netdev - Re: [RFC bpf-next v2 10/14] ice: Support rx timestamp metadata for xdp

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Date:   Mon, 7 Nov 2022 11:10:21 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Alexander Lobakin <alexandr.lobakin@...el.com>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, martin.lau@...ux.dev, song@...nel.org,
        yhs@...com, john.fastabend@...il.com, kpsingh@...nel.org,
        haoluo@...gle.com, jolsa@...nel.org,
        David Ahern <dsahern@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org
Subject: Re: [RFC bpf-next v2 10/14] ice: Support rx timestamp metadata for xdp

On Mon, Nov 7, 2022 at 9:33 AM Alexander Lobakin
<alexandr.lobakin@...el.com> wrote:
>
> From: Stanislav Fomichev <sdf@...gle.com>
> Date: Fri, 4 Nov 2022 11:21:47 -0700
>
> > On Fri, Nov 4, 2022 at 7:38 AM Alexander Lobakin
> > <alexandr.lobakin@...el.com> wrote:
> > >
> > > From: Stanislav Fomichev <sdf@...gle.com>
> > > Date: Thu,3 Nov 2022 20:25:28 -0700
>
> [...]
>
> > > Hey,
> > >
> > > FYI, our team wants to write a follow-up patch with ice support
> > > added, not like a draft, more of a mature code. I'm thinking of
> > > calling ice C function which would process Rx descriptors from
> > > that BPF code from the unrolling callback -- otherwise,
> > > implementing a couple hundred C code lines from ice_txrx_lib.c
> > > would be a bit too much :D
> >
> > Sounds good! I would gladly drop all/most of the driver changes for
> > the non-rfc posting :-)
> > I'll probably have a mlx4 one because there is a chance I might find
> > HW, but the rest I'll drop most likely.
> > (they are here to show how the driver changes might look like, hence
> > compile-tested only)
> >
> > Btw, does it make sense to have some small xsk selftest binary that
> > can be used to test the metadata with the real device?
> > The one I'm having right now depends on veth/namespaces; having a
> > similar one for the real hardware to qualify it sounds useful?
> > Something simple that sets up af_xdp for all queues, divers some
> > traffic, and exposes to the userspace consumer all the info about
> > frame metadata...
> > Or maybe there is something I can reuse already?
>
> There's XSk selftest already and recently Maciej added support for
> executing it on a physical device (via `-i <iface>` cmdline arg)[0].
> I guess the most optimal solution is to expand it to cover metadata
> cases as it has some sort of useful helper functions / infra? In the
> set I posted in June, I simply expanded xdp_meta selftest, but there
> weren't any XSk bits, so I don't think it's a way to go.

Yeah, I was also extending xskxceiver initially, but not sure we want
to put metadata in there (that test is already too big imo)?
Jesper also pointed out [0], so maybe that thing should live out-of-tree?

I got mlx4 working locally with a small xskxceiver-like selftest. I'll
probably include it in the next non-rfc submission and we can discuss
whether it makes sense to keep it or it's better to extend xskxceiver.

0: https://github.com/xdp-project/bpf-examples/tree/master/AF_XDP-interaction


> >
> >
> > > > +     } else if (func_id == xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_TIMESTAMP_SUPPORTED)) {
> > > > +             /* return true; */
> > > > +             bpf_patch_append(patch, BPF_MOV64_IMM(BPF_REG_0, 1));
> > > > +     } else if (func_id == xdp_metadata_kfunc_id(XDP_METADATA_KFUNC_RX_TIMESTAMP)) {
> > >
> > > [...]
> > >
> > > > --
> > > > 2.38.1.431.g37b22c650d-goog
> > >
> > > Thanks,
> > > Olek
>
> [0] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=a693ff3ed5610a07b1b0dd831d10f516e13cf6c6
>
> Thank,
> Olek