1 What: /sys/devices/system/cpu/ 2 Date: pre-git history 3 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 4 Description: 5 A collection of both global and individual CPU attributes 6 7 Individual CPU attributes are contained in subdirectories 8 named by the kernel's logical CPU number, e.g.: 9 10 /sys/devices/system/cpu/cpuX/ 11 12 What: /sys/devices/system/cpu/kernel_max 13 /sys/devices/system/cpu/offline 14 /sys/devices/system/cpu/online 15 /sys/devices/system/cpu/possible 16 /sys/devices/system/cpu/present 17 Date: December 2008 18 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 19 Description: CPU topology files that describe kernel limits related to 20 hotplug. Briefly: 21 22 kernel_max: the maximum cpu index allowed by the kernel 23 configuration. 24 25 offline: cpus that are not online because they have been 26 HOTPLUGGED off or exceed the limit of cpus allowed by the 27 kernel configuration (kernel_max above). 28 29 online: cpus that are online and being scheduled. 30 31 possible: cpus that have been allocated resources and can be 32 brought online if they are present. 33 34 present: cpus that have been identified as being present in 35 the system. 36 37 See Documentation/admin-guide/cputopology.rst for more information. 38 39 40 What: /sys/devices/system/cpu/probe 41 /sys/devices/system/cpu/release 42 Date: November 2009 43 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 44 Description: Dynamic addition and removal of CPU's. This is not hotplug 45 removal, this is meant complete removal/addition of the CPU 46 from the system. 47 48 probe: writes to this file will dynamically add a CPU to the 49 system. Information written to the file to add CPU's is 50 architecture specific. 51 52 release: writes to this file dynamically remove a CPU from 53 the system. Information written to the file to remove CPU's 54 is architecture specific. 55 56 What: /sys/devices/system/cpu/cpuX/node 57 Date: October 2009 58 Contact: Linux memory management mailing list <linux-mm@kvack.org> 59 Description: Discover NUMA node a CPU belongs to 60 61 When CONFIG_NUMA is enabled, a symbolic link that points 62 to the corresponding NUMA node directory. 63 64 For example, the following symlink is created for cpu42 65 in NUMA node 2: 66 67 /sys/devices/system/cpu/cpu42/node2 -> ../../node/node2 68 69 70 What: /sys/devices/system/cpu/cpuX/topology/core_siblings 71 /sys/devices/system/cpu/cpuX/topology/core_siblings_list 72 /sys/devices/system/cpu/cpuX/topology/physical_package_id 73 /sys/devices/system/cpu/cpuX/topology/thread_siblings 74 /sys/devices/system/cpu/cpuX/topology/thread_siblings_list 75 /sys/devices/system/cpu/cpuX/topology/ppin 76 Date: December 2008 77 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 78 Description: CPU topology files that describe a logical CPU's relationship 79 to other cores and threads in the same physical package. 80 81 One cpuX directory is created per logical CPU in the system, 82 e.g. /sys/devices/system/cpu/cpu42/. 83 84 Briefly, the files above are: 85 86 core_siblings: internal kernel map of cpuX's hardware threads 87 within the same physical_package_id. 88 89 core_siblings_list: human-readable list of the logical CPU 90 numbers within the same physical_package_id as cpuX. 91 92 physical_package_id: physical package id of cpuX. Typically 93 corresponds to a physical socket number, but the actual value 94 is architecture and platform dependent. 95 96 thread_siblings: internal kernel map of cpuX's hardware 97 threads within the same core as cpuX 98 99 thread_siblings_list: human-readable list of cpuX's hardware 100 threads within the same core as cpuX 101 102 ppin: human-readable Protected Processor Identification 103 Number of the socket the cpu# belongs to. There should be 104 one per physical_package_id. File is readable only to 105 admin. 106 107 See Documentation/admin-guide/cputopology.rst for more information. 108 109 110 What: /sys/devices/system/cpu/cpuidle/available_governors 111 /sys/devices/system/cpu/cpuidle/current_driver 112 /sys/devices/system/cpu/cpuidle/current_governor 113 /sys/devices/system/cpu/cpuidle/current_governer_ro 114 Date: September 2007 115 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 116 Description: Discover cpuidle policy and mechanism 117 118 Various CPUs today support multiple idle levels that are 119 differentiated by varying exit latencies and power 120 consumption during idle. 121 122 Idle policy (governor) is differentiated from idle mechanism 123 (driver). 124 125 available_governors: (RO) displays a space separated list of 126 available governors. 127 128 current_driver: (RO) displays current idle mechanism. 