diff --git a/tools/testing/selftests/kvm/s390x/memop.c b/tools/testing/selftests/kvm/s390x/memop.c
index d19c3ffdea3f..b9b673acb766 100644
--- a/tools/testing/selftests/kvm/s390x/memop.c
+++ b/tools/testing/selftests/kvm/s390x/memop.c
@@ -18,71 +18,82 @@
 static uint8_t mem1[65536];
 static uint8_t mem2[65536];
 
-static void guest_code(void)
-{
-	int i;
+struct test_default {
+	struct kvm_vm *kvm_vm;
+	struct kvm_run *run;
+	int size;
+};
 
-	for (;;) {
-		for (i = 0; i < sizeof(mem2); i++)
-			mem2[i] = mem1[i];
-		GUEST_SYNC(0);
-	}
+static struct test_default test_default_init(void *guest_code)
+{
+	struct test_default t;
+
+	t.size = min((size_t)kvm_check_cap(KVM_CAP_S390_MEM_OP), sizeof(mem1));
+	t.kvm_vm = vm_create_default(VCPU_ID, 0, guest_code);
+	t.run = vcpu_state(t.kvm_vm, VCPU_ID);
+	return t;
 }
 
-int main(int argc, char *argv[])
+static void guest_copy(void)
 {
-	struct kvm_vm *vm;
-	struct kvm_run *run;
+	memcpy(&mem2, &mem1, sizeof(mem2));
+	GUEST_SYNC(0);
+}
+
+static void test_copy(void)
+{
+	struct test_default t = test_default_init(guest_copy);
 	struct kvm_s390_mem_op ksmo;
-	int rv, i, maxsize;
-
-	setbuf(stdout, NULL);	/* Tell stdout not to buffer its content */
-
-	maxsize = kvm_check_cap(KVM_CAP_S390_MEM_OP);
-	if (!maxsize) {
-		print_skip("CAP_S390_MEM_OP not supported");
-		exit(KSFT_SKIP);
-	}
-	if (maxsize > sizeof(mem1))
-		maxsize = sizeof(mem1);
-
-	/* Create VM */
-	vm = vm_create_default(VCPU_ID, 0, guest_code);
-	run = vcpu_state(vm, VCPU_ID);
+	int i;
 
 	for (i = 0; i < sizeof(mem1); i++)
 		mem1[i] = i * i + i;
 
 	/* Set the first array */
-	ksmo.gaddr = addr_gva2gpa(vm, (uintptr_t)mem1);
+	ksmo.gaddr = addr_gva2gpa(t.kvm_vm, (uintptr_t)mem1);
 	ksmo.flags = 0;
-	ksmo.size = maxsize;
+	ksmo.size = t.size;
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_WRITE;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.ar = 0;
-	vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 
 	/* Let the guest code copy the first array to the second */
-	vcpu_run(vm, VCPU_ID);
-	TEST_ASSERT(run->exit_reason == KVM_EXIT_S390_SIEIC,
+	vcpu_run(t.kvm_vm, VCPU_ID);
+	TEST_ASSERT(t.run->exit_reason == KVM_EXIT_S390_SIEIC,
 		    "Unexpected exit reason: %u (%s)\n",
-		    run->exit_reason,
-		    exit_reason_str(run->exit_reason));
+		    t.run->exit_reason,
+		    exit_reason_str(t.run->exit_reason));
 
 	memset(mem2, 0xaa, sizeof(mem2));
 
 	/* Get the second array */
 	ksmo.gaddr = (uintptr_t)mem2;
 	ksmo.flags = 0;
-	ksmo.size = maxsize;
+	ksmo.size = t.size;
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_READ;
 	ksmo.buf = (uintptr_t)mem2;
 	ksmo.ar = 0;
-	vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 
-	TEST_ASSERT(!memcmp(mem1, mem2, maxsize),
+	TEST_ASSERT(!memcmp(mem1, mem2, t.size),
 		    "Memory contents do not match!");
 
+	kvm_vm_free(t.kvm_vm);
+}
+
+static void guest_idle(void)
+{
+	for (;;)
+		GUEST_SYNC(0);
+}
+
+static void test_errors(void)
+{
+	struct test_default t = test_default_init(guest_idle);
+	struct kvm_s390_mem_op ksmo;
+	int rv;
+
 	/* Check error conditions - first bad size: */
 	ksmo.gaddr = (uintptr_t)mem1;
 	ksmo.flags = 0;
@@ -90,7 +101,7 @@ int main(int argc, char *argv[])
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_WRITE;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.ar = 0;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && errno == E2BIG, "ioctl allows insane sizes");
 
