kernel/Documentation/ABI/testing/sysfs-devices-system-cpu, branch linux-rolling-stable

tick/nohz: Expose housekeeping CPUs in sysfs

2025-11-26T14:20:51Z

Expose the current system-defined list of housekeeping CPUs in a new sysfs file: /sys/devices/system/cpu/housekeeping. This provides userspace performance tuning tools and resource managers with a canonical, reliable method to accurately identify the cores responsible for essential kernel maintenance workloads (RCU, timer callbacks, and unbound workqueues). Currently, tooling must manually calculate the housekeeping set by parsing complex kernel boot parameters (like isolcpus= and nohz_full=) and system topology, which is prone to error. This dedicated file simplifies the configuration of low-latency workloads. Signed-off-by: Aaron Tomlin Link: https://patch.msgid.link/20251011012853.7539-2-atomlin@atomlin.com Signed-off-by: Greg Kroah-Hartman

x86/vmscape: Enable the mitigation

2025-08-14T17:37:33Z

Enable the previously added mitigation for VMscape. Add the cmdline vmscape={off|ibpb|force} and sysfs reporting. Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Borislav Petkov (AMD) Reviewed-by: Dave Hansen

x86/bugs: Add a Transient Scheduler Attacks mitigation

2025-06-17T15:17:02Z

Add the required features detection glue to bugs.c et all in order to support the TSA mitigation. Co-developed-by: Kim Phillips Signed-off-by: Kim Phillips Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Pawan Gupta

Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux

2025-05-28T21:55:35Z

Pull arm64 updates from Will Deacon: "The headline feature is the re-enablement of support for Arm's Scalable Matrix Extension (SME) thanks to a bumper crop of fixes from Mark Rutland. If matrices aren't your thing, then Ryan's page-table optimisation work is much more interesting. Summary: ACPI, EFI and PSCI: - Decouple Arm's "Software Delegated Exception Interface" (SDEI) support from the ACPI GHES code so that it can be used by platforms booted with device-tree - Remove unnecessary per-CPU tracking of the FPSIMD state across EFI runtime calls - Fix a node refcount imbalance in the PSCI device-tree code CPU Features: - Ensure register sanitisation is applied to fields in ID_AA64MMFR4 - Expose AIDR_EL1 to userspace via sysfs, primarily so that KVM guests can reliably query the underlying CPU types from the VMM - Re-enabling of SME support (CONFIG_ARM64_SME) as a result of fixes to our context-switching, signal handling and ptrace code Entry code: - Hook up TIF_NEED_RESCHED_LAZY so that CONFIG_PREEMPT_LAZY can be selected Memory management: - Prevent BSS exports from being used by the early PI code - Propagate level and stride information to the low-level TLB invalidation routines when operating on hugetlb entries - Use the page-table contiguous hint for vmap() mappings with VM_ALLOW_HUGE_VMAP where possible - Optimise vmalloc()/vmap() page-table updates to use "lazy MMU mode" and hook this up on arm64 so that the trailing DSB (used to publish the updates to the hardware walker) can be deferred until the end of the mapping operation - Extend mmap() randomisation for 52-bit virtual addresses (on par with 48-bit addressing) and remove limited support for randomisation of the linear map Perf and PMUs: - Add support for probing the CMN-S3 driver using ACPI - Minor driver fixes to the CMN, Arm-NI and amlogic PMU drivers Selftests: - Fix FPSIMD and SME tests to align with the freshly re-enabled SME support - Fix default setting of the OUTPUT variable so that tests are installed in the right location vDSO: - Replace raw counter access from inline assembly code with a call to the the __arch_counter_get_cntvct() helper function Miscellaneous: - Add some missing header inclusions to the CCA headers - Rework rendering of /proc/cpuinfo to follow the x86-approach and avoid repeated buffer expansion (the user-visible format remains identical) - Remove redundant selection of CONFIG_CRC32 - Extend early error message when failing to map the device-tree blob" * tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux: (83 commits) arm64: cputype: Add cputype definition for HIP12 arm64: el2_setup.h: Make __init_el2_fgt labels consistent, again perf/arm-cmn: Add CMN S3 ACPI binding arm64/boot: Disallow BSS exports to startup code arm64/boot: Move global CPU override variables out of BSS arm64/boot: Move init_pgdir[] and init_idmap_pgdir[] into __pi_ namespace perf/arm-cmn: Initialise cmn->cpu earlier kselftest/arm64: Set default OUTPUT path when undefined arm64: Update comment regarding values in __boot_cpu_mode arm64: mm: Drop redundant check in pmd_trans_huge() arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1 arm64/mm: Permit lazy_mmu_mode to be nested arm64/mm: Disable barrier batching in interrupt contexts arm64/cpuinfo: only show one cpu's info in c_show() arm64/mm: Batch barriers when updating kernel mappings mm/vmalloc: Enter lazy mmu mode while manipulating vmalloc ptes arm64/mm: Support huge pte-mapped pages in vmap mm/vmalloc: Gracefully unmap huge ptes mm/vmalloc: Warn on improper use of vunmap_range() arm64/mm: Hoist barriers out of set_ptes_anysz() loop ...

