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

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Nov 24, 2023 at 12:13:07PM +0000, Parav Pandit wrote:
> 
> 
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Friday, November 24, 2023 5:40 PM
> > 
> > On Fri, Nov 24, 2023 at 07:51:06PM +0800, Jason Wang wrote:
> > > On Fri, Nov 24, 2023 at 7:38âPM Michael S. Tsirkin <mst@redhat.com>
> > wrote:
> > > >
> > > > On Fri, Nov 24, 2023 at 11:07:53AM +0800, Jason Wang wrote:
> > > > > How TDISP/attestation is related to a specific device driver? How
> > > > > can a legacy DPDK driver break things like attestation here?
> > > > >
> > > > > > Hence it is not applicable.
> > > > >
> > > > > Wow. The legacy tunnel was just invented by you for just several
> > > > > months and soon became a second-class citizen in the proposal here?
> > > >
> > > > Legacy is not going to be a 1st class citizen and that was a
> > > > concious decision the TC made.
> > > > In particular we know straight
> > > > away that there is no way to make them safely work while preserving
> > > > assumptions confidential computing guests make (which I guess is
> > > > what you mean here).
> > >
> > > Probably, but I think we need to support its migration without TD.
> > 
> > Ah, migration of legacy guests is an interesting point.
> > Bringing up TD was just confusing.
> > 
> > I expect this to be rather painless to add precisely because this proposal does
> > not reply on either modern or legacy pci layout. But details need to be
> > thought through, I agree. I don't see why this is not applicable - definitely
> > people are used to be able to migrate these guests.
> >
> The current layout in device context is for the modern.
> The legacy one will be just another enum and struct that will be added subsequently.

Worth adding. The difficulty is when to send which state for
transitional devices. E.g. do they just always send both?
Don't shoot from the hip, Think about this, please and
address in the next version.


> > 
> > > > The whole point of isolating legacy mess in the special commands was
> > > > so we don't try to support them going forward, don't try to add new
> > > > features for legacy interfaces please.
> > >
> > > Thanks
> > >
> > >
> > > >
> > > > --
> > > > MST
> > > >
>