Re: [PATCH net-next] net: ag71xx: align the IP header behind DSA tags

[Simon Horman <horms@kernel.org>]

On Wed, Oct 07, 2026 at 10:44:49AM -0700, Rosen Penev wrote:
> The receive buffer offset includes NET_IP_ALIGN to get the IP header
> aligned behind a 14 byte Ethernet header. Most ag71xx devices use DSA
> switches whose tag sits in front of the EtherType, which moves the IP
> header by another 2 bytes. Every access to the IP and TCP headers then
> traps and gets emulated by the unaligned access handler, around 6 times
> per forwarded frame.
> 
> Take the headroom needed by the DSA tagger into account when choosing
> the offset.
> 
> TP-Link Archer C7 v2 (qca8k), median of 3 runs, Mbit/s:
> 
>                        before   after
>   routed up               743     855
>   routed down             660     749
>   local receive           554     572
> 
> The unaligned instruction counter no longer moves while forwarding.
> 
> Assisted-by: LLM
> Signed-off-by: Rosen Penev <rosenp@gmail.com>

Unfortunately this patch did not apply cleanly to net-next at the time it
was posted, so our CI did not run.

Please rebase and repost.

-- 
pw-bot: changes-requested