On Mon, Jan 22, 2024 at 6:23 PM Liang Chen <liangchen.linux@xxxxxxxxx> wrote:
>
> The RSS hash report is a feature that's part of the virtio specification.
> Currently, virtio backends like qemu, vdpa (mlx5), and potentially vhost
> (still a work in progress as per [1]) support this feature. While the
> capability to obtain the RSS hash has been enabled in the normal path,
> it's currently missing in the XDP path. Therefore, we are introducing XDP
> hints through kfuncs to allow XDP programs to access the RSS hash.
>
> Signed-off-by: Liang Chen <liangchen.linux@xxxxxxxxx>
> ---
> drivers/net/virtio_net.c | 56 ++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 56 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index d7ce4a1011ea..1463a4709e3c 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -4579,6 +4579,60 @@ static void virtnet_set_big_packets(struct virtnet_info *vi, const int mtu)
> }
> }
>
> +static int virtnet_xdp_rx_hash(const struct xdp_md *_ctx, u32 *hash,
> + enum xdp_rss_hash_type *rss_type)
> +{
> + const struct xdp_buff *xdp = (void *)_ctx;
> + struct virtio_net_hdr_v1_hash *hdr_hash;
> + struct virtnet_info *vi;
> +
> + if (!(xdp->rxq->dev->features & NETIF_F_RXHASH))
> + return -ENODATA;
> +
> + vi = netdev_priv(xdp->rxq->dev);
> + hdr_hash = (struct virtio_net_hdr_v1_hash *)(xdp->data - vi->hdr_len);
Is there a guarantee that the hdr is not modified?
Thanks
