diff options
| author | Stefan Hajnoczi <stefanha@redhat.com> | 2016-09-19 14:28:03 +0100 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2016-10-10 01:16:58 +0300 |
| commit | 2640d2a5ff08978d67bd87518d05d6b499488c9a (patch) | |
| tree | 88a07dc902c862587b0576bb7ebf0b9df12929a7 /hw/virtio/virtio.c | |
| parent | af78c91f574dcde3f0bd90914417e3570c5e9c69 (diff) | |
virtio: add virtio_detach_element()
During device reset or similar situations a VirtQueueElement needs to be
freed without pushing it onto the used ring or rewinding the virtqueue.
Extract a new function to do this.
Later patches add virtio_detach_element() calls to existing device so
that scatter-gather lists are unmapped and vq->inuse goes back to zero
during device reset. Currently some devices don't bother and simply
call g_free(elem) which is not a clean way to throw away a
VirtQueueElement.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Greg Kurz <groug@kaod.org>
Reviewed-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/virtio/virtio.c')
| -rw-r--r-- | hw/virtio/virtio.c | 27 |
1 files changed, 25 insertions, 2 deletions
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 18ce333457..46f79c9e14 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -264,12 +264,35 @@ static void virtqueue_unmap_sg(VirtQueue *vq, const VirtQueueElement *elem, 0, elem->out_sg[i].iov_len); } +/* virtqueue_detach_element: + * @vq: The #VirtQueue + * @elem: The #VirtQueueElement + * @len: number of bytes written + * + * Detach the element from the virtqueue. This function is suitable for device + * reset or other situations where a #VirtQueueElement is simply freed and will + * not be pushed or discarded. + */ +void virtqueue_detach_element(VirtQueue *vq, const VirtQueueElement *elem, + unsigned int len) +{ + vq->inuse--; + virtqueue_unmap_sg(vq, elem, len); +} + +/* virtqueue_discard: + * @vq: The #VirtQueue + * @elem: The #VirtQueueElement + * @len: number of bytes written + * + * Pretend the most recent element wasn't popped from the virtqueue. The next + * call to virtqueue_pop() will refetch the element. + */ void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem, unsigned int len) { vq->last_avail_idx--; - vq->inuse--; - virtqueue_unmap_sg(vq, elem, len); + virtqueue_detach_element(vq, elem, len); } /* virtqueue_rewind: |