[PATCH v5 15/44] KVM: SVM: Check pmu->version, not enable_pmu, when getting PMC MSRs

Sean Christopherson
2025-08-06T19:57:56Z

Gate access to PMC MSRs based on pmu->version, not on kvm->arch.enable_pmu,
to more accurately reflect KVM's behavior. This is a glorified nop, as
pmu->version and pmu->nr_arch_gp_counters can only be non-zero if
amd_pmu_refresh() is reached, kvm_pmu_refresh() invokes amd_pmu_refresh()
if and only if kvm->arch.enable_pmu is true, and amd_pmu_refresh() forces
pmu->version to be 1 or 2.

I.e. the following holds true:

!pmu->nr_arch_gp_counters || kvm->arch.enable_pmu == (pmu->version > 0)

and so the only way for amd_pmu_get_pmc() to return a non-NULL value is if
both kvm->arch.enable_pmu and pmu->version evaluate to true.

No real functional change intended.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/svm/pmu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 288f7f2a46f2..7b8577f3c57a 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -41,7 +41,7 @@ static inline struct kvm_pmc *get_gp_pmc_amd(struct kvm_pmu *pmu, u32 msr,
struct kvm_vcpu *vcpu = pmu_to_vcpu(pmu);
unsigned int idx;

- if (!vcpu->kvm->arch.enable_pmu)
+ if (!pmu->version)
return NULL;

switch (msr) {
--
2.50.1.565.gc32cd1483b-goog