KVM: x86/pmu: Constrain the num of guest counters with kvm_pmu_cap

Cap the number of general purpose counters enumerated on AMD to what KVM
actually supports, i.e. don't allow userspace to coerce KVM into thinking
there are more counters than actually exist, e.g. by enumerating
X86_FEATURE_PERFCTR_CORE in guest CPUID when its not supported.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Like Xu <likexu@tencent.com>
[sean: massage changelog]
Link: https://lore.kernel.org/r/20230603011058.1038821-10-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index e5c69062a909d3d0618f2679237b3bda3aece1ac..c03958063a76c7c1f89dc813ca59bca6eb1c8b85 100644 (file)
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -170,6 +170,9 @@ static void amd_pmu_refresh(struct kvm_vcpu *vcpu)
        else
                pmu->nr_arch_gp_counters = AMD64_NUM_COUNTERS;
 
+       pmu->nr_arch_gp_counters = min_t(unsigned int, pmu->nr_arch_gp_counters,
+                                        kvm_pmu_cap.num_counters_gp);
+
        pmu->counter_bitmask[KVM_PMC_GP] = ((u64)1 << 48) - 1;
        pmu->reserved_bits = 0xfffffff000280000ull;
        pmu->raw_event_mask = AMD64_RAW_EVENT_MASK;