--- /dev/null
+From 35848f68b07df3f917cb13fc3c134718669f569b Mon Sep 17 00:00:00 2001
+From: Jason Wang <jasowang@redhat.com>
+Date: Tue, 18 Jun 2013 13:04:23 +0800
+Subject: drivers: hv: switch to use mb() instead of smp_mb()
+
+From: Jason Wang <jasowang@redhat.com>
+
+commit 35848f68b07df3f917cb13fc3c134718669f569b upstream.
+
+Even if guest were compiled without SMP support, it could not assume that host
+wasn't. So switch to use mb() instead of smp_mb() to force memory barriers for
+UP guest.
+
+Signed-off-by: Jason Wang <jasowang@redhat.com>
+Cc: Haiyang Zhang <haiyangz@microsoft.com>
+Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+[bwh: Backported to 3.2:
+ - Drop changes to functions that don't exist here
+ - hv_ringbuffer_write() has only a write memory barrier]
+Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
+[hq: Backported to 3.4:
+ - Add the change in hv_ringbuffer_read]
+Signed-off-by: Qiang Huang <h.huangqiang@huawei.com>
+
+---
+ drivers/hv/ring_buffer.c | 4 ++--
+ drivers/hv/vmbus_drv.c | 2 +-
+ 2 files changed, 3 insertions(+), 3 deletions(-)
+
+--- a/drivers/hv/ring_buffer.c
++++ b/drivers/hv/ring_buffer.c
+@@ -383,7 +383,7 @@ int hv_ringbuffer_write(struct hv_ring_b
+ sizeof(u64));
+
+ /* Make sure we flush all writes before updating the writeIndex */
+- smp_wmb();
++ wmb();
+
+ /* Now, update the write location */
+ hv_set_next_write_location(outring_info, next_write_location);
+@@ -485,7 +485,7 @@ int hv_ringbuffer_read(struct hv_ring_bu
+ /* Make sure all reads are done before we update the read index since */
+ /* the writer may start writing to the read area once the read index */
+ /*is updated */
+- smp_mb();
++ mb();
+
+ /* Update the read index */
+ hv_set_next_read_location(inring_info, next_read_location);
+--- a/drivers/hv/vmbus_drv.c
++++ b/drivers/hv/vmbus_drv.c
+@@ -466,7 +466,7 @@ static void vmbus_on_msg_dpc(unsigned lo
+ * will not deliver any more messages since there is
+ * no empty slot
+ */
+- smp_mb();
++ mb();
+
+ if (msg->header.message_flags.msg_pending) {
+ /*