KVM: selftests: Add PMU feature framework, use in PMU event filter test

Add an X86_PMU_FEATURE_* framework to simplify probing architectural
events on Intel PMUs, which require checking the length of a bit vector
and the _absence_ of a "feature" bit.  Add helpers for both KVM and
"this CPU", and use the newfangled magic (along with X86_PROPERTY_*)
to  clean up pmu_event_filter_test.

No functional change intended.

Signed-off-by: Sean Christopherson <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: sean-jc

tools/testing/selftests/kvm/include/x86_64/processor.h

@@ -201,6 +201,8 @@ struct kvm_x86_cpu_property {
 
 #define X86_PROPERTY_MAX_BASIC_LEAF		KVM_X86_CPU_PROPERTY(0, 0, EAX, 0, 31)
 #define X86_PROPERTY_PMU_VERSION		KVM_X86_CPU_PROPERTY(0xa, 0, EAX, 0, 7)
+#define X86_PROPERTY_PMU_NR_GP_COUNTERS		KVM_X86_CPU_PROPERTY(0xa, 0, EAX, 8, 15)
+#define X86_PROPERTY_PMU_EBX_BIT_VECTOR_LENGTH	KVM_X86_CPU_PROPERTY(0xa, 0, EAX, 24, 31)
 
 #define X86_PROPERTY_XSTATE_MAX_SIZE_XCR0	KVM_X86_CPU_PROPERTY(0xd,  0, EBX,  0, 31)
 #define X86_PROPERTY_XSTATE_MAX_SIZE		KVM_X86_CPU_PROPERTY(0xd,  0, ECX,  0, 31)
@@ -221,6 +223,29 @@ struct kvm_x86_cpu_property {
 
 #define X86_PROPERTY_MAX_CENTAUR_LEAF		KVM_X86_CPU_PROPERTY(0xC0000000, 0, EAX, 0, 31)
 
+/*
+ * Intel's architectural PMU events are bizarre.  They have a "feature" bit
+ * 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.
+ *
+ * Wrap the "unavailable" feature to simplify checking whether or not a given
+ * architectural event is supported.
+ */
+struct kvm_x86_pmu_feature {
+	struct kvm_x86_cpu_feature anti_feature;
+};
+#define	KVM_X86_PMU_FEATURE(name, __bit)					\
+({										\
+	struct kvm_x86_pmu_feature feature = {					\
+		.anti_feature = KVM_X86_CPU_FEATURE(0xa, 0, EBX, __bit),	\
+	};									\
+										\
+	feature;								\
+})
+
+#define X86_PMU_FEATURE_BRANCH_INSNS_RETIRED	KVM_X86_PMU_FEATURE(BRANCH_INSNS_RETIRED, 5)
 
 /* Page table bitfield declarations */
 #define PTE_PRESENT_MASK        BIT_ULL(0)
@@ -535,6 +560,14 @@ static __always_inline bool this_cpu_has_p(struct kvm_x86_cpu_property property)
 	return max_leaf >= property.function;
 }
 
+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);
+
+	return nr_bits > feature.anti_feature.bit &&
+	       !this_cpu_has(feature.anti_feature);
+}
+
 #define SET_XMM(__var, __xmm) \
 	asm volatile("movq %0, %%"#__xmm : : "r"(__var) : #__xmm)
 
@@ -743,6 +776,14 @@ static __always_inline bool kvm_cpu_has_p(struct kvm_x86_cpu_property property)
 	return max_leaf >= property.function;
 }
 
+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);
+
+	return nr_bits > feature.anti_feature.bit &&
+	       !kvm_cpu_has(feature.anti_feature);
+}
+
 static inline size_t kvm_cpuid2_size(int nr_entries)
 {
 	return sizeof(struct kvm_cpuid2) +

tools/testing/selftests/kvm/x86_64/pmu_event_filter_test.c

@@ -21,29 +21,6 @@
 #define ARCH_PERFMON_EVENTSEL_OS			(1ULL << 17)
 #define ARCH_PERFMON_EVENTSEL_ENABLE			(1ULL << 22)
 
-union cpuid10_eax {
-	struct {
-		unsigned int version_id:8;
-		unsigned int num_counters:8;
-		unsigned int bit_width:8;
-		unsigned int mask_length:8;
-	} split;
-	unsigned int full;
-};
-
-union cpuid10_ebx {
-	struct {
-		unsigned int no_unhalted_core_cycles:1;
-		unsigned int no_instructions_retired:1;
-		unsigned int no_unhalted_reference_cycles:1;
-		unsigned int no_llc_reference:1;
-		unsigned int no_llc_misses:1;
-		unsigned int no_branch_instruction_retired:1;
-		unsigned int no_branch_misses_retired:1;
-	} split;
-	unsigned int full;
-};
-
 /* End of stuff taken from perf_event.h. */
 
 /* Oddly, this isn't in perf_event.h. */
@@ -380,30 +357,16 @@ static void test_pmu_config_disable(void (*guest_code)(void))
 }
 
 /*
- * Check for a non-zero PMU version, at least one general-purpose
- * counter per logical processor, an EBX bit vector of length greater
- * than 5, and EBX[5] clear.
- */
-static bool check_intel_pmu_leaf(const struct kvm_cpuid_entry2 *entry)
-{
-	union cpuid10_eax eax = { .full = entry->eax };
-	union cpuid10_ebx ebx = { .full = entry->ebx };
-
-	return eax.split.version_id && eax.split.num_counters > 0 &&
-		eax.split.mask_length > ARCH_PERFMON_BRANCHES_RETIRED &&
-		!ebx.split.no_branch_instruction_retired;
-}
-
-/*
- * Note that CPUID leaf 0xa is Intel-specific. This leaf should be
- * clear on AMD hardware.
+ * On Intel, check for a non-zero PMU version, at least one general-purpose
+ * counter per logical processor, and support for counting the number of branch
+ * instructions retired.
  */
 static bool use_intel_pmu(void)
 {
-	const struct kvm_cpuid_entry2 *entry;
-
-	entry = kvm_get_supported_cpuid_entry(0xa);
-	return is_intel_cpu() && check_intel_pmu_leaf(entry);
+	return is_intel_cpu() &&
+	       kvm_cpu_property(X86_PROPERTY_PMU_VERSION) &&
+	       kvm_cpu_property(X86_PROPERTY_PMU_NR_GP_COUNTERS) &&
+	       kvm_pmu_has(X86_PMU_FEATURE_BRANCH_INSNS_RETIRED);
 }
 
 static bool is_zen1(uint32_t eax)