From 2640d2a5ff08978d67bd87518d05d6b499488c9a Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Mon, 19 Sep 2016 14:28:03 +0100 Subject: 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 Acked-by: Greg Kurz Reviewed-by: Ladi Prosek Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/virtio/virtio.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) (limited to 'hw') diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 18ce333..46f79c9 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: -- cgit v1.1