Index: head/sys/dev/hyperv/include/vmbus.h
===================================================================
--- head/sys/dev/hyperv/include/vmbus.h	(revision 309029)
+++ head/sys/dev/hyperv/include/vmbus.h	(revision 309030)
@@ -1,184 +1,185 @@
 /*-
  * Copyright (c) 2016 Microsoft Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice unmodified, this list of conditions, and the following
  *    disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * $FreeBSD$
  */
 
 #ifndef _VMBUS_H_
 #define _VMBUS_H_
 
 #include <sys/param.h>
 #include <sys/bus.h>
 
 /*
  * VMBUS version is 32 bit, upper 16 bit for major_number and lower
  * 16 bit for minor_number.
  *
  * 0.13  --  Windows Server 2008
  * 1.1   --  Windows 7
  * 2.4   --  Windows 8
  * 3.0   --  Windows 8.1
  */
 #define VMBUS_VERSION_WS2008		((0 << 16) | (13))
 #define VMBUS_VERSION_WIN7		((1 << 16) | (1))
 #define VMBUS_VERSION_WIN8		((2 << 16) | (4))
 #define VMBUS_VERSION_WIN8_1		((3 << 16) | (0))
 
 #define VMBUS_VERSION_MAJOR(ver)	(((uint32_t)(ver)) >> 16)
 #define VMBUS_VERSION_MINOR(ver)	(((uint32_t)(ver)) & 0xffff)
 
 /*
  * GPA stuffs.
  */
 struct vmbus_gpa_range {
 	uint32_t	gpa_len;
 	uint32_t	gpa_ofs;
 	uint64_t	gpa_page[0];
 } __packed;
 
 /* This is actually vmbus_gpa_range.gpa_page[1] */
 struct vmbus_gpa {
 	uint32_t	gpa_len;
 	uint32_t	gpa_ofs;
 	uint64_t	gpa_page;
 } __packed;
 
 #define VMBUS_CHANPKT_SIZE_SHIFT	3
 
 #define VMBUS_CHANPKT_GETLEN(pktlen)	\
 	(((int)(pktlen)) << VMBUS_CHANPKT_SIZE_SHIFT)
 
 struct vmbus_chanpkt_hdr {
 	uint16_t	cph_type;	/* VMBUS_CHANPKT_TYPE_ */
 	uint16_t	cph_hlen;	/* header len, in 8 bytes */
 	uint16_t	cph_tlen;	/* total len, in 8 bytes */
 	uint16_t	cph_flags;	/* VMBUS_CHANPKT_FLAG_ */
 	uint64_t	cph_xactid;
 } __packed;
 
 #define VMBUS_CHANPKT_TYPE_INBAND	0x0006
 #define VMBUS_CHANPKT_TYPE_RXBUF	0x0007
 #define VMBUS_CHANPKT_TYPE_GPA		0x0009
 #define VMBUS_CHANPKT_TYPE_COMP		0x000b
 
 #define VMBUS_CHANPKT_FLAG_NONE		0
 #define VMBUS_CHANPKT_FLAG_RC		0x0001	/* report completion */
 
 #define VMBUS_CHANPKT_CONST_DATA(pkt)		\
 	(const void *)((const uint8_t *)(pkt) +	\
 	VMBUS_CHANPKT_GETLEN((pkt)->cph_hlen))
 
 /* Include padding */
 #define VMBUS_CHANPKT_DATALEN(pkt)		\
 	(VMBUS_CHANPKT_GETLEN((pkt)->cph_tlen) -\
 	 VMBUS_CHANPKT_GETLEN((pkt)->cph_hlen))
 
 struct vmbus_rxbuf_desc {
 	uint32_t	rb_len;
 	uint32_t	rb_ofs;
 } __packed;
 
 struct vmbus_chanpkt_rxbuf {
 	struct vmbus_chanpkt_hdr cp_hdr;
 	uint16_t	cp_rxbuf_id;
 	uint16_t	cp_rsvd;
 	uint32_t	cp_rxbuf_cnt;
 	struct vmbus_rxbuf_desc cp_rxbuf[];
 } __packed;
 
 struct vmbus_chan_br {
 	void		*cbr;
 	bus_addr_t	cbr_paddr;
 	int		cbr_txsz;
 	int		cbr_rxsz;
 };
 
 struct vmbus_channel;
 struct hyperv_guid;
 struct task;
 struct taskqueue;
 
 typedef void	(*vmbus_chan_callback_t)(struct vmbus_channel *, void *);
 
 static __inline struct vmbus_channel *
 vmbus_get_channel(device_t dev)
 {
 	return device_get_ivars(dev);
 }
 
 int		vmbus_chan_open(struct vmbus_channel *chan,
 		    int txbr_size, int rxbr_size, const void *udata, int udlen,
 		    vmbus_chan_callback_t cb, void *cbarg);
 int		vmbus_chan_open_br(struct vmbus_channel *chan,
 		    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);
 void		vmbus_chan_intr_drain(struct vmbus_channel *chan);
 void		vmbus_chan_run_task(struct vmbus_channel *chan,
 		    struct task *task);
 
 int		vmbus_chan_gpadl_connect(struct vmbus_channel *chan,
 		    bus_addr_t paddr, int size, uint32_t *gpadl);
 int		vmbus_chan_gpadl_disconnect(struct vmbus_channel *chan,
 		    uint32_t gpadl);
 
 void		vmbus_chan_cpu_set(struct vmbus_channel *chan, int cpu);
 void		vmbus_chan_cpu_rr(struct vmbus_channel *chan);
 void		vmbus_chan_set_readbatch(struct vmbus_channel *chan, bool on);
 
 struct vmbus_channel **
 		vmbus_subchan_get(struct vmbus_channel *pri_chan,
 		    int subchan_cnt);
 void		vmbus_subchan_rel(struct vmbus_channel **subchan,
 		    int subchan_cnt);
 void		vmbus_subchan_drain(struct vmbus_channel *pri_chan);
 
 int		vmbus_chan_recv(struct vmbus_channel *chan, void *data, int *dlen,
 		    uint64_t *xactid);
 int		vmbus_chan_recv_pkt(struct vmbus_channel *chan,
 		    struct vmbus_chanpkt_hdr *pkt, int *pktlen);
 
 int		vmbus_chan_send(struct vmbus_channel *chan, uint16_t type,
 		    uint16_t flags, void *data, int dlen, uint64_t xactid);
 int		vmbus_chan_send_sglist(struct vmbus_channel *chan,
 		    struct vmbus_gpa sg[], int sglen, void *data, int dlen,
 		    uint64_t xactid);
 int		vmbus_chan_send_prplist(struct vmbus_channel *chan,
 		    struct vmbus_gpa_range *prp, int prp_cnt, void *data,
 		    int dlen, uint64_t xactid);
 
 uint32_t	vmbus_chan_id(const struct vmbus_channel *chan);
 uint32_t	vmbus_chan_subidx(const struct vmbus_channel *chan);
 bool		vmbus_chan_is_primary(const struct vmbus_channel *chan);
+bool		vmbus_chan_is_revoked(const struct vmbus_channel *chan);
 const struct hyperv_guid *
 		vmbus_chan_guid_inst(const struct vmbus_channel *chan);
 int		vmbus_chan_prplist_nelem(int br_size, int prpcnt_max,
 		    int dlen_max);
 bool		vmbus_chan_rx_empty(const struct vmbus_channel *chan);
 bool		vmbus_chan_tx_empty(const struct vmbus_channel *chan);
 struct taskqueue *
 		vmbus_chan_mgmt_tq(const struct vmbus_channel *chan);
 
 #endif	/* !_VMBUS_H_ */
Index: head/sys/dev/hyperv/vmbus/vmbus_chan.c
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_chan.c	(revision 309029)
+++ head/sys/dev/hyperv/vmbus/vmbus_chan.c	(revision 309030)
@@ -1,1697 +1,1710 @@
 /*-
  * Copyright (c) 2009-2012,2016 Microsoft Corp.
  * Copyright (c) 2012 NetApp Inc.
  * Copyright (c) 2012 Citrix Inc.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice unmodified, this list of conditions, and the following
  *    disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
 #include <sys/bus.h>
 #include <sys/kernel.h>
 #include <sys/lock.h>
 #include <sys/malloc.h>
 #include <sys/mutex.h>
 #include <sys/smp.h>
 #include <sys/sysctl.h>
 #include <sys/systm.h>
 
 #include <machine/atomic.h>
 #include <machine/stdarg.h>
 
 #include <dev/hyperv/include/hyperv_busdma.h>
 #include <dev/hyperv/vmbus/hyperv_var.h>
 #include <dev/hyperv/vmbus/vmbus_reg.h>
 #include <dev/hyperv/vmbus/vmbus_var.h>
 #include <dev/hyperv/vmbus/vmbus_brvar.h>
 #include <dev/hyperv/vmbus/vmbus_chanvar.h>
 
 static void			vmbus_chan_update_evtflagcnt(
 				    struct vmbus_softc *,
 				    const struct vmbus_channel *);
 static void			vmbus_chan_close_internal(
 				    struct vmbus_channel *);
 static int			vmbus_chan_sysctl_mnf(SYSCTL_HANDLER_ARGS);
 static void			vmbus_chan_sysctl_create(
 				    struct vmbus_channel *);
 static struct vmbus_channel	*vmbus_chan_alloc(struct vmbus_softc *);
 static void			vmbus_chan_free(struct vmbus_channel *);
 static int			vmbus_chan_add(struct vmbus_channel *);
 static void			vmbus_chan_cpu_default(struct vmbus_channel *);
 static int			vmbus_chan_release(struct vmbus_channel *);
 static void			vmbus_chan_set_chmap(struct vmbus_channel *);
 static void			vmbus_chan_clear_chmap(struct vmbus_channel *);
 
 static void			vmbus_chan_ins_prilist(struct vmbus_softc *,
 				    struct vmbus_channel *);
 static void			vmbus_chan_rem_prilist(struct vmbus_softc *,
 				    struct vmbus_channel *);
 static void			vmbus_chan_ins_list(struct vmbus_softc *,
 				    struct vmbus_channel *);
 static void			vmbus_chan_rem_list(struct vmbus_softc *,
 				    struct vmbus_channel *);
 static void			vmbus_chan_ins_sublist(struct vmbus_channel *,
 				    struct vmbus_channel *);
 static void			vmbus_chan_rem_sublist(struct vmbus_channel *,
 				    struct vmbus_channel *);
 
 static void			vmbus_chan_task(void *, int);
 static void			vmbus_chan_task_nobatch(void *, int);
 static void			vmbus_chan_clrchmap_task(void *, int);
 static void			vmbus_prichan_attach_task(void *, int);
 static void			vmbus_subchan_attach_task(void *, int);
 static void			vmbus_prichan_detach_task(void *, int);
 static void			vmbus_subchan_detach_task(void *, int);
 
 static void			vmbus_chan_msgproc_choffer(struct vmbus_softc *,
 				    const struct vmbus_message *);
 static void			vmbus_chan_msgproc_chrescind(
 				    struct vmbus_softc *,
 				    const struct vmbus_message *);
 
 static int			vmbus_chan_printf(const struct vmbus_channel *,
 				    const char *, ...) __printflike(2, 3);
 
