Date:	Fri, 19 Dec 2014 14:31:46 +0530
From:	B Viswanath <marichika4@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Roopa Prabhu <roopa@...ulusnetworks.com>,
	"Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
	John Fastabend <john.r.fastabend@...el.com>,
	"Varlese, Marco" <marco.varlese@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Thomas Graf <tgraf@...g.ch>,
	"sfeldma@...il.com" <sfeldma@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH net-next v2 1/1] net: Support for switch port configuration

On 19 December 2014 at 13:57, Jiri Pirko <jiri@...nulli.us> wrote:
> Fri, Dec 19, 2014 at 06:14:57AM CET, marichika4@...il.com wrote:
>>On 19 December 2014 at 05:18, Roopa Prabhu <roopa@...ulusnetworks.com> wrote:
>>> On 12/18/14, 3:26 PM, Samudrala, Sridhar wrote:
<snipped for ease of reading>
>>>>
>>>>
>>>> We also need an interface to set per-switch attributes. Can this work?
>>>>     bridge link set dev sw0 sw_attr bcast_flooding 1 master
>>>> where sw0 is a bridge representing the hardware switch.
>>>
>>>
>>> Not today. We discussed this @ LPC, and one way to do this would be to have
>>> a device
>>> representing the switch asic. This is in the works.
>>
>>
>>Can I assume that on  platforms which house more than one asic (say
>>two 24 port asics, interconnected via a 10G link or equivalent, to get
>>a 48 port 'switch') , the 'rocker' driver (or similar) should expose
>>them as a single set of ports, and not as two 'switch ports' ?
>
> Well that really depends on particular implementation and drivers. If you
> have 2 pci-e devices, I think you should expose them as 2 entities. For
> sure, you can have the driver to do the masking for you. I don't believe
> that is correct though.
>

In a platform that houses two asic chips, IMO, the user is still
expected to manage the router as a single entity. The configuration
being applied on both asic devices need to be matching if not
identical, and may not be conflicting. The FDB is to be synchronized
so that (offloaded) switching can happen across the asics. Some of
this stuff is asic specific anyway. Another example is that of the
learning. The (hardware) learning can't be enabled on one asic, while
being disabled on another one. The general use cases I have seen are
all involving managing the 'router' as a single entity.  That the
'router' is implemented with two asics instead of a single asic (with
more ports) is to be treated as an implementation detail.  This is the
usual router management method that exists today.

I hope I make sense.

So I am trying to figure out what this single entity that will be used
from a user perspective. It can be a bridge, but our bridges are more
802.1q bridges. We can use the 'self' mode, but then it means that it
should reflect the entire port count, and not just an asic.

So I was trying to deduce that in our switchdevice model, the best bet
would be to leave the unification to the driver (i.e., to project the
multiple physical asics as a single virtual switch device). This
allows any 'switch' level configurations to the bridge in 'self' mode.

And  then we would need to consider stacking. Stacking differs from
this multi-asic scenario since  there would be multiple CPU involved.

Thanks
Vissu

>>
>>>
>>>
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