1 accept_memory= [MM] !! 1 acpi= [HW,ACPI,X86,ARM64]
2 Format: { eager | lazy <<
3 default: lazy <<
4 By default, unaccepted <<
5 avoid prolonged boot t <<
6 some runtime overhead <<
7 accepted. In most case <<
8 For some workloads or <<
9 accept_memory=eager ca <<
10 at once during boot. <<
11 <<
12 acpi= [HW,ACPI,X86,ARM64,RIS <<
13 Advanced Configuration 2 Advanced Configuration and Power Interface
14 Format: { force | on | 3 Format: { force | on | off | strict | noirq | rsdt |
15 copy_dsdt | !! 4 copy_dsdt }
16 force -- enable ACPI i 5 force -- enable ACPI if default was off
17 on -- enable ACPI but !! 6 on -- enable ACPI but allow fallback to DT [arm64]
18 off -- disable ACPI if 7 off -- disable ACPI if default was on
19 noirq -- do not use AC 8 noirq -- do not use ACPI for IRQ routing
20 strict -- Be less tole 9 strict -- Be less tolerant of platforms that are not
21 strictly ACPI 10 strictly ACPI specification compliant.
22 rsdt -- prefer RSDT ov 11 rsdt -- prefer RSDT over (default) XSDT
23 copy_dsdt -- copy DSDT 12 copy_dsdt -- copy DSDT to memory
24 nospcr -- disable cons !! 13 For ARM64, ONLY "acpi=off", "acpi=on" or "acpi=force"
25 default _seria <<
26 For ARM64, ONLY "acpi= <<
27 "acpi=nospcr" are avai <<
28 For RISCV64, ONLY "acp <<
29 are available 14 are available
30 15
31 See also Documentation !! 16 See also Documentation/power/runtime_pm.txt, 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 acpi_backlight=vendor
41 If set to vendor, pref !! 26 acpi_backlight=video
>> 27 If set to vendor, prefer vendor specific driver
42 (e.g. thinkpad_acpi, s 28 (e.g. thinkpad_acpi, sony_acpi, etc.) instead
43 of the ACPI video.ko d 29 of the ACPI video.ko driver.
44 If set to video, use t <<
45 If set to native, use <<
46 If set to none, disabl <<
47 30
48 acpi_force_32bit_fadt_addr [ACPI,EARLY !! 31 acpi_force_32bit_fadt_addr
49 force FADT to use 32 b 32 force FADT to use 32 bit addresses rather than the
50 64 bit X_* addresses. 33 64 bit X_* addresses. Some firmware have broken 64
51 bit addresses for forc 34 bit addresses for force ACPI ignore these and use
52 the older legacy 32 bi 35 the older legacy 32 bit addresses.
53 36
54 acpica_no_return_repair [HW, ACPI] 37 acpica_no_return_repair [HW, ACPI]
55 Disable AML predefined 38 Disable AML predefined validation mechanism
56 This mechanism can rep 39 This mechanism can repair the evaluation result to make
57 the return objects mor 40 the return objects more ACPI specification compliant.
58 This option is useful 41 This option is useful for developers to identify the
59 root cause of an AML i 42 root cause of an AML interpreter issue when the issue
60 has something to do wi 43 has something to do with the repair mechanism.
61 44
62 acpi.debug_layer= [HW,ACPI,ACPI_ 45 acpi.debug_layer= [HW,ACPI,ACPI_DEBUG]
63 acpi.debug_level= [HW,ACPI,ACPI_ 46 acpi.debug_level= [HW,ACPI,ACPI_DEBUG]
64 Format: <int> 47 Format: <int>
65 CONFIG_ACPI_DEBUG must 48 CONFIG_ACPI_DEBUG must be enabled to produce any ACPI
66 debug output. Bits in 49 debug output. Bits in debug_layer correspond to a
67 _COMPONENT in an ACPI 50 _COMPONENT in an ACPI source file, e.g.,
68 #define _COMPONENT !! 51 #define _COMPONENT ACPI_PCI_COMPONENT
69 Bits in debug_level co 52 Bits in debug_level correspond to a level in
70 ACPI_DEBUG_PRINT state 53 ACPI_DEBUG_PRINT statements, e.g.,
71 ACPI_DEBUG_PRINT(( 54 ACPI_DEBUG_PRINT((ACPI_DB_INFO, ...
72 The debug_level mask d 55 The debug_level mask defaults to "info". See
73 Documentation/firmware !! 56 Documentation/acpi/debug.txt for more information about
74 debug layers and level 57 debug layers and levels.
75 58
76 Enable processor drive 59 Enable processor driver info messages:
77 acpi.debug_layer=0 60 acpi.debug_layer=0x20000000
>> 61 Enable PCI/PCI interrupt routing info messages:
>> 62 acpi.debug_layer=0x400000
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: <int>
>> 117 Support masking of GPEs numbered from 0x00 to 0x7f.
132 118
133 acpi_no_auto_serialize [HW,ACPI] 119 acpi_no_auto_serialize [HW,ACPI]
134 Disable auto-serializa 120 Disable auto-serialization of AML methods
135 AML control methods th 121 AML control methods that contain the opcodes to create
136 named objects will be 122 named objects will be marked as "Serialized" by the
137 auto-serialization fea 123 auto-serialization feature.
138 This feature is enable 124 This feature is enabled by default.
139 This option allows to 125 This option allows to turn off the feature.
140 126
141 acpi_no_memhotplug [ACPI] Disable memo 127 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
142 kernels. 128 kernels.
143 129
144 acpi_no_static_ssdt [HW,ACPI,EARLY !! 130 acpi_no_static_ssdt [HW,ACPI]
145 Disable installation o 131 Disable installation of static SSDTs at early boot time
146 By default, SSDTs cont 132 By default, SSDTs contained in the RSDT/XSDT will be
147 installed automaticall 133 installed automatically and they will appear under
148 /sys/firmware/acpi/tab 134 /sys/firmware/acpi/tables.
149 This option turns off 135 This option turns off this feature.
150 Note that specifying t 136 Note that specifying this option does not affect
151 dynamic table installa 137 dynamic table installation which will install SSDT
152 tables to /sys/firmwar 138 tables to /sys/firmware/acpi/tables/dynamic.
153 139
154 acpi_no_watchdog [HW,ACPI,WDT] 140 acpi_no_watchdog [HW,ACPI,WDT]
155 Ignore the ACPI-based 141 Ignore the ACPI-based watchdog interface (WDAT) and let
156 a native driver contro 142 a native driver control the watchdog device instead.
157 143
158 acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] !! 144 acpi_rsdp= [ACPI,EFI,KEXEC]
159 Pass the RSDP address 145 Pass the RSDP address to the kernel, mostly used
160 on machines running EF 146 on machines running EFI runtime service to boot the
161 second kernel for kdum 147 second kernel for kdump.
162 148
163 acpi_os_name= [HW,ACPI] Tell ACPI BI 149 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
164 Format: To spoof as Wi 150 Format: To spoof as Windows 98: ="Microsoft Windows"
165 151
166 acpi_rev_override [ACPI] Override the 152 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167 of 2 which is mandated 153 of 2 which is mandated by ACPI 6) as the supported ACPI
168 specification revision 154 specification revision (when using this switch, it may
169 be necessary to carry 155 be necessary to carry out a cold reboot _twice_ in a
170 row to make it take ef 156 row to make it take effect on the platform firmware).
171 157
172 acpi_osi= [HW,ACPI] Modify list 158 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" 159 acpi_osi="string1" # add string1
174 acpi_osi="!string2" 160 acpi_osi="!string2" # remove string2
175 acpi_osi=!* 161 acpi_osi=!* # remove all strings
176 acpi_osi=! 162 acpi_osi=! # disable all built-in OS vendor
177 163 strings
178 acpi_osi=!! 164 acpi_osi=!! # enable all built-in OS vendor
179 165 strings
180 acpi_osi= 166 acpi_osi= # disable all strings
181 167
182 'acpi_osi=!' can be us 168 'acpi_osi=!' can be used in combination with single or
183 multiple 'acpi_osi="st 169 multiple 'acpi_osi="string1"' to support specific OS
184 vendor string(s). Not 170 vendor string(s). Note that such command can only
185 affect the default sta 171 affect the default state of the OS vendor strings, thus
186 it cannot affect the d 172 it cannot affect the default state of the feature group
187 strings and the curren 173 strings and the current state of the OS vendor strings,
188 specifying it multiple 174 specifying it multiple times through kernel command line
189 is meaningless. This 175 is meaningless. This command is useful when one do not
190 care about the state o 176 care about the state of the feature group strings which
191 should be controlled b 177 should be controlled by the OSPM.
192 Examples: 178 Examples:
193 1. 'acpi_osi=! acpi_ 179 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194 to 'acpi_osi="Win 180 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 can make '_OSI("W 181 can make '_OSI("Windows 2000")' TRUE.
196 182
197 'acpi_osi=' cannot be 183 'acpi_osi=' cannot be used in combination with other
198 'acpi_osi=' command li 184 'acpi_osi=' command lines, the _OSI method will not
199 exist in the ACPI name 185 exist in the ACPI namespace. NOTE that such command can
200 only affect the _OSI s 186 only affect the _OSI support state, thus specifying it
201 multiple times through 187 multiple times through kernel command line is also
202 meaningless. 188 meaningless.
203 Examples: 189 Examples:
204 1. 'acpi_osi=' can m 190 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205 FALSE. 191 FALSE.
206 192
207 'acpi_osi=!*' can be u 193 'acpi_osi=!*' can be used in combination with single or
208 multiple 'acpi_osi="st 194 multiple 'acpi_osi="string1"' to support specific
209 string(s). Note that 195 string(s). Note that such command can affect the
210 current state of both 196 current state of both the OS vendor strings and the
211 feature group strings, 197 feature group strings, thus specifying it multiple times
212 through kernel command 198 through kernel command line is meaningful. But it may
213 still not able to affe 199 still not able to affect the final state of a string if
214 there are quirks relat 200 there are quirks related to this string. This command
215 is useful when one wan 201 is useful when one want to control the state of the
216 feature group strings 202 feature group strings to debug BIOS issues related to
217 the OSPM features. 203 the OSPM features.
218 Examples: 204 Examples:
219 1. 'acpi_osi="Module 205 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220 '_OSI("Module Dev 206 '_OSI("Module Device")' FALSE.
221 2. 'acpi_osi=!* acpi 207 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222 '_OSI("Module Dev 208 '_OSI("Module Device")' TRUE.
223 3. 'acpi_osi=! acpi_ 209 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224 equivalent to 210 equivalent to
225 'acpi_osi=!* acpi 211 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226 and 212 and
227 'acpi_osi=!* acpi 213 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228 they all will mak 214 they all will make '_OSI("Windows 2000")' TRUE.
229 215
230 acpi_pm_good [X86] 216 acpi_pm_good [X86]
231 Override the pmtimer b 217 Override the pmtimer bug detection: force the kernel
232 to assume that this ma 218 to assume that this machine's pmtimer latches its value
233 and always returns goo 219 and always returns good values.
234 220
235 acpi_sci= [HW,ACPI,EARLY] ACPI S !! 221 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge 222 Format: { level | edge | high | low }
237 223
238 acpi_skip_timer_override [HW,ACPI,EARL !! 224 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore I 225 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIO 226 For broken nForce2 BIOS resulting in XT-PIC timer.
241 227
242 acpi_sleep= [HW,ACPI] Sleep option 228 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_ !! 229 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 s4_nohwsig, !! 230 old_ordering, nonvs, sci_force_enable }
245 sci_force_en !! 231 See Documentation/power/video.txt for information on
246 See Documentation/powe <<
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 <<
251 signature during resum <<
252 refuse to resume if it <<
253 the ACPI specification <<
254 Windows does not do th <<
255 on docking. So the def <<
256 and simply warn when t <<
257 s4_hwsig option is ena <<
258 s4_nohwsig prevents AC 235 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a !! 236 used during resume from hibernation.
260 old_ordering causes th 237 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 238 control method, with respect to putting devices into
262 low power states, to b 239 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 240 of _PTS is used by default).
264 nonvs prevents the ker 241 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 242 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 243 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 244 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 245 but some broken systems don't work without it).
269 nobl causes the intern <<
270 behave incorrectly in <<
271 suspend and resume to <<
272 246
273 acpi_use_timer_override [HW,ACPI,EARLY !! 247 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 248 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 249 that require a timer override, but don't have HPET
276 250
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 251 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 252 kernel's map of available physical RAM.
279 253
280 agp= [AGP] 254 agp= [AGP]
281 { off | try_unsupporte 255 { off | try_unsupported }
282 off: disable AGP suppo 256 off: disable AGP support
283 try_unsupported: try t 257 try_unsupported: try to drive unsupported chipsets
284 (may crash com 258 (may crash computer or cause data corruption)
285 259
286 ALSA [HW,ALSA] 260 ALSA [HW,ALSA]
287 See Documentation/soun !! 261 See Documentation/sound/alsa/alsa-parameters.txt
288 262
289 alignment= [KNL,ARM] 263 alignment= [KNL,ARM]
290 Allow the default user 264 Allow the default userspace alignment fault handler
291 behaviour to be specif 265 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 266 bit 1 enables fixups, and bit 2 sends a segfault.
293 267
294 align_va_addr= [X86-64] 268 align_va_addr= [X86-64]
295 Align virtual addresse 269 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 270 allocating a VMA at process creation time. This option
297 gives you up to 3% per 271 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 272 machines (where it is enabled by default) for a
299 CPU-intensive style be 273 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 274 a microbenchmark depending on workload and compiler.
301 275
302 32: only for 32-bit pr 276 32: only for 32-bit processes
303 64: only for 64-bit pr 277 64: only for 64-bit processes
304 on: enable for both 32 278 on: enable for both 32- and 64-bit processes
305 off: disable for both 279 off: disable for both 32- and 64-bit processes
306 280
307 alloc_snapshot [FTRACE] 281 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 282 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 283 main buffer is allocated. This is handy if debugging
310 and you need to use tr 284 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 285 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 286 to be done where GFP_KERNEL allocations are allowed.
313 287
314 allow_mismatched_32bit_el0 [ARM64,EARL <<
315 Allow execve() of 32-b <<
316 PER_LINUX32 personalit <<
317 subset of the CPUs sup <<
318 parameter is present, <<
319 EL0 is indicated by /s <<
320 and hot-unplug operati <<
321 <<
322 See Documentation/arch <<
323 information. <<
324 <<
325 amd_iommu= [HW,X86-64] 288 amd_iommu= [HW,X86-64]
326 Pass parameters to the 289 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 290 Possible values are:
328 fullflush - Deprecated !! 291 fullflush - enable flushing of IO/TLB entries when
>> 292 they are unmapped. Otherwise they are
>> 293 flushed before they will be reused, which
>> 294 is a lot of faster
329 off - do not ini 295 off - do not initialize any AMD IOMMU found in
330 the system 296 the system
331 force_isolation - Forc 297 force_isolation - Force device isolation for all
332 devi 298 devices. The IOMMU driver is not
333 allo 299 allowed anymore to lift isolation
334 requ 300 requirements as needed. This option
335 does 301 does not override iommu=pt
336 force_enable - Force e <<
337 to be b <<
338 option <<
339 pgtbl_v1 - Use v1 <<
340 pgtbl_v2 - Use v2 <<
341 irtcachedis - Disable <<
342 302
343 amd_iommu_dump= [HW,X86-64] 303 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 304 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 305 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 306 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 307 IOMMU initialization.
348 308
349 amd_iommu_intr= [HW,X86-64] 309 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 310 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 311 remapping modes:
352 legacy - Use legac 312 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 313 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 314 to inject interrupts directly into guest.
355 This mode 315 This mode requires kvm-amd.avic=1.
356 (Default 316 (Default when IOMMU HW support is present.)
357 317
358 amd_pstate= [X86,EARLY] <<
359 disable <<
360 Do not enable amd_ps <<
361 scaling driver for t <<
362 passive <<
363 Use amd_pstate with <<
364 In this mode autonom <<
365 Driver requests a de <<
366 tries to match the s <<
367 satisfied by guarant <<
368 active <<
369 Use amd_pstate_epp d <<
370 driver provides a hi <<
371 to bias toward perfo <<
372 to the CPPC firmware <<
373 calculate the runtim <<
374 frequency. <<
375 guided <<
376 Activate guided auto <<
377 maximum performance <<
378 selects a performanc <<
379 to the current workl <<
380 <<
381 amd_prefcore= <<
382 [X86] <<
383 disable <<
384 Disable amd-pstate p <<
385 <<
386 amijoy.map= [HW,JOY] Amiga joystic 318 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 319 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 320 Format: <a>,<b>
389 See also Documentation !! 321 See also Documentation/input/joystick.txt
390 322
391 analog.map= [HW,JOY] Analog joysti 323 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 324 Specifies type or capabilities of an analog joystick
393 connected to one of 16 325 connected to one of 16 gameports
394 Format: <type1>,<type2 326 Format: <type1>,<type2>,..<type16>
395 327
396 apc= [HW,SPARC] 328 apc= [HW,SPARC]
397 Power management funct 329 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 330 Format: noidle
399 Disable APC CPU standb 331 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 332 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 333 APC and your system crashes randomly.
402 334
403 apic= [APIC,X86,EARLY] Advan !! 335 apic= [APIC,X86-32] Advanced Programmable Interrupt Controller
404 Change the output verb !! 336 Change the output verbosity whilst booting
405 Format: { quiet (defau 337 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 338 Change the amount of debugging information output
407 when initialising the 339 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a <<
409 driver name. <<
410 Format: apic=driver_na <<
411 Examples: apic=bigsmp <<
412 340
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 341 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 342 Format: { bsp (default) | all | none }
415 bsp: External NMI is 343 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 344 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 345 backup of CPU 0
418 none: External NMI is 346 none: External NMI is masked for all CPUs. This is
419 useful so that a 347 useful so that a dump capture kernel won't be
420 shot down by NMI 348 shot down by NMI
421 349
422 autoconf= [IPV6] 350 autoconf= [IPV6]
423 See Documentation/netw !! 351 See Documentation/networking/ipv6.txt.
>> 352
>> 353 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 354 Limit apic dumping. The parameter defines the maximal
>> 355 number of local apics being dumped. Also it is possible
>> 356 to set it to "all" by meaning -- no limit here.
>> 357 Format: { 1 (default) | 2 | ... | all }.
>> 358 The parameter valid if only apic=debug or
>> 359 apic=verbose is specified.
>> 360 Example: apic=debug show_lapic=all
424 361
425 apm= [APM] Advanced Power M 362 apm= [APM] Advanced Power Management
426 See header of arch/x86 363 See header of arch/x86/kernel/apm_32.c.
427 364
428 apparmor= [APPARMOR] Disable or <<
429 Format: { "0" | "1" } <<
430 See security/apparmor/ <<
431 0 -- disable. <<
432 1 -- enable. <<
433 Default value is set v <<
434 <<
435 arcrimi= [HW,NET] ARCnet - "RIM 365 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 366 Format: <io>,<irq>,<nodeID>
437 367
438 arm64.no32bit_el0 [ARM64] Unconditiona <<
439 32 bit applications. <<
440 <<
441 arm64.nobti [ARM64] Unconditionall <<
442 Identification support <<
443 <<
444 arm64.nomops [ARM64] Unconditionall <<
445 Set instructions suppo <<
446 <<
447 arm64.nomte [ARM64] Unconditionall <<
448 support <<
449 <<
450 arm64.nopauth [ARM64] Unconditionall <<
451 support <<
452 <<
453 arm64.nosme [ARM64] Unconditionall <<
454 Extension support <<
455 <<
456 arm64.nosve [ARM64] Unconditionall <<
457 Extension support <<
458 <<
459 ataflop= [HW,M68k] 368 ataflop= [HW,M68k]
460 369
461 atarimouse= [HW,MOUSE] Atari Mouse 370 atarimouse= [HW,MOUSE] Atari Mouse
462 371
463 atkbd.extra= [HW] Enable extra LEDs 372 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 373 EzKey and similar keyboards
465 374
466 atkbd.reset= [HW] Reset keyboard du 375 atkbd.reset= [HW] Reset keyboard during initialization
467 376
468 atkbd.set= [HW] Select keyboard c 377 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 378 Format: <int> (2 = AT (default), 3 = PS/2)
470 379
471 atkbd.scroll= [HW] Enable scroll whe 380 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 381 keyboards
473 382
474 atkbd.softraw= [HW] Choose between sy 383 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 384 Format: <bool> (0 = real, 1 = synthetic (default))
476 385
477 atkbd.softrepeat= [HW] 386 atkbd.softrepeat= [HW]
478 Use software keyboard 387 Use software keyboard repeat
479 388
480 audit= [KNL] Enable the audit 389 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | !! 390 Format: { "0" | "1" } (0 = disabled, 1 = enabled)
482 0 | off - kernel audit !! 391 0 - kernel audit is disabled and can not be enabled
483 enabled until the !! 392 until the next reboot
484 unset - kernel audit i 393 unset - kernel audit is initialized but disabled and
485 will be fully enab 394 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit !! 395 1 - kernel audit is initialized and partially enabled,
487 enabled, storing a !! 396 storing at most audit_backlog_limit messages in
488 messages in RAM un !! 397 RAM until it is fully enabled by the userspace
489 userspace auditd. !! 398 auditd.
490 Default: unset 399 Default: unset
491 400
492 audit_backlog_limit= [KNL] Set the aud 401 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 402 Format: <int> (must be >=0)
494 Default: 64 403 Default: 64
495 404
496 bau= [X86_UV] Enable the BA 405 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 406 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 407 Format: { "0" | "1" }
499 0 - Disable the BAU. 408 0 - Disable the BAU.
500 1 - Enable the BAU. 409 1 - Enable the BAU.
501 unset - Disable the BA 410 unset - Disable the BAU.
502 411
503 baycom_epp= [HW,AX25] 412 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 413 Format: <io>,<mode>
505 414
506 baycom_par= [HW,AX25] BayCom Paral 415 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 416 Format: <io>,<mode>
508 See header of drivers/ 417 See header of drivers/net/hamradio/baycom_par.c.
509 418
510 baycom_ser_fdx= [HW,AX25] 419 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 420 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 421 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 422 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 423
515 baycom_ser_hdx= [HW,AX25] 424 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 425 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 426 Format: <io>,<irq>,<mode>
518 See header of drivers/ 427 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 428
520 bert_disable [ACPI] <<
521 Disable BERT OS suppor <<
522 <<
523 bgrt_disable [ACPI,X86,EARLY] <<
524 Disable BGRT to avoid <<
525 <<
526 blkdevparts= Manual partition parsi 429 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 430 embedded devices based on command line input.
528 See Documentation/bloc !! 431 See Documentation/block/cmdline-partition.txt
529 432
530 boot_delay= [KNL,EARLY] !! 433 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 434 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 435 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 436 Format: integer
537 437
538 bootconfig [KNL,EARLY] !! 438 bootmem_debug [KNL] Enable bootmem allocator debug messages.
539 Extended command line <<
540 and this will cause th <<
541 439
542 See Documentation/admi !! 440 bert_disable [ACPI]
>> 441 Disable BERT OS support on buggy BIOSes.
543 442
544 bttv.card= [HW,V4L] bttv (bt848 + 443 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 444 bttv.radio= Most important insmod options are available as
546 kernel args too. 445 kernel args too.
547 bttv.pll= See Documentation/admi !! 446 bttv.pll= See Documentation/video4linux/bttv/Insmod-options
548 bttv.tuner= 447 bttv.tuner=
549 448
550 bulk_remove=off [PPC] This parameter 449 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 450 firmware feature for flushing multiple hpte entries
552 at a time. 451 at a time.
553 452
554 c101= [NET] Moxa C101 synchr 453 c101= [NET] Moxa C101 synchronous serial card
555 454
556 cachesize= [BUGS=X86-32] Override 455 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 456 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 457 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 458 to fix known problems, but for some CPUs it is not
560 possible to determine 459 possible to determine what the correct size should be.
561 This option provides a 460 This option provides an override for these situations.
562 461
563 carrier_timeout= <<
564 [NET] Specifies amount <<
565 the kernel should wait <<
566 it waits 120 seconds. <<
567 <<
568 ca_keys= [KEYS] This parameter 462 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 463 the system trusted keyring to be used for certificate
570 trust validation. 464 trust validation.
571 format: { id:<keyid> | 465 format: { id:<keyid> | builtin }
572 466
573 cca= [MIPS,EARLY] Override !! 467 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 468 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 469 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 470 for platform specific values (SB1, Loongson3 and
577 others). 471 others).
578 472
579 ccw_timeout_log [S390] !! 473 ccw_timeout_log [S390]
580 See Documentation/arch !! 474 See Documentation/s390/CommonIO for details.
581 475
582 cgroup_disable= [KNL] Disable a partic !! 476 cgroup_disable= [KNL] Disable a particular controller
583 Format: {name of the c !! 477 Format: {name of the controller(s) to disable}
584 The effects of cgroup_ 478 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 479 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 480 a single hierarchy
587 - foo isn't visible as 481 - foo isn't visible as an individually mountable
588 subsystem 482 subsystem
589 - if foo is an optiona <<
590 disabled and corresp <<
591 created <<
592 {Currently only "memor 483 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 484 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 485 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" <<
596 stall information acco <<
597 486
598 cgroup_no_v1= [KNL] Disable cgroup c !! 487 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
599 Format: { { controller !! 488 Format: { controller[,controller...] | "all" }
600 [,{ controll <<
601 Like cgroup_disable, b 489 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 490 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c <<
604 named mounts. Specifyi <<
605 all v1 hierarchies. <<
606 <<
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 491
611 cgroup.memory= [KNL] Pass options to 492 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 493 Format: <string>
613 nosocket -- Disable so 494 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 495 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 496
617 checkreqprot= [SELINUX] Set initial !! 497 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 498 Format: { "0" | "1" }
619 See security/selinux/K 499 See security/selinux/Kconfig help text.
620 0 -- check protection 500 0 -- check protection applied by kernel (includes
621 any implied ex 501 any implied execute protection).
622 1 -- check protection 502 1 -- check protection requested by application.
623 Default value is set v 503 Default value is set via a kernel config option.
624 Value can be changed a 504 Value can be changed at runtime via
625 /sys/fs/selinu !! 505 /selinux/checkreqprot.
626 Setting checkreqprot t <<
627 506
628 cio_ignore= [S390] 507 cio_ignore= [S390]
629 See Documentation/arch !! 508 See Documentation/s390/CommonIO for details.
630 <<
631 clearcpuid=X[,X...] [X86] <<
632 Disable CPUID feature <<
633 arch/x86/include/asm/c <<
634 numbers X. Note the Li <<
635 stable over kernel opt <<
636 ones should be. <<
637 X can also be a string <<
638 in /proc/cpuinfo which <<
639 instability issue. How <<
640 in /proc/cpuinfo. <<
641 Note that using this o <<
642 Also note that user pr <<
643 or using the feature w <<
644 will still see it. Thi <<
645 being used by the kern <<
646 Also note the kernel m <<
647 some critical bits. <<
648 <<
649 clk_ignore_unused 509 clk_ignore_unused
650 [CLK] 510 [CLK]
651 Prevents the clock fra 511 Prevents the clock framework from automatically gating
652 clocks that have not b 512 clocks that have not been explicitly enabled by a Linux
653 device driver but are 513 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 514 by the bootloader/firmware. Note that this does not
655 force such clocks to b 515 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 516 those clocks in any way. This parameter is useful for
657 debug and development, 517 debug and development, but should not be needed on a
658 platform with proper d 518 platform with proper driver support. For more
659 information, see Docum !! 519 information, see Documentation/clk.txt.
660 520
661 clock= [BUGS=X86-32, HW] gett 521 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 522 [Deprecated]
663 Forces specified clock 523 Forces specified clocksource (if available) to be used
664 when calculating getti 524 when calculating gettimeofday(). If specified
665 clocksource is not ava 525 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 526 Format: { pit | tsc | cyclone | pmtmr }
667 527
668 clocksource= Override the default c 528 clocksource= Override the default clocksource
669 Format: <string> 529 Format: <string>
670 Override the default c 530 Override the default clocksource and use the clocksource
671 with the name specifie 531 with the name specified.
672 Some clocksource names 532 Some clocksource names to choose from, depending on
673 the platform: 533 the platform:
674 [all] jiffies (this is 534 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 535 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 536 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 537 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 538 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 539 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 540 [MIPS] MIPS
681 [PARISC] cr16 541 [PARISC] cr16
682 [S390] tod 542 [S390] tod
683 [SH] SuperH 543 [SH] SuperH
684 [SPARC64] tick 544 [SPARC64] tick
685 [X86-64] hpet,tsc 545 [X86-64] hpet,tsc
686 546
687 clocksource.arm_arch_timer.evtstrm= 547 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 548 [ARM,ARM64]
689 Format: <bool> 549 Format: <bool>
690 Enable/disable the eve 550 Enable/disable the eventstream feature of the ARM
691 architected timer so t 551 architected timer so that code using WFE-based polling
692 loops can be debugged 552 loops can be debugged more effectively on production
693 systems. 553 systems.
694 554
695 clocksource.verify_n_cpus= [KNL] !! 555 clearcpuid=BITNUM[,BITNUM...] [X86]
696 Limit the number of CP !! 556 Disable CPUID feature X for the kernel. See
697 marked with CLOCK_SOUR !! 557 arch/x86/include/asm/cpufeatures.h for the valid bit
698 are marked unstable du !! 558 numbers. Note the Linux specific bits are not necessarily
699 A negative value says !! 559 stable over kernel options, but the vendor specific
700 zero says not to check !! 560 ones should be.
701 nr_cpu_ids are silentl !! 561 Also note that user programs calling CPUID directly
702 The actual CPUs are ch !! 562 or using the feature without checking anything
703 no replacement if the !! 563 will still see it. This just prevents it from
704 !! 564 being used by the kernel or shown in /proc/cpuinfo.
705 clocksource-wdtest.holdoff= [KNL] !! 565 Also note the kernel might malfunction if you disable
706 Set the time in second !! 566 some critical bits.
707 watchdog test waits be <<
708 Defaults to zero when <<
709 10 seconds when built <<
710 567
711 cma=nn[MG]@[start[MG][-end[MG]]] 568 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 569 [ARM,X86,KNL]
713 Sets the size of kerne 570 Sets the size of kernel global memory area for
714 contiguous memory allo 571 contiguous memory allocations and optionally the
715 placement constraint b 572 placement constraint by the physical address range of
716 memory allocations. A 573 memory allocations. A value of 0 disables CMA
717 altogether. For more i 574 altogether. For more information, see
718 kernel/dma/contiguous. !! 575 include/linux/dma-contiguous.h
719 <<
720 cma_pernuma=nn[MG] <<
721 [KNL,CMA,EARLY] <<
722 Sets the size of kerne <<
723 contiguous memory allo <<
724 per-numa CMA altogethe <<
725 specified, the default <<
726 With per-numa CMA enab <<
727 first try to allocate <<
728 which is located in no <<
729 they will fallback to <<
730 <<
731 numa_cma=<node>:nn[MG][,<node>:nn[MG]] <<
732 [KNL,CMA,EARLY] <<
733 Sets the size of kerne <<
734 contiguous memory allo <<
735 area for the specified <<
736 <<
737 With numa CMA enabled, <<
738 first try to allocate <<
739 which is located in no <<
740 they will fallback to <<
741 576
742 cmo_free_hint= [PPC] Format: { yes | 577 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 578 Specify whether pages are marked as being inactive
744 when they are freed. 579 when they are freed. This is used in CMO environments
745 to determine OS memory 580 to determine OS memory pressure for page stealing by
746 a hypervisor. 581 a hypervisor.
747 Default: yes 582 Default: yes
748 583
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 584 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 585 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 586 allocations, by default set to 256K.
752 587
>> 588 code_bytes [X86] How many bytes of object code to print
>> 589 in an oops report.
>> 590 Range: 0 - 8192
>> 591 Default: 64
>> 592
753 com20020= [HW,NET] ARCnet - COM2 593 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 594 Format:
755 <io>[,<irq>[,<nodeID>[ 595 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 596
757 com90io= [HW,NET] ARCnet - COM9 597 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 598 Format: <io>[,<irq>]
759 599
760 com90xx= [HW,NET] 600 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 601 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 602 Format: <io>[,<irq>[,<memstart>]]
763 603
764 condev= [HW,S390] console devi 604 condev= [HW,S390] console device
765 conmode= 605 conmode=
766 606
767 con3215_drop= [S390,EARLY] 3215 cons <<
768 Format: y|n|Y|N|1|0 <<
769 When set to true, drop <<
770 the console buffer is <<
771 operator using a 3270 <<
772 x3270) does not have t <<
773 console output to adva <<
774 This leads to a much f <<
775 terminal emulator is a <<
776 emulator is used, this <<
777 <<
778 console= [KNL] Output console d 607 console= [KNL] Output console device and options.
779 608
780 tty<n> Use the virtual consol 609 tty<n> Use the virtual console device <n>.
781 610
782 ttyS<n>[,options] 611 ttyS<n>[,options]
783 ttyUSB0[,options] 612 ttyUSB0[,options]
784 Use the specified seri 613 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 614 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 615 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 616 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 617 omit it). Default is "9600n8".
789 618
790 See Documentation/admi 619 See Documentation/admin-guide/serial-console.rst for more
791 information. See 620 information. See
792 Documentation/networki !! 621 Documentation/networking/netconsole.txt for an
793 alternative. 622 alternative.
794 623
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] 624 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 625 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 626 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 627 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 628 uart[8250],0x<addr>[,options]
819 Start an early, polled 629 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 630 UART at the specified I/O port or MMIO address,
821 switching to the match 631 switching to the matching ttyS device later.
822 MMIO inter-register ad 632 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 633 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 634 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 635 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 636 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 637 the h/w is not re-initialized.
828 638
829 hvc<n> Use the hypervisor con 639 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 640 both Xen and PowerPC hypervisors.
831 641
832 { null | "" } !! 642 If the device connected to the port is not a TTY but a braille
833 Use to disable console !! 643 device, prepend "brl," before the device type, for instance
834 console messages disca <<
835 This must be the only <<
836 kernel command line. <<
837 <<
838 If the device connected to the <<
839 device, prepend "brl," before <<
840 console=brl,ttyS0 644 console=brl,ttyS0
841 For now, only VisioBraille is 645 For now, only VisioBraille is supported.
842 646
843 console_msg_format= <<
844 [KNL] Change console m <<
845 default <<
846 By default we print me <<
847 "[time stamp] text\n" <<
848 printed, depending on <<
849 `printk_time' param). <<
850 syslog <<
851 Switch to syslog forma <<
852 IOW, each message will <<
853 prefix. The format is <<
854 syscall, or to executi <<
855 from /proc/kmsg. <<
856 <<
857 consoleblank= [KNL] The console blan 647 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 !! 648 seconds. Defaults to 10*60 = 10mins. A value of 0
859 Defaults to 0. !! 649 disables the blank timer.
860 650
861 coredump_filter= 651 coredump_filter=
862 [KNL] Change the defau 652 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 653 /proc/<pid>/coredump_filter.
864 See also Documentation !! 654 See also Documentation/filesystems/proc.txt.
865 655
866 coresight_cpu_debug.enable 656 coresight_cpu_debug.enable
867 [ARM,ARM64] 657 [ARM,ARM64]
868 Format: <bool> 658 Format: <bool>
869 Enable/disable the CPU 659 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 660 0: default value, disable debugging
871 1: enable debugging at 661 1: enable debugging at boot time
872 662
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 663 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 664 disable the cpuidle sub-system
879 665
880 cpuidle.governor= <<
881 [CPU_IDLE] Name of the <<
882 <<
883 cpufreq.off=1 [CPU_FREQ] 666 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 667 disable the cpufreq sub-system
885 668
886 cpufreq.default_governor= <<
887 [CPU_FREQ] Name of the <<
888 policy to use. This go <<
889 kernel before the cpuf <<
890 <<
891 cpu_init_udelay=N 669 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 670 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 671 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 672 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 673 Default: 10000
896 674
897 cpuhp.parallel= !! 675 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 676 Format:
899 Format: <bool> !! 677 <first_slot>,<last_slot>,<port>,<enum_bit>[,<debug>]
900 Default is enabled if <<
901 the parameter has no e <<
902 <<
903 crash_kexec_post_notifiers <<
904 Run kdump after runnin <<
905 kmsg. This only for th <<
906 succeeds in any situat <<
907 Note that this also in <<
908 because some panic not <<
909 kernel more unstable. <<
910 678
911 crashkernel=size[KMG][@offset[KMG]] 679 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 680 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 681 upon panic. This parameter reserves the physical
914 memory region [offset, 682 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 683 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica !! 684 is selected automatically. Check
917 [KNL, X86-64, ARM64, R !! 685 Documentation/kdump/kdump.txt for further details.
918 under 4G first, and fa <<
919 4G when '@offset' hasn <<
920 See Documentation/admi <<
921 686
922 crashkernel=range1:size1[,range2:size2 687 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 688 [KNL] Same as above, but depends on the memory
924 in the running system. 689 in the running system. The syntax of range is
925 start-[end] where star 690 start-[end] where start and end are both
926 a memory unit (amount[ 691 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu !! 692 Documentation/kdump/kdump.txt for an example.
928 693
929 crashkernel=size[KMG],high 694 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 695 [KNL, x86_64] range could be above 4G. Allow kernel
931 above 4G. !! 696 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 697 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 698 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 699 available.
935 below 4G, if available <<
936 It will be ignored if 700 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 701 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 702 [KNL, x86_64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 703 is passed, kernel could allocate physical memory region
940 physical memory region !! 704 above 4G, that cause second kernel crash on system
941 crash on system that r !! 705 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 706 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 707 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 708 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 709 at least 256M below 4G automatically.
946 size is platform depen !! 710 This one let user to specify own low range under 4G
947 --> x86: max(swiotlb <<
948 --> arm64: 128MiB <<
949 --> riscv: 128MiB <<
950 --> loongarch: 128Mi <<
951 This one lets the user <<
952 for second kernel inst 711 for second kernel instead.
953 0: to disable low allo 712 0: to disable low allocation.
954 It will be ignored whe 713 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 714 or memory reserved is below 4G.
956 715
957 cryptomgr.notests 716 cryptomgr.notests
958 [KNL] Disable crypto s !! 717 [KNL] Disable crypto self-tests
959 718
960 cs89x0_dma= [HW,NET] 719 cs89x0_dma= [HW,NET]
961 Format: <dma> 720 Format: <dma>
962 721
963 cs89x0_media= [HW,NET] 722 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 723 Format: { rj45 | aui | bnc }
965 724
966 csdlock_debug= [KNL] Enable or disabl <<
967 function call handling <<
968 additional debug data <<
969 in case a hanging CPU <<
970 CPU is pinged again in <<
971 the hang situation. T <<
972 option depends on the <<
973 Kconfig option. <<
974 <<
975 dasd= [HW,NET] 725 dasd= [HW,NET]
976 See header of drivers/ 726 See header of drivers/s390/block/dasd_devmap.c.
977 727
978 db9.dev[2|3]= [HW,JOY] Multisystem j 728 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 729 (one device per port)
980 Format: <port#>,<type> 730 Format: <port#>,<type>
981 See also Documentation !! 731 See also Documentation/input/joystick-parport.txt
982 732
983 debug [KNL,EARLY] Enable ker !! 733 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 734 time. See
>> 735 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 736 details. Deprecated, see dyndbg.
