From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:40554) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TwZEL-0000Ja-29 for qemu-devel@nongnu.org; Sat, 19 Jan 2013 09:17:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TwZEJ-0002fM-Qh for qemu-devel@nongnu.org; Sat, 19 Jan 2013 09:17:08 -0500 Received: from mx4-phx2.redhat.com ([209.132.183.25]:49241) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TwZEJ-0002f8-Hy for qemu-devel@nongnu.org; Sat, 19 Jan 2013 09:17:07 -0500 Date: Sat, 19 Jan 2013 09:17:06 -0500 (EST) From: Paolo Bonzini Message-ID: <1737917148.8354027.1358605026448.JavaMail.root@redhat.com> In-Reply-To: <20130118200927.GA12992@amt.cnet> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] define qemukvm-1.2 machine type List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Marcelo Tosatti Cc: Anthony Liguori , qemu-devel@nongnu.org, Cole Robinson > On Fri, Jan 18, 2013 at 12:34:57PM -0500, Paolo Bonzini wrote: > > > > version_id and minimum_version_id should be changed to 2, as the > > > > comment indicates. > > > > > > But won't that mean we have to carry that patch forever, and > > > while we carry > > > that patch we can never migrate from Fedora qemu to an upstream > > > qemu instance? > > > I'd like to avoid carrying any incompatibility forward, if > > > possible. > > > > To some extent you have to choose between backwards- and forwards- > > compatibility. But I think that you can achieve what you want > > by leaving version_id to 3, while setting minimum_version_id to 2. > > What about > > "Problem is it uses acpi_load_old, when reading from qemu-kvm 1.2 (which > advertises format as V2), which reads 4*16 bits (instead of 16 bits) > for en/sts fields. So it can corrupt incoming migration data." That's if minimum_version_id==3. But if you set minimum_version_id==2, you fix incoming migration from qemu-kvm 1.2 (and break it from upstream QEMU 1.2). acpi_load_old will only be called for version 1. At the same time, because version_id==3 you will still have working migration to upstream QEMU 1.3 and future releases (and break backwards migration to qemu-kvm 1.2, but that's not a problem). Paolo