Design and implementation of virtual HPET in DVMM

AS well as in real physical environment, time subsystem is also a vital part in the distributed virtual environment. DVMM, based on multi-nodes and achieves single system image, has faced with the challenge of the time accuracy. High Precision Event Timers which is broad supported in current Linux kernel as a system clock source and can even be used to replace of PIT and TSC, can improve the accuracy of measuring time which relies on independent counters. For the DVMM, we design and implement the simulation of HPET, which includes HPET structure, HPET initialization, and callback function. GOS detects HPET device when system starting up. Then DVMM captures this action, simulates the time measuring with HPET, and keeps time much more accurately, in order to satisfy the requirement of the application. At last, we verify the HPET module by running the GOS.