[libvirt] [PATCH] qemu: Fix backwards compatibility of S390 guests

[Jiri Denemark]

On Wed, Jul 20, 2016 at 09:13:54 +0200, Boris Fiuczynski wrote:
> This patch reverts commit 73e4e10e62e4b1aea64b317be96af5e5488007d7
> and thereby disabling the panic device autogeneration for S390 guests.
> In addition tests are patched as well.
> 
> The reverted commit breaks backwards compatibility of S390 guests.
> As an example: A domain xml without a panic device can successfully
> be used to define on two hosts with different libvirt versions.
> Using this domain xml to define a domain on a host with libivrt v1.3.5
> makes it impossible to migrate the domain to a host with libvirt v1.3.4
> or older since libvirt v1.3.5 automatically added a panic device with
> model s390 which libvirt v1.3.4 or older rejects as unknown model.

In that case, the correct fix is not to revert this patch, but remove
the pvpanic device from a migratable XML.

Jirka