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 whilst 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= <<
564 [NET] Specifies amount <<
565 the kernel should wait <<
566 it waits 120 seconds. <<
567 <<
568 ca_keys= [KEYS] This parameter 464 ca_keys= [KEYS] This parameter identifies a specific key(s) on
569 the system trusted key 465 the system trusted keyring to be used for certificate
570 trust validation. 466 trust validation.
571 format: { id:<keyid> | 467 format: { id:<keyid> | builtin }
572 468
573 cca= [MIPS,EARLY] Override !! 469 cca= [MIPS] Override the kernel pages' cache coherency
574 algorithm. Accepted v 470 algorithm. Accepted values range from 0 to 7
575 inclusive. See arch/mi 471 inclusive. See arch/mips/include/asm/pgtable-bits.h
576 for platform specific 472 for platform specific values (SB1, Loongson3 and
577 others). 473 others).
578 474
579 ccw_timeout_log [S390] 475 ccw_timeout_log [S390]
580 See Documentation/arch !! 476 See Documentation/s390/CommonIO for details.
581 477
582 cgroup_disable= [KNL] Disable a partic !! 478 cgroup_disable= [KNL] Disable a particular controller
583 Format: {name of the c !! 479 Format: {name of the controller(s) to disable}
584 The effects of cgroup_ 480 The effects of cgroup_disable=foo are:
585 - foo isn't auto-mount 481 - foo isn't auto-mounted if you mount all cgroups in
586 a single hierarchy 482 a single hierarchy
587 - foo isn't visible as 483 - foo isn't visible as an individually mountable
588 subsystem 484 subsystem
589 - if foo is an optiona <<
590 disabled and corresp <<
591 created <<
592 {Currently only "memor 485 {Currently only "memory" controller deal with this and
593 cut the overhead, othe 486 cut the overhead, others just disable the usage. So
594 only cgroup_disable=me 487 only cgroup_disable=memory is actually worthy}
595 Specifying "pressure" <<
596 stall information acco <<
597 488
598 cgroup_no_v1= [KNL] Disable cgroup c !! 489 cgroup_no_v1= [KNL] Disable one, multiple, all cgroup controllers in v1
599 Format: { { controller !! 490 Format: { controller[,controller...] | "all" }
600 [,{ controll <<
601 Like cgroup_disable, b 491 Like cgroup_disable, but only applies to cgroup v1;
602 the blacklisted contro 492 the blacklisted controllers remain available in cgroup2.
603 "all" blacklists all c <<
604 named mounts. Specifyi <<
605 all v1 hierarchies. <<
606 <<
607 cgroup_favordynmods= [KNL] Enable or D <<
608 Format: { "true" | "fa <<
609 Defaults to the value <<
610 493
611 cgroup.memory= [KNL] Pass options to 494 cgroup.memory= [KNL] Pass options to the cgroup memory controller.
612 Format: <string> 495 Format: <string>
613 nosocket -- Disable so 496 nosocket -- Disable socket memory accounting.
614 nokmem -- Disable kern 497 nokmem -- Disable kernel memory accounting.
615 nobpf -- Disable BPF m <<
616 498
617 checkreqprot= [SELINUX] Set initial !! 499 checkreqprot [SELINUX] Set initial checkreqprot flag value.
618 Format: { "0" | "1" } 500 Format: { "0" | "1" }
619 See security/selinux/K 501 See security/selinux/Kconfig help text.
620 0 -- check protection 502 0 -- check protection applied by kernel (includes
621 any implied ex 503 any implied execute protection).
622 1 -- check protection 504 1 -- check protection requested by application.
623 Default value is set v 505 Default value is set via a kernel config option.
624 Value can be changed a 506 Value can be changed at runtime via
625 /sys/fs/selinu !! 507 /selinux/checkreqprot.
626 Setting checkreqprot t <<
627 508
628 cio_ignore= [S390] 509 cio_ignore= [S390]
629 See Documentation/arch !! 510 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 511 clk_ignore_unused
650 [CLK] 512 [CLK]
651 Prevents the clock fra 513 Prevents the clock framework from automatically gating
652 clocks that have not b 514 clocks that have not been explicitly enabled by a Linux
653 device driver but are 515 device driver but are enabled in hardware at reset or
654 by the bootloader/firm 516 by the bootloader/firmware. Note that this does not
655 force such clocks to b 517 force such clocks to be always-on nor does it reserve
656 those clocks in any wa 518 those clocks in any way. This parameter is useful for
657 debug and development, 519 debug and development, but should not be needed on a
658 platform with proper d 520 platform with proper driver support. For more
659 information, see Docum 521 information, see Documentation/driver-api/clk.rst.
660 522
661 clock= [BUGS=X86-32, HW] gett 523 clock= [BUGS=X86-32, HW] gettimeofday clocksource override.
662 [Deprecated] 524 [Deprecated]
663 Forces specified clock 525 Forces specified clocksource (if available) to be used
664 when calculating getti 526 when calculating gettimeofday(). If specified
665 clocksource is not ava 527 clocksource is not available, it defaults to PIT.
666 Format: { pit | tsc | 528 Format: { pit | tsc | cyclone | pmtmr }
667 529
668 clocksource= Override the default c 530 clocksource= Override the default clocksource
669 Format: <string> 531 Format: <string>
670 Override the default c 532 Override the default clocksource and use the clocksource
671 with the name specifie 533 with the name specified.
672 Some clocksource names 534 Some clocksource names to choose from, depending on
673 the platform: 535 the platform:
674 [all] jiffies (this is 536 [all] jiffies (this is the base, fallback clocksource)
675 [ACPI] acpi_pm 537 [ACPI] acpi_pm
676 [ARM] imx_timer1,OSTS, 538 [ARM] imx_timer1,OSTS,netx_timer,mpu_timer2,
677 pxa_timer,time 539 pxa_timer,timer3,32k_counter,timer0_1
678 [X86-32] pit,hpet,tsc; 540 [X86-32] pit,hpet,tsc;
679 scx200_hrt on 541 scx200_hrt on Geode; cyclone on IBM x440
680 [MIPS] MIPS 542 [MIPS] MIPS
681 [PARISC] cr16 543 [PARISC] cr16
682 [S390] tod 544 [S390] tod
683 [SH] SuperH 545 [SH] SuperH
684 [SPARC64] tick 546 [SPARC64] tick
685 [X86-64] hpet,tsc 547 [X86-64] hpet,tsc
686 548
687 clocksource.arm_arch_timer.evtstrm= 549 clocksource.arm_arch_timer.evtstrm=
688 [ARM,ARM64,EARLY] !! 550 [ARM,ARM64]
689 Format: <bool> 551 Format: <bool>
690 Enable/disable the eve 552 Enable/disable the eventstream feature of the ARM
691 architected timer so t 553 architected timer so that code using WFE-based polling
692 loops can be debugged 554 loops can be debugged more effectively on production
693 systems. 555 systems.
694 556
695 clocksource.verify_n_cpus= [KNL] !! 557 clearcpuid=BITNUM [X86]
696 Limit the number of CP !! 558 Disable CPUID feature X for the kernel. See
697 marked with CLOCK_SOUR !! 559 arch/x86/include/asm/cpufeatures.h for the valid bit
698 are marked unstable du !! 560 numbers. Note the Linux specific bits are not necessarily
699 A negative value says !! 561 stable over kernel options, but the vendor specific
700 zero says not to check !! 562 ones should be.
701 nr_cpu_ids are silentl !! 563 Also note that user programs calling CPUID directly
702 The actual CPUs are ch !! 564 or using the feature without checking anything
703 no replacement if the !! 565 will still see it. This just prevents it from
704 !! 566 being used by the kernel or shown in /proc/cpuinfo.
705 clocksource-wdtest.holdoff= [KNL] !! 567 Also note the kernel might malfunction if you disable
706 Set the time in second !! 568 some critical bits.
707 watchdog test waits be <<
708 Defaults to zero when <<
709 10 seconds when built <<
710 569
711 cma=nn[MG]@[start[MG][-end[MG]]] 570 cma=nn[MG]@[start[MG][-end[MG]]]
712 [KNL,CMA,EARLY] !! 571 [ARM,X86,KNL]
713 Sets the size of kerne 572 Sets the size of kernel global memory area for
714 contiguous memory allo 573 contiguous memory allocations and optionally the
715 placement constraint b 574 placement constraint by the physical address range of
716 memory allocations. A 575 memory allocations. A value of 0 disables CMA
717 altogether. For more i 576 altogether. For more information, see
718 kernel/dma/contiguous. !! 577 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 <<
741 578
742 cmo_free_hint= [PPC] Format: { yes | 579 cmo_free_hint= [PPC] Format: { yes | no }
743 Specify whether pages 580 Specify whether pages are marked as being inactive
744 when they are freed. 581 when they are freed. This is used in CMO environments
745 to determine OS memory 582 to determine OS memory pressure for page stealing by
746 a hypervisor. 583 a hypervisor.
747 Default: yes 584 Default: yes
748 585
749 coherent_pool=nn[KMG] [ARM,KNL,EARLY !! 586 coherent_pool=nn[KMG] [ARM,KNL]
750 Sets the size of memor 587 Sets the size of memory pool for coherent, atomic dma
751 allocations, by defaul 588 allocations, by default set to 256K.
752 589
753 com20020= [HW,NET] ARCnet - COM2 590 com20020= [HW,NET] ARCnet - COM20020 chipset
754 Format: 591 Format:
755 <io>[,<irq>[,<nodeID>[ 592 <io>[,<irq>[,<nodeID>[,<backplane>[,<ckp>[,<timeout>]]]]]
756 593
757 com90io= [HW,NET] ARCnet - COM9 594 com90io= [HW,NET] ARCnet - COM90xx chipset (IO-mapped buffers)
758 Format: <io>[,<irq>] 595 Format: <io>[,<irq>]
759 596
760 com90xx= [HW,NET] 597 com90xx= [HW,NET]
761 ARCnet - COM90xx chips 598 ARCnet - COM90xx chipset (memory-mapped buffers)
762 Format: <io>[,<irq>[,< 599 Format: <io>[,<irq>[,<memstart>]]
763 600
764 condev= [HW,S390] console devi 601 condev= [HW,S390] console device
765 conmode= 602 conmode=
766 603
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 604 console= [KNL] Output console device and options.
779 605
780 tty<n> Use the virtual consol 606 tty<n> Use the virtual console device <n>.
781 607
782 ttyS<n>[,options] 608 ttyS<n>[,options]
783 ttyUSB0[,options] 609 ttyUSB0[,options]
784 Use the specified seri 610 Use the specified serial port. The options are of
785 the form "bbbbpnf", wh 611 the form "bbbbpnf", where "bbbb" is the baud rate,
786 "p" is parity ("n", "o 612 "p" is parity ("n", "o", or "e"), "n" is number of
787 bits, and "f" is flow 613 bits, and "f" is flow control ("r" for RTS or
788 omit it). Default is 614 omit it). Default is "9600n8".
789 615
790 See Documentation/admi 616 See Documentation/admin-guide/serial-console.rst for more
791 information. See 617 information. See
792 Documentation/networki !! 618 Documentation/networking/netconsole.txt for an
793 alternative. 619 alternative.
794 620
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] 621 uart[8250],io,<addr>[,options]
815 uart[8250],mmio,<addr>[,option 622 uart[8250],mmio,<addr>[,options]
816 uart[8250],mmio16,<addr>[,opti 623 uart[8250],mmio16,<addr>[,options]
817 uart[8250],mmio32,<addr>[,opti 624 uart[8250],mmio32,<addr>[,options]
818 uart[8250],0x<addr>[,options] 625 uart[8250],0x<addr>[,options]
819 Start an early, polled 626 Start an early, polled-mode console on the 8250/16550
820 UART at the specified 627 UART at the specified I/O port or MMIO address,
821 switching to the match 628 switching to the matching ttyS device later.
822 MMIO inter-register ad 629 MMIO inter-register address stride is either 8-bit
823 (mmio), 16-bit (mmio16 630 (mmio), 16-bit (mmio16), or 32-bit (mmio32).
824 If none of [io|mmio|mm 631 If none of [io|mmio|mmio16|mmio32], <addr> is assumed
825 to be equivalent to 'm 632 to be equivalent to 'mmio'. 'options' are specified in
826 the same format descri 633 the same format described for ttyS above; if unspecified,
827 the h/w is not re-init 634 the h/w is not re-initialized.
828 635
829 hvc<n> Use the hypervisor con 636 hvc<n> Use the hypervisor console device <n>. This is for
830 both Xen and PowerPC h 637 both Xen and PowerPC hypervisors.
831 638
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 639 If the device connected to the port is not a TTY but a braille
839 device, prepend "brl," before 640 device, prepend "brl," before the device type, for instance
840 console=brl,ttyS0 641 console=brl,ttyS0
841 For now, only VisioBraille is 642 For now, only VisioBraille is supported.
842 643
843 console_msg_format= 644 console_msg_format=
844 [KNL] Change console m 645 [KNL] Change console messages format
845 default 646 default
846 By default we print me 647 By default we print messages on consoles in
847 "[time stamp] text\n" 648 "[time stamp] text\n" format (time stamp may not be
848 printed, depending on 649 printed, depending on CONFIG_PRINTK_TIME or
849 `printk_time' param). 650 `printk_time' param).
850 syslog 651 syslog
851 Switch to syslog forma 652 Switch to syslog format: "<%u>[time stamp] text\n"
852 IOW, each message will 653 IOW, each message will have a facility and loglevel
853 prefix. The format is 654 prefix. The format is similar to one used by syslog()
854 syscall, or to executi 655 syscall, or to executing "dmesg -S --raw" or to reading
855 from /proc/kmsg. 656 from /proc/kmsg.
856 657
857 consoleblank= [KNL] The console blan 658 consoleblank= [KNL] The console blank (screen saver) timeout in
858 seconds. A value of 0 659 seconds. A value of 0 disables the blank timer.
859 Defaults to 0. 660 Defaults to 0.
860 661
861 coredump_filter= 662 coredump_filter=
862 [KNL] Change the defau 663 [KNL] Change the default value for
863 /proc/<pid>/coredump_f 664 /proc/<pid>/coredump_filter.
864 See also Documentation !! 665 See also Documentation/filesystems/proc.txt.
865 666
866 coresight_cpu_debug.enable 667 coresight_cpu_debug.enable
867 [ARM,ARM64] 668 [ARM,ARM64]
868 Format: <bool> 669 Format: <bool>
869 Enable/disable the CPU 670 Enable/disable the CPU sampling based debugging.
870 0: default value, disa 671 0: default value, disable debugging
871 1: enable debugging at 672 1: enable debugging at boot time
872 673
873 cpcihp_generic= [HW,PCI] Generic port <<
874 Format: <<
875 <first_slot>,<last_slo <<
876 <<
877 cpuidle.off=1 [CPU_IDLE] 674 cpuidle.off=1 [CPU_IDLE]
878 disable the cpuidle su 675 disable the cpuidle sub-system
879 676
880 cpuidle.governor= <<
881 [CPU_IDLE] Name of the <<
882 <<
883 cpufreq.off=1 [CPU_FREQ] 677 cpufreq.off=1 [CPU_FREQ]
884 disable the cpufreq su 678 disable the cpufreq sub-system
885 679
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 680 cpu_init_udelay=N
892 [X86,EARLY] Delay for !! 681 [X86] Delay for N microsec between assert and de-assert
893 of APIC INIT to start 682 of APIC INIT to start processors. This delay occurs
894 on every CPU online, s 683 on every CPU online, such as boot, and resume from suspend.
895 Default: 10000 684 Default: 10000
896 685
897 cpuhp.parallel= !! 686 cpcihp_generic= [HW,PCI] Generic port I/O CompactPCI driver
898 [SMP] Enable/disable p !! 687 Format:
899 Format: <bool> !! 688 <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. <<
910 689
911 crashkernel=size[KMG][@offset[KMG]] 690 crashkernel=size[KMG][@offset[KMG]]
912 [KNL,EARLY] Using kexe !! 691 [KNL] Using kexec, Linux can switch to a 'crash kernel'
913 upon panic. This param 692 upon panic. This parameter reserves the physical
914 memory region [offset, 693 memory region [offset, offset + size] for that kernel
915 image. If '@offset' is 694 image. If '@offset' is omitted, then a suitable offset
916 is selected automatica !! 695 is selected automatically. Check
917 [KNL, X86-64, ARM64, R !! 696 Documentation/kdump/kdump.txt for further details.
918 under 4G first, and fa <<
919 4G when '@offset' hasn <<
920 See Documentation/admi <<
921 697
922 crashkernel=range1:size1[,range2:size2 698 crashkernel=range1:size1[,range2:size2,...][@offset]
923 [KNL] Same as above, b 699 [KNL] Same as above, but depends on the memory
924 in the running system. 700 in the running system. The syntax of range is
925 start-[end] where star 701 start-[end] where start and end are both
926 a memory unit (amount[ 702 a memory unit (amount[KMG]). See also
927 Documentation/admin-gu !! 703 Documentation/kdump/kdump.txt for an example.
928 704
929 crashkernel=size[KMG],high 705 crashkernel=size[KMG],high
930 [KNL, X86-64, ARM64, R !! 706 [KNL, x86_64] range could be above 4G. Allow kernel
931 above 4G. !! 707 to allocate physical memory region from top, so could
932 Allow kernel to alloca !! 708 be above 4G if system have more than 4G ram installed.
933 so could be above 4G i !! 709 Otherwise memory region will be allocated below 4G, if
934 installed. Otherwise m !! 710 available.
935 below 4G, if available <<
936 It will be ignored if 711 It will be ignored if crashkernel=X is specified.
937 crashkernel=size[KMG],low 712 crashkernel=size[KMG],low
938 [KNL, X86-64, ARM64, R !! 713 [KNL, x86_64] range under 4G. When crashkernel=X,high
939 When crashkernel=X,hig !! 714 is passed, kernel could allocate physical memory region
940 physical memory region !! 715 above 4G, that cause second kernel crash on system
941 crash on system that r !! 716 that require some amount of low memory, e.g. swiotlb
942 e.g. swiotlb requires !! 717 requires at least 64M+32K low memory, also enough extra
943 enough extra low memor !! 718 low memory is needed to make sure DMA buffers for 32-bit
944 for 32-bit devices won !! 719 devices won't run out. Kernel would try to allocate at
945 default size of memory !! 720 at least 256M below 4G automatically.
946 size is platform depen !! 721 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 722 for second kernel instead.
953 0: to disable low allo 723 0: to disable low allocation.
954 It will be ignored whe 724 It will be ignored when crashkernel=X,high is not used
955 or memory reserved is 725 or memory reserved is below 4G.
956 726
957 cryptomgr.notests 727 cryptomgr.notests
958 [KNL] Disable crypto s 728 [KNL] Disable crypto self-tests
959 729
960 cs89x0_dma= [HW,NET] 730 cs89x0_dma= [HW,NET]
961 Format: <dma> 731 Format: <dma>
962 732
963 cs89x0_media= [HW,NET] 733 cs89x0_media= [HW,NET]
964 Format: { rj45 | aui | 734 Format: { rj45 | aui | bnc }
965 735
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] 736 dasd= [HW,NET]
976 See header of drivers/ 737 See header of drivers/s390/block/dasd_devmap.c.
977 738
978 db9.dev[2|3]= [HW,JOY] Multisystem j 739 db9.dev[2|3]= [HW,JOY] Multisystem joystick support via parallel port
979 (one device per port) 740 (one device per port)
980 Format: <port#>,<type> 741 Format: <port#>,<type>
981 See also Documentation 742 See also Documentation/input/devices/joystick-parport.rst
982 743
983 debug [KNL,EARLY] Enable ker !! 744 ddebug_query= [KNL,DYNAMIC_DEBUG] Enable debug messages at early boot
>> 745 time. See
>> 746 Documentation/admin-guide/dynamic-debug-howto.rst for
>> 747 details. Deprecated, see dyndbg.
984 748
985 debug_boot_weak_hash !! 749 debug [KNL] Enable kernel debugging (events log level).
986 [KNL,EARLY] Enable pri <<
987 boot sequence. If ena <<
988 of siphash to hash poi <<
989 seeing instances of '( <<
990 value (hashed pointer) <<
991 insecure, please do no <<
992 750
993 debug_locks_verbose= 751 debug_locks_verbose=
994 [KNL] verbose locking !! 752 [KNL] verbose self-tests
995 Format: <int> !! 753 Format=<0|1>
996 Print debugging info w 754 Print debugging info while doing the locking API
997 self-tests. 755 self-tests.
998 Bitmask for the variou !! 756 We default to 0 (no extra messages), setting it to
999 (no extra messages), s !! 757 1 will print _a lot_ more information - normally
1000 will print _a_lot_ mo !! 758 only useful to kernel developers.
1001 useful to lockdep dev !! 759
>> 760 debug_objects [KNL] Enable object debugging
1002 761
1003 debug_objects [KNL,EARLY] Enable ob !! 762 no_debug_objects
>> 763 [KNL] Disable object debugging
1004 764
1005 debug_guardpage_minorder= 765 debug_guardpage_minorder=
1006 [KNL,EARLY] When CONF !! 766 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1007 parameter allows cont 767 parameter allows control of the order of pages that will
1008 be intentionally kept 768 be intentionally kept free (and hence protected) by the
1009 buddy allocator. Bigg 769 buddy allocator. Bigger value increase the probability
1010 of catching random me 770 of catching random memory corruption, but reduce the
1011 amount of memory for 771 amount of memory for normal system use. The maximum
1012 possible value is MAX !! 772 possible value is MAX_ORDER/2. Setting this parameter
1013 parameter to 1 or 2 s !! 773 to 1 or 2 should be enough to identify most random
1014 random memory corrupt !! 774 memory corruption problems caused by bugs in kernel or
1015 kernel or driver code !! 775 driver code when a CPU writes to (or reads from) a
1016 from) a random memory !! 776 random memory location. Note that there exists a class
1017 a class of memory cor !! 777 of memory corruptions problems caused by buggy H/W or
1018 H/W or F/W or by driv !! 778 F/W or by drivers badly programing DMA (basically when
1019 (basically when memor !! 779 memory is written at bus level and the CPU MMU is
1020 CPU MMU is bypassed) !! 780 bypassed) which are not detectable by
1021 CONFIG_DEBUG_PAGEALLO !! 781 CONFIG_DEBUG_PAGEALLOC, hence this option will not help
1022 help tracking down th !! 782 tracking down these problems.
1023 783
1024 debug_pagealloc= 784 debug_pagealloc=
1025 [KNL,EARLY] When CONF !! 785 [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
1026 enables the feature a !! 786 parameter enables the feature at boot time. In
1027 disabled and the syst !! 787 default, it is disabled. We can avoid allocating huge
1028 kernel built without !! 788 chunk of memory for debug pagealloc if we don't enable
1029 Note: to get most of !! 789 it at boot time and the system will work mostly same
1030 useful to also enable !! 790 with the kernel built without CONFIG_DEBUG_PAGEALLOC.
1031 on: enable the featur 791 on: enable the feature
1032 792
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 793 debugpat [X86] Enable PAT debugging
1049 794
1050 default_hugepagesz= !! 795 decnet.addr= [HW,NET]
1051 [HW] The size of the !! 796 Format: <area>[,<node>]
1052 the size represented !! 797 See also Documentation/networking/decnet.txt.
1053 APIs. In addition, t <<
1054 used for shmget(), mm <<
1055 filesystems. If not <<
1056 architecture's defaul <<
1057 sizes are architectur <<
1058 Documentation/admin-g <<
1059 Format: size[KMG] <<
1060 <<
1061 deferred_probe_timeout= <<
1062 [KNL] Debugging optio <<
1063 deferred probe to giv <<
1064 probe. Only specific <<
1065 drivers) that have op <<
1066 of 0 will timeout at <<
1067 out hasn't expired, i <<
1068 successful driver reg <<
1069 dump out devices stil <<
1070 retrying. <<
1071 <<
1072 delayacct [KNL] Enable per-task <<
1073 <<
1074 dell_smm_hwmon.ignore_dmi= <<
1075 [HW] Continue probing <<
1076 indicates that the dr <<
1077 hardware. <<
1078 <<
1079 dell_smm_hwmon.force= <<
1080 [HW] Activate driver <<
1081 not match list of sup <<
1082 blacklisted features. <<
1083 <<
1084 dell_smm_hwmon.power_status= <<
1085 [HW] Report power sta <<
1086 (disabled by default) <<
1087 798
1088 dell_smm_hwmon.restricted= !! 799 default_hugepagesz=
1089 [HW] Allow controllin !! 800 [same as hugepagesz=] The size of the default
1090 capability is set. !! 801 HugeTLB page size. This is the size represented by
1091 !! 802 the legacy /proc/ hugepages APIs, used for SHM, and
1092 dell_smm_hwmon.fan_mult= !! 803 default size when mounting hugetlbfs filesystems.
1093 [HW] Factor to multip !! 804 Defaults to the default architecture's huge page size
1094 !! 805 if not specified.
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 806
1110 dhash_entries= [KNL] 807 dhash_entries= [KNL]
1111 Set number of hash bu 808 Set number of hash buckets for dentry cache.
1112 809
1113 disable_1tb_segments [PPC,EARLY] !! 810 disable_1tb_segments [PPC]
1114 Disables the use of 1 811 Disables the use of 1TB hash page table segments. This
1115 causes the kernel to 812 causes the kernel to fall back to 256MB segments which
1116 can be useful when de 813 can be useful when debugging issues that require an SLB
1117 miss to occur. 814 miss to occur.
1118 815
1119 disable= [IPV6] 816 disable= [IPV6]
1120 See Documentation/net !! 817 See Documentation/networking/ipv6.txt.
1121 818
1122 disable_radix [PPC,EARLY] !! 819 disable_radix [PPC]
1123 Disable RADIX MMU mod 820 Disable RADIX MMU mode on POWER9
1124 821
1125 disable_tlbie [PPC] !! 822 disable_cpu_apicid= [X86,APIC,SMP]
1126 Disable TLBIE instruc !! 823 Format: <int>
1127 with KVM, with HASH M !! 824 The number of initial APIC ID for the
>> 825 corresponding CPU to be disabled at boot,
>> 826 mostly used for the kdump 2nd kernel to
>> 827 disable BSP to wake up multiple CPUs without
>> 828 causing system reset or hang due to sending
>> 829 INIT from AP to BSP.
1128 830
1129 disable_ddw [PPC/PSERIES,EARLY] !! 831 disable_ddw [PPC/PSERIES]
1130 Disable Dynamic DMA W !! 832 Disable Dynamic DMA Window support. Use this if
1131 to workaround buggy f 833 to workaround buggy firmware.
1132 834
1133 disable_ipv6= [IPV6] 835 disable_ipv6= [IPV6]
1134 See Documentation/net !! 836 See Documentation/networking/ipv6.txt.
1135 837
1136 disable_mtrr_cleanup [X86,EARLY] !! 838 disable_mtrr_cleanup [X86]
1137 The kernel tries to a 839 The kernel tries to adjust MTRR layout from continuous
1138 to discrete, to make 840 to discrete, to make X server driver able to add WB
1139 entry later. This par 841 entry later. This parameter disables that.
1140 842
1141 disable_mtrr_trim [X86, Intel and AMD !! 843 disable_mtrr_trim [X86, Intel and AMD only]
1142 By default the kernel 844 By default the kernel will trim any uncacheable
1143 memory out of your av 845 memory out of your available memory pool based on
1144 MTRR settings. This 846 MTRR settings. This parameter disables that behavior,
1145 possibly causing your 847 possibly causing your machine to run very slowly.
1146 848
1147 disable_timer_pin_1 [X86,EARLY] !! 849 disable_timer_pin_1 [X86]
1148 Disable PIN 1 of APIC 850 Disable PIN 1 of APIC timer
1149 Can be useful to work 851 Can be useful to work around chipset bugs.
1150 852
1151 dis_ucode_ldr [X86] Disable the mic 853 dis_ucode_ldr [X86] Disable the microcode loader.
1152 854
1153 dma_debug=off If the kernel is comp 855 dma_debug=off If the kernel is compiled with DMA_API_DEBUG support,
1154 this option disables 856 this option disables the debugging code at boot.
1155 857
1156 dma_debug_entries=<number> 858 dma_debug_entries=<number>
1157 This option allows to 859 This option allows to tune the number of preallocated
1158 entries for DMA-API d 860 entries for DMA-API debugging code. One entry is
1159 required per DMA-API 861 required per DMA-API allocation. Use this if the
1160 DMA-API debugging cod 862 DMA-API debugging code disables itself because the
1161 architectural default 863 architectural default is too low.
1162 864
1163 dma_debug_driver=<driver_name> 865 dma_debug_driver=<driver_name>
1164 With this option the 866 With this option the DMA-API debugging driver
1165 filter feature can be 867 filter feature can be enabled at boot time. Just
1166 pass the driver to fi 868 pass the driver to filter for as the parameter.
1167 The filter can be dis 869 The filter can be disabled or changed to another
1168 driver later using sy 870 driver later using sysfs.
1169 871
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] <<
1191 List of driver names <<
1192 matches with all driv <<
1193 rest of the listed dr <<
1194 match the *. <<
1195 Format: <driver_name1 <<
1196 <<
1197 drm.edid_firmware=[<connector>:]<file 872 drm.edid_firmware=[<connector>:]<file>[,[<connector>:]<file>]
1198 Broken monitors, grap 873 Broken monitors, graphic adapters, KVMs and EDIDless
1199 panels may send no or 874 panels may send no or incorrect EDID data sets.
1200 This parameter allows 875 This parameter allows to specify an EDID data sets
1201 in the /lib/firmware 876 in the /lib/firmware directory that are used instead.
1202 An EDID data set will !! 877 Generic built-in EDID data sets are used, if one of
1203 connector, if its nam !! 878 edid/1024x768.bin, edid/1280x1024.bin,
1204 the EDID name. Each c !! 879 edid/1680x1050.bin, or edid/1920x1080.bin is given
1205 data set by separatin !! 880 and no file with the same name exists. Details and
>> 881 instructions how to build your own EDID data are
>> 882 available in Documentation/EDID/HOWTO.txt. An EDID
>> 883 data set will only be used for a particular connector,
>> 884 if its name and a colon are prepended to the EDID
>> 885 name. Each connector may use a unique EDID data
>> 886 set by separating the files with a comma. An EDID
1206 data set with no conn 887 data set with no connector name will be used for
1207 any connectors not ex 888 any connectors not explicitly specified.
1208 889
1209 dscc4.setup= [NET] 890 dscc4.setup= [NET]
1210 891
1211 dt_cpu_ftrs= [PPC,EARLY] !! 892 dt_cpu_ftrs= [PPC]
1212 Format: {"off" | "kno 893 Format: {"off" | "known"}
1213 Control how the dt_cp 894 Control how the dt_cpu_ftrs device-tree binding is
1214 used for CPU feature 895 used for CPU feature discovery and setup (if it
1215 exists). 896 exists).
1216 off: Do not use it, f 897 off: Do not use it, fall back to legacy cpu table.
1217 known: Do not pass th 898 known: Do not pass through unknown features to guests
1218 or userspace, only th 899 or userspace, only those that the kernel is aware of.
1219 900
1220 dump_apple_properties [X86] 901 dump_apple_properties [X86]
1221 Dump name and content 902 Dump name and content of EFI device properties on
1222 x86 Macs. Useful for 903 x86 Macs. Useful for driver authors to determine
1223 what data is availabl 904 what data is available or for reverse-engineering.
1224 905
1225 dyndbg[="val"] [KNL,DYNAMIC_ 906 dyndbg[="val"] [KNL,DYNAMIC_DEBUG]
1226 <module>.dyndbg[="val"] !! 907 module.dyndbg[="val"]
1227 Enable debug messages 908 Enable debug messages at boot time. See
1228 Documentation/admin-g 909 Documentation/admin-guide/dynamic-debug-howto.rst
1229 for details. 910 for details.
1230 911
1231 early_ioremap_debug [KNL,EARLY] !! 912 nompx [X86] Disables Intel Memory Protection Extensions.
>> 913 See Documentation/x86/intel_mpx.txt for more
>> 914 information about the feature.
>> 915
>> 916 nopku [X86] Disable Memory Protection Keys CPU feature found
>> 917 in some Intel CPUs.
>> 918
>> 919 module.async_probe [KNL]
>> 920 Enable asynchronous probe on this module.
>> 921
>> 922 early_ioremap_debug [KNL]
1232 Enable debug messages 923 Enable debug messages in early_ioremap support. This
1233 is useful for trackin 924 is useful for tracking down temporary early mappings
1234 which are not unmappe 925 which are not unmapped.
1235 926
1236 earlycon= [KNL,EARLY] Output ea !! 927 earlycon= [KNL] Output early console device and options.
>> 928
>> 929 [ARM64] The early console is determined by the
>> 930 stdout-path property in device tree's chosen node,
>> 931 or determined by the ACPI SPCR table.
1237 932
1238 When used with no opt !! 933 [X86] When used with no options the early console is
1239 determined by stdout- !! 934 determined by the ACPI SPCR table.
1240 chosen node or the AC <<
1241 the platform. <<
1242 935
1243 cdns,<addr>[,options] 936 cdns,<addr>[,options]
1244 Start an early, polle 937 Start an early, polled-mode console on a Cadence
1245 (xuartps) serial port 938 (xuartps) serial port at the specified address. Only
1246 supported option is b 939 supported option is baud rate. If baud rate is not
1247 specified, the serial 940 specified, the serial port must already be setup and
1248 configured. 941 configured.
1249 942
1250 uart[8250],io,<addr>[,options !! 943 uart[8250],io,<addr>[,options]
1251 uart[8250],mmio,<addr>[,optio !! 944 uart[8250],mmio,<addr>[,options]
1252 uart[8250],mmio32,<addr>[,opt !! 945 uart[8250],mmio32,<addr>[,options]
1253 uart[8250],mmio32be,<addr>[,o !! 946 uart[8250],mmio32be,<addr>[,options]
1254 uart[8250],0x<addr>[,options] 947 uart[8250],0x<addr>[,options]
1255 Start an early, polle 948 Start an early, polled-mode console on the 8250/16550
1256 UART at the specified 949 UART at the specified I/O port or MMIO address.
1257 MMIO inter-register a 950 MMIO inter-register address stride is either 8-bit
1258 (mmio) or 32-bit (mmi 951 (mmio) or 32-bit (mmio32 or mmio32be).
1259 If none of [io|mmio|m 952 If none of [io|mmio|mmio32|mmio32be], <addr> is assumed
1260 to be equivalent to ' 953 to be equivalent to 'mmio'. 'options' are specified
1261 in the same format de 954 in the same format described for "console=ttyS<n>"; if
1262 unspecified, the h/w !! 955 unspecified, the h/w is not initialized.
1263 the uart clock freque <<
1264 to 'BASE_BAUD' * 16. <<
1265 956
1266 pl011,<addr> 957 pl011,<addr>
1267 pl011,mmio32,<addr> 958 pl011,mmio32,<addr>
1268 Start an early, polle 959 Start an early, polled-mode console on a pl011 serial
1269 port at the specified 960 port at the specified address. The pl011 serial port
1270 must already be setup 961 must already be setup and configured. Options are not
1271 yet supported. If 'm 962 yet supported. If 'mmio32' is specified, then only
1272 the driver will use o 963 the driver will use only 32-bit accessors to read/write
1273 the device registers. 964 the device registers.
1274 965
1275 liteuart,<addr> <<
1276 Start an early consol <<
1277 specified address. Th <<
1278 setup and configured. <<
1279 <<
1280 meson,<addr> 966 meson,<addr>
1281 Start an early, polle 967 Start an early, polled-mode console on a meson serial
1282 port at the specified 968 port at the specified address. The serial port must
1283 already be setup and 969 already be setup and configured. Options are not yet
1284 supported. 970 supported.
1285 971
1286 msm_serial,<addr> 972 msm_serial,<addr>
1287 Start an early, polle 973 Start an early, polled-mode console on an msm serial
1288 port at the specified 974 port at the specified address. The serial port
1289 must already be setup 975 must already be setup and configured. Options are not
1290 yet supported. 976 yet supported.
1291 977
1292 msm_serial_dm,<addr> 978 msm_serial_dm,<addr>
1293 Start an early, polle 979 Start an early, polled-mode console on an msm serial
1294 dm port at the specif 980 dm port at the specified address. The serial port
1295 must already be setup 981 must already be setup and configured. Options are not
1296 yet supported. 982 yet supported.
1297 983
1298 owl,<addr> 984 owl,<addr>
1299 Start an early, polle 985 Start an early, polled-mode console on a serial port
1300 of an Actions Semi So 986 of an Actions Semi SoC, such as S500 or S900, at the
1301 specified address. Th 987 specified address. The serial port must already be
1302 setup and configured. 988 setup and configured. Options are not yet supported.
1303 989
1304 rda,<addr> <<
1305 Start an early, polle <<
1306 of an RDA Micro SoC, <<
1307 specified address. Th <<
1308 setup and configured. <<
1309 <<
1310 sbi <<
1311 Use RISC-V SBI (Super <<
1312 console. <<
1313 <<
1314 smh Use ARM semihosting c 990 smh Use ARM semihosting calls for early console.
1315 991
1316 s3c2410,<addr> 992 s3c2410,<addr>
1317 s3c2412,<addr> 993 s3c2412,<addr>
1318 s3c2440,<addr> 994 s3c2440,<addr>
1319 s3c6400,<addr> 995 s3c6400,<addr>
1320 s5pv210,<addr> 996 s5pv210,<addr>
1321 exynos4210,<addr> 997 exynos4210,<addr>
1322 Use early console pro 998 Use early console provided by serial driver available
1323 on Samsung SoCs, requ 999 on Samsung SoCs, requires selecting proper type and
1324 a correct base addres 1000 a correct base address of the selected UART port. The
1325 serial port must alre 1001 serial port must already be setup and configured.
1326 Options are not yet s 1002 Options are not yet supported.
1327 1003
1328 lantiq,<addr> 1004 lantiq,<addr>
1329 Start an early, polle 1005 Start an early, polled-mode console on a lantiq serial
1330 (lqasc) port at the s 1006 (lqasc) port at the specified address. The serial port
1331 must already be setup 1007 must already be setup and configured. Options are not
1332 yet supported. 1008 yet supported.
1333 1009
1334 lpuart,<addr> 1010 lpuart,<addr>
1335 lpuart32,<addr> 1011 lpuart32,<addr>
1336 Use early console pro 1012 Use early console provided by Freescale LP UART driver
1337 found on Freescale Vy 1013 found on Freescale Vybrid and QorIQ LS1021A processors.
1338 A valid base address 1014 A valid base address must be provided, and the serial
1339 port must already be 1015 port must already be setup and configured.
1340 1016
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> 1017 ar3700_uart,<addr>
1348 Start an early, polle 1018 Start an early, polled-mode console on the
1349 Armada 3700 serial po 1019 Armada 3700 serial port at the specified
1350 address. The serial p 1020 address. The serial port must already be setup
1351 and configured. Optio 1021 and configured. Options are not yet supported.
1352 1022
1353 qcom_geni,<addr> 1023 qcom_geni,<addr>
1354 Start an early, polle 1024 Start an early, polled-mode console on a Qualcomm
1355 Generic Interface (GE 1025 Generic Interface (GENI) based serial port at the
1356 specified address. Th 1026 specified address. The serial port must already be
1357 setup and configured. 1027 setup and configured. Options are not yet supported.
