linux-kernel - Re: [PATCH] virtio_net: Support RX hash XDP hint

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Message-ID: <CAKhg4tK6ea27iKNAPe=-G9wfzNe4hh9=9fk0cpt0qyAVW1Fa1g@mail.gmail.com>
Date: Wed, 24 Jan 2024 10:27:09 +0800
From: Liang Chen <liangchen.linux@...il.com>
To: "Michael S. Tsirkin" <mst@...hat.com>
Cc: jasowang@...hat.com, virtualization@...ts.linux-foundation.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] virtio_net: Support RX hash XDP hint

On Tue, Jan 23, 2024 at 3:02 PM Michael S. Tsirkin <mst@...hat.com> wrote:
>
> On Mon, Jan 22, 2024 at 06:22:56PM +0800, Liang Chen 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@...il.com>
> > ---
> >  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);
> > +
> > +     switch (__le16_to_cpu(hdr_hash->hash_report)) {
> > +             case VIRTIO_NET_HASH_REPORT_TCPv4:
> > +                     *rss_type = XDP_RSS_TYPE_L4_IPV4_TCP;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_UDPv4:
> > +                     *rss_type = XDP_RSS_TYPE_L4_IPV4_UDP;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_TCPv6:
> > +                     *rss_type = XDP_RSS_TYPE_L4_IPV6_TCP;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_UDPv6:
> > +                     *rss_type = XDP_RSS_TYPE_L4_IPV6_UDP;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_TCPv6_EX:
> > +                     *rss_type = XDP_RSS_TYPE_L4_IPV6_TCP_EX;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_UDPv6_EX:
> > +                     *rss_type = XDP_RSS_TYPE_L4_IPV6_UDP_EX;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_IPv4:
> > +                     *rss_type = XDP_RSS_TYPE_L3_IPV4;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_IPv6:
> > +                     *rss_type = XDP_RSS_TYPE_L3_IPV6;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_IPv6_EX:
> > +                     *rss_type = XDP_RSS_TYPE_L3_IPV6_EX;
> > +                     break;
> > +             case VIRTIO_NET_HASH_REPORT_NONE:
> > +             default:
> > +                     *rss_type = XDP_RSS_TYPE_NONE;
> > +     }
> > +
> > +     *hash = __le32_to_cpu(hdr_hash->hash_value);
> > +     return 0;
> > +}
> > +
> > +static const struct xdp_metadata_ops virtnet_xdp_metadata_ops = {
> > +     .xmo_rx_hash                    = virtnet_xdp_rx_hash,
> > +};
> > +
> >  static int virtnet_probe(struct virtio_device *vdev)
> >  {
> >       int i, err = -ENOMEM;
> > @@ -4613,6 +4667,8 @@ static int virtnet_probe(struct virtio_device *vdev)
> >       dev->ethtool_ops = &virtnet_ethtool_ops;
> >       SET_NETDEV_DEV(dev, &vdev->dev);
> >
> > +     dev->xdp_metadata_ops = &virtnet_xdp_metadata_ops;
> > +
>
> How about making this assignment depend on
>
> xdp->rxq->dev->features & NETIF_F_RXHASH
>

Thanks! How about dev->hw_features & NETIF_F_RXHASH? dev->features &
NETIF_F_RXHASH has not been enabled at this point.

> ?
>
> >       /* Do we support "hardware" checksums? */
> >       if (virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
> >               /* This opens up the world of extra features. */
> > --
> > 2.40.1
>