From: Sandipan Das Date: Mon, 1 Jun 2026 14:58:46 +0000 (+0530) Subject: perf/x86/amd/core: Always use the NMI latency mitigation X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=73a4c02f94a98d94480c3e5c81450215a4da05ba;p=thirdparty%2Flinux.git perf/x86/amd/core: Always use the NMI latency mitigation Commit df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation to use a timestamp") fixed handling of late-arriving NMIs but limited the mitigation to processors having X86_FEATURE_PERFCTR_CORE. However, it is unclear if processors without this feature are also affected. When Mediated vPMU is enabled on affected hardware, it is also possible to bypass the fix inside KVM guests if X86_FEATURE_PERFCTR_CORE is removed from the guest CPUID (e.g. using "-cpu host,-perfctr-core" with QEMU). Hence, use the mitigation at all times. Fixes: df4d29732fda ("perf/x86/amd: Change/fix NMI latency mitigation to use a timestamp") Signed-off-by: Sandipan Das Signed-off-by: Peter Zijlstra (Intel) Link: https://patch.msgid.link/29a3c970da289ab8f24282933bdb36545c0403e8.1780325517.git.sandipan.das@amd.com --- diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c index 0c92ed5f464b1..abc84a92cd590 100644 --- a/arch/x86/events/amd/core.c +++ b/arch/x86/events/amd/core.c @@ -1412,12 +1412,12 @@ static int __init amd_core_pmu_init(void) u64 even_ctr_mask = 0ULL; int i; - if (!boot_cpu_has(X86_FEATURE_PERFCTR_CORE)) - return 0; - /* Avoid calculating the value each time in the NMI handler */ perf_nmi_window = msecs_to_jiffies(100); + if (!boot_cpu_has(X86_FEATURE_PERFCTR_CORE)) + return 0; + /* * If core performance counter extensions exists, we must use * MSR_F15H_PERF_CTL/MSR_F15H_PERF_CTR msrs. See also