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 != get_cpu()) {
229 smp_call_function_single(channel->target_cpu,
230 percpu_channel_deq, channel, true);
232 percpu_channel_deq(channel);
236 if (channel->primary_channel == NULL) {
237 spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
238 list_del(&channel->listentry);
239 spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
241 primary_channel = channel->primary_channel;
242 spin_lock_irqsave(&primary_channel->sc_lock, flags);
243 list_del(&channel->sc_list);
244 spin_unlock_irqrestore(&primary_channel->sc_lock, flags);
246 free_channel(channel);
249 void vmbus_free_channels(void)
251 struct vmbus_channel *channel;
253 list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
254 vmbus_device_unregister(channel->device_obj);
255 kfree(channel->device_obj);
256 free_channel(channel);
261 * vmbus_process_offer - Process the offer by creating a channel/device
262 * associated with this offer
264 static void vmbus_process_offer(struct work_struct *work)
266 struct vmbus_channel *newchannel = container_of(work,
267 struct vmbus_channel,
269 struct vmbus_channel *channel;
275 /* The next possible work is rescind handling */
276 INIT_WORK(&newchannel->work, vmbus_process_rescind_offer);
278 /* Make sure this is a new offer */
279 spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
281 list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
282 if (!uuid_le_cmp(channel->offermsg.offer.if_type,
283 newchannel->offermsg.offer.if_type) &&
284 !uuid_le_cmp(channel->offermsg.offer.if_instance,
285 newchannel->offermsg.offer.if_instance)) {
292 list_add_tail(&newchannel->listentry,
293 &vmbus_connection.chn_list);
297 spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
300 if (newchannel->target_cpu != get_cpu()) {
302 smp_call_function_single(newchannel->target_cpu,
306 percpu_channel_enq(newchannel);
312 * Check to see if this is a sub-channel.
314 if (newchannel->offermsg.offer.sub_channel_index != 0) {
316 * Process the sub-channel.
318 newchannel->primary_channel = channel;
319 spin_lock_irqsave(&channel->sc_lock, flags);
320 list_add_tail(&newchannel->sc_list, &channel->sc_list);
321 spin_unlock_irqrestore(&channel->sc_lock, flags);
323 if (newchannel->target_cpu != get_cpu()) {
325 smp_call_function_single(newchannel->target_cpu,
329 percpu_channel_enq(newchannel);
333 newchannel->state = CHANNEL_OPEN_STATE;
334 if (channel->sc_creation_callback != NULL)
335 channel->sc_creation_callback(newchannel);
340 free_channel(newchannel);
345 * This state is used to indicate a successful open
346 * so that when we do close the channel normally, we
347 * can cleanup properly
349 newchannel->state = CHANNEL_OPEN_STATE;
352 * Start the process of binding this offer to the driver
353 * We need to set the DeviceObject field before calling
354 * vmbus_child_dev_add()
356 newchannel->device_obj = vmbus_device_create(
357 &newchannel->offermsg.offer.if_type,
358 &newchannel->offermsg.offer.if_instance,
362 * Add the new device to the bus. This will kick off device-driver
363 * binding which eventually invokes the device driver's AddDevice()
366 ret = vmbus_device_register(newchannel->device_obj);
368 pr_err("unable to add child device object (relid %d)\n",
369 newchannel->offermsg.child_relid);
371 spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
372 list_del(&newchannel->listentry);
373 spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
374 kfree(newchannel->device_obj);
376 free_channel(newchannel);
388 * This is an array of device_ids (device types) that are performance critical.
389 * We attempt to distribute the interrupt load for these devices across
390 * all available CPUs.
392 static const struct hv_vmbus_device_id hp_devs[] = {
403 * We use this state to statically distribute the channel interrupt load.
408 * Starting with Win8, we can statically distribute the incoming
409 * channel interrupt load by binding a channel to VCPU. We
410 * implement here a simple round robin scheme for distributing
411 * the interrupt load.
412 * We will bind channels that are not performance critical to cpu 0 and
413 * performance critical channels (IDE, SCSI and Network) will be uniformly
414 * distributed across all available CPUs.
