From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1423628Ab3FUSbv (ORCPT ); Fri, 21 Jun 2013 14:31:51 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:47561 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1423383Ab3FUSbu (ORCPT ); Fri, 21 Jun 2013 14:31:50 -0400 Date: Fri, 21 Jun 2013 14:31:32 -0400 From: Konrad Rzeszutek Wilk To: John Stultz Cc: David Vrabel , xen-devel@lists.xen.org, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCHv5 0/4] xen: maintain an accurate persistent clock in more cases Message-ID: <20130621183132.GH15809@phenom.dumpdata.com> References: <1371755792-25962-1-git-send-email-david.vrabel@citrix.com> <51C36016.7010806@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <51C36016.7010806@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 20, 2013 at 01:03:34PM -0700, John Stultz wrote: > On 06/20/2013 12:16 PM, David Vrabel wrote: > >Xen guests use the Xen wallclock as their persistent clock. This is a > >software only clock in the hypervisor that is used by guests instead > >of a real hardware RTC. > > > >The kernel has limited support for updating the persistent clock or > >RTC when NTP is synced. This has the following limitations: > > > >* The persistent clock is not updated on step changes. This leaves a > > window where it will be incorrect (while NTP resyncs). > > > >* Xen guests use the Xen wallclock as their persistent clock. dom0 > > maintains this clock so it is persistent for domUs but not dom0 > > itself. > > > >These limitations mean that guests started before NTP is synchronized > >will start with an incorrect wallclock time and the hardware RTC will > >not be updated (as on bare metal). > > > >These series fixes the above limitations and depends on "x86: increase > >precision of x86_platform.get/set_wallclock()" which was previously > >posted. > > > >Changes since v4: > > > >Dropped the change to disable non-boot CPUs during suspend on Xen as > >migration downtime was too poor. Instead, provide > >hrtimers_late_resume() for use by Xen's resume code to replace the > >call of clock_was_set(). Fix two unused variable warnings. > > Ok, I've got these 4 in my pending stack. As long as Thomas doesn't > object to the first two, and it doesn't run into any trouble in > testing, I'll send them along for 3.12. (Acks from Xen maintainers > would be nice for the last two as well). Please consider them Acked-by. Thanks! > > Thanks for all the effort through all the revisions here! > > thanks > -john >