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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 commit973207ae3d("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:973207ae3d("cpufreq: intel_pstate: Rearrange max frequency updates handling code") Closes: https://bugzilla.kernel.org/show_bug.cgi?id=221068 Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Cc: 6.16+ <stable@vger.kernel.org> # 6.16+ Link: https://patch.msgid.link/20260225001752.890164-1-srinivas.pandruvada@linux.intel.com Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>