1358 1028
1359 efifb,[options] !! 1029 earlyprintk= [X86,SH,ARM,M68k,S390]
1360 Start an early, unacc <<
1361 memory mapped framebu <<
1362 coherent non-x86 syst <<
1363 the framebuffer, pass <<
1364 mapped with the corre <<
1365 <<
1366 linflex,<addr> <<
1367 Use early console pro <<
1368 serial driver for NXP <<
1369 address must be provi <<
1370 already be setup and <<
1371 <<
1372 earlyprintk= [X86,SH,ARM,M68k,S390 <<
1373 earlyprintk=vga 1030 earlyprintk=vga
>> 1031 earlyprintk=efi
1374 earlyprintk=sclp 1032 earlyprintk=sclp
1375 earlyprintk=xen 1033 earlyprintk=xen
1376 earlyprintk=serial[,t 1034 earlyprintk=serial[,ttySn[,baudrate]]
1377 earlyprintk=serial[,0 1035 earlyprintk=serial[,0x...[,baudrate]]
1378 earlyprintk=ttySn[,ba 1036 earlyprintk=ttySn[,baudrate]
1379 earlyprintk=dbgp[debu 1037 earlyprintk=dbgp[debugController#]
1380 earlyprintk=pciserial !! 1038 earlyprintk=pciserial,bus:device.function[,baudrate]
1381 earlyprintk=xdbc[xhci 1039 earlyprintk=xdbc[xhciController#]
1382 earlyprintk=bios <<
1383 1040
1384 earlyprintk is useful 1041 earlyprintk is useful when the kernel crashes before
1385 the normal console is 1042 the normal console is initialized. It is not enabled by
1386 default because it ha 1043 default because it has some cosmetic problems.
1387 1044
1388 Append ",keep" to not 1045 Append ",keep" to not disable it when the real console
1389 takes over. 1046 takes over.
1390 1047
1391 Only one of vga, seri !! 1048 Only one of vga, efi, serial, or usb debug port can
1392 be used at a time. 1049 be used at a time.
1393 1050
1394 Currently only ttyS0 1051 Currently only ttyS0 and ttyS1 may be specified by
1395 name. Other I/O port 1052 name. Other I/O ports may be explicitly specified
1396 on some architectures 1053 on some architectures (x86 and arm at least) by
1397 replacing ttySn with 1054 replacing ttySn with an I/O port address, like this:
1398 earlyprintk=s 1055 earlyprintk=serial,0x1008,115200
1399 You can find the port 1056 You can find the port for a given device in
1400 /proc/tty/driver/seri 1057 /proc/tty/driver/serial:
1401 2: uart:ST166 1058 2: uart:ST16650V2 port:00001008 irq:18 ...
1402 1059
1403 Interaction with the 1060 Interaction with the standard serial driver is not
1404 very good. 1061 very good.
1405 1062
1406 The VGA output is eve !! 1063 The VGA and EFI output is eventually overwritten by
1407 the real console. 1064 the real console.
1408 1065
1409 The xen option can on !! 1066 The xen output can only be used by Xen PV guests.
1410 1067
1411 The sclp output can o 1068 The sclp output can only be used on s390.
1412 1069
1413 The bios output can o <<
1414 <<
1415 The optional "force" <<
1416 PCI device even when <<
1417 UART class. <<
1418 <<
1419 edac_report= [HW,EDAC] Control how 1070 edac_report= [HW,EDAC] Control how to report EDAC event
1420 Format: {"on" | "off" 1071 Format: {"on" | "off" | "force"}
1421 on: enable EDAC to re 1072 on: enable EDAC to report H/W event. May be overridden
1422 by other higher prior 1073 by other higher priority error reporting module.
1423 off: disable H/W even 1074 off: disable H/W event reporting through EDAC.
1424 force: enforce the us 1075 force: enforce the use of EDAC to report H/W event.
1425 default: on. 1076 default: on.
1426 1077
>> 1078 ekgdboc= [X86,KGDB] Allow early kernel console debugging
>> 1079 ekgdboc=kbd
>> 1080
>> 1081 This is designed to be used in conjunction with
>> 1082 the boot argument: earlyprintk=vga
>> 1083
1427 edd= [EDD] 1084 edd= [EDD]
1428 Format: {"off" | "on" 1085 Format: {"off" | "on" | "skip[mbr]"}
1429 1086
1430 efi= [EFI,EARLY] !! 1087 efi= [EFI]
1431 Format: { "debug", "d !! 1088 Format: { "old_map", "nochunk", "noruntime", "debug" }
1432 "nochunk", !! 1089 old_map [X86-64]: switch to the old ioremap-based EFI
1433 "novamap", !! 1090 runtime services mapping. 32-bit still uses this one by
1434 debug: enable misc de !! 1091 default.
1435 disable_early_pci_dma <<
1436 PCI bridges while in <<
1437 nochunk: disable read 1092 nochunk: disable reading files in "chunks" in the EFI
1438 boot stub, as chunkin 1093 boot stub, as chunking can cause problems with some
1439 firmware implementati 1094 firmware implementations.
1440 noruntime : disable E 1095 noruntime : disable EFI runtime services support
1441 nosoftreserve: The EF !! 1096 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 1097
1451 efi_no_storage_paranoia [EFI,X86,EARL !! 1098 efi_no_storage_paranoia [EFI; X86]
1452 Using this parameter 1099 Using this parameter you can use more than 50% of
1453 your efi variable sto 1100 your efi variable storage. Use this parameter only if
1454 you are really sure t 1101 you are really sure that your UEFI does sane gc and
1455 fulfills the spec oth 1102 fulfills the spec otherwise your board may brick.
1456 1103
>> 1104 efi_fake_mem= nn[KMG]@ss[KMG]:aa[,nn[KMG]@ss[KMG]:aa,..] [EFI; X86]
>> 1105 Add arbitrary attribute to specific memory range by
>> 1106 updating original EFI memory map.
>> 1107 Region of memory which aa attribute is added to is
>> 1108 from ss to ss+nn.
>> 1109 If efi_fake_mem=2G@4G:0x10000,2G@0x10a0000000:0x10000
>> 1110 is specified, EFI_MEMORY_MORE_RELIABLE(0x10000)
>> 1111 attribute is added to range 0x100000000-0x180000000 and
>> 1112 0x10a0000000-0x1120000000.
>> 1113
>> 1114 Using this parameter you can do debugging of EFI memmap
>> 1115 related feature. For example, you can do debugging of
>> 1116 Address Range Mirroring feature even if your box
>> 1117 doesn't support it.
>> 1118
1457 efivar_ssdt= [EFI; X86] Name of an 1119 efivar_ssdt= [EFI; X86] Name of an EFI variable that contains an SSDT
1458 that is to be dynamic 1120 that is to be dynamically loaded by Linux. If there are
1459 multiple variables wi 1121 multiple variables with the same name but with different
1460 vendor GUIDs, all of 1122 vendor GUIDs, all of them will be loaded. See
1461 Documentation/admin-g !! 1123 Documentation/acpi/ssdt-overlays.txt for details.
1462 1124
1463 1125
1464 eisa_irq_edge= [PARISC,HW] 1126 eisa_irq_edge= [PARISC,HW]
1465 See header of drivers 1127 See header of drivers/parisc/eisa.c.
1466 1128
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] 1129 elanfreq= [X86-32]
1479 See comment before fu 1130 See comment before function elanfreq_setup() in
1480 arch/x86/kernel/cpu/c 1131 arch/x86/kernel/cpu/cpufreq/elanfreq.c.
1481 1132
1482 elfcorehdr=[size[KMG]@]offset[KMG] [P !! 1133 elevator= [IOSCHED]
>> 1134 Format: {"cfq" | "deadline" | "noop"}
>> 1135 See Documentation/block/cfq-iosched.txt and
>> 1136 Documentation/block/deadline-iosched.txt for details.
>> 1137
>> 1138 elfcorehdr=[size[KMG]@]offset[KMG] [IA64,PPC,SH,X86,S390]
1483 Specifies physical ad 1139 Specifies physical address of start of kernel core
1484 image elf header and 1140 image elf header and optionally the size. Generally
1485 kexec loader will pas 1141 kexec loader will pass this option to capture kernel.
1486 See Documentation/adm !! 1142 See Documentation/kdump/kdump.txt for details.
1487 1143
1488 enable_mtrr_cleanup [X86,EARLY] !! 1144 enable_mtrr_cleanup [X86]
1489 The kernel tries to a 1145 The kernel tries to adjust MTRR layout from continuous
1490 to discrete, to make 1146 to discrete, to make X server driver able to add WB
1491 entry later. This par 1147 entry later. This parameter enables that.
1492 1148
1493 enable_timer_pin_1 [X86] 1149 enable_timer_pin_1 [X86]
1494 Enable PIN 1 of APIC 1150 Enable PIN 1 of APIC timer
1495 Can be useful to work 1151 Can be useful to work around chipset bugs
1496 (in particular on som 1152 (in particular on some ATI chipsets).
1497 The kernel tries to s 1153 The kernel tries to set a reasonable default.
1498 1154
1499 enforcing= [SELINUX] Set initial !! 1155 enforcing [SELINUX] Set initial enforcing status.
1500 Format: {"0" | "1"} 1156 Format: {"0" | "1"}
1501 See security/selinux/ 1157 See security/selinux/Kconfig help text.
1502 0 -- permissive (log 1158 0 -- permissive (log only, no denials).
1503 1 -- enforcing (deny 1159 1 -- enforcing (deny and log).
1504 Default value is 0. 1160 Default value is 0.
1505 Value can be changed !! 1161 Value can be changed at runtime via /selinux/enforce.
1506 /sys/fs/selinux/enfor <<
1507 1162
1508 erst_disable [ACPI] 1163 erst_disable [ACPI]
1509 Disable Error Record 1164 Disable Error Record Serialization Table (ERST)
1510 support. 1165 support.
1511 1166
1512 ether= [HW,NET] Ethernet car 1167 ether= [HW,NET] Ethernet cards parameters
1513 This option is obsole 1168 This option is obsoleted by the "netdev=" option, which
1514 has equivalent usage. 1169 has equivalent usage. See its documentation for details.
1515 1170
1516 evm= [EVM] 1171 evm= [EVM]
1517 Format: { "fix" } 1172 Format: { "fix" }
1518 Permit 'security.evm' 1173 Permit 'security.evm' to be updated regardless of
1519 current integrity sta 1174 current integrity status.
1520 1175
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= 1176 failslab=
1530 fail_usercopy= <<
1531 fail_page_alloc= 1177 fail_page_alloc=
1532 fail_make_request=[KNL] 1178 fail_make_request=[KNL]
1533 General fault injecti 1179 General fault injection mechanism.
1534 Format: <interval>,<p 1180 Format: <interval>,<probability>,<space>,<times>
1535 See also Documentatio 1181 See also Documentation/fault-injection/.
1536 1182
1537 fb_tunnels= [NET] <<
1538 Format: { initns | no <<
1539 See Documentation/adm <<
1540 fb_tunnels_only_for_i <<
1541 <<
1542 floppy= [HW] 1183 floppy= [HW]
1543 See Documentation/adm !! 1184 See Documentation/blockdev/floppy.txt.
>> 1185
>> 1186 force_pal_cache_flush
>> 1187 [IA-64] Avoid check_sal_cache_flush which may hang on
>> 1188 buggy SAL_CACHE_FLUSH implementations. Using this
>> 1189 parameter will force ia64_sal_cache_flush to call
>> 1190 ia64_pal_cache_flush instead of SAL_CACHE_FLUSH.
1544 1191
1545 forcepae [X86-32] 1192 forcepae [X86-32]
1546 Forcefully enable Phy 1193 Forcefully enable Physical Address Extension (PAE).
1547 Many Pentium M system 1194 Many Pentium M systems disable PAE but may have a
1548 functionally usable P 1195 functionally usable PAE implementation.
1549 Warning: use of this 1196 Warning: use of this parameter will taint the kernel
1550 and may cause unknown 1197 and may cause unknown problems.
1551 1198
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] 1199 ftrace=[tracer]
1559 [FTRACE] will set and 1200 [FTRACE] will set and start the specified tracer
1560 as early as possible 1201 as early as possible in order to facilitate early
1561 boot debugging. 1202 boot debugging.
1562 1203
1563 ftrace_boot_snapshot !! 1204 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 1205 [FTRACE] will dump the trace buffers on oops.
1583 If no parameter is pa !! 1206 If no parameter is passed, ftrace will dump
1584 buffers of all CPUs, !! 1207 buffers of all CPUs, but if you pass orig_cpu, it will
1585 will dump only the bu !! 1208 dump only the buffer of the CPU that triggered the
1586 the oops, or the spec !! 1209 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 1210
1603 ftrace_filter=[function-list] 1211 ftrace_filter=[function-list]
1604 [FTRACE] Limit the fu 1212 [FTRACE] Limit the functions traced by the function
1605 tracer at boot up. fu !! 1213 tracer at boot up. function-list is a comma separated
1606 list of functions. Th 1214 list of functions. This list can be changed at run
1607 time by the set_ftrac 1215 time by the set_ftrace_filter file in the debugfs
1608 tracing directory. 1216 tracing directory.
1609 1217
1610 ftrace_notrace=[function-list] 1218 ftrace_notrace=[function-list]
1611 [FTRACE] Do not trace 1219 [FTRACE] Do not trace the functions specified in
1612 function-list. This l 1220 function-list. This list can be changed at run time
1613 by the set_ftrace_not 1221 by the set_ftrace_notrace file in the debugfs
1614 tracing directory. 1222 tracing directory.
1615 1223
1616 ftrace_graph_filter=[function-list] 1224 ftrace_graph_filter=[function-list]
1617 [FTRACE] Limit the to 1225 [FTRACE] Limit the top level callers functions traced
1618 by the function graph 1226 by the function graph tracer at boot up.
1619 function-list is a co !! 1227 function-list is a comma separated list of functions
1620 that can be changed a 1228 that can be changed at run time by the
1621 set_graph_function fi 1229 set_graph_function file in the debugfs tracing directory.
1622 1230
1623 ftrace_graph_notrace=[function-list] 1231 ftrace_graph_notrace=[function-list]
1624 [FTRACE] Do not trace 1232 [FTRACE] Do not trace from the functions specified in
1625 function-list. This !! 1233 function-list. This list is a comma separated list of
1626 functions that can be 1234 functions that can be changed at run time by the
1627 set_graph_notrace fil 1235 set_graph_notrace file in the debugfs tracing directory.
1628 1236
1629 ftrace_graph_max_depth=<uint> 1237 ftrace_graph_max_depth=<uint>
1630 [FTRACE] Used with th 1238 [FTRACE] Used with the function graph tracer. This is
1631 the max depth it will 1239 the max depth it will trace into a function. This value
1632 can be changed at run 1240 can be changed at run time by the max_graph_depth file
1633 in the tracefs tracin 1241 in the tracefs tracing directory. default: 0 (no limit)
1634 1242
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]= 1243 gamecon.map[2|3]=
1673 [HW,JOY] Multisystem 1244 [HW,JOY] Multisystem joystick and NES/SNES/PSX pad
1674 support via parallel 1245 support via parallel port (up to 5 devices per port)
1675 Format: <port#>,<pad1 1246 Format: <port#>,<pad1>,<pad2>,<pad3>,<pad4>,<pad5>
1676 See also Documentatio 1247 See also Documentation/input/devices/joystick-parport.rst
1677 1248
1678 gamma= [HW,DRM] 1249 gamma= [HW,DRM]
1679 1250
1680 gart_fix_e820= [X86-64,EARLY] disabl !! 1251 gart_fix_e820= [X86_64] disable the fix e820 for K8 GART
1681 Format: off | on 1252 Format: off | on
1682 default: on 1253 default: on
1683 1254
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 1255 gcov_persist= [GCOV] When non-zero (default), profiling data for
1705 kernel modules is sav 1256 kernel modules is saved and remains accessible via
1706 debugfs, even when th 1257 debugfs, even when the module is unloaded/reloaded.
1707 When zero, profiling 1258 When zero, profiling data is discarded and associated
1708 debugfs files are rem 1259 debugfs files are removed at module unload time.
1709 1260
1710 goldfish [X86] Enable the gold 1261 goldfish [X86] Enable the goldfish android emulator platform.
1711 Don't use this when y 1262 Don't use this when you are not running on the
1712 android emulator 1263 android emulator
1713 1264
1714 gpio-mockup.gpio_mockup_ranges <<
1715 [HW] Sets the ranges <<
1716 Format: <start1>,<end <<
1717 gpio-mockup.gpio_mockup_named_lines <<
1718 [HW] Let the driver k <<
1719 <<
1720 gpt [EFI] Forces disk wit 1265 gpt [EFI] Forces disk with valid GPT signature but
1721 invalid Protective MB 1266 invalid Protective MBR to be treated as GPT. If the
1722 primary GPT is corrup 1267 primary GPT is corrupted, it enables the backup/alternate
1723 GPT to be used instea 1268 GPT to be used instead.
1724 1269
1725 grcan.enable0= [HW] Configuration of 1270 grcan.enable0= [HW] Configuration of physical interface 0. Determines
1726 the "Enable 0" bit of 1271 the "Enable 0" bit of the configuration register.
1727 Format: 0 | 1 1272 Format: 0 | 1
1728 Default: 0 1273 Default: 0
1729 grcan.enable1= [HW] Configuration of 1274 grcan.enable1= [HW] Configuration of physical interface 1. Determines
1730 the "Enable 0" bit of 1275 the "Enable 0" bit of the configuration register.
1731 Format: 0 | 1 1276 Format: 0 | 1
1732 Default: 0 1277 Default: 0
1733 grcan.select= [HW] Select which phy 1278 grcan.select= [HW] Select which physical interface to use.
1734 Format: 0 | 1 1279 Format: 0 | 1
1735 Default: 0 1280 Default: 0
1736 grcan.txsize= [HW] Sets the size of 1281 grcan.txsize= [HW] Sets the size of the tx buffer.
1737 Format: <unsigned int 1282 Format: <unsigned int> such that (txsize & ~0x1fffc0) == 0.
1738 Default: 1024 1283 Default: 1024
1739 grcan.rxsize= [HW] Sets the size of 1284 grcan.rxsize= [HW] Sets the size of the rx buffer.
1740 Format: <unsigned int 1285 Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0.
1741 Default: 1024 1286 Default: 1024
1742 1287
1743 hardened_usercopy= !! 1288 gpio-mockup.gpio_mockup_ranges
1744 [KNL] Under CONFIG_HA !! 1289 [HW] Sets the ranges of gpiochip of for this device.
1745 hardening is enabled !! 1290 Format: <start1>,<end1>,<start2>,<end2>...
1746 usercopy checking is <<
1747 from reading or writi <<
1748 allocation boundaries <<
1749 against bounds-checki <<
1750 copy_to_user()/copy_f <<
1751 on Perform hardened user <<
1752 off Disable hardened user <<
1753 1291
1754 hardlockup_all_cpu_backtrace= 1292 hardlockup_all_cpu_backtrace=
1755 [KNL] Should the hard 1293 [KNL] Should the hard-lockup detector generate
1756 backtraces on all cpu 1294 backtraces on all cpus.
1757 Format: 0 | 1 !! 1295 Format: <integer>
1758 1296
1759 hashdist= [KNL,NUMA] Large hash 1297 hashdist= [KNL,NUMA] Large hashes allocated during boot
1760 are distributed acros 1298 are distributed across NUMA nodes. Defaults on
1761 for 64-bit NUMA, off 1299 for 64-bit NUMA, off otherwise.
1762 Format: 0 | 1 (for of 1300 Format: 0 | 1 (for off | on)
1763 1301
>> 1302 hcl= [IA-64] SGI's Hardware Graph compatibility layer
>> 1303
1764 hd= [EIDE] (E)IDE hard dr 1304 hd= [EIDE] (E)IDE hard drive subsystem geometry
1765 Format: <cyl>,<head>, 1305 Format: <cyl>,<head>,<sect>
1766 1306
1767 hest_disable [ACPI] 1307 hest_disable [ACPI]
1768 Disable Hardware Erro 1308 Disable Hardware Error Source Table (HEST) support;
1769 corresponding firmwar 1309 corresponding firmware-first mode error processing
1770 logic will be disable 1310 logic will be disabled.
1771 1311
1772 hibernate= [HIBERNATION] !! 1312 highmem=nn[KMG] [KNL,BOOT] forces the highmem zone to have an exact
1773 noresume Don't check i <<
1774 present durin <<
1775 nocompress Don't compres <<
1776 no Disable hiber <<
1777 protect_image Turn on image <<
1778 (that will se <<
1779 during restor <<
1780 <<
1781 hibernate.compressor= [HIBERNATION] <<
1782 used with hib <<
1783 Format: { lzo <<
1784 Default: lzo <<
1785 <<
1786 lzo: Select L <<
1787 compress/deco <<
1788 <<
1789 lz4: Select L <<
1790 compress/deco <<
1791 <<
1792 highmem=nn[KMG] [KNL,BOOT,EARLY] forc <<
1793 size of <nn>. This wo 1313 size of <nn>. This works even on boxes that have no
1794 highmem otherwise. Th 1314 highmem otherwise. This also works to reduce highmem
1795 size on bigger boxes. 1315 size on bigger boxes.
1796 1316
1797 highres= [KNL] Enable/disable 1317 highres= [KNL] Enable/disable high resolution timer mode.
1798 Valid parameters: "on 1318 Valid parameters: "on", "off"
1799 Default: "on" 1319 Default: "on"
1800 1320
1801 hlt [BUGS=ARM,SH] !! 1321 hisax= [HW,ISDN]
>> 1322 See Documentation/isdn/README.HiSax.
1802 1323
1803 hostname= [KNL,EARLY] Set the h !! 1324 hlt [BUGS=ARM,SH]
1804 Format: <string> <<
1805 This allows setting t <<
1806 startup. This sets th <<
1807 Using this parameter <<
1808 possible to ensure th <<
1809 any userspace process <<
1810 that a process may ca <<
1811 has been explicitly s <<
1812 process getting an in <<
1813 not exceed the maximu <<
1814 64 characters) and wi <<
1815 1325
1816 hpet= [X86-32,HPET] option 1326 hpet= [X86-32,HPET] option to control HPET usage
1817 Format: { enable (def 1327 Format: { enable (default) | disable | force |
1818 verbose } 1328 verbose }
1819 disable: disable HPET 1329 disable: disable HPET and use PIT instead
1820 force: allow force en 1330 force: allow force enabled of undocumented chips (ICH4,
1821 VIA, nVidia) 1331 VIA, nVidia)
1822 verbose: show content 1332 verbose: show contents of HPET registers during setup
1823 1333
1824 hpet_mmap= [X86, HPET_MMAP] Allo 1334 hpet_mmap= [X86, HPET_MMAP] Allow userspace to mmap HPET
1825 registers. Default s 1335 registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
1826 1336
1827 hugepages= [HW] Number of HugeTL !! 1337 hugepages= [HW,X86-32,IA-64] HugeTLB pages to allocate at boot.
1828 If this follows hugep !! 1338 hugepagesz= [HW,IA-64,PPC,X86-64] The size of the HugeTLB pages.
1829 the number of pages o !! 1339 On x86-64 and powerpc, this option can be specified
1830 If this is the first !! 1340 multiple times interleaved with hugepages= to reserve
1831 line, it specifies th !! 1341 huge pages of different sizes. Valid pages sizes on
1832 the default huge page !! 1342 x86-64 are 2M (when the CPU supports "pse") and 1G
1833 number of pages to al !! 1343 (when the CPU supports the "pdpe1gb" cpuinfo flag).
1834 See also Documentatio <<
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 1344
1878 hung_task_panic= 1345 hung_task_panic=
1879 [KNL] Should the hung 1346 [KNL] Should the hung task detector generate panics.
1880 Format: 0 | 1 !! 1347 Format: <integer>
1881 1348
1882 A value of 1 instruct !! 1349 A nonzero value instructs the kernel to panic when a
1883 hung task is detected 1350 hung task is detected. The default value is controlled
1884 by the CONFIG_BOOTPAR 1351 by the CONFIG_BOOTPARAM_HUNG_TASK_PANIC build-time
1885 option. The value sel 1352 option. The value selected by this boot parameter can
1886 be changed later by t 1353 be changed later by the kernel.hung_task_panic sysctl.
1887 1354
1888 hvc_iucv= [S390] Number of z/V 1355 hvc_iucv= [S390] Number of z/VM IUCV hypervisor console (HVC)
1889 terminal devi 1356 terminal devices. Valid values: 0..8
1890 hvc_iucv_allow= [S390] Comma-separat 1357 hvc_iucv_allow= [S390] Comma-separated list of z/VM user IDs.
1891 If specified, 1358 If specified, z/VM IUCV HVC accepts connections
1892 from listed z 1359 from listed z/VM user IDs only.
1893 !! 1360 keep_bootcon [KNL]
1894 hv_nopvspin [X86,HYPER_V,EARLY] !! 1361 Do not unregister boot console at start. This is only
1895 Disables the paravirt !! 1362 useful for debugging when something happens in the window
1896 which allow the hyper !! 1363 between unregistering the boot console and initializing
1897 on lock contention. !! 1364 the real console.
1898 1365
1899 i2c_bus= [HW] Override the 1366 i2c_bus= [HW] Override the default board specific I2C bus speed
1900 or register a 1367 or register an additional I2C bus that is not
1901 registered fr 1368 registered from board initialization code.
1902 Format: 1369 Format:
1903 <bus_id>,<clk 1370 <bus_id>,<clkrate>
1904 1371
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 1372 i8042.debug [HW] Toggle i8042 debug mode
1928 i8042.unmask_kbd_data 1373 i8042.unmask_kbd_data
1929 [HW] Enable printing 1374 [HW] Enable printing of interrupt data from the KBD port
1930 (disabled by def 1375 (disabled by default, and as a pre-condition
1931 requires that i8 1376 requires that i8042.debug=1 be enabled)
1932 i8042.direct [HW] Put keyboard por 1377 i8042.direct [HW] Put keyboard port into non-translated mode
1933 i8042.dumbkbd [HW] Pretend that con 1378 i8042.dumbkbd [HW] Pretend that controller can only read data from
1934 keyboard and can 1379 keyboard and cannot control its state
1935 (Don't attempt t 1380 (Don't attempt to blink the leds)
1936 i8042.noaux [HW] Don't check for 1381 i8042.noaux [HW] Don't check for auxiliary (== mouse) port
1937 i8042.nokbd [HW] Don't check/crea 1382 i8042.nokbd [HW] Don't check/create keyboard port
1938 i8042.noloop [HW] Disable the AUX 1383 i8042.noloop [HW] Disable the AUX Loopback command while probing
1939 for the AUX port 1384 for the AUX port
1940 i8042.nomux [HW] Don't check pres 1385 i8042.nomux [HW] Don't check presence of an active multiplexing
1941 controller 1386 controller
1942 i8042.nopnp [HW] Don't use ACPIPn 1387 i8042.nopnp [HW] Don't use ACPIPnP / PnPBIOS to discover KBD/AUX
1943 controllers 1388 controllers
1944 i8042.notimeout [HW] Ignore timeout c 1389 i8042.notimeout [HW] Ignore timeout condition signalled by controller
1945 i8042.reset [HW] Reset the contro 1390 i8042.reset [HW] Reset the controller during init, cleanup and
1946 suspend-to-ram t 1391 suspend-to-ram transitions, only during s2r
1947 transitions, or 1392 transitions, or never reset
1948 Format: { 1 | Y | y | 1393 Format: { 1 | Y | y | 0 | N | n }
1949 1, Y, y: always reset 1394 1, Y, y: always reset controller
1950 0, N, n: don't ever r 1395 0, N, n: don't ever reset controller
1951 Default: only on s2r 1396 Default: only on s2r transitions on x86; most other
1952 architectures force r 1397 architectures force reset to be always executed
1953 i8042.unlock [HW] Unlock (ignore) 1398 i8042.unlock [HW] Unlock (ignore) the keylock
1954 i8042.kbdreset [HW] Reset device con 1399 i8042.kbdreset [HW] Reset device connected to KBD port
1955 i8042.probe_defer <<
1956 [HW] Allow deferred p <<
1957 1400
1958 i810= [HW,DRM] 1401 i810= [HW,DRM]
1959 1402
>> 1403 i8k.ignore_dmi [HW] Continue probing hardware even if DMI data
>> 1404 indicates that the driver is running on unsupported
>> 1405 hardware.
>> 1406 i8k.force [HW] Activate i8k driver even if SMM BIOS signature
>> 1407 does not match list of supported models.
>> 1408 i8k.power_status
>> 1409 [HW] Report power status in /proc/i8k
>> 1410 (disabled by default)
>> 1411 i8k.restricted [HW] Allow controlling fans only if SYS_ADMIN
>> 1412 capability is set.
>> 1413
1960 i915.invert_brightness= 1414 i915.invert_brightness=
1961 [DRM] Invert the sens 1415 [DRM] Invert the sense of the variable that is used to
1962 set the brightness of 1416 set the brightness of the panel backlight. Normally a
1963 brightness value of 0 1417 brightness value of 0 indicates backlight switched off,
1964 and the maximum of th 1418 and the maximum of the brightness value sets the backlight
1965 to maximum brightness 1419 to maximum brightness. If this parameter is set to 0
1966 (default) and the mac 1420 (default) and the machine requires it, or this parameter
1967 is set to 1, a bright 1421 is set to 1, a brightness value of 0 sets the backlight
1968 to maximum brightness 1422 to maximum brightness, and the maximum of the brightness
1969 value switches the ba 1423 value switches the backlight off.
1970 -1 -- never invert br 1424 -1 -- never invert brightness
1971 0 -- machine default 1425 0 -- machine default
1972 1 -- force brightnes 1426 1 -- force brightness inversion
1973 1427
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] 1428 icn= [HW,ISDN]
1981 Format: <io>[,<membas 1429 Format: <io>[,<membase>[,<icn_id>[,<icn_id2>]]]
1982 1430
>> 1431 ide-core.nodma= [HW] (E)IDE subsystem
>> 1432 Format: =0.0 to prevent dma on hda, =0.1 hdb =1.0 hdc
>> 1433 .vlb_clock .pci_clock .noflush .nohpa .noprobe .nowerr
>> 1434 .cdrom .chs .ignore_cable are additional options
>> 1435 See Documentation/ide/ide.txt.
>> 1436
>> 1437 ide-generic.probe-mask= [HW] (E)IDE subsystem
>> 1438 Format: <int>
>> 1439 Probe mask for legacy ISA IDE ports. Depending on
>> 1440 platform up to 6 ports are supported, enabled by
>> 1441 setting corresponding bits in the mask to 1. The
>> 1442 default value is 0x0, which has a special meaning.
>> 1443 On systems that have PCI, it triggers scanning the
>> 1444 PCI bus for the first and the second port, which
>> 1445 are then probed. On systems without PCI the value
>> 1446 of 0x0 enables probing the two first ports as if it
>> 1447 was 0x3.
>> 1448
>> 1449 ide-pci-generic.all-generic-ide [HW] (E)IDE subsystem
>> 1450 Claim all unknown PCI IDE storage controllers.
1983 1451
1984 idle= [X86,EARLY] !! 1452 idle= [X86]
1985 Format: idle=poll, id 1453 Format: idle=poll, idle=halt, idle=nomwait
1986 Poll forces a polling 1454 Poll forces a polling idle loop that can slightly
1987 improve the performan 1455 improve the performance of waking up a idle CPU, but
1988 will use a lot of pow 1456 will use a lot of power and make the system run hot.
1989 Not recommended. 1457 Not recommended.
1990 idle=halt: Halt is fo 1458 idle=halt: Halt is forced to be used for CPU idle.
1991 In such case C2/C3 wo 1459 In such case C2/C3 won't be used again.
1992 idle=nomwait: Disable 1460 idle=nomwait: Disable mwait for CPU C-states
1993 1461
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 1462 ieee754= [MIPS] Select IEEE Std 754 conformance mode
2006 Format: { strict | le !! 1463 Format: { strict | legacy | 2008 | relaxed }
2007 Default: strict 1464 Default: strict
2008 1465
2009 Choose which programs 1466 Choose which programs will be accepted for execution
2010 based on the IEEE 754 1467 based on the IEEE 754 NaN encoding(s) supported by
2011 the FPU and the NaN e 1468 the FPU and the NaN encoding requested with the value
2012 of an ELF file header 1469 of an ELF file header flag individually set by each
2013 binary. Hardware imp 1470 binary. Hardware implementations are permitted to
2014 support either or bot 1471 support either or both of the legacy and the 2008 NaN
2015 encoding mode. 1472 encoding mode.
2016 1473
2017 Available settings ar 1474 Available settings are as follows:
2018 strict accept binari 1475 strict accept binaries that request a NaN encoding
2019 supported by 1476 supported by the FPU
2020 legacy only accept l 1477 legacy only accept legacy-NaN binaries, if supported
2021 by the FPU 1478 by the FPU
2022 2008 only accept 2 1479 2008 only accept 2008-NaN binaries, if supported
2023 by the FPU 1480 by the FPU
2024 relaxed accept any bi 1481 relaxed accept any binaries regardless of whether
2025 supported by 1482 supported by the FPU
2026 emulated accept any b <<
2027 if binary mod <<
2028 1483
2029 The FPU emulator is a 1484 The FPU emulator is always able to support both NaN
2030 encodings, so if no F 1485 encodings, so if no FPU hardware is present or it has
2031 been disabled with 'n 1486 been disabled with 'nofpu', then the settings of
2032 'legacy' and '2008' s 1487 'legacy' and '2008' strap the emulator accordingly,
2033 'relaxed' straps the 1488 'relaxed' straps the emulator for both legacy-NaN and
2034 2008-NaN, whereas 'st 1489 2008-NaN, whereas 'strict' enables legacy-NaN only on
2035 legacy processors and 1490 legacy processors and both NaN encodings on MIPS32 or
2036 MIPS64 CPUs. 1491 MIPS64 CPUs.
2037 1492
2038 The setting for ABS.f 1493 The setting for ABS.fmt/NEG.fmt instruction execution
2039 mode generally follow 1494 mode generally follows that for the NaN encoding,
2040 except where unsuppor 1495 except where unsupported by hardware.
2041 1496
2042 ignore_loglevel [KNL,EARLY] !! 1497 ignore_loglevel [KNL]
2043 Ignore loglevel setti 1498 Ignore loglevel setting - this will print /all/
2044 kernel messages to th 1499 kernel messages to the console. Useful for debugging.
2045 We also add it as pri 1500 We also add it as printk module parameter, so users
2046 could change it dynam 1501 could change it dynamically, usually by
2047 /sys/module/printk/pa 1502 /sys/module/printk/parameters/ignore_loglevel.
2048 1503
2049 ignore_rlimit_data 1504 ignore_rlimit_data
2050 Ignore RLIMIT_DATA se 1505 Ignore RLIMIT_DATA setting for data mappings,
2051 print warning at firs 1506 print warning at first misuse. Can be changed via
2052 /sys/module/kernel/pa 1507 /sys/module/kernel/parameters/ignore_rlimit_data.
2053 1508
2054 ihash_entries= [KNL] 1509 ihash_entries= [KNL]
2055 Set number of hash bu 1510 Set number of hash buckets for inode cache.
2056 1511
2057 ima_appraise= [IMA] appraise integr 1512 ima_appraise= [IMA] appraise integrity measurements
2058 Format: { "off" | "en 1513 Format: { "off" | "enforce" | "fix" | "log" }
2059 default: "enforce" 1514 default: "enforce"
2060 1515
2061 ima_appraise_tcb [IMA] Deprecated. U !! 1516 ima_appraise_tcb [IMA]
2062 The builtin appraise 1517 The builtin appraise policy appraises all files
2063 owned by uid=0. 1518 owned by uid=0.
2064 1519
2065 ima_canonical_fmt [IMA] 1520 ima_canonical_fmt [IMA]
2066 Use the canonical for 1521 Use the canonical format for the binary runtime
2067 measurements, instead 1522 measurements, instead of host native format.
2068 1523
2069 ima_hash= [IMA] 1524 ima_hash= [IMA]
2070 Format: { md5 | sha1 1525 Format: { md5 | sha1 | rmd160 | sha256 | sha384
2071 | sha512 | 1526 | sha512 | ... }
2072 default: "sha1" 1527 default: "sha1"
2073 1528
2074 The list of supported 1529 The list of supported hash algorithms is defined
2075 in crypto/hash_info.h 1530 in crypto/hash_info.h.
2076 1531
2077 ima_policy= [IMA] 1532 ima_policy= [IMA]
2078 The builtin policies 1533 The builtin policies to load during IMA setup.
2079 Format: "tcb | apprai 1534 Format: "tcb | appraise_tcb | secure_boot |
2080 fail_securel !! 1535 fail_securely"
2081 1536
2082 The "tcb" policy meas 1537 The "tcb" policy measures all programs exec'd, files
2083 mmap'd for exec, and 1538 mmap'd for exec, and all files opened with the read
2084 mode bit set by eithe 1539 mode bit set by either the effective uid (euid=0) or
2085 uid=0. 1540 uid=0.
2086 1541
2087 The "appraise_tcb" po 1542 The "appraise_tcb" policy appraises the integrity of
2088 all files owned by ro !! 1543 all files owned by root. (This is the equivalent
>> 1544 of ima_appraise_tcb.)
2089 1545
2090 The "secure_boot" pol 1546 The "secure_boot" policy appraises the integrity
2091 of files (eg. kexec k 1547 of files (eg. kexec kernel image, kernel modules,
2092 firmware, policy, etc 1548 firmware, policy, etc) based on file signatures.
2093 1549
2094 The "fail_securely" p 1550 The "fail_securely" policy forces file signature
2095 verification failure 1551 verification failure also on privileged mounted
2096 filesystems with the 1552 filesystems with the SB_I_UNVERIFIABLE_SIGNATURE
2097 flag. 1553 flag.
2098 1554
2099 The "critical_data" p <<
2100 critical data. <<
2101 <<
2102 ima_tcb [IMA] Deprecated. Us 1555 ima_tcb [IMA] Deprecated. Use ima_policy= instead.
2103 Load a policy which m 1556 Load a policy which meets the needs of the Trusted
2104 Computing Base. This 1557 Computing Base. This means IMA will measure all
2105 programs exec'd, file 1558 programs exec'd, files mmap'd for exec, and all files
2106 opened for read by ui 1559 opened for read by uid=0.
2107 1560
2108 ima_template= [IMA] 1561 ima_template= [IMA]
2109 Select one of defined 1562 Select one of defined IMA measurements template formats.
2110 Formats: { "ima" | "i !! 1563 Formats: { "ima" | "ima-ng" | "ima-sig" }
2111 "ima-sigv2 <<
2112 Default: "ima-ng" 1564 Default: "ima-ng"
2113 1565
2114 ima_template_fmt= 1566 ima_template_fmt=
2115 [IMA] Define a custom 1567 [IMA] Define a custom template format.
2116 Format: { "field1|... 1568 Format: { "field1|...|fieldN" }
2117 1569
2118 ima.ahash_minsize= [IMA] Minimum file 1570 ima.ahash_minsize= [IMA] Minimum file size for asynchronous hash usage
2119 Format: <min_file_siz 1571 Format: <min_file_size>
2120 Set the minimal file 1572 Set the minimal file size for using asynchronous hash.
2121 If left unspecified, 1573 If left unspecified, ahash usage is disabled.
2122 1574
2123 ahash performance var 1575 ahash performance varies for different data sizes on
2124 different crypto acce 1576 different crypto accelerators. This option can be used
2125 to achieve the best p 1577 to achieve the best performance for a particular HW.
2126 1578
2127 ima.ahash_bufsize= [IMA] Asynchronous 1579 ima.ahash_bufsize= [IMA] Asynchronous hash buffer size
2128 Format: <bufsize> 1580 Format: <bufsize>
2129 Set hashing buffer si 1581 Set hashing buffer size. Default: 4k.
2130 1582
2131 ahash performance var 1583 ahash performance varies for different chunk sizes on
2132 different crypto acce 1584 different crypto accelerators. This option can be used
2133 to achieve best perfo 1585 to achieve best performance for particular HW.
2134 1586
2135 init= [KNL] 1587 init= [KNL]
2136 Format: <full_path> 1588 Format: <full_path>
2137 Run specified binary 1589 Run specified binary instead of /sbin/init as init
2138 process. 1590 process.
2139 1591
2140 initcall_debug [KNL] Trace initcalls 1592 initcall_debug [KNL] Trace initcalls as they are executed. Useful
2141 for working out where 1593 for working out where the kernel is dying during
2142 startup. 1594 startup.
2143 1595
2144 initcall_blacklist= [KNL] Do not exe 1596 initcall_blacklist= [KNL] Do not execute a comma-separated list of
2145 initcall functions. 1597 initcall functions. Useful for debugging built-in
2146 modules and initcalls 1598 modules and initcalls.