984 737
985 debug_boot_weak_hash !! 738 debug [KNL] Enable kernel debugging (events log level).
986 [KNL,EARLY] Enable pri <<
987 boot sequence. If ena <<
988 of siphash to hash poi <<
989 seeing instances of '( <<
990 value (hashed pointer) <<
991 insecure, please do no <<
992 739
993 debug_locks_verbose= 740 debug_locks_verbose=
994 [KNL] verbose locking !! 741 [KNL] verbose self-tests
995 Format: <int> !! 742 Format=<0|1>
996 Print debugging info w 743 Print debugging info while doing the locking API
997 self-tests. 744 self-tests.
998 Bitmask for the variou !! 745 We default to 0 (no extra messages), setting it to
999 (no extra messages), s !! 746 1 will print _a lot_ more information - normally
1000 will print _a_lot_ mo !! 747 only useful to kernel developers.
1001 useful to lockdep dev !! 748
>> 749 debug_objects [KNL] Enable object debugging
1002 750
1003 debug_objects [KNL,EARLY] Enable ob !! 751 no_debug_objects
>> 752 [KNL] Disable object debugging
1004 753
1005 debug_guardpage_minorder= 754 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 755 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 756 parameter allows control of the order of pages that will
1008 be intentionally kept 757 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 758 buddy allocator. Bigger value increase the probability
1010 of catching random me 759 of catching random memory corruption, but reduce the
1011 amount of memory for 760 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 761 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 762 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 763 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 764 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 765 random memory location. Note that there exists a class
1017 a class of memory cor !! 766 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 767 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 768 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 769 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 770 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 771 tracking down these problems.
1023 772
1024 debug_pagealloc= 773 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 774 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1026 enables the feature a !! 775 parameter enables the feature at boot time. In
1027 disabled and the syst !! 776 default, it is disabled. We can avoid allocating huge
1028 kernel built without !! 777 chunk of memory for debug pagealloc if we don't enable
1029 Note: to get most of !! 778 it at boot time and the system will work mostly same
1030 useful to also enable !! 779 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
1031 on: enable the featur 780 on: enable the feature
1032 781
1033 debugfs= [KNL,EARLY] This para <<
1034 userspace and debugfs <<
1035 Format: { on, no-moun <<
1036 on: All functions <<
1037 no-mount: <<
1038 Filesystem is <<
1039 access APIs a <<
1040 its content. <<
1041 off: Filesystem is <<
1042 get a -EPERM <<
1043 or directorie <<
1044 This is equiv <<
1045 debugfs was n <<
1046 Default value is set <<
1047 <<
1048 debugpat [X86] Enable PAT debu 782 debugpat [X86] Enable PAT debugging
1049 783
1050 default_hugepagesz= 784 default_hugepagesz=
1051 [HW] The size of the !! 785 [same as hugepagesz=] The size of the default
1052 the size represented !! 786 HugeTLB page size. This is the size represented by
1053 APIs. In addition, t !! 787 the legacy /proc/ hugepages APIs, used for SHM, and
1054 used for shmget(), mm !! 788 default size when mounting hugetlbfs filesystems.
1055 filesystems. If not !! 789 Defaults to the default architecture's huge page size
1056 architecture's defaul !! 790 if not specified.
1057 sizes are architectur <<
1058 Documentation/admin-g <<
1059 Format: size[KMG] <<
1060 <<
1061 deferred_probe_timeout= <<
1062 [KNL] Debugging optio <<
1063 deferred probe to giv <<
1064 probe. Only specific <<
1065 drivers) that have op <<
1066 of 0 will timeout at <<
1067 out hasn't expired, i <<
1068 successful driver reg <<
1069 dump out devices stil <<
1070 retrying. <<
1071 <<
1072 delayacct [KNL] Enable per-task <<
1073 <<
1074 dell_smm_hwmon.ignore_dmi= <<
1075 [HW] Continue probing <<
1076 indicates that the dr <<
1077 hardware. <<
1078 <<
1079 dell_smm_hwmon.force= <<
1080 [HW] Activate driver <<
1081 not match list of sup <<
1082 blacklisted features. <<
1083 <<
1084 dell_smm_hwmon.power_status= <<
1085 [HW] Report power sta <<
1086 (disabled by default) <<
1087 <<
1088 dell_smm_hwmon.restricted= <<
1089 [HW] Allow controllin <<
1090 capability is set. <<
1091 <<
1092 dell_smm_hwmon.fan_mult= <<
1093 [HW] Factor to multip <<
1094 <<
1095 dell_smm_hwmon.fan_max= <<
1096 [HW] Maximum configur <<
1097 <<
1098 dfltcc= [HW,S390] <<
1099 Format: { on | off | <<
1100 on: s390 zlib h <<
1101 level 1 and <<
1102 off: No s390 zli <<
1103 def_only: s390 zlib h <<
1104 only (compr <<
1105 inf_only: s390 zlib h <<
1106 only (decom <<
1107 always: Same as 'on <<
1108 level alway <<
1109 791
1110 dhash_entries= [KNL] 792 dhash_entries= [KNL]
1111 Set number of hash bu 793 Set number of hash buckets for dentry cache.
1112 794
1113 disable_1tb_segments [PPC,EARLY] !! 795 disable_1tb_segments [PPC]
1114 Disables the use of 1 796 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 797 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 798 can be useful when debugging issues that require an SLB
1117 miss to occur. 799 miss to occur.
1118 800
1119 disable= [IPV6] 801 disable= [IPV6]
1120 See Documentation/net !! 802 See Documentation/networking/ipv6.txt.
1121 803
1122 disable_radix [PPC,EARLY] !! 804 disable_radix [PPC]
1123 Disable RADIX MMU mod 805 Disable RADIX MMU mode on POWER9
1124 806
1125 disable_tlbie [PPC] !! 807 disable_cpu_apicid= [X86,APIC,SMP]
1126 Disable TLBIE instruc !! 808 Format: <int>
1127 with KVM, with HASH M !! 809 The number of initial APIC ID for the
>> 810 corresponding CPU to be disabled at boot,
>> 811 mostly used for the kdump 2nd kernel to
>> 812 disable BSP to wake up multiple CPUs without
>> 813 causing system reset or hang due to sending
>> 814 INIT from AP to BSP.
1128 815
1129 disable_ddw [PPC/PSERIES,EARLY] !! 816 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W !! 817 Disable Dynamic DMA Window support. Use this if
1131 to workaround buggy f 818 to workaround buggy firmware.
1132 819
1133 disable_ipv6= [IPV6] 820 disable_ipv6= [IPV6]
1134 See Documentation/net !! 821 See Documentation/networking/ipv6.txt.
1135 822
1136 disable_mtrr_cleanup [X86,EARLY] !! 823 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 824 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 825 to discrete, to make X server driver able to add WB
1139 entry later. This par 826 entry later. This parameter disables that.
1140 827
1141 disable_mtrr_trim [X86, Intel and AMD !! 828 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 829 By default the kernel will trim any uncacheable
1143 memory out of your av 830 memory out of your available memory pool based on
1144 MTRR settings. This 831 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 832 possibly causing your machine to run very slowly.
1146 833
1147 disable_timer_pin_1 [X86,EARLY] !! 834 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 835 Disable PIN 1 of APIC timer
1149 Can be useful to work 836 Can be useful to work around chipset bugs.
1150 837
1151 dis_ucode_ldr [X86] Disable the mic 838 dis_ucode_ldr [X86] Disable the microcode loader.
1152 839
1153 dma_debug=off If the kernel is comp 840 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 841 this option disables the debugging code at boot.
1155 842
1156 dma_debug_entries=<number> 843 dma_debug_entries=<number>
1157 This option allows to 844 This option allows to tune the number of preallocated
1158 entries for DMA-API d 845 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 846 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 847 DMA-API debugging code disables itself because the
1161 architectural default 848 architectural default is too low.
1162 849
1163 dma_debug_driver=<driver_name> 850 dma_debug_driver=<driver_name>
1164 With this option the 851 With this option the DMA-API debugging driver
1165 filter feature can be 852 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 853 pass the driver to filter for as the parameter.
1167 The filter can be dis 854 The filter can be disabled or changed to another
1168 driver later using sy 855 driver later using sysfs.
1169 856
1170 reg_file_data_sampling= !! 857 drm_kms_helper.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1171 [X86] Controls mitiga <<
1172 Sampling (RFDS) vulne <<
1173 vulnerability which m <<
1174 kernel data values pr <<
1175 registers, vector reg <<
1176 RFDS only affects Int <<
1177 <<
1178 on: Turns ON the <<
1179 off: Turns OFF the <<
1180 <<
1181 This parameter overri <<
1182 by CONFIG_MITIGATION_ <<
1183 disabled when other V <<
1184 are enabled. In order <<
1185 VERW based mitigation <<
1186 <<
1187 For details see: <<
1188 Documentation/admin-g <<
1189 <<
1190 driver_async_probe= [KNL] <<
1191 List of driver names <<
1192 matches with all driv <<
1193 rest of the listed dr <<
1194 match the *. <<
1195 Format: <driver_name1 <<
1196 <<
1197 drm.edid_firmware=[<connector>:]<file <<
1198 Broken monitors, grap 858 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 859 panels may send no or incorrect EDID data sets.
1200 This parameter allows 860 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 861 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 862 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 863 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 864 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 865 and no file with the same name exists. Details and
>> 866 instructions how to build your own EDID data are
>> 867 available in Documentation/EDID/HOWTO.txt. An EDID
>> 868 data set will only be used for a particular connector,
>> 869 if its name and a colon are prepended to the EDID
>> 870 name. Each connector may use a unique EDID data
>> 871 set by separating the files with a comma. An EDID
1206 data set with no conn 872 data set with no connector name will be used for
1207 any connectors not ex 873 any connectors not explicitly specified.
1208 874
1209 dscc4.setup= [NET] 875 dscc4.setup= [NET]
1210 876
1211 dt_cpu_ftrs= [PPC,EARLY] !! 877 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 878 Format: {"off" | "known"}
1213 Control how the dt_cp 879 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 880 used for CPU feature discovery and setup (if it
1215 exists). 881 exists).
1216 off: Do not use it, f 882 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 883 known: Do not pass through unknown features to guests
1218 or userspace, only th 884 or userspace, only those that the kernel is aware of.
1219 885
1220 dump_apple_properties [X86] 886 dump_apple_properties [X86]
1221 Dump name and content 887 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 888 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 889 what data is available or for reverse-engineering.
1224 890
1225 dyndbg[="val"] [KNL,DYNAMIC_ 891 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] !! 892 module.dyndbg[="val"]
1227 Enable debug messages 893 Enable debug messages at boot time. See
1228 Documentation/admin-g 894 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 895 for details.
1230 896
1231 early_ioremap_debug [KNL,EARLY] !! 897 nompx [X86] Disables Intel Memory Protection Extensions.
>> 898 See Documentation/x86/intel_mpx.txt for more
>> 899 information about the feature.
>> 900
>> 901 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 902 in some Intel CPUs.
>> 903
>> 904 module.async_probe [KNL]
>> 905 Enable asynchronous probe on this module.
>> 906
>> 907 early_ioremap_debug [KNL]
1232 Enable debug messages 908 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 909 is useful for tracking down temporary early mappings
1234 which are not unmappe 910 which are not unmapped.
1235 911
1236 earlycon= [KNL,EARLY] Output ea !! 912 earlycon= [KNL] Output early console device and options.
1237 913
1238 When used with no opt 914 When used with no options, the early console is
1239 determined by stdout- !! 915 determined by the stdout-path property in device
1240 chosen node or the AC !! 916 tree's chosen node.
1241 the platform. <<
1242 917
1243 cdns,<addr>[,options] 918 cdns,<addr>[,options]
1244 Start an early, polle 919 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 920 (xuartps) serial port at the specified address. Only
1246 supported option is b 921 supported option is baud rate. If baud rate is not
1247 specified, the serial 922 specified, the serial port must already be setup and
1248 configured. 923 configured.
1249 924
1250 uart[8250],io,<addr>[,options !! 925 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 926 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 927 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 928 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 929 uart[8250],0x<addr>[,options]
1255 Start an early, polle 930 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 931 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 932 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 933 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 934 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 935 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 936 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 937 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 938
1266 pl011,<addr> 939 pl011,<addr>
1267 pl011,mmio32,<addr> 940 pl011,mmio32,<addr>
1268 Start an early, polle 941 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 942 port at the specified address. The pl011 serial port
1270 must already be setup 943 must already be setup and configured. Options are not
1271 yet supported. If 'm 944 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 945 the driver will use only 32-bit accessors to read/write
1273 the device registers. 946 the device registers.
1274 947
1275 liteuart,<addr> <<
1276 Start an early consol <<
1277 specified address. Th <<
1278 setup and configured. <<
1279 <<
1280 meson,<addr> 948 meson,<addr>
1281 Start an early, polle 949 Start an early, polled-mode console on a meson serial
1282 port at the specified 950 port at the specified address. The serial port must
1283 already be setup and 951 already be setup and configured. Options are not yet
1284 supported. 952 supported.
1285 953
1286 msm_serial,<addr> 954 msm_serial,<addr>
1287 Start an early, polle 955 Start an early, polled-mode console on an msm serial
1288 port at the specified 956 port at the specified address. The serial port
1289 must already be setup 957 must already be setup and configured. Options are not
1290 yet supported. 958 yet supported.
1291 959
1292 msm_serial_dm,<addr> 960 msm_serial_dm,<addr>
1293 Start an early, polle 961 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 962 dm port at the specified address. The serial port
1295 must already be setup 963 must already be setup and configured. Options are not
1296 yet supported. 964 yet supported.
1297 965
1298 owl,<addr> 966 owl,<addr>
1299 Start an early, polle 967 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 968 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 969 specified address. The serial port must already be
1302 setup and configured. 970 setup and configured. Options are not yet supported.
1303 971
1304 rda,<addr> <<
1305 Start an early, polle <<
1306 of an RDA Micro SoC, <<
1307 specified address. Th <<
1308 setup and configured. <<
1309 <<
1310 sbi <<
1311 Use RISC-V SBI (Super <<
1312 console. <<
1313 <<
1314 smh Use ARM semihosting c 972 smh Use ARM semihosting calls for early console.
1315 973
1316 s3c2410,<addr> 974 s3c2410,<addr>
1317 s3c2412,<addr> 975 s3c2412,<addr>
1318 s3c2440,<addr> 976 s3c2440,<addr>
1319 s3c6400,<addr> 977 s3c6400,<addr>
1320 s5pv210,<addr> 978 s5pv210,<addr>
1321 exynos4210,<addr> 979 exynos4210,<addr>
1322 Use early console pro 980 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 981 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 982 a correct base address of the selected UART port. The
1325 serial port must alre 983 serial port must already be setup and configured.
1326 Options are not yet s 984 Options are not yet supported.
1327 985
1328 lantiq,<addr> 986 lantiq,<addr>
1329 Start an early, polle 987 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 988 (lqasc) port at the specified address. The serial port
1331 must already be setup 989 must already be setup and configured. Options are not
1332 yet supported. 990 yet supported.
1333 991
1334 lpuart,<addr> 992 lpuart,<addr>
1335 lpuart32,<addr> 993 lpuart32,<addr>
1336 Use early console pro 994 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 995 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 996 A valid base address must be provided, and the serial
1339 port must already be 997 port must already be setup and configured.
1340 998
1341 ec_imx21,<addr> <<
1342 ec_imx6q,<addr> <<
1343 Start an early, polle <<
1344 Freescale i.MX UART a <<
1345 must already be setup <<
1346 <<
1347 ar3700_uart,<addr> 999 ar3700_uart,<addr>
1348 Start an early, polle 1000 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1001 Armada 3700 serial port at the specified
1350 address. The serial p 1002 address. The serial port must already be setup
1351 and configured. Optio 1003 and configured. Options are not yet supported.
1352 1004
1353 qcom_geni,<addr> !! 1005 earlyprintk= [X86,SH,BLACKFIN,ARM,M68k,S390]
1354 Start an early, polle <<
1355 Generic Interface (GE <<
1356 specified address. Th <<
1357 setup and configured. <<
1358 <<
1359 efifb,[options] <<
1360 Start an early, unacc <<
1361 memory mapped framebu <<
1362 coherent non-x86 syst <<
1363 the framebuffer, pass <<
1364 mapped with the corre <<
1365 <<
1366 linflex,<addr> <<
1367 Use early console pro <<
1368 serial driver for NXP <<
1369 address must be provi <<
1370 already be setup and <<
1371 <<
1372 earlyprintk= [X86,SH,ARM,M68k,S390 <<
1373 earlyprintk=vga 1006 earlyprintk=vga
>> 1007 earlyprintk=efi
1374 earlyprintk=sclp 1008 earlyprintk=sclp
1375 earlyprintk=xen 1009 earlyprintk=xen
1376 earlyprintk=serial[,t 1010 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1011 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1012 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1013 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1014 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1015 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1016
1384 earlyprintk is useful 1017 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1018 the normal console is initialized. It is not enabled by
1386 default because it ha 1019 default because it has some cosmetic problems.
1387 1020
1388 Append ",keep" to not 1021 Append ",keep" to not disable it when the real console
1389 takes over. 1022 takes over.
1390 1023
1391 Only one of vga, seri !! 1024 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1025 be used at a time.
1393 1026
1394 Currently only ttyS0 1027 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1028 name. Other I/O ports may be explicitly specified
1396 on some architectures 1029 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1030 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1031 earlyprintk=serial,0x1008,115200
1399 You can find the port 1032 You can find the port for a given device in
1400 /proc/tty/driver/seri 1033 /proc/tty/driver/serial:
1401 2: uart:ST166 1034 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1035
1403 Interaction with the 1036 Interaction with the standard serial driver is not
1404 very good. 1037 very good.
1405 1038
1406 The VGA output is eve !! 1039 The VGA and EFI output is eventually overwritten by
1407 the real console. 1040 the real console.
1408 1041
1409 The xen option can on !! 1042 The xen output can only be used by Xen PV guests.
1410 1043
1411 The sclp output can o 1044 The sclp output can only be used on s390.
1412 1045
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1046 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1047 PCI device even when its classcode is not of the
1417 UART class. 1048 UART class.
1418 1049
1419 edac_report= [HW,EDAC] Control how 1050 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1051 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1052 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1053 by other higher priority error reporting module.
1423 off: disable H/W even 1054 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1055 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1056 default: on.
1426 1057
>> 1058 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1059 ekgdboc=kbd
>> 1060
>> 1061 This is designed to be used in conjunction with
>> 1062 the boot argument: earlyprintk=vga
>> 1063
1427 edd= [EDD] 1064 edd= [EDD]
1428 Format: {"off" | "on" 1065 Format: {"off" | "on" | "skip[mbr]"}
1429 1066
1430 efi= [EFI,EARLY] !! 1067 efi= [EFI]
1431 Format: { "debug", "d !! 1068 Format: { "old_map", "nochunk", "noruntime", "debug" }
1432 "nochunk", !! 1069 old_map [X86-64]: switch to the old ioremap-based EFI
1433 "novamap", !! 1070 runtime services mapping. 32-bit still uses this one by
1434 debug: enable misc de !! 1071 default.
1435 disable_early_pci_dma <<
1436 PCI bridges while in <<
1437 nochunk: disable read 1072 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1073 boot stub, as chunking can cause problems with some
1439 firmware implementati 1074 firmware implementations.
1440 noruntime : disable E 1075 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF !! 1076 debug: enable misc debug output
1442 attribute may cause t <<
1443 memory range for a me <<
1444 claim. Specify efi=no <<
1445 reservation and treat <<
1446 (i.e. EFI_CONVENTIONA <<
1447 novamap: do not call <<
1448 no_disable_early_pci_ <<
1449 on all PCI bridges wh <<
1450 1077
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1078 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1079 Using this parameter you can use more than 50% of
1453 your efi variable sto 1080 your efi variable storage. Use this parameter only if
1454 you are really sure t 1081 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1082 fulfills the spec otherwise your board may brick.
1456 1083
>> 1084 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1085 Add arbitrary attribute to specific memory range by
>> 1086 updating original EFI memory map.
>> 1087 Region of memory which aa attribute is added to is
>> 1088 from ss to ss+nn.
>> 1089 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1090 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1091 attribute is added to range 0x100000000-0x180000000 and
>> 1092 0x10a0000000-0x1120000000.
>> 1093
>> 1094 Using this parameter you can do debugging of EFI memmap
>> 1095 related feature. For example, you can do debugging of
>> 1096 Address Range Mirroring feature even if your box
>> 1097 doesn't support it.
>> 1098
1457 efivar_ssdt= [EFI; X86] Name of an 1099 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1100 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1101 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1102 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g !! 1103 Documentation/acpi/ssdt-overlays.txt for details.
1462 1104
1463 1105
1464 eisa_irq_edge= [PARISC,HW] 1106 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1107 See header of drivers/parisc/eisa.c.
1466 1108
1467 ekgdboc= [X86,KGDB,EARLY] Allo <<
1468 Format: ekgdboc=kbd <<
1469 <<
1470 This is designed to b <<
1471 the boot argument: ea <<
1472 <<
1473 This parameter works <<
1474 but can only be used <<
1475 very early in the boo <<
1476 via a serial port see <<
1477 <<
1478 elanfreq= [X86-32] 1109 elanfreq= [X86-32]
1479 See comment before fu 1110 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1111 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1112
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1113 elevator= [IOSCHED]
>> 1114 Format: {"cfq" | "deadline" | "noop"}
>> 1115 See Documentation/block/cfq-iosched.txt and
>> 1116 Documentation/block/deadline-iosched.txt for details.
>> 1117
>> 1118 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1119 Specifies physical address of start of kernel core
1484 image elf header and 1120 image elf header and optionally the size. Generally
1485 kexec loader will pas 1121 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm !! 1122 See Documentation/kdump/kdump.txt for details.
1487 1123
1488 enable_mtrr_cleanup [X86,EARLY] !! 1124 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1125 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1126 to discrete, to make X server driver able to add WB
1491 entry later. This par 1127 entry later. This parameter enables that.
1492 1128
1493 enable_timer_pin_1 [X86] 1129 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1130 Enable PIN 1 of APIC timer
1495 Can be useful to work 1131 Can be useful to work around chipset bugs
1496 (in particular on som 1132 (in particular on some ATI chipsets).
1497 The kernel tries to s 1133 The kernel tries to set a reasonable default.
1498 1134
1499 enforcing= [SELINUX] Set initial !! 1135 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1136 Format: {"0" | "1"}
1501 See security/selinux/ 1137 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1138 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1139 1 -- enforcing (deny and log).
1504 Default value is 0. 1140 Default value is 0.
1505 Value can be changed !! 1141 Value can be changed at runtime via /selinux/enforce.
1506 /sys/fs/selinux/enfor <<
1507 1142
1508 erst_disable [ACPI] 1143 erst_disable [ACPI]
1509 Disable Error Record 1144 Disable Error Record Serialization Table (ERST)
1510 support. 1145 support.
1511 1146
1512 ether= [HW,NET] Ethernet car 1147 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1148 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1149 has equivalent usage. See its documentation for details.
1515 1150
1516 evm= [EVM] 1151 evm= [EVM]
1517 Format: { "fix" } 1152 Format: { "fix" }
1518 Permit 'security.evm' 1153 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1154 current integrity status.
1520 1155
1521 early_page_ext [KNL,EARLY] Enforces p <<
1522 stages so cover more <<
1523 Please note that as s <<
1524 might be disabled to <<
1525 memory initialization <<
1526 might take longer, es <<
1527 memory. Available wit <<
1528 <<
1529 failslab= 1156 failslab=
1530 fail_usercopy= <<
1531 fail_page_alloc= 1157 fail_page_alloc=
1532 fail_make_request=[KNL] 1158 fail_make_request=[KNL]
1533 General fault injecti 1159 General fault injection mechanism.
1534 Format: <interval>,<p 1160 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1161 See also Documentation/fault-injection/.
1536 1162
1537 fb_tunnels= [NET] <<
1538 Format: { initns | no <<
1539 See Documentation/adm <<
1540 fb_tunnels_only_for_i <<
1541 <<
1542 floppy= [HW] 1163 floppy= [HW]
1543 See Documentation/adm !! 1164 See Documentation/blockdev/floppy.txt.
>> 1165
>> 1166 force_pal_cache_flush
>> 1167 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1168 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1169 parameter will force ia64_sal_cache_flush to call
>> 1170 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1544 1171
1545 forcepae [X86-32] !! 1172 forcepae [X86-32]
1546 Forcefully enable Phy 1173 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1174 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1175 functionally usable PAE implementation.
1549 Warning: use of this 1176 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1177 and may cause unknown problems.
1551 1178
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] 1179 ftrace=[tracer]
1559 [FTRACE] will set and 1180 [FTRACE] will set and start the specified tracer
1560 as early as possible 1181 as early as possible in order to facilitate early
1561 boot debugging. 1182 boot debugging.
1562 1183
1563 ftrace_boot_snapshot !! 1184 ftrace_dump_on_oops[=orig_cpu]
1564 [FTRACE] On boot up, <<
1565 ftrace ring buffer th <<
1566 /sys/kernel/tracing/s <<
1567 This is useful if you <<
1568 boot up that is likel <<
1569 start up functionalit <<
1570 <<
1571 Optionally, the snaps <<
1572 instance that was cre <<
1573 line parameter. <<
1574 <<
1575 trace_instance=foo,sc <<
1576 <<
1577 The above will cause <<
1578 a snapshot at the end <<
1579 <<
1580 ftrace_dump_on_oops[=2(orig_cpu) | =< <<
1581 ,<instance>=2(orig_ <<
1582 [FTRACE] will dump th 1185 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1186 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1187 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1188 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1189 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 1190
1603 ftrace_filter=[function-list] 1191 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1192 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu !! 1193 tracer at boot up. function-list is a comma separated
1606 list of functions. Th 1194 list of functions. This list can be changed at run
1607 time by the set_ftrac 1195 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1196 tracing directory.
1609 1197
1610 ftrace_notrace=[function-list] 1198 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1199 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1200 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1201 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1202 tracing directory.
1615 1203
1616 ftrace_graph_filter=[function-list] 1204 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1205 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1206 by the function graph tracer at boot up.
1619 function-list is a co !! 1207 function-list is a comma separated list of functions
1620 that can be changed a 1208 that can be changed at run time by the
1621 set_graph_function fi 1209 set_graph_function file in the debugfs tracing directory.
1622 1210
1623 ftrace_graph_notrace=[function-list] 1211 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1212 [FTRACE] Do not trace from the functions specified in
1625 function-list. This !! 1213 function-list. This list is a comma separated list of
1626 functions that can be 1214 functions that can be changed at run time by the
1627 set_graph_notrace fil 1215 set_graph_notrace file in the debugfs tracing directory.
1628 1216
1629 ftrace_graph_max_depth=<uint> 1217 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1218 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1219 the max depth it will trace into a function. This value
1632 can be changed at run 1220 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1221 in the tracefs tracing directory. default: 0 (no limit)
1634 1222
1635 fw_devlink= [KNL,EARLY] Create de <<
1636 devices by scanning t <<
1637 consumer/supplier rel <<
1638 especially useful whe <<
1639 it ensures proper ord <<
1640 (suppliers first, the <<
1641 clean up (only after <<
1642 suspend/resume & runt <<
1643 suppliers). <<
1644 Format: { off | permi <<
1645 off -- Don't create <<
1646 permissive -- Create <<
1647 but use it on <<
1648 up (sync_stat <<
1649 on -- Create device <<
1650 to enforce pr <<
1651 rpm -- Like "on", bu <<
1652 <<
1653 fw_devlink.strict=<bool> <<
1654 [KNL,EARLY] Treat all <<
1655 dependencies. This on <<
1656 Format: <bool> <<
1657 <<
1658 fw_devlink.sync_state = <<
1659 [KNL,EARLY] When all <<
1660 probing, this paramet <<
1661 devices that haven't <<
1662 calls. <<
1663 Format: { strict | ti <<
1664 strict -- Default. Co <<
1665 probe success <<
1666 timeout -- Give up wa <<
1667 sync_state() <<
1668 received thei <<
1669 deferred_prob <<
1670 late_initcall <<
1671 <<
1672 gamecon.map[2|3]= 1223 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1224 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1225 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1226 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio !! 1227 See also Documentation/input/joystick-parport.txt
1677 1228
1678 gamma= [HW,DRM] 1229 gamma= [HW,DRM]
1679 1230
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1231 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1681 Format: off | on 1232 Format: off | on
1682 default: on 1233 default: on
1683 1234
1684 gather_data_sampling= 1235 gather_data_sampling=
1685 [X86,INTEL,EARLY] Con !! 1236 [X86,INTEL] Control the Gather Data Sampling (GDS)
1686 mitigation. 1237 mitigation.
1687 1238
1688 Gather Data Sampling 1239 Gather Data Sampling is a hardware vulnerability which
1689 allows unprivileged s 1240 allows unprivileged speculative access to data which was
1690 previously stored in 1241 previously stored in vector registers.
1691 1242
1692 This issue is mitigat 1243 This issue is mitigated by default in updated microcode.
1693 The mitigation may ha 1244 The mitigation may have a performance impact but can be
1694 disabled. On systems 1245 disabled. On systems without the microcode mitigation
1695 disabling AVX serves 1246 disabling AVX serves as a mitigation.
1696 1247
1697 force: Disable AVX t 1248 force: Disable AVX to mitigate systems without
1698 microcode mit 1249 microcode mitigation. No effect if the microcode
1699 mitigation is 1250 mitigation is present. Known to cause crashes in
1700 userspace wit 1251 userspace with buggy AVX enumeration.
1701 1252
1702 off: Disable GDS m !! 1253 off: Disable GDS mitigation.
1703 1254
1704 gcov_persist= [GCOV] When non-zero 1255 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1256 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1257 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1258 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1259 debugfs files are removed at module unload time.
1709 1260
1710 goldfish [X86] Enable the gold 1261 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1262 Don't use this when you are not running on the
1712 android emulator 1263 android emulator
1713 1264
1714 gpio-mockup.gpio_mockup_ranges <<
1715 [HW] Sets the ranges <<
1716 Format: <start1>,<end <<
1717 gpio-mockup.gpio_mockup_named_lines <<
1718 [HW] Let the driver k <<
1719 <<
1720 gpt [EFI] Forces disk wit 1265 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1266 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1267 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1268 GPT to be used instead.
1724 1269
1725 grcan.enable0= [HW] Configuration of 1270 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1271 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1272 Format: 0 | 1
1728 Default: 0 1273 Default: 0
1729 grcan.enable1= [HW] Configuration of 1274 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1275 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1276 Format: 0 | 1
1732 Default: 0 1277 Default: 0
1733 grcan.select= [HW] Select which phy 1278 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1279 Format: 0 | 1
1735 Default: 0 1280 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1281 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1282 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1283 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1284 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1285 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1286 Default: 1024
1742 1287
1743 hardened_usercopy= !! 1288 gpio-mockup.gpio_mockup_ranges
1744 [KNL] Under CONFIG_HA !! 1289 [HW] Sets the ranges of gpiochip of for this device.
1745 hardening is enabled !! 1290 Format: <start1>,<end1>,<start2>,<end2>...
1746 usercopy checking is <<
1747 from reading or writi <<
1748 allocation boundaries <<
1749 against bounds-checki <<
1750 copy_to_user()/copy_f <<
1751 on Perform hardened user <<
1752 off Disable hardened user <<
1753 1291
1754 hardlockup_all_cpu_backtrace= 1292 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1293 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1294 backtraces on all cpus.
1757 Format: 0 | 1 !! 1295 Format: <integer>
1758 1296
1759 hashdist= [KNL,NUMA] Large hash 1297 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1298 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1299 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1300 Format: 0 | 1 (for off | on)
1763 1301
>> 1302 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1303
1764 hd= [EIDE] (E)IDE hard dr 1304 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1305 Format: <cyl>,<head>,<sect>
1766 1306
1767 hest_disable [ACPI] 1307 hest_disable [ACPI]
1768 Disable Hardware Erro 1308 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1309 corresponding firmware-first mode error processing
1770 logic will be disable 1310 logic will be disabled.
1771 1311
1772 hibernate= [HIBERNATION] !! 1312 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1773 noresume Don't check i <<
1774 present durin <<
1775 nocompress Don't compres <<
1776 no Disable hiber <<
1777 protect_image Turn on image <<
1778 (that will se <<
1779 during restor <<
1780 <<
1781 hibernate.compressor= [HIBERNATION] <<
1782 used with hib <<
1783 Format: { lzo <<
1784 Default: lzo <<
1785 <<
1786 lzo: Select L <<
1787 compress/deco <<
1788 <<
1789 lz4: Select L <<
1790 compress/deco <<
1791 <<
1792 highmem=nn[KMG] [KNL,BOOT,EARLY] forc <<
1793 size of <nn>. This wo 1313 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1314 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1315 size on bigger boxes.
1796 1316
1797 highres= [KNL] Enable/disable 1317 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1318 Valid parameters: "on", "off"
1799 Default: "on" 1319 Default: "on"
1800 1320
1801 hlt [BUGS=ARM,SH] !! 1321 hisax= [HW,ISDN]
>> 1322 See Documentation/isdn/README.HiSax.
1802 1323
1803 hostname= [KNL,EARLY] Set the h !! 1324 hlt [BUGS=ARM,SH]
1804 Format: <string> <<
1805 This allows setting t <<
1806 startup. This sets th <<
1807 Using this parameter <<
1808 possible to ensure th <<
1809 any userspace process <<
1810 that a process may ca <<
1811 has been explicitly s <<
1812 process getting an in <<
1813 not exceed the maximu <<
1814 64 characters) and wi <<
1815 1325
1816 hpet= [X86-32,HPET] option 1326 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1327 Format: { enable (default) | disable | force |
1818 verbose } 1328 verbose }
1819 disable: disable HPET 1329 disable: disable HPET and use PIT instead
1820 force: allow force en 1330 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1331 VIA, nVidia)
1822 verbose: show content 1332 verbose: show contents of HPET registers during setup
1823 1333
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1334 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1335 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1336
1827 hugepages= [HW] Number of HugeTL !! 1337 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1828 If this follows hugep !! 1338 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1829 the number of pages o !! 1339 On x86-64 and powerpc, this option can be specified
1830 If this is the first !! 1340 multiple times interleaved with hugepages= to reserve
1831 line, it specifies th !! 1341 huge pages of different sizes. Valid pages sizes on
1832 the default huge page !! 1342 x86-64 are 2M (when the CPU supports "pse") and 1G
1833 number of pages to al !! 1343 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1834 See also Documentatio !! 1344
1835 Format: <integer> or !! 1345 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1836 <node>:<integ !! 1346 terminal devices. Valid values: 0..8
1837 !! 1347 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1838 hugepagesz= !! 1348 If specified, z/VM IUCV HVC accepts connections
1839 [HW] The size of the !! 1349 from listed z/VM user IDs only.
1840 conjunction with huge !! 1350
1841 pages of a specific s !! 1351 hwthread_map= [METAG] Comma-separated list of Linux cpu id to
1842 hugepagesz=X hugepage !! 1352 hardware thread id mappings.
1843 each supported huge p !! 1353 Format: <cpu>:<hwthread>
1844 architecture dependen <<
1845 Documentation/admin-g <<
1846 Format: size[KMG] <<
1847 <<
1848 hugetlb_cma= [HW,CMA,EARLY] The si <<
1849 of gigantic hugepages <<
1850 of a CMA area per nod <<
1851 Format: nn[KMGTPE] or <<
1852 <node>:nn[KMG <<
1853 <<
1854 Reserve a CMA area of <<
1855 hugepages using the C <<
1856 boot-time allocation <<
1857 <<
1858 hugetlb_free_vmemmap= <<
1859 [KNL] Requires CONFIG <<
1860 enabled. <<
1861 Control if HugeTLB Vm <<
1862 Allows heavy hugetlb <<
1863 memory (7 * PAGE_SIZE <<
1864 Format: { on | off (d <<
1865 <<
1866 on: enable HVO <<
1867 off: disable HVO <<
1868 <<
1869 Built with CONFIG_HUG <<
1870 the default is on. <<
1871 <<
1872 Note that the vmemmap <<
1873 memory block itself w <<
1874 enabled, those vmemma <<
1875 feature is enabled. <<
1876 the added memory bloc <<
1877 1354
1878 hung_task_panic= !! 1355 keep_bootcon [KNL]
1879 [KNL] Should the hung !! 1356 Do not unregister boot console at start. This is only
1880 Format: 0 | 1 !! 1357 useful for debugging when something happens in the window
1881 !! 1358 between unregistering the boot console and initializing
1882 A value of 1 instruct !! 1359 the real console.
1883 hung task is detected <<
1884 by the CONFIG_BOOTPAR <<
1885 option. The value sel <<
1886 be changed later by t <<
1887 <<
1888 hvc_iucv= [S390] Number of z/V <<
1889 terminal devi <<
1890 hvc_iucv_allow= [S390] Comma-separat <<
1891 If specified, <<
1892 from listed z <<
1893 <<
1894 hv_nopvspin [X86,HYPER_V,EARLY] <<
1895 Disables the paravirt <<
1896 which allow the hyper <<
1897 on lock contention. <<
1898 <<
1899 i2c_bus= [HW] Override the <<
1900 or register a <<
1901 registered fr <<
1902 Format: <<
1903 <bus_id>,<clk <<
1904 <<
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 1360
1912 Format: !! 1361 i2c_bus= [HW] Override the default board specific I2C bus speed
1913 <ACPI_HW_ID>:<prop_na !! 1362 or register an additional I2C bus that is not
1914 Where <val> is one of !! 1363 registered from board initialization code.
1915 Omit "=<val>" entirel !! 1364 Format:
1916 Unsigned number !! 1365 <bus_id>,<clkrate>
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 1366
1927 i8042.debug [HW] Toggle i8042 deb 1367 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1368 i8042.unmask_kbd_data
1929 [HW] Enable printing 1369 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1370 (disabled by default, and as a pre-condition
1931 requires that i8 1371 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1372 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1373 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1374 keyboard and cannot control its state
1935 (Don't attempt t 1375 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1376 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1377 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1378 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1379 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1380 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1381 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1382 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1383 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1384 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1385 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1386 suspend-to-ram transitions, only during s2r
1947 transitions, or 1387 transitions, or never reset
1948 Format: { 1 | Y | y | 1388 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1389 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1390 0, N, n: don't ever reset controller
1951 Default: only on s2r 1391 Default: only on s2r transitions on x86; most other
1952 architectures force r 1392 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1393 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con !! 1394 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer <<
1956 [HW] Allow deferred p <<
1957 1395
1958 i810= [HW,DRM] 1396 i810= [HW,DRM]
1959 1397
>> 1398 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1399 indicates that the driver is running on unsupported
>> 1400 hardware.
>> 1401 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1402 does not match list of supported models.
>> 1403 i8k.power_status
>> 1404 [HW] Report power status in /proc/i8k
>> 1405 (disabled by default)
>> 1406 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1407 capability is set.
>> 1408
1960 i915.invert_brightness= 1409 i915.invert_brightness=
1961 [DRM] Invert the sens 1410 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1411 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1412 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1413 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1414 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1415 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1416 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1417 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1418 value switches the backlight off.
