On Tue, Apr 16, 2024 at 2:20 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. > > 1. > https://lore.kernel.org/all/20231015141644.260646-1-akihiko.odaki@xxxxxxxxxx/#r > > Signed-off-by: Liang Chen <liangchen.linux@xxxxxxxxx> > --- > Changes from v7: > - use table lookup for rss hash type > Changes from v6: > - fix a coding style issue > Changes from v5: > - Preservation of the hash value has been dropped, following the conclusion > from discussions in V3 reviews. The virtio_net driver doesn't > accessing/using the virtio_net_hdr after the XDP program execution, so > nothing tragic should happen. As to the xdp program, if it smashes the > entry in virtio header, it is likely buggy anyways. Additionally, looking > up the Intel IGC driver, it also does not bother with this particular > aspect. > --- > drivers/net/virtio_net.c | 42 +++++++++++++++++++++++++++++++++ > include/uapi/linux/virtio_net.h | 1 + > 2 files changed, 43 insertions(+) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index c22d1118a133..1d750009f615 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -4621,6 +4621,47 @@ static void virtnet_set_big_packets(struct virtnet_info *vi, const int mtu) > } > } > > +static enum xdp_rss_hash_type > +virtnet_xdp_rss_type[VIRTIO_NET_HASH_REPORT_MAX_TABLE] = { > + [VIRTIO_NET_HASH_REPORT_NONE] = XDP_RSS_TYPE_NONE, > + [VIRTIO_NET_HASH_REPORT_IPv4] = XDP_RSS_TYPE_L3_IPV4, > + [VIRTIO_NET_HASH_REPORT_TCPv4] = XDP_RSS_TYPE_L4_IPV4_TCP, > + [VIRTIO_NET_HASH_REPORT_UDPv4] = XDP_RSS_TYPE_L4_IPV4_UDP, > + [VIRTIO_NET_HASH_REPORT_IPv6] = XDP_RSS_TYPE_L3_IPV6, > + [VIRTIO_NET_HASH_REPORT_TCPv6] = XDP_RSS_TYPE_L4_IPV6_TCP, > + [VIRTIO_NET_HASH_REPORT_UDPv6] = XDP_RSS_TYPE_L4_IPV6_UDP, > + [VIRTIO_NET_HASH_REPORT_IPv6_EX] = XDP_RSS_TYPE_L3_IPV6_EX, > + [VIRTIO_NET_HASH_REPORT_TCPv6_EX] = XDP_RSS_TYPE_L4_IPV6_TCP_EX, > + [VIRTIO_NET_HASH_REPORT_UDPv6_EX] = XDP_RSS_TYPE_L4_IPV6_UDP_EX > +}; > + > +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; > + u16 hash_report; > + > + 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); > + hash_report = __le16_to_cpu(hdr_hash->hash_report); > + > + if (hash_report >= VIRTIO_NET_HASH_REPORT_MAX_TABLE) > + hash_report = VIRTIO_NET_HASH_REPORT_NONE; > + > + *rss_type = virtnet_xdp_rss_type[hash_report]; > + *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; > @@ -4747,6 +4788,7 @@ static int virtnet_probe(struct virtio_device *vdev) > VIRTIO_NET_RSS_HASH_TYPE_UDP_EX); > > dev->hw_features |= NETIF_F_RXHASH; > + dev->xdp_metadata_ops = &virtnet_xdp_metadata_ops; > } > > if (vi->has_rss_hash_report) > diff --git a/include/uapi/linux/virtio_net.h b/include/uapi/linux/virtio_net.h > index cc65ef0f3c3e..3ee695450096 100644 > --- a/include/uapi/linux/virtio_net.h > +++ b/include/uapi/linux/virtio_net.h > @@ -176,6 +176,7 @@ struct virtio_net_hdr_v1_hash { > #define VIRTIO_NET_HASH_REPORT_IPv6_EX 7 > #define VIRTIO_NET_HASH_REPORT_TCPv6_EX 8 > #define VIRTIO_NET_HASH_REPORT_UDPv6_EX 9 > +#define VIRTIO_NET_HASH_REPORT_MAX_TABLE 10 This should not be part of uAPI. It may confuse the userspace. Others look good. Thanks > __le16 hash_report; > __le16 padding; > }; > -- > 2.40.1 >
