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

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Date:   Tue, 6 Dec 2022 23:23:53 -0800
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Stanislav Fomichev <sdf@...gle.com>
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 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?