[PATCH v12 11/11] KVM: vmx/pmu: Release guest LBR event via lazy release mechanism

[Like Xu]

The vPMU uses GUEST_LBR_IN_USE_IDX (bit 58) in 'pmu->pmc_in_use' to
indicate whether a guest LBR event is still needed by the vcpu. If the
vcpu no longer accesses LBR related registers within a scheduling time
slice, and the enable bit of LBR has been unset, vPMU will treat the
guest LBR event as a bland event of a vPMC counter and release it
as usual. Also the pass-through state of LBR records msrs is cancelled.

Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/pmu.c           |  7 +++++++
 arch/x86/kvm/pmu.h           |  4 ++++
 arch/x86/kvm/vmx/pmu_intel.c | 14 +++++++++++++-
 arch/x86/kvm/vmx/vmx.c       |  4 ++++
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 5053f4238218..e5b76f1c3ce8 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -458,6 +458,7 @@ void kvm_pmu_cleanup(struct kvm_vcpu *vcpu)
 	struct kvm_pmc *pmc = NULL;
 	DECLARE_BITMAP(bitmask, X86_PMC_IDX_MAX);
 	int i;
+	bool arch_cleanup = false;
 
 	pmu->need_cleanup = false;
 
@@ -469,8 +470,14 @@ void kvm_pmu_cleanup(struct kvm_vcpu *vcpu)
 
 		if (pmc && pmc->perf_event && !pmc_speculative_in_use(pmc))
 			pmc_stop_counter(pmc);
+
+		if (i == INTEL_GUEST_LBR_INUSE)
+			arch_cleanup = true;
 	}
 
+	if (arch_cleanup && kvm_x86_ops.pmu_ops->cleanup)
+		kvm_x86_ops.pmu_ops->cleanup(vcpu);
+
 	bitmap_zero(pmu->pmc_in_use, X86_PMC_IDX_MAX);
 }
 
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 095b84392b89..d5023eacd8ed 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -15,6 +15,9 @@
 #define VMWARE_BACKDOOR_PMC_REAL_TIME		0x10001
 #define VMWARE_BACKDOOR_PMC_APPARENT_TIME	0x10002
 
+/* Indicates whether Intel LBR msrs were accessed during the last time slice. */
+#define INTEL_GUEST_LBR_INUSE INTEL_PMC_IDX_FIXED_VLBR
+
 struct kvm_event_hw_type_mapping {
 	u8 eventsel;
 	u8 unit_mask;
@@ -38,6 +41,7 @@ struct kvm_pmu_ops {
 	void (*init)(struct kvm_vcpu *vcpu);
 	void (*reset)(struct kvm_vcpu *vcpu);
 	void (*deliver_pmi)(struct kvm_vcpu *vcpu);
+	void (*cleanup)(struct kvm_vcpu *vcpu);
 };
 
 static inline u64 pmc_bitmask(struct kvm_pmc *pmc)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 75ba0444b4d1..c1c5058acc90 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -303,6 +303,7 @@ static void intel_pmu_free_lbr_event(struct kvm_vcpu *vcpu)
 static bool access_lbr_record_msr(struct kvm_vcpu *vcpu,
 				     struct msr_data *msr_info, bool read)
 {
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	struct lbr_desc *lbr_desc = &to_vmx(vcpu)->lbr_desc;
 	u32 index = msr_info->index;
 
@@ -331,6 +332,7 @@ static bool access_lbr_record_msr(struct kvm_vcpu *vcpu,
 		msr_info->data = 0;
 	local_irq_enable();
 
+	__set_bit(INTEL_GUEST_LBR_INUSE, pmu->pmc_in_use);
 	return true;
 
 dummy:
@@ -483,6 +485,7 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vmcs_write64(GUEST_IA32_DEBUGCTL, data);
 		if (!msr_info->host_initiated && !to_vmx(vcpu)->lbr_desc.event)
 			intel_pmu_create_lbr_event(vcpu);
+		__set_bit(INTEL_GUEST_LBR_INUSE, pmu->pmc_in_use);
 		return 0;
 	default:
 		if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
@@ -584,7 +587,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		INTEL_PMC_MAX_GENERIC, pmu->nr_arch_fixed_counters);
 
 	if ((vcpu->arch.perf_capabilities & PMU_CAP_LBR_FMT) &&
-	    x86_perf_get_lbr(&lbr_desc->lbr))
+	    !x86_perf_get_lbr(&lbr_desc->lbr))
+		bitmap_set(pmu->all_valid_pmc_idx, INTEL_GUEST_LBR_INUSE, 1);
+	else
 		vcpu->arch.perf_capabilities &= ~PMU_CAP_LBR_FMT;
 
 	nested_vmx_pmu_entry_exit_ctls_update(vcpu);
@@ -672,6 +677,12 @@ static void intel_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
 		intel_pmu_legacy_freezing_lbrs_on_pmi(vcpu);
 }
 
+static void intel_pmu_cleanup(struct kvm_vcpu *vcpu)
+{
+	if (!(vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR))
+		intel_pmu_free_lbr_event(vcpu);
+}
+
 struct kvm_pmu_ops intel_pmu_ops = {
 	.find_arch_event = intel_find_arch_event,
 	.find_fixed_event = intel_find_fixed_event,
@@ -687,4 +698,5 @@ struct kvm_pmu_ops intel_pmu_ops = {
 	.init = intel_pmu_init,
 	.reset = intel_pmu_reset,
 	.deliver_pmi = intel_pmu_deliver_pmi,
+	.cleanup = intel_pmu_cleanup,
 };
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 800a26e3b571..8521fc640b95 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -3912,17 +3912,21 @@ static inline void vmx_lbr_enable_passthrough(struct kvm_vcpu *vcpu)
  */
 static void vmx_passthrough_lbr_msrs(struct kvm_vcpu *vcpu)
 {
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
 	struct lbr_desc *lbr_desc = &to_vmx(vcpu)->lbr_desc;
 
 	if (!lbr_desc->event) {
 		vmx_lbr_disable_passthrough(vcpu);
 		if (vmcs_read64(GUEST_IA32_DEBUGCTL) & DEBUGCTLMSR_LBR)
 			goto warn;
+		if (test_bit(INTEL_GUEST_LBR_INUSE, pmu->pmc_in_use))
+			goto warn;
 		return;
 	}
 
 	if (lbr_desc->event->state < PERF_EVENT_STATE_ACTIVE) {
 		vmx_lbr_disable_passthrough(vcpu);
+		__clear_bit(INTEL_GUEST_LBR_INUSE, pmu->pmc_in_use);
 		goto warn;
 	} else
 		vmx_lbr_enable_passthrough(vcpu);
-- 
2.21.3