netdev - Re: [PATCH net-next 1/4] mlx5: Make building eswitch configurable

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Date:   Fri, 27 Jan 2017 23:15:56 +0200
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Tom Herbert <tom@...bertland.com>
Cc:     Or Gerlitz <gerlitz.or@...il.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        David Miller <davem@...emloft.net>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Kernel Team <kernel-team@...com>
Subject: Re: [PATCH net-next 1/4] mlx5: Make building eswitch configurable

On Fri, Jan 27, 2017 at 8:42 PM, Tom Herbert <tom@...bertland.com> wrote:
> On Fri, Jan 27, 2017 at 10:28 AM, Saeed Mahameed
> <saeedm@....mellanox.co.il> wrote:
>> On Fri, Jan 27, 2017 at 8:16 PM, Tom Herbert <tom@...bertland.com> wrote:
>>> On Fri, Jan 27, 2017 at 10:05 AM, Saeed Mahameed
>>> <saeedm@....mellanox.co.il> wrote:
>>>> On Fri, Jan 27, 2017 at 7:50 PM, Tom Herbert <tom@...bertland.com> wrote:
>>>>> On Fri, Jan 27, 2017 at 9:38 AM, Saeed Mahameed
>>>>> <saeedm@....mellanox.co.il> wrote:
>>>>>> On Fri, Jan 27, 2017 at 7:34 AM, Or Gerlitz <gerlitz.or@...il.com> wrote:
>>>>>>> On Fri, Jan 27, 2017 at 1:32 AM, Tom Herbert <tom@...bertland.com> wrote:
>>>>>>>> Add a configuration option (CONFIG_MLX5_CORE_ESWITCH) for controlling
>>>>>>>> whether the eswitch code is built. Change Kconfig and Makefile
>>>>>>>> accordingly.
>>>>>>>
>>>>>>> Tom, FWIW, please note that the basic e-switch functionality is needed
>>>>>>> also when SRIOV isn't of use, this is for a multi host configuration.
>>>>>>>
>>>>>>
>>>>>> Right, set_l2_table_entry@...itch.c need to be called by PF for any UC
>>>>>> MAC address wanted by VF or PF.
>>>>>> To keep one flow in the code, the implementation is done as part of eswitch.
>>>>>>
>>>>>> so in multi-host configuration (where there are 4 PFs) each PF should
>>>>>> invoke set_l2_table_entry_cmd  for each one of its own UC MACs.
>>>>>>
>>>>>> populating the l2 table is done using the whole eswitch event driven
>>>>>> mechanisms, it is not easy and IMH not right to separate eswitch
>>>>>> tables from l2 table (same management logic, different tables).
>>>>>>
>>>>>> Anyways as Or stated this is just an FYI, eswitch needs to be enabled
>>>>>> on Multi-host configuration.
>>>>>>
>>>>> What indicate a multi-host configuration?
>>>>
>>>> nothing in the driver, it is transparent.
>>>>
>>> So then we always need the eswitch code to be built even if someone
>>> never uses any of it?
>>>
>>
>> yes.
>> but for your convenience all you need is to compile eswitch.c.
>> esiwtch_offoalds.c and en_rep.c can be compiled out for basic ethernet.
>>
> Well eswitch.c is 2200 LOC. en_rep.c and eswitch_offloads.c are 1600
> LOC. If we _must_ have eswitch.c then there's probably not much point
> then. But I am still finding it hard to fathom that eswitch has now
> become a mandatory component of Ethernet drivers/devices.
>

It is only mandatory for configurations that needs eswitch, where the
driver has no way to know about them, for a good old bare metal box,
eswitch is not needed.

we can do some work to strip the l2 table logic - needed for PFs to
work on multi-host - out of eswitch but again that would further
complicate the driver code since eswitch will still need to update l2
tables for VFs.


> Tom
>
>>>>>
>>>>>>> Or.
>>>>>>>
>>>>>>> My WW (and same for the rest of the IL team..) has ended so I will be
>>>>>>> able to further look on this series and comment on Sunday.