1970 -1 -- never invert br 1419 -1 -- never invert brightness
1971 0 -- machine default 1420 0 -- machine default
1972 1 -- force brightnes 1421 1 -- force brightness inversion
1973 1422
1974 ia32_emulation= [X86-64] <<
1975 Format: <bool> <<
1976 When true, allows loa <<
1977 syscalls, essentially <<
1978 boot time. When false <<
1979 <<
1980 icn= [HW,ISDN] 1423 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1424 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1425
>> 1426 ide-core.nodma= [HW] (E)IDE subsystem
>> 1427 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1428 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1429 .cdrom .chs .ignore_cable are additional options
>> 1430 See Documentation/ide/ide.txt.
>> 1431
>> 1432 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1433 Format: <int>
>> 1434 Probe mask for legacy ISA IDE ports. Depending on
>> 1435 platform up to 6 ports are supported, enabled by
>> 1436 setting corresponding bits in the mask to 1. The
>> 1437 default value is 0x0, which has a special meaning.
>> 1438 On systems that have PCI, it triggers scanning the
>> 1439 PCI bus for the first and the second port, which
>> 1440 are then probed. On systems without PCI the value
>> 1441 of 0x0 enables probing the two first ports as if it
>> 1442 was 0x3.
>> 1443
>> 1444 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1445 Claim all unknown PCI IDE storage controllers.
1983 1446
1984 idle= [X86,EARLY] !! 1447 idle= [X86]
1985 Format: idle=poll, id 1448 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1449 Poll forces a polling idle loop that can slightly
1987 improve the performan 1450 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1451 will use a lot of power and make the system run hot.
1989 Not recommended. 1452 Not recommended.
1990 idle=halt: Halt is fo 1453 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1454 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1455 idle=nomwait: Disable mwait for CPU C-states
1993 1456
1994 idxd.sva= [HW] <<
1995 Format: <bool> <<
1996 Allow force disabling <<
1997 support for the idxd <<
1998 true (1). <<
1999 <<
2000 idxd.tc_override= [HW] <<
2001 Format: <bool> <<
2002 Allow override of def <<
2003 for the device. By de <<
2004 <<
2005 ieee754= [MIPS] Select IEEE St 1457 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1458 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1459 Default: strict
2008 1460
2009 Choose which programs 1461 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1462 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1463 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1464 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1465 binary. Hardware implementations are permitted to
2014 support either or bot 1466 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1467 encoding mode.
2016 1468
2017 Available settings ar 1469 Available settings are as follows:
2018 strict accept binari 1470 strict accept binaries that request a NaN encoding
2019 supported by 1471 supported by the FPU
2020 legacy only accept l 1472 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1473 by the FPU
2022 2008 only accept 2 1474 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1475 by the FPU
2024 relaxed accept any bi 1476 relaxed accept any binaries regardless of whether
2025 supported by 1477 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1478
2029 The FPU emulator is a 1479 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1480 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1481 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1482 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1483 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1484 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1485 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1486 MIPS64 CPUs.
2037 1487
2038 The setting for ABS.f 1488 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1489 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1490 except where unsupported by hardware.
2041 1491
2042 ignore_loglevel [KNL,EARLY] !! 1492 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1493 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1494 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1495 We also add it as printk module parameter, so users
2046 could change it dynam 1496 could change it dynamically, usually by
2047 /sys/module/printk/pa 1497 /sys/module/printk/parameters/ignore_loglevel.
2048 1498
2049 ignore_rlimit_data 1499 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1500 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1501 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1502 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1503
2054 ihash_entries= [KNL] 1504 ihash_entries= [KNL]
2055 Set number of hash bu 1505 Set number of hash buckets for inode cache.
2056 1506
2057 ima_appraise= [IMA] appraise integr 1507 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1508 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1509 default: "enforce"
2060 1510
2061 ima_appraise_tcb [IMA] Deprecated. U !! 1511 ima_appraise_tcb [IMA]
2062 The builtin appraise 1512 The builtin appraise policy appraises all files
2063 owned by uid=0. 1513 owned by uid=0.
2064 1514
2065 ima_canonical_fmt [IMA] 1515 ima_canonical_fmt [IMA]
2066 Use the canonical for 1516 Use the canonical format for the binary runtime
2067 measurements, instead 1517 measurements, instead of host native format.
2068 1518
2069 ima_hash= [IMA] 1519 ima_hash= [IMA]
2070 Format: { md5 | sha1 1520 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1521 | sha512 | ... }
2072 default: "sha1" 1522 default: "sha1"
2073 1523
2074 The list of supported 1524 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1525 in crypto/hash_info.h.
2076 1526
2077 ima_policy= [IMA] 1527 ima_policy= [IMA]
2078 The builtin policies 1528 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai !! 1529 Format: "tcb | appraise_tcb | secure_boot"
2080 fail_securel <<
2081 1530
2082 The "tcb" policy meas 1531 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1532 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1533 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1534 uid=0.
2086 1535
2087 The "appraise_tcb" po 1536 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro !! 1537 all files owned by root. (This is the equivalent
>> 1538 of ima_appraise_tcb.)
2089 1539
2090 The "secure_boot" pol 1540 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1541 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1542 firmware, policy, etc) based on file signatures.
2093 1543
2094 The "fail_securely" p <<
2095 verification failure <<
2096 filesystems with the <<
2097 flag. <<
2098 <<
2099 The "critical_data" p <<
2100 critical data. <<
2101 <<
2102 ima_tcb [IMA] Deprecated. Us 1544 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1545 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1546 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1547 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1548 opened for read by uid=0.
2107 1549
2108 ima_template= [IMA] !! 1550 ima_template= [IMA]
2109 Select one of defined 1551 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1552 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1553 Default: "ima-ng"
2113 1554
2114 ima_template_fmt= 1555 ima_template_fmt=
2115 [IMA] Define a custom !! 1556 [IMA] Define a custom template format.
2116 Format: { "field1|... 1557 Format: { "field1|...|fieldN" }
2117 1558
2118 ima.ahash_minsize= [IMA] Minimum file 1559 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1560 Format: <min_file_size>
2120 Set the minimal file 1561 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1562 If left unspecified, ahash usage is disabled.
2122 1563
2123 ahash performance var 1564 ahash performance varies for different data sizes on
2124 different crypto acce 1565 different crypto accelerators. This option can be used
2125 to achieve the best p 1566 to achieve the best performance for a particular HW.
2126 1567
2127 ima.ahash_bufsize= [IMA] Asynchronous 1568 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1569 Format: <bufsize>
2129 Set hashing buffer si 1570 Set hashing buffer size. Default: 4k.
2130 1571
2131 ahash performance var 1572 ahash performance varies for different chunk sizes on
2132 different crypto acce 1573 different crypto accelerators. This option can be used
2133 to achieve best perfo 1574 to achieve best performance for particular HW.
2134 1575
2135 init= [KNL] 1576 init= [KNL]
2136 Format: <full_path> 1577 Format: <full_path>
2137 Run specified binary 1578 Run specified binary instead of /sbin/init as init
2138 process. 1579 process.
2139 1580
2140 initcall_debug [KNL] Trace initcalls 1581 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1582 for working out where the kernel is dying during
2142 startup. 1583 startup.
2143 1584
2144 initcall_blacklist= [KNL] Do not exe 1585 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1586 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1587 modules and initcalls.
2147 1588
2148 initramfs_async= [KNL] !! 1589 initrd= [BOOT] Specify the location of the initial ramdisk
2149 Format: <bool> <<
2150 Default: 1 <<
2151 This parameter contro <<
2152 image is unpacked asy <<
2153 with devices being pr <<
2154 initialized. This sho <<
2155 but as a debugging ai <<
2156 historical behaviour <<
2157 unpacking being compl <<
2158 late_ initcalls. <<
2159 <<
2160 initrd= [BOOT,EARLY] Specify <<
2161 <<
2162 initrdmem= [KNL,EARLY] Specify a <<
2163 load the initrd. If a <<
2164 specified in the boot <<
2165 setting. <<
2166 Format: ss[KMG],nn[KM <<
2167 Default is 0, 0 <<
2168 1590
2169 init_on_alloc= [MM,EARLY] Fill newly !! 1591 init_pkru= [x86] Specify the default memory protection keys rights
2170 zeroes. <<
2171 Format: 0 | 1 <<
2172 Default set by CONFIG <<
2173 <<
2174 init_on_free= [MM,EARLY] Fill freed <<
2175 Format: 0 | 1 <<
2176 Default set by CONFIG <<
2177 <<
2178 init_pkru= [X86] Specify the def <<
2179 register contents for 1592 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1593 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1594 override in debugfs after boot.
2182 1595
2183 inport.irq= [HW] Inport (ATI XL a 1596 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1597 Format: <irq>
2185 1598
2186 int_pln_enable [X86] Enable power li !! 1599 int_pln_enable [x86] Enable power limit notification interrupt
2187 1600
2188 integrity_audit=[IMA] 1601 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1602 Format: { "0" | "1" }
2190 0 -- basic integrity 1603 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1604 1 -- additional integrity auditing messages.
2192 1605
2193 intel_iommu= [DMAR] Intel IOMMU dr 1606 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1607 on
2195 Enable intel iommu dr 1608 Enable intel iommu driver.
2196 off 1609 off
2197 Disable intel iommu d 1610 Disable intel iommu driver.
2198 igfx_off [Default Off] 1611 igfx_off [Default Off]
2199 By default, gfx is ma 1612 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1613 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1614 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1615 this case, gfx device will use physical address for
2203 DMA. 1616 DMA.
>> 1617 forcedac [x86_64]
>> 1618 With this option iommu will not optimize to look
>> 1619 for io virtual address below 32-bit forcing dual
>> 1620 address cycle on pci bus for cards supporting greater
>> 1621 than 32-bit addressing. The default is to look
>> 1622 for translation below 32-bit and if not available
>> 1623 then look in the higher range.
2204 strict [Default Off] 1624 strict [Default Off]
2205 Deprecated, equivalen !! 1625 With this option on every unmap_single operation will
>> 1626 result in a hardware IOTLB flush operation as opposed
>> 1627 to batching them for performance.
2206 sp_off [Default Off] 1628 sp_off [Default Off]
2207 By default, super pag 1629 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1630 has the capability. With this option, super page will
2209 not be supported. 1631 not be supported.
2210 sm_on !! 1632 ecs_off [Default Off]
2211 Enable the Intel IOMM !! 1633 By default, extended context tables will be supported if
2212 advertises that it ha !! 1634 the hardware advertises that it has support both for the
2213 translation. !! 1635 extended tables themselves, and also PASID support. With
2214 sm_off !! 1636 this option set, extended tables will not be used even
2215 Disallow use of the I !! 1637 on hardware which claims to support them.
2216 tboot_noforce [Default Off] 1638 tboot_noforce [Default Off]
2217 Do not force the Inte 1639 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1640 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1641 could harm performance of some high-throughput
2220 devices like 40GBit n 1642 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1643 mapping is enabled.
2222 Note that using this 1644 Note that using this option lowers the security
2223 provided by tboot bec 1645 provided by tboot because it makes the system
2224 vulnerable to DMA att 1646 vulnerable to DMA attacks.
2225 1647
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1648 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1649 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1650 1 to 9 specify maximum depth of C-state.
2229 1651
2230 intel_pstate= [X86,EARLY] !! 1652 intel_pstate= [X86]
2231 disable !! 1653 disable
2232 Do not enable intel !! 1654 Do not enable intel_pstate as the default
2233 scaling driver for !! 1655 scaling driver for the supported processors
2234 active !! 1656 passive
2235 Use intel_pstate dr !! 1657 Use intel_pstate as a scaling driver, but configure it
2236 governors layer of !! 1658 to work with generic cpufreq governors (instead of
2237 algorithms for p-st !! 1659 enabling its internal governor). This mode cannot be
2238 P-state selection a !! 1660 used along with the hardware-managed P-states (HWP)
2239 intel_pstate in the !! 1661 feature.
2240 performance. The w !! 1662 force
2241 on whether or not t !! 1663 Enable intel_pstate on systems that prohibit it by default
2242 (HWP) feature has b !! 1664 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2243 and possibly on the !! 1665 instead of acpi-cpufreq may disable platform features, such
2244 passive !! 1666 as thermal controls and power capping, that rely on ACPI
2245 Use intel_pstate as !! 1667 P-States information being indicated to OSPM and therefore
2246 to work with generi !! 1668 should be used with caution. This option does not work with
2247 enabling its intern !! 1669 processors that aren't supported by the intel_pstate driver
2248 used along with the !! 1670 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2249 feature. !! 1671 no_hwp
2250 force !! 1672 Do not enable hardware P state control (HWP)
2251 Enable intel_pstate !! 1673 if available.
2252 in favor of acpi-cp !! 1674 hwp_only
2253 instead of acpi-cpu !! 1675 Only load intel_pstate on systems which support
2254 as thermal controls !! 1676 hardware P state control (HWP) if available.
2255 P-States informatio !! 1677 support_acpi_ppc
2256 should be used with !! 1678 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2257 processors that are !! 1679 Description Table, specifies preferred power management
2258 or on platforms tha !! 1680 profile as "Enterprise Server" or "Performance Server",
2259 no_hwp !! 1681 then this feature is turned on by default.
2260 Do not enable hardw !! 1682 per_cpu_perf_limits
2261 if available. !! 1683 Allow per-logical-CPU P-State performance control limits using
2262 hwp_only !! 1684 cpufreq sysfs interface
2263 Only load intel_pst <<
2264 hardware P state co <<
2265 support_acpi_ppc <<
2266 Enforce ACPI _PPC p <<
2267 Description Table, <<
2268 profile as "Enterpr <<
2269 then this feature i <<
2270 per_cpu_perf_limits <<
2271 Allow per-logical-C <<
2272 cpufreq sysfs inter <<
2273 1685
2274 intremap= [X86-64,Intel-IOMMU,E !! 1686 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 1687 on enable Interrupt Remapping (default)
2276 off disable Inter 1688 off disable Interrupt Remapping
2277 nosid disable Sourc 1689 nosid disable Source ID checking
2278 no_x2apic_optout 1690 no_x2apic_optout
2279 BIOS x2APIC o 1691 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 1692 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 1693
2284 iomem= Disable strict checki 1694 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 1695 strict regions from userspace.
2286 relaxed 1696 relaxed
2287 1697
2288 iommu= [X86,EARLY] !! 1698 iommu= [x86]
2289 off 1699 off
2290 force 1700 force
2291 noforce 1701 noforce
2292 biomerge 1702 biomerge
2293 panic 1703 panic
2294 nopanic 1704 nopanic
2295 merge 1705 merge
2296 nomerge 1706 nomerge
>> 1707 forcesac
2297 soft 1708 soft
2298 pt [X86] !! 1709 pt [x86, IA-64]
2299 nopt [X86] <<
2300 nobypass [PPC/POWERNV] 1710 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 1711 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 1712
2303 iommu.forcedac= [ARM64,X86,EARLY] Con <<
2304 Format: { "0" | "1" } <<
2305 0 - Try to allocate a <<
2306 falling back to the <<
2307 1 - Allocate directly <<
2308 forcing Dual Addres <<
2309 greater than 32-bit <<
2310 <<
2311 iommu.strict= [ARM64,X86,S390,EARLY <<
2312 Format: { "0" | "1" } <<
2313 0 - Lazy mode. <<
2314 Request that DMA un <<
2315 invalidation of har <<
2316 throughput at the c <<
2317 Will fall back to s <<
2318 the relevant IOMMU <<
2319 1 - Strict mode. <<
2320 DMA unmap operation <<
2321 synchronously. <<
2322 unset - Use value of <<
2323 Note: on x86, strict <<
2324 legacy driver-specifi <<
2325 <<
2326 iommu.passthrough= 1713 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 1714 [ARM64] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 1715 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 1716 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 1717 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of !! 1718 unset - Use IOMMU translation for DMA.
2332 1719
2333 io7= [HW] IO7 for Marvel-b !! 1720 io7= [HW] IO7 for Marvel based alpha systems
2334 See comment before ma 1721 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 1722 arch/alpha/kernel/core_marvel.c.
2336 1723
2337 io_delay= [X86,EARLY] I/O delay !! 1724 io_delay= [X86] I/O delay method
2338 0x80 1725 0x80
2339 Standard port 0x80 ba 1726 Standard port 0x80 based delay
2340 0xed 1727 0xed
2341 Alternate port 0xed b 1728 Alternate port 0xed based delay (needed on some systems)
2342 udelay 1729 udelay
2343 Simple two microsecon 1730 Simple two microseconds delay
2344 none 1731 none
2345 No delay 1732 No delay
2346 1733
2347 ip= [IP_PNP] 1734 ip= [IP_PNP]
2348 See Documentation/adm !! 1735 See Documentation/filesystems/nfs/nfsroot.txt.
2349 <<
2350 ipcmni_extend [KNL,EARLY] Extend th <<
2351 IPC identifiers from <<
2352 1736
2353 irqaffinity= [SMP] Set the default 1737 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 1738 The argument is a cpu list, as described above.
2355 1739
2356 irqchip.gicv2_force_probe= <<
2357 [ARM,ARM64,EARLY] <<
2358 Format: <bool> <<
2359 Force the kernel to l <<
2360 of a GICv2 controller <<
2361 exposed by the device <<
2362 <<
2363 irqchip.gicv3_nolpi= <<
2364 [ARM,ARM64,EARLY] <<
2365 Force the kernel to i <<
2366 LPIs (and by conseque <<
2367 that use the kernel a <<
2368 to let secondary kern <<
2369 LPIs. <<
2370 <<
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL <<
2372 Enables support for p <<
2373 requires the kernel t <<
2374 CONFIG_ARM64_PSEUDO_N <<
2375 <<
2376 irqfixup [HW] 1740 irqfixup [HW]
2377 When an interrupt is 1741 When an interrupt is not handled search all handlers
2378 for it. Intended to g 1742 for it. Intended to get systems with badly broken
2379 firmware running. 1743 firmware running.
2380 1744
2381 irqpoll [HW] 1745 irqpoll [HW]
2382 When an interrupt is 1746 When an interrupt is not handled search all handlers
2383 for it. Also check al 1747 for it. Also check all handlers each timer
2384 interrupt. Intended t 1748 interrupt. Intended to get systems with badly broken
2385 firmware running. 1749 firmware running.
2386 1750
2387 isapnp= [ISAPNP] 1751 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 1752 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 1753
2390 isolcpus= [KNL,SMP,ISOL] Isolat !! 1754 isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
2391 [Deprecated - use cpu !! 1755 The argument is a cpu list, as described above.
2392 Format: [flag-list,]< <<
2393 <<
2394 Specify one or more C <<
2395 specified in the flag <<
2396 <<
2397 nohz <<
2398 Disable the tick wh <<
2399 <<
2400 A residual 1Hz tick <<
2401 need to affine to h <<
2402 workqueue's affinit <<
2403 /sys/devices/virtua <<
2404 by using the 'domai <<
2405 <<
2406 NOTE: by default th <<
2407 so to protect indiv <<
2408 be configured manua <<
2409 <<
2410 domain <<
2411 Isolate from the ge <<
2412 algorithms. Note th <<
2413 is irreversible: it <<
2414 the domains once is <<
2415 advised to use cpus <<
2416 balancing through t <<
2417 It offers a much mo <<
2418 move in and out of <<
2419 <<
2420 You can move a proc <<
2421 the CPU affinity sy <<
2422 <cpu number> begins <<
2423 "number of CPUs in <<
2424 <<
2425 managed_irq <<
2426 <<
2427 Isolate from being <<
2428 which have an inter <<
2429 CPUs. The affinity <<
2430 handled by the kern <<
2431 the /proc/irq/* int <<
2432 <<
2433 This isolation is b <<
2434 if the automaticall <<
2435 device queue contai <<
2436 CPUs. If housekeepi <<
2437 interrupts are dire <<
2438 so that IO submitte <<
2439 cannot disturb the <<
2440 <<
2441 If a queue's affini <<
2442 CPUs then this para <<
2443 interrupt routing d <<
2444 only delivered when <<
2445 isolated CPUs submi <<
2446 housekeeping CPUs h <<
2447 queues. <<
2448 1756
2449 The format of <cpu-li !! 1757 This option can be used to specify one or more CPUs
>> 1758 to isolate from the general SMP balancing and scheduling
>> 1759 algorithms. You can move a process onto or off an
>> 1760 "isolated" CPU via the CPU affinity syscalls or cpuset.
>> 1761 <cpu number> begins at 0 and the maximum value is
>> 1762 "number of CPUs in system - 1".
>> 1763
>> 1764 This option is the preferred way to isolate CPUs. The
>> 1765 alternative -- manually setting the CPU mask of all
>> 1766 tasks in the system -- can cause problems and
>> 1767 suboptimal load balancer performance.
2450 1768
2451 iucv= [HW,NET] 1769 iucv= [HW,NET]
2452 1770
2453 ivrs_ioapic [HW,X86-64] !! 1771 ivrs_ioapic [HW,X86_64]
2454 Provide an override t 1772 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 1773 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 1774 example, to map IOAPIC-ID decimal 10 to
2457 !! 1775 PCI device 00:14.0 write the parameter as:
2458 For example, to map I <<
2459 PCI segment 0x1 and P <<
2460 write the parameter a <<
2461 ivrs_ioapic=1 <<
2462 <<
2463 Deprecated formats: <<
2464 * To map IOAPIC-ID de <<
2465 write the parameter <<
2466 ivrs_ioapic[1 1776 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 1777
2471 ivrs_hpet [HW,X86-64] !! 1778 ivrs_hpet [HW,X86_64]
2472 Provide an override t 1779 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 1780 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 1781 example, to map HPET-ID decimal 0 to
2475 !! 1782 PCI device 00:14.0 write the parameter as:
2476 For example, to map H <<
2477 PCI segment 0x1 and P <<
2478 write the parameter a <<
2479 ivrs_hpet=10@ <<
2480 <<
2481 Deprecated formats: <<
2482 * To map HPET-ID deci <<
2483 write the parameter <<
2484 ivrs_hpet[0]= 1783 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 1784
2489 ivrs_acpihid [HW,X86-64] !! 1785 ivrs_acpihid [HW,X86_64]
2490 Provide an override t 1786 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 1787 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 1788 example, to map UART-HID:UID AMD0020:0 to
2493 !! 1789 PCI device 00:14.5 write the parameter as:
2494 For example, to map U <<
2495 PCI segment 0x1 and P <<
2496 write the parameter a <<
2497 ivrs_acpihid= <<
2498 <<
2499 Deprecated formats: <<
2500 * To map UART-HID:UID <<
2501 PCI device ID 00:14 <<
2502 ivrs_acpihid[ 1790 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 1791
2507 js= [HW,JOY] Analog joyst 1792 js= [HW,JOY] Analog joystick
2508 See Documentation/inp !! 1793 See Documentation/input/joystick.txt.
>> 1794
>> 1795 nokaslr [KNL]
>> 1796 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 1797 kernel and module base offset ASLR (Address Space
>> 1798 Layout Randomization).
2509 1799
2510 kasan_multi_shot 1800 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 1801 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 1802 report on every invalid memory access. Without this
2513 parameter KASAN will 1803 parameter KASAN will print report only for the first
2514 invalid access. 1804 invalid access.
2515 1805
2516 keep_bootcon [KNL,EARLY] !! 1806 keepinitrd [HW,ARM]
2517 Do not unregister boo <<
2518 useful for debugging <<
2519 between unregistering <<
2520 the real console. <<
2521 <<
2522 keepinitrd [HW,ARM] See retain_i <<
2523 1807
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 1808 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | !! 1809 Format: nn[KMGTPE] | "mirror"
2526 This parameter specif !! 1810 This parameter
2527 the kernel for non-mo !! 1811 specifies the amount of memory usable by the kernel
2528 amount is spread even !! 1812 for non-movable allocations. The requested amount is
2529 system as ZONE_NORMAL !! 1813 spread evenly throughout all nodes in the system. The
2530 movable memory in its !! 1814 remaining memory in each node is used for Movable
2531 event, a node is too !! 1815 pages. In the event, a node is too small to have both
2532 ZONE_MOVABLE, kernelc !! 1816 kernelcore and Movable pages, kernelcore pages will
2533 other nodes will have !! 1817 take priority and other nodes will have a larger number
2534 !! 1818 of Movable pages. The Movable zone is used for the
2535 ZONE_MOVABLE is used !! 1819 allocation of pages that may be reclaimed or moved
2536 may be reclaimed or m !! 1820 by the page migration subsystem. This means that
2537 subsystem. Note that !! 1821 HugeTLB pages may not be allocated from this zone.
2538 still use the HighMem !! 1822 Note that allocations like PTEs-from-HighMem still
>> 1823 use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 1824 zone if it does not.
2540 1825
2541 It is possible to spe !! 1826 Instead of specifying the amount of memory (nn[KMGTPE]),
2542 the form of "nn[KMGTP !! 1827 you can specify "mirror" option. In case "mirror"
2543 memory in the form of <<
2544 option is specified, 1828 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 1829 for non-movable allocations and remaining memory is used
2546 for Movable pages. " !! 1830 for Movable pages. nn[KMGTPE] and "mirror" are exclusive,
2547 are exclusive, so you !! 1831 so you can NOT specify nn[KMGTPE] and "mirror" at the same
>> 1832 time.
2548 1833
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 1834 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 1835 Format: <Controller#>[,poll interval]
2551 The controller # is t 1836 The controller # is the number of the ehci usb debug
2552 port as it is probed 1837 port as it is probed via PCI. The poll interval is
2553 optional and is the n 1838 optional and is the number seconds in between
2554 each poll cycle to th 1839 each poll cycle to the debug port in case you need
2555 the functionality for 1840 the functionality for interrupting the kernel with
2556 gdb or control-c on t 1841 gdb or control-c on the dbgp connection. When
2557 not using this parame 1842 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 1843 the kernel debugger.
2559 1844
2560 kgdboc= [KGDB,HW] kgdb over c 1845 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 1846 Requires a tty driver that supports console polling,
2562 or a supported pollin 1847 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 1848 Serial only format: <serial_device>[,baud]
2564 keyboard only format 1849 keyboard only format: kbd
2565 keyboard and serial 1850 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 1851 Optional Kernel mode setting:
2567 kms, kbd format: kms 1852 kms, kbd format: kms,kbd
2568 kms, kbd and serial 1853 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 1854
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 1855 kgdbwait [KGDB] Stop kernel execution and enter the
2571 If the boot console p <<
2572 characters and can wo <<
2573 this parameter to tel <<
2574 until the normal cons <<
2575 be used together with <<
2576 specifies the normal <<
2577 <<
2578 The name of the early <<
2579 as the value of this <<
2580 the early console mig <<
2581 name passed to kgdboc <<
2582 blank and the first b <<
2583 read() will be picked <<
2584 <<
2585 kgdbwait [KGDB,EARLY] Stop ker <<
2586 kernel debugger at th 1856 kernel debugger at the earliest opportunity.
2587 1857
2588 kmac= [MIPS] Korina etherne !! 1858 kmac= [MIPS] korina ethernet MAC address.
2589 Configure the RouterB 1859 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 1860 Ethernet adapter MAC address.
2591 1861
2592 kmemleak= [KNL,EARLY] Boot-time !! 1862 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 1863 Valid arguments: on, off
2594 Default: on 1864 Default: on
2595 Built with CONFIG_DEB 1865 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 1866 the default is off.
2597 1867
2598 kprobe_event=[probe-list] !! 1868 kpti= [ARM64] Control page table isolation of user
2599 [FTRACE] Add kprobe e !! 1869 and kernel address spaces.
2600 The probe-list is a s <<
2601 definitions. Each def <<
2602 interface, but the pa <<
2603 For example, to add a <<
2604 arg1 and arg2, add to <<
2605 <<
2606 kprobe_event=p, <<
2607 <<
2608 See also Documentatio <<
2609 Boot Parameter" secti <<
2610 <<
2611 kpti= [ARM64,EARLY] Control <<
2612 user and kernel addre <<
2613 Default: enabled on c 1870 Default: enabled on cores which need mitigation.
2614 0: force disabled 1871 0: force disabled
2615 1: force enabled 1872 1: force enabled
2616 1873
2617 kunit.enable= [KUNIT] Enable execut <<
2618 CONFIG_KUNIT to be se <<
2619 default value can be <<
2620 KUNIT_DEFAULT_ENABLED <<
2621 Default is 1 (enabled <<
2622 <<
2623 kvm.ignore_msrs=[KVM] Ignore guest ac 1874 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 1875 Default is 0 (don't ignore, but inject #GP)
2625 1876
2626 kvm.eager_page_split= !! 1877 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
2627 [KVM,X86] Controls wh !! 1878 KVM MMU at runtime.
2628 proactively split all !! 1879 Default is 0 (off)
2629 Eager page splitting <<
2630 execution by eliminat <<
2631 and MMU lock contenti <<
2632 required to split hug <<
2633 <<
2634 VM workloads that rar <<
2635 only to a small regio <<
2636 disabling eager page <<
2637 still be used for rea <<
2638 <<
2639 The behavior of eager <<
2640 KVM_DIRTY_LOG_INITIAL <<
2641 disabled, all huge pa <<
2642 split when dirty logg <<
2643 enabled, eager page s <<
2644 the KVM_CLEAR_DIRTY i <<
2645 cleared. <<
2646 <<
2647 Eager page splitting <<
2648 <<
2649 Default is Y (on). <<
2650 <<
2651 kvm.enable_vmware_backdoor=[KVM] Supp <<
2652 Default is <<
2653 1880
2654 kvm.nx_huge_pages= 1881 kvm.nx_huge_pages=
2655 [KVM] Controls the so 1882 [KVM] Controls the software workaround for the
2656 X86_BUG_ITLB_MULTIHIT 1883 X86_BUG_ITLB_MULTIHIT bug.
2657 force : Always depl 1884 force : Always deploy workaround.
2658 off : Never deplo 1885 off : Never deploy workaround.
2659 auto : Deploy work 1886 auto : Deploy workaround based on the presence of
2660 X86_BUG_ITL 1887 X86_BUG_ITLB_MULTIHIT.
2661 1888
2662 Default is 'auto'. 1889 Default is 'auto'.
2663 1890
2664 If the software worka 1891 If the software workaround is enabled for the host,
2665 guests do need not to 1892 guests do need not to enable it for nested guests.
2666 1893
2667 kvm.nx_huge_pages_recovery_ratio= 1894 kvm.nx_huge_pages_recovery_ratio=
2668 [KVM] Controls how ma 1895 [KVM] Controls how many 4KiB pages are periodically zapped
2669 back to huge pages. 1896 back to huge pages. 0 disables the recovery, otherwise if
2670 the value is N KVM wi 1897 the value is N KVM will zap 1/Nth of the 4KiB pages every
2671 period (see below). !! 1898 minute. The default is 60.
2672 1899
2673 kvm.nx_huge_pages_recovery_period_ms= !! 1900 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2674 [KVM] Controls the ti !! 1901 Default is 1 (enabled)
2675 back to huge pages. I !! 1902
2676 zap a portion (see ra !! 1903 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2677 If the value is 0 (th !! 1904 for all guests.
2678 on the ratio, such th !! 1905 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2679 <<
2680 kvm-amd.nested= [KVM,AMD] Control nes <<
2681 KVM/SVM. Default is 1 <<
2682 <<
2683 kvm-amd.npt= [KVM,AMD] Control KVM <<
2684 a.k.a. Two-Dimensiona <<
2685 (enabled). Disable by <<
2686 for NPT. <<
2687 <<
2688 kvm-arm.mode= <<
2689 [KVM,ARM,EARLY] Selec <<
2690 operation. <<
2691 <<
2692 none: Forcefully disa <<
2693 <<
2694 nvhe: Standard nVHE-b <<
2695 protected guest <<
2696 <<
2697 protected: nVHE-based <<
2698 state is k <<
2699 <<
2700 nested: VHE-based mod <<
2701 virtualizatio <<
2702 hardware. <<
2703 <<
2704 Defaults to VHE/nVHE <<
2705 mode to "protected" w <<
2706 for the host. "nested <<
2707 used with extreme cau <<
2708 1906
2709 kvm-arm.vgic_v3_group0_trap= 1907 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 1908 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 1909 system registers
2712 1910
2713 kvm-arm.vgic_v3_group1_trap= 1911 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 1912 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 1913 system registers
2716 1914
2717 kvm-arm.vgic_v3_common_trap= 1915 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 1916 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 1917 system registers
2720 1918
2721 kvm-arm.vgic_v4_enable= !! 1919 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2722 [KVM,ARM,EARLY] Allow !! 1920 (virtualized MMU) support on capable Intel chips.
2723 injection of LPIs. !! 1921 Default is 1 (enabled)
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 <<
2743 kvm_cma_resv_ratio=n [PPC,EARLY] <<
2744 Reserves given percen <<
2745 contiguous memory all <<
2746 allocation. <<
2747 By default it reserve <<
2748 Format: <integer> <<
2749 Default: 5 <<
2750 <<
2751 kvm-intel.ept= [KVM,Intel] Control K <<
2752 a.k.a. Two-Dimensiona <<
2753 (enabled). Disable by <<
2754 for EPT. <<
2755 1922
2756 kvm-intel.emulate_invalid_guest_state 1923 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 1924 [KVM,Intel] Disable emulation of invalid guest state.
2758 state. Ignored if kvm !! 1925 Ignored if kvm-intel.enable_unrestricted_guest=1, as
2759 as guest state is nev !! 1926 guest state is never invalid for unrestricted guests.
2760 guests. This param do !! 1927 This param doesn't apply to nested guests (L2), as KVM
2761 as KVM never emulates !! 1928 never emulates invalid L2 guest state.
2762 Default is 1 (enabled !! 1929 Default is 1 (enabled)
2763 1930
2764 kvm-intel.flexpriority= 1931 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 1932 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 1933 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 1934
2769 kvm-intel.nested= 1935 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 1936 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 1937 Default is 0 (disabled)
2772 1938
2773 kvm-intel.unrestricted_guest= 1939 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 1940 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 1941 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 1942 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 1943
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 1944 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 1945 CVE-2018-3620.
2781 1946
2782 Valid arguments: neve 1947 Valid arguments: never, cond, always
2783 1948
2784 always: L1D cache flu 1949 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 1950 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 1951 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 1952 never: Disables the mitigation
2788 1953
2789 Default is cond (do L 1954 Default is cond (do L1 cache flush in specific instances)
2790 1955
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 1956 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 1957 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 1958 Default is 1 (enabled)
2794 for it. <<
2795 <<
2796 l1d_flush= [X86,INTEL,EARLY] <<
2797 Control mitigation fo <<
2798 <<
2799 Certain CPUs are vuln <<
2800 internal buffers whic <<
2801 disclosure gadget und <<
2802 <<
2803 In vulnerable process <<
2804 forwarded data can be <<
2805 attack, to access dat <<
2806 not have direct acces <<
2807 <<
2808 This parameter contro <<
2809 options are: <<
2810 <<
2811 on - enable t <<
2812 1959
2813 l1tf= [X86,EARLY] Control m !! 1960 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 1961 affected CPUs
2815 1962
2816 The kernel PTE invers 1963 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 1964 enabled and cannot be disabled.
2818 1965
2819 full 1966 full
2820 Provides all 1967 Provides all available mitigations for the
2821 L1TF vulnerab 1968 L1TF vulnerability. Disables SMT and
2822 enables all m 1969 enables all mitigations in the
2823 hypervisors, 1970 hypervisors, i.e. unconditional L1D flush.
2824 1971
2825 SMT control a 1972 SMT control and L1D flush control via the
2826 sysfs interfa 1973 sysfs interface is still possible after
2827 boot. Hyperv 1974 boot. Hypervisors will issue a warning
2828 when the firs 1975 when the first VM is started in a
2829 potentially i 1976 potentially insecure configuration,
2830 i.e. SMT enab 1977 i.e. SMT enabled or L1D flush disabled.
2831 1978
2832 full,force 1979 full,force
2833 Same as 'full 1980 Same as 'full', but disables SMT and L1D
2834 flush runtime 1981 flush runtime control. Implies the
2835 'nosmt=force' 1982 'nosmt=force' command line option.
2836 (i.e. sysfs c 1983 (i.e. sysfs control of SMT is disabled.)
2837 1984
2838 flush 1985 flush
2839 Leaves SMT en 1986 Leaves SMT enabled and enables the default
2840 hypervisor mi 1987 hypervisor mitigation, i.e. conditional
2841 L1D flush. 1988 L1D flush.
2842 1989
2843 SMT control a 1990 SMT control and L1D flush control via the
2844 sysfs interfa 1991 sysfs interface is still possible after
2845 boot. Hyperv 1992 boot. Hypervisors will issue a warning
2846 when the firs 1993 when the first VM is started in a
2847 potentially i 1994 potentially insecure configuration,
2848 i.e. SMT enab 1995 i.e. SMT enabled or L1D flush disabled.
2849 1996
2850 flush,nosmt 1997 flush,nosmt
2851 1998
2852 Disables SMT 1999 Disables SMT and enables the default
2853 hypervisor mi 2000 hypervisor mitigation.
2854 2001
2855 SMT control a 2002 SMT control and L1D flush control via the
2856 sysfs interfa 2003 sysfs interface is still possible after
2857 boot. Hyperv 2004 boot. Hypervisors will issue a warning
2858 when the firs 2005 when the first VM is started in a
2859 potentially i 2006 potentially insecure configuration,
2860 i.e. SMT enab 2007 i.e. SMT enabled or L1D flush disabled.
2861 2008
2862 flush,nowarn 2009 flush,nowarn
2863 Same as 'flus 2010 Same as 'flush', but hypervisors will not
2864 warn when a V 2011 warn when a VM is started in a potentially
2865 insecure conf 2012 insecure configuration.
2866 2013
2867 off 2014 off
2868 Disables hype 2015 Disables hypervisor mitigations and doesn't
2869 emit any warn 2016 emit any warnings.
2870 It also drops 2017 It also drops the swap size and available
2871 RAM limit res 2018 RAM limit restriction on both hypervisor and
2872 bare metal. 2019 bare metal.
2873 2020
2874 Default is 'flush'. 2021 Default is 'flush'.
2875 2022
2876 For details see: Docu 2023 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2024
2878 l2cr= [PPC] 2025 l2cr= [PPC]
2879 2026
2880 l3cr= [PPC] 2027 l3cr= [PPC]
2881 2028
2882 lapic [X86-32,APIC,EARLY] E !! 2029 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2030 disabled it.
2884 2031
2885 lapic= [X86,APIC] Do not use !! 2032 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2886 value for LAPIC timer 2033 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2034 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline <<
2889 2035
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2036 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2037 in C2 power state.
2892 2038
2893 libata.dma= [LIBATA] DMA control 2039 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2040 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2041 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2042 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2043 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2044 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2045 for disks and CDROMs, but not CFs.
2900 2046
2901 libata.ignore_hpa= [LIBATA] Igno 2047 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2048 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2049 libata.ignore_hpa=1 ignore limits, using full disk
2904 2050
2905 libata.noacpi [LIBATA] Disables use 2051 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2052 when set.
2907 Format: <int> 2053 Format: <int>
2908 2054
2909 libata.force= [LIBATA] Force config !! 2055 libata.force= [LIBATA] Force configurations. The format is comma
2910 separated list of "[I !! 2056 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2057 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2058 matching port, link or device. Basically, it matches
2913 printed on console by !! 2059 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2060 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2061 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2062 configuration applies to all ports, links and devices.
2917 2063
2918 If only DEVICE is omi 2064 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2065 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2066 number of 0 either selects the first device or the
2921 first fan-out link be 2067 first fan-out link behind PMP device. It does not
2922 select the host link. 2068 select the host link. DEVICE number of 15 selects the
2923 host link and device 2069 host link and device attached to it.
