From 09efe653559295d2c9e73421f2f887c09898e41e Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Fri, 12 Jun 2009 22:27:11 -0600
Subject: [PATCH] --- yaml --- r: 148001 b: refs/heads/master c:
 95c517c09bad31a03e22f2fdb5f0aa26a490a92d h: refs/heads/master i:   147999:
 69879e5d673008580fbb373f278c4918bd4678db v: v3

---
 [refs]                              | 2 +-
 trunk/Documentation/lguest/lguest.c | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index deb7ad988c6b..42798dca517c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 38bc2b8c56a2e212bbd19de7cf9976dcc7bf9953
+refs/heads/master: 95c517c09bad31a03e22f2fdb5f0aa26a490a92d
diff --git a/trunk/Documentation/lguest/lguest.c b/trunk/Documentation/lguest/lguest.c
index 84c471b07c27..20f8253881b3 100644
--- a/trunk/Documentation/lguest/lguest.c
+++ b/trunk/Documentation/lguest/lguest.c
@@ -151,6 +151,9 @@ struct virtqueue
 	/* Last available index we saw. */
 	u16 last_avail_idx;
 
+	/* How many are used since we sent last irq? */
+	unsigned int pending_used;
+
 	/* Eventfd where Guest notifications arrive. */
 	int eventfd;
 
@@ -556,6 +559,11 @@ static void trigger_irq(struct virtqueue *vq)
 {
 	unsigned long buf[] = { LHREQ_IRQ, vq->config.irq };
 
+	/* Don't inform them if nothing used. */
+	if (!vq->pending_used)
+		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)
@@ -647,6 +655,7 @@ static void add_used(struct virtqueue *vq, unsigned int head, int len)
 	/* Make sure buffer is written before we update index. */
 	wmb();
 	vq->vring.used->idx++;
+	vq->pending_used++;
 }
 
 /* And here's the combo meal deal.  Supersize me! */