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

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Date:   Wed, 7 Dec 2022 10:05:46 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Martin KaFai Lau <martin.lau@...ux.dev>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, 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,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Subject: Re: [PATCH bpf-next v3 03/12] bpf: XDP metadata RX kfuncs

On Tue, Dec 6, 2022 at 11:24 PM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 12/6/22 8:52 PM, Stanislav Fomichev wrote:
> > 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.
>
> It errors out for all kfunc here though. or it meant to error out for the
> XDP_METADATA_KFUNC_* only?

Ah, good point, I was somewhat assuming that xdp doesn't use kfuncs
right now and I can just assume that kfunc == metadata_kfunc.
Will make this more selective, thanks!