2924 2070
2925 The VAL specifies the 2071 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2072 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2073 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2074 The following configurations can be forced.
2929 2075
2930 * Cable type: 40c, 80 2076 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2077 Any ID with matching PORT is used.
2932 2078
2933 * SATA link speed lim 2079 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2080
2935 * Transfer mode: pio[ 2081 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2082 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2083 allowed.
2938 2084
2939 * nohrst, nosrst, nor <<
2940 resets. <<
2941 <<
2942 * rstonce: only attem <<
2943 link recovery. <<
2944 <<
2945 * [no]dbdelay: Enable <<
2946 before debouncing a <<
2947 detection. <<
2948 <<
2949 * [no]ncq: Turn on or 2085 * [no]ncq: Turn on or off NCQ.
2950 2086
2951 * [no]ncqtrim: Enable !! 2087 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 <<
2953 * [no]ncqati: Enable <<
2954 <<
2955 * [no]trim: Enable or <<
2956 <<
2957 * trim_zero: Indicate <<
2958 <<
2959 * max_trim_128m: Set <<
2960 <<
2961 * [no]dma: Turn on or <<
2962 <<
2963 * atapi_dmadir: Enabl <<
2964 <<
2965 * atapi_mod16_dma: En <<
2966 commands that are n <<
2967 2088
2968 * [no]dmalog: Enable !! 2089 * nohrst, nosrst, norst: suppress hard, soft
2969 READ LOG DMA EXT co !! 2090 and both resets.
2970 2091
2971 * [no]iddevlog: Enabl !! 2092 * rstonce: only attempt one reset during
2972 identify device dat !! 2093 hot-unplug link recovery
2973 2094
2974 * [no]logdir: Enable !! 2095 * dump_id: dump IDENTIFY data.
2975 purpose log directo <<
2976 2096
2977 * max_sec_128: Set tr !! 2097 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2978 <<
2979 * max_sec_1024: Set o <<
2980 1024 sectors. <<
2981 <<
2982 * max_sec_lba48: Set <<
2983 65535 sectors. <<
2984 <<
2985 * [no]lpm: Enable or <<
2986 <<
2987 * [no]setxfer: Indica <<
2988 should be skipped. <<
2989 <<
2990 * [no]fua: Disable or <<
2991 support for devices <<
2992 <<
2993 * dump_id: Dump IDENT <<
2994 2098
2995 * disable: Disable th 2099 * disable: Disable this device.
2996 2100
2997 If there are multiple 2101 If there are multiple matching configurations changing
2998 the same attribute, t 2102 the same attribute, the last one is used.
2999 2103
3000 load_ramdisk= [RAM] [Deprecated] !! 2104 memblock=debug [KNL] Enable memblock debug messages.
>> 2105
>> 2106 load_ramdisk= [RAM] List of ramdisks to load from floppy
>> 2107 See Documentation/blockdev/ramdisk.txt.
3001 2108
3002 lockd.nlm_grace_period=P [NFS] Assig 2109 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2110 Format: <integer>
3004 2111
3005 lockd.nlm_tcpport=N [NFS] Assign 2112 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2113 Format: <integer>
3007 2114
3008 lockd.nlm_timeout=T [NFS] Assign 2115 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2116 Format: <integer>
3010 2117
3011 lockd.nlm_udpport=M [NFS] Assign 2118 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2119 Format: <integer>
3013 2120
3014 lockdown= [SECURITY,EARLY] <<
3015 { integrity | confide <<
3016 Enable the kernel loc <<
3017 integrity, kernel fea <<
3018 modify the running ke <<
3019 confidentiality, kern <<
3020 to extract confidenti <<
3021 are also disabled. <<
3022 <<
3023 locktorture.acq_writer_lim= [KNL] <<
3024 Set the time limit in <<
3025 acquisition. Acquisi <<
3026 will result in a spla <<
3027 <<
3028 locktorture.bind_readers= [KNL] <<
3029 Specify the list of C <<
3030 to be bound. <<
3031 <<
3032 locktorture.bind_writers= [KNL] <<
3033 Specify the list of C <<
3034 to be bound. <<
3035 <<
3036 locktorture.call_rcu_chains= [KNL] <<
3037 Specify the number of <<
3038 chains to set up. Th <<
3039 there is a high proba <<
3040 in progress at any gi <<
3041 which disables these <<
3042 <<
3043 locktorture.long_hold= [KNL] <<
3044 Specify the duration <<
3045 occasional long-durat <<
3046 to 100 milliseconds. <<
3047 <<
3048 locktorture.nested_locks= [KNL] <<
3049 Specify the maximum l <<
3050 locktorture is to exe <<
3051 (MAX_NESTED_LOCKS). <<
3052 Note that this parame <<
3053 of locks that do not <<
3054 <<
3055 locktorture.nreaders_stress= [KNL] 2121 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2122 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2123 Defaults to being automatically set based on the
3058 number of online CPUs 2124 number of online CPUs.
3059 2125
3060 locktorture.nwriters_stress= [KNL] 2126 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2127 Set the number of locking write-acquisition kthreads.
3062 2128
3063 locktorture.onoff_holdoff= [KNL] 2129 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2130 Set time (s) after boot for CPU-hotplug testing.
3065 2131
3066 locktorture.onoff_interval= [KNL] 2132 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2133 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2134 zero to disable CPU-hotplug testing.
3069 2135
3070 locktorture.rt_boost= [KNL] <<
3071 Do periodic testing o <<
3072 boosting. Select 0 t <<
3073 only rt_mutex, and 2 <<
3074 Defaults to 2, which <<
3075 odd choice, but which <<
3076 non-real-time spinloc <<
3077 of preemption. Note <<
3078 disable boosting. <<
3079 <<
3080 locktorture.rt_boost_factor= [KNL] <<
3081 Number that determine <<
3082 long priority boostin <<
3083 scaled down by the nu <<
3084 number of boosts per <<
3085 constant as the numbe <<
3086 On the other hand, th <<
3087 increases with the nu <<
3088 <<
3089 locktorture.shuffle_interval= [KNL] 2136 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2137 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2138 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2139 mode during the locktorture test.
3093 2140
3094 locktorture.shutdown_secs= [KNL] 2141 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2142 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2143 is useful for hands-off automated testing.
3097 2144
3098 locktorture.stat_interval= [KNL] 2145 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2146 Time (s) between statistics printk()s.
3100 2147
3101 locktorture.stutter= [KNL] 2148 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2149 Time (s) to stutter testing, for example,
3103 specifying five secon 2150 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2151 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2152 This tests the locking primitive's ability to
3106 transition abruptly t 2153 transition abruptly to and from idle.
3107 2154
>> 2155 locktorture.torture_runnable= [BOOT]
>> 2156 Start locktorture running at boot time.
>> 2157
3108 locktorture.torture_type= [KNL] 2158 locktorture.torture_type= [KNL]
3109 Specify the locking i 2159 Specify the locking implementation to test.
3110 2160
3111 locktorture.verbose= [KNL] 2161 locktorture.verbose= [KNL]
3112 Enable additional pri 2162 Enable additional printk() statements.
3113 2163
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2164 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2165 Format: <irq>
3120 2166
3121 loglevel= [KNL,EARLY] !! 2167 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2168 console loglevel will be printed to the console. It can
3124 also be changed with 2169 also be changed with klogd or other programs. The
3125 loglevels are defined 2170 loglevels are defined as follows:
3126 2171
3127 0 (KERN_EMERG) 2172 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2173 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2174 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2175 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2176 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2177 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2178 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2179 7 (KERN_DEBUG) debug-level messages
3135 2180
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2181 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2182 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2183 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2184 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2185 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2186 that allows to increase the default size depending on
3142 parameter that allows !! 2187 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2188
3146 logo.nologo [FB] Disables display 2189 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2190 This may be used to provide more screen space for
3148 kernel log messages a 2191 kernel log messages and is useful when debugging
3149 kernel boot problems. 2192 kernel boot problems.
3150 2193
3151 lp=0 [LP] Specify paral 2194 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2195 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2196 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2197 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2198 specified in addition to the ports) causes
3156 attached prin 2199 attached printers to be reset. Using
3157 lp=port1,port 2200 lp=port1,port2,... specifies the parallel ports
3158 to associate 2201 to associate lp devices with, starting with
3159 lp0. A port s 2202 lp0. A port specification may be 'none' to skip
3160 that lp devic 2203 that lp device, or a parport name such as
3161 'parport0'. S 2204 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2205 port specification list means that device IDs
3163 from each por 2206 from each port should be examined, to see if
3164 an IEEE 1284- 2207 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2208 so, the driver will manage that printer.
3166 See also head 2209 See also header of drivers/char/lp.c.
3167 2210
3168 lpj=n [KNL] 2211 lpj=n [KNL]
3169 Sets loops_per_jiffy 2212 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2213 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2214 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2215 the correct value for your kernel, boot with normal
3173 autodetection and see 2216 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2217 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2218 which is likely to cause problems if your CPUs need
3176 significantly diverge 2219 significantly divergent settings. An incorrect value
3177 will cause delays in 2220 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2221 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2222 unlikely, in the extreme case this might damage your
3180 hardware. 2223 hardware.
3181 2224
3182 lsm.debug [SECURITY] Enable LSM !! 2225 ltpc= [NET]
>> 2226 Format: <io>,<irq>,<dma>
3183 2227
3184 lsm=lsm1,...,lsmN !! 2228 machvec= [IA-64] Force the use of a particular machine-vector
3185 [SECURITY] Choose ord !! 2229 (machvec) in a generic kernel.
3186 overrides CONFIG_LSM, !! 2230 Example: machvec=hpzx1_swiotlb
3187 2231
3188 machtype= [Loongson] Share the !! 2232 machtype= [Loongson] Share the same kernel image file between different
3189 different yeeloong la !! 2233 yeeloong laptop.
3190 Example: machtype=lem 2234 Example: machtype=lemote-yeeloong-2f-7inch
3191 2235
3192 maxcpus= [SMP,EARLY] Maximum n !! 2236 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2237 than or equal to this physical address is ignored.
>> 2238
>> 2239 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2240 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2241 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2242 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2243 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2244 only takes effect during system bootup.
3198 While n=0 is a specia 2245 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2246 which also disables the IO APIC.
3200 2247
3201 max_loop= [LOOP] The number of 2248 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2249 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2250 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2251 of statically allocating a predefined number, loop
3205 devices can be reques 2252 devices can be requested on-demand with the
3206 /dev/loop-control int 2253 /dev/loop-control interface.
3207 2254
3208 mce [X86-32] Machine Chec 2255 mce [X86-32] Machine Check Exception
3209 2256
3210 mce=option [X86-64] See Document !! 2257 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
3211 2258
3212 md= [HW] RAID subsystems 2259 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2260 See Documentation/admin-guide/md.rst.
3214 2261
3215 mdacon= [MDA] 2262 mdacon= [MDA]
3216 Format: <first>,<last 2263 Format: <first>,<last>
3217 Specifies range of co 2264 Specifies range of consoles to be captured by the MDA.
3218 2265
3219 mds= [X86,INTEL,EARLY] !! 2266 mds= [X86,INTEL]
3220 Control mitigation fo 2267 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2268 Sampling (MDS) vulnerability.
3222 2269
3223 Certain CPUs are vuln 2270 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2271 internal buffers which can forward information to a
3225 disclosure gadget und 2272 disclosure gadget under certain conditions.
3226 2273
3227 In vulnerable process 2274 In vulnerable processors, the speculatively
3228 forwarded data can be 2275 forwarded data can be used in a cache side channel
3229 attack, to access dat 2276 attack, to access data to which the attacker does
3230 not have direct acces 2277 not have direct access.
3231 2278
3232 This parameter contro 2279 This parameter controls the MDS mitigation. The
3233 options are: 2280 options are:
3234 2281
3235 full - Enable M 2282 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2283 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2284 SMT on vulnerable CPUs
3238 off - Uncondit 2285 off - Unconditionally disable MDS mitigation
3239 2286
3240 On TAA-affected machi 2287 On TAA-affected machines, mds=off can be prevented by
3241 an active TAA mitigat 2288 an active TAA mitigation as both vulnerabilities are
3242 mitigated with the sa 2289 mitigated with the same mechanism so in order to disable
3243 this mitigation, you 2290 this mitigation, you need to specify tsx_async_abort=off
3244 too. 2291 too.
3245 2292
3246 Not specifying this o 2293 Not specifying this option is equivalent to
3247 mds=full. 2294 mds=full.
3248 2295
3249 For details see: Docu 2296 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2297
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2298 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3252 Must be specified, ot !! 2299 Amount of memory to be used when the kernel is not able
3253 !! 2300 to see the whole system memory or for test.
3254 mem=nn[KMG] [KNL,BOOT,EARLY] Forc <<
3255 of memory Amount of m <<
3256 as follows: <<
3257 <<
3258 1 for test; <<
3259 2 when the kernel is <<
3260 3 memory that lies af <<
3261 the hypervisor, then <<
3262 4 to limit the memory <<
3263 <<
3264 [ARC,MICROBLAZE] - th <<
3265 high memory is not af <<
3266 <<
3267 [ARM64] - only limits <<
3268 mapping. The NOMAP re <<
3269 <<
3270 [X86] Work as limitin 2301 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2302 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2303 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2304 belonging to unused RAM.
3274 2305
3275 Note that this only t <<
3276 in above case 3, memo <<
3277 if system memory of h <<
3278 <<
3279 mem=nn[KMG]@ss[KMG] <<
3280 [ARM,MIPS,EARLY] - ov <<
3281 reported by firmware. <<
3282 Define a memory regio <<
3283 ss[KMG]. <<
3284 Multiple different re <<
3285 multiple mem= paramet <<
3286 <<
3287 mem=nopentium [BUGS=X86-32] Disable 2306 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2307 memory.
3289 2308
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2309 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2310 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2311 per-device physically contiguous DMA buffers.
3295 2312
3296 memhp_default_state=online/offline/on !! 2313 memhp_default_state=online/offline
3297 [KNL] Set the initial 2314 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2315 onlining policy. If not specified, the default value is
3299 set according to the 2316 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2317 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2318 option.
3302 See Documentation/adm !! 2319 See Documentation/memory-hotplug.txt.
3303 2320
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2321 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2322 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2323 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2324 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2325 option description.
3309 2326
3310 memmap=nn[KMG]@ss[KMG] 2327 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2328 [KNL] Force usage of a specific region of memory.
3312 Region of memory to b 2329 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2330 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2331 which limits max address to nn[KMG].
3315 Multiple different re 2332 Multiple different regions can be specified,
3316 comma delimited. 2333 comma delimited.
3317 Example: 2334 Example:
3318 memmap=100M@2 2335 memmap=100M@2G,100M#3G,1G!1024G
3319 2336
3320 memmap=nn[KMG]#ss[KMG] 2337 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2338 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2339 Region of memory to be marked is from ss to ss+nn.
3323 2340
3324 memmap=nn[KMG]$ss[KMG] 2341 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2342 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2343 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2344 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2345 memmap=64K$0x18690000
3329 or 2346 or
3330 memmap=0x100 2347 memmap=0x10000$0x18690000
3331 Some bootloaders may 2348 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2349 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2350 will be eaten.
3334 2351
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2352 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2353 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2354 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2355 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2356 and is NVDIMM or ADR memory.
3340 2357
3341 memmap=<size>%<offset>-<oldtype>+<new !! 2358 memory_corruption_check=0/1 [X86]
3342 [KNL,ACPI,EARLY] Conv <<
3343 from <oldtype> to <ne <<
3344 out, the whole region <<
3345 even if previously un <<
3346 out, matching memory <<
3347 specified as e820 typ <<
3348 3 = ACPI, 12 = PRAM. <<
3349 <<
3350 memory_corruption_check=0/1 [X86,EARL <<
3351 Some BIOSes seem to c 2359 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2360 memory when doing things like suspend/resume.
3353 Setting this option w 2361 Setting this option will scan the memory
3354 looking for corruptio 2362 looking for corruption. Enabling this will
3355 both detect corruptio 2363 both detect corruption and prevent the kernel
3356 from using the memory 2364 from using the memory being corrupted.
3357 However, its intended 2365 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2366 repeatable BIOS-originated corruption always
3359 affects the same memo 2367 affects the same memory, you can use memmap=
3360 to prevent the kernel 2368 to prevent the kernel from using that memory.
3361 2369
3362 memory_corruption_check_size=size [X8 !! 2370 memory_corruption_check_size=size [X86]
3363 By default it checks 2371 By default it checks for corruption in the low
3364 64k, making this memo 2372 64k, making this memory unavailable for normal
3365 use. Use this parame 2373 use. Use this parameter to scan for
3366 corruption in more or 2374 corruption in more or less memory.
3367 2375
3368 memory_corruption_check_period=second !! 2376 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2377 By default it checks for corruption every 60
3370 seconds. Use this pa 2378 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2379 other rate. 0 disables periodic checking.
3372 2380
3373 memory_hotplug.memmap_on_memory !! 2381 memtest= [KNL,X86,ARM] Enable memtest
3374 [KNL,X86,ARM] Boolean <<
3375 Format: {on | off (de <<
3376 When enabled, runtime <<
3377 allocate its internal <<
3378 those vmemmap pages c <<
3379 if hugetlb_free_vmemm <<
3380 hotadded memory which <<
3381 lot of memory without <<
3382 memory to do so. <<
3383 This feature is disab <<
3384 has some implication <<
3385 allocations in some c <<
3386 memory blocks). <<
3387 The state of the flag <<
3388 /sys/module/memory_ho <<
3389 Note that even when e <<
3390 the feature is not ef <<
3391 <<
3392 memtest= [KNL,X86,ARM,M68K,PPC <<
3393 Format: <integer> 2382 Format: <integer>
3394 default : 0 <disable> 2383 default : 0 <disable>
3395 Specifies the number 2384 Specifies the number of memtest passes to be
3396 performed. Each pass 2385 performed. Each pass selects another test
3397 pattern from a given 2386 pattern from a given set of patterns. Memtest
3398 fills the memory with 2387 fills the memory with this pattern, validates
3399 memory contents and r 2388 memory contents and reserves bad memory
3400 regions that are dete 2389 regions that are detected.
3401 2390
3402 mem_encrypt= [X86-64] AMD Secure M 2391 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2392 Valid arguments: on, off
3404 Default: off !! 2393 Default (depends on kernel configuration option):
>> 2394 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2395 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2396 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2397 mem_encrypt=off: Do not activate SME
3407 2398
3408 Refer to Documentatio !! 2399 Refer to Documentation/x86/amd-memory-encryption.txt
3409 for details on when m 2400 for details on when memory encryption can be activated.
3410 2401
3411 mem_sleep_default= [SUSPEND] Def 2402 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2403 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2404 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2405 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm !! 2406 See Documentation/power/states.txt.
>> 2407
>> 2408 meye.*= [HW] Set MotionEye Camera parameters
>> 2409 See Documentation/video4linux/meye.txt.
>> 2410
>> 2411 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2412 Multi-Function General Purpose Timers on AMD Geode
>> 2413 platforms.
3416 2414
3417 mfgptfix [X86-32] Fix MFGPT ti 2415 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2416 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2417 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2418 problem by letting the user disable the workaround.
3421 2419
3422 mga= [HW,DRM] 2420 mga= [HW,DRM]
3423 2421
3424 microcode.force_minrev= [X86] !! 2422 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2423 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2424
3429 mini2440= [ARM,HW,KNL] 2425 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2426 Format:[0..2][b][c][t]
3431 Default: "0tb" 2427 Default: "0tb"
3432 MINI2440 configuratio 2428 MINI2440 configuration specification:
3433 0 - The attached scre 2429 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2430 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2431 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2432 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2433 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2434 unconfigured.
3439 b - Enable backlight. 2435 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2436 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2437 LED. This parameter is not necessary when using the
3442 VGA shield. 2438 VGA shield.
3443 c - Enable the s3c ca 2439 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2440 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2441 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2442 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2443 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ !! 2444 http://repo.or.cz/w/linux-2.6/mini2440.git
3449 2445
3450 mitigations= 2446 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 2447 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 2448 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 2449 arch-independent options, each of which is an
3454 aggregation of existi 2450 aggregation of existing arch-specific options.
3455 2451
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 2452 off
3460 Disable all o 2453 Disable all optional CPU mitigations. This
3461 improves syst 2454 improves system performance, but it may also
3462 expose users 2455 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 2456 Equivalent to: gather_data_sampling=off [X86]
3464 !! 2457 kpti=0 [ARM64]
3465 2458 kvm.nx_huge_pages=off [X86]
3466 2459 l1tf=off [X86]
3467 2460 mds=off [X86]
3468 2461 mmio_stale_data=off [X86]
3469 2462 no_entry_flush [PPC]
3470 2463 no_uaccess_flush [PPC]
3471 2464 nobp=0 [S390]
3472 2465 nopti [X86,PPC]
3473 !! 2466 nospectre_v1 [PPC]
3474 !! 2467 nospectre_v1 [X86]
3475 2468 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 2469 spec_store_bypass_disable=off [X86,PPC]
3480 <<
3481 2470 spectre_v2_user=off [X86]
3482 <<
3483 2471 ssbd=force-off [ARM64]
3484 2472 tsx_async_abort=off [X86]
3485 2473
3486 Exceptions: 2474 Exceptions:
3487 2475 This does not have any effect on
3488 2476 kvm.nx_huge_pages when
3489 2477 kvm.nx_huge_pages=force.
3490 2478
3491 auto (default) 2479 auto (default)
3492 Mitigate all 2480 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 2481 enabled, even if it's vulnerable. This is for
3494 users who don 2482 users who don't want to be surprised by SMT
3495 getting disab 2483 getting disabled across kernel upgrades, or who
3496 have other wa 2484 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 2485 Equivalent to: (default behavior)
3498 2486
3499 auto,nosmt 2487 auto,nosmt
3500 Mitigate all 2488 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 2489 if needed. This is for users who always want to
3502 be fully miti 2490 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 2491 Equivalent to: l1tf=flush,nosmt [X86]
3504 2492 mds=full,nosmt [X86]
3505 2493 tsx_async_abort=full,nosmt [X86]
3506 2494 mmio_stale_data=full,nosmt [X86]
3507 <<
3508 2495
3509 mminit_loglevel= 2496 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 2497 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 2498 parameter allows control of the logging verbosity for
3512 the additional memory 2499 the additional memory initialisation checks. A value
3513 of 0 disables mminit 2500 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 2501 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 2502 so loglevel=8 may also need to be specified.
3516 2503
3517 mmio_stale_data= 2504 mmio_stale_data=
3518 [X86,INTEL,EARLY] Con !! 2505 [X86,INTEL] Control mitigation for the Processor
3519 MMIO Stale Data vulne 2506 MMIO Stale Data vulnerabilities.
3520 2507
3521 Processor MMIO Stale 2508 Processor MMIO Stale Data is a class of
3522 vulnerabilities that 2509 vulnerabilities that may expose data after an MMIO
3523 operation. Exposed da 2510 operation. Exposed data could originate or end in
3524 the same CPU buffers 2511 the same CPU buffers as affected by MDS and TAA.
3525 Therefore, similar to 2512 Therefore, similar to MDS and TAA, the mitigation
3526 is to clear the affec 2513 is to clear the affected CPU buffers.
3527 2514
3528 This parameter contro 2515 This parameter controls the mitigation. The
3529 options are: 2516 options are:
3530 2517
3531 full - Enable m 2518 full - Enable mitigation on vulnerable CPUs
3532 2519
3533 full,nosmt - Enable m 2520 full,nosmt - Enable mitigation and disable SMT on
3534 vulnerab 2521 vulnerable CPUs.
3535 2522
3536 off - Uncondit 2523 off - Unconditionally disable mitigation
3537 2524
3538 On MDS or TAA affecte 2525 On MDS or TAA affected machines,
3539 mmio_stale_data=off c 2526 mmio_stale_data=off can be prevented by an active
3540 MDS or TAA mitigation 2527 MDS or TAA mitigation as these vulnerabilities are
3541 mitigated with the sa 2528 mitigated with the same mechanism so in order to
3542 disable this mitigati 2529 disable this mitigation, you need to specify
3543 mds=off and tsx_async 2530 mds=off and tsx_async_abort=off too.
3544 2531
3545 Not specifying this o 2532 Not specifying this option is equivalent to
3546 mmio_stale_data=full. 2533 mmio_stale_data=full.
3547 2534
3548 For details see: 2535 For details see:
3549 Documentation/admin-g 2536 Documentation/admin-guide/hw-vuln/processor_mmio_stale_data.rst
3550 2537
3551 <module>.async_probe[=<bool>] [KNL] <<
3552 If no <bool> value is <<
3553 specified is not a va <<
3554 probe on this module. <<
3555 asynchronous probe on <<
3556 <bool> value. See als <<
3557 <<
3558 module.async_probe=<bool> <<
3559 [KNL] When set to tru <<
3560 by default. To enable <<
3561 specific module, use <<
3562 is documented under < <<
3563 module.async_probe an <<
3564 specified, <module>.a <<
3565 the specific module. <<
3566 <<
3567 module.enable_dups_trace <<
3568 [KNL] When CONFIG_MOD <<
3569 this means that dupli <<
3570 trigger a WARN_ON() i <<
3571 if MODULE_DEBUG_AUTOL <<
3572 will always be issued <<
3573 module.sig_enforce 2538 module.sig_enforce
3574 [KNL] When CONFIG_MOD 2539 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 2540 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 2541 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 2542 is always true, so this option does nothing.
3578 2543
3579 module_blacklist= [KNL] Do not load 2544 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 2545 modules. Useful for debugging problem modules.
3581 2546
3582 mousedev.tap_time= 2547 mousedev.tap_time=
3583 [MOUSE] Maximum time 2548 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 2549 leaving touchpad surface for touch to be considered
3585 a tap and be reported 2550 a tap and be reported as a left button click (for
3586 touchpads working in 2551 touchpads working in absolute mode only).
3587 Format: <msecs> 2552 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 2553 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 2554 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 2555 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 2556 reporting absolute coordinates, such as tablets
3592 2557
3593 movablecore= [KNL,X86,PPC,EARLY] !! 2558 movablecore=nn[KMG] [KNL,X86,IA-64,PPC] This parameter
3594 Format: nn[KMGTPE] | !! 2559 is similar to kernelcore except it specifies the
3595 This parameter is the !! 2560 amount of memory used for migratable allocations.
3596 specifies the amount !! 2561 If both kernelcore and movablecore is specified,
3597 allocations. If both !! 2562 then kernelcore will be at *least* the specified
3598 specified, then kerne !! 2563 value but may be more. If movablecore on its own
3599 specified value but m !! 2564 is specified, the administrator must be careful
3600 own is specified, the <<
3601 that the amount of me 2565 that the amount of memory usable for all allocations
3602 is not too small. 2566 is not too small.
3603 2567
3604 movable_node [KNL,EARLY] Boot-time !! 2568 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 2569 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 2570 of such nodes will be usable only for movable
3607 allocations which rul 2571 allocations which rules out almost all kernel
3608 allocations. Use with 2572 allocations. Use with caution!
3609 2573
3610 MTD_Partition= [MTD] 2574 MTD_Partition= [MTD]
3611 Format: <name>,<regio 2575 Format: <name>,<region-number>,<size>,<offset>
3612 2576
3613 MTD_Region= [MTD] Format: 2577 MTD_Region= [MTD] Format:
3614 <name>,<region-number 2578 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 2579
3616 mtdparts= [MTD] 2580 mtdparts= [MTD]
3617 See drivers/mtd/parse !! 2581 See drivers/mtd/cmdlinepart.c.
>> 2582
>> 2583 multitce=off [PPC] This parameter disables the use of the pSeries
>> 2584 firmware feature for updating multiple TCE entries
>> 2585 at a time.
>> 2586
>> 2587 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 2588
>> 2589 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 2590
>> 2591 boundary - index of last SLC block on Flex-OneNAND.
>> 2592 The remaining blocks are configured as MLC blocks.
>> 2593 lock - Configure if Flex-OneNAND boundary should be locked.
>> 2594 Once locked, the boundary cannot be changed.
>> 2595 1 indicates lock status, 0 indicates unlock status.
>> 2596
>> 2597 mtdset= [ARM]
>> 2598 ARM/S3C2412 JIVE boot control
>> 2599
>> 2600 See arch/arm/mach-s3c2412/mach-jive.c
3618 2601
3619 mtouchusb.raw_coordinates= 2602 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 2603 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 2604 ('y', default) or cooked coordinates ('n')
3622 2605
3623 mtrr=debug [X86,EARLY] !! 2606 mtrr_chunk_size=nn[KMG] [X86]
3624 Enable printing debug <<
3625 registers at boot tim <<
3626 <<
3627 mtrr_chunk_size=nn[KMG,X86,EARLY] <<
3628 used for mtrr cleanup 2607 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 2608 that could hold holes aka. UC entries.
3630 2609
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 2610 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 2611 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 2612 Default is 1.
3634 Large value could pre 2613 Large value could prevent small alignment from
3635 using up MTRRs. 2614 using up MTRRs.
3636 2615
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 2616 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 2617 Format: <integer>
3639 Range: 0,7 : spare re 2618 Range: 0,7 : spare reg number
3640 Default : 1 2619 Default : 1
3641 Used for mtrr cleanup 2620 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 2621 Set to 2 or more if your graphical card needs more.
3643 2622
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 2623 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 2624
3650 netdev= [NET] Network devices 2625 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 2626 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 2627 Note that mem_start is often overloaded to mean
3653 something different a 2628 something different and driver-specific.
3654 This usage is only do 2629 This usage is only documented in each driver source
3655 file if at all. 2630 file if at all.
3656 2631
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 2632 nf_conntrack.acct=
3663 [NETFILTER] Enable co 2633 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 2634 0 to disable accounting
3665 1 to enable accountin 2635 1 to enable accounting
3666 Default value is 0. 2636 Default value is 0.
3667 2637
3668 nfs.cache_getent= !! 2638 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 2639 See Documentation/filesystems/nfs/nfsroot.txt.
3670 to update the NFS cli <<
3671 2640
3672 nfs.cache_getent_timeout= !! 2641 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 2642 See Documentation/filesystems/nfs/nfsroot.txt.
3674 update a cache entry !! 2643
>> 2644 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 2645 See Documentation/filesystems/nfs/nfsroot.txt.
3675 2646
3676 nfs.callback_nr_threads= 2647 nfs.callback_nr_threads=
3677 [NFSv4] set the total 2648 [NFSv4] set the total number of threads that the
3678 NFS client will assig 2649 NFS client will assign to service NFSv4 callback
3679 requests. 2650 requests.
3680 2651
3681 nfs.callback_tcpport= 2652 nfs.callback_tcpport=
3682 [NFS] set the TCP por 2653 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 2654 channel should listen.
3684 2655
3685 nfs.delay_retrans= !! 2656 nfs.cache_getent=
3686 [NFS] specifies the n !! 2657 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 2658 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 2659
3689 Only applies if the s !! 2660 nfs.cache_getent_timeout=
3690 and the specified val !! 2661 [NFS] sets the timeout after which an attempt to
>> 2662 update a cache entry is deemed to have failed.
>> 2663
>> 2664 nfs.idmap_cache_timeout=
>> 2665 [NFS] set the maximum lifetime for idmapper cache
>> 2666 entries.
3691 2667
3692 nfs.enable_ino64= 2668 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 2669 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 2670 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 2671 number for the readdir() and stat() syscalls instead
3696 of returning the full 2672 of returning the full 64-bit number.
3697 The default is to ret 2673 The default is to return 64-bit inode numbers.
3698 2674
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 2675 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 2676 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 2677 slots the client will assign to the callback
3706 channel. This determi 2678 channel. This determines the maximum number of
3707 callbacks the client 2679 callbacks the client will process in parallel for
3708 a particular server. 2680 a particular server.
3709 2681
3710 nfs.max_session_slots= 2682 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 2683 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 2684 the client will attempt to negotiate with the server.
3713 This limits the numbe 2685 This limits the number of simultaneous RPC requests
3714 that the client can s 2686 that the client can send to the NFSv4.1 server.
3715 Note that there is li 2687 Note that there is little point in setting this
3716 value higher than the 2688 value higher than the max_tcp_slot_table_limit.
3717 2689
3718 nfs.nfs4_disable_idmapping= 2690 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 2691 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 2692 ensures that both the RPC level authentication
3721 scheme and the NFS le 2693 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 2694 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 2695 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 2696 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 2697 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 2698 Servers that do not support this mode of operation
3727 will be autodetected 2699 will be autodetected by the client, and it will fall
3728 back to using the idm 2700 back to using the idmapper.
3729 To turn off this beha 2701 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 2702 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 2703 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 2704 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 2705 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 2706 UUID that is generated at system install time.
3736 2707
3737 nfs.recover_lost_locks= !! 2708 nfs.send_implementation_id =
>> 2709 [NFSv4.1] Send client implementation identification
>> 2710 information in exchange_id requests.
>> 2711 If zero, no implementation identification information
>> 2712 will be sent.
>> 2713 The default is to send the implementation identification
>> 2714 information.
>> 2715
>> 2716 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 2717 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 2718 to a lease timeout on the server. Please note that
3740 doing this risks data 2719 doing this risks data corruption, since there are
3741 no guarantees that th 2720 no guarantees that the file will remain unchanged
3742 after the locks are l 2721 after the locks are lost.
3743 If you want to enable 2722 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 2723 attempting to recover these locks, then set this
3745 parameter to '1'. 2724 parameter to '1'.
3746 The default parameter 2725 The default parameter value of '0' causes the kernel
3747 not to attempt recove 2726 not to attempt recovery of lost locks.
3748 2727
3749 nfs.send_implementation_id= !! 2728 nfs4.layoutstats_timer =
3750 [NFSv4.1] Send client <<
3751 information in exchan <<
3752 If zero, no implement <<
3753 will be sent. <<
3754 The default is to sen <<
3755 information. <<
3756 <<
3757 nfs4.layoutstats_timer= <<
3758 [NFSv4.2] Change the 2729 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 2730 layoutstats to the pNFS metadata server.
3760 2731
3761 Setting this to value 2732 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 2733 whatever value is the default set by the layout
3763 driver. A non-zero va 2734 driver. A non-zero value sets the minimum interval
3764 in seconds between la 2735 in seconds between layoutstats transmissions.
3765 2736
3766 nfsd.inter_copy_offload_enable= <<
3767 [NFSv4.2] When set to <<
3768 server-to-server copi <<
3769 the destination of th <<
3770 <<
3771 nfsd.nfs4_disable_idmapping= 2737 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 2738 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 2739 server will return only numeric uids and gids to
3774 clients using auth_sy 2740 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 2741 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 2742 migration from NFSv2/v3.
3777 2743
3778 nfsd.nfsd4_ssc_umount_timeout= <<
3779 [NFSv4.2] When used a <<
3780 server-to-server copy <<
3781 the source server. I <<
3782 it will be needed aga <<
3783 used for the number o <<
3784 this parameter. <<
3785 <<
3786 nfsaddrs= [NFS] Deprecated. Us <<
3787 See Documentation/adm <<
3788 <<
3789 nfsroot= [NFS] nfs root filesy <<
3790 See Documentation/adm <<
3791 <<
3792 nfsrootdebug [NFS] enable nfsroot <<
3793 See Documentation/adm <<
3794 <<
3795 nmi_backtrace.backtrace_idle [KNL] <<
3796 Dump stacks even of i <<
3797 NMI stack-backtrace r <<
3798 <<
3799 nmi_debug= [KNL,SH] Specify one 2744 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 2745 when a NMI is triggered.
3801 Format: [state][,regs 2746 Format: [state][,regs][,debounce][,die]
3802 2747
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 2748 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 2749 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 2750 Valid num: 0 or 1
3806 0 - turn hardlockup d 2751 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 2752 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 2753 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n !! 2754 timeout occurs (or 'nopanic' to override the opposite
3812 watchdog, if CONFIG_B !! 2755 default). To disable both hard and soft lockup detectors,
3813 To disable both hard <<
3814 please see 'nowatchdo 2756 please see 'nowatchdog'.
3815 This is useful when y 2757 This is useful when you use a panic=... timeout and
3816 need the box quickly 2758 need the box quickly up again.
3817 2759
3818 These settings can be !! 2760 netpoll.carrier_timeout=
3819 the nmi_watchdog and !! 2761 [NET] Specifies amount of time (in seconds) that
>> 2762 netpoll should wait for a carrier. By default netpoll
>> 2763 waits 4 seconds.
3820 2764
3821 no387 [BUGS=X86-32] Tells t 2765 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 2766 emulation library even if a 387 maths coprocessor
3823 is present. 2767 is present.
3824 2768
3825 no4lvl [RISCV,EARLY] Disable <<
3826 Forces kernel to use <<
3827 <<
3828 no5lvl [X86-64,RISCV,EARLY] <<
3829 kernel to use 4-level <<
3830 <<
3831 noalign [KNL,ARM] <<
3832 <<
3833 noapic [SMP,APIC,EARLY] Tell <<
3834 IOAPICs that may be p <<
3835 <<
3836 noautogroup Disable scheduler aut <<
3837 <<
3838 nocache [ARM,EARLY] <<
3839 <<
3840 no_console_suspend 2769 no_console_suspend
3841 [HW] Never suspend th 2770 [HW] Never suspend the console
3842 Disable suspending of 2771 Disable suspending of consoles during suspend and
3843 hibernate operations. 2772 hibernate operations. Once disabled, debugging
3844 messages can reach va 2773 messages can reach various consoles while the rest
3845 of the system is bein 2774 of the system is being put to sleep (ie, while
3846 debugging driver susp 2775 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 2776 not work reliably with all consoles, but is known
3848 to work with serial a 2777 to work with serial and VGA consoles.
3849 To facilitate more fl 2778 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 2779 console_suspend, a printk module parameter to control
3851 it. Users could use c 2780 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 2781 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 2782 turn on/off it dynamically.
3854 2783
3855 no_debug_objects !! 2784 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
3856 [KNL,EARLY] Disable o !! 2785 caches in the slab allocator. Saves per-node memory,
>> 2786 but will impact performance.
>> 2787
>> 2788 noalign [KNL,ARM]
>> 2789
>> 2790 noaltinstr [S390] Disables alternative instructions patching
>> 2791 (CPU alternatives feature).
>> 2792
>> 2793 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 2794 IOAPICs that may be present in the system.
>> 2795
>> 2796 noautogroup Disable scheduler automatic task group creation.
>> 2797
>> 2798 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 2799 on "Classic" PPC cores.
>> 2800
>> 2801 nocache [ARM]
>> 2802
>> 2803 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 2804
>> 2805 nodelayacct [KNL] Disable per-task delay accounting
3857 2806
3858 nodsp [SH] Disable hardware 2807 nodsp [SH] Disable hardware DSP at boot time.
3859 2808
3860 noefi [EFI,EARLY] Disable E !! 2809 noefi Disable EFI runtime services support.
>> 2810
>> 2811 no_entry_flush [PPC] Don't flush the L1-D cache when entering the kernel.
>> 2812
>> 2813 noexec [IA-64]
>> 2814
>> 2815 noexec [X86]
>> 2816 On X86-32 available only on PAE configured kernels.
>> 2817 noexec=on: enable non-executable mappings (default)
>> 2818 noexec=off: disable non-executable mappings
>> 2819
>> 2820 nosmap [X86]
>> 2821 Disable SMAP (Supervisor Mode Access Prevention)
>> 2822 even if it is supported by processor.
