drivers/hv/channel_mgmt.c

   1 /*
   2  * Copyright (c) 2009, Microsoft Corporation.
   3  *
   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.
   7  *
   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
  11  * more details.
  12  *
  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.
  16  *
  17  * Authors:
  18  *   Haiyang Zhang <haiyangz@microsoft.com>
  19  *   Hank Janssen  <hjanssen@microsoft.com>
  20  */
  21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22
  23 #include <linux/kernel.h>
  24 #include <linux/interrupt.h>
  25 #include <linux/sched.h>
  26 #include <linux/wait.h>
  27 #include <linux/mm.h>
  28 #include <linux/slab.h>
  29 #include <linux/list.h>
  30 #include <linux/module.h>
  31 #include <linux/completion.h>
  32 #include <linux/delay.h>
  33 #include <linux/hyperv.h>
  34 #include <asm/mshyperv.h>
  35
  36 #include "hyperv_vmbus.h"
  37
  38 static void init_vp_index(struct vmbus_channel *channel, u16 dev_type);
  39
  40 static const struct vmbus_device vmbus_devs[] = {
  41         /* IDE */
  42         { .dev_type = HV_IDE,
  43           HV_IDE_GUID,
  44           .perf_device = true,
  45         },
  46
  47         /* SCSI */
  48         { .dev_type = HV_SCSI,
  49           HV_SCSI_GUID,
  50           .perf_device = true,
  51         },
  52
  53         /* Fibre Channel */
  54         { .dev_type = HV_FC,
  55           HV_SYNTHFC_GUID,
  56           .perf_device = true,
  57         },
  58
  59         /* Synthetic NIC */
  60         { .dev_type = HV_NIC,
  61           HV_NIC_GUID,
  62           .perf_device = true,
  63         },
  64
  65         /* Network Direct */
  66         { .dev_type = HV_ND,
  67           HV_ND_GUID,
  68           .perf_device = true,
  69         },
  70
  71         /* PCIE */
  72         { .dev_type = HV_PCIE,
  73           HV_PCIE_GUID,
  74           .perf_device = false,
  75         },
  76
  77         /* Synthetic Frame Buffer */
  78         { .dev_type = HV_FB,
  79           HV_SYNTHVID_GUID,
  80           .perf_device = false,
  81         },
  82
  83         /* Synthetic Keyboard */
  84         { .dev_type = HV_KBD,
  85           HV_KBD_GUID,
  86           .perf_device = false,
  87         },
  88
  89         /* Synthetic MOUSE */
  90         { .dev_type = HV_MOUSE,
  91           HV_MOUSE_GUID,
  92           .perf_device = false,
  93         },
  94
  95         /* KVP */
  96         { .dev_type = HV_KVP,
  97           HV_KVP_GUID,
  98           .perf_device = false,
  99         },
 100
 101         /* Time Synch */
 102         { .dev_type = HV_TS,
 103           HV_TS_GUID,
 104           .perf_device = false,
 105         },
 106
 107         /* Heartbeat */
 108         { .dev_type = HV_HB,
 109           HV_HEART_BEAT_GUID,
 110           .perf_device = false,
 111         },
 112
 113         /* Shutdown */
 114         { .dev_type = HV_SHUTDOWN,
 115           HV_SHUTDOWN_GUID,
 116           .perf_device = false,
 117         },
 118
 119         /* File copy */
 120         { .dev_type = HV_FCOPY,
 121           HV_FCOPY_GUID,
 122           .perf_device = false,
 123         },
 124
 125         /* Backup */
 126         { .dev_type = HV_BACKUP,
 127           HV_VSS_GUID,
 128           .perf_device = false,
 129         },
 130
 131         /* Dynamic Memory */
 132         { .dev_type = HV_DM,
 133           HV_DM_GUID,
 134           .perf_device = false,
 135         },
 136
 137         /* Unknown GUID */
 138         { .dev_type = HV_UNKNOWN,
 139           .perf_device = false,
 140         },
 141 };
 142
 143 static const struct {
 144         guid_t guid;
 145 } vmbus_unsupported_devs[] = {
 146         { HV_AVMA1_GUID },
 147         { HV_AVMA2_GUID },
 148         { HV_RDV_GUID   },
 149 };
 150
 151 /*
 152  * The rescinded channel may be blocked waiting for a response from the host;
 153  * take care of that.
