netdev - Re: [PATCH net-next v4 1/4] net: dsa: add support for DSA rx offloading via metadata dst

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Message-ID: <20221114181926.ms5yl5rwzx7oonzn@skbuf>
Date:   Mon, 14 Nov 2022 20:19:26 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Felix Fietkau <nbd@....name>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Andrew Lunn <andrew@...n.ch>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v4 1/4] net: dsa: add support for DSA rx
 offloading via metadata dst

On Mon, Nov 14, 2022 at 09:59:09AM -0800, Florian Fainelli wrote:
> On 11/14/22 04:42, Felix Fietkau wrote:
> > If a metadata dst is present with the type METADATA_HW_PORT_MUX on a dsa cpu
> > port netdev, assume that it carries the port number and that there is no DSA
> > tag present in the skb data.
> > 
> > Signed-off-by: Felix Fietkau <nbd@....name>
> 
> Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
> 
> Is the plan to use the lwoer bits of the 32-bit port_id as the port number
> for now, and we can use the remaining 24 or so bits for passing
> classification (reason why we forward the packet, QoS etc. ) information in
> the future?
> 
> Might be time for me to revive the systemport patches supporting Broadcom
> tags in the the DMA descriptor.

It's not really clear how to expand the HW_PORT_MUX model to provide QoS
info and trap reason, without switching to per-packet allocation, which
is what Jakub seemingly wanted to avoid with skb extensions (among other
more minor things).

https://patchwork.kernel.org/project/netdevbpf/patch/20221104174151.439008-4-maxime.chevallier@bootlin.com/#25078661

Felix didn't present a need for more than the port id either, so this is
why we have what we have right now.