 /*
  * Vmbus channel message processing.
  */
 static const vmbus_chanmsg_proc_t
 vmbus_chan_msgprocs[VMBUS_CHANMSG_TYPE_MAX] = {
 	VMBUS_CHANMSG_PROC(CHOFFER,	vmbus_chan_msgproc_choffer),
 	VMBUS_CHANMSG_PROC(CHRESCIND,	vmbus_chan_msgproc_chrescind),
 
 	VMBUS_CHANMSG_PROC_WAKEUP(CHOPEN_RESP),
 	VMBUS_CHANMSG_PROC_WAKEUP(GPADL_CONNRESP),
 	VMBUS_CHANMSG_PROC_WAKEUP(GPADL_DISCONNRESP)
 };
 
 /*
  * Notify host that there are data pending on our TX bufring.
  */
 static __inline void
 vmbus_chan_signal_tx(const struct vmbus_channel *chan)
 {
 	atomic_set_long(chan->ch_evtflag, chan->ch_evtflag_mask);
 	if (chan->ch_txflags & VMBUS_CHAN_TXF_HASMNF)
 		atomic_set_int(chan->ch_montrig, chan->ch_montrig_mask);
 	else
 		hypercall_signal_event(chan->ch_monprm_dma.hv_paddr);
 }
 
 static void
 vmbus_chan_ins_prilist(struct vmbus_softc *sc, struct vmbus_channel *chan)
 {
 
 	mtx_assert(&sc->vmbus_prichan_lock, MA_OWNED);
 	if (atomic_testandset_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_ONPRIL_SHIFT))
 		panic("channel is already on the prilist");
 	TAILQ_INSERT_TAIL(&sc->vmbus_prichans, chan, ch_prilink);
 }
 
 static void
 vmbus_chan_rem_prilist(struct vmbus_softc *sc, struct vmbus_channel *chan)
 {
 
 	mtx_assert(&sc->vmbus_prichan_lock, MA_OWNED);
 	if (atomic_testandclear_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_ONPRIL_SHIFT) == 0)
 		panic("channel is not on the prilist");
 	TAILQ_REMOVE(&sc->vmbus_prichans, chan, ch_prilink);
 }
 
 static void
 vmbus_chan_ins_sublist(struct vmbus_channel *prichan,
     struct vmbus_channel *chan)
 {
 
 	mtx_assert(&prichan->ch_subchan_lock, MA_OWNED);
 
 	if (atomic_testandset_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_ONSUBL_SHIFT))
 		panic("channel is already on the sublist");
 	TAILQ_INSERT_TAIL(&prichan->ch_subchans, chan, ch_sublink);
 
 	/* Bump sub-channel count. */
 	prichan->ch_subchan_cnt++;
 }
 
 static void
 vmbus_chan_rem_sublist(struct vmbus_channel *prichan,
     struct vmbus_channel *chan)
 {
 
 	mtx_assert(&prichan->ch_subchan_lock, MA_OWNED);
 
 	KASSERT(prichan->ch_subchan_cnt > 0,
 	    ("invalid subchan_cnt %d", prichan->ch_subchan_cnt));
 	prichan->ch_subchan_cnt--;
 
 	if (atomic_testandclear_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_ONSUBL_SHIFT) == 0)
 		panic("channel is not on the sublist");
 	TAILQ_REMOVE(&prichan->ch_subchans, chan, ch_sublink);
 }
 
 static void
 vmbus_chan_ins_list(struct vmbus_softc *sc, struct vmbus_channel *chan)
 {
 
 	mtx_assert(&sc->vmbus_chan_lock, MA_OWNED);
 	if (atomic_testandset_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_ONLIST_SHIFT))
 		panic("channel is already on the list");
 	TAILQ_INSERT_TAIL(&sc->vmbus_chans, chan, ch_link);
 }
 
 static void
 vmbus_chan_rem_list(struct vmbus_softc *sc, struct vmbus_channel *chan)
 {
 
 	mtx_assert(&sc->vmbus_chan_lock, MA_OWNED);
 	if (atomic_testandclear_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_ONLIST_SHIFT) == 0)
 		panic("channel is not on the list");
 	TAILQ_REMOVE(&sc->vmbus_chans, chan, ch_link);
 }
 
 static int
 vmbus_chan_sysctl_mnf(SYSCTL_HANDLER_ARGS)
 {
 	struct vmbus_channel *chan = arg1;
 	int mnf = 0;
 
 	if (chan->ch_txflags & VMBUS_CHAN_TXF_HASMNF)
 		mnf = 1;
 	return sysctl_handle_int(oidp, &mnf, 0, req);
 }
 
 static void
 vmbus_chan_sysctl_create(struct vmbus_channel *chan)
 {
 	struct sysctl_oid *ch_tree, *chid_tree, *br_tree;
 	struct sysctl_ctx_list *ctx;
 	uint32_t ch_id;
 	char name[16];
 
 	/*
 	 * Add sysctl nodes related to this channel to this
 	 * channel's sysctl ctx, so that they can be destroyed
 	 * independently upon close of this channel, which can
 	 * happen even if the device is not detached.
 	 */
 	ctx = &chan->ch_sysctl_ctx;
 	sysctl_ctx_init(ctx);
 
 	/*
 	 * Create dev.NAME.UNIT.channel tree.
 	 */
 	ch_tree = SYSCTL_ADD_NODE(ctx,
 	    SYSCTL_CHILDREN(device_get_sysctl_tree(chan->ch_dev)),
 	    OID_AUTO, "channel", CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "");
 	if (ch_tree == NULL)
 		return;
 
 	/*
 	 * Create dev.NAME.UNIT.channel.CHANID tree.
 	 */
 	if (VMBUS_CHAN_ISPRIMARY(chan))
 		ch_id = chan->ch_id;
 	else
 		ch_id = chan->ch_prichan->ch_id;
 	snprintf(name, sizeof(name), "%d", ch_id);
 	chid_tree = SYSCTL_ADD_NODE(ctx, SYSCTL_CHILDREN(ch_tree),
 	    OID_AUTO, name, CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "");
 	if (chid_tree == NULL)
 		return;
 
 	if (!VMBUS_CHAN_ISPRIMARY(chan)) {
 		/*
 		 * Create dev.NAME.UNIT.channel.CHANID.sub tree.
 		 */
 		ch_tree = SYSCTL_ADD_NODE(ctx, SYSCTL_CHILDREN(chid_tree),
 		    OID_AUTO, "sub", CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "");
 		if (ch_tree == NULL)
 			return;
 
 		/*
 		 * Create dev.NAME.UNIT.channel.CHANID.sub.SUBIDX tree.
 		 *
 		 * NOTE:
 		 * chid_tree is changed to this new sysctl tree.
 		 */
 		snprintf(name, sizeof(name), "%d", chan->ch_subidx);
 		chid_tree = SYSCTL_ADD_NODE(ctx, SYSCTL_CHILDREN(ch_tree),
 		    OID_AUTO, name, CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "");
 		if (chid_tree == NULL)
 			return;
 
 		SYSCTL_ADD_UINT(ctx, SYSCTL_CHILDREN(chid_tree), OID_AUTO,
 		    "chanid", CTLFLAG_RD, &chan->ch_id, 0, "channel id");
 	}
 
 	SYSCTL_ADD_UINT(ctx, SYSCTL_CHILDREN(chid_tree), OID_AUTO,
 	    "cpu", CTLFLAG_RD, &chan->ch_cpuid, 0, "owner CPU id");
 	SYSCTL_ADD_PROC(ctx, SYSCTL_CHILDREN(chid_tree), OID_AUTO,
 	    "mnf", CTLTYPE_INT | CTLFLAG_RD | CTLFLAG_MPSAFE,
 	    chan, 0, vmbus_chan_sysctl_mnf, "I",
 	    "has monitor notification facilities");
 
 	br_tree = SYSCTL_ADD_NODE(ctx, SYSCTL_CHILDREN(chid_tree), OID_AUTO,
 	    "br", CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "");
 	if (br_tree != NULL) {
 		/*
 		 * Create sysctl tree for RX bufring.
 		 */
 		vmbus_br_sysctl_create(ctx, br_tree, &chan->ch_rxbr.rxbr, "rx");
 		/*
 		 * Create sysctl tree for TX bufring.
 		 */
 		vmbus_br_sysctl_create(ctx, br_tree, &chan->ch_txbr.txbr, "tx");
 	}
 }
 
 int
 vmbus_chan_open(struct vmbus_channel *chan, int txbr_size, int rxbr_size,
     const void *udata, int udlen, vmbus_chan_callback_t cb, void *cbarg)
 {
 	struct vmbus_chan_br cbr;
 	int error;
 
