KVM: selftests: Split PMU caps sub-tests to avoid writing MSR after KVM_RUN

Split the PERF_CAPABILITIES subtests into two parts so that the LBR format
testcases don't execute after KVM_RUN.  Similar to the guest CPUID model,
KVM will soon disallow changing PERF_CAPABILITIES after KVM_RUN, at which
point attempting to set the MSR after KVM_RUN will yield false positives
and/or false negatives depending on what the test is trying to do.

Land the LBR format test in a more generic "immutable features" test in
anticipation of expanding its scope to other immutable features.

Link: https://lore.kernel.org/r/20230311004618.920745-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

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 c280ba1e6572449923fc1958c47ccda4460dcf22..ac08c0fdd84d56ca18f076eca496ce892800b15b 100644 (file)
--- a/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c
+++ b/tools/testing/selftests/kvm/x86_64/vmx_pmu_caps_test.c
@@ -41,24 +41,10 @@ static void guest_code(void)
        wrmsr(MSR_IA32_PERF_CAPABILITIES, PMU_CAP_LBR_FMT);
 }
 
-int main(int argc, char *argv[])
+static void test_fungible_perf_capabilities(union perf_capabilities host_cap)
 {
-       struct kvm_vm *vm;
        struct kvm_vcpu *vcpu;
-       int ret;
-       union perf_capabilities host_cap;
-       uint64_t val;
-
-       host_cap.capabilities = kvm_get_feature_msr(MSR_IA32_PERF_CAPABILITIES);
-       host_cap.capabilities &= (PMU_CAP_FW_WRITES | PMU_CAP_LBR_FMT);
-
-       /* Create VM */
-       vm = vm_create_with_one_vcpu(&vcpu, guest_code);
-
-       TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_PDCM));
-
-       TEST_REQUIRE(kvm_cpu_has_p(X86_PROPERTY_PMU_VERSION));
-       TEST_REQUIRE(kvm_cpu_property(X86_PROPERTY_PMU_VERSION) > 0);
+       struct kvm_vm *vm = vm_create_with_one_vcpu(&vcpu, guest_code);
 
        /* testcase 1, set capabilities when we have PDCM bit */
        vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, PMU_CAP_FW_WRITES);
@@ -70,7 +56,16 @@ int main(int argc, char *argv[])
        vcpu_run(vcpu);
        ASSERT_EQ(vcpu_get_msr(vcpu, MSR_IA32_PERF_CAPABILITIES), PMU_CAP_FW_WRITES);
 
-       /* testcase 2, check valid LBR formats are accepted */
+       kvm_vm_free(vm);
+}
+
+static void test_immutable_perf_capabilities(union perf_capabilities host_cap)
+{
+       struct kvm_vcpu *vcpu;
+       struct kvm_vm *vm = vm_create_with_one_vcpu(&vcpu, NULL);
+       uint64_t val;
+       int ret;
+
        vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, 0);
        ASSERT_EQ(vcpu_get_msr(vcpu, MSR_IA32_PERF_CAPABILITIES), 0);
 
@@ -78,8 +73,8 @@ int main(int argc, char *argv[])
        ASSERT_EQ(vcpu_get_msr(vcpu, MSR_IA32_PERF_CAPABILITIES), (u64)host_cap.lbr_format);
 
        /*
-        * Testcase 3, check that an "invalid" LBR format is rejected.  Only an
-        * exact match of the host's format (and 0/disabled) is allowed.
+        * KVM only supports the host's native LBR format, as well as '0' (to
+        * disable LBR support).  Verify KVM rejects all other LBR formats.
         */
        for (val = 1; val <= PMU_CAP_LBR_FMT; val++) {
                if (val == (host_cap.capabilities & PMU_CAP_LBR_FMT))
@@ -88,7 +83,23 @@ int main(int argc, char *argv[])
                ret = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, val);
                TEST_ASSERT(!ret, "Bad LBR FMT = 0x%lx didn't fail", val);
        }
+       kvm_vm_free(vm);
+}
+
+int main(int argc, char *argv[])
+{
+       union perf_capabilities host_cap;
+
+       TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_PDCM));
+
+       TEST_REQUIRE(kvm_cpu_has_p(X86_PROPERTY_PMU_VERSION));
+       TEST_REQUIRE(kvm_cpu_property(X86_PROPERTY_PMU_VERSION) > 0);
+
+       host_cap.capabilities = kvm_get_feature_msr(MSR_IA32_PERF_CAPABILITIES);
+       host_cap.capabilities &= (PMU_CAP_FW_WRITES | PMU_CAP_LBR_FMT);
+
+       test_fungible_perf_capabilities(host_cap);
+       test_immutable_perf_capabilities(host_cap);
 
        printf("Completed perf capability tests.\n");
-       kvm_vm_free(vm);
 }