netdev - Re: [PATCH bpf-next v3 03/12] bpf: XDP metadata RX kfuncs

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Date:   Tue, 6 Dec 2022 20:52:32 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.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>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 03/12] bpf: XDP metadata RX kfuncs

On Tue, Dec 6, 2022 at 8:29 PM Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
>
> On Mon, Dec 05, 2022 at 06:45:45PM -0800, Stanislav Fomichev wrote:
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index fc4e313a4d2e..00951a59ee26 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -15323,6 +15323,24 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
> >               return -EINVAL;
> >       }
> >
> > +     *cnt = 0;
> > +
> > +     if (resolve_prog_type(env->prog) == BPF_PROG_TYPE_XDP) {
> > +             if (bpf_prog_is_offloaded(env->prog->aux)) {
> > +                     verbose(env, "no metadata kfuncs offload\n");
> > +                     return -EINVAL;
> > +             }
>
> If I'm reading this correctly than this error will trigger
> for any XDP prog trying to use a kfunc?

bpf_prog_is_offloaded() should return true only when the program is
fully offloaded to the device (like nfp). So here the intent is to
reject kfunc programs because nft should somehow implement them first.
Unless I'm not setting offload_requested somewhere, not sure I see the
problem. LMK if I missed something.

> I was hoping that BPF CI can prove my point, but it failed to
> build your newly added xdp_hw_metadata.c test.

Ugh, will take a look, thank you!