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>
132 117
133 acpi_no_auto_serialize [HW,ACPI] 118 acpi_no_auto_serialize [HW,ACPI]
134 Disable auto-serializa 119 Disable auto-serialization of AML methods
135 AML control methods th 120 AML control methods that contain the opcodes to create
136 named objects will be 121 named objects will be marked as "Serialized" by the
137 auto-serialization fea 122 auto-serialization feature.
138 This feature is enable 123 This feature is enabled by default.
139 This option allows to 124 This option allows to turn off the feature.
140 125
141 acpi_no_memhotplug [ACPI] Disable memo 126 acpi_no_memhotplug [ACPI] Disable memory hotplug. Useful for kdump
142 kernels. 127 kernels.
143 128
144 acpi_no_static_ssdt [HW,ACPI,EARLY !! 129 acpi_no_static_ssdt [HW,ACPI]
145 Disable installation o 130 Disable installation of static SSDTs at early boot time
146 By default, SSDTs cont 131 By default, SSDTs contained in the RSDT/XSDT will be
147 installed automaticall 132 installed automatically and they will appear under
148 /sys/firmware/acpi/tab 133 /sys/firmware/acpi/tables.
149 This option turns off 134 This option turns off this feature.
150 Note that specifying t 135 Note that specifying this option does not affect
151 dynamic table installa 136 dynamic table installation which will install SSDT
152 tables to /sys/firmwar 137 tables to /sys/firmware/acpi/tables/dynamic.
153 138
154 acpi_no_watchdog [HW,ACPI,WDT] !! 139 acpi_rsdp= [ACPI,EFI,KEXEC]
155 Ignore the ACPI-based <<
156 a native driver contro <<
157 <<
158 acpi_rsdp= [ACPI,EFI,KEXEC,EARLY] <<
159 Pass the RSDP address 140 Pass the RSDP address to the kernel, mostly used
160 on machines running EF 141 on machines running EFI runtime service to boot the
161 second kernel for kdum 142 second kernel for kdump.
162 143
163 acpi_os_name= [HW,ACPI] Tell ACPI BI 144 acpi_os_name= [HW,ACPI] Tell ACPI BIOS the name of the OS
164 Format: To spoof as Wi 145 Format: To spoof as Windows 98: ="Microsoft Windows"
165 146
166 acpi_rev_override [ACPI] Override the 147 acpi_rev_override [ACPI] Override the _REV object to return 5 (instead
167 of 2 which is mandated 148 of 2 which is mandated by ACPI 6) as the supported ACPI
168 specification revision 149 specification revision (when using this switch, it may
169 be necessary to carry 150 be necessary to carry out a cold reboot _twice_ in a
170 row to make it take ef 151 row to make it take effect on the platform firmware).
171 152
172 acpi_osi= [HW,ACPI] Modify list 153 acpi_osi= [HW,ACPI] Modify list of supported OS interface strings
173 acpi_osi="string1" 154 acpi_osi="string1" # add string1
174 acpi_osi="!string2" 155 acpi_osi="!string2" # remove string2
175 acpi_osi=!* 156 acpi_osi=!* # remove all strings
176 acpi_osi=! 157 acpi_osi=! # disable all built-in OS vendor
177 158 strings
178 acpi_osi=!! 159 acpi_osi=!! # enable all built-in OS vendor
179 160 strings
180 acpi_osi= 161 acpi_osi= # disable all strings
181 162
182 'acpi_osi=!' can be us 163 'acpi_osi=!' can be used in combination with single or
183 multiple 'acpi_osi="st 164 multiple 'acpi_osi="string1"' to support specific OS
184 vendor string(s). Not 165 vendor string(s). Note that such command can only
185 affect the default sta 166 affect the default state of the OS vendor strings, thus
186 it cannot affect the d 167 it cannot affect the default state of the feature group
187 strings and the curren 168 strings and the current state of the OS vendor strings,
188 specifying it multiple 169 specifying it multiple times through kernel command line
189 is meaningless. This 170 is meaningless. This command is useful when one do not
190 care about the state o 171 care about the state of the feature group strings which
191 should be controlled b 172 should be controlled by the OSPM.
192 Examples: 173 Examples:
193 1. 'acpi_osi=! acpi_ 174 1. 'acpi_osi=! acpi_osi="Windows 2000"' is equivalent
194 to 'acpi_osi="Win 175 to 'acpi_osi="Windows 2000" acpi_osi=!', they all
195 can make '_OSI("W 176 can make '_OSI("Windows 2000")' TRUE.
196 177
197 'acpi_osi=' cannot be 178 'acpi_osi=' cannot be used in combination with other
198 'acpi_osi=' command li 179 'acpi_osi=' command lines, the _OSI method will not
199 exist in the ACPI name 180 exist in the ACPI namespace. NOTE that such command can
200 only affect the _OSI s 181 only affect the _OSI support state, thus specifying it
201 multiple times through 182 multiple times through kernel command line is also
202 meaningless. 183 meaningless.
203 Examples: 184 Examples:
204 1. 'acpi_osi=' can m 185 1. 'acpi_osi=' can make 'CondRefOf(_OSI, Local1)'
205 FALSE. 186 FALSE.
206 187
207 'acpi_osi=!*' can be u 188 'acpi_osi=!*' can be used in combination with single or
208 multiple 'acpi_osi="st 189 multiple 'acpi_osi="string1"' to support specific
209 string(s). Note that 190 string(s). Note that such command can affect the
210 current state of both 191 current state of both the OS vendor strings and the
211 feature group strings, 192 feature group strings, thus specifying it multiple times
212 through kernel command 193 through kernel command line is meaningful. But it may
213 still not able to affe 194 still not able to affect the final state of a string if
214 there are quirks relat 195 there are quirks related to this string. This command
215 is useful when one wan 196 is useful when one want to control the state of the
216 feature group strings 197 feature group strings to debug BIOS issues related to
217 the OSPM features. 198 the OSPM features.
218 Examples: 199 Examples:
219 1. 'acpi_osi="Module 200 1. 'acpi_osi="Module Device" acpi_osi=!*' can make
220 '_OSI("Module Dev 201 '_OSI("Module Device")' FALSE.
221 2. 'acpi_osi=!* acpi 202 2. 'acpi_osi=!* acpi_osi="Module Device"' can make
222 '_OSI("Module Dev 203 '_OSI("Module Device")' TRUE.
223 3. 'acpi_osi=! acpi_ 204 3. 'acpi_osi=! acpi_osi=!* acpi_osi="Windows 2000"' is
224 equivalent to 205 equivalent to
225 'acpi_osi=!* acpi 206 'acpi_osi=!* acpi_osi=! acpi_osi="Windows 2000"'
226 and 207 and
227 'acpi_osi=!* acpi 208 'acpi_osi=!* acpi_osi="Windows 2000" acpi_osi=!',
228 they all will mak 209 they all will make '_OSI("Windows 2000")' TRUE.
229 210
230 acpi_pm_good [X86] 211 acpi_pm_good [X86]
231 Override the pmtimer b 212 Override the pmtimer bug detection: force the kernel
232 to assume that this ma 213 to assume that this machine's pmtimer latches its value
233 and always returns goo 214 and always returns good values.
234 215
235 acpi_sci= [HW,ACPI,EARLY] ACPI S !! 216 acpi_sci= [HW,ACPI] ACPI System Control Interrupt trigger mode
236 Format: { level | edge 217 Format: { level | edge | high | low }
237 218
238 acpi_skip_timer_override [HW,ACPI,EARL !! 219 acpi_skip_timer_override [HW,ACPI]
239 Recognize and ignore I 220 Recognize and ignore IRQ0/pin2 Interrupt Override.
240 For broken nForce2 BIO 221 For broken nForce2 BIOS resulting in XT-PIC timer.
241 222
242 acpi_sleep= [HW,ACPI] Sleep option 223 acpi_sleep= [HW,ACPI] Sleep options
243 Format: { s3_bios, s3_ !! 224 Format: { s3_bios, s3_mode, s3_beep, s4_nohwsig,
244 s4_nohwsig, !! 225 old_ordering, nonvs, sci_force_enable, nobl }
245 sci_force_en !! 226 See Documentation/power/video.txt for information on
246 See Documentation/powe <<
247 s3_bios and s3_mode. 227 s3_bios and s3_mode.
248 s3_beep is for debuggi 228 s3_beep is for debugging; it makes the PC's speaker beep
249 as soon as the kernel' 229 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 230 s4_nohwsig prevents ACPI hardware signature from being
259 used (or even warned a !! 231 used during resume from hibernation.
260 old_ordering causes th 232 old_ordering causes the ACPI 1.0 ordering of the _PTS
261 control method, with r 233 control method, with respect to putting devices into
262 low power states, to b 234 low power states, to be enforced (the ACPI 2.0 ordering
263 of _PTS is used by def 235 of _PTS is used by default).
264 nonvs prevents the ker 236 nonvs prevents the kernel from saving/restoring the
265 ACPI NVS memory during 237 ACPI NVS memory during suspend/hibernation and resume.
266 sci_force_enable cause 238 sci_force_enable causes the kernel to set SCI_EN directly
267 on resume from S1/S3 ( 239 on resume from S1/S3 (which is against the ACPI spec,
268 but some broken system 240 but some broken systems don't work without it).
269 nobl causes the intern 241 nobl causes the internal blacklist of systems known to
270 behave incorrectly in 242 behave incorrectly in some ways with respect to system
271 suspend and resume to 243 suspend and resume to be ignored (use wisely).
272 244
273 acpi_use_timer_override [HW,ACPI,EARLY !! 245 acpi_use_timer_override [HW,ACPI]
274 Use timer override. Fo 246 Use timer override. For some broken Nvidia NF5 boards
275 that require a timer o 247 that require a timer override, but don't have HPET
276 248
277 add_efi_memmap [EFI,X86,EARLY] Includ !! 249 add_efi_memmap [EFI; X86] Include EFI memory map in
278 kernel's map of availa 250 kernel's map of available physical RAM.
279 251
280 agp= [AGP] 252 agp= [AGP]
281 { off | try_unsupporte 253 { off | try_unsupported }
282 off: disable AGP suppo 254 off: disable AGP support
283 try_unsupported: try t 255 try_unsupported: try to drive unsupported chipsets
284 (may crash com 256 (may crash computer or cause data corruption)
285 257
286 ALSA [HW,ALSA] 258 ALSA [HW,ALSA]
287 See Documentation/soun 259 See Documentation/sound/alsa-configuration.rst
288 260
289 alignment= [KNL,ARM] 261 alignment= [KNL,ARM]
290 Allow the default user 262 Allow the default userspace alignment fault handler
291 behaviour to be specif 263 behaviour to be specified. Bit 0 enables warnings,
292 bit 1 enables fixups, 264 bit 1 enables fixups, and bit 2 sends a segfault.
293 265
294 align_va_addr= [X86-64] 266 align_va_addr= [X86-64]
295 Align virtual addresse 267 Align virtual addresses by clearing slice [14:12] when
296 allocating a VMA at pr 268 allocating a VMA at process creation time. This option
297 gives you up to 3% per 269 gives you up to 3% performance improvement on AMD F15h
298 machines (where it is 270 machines (where it is enabled by default) for a
299 CPU-intensive style be 271 CPU-intensive style benchmark, and it can vary highly in
300 a microbenchmark depen 272 a microbenchmark depending on workload and compiler.
301 273
302 32: only for 32-bit pr 274 32: only for 32-bit processes
303 64: only for 64-bit pr 275 64: only for 64-bit processes
304 on: enable for both 32 276 on: enable for both 32- and 64-bit processes
305 off: disable for both 277 off: disable for both 32- and 64-bit processes
306 278
307 alloc_snapshot [FTRACE] 279 alloc_snapshot [FTRACE]
308 Allocate the ftrace sn 280 Allocate the ftrace snapshot buffer on boot up when the
309 main buffer is allocat 281 main buffer is allocated. This is handy if debugging
310 and you need to use tr 282 and you need to use tracing_snapshot() on boot up, and
311 do not want to use tra 283 do not want to use tracing_snapshot_alloc() as it needs
312 to be done where GFP_K 284 to be done where GFP_KERNEL allocations are allowed.
313 285
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] 286 amd_iommu= [HW,X86-64]
326 Pass parameters to the 287 Pass parameters to the AMD IOMMU driver in the system.
327 Possible values are: 288 Possible values are:
328 fullflush - Deprecated !! 289 fullflush - enable flushing of IO/TLB entries when
>> 290 they are unmapped. Otherwise they are
>> 291 flushed before they will be reused, which
>> 292 is a lot of faster
329 off - do not ini 293 off - do not initialize any AMD IOMMU found in
330 the system 294 the system
331 force_isolation - Forc 295 force_isolation - Force device isolation for all
332 devi 296 devices. The IOMMU driver is not
333 allo 297 allowed anymore to lift isolation
334 requ 298 requirements as needed. This option
335 does 299 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 <<
342 300
343 amd_iommu_dump= [HW,X86-64] 301 amd_iommu_dump= [HW,X86-64]
344 Enable AMD IOMMU drive 302 Enable AMD IOMMU driver option to dump the ACPI table
345 for AMD IOMMU. With th 303 for AMD IOMMU. With this option enabled, AMD IOMMU
346 driver will print ACPI 304 driver will print ACPI tables for AMD IOMMU during
347 IOMMU initialization. 305 IOMMU initialization.
348 306
349 amd_iommu_intr= [HW,X86-64] 307 amd_iommu_intr= [HW,X86-64]
350 Specifies one of the f 308 Specifies one of the following AMD IOMMU interrupt
351 remapping modes: 309 remapping modes:
352 legacy - Use legac 310 legacy - Use legacy interrupt remapping mode.
353 vapic - Use virtu 311 vapic - Use virtual APIC mode, which allows IOMMU
354 to inject 312 to inject interrupts directly into guest.
355 This mode 313 This mode requires kvm-amd.avic=1.
356 (Default 314 (Default when IOMMU HW support is present.)
357 315
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 316 amijoy.map= [HW,JOY] Amiga joystick support
387 Map of devices attache 317 Map of devices attached to JOY0DAT and JOY1DAT
388 Format: <a>,<b> 318 Format: <a>,<b>
389 See also Documentation 319 See also Documentation/input/joydev/joystick.rst
390 320
391 analog.map= [HW,JOY] Analog joysti 321 analog.map= [HW,JOY] Analog joystick and gamepad support
392 Specifies type or capa 322 Specifies type or capabilities of an analog joystick
393 connected to one of 16 323 connected to one of 16 gameports
394 Format: <type1>,<type2 324 Format: <type1>,<type2>,..<type16>
395 325
396 apc= [HW,SPARC] 326 apc= [HW,SPARC]
397 Power management funct 327 Power management functions (SPARCstation-4/5 + deriv.)
398 Format: noidle 328 Format: noidle
399 Disable APC CPU standb 329 Disable APC CPU standby support. SPARCstation-Fox does
400 not play well with APC 330 not play well with APC CPU idle - disable it if you have
401 APC and your system cr 331 APC and your system crashes randomly.
402 332
403 apic= [APIC,X86,EARLY] Advan !! 333 apic= [APIC,X86] Advanced Programmable Interrupt Controller
404 Change the output verb 334 Change the output verbosity while booting
405 Format: { quiet (defau 335 Format: { quiet (default) | verbose | debug }
406 Change the amount of d 336 Change the amount of debugging information output
407 when initialising the 337 when initialising the APIC and IO-APIC components.
408 For X86-32, this can a 338 For X86-32, this can also be used to specify an APIC
409 driver name. 339 driver name.
410 Format: apic=driver_na 340 Format: apic=driver_name
411 Examples: apic=bigsmp 341 Examples: apic=bigsmp
412 342
413 apic_extnmi= [APIC,X86,EARLY] Exter !! 343 apic_extnmi= [APIC,X86] External NMI delivery setting
414 Format: { bsp (default 344 Format: { bsp (default) | all | none }
415 bsp: External NMI is 345 bsp: External NMI is delivered only to CPU 0
416 all: External NMIs ar 346 all: External NMIs are broadcast to all CPUs as a
417 backup of CPU 0 347 backup of CPU 0
418 none: External NMI is 348 none: External NMI is masked for all CPUs. This is
419 useful so that a 349 useful so that a dump capture kernel won't be
420 shot down by NMI 350 shot down by NMI
421 351
422 autoconf= [IPV6] 352 autoconf= [IPV6]
423 See Documentation/netw !! 353 See Documentation/networking/ipv6.txt.
>> 354
>> 355 show_lapic= [APIC,X86] Advanced Programmable Interrupt Controller
>> 356 Limit apic dumping. The parameter defines the maximal
>> 357 number of local apics being dumped. Also it is possible
>> 358 to set it to "all" by meaning -- no limit here.
>> 359 Format: { 1 (default) | 2 | ... | all }.
>> 360 The parameter valid if only apic=debug or
>> 361 apic=verbose is specified.
>> 362 Example: apic=debug show_lapic=all
424 363
425 apm= [APM] Advanced Power M 364 apm= [APM] Advanced Power Management
426 See header of arch/x86 365 See header of arch/x86/kernel/apm_32.c.
427 366
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 367 arcrimi= [HW,NET] ARCnet - "RIM I" (entirely mem-mapped) cards
436 Format: <io>,<irq>,<no 368 Format: <io>,<irq>,<nodeID>
437 369
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] 370 ataflop= [HW,M68k]
460 371
461 atarimouse= [HW,MOUSE] Atari Mouse 372 atarimouse= [HW,MOUSE] Atari Mouse
462 373
463 atkbd.extra= [HW] Enable extra LEDs 374 atkbd.extra= [HW] Enable extra LEDs and keys on IBM RapidAccess,
464 EzKey and similar keyb 375 EzKey and similar keyboards
465 376
466 atkbd.reset= [HW] Reset keyboard du 377 atkbd.reset= [HW] Reset keyboard during initialization
467 378
468 atkbd.set= [HW] Select keyboard c 379 atkbd.set= [HW] Select keyboard code set
469 Format: <int> (2 = AT 380 Format: <int> (2 = AT (default), 3 = PS/2)
470 381
471 atkbd.scroll= [HW] Enable scroll whe 382 atkbd.scroll= [HW] Enable scroll wheel on MS Office and similar
472 keyboards 383 keyboards
473 384
474 atkbd.softraw= [HW] Choose between sy 385 atkbd.softraw= [HW] Choose between synthetic and real raw mode
475 Format: <bool> (0 = re 386 Format: <bool> (0 = real, 1 = synthetic (default))
476 387
477 atkbd.softrepeat= [HW] 388 atkbd.softrepeat= [HW]
478 Use software keyboard 389 Use software keyboard repeat
479 390
480 audit= [KNL] Enable the audit 391 audit= [KNL] Enable the audit sub-system
481 Format: { "0" | "1" | 392 Format: { "0" | "1" | "off" | "on" }
482 0 | off - kernel audit 393 0 | off - kernel audit is disabled and can not be
483 enabled until the 394 enabled until the next reboot
484 unset - kernel audit i 395 unset - kernel audit is initialized but disabled and
485 will be fully enab 396 will be fully enabled by the userspace auditd.
486 1 | on - kernel audit 397 1 | on - kernel audit is initialized and partially
487 enabled, storing a 398 enabled, storing at most audit_backlog_limit
488 messages in RAM un 399 messages in RAM until it is fully enabled by the
489 userspace auditd. 400 userspace auditd.
490 Default: unset 401 Default: unset
491 402
492 audit_backlog_limit= [KNL] Set the aud 403 audit_backlog_limit= [KNL] Set the audit queue size limit.
493 Format: <int> (must be 404 Format: <int> (must be >=0)
494 Default: 64 405 Default: 64
495 406
496 bau= [X86_UV] Enable the BA 407 bau= [X86_UV] Enable the BAU on SGI UV. The default
497 behavior is to disable 408 behavior is to disable the BAU (i.e. bau=0).
498 Format: { "0" | "1" } 409 Format: { "0" | "1" }
499 0 - Disable the BAU. 410 0 - Disable the BAU.
500 1 - Enable the BAU. 411 1 - Enable the BAU.
501 unset - Disable the BA 412 unset - Disable the BAU.
502 413
503 baycom_epp= [HW,AX25] 414 baycom_epp= [HW,AX25]
504 Format: <io>,<mode> 415 Format: <io>,<mode>
505 416
506 baycom_par= [HW,AX25] BayCom Paral 417 baycom_par= [HW,AX25] BayCom Parallel Port AX.25 Modem
507 Format: <io>,<mode> 418 Format: <io>,<mode>
508 See header of drivers/ 419 See header of drivers/net/hamradio/baycom_par.c.
509 420
510 baycom_ser_fdx= [HW,AX25] 421 baycom_ser_fdx= [HW,AX25]
511 BayCom Serial Port AX. 422 BayCom Serial Port AX.25 Modem (Full Duplex Mode)
512 Format: <io>,<irq>,<mo 423 Format: <io>,<irq>,<mode>[,<baud>]
513 See header of drivers/ 424 See header of drivers/net/hamradio/baycom_ser_fdx.c.
514 425
515 baycom_ser_hdx= [HW,AX25] 426 baycom_ser_hdx= [HW,AX25]
516 BayCom Serial Port AX. 427 BayCom Serial Port AX.25 Modem (Half Duplex Mode)
517 Format: <io>,<irq>,<mo 428 Format: <io>,<irq>,<mode>
518 See header of drivers/ 429 See header of drivers/net/hamradio/baycom_ser_hdx.c.
519 430
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 431 blkdevparts= Manual partition parsing of block device(s) for
527 embedded devices based 432 embedded devices based on command line input.
528 See Documentation/bloc !! 433 See Documentation/block/cmdline-partition.txt
529 434
530 boot_delay= [KNL,EARLY] !! 435 boot_delay= Milliseconds to delay each printk during boot.
531 Milliseconds to delay !! 436 Values larger than 10 seconds (10000) are changed to
532 Only works if CONFIG_B !! 437 no delay (0).
533 and you may also have <<
534 values larger than 10 <<
535 erroneous and ignored. <<
536 Format: integer 438 Format: integer
537 439
538 bootconfig [KNL,EARLY] !! 440 bootmem_debug [KNL] Enable bootmem allocator debug messages.
539 Extended command line <<
540 and this will cause th <<
541 441
542 See Documentation/admi !! 442 bert_disable [ACPI]
>> 443 Disable BERT OS support on buggy BIOSes.
543 444
544 bttv.card= [HW,V4L] bttv (bt848 + 445 bttv.card= [HW,V4L] bttv (bt848 + bt878 based grabber cards)
545 bttv.radio= Most important insmod 446 bttv.radio= Most important insmod options are available as
546 kernel args too. 447 kernel args too.
547 bttv.pll= See Documentation/admi !! 448 bttv.pll= See Documentation/media/v4l-drivers/bttv.rst
548 bttv.tuner= 449 bttv.tuner=
549 450
550 bulk_remove=off [PPC] This parameter 451 bulk_remove=off [PPC] This parameter disables the use of the pSeries
551 firmware feature for f 452 firmware feature for flushing multiple hpte entries
552 at a time. 453 at a time.
553 454
554 c101= [NET] Moxa C101 synchr 455 c101= [NET] Moxa C101 synchronous serial card
555 456
556 cachesize= [BUGS=X86-32] Override 457 cachesize= [BUGS=X86-32] Override level 2 CPU cache size detection.
557 Sometimes CPU hardware 458 Sometimes CPU hardware bugs make them report the cache
558 size incorrectly. The 459 size incorrectly. The kernel will attempt work arounds
559 to fix known problems, 460 to fix known problems, but for some CPUs it is not
560 possible to determine 461 possible to determine what the correct size should be.
561 This option provides a 462 This option provides an override for these situations.
562 463
563 carrier_timeout= 464 carrier_timeout=
564 [NET] Specifies amount 465 [NET] Specifies amount of time (in seconds) that
565 the kernel should wait 466 the kernel should wait for a network carrier. By default
566 it waits 120 seconds. 467 it waits 120 seconds.
567 468
568 ca_keys= [KEYS] This parameter 469 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 470 the system trusted keyring to be used for certificate
570 trust validation. 471 trust validation.
571 format: { id:<keyid> | 472 format: { id:<keyid> | builtin }
572 473
573 cca= [MIPS,EARLY] Override !! 474 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 475 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 476 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 477 for platform specific values (SB1, Loongson3 and
577 others). 478 others).
578 479
579 ccw_timeout_log [S390] 480 ccw_timeout_log [S390]
580 See Documentation/arch !! 481 See Documentation/s390/CommonIO for details.
581 482
582 cgroup_disable= [KNL] Disable a partic !! 483 cgroup_disable= [KNL] Disable a particular controller
583 Format: {name of the c !! 484 Format: {name of the controller(s) to disable}
584 The effects of cgroup_ 485 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 486 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 487 a single hierarchy
587 - foo isn't visible as 488 - foo isn't visible as an individually mountable
588 subsystem 489 subsystem
589 - if foo is an optiona <<
590 disabled and corresp <<
591 created <<
592 {Currently only "memor 490 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 491 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 492 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" <<
596 stall information acco <<
597 493
598 cgroup_no_v1= [KNL] Disable cgroup c 494 cgroup_no_v1= [KNL] Disable cgroup controllers and named hierarchies in v1
599 Format: { { controller 495 Format: { { controller | "all" | "named" }
600 [,{ controll 496 [,{ controller | "all" | "named" }...] }
601 Like cgroup_disable, b 497 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 498 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c 499 "all" blacklists all controllers and "named" disables
604 named mounts. Specifyi 500 named mounts. Specifying both "all" and "named" disables
605 all v1 hierarchies. 501 all v1 hierarchies.
606 502
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 <<
611 cgroup.memory= [KNL] Pass options to 503 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 504 Format: <string>
613 nosocket -- Disable so 505 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 506 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 507
617 checkreqprot= [SELINUX] Set initial !! 508 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 509 Format: { "0" | "1" }
619 See security/selinux/K 510 See security/selinux/Kconfig help text.
620 0 -- check protection 511 0 -- check protection applied by kernel (includes
621 any implied ex 512 any implied execute protection).
622 1 -- check protection 513 1 -- check protection requested by application.
623 Default value is set v 514 Default value is set via a kernel config option.
624 Value can be changed a 515 Value can be changed at runtime via
625 /sys/fs/selinu !! 516 /selinux/checkreqprot.
626 Setting checkreqprot t <<
627 517
628 cio_ignore= [S390] 518 cio_ignore= [S390]
629 See Documentation/arch !! 519 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 520 clk_ignore_unused
650 [CLK] 521 [CLK]
651 Prevents the clock fra 522 Prevents the clock framework from automatically gating
652 clocks that have not b 523 clocks that have not been explicitly enabled by a Linux
653 device driver but are 524 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 525 by the bootloader/firmware. Note that this does not
655 force such clocks to b 526 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 527 those clocks in any way. This parameter is useful for
657 debug and development, 528 debug and development, but should not be needed on a
658 platform with proper d 529 platform with proper driver support. For more
659 information, see Docum 530 information, see Documentation/driver-api/clk.rst.
660 531
661 clock= [BUGS=X86-32, HW] gett 532 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 533 [Deprecated]
663 Forces specified clock 534 Forces specified clocksource (if available) to be used
664 when calculating getti 535 when calculating gettimeofday(). If specified
665 clocksource is not ava 536 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 537 Format: { pit | tsc | cyclone | pmtmr }
667 538
668 clocksource= Override the default c 539 clocksource= Override the default clocksource
669 Format: <string> 540 Format: <string>
670 Override the default c 541 Override the default clocksource and use the clocksource
671 with the name specifie 542 with the name specified.
672 Some clocksource names 543 Some clocksource names to choose from, depending on
673 the platform: 544 the platform:
674 [all] jiffies (this is 545 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 546 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 547 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 548 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 549 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 550 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 551 [MIPS] MIPS
681 [PARISC] cr16 552 [PARISC] cr16
682 [S390] tod 553 [S390] tod
683 [SH] SuperH 554 [SH] SuperH
684 [SPARC64] tick 555 [SPARC64] tick
685 [X86-64] hpet,tsc 556 [X86-64] hpet,tsc
686 557
687 clocksource.arm_arch_timer.evtstrm= 558 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 559 [ARM,ARM64]
689 Format: <bool> 560 Format: <bool>
690 Enable/disable the eve 561 Enable/disable the eventstream feature of the ARM
691 architected timer so t 562 architected timer so that code using WFE-based polling
692 loops can be debugged 563 loops can be debugged more effectively on production
693 systems. 564 systems.
694 565
695 clocksource.verify_n_cpus= [KNL] !! 566 clearcpuid=BITNUM [X86]
696 Limit the number of CP !! 567 Disable CPUID feature X for the kernel. See
697 marked with CLOCK_SOUR !! 568 arch/x86/include/asm/cpufeatures.h for the valid bit
698 are marked unstable du !! 569 numbers. Note the Linux specific bits are not necessarily
699 A negative value says !! 570 stable over kernel options, but the vendor specific
700 zero says not to check !! 571 ones should be.
701 nr_cpu_ids are silentl !! 572 Also note that user programs calling CPUID directly
702 The actual CPUs are ch !! 573 or using the feature without checking anything
703 no replacement if the !! 574 will still see it. This just prevents it from
704 !! 575 being used by the kernel or shown in /proc/cpuinfo.
705 clocksource-wdtest.holdoff= [KNL] !! 576 Also note the kernel might malfunction if you disable
706 Set the time in second !! 577 some critical bits.
707 watchdog test waits be <<
708 Defaults to zero when <<
709 10 seconds when built <<
710 578
711 cma=nn[MG]@[start[MG][-end[MG]]] 579 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 580 [ARM,X86,KNL]
713 Sets the size of kerne 581 Sets the size of kernel global memory area for
714 contiguous memory allo 582 contiguous memory allocations and optionally the
715 placement constraint b 583 placement constraint by the physical address range of
716 memory allocations. A 584 memory allocations. A value of 0 disables CMA
717 altogether. For more i 585 altogether. For more information, see
718 kernel/dma/contiguous. !! 586 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 <<
741 587
742 cmo_free_hint= [PPC] Format: { yes | 588 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 589 Specify whether pages are marked as being inactive
744 when they are freed. 590 when they are freed. This is used in CMO environments
745 to determine OS memory 591 to determine OS memory pressure for page stealing by
746 a hypervisor. 592 a hypervisor.
747 Default: yes 593 Default: yes
748 594
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 595 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 596 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 597 allocations, by default set to 256K.
752 598
753 com20020= [HW,NET] ARCnet - COM2 599 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 600 Format:
755 <io>[,<irq>[,<nodeID>[ 601 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 602
757 com90io= [HW,NET] ARCnet - COM9 603 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 604 Format: <io>[,<irq>]
759 605
760 com90xx= [HW,NET] 606 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 607 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 608 Format: <io>[,<irq>[,<memstart>]]
763 609
764 condev= [HW,S390] console devi 610 condev= [HW,S390] console device
765 conmode= 611 conmode=
766 612
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 613 console= [KNL] Output console device and options.
779 614
780 tty<n> Use the virtual consol 615 tty<n> Use the virtual console device <n>.
781 616
782 ttyS<n>[,options] 617 ttyS<n>[,options]
783 ttyUSB0[,options] 618 ttyUSB0[,options]
784 Use the specified seri 619 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 620 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 621 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 622 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 623 omit it). Default is "9600n8".
789 624
790 See Documentation/admi 625 See Documentation/admin-guide/serial-console.rst for more
791 information. See 626 information. See
792 Documentation/networki !! 627 Documentation/networking/netconsole.txt for an
793 alternative. 628 alternative.