416 static void init_vp_index(struct vmbus_channel *channel, const uuid_le *type_guid)
420 bool perf_chn = false;
421 u32 max_cpus = num_online_cpus();
423 for (i = IDE; i < MAX_PERF_CHN; i++) {
424 if (!memcmp(type_guid->b, hp_devs[i].guid,
430 if ((vmbus_proto_version == VERSION_WS2008) ||
431 (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) {
433 * Prior to win8, all channel interrupts are
434 * delivered on cpu 0.
435 * Also if the channel is not a performance critical
436 * channel, bind it to cpu 0.
438 channel->target_cpu = 0;
439 channel->target_vp = 0;
442 cur_cpu = (++next_vp % max_cpus);
443 channel->target_cpu = cur_cpu;
444 channel->target_vp = hv_context.vp_index[cur_cpu];
448 * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
451 static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
453 struct vmbus_channel_offer_channel *offer;
454 struct vmbus_channel *newchannel;
456 offer = (struct vmbus_channel_offer_channel *)hdr;
458 /* Allocate the channel object and save this offer. */
459 newchannel = alloc_channel();
461 pr_err("Unable to allocate channel object\n");
466 * By default we setup state to enable batched
467 * reading. A specific service can choose to
468 * disable this prior to opening the channel.
470 newchannel->batched_reading = true;
473 * Setup state for signalling the host.
475 newchannel->sig_event = (struct hv_input_signal_event *)
476 (ALIGN((unsigned long)
477 &newchannel->sig_buf,
478 HV_HYPERCALL_PARAM_ALIGN));
480 newchannel->sig_event->connectionid.asu32 = 0;
481 newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
482 newchannel->sig_event->flag_number = 0;
483 newchannel->sig_event->rsvdz = 0;
485 if (vmbus_proto_version != VERSION_WS2008) {
486 newchannel->is_dedicated_interrupt =
487 (offer->is_dedicated_interrupt != 0);
488 newchannel->sig_event->connectionid.u.id =
489 offer->connection_id;
492 init_vp_index(newchannel, &offer->offer.if_type);
494 memcpy(&newchannel->offermsg, offer,
495 sizeof(struct vmbus_channel_offer_channel));
496 newchannel->monitor_grp = (u8)offer->monitorid / 32;
497 newchannel->monitor_bit = (u8)offer->monitorid % 32;
499 INIT_WORK(&newchannel->work, vmbus_process_offer);
500 queue_work(newchannel->controlwq, &newchannel->work);
504 * vmbus_onoffer_rescind - Rescind offer handler.
506 * We queue a work item to process this offer synchronously
508 static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
510 struct vmbus_channel_rescind_offer *rescind;
511 struct vmbus_channel *channel;
513 rescind = (struct vmbus_channel_rescind_offer *)hdr;
514 channel = relid2channel(rescind->child_relid);
517 /* Just return here, no channel found */
520 /* work is initialized for vmbus_process_rescind_offer() from
521 * vmbus_process_offer() where the channel got created */
522 queue_work(channel->controlwq, &channel->work);
526 * vmbus_onoffers_delivered -
527 * This is invoked when all offers have been delivered.
529 * Nothing to do here.
531 static void vmbus_onoffers_delivered(
532 struct vmbus_channel_message_header *hdr)
537 * vmbus_onopen_result - Open result handler.
539 * This is invoked when we received a response to our channel open request.
540 * Find the matching request, copy the response and signal the requesting
543 static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr)
545 struct vmbus_channel_open_result *result;
546 struct vmbus_channel_msginfo *msginfo;
547 struct vmbus_channel_message_header *requestheader;
548 struct vmbus_channel_open_channel *openmsg;
551 result = (struct vmbus_channel_open_result *)hdr;
554 * Find the open msg, copy the result and signal/unblock the wait event
556 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
558 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
561 (struct vmbus_channel_message_header *)msginfo->msg;
563 if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) {
565 (struct vmbus_channel_open_channel *)msginfo->msg;
566 if (openmsg->child_relid == result->child_relid &&
567 openmsg->openid == result->openid) {
568 memcpy(&msginfo->response.open_result,
571 struct vmbus_channel_open_result));
572 complete(&msginfo->waitevent);
577 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
581 * vmbus_ongpadl_created - GPADL created handler.
