linux-kernel - Re: [PATCH v3 7/7] eni_vdpa: add vDPA driver for Alibaba ENI

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Message-ID: <CACGkMEs+s1ArZqgPqwJ2VLMxO9GWqfZNPeLv9BFoHvn6TFHndQ@mail.gmail.com>
Date:   Tue, 28 Sep 2021 10:17:04 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     Wu Zongyong <wuzongyong@...ux.alibaba.com>,
        virtualization <virtualization@...ts.linux-foundation.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        wei.yang1@...ux.alibaba.com
Subject: Re: [PATCH v3 7/7] eni_vdpa: add vDPA driver for Alibaba ENI

On Mon, Sep 27, 2021 at 6:36 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Sun, Sep 26, 2021 at 12:18:26PM +0800, Jason Wang wrote:
> > > > I wonder if the following can work with ENI:
> > > >
> > > > -device virtio-net-pci,mrg_rxbuf=off
> > > >
> > > > ?
> > >
> > > ENI didn't work.
> > > I will remove F_MRG_RXBUF when get_features.
> >
> > I think we need to fail FEATURE_OK if F_MRG_RXBUF is not negotiated.
> > Since VERSION_1 requires a fixed header length even if F_MRG_RXBUF is
> > not negotiated.
> >
> > But this trick doesn't come for free. If some driver doesn't support
> > mrg_rxbuf, it won't work.
> >
> > Thanks
>
> Yea. Ugh. Down the road I think we'll add legacy support to vdpa on
> strongly ordered systems.

I don't see the connection, can you explain why?

> Doing it in userspace is just too messy imho.
> But yes, this kind of hack is probably ok for weakly ordered systems.
> BTW we need to set VIRTIO_F_ORDER_PLATFORM, right?

Right.

Thanks

>
> --
> MST
>