794 629
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] 630 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 631 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 632 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 633 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 634 uart[8250],0x<addr>[,options]
819 Start an early, polled 635 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 636 UART at the specified I/O port or MMIO address,
821 switching to the match 637 switching to the matching ttyS device later.
822 MMIO inter-register ad 638 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 639 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 640 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 641 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 642 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 643 the h/w is not re-initialized.
828 644
829 hvc<n> Use the hypervisor con 645 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 646 both Xen and PowerPC hypervisors.
831 647
832 { null | "" } <<
833 Use to disable console <<
834 console messages disca <<
835 This must be the only <<
836 kernel command line. <<
837 <<
838 If the device connected to the 648 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 649 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 650 console=brl,ttyS0
841 For now, only VisioBraille is 651 For now, only VisioBraille is supported.
842 652
843 console_msg_format= 653 console_msg_format=
844 [KNL] Change console m 654 [KNL] Change console messages format
845 default 655 default
846 By default we print me 656 By default we print messages on consoles in
847 "[time stamp] text\n" 657 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 658 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 659 `printk_time' param).
850 syslog 660 syslog
851 Switch to syslog forma 661 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 662 IOW, each message will have a facility and loglevel
853 prefix. The format is 663 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 664 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 665 from /proc/kmsg.
856 666
857 consoleblank= [KNL] The console blan 667 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 668 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 669 Defaults to 0.
860 670
861 coredump_filter= 671 coredump_filter=
862 [KNL] Change the defau 672 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 673 /proc/<pid>/coredump_filter.
864 See also Documentation !! 674 See also Documentation/filesystems/proc.txt.
865 675
866 coresight_cpu_debug.enable 676 coresight_cpu_debug.enable
867 [ARM,ARM64] 677 [ARM,ARM64]
868 Format: <bool> 678 Format: <bool>
869 Enable/disable the CPU 679 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 680 0: default value, disable debugging
871 1: enable debugging at 681 1: enable debugging at boot time
872 682
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 683 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 684 disable the cpuidle sub-system
879 685
880 cpuidle.governor= 686 cpuidle.governor=
881 [CPU_IDLE] Name of the 687 [CPU_IDLE] Name of the cpuidle governor to use.
882 688
883 cpufreq.off=1 [CPU_FREQ] 689 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 690 disable the cpufreq sub-system
885 691
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 692 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 693 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 694 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 695 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 696 Default: 10000
896 697
897 cpuhp.parallel= !! 698 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 699 Format:
899 Format: <bool> !! 700 <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. <<
910 701
911 crashkernel=size[KMG][@offset[KMG]] 702 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 703 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 704 upon panic. This parameter reserves the physical
914 memory region [offset, 705 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 706 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica 707 is selected automatically.
917 [KNL, X86-64, ARM64, R !! 708 [KNL, x86_64] select a region under 4G first, and
918 under 4G first, and fa !! 709 fall back to reserve region above 4G when '@offset'
919 4G when '@offset' hasn !! 710 hasn't been specified.
920 See Documentation/admi !! 711 See Documentation/kdump/kdump.txt for further details.
921 712
922 crashkernel=range1:size1[,range2:size2 713 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 714 [KNL] Same as above, but depends on the memory
924 in the running system. 715 in the running system. The syntax of range is
925 start-[end] where star 716 start-[end] where start and end are both
926 a memory unit (amount[ 717 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu !! 718 Documentation/kdump/kdump.txt for an example.
928 719
929 crashkernel=size[KMG],high 720 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 721 [KNL, x86_64] range could be above 4G. Allow kernel
931 above 4G. !! 722 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 723 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 724 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 725 available.
935 below 4G, if available <<
936 It will be ignored if 726 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 727 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 728 [KNL, x86_64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 729 is passed, kernel could allocate physical memory region
940 physical memory region !! 730 above 4G, that cause second kernel crash on system
941 crash on system that r !! 731 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 732 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 733 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 734 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 735 at least 256M below 4G automatically.
946 size is platform depen !! 736 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 737 for second kernel instead.
953 0: to disable low allo 738 0: to disable low allocation.
954 It will be ignored whe 739 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 740 or memory reserved is below 4G.
956 741
957 cryptomgr.notests 742 cryptomgr.notests
958 [KNL] Disable crypto s 743 [KNL] Disable crypto self-tests
959 744
960 cs89x0_dma= [HW,NET] 745 cs89x0_dma= [HW,NET]
961 Format: <dma> 746 Format: <dma>
962 747
963 cs89x0_media= [HW,NET] 748 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 749 Format: { rj45 | aui | bnc }
965 750
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] 751 dasd= [HW,NET]
976 See header of drivers/ 752 See header of drivers/s390/block/dasd_devmap.c.
977 753
978 db9.dev[2|3]= [HW,JOY] Multisystem j 754 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 755 (one device per port)
980 Format: <port#>,<type> 756 Format: <port#>,<type>
981 See also Documentation 757 See also Documentation/input/devices/joystick-parport.rst
982 758
983 debug [KNL,EARLY] Enable ker !! 759 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 760 time. See
>> 761 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 762 details. Deprecated, see dyndbg.
>> 763
>> 764 debug [KNL] Enable kernel debugging (events log level).
984 765
985 debug_boot_weak_hash 766 debug_boot_weak_hash
986 [KNL,EARLY] Enable pri !! 767 [KNL] Enable printing [hashed] pointers early in the
987 boot sequence. If ena 768 boot sequence. If enabled, we use a weak hash instead
988 of siphash to hash poi 769 of siphash to hash pointers. Use this option if you are
989 seeing instances of '( 770 seeing instances of '(___ptrval___)') and need to see a
990 value (hashed pointer) 771 value (hashed pointer) instead. Cryptographically
991 insecure, please do no 772 insecure, please do not use on production kernels.
992 773
993 debug_locks_verbose= 774 debug_locks_verbose=
994 [KNL] verbose locking !! 775 [KNL] verbose self-tests
995 Format: <int> !! 776 Format=<0|1>
996 Print debugging info w 777 Print debugging info while doing the locking API
997 self-tests. 778 self-tests.
998 Bitmask for the variou !! 779 We default to 0 (no extra messages), setting it to
999 (no extra messages), s !! 780 1 will print _a lot_ more information - normally
1000 will print _a_lot_ mo !! 781 only useful to kernel developers.
1001 useful to lockdep dev !! 782
>> 783 debug_objects [KNL] Enable object debugging
1002 784
1003 debug_objects [KNL,EARLY] Enable ob !! 785 no_debug_objects
>> 786 [KNL] Disable object debugging
1004 787
1005 debug_guardpage_minorder= 788 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 789 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 790 parameter allows control of the order of pages that will
1008 be intentionally kept 791 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 792 buddy allocator. Bigger value increase the probability
1010 of catching random me 793 of catching random memory corruption, but reduce the
1011 amount of memory for 794 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 795 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 796 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 797 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 798 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 799 random memory location. Note that there exists a class
1017 a class of memory cor !! 800 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 801 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 802 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 803 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 804 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 805 tracking down these problems.
1023 806
1024 debug_pagealloc= 807 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 808 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1026 enables the feature a !! 809 parameter enables the feature at boot time. In
1027 disabled and the syst !! 810 default, it is disabled. We can avoid allocating huge
1028 kernel built without !! 811 chunk of memory for debug pagealloc if we don't enable
1029 Note: to get most of !! 812 it at boot time and the system will work mostly same
1030 useful to also enable !! 813 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
1031 on: enable the featur 814 on: enable the feature
1032 815
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 816 debugpat [X86] Enable PAT debugging
1049 817
>> 818 decnet.addr= [HW,NET]
>> 819 Format: <area>[,<node>]
>> 820 See also Documentation/networking/decnet.txt.
>> 821
1050 default_hugepagesz= 822 default_hugepagesz=
1051 [HW] The size of the !! 823 [same as hugepagesz=] The size of the default
1052 the size represented !! 824 HugeTLB page size. This is the size represented by
1053 APIs. In addition, t !! 825 the legacy /proc/ hugepages APIs, used for SHM, and
1054 used for shmget(), mm !! 826 default size when mounting hugetlbfs filesystems.
1055 filesystems. If not !! 827 Defaults to the default architecture's huge page size
1056 architecture's defaul !! 828 if not specified.
1057 sizes are architectur <<
1058 Documentation/admin-g <<
1059 Format: size[KMG] <<
1060 829
1061 deferred_probe_timeout= 830 deferred_probe_timeout=
1062 [KNL] Debugging optio 831 [KNL] Debugging option to set a timeout in seconds for
1063 deferred probe to giv 832 deferred probe to give up waiting on dependencies to
1064 probe. Only specific 833 probe. Only specific dependencies (subsystems or
1065 drivers) that have op !! 834 drivers) that have opted in will be ignored. A timeout of 0
1066 of 0 will timeout at !! 835 will timeout at the end of initcalls. This option will also
1067 out hasn't expired, i <<
1068 successful driver reg <<
1069 dump out devices stil 836 dump out devices still on the deferred probe list after
1070 retrying. 837 retrying.
1071 838
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 <<
1110 dhash_entries= [KNL] 839 dhash_entries= [KNL]
1111 Set number of hash bu 840 Set number of hash buckets for dentry cache.
1112 841
1113 disable_1tb_segments [PPC,EARLY] !! 842 disable_1tb_segments [PPC]
1114 Disables the use of 1 843 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 844 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 845 can be useful when debugging issues that require an SLB
1117 miss to occur. 846 miss to occur.
1118 847
1119 disable= [IPV6] 848 disable= [IPV6]
1120 See Documentation/net !! 849 See Documentation/networking/ipv6.txt.
>> 850
>> 851 hardened_usercopy=
>> 852 [KNL] Under CONFIG_HARDENED_USERCOPY, whether
>> 853 hardening is enabled for this boot. Hardened
>> 854 usercopy checking is used to protect the kernel
>> 855 from reading or writing beyond known memory
>> 856 allocation boundaries as a proactive defense
>> 857 against bounds-checking flaws in the kernel's
>> 858 copy_to_user()/copy_from_user() interface.
>> 859 on Perform hardened usercopy checks (default).
>> 860 off Disable hardened usercopy checks.
1121 861
1122 disable_radix [PPC,EARLY] !! 862 disable_radix [PPC]
1123 Disable RADIX MMU mod 863 Disable RADIX MMU mode on POWER9
1124 864
1125 disable_tlbie [PPC] !! 865 disable_cpu_apicid= [X86,APIC,SMP]
1126 Disable TLBIE instruc !! 866 Format: <int>
1127 with KVM, with HASH M !! 867 The number of initial APIC ID for the
>> 868 corresponding CPU to be disabled at boot,
>> 869 mostly used for the kdump 2nd kernel to
>> 870 disable BSP to wake up multiple CPUs without
>> 871 causing system reset or hang due to sending
>> 872 INIT from AP to BSP.
>> 873
>> 874 perf_v4_pmi= [X86,INTEL]
>> 875 Format: <bool>
>> 876 Disable Intel PMU counter freezing feature.
>> 877 The feature only exists starting from
>> 878 Arch Perfmon v4 (Skylake and newer).
1128 879
1129 disable_ddw [PPC/PSERIES,EARLY] !! 880 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W !! 881 Disable Dynamic DMA Window support. Use this if
1131 to workaround buggy f 882 to workaround buggy firmware.
1132 883
1133 disable_ipv6= [IPV6] 884 disable_ipv6= [IPV6]
1134 See Documentation/net !! 885 See Documentation/networking/ipv6.txt.
1135 886
1136 disable_mtrr_cleanup [X86,EARLY] !! 887 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 888 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 889 to discrete, to make X server driver able to add WB
1139 entry later. This par 890 entry later. This parameter disables that.
1140 891
1141 disable_mtrr_trim [X86, Intel and AMD !! 892 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 893 By default the kernel will trim any uncacheable
1143 memory out of your av 894 memory out of your available memory pool based on
1144 MTRR settings. This 895 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 896 possibly causing your machine to run very slowly.
1146 897
1147 disable_timer_pin_1 [X86,EARLY] !! 898 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 899 Disable PIN 1 of APIC timer
1149 Can be useful to work 900 Can be useful to work around chipset bugs.
1150 901
1151 dis_ucode_ldr [X86] Disable the mic 902 dis_ucode_ldr [X86] Disable the microcode loader.
1152 903
1153 dma_debug=off If the kernel is comp 904 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 905 this option disables the debugging code at boot.
1155 906
1156 dma_debug_entries=<number> 907 dma_debug_entries=<number>
1157 This option allows to 908 This option allows to tune the number of preallocated
1158 entries for DMA-API d 909 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 910 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 911 DMA-API debugging code disables itself because the
1161 architectural default 912 architectural default is too low.
1162 913
1163 dma_debug_driver=<driver_name> 914 dma_debug_driver=<driver_name>
1164 With this option the 915 With this option the DMA-API debugging driver
1165 filter feature can be 916 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 917 pass the driver to filter for as the parameter.
1167 The filter can be dis 918 The filter can be disabled or changed to another
1168 driver later using sy 919 driver later using sysfs.
1169 920
1170 reg_file_data_sampling= <<
1171 [X86] Controls mitiga <<
1172 Sampling (RFDS) vulne <<
1173 vulnerability which m <<
1174 kernel data values pr <<
1175 registers, vector reg <<
1176 RFDS only affects Int <<
1177 <<
1178 on: Turns ON the <<
1179 off: Turns OFF the <<
1180 <<
1181 This parameter overri <<
1182 by CONFIG_MITIGATION_ <<
1183 disabled when other V <<
1184 are enabled. In order <<
1185 VERW based mitigation <<
1186 <<
1187 For details see: <<
1188 Documentation/admin-g <<
1189 <<
1190 driver_async_probe= [KNL] 921 driver_async_probe= [KNL]
1191 List of driver names !! 922 List of driver names to be probed asynchronously.
1192 matches with all driv <<
1193 rest of the listed dr <<
1194 match the *. <<
1195 Format: <driver_name1 923 Format: <driver_name1>,<driver_name2>...
1196 924
1197 drm.edid_firmware=[<connector>:]<file 925 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 926 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 927 panels may send no or incorrect EDID data sets.
1200 This parameter allows 928 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 929 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 930 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 931 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 932 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 933 and no file with the same name exists. Details and
>> 934 instructions how to build your own EDID data are
>> 935 available in Documentation/EDID/HOWTO.txt. An EDID
>> 936 data set will only be used for a particular connector,
>> 937 if its name and a colon are prepended to the EDID
>> 938 name. Each connector may use a unique EDID data
>> 939 set by separating the files with a comma. An EDID
1206 data set with no conn 940 data set with no connector name will be used for
1207 any connectors not ex 941 any connectors not explicitly specified.
1208 942
1209 dscc4.setup= [NET] 943 dscc4.setup= [NET]
1210 944
1211 dt_cpu_ftrs= [PPC,EARLY] !! 945 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 946 Format: {"off" | "known"}
1213 Control how the dt_cp 947 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 948 used for CPU feature discovery and setup (if it
1215 exists). 949 exists).
1216 off: Do not use it, f 950 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 951 known: Do not pass through unknown features to guests
1218 or userspace, only th 952 or userspace, only those that the kernel is aware of.
1219 953
1220 dump_apple_properties [X86] 954 dump_apple_properties [X86]
1221 Dump name and content 955 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 956 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 957 what data is available or for reverse-engineering.
1224 958
1225 dyndbg[="val"] [KNL,DYNAMIC_ 959 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] !! 960 module.dyndbg[="val"]
1227 Enable debug messages 961 Enable debug messages at boot time. See
1228 Documentation/admin-g 962 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 963 for details.
1230 964
1231 early_ioremap_debug [KNL,EARLY] !! 965 nompx [X86] Disables Intel Memory Protection Extensions.
>> 966 See Documentation/x86/intel_mpx.txt for more
>> 967 information about the feature.
>> 968
>> 969 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 970 in some Intel CPUs.
>> 971
>> 972 module.async_probe [KNL]
>> 973 Enable asynchronous probe on this module.
>> 974
>> 975 early_ioremap_debug [KNL]
1232 Enable debug messages 976 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 977 is useful for tracking down temporary early mappings
1234 which are not unmappe 978 which are not unmapped.
1235 979
1236 earlycon= [KNL,EARLY] Output ea !! 980 earlycon= [KNL] Output early console device and options.
>> 981
>> 982 [ARM64] The early console is determined by the
>> 983 stdout-path property in device tree's chosen node,
>> 984 or determined by the ACPI SPCR table.
1237 985
1238 When used with no opt !! 986 [X86] When used with no options the early console is
1239 determined by stdout- !! 987 determined by the ACPI SPCR table.
1240 chosen node or the AC <<
1241 the platform. <<
1242 988
1243 cdns,<addr>[,options] 989 cdns,<addr>[,options]
1244 Start an early, polle 990 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 991 (xuartps) serial port at the specified address. Only
1246 supported option is b 992 supported option is baud rate. If baud rate is not
1247 specified, the serial 993 specified, the serial port must already be setup and
1248 configured. 994 configured.
1249 995
1250 uart[8250],io,<addr>[,options !! 996 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 997 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 998 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 999 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 1000 uart[8250],0x<addr>[,options]
1255 Start an early, polle 1001 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 1002 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 1003 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 1004 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 1005 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 1006 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 1007 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 1008 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 1009
1266 pl011,<addr> 1010 pl011,<addr>
1267 pl011,mmio32,<addr> 1011 pl011,mmio32,<addr>
1268 Start an early, polle 1012 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 1013 port at the specified address. The pl011 serial port
1270 must already be setup 1014 must already be setup and configured. Options are not
1271 yet supported. If 'm 1015 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 1016 the driver will use only 32-bit accessors to read/write
1273 the device registers. 1017 the device registers.
1274 1018
1275 liteuart,<addr> <<
1276 Start an early consol <<
1277 specified address. Th <<
1278 setup and configured. <<
1279 <<
1280 meson,<addr> 1019 meson,<addr>
1281 Start an early, polle 1020 Start an early, polled-mode console on a meson serial
1282 port at the specified 1021 port at the specified address. The serial port must
1283 already be setup and 1022 already be setup and configured. Options are not yet
1284 supported. 1023 supported.
1285 1024
1286 msm_serial,<addr> 1025 msm_serial,<addr>
1287 Start an early, polle 1026 Start an early, polled-mode console on an msm serial
1288 port at the specified 1027 port at the specified address. The serial port
1289 must already be setup 1028 must already be setup and configured. Options are not
1290 yet supported. 1029 yet supported.
1291 1030
1292 msm_serial_dm,<addr> 1031 msm_serial_dm,<addr>
1293 Start an early, polle 1032 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 1033 dm port at the specified address. The serial port
1295 must already be setup 1034 must already be setup and configured. Options are not
1296 yet supported. 1035 yet supported.
1297 1036
1298 owl,<addr> 1037 owl,<addr>
1299 Start an early, polle 1038 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 1039 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 1040 specified address. The serial port must already be
1302 setup and configured. 1041 setup and configured. Options are not yet supported.
1303 1042
1304 rda,<addr> 1043 rda,<addr>
1305 Start an early, polle 1044 Start an early, polled-mode console on a serial port
1306 of an RDA Micro SoC, 1045 of an RDA Micro SoC, such as RDA8810PL, at the
1307 specified address. Th 1046 specified address. The serial port must already be
1308 setup and configured. 1047 setup and configured. Options are not yet supported.
1309 1048
1310 sbi <<
1311 Use RISC-V SBI (Super <<
1312 console. <<
1313 <<
1314 smh Use ARM semihosting c 1049 smh Use ARM semihosting calls for early console.
1315 1050
1316 s3c2410,<addr> 1051 s3c2410,<addr>
1317 s3c2412,<addr> 1052 s3c2412,<addr>
1318 s3c2440,<addr> 1053 s3c2440,<addr>
1319 s3c6400,<addr> 1054 s3c6400,<addr>
1320 s5pv210,<addr> 1055 s5pv210,<addr>
1321 exynos4210,<addr> 1056 exynos4210,<addr>
1322 Use early console pro 1057 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 1058 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1059 a correct base address of the selected UART port. The
1325 serial port must alre 1060 serial port must already be setup and configured.
1326 Options are not yet s 1061 Options are not yet supported.
1327 1062
1328 lantiq,<addr> 1063 lantiq,<addr>
1329 Start an early, polle 1064 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1065 (lqasc) port at the specified address. The serial port
1331 must already be setup 1066 must already be setup and configured. Options are not
1332 yet supported. 1067 yet supported.
1333 1068
1334 lpuart,<addr> 1069 lpuart,<addr>
1335 lpuart32,<addr> 1070 lpuart32,<addr>
1336 Use early console pro 1071 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1072 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1073 A valid base address must be provided, and the serial
1339 port must already be 1074 port must already be setup and configured.
1340 1075
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> 1076 ar3700_uart,<addr>
1348 Start an early, polle 1077 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1078 Armada 3700 serial port at the specified
1350 address. The serial p 1079 address. The serial port must already be setup
1351 and configured. Optio 1080 and configured. Options are not yet supported.
1352 1081
1353 qcom_geni,<addr> 1082 qcom_geni,<addr>
1354 Start an early, polle 1083 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1084 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1085 specified address. The serial port must already be
1357 setup and configured. 1086 setup and configured. Options are not yet supported.
1358 1087
1359 efifb,[options] 1088 efifb,[options]
1360 Start an early, unacc 1089 Start an early, unaccelerated console on the EFI
1361 memory mapped framebu 1090 memory mapped framebuffer (if available). On cache
1362 coherent non-x86 syst 1091 coherent non-x86 systems that use system memory for
1363 the framebuffer, pass 1092 the framebuffer, pass the 'ram' option so that it is
1364 mapped with the corre 1093 mapped with the correct attributes.
1365 1094
1366 linflex,<addr> !! 1095 earlyprintk= [X86,SH,ARM,M68k,S390]
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 1096 earlyprintk=vga
1374 earlyprintk=sclp 1097 earlyprintk=sclp
1375 earlyprintk=xen 1098 earlyprintk=xen
1376 earlyprintk=serial[,t 1099 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1100 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1101 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1102 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial 1103 earlyprintk=pciserial[,force],bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1104 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1105
1384 earlyprintk is useful 1106 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1107 the normal console is initialized. It is not enabled by
1386 default because it ha 1108 default because it has some cosmetic problems.
1387 1109
1388 Append ",keep" to not 1110 Append ",keep" to not disable it when the real console
1389 takes over. 1111 takes over.
1390 1112
1391 Only one of vga, seri !! 1113 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1114 be used at a time.
1393 1115
1394 Currently only ttyS0 1116 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1117 name. Other I/O ports may be explicitly specified
1396 on some architectures 1118 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1119 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1120 earlyprintk=serial,0x1008,115200
1399 You can find the port 1121 You can find the port for a given device in
1400 /proc/tty/driver/seri 1122 /proc/tty/driver/serial:
1401 2: uart:ST166 1123 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1124
1403 Interaction with the 1125 Interaction with the standard serial driver is not
1404 very good. 1126 very good.
1405 1127
1406 The VGA output is eve !! 1128 The VGA and EFI output is eventually overwritten by
1407 the real console. 1129 the real console.
1408 1130
1409 The xen option can on !! 1131 The xen output can only be used by Xen PV guests.
1410 1132
1411 The sclp output can o 1133 The sclp output can only be used on s390.
1412 1134
1413 The bios output can o <<
1414 <<
1415 The optional "force" 1135 The optional "force" to "pciserial" enables use of a
1416 PCI device even when 1136 PCI device even when its classcode is not of the
1417 UART class. 1137 UART class.
1418 1138
1419 edac_report= [HW,EDAC] Control how 1139 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1140 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1141 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1142 by other higher priority error reporting module.
1423 off: disable H/W even 1143 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1144 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1145 default: on.
1426 1146
>> 1147 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1148 ekgdboc=kbd
>> 1149
>> 1150 This is designed to be used in conjunction with
>> 1151 the boot argument: earlyprintk=vga
>> 1152
1427 edd= [EDD] 1153 edd= [EDD]
1428 Format: {"off" | "on" 1154 Format: {"off" | "on" | "skip[mbr]"}
1429 1155
1430 efi= [EFI,EARLY] !! 1156 efi= [EFI]
1431 Format: { "debug", "d !! 1157 Format: { "old_map", "nochunk", "noruntime", "debug" }
1432 "nochunk", !! 1158 old_map [X86-64]: switch to the old ioremap-based EFI
1433 "novamap", !! 1159 runtime services mapping. 32-bit still uses this one by
1434 debug: enable misc de !! 1160 default.
1435 disable_early_pci_dma <<
1436 PCI bridges while in <<
1437 nochunk: disable read 1161 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1162 boot stub, as chunking can cause problems with some
1439 firmware implementati 1163 firmware implementations.
1440 noruntime : disable E 1164 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF !! 1165 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 1166
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1167 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1168 Using this parameter you can use more than 50% of
1453 your efi variable sto 1169 your efi variable storage. Use this parameter only if
1454 you are really sure t 1170 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1171 fulfills the spec otherwise your board may brick.
1456 1172
>> 1173 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1174 Add arbitrary attribute to specific memory range by
>> 1175 updating original EFI memory map.
>> 1176 Region of memory which aa attribute is added to is
>> 1177 from ss to ss+nn.
>> 1178 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1179 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1180 attribute is added to range 0x100000000-0x180000000 and
>> 1181 0x10a0000000-0x1120000000.
>> 1182
>> 1183 Using this parameter you can do debugging of EFI memmap
>> 1184 related feature. For example, you can do debugging of
>> 1185 Address Range Mirroring feature even if your box
>> 1186 doesn't support it.
>> 1187
1457 efivar_ssdt= [EFI; X86] Name of an 1188 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1189 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1190 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1191 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g !! 1192 Documentation/acpi/ssdt-overlays.txt for details.
1462 1193
1463 1194
1464 eisa_irq_edge= [PARISC,HW] 1195 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1196 See header of drivers/parisc/eisa.c.
1466 1197
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] 1198 elanfreq= [X86-32]
1479 See comment before fu 1199 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1200 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1201
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1202 elevator= [IOSCHED]
>> 1203 Format: { "mq-deadline" | "kyber" | "bfq" }
>> 1204 See Documentation/block/deadline-iosched.txt,
>> 1205 Documentation/block/kyber-iosched.txt and
>> 1206 Documentation/block/bfq-iosched.txt for details.
>> 1207
>> 1208 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1209 Specifies physical address of start of kernel core
1484 image elf header and 1210 image elf header and optionally the size. Generally
1485 kexec loader will pas 1211 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm !! 1212 See Documentation/kdump/kdump.txt for details.
1487 1213
1488 enable_mtrr_cleanup [X86,EARLY] !! 1214 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1215 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1216 to discrete, to make X server driver able to add WB
1491 entry later. This par 1217 entry later. This parameter enables that.
1492 1218
1493 enable_timer_pin_1 [X86] 1219 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1220 Enable PIN 1 of APIC timer
1495 Can be useful to work 1221 Can be useful to work around chipset bugs
1496 (in particular on som 1222 (in particular on some ATI chipsets).
1497 The kernel tries to s 1223 The kernel tries to set a reasonable default.
1498 1224
1499 enforcing= [SELINUX] Set initial !! 1225 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1226 Format: {"0" | "1"}
1501 See security/selinux/ 1227 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1228 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1229 1 -- enforcing (deny and log).
1504 Default value is 0. 1230 Default value is 0.
1505 Value can be changed !! 1231 Value can be changed at runtime via /selinux/enforce.
1506 /sys/fs/selinux/enfor <<
1507 1232
1508 erst_disable [ACPI] 1233 erst_disable [ACPI]
1509 Disable Error Record 1234 Disable Error Record Serialization Table (ERST)
1510 support. 1235 support.
1511 1236
1512 ether= [HW,NET] Ethernet car 1237 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1238 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1239 has equivalent usage. See its documentation for details.
1515 1240
1516 evm= [EVM] 1241 evm= [EVM]
1517 Format: { "fix" } 1242 Format: { "fix" }
1518 Permit 'security.evm' 1243 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1244 current integrity status.
1520 1245
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= 1246 failslab=
1530 fail_usercopy= <<
1531 fail_page_alloc= 1247 fail_page_alloc=
1532 fail_make_request=[KNL] 1248 fail_make_request=[KNL]
1533 General fault injecti 1249 General fault injection mechanism.
1534 Format: <interval>,<p 1250 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1251 See also Documentation/fault-injection/.
1536 1252
1537 fb_tunnels= [NET] <<
1538 Format: { initns | no <<
1539 See Documentation/adm <<
1540 fb_tunnels_only_for_i <<
1541 <<
1542 floppy= [HW] 1253 floppy= [HW]
1543 See Documentation/adm !! 1254 See Documentation/blockdev/floppy.txt.
>> 1255
>> 1256 force_pal_cache_flush
>> 1257 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1258 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1259 parameter will force ia64_sal_cache_flush to call
>> 1260 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1544 1261
1545 forcepae [X86-32] 1262 forcepae [X86-32]
1546 Forcefully enable Phy 1263 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1264 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1265 functionally usable PAE implementation.
1549 Warning: use of this 1266 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1267 and may cause unknown problems.
1551 1268
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] 1269 ftrace=[tracer]
1559 [FTRACE] will set and 1270 [FTRACE] will set and start the specified tracer
1560 as early as possible 1271 as early as possible in order to facilitate early
1561 boot debugging. 1272 boot debugging.
1562 1273
1563 ftrace_boot_snapshot !! 1274 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 1275 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1276 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1277 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1278 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1279 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 1280
1603 ftrace_filter=[function-list] 1281 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1282 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu !! 1283 tracer at boot up. function-list is a comma separated
1606 list of functions. Th 1284 list of functions. This list can be changed at run
1607 time by the set_ftrac 1285 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1286 tracing directory.
1609 1287
1610 ftrace_notrace=[function-list] 1288 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1289 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1290 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1291 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1292 tracing directory.
1615 1293
1616 ftrace_graph_filter=[function-list] 1294 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1295 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1296 by the function graph tracer at boot up.
1619 function-list is a co !! 1297 function-list is a comma separated list of functions
1620 that can be changed a 1298 that can be changed at run time by the
1621 set_graph_function fi 1299 set_graph_function file in the debugfs tracing directory.
1622 1300
1623 ftrace_graph_notrace=[function-list] 1301 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1302 [FTRACE] Do not trace from the functions specified in
1625 function-list. This !! 1303 function-list. This list is a comma separated list of
1626 functions that can be 1304 functions that can be changed at run time by the
1627 set_graph_notrace fil 1305 set_graph_notrace file in the debugfs tracing directory.
1628 1306
1629 ftrace_graph_max_depth=<uint> 1307 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1308 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1309 the max depth it will trace into a function. This value
1632 can be changed at run 1310 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1311 in the tracefs tracing directory. default: 0 (no limit)
1634 1312
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]= 1313 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1314 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1315 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1316 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1317 See also Documentation/input/devices/joystick-parport.rst
1677 1318
1678 gamma= [HW,DRM] 1319 gamma= [HW,DRM]
1679 1320
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1321 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1681 Format: off | on 1322 Format: off | on
1682 default: on 1323 default: on
1683 1324
1684 gather_data_sampling= <<
1685 [X86,INTEL,EARLY] Con <<
1686 mitigation. <<
1687 <<
1688 Gather Data Sampling <<
1689 allows unprivileged s <<
1690 previously stored in <<
1691 <<
1692 This issue is mitigat <<
1693 The mitigation may ha <<
1694 disabled. On systems <<
1695 disabling AVX serves <<
1696 <<
1697 force: Disable AVX t <<
1698 microcode mit <<
1699 mitigation is <<
1700 userspace wit <<
1701 <<
1702 off: Disable GDS m <<
1703 <<
1704 gcov_persist= [GCOV] When non-zero 1325 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1326 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1327 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1328 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1329 debugfs files are removed at module unload time.
