Re: vDPA bus driver selection

[Stefano Garzarella <sgarzare@redhat.com>]

Hi Parav,

On Wed, Oct 27, 2021 at 03:21:15PM +0000, Parav Pandit wrote:
>Hi Stefano,
>
>> From: Stefano Garzarella <sgarzare@redhat.com>
>> Sent: Wednesday, October 27, 2021 8:04 PM
>>
>> Hi folks,
>> I was trying to understand if we have a way to specify which vDPA bus driver
>> (e.g. vhost-vdpa, virtio-vdpa) a device should use.
>> IIUC we don't have it, and the first registered driver is used when a new device
>> is registered.
>>
>> I was thinking if it makes sense to extend the management API to specify which
>> bus driver to use for a device. A use case could be for example a single host
>> handling VMs and bare-metal containers, so we would have both virtio-vdpa
>> and vhost-vdpa loaded and we want to attach some devices to VMs through
>> vhost-vdpa and others to containers through virtio-vdpa.
>>
>> What do you think?
>>
>One option is, user keeps the drivers_autoprobe disabled for the vdpa bus using,
>
>$ vdpa/vdpa dev add mgmtdev vdpasim_net name vdpa0 mac 00:11:22:33:44:55
>$ echo 0 > /sys/bus/vdpa/drivers_autoprobe
>
>And after vdpa device creation, it manually binds to the desired driver such as,
>
>$ echo vdpa0 > /sys/bus/vdpa/drivers/virtio_vdpa/bind
>Or
>$ echo vdpa0 > /sys/bus/vdpa/drivers/vhost_vdpa/bind

Cool, I didn't know that. This is very useful, but do you think it might 
be better to integrate it with the netlink API and specify at creation 
which bus driver to use?

>
>In an case of VDUSE, it makes more sense to bind to the one of the 
>above driver after user space has connected the use space backend to 
>the kernel device.

Yep, make sense.

Thanks,
Stefano

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