2147 1599
2148 initramfs_async= [KNL] !! 1600 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 1601
2174 init_on_free= [MM,EARLY] Fill freed !! 1602 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 1603 register contents for all processes. 0x55555554 by
2180 default (disallow acc 1604 default (disallow access to all but pkey 0). Can
2181 override in debugfs a 1605 override in debugfs after boot.
2182 1606
2183 inport.irq= [HW] Inport (ATI XL a 1607 inport.irq= [HW] Inport (ATI XL and Microsoft) busmouse driver
2184 Format: <irq> 1608 Format: <irq>
2185 1609
2186 int_pln_enable [X86] Enable power li !! 1610 int_pln_enable [x86] Enable power limit notification interrupt
2187 1611
2188 integrity_audit=[IMA] 1612 integrity_audit=[IMA]
2189 Format: { "0" | "1" } 1613 Format: { "0" | "1" }
2190 0 -- basic integrity 1614 0 -- basic integrity auditing messages. (Default)
2191 1 -- additional integ 1615 1 -- additional integrity auditing messages.
2192 1616
2193 intel_iommu= [DMAR] Intel IOMMU dr 1617 intel_iommu= [DMAR] Intel IOMMU driver (DMAR) option
2194 on 1618 on
2195 Enable intel iommu dr 1619 Enable intel iommu driver.
2196 off 1620 off
2197 Disable intel iommu d 1621 Disable intel iommu driver.
2198 igfx_off [Default Off] 1622 igfx_off [Default Off]
2199 By default, gfx is ma 1623 By default, gfx is mapped as normal device. If a gfx
2200 device has a dedicate 1624 device has a dedicated DMAR unit, the DMAR unit is
2201 bypassed by not enabl 1625 bypassed by not enabling DMAR with this option. In
2202 this case, gfx device 1626 this case, gfx device will use physical address for
2203 DMA. 1627 DMA.
>> 1628 forcedac [x86_64]
>> 1629 With this option iommu will not optimize to look
>> 1630 for io virtual address below 32-bit forcing dual
>> 1631 address cycle on pci bus for cards supporting greater
>> 1632 than 32-bit addressing. The default is to look
>> 1633 for translation below 32-bit and if not available
>> 1634 then look in the higher range.
2204 strict [Default Off] 1635 strict [Default Off]
2205 Deprecated, equivalen !! 1636 With this option on every unmap_single operation will
>> 1637 result in a hardware IOTLB flush operation as opposed
>> 1638 to batching them for performance.
2206 sp_off [Default Off] 1639 sp_off [Default Off]
2207 By default, super pag 1640 By default, super page will be supported if Intel IOMMU
2208 has the capability. W 1641 has the capability. With this option, super page will
2209 not be supported. 1642 not be supported.
2210 sm_on !! 1643 ecs_off [Default Off]
2211 Enable the Intel IOMM !! 1644 By default, extended context tables will be supported if
2212 advertises that it ha !! 1645 the hardware advertises that it has support both for the
2213 translation. !! 1646 extended tables themselves, and also PASID support. With
2214 sm_off !! 1647 this option set, extended tables will not be used even
2215 Disallow use of the I !! 1648 on hardware which claims to support them.
2216 tboot_noforce [Default Off] 1649 tboot_noforce [Default Off]
2217 Do not force the Inte 1650 Do not force the Intel IOMMU enabled under tboot.
2218 By default, tboot wil 1651 By default, tboot will force Intel IOMMU on, which
2219 could harm performanc 1652 could harm performance of some high-throughput
2220 devices like 40GBit n 1653 devices like 40GBit network cards, even if identity
2221 mapping is enabled. 1654 mapping is enabled.
2222 Note that using this 1655 Note that using this option lowers the security
2223 provided by tboot bec 1656 provided by tboot because it makes the system
2224 vulnerable to DMA att 1657 vulnerable to DMA attacks.
2225 1658
2226 intel_idle.max_cstate= [KNL,HW,ACPI, 1659 intel_idle.max_cstate= [KNL,HW,ACPI,X86]
2227 0 disables inte 1660 0 disables intel_idle and fall back on acpi_idle.
2228 1 to 9 specify maxim 1661 1 to 9 specify maximum depth of C-state.
2229 1662
2230 intel_pstate= [X86,EARLY] !! 1663 intel_pstate= [X86]
2231 disable 1664 disable
2232 Do not enable intel 1665 Do not enable intel_pstate as the default
2233 scaling driver for 1666 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 1667 passive
2245 Use intel_pstate as 1668 Use intel_pstate as a scaling driver, but configure it
2246 to work with generi 1669 to work with generic cpufreq governors (instead of
2247 enabling its intern 1670 enabling its internal governor). This mode cannot be
2248 used along with the 1671 used along with the hardware-managed P-states (HWP)
2249 feature. 1672 feature.
2250 force 1673 force
2251 Enable intel_pstate 1674 Enable intel_pstate on systems that prohibit it by default
2252 in favor of acpi-cp 1675 in favor of acpi-cpufreq. Forcing the intel_pstate driver
2253 instead of acpi-cpu 1676 instead of acpi-cpufreq may disable platform features, such
2254 as thermal controls 1677 as thermal controls and power capping, that rely on ACPI
2255 P-States informatio 1678 P-States information being indicated to OSPM and therefore
2256 should be used with 1679 should be used with caution. This option does not work with
2257 processors that are 1680 processors that aren't supported by the intel_pstate driver
2258 or on platforms tha 1681 or on platforms that use pcc-cpufreq instead of acpi-cpufreq.
2259 no_hwp 1682 no_hwp
2260 Do not enable hardw 1683 Do not enable hardware P state control (HWP)
2261 if available. 1684 if available.
2262 hwp_only 1685 hwp_only
2263 Only load intel_pst 1686 Only load intel_pstate on systems which support
2264 hardware P state co 1687 hardware P state control (HWP) if available.
2265 support_acpi_ppc 1688 support_acpi_ppc
2266 Enforce ACPI _PPC p 1689 Enforce ACPI _PPC performance limits. If the Fixed ACPI
2267 Description Table, 1690 Description Table, specifies preferred power management
2268 profile as "Enterpr 1691 profile as "Enterprise Server" or "Performance Server",
2269 then this feature i 1692 then this feature is turned on by default.
2270 per_cpu_perf_limits 1693 per_cpu_perf_limits
2271 Allow per-logical-C 1694 Allow per-logical-CPU P-State performance control limits using
2272 cpufreq sysfs inter 1695 cpufreq sysfs interface
2273 1696
2274 intremap= [X86-64,Intel-IOMMU,E !! 1697 intremap= [X86-64, Intel-IOMMU]
2275 on enable Interr 1698 on enable Interrupt Remapping (default)
2276 off disable Inter 1699 off disable Interrupt Remapping
2277 nosid disable Sourc 1700 nosid disable Source ID checking
2278 no_x2apic_optout 1701 no_x2apic_optout
2279 BIOS x2APIC o 1702 BIOS x2APIC opt-out request will be ignored
2280 nopost disable Inter 1703 nopost disable Interrupt Posting
2281 posted_msi <<
2282 enable MSIs d <<
2283 1704
2284 iomem= Disable strict checki 1705 iomem= Disable strict checking of access to MMIO memory
2285 strict regions from userspac 1706 strict regions from userspace.
2286 relaxed 1707 relaxed
2287 1708
2288 iommu= [X86,EARLY] !! 1709 iommu= [x86]
2289 off 1710 off
2290 force 1711 force
2291 noforce 1712 noforce
2292 biomerge 1713 biomerge
2293 panic 1714 panic
2294 nopanic 1715 nopanic
2295 merge 1716 merge
2296 nomerge 1717 nomerge
2297 soft 1718 soft
2298 pt [X86] !! 1719 pt [x86, IA-64]
2299 nopt [X86] <<
2300 nobypass [PPC/POWERNV] 1720 nobypass [PPC/POWERNV]
2301 Disable IOMMU bypass, 1721 Disable IOMMU bypass, using IOMMU for PCI devices.
2302 1722
2303 iommu.forcedac= [ARM64,X86,EARLY] Con <<
2304 Format: { "0" | "1" } <<
2305 0 - Try to allocate a <<
2306 falling back to the <<
2307 1 - Allocate directly <<
2308 forcing Dual Addres <<
2309 greater than 32-bit <<
2310 <<
2311 iommu.strict= [ARM64,X86,S390,EARLY <<
2312 Format: { "0" | "1" } <<
2313 0 - Lazy mode. <<
2314 Request that DMA un <<
2315 invalidation of har <<
2316 throughput at the c <<
2317 Will fall back to s <<
2318 the relevant IOMMU <<
2319 1 - Strict mode. <<
2320 DMA unmap operation <<
2321 synchronously. <<
2322 unset - Use value of <<
2323 Note: on x86, strict <<
2324 legacy driver-specifi <<
2325 <<
2326 iommu.passthrough= 1723 iommu.passthrough=
2327 [ARM64,X86,EARLY] Con !! 1724 [ARM64] Configure DMA to bypass the IOMMU by default.
2328 Format: { "0" | "1" } 1725 Format: { "0" | "1" }
2329 0 - Use IOMMU transla 1726 0 - Use IOMMU translation for DMA.
2330 1 - Bypass the IOMMU 1727 1 - Bypass the IOMMU for DMA.
2331 unset - Use value of !! 1728 unset - Use IOMMU translation for DMA.
2332 1729
2333 io7= [HW] IO7 for Marvel-b !! 1730 io7= [HW] IO7 for Marvel based alpha systems
2334 See comment before ma 1731 See comment before marvel_specify_io7 in
2335 arch/alpha/kernel/cor 1732 arch/alpha/kernel/core_marvel.c.
2336 1733
2337 io_delay= [X86,EARLY] I/O delay !! 1734 io_delay= [X86] I/O delay method
2338 0x80 1735 0x80
2339 Standard port 0x80 ba 1736 Standard port 0x80 based delay
2340 0xed 1737 0xed
2341 Alternate port 0xed b 1738 Alternate port 0xed based delay (needed on some systems)
2342 udelay 1739 udelay
2343 Simple two microsecon 1740 Simple two microseconds delay
2344 none 1741 none
2345 No delay 1742 No delay
2346 1743
2347 ip= [IP_PNP] 1744 ip= [IP_PNP]
2348 See Documentation/adm !! 1745 See Documentation/filesystems/nfs/nfsroot.txt.
2349 <<
2350 ipcmni_extend [KNL,EARLY] Extend th <<
2351 IPC identifiers from <<
2352 1746
2353 irqaffinity= [SMP] Set the default 1747 irqaffinity= [SMP] Set the default irq affinity mask
2354 The argument is a cpu 1748 The argument is a cpu list, as described above.
2355 1749
2356 irqchip.gicv2_force_probe= 1750 irqchip.gicv2_force_probe=
2357 [ARM,ARM64,EARLY] !! 1751 [ARM, ARM64]
2358 Format: <bool> 1752 Format: <bool>
2359 Force the kernel to l 1753 Force the kernel to look for the second 4kB page
2360 of a GICv2 controller 1754 of a GICv2 controller even if the memory range
2361 exposed by the device 1755 exposed by the device tree is too small.
2362 1756
2363 irqchip.gicv3_nolpi= 1757 irqchip.gicv3_nolpi=
2364 [ARM,ARM64,EARLY] !! 1758 [ARM, ARM64]
2365 Force the kernel to i 1759 Force the kernel to ignore the availability of
2366 LPIs (and by conseque 1760 LPIs (and by consequence ITSs). Intended for system
2367 that use the kernel a 1761 that use the kernel as a bootloader, and thus want
2368 to let secondary kern 1762 to let secondary kernels in charge of setting up
2369 LPIs. 1763 LPIs.
2370 1764
2371 irqchip.gicv3_pseudo_nmi= [ARM64,EARL <<
2372 Enables support for p <<
2373 requires the kernel t <<
2374 CONFIG_ARM64_PSEUDO_N <<
2375 <<
2376 irqfixup [HW] 1765 irqfixup [HW]
2377 When an interrupt is 1766 When an interrupt is not handled search all handlers
2378 for it. Intended to g 1767 for it. Intended to get systems with badly broken
2379 firmware running. 1768 firmware running.
2380 1769
2381 irqpoll [HW] 1770 irqpoll [HW]
2382 When an interrupt is 1771 When an interrupt is not handled search all handlers
2383 for it. Also check al 1772 for it. Also check all handlers each timer
2384 interrupt. Intended t 1773 interrupt. Intended to get systems with badly broken
2385 firmware running. 1774 firmware running.
2386 1775
2387 isapnp= [ISAPNP] 1776 isapnp= [ISAPNP]
2388 Format: <RDP>,<reset> 1777 Format: <RDP>,<reset>,<pci_scan>,<verbosity>
2389 1778
2390 isolcpus= [KNL,SMP,ISOL] Isolat 1779 isolcpus= [KNL,SMP,ISOL] Isolate a given set of CPUs from disturbance.
2391 [Deprecated - use cpu 1780 [Deprecated - use cpusets instead]
2392 Format: [flag-list,]< 1781 Format: [flag-list,]<cpu-list>
2393 1782
2394 Specify one or more C 1783 Specify one or more CPUs to isolate from disturbances
2395 specified in the flag 1784 specified in the flag list (default: domain):
2396 1785
2397 nohz 1786 nohz
2398 Disable the tick wh 1787 Disable the tick when a single task runs.
2399 1788
2400 A residual 1Hz tick 1789 A residual 1Hz tick is offloaded to workqueues, which you
2401 need to affine to h 1790 need to affine to housekeeping through the global
2402 workqueue's affinit 1791 workqueue's affinity configured via the
2403 /sys/devices/virtua 1792 /sys/devices/virtual/workqueue/cpumask sysfs file, or
2404 by using the 'domai 1793 by using the 'domain' flag described below.
2405 1794
2406 NOTE: by default th 1795 NOTE: by default the global workqueue runs on all CPUs,
2407 so to protect indiv 1796 so to protect individual CPUs the 'cpumask' file has to
2408 be configured manua 1797 be configured manually after bootup.
2409 1798
2410 domain 1799 domain
2411 Isolate from the ge 1800 Isolate from the general SMP balancing and scheduling
2412 algorithms. Note th 1801 algorithms. Note that performing domain isolation this way
2413 is irreversible: it 1802 is irreversible: it's not possible to bring back a CPU to
2414 the domains once is 1803 the domains once isolated through isolcpus. It's strongly
2415 advised to use cpus 1804 advised to use cpusets instead to disable scheduler load
2416 balancing through t 1805 balancing through the "cpuset.sched_load_balance" file.
2417 It offers a much mo 1806 It offers a much more flexible interface where CPUs can
2418 move in and out of 1807 move in and out of an isolated set anytime.
2419 1808
2420 You can move a proc 1809 You can move a process onto or off an "isolated" CPU via
2421 the CPU affinity sy 1810 the CPU affinity syscalls or cpuset.
2422 <cpu number> begins 1811 <cpu number> begins at 0 and the maximum value is
2423 "number of CPUs in 1812 "number of CPUs in system - 1".
2424 1813
2425 managed_irq !! 1814 The format of <cpu-list> is described above.
2426 1815
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 1816
2449 The format of <cpu-li <<
2450 1817
2451 iucv= [HW,NET] 1818 iucv= [HW,NET]
2452 1819
2453 ivrs_ioapic [HW,X86-64] !! 1820 ivrs_ioapic [HW,X86_64]
2454 Provide an override t 1821 Provide an override to the IOAPIC-ID<->DEVICE-ID
2455 mapping provided in t !! 1822 mapping provided in the IVRS ACPI table. For
2456 By default, PCI segme !! 1823 example, to map IOAPIC-ID decimal 10 to
2457 !! 1824 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 1825 ivrs_ioapic[10]=00:14.0
2467 * To map IOAPIC-ID de <<
2468 PCI device 00:14.0 <<
2469 ivrs_ioapic[1 <<
2470 1826
2471 ivrs_hpet [HW,X86-64] !! 1827 ivrs_hpet [HW,X86_64]
2472 Provide an override t 1828 Provide an override to the HPET-ID<->DEVICE-ID
2473 mapping provided in t !! 1829 mapping provided in the IVRS ACPI table. For
2474 By default, PCI segme !! 1830 example, to map HPET-ID decimal 0 to
2475 !! 1831 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]= 1832 ivrs_hpet[0]=00:14.0
2485 * To map HPET-ID deci <<
2486 PCI device 00:14.0 <<
2487 ivrs_ioapic[1 <<
2488 1833
2489 ivrs_acpihid [HW,X86-64] !! 1834 ivrs_acpihid [HW,X86_64]
2490 Provide an override t 1835 Provide an override to the ACPI-HID:UID<->DEVICE-ID
2491 mapping provided in t !! 1836 mapping provided in the IVRS ACPI table. For
2492 By default, PCI segme !! 1837 example, to map UART-HID:UID AMD0020:0 to
2493 !! 1838 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[ 1839 ivrs_acpihid[00:14.5]=AMD0020:0
2503 * To map UART-HID:UID <<
2504 PCI device ID 00:14 <<
2505 ivrs_acpihid[ <<
2506 1840
2507 js= [HW,JOY] Analog joyst 1841 js= [HW,JOY] Analog joystick
2508 See Documentation/inp 1842 See Documentation/input/joydev/joystick.rst.
2509 1843
>> 1844 nokaslr [KNL]
>> 1845 When CONFIG_RANDOMIZE_BASE is set, this disables
>> 1846 kernel and module base offset ASLR (Address Space
>> 1847 Layout Randomization).
>> 1848
2510 kasan_multi_shot 1849 kasan_multi_shot
2511 [KNL] Enforce KASAN ( 1850 [KNL] Enforce KASAN (Kernel Address Sanitizer) to print
2512 report on every inval 1851 report on every invalid memory access. Without this
2513 parameter KASAN will 1852 parameter KASAN will print report only for the first
2514 invalid access. 1853 invalid access.
2515 1854
2516 keep_bootcon [KNL,EARLY] !! 1855 keepinitrd [HW,ARM]
2517 Do not unregister boo <<
2518 useful for debugging <<
2519 between unregistering <<
2520 the real console. <<
2521 <<
2522 keepinitrd [HW,ARM] See retain_i <<
2523 1856
2524 kernelcore= [KNL,X86,PPC,EARLY] !! 1857 kernelcore= [KNL,X86,IA-64,PPC]
2525 Format: nn[KMGTPE] | 1858 Format: nn[KMGTPE] | nn% | "mirror"
2526 This parameter specif 1859 This parameter specifies the amount of memory usable by
2527 the kernel for non-mo 1860 the kernel for non-movable allocations. The requested
2528 amount is spread even 1861 amount is spread evenly throughout all nodes in the
2529 system as ZONE_NORMAL 1862 system as ZONE_NORMAL. The remaining memory is used for
2530 movable memory in its 1863 movable memory in its own zone, ZONE_MOVABLE. In the
2531 event, a node is too 1864 event, a node is too small to have both ZONE_NORMAL and
2532 ZONE_MOVABLE, kernelc 1865 ZONE_MOVABLE, kernelcore memory will take priority and
2533 other nodes will have 1866 other nodes will have a larger ZONE_MOVABLE.
2534 1867
2535 ZONE_MOVABLE is used 1868 ZONE_MOVABLE is used for the allocation of pages that
2536 may be reclaimed or m 1869 may be reclaimed or moved by the page migration
2537 subsystem. Note that 1870 subsystem. Note that allocations like PTEs-from-HighMem
2538 still use the HighMem 1871 still use the HighMem zone if it exists, and the Normal
2539 zone if it does not. 1872 zone if it does not.
2540 1873
2541 It is possible to spe 1874 It is possible to specify the exact amount of memory in
2542 the form of "nn[KMGTP 1875 the form of "nn[KMGTPE]", a percentage of total system
2543 memory in the form of 1876 memory in the form of "nn%", or "mirror". If "mirror"
2544 option is specified, 1877 option is specified, mirrored (reliable) memory is used
2545 for non-movable alloc 1878 for non-movable allocations and remaining memory is used
2546 for Movable pages. " 1879 for Movable pages. "nn[KMGTPE]", "nn%", and "mirror"
2547 are exclusive, so you 1880 are exclusive, so you cannot specify multiple forms.
2548 1881
2549 kgdbdbgp= [KGDB,HW,EARLY] kgdb !! 1882 kgdbdbgp= [KGDB,HW] kgdb over EHCI usb debug port.
2550 Format: <Controller#> 1883 Format: <Controller#>[,poll interval]
2551 The controller # is t 1884 The controller # is the number of the ehci usb debug
2552 port as it is probed 1885 port as it is probed via PCI. The poll interval is
2553 optional and is the n 1886 optional and is the number seconds in between
2554 each poll cycle to th 1887 each poll cycle to the debug port in case you need
2555 the functionality for 1888 the functionality for interrupting the kernel with
2556 gdb or control-c on t 1889 gdb or control-c on the dbgp connection. When
2557 not using this parame 1890 not using this parameter you use sysrq-g to break into
2558 the kernel debugger. 1891 the kernel debugger.
2559 1892
2560 kgdboc= [KGDB,HW] kgdb over c 1893 kgdboc= [KGDB,HW] kgdb over consoles.
2561 Requires a tty driver 1894 Requires a tty driver that supports console polling,
2562 or a supported pollin 1895 or a supported polling keyboard driver (non-usb).
2563 Serial only format: 1896 Serial only format: <serial_device>[,baud]
2564 keyboard only format 1897 keyboard only format: kbd
2565 keyboard and serial 1898 keyboard and serial format: kbd,<serial_device>[,baud]
2566 Optional Kernel mode 1899 Optional Kernel mode setting:
2567 kms, kbd format: kms 1900 kms, kbd format: kms,kbd
2568 kms, kbd and serial 1901 kms, kbd and serial format: kms,kbd,<ser_dev>[,baud]
2569 1902
2570 kgdboc_earlycon= [KGDB,HW,EARL !! 1903 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 1904 kernel debugger at the earliest opportunity.
2587 1905
2588 kmac= [MIPS] Korina etherne !! 1906 kmac= [MIPS] korina ethernet MAC address.
2589 Configure the RouterB 1907 Configure the RouterBoard 532 series on-chip
2590 Ethernet adapter MAC 1908 Ethernet adapter MAC address.
2591 1909
2592 kmemleak= [KNL,EARLY] Boot-time !! 1910 kmemleak= [KNL] Boot-time kmemleak enable/disable
2593 Valid arguments: on, 1911 Valid arguments: on, off
2594 Default: on 1912 Default: on
2595 Built with CONFIG_DEB 1913 Built with CONFIG_DEBUG_KMEMLEAK_DEFAULT_OFF=y,
2596 the default is off. 1914 the default is off.
2597 1915
2598 kprobe_event=[probe-list] <<
2599 [FTRACE] Add kprobe e <<
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 <<
2614 0: force disabled <<
2615 1: force enabled <<
2616 <<
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 1916 kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
2624 Default is 0 (don't i 1917 Default is 0 (don't ignore, but inject #GP)
2625 1918
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 1919 kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
2652 Default is 1920 Default is false (don't support).
2653 1921
2654 kvm.nx_huge_pages= !! 1922 kvm.mmu_audit= [KVM] This is a R/W parameter which allows audit
2655 [KVM] Controls the so !! 1923 KVM MMU at runtime.
2656 X86_BUG_ITLB_MULTIHIT !! 1924 Default is 0 (off)
2657 force : Always depl !! 1925
2658 off : Never deplo !! 1926 kvm-amd.nested= [KVM,AMD] Allow nested virtualization in KVM/SVM.
2659 auto : Deploy work !! 1927 Default is 1 (enabled)
2660 X86_BUG_ITL !! 1928
2661 !! 1929 kvm-amd.npt= [KVM,AMD] Disable nested paging (virtualized MMU)
2662 Default is 'auto'. !! 1930 for all guests.
2663 !! 1931 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 1932
2709 kvm-arm.vgic_v3_group0_trap= 1933 kvm-arm.vgic_v3_group0_trap=
2710 [KVM,ARM,EARLY] Trap !! 1934 [KVM,ARM] Trap guest accesses to GICv3 group-0
2711 system registers 1935 system registers
2712 1936
2713 kvm-arm.vgic_v3_group1_trap= 1937 kvm-arm.vgic_v3_group1_trap=
2714 [KVM,ARM,EARLY] Trap !! 1938 [KVM,ARM] Trap guest accesses to GICv3 group-1
2715 system registers 1939 system registers
2716 1940
2717 kvm-arm.vgic_v3_common_trap= 1941 kvm-arm.vgic_v3_common_trap=
2718 [KVM,ARM,EARLY] Trap !! 1942 [KVM,ARM] Trap guest accesses to GICv3 common
2719 system registers 1943 system registers
2720 1944
2721 kvm-arm.vgic_v4_enable= 1945 kvm-arm.vgic_v4_enable=
2722 [KVM,ARM,EARLY] Allow !! 1946 [KVM,ARM] Allow use of GICv4 for direct injection of
2723 injection of LPIs. !! 1947 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 1948
2751 kvm-intel.ept= [KVM,Intel] Control K !! 1949 kvm-intel.ept= [KVM,Intel] Disable extended page tables
2752 a.k.a. Two-Dimensiona !! 1950 (virtualized MMU) support on capable Intel chips.
2753 (enabled). Disable by !! 1951 Default is 1 (enabled)
2754 for EPT. <<
2755 1952
2756 kvm-intel.emulate_invalid_guest_state 1953 kvm-intel.emulate_invalid_guest_state=
2757 [KVM,Intel] Control w !! 1954 [KVM,Intel] Enable emulation of invalid guest states
2758 state. Ignored if kvm !! 1955 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 1956
2764 kvm-intel.flexpriority= 1957 kvm-intel.flexpriority=
2765 [KVM,Intel] Control K !! 1958 [KVM,Intel] Disable FlexPriority feature (TPR shadow).
2766 (TPR shadow). Default !! 1959 Default is 1 (enabled)
2767 hardware lacks suppor <<
2768 1960
2769 kvm-intel.nested= 1961 kvm-intel.nested=
2770 [KVM,Intel] Control n !! 1962 [KVM,Intel] Enable VMX nesting (nVMX).
2771 KVM/VMX. Default is 1 !! 1963 Default is 0 (disabled)
2772 1964
2773 kvm-intel.unrestricted_guest= 1965 kvm-intel.unrestricted_guest=
2774 [KVM,Intel] Control K !! 1966 [KVM,Intel] Disable unrestricted guest feature
2775 feature (virtualized !! 1967 (virtualized real and unpaged mode) on capable
2776 is 1 (enabled). Disab !! 1968 Intel chips. Default is 1 (enabled)
2777 hardware lacks suppor <<
2778 1969
2779 kvm-intel.vmentry_l1d_flush=[KVM,Inte 1970 kvm-intel.vmentry_l1d_flush=[KVM,Intel] Mitigation for L1 Terminal Fault
2780 CVE-2018-3620. 1971 CVE-2018-3620.
2781 1972
2782 Valid arguments: neve 1973 Valid arguments: never, cond, always
2783 1974
2784 always: L1D cache flu 1975 always: L1D cache flush on every VMENTER.
2785 cond: Flush L1D on 1976 cond: Flush L1D on VMENTER only when the code between
2786 VMEXIT and VM 1977 VMEXIT and VMENTER can leak host memory.
2787 never: Disables the 1978 never: Disables the mitigation
2788 1979
2789 Default is cond (do L 1980 Default is cond (do L1 cache flush in specific instances)
2790 1981
2791 kvm-intel.vpid= [KVM,Intel] Control K !! 1982 kvm-intel.vpid= [KVM,Intel] Disable Virtual Processor Identification
2792 Identification featur !! 1983 feature (tagged TLBs) on capable Intel chips.
2793 (enabled). Disable by !! 1984 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 1985
2813 l1tf= [X86,EARLY] Control m !! 1986 l1tf= [X86] Control mitigation of the L1TF vulnerability on
2814 affected CPUs 1987 affected CPUs
2815 1988
2816 The kernel PTE invers 1989 The kernel PTE inversion protection is unconditionally
2817 enabled and cannot be 1990 enabled and cannot be disabled.
2818 1991
2819 full 1992 full
2820 Provides all 1993 Provides all available mitigations for the
2821 L1TF vulnerab 1994 L1TF vulnerability. Disables SMT and
2822 enables all m 1995 enables all mitigations in the
2823 hypervisors, 1996 hypervisors, i.e. unconditional L1D flush.
2824 1997
2825 SMT control a 1998 SMT control and L1D flush control via the
2826 sysfs interfa 1999 sysfs interface is still possible after
2827 boot. Hyperv 2000 boot. Hypervisors will issue a warning
2828 when the firs 2001 when the first VM is started in a
2829 potentially i 2002 potentially insecure configuration,
2830 i.e. SMT enab 2003 i.e. SMT enabled or L1D flush disabled.
2831 2004
2832 full,force 2005 full,force
2833 Same as 'full 2006 Same as 'full', but disables SMT and L1D
2834 flush runtime 2007 flush runtime control. Implies the
2835 'nosmt=force' 2008 'nosmt=force' command line option.
2836 (i.e. sysfs c 2009 (i.e. sysfs control of SMT is disabled.)
2837 2010
2838 flush 2011 flush
2839 Leaves SMT en 2012 Leaves SMT enabled and enables the default
2840 hypervisor mi 2013 hypervisor mitigation, i.e. conditional
2841 L1D flush. 2014 L1D flush.
2842 2015
2843 SMT control a 2016 SMT control and L1D flush control via the
2844 sysfs interfa 2017 sysfs interface is still possible after
2845 boot. Hyperv 2018 boot. Hypervisors will issue a warning
2846 when the firs 2019 when the first VM is started in a
2847 potentially i 2020 potentially insecure configuration,
2848 i.e. SMT enab 2021 i.e. SMT enabled or L1D flush disabled.
2849 2022
2850 flush,nosmt 2023 flush,nosmt
2851 2024
2852 Disables SMT 2025 Disables SMT and enables the default
2853 hypervisor mi 2026 hypervisor mitigation.
2854 2027
2855 SMT control a 2028 SMT control and L1D flush control via the
2856 sysfs interfa 2029 sysfs interface is still possible after
2857 boot. Hyperv 2030 boot. Hypervisors will issue a warning
2858 when the firs 2031 when the first VM is started in a
2859 potentially i 2032 potentially insecure configuration,
2860 i.e. SMT enab 2033 i.e. SMT enabled or L1D flush disabled.
2861 2034
2862 flush,nowarn 2035 flush,nowarn
2863 Same as 'flus 2036 Same as 'flush', but hypervisors will not
2864 warn when a V 2037 warn when a VM is started in a potentially
2865 insecure conf 2038 insecure configuration.
2866 2039
2867 off 2040 off
2868 Disables hype 2041 Disables hypervisor mitigations and doesn't
2869 emit any warn 2042 emit any warnings.
2870 It also drops <<
2871 RAM limit res <<
2872 bare metal. <<
2873 2043
2874 Default is 'flush'. 2044 Default is 'flush'.
2875 2045
2876 For details see: Docu !! 2046 For details see: Documentation/admin-guide/l1tf.rst
2877 2047
2878 l2cr= [PPC] 2048 l2cr= [PPC]
2879 2049
2880 l3cr= [PPC] 2050 l3cr= [PPC]
2881 2051
2882 lapic [X86-32,APIC,EARLY] E !! 2052 lapic [X86-32,APIC] Enable the local APIC even if BIOS
2883 disabled it. 2053 disabled it.
2884 2054
2885 lapic= [X86,APIC] Do not use !! 2055 lapic= [x86,APIC] "notscdeadline" Do not use TSC deadline
2886 value for LAPIC timer 2056 value for LAPIC timer one-shot implementation. Default
2887 back to the programma 2057 back to the programmable timer unit in the LAPIC.
2888 Format: notscdeadline <<
2889 2058
2890 lapic_timer_c2_ok [X86,APIC,EAR !! 2059 lapic_timer_c2_ok [X86,APIC] trust the local apic timer
2891 in C2 power state. 2060 in C2 power state.
2892 2061
2893 libata.dma= [LIBATA] DMA control 2062 libata.dma= [LIBATA] DMA control
2894 libata.dma=0 Dis 2063 libata.dma=0 Disable all PATA and SATA DMA
2895 libata.dma=1 PAT 2064 libata.dma=1 PATA and SATA Disk DMA only
2896 libata.dma=2 ATA 2065 libata.dma=2 ATAPI (CDROM) DMA only
2897 libata.dma=4 Com 2066 libata.dma=4 Compact Flash DMA only
2898 Combinations also wor 2067 Combinations also work, so libata.dma=3 enables DMA
2899 for disks and CDROMs, 2068 for disks and CDROMs, but not CFs.
2900 2069
2901 libata.ignore_hpa= [LIBATA] Igno 2070 libata.ignore_hpa= [LIBATA] Ignore HPA limit
2902 libata.ignore_hpa=0 2071 libata.ignore_hpa=0 keep BIOS limits (default)
2903 libata.ignore_hpa=1 2072 libata.ignore_hpa=1 ignore limits, using full disk
2904 2073
2905 libata.noacpi [LIBATA] Disables use 2074 libata.noacpi [LIBATA] Disables use of ACPI in libata suspend/resume
2906 when set. 2075 when set.
2907 Format: <int> 2076 Format: <int>
2908 2077
2909 libata.force= [LIBATA] Force config !! 2078 libata.force= [LIBATA] Force configurations. The format is comma
2910 separated list of "[I !! 2079 separated list of "[ID:]VAL" where ID is
2911 PORT and DEVICE are d !! 2080 PORT[.DEVICE]. PORT and DEVICE are decimal numbers
2912 or device. Basically !! 2081 matching port, link or device. Basically, it matches
2913 printed on console by !! 2082 the ATA ID string printed on console by libata. If
2914 omitted, the last POR !! 2083 the whole ID part is omitted, the last PORT and DEVICE
2915 ID hasn't been specif !! 2084 values are used. If ID hasn't been specified yet, the
2916 to all ports, links a !! 2085 configuration applies to all ports, links and devices.
2917 2086
2918 If only DEVICE is omi 2087 If only DEVICE is omitted, the parameter applies to
2919 the port and all link 2088 the port and all links and devices behind it. DEVICE
2920 number of 0 either se 2089 number of 0 either selects the first device or the
2921 first fan-out link be 2090 first fan-out link behind PMP device. It does not
2922 select the host link. 2091 select the host link. DEVICE number of 15 selects the
2923 host link and device 2092 host link and device attached to it.
2924 2093
2925 The VAL specifies the 2094 The VAL specifies the configuration to force. As long
2926 as there is no ambigu !! 2095 as there's no ambiguity shortcut notation is allowed.
2927 For example, both 1.5 2096 For example, both 1.5 and 1.5G would work for 1.5Gbps.
2928 The following configu 2097 The following configurations can be forced.
2929 2098
2930 * Cable type: 40c, 80 2099 * Cable type: 40c, 80c, short40c, unk, ign or sata.
2931 Any ID with matchin 2100 Any ID with matching PORT is used.
2932 2101
2933 * SATA link speed lim 2102 * SATA link speed limit: 1.5Gbps or 3.0Gbps.
2934 2103
2935 * Transfer mode: pio[ 2104 * Transfer mode: pio[0-7], mwdma[0-4] and udma[0-7].
2936 udma[/][16,25,33,44 2105 udma[/][16,25,33,44,66,100,133] notation is also
2937 allowed. 2106 allowed.
2938 2107
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 2108 * [no]ncq: Turn on or off NCQ.
2950 2109
2951 * [no]ncqtrim: Enable !! 2110 * [no]ncqtrim: Turn off queued DSM TRIM.
2952 <<
2953 * [no]ncqati: Enable <<
2954 <<
2955 * [no]trim: Enable or <<
2956 <<
2957 * trim_zero: Indicate <<
2958 <<
2959 * max_trim_128m: Set <<
2960 <<
2961 * [no]dma: Turn on or <<
2962 <<
2963 * atapi_dmadir: Enabl <<
2964 <<
2965 * atapi_mod16_dma: En <<
2966 commands that are n <<
2967 <<
2968 * [no]dmalog: Enable <<
2969 READ LOG DMA EXT co <<
2970 2111
2971 * [no]iddevlog: Enabl !! 2112 * nohrst, nosrst, norst: suppress hard, soft
2972 identify device dat !! 2113 and both resets.
2973 2114
2974 * [no]logdir: Enable !! 2115 * rstonce: only attempt one reset during
2975 purpose log directo !! 2116 hot-unplug link recovery
2976 2117
2977 * max_sec_128: Set tr !! 2118 * dump_id: dump IDENTIFY data.
2978 2119
2979 * max_sec_1024: Set o !! 2120 * atapi_dmadir: Enable ATAPI DMADIR bridge support
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 2121
2995 * disable: Disable th 2122 * disable: Disable this device.
2996 2123
2997 If there are multiple 2124 If there are multiple matching configurations changing
2998 the same attribute, t 2125 the same attribute, the last one is used.
2999 2126
3000 load_ramdisk= [RAM] [Deprecated] !! 2127 memblock=debug [KNL] Enable memblock debug messages.
>> 2128
>> 2129 load_ramdisk= [RAM] List of ramdisks to load from floppy
>> 2130 See Documentation/blockdev/ramdisk.txt.
3001 2131
3002 lockd.nlm_grace_period=P [NFS] Assig 2132 lockd.nlm_grace_period=P [NFS] Assign grace period.
3003 Format: <integer> 2133 Format: <integer>
3004 2134
3005 lockd.nlm_tcpport=N [NFS] Assign 2135 lockd.nlm_tcpport=N [NFS] Assign TCP port.
3006 Format: <integer> 2136 Format: <integer>
3007 2137
3008 lockd.nlm_timeout=T [NFS] Assign 2138 lockd.nlm_timeout=T [NFS] Assign timeout value.
3009 Format: <integer> 2139 Format: <integer>
3010 2140
3011 lockd.nlm_udpport=M [NFS] Assign 2141 lockd.nlm_udpport=M [NFS] Assign UDP port.
3012 Format: <integer> 2142 Format: <integer>
3013 2143
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] 2144 locktorture.nreaders_stress= [KNL]
3056 Set the number of loc 2145 Set the number of locking read-acquisition kthreads.
3057 Defaults to being aut 2146 Defaults to being automatically set based on the
3058 number of online CPUs 2147 number of online CPUs.
3059 2148
3060 locktorture.nwriters_stress= [KNL] 2149 locktorture.nwriters_stress= [KNL]
3061 Set the number of loc 2150 Set the number of locking write-acquisition kthreads.
3062 2151
3063 locktorture.onoff_holdoff= [KNL] 2152 locktorture.onoff_holdoff= [KNL]
3064 Set time (s) after bo 2153 Set time (s) after boot for CPU-hotplug testing.
3065 2154
3066 locktorture.onoff_interval= [KNL] 2155 locktorture.onoff_interval= [KNL]
3067 Set time (s) between 2156 Set time (s) between CPU-hotplug operations, or
3068 zero to disable CPU-h 2157 zero to disable CPU-hotplug testing.
3069 2158
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] 2159 locktorture.shuffle_interval= [KNL]
3090 Set task-shuffle inte 2160 Set task-shuffle interval (jiffies). Shuffling
3091 tasks allows some CPU 2161 tasks allows some CPUs to go into dyntick-idle
3092 mode during the lockt 2162 mode during the locktorture test.
3093 2163
3094 locktorture.shutdown_secs= [KNL] 2164 locktorture.shutdown_secs= [KNL]
3095 Set time (s) after bo 2165 Set time (s) after boot system shutdown. This
3096 is useful for hands-o 2166 is useful for hands-off automated testing.
3097 2167
3098 locktorture.stat_interval= [KNL] 2168 locktorture.stat_interval= [KNL]
3099 Time (s) between stat 2169 Time (s) between statistics printk()s.
3100 2170
3101 locktorture.stutter= [KNL] 2171 locktorture.stutter= [KNL]
3102 Time (s) to stutter t 2172 Time (s) to stutter testing, for example,
3103 specifying five secon 2173 specifying five seconds causes the test to run for
3104 five seconds, wait fo 2174 five seconds, wait for five seconds, and so on.
