cpufreq: CPPC: Add sysfs documentation for perf_limited

Add ABI documentation for the Performance Limited Register sysfs
interface in the cppc_cpufreq driver.

Signed-off-by: Sumit Gupta <sumitg@nvi

cpufreq: CPPC: Add sysfs documentation for perf_limited

Add ABI documentation for the Performance Limited Register sysfs
interface in the cppc_cpufreq driver.

Signed-off-by: Sumit Gupta <sumitg@nvidia.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
Reviewed-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Link: https://patch.msgid.link/20260206142658.72583-8-sumitg@nvidia.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

show more ...

tick/nohz: Expose housekeeping CPUs in sysfs

Expose the current system-defined list of housekeeping CPUs in a new
sysfs file: /sys/devices/system/cpu/housekeeping.

This provides userspace performan

tick/nohz: Expose housekeeping CPUs in sysfs

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 <atomlin@atomlin.com>
Link: https://patch.msgid.link/20251011012853.7539-2-atomlin@atomlin.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

show more ...

x86/vmscape: Enable the mitigation

Enable the previously added mitigation for VMscape. Add the cmdline
vmscape={off|ibpb|force} and sysfs reporting.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@li

x86/vmscape: Enable the mitigation

Enable the previously added mitigation for VMscape. Add the cmdline
vmscape={off|ibpb|force} and sysfs reporting.

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>

show more ...

x86/bugs: Add a Transient Scheduler Attacks mitigation

Add the required features detection glue to bugs.c et all in order to
support the TSA mitigation.

Co-developed-by: Kim Phillips <kim.phillips@

x86/bugs: Add a Transient Scheduler Attacks mitigation

Add the required features detection glue to bugs.c et all in order to
support the TSA mitigation.

Co-developed-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>

show more ...

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

Pull arm64 updates from Will Deacon:
"The headline feature is the re-enablement of support for Arm's
Scalab

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

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
...

show more ...

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

Pull power management updates from Rafael Wysocki:
"Once again, the changes are dominated by cpufreq updates

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

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()
...

show more ...

Merge branch 'pm-cpuidle'

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 cpuid

Merge branch 'pm-cpuidle'

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

show more ...

Merge branch 'pm-cpufreq'

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 cor

Merge branch 'pm-cpufreq'

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()
...

show more ...

cpufreq: CPPC: Add support for autonomous selection

Add sysfs interfaces for CPPC autonomous selection in the cppc_cpufreq
driver.

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Reviewed-by:

cpufreq: CPPC: Add support for autonomous selection

Add sysfs interfaces for CPPC autonomous selection in the cppc_cpufreq
driver.

Signed-off-by: Lifeng Zheng <zhenglifeng1@huawei.com>
Reviewed-by: Sumit Gupta <sumitg@nvidia.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://patch.msgid.link/20250507031941.2812701-1-zhenglifeng1@huawei.com
[ rjw: Subject edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

show more ...

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

Conflicts:
Documentation/admin-guide/hw-vuln/index.rst
arch/x86/include/asm/cpufeatures.h
arch/x86/kernel/alternat

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

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 <mingo@kernel.org>

show more ...

x86/its: Enable Indirect Target Selection mitigation

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 ha

x86/its: Enable Indirect Target Selection mitigation

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 <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>

show more ...

arm64: Expose AIDR_EL1 via sysfs

The KVM PV ABI recently added a feature that allows the VM to discover
the set of physical CPU implementations, identified by a tuple of
{MIDR_EL1, REVIDR_EL1, AIDR_

arm64: Expose AIDR_EL1 via sysfs

The KVM PV ABI recently added a feature that allows the VM to discover
the set of physical CPU implementations, identified by a tuple of
{MIDR_EL1, REVIDR_EL1, AIDR_EL1}. Unlike other KVM PV features, the
expectation is that the VMM implements the hypercall instead of KVM as
it has the authoritative view of where the VM gets scheduled.

