diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a03530795707..9bb9d7f078fc 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8225,7 +8225,13 @@ static int emulator_read_write_onepage(unsigned long addr, void *val,
 	WARN_ON(vcpu->mmio_nr_fragments >= KVM_MAX_MMIO_FRAGMENTS);
 	frag = &vcpu->mmio_fragments[vcpu->mmio_nr_fragments++];
 	frag->gpa = gpa;
-	frag->data = val;
+	if (write && bytes <= 8u) {
+		frag->val = 0;
+		frag->data = &frag->val;
+		memcpy(&frag->val, val, bytes);
+	} else {
+		frag->data = val;
+	}
 	frag->len = bytes;
 	return X86EMUL_CONTINUE;
 }
@@ -8240,6 +8246,9 @@ static int emulator_read_write(struct x86_emulate_ctxt *ctxt,
 	gpa_t gpa;
 	int rc;
 
+	if (WARN_ON_ONCE((bytes > 8u || !ops->write) && object_is_on_stack(val)))
+		return X86EMUL_UNHANDLEABLE;
+
 	if (ops->read_write_prepare &&
 		  ops->read_write_prepare(vcpu, val, bytes))
 		return X86EMUL_CONTINUE;
@@ -11846,6 +11855,9 @@ static int complete_emulated_mmio(struct kvm_vcpu *vcpu)
 		frag++;
 		vcpu->mmio_cur_fragment++;
 	} else {
+		if (WARN_ON_ONCE(frag->data == &frag->val))
+			return -EIO;
+
 		/* Go forward to the next mmio piece. */
 		frag->data += len;
 		frag->gpa += len;
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 34759a262b28..abb309372035 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -318,7 +318,8 @@ static inline bool kvm_vcpu_can_poll(ktime_t cur, ktime_t stop)
 struct kvm_mmio_fragment {
 	gpa_t gpa;
 	void *data;
-	unsigned len;
+	u64 val;
+	unsigned int len;
 };
 
 struct kvm_vcpu {