 	/*
 	 * Allocate the TX+RX bufrings.
 	 */
 	KASSERT(chan->ch_bufring == NULL, ("bufrings are allocated"));
 	chan->ch_bufring = hyperv_dmamem_alloc(bus_get_dma_tag(chan->ch_dev),
 	    PAGE_SIZE, 0, txbr_size + rxbr_size, &chan->ch_bufring_dma,
 	    BUS_DMA_WAITOK);
 	if (chan->ch_bufring == NULL) {
 		vmbus_chan_printf(chan, "bufring allocation failed\n");
 		return (ENOMEM);
 	}
 
 	cbr.cbr = chan->ch_bufring;
 	cbr.cbr_paddr = chan->ch_bufring_dma.hv_paddr;
 	cbr.cbr_txsz = txbr_size;
 	cbr.cbr_rxsz = rxbr_size;
 
 	error = vmbus_chan_open_br(chan, &cbr, udata, udlen, cb, cbarg);
 	if (error) {
 		hyperv_dmamem_free(&chan->ch_bufring_dma, chan->ch_bufring);
 		chan->ch_bufring = NULL;
 	}
 	return (error);
 }
 
 int
 vmbus_chan_open_br(struct vmbus_channel *chan, const struct vmbus_chan_br *cbr,
     const void *udata, int udlen, vmbus_chan_callback_t cb, void *cbarg)
 {
 	struct vmbus_softc *sc = chan->ch_vmbus;
 	const struct vmbus_chanmsg_chopen_resp *resp;
 	const struct vmbus_message *msg;
 	struct vmbus_chanmsg_chopen *req;
 	struct vmbus_msghc *mh;
 	uint32_t status;
 	int error, txbr_size, rxbr_size;
 	task_fn_t *task_fn;
 	uint8_t *br;
 
 	if (udlen > VMBUS_CHANMSG_CHOPEN_UDATA_SIZE) {
 		vmbus_chan_printf(chan,
 		    "invalid udata len %d for chan%u\n", udlen, chan->ch_id);
 		return EINVAL;
 	}
 
 	br = cbr->cbr;
 	txbr_size = cbr->cbr_txsz;
 	rxbr_size = cbr->cbr_rxsz;
 	KASSERT((txbr_size & PAGE_MASK) == 0,
 	    ("send bufring size is not multiple page"));
 	KASSERT((rxbr_size & PAGE_MASK) == 0,
 	    ("recv bufring size is not multiple page"));
 	KASSERT((cbr->cbr_paddr & PAGE_MASK) == 0,
 	    ("bufring is not page aligned"));
 
 	/*
 	 * Zero out the TX/RX bufrings, in case that they were used before.
 	 */
 	memset(br, 0, txbr_size + rxbr_size);
 
 	if (atomic_testandset_int(&chan->ch_stflags,
 	    VMBUS_CHAN_ST_OPENED_SHIFT))
 		panic("double-open chan%u", chan->ch_id);
 
 	chan->ch_cb = cb;
 	chan->ch_cbarg = cbarg;
 
 	vmbus_chan_update_evtflagcnt(sc, chan);
 
 	chan->ch_tq = VMBUS_PCPU_GET(chan->ch_vmbus, event_tq, chan->ch_cpuid);
 	if (chan->ch_flags & VMBUS_CHAN_FLAG_BATCHREAD)
 		task_fn = vmbus_chan_task;
 	else
 		task_fn = vmbus_chan_task_nobatch;
 	TASK_INIT(&chan->ch_task, 0, task_fn, chan);
 
 	/* TX bufring comes first */
 	vmbus_txbr_setup(&chan->ch_txbr, br, txbr_size);
 	/* RX bufring immediately follows TX bufring */
 	vmbus_rxbr_setup(&chan->ch_rxbr, br + txbr_size, rxbr_size);
 
 	/* Create sysctl tree for this channel */
 	vmbus_chan_sysctl_create(chan);
 
 	/*
 	 * Connect the bufrings, both RX and TX, to this channel.
 	 */
 	error = vmbus_chan_gpadl_connect(chan, cbr->cbr_paddr,
 	    txbr_size + rxbr_size, &chan->ch_bufring_gpadl);
 	if (error) {
 		vmbus_chan_printf(chan,
 		    "failed to connect bufring GPADL to chan%u\n", chan->ch_id);
 		goto failed;
 	}
 
 	/*
 	 * Install this channel, before it is opened, but after everything
 	 * else has been setup.
 	 */
 	vmbus_chan_set_chmap(chan);
 
 	/*
 	 * Open channel w/ the bufring GPADL on the target CPU.
 	 */
 	mh = vmbus_msghc_get(sc, sizeof(*req));
 	if (mh == NULL) {
 		vmbus_chan_printf(chan,
 		    "can not get msg hypercall for chopen(chan%u)\n",
 		    chan->ch_id);
 		error = ENXIO;
 		goto failed;
 	}
 
 	req = vmbus_msghc_dataptr(mh);
 	req->chm_hdr.chm_type = VMBUS_CHANMSG_TYPE_CHOPEN;
 	req->chm_chanid = chan->ch_id;
 	req->chm_openid = chan->ch_id;
 	req->chm_gpadl = chan->ch_bufring_gpadl;
 	req->chm_vcpuid = chan->ch_vcpuid;
 	req->chm_txbr_pgcnt = txbr_size >> PAGE_SHIFT;
 	if (udlen > 0)
 		memcpy(req->chm_udata, udata, udlen);
 
 	error = vmbus_msghc_exec(sc, mh);
 	if (error) {
 		vmbus_chan_printf(chan,
 		    "chopen(chan%u) msg hypercall exec failed: %d\n",
 		    chan->ch_id, error);
 		vmbus_msghc_put(sc, mh);
 		goto failed;
 	}
 
 	msg = vmbus_msghc_wait_result(sc, mh);
 	resp = (const struct vmbus_chanmsg_chopen_resp *)msg->msg_data;
 	status = resp->chm_status;
 
 	vmbus_msghc_put(sc, mh);
 
 	if (status == 0) {
 		if (bootverbose) {
 			vmbus_chan_printf(chan, "chan%u opened\n", chan->ch_id);
 		}
 		return 0;
 	}
 
 	vmbus_chan_printf(chan, "failed to open chan%u\n", chan->ch_id);
 	error = ENXIO;
 
 failed:
 	vmbus_chan_clear_chmap(chan);
 	if (chan->ch_bufring_gpadl) {
 		vmbus_chan_gpadl_disconnect(chan, chan->ch_bufring_gpadl);
 		chan->ch_bufring_gpadl = 0;
 	}
 	atomic_clear_int(&chan->ch_stflags, VMBUS_CHAN_ST_OPENED);
 	return error;
 }
 
 int
 vmbus_chan_gpadl_connect(struct vmbus_channel *chan, bus_addr_t paddr,
     int size, uint32_t *gpadl0)
 {
 	struct vmbus_softc *sc = chan->ch_vmbus;
 	struct vmbus_msghc *mh;
 	struct vmbus_chanmsg_gpadl_conn *req;
 	const struct vmbus_message *msg;
 	size_t reqsz;
 	uint32_t gpadl, status;
 	int page_count, range_len, i, cnt, error;
 	uint64_t page_id;
 
 	/*
 	 * Preliminary checks.
 	 */
 
 	KASSERT((size & PAGE_MASK) == 0,
 	    ("invalid GPA size %d, not multiple page size", size));
 	page_count = size >> PAGE_SHIFT;
 
 	KASSERT((paddr & PAGE_MASK) == 0,
 	    ("GPA is not page aligned %jx", (uintmax_t)paddr));
 	page_id = paddr >> PAGE_SHIFT;
 
 	range_len = __offsetof(struct vmbus_gpa_range, gpa_page[page_count]);
 	/*
 	 * We don't support multiple GPA ranges.
 	 */
 	if (range_len > UINT16_MAX) {
 		vmbus_chan_printf(chan, "GPA too large, %d pages\n",
 		    page_count);
 		return EOPNOTSUPP;
 	}
 
 	/*
 	 * Allocate GPADL id.
 	 */
 	gpadl = vmbus_gpadl_alloc(sc);
 	*gpadl0 = gpadl;
 
 	/*
 	 * Connect this GPADL to the target channel.
 	 *
 	 * NOTE:
 	 * Since each message can only hold small set of page
 	 * addresses, several messages may be required to
 	 * complete the connection.
 	 */
 	if (page_count > VMBUS_CHANMSG_GPADL_CONN_PGMAX)
 		cnt = VMBUS_CHANMSG_GPADL_CONN_PGMAX;
 	else
 		cnt = page_count;
 	page_count -= cnt;
 
 	reqsz = __offsetof(struct vmbus_chanmsg_gpadl_conn,
 	    chm_range.gpa_page[cnt]);
 	mh = vmbus_msghc_get(sc, reqsz);
 	if (mh == NULL) {
 		vmbus_chan_printf(chan,
 		    "can not get msg hypercall for gpadl_conn(chan%u)\n",
 		    chan->ch_id);
 		return EIO;
 	}
 
 	req = vmbus_msghc_dataptr(mh);
 	req->chm_hdr.chm_type = VMBUS_CHANMSG_TYPE_GPADL_CONN;
 	req->chm_chanid = chan->ch_id;
 	req->chm_gpadl = gpadl;
 	req->chm_range_len = range_len;
 	req->chm_range_cnt = 1;
 	req->chm_range.gpa_len = size;
 	req->chm_range.gpa_ofs = 0;
 	for (i = 0; i < cnt; ++i)
 		req->chm_range.gpa_page[i] = page_id++;
 
 	error = vmbus_msghc_exec(sc, mh);
 	if (error) {
 		vmbus_chan_printf(chan,
 		    "gpadl_conn(chan%u) msg hypercall exec failed: %d\n",
 		    chan->ch_id, error);
 		vmbus_msghc_put(sc, mh);
 		return error;
 	}
 
 	while (page_count > 0) {
 		struct vmbus_chanmsg_gpadl_subconn *subreq;
 
 		if (page_count > VMBUS_CHANMSG_GPADL_SUBCONN_PGMAX)
 			cnt = VMBUS_CHANMSG_GPADL_SUBCONN_PGMAX;
 		else
 			cnt = page_count;
 		page_count -= cnt;
 
 		reqsz = __offsetof(struct vmbus_chanmsg_gpadl_subconn,
 		    chm_gpa_page[cnt]);
 		vmbus_msghc_reset(mh, reqsz);
 
 		subreq = vmbus_msghc_dataptr(mh);
 		subreq->chm_hdr.chm_type = VMBUS_CHANMSG_TYPE_GPADL_SUBCONN;
 		subreq->chm_gpadl = gpadl;
 		for (i = 0; i < cnt; ++i)
 			subreq->chm_gpa_page[i] = page_id++;
 
 		vmbus_msghc_exec_noresult(mh);
 	}
 	KASSERT(page_count == 0, ("invalid page count %d", page_count));
 
 	msg = vmbus_msghc_wait_result(sc, mh);
 	status = ((const struct vmbus_chanmsg_gpadl_connresp *)
 	    msg->msg_data)->chm_status;
 
 	vmbus_msghc_put(sc, mh);
 
 	if (status != 0) {
 		vmbus_chan_printf(chan, "gpadl_conn(chan%u) failed: %u\n",
 		    chan->ch_id, status);
 		return EIO;
 	} else {
 		if (bootverbose) {
 			vmbus_chan_printf(chan,
 			    "gpadl_conn(chan%u) succeeded\n", chan->ch_id);
 		}
 	}
 	return 0;
 }
 
