[PATCH v6 07/10] KVM: x86/pmu: Constrain the num of guest counters with kvm_pmu_cap

[Like Xu]

From: Like Xu <likexu@xxxxxxxxxxx>

A sanity check is added to limit the number of AMD guest counters,
which help avoid a situation if KVM only has access to 4 counters, but
user space sets guest X86_FEATURE_PERFCTR_CORE anyways.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
---
 arch/x86/kvm/svm/pmu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index e5c69062a909..c03958063a76 100644
--- 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;
-- 
2.40.1