2 * Copyright (c) 2009, Microsoft Corporation.
4 * This program is free software; you can redistribute it and/or modify it
5 * under the terms and conditions of the GNU General Public License,
6 * version 2, as published by the Free Software Foundation.
8 * This program is distributed in the hope it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
13 * You should have received a copy of the GNU General Public License along with
14 * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
15 * Place - Suite 330, Boston, MA 02111-1307 USA.
18 * Haiyang Zhang <haiyangz@microsoft.com>
19 * Hank Janssen <hjanssen@microsoft.com>
21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
23 #include <linux/kernel.h>
24 #include <linux/sched.h>
25 #include <linux/wait.h>
27 #include <linux/slab.h>
28 #include <linux/list.h>
29 #include <linux/module.h>
30 #include <linux/completion.h>
31 #include <linux/hyperv.h>
33 #include "hyperv_vmbus.h"
35 struct vmbus_channel_message_table_entry {
36 enum vmbus_channel_message_type message_type;
37 void (*message_handler)(struct vmbus_channel_message_header *msg);
42 * vmbus_prep_negotiate_resp() - Create default response for Hyper-V Negotiate message
43 * @icmsghdrp: Pointer to msg header structure
44 * @icmsg_negotiate: Pointer to negotiate message structure
45 * @buf: Raw buffer channel data
47 * @icmsghdrp is of type &struct icmsg_hdr.
48 * @negop is of type &struct icmsg_negotiate.
49 * Set up and fill in default negotiate response message.
51 * The fw_version specifies the framework version that
52 * we can support and srv_version specifies the service
53 * version we can support.
55 * Mainly used by Hyper-V drivers.
57 bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
58 struct icmsg_negotiate *negop, u8 *buf,
59 int fw_version, int srv_version)
61 int icframe_major, icframe_minor;
62 int icmsg_major, icmsg_minor;
63 int fw_major, fw_minor;
64 int srv_major, srv_minor;
66 bool found_match = false;
68 icmsghdrp->icmsgsize = 0x10;
69 fw_major = (fw_version >> 16);
70 fw_minor = (fw_version & 0xFFFF);
72 srv_major = (srv_version >> 16);
73 srv_minor = (srv_version & 0xFFFF);
75 negop = (struct icmsg_negotiate *)&buf[
76 sizeof(struct vmbuspipe_hdr) +
77 sizeof(struct icmsg_hdr)];
79 icframe_major = negop->icframe_vercnt;
82 icmsg_major = negop->icmsg_vercnt;
86 * Select the framework version number we will
90 for (i = 0; i < negop->icframe_vercnt; i++) {
91 if ((negop->icversion_data[i].major == fw_major) &&
92 (negop->icversion_data[i].minor == fw_minor)) {
93 icframe_major = negop->icversion_data[i].major;
94 icframe_minor = negop->icversion_data[i].minor;
104 for (i = negop->icframe_vercnt;
105 (i < negop->icframe_vercnt + negop->icmsg_vercnt); i++) {
106 if ((negop->icversion_data[i].major == srv_major) &&
107 (negop->icversion_data[i].minor == srv_minor)) {
108 icmsg_major = negop->icversion_data[i].major;
109 icmsg_minor = negop->icversion_data[i].minor;
115 * Respond with the framework and service
116 * version numbers we can support.
121 negop->icframe_vercnt = 0;
122 negop->icmsg_vercnt = 0;
124 negop->icframe_vercnt = 1;
125 negop->icmsg_vercnt = 1;
128 negop->icversion_data[0].major = icframe_major;
129 negop->icversion_data[0].minor = icframe_minor;
130 negop->icversion_data[1].major = icmsg_major;
131 negop->icversion_data[1].minor = icmsg_minor;
135 EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);
138 * alloc_channel - Allocate and initialize a vmbus channel object
140 static struct vmbus_channel *alloc_channel(void)
142 struct vmbus_channel *channel;
144 channel = kzalloc(sizeof(*channel), GFP_ATOMIC);
148 spin_lock_init(&channel->inbound_lock);
149 spin_lock_init(&channel->sc_lock);
151 INIT_LIST_HEAD(&channel->sc_list);
152 INIT_LIST_HEAD(&channel->percpu_list);
154 channel->controlwq = create_workqueue("hv_vmbus_ctl");
155 if (!channel->controlwq) {
164 * release_hannel - Release the vmbus channel object itself
166 static void release_channel(struct work_struct *work)
168 struct vmbus_channel *channel = container_of(work,
169 struct vmbus_channel,
172 destroy_workqueue(channel->controlwq);
178 * free_channel - Release the resources used by the vmbus channel object
180 static void free_channel(struct vmbus_channel *channel)
184 * We have to release the channel's workqueue/thread in the vmbus's
185 * workqueue/thread context
186 * ie we can't destroy ourselves.
