Re: [PATCH RFC net-next 05/19] net: dsa: tag_ar9331: add GRO callbacks

From: Florian Fainelli <f.fainelli@gmail.com>
To: Vladimir Oltean <olteanv@gmail.com>,
	Alexander Lobakin <alobakin@dlink.ru>
Cc: "David S. Miller" <davem@davemloft.net>,
	Edward Cree <ecree@solarflare.com>, Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Hauke Mehrtens <hauke@hauke-m.de>,
	Sean Wang <sean.wang@mediatek.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	Jiri Pirko <jiri@mellanox.com>,
	Eric Dumazet <edumazet@google.com>,
	Paolo Abeni <pabeni@redhat.com>,
	Jakub Kicinski <jakub.kicinski@netronome.com>,
	Taehee Yoo <ap420073@gmail.com>,
	Stephen Hemminger <stephen@networkplumber.org>,
	Stanislav Fomichev <sdf@google.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Song Liu <songliubraving@fb.com>,
	Matteo Croce <mcroce@redhat.com>,
	Jakub Sitnicki <jakub@cloudflare.com>,
	Paul Blakey <paulb@mellanox.com>,
	Yoshiki Komachi <komachi.yoshiki@gmail.com>,
	netdev <netdev@vger.kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-arm-kernel@lists.infradead.org>,
	"moderated list:ARM/Mediatek SoC support" 
	<linux-mediatek@lists.infradead.org>
Subject: Re: [PATCH RFC net-next 05/19] net: dsa: tag_ar9331: add GRO callbacks
Date: Tue, 14 Jan 2020 13:56:11 -0800	[thread overview]
Message-ID: <129bf2bc-c0e9-02a3-7d40-0f7920803769@gmail.com> (raw)
In-Reply-To: <CA+h21hqZoLrU7nL3Vo0KcmFnOxNxQPwoOVSEd6styyjK7XO+5w@mail.gmail.com>

On 1/13/20 2:28 AM, Vladimir Oltean wrote:
> On Mon, 13 Jan 2020 at 11:46, Alexander Lobakin <alobakin@dlink.ru> wrote:
>>
>> Vladimir Oltean wrote 13.01.2020 12:42:
>>> Hi Alexander,
>>>
>>> On Mon, 13 Jan 2020 at 11:22, Alexander Lobakin <alobakin@dlink.ru>
>>> wrote:
>>>>
>>>> CPU ports can't be bridged anyway
>>>>
>>>> Regards,
>>>> ᚷ ᛖ ᚢ ᚦ ᚠ ᚱ
>>>
>>> The fact that CPU ports can't be bridged is already not ideal.
>>> One can have a DSA switch with cascaded switches on each port, so it
>>> acts like N DSA masters (not as DSA links, since the taggers are
>>> incompatible), with each switch forming its own tree. It is desirable
>>> that the ports of the DSA switch on top are bridged, so that
>>> forwarding between cascaded switches does not pass through the CPU.
>>
>> Oh, I see. But currently DSA infra forbids the adding DSA masters to
>> bridges IIRC. Can't name it good or bad decision, but was introduced
>> to prevent accidental packet flow breaking on DSA setups.
>>
> 
> I just wanted to point out that some people are going to be looking at
> ways by which the ETH_P_XDSA handler can be made to play nice with the
> master's rx_handler, and that it would be nice to at least not make
> the limitation worse than it is by converting everything to
> rx_handlers (which "currently" can't be stacked, from the comments in
> netdevice.h).

I am not sure this would change the situation much, today we cannot have
anything but switch tags travel on the DSA master network device,
whether we accomplish the RX tap through a special skb->protocol value
or via rx_handler, it probably does not functionally matter, but it
could change the performance.
-- 
Florian