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

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Date:   Mon,  7 Nov 2022 18:11:30 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Alexander Lobakin <alexandr.lobakin@...el.com>,
        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

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.

> 
> 
> > > +     } 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