 /*
  * Disconnect the GPA from the target channel
  */
 int
 vmbus_chan_gpadl_disconnect(struct vmbus_channel *chan, uint32_t gpadl)
 {
 	struct vmbus_softc *sc = chan->ch_vmbus;
 	struct vmbus_msghc *mh;
 	struct vmbus_chanmsg_gpadl_disconn *req;
 	int error;
 
 	mh = vmbus_msghc_get(sc, sizeof(*req));
 	if (mh == NULL) {
 		vmbus_chan_printf(chan,
 		    "can not get msg hypercall for gpadl_disconn(chan%u)\n",
 		    chan->ch_id);
 		return EBUSY;
 	}
 
 	req = vmbus_msghc_dataptr(mh);
 	req->chm_hdr.chm_type = VMBUS_CHANMSG_TYPE_GPADL_DISCONN;
 	req->chm_chanid = chan->ch_id;
 	req->chm_gpadl = gpadl;
 
 	error = vmbus_msghc_exec(sc, mh);
 	if (error) {
 		vmbus_chan_printf(chan,
 		    "gpadl_disconn(chan%u) msg hypercall exec failed: %d\n",
 		    chan->ch_id, error);
 		vmbus_msghc_put(sc, mh);
 		return error;
 	}
 
 	vmbus_msghc_wait_result(sc, mh);
 	/* Discard result; no useful information */
 	vmbus_msghc_put(sc, mh);
 
 	return 0;
 }
 
 static void
 vmbus_chan_clrchmap_task(void *xchan, int pending __unused)
 {
 	struct vmbus_channel *chan = xchan;
 
 	critical_enter();
 	chan->ch_vmbus->vmbus_chmap[chan->ch_id] = NULL;
 	critical_exit();
 }
 
 static void
 vmbus_chan_clear_chmap(struct vmbus_channel *chan)
 {
 	struct task chmap_task;
 
 	TASK_INIT(&chmap_task, 0, vmbus_chan_clrchmap_task, chan);
 	taskqueue_enqueue(chan->ch_tq, &chmap_task);
 	taskqueue_drain(chan->ch_tq, &chmap_task);
 }
 
 static void
 vmbus_chan_set_chmap(struct vmbus_channel *chan)
 {
 	__compiler_membar();
 	chan->ch_vmbus->vmbus_chmap[chan->ch_id] = chan;
 }
 
 static void
 vmbus_chan_close_internal(struct vmbus_channel *chan)
 {
 	struct vmbus_softc *sc = chan->ch_vmbus;
 	struct vmbus_msghc *mh;
 	struct vmbus_chanmsg_chclose *req;
 	int error;
 
 	/* TODO: stringent check */
 	atomic_clear_int(&chan->ch_stflags, VMBUS_CHAN_ST_OPENED);
 
 	/*
 	 * Free this channel's sysctl tree attached to its device's
 	 * sysctl tree.
 	 */
 	sysctl_ctx_free(&chan->ch_sysctl_ctx);
 
 	/*
 	 * NOTE:
 	 * Order is critical.  This channel _must_ be uninstalled first,
 	 * else the channel task may be enqueued by the IDT after it has
 	 * been drained.
 	 */
 	vmbus_chan_clear_chmap(chan);
 	taskqueue_drain(chan->ch_tq, &chan->ch_task);
 	chan->ch_tq = NULL;
 
 	/*
 	 * Close this channel.
 	 */
 	mh = vmbus_msghc_get(sc, sizeof(*req));
 	if (mh == NULL) {
 		vmbus_chan_printf(chan,
 		    "can not get msg hypercall for chclose(chan%u)\n",
 		    chan->ch_id);
 		return;
 	}
 
 	req = vmbus_msghc_dataptr(mh);
 	req->chm_hdr.chm_type = VMBUS_CHANMSG_TYPE_CHCLOSE;
 	req->chm_chanid = chan->ch_id;
 
 	error = vmbus_msghc_exec_noresult(mh);
 	vmbus_msghc_put(sc, mh);
 
 	if (error) {
 		vmbus_chan_printf(chan,
 		    "chclose(chan%u) msg hypercall exec failed: %d\n",
 		    chan->ch_id, error);
 		return;
 	} else if (bootverbose) {
 		vmbus_chan_printf(chan, "close chan%u\n", chan->ch_id);
 	}
 
 	/*
 	 * Disconnect the TX+RX bufrings from this channel.
 	 */
 	if (chan->ch_bufring_gpadl) {
 		vmbus_chan_gpadl_disconnect(chan, chan->ch_bufring_gpadl);
 		chan->ch_bufring_gpadl = 0;
 	}
 
 	/*
 	 * Destroy the TX+RX bufrings.
 	 */
 	if (chan->ch_bufring != NULL) {
 		hyperv_dmamem_free(&chan->ch_bufring_dma, chan->ch_bufring);
 		chan->ch_bufring = NULL;
 	}
 }
 
 /*
  * Caller should make sure that all sub-channels have
  * been added to 'chan' and all to-be-closed channels
  * are not being opened.
  */
 void
 vmbus_chan_close(struct vmbus_channel *chan)
 {
 	int subchan_cnt;
 
 	if (!VMBUS_CHAN_ISPRIMARY(chan)) {
 		/*
 		 * Sub-channel is closed when its primary channel
 		 * is closed; done.
 		 */
 		return;
 	}
 
 	/*
 	 * Close all sub-channels, if any.
 	 */
 	subchan_cnt = chan->ch_subchan_cnt;
 	if (subchan_cnt > 0) {
 		struct vmbus_channel **subchan;
 		int i;
 
 		subchan = vmbus_subchan_get(chan, subchan_cnt);
 		for (i = 0; i < subchan_cnt; ++i)
 			vmbus_chan_close_internal(subchan[i]);
 		vmbus_subchan_rel(subchan, subchan_cnt);
 	}
 
 	/* Then close the primary channel. */
 	vmbus_chan_close_internal(chan);
 }
 
 void
 vmbus_chan_intr_drain(struct vmbus_channel *chan)
 {
 
 	taskqueue_drain(chan->ch_tq, &chan->ch_task);
 }
 
 int
 vmbus_chan_send(struct vmbus_channel *chan, uint16_t type, uint16_t flags,
     void *data, int dlen, uint64_t xactid)
 {
 	struct vmbus_chanpkt pkt;
 	int pktlen, pad_pktlen, hlen, error;
 	uint64_t pad = 0;
 	struct iovec iov[3];
 	boolean_t send_evt;
 
 	hlen = sizeof(pkt);
 	pktlen = hlen + dlen;
 	pad_pktlen = VMBUS_CHANPKT_TOTLEN(pktlen);
 	KASSERT(pad_pktlen <= vmbus_txbr_maxpktsz(&chan->ch_txbr),
 	    ("invalid packet size %d", pad_pktlen));
 
 	pkt.cp_hdr.cph_type = type;
 	pkt.cp_hdr.cph_flags = flags;
 	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_hlen, hlen);
 	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_tlen, pad_pktlen);
 	pkt.cp_hdr.cph_xactid = xactid;
 
 	iov[0].iov_base = &pkt;
 	iov[0].iov_len = hlen;
 	iov[1].iov_base = data;
 	iov[1].iov_len = dlen;
 	iov[2].iov_base = &pad;
 	iov[2].iov_len = pad_pktlen - pktlen;
 
 	error = vmbus_txbr_write(&chan->ch_txbr, iov, 3, &send_evt);
 	if (!error && send_evt)
 		vmbus_chan_signal_tx(chan);
 	return error;
 }
 
 int
 vmbus_chan_send_sglist(struct vmbus_channel *chan,
     struct vmbus_gpa sg[], int sglen, void *data, int dlen, uint64_t xactid)
 {
 	struct vmbus_chanpkt_sglist pkt;
 	int pktlen, pad_pktlen, hlen, error;
 	struct iovec iov[4];
 	boolean_t send_evt;
 	uint64_t pad = 0;
 
 	hlen = __offsetof(struct vmbus_chanpkt_sglist, cp_gpa[sglen]);
 	pktlen = hlen + dlen;
 	pad_pktlen = VMBUS_CHANPKT_TOTLEN(pktlen);
 	KASSERT(pad_pktlen <= vmbus_txbr_maxpktsz(&chan->ch_txbr),
 	    ("invalid packet size %d", pad_pktlen));
 
 	pkt.cp_hdr.cph_type = VMBUS_CHANPKT_TYPE_GPA;
 	pkt.cp_hdr.cph_flags = VMBUS_CHANPKT_FLAG_RC;
 	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_hlen, hlen);
 	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_tlen, pad_pktlen);
 	pkt.cp_hdr.cph_xactid = xactid;
 	pkt.cp_rsvd = 0;
 	pkt.cp_gpa_cnt = sglen;
 
