[PATCH v7 07/19] KVM: selftests: Extend {kvm,this}_pmu_has() to support fixed counters

Sean Christopherson
2023-11-08T00:31:54Z

Extend the kvm_x86_pmu_feature framework to allow querying for fixed
counters via {kvm,this}_pmu_has(). Like architectural events, checking
for a fixed counter annoyingly requires checking multiple CPUID fields, as
a fixed counter exists if:

FxCtr[i]_is_supported := ECX[i] || (EDX[4:0] > i);

Note, KVM currently doesn't actually support exposing fixed counters via
the bitmask, but that will hopefully change sooner than later, and Intel's
SDM explicitly "recommends" checking both the number of counters and the
mask.

Rename the intermedate "anti_feature" field to simply 'f' since the fixed
counter bitmask (thankfully) doesn't have reversed polarity like the
architectural events bitmask.

Note, ideally the helpers would use BUILD_BUG_ON() to assert on the
incoming register, but the expected usage in PMU tests can't guarantee the
inputs are compile-time constants.

Opportunistically define macros for all of the known architectural events
and fixed counters.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
.../selftests/kvm/include/x86_64/processor.h | 65 ++++++++++++++-----
1 file changed, 47 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 2d9771151dd9..64aecb3dcf60 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -281,24 +281,41 @@ struct kvm_x86_cpu_property {
* that indicates the feature is _not_ supported, and a property that states
* the length of the bit mask of unsupported features. A feature is supported
* if the size of the bit mask is larger than the "unavailable" bit, and said
- * bit is not set.
+ * bit is not set. Fixed counters also bizarre enumeration, but inverted from
+ * arch events for general purpose counters. Fixed counters are supported if a
+ * feature flag is set **OR** the total number of fixed counters is greater
+ * than index of the counter.
*
- * Wrap the "unavailable" feature to simplify checking whether or not a given
- * architectural event is supported.
+ * Wrap the events for general purpose and fixed counters to simplify checking
+ * whether or not a given architectural event is supported.
*/
struct kvm_x86_pmu_feature {
- struct kvm_x86_cpu_feature anti_feature;
+ struct kvm_x86_cpu_feature f;
};
-#define KVM_X86_PMU_FEATURE(__bit) \
-({ \
- struct kvm_x86_pmu_feature feature = { \
- .anti_feature = KVM_X86_CPU_FEATURE(0xa, 0, EBX, __bit), \
- }; \
- \
- feature; \
+#define KVM_X86_PMU_FEATURE(__reg, __bit) \
+({ \
+ struct kvm_x86_pmu_feature feature = { \
+ .f = KVM_X86_CPU_FEATURE(0xa, 0, __reg, __bit), \
+ }; \
+ \
+ kvm_static_assert(KVM_CPUID_##__reg == KVM_CPUID_EBX || \
+ KVM_CPUID_##__reg == KVM_CPUID_ECX); \
+ feature; \
})

-#define X86_PMU_FEATURE_BRANCH_INSNS_RETIRED KVM_X86_PMU_FEATURE(5)
+#define X86_PMU_FEATURE_CPU_CYCLES KVM_X86_PMU_FEATURE(EBX, 0)
+#define X86_PMU_FEATURE_INSNS_RETIRED KVM_X86_PMU_FEATURE(EBX, 1)
+#define X86_PMU_FEATURE_REFERENCE_CYCLES KVM_X86_PMU_FEATURE(EBX, 2)
+#define X86_PMU_FEATURE_LLC_REFERENCES KVM_X86_PMU_FEATURE(EBX, 3)
+#define X86_PMU_FEATURE_LLC_MISSES KVM_X86_PMU_FEATURE(EBX, 4)
+#define X86_PMU_FEATURE_BRANCH_INSNS_RETIRED KVM_X86_PMU_FEATURE(EBX, 5)
+#define X86_PMU_FEATURE_BRANCHES_MISPREDICTED KVM_X86_PMU_FEATURE(EBX, 6)
+#define X86_PMU_FEATURE_TOPDOWN_SLOTS KVM_X86_PMU_FEATURE(EBX, 7)
+
+#define X86_PMU_FEATURE_INSNS_RETIRED_FIXED KVM_X86_PMU_FEATURE(ECX, 0)
+#define X86_PMU_FEATURE_CPU_CYCLES_FIXED KVM_X86_PMU_FEATURE(ECX, 1)
+#define X86_PMU_FEATURE_REFERENCE_TSC_CYCLES_FIXED KVM_X86_PMU_FEATURE(ECX, 2)
+#define X86_PMU_FEATURE_TOPDOWN_SLOTS_FIXED KVM_X86_PMU_FEATURE(ECX, 3)

static inline unsigned int x86_family(unsigned int eax)
{
@@ -697,10 +714,16 @@ static __always_inline bool this_cpu_has_p(struct kvm_x86_cpu_property property)

static inline bool this_pmu_has(struct kvm_x86_pmu_feature feature)
{
- uint32_t nr_bits = this_cpu_property(X86_PROPERTY_PMU_EBX_BIT_VECTOR_LENGTH);
+ uint32_t nr_bits;

- return nr_bits > feature.anti_feature.bit &&
- !this_cpu_has(feature.anti_feature);
+ if (feature.f.reg == KVM_CPUID_EBX) {
+ nr_bits = this_cpu_property(X86_PROPERTY_PMU_EBX_BIT_VECTOR_LENGTH);
+ return nr_bits > feature.f.bit && !this_cpu_has(feature.f);
+ }
+
+ GUEST_ASSERT(feature.f.reg == KVM_CPUID_ECX);
+ nr_bits = this_cpu_property(X86_PROPERTY_PMU_NR_FIXED_COUNTERS);
+ return nr_bits > feature.f.bit || this_cpu_has(feature.f);
}

static __always_inline uint64_t this_cpu_supported_xcr0(void)
@@ -916,10 +939,16 @@ static __always_inline bool kvm_cpu_has_p(struct kvm_x86_cpu_property property)

static inline bool kvm_pmu_has(struct kvm_x86_pmu_feature feature)
{
- uint32_t nr_bits = kvm_cpu_property(X86_PROPERTY_PMU_EBX_BIT_VECTOR_LENGTH);
+ uint32_t nr_bits;

- return nr_bits > feature.anti_feature.bit &&
- !kvm_cpu_has(feature.anti_feature);
+ if (feature.f.reg == KVM_CPUID_EBX) {
+ nr_bits = kvm_cpu_property(X86_PROPERTY_PMU_EBX_BIT_VECTOR_LENGTH);
+ return nr_bits > feature.f.bit && !kvm_cpu_has(feature.f);
+ }
+
+ TEST_ASSERT_EQ(feature.f.reg, KVM_CPUID_ECX);
+ nr_bits = kvm_cpu_property(X86_PROPERTY_PMU_NR_FIXED_COUNTERS);
+ return nr_bits > feature.f.bit || kvm_cpu_has(feature.f);
}

static __always_inline uint64_t kvm_cpu_supported_xcr0(void)
--
2.42.0.869.gea05f2083d-goog