188 INIT_WORK(&channel->work, release_channel);
189 queue_work(vmbus_connection.work_queue, &channel->work);
192 static void percpu_channel_enq(void *arg)
194 struct vmbus_channel *channel = arg;
195 int cpu = smp_processor_id();
197 list_add_tail(&channel->percpu_list, &hv_context.percpu_list[cpu]);
200 static void percpu_channel_deq(void *arg)
202 struct vmbus_channel *channel = arg;
204 list_del(&channel->percpu_list);
208 * vmbus_process_rescind_offer -
209 * Rescind the offer by initiating a device removal
211 static void vmbus_process_rescind_offer(struct work_struct *work)
213 struct vmbus_channel *channel = container_of(work,
214 struct vmbus_channel,
217 struct vmbus_channel *primary_channel;
218 struct vmbus_channel_relid_released msg;
220 if (channel->device_obj)
221 vmbus_device_unregister(channel->device_obj);
222 memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
223 msg.child_relid = channel->offermsg.child_relid;
224 msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
225 vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released));
227 if (channel->target_cpu != smp_processor_id())
228 smp_call_function_single(channel->target_cpu,
229 percpu_channel_deq, channel, true);
231 percpu_channel_deq(channel);
233 if (channel->primary_channel == NULL) {
234 spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
235 list_del(&channel->listentry);
236 spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
238 primary_channel = channel->primary_channel;
239 spin_lock_irqsave(&primary_channel->sc_lock, flags);
240 list_del(&channel->sc_list);
241 spin_unlock_irqrestore(&primary_channel->sc_lock, flags);
243 free_channel(channel);
246 void vmbus_free_channels(void)
248 struct vmbus_channel *channel;
250 list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
251 vmbus_device_unregister(channel->device_obj);
252 kfree(channel->device_obj);
253 free_channel(channel);
258 * vmbus_process_offer - Process the offer by creating a channel/device
259 * associated with this offer
261 static void vmbus_process_offer(struct work_struct *work)
263 struct vmbus_channel *newchannel = container_of(work,
264 struct vmbus_channel,
266 struct vmbus_channel *channel;
272 /* The next possible work is rescind handling */
273 INIT_WORK(&newchannel->work, vmbus_process_rescind_offer);
275 /* Make sure this is a new offer */
276 spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
278 list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
279 if (!uuid_le_cmp(channel->offermsg.offer.if_type,
280 newchannel->offermsg.offer.if_type) &&
281 !uuid_le_cmp(channel->offermsg.offer.if_instance,
282 newchannel->offermsg.offer.if_instance)) {
289 list_add_tail(&newchannel->listentry,
290 &vmbus_connection.chn_list);
294 spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
297 if (newchannel->target_cpu != smp_processor_id())
298 smp_call_function_single(newchannel->target_cpu,
302 percpu_channel_enq(newchannel);
306 * Check to see if this is a sub-channel.
308 if (newchannel->offermsg.offer.sub_channel_index != 0) {
310 * Process the sub-channel.
312 newchannel->primary_channel = channel;
313 spin_lock_irqsave(&channel->sc_lock, flags);
314 list_add_tail(&newchannel->sc_list, &channel->sc_list);
315 spin_unlock_irqrestore(&channel->sc_lock, flags);
317 if (newchannel->target_cpu != smp_processor_id())
318 smp_call_function_single(newchannel->target_cpu,
322 percpu_channel_enq(newchannel);
324 newchannel->state = CHANNEL_OPEN_STATE;
325 if (channel->sc_creation_callback != NULL)
326 channel->sc_creation_callback(newchannel);
331 free_channel(newchannel);
336 * This state is used to indicate a successful open
337 * so that when we do close the channel normally, we
338 * can cleanup properly
340 newchannel->state = CHANNEL_OPEN_STATE;
343 * Start the process of binding this offer to the driver
344 * We need to set the DeviceObject field before calling
345 * vmbus_child_dev_add()
347 newchannel->device_obj = vmbus_device_create(
348 &newchannel->offermsg.offer.if_type,
349 &newchannel->offermsg.offer.if_instance,
353 * Add the new device to the bus. This will kick off device-driver
354 * binding which eventually invokes the device driver's AddDevice()
357 ret = vmbus_device_register(newchannel->device_obj);
359 pr_err("unable to add child device object (relid %d)\n",
360 newchannel->offermsg.child_relid);
362 spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
363 list_del(&newchannel->listentry);
364 spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
365 kfree(newchannel->device_obj);
367 free_channel(newchannel);
379 * This is an array of device_ids (device types) that are performance critical.
