[PATCH v11 09/11] KVM: x86/pmu: Release guest LBR event via vPMU lazy release mechanism

Like Xu
2020-05-14T08:31:53Z

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
passthrough state of LBR records msrs is cancelled.

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 | 11 +++++++++++
3 files changed, 24 insertions(+)

diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index 5053f4238218..d0dece055605 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -451,6 +451,12 @@ static inline bool pmc_speculative_in_use(struct kvm_pmc *pmc)
return pmc->eventsel & ARCH_PERFMON_EVENTSEL_ENABLE;
}

+static inline 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)
{
@@ -469,6 +475,9 @@ void kvm_pmu_cleanup(struct kvm_vcpu *vcpu)

if (pmc && pmc->perf_event && !pmc_speculative_in_use(pmc))
pmc_stop_counter(pmc);
+
+ if (i == GUEST_LBR_IN_USE_IDX && pmu->lbr_event)
+ 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 ed96cbb40757..78f0cfe1622f 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 LBR msrs were accessed during the last time slice. */
+#define GUEST_LBR_IN_USE_IDX 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 (*lbr_cleanup)(struct kvm_vcpu *vcpu);
};

static inline bool event_is_oncpu(struct perf_event *event)
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 8f9c837c7dca..ea4faae56473 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -353,6 +353,7 @@ static bool intel_pmu_access_lbr_msr(struct kvm_vcpu *vcpu,
msr_info->data = 0;
local_irq_enable();

+ __set_bit(GUEST_LBR_IN_USE_IDX, pmu->pmc_in_use);
return true;
}

@@ -460,6 +461,7 @@ 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 && !pmu->lbr_event)
intel_pmu_create_lbr_event(vcpu);
+ __set_bit(GUEST_LBR_IN_USE_IDX, pmu->pmc_in_use);
return 0;
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0))) {
@@ -555,6 +557,8 @@ 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);
+ if (lbr_is_enabled(vcpu))
+ bitmap_set(pmu->all_valid_pmc_idx, GUEST_LBR_IN_USE_IDX, 1);

nested_vmx_pmu_entry_exit_ctls_update(vcpu);
}
@@ -636,6 +640,12 @@ static void intel_pmu_deliver_pmi(struct kvm_vcpu *vcpu)
intel_pmu_legacy_freezing_lbrs_on_pmi(vcpu);
}

+static void intel_pmu_lbr_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,
@@ -651,4 +661,5 @@ struct kvm_pmu_ops intel_pmu_ops = {
.init = intel_pmu_init,
.reset = intel_pmu_reset,
.deliver_pmi = intel_pmu_deliver_pmi,
+ .lbr_cleanup = intel_pmu_lbr_cleanup,
};
--
2.21.3