129 130 current_governor: (RW) displays current idle policy. Users can 131 switch the governor at runtime by writing to this file. 132 133 current_governor_ro: (RO) displays current idle policy. 134 135 See Documentation/admin-guide/pm/cpuidle.rst and 136 Documentation/driver-api/pm/cpuidle.rst for more information. 137 138 139 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/name 140 /sys/devices/system/cpu/cpuX/cpuidle/stateN/latency 141 /sys/devices/system/cpu/cpuX/cpuidle/stateN/power 142 /sys/devices/system/cpu/cpuX/cpuidle/stateN/time 143 /sys/devices/system/cpu/cpuX/cpuidle/stateN/usage 144 /sys/devices/system/cpu/cpuX/cpuidle/stateN/above 145 /sys/devices/system/cpu/cpuX/cpuidle/stateN/below 146 Date: September 2007 147 KernelVersion: v2.6.24 148 Contact: Linux power management list <linux-pm@vger.kernel.org> 149 Description: 150 The directory /sys/devices/system/cpu/cpuX/cpuidle contains per 151 logical CPU specific cpuidle information for each online cpu X. 152 The processor idle states which are available for use have the 153 following attributes: 154 155 ======== ==== ================================================= 156 name: (RO) Name of the idle state (string). 157 158 latency: (RO) The latency to exit out of this idle state (in 159 microseconds). 160 161 power: (RO) The power consumed while in this idle state (in 162 milliwatts). 163 164 time: (RO) The total time spent in this idle state 165 (in microseconds). 166 167 usage: (RO) Number of times this state was entered (a count). 168 169 above: (RO) Number of times this state was entered, but the 170 observed CPU idle duration was too short for it 171 (a count). 172 173 below: (RO) Number of times this state was entered, but the 174 observed CPU idle duration was too long for it 175 (a count). 176 ======== ==== ================================================= 177 178 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/desc 179 Date: February 2008 180 KernelVersion: v2.6.25 181 Contact: Linux power management list <linux-pm@vger.kernel.org> 182 Description: 183 (RO) A small description about the idle state (string). 184 185 186 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/disable 187 Date: March 2012 188 KernelVersion: v3.10 189 Contact: Linux power management list <linux-pm@vger.kernel.org> 190 Description: 191 (RW) Option to disable this idle state (bool). The behavior and 192 the effect of the disable variable depends on the implementation 193 of a particular governor. In the ladder governor, for example, 194 it is not coherent, i.e. if one is disabling a light state, then 195 all deeper states are disabled as well, but the disable variable 196 does not reflect it. Likewise, if one enables a deep state but a 197 lighter state still is disabled, then this has no effect. 198 199 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/default_status 200 Date: December 2019 201 KernelVersion: v5.6 202 Contact: Linux power management list <linux-pm@vger.kernel.org> 203 Description: 204 (RO) The default status of this state, "enabled" or "disabled". 205 206 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/residency 207 Date: March 2014 208 KernelVersion: v3.15 209 Contact: Linux power management list <linux-pm@vger.kernel.org> 210 Description: 211 (RO) Display the target residency i.e. the minimum amount of 212 time (in microseconds) this cpu should spend in this idle state 213 to make the transition worth the effort. 214 215 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/ 216 Date: March 2018 217 KernelVersion: v4.17 218 Contact: Linux power management list <linux-pm@vger.kernel.org> 219 Description: 220 Idle state usage statistics related to suspend-to-idle. 221 222 This attribute group is only present for states that can be 223 used in suspend-to-idle with suspended timekeeping. 224 225 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/time 226 Date: March 2018 227 KernelVersion: v4.17 228 Contact: Linux power management list <linux-pm@vger.kernel.org> 229 Description: 230 Total time spent by the CPU in suspend-to-idle (with scheduler 231 tick suspended) after requesting this state. 232 233 What: /sys/devices/system/cpu/cpuX/cpuidle/state<N>/s2idle/usage 234 Date: March 2018 235 KernelVersion: v4.17 236 Contact: Linux power management list <linux-pm@vger.kernel.org> 237 Description: 238 Total number of times this state has been requested by the CPU 239 while entering suspend-to-idle. 240 241 What: /sys/devices/system/cpu/cpuX/cpufreq/* 242 Date: pre-git history 243 Contact: linux-pm@vger.kernel.org 244 Description: Discover and change clock speed of CPUs 245 246 Clock scaling allows you to change the clock speed of the 247 CPUs on the fly. This is a nice method to save battery 248 power, because the lower the clock speed, the less power 249 the CPU consumes. 