Re: [Qemu-devel] [PATCH 2/4] pc/q35: drop compatiility with old bios types

[Michael S. Tsirkin]

On Mon, Feb 15, 2016 at 11:58:24AM +0100, Gerd Hoffmann wrote:
> On So, 2016-02-07 at 12:29 +0200, Michael S. Tsirkin wrote:
> > We don't ship bios without support for loading ACPI anymore, and old q35
> > machine types don't allow migrating such bios.  Drop it, as well as
> > has_*mr flags that are there for migration compatibility.
> 
> Wouldn't that break migration between 2.5 and 2.6 with -M q35-1.6 ?

I think I said this somewhere but I'll repeat it here: I think we should
just mark the old machine types non migrateable.

> It's also a guest-visible change as acpi tables change ...

acpi tables change yes but not too much - there are just bugfixes.  We
change acpi tables without versioning within reason.
For example, recent change by Igor completely removed SSDT and
affected old machine types too.

> I'm all for cleaning up this old cruft, but I think it would be cleaner
> to just drop the old (pre-migration support) q35 machine types instead
> of changing them in subtle ways ...
> 
> cheers,
>   Gerd

Easier, sure. Not sure about the cleaner ...

-- 
MST