3105 This tests the lockin 2175 This tests the locking primitive's ability to
3106 transition abruptly t 2176 transition abruptly to and from idle.
3107 2177
3108 locktorture.torture_type= [KNL] 2178 locktorture.torture_type= [KNL]
3109 Specify the locking i 2179 Specify the locking implementation to test.
3110 2180
3111 locktorture.verbose= [KNL] 2181 locktorture.verbose= [KNL]
3112 Enable additional pri 2182 Enable additional printk() statements.
3113 2183
3114 locktorture.writer_fifo= [KNL] <<
3115 Run the write-side lo <<
3116 sched_set_fifo() real <<
3117 <<
3118 logibm.irq= [HW,MOUSE] Logitech B 2184 logibm.irq= [HW,MOUSE] Logitech Bus Mouse Driver
3119 Format: <irq> 2185 Format: <irq>
3120 2186
3121 loglevel= [KNL,EARLY] !! 2187 loglevel= All Kernel Messages with a loglevel smaller than the
3122 All Kernel Messages w <<
3123 console loglevel will 2188 console loglevel will be printed to the console. It can
3124 also be changed with 2189 also be changed with klogd or other programs. The
3125 loglevels are defined 2190 loglevels are defined as follows:
3126 2191
3127 0 (KERN_EMERG) 2192 0 (KERN_EMERG) system is unusable
3128 1 (KERN_ALERT) 2193 1 (KERN_ALERT) action must be taken immediately
3129 2 (KERN_CRIT) 2194 2 (KERN_CRIT) critical conditions
3130 3 (KERN_ERR) 2195 3 (KERN_ERR) error conditions
3131 4 (KERN_WARNING) 2196 4 (KERN_WARNING) warning conditions
3132 5 (KERN_NOTICE) 2197 5 (KERN_NOTICE) normal but significant condition
3133 6 (KERN_INFO) 2198 6 (KERN_INFO) informational
3134 7 (KERN_DEBUG) 2199 7 (KERN_DEBUG) debug-level messages
3135 2200
3136 log_buf_len=n[KMG] [KNL,EARLY] !! 2201 log_buf_len=n[KMG] Sets the size of the printk ring buffer,
3137 Sets the size of the !! 2202 in bytes. n must be a power of two and greater
3138 n must be a power of !! 2203 than the minimal size. The minimal size is defined
3139 minimal size. The min !! 2204 by LOG_BUF_SHIFT kernel config parameter. There is
3140 LOG_BUF_SHIFT kernel !! 2205 also CONFIG_LOG_CPU_MAX_BUF_SHIFT config parameter
3141 is also CONFIG_LOG_CP !! 2206 that allows to increase the default size depending on
3142 parameter that allows !! 2207 the number of CPUs. See init/Kconfig for more details.
3143 depending on the numb <<
3144 for more details. <<
3145 2208
3146 logo.nologo [FB] Disables display 2209 logo.nologo [FB] Disables display of the built-in Linux logo.
3147 This may be used to p 2210 This may be used to provide more screen space for
3148 kernel log messages a 2211 kernel log messages and is useful when debugging
3149 kernel boot problems. 2212 kernel boot problems.
3150 2213
3151 lp=0 [LP] Specify paral 2214 lp=0 [LP] Specify parallel ports to use, e.g,
3152 lp=port[,port...] lp=none,parpo 2215 lp=port[,port...] lp=none,parport0 (lp0 not configured, lp1 uses
3153 lp=reset first paralle 2216 lp=reset first parallel port). 'lp=0' disables the
3154 lp=auto printer drive 2217 lp=auto printer driver. 'lp=reset' (which can be
3155 specified in 2218 specified in addition to the ports) causes
3156 attached prin 2219 attached printers to be reset. Using
3157 lp=port1,port 2220 lp=port1,port2,... specifies the parallel ports
3158 to associate 2221 to associate lp devices with, starting with
3159 lp0. A port s 2222 lp0. A port specification may be 'none' to skip
3160 that lp devic 2223 that lp device, or a parport name such as
3161 'parport0'. S 2224 'parport0'. Specifying 'lp=auto' instead of a
3162 port specific 2225 port specification list means that device IDs
3163 from each por 2226 from each port should be examined, to see if
3164 an IEEE 1284- 2227 an IEEE 1284-compliant printer is attached; if
3165 so, the drive 2228 so, the driver will manage that printer.
3166 See also head 2229 See also header of drivers/char/lp.c.
3167 2230
3168 lpj=n [KNL] 2231 lpj=n [KNL]
3169 Sets loops_per_jiffy 2232 Sets loops_per_jiffy to given constant, thus avoiding
3170 time-consuming boot-t 2233 time-consuming boot-time autodetection (up to 250 ms per
3171 CPU). 0 enables autod 2234 CPU). 0 enables autodetection (default). To determine
3172 the correct value for 2235 the correct value for your kernel, boot with normal
3173 autodetection and see 2236 autodetection and see what value is printed. Note that
3174 on SMP systems the pr 2237 on SMP systems the preset will be applied to all CPUs,
3175 which is likely to ca 2238 which is likely to cause problems if your CPUs need
3176 significantly diverge 2239 significantly divergent settings. An incorrect value
3177 will cause delays in 2240 will cause delays in the kernel to be wrong, leading to
3178 unpredictable I/O err 2241 unpredictable I/O errors and other breakage. Although
3179 unlikely, in the extr 2242 unlikely, in the extreme case this might damage your
3180 hardware. 2243 hardware.
3181 2244
3182 lsm.debug [SECURITY] Enable LSM !! 2245 ltpc= [NET]
>> 2246 Format: <io>,<irq>,<dma>
3183 2247
3184 lsm=lsm1,...,lsmN !! 2248 machvec= [IA-64] Force the use of a particular machine-vector
3185 [SECURITY] Choose ord !! 2249 (machvec) in a generic kernel.
3186 overrides CONFIG_LSM, !! 2250 Example: machvec=hpzx1_swiotlb
3187 2251
3188 machtype= [Loongson] Share the !! 2252 machtype= [Loongson] Share the same kernel image file between different
3189 different yeeloong la !! 2253 yeeloong laptop.
3190 Example: machtype=lem 2254 Example: machtype=lemote-yeeloong-2f-7inch
3191 2255
3192 maxcpus= [SMP,EARLY] Maximum n !! 2256 max_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory greater
>> 2257 than or equal to this physical address is ignored.
>> 2258
>> 2259 maxcpus= [SMP] Maximum number of processors that an SMP kernel
3193 will bring up during 2260 will bring up during bootup. maxcpus=n : n >= 0 limits
3194 the kernel to bring u 2261 the kernel to bring up 'n' processors. Surely after
3195 bootup you can bring 2262 bootup you can bring up the other plugged cpu by executing
3196 "echo 1 > /sys/device 2263 "echo 1 > /sys/devices/system/cpu/cpuX/online". So maxcpus
3197 only takes effect dur 2264 only takes effect during system bootup.
3198 While n=0 is a specia 2265 While n=0 is a special case, it is equivalent to "nosmp",
3199 which also disables t 2266 which also disables the IO APIC.
3200 2267
3201 max_loop= [LOOP] The number of 2268 max_loop= [LOOP] The number of loop block devices that get
3202 (loop.max_loop) unconditionally pre-c 2269 (loop.max_loop) unconditionally pre-created at init time. The default
3203 number is configured 2270 number is configured by BLK_DEV_LOOP_MIN_COUNT. Instead
3204 of statically allocat 2271 of statically allocating a predefined number, loop
3205 devices can be reques 2272 devices can be requested on-demand with the
3206 /dev/loop-control int 2273 /dev/loop-control interface.
3207 2274
3208 mce [X86-32] Machine Chec 2275 mce [X86-32] Machine Check Exception
3209 2276
3210 mce=option [X86-64] See Document !! 2277 mce=option [X86-64] See Documentation/x86/x86_64/boot-options.txt
3211 2278
3212 md= [HW] RAID subsystems 2279 md= [HW] RAID subsystems devices and level
3213 See Documentation/adm 2280 See Documentation/admin-guide/md.rst.
3214 2281
3215 mdacon= [MDA] 2282 mdacon= [MDA]
3216 Format: <first>,<last 2283 Format: <first>,<last>
3217 Specifies range of co 2284 Specifies range of consoles to be captured by the MDA.
3218 2285
3219 mds= [X86,INTEL,EARLY] !! 2286 mem=nn[KMG] [KNL,BOOT] Force usage of a specific amount of memory
3220 Control mitigation fo !! 2287 Amount of memory to be used when the kernel is not able
3221 Sampling (MDS) vulner !! 2288 to see the whole system memory or for test.
3222 <<
3223 Certain CPUs are vuln <<
3224 internal buffers whic <<
3225 disclosure gadget und <<
3226 <<
3227 In vulnerable process <<
3228 forwarded data can be <<
3229 attack, to access dat <<
3230 not have direct acces <<
3231 <<
3232 This parameter contro <<
3233 options are: <<
3234 <<
3235 full - Enable M <<
3236 full,nosmt - Enable M <<
3237 SMT on v <<
3238 off - Uncondit <<
3239 <<
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 <<
3247 mds=full. <<
3248 <<
3249 For details see: Docu <<
3250 <<
3251 mem=nn[KMG] [HEXAGON,EARLY] Set t <<
3252 Must be specified, ot <<
3253 <<
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 2289 [X86] Work as limiting max address. Use together
3271 with memmap= to avoid 2290 with memmap= to avoid physical address space collisions.
3272 Without memmap= PCI d 2291 Without memmap= PCI devices could be placed at addresses
3273 belonging to unused R 2292 belonging to unused RAM.
3274 2293
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 2294 mem=nopentium [BUGS=X86-32] Disable usage of 4MB pages for kernel
3288 memory. 2295 memory.
3289 2296
3290 memblock=debug [KNL,EARLY] Enable me <<
3291 <<
3292 memchunk=nn[KMG] 2297 memchunk=nn[KMG]
3293 [KNL,SH] Allow user t 2298 [KNL,SH] Allow user to override the default size for
3294 per-device physically 2299 per-device physically contiguous DMA buffers.
3295 2300
3296 memhp_default_state=online/offline/on !! 2301 memhp_default_state=online/offline
3297 [KNL] Set the initial 2302 [KNL] Set the initial state for the memory hotplug
3298 onlining policy. If n 2303 onlining policy. If not specified, the default value is
3299 set according to the 2304 set according to the
3300 CONFIG_MEMORY_HOTPLUG 2305 CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE kernel config
3301 option. 2306 option.
3302 See Documentation/adm !! 2307 See Documentation/memory-hotplug.txt.
3303 2308
3304 memmap=exactmap [KNL,X86,EARLY] Enabl !! 2309 memmap=exactmap [KNL,X86] Enable setting of an exact
3305 E820 memory map, as s 2310 E820 memory map, as specified by the user.
3306 Such memmap=exactmap 2311 Such memmap=exactmap lines can be constructed based on
3307 BIOS output or other 2312 BIOS output or other requirements. See the memmap=nn@ss
3308 option description. 2313 option description.
3309 2314
3310 memmap=nn[KMG]@ss[KMG] 2315 memmap=nn[KMG]@ss[KMG]
3311 [KNL, X86,MIPS,XTENSA !! 2316 [KNL] Force usage of a specific region of memory.
3312 Region of memory to b 2317 Region of memory to be used is from ss to ss+nn.
3313 If @ss[KMG] is omitte 2318 If @ss[KMG] is omitted, it is equivalent to mem=nn[KMG],
3314 which limits max addr 2319 which limits max address to nn[KMG].
3315 Multiple different re 2320 Multiple different regions can be specified,
3316 comma delimited. 2321 comma delimited.
3317 Example: 2322 Example:
3318 memmap=100M@2 2323 memmap=100M@2G,100M#3G,1G!1024G
3319 2324
3320 memmap=nn[KMG]#ss[KMG] 2325 memmap=nn[KMG]#ss[KMG]
3321 [KNL,ACPI,EARLY] Mark !! 2326 [KNL,ACPI] Mark specific memory as ACPI data.
3322 Region of memory to b 2327 Region of memory to be marked is from ss to ss+nn.
3323 2328
3324 memmap=nn[KMG]$ss[KMG] 2329 memmap=nn[KMG]$ss[KMG]
3325 [KNL,ACPI,EARLY] Mark !! 2330 [KNL,ACPI] Mark specific memory as reserved.
3326 Region of memory to b 2331 Region of memory to be reserved is from ss to ss+nn.
3327 Example: Exclude memo 2332 Example: Exclude memory from 0x18690000-0x1869ffff
3328 memmap=64K$0 2333 memmap=64K$0x18690000
3329 or 2334 or
3330 memmap=0x100 2335 memmap=0x10000$0x18690000
3331 Some bootloaders may 2336 Some bootloaders may need an escape character before '$',
3332 like Grub2, otherwise 2337 like Grub2, otherwise '$' and the following number
3333 will be eaten. 2338 will be eaten.
3334 2339
3335 memmap=nn[KMG]!ss[KMG,EARLY] !! 2340 memmap=nn[KMG]!ss[KMG]
3336 [KNL,X86] Mark specif 2341 [KNL,X86] Mark specific memory as protected.
3337 Region of memory to b 2342 Region of memory to be used, from ss to ss+nn.
3338 The memory region may 2343 The memory region may be marked as e820 type 12 (0xc)
3339 and is NVDIMM or ADR 2344 and is NVDIMM or ADR memory.
3340 2345
3341 memmap=<size>%<offset>-<oldtype>+<new 2346 memmap=<size>%<offset>-<oldtype>+<newtype>
3342 [KNL,ACPI,EARLY] Conv !! 2347 [KNL,ACPI] Convert memory within the specified region
3343 from <oldtype> to <ne 2348 from <oldtype> to <newtype>. If "-<oldtype>" is left
3344 out, the whole region 2349 out, the whole region will be marked as <newtype>,
3345 even if previously un 2350 even if previously unavailable. If "+<newtype>" is left
3346 out, matching memory 2351 out, matching memory will be removed. Types are
3347 specified as e820 typ 2352 specified as e820 types, e.g., 1 = RAM, 2 = reserved,
3348 3 = ACPI, 12 = PRAM. 2353 3 = ACPI, 12 = PRAM.
3349 2354
3350 memory_corruption_check=0/1 [X86,EARL !! 2355 memory_corruption_check=0/1 [X86]
3351 Some BIOSes seem to c 2356 Some BIOSes seem to corrupt the first 64k of
3352 memory when doing thi 2357 memory when doing things like suspend/resume.
3353 Setting this option w 2358 Setting this option will scan the memory
3354 looking for corruptio 2359 looking for corruption. Enabling this will
3355 both detect corruptio 2360 both detect corruption and prevent the kernel
3356 from using the memory 2361 from using the memory being corrupted.
3357 However, its intended 2362 However, its intended as a diagnostic tool; if
3358 repeatable BIOS-origi 2363 repeatable BIOS-originated corruption always
3359 affects the same memo 2364 affects the same memory, you can use memmap=
3360 to prevent the kernel 2365 to prevent the kernel from using that memory.
3361 2366
3362 memory_corruption_check_size=size [X8 !! 2367 memory_corruption_check_size=size [X86]
3363 By default it checks 2368 By default it checks for corruption in the low
3364 64k, making this memo 2369 64k, making this memory unavailable for normal
3365 use. Use this parame 2370 use. Use this parameter to scan for
3366 corruption in more or 2371 corruption in more or less memory.
3367 2372
3368 memory_corruption_check_period=second !! 2373 memory_corruption_check_period=seconds [X86]
3369 By default it checks 2374 By default it checks for corruption every 60
3370 seconds. Use this pa 2375 seconds. Use this parameter to check at some
3371 other rate. 0 disabl 2376 other rate. 0 disables periodic checking.
3372 2377
3373 memory_hotplug.memmap_on_memory !! 2378 memtest= [KNL,X86,ARM] Enable memtest
3374 [KNL,X86,ARM] Boolean <<
3375 Format: {on | off (de <<
3376 When enabled, runtime <<
3377 allocate its internal <<
3378 those vmemmap pages c <<
3379 if hugetlb_free_vmemm <<
3380 hotadded memory which <<
3381 lot of memory without <<
3382 memory to do so. <<
3383 This feature is disab <<
3384 has some implication <<
3385 allocations in some c <<
3386 memory blocks). <<
3387 The state of the flag <<
3388 /sys/module/memory_ho <<
3389 Note that even when e <<
3390 the feature is not ef <<
3391 <<
3392 memtest= [KNL,X86,ARM,M68K,PPC <<
3393 Format: <integer> 2379 Format: <integer>
3394 default : 0 <disable> 2380 default : 0 <disable>
3395 Specifies the number 2381 Specifies the number of memtest passes to be
3396 performed. Each pass 2382 performed. Each pass selects another test
3397 pattern from a given 2383 pattern from a given set of patterns. Memtest
3398 fills the memory with 2384 fills the memory with this pattern, validates
3399 memory contents and r 2385 memory contents and reserves bad memory
3400 regions that are dete 2386 regions that are detected.
3401 2387
3402 mem_encrypt= [X86-64] AMD Secure M 2388 mem_encrypt= [X86-64] AMD Secure Memory Encryption (SME) control
3403 Valid arguments: on, 2389 Valid arguments: on, off
3404 Default: off !! 2390 Default (depends on kernel configuration option):
>> 2391 on (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=y)
>> 2392 off (CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT=n)
3405 mem_encrypt=on: 2393 mem_encrypt=on: Activate SME
3406 mem_encrypt=off: 2394 mem_encrypt=off: Do not activate SME
3407 2395
3408 Refer to Documentatio !! 2396 Refer to Documentation/x86/amd-memory-encryption.txt
3409 for details on when m 2397 for details on when memory encryption can be activated.
3410 2398
3411 mem_sleep_default= [SUSPEND] Def 2399 mem_sleep_default= [SUSPEND] Default system suspend mode:
3412 s2idle - Suspend-To- 2400 s2idle - Suspend-To-Idle
3413 shallow - Power-On Su 2401 shallow - Power-On Suspend or equivalent (if supported)
3414 deep - Suspend-To- 2402 deep - Suspend-To-RAM or equivalent (if supported)
3415 See Documentation/adm 2403 See Documentation/admin-guide/pm/sleep-states.rst.
3416 2404
>> 2405 meye.*= [HW] Set MotionEye Camera parameters
>> 2406 See Documentation/media/v4l-drivers/meye.rst.
>> 2407
>> 2408 mfgpt_irq= [IA-32] Specify the IRQ to use for the
>> 2409 Multi-Function General Purpose Timers on AMD Geode
>> 2410 platforms.
>> 2411
3417 mfgptfix [X86-32] Fix MFGPT ti 2412 mfgptfix [X86-32] Fix MFGPT timers on AMD Geode platforms when
3418 the BIOS has incorrec 2413 the BIOS has incorrectly applied a workaround. TinyBIOS
3419 version 0.98 is known 2414 version 0.98 is known to be affected, 0.99 fixes the
3420 problem by letting th 2415 problem by letting the user disable the workaround.
3421 2416
3422 mga= [HW,DRM] 2417 mga= [HW,DRM]
3423 2418
3424 microcode.force_minrev= [X86] !! 2419 min_addr=nn[KMG] [KNL,BOOT,ia64] All physical memory below this
3425 Format: <bool> !! 2420 physical address is ignored.
3426 Enable or disable the <<
3427 enforcement for the r <<
3428 2421
3429 mini2440= [ARM,HW,KNL] 2422 mini2440= [ARM,HW,KNL]
3430 Format:[0..2][b][c][t 2423 Format:[0..2][b][c][t]
3431 Default: "0tb" 2424 Default: "0tb"
3432 MINI2440 configuratio 2425 MINI2440 configuration specification:
3433 0 - The attached scre 2426 0 - The attached screen is the 3.5" TFT
3434 1 - The attached scre 2427 1 - The attached screen is the 7" TFT
3435 2 - The VGA Shield is 2428 2 - The VGA Shield is attached (1024x768)
3436 Leaving out the scree 2429 Leaving out the screen size parameter will not load
3437 the TFT driver, and t 2430 the TFT driver, and the framebuffer will be left
3438 unconfigured. 2431 unconfigured.
3439 b - Enable backlight. 2432 b - Enable backlight. The TFT backlight pin will be
3440 linked to the kernel 2433 linked to the kernel VESA blanking code and a GPIO
3441 LED. This parameter i 2434 LED. This parameter is not necessary when using the
3442 VGA shield. 2435 VGA shield.
3443 c - Enable the s3c ca 2436 c - Enable the s3c camera interface.
3444 t - Reserved for enab 2437 t - Reserved for enabling touchscreen support. The
3445 touchscreen support i 2438 touchscreen support is not enabled in the mainstream
3446 kernel as of 2.6.30, 2439 kernel as of 2.6.30, a preliminary port can be found
3447 in the "bleeding edge 2440 in the "bleeding edge" mini2440 support kernel at
3448 https://repo.or.cz/w/ !! 2441 http://repo.or.cz/w/linux-2.6/mini2440.git
3449 <<
3450 mitigations= <<
3451 [X86,PPC,S390,ARM64,E <<
3452 CPU vulnerabilities. <<
3453 arch-independent opti <<
3454 aggregation of existi <<
3455 <<
3456 Note, "mitigations" i <<
3457 kernel was built with <<
3458 <<
3459 off <<
3460 Disable all o <<
3461 improves syst <<
3462 expose users <<
3463 Equivalent to <<
3464 <<
3465 <<
3466 <<
3467 <<
3468 <<
3469 <<
3470 <<
3471 <<
3472 <<
3473 <<
3474 <<
3475 <<
3476 <<
3477 <<
3478 <<
3479 <<
3480 <<
3481 <<
3482 <<
3483 <<
3484 <<
3485 <<
3486 Exceptions: <<
3487 <<
3488 <<
3489 <<
3490 <<
3491 auto (default) <<
3492 Mitigate all <<
3493 enabled, even <<
3494 users who don <<
3495 getting disab <<
3496 have other wa <<
3497 Equivalent to <<
3498 <<
3499 auto,nosmt <<
3500 Mitigate all <<
3501 if needed. T <<
3502 be fully miti <<
3503 Equivalent to <<
3504 <<
3505 <<
3506 <<
3507 <<
3508 2442
3509 mminit_loglevel= 2443 mminit_loglevel=
3510 [KNL,EARLY] When CONF !! 2444 [KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this
3511 parameter allows cont 2445 parameter allows control of the logging verbosity for
3512 the additional memory 2446 the additional memory initialisation checks. A value
3513 of 0 disables mminit 2447 of 0 disables mminit logging and a level of 4 will
3514 log everything. Infor 2448 log everything. Information is printed at KERN_DEBUG
3515 so loglevel=8 may als 2449 so loglevel=8 may also need to be specified.
3516 2450
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 2451 module.sig_enforce
3574 [KNL] When CONFIG_MOD 2452 [KNL] When CONFIG_MODULE_SIG is set, this means that
3575 modules without (vali 2453 modules without (valid) signatures will fail to load.
3576 Note that if CONFIG_M 2454 Note that if CONFIG_MODULE_SIG_FORCE is set, that
3577 is always true, so th 2455 is always true, so this option does nothing.
3578 2456
3579 module_blacklist= [KNL] Do not load 2457 module_blacklist= [KNL] Do not load a comma-separated list of
3580 modules. Useful for 2458 modules. Useful for debugging problem modules.
3581 2459
3582 mousedev.tap_time= 2460 mousedev.tap_time=
3583 [MOUSE] Maximum time 2461 [MOUSE] Maximum time between finger touching and
3584 leaving touchpad surf 2462 leaving touchpad surface for touch to be considered
3585 a tap and be reported 2463 a tap and be reported as a left button click (for
3586 touchpads working in 2464 touchpads working in absolute mode only).
3587 Format: <msecs> 2465 Format: <msecs>
3588 mousedev.xres= [MOUSE] Horizontal sc 2466 mousedev.xres= [MOUSE] Horizontal screen resolution, used for devices
3589 reporting absolute co 2467 reporting absolute coordinates, such as tablets
3590 mousedev.yres= [MOUSE] Vertical scre 2468 mousedev.yres= [MOUSE] Vertical screen resolution, used for devices
3591 reporting absolute co 2469 reporting absolute coordinates, such as tablets
3592 2470
3593 movablecore= [KNL,X86,PPC,EARLY] !! 2471 movablecore= [KNL,X86,IA-64,PPC]
3594 Format: nn[KMGTPE] | 2472 Format: nn[KMGTPE] | nn%
3595 This parameter is the 2473 This parameter is the complement to kernelcore=, it
3596 specifies the amount 2474 specifies the amount of memory used for migratable
3597 allocations. If both 2475 allocations. If both kernelcore and movablecore is
3598 specified, then kerne 2476 specified, then kernelcore will be at *least* the
3599 specified value but m 2477 specified value but may be more. If movablecore on its
3600 own is specified, the 2478 own is specified, the administrator must be careful
3601 that the amount of me 2479 that the amount of memory usable for all allocations
3602 is not too small. 2480 is not too small.
3603 2481
3604 movable_node [KNL,EARLY] Boot-time !! 2482 movable_node [KNL] Boot-time switch to make hotplugable memory
3605 NUMA nodes to be mova 2483 NUMA nodes to be movable. This means that the memory
3606 of such nodes will be 2484 of such nodes will be usable only for movable
3607 allocations which rul 2485 allocations which rules out almost all kernel
3608 allocations. Use with 2486 allocations. Use with caution!
3609 2487
3610 MTD_Partition= [MTD] 2488 MTD_Partition= [MTD]
3611 Format: <name>,<regio 2489 Format: <name>,<region-number>,<size>,<offset>
3612 2490
3613 MTD_Region= [MTD] Format: 2491 MTD_Region= [MTD] Format:
3614 <name>,<region-number 2492 <name>,<region-number>[,<base>,<size>,<buswidth>,<altbuswidth>]
3615 2493
3616 mtdparts= [MTD] 2494 mtdparts= [MTD]
3617 See drivers/mtd/parse !! 2495 See drivers/mtd/cmdlinepart.c.
>> 2496
>> 2497 multitce=off [PPC] This parameter disables the use of the pSeries
>> 2498 firmware feature for updating multiple TCE entries
>> 2499 at a time.
>> 2500
>> 2501 onenand.bdry= [HW,MTD] Flex-OneNAND Boundary Configuration
>> 2502
>> 2503 Format: [die0_boundary][,die0_lock][,die1_boundary][,die1_lock]
>> 2504
>> 2505 boundary - index of last SLC block on Flex-OneNAND.
>> 2506 The remaining blocks are configured as MLC blocks.
>> 2507 lock - Configure if Flex-OneNAND boundary should be locked.
>> 2508 Once locked, the boundary cannot be changed.
>> 2509 1 indicates lock status, 0 indicates unlock status.
>> 2510
>> 2511 mtdset= [ARM]
>> 2512 ARM/S3C2412 JIVE boot control
>> 2513
>> 2514 See arch/arm/mach-s3c2412/mach-jive.c
3618 2515
3619 mtouchusb.raw_coordinates= 2516 mtouchusb.raw_coordinates=
3620 [HW] Make the MicroTo 2517 [HW] Make the MicroTouch USB driver use raw coordinates
3621 ('y', default) or coo 2518 ('y', default) or cooked coordinates ('n')
3622 2519
3623 mtrr=debug [X86,EARLY] !! 2520 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 2521 used for mtrr cleanup. It is largest continuous chunk
3629 that could hold holes 2522 that could hold holes aka. UC entries.
3630 2523
3631 mtrr_gran_size=nn[KMG,X86,EARLY] !! 2524 mtrr_gran_size=nn[KMG] [X86]
3632 Used for mtrr cleanup 2525 Used for mtrr cleanup. It is granularity of mtrr block.
3633 Default is 1. 2526 Default is 1.
3634 Large value could pre 2527 Large value could prevent small alignment from
3635 using up MTRRs. 2528 using up MTRRs.
3636 2529
3637 mtrr_spare_reg_nr=n [X86,EARLY] !! 2530 mtrr_spare_reg_nr=n [X86]
3638 Format: <integer> 2531 Format: <integer>
3639 Range: 0,7 : spare re 2532 Range: 0,7 : spare reg number
3640 Default : 1 2533 Default : 1
3641 Used for mtrr cleanup 2534 Used for mtrr cleanup. It is spare mtrr entries number.
3642 Set to 2 or more if y 2535 Set to 2 or more if your graphical card needs more.
3643 2536
3644 multitce=off [PPC] This parameter <<
3645 firmware feature for <<
3646 at a time. <<
3647 <<
3648 n2= [NET] SDL Inc. RISCom 2537 n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
3649 2538
3650 netdev= [NET] Network devices 2539 netdev= [NET] Network devices parameters
3651 Format: <irq>,<io>,<m 2540 Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
3652 Note that mem_start i 2541 Note that mem_start is often overloaded to mean
3653 something different a 2542 something different and driver-specific.
3654 This usage is only do 2543 This usage is only documented in each driver source
3655 file if at all. 2544 file if at all.
3656 2545
3657 netpoll.carrier_timeout= <<
3658 [NET] Specifies amoun <<
3659 netpoll should wait f <<
3660 waits 4 seconds. <<
3661 <<
3662 nf_conntrack.acct= 2546 nf_conntrack.acct=
3663 [NETFILTER] Enable co 2547 [NETFILTER] Enable connection tracking flow accounting
3664 0 to disable accounti 2548 0 to disable accounting
3665 1 to enable accountin 2549 1 to enable accounting
3666 Default value is 0. 2550 Default value is 0.
3667 2551
3668 nfs.cache_getent= !! 2552 nfsaddrs= [NFS] Deprecated. Use ip= instead.
3669 [NFS] sets the pathna !! 2553 See Documentation/filesystems/nfs/nfsroot.txt.
3670 to update the NFS cli <<
3671 2554
3672 nfs.cache_getent_timeout= !! 2555 nfsroot= [NFS] nfs root filesystem for disk-less boxes.
3673 [NFS] sets the timeou !! 2556 See Documentation/filesystems/nfs/nfsroot.txt.
3674 update a cache entry !! 2557
>> 2558 nfsrootdebug [NFS] enable nfsroot debugging messages.
>> 2559 See Documentation/filesystems/nfs/nfsroot.txt.
3675 2560
3676 nfs.callback_nr_threads= 2561 nfs.callback_nr_threads=
3677 [NFSv4] set the total 2562 [NFSv4] set the total number of threads that the
3678 NFS client will assig 2563 NFS client will assign to service NFSv4 callback
3679 requests. 2564 requests.
3680 2565
3681 nfs.callback_tcpport= 2566 nfs.callback_tcpport=
3682 [NFS] set the TCP por 2567 [NFS] set the TCP port on which the NFSv4 callback
3683 channel should listen 2568 channel should listen.
3684 2569
3685 nfs.delay_retrans= !! 2570 nfs.cache_getent=
3686 [NFS] specifies the n !! 2571 [NFS] sets the pathname to the program which is used
3687 retries the request b !! 2572 to update the NFS client cache entries.
3688 after a reply of NFS4 !! 2573
3689 Only applies if the s !! 2574 nfs.cache_getent_timeout=
3690 and the specified val !! 2575 [NFS] sets the timeout after which an attempt to
>> 2576 update a cache entry is deemed to have failed.
>> 2577
>> 2578 nfs.idmap_cache_timeout=
>> 2579 [NFS] set the maximum lifetime for idmapper cache
>> 2580 entries.
3691 2581
3692 nfs.enable_ino64= 2582 nfs.enable_ino64=
3693 [NFS] enable 64-bit i 2583 [NFS] enable 64-bit inode numbers.
3694 If zero, the NFS clie 2584 If zero, the NFS client will fake up a 32-bit inode
3695 number for the readdi 2585 number for the readdir() and stat() syscalls instead
3696 of returning the full 2586 of returning the full 64-bit number.
3697 The default is to ret 2587 The default is to return 64-bit inode numbers.
3698 2588
3699 nfs.idmap_cache_timeout= <<
3700 [NFS] set the maximum <<
3701 entries. <<
3702 <<
3703 nfs.max_session_cb_slots= 2589 nfs.max_session_cb_slots=
3704 [NFSv4.1] Sets the ma 2590 [NFSv4.1] Sets the maximum number of session
3705 slots the client will 2591 slots the client will assign to the callback
3706 channel. This determi 2592 channel. This determines the maximum number of
3707 callbacks the client 2593 callbacks the client will process in parallel for
3708 a particular server. 2594 a particular server.
3709 2595
3710 nfs.max_session_slots= 2596 nfs.max_session_slots=
3711 [NFSv4.1] Sets the ma 2597 [NFSv4.1] Sets the maximum number of session slots
3712 the client will attem 2598 the client will attempt to negotiate with the server.
3713 This limits the numbe 2599 This limits the number of simultaneous RPC requests
3714 that the client can s 2600 that the client can send to the NFSv4.1 server.
3715 Note that there is li 2601 Note that there is little point in setting this
3716 value higher than the 2602 value higher than the max_tcp_slot_table_limit.
3717 2603
3718 nfs.nfs4_disable_idmapping= 2604 nfs.nfs4_disable_idmapping=
3719 [NFSv4] When set to t 2605 [NFSv4] When set to the default of '1', this option
3720 ensures that both the 2606 ensures that both the RPC level authentication
3721 scheme and the NFS le 2607 scheme and the NFS level operations agree to use
3722 numeric uids/gids if 2608 numeric uids/gids if the mount is using the
3723 'sec=sys' security fl 2609 'sec=sys' security flavour. In effect it is
3724 disabling idmapping, 2610 disabling idmapping, which can make migration from
3725 legacy NFSv2/v3 syste 2611 legacy NFSv2/v3 systems to NFSv4 easier.
3726 Servers that do not s 2612 Servers that do not support this mode of operation
3727 will be autodetected 2613 will be autodetected by the client, and it will fall
3728 back to using the idm 2614 back to using the idmapper.
3729 To turn off this beha 2615 To turn off this behaviour, set the value to '0'.
3730 <<
3731 nfs.nfs4_unique_id= 2616 nfs.nfs4_unique_id=
3732 [NFS4] Specify an add 2617 [NFS4] Specify an additional fixed unique ident-
3733 ification string that 2618 ification string that NFSv4 clients can insert into
3734 their nfs_client_id4 2619 their nfs_client_id4 string. This is typically a
3735 UUID that is generate 2620 UUID that is generated at system install time.
3736 2621
3737 nfs.recover_lost_locks= !! 2622 nfs.send_implementation_id =
>> 2623 [NFSv4.1] Send client implementation identification
>> 2624 information in exchange_id requests.
>> 2625 If zero, no implementation identification information
>> 2626 will be sent.
>> 2627 The default is to send the implementation identification
>> 2628 information.
>> 2629
>> 2630 nfs.recover_lost_locks =
3738 [NFSv4] Attempt to re 2631 [NFSv4] Attempt to recover locks that were lost due
3739 to a lease timeout on 2632 to a lease timeout on the server. Please note that
3740 doing this risks data 2633 doing this risks data corruption, since there are
3741 no guarantees that th 2634 no guarantees that the file will remain unchanged
3742 after the locks are l 2635 after the locks are lost.
3743 If you want to enable 2636 If you want to enable the kernel legacy behaviour of
3744 attempting to recover 2637 attempting to recover these locks, then set this
3745 parameter to '1'. 2638 parameter to '1'.
3746 The default parameter 2639 The default parameter value of '0' causes the kernel
3747 not to attempt recove 2640 not to attempt recovery of lost locks.
3748 2641
3749 nfs.send_implementation_id= !! 2642 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 2643 [NFSv4.2] Change the rate at which the kernel sends
3759 layoutstats to the pN 2644 layoutstats to the pNFS metadata server.
3760 2645
3761 Setting this to value 2646 Setting this to value to 0 causes the kernel to use
3762 whatever value is the 2647 whatever value is the default set by the layout
3763 driver. A non-zero va 2648 driver. A non-zero value sets the minimum interval
3764 in seconds between la 2649 in seconds between layoutstats transmissions.
3765 2650
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= 2651 nfsd.nfs4_disable_idmapping=
3772 [NFSv4] When set to t 2652 [NFSv4] When set to the default of '1', the NFSv4
3773 server will return on 2653 server will return only numeric uids and gids to
3774 clients using auth_sy 2654 clients using auth_sys, and will accept numeric uids
3775 and gids from such cl 2655 and gids from such clients. This is intended to ease
3776 migration from NFSv2/ 2656 migration from NFSv2/v3.
3777 2657
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 2658 nmi_debug= [KNL,SH] Specify one or more actions to take
3800 when a NMI is trigger 2659 when a NMI is triggered.
3801 Format: [state][,regs 2660 Format: [state][,regs][,debounce][,die]
3802 2661
3803 nmi_watchdog= [KNL,BUGS=X86] Debugg 2662 nmi_watchdog= [KNL,BUGS=X86] Debugging features for SMP kernels
3804 Format: [panic,][nopa !! 2663 Format: [panic,][nopanic,][num]
3805 Valid num: 0 or 1 2664 Valid num: 0 or 1
3806 0 - turn hardlockup d 2665 0 - turn hardlockup detector in nmi_watchdog off
3807 1 - turn hardlockup d 2666 1 - turn hardlockup detector in nmi_watchdog on
3808 rNNN - configure the <<
3809 <<
3810 When panic is specifi 2667 When panic is specified, panic when an NMI watchdog
3811 timeout occurs (or 'n !! 2668 timeout occurs (or 'nopanic' to override the opposite
3812 watchdog, if CONFIG_B !! 2669 default). To disable both hard and soft lockup detectors,
3813 To disable both hard <<
3814 please see 'nowatchdo 2670 please see 'nowatchdog'.
3815 This is useful when y 2671 This is useful when you use a panic=... timeout and
3816 need the box quickly 2672 need the box quickly up again.
3817 2673
3818 These settings can be 2674 These settings can be accessed at runtime via
3819 the nmi_watchdog and 2675 the nmi_watchdog and hardlockup_panic sysctls.
3820 2676
>> 2677 netpoll.carrier_timeout=
>> 2678 [NET] Specifies amount of time (in seconds) that
>> 2679 netpoll should wait for a carrier. By default netpoll
>> 2680 waits 4 seconds.
>> 2681
3821 no387 [BUGS=X86-32] Tells t 2682 no387 [BUGS=X86-32] Tells the kernel to use the 387 maths
3822 emulation library eve 2683 emulation library even if a 387 maths coprocessor
3823 is present. 2684 is present.
3824 2685
3825 no4lvl [RISCV,EARLY] Disable !! 2686 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 2687 kernel to use 4-level paging instead.
3830 2688
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 2689 no_console_suspend
3841 [HW] Never suspend th 2690 [HW] Never suspend the console
3842 Disable suspending of 2691 Disable suspending of consoles during suspend and
3843 hibernate operations. 2692 hibernate operations. Once disabled, debugging
3844 messages can reach va 2693 messages can reach various consoles while the rest
3845 of the system is bein 2694 of the system is being put to sleep (ie, while
3846 debugging driver susp 2695 debugging driver suspend/resume hooks). This may
3847 not work reliably wit 2696 not work reliably with all consoles, but is known
3848 to work with serial a 2697 to work with serial and VGA consoles.
3849 To facilitate more fl 2698 To facilitate more flexible debugging, we also add
3850 console_suspend, a pr 2699 console_suspend, a printk module parameter to control
3851 it. Users could use c 2700 it. Users could use console_suspend (usually
3852 /sys/module/printk/pa 2701 /sys/module/printk/parameters/console_suspend) to
3853 turn on/off it dynami 2702 turn on/off it dynamically.
3854 2703
3855 no_debug_objects !! 2704 noaliencache [MM, NUMA, SLAB] Disables the allocation of alien
3856 [KNL,EARLY] Disable o !! 2705 caches in the slab allocator. Saves per-node memory,
>> 2706 but will impact performance.
>> 2707
>> 2708 noalign [KNL,ARM]
>> 2709
>> 2710 noaltinstr [S390] Disables alternative instructions patching
>> 2711 (CPU alternatives feature).
>> 2712
>> 2713 noapic [SMP,APIC] Tells the kernel to not make use of any
>> 2714 IOAPICs that may be present in the system.