 	iov[0].iov_base = &pkt;
 	iov[0].iov_len = sizeof(pkt);
 	iov[1].iov_base = sg;
 	iov[1].iov_len = sizeof(struct vmbus_gpa) * sglen;
 	iov[2].iov_base = data;
 	iov[2].iov_len = dlen;
 	iov[3].iov_base = &pad;
 	iov[3].iov_len = pad_pktlen - pktlen;
 
 	error = vmbus_txbr_write(&chan->ch_txbr, iov, 4, &send_evt);
 	if (!error && send_evt)
 		vmbus_chan_signal_tx(chan);
 	return error;
 }
 
 int
 vmbus_chan_send_prplist(struct vmbus_channel *chan,
     struct vmbus_gpa_range *prp, int prp_cnt, void *data, int dlen,
     uint64_t xactid)
 {
 	struct vmbus_chanpkt_prplist pkt;
 	int pktlen, pad_pktlen, hlen, error;
 	struct iovec iov[4];
 	boolean_t send_evt;
 	uint64_t pad = 0;
 
 	hlen = __offsetof(struct vmbus_chanpkt_prplist,
 	    cp_range[0].gpa_page[prp_cnt]);
 	pktlen = hlen + dlen;
 	pad_pktlen = VMBUS_CHANPKT_TOTLEN(pktlen);
 	KASSERT(pad_pktlen <= vmbus_txbr_maxpktsz(&chan->ch_txbr),
 	    ("invalid packet size %d", pad_pktlen));
 
 	pkt.cp_hdr.cph_type = VMBUS_CHANPKT_TYPE_GPA;
 	pkt.cp_hdr.cph_flags = VMBUS_CHANPKT_FLAG_RC;
 	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_hlen, hlen);
 	VMBUS_CHANPKT_SETLEN(pkt.cp_hdr.cph_tlen, pad_pktlen);
 	pkt.cp_hdr.cph_xactid = xactid;
 	pkt.cp_rsvd = 0;
 	pkt.cp_range_cnt = 1;
 
 	iov[0].iov_base = &pkt;
 	iov[0].iov_len = sizeof(pkt);
 	iov[1].iov_base = prp;
 	iov[1].iov_len = __offsetof(struct vmbus_gpa_range, gpa_page[prp_cnt]);
 	iov[2].iov_base = data;
 	iov[2].iov_len = dlen;
 	iov[3].iov_base = &pad;
 	iov[3].iov_len = pad_pktlen - pktlen;
 
 	error = vmbus_txbr_write(&chan->ch_txbr, iov, 4, &send_evt);
 	if (!error && send_evt)
 		vmbus_chan_signal_tx(chan);
 	return error;
 }
 
 int
 vmbus_chan_recv(struct vmbus_channel *chan, void *data, int *dlen0,
     uint64_t *xactid)
 {
 	struct vmbus_chanpkt_hdr pkt;
 	int error, dlen, hlen;
 
 	error = vmbus_rxbr_peek(&chan->ch_rxbr, &pkt, sizeof(pkt));
 	if (error)
 		return (error);
 
 	if (__predict_false(pkt.cph_hlen < VMBUS_CHANPKT_HLEN_MIN)) {
 		vmbus_chan_printf(chan, "invalid hlen %u\n", pkt.cph_hlen);
 		/* XXX this channel is dead actually. */
 		return (EIO);
 	}
 	if (__predict_false(pkt.cph_hlen > pkt.cph_tlen)) {
 		vmbus_chan_printf(chan, "invalid hlen %u and tlen %u\n",
 		    pkt.cph_hlen, pkt.cph_tlen);
 		/* XXX this channel is dead actually. */
 		return (EIO);
 	}
 
 	hlen = VMBUS_CHANPKT_GETLEN(pkt.cph_hlen);
 	dlen = VMBUS_CHANPKT_GETLEN(pkt.cph_tlen) - hlen;
 
 	if (*dlen0 < dlen) {
 		/* Return the size of this packet's data. */
 		*dlen0 = dlen;
 		return (ENOBUFS);
 	}
 
 	*xactid = pkt.cph_xactid;
 	*dlen0 = dlen;
 
 	/* Skip packet header */
 	error = vmbus_rxbr_read(&chan->ch_rxbr, data, dlen, hlen);
 	KASSERT(!error, ("vmbus_rxbr_read failed"));
 
 	return (0);
 }
 
 int
 vmbus_chan_recv_pkt(struct vmbus_channel *chan,
     struct vmbus_chanpkt_hdr *pkt, int *pktlen0)
 {
 	int error, pktlen, pkt_hlen;
 
 	pkt_hlen = sizeof(*pkt);
 	error = vmbus_rxbr_peek(&chan->ch_rxbr, pkt, pkt_hlen);
 	if (error)
 		return (error);
 
 	if (__predict_false(pkt->cph_hlen < VMBUS_CHANPKT_HLEN_MIN)) {
 		vmbus_chan_printf(chan, "invalid hlen %u\n", pkt->cph_hlen);
 		/* XXX this channel is dead actually. */
 		return (EIO);
 	}
 	if (__predict_false(pkt->cph_hlen > pkt->cph_tlen)) {
 		vmbus_chan_printf(chan, "invalid hlen %u and tlen %u\n",
 		    pkt->cph_hlen, pkt->cph_tlen);
 		/* XXX this channel is dead actually. */
 		return (EIO);
 	}
 
 	pktlen = VMBUS_CHANPKT_GETLEN(pkt->cph_tlen);
 	if (*pktlen0 < pktlen) {
 		/* Return the size of this packet. */
 		*pktlen0 = pktlen;
 		return (ENOBUFS);
 	}
 	*pktlen0 = pktlen;
 
 	/*
 	 * Skip the fixed-size packet header, which has been filled
 	 * by the above vmbus_rxbr_peek().
 	 */
 	error = vmbus_rxbr_read(&chan->ch_rxbr, pkt + 1,
 	    pktlen - pkt_hlen, pkt_hlen);
 	KASSERT(!error, ("vmbus_rxbr_read failed"));
 
 	return (0);
 }
 
 static void
 vmbus_chan_task(void *xchan, int pending __unused)
 {
 	struct vmbus_channel *chan = xchan;
 	vmbus_chan_callback_t cb = chan->ch_cb;
 	void *cbarg = chan->ch_cbarg;
 
 	/*
 	 * Optimize host to guest signaling by ensuring:
 	 * 1. While reading the channel, we disable interrupts from
 	 *    host.
 	 * 2. Ensure that we process all posted messages from the host
 	 *    before returning from this callback.
 	 * 3. Once we return, enable signaling from the host. Once this
 	 *    state is set we check to see if additional packets are
 	 *    available to read. In this case we repeat the process.
 	 *
 	 * NOTE: Interrupt has been disabled in the ISR.
 	 */
 	for (;;) {
 		uint32_t left;
 
 		cb(chan, cbarg);
 
 		left = vmbus_rxbr_intr_unmask(&chan->ch_rxbr);
 		if (left == 0) {
 			/* No more data in RX bufring; done */
 			break;
 		}
 		vmbus_rxbr_intr_mask(&chan->ch_rxbr);
 	}
 }
 
 static void
 vmbus_chan_task_nobatch(void *xchan, int pending __unused)
 {
 	struct vmbus_channel *chan = xchan;
 
 	chan->ch_cb(chan, chan->ch_cbarg);
 }
 
 static __inline void
 vmbus_event_flags_proc(struct vmbus_softc *sc, volatile u_long *event_flags,
     int flag_cnt)
 {
 	int f;
 
 	for (f = 0; f < flag_cnt; ++f) {
 		uint32_t chid_base;
 		u_long flags;
 		int chid_ofs;
 
 		if (event_flags[f] == 0)
 			continue;
 
 		flags = atomic_swap_long(&event_flags[f], 0);
 		chid_base = f << VMBUS_EVTFLAG_SHIFT;
 
 		while ((chid_ofs = ffsl(flags)) != 0) {
 			struct vmbus_channel *chan;
 
 			--chid_ofs; /* NOTE: ffsl is 1-based */
 			flags &= ~(1UL << chid_ofs);
 
 			chan = sc->vmbus_chmap[chid_base + chid_ofs];
 			if (__predict_false(chan == NULL)) {
 				/* Channel is closed. */
 				continue;
 			}
 			__compiler_membar();
 
 			if (chan->ch_flags & VMBUS_CHAN_FLAG_BATCHREAD)
 				vmbus_rxbr_intr_mask(&chan->ch_rxbr);
 			taskqueue_enqueue(chan->ch_tq, &chan->ch_task);
 		}
 	}
 }
 
 void
 vmbus_event_proc(struct vmbus_softc *sc, int cpu)
 {
 	struct vmbus_evtflags *eventf;
 
 	/*
 	 * On Host with Win8 or above, the event page can be checked directly
 	 * to get the id of the channel that has the pending interrupt.
 	 */
 	eventf = VMBUS_PCPU_GET(sc, event_flags, cpu) + VMBUS_SINT_MESSAGE;
 	vmbus_event_flags_proc(sc, eventf->evt_flags,
 	    VMBUS_PCPU_GET(sc, event_flags_cnt, cpu));
 }
 
 void
 vmbus_event_proc_compat(struct vmbus_softc *sc, int cpu)
 {
 	struct vmbus_evtflags *eventf;
 
 	eventf = VMBUS_PCPU_GET(sc, event_flags, cpu) + VMBUS_SINT_MESSAGE;
 	if (atomic_testandclear_long(&eventf->evt_flags[0], 0)) {
 		vmbus_event_flags_proc(sc, sc->vmbus_rx_evtflags,
 		    VMBUS_CHAN_MAX_COMPAT >> VMBUS_EVTFLAG_SHIFT);
 	}
 }
 
 static void
 vmbus_chan_update_evtflagcnt(struct vmbus_softc *sc,
     const struct vmbus_channel *chan)
 {
 	volatile int *flag_cnt_ptr;
 	int flag_cnt;
 
 	flag_cnt = (chan->ch_id / VMBUS_EVTFLAG_LEN) + 1;
 	flag_cnt_ptr = VMBUS_PCPU_PTR(sc, event_flags_cnt, chan->ch_cpuid);
 
 	for (;;) {
 		int old_flag_cnt;
 
