[PATCH v9 08/10] KVM: x86/pmu: Release guest LBR event via vPMU lazy release mechanism

[Like Xu]

The guest LBR event uses bit 58 in pmu->pmc_in_use (which is also the
LBRS_FROZEN bit in GLOBAL_STATUS) to indicate whether the event is still
needed by the vcpu. If the guest no longer accesses the LBR related MSRs
within a scheduling time slice and the enable bit of LBR is unset, vPMU
would treat the guest LBR event as a bland event of a vPMC counter and
release it as usual and the pass-through state of stack MSRs is canceled.

Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
---
 arch/x86/kvm/pmu.c           |  9 +++++++++
 arch/x86/kvm/pmu.h           |  4 ++++
 arch/x86/kvm/vmx/pmu_intel.c | 16 ++++++++++++++++
 3 files changed, 29 insertions(+)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 84b5ec50ca6d..57859ff8b118 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -449,6 +449,12 @@ static inline bool pmc_speculative_in_use(struct kvm_pmc *pmc)
 	return pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE;
 }
 
+void kvm_pmu_lbr_cleanup(struct kvm_vcpu *vcpu)
+{
+	if (kvm_x86_ops->pmu_ops->lbr_cleanup)
+		kvm_x86_ops->pmu_ops->lbr_cleanup(vcpu);
+}
+
 /* Release perf_events for vPMCs that have been unused for a full time slice.  */
 void kvm_pmu_cleanup(struct kvm_vcpu *vcpu)
 {
@@ -467,6 +473,9 @@ void kvm_pmu_cleanup(struct kvm_vcpu *vcpu)
 
 		if (pmc && pmc->perf_event && !pmc_speculative_in_use(pmc))
 			pmc_stop_counter(pmc);
+
+		if (i == KVM_PMU_LBR_IN_USE_IDX)
+			kvm_pmu_lbr_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 3ddff3972b8d..d4ef7ec3331d 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
 
+/* Indicate if the LBR MSRs were accessed during a time slice */
+#define KVM_PMU_LBR_IN_USE_IDX GLOBAL_STATUS_LBRS_FROZEN_BIT
+
 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);
 	bool (*lbr_setup)(struct kvm_vcpu *vcpu);
+	void (*lbr_cleanup)(struct kvm_vcpu *vcpu);
 	void (*availability_check)(struct kvm_vcpu *vcpu);
 };
 
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 92627f31cda3..bbb5f4c63f52 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -316,6 +316,7 @@ static bool intel_pmu_access_lbr_msr(struct kvm_vcpu *vcpu,
 		msr_info->data = 0;
 	local_irq_enable();
 
+	__set_bit(KVM_PMU_LBR_IN_USE_IDX, pmu->pmc_in_use);
 	return true;
 }
 
@@ -415,6 +416,8 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 			wrmsrl_safe(MSR_CORE_PERF_GLOBAL_OVF_CTRL,
 					GLOBAL_STATUS_LBRS_FROZEN);
 		}
+		if (pmu->lbr_event)
+			__set_bit(KVM_PMU_LBR_IN_USE_IDX, pmu->pmc_in_use);
 		return 0;
 	default:
 		if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0))) {
@@ -508,6 +511,7 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu)
 		0, pmu->nr_arch_gp_counters);
 	bitmap_set(pmu->all_valid_pmc_idx,
 		INTEL_PMC_MAX_GENERIC, pmu->nr_arch_fixed_counters);
+	bitmap_set(pmu->all_valid_pmc_idx, KVM_PMU_LBR_IN_USE_IDX, 1);
 
 	nested_vmx_pmu_entry_exit_ctls_update(vcpu);
 }
@@ -620,6 +624,17 @@ void intel_pmu_availability_check(struct kvm_vcpu *vcpu)
 		intel_pmu_lbr_availability_check(vcpu);
 }
 
+static void intel_pmu_cleanup_lbr(struct kvm_vcpu *vcpu)
+{
+	struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
+
+	if (!pmu->lbr_event)
+		return;
+
+	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,
@@ -636,4 +651,5 @@ struct kvm_pmu_ops intel_pmu_ops = {
 	.reset = intel_pmu_reset,
 	.lbr_setup = intel_pmu_setup_lbr,
 	.availability_check = intel_pmu_availability_check,
+	.lbr_cleanup = intel_pmu_cleanup_lbr,
 };
-- 
2.21.1