3861 2823
3862 no_entry_flush [PPC,EARLY] Don't flu !! 2824 nosmep [X86]
>> 2825 Disable SMEP (Supervisor Mode Execution Prevention)
>> 2826 even if it is supported by processor.
3863 2827
3864 noexec32 [X86-64] 2828 noexec32 [X86-64]
3865 This affects only 32- 2829 This affects only 32-bit executables.
3866 noexec32=on: enable n 2830 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 2831 read doesn't imply executable mappings
3868 noexec32=off: disable 2832 noexec32=off: disable non-executable mappings
3869 read implies 2833 read implies executable mappings
3870 2834
3871 no_file_caps Tells the kernel not <<
3872 only way then for a f <<
3873 is to be setuid root <<
3874 <<
3875 nofpu [MIPS,SH] Disable har 2835 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 2836
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 2837 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 2838 register save and restore. The kernel will only save
3881 legacy floating-point 2839 legacy floating-point registers on task switch.
3882 2840
3883 no_hash_pointers !! 2841 nohugeiomap [KNL,x86] Disable kernel huge I/O mappings.
3884 [KNL,EARLY] <<
3885 Force pointers printe <<
3886 unhashed. By default <<
3887 format string, that p <<
3888 by hashing the pointe <<
3889 that hides actual ker <<
3890 users, but it also ma <<
3891 difficult since unequ <<
3892 compared. However, i <<
3893 specified, then all n <<
3894 value printed. This o <<
3895 debugging the kernel. <<
3896 kernels. <<
3897 2842
3898 nohibernate [HIBERNATION] Disable !! 2843 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 2844 Equivalent to smt=1.
>> 2845
>> 2846 [KNL,x86] Disable symmetric multithreading (SMT).
>> 2847 nosmt=force: Force disable SMT, cannot be undone
>> 2848 via the sysfs control file.
>> 2849
>> 2850 nospectre_v1 [X66, PPC] Disable mitigations for Spectre Variant 1
>> 2851 (bounds check bypass). With this option data leaks
>> 2852 are possible in the system.
>> 2853
>> 2854 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 2855 the Spectre variant 2 (indirect branch prediction)
>> 2856 vulnerability. System may allow data leaks with this
>> 2857 option.
>> 2858
>> 2859 nospec_store_bypass_disable
>> 2860 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 2861
>> 2862 no_uaccess_flush
>> 2863 [PPC] Don't flush the L1-D cache after accessing user data.
>> 2864
>> 2865 noxsave [BUGS=X86] Disables x86 extended register state save
>> 2866 and restore using xsave. The kernel will fallback to
>> 2867 enabling legacy floating-point and sse state.
>> 2868
>> 2869 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 2870 register states. The kernel will fall back to use
>> 2871 xsave to save the states. By using this parameter,
>> 2872 performance of saving the states is degraded because
>> 2873 xsave doesn't support modified optimization while
>> 2874 xsaveopt supports it on xsaveopt enabled systems.
>> 2875
>> 2876 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 2877 restoring x86 extended register state in compacted
>> 2878 form of xsave area. The kernel will fall back to use
>> 2879 xsaveopt and xrstor to save and restore the states
>> 2880 in standard form of xsave area. By using this
>> 2881 parameter, xsave area per process might occupy more
>> 2882 memory on xsaves enabled systems.
3899 2883
3900 nohlt [ARM,ARM64,MICROBLAZE !! 2884 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
3901 busy wait in do_idle( !! 2885 wfi(ARM) instruction doesn't work correctly and not to
3902 implementation; requi !! 2886 use it. This is also useful when using JTAG debugger.
3903 to be effective. This <<
3904 sleep(SH) or wfi(ARM, <<
3905 correctly or when doi <<
3906 the impact of the sle <<
3907 useful when using JTA <<
3908 2887
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA !! 2888 no_file_caps Tells the kernel not to honor file capabilities. The
>> 2889 only way then for a file to be executed with privilege
>> 2890 is to be setuid root or executed by root.
3910 2891
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA !! 2892 nohalt [IA-64] Tells the kernel not to use the power saving
>> 2893 function PAL_HALT_LIGHT when idle. This increases
>> 2894 power-consumption. On the positive side, it reduces
>> 2895 interrupt wake-up latency, which may improve performance
>> 2896 in certain environments such as networked servers or
>> 2897 real-time systems.
>> 2898
>> 2899 nohibernate [HIBERNATION] Disable hibernation and resume.
3912 2900
3913 nohz= [KNL] Boottime enable 2901 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 2902 Valid arguments: on, off
3915 Default: on 2903 Default: on
3916 2904
3917 nohz_full= [KNL,BOOT,SMP,ISOL] !! 2905 nohz_full= [KNL,BOOT]
3918 The argument is a cpu 2906 The argument is a cpu list, as described above.
3919 In kernels built with 2907 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 2908 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 2909 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 2910 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 2911 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 2912 just as if they had also been called out in the
3925 rcu_nocbs= boot param 2913 rcu_nocbs= boot parameter.
3926 2914
3927 Note that this argume !! 2915 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 2916
>> 2917 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 2918 disable unhandled interrupt sources.
>> 2919
>> 2920 no_timer_check [X86,APIC] Disables the code which tests for
>> 2921 broken timer IRQ sources.
>> 2922
>> 2923 noisapnp [ISAPNP] Disables ISA PnP code.
3929 2924
3930 noinitrd [RAM] Tells the kerne 2925 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 2926 initial RAM disk.
3932 2927
3933 nointremap [X86-64,Intel-IOMMU,E !! 2928 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 2929 remapping.
3935 [Deprecated - use int 2930 [Deprecated - use intremap=off]
3936 2931
3937 noinvpcid [X86,EARLY] Disable t !! 2932 nointroute [IA-64]
3938 2933
3939 noiotrap [SH] Disables trapped !! 2934 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 2935
3941 noirqdebug [X86-32] Disables the !! 2936 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 2937
3944 noisapnp [ISAPNP] Disables ISA !! 2938 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3945 2939
3946 nokaslr [KNL,EARLY] !! 2940 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 <<
3951 no-kvmapf [X86,KVM,EARLY] Disab <<
3952 fault handling. 2941 fault handling.
3953 2942
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 2943 no-vmw-sched-clock
>> 2944 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 2945 clock and use the default one.
3955 2946
3956 nolapic [X86-32,APIC,EARLY] D !! 2947 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
>> 2948 steal time is computed, but won't influence scheduler
>> 2949 behaviour
3957 2950
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 2951 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3959 2952
3960 nomce [X86-32] Disable Mach !! 2953 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3961 2954
3962 nomfgpt [X86-32] Disable Mult !! 2955 noltlbs [PPC] Do not use large page/tlb entries for kernel
3963 Timer usage (for AMD !! 2956 lowmem mapping on PPC40x and PPC8xx
3964 2957
3965 nomodeset Disable kernel modese !! 2958 nomca [IA-64] Disable machine check abort handling
3966 sets up a display mod <<
3967 for output. With nomo <<
3968 not load if they coul <<
3969 initialized output. O <<
3970 be available for use. <<
3971 perform display-mode <<
3972 2959
3973 Useful as error fallb !! 2960 nomce [X86-32] Disable Machine Check Exception
3974 2961
3975 nomodule Disable module load !! 2962 nomfgpt [X86-32] Disable Multi-Function General Purpose
>> 2963 Timer usage (for AMD Geode machines).
3976 2964
3977 nonmi_ipi [X86] Disable using N 2965 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 2966 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 2967 irq.
3980 2968
3981 nopat [X86,EARLY] Disable P !! 2969 nomodule Disable module load
3982 pagetables) support. <<
3983 <<
3984 nopcid [X86-64,EARLY] Disabl <<
3985 <<
3986 nopku [X86] Disable Memory <<
3987 in some Intel CPUs. <<
3988 2970
3989 nopti [X86-64,EARLY] !! 2971 nopat [X86] Disable PAT (page attribute table extension of
3990 Equivalent to pti=off !! 2972 pagetables) support.
3991 2973
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 2974 nopcid [X86-64] Disable the PCID cpu feature.
3993 Disables the PV optim <<
3994 as generic guest with <<
3995 XEN HVM, KVM, HYPER_V <<
3996 <<
3997 nopvspin [X86,XEN,KVM,EARLY] <<
3998 Disables the qspinloc <<
3999 which allow the hyper <<
4000 contention. <<
4001 2975
4002 norandmaps Don't use address spa 2976 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 2977 echo 0 > /proc/sys/kernel/randomize_va_space
4004 2978
4005 noreplace-smp [X86-32,SMP] Don't re 2979 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 2980 with UP alternatives
4007 2981
>> 2982 nordrand [X86] Disable kernel use of the RDRAND and
>> 2983 RDSEED instructions even if they are supported
>> 2984 by the processor. RDRAND and RDSEED are still
>> 2985 available to user space applications.
>> 2986
4008 noresume [SWSUSP] Disables res 2987 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 2988 space.
4010 2989
4011 no-scroll [VGA] Disables scroll 2990 no-scroll [VGA] Disables scrollback.
4012 This is required for 2991 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 2992 reader made by F.H. Papenmeier (Germany).
4014 2993
4015 nosgx [X86-64,SGX,EARLY] Di !! 2994 nosbagart [IA-64]
4016 2995
4017 nosmap [PPC,EARLY] !! 2996 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 2997
4021 nosmep [PPC64s,EARLY] !! 2998 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 <<
4025 nosmp [SMP,EARLY] Tells an <<
4026 and disable the IO AP 2999 and disable the IO APIC. legacy for "maxcpus=0".
4027 3000
4028 nosmt [KNL,MIPS,PPC,S390,EA <<
4029 Equivalent to smt=1. <<
4030 <<
4031 [KNL,X86,PPC] Disable <<
4032 nosmt=force: Force di <<
4033 via the <<
4034 <<
4035 nosoftlockup [KNL] Disable the sof 3001 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3002
4037 nospec_store_bypass_disable <<
4038 [HW,EARLY] Disable al <<
4039 Store Bypass vulnerab <<
4040 <<
4041 nospectre_bhb [ARM64,EARLY] Disable <<
4042 history injection) vu <<
4043 with this option. <<
4044 <<
4045 nospectre_v1 [X86,PPC,EARLY] Disab <<
4046 (bounds check bypass) <<
4047 possible in the syste <<
4048 <<
4049 nospectre_v2 [X86,PPC_E500,ARM64,E <<
4050 for the Spectre varia <<
4051 prediction) vulnerabi <<
4052 leaks with this optio <<
4053 <<
4054 no-steal-acc [X86,PV_OPS,ARM64,PPC <<
4055 Disable paravirtualiz <<
4056 is computed, but won' <<
4057 <<
4058 nosync [HW,M68K] Disables sy 3003 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3004
4060 no_timer_check [X86,APIC] Disables t !! 3005 notsc [BUGS=X86-32] Disable Time Stamp Counter
4061 broken timer IRQ sour <<
4062 <<
4063 no_uaccess_flush <<
4064 [PPC,EARLY] Don't flu <<
4065 <<
4066 novmcoredd [KNL,KDUMP] <<
4067 Disable device dump. <<
4068 append dump data to v <<
4069 specified debug info. <<
4070 without any limit and <<
4071 so this may cause sig <<
4072 device dump can help <<
4073 data will be no longe <<
4074 is only available whe <<
4075 is set. <<
4076 <<
4077 no-vmw-sched-clock <<
4078 [X86,PV_OPS,EARLY] Di <<
4079 scheduler clock and u <<
4080 3006
4081 nowatchdog [KNL] Disable both lo 3007 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w !! 3008 soft-lockup and NMI watchdog (hard-lockup).
4083 3009
4084 nowb [ARM,EARLY] !! 3010 nowb [ARM]
4085 <<
4086 nox2apic [X86-64,APIC,EARLY] D <<
4087 <<
4088 NOTE: this parameter <<
4089 LEGACY_XAPIC_DISABLED <<
4090 IA32_XAPIC_DISABLE_ST <<
4091 <<
4092 noxsave [BUGS=X86] Disables x <<
4093 and restore using xsa <<
4094 enabling legacy float <<
4095 3011
4096 noxsaveopt [X86] Disables xsaveo !! 3012 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4097 register states. The <<
4098 xsave to save the sta <<
4099 performance of saving <<
4100 xsave doesn't support <<
4101 xsaveopt supports it <<
4102 3013
4103 noxsaves [X86] Disables xsaves !! 3014 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4104 restoring x86 extende !! 3015 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4105 form of xsave area. T !! 3016 Some features depend on CPU0. Known dependencies are:
4106 xsaveopt and xrstor t !! 3017 1. Resume from suspend/hibernate depends on CPU0.
4107 in standard form of x !! 3018 Suspend/hibernate will fail if CPU0 is offline and you
4108 parameter, xsave area !! 3019 need to online CPU0 before suspend/hibernate.
4109 memory on xsaves enab !! 3020 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 3021 removed if a PIC interrupt is detected.
>> 3022 It's said poweroff/reboot may depend on CPU0 on some
>> 3023 machines although I haven't seen such issues so far
>> 3024 after CPU0 is offline on a few tested machines.
>> 3025 If the dependencies are under your control, you can
>> 3026 turn on cpu0_hotplug.
>> 3027
>> 3028 nps_mtm_hs_ctr= [KNL,ARC]
>> 3029 This parameter sets the maximum duration, in
>> 3030 cycles, each HW thread of the CTOP can run
>> 3031 without interruptions, before HW switches it.
>> 3032 The actual maximum duration is 16 times this
>> 3033 parameter's value.
>> 3034 Format: integer between 1 and 255
>> 3035 Default: 255
>> 3036
>> 3037 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3038 purges which is reported from either PAL_VM_SUMMARY or
>> 3039 SAL PALO.
4110 3040
4111 nr_cpus= [SMP,EARLY] Maximum n !! 3041 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4112 could support. nr_cp 3042 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3043 support 'n' processors. It could be larger than the
4114 number of already plu 3044 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3045 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3046 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3047 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3048 hot plugging.
4119 3049
4120 nr_uarts= [SERIAL] maximum numb 3050 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3051
4122 numa=off [KNL, ARM64, PPC, RIS !! 3052 numa_balancing= [KNL,X86] Enable or disable automatic NUMA balancing.
4123 Disable NUMA, Only se <<
4124 spanning all memory. <<
4125 <<
4126 numa_balancing= [KNL,ARM64,PPC,RISCV, <<
4127 NUMA balancing. <<
4128 Allowed values are en 3053 Allowed values are enable and disable
4129 3054
4130 numa_zonelist_order= [KNL, BOOT] Sele 3055 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3056 'node', 'default' can be specified
4132 This can be set from 3057 This can be set from sysctl after boot.
4133 See Documentation/adm !! 3058 See Documentation/sysctl/vm.txt for details.
4134 3059
4135 ohci1394_dma=early [HW,EARLY] en !! 3060 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor !! 3061 See Documentation/debugging-via-ohci1394.txt for more
4137 info. 3062 info.
4138 3063
4139 olpc_ec_timeout= [OLPC] ms delay when 3064 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3065 Rather than timing out after 20 ms if an EC
4141 command is not proper 3066 command is not properly ACKed, override the length
4142 of the timeout. We h 3067 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3068 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3069 interrupts *may* be lost!
4145 3070
4146 omap_mux= [OMAP] Override bootl 3071 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3072 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3073 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3074 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3075
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 3076 oprofile.timer= [HW]
>> 3077 Use timer interrupt instead of performance counters
4152 3078
4153 Format: [die0_boundar !! 3079 oprofile.cpu_type= Force an oprofile cpu type
>> 3080 This might be useful if you have an older oprofile
>> 3081 userland or if you want common events.
>> 3082 Format: { arch_perfmon }
>> 3083 arch_perfmon: [X86] Force use of architectural
>> 3084 perfmon on Intel CPUs instead of the
>> 3085 CPU specific event set.
>> 3086 timer: [X86] Force use of architectural NMI
>> 3087 timer mode (see also oprofile.timer
>> 3088 for generic hr timer mode)
4154 3089
4155 boundary - index of l !! 3090 oops=panic Always panic on oopses. Default is to just kill the
4156 The remain <<
4157 lock - Configure <<
4158 Once locke <<
4159 1 indicate <<
4160 <<
4161 oops=panic [KNL,EARLY] <<
4162 Always panic on oopse <<
4163 process, but there is 3091 process, but there is a small probability of
4164 deadlocking the machi 3092 deadlocking the machine.
4165 This will also cause 3093 This will also cause panics on machine check exceptions.
4166 Useful together with 3094 Useful together with panic=30 to trigger a reboot.
4167 3095
4168 page_alloc.shuffle= !! 3096 OSS [HW,OSS]
4169 [KNL] Boolean flag to !! 3097 See Documentation/sound/oss/oss-parameters.txt
4170 should randomize its <<
4171 used to enable/disabl <<
4172 the flag can be read <<
4173 /sys/module/page_allo <<
4174 This parameter is onl <<
4175 3098
4176 page_owner= [KNL,EARLY] Boot-time !! 3099 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3100 Storage of the information about who allocated
4178 each page is disabled 3101 each page is disabled in default. With this switch,
4179 we can turn it on. 3102 we can turn it on.
4180 on: enable the featur 3103 on: enable the feature
4181 3104
4182 page_poison= [KNL,EARLY] Boot-time !! 3105 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd !! 3106 poisoning on the buddy allocator.
4184 CONFIG_PAGE_POISONING !! 3107 off: turn off poisoning
4185 off: turn off poisoni <<
4186 on: turn on poisoning 3108 on: turn on poisoning
4187 3109
4188 page_reporting.page_reporting_order= <<
4189 [KNL] Minimal page re <<
4190 Format: <integer> <<
4191 Adjust the minimal pa <<
4192 reporting is disabled <<
4193 <<
4194 panic= [KNL] Kernel behaviou 3110 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3111 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3112 timeout = 0: wait forever
4197 timeout < 0: reboot i 3113 timeout < 0: reboot immediately
4198 Format: <timeout> 3114 Format: <timeout>
4199 3115
4200 panic_on_taint= [KNL,EARLY] !! 3116 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4201 Bitmask for condition <<
4202 Format: <hex>[,nouser <<
4203 Hexadecimal bitmask r <<
4204 that will cause the k <<
4205 called with any of th <<
4206 The optional switch " <<
4207 prevent userspace for <<
4208 /proc/sys/kernel/tain <<
4209 bitmask set on panic_ <<
4210 See Documentation/adm <<
4211 extra details on the <<
4212 to compose the bitmas <<
4213 <<
4214 panic_on_warn=1 panic() instead of WA <<
4215 on a WARN(). 3117 on a WARN().
4216 3118
4217 panic_print= Bitmask for printing !! 3119 crash_kexec_post_notifiers
4218 User can chose combin !! 3120 Run kdump after running panic-notifiers and dumping
4219 bit 0: print all task !! 3121 kmsg. This only for the users who doubt kdump always
4220 bit 1: print system m !! 3122 succeeds in any situation.
4221 bit 2: print timer in !! 3123 Note that this also increases risks of kdump failure,
4222 bit 3: print locks in !! 3124 because some panic notifiers can make the crashed
4223 bit 4: print ftrace b !! 3125 kernel more unstable.
4224 bit 5: print all prin <<
4225 bit 6: print all CPUs <<
4226 bit 7: print only tas <<
4227 *Be aware* that this <<
4228 so there are risks of <<
4229 Use this option caref <<
4230 bigger log buffer wit <<
4231 3126
4232 parkbd.port= [HW] Parallel port nu 3127 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3128 connected to, default is 0.
4234 Format: <parport#> 3129 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3130 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3131 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3132 Format: <mode>
4238 3133
4239 parport= [HW,PPT] Specify para 3134 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3135 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3136 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3137 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3138 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3139 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3140 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3141 should be numbers, or 'auto' (for using detected
4247 settings on that part 3142 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3143 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3144 Parallel ports are assigned in the order they
4250 are specified on the 3145 are specified on the command line, starting
4251 with parport0. 3146 with parport0.
4252 3147
4253 parport_init_mode= [HW,PPT] 3148 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3149 Configure VIA parallel port to operate in
4255 a specific mode. This 3150 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3151 computer where firmware has no options for setting
4257 up parallel port mode 3152 up parallel port mode and sets it to spp.
4258 Currently this functi 3153 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3154 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3155
4261 pata_legacy.all= [HW,LIBATA] !! 3156 pause_on_oops=
4262 Format: <int> <<
4263 Set to non-zero to pr <<
4264 port ranges on PCI sy <<
4265 has been found at eit <<
4266 <<
4267 pata_legacy.autospeed= [HW,LIBATA] <<
4268 Format: <int> <<
4269 Set to non-zero if a <<
4270 changes. Disabled by <<
4271 <<
4272 pata_legacy.ht6560a= [HW,LIBATA] <<
4273 Format: <int> <<
4274 Set to 1, 2, or 3 for <<
4275 the secondary channel <<
4276 Disabled by default. <<
4277 <<
4278 pata_legacy.ht6560b= [HW,LIBATA] <<
4279 Format: <int> <<
4280 Set to 1, 2, or 3 for <<
4281 the secondary channel <<
4282 Disabled by default. <<
4283 <<
4284 pata_legacy.iordy_mask= [HW,LIBATA] <<
4285 Format: <int> <<
4286 IORDY enable mask. S <<
4287 for the respective ch <<
4288 legacy channel handle <<
4289 the second channel, a <<
4290 correspond to the pri <<
4291 legacy channel, and s <<
4292 bus and the use of ot <<
4293 with the sequence. B <<
4294 all channels. <<
4295 <<
4296 pata_legacy.opti82c46x= [HW,LIBATA] <<
4297 Format: <int> <<
4298 Set to 1, 2, or 3 for <<
4299 channel, the secondar <<
4300 respectively. Disabl <<
4301 <<
4302 pata_legacy.opti82c611a= [HW,L <<
4303 Format: <int> <<
4304 Set to 1, 2, or 3 for <<
4305 channel, the secondar <<
4306 respectively. Disabl <<
4307 <<
4308 pata_legacy.pio_mask= [HW,LIBATA] <<
4309 Format: <int> <<
4310 PIO mode mask for aut <<
4311 bits to allow the use <<
4312 Bit 0 is for mode 0, <<
4313 All modes allowed by <<
4314 <<
4315 pata_legacy.probe_all= [HW,LIBATA] <<
4316 Format: <int> <<
4317 Set to non-zero to pr <<
4318 port ranges on PCI sy <<
4319 <<
4320 pata_legacy.probe_mask= [HW,LIBATA] <<
4321 Format: <int> <<
4322 Probe mask for legacy <<
4323 platform configuratio <<
4324 options up to 6 legac <<
4325 0x170, 0x1e8, 0x168, <<
4326 of individual ports c <<
4327 corresponding bits in <<
4328 the first port in the <<
4329 By default all suppor <<
4330 <<
4331 pata_legacy.qdi= [HW,LIBATA] <<
4332 Format: <int> <<
4333 Set to non-zero to pr <<
4334 set to 1 if CONFIG_PA <<
4335 <<
4336 pata_legacy.winbond= [HW,LIBATA] <<
4337 Format: <int> <<
4338 Set to non-zero to pr <<
4339 the standard I/O port <<
4340 value given is the I/ <<
4341 By default set to 1 i <<
4342 0 otherwise. <<
4343 <<
4344 pata_platform.pio_mask= [HW,LIBATA] <<
4345 Format: <int> <<
4346 Supported PIO mode ma <<
4347 the use of the respec <<
4348 mode 0, bit 1 is for <<
4349 allowed by default. <<
4350 <<
4351 pause_on_oops=<int> <<
4352 Halt all CPUs after t 3157 Halt all CPUs after the first oops has been printed for
4353 the specified number 3158 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3159 your oopses keep scrolling off the screen.
4355 3160
4356 pcbit= [HW,ISDN] 3161 pcbit= [HW,ISDN]
4357 3162
4358 pci=option[,option...] [PCI,EARLY] v !! 3163 pcd. [PARIDE]
4359 !! 3164 See header of drivers/block/paride/pcd.c.
4360 Some options !! 3165 See also Documentation/blockdev/paride.txt.
4361 or a set of d !! 3166
4362 specified in !! 3167 pci=option[,option...] [PCI] various PCI subsystem options:
4363 !! 3168 earlydump [X86] dump PCI config space before the kernel
4364 [<domain>:]<b !! 3169 changes anything
4365 pci:<vendor>: <<
4366 <<
4367 Note: the fir <<
4368 bus/device/fu <<
4369 if new hardwa <<
4370 firmware chan <<
4371 by other kern <<
4372 domain is lef <<
4373 taken to be z <<
4374 to a device t <<
4375 addresses can <<
4376 address (this <<
4377 renumbering i <<
4378 selects devic <<
4379 configuration <<
4380 devices in th <<
4381 <<
4382 earlydump dump PCI conf <<
4383 changes anyth <<
4384 off [X86] don't p 3170 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3171 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3172 the hardware directly. Use this if your machine
4387 has a non-sta 3173 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3174 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3175 hardware access methods are allowed. Use this
4390 if you experi 3176 if you experience crashes upon bootup and you
4391 suspect they 3177 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3178 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3179 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3180 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3181 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3182 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3183 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3184 bus number. The config space is then accessed
4399 through ports 3185 through ports 0xC000-0xCFFF).
4400 See http://wi 3186 See http://wiki.osdev.org/PCI for more info
4401 on the config 3187 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3188 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3189 enabled, this kernel boot option can be used to
4404 disable the u 3190 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3191 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3192 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3193 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3194 Configuration
4409 check_enable_amd_mmconf [X86] 3195 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3196 properly configured MMIO access to PCI
4411 config space 3197 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3198 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3199 enabled, this kernel boot option can be used to
4414 disable the u 3200 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3201 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3202 Safety option to keep boot IRQs enabled. This
4417 should never 3203 should never be necessary.
4418 ioapicreroute [APIC] Enable 3204 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3205 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3206 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3207 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3208 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3209 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3210 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3211 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3212 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3213 routing table. These calls are known to be buggy
4428 on several ma 3214 on several machines and they hang the machine
4429 when used, bu 3215 when used, but on other computers it's the only
4430 way to get th 3216 way to get the interrupt routing table. Try
4431 this option i 3217 this option if the kernel is unable to allocate
4432 IRQs or disco 3218 IRQs or discover secondary PCI buses on your
4433 motherboard. 3219 motherboard.
4434 rom [X86] Assign 3220 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3221 Use with caution as certain devices share
4436 address decod 3222 address decoders between ROMs and other
4437 resources. 3223 resources.
4438 norom [X86] Do not 3224 norom [X86] Do not assign address space to
4439 expansion ROM 3225 expansion ROMs that do not already have
4440 BIOS assigned 3226 BIOS assigned address ranges.
4441 nobar [X86] Do not 3227 nobar [X86] Do not assign address space to the
4442 BARs that wer 3228 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3229 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3230 assigned automatically to PCI devices. You can
4445 make the kern 3231 make the kernel exclude IRQs of your ISA cards
4446 this way. 3232 this way.
4447 pirqaddr=0xAAAAA [X86] 3233 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3234 of the PIRQ table (normally generated
4449 by the BIOS) 3235 by the BIOS) if it is outside the
4450 F0000h-100000 3236 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3237 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3238 useful if the kernel is unable to find your
4453 secondary bus 3239 secondary buses and you want to tell it
4454 explicitly wh 3240 explicitly which ones they are.
4455 assign-busses [X86] Always 3241 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3242 numbers ourselves, overriding
4457 whatever the 3243 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3244 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3245 in the BIOS $PIR table. This is needed on
4460 some systems 3246 some systems with broken BIOSes, notably
4461 some HP Pavil 3247 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3248 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3249 IRQ routing is enabled.
4464 noacpi [X86] Do not 3250 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3251 or for PCI scanning.
4466 use_crs [X86] Use PCI 3252 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3253 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3254 is enabled by default. If you need to use this,
4469 please report 3255 please report a bug.
4470 nocrs [X86] Ignore 3256 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t !! 3257 If you need to use this, please report a bug.
4472 use_e820 [X86] Use E82 <<
4473 PCI host brid <<
4474 for BIOS defe <<
4475 If you need t <<
4476 <linux-pci@vge <<
4477 no_e820 [X86] Ignore <<
4478 bridge window <<
4479 hardware. If <<
4480 a bug to <linu <<
4481 routeirq Do IRQ routin 3258 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3259 This is normally done in pci_enable_device(),
4483 so this optio 3260 so this option is a temporary workaround
4484 for broken dr 3261 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3262 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3263 handle more pci cards
4487 noearly [X86] Don't d 3264 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3265 This might help on some broken boards which
4489 machine check 3266 machine check when some devices' config space
4490 is read. But 3267 is read. But various workarounds are disabled
4491 and some IOMM 3268 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3269 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3270 This sorting is done to get a device
4494 order compati 3271 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3272 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3273 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3274 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3275 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3276 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3277 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3278 based on its parent bus. Also set MRRS (Max
4502 Read Request 3279 Read Request Size) to the largest supported
4503 value (no lar 3280 value (no larger than the MPS that the device
4504 or bus can su 3281 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3282 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3283 every device is guaranteed to support. This
4507 configuration 3284 configuration allows peer-to-peer DMA between
4508 any pair of d 3285 any pair of devices, possibly at the cost of
4509 reduced perfo 3286 reduced performance. This also guarantees
4510 that hot-adde 3287 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3288 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3289 reserved for the CardBus bridge's IO window.
4513 The default v 3290 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3291 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3292 reserved for the CardBus bridge's memory
4516 window. The d 3293 window. The default value is 64 megabytes.
4517 resource_alignment= 3294 resource_alignment=
4518 Format: 3295 Format:
4519 [<order of ali !! 3296 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
>> 3297 [<order of align>@]pci:<vendor>:<device>\
>> 3298 [:<subvendor>:<subdevice>][; ...]
4520 Specifies ali 3299 Specifies alignment and device to reassign
4521 aligned memor !! 3300 aligned memory resources.
4522 specify the d <<
4523 If <order of 3301 If <order of align> is not specified,
4524 PAGE_SIZE is 3302 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri !! 3303 PCI-PCI bridge can be specified, if resource
4526 windows need 3304 windows need to be expanded.
4527 To specify th 3305 To specify the alignment for several
4528 instances of 3306 instances of a device, the PCI vendor,
4529 device, subve 3307 device, subvendor, and subdevice may be
4530 specified, e. !! 3308 specified, e.g., 4096@pci:8086:9c22:103c:198f
4531 for 4096-byte <<
4532 ecrc= Enable/disabl 3309 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3310 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3311 bios: Use BIOS/firmware settings. This is the
4537 the default. 3312 the default.
4538 off: Turn ECR 3313 off: Turn ECRC off
4539 on: Turn ECRC 3314 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3315 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3316 reserved for hotplug bridge's IO window.
4542 Default size 3317 Default size is 256 bytes.
4543 hpmmiosize=nn[KMG] The f <<
4544 reserved for <<
4545 Default size <<
4546 hpmmioprefsize=nn[KMG] The f <<
4547 reserved for <<
4548 Default size <<
4549 hpmemsize=nn[KMG] The f 3318 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for !! 3319 reserved for hotplug bridge's memory window.
4551 MMIO_PREF win <<
4552 Default size 3320 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3321 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3322 reserved for buses below a hotplug bridge.
4555 Default is 1. 3323 Default is 1.
4556 realloc= Enable/disabl 3324 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3325 if allocations done by BIOS are too small to
4558 accommodate r 3326 accommodate resources required by all child
4559 devices. 3327 devices.
4560 off: Turn rea 3328 off: Turn realloc off
4561 on: Turn real 3329 on: Turn realloc on
4562 realloc same as reall 3330 realloc same as realloc=on
4563 noari do not use PC 3331 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- <<
4565 do not use PC <<
4566 pcie_scan_all Scan all poss 3332 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 3333 only look for one device below a PCIe downstream
4568 port. 3334 port.
4569 big_root_window Try to add a <<
4570 root complex <<
4571 can resize a <<
4572 Adding the wi <<
4573 conflict with <<
4574 taints the ke <<
4575 disable_acs_redir=<pci_dev>[; <<
4576 Specify one o <<
4577 specified abo <<
4578 Each device s <<
4579 redirect capa <<
4580 allow P2P tra <<
4581 bridges witho <<
4582 this removes <<
4583 may put more <<
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 <<
4617 nomio [S390] Do not <<
4618 norid [S390] ignore <<
4619 one PCI domai <<
4620 3335
4621 pcie_aspm= [PCIE] Forcibly enabl !! 3336 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 3337 Management.
4623 off Don't touch ASPM conf !! 3338 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 3339 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 3340 WARNING: Forcing ASPM on may cause system lockups.
4627 3341
4628 pcie_ports= [PCIE] PCIe port serv !! 3342 pcie_hp= [PCIE] PCI Express Hotplug driver options:
4629 native Use native PCIe servi !! 3343 nomsi Do not use MSI for PCI Express Native Hotplug (this
4630 even if the platform !! 3344 makes all PCIe ports use INTx for hotplug services).
4631 use them. This may c !! 3345
4632 also tries to use the !! 3346 pcie_ports= [PCIE] PCIe ports handling:
4633 dpc-native Use native PC !! 3347 auto Ask the BIOS whether or not to use native PCIe services
4634 cause conflic !! 3348 associated with PCIe ports (PME, hot-plug, AER). Use
4635 compat Disable native PCIe s !! 3349 them only if that is allowed by the BIOS.
4636 hotplug). !! 3350 native Use native PCIe services associated with PCIe ports
>> 3351 unconditionally.
>> 3352 compat Treat PCIe ports as PCI-to-PCI bridges, disable the PCIe
>> 3353 ports driver.
4637 3354
4638 pcie_port_pm= [PCIE] PCIe port powe 3355 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 3356 off Disable power management of all PCIe ports
4640 force Forcibly enable power 3357 force Forcibly enable power management of all PCIe ports
4641 3358
4642 pcie_pme= [PCIE,PM] Native PCIe 3359 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 3360 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 3361 all PCIe root ports use INTx for all services).
4645 3362
4646 pcmv= [HW,PCMCIA] BadgePAD 3363 pcmv= [HW,PCMCIA] BadgePAD 4
4647 3364
4648 pd_ignore_unused 3365 pd_ignore_unused
4649 [PM] 3366 [PM]
4650 Keep all power-domain 3367 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 3368 even if no driver has claimed them. This is useful
4652 for debug and develop 3369 for debug and development, but should not be
4653 needed on a platform 3370 needed on a platform with proper driver support.
4654 3371
>> 3372 pd. [PARIDE]
>> 3373 See Documentation/blockdev/paride.txt.
>> 3374
4655 pdcchassis= [PARISC,HW] Disable/E 3375 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 3376 boot time.
4657 Format: { 0 | 1 } 3377 Format: { 0 | 1 }
4658 See arch/parisc/kerne 3378 See arch/parisc/kernel/pdc_chassis.c
4659 3379
4660 percpu_alloc= [MM,EARLY] !! 3380 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 3381 Currently supported values are "embed" and "page".
4663 Archs may support sub 3382 Archs may support subset or none of the selections.
4664 See comments in mm/pe 3383 See comments in mm/percpu.c for details on each
4665 allocator. This para 3384 allocator. This parameter is primarily for debugging
4666 and performance compa 3385 and performance comparison.
4667 3386
>> 3387 pf. [PARIDE]
>> 3388 See Documentation/blockdev/paride.txt.
>> 3389
>> 3390 pg. [PARIDE]
>> 3391 See Documentation/blockdev/paride.txt.
>> 3392
4668 pirq= [SMP,APIC] Manual mp- 3393 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 3394 See Documentation/x86/i386/IO-APIC.txt.
4670 3395
4671 plip= [PPT,NET] Parallel po 3396 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 3397 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio !! 3398 See also Documentation/parport.txt.
4674 3399
4675 pmtmr= [X86] Manual setup of 3400 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 3401 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 3402 e.g. pmtmr=0x508
4678 3403
4679 pmu_override= [PPC] Override the PM <<
4680 This option takes ove <<
4681 longer usable by perf <<
4682 PMU counters by setti <<
4683 cleared). If a number <<
4684 that number, otherwis <<
4685 remains 0. <<
4686 <<
4687 pm_debug_messages [SUSPEND,KNL] <<
4688 Enable suspend/resume <<
4689 <<
4690 pnp.debug=1 [PNP] 3404 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 3405 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 3406 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 3407 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 3408 current resource usage; turning this on also shows
4695 possible settings and 3409 possible settings and some assignment information.
4696 3410
4697 pnpacpi= [ACPI] 3411 pnpacpi= [ACPI]
4698 { off } 3412 { off }
4699 3413
4700 pnpbios= [ISAPNP] 3414 pnpbios= [ISAPNP]
4701 { on | off | curr | r 3415 { on | off | curr | res | no-curr | no-res }
4702 3416
4703 pnp_reserve_irq= 3417 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 3418 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 3419
4706 pnp_reserve_dma= 3420 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 3421 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 3422
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 3423 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 3424 Ranges are in pairs (I/O port base and size).
4711 3425
4712 pnp_reserve_mem= 3426 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 3427 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 3428 autoconfiguration.
4715 Ranges are in pairs ( 3429 Ranges are in pairs (memory base and size).
4716 3430
4717 ports= [IP_VS_FTP] IPVS ftp 3431 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 3432 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 3433 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 3434 may be specified.
4721 Format: <port>,<port> 3435 Format: <port>,<port>....
4722 3436
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 3437 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 3438 It specifically disables cpuidle and sets the
4730 platform machine desc 3439 platform machine description specific power_save
4731 function to NULL. On 3440 function to NULL. On Idle the CPU just reduces
4732 execution priority. 3441 execution priority.
4733 3442
4734 ppc_strict_facility_enable 3443 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 3444 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 3445 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 3446 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 3447 There is some performance impact when enabling this.
4739 3448
4740 ppc_tm= [PPC,EARLY] <<
4741 Format: {"off"} <<
4742 Disable Hardware Tran <<
4743 <<
4744 preempt= [KNL] <<
4745 Select preemption mod <<
4746 none - Limited to con <<
4747 voluntary - Limited t <<
4748 full - Any section th <<
4749 can be preempt <<
4750 contended spin <<
4751 explicitly pre <<
4752 <<
4753 print-fatal-signals= 3449 print-fatal-signals=
4754 [KNL] debug: print fa 3450 [KNL] debug: print fatal signals
4755 3451
4756 If enabled, warn abou 3452 If enabled, warn about various signal handling
4757 related application a 3453 related application anomalies: too many signals,
4758 too many POSIX.1 time 3454 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 3455 coredump - etc.
4760 3456
4761 If you hit the warnin 3457 If you hit the warning due to signal overflow,
4762 you might want to try 3458 you might want to try "ulimit -i unlimited".
4763 3459
4764 default: off. 3460 default: off.
4765 3461
4766 printk.always_kmsg_dump= 3462 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 3463 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 3464 panics
4769 Format: <bool> (1/Y/ 3465 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 3466 default: disabled
4771 3467
4772 printk.console_no_auto_verbose= <<
4773 Disable console logle <<
4774 or lockdep-detected i <<
4775 With an exception to <<
4776 serial console, keepi <<
4777 in order to provide m <<
4778 Format: <bool> <<
4779 default: 0 (auto_verb <<
4780 <<
4781 printk.devkmsg={on,off,ratelimit} 3468 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 3469 Control writing to /dev/kmsg.