 154  */
 155 static void vmbus_rescind_cleanup(struct vmbus_channel *channel)
 156 {
 157         struct vmbus_channel_msginfo *msginfo;
 158         unsigned long flags;
 159
 160
 161         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 162         channel->rescind = true;
 163         list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
 164                                 msglistentry) {
 165
 166                 if (msginfo->waiting_channel == channel) {
 167                         complete(&msginfo->waitevent);
 168                         break;
 169                 }
 170         }
 171         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 172 }
 173
 174 static bool is_unsupported_vmbus_devs(const guid_t *guid)
 175 {
 176         int i;
 177
 178         for (i = 0; i < ARRAY_SIZE(vmbus_unsupported_devs); i++)
 179                 if (guid_equal(guid, &vmbus_unsupported_devs[i].guid))
 180                         return true;
 181         return false;
 182 }
 183
 184 static u16 hv_get_dev_type(const struct vmbus_channel *channel)
 185 {
 186         const guid_t *guid = &channel->offermsg.offer.if_type;
 187         u16 i;
 188
 189         if (is_hvsock_channel(channel) || is_unsupported_vmbus_devs(guid))
 190                 return HV_UNKNOWN;
 191
 192         for (i = HV_IDE; i < HV_UNKNOWN; i++) {
 193                 if (guid_equal(guid, &vmbus_devs[i].guid))
 194                         return i;
 195         }
 196         pr_info("Unknown GUID: %pUl\n", guid);
 197         return i;
 198 }
 199
 200 /**
 201  * vmbus_prep_negotiate_resp() - Create default response for Negotiate message
 202  * @icmsghdrp: Pointer to msg header structure
 203  * @buf: Raw buffer channel data
 204  * @fw_version: The framework versions we can support.
 205  * @fw_vercnt: The size of @fw_version.
 206  * @srv_version: The service versions we can support.
 207  * @srv_vercnt: The size of @srv_version.
 208  * @nego_fw_version: The selected framework version.
 209  * @nego_srv_version: The selected service version.
 210  *
 211  * Note: Versions are given in decreasing order.
 212  *
 213  * Set up and fill in default negotiate response message.
 214  * Mainly used by Hyper-V drivers.
 215  */
 216 bool vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
 217                                 u8 *buf, const int *fw_version, int fw_vercnt,
 218                                 const int *srv_version, int srv_vercnt,
 219                                 int *nego_fw_version, int *nego_srv_version)
 220 {
 221         int icframe_major, icframe_minor;
 222         int icmsg_major, icmsg_minor;
 223         int fw_major, fw_minor;
 224         int srv_major, srv_minor;
 225         int i, j;
 226         bool found_match = false;
 227         struct icmsg_negotiate *negop;
 228
 229         icmsghdrp->icmsgsize = 0x10;
 230         negop = (struct icmsg_negotiate *)&buf[
 231                 sizeof(struct vmbuspipe_hdr) +
 232                 sizeof(struct icmsg_hdr)];
 233
 234         icframe_major = negop->icframe_vercnt;
 235         icframe_minor = 0;
 236
 237         icmsg_major = negop->icmsg_vercnt;
 238         icmsg_minor = 0;
 239
 240         /*
 241          * Select the framework version number we will
 242          * support.
 243          */
 244
 245         for (i = 0; i < fw_vercnt; i++) {
 246                 fw_major = (fw_version[i] >> 16);
 247                 fw_minor = (fw_version[i] & 0xFFFF);
 248
 249                 for (j = 0; j < negop->icframe_vercnt; j++) {
 250                         if ((negop->icversion_data[j].major == fw_major) &&
 251                             (negop->icversion_data[j].minor == fw_minor)) {
 252                                 icframe_major = negop->icversion_data[j].major;
 253                                 icframe_minor = negop->icversion_data[j].minor;
 254                                 found_match = true;
 255                                 break;
 256                         }
 257                 }
 258
 259                 if (found_match)
 260                         break;
 261         }
 262
 263         if (!found_match)
 264                 goto fw_error;
 265
 266         found_match = false;
 267
 268         for (i = 0; i < srv_vercnt; i++) {
 269                 srv_major = (srv_version[i] >> 16);
 270                 srv_minor = (srv_version[i] & 0xFFFF);
 271
 272                 for (j = negop->icframe_vercnt;
 273                         (j < negop->icframe_vercnt + negop->icmsg_vercnt);
 274                         j++) {
 275
 276                         if ((negop->icversion_data[j].major == srv_major) &&
 277                                 (negop->icversion_data[j].minor == srv_minor)) {
 278
 279                                 icmsg_major = negop->icversion_data[j].major;
 280                                 icmsg_minor = negop->icversion_data[j].minor;
 281                                 found_match = true;
 282                                 break;
 283                         }
 284                 }
 285
 286                 if (found_match)
 287                         break;
 288         }
 289
 290         /*
 291          * Respond with the framework and service
 292          * version numbers we can support.