>> 2715
>> 2716 noautogroup Disable scheduler automatic task group creation.
>> 2717
>> 2718 nobats [PPC] Do not use BATs for mapping kernel lowmem
>> 2719 on "Classic" PPC cores.
>> 2720
>> 2721 nocache [ARM]
>> 2722
>> 2723 noclflush [BUGS=X86] Don't use the CLFLUSH instruction
>> 2724
>> 2725 nodelayacct [KNL] Disable per-task delay accounting
3857 2726
3858 nodsp [SH] Disable hardware 2727 nodsp [SH] Disable hardware DSP at boot time.
3859 2728
3860 noefi [EFI,EARLY] Disable E !! 2729 noefi Disable EFI runtime services support.
3861 2730
3862 no_entry_flush [PPC,EARLY] Don't flu !! 2731 noexec [IA-64]
>> 2732
>> 2733 noexec [X86]
>> 2734 On X86-32 available only on PAE configured kernels.
>> 2735 noexec=on: enable non-executable mappings (default)
>> 2736 noexec=off: disable non-executable mappings
>> 2737
>> 2738 nosmap [X86]
>> 2739 Disable SMAP (Supervisor Mode Access Prevention)
>> 2740 even if it is supported by processor.
>> 2741
>> 2742 nosmep [X86]
>> 2743 Disable SMEP (Supervisor Mode Execution Prevention)
>> 2744 even if it is supported by processor.
3863 2745
3864 noexec32 [X86-64] 2746 noexec32 [X86-64]
3865 This affects only 32- 2747 This affects only 32-bit executables.
3866 noexec32=on: enable n 2748 noexec32=on: enable non-executable mappings (default)
3867 read doesn't 2749 read doesn't imply executable mappings
3868 noexec32=off: disable 2750 noexec32=off: disable non-executable mappings
3869 read implies 2751 read implies executable mappings
3870 2752
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 2753 nofpu [MIPS,SH] Disable hardware FPU at boot time.
3876 2754
3877 nofsgsbase [X86] Disables FSGSBA <<
3878 <<
3879 nofxsr [BUGS=X86-32] Disable 2755 nofxsr [BUGS=X86-32] Disables x86 floating point extended
3880 register save and res 2756 register save and restore. The kernel will only save
3881 legacy floating-point 2757 legacy floating-point registers on task switch.
3882 2758
3883 no_hash_pointers !! 2759 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 2760
3898 nohibernate [HIBERNATION] Disable !! 2761 nosmt [KNL,S390] Disable symmetric multithreading (SMT).
>> 2762 Equivalent to smt=1.
>> 2763
>> 2764 [KNL,x86] Disable symmetric multithreading (SMT).
>> 2765 nosmt=force: Force disable SMT, cannot be undone
>> 2766 via the sysfs control file.
>> 2767
>> 2768 nospectre_v2 [X86] Disable all mitigations for the Spectre variant 2
>> 2769 (indirect branch prediction) vulnerability. System may
>> 2770 allow data leaks with this option, which is equivalent
>> 2771 to spectre_v2=off.
>> 2772
>> 2773 nospec_store_bypass_disable
>> 2774 [HW] Disable all mitigations for the Speculative Store Bypass vulnerability
>> 2775
>> 2776 noxsave [BUGS=X86] Disables x86 extended register state save
>> 2777 and restore using xsave. The kernel will fallback to
>> 2778 enabling legacy floating-point and sse state.
3899 2779
3900 nohlt [ARM,ARM64,MICROBLAZE !! 2780 noxsaveopt [X86] Disables xsaveopt used in saving x86 extended
3901 busy wait in do_idle( !! 2781 register states. The kernel will fall back to use
3902 implementation; requi !! 2782 xsave to save the states. By using this parameter,
3903 to be effective. This !! 2783 performance of saving the states is degraded because
3904 sleep(SH) or wfi(ARM, !! 2784 xsave doesn't support modified optimization while
3905 correctly or when doi !! 2785 xsaveopt supports it on xsaveopt enabled systems.
3906 the impact of the sle <<
3907 useful when using JTA <<
3908 2786
3909 nohugeiomap [KNL,X86,PPC,ARM64,EA !! 2787 noxsaves [X86] Disables xsaves and xrstors used in saving and
>> 2788 restoring x86 extended register state in compacted
>> 2789 form of xsave area. The kernel will fall back to use
>> 2790 xsaveopt and xrstor to save and restore the states
>> 2791 in standard form of xsave area. By using this
>> 2792 parameter, xsave area per process might occupy more
>> 2793 memory on xsaves enabled systems.
3910 2794
3911 nohugevmalloc [KNL,X86,PPC,ARM64,EA !! 2795 nohlt [BUGS=ARM,SH] Tells the kernel that the sleep(SH) or
>> 2796 wfi(ARM) instruction doesn't work correctly and not to
>> 2797 use it. This is also useful when using JTAG debugger.
>> 2798
>> 2799 no_file_caps Tells the kernel not to honor file capabilities. The
>> 2800 only way then for a file to be executed with privilege
>> 2801 is to be setuid root or executed by root.
>> 2802
>> 2803 nohalt [IA-64] Tells the kernel not to use the power saving
>> 2804 function PAL_HALT_LIGHT when idle. This increases
>> 2805 power-consumption. On the positive side, it reduces
>> 2806 interrupt wake-up latency, which may improve performance
>> 2807 in certain environments such as networked servers or
>> 2808 real-time systems.
>> 2809
>> 2810 nohibernate [HIBERNATION] Disable hibernation and resume.
3912 2811
3913 nohz= [KNL] Boottime enable 2812 nohz= [KNL] Boottime enable/disable dynamic ticks
3914 Valid arguments: on, 2813 Valid arguments: on, off
3915 Default: on 2814 Default: on
3916 2815
3917 nohz_full= [KNL,BOOT,SMP,ISOL] 2816 nohz_full= [KNL,BOOT,SMP,ISOL]
3918 The argument is a cpu 2817 The argument is a cpu list, as described above.
3919 In kernels built with 2818 In kernels built with CONFIG_NO_HZ_FULL=y, set
3920 the specified list of 2819 the specified list of CPUs whose tick will be stopped
3921 whenever possible. Th 2820 whenever possible. The boot CPU will be forced outside
3922 the range to maintain 2821 the range to maintain the timekeeping. Any CPUs
3923 in this list will hav 2822 in this list will have their RCU callbacks offloaded,
3924 just as if they had a 2823 just as if they had also been called out in the
3925 rcu_nocbs= boot param 2824 rcu_nocbs= boot parameter.
3926 2825
3927 Note that this argume !! 2826 noiotrap [SH] Disables trapped I/O port accesses.
3928 the CONFIG_RCU_NOCB_C !! 2827
>> 2828 noirqdebug [X86-32] Disables the code which attempts to detect and
>> 2829 disable unhandled interrupt sources.
>> 2830
>> 2831 no_timer_check [X86,APIC] Disables the code which tests for
>> 2832 broken timer IRQ sources.
>> 2833
>> 2834 noisapnp [ISAPNP] Disables ISA PnP code.
3929 2835
3930 noinitrd [RAM] Tells the kerne 2836 noinitrd [RAM] Tells the kernel not to load any configured
3931 initial RAM disk. 2837 initial RAM disk.
3932 2838
3933 nointremap [X86-64,Intel-IOMMU,E !! 2839 nointremap [X86-64, Intel-IOMMU] Do not enable interrupt
3934 remapping. 2840 remapping.
3935 [Deprecated - use int 2841 [Deprecated - use intremap=off]
3936 2842
3937 noinvpcid [X86,EARLY] Disable t !! 2843 nointroute [IA-64]
3938 2844
3939 noiotrap [SH] Disables trapped !! 2845 noinvpcid [X86] Disable the INVPCID cpu feature.
3940 2846
3941 noirqdebug [X86-32] Disables the !! 2847 nojitter [IA-64] Disables jitter checking for ITC timers.
3942 disable unhandled int <<
3943 2848
3944 noisapnp [ISAPNP] Disables ISA !! 2849 no-kvmclock [X86,KVM] Disable paravirtualized KVM clock driver
3945 <<
3946 nokaslr [KNL,EARLY] <<
3947 When CONFIG_RANDOMIZE <<
3948 kernel and module bas <<
3949 Layout Randomization) <<
3950 2850
3951 no-kvmapf [X86,KVM,EARLY] Disab !! 2851 no-kvmapf [X86,KVM] Disable paravirtualized asynchronous page
3952 fault handling. 2852 fault handling.
3953 2853
3954 no-kvmclock [X86,KVM,EARLY] Disab !! 2854 no-vmw-sched-clock
>> 2855 [X86,PV_OPS] Disable paravirtualized VMware scheduler
>> 2856 clock and use the default one.
>> 2857
>> 2858 no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
>> 2859 steal time is computed, but won't influence scheduler
>> 2860 behaviour
>> 2861
>> 2862 nolapic [X86-32,APIC] Do not enable or use the local APIC.
3955 2863
3956 nolapic [X86-32,APIC,EARLY] D !! 2864 nolapic_timer [X86-32,APIC] Do not use the local APIC timer.
3957 2865
3958 nolapic_timer [X86-32,APIC,EARLY] D !! 2866 noltlbs [PPC] Do not use large page/tlb entries for kernel
>> 2867 lowmem mapping on PPC40x and PPC8xx
>> 2868
>> 2869 nomca [IA-64] Disable machine check abort handling
3959 2870
3960 nomce [X86-32] Disable Mach 2871 nomce [X86-32] Disable Machine Check Exception
3961 2872
3962 nomfgpt [X86-32] Disable Mult 2873 nomfgpt [X86-32] Disable Multi-Function General Purpose
3963 Timer usage (for AMD 2874 Timer usage (for AMD Geode machines).
3964 2875
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 2876 nonmi_ipi [X86] Disable using NMI IPIs during panic/reboot to
3978 shutdown the other cp 2877 shutdown the other cpus. Instead use the REBOOT_VECTOR
3979 irq. 2878 irq.
3980 2879
3981 nopat [X86,EARLY] Disable P !! 2880 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 2881
3989 nopti [X86-64,EARLY] !! 2882 nopat [X86] Disable PAT (page attribute table extension of
3990 Equivalent to pti=off !! 2883 pagetables) support.
3991 2884
3992 nopv= [X86,XEN,KVM,HYPER_V, !! 2885 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 2886
4002 norandmaps Don't use address spa 2887 norandmaps Don't use address space randomization. Equivalent to
4003 echo 0 > /proc/sys/ke 2888 echo 0 > /proc/sys/kernel/randomize_va_space
4004 2889
4005 noreplace-smp [X86-32,SMP] Don't re 2890 noreplace-smp [X86-32,SMP] Don't replace SMP instructions
4006 with UP alternatives 2891 with UP alternatives
4007 2892
>> 2893 nordrand [X86] Disable kernel use of the RDRAND and
>> 2894 RDSEED instructions even if they are supported
>> 2895 by the processor. RDRAND and RDSEED are still
>> 2896 available to user space applications.
>> 2897
4008 noresume [SWSUSP] Disables res 2898 noresume [SWSUSP] Disables resume and restores original swap
4009 space. 2899 space.
4010 2900
4011 no-scroll [VGA] Disables scroll 2901 no-scroll [VGA] Disables scrollback.
4012 This is required for 2902 This is required for the Braillex ib80-piezo Braille
4013 reader made by F.H. P 2903 reader made by F.H. Papenmeier (Germany).
4014 2904
4015 nosgx [X86-64,SGX,EARLY] Di !! 2905 nosbagart [IA-64]
4016 2906
4017 nosmap [PPC,EARLY] !! 2907 nosep [BUGS=X86-32] Disables x86 SYSENTER/SYSEXIT support.
4018 Disable SMAP (Supervi <<
4019 even if it is support <<
4020 <<
4021 nosmep [PPC64s,EARLY] <<
4022 Disable SMEP (Supervi <<
4023 even if it is support <<
4024 2908
4025 nosmp [SMP,EARLY] Tells an !! 2909 nosmp [SMP] Tells an SMP kernel to act as a UP kernel,
4026 and disable the IO AP 2910 and disable the IO APIC. legacy for "maxcpus=0".
4027 2911
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 2912 nosoftlockup [KNL] Disable the soft-lockup detector.
4036 2913
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 2914 nosync [HW,M68K] Disables sync negotiation for all devices.
4059 2915
4060 no_timer_check [X86,APIC] Disables t !! 2916 notsc [BUGS=X86-32] Disable Time Stamp Counter
4061 broken timer IRQ sour <<
4062 <<
4063 no_uaccess_flush <<
4064 [PPC,EARLY] Don't flu <<
4065 <<
4066 novmcoredd [KNL,KDUMP] <<
4067 Disable device dump. <<
4068 append dump data to v <<
4069 specified debug info. <<
4070 without any limit and <<
4071 so this may cause sig <<
4072 device dump can help <<
4073 data will be no longe <<
4074 is only available whe <<
4075 is set. <<
4076 <<
4077 no-vmw-sched-clock <<
4078 [X86,PV_OPS,EARLY] Di <<
4079 scheduler clock and u <<
4080 2917
4081 nowatchdog [KNL] Disable both lo 2918 nowatchdog [KNL] Disable both lockup detectors, i.e.
4082 soft-lockup and NMI w 2919 soft-lockup and NMI watchdog (hard-lockup).
4083 2920
4084 nowb [ARM,EARLY] !! 2921 nowb [ARM]
4085 <<
4086 nox2apic [X86-64,APIC,EARLY] D <<
4087 2922
4088 NOTE: this parameter !! 2923 nox2apic [X86-64,APIC] Do not enable x2APIC mode.
4089 LEGACY_XAPIC_DISABLED <<
4090 IA32_XAPIC_DISABLE_ST <<
4091 2924
4092 noxsave [BUGS=X86] Disables x !! 2925 cpu0_hotplug [X86] Turn on CPU0 hotplug feature when
4093 and restore using xsa !! 2926 CONFIG_BOOTPARAM_HOTPLUG_CPU0 is off.
4094 enabling legacy float !! 2927 Some features depend on CPU0. Known dependencies are:
>> 2928 1. Resume from suspend/hibernate depends on CPU0.
>> 2929 Suspend/hibernate will fail if CPU0 is offline and you
>> 2930 need to online CPU0 before suspend/hibernate.
>> 2931 2. PIC interrupts also depend on CPU0. CPU0 can't be
>> 2932 removed if a PIC interrupt is detected.
>> 2933 It's said poweroff/reboot may depend on CPU0 on some
>> 2934 machines although I haven't seen such issues so far
>> 2935 after CPU0 is offline on a few tested machines.
>> 2936 If the dependencies are under your control, you can
>> 2937 turn on cpu0_hotplug.
>> 2938
>> 2939 nps_mtm_hs_ctr= [KNL,ARC]
>> 2940 This parameter sets the maximum duration, in
>> 2941 cycles, each HW thread of the CTOP can run
>> 2942 without interruptions, before HW switches it.
>> 2943 The actual maximum duration is 16 times this
>> 2944 parameter's value.
>> 2945 Format: integer between 1 and 255
>> 2946 Default: 255
>> 2947
>> 2948 nptcg= [IA-64] Override max number of concurrent global TLB
>> 2949 purges which is reported from either PAL_VM_SUMMARY or
>> 2950 SAL PALO.
4095 2951
4096 noxsaveopt [X86] Disables xsaveo !! 2952 nr_cpus= [SMP] Maximum number of processors that an SMP kernel
4097 register states. The <<
4098 xsave to save the sta <<
4099 performance of saving <<
4100 xsave doesn't support <<
4101 xsaveopt supports it <<
4102 <<
4103 noxsaves [X86] Disables xsaves <<
4104 restoring x86 extende <<
4105 form of xsave area. T <<
4106 xsaveopt and xrstor t <<
4107 in standard form of x <<
4108 parameter, xsave area <<
4109 memory on xsaves enab <<
4110 <<
4111 nr_cpus= [SMP,EARLY] Maximum n <<
4112 could support. nr_cp 2953 could support. nr_cpus=n : n >= 1 limits the kernel to
4113 support 'n' processor 2954 support 'n' processors. It could be larger than the
4114 number of already plu 2955 number of already plugged CPU during bootup, later in
4115 runtime you can physi 2956 runtime you can physically add extra cpu until it reaches
4116 n. So during boot up 2957 n. So during boot up some boot time memory for per-cpu
4117 variables need be pre 2958 variables need be pre-allocated for later physical cpu
4118 hot plugging. 2959 hot plugging.
4119 2960
4120 nr_uarts= [SERIAL] maximum numb 2961 nr_uarts= [SERIAL] maximum number of UARTs to be registered.
4121 2962
4122 numa=off [KNL, ARM64, PPC, RIS !! 2963 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 2964 Allowed values are enable and disable
4129 2965
4130 numa_zonelist_order= [KNL, BOOT] Sele 2966 numa_zonelist_order= [KNL, BOOT] Select zonelist order for NUMA.
4131 'node', 'default' can 2967 'node', 'default' can be specified
4132 This can be set from 2968 This can be set from sysctl after boot.
4133 See Documentation/adm !! 2969 See Documentation/sysctl/vm.txt for details.
4134 2970
4135 ohci1394_dma=early [HW,EARLY] en !! 2971 ohci1394_dma=early [HW] enable debugging via the ohci1394 driver.
4136 See Documentation/cor !! 2972 See Documentation/debugging-via-ohci1394.txt for more
4137 info. 2973 info.
4138 2974
4139 olpc_ec_timeout= [OLPC] ms delay when 2975 olpc_ec_timeout= [OLPC] ms delay when issuing EC commands
4140 Rather than timing ou 2976 Rather than timing out after 20 ms if an EC
4141 command is not proper 2977 command is not properly ACKed, override the length
4142 of the timeout. We h 2978 of the timeout. We have interrupts disabled while
4143 waiting for the ACK, 2979 waiting for the ACK, so if this is set too high
4144 interrupts *may* be l 2980 interrupts *may* be lost!
4145 2981
4146 omap_mux= [OMAP] Override bootl 2982 omap_mux= [OMAP] Override bootloader pin multiplexing.
4147 Format: <mux_mode0.mo 2983 Format: <mux_mode0.mode_name=value>...
4148 For example, to overr 2984 For example, to override I2C bus2:
4149 omap_mux=i2c2_scl.i2c 2985 omap_mux=i2c2_scl.i2c2_scl=0x100,i2c2_sda.i2c2_sda=0x100
4150 2986
4151 onenand.bdry= [HW,MTD] Flex-OneNAND !! 2987 oprofile.timer= [HW]
>> 2988 Use timer interrupt instead of performance counters
4152 2989
4153 Format: [die0_boundar !! 2990 oprofile.cpu_type= Force an oprofile cpu type
>> 2991 This might be useful if you have an older oprofile
>> 2992 userland or if you want common events.
>> 2993 Format: { arch_perfmon }
>> 2994 arch_perfmon: [X86] Force use of architectural
>> 2995 perfmon on Intel CPUs instead of the
>> 2996 CPU specific event set.
>> 2997 timer: [X86] Force use of architectural NMI
>> 2998 timer mode (see also oprofile.timer
>> 2999 for generic hr timer mode)
4154 3000
4155 boundary - index of l !! 3001 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 3002 process, but there is a small probability of
4164 deadlocking the machi 3003 deadlocking the machine.
4165 This will also cause 3004 This will also cause panics on machine check exceptions.
4166 Useful together with 3005 Useful together with panic=30 to trigger a reboot.
4167 3006
4168 page_alloc.shuffle= !! 3007 page_owner= [KNL] Boot-time page_owner enabling option.
4169 [KNL] Boolean flag to <<
4170 should randomize its <<
4171 used to enable/disabl <<
4172 the flag can be read <<
4173 /sys/module/page_allo <<
4174 This parameter is onl <<
4175 <<
4176 page_owner= [KNL,EARLY] Boot-time <<
4177 Storage of the inform 3008 Storage of the information about who allocated
4178 each page is disabled 3009 each page is disabled in default. With this switch,
4179 we can turn it on. 3010 we can turn it on.
4180 on: enable the featur 3011 on: enable the feature
4181 3012
4182 page_poison= [KNL,EARLY] Boot-time !! 3013 page_poison= [KNL] Boot-time parameter changing the state of
4183 poisoning on the budd !! 3014 poisoning on the buddy allocator.
4184 CONFIG_PAGE_POISONING !! 3015 off: turn off poisoning
4185 off: turn off poisoni <<
4186 on: turn on poisoning 3016 on: turn on poisoning
4187 3017
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 3018 panic= [KNL] Kernel behaviour on panic: delay <timeout>
4195 timeout > 0: seconds 3019 timeout > 0: seconds before rebooting
4196 timeout = 0: wait for 3020 timeout = 0: wait forever
4197 timeout < 0: reboot i 3021 timeout < 0: reboot immediately
4198 Format: <timeout> 3022 Format: <timeout>
4199 3023
4200 panic_on_taint= [KNL,EARLY] !! 3024 panic_on_warn panic() instead of WARN(). Useful to cause kdump
4201 Bitmask for condition <<
4202 Format: <hex>[,nouser <<
4203 Hexadecimal bitmask r <<
4204 that will cause the k <<
4205 called with any of th <<
4206 The optional switch " <<
4207 prevent userspace for <<
4208 /proc/sys/kernel/tain <<
4209 bitmask set on panic_ <<
4210 See Documentation/adm <<
4211 extra details on the <<
4212 to compose the bitmas <<
4213 <<
4214 panic_on_warn=1 panic() instead of WA <<
4215 on a WARN(). 3025 on a WARN().
4216 3026
4217 panic_print= Bitmask for printing !! 3027 crash_kexec_post_notifiers
4218 User can chose combin !! 3028 Run kdump after running panic-notifiers and dumping
4219 bit 0: print all task !! 3029 kmsg. This only for the users who doubt kdump always
4220 bit 1: print system m !! 3030 succeeds in any situation.
4221 bit 2: print timer in !! 3031 Note that this also increases risks of kdump failure,
4222 bit 3: print locks in !! 3032 because some panic notifiers can make the crashed
4223 bit 4: print ftrace b !! 3033 kernel more unstable.
4224 bit 5: print all prin <<
4225 bit 6: print all CPUs <<
4226 bit 7: print only tas <<
4227 *Be aware* that this <<
4228 so there are risks of <<
4229 Use this option caref <<
4230 bigger log buffer wit <<
4231 3034
4232 parkbd.port= [HW] Parallel port nu 3035 parkbd.port= [HW] Parallel port number the keyboard adapter is
4233 connected to, default 3036 connected to, default is 0.
4234 Format: <parport#> 3037 Format: <parport#>
4235 parkbd.mode= [HW] Parallel port ke 3038 parkbd.mode= [HW] Parallel port keyboard adapter mode of operation,
4236 0 for XT, 1 for AT (d 3039 0 for XT, 1 for AT (default is AT).
4237 Format: <mode> 3040 Format: <mode>
4238 3041
4239 parport= [HW,PPT] Specify para 3042 parport= [HW,PPT] Specify parallel ports. 0 disables.
4240 Format: { 0 | auto | 3043 Format: { 0 | auto | 0xBBB[,IRQ[,DMA]] }
4241 Use 'auto' to force t 3044 Use 'auto' to force the driver to use any
4242 IRQ/DMA settings dete 3045 IRQ/DMA settings detected (the default is to
4243 ignore detected IRQ/D 3046 ignore detected IRQ/DMA settings because of
4244 possible conflicts). 3047 possible conflicts). You can specify the base
4245 address, IRQ, and DMA 3048 address, IRQ, and DMA settings; IRQ and DMA
4246 should be numbers, or 3049 should be numbers, or 'auto' (for using detected
4247 settings on that part 3050 settings on that particular port), or 'nofifo'
4248 (to avoid using a FIF 3051 (to avoid using a FIFO even if it is detected).
4249 Parallel ports are as 3052 Parallel ports are assigned in the order they
4250 are specified on the 3053 are specified on the command line, starting
4251 with parport0. 3054 with parport0.
4252 3055
4253 parport_init_mode= [HW,PPT] 3056 parport_init_mode= [HW,PPT]
4254 Configure VIA paralle 3057 Configure VIA parallel port to operate in
4255 a specific mode. This 3058 a specific mode. This is necessary on Pegasos
4256 computer where firmwa 3059 computer where firmware has no options for setting
4257 up parallel port mode 3060 up parallel port mode and sets it to spp.
4258 Currently this functi 3061 Currently this function knows 686a and 8231 chips.
4259 Format: [spp|ps2|epp| 3062 Format: [spp|ps2|epp|ecp|ecpepp]
4260 3063
4261 pata_legacy.all= [HW,LIBATA] !! 3064 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 3065 Halt all CPUs after the first oops has been printed for
4353 the specified number 3066 the specified number of seconds. This is to be used if
4354 your oopses keep scro 3067 your oopses keep scrolling off the screen.
4355 3068
4356 pcbit= [HW,ISDN] 3069 pcbit= [HW,ISDN]
4357 3070
4358 pci=option[,option...] [PCI,EARLY] v !! 3071 pcd. [PARIDE]
>> 3072 See header of drivers/block/paride/pcd.c.
>> 3073 See also Documentation/blockdev/paride.txt.
4359 3074
4360 Some options !! 3075 pci=option[,option...] [PCI] various PCI subsystem options:
4361 or a set of d !! 3076 earlydump [X86] dump PCI config space before the kernel
4362 specified in <<
4363 <<
4364 [<domain>:]<b <<
4365 pci:<vendor>: <<
4366 <<
4367 Note: the fir <<
4368 bus/device/fu <<
4369 if new hardwa <<
4370 firmware chan <<
4371 by other kern <<
4372 domain is lef <<
4373 taken to be z <<
4374 to a device t <<
4375 addresses can <<
4376 address (this <<
4377 renumbering i <<
4378 selects devic <<
4379 configuration <<
4380 devices in th <<
4381 <<
4382 earlydump dump PCI conf <<
4383 changes anyth 3077 changes anything
4384 off [X86] don't p 3078 off [X86] don't probe for the PCI bus
4385 bios [X86-32] forc 3079 bios [X86-32] force use of PCI BIOS, don't access
4386 the hardware 3080 the hardware directly. Use this if your machine
4387 has a non-sta 3081 has a non-standard PCI host bridge.
4388 nobios [X86-32] disa 3082 nobios [X86-32] disallow use of PCI BIOS, only direct
4389 hardware acce 3083 hardware access methods are allowed. Use this
4390 if you experi 3084 if you experience crashes upon bootup and you
4391 suspect they 3085 suspect they are caused by the BIOS.
4392 conf1 [X86] Force u 3086 conf1 [X86] Force use of PCI Configuration Access
4393 Mechanism 1 ( 3087 Mechanism 1 (config address in IO port 0xCF8,
4394 data in IO po 3088 data in IO port 0xCFC, both 32-bit).
4395 conf2 [X86] Force u 3089 conf2 [X86] Force use of PCI Configuration Access
4396 Mechanism 2 ( 3090 Mechanism 2 (IO port 0xCF8 is an 8-bit port for
4397 the function, 3091 the function, IO port 0xCFA, also 8-bit, sets
4398 bus number. T 3092 bus number. The config space is then accessed
4399 through ports 3093 through ports 0xC000-0xCFFF).
4400 See http://wi 3094 See http://wiki.osdev.org/PCI for more info
4401 on the config 3095 on the configuration access mechanisms.
4402 noaer [PCIE] If the 3096 noaer [PCIE] If the PCIEAER kernel config parameter is
4403 enabled, this 3097 enabled, this kernel boot option can be used to
4404 disable the u 3098 disable the use of PCIE advanced error reporting.
4405 nodomains [PCI] Disable 3099 nodomains [PCI] Disable support for multiple PCI
4406 root domains 3100 root domains (aka PCI segments, in ACPI-speak).
4407 nommconf [X86] Disable 3101 nommconf [X86] Disable use of MMCONFIG for PCI
4408 Configuration 3102 Configuration
4409 check_enable_amd_mmconf [X86] 3103 check_enable_amd_mmconf [X86] check for and enable
4410 properly conf 3104 properly configured MMIO access to PCI
4411 config space 3105 config space on AMD family 10h CPU
4412 nomsi [MSI] If the 3106 nomsi [MSI] If the PCI_MSI kernel config parameter is
4413 enabled, this 3107 enabled, this kernel boot option can be used to
4414 disable the u 3108 disable the use of MSI interrupts system-wide.
4415 noioapicquirk [APIC] Disabl 3109 noioapicquirk [APIC] Disable all boot interrupt quirks.
4416 Safety option 3110 Safety option to keep boot IRQs enabled. This
4417 should never 3111 should never be necessary.
4418 ioapicreroute [APIC] Enable 3112 ioapicreroute [APIC] Enable rerouting of boot IRQs to the
4419 primary IO-AP 3113 primary IO-APIC for bridges that cannot disable
4420 boot IRQs. Th 3114 boot IRQs. This fixes a source of spurious IRQs
4421 when the syst 3115 when the system masks IRQs.
4422 noioapicreroute [APIC] Disabl 3116 noioapicreroute [APIC] Disable workaround that uses the
4423 boot IRQ equi 3117 boot IRQ equivalent of an IRQ that connects to
4424 a chipset whe 3118 a chipset where boot IRQs cannot be disabled.
4425 The opposite 3119 The opposite of ioapicreroute.
4426 biosirq [X86-32] Use 3120 biosirq [X86-32] Use PCI BIOS calls to get the interrupt
4427 routing table 3121 routing table. These calls are known to be buggy
4428 on several ma 3122 on several machines and they hang the machine
4429 when used, bu 3123 when used, but on other computers it's the only
4430 way to get th 3124 way to get the interrupt routing table. Try
4431 this option i 3125 this option if the kernel is unable to allocate
4432 IRQs or disco 3126 IRQs or discover secondary PCI buses on your
4433 motherboard. 3127 motherboard.
4434 rom [X86] Assign 3128 rom [X86] Assign address space to expansion ROMs.
4435 Use with caut 3129 Use with caution as certain devices share
4436 address decod 3130 address decoders between ROMs and other
4437 resources. 3131 resources.
4438 norom [X86] Do not 3132 norom [X86] Do not assign address space to
4439 expansion ROM 3133 expansion ROMs that do not already have
4440 BIOS assigned 3134 BIOS assigned address ranges.
4441 nobar [X86] Do not 3135 nobar [X86] Do not assign address space to the
4442 BARs that wer 3136 BARs that weren't assigned by the BIOS.
4443 irqmask=0xMMMM [X86] Set a b 3137 irqmask=0xMMMM [X86] Set a bit mask of IRQs allowed to be
4444 assigned auto 3138 assigned automatically to PCI devices. You can
4445 make the kern 3139 make the kernel exclude IRQs of your ISA cards
4446 this way. 3140 this way.
4447 pirqaddr=0xAAAAA [X86] 3141 pirqaddr=0xAAAAA [X86] Specify the physical address
4448 of the PIRQ t 3142 of the PIRQ table (normally generated
4449 by the BIOS) 3143 by the BIOS) if it is outside the
4450 F0000h-100000 3144 F0000h-100000h range.
4451 lastbus=N [X86] Scan al 3145 lastbus=N [X86] Scan all buses thru bus #N. Can be
4452 useful if the 3146 useful if the kernel is unable to find your
4453 secondary bus 3147 secondary buses and you want to tell it
4454 explicitly wh 3148 explicitly which ones they are.
4455 assign-busses [X86] Always 3149 assign-busses [X86] Always assign all PCI bus
4456 numbers ourse 3150 numbers ourselves, overriding
4457 whatever the 3151 whatever the firmware may have done.
4458 usepirqmask [X86] Honor t 3152 usepirqmask [X86] Honor the possible IRQ mask stored
4459 in the BIOS $ 3153 in the BIOS $PIR table. This is needed on
4460 some systems 3154 some systems with broken BIOSes, notably
4461 some HP Pavil 3155 some HP Pavilion N5400 and Omnibook XE3
4462 notebooks. Th 3156 notebooks. This will have no effect if ACPI
4463 IRQ routing i 3157 IRQ routing is enabled.
4464 noacpi [X86] Do not 3158 noacpi [X86] Do not use ACPI for IRQ routing
4465 or for PCI sc 3159 or for PCI scanning.
4466 use_crs [X86] Use PCI 3160 use_crs [X86] Use PCI host bridge window information
4467 from ACPI. O 3161 from ACPI. On BIOSes from 2008 or later, this
4468 is enabled by 3162 is enabled by default. If you need to use this,
4469 please report 3163 please report a bug.
4470 nocrs [X86] Ignore 3164 nocrs [X86] Ignore PCI host bridge windows from ACPI.
4471 If you need t 3165 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 3166 routeirq Do IRQ routing for all PCI devices.
4482 This is norma 3167 This is normally done in pci_enable_device(),
4483 so this optio 3168 so this option is a temporary workaround
4484 for broken dr 3169 for broken drivers that don't call it.
4485 skip_isa_align [X86] do not 3170 skip_isa_align [X86] do not align io start addr, so can
4486 handle more p 3171 handle more pci cards
4487 noearly [X86] Don't d 3172 noearly [X86] Don't do any early type 1 scanning.
4488 This might he 3173 This might help on some broken boards which
4489 machine check 3174 machine check when some devices' config space
4490 is read. But 3175 is read. But various workarounds are disabled
4491 and some IOMM 3176 and some IOMMU drivers will not work.
4492 bfsort Sort PCI devi 3177 bfsort Sort PCI devices into breadth-first order.
4493 This sorting 3178 This sorting is done to get a device
4494 order compati 3179 order compatible with older (<= 2.4) kernels.
4495 nobfsort Don't sort PC 3180 nobfsort Don't sort PCI devices into breadth-first order.
4496 pcie_bus_tune_off Disab 3181 pcie_bus_tune_off Disable PCIe MPS (Max Payload Size)
4497 tuning and us 3182 tuning and use the BIOS-configured MPS defaults.
4498 pcie_bus_safe Set every dev 3183 pcie_bus_safe Set every device's MPS to the largest value
4499 supported by 3184 supported by all devices below the root complex.
4500 pcie_bus_perf Set device MP 3185 pcie_bus_perf Set device MPS to the largest allowable MPS
4501 based on its 3186 based on its parent bus. Also set MRRS (Max
4502 Read Request 3187 Read Request Size) to the largest supported
4503 value (no lar 3188 value (no larger than the MPS that the device
4504 or bus can su 3189 or bus can support) for best performance.
4505 pcie_bus_peer2peer Set e 3190 pcie_bus_peer2peer Set every device's MPS to 128B, which
4506 every device 3191 every device is guaranteed to support. This
4507 configuration 3192 configuration allows peer-to-peer DMA between
4508 any pair of d 3193 any pair of devices, possibly at the cost of
4509 reduced perfo 3194 reduced performance. This also guarantees
4510 that hot-adde 3195 that hot-added devices will work.
4511 cbiosize=nn[KMG] The f 3196 cbiosize=nn[KMG] The fixed amount of bus space which is
4512 reserved for 3197 reserved for the CardBus bridge's IO window.
4513 The default v 3198 The default value is 256 bytes.
4514 cbmemsize=nn[KMG] The f 3199 cbmemsize=nn[KMG] The fixed amount of bus space which is
4515 reserved for 3200 reserved for the CardBus bridge's memory
4516 window. The d 3201 window. The default value is 64 megabytes.
4517 resource_alignment= 3202 resource_alignment=
4518 Format: 3203 Format:
4519 [<order of ali !! 3204 [<order of align>@][<domain>:]<bus>:<slot>.<func>[; ...]
>> 3205 [<order of align>@]pci:<vendor>:<device>\
>> 3206 [:<subvendor>:<subdevice>][; ...]
4520 Specifies ali 3207 Specifies alignment and device to reassign
4521 aligned memor !! 3208 aligned memory resources.
4522 specify the d <<
4523 If <order of 3209 If <order of align> is not specified,
4524 PAGE_SIZE is 3210 PAGE_SIZE is used as alignment.
4525 A PCI-PCI bri !! 3211 PCI-PCI bridge can be specified, if resource
4526 windows need 3212 windows need to be expanded.
4527 To specify th 3213 To specify the alignment for several
4528 instances of 3214 instances of a device, the PCI vendor,
4529 device, subve 3215 device, subvendor, and subdevice may be
4530 specified, e. !! 3216 specified, e.g., 4096@pci:8086:9c22:103c:198f
4531 for 4096-byte <<
4532 ecrc= Enable/disabl 3217 ecrc= Enable/disable PCIe ECRC (transaction layer
4533 end-to-end CR !! 3218 end-to-end CRC checking).
4534 OS has native <<
4535 ACPI _OSC or <<
4536 bios: Use BIO 3219 bios: Use BIOS/firmware settings. This is the
4537 the default. 3220 the default.
4538 off: Turn ECR 3221 off: Turn ECRC off
4539 on: Turn ECRC 3222 on: Turn ECRC on.
4540 hpiosize=nn[KMG] The f 3223 hpiosize=nn[KMG] The fixed amount of bus space which is
4541 reserved for 3224 reserved for hotplug bridge's IO window.
4542 Default size 3225 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 3226 hpmemsize=nn[KMG] The fixed amount of bus space which is
4550 reserved for !! 3227 reserved for hotplug bridge's memory window.
4551 MMIO_PREF win <<
4552 Default size 3228 Default size is 2 megabytes.
4553 hpbussize=nn The minimum a 3229 hpbussize=nn The minimum amount of additional bus numbers
4554 reserved for 3230 reserved for buses below a hotplug bridge.
4555 Default is 1. 3231 Default is 1.
4556 realloc= Enable/disabl 3232 realloc= Enable/disable reallocating PCI bridge resources
4557 if allocation 3233 if allocations done by BIOS are too small to
4558 accommodate r 3234 accommodate resources required by all child
4559 devices. 3235 devices.
4560 off: Turn rea 3236 off: Turn realloc off
4561 on: Turn real 3237 on: Turn realloc on
4562 realloc same as reall 3238 realloc same as realloc=on
4563 noari do not use PC 3239 noari do not use PCIe ARI.
4564 noats [PCIE, Intel- 3240 noats [PCIE, Intel-IOMMU, AMD-IOMMU]
4565 do not use PC 3241 do not use PCIe ATS (and IOMMU device IOTLB).
4566 pcie_scan_all Scan all poss 3242 pcie_scan_all Scan all possible PCIe devices. Otherwise we
4567 only look for 3243 only look for one device below a PCIe downstream
4568 port. 3244 port.
4569 big_root_window Try to add a 3245 big_root_window Try to add a big 64bit memory window to the PCIe
4570 root complex 3246 root complex on AMD CPUs. Some GFX hardware
4571 can resize a 3247 can resize a BAR to allow access to all VRAM.
4572 Adding the wi 3248 Adding the window is slightly risky (it may
4573 conflict with 3249 conflict with unreported devices), so this
4574 taints the ke 3250 taints the kernel.
4575 disable_acs_redir=<pci_dev>[; <<
4576 Specify one o <<
4577 specified abo <<
4578 Each device s <<
4579 redirect capa <<
4580 allow P2P tra <<
4581 bridges witho <<
4582 this removes <<
4583 may put more <<
4584 config_acs= <<
4585 Format: <<
4586 <ACS flags>@<p <<
4587 Specify one o <<
4588 specified abo <<
4589 and separated <<
4590 capabilities <<
4591 unchanged bas <<
4592 flags. <<
4593 <<
4594 ACS Flags is <<
4595 bit-0 : ACS <<
4596 bit-1 : ACS <<
4597 bit-2 : ACS <<
4598 bit-3 : ACS <<
4599 bit-4 : ACS <<
4600 bit-5 : ACS <<
4601 bit-6 : ACS <<
4602 Each bit can <<
4603 '0' – for <<
4604 '1' – for <<
4605 'x' – unc <<
4606 For example, <<
4607 pci=config_ <<
4608 would configu <<
4609 ACS to enable <<
4610 Translation B <<
4611 Validation un <<
4612 or firmware s <<
4613 <<
4614 Note: this ma <<
4615 and may put m <<
4616 force_floating [S390] Force <<
4617 nomio [S390] Do not <<
4618 norid [S390] ignore <<
4619 one PCI domai <<
4620 3251
4621 pcie_aspm= [PCIE] Forcibly enabl !! 3252 pcie_aspm= [PCIE] Forcibly enable or disable PCIe Active State Power
4622 Management. 3253 Management.
4623 off Don't touch ASPM conf !! 3254 off Disable ASPM.
