2019-08-09 06:51:07

by Pankaj Gupta

Subject: [PATCH v3 2/2] virtio: decrement avail idx with buffer detach for packed ring

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 <[email protected]>
---
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

2019-08-10 18:15:02

by Michael S. Tsirkin

Subject: Re: [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 <[email protected]>

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

2019-08-12 04:48:05

by Jason Wang

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 <[email protected]>
> ---
> 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 <[email protected]>

2019-08-12 05:06:40

by Pankaj Gupta

Subject: Re: [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 <[email protected]>
>
> I would make this patch 1, not patch 2, otherwise
> patch 1 corrupts the ring.

Sure. Will post this patch as patch 1 in next version.

Thanks,
Pankaj

>
>
> > ---
> > 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
>

2019-08-12 05:38:18

by Pankaj Gupta

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 <[email protected]>
> > ---
> > 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 <[email protected]>

Thank you, Jason.

Best regards,
Pankaj

>
>
>