Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753531Ab0HXAww (ORCPT ); Mon, 23 Aug 2010 20:52:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:26322 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751478Ab0HXAwt (ORCPT ); Mon, 23 Aug 2010 20:52:49 -0400 Message-ID: <4C7317D9.5080002@redhat.com> Date: Mon, 23 Aug 2010 14:52:41 -1000 From: Zachary Amsden User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100621 Fedora/3.0.5-1.fc13 Thunderbird/3.0.5 MIME-Version: 1.0 To: Glauber Costa CC: kvm@vger.kernel.org, Avi Kivity , Marcelo Tosatti , Thomas Gleixner , John Stultz , linux-kernel@vger.kernel.org Subject: Re: [KVM timekeeping 05/35] Move TSC reset out of vmcb_init References: <1282291669-25709-1-git-send-email-zamsden@redhat.com> <1282291669-25709-6-git-send-email-zamsden@redhat.com> <20100820170849.GC2937@mothafucka.localdomain> In-Reply-To: <20100820170849.GC2937@mothafucka.localdomain> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1146 Lines: 25 On 08/20/2010 07:08 AM, Glauber Costa wrote: > On Thu, Aug 19, 2010 at 10:07:19PM -1000, Zachary Amsden wrote: > >> The VMCB is reset whenever we receive a startup IPI, so Linux is setting >> TSC back to zero happens very late in the boot process and destabilizing >> the TSC. Instead, just set TSC to zero once at VCPU creation time. >> >> Why the separate patch? So git-bisect is your friend. >> >> Signed-off-by: Zachary Amsden >> > Shouldn't we set for whatever value the BSP already has, and then the BSP to > zero? Since vcpus are initialized at different times, this pretty much > guarantees that the guest will have desynchronized tsc at all cases > (not that if it was better before...) > Yes, we should - but it takes a lot more machinery to do that, and so it happens later in the series. You have to match the offsets for the BSP and other vcpus... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/