hyperv/vmbus: Define type for channel messages.

And fix message processing; only channel messages are supported.

MFC after:	1 week
Sponsored by:	Microsoft OSTC
Differential Revision:	https://reviews.freebsd.org/D6706

sys/dev/hyperv/vmbus/hv_connection.c

@@ -373,8 +373,8 @@ int hv_vmbus_post_message(void *buffer, size_t bufferLen)
 	 * insufficient resources. 20 times should suffice in practice.
 	 */
 	for (retries = 0; retries < 20; retries++) {
-		ret = hv_vmbus_post_msg_via_msg_ipc(connId, 1, buffer,
-						    bufferLen);
+		ret = hv_vmbus_post_msg_via_msg_ipc(connId,
+		    VMBUS_MSGTYPE_CHANNEL, buffer, bufferLen);
 		if (ret == HV_STATUS_SUCCESS)
 			return (0);
 

sys/dev/hyperv/vmbus/vmbus.c

@@ -85,8 +85,13 @@ vmbus_msg_task(void *xsc, int pending __unused)
 		hv_vmbus_channel_msg_header *hdr;
 		hv_vmbus_channel_msg_type msg_type;
 
-		if (msg->msg_type == VMBUS_MSGTYPE_NONE)
-			break; /* no message */
+		if (msg->msg_type == VMBUS_MSGTYPE_NONE) {
+			/* No message */
+			break;
+		} else if (msg->msg_type != VMBUS_MSGTYPE_CHANNEL) {
+			/* Not a channel message */
+			goto handled;
+		}
 
 		/* XXX: update messageHandler interface */
 		hdr = __DEVOLATILE(hv_vmbus_channel_msg_header *,

sys/dev/hyperv/vmbus/vmbus_reg.h

@@ -49,6 +49,7 @@ struct vmbus_message {
 CTASSERT(sizeof(struct vmbus_message) == VMBUS_MSG_SIZE);
 
 #define VMBUS_MSGTYPE_NONE		0
+#define VMBUS_MSGTYPE_CHANNEL		1
 #define VMBUS_MSGTYPE_TIMER_EXPIRED	0x80000010
 
 #define VMBUS_MSGFLAG_PENDING		0x01