4783 on - unlimited loggin 3470 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 3471 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 3472 ratelimit - ratelimit the logging
4786 Default: ratelimit 3473 Default: ratelimit
4787 3474
4788 printk.time= Show timing data pref 3475 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 3476 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 3477
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] 3478 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 3479 Limit processor to maximum C-state
4803 max_cstate=9 override 3480 max_cstate=9 overrides any DMI blacklist limit.
4804 3481
4805 processor.nocst [HW,ACPI] 3482 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 3483 Ignore the _CST method to determine C-states,
4807 instead using the leg 3484 instead using the legacy FADT method
4808 3485
4809 profile= [KNL] Enable kernel p 3486 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype !! 3487 Format: [schedule,]<number>
4811 Param: <profiletype>: <<
4812 [defaults to <<
4813 Param: "schedule" - p 3488 Param: "schedule" - profile schedule points.
4814 Param: "kvm" - profil <<
4815 Param: <number> - ste 3489 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 3490 statistical time based profiling.
>> 3491 Param: "sleep" - profile D-state sleeping (millisecs).
>> 3492 Requires CONFIG_SCHEDSTATS
>> 3493 Param: "kvm" - profile VM exits.
4817 3494
4818 prompt_ramdisk= [RAM] [Deprecated] !! 3495 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
4819 !! 3496 before loading.
4820 prot_virt= [S390] enable hosting !! 3497 See Documentation/blockdev/ramdisk.txt.
4821 isolated from the hyp <<
4822 that). If enabled, th <<
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> <<
4826 <<
4827 psi= [KNL] Enable or disab <<
4828 tracking. <<
4829 Format: <bool> <<
4830 3498
4831 psmouse.proto= [HW,MOUSE] Highest PS 3499 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 3500 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 3501 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 3502 per second.
4835 psmouse.resetafter= [HW,MOUSE] 3503 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 3504 Try to reset the device after so many bad packets
4837 (0 = never). 3505 (0 = never).
4838 psmouse.resolution= 3506 psmouse.resolution=
4839 [HW,MOUSE] Set desire 3507 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 3508 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 3509 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 3510 0 = disabled, 1 = enabled (default).
4843 3511
4844 pstore.backend= Specify the name of t 3512 pstore.backend= Specify the name of the pstore backend to use
4845 3513
4846 pti= [X86-64] Control Page !! 3514 pt. [PARIDE]
>> 3515 See Documentation/blockdev/paride.txt.
>> 3516
>> 3517 pti= [X86_64] Control Page Table Isolation of user and
4847 kernel address spaces 3518 kernel address spaces. Disabling this feature
4848 removes hardening, bu 3519 removes hardening, but improves performance of
4849 system calls and inte 3520 system calls and interrupts.
4850 3521
4851 on - unconditionall 3522 on - unconditionally enable
4852 off - unconditionall 3523 off - unconditionally disable
4853 auto - kernel detects 3524 auto - kernel detects whether your CPU model is
4854 vulnerable to 3525 vulnerable to issues that PTI mitigates
4855 3526
4856 Not specifying this o 3527 Not specifying this option is equivalent to pti=auto.
4857 3528
>> 3529 nopti [X86_64]
>> 3530 Equivalent to pti=off
>> 3531
4858 pty.legacy_count= 3532 pty.legacy_count=
4859 [KNL] Number of legac 3533 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 3534 default number.
4861 3535
4862 quiet [KNL,EARLY] Disable m !! 3536 quiet [KNL] Disable most log messages
4863 3537
4864 r128= [HW,DRM] 3538 r128= [HW,DRM]
4865 3539
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 3540 raid= [HW,RAID]
4871 See Documentation/adm 3541 See Documentation/admin-guide/md.rst.
4872 3542
4873 ramdisk_size= [RAM] Sizes of RAM di 3543 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm !! 3544 See Documentation/blockdev/ramdisk.txt.
4875 <<
4876 ramdisk_start= [RAM] RAM disk image <<
4877 3545
4878 random.trust_cpu=off !! 3546 random.trust_cpu={on,off}
4879 [KNL,EARLY] Disable t !! 3547 [KNL] Enable or disable trusting the use of the
4880 random number generat !! 3548 CPU's random number generator (if available) to
4881 initialize the kernel !! 3549 fully seed the kernel's CRNG. Default is controlled
4882 !! 3550 by CONFIG_RANDOM_TRUST_CPU.
4883 random.trust_bootloader=off !! 3551
4884 [KNL,EARLY] Disable t !! 3552 random.trust_bootloader={on,off}
4885 passed by the bootloa !! 3553 [KNL] Enable or disable trusting the use of a
4886 initialize the kernel !! 3554 seed passed by the bootloader (if available) to
4887 !! 3555 fully seed the kernel's CRNG. Default is controlled
4888 randomize_kstack_offset= !! 3556 by CONFIG_RANDOM_TRUST_BOOTLOADER.
4889 [KNL,EARLY] Enable or <<
4890 randomization, which <<
4891 entropy, frustrating <<
4892 that depend on stack <<
4893 cross-syscall address <<
4894 available on architec <<
4895 CONFIG_HAVE_ARCH_RAND <<
4896 Format: <bool> (1/Y/ <<
4897 Default is CONFIG_RAN <<
4898 3557
4899 ras=option[,option,...] [KNL] RAS-spe 3558 ras=option[,option,...] [KNL] RAS-specific options
4900 3559
4901 cec_disable [X86] 3560 cec_disable [X86]
4902 Disable the C 3561 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 3562 see CONFIG_RAS_CEC help text.
4904 3563
4905 rcu_nocbs[=cpu-list] !! 3564 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 3565 The argument is a cpu list, as described above.
4907 as described above. <<
4908 <<
4909 In kernels built with <<
4910 enable the no-callbac <<
4911 such CPUs' callbacks <<
4912 softirq context. Inv <<
4913 callbacks will instea <<
4914 kthreads created for <<
4915 "p" for RCU-preempt, <<
4916 for the kthreads that <<
4917 "N" is the CPU number <<
4918 the offloaded CPUs, w <<
4919 and real-time workloa <<
4920 energy efficiency for <<
4921 <<
4922 If a cpulist is passe <<
4923 list of CPUs is set t <<
4924 <<
4925 Otherwise, if the '=' <<
4926 arguments are omitted <<
4927 no-callback mode from <<
4928 toggled at runtime vi <<
4929 3566
4930 Note that this argume !! 3567 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4931 the CONFIG_RCU_NOCB_C !! 3568 the specified list of CPUs to be no-callback CPUs.
>> 3569 Invocation of these CPUs' RCU callbacks will
>> 3570 be offloaded to "rcuox/N" kthreads created for
>> 3571 that purpose, where "x" is "b" for RCU-bh, "p"
>> 3572 for RCU-preempt, and "s" for RCU-sched, and "N"
>> 3573 is the CPU number. This reduces OS jitter on the
>> 3574 offloaded CPUs, which can be useful for HPC and
>> 3575 real-time workloads. It can also improve energy
>> 3576 efficiency for asymmetric multiprocessors.
4932 3577
4933 rcu_nocb_poll [KNL] 3578 rcu_nocb_poll [KNL]
4934 Rather than requiring 3579 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 3580 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 3581 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 3582 make these kthreads poll for callbacks.
4938 This improves the rea 3583 This improves the real-time response for the
4939 offloaded CPUs by rel 3584 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 3585 wake up the corresponding kthread, but degrades
4941 energy efficiency by 3586 energy efficiency by requiring that the kthreads
4942 periodically wake up 3587 periodically wake up to do the polling.
4943 3588
4944 rcutree.blimit= [KNL] 3589 rcutree.blimit= [KNL]
4945 Set maximum number of 3590 Set maximum number of finished RCU callbacks to
4946 process in one batch. 3591 process in one batch.
4947 3592
4948 rcutree.do_rcu_barrier= [KNL] <<
4949 Request a call to rcu <<
4950 throttled so that use <<
4951 hammer on the sysfs v <<
4952 If triggered before t <<
4953 is fully active, this <<
4954 <<
4955 rcutree.dump_tree= [KNL] 3593 rcutree.dump_tree= [KNL]
4956 Dump the structure of 3594 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 3595 out at early boot. This is used for diagnostic
4958 purposes, to verify c 3596 purposes, to verify correct tree setup.
4959 3597
4960 rcutree.gp_cleanup_delay= [KNL] 3598 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 3599 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 3600 RCU grace-period cleanup.
4963 3601
4964 rcutree.gp_init_delay= [KNL] 3602 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 3603 Set the number of jiffies to delay each step of
4966 RCU grace-period init 3604 RCU grace-period initialization.
4967 3605
4968 rcutree.gp_preinit_delay= [KNL] 3606 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 3607 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 3608 RCU grace-period pre-initialization, that is,
4971 the propagation of re 3609 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 3610 the rcu_node combining tree.
4973 3611
>> 3612 rcutree.rcu_fanout_exact= [KNL]
>> 3613 Disable autobalancing of the rcu_node combining
>> 3614 tree. This is used by rcutorture, and might
>> 3615 possibly be useful for architectures having high
>> 3616 cache-to-cache transfer latencies.
>> 3617
>> 3618 rcutree.rcu_fanout_leaf= [KNL]
>> 3619 Change the number of CPUs assigned to each
>> 3620 leaf rcu_node structure. Useful for very
>> 3621 large systems, which will choose the value 64,
>> 3622 and for NUMA systems with large remote-access
>> 3623 latencies, which will choose a value aligned
>> 3624 with the appropriate hardware boundaries.
>> 3625
>> 3626 rcutree.jiffies_till_sched_qs= [KNL]
>> 3627 Set required age in jiffies for a
>> 3628 given grace period before RCU starts
>> 3629 soliciting quiescent-state help from
>> 3630 rcu_note_context_switch().
>> 3631
4974 rcutree.jiffies_till_first_fqs= [KNL] 3632 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 3633 Set delay from grace-period initialization to
4976 first attempt to forc 3634 first attempt to force quiescent states.
4977 Units are jiffies, mi 3635 Units are jiffies, minimum value is zero,
4978 and maximum value is 3636 and maximum value is HZ.
4979 3637
4980 rcutree.jiffies_till_next_fqs= [KNL] 3638 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 3639 Set delay between subsequent attempts to force
4982 quiescent states. Un 3640 quiescent states. Units are jiffies, minimum
4983 value is one, and max 3641 value is one, and maximum value is HZ.
4984 3642
4985 rcutree.jiffies_till_sched_qs= [KNL] <<
4986 Set required age in j <<
4987 given grace period be <<
4988 soliciting quiescent- <<
4989 rcu_note_context_swit <<
4990 If not specified, the <<
4991 a value based on the <<
4992 of rcutree.jiffies_ti <<
4993 and rcutree.jiffies_t <<
4994 This calculated value <<
4995 rcutree.jiffies_to_sc <<
4996 rcutree.jiffies_to_sc <<
4997 overwritten. <<
4998 <<
4999 rcutree.kthread_prio= [KNL,BOOT] 3643 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 3644 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 3645 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 3646 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 3647 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 3648 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 3649 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 3650 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 3651 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 3652 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 3653
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 3654 rcutree.rcu_nocb_leader_stride= [KNL]
5013 On callback-offloaded !! 3655 Set the number of NOCB kthread groups, which
5014 RCU reduces the lock !! 3656 defaults to the square root of the number of
5015 otherwise be caused b !! 3657 CPUs. Larger numbers reduces the wakeup overhead
5016 use of the ->nocb_byp !! 3658 on the per-CPU grace-period kthreads, but increases
5017 common non-flooded ca !! 3659 that same overhead on each group's leader.
5018 the main ->cblist in <<
5019 overhead of the ->noc <<
5020 But if there are too <<
5021 a single jiffy, RCU p <<
5022 the ->nocb_bypass que <<
5023 many" is supplied by <<
5024 <<
5025 rcutree.nohz_full_patience_delay= [KN <<
5026 On callback-offloaded <<
5027 disturbing RCU unless <<
5028 reached the specified <<
5029 Defaults to zero. La <<
5030 at five seconds. All <<
5031 to the nearest value <<
5032 3660
5033 rcutree.qhimark= [KNL] 3661 rcutree.qhimark= [KNL]
5034 Set threshold of queu 3662 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 3663 batch limiting is disabled.
5036 3664
5037 rcutree.qlowmark= [KNL] 3665 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 3666 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 3667 batch limiting is re-enabled.
5040 3668
5041 rcutree.qovld= [KNL] !! 3669 rcutree.rcu_idle_gp_delay= [KNL]
5042 Set threshold of queu !! 3670 Set wakeup interval for idle CPUs that have
5043 RCU's force-quiescent !! 3671 RCU callbacks (RCU_FAST_NO_HZ=y).
5044 enlist help from cond !! 3672
5045 help CPUs more quickl !! 3673 rcutree.rcu_idle_lazy_gp_delay= [KNL]
5046 Set to less than zero !! 3674 Set wakeup interval for idle CPUs that have
5047 on rcutree.qhimark at !! 3675 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
5048 disable more aggressi !! 3676 Lazy RCU callbacks are those which RCU can
5049 !! 3677 prove do nothing more than free memory.
5050 rcutree.rcu_delay_page_cache_fill_mse <<
5051 Set the page-cache re <<
5052 in response to low-me <<
5053 of permitted values i <<
5054 <<
5055 rcutree.rcu_divisor= [KNL] <<
5056 Set the shift-right c <<
5057 the callback-invocati <<
5058 the number of callbac <<
5059 The result will be bo <<
5060 the rcutree.blimit ke <<
5061 callbacks, the softir <<
5062 order to allow the CP <<
5063 <<
5064 Please note that this <<
5065 limit applies only to <<
5066 invocation. Offloade <<
5067 invoked in the contex <<
5068 scheduler will preemp <<
5069 <<
5070 rcutree.rcu_fanout_exact= [KNL] <<
5071 Disable autobalancing <<
5072 tree. This is used b <<
5073 possibly be useful fo <<
5074 cache-to-cache transf <<
5075 <<
5076 rcutree.rcu_fanout_leaf= [KNL] <<
5077 Change the number of <<
5078 leaf rcu_node structu <<
5079 large systems, which <<
5080 and for NUMA systems <<
5081 latencies, which will <<
5082 with the appropriate <<
5083 <<
5084 rcutree.rcu_min_cached_objs= [KNL] <<
5085 Minimum number of obj <<
5086 maintained per one CP <<
5087 to PAGE_SIZE. The cac <<
5088 pressure to page allo <<
5089 whole algorithm to be <<
5090 condition. <<
5091 <<
5092 rcutree.rcu_nocb_gp_stride= [KNL] <<
5093 Set the number of NOC <<
5094 each group, which def <<
5095 of the number of CPUs <<
5096 the wakeup overhead o <<
5097 kthread, but increase <<
5098 each group's NOCB gra <<
5099 3678
5100 rcutree.rcu_kick_kthreads= [KNL] 3679 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 3680 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 3681 wake_up() if it sleeps three times longer than
5103 it should at force-qu 3682 it should at force-quiescent-state time.
5104 This wake_up() will b 3683 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 3684 WARN_ONCE() splat and an ftrace_dump().
5106 3685
5107 rcutree.rcu_resched_ns= [KNL] !! 3686 rcuperf.gp_async= [KNL]
5108 Limit the time spend <<
5109 callbacks to the spec <<
5110 By default, this limi <<
5111 every 32 callbacks in <<
5112 inflicted by local_cl <<
5113 <<
5114 rcutree.rcu_unlock_delay= [KNL] <<
5115 In CONFIG_RCU_STRICT_ <<
5116 this specifies an rcu <<
5117 in microseconds. Thi <<
5118 Larger delays increas <<
5119 catching RCU pointer <<
5120 of RCU-protected poin <<
5121 rcu_read_unlock() has <<
5122 <<
5123 rcutree.sysrq_rcu= [KNL] <<
5124 Commandeer a sysrq ke <<
5125 rcu_node tree with an <<
5126 why a new grace perio <<
5127 <<
5128 rcutree.use_softirq= [KNL] <<
5129 If set to zero, move <<
5130 per-CPU rcuc kthreads <<
5131 value, meaning that R <<
5132 Specify rcutree.use_s <<
5133 <<
5134 But note that CONFIG_ <<
5135 this kernel boot para <<
5136 to zero. <<
5137 <<
5138 rcutree.enable_rcu_lazy= [KNL] <<
5139 To save power, batch <<
5140 delay, memory pressur <<
5141 big. <<
5142 <<
5143 rcutree.rcu_normal_wake_from_gp= [KNL <<
5144 Reduces a latency of <<
5145 maintains its own tra <<
5146 does not interact wit <<
5147 use a call_rcu[_hurry <<
5148 normal grace period. <<
5149 <<
5150 How to enable it: <<
5151 <<
5152 echo 1 > /sys/module/ <<
5153 or pass a boot parame <<
5154 <<
5155 Default is 0. <<
5156 <<
5157 rcuscale.gp_async= [KNL] <<
5158 Measure performance o 3687 Measure performance of asynchronous
5159 grace-period primitiv 3688 grace-period primitives such as call_rcu().
5160 3689
5161 rcuscale.gp_async_max= [KNL] !! 3690 rcuperf.gp_async_max= [KNL]
5162 Specify the maximum n 3691 Specify the maximum number of outstanding
5163 callbacks per writer 3692 callbacks per writer thread. When a writer
5164 thread exceeds this l 3693 thread exceeds this limit, it invokes the
5165 corresponding flavor 3694 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 3695 previously posted callbacks to drain.
5167 3696
5168 rcuscale.gp_exp= [KNL] !! 3697 rcuperf.gp_exp= [KNL]
5169 Measure performance o 3698 Measure performance of expedited synchronous
5170 grace-period primitiv 3699 grace-period primitives.
5171 3700
5172 rcuscale.holdoff= [KNL] !! 3701 rcuperf.holdoff= [KNL]
5173 Set test-start holdof 3702 Set test-start holdoff period. The purpose of
5174 this parameter is to 3703 this parameter is to delay the start of the
5175 test until boot compl 3704 test until boot completes in order to avoid
5176 interference. 3705 interference.
5177 3706
5178 rcuscale.kfree_by_call_rcu= [KNL] !! 3707 rcuperf.nreaders= [KNL]
5179 In kernels built with <<
5180 call_rcu() instead of <<
5181 <<
5182 rcuscale.kfree_mult= [KNL] <<
5183 Instead of allocating <<
5184 allocate one of kfree <<
5185 Defaults to 1. <<
5186 <<
5187 rcuscale.kfree_rcu_test= [KNL] <<
5188 Set to measure perfor <<
5189 <<
5190 rcuscale.kfree_rcu_test_double= [KNL] <<
5191 Test the double-argum <<
5192 If this parameter has <<
5193 rcuscale.kfree_rcu_te <<
5194 and double-argument v <<
5195 <<
5196 rcuscale.kfree_rcu_test_single= [KNL] <<
5197 Test the single-argum <<
5198 If this parameter has <<
5199 rcuscale.kfree_rcu_te <<
5200 and double-argument v <<
5201 <<
5202 rcuscale.kfree_nthreads= [KNL] <<
5203 The number of threads <<
5204 <<
5205 rcuscale.kfree_alloc_num= [KNL] <<
5206 Number of allocations <<
5207 <<
5208 rcuscale.kfree_loops= [KNL] <<
5209 Number of loops doing <<
5210 of allocations and fr <<
5211 <<
5212 rcuscale.minruntime= [KNL] <<
5213 Set the minimum test <<
5214 does not affect the d <<
5215 but instead allows be <<
5216 like CPU consumption. <<
5217 <<
5218 rcuscale.nreaders= [KNL] <<
5219 Set number of RCU rea 3708 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 3709 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 3710 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 3711 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 3712 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 3713 A value of "n" less than or equal to -N selects
5225 a single reader. 3714 a single reader.
5226 3715
5227 rcuscale.nwriters= [KNL] !! 3716 rcuperf.nwriters= [KNL]
5228 Set number of RCU wri 3717 Set number of RCU writers. The values operate
5229 the same as for rcusc !! 3718 the same as for rcuperf.nreaders.
5230 N, where N is the num 3719 N, where N is the number of CPUs
5231 3720
5232 rcuscale.scale_type= [KNL] !! 3721 rcuperf.perf_runnable= [BOOT]
>> 3722 Start rcuperf running at boot time.
>> 3723
>> 3724 rcuperf.perf_type= [KNL]
5233 Specify the RCU imple 3725 Specify the RCU implementation to test.
5234 3726
5235 rcuscale.shutdown= [KNL] !! 3727 rcuperf.shutdown= [KNL]
5236 Shut the system down 3728 Shut the system down after performance tests
5237 complete. This is us 3729 complete. This is useful for hands-off automated
5238 testing. 3730 testing.
5239 3731
5240 rcuscale.verbose= [KNL] !! 3732 rcuperf.verbose= [KNL]
5241 Enable additional pri 3733 Enable additional printk() statements.
5242 3734
5243 rcuscale.writer_holdoff= [KNL] !! 3735 rcuperf.writer_holdoff= [KNL]
5244 Write-side holdoff be 3736 Write-side holdoff between grace periods,
5245 in microseconds. The 3737 in microseconds. The default of zero says
5246 no holdoff. 3738 no holdoff.
5247 3739
5248 rcuscale.writer_holdoff_jiffies= [KNL !! 3740 rcutorture.cbflood_inter_holdoff= [KNL]
5249 Additional write-side !! 3741 Set holdoff time (jiffies) between successive
5250 periods, but in jiffi !! 3742 callback-flood tests.
5251 says no holdoff. !! 3743
>> 3744 rcutorture.cbflood_intra_holdoff= [KNL]
>> 3745 Set holdoff time (jiffies) between successive
>> 3746 bursts of callbacks within a given callback-flood
>> 3747 test.
>> 3748
>> 3749 rcutorture.cbflood_n_burst= [KNL]
>> 3750 Set the number of bursts making up a given
>> 3751 callback-flood test. Set this to zero to
>> 3752 disable callback-flood testing.
>> 3753
>> 3754 rcutorture.cbflood_n_per_burst= [KNL]
>> 3755 Set the number of callbacks to be registered
>> 3756 in a given burst of a callback-flood test.
5252 3757
5253 rcutorture.fqs_duration= [KNL] 3758 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 3759 Set duration of force_quiescent_state bursts
5255 in microseconds. 3760 in microseconds.
5256 3761
5257 rcutorture.fqs_holdoff= [KNL] 3762 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 3763 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 3764 in microseconds.
5260 3765
5261 rcutorture.fqs_stutter= [KNL] 3766 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 3767 Set wait time between force_quiescent_state bursts
5263 in seconds. 3768 in seconds.
5264 3769
5265 rcutorture.fwd_progress= [KNL] <<
5266 Specifies the number <<
5267 for RCU grace-period <<
5268 for the types of RCU <<
5269 Defaults to 1 kthread <<
5270 greater than the numb <<
5271 of CPUs to be used. <<
5272 <<
5273 rcutorture.fwd_progress_div= [KNL] <<
5274 Specify the fraction <<
5275 period to do tight-lo <<
5276 <<
5277 rcutorture.fwd_progress_holdoff= [KNL <<
5278 Number of seconds to <<
5279 forward-progress test <<
5280 <<
5281 rcutorture.fwd_progress_need_resched= <<
5282 Enclose cond_resched( <<
5283 need_resched() during <<
5284 testing. <<
5285 <<
5286 rcutorture.gp_cond= [KNL] 3770 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 3771 Use conditional/asynchronous update-side
5288 primitives, if availa 3772 primitives, if available.
5289 3773
5290 rcutorture.gp_exp= [KNL] 3774 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 3775 Use expedited update-side primitives, if available.
5292 3776
5293 rcutorture.gp_normal= [KNL] 3777 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 3778 Use normal (non-expedited) asynchronous
5295 update-side primitive 3779 update-side primitives, if available.
5296 3780
5297 rcutorture.gp_sync= [KNL] 3781 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 3782 Use normal (non-expedited) synchronous
5299 update-side primitive 3783 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 3784 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 3785 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 3786 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 3787 they are all non-zero.
5304 3788
5305 rcutorture.irqreader= [KNL] <<
5306 Run RCU readers from <<
5307 accurately, from a ti <<
5308 flavors take kindly t <<
5309 <<
5310 rcutorture.leakpointer= [KNL] <<
5311 Leak an RCU-protected <<
5312 This can of course re <<
5313 intended to test the <<
5314 CONFIG_RCU_STRICT_GRA <<
5315 such leaks. <<
5316 <<
5317 rcutorture.n_barrier_cbs= [KNL] 3789 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 3790 Set callbacks/threads for rcu_barrier() testing.
5319 3791
5320 rcutorture.nfakewriters= [KNL] 3792 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 3793 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 3794 stress RCU, they don't participate in the actual
5323 test, hence the "fake 3795 test, hence the "fake".
5324 3796
5325 rcutorture.nocbs_nthreads= [KNL] <<
5326 Set number of RCU cal <<
5327 Zero (the default) di <<
5328 <<
5329 rcutorture.nocbs_toggle= [KNL] <<
5330 Set the delay in mill <<
5331 callback-offload togg <<
5332 <<
5333 rcutorture.nreaders= [KNL] 3797 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 3798 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 3799 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 3800 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 3801 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 3802 (the number of CPUs), -3 selects N+1, and so on.
5339 3803
5340 rcutorture.object_debug= [KNL] 3804 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 3805 Enable debug-object double-call_rcu() testing.
5342 3806
5343 rcutorture.onoff_holdoff= [KNL] 3807 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 3808 Set time (s) after boot for CPU-hotplug testing.
5345 3809
5346 rcutorture.onoff_interval= [KNL] 3810 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be !! 3811 Set time (s) between CPU-hotplug operations, or
5348 or zero to disable CP !! 3812 zero to disable CPU-hotplug testing.
5349 <<
5350 rcutorture.read_exit= [KNL] <<
5351 Set the number of rea <<
5352 to test the interacti <<
5353 task-exit processing. <<
5354 <<
5355 rcutorture.read_exit_burst= [KNL] <<
5356 The number of times i <<
5357 episode that a set of <<
5358 is spawned. <<
5359 <<
5360 rcutorture.read_exit_delay= [KNL] <<
5361 The delay, in seconds <<
5362 read-then-exit testin <<
5363 3813
5364 rcutorture.shuffle_interval= [KNL] 3814 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 3815 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 3816 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 3817 during the rcutorture test.
5368 3818
5369 rcutorture.shutdown_secs= [KNL] 3819 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 3820 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 3821 is useful for hands-off automated testing.
5372 3822
5373 rcutorture.stall_cpu= [KNL] 3823 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 3824 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 3825 warnings, zero to disable.
5376 3826
5377 rcutorture.stall_cpu_block= [KNL] <<
5378 Sleep while stalling <<
5379 in warnings from pree <<
5380 any other stall-relat <<
5381 in kernels built with <<
5382 CONFIG_PREEMPT_COUNT= <<
5383 cause the CPU to pass <<
5384 Given CONFIG_PREEMPTI <<
5385 RCU CPU stall warning <<
5386 in scheduling-while-a <<
5387 <<
5388 Use of this module pa <<
5389 <<
5390 <<
5391 rcutorture.stall_cpu_holdoff= [KNL] 3827 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 3828 Time to wait (s) after boot before inducing stall.
5393 3829
5394 rcutorture.stall_cpu_irqsoff= [KNL] <<
5395 Disable interrupts wh <<
5396 <<
5397 rcutorture.stall_gp_kthread= [KNL] <<
5398 Duration (s) of force <<
5399 grace-period kthread <<
5400 warnings, zero to dis <<
5401 and stall_gp_kthread <<
5402 kthread is starved fi <<
5403 <<
5404 rcutorture.stat_interval= [KNL] 3830 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 3831 Time (s) between statistics printk()s.
5406 3832
5407 rcutorture.stutter= [KNL] 3833 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 3834 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 3835 five seconds causes the test to run for five seconds,
5410 wait for five seconds 3836 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 3837 ability to transition abruptly to and from idle.
5412 3838
5413 rcutorture.test_boost= [KNL] 3839 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 3840 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 3841 "Maybe" means test if the RCU implementation
5416 under test support RC 3842 under test support RCU priority boosting.
5417 3843
5418 rcutorture.test_boost_duration= [KNL] 3844 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 3845 Duration (s) of each individual boost test.
5420 3846
5421 rcutorture.test_boost_interval= [KNL] 3847 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 3848 Interval (s) between each boost test.
5423 3849
5424 rcutorture.test_no_idle_hz= [KNL] 3850 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 3851 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 3852 rcutorture.shuffle_interval parameter.
5427 3853
>> 3854 rcutorture.torture_runnable= [BOOT]
>> 3855 Start rcutorture running at boot time.
>> 3856
5428 rcutorture.torture_type= [KNL] 3857 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 3858 Specify the RCU implementation to test.
5430 3859
5431 rcutorture.verbose= [KNL] 3860 rcutorture.verbose= [KNL]
5432 Enable additional pri 3861 Enable additional printk() statements.
5433 3862
5434 rcupdate.rcu_cpu_stall_ftrace_dump= [ <<
5435 Dump ftrace buffer af <<
5436 stall warning. <<
5437 <<
5438 rcupdate.rcu_cpu_stall_notifiers= [KN <<
5439 Provide RCU CPU stall <<
5440 warnings in the RCU_C <<
5441 option's help text. <<
5442 do not want rcupdate. <<
5443 <<
5444 rcupdate.rcu_cpu_stall_suppress= [KNL 3863 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 3864 Suppress RCU CPU stall warning messages.
5446 3865
5447 rcupdate.rcu_cpu_stall_suppress_at_bo <<
5448 Suppress RCU CPU stal <<
5449 rcutorture writer sta <<
5450 during early boot, th <<
5451 before the init task <<
5452 <<
5453 rcupdate.rcu_cpu_stall_timeout= [KNL] 3866 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 3867 Set timeout for RCU CPU stall warning messages.
5455 The value is in secon <<
5456 value is 300 seconds. <<
5457 <<
5458 rcupdate.rcu_exp_cpu_stall_timeout= [ <<
5459 Set timeout for exped <<
5460 messages. The value <<
5461 and the maximum allow <<
5462 milliseconds. Please <<
5463 adjusted to an arch t <<
5464 Setting this to zero <<
5465 rcupdate.rcu_cpu_stal <<
5466 conversion from secon <<
5467 <<
5468 rcupdate.rcu_cpu_stall_cputime= [KNL] <<
5469 Provide statistics on <<
5470 interrupts and tasks <<
5471 multiple continuous R <<
5472 begin at half of the <<
5473 <<
5474 rcupdate.rcu_exp_stall_task_details= <<
5475 Print stack dumps of <<
5476 current expedited RCU <<
5477 expedited RCU CPU sta <<
5478 3868
5479 rcupdate.rcu_expedited= [KNL] 3869 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 3870 Use expedited grace-period primitives, for
5481 example, synchronize_ 3871 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 3872 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 3873 but can increase CPU utilization, degrade
5484 real-time latency, an 3874 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 3875 No effect on CONFIG_TINY_RCU kernels.
5486 3876
5487 rcupdate.rcu_normal= [KNL] 3877 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 3878 Use only normal grace-period primitives,
5489 for example, synchron 3879 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 3880 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 3881 real-time latency, CPU utilization, and
5492 energy efficiency, bu 3882 energy efficiency, but can expose users to
5493 increased grace-perio 3883 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 3884 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 3885 CONFIG_TINY_RCU kernels.
5496 3886
5497 rcupdate.rcu_normal_after_boot= [KNL] 3887 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 3888 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 3889 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 3890 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 3891 on CONFIG_TINY_RCU kernels.
5502 3892
5503 But note that CONFIG_ <<
5504 this kernel boot para <<
5505 it to the value one, <<
5506 post-boot attempt at <<
5507 period to instead use <<
5508 grace-period processi <<
5509 <<
5510 rcupdate.rcu_task_collapse_lim= [KNL] <<
5511 Set the maximum numbe <<
5512 at the beginning of a <<
5513 the RCU Tasks flavors <<
5514 a single callback que <<
5515 occurs when rcupdate. <<
5516 set to the default va <<
5517 <<
5518 rcupdate.rcu_task_contend_lim= [KNL] <<
5519 Set the minimum numbe <<
5520 lock-contention event <<
5521 cause the RCU Tasks f <<
5522 callback queuing. Th <<
5523 when rcupdate.rcu_tas <<
5524 the default value of <<
5525 <<
5526 rcupdate.rcu_task_enqueue_lim= [KNL] <<
5527 Set the number of cal <<
5528 RCU Tasks family of R <<
5529 of -1 allows this to <<
5530 dynamically) adjusted <<
5531 for use in testing. <<
5532 <<
5533 rcupdate.rcu_task_ipi_delay= [KNL] <<
5534 Set time in jiffies d <<
5535 avoid sending IPIs, s <<
5536 of a given grace peri <<
5537 number avoids disturb <<
5538 but lengthens grace p <<
5539 <<
5540 rcupdate.rcu_task_lazy_lim= [KNL] <<
5541 Number of callbacks o <<
5542 cancel laziness on th <<
5543 cancellation of lazin <<
5544 doing so increases th <<
5545 callback flooding. <<
5546 <<
5547 rcupdate.rcu_task_stall_info= [KNL] <<
5548 Set initial timeout i <<
5549 informational message <<
5550 of the problem for th <<
5551 wait for ten minutes. <<
5552 only printed prior to <<
5553 for a given grace per <<
5554 less than or equal to <<
5555 seconds. A change in <<
5556 until the beginning o <<
5557 <<
5558 rcupdate.rcu_task_stall_info_mult= [K <<
5559 Multiplier for time i <<
5560 RCU task stall inform <<
5561 RCU tasks grace perio <<
5562 to one through ten, i <<
5563 the value three, so t <<
5564 message is printed 10 <<
5565 period, the second at <<
5566 160 seconds, and then <<
5567 seconds would prevent <<
5568 <<
5569 rcupdate.rcu_task_stall_timeout= [KNL 3893 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 3894 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 3895 messages. Disable with a value less than or equal
5572 than or equal to zero !! 3896 to zero.
5573 A change in value doe <<
5574 the beginning of the <<
5575 <<
5576 rcupdate.rcu_tasks_lazy_ms= [KNL] <<
5577 Set timeout in millis <<
5578 callback batching for <<
5579 A negative value will <<
5580 of zero will disable <<
5581 always disabled for s <<
5582 <<
5583 rcupdate.rcu_tasks_rude_lazy_ms= [KNL <<
5584 Set timeout in millis <<
5585 Rude asynchronous cal <<
5586 call_rcu_tasks_rude() <<
5587 will take the default <<
5588 disable batching. Ba <<
5589 for synchronize_rcu_t <<
5590 <<
5591 rcupdate.rcu_tasks_trace_lazy_ms= [KN <<
5592 Set timeout in millis <<
5593 Trace asynchronous ca <<
5594 call_rcu_tasks_trace( <<
5595 will take the default <<
5596 disable batching. Ba <<
5597 for synchronize_rcu_t <<
5598 3897
5599 rcupdate.rcu_self_test= [KNL] 3898 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 3899 Run the RCU early boot self tests
5601 3900
>> 3901 rcupdate.rcu_self_test_bh= [KNL]
>> 3902 Run the RCU bh early boot self tests
>> 3903
>> 3904 rcupdate.rcu_self_test_sched= [KNL]
>> 3905 Run the RCU sched early boot self tests
>> 3906
5602 rdinit= [KNL] 3907 rdinit= [KNL]
5603 Format: <full_path> 3908 Format: <full_path>
5604 Run specified binary 3909 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 3910 used for early userspace startup. See initrd.
5606 3911
5607 rdrand= [X86,EARLY] !! 3912 rdrand= [X86]
5608 force - Override the 3913 force - Override the decision by the kernel to hide the
5609 advertisement 3914 advertisement of RDRAND support (this affects
5610 certain AMD p 3915 certain AMD processors because of buggy BIOS
5611 support, spec 3916 support, specifically around the suspend/resume
5612 path). 3917 path).
5613 3918
5614 rdt= [HW,X86,RDT] 3919 rdt= [HW,X86,RDT]
5615 Turn on/off individua 3920 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc !! 3921 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, mba.
5617 mba, smba, bmec. <<
5618 E.g. to turn on cmt a 3922 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 3923 rdt=cmt,!mba
5620 3924
5621 reboot= [KNL] 3925 reboot= [KNL]
5622 Format (x86 or x86_64 3926 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 3927 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 3928 [[,]s[mp]#### \
5625 [[,]b[ios] | 3929 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 3930 [[,]f[orce]
5627 Where reboot_mode is !! 3931 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
5628 (pref <<
5629 reboo <<
5630 reboot_type is 3932 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 3933 reboot_force is either force or not specified,
5632 reboot_cpu is s 3934 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 3935 to be used for rebooting.
5634 3936
5635 refscale.holdoff= [KNL] <<
5636 Set test-start holdof <<
5637 this parameter is to <<
5638 test until boot compl <<
5639 interference. <<
5640 <<
5641 refscale.lookup_instances= [KNL] <<
5642 Number of data elemen <<
5643 SLAB_TYPESAFE_BY_RCU <<
5644 is negated and multip <<
5645 zero specifies nr_cpu <<
5646 <<
5647 refscale.loops= [KNL] <<
5648 Set the number of loo <<
5649 primitive under test. <<
5650 reduces noise due to <<
5651 but the default has a <<
5652 noise to a handful of <<
5653 x86 laptops. <<
5654 <<
5655 refscale.nreaders= [KNL] <<
5656 Set number of readers <<
5657 selects N, where N is <<
5658 of CPUs. A value of <<
5659 <<
5660 refscale.nruns= [KNL] <<
5661 Set number of runs, e <<
5662 the console log. <<
5663 <<
5664 refscale.readdelay= [KNL] <<
5665 Set the read-side cri <<
5666 measured in microseco <<
5667 <<
5668 refscale.scale_type= [KNL] <<
5669 Specify the read-prot <<
5670 <<
5671 refscale.shutdown= [KNL] <<
5672 Shut down the system <<
5673 test. This defaults <<
5674 refscale is built int <<
5675 it running) when refs <<
5676 <<
5677 refscale.verbose= [KNL] <<
5678 Enable additional pri <<
5679 <<
5680 refscale.verbose_batched= [KNL] <<
5681 Batch the additional <<
5682 (the default) or nega <<
5683 print every Nth verbo <<
5684 specified. <<
5685 <<
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= 3937 relax_domain_level=
5694 [KNL, SMP] Set schedu 3938 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm !! 3939 See Documentation/cgroup-v1/cpusets.txt.
5696 3940
5697 reserve= [KNL,BUGS] Force kern !! 3941 reserve= [KNL,BUGS] Force the kernel to ignore some iomem area
5698 Format: <base1>,<size <<
5699 Reserve I/O ports or <<
5700 them. If <base> is l <<
5701 is assumed to be I/O <<
5702 <<
5703 reserve_mem= [RAM] <<
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 3942
5720 The format is size:al !! 3943 reservetop= [X86-32]
5721 12 megabytes of 4096 <<
5722 <<
5723 reserve_mem=12M:4096: <<
5724 <<
5725 reservetop= [X86-32,EARLY] <<
5726 Format: nn[KMG] 3944 Format: nn[KMG]
5727 Reserves a hole at th 3945 Reserves a hole at the top of the kernel virtual
5728 address space. 3946 address space.