To do this the VMM needs to know the values of these registers on any
CPU in the system. While MIDR_EL1 and REVIDR_EL1 are already exposed,
AIDR_EL1 is not. Provide it in sysfs along with the other identification
registers.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20250403231626.3181116-1-oliver.upton@linux.dev
Signed-off-by: Will Deacon <will@kernel.org>

show more ...

x86/cpu: Help users notice when running old Intel microcode

Old microcode is bad for users and for kernel developers.

For users, it exposes them to known fixed security and/or functional
issues. Th

x86/cpu: Help users notice when running old Intel microcode

Old microcode is bad for users and for kernel developers.

For users, it exposes them to known fixed security and/or functional
issues. These obviously rarely result in instant dumpster fires in
every environment. But it is as important to keep your microcode up
to date as it is to keep your kernel up to date.

Old microcode also makes kernels harder to debug. A developer looking
at an oops need to consider kernel bugs, known CPU issues and unknown
CPU issues as possible causes. If they know the microcode is up to
date, they can mostly eliminate known CPU issues as the cause.

Make it easier to tell if CPU microcode is out of date. Add a list
of released microcode. If the loaded microcode is older than the
release, tell users in a place that folks can find it:

/sys/devices/system/cpu/vulnerabilities/old_microcode

Tell kernel kernel developers about it with the existing taint
flag:

TAINT_CPU_OUT_OF_SPEC

== Discussion ==

When a user reports a potential kernel issue, it is very common
to ask them to reproduce the issue on mainline. Running mainline,
they will (independently from the distro) acquire a more up-to-date
microcode version list. If their microcode is old, they will
get a warning about the taint and kernel developers can take that
into consideration when debugging.

Just like any other entry in "vulnerabilities/", users are free to
make their own assessment of their exposure.

== Microcode Revision Discussion ==

The microcode versions in the table were generated from the Intel
microcode git repo:

8ac9378a8487 ("microcode-20241112 Release")

which as of this writing lags behind the latest microcode-20250211.

It can be argued that the versions that the kernel picks to call "old"
should be a revision or two old. Which specific version is picked is
less important to me than picking *a* version and enforcing it.

This repository contains only microcode versions that Intel has deemed
to be OS-loadable. It is quite possible that the BIOS has loaded a
newer microcode than the latest in this repo. If this happens, the
system is considered to have new microcode, not old.

Specifically, the sysfs file and taint flag answer the question:

Is the CPU running on the latest OS-loadable microcode,
or something even later that the BIOS loaded?

In other words, Intel never publishes an authoritative list of CPUs
and latest microcode revisions. Until it does, this is the best that
Linux can do.

Also note that the "intel-ucode-defs.h" file is simple, ugly and
has lots of magic numbers. That's on purpose and should allow a
single file to be shared across lots of stable kernel regardless of if
they have the new "VFM" infrastructure or not. It was generated with
a dumb script.

== FAQ ==

Q: Does this tell me if my system is secure or insecure?
A: No. It only tells you if your microcode was old when the
system booted.

Q: Should the kernel warn if the microcode list itself is too old?
A: No. New kernels will get new microcode lists, both mainline
and stable. The only way to have an old list is to be running
an old kernel in which case you have bigger problems.

Q: Is this for security or functional issues?
A: Both.

Q: If a given microcode update only has functional problems but
no security issues, will it be considered old?
A: Yes. All microcode image versions within a microcode release
are treated identically. Intel appears to make security
updates without disclosing them in the release notes. Thus,
all updates are considered to be security-relevant.

Q: Who runs old microcode?
A: Anybody with an old distro. This happens all the time inside
of Intel where there are lots of weird systems in labs that
might not be getting regular distro updates and might also
be running rather exotic microcode images.

