KVM: ioapic: Record edge-triggered interrupts delivery status

This patch fixes the bug discussed in
https://www.mail-archive.com/kvm@vger.kernel.org/msg109813.html

This patch uses a new field named irr_delivered to record the
delivery status of edge-triggered interrupts, and clears the
delivered interrupts in kvm_get_ioapic. So it has the same effect
of commit 0bc830b05c667218d703f2026ec866c49df974fc
("KVM: ioapic: clear IRR for edge-triggered interrupts at delivery")
while avoids the bug of Windows guests.

Signed-off-by: Wincy Van <fanwenyi0529@gmail.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/ioapic.c

@@ -206,6 +206,8 @@ static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
 
 	old_irr = ioapic->irr;
 	ioapic->irr |= mask;
+	if (edge)
+		ioapic->irr_delivered &= ~mask;
 	if ((edge && old_irr == ioapic->irr) ||
 	    (!edge && entry.fields.remote_irr)) {
 		ret = 0;
@@ -349,7 +351,7 @@ static int ioapic_service(struct kvm_ioapic *ioapic, int irq, bool line_status)
 	irqe.shorthand = 0;
 
 	if (irqe.trig_mode == IOAPIC_EDGE_TRIG)
-		ioapic->irr &= ~(1 << irq);
+		ioapic->irr_delivered |= 1 << irq;
 
 	if (irq == RTC_GSI && line_status) {
 		/*
@@ -597,6 +599,7 @@ static void kvm_ioapic_reset(struct kvm_ioapic *ioapic)
 	ioapic->base_address = IOAPIC_DEFAULT_BASE_ADDRESS;
 	ioapic->ioregsel = 0;
 	ioapic->irr = 0;
+	ioapic->irr_delivered = 0;
 	ioapic->id = 0;
 	memset(ioapic->irq_eoi, 0x00, IOAPIC_NUM_PINS);
 	rtc_irq_eoi_tracking_reset(ioapic);
@@ -654,6 +657,7 @@ int kvm_get_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state)
 
 	spin_lock(&ioapic->lock);
 	memcpy(state, ioapic, sizeof(struct kvm_ioapic_state));
+	state->irr &= ~ioapic->irr_delivered;
 	spin_unlock(&ioapic->lock);
 	return 0;
 }
@@ -667,6 +671,7 @@ int kvm_set_ioapic(struct kvm *kvm, struct kvm_ioapic_state *state)
 	spin_lock(&ioapic->lock);
 	memcpy(ioapic, state, sizeof(struct kvm_ioapic_state));
 	ioapic->irr = 0;
+	ioapic->irr_delivered = 0;
 	update_handled_vectors(ioapic);
 	kvm_vcpu_request_scan_ioapic(kvm);
 	kvm_ioapic_inject_all(ioapic, state->irr);

arch/x86/kvm/ioapic.h

@@ -77,6 +77,7 @@ struct kvm_ioapic {
 	struct rtc_status rtc_status;
 	struct delayed_work eoi_inject;
 	u32 irq_eoi[IOAPIC_NUM_PINS];
+	u32 irr_delivered;
 };
 
 #ifdef DEBUG