Re: [Qemu-devel] [PATCH v3 2/7] hpet: Save/restore cached RTC IRQ level

[Jan Kiszka <jan.kiszka@web.de>]

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On 2012-01-31 22:02, Anthony Liguori wrote:
> On 01/31/2012 11:41 AM, Jan Kiszka wrote:
>> In legacy mode, the HPET suppresses the RTC interrupt delivery via IRQ
>> 8 but keeps track of the RTC output level and applies it when legacy
>> mode is turned off again. This value has to be preserved across save/
>> restore as it cannot be reconstructed otherwise.
>>
>> Signed-off-by: Jan Kiszka<jan.kiszka@siemens.com>
>> ---
>>   hw/hpet.c |   26 ++++++++++++++++++++++++++
>>   1 files changed, 26 insertions(+), 0 deletions(-)
>>
>> diff --git a/hw/hpet.c b/hw/hpet.c
>> index aba9ea9..39b291f 100644
>> --- a/hw/hpet.c
>> +++ b/hw/hpet.c
>> @@ -240,6 +240,24 @@ static int hpet_post_load(void *opaque, int
>> version_id)
>>       return 0;
>>   }
>>
>> +static bool hpet_rtc_irq_level_needed(void *opaque)
>> +{
>> +    HPETState *s = opaque;
>> +
>> +    return s->rtc_irq_level != 0;
>> +}
>> +
>> +static const VMStateDescription vmstate_hpet_rtc_irq_level = {
>> +    .name = "hpet/rtc_irq_level",
>> +    .version_id = 1,
>> +    .minimum_version_id = 1,
>> +    .minimum_version_id_old = 1,
>> +    .fields      = (VMStateField[]) {
>> +        VMSTATE_UINT8(rtc_irq_level, HPETState),
>> +        VMSTATE_END_OF_LIST()
>> +    }
>> +};
>> +
> 
> This won't work.  We don't clear rtc_irq_level on reset so rtc_irq_level
> may be high or low after reset.  As such, we can't use a subsection
> here.  We need to bump the savevm state.

rtc_irq_level is updated during reset by the connected RTC device. It
clears its IRQ line.

Jan


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