kernel/drivers/cpufreq/intel_pstate.c, branch linux-rolling-lts

cpufreq: intel_pstate: Fix NULL pointer dereference in update_cpu_qos_request()

2026-03-19T15:08:32Z

commit ab39cc4cb8ceecdc2b61747433e7237f1ac2b789 upstream. The update_cpu_qos_request() function attempts to initialize the 'freq' variable by dereferencing 'cpudata' before verifying if the 'policy' is valid. This issue occurs on systems booted with the "nosmt" parameter, where all_cpu_data[cpu] is NULL for the SMT sibling threads. As a result, any call to update_qos_requests() will result in a NULL pointer dereference as the code will attempt to access pstate.turbo_freq using the NULL cpudata pointer. Also, pstate.turbo_freq may be updated by intel_pstate_get_hwp_cap() after initializing the 'freq' variable, so it is better to defer the 'freq' until intel_pstate_get_hwp_cap() has been called. Fix this by deferring the 'freq' assignment until after the policy and driver_data have been validated. Fixes: ae1bdd23b99f ("cpufreq: intel_pstate: Adjust frequency percentage computations") Reported-by: Jirka Hladky Closes: https://lore.kernel.org/all/CAE4VaGDfiPvz3AzrwrwM4kWB3SCkMci25nPO8W1JmTBd=xHzZg@mail.gmail.com/ Signed-off-by: David Arcari Cc: 6.18+ # 6.18+ [ rjw: Added one paragraph to the changelog ] Link: https://patch.msgid.link/20260224122106.228116-1-darcari@redhat.com Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman

cpufreq: intel_pstate: Fix crash during turbo disable

2026-03-12T11:09:40Z

commit 6b050482ec40569429d963ac52afa878691b04c9 upstream. When the system is booted with kernel command line argument "nosmt" or "maxcpus" to limit the number of CPUs, disabling turbo via: echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo results in a crash: PF: supervisor read access in kernel mode PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: Oops: 0000 [#1] SMP PTI ... RIP: 0010:store_no_turbo+0x100/0x1f0 ... This occurs because for_each_possible_cpu() returns CPUs even if they are not online. For those CPUs, all_cpu_data[] will be NULL. Since commit 973207ae3d7c ("cpufreq: intel_pstate: Rearrange max frequency updates handling code"), all_cpu_data[] is dereferenced even for CPUs which are not online, causing the NULL pointer dereference. To fix that, pass CPU number to intel_pstate_update_max_freq() and use all_cpu_data[] for those CPUs for which there is a valid cpufreq policy. Fixes: 973207ae3d7c ("cpufreq: intel_pstate: Rearrange max frequency updates handling code") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221068 Signed-off-by: Srinivas Pandruvada Cc: 6.16+ # 6.16+ Link: https://patch.msgid.link/20260225001752.890164-1-srinivas.pandruvada@linux.intel.com Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman

cpufreq: intel_pstate: Enable asym capacity only when CPU SMT is not possible

2026-02-26T22:59:01Z

[ Upstream commit 1fedbb589448bee9f20bb2ed9c850d1d2cf9963c ] According to the description in the intel_pstate.rst documentation, Capacity-Aware Scheduling and Energy-Aware Scheduling are only supported on a hybrid processor without SMT. Previously, the system used sched_smt_active() for judgment, which is not a strict condition because users can switch it on or off via /sys at any time. This could lead to incorrect driver settings in certain scenarios. For example, on a CPU that supports SMT, a user can disable SMT via the nosmt parameter to enable asym capacity, and then re-enable SMT via /sys. In such cases, some settings in the driver would no longer be correct. To address this issue, replace sched_smt_active() with cpu_smt_possible(), and only enable asym capacity when CPU SMT is not possible. Fixes: 929ebc93ccaa ("cpufreq: intel_pstate: Set asymmetric CPU capacity on hybrid systems") Signed-off-by: Yaxiong Tian [ rjw: Subject and changelog edits ] Link: https://patch.msgid.link/20260203024852.301066-1-tianyaxiong@kylinos.cn Signed-off-by: Rafael J. Wysocki Signed-off-by: Sasha Levin

cpufreq: intel_pstate: Check IDA only before MSR_IA32_PERF_CTL writes

2025-11-12T16:59:37Z

Commit ac4e04d9e378 ("cpufreq: intel_pstate: Unchecked MSR aceess in legacy mode") introduced a check for feature X86_FEATURE_IDA to verify turbo mode support. Although this is the correct way to check for turbo mode support, it causes issues on some platforms that disable turbo during OS boot, but enable it later [1]. Before adding this feature check, users were able to get turbo mode frequencies by writing 0 to /sys/devices/system/cpu/intel_pstate/no_turbo post-boot. To restore the old behavior on the affected systems while still addressing the unchecked MSR issue on some Skylake-X systems, check X86_FEATURE_IDA only immediately before updates of MSR_IA32_PERF_CTL that may involve setting the Turbo Engage Bit (bit 32). Fixes: ac4e04d9e378 ("cpufreq: intel_pstate: Unchecked MSR aceess in legacy mode") Reported-by: Aaron Rainbolt Closes: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2122531 [1] Tested-by: Aaron Rainbolt Signed-off-by: Srinivas Pandruvada [ rjw: Subject adjustment, changelog edits ] Link: https://patch.msgid.link/20251111010840.141490-1-srinivas.pandruvada@linux.intel.com Signed-off-by: Rafael J. Wysocki

