Kernel: WARNING calibrate_APIC_clock: the APIC timer calibration may be wrong appear on Guest 5.x Linux VM's

This was due to the MAX_DIFFERENCE parameter value (in the APIC calibration loop) of 1000 cycles being too aggressive for virtual guests. APIC (Advanced Programmable Interrupt Controllers) and TSC (Time Stamp Counter) reads normally take longer than 1000 cycles when performed from inside a virtual guest, due to processors being scheduled away from and then back onto the guest. With this update, the MAX_DIFFERENCE parameter value has been increased to 10,000 for virtual guests.

These messages can be stopped by adding ‘apiccalibrationdiff=10000’ to guest kernel in /etc/grub.conf.