5729 3947
>> 3948 reservelow= [X86]
>> 3949 Format: nn[K]
>> 3950 Set the amount of memory to reserve for BIOS at
>> 3951 the bottom of the address space.
>> 3952
5730 reset_devices [KNL] Force drivers t 3953 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 3954 during initialization.
5732 3955
5733 resume= [SWSUSP] 3956 resume= [SWSUSP]
5734 Specify the partition 3957 Specify the partition device for software suspend
5735 Format: 3958 Format:
5736 {/dev/<dev> | PARTUUI 3959 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 3960
5738 resume_offset= [SWSUSP] 3961 resume_offset= [SWSUSP]
5739 Specify the offset fr 3962 Specify the offset from the beginning of the partition
5740 given by "resume=" at 3963 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 3964 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po !! 3965 See Documentation/power/swsusp-and-swap-files.txt
5743 3966
5744 resumedelay= [HIBERNATION] Delay ( 3967 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 3968 read the resume files
5746 3969
5747 resumewait [HIBERNATION] Wait (i 3970 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 3971 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 3972 (e.g. USB and MMC devices).
5750 3973
5751 retain_initrd [RAM] Keep initrd mem !! 3974 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 3975 noresume Don't check if there's a hibernation image
>> 3976 present during boot.
>> 3977 nocompress Don't compress/decompress hibernation images.
>> 3978 no Disable hibernation and resume.
>> 3979 protect_image Turn on image protection during restoration
>> 3980 (that will set all pages holding image data
>> 3981 during restoration read-only).
>> 3982
>> 3983 retain_initrd [RAM] Keep initrd memory after extraction
5753 3984
5754 retbleed= [X86] Control mitigat 3985 retbleed= [X86] Control mitigation of RETBleed (Arbitrary
5755 Speculative Code Exec 3986 Speculative Code Execution with Return Instructions)
5756 vulnerability. 3987 vulnerability.
5757 3988
5758 AMD-based UNRET and I !! 3989 off - unconditionally disable
5759 sibling threads from !! 3990 auto - automatically select a migitation
5760 sibling threads. For <<
5761 cessors that support <<
5762 that don't. <<
5763 <<
5764 off - no mit <<
5765 auto - automa <<
5766 auto,nosmt - automa <<
5767 disabl <<
5768 the fu <<
5769 and ol <<
5770 ibpb - On AMD <<
5771 window <<
5772 Safe, <<
5773 enable <<
5774 on Int <<
5775 ibpb,nosmt - Like " <<
5776 when S <<
5777 the al <<
5778 have S <<
5779 unret - Force <<
5780 only e <<
5781 system <<
5782 unret,nosmt - Like u <<
5783 is not <<
5784 system <<
5785 3991
5786 Selecting 'auto' will 3992 Selecting 'auto' will choose a mitigation method at run
5787 time according to the 3993 time according to the CPU.
5788 3994
5789 Not specifying this o 3995 Not specifying this option is equivalent to retbleed=auto.
5790 3996
5791 rfkill.default_state= 3997 rfkill.default_state=
5792 0 "airplane mode". All 3998 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 3999 etc. communication is blocked by default.
5794 1 Unblocked. 4000 1 Unblocked.
5795 4001
5796 rfkill.master_switch_mode= 4002 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 4003 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 4004 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 4005 blocked and the previous configuration.
5800 2 The "airplane mode" b 4006 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 4007 blocked and everything unblocked.
5802 4008
>> 4009 rhash_entries= [KNL,NET]
>> 4010 Set number of hash buckets for route cache
>> 4011
5803 ring3mwait=disable 4012 ring3mwait=disable
5804 [KNL] Disable ring 3 4013 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 4014 CPUs.
5806 4015
5807 riscv_isa_fallback [RISCV,EARLY] <<
5808 When CONFIG_RISCV_ISA <<
5809 falling back to detec <<
5810 "riscv,isa" property <<
5811 replacement propertie <<
5812 entry for RISCV_ISA_F <<
5813 <<
5814 ro [KNL] Mount root devi 4016 ro [KNL] Mount root device read-only on boot
5815 4017
5816 rodata= [KNL,EARLY] !! 4018 rodata= [KNL]
5817 on Mark read-only kernel 4019 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 4020 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 4021
5822 rockchip.usb_uart 4022 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 4023 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 4024 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 4025 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 4026 port and the regular usb controller gets disabled.
5828 4027
5829 root= [KNL] Root filesystem 4028 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 4029 See name_to_dev_t comment in init/do_mounts.c.
5831 see the early_lookup_ <<
5832 block/early-lookup.c <<
5833 Alternatively this ca <<
5834 ramdisk, "nfs" and "c <<
5835 system, or "mtd" and <<
5836 4030
5837 rootdelay= [KNL] Delay (in secon 4031 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 4032 mount the root filesystem
5839 4033
5840 rootflags= [KNL] Set root filesy 4034 rootflags= [KNL] Set root filesystem mount option string
5841 4035
5842 rootfstype= [KNL] Set root filesy 4036 rootfstype= [KNL] Set root filesystem type
5843 4037
5844 rootwait [KNL] Wait (indefinit 4038 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 4039 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 4040 (e.g. USB and MMC devices).
5847 4041
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 4042 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 4043 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 4044 Memory area to be used by remote processor image,
5855 managed by CMA. 4045 managed by CMA.
5856 4046
5857 rw [KNL] Mount root devi 4047 rw [KNL] Mount root device read-write on boot
5858 4048
5859 S [KNL] Run init in sin 4049 S [KNL] Run init in single mode
5860 4050
5861 s390_iommu= [HW,S390] 4051 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 4052 Set s390 IOTLB flushing mode
5863 strict 4053 strict
5864 With strict flushing !! 4054 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 4055 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 4056 which is faster.
5867 iommu.strict=1. <<
5868 <<
5869 s390_iommu_aperture= [KNL,S390] <<
5870 Specifies the size of <<
5871 accessible through th <<
5872 factor of the size of <<
5873 The default is 1 mean <<
5874 as many DMA addresses <<
5875 if supported by hardw <<
5876 once. With a value of <<
5877 and so on. As a speci <<
5878 restrictions other th <<
5879 cost of significant a <<
5880 4057
5881 sa1100ir [NET] 4058 sa1100ir [NET]
5882 See drivers/net/irda/ 4059 See drivers/net/irda/sa1100_ir.c.
5883 4060
5884 sched_verbose [KNL,EARLY] Enables v !! 4061 sbni= [NET] Granch SBNI12 leased line adapter
>> 4062
>> 4063 sched_debug [KNL] Enables verbose scheduler debug messages.
5885 4064
5886 schedstats= [KNL,X86] Enable or d 4065 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 4066 Allowed values are enable and disable. This feature
5888 incurs a small amount 4067 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 4068 but is useful for debugging and performance tuning.
5890 4069
5891 sched_thermal_decay_shift= !! 4070 skew_tick= [KNL] Offset the periodic timer tick per cpu to mitigate
5892 [Deprecated] <<
5893 [KNL, SMP] Set a deca <<
5894 pressure signal. Ther <<
5895 default decay period <<
5896 signals(usually 32 ms <<
5897 sched_thermal_decay_s <<
5898 period for the therma <<
5899 value. <<
5900 i.e. with the default <<
5901 sched_thermal_decay_s <<
5902 1 <<
5903 2 <<
5904 and so on. <<
5905 Format: integer betwe <<
5906 Default is 0. <<
5907 <<
5908 scftorture.holdoff= [KNL] <<
5909 Number of seconds to <<
5910 test. Defaults to ze <<
5911 to 10 seconds for bui <<
5912 tests. <<
5913 <<
5914 scftorture.longwait= [KNL] <<
5915 Request ridiculously <<
5916 up to the chosen limi <<
5917 default) disables thi <<
5918 that requesting even <<
5919 seconds can result in <<
5920 softlockup complaints <<
5921 <<
5922 scftorture.nthreads= [KNL] <<
5923 Number of kthreads to <<
5924 smp_call_function() f <<
5925 The default of -1 spe <<
5926 equal to the number o <<
5927 <<
5928 scftorture.onoff_holdoff= [KNL] <<
5929 Number seconds to wai <<
5930 test before initiatin <<
5931 <<
5932 scftorture.onoff_interval= [KNL] <<
5933 Number seconds to wai <<
5934 CPU-hotplug operation <<
5935 is the default) disab <<
5936 <<
5937 scftorture.shutdown_secs= [KNL] <<
5938 The number of seconds <<
5939 test after which to s <<
5940 default of zero avoid <<
5941 Non-zero values are u <<
5942 <<
5943 scftorture.stat_interval= [KNL] <<
5944 The number of seconds <<
5945 current test statisti <<
5946 of zero disables stat <<
5947 <<
5948 scftorture.stutter_cpus= [KNL] <<
5949 The number of jiffies <<
5950 to the set of CPUs un <<
5951 <<
5952 scftorture.use_cpus_read_lock= [KNL] <<
5953 Use use_cpus_read_loc <<
5954 preempt_disable() to <<
5955 while invoking one of <<
5956 functions. <<
5957 <<
5958 scftorture.verbose= [KNL] <<
5959 Enable additional pri <<
5960 <<
5961 scftorture.weight_single= [KNL] <<
5962 The probability weigh <<
5963 smp_call_function_sin <<
5964 "wait" parameter. A <<
5965 default if all other <<
5966 if at least one weigh <<
5967 value of -1 will inst <<
5968 <<
5969 scftorture.weight_single_wait= [KNL] <<
5970 The probability weigh <<
5971 smp_call_function_sin <<
5972 non-zero "wait" param <<
5973 <<
5974 scftorture.weight_many= [KNL] <<
5975 The probability weigh <<
5976 smp_call_function_man <<
5977 "wait" parameter. Se <<
5978 Note well that settin <<
5979 this weighting can pl <<
5980 on the system. <<
5981 <<
5982 scftorture.weight_many_wait= [KNL] <<
5983 The probability weigh <<
5984 smp_call_function_man <<
5985 non-zero "wait" param <<
5986 and weight_many. <<
5987 <<
5988 scftorture.weight_all= [KNL] <<
5989 The probability weigh <<
5990 smp_call_function_all <<
5991 "wait" parameter. Se <<
5992 weight_many. <<
5993 <<
5994 scftorture.weight_all_wait= [KNL] <<
5995 The probability weigh <<
5996 smp_call_function_all <<
5997 non-zero "wait" param <<
5998 and weight_many. <<
5999 <<
6000 skew_tick= [KNL,EARLY] Offset th <<
6001 xtime_lock contention 4071 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 4072 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 4073 Format: { "0" | "1" }
6004 0 -- disable. (may be 4074 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 4075 1 -- enable.
6006 Note: increases power 4076 Note: increases power consumption, thus should only be
6007 enabled if running ji 4077 enabled if running jitter sensitive (HPC/RT) workloads.
6008 4078
6009 security= [SECURITY] Choose a l !! 4079 security= [SECURITY] Choose a security module to enable at boot.
6010 enable at boot. This !! 4080 If this boot parameter is not specified, only the first
6011 "lsm=" parameter. !! 4081 security module asking for security registration will be
>> 4082 loaded. An invalid security module name will be treated
>> 4083 as if no module has been chosen.
6012 4084
6013 selinux= [SELINUX] Disable or 4085 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 4086 Format: { "0" | "1" }
6015 See security/selinux/ 4087 See security/selinux/Kconfig help text.
6016 0 -- disable. 4088 0 -- disable.
6017 1 -- enable. 4089 1 -- enable.
6018 Default value is 1. !! 4090 Default value is set via kernel config option.
>> 4091 If enabled at boot time, /selinux/disable can be used
>> 4092 later to disable prior to initial policy load.
6019 4093
6020 serialnumber [BUGS=X86-32] !! 4094 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 4095 Format: { "0" | "1" }
>> 4096 See security/apparmor/Kconfig help text
>> 4097 0 -- disable.
>> 4098 1 -- enable.
>> 4099 Default value is set via kernel config option.
6021 4100
6022 sev=option[,option...] [X86-64] See D !! 4101 serialnumber [BUGS=X86-32]
6023 4102
6024 shapers= [NET] 4103 shapers= [NET]
6025 Maximal number of sha 4104 Maximal number of shapers.
6026 4105
6027 show_lapic= [APIC,X86] Advanced P !! 4106 simeth= [IA-64]
6028 Limit apic dumping. T !! 4107 simscsi=
6029 number of local apics !! 4108
6030 to set it to "all" by !! 4109 slram= [HW,MTD]
6031 Format: { 1 (default) !! 4110
6032 The parameter valid i !! 4111 slab_nomerge [MM]
6033 apic=verbose is speci !! 4112 Disable merging of slabs with similar size. May be
6034 Example: apic=debug s !! 4113 necessary if there is some reason to distinguish
>> 4114 allocs to different slabs, especially in hardened
>> 4115 environments where the risk of heap overflows and
>> 4116 layout control by attackers can usually be
>> 4117 frustrated by disabling merging. This will reduce
>> 4118 most of the exposure of a heap attack to a single
>> 4119 cache (risks via metadata attacks are mostly
>> 4120 unchanged). Debug options disable merging on their
>> 4121 own.
>> 4122 For more information see Documentation/vm/slub.txt.
>> 4123
>> 4124 slab_max_order= [MM, SLAB]
>> 4125 Determines the maximum allowed order for slabs.
>> 4126 A high setting may cause OOMs due to memory
>> 4127 fragmentation. Defaults to 1 for systems with
>> 4128 more than 32MB of RAM, 0 otherwise.
6035 4129
6036 slab_debug[=options[,slabs][;[options !! 4130 slub_debug[=options[,slabs]] [MM, SLUB]
6037 Enabling slab_debug a !! 4131 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 4132 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 4133 slub_debug can create guard zones around objects and
6040 may poison objects wh 4134 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 4135 last alloc / free. For more information see
6042 Documentation/mm/slub !! 4136 Documentation/vm/slub.txt.
6043 (slub_debug legacy na <<
6044 4137
6045 slab_max_order= [MM] !! 4138 slub_memcg_sysfs= [MM, SLUB]
>> 4139 Determines whether to enable sysfs directories for
>> 4140 memory cgroup sub-caches. 1 to enable, 0 to disable.
>> 4141 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
>> 4142 Enabling this can lead to a very high number of debug
>> 4143 directories and files being created under
>> 4144 /sys/kernel/slub.
>> 4145
>> 4146 slub_max_order= [MM, SLUB]
6046 Determines the maximu 4147 Determines the maximum allowed order for slabs.
6047 A high setting may ca 4148 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 4149 fragmentation. For more information see
6049 Documentation/mm/slub !! 4150 Documentation/vm/slub.txt.
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 4151
6057 slab_min_objects= [MM] !! 4152 slub_min_objects= [MM, SLUB]
6058 The minimum number of 4153 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 4154 increase the slab order up to slub_max_order to
6060 generate a sufficient 4155 generate a sufficiently large slab able to contain
6061 the number of objects 4156 the number of objects indicated. The higher the number
6062 of objects the smalle 4157 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 4158 and the less frequently locks need to be acquired.
6064 For more information !! 4159 For more information see Documentation/vm/slub.txt.
6065 (slub_min_objects leg <<
6066 4160
6067 slab_min_order= [MM] !! 4161 slub_min_order= [MM, SLUB]
6068 Determines the minimu 4162 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 4163 lower than slub_max_order.
6070 Documentation/mm/slub !! 4164 For more information see Documentation/vm/slub.txt.
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 <<
6085 (slub_nomerge legacy <<
6086 4165
6087 slram= [HW,MTD] !! 4166 slub_nomerge [MM, SLUB]
>> 4167 Same with slab_nomerge. This is supported for legacy.
>> 4168 See slab_nomerge for more information.
6088 4169
6089 smart2= [HW] 4170 smart2= [HW]
6090 Format: <io1>[,<io2>[ 4171 Format: <io1>[,<io2>[,...,<io8>]]
6091 4172
6092 smp.csd_lock_timeout= [KNL] <<
6093 Specify the period of <<
6094 that smp_call_functio <<
6095 for a CPU to release <<
6096 useful when diagnosin <<
6097 disabling interrupts <<
6098 of time. Defaults to <<
6099 setting a value of ze <<
6100 This feature may be m <<
6101 using the csdlock_deb <<
6102 <<
6103 smp.panic_on_ipistall= [KNL] <<
6104 If a csd_lock_timeout <<
6105 the specified number <<
6106 system. By default, <<
6107 take as long as they <<
6108 for this value provid <<
6109 <<
6110 smsc-ircc2.nopnp [HW] Don't us 4173 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 4174 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 4175 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 4176 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 4177 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 4178 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 4179 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 4180 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 4181 1: Fast pin select (default)
6119 2: ATC IRMode 4182 2: ATC IRMode
6120 4183
6121 smt= [KNL,MIPS,S390,EARLY] !! 4184 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 4185 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 4186 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 4187 actual hardware limit.
6125 Format: <integer> 4188 Format: <integer>
6126 Default: -1 (no limit 4189 Default: -1 (no limit)
6127 4190
6128 softlockup_panic= 4191 softlockup_panic=
6129 [KNL] Should the soft 4192 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 !! 4193 Format: <integer>
6131 <<
6132 A value of 1 instruct <<
6133 to panic the machine <<
6134 also controlled by th <<
6135 and CONFIG_BOOTPARAM_ <<
6136 respective build-time <<
6137 4194
6138 softlockup_all_cpu_backtrace= 4195 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 4196 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 4197 backtraces on all cpus.
6141 Format: 0 | 1 !! 4198 Format: <integer>
6142 4199
6143 sonypi.*= [HW] Sony Programmabl 4200 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm !! 4201 See Documentation/laptops/sonypi.txt
6145 <<
6146 spectre_bhi= [X86] Control mitigat <<
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 4202
6161 spectre_v2= [X86,EARLY] Control m !! 4203 spectre_v2= [X86] Control mitigation of Spectre variant 2
6162 (indirect branch spec 4204 (indirect branch speculation) vulnerability.
6163 The default operation 4205 The default operation protects the kernel from
6164 user space attacks. 4206 user space attacks.
6165 4207
6166 on - unconditionall 4208 on - unconditionally enable, implies
6167 spectre_v2_use 4209 spectre_v2_user=on
6168 off - unconditionall 4210 off - unconditionally disable, implies
6169 spectre_v2_use 4211 spectre_v2_user=off
6170 auto - kernel detects 4212 auto - kernel detects whether your CPU model is
6171 vulnerable 4213 vulnerable
6172 4214
6173 Selecting 'on' will, 4215 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 4216 mitigation method at run time according to the
6175 CPU, the available mi 4217 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 4218 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 4219 compiler with which the kernel was built.
6178 4220
6179 Selecting 'on' will a 4221 Selecting 'on' will also enable the mitigation
6180 against user space to 4222 against user space to user space task attacks.
6181 4223
6182 Selecting 'off' will 4224 Selecting 'off' will disable both the kernel and
6183 the user space protec 4225 the user space protections.
6184 4226
6185 Specific mitigations 4227 Specific mitigations can also be selected manually:
6186 4228
6187 retpoline - r 4229 retpoline - replace indirect branches
6188 retpoline,generic - R 4230 retpoline,generic - Retpolines
6189 retpoline,lfence - L 4231 retpoline,lfence - LFENCE; indirect branch
6190 retpoline,amd - a 4232 retpoline,amd - alias for retpoline,lfence
6191 eibrs - E !! 4233 eibrs - enhanced IBRS
6192 eibrs,retpoline - E !! 4234 eibrs,retpoline - enhanced IBRS + Retpolines
6193 eibrs,lfence - E !! 4235 eibrs,lfence - enhanced IBRS + LFENCE
6194 ibrs - u 4236 ibrs - use IBRS to protect kernel
6195 4237
6196 Not specifying this o 4238 Not specifying this option is equivalent to
6197 spectre_v2=auto. 4239 spectre_v2=auto.
6198 4240
6199 spectre_v2_user= 4241 spectre_v2_user=
6200 [X86] Control mitigat 4242 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 4243 (indirect branch speculation) vulnerability between
6202 user space tasks 4244 user space tasks
6203 4245
6204 on - Uncondition 4246 on - Unconditionally enable mitigations. Is
6205 enforced by 4247 enforced by spectre_v2=on
6206 4248
6207 off - Uncondition 4249 off - Unconditionally disable mitigations. Is
6208 enforced by 4250 enforced by spectre_v2=off
6209 4251
6210 prctl - Indirect br 4252 prctl - Indirect branch speculation is enabled,
6211 but mitigat 4253 but mitigation can be enabled via prctl
6212 per thread. 4254 per thread. The mitigation control state
6213 is inherite 4255 is inherited on fork.
6214 4256
6215 prctl,ibpb 4257 prctl,ibpb
6216 - Like "prctl 4258 - Like "prctl" above, but only STIBP is
6217 controlled 4259 controlled per thread. IBPB is issued
6218 always when 4260 always when switching between different user
6219 space proce 4261 space processes.
6220 4262
6221 seccomp 4263 seccomp
6222 - Same as "pr 4264 - Same as "prctl" above, but all seccomp
6223 threads wil 4265 threads will enable the mitigation unless
6224 they explic 4266 they explicitly opt out.
6225 4267
6226 seccomp,ibpb 4268 seccomp,ibpb
6227 - Like "secco 4269 - Like "seccomp" above, but only STIBP is
6228 controlled 4270 controlled per thread. IBPB is issued
6229 always when 4271 always when switching between different
6230 user space 4272 user space processes.
6231 4273
6232 auto - Kernel sele 4274 auto - Kernel selects the mitigation depending on
6233 the availab 4275 the available CPU features and vulnerability.
6234 4276
6235 Default mitigation: " !! 4277 Default mitigation:
>> 4278 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
6236 4279
6237 Not specifying this o 4280 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 4281 spectre_v2_user=auto.
6239 4282
6240 spec_rstack_overflow= <<
6241 [X86,EARLY] Control R <<
6242 <<
6243 off - Dis <<
6244 microcode - Ena <<
6245 safe-ret - Ena <<
6246 ibpb - Ena <<
6247 ker <<
6248 ibpb-vmexit - Iss <<
6249 (cl <<
6250 <<
6251 spec_store_bypass_disable= 4283 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 4284 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 4285 (Speculative Store Bypass vulnerability)
6254 4286
6255 Certain CPUs are vuln 4287 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 4288 a common industry wide performance optimization known
6257 as "Speculative Store 4289 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 4290 to the same memory location may not be observed by
6259 later loads during sp 4291 later loads during speculative execution. The idea
6260 is that such stores a 4292 is that such stores are unlikely and that they can
6261 be detected prior to 4293 be detected prior to instruction retirement at the
6262 end of a particular s 4294 end of a particular speculation execution window.
6263 4295
6264 In vulnerable process 4296 In vulnerable processors, the speculatively forwarded
6265 store can be used in 4297 store can be used in a cache side channel attack, for
6266 example to read memor 4298 example to read memory to which the attacker does not
6267 directly have access 4299 directly have access (e.g. inside sandboxed code).
6268 4300
6269 This parameter contro 4301 This parameter controls whether the Speculative Store
6270 Bypass optimization i 4302 Bypass optimization is used.
6271 4303
6272 On x86 the options ar <<
6273 <<
6274 on - Uncondition 4304 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 4305 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 4306 auto - Kernel detects whether the CPU model contains an
6277 implementat 4307 implementation of Speculative Store Bypass and
6278 picks the m 4308 picks the most appropriate mitigation. If the
6279 CPU is not 4309 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 4310 CPU is vulnerable the default mitigation is
6281 architectur 4311 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 4312 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 4313 via prctl. Speculative Store Bypass is enabled
6284 for a proce 4314 for a process by default. The state of the control
6285 is inherite 4315 is inherited on fork.
6286 seccomp - Same as "pr 4316 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 4317 will disable SSB unless they explicitly opt out.
6288 4318
6289 Default mitigations: <<
6290 X86: "prctl" <<
6291 <<
6292 On powerpc the option <<
6293 <<
6294 on,auto - On Power8 a <<
6295 barrier on <<
6296 perform a s <<
6297 exit. <<
6298 off - No action. <<
6299 <<
6300 Not specifying this o 4319 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 4320 spec_store_bypass_disable=auto.
6302 4321
6303 split_lock_detect= !! 4322 Default mitigations:
6304 [X86] Enable split lo !! 4323 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6305 <<
6306 When enabled (and if <<
6307 instructions that acc <<
6308 boundaries will resul <<
6309 for split lock detect <<
6310 bus lock detection. <<
6311 <<
6312 off - not enabled <<
6313 <<
6314 warn - the kernel <<
6315 about appli <<
6316 exception o <<
6317 the default <<
6318 detection o <<
6319 behavior is <<
6320 enabled in <<
6321 <<
6322 fatal - the kernel <<
6323 that trigge <<
6324 exception. <<
6325 both featur <<
6326 <<
6327 ratelimit:N - <<
6328 Set system <<
6329 per second <<
6330 0 < N <= 10 <<
6331 <<
6332 N/A for spl <<
6333 <<
6334 <<
6335 If an #AC exception i <<
6336 firmware (i.e. not wh <<
6337 the kernel will oops <<
6338 mode. <<
6339 4324
6340 #DB exception for bus !! 4325 spia_io_base= [HW,MTD]
6341 CPL > 0. !! 4326 spia_fio_base=
>> 4327 spia_pedr=
>> 4328 spia_peddr=
6342 4329
6343 srbds= [X86,INTEL,EARLY] !! 4330 srbds= [X86,INTEL]
6344 Control the Special R 4331 Control the Special Register Buffer Data Sampling
6345 (SRBDS) mitigation. 4332 (SRBDS) mitigation.
6346 4333
6347 Certain CPUs are vuln 4334 Certain CPUs are vulnerable to an MDS-like
6348 exploit which can lea 4335 exploit which can leak bits from the random
6349 number generator. 4336 number generator.
6350 4337
6351 By default, this issu 4338 By default, this issue is mitigated by
6352 microcode. However, 4339 microcode. However, the microcode fix can cause
6353 the RDRAND and RDSEED 4340 the RDRAND and RDSEED instructions to become
6354 much slower. Among o 4341 much slower. Among other effects, this will
6355 result in reduced thr 4342 result in reduced throughput from /dev/urandom.
6356 4343
6357 The microcode mitigat 4344 The microcode mitigation can be disabled with
6358 the following option: 4345 the following option:
6359 4346
6360 off: Disable mitig 4347 off: Disable mitigation and remove
6361 performance i 4348 performance impact to RDRAND and RDSEED
6362 4349
6363 srcutree.big_cpu_lim [KNL] <<
6364 Specifies the number <<
6365 large system, such th <<
6366 should immediately al <<
6367 This kernel-boot para <<
6368 but takes effect only <<
6369 bits of srcutree.conv <<
6370 (decide at boot). <<
6371 <<
6372 srcutree.convert_to_big [KNL] <<
6373 Specifies under what <<
6374 srcu_struct structure <<
6375 form, that is, with a <<
6376 <<
6377 0: Never. <<
6378 1: At ini <<
6379 2: When r <<
6380 3: Decide <<
6381 0x1X: Above <<
6382 <<
6383 Either way, the srcu_ <<
6384 on the actual runtime <<
6385 instead of the compil <<
6386 <<
6387 srcutree.counter_wrap_check [KNL] 4350 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 4351 Specifies how frequently to check for
6389 grace-period sequence 4352 grace-period sequence counter wrap for the
6390 srcu_data structure's 4353 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 4354 The greater the number of bits set in this kernel
6392 parameter, the less f 4355 parameter, the less frequently counter wrap will
6393 be checked for. Note 4356 be checked for. Note that the bottom two bits
6394 are ignored. 4357 are ignored.
6395 4358
6396 srcutree.exp_holdoff [KNL] 4359 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 4360 Specifies how many nanoseconds must elapse
6398 since the end of the 4361 since the end of the last SRCU grace period for
6399 a given srcu_struct u 4362 a given srcu_struct until the next normal SRCU
6400 grace period will be 4363 grace period will be considered for automatic
6401 expediting. Set to z 4364 expediting. Set to zero to disable automatic
6402 expediting. 4365 expediting.
6403 4366
6404 srcutree.srcu_max_nodelay [KNL] !! 4367 ssbd= [ARM64,HW]
6405 Specifies the number <<
6406 per jiffy for which t <<
6407 worker thread will be <<
6408 delay. Beyond this li <<
6409 be rescheduled with a <<
6410 <<
6411 srcutree.srcu_max_nodelay_phase [KNL] <<
6412 Specifies the per-gra <<
6413 non-sleeping polls of <<
6414 grace period worker t <<
6415 with a sleep delay of <<
6416 rescan of the readers <<
6417 <<
6418 srcutree.srcu_retry_check_delay [KNL] <<
6419 Specifies number of m <<
6420 delay between each no <<
6421 <<
6422 srcutree.small_contention_lim [KNL] <<
6423 Specifies the number <<
6424 events per jiffy will <<
6425 initiating a conversi <<
6426 structure to big form <<
6427 srcutree.convert_to_b <<
6428 set for contention-ba <<
6429 <<
6430 ssbd= [ARM64,HW,EARLY] <<
6431 Speculative Store Byp 4368 Speculative Store Bypass Disable control
6432 4369
6433 On CPUs that are vuln 4370 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 4371 Store Bypass vulnerability and offer a
6435 firmware based mitiga 4372 firmware based mitigation, this parameter
6436 indicates how the mit 4373 indicates how the mitigation should be used:
6437 4374
6438 force-on: Unconditio 4375 force-on: Unconditionally enable mitigation for
6439 for both k 4376 for both kernel and userspace
6440 force-off: Unconditio 4377 force-off: Unconditionally disable mitigation for
6441 for both k 4378 for both kernel and userspace
6442 kernel: Always ena 4379 kernel: Always enable mitigation in the
6443 kernel, an 4380 kernel, and offer a prctl interface
6444 to allow u 4381 to allow userspace to register its
6445 interest i 4382 interest in being mitigated too.
6446 4383
6447 stack_guard_gap= [MM] 4384 stack_guard_gap= [MM]
6448 override the default 4385 override the default stack gap protection. The value
6449 is in page units and 4386 is in page units and it defines how many pages prior
6450 to (for stacks growin 4387 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 4388 growing up) the main stack are reserved for no other
6452 mapping. Default valu 4389 mapping. Default value is 256 pages.
6453 4390
6454 stack_depot_disable= [KNL,EARLY] <<
6455 Setting this to true <<
6456 disable the stack dep <<
6457 consumed by the stack <<
6458 to false. <<
6459 <<
6460 stacktrace [FTRACE] 4391 stacktrace [FTRACE]
6461 Enabled the stack tra 4392 Enabled the stack tracer on boot up.
6462 4393
6463 stacktrace_filter=[function-list] 4394 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 4395 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up !! 4396 will trace at boot up. function-list is a comma separated
6466 list of functions. Th 4397 list of functions. This list can be changed at run
6467 time by the stack_tra 4398 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 4399 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 4400 and the stacktrace above is not needed.
6470 4401
6471 sti= [PARISC,HW] 4402 sti= [PARISC,HW]
6472 Format: <num> 4403 Format: <num>
6473 Set the STI (builtin 4404 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 4405 machines) console (graphic card) which should be used
6475 as the initial boot-c 4406 as the initial boot-console.
6476 See also comment in d 4407 See also comment in drivers/video/console/sticore.c.
6477 4408
6478 sti_font= [HW] 4409 sti_font= [HW]
6479 See comment in driver 4410 See comment in drivers/video/console/sticore.c.
6480 4411
6481 stifb= [HW] 4412 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 4413 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 4414
6484 strict_sas_size= <<
6485 [X86] <<
6486 Format: <bool> <<
6487 Enable or disable str <<
6488 against the required <<
6489 depends on the suppor <<
6490 be used to filter out <<
6491 not yet been made awa <<
6492 <<
6493 stress_hpt [PPC,EARLY] <<
6494 Limits the number of <<
6495 page table to increas <<
6496 faults on kernel addr <<
6497 <<
6498 stress_slb [PPC,EARLY] <<
6499 Limits the number of <<
6500 them frequently to in <<
6501 on kernel addresses. <<
6502 <<
6503 sunrpc.min_resvport= 4415 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 4416 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 4417 [NFS,SUNRPC]
6506 SunRPC servers often 4418 SunRPC servers often require that client requests
6507 originate from a priv 4419 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 4420 range 0 < portnr < 1024).
6509 An administrator who 4421 An administrator who wishes to reserve some of these
6510 ports for other uses 4422 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 4423 kernel's sunrpc client considers to be privileged
6512 using these two param 4424 using these two parameters to set the minimum and
6513 maximum port values. 4425 maximum port values.
6514 4426
6515 sunrpc.svc_rpc_per_connection_limit= 4427 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 4428 [NFS,SUNRPC]
6517 Limit the number of r 4429 Limit the number of requests that the server will
6518 process in parallel f 4430 process in parallel from a single connection.
6519 The default value is 4431 The default value is 0 (no limit).
6520 4432
6521 sunrpc.pool_mode= 4433 sunrpc.pool_mode=
6522 [NFS] 4434 [NFS]
6523 Control how the NFS s 4435 Control how the NFS server code allocates CPUs to
6524 service thread pools. 4436 service thread pools. Depending on how many NICs
6525 you have and where th 4437 you have and where their interrupts are bound, this
6526 option will affect wh 4438 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 4439 Note: this parameter cannot be changed while the
6528 NFS server is running 4440 NFS server is running.
6529 4441
6530 auto the serve 4442 auto the server chooses an appropriate mode
6531 automatic 4443 automatically using heuristics
6532 global a single 4444 global a single global pool contains all CPUs
6533 percpu one pool 4445 percpu one pool for each CPU
6534 pernode one pool 4446 pernode one pool for each NUMA node (equivalent
6535 to global 4447 to global on non-NUMA machines)
6536 4448
6537 sunrpc.tcp_slot_table_entries= 4449 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 4450 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 4451 [NFS,SUNRPC]
6540 Sets the upper limit 4452 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 4453 RPC calls that can be sent from the client to a
6542 server. Increasing th 4454 server. Increasing these values may allow you to
6543 improve throughput, b 4455 improve throughput, but will also increase the
6544 amount of memory rese 4456 amount of memory reserved for use by the client.
6545 4457
6546 suspend.pm_test_delay= 4458 suspend.pm_test_delay=
6547 [SUSPEND] 4459 [SUSPEND]
6548 Sets the number of se 4460 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 4461 mode before resuming the system (see
6550 /sys/power/pm_test). 4462 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 4463 is set. Default value is 5.
6552 4464
6553 svm= [PPC] !! 4465 swapaccount=[0|1]
6554 Format: { on | off | !! 4466 [KNL] Enable accounting of swap in memory resource
6555 This parameter contro !! 4467 controller if no parameter or 1 is given or disable
6556 Execution Facility on !! 4468 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
6557 4469
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 4470 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in !! 4471 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 4472 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 4473 force -- force using of bounce buffers even if they
6565 wouldn't be 4474 wouldn't be automatically used by the kernel
6566 noforce -- Never use 4475 noforce -- Never use bounce buffers (for debugging)
6567 4476
6568 switches= [HW,M68k,EARLY] !! 4477 switches= [HW,M68k]
6569 4478
6570 sysctl.*= [KNL] !! 4479 sysfs.deprecated=0|1 [KNL]
6571 Set a sysctl paramete !! 4480 Enable/disable old style sysfs layout for old udev
6572 process, as if the va !! 4481 on older distributions. When this option is enabled
6573 /proc/sys/... file. B !! 4482 very new udev will not work anymore. When this option
6574 separators. Unrecogni !! 4483 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
6575 are reported in the k !! 4484 in older udev will not work anymore.
6576 later by a loaded mod !! 4485 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
6577 Example: sysctl.vm.sw !! 4486 the kernel configuration.
6578 4487
6579 sysrq_always_enabled 4488 sysrq_always_enabled
6580 [KNL] 4489 [KNL]
6581 Ignore sysrq setting 4490 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 4491 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 4492 Useful for debugging.
6584 4493
6585 tcpmhash_entries= [KNL,NET] 4494 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 4495 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 4496 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 4497 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum !! 4498 cache size. See Documentation/networking/ip-sysctl.txt
6590 "tcp_no_metrics_save" 4499 "tcp_no_metrics_save" section for more details.
6591 4500
6592 tdfx= [HW,DRM] 4501 tdfx= [HW,DRM]
6593 4502
6594 test_suspend= [SUSPEND] !! 4503 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 4504 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 4505 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 4506 as the system sleep state during system startup with
6599 the optional capabili 4507 the optional capability to repeat N number of times.
6600 The system is woken f 4508 The system is woken from this state using a
6601 wakeup-capable RTC al 4509 wakeup-capable RTC alarm.
6602 4510
6603 thash_entries= [KNL,NET] 4511 thash_entries= [KNL,NET]
6604 Set number of hash bu 4512 Set number of hash buckets for TCP connection
6605 4513
6606 thermal.act= [HW,ACPI] 4514 thermal.act= [HW,ACPI]
6607 -1: disable all activ 4515 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 4516 <degrees C>: override all lowest active trip points
6609 4517
6610 thermal.crt= [HW,ACPI] 4518 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 4519 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 4520 <degrees C>: override all critical trip points
6613 4521
>> 4522 thermal.nocrt= [HW,ACPI]
>> 4523 Set to disable actions on ACPI thermal zone
>> 4524 critical and hot trip points.
>> 4525
6614 thermal.off= [HW,ACPI] 4526 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 4527 1: disable ACPI thermal control
6616 4528
6617 thermal.psv= [HW,ACPI] 4529 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 4530 -1: disable all passive trip points
6619 <degrees C>: override 4531 <degrees C>: override all passive trip points to this
6620 value 4532 value
6621 4533
6622 thermal.tzp= [HW,ACPI] 4534 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 4535 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 4536 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 4537 0: no polling (default)
6626 4538
6627 threadirqs [KNL,EARLY] !! 4539 threadirqs [KNL]
6628 Force threading of al 4540 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 4541 marked explicitly IRQF_NO_THREAD.
6630 4542
6631 topology= [S390,EARLY] !! 4543 tmem [KNL,XEN]
>> 4544 Enable the Transcendent memory driver if built-in.
>> 4545
>> 4546 tmem.cleancache=0|1 [KNL, XEN]
>> 4547 Default is on (1). Disable the usage of the cleancache
>> 4548 API to send anonymous pages to the hypervisor.
>> 4549
>> 4550 tmem.frontswap=0|1 [KNL, XEN]
>> 4551 Default is on (1). Disable the usage of the frontswap
>> 4552 API to send swap pages to the hypervisor. If disabled
>> 4553 the selfballooning and selfshrinking are force disabled.
>> 4554
>> 4555 tmem.selfballooning=0|1 [KNL, XEN]
>> 4556 Default is on (1). Disable the driving of swap pages
>> 4557 to the hypervisor.
>> 4558
>> 4559 tmem.selfshrinking=0|1 [KNL, XEN]
>> 4560 Default is on (1). Partial swapoff that immediately
>> 4561 transfers pages from Xen hypervisor back to the
>> 4562 kernel based on different criteria.
>> 4563
>> 4564 topology= [S390]
6632 Format: {off | on} 4565 Format: {off | on}
6633 Specify if the kernel 4566 Specify if the kernel should make use of the cpu
6634 topology information 4567 topology information if the hardware supports this.
6635 The scheduler will ma 4568 The scheduler will make use of this information and
6636 e.g. base its process 4569 e.g. base its process migration decisions on it.