1709 1330
1710 goldfish [X86] Enable the gold 1331 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1332 Don't use this when you are not running on the
1712 android emulator 1333 android emulator
1713 1334
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 1335 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1336 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1337 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1338 GPT to be used instead.
1724 1339
1725 grcan.enable0= [HW] Configuration of 1340 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1341 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1342 Format: 0 | 1
1728 Default: 0 1343 Default: 0
1729 grcan.enable1= [HW] Configuration of 1344 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1345 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1346 Format: 0 | 1
1732 Default: 0 1347 Default: 0
1733 grcan.select= [HW] Select which phy 1348 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1349 Format: 0 | 1
1735 Default: 0 1350 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1351 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1352 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1353 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1354 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1355 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1356 Default: 1024
1742 1357
1743 hardened_usercopy= !! 1358 gpio-mockup.gpio_mockup_ranges
1744 [KNL] Under CONFIG_HA !! 1359 [HW] Sets the ranges of gpiochip of for this device.
1745 hardening is enabled !! 1360 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 1361
1754 hardlockup_all_cpu_backtrace= 1362 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1363 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1364 backtraces on all cpus.
1757 Format: 0 | 1 !! 1365 Format: <integer>
1758 1366
1759 hashdist= [KNL,NUMA] Large hash 1367 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1368 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1369 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1370 Format: 0 | 1 (for off | on)
1763 1371
>> 1372 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1373
1764 hd= [EIDE] (E)IDE hard dr 1374 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1375 Format: <cyl>,<head>,<sect>
1766 1376
1767 hest_disable [ACPI] 1377 hest_disable [ACPI]
1768 Disable Hardware Erro 1378 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1379 corresponding firmware-first mode error processing
1770 logic will be disable 1380 logic will be disabled.
1771 1381
1772 hibernate= [HIBERNATION] !! 1382 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 1383 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1384 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1385 size on bigger boxes.
1796 1386
1797 highres= [KNL] Enable/disable 1387 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1388 Valid parameters: "on", "off"
1799 Default: "on" 1389 Default: "on"
1800 1390
1801 hlt [BUGS=ARM,SH] !! 1391 hisax= [HW,ISDN]
>> 1392 See Documentation/isdn/README.HiSax.
1802 1393
1803 hostname= [KNL,EARLY] Set the h !! 1394 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 1395
1816 hpet= [X86-32,HPET] option 1396 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1397 Format: { enable (default) | disable | force |
1818 verbose } 1398 verbose }
1819 disable: disable HPET 1399 disable: disable HPET and use PIT instead
1820 force: allow force en 1400 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1401 VIA, nVidia)
1822 verbose: show content 1402 verbose: show contents of HPET registers during setup
1823 1403
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1404 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1405 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1406
1827 hugepages= [HW] Number of HugeTL !! 1407 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1828 If this follows hugep !! 1408 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1829 the number of pages o !! 1409 On x86-64 and powerpc, this option can be specified
1830 If this is the first !! 1410 multiple times interleaved with hugepages= to reserve
1831 line, it specifies th !! 1411 huge pages of different sizes. Valid pages sizes on
1832 the default huge page !! 1412 x86-64 are 2M (when the CPU supports "pse") and 1G
1833 number of pages to al !! 1413 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1834 See also Documentatio <<
1835 Format: <integer> or <<
1836 <node>:<integ <<
1837 <<
1838 hugepagesz= <<
1839 [HW] The size of the <<
1840 conjunction with huge <<
1841 pages of a specific s <<
1842 hugepagesz=X hugepage <<
1843 each supported huge p <<
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 1414
1878 hung_task_panic= 1415 hung_task_panic=
1879 [KNL] Should the hung 1416 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 !! 1417 Format: <integer>
1881 1418
1882 A value of 1 instruct !! 1419 A nonzero value instructs the kernel to panic when a
1883 hung task is detected 1420 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1421 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1422 option. The value selected by this boot parameter can
1886 be changed later by t 1423 be changed later by the kernel.hung_task_panic sysctl.
1887 1424
1888 hvc_iucv= [S390] Number of z/V 1425 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1426 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1427 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1428 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1429 from listed z/VM user IDs only.
1893 1430
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1431 hv_nopvspin [X86,HYPER_V] Disables the paravirt spinlock optimizations
1895 Disables the paravirt !! 1432 which allow the hypervisor to 'idle' the
1896 which allow the hyper !! 1433 guest on lock contention.
1897 on lock contention. !! 1434
>> 1435 keep_bootcon [KNL]
>> 1436 Do not unregister boot console at start. This is only
>> 1437 useful for debugging when something happens in the window
>> 1438 between unregistering the boot console and initializing
>> 1439 the real console.
1898 1440
1899 i2c_bus= [HW] Override the 1441 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1442 or register an additional I2C bus that is not
1901 registered fr 1443 registered from board initialization code.
1902 Format: 1444 Format:
1903 <bus_id>,<clk 1445 <bus_id>,<clkrate>
1904 1446
1905 i2c_touchscreen_props= [HW,ACPI,X86] <<
1906 Set device-properties <<
1907 touchscreen, to e.g. <<
1908 mounted touchscreens. <<
1909 submit a drivers/plat <<
1910 adding a DMI quirk fo <<
1911 <<
1912 Format: <<
1913 <ACPI_HW_ID>:<prop_na <<
1914 Where <val> is one of <<
1915 Omit "=<val>" entirel <<
1916 Unsigned number <<
1917 Anything else <<
1918 <<
1919 Examples (split over <<
1920 i2c_touchscreen_props <<
1921 touchscreen-inverted- <<
1922 <<
1923 i2c_touchscreen_props <<
1924 touchscreen-size-y=10 <<
1925 firmware-name=gsl1680 <<
1926 <<
1927 i8042.debug [HW] Toggle i8042 deb 1447 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1448 i8042.unmask_kbd_data
1929 [HW] Enable printing 1449 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1450 (disabled by default, and as a pre-condition
1931 requires that i8 1451 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1452 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1453 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1454 keyboard and cannot control its state
1935 (Don't attempt t 1455 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1456 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1457 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1458 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1459 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1460 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1461 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1462 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1463 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1464 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1465 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1466 suspend-to-ram transitions, only during s2r
1947 transitions, or 1467 transitions, or never reset
1948 Format: { 1 | Y | y | 1468 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1469 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1470 0, N, n: don't ever reset controller
1951 Default: only on s2r 1471 Default: only on s2r transitions on x86; most other
1952 architectures force r 1472 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1473 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1474 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer <<
1956 [HW] Allow deferred p <<
1957 1475
1958 i810= [HW,DRM] 1476 i810= [HW,DRM]
1959 1477
>> 1478 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1479 indicates that the driver is running on unsupported
>> 1480 hardware.
>> 1481 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1482 does not match list of supported models.
>> 1483 i8k.power_status
>> 1484 [HW] Report power status in /proc/i8k
>> 1485 (disabled by default)
>> 1486 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1487 capability is set.
>> 1488
1960 i915.invert_brightness= 1489 i915.invert_brightness=
1961 [DRM] Invert the sens 1490 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1491 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1492 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1493 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1494 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1495 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1496 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1497 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1498 value switches the backlight off.
1970 -1 -- never invert br 1499 -1 -- never invert brightness
1971 0 -- machine default 1500 0 -- machine default
1972 1 -- force brightnes 1501 1 -- force brightness inversion
1973 1502
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] 1503 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1504 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1505
>> 1506 ide-core.nodma= [HW] (E)IDE subsystem
>> 1507 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1508 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1509 .cdrom .chs .ignore_cable are additional options
>> 1510 See Documentation/ide/ide.txt.
>> 1511
>> 1512 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1513 Format: <int>
>> 1514 Probe mask for legacy ISA IDE ports. Depending on
>> 1515 platform up to 6 ports are supported, enabled by
>> 1516 setting corresponding bits in the mask to 1. The
>> 1517 default value is 0x0, which has a special meaning.
>> 1518 On systems that have PCI, it triggers scanning the
>> 1519 PCI bus for the first and the second port, which
>> 1520 are then probed. On systems without PCI the value
>> 1521 of 0x0 enables probing the two first ports as if it
>> 1522 was 0x3.
>> 1523
>> 1524 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1525 Claim all unknown PCI IDE storage controllers.
1983 1526
1984 idle= [X86,EARLY] !! 1527 idle= [X86]
1985 Format: idle=poll, id 1528 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1529 Poll forces a polling idle loop that can slightly
1987 improve the performan 1530 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1531 will use a lot of power and make the system run hot.
1989 Not recommended. 1532 Not recommended.
1990 idle=halt: Halt is fo 1533 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1534 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1535 idle=nomwait: Disable mwait for CPU C-states
1993 1536
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 1537 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1538 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1539 Default: strict
2008 1540
2009 Choose which programs 1541 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1542 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1543 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1544 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1545 binary. Hardware implementations are permitted to
2014 support either or bot 1546 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1547 encoding mode.
2016 1548
2017 Available settings ar 1549 Available settings are as follows:
2018 strict accept binari 1550 strict accept binaries that request a NaN encoding
2019 supported by 1551 supported by the FPU
2020 legacy only accept l 1552 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1553 by the FPU
2022 2008 only accept 2 1554 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1555 by the FPU
2024 relaxed accept any bi 1556 relaxed accept any binaries regardless of whether
2025 supported by 1557 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1558
2029 The FPU emulator is a 1559 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1560 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1561 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1562 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1563 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1564 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1565 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1566 MIPS64 CPUs.
2037 1567
2038 The setting for ABS.f 1568 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1569 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1570 except where unsupported by hardware.
2041 1571
2042 ignore_loglevel [KNL,EARLY] !! 1572 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1573 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1574 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1575 We also add it as printk module parameter, so users
2046 could change it dynam 1576 could change it dynamically, usually by
2047 /sys/module/printk/pa 1577 /sys/module/printk/parameters/ignore_loglevel.
2048 1578
2049 ignore_rlimit_data 1579 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1580 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1581 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1582 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1583
2054 ihash_entries= [KNL] 1584 ihash_entries= [KNL]
2055 Set number of hash bu 1585 Set number of hash buckets for inode cache.
2056 1586
2057 ima_appraise= [IMA] appraise integr 1587 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1588 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1589 default: "enforce"
2060 1590
2061 ima_appraise_tcb [IMA] Deprecated. U 1591 ima_appraise_tcb [IMA] Deprecated. Use ima_policy= instead.
2062 The builtin appraise 1592 The builtin appraise policy appraises all files
2063 owned by uid=0. 1593 owned by uid=0.
2064 1594
2065 ima_canonical_fmt [IMA] 1595 ima_canonical_fmt [IMA]
2066 Use the canonical for 1596 Use the canonical format for the binary runtime
2067 measurements, instead 1597 measurements, instead of host native format.
2068 1598
2069 ima_hash= [IMA] 1599 ima_hash= [IMA]
2070 Format: { md5 | sha1 1600 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1601 | sha512 | ... }
2072 default: "sha1" 1602 default: "sha1"
2073 1603
2074 The list of supported 1604 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1605 in crypto/hash_info.h.
2076 1606
2077 ima_policy= [IMA] 1607 ima_policy= [IMA]
2078 The builtin policies 1608 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1609 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel !! 1610 fail_securely"
2081 1611
2082 The "tcb" policy meas 1612 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1613 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1614 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1615 uid=0.
2086 1616
2087 The "appraise_tcb" po 1617 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro 1618 all files owned by root.
2089 1619
2090 The "secure_boot" pol 1620 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1621 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1622 firmware, policy, etc) based on file signatures.
2093 1623
2094 The "fail_securely" p 1624 The "fail_securely" policy forces file signature
2095 verification failure 1625 verification failure also on privileged mounted
2096 filesystems with the 1626 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1627 flag.
2098 1628
2099 The "critical_data" p <<
2100 critical data. <<
2101 <<
2102 ima_tcb [IMA] Deprecated. Us 1629 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1630 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1631 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1632 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1633 opened for read by uid=0.
2107 1634
2108 ima_template= [IMA] 1635 ima_template= [IMA]
2109 Select one of defined 1636 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1637 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1638 Default: "ima-ng"
2113 1639
2114 ima_template_fmt= 1640 ima_template_fmt=
2115 [IMA] Define a custom 1641 [IMA] Define a custom template format.
2116 Format: { "field1|... 1642 Format: { "field1|...|fieldN" }
2117 1643
2118 ima.ahash_minsize= [IMA] Minimum file 1644 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1645 Format: <min_file_size>
2120 Set the minimal file 1646 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1647 If left unspecified, ahash usage is disabled.
2122 1648
2123 ahash performance var 1649 ahash performance varies for different data sizes on
2124 different crypto acce 1650 different crypto accelerators. This option can be used
2125 to achieve the best p 1651 to achieve the best performance for a particular HW.
2126 1652
2127 ima.ahash_bufsize= [IMA] Asynchronous 1653 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1654 Format: <bufsize>
2129 Set hashing buffer si 1655 Set hashing buffer size. Default: 4k.
2130 1656
2131 ahash performance var 1657 ahash performance varies for different chunk sizes on
2132 different crypto acce 1658 different crypto accelerators. This option can be used
2133 to achieve best perfo 1659 to achieve best performance for particular HW.
2134 1660
2135 init= [KNL] 1661 init= [KNL]
2136 Format: <full_path> 1662 Format: <full_path>
2137 Run specified binary 1663 Run specified binary instead of /sbin/init as init
2138 process. 1664 process.
2139 1665
2140 initcall_debug [KNL] Trace initcalls 1666 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1667 for working out where the kernel is dying during
2142 startup. 1668 startup.
2143 1669
2144 initcall_blacklist= [KNL] Do not exe 1670 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1671 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1672 modules and initcalls.
2147 1673
2148 initramfs_async= [KNL] !! 1674 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 <<
2169 init_on_alloc= [MM,EARLY] Fill newly <<
2170 zeroes. <<
2171 Format: 0 | 1 <<
2172 Default set by CONFIG <<
2173 1675
2174 init_on_free= [MM,EARLY] Fill freed !! 1676 init_pkru= [x86] Specify the default memory protection keys rights
2175 Format: 0 | 1 <<
2176 Default set by CONFIG <<
2177 <<
2178 init_pkru= [X86] Specify the def <<
2179 register contents for 1677 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1678 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1679 override in debugfs after boot.
2182 1680
2183 inport.irq= [HW] Inport (ATI XL a 1681 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1682 Format: <irq>
2185 1683
2186 int_pln_enable [X86] Enable power li !! 1684 int_pln_enable [x86] Enable power limit notification interrupt
2187 1685
2188 integrity_audit=[IMA] 1686 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1687 Format: { "0" | "1" }
2190 0 -- basic integrity 1688 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1689 1 -- additional integrity auditing messages.
2192 1690
2193 intel_iommu= [DMAR] Intel IOMMU dr 1691 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1692 on
2195 Enable intel iommu dr 1693 Enable intel iommu driver.
2196 off 1694 off
2197 Disable intel iommu d 1695 Disable intel iommu driver.
2198 igfx_off [Default Off] 1696 igfx_off [Default Off]
2199 By default, gfx is ma 1697 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1698 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1699 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1700 this case, gfx device will use physical address for
2203 DMA. 1701 DMA.
>> 1702 forcedac [x86_64]
>> 1703 With this option iommu will not optimize to look
>> 1704 for io virtual address below 32-bit forcing dual
>> 1705 address cycle on pci bus for cards supporting greater
>> 1706 than 32-bit addressing. The default is to look
>> 1707 for translation below 32-bit and if not available
>> 1708 then look in the higher range.
2204 strict [Default Off] 1709 strict [Default Off]
2205 Deprecated, equivalen !! 1710 With this option on every unmap_single operation will
>> 1711 result in a hardware IOTLB flush operation as opposed
>> 1712 to batching them for performance.
2206 sp_off [Default Off] 1713 sp_off [Default Off]
2207 By default, super pag 1714 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1715 has the capability. With this option, super page will
2209 not be supported. 1716 not be supported.
2210 sm_on !! 1717 sm_on [Default Off]
2211 Enable the Intel IOMM !! 1718 By default, scalable mode will be disabled even if the
2212 advertises that it ha !! 1719 hardware advertises that it has support for the scalable
2213 translation. !! 1720 mode translation. With this option set, scalable mode
2214 sm_off !! 1721 will be used on hardware which claims to support it.
2215 Disallow use of the I <<
2216 tboot_noforce [Default Off] 1722 tboot_noforce [Default Off]
2217 Do not force the Inte 1723 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1724 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1725 could harm performance of some high-throughput
2220 devices like 40GBit n 1726 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1727 mapping is enabled.
2222 Note that using this 1728 Note that using this option lowers the security
2223 provided by tboot bec 1729 provided by tboot because it makes the system
2224 vulnerable to DMA att 1730 vulnerable to DMA attacks.
2225 1731
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1732 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1733 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1734 1 to 9 specify maximum depth of C-state.
2229 1735
2230 intel_pstate= [X86,EARLY] !! 1736 intel_pstate= [X86]
2231 disable 1737 disable
2232 Do not enable intel 1738 Do not enable intel_pstate as the default
2233 scaling driver for 1739 scaling driver for the supported processors
2234 active <<
2235 Use intel_pstate dr <<
2236 governors layer of <<
2237 algorithms for p-st <<
2238 P-state selection a <<
2239 intel_pstate in the <<
2240 performance. The w <<
2241 on whether or not t <<
2242 (HWP) feature has b <<
2243 and possibly on the <<
2244 passive 1740 passive
2245 Use intel_pstate as 1741 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 1742 to work with generic cpufreq governors (instead of
2247 enabling its intern 1743 enabling its internal governor). This mode cannot be
2248 used along with the 1744 used along with the hardware-managed P-states (HWP)
2249 feature. 1745 feature.
2250 force 1746 force
2251 Enable intel_pstate 1747 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 1748 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 1749 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 1750 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 1751 P-States information being indicated to OSPM and therefore
2256 should be used with 1752 should be used with caution. This option does not work with
2257 processors that are 1753 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 1754 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 1755 no_hwp
2260 Do not enable hardw 1756 Do not enable hardware P state control (HWP)
2261 if available. 1757 if available.
2262 hwp_only 1758 hwp_only
2263 Only load intel_pst 1759 Only load intel_pstate on systems which support
2264 hardware P state co 1760 hardware P state control (HWP) if available.
2265 support_acpi_ppc 1761 support_acpi_ppc
2266 Enforce ACPI _PPC p 1762 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 1763 Description Table, specifies preferred power management
2268 profile as "Enterpr 1764 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 1765 then this feature is turned on by default.
2270 per_cpu_perf_limits 1766 per_cpu_perf_limits
2271 Allow per-logical-C 1767 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 1768 cpufreq sysfs interface
2273 1769
2274 intremap= [X86-64,Intel-IOMMU,E !! 1770 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 1771 on enable Interrupt Remapping (default)
2276 off disable Inter 1772 off disable Interrupt Remapping
2277 nosid disable Sourc 1773 nosid disable Source ID checking
2278 no_x2apic_optout 1774 no_x2apic_optout
2279 BIOS x2APIC o 1775 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 1776 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 1777
2284 iomem= Disable strict checki 1778 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 1779 strict regions from userspace.
2286 relaxed 1780 relaxed
2287 1781
2288 iommu= [X86,EARLY] !! 1782 iommu= [x86]
2289 off 1783 off
2290 force 1784 force
2291 noforce 1785 noforce
2292 biomerge 1786 biomerge
2293 panic 1787 panic
2294 nopanic 1788 nopanic
2295 merge 1789 merge
2296 nomerge 1790 nomerge
2297 soft 1791 soft
2298 pt [X86] !! 1792 pt [x86]
2299 nopt [X86] !! 1793 nopt [x86]
2300 nobypass [PPC/POWERNV] 1794 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 1795 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 1796
2303 iommu.forcedac= [ARM64,X86,EARLY] Con !! 1797 iommu.strict= [ARM64] Configure TLB invalidation behaviour
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" } 1798 Format: { "0" | "1" }
2313 0 - Lazy mode. 1799 0 - Lazy mode.
2314 Request that DMA un 1800 Request that DMA unmap operations use deferred
2315 invalidation of har 1801 invalidation of hardware TLBs, for increased
2316 throughput at the c 1802 throughput at the cost of reduced device isolation.
2317 Will fall back to s 1803 Will fall back to strict mode if not supported by
2318 the relevant IOMMU 1804 the relevant IOMMU driver.
2319 1 - Strict mode. !! 1805 1 - Strict mode (default).
2320 DMA unmap operation 1806 DMA unmap operations invalidate IOMMU hardware TLBs
2321 synchronously. 1807 synchronously.
2322 unset - Use value of <<
2323 Note: on x86, strict <<
2324 legacy driver-specifi <<
2325 1808
2326 iommu.passthrough= 1809 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 1810 [ARM64] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 1811 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 1812 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 1813 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of 1814 unset - Use value of CONFIG_IOMMU_DEFAULT_PASSTHROUGH.
2332 1815
2333 io7= [HW] IO7 for Marvel-b !! 1816 io7= [HW] IO7 for Marvel based alpha systems
2334 See comment before ma 1817 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 1818 arch/alpha/kernel/core_marvel.c.
2336 1819
2337 io_delay= [X86,EARLY] I/O delay !! 1820 io_delay= [X86] I/O delay method
2338 0x80 1821 0x80
2339 Standard port 0x80 ba 1822 Standard port 0x80 based delay
2340 0xed 1823 0xed
2341 Alternate port 0xed b 1824 Alternate port 0xed based delay (needed on some systems)
2342 udelay 1825 udelay
2343 Simple two microsecon 1826 Simple two microseconds delay
2344 none 1827 none
2345 No delay 1828 No delay
2346 1829
2347 ip= [IP_PNP] 1830 ip= [IP_PNP]
2348 See Documentation/adm !! 1831 See Documentation/filesystems/nfs/nfsroot.txt.
2349 1832
2350 ipcmni_extend [KNL,EARLY] Extend th !! 1833 ipcmni_extend [KNL] Extend the maximum number of unique System V
2351 IPC identifiers from 1834 IPC identifiers from 32,768 to 16,777,216.
2352 1835
2353 irqaffinity= [SMP] Set the default 1836 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 1837 The argument is a cpu list, as described above.
2355 1838
2356 irqchip.gicv2_force_probe= 1839 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 1840 [ARM, ARM64]
2358 Format: <bool> 1841 Format: <bool>
2359 Force the kernel to l 1842 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 1843 of a GICv2 controller even if the memory range
2361 exposed by the device 1844 exposed by the device tree is too small.
2362 1845
2363 irqchip.gicv3_nolpi= 1846 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 1847 [ARM, ARM64]
2365 Force the kernel to i 1848 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 1849 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 1850 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 1851 to let secondary kernels in charge of setting up
2369 LPIs. 1852 LPIs.
2370 1853
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL !! 1854 irqchip.gicv3_pseudo_nmi= [ARM64]
2372 Enables support for p 1855 Enables support for pseudo-NMIs in the kernel. This
2373 requires the kernel t 1856 requires the kernel to be built with
2374 CONFIG_ARM64_PSEUDO_N 1857 CONFIG_ARM64_PSEUDO_NMI.
2375 1858
2376 irqfixup [HW] 1859 irqfixup [HW]
2377 When an interrupt is 1860 When an interrupt is not handled search all handlers
2378 for it. Intended to g 1861 for it. Intended to get systems with badly broken
2379 firmware running. 1862 firmware running.
2380 1863
2381 irqpoll [HW] 1864 irqpoll [HW]
2382 When an interrupt is 1865 When an interrupt is not handled search all handlers
2383 for it. Also check al 1866 for it. Also check all handlers each timer
2384 interrupt. Intended t 1867 interrupt. Intended to get systems with badly broken
2385 firmware running. 1868 firmware running.
2386 1869
2387 isapnp= [ISAPNP] 1870 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 1871 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 1872
2390 isolcpus= [KNL,SMP,ISOL] Isolat 1873 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 1874 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 1875 Format: [flag-list,]<cpu-list>
2393 1876
2394 Specify one or more C 1877 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 1878 specified in the flag list (default: domain):
2396 1879
2397 nohz 1880 nohz
2398 Disable the tick wh 1881 Disable the tick when a single task runs.
2399 1882
2400 A residual 1Hz tick 1883 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 1884 need to affine to housekeeping through the global
2402 workqueue's affinit 1885 workqueue's affinity configured via the
2403 /sys/devices/virtua 1886 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 1887 by using the 'domain' flag described below.
2405 1888
2406 NOTE: by default th 1889 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 1890 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 1891 be configured manually after bootup.
2409 1892
2410 domain 1893 domain
2411 Isolate from the ge 1894 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 1895 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 1896 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 1897 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 1898 advised to use cpusets instead to disable scheduler load
2416 balancing through t 1899 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 1900 It offers a much more flexible interface where CPUs can
2418 move in and out of 1901 move in and out of an isolated set anytime.
2419 1902
2420 You can move a proc 1903 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 1904 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 1905 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 1906 "number of CPUs in system - 1".
2424 1907
2425 managed_irq !! 1908 The format of <cpu-list> is described above.
2426 1909
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 1910
2449 The format of <cpu-li <<
2450 1911
2451 iucv= [HW,NET] 1912 iucv= [HW,NET]
2452 1913
2453 ivrs_ioapic [HW,X86-64] !! 1914 ivrs_ioapic [HW,X86_64]
2454 Provide an override t 1915 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 1916 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 1917 example, to map IOAPIC-ID decimal 10 to
2457 !! 1918 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 1919 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 1920
2471 ivrs_hpet [HW,X86-64] !! 1921 ivrs_hpet [HW,X86_64]
2472 Provide an override t 1922 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 1923 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 1924 example, to map HPET-ID decimal 0 to
2475 !! 1925 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]= 1926 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 1927
2489 ivrs_acpihid [HW,X86-64] !! 1928 ivrs_acpihid [HW,X86_64]
2490 Provide an override t 1929 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 1930 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 1931 example, to map UART-HID:UID AMD0020:0 to
2493 !! 1932 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[ 1933 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 1934
2507 js= [HW,JOY] Analog joyst 1935 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 1936 See Documentation/input/joydev/joystick.rst.
2509 1937
>> 1938 nokaslr [KNL]
>> 1939 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 1940 kernel and module base offset ASLR (Address Space
>> 1941 Layout Randomization).
>> 1942
2510 kasan_multi_shot 1943 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 1944 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 1945 report on every invalid memory access. Without this
2513 parameter KASAN will 1946 parameter KASAN will print report only for the first
2514 invalid access. 1947 invalid access.
2515 1948
2516 keep_bootcon [KNL,EARLY] !! 1949 keepinitrd [HW,ARM]
2517 Do not unregister boo <<
2518 useful for debugging <<
2519 between unregistering <<
2520 the real console. <<
2521 1950
2522 keepinitrd [HW,ARM] See retain_i !! 1951 kernelcore= [KNL,X86,IA-64,PPC]
2523 <<
2524 kernelcore= [KNL,X86,PPC,EARLY] <<
2525 Format: nn[KMGTPE] | 1952 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 1953 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 1954 the kernel for non-movable allocations. The requested
2528 amount is spread even 1955 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 1956 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 1957 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 1958 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 1959 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 1960 other nodes will have a larger ZONE_MOVABLE.
2534 1961
2535 ZONE_MOVABLE is used 1962 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 1963 may be reclaimed or moved by the page migration
2537 subsystem. Note that 1964 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 1965 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 1966 zone if it does not.
2540 1967
2541 It is possible to spe 1968 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 1969 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 1970 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 1971 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 1972 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 1973 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 1974 are exclusive, so you cannot specify multiple forms.
2548 1975
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 1976 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 1977 Format: <Controller#>[,poll interval]
2551 The controller # is t 1978 The controller # is the number of the ehci usb debug
2552 port as it is probed 1979 port as it is probed via PCI. The poll interval is
2553 optional and is the n 1980 optional and is the number seconds in between
2554 each poll cycle to th 1981 each poll cycle to the debug port in case you need
2555 the functionality for 1982 the functionality for interrupting the kernel with
2556 gdb or control-c on t 1983 gdb or control-c on the dbgp connection. When
2557 not using this parame 1984 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 1985 the kernel debugger.
2559 1986
2560 kgdboc= [KGDB,HW] kgdb over c 1987 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 1988 Requires a tty driver that supports console polling,
2562 or a supported pollin 1989 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 1990 Serial only format: <serial_device>[,baud]
2564 keyboard only format 1991 keyboard only format: kbd
2565 keyboard and serial 1992 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 1993 Optional Kernel mode setting:
2567 kms, kbd format: kms 1994 kms, kbd format: kms,kbd
2568 kms, kbd and serial 1995 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 1996
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 1997 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 1998 kernel debugger at the earliest opportunity.
2587 1999
2588 kmac= [MIPS] Korina etherne !! 2000 kmac= [MIPS] korina ethernet MAC address.
2589 Configure the RouterB 2001 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 2002 Ethernet adapter MAC address.
2591 2003
2592 kmemleak= [KNL,EARLY] Boot-time !! 2004 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 2005 Valid arguments: on, off
2594 Default: on 2006 Default: on
2595 Built with CONFIG_DEB 2007 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 2008 the default is off.
2597 2009
2598 kprobe_event=[probe-list] !! 2010 kpti= [ARM64] Control page table isolation of user
2599 [FTRACE] Add kprobe e !! 2011 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 2012 Default: enabled on cores which need mitigation.
2614 0: force disabled 2013 0: force disabled
2615 1: force enabled 2014 1: force enabled
2616 2015
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 2016 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 2017 Default is 0 (don't ignore, but inject #GP)
2625 2018
2626 kvm.eager_page_split= <<
2627 [KVM,X86] Controls wh <<
2628 proactively split all <<
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 2019 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 2020 Default is false (don't support).
2653 2021
2654 kvm.nx_huge_pages= !! 2022 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
2655 [KVM] Controls the so !! 2023 KVM MMU at runtime.
2656 X86_BUG_ITLB_MULTIHIT !! 2024 Default is 0 (off)
2657 force : Always depl !! 2025
2658 off : Never deplo !! 2026 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2659 auto : Deploy work !! 2027 Default is 1 (enabled)
2660 X86_BUG_ITL !! 2028
2661 !! 2029 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2662 Default is 'auto'. !! 2030 for all guests.
2663 !! 2031 Default is 1 (enabled) if in 64-bit or 32-bit PAE mode.
2664 If the software worka <<
2665 guests do need not to <<
2666 <<
2667 kvm.nx_huge_pages_recovery_ratio= <<
2668 [KVM] Controls how ma <<
2669 back to huge pages. <<
2670 the value is N KVM wi <<
2671 period (see below). <<
2672 <<
2673 kvm.nx_huge_pages_recovery_period_ms= <<
2674 [KVM] Controls the ti <<
2675 back to huge pages. I <<
2676 zap a portion (see ra <<
2677 If the value is 0 (th <<
2678 on the ratio, such th <<
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 2032
2709 kvm-arm.vgic_v3_group0_trap= 2033 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 2034 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 2035 system registers
2712 2036
2713 kvm-arm.vgic_v3_group1_trap= 2037 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 2038 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 2039 system registers
2716 2040
2717 kvm-arm.vgic_v3_common_trap= 2041 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 2042 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 2043 system registers
2720 2044
2721 kvm-arm.vgic_v4_enable= 2045 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 2046 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 2047 LPIs.