4624 configuration done by <<
4625 force Enable ASPM even on d 3255 force Enable ASPM even on devices that claim not to support it.
4626 WARNING: Forcing ASPM 3256 WARNING: Forcing ASPM on may cause system lockups.
4627 3257
4628 pcie_ports= [PCIE] PCIe port serv 3258 pcie_ports= [PCIE] PCIe port services handling:
4629 native Use native PCIe servi 3259 native Use native PCIe services (PME, AER, DPC, PCIe hotplug)
4630 even if the platform 3260 even if the platform doesn't give the OS permission to
4631 use them. This may c 3261 use them. This may cause conflicts if the platform
4632 also tries to use the 3262 also tries to use these services.
4633 dpc-native Use native PC <<
4634 cause conflic <<
4635 compat Disable native PCIe s 3263 compat Disable native PCIe services (PME, AER, DPC, PCIe
4636 hotplug). 3264 hotplug).
4637 3265
4638 pcie_port_pm= [PCIE] PCIe port powe 3266 pcie_port_pm= [PCIE] PCIe port power management handling:
4639 off Disable power managem 3267 off Disable power management of all PCIe ports
4640 force Forcibly enable power 3268 force Forcibly enable power management of all PCIe ports
4641 3269
4642 pcie_pme= [PCIE,PM] Native PCIe 3270 pcie_pme= [PCIE,PM] Native PCIe PME signaling options:
4643 nomsi Do not use MSI for na 3271 nomsi Do not use MSI for native PCIe PME signaling (this makes
4644 all PCIe root ports u 3272 all PCIe root ports use INTx for all services).
4645 3273
4646 pcmv= [HW,PCMCIA] BadgePAD 3274 pcmv= [HW,PCMCIA] BadgePAD 4
4647 3275
4648 pd_ignore_unused 3276 pd_ignore_unused
4649 [PM] 3277 [PM]
4650 Keep all power-domain 3278 Keep all power-domains already enabled by bootloader on,
4651 even if no driver has 3279 even if no driver has claimed them. This is useful
4652 for debug and develop 3280 for debug and development, but should not be
4653 needed on a platform 3281 needed on a platform with proper driver support.
4654 3282
>> 3283 pd. [PARIDE]
>> 3284 See Documentation/blockdev/paride.txt.
>> 3285
4655 pdcchassis= [PARISC,HW] Disable/E 3286 pdcchassis= [PARISC,HW] Disable/Enable PDC Chassis Status codes at
4656 boot time. 3287 boot time.
4657 Format: { 0 | 1 } 3288 Format: { 0 | 1 }
4658 See arch/parisc/kerne 3289 See arch/parisc/kernel/pdc_chassis.c
4659 3290
4660 percpu_alloc= [MM,EARLY] !! 3291 percpu_alloc= Select which percpu first chunk allocator to use.
4661 Select which percpu f <<
4662 Currently supported v 3292 Currently supported values are "embed" and "page".
4663 Archs may support sub 3293 Archs may support subset or none of the selections.
4664 See comments in mm/pe 3294 See comments in mm/percpu.c for details on each
4665 allocator. This para 3295 allocator. This parameter is primarily for debugging
4666 and performance compa 3296 and performance comparison.
4667 3297
>> 3298 pf. [PARIDE]
>> 3299 See Documentation/blockdev/paride.txt.
>> 3300
>> 3301 pg. [PARIDE]
>> 3302 See Documentation/blockdev/paride.txt.
>> 3303
4668 pirq= [SMP,APIC] Manual mp- 3304 pirq= [SMP,APIC] Manual mp-table setup
4669 See Documentation/arc !! 3305 See Documentation/x86/i386/IO-APIC.txt.
4670 3306
4671 plip= [PPT,NET] Parallel po 3307 plip= [PPT,NET] Parallel port network link
4672 Format: { parport<nr> 3308 Format: { parport<nr> | timid | 0 }
4673 See also Documentatio 3309 See also Documentation/admin-guide/parport.rst.
4674 3310
4675 pmtmr= [X86] Manual setup of 3311 pmtmr= [X86] Manual setup of pmtmr I/O Port.
4676 Override pmtimer IOPo 3312 Override pmtimer IOPort with a hex value.
4677 e.g. pmtmr=0x508 3313 e.g. pmtmr=0x508
4678 3314
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] 3315 pnp.debug=1 [PNP]
4691 Enable PNP debug mess 3316 Enable PNP debug messages (depends on the
4692 CONFIG_PNP_DEBUG_MESS 3317 CONFIG_PNP_DEBUG_MESSAGES option). Change at run-time
4693 via /sys/module/pnp/p 3318 via /sys/module/pnp/parameters/debug. We always show
4694 current resource usag 3319 current resource usage; turning this on also shows
4695 possible settings and 3320 possible settings and some assignment information.
4696 3321
4697 pnpacpi= [ACPI] 3322 pnpacpi= [ACPI]
4698 { off } 3323 { off }
4699 3324
4700 pnpbios= [ISAPNP] 3325 pnpbios= [ISAPNP]
4701 { on | off | curr | r 3326 { on | off | curr | res | no-curr | no-res }
4702 3327
4703 pnp_reserve_irq= 3328 pnp_reserve_irq=
4704 [ISAPNP] Exclude IRQs 3329 [ISAPNP] Exclude IRQs for the autoconfiguration
4705 3330
4706 pnp_reserve_dma= 3331 pnp_reserve_dma=
4707 [ISAPNP] Exclude DMAs 3332 [ISAPNP] Exclude DMAs for the autoconfiguration
4708 3333
4709 pnp_reserve_io= [ISAPNP] Exclude I/O 3334 pnp_reserve_io= [ISAPNP] Exclude I/O ports for the autoconfiguration
4710 Ranges are in pairs ( 3335 Ranges are in pairs (I/O port base and size).
4711 3336
4712 pnp_reserve_mem= 3337 pnp_reserve_mem=
4713 [ISAPNP] Exclude memo 3338 [ISAPNP] Exclude memory regions for the
4714 autoconfiguration. 3339 autoconfiguration.
4715 Ranges are in pairs ( 3340 Ranges are in pairs (memory base and size).
4716 3341
4717 ports= [IP_VS_FTP] IPVS ftp 3342 ports= [IP_VS_FTP] IPVS ftp helper module
4718 Default is 21. 3343 Default is 21.
4719 Up to 8 (IP_VS_APP_MA 3344 Up to 8 (IP_VS_APP_MAX_PORTS) ports
4720 may be specified. 3345 may be specified.
4721 Format: <port>,<port> 3346 Format: <port>,<port>....
4722 3347
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 3348 powersave=off [PPC] This option disables power saving features.
4729 It specifically disab 3349 It specifically disables cpuidle and sets the
4730 platform machine desc 3350 platform machine description specific power_save
4731 function to NULL. On 3351 function to NULL. On Idle the CPU just reduces
4732 execution priority. 3352 execution priority.
4733 3353
4734 ppc_strict_facility_enable 3354 ppc_strict_facility_enable
4735 [PPC,ENABLE] This opt !! 3355 [PPC] This option catches any kernel floating point,
4736 Altivec, VSX and SPE 3356 Altivec, VSX and SPE outside of regions specifically
4737 allowed (eg kernel_en 3357 allowed (eg kernel_enable_fpu()/kernel_disable_fpu()).
4738 There is some perform 3358 There is some performance impact when enabling this.
4739 3359
4740 ppc_tm= [PPC,EARLY] !! 3360 ppc_tm= [PPC]
4741 Format: {"off"} 3361 Format: {"off"}
4742 Disable Hardware Tran 3362 Disable Hardware Transactional Memory
4743 3363
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= 3364 print-fatal-signals=
4754 [KNL] debug: print fa 3365 [KNL] debug: print fatal signals
4755 3366
4756 If enabled, warn abou 3367 If enabled, warn about various signal handling
4757 related application a 3368 related application anomalies: too many signals,
4758 too many POSIX.1 time 3369 too many POSIX.1 timers, fatal signals causing a
4759 coredump - etc. 3370 coredump - etc.
4760 3371
4761 If you hit the warnin 3372 If you hit the warning due to signal overflow,
4762 you might want to try 3373 you might want to try "ulimit -i unlimited".
4763 3374
4764 default: off. 3375 default: off.
4765 3376
4766 printk.always_kmsg_dump= 3377 printk.always_kmsg_dump=
4767 Trigger kmsg_dump for 3378 Trigger kmsg_dump for cases other than kernel oops or
4768 panics 3379 panics
4769 Format: <bool> (1/Y/ 3380 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4770 default: disabled 3381 default: disabled
4771 3382
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} 3383 printk.devkmsg={on,off,ratelimit}
4782 Control writing to /d 3384 Control writing to /dev/kmsg.
4783 on - unlimited loggin 3385 on - unlimited logging to /dev/kmsg from userspace
4784 off - logging to /dev 3386 off - logging to /dev/kmsg disabled
4785 ratelimit - ratelimit 3387 ratelimit - ratelimit the logging
4786 Default: ratelimit 3388 Default: ratelimit
4787 3389
4788 printk.time= Show timing data pref 3390 printk.time= Show timing data prefixed to each printk message line
4789 Format: <bool> (1/Y/ 3391 Format: <bool> (1/Y/y=enable, 0/N/n=disable)
4790 3392
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] 3393 processor.max_cstate= [HW,ACPI]
4802 Limit processor to ma 3394 Limit processor to maximum C-state
4803 max_cstate=9 override 3395 max_cstate=9 overrides any DMI blacklist limit.
4804 3396
4805 processor.nocst [HW,ACPI] 3397 processor.nocst [HW,ACPI]
4806 Ignore the _CST metho 3398 Ignore the _CST method to determine C-states,
4807 instead using the leg 3399 instead using the legacy FADT method
4808 3400
4809 profile= [KNL] Enable kernel p 3401 profile= [KNL] Enable kernel profiling via /proc/profile
4810 Format: [<profiletype 3402 Format: [<profiletype>,]<number>
4811 Param: <profiletype>: !! 3403 Param: <profiletype>: "schedule", "sleep", or "kvm"
4812 [defaults to 3404 [defaults to kernel profiling]
4813 Param: "schedule" - p 3405 Param: "schedule" - profile schedule points.
>> 3406 Param: "sleep" - profile D-state sleeping (millisecs).
>> 3407 Requires CONFIG_SCHEDSTATS
4814 Param: "kvm" - profil 3408 Param: "kvm" - profile VM exits.
4815 Param: <number> - ste 3409 Param: <number> - step/bucket size as a power of 2 for
4816 statistical t 3410 statistical time based profiling.
4817 3411
4818 prompt_ramdisk= [RAM] [Deprecated] !! 3412 prompt_ramdisk= [RAM] List of RAM disks to prompt for floppy disk
4819 !! 3413 before loading.
4820 prot_virt= [S390] enable hosting !! 3414 See Documentation/blockdev/ramdisk.txt.
4821 isolated from the hyp <<
4822 that). If enabled, th <<
4823 might be overridden e <<
4824 Layout Randomization <<
4825 Format: <bool> <<
4826 <<
4827 psi= [KNL] Enable or disab <<
4828 tracking. <<
4829 Format: <bool> <<
4830 3415
4831 psmouse.proto= [HW,MOUSE] Highest PS 3416 psmouse.proto= [HW,MOUSE] Highest PS2 mouse protocol extension to
4832 probe for; one of (ba 3417 probe for; one of (bare|imps|exps|lifebook|any).
4833 psmouse.rate= [HW,MOUSE] Set desire 3418 psmouse.rate= [HW,MOUSE] Set desired mouse report rate, in reports
4834 per second. 3419 per second.
4835 psmouse.resetafter= [HW,MOUSE] 3420 psmouse.resetafter= [HW,MOUSE]
4836 Try to reset the devi 3421 Try to reset the device after so many bad packets
4837 (0 = never). 3422 (0 = never).
4838 psmouse.resolution= 3423 psmouse.resolution=
4839 [HW,MOUSE] Set desire 3424 [HW,MOUSE] Set desired mouse resolution, in dpi.
4840 psmouse.smartscroll= 3425 psmouse.smartscroll=
4841 [HW,MOUSE] Controls L 3426 [HW,MOUSE] Controls Logitech smartscroll autorepeat.
4842 0 = disabled, 1 = ena 3427 0 = disabled, 1 = enabled (default).
4843 3428
4844 pstore.backend= Specify the name of t 3429 pstore.backend= Specify the name of the pstore backend to use
4845 3430
4846 pti= [X86-64] Control Page !! 3431 pt. [PARIDE]
>> 3432 See Documentation/blockdev/paride.txt.
>> 3433
>> 3434 pti= [X86_64] Control Page Table Isolation of user and
4847 kernel address spaces 3435 kernel address spaces. Disabling this feature
4848 removes hardening, bu 3436 removes hardening, but improves performance of
4849 system calls and inte 3437 system calls and interrupts.
4850 3438
4851 on - unconditionall 3439 on - unconditionally enable
4852 off - unconditionall 3440 off - unconditionally disable
4853 auto - kernel detects 3441 auto - kernel detects whether your CPU model is
4854 vulnerable to 3442 vulnerable to issues that PTI mitigates
4855 3443
4856 Not specifying this o 3444 Not specifying this option is equivalent to pti=auto.
4857 3445
>> 3446 nopti [X86_64]
>> 3447 Equivalent to pti=off
>> 3448
4858 pty.legacy_count= 3449 pty.legacy_count=
4859 [KNL] Number of legac 3450 [KNL] Number of legacy pty's. Overwrites compiled-in
4860 default number. 3451 default number.
4861 3452
4862 quiet [KNL,EARLY] Disable m !! 3453 quiet [KNL] Disable most log messages
4863 3454
4864 r128= [HW,DRM] 3455 r128= [HW,DRM]
4865 3456
4866 radix_hcall_invalidate=on [PPC/PSERI <<
4867 Disable RADIX GTSE fe <<
4868 invalidate. <<
4869 <<
4870 raid= [HW,RAID] 3457 raid= [HW,RAID]
4871 See Documentation/adm 3458 See Documentation/admin-guide/md.rst.
4872 3459
4873 ramdisk_size= [RAM] Sizes of RAM di 3460 ramdisk_size= [RAM] Sizes of RAM disks in kilobytes
4874 See Documentation/adm !! 3461 See Documentation/blockdev/ramdisk.txt.
4875 <<
4876 ramdisk_start= [RAM] RAM disk image <<
4877 <<
4878 random.trust_cpu=off <<
4879 [KNL,EARLY] Disable t <<
4880 random number generat <<
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 3462
4899 ras=option[,option,...] [KNL] RAS-spe 3463 ras=option[,option,...] [KNL] RAS-specific options
4900 3464
4901 cec_disable [X86] 3465 cec_disable [X86]
4902 Disable the C 3466 Disable the Correctable Errors Collector,
4903 see CONFIG_RA 3467 see CONFIG_RAS_CEC help text.
4904 3468
4905 rcu_nocbs[=cpu-list] !! 3469 rcu_nocbs= [KNL]
4906 [KNL] The optional ar !! 3470 The argument is a cpu list, as described above.
4907 as described above. <<
4908 <<
4909 In kernels built with <<
4910 enable the no-callbac <<
4911 such CPUs' callbacks <<
4912 softirq context. Inv <<
4913 callbacks will instea <<
4914 kthreads created for <<
4915 "p" for RCU-preempt, <<
4916 for the kthreads that <<
4917 "N" is the CPU number <<
4918 the offloaded CPUs, w <<
4919 and real-time workloa <<
4920 energy efficiency for <<
4921 <<
4922 If a cpulist is passe <<
4923 list of CPUs is set t <<
4924 <<
4925 Otherwise, if the '=' <<
4926 arguments are omitted <<
4927 no-callback mode from <<
4928 toggled at runtime vi <<
4929 3471
4930 Note that this argume !! 3472 In kernels built with CONFIG_RCU_NOCB_CPU=y, set
4931 the CONFIG_RCU_NOCB_C !! 3473 the specified list of CPUs to be no-callback CPUs.
>> 3474 Invocation of these CPUs' RCU callbacks will
>> 3475 be offloaded to "rcuox/N" kthreads created for
>> 3476 that purpose, where "x" is "b" for RCU-bh, "p"
>> 3477 for RCU-preempt, and "s" for RCU-sched, and "N"
>> 3478 is the CPU number. This reduces OS jitter on the
>> 3479 offloaded CPUs, which can be useful for HPC and
>> 3480 real-time workloads. It can also improve energy
>> 3481 efficiency for asymmetric multiprocessors.
4932 3482
4933 rcu_nocb_poll [KNL] 3483 rcu_nocb_poll [KNL]
4934 Rather than requiring 3484 Rather than requiring that offloaded CPUs
4935 (specified by rcu_noc 3485 (specified by rcu_nocbs= above) explicitly
4936 awaken the correspond 3486 awaken the corresponding "rcuoN" kthreads,
4937 make these kthreads p 3487 make these kthreads poll for callbacks.
4938 This improves the rea 3488 This improves the real-time response for the
4939 offloaded CPUs by rel 3489 offloaded CPUs by relieving them of the need to
4940 wake up the correspon 3490 wake up the corresponding kthread, but degrades
4941 energy efficiency by 3491 energy efficiency by requiring that the kthreads
4942 periodically wake up 3492 periodically wake up to do the polling.
4943 3493
4944 rcutree.blimit= [KNL] 3494 rcutree.blimit= [KNL]
4945 Set maximum number of 3495 Set maximum number of finished RCU callbacks to
4946 process in one batch. 3496 process in one batch.
4947 3497
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] 3498 rcutree.dump_tree= [KNL]
4956 Dump the structure of 3499 Dump the structure of the rcu_node combining tree
4957 out at early boot. T 3500 out at early boot. This is used for diagnostic
4958 purposes, to verify c 3501 purposes, to verify correct tree setup.
4959 3502
4960 rcutree.gp_cleanup_delay= [KNL] 3503 rcutree.gp_cleanup_delay= [KNL]
4961 Set the number of jif 3504 Set the number of jiffies to delay each step of
4962 RCU grace-period clea 3505 RCU grace-period cleanup.
4963 3506
4964 rcutree.gp_init_delay= [KNL] 3507 rcutree.gp_init_delay= [KNL]
4965 Set the number of jif 3508 Set the number of jiffies to delay each step of
4966 RCU grace-period init 3509 RCU grace-period initialization.
4967 3510
4968 rcutree.gp_preinit_delay= [KNL] 3511 rcutree.gp_preinit_delay= [KNL]
4969 Set the number of jif 3512 Set the number of jiffies to delay each step of
4970 RCU grace-period pre- 3513 RCU grace-period pre-initialization, that is,
4971 the propagation of re 3514 the propagation of recent CPU-hotplug changes up
4972 the rcu_node combinin 3515 the rcu_node combining tree.
4973 3516
>> 3517 rcutree.rcu_fanout_exact= [KNL]
>> 3518 Disable autobalancing of the rcu_node combining
>> 3519 tree. This is used by rcutorture, and might
>> 3520 possibly be useful for architectures having high
>> 3521 cache-to-cache transfer latencies.
>> 3522
>> 3523 rcutree.rcu_fanout_leaf= [KNL]
>> 3524 Change the number of CPUs assigned to each
>> 3525 leaf rcu_node structure. Useful for very
>> 3526 large systems, which will choose the value 64,
>> 3527 and for NUMA systems with large remote-access
>> 3528 latencies, which will choose a value aligned
>> 3529 with the appropriate hardware boundaries.
>> 3530
>> 3531 rcutree.jiffies_till_sched_qs= [KNL]
>> 3532 Set required age in jiffies for a
>> 3533 given grace period before RCU starts
>> 3534 soliciting quiescent-state help from
>> 3535 rcu_note_context_switch().
>> 3536
4974 rcutree.jiffies_till_first_fqs= [KNL] 3537 rcutree.jiffies_till_first_fqs= [KNL]
4975 Set delay from grace- 3538 Set delay from grace-period initialization to
4976 first attempt to forc 3539 first attempt to force quiescent states.
4977 Units are jiffies, mi 3540 Units are jiffies, minimum value is zero,
4978 and maximum value is 3541 and maximum value is HZ.
4979 3542
4980 rcutree.jiffies_till_next_fqs= [KNL] 3543 rcutree.jiffies_till_next_fqs= [KNL]
4981 Set delay between sub 3544 Set delay between subsequent attempts to force
4982 quiescent states. Un 3545 quiescent states. Units are jiffies, minimum
4983 value is one, and max 3546 value is one, and maximum value is HZ.
4984 3547
4985 rcutree.jiffies_till_sched_qs= [KNL] <<
4986 Set required age in j <<
4987 given grace period be <<
4988 soliciting quiescent- <<
4989 rcu_note_context_swit <<
4990 If not specified, the <<
4991 a value based on the <<
4992 of rcutree.jiffies_ti <<
4993 and rcutree.jiffies_t <<
4994 This calculated value <<
4995 rcutree.jiffies_to_sc <<
4996 rcutree.jiffies_to_sc <<
4997 overwritten. <<
4998 <<
4999 rcutree.kthread_prio= [KNL,BOOT] 3548 rcutree.kthread_prio= [KNL,BOOT]
5000 Set the SCHED_FIFO pr 3549 Set the SCHED_FIFO priority of the RCU per-CPU
5001 kthreads (rcuc/N). Th 3550 kthreads (rcuc/N). This value is also used for
5002 the priority of the R 3551 the priority of the RCU boost threads (rcub/N)
5003 and for the RCU grace 3552 and for the RCU grace-period kthreads (rcu_bh,
5004 rcu_preempt, and rcu_ 3553 rcu_preempt, and rcu_sched). If RCU_BOOST is
5005 set, valid values are 3554 set, valid values are 1-99 and the default is 1
5006 (the least-favored pr 3555 (the least-favored priority). Otherwise, when
5007 RCU_BOOST is not set, 3556 RCU_BOOST is not set, valid values are 0-99 and
5008 the default is zero ( 3557 the default is zero (non-realtime operation).
5009 When RCU_NOCB_CPU is <<
5010 priority of NOCB call <<
5011 3558
5012 rcutree.nocb_nobypass_lim_per_jiffy= !! 3559 rcutree.rcu_nocb_leader_stride= [KNL]
5013 On callback-offloaded !! 3560 Set the number of NOCB kthread groups, which
5014 RCU reduces the lock !! 3561 defaults to the square root of the number of
5015 otherwise be caused b !! 3562 CPUs. Larger numbers reduces the wakeup overhead
5016 use of the ->nocb_byp !! 3563 on the per-CPU grace-period kthreads, but increases
5017 common non-flooded ca !! 3564 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 3565
5033 rcutree.qhimark= [KNL] 3566 rcutree.qhimark= [KNL]
5034 Set threshold of queu 3567 Set threshold of queued RCU callbacks beyond which
5035 batch limiting is dis 3568 batch limiting is disabled.
5036 3569
5037 rcutree.qlowmark= [KNL] 3570 rcutree.qlowmark= [KNL]
5038 Set threshold of queu 3571 Set threshold of queued RCU callbacks below which
5039 batch limiting is re- 3572 batch limiting is re-enabled.
5040 3573
5041 rcutree.qovld= [KNL] !! 3574 rcutree.rcu_idle_gp_delay= [KNL]
5042 Set threshold of queu !! 3575 Set wakeup interval for idle CPUs that have
5043 RCU's force-quiescent !! 3576 RCU callbacks (RCU_FAST_NO_HZ=y).
5044 enlist help from cond !! 3577
5045 help CPUs more quickl !! 3578 rcutree.rcu_idle_lazy_gp_delay= [KNL]
5046 Set to less than zero !! 3579 Set wakeup interval for idle CPUs that have
5047 on rcutree.qhimark at !! 3580 only "lazy" RCU callbacks (RCU_FAST_NO_HZ=y).
5048 disable more aggressi !! 3581 Lazy RCU callbacks are those which RCU can
5049 !! 3582 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 3583
5100 rcutree.rcu_kick_kthreads= [KNL] 3584 rcutree.rcu_kick_kthreads= [KNL]
5101 Cause the grace-perio 3585 Cause the grace-period kthread to get an extra
5102 wake_up() if it sleep 3586 wake_up() if it sleeps three times longer than
5103 it should at force-qu 3587 it should at force-quiescent-state time.
5104 This wake_up() will b 3588 This wake_up() will be accompanied by a
5105 WARN_ONCE() splat and 3589 WARN_ONCE() splat and an ftrace_dump().
5106 3590
5107 rcutree.rcu_resched_ns= [KNL] !! 3591 rcuperf.gp_async= [KNL]
5108 Limit the time spend <<
5109 callbacks to the spec <<
5110 By default, this limi <<
5111 every 32 callbacks in <<
5112 inflicted by local_cl <<
5113 <<
5114 rcutree.rcu_unlock_delay= [KNL] <<
5115 In CONFIG_RCU_STRICT_ <<
5116 this specifies an rcu <<
5117 in microseconds. Thi <<
5118 Larger delays increas <<
5119 catching RCU pointer <<
5120 of RCU-protected poin <<
5121 rcu_read_unlock() has <<
5122 <<
5123 rcutree.sysrq_rcu= [KNL] <<
5124 Commandeer a sysrq ke <<
5125 rcu_node tree with an <<
5126 why a new grace perio <<
5127 <<
5128 rcutree.use_softirq= [KNL] <<
5129 If set to zero, move <<
5130 per-CPU rcuc kthreads <<
5131 value, meaning that R <<
5132 Specify rcutree.use_s <<
5133 <<
5134 But note that CONFIG_ <<
5135 this kernel boot para <<
5136 to zero. <<
5137 <<
5138 rcutree.enable_rcu_lazy= [KNL] <<
5139 To save power, batch <<
5140 delay, memory pressur <<
5141 big. <<
5142 <<
5143 rcutree.rcu_normal_wake_from_gp= [KNL <<
5144 Reduces a latency of <<
5145 maintains its own tra <<
5146 does not interact wit <<
5147 use a call_rcu[_hurry <<
5148 normal grace period. <<
5149 <<
5150 How to enable it: <<
5151 <<
5152 echo 1 > /sys/module/ <<
5153 or pass a boot parame <<
5154 <<
5155 Default is 0. <<
5156 <<
5157 rcuscale.gp_async= [KNL] <<
5158 Measure performance o 3592 Measure performance of asynchronous
5159 grace-period primitiv 3593 grace-period primitives such as call_rcu().
5160 3594
5161 rcuscale.gp_async_max= [KNL] !! 3595 rcuperf.gp_async_max= [KNL]
5162 Specify the maximum n 3596 Specify the maximum number of outstanding
5163 callbacks per writer 3597 callbacks per writer thread. When a writer
5164 thread exceeds this l 3598 thread exceeds this limit, it invokes the
5165 corresponding flavor 3599 corresponding flavor of rcu_barrier() to allow
5166 previously posted cal 3600 previously posted callbacks to drain.
5167 3601
5168 rcuscale.gp_exp= [KNL] !! 3602 rcuperf.gp_exp= [KNL]
5169 Measure performance o 3603 Measure performance of expedited synchronous
5170 grace-period primitiv 3604 grace-period primitives.
5171 3605
5172 rcuscale.holdoff= [KNL] !! 3606 rcuperf.holdoff= [KNL]
5173 Set test-start holdof 3607 Set test-start holdoff period. The purpose of
5174 this parameter is to 3608 this parameter is to delay the start of the
5175 test until boot compl 3609 test until boot completes in order to avoid
5176 interference. 3610 interference.
5177 3611
5178 rcuscale.kfree_by_call_rcu= [KNL] !! 3612 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 3613 Set number of RCU readers. The value -1 selects
5220 N, where N is the num 3614 N, where N is the number of CPUs. A value
5221 "n" less than -1 sele 3615 "n" less than -1 selects N-n+1, where N is again
5222 the number of CPUs. 3616 the number of CPUs. For example, -2 selects N
5223 (the number of CPUs), 3617 (the number of CPUs), -3 selects N+1, and so on.
5224 A value of "n" less t 3618 A value of "n" less than or equal to -N selects
5225 a single reader. 3619 a single reader.
5226 3620
5227 rcuscale.nwriters= [KNL] !! 3621 rcuperf.nwriters= [KNL]
5228 Set number of RCU wri 3622 Set number of RCU writers. The values operate
5229 the same as for rcusc !! 3623 the same as for rcuperf.nreaders.
5230 N, where N is the num 3624 N, where N is the number of CPUs
5231 3625
5232 rcuscale.scale_type= [KNL] !! 3626 rcuperf.perf_type= [KNL]
5233 Specify the RCU imple 3627 Specify the RCU implementation to test.
5234 3628
5235 rcuscale.shutdown= [KNL] !! 3629 rcuperf.shutdown= [KNL]
5236 Shut the system down 3630 Shut the system down after performance tests
5237 complete. This is us 3631 complete. This is useful for hands-off automated
5238 testing. 3632 testing.
5239 3633
5240 rcuscale.verbose= [KNL] !! 3634 rcuperf.verbose= [KNL]
5241 Enable additional pri 3635 Enable additional printk() statements.
5242 3636
5243 rcuscale.writer_holdoff= [KNL] !! 3637 rcuperf.writer_holdoff= [KNL]
5244 Write-side holdoff be 3638 Write-side holdoff between grace periods,
5245 in microseconds. The 3639 in microseconds. The default of zero says
5246 no holdoff. 3640 no holdoff.
5247 3641
5248 rcuscale.writer_holdoff_jiffies= [KNL !! 3642 rcutorture.cbflood_inter_holdoff= [KNL]
5249 Additional write-side !! 3643 Set holdoff time (jiffies) between successive
5250 periods, but in jiffi !! 3644 callback-flood tests.
5251 says no holdoff. !! 3645
>> 3646 rcutorture.cbflood_intra_holdoff= [KNL]
>> 3647 Set holdoff time (jiffies) between successive
>> 3648 bursts of callbacks within a given callback-flood
>> 3649 test.
>> 3650
>> 3651 rcutorture.cbflood_n_burst= [KNL]
>> 3652 Set the number of bursts making up a given
>> 3653 callback-flood test. Set this to zero to
>> 3654 disable callback-flood testing.
>> 3655
>> 3656 rcutorture.cbflood_n_per_burst= [KNL]
>> 3657 Set the number of callbacks to be registered
>> 3658 in a given burst of a callback-flood test.
5252 3659
5253 rcutorture.fqs_duration= [KNL] 3660 rcutorture.fqs_duration= [KNL]
5254 Set duration of force 3661 Set duration of force_quiescent_state bursts
5255 in microseconds. 3662 in microseconds.
5256 3663
5257 rcutorture.fqs_holdoff= [KNL] 3664 rcutorture.fqs_holdoff= [KNL]
5258 Set holdoff time with 3665 Set holdoff time within force_quiescent_state bursts
5259 in microseconds. 3666 in microseconds.
5260 3667
5261 rcutorture.fqs_stutter= [KNL] 3668 rcutorture.fqs_stutter= [KNL]
5262 Set wait time between 3669 Set wait time between force_quiescent_state bursts
5263 in seconds. 3670 in seconds.
5264 3671
5265 rcutorture.fwd_progress= [KNL] <<
5266 Specifies the number <<
5267 for RCU grace-period <<
5268 for the types of RCU <<
5269 Defaults to 1 kthread <<
5270 greater than the numb <<
5271 of CPUs to be used. <<
5272 <<
5273 rcutorture.fwd_progress_div= [KNL] <<
5274 Specify the fraction <<
5275 period to do tight-lo <<
5276 <<
5277 rcutorture.fwd_progress_holdoff= [KNL <<
5278 Number of seconds to <<
5279 forward-progress test <<
5280 <<
5281 rcutorture.fwd_progress_need_resched= <<
5282 Enclose cond_resched( <<
5283 need_resched() during <<
5284 testing. <<
5285 <<
5286 rcutorture.gp_cond= [KNL] 3672 rcutorture.gp_cond= [KNL]
5287 Use conditional/async 3673 Use conditional/asynchronous update-side
5288 primitives, if availa 3674 primitives, if available.
5289 3675
5290 rcutorture.gp_exp= [KNL] 3676 rcutorture.gp_exp= [KNL]
5291 Use expedited update- 3677 Use expedited update-side primitives, if available.
5292 3678
5293 rcutorture.gp_normal= [KNL] 3679 rcutorture.gp_normal= [KNL]
5294 Use normal (non-exped 3680 Use normal (non-expedited) asynchronous
5295 update-side primitive 3681 update-side primitives, if available.
5296 3682
5297 rcutorture.gp_sync= [KNL] 3683 rcutorture.gp_sync= [KNL]
5298 Use normal (non-exped 3684 Use normal (non-expedited) synchronous
5299 update-side primitive 3685 update-side primitives, if available. If all
5300 of rcutorture.gp_cond 3686 of rcutorture.gp_cond=, rcutorture.gp_exp=,
5301 rcutorture.gp_normal= 3687 rcutorture.gp_normal=, and rcutorture.gp_sync=
5302 are zero, rcutorture 3688 are zero, rcutorture acts as if is interpreted
5303 they are all non-zero 3689 they are all non-zero.
5304 3690
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] 3691 rcutorture.n_barrier_cbs= [KNL]
5318 Set callbacks/threads 3692 Set callbacks/threads for rcu_barrier() testing.
5319 3693
5320 rcutorture.nfakewriters= [KNL] 3694 rcutorture.nfakewriters= [KNL]
5321 Set number of concurr 3695 Set number of concurrent RCU writers. These just
5322 stress RCU, they don' 3696 stress RCU, they don't participate in the actual
5323 test, hence the "fake 3697 test, hence the "fake".
5324 3698
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] 3699 rcutorture.nreaders= [KNL]
5334 Set number of RCU rea 3700 Set number of RCU readers. The value -1 selects
5335 N-1, where N is the n 3701 N-1, where N is the number of CPUs. A value
5336 "n" less than -1 sele 3702 "n" less than -1 selects N-n-2, where N is again
5337 the number of CPUs. 3703 the number of CPUs. For example, -2 selects N
5338 (the number of CPUs), 3704 (the number of CPUs), -3 selects N+1, and so on.
5339 3705
5340 rcutorture.object_debug= [KNL] 3706 rcutorture.object_debug= [KNL]
5341 Enable debug-object d 3707 Enable debug-object double-call_rcu() testing.
5342 3708
5343 rcutorture.onoff_holdoff= [KNL] 3709 rcutorture.onoff_holdoff= [KNL]
5344 Set time (s) after bo 3710 Set time (s) after boot for CPU-hotplug testing.
5345 3711
5346 rcutorture.onoff_interval= [KNL] 3712 rcutorture.onoff_interval= [KNL]
5347 Set time (jiffies) be !! 3713 Set time (s) between CPU-hotplug operations, or
5348 or zero to disable CP !! 3714 zero to disable CPU-hotplug testing.
5349 <<
5350 rcutorture.read_exit= [KNL] <<
5351 Set the number of rea <<
5352 to test the interacti <<
5353 task-exit processing. <<
5354 <<
5355 rcutorture.read_exit_burst= [KNL] <<
5356 The number of times i <<
5357 episode that a set of <<
5358 is spawned. <<
5359 <<
5360 rcutorture.read_exit_delay= [KNL] <<
5361 The delay, in seconds <<
5362 read-then-exit testin <<
5363 3715
5364 rcutorture.shuffle_interval= [KNL] 3716 rcutorture.shuffle_interval= [KNL]
5365 Set task-shuffle inte 3717 Set task-shuffle interval (s). Shuffling tasks
5366 allows some CPUs to g 3718 allows some CPUs to go into dyntick-idle mode
5367 during the rcutorture 3719 during the rcutorture test.
5368 3720
5369 rcutorture.shutdown_secs= [KNL] 3721 rcutorture.shutdown_secs= [KNL]
5370 Set time (s) after bo 3722 Set time (s) after boot system shutdown. This
5371 is useful for hands-o 3723 is useful for hands-off automated testing.
5372 3724
5373 rcutorture.stall_cpu= [KNL] 3725 rcutorture.stall_cpu= [KNL]
5374 Duration of CPU stall 3726 Duration of CPU stall (s) to test RCU CPU stall
5375 warnings, zero to dis 3727 warnings, zero to disable.
5376 3728
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] 3729 rcutorture.stall_cpu_holdoff= [KNL]
5392 Time to wait (s) afte 3730 Time to wait (s) after boot before inducing stall.
5393 3731
5394 rcutorture.stall_cpu_irqsoff= [KNL] 3732 rcutorture.stall_cpu_irqsoff= [KNL]
5395 Disable interrupts wh 3733 Disable interrupts while stalling if set.
5396 3734
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] 3735 rcutorture.stat_interval= [KNL]
5405 Time (s) between stat 3736 Time (s) between statistics printk()s.
5406 3737
5407 rcutorture.stutter= [KNL] 3738 rcutorture.stutter= [KNL]
5408 Time (s) to stutter t 3739 Time (s) to stutter testing, for example, specifying
5409 five seconds causes t 3740 five seconds causes the test to run for five seconds,
5410 wait for five seconds 3741 wait for five seconds, and so on. This tests RCU's
5411 ability to transition 3742 ability to transition abruptly to and from idle.
5412 3743
5413 rcutorture.test_boost= [KNL] 3744 rcutorture.test_boost= [KNL]
5414 Test RCU priority boo 3745 Test RCU priority boosting? 0=no, 1=maybe, 2=yes.
5415 "Maybe" means test if 3746 "Maybe" means test if the RCU implementation
5416 under test support RC 3747 under test support RCU priority boosting.
5417 3748
5418 rcutorture.test_boost_duration= [KNL] 3749 rcutorture.test_boost_duration= [KNL]
5419 Duration (s) of each 3750 Duration (s) of each individual boost test.
5420 3751
5421 rcutorture.test_boost_interval= [KNL] 3752 rcutorture.test_boost_interval= [KNL]
5422 Interval (s) between 3753 Interval (s) between each boost test.
5423 3754
5424 rcutorture.test_no_idle_hz= [KNL] 3755 rcutorture.test_no_idle_hz= [KNL]
5425 Test RCU's dyntick-id 3756 Test RCU's dyntick-idle handling. See also the
5426 rcutorture.shuffle_in 3757 rcutorture.shuffle_interval parameter.
5427 3758
5428 rcutorture.torture_type= [KNL] 3759 rcutorture.torture_type= [KNL]
5429 Specify the RCU imple 3760 Specify the RCU implementation to test.
5430 3761
5431 rcutorture.verbose= [KNL] 3762 rcutorture.verbose= [KNL]
5432 Enable additional pri 3763 Enable additional printk() statements.
5433 3764
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 3765 rcupdate.rcu_cpu_stall_suppress= [KNL]
5445 Suppress RCU CPU stal 3766 Suppress RCU CPU stall warning messages.
5446 3767
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] 3768 rcupdate.rcu_cpu_stall_timeout= [KNL]
5454 Set timeout for RCU C 3769 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 3770
5479 rcupdate.rcu_expedited= [KNL] 3771 rcupdate.rcu_expedited= [KNL]
5480 Use expedited grace-p 3772 Use expedited grace-period primitives, for
5481 example, synchronize_ 3773 example, synchronize_rcu_expedited() instead
5482 of synchronize_rcu(). 3774 of synchronize_rcu(). This reduces latency,
5483 but can increase CPU 3775 but can increase CPU utilization, degrade
5484 real-time latency, an 3776 real-time latency, and degrade energy efficiency.
