diff --git a/arch/um/drivers/vhost_user.h b/arch/um/drivers/vhost_user.h
index 8aee9919581e..45ff5ea22fea 100644
--- a/arch/um/drivers/vhost_user.h
+++ b/arch/um/drivers/vhost_user.h
@@ -6,9 +6,11 @@
 
 /* Message flags */
 #define VHOST_USER_FLAG_REPLY		BIT(2)
+#define VHOST_USER_FLAG_NEED_REPLY	BIT(3)
 /* Feature bits */
 #define VHOST_USER_F_PROTOCOL_FEATURES	30
 /* Protocol feature bits */
+#define VHOST_USER_PROTOCOL_F_REPLY_ACK		3
 #define VHOST_USER_PROTOCOL_F_SLAVE_REQ		5
 #define VHOST_USER_PROTOCOL_F_CONFIG		9
 /* Vring state index masks */
@@ -20,7 +22,8 @@
 /* Supported transport features */
 #define VHOST_USER_SUPPORTED_F		BIT_ULL(VHOST_USER_F_PROTOCOL_FEATURES)
 /* Supported protocol features */
-#define VHOST_USER_SUPPORTED_PROTOCOL_F	(BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ) | \
+#define VHOST_USER_SUPPORTED_PROTOCOL_F	(BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK) | \
+					 BIT_ULL(VHOST_USER_PROTOCOL_F_SLAVE_REQ) | \
 					 BIT_ULL(VHOST_USER_PROTOCOL_F_CONFIG))
 
 enum vhost_user_request {
diff --git a/arch/um/drivers/virtio_uml.c b/arch/um/drivers/virtio_uml.c
index ea4d9c1784d2..fc8c52cff5aa 100644
--- a/arch/um/drivers/virtio_uml.c
+++ b/arch/um/drivers/virtio_uml.c
@@ -160,30 +160,64 @@ static int vhost_user_recv_req(struct virtio_uml_device *vu_dev,
 	if (rc)
 		return rc;
 
-	if (msg->header.flags != VHOST_USER_VERSION)
+	if ((msg->header.flags & ~VHOST_USER_FLAG_NEED_REPLY) !=
+			VHOST_USER_VERSION)
 		return -EPROTO;
 
 	return 0;
 }
 
 static int vhost_user_send(struct virtio_uml_device *vu_dev,
-			   struct vhost_user_msg *msg,
+			   bool need_response, struct vhost_user_msg *msg,
 			   int *fds, size_t num_fds)
 {
 	size_t size = sizeof(msg->header) + msg->header.size;
+	bool request_ack;
+	int rc;
 
 	msg->header.flags |= VHOST_USER_VERSION;
-	return full_sendmsg_fds(vu_dev->sock, msg, size, fds, num_fds);
+
+	/*
+	 * The need_response flag indicates that we already need a response,
+	 * e.g. to read the features. In these cases, don't request an ACK as
+	 * it is meaningless. Also request an ACK only if supported.
+	 */
+	request_ack = !need_response;
+	if (!(vu_dev->protocol_features &
+			BIT_ULL(VHOST_USER_PROTOCOL_F_REPLY_ACK)))
+		request_ack = false;
+
+	if (request_ack)
+		msg->header.flags |= VHOST_USER_FLAG_NEED_REPLY;
+
+	rc = full_sendmsg_fds(vu_dev->sock, msg, size, fds, num_fds);
+	if (rc < 0)
+		return rc;
+
+	if (request_ack) {
+		uint64_t status;
+
+		rc = vhost_user_recv_u64(vu_dev, &status);
+		if (rc)
+			return rc;
+
+		if (status) {
+			vu_err(vu_dev, "slave reports error: %llu\n", status);
+			return -EIO;
+		}
+	}
+
+	return 0;
 }
 
 static int vhost_user_send_no_payload(struct virtio_uml_device *vu_dev,
-				      u32 request)
+				      bool need_response, u32 request)
 {
 	struct vhost_user_msg msg = {
 		.header.request = request,
 	};
 
-	return vhost_user_send(vu_dev, &msg, NULL, 0);
+	return vhost_user_send(vu_dev, need_response, &msg, NULL, 0);
 }
 
 static int vhost_user_send_no_payload_fd(struct virtio_uml_device *vu_dev,
@@ -193,7 +227,7 @@ static int vhost_user_send_no_payload_fd(struct virtio_uml_device *vu_dev,
 		.header.request = request,
 	};
 
-	return vhost_user_send(vu_dev, &msg, &fd, 1);
+	return vhost_user_send(vu_dev, false, &msg, &fd, 1);
 }
 
 static int vhost_user_send_u64(struct virtio_uml_device *vu_dev,
@@ -205,18 +239,19 @@ static int vhost_user_send_u64(struct virtio_uml_device *vu_dev,
 		.payload.integer = value,
 	};
 
-	return vhost_user_send(vu_dev, &msg, NULL, 0);
+	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
 }
 
 static int vhost_user_set_owner(struct virtio_uml_device *vu_dev)
 {
-	return vhost_user_send_no_payload(vu_dev, VHOST_USER_SET_OWNER);
+	return vhost_user_send_no_payload(vu_dev, false, VHOST_USER_SET_OWNER);
 }
 
 static int vhost_user_get_features(struct virtio_uml_device *vu_dev,
 				   u64 *features)
 {
-	int rc = vhost_user_send_no_payload(vu_dev, VHOST_USER_GET_FEATURES);
+	int rc = vhost_user_send_no_payload(vu_dev, true,
+					    VHOST_USER_GET_FEATURES);
 
 	if (rc)
 		return rc;
@@ -232,7 +267,7 @@ static int vhost_user_set_features(struct virtio_uml_device *vu_dev,
 static int vhost_user_get_protocol_features(struct virtio_uml_device *vu_dev,
 					    u64 *protocol_features)
 {
-	int rc = vhost_user_send_no_payload(vu_dev,
+	int rc = vhost_user_send_no_payload(vu_dev, true,
 			VHOST_USER_GET_PROTOCOL_FEATURES);
 
 	if (rc)
@@ -247,9 +282,32 @@ static int vhost_user_set_protocol_features(struct virtio_uml_device *vu_dev,
 				   protocol_features);
 }
 
