[Qemu-devel] x86: PMTIMER calibration sometimes fails

[Thomas De Schampheleire]

Hi,

I am running an x86 based Linux system under qemu. Linux boots up
correctly in most cases, however sometimes the PMTIMER fails to
calibrate correctly:

[    0.000000] Fast TSC calibration failed
[    0.000000] TSC: Unable to calibrate against PIT
[    0.000000] TSC: HPET/PMTIMER calibration failed.
[    0.000000] Marking TSC unstable due to could not calculate TSC khz
[    0.010998] Calibrating delay loop... 1011.71 BogoMIPS (lpj=505856)

while the following messages appears in a good situation:

[    0.000000] Fast TSC calibration failed
[    0.000000] TSC: Unable to calibrate against PIT
[    0.000000] TSC: using PMTIMER reference calibration
[    0.000000] Detected 2258.151 MHz processor.
[    0.009099] Calibrating delay loop (skipped), value calculated
using timer frequency.. 4516.30 BogoMIPS (lpj=2258151)

HPET is deliberately disabled.

Both situations occur with the same Linux kernel configuration, so I
am assuming this is a qemu problem.
I have the impression that in a bad situation, the boot messages
scroll by slower, indicating a slower emulation than in the good case
(as the timings seen by the kernel are approximately the same).

Please find in attachment the full boot log of a good and bad
situation, plus the kernel configuration.

Have you seen this problem before? Do you have any idea how to fix it?

Thanks,
Thomas

bootmsg-good
Description: Binary data

bootmsg-bad
Description: Binary data

.config
Description: Binary data