linux-kernel - Re: [PATCH bpf-next v2 0/3] XDP metadata: Rx checksum/GSO hint; Tx GSO offload

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Message-ID: <67156d3447444_14e182944b@willemb.c.googlers.com.notmuch>
Date: Sun, 20 Oct 2024 16:51:00 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Stanislav Fomichev <stfomichev@...il.com>, 
 Muyang Tian <tianmuyang@...wei.com>
Cc: bpf@...r.kernel.org, 
 "David S . Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, 
 Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, 
 Donald Hunter <donald.hunter@...il.com>, 
 Björn Töpel <bjorn@...nel.org>, 
 Magnus Karlsson <magnus.karlsson@...el.com>, 
 Maciej Fijalkowski <maciej.fijalkowski@...el.com>, 
 Jonathan Lemon <jonathan.lemon@...il.com>, 
 Alexei Starovoitov <ast@...nel.org>, 
 Daniel Borkmann <daniel@...earbox.net>, 
 Jesper Dangaard Brouer <hawk@...nel.org>, 
 John Fastabend <john.fastabend@...il.com>, 
 netdev@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 linux-doc@...r.kernel.org, 
 yanan@...wei.com, 
 xiesongyang@...wei.com, 
 wuchangye@...wei.com, 
 liuxin350@...wei.com, 
 zhangmingyi5@...wei.com, 
 liwei883@...wei.com, 
 willemb@...gle.com
Subject: Re: [PATCH bpf-next v2 0/3] XDP metadata: Rx checksum/GSO hint; Tx
 GSO offload

Stanislav Fomichev wrote:
> On 10/18, Muyang Tian wrote:
> > This series introduce XDP metadata functionality, including Rx checksum/GSO hint
> > and Tx GSO offload. This is aimed to transfer control fields when processing jumbo
> > frames between VMs.
> 
> Ideally, the series should also have the implementation of these hints
> for a couple of devices and appropriate selftest updates to exercise
> them.

+1

> For GSO, CC Willem going forward (I don't think I understand why
> we want to have gso_type in the TX hint; something like header_len
> seems like a better fit).

GSO on Tx makes sense. To be able to program hardware USO, say.

GSO on Rx is less obvious. Is this for HW-GRO? In general, some usage
context will be helpful.

Two implementation questions:

- why define an XDP specific type for checksum types, but reuse the
  netdev type for gso_type?
- why u32 gso_type, when it is a u8 in skb_shared_info?

> Please also don't post v3 yet and allow at least a week for the initial
> reviewers to catch up..