diff options
| -rw-r--r-- | hw/virtio/virtio.c | 22 | ||||
| -rw-r--r-- | include/hw/virtio/virtio.h | 1 |
2 files changed, 23 insertions, 0 deletions
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index e8a13a50bf..fcf3358d6c 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -272,6 +272,28 @@ void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem, virtqueue_unmap_sg(vq, elem, len); } +/* virtqueue_rewind: + * @vq: The #VirtQueue + * @num: Number of elements to push back + * + * Pretend that elements weren't popped from the virtqueue. The next + * virtqueue_pop() will refetch the oldest element. + * + * Use virtqueue_discard() instead if you have a VirtQueueElement. + * + * Returns: true on success, false if @num is greater than the number of in use + * elements. + */ +bool virtqueue_rewind(VirtQueue *vq, unsigned int num) +{ + if (num > vq->inuse) { + return false; + } + vq->last_avail_idx -= num; + vq->inuse -= num; + return true; +} + void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len, unsigned int idx) { diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h index d2490c1975..f05559d569 100644 --- a/include/hw/virtio/virtio.h +++ b/include/hw/virtio/virtio.h @@ -154,6 +154,7 @@ void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem, void virtqueue_flush(VirtQueue *vq, unsigned int count); void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len); +bool virtqueue_rewind(VirtQueue *vq, unsigned int num); void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len, unsigned int idx); |