diff --git a/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c b/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c
index c6691cff4e199369d7176ee8798531097f354521..629dd8579b739110c5cb26f4109826d5bbc13ddb 100644
--- a/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c
+++ b/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c
@@ -3,6 +3,7 @@
 #include <fcntl.h>
 #include <pthread.h>
 #include <sched.h>
+#include <semaphore.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -26,18 +27,20 @@
 #define MEM_REGION_SIZE		0x200000
 #define MEM_REGION_SLOT		10
 
-static void guest_code(void)
+static const uint64_t MMIO_VAL = 0xbeefull;
+
+static sem_t vcpu_ready;
+
+static inline uint64_t guest_spin_on_val(uint64_t spin_val)
 {
 	uint64_t val;
 
 	do {
 		val = READ_ONCE(*((uint64_t *)MEM_REGION_GPA));
-	} while (!val);
-
-	if (val != 1)
-		ucall(UCALL_ABORT, 1, val);
+	} while (val == spin_val);
 
-	GUEST_DONE();
+	GUEST_SYNC(0);
+	return val;
 }
 
 static void *vcpu_worker(void *data)
@@ -49,25 +52,60 @@ static void *vcpu_worker(void *data)
 
 	/*
 	 * Loop until the guest is done.  Re-enter the guest on all MMIO exits,
-	 * which will occur if the guest attempts to access a memslot while it
-	 * is being moved.
+	 * which will occur if the guest attempts to access a memslot after it
+	 * has been deleted or while it is being moved .
 	 */
 	run = vcpu_state(vm, VCPU_ID);
-	do {
+
+	while (1) {
 		vcpu_run(vm, VCPU_ID);
-	} while (run->exit_reason == KVM_EXIT_MMIO);
 
-	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
-		    "Unexpected exit reason = %d", run->exit_reason);
+		if (run->exit_reason == KVM_EXIT_IO) {
+			cmd = get_ucall(vm, VCPU_ID, &uc);
+			if (cmd != UCALL_SYNC)
+				break;
+
+			sem_post(&vcpu_ready);
+			continue;
+		}
+
+		if (run->exit_reason != KVM_EXIT_MMIO)
+			break;
+
+		TEST_ASSERT(!run->mmio.is_write, "Unexpected exit mmio write");
+		TEST_ASSERT(run->mmio.len == 8,
+			    "Unexpected exit mmio size = %u", run->mmio.len);
+
+		TEST_ASSERT(run->mmio.phys_addr == MEM_REGION_GPA,
+			    "Unexpected exit mmio address = 0x%llx",
+			    run->mmio.phys_addr);
+		memcpy(run->mmio.data, &MMIO_VAL, 8);
+	}
+
+	if (run->exit_reason == KVM_EXIT_IO && cmd == UCALL_ABORT)
+		TEST_FAIL("%s at %s:%ld, val = %lu", (const char *)uc.args[0],
+			  __FILE__, uc.args[1], uc.args[2]);
 
-	cmd = get_ucall(vm, VCPU_ID, &uc);
-	TEST_ASSERT(cmd == UCALL_DONE, "Unexpected val in guest = %lu", uc.args[0]);
 	return NULL;
 }
 
-static void test_move_memory_region(void)
+static void wait_for_vcpu(void)
+{
+	struct timespec ts;
+
+	TEST_ASSERT(!clock_gettime(CLOCK_REALTIME, &ts),
+		    "clock_gettime() failed: %d\n", errno);
+
+	ts.tv_sec += 2;
+	TEST_ASSERT(!sem_timedwait(&vcpu_ready, &ts),
+		    "sem_timedwait() failed: %d\n", errno);
+
+	/* Wait for the vCPU thread to reenter the guest. */
+	usleep(100000);
+}
+
+static struct kvm_vm *spawn_vm(pthread_t *vcpu_thread, void *guest_code)
 {
-	pthread_t vcpu_thread;
 	struct kvm_vm *vm;
 	uint64_t *hva;
 	uint64_t gpa;
@@ -93,10 +131,45 @@ static void test_move_memory_region(void)
 	hva = addr_gpa2hva(vm, MEM_REGION_GPA);
 	memset(hva, 0, 2 * 4096);
 
-	pthread_create(&vcpu_thread, NULL, vcpu_worker, vm);
+	pthread_create(vcpu_thread, NULL, vcpu_worker, vm);
 
 	/* Ensure the guest thread is spun up. */
-	usleep(100000);
+	wait_for_vcpu();
+
+	return vm;
+}
+
+
+static void guest_code_move_memory_region(void)
+{
+	uint64_t val;
+
+	GUEST_SYNC(0);
+
+	/*
+	 * Spin until the memory region is moved to a misaligned address.  This
+	 * may or may not trigger MMIO, as the window where the memslot is
+	 * invalid is quite small.
+	 */
+	val = guest_spin_on_val(0);
+	GUEST_ASSERT_1(val == 1 || val == MMIO_VAL, val);
+
+	/* Spin until the memory region is realigned. */
+	val = guest_spin_on_val(MMIO_VAL);
+	GUEST_ASSERT_1(val == 1, val);
+
+	GUEST_DONE();
+}
+
+static void test_move_memory_region(void)
+{
+	pthread_t vcpu_thread;
+	struct kvm_vm *vm;
+	uint64_t *hva;
+
+	vm = spawn_vm(&vcpu_thread, guest_code_move_memory_region);
+
+	hva = addr_gpa2hva(vm, MEM_REGION_GPA);
 
 	/*
 	 * Shift the region's base GPA.  The guest should not see "2" as the
@@ -106,6 +179,11 @@ static void test_move_memory_region(void)
 	vm_mem_region_move(vm, MEM_REGION_SLOT, MEM_REGION_GPA - 4096);
 	WRITE_ONCE(*hva, 2);
 
+	/*
+	 * The guest _might_ see an invalid memslot and trigger MMIO, but it's
+	 * a tiny window.  Spin and defer the sync until the memslot is
+	 * restored and guest behavior is once again deterministic.
+	 */
 	usleep(100000);
 
 	/*
@@ -116,6 +194,9 @@ static void test_move_memory_region(void)
 
 	/* Restore the original base, the guest should see "1". */
 	vm_mem_region_move(vm, MEM_REGION_SLOT, MEM_REGION_GPA);
+	wait_for_vcpu();
+	/* Defered sync from when the memslot was misaligned (above). */
+	wait_for_vcpu();
 
 	pthread_join(vcpu_thread, NULL);