netdev - Re: [PATCH vhost v6 09/10] virtio_net: set premapped mode by find

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Message-ID: <CACGkMEuBhfMwrfaiburLG7gFw36GuVHSbRTtK+FycrGFVTgOcA@mail.gmail.com>
Date: Fri, 29 Mar 2024 11:20:08 +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 v6 09/10] virtio_net: set premapped mode by find_vqs()

On Thu, Mar 28, 2024 at 4:27 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
>
> On Thu, 28 Mar 2024 16:05:02 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > On Wed, Mar 27, 2024 at 7:14 PM Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> > >
> > > Now, the virtio core can set the premapped mode by find_vqs().
> > > If the premapped can be enabled, the dma array will not be
> > > allocated. So virtio-net use the api of find_vqs to enable the
> > > premapped.
> > >
> > > Judge the premapped mode by the vq->premapped instead of saving
> > > local variable.
> > >
> > > Signed-off-by: Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
> > > ---
> >
> > I wonder what's the reason to keep a fallback when premapped is not enabled?
>
> Rethink this.
>
> I think you are right. We can remove the fallback.
>
> Because we have the virtio dma apis that wrap all the cases.
> So I will remove the fallback from the virtio-net in next version.

Ok.

>
> But we still need to export the premapped to the drivers.
> Because we can enable the AF_XDP only when premapped is true.

I may miss something but it should work like

enable AF_XDP -> enable remapping

So can we fail during remapping enablement?

THanks

>
> Thanks
>
>
> >
> > Thanks
> >
>