 		old_flag_cnt = *flag_cnt_ptr;
 		if (old_flag_cnt >= flag_cnt)
 			break;
 		if (atomic_cmpset_int(flag_cnt_ptr, old_flag_cnt, flag_cnt)) {
 			if (bootverbose) {
 				vmbus_chan_printf(chan,
 				    "chan%u update cpu%d flag_cnt to %d\n",
 				    chan->ch_id, chan->ch_cpuid, flag_cnt);
 			}
 			break;
 		}
 	}
 }
 
 static struct vmbus_channel *
 vmbus_chan_alloc(struct vmbus_softc *sc)
 {
 	struct vmbus_channel *chan;
 
 	chan = malloc(sizeof(*chan), M_DEVBUF, M_WAITOK | M_ZERO);
 
 	chan->ch_monprm = hyperv_dmamem_alloc(bus_get_dma_tag(sc->vmbus_dev),
 	    HYPERCALL_PARAM_ALIGN, 0, sizeof(struct hyperv_mon_param),
 	    &chan->ch_monprm_dma, BUS_DMA_WAITOK | BUS_DMA_ZERO);
 	if (chan->ch_monprm == NULL) {
 		device_printf(sc->vmbus_dev, "monprm alloc failed\n");
 		free(chan, M_DEVBUF);
 		return NULL;
 	}
 
 	chan->ch_vmbus = sc;
 	mtx_init(&chan->ch_subchan_lock, "vmbus subchan", NULL, MTX_DEF);
 	TAILQ_INIT(&chan->ch_subchans);
 	vmbus_rxbr_init(&chan->ch_rxbr);
 	vmbus_txbr_init(&chan->ch_txbr);
 
 	return chan;
 }
 
 static void
 vmbus_chan_free(struct vmbus_channel *chan)
 {
 
 	KASSERT(TAILQ_EMPTY(&chan->ch_subchans) && chan->ch_subchan_cnt == 0,
 	    ("still owns sub-channels"));
 	KASSERT((chan->ch_stflags &
 	    (VMBUS_CHAN_ST_OPENED |
 	     VMBUS_CHAN_ST_ONPRIL |
 	     VMBUS_CHAN_ST_ONSUBL |
 	     VMBUS_CHAN_ST_ONLIST)) == 0, ("free busy channel"));
 	hyperv_dmamem_free(&chan->ch_monprm_dma, chan->ch_monprm);
 	mtx_destroy(&chan->ch_subchan_lock);
 	vmbus_rxbr_deinit(&chan->ch_rxbr);
 	vmbus_txbr_deinit(&chan->ch_txbr);
 	free(chan, M_DEVBUF);
 }
 
 static int
 vmbus_chan_add(struct vmbus_channel *newchan)
 {
 	struct vmbus_softc *sc = newchan->ch_vmbus;
 	struct vmbus_channel *prichan;
 
 	if (newchan->ch_id == 0) {
 		/*
 		 * XXX
 		 * Chan0 will neither be processed nor should be offered;
 		 * skip it.
 		 */
 		device_printf(sc->vmbus_dev, "got chan0 offer, discard\n");
 		return EINVAL;
 	} else if (newchan->ch_id >= VMBUS_CHAN_MAX) {
 		device_printf(sc->vmbus_dev, "invalid chan%u offer\n",
 		    newchan->ch_id);
 		return EINVAL;
 	}
 
 	mtx_lock(&sc->vmbus_prichan_lock);
 	TAILQ_FOREACH(prichan, &sc->vmbus_prichans, ch_prilink) {
 		/*
 		 * Sub-channel will have the same type GUID and instance
 		 * GUID as its primary channel.
 		 */
 		if (memcmp(&prichan->ch_guid_type, &newchan->ch_guid_type,
 		    sizeof(struct hyperv_guid)) == 0 &&
 		    memcmp(&prichan->ch_guid_inst, &newchan->ch_guid_inst,
 		    sizeof(struct hyperv_guid)) == 0)
 			break;
 	}
 	if (VMBUS_CHAN_ISPRIMARY(newchan)) {
 		if (prichan == NULL) {
 			/* Install the new primary channel */
 			vmbus_chan_ins_prilist(sc, newchan);
 			mtx_unlock(&sc->vmbus_prichan_lock);
 			goto done;
 		} else {
 			mtx_unlock(&sc->vmbus_prichan_lock);
 			device_printf(sc->vmbus_dev,
 			    "duplicated primary chan%u\n", newchan->ch_id);
 			return EINVAL;
 		}
 	} else { /* Sub-channel */
 		if (prichan == NULL) {
 			mtx_unlock(&sc->vmbus_prichan_lock);
 			device_printf(sc->vmbus_dev,
 			    "no primary chan for chan%u\n", newchan->ch_id);
 			return EINVAL;
 		}
 		/*
 		 * Found the primary channel for this sub-channel and
 		 * move on.
 		 *
 		 * XXX refcnt prichan
 		 */
 	}
 	mtx_unlock(&sc->vmbus_prichan_lock);
 
 	/*
 	 * This is a sub-channel; link it with the primary channel.
 	 */
 	KASSERT(!VMBUS_CHAN_ISPRIMARY(newchan),
 	    ("new channel is not sub-channel"));
 	KASSERT(prichan != NULL, ("no primary channel"));
 
 	newchan->ch_prichan = prichan;
 	newchan->ch_dev = prichan->ch_dev;
 
 	mtx_lock(&prichan->ch_subchan_lock);
 	vmbus_chan_ins_sublist(prichan, newchan);
 	mtx_unlock(&prichan->ch_subchan_lock);
 	/*
 	 * Notify anyone that is interested in this sub-channel,
 	 * after this sub-channel is setup.
 	 */
 	wakeup(prichan);
 done:
 	/*
-	 * Hook this channel up for later rescind.
+	 * Hook this channel up for later revocation.
 	 */
 	mtx_lock(&sc->vmbus_chan_lock);
 	vmbus_chan_ins_list(sc, newchan);
 	mtx_unlock(&sc->vmbus_chan_lock);
 
 	if (bootverbose) {
 		vmbus_chan_printf(newchan, "chan%u subidx%u offer\n",
 		    newchan->ch_id, newchan->ch_subidx);
 	}
 
 	/* Select default cpu for this channel. */
 	vmbus_chan_cpu_default(newchan);
 
 	return 0;
 }
 
 void
 vmbus_chan_cpu_set(struct vmbus_channel *chan, int cpu)
 {
 	KASSERT(cpu >= 0 && cpu < mp_ncpus, ("invalid cpu %d", cpu));
 
 	if (chan->ch_vmbus->vmbus_version == VMBUS_VERSION_WS2008 ||
 	    chan->ch_vmbus->vmbus_version == VMBUS_VERSION_WIN7) {
 		/* Only cpu0 is supported */
 		cpu = 0;
 	}
 
 	chan->ch_cpuid = cpu;
 	chan->ch_vcpuid = VMBUS_PCPU_GET(chan->ch_vmbus, vcpuid, cpu);
 
 	if (bootverbose) {
 		vmbus_chan_printf(chan,
 		    "chan%u assigned to cpu%u [vcpu%u]\n",
 		    chan->ch_id, chan->ch_cpuid, chan->ch_vcpuid);
 	}
 }
 
 void
 vmbus_chan_cpu_rr(struct vmbus_channel *chan)
 {
 	static uint32_t vmbus_chan_nextcpu;
 	int cpu;
 
 	cpu = atomic_fetchadd_int(&vmbus_chan_nextcpu, 1) % mp_ncpus;
 	vmbus_chan_cpu_set(chan, cpu);
 }
 
 static void
 vmbus_chan_cpu_default(struct vmbus_channel *chan)
 {
 	/*
 	 * By default, pin the channel to cpu0.  Devices having
 	 * special channel-cpu mapping requirement should call
 	 * vmbus_chan_cpu_{set,rr}().
 	 */
 	vmbus_chan_cpu_set(chan, 0);
 }
 
 static void
 vmbus_chan_msgproc_choffer(struct vmbus_softc *sc,
     const struct vmbus_message *msg)
 {
 	const struct vmbus_chanmsg_choffer *offer;
 	struct vmbus_channel *chan;
 	task_fn_t *detach_fn, *attach_fn;
 	int error;
 
 	offer = (const struct vmbus_chanmsg_choffer *)msg->msg_data;
 
 	chan = vmbus_chan_alloc(sc);
 	if (chan == NULL) {
 		device_printf(sc->vmbus_dev, "allocate chan%u failed\n",
 		    offer->chm_chanid);
 		return;
 	}
 
 	chan->ch_id = offer->chm_chanid;
 	chan->ch_subidx = offer->chm_subidx;
 	chan->ch_guid_type = offer->chm_chtype;
 	chan->ch_guid_inst = offer->chm_chinst;
 
 	/* Batch reading is on by default */
 	chan->ch_flags |= VMBUS_CHAN_FLAG_BATCHREAD;
 
 	chan->ch_monprm->mp_connid = VMBUS_CONNID_EVENT;
 	if (sc->vmbus_version != VMBUS_VERSION_WS2008)
 		chan->ch_monprm->mp_connid = offer->chm_connid;
 
 	if (offer->chm_flags1 & VMBUS_CHOFFER_FLAG1_HASMNF) {
 		int trig_idx;
 
 		/*
 		 * Setup MNF stuffs.
 		 */
 		chan->ch_txflags |= VMBUS_CHAN_TXF_HASMNF;
 
 		trig_idx = offer->chm_montrig / VMBUS_MONTRIG_LEN;
 		if (trig_idx >= VMBUS_MONTRIGS_MAX)
 			panic("invalid monitor trigger %u", offer->chm_montrig);
 		chan->ch_montrig =
 		    &sc->vmbus_mnf2->mnf_trigs[trig_idx].mt_pending;
 
 		chan->ch_montrig_mask =
 		    1 << (offer->chm_montrig % VMBUS_MONTRIG_LEN);
 	}
 
 	/*
 	 * Setup event flag.
 	 */
 	chan->ch_evtflag =
 	    &sc->vmbus_tx_evtflags[chan->ch_id >> VMBUS_EVTFLAG_SHIFT];
 	chan->ch_evtflag_mask = 1UL << (chan->ch_id & VMBUS_EVTFLAG_MASK);
 