380 * We attempt to distribute the interrupt load for these devices across
381 * all available CPUs.
383 static const struct hv_vmbus_device_id hp_devs[] = {
394 * We use this state to statically distribute the channel interrupt load.
399 * Starting with Win8, we can statically distribute the incoming
400 * channel interrupt load by binding a channel to VCPU. We
401 * implement here a simple round robin scheme for distributing
402 * the interrupt load.
403 * We will bind channels that are not performance critical to cpu 0 and
404 * performance critical channels (IDE, SCSI and Network) will be uniformly
405 * distributed across all available CPUs.
407 static void init_vp_index(struct vmbus_channel *channel, uuid_le *type_guid)
411 bool perf_chn = false;
412 u32 max_cpus = num_online_cpus();
414 for (i = IDE; i < MAX_PERF_CHN; i++) {
415 if (!memcmp(type_guid->b, hp_devs[i].guid,
421 if ((vmbus_proto_version == VERSION_WS2008) ||
422 (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) {
424 * Prior to win8, all channel interrupts are
425 * delivered on cpu 0.
426 * Also if the channel is not a performance critical
427 * channel, bind it to cpu 0.
429 channel->target_cpu = 0;
430 channel->target_vp = 0;
433 cur_cpu = (++next_vp % max_cpus);
434 channel->target_cpu = cur_cpu;
435 channel->target_vp = hv_context.vp_index[cur_cpu];
439 * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
442 static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
444 struct vmbus_channel_offer_channel *offer;
445 struct vmbus_channel *newchannel;
447 offer = (struct vmbus_channel_offer_channel *)hdr;
449 /* Allocate the channel object and save this offer. */
450 newchannel = alloc_channel();
452 pr_err("Unable to allocate channel object\n");
457 * By default we setup state to enable batched
458 * reading. A specific service can choose to
459 * disable this prior to opening the channel.
461 newchannel->batched_reading = true;
464 * Setup state for signalling the host.
466 newchannel->sig_event = (struct hv_input_signal_event *)
467 (ALIGN((unsigned long)
468 &newchannel->sig_buf,
469 HV_HYPERCALL_PARAM_ALIGN));
471 newchannel->sig_event->connectionid.asu32 = 0;
472 newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
473 newchannel->sig_event->flag_number = 0;
474 newchannel->sig_event->rsvdz = 0;
476 if (vmbus_proto_version != VERSION_WS2008) {
477 newchannel->is_dedicated_interrupt =
478 (offer->is_dedicated_interrupt != 0);
479 newchannel->sig_event->connectionid.u.id =
480 offer->connection_id;
483 init_vp_index(newchannel, &offer->offer.if_type);
485 memcpy(&newchannel->offermsg, offer,
486 sizeof(struct vmbus_channel_offer_channel));
487 newchannel->monitor_grp = (u8)offer->monitorid / 32;
488 newchannel->monitor_bit = (u8)offer->monitorid % 32;
490 INIT_WORK(&newchannel->work, vmbus_process_offer);
491 queue_work(newchannel->controlwq, &newchannel->work);
495 * vmbus_onoffer_rescind - Rescind offer handler.
497 * We queue a work item to process this offer synchronously
499 static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
501 struct vmbus_channel_rescind_offer *rescind;
502 struct vmbus_channel *channel;
504 rescind = (struct vmbus_channel_rescind_offer *)hdr;
505 channel = relid2channel(rescind->child_relid);
508 /* Just return here, no channel found */
511 /* work is initialized for vmbus_process_rescind_offer() from
512 * vmbus_process_offer() where the channel got created */
513 queue_work(channel->controlwq, &channel->work);
517 * vmbus_onoffers_delivered -
518 * This is invoked when all offers have been delivered.
520 * Nothing to do here.
522 static void vmbus_onoffers_delivered(
523 struct vmbus_channel_message_header *hdr)
528 * vmbus_onopen_result - Open result handler.
530 * This is invoked when we received a response to our channel open request.
