Am 23.12.2010 21:45, Zachary Amsden wrote: > On 12/17/2010 04:58 AM, Jan Kiszka wrote: >> By default, we base the mc146818 RTC on the host clock (CLOCK_REALTIME). >> This works fine if only the frequency of the host clock is tuned (e.g. >> by NTP) or if it is set to a future time. However, if the host is tuned >> backward, e.g. because NTP obtained the correct time after the guest was >> already started or the admin decided to tune the local time, we see an >> unpleasant effect in the guest: The RTC will stall for the period the >> host clock is set back. >> >> This series tries to address the issue more gracefully. By detecting >> those warps and providing a callback mechanism to device models, the >> RTC is enabled to update its timers and register content immediately. >> Tested successfully with a hwclock readout loop in a Linux guest while >> fiddling with the host time. >> >> Note that if this kind of RTC adjustment is not wanted, the user is >> still free to decouple the RTC from the host clock and base it on the >> VM clock - just like before. >> > > Did you test this with a Windows guest? They rely heavily on RTC, this > is probably a better behavior for that case. I'd be curious if Windows > accepts the RTC register changing underneath it, but based on earlier > versions of Windows Time Service, would be surprised if it did not.
I haven't tried with Windows yet. When does it read the RTC and how can I check the outcome? Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux
