1 files changed, 56 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/x86_64/xss_msr_test.c b/tools/testing/selftests/kvm/x86_64/xss_msr_test.c
new file mode 100644
index 000000000..e0ddf4736
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/xss_msr_test.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019, Google LLC.
+ *
+ * Tests for the IA32_XSS MSR.
+ */
+
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "vmx.h"
+
+#define MSR_BITS      64
+
+int main(int argc, char *argv[])
+{
+	bool xss_in_msr_list;
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+	uint64_t xss_val;
+	int i, r;
+
+	/* Create VM */
+	vm = vm_create_with_one_vcpu(&vcpu, NULL);
+
+	TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_XSAVES));
+
+	xss_val = vcpu_get_msr(vcpu, MSR_IA32_XSS);
+	TEST_ASSERT(xss_val == 0,
+		    "MSR_IA32_XSS should be initialized to zero\n");
+
+	vcpu_set_msr(vcpu, MSR_IA32_XSS, xss_val);
+
+	/*
+	 * At present, KVM only supports a guest IA32_XSS value of 0. Verify
+	 * that trying to set the guest IA32_XSS to an unsupported value fails.
+	 * Also, in the future when a non-zero value succeeds check that
+	 * IA32_XSS is in the list of MSRs to save/restore.
+	 */
+	xss_in_msr_list = kvm_msr_is_in_save_restore_list(MSR_IA32_XSS);
+	for (i = 0; i < MSR_BITS; ++i) {
+		r = _vcpu_set_msr(vcpu, MSR_IA32_XSS, 1ull << i);
+
+		/*
+		 * Setting a list of MSRs returns the entry that "faulted", or
+		 * the last entry +1 if all MSRs were successfully written.
+		 */
+		TEST_ASSERT(!r || r == 1, KVM_IOCTL_ERROR(KVM_SET_MSRS, r));
+		TEST_ASSERT(r != 1 || xss_in_msr_list,
+			    "IA32_XSS was able to be set, but was not in save/restore list");
+	}
+
+	kvm_vm_free(vm);
+}