583 * This is invoked when we received a response to our gpadl create request.
584 * Find the matching request, copy the response and signal the requesting
587 static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr)
589 struct vmbus_channel_gpadl_created *gpadlcreated;
590 struct vmbus_channel_msginfo *msginfo;
591 struct vmbus_channel_message_header *requestheader;
592 struct vmbus_channel_gpadl_header *gpadlheader;
595 gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr;
598 * Find the establish msg, copy the result and signal/unblock the wait
601 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
603 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
606 (struct vmbus_channel_message_header *)msginfo->msg;
608 if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) {
610 (struct vmbus_channel_gpadl_header *)requestheader;
612 if ((gpadlcreated->child_relid ==
613 gpadlheader->child_relid) &&
614 (gpadlcreated->gpadl == gpadlheader->gpadl)) {
615 memcpy(&msginfo->response.gpadl_created,
618 struct vmbus_channel_gpadl_created));
619 complete(&msginfo->waitevent);
624 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
628 * vmbus_ongpadl_torndown - GPADL torndown handler.
630 * This is invoked when we received a response to our gpadl teardown request.
631 * Find the matching request, copy the response and signal the requesting
634 static void vmbus_ongpadl_torndown(
635 struct vmbus_channel_message_header *hdr)
637 struct vmbus_channel_gpadl_torndown *gpadl_torndown;
638 struct vmbus_channel_msginfo *msginfo;
639 struct vmbus_channel_message_header *requestheader;
640 struct vmbus_channel_gpadl_teardown *gpadl_teardown;
643 gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr;
646 * Find the open msg, copy the result and signal/unblock the wait event
648 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
650 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
653 (struct vmbus_channel_message_header *)msginfo->msg;
655 if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) {
657 (struct vmbus_channel_gpadl_teardown *)requestheader;
659 if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) {
660 memcpy(&msginfo->response.gpadl_torndown,
663 struct vmbus_channel_gpadl_torndown));
664 complete(&msginfo->waitevent);
669 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
673 * vmbus_onversion_response - Version response handler
675 * This is invoked when we received a response to our initiate contact request.
676 * Find the matching request, copy the response and signal the requesting
679 static void vmbus_onversion_response(
680 struct vmbus_channel_message_header *hdr)
682 struct vmbus_channel_msginfo *msginfo;
683 struct vmbus_channel_message_header *requestheader;
684 struct vmbus_channel_version_response *version_response;
687 version_response = (struct vmbus_channel_version_response *)hdr;
688 spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
690 list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
693 (struct vmbus_channel_message_header *)msginfo->msg;
695 if (requestheader->msgtype ==
696 CHANNELMSG_INITIATE_CONTACT) {
697 memcpy(&msginfo->response.version_response,
699 sizeof(struct vmbus_channel_version_response));
700 complete(&msginfo->waitevent);
703 spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
706 /* Channel message dispatch table */
707 static struct vmbus_channel_message_table_entry
708 channel_message_table[CHANNELMSG_COUNT] = {
709 {CHANNELMSG_INVALID, NULL},
710 {CHANNELMSG_OFFERCHANNEL, vmbus_onoffer},
711 {CHANNELMSG_RESCIND_CHANNELOFFER, vmbus_onoffer_rescind},
712 {CHANNELMSG_REQUESTOFFERS, NULL},
713 {CHANNELMSG_ALLOFFERS_DELIVERED, vmbus_onoffers_delivered},
714 {CHANNELMSG_OPENCHANNEL, NULL},
715 {CHANNELMSG_OPENCHANNEL_RESULT, vmbus_onopen_result},
716 {CHANNELMSG_CLOSECHANNEL, NULL},
717 {CHANNELMSG_GPADL_HEADER, NULL},
718 {CHANNELMSG_GPADL_BODY, NULL},
719 {CHANNELMSG_GPADL_CREATED, vmbus_ongpadl_created},
720 {CHANNELMSG_GPADL_TEARDOWN, NULL},
721 {CHANNELMSG_GPADL_TORNDOWN, vmbus_ongpadl_torndown},
722 {CHANNELMSG_RELID_RELEASED, NULL},
723 {CHANNELMSG_INITIATE_CONTACT, NULL},
724 {CHANNELMSG_VERSION_RESPONSE, vmbus_onversion_response},
725 {CHANNELMSG_UNLOAD, NULL},
729 * vmbus_onmessage - Handler for channel protocol messages.