2724 <<
2725 kvm-arm.wfe_trap_policy= <<
2726 [KVM,ARM] Control whe <<
2727 KVM VMs. Traps are al <<
2728 CPU architecture. <<
2729 <<
2730 trap: set WFE instruc <<
2731 <<
2732 notrap: clear WFE ins <<
2733 <<
2734 kvm-arm.wfi_trap_policy= <<
2735 [KVM,ARM] Control whe <<
2736 KVM VMs. Traps are al <<
2737 CPU architecture. <<
2738 <<
2739 trap: set WFI instruc <<
2740 <<
2741 notrap: clear WFI ins <<
2742 <<
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 2048
2751 kvm-intel.ept= [KVM,Intel] Control K !! 2049 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 2050 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 2051 Default is 1 (enabled)
2754 for EPT. <<
2755 2052
2756 kvm-intel.emulate_invalid_guest_state 2053 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 2054 [KVM,Intel] Enable emulation of invalid guest states
2758 state. Ignored if kvm !! 2055 Default is 0 (disabled)
2759 as guest state is nev <<
2760 guests. This param do <<
2761 as KVM never emulates <<
2762 Default is 1 (enabled <<
2763 2056
2764 kvm-intel.flexpriority= 2057 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 2058 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 2059 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 2060
2769 kvm-intel.nested= 2061 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 2062 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 2063 Default is 0 (disabled)
2772 2064
2773 kvm-intel.unrestricted_guest= 2065 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 2066 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 2067 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 2068 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 2069
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 2070 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 2071 CVE-2018-3620.
2781 2072
2782 Valid arguments: neve 2073 Valid arguments: never, cond, always
2783 2074
2784 always: L1D cache flu 2075 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 2076 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 2077 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 2078 never: Disables the mitigation
2788 2079
2789 Default is cond (do L 2080 Default is cond (do L1 cache flush in specific instances)
2790 2081
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 2082 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 2083 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 2084 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 2085
2813 l1tf= [X86,EARLY] Control m !! 2086 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 2087 affected CPUs
2815 2088
2816 The kernel PTE invers 2089 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 2090 enabled and cannot be disabled.
2818 2091
2819 full 2092 full
2820 Provides all 2093 Provides all available mitigations for the
2821 L1TF vulnerab 2094 L1TF vulnerability. Disables SMT and
2822 enables all m 2095 enables all mitigations in the
2823 hypervisors, 2096 hypervisors, i.e. unconditional L1D flush.
2824 2097
2825 SMT control a 2098 SMT control and L1D flush control via the
2826 sysfs interfa 2099 sysfs interface is still possible after
2827 boot. Hyperv 2100 boot. Hypervisors will issue a warning
2828 when the firs 2101 when the first VM is started in a
2829 potentially i 2102 potentially insecure configuration,
2830 i.e. SMT enab 2103 i.e. SMT enabled or L1D flush disabled.
2831 2104
2832 full,force 2105 full,force
2833 Same as 'full 2106 Same as 'full', but disables SMT and L1D
2834 flush runtime 2107 flush runtime control. Implies the
2835 'nosmt=force' 2108 'nosmt=force' command line option.
2836 (i.e. sysfs c 2109 (i.e. sysfs control of SMT is disabled.)
2837 2110
2838 flush 2111 flush
2839 Leaves SMT en 2112 Leaves SMT enabled and enables the default
2840 hypervisor mi 2113 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2114 L1D flush.
2842 2115
2843 SMT control a 2116 SMT control and L1D flush control via the
2844 sysfs interfa 2117 sysfs interface is still possible after
2845 boot. Hyperv 2118 boot. Hypervisors will issue a warning
2846 when the firs 2119 when the first VM is started in a
2847 potentially i 2120 potentially insecure configuration,
2848 i.e. SMT enab 2121 i.e. SMT enabled or L1D flush disabled.
2849 2122
2850 flush,nosmt 2123 flush,nosmt
2851 2124
2852 Disables SMT 2125 Disables SMT and enables the default
2853 hypervisor mi 2126 hypervisor mitigation.
2854 2127
2855 SMT control a 2128 SMT control and L1D flush control via the
2856 sysfs interfa 2129 sysfs interface is still possible after
2857 boot. Hyperv 2130 boot. Hypervisors will issue a warning
2858 when the firs 2131 when the first VM is started in a
2859 potentially i 2132 potentially insecure configuration,
2860 i.e. SMT enab 2133 i.e. SMT enabled or L1D flush disabled.
2861 2134
2862 flush,nowarn 2135 flush,nowarn
2863 Same as 'flus 2136 Same as 'flush', but hypervisors will not
2864 warn when a V 2137 warn when a VM is started in a potentially
2865 insecure conf 2138 insecure configuration.
2866 2139
2867 off 2140 off
2868 Disables hype 2141 Disables hypervisor mitigations and doesn't
2869 emit any warn 2142 emit any warnings.
2870 It also drops 2143 It also drops the swap size and available
2871 RAM limit res 2144 RAM limit restriction on both hypervisor and
2872 bare metal. 2145 bare metal.
2873 2146
2874 Default is 'flush'. 2147 Default is 'flush'.
2875 2148
2876 For details see: Docu 2149 For details see: Documentation/admin-guide/hw-vuln/l1tf.rst
2877 2150
2878 l2cr= [PPC] 2151 l2cr= [PPC]
2879 2152
2880 l3cr= [PPC] 2153 l3cr= [PPC]
2881 2154
2882 lapic [X86-32,APIC,EARLY] E !! 2155 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2156 disabled it.
2884 2157
2885 lapic= [X86,APIC] Do not use !! 2158 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2886 value for LAPIC timer 2159 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2160 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline <<
2889 2161
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2162 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2163 in C2 power state.
2892 2164
2893 libata.dma= [LIBATA] DMA control 2165 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2166 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2167 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2168 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2169 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2170 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2171 for disks and CDROMs, but not CFs.
2900 2172
2901 libata.ignore_hpa= [LIBATA] Igno 2173 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2174 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2175 libata.ignore_hpa=1 ignore limits, using full disk
2904 2176
2905 libata.noacpi [LIBATA] Disables use 2177 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2178 when set.
2907 Format: <int> 2179 Format: <int>
2908 2180
2909 libata.force= [LIBATA] Force config !! 2181 libata.force= [LIBATA] Force configurations. The format is comma
2910 separated list of "[I !! 2182 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2183 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2184 matching port, link or device. Basically, it matches
2913 printed on console by !! 2185 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2186 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2187 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2188 configuration applies to all ports, links and devices.
2917 2189
2918 If only DEVICE is omi 2190 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2191 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2192 number of 0 either selects the first device or the
2921 first fan-out link be 2193 first fan-out link behind PMP device. It does not
2922 select the host link. 2194 select the host link. DEVICE number of 15 selects the
2923 host link and device 2195 host link and device attached to it.
2924 2196
2925 The VAL specifies the 2197 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2198 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2199 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2200 The following configurations can be forced.
2929 2201
2930 * Cable type: 40c, 80 2202 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2203 Any ID with matching PORT is used.
2932 2204
2933 * SATA link speed lim 2205 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2206
2935 * Transfer mode: pio[ 2207 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2208 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2209 allowed.
2938 2210
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 2211 * [no]ncq: Turn on or off NCQ.
2950 2212
2951 * [no]ncqtrim: Enable !! 2213 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 <<
2953 * [no]ncqati: Enable <<
2954 2214
2955 * [no]trim: Enable or !! 2215 * nohrst, nosrst, norst: suppress hard, soft
>> 2216 and both resets.
2956 2217
2957 * trim_zero: Indicate !! 2218 * rstonce: only attempt one reset during
>> 2219 hot-unplug link recovery
2958 2220
2959 * max_trim_128m: Set !! 2221 * dump_id: dump IDENTIFY data.
2960 2222
2961 * [no]dma: Turn on or !! 2223 * atapi_dmadir: Enable ATAPI DMADIR bridge support
2962 <<
2963 * atapi_dmadir: Enabl <<
2964 <<
2965 * atapi_mod16_dma: En <<
2966 commands that are n <<
2967 <<
2968 * [no]dmalog: Enable <<
2969 READ LOG DMA EXT co <<
2970 <<
2971 * [no]iddevlog: Enabl <<
2972 identify device dat <<
2973 <<
2974 * [no]logdir: Enable <<
2975 purpose log directo <<
2976 <<
2977 * max_sec_128: Set tr <<
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 2224
2995 * disable: Disable th 2225 * disable: Disable this device.
2996 2226
2997 If there are multiple 2227 If there are multiple matching configurations changing
2998 the same attribute, t 2228 the same attribute, the last one is used.
2999 2229
3000 load_ramdisk= [RAM] [Deprecated] !! 2230 memblock=debug [KNL] Enable memblock debug messages.
>> 2231
>> 2232 load_ramdisk= [RAM] List of ramdisks to load from floppy
>> 2233 See Documentation/blockdev/ramdisk.txt.
3001 2234
3002 lockd.nlm_grace_period=P [NFS] Assig 2235 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2236 Format: <integer>
3004 2237
3005 lockd.nlm_tcpport=N [NFS] Assign 2238 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2239 Format: <integer>
3007 2240
3008 lockd.nlm_timeout=T [NFS] Assign 2241 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2242 Format: <integer>
3010 2243
3011 lockd.nlm_udpport=M [NFS] Assign 2244 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2245 Format: <integer>
3013 2246
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] 2247 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2248 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2249 Defaults to being automatically set based on the
3058 number of online CPUs 2250 number of online CPUs.
3059 2251
3060 locktorture.nwriters_stress= [KNL] 2252 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2253 Set the number of locking write-acquisition kthreads.
3062 2254
3063 locktorture.onoff_holdoff= [KNL] 2255 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2256 Set time (s) after boot for CPU-hotplug testing.
3065 2257
3066 locktorture.onoff_interval= [KNL] 2258 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2259 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2260 zero to disable CPU-hotplug testing.
3069 2261
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] 2262 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2263 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2264 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2265 mode during the locktorture test.
3093 2266
3094 locktorture.shutdown_secs= [KNL] 2267 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2268 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2269 is useful for hands-off automated testing.
3097 2270
3098 locktorture.stat_interval= [KNL] 2271 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2272 Time (s) between statistics printk()s.
3100 2273
3101 locktorture.stutter= [KNL] 2274 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2275 Time (s) to stutter testing, for example,
3103 specifying five secon 2276 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2277 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2278 This tests the locking primitive's ability to
3106 transition abruptly t 2279 transition abruptly to and from idle.
3107 2280
3108 locktorture.torture_type= [KNL] 2281 locktorture.torture_type= [KNL]
3109 Specify the locking i 2282 Specify the locking implementation to test.
3110 2283
3111 locktorture.verbose= [KNL] 2284 locktorture.verbose= [KNL]
3112 Enable additional pri 2285 Enable additional printk() statements.
3113 2286
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2287 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2288 Format: <irq>
3120 2289
3121 loglevel= [KNL,EARLY] !! 2290 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2291 console loglevel will be printed to the console. It can
3124 also be changed with 2292 also be changed with klogd or other programs. The
3125 loglevels are defined 2293 loglevels are defined as follows:
3126 2294
3127 0 (KERN_EMERG) 2295 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2296 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2297 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2298 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2299 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2300 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2301 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2302 7 (KERN_DEBUG) debug-level messages
3135 2303
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2304 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2305 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2306 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2307 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2308 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2309 that allows to increase the default size depending on
3142 parameter that allows !! 2310 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2311
3146 logo.nologo [FB] Disables display 2312 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2313 This may be used to provide more screen space for
3148 kernel log messages a 2314 kernel log messages and is useful when debugging
3149 kernel boot problems. 2315 kernel boot problems.
3150 2316
3151 lp=0 [LP] Specify paral 2317 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2318 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2319 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2320 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2321 specified in addition to the ports) causes
3156 attached prin 2322 attached printers to be reset. Using
3157 lp=port1,port 2323 lp=port1,port2,... specifies the parallel ports
3158 to associate 2324 to associate lp devices with, starting with
3159 lp0. A port s 2325 lp0. A port specification may be 'none' to skip
3160 that lp devic 2326 that lp device, or a parport name such as
3161 'parport0'. S 2327 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2328 port specification list means that device IDs
3163 from each por 2329 from each port should be examined, to see if
3164 an IEEE 1284- 2330 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2331 so, the driver will manage that printer.
3166 See also head 2332 See also header of drivers/char/lp.c.
3167 2333
3168 lpj=n [KNL] 2334 lpj=n [KNL]
3169 Sets loops_per_jiffy 2335 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2336 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2337 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2338 the correct value for your kernel, boot with normal
3173 autodetection and see 2339 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2340 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2341 which is likely to cause problems if your CPUs need
3176 significantly diverge 2342 significantly divergent settings. An incorrect value
3177 will cause delays in 2343 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2344 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2345 unlikely, in the extreme case this might damage your
3180 hardware. 2346 hardware.
3181 2347
>> 2348 ltpc= [NET]
>> 2349 Format: <io>,<irq>,<dma>
>> 2350
3182 lsm.debug [SECURITY] Enable LSM 2351 lsm.debug [SECURITY] Enable LSM initialization debugging output.
3183 2352
3184 lsm=lsm1,...,lsmN 2353 lsm=lsm1,...,lsmN
3185 [SECURITY] Choose ord 2354 [SECURITY] Choose order of LSM initialization. This
3186 overrides CONFIG_LSM, 2355 overrides CONFIG_LSM, and the "security=" parameter.
3187 2356
3188 machtype= [Loongson] Share the !! 2357 machvec= [IA-64] Force the use of a particular machine-vector
3189 different yeeloong la !! 2358 (machvec) in a generic kernel.
>> 2359 Example: machvec=hpzx1_swiotlb
>> 2360
>> 2361 machtype= [Loongson] Share the same kernel image file between different
>> 2362 yeeloong laptop.
3190 Example: machtype=lem 2363 Example: machtype=lemote-yeeloong-2f-7inch
3191 2364
3192 maxcpus= [SMP,EARLY] Maximum n !! 2365 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2366 than or equal to this physical address is ignored.
>> 2367
>> 2368 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2369 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2370 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2371 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2372 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2373 only takes effect during system bootup.
3198 While n=0 is a specia 2374 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2375 which also disables the IO APIC.
3200 2376
3201 max_loop= [LOOP] The number of 2377 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2378 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2379 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2380 of statically allocating a predefined number, loop
3205 devices can be reques 2381 devices can be requested on-demand with the
3206 /dev/loop-control int 2382 /dev/loop-control interface.
3207 2383
3208 mce [X86-32] Machine Chec 2384 mce [X86-32] Machine Check Exception
3209 2385
3210 mce=option [X86-64] See Document !! 2386 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
3211 2387
3212 md= [HW] RAID subsystems 2388 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2389 See Documentation/admin-guide/md.rst.
3214 2390
3215 mdacon= [MDA] 2391 mdacon= [MDA]
3216 Format: <first>,<last 2392 Format: <first>,<last>
3217 Specifies range of co 2393 Specifies range of consoles to be captured by the MDA.
3218 2394
3219 mds= [X86,INTEL,EARLY] !! 2395 mds= [X86,INTEL]
3220 Control mitigation fo 2396 Control mitigation for the Micro-architectural Data
3221 Sampling (MDS) vulner 2397 Sampling (MDS) vulnerability.
3222 2398
3223 Certain CPUs are vuln 2399 Certain CPUs are vulnerable to an exploit against CPU
3224 internal buffers whic 2400 internal buffers which can forward information to a
3225 disclosure gadget und 2401 disclosure gadget under certain conditions.
3226 2402
3227 In vulnerable process 2403 In vulnerable processors, the speculatively
3228 forwarded data can be 2404 forwarded data can be used in a cache side channel
3229 attack, to access dat 2405 attack, to access data to which the attacker does
3230 not have direct acces 2406 not have direct access.
3231 2407
3232 This parameter contro 2408 This parameter controls the MDS mitigation. The
3233 options are: 2409 options are:
3234 2410
3235 full - Enable M 2411 full - Enable MDS mitigation on vulnerable CPUs
3236 full,nosmt - Enable M 2412 full,nosmt - Enable MDS mitigation and disable
3237 SMT on v 2413 SMT on vulnerable CPUs
3238 off - Uncondit 2414 off - Unconditionally disable MDS mitigation
3239 2415
3240 On TAA-affected machi <<
3241 an active TAA mitigat <<
3242 mitigated with the sa <<
3243 this mitigation, you <<
3244 too. <<
3245 <<
3246 Not specifying this o 2416 Not specifying this option is equivalent to
3247 mds=full. 2417 mds=full.
3248 2418
3249 For details see: Docu 2419 For details see: Documentation/admin-guide/hw-vuln/mds.rst
3250 2420
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t !! 2421 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3252 Must be specified, ot !! 2422 Amount of memory to be used when the kernel is not able
3253 !! 2423 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 2424 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2425 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2426 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2427 belonging to unused RAM.
3274 2428
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 2429 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2430 memory.
3289 2431
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2432 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2433 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2434 per-device physically contiguous DMA buffers.
3295 2435
3296 memhp_default_state=online/offline/on !! 2436 memhp_default_state=online/offline
3297 [KNL] Set the initial 2437 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2438 onlining policy. If not specified, the default value is
3299 set according to the 2439 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2440 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2441 option.
3302 See Documentation/adm !! 2442 See Documentation/memory-hotplug.txt.
3303 2443
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2444 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2445 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2446 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2447 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2448 option description.
3309 2449
3310 memmap=nn[KMG]@ss[KMG] 2450 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2451 [KNL] Force usage of a specific region of memory.
3312 Region of memory to b 2452 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2453 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2454 which limits max address to nn[KMG].
3315 Multiple different re 2455 Multiple different regions can be specified,
3316 comma delimited. 2456 comma delimited.
3317 Example: 2457 Example:
3318 memmap=100M@2 2458 memmap=100M@2G,100M#3G,1G!1024G
3319 2459
3320 memmap=nn[KMG]#ss[KMG] 2460 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2461 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2462 Region of memory to be marked is from ss to ss+nn.
3323 2463
3324 memmap=nn[KMG]$ss[KMG] 2464 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2465 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2466 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2467 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2468 memmap=64K$0x18690000
3329 or 2469 or
3330 memmap=0x100 2470 memmap=0x10000$0x18690000
3331 Some bootloaders may 2471 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2472 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2473 will be eaten.
3334 2474
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2475 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2476 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2477 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2478 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2479 and is NVDIMM or ADR memory.
3340 2480
3341 memmap=<size>%<offset>-<oldtype>+<new 2481 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 2482 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 2483 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 2484 out, the whole region will be marked as <newtype>,
3345 even if previously un 2485 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 2486 out, matching memory will be removed. Types are
3347 specified as e820 typ 2487 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 2488 3 = ACPI, 12 = PRAM.
3349 2489
3350 memory_corruption_check=0/1 [X86,EARL !! 2490 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 2491 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2492 memory when doing things like suspend/resume.
3353 Setting this option w 2493 Setting this option will scan the memory
3354 looking for corruptio 2494 looking for corruption. Enabling this will
3355 both detect corruptio 2495 both detect corruption and prevent the kernel
3356 from using the memory 2496 from using the memory being corrupted.
3357 However, its intended 2497 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2498 repeatable BIOS-originated corruption always
3359 affects the same memo 2499 affects the same memory, you can use memmap=
3360 to prevent the kernel 2500 to prevent the kernel from using that memory.
3361 2501
3362 memory_corruption_check_size=size [X8 !! 2502 memory_corruption_check_size=size [X86]
3363 By default it checks 2503 By default it checks for corruption in the low
3364 64k, making this memo 2504 64k, making this memory unavailable for normal
3365 use. Use this parame 2505 use. Use this parameter to scan for
3366 corruption in more or 2506 corruption in more or less memory.
3367 2507
3368 memory_corruption_check_period=second !! 2508 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2509 By default it checks for corruption every 60
3370 seconds. Use this pa 2510 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2511 other rate. 0 disables periodic checking.
3372 2512
3373 memory_hotplug.memmap_on_memory !! 2513 memtest= [KNL,X86,ARM,PPC] 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> 2514 Format: <integer>
3394 default : 0 <disable> 2515 default : 0 <disable>
3395 Specifies the number 2516 Specifies the number of memtest passes to be
3396 performed. Each pass 2517 performed. Each pass selects another test
3397 pattern from a given 2518 pattern from a given set of patterns. Memtest
3398 fills the memory with 2519 fills the memory with this pattern, validates
3399 memory contents and r 2520 memory contents and reserves bad memory
3400 regions that are dete 2521 regions that are detected.
3401 2522
3402 mem_encrypt= [X86-64] AMD Secure M 2523 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2524 Valid arguments: on, off
3404 Default: off !! 2525 Default (depends on kernel configuration option):
>> 2526 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2527 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2528 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2529 mem_encrypt=off: Do not activate SME
3407 2530
3408 Refer to Documentatio !! 2531 Refer to Documentation/x86/amd-memory-encryption.txt
3409 for details on when m 2532 for details on when memory encryption can be activated.
3410 2533
3411 mem_sleep_default= [SUSPEND] Def 2534 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2535 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2536 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2537 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 2538 See Documentation/admin-guide/pm/sleep-states.rst.
3416 2539
>> 2540 meye.*= [HW] Set MotionEye Camera parameters
>> 2541 See Documentation/media/v4l-drivers/meye.rst.
>> 2542
>> 2543 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2544 Multi-Function General Purpose Timers on AMD Geode
>> 2545 platforms.
>> 2546
3417 mfgptfix [X86-32] Fix MFGPT ti 2547 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2548 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2549 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2550 problem by letting the user disable the workaround.
3421 2551
3422 mga= [HW,DRM] 2552 mga= [HW,DRM]
3423 2553
3424 microcode.force_minrev= [X86] !! 2554 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2555 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2556
3429 mini2440= [ARM,HW,KNL] 2557 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2558 Format:[0..2][b][c][t]
3431 Default: "0tb" 2559 Default: "0tb"
3432 MINI2440 configuratio 2560 MINI2440 configuration specification:
3433 0 - The attached scre 2561 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2562 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2563 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2564 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2565 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2566 unconfigured.
3439 b - Enable backlight. 2567 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2568 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2569 LED. This parameter is not necessary when using the
3442 VGA shield. 2570 VGA shield.
3443 c - Enable the s3c ca 2571 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2572 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2573 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2574 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2575 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ !! 2576 http://repo.or.cz/w/linux-2.6/mini2440.git
3449 2577
3450 mitigations= 2578 mitigations=
3451 [X86,PPC,S390,ARM64,E !! 2579 [X86,PPC,S390,ARM64] Control optional mitigations for
3452 CPU vulnerabilities. 2580 CPU vulnerabilities. This is a set of curated,
3453 arch-independent opti 2581 arch-independent options, each of which is an
3454 aggregation of existi 2582 aggregation of existing arch-specific options.
3455 2583
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off 2584 off
3460 Disable all o 2585 Disable all optional CPU mitigations. This
3461 improves syst 2586 improves system performance, but it may also
3462 expose users 2587 expose users to several CPU vulnerabilities.
3463 Equivalent to !! 2588 Equivalent to: nopti [X86,PPC]
3464 !! 2589 kpti=0 [ARM64]
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 2590 nospectre_v1 [X86,PPC]
>> 2591 nobp=0 [S390]
3475 2592 nospectre_v2 [X86,PPC,S390,ARM64]
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 2593 spectre_v2_user=off [X86]
3482 !! 2594 spec_store_bypass_disable=off [X86,PPC]
3483 2595 ssbd=force-off [ARM64]
3484 !! 2596 l1tf=off [X86]
3485 !! 2597 mds=off [X86]
3486 Exceptions: <<
3487 <<
3488 <<
3489 <<
3490 2598
3491 auto (default) 2599 auto (default)
3492 Mitigate all 2600 Mitigate all CPU vulnerabilities, but leave SMT
3493 enabled, even 2601 enabled, even if it's vulnerable. This is for
3494 users who don 2602 users who don't want to be surprised by SMT
3495 getting disab 2603 getting disabled across kernel upgrades, or who
3496 have other wa 2604 have other ways of avoiding SMT-based attacks.
3497 Equivalent to 2605 Equivalent to: (default behavior)
3498 2606
3499 auto,nosmt 2607 auto,nosmt
3500 Mitigate all 2608 Mitigate all CPU vulnerabilities, disabling SMT
3501 if needed. T 2609 if needed. This is for users who always want to
3502 be fully miti 2610 be fully mitigated, even if it means losing SMT.
3503 Equivalent to 2611 Equivalent to: l1tf=flush,nosmt [X86]
3504 2612 mds=full,nosmt [X86]
3505 <<
3506 <<
3507 <<
3508 2613
3509 mminit_loglevel= 2614 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 2615 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 2616 parameter allows control of the logging verbosity for
3512 the additional memory 2617 the additional memory initialisation checks. A value
3513 of 0 disables mminit 2618 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 2619 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 2620 so loglevel=8 may also need to be specified.
3516 2621
3517 mmio_stale_data= <<
3518 [X86,INTEL,EARLY] Con <<
3519 MMIO Stale Data vulne <<
3520 <<
3521 Processor MMIO Stale <<
3522 vulnerabilities that <<
3523 operation. Exposed da <<
3524 the same CPU buffers <<
3525 Therefore, similar to <<
3526 is to clear the affec <<
3527 <<
3528 This parameter contro <<
3529 options are: <<
3530 <<
3531 full - Enable m <<
3532 <<
3533 full,nosmt - Enable m <<
3534 vulnerab <<
3535 <<
3536 off - Uncondit <<
3537 <<
3538 On MDS or TAA affecte <<
3539 mmio_stale_data=off c <<
3540 MDS or TAA mitigation <<
3541 mitigated with the sa <<
3542 disable this mitigati <<
3543 mds=off and tsx_async <<
3544 <<
3545 Not specifying this o <<
3546 mmio_stale_data=full. <<
3547 <<
3548 For details see: <<
3549 Documentation/admin-g <<
3550 <<
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 2622 module.sig_enforce
3574 [KNL] When CONFIG_MOD 2623 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 2624 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 2625 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 2626 is always true, so this option does nothing.
3578 2627
3579 module_blacklist= [KNL] Do not load 2628 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 2629 modules. Useful for debugging problem modules.
3581 2630
3582 mousedev.tap_time= 2631 mousedev.tap_time=
3583 [MOUSE] Maximum time 2632 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 2633 leaving touchpad surface for touch to be considered
3585 a tap and be reported 2634 a tap and be reported as a left button click (for
3586 touchpads working in 2635 touchpads working in absolute mode only).
3587 Format: <msecs> 2636 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 2637 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 2638 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 2639 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 2640 reporting absolute coordinates, such as tablets
3592 2641
3593 movablecore= [KNL,X86,PPC,EARLY] !! 2642 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 2643 Format: nn[KMGTPE] | nn%
3595 This parameter is the 2644 This parameter is the complement to kernelcore=, it
3596 specifies the amount 2645 specifies the amount of memory used for migratable
3597 allocations. If both 2646 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 2647 specified, then kernelcore will be at *least* the
3599 specified value but m 2648 specified value but may be more. If movablecore on its
3600 own is specified, the 2649 own is specified, the administrator must be careful
3601 that the amount of me 2650 that the amount of memory usable for all allocations
3602 is not too small. 2651 is not too small.
3603 2652
3604 movable_node [KNL,EARLY] Boot-time !! 2653 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 2654 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 2655 of such nodes will be usable only for movable
3607 allocations which rul 2656 allocations which rules out almost all kernel
3608 allocations. Use with 2657 allocations. Use with caution!
3609 2658
3610 MTD_Partition= [MTD] 2659 MTD_Partition= [MTD]
3611 Format: <name>,<regio 2660 Format: <name>,<region-number>,<size>,<offset>
3612 2661
3613 MTD_Region= [MTD] Format: 2662 MTD_Region= [MTD] Format:
3614 <name>,<region-number 2663 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 2664
3616 mtdparts= [MTD] 2665 mtdparts= [MTD]
3617 See drivers/mtd/parse !! 2666 See drivers/mtd/cmdlinepart.c.
>> 2667
>> 2668 multitce=off [PPC] This parameter disables the use of the pSeries
>> 2669 firmware feature for updating multiple TCE entries
>> 2670 at a time.
>> 2671
>> 2672 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 2673
>> 2674 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 2675
>> 2676 boundary - index of last SLC block on Flex-OneNAND.
>> 2677 The remaining blocks are configured as MLC blocks.
>> 2678 lock - Configure if Flex-OneNAND boundary should be locked.
>> 2679 Once locked, the boundary cannot be changed.
>> 2680 1 indicates lock status, 0 indicates unlock status.
>> 2681
>> 2682 mtdset= [ARM]
>> 2683 ARM/S3C2412 JIVE boot control
>> 2684
>> 2685 See arch/arm/mach-s3c2412/mach-jive.c
3618 2686
3619 mtouchusb.raw_coordinates= 2687 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 2688 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 2689 ('y', default) or cooked coordinates ('n')
3622 2690
3623 mtrr=debug [X86,EARLY] !! 2691 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 2692 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 2693 that could hold holes aka. UC entries.
3630 2694
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 2695 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 2696 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 2697 Default is 1.
3634 Large value could pre 2698 Large value could prevent small alignment from
3635 using up MTRRs. 2699 using up MTRRs.
3636 2700
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 2701 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 2702 Format: <integer>
3639 Range: 0,7 : spare re 2703 Range: 0,7 : spare reg number
3640 Default : 1 2704 Default : 1
3641 Used for mtrr cleanup 2705 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 2706 Set to 2 or more if your graphical card needs more.
3643 2707
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 2708 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 2709
3650 netdev= [NET] Network devices 2710 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 2711 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 2712 Note that mem_start is often overloaded to mean
3653 something different a 2713 something different and driver-specific.
3654 This usage is only do 2714 This usage is only documented in each driver source
3655 file if at all. 2715 file if at all.
3656 2716
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 2717 nf_conntrack.acct=
3663 [NETFILTER] Enable co 2718 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 2719 0 to disable accounting
3665 1 to enable accountin 2720 1 to enable accounting
3666 Default value is 0. 2721 Default value is 0.
3667 2722
3668 nfs.cache_getent= !! 2723 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 2724 See Documentation/filesystems/nfs/nfsroot.txt.
3670 to update the NFS cli <<
3671 2725
3672 nfs.cache_getent_timeout= !! 2726 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 2727 See Documentation/filesystems/nfs/nfsroot.txt.
3674 update a cache entry !! 2728
>> 2729 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 2730 See Documentation/filesystems/nfs/nfsroot.txt.
3675 2731
3676 nfs.callback_nr_threads= 2732 nfs.callback_nr_threads=
3677 [NFSv4] set the total 2733 [NFSv4] set the total number of threads that the
3678 NFS client will assig 2734 NFS client will assign to service NFSv4 callback
3679 requests. 2735 requests.
3680 2736
3681 nfs.callback_tcpport= 2737 nfs.callback_tcpport=
3682 [NFS] set the TCP por 2738 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 2739 channel should listen.
3684 2740
3685 nfs.delay_retrans= !! 2741 nfs.cache_getent=
3686 [NFS] specifies the n !! 2742 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 2743 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 2744
3689 Only applies if the s !! 2745 nfs.cache_getent_timeout=
3690 and the specified val !! 2746 [NFS] sets the timeout after which an attempt to
>> 2747 update a cache entry is deemed to have failed.