Merge tag 'pm-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

2025-05-27T23:48:47Z

Pull power management updates from Rafael Wysocki: "Once again, the changes are dominated by cpufreq updates, but this time the majority of them are cpufreq core changes, mostly related to the introduction of policy locking guards and __free() usage, and fixes related to boost handling. Still, there is also a significant update of the intel_pstate driver making it register an energy model when running on a hybrid platform which is used for enabling energy-aware scheduling (EAS) if the driver operates in the passive mode (and schedutil is used as the cpufreq governor for all CPUs which is the passive mode default). There are some amd-pstate driver updates too, for a good measure, including the "Requested CPU Min frequency" BIOS option support and new online/offline callbacks. In the cpuidle space, the most significant change is the addition of a C1 demotion on/off sysfs knob to intel_idle which should help some users to configure their systems more precisely. There is also the conversion of the PSCI cpuidle driver to a faux device one and there are two small updates of cpuidle governors. Device power management is also modified quite a bit, especially the handling of devices with asynchronous suspend and resume enabled during system transitions. They are now going to be handled more asynchronously during suspend transitions and somewhat less aggressively during resume transitions. Apart from the above, the operating performance points (OPP) library is now going to use mutex locking guards and scope-based cleanup helpers and there is the usual bunch of assorted fixes and code cleanups. Specifics: - Fix potential division-by-zero error in em_compute_costs() (Yaxiong Tian) - Fix typos in energy model documentation and example driver code (Moon Hee Lee, Atul Kumar Pant) - Rearrange the energy model management code and add a new function for adjusting a CPU energy model after adjusting the capacity of the given CPU to it (Rafael Wysocki) - Refactor cpufreq_online(), add and use cpufreq policy locking guards, use __free() in policy reference counting, and clean up core cpufreq code on top of that (Rafael Wysocki) - Fix boost handling on CPU suspend/resume and sysfs updates (Viresh Kumar) - Fix des_perf clamping with max_perf in amd_pstate_update() (Dhananjay Ugwekar) - Add offline, online and suspend callbacks to the amd-pstate driver, rename and use the existing amd_pstate_epp callbacks in it (Dhananjay Ugwekar) - Add support for the "Requested CPU Min frequency" BIOS option to the amd-pstate driver (Dhananjay Ugwekar) - Reset amd-pstate driver mode after running selftests (Swapnil Sapkal) - Avoid shadowing ret in amd_pstate_ut_check_driver() (Nathan Chancellor) - Add helper for governor checks to the schedutil cpufreq governor and move cpufreq-specific EAS checks to cpufreq (Rafael Wysocki) - Populate the cpu_capacity sysfs entries from the intel_pstate driver after registering asym capacity support (Ricardo Neri) - Add support for enabling Energy-aware scheduling (EAS) to the intel_pstate driver when operating in the passive mode on a hybrid platform (Rafael Wysocki) - Drop redundant cpus_read_lock() from store_local_boost() in the cpufreq core (Seyediman Seyedarab) - Replace sscanf() with kstrtouint() in the cpufreq code and use a symbol instead of a raw number in it (Bowen Yu) - Add support for autonomous CPU performance state selection to the CPPC cpufreq driver (Lifeng Zheng) - OPP: Add dev_pm_opp_set_level() (Praveen Talari) - Introduce scope-based cleanup headers and mutex locking guards in OPP core (Viresh Kumar) - Switch OPP to use kmemdup_array() (Zhang Enpei) - Optimize bucket assignment when next_timer_ns equals KTIME_MAX in the menu cpuidle governor (Zhongqiu Han) - Convert the cpuidle PSCI driver to a faux device one (Sudeep Holla) - Add C1 demotion on/off sysfs knob to the intel_idle driver (Artem Bityutskiy) - Fix typos in two comments in the teo cpuidle governor (Atul Kumar Pant) - Fix denying of auto suspend in pm_suspend_timer_fn() (Charan Teja Kalla) - Move debug runtime PM attributes to runtime_attrs[] (Rafael Wysocki) - Add new devm_ functions for enabling runtime PM and runtime PM reference counting (Bence Csókás) - Remove size arguments from strscpy() calls in the hibernation core code (Thorsten Blum) - Adjust the handling of devices with asynchronous suspend enabled during system suspend and resume to start resuming them immediately after resuming their parents and to start suspending such a device immediately after suspending its first child (Rafael Wysocki) - Adjust messages printed during tasks freezing to avoid using pr_cont() (Andrew Sayers, Paul Menzel) - Clean up unnecessary usage of !! in pm_print_times_init() (Zihuan Zhang) - Add missing wakeup source attribute relax_count to sysfs and remove the space character at the end ofi the string produced by pm_show_wakelocks() (Zijun Hu) - Add configurable pm_test delay for hibernation (Zihuan Zhang) - Disable asynchronous suspend in ucsi_ccg_probe() to prevent the cypd4226 device on Tegra boards from suspending prematurely (Jon Hunter) - Unbreak printing PM debug messages during hibernation and clean up some related code (Rafael Wysocki) - Add a systemd service to run cpupower and change cpupower binding's Makefile to use -lcpupower (John B. Wyatt IV, Francesco Poli)" * tag 'pm-6.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (72 commits) cpufreq: CPPC: Add support for autonomous selection cpufreq: Update sscanf() to kstrtouint() cpufreq: Replace magic number OPP: switch to use kmemdup_array() PM: freezer: Rewrite restarting tasks log to remove stray *done.* PM: runtime: fix denying of auto suspend in pm_suspend_timer_fn() cpufreq: drop redundant cpus_read_lock() from store_local_boost() cpupower: do not install files to /etc/default/ cpupower: do not call systemctl at install time cpupower: do not write DESTDIR to cpupower.service PM: sleep: Introduce pm_sleep_transition_in_progress() cpufreq/amd-pstate: Avoid shadowing ret in amd_pstate_ut_check_driver() cpufreq: intel_pstate: Document hybrid processor support cpufreq: intel_pstate: EAS: Increase cost for CPUs using L3 cache cpufreq: intel_pstate: EAS support for hybrid platforms PM: EM: Introduce em_adjust_cpu_capacity() PM: EM: Move CPU capacity check to em_adjust_new_capacity() PM: EM: Documentation: Fix typos in example driver code cpufreq: Drop policy locking from cpufreq_policy_is_good_for_eas() PM: sleep: Introduce pm_suspend_in_progress() ...

