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

["Daniel P. Berrange" <berrange@redhat.com>]

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.

Regards,
Daniel
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