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

[Jason Wang]

On Fri, Feb 24, 2023 at 3:38 AM Rob Bradford via B4 Relay
<devnull+rbradford.rivosinc.com@xxxxxxxxxx> wrote:
>
> From: Rob Bradford <rbradford@xxxxxxxxxxxx>
>
> 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 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:
>
> [    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@xxxxxxxxxxxx>
> ---
> 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@xxxxxxxxxxxx
> ---
>  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@xxxxxxxxxxxx>
>