On 1/10/2024 7:02 AM, Sean Christopherson wrote:
Explicitly check for attempts to read unsupported PMC types instead of
letting the bounds check fail. Functionally, letting the check fail is
ok, but it's unnecessarily subtle and does a poor job of documenting the
architectural behavior that KVM is emulating.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/kvm/vmx/pmu_intel.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index c37dd3aa056b..b41bdb0a0995 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -26,6 +26,7 @@
* further confuse things, non-architectural PMUs use bit 31 as a flag for
* "fast" reads, whereas the "type" is an explicit value.
*/
+#define INTEL_RDPMC_GP 0
#define INTEL_RDPMC_FIXED INTEL_PMC_FIXED_RDPMC_BASE
#define INTEL_RDPMC_TYPE_MASK GENMASK(31, 16)
@@ -89,21 +90,29 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
return NULL;
/*
- * Fixed PMCs are supported on all architectural PMUs. Note, KVM only
- * emulates fixed PMCs for PMU v2+, but the flag itself is still valid,
- * i.e. let RDPMC fail due to accessing a non-existent counter.
+ * General Purpose (GP) PMCs are supported on all PMUs, and fixed PMCs
+ * are supported on all architectural PMUs, i.e. on all virtual PMUs
+ * supported by KVM. Note, KVM only emulates fixed PMCs for PMU v2+,
+ * but the type itself is still valid, i.e. let RDPMC fail due to
+ * accessing a non-existent counter. Reject attempts to read all other
+ * types, which are unknown/unsupported.
*/
- idx &= ~INTEL_RDPMC_FIXED;
- if (type == INTEL_RDPMC_FIXED) {
+ switch (type) {
+ case INTEL_RDPMC_FIXED:
counters = pmu->fixed_counters;
num_counters = pmu->nr_arch_fixed_counters;
bitmask = pmu->counter_bitmask[KVM_PMC_FIXED];
- } else {
+ break;
+ case INTEL_RDPMC_GP:
counters = pmu->gp_counters;
num_counters = pmu->nr_arch_gp_counters;
bitmask = pmu->counter_bitmask[KVM_PMC_GP];
+ break;
+ default:
+ return NULL;
}
+ idx &= INTEL_RDPMC_INDEX_MASK;
if (idx >= num_counters)
return NULL;
Reviewed-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
