Re: [RFC PATCH] kvm: Extend irqfd to support level interrupts

[Avi Kivity <avi@redhat.com>]

On 06/18/2012 11:52 AM, Jan Kiszka wrote:
>> 
>> I don't understand how this works.  A level IRQ isn't de-asserted by the
>> EOI, it's de-asserted by its source.
>> 
>> Consider the following sequence:
>> 
>> device        guest
>> 
>>   event
>>    assert
>>               interrupt
>>                interrupt handler
>>                 handle event
>>                 clear ISR bit
>>    deassert
>>   event
>>     assert
>>                EOI
>> 
>> What should happen is that the interrupt will be redelivered
>> immmediately after the EOI, but that won't happen with your API since
>> the EOI ack notifier will deassert the interrupt and nothing will
>> re-assert it.
> 
> As it's level triggered and we unmask the physical source, another
> host-side interrupt will be triggered and then reported to the guest.

That works for real devices.  What about emulated devices (vhost,
msi-less ivshmem clone)?

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