From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=38839 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1ObguE-0000KT-5W for qemu-devel@nongnu.org; Wed, 21 Jul 2010 17:32:47 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1ObguC-00019n-Dc for qemu-devel@nongnu.org; Wed, 21 Jul 2010 17:32:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51867) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1ObguC-00019Z-1l for qemu-devel@nongnu.org; Wed, 21 Jul 2010 17:32:44 -0400 Date: Wed, 21 Jul 2010 22:32:38 +0100 From: "Daniel P. Berrange" Subject: Re: [Qemu-devel] [PATCH] move 'unsafe' to end of caching modes in help Message-ID: <20100721213238.GB28871@redhat.com> References: <4C4704FC020000480009AB6E@sinclair.provo.novell.com> <4C475EC0.2000805@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C475EC0.2000805@codemonkey.ws> Reply-To: "Daniel P. Berrange" List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: qemu-devel@nongnu.org, Bruce Rogers 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 > > > > 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. 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 -- |: 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 :|