linux-kernel - [PATCH 2/6] KVM: x86/pmu: Reset the PMU, i.e. stop counters, before refreshing

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Message-ID: <20231023234000.2499267-3-seanjc@google.com>
Date:   Mon, 23 Oct 2023 16:39:56 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mingwei Zhang <mizhang@...gle.com>,
        Roman Kagan <rkagan@...zon.de>,
        Jim Mattson <jmattson@...gle.com>,
        Dapeng Mi <dapeng1.mi@...ux.intel.com>,
        Like Xu <like.xu.linux@...il.com>
Subject: [PATCH 2/6] KVM: x86/pmu: Reset the PMU, i.e. stop counters, before refreshing

Stop all counters and release all perf events before refreshing the vPMU,
i.e. before reconfiguring the vPMU to respond to changes in the vCPU
model.

Clear need_cleanup in kvm_pmu_reset() as well so that KVM doesn't
prematurely stop counters, e.g. if KVM enters the guest and enables
counters before the vCPU is scheduled out.

Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/pmu.c | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 027e9c3c2b93..dc8e8e907cfb 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -657,25 +657,14 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	return 0;
 }
 
-/* refresh PMU settings. This function generally is called when underlying
- * settings are changed (such as changes of PMU CPUID by guest VMs), which
- * should rarely happen.
- */
-void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
-{
-	if (KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm))
-		return;
-
-	bitmap_zero(vcpu_to_pmu(vcpu)->all_valid_pmc_idx, X86_PMC_IDX_MAX);
-	static_call(kvm_x86_pmu_refresh)(vcpu);
-}
-
 void kvm_pmu_reset(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	struct kvm_pmc *pmc;
 	int i;
 
+	pmu->need_cleanup = false;
+
 	bitmap_zero(pmu->reprogram_pmi, X86_PMC_IDX_MAX);
 
 	for_each_set_bit(i, pmu->all_valid_pmc_idx, X86_PMC_IDX_MAX) {
@@ -695,6 +684,26 @@ void kvm_pmu_reset(struct kvm_vcpu *vcpu)
 	static_call_cond(kvm_x86_pmu_reset)(vcpu);
 }
 
+
+/*
+ * Refresh the PMU configuration for the vCPU, e.g. if userspace changes CPUID
+ * and/or PERF_CAPABILITIES.
+ */
+void kvm_pmu_refresh(struct kvm_vcpu *vcpu)
+{
+	if (KVM_BUG_ON(kvm_vcpu_has_run(vcpu), vcpu->kvm))
+		return;
+
+	/*
+	 * Stop/release all existing counters/events before realizing the new
+	 * vPMU model.
+	 */
+	kvm_pmu_reset(vcpu);
+
+	bitmap_zero(vcpu_to_pmu(vcpu)->all_valid_pmc_idx, X86_PMC_IDX_MAX);
+	static_call(kvm_x86_pmu_refresh)(vcpu);
+}
+
 void kvm_pmu_init(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
-- 
2.42.0.758.gaed0368e0e-goog