[Xen-devel] Time went backwards

["Niraj Tolia" <ntolia@xxxxxxxxx>]

Hi,

I have been experimenting with frequency scaling on a 4 core (2
sockets) AMD Opteron processors. The versions of Xen I have tested
with include xen-testing as well as xen-unstable (cs 17042). For both
these versions, I am using the linux 2.6.18-8 tree and have passed
cpufreq=dom0-kernel to the xen command line.

However, I get plenty of "Time went backwards" whenever I attempt to
change frequency. Does anyone know how this can be fixed?

% grep name /proc/cpuinfo | head -1
model name      : Dual-Core AMD Opteron(tm) Processor 2216 HE


powernow-k8: error - out of sync, fix 0x10 0x10, vid 0xe 0xc
powernow-k8: error - out of sync, fix 0x10 0x2, vid 0xc 0x12
Timer ISR/2: Time went backwards: delta=-20028937 delta_cpu=19939076
shadow=44550204818 off=949766763 processed=45520000000
cpu_processed=45480031987
 0: 45480000000
 1: 45520031987
 2: 45480031987
 3: 45490031987
Timer ISR/3: Time went backwards: delta=-19936433 delta_cpu=20031580
shadow=44552171478 off=957893422 processed=45530000000
cpu_processed=45490031987
 0: 45480000000
 1: 45520031987
 2: 45490031987
 3: 45490031987
Timer ISR/0: Time went backwards: delta=-19953088 delta_cpu=30046912
shadow=45494036645 off=16011896 processed=45530000000
cpu_processed=45480000000
 0: 45480000000
 1: 45520031987
 2: 45490031987
 3: 45500031987

(lots more Time went backwards messages follow these)

Thanks,
Niraj

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