531 * Find the matching request, copy the response and signal the requesting
534 static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr)
536 struct vmbus_channel_open_result *result;
537 struct vmbus_channel_msginfo *msginfo;
538 struct vmbus_channel_message_header *requestheader;
539 struct vmbus_channel_open_channel *openmsg;
542 result = (struct vmbus_channel_open_result *)hdr;
545 * Find the open msg, copy the result and signal/unblock the wait event
547 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
549 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
552 (struct vmbus_channel_message_header *)msginfo->msg;
554 if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) {
556 (struct vmbus_channel_open_channel *)msginfo->msg;
557 if (openmsg->child_relid == result->child_relid &&
558 openmsg->openid == result->openid) {
559 memcpy(&msginfo->response.open_result,
562 struct vmbus_channel_open_result));
563 complete(&msginfo->waitevent);
568 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
572 * vmbus_ongpadl_created - GPADL created handler.
574 * This is invoked when we received a response to our gpadl create request.
575 * Find the matching request, copy the response and signal the requesting
578 static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr)
580 struct vmbus_channel_gpadl_created *gpadlcreated;
581 struct vmbus_channel_msginfo *msginfo;
582 struct vmbus_channel_message_header *requestheader;
583 struct vmbus_channel_gpadl_header *gpadlheader;
586 gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr;
589 * Find the establish msg, copy the result and signal/unblock the wait
592 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
594 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
597 (struct vmbus_channel_message_header *)msginfo->msg;
599 if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) {
601 (struct vmbus_channel_gpadl_header *)requestheader;
603 if ((gpadlcreated->child_relid ==
604 gpadlheader->child_relid) &&
605 (gpadlcreated->gpadl == gpadlheader->gpadl)) {
606 memcpy(&msginfo->response.gpadl_created,
609 struct vmbus_channel_gpadl_created));
610 complete(&msginfo->waitevent);
615 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
619 * vmbus_ongpadl_torndown - GPADL torndown handler.
621 * This is invoked when we received a response to our gpadl teardown request.
622 * Find the matching request, copy the response and signal the requesting
625 static void vmbus_ongpadl_torndown(
626 struct vmbus_channel_message_header *hdr)
628 struct vmbus_channel_gpadl_torndown *gpadl_torndown;
629 struct vmbus_channel_msginfo *msginfo;
630 struct vmbus_channel_message_header *requestheader;
631 struct vmbus_channel_gpadl_teardown *gpadl_teardown;
634 gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr;
637 * Find the open msg, copy the result and signal/unblock the wait event
639 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
641 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
644 (struct vmbus_channel_message_header *)msginfo->msg;
646 if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) {
648 (struct vmbus_channel_gpadl_teardown *)requestheader;
650 if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) {
651 memcpy(&msginfo->response.gpadl_torndown,
654 struct vmbus_channel_gpadl_torndown));
655 complete(&msginfo->waitevent);
660 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
664 * vmbus_onversion_response - Version response handler
666 * This is invoked when we received a response to our initiate contact request.
667 * Find the matching request, copy the response and signal the requesting
670 static void vmbus_onversion_response(
671 struct vmbus_channel_message_header *hdr)
673 struct vmbus_channel_msginfo *msginfo;
674 struct vmbus_channel_message_header *requestheader;
675 struct vmbus_channel_version_response *version_response;
678 version_response = (struct vmbus_channel_version_response *)hdr;
679 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
681 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
684 (struct vmbus_channel_message_header *)msginfo->msg;
686 if (requestheader->msgtype ==
687 CHANNELMSG_INITIATE_CONTACT) {
688 memcpy(&msginfo->response.version_response,
690 sizeof(struct vmbus_channel_version_response));
691 complete(&msginfo->waitevent);
694 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
697 /* Channel message dispatch table */
698 static struct vmbus_channel_message_table_entry
699 channel_message_table[CHANNELMSG_COUNT] = {
700 {CHANNELMSG_INVALID, NULL},
701 {CHANNELMSG_OFFERCHANNEL, vmbus_onoffer},
702 {CHANNELMSG_RESCIND_CHANNELOFFER, vmbus_onoffer_rescind},
703 {CHANNELMSG_REQUESTOFFERS, NULL},
704 {CHANNELMSG_ALLOFFERS_DELIVERED, vmbus_onoffers_delivered},
705 {CHANNELMSG_OPENCHANNEL, NULL},
706 {CHANNELMSG_OPENCHANNEL_RESULT, vmbus_onopen_result},
707 {CHANNELMSG_CLOSECHANNEL, NULL},
708 {CHANNELMSG_GPADL_HEADER, NULL},
709 {CHANNELMSG_GPADL_BODY, NULL},
710 {CHANNELMSG_GPADL_CREATED, vmbus_ongpadl_created},
711 {CHANNELMSG_GPADL_TEARDOWN, NULL},
712 {CHANNELMSG_GPADL_TORNDOWN, vmbus_ongpadl_torndown},
713 {CHANNELMSG_RELID_RELEASED, NULL},
714 {CHANNELMSG_INITIATE_CONTACT, NULL},
715 {CHANNELMSG_VERSION_RESPONSE, vmbus_onversion_response},
716 {CHANNELMSG_UNLOAD, NULL},
720 * vmbus_onmessage - Handler for channel protocol messages.
