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[Xen-devel] Re: [PATCH] [Bugfix][pv-ops] Guest get stucked after migrati

To: xen-devel@xxxxxxxxxxxxxxxxxxx, Jeremy Fitzhardinge <Jeremy.Fitzhardinge@xxxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] [Bugfix][pv-ops] Guest get stucked after migration
From: Frank Pan <frankpzh@xxxxxxxxx>
Date: Tue, 22 Mar 2011 12:35:47 +0800
Delivery-date: Mon, 21 Mar 2011 21:36:41 -0700
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Add Stefano Stabellini, who made the commit of xen_hvm_suspend in the git tree.

Stefano, do you have any idea?

On Tue, Mar 22, 2011 at 12:19 PM, Frank Pan <frankpzh@xxxxxxxxx> wrote:
> On Tue, Mar 22, 2011 at 2:26 AM, Frank Pan <frankpzh@xxxxxxxxx> wrote:
>> In recent pv-ops kernel, pvclock is not guaranteed as monotone.
>> After a migration, pvclock can produce smaller cycle count.
>> [The test is performed on next-2.6.32 tree]
>> The issue occured when uptime(sender) > uptime(target), and with
>> CONFIG_GENERIC_TIME. The guest get stucked after the migration,
>> doing a huge loop inside update_wall_time, until the overflow of
>> 64-bit unsigned offset.
>> The following patch fixed this issue by introducing a global sign.
>> Xen pvclock will update the cycle_last with the newest cycle count
>> on the first read after migration.
> It seems the issue is not that simple. This issue can be well solved by
> the suspend/resume code of timekeeper sysdev. However, the recent
> code may think this is not necessary on hvm domain. (How can I find the
> reason here?)
> I don't know if it's ok to add a pair of sysdev_suspend/sysdev_resume inside
> xen_hvm_suspend. If not, this patch can be a quickfix/solution.
> Any ideas on this issue?
> --
> 潘震皓, Frank Pan
> Computer Science and Technology
> Tsinghua University

潘震皓, Frank Pan

Computer Science and Technology
Tsinghua University

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