From 6b050482ec40569429d963ac52afa878691b04c9 Mon Sep 17 00:00:00 2001 From: Srinivas Pandruvada Date: Tue, 24 Feb 2026 16:17:52 -0800 Subject: [PATCH] cpufreq: intel_pstate: Fix crash during turbo disable 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 --- drivers/cpufreq/intel_pstate.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index bdc37080d319..11c58af41900 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -1476,13 +1476,13 @@ static void __intel_pstate_update_max_freq(struct cpufreq_policy *policy, refresh_frequency_limits(policy); } -static bool intel_pstate_update_max_freq(struct cpudata *cpudata) +static bool intel_pstate_update_max_freq(int cpu) { - struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpudata->cpu); + struct cpufreq_policy *policy __free(put_cpufreq_policy) = cpufreq_cpu_get(cpu); if (!policy) return false; - __intel_pstate_update_max_freq(policy, cpudata); + __intel_pstate_update_max_freq(policy, all_cpu_data[cpu]); return true; } @@ -1501,7 +1501,7 @@ static void intel_pstate_update_limits_for_all(void) int cpu; for_each_possible_cpu(cpu) - intel_pstate_update_max_freq(all_cpu_data[cpu]); + intel_pstate_update_max_freq(cpu); mutex_lock(&hybrid_capacity_lock); @@ -1910,7 +1910,7 @@ static void intel_pstate_notify_work(struct work_struct *work) struct cpudata *cpudata = container_of(to_delayed_work(work), struct cpudata, hwp_notify_work); - if (intel_pstate_update_max_freq(cpudata)) { + if (intel_pstate_update_max_freq(cpudata->cpu)) { /* * The driver will not be unregistered while this function is * running, so update the capacity without acquiring the driver