From: Vladimir Oltean <olteanv@gmail.com>
To: Tobias Waldekranz <tobias@waldekranz.com>
Cc: andrew@lunn.ch, vivien.didelot@gmail.com, f.fainelli@gmail.com,
netdev@vger.kernel.org
Subject: Re: [RFC PATCH 0/4] net: dsa: link aggregation support
Date: Tue, 27 Oct 2020 14:27:20 +0200 [thread overview]
Message-ID: <20201027122720.6jm4vuivi7tozzdq@skbuf> (raw)
In-Reply-To: <20201027105117.23052-1-tobias@waldekranz.com>
Hi Tobias,
On Tue, Oct 27, 2020 at 11:51:13AM +0100, Tobias Waldekranz wrote:
> I would really appreciate feedback on the following:
>
> All LAG configuration is cached in `struct dsa_lag`s. I realize that
> the standard M.O. of DSA is to read back information from hardware
> when required. With LAGs this becomes very tricky though. For example,
> the change of a link state on one switch will require re-balancing of
> LAG hash buckets on another one, which in turn depends on the total
> number of active links in the LAG. Do you agree that this is
> motivated?
I don't really have an issue with that.
> The LAG driver ops all receive the LAG netdev as an argument when this
> information is already available through the port's lag pointer. This
> was done to match the way that the bridge netdev is passed to all VLAN
> ops even though it is in the port's bridge_dev. Is there a reason for
> this or should I just remove it from the LAG ops?
Maybe because on "leave", the bridge/LAG net device pointer inside
struct dsa_port is first set to NULL, then the DSA notifier is called?
> At least on mv88e6xxx, the exact source port is not available when
> packets are received on the CPU. The way I see it, there are two ways
> around that problem:
>
> - Inject the packet directly on the LAG device (what this series
> does). Feels right because it matches all that we actually know; the
> packet came in on the LAG. It does complicate dsa_switch_rcv
> somewhat as we can no longer assume that skb->dev is a DSA port.
>
> - Inject the packet on "the designated port", i.e. some port in the
> LAG. This lets us keep the current Rx path untouched. The problem is
> that (a) the port would have to be dynamically updated to match the
> expectations of the LAG driver (team/bond) as links are
> enabled/disabled and (b) we would be presenting a lie because
> packets would appear to ingress on netdevs that they might not in
> fact have been physically received on.
Since ocelot/felix does not have this restriction, and supports
individual port addressing even under a LAG, you can imagine I am not
very happy to see the RX data path punishing everyone else that is not
mv88e6xxx.
> (mv88e6xxx) What is the policy regarding the use of DSA vs. EDSA? It
> seems like all chips capable of doing EDSA are using that, except for
> the Peridot.
I have no documentation whatsoever for mv88e6xxx, but just wondering,
what is the benefit brought by EDSA here vs DSA? Does DSA have the
same restriction when the ports are in a LAG?
next prev parent reply other threads:[~2020-10-27 12:27 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-27 10:51 [RFC PATCH 0/4] net: dsa: link aggregation support Tobias Waldekranz
2020-10-27 10:51 ` [RFC PATCH 1/4] net: dsa: mv88e6xxx: use ethertyped dsa for 6390/6390X Tobias Waldekranz
2020-10-27 14:52 ` Marek Behun
2020-10-27 14:54 ` Marek Behun
2020-10-27 14:58 ` Marek Behun
2020-10-27 10:51 ` [RFC PATCH 2/4] net: dsa: link aggregation support Tobias Waldekranz
2020-10-28 0:58 ` Vladimir Oltean
2020-10-28 14:03 ` Tobias Waldekranz
2020-10-27 10:51 ` [RFC PATCH 3/4] net: dsa: mv88e6xxx: " Tobias Waldekranz
2020-10-27 10:51 ` [RFC PATCH 4/4] net: dsa: tag_edsa: support reception of packets from lag devices Tobias Waldekranz
2020-10-28 12:05 ` Vladimir Oltean
2020-10-28 15:28 ` Tobias Waldekranz
2020-10-28 18:18 ` Vladimir Oltean
2020-10-28 22:31 ` Tobias Waldekranz
2020-10-28 23:08 ` Vladimir Oltean
2020-10-29 7:47 ` Tobias Waldekranz
2020-10-30 9:21 ` Vladimir Oltean
2020-11-01 11:31 ` Ido Schimmel
2020-10-27 12:27 ` Vladimir Oltean [this message]
2020-10-27 14:29 ` [RFC PATCH 0/4] net: dsa: link aggregation support Andrew Lunn
2020-10-27 14:59 ` Tobias Waldekranz
2020-10-27 14:00 ` Andrew Lunn
2020-10-27 15:09 ` Tobias Waldekranz
2020-10-27 15:05 ` Marek Behun
2020-10-27 15:23 ` Andrew Lunn
2020-10-27 18:25 ` Tobias Waldekranz
2020-10-27 18:33 ` Marek Behun
2020-10-27 19:04 ` Vladimir Oltean
2020-10-27 19:21 ` Tobias Waldekranz
2020-10-27 19:00 ` Vladimir Oltean
2020-10-27 19:37 ` Tobias Waldekranz
2020-10-27 20:02 ` Vladimir Oltean
2020-10-27 20:53 ` Tobias Waldekranz
2020-10-27 22:32 ` Vladimir Oltean
2020-10-28 0:27 ` Tobias Waldekranz
2020-10-28 22:35 ` Marek Behun
2020-10-27 22:36 ` Andrew Lunn
2020-10-28 0:45 ` Tobias Waldekranz
2020-10-28 1:03 ` Andrew Lunn
2020-11-11 4:28 ` Florian Fainelli
2020-11-19 10:51 ` Vladimir Oltean
2020-11-19 11:52 ` Tobias Waldekranz
2020-11-19 18:12 ` Vladimir Oltean
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