250 251 There are many knobs to tweak in this directory. 252 253 See files in Documentation/cpu-freq/ for more information. 254 255 256 What: /sys/devices/system/cpu/cpuX/cpufreq/freqdomain_cpus 257 Date: June 2013 258 Contact: linux-pm@vger.kernel.org 259 Description: Discover CPUs in the same CPU frequency coordination domain 260 261 freqdomain_cpus is the list of CPUs (online+offline) that share 262 the same clock/freq domain (possibly at the hardware level). 263 That information may be hidden from the cpufreq core and the 264 value of related_cpus may be different from freqdomain_cpus. This 265 attribute is useful for user space DVFS controllers to get better 266 power/performance results for platforms using acpi-cpufreq. 267 268 This file is only present if the acpi-cpufreq or the cppc-cpufreq 269 drivers are in use. 270 271 272 What: /sys/devices/system/cpu/cpu*/cache/index3/cache_disable_{0,1} 273 Date: August 2008 274 KernelVersion: 2.6.27 275 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 276 Description: Disable L3 cache indices 277 278 These files exist in every CPU's cache/index3 directory. Each 279 cache_disable_{0,1} file corresponds to one disable slot which 280 can be used to disable a cache index. Reading from these files 281 on a processor with this functionality will return the currently 282 disabled index for that node. There is one L3 structure per 283 node, or per internal node on MCM machines. Writing a valid 284 index to one of these files will cause the specified cache 285 index to be disabled. 286 287 All AMD processors with L3 caches provide this functionality. 288 For details, see BKDGs at 289 https://www.amd.com/en/support/tech-docs?keyword=bios+kernel 290 291 292 What: /sys/devices/system/cpu/cpufreq/boost 293 Date: August 2012 294 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 295 Description: Processor frequency boosting control 296 297 This switch controls the boost setting for the whole system. 298 Boosting allows the CPU and the firmware to run at a frequency 299 beyond its nominal limit. 300 301 More details can be found in 302 Documentation/admin-guide/pm/cpufreq.rst 303 304 305 What: /sys/devices/system/cpu/cpuX/crash_notes 306 /sys/devices/system/cpu/cpuX/crash_notes_size 307 Date: April 2013 308 Contact: kexec@lists.infradead.org 309 Description: address and size of the percpu note. 310 311 crash_notes: the physical address of the memory that holds the 312 note of cpuX. 313 314 crash_notes_size: size of the note of cpuX. 315 316 317 What: /sys/devices/system/cpu/intel_pstate/max_perf_pct 318 /sys/devices/system/cpu/intel_pstate/min_perf_pct 319 /sys/devices/system/cpu/intel_pstate/no_turbo 320 Date: February 2013 321 Contact: linux-pm@vger.kernel.org 322 Description: Parameters for the Intel P-state driver 323 324 Logic for selecting the current P-state in Intel 325 Sandybridge+ processors. The three knobs control 326 limits for the P-state that will be requested by the 327 driver. 328 329 max_perf_pct: limits the maximum P state that will be requested by 330 the driver stated as a percentage of the available performance. 331 332 min_perf_pct: limits the minimum P state that will be requested by 333 the driver stated as a percentage of the available performance. 334 335 no_turbo: limits the driver to selecting P states below the turbo 336 frequency range. 337 338 More details can be found in 339 Documentation/admin-guide/pm/intel_pstate.rst 340 341 What: /sys/devices/system/cpu/cpu*/cache/index*/<set_of_attributes_mentioned_below> 342 Date: July 2014(documented, existed before August 2008) 343 Contact: Sudeep Holla <sudeep.holla@arm.com> 344 Linux kernel mailing list <linux-kernel@vger.kernel.org> 345 Description: Parameters for the CPU cache attributes 346 347 allocation_policy: 348 - WriteAllocate: 349 allocate a memory location to a cache line 350 on a cache miss because of a write 351 - ReadAllocate: 352 allocate a memory location to a cache line 353 on a cache miss because of a read 354 - ReadWriteAllocate: 355 both writeallocate and readallocate 356 357 coherency_line_size: 358 the minimum amount of data in bytes that gets 359 transferred from memory to cache 360 361 level: 362 the cache hierarchy in the multi-level cache configuration 363 364 number_of_sets: 365 total number of sets in the cache, a set is a 366 collection of cache lines with the same cache index 367 368 physical_line_partition: 369 number of physical cache line per cache tag 370 371 shared_cpu_list: 372 the list of logical cpus sharing the cache 373 374 shared_cpu_map: 375 logical cpu mask containing the list of cpus sharing 376 the cache 377 378 size: 379 the total cache size in kB 