tools/virtio: Extract virtqueue initialization in vq_reset

So we can reset after that in the main loop.
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Link: https://lore.kernel.org/r/20200418102217.32327-7-eperezma@redhat.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

tools/virtio/virtio_test.c

@@ -94,6 +94,19 @@ void vhost_vq_setup(struct vdev_info *dev, struct vq_info *info)
 	assert(r >= 0);
 }
 
+static void vq_reset(struct vq_info *info, int num, struct virtio_device *vdev)
+{
+	if (info->vq)
+		vring_del_virtqueue(info->vq);
+
+	memset(info->ring, 0, vring_size(num, 4096));
+	vring_init(&info->vring, num, info->ring, 4096);
+	info->vq = __vring_new_virtqueue(info->idx, info->vring, vdev, true,
+					 false, vq_notify, vq_callback, "test");
+	assert(info->vq);
+	info->vq->priv = info;
+}
+
 static void vq_info_add(struct vdev_info *dev, int num)
 {
 	struct vq_info *info = &dev->vqs[dev->nvqs];
@@ -103,13 +116,7 @@ static void vq_info_add(struct vdev_info *dev, int num)
 	info->call = eventfd(0, EFD_NONBLOCK);
 	r = posix_memalign(&info->ring, 4096, vring_size(num, 4096));
 	assert(r >= 0);
-	memset(info->ring, 0, vring_size(num, 4096));
-	vring_init(&info->vring, num, info->ring, 4096);
-	info->vq =
-		__vring_new_virtqueue(info->idx, info->vring, &dev->vdev, true,
-				      false, vq_notify, vq_callback, "test");
-	assert(info->vq);
-	info->vq->priv = info;
+	vq_reset(info, num, &dev->vdev);
 	vhost_vq_setup(dev, info);
 	dev->fds[info->idx].fd = info->call;
 	dev->fds[info->idx].events = POLLIN;