Re: [Xen-devel] Time Change Issue Xen 4.1

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.11.11 at 19:39, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> 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.

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
> 
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