Public bug reported:
Binary package hint: kvm
Description of problem:
Guest kernel can't read TSC frequency from the hypervisor on hardy and interpid
causing unstable TSC clocksource even if host has constant_tsc processor flag.
This causes clock drifting on high load and freezing of guests with more than
one cpu.
How reproducible:
Easily
Steps to Reproduce:
1. Boot host kernel with clocksource=tsc
2. Boot guest kernel with clocksource=tsc
3. dmesg | egrep "(tsc|TSC)" on guest
Actual results:
Hardy:
kernel version 2.6.24-24.53
[8739129.899892] Time: tsc clocksource has been installed.
[8739131.245835] Clocksource tsc unstable (delta = 144317765 ns)
Interpid:
kernel version: 2.6.27-14.41
[ 0.000000] TSC: Unable to calibrate against PIT
[ 0.000000] TSC: using PMTIMER reference calibration
Expected results:
kernel should read frequency from the hypervisor that results in stable TSC
clocksource.
Aditional info:
I have tried this on jaunty host, but i'm not really sure if that matters,
since the hypervisor supports it. Tried with CentOS 5.3, 2.6.18-164.el5 kernel
and worked as expected.
relevant dmesg part from CentOS:
kvm_get_tsc_khz: cpu 0, msr 0:1101001
TSC: Frequency read from the hypervisor
Time: tsc clocksource has been installed.
** Affects: kvm (Ubuntu)
Importance: Undecided
Status: New
** Tags: clocksouce kvm tsc
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Guest kernel can't read TSC frequency from the hypervisor
https://bugs.launchpad.net/bugs/444531
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