Re: [Qemu-devel] storing machine data in qcow images?

[Andrea Bolognani]

On Thu, 2018-06-07 at 15:45 +0100, Dr. David Alan Gilbert wrote:
> * Andrea Bolognani (address@hidden) wrote:
> > On Thu, 2018-06-07 at 14:49 +0100, Dr. David Alan Gilbert wrote:
> > > Including the nvram and efi makes me nervous; but I can see why together
> > > they might work.  However, there's no guarantee that EFI has been tested
> > > with the QEMU it's used on and ... that could be trouble.
> > 
> > If the QEMU binary doesn't support EFI, then a guest expecting
> > EFI won't be able to start regardless of where the EFI ROM came
> > from.
> 
> No, I mean if the QEMU doesn't support that *particular* EFI.

I could be wrong, but I feel like it's significantly less likely
that a random QEMU binary won't like a random EFI ROM than it is
for a random EFI ROM to not like a random EFI NVRAM.

> > > Also, if we're going to start including the EFI rom then that would have
> > > to be migrated with the VM so that after a restart on a different host
> > > it's still using the right ROM that's compatible with it's varfile.
> > 
> > That's a problem that needs to be addressed anyway, because even
> > as it is now you could easily find yourself trying and failing
> > to migrate a guest between two hosts that have different and
> > incompatible EFI ROMs installed.
> 
> True; although I was working on the basis that vendors who cared about
> migration compatibility would couple the EFI versions with machine types
> to ensure that the variable data didn't become incompatible.

As far as I know, nobody is actually doing this at the moment.

-- 
Andrea Bolognani / Red Hat / Virtualization