On Mon, 19 Sep 2016 14:28:03 +0100
Stefan Hajnoczi <stefa...@redhat.com> wrote:
> 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 <stefa...@redhat.com>
> ---
FWIW
Acked-by: Greg Kurz <gr...@kaod.org>
> hw/virtio/virtio.c | 27 +++++++++++++++++++++++++--
> include/hw/virtio/virtio.h | 2 ++
> 2 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index fcf3358..adcef45 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:
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index f05559d..ad1e2d6 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -152,6 +152,8 @@ void *virtqueue_alloc_element(size_t sz, unsigned
> out_num, unsigned in_num);
> void virtqueue_push(VirtQueue *vq, const VirtQueueElement *elem,
> unsigned int len);
> void virtqueue_flush(VirtQueue *vq, unsigned int count);
> +void virtqueue_detach_element(VirtQueue *vq, const VirtQueueElement *elem,
> + unsigned int len);
> void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
> unsigned int len);
> bool virtqueue_rewind(VirtQueue *vq, unsigned int num);
