netdev - Re: [PATCH v2] virtio-net: Fix probe of virtio-net on kvmtool

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Message-ID: <1677579113.5159256-2-xuanzhuo@linux.alibaba.com>
Date:   Tue, 28 Feb 2023 18:11:53 +0800
From:   Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
To:     Xuan Zhuo <xuanzhuo@...ux.alibaba.com>
Cc:     "Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>, rbradford@...osinc.com,
        Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH v2] virtio-net: Fix probe of virtio-net on kvmtool

On Tue, 28 Feb 2023 18:06:38 +0800, Xuan Zhuo <xuanzhuo@...ux.alibaba.com> wrote:
> On Fri, 24 Feb 2023 11:11:37 +0800, Jason Wang <jasowang@...hat.com> wrote:
> > On Fri, Feb 24, 2023 at 3:38 AM Rob Bradford via B4 Relay
> > <devnull+rbradford.rivosinc.com@...nel.org> wrote:
> > >
> > > From: Rob Bradford <rbradford@...osinc.com>
> > >
> > > kvmtool does not support the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature
> > > but does advertise the VIRTIO_NET_F_GUEST_TSO{4,6} features. Check that
> > > the VIRTIO_NET_F_CTRL_GUEST_OFFLOADS feature is present before setting
> > > the NETIF_F_GRO_HW feature bit as otherwise
>
> Here are settings for dev->features and dev->hw_features.

What I want to say is that in normal circumstances, ethtool will identify it and
will not directly modify the backend, if there is no VIRTIO_NET_F_CTRL_GUEST_OFFLOADS.

Thanks.

>
>
> > > an attempt will be made to
> > > program the virtio-net device using the ctrl queue which will fail.
> > >
> > > This resolves the following error when running on kvmtool:
>
> Can you talk about it in detail what it did?
>
> Thanks.
>
> > >
> > > [    1.865992] net eth0: Fail to set guest offload.
> > > [    1.872491] virtio_net virtio2 eth0: set_features() failed (-22); wanted 0x0000000000134829, left 0x0080000000134829
> > >
> > > Signed-off-by: Rob Bradford <rbradford@...osinc.com>
> > > ---
> > > Changes in v2:
> > > - Use parentheses to group logical OR of features
> > > - Link to v1:
> > >   https://lore.kernel.org/r/20230223-virtio-net-kvmtool-v1-1-fc23d29b9d7a@rivosinc.com
> > > ---
> > >  drivers/net/virtio_net.c | 7 +++----
> > >  1 file changed, 3 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > index 61e33e4dd0cd..f8341d1a4ccd 100644
> > > --- a/drivers/net/virtio_net.c
> > > +++ b/drivers/net/virtio_net.c
> > > @@ -3780,10 +3780,9 @@ static int virtnet_probe(struct virtio_device *vdev)
> > >         }
> > >         if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_CSUM))
> > >                 dev->features |= NETIF_F_RXCSUM;
> > > -       if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> > > -           virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6))
> > > -               dev->features |= NETIF_F_GRO_HW;
> > > -       if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS))
> > > +       if ((virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> > > +           virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6)) &&
> > > +           virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS))
> > >                 dev->hw_features |= NETIF_F_GRO_HW;
> >
> > Does this mean we won't have NETIF_F_GRO_HW when only TSO4/TSO6 are
> > supported but not GUEST_OFFLOADS?
> >
> > Is this intended?
> >
> > Thanks
> >
> > >
> > >         dev->vlan_features = dev->features;
> > >
> > > ---
> > > base-commit: c39cea6f38eefe356d64d0bc1e1f2267e282cdd3
> > > change-id: 20230223-virtio-net-kvmtool-87f37515be22
> > >
> > > Best regards,
> > > --
> > > Rob Bradford <rbradford@...osinc.com>
> > >
> >
> > _______________________________________________
> > Virtualization mailing list
> > Virtualization@...ts.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/virtualization

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