are available for
7354 unbound workqueues. 7200 unbound workqueues.
7355 7201
7356 workqueue.watchdog_thresh= 7202 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 7203 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 7204 warn stall conditions and dump internal state to
7359 help debugging. 0 di 7205 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 7206 detection; otherwise, it's the stall threshold
7361 duration in seconds. 7207 duration in seconds. The default value is 30 and
7362 it can be updated at 7208 it can be updated at runtime by writing to the
7363 corresponding sysfs f 7209 corresponding sysfs file.
7364 7210
7365 workqueue.cpu_intensive_thresh_us= 7211 workqueue.cpu_intensive_thresh_us=
7366 Per-cpu work items wh 7212 Per-cpu work items which run for longer than this
7367 threshold are automat 7213 threshold are automatically considered CPU intensive
7368 and excluded from con 7214 and excluded from concurrency management to prevent
7369 them from noticeably 7215 them from noticeably delaying other per-cpu work
7370 items. Default is 100 7216 items. Default is 10000 (10ms).
7371 7217
7372 If CONFIG_WQ_CPU_INTE 7218 If CONFIG_WQ_CPU_INTENSIVE_REPORT is set, the kernel
7373 will report the work 7219 will report the work functions which violate this
7374 threshold repeatedly. 7220 threshold repeatedly. They are likely good
7375 candidates for using 7221 candidates for using WQ_UNBOUND workqueues instead.
7376 7222
7377 workqueue.cpu_intensive_warning_thres <<
7378 If CONFIG_WQ_CPU_INTE <<
7379 will report the work <<
7380 intensive_threshold_u <<
7381 spurious warnings, st <<
7382 function has violated <<
7383 <<
7384 The default is 4 time <<
7385 <<
7386 workqueue.power_efficient 7223 workqueue.power_efficient
7387 Per-cpu workqueues ar 7224 Per-cpu workqueues are generally preferred because
7388 they show better perf 7225 they show better performance thanks to cache
7389 locality; unfortunate 7226 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 7227 be more power hungry than unbound workqueues.
7391 7228
7392 Enabling this makes t 7229 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 7230 were observed to contribute significantly to power
7394 consumption unbound, 7231 consumption unbound, leading to measurably lower
7395 power usage at the co 7232 power usage at the cost of small performance
7396 overhead. 7233 overhead.
7397 7234
7398 The default value of 7235 The default value of this parameter is determined by
7399 the config option CON 7236 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 7237
7401 workqueue.default_affinity_scope= 7238 workqueue.default_affinity_scope=
7402 Select the default af 7239 Select the default affinity scope to use for unbound
7403 workqueues. Can be on 7240 workqueues. Can be one of "cpu", "smt", "cache",
7404 "numa" and "system". 7241 "numa" and "system". Default is "cache". For more
7405 information, see the 7242 information, see the Affinity Scopes section in
7406 Documentation/core-ap 7243 Documentation/core-api/workqueue.rst.
7407 7244
7408 This can be changed a 7245 This can be changed after boot by writing to the
7409 matching /sys/module/ 7246 matching /sys/module/workqueue/parameters file. All
7410 workqueues with the " 7247 workqueues with the "default" affinity scope will be
7411 updated accordingly. !! 7248 updated accordignly.
7412 7249
7413 workqueue.debug_force_rr_cpu 7250 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 7251 Workqueue used to implicitly guarantee that work
7415 items queued without 7252 items queued without explicit CPU specified are put
7416 on the local CPU. Th 7253 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 7254 and while local CPU is still preferred work items
7418 may be put on foreign 7255 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 7256 forces round-robin CPU selection to flush out
7420 usages which depend o 7257 usages which depend on the now broken guarantee.
7421 When enabled, memory 7258 When enabled, memory and cache locality will be
7422 impacted. 7259 impacted.
7423 7260
7424 writecombine= [LOONGARCH,EARLY] Con !! 7261 writecombine= [LOONGARCH] Control the MAT (Memory Access Type) of
7425 Type) of ioremap_wc() !! 7262 ioremap_wc().
7426 7263
7427 on - Enable writeco 7264 on - Enable writecombine, use WUC for ioremap_wc()
7428 off - Disable writec 7265 off - Disable writecombine, use SUC for ioremap_wc()
7429 7266
7430 x2apic_phys [X86-64,APIC,EARLY] U !! 7267 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7431 default x2apic cluste 7268 default x2apic cluster mode on platforms
7432 supporting x2apic. 7269 supporting x2apic.
7433 7270
7434 xen_512gb_limit [KNL,X86-64,X 7271 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 7272 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 7273 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 7274 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 7275 save/restore/migration must be enabled to handle larger
7439 domains. 7276 domains.
7440 7277
7441 xen_emul_unplug= [HW,X !! 7278 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 7279 Unplug Xen emulated devices
7443 Format: [unplug0,][un 7280 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 7281 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 7282 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 7283 nics -- unplug network devices
7447 all -- unplug all emu 7284 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 7285 unnecessary -- unplugging emulated devices is
7449 unnecessary e 7286 unnecessary even if the host did not respond to
7450 the unplug pr 7287 the unplug protocol
7451 never -- do not unplu 7288 never -- do not unplug even if version check succeeds
7452 7289
7453 xen_legacy_crash [X86,XEN,EARL !! 7290 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 7291 Crash from Xen panic notifier, without executing late
7455 panic() code such as 7292 panic() code such as dumping handler.
