Hello everyone,

I like to submit patch to add a new function for 'time drift check' for 
guest running on KVM.

The TimeDrift design logic is below:
1. Set the host as the NTP server
2. Guest only sync it's clock with host *once* when it booted up.
* if the offset value of ntpdate large than 1 sec, the guest will sync 
the clock with host.
* if the offset value of ntpdate less than 1 sec, the guest doesn't need 
sync it's clock with host.

3. Then the cpu stress testing will running on guest.
* a C program will give the real load to guest cpu
4.when the cpustress testing finished. running the commandline <ntpdate 
-q host-ip> totally 20 times on guest to query the time from host and 
judge whether the guest clock has drift or not.

The details of my patch is attached.

thanks.

Bear.