 293          */
 294
 295 fw_error:
 296         if (!found_match) {
 297                 negop->icframe_vercnt = 0;
 298                 negop->icmsg_vercnt = 0;
 299         } else {
 300                 negop->icframe_vercnt = 1;
 301                 negop->icmsg_vercnt = 1;
 302         }
 303
 304         if (nego_fw_version)
 305                 *nego_fw_version = (icframe_major << 16) | icframe_minor;
 306
 307         if (nego_srv_version)
 308                 *nego_srv_version = (icmsg_major << 16) | icmsg_minor;
 309
 310         negop->icversion_data[0].major = icframe_major;
 311         negop->icversion_data[0].minor = icframe_minor;
 312         negop->icversion_data[1].major = icmsg_major;
 313         negop->icversion_data[1].minor = icmsg_minor;
 314         return found_match;
 315 }
 316
 317 EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);
 318
 319 /*
 320  * alloc_channel - Allocate and initialize a vmbus channel object
 321  */
 322 static struct vmbus_channel *alloc_channel(void)
 323 {
 324         struct vmbus_channel *channel;
 325
 326         channel = kzalloc(sizeof(*channel), GFP_ATOMIC);
 327         if (!channel)
 328                 return NULL;
 329
 330         spin_lock_init(&channel->lock);
 331         init_completion(&channel->rescind_event);
 332
 333         INIT_LIST_HEAD(&channel->sc_list);
 334         INIT_LIST_HEAD(&channel->percpu_list);
 335
 336         tasklet_init(&channel->callback_event,
 337                      vmbus_on_event, (unsigned long)channel);
 338
 339         return channel;
 340 }
 341
 342 /*
 343  * free_channel - Release the resources used by the vmbus channel object
 344  */
 345 static void free_channel(struct vmbus_channel *channel)
 346 {
 347         tasklet_kill(&channel->callback_event);
 348
 349         kobject_put(&channel->kobj);
 350 }
 351
 352 static void percpu_channel_enq(void *arg)
 353 {
 354         struct vmbus_channel *channel = arg;
 355         struct hv_per_cpu_context *hv_cpu
 356                 = this_cpu_ptr(hv_context.cpu_context);
 357
 358         list_add_tail_rcu(&channel->percpu_list, &hv_cpu->chan_list);
 359 }
 360
 361 static void percpu_channel_deq(void *arg)
 362 {
 363         struct vmbus_channel *channel = arg;
 364
 365         list_del_rcu(&channel->percpu_list);
 366 }
 367
 368
 369 static void vmbus_release_relid(u32 relid)
 370 {
 371         struct vmbus_channel_relid_released msg;
 372         int ret;
 373
 374         memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
 375         msg.child_relid = relid;
 376         msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
 377         ret = vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released),
 378                              true);
 379
 380         trace_vmbus_release_relid(&msg, ret);
 381 }
 382
 383 void hv_process_channel_removal(struct vmbus_channel *channel)
 384 {
 385         struct vmbus_channel *primary_channel;
 386         unsigned long flags;
 387
 388         BUG_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));
 389         BUG_ON(!channel->rescind);
 390
 391         if (channel->target_cpu != get_cpu()) {
 392                 put_cpu();
 393                 smp_call_function_single(channel->target_cpu,
 394                                          percpu_channel_deq, channel, true);
 395         } else {
 396                 percpu_channel_deq(channel);
 397                 put_cpu();
 398         }
 399
 400         if (channel->primary_channel == NULL) {
 401                 list_del(&channel->listentry);
 402
 403                 primary_channel = channel;
 404         } else {
 405                 primary_channel = channel->primary_channel;
 406                 spin_lock_irqsave(&primary_channel->lock, flags);
 407                 list_del(&channel->sc_list);
 408                 spin_unlock_irqrestore(&primary_channel->lock, flags);
 409         }
 410
 411         /*
 412          * We need to free the bit for init_vp_index() to work in the case
 413          * of sub-channel, when we reload drivers like hv_netvsc.
