Index: sys/dev/hyperv/include/vmbus.h
===================================================================
--- sys/dev/hyperv/include/vmbus.h
+++ sys/dev/hyperv/include/vmbus.h
@@ -116,6 +116,7 @@
 };
 
 struct vmbus_channel;
+struct vmbus_xact_ctx;
 struct hyperv_guid;
 struct task;
 struct taskqueue;
@@ -138,6 +139,9 @@
 void		vmbus_chan_intr_drain(struct vmbus_channel *chan);
 void		vmbus_chan_run_task(struct vmbus_channel *chan,
 		    struct task *task);
+void		vmbus_chan_set_orphan(struct vmbus_channel *chan,
+		    struct vmbus_xact_ctx *);
+void		vmbus_chan_unset_orphan(struct vmbus_channel *chan);
 
 int		vmbus_chan_gpadl_connect(struct vmbus_channel *chan,
 		    bus_addr_t paddr, int size, uint32_t *gpadl);
Index: sys/dev/hyperv/vmbus/vmbus_chan.c
===================================================================
--- sys/dev/hyperv/vmbus/vmbus_chan.c
+++ sys/dev/hyperv/vmbus/vmbus_chan.c
@@ -43,6 +43,7 @@
 #include <machine/stdarg.h>
 
 #include <dev/hyperv/include/hyperv_busdma.h>
+#include <dev/hyperv/include/vmbus_xact.h>
 #include <dev/hyperv/vmbus/hyperv_var.h>
 #include <dev/hyperv/vmbus/vmbus_reg.h>
 #include <dev/hyperv/vmbus/vmbus_var.h>
@@ -1115,6 +1116,7 @@
 
 	chan->ch_vmbus = sc;
 	mtx_init(&chan->ch_subchan_lock, "vmbus subchan", NULL, MTX_DEF);
+	sx_init(&chan->ch_orphan_lock, "vmbus chorphan");
 	TAILQ_INIT(&chan->ch_subchans);
 	vmbus_rxbr_init(&chan->ch_rxbr);
 	vmbus_txbr_init(&chan->ch_txbr);
@@ -1133,8 +1135,12 @@
 	     VMBUS_CHAN_ST_ONPRIL |
 	     VMBUS_CHAN_ST_ONSUBL |
 	     VMBUS_CHAN_ST_ONLIST)) == 0, ("free busy channel"));
+	KASSERT(chan->ch_orphan_xact == NULL,
+	    ("still has orphan xact installed"));
+
 	hyperv_dmamem_free(&chan->ch_monprm_dma, chan->ch_monprm);
 	mtx_destroy(&chan->ch_subchan_lock);
+	sx_destroy(&chan->ch_orphan_lock);
 	vmbus_rxbr_deinit(&chan->ch_rxbr);
 	vmbus_txbr_deinit(&chan->ch_txbr);
 	free(chan, M_DEVBUF);
@@ -1403,10 +1409,21 @@
 		mtx_unlock(&sc->vmbus_prichan_lock);
 	}
 
+	/*
+	 * NOTE:
+	 * The following processing order is critical:
+	 * Set the REVOKED state flag before orphaning the installed xact.
+	 */
+
 	if (atomic_testandset_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_REVOKED_SHIFT))
 		panic("channel has already been revoked");
 
+	sx_xlock(&chan->ch_orphan_lock);
+	if (chan->ch_orphan_xact != NULL)
+		vmbus_xact_ctx_orphan(chan->ch_orphan_xact);
+	sx_xunlock(&chan->ch_orphan_lock);
+
 	if (bootverbose)
 		vmbus_chan_printf(chan, "chan%u revoked\n", note->chm_chanid);
 
@@ -1708,3 +1725,21 @@
 		return (true);
 	return (false);
 }
+
+void
+vmbus_chan_set_orphan(struct vmbus_channel *chan, struct vmbus_xact_ctx *xact)
+{
+
+	sx_xlock(&chan->ch_orphan_lock);
+	chan->ch_orphan_xact = xact;
+	sx_xunlock(&chan->ch_orphan_lock);
+}
+
+void
+vmbus_chan_unset_orphan(struct vmbus_channel *chan)
+{
+
+	sx_xlock(&chan->ch_orphan_lock);
+	chan->ch_orphan_xact = NULL;
+	sx_xunlock(&chan->ch_orphan_lock);
+}
Index: sys/dev/hyperv/vmbus/vmbus_chanvar.h
===================================================================
--- sys/dev/hyperv/vmbus/vmbus_chanvar.h
+++ sys/dev/hyperv/vmbus/vmbus_chanvar.h
@@ -33,8 +33,9 @@
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/queue.h>
-#include <sys/taskqueue.h>
 #include <sys/sysctl.h>
+#include <sys/sx.h>
+#include <sys/taskqueue.h>
 
 #include <dev/hyperv/include/hyperv.h>
 #include <dev/hyperv/include/hyperv_busdma.h>
@@ -138,6 +139,9 @@
 	struct hyperv_guid		ch_guid_type;
 	struct hyperv_guid		ch_guid_inst;
 
+	struct sx			ch_orphan_lock;
+	struct vmbus_xact_ctx		*ch_orphan_xact;
+
 	struct sysctl_ctx_list		ch_sysctl_ctx;
 } __aligned(CACHE_LINE_SIZE);