netdev - Re: [PATCH vhost 5/6] virtio_net: enable premapped by default

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Message-ID: <CACGkMEtZQ6FRqqzjo3Yc_uxw2uopf4+30G-33y3oi-ruHtUTUg@mail.gmail.com>
Date: Fri, 19 Apr 2024 08:44:12 +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 5/6] virtio_net: enable premapped by default

On Thu, Apr 18, 2024 at 4:37 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> On Thu, 18 Apr 2024 14:26:33 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > On Thu, Apr 11, 2024 at 10:51 AM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> > >
> > > Currently, big, merge, and small modes all support the premapped mode.
> > > We can now enable premapped mode by default. Furthermore,
> > > virtqueue_set_dma_premapped() must succeed when called immediately after
> > > find_vqs(). Consequently, we can assume that premapped mode is always
> > > enabled.
> > >
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > > ---
> > >  drivers/net/virtio_net.c | 12 +++++-------
> > >  1 file changed, 5 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 7ea7e9bcd5d7..f0faf7c0fe59 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -860,15 +860,13 @@ static void *virtnet_rq_alloc(struct receive_queue *rq, u32 size, gfp_t gfp)
> > >
> > >  static void virtnet_rq_set_premapped(struct virtnet_info *vi)
> > >  {
> > > -       int i;
> > > -
> > > -       /* disable for big mode */
> > > -       if (!vi->mergeable_rx_bufs && vi->big_packets)
> > > -               return;
> > > +       int i, err;
> > >
> > >         for (i = 0; i < vi->max_queue_pairs; i++) {
> > > -               if (virtqueue_set_dma_premapped(vi->rq[i].vq))
> > > -                       continue;
> > > +               err = virtqueue_set_dma_premapped(vi->rq[i].vq);
> > > +
> > > +               /* never happen */
> > > +               BUG_ON(err);
> >
> > Nit:
> >
> > Maybe just a BUG_ON(virtqueue_set_dma_premapped()).
>
> OK
>
>
> >
> > Btw, if there's no way to disable pre mapping, maybe it's better to
> > rename virtqueue_set_dma_premapped() to
> > virtqueue_enable_dma_premapped(ing).
>
> This patch will add a way to disable pre mapping.
>
>         https://lore.kernel.org/all/20240327111430.108787-11-xuanzhuo@linux.alibaba.com/
>
> Thanks.

Ok, fine.

Thanks

>
>
> >
> > Thanks
> >
> > >
> > >                 vi->rq[i].do_dma = true;
> > >         }
> > > --
> > > 2.32.0.3.g01195cf9f
> > >
> >
>