 414          */
 415         if (channel->affinity_policy == HV_LOCALIZED)
 416                 cpumask_clear_cpu(channel->target_cpu,
 417                                   &primary_channel->alloced_cpus_in_node);
 418
 419         vmbus_release_relid(channel->offermsg.child_relid);
 420
 421         free_channel(channel);
 422 }
 423
 424 void vmbus_free_channels(void)
 425 {
 426         struct vmbus_channel *channel, *tmp;
 427
 428         list_for_each_entry_safe(channel, tmp, &vmbus_connection.chn_list,
 429                 listentry) {
 430                 /* hv_process_channel_removal() needs this */
 431                 channel->rescind = true;
 432
 433                 vmbus_device_unregister(channel->device_obj);
 434         }
 435 }
 436
 437 /* Note: the function can run concurrently for primary/sub channels. */
 438 static void vmbus_add_channel_work(struct work_struct *work)
 439 {
 440         struct vmbus_channel *newchannel =
 441                 container_of(work, struct vmbus_channel, add_channel_work);
 442         struct vmbus_channel *primary_channel = newchannel->primary_channel;
 443         unsigned long flags;
 444         u16 dev_type;
 445         int ret;
 446
 447         dev_type = hv_get_dev_type(newchannel);
 448
 449         init_vp_index(newchannel, dev_type);
 450
 451         if (newchannel->target_cpu != get_cpu()) {
 452                 put_cpu();
 453                 smp_call_function_single(newchannel->target_cpu,
 454                                          percpu_channel_enq,
 455                                          newchannel, true);
 456         } else {
 457                 percpu_channel_enq(newchannel);
 458                 put_cpu();
 459         }
 460
 461         /*
 462          * This state is used to indicate a successful open
 463          * so that when we do close the channel normally, we
 464          * can cleanup properly.
 465          */
 466         newchannel->state = CHANNEL_OPEN_STATE;
 467
 468         if (primary_channel != NULL) {
 469                 /* newchannel is a sub-channel. */
 470                 struct hv_device *dev = primary_channel->device_obj;
 471
 472                 if (vmbus_add_channel_kobj(dev, newchannel))
 473                         goto err_deq_chan;
 474
 475                 if (primary_channel->sc_creation_callback != NULL)
 476                         primary_channel->sc_creation_callback(newchannel);
 477
 478                 newchannel->probe_done = true;
 479                 return;
 480         }
 481
 482         /*
 483          * Start the process of binding the primary channel to the driver
 484          */
 485         newchannel->device_obj = vmbus_device_create(
 486                 &newchannel->offermsg.offer.if_type,
 487                 &newchannel->offermsg.offer.if_instance,
 488                 newchannel);
 489         if (!newchannel->device_obj)
 490                 goto err_deq_chan;
 491
 492         newchannel->device_obj->device_id = dev_type;
 493         /*
 494          * Add the new device to the bus. This will kick off device-driver
 495          * binding which eventually invokes the device driver's AddDevice()
 496          * method.
 497          */
 498         ret = vmbus_device_register(newchannel->device_obj);
 499
 500         if (ret != 0) {
 501                 pr_err("unable to add child device object (relid %d)\n",
 502                         newchannel->offermsg.child_relid);
 503                 kfree(newchannel->device_obj);
 504                 goto err_deq_chan;
 505         }
 506
 507         newchannel->probe_done = true;
 508         return;
 509
 510 err_deq_chan:
 511         mutex_lock(&vmbus_connection.channel_mutex);
 512
 513         /*
 514          * We need to set the flag, otherwise
 515          * vmbus_onoffer_rescind() can be blocked.
