[PATCH v4 09/12] KVM: x86/pmu: Forget PERFCTR_CORE if the min num of counters isn't met

[Like Xu]

From: Like Xu <likexu@xxxxxxxxxxx>

KVM should sanity check the number of counters enumerated by perf and
explicitly drop PERFCTR_CORE support if the min isn't met. E.g. if KVM
needs 6 counters and perf says there are 4, then something is wrong and
enumerating 6 to the guest is only going to cause more issues.

Opportunistically, the existing kvm_cpu_cap_check_and_set() makes it
easier 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 | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index dd21e8b1a259..f4a4691b4f4e 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4910,9 +4910,14 @@ 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) {
+		if (kvm_pmu_cap.num_counters_gp < AMD64_NUM_COUNTERS_CORE) {
+			kvm_pmu_cap.num_counters_gp = AMD64_NUM_COUNTERS;
+		} else {
+			/* AMD PMU PERFCTR_CORE CPUID */
+			kvm_cpu_cap_check_and_set(X86_FEATURE_PERFCTR_CORE);
+		}
+	}
 
 	/* CPUID 0x8000001F (SME/SEV features) */
 	sev_set_cpu_caps();
-- 
2.39.1