From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [PATCH 5/5] x86/xen: sync the CMOS RTC as well as the Xen wallclock Date: Fri, 28 Jun 2013 18:09:15 +0200 (CEST) Message-ID: References: <1372329348-20841-1-git-send-email-david.vrabel@citrix.com> <1372329348-20841-6-git-send-email-david.vrabel@citrix.com> <51CDB0A1.6080409@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <51CDB0A1.6080409@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: David Vrabel Cc: John Stultz , linux-kernel@vger.kernel.org, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Fri, 28 Jun 2013, David Vrabel wrote: > > Before: > > Xen wallclock set when time is stepped. > Xen wallclock set every 11 minutes (by sync_cmos_clock()). > Hardware RTC never set. > > After: > > Xen wallclock set when time is stepped. > Xen wallclock set every 11 minutes (in pvclock gtod notifier). Ah, you are emulating the sync_cmos_clock() behaviour for the xen wallclock via the periodic pvclock_gtod notifier call. > Hardware RTC set every 11 minutes (by sync_cmos_clock()). > > I'll update the changelog to be more descriptive: > > Adjustments to Xen's persistent clock via update_persistent_clock() > don't actually persist, as the Xen wallclock is a software only clock > and modifications to it do not modify the underlying CMOS RTC. > > The x86_platform.set_wallclock hook can be used to keep the hardware > RTC synchronized (as on bare metal). If (in dom0) we make the Xen > wallclock periodically synchronized by the pvclock_gtod notifier, the > set_wallclock hook need not update the Xen wallclock and the native > implementation can be used. Yep. I'll pick that up. Thanks, tglx