380 381 type: 382 - Instruction: cache that only holds instructions 383 - Data: cache that only caches data 384 - Unified: cache that holds both data and instructions 385 386 ways_of_associativity: 387 degree of freedom in placing a particular block 388 of memory in the cache 389 390 write_policy: 391 - WriteThrough: 392 data is written to both the cache line 393 and to the block in the lower-level memory 394 - WriteBack: 395 data is written only to the cache line and 396 the modified cache line is written to main 397 memory only when it is replaced 398 399 400 What: /sys/devices/system/cpu/cpu*/cache/index*/id 401 Date: September 2016 402 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 403 Description: Cache id 404 405 The id provides a unique number for a specific instance of 406 a cache of a particular type. E.g. there may be a level 407 3 unified cache on each socket in a server and we may 408 assign them ids 0, 1, 2, ... 409 410 Note that id value can be non-contiguous. E.g. level 1 411 caches typically exist per core, but there may not be a 412 power of two cores on a socket, so these caches may be 413 numbered 0, 1, 2, 3, 4, 5, 8, 9, 10, ... 414 415 What: /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats 416 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/turbo_stat 417 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/sub_turbo_stat 418 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/unthrottle 419 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/powercap 420 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overtemp 421 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/supply_fault 422 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/overcurrent 423 /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats/occ_reset 424 Date: March 2016 425 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 426 Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org> 427 Description: POWERNV CPUFreq driver's frequency throttle stats directory and 428 attributes 429 430 'cpuX/cpufreq/throttle_stats' directory contains the CPU frequency 431 throttle stat attributes for the chip. The throttle stats of a cpu 432 is common across all the cpus belonging to a chip. Below are the 433 throttle attributes exported in the 'throttle_stats' directory: 434 435 - turbo_stat : This file gives the total number of times the max 436 frequency is throttled to lower frequency in turbo (at and above 437 nominal frequency) range of frequencies. 438 439 - sub_turbo_stat : This file gives the total number of times the 440 max frequency is throttled to lower frequency in sub-turbo(below 441 nominal frequency) range of frequencies. 442 443 - unthrottle : This file gives the total number of times the max 444 frequency is unthrottled after being throttled. 445 446 - powercap : This file gives the total number of times the max 447 frequency is throttled due to 'Power Capping'. 448 449 - overtemp : This file gives the total number of times the max 450 frequency is throttled due to 'CPU Over Temperature'. 451 452 - supply_fault : This file gives the total number of times the 453 max frequency is throttled due to 'Power Supply Failure'. 454 455 - overcurrent : This file gives the total number of times the 456 max frequency is throttled due to 'Overcurrent'. 457 458 - occ_reset : This file gives the total number of times the max 459 frequency is throttled due to 'OCC Reset'. 460 461 The sysfs attributes representing different throttle reasons like 462 powercap, overtemp, supply_fault, overcurrent and occ_reset map to 463 the reasons provided by OCC firmware for throttling the frequency. 464 465 What: /sys/devices/system/cpu/cpufreq/policyX/throttle_stats 466 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/turbo_stat 467 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/sub_turbo_stat 468 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/unthrottle 469 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/powercap 470 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overtemp 471 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/supply_fault 472 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/overcurrent 473 /sys/devices/system/cpu/cpufreq/policyX/throttle_stats/occ_reset 474 Date: March 2016 475 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 476 Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org> 477 Description: POWERNV CPUFreq driver's frequency throttle stats directory and 478 attributes 479 480 'policyX/throttle_stats' directory and all the attributes are same as 481 the /sys/devices/system/cpu/cpuX/cpufreq/throttle_stats directory and 482 attributes which give the frequency throttle information of