From: Sean Christopherson Date: Wed, 8 Feb 2023 20:42:30 +0000 (+0000) Subject: perf/x86: Refuse to export capabilities for hybrid PMUs X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=4b4191b8ae1278bde3642acaaef8f92810ed111a;p=linux.git perf/x86: Refuse to export capabilities for hybrid PMUs Now that KVM disables vPMU support on hybrid CPUs, WARN and return zeros if perf_get_x86_pmu_capability() is invoked on a hybrid CPU. The helper doesn't provide an accurate accounting of the PMU capabilities for hybrid CPUs and needs to be enhanced if KVM, or anything else outside of perf, wants to act on the PMU capabilities. Cc: stable@vger.kernel.org Cc: Andrew Cooper Cc: Peter Zijlstra Cc: Kan Liang Cc: Andi Kleen Link: https://lore.kernel.org/all/20220818181530.2355034-1-kan.liang@linux.intel.com Signed-off-by: Sean Christopherson Message-Id: <20230208204230.1360502-3-seanjc@google.com> Signed-off-by: Paolo Bonzini --- diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c index 85a63a41c4718..d096b04bf80e8 100644 --- a/arch/x86/events/core.c +++ b/arch/x86/events/core.c @@ -2974,17 +2974,19 @@ unsigned long perf_misc_flags(struct pt_regs *regs) void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap) { - if (!x86_pmu_initialized()) { + /* This API doesn't currently support enumerating hybrid PMUs. */ + if (WARN_ON_ONCE(cpu_feature_enabled(X86_FEATURE_HYBRID_CPU)) || + !x86_pmu_initialized()) { memset(cap, 0, sizeof(*cap)); return; } - cap->version = x86_pmu.version; /* - * KVM doesn't support the hybrid PMU yet. - * Return the common value in global x86_pmu, - * which available for all cores. + * Note, hybrid CPU models get tracked as having hybrid PMUs even when + * all E-cores are disabled via BIOS. When E-cores are disabled, the + * base PMU holds the correct number of counters for P-cores. */ + cap->version = x86_pmu.version; cap->num_counters_gp = x86_pmu.num_counters; cap->num_counters_fixed = x86_pmu.num_counters_fixed; cap->bit_width_gp = x86_pmu.cntval_bits;