On Mon, Jan 05, 2009 at 10:59:01PM +0200, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> On Sun, Jan 04, 2009 at 06:14:45PM +0200, Avi Kivity wrote:
>>
>>> While the PIT is masked the guest cannot ack the irq, so the reinject logic
>>> will never allow the interrupt to be injected.
>>>
>>> Fix by resetting the reinjection counters on unmask.
>>>
>>> Unbreaks Xen.
>>>
>>> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
>>> index 528daad..d78d430 100644
>>> --- a/arch/x86/kvm/i8254.c
>>> +++ b/arch/x86/kvm/i8254.c
>>> @@ -539,6 +539,16 @@ void kvm_pit_reset(struct kvm_pit *pit)
>>> pit->pit_state.irq_ack = 1;
>>> }
>>> +static void pit_mask_notifer(struct kvm_irq_mask_notifier *kimn,
>>> int mask)
>>> +{
>>> + struct kvm_pit *pit = container_of(kimn, struct kvm_pit, mask_notifier);
>>> +
>>> + if (!mask) {
>>> + atomic_set(&pit->pit_state.pit_timer.pending, 0);
>>> + pit->pit_state.irq_ack = 1;
>>> + }
>>> +}
>>>
>>
>> I'm not sure about zeroing the counter here. The guest can mask the
>> interrupt during normal operation, and in such cases you want the
>> pending count to be retained (and reinjected later).
>>
>> I suppose setting irq_ack to one is enough.
>>
>
> I'm worried about:
>
> - boot guest using local apic timer
> - reset
> - boot with pit timer
> - a zillion interrupts
>
> So at the very least, we need a limiter.
Or have a new notifier on kvm_pic_reset, instead of simply acking one
pending irq? That seems the appropriate place to zero the counter.
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