the chip. 483 484 What: /sys/devices/system/cpu/cpuX/regs/ 485 /sys/devices/system/cpu/cpuX/regs/identification/ 486 /sys/devices/system/cpu/cpuX/regs/identification/midr_el1 487 /sys/devices/system/cpu/cpuX/regs/identification/revidr_el1 488 /sys/devices/system/cpu/cpuX/regs/identification/smidr_el1 489 Date: June 2016 490 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org> 491 Description: AArch64 CPU registers 492 493 'identification' directory exposes the CPU ID registers for 494 identifying model and revision of the CPU and SMCU. 495 496 What: /sys/devices/system/cpu/aarch32_el0 497 Date: May 2021 498 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org> 499 Description: Identifies the subset of CPUs in the system that can execute 500 AArch32 (32-bit ARM) applications. If present, the same format as 501 /sys/devices/system/cpu/{offline,online,possible,present} is used. 502 If absent, then all or none of the CPUs can execute AArch32 503 applications and execve() will behave accordingly. 504 505 What: /sys/devices/system/cpu/cpuX/cpu_capacity 506 Date: December 2016 507 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 508 Description: information about CPUs heterogeneity. 509 510 cpu_capacity: capacity of cpuX. 511 512 What: /sys/devices/system/cpu/vulnerabilities 513 /sys/devices/system/cpu/vulnerabilities/gather_data_sampling 514 /sys/devices/system/cpu/vulnerabilities/itlb_multihit 515 /sys/devices/system/cpu/vulnerabilities/l1tf 516 /sys/devices/system/cpu/vulnerabilities/mds 517 /sys/devices/system/cpu/vulnerabilities/meltdown 518 /sys/devices/system/cpu/vulnerabilities/mmio_stale_data 519 /sys/devices/system/cpu/vulnerabilities/reg_file_data_sampling 520 /sys/devices/system/cpu/vulnerabilities/retbleed 521 /sys/devices/system/cpu/vulnerabilities/spec_store_bypass 522 /sys/devices/system/cpu/vulnerabilities/spectre_v1 523 /sys/devices/system/cpu/vulnerabilities/spectre_v2 524 /sys/devices/system/cpu/vulnerabilities/srbds 525 /sys/devices/system/cpu/vulnerabilities/tsx_async_abort 526 Date: January 2018 527 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 528 Description: Information about CPU vulnerabilities 529 530 The files are named after the code names of CPU 531 vulnerabilities. The output of those files reflects the 532 state of the CPUs in the system. Possible output values: 533 534 ================ ============================================== 535 "Not affected" CPU is not affected by the vulnerability 536 "Vulnerable" CPU is affected and no mitigation in effect 537 "Mitigation: $M" CPU is affected and mitigation $M is in effect 538 ================ ============================================== 539 540 See also: Documentation/admin-guide/hw-vuln/index.rst 541 542 What: /sys/devices/system/cpu/smt 543 /sys/devices/system/cpu/smt/active 544 /sys/devices/system/cpu/smt/control 545 Date: June 2018 546 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 547 Description: Control Symmetric Multi Threading (SMT) 548 549 active: Tells whether SMT is active (enabled and siblings online) 550 551 control: Read/write interface to control SMT. Possible 552 values: 553 554 ================ ========================================= 555 "on" SMT is enabled 556 "off" SMT is disabled 557 "<N>" SMT is enabled with N threads per core. 558 "forceoff" SMT is force disabled. Cannot be changed. 559 "notsupported" SMT is not supported by the CPU 560 "notimplemented" SMT runtime toggling is not 561 implemented for the architecture 562 ================ ========================================= 563 564 If control status is "forceoff" or "notsupported" writes 565 are rejected. Note that enabling SMT on PowerPC skips 566 offline cores. 567 568 What: /sys/devices/system/cpu/cpuX/power/energy_perf_bias 569 Date: March 2019 570 Contact: linux-pm@vger.kernel.org 571 Description: Intel Energy and Performance Bias Hint (EPB) 572 573 EPB for the given CPU in a sliding scale 0 - 15, where a value 574 of 0 corresponds to a hint preference for highest performance 575 and a value of 15 corresponds to the maximum energy savings. 576 577 In order to change the EPB value for the CPU, write either 578 a number in the 0 - 15 sliding scale above, or one of the 579 strings: "performance", "balance-performance", "normal", 580 "balance-power", "power" (that represent values reflected by 581 their meaning), to this attribute. 582 583 This attribute is present for all online CPUs supporting the 584 Intel EPB feature. 585 586 What: /sys/devices/system/cpu/umwait_control 587 /sys/devices/system/cpu/umwait_control/enable_c02 588 /sys/devices/system/cpu/umwait_control/max_time 589 Date: May 2019 590 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 591 Description: Umwait control 592 593 enable_c02: Read/write interface to control umwait C0.2 state 594 Read returns C0.2 state status: 595 0: C0.2 is disabled 596 1: C0.2 is enabled 597 598 Write 'y' or '1' or 'on' to enable C0.2 state. 599 Write 'n' or '0' or 'off' to disable C0.2 state. 600 601 The interface is case insensitive. 602 603 max_time: Read/write interface to control umwait maximum time 604 in TSC-quanta that the CPU can reside in either C0.1 605 or C0.2 state. The time is an unsigned 32-bit number. 606 Note that a value of zero means there is no limit. 607 Low order two bits must be zero. 608 609 What: /sys/devices/system/cpu/sev 610 /sys/devices/system/cpu/sev/vmpl 611 Date: May 2024 612 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 613 Description: Secure Encrypted Virtualization (SEV) information 614 615 This directory is only present when running as an SEV-SNP guest. 616 617 vmpl: Reports the Virtual Machine Privilege Level (VMPL) at which 618 the SEV-SNP guest is running. 619 620 621 What: /sys/devices/system/cpu/svm 622 Date: August 2019 623 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 624 Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org> 625 Description: Secure Virtual Machine 626 627 If 1, it means the system is using the Protected Execution 628 Facility in POWER9 and newer processors. i.e., it is a Secure 629 Virtual Machine. 630 631 What: /sys/devices/system/cpu/cpuX/purr 632 Date: Apr 2005 633 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org> 634 Description: PURR ticks for this CPU since the system boot. 635 636 The Processor Utilization Resources Register (PURR) is 637 a 64-bit counter which provides an estimate of the 638 resources used by the CPU thread. The contents of this 639 register increases monotonically. This sysfs interface 640 exposes the number of PURR ticks for cpuX. 641 642 What: /sys/devices/system/cpu/cpuX/spurr 643 Date: Dec 2006 644 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org> 645 Description: SPURR ticks for this CPU since the system boot. 646 647 The Scaled Processor Utilization Resources Register 648 (SPURR) is a 64-bit counter that provides a frequency 649 invariant estimate of the resources used by the CPU 650 thread. The contents of this register increases 651 monotonically. This sysfs interface exposes the number 652 of SPURR ticks for cpuX. 653 654 What: /sys/devices/system/cpu/cpuX/idle_purr 655 Date: Apr 2020 656 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org> 657 Description: PURR ticks for cpuX when it was idle. 658 659 This sysfs interface exposes the number of PURR ticks 660 for cpuX when it was idle. 661 662 What: /sys/devices/system/cpu/cpuX/idle_spurr 663 Date: Apr 2020 664 Contact: Linux for PowerPC mailing list <linuxppc-dev@lists.ozlabs.org> 665 Description: SPURR ticks for cpuX when it was idle. 666 667 This sysfs interface exposes the number of SPURR ticks 668 for cpuX when it was idle. 669 670 What: /sys/devices/system/cpu/cpuX/mte_tcf_preferred 671 Date: July 2021 672 Contact: Linux ARM Kernel Mailing list <linux-arm-kernel@lists.infradead.org> 673 Description: Preferred MTE tag checking mode 674 675 When a user program specifies more than one MTE tag checking 676 mode, this sysfs node is used to specify which mode should 677 be preferred when scheduling a task on that CPU. Possible 678 values: 679 680 ================ ============================================== 681 "sync" Prefer synchronous mode 682 "asymm" Prefer asymmetric mode 683 "async" Prefer asynchronous mode 684 ================ ============================================== 685 686 See also: Documentation/arch/arm64/memory-tagging-extension.rst 687 688 What: /sys/devices/system/cpu/nohz_full 689 Date: Apr 2015 690 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 691 Description: 692 (RO) the list of CPUs that are in nohz_full mode. 693 These CPUs are set by boot parameter "nohz_full=". 694 695 What: /sys/devices/system/cpu/isolated 696 Date: Apr 2015 697 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 698 Description: 699 (RO) the list of CPUs that are isolated and don't 700 participate in load balancing. These CPUs are set by 701 boot parameter "isolcpus=". 702 703 What: /sys/devices/system/cpu/crash_hotplug 704 Date: Aug 2023 705 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 706 Description: 707 (RO) indicates whether or not the kernel updates relevant kexec 708 segments on memory hot un/plug and/or on/offline events, avoiding the 709 need to reload kdump kernel. 710 711 What: /sys/devices/system/cpu/enabled 712 Date: Nov 2022 713 Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org> 714 Description: 715 (RO) the list of CPUs that can be brought online. 716