 	/*
 	 * Setup attach and detach tasks.
 	 */
 	if (VMBUS_CHAN_ISPRIMARY(chan)) {
 		chan->ch_mgmt_tq = sc->vmbus_devtq;
 		attach_fn = vmbus_prichan_attach_task;
 		detach_fn = vmbus_prichan_detach_task;
 	} else {
 		chan->ch_mgmt_tq = sc->vmbus_subchtq;
 		attach_fn = vmbus_subchan_attach_task;
 		detach_fn = vmbus_subchan_detach_task;
 	}
 	TASK_INIT(&chan->ch_attach_task, 0, attach_fn, chan);
 	TASK_INIT(&chan->ch_detach_task, 0, detach_fn, chan);
 
 	error = vmbus_chan_add(chan);
 	if (error) {
 		device_printf(sc->vmbus_dev, "add chan%u failed: %d\n",
 		    chan->ch_id, error);
 		vmbus_chan_free(chan);
 		return;
 	}
 	taskqueue_enqueue(chan->ch_mgmt_tq, &chan->ch_attach_task);
 }
 
 static void
 vmbus_chan_msgproc_chrescind(struct vmbus_softc *sc,
     const struct vmbus_message *msg)
 {
 	const struct vmbus_chanmsg_chrescind *note;
 	struct vmbus_channel *chan;
 
 	note = (const struct vmbus_chanmsg_chrescind *)msg->msg_data;
 	if (note->chm_chanid > VMBUS_CHAN_MAX) {
-		device_printf(sc->vmbus_dev, "invalid rescinded chan%u\n",
+		device_printf(sc->vmbus_dev, "invalid revoked chan%u\n",
 		    note->chm_chanid);
 		return;
 	}
 
 	/*
 	 * Find and remove the target channel from the channel list.
 	 */
 	mtx_lock(&sc->vmbus_chan_lock);
 	TAILQ_FOREACH(chan, &sc->vmbus_chans, ch_link) {
 		if (chan->ch_id == note->chm_chanid)
 			break;
 	}
 	if (chan == NULL) {
 		mtx_unlock(&sc->vmbus_chan_lock);
 		device_printf(sc->vmbus_dev, "chan%u is not offered\n",
 		    note->chm_chanid);
 		return;
 	}
 	vmbus_chan_rem_list(sc, chan);
 	mtx_unlock(&sc->vmbus_chan_lock);
 
 	if (VMBUS_CHAN_ISPRIMARY(chan)) {
 		/*
 		 * The target channel is a primary channel; remove the
 		 * target channel from the primary channel list now,
 		 * instead of later, so that it will not be found by
 		 * other sub-channel offers, which are processed in
 		 * this thread.
 		 */
 		mtx_lock(&sc->vmbus_prichan_lock);
 		vmbus_chan_rem_prilist(sc, chan);
 		mtx_unlock(&sc->vmbus_prichan_lock);
 	}
 
+	if (atomic_testandset_int(&chan->ch_stflags,
+	    VMBUS_CHAN_ST_REVOKED_SHIFT))
+		panic("channel has already been revoked");
+
 	if (bootverbose)
-		vmbus_chan_printf(chan, "chan%u rescinded\n", note->chm_chanid);
+		vmbus_chan_printf(chan, "chan%u revoked\n", note->chm_chanid);
 
 	/* Detach the target channel. */
 	taskqueue_enqueue(chan->ch_mgmt_tq, &chan->ch_detach_task);
 }
 
 static int
 vmbus_chan_release(struct vmbus_channel *chan)
 {
 	struct vmbus_softc *sc = chan->ch_vmbus;
 	struct vmbus_chanmsg_chfree *req;
 	struct vmbus_msghc *mh;
 	int error;
 
 	mh = vmbus_msghc_get(sc, sizeof(*req));
 	if (mh == NULL) {
 		vmbus_chan_printf(chan,
 		    "can not get msg hypercall for chfree(chan%u)\n",
 		    chan->ch_id);
 		return (ENXIO);
 	}
 
 	req = vmbus_msghc_dataptr(mh);
 	req->chm_hdr.chm_type = VMBUS_CHANMSG_TYPE_CHFREE;
 	req->chm_chanid = chan->ch_id;
 
 	error = vmbus_msghc_exec_noresult(mh);
 	vmbus_msghc_put(sc, mh);
 
 	if (error) {
 		vmbus_chan_printf(chan,
 		    "chfree(chan%u) msg hypercall exec failed: %d\n",
 		    chan->ch_id, error);
 	} else {
 		if (bootverbose)
 			vmbus_chan_printf(chan, "chan%u freed\n", chan->ch_id);
 	}
 	return (error);
 }
 
 static void
 vmbus_prichan_detach_task(void *xchan, int pending __unused)
 {
 	struct vmbus_channel *chan = xchan;
 
 	KASSERT(VMBUS_CHAN_ISPRIMARY(chan),
 	    ("chan%u is not primary channel", chan->ch_id));
 
 	/* Delete and detach the device associated with this channel. */
 	vmbus_delete_child(chan);
 
 	/* Release this channel (back to vmbus). */
 	vmbus_chan_release(chan);
 
 	/* Free this channel's resource. */
 	vmbus_chan_free(chan);
 }
 
 static void
 vmbus_subchan_detach_task(void *xchan, int pending __unused)
 {
 	struct vmbus_channel *chan = xchan;
 	struct vmbus_channel *pri_chan = chan->ch_prichan;
 
 	KASSERT(!VMBUS_CHAN_ISPRIMARY(chan),
 	    ("chan%u is primary channel", chan->ch_id));
 
 	/* Release this channel (back to vmbus). */
 	vmbus_chan_release(chan);
 
 	/* Unlink from its primary channel's sub-channel list. */
 	mtx_lock(&pri_chan->ch_subchan_lock);
 	vmbus_chan_rem_sublist(pri_chan, chan);
 	mtx_unlock(&pri_chan->ch_subchan_lock);
 	/* Notify anyone that is waiting for this sub-channel to vanish. */
 	wakeup(pri_chan);
 
 	/* Free this channel's resource. */
 	vmbus_chan_free(chan);
 }
 
 static void
 vmbus_prichan_attach_task(void *xchan, int pending __unused)
 {
 
 	/*
 	 * Add device for this primary channel.
 	 */
 	vmbus_add_child(xchan);
 }
 
 static void
 vmbus_subchan_attach_task(void *xchan __unused, int pending __unused)
 {
 
 	/* Nothing */
 }
 
 void
 vmbus_chan_destroy_all(struct vmbus_softc *sc)
 {
 
 	/*
 	 * Detach all devices and destroy the corresponding primary
 	 * channels.
 	 */
 	for (;;) {
 		struct vmbus_channel *chan;
 
 		mtx_lock(&sc->vmbus_chan_lock);
 		TAILQ_FOREACH(chan, &sc->vmbus_chans, ch_link) {
 			if (VMBUS_CHAN_ISPRIMARY(chan))
 				break;
 		}
 		if (chan == NULL) {
 			/* No more primary channels; done. */
 			mtx_unlock(&sc->vmbus_chan_lock);
 			break;
 		}
 		vmbus_chan_rem_list(sc, chan);
 		mtx_unlock(&sc->vmbus_chan_lock);
 
 		mtx_lock(&sc->vmbus_prichan_lock);
 		vmbus_chan_rem_prilist(sc, chan);
 		mtx_unlock(&sc->vmbus_prichan_lock);
 
 		taskqueue_enqueue(chan->ch_mgmt_tq, &chan->ch_detach_task);
 	}
 }
 
 struct vmbus_channel **
 vmbus_subchan_get(struct vmbus_channel *pri_chan, int subchan_cnt)
 {
 	struct vmbus_channel **ret, *chan;
 	int i;
 
 	KASSERT(subchan_cnt > 0, ("invalid sub-channel count %d", subchan_cnt));
 
 	ret = malloc(subchan_cnt * sizeof(struct vmbus_channel *), M_TEMP,
 	    M_WAITOK);
 
 	mtx_lock(&pri_chan->ch_subchan_lock);
 
 	while (pri_chan->ch_subchan_cnt < subchan_cnt)
 		mtx_sleep(pri_chan, &pri_chan->ch_subchan_lock, 0, "subch", 0);
 
 	i = 0;
 	TAILQ_FOREACH(chan, &pri_chan->ch_subchans, ch_sublink) {
 		/* TODO: refcnt chan */
 		ret[i] = chan;
 
 		++i;
 		if (i == subchan_cnt)
 			break;
 	}
 	KASSERT(i == subchan_cnt, ("invalid subchan count %d, should be %d",
 	    pri_chan->ch_subchan_cnt, subchan_cnt));
 
 	mtx_unlock(&pri_chan->ch_subchan_lock);
 
 	return ret;
 }
 
 void
 vmbus_subchan_rel(struct vmbus_channel **subchan, int subchan_cnt __unused)
 {
 
 	free(subchan, M_TEMP);
 }
 
 void
 vmbus_subchan_drain(struct vmbus_channel *pri_chan)
 {
 	mtx_lock(&pri_chan->ch_subchan_lock);
 	while (pri_chan->ch_subchan_cnt > 0)
 		mtx_sleep(pri_chan, &pri_chan->ch_subchan_lock, 0, "dsubch", 0);
 	mtx_unlock(&pri_chan->ch_subchan_lock);
 }
 
 void
 vmbus_chan_msgproc(struct vmbus_softc *sc, const struct vmbus_message *msg)
 {
 	vmbus_chanmsg_proc_t msg_proc;
 	uint32_t msg_type;
 
 	msg_type = ((const struct vmbus_chanmsg_hdr *)msg->msg_data)->chm_type;
 	KASSERT(msg_type < VMBUS_CHANMSG_TYPE_MAX,
 	    ("invalid message type %u", msg_type));
 
 	msg_proc = vmbus_chan_msgprocs[msg_type];
 	if (msg_proc != NULL)
 		msg_proc(sc, msg);
 }
 
