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

[Sean Christopherson]

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@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 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