>> 2748
>> 2749 nfs.idmap_cache_timeout=
>> 2750 [NFS] set the maximum lifetime for idmapper cache
>> 2751 entries.
3691 2752
3692 nfs.enable_ino64= 2753 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 2754 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 2755 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 2756 number for the readdir() and stat() syscalls instead
3696 of returning the full 2757 of returning the full 64-bit number.
3697 The default is to ret 2758 The default is to return 64-bit inode numbers.
3698 2759
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 2760 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 2761 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 2762 slots the client will assign to the callback
3706 channel. This determi 2763 channel. This determines the maximum number of
3707 callbacks the client 2764 callbacks the client will process in parallel for
3708 a particular server. 2765 a particular server.
3709 2766
3710 nfs.max_session_slots= 2767 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 2768 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 2769 the client will attempt to negotiate with the server.
3713 This limits the numbe 2770 This limits the number of simultaneous RPC requests
3714 that the client can s 2771 that the client can send to the NFSv4.1 server.
3715 Note that there is li 2772 Note that there is little point in setting this
3716 value higher than the 2773 value higher than the max_tcp_slot_table_limit.
3717 2774
3718 nfs.nfs4_disable_idmapping= 2775 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 2776 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 2777 ensures that both the RPC level authentication
3721 scheme and the NFS le 2778 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 2779 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 2780 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 2781 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 2782 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 2783 Servers that do not support this mode of operation
3727 will be autodetected 2784 will be autodetected by the client, and it will fall
3728 back to using the idm 2785 back to using the idmapper.
3729 To turn off this beha 2786 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 2787 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 2788 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 2789 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 2790 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 2791 UUID that is generated at system install time.
3736 2792
3737 nfs.recover_lost_locks= !! 2793 nfs.send_implementation_id =
>> 2794 [NFSv4.1] Send client implementation identification
>> 2795 information in exchange_id requests.
>> 2796 If zero, no implementation identification information
>> 2797 will be sent.
>> 2798 The default is to send the implementation identification
>> 2799 information.
>> 2800
>> 2801 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 2802 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 2803 to a lease timeout on the server. Please note that
3740 doing this risks data 2804 doing this risks data corruption, since there are
3741 no guarantees that th 2805 no guarantees that the file will remain unchanged
3742 after the locks are l 2806 after the locks are lost.
3743 If you want to enable 2807 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 2808 attempting to recover these locks, then set this
3745 parameter to '1'. 2809 parameter to '1'.
3746 The default parameter 2810 The default parameter value of '0' causes the kernel
3747 not to attempt recove 2811 not to attempt recovery of lost locks.
3748 2812
3749 nfs.send_implementation_id= !! 2813 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 2814 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 2815 layoutstats to the pNFS metadata server.
3760 2816
3761 Setting this to value 2817 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 2818 whatever value is the default set by the layout
3763 driver. A non-zero va 2819 driver. A non-zero value sets the minimum interval
3764 in seconds between la 2820 in seconds between layoutstats transmissions.
3765 2821
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= 2822 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 2823 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 2824 server will return only numeric uids and gids to
3774 clients using auth_sy 2825 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 2826 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 2827 migration from NFSv2/v3.
3777 2828
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 2829 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 2830 when a NMI is triggered.
3801 Format: [state][,regs 2831 Format: [state][,regs][,debounce][,die]
3802 2832
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 2833 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 2834 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 2835 Valid num: 0 or 1
3806 0 - turn hardlockup d 2836 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 2837 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 2838 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n !! 2839 timeout occurs (or 'nopanic' to override the opposite
3812 watchdog, if CONFIG_B !! 2840 default). To disable both hard and soft lockup detectors,
3813 To disable both hard <<
3814 please see 'nowatchdo 2841 please see 'nowatchdog'.
3815 This is useful when y 2842 This is useful when you use a panic=... timeout and
3816 need the box quickly 2843 need the box quickly up again.
3817 2844
3818 These settings can be 2845 These settings can be accessed at runtime via
3819 the nmi_watchdog and 2846 the nmi_watchdog and hardlockup_panic sysctls.
3820 2847
>> 2848 netpoll.carrier_timeout=
>> 2849 [NET] Specifies amount of time (in seconds) that
>> 2850 netpoll should wait for a carrier. By default netpoll
>> 2851 waits 4 seconds.
>> 2852
3821 no387 [BUGS=X86-32] Tells t 2853 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 2854 emulation library even if a 387 maths coprocessor
3823 is present. 2855 is present.
3824 2856
3825 no4lvl [RISCV,EARLY] Disable !! 2857 no5lvl [X86-64] Disable 5-level paging mode. Forces
3826 Forces kernel to use <<
3827 <<
3828 no5lvl [X86-64,RISCV,EARLY] <<
3829 kernel to use 4-level 2858 kernel to use 4-level paging instead.
3830 2859
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 2860 no_console_suspend
3841 [HW] Never suspend th 2861 [HW] Never suspend the console
3842 Disable suspending of 2862 Disable suspending of consoles during suspend and
3843 hibernate operations. 2863 hibernate operations. Once disabled, debugging
3844 messages can reach va 2864 messages can reach various consoles while the rest
3845 of the system is bein 2865 of the system is being put to sleep (ie, while
3846 debugging driver susp 2866 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 2867 not work reliably with all consoles, but is known
3848 to work with serial a 2868 to work with serial and VGA consoles.
3849 To facilitate more fl 2869 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 2870 console_suspend, a printk module parameter to control
3851 it. Users could use c 2871 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 2872 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 2873 turn on/off it dynamically.
3854 2874
3855 no_debug_objects !! 2875 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
3856 [KNL,EARLY] Disable o !! 2876 caches in the slab allocator. Saves per-node memory,
>> 2877 but will impact performance.
>> 2878
>> 2879 noalign [KNL,ARM]
>> 2880
>> 2881 noaltinstr [S390] Disables alternative instructions patching
>> 2882 (CPU alternatives feature).
>> 2883
>> 2884 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 2885 IOAPICs that may be present in the system.
>> 2886
>> 2887 noautogroup Disable scheduler automatic task group creation.
>> 2888
>> 2889 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 2890 on "Classic" PPC cores.
>> 2891
>> 2892 nocache [ARM]
>> 2893
>> 2894 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 2895
>> 2896 nodelayacct [KNL] Disable per-task delay accounting
3857 2897
3858 nodsp [SH] Disable hardware 2898 nodsp [SH] Disable hardware DSP at boot time.
3859 2899
3860 noefi [EFI,EARLY] Disable E !! 2900 noefi Disable EFI runtime services support.
3861 2901
3862 no_entry_flush [PPC,EARLY] Don't flu !! 2902 noexec [IA-64]
>> 2903
>> 2904 noexec [X86]
>> 2905 On X86-32 available only on PAE configured kernels.
>> 2906 noexec=on: enable non-executable mappings (default)
>> 2907 noexec=off: disable non-executable mappings
>> 2908
>> 2909 nosmap [X86,PPC]
>> 2910 Disable SMAP (Supervisor Mode Access Prevention)
>> 2911 even if it is supported by processor.
>> 2912
>> 2913 nosmep [X86,PPC]
>> 2914 Disable SMEP (Supervisor Mode Execution Prevention)
>> 2915 even if it is supported by processor.
3863 2916
3864 noexec32 [X86-64] 2917 noexec32 [X86-64]
3865 This affects only 32- 2918 This affects only 32-bit executables.
3866 noexec32=on: enable n 2919 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 2920 read doesn't imply executable mappings
3868 noexec32=off: disable 2921 noexec32=off: disable non-executable mappings
3869 read implies 2922 read implies executable mappings
3870 2923
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 2924 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 2925
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 2926 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 2927 register save and restore. The kernel will only save
3881 legacy floating-point 2928 legacy floating-point registers on task switch.
3882 2929
3883 no_hash_pointers !! 2930 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 2931
3898 nohibernate [HIBERNATION] Disable !! 2932 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 2933 Equivalent to smt=1.
3899 2934
3900 nohlt [ARM,ARM64,MICROBLAZE !! 2935 [KNL,x86] Disable symmetric multithreading (SMT).
3901 busy wait in do_idle( !! 2936 nosmt=force: Force disable SMT, cannot be undone
3902 implementation; requi !! 2937 via the sysfs control file.
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 2938
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA !! 2939 nospectre_v1 [X86,PPC] Disable mitigations for Spectre Variant 1
>> 2940 (bounds check bypass). With this option data leaks are
>> 2941 possible in the system.
3910 2942
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA !! 2943 nospectre_v2 [X86,PPC_FSL_BOOK3E,ARM64] Disable all mitigations for
>> 2944 the Spectre variant 2 (indirect branch prediction)
>> 2945 vulnerability. System may allow data leaks with this
>> 2946 option.
>> 2947
>> 2948 nospec_store_bypass_disable
>> 2949 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 2950
>> 2951 noxsave [BUGS=X86] Disables x86 extended register state save
>> 2952 and restore using xsave. The kernel will fallback to
>> 2953 enabling legacy floating-point and sse state.
>> 2954
>> 2955 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
>> 2956 register states. The kernel will fall back to use
>> 2957 xsave to save the states. By using this parameter,
>> 2958 performance of saving the states is degraded because
>> 2959 xsave doesn't support modified optimization while
>> 2960 xsaveopt supports it on xsaveopt enabled systems.
>> 2961
>> 2962 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 2963 restoring x86 extended register state in compacted
>> 2964 form of xsave area. The kernel will fall back to use
>> 2965 xsaveopt and xrstor to save and restore the states
>> 2966 in standard form of xsave area. By using this
>> 2967 parameter, xsave area per process might occupy more
>> 2968 memory on xsaves enabled systems.
>> 2969
>> 2970 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
>> 2971 wfi(ARM) instruction doesn't work correctly and not to
>> 2972 use it. This is also useful when using JTAG debugger.
>> 2973
>> 2974 no_file_caps Tells the kernel not to honor file capabilities. The
>> 2975 only way then for a file to be executed with privilege
>> 2976 is to be setuid root or executed by root.
>> 2977
>> 2978 nohalt [IA-64] Tells the kernel not to use the power saving
>> 2979 function PAL_HALT_LIGHT when idle. This increases
>> 2980 power-consumption. On the positive side, it reduces
>> 2981 interrupt wake-up latency, which may improve performance
>> 2982 in certain environments such as networked servers or
>> 2983 real-time systems.
>> 2984
>> 2985 nohibernate [HIBERNATION] Disable hibernation and resume.
3912 2986
3913 nohz= [KNL] Boottime enable 2987 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 2988 Valid arguments: on, off
3915 Default: on 2989 Default: on
3916 2990
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 2991 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 2992 The argument is a cpu list, as described above.
3919 In kernels built with 2993 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 2994 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 2995 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 2996 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 2997 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 2998 just as if they had also been called out in the
3925 rcu_nocbs= boot param 2999 rcu_nocbs= boot parameter.
3926 3000
3927 Note that this argume !! 3001 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 3002
>> 3003 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 3004 disable unhandled interrupt sources.
>> 3005
>> 3006 no_timer_check [X86,APIC] Disables the code which tests for
>> 3007 broken timer IRQ sources.
>> 3008
>> 3009 noisapnp [ISAPNP] Disables ISA PnP code.
3929 3010
3930 noinitrd [RAM] Tells the kerne 3011 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 3012 initial RAM disk.
3932 3013
3933 nointremap [X86-64,Intel-IOMMU,E !! 3014 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 3015 remapping.
3935 [Deprecated - use int 3016 [Deprecated - use intremap=off]
3936 3017
3937 noinvpcid [X86,EARLY] Disable t !! 3018 nointroute [IA-64]
3938 <<
3939 noiotrap [SH] Disables trapped <<
3940 3019
3941 noirqdebug [X86-32] Disables the !! 3020 noinvpcid [X86] Disable the INVPCID cpu feature.
3942 disable unhandled int <<
3943 3021
3944 noisapnp [ISAPNP] Disables ISA !! 3022 nojitter [IA-64] Disables jitter checking for ITC timers.
3945 3023
3946 nokaslr [KNL,EARLY] !! 3024 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 3025
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 3026 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 3027 fault handling.
3953 3028
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 3029 no-vmw-sched-clock
>> 3030 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 3031 clock and use the default one.
>> 3032
>> 3033 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
>> 3034 steal time is computed, but won't influence scheduler
>> 3035 behaviour
>> 3036
>> 3037 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3955 3038
3956 nolapic [X86-32,APIC,EARLY] D !! 3039 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3957 3040
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 3041 noltlbs [PPC] Do not use large page/tlb entries for kernel
>> 3042 lowmem mapping on PPC40x and PPC8xx
>> 3043
>> 3044 nomca [IA-64] Disable machine check abort handling
3959 3045
3960 nomce [X86-32] Disable Mach 3046 nomce [X86-32] Disable Machine Check Exception
3961 3047
3962 nomfgpt [X86-32] Disable Mult 3048 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 3049 Timer usage (for AMD Geode machines).
3964 3050
3965 nomodeset Disable kernel modese <<
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 <<
3973 Useful as error fallb <<
3974 <<
3975 nomodule Disable module load <<
3976 <<
3977 nonmi_ipi [X86] Disable using N 3051 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 3052 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 3053 irq.
3980 3054
3981 nopat [X86,EARLY] Disable P !! 3055 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 3056
3989 nopti [X86-64,EARLY] !! 3057 nopat [X86] Disable PAT (page attribute table extension of
3990 Equivalent to pti=off !! 3058 pagetables) support.
3991 3059
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 3060 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 3061
4002 norandmaps Don't use address spa 3062 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 3063 echo 0 > /proc/sys/kernel/randomize_va_space
4004 3064
4005 noreplace-smp [X86-32,SMP] Don't re 3065 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 3066 with UP alternatives
4007 3067
>> 3068 nordrand [X86] Disable kernel use of the RDRAND and
>> 3069 RDSEED instructions even if they are supported
>> 3070 by the processor. RDRAND and RDSEED are still
>> 3071 available to user space applications.
>> 3072
4008 noresume [SWSUSP] Disables res 3073 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 3074 space.
4010 3075
4011 no-scroll [VGA] Disables scroll 3076 no-scroll [VGA] Disables scrollback.
4012 This is required for 3077 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 3078 reader made by F.H. Papenmeier (Germany).
4014 3079
4015 nosgx [X86-64,SGX,EARLY] Di !! 3080 nosbagart [IA-64]
4016 3081
4017 nosmap [PPC,EARLY] !! 3082 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 3083
4021 nosmep [PPC64s,EARLY] !! 3084 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 3085 and disable the IO APIC. legacy for "maxcpus=0".
4027 3086
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 3087 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 3088
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 3089 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 3090
4060 no_timer_check [X86,APIC] Disables t <<
4061 broken timer IRQ sour <<
4062 <<
4063 no_uaccess_flush <<
4064 [PPC,EARLY] Don't flu <<
4065 <<
4066 novmcoredd [KNL,KDUMP] <<
4067 Disable device dump. <<
4068 append dump data to v <<
4069 specified debug info. <<
4070 without any limit and <<
4071 so this may cause sig <<
4072 device dump can help <<
4073 data will be no longe <<
4074 is only available whe <<
4075 is set. <<
4076 <<
4077 no-vmw-sched-clock <<
4078 [X86,PV_OPS,EARLY] Di <<
4079 scheduler clock and u <<
4080 <<
4081 nowatchdog [KNL] Disable both lo 3091 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 3092 soft-lockup and NMI watchdog (hard-lockup).
4083 3093
4084 nowb [ARM,EARLY] !! 3094 nowb [ARM]
4085 3095
4086 nox2apic [X86-64,APIC,EARLY] D !! 3096 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4087 3097
4088 NOTE: this parameter !! 3098 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4089 LEGACY_XAPIC_DISABLED !! 3099 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4090 IA32_XAPIC_DISABLE_ST !! 3100 Some features depend on CPU0. Known dependencies are:
>> 3101 1. Resume from suspend/hibernate depends on CPU0.
>> 3102 Suspend/hibernate will fail if CPU0 is offline and you
>> 3103 need to online CPU0 before suspend/hibernate.
>> 3104 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 3105 removed if a PIC interrupt is detected.
>> 3106 It's said poweroff/reboot may depend on CPU0 on some
>> 3107 machines although I haven't seen such issues so far
>> 3108 after CPU0 is offline on a few tested machines.
>> 3109 If the dependencies are under your control, you can
>> 3110 turn on cpu0_hotplug.
>> 3111
>> 3112 nps_mtm_hs_ctr= [KNL,ARC]
>> 3113 This parameter sets the maximum duration, in
>> 3114 cycles, each HW thread of the CTOP can run
>> 3115 without interruptions, before HW switches it.
>> 3116 The actual maximum duration is 16 times this
>> 3117 parameter's value.
>> 3118 Format: integer between 1 and 255
>> 3119 Default: 255
>> 3120
>> 3121 nptcg= [IA-64] Override max number of concurrent global TLB
>> 3122 purges which is reported from either PAL_VM_SUMMARY or
>> 3123 SAL PALO.
4091 3124
4092 noxsave [BUGS=X86] Disables x !! 3125 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4093 and restore using xsa <<
4094 enabling legacy float <<
4095 <<
4096 noxsaveopt [X86] Disables xsaveo <<
4097 register states. The <<
4098 xsave to save the sta <<
4099 performance of saving <<
4100 xsave doesn't support <<
4101 xsaveopt supports it <<
4102 <<
4103 noxsaves [X86] Disables xsaves <<
4104 restoring x86 extende <<
4105 form of xsave area. T <<
4106 xsaveopt and xrstor t <<
4107 in standard form of x <<
4108 parameter, xsave area <<
4109 memory on xsaves enab <<
4110 <<
4111 nr_cpus= [SMP,EARLY] Maximum n <<
4112 could support. nr_cp 3126 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 3127 support 'n' processors. It could be larger than the
4114 number of already plu 3128 number of already plugged CPU during bootup, later in
4115 runtime you can physi 3129 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 3130 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 3131 variables need be pre-allocated for later physical cpu
4118 hot plugging. 3132 hot plugging.
4119 3133
4120 nr_uarts= [SERIAL] maximum numb 3134 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 3135
4122 numa=off [KNL, ARM64, PPC, RIS !! 3136 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 3137 Allowed values are enable and disable
4129 3138
4130 numa_zonelist_order= [KNL, BOOT] Sele 3139 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 3140 'node', 'default' can be specified
4132 This can be set from 3141 This can be set from sysctl after boot.
4133 See Documentation/adm !! 3142 See Documentation/sysctl/vm.txt for details.
4134 3143
4135 ohci1394_dma=early [HW,EARLY] en !! 3144 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor !! 3145 See Documentation/debugging-via-ohci1394.txt for more
4137 info. 3146 info.
4138 3147
4139 olpc_ec_timeout= [OLPC] ms delay when 3148 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 3149 Rather than timing out after 20 ms if an EC
4141 command is not proper 3150 command is not properly ACKed, override the length
4142 of the timeout. We h 3151 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 3152 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 3153 interrupts *may* be lost!
4145 3154
4146 omap_mux= [OMAP] Override bootl 3155 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 3156 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 3157 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 3158 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 3159
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 3160 oprofile.timer= [HW]
>> 3161 Use timer interrupt instead of performance counters
4152 3162
4153 Format: [die0_boundar !! 3163 oprofile.cpu_type= Force an oprofile cpu type
>> 3164 This might be useful if you have an older oprofile
>> 3165 userland or if you want common events.
>> 3166 Format: { arch_perfmon }
>> 3167 arch_perfmon: [X86] Force use of architectural
>> 3168 perfmon on Intel CPUs instead of the
>> 3169 CPU specific event set.
>> 3170 timer: [X86] Force use of architectural NMI
>> 3171 timer mode (see also oprofile.timer
>> 3172 for generic hr timer mode)
4154 3173
4155 boundary - index of l !! 3174 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 3175 process, but there is a small probability of
4164 deadlocking the machi 3176 deadlocking the machine.
4165 This will also cause 3177 This will also cause panics on machine check exceptions.
4166 Useful together with 3178 Useful together with panic=30 to trigger a reboot.
4167 3179
4168 page_alloc.shuffle= 3180 page_alloc.shuffle=
4169 [KNL] Boolean flag to 3181 [KNL] Boolean flag to control whether the page allocator
4170 should randomize its !! 3182 should randomize its free lists. The randomization may
4171 used to enable/disabl !! 3183 be automatically enabled if the kernel detects it is
4172 the flag can be read !! 3184 running on a platform with a direct-mapped memory-side
>> 3185 cache, and this parameter can be used to
>> 3186 override/disable that behavior. The state of the flag
>> 3187 can be read from sysfs at:
4173 /sys/module/page_allo 3188 /sys/module/page_alloc/parameters/shuffle.
4174 This parameter is onl <<
4175 3189
4176 page_owner= [KNL,EARLY] Boot-time !! 3190 page_owner= [KNL] Boot-time page_owner enabling option.
4177 Storage of the inform 3191 Storage of the information about who allocated
4178 each page is disabled 3192 each page is disabled in default. With this switch,
4179 we can turn it on. 3193 we can turn it on.
4180 on: enable the featur 3194 on: enable the feature
4181 3195
4182 page_poison= [KNL,EARLY] Boot-time !! 3196 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd 3197 poisoning on the buddy allocator, available with
4184 CONFIG_PAGE_POISONING 3198 CONFIG_PAGE_POISONING=y.
4185 off: turn off poisoni 3199 off: turn off poisoning (default)
4186 on: turn on poisoning 3200 on: turn on poisoning
4187 3201
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 3202 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3203 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3204 timeout = 0: wait forever
4197 timeout < 0: reboot i 3205 timeout < 0: reboot immediately
4198 Format: <timeout> 3206 Format: <timeout>
4199 3207
4200 panic_on_taint= [KNL,EARLY] <<
4201 Bitmask for condition <<
4202 Format: <hex>[,nouser <<
4203 Hexadecimal bitmask r <<
4204 that will cause the k <<
4205 called with any of th <<
4206 The optional switch " <<
4207 prevent userspace for <<
4208 /proc/sys/kernel/tain <<
4209 bitmask set on panic_ <<
4210 See Documentation/adm <<
4211 extra details on the <<
4212 to compose the bitmas <<
4213 <<
4214 panic_on_warn=1 panic() instead of WA <<
4215 on a WARN(). <<
4216 <<
4217 panic_print= Bitmask for printing 3208 panic_print= Bitmask for printing system info when panic happens.
4218 User can chose combin 3209 User can chose combination of the following bits:
4219 bit 0: print all task 3210 bit 0: print all tasks info
4220 bit 1: print system m 3211 bit 1: print system memory info
4221 bit 2: print timer in 3212 bit 2: print timer info
4222 bit 3: print locks in 3213 bit 3: print locks info if CONFIG_LOCKDEP is on
4223 bit 4: print ftrace b 3214 bit 4: print ftrace buffer
4224 bit 5: print all prin 3215 bit 5: print all printk messages in buffer
4225 bit 6: print all CPUs !! 3216
4226 bit 7: print only tas !! 3217 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4227 *Be aware* that this !! 3218 on a WARN().
4228 so there are risks of !! 3219
4229 Use this option caref !! 3220 crash_kexec_post_notifiers
4230 bigger log buffer wit !! 3221 Run kdump after running panic-notifiers and dumping
>> 3222 kmsg. This only for the users who doubt kdump always
>> 3223 succeeds in any situation.
>> 3224 Note that this also increases risks of kdump failure,
>> 3225 because some panic notifiers can make the crashed
>> 3226 kernel more unstable.
4231 3227
4232 parkbd.port= [HW] Parallel port nu 3228 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3229 connected to, default is 0.
4234 Format: <parport#> 3230 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3231 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3232 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3233 Format: <mode>
4238 3234
4239 parport= [HW,PPT] Specify para 3235 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3236 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3237 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3238 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3239 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3240 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3241 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3242 should be numbers, or 'auto' (for using detected
4247 settings on that part 3243 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3244 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3245 Parallel ports are assigned in the order they
4250 are specified on the 3246 are specified on the command line, starting
4251 with parport0. 3247 with parport0.
4252 3248
4253 parport_init_mode= [HW,PPT] 3249 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3250 Configure VIA parallel port to operate in
4255 a specific mode. This 3251 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3252 computer where firmware has no options for setting
4257 up parallel port mode 3253 up parallel port mode and sets it to spp.
4258 Currently this functi 3254 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3255 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3256
4261 pata_legacy.all= [HW,LIBATA] !! 3257 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 3258 Halt all CPUs after the first oops has been printed for
4353 the specified number 3259 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3260 your oopses keep scrolling off the screen.
4355 3261
4356 pcbit= [HW,ISDN] 3262 pcbit= [HW,ISDN]
4357 3263
4358 pci=option[,option...] [PCI,EARLY] v !! 3264 pcd. [PARIDE]
>> 3265 See header of drivers/block/paride/pcd.c.
>> 3266 See also Documentation/blockdev/paride.txt.
>> 3267
>> 3268 pci=option[,option...] [PCI] various PCI subsystem options.
4359 3269
4360 Some options 3270 Some options herein operate on a specific device
4361 or a set of d 3271 or a set of devices (<pci_dev>). These are
4362 specified in 3272 specified in one of the following formats:
4363 3273
4364 [<domain>:]<b 3274 [<domain>:]<bus>:<dev>.<func>[/<dev>.<func>]*
4365 pci:<vendor>: 3275 pci:<vendor>:<device>[:<subvendor>:<subdevice>]
4366 3276
4367 Note: the fir 3277 Note: the first format specifies a PCI
4368 bus/device/fu 3278 bus/device/function address which may change
4369 if new hardwa 3279 if new hardware is inserted, if motherboard
4370 firmware chan 3280 firmware changes, or due to changes caused
4371 by other kern 3281 by other kernel parameters. If the
4372 domain is lef 3282 domain is left unspecified, it is
4373 taken to be z 3283 taken to be zero. Optionally, a path
4374 to a device t 3284 to a device through multiple device/function
4375 addresses can 3285 addresses can be specified after the base
4376 address (this 3286 address (this is more robust against
4377 renumbering i 3287 renumbering issues). The second format
4378 selects devic 3288 selects devices using IDs from the
4379 configuration 3289 configuration space which may match multiple
4380 devices in th 3290 devices in the system.
4381 3291
4382 earlydump dump PCI conf 3292 earlydump dump PCI config space before the kernel
4383 changes anyth 3293 changes anything
4384 off [X86] don't p 3294 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3295 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3296 the hardware directly. Use this if your machine
4387 has a non-sta 3297 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3298 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3299 hardware access methods are allowed. Use this
4390 if you experi 3300 if you experience crashes upon bootup and you
4391 suspect they 3301 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3302 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3303 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3304 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3305 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3306 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3307 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3308 bus number. The config space is then accessed
4399 through ports 3309 through ports 0xC000-0xCFFF).
4400 See http://wi 3310 See http://wiki.osdev.org/PCI for more info
4401 on the config 3311 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3312 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3313 enabled, this kernel boot option can be used to
4404 disable the u 3314 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3315 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3316 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3317 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3318 Configuration
4409 check_enable_amd_mmconf [X86] 3319 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3320 properly configured MMIO access to PCI
4411 config space 3321 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3322 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3323 enabled, this kernel boot option can be used to
4414 disable the u 3324 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3325 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3326 Safety option to keep boot IRQs enabled. This
4417 should never 3327 should never be necessary.
4418 ioapicreroute [APIC] Enable 3328 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3329 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3330 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3331 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3332 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3333 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3334 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3335 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3336 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3337 routing table. These calls are known to be buggy
4428 on several ma 3338 on several machines and they hang the machine
4429 when used, bu 3339 when used, but on other computers it's the only
4430 way to get th 3340 way to get the interrupt routing table. Try
4431 this option i 3341 this option if the kernel is unable to allocate
4432 IRQs or disco 3342 IRQs or discover secondary PCI buses on your
4433 motherboard. 3343 motherboard.
4434 rom [X86] Assign 3344 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3345 Use with caution as certain devices share
4436 address decod 3346 address decoders between ROMs and other
4437 resources. 3347 resources.
4438 norom [X86] Do not 3348 norom [X86] Do not assign address space to
4439 expansion ROM 3349 expansion ROMs that do not already have
4440 BIOS assigned 3350 BIOS assigned address ranges.
4441 nobar [X86] Do not 3351 nobar [X86] Do not assign address space to the
4442 BARs that wer 3352 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3353 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3354 assigned automatically to PCI devices. You can
4445 make the kern 3355 make the kernel exclude IRQs of your ISA cards
4446 this way. 3356 this way.
4447 pirqaddr=0xAAAAA [X86] 3357 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3358 of the PIRQ table (normally generated
4449 by the BIOS) 3359 by the BIOS) if it is outside the
4450 F0000h-100000 3360 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3361 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3362 useful if the kernel is unable to find your
4453 secondary bus 3363 secondary buses and you want to tell it
4454 explicitly wh 3364 explicitly which ones they are.
4455 assign-busses [X86] Always 3365 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3366 numbers ourselves, overriding
4457 whatever the 3367 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3368 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3369 in the BIOS $PIR table. This is needed on
4460 some systems 3370 some systems with broken BIOSes, notably
4461 some HP Pavil 3371 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3372 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3373 IRQ routing is enabled.
4464 noacpi [X86] Do not 3374 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3375 or for PCI scanning.
4466 use_crs [X86] Use PCI 3376 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3377 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3378 is enabled by default. If you need to use this,
4469 please report 3379 please report a bug.
4470 nocrs [X86] Ignore 3380 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 3381 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 3382 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3383 This is normally done in pci_enable_device(),
4483 so this optio 3384 so this option is a temporary workaround
4484 for broken dr 3385 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3386 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3387 handle more pci cards
4487 noearly [X86] Don't d 3388 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3389 This might help on some broken boards which
4489 machine check 3390 machine check when some devices' config space
4490 is read. But 3391 is read. But various workarounds are disabled
4491 and some IOMM 3392 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3393 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3394 This sorting is done to get a device
4494 order compati 3395 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3396 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3397 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3398 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3399 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3400 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3401 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3402 based on its parent bus. Also set MRRS (Max
4502 Read Request 3403 Read Request Size) to the largest supported
4503 value (no lar 3404 value (no larger than the MPS that the device
4504 or bus can su 3405 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3406 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3407 every device is guaranteed to support. This
4507 configuration 3408 configuration allows peer-to-peer DMA between
4508 any pair of d 3409 any pair of devices, possibly at the cost of
4509 reduced perfo 3410 reduced performance. This also guarantees
4510 that hot-adde 3411 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3412 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3413 reserved for the CardBus bridge's IO window.
4513 The default v 3414 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3415 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3416 reserved for the CardBus bridge's memory
4516 window. The d 3417 window. The default value is 64 megabytes.
4517 resource_alignment= 3418 resource_alignment=
4518 Format: 3419 Format:
4519 [<order of ali 3420 [<order of align>@]<pci_dev>[; ...]
4520 Specifies ali 3421 Specifies alignment and device to reassign
4521 aligned memor 3422 aligned memory resources. How to
4522 specify the d 3423 specify the device is described above.
4523 If <order of 3424 If <order of align> is not specified,
4524 PAGE_SIZE is 3425 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri !! 3426 PCI-PCI bridge can be specified, if resource
4526 windows need 3427 windows need to be expanded.
