[PATCH v5 09/13] KVM: selftests: Test Intel PMU architectural events on fixed counters

Sean Christopherson
2023-10-24T00:27:14Z

From: Jinrong Liang <cloudliang@tencent.com>

Update test to cover Intel PMU architectural events on fixed counters.
Per Intel SDM, PMU users can also count architecture performance events
on fixed counters (specifically, FIXED_CTR0 for the retired instructions
and FIXED_CTR1 for cpu core cycles event). Therefore, if guest's CPUID
indicates that an architecture event is not available, the corresponding
fixed counter will also not count that event.

Co-developed-by: Like Xu <likexu@tencent.com>
Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Jinrong Liang <cloudliang@tencent.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
.../selftests/kvm/x86_64/pmu_counters_test.c | 54 ++++++++++++++++---
1 file changed, 46 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
index 2a6336b994d5..410d09f788ef 100644
--- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
+++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
@@ -85,23 +85,44 @@ static void guest_measure_pmu_v1(struct kvm_x86_pmu_feature event,
GUEST_DONE();
}

+#define X86_PMU_FEATURE_NULL \
+({ \
+ struct kvm_x86_pmu_feature feature = {}; \
+ \
+ feature; \
+})
+
+static bool pmu_is_null_feature(struct kvm_x86_pmu_feature event)
+{
+ return !(*(u64 *)&event);
+}
+
static void guest_measure_loop(uint8_t idx)
{
const struct {
struct kvm_x86_pmu_feature gp_event;
+ struct kvm_x86_pmu_feature fixed_event;
} intel_event_to_feature[] = {
- [INTEL_ARCH_CPU_CYCLES] = { X86_PMU_FEATURE_CPU_CYCLES },
- [INTEL_ARCH_INSTRUCTIONS_RETIRED] = { X86_PMU_FEATURE_INSNS_RETIRED },
- [INTEL_ARCH_REFERENCE_CYCLES] = { X86_PMU_FEATURE_REFERENCE_CYCLES },
- [INTEL_ARCH_LLC_REFERENCES] = { X86_PMU_FEATURE_LLC_REFERENCES },
- [INTEL_ARCH_LLC_MISSES] = { X86_PMU_FEATURE_LLC_MISSES },
- [INTEL_ARCH_BRANCHES_RETIRED] = { X86_PMU_FEATURE_BRANCH_INSNS_RETIRED },
- [INTEL_ARCH_BRANCHES_MISPREDICTED] = { X86_PMU_FEATURE_BRANCHES_MISPREDICTED },
+ [INTEL_ARCH_CPU_CYCLES] = { X86_PMU_FEATURE_CPU_CYCLES, X86_PMU_FEATURE_CPU_CYCLES_FIXED },
+ [INTEL_ARCH_INSTRUCTIONS_RETIRED] = { X86_PMU_FEATURE_INSNS_RETIRED, X86_PMU_FEATURE_INSNS_RETIRED_FIXED },
+ /*
+ * Note, the fixed counter for reference cycles is NOT the same
+ * as the general purpose architectural event (because the GP
+ * event is garbage). The fixed counter explicitly counts at
+ * the same frequency as the TSC, whereas the GP event counts
+ * at a fixed, but uarch specific, frequency. Bundle them here
+ * for simplicity.
+ */
+ [INTEL_ARCH_REFERENCE_CYCLES] = { X86_PMU_FEATURE_REFERENCE_CYCLES, X86_PMU_FEATURE_REFERENCE_CYCLES_FIXED },
+ [INTEL_ARCH_LLC_REFERENCES] = { X86_PMU_FEATURE_LLC_REFERENCES, X86_PMU_FEATURE_NULL },
+ [INTEL_ARCH_LLC_MISSES] = { X86_PMU_FEATURE_LLC_MISSES, X86_PMU_FEATURE_NULL },
+ [INTEL_ARCH_BRANCHES_RETIRED] = { X86_PMU_FEATURE_BRANCH_INSNS_RETIRED, X86_PMU_FEATURE_NULL },
+ [INTEL_ARCH_BRANCHES_MISPREDICTED] = { X86_PMU_FEATURE_BRANCHES_MISPREDICTED, X86_PMU_FEATURE_NULL },
};

uint32_t nr_gp_counters = this_cpu_property(X86_PROPERTY_PMU_NR_GP_COUNTERS);
uint32_t pmu_version = this_cpu_property(X86_PROPERTY_PMU_VERSION);
- struct kvm_x86_pmu_feature gp_event;
+ struct kvm_x86_pmu_feature gp_event, fixed_event;
uint32_t counter_msr;
unsigned int i;

@@ -132,6 +153,23 @@ static void guest_measure_loop(uint8_t idx)
GUEST_ASSERT_EQ(this_pmu_has(gp_event), !!_rdpmc(i));
}

+ fixed_event = intel_event_to_feature[idx].fixed_event;
+ if (pmu_is_null_feature(fixed_event) || !this_pmu_has(fixed_event))
+ goto done;
+
+ i = fixed_event.f.bit;
+
+ wrmsr(MSR_CORE_PERF_FIXED_CTR0 + i, 0);
+ wrmsr(MSR_CORE_PERF_FIXED_CTR_CTRL, BIT_ULL(4 * i));
+
+ wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, BIT_ULL(PMC_IDX_FIXED + i));
+ __asm__ __volatile__("loop ." : "+c"((int){NUM_BRANCHES}));
+ wrmsr(MSR_CORE_PERF_GLOBAL_CTRL, 0);
+
+ if (pmu_is_intel_event_stable(idx))
+ GUEST_ASSERT_NE(_rdpmc(PMC_FIXED_RDPMC_BASE | i), 0);
+
+done:
GUEST_DONE();
}

--
2.42.0.758.gaed0368e0e-goog