731 * This is invoked in the vmbus worker thread context.
733 void vmbus_onmessage(void *context)
735 struct hv_message *msg = context;
736 struct vmbus_channel_message_header *hdr;
739 hdr = (struct vmbus_channel_message_header *)msg->u.payload;
740 size = msg->header.payload_size;
742 if (hdr->msgtype >= CHANNELMSG_COUNT) {
743 pr_err("Received invalid channel message type %d size %d\n",
745 print_hex_dump_bytes("", DUMP_PREFIX_NONE,
746 (unsigned char *)msg->u.payload, size);
750 if (channel_message_table[hdr->msgtype].message_handler)
751 channel_message_table[hdr->msgtype].message_handler(hdr);
753 pr_err("Unhandled channel message type %d\n", hdr->msgtype);
757 * vmbus_request_offers - Send a request to get all our pending offers.
759 int vmbus_request_offers(void)
761 struct vmbus_channel_message_header *msg;
762 struct vmbus_channel_msginfo *msginfo;
765 msginfo = kmalloc(sizeof(*msginfo) +
766 sizeof(struct vmbus_channel_message_header),
771 init_completion(&msginfo->waitevent);
773 msg = (struct vmbus_channel_message_header *)msginfo->msg;
775 msg->msgtype = CHANNELMSG_REQUESTOFFERS;
778 ret = vmbus_post_msg(msg,
779 sizeof(struct vmbus_channel_message_header));
781 pr_err("Unable to request offers - %d\n", ret);
786 t = wait_for_completion_timeout(&msginfo->waitevent, 5*HZ);
801 * Retrieve the (sub) channel on which to send an outgoing request.
802 * When a primary channel has multiple sub-channels, we choose a
803 * channel whose VCPU binding is closest to the VCPU on which
804 * this call is being made.
806 struct vmbus_channel *vmbus_get_outgoing_channel(struct vmbus_channel *primary)
808 struct list_head *cur, *tmp;
809 int cur_cpu = hv_context.vp_index[smp_processor_id()];
810 struct vmbus_channel *cur_channel;
811 struct vmbus_channel *outgoing_channel = primary;
812 int cpu_distance, new_cpu_distance;
814 if (list_empty(&primary->sc_list))
815 return outgoing_channel;
817 list_for_each_safe(cur, tmp, &primary->sc_list) {
818 cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
819 if (cur_channel->state != CHANNEL_OPENED_STATE)
822 if (cur_channel->target_vp == cur_cpu)
825 cpu_distance = ((outgoing_channel->target_vp > cur_cpu) ?
826 (outgoing_channel->target_vp - cur_cpu) :
827 (cur_cpu - outgoing_channel->target_vp));
829 new_cpu_distance = ((cur_channel->target_vp > cur_cpu) ?
830 (cur_channel->target_vp - cur_cpu) :
831 (cur_cpu - cur_channel->target_vp));
833 if (cpu_distance < new_cpu_distance)
836 outgoing_channel = cur_channel;
839 return outgoing_channel;
841 EXPORT_SYMBOL_GPL(vmbus_get_outgoing_channel);
843 static void invoke_sc_cb(struct vmbus_channel *primary_channel)
845 struct list_head *cur, *tmp;
846 struct vmbus_channel *cur_channel;
848 if (primary_channel->sc_creation_callback == NULL)
851 list_for_each_safe(cur, tmp, &primary_channel->sc_list) {
852 cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
854 primary_channel->sc_creation_callback(cur_channel);
858 void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
859 void (*sc_cr_cb)(struct vmbus_channel *new_sc))
861 primary_channel->sc_creation_callback = sc_cr_cb;
863 EXPORT_SYMBOL_GPL(vmbus_set_sc_create_callback);
865 bool vmbus_are_subchannels_present(struct vmbus_channel *primary)
869 ret = !list_empty(&primary->sc_list);
873 * Invoke the callback on sub-channel creation.
874 * This will present a uniform interface to the
877 invoke_sc_cb(primary);
882 EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);