[Bug 444531] [NEW] Guest kernel can't read TSC frequency from the hypervisor

[Radovan Pútec]

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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