On Thu, Feb 23, 2023 at 07:38:25PM +0000, Rob Bradford via B4 Relay 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;
This will disable GRO/LRO on kvmtool completely causing a significant
performance regression.
Jason, isn't this what
commit dbcf24d153884439dad30484a0e3f02350692e4c
Author: Jason Wang <jasowang@xxxxxxxxxx>
Date: Tue Aug 17 16:06:59 2021 +0800
virtio-net: use NETIF_F_GRO_HW instead of NETIF_F_LRO
was supposed to address?
And apropos this:
Fix this by using NETIF_F_GRO_HW instead. Though the spec does not
guarantee packets to be re-segmented as the original ones,
we can add that to the spec, possibly with a flag for devices to
differentiate between GRO and LRO.
this never happened. What's the plan exactly?
> dev->vlan_features = dev->features;
>
> ---
> base-commit: c39cea6f38eefe356d64d0bc1e1f2267e282cdd3
> change-id: 20230223-virtio-net-kvmtool-87f37515be22
>
> Best regards,
> --
> Rob Bradford <rbradford@xxxxxxxxxxxx>
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