From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] [PATCH 1/1] kvm: support TSC deadline MSR Date: Mon, 10 Oct 2011 10:10:58 -0500 Message-ID: <4E930B02.30702@codemonkey.ws> References: <4E8B4826.8030500@redhat.com> <20111004222015.GB2926@amt.cnet> <4E930711.4020208@us.ibm.com> <4E93080A.6040603@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Liu, Jinsong" , Marcelo Tosatti , qemu-devel@nongnu.org, kvm@vger.kernel.org To: Avi Kivity Return-path: Received: from mail-gx0-f174.google.com ([209.85.161.174]:40919 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750756Ab1JJPLD (ORCPT ); Mon, 10 Oct 2011 11:11:03 -0400 Received: by ggnv2 with SMTP id v2so4576421ggn.19 for ; Mon, 10 Oct 2011 08:11:02 -0700 (PDT) In-Reply-To: <4E93080A.6040603@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10/10/2011 09:58 AM, Avi Kivity wrote: > On 10/10/2011 04:54 PM, Anthony Liguori wrote: >> On 10/04/2011 05:20 PM, Marcelo Tosatti wrote: >>> On Tue, Oct 04, 2011 at 07:53:42PM +0200, Avi Kivity wrote: >>>> On 10/03/2011 10:55 PM, Marcelo Tosatti wrote: >>>>> From: "Liu, Jinsong" >>>>> >>>>> KVM add emulation of lapic tsc deadline timer for guest. >>>>> This patch is co-operation work at qemu side. >>>>> >>>>> -#define CPU_SAVE_VERSION 12 >>>>> +#define CPU_SAVE_VERSION 13 >>>>> >>>>> >>>> >>>> Unfortunate. Can't we use subsections? >>> >>> Yes, i'll look into it tomorrow. >> >> Subsections are still broken at the moment although Juan has some patches. >> Bumping the version is the safe thing to do. >> > > 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. Once any device bumps a version id, migration is incompatible. Subsections are nice for stable branches, but they don't solve inter-version compatibility. Most importantly, subsections are broken today so until we straighten things out there, we can't rely on them. Regards, Anthony Liguori