My 2.6.32-rc7 kvm (both guest+host, x86_64) hangs w/o "nolapic" here:

  while (lapic_cal_loops <= LAPIC_CAL_LOOPS)
     cpu_relax();

because lapic_cal_loops never changes from -1.

Code was last changed by
commit 2f04fa888d270951b9e0fe9e641ddd560d77ad1b
Author: Yinghai Lu <yhlu.kernel@gmail.com>
Date:   Sun Aug 24 02:01:54 2008 -0700

    x86: apic copy calibrate_APIC_clock to each other in apic_32/64.c

but I haven't tested reverting that.

johannes