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

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Message-ID: <1713429342.96617-2-xuanzhuo@linux.alibaba.com>
Date: Thu, 18 Apr 2024 16:35:42 +0800
From: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To: Jason Wang <jasowang@...hat.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, 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.


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