From: Like Xu <like.xu@xxxxxxxxx>
This patch adds support to KVM to save/restore the lbr stack on vCPU
context switching.
When the guest sets the ACTIVE bit of MSR_KVM_PV_LBR_CTRL, a perf event
is created on the host for the related vCPU. This perf event ensures the
LBR stack to be saved/restored when the vCPU thread is scheduled out/in.
The perf event is removed and freed when the guest clears the ACTIVE
bit.
Signed-off-by: Like Xu <like.xu@xxxxxxxxx>
Signed-off-by: Wei Wang <wei.w.wang@xxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 2 ++
arch/x86/kvm/cpuid.c | 3 +-
arch/x86/kvm/pmu_intel.c | 71 ++++++++++++++++++++++++++++++++++++++++-
3 files changed, 74 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5db5ba3..cfbe90f 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -432,6 +432,8 @@ struct kvm_pmu {
struct kvm_pmc fixed_counters[INTEL_PMC_MAX_FIXED];
struct irq_work irq_work;
u64 reprogram_pmi;
+ u64 kvm_pv_lbr_ctrl;
+ struct perf_event *guest_lbr_event;
};
struct kvm_pmu_ops;
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 3b8a57b..8550eee 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -622,7 +622,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
(1 << KVM_FEATURE_PV_UNHALT) |
(1 << KVM_FEATURE_PV_TLB_FLUSH) |
(1 << KVM_FEATURE_ASYNC_PF_VMEXIT) |
- (1 << KVM_FEATURE_PV_SEND_IPI);
+ (1 << KVM_FEATURE_PV_SEND_IPI) |
+ (1 << KVM_FEATURE_PV_LBR_CTRL);
if (sched_info_on())
entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
diff --git a/arch/x86/kvm/pmu_intel.c b/arch/x86/kvm/pmu_intel.c
index 5ab4a36..27c028d 100644
--- a/arch/x86/kvm/pmu_intel.c
+++ b/arch/x86/kvm/pmu_intel.c
@@ -67,6 +67,62 @@ static void global_ctrl_changed(struct kvm_pmu *pmu, u64 data)
reprogram_counter(pmu, bit);
}
+static void guest_lbr_event_create(struct kvm_pmu *pmu)
+{
+ struct perf_event *event;
+ struct perf_event_attr attr = {
+ .type = PERF_TYPE_RAW,
+ .size = sizeof(attr),
+ .pinned = true,
+ .exclude_host = true,
+ .sample_type = PERF_SAMPLE_BRANCH_STACK,
+ .branch_sample_type = PERF_SAMPLE_BRANCH_CALL_STACK |
+ PERF_SAMPLE_BRANCH_USER |
+ PERF_SAMPLE_BRANCH_KERNEL,
+ };
+
+ if (unlikely(pmu->guest_lbr_event)) {
+ pr_err("%s: guest_lbr_event already created\n", __func__);
+ return;
+ }
+
+ event = perf_event_create_kernel_counter(&attr, -1, current, NULL,
+ NULL);
+ if (IS_ERR(event)) {
+ pr_err("%s: failed %ld\n", __func__, PTR_ERR(event));
+ return;
+ }
+ pmu->guest_lbr_event = event;
+}
+
+void guest_lbr_event_release(struct kvm_pmu *pmu)
+{
+ struct perf_event *event = pmu->guest_lbr_event;
+
+ if (unlikely(!pmu->guest_lbr_event)) {
+ pr_err("%s: guest_lbr_event already freed\n", __func__);
+ return;
+ }
+
+ if (event) {
+ event->pmu->stop(event, PERF_EF_UPDATE);
+ perf_event_release_kernel(event);
+ }
+ pmu->guest_lbr_event = NULL;
+}
+
+static void kvm_pv_lbr_ctrl_changed(struct kvm_pmu *pmu, u64 data)
+{
+ bool guest_lbr_active = data & KVM_PV_LBR_CTRL_ACTIVE;
+
+ if (guest_lbr_active)
+ guest_lbr_event_create(pmu);
+ else
+ guest_lbr_event_release(pmu);
+
+ pmu->kvm_pv_lbr_ctrl = data;
+}
+
static unsigned intel_find_arch_event(struct kvm_pmu *pmu,
u8 event_select,
u8 unit_mask)
@@ -145,7 +201,7 @@ static struct kvm_pmc *intel_msr_idx_to_pmc(struct kvm_vcpu *vcpu,
static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
{
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
- int ret;
+ int ret = 0;
switch (msr) {
case MSR_CORE_PERF_FIXED_CTR_CTRL:
@@ -154,6 +210,10 @@ static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
ret = pmu->version > 1;
break;
+ case MSR_KVM_PV_LBR_CTRL:
+ if (vcpu->kvm->arch.guest_lbr)
+ ret = 1;
+ break;
default:
ret = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0) ||
get_gp_pmc(pmu, msr, MSR_P6_EVNTSEL0) ||
@@ -182,6 +242,9 @@ static int intel_pmu_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *data)
case MSR_CORE_PERF_GLOBAL_OVF_CTRL:
*data = pmu->global_ovf_ctrl;
return 0;
+ case MSR_KVM_PV_LBR_CTRL:
+ *data = pmu->kvm_pv_lbr_ctrl;
+ return 0;
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
(pmc = get_fixed_pmc(pmu, msr))) {
@@ -234,6 +297,11 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
return 0;
}
break;
+ case MSR_KVM_PV_LBR_CTRL:
+ if (pmu->kvm_pv_lbr_ctrl == data)
+ return 0;
+ kvm_pv_lbr_ctrl_changed(pmu, data);
+ return 0;
default:
if ((pmc = get_gp_pmc(pmu, msr, MSR_IA32_PERFCTR0)) ||
(pmc = get_fixed_pmc(pmu, msr))) {
@@ -340,6 +408,7 @@ static void intel_pmu_reset(struct kvm_vcpu *vcpu)
pmu->fixed_ctr_ctrl = pmu->global_ctrl = pmu->global_status =
pmu->global_ovf_ctrl = 0;
+ pmu->kvm_pv_lbr_ctrl = 0;
}
struct kvm_pmu_ops intel_pmu_ops = {
--
2.7.4
