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From: David Vrabel <david.vrabel@citrix.com>
To: Philipp Hahn <hahn@univention.de>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: [BUG 2.6.32.y] Broken PV migration between hosts with	different uptime, non-monotonic time?
Date: Fri, 4 May 2012 14:20:13 +0100	[thread overview]
Message-ID: <4FA3D78D.3000201@citrix.com> (raw)
In-Reply-To: <201205041510.56986.hahn@univention.de>

On 04/05/12 14:10, Philipp Hahn wrote:
> Hello David,
> 
> On Friday 04 May 2012 12:39:03 David Vrabel wrote:
>> On 04/05/12 09:54, Philipp Hahn wrote:
>>> I encountered the following bug when migrating a Linux-2.6.32.54 PV
>>> domain on Xen-3.4.3 between different hosts, whose uptime differs by
>>> several minutes
> ... 
>> Xen 3.4 doesn't ensure that the TSC is stable across migrates (Xen 4.0
>> does).  If the host CPU has the CONSTANT_TSC bit in the Advanced Power
>> Management CPUID leaf it will pass this through to the guest which makes
>> the guest think the TSC is stable.
>>
>> Can you try this libxc patch?
>>
>> 8<------------------------
>> libxc: clear CONSTANT_TSC bit in Advanced Power Management CPUID leaf
> 
> Excellent, that fixes the problem for me and makes perfect sense for me, since 
> AFAIK 2.6.37 also received a big TSC patch which is not part of 2.6.32.y 
> backport.

Thanks for testing! I could never repro the migration failures.

David

      reply	other threads:[~2012-05-04 13:20 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-04  8:54 [BUG 2.6.32.y] Broken PV migration between hosts with different uptime, non-monotonic time? Philipp Hahn
2012-05-04 10:39 ` David Vrabel
2012-05-04 13:10   ` Philipp Hahn
2012-05-04 13:20     ` David Vrabel [this message]

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