selftests: kvm/x86: Test the flags in MSR filtering and MSR exiting

When using the flags in KVM_X86_SET_MSR_FILTER and
KVM_CAP_X86_USER_SPACE_MSR it is expected that an attempt to write to
any of the unused bits will fail.  Add testing to walk over every bit
in each of the flag fields in MSR filtering and MSR exiting to verify
that unused bits return and error and used bits, i.e. valid bits,
succeed.
Signed-off-by: Aaron Lewis <aaronlewis@google.com>
Message-Id: <20220921151525.904162-6-aaronlewis@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

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

@@ -733,6 +733,89 @@ static void test_msr_permission_bitmap(void)
 	kvm_vm_free(vm);
 }
 
+#define test_user_exit_msr_ioctl(vm, cmd, arg, flag, valid_mask)	\
+({									\
+	int r = __vm_ioctl(vm, cmd, arg);				\
+									\
+	if (flag & valid_mask)						\
+		TEST_ASSERT(!r, __KVM_IOCTL_ERROR(#cmd, r));		\
+	else								\
+		TEST_ASSERT(r == -1 && errno == EINVAL,			\
+			    "Wanted EINVAL for %s with flag = 0x%llx, got  rc: %i errno: %i (%s)", \
+			    #cmd, flag, r, errno,  strerror(errno));	\
+})
+
+static void run_user_space_msr_flag_test(struct kvm_vm *vm)
+{
+	struct kvm_enable_cap cap = { .cap = KVM_CAP_X86_USER_SPACE_MSR };
+	int nflags = sizeof(cap.args[0]) * BITS_PER_BYTE;
+	int rc;
+	int i;
+
+	rc = kvm_check_cap(KVM_CAP_X86_USER_SPACE_MSR);
+	TEST_ASSERT(rc, "KVM_CAP_X86_USER_SPACE_MSR is available");
+
+	for (i = 0; i < nflags; i++) {
+		cap.args[0] = BIT_ULL(i);
+		test_user_exit_msr_ioctl(vm, KVM_ENABLE_CAP, &cap,
+			   BIT_ULL(i), KVM_MSR_EXIT_REASON_VALID_MASK);
+	}
+}
+
+static void run_msr_filter_flag_test(struct kvm_vm *vm)
+{
+	u64 deny_bits = 0;
+	struct kvm_msr_filter filter = {
+		.flags = KVM_MSR_FILTER_DEFAULT_ALLOW,
+		.ranges = {
+			{
+				.flags = KVM_MSR_FILTER_READ,
+				.nmsrs = 1,
+				.base = 0,
+				.bitmap = (uint8_t *)&deny_bits,
+			},
+		},
+	};
+	int nflags;
+	int rc;
+	int i;
+
+	rc = kvm_check_cap(KVM_CAP_X86_MSR_FILTER);
+	TEST_ASSERT(rc, "KVM_CAP_X86_MSR_FILTER is available");
+
+	nflags = sizeof(filter.flags) * BITS_PER_BYTE;
+	for (i = 0; i < nflags; i++) {
+		filter.flags = BIT_ULL(i);
+		test_user_exit_msr_ioctl(vm, KVM_X86_SET_MSR_FILTER, &filter,
+			   BIT_ULL(i), KVM_MSR_FILTER_VALID_MASK);
+	}
+
+	filter.flags = KVM_MSR_FILTER_DEFAULT_ALLOW;
+	nflags = sizeof(filter.ranges[0].flags) * BITS_PER_BYTE;
+	for (i = 0; i < nflags; i++) {
+		filter.ranges[0].flags = BIT_ULL(i);
+		test_user_exit_msr_ioctl(vm, KVM_X86_SET_MSR_FILTER, &filter,
+			   BIT_ULL(i), KVM_MSR_FILTER_RANGE_VALID_MASK);
+	}
+}
+
+/* Test that attempts to write to the unused bits in a flag fails. */
+static void test_user_exit_msr_flags(void)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+
+	vm = vm_create_with_one_vcpu(&vcpu, NULL);
+
+	/* Test flags for KVM_CAP_X86_USER_SPACE_MSR. */
+	run_user_space_msr_flag_test(vm);
+
+	/* Test flags and range flags for KVM_X86_SET_MSR_FILTER. */
+	run_msr_filter_flag_test(vm);
+
+	kvm_vm_free(vm);
+}
+
 int main(int argc, char *argv[])
 {
 	/* Tell stdout not to buffer its content */
@@ -744,5 +827,7 @@ int main(int argc, char *argv[])
 
 	test_msr_permission_bitmap();
 
+	test_user_exit_msr_flags();
+
 	return 0;
 }