diff options
author | Stefan Hajnoczi <stefanha@redhat.com> | 2016-09-07 17:20:48 +0200 |
---|---|---|
committer | Michael S. Tsirkin <mst@redhat.com> | 2016-09-09 20:58:34 +0300 |
commit | 297a75e6c55d91db2704a3d6e4029d99c7df51fd (patch) | |
tree | 43f752f0502cecc089680c1a08dc6b5cb6c3da9c /hw | |
parent | 104e70cae78bd4afd95d948c6aff188f10508a9c (diff) |
virtio: add virtqueue_rewind()
virtqueue_discard() requires a VirtQueueElement but virtio-balloon does
not migrate its in-use element. Introduce a new function that is
similar to virtqueue_discard() but doesn't require a VirtQueueElement.
This will allow virtio-balloon to access element again after migration
with the usual proviso that the guest may have modified the vring since
last time.
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Roman Kagan <rkagan@virtuozzo.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'hw')
-rw-r--r-- | hw/virtio/virtio.c | 22 |
1 files changed, 22 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) { |