[libvirt] [PATCH 0/2] qemu: Support for QXL heads

[Martin Kletzander]

On Thu, Mar 10, 2016 at 03:46:42PM +0100, Christophe Fergeau wrote:
>Hey,
>
>On Thu, Mar 10, 2016 at 03:20:59PM +0100, Martin Kletzander wrote:
>> So this is an old, tiny series that was posted some time ago; actually
>> a lot of time ago.  I complained because of two things.  First one
>> being that there are no tests, so this series has them in.  The second
>> one was that this could break migration from old code since the
>> parameter was not used before.  So I coded up a migration flag,
>> handled all the special cases and then started testing it.  And while
>> testing it, I've found out that QEMU doesn't care at all about this
>> parameter being there and there is no point in keeping it
>> super-stable, especially when it can be changed on the fly.  So I
>> removed all that code and ended up with tiny series very similar to
>> previous attempts by various people.
>
>I think the main problem was that if you upgrade from a QEMU which did
>not care to a QEMU with the option and a libvirt which supports it,
>suddenly your VMs are going to go from supporting multiple heads (4) to
>only supporting one as older libvirt always add a 'heads=1' to the XML.
>

I'm not sure how to handle this, but I was under the impression that
this can be changed on the fly.  If libvirt doesn't support that, then
we should enable it.  But anyway not adding max_outputs= to commandline
when migrating from older libvirt could break something the other way
around as well.

/me quickly searches reflog for that migration code...

>Christophe
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