When a guest OS performs an RTC change action, we wish this event be
captured by developers, and then they can decide what to do with it.
(e.g., whether to change physical RTC)
There are some facts that makes RTC change event a bit complicated:
- There are 7 RTC date/time regs (year, month…). They can only be
updated one by one.
- RTC time is not reliable before date/time update is finished.
- Guests can update RTC date/time regs in any order.
- Guests may update RTC date/time regs during either RTC halted or not
halted.
A single date/time update event is not reliable. We have to wait for
the guest to finish the update process. So the DM's event handler
sets up a timer, and wait for some time (1 second). If no more change
happens befor the timer expires, we can conclude that the RTC
change has been done. Then the rtc change event is emitted.
This logic of event handler can be used to process HV vrtc time change
event too.
Tracked-On: #8547
Signed-off-by: Wu Zhou <wu.zhou@intel.com>
Reviewed-by: Jian Jun Chen <jian.jun.chen@intel.com>
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