From: Like Xu <likexu@xxxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
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 7584eb85410b..683f1b480fcb 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4928,9 +4928,18 @@ 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();
--
2.40.0
