Re: [kvm-commits] KVM: Fix ioapic level-triggered interrupt redelivery

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Dong, Eddie wrote:
>> diff --git a/drivers/kvm/ioapic.c b/drivers/kvm/ioapic.c
>> index 3ee13c3..b8c7da4 100644
>> --- a/drivers/kvm/ioapic.c
>> +++ b/drivers/kvm/ioapic.c
>> @@ -243,17 +243,10 @@ void kvm_ioapic_set_irq(struct
>> kvm_ioapic *ioapic, int irq, int level)
>> 		entry = ioapic->redirtbl[irq];
>> 		if (!level)
>> 			ioapic->irr &= ~mask;
>> -		if (entry.fields.trig_mode) {	/* level triggered */
>> -			if (level && !entry.fields.remote_irr) {
>> -				ioapic->irr |= mask;
>> -				ioapic_service(ioapic, irq);
>> -			}
>> -		} else if (level && !(ioapic->irr & mask)) {
>> -			/*
>> -			 * edge triggered
>> -			 */
>> +		else {
>> 			ioapic->irr |= mask;
>> -			ioapic_service(ioapic, irq);
>> +			if (!entry.fields.trig_mode ||
>> !entry.fields.remote_irr)
>> +				ioapic_service(ioapic, irq);
>>     
>
> Good fix for ioapic->irr to indicate the line state. But
> I think this one will cause a redunadant edge trigger IRQ. A device 
> model may repeat call SET_IRQ_LINE state even w/o state change
>  (thus no IRQ), with this logic, a redunadnat IRQ will happen.
>
> if (!entry.fields.trig_mode ||           =====> 
> 	if ((!entry.fields.trig_mode && (old_irr & mask ==0)) ||
>
>   

Thanks, I'll do that.

> Also architectually level = 0 may also mean an IRQ to IOAPIC
>  if the polarity is negative though today we may not see this. 
> But this change will expose the risk, and the propose of pass-through
>  hardware device will change the polarity.
>   

Sure, if you run Xen + pci passthrough with the polarity reversal on kvm :)

We do want a correct polarity implementation -- I'll do that later on.  
I certainly won't say no to patches...

-- 
error compiling committee.c: too many arguments to function


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