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Date: Sun, 19 Apr 2009 17:06:42 +0300
From: Dor Laor <dlaor@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] Change RTC time drift IRQ re-injection
References: <20090406132526.GA9153@redhat.com> <49E9E9D2.509@us.ibm.com>
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To: qemu-devel@nongnu.org

Anthony Liguori wrote:
> Gleb Natapov wrote:
>> Currently IRQ are reinjected as soon as they are acknowledged to
>> the RTC, but Windows sometimes do acknowledgement in a loop with
>> global interrupt disabled waiting for interrupt to be cleared and
>> it does not mask RTC vector in PIC/APIC while doing this. In such
>> situation interrupt injection always fails and RTC interrupt is never
>> cleared.
>>
>> Instead of reinjecting coalesced IRQs on acknowledgement the patch below
>> reinjects them by accelerating RTC clock a bit. This way RTC interrupt
>> is not constantly raced after coalesced interrupt.
>>
>> Signed-off-by: Gleb Natapov <gleb@redhat.com>
>>              s->cmos_data[RTC_REG_C] = 0x00;
>>              break;
>>          default:
>> @@ -512,6 +539,7 @@ static void rtc_save_td(QEMUFile *f, void *opaque)
>>  
>>      qemu_put_be32(f, s->irq_coalesced);
>>      qemu_put_be32(f, s->period);
>> +    qemu_put_timer(f, s->coalesced_timer);
>>  }
>>  
>>  static int rtc_load_td(QEMUFile *f, void *opaque, int version_id)
>> @@ -523,6 +551,7 @@ static int rtc_load_td(QEMUFile *f, void *opaque, 
>> int version_id)
>>  
>>      s->irq_coalesced = qemu_get_be32(f);
>>      s->period = qemu_get_be32(f);
>> +    qemu_get_timer(f, s->coalesced_timer);
>>      return 0;
>>   
>
> If you're adding something to the savevm format, you have to increment 
> the version_id and handle older versions correctly.
>
>
Actually, it is not a must to save this boolean, you can assume it is 
set and schedule it for the current time on the load.