Re: [Qemu-devel] [PATCH] Remove hardcoded xen-platform device initialization

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Paolo Bonzini [mailto:paolo.bonzini@gmail.com] On Behalf Of Paolo
> Bonzini
> Sent: 14 June 2013 14:53
> To: Paul Durrant
> Cc: Stefano Stabellini; qemu-devel@nongnu.org; xen-devel@lists.xen.org
> Subject: Re: [PATCH] Remove hardcoded xen-platform device initialization
> 
> Il 14/06/2013 04:50, Paul Durrant ha scritto:
> >> > This patch is problematic because we can't know for sure the version of
> >> > upstream QEMU that is going to be used with Xen.
> >> > If we apply this patch and QEMU 1.5 is going to be used with Xen 4.2,
> >> > guests won't be able to use PV drivers.
> >> >
> > Is there not a compatibility matrix? The hardcoded init. is just blatantly the
> wrong thing to be doing and it needs to go.
> >
> > Could my accompanying toolstack patch not be backported to the next 4.2
> release as mitigation?
> 
> I think Ian is right.  You should revert the toolstack patch and not
> apply this one for now.  Then aim at using "-M pc" in 4.4 (and require
> 1.6 or 1.7), so that there is no need for a compatibility matrix.
> 

As I said in another mail on the thread, I don't think we'll ever be able to use -M pc, so I'm planning to create a xenfv-2.0 machine type and leave xenfv with the hardcoded device creation semantic. Then I'll add code to libxl to parse qemu's response to -M help and choose xenfv-2.0 if it exists (and specify the -device argument accordingly).

  Paul