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

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Message-ID: <98cd205b-fabe-a2ee-e9c0-51e269b78976@amd.com>
Date:   Mon, 20 Feb 2023 15:54:25 -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 2/20/23 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.

Thanks,
sln