RE: [virtio-comment] [PATCH v1 1/8] admin: Add theory of operation for device migration

[Parav Pandit <parav@nvidia.com>]

> From: Michael S. Tsirkin <mst@redhat.com>
> Sent: Wednesday, October 18, 2023 3:50 PM
> 
> On Wed, Oct 18, 2023 at 08:16:01AM +0000, Parav Pandit wrote:
> > > This doesn't happen yet. For example, a VF with adminq that can be
> > > isolated with PASID makes some sense.
> > PASID is for the process of user space.
> > Kernel space do not consume a PASID.
> 
> It could if we need it to.
> 
> > Depending on the PASID can work for mediation approach only.
> > Last I heard is the cpu or kernel took the support out of it as some special
> instruction did not work for that cpu.
> 
> Are you talking about ENQCMD things? That's nice but I don't think it's
> necessary for isolation here.
>
Yes. I believe SVA is disabled.
 
> ...
> 
> > > The reason why I see it is different from FLR is that
> > >
> > > 1) D3cold requires the VF to be off the power
> > > 2) State transition might takes more than what FLR did, PCI seems
> > > only cover the minimum delay but not maximum which may have
> > > implications for downtime
> > >
> > D3cold is not controlled by the guest driver.
> > PM register can change D0 to D3hot.
> 
> It likely makes sense to document how all this interacts with things like PM and
> other pci config. maybe you did in v2 didn't look at it yet.
> 
Yeah, v2 covered it. Please see.
I didn't repeat what pci already covers for D3hot and D3 cold.