From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754938Ab0J0SxX (ORCPT ); Wed, 27 Oct 2010 14:53:23 -0400 Received: from claw.goop.org ([74.207.240.146]:41817 "EHLO claw.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752793Ab0J0SxV (ORCPT ); Wed, 27 Oct 2010 14:53:21 -0400 Message-ID: <4CC8751E.40306@goop.org> Date: Wed, 27 Oct 2010 11:53:18 -0700 From: Jeremy Fitzhardinge User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Lightning/1.0b3pre Thunderbird/3.1.4 MIME-Version: 1.0 To: Glauber Costa CC: "Xen-devel@lists.xensource.com" , kvm-devel , Eelco Dolstra , the arch/x86 maintainers , Linux Kernel Mailing List , Linux Virtualization , Olivier Hanesse , Avi Kivity , "H. Peter Anvin" Subject: Re: [Xen-devel] Re: [PATCH] x86/pvclock-xen: zero last_value on resume References: <4CC708DE.1070000@goop.org> <1288115334.3530.7.camel@mothafucka.localdomain> In-Reply-To: <1288115334.3530.7.camel@mothafucka.localdomain> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/26/2010 10:48 AM, Glauber Costa wrote: > On Tue, 2010-10-26 at 09:59 -0700, Jeremy Fitzhardinge wrote: >> If the guest domain has been suspend/resumed or migrated, then the >> system clock backing the pvclock clocksource may revert to a smaller >> value (ie, can be non-monotonic across the migration/save-restore). >> Make sure we zero last_value in that case so that the domain >> continues to see clock updates. >> >> [ I don't know if kvm needs an analogous fix or not. ] > After migration, save/restore, etc, we issue an ioctl where we tell > the host the last clock value. That (in theory) guarantees monotonicity. > > I am not opposed to this patch in any way, however. Thanks. HPA, do you want to take this, or shall I send it on? Thanks, J