[PATCH v7 11/19] KVM: selftests: Test consistency of CPUID with num of gp counters

Sean Christopherson
2023-11-08T00:32:03Z

From: Jinrong Liang <cloudliang@tencent.com>

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 <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 | 91 +++++++++++++++++++
1 file changed, 91 insertions(+)

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 9cd308417aeb..6f2d3a64a118 100644
--- a/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
+++ b/tools/testing/selftests/kvm/x86_64/pmu_counters_test.c
@@ -270,9 +270,95 @@ 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) \
+
+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++) {
+ 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 ? 0xffff : 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, 0xffff);
+ 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(val == expected_val,
+ "Expected RDMSR(0x%x) to yield 0x%lx, got 0x%lx",
+ msr, expected_val, 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 +422,11 @@ 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);
}
}
}
--
2.42.0.869.gea05f2083d-goog