5485 No effect on CONFIG_T 3777 No effect on CONFIG_TINY_RCU kernels.
5486 3778
5487 rcupdate.rcu_normal= [KNL] 3779 rcupdate.rcu_normal= [KNL]
5488 Use only normal grace 3780 Use only normal grace-period primitives,
5489 for example, synchron 3781 for example, synchronize_rcu() instead of
5490 synchronize_rcu_exped 3782 synchronize_rcu_expedited(). This improves
5491 real-time latency, CP 3783 real-time latency, CPU utilization, and
5492 energy efficiency, bu 3784 energy efficiency, but can expose users to
5493 increased grace-perio 3785 increased grace-period latency. This parameter
5494 overrides rcupdate.rc 3786 overrides rcupdate.rcu_expedited. No effect on
5495 CONFIG_TINY_RCU kerne 3787 CONFIG_TINY_RCU kernels.
5496 3788
5497 rcupdate.rcu_normal_after_boot= [KNL] 3789 rcupdate.rcu_normal_after_boot= [KNL]
5498 Once boot has complet 3790 Once boot has completed (that is, after
5499 rcu_end_inkernel_boot 3791 rcu_end_inkernel_boot() has been invoked), use
5500 only normal grace-per 3792 only normal grace-period primitives. No effect
5501 on CONFIG_TINY_RCU ke 3793 on CONFIG_TINY_RCU kernels.
5502 3794
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 3795 rcupdate.rcu_task_stall_timeout= [KNL]
5570 Set timeout in jiffie !! 3796 Set timeout in jiffies for RCU task stall warning
5571 warning messages. Di !! 3797 messages. Disable with a value less than or equal
5572 than or equal to zero !! 3798 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 3799
5599 rcupdate.rcu_self_test= [KNL] 3800 rcupdate.rcu_self_test= [KNL]
5600 Run the RCU early boo 3801 Run the RCU early boot self tests
5601 3802
>> 3803 rcupdate.rcu_self_test_bh= [KNL]
>> 3804 Run the RCU bh early boot self tests
>> 3805
>> 3806 rcupdate.rcu_self_test_sched= [KNL]
>> 3807 Run the RCU sched early boot self tests
>> 3808
5602 rdinit= [KNL] 3809 rdinit= [KNL]
5603 Format: <full_path> 3810 Format: <full_path>
5604 Run specified binary 3811 Run specified binary instead of /init from the ramdisk,
5605 used for early usersp 3812 used for early userspace startup. See initrd.
5606 3813
5607 rdrand= [X86,EARLY] <<
5608 force - Override the <<
5609 advertisement <<
5610 certain AMD p <<
5611 support, spec <<
5612 path). <<
5613 <<
5614 rdt= [HW,X86,RDT] 3814 rdt= [HW,X86,RDT]
5615 Turn on/off individua 3815 Turn on/off individual RDT features. List is:
5616 cmt, mbmtotal, mbmloc 3816 cmt, mbmtotal, mbmlocal, l3cat, l3cdp, l2cat, l2cdp,
5617 mba, smba, bmec. !! 3817 mba.
5618 E.g. to turn on cmt a 3818 E.g. to turn on cmt and turn off mba use:
5619 rdt=cmt,!mba 3819 rdt=cmt,!mba
5620 3820
5621 reboot= [KNL] 3821 reboot= [KNL]
5622 Format (x86 or x86_64 3822 Format (x86 or x86_64):
5623 [w[arm] | c[o !! 3823 [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \
5624 [[,]s[mp]#### 3824 [[,]s[mp]#### \
5625 [[,]b[ios] | 3825 [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \
5626 [[,]f[orce] 3826 [[,]f[orce]
5627 Where reboot_mode is !! 3827 Where reboot_mode is one of warm (soft) or cold (hard) or gpio,
5628 (pref <<
5629 reboo <<
5630 reboot_type is 3828 reboot_type is one of bios, acpi, kbd, triple, efi, or pci,
5631 reboot_force is 3829 reboot_force is either force or not specified,
5632 reboot_cpu is s 3830 reboot_cpu is s[mp]#### with #### being the processor
5633 to be 3831 to be used for rebooting.
5634 3832
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= 3833 relax_domain_level=
5694 [KNL, SMP] Set schedu 3834 [KNL, SMP] Set scheduler's default relax_domain_level.
5695 See Documentation/adm !! 3835 See Documentation/cgroup-v1/cpusets.txt.
5696 3836
5697 reserve= [KNL,BUGS] Force kern 3837 reserve= [KNL,BUGS] Force kernel to ignore I/O ports or memory
5698 Format: <base1>,<size 3838 Format: <base1>,<size1>[,<base2>,<size2>,...]
5699 Reserve I/O ports or 3839 Reserve I/O ports or memory so the kernel won't use
5700 them. If <base> is l 3840 them. If <base> is less than 0x10000, the region
5701 is assumed to be I/O 3841 is assumed to be I/O ports; otherwise it is memory.
5702 3842
5703 reserve_mem= [RAM] !! 3843 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] 3844 Format: nn[KMG]
5727 Reserves a hole at th 3845 Reserves a hole at the top of the kernel virtual
5728 address space. 3846 address space.
5729 3847
>> 3848 reservelow= [X86]
>> 3849 Format: nn[K]
>> 3850 Set the amount of memory to reserve for BIOS at
>> 3851 the bottom of the address space.
>> 3852
5730 reset_devices [KNL] Force drivers t 3853 reset_devices [KNL] Force drivers to reset the underlying device
5731 during initialization 3854 during initialization.
5732 3855
5733 resume= [SWSUSP] 3856 resume= [SWSUSP]
5734 Specify the partition 3857 Specify the partition device for software suspend
5735 Format: 3858 Format:
5736 {/dev/<dev> | PARTUUI 3859 {/dev/<dev> | PARTUUID=<uuid> | <int>:<int> | <hex>}
5737 3860
5738 resume_offset= [SWSUSP] 3861 resume_offset= [SWSUSP]
5739 Specify the offset fr 3862 Specify the offset from the beginning of the partition
5740 given by "resume=" at 3863 given by "resume=" at which the swap header is located,
5741 in <PAGE_SIZE> units 3864 in <PAGE_SIZE> units (needed only for swap files).
5742 See Documentation/po !! 3865 See Documentation/power/swsusp-and-swap-files.txt
5743 3866
5744 resumedelay= [HIBERNATION] Delay ( 3867 resumedelay= [HIBERNATION] Delay (in seconds) to pause before attempting to
5745 read the resume files 3868 read the resume files
5746 3869
5747 resumewait [HIBERNATION] Wait (i 3870 resumewait [HIBERNATION] Wait (indefinitely) for resume device to show up.
5748 Useful for devices th 3871 Useful for devices that are detected asynchronously
5749 (e.g. USB and MMC dev 3872 (e.g. USB and MMC devices).
5750 3873
5751 retain_initrd [RAM] Keep initrd mem !! 3874 hibernate= [HIBERNATION]
5752 be accessible via /sy !! 3875 noresume Don't check if there's a hibernation image
5753 !! 3876 present during boot.
5754 retbleed= [X86] Control mitigat !! 3877 nocompress Don't compress/decompress hibernation images.
5755 Speculative Code Exec !! 3878 no Disable hibernation and resume.
5756 vulnerability. !! 3879 protect_image Turn on image protection during restoration
5757 !! 3880 (that will set all pages holding image data
5758 AMD-based UNRET and I !! 3881 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 3882
5789 Not specifying this o !! 3883 retain_initrd [RAM] Keep initrd memory after extraction
5790 3884
5791 rfkill.default_state= 3885 rfkill.default_state=
5792 0 "airplane mode". All 3886 0 "airplane mode". All wifi, bluetooth, wimax, gps, fm,
5793 etc. communication is 3887 etc. communication is blocked by default.
5794 1 Unblocked. 3888 1 Unblocked.
5795 3889
5796 rfkill.master_switch_mode= 3890 rfkill.master_switch_mode=
5797 0 The "airplane mode" b 3891 0 The "airplane mode" button does nothing.
5798 1 The "airplane mode" b 3892 1 The "airplane mode" button toggles between everything
5799 blocked and the previ 3893 blocked and the previous configuration.
5800 2 The "airplane mode" b 3894 2 The "airplane mode" button toggles between everything
5801 blocked and everythin 3895 blocked and everything unblocked.
5802 3896
>> 3897 rhash_entries= [KNL,NET]
>> 3898 Set number of hash buckets for route cache
>> 3899
5803 ring3mwait=disable 3900 ring3mwait=disable
5804 [KNL] Disable ring 3 3901 [KNL] Disable ring 3 MONITOR/MWAIT feature on supported
5805 CPUs. 3902 CPUs.
5806 3903
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 3904 ro [KNL] Mount root device read-only on boot
5815 3905
5816 rodata= [KNL,EARLY] !! 3906 rodata= [KNL]
5817 on Mark read-only kernel 3907 on Mark read-only kernel memory as read-only (default).
5818 off Leave read-only kerne 3908 off Leave read-only kernel memory writable for debugging.
5819 full Mark read-only kernel <<
5820 [arm64] <<
5821 3909
5822 rockchip.usb_uart 3910 rockchip.usb_uart
5823 [EARLY] <<
5824 Enable the uart passt 3911 Enable the uart passthrough on the designated usb port
5825 on Rockchip SoCs. Whe 3912 on Rockchip SoCs. When active, the signals of the
5826 debug-uart get routed 3913 debug-uart get routed to the D+ and D- pins of the usb
5827 port and the regular 3914 port and the regular usb controller gets disabled.
5828 3915
5829 root= [KNL] Root filesystem 3916 root= [KNL] Root filesystem
5830 Usually this a a bloc !! 3917 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 3918
5837 rootdelay= [KNL] Delay (in secon 3919 rootdelay= [KNL] Delay (in seconds) to pause before attempting to
5838 mount the root filesy 3920 mount the root filesystem
5839 3921
5840 rootflags= [KNL] Set root filesy 3922 rootflags= [KNL] Set root filesystem mount option string
5841 3923
5842 rootfstype= [KNL] Set root filesy 3924 rootfstype= [KNL] Set root filesystem type
5843 3925
5844 rootwait [KNL] Wait (indefinit 3926 rootwait [KNL] Wait (indefinitely) for root device to show up.
5845 Useful for devices th 3927 Useful for devices that are detected asynchronously
5846 (e.g. USB and MMC dev 3928 (e.g. USB and MMC devices).
5847 3929
5848 rootwait= [KNL] Maximum time (i <<
5849 to show up before att <<
5850 filesystem. <<
5851 <<
5852 rproc_mem=nn[KMG][@address] 3930 rproc_mem=nn[KMG][@address]
5853 [KNL,ARM,CMA] Remotep 3931 [KNL,ARM,CMA] Remoteproc physical memory block.
5854 Memory area to be use 3932 Memory area to be used by remote processor image,
5855 managed by CMA. 3933 managed by CMA.
5856 3934
5857 rw [KNL] Mount root devi 3935 rw [KNL] Mount root device read-write on boot
5858 3936
5859 S [KNL] Run init in sin 3937 S [KNL] Run init in single mode
5860 3938
5861 s390_iommu= [HW,S390] 3939 s390_iommu= [HW,S390]
5862 Set s390 IOTLB flushi 3940 Set s390 IOTLB flushing mode
5863 strict 3941 strict
5864 With strict flushing !! 3942 With strict flushing every unmap operation will result in
5865 in an IOTLB flush. De !! 3943 an IOTLB flush. Default is lazy flushing before reuse,
5866 reuse, which is faste !! 3944 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 3945
5881 sa1100ir [NET] 3946 sa1100ir [NET]
5882 See drivers/net/irda/ 3947 See drivers/net/irda/sa1100_ir.c.
5883 3948
5884 sched_verbose [KNL,EARLY] Enables v !! 3949 sbni= [NET] Granch SBNI12 leased line adapter
>> 3950
>> 3951 sched_debug [KNL] Enables verbose scheduler debug messages.
5885 3952
5886 schedstats= [KNL,X86] Enable or d 3953 schedstats= [KNL,X86] Enable or disable scheduled statistics.
5887 Allowed values are en 3954 Allowed values are enable and disable. This feature
5888 incurs a small amount 3955 incurs a small amount of overhead in the scheduler
5889 but is useful for deb 3956 but is useful for debugging and performance tuning.
5890 3957
5891 sched_thermal_decay_shift= !! 3958 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 3959 xtime_lock contention on larger systems, and/or RCU lock
6002 contention on all sys 3960 contention on all systems with CONFIG_MAXSMP set.
6003 Format: { "0" | "1" } 3961 Format: { "0" | "1" }
6004 0 -- disable. (may be 3962 0 -- disable. (may be 1 via CONFIG_CMDLINE="skew_tick=1"
6005 1 -- enable. 3963 1 -- enable.
6006 Note: increases power 3964 Note: increases power consumption, thus should only be
6007 enabled if running ji 3965 enabled if running jitter sensitive (HPC/RT) workloads.
6008 3966
6009 security= [SECURITY] Choose a l !! 3967 security= [SECURITY] Choose a security module to enable at boot.
6010 enable at boot. This !! 3968 If this boot parameter is not specified, only the first
6011 "lsm=" parameter. !! 3969 security module asking for security registration will be
>> 3970 loaded. An invalid security module name will be treated
>> 3971 as if no module has been chosen.
6012 3972
6013 selinux= [SELINUX] Disable or 3973 selinux= [SELINUX] Disable or enable SELinux at boot time.
6014 Format: { "0" | "1" } 3974 Format: { "0" | "1" }
6015 See security/selinux/ 3975 See security/selinux/Kconfig help text.
6016 0 -- disable. 3976 0 -- disable.
6017 1 -- enable. 3977 1 -- enable.
6018 Default value is 1. !! 3978 Default value is set via kernel config option.
>> 3979 If enabled at boot time, /selinux/disable can be used
>> 3980 later to disable prior to initial policy load.
6019 3981
6020 serialnumber [BUGS=X86-32] !! 3982 apparmor= [APPARMOR] Disable or enable AppArmor at boot time
>> 3983 Format: { "0" | "1" }
>> 3984 See security/apparmor/Kconfig help text
>> 3985 0 -- disable.
>> 3986 1 -- enable.
>> 3987 Default value is set via kernel config option.
6021 3988
6022 sev=option[,option...] [X86-64] See D !! 3989 serialnumber [BUGS=X86-32]
6023 3990
6024 shapers= [NET] 3991 shapers= [NET]
6025 Maximal number of sha 3992 Maximal number of shapers.
6026 3993
6027 show_lapic= [APIC,X86] Advanced P !! 3994 simeth= [IA-64]
6028 Limit apic dumping. T !! 3995 simscsi=
6029 number of local apics !! 3996
6030 to set it to "all" by !! 3997 slram= [HW,MTD]
6031 Format: { 1 (default) !! 3998
6032 The parameter valid i !! 3999 slab_nomerge [MM]
6033 apic=verbose is speci !! 4000 Disable merging of slabs with similar size. May be
6034 Example: apic=debug s !! 4001 necessary if there is some reason to distinguish
>> 4002 allocs to different slabs, especially in hardened
>> 4003 environments where the risk of heap overflows and
>> 4004 layout control by attackers can usually be
>> 4005 frustrated by disabling merging. This will reduce
>> 4006 most of the exposure of a heap attack to a single
>> 4007 cache (risks via metadata attacks are mostly
>> 4008 unchanged). Debug options disable merging on their
>> 4009 own.
>> 4010 For more information see Documentation/vm/slub.rst.
>> 4011
>> 4012 slab_max_order= [MM, SLAB]
>> 4013 Determines the maximum allowed order for slabs.
>> 4014 A high setting may cause OOMs due to memory
>> 4015 fragmentation. Defaults to 1 for systems with
>> 4016 more than 32MB of RAM, 0 otherwise.
6035 4017
6036 slab_debug[=options[,slabs][;[options !! 4018 slub_debug[=options[,slabs]] [MM, SLUB]
6037 Enabling slab_debug a !! 4019 Enabling slub_debug allows one to determine the
6038 culprit if slab objec 4020 culprit if slab objects become corrupted. Enabling
6039 slab_debug can create !! 4021 slub_debug can create guard zones around objects and
6040 may poison objects wh 4022 may poison objects when not in use. Also tracks the
6041 last alloc / free. Fo 4023 last alloc / free. For more information see
6042 Documentation/mm/slub !! 4024 Documentation/vm/slub.rst.
6043 (slub_debug legacy na !! 4025
>> 4026 slub_memcg_sysfs= [MM, SLUB]
>> 4027 Determines whether to enable sysfs directories for
>> 4028 memory cgroup sub-caches. 1 to enable, 0 to disable.
>> 4029 The default is determined by CONFIG_SLUB_MEMCG_SYSFS_ON.
>> 4030 Enabling this can lead to a very high number of debug
>> 4031 directories and files being created under
>> 4032 /sys/kernel/slub.
6044 4033
6045 slab_max_order= [MM] !! 4034 slub_max_order= [MM, SLUB]
6046 Determines the maximu 4035 Determines the maximum allowed order for slabs.
6047 A high setting may ca 4036 A high setting may cause OOMs due to memory
6048 fragmentation. For mo 4037 fragmentation. For more information see
6049 Documentation/mm/slub !! 4038 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 4039
6057 slab_min_objects= [MM] !! 4040 slub_min_objects= [MM, SLUB]
6058 The minimum number of 4041 The minimum number of objects per slab. SLUB will
6059 increase the slab ord !! 4042 increase the slab order up to slub_max_order to
6060 generate a sufficient 4043 generate a sufficiently large slab able to contain
6061 the number of objects 4044 the number of objects indicated. The higher the number
6062 of objects the smalle 4045 of objects the smaller the overhead of tracking slabs
6063 and the less frequent 4046 and the less frequently locks need to be acquired.
6064 For more information !! 4047 For more information see Documentation/vm/slub.rst.
6065 (slub_min_objects leg <<
6066 4048
6067 slab_min_order= [MM] !! 4049 slub_min_order= [MM, SLUB]
6068 Determines the minimu 4050 Determines the minimum page order for slabs. Must be
6069 lower or equal to sla !! 4051 lower than slub_max_order.
6070 Documentation/mm/slub !! 4052 For more information see Documentation/vm/slub.rst.
6071 (slub_min_order legac <<
6072 4053
6073 slab_nomerge [MM] !! 4054 slub_nomerge [MM, SLUB]
6074 Disable merging of sl !! 4055 Same with slab_nomerge. This is supported for legacy.
6075 necessary if there is !! 4056 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 4057
6089 smart2= [HW] 4058 smart2= [HW]
6090 Format: <io1>[,<io2>[ 4059 Format: <io1>[,<io2>[,...,<io8>]]
6091 4060
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 4061 smsc-ircc2.nopnp [HW] Don't use PNP to discover SMC devices
6111 smsc-ircc2.ircc_cfg= [HW] Device c 4062 smsc-ircc2.ircc_cfg= [HW] Device configuration I/O port
6112 smsc-ircc2.ircc_sir= [HW] SIR base 4063 smsc-ircc2.ircc_sir= [HW] SIR base I/O port
6113 smsc-ircc2.ircc_fir= [HW] FIR base 4064 smsc-ircc2.ircc_fir= [HW] FIR base I/O port
6114 smsc-ircc2.ircc_irq= [HW] IRQ line 4065 smsc-ircc2.ircc_irq= [HW] IRQ line
6115 smsc-ircc2.ircc_dma= [HW] DMA chan 4066 smsc-ircc2.ircc_dma= [HW] DMA channel
6116 smsc-ircc2.ircc_transceiver= [HW] Tra 4067 smsc-ircc2.ircc_transceiver= [HW] Transceiver type:
6117 0: Toshiba Sa 4068 0: Toshiba Satellite 1800 (GP data pin select)
6118 1: Fast pin s 4069 1: Fast pin select (default)
6119 2: ATC IRMode 4070 2: ATC IRMode
6120 4071
6121 smt= [KNL,MIPS,S390,EARLY] !! 4072 smt [KNL,S390] Set the maximum number of threads (logical
6122 (logical CPUs) to use !! 4073 CPUs) to use per physical CPU on systems capable of
6123 capable of symmetric !! 4074 symmetric multithreading (SMT). Will be capped to the
6124 be capped to the actu !! 4075 actual hardware limit.
6125 Format: <integer> 4076 Format: <integer>
6126 Default: -1 (no limit 4077 Default: -1 (no limit)
6127 4078
6128 softlockup_panic= 4079 softlockup_panic=
6129 [KNL] Should the soft 4080 [KNL] Should the soft-lockup detector generate panics.
6130 Format: 0 | 1 !! 4081 Format: <integer>
6131 4082
6132 A value of 1 instruct !! 4083 A nonzero value instructs the soft-lockup detector
6133 to panic the machine !! 4084 to panic the machine when a soft-lockup occurs. This
6134 also controlled by th !! 4085 is also controlled by CONFIG_BOOTPARAM_SOFTLOCKUP_PANIC
6135 and CONFIG_BOOTPARAM_ !! 4086 which is the respective build-time switch to that
6136 respective build-time !! 4087 functionality.
6137 4088
6138 softlockup_all_cpu_backtrace= 4089 softlockup_all_cpu_backtrace=
6139 [KNL] Should the soft 4090 [KNL] Should the soft-lockup detector generate
6140 backtraces on all cpu 4091 backtraces on all cpus.
6141 Format: 0 | 1 !! 4092 Format: <integer>
6142 4093
6143 sonypi.*= [HW] Sony Programmabl 4094 sonypi.*= [HW] Sony Programmable I/O Control Device driver
6144 See Documentation/adm !! 4095 See Documentation/laptops/sonypi.txt
6145 <<
6146 spectre_bhi= [X86] Control mitigat <<
6147 (BHI) vulnerability. <<
6148 deployment of the HW <<
6149 clearing sequence. <<
6150 <<
6151 on - (default) En <<
6152 needed. Thi <<
6153 both syscall <<
6154 vmexit - On systems w <<
6155 available, e <<
6156 ONLY. On su <<
6157 protected fr <<
6158 may still be <<
6159 off - Disable the <<
6160 4096
6161 spectre_v2= [X86,EARLY] Control m !! 4097 spectre_v2= [X86] Control mitigation of Spectre variant 2
6162 (indirect branch spec 4098 (indirect branch speculation) vulnerability.
6163 The default operation <<
6164 user space attacks. <<
6165 4099
6166 on - unconditionall !! 4100 on - unconditionally enable
6167 spectre_v2_use !! 4101 off - unconditionally disable
6168 off - unconditionall <<
6169 spectre_v2_use <<
6170 auto - kernel detects 4102 auto - kernel detects whether your CPU model is
6171 vulnerable 4103 vulnerable
6172 4104
6173 Selecting 'on' will, 4105 Selecting 'on' will, and 'auto' may, choose a
6174 mitigation method at 4106 mitigation method at run time according to the
6175 CPU, the available mi 4107 CPU, the available microcode, the setting of the
6176 CONFIG_MITIGATION_RET !! 4108 CONFIG_RETPOLINE configuration option, and the
6177 and the compiler with !! 4109 compiler with which the kernel was built.
6178 <<
6179 Selecting 'on' will a <<
6180 against user space to <<
6181 <<
6182 Selecting 'off' will <<
6183 the user space protec <<
6184 4110
6185 Specific mitigations 4111 Specific mitigations can also be selected manually:
6186 4112
6187 retpoline - r 4113 retpoline - replace indirect branches
6188 retpoline,generic - R !! 4114 retpoline,generic - google's original retpoline
6189 retpoline,lfence - L !! 4115 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 4116
6196 Not specifying this o 4117 Not specifying this option is equivalent to
6197 spectre_v2=auto. 4118 spectre_v2=auto.
6198 4119
6199 spectre_v2_user= <<
6200 [X86] Control mitigat <<
6201 (indirect branch spec <<
6202 user space tasks <<
6203 <<
6204 on - Uncondition <<
6205 enforced by <<
6206 <<
6207 off - Uncondition <<
6208 enforced by <<
6209 <<
6210 prctl - Indirect br <<
6211 but mitigat <<
6212 per thread. <<
6213 is inherite <<
6214 <<
6215 prctl,ibpb <<
6216 - Like "prctl <<
6217 controlled <<
6218 always when <<
6219 space proce <<
6220 <<
6221 seccomp <<
6222 - Same as "pr <<
6223 threads wil <<
6224 they explic <<
6225 <<
6226 seccomp,ibpb <<
6227 - Like "secco <<
6228 controlled <<
6229 always when <<
6230 user space <<
6231 <<
6232 auto - Kernel sele <<
6233 the availab <<
6234 <<
6235 Default mitigation: " <<
6236 <<
6237 Not specifying this o <<
6238 spectre_v2_user=auto. <<
6239 <<
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= 4120 spec_store_bypass_disable=
6252 [HW,EARLY] Control Sp !! 4121 [HW] Control Speculative Store Bypass (SSB) Disable mitigation
6253 (Speculative Store By 4122 (Speculative Store Bypass vulnerability)
6254 4123
6255 Certain CPUs are vuln 4124 Certain CPUs are vulnerable to an exploit against a
6256 a common industry wid 4125 a common industry wide performance optimization known
6257 as "Speculative Store 4126 as "Speculative Store Bypass" in which recent stores
6258 to the same memory lo 4127 to the same memory location may not be observed by
6259 later loads during sp 4128 later loads during speculative execution. The idea
6260 is that such stores a 4129 is that such stores are unlikely and that they can
6261 be detected prior to 4130 be detected prior to instruction retirement at the
6262 end of a particular s 4131 end of a particular speculation execution window.
6263 4132
6264 In vulnerable process 4133 In vulnerable processors, the speculatively forwarded
6265 store can be used in 4134 store can be used in a cache side channel attack, for
6266 example to read memor 4135 example to read memory to which the attacker does not
6267 directly have access 4136 directly have access (e.g. inside sandboxed code).
6268 4137
6269 This parameter contro 4138 This parameter controls whether the Speculative Store
6270 Bypass optimization i 4139 Bypass optimization is used.
6271 4140
6272 On x86 the options ar <<
6273 <<
6274 on - Uncondition 4141 on - Unconditionally disable Speculative Store Bypass
6275 off - Uncondition 4142 off - Unconditionally enable Speculative Store Bypass
6276 auto - Kernel dete 4143 auto - Kernel detects whether the CPU model contains an
6277 implementat 4144 implementation of Speculative Store Bypass and
6278 picks the m 4145 picks the most appropriate mitigation. If the
6279 CPU is not 4146 CPU is not vulnerable, "off" is selected. If the
6280 CPU is vuln 4147 CPU is vulnerable the default mitigation is
6281 architectur 4148 architecture and Kconfig dependent. See below.
6282 prctl - Control Spe 4149 prctl - Control Speculative Store Bypass per thread
6283 via prctl. 4150 via prctl. Speculative Store Bypass is enabled
6284 for a proce 4151 for a process by default. The state of the control
6285 is inherite 4152 is inherited on fork.
6286 seccomp - Same as "pr 4153 seccomp - Same as "prctl" above, but all seccomp threads
6287 will disabl 4154 will disable SSB unless they explicitly opt out.
6288 4155
6289 Default mitigations: <<
6290 X86: "prctl" <<
6291 <<
6292 On powerpc the option <<
6293 <<
6294 on,auto - On Power8 a <<
6295 barrier on <<
6296 perform a s <<
6297 exit. <<
6298 off - No action. <<
6299 <<
6300 Not specifying this o 4156 Not specifying this option is equivalent to
6301 spec_store_bypass_dis 4157 spec_store_bypass_disable=auto.
6302 4158
6303 split_lock_detect= !! 4159 Default mitigations:
6304 [X86] Enable split lo !! 4160 X86: If CONFIG_SECCOMP=y "seccomp", otherwise "prctl"
6305 4161
6306 When enabled (and if !! 4162 spia_io_base= [HW,MTD]
6307 instructions that acc !! 4163 spia_fio_base=
6308 boundaries will resul !! 4164 spia_pedr=
6309 for split lock detect !! 4165 spia_peddr=
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 4166
6387 srcutree.counter_wrap_check [KNL] 4167 srcutree.counter_wrap_check [KNL]
6388 Specifies how frequen 4168 Specifies how frequently to check for
6389 grace-period sequence 4169 grace-period sequence counter wrap for the
6390 srcu_data structure's 4170 srcu_data structure's ->srcu_gp_seq_needed field.
6391 The greater the numbe 4171 The greater the number of bits set in this kernel
6392 parameter, the less f 4172 parameter, the less frequently counter wrap will
6393 be checked for. Note 4173 be checked for. Note that the bottom two bits
6394 are ignored. 4174 are ignored.
6395 4175
6396 srcutree.exp_holdoff [KNL] 4176 srcutree.exp_holdoff [KNL]
6397 Specifies how many na 4177 Specifies how many nanoseconds must elapse
6398 since the end of the 4178 since the end of the last SRCU grace period for
6399 a given srcu_struct u 4179 a given srcu_struct until the next normal SRCU
6400 grace period will be 4180 grace period will be considered for automatic
6401 expediting. Set to z 4181 expediting. Set to zero to disable automatic
6402 expediting. 4182 expediting.
6403 4183
6404 srcutree.srcu_max_nodelay [KNL] !! 4184 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 4185 Speculative Store Bypass Disable control
6432 4186
6433 On CPUs that are vuln 4187 On CPUs that are vulnerable to the Speculative
6434 Store Bypass vulnerab 4188 Store Bypass vulnerability and offer a
6435 firmware based mitiga 4189 firmware based mitigation, this parameter
6436 indicates how the mit 4190 indicates how the mitigation should be used:
6437 4191
6438 force-on: Unconditio 4192 force-on: Unconditionally enable mitigation for
6439 for both k 4193 for both kernel and userspace
6440 force-off: Unconditio 4194 force-off: Unconditionally disable mitigation for
6441 for both k 4195 for both kernel and userspace
6442 kernel: Always ena 4196 kernel: Always enable mitigation in the
6443 kernel, an 4197 kernel, and offer a prctl interface
6444 to allow u 4198 to allow userspace to register its
6445 interest i 4199 interest in being mitigated too.
6446 4200
6447 stack_guard_gap= [MM] 4201 stack_guard_gap= [MM]
6448 override the default 4202 override the default stack gap protection. The value
6449 is in page units and 4203 is in page units and it defines how many pages prior
6450 to (for stacks growin 4204 to (for stacks growing down) resp. after (for stacks
6451 growing up) the main 4205 growing up) the main stack are reserved for no other
6452 mapping. Default valu 4206 mapping. Default value is 256 pages.
6453 4207
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] 4208 stacktrace [FTRACE]
6461 Enabled the stack tra 4209 Enabled the stack tracer on boot up.
6462 4210
6463 stacktrace_filter=[function-list] 4211 stacktrace_filter=[function-list]
6464 [FTRACE] Limit the fu 4212 [FTRACE] Limit the functions that the stack tracer
6465 will trace at boot up !! 4213 will trace at boot up. function-list is a comma separated
6466 list of functions. Th 4214 list of functions. This list can be changed at run
6467 time by the stack_tra 4215 time by the stack_trace_filter file in the debugfs
6468 tracing directory. No 4216 tracing directory. Note, this enables stack tracing
6469 and the stacktrace ab 4217 and the stacktrace above is not needed.
6470 4218
6471 sti= [PARISC,HW] 4219 sti= [PARISC,HW]
6472 Format: <num> 4220 Format: <num>
6473 Set the STI (builtin 4221 Set the STI (builtin display/keyboard on the HP-PARISC
6474 machines) console (gr 4222 machines) console (graphic card) which should be used
6475 as the initial boot-c 4223 as the initial boot-console.
6476 See also comment in d 4224 See also comment in drivers/video/console/sticore.c.
6477 4225
6478 sti_font= [HW] 4226 sti_font= [HW]
6479 See comment in driver 4227 See comment in drivers/video/console/sticore.c.
6480 4228
6481 stifb= [HW] 4229 stifb= [HW]
6482 Format: bpp:<bpp1>[:< 4230 Format: bpp:<bpp1>[:<bpp2>[:<bpp3>...]]
6483 4231
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= 4232 sunrpc.min_resvport=
6504 sunrpc.max_resvport= 4233 sunrpc.max_resvport=
6505 [NFS,SUNRPC] 4234 [NFS,SUNRPC]
6506 SunRPC servers often 4235 SunRPC servers often require that client requests
6507 originate from a priv 4236 originate from a privileged port (i.e. a port in the
6508 range 0 < portnr < 10 4237 range 0 < portnr < 1024).
6509 An administrator who 4238 An administrator who wishes to reserve some of these
6510 ports for other uses 4239 ports for other uses may adjust the range that the
6511 kernel's sunrpc clien 4240 kernel's sunrpc client considers to be privileged
6512 using these two param 4241 using these two parameters to set the minimum and
6513 maximum port values. 4242 maximum port values.
6514 4243
6515 sunrpc.svc_rpc_per_connection_limit= 4244 sunrpc.svc_rpc_per_connection_limit=
6516 [NFS,SUNRPC] 4245 [NFS,SUNRPC]
6517 Limit the number of r 4246 Limit the number of requests that the server will
6518 process in parallel f 4247 process in parallel from a single connection.
6519 The default value is 4248 The default value is 0 (no limit).
6520 4249
6521 sunrpc.pool_mode= 4250 sunrpc.pool_mode=
6522 [NFS] 4251 [NFS]
6523 Control how the NFS s 4252 Control how the NFS server code allocates CPUs to
6524 service thread pools. 4253 service thread pools. Depending on how many NICs
6525 you have and where th 4254 you have and where their interrupts are bound, this
6526 option will affect wh 4255 option will affect which CPUs will do NFS serving.
6527 Note: this parameter 4256 Note: this parameter cannot be changed while the
6528 NFS server is running 4257 NFS server is running.
6529 4258
6530 auto the serve 4259 auto the server chooses an appropriate mode
6531 automatic 4260 automatically using heuristics
6532 global a single 4261 global a single global pool contains all CPUs
6533 percpu one pool 4262 percpu one pool for each CPU
6534 pernode one pool 4263 pernode one pool for each NUMA node (equivalent
6535 to global 4264 to global on non-NUMA machines)
6536 4265
6537 sunrpc.tcp_slot_table_entries= 4266 sunrpc.tcp_slot_table_entries=
6538 sunrpc.udp_slot_table_entries= 4267 sunrpc.udp_slot_table_entries=
6539 [NFS,SUNRPC] 4268 [NFS,SUNRPC]
6540 Sets the upper limit 4269 Sets the upper limit on the number of simultaneous
6541 RPC calls that can be 4270 RPC calls that can be sent from the client to a
6542 server. Increasing th 4271 server. Increasing these values may allow you to
6543 improve throughput, b 4272 improve throughput, but will also increase the
6544 amount of memory rese 4273 amount of memory reserved for use by the client.
6545 4274
6546 suspend.pm_test_delay= 4275 suspend.pm_test_delay=
6547 [SUSPEND] 4276 [SUSPEND]
6548 Sets the number of se 4277 Sets the number of seconds to remain in a suspend test
6549 mode before resuming 4278 mode before resuming the system (see
6550 /sys/power/pm_test). 4279 /sys/power/pm_test). Only available when CONFIG_PM_DEBUG
6551 is set. Default value 4280 is set. Default value is 5.
6552 4281
6553 svm= [PPC] !! 4282 swapaccount=[0|1]
6554 Format: { on | off | !! 4283 [KNL] Enable accounting of swap in memory resource
6555 This parameter contro !! 4284 controller if no parameter or 1 is given or disable
6556 Execution Facility on !! 4285 it if 0 is given (See Documentation/cgroup-v1/memory.txt)
6557 4286
6558 swiotlb= [ARM,PPC,MIPS,X86,S39 !! 4287 swiotlb= [ARM,IA-64,PPC,MIPS,X86]
6559 Format: { <int> [,<in !! 4288 Format: { <int> | force | noforce }
6560 <int> -- Number of I/ 4289 <int> -- Number of I/O TLB slabs
6561 <int> -- Second integ <<
6562 areas with t <<
6563 to a power o <<
6564 force -- force using 4290 force -- force using of bounce buffers even if they
6565 wouldn't be 4291 wouldn't be automatically used by the kernel
6566 noforce -- Never use 4292 noforce -- Never use bounce buffers (for debugging)
6567 4293
6568 switches= [HW,M68k,EARLY] !! 4294 switches= [HW,M68k]
6569 4295
6570 sysctl.*= [KNL] !! 4296 sysfs.deprecated=0|1 [KNL]
6571 Set a sysctl paramete !! 4297 Enable/disable old style sysfs layout for old udev
6572 process, as if the va !! 4298 on older distributions. When this option is enabled
6573 /proc/sys/... file. B !! 4299 very new udev will not work anymore. When this option
6574 separators. Unrecogni !! 4300 is disabled (or CONFIG_SYSFS_DEPRECATED not compiled)
6575 are reported in the k !! 4301 in older udev will not work anymore.
6576 later by a loaded mod !! 4302 Default depends on CONFIG_SYSFS_DEPRECATED_V2 set in
6577 Example: sysctl.vm.sw !! 4303 the kernel configuration.
6578 4304
6579 sysrq_always_enabled 4305 sysrq_always_enabled
6580 [KNL] 4306 [KNL]
6581 Ignore sysrq setting 4307 Ignore sysrq setting - this boot parameter will
6582 neutralize any effect 4308 neutralize any effect of /proc/sys/kernel/sysrq.
6583 Useful for debugging. 4309 Useful for debugging.
6584 4310
6585 tcpmhash_entries= [KNL,NET] 4311 tcpmhash_entries= [KNL,NET]
6586 Set the number of tcp 4312 Set the number of tcp_metrics_hash slots.
6587 Default value is 8192 4313 Default value is 8192 or 16384 depending on total
6588 ram pages. This is us 4314 ram pages. This is used to specify the TCP metrics
6589 cache size. See Docum !! 4315 cache size. See Documentation/networking/ip-sysctl.txt
6590 "tcp_no_metrics_save" 4316 "tcp_no_metrics_save" section for more details.
6591 4317
6592 tdfx= [HW,DRM] 4318 tdfx= [HW,DRM]
6593 4319
6594 test_suspend= [SUSPEND] !! 4320 test_suspend= [SUSPEND][,N]
6595 Format: { "mem" | "st <<
6596 Specify "mem" (for Su 4321 Specify "mem" (for Suspend-to-RAM) or "standby" (for
6597 standby suspend) or " 4322 standby suspend) or "freeze" (for suspend type freeze)
6598 as the system sleep s 4323 as the system sleep state during system startup with
6599 the optional capabili 4324 the optional capability to repeat N number of times.
6600 The system is woken f 4325 The system is woken from this state using a
6601 wakeup-capable RTC al 4326 wakeup-capable RTC alarm.
6602 4327
6603 thash_entries= [KNL,NET] 4328 thash_entries= [KNL,NET]
6604 Set number of hash bu 4329 Set number of hash buckets for TCP connection
6605 4330
6606 thermal.act= [HW,ACPI] 4331 thermal.act= [HW,ACPI]
6607 -1: disable all activ 4332 -1: disable all active trip points in all thermal zones
6608 <degrees C>: override 4333 <degrees C>: override all lowest active trip points
6609 4334
6610 thermal.crt= [HW,ACPI] 4335 thermal.crt= [HW,ACPI]
6611 -1: disable all criti 4336 -1: disable all critical trip points in all thermal zones
6612 <degrees C>: override 4337 <degrees C>: override all critical trip points
6613 4338
>> 4339 thermal.nocrt= [HW,ACPI]
>> 4340 Set to disable actions on ACPI thermal zone
>> 4341 critical and hot trip points.
>> 4342
6614 thermal.off= [HW,ACPI] 4343 thermal.off= [HW,ACPI]
6615 1: disable ACPI therm 4344 1: disable ACPI thermal control
6616 4345
6617 thermal.psv= [HW,ACPI] 4346 thermal.psv= [HW,ACPI]
6618 -1: disable all passi 4347 -1: disable all passive trip points
6619 <degrees C>: override 4348 <degrees C>: override all passive trip points to this
6620 value 4349 value
6621 4350
6622 thermal.tzp= [HW,ACPI] 4351 thermal.tzp= [HW,ACPI]
6623 Specify global defaul 4352 Specify global default ACPI thermal zone polling rate
6624 <deci-seconds>: poll 4353 <deci-seconds>: poll all this frequency
6625 0: no polling (defaul 4354 0: no polling (default)
6626 4355
6627 threadirqs [KNL,EARLY] !! 4356 threadirqs [KNL]
6628 Force threading of al 4357 Force threading of all interrupt handlers except those
6629 marked explicitly IRQ 4358 marked explicitly IRQF_NO_THREAD.
