Re: [PATCH bpf V7 3/7] xdp: rss hash types representation

[Jesper Dangaard Brouer]

On 10/04/2023 17.04, Simon Horman wrote:
> On Sat, Apr 08, 2023 at 09:24:51PM +0200, Jesper Dangaard Brouer wrote:
> > The RSS hash type specifies what portion of packet data NIC hardware used
> > when calculating RSS hash value. The RSS types are focused on Internet
> > traffic protocols at OSI layers L3 and L4. L2 (e.g. ARP) often get hash
> > value zero and no RSS type. For L3 focused on IPv4 vs. IPv6, and L4
> > primarily TCP vs UDP, but some hardware supports SCTP.
> >
> > Hardware RSS types are differently encoded for each hardware NIC. Most
> > hardware represent RSS hash type as a number. Determining L3 vs L4 often
> > requires a mapping table as there often isn't a pattern or sorting
> > according to ISO layer.
> >
> > The patch introduce a XDP RSS hash type (enum xdp_rss_hash_type) that
> > contain combinations to be used by drivers, which gets build up with bits
> > from enum xdp_rss_type_bits. Both enum xdp_rss_type_bits and
> > xdp_rss_hash_type get exposed to BPF via BTF, and it is up to the
> > BPF-programmer to match using these defines.
> >
> > This proposal change the kfunc API bpf_xdp_metadata_rx_hash() adding
> > a pointer value argument for provide the RSS hash type.
> >
> > Change function signature for all xmo_rx_hash calls in drivers to make it
> > compile. The RSS type implementations for each driver comes as separate
> > patches.
> >
> > Fixes: 3d76a4d3d4e5 ("bpf: XDP metadata RX kfuncs")
> > Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> > Acked-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> > Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
> > ---
> >   drivers/net/ethernet/mellanox/mlx4/en_rx.c       |    3 +
> >   drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c |    3 +
> >   drivers/net/veth.c                               |    3 +
> >   include/linux/netdevice.h                        |    3 +
> >   include/net/xdp.h                                |   45 ++++++++++++++++++++++
> >   net/core/xdp.c                                   |   10 ++++-
> >   6 files changed, 62 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/mellanox/mlx4/en_rx.c b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> > index 4b5e459b6d49..73d10aa4c503 100644
> > --- a/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> > +++ b/drivers/net/ethernet/mellanox/mlx4/en_rx.c
> > @@ -681,7 +681,8 @@ int mlx4_en_xdp_rx_timestamp(const struct xdp_md *ctx, u64 *timestamp)
> >   	return 0;
> >   }
> >   
> > -int mlx4_en_xdp_rx_hash(const struct xdp_md *ctx, u32 *hash)
> > +int mlx4_en_xdp_rx_hash(const struct xdp_md *ctx, u32 *hash,
> > +			enum xdp_rss_hash_type *rss_type)
> >   {
> >   	struct mlx4_en_xdp_buff *_ctx = (void *)ctx;
> >   
>
> Hi Jesper,
>
> I think you also need to update the declaration of mlx4_en_xdp_rx_hash()
> in mlx4_en.h.

Thanks a lot for spotting this. fixed in V8.
--Jesper