Index: head/sys/dev/hyperv/include/hyperv.h
===================================================================
--- head/sys/dev/hyperv/include/hyperv.h
+++ head/sys/dev/hyperv/include/hyperv.h
@@ -717,6 +717,7 @@
 struct hv_vmbus_channel **
 		vmbus_get_subchan(struct hv_vmbus_channel *pri_chan, int subchan_cnt);
 void		vmbus_rel_subchan(struct hv_vmbus_channel **subchan, int subchan_cnt);
+void		vmbus_drain_subchan(struct hv_vmbus_channel *pri_chan);
 
 /**
  * @brief Get physical address from virtual
Index: head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
===================================================================
--- head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
+++ head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
@@ -345,6 +345,7 @@
 static void hn_set_tx_chimney_size(struct hn_softc *, int);
 static void hn_channel_attach(struct hn_softc *, struct hv_vmbus_channel *);
 static void hn_subchan_attach(struct hn_softc *, struct hv_vmbus_channel *);
+static void hn_subchan_setup(struct hn_softc *);
 
 static int hn_transmit(struct ifnet *, struct mbuf *);
 static void hn_xmit_qflush(struct ifnet *);
@@ -575,25 +576,8 @@
 	device_printf(dev, "%d TX ring, %d RX ring\n",
 	    sc->hn_tx_ring_inuse, sc->hn_rx_ring_inuse);
 
-	if (sc->net_dev->num_channel > 1) {
-		struct hv_vmbus_channel **subchan;
-		int subchan_cnt = sc->net_dev->num_channel - 1;
-		int i;
-
-		/* Wait for sub-channels setup to complete. */
-		subchan = vmbus_get_subchan(pri_chan, subchan_cnt);
-
-		/* Attach the sub-channels. */
-		for (i = 0; i < subchan_cnt; ++i) {
-			/* NOTE: Calling order is critical. */
-			hn_subchan_attach(sc, subchan[i]);
-			hv_nv_subchan_attach(subchan[i]);
-		}
-
-		/* Release the sub-channels */
-		vmbus_rel_subchan(subchan, subchan_cnt);
-		device_printf(dev, "%d sub-channels setup done\n", subchan_cnt);
-	}
+	if (sc->net_dev->num_channel > 1)
+		hn_subchan_setup(sc);
 
 #if __FreeBSD_version >= 1100099
 	if (sc->hn_rx_ring_inuse > 1) {
@@ -1620,6 +1604,10 @@
 			NV_UNLOCK(sc);
 			break;
 		}
+
+		/* Wait for subchannels to be destroyed */
+		vmbus_drain_subchan(hn_dev->channel);
+
 		error = hv_rf_on_device_add(hn_dev, &device_info,
 		    sc->hn_rx_ring_inuse);
 		if (error) {
@@ -1628,6 +1616,26 @@
 			NV_UNLOCK(sc);
 			break;
 		}
+		KASSERT(sc->hn_rx_ring_cnt == sc->net_dev->num_channel,
+		    ("RX ring count %d and channel count %u mismatch",
+		     sc->hn_rx_ring_cnt, sc->net_dev->num_channel));
+		if (sc->net_dev->num_channel > 1) {
+			int r;
+
+			/*
+			 * Skip the rings on primary channel; they are
+			 * handled by the hv_rf_on_device_add() above.
+			 */
+			for (r = 1; r < sc->hn_rx_ring_cnt; ++r) {
+				sc->hn_rx_ring[r].hn_rx_flags &=
+				    ~HN_RX_FLAG_ATTACHED;
+			}
+			for (r = 1; r < sc->hn_tx_ring_cnt; ++r) {
+				sc->hn_tx_ring[r].hn_tx_flags &=
+				    ~HN_TX_FLAG_ATTACHED;
+			}
+			hn_subchan_setup(sc);
+		}
 
 		sc->hn_tx_chimney_max = sc->net_dev->send_section_size;
 		if (sc->hn_tx_ring[0].hn_tx_chimney_size >
@@ -2980,6 +2988,29 @@
 }
 