Q: If I update my microcode after booting will it stop saying
"Vulnerable"?
A: No. Just like all the other vulnerabilies, you need to
reboot before the kernel will reassess your vulnerability.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "Ahmed S. Darwish" <darwi@linutronix.de>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: John Ogness <john.ogness@linutronix.de>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/all/20250421195659.CF426C07%40davehans-spike.ostc.intel.com
(cherry picked from commit 9127865b15eb0a1bd05ad7efe29489c44394bdc1)

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Documentation: ABI: testing: document the new cpuidle sysfs file

Mention the new 'intel_c1_demotion' sysfs file in the "cpuidle" section
and refer to "Documentation/admin-guide/pm/intel_idle.rst" fo

Documentation: ABI: testing: document the new cpuidle sysfs file

Mention the new 'intel_c1_demotion' sysfs file in the "cpuidle" section
and refer to "Documentation/admin-guide/pm/intel_idle.rst" for more
information.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://patch.msgid.link/20250317135541.1471754-4-dedekind1@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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Document/kexec: generalize crash hotplug description

Commit 79365026f869 ("crash: add a new kexec flag for hotplug support")
generalizes the crash hotplug support to allow architectures to update
mu

Document/kexec: generalize crash hotplug description

Commit 79365026f869 ("crash: add a new kexec flag for hotplug support")
generalizes the crash hotplug support to allow architectures to update
multiple kexec segments on CPU/Memory hotplug and not just elfcorehdr.
Therefore, update the relevant kernel documentation to reflect the same.

No functional change.

Link: https://lkml.kernel.org/r/20240812041651.703156-1-sourabhjain@linux.ibm.com
Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Reviewed-by: Petr Tesarik <ptesarik@suse.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Hari Bathini <hbathini@linux.ibm.com>
Cc: Petr Tesarik <petr@tesarici.cz>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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cpu/SMT: Enable SMT only if a core is online

If a core is offline then enabling SMT should not online CPUs of
this core. By enabling SMT, what is intended is either changing the SMT
value from "off"

cpu/SMT: Enable SMT only if a core is online

If a core is offline then enabling SMT should not online CPUs of
this core. By enabling SMT, what is intended is either changing the SMT
value from "off" to "on" or setting the SMT level (threads per core) from a
lower to higher value.

On PowerPC the ppc64_cpu utility can be used, among other things, to
perform the following functions:

ppc64_cpu --cores-on # Get the number of online cores
ppc64_cpu --cores-on=X # Put exactly X cores online
ppc64_cpu --offline-cores=X[,Y,...] # Put specified cores offline
ppc64_cpu --smt={on|off|value} # Enable, disable or change SMT level

If the user has decided to offline certain cores, enabling SMT should
not online CPUs in those cores. This patch fixes the issue and changes
the behaviour as described, by introducing an arch specific function
topology_is_core_online(). It is currently implemented only for PowerPC.

Fixes: 73c58e7e1412 ("powerpc: Add HOTPLUG_SMT support")
Reported-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Closes: https://groups.google.com/g/powerpc-utils-devel/c/wrwVzAAnRlI/m/5KJSoqP4BAAJ
Signed-off-by: Nysal Jan K.A <nysal@linux.ibm.com>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240731030126.956210-2-nysal@linux.ibm.com

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Merge tag 'x86_sev_for_v6.11_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 SEV updates from Borislav Petkov:

- Add support for running the kernel in a SEV-SNP guest, over

Merge tag 'x86_sev_for_v6.11_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 SEV updates from Borislav Petkov:

- Add support for running the kernel in a SEV-SNP guest, over a Secure
VM Service Module (SVSM).

When running over a SVSM, different services can run at different
protection levels, apart from the guest OS but still within the
secure SNP environment. They can provide services to the guest, like
a vTPM, for example.

This series adds the required facilities to interface with such a
SVSM module.

- The usual fixlets, refactoring and cleanups

[ And as always: "SEV" is AMD's "Secure Encrypted Virtualization".

