Drivers: hv: vmbus: Use the new virt_xx barrier code

BugLink: http://bugs.launchpad.net/bugs/1616677

Use the virt_xx barriers that have been defined for use in virtual machines.
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(back ported from commit dcd0eeca)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

 Conflicts:
	drivers/hv/ring_buffer.c
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Kamal Mostafa <kamal@canonical.com>

drivers/hv/ring_buffer.c

@@ -33,14 +33,14 @@
 void hv_begin_read(struct hv_ring_buffer_info *rbi)
 {
 	rbi->ring_buffer->interrupt_mask = 1;
-	mb();
+	virt_mb();
 }
 
 u32 hv_end_read(struct hv_ring_buffer_info *rbi)
 {
 
 	rbi->ring_buffer->interrupt_mask = 0;
-	mb();
+	virt_mb();
 
 	/*
 	 * Now check to see if the ring buffer is still empty.
@@ -68,12 +68,12 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi)
 
 static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
 {
-	mb();
+	virt_mb();
 	if (READ_ONCE(rbi->ring_buffer->interrupt_mask))
 		return false;
 
 	/* check interrupt_mask before read_index */
-	rmb();
+	virt_rmb();
 	/*
 	 * This is the only case we need to signal when the
 	 * ring transitions from being empty to non-empty.
@@ -317,7 +317,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 					     sizeof(u64));
 
 	/* Issue a full memory barrier before updating the write index */
-	mb();
+	virt_mb();
 
 	/* Now, update the write location */
 	hv_set_next_write_location(outring_info, next_write_location);
@@ -393,7 +393,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 	 * the writer may start writing to the read area once the read index
 	 * is updated.
 	 */
-	mb();
+	virt_mb();
 
 	/* Update the read index */
 	hv_set_next_read_location(inring_info, next_read_location);