From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:53869) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RDHnF-0000i4-Qg for qemu-devel@nongnu.org; Mon, 10 Oct 2011 11:29:30 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RDHnE-0001PA-Pu for qemu-devel@nongnu.org; Mon, 10 Oct 2011 11:29:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:10199) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RDHnE-0001Ow-Ie for qemu-devel@nongnu.org; Mon, 10 Oct 2011 11:29:28 -0400 Message-ID: <4E930F52.5050603@redhat.com> Date: Mon, 10 Oct 2011 17:29:22 +0200 From: Avi Kivity MIME-Version: 1.0 References: <4E8B4826.8030500@redhat.com> <20111004222015.GB2926@amt.cnet> <4E930711.4020208@us.ibm.com> <4E93080A.6040603@redhat.com> <4E930B02.30702@codemonkey.ws> In-Reply-To: <4E930B02.30702@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/1] kvm: support TSC deadline MSR List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: "Liu, Jinsong" , Marcelo Tosatti , qemu-devel@nongnu.org, kvm@vger.kernel.org On 10/10/2011 05:10 PM, Anthony Liguori wrote: >> It's irreversible, once we release a version with a bumped ID we >> can't go back. > > > But the question is whether we've bumped *any* versions of common > devices since 0.15 because if so, it's moot here. What's the answer? And if the answer is we did, why did we? > Once any device bumps a version id, migration is incompatible. > > Subsections are nice for stable branches, but they don't solve > inter-version compatibility. Why not? Though I agree it's a long shot to get it to work, since there are so many changes and it's easy to get any one of them wrong. You had an idea once to fingerprint the migration format and compare it across versions? I assume the almighty visitor can make this very simple? > Most importantly, subsections are broken today so until we > straighten things out there, we can't rely on them. > Let's not throw a permanent baby out with the temporary bath water. -- error compiling committee.c: too many arguments to function