From a634c76b2c1a642d11f5d6e1810181daedcbe0ab Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 9 Jan 2024 15:02:31 -0800 Subject: [PATCH] KVM: x86/pmu: Explicitly check for RDPMC of unsupported Intel PMC types MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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. Reviewed-by: Dapeng Mi  Tested-by: Dapeng Mi Link: https://lore.kernel.org/r/20240109230250.424295-12-seanjc@google.com Signed-off-by: Sean Christopherson --- 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 c37dd3aa056b7..b41bdb0a09950 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; -- 2.30.2