Re: [net-next v2 1/1] virtual-bus: Implementation of Virtual Bus

[Jason Wang <jasowang@redhat.com>]

On 2019/11/20 下午9:41, Jason Gunthorpe wrote:
> On Wed, Nov 20, 2019 at 12:07:59PM +0800, Jason Wang wrote:
>
>> 1) create sub fucntion and do must to have pre configuration through devlink
>> 2) only after sub function is created one more available instance was added
>> and shown through sysfs
>> 3) user can choose to create and use that mdev instance as it did for other
>> type of device like vGPU
>> 4) devlink can still use to report other stuffs
> Why do we want the extra step #3? The user already indicated they want
> a mdev via #1


It's about the compatibility, but if you wish, I think we can develop 
devlink based lifecycle for mdev for sure.


>
> I have the same question for the PF and VF cases, why doesn't a mdev
> get created automatically when the VF is probed? Why does this need
> the guid stuff?


All you said here is possible, it's a design choice for the management 
interface.


>
> The guid stuff was intended for, essentially, multi-function devices
> that could be sliced up, I don't think it makes sense to use it for
> single-function VF devices like the ICF driver.


It doesn't harm, and indeed we have other choice, we can do it gradually 
on top.


>
> Overall the guid thing should be optional. Drivers providing mdev
> should be able to use another scheme, like devlink, to on demand
> create their mdevs.


Yes, that's for sure. I'm not against to devlink for mdev/subdev, I just 
say we should not make devlink the only choice for mdev/subdev.

Thanks


>
> Jason
>