netdev - Re: [PATCH RFCv2 bpf-next 00/18] XDP-hints: XDP gaining access to HW offload hints via BTF

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Message-ID: <20221006075927.39e43e6b@kernel.org>
Date:   Thu, 6 Oct 2022 07:59:27 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc:     Stanislav Fomichev <sdf@...gle.com>, brouer@...hat.com,
        Martin KaFai Lau <martin.lau@...ux.dev>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, xdp-hints@...-project.net,
        larysa.zaremba@...el.com, memxor@...il.com,
        Lorenzo Bianconi <lorenzo@...nel.org>, mtahhan@...hat.com,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Daniel Borkmann <borkmann@...earbox.net>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        dave@...cker.co.uk, Magnus Karlsson <magnus.karlsson@...el.com>,
        bjorn@...nel.org
Subject: Re: [PATCH RFCv2 bpf-next 00/18] XDP-hints: XDP gaining access to
 HW offload hints via BTF

On Wed, 5 Oct 2022 16:19:30 +0200 Jesper Dangaard Brouer wrote:
> >> Since you mentioned it... FWIW that was always my preference rather than
> >> the BTF magic :)  The jited image would have to be per-driver like we
> >> do for BPF offload but that's easy to do from the technical
> >> perspective (I doubt many deployments bind the same prog to multiple
> >> HW devices)..  
> 
> On the technical side we do have the ifindex that can be passed along
> which is currently used for getting XDP hardware offloading to work.
> But last time I tried this, I failed due to BPF tail call maps.

FWIW the tail call map should be solvable by enforcing that the map 
is also pinned and so are all the programs in it. Perhaps I find that
less ugly than others.. since that's what the offload path did :)

> (It's not going to fly for other reasons, see redirect below).