Re: [Qemu-devel] [PATCH] move 'unsafe' to end of caching modes in help

[Anthony Liguori]

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<address@hidden>
> > >
> > >        
> > 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.

Regards,

Anthony Liguori

>   The QMP patches I
> sent a few weeks back now to add ability to query capabilities were
> intended to provide the neccessary support in QEMU for us to use
> instead of -help. Given that QMP isn't going to be declared stable
> in 0.13 though, it looks like we'll be continuing to use -help
> until the 0.14 release of QEMU.
>
>
> Regards,
> Daniel
>