I can't be the only one who gets all the newer x86 TLA's confused,
can I?
- Linus ]

* tag 'x86_sev_for_v6.11_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Documentation/ABI/configfs-tsm: Fix an unexpected indentation silly
x86/sev: Do RMP memory coverage check after max_pfn has been set
x86/sev: Move SEV compilation units
virt: sev-guest: Mark driver struct with __refdata to prevent section mismatch
x86/sev: Allow non-VMPL0 execution when an SVSM is present
x86/sev: Extend the config-fs attestation support for an SVSM
x86/sev: Take advantage of configfs visibility support in TSM
fs/configfs: Add a callback to determine attribute visibility
sev-guest: configfs-tsm: Allow the privlevel_floor attribute to be updated
virt: sev-guest: Choose the VMPCK key based on executing VMPL
x86/sev: Provide guest VMPL level to userspace
x86/sev: Provide SVSM discovery support
x86/sev: Use the SVSM to create a vCPU when not in VMPL0
x86/sev: Perform PVALIDATE using the SVSM when not at VMPL0
x86/sev: Use kernel provided SVSM Calling Areas
x86/sev: Check for the presence of an SVSM in the SNP secrets page
x86/irqflags: Provide native versions of the local_irq_save()/restore()

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cpumask: Add enabled cpumask for present CPUs that can be brought online

The 'offline' file in sysfs shows all offline CPUs, including those
that aren't present. User-space is expected to remove not

cpumask: Add enabled cpumask for present CPUs that can be brought online

The 'offline' file in sysfs shows all offline CPUs, including those
that aren't present. User-space is expected to remove not-present CPUs
from this list to learn which CPUs could be brought online.

CPUs can be present but not-enabled. These CPUs can't be brought online
until the firmware policy changes, which comes with an ACPI notification
that will register the CPUs.

With only the offline and present files, user-space is unable to
determine which CPUs it can try to bring online. Add a new CPU mask
that shows this based on all the registered CPUs.

Signed-off-by: James Morse <james.morse@arm.com>
Tested-by: Miguel Luis <miguel.luis@oracle.com>
Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
Tested-by: Jianyong Wu <jianyong.wu@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/20240529133446.28446-20-Jonathan.Cameron@huawei.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

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x86/sev: Provide guest VMPL level to userspace

Requesting an attestation report from userspace involves providing the VMPL
level for the report. Currently any value from 0-3 is valid because Linux
e

x86/sev: Provide guest VMPL level to userspace

Requesting an attestation report from userspace involves providing the VMPL
level for the report. Currently any value from 0-3 is valid because Linux
enforces running at VMPL0.

When an SVSM is present, though, Linux will not be running at VMPL0 and only
VMPL values starting at the VMPL level Linux is running at to 3 are valid. In
order to allow userspace to determine the minimum VMPL value that can be
supplied to an attestation report, create a sysfs entry that can be used to
retrieve the current VMPL level of the kernel.

[ bp: Add CONFIG_SYSFS ifdeffery. ]

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/fff846da0d8d561f9fdaf297dcf8cd907545a25b.1717600736.git.thomas.lendacky@amd.com

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Documentation: Fix the address of the linuxppc-dev mailing list

This list was moved many years ago.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Michael Ellerman <mpe@eller

Documentation: Fix the address of the linuxppc-dev mailing list

This list was moved many years ago.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240503121012.3ba5000b@canb.auug.org.au

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x86/rfds: Mitigate Register File Data Sampling (RFDS)

RFDS is a CPU vulnerability that may allow userspace to infer kernel
stale data previously used in floating point registers, vector registers
an

x86/rfds: Mitigate Register File Data Sampling (RFDS)

RFDS is a CPU vulnerability that may allow userspace to infer kernel
stale data previously used in floating point registers, vector registers
and integer registers. RFDS only affects certain Intel Atom processors.

Intel released a microcode update that uses VERW instruction to clear
the affected CPU buffers. Unlike MDS, none of the affected cores support
SMT.

