Re: [PATCH v6 2/4] vhost-vdpa: introduce SUSPEND backend feature bit

[Stefano Garzarella]

On Fri, Jul 08, 2022 at 01:38:45PM +0200, Eugenio Perez Martin wrote:
> On Tue, Jun 28, 2022 at 3:43 PM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
> > On Thu, Jun 23, 2022 at 06:07:36PM +0200, Eugenio Pérez wrote:
> > >Userland knows if it can suspend the device or not by checking this feature
> > >bit.
> > >
> > >It's only offered if the vdpa driver backend implements the suspend()
> > >operation callback, and to offer it or userland to ack it if the backend
> > >does not offer that callback is an error.
> >
> > Should we document in the previous patch that the callback must be
> > implemented only if the drive/device support it?
>
> It's marked as optional in the doc, following other optional callbacks
> like set_group_asid for example. But I'm ok with documenting this
> behavior further.
>
> > The rest LGTM although I have a doubt whether it is better to move this
> > patch after patch 3, or merge it with patch 3, for bisectability since
> > we enable the feature here but if the userspace calls ioctl() with
> > VHOST_VDPA_SUSPEND we reply back that it is not supported.
>
> I'm fine with moving it, but we will have that behavior with all the
> devices anyway. Regarding userspace, we just replace ENOIOCTL with
> EOPNOTSUPP. Or I'm missing something?

Yep, you're right, this is fine! ;-)

Stefano