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

Like Xu
2020-03-13T02:19:27Z

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@linux.intel.com>
---
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