From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [PATCH 0/2] Make savevm versioning compatible with upstream QEMU Date: Thu, 30 Apr 2009 08:35:34 -0500 Message-ID: <49F9A926.5050909@us.ibm.com> References: <1241038430-7444-1-git-send-email-aliguori@us.ibm.com> <49F9A7D3.9040402@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from e35.co.us.ibm.com ([32.97.110.153]:44228 "EHLO e35.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763009AbZD3Nfo (ORCPT ); Thu, 30 Apr 2009 09:35:44 -0400 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e35.co.us.ibm.com (8.13.1/8.13.1) with ESMTP id n3UDU2TW011608 for ; Thu, 30 Apr 2009 07:30:02 -0600 Received: from d03av01.boulder.ibm.com (d03av01.boulder.ibm.com [9.17.195.167]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v9.2) with ESMTP id n3UDZZwU236816 for ; Thu, 30 Apr 2009 07:35:39 -0600 Received: from d03av01.boulder.ibm.com (loopback [127.0.0.1]) by d03av01.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id n3UDZZMw021699 for ; Thu, 30 Apr 2009 07:35:35 -0600 In-Reply-To: <49F9A7D3.9040402@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Avi Kivity wrote: > Anthony Liguori wrote: >> Right now, there is no way savevm versioning can be compatible with >> upstream >> QEMU because KVM adds fields to existing savevm structures without >> incrementing >> the versions. >> >> If you assume that KVM will eventually merge into upstream QEMU, this >> means that >> eventually KVM is going to have to break backwards compatibility with >> itself >> to resolve this issue in a non-graceful way. >> >> So let's do that now instead of doing it later when the situation is >> only worse. >> >> I'm happy to allocate particular version identifiers for KVM to avoid >> future >> conflicts. I believe we should try to eliminate the existing >> differences so >> that we can converge in the future on a common versioning scheme. >> > > Applied both, thanks. > > I think we can avoid the need to synchronize too much by saving > kvm-specific state for device "x" using id "x-kvm"; this allows the > two to evolve independently. I need to add save/restore support to upstream QEMU so this is a good excuse to just merge the changes in KVM upstream. So hopefully this will become a non issue. If something arises and you need more savevm state, introduce a new section suffixed or prefixed with kvm. Alternatively, ask and I can reserve an ID upstream. For virtio-net, we just need to get the vnet stuff merged upstream. -- Regards, Anthony Liguori