Re: [Xen-devel] Time Skewing on Windows XP

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.03.13 at 17:30, Tim Deegan <tim@xxxxxxx> wrote:
> At 16:06 +0000 on 14 Mar (1363277205), Jan Beulich wrote:
>> >>> On 14.03.13 at 16:16, Suravee Suthikulanit 
>> >>> <suravee.suthikulpanit@xxxxxxx> 
> wrote:
>> > I finally traced the issue back to the patch that this first happened.  
> This 
>> > bug started in the patch :
>> > 
>> > H86/HVM: assorted RTC emulation adjustment (w/ git commit id 
>> > 620d5dad54008e40798c4a0c4322aef274c36fa3)
>> > 
>> > I believe there are some issues with the changes in rtc_ioport_read in the 
>> > arch/x86/hvm/rtc.c and in the pt_update_irq().
>> 
>> One thing you may want to try is remove the call from REG_C
>> read to rtc_timer_update() again - on a second thought it may
>> be wrong to do it here, as (other than check_update_timer()
>> and alarm_timer_update()) the function doesn't change with
>> RTC_PF getting cleared (i.e. I may have wrongly added the call
>> in analogy to the other two).
> 
> The call is needed because of the new code in rtc_periodic_interrupt()
> that disables the timer if a second passes with no RTC_C read to clear
> the RTC_PF flag. 

Ah, right, of course. You see that it was many months back that I
wrote that code.

So we could filter on this periodic timer not currently being active
(which ought to be better than your calling into
create_periodic_time() with just the time delta adjusted).

> I suspect that getting rid of that (i.e. going back to running the timer
> all the time if the guest asks for interrupts) will fix it. 

But would get us back into the not spec conforming way of working...

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel