netdev - Re: [RFC bpf-next 0/7] bpf: netdev TX metadata

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Message-ID: <20230615185046.3c9133ea@kernel.org>
Date: Thu, 15 Jun 2023 18:50:46 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Stanislav Fomichev <sdf@...gle.com>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>, Toke Høiland-Jørgensen <toke@...nel.org>, bpf
 <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann
 <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai
 Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>, Yonghong Song
 <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh
 <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>, Jiri Olsa
 <jolsa@...nel.org>, Willem de Bruijn <willemb@...gle.com>, David Ahern
 <dsahern@...nel.org>, "Karlsson, Magnus" <magnus.karlsson@...el.com>,
 Björn Töpel <bjorn@...nel.org>, "Fijalkowski, Maciej"
 <maciej.fijalkowski@...el.com>, Network Development
 <netdev@...r.kernel.org>
Subject: Re: [RFC bpf-next 0/7] bpf: netdev TX metadata

On Thu, 15 Jun 2023 09:31:19 -0700 Stanislav Fomichev wrote:
> Timestamp might be a bit of an outlier here where it's just setting
> some bit in some existing descriptor.
> For some features, the drivers might have to reserve extra descriptors
> and I'm not sure how safe it would be to let the programs arbitrarily
> mess with the descriptor queues like that.

I was gonna say, most NICs will have some form of descriptor chaining,
with strict ordering, to perform reasonably with small packets.

> I'll probably keep this kfunc approach for v2 rfc for now (will try to
> get rid of the complicated attachment at least), but let's keep
> discussing.

SGTM, FWIW.