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SubjectRe: [PATCH v3 2/2] virtio: decrement avail idx with buffer detach for packed ring
On Fri, Aug 09, 2019 at 12:18:47PM +0530, Pankaj Gupta wrote:
> This patch decrements 'next_avail_idx' count when detaching a buffer
> from vq for packed ring code. Split ring code already does this in
> virtqueue_detach_unused_buf_split function. This updates the
> 'next_avail_idx' to the previous correct index after an unused buffer
> is detatched from the vq.
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>

I would make this patch 1, not patch 2, otherwise
patch 1 corrupts the ring.


> ---
> drivers/virtio/virtio_ring.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index c8be1c4f5b55..7c69181113e2 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -1537,6 +1537,12 @@ static void *virtqueue_detach_unused_buf_packed(struct virtqueue *_vq)
> /* detach_buf clears data, so grab it now. */
> buf = vq->packed.desc_state[i].data;
> detach_buf_packed(vq, i, NULL);
> + vq->packed.next_avail_idx--;
> + if (vq->packed.next_avail_idx < 0) {
> + vq->packed.next_avail_idx = vq->packed.vring.num - 1;
> + vq->packed.avail_wrap_counter ^= 1;
> + }
> +
> END_USE(vq);
> return buf;
> }
> --
> 2.20.1

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