On Thu, Jan 12, 2012 at 12:00:06AM +0000, Zhang, Yang Z wrote: > > -----Original Message----- > > From: Marcelo Tosatti [mailto:mtosa...@redhat.com] > > > > Regarding the UIP bit, a guest could read it in a loop and wait for the > > value to > > change. But you can emulate it in cmos_ioport_read by reading the host time, > > that is, return 1 during 244us, 0 for remaining of the second, and have > > that in sync > > with update-cycle-ended interrupt if its enabled. > Yes. Guest may use the loop to read RTC, but the point is the guest is > waiting for the UIP changed to 0. If this bit always equal to 0 , guest will > never go into the loop. For real RTC, this may wrong, because the RTC cannot > give you the valid value during the update cycle. But the virtual RTC > doesn't' need this logic, whenever you read it, it will always return the > right value to you.
Can't it wait a change from 0 to 1?
