Re: vDPA bus driver selection

From: Jason Wang <jasowang@redhat.com>
To: Stefano Garzarella <sgarzare@redhat.com>
Cc: Eli Cohen <elic@nvidia.com>,
	Linux Virtualization <virtualization@lists.linux-foundation.org>,
	"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: vDPA bus driver selection
Date: Fri, 29 Oct 2021 10:31:22 +0800	[thread overview]
Message-ID: <CACGkMEtNAQDg9b03Xv3JRUX0EGXAv9JFogHGkpRbfgVghOiuuQ@mail.gmail.com> (raw)
In-Reply-To: <20211028094711.e6mm7ump5mrl7jpf@steredhat>

On Thu, Oct 28, 2021 at 5:47 PM Stefano Garzarella <sgarzare@redhat.com> wrote:
>
> On Thu, Oct 28, 2021 at 10:24:47AM +0800, Jason Wang wrote:
> >On Thu, Oct 28, 2021 at 4:16 AM Michael S. Tsirkin <mst@redhat.com> wrote:
> >>
> >> 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.
> >
> >Actually, we want to support this in the first version of vDPA bus.
> >But for some reason it was dropped. The idea is to specify the device
> >type 'virtio' or 'vhost'. But a concern is that, it may encourage
> >vendor to implement e.g virtio specific device (without DMA
> >isolation).
>
> Yep, I see the issue about device type, so I think make sense to require
> the support of both, how it is now basically.
>
> So instead of defining the type of the device, we could provide the
> possibility to choose which bus to connect it to,

I think you meant the "bus driver" here?

> in this way we
> continue to require that both are supported.
>
> As Michael suggested, instead of specify it at the creation time as was
> in my original idea, we can provide an API to attach/detach a device to
> a specific vDPA bus.

Does such an API exist in driver core?

>
> Of course, providing a default behaviour like now, which connects to the
> first registered.

If we want to change this, we can introduce "driver_override".

Thanks

>
> Thanks,
> Stefano
>

_______________________________________________
Virtualization mailing list
Virtualization@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/virtualization