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

>>> On 14.03.13 at 17:38, Suravee Suthikulanit <suravee.suthikulpanit@xxxxxxx>
> On 3/14/2013 11:34 AM, Jan Beulich wrote:
>>>>> On 14.03.13 at 17:21, Suravee Suthikulanit 
>>>>> <suravee.suthikulpanit@xxxxxxx> 
> wrote:
>>> On 3/14/2013 11:06 AM, 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).
>>> If I do the followings, things start working again:
>>> 1. remove the rtc_timer_update() in the rtc_ioport_read()
>>> 2. Revert back the "rtc_periodic_cb()" and remove the
>>> "rtc_periodic_interrupt()"
>>> What was the purpose of changing the "rtc_periodic_cb()" to
>>> "rtc_periodic_interrupt()" ?
>> The main point was to be able to call rtc_toggle_irq() from that
>> function (to get RTC_IRQF properly set), instead of
>> pt_update_irq() doing only the IRQ deassert/assert pair.
>> So removing just the questionable call to rtc_timer_update()
>> doesn't help?
> Removing just the call to "rtc_timer_update" causes XP failed to boot 
> and hanged.  It seems like it did not get the right timer interrupt it 
> was looking for.

As was meanwhile also clarified by Tim. And as said in a response
to him - we may want to gate the call on a check whether the
periodic timer is actually inactive.


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