Merge branch 'pm-cpuidle'

2025-05-26T19:18:34Z

Merge cpuidle updates for 6.16-rc1: - Optimize bucket assignment when next_timer_ns equals KTIME_MAX in the menu cpuidle governor (Zhongqiu Han). - Convert the cpuidle PSCI driver to a faux device one (Sudeep Holla). - Add C1 demotion on/off sysfs knob to the intel_idle driver (Artem Bityutskiy). - Fix typos in two comments in the teo cpuidle governor (Atul Kumar Pant). * pm-cpuidle: cpuidle: psci: Avoid initializing faux device if no DT idle states are present Documentation: ABI: testing: document the new cpuidle sysfs file Documentation: admin-guide: pm: Document intel_idle C1 demotion intel_idle: Add C1 demotion on/off sysfs knob cpuidle: psci: Transition to the faux device interface cpuidle: menu: Optimize bucket assignment when next_timer_ns equals KTIME_MAX cpuidle: teo: Fix typos in two comments

Merge branch 'pm-cpufreq'

2025-05-26T18:19:40Z

Merge cpufreq updates for 6.16-rc1: - Refactor cpufreq_online(), add and use cpufreq policy locking guards, use __free() in policy reference counting, and clean up core cpufreq code on top of that (Rafael Wysocki). - Fix boost handling on CPU suspend/resume and sysfs updates (Viresh Kumar). - Fix des_perf clamping with max_perf in amd_pstate_update() (Dhananjay Ugwekar). - Add offline, online and suspend callbacks to the amd-pstate driver, rename and use the existing amd_pstate_epp callbacks in it (Dhananjay Ugwekar). - Add support for the "Requested CPU Min frequency" BIOS option to the amd-pstate driver (Dhananjay Ugwekar). - Reset amd-pstate driver mode after running selftests (Swapnil Sapkal). - Add helper for governor checks to the schedutil cpufreq governor and move cpufreq-specific EAS checks to cpufreq (Rafael Wysocki). - Populate the cpu_capacity sysfs entries from the intel_pstate driver after registering asym capacity support (Ricardo Neri). - Add support for enabling Energy-aware scheduling (EAS) to the intel_pstate driver when operating in the passive mode on a hybrid platform (Rafael Wysocki). - Avoid shadowing ret in amd_pstate_ut_check_driver() (Nathan Chancellor). - Drop redundant cpus_read_lock() from store_local_boost() in the cpufreq core (Seyediman Seyedarab). - Replace sscanf() with kstrtouint() in the cpufreq code and use a symbol instead of a raw number in it (Bowen Yu). - Add support for autonomous CPU performance state selection to the CPPC cpufreq driver (Lifeng Zheng). * pm-cpufreq: (31 commits) cpufreq: CPPC: Add support for autonomous selection cpufreq: Update sscanf() to kstrtouint() cpufreq: Replace magic number cpufreq: drop redundant cpus_read_lock() from store_local_boost() cpufreq/amd-pstate: Avoid shadowing ret in amd_pstate_ut_check_driver() cpufreq: intel_pstate: Document hybrid processor support cpufreq: intel_pstate: EAS: Increase cost for CPUs using L3 cache cpufreq: intel_pstate: EAS support for hybrid platforms cpufreq: Drop policy locking from cpufreq_policy_is_good_for_eas() cpufreq: intel_pstate: Populate the cpu_capacity sysfs entries arch_topology: Relocate cpu_scale to topology.