6637 Default is on. 4570 Default is on.
6638 4571
6639 torture.disable_onoff_at_boot= [KNL] !! 4572 topology_updates= [KNL, PPC, NUMA]
6640 Prevent the CPU-hotpl !! 4573 Format: {off}
6641 until after init has !! 4574 Specify if the kernel should ignore (off)
6642 !! 4575 topology updates sent by the hypervisor to this
6643 torture.ftrace_dump_at_shutdown= [KNL !! 4576 LPAR.
6644 Dump the ftrace buffe <<
6645 even if there were no <<
6646 very costly operation <<
6647 are running concurren <<
6648 with rotating-rust st <<
6649 <<
6650 torture.verbose_sleep_frequency= [KNL <<
6651 Specifies how many ve <<
6652 emitted between each <<
6653 disables verbose-prin <<
6654 4577
6655 torture.verbose_sleep_duration= [KNL] !! 4578 tp720= [HW,PS2]
6656 Duration of each verb <<
6657 4579
6658 tpm_suspend_pcr=[HW,TPM] 4580 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 4581 Format: integer pcr id
6660 Specify that at suspe 4582 Specify that at suspend time, the tpm driver
6661 should extend the spe 4583 should extend the specified pcr with zeros,
6662 as a workaround for s 4584 as a workaround for some chips which fail to
6663 flush the last writte 4585 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 4586 This will guarantee that all the other pcrs
6665 are saved. 4587 are saved.
6666 4588
6667 tpm_tis.interrupts= [HW,TPM] <<
6668 Enable interrupts for <<
6669 for the FIFO interfac <<
6670 (0). For more informa <<
6671 defined by Trusted Co <<
6672 https://trustedcomput <<
6673 <<
6674 tp_printk [FTRACE] <<
6675 Have the tracepoints <<
6676 tracing ring buffer. <<
6677 where the system hang <<
6678 option for reading th <<
6679 ftrace_dump_on_oops. <<
6680 <<
6681 To turn off having tr <<
6682 echo 0 > /proc/sys/k <<
6683 Note, echoing 1 into <<
6684 tp_printk kernel cmdl <<
6685 <<
6686 The tp_printk_stop_on <<
6687 to stop the printing <<
6688 late_initcall_sync. <<
6689 <<
6690 ** CAUTION ** <<
6691 <<
6692 Having tracepoints se <<
6693 frequency tracepoints <<
6694 the system to live lo <<
6695 <<
6696 tp_printk_stop_on_boot [FTRACE] <<
6697 When tp_printk (above <<
6698 on the console. It ma <<
6699 printing of events du <<
6700 make the system inope <<
6701 <<
6702 This command line opt <<
6703 to console at the lat <<
6704 <<
6705 trace_buf_size=nn[KMG] 4589 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 4590 [FTRACE] will set tracing buffer size on each cpu.
6707 4591
6708 trace_clock= [FTRACE] Set the cloc <<
6709 at boot up. <<
6710 local - Use the per C <<
6711 (converted in <<
6712 depending on <<
6713 in sync betwe <<
6714 global - Event time s <<
6715 CPUs. May be <<
6716 but better fo <<
6717 counter - Simple coun <<
6718 note, some co <<
6719 infrastructur <<
6720 once per even <<
6721 uptime - Use jiffies <<
6722 perf - Use the same c <<
6723 mono - Use ktime_get_ <<
6724 mono_raw - Use ktime_ <<
6725 stamps. <<
6726 boot - Use ktime_get_ <<
6727 Architectures may add <<
6728 Documentation/trace/f <<
6729 <<
6730 trace_event=[event-list] 4592 trace_event=[event-list]
6731 [FTRACE] Set and star 4593 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 4594 to facilitate early boot debugging. The event-list is a
6733 comma-separated list !! 4595 comma separated list of trace events to enable. See
6734 also Documentation/tr !! 4596 also Documentation/trace/events.txt
6735 <<
6736 trace_instance=[instance-info] <<
6737 [FTRACE] Create a rin <<
6738 This will be listed i <<
6739 <<
6740 /sys/kernel/t <<
6741 <<
6742 Events can be enabled <<
6743 via: <<
6744 <<
6745 trace_instanc <<
6746 <<
6747 Note, the "<system*>: <<
6748 unique. <<
6749 <<
6750 trace_instanc <<
6751 <<
6752 will enable the "sche <<
6753 the same thing would <<
6754 event, and all events <<
6755 4597
6756 trace_options=[option-list] 4598 trace_options=[option-list]
6757 [FTRACE] Enable or di 4599 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 4600 The option-list is a comma delimited list of options
6759 that can be enabled o 4601 that can be enabled or disabled just as if you were
6760 to echo the option na 4602 to echo the option name into
6761 4603
6762 /sys/kernel/traci !! 4604 /sys/kernel/debug/tracing/trace_options
6763 4605
6764 For example, to enabl 4606 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 4607 stack trace of each event), add to the command line:
6766 4608
6767 trace_options=s 4609 trace_options=stacktrace
6768 4610
6769 See also Documentatio !! 4611 See also Documentation/trace/ftrace.txt "trace options"
6770 section. 4612 section.
6771 4613
6772 trace_trigger=[trigger-list] !! 4614 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 4615 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 4616 tracing ring buffer. This is useful for early boot up
6775 filter. !! 4617 where the system hangs or reboots and does not give the
6776 !! 4618 option for reading the tracing buffer or performing a
6777 The format is is "tra !! 4619 ftrace_dump_on_oops.
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 4620
6784 The above will enable !! 4621 To turn off having tracepoints sent to printk,
6785 event but only trigge !! 4622 echo 0 > /proc/sys/kernel/tracepoint_printk
6786 event is "2" (TASK_UN !! 4623 Note, echoing 1 into this file without the
>> 4624 tracepoint_printk kernel cmdline option has no effect.
6787 4625
6788 See also "Event trigg !! 4626 ** CAUTION **
6789 4627
>> 4628 Having tracepoints sent to printk() and activating high
>> 4629 frequency tracepoints such as irq or sched, can cause
>> 4630 the system to live lock.
6790 4631
6791 traceoff_on_warning 4632 traceoff_on_warning
6792 [FTRACE] enable this 4633 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 4634 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 4635 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 4636 file located in /sys/kernel/debug/tracing/
6796 4637
6797 This option is useful 4638 This option is useful, as it disables the trace before
6798 the WARNING dump is c 4639 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 4640 be filled with content caused by the warning output.
6800 4641
6801 This option can also 4642 This option can also be set at run time via the sysctl
6802 option: kernel/trace 4643 option: kernel/traceoff_on_warning
6803 4644
6804 transparent_hugepage= 4645 transparent_hugepage=
6805 [KNL] 4646 [KNL]
6806 Format: [always|madvi 4647 Format: [always|madvise|never]
6807 Can be used to contro 4648 Can be used to control the default behavior of the system
6808 with respect to trans 4649 with respect to transparent hugepages.
6809 See Documentation/adm !! 4650 See Documentation/vm/transhuge.txt for more details.
6810 for more details. <<
6811 <<
6812 trusted.source= [KEYS] <<
6813 Format: <string> <<
6814 This parameter identi <<
6815 for trusted keys impl <<
6816 sources: <<
6817 - "tpm" <<
6818 - "tee" <<
6819 - "caam" <<
6820 - "dcp" <<
6821 If not specified then <<
6822 the trust source list <<
6823 first trust source as <<
6824 successfully during i <<
6825 <<
6826 trusted.rng= [KEYS] <<
6827 Format: <string> <<
6828 The RNG used to gener <<
6829 Can be one of: <<
6830 - "kernel" <<
6831 - the same value as t <<
6832 - "default" <<
6833 If not specified, "de <<
6834 the RNG's choice is l <<
6835 <<
6836 trusted.dcp_use_otp_key <<
6837 This is intended to b <<
6838 trusted.source=dcp an <<
6839 instead of the DCP UN <<
6840 <<
6841 trusted.dcp_skip_zk_test <<
6842 This is intended to b <<
6843 trusted.source=dcp an <<
6844 blob key is all zeros <<
6845 having this key zero' <<
6846 scenarios. <<
6847 4651
6848 tsc= Disable clocksource s 4652 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 4653 Format: <string>
6850 [x86] reliable: mark 4654 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 4655 disables clocksource verification at runtime, as well
6852 as the stability chec 4656 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 4657 high-resolution timer mode on older hardware, and in
6854 virtualized environme 4658 virtualized environment.
6855 [x86] noirqtime: Do n 4659 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 4660 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 4661 platforms where RDTSC is slow and this accounting
6858 can add overhead. 4662 can add overhead.
6859 [x86] unstable: mark <<
6860 marks the TSC uncondi <<
6861 avoids any further wo <<
6862 [x86] nowatchdog: dis <<
6863 in situations with st <<
6864 interruptions from cl <<
6865 acceptable). <<
6866 [x86] recalibrate: fo <<
6867 (HPET or PM timer) on <<
6868 obtained from HW or F <<
6869 Warn if the differenc <<
6870 [x86] watchdog: Use T <<
6871 which to check other <<
6872 only on systems where <<
6873 This will be suppress <<
6874 can be overridden by <<
6875 message will flag any <<
6876 <<
6877 tsc_early_khz= [X86,EARLY] Skip earl <<
6878 value instead. Useful <<
6879 procedure is not reli <<
6880 with CPUID.16h suppor <<
6881 Format: <unsigned int <<
6882 4663
6883 tsx= [X86] Control Transac 4664 tsx= [X86] Control Transactional Synchronization
6884 Extensions (TSX) feat 4665 Extensions (TSX) feature in Intel processors that
6885 support TSX control. 4666 support TSX control.
6886 4667
6887 This parameter contro 4668 This parameter controls the TSX feature. The options are:
6888 4669
6889 on - Enable TSX 4670 on - Enable TSX on the system. Although there are
6890 mitigations f 4671 mitigations for all known security vulnerabilities,
6891 TSX has been 4672 TSX has been known to be an accelerator for
6892 several previ 4673 several previous speculation-related CVEs, and
6893 so there may 4674 so there may be unknown security risks associated
6894 with leaving 4675 with leaving it enabled.
6895 4676
6896 off - Disable TSX 4677 off - Disable TSX on the system. (Note that this
6897 option takes 4678 option takes effect only on newer CPUs which are
6898 not vulnerabl 4679 not vulnerable to MDS, i.e., have
6899 MSR_IA32_ARCH 4680 MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get
6900 the new IA32_ 4681 the new IA32_TSX_CTRL MSR through a microcode
6901 update. This 4682 update. This new MSR allows for the reliable
6902 deactivation 4683 deactivation of the TSX functionality.)
6903 4684
6904 auto - Disable TSX 4685 auto - Disable TSX if X86_BUG_TAA is present,
6905 otherwise e 4686 otherwise enable TSX on the system.
6906 4687
6907 Not specifying this o 4688 Not specifying this option is equivalent to tsx=off.
6908 4689
6909 See Documentation/adm 4690 See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6910 for more details. 4691 for more details.
6911 4692
6912 tsx_async_abort= [X86,INTEL,EARLY] Co !! 4693 tsx_async_abort= [X86,INTEL] Control mitigation for the TSX Async
6913 Abort (TAA) vulnerabi 4694 Abort (TAA) vulnerability.
6914 4695
6915 Similar to Micro-arch 4696 Similar to Micro-architectural Data Sampling (MDS)
6916 certain CPUs that sup 4697 certain CPUs that support Transactional
6917 Synchronization Exten 4698 Synchronization Extensions (TSX) are vulnerable to an
6918 exploit against CPU i 4699 exploit against CPU internal buffers which can forward
6919 information to a disc 4700 information to a disclosure gadget under certain
6920 conditions. 4701 conditions.
6921 4702
6922 In vulnerable process 4703 In vulnerable processors, the speculatively forwarded
6923 data can be used in a 4704 data can be used in a cache side channel attack, to
6924 access data to which 4705 access data to which the attacker does not have direct
6925 access. 4706 access.
6926 4707
6927 This parameter contro 4708 This parameter controls the TAA mitigation. The
6928 options are: 4709 options are:
6929 4710
6930 full - Enable T 4711 full - Enable TAA mitigation on vulnerable CPUs
6931 if TSX i 4712 if TSX is enabled.
6932 4713
6933 full,nosmt - Enable T 4714 full,nosmt - Enable TAA mitigation and disable SMT on
6934 vulnerab 4715 vulnerable CPUs. If TSX is disabled, SMT
6935 is not d 4716 is not disabled because CPU is not
6936 vulnerab 4717 vulnerable to cross-thread TAA attacks.
6937 off - Uncondit 4718 off - Unconditionally disable TAA mitigation
6938 4719
6939 On MDS-affected machi 4720 On MDS-affected machines, tsx_async_abort=off can be
6940 prevented by an activ 4721 prevented by an active MDS mitigation as both vulnerabilities
6941 are mitigated with th 4722 are mitigated with the same mechanism so in order to disable
6942 this mitigation, you 4723 this mitigation, you need to specify mds=off too.
6943 4724
6944 Not specifying this o 4725 Not specifying this option is equivalent to
6945 tsx_async_abort=full. 4726 tsx_async_abort=full. On CPUs which are MDS affected
6946 and deploy MDS mitiga 4727 and deploy MDS mitigation, TAA mitigation is not
6947 required and doesn't 4728 required and doesn't provide any additional
6948 mitigation. 4729 mitigation.
6949 4730
6950 For details see: 4731 For details see:
6951 Documentation/admin-g 4732 Documentation/admin-guide/hw-vuln/tsx_async_abort.rst
6952 4733
6953 turbografx.map[2|3]= [HW,JOY] 4734 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 4735 TurboGraFX parallel port interface
6955 Format: 4736 Format:
6956 <port#>,<js1>,<js2>,< 4737 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio !! 4738 See also Documentation/input/joystick-parport.txt
6958 4739
6959 udbg-immortal [PPC] When debugging 4740 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 4741 happen after console_init() and before a proper
6961 console driver takes 4742 console driver takes over, this boot options might
6962 help "seeing" what's 4743 help "seeing" what's going on.
6963 4744
6964 uhash_entries= [KNL,NET] 4745 uhash_entries= [KNL,NET]
6965 Set number of hash bu 4746 Set number of hash buckets for UDP/UDP-Lite connections
6966 4747
6967 uhci-hcd.ignore_oc= 4748 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 4749 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 4750 Some badly-designed motherboards generate lots of
6970 bogus events, for por 4751 bogus events, for ports that aren't wired to
6971 anything. Set this p 4752 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 4753 Note that genuine overcurrent events won't be
6973 reported either. 4754 reported either.
6974 4755
6975 unknown_nmi_panic 4756 unknown_nmi_panic
6976 [X86] Cause panic on 4757 [X86] Cause panic on unknown NMI.
6977 4758
6978 unwind_debug [X86-64,EARLY] <<
6979 Enable unwinder debug <<
6980 useful for debugging <<
6981 conditions, including <<
6982 bad/missing unwinder <<
6983 <<
6984 usbcore.authorized_default= 4759 usbcore.authorized_default=
6985 [USB] Default USB dev 4760 [USB] Default USB device authorization:
6986 (default -1 = authori !! 4761 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 !! 4762 0 = not authorized, 1 = authorized)
6988 if device connected t <<
6989 4763
6990 usbcore.autosuspend= 4764 usbcore.autosuspend=
6991 [USB] The autosuspend 4765 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 4766 for newly-detected USB devices (default 2). This
6993 is the time required 4767 is the time required before an idle device will be
6994 autosuspended. Devic 4768 autosuspended. Devices for which the delay is set
6995 to a negative value w 4769 to a negative value won't be autosuspended at all.
6996 4770
6997 usbcore.usbfs_snoop= 4771 usbcore.usbfs_snoop=
6998 [USB] Set to log all 4772 [USB] Set to log all usbfs traffic (default 0 = off).
6999 4773
7000 usbcore.usbfs_snoop_max= 4774 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 4775 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 4776 (default = 65536).
7003 4777
7004 usbcore.blinkenlights= 4778 usbcore.blinkenlights=
7005 [USB] Set to cycle le 4779 [USB] Set to cycle leds on hubs (default 0 = off).
7006 4780
7007 usbcore.old_scheme_first= 4781 usbcore.old_scheme_first=
7008 [USB] Start with the 4782 [USB] Start with the old device initialization
7009 scheme (default 0 = o 4783 scheme (default 0 = off).
7010 4784
7011 usbcore.usbfs_memory_mb= 4785 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 4786 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 4787 usbfs (default = 16, 0 = max = 2047).
7014 4788
7015 usbcore.use_both_schemes= 4789 usbcore.use_both_schemes=
7016 [USB] Try the other d 4790 [USB] Try the other device initialization scheme
7017 if the first one fail 4791 if the first one fails (default 1 = enabled).
7018 4792
7019 usbcore.initial_descriptor_timeout= 4793 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 4794 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO !! 4795 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 4796 (default 5000 = 5.0 seconds).
7023 4797
7024 usbcore.nousb [USB] Disable the USB 4798 usbcore.nousb [USB] Disable the USB subsystem
7025 4799
7026 usbcore.quirks= <<
7027 [USB] A list of quirk <<
7028 usb core quirk list. <<
7029 commas. Each entry ha <<
7030 VendorID:ProductID:Fl <<
7031 numbers and Flags is <<
7032 will change the built <<
7033 clear and clearing it <<
7034 the following meaning <<
7035 a = USB_QUIRK <<
7036 descr <<
7037 a 255 <<
7038 b = USB_QUIRK <<
7039 corre <<
7040 c = USB_QUIRK <<
7041 Set-I <<
7042 d = USB_QUIRK <<
7043 handl <<
7044 strin <<
7045 e = USB_QUIRK <<
7046 (e.g <<
7047 f = USB_QUIRK <<
7048 more <<
7049 bNumI <<
7050 talki <<
7051 g = USB_QUIRK <<
7052 durin <<
7053 the d <<
7054 h = USB_QUIRK <<
7055 high <<
7056 endpo <<
7057 requi <<
7058 micro <<
7059 calcu <<
7060 (bInt <<
7061 Devic <<
7062 bInte <<
7063 calcu <<
7064 varia <<
7065 i = USB_QUIRK <<
7066 handl <<
7067 reque <<
7068 j = USB_QUIRK <<
7069 gener <<
7070 remot <<
7071 k = USB_QUIRK <<
7072 Power <<
7073 l = USB_QUIRK <<
7074 (Devi <<
7075 frame <<
7076 calcu <<
7077 m = USB_QUIRK <<
7078 to be <<
7079 preve <<
7080 n = USB_QUIRK <<
7081 pause <<
7082 o = USB_QUIRK <<
7083 delay <<
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: <<
7088 <<
7089 usbhid.mousepoll= 4800 usbhid.mousepoll=
7090 [USBHID] The interval 4801 [USBHID] The interval which mice are to be polled at.
7091 4802
7092 usbhid.jspoll= 4803 usbhid.jspoll=
7093 [USBHID] The interval 4804 [USBHID] The interval which joysticks are to be polled at.
7094 4805
7095 usbhid.kbpoll= <<
7096 [USBHID] The interval <<
7097 <<
7098 usb-storage.delay_use= 4806 usb-storage.delay_use=
7099 [UMS] The delay in se 4807 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 4808 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 4809
7105 usb-storage.quirks= 4810 usb-storage.quirks=
7106 [UMS] A list of quirk 4811 [UMS] A list of quirks entries to supplement or
7107 override the built-in 4812 override the built-in unusual_devs list. List
7108 entries are separated 4813 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 4814 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 4815 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 4816 Flags is a set of characters, each corresponding
7112 to a common usb-stora 4817 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 4818 a = SANE_SENSE (collect more than 18 bytes
7114 of se 4819 of sense data, not on uas);
7115 b = BAD_SENSE 4820 b = BAD_SENSE (don't collect more than 18
7116 bytes 4821 bytes of sense data, not on uas);
7117 c = FIX_CAPAC 4822 c = FIX_CAPACITY (decrease the reported
7118 devic 4823 device capacity by one sector);
7119 d = NO_READ_D 4824 d = NO_READ_DISC_INFO (don't use
7120 READ_ 4825 READ_DISC_INFO command, not on uas);
7121 e = NO_READ_C 4826 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 4827 READ_CAPACITY_16 command);
7123 f = NO_REPORT 4828 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 4829 command, uas only);
7125 g = MAX_SECTO 4830 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 4831 240 sectors at a time, uas only);
7127 h = CAPACITY_ 4832 h = CAPACITY_HEURISTICS (decrease the
7128 repor 4833 reported device capacity by one
7129 secto 4834 sector if the number is odd);
7130 i = IGNORE_DE 4835 i = IGNORE_DEVICE (don't bind to this
7131 devic 4836 device);
7132 j = NO_REPORT 4837 j = NO_REPORT_LUNS (don't use report luns
7133 comma 4838 command, uas only);
7134 k = NO_SAME ( 4839 k = NO_SAME (do not use WRITE_SAME, uas only)
7135 l = NOT_LOCKA 4840 l = NOT_LOCKABLE (don't try to lock and
7136 unloc 4841 unlock ejectable media, not on uas);
7137 m = MAX_SECTO 4842 m = MAX_SECTORS_64 (don't transfer more
7138 than 4843 than 64 sectors = 32 KB at a time,
7139 not o 4844 not on uas);
7140 n = INITIAL_R 4845 n = INITIAL_READ10 (force a retry of the
7141 initi 4846 initial READ(10) command, not on uas);
7142 o = CAPACITY_ 4847 o = CAPACITY_OK (accept the capacity
7143 repor 4848 reported by the device, not on uas);
7144 p = WRITE_CAC 4849 p = WRITE_CACHE (the device cache is ON
7145 by de 4850 by default, not on uas);
7146 r = IGNORE_RE 4851 r = IGNORE_RESIDUE (the device reports
7147 bogus 4852 bogus residue values, not on uas);
7148 s = SINGLE_LU 4853 s = SINGLE_LUN (the device has only one
7149 Logic 4854 Logical Unit);
7150 t = NO_ATA_1X 4855 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 4856 commands, uas only);
7152 u = IGNORE_UA 4857 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 4858 w = NO_WP_DETECT (don't test whether the
7154 mediu 4859 medium is write-protected).
7155 y = ALWAYS_SY 4860 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even 4861 even if the device claims no cache,
7157 not o 4862 not on uas)
7158 Example: quirks=0419: 4863 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 4864
7160 user_debug= [KNL,ARM] 4865 user_debug= [KNL,ARM]
7161 Format: <int> 4866 Format: <int>
7162 See arch/arm/Kconfig. 4867 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 4868 1 - undefined instruction events
7164 2 - system c 4869 2 - system calls
7165 4 - invalid 4870 4 - invalid data aborts
7166 8 - SIGSEGV 4871 8 - SIGSEGV faults
7167 16 - SIGBUS f 4872 16 - SIGBUS faults
7168 Example: user_debug=3 4873 Example: user_debug=31
7169 4874
7170 userpte= 4875 userpte=
7171 [X86,EARLY] Flags con !! 4876 [X86] Flags controlling user PTE allocations.
7172 4877
7173 nohigh = do n 4878 nohigh = do not allocate PTE pages in
7174 HIGHM 4879 HIGHMEM regardless of setting
7175 of CO 4880 of CONFIG_HIGHPTE.
7176 4881
7177 vdso= [X86,SH,SPARC] !! 4882 vdso= [X86,SH]
7178 On X86_32, this is an 4883 On X86_32, this is an alias for vdso32=. Otherwise:
7179 4884
7180 vdso=1: enable VDSO ( 4885 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 4886 vdso=0: disable VDSO mapping
7182 4887
7183 vdso32= [X86] Control the 32- 4888 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 4889 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 4890 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 4891
7187 See the help text for 4892 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 4893 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 4894 vdso32=0; otherwise, the default is vdso32=1.
7190 4895
7191 For compatibility wit 4896 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 4897 alias for vdso32=0.
7193 4898
7194 Try vdso32=0 if you e 4899 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 4900 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 4901
7197 video= [FB,EARLY] Frame buff !! 4902 vector= [IA-64,SMP]
7198 See Documentation/fb/ !! 4903 vector=percpu: enable percpu vector domain
>> 4904
>> 4905 video= [FB] Frame buffer configuration
>> 4906 See Documentation/fb/modedb.txt.
7199 4907
7200 video.brightness_switch_enabled= [ACP !! 4908 video.brightness_switch_enabled= [0,1]
7201 Format: [0|1] <<
7202 If set to 1, on recei 4909 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 4910 generated by hotkey, video driver will adjust brightness
7204 level and then send o 4911 level and then send out the event to user space through
7205 the allocated input d !! 4912 the allocated input device; If set to 0, video driver
7206 will only send out th 4913 will only send out the event without touching backlight
7207 brightness level. 4914 brightness level.
7208 default: 1 4915 default: 1
7209 4916
7210 virtio_mmio.device= 4917 virtio_mmio.device=
7211 [VMMIO] Memory mapped 4918 [VMMIO] Memory mapped virtio (platform) device.
7212 4919
7213 <size>@<basead 4920 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 4921 where:
7215 <size> := 4922 <size> := size (can use standard suffixes
7216 4923 like K, M and G)
7217 <baseaddr> := 4924 <baseaddr> := physical base address
7218 <irq> := 4925 <irq> := interrupt number (as passed to
7219 4926 request_irq())
7220 <id> := 4927 <id> := (optional) platform device id
7221 example: 4928 example:
7222 virtio_mmio.d 4929 virtio_mmio.device=1K@0x100b0000:48:7
7223 4930
7224 Can be used multiple 4931 Can be used multiple times for multiple devices.
7225 4932
7226 vga= [BOOT,X86-32] Select 4933 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 4934 See Documentation/x86/boot.txt and
7228 Documentation/admin-g !! 4935 Documentation/svga.txt.
7229 Use vga=ask for menu. 4936 Use vga=ask for menu.
7230 This is actually a bo 4937 This is actually a boot loader parameter; the value is
7231 passed to the kernel 4938 passed to the kernel using a special protocol.
7232 4939
7233 vm_debug[=options] [KNL] Availab !! 4940 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7234 May slow down system !! 4941 size of <nn>. This can be used to increase the
7235 enabled on systems wi !! 4942 minimum size (128MB on x86). It can also be used to
7236 All options are enabl !! 4943 decrease the size and leave more room for directly
7237 interface is meant to !! 4944 mapped kernel RAM.
7238 enabling or disabling <<
7239 debugging features. <<
7240 <<
7241 Available options are <<
7242 P Enable page s <<
7243 - Disable all o <<
7244 <<
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc <<
7246 exact size of <nn>. T <<
7247 the minimum size (128 <<
7248 It can also be used t <<
7249 for directly mapped k <<
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 4945
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 4946 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 4947 Sets the memory size reserved for contiguous memory
7256 allocations for the v 4948 allocations for the vmcp device driver.
7257 4949
7258 vmhalt= [KNL,S390] Perform z/ 4950 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 4951 Format: <command>
7260 4952
7261 vmpanic= [KNL,S390] Perform z/ 4953 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 4954 Format: <command>
7263 4955
7264 vmpoff= [KNL,S390] Perform z/ 4956 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 4957 Format: <command>
7266 4958
7267 vsyscall= [X86-64,EARLY] !! 4959 vsyscall= [X86-64]
7268 Controls the behavior 4960 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 4961 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 4962 code). Most statically-linked binaries and older
7271 versions of glibc use 4963 versions of glibc use these calls. Because these
7272 functions are at fixe 4964 functions are at fixed addresses, they make nice
7273 targets for exploits 4965 targets for exploits that can control RIP.
7274 4966
7275 emulate Vsyscalls !! 4967 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 4968 emulated reasonably safely.
7277 readable. !! 4969
7278 !! 4970 native Vsyscalls are native syscall instructions.
7279 xonly [default] !! 4971 This is a little bit faster than trapping
7280 emulated !! 4972 and makes a few dynamic recompilers work
7281 page is n !! 4973 better than they would in emulation mode.
>> 4974 It also makes exploits much easier to write.
7282 4975
7283 none Vsyscalls 4976 none Vsyscalls don't work at all. This makes
7284 them quit 4977 them quite hard to use for exploits but
7285 might bre 4978 might break your system.
7286 4979
7287 vt.color= [VT] Default text col 4980 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 4981 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 4982 Default: 0x07 = light gray on black.
7290 4983
7291 vt.cur_default= [VT] Default cursor s 4984 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 4985 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 4986 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 4987 see VGA-softcursor.txt. Default: 2 = underline.
7295 4988
7296 vt.default_blu= [VT] 4989 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 4990 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 4991 Change the default blue palette of the console.
7299 This is a 16-member a 4992 This is a 16-member array composed of values
7300 ranging from 0-255. 4993 ranging from 0-255.
7301 4994
7302 vt.default_grn= [VT] 4995 vt.default_grn= [VT]
7303 Format: <green0>,<gre 4996 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 4997 Change the default green palette of the console.
7305 This is a 16-member a 4998 This is a 16-member array composed of values
7306 ranging from 0-255. 4999 ranging from 0-255.
7307 5000
7308 vt.default_red= [VT] 5001 vt.default_red= [VT]
7309 Format: <red0>,<red1> 5002 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 5003 Change the default red palette of the console.
7311 This is a 16-member a 5004 This is a 16-member array composed of values
7312 ranging from 0-255. 5005 ranging from 0-255.
7313 5006
7314 vt.default_utf8= 5007 vt.default_utf8=
7315 [VT] 5008 [VT]
7316 Format=<0|1> 5009 Format=<0|1>
7317 Set system-wide defau 5010 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 5011 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 5012 newly opened terminals.
7320 5013
7321 vt.global_cursor_default= 5014 vt.global_cursor_default=
7322 [VT] 5015 [VT]
7323 Format=<-1|0|1> 5016 Format=<-1|0|1>
7324 Set system-wide defau 5017 Set system-wide default for whether a cursor
7325 is shown on new VTs. 5018 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 5019 i.e. cursors will be created by default unless
7327 overridden by individ 5020 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 5021 cursors, 1 will display them.
7329 5022
7330 vt.italic= [VT] Default color fo 5023 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 5024 Default: 2 = green.
7332 5025
7333 vt.underline= [VT] Default color fo 5026 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 5027 Default: 3 = cyan.
7335 5028
7336 watchdog timers [HW,WDT] For informat 5029 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat !! 5030 see Documentation/watchdog/watchdog-parameters.txt
7338 or other driver-speci 5031 or other driver-specific files in the
7339 Documentation/watchdo 5032 Documentation/watchdog/ directory.
7340 5033
7341 watchdog_thresh= <<
7342 [KNL] <<
7343 Set the hard lockup d <<
7344 threshold in seconds. <<
7345 threshold is set to t <<
7346 disables both lockup <<
7347 seconds. <<
7348 <<
7349 workqueue.unbound_cpus= <<
7350 [KNL,SMP] Specify to <<
7351 to use in unbound wor <<
7352 Format: <cpu-list> <<
7353 By default, all onlin <<
7354 unbound workqueues. <<
7355 <<
7356 workqueue.watchdog_thresh= 5034 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 5035 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 5036 warn stall conditions and dump internal state to
7359 help debugging. 0 di 5037 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 5038 detection; otherwise, it's the stall threshold
7361 duration in seconds. 5039 duration in seconds. The default value is 30 and
7362 it can be updated at 5040 it can be updated at runtime by writing to the
7363 corresponding sysfs f 5041 corresponding sysfs file.
7364 5042
7365 workqueue.cpu_intensive_thresh_us= !! 5043 workqueue.disable_numa
7366 Per-cpu work items wh !! 5044 By default, all work items queued to unbound
7367 threshold are automat !! 5045 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 5046 issued on, which results in better behavior in
7369 them from noticeably !! 5047 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 5048 whatever reason, this option can be used. Note
7371 !! 5049 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 5050 workqueues visible under /sys/bus/workqueue/.
7373 will report the work <<
7374 threshold repeatedly. <<
7375 candidates for using <<
7376 <<
7377 workqueue.cpu_intensive_warning_thres <<
7378 If CONFIG_WQ_CPU_INTE <<
7379 will report the work <<
7380 intensive_threshold_u <<
7381 spurious warnings, st <<
7382 function has violated <<
7383 <<
7384 The default is 4 time <<
7385 5051
7386 workqueue.power_efficient 5052 workqueue.power_efficient
7387 Per-cpu workqueues ar 5053 Per-cpu workqueues are generally preferred because
7388 they show better perf 5054 they show better performance thanks to cache
7389 locality; unfortunate 5055 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 5056 be more power hungry than unbound workqueues.
7391 5057
7392 Enabling this makes t 5058 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 5059 were observed to contribute significantly to power
7394 consumption unbound, 5060 consumption unbound, leading to measurably lower
7395 power usage at the co 5061 power usage at the cost of small performance
7396 overhead. 5062 overhead.
7397 5063
7398 The default value of 5064 The default value of this parameter is determined by
7399 the config option CON 5065 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 5066
7401 workqueue.default_affinity_scope= <<
7402 Select the default af <<
7403 workqueues. Can be on <<
7404 "numa" and "system". <<
7405 information, see the <<
7406 Documentation/core-ap <<
7407 <<
7408 This can be changed a <<
7409 matching /sys/module/ <<
7410 workqueues with the " <<
7411 updated accordingly. <<
7412 <<
7413 workqueue.debug_force_rr_cpu 5067 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 5068 Workqueue used to implicitly guarantee that work
7415 items queued without 5069 items queued without explicit CPU specified are put
7416 on the local CPU. Th 5070 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 5071 and while local CPU is still preferred work items
7418 may be put on foreign 5072 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 5073 forces round-robin CPU selection to flush out
7420 usages which depend o 5074 usages which depend on the now broken guarantee.
7421 When enabled, memory 5075 When enabled, memory and cache locality will be
7422 impacted. 5076 impacted.
7423 5077
7424 writecombine= [LOONGARCH,EARLY] Con !! 5078 x2apic_phys [X86-64,APIC] Use x2apic physical mode instead of
7425 Type) of ioremap_wc() <<
7426 <<
7427 on - Enable writeco <<
7428 off - Disable writec <<
7429 <<
7430 x2apic_phys [X86-64,APIC,EARLY] U <<
7431 default x2apic cluste 5079 default x2apic cluster mode on platforms
7432 supporting x2apic. 5080 supporting x2apic.
7433 5081
>> 5082 x86_intel_mid_timer= [X86-32,APBT]
>> 5083 Choose timer option for x86 Intel MID platform.
>> 5084 Two valid options are apbt timer only and lapic timer
>> 5085 plus one apbt timer for broadcast timer.
>> 5086 x86_intel_mid_timer=apbt_only | lapic_and_apbt
>> 5087
7434 xen_512gb_limit [KNL,X86-64,X 5088 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 5089 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 5090 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 5091 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 5092 save/restore/migration must be enabled to handle larger
7439 domains. 5093 domains.
7440 5094
7441 xen_emul_unplug= [HW,X !! 5095 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 5096 Unplug Xen emulated devices
7443 Format: [unplug0,][un 5097 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 5098 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 5099 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 5100 nics -- unplug network devices
7447 all -- unplug all emu 5101 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 5102 unnecessary -- unplugging emulated devices is
7449 unnecessary e 5103 unnecessary even if the host did not respond to
7450 the unplug pr 5104 the unplug protocol
7451 never -- do not unplu 5105 never -- do not unplug even if version check succeeds
7452 5106
7453 xen_legacy_crash [X86,XEN,EARL !! 5107 xen_legacy_crash [X86,XEN]
7454 Crash from Xen panic 5108 Crash from Xen panic notifier, without executing late
7455 panic() code such as 5109 panic() code such as dumping handler.
7456 5110
7457 xen_mc_debug [X86,XEN,EARLY] !! 5111 xen_nopvspin [X86,XEN]
7458 Enable multicall debu !! 5112 Disables the ticketlock slowpath using Xen PV
7459 Enabling this feature !! 5113 optimizations.
7460 bit, so it should onl <<
7461 debug data in case of <<
7462 <<
7463 xen_msr_safe= [X86,XEN,EARLY] <<
7464 Format: <bool> <<
7465 Select whether to alw <<
7466 access functions when <<
7467 default value is cont <<
7468 5114
7469 xen_nopv [X86] 5115 xen_nopv [X86]
7470 Disables the PV optim 5116 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 5117 run as generic HVM guest with no PV drivers.
7472 This option is obsole <<
7473 has equivalent effect <<
7474 <<
7475 xen_no_vector_callback <<
7476 [KNL,X86,XEN,EARLY] D <<
7477 event channel interru <<
7478 <<
7479 xen_scrub_pages= [XEN] <<
7480 Boolean option to con <<
7481 to Xen, for use by ot <<
7482 with /sys/devices/sys <<
7483 Default value control <<
7484 <<
7485 xen_timer_slop= [X86-64,XEN,EARLY] <<
7486 Set the timer slop (i <<
7487 timers (default is 10 <<
7488 delta of virtualized <<
7489 improve timer resolut <<
7490 more timer interrupts <<
7491 5118
7492 xen.balloon_boot_timeout= [XEN] 5119 xen.balloon_boot_timeout= [XEN]
7493 The time (in seconds) 5120 The time (in seconds) to wait before giving up to boot
7494 in case initial ballo 5121 in case initial ballooning fails to free enough memory.
7495 Applies only when run 5122 Applies only when running as HVM or PVH guest and
7496 started with less mem 5123 started with less memory configured than allowed at
7497 max. Default is 180. 5124 max. Default is 180.
7498 5125
7499 xen.event_eoi_delay= [XEN] 5126 xen.event_eoi_delay= [XEN]
7500 How long to delay EOI 5127 How long to delay EOI handling in case of event
7501 storms (jiffies). Def 5128 storms (jiffies). Default is 10.
7502 5129
7503 xen.event_loop_timeout= [XEN] 5130 xen.event_loop_timeout= [XEN]
7504 After which time (jif 5131 After which time (jiffies) the event handling loop
7505 should start to delay 5132 should start to delay EOI handling. Default is 2.
7506 5133
7507 xen.fifo_events= [XEN] <<
7508 Boolean parameter to <<
7509 even if available. No <<
7510 preferred over the 2- <<
7511 fairer and the number <<
7512 much higher. Default <<
7513 <<
7514 xirc2ps_cs= [NET,PCMCIA] 5134 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 5135 Format:
7516 <irq>,<irq_mask>,<io> 5136 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 <<
7518 xive= [PPC] <<
7519 By default on POWER9 <<
7520 natively use the XIVE <<
7521 allows the fallback f <<
7522 <<
7523 off Fallback to <<
7524 controller <<
7525 platforms. <<
7526 <<
7527 xive.store-eoi=off [PPC] <<
7528 By default on POWER10 <<
7529 stores for EOI handli <<
7530 is active. This optio <<
7531 loads instead, as on <<
7532 <<
7533 xhci-hcd.quirks [USB,KNL] <<
7534 A hex value specifyin <<
7535 host controller quirk <<
7536 consulted in header d <<
7537 <<
7538 xmon [PPC,EARLY] <<
7539 Format: { early | on <<
7540 Controls if xmon debu <<
7541 Passing only "xmon" i <<
7542 early Call xmon as <<
7543 debugger is c <<
7544 on xmon debugger <<
7545 is only calle <<
7546 i.e. either " <<
7547 with CONFIG_X <<
7548 rw xmon debugger <<
7549 is called onl <<
7550 meaning SPR r <<
7551 can be writte <<
7552 ro same as "rw" <<
7553 memory, and o <<
7554 xmon commands <<
7555 off xmon is disab <<
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