[libvirt] Re: Changing the QEMU svn VERSION string

Daniel P. Berrange berrange at redhat.com
Tue Apr 7 09:04:05 UTC 2009

On Mon, Apr 06, 2009 at 09:37:55PM -0500, Anthony Liguori wrote:
> Hi,
> I'd like to update the VERSION string in QEMU's svn tree.  Right now, 
> it's 0.10.0 and since we have a 0.10.2 release, that's somewhat confusing.
> I don't want to make it 0.11.0 either because that's not going to be 
> reliable from a feature detection perspective.  What I would like is to 
> make it 0.11.0-devel or something similar to that.
> Being the nice guy I am, I thought I would check that this didn't make 
> libvirt go bonkers :-)  This is the relevant detection code in libvirt:
> if (sscanf(help, "QEMU PC emulator version %u.%u.%u (kvm-%u)",
>           &major, &minor, &micro, &kvm_version) != 4)
>     kvm_version = 0;
> if (!kvm_version && sscanf(help, "QEMU PC emulator version u.%u.%u",
>     &major, &minor, &micro) != 3)
>     goto cleanup2;
> If I change SVN to 0.11.0-devel, that's going to break the KVM string 
> although the QEMU string will continue to work.  Avi could potentially 
> carry a patch to keep it 0.10.x and since kvm-%u will be used to 
> identify features, that should keep things working.

The only things we use the KVM version for are to decide whether migration
and vnet_hdr flag for tun devices is supported. These checks are already 
outdated since 0.10.0 QEMU now has support for migration, and thus needs
updating. So if you choose to go with '0.11.0-devel' it won't cause any 
huge problems for us, and I'll change this code to make it more forgiving
of version number string changes in future.

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