722 * This is invoked in the vmbus worker thread context.
724 void vmbus_onmessage(void *context)
726 struct hv_message *msg = context;
727 struct vmbus_channel_message_header *hdr;
730 hdr = (struct vmbus_channel_message_header *)msg->u.payload;
731 size = msg->header.payload_size;
733 if (hdr->msgtype >= CHANNELMSG_COUNT) {
734 pr_err("Received invalid channel message type %d size %d\n",
736 print_hex_dump_bytes("", DUMP_PREFIX_NONE,
737 (unsigned char *)msg->u.payload, size);
741 if (channel_message_table[hdr->msgtype].message_handler)
742 channel_message_table[hdr->msgtype].message_handler(hdr);
744 pr_err("Unhandled channel message type %d\n", hdr->msgtype);
748 * vmbus_request_offers - Send a request to get all our pending offers.
750 int vmbus_request_offers(void)
752 struct vmbus_channel_message_header *msg;
753 struct vmbus_channel_msginfo *msginfo;
756 msginfo = kmalloc(sizeof(*msginfo) +
757 sizeof(struct vmbus_channel_message_header),
762 init_completion(&msginfo->waitevent);
764 msg = (struct vmbus_channel_message_header *)msginfo->msg;
766 msg->msgtype = CHANNELMSG_REQUESTOFFERS;
769 ret = vmbus_post_msg(msg,
770 sizeof(struct vmbus_channel_message_header));
772 pr_err("Unable to request offers - %d\n", ret);
777 t = wait_for_completion_timeout(&msginfo->waitevent, 5*HZ);
792 * Retrieve the (sub) channel on which to send an outgoing request.
793 * When a primary channel has multiple sub-channels, we choose a
794 * channel whose VCPU binding is closest to the VCPU on which
795 * this call is being made.
797 struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
799 struct list_head *cur, *tmp;
800 int cur_cpu = hv_context.vp_index[smp_processor_id()];
801 struct vmbus_channel *cur_channel;
802 struct vmbus_channel *outgoing_channel = primary;
803 int cpu_distance, new_cpu_distance;
805 if (list_empty(&primary->sc_list))
806 return outgoing_channel;
808 list_for_each_safe(cur, tmp, &primary->sc_list) {
809 cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
810 if (cur_channel->state != CHANNEL_OPENED_STATE)
813 if (cur_channel->target_vp == cur_cpu)
816 cpu_distance = ((outgoing_channel->target_vp > cur_cpu) ?
817 (outgoing_channel->target_vp - cur_cpu) :
818 (cur_cpu - outgoing_channel->target_vp));
820 new_cpu_distance = ((cur_channel->target_vp > cur_cpu) ?
821 (cur_channel->target_vp - cur_cpu) :
822 (cur_cpu - cur_channel->target_vp));
824 if (cpu_distance < new_cpu_distance)
827 outgoing_channel = cur_channel;
830 return outgoing_channel;
832 EXPORT_SYMBOL_GPL(vmbus_get_outgoing_channel);
834 static void invoke_sc_cb(struct vmbus_channel *primary_channel)
836 struct list_head *cur, *tmp;
837 struct vmbus_channel *cur_channel;
839 if (primary_channel->sc_creation_callback == NULL)
842 list_for_each_safe(cur, tmp, &primary_channel->sc_list) {
843 cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
845 primary_channel->sc_creation_callback(cur_channel);
849 void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
850 void (*sc_cr_cb)(struct vmbus_channel *new_sc))
852 primary_channel->sc_creation_callback = sc_cr_cb;
854 EXPORT_SYMBOL_GPL(vmbus_set_sc_create_callback);
856 bool vmbus_are_subchannels_present(struct vmbus_channel *primary)
860 ret = !list_empty(&primary->sc_list);
864 * Invoke the callback on sub-channel creation.
865 * This will present a uniform interface to the
868 invoke_sc_cb(primary);
873 EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);