[PATCH 2/2] KVM: selftests: Add PEBS test for MSR_IA32_PERF_CAPABILITIES

[Jinrong Liang]

From: Jinrong Liang <cloudliang@xxxxxxxxxxx>

This commit adds a PEBS test that verifies all possible combinations
of PEBS-related bits in MSR_IA32_PERF_CAPABILITIES. This comprehensive
test ensures the accuracy of the PEBS feature.

Signed-off-by: Jinrong Liang <cloudliang@xxxxxxxxxxx>
---
 .../selftests/kvm/x86_64/vmx_pmu_caps_test.c  | 71 +++++++++++++++++++
 1 file changed, 71 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c b/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c
index 02903084598f..c1b1ba44bc26 100644
--- a/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c
+++ b/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c
@@ -21,6 +21,12 @@
 
 #define MAX_LINEAR_ADDR_MASK		GENMASK_ULL(15, 8)
 #define ADDR_OFS_BIT			8
+#define PMU_CAP_LBR_FMT		0x3f
+#define PMU_CAP_SMM_FREEZE		BIT_ULL(12)
+#define PMU_CAP_FW_WRITES		BIT_ULL(13)
+#define PMU_CAP_PERF_METRICS_AVAILABLE	BIT_ULL(PERF_CAP_METRICS_IDX)
+#define PMU_CAP_PEBS_OUTPUT_PT_AVAIL	BIT_ULL(PERF_CAP_PT_IDX)
+#define PMU_CAP_PEBS_ALL		(PERF_CAP_PEBS_MASK | PMU_CAP_PEBS_OUTPUT_PT_AVAIL)
 
 union perf_capabilities {
 	struct {
@@ -331,6 +337,70 @@ static void test_ds_area_noncanonical_address(union perf_capabilities host_cap)
 	kvm_vm_free(vm);
 }
 
+static void test_pebs_bit_combinations(union perf_capabilities host_cap)
+{
+	int ret;
+	uint64_t pebs_val, val;
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm = vm_create_with_one_vcpu(&vcpu, NULL);
+
+	TEST_REQUIRE(kvm_cpu_property(X86_PROPERTY_PMU_VERSION) > 1);
+	TEST_REQUIRE(host_cap.capabilities & PERF_CAP_PEBS_FORMAT);
+	TEST_REQUIRE(vcpu_get_msr(vcpu, MSR_IA32_MISC_ENABLE) &
+		     MSR_IA32_MISC_ENABLE_PEBS_UNAVAIL);
+
+	/*
+	 * Test if PEBS_REC_FMT is set and the value is the same as host,
+	 * the other PEBS bits are allowed to be set only if they are the
+	 * same as host.
+	 */
+	pebs_val = host_cap.capabilities & PMU_CAP_PEBS_ALL;
+
+	vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, pebs_val);
+	ASSERT_EQ(vcpu_get_msr(vcpu, MSR_IA32_PERF_CAPABILITIES),
+		  (u64)pebs_val);
+
+	/* Test all PEBS bit combinations. */
+	for (val = 0x0; val <= (~0ul & PMU_CAP_PEBS_ALL); val++) {
+		/* Skips values that are not related to PEBS. */
+		if (val & (PMU_CAP_LBR_FMT | PMU_CAP_SMM_FREEZE |
+		    PMU_CAP_FW_WRITES | PMU_CAP_PERF_METRICS_AVAILABLE))
+			continue;
+
+		/*
+		 * Test that value of PEBS is rejected when the KVM doesn't
+		 * supports Intel PT.
+		 */
+		if ((val & PMU_CAP_PEBS_OUTPUT_PT_AVAIL) &&
+		    (!(host_cap.capabilities & PMU_CAP_PEBS_OUTPUT_PT_AVAIL))) {
+			ret = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, val);
+			TEST_ASSERT(!ret, "Bad PEBS auxiliary bits = 0x%lx didn't fail", val);
+
+			continue;
+		}
+
+		/*
+		 * Test that value of PEBS is rejected when carrying
+		 * PEBS_REC_FMT if the value of PEBS is not equal to host.
+		 */
+		if ((val & PERF_CAP_PEBS_FORMAT) && val != pebs_val) {
+			ret = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, val);
+			TEST_ASSERT(!ret, "Bad PEBS auxiliary bits = 0x%lx didn't fail", val);
+
+			continue;
+		}
+
+		/*
+		 * Test that PEBS bits can be written simultaneously or
+		 * independently if PEBS_REC_FMT is not carried.
+		 */
+		vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, val);
+		ASSERT_EQ(vcpu_get_msr(vcpu, MSR_IA32_PERF_CAPABILITIES), val);
+	}
+
+	kvm_vm_free(vm);
+}
+
 int main(int argc, char *argv[])
 {
 	union perf_capabilities host_cap;
@@ -352,4 +422,5 @@ int main(int argc, char *argv[])
 	test_guest_wrmsr_perf_capabilities(host_cap);
 	test_lbr_perf_capabilities(host_cap);
 	test_ds_area_noncanonical_address(host_cap);
+	test_pebs_bit_combinations(host_cap);
 }
-- 
2.31.1