Add RFDS bug infrastructure and enable the VERW based mitigation by
default, that clears the affected buffers just before exiting to
userspace. Also add sysfs reporting and cmdline parameter
"reg_file_data_sampling" to control the mitigation.

For details see:
Documentation/admin-guide/hw-vuln/reg-file-data-sampling.rst

Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>

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Documentation: Drop or replace remaining mentions of IA64

Drop or update mentions of IA64, as appropriate.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Merge tag 'mm-nonmm-stable-2023-08-28-22-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull non-MM updates from Andrew Morton:

- An extensive rework of kexec and crash Kconfig from

Merge tag 'mm-nonmm-stable-2023-08-28-22-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Pull non-MM updates from Andrew Morton:

- An extensive rework of kexec and crash Kconfig from Eric DeVolder
("refactor Kconfig to consolidate KEXEC and CRASH options")

- kernel.h slimming work from Andy Shevchenko ("kernel.h: Split out a
couple of macros to args.h")

- gdb feature work from Kuan-Ying Lee ("Add GDB memory helper
commands")

- vsprintf inclusion rationalization from Andy Shevchenko
("lib/vsprintf: Rework header inclusions")

- Switch the handling of kdump from a udev scheme to in-kernel
handling, by Eric DeVolder ("crash: Kernel handling of CPU and memory
hot un/plug")

- Many singleton patches to various parts of the tree

* tag 'mm-nonmm-stable-2023-08-28-22-48' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (81 commits)
document while_each_thread(), change first_tid() to use for_each_thread()
drivers/char/mem.c: shrink character device's devlist[] array
x86/crash: optimize CPU changes
crash: change crash_prepare_elf64_headers() to for_each_possible_cpu()
crash: hotplug support for kexec_load()
x86/crash: add x86 crash hotplug support
crash: memory and CPU hotplug sysfs attributes
kexec: exclude elfcorehdr from the segment digest
crash: add generic infrastructure for crash hotplug support
crash: move a few code bits to setup support of crash hotplug
kstrtox: consistently use _tolower()
kill do_each_thread()
nilfs2: fix WARNING in mark_buffer_dirty due to discarded buffer reuse
scripts/bloat-o-meter: count weak symbol sizes
treewide: drop CONFIG_EMBEDDED
lockdep: fix static memory detection even more
lib/vsprintf: declare no_hash_pointers in sprintf.h
lib/vsprintf: split out sprintf() and friends
kernel/fork: stop playing lockless games for exe_file replacement
adfs: delete unused "union adfs_dirtail" definition
...

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Merge tag 'smp-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull CPU hotplug updates from Thomas Gleixner:
"Updates for the CPU hotplug core:

- Support partial SMT

Merge tag 'smp-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull CPU hotplug updates from Thomas Gleixner:
"Updates for the CPU hotplug core:

- Support partial SMT enablement.

So far the sysfs SMT control only allows to toggle between SMT on
and off. That's sufficient for x86 which usually has at max two
threads except for the Xeon PHI platform which has four threads per
core

Though PowerPC has up to 16 threads per core and so far it's only
possible to control the number of enabled threads per core via a
command line option. There is some way to control this at runtime,
but that lacks enforcement and the usability is awkward

This update expands the sysfs interface and the core infrastructure
to accept numerical values so PowerPC can build SMT runtime control
for partial SMT enablement on top

The core support has also been provided to the PowerPC maintainers
who added the PowerPC related changes on top

- Minor cleanups and documentation updates"

* tag 'smp-core-2023-08-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
Documentation: core-api/cpuhotplug: Fix state names
cpu/hotplug: Remove unused function declaration cpu_set_state_online()
cpu/SMT: Fix cpu_smt_possible() comment
cpu/SMT: Allow enabling partial SMT states via sysfs
cpu/SMT: Create topology_smt_thread_allowed()
cpu/SMT: Remove topology_smt_supported()
cpu/SMT: Store the current/max number of threads
cpu/SMT: Move smt/control simple exit cases earlier
cpu/SMT: Move SMT prototypes into cpu_smt.h
cpu/hotplug: Remove dependancy against cpu_primary_thread_mask

