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Date: Sun, 25 Oct 2009 14:22:18 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
To: virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
	Rusty Russell <rusty@rustcorp.com.au>
Subject: [PATCH] virtio: order used ring after used index read
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diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index f536005..4c4df3e 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -285,6 +285,9 @@ static void *vring_get_buf(struct virtqueue *_vq, unsigned int *len)
 		return NULL;
 	}
 
+        /* Only get used array entries after they have been exposed by host. */
+	rmb();
+
 	i = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].id;
 	*len = vq->vring.used->ring[vq->last_used_idx%vq->vring.num].len;