 516          */
 517         newchannel->probe_done = true;
 518
 519         if (primary_channel == NULL) {
 520                 list_del(&newchannel->listentry);
 521         } else {
 522                 spin_lock_irqsave(&primary_channel->lock, flags);
 523                 list_del(&newchannel->sc_list);
 524                 spin_unlock_irqrestore(&primary_channel->lock, flags);
 525         }
 526
 527         mutex_unlock(&vmbus_connection.channel_mutex);
 528
 529         if (newchannel->target_cpu != get_cpu()) {
 530                 put_cpu();
 531                 smp_call_function_single(newchannel->target_cpu,
 532                                          percpu_channel_deq,
 533                                          newchannel, true);
 534         } else {
 535                 percpu_channel_deq(newchannel);
 536                 put_cpu();
 537         }
 538
 539         vmbus_release_relid(newchannel->offermsg.child_relid);
 540
 541         free_channel(newchannel);
 542 }
 543
 544 /*
 545  * vmbus_process_offer - Process the offer by creating a channel/device
 546  * associated with this offer
 547  */
 548 static void vmbus_process_offer(struct vmbus_channel *newchannel)
 549 {
 550         struct vmbus_channel *channel;
 551         struct workqueue_struct *wq;
 552         unsigned long flags;
 553         bool fnew = true;
 554
 555         mutex_lock(&vmbus_connection.channel_mutex);
 556
 557         /*
 558          * Now that we have acquired the channel_mutex,
 559          * we can release the potentially racing rescind thread.
 560          */
 561         atomic_dec(&vmbus_connection.offer_in_progress);
 562
 563         list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
 564                 if (guid_equal(&channel->offermsg.offer.if_type,
 565                                &newchannel->offermsg.offer.if_type) &&
 566                     guid_equal(&channel->offermsg.offer.if_instance,
 567                                &newchannel->offermsg.offer.if_instance)) {
 568                         fnew = false;
 569                         break;
 570                 }
 571         }
 572
 573         if (fnew)
 574                 list_add_tail(&newchannel->listentry,
 575                               &vmbus_connection.chn_list);
 576         else {
 577                 /*
 578                  * Check to see if this is a valid sub-channel.
 579                  */
 580                 if (newchannel->offermsg.offer.sub_channel_index == 0) {
 581                         mutex_unlock(&vmbus_connection.channel_mutex);
 582                         /*
 583                          * Don't call free_channel(), because newchannel->kobj
 584                          * is not initialized yet.
 585                          */
 586                         kfree(newchannel);
 587                         WARN_ON_ONCE(1);
 588                         return;
 589                 }
 590                 /*
 591                  * Process the sub-channel.
 592                  */
 593                 newchannel->primary_channel = channel;
 594                 spin_lock_irqsave(&channel->lock, flags);
 595                 list_add_tail(&newchannel->sc_list, &channel->sc_list);
 596                 spin_unlock_irqrestore(&channel->lock, flags);
 597         }
 598
 599         mutex_unlock(&vmbus_connection.channel_mutex);
 600
 601         /*
 602          * vmbus_process_offer() mustn't call channel->sc_creation_callback()
 603          * directly for sub-channels, because sc_creation_callback() ->
 604          * vmbus_open() may never get the host's response to the
 605          * OPEN_CHANNEL message (the host may rescind a channel at any time,
 606          * e.g. in the case of hot removing a NIC), and vmbus_onoffer_rescind()
 607          * may not wake up the vmbus_open() as it's blocked due to a non-zero
 608          * vmbus_connection.offer_in_progress, and finally we have a deadlock.
 609          *
 610          * The above is also true for primary channels, if the related device
 611          * drivers use sync probing mode by default.
 612          *
 613          * And, usually the handling of primary channels and sub-channels can
 614          * depend on each other, so we should offload them to different
 615          * workqueues to avoid possible deadlock, e.g. in sync-probing mode,
 616          * NIC1's netvsc_subchan_work() can race with NIC2's netvsc_probe() ->
 617          * rtnl_lock(), and causes deadlock: the former gets the rtnl_lock
 618          * and waits for all the sub-channels to appear, but the latter
 619          * can't get the rtnl_lock and this blocks the handling of
 620          * sub-channels.
