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Date: Thu, 22 Jul 2010 10:45:58 -0300
From: Luiz Capitulino <lcapitulino@redhat.com>
Subject: Re: [Qemu-devel] [PATCH] move 'unsafe' to end of caching modes in help
Message-ID: <20100722104558.2012e027@redhat.com>
In-Reply-To: <4C475EC0.2000805@codemonkey.ws>
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org, Bruce Rogers <brogers@novell.com>

On Wed, 21 Jul 2010 15:55:28 -0500
Anthony Liguori <anthony@codemonkey.ws> 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<brogers@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.

IMHO, we should try to not break it as much as we can while QMP
isn't stable yet, just like we do for the user monitor.