Re: [virtio-comment] RE: [PATCH V2 3/6] virtio: dont reset vqs when SUSPEND

[Jason Wang <jasowang@redhat.com>]

On Fri, Nov 24, 2023 at 2:20âPM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Fri, Nov 24, 2023 at 11:25:41AM +0800, Jason Wang wrote:
> > On Wed, Nov 22, 2023 at 2:32âPM Parav Pandit <parav@nvidia.com> wrote:
> > >
> > >
> > > > From: Jason Wang <jasowang@redhat.com>
> > > > Sent: Wednesday, November 22, 2023 10:59 AM
> > > >
> > > > On Wed, Nov 22, 2023 at 5:18âAM Michael S. Tsirkin <mst@redhat.com>
> > > > wrote:
> > > > >
> > > > > On Tue, Nov 21, 2023 at 03:33:07PM +0800, Jason Wang wrote:
> > > > > > > Lingshan claimed that suspending device is for live migration in commit
> > > > log and in discussion he portray it as some basic facility unrelated to device
> > > > migration such as debug etc.
> > > > > > > Instead of claiming it as some non_device_migration facility does not
> > > > make sense.
> > > > > >
> > > > > > It is used for migration for sure.
> > > > >
> > > > > Well having a generic facility to stop device sounds like a nice thing.
> > > > > However the devil is in the detail. A lot of detail here seems very
> > > > > much tailored to a very specific implementation in mind.
> > > > > So thinking through how it will work e.g. for power management would
> > > > > be a good excercise to figure out how it should work in detail.
> > > >
> > > > It might work in the case where there's no PM support in the transport. E.g for
> > > > MMIO devices.
> > > >
> > > MMIO should implement PM like other transport. That brings the equivalency principle.
> > >
> >
> > MMIO are usually platform devices. I don't see the point.
> >
> > Thanks
>
> I don't understand what you are saying. Why does it make sense to
> suspend individual platform devices when they are suspended
> with the whole platform?

It is because we don't need to suspend the whole platform to migrate
the virtio-MMIO device.

Thanks

>
> --
> MST
>