From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 2/3] qemu-x86: Add tsc_freq option to -cpu Date: Tue, 19 Jul 2011 18:55:27 +0300 Message-ID: <4E25A8EF.5010302@redhat.com> References: <1310047993-7649-1-git-send-email-joerg.roedel@amd.com> <1310047993-7649-3-git-send-email-joerg.roedel@amd.com> <20110719114658.GA28500@amt.cnet> <4E257695.4010906@redhat.com> <20110719133003.GG24072@8bytes.org> <4E258C7B.6040005@redhat.com> <4E258CE9.4080203@redhat.com> <20110719141458.GH24072@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , Joerg Roedel , kvm@vger.kernel.org, qemu-devel@nongnu.org To: Joerg Roedel Return-path: Received: from mx1.redhat.com ([209.132.183.28]:55986 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751481Ab1GSPzh (ORCPT ); Tue, 19 Jul 2011 11:55:37 -0400 In-Reply-To: <20110719141458.GH24072@8bytes.org> Sender: kvm-owner@vger.kernel.org List-ID: On 07/19/2011 05:14 PM, Joerg Roedel wrote: > On Tue, Jul 19, 2011 at 04:55:53PM +0300, Avi Kivity wrote: > > On 07/19/2011 04:54 PM, Avi Kivity wrote: > >> On 07/19/2011 04:30 PM, Joerg Roedel wrote: > > >>> Hmm, I planned to do the VMSTATE thing in a follow-on patch-set. The > >>> plan is to read the VCPU tsc_freq at guest start time on !tsc-scale > >>> hosts and migrate it over so that the destination host can set the > >>> tsc-freq if it supports tsc-scaling. > >> > >> This can be done by a management tool if desired. > >> > > > > Although, if we do this unconditionally (that is, also for tsc-scale > > hosts) then we get stable tsc even without supplying a tsc frequency > > argument... need to think about this. > > It has the advantage that it "just works", without the need to extend > management tools and the like. And it makes migration more transparent > to the guests. > Yes, exactly. The flip side is that automagic stuff is sometimes unexpected and leads to breakage. I'm not sure what the right thing is. -- error compiling committee.c: too many arguments to function