 static void
+hn_subchan_setup(struct hn_softc *sc)
+{
+	struct hv_device *device_ctx = vmbus_get_devctx(sc->hn_dev);
+	struct hv_vmbus_channel **subchan;
+	int subchan_cnt = sc->net_dev->num_channel - 1;
+	int i;
+
+	/* Wait for sub-channels setup to complete. */
+	subchan = vmbus_get_subchan(device_ctx->channel, subchan_cnt);
+
+	/* Attach the sub-channels. */
+	for (i = 0; i < subchan_cnt; ++i) {
+		/* NOTE: Calling order is critical. */
+		hn_subchan_attach(sc, subchan[i]);
+		hv_nv_subchan_attach(subchan[i]);
+	}
+
+	/* Release the sub-channels */
+	vmbus_rel_subchan(subchan, subchan_cnt);
+	if_printf(sc->hn_ifp, "%d sub-channels setup done\n", subchan_cnt);
+}
+
+static void
 hn_tx_taskq_create(void *arg __unused)
 {
 	if (!hn_share_tx_taskq)
Index: head/sys/dev/hyperv/vmbus/hv_channel_mgmt.c
===================================================================
--- head/sys/dev/hyperv/vmbus/hv_channel_mgmt.c
+++ head/sys/dev/hyperv/vmbus/hv_channel_mgmt.c
@@ -367,6 +367,54 @@
 	if (HV_VMBUS_CHAN_ISPRIMARY(chan)) {
 		/* Only primary channel owns the hv_device */
 		hv_vmbus_child_device_unregister(chan->device);
+		/* NOTE: DO NOT free primary channel for now */
+	} else {
+		struct vmbus_softc *sc = chan->vmbus_sc;
+		struct hv_vmbus_channel *pri_chan = chan->primary_channel;
+		struct vmbus_chanmsg_chfree *req;
+		struct vmbus_msghc *mh;
+		int error;
+
+		mh = vmbus_msghc_get(sc, sizeof(*req));
+		if (mh == NULL) {
+			device_printf(sc->vmbus_dev,
+			    "can not get msg hypercall for chfree(chan%u)\n",
+			    chan->offer_msg.child_rel_id);
+			goto remove;
+		}
+
+		req = vmbus_msghc_dataptr(mh);
+		req->chm_hdr.chm_type = VMBUS_CHANMSG_TYPE_CHFREE;
+		req->chm_chanid = chan->offer_msg.child_rel_id;
+
+		error = vmbus_msghc_exec_noresult(mh);
+		vmbus_msghc_put(sc, mh);
+
+		if (error) {
+			device_printf(sc->vmbus_dev,
+			    "chfree(chan%u) failed: %d",
+			    chan->offer_msg.child_rel_id, error);
+			/* NOTE: Move on! */
+		} else {
+			if (bootverbose) {
+				device_printf(sc->vmbus_dev, "chan%u freed\n",
+				    chan->offer_msg.child_rel_id);
+			}
+		}
+remove:
+		mtx_lock(&sc->vmbus_chlist_lock);
+		TAILQ_REMOVE(&sc->vmbus_chlist, chan, ch_link);
+		mtx_unlock(&sc->vmbus_chlist_lock);
+
+		mtx_lock(&pri_chan->sc_lock);
+		TAILQ_REMOVE(&pri_chan->sc_list_anchor, chan, sc_list_entry);
+		KASSERT(pri_chan->subchan_cnt > 0,
+		    ("invalid subchan_cnt %d", pri_chan->subchan_cnt));
+		pri_chan->subchan_cnt--;
+		mtx_unlock(&pri_chan->sc_lock);
+		wakeup(pri_chan);
+
+		hv_vmbus_free_vmbus_channel(chan);
 	}
 }
 
@@ -504,6 +552,15 @@
 }
 
 void
+vmbus_drain_subchan(struct hv_vmbus_channel *pri_chan)
+{
+	mtx_lock(&pri_chan->sc_lock);
+	while (pri_chan->subchan_cnt > 0)
+		mtx_sleep(pri_chan, &pri_chan->sc_lock, 0, "dsubch", 0);
+	mtx_unlock(&pri_chan->sc_lock);
+}
+
+void
 vmbus_chan_msgproc(struct vmbus_softc *sc, const struct vmbus_message *msg)
 {
 	vmbus_chanmsg_proc_t msg_proc;
Index: head/sys/dev/hyperv/vmbus/vmbus_reg.h
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_reg.h
+++ head/sys/dev/hyperv/vmbus/vmbus_reg.h
@@ -102,6 +102,7 @@
 #define VMBUS_CHANMSG_TYPE_GPADL_CONNRESP	10	/* RESP */
 #define VMBUS_CHANMSG_TYPE_GPADL_DISCONN	11	/* REQ */
 #define VMBUS_CHANMSG_TYPE_GPADL_DISCONNRESP	12	/* RESP */
+#define VMBUS_CHANMSG_TYPE_CHFREE		13	/* REQ */
 #define VMBUS_CHANMSG_TYPE_CONNECT		14	/* REQ */
 #define VMBUS_CHANMSG_TYPE_CONNECT_RESP		15	/* RESP */
 #define VMBUS_CHANMSG_TYPE_DISCONNECT		16	/* REQ */
@@ -206,4 +207,10 @@
 	uint32_t	chm_gpadl;
 } __packed;
 
+/* VMBUS_CHANMSG_TYPE_CHFREE */
+struct vmbus_chanmsg_chfree {
+	struct vmbus_chanmsg_hdr chm_hdr;
+	uint32_t	chm_chanid;
+} __packed;
+
 #endif	/* !_VMBUS_REG_H_ */