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

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

On Tue, Nov 07, 2023 at 12:05:12PM +0800, Jason Wang wrote:
> > > > > One thing that you ignore is that, hypervisor can use what you
> > > > > invented as a transport for VF, no?
> > > > >
> > > > No. by design,
> > >
> > > It works like hypervisor traps the virito config and forwards it to admin
> > > virtqueue and starts the device via device context.
> > It needs more granular support than the management framework of device context.
> 
> It doesn't otherwise it is a design defect as you can't recover the
> device context in the destination.
> 
> Let me give you an example:
> 
> 1) in the case of live migration, dst receive migration byte flows and
> convert them into device context
> 2) in the case of transporting, hypervisor traps virtio config and
> convert them into the device context
> 
> I don't see anything different in this case. Or can you give me an example?

"trap virtio config" means "trap writes into virtio config" presumably?
config can change itself without driver doing anything. Hypervisor
can't trap it then. This is one of the problems with Lingshan's
SUSPEND bit - what happens with these config changes in underspecified.

-- 
MST