4527 To specify th 3428 To specify the alignment for several
4528 instances of 3429 instances of a device, the PCI vendor,
4529 device, subve 3430 device, subvendor, and subdevice may be
4530 specified, e. !! 3431 specified, e.g., 4096@pci:8086:9c22:103c:198f
4531 for 4096-byte <<
4532 ecrc= Enable/disabl 3432 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3433 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3434 bios: Use BIOS/firmware settings. This is the
4537 the default. 3435 the default.
4538 off: Turn ECR 3436 off: Turn ECRC off
4539 on: Turn ECRC 3437 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3438 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3439 reserved for hotplug bridge's IO window.
4542 Default size 3440 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 3441 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for !! 3442 reserved for hotplug bridge's memory window.
4551 MMIO_PREF win <<
4552 Default size 3443 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3444 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3445 reserved for buses below a hotplug bridge.
4555 Default is 1. 3446 Default is 1.
4556 realloc= Enable/disabl 3447 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3448 if allocations done by BIOS are too small to
4558 accommodate r 3449 accommodate resources required by all child
4559 devices. 3450 devices.
4560 off: Turn rea 3451 off: Turn realloc off
4561 on: Turn real 3452 on: Turn realloc on
4562 realloc same as reall 3453 realloc same as realloc=on
4563 noari do not use PC 3454 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 3455 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 3456 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 3457 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 3458 only look for one device below a PCIe downstream
4568 port. 3459 port.
4569 big_root_window Try to add a 3460 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 3461 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 3462 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 3463 Adding the window is slightly risky (it may
4573 conflict with 3464 conflict with unreported devices), so this
4574 taints the ke 3465 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; 3466 disable_acs_redir=<pci_dev>[; ...]
4576 Specify one o 3467 Specify one or more PCI devices (in the format
4577 specified abo 3468 specified above) separated by semicolons.
4578 Each device s 3469 Each device specified will have the PCI ACS
4579 redirect capa 3470 redirect capabilities forced off which will
4580 allow P2P tra 3471 allow P2P traffic between devices through
4581 bridges witho 3472 bridges without forcing it upstream. Note:
4582 this removes 3473 this removes isolation between devices and
4583 may put more 3474 may put more devices in an IOMMU group.
4584 config_acs= <<
4585 Format: <<
4586 <ACS flags>@<p <<
4587 Specify one o <<
4588 specified abo <<
4589 and separated <<
4590 capabilities <<
4591 unchanged bas <<
4592 flags. <<
4593 <<
4594 ACS Flags is <<
4595 bit-0 : ACS <<
4596 bit-1 : ACS <<
4597 bit-2 : ACS <<
4598 bit-3 : ACS <<
4599 bit-4 : ACS <<
4600 bit-5 : ACS <<
4601 bit-6 : ACS <<
4602 Each bit can <<
4603 '0' – for <<
4604 '1' – for <<
4605 'x' – unc <<
4606 For example, <<
4607 pci=config_ <<
4608 would configu <<
4609 ACS to enable <<
4610 Translation B <<
4611 Validation un <<
4612 or firmware s <<
4613 <<
4614 Note: this ma <<
4615 and may put m <<
4616 force_floating [S390] Force 3475 force_floating [S390] Force usage of floating interrupts.
4617 nomio [S390] Do not 3476 nomio [S390] Do not use MIO instructions.
4618 norid [S390] ignore <<
4619 one PCI domai <<
4620 3477
4621 pcie_aspm= [PCIE] Forcibly enabl !! 3478 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 3479 Management.
4623 off Don't touch ASPM conf !! 3480 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 3481 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 3482 WARNING: Forcing ASPM on may cause system lockups.
4627 3483
4628 pcie_ports= [PCIE] PCIe port serv 3484 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 3485 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 3486 even if the platform doesn't give the OS permission to
4631 use them. This may c 3487 use them. This may cause conflicts if the platform
4632 also tries to use the 3488 also tries to use these services.
4633 dpc-native Use native PC <<
4634 cause conflic <<
4635 compat Disable native PCIe s 3489 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 3490 hotplug).
4637 3491
4638 pcie_port_pm= [PCIE] PCIe port powe 3492 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 3493 off Disable power management of all PCIe ports
4640 force Forcibly enable power 3494 force Forcibly enable power management of all PCIe ports
4641 3495
4642 pcie_pme= [PCIE,PM] Native PCIe 3496 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 3497 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 3498 all PCIe root ports use INTx for all services).
4645 3499
4646 pcmv= [HW,PCMCIA] BadgePAD 3500 pcmv= [HW,PCMCIA] BadgePAD 4
4647 3501
4648 pd_ignore_unused 3502 pd_ignore_unused
4649 [PM] 3503 [PM]
4650 Keep all power-domain 3504 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 3505 even if no driver has claimed them. This is useful
4652 for debug and develop 3506 for debug and development, but should not be
4653 needed on a platform 3507 needed on a platform with proper driver support.
4654 3508
>> 3509 pd. [PARIDE]
>> 3510 See Documentation/blockdev/paride.txt.
>> 3511
4655 pdcchassis= [PARISC,HW] Disable/E 3512 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 3513 boot time.
4657 Format: { 0 | 1 } 3514 Format: { 0 | 1 }
4658 See arch/parisc/kerne 3515 See arch/parisc/kernel/pdc_chassis.c
4659 3516
4660 percpu_alloc= [MM,EARLY] !! 3517 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 3518 Currently supported values are "embed" and "page".
4663 Archs may support sub 3519 Archs may support subset or none of the selections.
4664 See comments in mm/pe 3520 See comments in mm/percpu.c for details on each
4665 allocator. This para 3521 allocator. This parameter is primarily for debugging
4666 and performance compa 3522 and performance comparison.
4667 3523
>> 3524 pf. [PARIDE]
>> 3525 See Documentation/blockdev/paride.txt.
>> 3526
>> 3527 pg. [PARIDE]
>> 3528 See Documentation/blockdev/paride.txt.
>> 3529
4668 pirq= [SMP,APIC] Manual mp- 3530 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 3531 See Documentation/x86/i386/IO-APIC.txt.
4670 3532
4671 plip= [PPT,NET] Parallel po 3533 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 3534 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 3535 See also Documentation/admin-guide/parport.rst.
4674 3536
4675 pmtmr= [X86] Manual setup of 3537 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 3538 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 3539 e.g. pmtmr=0x508
4678 3540
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] 3541 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 3542 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 3543 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 3544 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 3545 current resource usage; turning this on also shows
4695 possible settings and 3546 possible settings and some assignment information.
4696 3547
4697 pnpacpi= [ACPI] 3548 pnpacpi= [ACPI]
4698 { off } 3549 { off }
4699 3550
4700 pnpbios= [ISAPNP] 3551 pnpbios= [ISAPNP]
4701 { on | off | curr | r 3552 { on | off | curr | res | no-curr | no-res }
4702 3553
4703 pnp_reserve_irq= 3554 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 3555 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 3556
4706 pnp_reserve_dma= 3557 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 3558 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 3559
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 3560 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 3561 Ranges are in pairs (I/O port base and size).
4711 3562
4712 pnp_reserve_mem= 3563 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 3564 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 3565 autoconfiguration.
4715 Ranges are in pairs ( 3566 Ranges are in pairs (memory base and size).
4716 3567
4717 ports= [IP_VS_FTP] IPVS ftp 3568 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 3569 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 3570 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 3571 may be specified.
4721 Format: <port>,<port> 3572 Format: <port>,<port>....
4722 3573
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 3574 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 3575 It specifically disables cpuidle and sets the
4730 platform machine desc 3576 platform machine description specific power_save
4731 function to NULL. On 3577 function to NULL. On Idle the CPU just reduces
4732 execution priority. 3578 execution priority.
4733 3579
4734 ppc_strict_facility_enable 3580 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 3581 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 3582 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 3583 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 3584 There is some performance impact when enabling this.
4739 3585
4740 ppc_tm= [PPC,EARLY] !! 3586 ppc_tm= [PPC]
4741 Format: {"off"} 3587 Format: {"off"}
4742 Disable Hardware Tran 3588 Disable Hardware Transactional Memory
4743 3589
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= 3590 print-fatal-signals=
4754 [KNL] debug: print fa 3591 [KNL] debug: print fatal signals
4755 3592
4756 If enabled, warn abou 3593 If enabled, warn about various signal handling
4757 related application a 3594 related application anomalies: too many signals,
4758 too many POSIX.1 time 3595 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 3596 coredump - etc.
4760 3597
4761 If you hit the warnin 3598 If you hit the warning due to signal overflow,
4762 you might want to try 3599 you might want to try "ulimit -i unlimited".
4763 3600
4764 default: off. 3601 default: off.
4765 3602
4766 printk.always_kmsg_dump= 3603 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 3604 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 3605 panics
4769 Format: <bool> (1/Y/ 3606 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 3607 default: disabled
4771 3608
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} 3609 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 3610 Control writing to /dev/kmsg.
4783 on - unlimited loggin 3611 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 3612 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 3613 ratelimit - ratelimit the logging
4786 Default: ratelimit 3614 Default: ratelimit
4787 3615
4788 printk.time= Show timing data pref 3616 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 3617 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 3618
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] 3619 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 3620 Limit processor to maximum C-state
4803 max_cstate=9 override 3621 max_cstate=9 overrides any DMI blacklist limit.
4804 3622
4805 processor.nocst [HW,ACPI] 3623 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 3624 Ignore the _CST method to determine C-states,
4807 instead using the leg 3625 instead using the legacy FADT method
4808 3626
4809 profile= [KNL] Enable kernel p 3627 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 3628 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 3629 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 3630 [defaults to kernel profiling]
4813 Param: "schedule" - p 3631 Param: "schedule" - profile schedule points.
>> 3632 Param: "sleep" - profile D-state sleeping (millisecs).
>> 3633 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 3634 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 3635 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 3636 statistical time based profiling.
4817 3637
4818 prompt_ramdisk= [RAM] [Deprecated] !! 3638 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
4819 !! 3639 before loading.
4820 prot_virt= [S390] enable hosting !! 3640 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 3641
4827 psi= [KNL] Enable or disab 3642 psi= [KNL] Enable or disable pressure stall information
4828 tracking. 3643 tracking.
4829 Format: <bool> 3644 Format: <bool>
4830 3645
4831 psmouse.proto= [HW,MOUSE] Highest PS 3646 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 3647 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 3648 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 3649 per second.
4835 psmouse.resetafter= [HW,MOUSE] 3650 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 3651 Try to reset the device after so many bad packets
4837 (0 = never). 3652 (0 = never).
4838 psmouse.resolution= 3653 psmouse.resolution=
4839 [HW,MOUSE] Set desire 3654 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 3655 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 3656 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 3657 0 = disabled, 1 = enabled (default).
4843 3658
4844 pstore.backend= Specify the name of t 3659 pstore.backend= Specify the name of the pstore backend to use
4845 3660
4846 pti= [X86-64] Control Page !! 3661 pt. [PARIDE]
>> 3662 See Documentation/blockdev/paride.txt.
>> 3663
>> 3664 pti= [X86_64] Control Page Table Isolation of user and
4847 kernel address spaces 3665 kernel address spaces. Disabling this feature
4848 removes hardening, bu 3666 removes hardening, but improves performance of
4849 system calls and inte 3667 system calls and interrupts.
4850 3668
4851 on - unconditionall 3669 on - unconditionally enable
4852 off - unconditionall 3670 off - unconditionally disable
4853 auto - kernel detects 3671 auto - kernel detects whether your CPU model is
4854 vulnerable to 3672 vulnerable to issues that PTI mitigates
4855 3673
4856 Not specifying this o 3674 Not specifying this option is equivalent to pti=auto.
4857 3675
>> 3676 nopti [X86_64]
>> 3677 Equivalent to pti=off
>> 3678
4858 pty.legacy_count= 3679 pty.legacy_count=
4859 [KNL] Number of legac 3680 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 3681 default number.
4861 3682
4862 quiet [KNL,EARLY] Disable m !! 3683 quiet [KNL] Disable most log messages
4863 3684
4864 r128= [HW,DRM] 3685 r128= [HW,DRM]
4865 3686
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 3687 raid= [HW,RAID]
4871 See Documentation/adm 3688 See Documentation/admin-guide/md.rst.
4872 3689
4873 ramdisk_size= [RAM] Sizes of RAM di 3690 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm !! 3691 See Documentation/blockdev/ramdisk.txt.
4875 3692
4876 ramdisk_start= [RAM] RAM disk image !! 3693 random.trust_cpu={on,off}
4877 !! 3694 [KNL] Enable or disable trusting the use of the
4878 random.trust_cpu=off !! 3695 CPU's random number generator (if available) to
4879 [KNL,EARLY] Disable t !! 3696 fully seed the kernel's CRNG. Default is controlled
4880 random number generat !! 3697 by CONFIG_RANDOM_TRUST_CPU.
4881 initialize the kernel <<
4882 <<
4883 random.trust_bootloader=off <<
4884 [KNL,EARLY] Disable t <<
4885 passed by the bootloa <<
4886 initialize the kernel <<
4887 <<
4888 randomize_kstack_offset= <<
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 3698
4899 ras=option[,option,...] [KNL] RAS-spe 3699 ras=option[,option,...] [KNL] RAS-specific options
4900 3700
4901 cec_disable [X86] 3701 cec_disable [X86]
4902 Disable the C 3702 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 3703 see CONFIG_RAS_CEC help text.
4904 3704
4905 rcu_nocbs[=cpu-list] !! 3705 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 3706 The argument is a cpu list, as described above,
4907 as described above. !! 3707 except that the string "all" can be used to
4908 !! 3708 specify every CPU on the system.
4909 In kernels built with !! 3709
4910 enable the no-callbac !! 3710 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4911 such CPUs' callbacks !! 3711 the specified list of CPUs to be no-callback CPUs.
4912 softirq context. Inv !! 3712 Invocation of these CPUs' RCU callbacks will be
4913 callbacks will instea !! 3713 offloaded to "rcuox/N" kthreads created for that
4914 kthreads created for !! 3714 purpose, where "x" is "p" for RCU-preempt, and
4915 "p" for RCU-preempt, !! 3715 "s" for RCU-sched, and "N" is the CPU number.
4916 for the kthreads that !! 3716 This reduces OS jitter on the offloaded CPUs,
4917 "N" is the CPU number !! 3717 which can be useful for HPC and real-time
4918 the offloaded CPUs, w !! 3718 workloads. It can also improve energy efficiency
4919 and real-time workloa !! 3719 for asymmetric multiprocessors.
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 <<
4930 Note that this argume <<
4931 the CONFIG_RCU_NOCB_C <<
4932 3720
4933 rcu_nocb_poll [KNL] 3721 rcu_nocb_poll [KNL]
4934 Rather than requiring 3722 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 3723 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 3724 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 3725 make these kthreads poll for callbacks.
4938 This improves the rea 3726 This improves the real-time response for the
4939 offloaded CPUs by rel 3727 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 3728 wake up the corresponding kthread, but degrades
4941 energy efficiency by 3729 energy efficiency by requiring that the kthreads
4942 periodically wake up 3730 periodically wake up to do the polling.
4943 3731
4944 rcutree.blimit= [KNL] 3732 rcutree.blimit= [KNL]
4945 Set maximum number of 3733 Set maximum number of finished RCU callbacks to
4946 process in one batch. 3734 process in one batch.
4947 3735
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] 3736 rcutree.dump_tree= [KNL]
4956 Dump the structure of 3737 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 3738 out at early boot. This is used for diagnostic
4958 purposes, to verify c 3739 purposes, to verify correct tree setup.
4959 3740
4960 rcutree.gp_cleanup_delay= [KNL] 3741 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 3742 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 3743 RCU grace-period cleanup.
4963 3744
4964 rcutree.gp_init_delay= [KNL] 3745 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 3746 Set the number of jiffies to delay each step of
4966 RCU grace-period init 3747 RCU grace-period initialization.
4967 3748
4968 rcutree.gp_preinit_delay= [KNL] 3749 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 3750 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 3751 RCU grace-period pre-initialization, that is,
4971 the propagation of re 3752 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 3753 the rcu_node combining tree.
4973 3754
>> 3755 rcutree.rcu_fanout_exact= [KNL]
>> 3756 Disable autobalancing of the rcu_node combining
>> 3757 tree. This is used by rcutorture, and might
>> 3758 possibly be useful for architectures having high
>> 3759 cache-to-cache transfer latencies.
>> 3760
>> 3761 rcutree.rcu_fanout_leaf= [KNL]
>> 3762 Change the number of CPUs assigned to each
>> 3763 leaf rcu_node structure. Useful for very
>> 3764 large systems, which will choose the value 64,
>> 3765 and for NUMA systems with large remote-access
>> 3766 latencies, which will choose a value aligned
>> 3767 with the appropriate hardware boundaries.
>> 3768
4974 rcutree.jiffies_till_first_fqs= [KNL] 3769 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 3770 Set delay from grace-period initialization to
4976 first attempt to forc 3771 first attempt to force quiescent states.
4977 Units are jiffies, mi 3772 Units are jiffies, minimum value is zero,
4978 and maximum value is 3773 and maximum value is HZ.
4979 3774
4980 rcutree.jiffies_till_next_fqs= [KNL] 3775 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 3776 Set delay between subsequent attempts to force
4982 quiescent states. Un 3777 quiescent states. Units are jiffies, minimum
4983 value is one, and max 3778 value is one, and maximum value is HZ.
4984 3779
4985 rcutree.jiffies_till_sched_qs= [KNL] 3780 rcutree.jiffies_till_sched_qs= [KNL]
4986 Set required age in j 3781 Set required age in jiffies for a
4987 given grace period be 3782 given grace period before RCU starts
4988 soliciting quiescent- 3783 soliciting quiescent-state help from
4989 rcu_note_context_swit 3784 rcu_note_context_switch() and cond_resched().
4990 If not specified, the 3785 If not specified, the kernel will calculate
4991 a value based on the 3786 a value based on the most recent settings
4992 of rcutree.jiffies_ti 3787 of rcutree.jiffies_till_first_fqs
4993 and rcutree.jiffies_t 3788 and rcutree.jiffies_till_next_fqs.
4994 This calculated value 3789 This calculated value may be viewed in
4995 rcutree.jiffies_to_sc 3790 rcutree.jiffies_to_sched_qs. Any attempt to set
4996 rcutree.jiffies_to_sc 3791 rcutree.jiffies_to_sched_qs will be cheerfully
4997 overwritten. 3792 overwritten.
4998 3793
4999 rcutree.kthread_prio= [KNL,BOOT] 3794 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 3795 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 3796 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 3797 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 3798 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 3799 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 3800 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 3801 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 3802 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 3803 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 3804
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 3805 rcutree.rcu_nocb_leader_stride= [KNL]
5013 On callback-offloaded !! 3806 Set the number of NOCB kthread groups, which
5014 RCU reduces the lock !! 3807 defaults to the square root of the number of
5015 otherwise be caused b !! 3808 CPUs. Larger numbers reduces the wakeup overhead
5016 use of the ->nocb_byp !! 3809 on the per-CPU grace-period kthreads, but increases
5017 common non-flooded ca !! 3810 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 3811
5033 rcutree.qhimark= [KNL] 3812 rcutree.qhimark= [KNL]
5034 Set threshold of queu 3813 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 3814 batch limiting is disabled.
5036 3815
5037 rcutree.qlowmark= [KNL] 3816 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 3817 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 3818 batch limiting is re-enabled.
5040 3819
5041 rcutree.qovld= [KNL] !! 3820 rcutree.rcu_idle_gp_delay= [KNL]
5042 Set threshold of queu !! 3821 Set wakeup interval for idle CPUs that have
5043 RCU's force-quiescent !! 3822 RCU callbacks (RCU_FAST_NO_HZ=y).
5044 enlist help from cond !! 3823
5045 help CPUs more quickl !! 3824 rcutree.rcu_idle_lazy_gp_delay= [KNL]
5046 Set to less than zero !! 3825 Set wakeup interval for idle CPUs that have
5047 on rcutree.qhimark at !! 3826 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
5048 disable more aggressi !! 3827 Lazy RCU callbacks are those which RCU can
5049 !! 3828 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 3829
5100 rcutree.rcu_kick_kthreads= [KNL] 3830 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 3831 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 3832 wake_up() if it sleeps three times longer than
5103 it should at force-qu 3833 it should at force-quiescent-state time.
5104 This wake_up() will b 3834 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 3835 WARN_ONCE() splat and an ftrace_dump().
5106 3836
5107 rcutree.rcu_resched_ns= [KNL] <<
5108 Limit the time spend <<
5109 callbacks to the spec <<
5110 By default, this limi <<
5111 every 32 callbacks in <<
5112 inflicted by local_cl <<
5113 <<
5114 rcutree.rcu_unlock_delay= [KNL] <<
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] 3837 rcutree.sysrq_rcu= [KNL]
5124 Commandeer a sysrq ke 3838 Commandeer a sysrq key to dump out Tree RCU's
5125 rcu_node tree with an 3839 rcu_node tree with an eye towards determining
5126 why a new grace perio 3840 why a new grace period has not yet started.
5127 3841
5128 rcutree.use_softirq= [KNL] !! 3842 rcuperf.gp_async= [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 3843 Measure performance of asynchronous
5159 grace-period primitiv 3844 grace-period primitives such as call_rcu().
5160 3845
5161 rcuscale.gp_async_max= [KNL] !! 3846 rcuperf.gp_async_max= [KNL]
5162 Specify the maximum n 3847 Specify the maximum number of outstanding
5163 callbacks per writer 3848 callbacks per writer thread. When a writer
5164 thread exceeds this l 3849 thread exceeds this limit, it invokes the
5165 corresponding flavor 3850 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 3851 previously posted callbacks to drain.
5167 3852
5168 rcuscale.gp_exp= [KNL] !! 3853 rcuperf.gp_exp= [KNL]
5169 Measure performance o 3854 Measure performance of expedited synchronous
5170 grace-period primitiv 3855 grace-period primitives.
5171 3856
5172 rcuscale.holdoff= [KNL] !! 3857 rcuperf.holdoff= [KNL]
5173 Set test-start holdof 3858 Set test-start holdoff period. The purpose of
5174 this parameter is to 3859 this parameter is to delay the start of the
5175 test until boot compl 3860 test until boot completes in order to avoid
5176 interference. 3861 interference.
5177 3862
5178 rcuscale.kfree_by_call_rcu= [KNL] !! 3863 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 3864 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 3865 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 3866 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 3867 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 3868 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 3869 A value of "n" less than or equal to -N selects
5225 a single reader. 3870 a single reader.
5226 3871
5227 rcuscale.nwriters= [KNL] !! 3872 rcuperf.nwriters= [KNL]
5228 Set number of RCU wri 3873 Set number of RCU writers. The values operate
5229 the same as for rcusc !! 3874 the same as for rcuperf.nreaders.
5230 N, where N is the num 3875 N, where N is the number of CPUs
5231 3876
5232 rcuscale.scale_type= [KNL] !! 3877 rcuperf.perf_type= [KNL]
5233 Specify the RCU imple 3878 Specify the RCU implementation to test.
5234 3879
5235 rcuscale.shutdown= [KNL] !! 3880 rcuperf.shutdown= [KNL]
5236 Shut the system down 3881 Shut the system down after performance tests
5237 complete. This is us 3882 complete. This is useful for hands-off automated
5238 testing. 3883 testing.
5239 3884
5240 rcuscale.verbose= [KNL] !! 3885 rcuperf.verbose= [KNL]
5241 Enable additional pri 3886 Enable additional printk() statements.
5242 3887
5243 rcuscale.writer_holdoff= [KNL] !! 3888 rcuperf.writer_holdoff= [KNL]
5244 Write-side holdoff be 3889 Write-side holdoff between grace periods,
5245 in microseconds. The 3890 in microseconds. The default of zero says
5246 no holdoff. 3891 no holdoff.
5247 3892
5248 rcuscale.writer_holdoff_jiffies= [KNL <<
5249 Additional write-side <<
5250 periods, but in jiffi <<
5251 says no holdoff. <<
5252 <<
5253 rcutorture.fqs_duration= [KNL] 3893 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 3894 Set duration of force_quiescent_state bursts
5255 in microseconds. 3895 in microseconds.
5256 3896
5257 rcutorture.fqs_holdoff= [KNL] 3897 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 3898 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 3899 in microseconds.
5260 3900
5261 rcutorture.fqs_stutter= [KNL] 3901 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 3902 Set wait time between force_quiescent_state bursts
5263 in seconds. 3903 in seconds.
5264 3904
5265 rcutorture.fwd_progress= [KNL] 3905 rcutorture.fwd_progress= [KNL]
5266 Specifies the number !! 3906 Enable RCU grace-period forward-progress testing
5267 for RCU grace-period <<
5268 for the types of RCU 3907 for the types of RCU supporting this notion.
5269 Defaults to 1 kthread <<
5270 greater than the numb <<
5271 of CPUs to be used. <<
5272 3908
5273 rcutorture.fwd_progress_div= [KNL] 3909 rcutorture.fwd_progress_div= [KNL]
5274 Specify the fraction 3910 Specify the fraction of a CPU-stall-warning
5275 period to do tight-lo 3911 period to do tight-loop forward-progress testing.
5276 3912
5277 rcutorture.fwd_progress_holdoff= [KNL 3913 rcutorture.fwd_progress_holdoff= [KNL]
5278 Number of seconds to 3914 Number of seconds to wait between successive
5279 forward-progress test 3915 forward-progress tests.
5280 3916
5281 rcutorture.fwd_progress_need_resched= 3917 rcutorture.fwd_progress_need_resched= [KNL]
5282 Enclose cond_resched( 3918 Enclose cond_resched() calls within checks for
5283 need_resched() during 3919 need_resched() during tight-loop forward-progress
5284 testing. 3920 testing.
5285 3921
5286 rcutorture.gp_cond= [KNL] 3922 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 3923 Use conditional/asynchronous update-side
5288 primitives, if availa 3924 primitives, if available.
5289 3925
5290 rcutorture.gp_exp= [KNL] 3926 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 3927 Use expedited update-side primitives, if available.
5292 3928
5293 rcutorture.gp_normal= [KNL] 3929 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 3930 Use normal (non-expedited) asynchronous
5295 update-side primitive 3931 update-side primitives, if available.
5296 3932
5297 rcutorture.gp_sync= [KNL] 3933 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 3934 Use normal (non-expedited) synchronous
5299 update-side primitive 3935 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 3936 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 3937 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 3938 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 3939 they are all non-zero.
5304 3940
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] 3941 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 3942 Set callbacks/threads for rcu_barrier() testing.
5319 3943
5320 rcutorture.nfakewriters= [KNL] 3944 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 3945 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 3946 stress RCU, they don't participate in the actual
5323 test, hence the "fake 3947 test, hence the "fake".
5324 3948
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] 3949 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 3950 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 3951 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 3952 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 3953 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 3954 (the number of CPUs), -3 selects N+1, and so on.
5339 3955
5340 rcutorture.object_debug= [KNL] 3956 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 3957 Enable debug-object double-call_rcu() testing.
5342 3958
5343 rcutorture.onoff_holdoff= [KNL] 3959 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 3960 Set time (s) after boot for CPU-hotplug testing.
5345 3961
5346 rcutorture.onoff_interval= [KNL] 3962 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be 3963 Set time (jiffies) between CPU-hotplug operations,
5348 or zero to disable CP 3964 or zero to disable CPU-hotplug testing.
5349 3965
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 <<
5364 rcutorture.shuffle_interval= [KNL] 3966 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 3967 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 3968 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 3969 during the rcutorture test.
5368 3970
5369 rcutorture.shutdown_secs= [KNL] 3971 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 3972 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 3973 is useful for hands-off automated testing.
5372 3974
5373 rcutorture.stall_cpu= [KNL] 3975 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 3976 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 3977 warnings, zero to disable.
5376 3978
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] 3979 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 3980 Time to wait (s) after boot before inducing stall.
5393 3981
5394 rcutorture.stall_cpu_irqsoff= [KNL] 3982 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 3983 Disable interrupts while stalling if set.
5396 3984
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] 3985 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 3986 Time (s) between statistics printk()s.
5406 3987
5407 rcutorture.stutter= [KNL] 3988 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 3989 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 3990 five seconds causes the test to run for five seconds,
5410 wait for five seconds 3991 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 3992 ability to transition abruptly to and from idle.
5412 3993
5413 rcutorture.test_boost= [KNL] 3994 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 3995 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 3996 "Maybe" means test if the RCU implementation
5416 under test support RC 3997 under test support RCU priority boosting.
5417 3998
5418 rcutorture.test_boost_duration= [KNL] 3999 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 4000 Duration (s) of each individual boost test.
5420 4001
5421 rcutorture.test_boost_interval= [KNL] 4002 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 4003 Interval (s) between each boost test.
5423 4004
5424 rcutorture.test_no_idle_hz= [KNL] 4005 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 4006 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 4007 rcutorture.shuffle_interval parameter.
5427 4008
5428 rcutorture.torture_type= [KNL] 4009 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 4010 Specify the RCU implementation to test.
5430 4011
5431 rcutorture.verbose= [KNL] 4012 rcutorture.verbose= [KNL]
5432 Enable additional pri 4013 Enable additional printk() statements.
5433 4014
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 4015 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 4016 Suppress RCU CPU stall warning messages.
5446 4017
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] 4018 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 4019 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 4020
5479 rcupdate.rcu_expedited= [KNL] 4021 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 4022 Use expedited grace-period primitives, for
5481 example, synchronize_ 4023 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 4024 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 4025 but can increase CPU utilization, degrade
5484 real-time latency, an 4026 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 4027 No effect on CONFIG_TINY_RCU kernels.
5486 4028
5487 rcupdate.rcu_normal= [KNL] 4029 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 4030 Use only normal grace-period primitives,
5489 for example, synchron 4031 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 4032 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 4033 real-time latency, CPU utilization, and
5492 energy efficiency, bu 4034 energy efficiency, but can expose users to
5493 increased grace-perio 4035 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 4036 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 4037 CONFIG_TINY_RCU kernels.
5496 4038
5497 rcupdate.rcu_normal_after_boot= [KNL] 4039 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 4040 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 4041 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 4042 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 4043 on CONFIG_TINY_RCU kernels.
5502 4044
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 4045 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 4046 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 4047 messages. Disable with a value less than or equal
5572 than or equal to zero !! 4048 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 4049
5599 rcupdate.rcu_self_test= [KNL] 4050 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 4051 Run the RCU early boot self tests
5601 4052
5602 rdinit= [KNL] 4053 rdinit= [KNL]
5603 Format: <full_path> 4054 Format: <full_path>
5604 Run specified binary 4055 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 4056 used for early userspace startup. See initrd.
5606 4057
5607 rdrand= [X86,EARLY] !! 4058 rdrand= [X86]
5608 force - Override the 4059 force - Override the decision by the kernel to hide the
5609 advertisement 4060 advertisement of RDRAND support (this affects
5610 certain AMD p 4061 certain AMD processors because of buggy BIOS
5611 support, spec 4062 support, specifically around the suspend/resume
5612 path). 4063 path).
5613 4064
5614 rdt= [HW,X86,RDT] 4065 rdt= [HW,X86,RDT]
5615 Turn on/off individua 4066 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 4067 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 4068 mba.
