On Wed, 17 Aug 2022 21:57:16 +0800, Guo Zhi <qtxuning1999 at sjtu.edu.cn>
wrote:> We didn't unmask F_NEXT flag in desc_extra in the end of a chain,
> unmask it so that we can access desc_extra to get next information.
I think we should state the purpose of this.
>
> Signed-off-by: Guo Zhi <qtxuning1999 at sjtu.edu.cn>
> ---
> drivers/virtio/virtio_ring.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index a5ec724c01d8..1c1b3fa376a2 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -567,7 +567,7 @@ static inline int virtqueue_add_split(struct virtqueue
*_vq,
> }
> /* Last one doesn't continue. */
> desc[prev].flags &= cpu_to_virtio16(_vq->vdev,
~VRING_DESC_F_NEXT);
> - if (!indirect && vq->use_dma_api)
> + if (!indirect)
> vq->split.desc_extra[prev & (vq->split.vring.num - 1)].flags
&> ~VRING_DESC_F_NEXT;
>
> @@ -584,6 +584,8 @@ static inline int virtqueue_add_split(struct virtqueue
*_vq,
> total_sg * sizeof(struct vring_desc),
> VRING_DESC_F_INDIRECT,
> false);
> + vq->split.desc_extra[head & (vq->split.vring.num - 1)].flags
&> + ~VRING_DESC_F_NEXT;
This seems unnecessary.
> }
>
> /* We're using some buffers from the free list. */
> @@ -693,7 +695,7 @@ static void detach_buf_split(struct vring_virtqueue
*vq, unsigned int head,
> /* Put back on free list: unmap first-level descriptors and find end */
> i = head;
>
> - while (vq->split.vring.desc[i].flags & nextflag) {
> + while (vq->split.desc_extra[i].flags & nextflag) {
nextflag is __virtio16
You can use VRING_DESC_F_NEXT directly.
Thanks.
> vring_unmap_one_split(vq, i);
> i = vq->split.desc_extra[i].next;
> vq->vq.num_free++;
> --
> 2.17.1
>