From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Michael S. Tsirkin" Subject: Re: [Qemu-devel] [PATCHv4 3/4] cpuid: disable pv eoi for 1.1 and older compat types Date: Wed, 29 Aug 2012 13:32:26 +0300 Message-ID: <20120829103226.GE5225@redhat.com> References: <20120828191338.GE6223@otherpad.lan.raisama.net> <20120828213527.GB5817@redhat.com> <20120828220242.GW2886@otherpad.lan.raisama.net> <20120828222113.GA5970@redhat.com> <20120829095903.GB32031@amt.cnet> <20120829100334.GB561@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Eduardo Habkost , Anthony Liguori , avi@redhat.com, gleb@redhat.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, Jan Kiszka , Blue Swirl To: Marcelo Tosatti Return-path: Received: from mx1.redhat.com ([209.132.183.28]:43000 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751751Ab2H2KbN (ORCPT ); Wed, 29 Aug 2012 06:31:13 -0400 Content-Disposition: inline In-Reply-To: <20120829100334.GB561@amt.cnet> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Aug 29, 2012 at 07:03:34AM -0300, Marcelo Tosatti wrote: > On Wed, Aug 29, 2012 at 06:59:03AM -0300, Marcelo Tosatti wrote: > > > I don't understand. What is the problem with the proposal? > > > What will not work with our protocol? > > > Can you give an example please? > > > > > > > > > > > Too late for 1.2? > > > > > > > > Absolutely (in my opinion). > > > > My concern here is that you are introducing infrastructure by using > > _one example_, claiming it to solve a general problem, without the > > appropriate amount of energy spent in this solution. > > > > Using old machines is supposed to be supported on older guests. > > > > Michael, not migrating the PVEOI MSR actually crashes the guest? > > Which is irrelevant since it won't be able to migrate to an older > qemu. > With this patch, -M pc-1.1 migrates fine to an older qemu and no crash. Without, PV EOI bit in CPUID is set on source so we have a problem. -- MST