vhost-user: factor out "vhost_user_write_sync"

The tails of the "vhost_user_set_vring_addr" and "vhost_user_set_u64"
functions are now byte-for-byte identical. Factor the common tail out to a
new function called "vhost_user_write_sync".

This is purely refactoring -- no observable change.

Cc: "Michael S. Tsirkin" <mst@redhat.com> (supporter:vhost)
Cc: Eugenio Perez Martin <eperezma@redhat.com>
Cc: German Maglione <gmaglione@redhat.com>
Cc: Liu Jiang <gerry@linux.alibaba.com>
Cc: Sergio Lopez Pascual <slp@redhat.com>
Cc: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Tested-by: Albert Esteve <aesteve@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20231002203221.17241-4-lersek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/virtio/vhost-user.c

@@ -1310,43 +1310,51 @@ static int enforce_reply(struct vhost_dev *dev,
     return vhost_user_get_features(dev, &dummy);
 }
 
-static int vhost_user_set_vring_addr(struct vhost_dev *dev,
-                                     struct vhost_vring_addr *addr)
+/* Note: "msg->hdr.flags" may be modified. */
+static int vhost_user_write_sync(struct vhost_dev *dev, VhostUserMsg *msg,
+                                 bool wait_for_reply)
 {
     int ret;
-    VhostUserMsg msg = {
-        .hdr.request = VHOST_USER_SET_VRING_ADDR,
-        .hdr.flags = VHOST_USER_VERSION,
-        .payload.addr = *addr,
-        .hdr.size = sizeof(msg.payload.addr),
-    };
-
-    /*
-     * wait for a reply if logging is enabled to make sure
-     * backend is actually logging changes
-     */
-    bool wait_for_reply = addr->flags & (1 << VHOST_VRING_F_LOG);
 
     if (wait_for_reply) {
         bool reply_supported = virtio_has_feature(dev->protocol_features,
                                           VHOST_USER_PROTOCOL_F_REPLY_ACK);
         if (reply_supported) {
-            msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
+            msg->hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
         }
     }
 
-    ret = vhost_user_write(dev, &msg, NULL, 0);
+    ret = vhost_user_write(dev, msg, NULL, 0);
     if (ret < 0) {
         return ret;
     }
 
     if (wait_for_reply) {
-        return enforce_reply(dev, &msg);
+        return enforce_reply(dev, msg);
     }
 
     return 0;
 }
 
+static int vhost_user_set_vring_addr(struct vhost_dev *dev,
+                                     struct vhost_vring_addr *addr)
+{
+    VhostUserMsg msg = {
+        .hdr.request = VHOST_USER_SET_VRING_ADDR,
+        .hdr.flags = VHOST_USER_VERSION,
+        .payload.addr = *addr,
+        .hdr.size = sizeof(msg.payload.addr),
+    };
+
+    /*
+     * wait for a reply if logging is enabled to make sure
+     * backend is actually logging changes
+     */
+    bool wait_for_reply = addr->flags & (1 << VHOST_VRING_F_LOG);
+
+    return vhost_user_write_sync(dev, &msg, wait_for_reply);
+}
+
 static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64,
                               bool wait_for_reply)
 {
@@ -1356,26 +1364,8 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64,
         .payload.u64 = u64,
         .hdr.size = sizeof(msg.payload.u64),
     };
-    int ret;
 
-    if (wait_for_reply) {
-        bool reply_supported = virtio_has_feature(dev->protocol_features,
-                                          VHOST_USER_PROTOCOL_F_REPLY_ACK);
-        if (reply_supported) {
-            msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
-        }
-    }
-
-    ret = vhost_user_write(dev, &msg, NULL, 0);
-    if (ret < 0) {
-        return ret;
-    }
-
-    if (wait_for_reply) {
-        return enforce_reply(dev, &msg);
-    }
-
-    return 0;
+    return vhost_user_write_sync(dev, &msg, wait_for_reply);
 }
 
 static int vhost_user_set_status(struct vhost_dev *dev, uint8_t status)