From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] Re: KVM call minutes for June 8 Date: Wed, 09 Jun 2010 11:22:55 -0500 Message-ID: <4C0FBFDF.5050009@codemonkey.ws> References: <20100608150500.GA28492@x200.localdomain> <4C0E694F.8040607@codemonkey.ws> <20100608175952.5f43ea8f@redhat.com> <4C0EB281.80907@codemonkey.ws> <20100609121820.1f3bb47a@redhat.com> <20100609153107.GE28326@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Luiz Capitulino , Chris Wright , qemu-devel@nongnu.org, kvm-devel , armbru@redhat.com, Kevin Wolf To: "Daniel P. Berrange" Return-path: Received: from mail-iw0-f174.google.com ([209.85.214.174]:51503 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757576Ab0FIQW7 (ORCPT ); Wed, 9 Jun 2010 12:22:59 -0400 Received: by iwn37 with SMTP id 37so5997370iwn.19 for ; Wed, 09 Jun 2010 09:22:58 -0700 (PDT) In-Reply-To: <20100609153107.GE28326@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 06/09/2010 10:31 AM, Daniel P. Berrange wrote: >> However, libvirt was counting on this feature and on the snapshot commands >> to switch from the text Monitor. We have two options: >> >> 1. Ask them to wait one more release (not so good for us) >> 2. Try to find a way to have those features in for 0.13 >> >> Daniel has commented to me that making the snapshot commands synchronous >> for 0.13 wouldn't be that bad, what do you think? >> > The thought is that changing a command from synchronous to asynchronous is > not an ABI incompatible change. An existing app simply won't know to take > advantage of the new possibilities that async commands offer. > It's not QMP that's the major issue with savevm. The major issue is actually the way snapshots are saved in qcow2. You need to know the size of the snapshot prior to creating the snapshot which is not possible if you want to make snapshots live. In order to support this functionality, we'll probably have to introduce a new snapshot format in qcow2. Honestly, I would recommend not supporting snapshots in libvirt until we did the work to make snapshots live. Snapshots can cause guests to generate errors as it stands today and fixing that will almost certainly result in backwards compatibility considerations. If we did put savevm in QMP today, we would need to provide an interface that let applications detect when we eventually fix this. Regards, Anthony Liguori > Regards, > Daniel > From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=55470 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OMO3U-0004BW-FR for qemu-devel@nongnu.org; Wed, 09 Jun 2010 12:23:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OMO3T-0002TI-1W for qemu-devel@nongnu.org; Wed, 09 Jun 2010 12:23:04 -0400 Received: from mail-iw0-f173.google.com ([209.85.214.173]:56805) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OMO3S-0002Sz-Rm for qemu-devel@nongnu.org; Wed, 09 Jun 2010 12:23:03 -0400 Received: by iwn10 with SMTP id 10so1918420iwn.4 for ; Wed, 09 Jun 2010 09:23:00 -0700 (PDT) Message-ID: <4C0FBFDF.5050009@codemonkey.ws> Date: Wed, 09 Jun 2010 11:22:55 -0500 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: KVM call minutes for June 8 References: <20100608150500.GA28492@x200.localdomain> <4C0E694F.8040607@codemonkey.ws> <20100608175952.5f43ea8f@redhat.com> <4C0EB281.80907@codemonkey.ws> <20100609121820.1f3bb47a@redhat.com> <20100609153107.GE28326@redhat.com> In-Reply-To: <20100609153107.GE28326@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Chris Wright , Kevin Wolf , kvm-devel , armbru@redhat.com, qemu-devel@nongnu.org, Luiz Capitulino On 06/09/2010 10:31 AM, Daniel P. Berrange wrote: >> However, libvirt was counting on this feature and on the snapshot commands >> to switch from the text Monitor. We have two options: >> >> 1. Ask them to wait one more release (not so good for us) >> 2. Try to find a way to have those features in for 0.13 >> >> Daniel has commented to me that making the snapshot commands synchronous >> for 0.13 wouldn't be that bad, what do you think? >> > The thought is that changing a command from synchronous to asynchronous is > not an ABI incompatible change. An existing app simply won't know to take > advantage of the new possibilities that async commands offer. > It's not QMP that's the major issue with savevm. The major issue is actually the way snapshots are saved in qcow2. You need to know the size of the snapshot prior to creating the snapshot which is not possible if you want to make snapshots live. In order to support this functionality, we'll probably have to introduce a new snapshot format in qcow2. Honestly, I would recommend not supporting snapshots in libvirt until we did the work to make snapshots live. Snapshots can cause guests to generate errors as it stands today and fixing that will almost certainly result in backwards compatibility considerations. If we did put savevm in QMP today, we would need to provide an interface that let applications detect when we eventually fix this. Regards, Anthony Liguori > Regards, > Daniel >