7456 7293
7457 xen_mc_debug [X86,XEN,EARLY] !! 7294 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> 7295 Format: <bool>
7465 Select whether to alw 7296 Select whether to always use non-faulting (safe) MSR
7466 access functions when 7297 access functions when running as Xen PV guest. The
7467 default value is cont 7298 default value is controlled by CONFIG_XEN_PV_MSR_SAFE.
7468 7299
>> 7300 xen_nopvspin [X86,XEN]
>> 7301 Disables the qspinlock slowpath using Xen PV optimizations.
>> 7302 This parameter is obsoleted by "nopvspin" parameter, which
>> 7303 has equivalent effect for XEN platform.
>> 7304
7469 xen_nopv [X86] 7305 xen_nopv [X86]
7470 Disables the PV optim 7306 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 7307 run as generic HVM guest with no PV drivers.
7472 This option is obsole 7308 This option is obsoleted by the "nopv" option, which
7473 has equivalent effect 7309 has equivalent effect for XEN platform.
7474 7310
7475 xen_no_vector_callback 7311 xen_no_vector_callback
7476 [KNL,X86,XEN,EARLY] D !! 7312 [KNL,X86,XEN] Disable the vector callback for Xen
7477 event channel interru 7313 event channel interrupts.
7478 7314
7479 xen_scrub_pages= [XEN] 7315 xen_scrub_pages= [XEN]
7480 Boolean option to con 7316 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 7317 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 7318 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 7319 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 7320
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 7321 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 7322 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 7323 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 7324 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 7325 improve timer resolution at the expense of processing
7490 more timer interrupts 7326 more timer interrupts.
7491 7327
7492 xen.balloon_boot_timeout= [XEN] 7328 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 7329 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 7330 in case initial ballooning fails to free enough memory.
7495 Applies only when run 7331 Applies only when running as HVM or PVH guest and
7496 started with less mem 7332 started with less memory configured than allowed at
7497 max. Default is 180. 7333 max. Default is 180.
7498 7334
7499 xen.event_eoi_delay= [XEN] 7335 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 7336 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 7337 storms (jiffies). Default is 10.
7502 7338
7503 xen.event_loop_timeout= [XEN] 7339 xen.event_loop_timeout= [XEN]
7504 After which time (jif 7340 After which time (jiffies) the event handling loop
7505 should start to delay 7341 should start to delay EOI handling. Default is 2.
7506 7342
7507 xen.fifo_events= [XEN] 7343 xen.fifo_events= [XEN]
7508 Boolean parameter to 7344 Boolean parameter to disable using fifo event handling
7509 even if available. No 7345 even if available. Normally fifo event handling is
7510 preferred over the 2- 7346 preferred over the 2-level event handling, as it is
7511 fairer and the number 7347 fairer and the number of possible event channels is
7512 much higher. Default 7348 much higher. Default is on (use fifo events).
7513 7349
7514 xirc2ps_cs= [NET,PCMCIA] 7350 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 7351 Format:
7516 <irq>,<irq_mask>,<io> 7352 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 7353
7518 xive= [PPC] 7354 xive= [PPC]
7519 By default on POWER9 7355 By default on POWER9 and above, the kernel will
7520 natively use the XIVE 7356 natively use the XIVE interrupt controller. This option
7521 allows the fallback f 7357 allows the fallback firmware mode to be used:
7522 7358
7523 off Fallback to 7359 off Fallback to firmware control of XIVE interrupt
7524 controller 7360 controller on both pseries and powernv
7525 platforms. 7361 platforms. Only useful on POWER9 and above.
7526 7362
7527 xive.store-eoi=off [PPC] 7363 xive.store-eoi=off [PPC]
7528 By default on POWER10 7364 By default on POWER10 and above, the kernel will use
7529 stores for EOI handli 7365 stores for EOI handling when the XIVE interrupt mode
7530 is active. This optio 7366 is active. This option allows the XIVE driver to use
7531 loads instead, as on 7367 loads instead, as on POWER9.
7532 7368
7533 xhci-hcd.quirks [USB,KNL] 7369 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 7370 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 7371 host controller quirks. Meaning of each bit can be
7536 consulted in header d 7372 consulted in header drivers/usb/host/xhci.h.
7537 7373
7538 xmon [PPC,EARLY] !! 7374 xmon [PPC]
7539 Format: { early | on 7375 Format: { early | on | rw | ro | off }
7540 Controls if xmon debu 7376 Controls if xmon debugger is enabled. Default is off.
7541 Passing only "xmon" i 7377 Passing only "xmon" is equivalent to "xmon=early".
7542 early Call xmon as 7378 early Call xmon as early as possible on boot; xmon
7543 debugger is c 7379 debugger is called from setup_arch().
7544 on xmon debugger 7380 on xmon debugger hooks will be installed so xmon
7545 is only calle 7381 is only called on a kernel crash. Default mode,
7546 i.e. either " 7382 i.e. either "ro" or "rw" mode, is controlled
7547 with CONFIG_X 7383 with CONFIG_XMON_DEFAULT_RO_MODE.
7548 rw xmon debugger 7384 rw xmon debugger hooks will be installed so xmon
7549 is called onl 7385 is called only on a kernel crash, mode is write,
7550 meaning SPR r 7386 meaning SPR registers, memory and, other data
7551 can be writte 7387 can be written using xmon commands.
7552 ro same as "rw" 7388 ro same as "rw" option above but SPR registers,
7553 memory, and o 7389 memory, and other data can't be written using
7554 xmon commands 7390 xmon commands.
7555 off xmon is disab 7391 off xmon is disabled.
>> 7392
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