Hi, My guest system is 2 cpu smp environment and use icount=0 to measure the total instructions.I called cpu_get_icount() when the cpu switches in vl.c Sometimes the return value of cpu_get_icount() increased a lot (> 1 million) but the cpu actually is in halted state.Normally, the return value should not increase if the cpu is in halted state since no instructions were executed. That is also what I observed most of time. But occasionally the return value increased a lot and affected my experiment results.Did I do anything wrong here?Thanks in advance. Regards,Tommy _________________________________________________________________ Windows 7: Unclutter your desktop. http://go.microsoft.com/?linkid=9690331&ocid=PID24727::T:WLMTAGL:ON:WL:en-US:WWL_WIN_evergreen:112009