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crash: memory and CPU hotplug sysfs attributes

Introduce the crash_hotplug attribute for memory and CPUs for use by
userspace. These attributes directly facilitate the udev rule for
managing usersp

crash: memory and CPU hotplug sysfs attributes

Introduce the crash_hotplug attribute for memory and CPUs for use by
userspace. These attributes directly facilitate the udev rule for
managing userspace re-loading of the crash kernel upon hot un/plug
changes.

For memory, expose the crash_hotplug attribute to the
/sys/devices/system/memory directory. For example:

# udevadm info --attribute-walk /sys/devices/system/memory/memory81
looking at device '/devices/system/memory/memory81':
KERNEL=="memory81"
SUBSYSTEM=="memory"
DRIVER==""
ATTR{online}=="1"
ATTR{phys_device}=="0"
ATTR{phys_index}=="00000051"
ATTR{removable}=="1"
ATTR{state}=="online"
ATTR{valid_zones}=="Movable"

looking at parent device '/devices/system/memory':
KERNELS=="memory"
SUBSYSTEMS==""
DRIVERS==""
ATTRS{auto_online_blocks}=="offline"
ATTRS{block_size_bytes}=="8000000"
ATTRS{crash_hotplug}=="1"

For CPUs, expose the crash_hotplug attribute to the
/sys/devices/system/cpu directory. For example:

# udevadm info --attribute-walk /sys/devices/system/cpu/cpu0
looking at device '/devices/system/cpu/cpu0':
KERNEL=="cpu0"
SUBSYSTEM=="cpu"
DRIVER=="processor"
ATTR{crash_notes}=="277c38600"
ATTR{crash_notes_size}=="368"
ATTR{online}=="1"

looking at parent device '/devices/system/cpu':
KERNELS=="cpu"
SUBSYSTEMS==""
DRIVERS==""
ATTRS{crash_hotplug}=="1"
ATTRS{isolated}==""
ATTRS{kernel_max}=="8191"
ATTRS{nohz_full}==" (null)"
ATTRS{offline}=="4-7"
ATTRS{online}=="0-3"
ATTRS{possible}=="0-7"
ATTRS{present}=="0-3"

With these sysfs attributes in place, it is possible to efficiently
instruct the udev rule to skip crash kernel reloading for kernels
configured with crash hotplug support.

For example, the following is the proposed udev rule change for RHEL
system 98-kexec.rules (as the first lines of the rule file):

# The kernel updates the crash elfcorehdr for CPU and memory changes
SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"

When examined in the context of 98-kexec.rules, the above rules test if
crash_hotplug is set, and if so, the userspace initiated
unload-then-reload of the crash kernel is skipped.

CPU and memory checks are separated in accordance with CONFIG_HOTPLUG_CPU
and CONFIG_MEMORY_HOTPLUG kernel config options. If an architecture
supports, for example, memory hotplug but not CPU hotplug, then the
/sys/devices/system/memory/crash_hotplug attribute file is present, but
the /sys/devices/system/cpu/crash_hotplug attribute file will NOT be
present. Thus the udev rule skips userspace processing of memory hot
un/plug events, but the udev rule will evaluate false for CPU events, thus
allowing userspace to process CPU hot un/plug events (ie the
unload-then-reload of the kdump capture kernel).

Link: https://lkml.kernel.org/r/20230814214446.6659-5-eric.devolder@oracle.com
Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
Reviewed-by: Sourabh Jain <sourabhjain@linux.ibm.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Akhil Raj <lf32.dev@gmail.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Takashi Iwai <tiwai@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Cc: Valentin Schneider <vschneid@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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