Re: [Qemu-devel] Re: [PATCH] Revive -version 'QEMU PC Emulator...'

[Luiz Capitulino <lcapitulino@redhat.com>]

On Thu, 13 May 2010 14:21:02 +0100
"Daniel P. Berrange" <berrange@redhat.com> wrote:

> On Thu, May 13, 2010 at 03:07:49PM +0200, Jes Sorensen wrote:
> > On 05/13/10 15:04, Cole Robinson wrote:
> > > On 05/13/2010 04:35 AM, Jes Sorensen wrote:
> > >> On 05/12/10 22:48, Cole Robinson wrote:
> > >> I think rather than 1, it would be better to add a patch to libvirt to
> > >> catch both formats. I know Chris Lalancette already cooked up a patch
> > >> for this. Combined with the 2) patch I just posted, and 3) I think that
> > >> should take care of the problems.
> > > 
> > > It doesn't solve the problem for existing libvirt installations. It's
> > > not uncommon for users to track just the latest kvm releases without
> > > upgrading libvirt: any future qemu or kvm release will break every
> > > version of libvirt that exists today. Given that unfortunate case, I
> > > still recommend reverting the 'PC' change at least for long enough for a
> > > few fixed libvirt releases to make it into the wild.
> > 
> > But that is no different from what we have today. Users who update their
> > qemu and see issues with libvirt can also be asked to update libvirt. I
> > have already had several cases where I needed to do that anyway.
> 
> The general policy of QEMU has been to try and avoid  known breakage of
> existing apps unless unavoidable. This change introduced 100% guarenteed
> breakage of every single deployment that exists today, for the sake of
> removing 2 characters from a string. I really don't think this is a good
> cost/benefit tradeoff & agree with Cole that I'd like to see this reverted
> for the 0.13 release, and re-considered in a later release once we've had
> a chance to get a preventative fix out for libvirt using -version-string
> or equivalent.

 Agreed, we should improve client's life, not contribute with additional
headaches.

 Regarding Cole's suggestion, instead of adding a new -version parameter
you could connect to QMP, get this information from it and re-run QEMU,
not sure if it's worth the trouble though.