From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: Time Change Issue Xen 4.1 Date: Mon, 14 Nov 2011 13:00:45 -0500 Message-ID: <20111114180045.GA14517@phenom.dumpdata.com> References: <4EBD5AA0.3090906@webanywhere.co.uk> <20111111183913.GA9283@phenom.dumpdata.com> <4EC0F20D0200007800060B7D@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4EC0F20D0200007800060B7D@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Jan Beulich Cc: Jeremy Fitzhardinge , xen-devel@lists.xensource.com, keir.xen@gmail.com, Niall Fleming , pbonzini@redhat.com, lersek@redhat.com List-Id: xen-devel@lists.xenproject.org On Mon, Nov 14, 2011 at 09:48:45AM +0000, Jan Beulich wrote: > >>> On 11.11.11 at 19:39, Konrad Rzeszutek Wilk wrote: > > On Fri, Nov 11, 2011 at 05:25:52PM +0000, Niall Fleming wrote: > >> Hi all, > >> > >> Already posted this over in xen-users and Konrad confirms it as a > >> bug and suggested to repost > >> it over here! > > > > Laszlo, Paolo, Jan, you guys haven't seen domething like this? It looks > > like a hypervisor issue where the wallclock time is not really dispursed > > in the shared_info. > > Hypervisor? Upstream up to and including 3.1 just doesn't issue the > necessary hypercalls. This was fixed only recently through patches > from Jeremy. We had a different issue in that respect in the forward > ported Linux trees, but that got fixed a couple of months ago, too. Right. With those patches too (he used the xen-settime patch set which has it). The hypercall is done (and the do_settime gets called) and the results are saved in the RTC. And the wc_sec and wc_nsec are updated and propagated. The problem is that wc_sec and wc_nsec are only propagated to the existing guests. If you launch a new guest after the 'hwclock', the new guests retains the old wallclock time. > > This not working in Jeremy's 2.6.32 tree is odd though, but I'm not > certain which branches the necessary code would on. > > >> > >> Issue is that changing the time in dom0 doesn't take effect on the > >> VMs until a reboot of dom0. > >> The testing example below illustrates what I mean.... > >> > >> Synopsis of testing: > >> > >> Booted the physical machine, date tells me it's 17:15:45. Hwclock agrees. > >> Booted a VM (using xl as xm seems to be labouring under the > >> impression that blockdev is missing - it isn't) > >> The login prompt displays the time as 17:17, which is the expected > >> behaviour. > >> Changed the time in dom0 - (date +%T -s 12:00:00), synced to hwclock. > >> Check that date and hwclock match - they do. > >> Destroy the VM and recreate. > >> The login prompt displays the time as 17:22. Unexpected! > >> > >> > >> Kernel: I git cloned tag v3.1 from the kernel.org linux.git, and > >> applied xen-settime patches > >> Also tested with jeremy-git-xen-next-2.6.32 (.41/.46) without patch, > >> they wouldn't apply. > >> Xen: 4.1.1/4.1.2 > >> Distribution: Gentoo > >> > >> It still doesn't work. > >> > >> I've tested that the issue also exists in Debian Squeeze (with > >> linux-image-3.0.0 from testing as 2.6.32-5 is broken > >> on my hardware). > >> -- > >> > >> *Niall Fleming BSc. (Hons)* > >> Systems Administrator > >> Webanywhere Limited > >> > >> Phone: 0800 862 0131 Ext: 203 > >> Web: http://www.webanywhere.co.uk > >> > >> Aire Valley Business Centre, Lawkholme Lane, Keighley, BD21 3BB > >> Registered in England with company number 4881346 > > > >> _______________________________________________ > >> Xen-devel mailing list > >> Xen-devel@lists.xensource.com > >> http://lists.xensource.com/xen-devel > >