linux-kernel - [PATCH 5.19 1105/1157] KVM: x86/pmu: Accept 0 for absent PMU MSRs when host-initiated if !enable

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Message-Id: <20220815180524.471198308@linuxfoundation.org>
Date:   Mon, 15 Aug 2022 20:07:41 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Like Xu <likexu@...cent.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.19 1105/1157] KVM: x86/pmu: Accept 0 for absent PMU MSRs when host-initiated if !enable_pmu

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

[ Upstream commit 8e6a58e28b34e8d247e772159b8fa8f6bae39192 ]

Whenever an MSR is part of KVM_GET_MSR_INDEX_LIST, as is the case for
MSR_K7_EVNTSEL0 or MSR_F15H_PERF_CTL0, it has to be always retrievable
and settable with KVM_GET_MSR and KVM_SET_MSR.

Accept a zero value for these MSRs to obey the contract.

Signed-off-by: Like Xu <likexu@...cent.com>
Message-Id: <20220601031925.59693-1-likexu@...cent.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/pmu.c     |  8 ++++++++
 arch/x86/kvm/svm/pmu.c | 11 ++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 3f868fed9114..2334ddfbbab2 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -433,11 +433,19 @@ static void kvm_pmu_mark_pmc_in_use(struct kvm_vcpu *vcpu, u32 msr)
 
 int kvm_pmu_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
+	if (msr_info->host_initiated && !vcpu->kvm->arch.enable_pmu) {
+		msr_info->data = 0;
+		return 0;
+	}
+
 	return static_call(kvm_x86_pmu_get_msr)(vcpu, msr_info);
 }
 
 int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 {
+	if (msr_info->host_initiated && !vcpu->kvm->arch.enable_pmu)
+		return !!msr_info->data;
+
 	kvm_pmu_mark_pmc_in_use(vcpu, msr_info->index);
 	return static_call(kvm_x86_pmu_set_msr)(vcpu, msr_info);
 }
diff --git a/arch/x86/kvm/svm/pmu.c b/arch/x86/kvm/svm/pmu.c
index 136039fc6d01..d93ecb25fe17 100644
--- a/arch/x86/kvm/svm/pmu.c
+++ b/arch/x86/kvm/svm/pmu.c
@@ -232,7 +232,16 @@ static struct kvm_pmc *amd_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
 static bool amd_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
 {
 	/* All MSRs refer to exactly one PMC, so msr_idx_to_pmc is enough.  */
-	return false;
+	if (!host_initiated)
+		return false;
+
+	switch (msr) {
+	case MSR_K7_EVNTSEL0 ... MSR_K7_PERFCTR3:
+	case MSR_F15H_PERF_CTL0 ... MSR_F15H_PERF_CTR5:
+		return true;
+	default:
+		return false;
+	}
 }
 
 static struct kvm_pmc *amd_msr_idx_to_pmc(struct kvm_vcpu *vcpu, u32 msr)
-- 
2.35.1