linux-kernel - [PATCH V5 07/10] KVM: x86/pmu: Constrain the num of guest counters with kvm_pmu

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Date:   Mon, 10 Apr 2023 18:50:53 +0800
From:   Like Xu <like.xu.linux@...il.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH V5 07/10] KVM: x86/pmu: Constrain the num of guest counters with kvm_pmu_cap

From: Like Xu <likexu@...cent.com>

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@...gle.com>
Signed-off-by: Like Xu <likexu@...cent.com>
---
 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 70143275e0a7..825b9cc26ae5 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;
-- 
2.40.0