Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Like Xu <> | Subject | [PATCH v6 06/10] KVM: x86/pmu: Forget PERFCTR_CORE if the min num of counters isn't met | Date | Tue, 30 May 2023 14:04:19 +0800 |
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From: Like Xu <likexu@tencent.com>
A sanity check on the number of counters enumerated by perf is added. PERFCTR_CORE support is explicitly dropped if the min number isn't met. E.g. if KVM needs 6 counters and perf says there are 4, then something is wrong and enumerating 6 to a guest is only going to cause more issues.
Opportunistically, the kvm_cpu_cap_check_and_set() is applied to simplify the host check before setting the PERFCTR_CORE flag.
Suggested-by: Sean Christopherson <seanjc@google.com> Signed-off-by: Like Xu <likexu@tencent.com> --- arch/x86/kvm/svm/svm.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index ca32389f3c36..d9669e3cc00a 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -5025,9 +5025,18 @@ static __init void svm_set_cpu_caps(void) boot_cpu_has(X86_FEATURE_AMD_SSBD)) kvm_cpu_cap_set(X86_FEATURE_VIRT_SSBD); - /* AMD PMU PERFCTR_CORE CPUID */ - if (enable_pmu && boot_cpu_has(X86_FEATURE_PERFCTR_CORE)) - kvm_cpu_cap_set(X86_FEATURE_PERFCTR_CORE); + if (enable_pmu) { + /* + * Enumerate support for PERFCTR_CORE if and only if KVM has + * access to enough counters to virtualize "core" support, + * otherwise limit vPMU support to the legacy number of counters. + */ + if (kvm_pmu_cap.num_counters_gp < AMD64_NUM_COUNTERS_CORE) + kvm_pmu_cap.num_counters_gp = min(AMD64_NUM_COUNTERS, + kvm_pmu_cap.num_counters_gp); + else + kvm_cpu_cap_check_and_set(X86_FEATURE_PERFCTR_CORE); + } /* CPUID 0x8000001F (SME/SEV features) */ sev_set_cpu_caps(); -- 2.40.1
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