Re: KVM: fix i8259 reset irq acking

[Marcelo Tosatti <mtosatti@redhat.com>]

On Wed, Aug 13, 2008 at 01:40:34PM +0300, Avi Kivity wrote:
> Marcelo Tosatti wrote:
>> The irq ack during pic reset has three problems:
>>
>> - Ignores slave/master PIC, using gsi 0-8 for both.
>> - Generates an ACK even if the APIC is in control.
>> - Depends upon IMR being clear, which is broken if the irq was masked 
>> at the time it was generated.
>>
>> The last one causes the BIOS to hang after the first reboot of Windows
>> installation, since PIT interrupts stop.
>>
>> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>>
>>
>> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
>> index de70499..2b42d48 100644
>> --- a/arch/x86/kvm/i8259.c
>> +++ b/arch/x86/kvm/i8259.c
>> @@ -195,14 +195,18 @@ int kvm_pic_read_irq(struct kvm *kvm)
>>   void kvm_pic_reset(struct kvm_kpic_state *s)
>>  {
>> -	int irq;
>> +	int irq, irqbase;
>>  	struct kvm *kvm = s->pics_state->irq_request_opaque;
>>  -	for (irq = 0; irq < PIC_NUM_PINS; irq++) {
>> -		if (!(s->imr & (1 << irq)) && (s->irr & (1 << irq) ||
>> -		    s->isr & (1 << irq)))
>> -			kvm_notify_acked_irq(kvm, irq);
>> -	}
>> +	if (s == &s->pics_state->pics[0])
>> +		irqbase = 0;
>> +	else
>> +		irqbase = 8;
>> +
>> +	if (!kvm_lapic_enabled(kvm->vcpus[0]))
>>   
>
> What if the lapic is enabled and passes through PIC interrupts in EXTINT  
> mode?
>
> btw, this will oops if we have no vcpu 0.

True. How's this:

The irq ack during pic reset has three problems:

- Ignores slave/master PIC, using gsi 0-8 for both.
- Generates an ACK even if the APIC is in control.
- Depends upon IMR being clear, which is broken if the irq was masked 
at the time it was generated.

The last one causes the BIOS to hang after the first reboot of
Windows
installation, since PIT interrupts stop.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>


diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index de70499..59a2201 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -195,13 +195,23 @@ int kvm_pic_read_irq(struct kvm *kvm)
 
 void kvm_pic_reset(struct kvm_kpic_state *s)
 {
-	int irq;
+	int irq, irqbase;
 	struct kvm *kvm = s->pics_state->irq_request_opaque;
+	struct kvm_vcpu *vcpu0 = kvm->vcpus[0];
+
+	if (s == &s->pics_state->pics[0])
+		irqbase = 0;
+	else
+		irqbase = 8;
 
 	for (irq = 0; irq < PIC_NUM_PINS; irq++) {
-		if (!(s->imr & (1 << irq)) && (s->irr & (1 << irq) ||
-		    s->isr & (1 << irq)))
-			kvm_notify_acked_irq(kvm, irq);
+		union ioapic_redir_entry entry;
+		entry = kvm->arch.vioapic->redirtbl[irq+irqbase];
+		if ((vcpu0 && !kvm_lapic_enabled(vcpu0)) ||
+	     	     entry.fields.delivery_mode == IOAPIC_EXTINT) {
+			if (s->irr & (1 << irq) || s->isr & (1 << irq))
+				kvm_notify_acked_irq(kvm, irq+irqbase);
+		}
 	}
 	s->last_irr = 0;
 	s->irr = 0;