Re: Out-of-Process Device Emulation session at KVM Forum 2020

[Michael S. Tsirkin]

On Fri, Oct 30, 2020 at 11:13:59AM +0000, Stefan Hajnoczi wrote:
> > > 3. The device can save/load opaque blobs. This is the initial VFIO
> > > approach.
> >
> >
> > I still don't get why it must be opaque.
> 
> If the device state format needs to be in the VMM then each device
> needs explicit enablement in each VMM (QEMU, cloud-hypervisor, etc).

And QEMU cares why exactly?

> Let's invert the question: why does the VMM need to understand the
> device state of a _passthrough_ device?

To support cross version migration and compatibility checks.
This problem is harder than it appears, I don't think vendors
will do a good job of it without any guidance and standards.

-- 
MST