Merge back earlier cpufreq material for 6.18

2025-09-24T19:32:28Z

cpufreq: intel_pstate: Use likely() optimization in intel_pstate_sample()

2025-09-19T21:21:01Z

The comment above the condition `if (cpu->last_sample_time)` clearly indicates that the branch is taken for the vast majority of invocations after the first sample in a cycle. The first sample is a one-time initialization case. Add likely() hint to the condition to improve branch prediction for this performance-critical path in intel_pstate_sample(). Signed-off-by: Yaxiong Tian Signed-off-by: Rafael J. Wysocki

cpufreq: intel_pstate: Enable HWP without EPP if DEC is enabled

2025-09-19T21:05:54Z

So far, HWP has never been enabled without EPP (Energy-Performance Preference) interface support, since the lack of the latter indicates an incomplete implementation of HWP, which was the case on early development vehicle platforms. However, HWP can be expected to work if DEC (Dynamic Efficiency Control) is enabled as indicated by setting bit 27 in MSR_IA32_POWER_CTL (DEC enable bit). Accordingly, allow HWP to be enabled if the EPP interface is not supported so long as DEC is enabled in the processor. Still, the EPP control sysfs interface is useless when EPP is not supported, so do not expose it in that case. Link: https://lore.kernel.org/linux-pm/20250904000608.260817-2-srinivas.pandruvada@linux.intel.com/ Signed-off-by: Srinivas Pandruvada Co-developed-by: Srinivas Pandruvada Signed-off-by: Rafael J. Wysocki

PM: EM: Add function for registering a PD without capacity update

2025-09-10T10:03:19Z

The intel_pstate driver manages CPU capacity changes itself and it does not need an update of the capacity of all CPUs in the system to be carried out after registering a PD. Moreover, in some configurations (for instance, an SMT-capable hybrid x86 system booted with nosmt in the kernel command line) the em_check_capacity_update() call at the end of em_dev_register_perf_domain() always fails and reschedules itself to run once again in 1 s, so effectively it runs in vain every 1 s forever. To address this, introduce a new variant of em_dev_register_perf_domain(), called em_dev_register_pd_no_update(), that does not invoke em_check_capacity_update(), and make intel_pstate use it instead of the original. Fixes: 7b010f9b9061 ("cpufreq: intel_pstate: EAS support for hybrid platforms") Closes: https://lore.kernel.org/linux-pm/40212796-734c-4140-8a85-854f72b8144d@panix.com/ Reported-by: Kenneth R. Crudup Tested-by: Kenneth R. Crudup Cc: 6.16+ # 6.16+ Signed-off-by: Rafael J. Wysocki

cpufreq: intel_pstate: Adjust frequency percentage computations

2025-09-09T10:58:55Z

Adjust frequency percentage computations in update_cpu_qos_request() to avoid going above the exact numerical percentage in the FREQ_QOS_MAX case. Signed-off-by: Rafael J. Wysocki Acked-by: Zihuan Zhang Link: https://patch.msgid.link/3395556.44csPzL39Z@rafael.j.wysocki [ rjw: Rename "cpu" to "cpudata" and "cpunum" to "cpu" ] Signed-off-by: Rafael J. Wysocki

cpufreq: intel_pstate: Rearrange freq QoS updates using __free()

2025-09-09T10:58:54Z

Move the code from the for_each_possible_cpu() loop in update_qos_request() to a separate function and use __free() for cpufreq policy reference counting in it to avoid having to call cpufreq_cpu_put() repeatedly (or using goto). While at it, rename update_qos_request() to update_qos_requests() because it updates multiple requests in one go. No intentional functional impact. Link: https://lore.kernel.org/linux-pm/CAJZ5v0gN1T5woSF0tO=TbAh+2-sWzxFjWyDbB7wG2TFCOU01iQ@mail.gmail.com/ Signed-off-by: Rafael J. Wysocki Reviewed-by: Zihuan Zhang Link: https://patch.msgid.link/3026597.e9J7NaK4W3@rafael.j.wysocki [ rjw: Rename "cpu" to "cpudata" and "cpunum" to "cpu" in new code ] Signed-off-by: Rafael J. Wysocki