+static void vhost_user_reply(struct virtio_uml_device *vu_dev,
+			     struct vhost_user_msg *msg, int response)
+{
+	struct vhost_user_msg reply = {
+		.payload.integer = response,
+	};
+	size_t size = sizeof(reply.header) + sizeof(reply.payload.integer);
+	int rc;
+
+	reply.header = msg->header;
+	reply.header.flags &= ~VHOST_USER_FLAG_NEED_REPLY;
+	reply.header.flags |= VHOST_USER_FLAG_REPLY;
+	reply.header.size = sizeof(reply.payload.integer);
+
+	rc = full_sendmsg_fds(vu_dev->req_fd, &reply, size, NULL, 0);
+
+	if (rc)
+		vu_err(vu_dev,
+		       "sending reply to slave request failed: %d (size %zu)\n",
+		       rc, size);
+}
+
 static irqreturn_t vu_req_interrupt(int irq, void *data)
 {
 	struct virtio_uml_device *vu_dev = data;
+	int response = 1;
 	struct {
 		struct vhost_user_msg msg;
 		u8 extra_payload[512];
@@ -266,6 +324,7 @@ static irqreturn_t vu_req_interrupt(int irq, void *data)
 	switch (msg.msg.header.request) {
 	case VHOST_USER_SLAVE_CONFIG_CHANGE_MSG:
 		virtio_config_changed(&vu_dev->vdev);
+		response = 0;
 		break;
 	case VHOST_USER_SLAVE_IOTLB_MSG:
 		/* not supported - VIRTIO_F_IOMMU_PLATFORM */
@@ -276,6 +335,9 @@ static irqreturn_t vu_req_interrupt(int irq, void *data)
 		       msg.msg.header.request);
 	}
 
+	if (msg.msg.header.flags & VHOST_USER_FLAG_NEED_REPLY)
+		vhost_user_reply(vu_dev, &msg.msg, response);
+
 	return IRQ_HANDLED;
 }
 
@@ -365,7 +427,7 @@ static void vhost_user_get_config(struct virtio_uml_device *vu_dev,
 	msg->payload.config.offset = 0;
 	msg->payload.config.size = cfg_size;
 
-	rc = vhost_user_send(vu_dev, msg, NULL, 0);
+	rc = vhost_user_send(vu_dev, true, msg, NULL, 0);
 	if (rc) {
 		vu_err(vu_dev, "sending VHOST_USER_GET_CONFIG failed: %d\n",
 		       rc);
@@ -416,7 +478,7 @@ static void vhost_user_set_config(struct virtio_uml_device *vu_dev,
 	msg->payload.config.size = len;
 	memcpy(msg->payload.config.payload, buf, len);
 
-	rc = vhost_user_send(vu_dev, msg, NULL, 0);
+	rc = vhost_user_send(vu_dev, false, msg, NULL, 0);
 	if (rc)
 		vu_err(vu_dev, "sending VHOST_USER_SET_CONFIG failed: %d\n",
 		       rc);
@@ -506,7 +568,8 @@ static int vhost_user_set_mem_table(struct virtio_uml_device *vu_dev)
 			return rc;
 	}
 
-	return vhost_user_send(vu_dev, &msg, fds, msg.payload.mem_regions.num);
+	return vhost_user_send(vu_dev, false, &msg, fds,
+			       msg.payload.mem_regions.num);
 }
 
 static int vhost_user_set_vring_state(struct virtio_uml_device *vu_dev,
@@ -519,7 +582,7 @@ static int vhost_user_set_vring_state(struct virtio_uml_device *vu_dev,
 		.payload.vring_state.num = num,
 	};
 
-	return vhost_user_send(vu_dev, &msg, NULL, 0);
+	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
 }
 
 static int vhost_user_set_vring_num(struct virtio_uml_device *vu_dev,
@@ -550,7 +613,7 @@ static int vhost_user_set_vring_addr(struct virtio_uml_device *vu_dev,
 		.payload.vring_addr.log = log,
 	};
 
-	return vhost_user_send(vu_dev, &msg, NULL, 0);
+	return vhost_user_send(vu_dev, false, &msg, NULL, 0);
 }
 
 static int vhost_user_set_vring_fd(struct virtio_uml_device *vu_dev,
@@ -566,9 +629,9 @@ static int vhost_user_set_vring_fd(struct virtio_uml_device *vu_dev,
 		return -EINVAL;
 	if (fd < 0) {
 		msg.payload.integer |= VHOST_USER_VRING_POLL_MASK;
-		return vhost_user_send(vu_dev, &msg, NULL, 0);
+		return vhost_user_send(vu_dev, false, &msg, NULL, 0);
 	}
-	return vhost_user_send(vu_dev, &msg, &fd, 1);
+	return vhost_user_send(vu_dev, false, &msg, &fd, 1);
 }
 
 static int vhost_user_set_vring_call(struct virtio_uml_device *vu_dev,