From: Like Xu <likexu@xxxxxxxxxxx>
When a guest counter is configured as a PEBS counter through
IA32_PEBS_ENABLE, a guest PEBS event will be reprogrammed by
configuring a non-zero precision level in the perf_event_attr.
The guest PEBS overflow PMI bit would be set in the guest
GLOBAL_STATUS MSR when PEBS facility generates a PEBS
overflow PMI based on guest IA32_DS_AREA MSR.
Even with the same counter index and the same event code and
mask, guest PEBS events will not be reused for non-PEBS events.
Originally-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Co-developed-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Signed-off-by: Like Xu <likexu@xxxxxxxxxxx>
Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
arch/x86/kvm/pmu.c | 36 +++++++++++++++++++++++++++++++++---
1 file changed, 33 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kvm/pmu.c b/arch/x86/kvm/pmu.c
index a20207ee4014..8934261e9563 100644
--- a/arch/x86/kvm/pmu.c
+++ b/arch/x86/kvm/pmu.c
@@ -58,15 +58,22 @@ static void kvm_pmi_trigger_fn(struct irq_work *irq_work)
static inline void __kvm_perf_overflow(struct kvm_pmc *pmc, bool in_pmi)
{
struct kvm_pmu *pmu = pmc_to_pmu(pmc);
+ bool skip_pmi = false;
/* Ignore counters that have been reprogrammed already. */
if (test_and_set_bit(pmc->idx, pmu->reprogram_pmi))
return;
- __set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
+ if (pmc->perf_event && pmc->perf_event->attr.precise_ip) {
+ /* Indicate PEBS overflow PMI to guest. */
+ skip_pmi = __test_and_set_bit(GLOBAL_STATUS_BUFFER_OVF_BIT,
+ (unsigned long *)&pmu->global_status);
+ } else {
+ __set_bit(pmc->idx, (unsigned long *)&pmu->global_status);
+ }
kvm_make_request(KVM_REQ_PMU, pmc->vcpu);
- if (!pmc->intr)
+ if (!pmc->intr || skip_pmi)
return;
/*
@@ -97,6 +104,7 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
bool exclude_kernel, bool intr,
bool in_tx, bool in_tx_cp)
{
+ struct kvm_pmu *pmu = pmc_to_pmu(pmc);
struct perf_event *event;
struct perf_event_attr attr = {
.type = type,
@@ -108,6 +116,7 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
.exclude_kernel = exclude_kernel,
.config = config,
};
+ bool pebs = test_bit(pmc->idx, (unsigned long *)&pmu->pebs_enable);
attr.sample_period = get_sample_period(pmc, pmc->counter);
@@ -122,6 +131,23 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
attr.sample_period = 0;
attr.config |= HSW_IN_TX_CHECKPOINTED;
}
+ if (pebs) {
+ /*
+ * The non-zero precision level of guest event makes the ordinary
+ * guest event becomes a guest PEBS event and triggers the host
+ * PEBS PMI handler to determine whether the PEBS overflow PMI
+ * comes from the host counters or the guest.
+ *
+ * For most PEBS hardware events, the difference in the software
+ * precision levels of guest and host PEBS events will not affect
+ * the accuracy of the PEBS profiling result, because the "event IP"
+ * in the PEBS record is calibrated on the guest side.
+ *
+ * On Icelake everything is fine. Other hardware (GLC+, TNT+) that
+ * could possibly care here is unsupported and needs changes.
+ */
+ attr.precise_ip = 1;
+ }
event = perf_event_create_kernel_counter(&attr, -1, current,
kvm_perf_overflow, pmc);
@@ -135,7 +161,7 @@ static void pmc_reprogram_counter(struct kvm_pmc *pmc, u32 type,
pmc_to_pmu(pmc)->event_count++;
clear_bit(pmc->idx, pmc_to_pmu(pmc)->reprogram_pmi);
pmc->is_paused = false;
- pmc->intr = intr;
+ pmc->intr = intr || pebs;
}
static void pmc_pause_counter(struct kvm_pmc *pmc)
@@ -161,6 +187,10 @@ static bool pmc_resume_counter(struct kvm_pmc *pmc)
get_sample_period(pmc, pmc->counter)))
return false;
+ if (!test_bit(pmc->idx, (unsigned long *)&pmc_to_pmu(pmc)->pebs_enable) &&
+ pmc->perf_event->attr.precise_ip)
+ return false;
+
/* reuse perf_event to serve as pmc_reprogram_counter() does*/
perf_event_enable(pmc->perf_event);
pmc->is_paused = false;
--
2.33.1
