Index: head/sys/dev/hyperv/include/vmbus.h
===================================================================
--- head/sys/dev/hyperv/include/vmbus.h
+++ head/sys/dev/hyperv/include/vmbus.h
@@ -131,6 +131,7 @@
 
 /*
  * vmbus_chan_open_br()
+ *
  * Return values:
  * 0			Succeeded.
  * EISCONN		Failed, and the memory passed through 'br' is still
@@ -139,6 +140,24 @@
  * other values		Failed.  The memory passed through 'br' is no longer
  *			connected.  Callers are free to do anything with the
  *			memory passed through 'br'.
+ *
+ *
+ *
+ * vmbus_chan_close_direct()
+ *
+ * NOTE:
+ * Callers of this function _must_ make sure to close all sub-channels before
+ * closing the primary channel.
+ *
+ * Return values:
+ * 0			Succeeded.
+ * EISCONN		Failed, and the memory associated with the bufring
+ *			is still connected.  Callers must _not_ free the the
+ *			memory associated with the bufring, if this error
+ *			happens.
+ * other values		Failed.  The memory associated with the bufring is
+ *			no longer connected.  Callers are free to do anything
+ *			with the memory associated with the bufring.
  */
 int		vmbus_chan_open(struct vmbus_channel *chan,
 		    int txbr_size, int rxbr_size, const void *udata, int udlen,
@@ -147,6 +166,7 @@
 		    const struct vmbus_chan_br *cbr, const void *udata,
 		    int udlen, vmbus_chan_callback_t cb, void *cbarg);
 void		vmbus_chan_close(struct vmbus_channel *chan);
+int		vmbus_chan_close_direct(struct vmbus_channel *chan);
 void		vmbus_chan_intr_drain(struct vmbus_channel *chan);
 void		vmbus_chan_run_task(struct vmbus_channel *chan,
 		    struct task *task);
Index: head/sys/dev/hyperv/vmbus/vmbus_chan.c
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_chan.c
+++ head/sys/dev/hyperv/vmbus/vmbus_chan.c
@@ -851,6 +851,41 @@
 	return (error);
 }
 
+int
+vmbus_chan_close_direct(struct vmbus_channel *chan)
+{
+	int error;
+
+#ifdef INVARIANTS
+	if (VMBUS_CHAN_ISPRIMARY(chan)) {
+		struct vmbus_channel *subchan;
+
+		/*
+		 * All sub-channels _must_ have been closed, or are _not_
+		 * opened at all.
+		 */
+		mtx_lock(&chan->ch_subchan_lock);
+		TAILQ_FOREACH(subchan, &chan->ch_subchans, ch_sublink) {
+			KASSERT(
+			   (subchan->ch_stflags & VMBUS_CHAN_ST_OPENED) == 0,
+			   ("chan%u: subchan%u is still opened",
+			    chan->ch_id, subchan->ch_subidx));
+		}
+		mtx_unlock(&chan->ch_subchan_lock);
+	}
+#endif
+
+	error = vmbus_chan_close_internal(chan);
+	if (!VMBUS_CHAN_ISPRIMARY(chan)) {
+		/*
+		 * This sub-channel is referenced, when it is linked to
+		 * the primary channel; drop that reference now.
+		 */
+		vmbus_chan_detach(chan);
+	}
+	return (error);
+}
+
 /*
  * Caller should make sure that all sub-channels have
  * been added to 'chan' and all to-be-closed channels