netdev - Re: [patch net-next 0/3] net: devlink: Finish network namespace support

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Date:   Wed, 31 Jul 2019 16:31:52 -0600
From:   David Ahern <dsahern@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org,
        davem@...emloft.net, sthemmin@...rosoft.com, mlxsw@...lanox.com
Subject: Re: [patch net-next 0/3] net: devlink: Finish network namespace
 support

On 7/31/19 4:28 PM, Jakub Kicinski wrote:
> On Wed, 31 Jul 2019 16:07:31 -0600, David Ahern wrote:
>> On 7/31/19 4:02 PM, Jakub Kicinski wrote:
>>> Can you elaborate further? Ports for most purposes are represented by
>>> netdevices. Devlink port instances expose global topological view of
>>> the ports which is primarily relevant if you can see the entire ASIC.
>>> I think the global configuration and global view of resources is still
>>> the most relevant need, so in your diagram you must account for some
>>> "all-seeing" instance, e.g.:
>>>
>>>    namespace 1 |  namespace 2  | ... | namespace N
>>>                |               |     |
>>>   { ports 1 }  |   { ports 2 } | ... | { ports N }
>>>                |               |     |
>>> subdevlink 1   | subdevlink 2  | ... |  subdevlink N
>>>          \______      |              _______/
>>>                  master ASIC devlink
>>>   =================================================
>>>                    driver
>>>
>>> No?
>>
>> sure, there could be a master devlink visible to the user if that makes
>> sense or the driver can account for it behind the scenes as the sum of
>> the devlink instances.
>>
>> The goal is to allow ports within an asic [1] to be divided across
>> network namespace where each namespace sees a subset of the ports. This
>> allows creating multiple logical switches from a single physical asic.
>>
>> [1] within constraints imposed by the driver/hardware - for example to
>> account for resources shared by a set of ports. e.g., front panel ports
>> 1 - 4 have shared resources and must always be in the same devlink instance.
> 
> So the ASIC would start out all partitioned? Presumably some would
> still like to use it non-partitioned? What follows there must be a top
> level instance to decide on partitioning, and moving resources between
> sub-instances.
> 
> Right now I don't think there is much info in devlink ports which would
> be relevant without full view of the ASIC..
> 

not sure how it would play out. really just 'thinking out loud' about
the above use case to make sure devlink with proper namespace support
allows it - or does not prevent it.