5618 E.g. to turn on cmt a 4069 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 4070 rdt=cmt,!mba
5620 4071
5621 reboot= [KNL] 4072 reboot= [KNL]
5622 Format (x86 or x86_64 4073 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 4074 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 4075 [[,]s[mp]#### \
5625 [[,]b[ios] | 4076 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 4077 [[,]f[orce]
5627 Where reboot_mode is 4078 Where reboot_mode is one of warm (soft) or cold (hard) or gpio
5628 (pref 4079 (prefix with 'panic_' to set mode for panic
5629 reboo 4080 reboot only),
5630 reboot_type is 4081 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 4082 reboot_force is either force or not specified,
5632 reboot_cpu is s 4083 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 4084 to be used for rebooting.
5634 4085
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= 4086 relax_domain_level=
5694 [KNL, SMP] Set schedu 4087 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm !! 4088 See Documentation/cgroup-v1/cpusets.txt.
5696 4089
5697 reserve= [KNL,BUGS] Force kern 4090 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 4091 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 4092 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 4093 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 4094 is assumed to be I/O ports; otherwise it is memory.
5702 4095
5703 reserve_mem= [RAM] !! 4096 reservetop= [X86-32]
5704 Format: nn[KNG]:<alig <<
5705 Reserve physical memo <<
5706 other subsystems can <<
5707 used for systems that <<
5708 line will try to rese <<
5709 soft reboots. Note, i <<
5710 location. For example <<
5711 or if booting a diffe <<
5712 places the kernel at <<
5713 was from a previous b <<
5714 different location. <<
5715 Any subsystem using t <<
5716 that the contents of <<
5717 boot, as there may be <<
5718 located at the same l <<
5719 <<
5720 The format is size:al <<
5721 12 megabytes of 4096 <<
5722 <<
5723 reserve_mem=12M:4096: <<
5724 <<
5725 reservetop= [X86-32,EARLY] <<
5726 Format: nn[KMG] 4097 Format: nn[KMG]
5727 Reserves a hole at th 4098 Reserves a hole at the top of the kernel virtual
5728 address space. 4099 address space.
5729 4100
>> 4101 reservelow= [X86]
>> 4102 Format: nn[K]
>> 4103 Set the amount of memory to reserve for BIOS at
>> 4104 the bottom of the address space.
>> 4105
5730 reset_devices [KNL] Force drivers t 4106 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 4107 during initialization.
5732 4108
5733 resume= [SWSUSP] 4109 resume= [SWSUSP]
5734 Specify the partition 4110 Specify the partition device for software suspend
5735 Format: 4111 Format:
5736 {/dev/<dev> | PARTUUI 4112 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 4113
5738 resume_offset= [SWSUSP] 4114 resume_offset= [SWSUSP]
5739 Specify the offset fr 4115 Specify the offset from the beginning of the partition
5740 given by "resume=" at 4116 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 4117 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po !! 4118 See Documentation/power/swsusp-and-swap-files.txt
5743 4119
5744 resumedelay= [HIBERNATION] Delay ( 4120 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 4121 read the resume files
5746 4122
5747 resumewait [HIBERNATION] Wait (i 4123 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 4124 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 4125 (e.g. USB and MMC devices).
5750 4126
5751 retain_initrd [RAM] Keep initrd mem !! 4127 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 4128 noresume Don't check if there's a hibernation image
5753 !! 4129 present during boot.
5754 retbleed= [X86] Control mitigat !! 4130 nocompress Don't compress/decompress hibernation images.
5755 Speculative Code Exec !! 4131 no Disable hibernation and resume.
5756 vulnerability. !! 4132 protect_image Turn on image protection during restoration
5757 !! 4133 (that will set all pages holding image data
5758 AMD-based UNRET and I !! 4134 during restoration read-only).
5759 sibling threads from <<
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 <<
5786 Selecting 'auto' will <<
5787 time according to the <<
5788 4135
5789 Not specifying this o !! 4136 retain_initrd [RAM] Keep initrd memory after extraction
5790 4137
5791 rfkill.default_state= 4138 rfkill.default_state=
5792 0 "airplane mode". All 4139 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 4140 etc. communication is blocked by default.
5794 1 Unblocked. 4141 1 Unblocked.
5795 4142
5796 rfkill.master_switch_mode= 4143 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 4144 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 4145 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 4146 blocked and the previous configuration.
5800 2 The "airplane mode" b 4147 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 4148 blocked and everything unblocked.
5802 4149
>> 4150 rhash_entries= [KNL,NET]
>> 4151 Set number of hash buckets for route cache
>> 4152
5803 ring3mwait=disable 4153 ring3mwait=disable
5804 [KNL] Disable ring 3 4154 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 4155 CPUs.
5806 4156
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 4157 ro [KNL] Mount root device read-only on boot
5815 4158
5816 rodata= [KNL,EARLY] !! 4159 rodata= [KNL]
5817 on Mark read-only kernel 4160 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 4161 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 4162
5822 rockchip.usb_uart 4163 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 4164 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 4165 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 4166 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 4167 port and the regular usb controller gets disabled.
5828 4168
5829 root= [KNL] Root filesystem 4169 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 4170 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 4171
5837 rootdelay= [KNL] Delay (in secon 4172 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 4173 mount the root filesystem
5839 4174
5840 rootflags= [KNL] Set root filesy 4175 rootflags= [KNL] Set root filesystem mount option string
5841 4176
5842 rootfstype= [KNL] Set root filesy 4177 rootfstype= [KNL] Set root filesystem type
5843 4178
5844 rootwait [KNL] Wait (indefinit 4179 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 4180 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 4181 (e.g. USB and MMC devices).
5847 4182
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 4183 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 4184 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 4185 Memory area to be used by remote processor image,
5855 managed by CMA. 4186 managed by CMA.
5856 4187
5857 rw [KNL] Mount root devi 4188 rw [KNL] Mount root device read-write on boot
5858 4189
5859 S [KNL] Run init in sin 4190 S [KNL] Run init in single mode
5860 4191
5861 s390_iommu= [HW,S390] 4192 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 4193 Set s390 IOTLB flushing mode
5863 strict 4194 strict
5864 With strict flushing !! 4195 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 4196 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 4197 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 4198
5881 sa1100ir [NET] 4199 sa1100ir [NET]
5882 See drivers/net/irda/ 4200 See drivers/net/irda/sa1100_ir.c.
5883 4201
5884 sched_verbose [KNL,EARLY] Enables v !! 4202 sbni= [NET] Granch SBNI12 leased line adapter
>> 4203
>> 4204 sched_debug [KNL] Enables verbose scheduler debug messages.
5885 4205
5886 schedstats= [KNL,X86] Enable or d 4206 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 4207 Allowed values are enable and disable. This feature
5888 incurs a small amount 4208 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 4209 but is useful for debugging and performance tuning.
5890 4210
5891 sched_thermal_decay_shift= !! 4211 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 4212 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 4213 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 4214 Format: { "0" | "1" }
6004 0 -- disable. (may be 4215 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 4216 1 -- enable.
6006 Note: increases power 4217 Note: increases power consumption, thus should only be
6007 enabled if running ji 4218 enabled if running jitter sensitive (HPC/RT) workloads.
6008 4219
6009 security= [SECURITY] Choose a l 4220 security= [SECURITY] Choose a legacy "major" security module to
6010 enable at boot. This 4221 enable at boot. This has been deprecated by the
6011 "lsm=" parameter. 4222 "lsm=" parameter.
6012 4223
6013 selinux= [SELINUX] Disable or 4224 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 4225 Format: { "0" | "1" }
6015 See security/selinux/ 4226 See security/selinux/Kconfig help text.
6016 0 -- disable. 4227 0 -- disable.
6017 1 -- enable. 4228 1 -- enable.
6018 Default value is 1. !! 4229 Default value is set via kernel config option.
>> 4230 If enabled at boot time, /selinux/disable can be used
>> 4231 later to disable prior to initial policy load.
6019 4232
6020 serialnumber [BUGS=X86-32] !! 4233 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 4234 Format: { "0" | "1" }
>> 4235 See security/apparmor/Kconfig help text
>> 4236 0 -- disable.
>> 4237 1 -- enable.
>> 4238 Default value is set via kernel config option.
6021 4239
6022 sev=option[,option...] [X86-64] See D !! 4240 serialnumber [BUGS=X86-32]
6023 4241
6024 shapers= [NET] 4242 shapers= [NET]
6025 Maximal number of sha 4243 Maximal number of shapers.
6026 4244
6027 show_lapic= [APIC,X86] Advanced P !! 4245 simeth= [IA-64]
6028 Limit apic dumping. T !! 4246 simscsi=
6029 number of local apics !! 4247
6030 to set it to "all" by !! 4248 slram= [HW,MTD]
6031 Format: { 1 (default) !! 4249
6032 The parameter valid i !! 4250 slab_nomerge [MM]
6033 apic=verbose is speci !! 4251 Disable merging of slabs with similar size. May be
6034 Example: apic=debug s !! 4252 necessary if there is some reason to distinguish
>> 4253 allocs to different slabs, especially in hardened
>> 4254 environments where the risk of heap overflows and
>> 4255 layout control by attackers can usually be
>> 4256 frustrated by disabling merging. This will reduce
>> 4257 most of the exposure of a heap attack to a single
>> 4258 cache (risks via metadata attacks are mostly
>> 4259 unchanged). Debug options disable merging on their
>> 4260 own.
>> 4261 For more information see Documentation/vm/slub.rst.
>> 4262
>> 4263 slab_max_order= [MM, SLAB]
>> 4264 Determines the maximum allowed order for slabs.
>> 4265 A high setting may cause OOMs due to memory
>> 4266 fragmentation. Defaults to 1 for systems with
>> 4267 more than 32MB of RAM, 0 otherwise.
6035 4268
6036 slab_debug[=options[,slabs][;[options !! 4269 slub_debug[=options[,slabs]] [MM, SLUB]
6037 Enabling slab_debug a !! 4270 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 4271 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 4272 slub_debug can create guard zones around objects and
6040 may poison objects wh 4273 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 4274 last alloc / free. For more information see
6042 Documentation/mm/slub !! 4275 Documentation/vm/slub.rst.
6043 (slub_debug legacy na !! 4276
>> 4277 slub_memcg_sysfs= [MM, SLUB]
>> 4278 Determines whether to enable sysfs directories for
>> 4279 memory cgroup sub-caches. 1 to enable, 0 to disable.
>> 4280 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
>> 4281 Enabling this can lead to a very high number of debug
>> 4282 directories and files being created under
>> 4283 /sys/kernel/slub.
6044 4284
6045 slab_max_order= [MM] !! 4285 slub_max_order= [MM, SLUB]
6046 Determines the maximu 4286 Determines the maximum allowed order for slabs.
6047 A high setting may ca 4287 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 4288 fragmentation. For more information see
6049 Documentation/mm/slub !! 4289 Documentation/vm/slub.rst.
6050 (slub_max_order legac <<
6051 <<
6052 slab_merge [MM] <<
6053 Enable merging of sla <<
6054 kernel is built witho <<
6055 (slub_merge legacy na <<
6056 4290
6057 slab_min_objects= [MM] !! 4291 slub_min_objects= [MM, SLUB]
6058 The minimum number of 4292 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 4293 increase the slab order up to slub_max_order to
6060 generate a sufficient 4294 generate a sufficiently large slab able to contain
6061 the number of objects 4295 the number of objects indicated. The higher the number
6062 of objects the smalle 4296 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 4297 and the less frequently locks need to be acquired.
6064 For more information !! 4298 For more information see Documentation/vm/slub.rst.
6065 (slub_min_objects leg <<
6066 4299
6067 slab_min_order= [MM] !! 4300 slub_min_order= [MM, SLUB]
6068 Determines the minimu 4301 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 4302 lower than slub_max_order.
6070 Documentation/mm/slub !! 4303 For more information see Documentation/vm/slub.rst.
6071 (slub_min_order legac <<
6072 4304
6073 slab_nomerge [MM] !! 4305 slub_nomerge [MM, SLUB]
6074 Disable merging of sl !! 4306 Same with slab_nomerge. This is supported for legacy.
6075 necessary if there is !! 4307 See slab_nomerge for more information.
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 <<
6087 slram= [HW,MTD] <<
6088 4308
6089 smart2= [HW] 4309 smart2= [HW]
6090 Format: <io1>[,<io2>[ 4310 Format: <io1>[,<io2>[,...,<io8>]]
6091 4311
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 4312 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 4313 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 4314 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 4315 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 4316 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 4317 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 4318 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 4319 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 4320 1: Fast pin select (default)
6119 2: ATC IRMode 4321 2: ATC IRMode
6120 4322
6121 smt= [KNL,MIPS,S390,EARLY] !! 4323 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 4324 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 4325 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 4326 actual hardware limit.
6125 Format: <integer> 4327 Format: <integer>
6126 Default: -1 (no limit 4328 Default: -1 (no limit)
6127 4329
6128 softlockup_panic= 4330 softlockup_panic=
6129 [KNL] Should the soft 4331 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 !! 4332 Format: <integer>
6131 4333
6132 A value of 1 instruct !! 4334 A nonzero value instructs the soft-lockup detector
6133 to panic the machine !! 4335 to panic the machine when a soft-lockup occurs. This
6134 also controlled by th !! 4336 is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
6135 and CONFIG_BOOTPARAM_ !! 4337 which is the respective build-time switch to that
6136 respective build-time !! 4338 functionality.
6137 4339
6138 softlockup_all_cpu_backtrace= 4340 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 4341 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 4342 backtraces on all cpus.
6141 Format: 0 | 1 !! 4343 Format: <integer>
6142 4344
6143 sonypi.*= [HW] Sony Programmabl 4345 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm !! 4346 See Documentation/laptops/sonypi.txt
6145 4347
6146 spectre_bhi= [X86] Control mitigat !! 4348 spectre_v2= [X86] Control mitigation of Spectre variant 2
6147 (BHI) vulnerability. <<
6148 deployment of the HW <<
6149 clearing sequence. <<
6150 <<
6151 on - (default) En <<
6152 needed. Thi <<
6153 both syscall <<
6154 vmexit - On systems w <<
6155 available, e <<
6156 ONLY. On su <<
6157 protected fr <<
6158 may still be <<
6159 off - Disable the <<
6160 <<
6161 spectre_v2= [X86,EARLY] Control m <<
6162 (indirect branch spec 4349 (indirect branch speculation) vulnerability.
6163 The default operation 4350 The default operation protects the kernel from
6164 user space attacks. 4351 user space attacks.
6165 4352
6166 on - unconditionall 4353 on - unconditionally enable, implies
6167 spectre_v2_use 4354 spectre_v2_user=on
6168 off - unconditionall 4355 off - unconditionally disable, implies
6169 spectre_v2_use 4356 spectre_v2_user=off
6170 auto - kernel detects 4357 auto - kernel detects whether your CPU model is
6171 vulnerable 4358 vulnerable
6172 4359
6173 Selecting 'on' will, 4360 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 4361 mitigation method at run time according to the
6175 CPU, the available mi 4362 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 4363 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 4364 compiler with which the kernel was built.
6178 4365
6179 Selecting 'on' will a 4366 Selecting 'on' will also enable the mitigation
6180 against user space to 4367 against user space to user space task attacks.
6181 4368
6182 Selecting 'off' will 4369 Selecting 'off' will disable both the kernel and
6183 the user space protec 4370 the user space protections.
6184 4371
6185 Specific mitigations 4372 Specific mitigations can also be selected manually:
6186 4373
6187 retpoline - r 4374 retpoline - replace indirect branches
6188 retpoline,generic - R !! 4375 retpoline,generic - google's original retpoline
6189 retpoline,lfence - L !! 4376 retpoline,amd - AMD-specific minimal thunk
6190 retpoline,amd - a <<
6191 eibrs - E <<
6192 eibrs,retpoline - E <<
6193 eibrs,lfence - E <<
6194 ibrs - u <<
6195 4377
6196 Not specifying this o 4378 Not specifying this option is equivalent to
6197 spectre_v2=auto. 4379 spectre_v2=auto.
6198 4380
6199 spectre_v2_user= 4381 spectre_v2_user=
6200 [X86] Control mitigat 4382 [X86] Control mitigation of Spectre variant 2
6201 (indirect branch spec 4383 (indirect branch speculation) vulnerability between
6202 user space tasks 4384 user space tasks
6203 4385
6204 on - Uncondition 4386 on - Unconditionally enable mitigations. Is
6205 enforced by 4387 enforced by spectre_v2=on
6206 4388
6207 off - Uncondition 4389 off - Unconditionally disable mitigations. Is
6208 enforced by 4390 enforced by spectre_v2=off
6209 4391
6210 prctl - Indirect br 4392 prctl - Indirect branch speculation is enabled,
6211 but mitigat 4393 but mitigation can be enabled via prctl
6212 per thread. 4394 per thread. The mitigation control state
6213 is inherite 4395 is inherited on fork.
6214 4396
6215 prctl,ibpb 4397 prctl,ibpb
6216 - Like "prctl 4398 - Like "prctl" above, but only STIBP is
6217 controlled 4399 controlled per thread. IBPB is issued
6218 always when 4400 always when switching between different user
6219 space proce 4401 space processes.
6220 4402
6221 seccomp 4403 seccomp
6222 - Same as "pr 4404 - Same as "prctl" above, but all seccomp
6223 threads wil 4405 threads will enable the mitigation unless
6224 they explic 4406 they explicitly opt out.
6225 4407
6226 seccomp,ibpb 4408 seccomp,ibpb
6227 - Like "secco 4409 - Like "seccomp" above, but only STIBP is
6228 controlled 4410 controlled per thread. IBPB is issued
6229 always when 4411 always when switching between different
6230 user space 4412 user space processes.
6231 4413
6232 auto - Kernel sele 4414 auto - Kernel selects the mitigation depending on
6233 the availab 4415 the available CPU features and vulnerability.
6234 4416
6235 Default mitigation: " !! 4417 Default mitigation:
>> 4418 If CONFIG_SECCOMP=y then "seccomp", otherwise "prctl"
6236 4419
6237 Not specifying this o 4420 Not specifying this option is equivalent to
6238 spectre_v2_user=auto. 4421 spectre_v2_user=auto.
6239 4422
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= 4423 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 4424 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 4425 (Speculative Store Bypass vulnerability)
6254 4426
6255 Certain CPUs are vuln 4427 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 4428 a common industry wide performance optimization known
6257 as "Speculative Store 4429 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 4430 to the same memory location may not be observed by
6259 later loads during sp 4431 later loads during speculative execution. The idea
6260 is that such stores a 4432 is that such stores are unlikely and that they can
6261 be detected prior to 4433 be detected prior to instruction retirement at the
6262 end of a particular s 4434 end of a particular speculation execution window.
6263 4435
6264 In vulnerable process 4436 In vulnerable processors, the speculatively forwarded
6265 store can be used in 4437 store can be used in a cache side channel attack, for
6266 example to read memor 4438 example to read memory to which the attacker does not
6267 directly have access 4439 directly have access (e.g. inside sandboxed code).
6268 4440
6269 This parameter contro 4441 This parameter controls whether the Speculative Store
6270 Bypass optimization i 4442 Bypass optimization is used.
6271 4443
6272 On x86 the options ar 4444 On x86 the options are:
6273 4445
6274 on - Uncondition 4446 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 4447 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 4448 auto - Kernel detects whether the CPU model contains an
6277 implementat 4449 implementation of Speculative Store Bypass and
6278 picks the m 4450 picks the most appropriate mitigation. If the
6279 CPU is not 4451 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 4452 CPU is vulnerable the default mitigation is
6281 architectur 4453 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 4454 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 4455 via prctl. Speculative Store Bypass is enabled
6284 for a proce 4456 for a process by default. The state of the control
6285 is inherite 4457 is inherited on fork.
6286 seccomp - Same as "pr 4458 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 4459 will disable SSB unless they explicitly opt out.
6288 4460
6289 Default mitigations: 4461 Default mitigations:
6290 X86: "prctl" !! 4462 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6291 4463
6292 On powerpc the option 4464 On powerpc the options are:
6293 4465
6294 on,auto - On Power8 a 4466 on,auto - On Power8 and Power9 insert a store-forwarding
6295 barrier on 4467 barrier on kernel entry and exit. On Power7
6296 perform a s 4468 perform a software flush on kernel entry and
6297 exit. 4469 exit.
6298 off - No action. 4470 off - No action.
6299 4471
6300 Not specifying this o 4472 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 4473 spec_store_bypass_disable=auto.
6302 4474
6303 split_lock_detect= !! 4475 spia_io_base= [HW,MTD]
6304 [X86] Enable split lo !! 4476 spia_fio_base=
6305 !! 4477 spia_pedr=
6306 When enabled (and if !! 4478 spia_peddr=
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 <<
6340 #DB exception for bus <<
6341 CPL > 0. <<
6342 <<
6343 srbds= [X86,INTEL,EARLY] <<
6344 Control the Special R <<
6345 (SRBDS) mitigation. <<
6346 <<
6347 Certain CPUs are vuln <<
6348 exploit which can lea <<
6349 number generator. <<
6350 <<
6351 By default, this issu <<
6352 microcode. However, <<
6353 the RDRAND and RDSEED <<
6354 much slower. Among o <<
6355 result in reduced thr <<
6356 <<
6357 The microcode mitigat <<
6358 the following option: <<
6359 <<
6360 off: Disable mitig <<
6361 performance i <<
6362 <<
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 4479
6387 srcutree.counter_wrap_check [KNL] 4480 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 4481 Specifies how frequently to check for
6389 grace-period sequence 4482 grace-period sequence counter wrap for the
6390 srcu_data structure's 4483 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 4484 The greater the number of bits set in this kernel
6392 parameter, the less f 4485 parameter, the less frequently counter wrap will
6393 be checked for. Note 4486 be checked for. Note that the bottom two bits
6394 are ignored. 4487 are ignored.
6395 4488
6396 srcutree.exp_holdoff [KNL] 4489 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 4490 Specifies how many nanoseconds must elapse
6398 since the end of the 4491 since the end of the last SRCU grace period for
6399 a given srcu_struct u 4492 a given srcu_struct until the next normal SRCU
6400 grace period will be 4493 grace period will be considered for automatic
6401 expediting. Set to z 4494 expediting. Set to zero to disable automatic
6402 expediting. 4495 expediting.
6403 4496
6404 srcutree.srcu_max_nodelay [KNL] !! 4497 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 4498 Speculative Store Bypass Disable control
6432 4499
6433 On CPUs that are vuln 4500 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 4501 Store Bypass vulnerability and offer a
6435 firmware based mitiga 4502 firmware based mitigation, this parameter
6436 indicates how the mit 4503 indicates how the mitigation should be used:
6437 4504
6438 force-on: Unconditio 4505 force-on: Unconditionally enable mitigation for
6439 for both k 4506 for both kernel and userspace
6440 force-off: Unconditio 4507 force-off: Unconditionally disable mitigation for
6441 for both k 4508 for both kernel and userspace
6442 kernel: Always ena 4509 kernel: Always enable mitigation in the
6443 kernel, an 4510 kernel, and offer a prctl interface
6444 to allow u 4511 to allow userspace to register its
6445 interest i 4512 interest in being mitigated too.
6446 4513
6447 stack_guard_gap= [MM] 4514 stack_guard_gap= [MM]
6448 override the default 4515 override the default stack gap protection. The value
6449 is in page units and 4516 is in page units and it defines how many pages prior
6450 to (for stacks growin 4517 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 4518 growing up) the main stack are reserved for no other
6452 mapping. Default valu 4519 mapping. Default value is 256 pages.
6453 4520
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] 4521 stacktrace [FTRACE]
6461 Enabled the stack tra 4522 Enabled the stack tracer on boot up.
6462 4523
6463 stacktrace_filter=[function-list] 4524 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 4525 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up !! 4526 will trace at boot up. function-list is a comma separated
6466 list of functions. Th 4527 list of functions. This list can be changed at run
6467 time by the stack_tra 4528 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 4529 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 4530 and the stacktrace above is not needed.
6470 4531
6471 sti= [PARISC,HW] 4532 sti= [PARISC,HW]
6472 Format: <num> 4533 Format: <num>
6473 Set the STI (builtin 4534 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 4535 machines) console (graphic card) which should be used
6475 as the initial boot-c 4536 as the initial boot-console.
6476 See also comment in d 4537 See also comment in drivers/video/console/sticore.c.
6477 4538
6478 sti_font= [HW] 4539 sti_font= [HW]
6479 See comment in driver 4540 See comment in drivers/video/console/sticore.c.
6480 4541
6481 stifb= [HW] 4542 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 4543 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 4544
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= 4545 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 4546 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 4547 [NFS,SUNRPC]
6506 SunRPC servers often 4548 SunRPC servers often require that client requests
6507 originate from a priv 4549 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 4550 range 0 < portnr < 1024).
6509 An administrator who 4551 An administrator who wishes to reserve some of these
6510 ports for other uses 4552 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 4553 kernel's sunrpc client considers to be privileged
6512 using these two param 4554 using these two parameters to set the minimum and
6513 maximum port values. 4555 maximum port values.
6514 4556
6515 sunrpc.svc_rpc_per_connection_limit= 4557 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 4558 [NFS,SUNRPC]
6517 Limit the number of r 4559 Limit the number of requests that the server will
6518 process in parallel f 4560 process in parallel from a single connection.
6519 The default value is 4561 The default value is 0 (no limit).
6520 4562
6521 sunrpc.pool_mode= 4563 sunrpc.pool_mode=
6522 [NFS] 4564 [NFS]
6523 Control how the NFS s 4565 Control how the NFS server code allocates CPUs to
6524 service thread pools. 4566 service thread pools. Depending on how many NICs
6525 you have and where th 4567 you have and where their interrupts are bound, this
6526 option will affect wh 4568 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 4569 Note: this parameter cannot be changed while the
6528 NFS server is running 4570 NFS server is running.
6529 4571
6530 auto the serve 4572 auto the server chooses an appropriate mode
6531 automatic 4573 automatically using heuristics
6532 global a single 4574 global a single global pool contains all CPUs
6533 percpu one pool 4575 percpu one pool for each CPU
6534 pernode one pool 4576 pernode one pool for each NUMA node (equivalent
6535 to global 4577 to global on non-NUMA machines)
6536 4578
6537 sunrpc.tcp_slot_table_entries= 4579 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 4580 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 4581 [NFS,SUNRPC]
6540 Sets the upper limit 4582 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 4583 RPC calls that can be sent from the client to a
6542 server. Increasing th 4584 server. Increasing these values may allow you to
6543 improve throughput, b 4585 improve throughput, but will also increase the
6544 amount of memory rese 4586 amount of memory reserved for use by the client.
6545 4587
6546 suspend.pm_test_delay= 4588 suspend.pm_test_delay=
6547 [SUSPEND] 4589 [SUSPEND]
6548 Sets the number of se 4590 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 4591 mode before resuming the system (see
6550 /sys/power/pm_test). 4592 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 4593 is set. Default value is 5.
6552 4594
6553 svm= [PPC] !! 4595 swapaccount=[0|1]
6554 Format: { on | off | !! 4596 [KNL] Enable accounting of swap in memory resource
6555 This parameter contro !! 4597 controller if no parameter or 1 is given or disable
6556 Execution Facility on !! 4598 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
6557 4599
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 4600 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in !! 4601 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 4602 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 4603 force -- force using of bounce buffers even if they
6565 wouldn't be 4604 wouldn't be automatically used by the kernel
6566 noforce -- Never use 4605 noforce -- Never use bounce buffers (for debugging)
6567 4606
6568 switches= [HW,M68k,EARLY] !! 4607 switches= [HW,M68k]
6569 4608
6570 sysctl.*= [KNL] !! 4609 sysfs.deprecated=0|1 [KNL]
6571 Set a sysctl paramete !! 4610 Enable/disable old style sysfs layout for old udev
6572 process, as if the va !! 4611 on older distributions. When this option is enabled
6573 /proc/sys/... file. B !! 4612 very new udev will not work anymore. When this option
6574 separators. Unrecogni !! 4613 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
6575 are reported in the k !! 4614 in older udev will not work anymore.
6576 later by a loaded mod !! 4615 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
6577 Example: sysctl.vm.sw !! 4616 the kernel configuration.
6578 4617
6579 sysrq_always_enabled 4618 sysrq_always_enabled
6580 [KNL] 4619 [KNL]
6581 Ignore sysrq setting 4620 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 4621 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 4622 Useful for debugging.
6584 4623
6585 tcpmhash_entries= [KNL,NET] 4624 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 4625 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 4626 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 4627 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum !! 4628 cache size. See Documentation/networking/ip-sysctl.txt
6590 "tcp_no_metrics_save" 4629 "tcp_no_metrics_save" section for more details.
6591 4630
6592 tdfx= [HW,DRM] 4631 tdfx= [HW,DRM]
6593 4632
6594 test_suspend= [SUSPEND] !! 4633 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 4634 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 4635 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 4636 as the system sleep state during system startup with
6599 the optional capabili 4637 the optional capability to repeat N number of times.
6600 The system is woken f 4638 The system is woken from this state using a
6601 wakeup-capable RTC al 4639 wakeup-capable RTC alarm.
6602 4640
6603 thash_entries= [KNL,NET] 4641 thash_entries= [KNL,NET]
6604 Set number of hash bu 4642 Set number of hash buckets for TCP connection
6605 4643
6606 thermal.act= [HW,ACPI] 4644 thermal.act= [HW,ACPI]
6607 -1: disable all activ 4645 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 4646 <degrees C>: override all lowest active trip points
6609 4647
6610 thermal.crt= [HW,ACPI] 4648 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 4649 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 4650 <degrees C>: override all critical trip points
6613 4651
>> 4652 thermal.nocrt= [HW,ACPI]
>> 4653 Set to disable actions on ACPI thermal zone
>> 4654 critical and hot trip points.
>> 4655
6614 thermal.off= [HW,ACPI] 4656 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 4657 1: disable ACPI thermal control
6616 4658
6617 thermal.psv= [HW,ACPI] 4659 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 4660 -1: disable all passive trip points
6619 <degrees C>: override 4661 <degrees C>: override all passive trip points to this
6620 value 4662 value
6621 4663
6622 thermal.tzp= [HW,ACPI] 4664 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 4665 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 4666 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 4667 0: no polling (default)
6626 4668
6627 threadirqs [KNL,EARLY] !! 4669 threadirqs [KNL]
6628 Force threading of al 4670 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 4671 marked explicitly IRQF_NO_THREAD.
6630 4672
6631 topology= [S390,EARLY] !! 4673 tmem [KNL,XEN]
>> 4674 Enable the Transcendent memory driver if built-in.
>> 4675
>> 4676 tmem.cleancache=0|1 [KNL, XEN]
>> 4677 Default is on (1). Disable the usage of the cleancache
>> 4678 API to send anonymous pages to the hypervisor.
>> 4679
>> 4680 tmem.frontswap=0|1 [KNL, XEN]
>> 4681 Default is on (1). Disable the usage of the frontswap
>> 4682 API to send swap pages to the hypervisor. If disabled
>> 4683 the selfballooning and selfshrinking are force disabled.
>> 4684
>> 4685 tmem.selfballooning=0|1 [KNL, XEN]
>> 4686 Default is on (1). Disable the driving of swap pages
>> 4687 to the hypervisor.
>> 4688
>> 4689 tmem.selfshrinking=0|1 [KNL, XEN]
>> 4690 Default is on (1). Partial swapoff that immediately
>> 4691 transfers pages from Xen hypervisor back to the
>> 4692 kernel based on different criteria.
>> 4693
>> 4694 topology= [S390]
6632 Format: {off | on} 4695 Format: {off | on}
6633 Specify if the kernel 4696 Specify if the kernel should make use of the cpu
6634 topology information 4697 topology information if the hardware supports this.
