KVM: ioapic: extract body of kvm_ioapic_set_irq

We will reuse it to process a nonzero IRR that is passed to KVM_SET_IRQCHIP.
Reviewed-by: NAlex Williamson <alex.williamson@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

virt/kvm/ioapic.c

@@ -163,6 +163,55 @@ static bool rtc_irq_check_coalesced(struct kvm_ioapic *ioapic)
 	return false;
 }
 
+static int ioapic_set_irq(struct kvm_ioapic *ioapic, unsigned int irq,
+		int irq_level, bool line_status)
+{
+	union kvm_ioapic_redirect_entry entry;
+	u32 mask = 1 << irq;
+	u32 old_irr;
+	int edge, ret;
+
+	entry = ioapic->redirtbl[irq];
+	edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);
+
+	if (!irq_level) {
+		ioapic->irr &= ~mask;
+		ret = 1;
+		goto out;
+	}
+
+	/*
+	 * Return 0 for coalesced interrupts; for edge-triggered interrupts,
+	 * this only happens if a previous edge has not been delivered due
+	 * do masking.  For level interrupts, the remote_irr field tells
+	 * us if the interrupt is waiting for an EOI.
+	 *
+	 * RTC is special: it is edge-triggered, but userspace likes to know
+	 * if it has been already ack-ed via EOI because coalesced RTC
+	 * interrupts lead to time drift in Windows guests.  So we track
+	 * EOI manually for the RTC interrupt.
+	 */
+	if (irq == RTC_GSI && line_status &&
+		rtc_irq_check_coalesced(ioapic)) {
+		ret = 0;
+		goto out;
+	}
+
+	old_irr = ioapic->irr;
+	ioapic->irr |= mask;
+	if ((edge && old_irr == ioapic->irr) ||
+	    (!edge && entry.fields.remote_irr)) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = ioapic_service(ioapic, irq, line_status);
+
+out:
+	trace_kvm_ioapic_set_irq(entry.bits, irq, ret == 0);
+	return ret;
+}
+
 static void update_handled_vectors(struct kvm_ioapic *ioapic)
 {
 	DECLARE_BITMAP(handled_vectors, 256);
@@ -308,38 +357,15 @@ static int ioapic_service(struct kvm_ioapic *ioapic, int irq, bool line_status)
 int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int irq_source_id,
 		       int level, bool line_status)
 {
-	u32 old_irr;
-	u32 mask = 1 << irq;
-	union kvm_ioapic_redirect_entry entry;
 	int ret, irq_level;
 
 	BUG_ON(irq < 0 || irq >= IOAPIC_NUM_PINS);
 
 	spin_lock(&ioapic->lock);
-	old_irr = ioapic->irr;
 	irq_level = __kvm_irq_line_state(&ioapic->irq_states[irq],
 					 irq_source_id, level);
-	entry = ioapic->redirtbl[irq];
-	if (!irq_level) {
-		ioapic->irr &= ~mask;
-		ret = 1;
-	} else {
-		int edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);
+	ret = ioapic_set_irq(ioapic, irq, irq_level, line_status);
 
-		if (irq == RTC_GSI && line_status &&
-			rtc_irq_check_coalesced(ioapic)) {
-			ret = 0; /* coalesced */
-			goto out;
-		}
-		ioapic->irr |= mask;
-		if ((edge && old_irr != ioapic->irr) ||
-		    (!edge && !entry.fields.remote_irr))
-			ret = ioapic_service(ioapic, irq, line_status);
-		else
-			ret = 0; /* report coalesced interrupt */
-	}
-out:
-	trace_kvm_ioapic_set_irq(entry.bits, irq, ret == 0);
 	spin_unlock(&ioapic->lock);
 
 	return ret;