Thanks! Yes something to improve:
On Mon, Mar 16, 2026 at 03:21:52PM +0800, Di Zhu wrote:
> Although VIRTIO_NET_F_CTRL_GUEST_OFFLOADS is negotiated, which indicates
> the device supports dynamic control of guest offloads, it does not
> necessarily mean the device supports specific hardware GRO features.
>
> If none of the features defined in GUEST_OFFLOAD_GRO_HW_MASK (such as
> TSO4, TSO6, or UFO) are present in vi->guest_offloads_capable, the
> device effectively lacks the hardware capability to perform GRO.
So what is the user-visible problem this is trying to address?
>
> So, making NETIF_F_GRO_HW conditional on these feature bits ensures the
> stack does not enable an unsupported hardware offload configuration.
I guess the assumption is that without this, something
enables such a config? Which stack is this and what happens then?
> Fixes: a02e8964eaf9 ("virtio-net: ethtool configurable LRO")
> Signed-off-by: Di Zhu <[email protected]>
judging by this, has something to do with LRO?
> ---
> /* v2 */
> -make the modified logic clearer
> ---
> drivers/net/virtio_net.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 72d6a9c6a5a2..b233c99925e9 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -6781,8 +6781,6 @@ static int virtnet_probe(struct virtio_device *vdev)
> 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))
> - dev->hw_features |= NETIF_F_GRO_HW;
>
> dev->vlan_features = dev->features;
> dev->xdp_features = NETDEV_XDP_ACT_BASIC | NETDEV_XDP_ACT_REDIRECT |
> @@ -7058,6 +7056,10 @@ static int virtnet_probe(struct virtio_device *vdev)
> }
> vi->guest_offloads_capable = vi->guest_offloads;
>
> + if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS) &&
> + (vi->guest_offloads_capable & GUEST_OFFLOAD_GRO_HW_MASK))
> + dev->hw_features |= NETIF_F_GRO_HW;
> +
> rtnl_unlock();
>
> err = virtnet_cpu_notif_add(vi);
> --
> 2.34.1
>
