[PATCH v3 17/21] KVM: selftests: Test post-KVM_RUN writes to PERF_CAPABILITIES

[Sean Christopherson]

Now that KVM disallows changing PERF_CAPABILITIES after KVM_RUN, expand
the host side checks to verify KVM rejects any attempts to change bits
from userspace.

Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 .../selftests/kvm/x86_64/vmx_pmu_caps_test.c        | 13 +++++++++++++
 1 file changed, 13 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 44fc6101a547..6fc86f5eba0b 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
@@ -85,6 +85,7 @@ static void test_guest_wrmsr_perf_capabilities(union perf_capabilities host_cap)
 	struct kvm_vcpu *vcpu;
 	struct kvm_vm *vm = vm_create_with_one_vcpu(&vcpu, guest_code);
 	struct ucall uc;
+	int r, i;
 
 	vm_init_descriptor_tables(vm);
 	vcpu_init_descriptor_tables(vcpu);
@@ -106,6 +107,18 @@ static void test_guest_wrmsr_perf_capabilities(union perf_capabilities host_cap)
 
 	ASSERT_EQ(vcpu_get_msr(vcpu, MSR_IA32_PERF_CAPABILITIES), host_cap.capabilities);
 
+	vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, host_cap.capabilities);
+
+	r = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES, 0);
+	TEST_ASSERT(!r, "Post-KVM_RUN write '0' didn't fail");
+
+	for (i = 0; i < 64; i++) {
+		r = _vcpu_set_msr(vcpu, MSR_IA32_PERF_CAPABILITIES,
+				  host_cap.capabilities ^ BIT_ULL(i));
+		TEST_ASSERT(!r, "Post-KVM_RUN write '0x%llx'didn't fail",
+			    host_cap.capabilities ^ BIT_ULL(i));
+	}
+
 	kvm_vm_free(vm);
 }
 
-- 
2.40.0.rc1.284.g88254d51c5-goog