KVM: selftests: Test consistency of CPUID with num of gp counters

Add a test to verify that KVM correctly emulates MSR-based accesses to
general purpose counters based on guest CPUID, e.g. that accesses to
non-existent counters #GP and accesses to existent counters succeed.

Note, for compatibility reasons, KVM does not emulate #GP when
MSR_P6_PERFCTR[0|1] is not present (writes should be dropped).

Co-developed-by: Like Xu <[email protected]>
Signed-off-by: Like Xu <[email protected]>
Signed-off-by: Jinrong Liang <[email protected]>
Co-developed-by: Sean Christopherson <[email protected]>
Tested-by: Dapeng Mi <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

Author: Jinrong Liang

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

@@ -270,9 +270,103 @@ static void test_arch_events(uint8_t pmu_version, uint64_t perf_capabilities,
 	kvm_vm_free(vm);
 }
 
+/*
+ * Limit testing to MSRs that are actually defined by Intel (in the SDM).  MSRs
+ * that aren't defined counter MSRs *probably* don't exist, but there's no
+ * guarantee that currently undefined MSR indices won't be used for something
+ * other than PMCs in the future.
+ */
+#define MAX_NR_GP_COUNTERS	8
+#define MAX_NR_FIXED_COUNTERS	3
+
+#define GUEST_ASSERT_PMC_MSR_ACCESS(insn, msr, expect_gp, vector)		\
+__GUEST_ASSERT(expect_gp ? vector == GP_VECTOR : !vector,			\
+	       "Expected %s on " #insn "(0x%x), got vector %u",			\
+	       expect_gp ? "#GP" : "no fault", msr, vector)			\
+
+#define GUEST_ASSERT_PMC_VALUE(insn, msr, val, expected)			\
+	__GUEST_ASSERT(val == expected_val,					\
+		       "Expected " #insn "(0x%x) to yield 0x%lx, got 0x%lx",	\
+		       msr, expected_val, val);
+
+static void guest_rd_wr_counters(uint32_t base_msr, uint8_t nr_possible_counters,
+				 uint8_t nr_counters)
+{
+	uint8_t i;
+
+	for (i = 0; i < nr_possible_counters; i++) {
+		/*
+		 * TODO: Test a value that validates full-width writes and the
+		 * width of the counters.
+		 */
+		const uint64_t test_val = 0xffff;
+		const uint32_t msr = base_msr + i;
+		const bool expect_success = i < nr_counters;
+
+		/*
+		 * KVM drops writes to MSR_P6_PERFCTR[0|1] if the counters are
+		 * unsupported, i.e. doesn't #GP and reads back '0'.
+		 */
+		const uint64_t expected_val = expect_success ? test_val : 0;
+		const bool expect_gp = !expect_success && msr != MSR_P6_PERFCTR0 &&
+				       msr != MSR_P6_PERFCTR1;
+		uint8_t vector;
+		uint64_t val;
+
+		vector = wrmsr_safe(msr, test_val);
+		GUEST_ASSERT_PMC_MSR_ACCESS(WRMSR, msr, expect_gp, vector);
+
+		vector = rdmsr_safe(msr, &val);
+		GUEST_ASSERT_PMC_MSR_ACCESS(RDMSR, msr, expect_gp, vector);
+
+		/* On #GP, the result of RDMSR is undefined. */
+		if (!expect_gp)
+			GUEST_ASSERT_PMC_VALUE(RDMSR, msr, val, expected_val);
+
+		vector = wrmsr_safe(msr, 0);
+		GUEST_ASSERT_PMC_MSR_ACCESS(WRMSR, msr, expect_gp, vector);
+	}
+	GUEST_DONE();
+}
+
+static void guest_test_gp_counters(void)
+{
+	uint8_t nr_gp_counters = 0;
+	uint32_t base_msr;
+
+	if (guest_get_pmu_version())
+		nr_gp_counters = this_cpu_property(X86_PROPERTY_PMU_NR_GP_COUNTERS);
+
+	if (this_cpu_has(X86_FEATURE_PDCM) &&
+	    rdmsr(MSR_IA32_PERF_CAPABILITIES) & PMU_CAP_FW_WRITES)
+		base_msr = MSR_IA32_PMC0;
+	else
+		base_msr = MSR_IA32_PERFCTR0;
+
+	guest_rd_wr_counters(base_msr, MAX_NR_GP_COUNTERS, nr_gp_counters);
+}
+
+static void test_gp_counters(uint8_t pmu_version, uint64_t perf_capabilities,
+			     uint8_t nr_gp_counters)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+
+	vm = pmu_vm_create_with_one_vcpu(&vcpu, guest_test_gp_counters,
+					 pmu_version, perf_capabilities);
+
+	vcpu_set_cpuid_property(vcpu, X86_PROPERTY_PMU_NR_GP_COUNTERS,
+				nr_gp_counters);
+
+	run_vcpu(vcpu);
+
+	kvm_vm_free(vm);
+}
+
 static void test_intel_counters(void)
 {
 	uint8_t nr_arch_events = kvm_cpu_property(X86_PROPERTY_PMU_EBX_BIT_VECTOR_LENGTH);
+	uint8_t nr_gp_counters = kvm_cpu_property(X86_PROPERTY_PMU_NR_GP_COUNTERS);
 	uint8_t pmu_version = kvm_cpu_property(X86_PROPERTY_PMU_VERSION);
 	unsigned int i;
 	uint8_t v, j;
@@ -336,6 +430,11 @@ static void test_intel_counters(void)
 				for (k = 0; k < nr_arch_events; k++)
 					test_arch_events(v, perf_caps[i], j, BIT(k));
 			}
+
+			pr_info("Testing GP counters, PMU version %u, perf_caps = %lx\n",
+				v, perf_caps[i]);
+			for (j = 0; j <= nr_gp_counters; j++)
+				test_gp_counters(v, perf_caps[i], j);
 		}
 	}
 }