6630 4359
6631 topology= [S390,EARLY] !! 4360 tmem [KNL,XEN]
>> 4361 Enable the Transcendent memory driver if built-in.
>> 4362
>> 4363 tmem.cleancache=0|1 [KNL, XEN]
>> 4364 Default is on (1). Disable the usage of the cleancache
>> 4365 API to send anonymous pages to the hypervisor.
>> 4366
>> 4367 tmem.frontswap=0|1 [KNL, XEN]
>> 4368 Default is on (1). Disable the usage of the frontswap
>> 4369 API to send swap pages to the hypervisor. If disabled
>> 4370 the selfballooning and selfshrinking are force disabled.
>> 4371
>> 4372 tmem.selfballooning=0|1 [KNL, XEN]
>> 4373 Default is on (1). Disable the driving of swap pages
>> 4374 to the hypervisor.
>> 4375
>> 4376 tmem.selfshrinking=0|1 [KNL, XEN]
>> 4377 Default is on (1). Partial swapoff that immediately
>> 4378 transfers pages from Xen hypervisor back to the
>> 4379 kernel based on different criteria.
>> 4380
>> 4381 topology= [S390]
6632 Format: {off | on} 4382 Format: {off | on}
6633 Specify if the kernel 4383 Specify if the kernel should make use of the cpu
6634 topology information 4384 topology information if the hardware supports this.
6635 The scheduler will ma 4385 The scheduler will make use of this information and
6636 e.g. base its process 4386 e.g. base its process migration decisions on it.
6637 Default is on. 4387 Default is on.
6638 4388
6639 torture.disable_onoff_at_boot= [KNL] !! 4389 topology_updates= [KNL, PPC, NUMA]
6640 Prevent the CPU-hotpl !! 4390 Format: {off}
6641 until after init has !! 4391 Specify if the kernel should ignore (off)
6642 !! 4392 topology updates sent by the hypervisor to this
6643 torture.ftrace_dump_at_shutdown= [KNL !! 4393 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 4394
6655 torture.verbose_sleep_duration= [KNL] !! 4395 tp720= [HW,PS2]
6656 Duration of each verb <<
6657 4396
6658 tpm_suspend_pcr=[HW,TPM] 4397 tpm_suspend_pcr=[HW,TPM]
6659 Format: integer pcr i 4398 Format: integer pcr id
6660 Specify that at suspe 4399 Specify that at suspend time, the tpm driver
6661 should extend the spe 4400 should extend the specified pcr with zeros,
6662 as a workaround for s 4401 as a workaround for some chips which fail to
6663 flush the last writte 4402 flush the last written pcr on TPM_SaveState.
6664 This will guarantee t 4403 This will guarantee that all the other pcrs
6665 are saved. 4404 are saved.
6666 4405
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] 4406 trace_buf_size=nn[KMG]
6706 [FTRACE] will set tra 4407 [FTRACE] will set tracing buffer size on each cpu.
6707 4408
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] 4409 trace_event=[event-list]
6731 [FTRACE] Set and star 4410 [FTRACE] Set and start specified trace events in order
6732 to facilitate early b 4411 to facilitate early boot debugging. The event-list is a
6733 comma-separated list !! 4412 comma separated list of trace events to enable. See
6734 also Documentation/tr 4413 also Documentation/trace/events.rst
6735 4414
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] 4415 trace_options=[option-list]
6757 [FTRACE] Enable or di 4416 [FTRACE] Enable or disable tracer options at boot.
6758 The option-list is a 4417 The option-list is a comma delimited list of options
6759 that can be enabled o 4418 that can be enabled or disabled just as if you were
6760 to echo the option na 4419 to echo the option name into
6761 4420
6762 /sys/kernel/traci !! 4421 /sys/kernel/debug/tracing/trace_options
6763 4422
6764 For example, to enabl 4423 For example, to enable stacktrace option (to dump the
6765 stack trace of each e 4424 stack trace of each event), add to the command line:
6766 4425
6767 trace_options=s 4426 trace_options=stacktrace
6768 4427
6769 See also Documentatio 4428 See also Documentation/trace/ftrace.rst "trace options"
6770 section. 4429 section.
6771 4430
6772 trace_trigger=[trigger-list] !! 4431 tp_printk[FTRACE]
6773 [FTRACE] Add a event !! 4432 Have the tracepoints sent to printk as well as the
6774 Set a trigger on top !! 4433 tracing ring buffer. This is useful for early boot up
6775 filter. !! 4434 where the system hangs or reboots and does not give the
6776 !! 4435 option for reading the tracing buffer or performing a
6777 The format is is "tra !! 4436 ftrace_dump_on_oops.
6778 Where more than one t <<
6779 <<
6780 For example: <<
6781 <<
6782 trace_trigger="sche <<
6783 4437
6784 The above will enable !! 4438 To turn off having tracepoints sent to printk,
6785 event but only trigge !! 4439 echo 0 > /proc/sys/kernel/tracepoint_printk
6786 event is "2" (TASK_UN !! 4440 Note, echoing 1 into this file without the
>> 4441 tracepoint_printk kernel cmdline option has no effect.
6787 4442
6788 See also "Event trigg !! 4443 ** CAUTION **
6789 4444
>> 4445 Having tracepoints sent to printk() and activating high
>> 4446 frequency tracepoints such as irq or sched, can cause
>> 4447 the system to live lock.
6790 4448
6791 traceoff_on_warning 4449 traceoff_on_warning
6792 [FTRACE] enable this 4450 [FTRACE] enable this option to disable tracing when a
6793 warning is hit. This 4451 warning is hit. This turns off "tracing_on". Tracing can
6794 be enabled again by e 4452 be enabled again by echoing '1' into the "tracing_on"
6795 file located in /sys/ !! 4453 file located in /sys/kernel/debug/tracing/
6796 4454
6797 This option is useful 4455 This option is useful, as it disables the trace before
6798 the WARNING dump is c 4456 the WARNING dump is called, which prevents the trace to
6799 be filled with conten 4457 be filled with content caused by the warning output.
6800 4458
6801 This option can also 4459 This option can also be set at run time via the sysctl
6802 option: kernel/trace 4460 option: kernel/traceoff_on_warning
6803 4461
6804 transparent_hugepage= 4462 transparent_hugepage=
6805 [KNL] 4463 [KNL]
6806 Format: [always|madvi 4464 Format: [always|madvise|never]
6807 Can be used to contro 4465 Can be used to control the default behavior of the system
6808 with respect to trans 4466 with respect to transparent hugepages.
6809 See Documentation/adm 4467 See Documentation/admin-guide/mm/transhuge.rst
6810 for more details. 4468 for more details.
6811 4469
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 4470 tsc= Disable clocksource stability checks for TSC.
6849 Format: <string> 4471 Format: <string>
6850 [x86] reliable: mark 4472 [x86] reliable: mark tsc clocksource as reliable, this
6851 disables clocksource 4473 disables clocksource verification at runtime, as well
6852 as the stability chec 4474 as the stability checks done at bootup. Used to enable
6853 high-resolution timer 4475 high-resolution timer mode on older hardware, and in
6854 virtualized environme 4476 virtualized environment.
6855 [x86] noirqtime: Do n 4477 [x86] noirqtime: Do not use TSC to do irq accounting.
6856 Used to run time disa 4478 Used to run time disable IRQ_TIME_ACCOUNTING on any
6857 platforms where RDTSC 4479 platforms where RDTSC is slow and this accounting
6858 can add overhead. 4480 can add overhead.
6859 [x86] unstable: mark 4481 [x86] unstable: mark the TSC clocksource as unstable, this
6860 marks the TSC uncondi 4482 marks the TSC unconditionally unstable at bootup and
6861 avoids any further wo 4483 avoids any further wobbles once the TSC watchdog notices.
6862 [x86] nowatchdog: dis <<
6863 in situations with st <<
6864 interruptions from cl <<
6865 acceptable). <<
6866 [x86] recalibrate: fo <<
6867 (HPET or PM timer) on <<
6868 obtained from HW or F <<
6869 Warn if the differenc <<
6870 [x86] watchdog: Use T <<
6871 which to check other <<
6872 only on systems where <<
6873 This will be suppress <<
6874 can be overridden by <<
6875 message will flag any <<
6876 <<
6877 tsc_early_khz= [X86,EARLY] Skip earl <<
6878 value instead. Useful <<
6879 procedure is not reli <<
6880 with CPUID.16h suppor <<
6881 Format: <unsigned int <<
6882 <<
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 4484
6953 turbografx.map[2|3]= [HW,JOY] 4485 turbografx.map[2|3]= [HW,JOY]
6954 TurboGraFX parallel p 4486 TurboGraFX parallel port interface
6955 Format: 4487 Format:
6956 <port#>,<js1>,<js2>,< 4488 <port#>,<js1>,<js2>,<js3>,<js4>,<js5>,<js6>,<js7>
6957 See also Documentatio 4489 See also Documentation/input/devices/joystick-parport.rst
6958 4490
6959 udbg-immortal [PPC] When debugging 4491 udbg-immortal [PPC] When debugging early kernel crashes that
6960 happen after console_ 4492 happen after console_init() and before a proper
6961 console driver takes 4493 console driver takes over, this boot options might
6962 help "seeing" what's 4494 help "seeing" what's going on.
6963 4495
6964 uhash_entries= [KNL,NET] 4496 uhash_entries= [KNL,NET]
6965 Set number of hash bu 4497 Set number of hash buckets for UDP/UDP-Lite connections
6966 4498
6967 uhci-hcd.ignore_oc= 4499 uhci-hcd.ignore_oc=
6968 [USB] Ignore overcurr 4500 [USB] Ignore overcurrent events (default N).
6969 Some badly-designed m 4501 Some badly-designed motherboards generate lots of
6970 bogus events, for por 4502 bogus events, for ports that aren't wired to
6971 anything. Set this p 4503 anything. Set this parameter to avoid log spamming.
6972 Note that genuine ove 4504 Note that genuine overcurrent events won't be
6973 reported either. 4505 reported either.
6974 4506
6975 unknown_nmi_panic 4507 unknown_nmi_panic
6976 [X86] Cause panic on 4508 [X86] Cause panic on unknown NMI.
6977 4509
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= 4510 usbcore.authorized_default=
6985 [USB] Default USB dev 4511 [USB] Default USB device authorization:
6986 (default -1 = authori !! 4512 (default -1 = authorized except for wireless USB,
6987 0 = not authorized, 1 !! 4513 0 = not authorized, 1 = authorized)
6988 if device connected t <<
6989 4514
6990 usbcore.autosuspend= 4515 usbcore.autosuspend=
6991 [USB] The autosuspend 4516 [USB] The autosuspend time delay (in seconds) used
6992 for newly-detected US 4517 for newly-detected USB devices (default 2). This
6993 is the time required 4518 is the time required before an idle device will be
6994 autosuspended. Devic 4519 autosuspended. Devices for which the delay is set
6995 to a negative value w 4520 to a negative value won't be autosuspended at all.
6996 4521
6997 usbcore.usbfs_snoop= 4522 usbcore.usbfs_snoop=
6998 [USB] Set to log all 4523 [USB] Set to log all usbfs traffic (default 0 = off).
6999 4524
7000 usbcore.usbfs_snoop_max= 4525 usbcore.usbfs_snoop_max=
7001 [USB] Maximum number 4526 [USB] Maximum number of bytes to snoop in each URB
7002 (default = 65536). 4527 (default = 65536).
7003 4528
7004 usbcore.blinkenlights= 4529 usbcore.blinkenlights=
7005 [USB] Set to cycle le 4530 [USB] Set to cycle leds on hubs (default 0 = off).
7006 4531
7007 usbcore.old_scheme_first= 4532 usbcore.old_scheme_first=
7008 [USB] Start with the 4533 [USB] Start with the old device initialization
7009 scheme (default 0 = o 4534 scheme (default 0 = off).
7010 4535
7011 usbcore.usbfs_memory_mb= 4536 usbcore.usbfs_memory_mb=
7012 [USB] Memory limit (i 4537 [USB] Memory limit (in MB) for buffers allocated by
7013 usbfs (default = 16, 4538 usbfs (default = 16, 0 = max = 2047).
7014 4539
7015 usbcore.use_both_schemes= 4540 usbcore.use_both_schemes=
7016 [USB] Try the other d 4541 [USB] Try the other device initialization scheme
7017 if the first one fail 4542 if the first one fails (default 1 = enabled).
7018 4543
7019 usbcore.initial_descriptor_timeout= 4544 usbcore.initial_descriptor_timeout=
7020 [USB] Specifies timeo 4545 [USB] Specifies timeout for the initial 64-byte
7021 USB_REQ_GET_DESCRIPTO 4546 USB_REQ_GET_DESCRIPTOR request in milliseconds
7022 (default 5000 = 5.0 s 4547 (default 5000 = 5.0 seconds).
7023 4548
7024 usbcore.nousb [USB] Disable the USB 4549 usbcore.nousb [USB] Disable the USB subsystem
7025 4550
7026 usbcore.quirks= 4551 usbcore.quirks=
7027 [USB] A list of quirk 4552 [USB] A list of quirk entries to augment the built-in
7028 usb core quirk list. 4553 usb core quirk list. List entries are separated by
7029 commas. Each entry ha 4554 commas. Each entry has the form
7030 VendorID:ProductID:Fl 4555 VendorID:ProductID:Flags. The IDs are 4-digit hex
7031 numbers and Flags is 4556 numbers and Flags is a set of letters. Each letter
7032 will change the built 4557 will change the built-in quirk; setting it if it is
7033 clear and clearing it 4558 clear and clearing it if it is set. The letters have
7034 the following meaning 4559 the following meanings:
7035 a = USB_QUIRK 4560 a = USB_QUIRK_STRING_FETCH_255 (string
7036 descr 4561 descriptors must not be fetched using
7037 a 255 4562 a 255-byte read);
7038 b = USB_QUIRK 4563 b = USB_QUIRK_RESET_RESUME (device can't resume
7039 corre 4564 correctly so reset it instead);
7040 c = USB_QUIRK 4565 c = USB_QUIRK_NO_SET_INTF (device can't handle
7041 Set-I 4566 Set-Interface requests);
7042 d = USB_QUIRK 4567 d = USB_QUIRK_CONFIG_INTF_STRINGS (device can't
7043 handl 4568 handle its Configuration or Interface
7044 strin 4569 strings);
7045 e = USB_QUIRK 4570 e = USB_QUIRK_RESET (device can't be reset
7046 (e.g 4571 (e.g morph devices), don't use reset);
7047 f = USB_QUIRK 4572 f = USB_QUIRK_HONOR_BNUMINTERFACES (device has
7048 more 4573 more interface descriptions than the
7049 bNumI 4574 bNumInterfaces count, and can't handle
7050 talki 4575 talking to these interfaces);
7051 g = USB_QUIRK 4576 g = USB_QUIRK_DELAY_INIT (device needs a pause
7052 durin 4577 during initialization, after we read
7053 the d 4578 the device descriptor);
7054 h = USB_QUIRK 4579 h = USB_QUIRK_LINEAR_UFRAME_INTR_BINTERVAL (For
7055 high 4580 high speed and super speed interrupt
7056 endpo 4581 endpoints, the USB 2.0 and USB 3.0 spec
7057 requi 4582 require the interval in microframes (1
7058 micro 4583 microframe = 125 microseconds) to be
7059 calcu 4584 calculated as interval = 2 ^
7060 (bInt 4585 (bInterval-1).
7061 Devic 4586 Devices with this quirk report their
7062 bInte 4587 bInterval as the result of this
7063 calcu 4588 calculation instead of the exponent
7064 varia 4589 variable used in the calculation);
7065 i = USB_QUIRK 4590 i = USB_QUIRK_DEVICE_QUALIFIER (device can't
7066 handl 4591 handle device_qualifier descriptor
7067 reque 4592 requests);
7068 j = USB_QUIRK 4593 j = USB_QUIRK_IGNORE_REMOTE_WAKEUP (device
7069 gener 4594 generates spurious wakeup, ignore
7070 remot 4595 remote wakeup capability);
7071 k = USB_QUIRK 4596 k = USB_QUIRK_NO_LPM (device can't handle Link
7072 Power 4597 Power Management);
7073 l = USB_QUIRK 4598 l = USB_QUIRK_LINEAR_FRAME_INTR_BINTERVAL
7074 (Devi 4599 (Device reports its bInterval as linear
7075 frame 4600 frames instead of the USB 2.0
7076 calcu 4601 calculation);
7077 m = USB_QUIRK 4602 m = USB_QUIRK_DISCONNECT_SUSPEND (Device needs
7078 to be 4603 to be disconnected before suspend to
7079 preve 4604 prevent spurious wakeup);
7080 n = USB_QUIRK 4605 n = USB_QUIRK_DELAY_CTRL_MSG (Device needs a
7081 pause 4606 pause after every control message);
7082 o = USB_QUIRK <<
7083 delay <<
7084 p = USB_QUIRK <<
7085 (Redu <<
7086 reque <<
7087 Example: quirks=0781: 4607 Example: quirks=0781:5580:bk,0a5c:5834:gij
7088 4608
7089 usbhid.mousepoll= 4609 usbhid.mousepoll=
7090 [USBHID] The interval 4610 [USBHID] The interval which mice are to be polled at.
7091 4611
7092 usbhid.jspoll= 4612 usbhid.jspoll=
7093 [USBHID] The interval 4613 [USBHID] The interval which joysticks are to be polled at.
7094 4614
7095 usbhid.kbpoll= 4615 usbhid.kbpoll=
7096 [USBHID] The interval 4616 [USBHID] The interval which keyboards are to be polled at.
7097 4617
7098 usb-storage.delay_use= 4618 usb-storage.delay_use=
7099 [UMS] The delay in se 4619 [UMS] The delay in seconds before a new device is
7100 scanned for Logical U 4620 scanned for Logical Units (default 1).
7101 Optionally the delay <<
7102 suffix with "ms". <<
7103 Example: delay_use=25 <<
7104 4621
7105 usb-storage.quirks= 4622 usb-storage.quirks=
7106 [UMS] A list of quirk 4623 [UMS] A list of quirks entries to supplement or
7107 override the built-in 4624 override the built-in unusual_devs list. List
7108 entries are separated 4625 entries are separated by commas. Each entry has
7109 the form VID:PID:Flag 4626 the form VID:PID:Flags where VID and PID are Vendor
7110 and Product ID values 4627 and Product ID values (4-digit hex numbers) and
7111 Flags is a set of cha 4628 Flags is a set of characters, each corresponding
7112 to a common usb-stora 4629 to a common usb-storage quirk flag as follows:
7113 a = SANE_SENS 4630 a = SANE_SENSE (collect more than 18 bytes
7114 of se !! 4631 of sense data);
7115 b = BAD_SENSE 4632 b = BAD_SENSE (don't collect more than 18
7116 bytes !! 4633 bytes of sense data);
7117 c = FIX_CAPAC 4634 c = FIX_CAPACITY (decrease the reported
7118 devic 4635 device capacity by one sector);
7119 d = NO_READ_D 4636 d = NO_READ_DISC_INFO (don't use
7120 READ_ !! 4637 READ_DISC_INFO command);
7121 e = NO_READ_C 4638 e = NO_READ_CAPACITY_16 (don't use
7122 READ_ 4639 READ_CAPACITY_16 command);
7123 f = NO_REPORT 4640 f = NO_REPORT_OPCODES (don't use report opcodes
7124 comma 4641 command, uas only);
7125 g = MAX_SECTO 4642 g = MAX_SECTORS_240 (don't transfer more than
7126 240 s 4643 240 sectors at a time, uas only);
7127 h = CAPACITY_ 4644 h = CAPACITY_HEURISTICS (decrease the
7128 repor 4645 reported device capacity by one
7129 secto 4646 sector if the number is odd);
7130 i = IGNORE_DE 4647 i = IGNORE_DEVICE (don't bind to this
7131 devic 4648 device);
7132 j = NO_REPORT 4649 j = NO_REPORT_LUNS (don't use report luns
7133 comma 4650 command, uas only);
7134 k = NO_SAME ( <<
7135 l = NOT_LOCKA 4651 l = NOT_LOCKABLE (don't try to lock and
7136 unloc !! 4652 unlock ejectable media);
7137 m = MAX_SECTO 4653 m = MAX_SECTORS_64 (don't transfer more
7138 than !! 4654 than 64 sectors = 32 KB at a time);
7139 not o <<
7140 n = INITIAL_R 4655 n = INITIAL_READ10 (force a retry of the
7141 initi !! 4656 initial READ(10) command);
7142 o = CAPACITY_ 4657 o = CAPACITY_OK (accept the capacity
7143 repor !! 4658 reported by the device);
7144 p = WRITE_CAC 4659 p = WRITE_CACHE (the device cache is ON
7145 by de !! 4660 by default);
7146 r = IGNORE_RE 4661 r = IGNORE_RESIDUE (the device reports
7147 bogus !! 4662 bogus residue values);
7148 s = SINGLE_LU 4663 s = SINGLE_LUN (the device has only one
7149 Logic 4664 Logical Unit);
7150 t = NO_ATA_1X 4665 t = NO_ATA_1X (don't allow ATA(12) and ATA(16)
7151 comma 4666 commands, uas only);
7152 u = IGNORE_UA 4667 u = IGNORE_UAS (don't bind to the uas driver);
7153 w = NO_WP_DET 4668 w = NO_WP_DETECT (don't test whether the
7154 mediu 4669 medium is write-protected).
7155 y = ALWAYS_SY 4670 y = ALWAYS_SYNC (issue a SYNCHRONIZE_CACHE
7156 even !! 4671 even if the device claims no cache)
7157 not o <<
7158 Example: quirks=0419: 4672 Example: quirks=0419:aaf5:rl,0421:0433:rc
7159 4673
7160 user_debug= [KNL,ARM] 4674 user_debug= [KNL,ARM]
7161 Format: <int> 4675 Format: <int>
7162 See arch/arm/Kconfig. 4676 See arch/arm/Kconfig.debug help text.
7163 1 - undefine 4677 1 - undefined instruction events
7164 2 - system c 4678 2 - system calls
7165 4 - invalid 4679 4 - invalid data aborts
7166 8 - SIGSEGV 4680 8 - SIGSEGV faults
7167 16 - SIGBUS f 4681 16 - SIGBUS faults
7168 Example: user_debug=3 4682 Example: user_debug=31
7169 4683
7170 userpte= 4684 userpte=
7171 [X86,EARLY] Flags con !! 4685 [X86] Flags controlling user PTE allocations.
7172 4686
7173 nohigh = do n 4687 nohigh = do not allocate PTE pages in
7174 HIGHM 4688 HIGHMEM regardless of setting
7175 of CO 4689 of CONFIG_HIGHPTE.
7176 4690
7177 vdso= [X86,SH,SPARC] !! 4691 vdso= [X86,SH]
7178 On X86_32, this is an 4692 On X86_32, this is an alias for vdso32=. Otherwise:
7179 4693
7180 vdso=1: enable VDSO ( 4694 vdso=1: enable VDSO (the default)
7181 vdso=0: disable VDSO 4695 vdso=0: disable VDSO mapping
7182 4696
7183 vdso32= [X86] Control the 32- 4697 vdso32= [X86] Control the 32-bit vDSO
7184 vdso32=1: enable 32-b 4698 vdso32=1: enable 32-bit VDSO
7185 vdso32=0 or vdso32=2: 4699 vdso32=0 or vdso32=2: disable 32-bit VDSO
7186 4700
7187 See the help text for 4701 See the help text for CONFIG_COMPAT_VDSO for more
7188 details. If CONFIG_C 4702 details. If CONFIG_COMPAT_VDSO is set, the default is
7189 vdso32=0; otherwise, 4703 vdso32=0; otherwise, the default is vdso32=1.
7190 4704
7191 For compatibility wit 4705 For compatibility with older kernels, vdso32=2 is an
7192 alias for vdso32=0. 4706 alias for vdso32=0.
7193 4707
7194 Try vdso32=0 if you e 4708 Try vdso32=0 if you encounter an error that says:
7195 dl_main: Assertion `( 4709 dl_main: Assertion `(void *) ph->p_vaddr == _rtld_local._dl_sysinfo_dso' failed!
7196 4710
7197 video= [FB,EARLY] Frame buff !! 4711 vector= [IA-64,SMP]
7198 See Documentation/fb/ !! 4712 vector=percpu: enable percpu vector domain
>> 4713
>> 4714 video= [FB] Frame buffer configuration
>> 4715 See Documentation/fb/modedb.txt.
7199 4716
7200 video.brightness_switch_enabled= [ACP !! 4717 video.brightness_switch_enabled= [0,1]
7201 Format: [0|1] <<
7202 If set to 1, on recei 4718 If set to 1, on receiving an ACPI notify event
7203 generated by hotkey, 4719 generated by hotkey, video driver will adjust brightness
7204 level and then send o 4720 level and then send out the event to user space through
7205 the allocated input d !! 4721 the allocated input device; If set to 0, video driver
7206 will only send out th 4722 will only send out the event without touching backlight
7207 brightness level. 4723 brightness level.
7208 default: 1 4724 default: 1
7209 4725
7210 virtio_mmio.device= 4726 virtio_mmio.device=
7211 [VMMIO] Memory mapped 4727 [VMMIO] Memory mapped virtio (platform) device.
7212 4728
7213 <size>@<basead 4729 <size>@<baseaddr>:<irq>[:<id>]
7214 where: 4730 where:
7215 <size> := 4731 <size> := size (can use standard suffixes
7216 4732 like K, M and G)
7217 <baseaddr> := 4733 <baseaddr> := physical base address
7218 <irq> := 4734 <irq> := interrupt number (as passed to
7219 4735 request_irq())
7220 <id> := 4736 <id> := (optional) platform device id
7221 example: 4737 example:
7222 virtio_mmio.d 4738 virtio_mmio.device=1K@0x100b0000:48:7
7223 4739
7224 Can be used multiple 4740 Can be used multiple times for multiple devices.
7225 4741
7226 vga= [BOOT,X86-32] Select 4742 vga= [BOOT,X86-32] Select a particular video mode
7227 See Documentation/arc !! 4743 See Documentation/x86/boot.txt and
7228 Documentation/admin-g !! 4744 Documentation/svga.txt.
7229 Use vga=ask for menu. 4745 Use vga=ask for menu.
7230 This is actually a bo 4746 This is actually a boot loader parameter; the value is
7231 passed to the kernel 4747 passed to the kernel using a special protocol.
7232 4748
7233 vm_debug[=options] [KNL] Availab !! 4749 vmalloc=nn[KMG] [KNL,BOOT] Forces the vmalloc area to have an exact
7234 May slow down system !! 4750 size of <nn>. This can be used to increase the
7235 enabled on systems wi !! 4751 minimum size (128MB on x86). It can also be used to
7236 All options are enabl !! 4752 decrease the size and leave more room for directly
7237 interface is meant to !! 4753 mapped kernel RAM.
7238 enabling or disabling <<
7239 debugging features. <<
7240 <<
7241 Available options are <<
7242 P Enable page s <<
7243 - Disable all o <<
7244 <<
7245 vmalloc=nn[KMG] [KNL,BOOT,EARLY] Forc <<
7246 exact size of <nn>. T <<
7247 the minimum size (128 <<
7248 It can also be used t <<
7249 for directly mapped k <<
7250 not exist on many oth <<
7251 loongarch, arc, csky, <<
7252 parisc, m64k, powerpc <<
7253 4754
7254 vmcp_cma=nn[MG] [KNL,S390,EARLY] !! 4755 vmcp_cma=nn[MG] [KNL,S390]
7255 Sets the memory size 4756 Sets the memory size reserved for contiguous memory
7256 allocations for the v 4757 allocations for the vmcp device driver.
7257 4758
7258 vmhalt= [KNL,S390] Perform z/ 4759 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
7259 Format: <command> 4760 Format: <command>
7260 4761
7261 vmpanic= [KNL,S390] Perform z/ 4762 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
7262 Format: <command> 4763 Format: <command>
7263 4764
7264 vmpoff= [KNL,S390] Perform z/ 4765 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
7265 Format: <command> 4766 Format: <command>
7266 4767
7267 vsyscall= [X86-64,EARLY] !! 4768 vsyscall= [X86-64]
7268 Controls the behavior 4769 Controls the behavior of vsyscalls (i.e. calls to
7269 fixed addresses of 0x 4770 fixed addresses of 0xffffffffff600x00 from legacy
7270 code). Most statical 4771 code). Most statically-linked binaries and older
7271 versions of glibc use 4772 versions of glibc use these calls. Because these
7272 functions are at fixe 4773 functions are at fixed addresses, they make nice
7273 targets for exploits 4774 targets for exploits that can control RIP.
7274 4775
7275 emulate Vsyscalls !! 4776 emulate [default] Vsyscalls turn into traps and are
7276 reasonabl !! 4777 emulated reasonably safely.
7277 readable. !! 4778
7278 !! 4779 native Vsyscalls are native syscall instructions.
7279 xonly [default] !! 4780 This is a little bit faster than trapping
7280 emulated !! 4781 and makes a few dynamic recompilers work
7281 page is n !! 4782 better than they would in emulation mode.
>> 4783 It also makes exploits much easier to write.
7282 4784
7283 none Vsyscalls 4785 none Vsyscalls don't work at all. This makes
7284 them quit 4786 them quite hard to use for exploits but
7285 might bre 4787 might break your system.
7286 4788
7287 vt.color= [VT] Default text col 4789 vt.color= [VT] Default text color.
7288 Format: 0xYX, X = for 4790 Format: 0xYX, X = foreground, Y = background.
7289 Default: 0x07 = light 4791 Default: 0x07 = light gray on black.
7290 4792
7291 vt.cur_default= [VT] Default cursor s 4793 vt.cur_default= [VT] Default cursor shape.
7292 Format: 0xCCBBAA, whe 4794 Format: 0xCCBBAA, where AA, BB, and CC are the same as
7293 the parameters of the 4795 the parameters of the <Esc>[?A;B;Cc escape sequence;
7294 see VGA-softcursor.tx 4796 see VGA-softcursor.txt. Default: 2 = underline.
7295 4797
7296 vt.default_blu= [VT] 4798 vt.default_blu= [VT]
7297 Format: <blue0>,<blue 4799 Format: <blue0>,<blue1>,<blue2>,...,<blue15>
7298 Change the default bl 4800 Change the default blue palette of the console.
7299 This is a 16-member a 4801 This is a 16-member array composed of values
7300 ranging from 0-255. 4802 ranging from 0-255.
7301 4803
7302 vt.default_grn= [VT] 4804 vt.default_grn= [VT]
7303 Format: <green0>,<gre 4805 Format: <green0>,<green1>,<green2>,...,<green15>
7304 Change the default gr 4806 Change the default green palette of the console.
7305 This is a 16-member a 4807 This is a 16-member array composed of values
7306 ranging from 0-255. 4808 ranging from 0-255.
7307 4809
7308 vt.default_red= [VT] 4810 vt.default_red= [VT]
7309 Format: <red0>,<red1> 4811 Format: <red0>,<red1>,<red2>,...,<red15>
7310 Change the default re 4812 Change the default red palette of the console.
7311 This is a 16-member a 4813 This is a 16-member array composed of values
7312 ranging from 0-255. 4814 ranging from 0-255.
7313 4815
7314 vt.default_utf8= 4816 vt.default_utf8=
7315 [VT] 4817 [VT]
7316 Format=<0|1> 4818 Format=<0|1>
7317 Set system-wide defau 4819 Set system-wide default UTF-8 mode for all tty's.
7318 Default is 1, i.e. UT 4820 Default is 1, i.e. UTF-8 mode is enabled for all
7319 newly opened terminal 4821 newly opened terminals.
7320 4822
7321 vt.global_cursor_default= 4823 vt.global_cursor_default=
7322 [VT] 4824 [VT]
7323 Format=<-1|0|1> 4825 Format=<-1|0|1>
7324 Set system-wide defau 4826 Set system-wide default for whether a cursor
7325 is shown on new VTs. 4827 is shown on new VTs. Default is -1,
7326 i.e. cursors will be 4828 i.e. cursors will be created by default unless
7327 overridden by individ 4829 overridden by individual drivers. 0 will hide
7328 cursors, 1 will displ 4830 cursors, 1 will display them.
7329 4831
7330 vt.italic= [VT] Default color fo 4832 vt.italic= [VT] Default color for italic text; 0-15.
7331 Default: 2 = green. 4833 Default: 2 = green.
7332 4834
7333 vt.underline= [VT] Default color fo 4835 vt.underline= [VT] Default color for underlined text; 0-15.
7334 Default: 3 = cyan. 4836 Default: 3 = cyan.
7335 4837
7336 watchdog timers [HW,WDT] For informat 4838 watchdog timers [HW,WDT] For information on watchdog timers,
7337 see Documentation/wat !! 4839 see Documentation/watchdog/watchdog-parameters.txt
7338 or other driver-speci 4840 or other driver-specific files in the
7339 Documentation/watchdo 4841 Documentation/watchdog/ directory.
7340 4842
7341 watchdog_thresh= <<
7342 [KNL] <<
7343 Set the hard lockup d <<
7344 threshold in seconds. <<
7345 threshold is set to t <<
7346 disables both lockup <<
7347 seconds. <<
7348 <<
7349 workqueue.unbound_cpus= <<
7350 [KNL,SMP] Specify to <<
7351 to use in unbound wor <<
7352 Format: <cpu-list> <<
7353 By default, all onlin <<
7354 unbound workqueues. <<
7355 <<
7356 workqueue.watchdog_thresh= 4843 workqueue.watchdog_thresh=
7357 If CONFIG_WQ_WATCHDOG 4844 If CONFIG_WQ_WATCHDOG is configured, workqueue can
7358 warn stall conditions 4845 warn stall conditions and dump internal state to
7359 help debugging. 0 di 4846 help debugging. 0 disables workqueue stall
7360 detection; otherwise, 4847 detection; otherwise, it's the stall threshold
7361 duration in seconds. 4848 duration in seconds. The default value is 30 and
7362 it can be updated at 4849 it can be updated at runtime by writing to the
7363 corresponding sysfs f 4850 corresponding sysfs file.
7364 4851
7365 workqueue.cpu_intensive_thresh_us= !! 4852 workqueue.disable_numa
7366 Per-cpu work items wh !! 4853 By default, all work items queued to unbound
7367 threshold are automat !! 4854 workqueues are affine to the NUMA nodes they're
7368 and excluded from con !! 4855 issued on, which results in better behavior in
7369 them from noticeably !! 4856 general. If NUMA affinity needs to be disabled for
7370 items. Default is 100 !! 4857 whatever reason, this option can be used. Note
7371 !! 4858 that this also can be controlled per-workqueue for
7372 If CONFIG_WQ_CPU_INTE !! 4859 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 4860
7386 workqueue.power_efficient 4861 workqueue.power_efficient
7387 Per-cpu workqueues ar 4862 Per-cpu workqueues are generally preferred because
7388 they show better perf 4863 they show better performance thanks to cache
7389 locality; unfortunate 4864 locality; unfortunately, per-cpu workqueues tend to
7390 be more power hungry 4865 be more power hungry than unbound workqueues.
7391 4866
7392 Enabling this makes t 4867 Enabling this makes the per-cpu workqueues which
7393 were observed to cont 4868 were observed to contribute significantly to power
7394 consumption unbound, 4869 consumption unbound, leading to measurably lower
7395 power usage at the co 4870 power usage at the cost of small performance
7396 overhead. 4871 overhead.
7397 4872
7398 The default value of 4873 The default value of this parameter is determined by
7399 the config option CON 4874 the config option CONFIG_WQ_POWER_EFFICIENT_DEFAULT.
7400 4875
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 4876 workqueue.debug_force_rr_cpu
7414 Workqueue used to imp 4877 Workqueue used to implicitly guarantee that work
7415 items queued without 4878 items queued without explicit CPU specified are put
7416 on the local CPU. Th 4879 on the local CPU. This guarantee is no longer true
7417 and while local CPU i 4880 and while local CPU is still preferred work items
7418 may be put on foreign 4881 may be put on foreign CPUs. This debug option
7419 forces round-robin CP 4882 forces round-robin CPU selection to flush out
7420 usages which depend o 4883 usages which depend on the now broken guarantee.
7421 When enabled, memory 4884 When enabled, memory and cache locality will be
7422 impacted. 4885 impacted.
7423 4886
7424 writecombine= [LOONGARCH,EARLY] Con !! 4887 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 4888 default x2apic cluster mode on platforms
7432 supporting x2apic. 4889 supporting x2apic.
7433 4890
>> 4891 x86_intel_mid_timer= [X86-32,APBT]
>> 4892 Choose timer option for x86 Intel MID platform.
>> 4893 Two valid options are apbt timer only and lapic timer
>> 4894 plus one apbt timer for broadcast timer.
>> 4895 x86_intel_mid_timer=apbt_only | lapic_and_apbt
>> 4896
7434 xen_512gb_limit [KNL,X86-64,X 4897 xen_512gb_limit [KNL,X86-64,XEN]
7435 Restricts the kernel 4898 Restricts the kernel running paravirtualized under Xen
7436 to use only up to 512 4899 to use only up to 512 GB of RAM. The reason to do so is
7437 crash analysis tools 4900 crash analysis tools and Xen tools for doing domain
7438 save/restore/migratio 4901 save/restore/migration must be enabled to handle larger
7439 domains. 4902 domains.
7440 4903
7441 xen_emul_unplug= [HW,X !! 4904 xen_emul_unplug= [HW,X86,XEN]
7442 Unplug Xen emulated d 4905 Unplug Xen emulated devices
7443 Format: [unplug0,][un 4906 Format: [unplug0,][unplug1]
7444 ide-disks -- unplug p 4907 ide-disks -- unplug primary master IDE devices
7445 aux-ide-disks -- unpl 4908 aux-ide-disks -- unplug non-primary-master IDE devices
7446 nics -- unplug networ 4909 nics -- unplug network devices
7447 all -- unplug all emu 4910 all -- unplug all emulated devices (NICs and IDE disks)
7448 unnecessary -- unplug 4911 unnecessary -- unplugging emulated devices is
7449 unnecessary e 4912 unnecessary even if the host did not respond to
7450 the unplug pr 4913 the unplug protocol
7451 never -- do not unplu 4914 never -- do not unplug even if version check succeeds
7452 4915
7453 xen_legacy_crash [X86,XEN,EARL !! 4916 xen_nopvspin [X86,XEN]
7454 Crash from Xen panic !! 4917 Disables the ticketlock slowpath using Xen PV
7455 panic() code such as !! 4918 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 4919
7469 xen_nopv [X86] 4920 xen_nopv [X86]
7470 Disables the PV optim 4921 Disables the PV optimizations forcing the HVM guest to
7471 run as generic HVM gu 4922 run as generic HVM guest with no PV drivers.
7472 This option is obsole <<
7473 has equivalent effect <<
7474 <<
7475 xen_no_vector_callback <<
7476 [KNL,X86,XEN,EARLY] D <<
7477 event channel interru <<
7478 <<
7479 xen_scrub_pages= [XEN] <<
7480 Boolean option to con <<
7481 to Xen, for use by ot <<
7482 with /sys/devices/sys <<
7483 Default value control <<
7484 <<
7485 xen_timer_slop= [X86-64,XEN,EARLY] <<
7486 Set the timer slop (i <<
7487 timers (default is 10 <<
7488 delta of virtualized <<
7489 improve timer resolut <<
7490 more timer interrupts <<
7491 <<
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 4923
7514 xirc2ps_cs= [NET,PCMCIA] 4924 xirc2ps_cs= [NET,PCMCIA]
7515 Format: 4925 Format:
7516 <irq>,<irq_mask>,<io> 4926 <irq>,<irq_mask>,<io>,<full_duplex>,<do_sound>,<lockup_hack>[,<irq2>[,<irq3>[,<irq4>]]]
7517 4927
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] 4928 xhci-hcd.quirks [USB,KNL]
7534 A hex value specifyin 4929 A hex value specifying bitmask with supplemental xhci
7535 host controller quirk 4930 host controller quirks. Meaning of each bit can be
7536 consulted in header d 4931 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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