On Wed, Jul 21, 2010 at 04:45:46PM -0500, Anthony Liguori wrote: > On 07/21/2010 04:32 PM, Daniel P. Berrange wrote: > >On Wed, Jul 21, 2010 at 03:55:28PM -0500, Anthony Liguori wrote: > > > >>On 07/21/2010 03:32 PM, Bruce Rogers wrote: > >> > >>>Libvirt parses qemu help output to determine qemu features. In particular > >>> it probes for the following: "cache=writethrough|writeback|none". The > >>> addition of the unsafe cache mode was inserted within this string, as > >>> opposed to being added to the end, which impacted libvirt's probe. > >>> Unbreak libvirt by keeping the existing cache modes intact and add > >>> unsafe to the end. > >>> > >>>This problem only manifests itself if a caching mode is explicitly > >>>specified in the libvirt xml, in which case older syntax for caching is > >>>passed to qemu, which it no longer understands. > >>> > >>>Signed-off-by: Bruce Rogers<brog...@novell.com> > >>> > >>> > >>Errr, libvirt is still doing this? > >> > >>This comes up frequently and it's a real PITA. Help text is not a > >>feature probing interface. This is a libvirt bug and it needs to be > >>fixed in libvirt > >> > >Of course, there is no viable alternative yet. > > Yes there is. Use the version number.
The version number is not suitable, because features can be removed at compile time and/or added via patch backports. The only reliable way is to query the QEMU binary to ask it what it actually supports. Regards, Daniel -- |: Red Hat, Engineering, London -o- http://people.redhat.com/berrange/ :| |: http://libvirt.org -o- http://virt-manager.org -o- http://deltacloud.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: GnuPG: 7D3B9505 -o- F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|
