linux-kernel - Re: [PATCH v3 2/2] virtio: decrement avail idx with buffer detach for packed ring

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Date:   Mon, 12 Aug 2019 01:37:26 -0400 (EDT)
From:   Pankaj Gupta <pagupta@...hat.com>
To:     Jason Wang <jasowang@...hat.com>
Cc:     amit@...nel.org, mst@...hat.com, arnd@...db.de,
        gregkh@...uxfoundation.org,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, xiaohli@...hat.com
Subject: Re: [PATCH v3 2/2] virtio: decrement avail idx with buffer detach
 for packed ring


> 
> On 2019/8/9 下午2:48, 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@...hat.com>
> > ---
> >   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;
> >   	}
> 
> 
> Acked-by: Jason Wang <jasowang@...hat.com>

Thank you, Jason.

Best regards,
Pankaj

> 
> 
>