selftests: kvm: fix vmx_set_nested_state_test

vmx_set_nested_state_test is trying to use the KVM_STATE_NESTED_EVMCS without
enabling enlightened VMCS first.  Correct the outcome of the test, and actually
test that it succeeds after the capability is enabled.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

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

@@ -25,6 +25,8 @@
 #define VMCS12_REVISION 0x11e57ed0
 #define VCPU_ID 5
 
+bool have_evmcs;
+
 void test_nested_state(struct kvm_vm *vm, struct kvm_nested_state *state)
 {
 	vcpu_nested_state_set(vm, VCPU_ID, state, false);
@@ -75,8 +77,9 @@ void set_default_vmx_state(struct kvm_nested_state *state, int size)
 {
 	memset(state, 0, size);
 	state->flags = KVM_STATE_NESTED_GUEST_MODE  |
-			KVM_STATE_NESTED_RUN_PENDING |
-			KVM_STATE_NESTED_EVMCS;
+			KVM_STATE_NESTED_RUN_PENDING;
+	if (have_evmcs)
+		state->flags |= KVM_STATE_NESTED_EVMCS;
 	state->format = 0;
 	state->size = size;
 	state->hdr.vmx.vmxon_pa = 0x1000;
@@ -126,13 +129,19 @@ void test_vmx_nested_state(struct kvm_vm *vm)
 	/*
 	 * Setting vmxon_pa == -1ull and vmcs_pa == -1ull exits early without
 	 * setting the nested state but flags other than eVMCS must be clear.
+	 * The eVMCS flag can be set if the enlightened VMCS capability has
+	 * been enabled.
 	 */
 	set_default_vmx_state(state, state_sz);
 	state->hdr.vmx.vmxon_pa = -1ull;
 	state->hdr.vmx.vmcs12_pa = -1ull;
 	test_nested_state_expect_einval(vm, state);
 
-	state->flags = KVM_STATE_NESTED_EVMCS;
+	state->flags &= KVM_STATE_NESTED_EVMCS;
+	if (have_evmcs) {
+		test_nested_state_expect_einval(vm, state);
+		vcpu_enable_evmcs(vm, VCPU_ID);
+	}
 	test_nested_state(vm, state);
 
 	/* It is invalid to have vmxon_pa == -1ull and SMM flags non-zero. */
@@ -217,6 +226,8 @@ int main(int argc, char *argv[])
 	struct kvm_nested_state state;
 	struct kvm_cpuid_entry2 *entry = kvm_get_supported_cpuid_entry(1);
 
+	have_evmcs = kvm_check_cap(KVM_CAP_HYPERV_ENLIGHTENED_VMCS);
+
 	if (!kvm_check_cap(KVM_CAP_NESTED_STATE)) {
 		printf("KVM_CAP_NESTED_STATE not available, skipping test\n");
 		exit(KSFT_SKIP);