Drivers: hv: vmbus: remove code duplication in message handling

BugLink: http://bugs.launchpad.net/bugs/1541585

We have 3 functions dealing with messages and they all implement
the same logic to finalize reads, move it to vmbus_signal_eom().
Suggested-by: Radim Krcmar <rkrcmar@redhat.com>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Radim Kr.má<rkrcmar@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 0f70b669)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/hv/channel_mgmt.c

@@ -614,15 +614,7 @@ static void vmbus_wait_for_unload(void)
 		if (hdr->msgtype == CHANNELMSG_UNLOAD_RESPONSE)
 			unloaded = true;
 
-		msg->header.message_type = HVMSG_NONE;
-		/*
-		 * header.message_type needs to be written before we do
-		 * wrmsrl() below.
-		 */
-		mb();
-
-		if (msg->header.message_flags.msg_pending)
-			wrmsrl(HV_X64_MSR_EOM, 0);
+		vmbus_signal_eom(msg);
 
 		if (unloaded)
 			break;

drivers/hv/hyperv_vmbus.h

@@ -619,6 +619,30 @@ struct vmbus_channel_message_table_entry {
 extern struct vmbus_channel_message_table_entry
 	channel_message_table[CHANNELMSG_COUNT];
 
+/* Free the message slot and signal end-of-message if required */
+static inline void vmbus_signal_eom(struct hv_message *msg)
+{
+	msg->header.message_type = HVMSG_NONE;
+
+	/*
+	 * Make sure the write to MessageType (ie set to
+	 * HVMSG_NONE) happens before we read the
+	 * MessagePending and EOMing. Otherwise, the EOMing
+	 * will not deliver any more messages since there is
+	 * no empty slot
+	 */
+	mb();
+
+	if (msg->header.message_flags.msg_pending) {
+		/*
+		 * This will cause message queue rescan to
+		 * possibly deliver another msg from the
+		 * hypervisor
+		 */
+		wrmsrl(HV_X64_MSR_EOM, 0);
+	}
+}
+
 /* General vmbus interface */
 
 struct hv_device *vmbus_device_create(const uuid_le *type,

drivers/hv/vmbus_drv.c

@@ -708,25 +708,7 @@ static void hv_process_timer_expiration(struct hv_message *msg, int cpu)
 	if (dev->event_handler)
 		dev->event_handler(dev);
 
-	msg->header.message_type = HVMSG_NONE;
-
-	/*
-	 * Make sure the write to MessageType (ie set to
-	 * HVMSG_NONE) happens before we read the
-	 * MessagePending and EOMing. Otherwise, the EOMing
-	 * will not deliver any more messages since there is
-	 * no empty slot
-	 */
-	mb();
-
-	if (msg->header.message_flags.msg_pending) {
-		/*
-		 * This will cause message queue rescan to
-		 * possibly deliver another msg from the
-		 * hypervisor
-		 */
-		wrmsrl(HV_X64_MSR_EOM, 0);
-	}
+	vmbus_signal_eom(msg);
 }
 
 void vmbus_on_msg_dpc(unsigned long data)
@@ -764,25 +746,7 @@ void vmbus_on_msg_dpc(unsigned long data)
 		entry->message_handler(hdr);
 
 msg_handled:
-	msg->header.message_type = HVMSG_NONE;
-
-	/*
-	 * Make sure the write to MessageType (ie set to
-	 * HVMSG_NONE) happens before we read the
-	 * MessagePending and EOMing. Otherwise, the EOMing
-	 * will not deliver any more messages since there is
-	 * no empty slot
-	 */
-	mb();
-
-	if (msg->header.message_flags.msg_pending) {
-		/*
-		 * This will cause message queue rescan to
-		 * possibly deliver another msg from the
-		 * hypervisor
-		 */
-		wrmsrl(HV_X64_MSR_EOM, 0);
-	}
+	vmbus_signal_eom(msg);
 }
 
 static void vmbus_isr(void)