On Tue, Jul 10, 2018 at 01:50:03PM +0800, Jason Wang wrote:

On 2018年07月09日 15:22, Tiwei Bie wrote:

quoted

@@ -1059,9 +1059,19 @@ static bool virtqueue_kick_prepare_packed(struct virtqueue *_vq)
  	 * suppressions. */
  	virtio_mb(vq->weak_barriers);
+	old = vq->next_avail_idx - vq->num_added;
+	new = vq->next_avail_idx;
+	vq->num_added = 0;
+
  	snapshot = *(u32 *)vq->vring_packed.device;

I think we should use READ_ONCE() to prevent compiler from re-reading.

I'll do it. Thanks!

Best regards,
Tiwei Bie

quoted

+	off_wrap = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot & 0xffff));
  	flags = virtio16_to_cpu(_vq->vdev, (__virtio16)(snapshot >> 16)) & 0x3;
+	wrap_counter = off_wrap >> 15;
+	event_idx = off_wrap & ~(1 << 15);
+	if (wrap_counter != vq->avail_wrap_counter)
+		event_idx -= vq->vring_packed.num;

Thanks