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

Like Xu
2023-02-14T05:09:18Z

From: Like Xu <likexu@tencent.com>

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@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
---
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