Re: [PATCH] hw/i8254: fix vmstate load

[Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>]

On 15.03.2021 23:13, Dr. David Alan Gilbert wrote:
> * Pavel Dovgalyuk (pavel.dovgalyuk@ispras.ru) wrote:
>> QEMU timer of channel 0 in i8254 is used to raise irq
>> at the specified moment of time. This irq can be disabled
>> with irq_disabled flag. But when vmstate of the pit is
>> loaded, timer may be rearmed despite the disabled interrupts.
>> This patch adds irq_disabled flag check to fix that.
>>
>> Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
> 
> Hi Pavel,
>    I'm curious, did you see this cause a problem on a particular guest
> OS?

That was Windows 7 on i386.
I found this when tested reverse debugging.

> 
> Dave
> 
>> ---
>>   hw/timer/i8254.c |    2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/timer/i8254.c b/hw/timer/i8254.c
>> index c01ee2c72a..c8388ea432 100644
>> --- a/hw/timer/i8254.c
>> +++ b/hw/timer/i8254.c
>> @@ -324,7 +324,7 @@ static void pit_post_load(PITCommonState *s)
>>   {
>>       PITChannelState *sc = &s->channels[0];
>>   
>> -    if (sc->next_transition_time != -1) {
>> +    if (sc->next_transition_time != -1 && !sc->irq_disabled) {
>>           timer_mod(sc->irq_timer, sc->next_transition_time);
>>       } else {
>>           timer_del(sc->irq_timer);
>>
>>