[h|c] cpufreq/sched: Move cpufreq-specific EAS checks to cpufreq cpufreq/sched: schedutil: Add helper for governor checks amd-pstate-ut: Reset amd-pstate driver mode after running selftests cpufreq/amd-pstate: Add support for the "Requested CPU Min frequency" BIOS option cpufreq/amd-pstate: Add offline, online and suspend callbacks for amd_pstate_driver cpufreq: Force sync policy boost with global boost on sysfs update cpufreq: Preserve policy's boost state after resume cpufreq: Introduce policy_set_boost() cpufreq: Don't unnecessarily call set_boost() ...

cpufreq: CPPC: Add support for autonomous selection

2025-05-21T20:47:44Z

Add sysfs interfaces for CPPC autonomous selection in the cppc_cpufreq driver. Signed-off-by: Lifeng Zheng Reviewed-by: Sumit Gupta Acked-by: Viresh Kumar Link: https://patch.msgid.link/20250507031941.2812701-1-zhenglifeng1@huawei.com [ rjw: Subject edits ] Signed-off-by: Rafael J. Wysocki

Merge commit 'its-for-linus-20250509-merge' into x86/core, to resolve conflicts

2025-05-13T08:47:10Z

Conflicts: Documentation/admin-guide/hw-vuln/index.rst arch/x86/include/asm/cpufeatures.h arch/x86/kernel/alternative.c arch/x86/kernel/cpu/bugs.c arch/x86/kernel/cpu/common.c drivers/base/cpu.c include/linux/cpu.h Signed-off-by: Ingo Molnar

x86/its: Enable Indirect Target Selection mitigation

2025-05-09T20:22:05Z

Indirect Target Selection (ITS) is a bug in some pre-ADL Intel CPUs with eIBRS. It affects prediction of indirect branch and RETs in the lower half of cacheline. Due to ITS such branches may get wrongly predicted to a target of (direct or indirect) branch that is located in the upper half of the cacheline. Scope of impact =============== Guest/host isolation -------------------- When eIBRS is used for guest/host isolation, the indirect branches in the VMM may still be predicted with targets corresponding to branches in the guest. Intra-mode ---------- cBPF or other native gadgets can be used for intra-mode training and disclosure using ITS. User/kernel isolation --------------------- When eIBRS is enabled user/kernel isolation is not impacted. Indirect Branch Prediction Barrier (IBPB) ----------------------------------------- After an IBPB, indirect branches may be predicted with targets corresponding to direct branches which were executed prior to IBPB. This is mitigated by a microcode update. Add cmdline parameter indirect_target_selection=off|on|force to control the mitigation to relocate the affected branches to an ITS-safe thunk i.e. located in the upper half of cacheline. Also add the sysfs reporting. When retpoline mitigation is deployed, ITS safe-thunks are not needed, because retpoline sequence is already ITS-safe. Similarly, when call depth tracking (CDT) mitigation is deployed (retbleed=stuff), ITS safe return thunk is not used, as CDT prevents RSB-underflow. To not overcomplicate things, ITS mitigation is not supported with spectre-v2 lfence;jmp mitigation. Moreover, it is less practical to deploy lfence;jmp mitigation on ITS affected parts anyways. Signed-off-by: Pawan Gupta Signed-off-by: Dave Hansen Reviewed-by: Josh Poimboeuf Reviewed-by: Alexandre Chartre