[PATCH] avoid redeliver of edge interrupt before next edge

[Gleb Natapov <gleb@redhat.com>]

The check for an edge is broken in current ioapic code. ioapic->irr is
cleared on each edge interrupt by ioapic_service() and this makes
old_irr != ioapic->irr condition in kvm_ioapic_set_irq() to be always
true. The patch fixes the code to properly recognise edge.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 124ecf7..74c4b5f 100644
--- a/virt/kvm/ioapic.c
+++ b/virt/kvm/ioapic.c
@@ -95,8 +95,6 @@ static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx)
 		if (injected && pent->fields.trig_mode == IOAPIC_LEVEL_TRIG)
 			pent->fields.remote_irr = 1;
 	}
-	if (!pent->fields.trig_mode)
-		ioapic->irr &= ~(1 << idx);
 
 	return injected;
 }
@@ -118,28 +116,34 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
 	case IOAPIC_REG_ARB_ID:
 		break;
 
-	default:
+	default: {
+		union kvm_ioapic_redirect_entry *e;
+		
 		index = (ioapic->ioregsel - 0x10) >> 1;
 
 		ioapic_debug("change redir index %x val %x\n", index, val);
 		if (index >= IOAPIC_NUM_PINS)
 			return;
-		mask_before = ioapic->redirtbl[index].fields.mask;
+
+		e = &ioapic->redirtbl[index];
+		mask_before = e->fields.mask;
 		if (ioapic->ioregsel & 1) {
-			ioapic->redirtbl[index].bits &= 0xffffffff;
-			ioapic->redirtbl[index].bits |= (u64) val << 32;
+			e->bits &= 0xffffffff;
+			e->bits |= (u64) val << 32;
 		} else {
-			ioapic->redirtbl[index].bits &= ~0xffffffffULL;
-			ioapic->redirtbl[index].bits |= (u32) val;
-			ioapic->redirtbl[index].fields.remote_irr = 0;
+			e->bits &= ~0xffffffffULL;
+			e->bits |= (u32) val;
+			e->fields.remote_irr = 0;
 		}
-		mask_after = ioapic->redirtbl[index].fields.mask;
+		mask_after = e->fields.mask;
 		if (mask_before != mask_after)
 			kvm_fire_mask_notifiers(ioapic->kvm, index, mask_after);
-		if (ioapic->irr & (1 << index))
+		if (e->fields.trig_mode == IOAPIC_LEVEL_TRIG &&
+		    (ioapic->irr & (1 << index)))
 			ioapic_service(ioapic, index);
 		break;
 	}
+	}
 }
 
 static int ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
@@ -186,9 +190,10 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level)
 		if (!level)
 			ioapic->irr &= ~mask;
 		else {
+			int edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);
 			ioapic->irr |= mask;
-			if ((!entry.fields.trig_mode && old_irr != ioapic->irr)
-			    || !entry.fields.remote_irr)
+			if ((edge && old_irr != ioapic->irr) ||
+			    (!edge && !entry.fields.remote_irr))
 				ret = ioapic_service(ioapic, irq);
 		}
 	}
--
			Gleb.