Drivers: hv: vmbus: Move some ring buffer functions to hyperv.h

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

In preparation for implementing APIs for in-place consumption of VMBUS
packets, movve some ring buffer functionality into hyperv.h
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(back ported from commit 687f32e6)
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

@@ -84,52 +84,6 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
 	return false;
 }
 
-/*
- * To optimize the flow management on the send-side,
- * when the sender is blocked because of lack of
- * sufficient space in the ring buffer, potential the
- * consumer of the ring buffer can signal the producer.
- * This is controlled by the following parameters:
- *
- * 1. pending_send_sz: This is the size in bytes that the
- *    producer is trying to send.
- * 2. The feature bit feat_pending_send_sz set to indicate if
- *    the consumer of the ring will signal when the ring
- *    state transitions from being full to a state where
- *    there is room for the producer to send the pending packet.
- */
-
-static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
-{
-	u32 cur_write_sz;
-	u32 pending_sz;
-
-	/*
-	 * Issue a full memory barrier before making the signaling decision.
-	 * Here is the reason for having this barrier:
-	 * If the reading of the pend_sz (in this function)
-	 * were to be reordered and read before we commit the new read
-	 * index (in the calling function)  we could
-	 * have a problem. If the host were to set the pending_sz after we
-	 * have sampled pending_sz and go to sleep before we commit the
-	 * read index, we could miss sending the interrupt. Issue a full
-	 * memory barrier to address this.
-	 */
-	mb();
-
-	pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
-	/* If the other end is not blocked on write don't bother. */
-	if (pending_sz == 0)
-		return false;
-
-	cur_write_sz = hv_get_bytes_to_write(rbi);
-
-	if (cur_write_sz >= pending_sz)
-		return true;
-
-	return false;
-}
-
 /* Get the next write location for the specified ring buffer. */
 static inline u32
 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
@@ -180,15 +134,6 @@ hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
 	ring_info->ring_buffer->read_index = next_read_location;
 }
 
-
-/* Get the start of the ring buffer. */
-static inline void *
-hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
-{
-	return (void *)ring_info->ring_buffer->buffer;
-}
-
-
 /* Get the size of the ring buffer. */
 static inline u32
 hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)

include/linux/hyperv.h

@@ -1366,4 +1366,58 @@ extern __u32 vmbus_proto_version;
 int vmbus_send_tl_connect_request(const uuid_le *shv_guest_servie_id,
 				  const uuid_le *shv_host_servie_id);
 void vmbus_set_event(struct vmbus_channel *channel);
+
+/* Get the start of the ring buffer. */
+static inline void *
+hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
+{
+	return (void *)ring_info->ring_buffer->buffer;
+}
+
+/*
+ * To optimize the flow management on the send-side,
+ * when the sender is blocked because of lack of
+ * sufficient space in the ring buffer, potential the
+ * consumer of the ring buffer can signal the producer.
+ * This is controlled by the following parameters:
+ *
+ * 1. pending_send_sz: This is the size in bytes that the
+ *    producer is trying to send.
+ * 2. The feature bit feat_pending_send_sz set to indicate if
+ *    the consumer of the ring will signal when the ring
+ *    state transitions from being full to a state where
+ *    there is room for the producer to send the pending packet.
+ */
+
+static inline  bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
+{
+	u32 cur_write_sz;
+	u32 pending_sz;
+
+	/*
+	 * Issue a full memory barrier before making the signaling decision.
+	 * Here is the reason for having this barrier:
+	 * If the reading of the pend_sz (in this function)
+	 * were to be reordered and read before we commit the new read
+	 * index (in the calling function)  we could
+	 * have a problem. If the host were to set the pending_sz after we
+	 * have sampled pending_sz and go to sleep before we commit the
+	 * read index, we could miss sending the interrupt. Issue a full
+	 * memory barrier to address this.
+	 */
+	virt_mb();
+
+	pending_sz = READ_ONCE(rbi->ring_buffer->pending_send_sz);
+	/* If the other end is not blocked on write don't bother. */
+	if (pending_sz == 0)
+		return false;
+
+	cur_write_sz = hv_get_bytes_to_write(rbi);
+
+	if (cur_write_sz >= pending_sz)
+		return true;
+
+	return false;
+}
+
 #endif /* _HYPERV_H */