 void
 vmbus_chan_set_readbatch(struct vmbus_channel *chan, bool on)
 {
 	if (!on)
 		chan->ch_flags &= ~VMBUS_CHAN_FLAG_BATCHREAD;
 	else
 		chan->ch_flags |= VMBUS_CHAN_FLAG_BATCHREAD;
 }
 
 uint32_t
 vmbus_chan_id(const struct vmbus_channel *chan)
 {
 	return chan->ch_id;
 }
 
 uint32_t
 vmbus_chan_subidx(const struct vmbus_channel *chan)
 {
 	return chan->ch_subidx;
 }
 
 bool
 vmbus_chan_is_primary(const struct vmbus_channel *chan)
 {
 	if (VMBUS_CHAN_ISPRIMARY(chan))
 		return true;
 	else
 		return false;
 }
 
 const struct hyperv_guid *
 vmbus_chan_guid_inst(const struct vmbus_channel *chan)
 {
 	return &chan->ch_guid_inst;
 }
 
 int
 vmbus_chan_prplist_nelem(int br_size, int prpcnt_max, int dlen_max)
 {
 	int elem_size;
 
 	elem_size = __offsetof(struct vmbus_chanpkt_prplist,
 	    cp_range[0].gpa_page[prpcnt_max]);
 	elem_size += dlen_max;
 	elem_size = VMBUS_CHANPKT_TOTLEN(elem_size);
 
 	return (vmbus_br_nelem(br_size, elem_size));
 }
 
 bool
 vmbus_chan_tx_empty(const struct vmbus_channel *chan)
 {
 
 	return (vmbus_txbr_empty(&chan->ch_txbr));
 }
 
 bool
 vmbus_chan_rx_empty(const struct vmbus_channel *chan)
 {
 
 	return (vmbus_rxbr_empty(&chan->ch_rxbr));
 }
 
 static int
 vmbus_chan_printf(const struct vmbus_channel *chan, const char *fmt, ...)
 {
 	va_list ap;
 	device_t dev;
 	int retval;
 
 	if (chan->ch_dev == NULL || !device_is_alive(chan->ch_dev))
 		dev = chan->ch_vmbus->vmbus_dev;
 	else
 		dev = chan->ch_dev;
 
 	retval = device_print_prettyname(dev);
 	va_start(ap, fmt);
 	retval += vprintf(fmt, ap);
 	va_end(ap);
 
 	return (retval);
 }
 
 void
 vmbus_chan_run_task(struct vmbus_channel *chan, struct task *task)
 {
 
 	taskqueue_enqueue(chan->ch_tq, task);
 	taskqueue_drain(chan->ch_tq, task);
 }
 
 struct taskqueue *
 vmbus_chan_mgmt_tq(const struct vmbus_channel *chan)
 {
 
 	return (chan->ch_mgmt_tq);
+}
+
+bool
+vmbus_chan_is_revoked(const struct vmbus_channel *chan)
+{
+
+	if (chan->ch_stflags & VMBUS_CHAN_ST_REVOKED)
+		return (true);
+	return (false);
 }
Index: head/sys/dev/hyperv/vmbus/vmbus_chanvar.h
===================================================================
--- head/sys/dev/hyperv/vmbus/vmbus_chanvar.h	(revision 309029)
+++ head/sys/dev/hyperv/vmbus/vmbus_chanvar.h	(revision 309030)
@@ -1,176 +1,178 @@
 /*-
  * Copyright (c) 2016 Microsoft Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice unmodified, this list of conditions, and the following
  *    disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * $FreeBSD$
  */
 
 #ifndef _VMBUS_CHANVAR_H_
 #define _VMBUS_CHANVAR_H_
 
 #include <sys/param.h>
 #include <sys/lock.h>
 #include <sys/mutex.h>
 #include <sys/queue.h>
 #include <sys/taskqueue.h>
 #include <sys/sysctl.h>
 
 #include <dev/hyperv/include/hyperv.h>
 #include <dev/hyperv/include/hyperv_busdma.h>
 #include <dev/hyperv/include/vmbus.h>
 #include <dev/hyperv/vmbus/vmbus_brvar.h>
 
 struct vmbus_channel {
 	/*
 	 * NOTE:
 	 * Fields before ch_txbr are only accessed on this channel's
 	 * target CPU.
 	 */
 	uint32_t			ch_flags;	/* VMBUS_CHAN_FLAG_ */
 
 	/*
 	 * RX bufring; immediately following ch_txbr.
 	 */
 	struct vmbus_rxbr		ch_rxbr;
 
 	struct taskqueue		*ch_tq;
 	struct task			ch_task;
 	vmbus_chan_callback_t		ch_cb;
 	void				*ch_cbarg;
 
 	/*
 	 * TX bufring; at the beginning of ch_bufring.
 	 *
 	 * NOTE:
 	 * Put TX bufring and the following MNF/evtflag to a new
 	 * cacheline, since they will be accessed on all CPUs by
 	 * locking ch_txbr first.
 	 *
 	 * XXX
 	 * TX bufring and following MNF/evtflags do _not_ fit in
 	 * one 64B cacheline.
 	 */
 	struct vmbus_txbr		ch_txbr __aligned(CACHE_LINE_SIZE);
 	uint32_t			ch_txflags;	/* VMBUS_CHAN_TXF_ */
 
 	/*
 	 * These are based on the vmbus_chanmsg_choffer.chm_montrig.
 	 * Save it here for easy access.
 	 */
 	uint32_t			ch_montrig_mask;/* MNF trig mask */
 	volatile uint32_t		*ch_montrig;	/* MNF trigger loc. */
 
 	/*
 	 * These are based on the vmbus_chanmsg_choffer.chm_chanid.
 	 * Save it here for easy access.
 	 */
 	u_long				ch_evtflag_mask;/* event flag */
 	volatile u_long			*ch_evtflag;	/* event flag loc. */
 
 	/*
 	 * Rarely used fields.
 	 */
 
 	struct hyperv_mon_param		*ch_monprm;
 	struct hyperv_dma		ch_monprm_dma;
 
 	uint32_t			ch_id;		/* channel id */
 	device_t			ch_dev;
 	struct vmbus_softc		*ch_vmbus;
 
 	int				ch_cpuid;	/* owner cpu */
 	/*
 	 * Virtual cpuid for ch_cpuid; it is used to communicate cpuid
 	 * related information w/ Hyper-V.  If MSR_HV_VP_INDEX does not
 	 * exist, ch_vcpuid will always be 0 for compatibility.
 	 */
 	uint32_t			ch_vcpuid;
 
 	/*
 	 * If this is a primary channel, ch_subchan* fields
 	 * contain sub-channels belonging to this primary
 	 * channel.
 	 */
 	struct mtx			ch_subchan_lock;
 	TAILQ_HEAD(, vmbus_channel)	ch_subchans;
 	int				ch_subchan_cnt;
 
 	/* If this is a sub-channel */
 	TAILQ_ENTRY(vmbus_channel)	ch_sublink;	/* sub-channel link */
 	struct vmbus_channel		*ch_prichan;	/* owner primary chan */
 
 	void				*ch_bufring;	/* TX+RX bufrings */
 	struct hyperv_dma		ch_bufring_dma;
 	uint32_t			ch_bufring_gpadl;
 
 	struct task			ch_attach_task;	/* run in ch_mgmt_tq */
 	struct task			ch_detach_task;	/* run in ch_mgmt_tq */
 	struct taskqueue		*ch_mgmt_tq;
 
 	/* If this is a primary channel */
 	TAILQ_ENTRY(vmbus_channel)	ch_prilink;	/* primary chan link */
 
 	TAILQ_ENTRY(vmbus_channel)	ch_link;	/* channel link */
 	uint32_t			ch_subidx;	/* subchan index */
 	volatile uint32_t		ch_stflags;	/* atomic-op */
 							/* VMBUS_CHAN_ST_ */
 	struct hyperv_guid		ch_guid_type;
 	struct hyperv_guid		ch_guid_inst;
 
 	struct sysctl_ctx_list		ch_sysctl_ctx;
 } __aligned(CACHE_LINE_SIZE);
 
 #define VMBUS_CHAN_ISPRIMARY(chan)	((chan)->ch_subidx == 0)
 
 /*
  * If this flag is set, this channel's interrupt will be masked in ISR,
  * and the RX bufring will be drained before this channel's interrupt is
  * unmasked.
  *
  * This flag is turned on by default.  Drivers can turn it off according
  * to their own requirement.
  */
 #define VMBUS_CHAN_FLAG_BATCHREAD	0x0002
 
 #define VMBUS_CHAN_TXF_HASMNF		0x0001
 
 #define VMBUS_CHAN_ST_OPENED_SHIFT	0
 #define VMBUS_CHAN_ST_ONPRIL_SHIFT	1
 #define VMBUS_CHAN_ST_ONSUBL_SHIFT	2
 #define VMBUS_CHAN_ST_ONLIST_SHIFT	3
+#define VMBUS_CHAN_ST_REVOKED_SHIFT	4	/* sticky */
 #define VMBUS_CHAN_ST_OPENED		(1 << VMBUS_CHAN_ST_OPENED_SHIFT)
 #define VMBUS_CHAN_ST_ONPRIL		(1 << VMBUS_CHAN_ST_ONPRIL_SHIFT)
 #define VMBUS_CHAN_ST_ONSUBL		(1 << VMBUS_CHAN_ST_ONSUBL_SHIFT)
 #define VMBUS_CHAN_ST_ONLIST		(1 << VMBUS_CHAN_ST_ONLIST_SHIFT)
+#define VMBUS_CHAN_ST_REVOKED		(1 << VMBUS_CHAN_ST_REVOKED_SHIFT)
 
 struct vmbus_softc;
 struct vmbus_message;
 
 void		vmbus_event_proc(struct vmbus_softc *, int);
 void		vmbus_event_proc_compat(struct vmbus_softc *, int);
 void		vmbus_chan_msgproc(struct vmbus_softc *,
 		    const struct vmbus_message *);
 void		vmbus_chan_destroy_all(struct vmbus_softc *);
 
 #endif	/* !_VMBUS_CHANVAR_H_ */