netdev - Re: [PATCH vhost v3 2/4] virtio_net: big mode skip the unmap check

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Date: Thu, 25 Apr 2024 14:04:38 +0800
From: Jason Wang <jasowang@...hat.com>
To: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc: virtualization@...ts.linux.dev, "Michael S. Tsirkin" <mst@...hat.com>, 
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH vhost v3 2/4] virtio_net: big mode skip the unmap check

On Thu, Apr 25, 2024 at 10:37 AM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> On Thu, 25 Apr 2024 10:11:55 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > On Wed, Apr 24, 2024 at 4:17 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> > >
> > > The virtio-net big mode did not enable premapped mode,
> > > so we did not need to check the unmap. And the subsequent
> > > commit will remove the failover code for failing enable
> > > premapped for merge and small mode. So we need to remove
> > > the checking do_dma code in the big mode path.
> > >
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > > ---
> > >  drivers/net/virtio_net.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index c22d1118a133..16d84c95779c 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -820,7 +820,7 @@ static void virtnet_rq_unmap_free_buf(struct virtqueue *vq, void *buf)
> > >
> > >         rq = &vi->rq[i];
> > >
> > > -       if (rq->do_dma)
> > > +       if (!vi->big_packets || vi->mergeable_rx_bufs)
> >
> > This seems to be equivalent to
> >
> > if (!vi->big_packets)
>
>
> If VIRTIO_NET_F_MRG_RXBUF and guest_gso are coexisting,
> big_packets and mergeable_rx_bufs are all true.
> !vi->big_packets only means the small.
>
> Did I miss something?

Nope, you are right.

The big_packets are kind of misleading as it doesn't mean big mode.

Acked-by: Jason Wang <jasowang@...hat.com>

Thanks

>
> Thanks.
>
>
> >
> >
> > >                 virtnet_rq_unmap(rq, buf, 0);
> > >
> > >         virtnet_rq_free_buf(vi, rq, buf);
> > > @@ -2128,7 +2128,7 @@ static int virtnet_receive(struct receive_queue *rq, int budget,
> > >                 }
> > >         } else {
> > >                 while (packets < budget &&
> > > -                      (buf = virtnet_rq_get_buf(rq, &len, NULL)) != NULL) {
> > > +                      (buf = virtqueue_get_buf(rq->vq, &len)) != NULL) {
> > >                         receive_buf(vi, rq, buf, len, NULL, xdp_xmit, &stats);
> > >                         packets++;
> > >                 }
> >
> > Other part looks good.
> >
> > Thanks
> >
> > > --
> > > 2.32.0.3.g01195cf9f
> > >
> >
>