6635 The scheduler will ma 4698 The scheduler will make use of this information and
6636 e.g. base its process 4699 e.g. base its process migration decisions on it.
6637 Default is on. 4700 Default is on.
6638 4701
6639 torture.disable_onoff_at_boot= [KNL] !! 4702 topology_updates= [KNL, PPC, NUMA]
6640 Prevent the CPU-hotpl !! 4703 Format: {off}
6641 until after init has !! 4704 Specify if the kernel should ignore (off)
6642 !! 4705 topology updates sent by the hypervisor to this
6643 torture.ftrace_dump_at_shutdown= [KNL !! 4706 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 4707
6655 torture.verbose_sleep_duration= [KNL] !! 4708 tp720= [HW,PS2]
6656 Duration of each verb <<
6657 4709
6658 tpm_suspend_pcr=[HW,TPM] 4710 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 4711 Format: integer pcr id
6660 Specify that at suspe 4712 Specify that at suspend time, the tpm driver
6661 should extend the spe 4713 should extend the specified pcr with zeros,
6662 as a workaround for s 4714 as a workaround for some chips which fail to
6663 flush the last writte 4715 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 4716 This will guarantee that all the other pcrs
6665 are saved. 4717 are saved.
6666 4718
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] 4719 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 4720 [FTRACE] will set tracing buffer size on each cpu.
6707 4721
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] 4722 trace_event=[event-list]
6731 [FTRACE] Set and star 4723 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 4724 to facilitate early boot debugging. The event-list is a
6733 comma-separated list !! 4725 comma separated list of trace events to enable. See
6734 also Documentation/tr 4726 also Documentation/trace/events.rst
6735 4727
6736 trace_instance=[instance-info] <<
6737 [FTRACE] Create a rin <<
6738 This will be listed i <<
6739 <<
6740 /sys/kernel/t <<
6741 <<
6742 Events can be enabled <<
6743 via: <<
6744 <<
6745 trace_instanc <<
6746 <<
6747 Note, the "<system*>: <<
6748 unique. <<
6749 <<
6750 trace_instanc <<
6751 <<
6752 will enable the "sche <<
6753 the same thing would <<
6754 event, and all events <<
6755 <<
6756 trace_options=[option-list] 4728 trace_options=[option-list]
6757 [FTRACE] Enable or di 4729 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 4730 The option-list is a comma delimited list of options
6759 that can be enabled o 4731 that can be enabled or disabled just as if you were
6760 to echo the option na 4732 to echo the option name into
6761 4733
6762 /sys/kernel/traci !! 4734 /sys/kernel/debug/tracing/trace_options
6763 4735
6764 For example, to enabl 4736 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 4737 stack trace of each event), add to the command line:
6766 4738
6767 trace_options=s 4739 trace_options=stacktrace
6768 4740
6769 See also Documentatio 4741 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 4742 section.
6771 4743
6772 trace_trigger=[trigger-list] !! 4744 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 4745 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 4746 tracing ring buffer. This is useful for early boot up
6775 filter. !! 4747 where the system hangs or reboots and does not give the
6776 !! 4748 option for reading the tracing buffer or performing a
6777 The format is is "tra !! 4749 ftrace_dump_on_oops.
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 4750
6784 The above will enable !! 4751 To turn off having tracepoints sent to printk,
6785 event but only trigge !! 4752 echo 0 > /proc/sys/kernel/tracepoint_printk
6786 event is "2" (TASK_UN !! 4753 Note, echoing 1 into this file without the
>> 4754 tracepoint_printk kernel cmdline option has no effect.
6787 4755
6788 See also "Event trigg !! 4756 ** CAUTION **
6789 4757
>> 4758 Having tracepoints sent to printk() and activating high
>> 4759 frequency tracepoints such as irq or sched, can cause
>> 4760 the system to live lock.
6790 4761
6791 traceoff_on_warning 4762 traceoff_on_warning
6792 [FTRACE] enable this 4763 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 4764 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 4765 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 4766 file located in /sys/kernel/debug/tracing/
6796 4767
6797 This option is useful 4768 This option is useful, as it disables the trace before
6798 the WARNING dump is c 4769 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 4770 be filled with content caused by the warning output.
6800 4771
6801 This option can also 4772 This option can also be set at run time via the sysctl
6802 option: kernel/trace 4773 option: kernel/traceoff_on_warning
6803 4774
6804 transparent_hugepage= 4775 transparent_hugepage=
6805 [KNL] 4776 [KNL]
6806 Format: [always|madvi 4777 Format: [always|madvise|never]
6807 Can be used to contro 4778 Can be used to control the default behavior of the system
6808 with respect to trans 4779 with respect to transparent hugepages.
6809 See Documentation/adm 4780 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 4781 for more details.
6811 4782
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 <<
6848 tsc= Disable clocksource s 4783 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 4784 Format: <string>
6850 [x86] reliable: mark 4785 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 4786 disables clocksource verification at runtime, as well
6852 as the stability chec 4787 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 4788 high-resolution timer mode on older hardware, and in
6854 virtualized environme 4789 virtualized environment.
6855 [x86] noirqtime: Do n 4790 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 4791 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 4792 platforms where RDTSC is slow and this accounting
6858 can add overhead. 4793 can add overhead.
6859 [x86] unstable: mark 4794 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 4795 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 4796 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis 4797 [x86] nowatchdog: disable clocksource watchdog. Used
6863 in situations with st 4798 in situations with strict latency requirements (where
6864 interruptions from cl 4799 interruptions from clocksource watchdog are not
6865 acceptable). 4800 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 <<
6883 tsx= [X86] Control Transac <<
6884 Extensions (TSX) feat <<
6885 support TSX control. <<
6886 <<
6887 This parameter contro <<
6888 <<
6889 on - Enable TSX <<
6890 mitigations f <<
6891 TSX has been <<
6892 several previ <<
6893 so there may <<
6894 with leaving <<
6895 <<
6896 off - Disable TSX <<
6897 option takes <<
6898 not vulnerabl <<
6899 MSR_IA32_ARCH <<
6900 the new IA32_ <<
6901 update. This <<
6902 deactivation <<
6903 <<
6904 auto - Disable TSX <<
6905 otherwise e <<
6906 <<
6907 Not specifying this o <<
6908 <<
6909 See Documentation/adm <<
6910 for more details. <<
6911 <<
6912 tsx_async_abort= [X86,INTEL,EARLY] Co <<
6913 Abort (TAA) vulnerabi <<
6914 <<
6915 Similar to Micro-arch <<
6916 certain CPUs that sup <<
6917 Synchronization Exten <<
6918 exploit against CPU i <<
6919 information to a disc <<
6920 conditions. <<
6921 <<
6922 In vulnerable process <<
6923 data can be used in a <<
6924 access data to which <<
6925 access. <<
6926 <<
6927 This parameter contro <<
6928 options are: <<
6929 <<
6930 full - Enable T <<
6931 if TSX i <<
6932 <<
6933 full,nosmt - Enable T <<
6934 vulnerab <<
6935 is not d <<
6936 vulnerab <<
6937 off - Uncondit <<
6938 <<
6939 On MDS-affected machi <<
6940 prevented by an activ <<
6941 are mitigated with th <<
6942 this mitigation, you <<
6943 <<
6944 Not specifying this o <<
6945 tsx_async_abort=full. <<
6946 and deploy MDS mitiga <<
6947 required and doesn't <<
6948 mitigation. <<
6949 <<
6950 For details see: <<
6951 Documentation/admin-g <<
6952 4801
6953 turbografx.map[2|3]= [HW,JOY] 4802 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 4803 TurboGraFX parallel port interface
6955 Format: 4804 Format:
6956 <port#>,<js1>,<js2>,< 4805 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 4806 See also Documentation/input/devices/joystick-parport.rst
6958 4807
6959 udbg-immortal [PPC] When debugging 4808 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 4809 happen after console_init() and before a proper
6961 console driver takes 4810 console driver takes over, this boot options might
6962 help "seeing" what's 4811 help "seeing" what's going on.
6963 4812
6964 uhash_entries= [KNL,NET] 4813 uhash_entries= [KNL,NET]
6965 Set number of hash bu 4814 Set number of hash buckets for UDP/UDP-Lite connections
6966 4815
6967 uhci-hcd.ignore_oc= 4816 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 4817 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 4818 Some badly-designed motherboards generate lots of
6970 bogus events, for por 4819 bogus events, for ports that aren't wired to
6971 anything. Set this p 4820 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 4821 Note that genuine overcurrent events won't be
6973 reported either. 4822 reported either.
6974 4823
6975 unknown_nmi_panic 4824 unknown_nmi_panic
6976 [X86] Cause panic on 4825 [X86] Cause panic on unknown NMI.
6977 4826
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= 4827 usbcore.authorized_default=
6985 [USB] Default USB dev 4828 [USB] Default USB device authorization:
6986 (default -1 = authori !! 4829 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 4830 0 = not authorized, 1 = authorized, 2 = authorized
6988 if device connected t 4831 if device connected to internal port)
6989 4832
6990 usbcore.autosuspend= 4833 usbcore.autosuspend=
6991 [USB] The autosuspend 4834 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 4835 for newly-detected USB devices (default 2). This
6993 is the time required 4836 is the time required before an idle device will be
6994 autosuspended. Devic 4837 autosuspended. Devices for which the delay is set
6995 to a negative value w 4838 to a negative value won't be autosuspended at all.
6996 4839
6997 usbcore.usbfs_snoop= 4840 usbcore.usbfs_snoop=
6998 [USB] Set to log all 4841 [USB] Set to log all usbfs traffic (default 0 = off).
6999 4842
7000 usbcore.usbfs_snoop_max= 4843 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 4844 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 4845 (default = 65536).
7003 4846
7004 usbcore.blinkenlights= 4847 usbcore.blinkenlights=
7005 [USB] Set to cycle le 4848 [USB] Set to cycle leds on hubs (default 0 = off).
7006 4849
7007 usbcore.old_scheme_first= 4850 usbcore.old_scheme_first=
7008 [USB] Start with the 4851 [USB] Start with the old device initialization
7009 scheme (default 0 = o !! 4852 scheme, applies only to low and full-speed devices
>> 4853 (default 0 = off).
7010 4854
7011 usbcore.usbfs_memory_mb= 4855 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 4856 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 4857 usbfs (default = 16, 0 = max = 2047).
7014 4858
7015 usbcore.use_both_schemes= 4859 usbcore.use_both_schemes=
7016 [USB] Try the other d 4860 [USB] Try the other device initialization scheme
7017 if the first one fail 4861 if the first one fails (default 1 = enabled).
7018 4862
7019 usbcore.initial_descriptor_timeout= 4863 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 4864 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 4865 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 4866 (default 5000 = 5.0 seconds).
7023 4867
7024 usbcore.nousb [USB] Disable the USB 4868 usbcore.nousb [USB] Disable the USB subsystem
7025 4869
7026 usbcore.quirks= 4870 usbcore.quirks=
7027 [USB] A list of quirk 4871 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 4872 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 4873 commas. Each entry has the form
7030 VendorID:ProductID:Fl 4874 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 4875 numbers and Flags is a set of letters. Each letter
7032 will change the built 4876 will change the built-in quirk; setting it if it is
7033 clear and clearing it 4877 clear and clearing it if it is set. The letters have
7034 the following meaning 4878 the following meanings:
7035 a = USB_QUIRK 4879 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 4880 descriptors must not be fetched using
7037 a 255 4881 a 255-byte read);
7038 b = USB_QUIRK 4882 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 4883 correctly so reset it instead);
7040 c = USB_QUIRK 4884 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 4885 Set-Interface requests);
7042 d = USB_QUIRK 4886 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 4887 handle its Configuration or Interface
7044 strin 4888 strings);
7045 e = USB_QUIRK 4889 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 4890 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 4891 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 4892 more interface descriptions than the
7049 bNumI 4893 bNumInterfaces count, and can't handle
7050 talki 4894 talking to these interfaces);
7051 g = USB_QUIRK 4895 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 4896 during initialization, after we read
7053 the d 4897 the device descriptor);
7054 h = USB_QUIRK 4898 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 4899 high speed and super speed interrupt
7056 endpo 4900 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 4901 require the interval in microframes (1
7058 micro 4902 microframe = 125 microseconds) to be
7059 calcu 4903 calculated as interval = 2 ^
7060 (bInt 4904 (bInterval-1).
7061 Devic 4905 Devices with this quirk report their
7062 bInte 4906 bInterval as the result of this
7063 calcu 4907 calculation instead of the exponent
7064 varia 4908 variable used in the calculation);
7065 i = USB_QUIRK 4909 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 4910 handle device_qualifier descriptor
7067 reque 4911 requests);
7068 j = USB_QUIRK 4912 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 4913 generates spurious wakeup, ignore
7070 remot 4914 remote wakeup capability);
7071 k = USB_QUIRK 4915 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 4916 Power Management);
7073 l = USB_QUIRK 4917 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 4918 (Device reports its bInterval as linear
7075 frame 4919 frames instead of the USB 2.0
7076 calcu 4920 calculation);
7077 m = USB_QUIRK 4921 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 4922 to be disconnected before suspend to
7079 preve 4923 prevent spurious wakeup);
7080 n = USB_QUIRK 4924 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 4925 pause after every control message);
7082 o = USB_QUIRK 4926 o = USB_QUIRK_HUB_SLOW_RESET (Hub needs extra
7083 delay 4927 delay after resetting its port);
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 4928 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 4929
7089 usbhid.mousepoll= 4930 usbhid.mousepoll=
7090 [USBHID] The interval 4931 [USBHID] The interval which mice are to be polled at.
7091 4932
7092 usbhid.jspoll= 4933 usbhid.jspoll=
7093 [USBHID] The interval 4934 [USBHID] The interval which joysticks are to be polled at.
7094 4935
7095 usbhid.kbpoll= 4936 usbhid.kbpoll=
7096 [USBHID] The interval 4937 [USBHID] The interval which keyboards are to be polled at.
7097 4938
7098 usb-storage.delay_use= 4939 usb-storage.delay_use=
7099 [UMS] The delay in se 4940 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 4941 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 4942
7105 usb-storage.quirks= 4943 usb-storage.quirks=
7106 [UMS] A list of quirk 4944 [UMS] A list of quirks entries to supplement or
7107 override the built-in 4945 override the built-in unusual_devs list. List
7108 entries are separated 4946 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 4947 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 4948 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 4949 Flags is a set of characters, each corresponding
7112 to a common usb-stora 4950 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 4951 a = SANE_SENSE (collect more than 18 bytes
7114 of se !! 4952 of sense data);
7115 b = BAD_SENSE 4953 b = BAD_SENSE (don't collect more than 18
7116 bytes !! 4954 bytes of sense data);
7117 c = FIX_CAPAC 4955 c = FIX_CAPACITY (decrease the reported
7118 devic 4956 device capacity by one sector);
7119 d = NO_READ_D 4957 d = NO_READ_DISC_INFO (don't use
7120 READ_ !! 4958 READ_DISC_INFO command);
7121 e = NO_READ_C 4959 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 4960 READ_CAPACITY_16 command);
7123 f = NO_REPORT 4961 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 4962 command, uas only);
7125 g = MAX_SECTO 4963 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 4964 240 sectors at a time, uas only);
7127 h = CAPACITY_ 4965 h = CAPACITY_HEURISTICS (decrease the
7128 repor 4966 reported device capacity by one
7129 secto 4967 sector if the number is odd);
7130 i = IGNORE_DE 4968 i = IGNORE_DEVICE (don't bind to this
7131 devic 4969 device);
7132 j = NO_REPORT 4970 j = NO_REPORT_LUNS (don't use report luns
7133 comma 4971 command, uas only);
7134 k = NO_SAME ( <<
7135 l = NOT_LOCKA 4972 l = NOT_LOCKABLE (don't try to lock and
7136 unloc !! 4973 unlock ejectable media);
7137 m = MAX_SECTO 4974 m = MAX_SECTORS_64 (don't transfer more
7138 than !! 4975 than 64 sectors = 32 KB at a time);
7139 not o <<
7140 n = INITIAL_R 4976 n = INITIAL_READ10 (force a retry of the
7141 initi !! 4977 initial READ(10) command);
7142 o = CAPACITY_ 4978 o = CAPACITY_OK (accept the capacity
7143 repor !! 4979 reported by the device);
7144 p = WRITE_CAC 4980 p = WRITE_CACHE (the device cache is ON
7145 by de !! 4981 by default);
7146 r = IGNORE_RE 4982 r = IGNORE_RESIDUE (the device reports
7147 bogus !! 4983 bogus residue values);
7148 s = SINGLE_LU 4984 s = SINGLE_LUN (the device has only one
7149 Logic 4985 Logical Unit);
7150 t = NO_ATA_1X 4986 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 4987 commands, uas only);
7152 u = IGNORE_UA 4988 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 4989 w = NO_WP_DETECT (don't test whether the
7154 mediu 4990 medium is write-protected).
7155 y = ALWAYS_SY 4991 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even !! 4992 even if the device claims no cache)
7157 not o <<
7158 Example: quirks=0419: 4993 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 4994
7160 user_debug= [KNL,ARM] 4995 user_debug= [KNL,ARM]
7161 Format: <int> 4996 Format: <int>
7162 See arch/arm/Kconfig. 4997 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 4998 1 - undefined instruction events
7164 2 - system c 4999 2 - system calls
7165 4 - invalid 5000 4 - invalid data aborts
7166 8 - SIGSEGV 5001 8 - SIGSEGV faults
7167 16 - SIGBUS f 5002 16 - SIGBUS faults
7168 Example: user_debug=3 5003 Example: user_debug=31
7169 5004
7170 userpte= 5005 userpte=
7171 [X86,EARLY] Flags con !! 5006 [X86] Flags controlling user PTE allocations.
7172 5007
7173 nohigh = do n 5008 nohigh = do not allocate PTE pages in
7174 HIGHM 5009 HIGHMEM regardless of setting
7175 of CO 5010 of CONFIG_HIGHPTE.
7176 5011
7177 vdso= [X86,SH,SPARC] !! 5012 vdso= [X86,SH]
7178 On X86_32, this is an 5013 On X86_32, this is an alias for vdso32=. Otherwise:
7179 5014
7180 vdso=1: enable VDSO ( 5015 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 5016 vdso=0: disable VDSO mapping
7182 5017
7183 vdso32= [X86] Control the 32- 5018 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 5019 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 5020 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 5021
7187 See the help text for 5022 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 5023 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 5024 vdso32=0; otherwise, the default is vdso32=1.
7190 5025
7191 For compatibility wit 5026 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 5027 alias for vdso32=0.
7193 5028
7194 Try vdso32=0 if you e 5029 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 5030 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 5031
7197 video= [FB,EARLY] Frame buff !! 5032 vector= [IA-64,SMP]
7198 See Documentation/fb/ !! 5033 vector=percpu: enable percpu vector domain
7199 5034
7200 video.brightness_switch_enabled= [ACP !! 5035 video= [FB] Frame buffer configuration
7201 Format: [0|1] !! 5036 See Documentation/fb/modedb.txt.
>> 5037
>> 5038 video.brightness_switch_enabled= [0,1]
7202 If set to 1, on recei 5039 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 5040 generated by hotkey, video driver will adjust brightness
7204 level and then send o 5041 level and then send out the event to user space through
7205 the allocated input d !! 5042 the allocated input device; If set to 0, video driver
7206 will only send out th 5043 will only send out the event without touching backlight
7207 brightness level. 5044 brightness level.
7208 default: 1 5045 default: 1
7209 5046
7210 virtio_mmio.device= 5047 virtio_mmio.device=
7211 [VMMIO] Memory mapped 5048 [VMMIO] Memory mapped virtio (platform) device.
7212 5049
7213 <size>@<basead 5050 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 5051 where:
7215 <size> := 5052 <size> := size (can use standard suffixes
7216 5053 like K, M and G)
7217 <baseaddr> := 5054 <baseaddr> := physical base address
7218 <irq> := 5055 <irq> := interrupt number (as passed to
7219 5056 request_irq())
7220 <id> := 5057 <id> := (optional) platform device id
7221 example: 5058 example:
7222 virtio_mmio.d 5059 virtio_mmio.device=1K@0x100b0000:48:7
7223 5060
7224 Can be used multiple 5061 Can be used multiple times for multiple devices.
7225 5062
7226 vga= [BOOT,X86-32] Select 5063 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 5064 See Documentation/x86/boot.txt and
7228 Documentation/admin-g !! 5065 Documentation/svga.txt.
7229 Use vga=ask for menu. 5066 Use vga=ask for menu.
7230 This is actually a bo 5067 This is actually a boot loader parameter; the value is
7231 passed to the kernel 5068 passed to the kernel using a special protocol.
7232 5069
7233 vm_debug[=options] [KNL] Availab 5070 vm_debug[=options] [KNL] Available with CONFIG_DEBUG_VM=y.
7234 May slow down system 5071 May slow down system boot speed, especially when
7235 enabled on systems wi 5072 enabled on systems with a large amount of memory.
7236 All options are enabl 5073 All options are enabled by default, and this
7237 interface is meant to 5074 interface is meant to allow for selectively
7238 enabling or disabling 5075 enabling or disabling specific virtual memory
7239 debugging features. 5076 debugging features.
7240 5077
7241 Available options are 5078 Available options are:
7242 P Enable page s 5079 P Enable page structure init time poisoning
7243 - Disable all o 5080 - Disable all of the above options
7244 5081
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc !! 5082 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7246 exact size of <nn>. T !! 5083 size of <nn>. This can be used to increase the
7247 the minimum size (128 !! 5084 minimum size (128MB on x86). It can also be used to
7248 It can also be used t !! 5085 decrease the size and leave more room for directly
7249 for directly mapped k !! 5086 mapped kernel RAM.
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 5087
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 5088 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 5089 Sets the memory size reserved for contiguous memory
7256 allocations for the v 5090 allocations for the vmcp device driver.
7257 5091
7258 vmhalt= [KNL,S390] Perform z/ 5092 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 5093 Format: <command>
7260 5094
7261 vmpanic= [KNL,S390] Perform z/ 5095 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 5096 Format: <command>
7263 5097
7264 vmpoff= [KNL,S390] Perform z/ 5098 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 5099 Format: <command>
7266 5100
7267 vsyscall= [X86-64,EARLY] !! 5101 vsyscall= [X86-64]
7268 Controls the behavior 5102 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 5103 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 5104 code). Most statically-linked binaries and older
7271 versions of glibc use 5105 versions of glibc use these calls. Because these
7272 functions are at fixe 5106 functions are at fixed addresses, they make nice
7273 targets for exploits 5107 targets for exploits that can control RIP.
7274 5108
7275 emulate Vsyscalls !! 5109 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 5110 emulated reasonably safely.
7277 readable. <<
7278 <<
7279 xonly [default] <<
7280 emulated <<
7281 page is n <<
7282 5111
7283 none Vsyscalls 5112 none Vsyscalls don't work at all. This makes
7284 them quit 5113 them quite hard to use for exploits but
7285 might bre 5114 might break your system.
7286 5115
7287 vt.color= [VT] Default text col 5116 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 5117 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 5118 Default: 0x07 = light gray on black.
7290 5119
7291 vt.cur_default= [VT] Default cursor s 5120 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 5121 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 5122 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 5123 see VGA-softcursor.txt. Default: 2 = underline.
7295 5124
7296 vt.default_blu= [VT] 5125 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 5126 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 5127 Change the default blue palette of the console.
7299 This is a 16-member a 5128 This is a 16-member array composed of values
7300 ranging from 0-255. 5129 ranging from 0-255.
7301 5130
7302 vt.default_grn= [VT] 5131 vt.default_grn= [VT]
7303 Format: <green0>,<gre 5132 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 5133 Change the default green palette of the console.
7305 This is a 16-member a 5134 This is a 16-member array composed of values
7306 ranging from 0-255. 5135 ranging from 0-255.
7307 5136
7308 vt.default_red= [VT] 5137 vt.default_red= [VT]
7309 Format: <red0>,<red1> 5138 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 5139 Change the default red palette of the console.
7311 This is a 16-member a 5140 This is a 16-member array composed of values
7312 ranging from 0-255. 5141 ranging from 0-255.
7313 5142
7314 vt.default_utf8= 5143 vt.default_utf8=
7315 [VT] 5144 [VT]
7316 Format=<0|1> 5145 Format=<0|1>
7317 Set system-wide defau 5146 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 5147 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 5148 newly opened terminals.
7320 5149
7321 vt.global_cursor_default= 5150 vt.global_cursor_default=
7322 [VT] 5151 [VT]
7323 Format=<-1|0|1> 5152 Format=<-1|0|1>
7324 Set system-wide defau 5153 Set system-wide default for whether a cursor
7325 is shown on new VTs. 5154 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 5155 i.e. cursors will be created by default unless
7327 overridden by individ 5156 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 5157 cursors, 1 will display them.
7329 5158
7330 vt.italic= [VT] Default color fo 5159 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 5160 Default: 2 = green.
7332 5161
7333 vt.underline= [VT] Default color fo 5162 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 5163 Default: 3 = cyan.
7335 5164
7336 watchdog timers [HW,WDT] For informat 5165 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat !! 5166 see Documentation/watchdog/watchdog-parameters.txt
7338 or other driver-speci 5167 or other driver-specific files in the
7339 Documentation/watchdo 5168 Documentation/watchdog/ directory.
7340 5169
7341 watchdog_thresh= 5170 watchdog_thresh=
7342 [KNL] 5171 [KNL]
7343 Set the hard lockup d 5172 Set the hard lockup detector stall duration
7344 threshold in seconds. 5173 threshold in seconds. The soft lockup detector
7345 threshold is set to t 5174 threshold is set to twice the value. A value of 0
7346 disables both lockup 5175 disables both lockup detectors. Default is 10
7347 seconds. 5176 seconds.
7348 5177
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= 5178 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 5179 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 5180 warn stall conditions and dump internal state to
7359 help debugging. 0 di 5181 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 5182 detection; otherwise, it's the stall threshold
7361 duration in seconds. 5183 duration in seconds. The default value is 30 and
7362 it can be updated at 5184 it can be updated at runtime by writing to the
7363 corresponding sysfs f 5185 corresponding sysfs file.
7364 5186
7365 workqueue.cpu_intensive_thresh_us= !! 5187 workqueue.disable_numa
7366 Per-cpu work items wh !! 5188 By default, all work items queued to unbound
7367 threshold are automat !! 5189 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 5190 issued on, which results in better behavior in
7369 them from noticeably !! 5191 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 5192 whatever reason, this option can be used. Note
7371 !! 5193 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 5194 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 5195
7386 workqueue.power_efficient 5196 workqueue.power_efficient
7387 Per-cpu workqueues ar 5197 Per-cpu workqueues are generally preferred because
7388 they show better perf 5198 they show better performance thanks to cache
7389 locality; unfortunate 5199 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 5200 be more power hungry than unbound workqueues.
7391 5201
7392 Enabling this makes t 5202 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 5203 were observed to contribute significantly to power
7394 consumption unbound, 5204 consumption unbound, leading to measurably lower
7395 power usage at the co 5205 power usage at the cost of small performance
7396 overhead. 5206 overhead.
7397 5207
7398 The default value of 5208 The default value of this parameter is determined by
7399 the config option CON 5209 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 5210
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 5211 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 5212 Workqueue used to implicitly guarantee that work
7415 items queued without 5213 items queued without explicit CPU specified are put
7416 on the local CPU. Th 5214 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 5215 and while local CPU is still preferred work items
7418 may be put on foreign 5216 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 5217 forces round-robin CPU selection to flush out
7420 usages which depend o 5218 usages which depend on the now broken guarantee.
7421 When enabled, memory 5219 When enabled, memory and cache locality will be
7422 impacted. 5220 impacted.
7423 5221
7424 writecombine= [LOONGARCH,EARLY] Con !! 5222 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 5223 default x2apic cluster mode on platforms
7432 supporting x2apic. 5224 supporting x2apic.
7433 5225
>> 5226 x86_intel_mid_timer= [X86-32,APBT]
>> 5227 Choose timer option for x86 Intel MID platform.
>> 5228 Two valid options are apbt timer only and lapic timer
>> 5229 plus one apbt timer for broadcast timer.
>> 5230 x86_intel_mid_timer=apbt_only | lapic_and_apbt
>> 5231
7434 xen_512gb_limit [KNL,X86-64,X 5232 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 5233 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 5234 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 5235 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 5236 save/restore/migration must be enabled to handle larger
7439 domains. 5237 domains.
7440 5238
7441 xen_emul_unplug= [HW,X !! 5239 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 5240 Unplug Xen emulated devices
7443 Format: [unplug0,][un 5241 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 5242 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 5243 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 5244 nics -- unplug network devices
7447 all -- unplug all emu 5245 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 5246 unnecessary -- unplugging emulated devices is
7449 unnecessary e 5247 unnecessary even if the host did not respond to
7450 the unplug pr 5248 the unplug protocol
7451 never -- do not unplu 5249 never -- do not unplug even if version check succeeds
7452 5250
7453 xen_legacy_crash [X86,XEN,EARL !! 5251 xen_nopvspin [X86,XEN]
7454 Crash from Xen panic !! 5252 Disables the ticketlock slowpath using Xen PV
7455 panic() code such as !! 5253 optimizations.
7456 <<
7457 xen_mc_debug [X86,XEN,EARLY] <<
7458 Enable multicall debu <<
7459 Enabling this feature <<
7460 bit, so it should onl <<
7461 debug data in case of <<
7462 <<
7463 xen_msr_safe= [X86,XEN,EARLY] <<
7464 Format: <bool> <<
7465 Select whether to alw <<
7466 access functions when <<
7467 default value is cont <<
7468 5254
7469 xen_nopv [X86] 5255 xen_nopv [X86]
7470 Disables the PV optim 5256 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 5257 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 5258
7479 xen_scrub_pages= [XEN] 5259 xen_scrub_pages= [XEN]
7480 Boolean option to con 5260 Boolean option to control scrubbing pages before giving them back
7481 to Xen, for use by ot 5261 to Xen, for use by other domains. Can be also changed at runtime
7482 with /sys/devices/sys 5262 with /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
7483 Default value control 5263 Default value controlled with CONFIG_XEN_SCRUB_PAGES_DEFAULT.
7484 5264
7485 xen_timer_slop= [X86-64,XEN,EARLY] !! 5265 xen_timer_slop= [X86-64,XEN]
7486 Set the timer slop (i 5266 Set the timer slop (in nanoseconds) for the virtual Xen
7487 timers (default is 10 5267 timers (default is 100000). This adjusts the minimum
7488 delta of virtualized 5268 delta of virtualized Xen timers, where lower values
7489 improve timer resolut 5269 improve timer resolution at the expense of processing
7490 more timer interrupts 5270 more timer interrupts.
7491 5271
7492 xen.balloon_boot_timeout= [XEN] <<
7493 The time (in seconds) <<
7494 in case initial ballo <<
7495 Applies only when run <<
7496 started with less mem <<
7497 max. Default is 180. <<
7498 <<
7499 xen.event_eoi_delay= [XEN] <<
7500 How long to delay EOI <<
7501 storms (jiffies). Def <<
7502 <<
7503 xen.event_loop_timeout= [XEN] <<
7504 After which time (jif <<
7505 should start to delay <<
7506 <<
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] 5272 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 5273 Format:
7516 <irq>,<irq_mask>,<io> 5274 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 5275
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] 5276 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 5277 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 5278 host controller quirks. Meaning of each bit can be
7536 consulted in header d 5279 consulted in header drivers/usb/host/xhci.h.
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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