virtio_ring: split: extract the logic of vring init

Separate the logic of initializing vring, and subsequent patches will
call it separately.

This function completes the variable initialization of split vring. It
together with the logic of atatch constitutes the initialization of
vring.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20220801063902.129329-13-xuanzhuo@linux.alibaba.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

drivers/virtio/virtio_ring.c

@@ -938,6 +938,25 @@ static void *virtqueue_detach_unused_buf_split(struct virtqueue *_vq)
 	return NULL;
 }
 
+static void virtqueue_vring_init_split(struct vring_virtqueue_split *vring_split,
+				       struct vring_virtqueue *vq)
+{
+	struct virtio_device *vdev;
+
+	vdev = vq->vq.vdev;
+
+	vring_split->avail_flags_shadow = 0;
+	vring_split->avail_idx_shadow = 0;
+
+	/* No callback?  Tell other side not to bother us. */
+	if (!vq->vq.callback) {
+		vring_split->avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
+		if (!vq->event)
+			vring_split->vring.avail->flags = cpu_to_virtio16(vdev,
+					vring_split->avail_flags_shadow);
+	}
+}
+
 static int vring_alloc_state_extra_split(struct vring_virtqueue_split *vring_split)
 {
 	struct vring_desc_state_split *state;
@@ -2302,16 +2321,6 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
 	vq->split.queue_size_in_bytes = 0;
 
 	vq->split.vring = vring_split->vring;
-	vq->split.avail_flags_shadow = 0;
-	vq->split.avail_idx_shadow = 0;
-
-	/* No callback?  Tell other side not to bother us. */
-	if (!callback) {
-		vq->split.avail_flags_shadow |= VRING_AVAIL_F_NO_INTERRUPT;
-		if (!vq->event)
-			vq->split.vring.avail->flags = cpu_to_virtio16(vdev,
-					vq->split.avail_flags_shadow);
-	}
 
 	err = vring_alloc_state_extra_split(vring_split);
 	if (err) {
@@ -2325,6 +2334,8 @@ static struct virtqueue *__vring_new_virtqueue(unsigned int index,
 	vq->split.desc_state = vring_split->desc_state;
 	vq->split.desc_extra = vring_split->desc_extra;
 
+	virtqueue_vring_init_split(vring_split, vq);
+
 	virtqueue_init(vq, vring_split->vring.num);
 
 	spin_lock(&vdev->vqs_list_lock);