netdev - Re: [PATCH bpf-next v3 01/12] bpf: Document XDP RX metadata

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Date:   Thu, 8 Dec 2022 11:06:59 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Jakub Kicinski <kuba@...nel.org>
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>,
        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 01/12] bpf: Document XDP RX metadata

On Wed, Dec 7, 2022 at 8:26 PM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Mon,  5 Dec 2022 18:45:43 -0800 Stanislav Fomichev wrote:
> > +- ``bpf_xdp_metadata_rx_timestamp_supported`` returns true/false to
> > +  indicate whether the device supports RX timestamps
> > +- ``bpf_xdp_metadata_rx_timestamp`` returns packet RX timestamp
> > +- ``bpf_xdp_metadata_rx_hash_supported`` returns true/false to
> > +  indicate whether the device supports RX hash
> > +- ``bpf_xdp_metadata_rx_hash`` returns packet RX hash
>
> Would you mind pointing to the discussion about the separate
> _supported() kfuncs? I recall folks had concerns about the function
> call overhead, and now we have 2 calls per field? :S

Take a look at [0] and [1]. I'm still assuming that we might support
some restricted set of kfuncs that can be unrolled so keeping this
simple/separate apis.

0: https://lore.kernel.org/bpf/CAADnVQJMvPjXCtKNH+WCryPmukgbWTrJyHqxrnO=2YraZEukPg@mail.gmail.com
1: https://lore.kernel.org/bpf/Y4XZkZJHVvLgTIk9@lavr/