Re: [Xen-devel] Xen 4 TSC problems

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 09/15/2011 01:24 AM, Konrad Rzeszutek Wilk wrote:
> On Tue, Sep 13, 2011 at 09:16:27AM +0200, Philippe Simonet wrote:
>> Hi Xen developers
> Lets try this again, this time Cc-ing Jeremy.
>> i just would like to inform you that I have exactly the same problem
>> with Debian squeeze and xen, with
>> 50 seconds time jump on my dom0 and domu. NTP is running on all
>> dom0/domuU, clocksource is 'xen'
>> everywhere.
>>
>> some messages :
>> syslog :
>> Sep 11 13:56:50 dnsit22 kernel: [571603.359863] Clocksource tsc
>> unstable (delta = -2999662111513 ns)
>>
>> xm dmesg :
>> ...
>> (XEN) Platform timer is 14.318MHz HPET
>> ...
>> (XEN) Platform timer appears to have unexpectedly wrapped 10 or more times.
>> (XEN) TSC marked as reliable, warp = 0 (count=2)
>> ...
>>
>> I had some contact with Olivier Hanesse and it indicates that he
>> doesn't have any solution for this problem,
>> and all what was proposed in February didn't solved this problem.

That looks like Xen itself is having problems keeping track of time.  If
it can't manage it, then there's not much the guest kernels can do about it.

>
> Which was the max_cstate=0 ?
> ..
>> config :
>> --------------------------------------
>> Linux dnsit22.swissptt.ch 2.6.32-5-xen-amd64 #1 SMP Tue Jun 14
>> 12:46:30 UTC 2011 x86_64 GNU/Linux
>> --------------------------------------
>> HP DL385
>> --------------------------------------
>> vendor_id       : AuthenticAMD
>> cpu family      : 16
>> model           : 9
>> model name      : AMD Opteron(tm) Processor 6174
>> stepping        : 1
>> cpu MHz         : 3058776.574
> OK, that is really messed up. Your house must be on fire for the machine
> to be running at 3058GHz!
>
> Jeremy, this sounds familiar - did we have a patch for this in
> your 2.6.32 tree?

Not that I can think of.  All I can suggest from the kernel side is that
perhaps some of the ACPI power stuff isn't being set up properly, and
that makes the CPU do very strange things with its TSC/power states in
general.

    J


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