Patch "Drivers: hv: vmbus: Fix a Host signaling bug" has been added to the 4.4-stable tree

@@ -630,10 +630,19 @@ int vmbus_sendpacket_ctl(struct vmbus_ch
 	 *    on the ring. We will not signal if more data is
 	 *    to be placed.
 	 *
+	 * Based on the channel signal state, we will decide
+	 * which signaling policy will be applied.
+	 *
 	 * If we cannot write to the ring-buffer; signal the host
 	 * even if we may not have written anything. This is a rare
 	 * enough condition that it should not matter.
 	 */
+
+	if (channel->signal_policy)
+		signal = true;
+	else
+		kick_q = true;
+
 	if (((ret == 0) && kick_q && signal) || (ret))
 		vmbus_setevent(channel);
 

@@ -733,10 +742,19 @@ int vmbus_sendpacket_pagebuffer_ctl(stru
 	 *    on the ring. We will not signal if more data is
 	 *    to be placed.
 	 *
+	 * Based on the channel signal state, we will decide
+	 * which signaling policy will be applied.
+	 *
 	 * If we cannot write to the ring-buffer; signal the host
 	 * even if we may not have written anything. This is a rare
 	 * enough condition that it should not matter.
 	 */
+
+	if (channel->signal_policy)
+		signal = true;
+	else
+		kick_q = true;
+
 	if (((ret == 0) && kick_q && signal) || (ret))
 		vmbus_setevent(channel);
 

@@ -630,6 +630,11 @@ struct hv_input_signal_event_buffer {
 	struct hv_input_signal_event event;
 };
 
+enum hv_signal_policy {
+	HV_SIGNAL_POLICY_DEFAULT = 0,
+	HV_SIGNAL_POLICY_EXPLICIT,
+};
+
 struct vmbus_channel {
 	/* Unique channel id */
 	int id;

@@ -757,8 +762,21 @@ struct vmbus_channel {
 	 * link up channels based on their CPU affinity.
 	 */
 	struct list_head percpu_list;
+	/*
+	 * Host signaling policy: The default policy will be
+	 * based on the ring buffer state. We will also support
+	 * a policy where the client driver can have explicit
+	 * signaling control.
+	 */
+	enum hv_signal_policy  signal_policy;
 };
 
+static inline void set_channel_signal_state(struct vmbus_channel *c,
+					    enum hv_signal_policy policy)
+{
+	c->signal_policy = policy;
+}
+
 static inline void set_channel_read_state(struct vmbus_channel *c, bool state)
 {
 	c->batched_reading = state;