---

yaml
---
r: 164915
b: refs/heads/master
c: ca60a42
h: refs/heads/master
i:
  164913: 922626a
  164911: 5b1fbc2
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 6c189d8312246af776c2587c233d6afcf3714438
+refs/heads/master: ca60a42c9be41c07ebcc2ec8c43dd1be53f147bf

trunk/Documentation/lguest/lguest.c

@@ -134,6 +134,9 @@ struct device {
 	/* Is it operational */
 	bool running;
 
+	/* Does Guest want an intrrupt on empty? */
+	bool irq_on_empty;
+
 	/* Device-specific data. */
 	void *priv;
 };
@@ -624,10 +627,13 @@ static void trigger_irq(struct virtqueue *vq)
 		return;
 	vq->pending_used = 0;
 
-	/* If they don't want an interrupt, don't send one, unless empty. */
-	if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
-	    && lg_last_avail(vq) != vq->vring.avail->idx)
-		return;
+	/* If they don't want an interrupt, don't send one... */
+	if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) {
+		/* ... unless they've asked us to force one on empty. */
+		if (!vq->dev->irq_on_empty
+		    || lg_last_avail(vq) != vq->vring.avail->idx)
+			return;
+	}
 
 	/* Send the Guest an interrupt tell them we used something up. */
 	if (write(lguest_fd, buf, sizeof(buf)) != 0)
@@ -1043,6 +1049,15 @@ static void create_thread(struct virtqueue *vq)
 	close(vq->eventfd);
 }
 
+static bool accepted_feature(struct device *dev, unsigned int bit)
+{
+	const u8 *features = get_feature_bits(dev) + dev->feature_len;
+
+	if (dev->feature_len < bit / CHAR_BIT)
+		return false;
+	return features[bit / CHAR_BIT] & (1 << (bit % CHAR_BIT));
+}
+
 static void start_device(struct device *dev)
 {
 	unsigned int i;
@@ -1056,6 +1071,8 @@ static void start_device(struct device *dev)
 		verbose(" %02x", get_feature_bits(dev)
 			[dev->feature_len+i]);
 
+	dev->irq_on_empty = accepted_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
+
 	for (vq = dev->vq; vq; vq = vq->next) {
 		if (vq->service)
 			create_thread(vq);