netdev - Re: [PATCH v3 net-next 01/14] devlink: add enable

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Date:   Tue, 21 Feb 2023 13:55:29 -0800
From:   Shannon Nelson <shannon.nelson@....com>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        drivers@...sando.io, brett.creeley@....com
Subject: Re: [PATCH v3 net-next 01/14] devlink: add enable_migration parameter

On 2/21/23 4:33 AM, Jiri Pirko wrote:
> Tue, Feb 21, 2023 at 12:54:25AM CET, shannon.nelson@....com wrote:
>> On 2/20/23 12:22 AM, Jiri Pirko wrote:
>>> Fri, Feb 17, 2023 at 11:55:45PM CET, shannon.nelson@....com wrote:
>>>> Add a new device generic parameter to enable/disable support
>>>> for live migration in the devlink device.  This is intended
>>>> primarily for a core device that supports other ports/VFs/SFs.
>>>> Those dependent ports may need their own migratable parameter
>>>> for individual enable/disable control.
>>>>
>>>> Examples:
>>>>    $ devlink dev param set pci/0000:07:00.0 name enable_migration value true cmode runtime
>>>>    $ devlink dev param show pci/0000:07:00.0 name enable_migration
>>>>    pci/0000:07:00.0:
>>>>      name enable_migration type generic
>>>>        values:
>>>>          cmode runtime value true
>>>>
>>>> Signed-off-by: Shannon Nelson <shannon.nelson@....com>
>>>
>>> Could you please elaborate why exactly is this needed?
>>>
>>>   From my perspective, the migration capability is something that
>>> is related to the actual function (VF/SF).
>>>
>>> When instantiating/configuring SF/VF, the admin ask for the particular
>>> function to support live migration. We have port function caps now,
>>> which is exactly where this makes sense.
>>>
>>> See DEVLINK_PORT_FN_CAP_MIGRATABLE.
>>
>> Hi Jiri,
>>
>> Thanks for your questions.  My apologies for not getting your name into the
>> To: list – a late Friday afternoon miss.
>>
>> This enable_migration flag is intended to be similar to the enable_vnet,
>> enable_rdma, and similar existing parameters that are used by other core
>> devices.
>>
>> Our pds_core device can be used to support several features (currently VFio
>> and vDPA), and this gives the user a way to control how many of the features
>> are made available in any particular configuration.  This is to be enabled to
>> turn on support for our pds_vfio client devices as a whole, not individually
>> port-by-port.  I understand FN_CAP_MIGRATABLE to be applied to an individual
>> devlink port, which could be used in conjunction with this once the general
>> feature is enable in pds_core.
> 
> Okay, that sounds legit. Could yout please extend the patch description
> with this? Thanks!

Will do - thanks.
sln