 	/* Zero size: */
@@ -100,65 +111,65 @@ int main(int argc, char *argv[])
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_WRITE;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.ar = 0;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && (errno == EINVAL || errno == ENOMEM),
 		    "ioctl allows 0 as size");
 
 	/* Bad flags: */
 	ksmo.gaddr = (uintptr_t)mem1;
 	ksmo.flags = -1;
-	ksmo.size = maxsize;
+	ksmo.size = t.size;
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_WRITE;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.ar = 0;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && errno == EINVAL, "ioctl allows all flags");
 
 	/* Bad operation: */
 	ksmo.gaddr = (uintptr_t)mem1;
 	ksmo.flags = 0;
-	ksmo.size = maxsize;
+	ksmo.size = t.size;
 	ksmo.op = -1;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.ar = 0;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && errno == EINVAL, "ioctl allows bad operations");
 
 	/* Bad guest address: */
 	ksmo.gaddr = ~0xfffUL;
 	ksmo.flags = KVM_S390_MEMOP_F_CHECK_ONLY;
-	ksmo.size = maxsize;
+	ksmo.size = t.size;
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_WRITE;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.ar = 0;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv > 0, "ioctl does not report bad guest memory access");
 
 	/* Bad host address: */
 	ksmo.gaddr = (uintptr_t)mem1;
 	ksmo.flags = 0;
-	ksmo.size = maxsize;
+	ksmo.size = t.size;
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_WRITE;
 	ksmo.buf = 0;
 	ksmo.ar = 0;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && errno == EFAULT,
 		    "ioctl does not report bad host memory address");
 
 	/* Bad access register: */
-	run->psw_mask &= ~(3UL << (63 - 17));
-	run->psw_mask |= 1UL << (63 - 17);  /* Enable AR mode */
-	vcpu_run(vm, VCPU_ID);              /* To sync new state to SIE block */
+	t.run->psw_mask &= ~(3UL << (63 - 17));
+	t.run->psw_mask |= 1UL << (63 - 17);  /* Enable AR mode */
+	vcpu_run(t.kvm_vm, VCPU_ID);              /* To sync new state to SIE block */
 	ksmo.gaddr = (uintptr_t)mem1;
 	ksmo.flags = 0;
-	ksmo.size = maxsize;
+	ksmo.size = t.size;
 	ksmo.op = KVM_S390_MEMOP_LOGICAL_WRITE;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.ar = 17;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && errno == EINVAL, "ioctl allows ARs > 15");
-	run->psw_mask &= ~(3UL << (63 - 17));   /* Disable AR mode */
-	vcpu_run(vm, VCPU_ID);                  /* Run to sync new state */
+	t.run->psw_mask &= ~(3UL << (63 - 17));   /* Disable AR mode */
+	vcpu_run(t.kvm_vm, VCPU_ID);                  /* Run to sync new state */
 
 	/* Check that the SIDA calls are rejected for non-protected guests */
 	ksmo.gaddr = 0;
@@ -167,15 +178,31 @@ int main(int argc, char *argv[])
 	ksmo.op = KVM_S390_MEMOP_SIDA_READ;
 	ksmo.buf = (uintptr_t)mem1;
 	ksmo.sida_offset = 0x1c0;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && errno == EINVAL,
 		    "ioctl does not reject SIDA_READ in non-protected mode");
 	ksmo.op = KVM_S390_MEMOP_SIDA_WRITE;
-	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
+	rv = _vcpu_ioctl(t.kvm_vm, VCPU_ID, KVM_S390_MEM_OP, &ksmo);
 	TEST_ASSERT(rv == -1 && errno == EINVAL,
 		    "ioctl does not reject SIDA_WRITE in non-protected mode");
 
-	kvm_vm_free(vm);
+	kvm_vm_free(t.kvm_vm);
+}
+
+int main(int argc, char *argv[])
+{
+	int memop_cap;
+
+	setbuf(stdout, NULL);	/* Tell stdout not to buffer its content */
+
+	memop_cap = kvm_check_cap(KVM_CAP_S390_MEM_OP);
+	if (!memop_cap) {
+		print_skip("CAP_S390_MEM_OP not supported");
+		exit(KSFT_SKIP);
+	}
+
+	test_copy();
+	test_errors();
 
 	return 0;
 }