diff --git a/tools/testing/selftests/kvm/mmu_stress_test.c b/tools/testing/selftests/kvm/mmu_stress_test.c
index 0918fade9267..d9c76b4c0d88 100644
--- a/tools/testing/selftests/kvm/mmu_stress_test.c
+++ b/tools/testing/selftests/kvm/mmu_stress_test.c
@@ -17,6 +17,8 @@
 #include "processor.h"
 #include "ucall_common.h"
 
+static bool mprotect_ro_done;
+
 static void guest_code(uint64_t start_gpa, uint64_t end_gpa, uint64_t stride)
 {
 	uint64_t gpa;
@@ -32,6 +34,42 @@ static void guest_code(uint64_t start_gpa, uint64_t end_gpa, uint64_t stride)
 		*((volatile uint64_t *)gpa);
 	GUEST_SYNC(2);
 
+	/*
+	 * Write to the region while mprotect(PROT_READ) is underway.  Keep
+	 * looping until the memory is guaranteed to be read-only, otherwise
+	 * vCPUs may complete their writes and advance to the next stage
+	 * prematurely.
+	 *
+	 * For architectures that support skipping the faulting instruction,
+	 * generate the store via inline assembly to ensure the exact length
+	 * of the instruction is known and stable (vcpu_arch_put_guest() on
+	 * fixed-length architectures should work, but the cost of paranoia
+	 * is low in this case).  For x86, hand-code the exact opcode so that
+	 * there is no room for variability in the generated instruction.
+	 */
+	do {
+		for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
+#ifdef __x86_64__
+			asm volatile(".byte 0x48,0x89,0x00" :: "a"(gpa) : "memory"); /* mov %rax, (%rax) */
+#elif defined(__aarch64__)
+			asm volatile("str %0, [%0]" :: "r" (gpa) : "memory");
+#else
+			vcpu_arch_put_guest(*((volatile uint64_t *)gpa), gpa);
+#endif
+	} while (!READ_ONCE(mprotect_ro_done));
+
+	/*
+	 * Only architectures that write the entire range can explicitly sync,
+	 * as other architectures will be stuck on the write fault.
+	 */
+#if defined(__x86_64__) || defined(__aarch64__)
+	GUEST_SYNC(3);
+#endif
+
+	for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
+		vcpu_arch_put_guest(*((volatile uint64_t *)gpa), gpa);
+	GUEST_SYNC(4);
+
 	GUEST_ASSERT(0);
 }
 
@@ -79,6 +117,7 @@ static void *vcpu_worker(void *data)
 	struct vcpu_info *info = data;
 	struct kvm_vcpu *vcpu = info->vcpu;
 	struct kvm_vm *vm = vcpu->vm;
+	int r;
 
 	vcpu_args_set(vcpu, 3, info->start_gpa, info->end_gpa, vm->page_size);
 
@@ -101,6 +140,57 @@ static void *vcpu_worker(void *data)
 
 	/* Stage 2, read all of guest memory, which is now read-only. */
 	run_vcpu(vcpu, 2);
+
+	/*
+	 * Stage 3, write guest memory and verify KVM returns -EFAULT for once
+	 * the mprotect(PROT_READ) lands.  Only architectures that support
+	 * validating *all* of guest memory sync for this stage, as vCPUs will
+	 * be stuck on the faulting instruction for other architectures.  Go to
+	 * stage 3 without a rendezvous
+	 */
+	do {
+		r = _vcpu_run(vcpu);
+	} while (!r);
+	TEST_ASSERT(r == -1 && errno == EFAULT,
+		    "Expected EFAULT on write to RO memory, got r = %d, errno = %d", r, errno);
+
+#if defined(__x86_64__) || defined(__aarch64__)
+	/*
+	 * Verify *all* writes from the guest hit EFAULT due to the VMA now
+	 * being read-only.  x86 and arm64 only at this time as skipping the
+	 * instruction that hits the EFAULT requires advancing the program
+	 * counter, which is arch specific and relies on inline assembly.
+	 */
+#ifdef __x86_64__
+	vcpu->run->kvm_valid_regs = KVM_SYNC_X86_REGS;
+#endif
+	for (;;) {
+		r = _vcpu_run(vcpu);
+		if (!r)
+			break;
+		TEST_ASSERT_EQ(errno, EFAULT);
+#if defined(__x86_64__)
+		WRITE_ONCE(vcpu->run->kvm_dirty_regs, KVM_SYNC_X86_REGS);
+		vcpu->run->s.regs.regs.rip += 3;
+#elif defined(__aarch64__)
+		vcpu_set_reg(vcpu, ARM64_CORE_REG(regs.pc),
+			     vcpu_get_reg(vcpu, ARM64_CORE_REG(regs.pc)) + 4);
+#endif
+
+	}
+	assert_sync_stage(vcpu, 3);
+#endif /* __x86_64__ || __aarch64__ */
+	rendezvous_with_boss();
+
+	/*
+	 * Stage 4.  Run to completion, waiting for mprotect(PROT_WRITE) to
+	 * make the memory writable again.
+	 */
+	do {
+		r = _vcpu_run(vcpu);
+	} while (r && errno == EFAULT);
+	TEST_ASSERT_EQ(r, 0);
+	assert_sync_stage(vcpu, 4);
 	rendezvous_with_boss();
 
 	return NULL;
@@ -183,7 +273,7 @@ int main(int argc, char *argv[])
 	const uint64_t start_gpa = SZ_4G;
 	const int first_slot = 1;
 
-	struct timespec time_start, time_run1, time_reset, time_run2, time_ro;
+	struct timespec time_start, time_run1, time_reset, time_run2, time_ro, time_rw;
 	uint64_t max_gpa, gpa, slot_size, max_mem, i;
 	int max_slots, slot, opt, fd;
 	bool hugepages = false;
@@ -288,19 +378,27 @@ int main(int argc, char *argv[])
 	rendezvous_with_vcpus(&time_run2, "run 2");
 
 	mprotect(mem, slot_size, PROT_READ);
+	usleep(10);
+	mprotect_ro_done = true;
+	sync_global_to_guest(vm, mprotect_ro_done);
+
 	rendezvous_with_vcpus(&time_ro, "mprotect RO");
+	mprotect(mem, slot_size, PROT_READ | PROT_WRITE);
+	rendezvous_with_vcpus(&time_rw, "mprotect RW");
 
+	time_rw    = timespec_sub(time_rw,     time_ro);
 	time_ro    = timespec_sub(time_ro,     time_run2);
 	time_run2  = timespec_sub(time_run2,   time_reset);
 	time_reset = timespec_sub(time_reset,  time_run1);
 	time_run1  = timespec_sub(time_run1,   time_start);
 
 	pr_info("run1 = %ld.%.9lds, reset = %ld.%.9lds, run2 = %ld.%.9lds, "
-		"ro = %ld.%.9lds\n",
+		"ro = %ld.%.9lds, rw = %ld.%.9lds\n",
 		time_run1.tv_sec, time_run1.tv_nsec,
 		time_reset.tv_sec, time_reset.tv_nsec,
 		time_run2.tv_sec, time_run2.tv_nsec,
-		time_ro.tv_sec, time_ro.tv_nsec);
+		time_ro.tv_sec, time_ro.tv_nsec,
+		time_rw.tv_sec, time_rw.tv_nsec);
 
 	/*
 	 * Delete even numbered slots (arbitrary) and unmap the first half of