 621          */
 622         INIT_WORK(&newchannel->add_channel_work, vmbus_add_channel_work);
 623         wq = fnew ? vmbus_connection.handle_primary_chan_wq :
 624                     vmbus_connection.handle_sub_chan_wq;
 625         queue_work(wq, &newchannel->add_channel_work);
 626 }
 627
 628 /*
 629  * We use this state to statically distribute the channel interrupt load.
 630  */
 631 static int next_numa_node_id;
 632 /*
 633  * init_vp_index() accesses global variables like next_numa_node_id, and
 634  * it can run concurrently for primary channels and sub-channels: see
 635  * vmbus_process_offer(), so we need the lock to protect the global
 636  * variables.
 637  */
 638 static DEFINE_SPINLOCK(bind_channel_to_cpu_lock);
 639
 640 /*
 641  * Starting with Win8, we can statically distribute the incoming
 642  * channel interrupt load by binding a channel to VCPU.
 643  * We distribute the interrupt loads to one or more NUMA nodes based on
 644  * the channel's affinity_policy.
 645  *
 646  * For pre-win8 hosts or non-performance critical channels we assign the
 647  * first CPU in the first NUMA node.
 648  */
 649 static void init_vp_index(struct vmbus_channel *channel, u16 dev_type)
 650 {
 651         u32 cur_cpu;
 652         bool perf_chn = vmbus_devs[dev_type].perf_device;
 653         struct vmbus_channel *primary = channel->primary_channel;
 654         int next_node;
 655         cpumask_var_t available_mask;
 656         struct cpumask *alloced_mask;
 657
 658         if ((vmbus_proto_version == VERSION_WS2008) ||
 659             (vmbus_proto_version == VERSION_WIN7) || (!perf_chn) ||
 660             !alloc_cpumask_var(&available_mask, GFP_KERNEL)) {
 661                 /*
 662                  * Prior to win8, all channel interrupts are
 663                  * delivered on cpu 0.
 664                  * Also if the channel is not a performance critical
 665                  * channel, bind it to cpu 0.
 666                  * In case alloc_cpumask_var() fails, bind it to cpu 0.
 667                  */
 668                 channel->numa_node = 0;
 669                 channel->target_cpu = 0;
 670                 channel->target_vp = hv_cpu_number_to_vp_number(0);
 671                 return;
 672         }
 673
 674         spin_lock(&bind_channel_to_cpu_lock);
 675
 676         /*
 677          * Based on the channel affinity policy, we will assign the NUMA
 678          * nodes.
 679          */
 680
 681         if ((channel->affinity_policy == HV_BALANCED) || (!primary)) {
 682                 while (true) {
 683                         next_node = next_numa_node_id++;
 684                         if (next_node == nr_node_ids) {
 685                                 next_node = next_numa_node_id = 0;
 686                                 continue;
 687                         }
 688                         if (cpumask_empty(cpumask_of_node(next_node)))
 689                                 continue;
 690                         break;
 691                 }
 692                 channel->numa_node = next_node;
 693                 primary = channel;
 694         }
 695         alloced_mask = &hv_context.hv_numa_map[primary->numa_node];
 696
 697         if (cpumask_weight(alloced_mask) ==
 698             cpumask_weight(cpumask_of_node(primary->numa_node))) {
 699                 /*
 700                  * We have cycled through all the CPUs in the node;
 701                  * reset the alloced map.
 702                  */
 703                 cpumask_clear(alloced_mask);
 704         }
 705
 706         cpumask_xor(available_mask, alloced_mask,
 707                     cpumask_of_node(primary->numa_node));
 708
 709         cur_cpu = -1;
 710
 711         if (primary->affinity_policy == HV_LOCALIZED) {
 712                 /*
 713                  * Normally Hyper-V host doesn't create more subchannels
 714                  * than there are VCPUs on the node but it is possible when not
 715                  * all present VCPUs on the node are initialized by guest.
 716                  * Clear the alloced_cpus_in_node to start over.
 717                  */
 718                 if (cpumask_equal(&primary->alloced_cpus_in_node,
 719                                   cpumask_of_node(primary->numa_node)))
 720                         cpumask_clear(&primary->alloced_cpus_in_node);
 721         }
 722
 723         while (true) {
 724                 cur_cpu = cpumask_next(cur_cpu, available_mask);
 725                 if (cur_cpu >= nr_cpu_ids) {
 726                         cur_cpu = -1;
 727                         cpumask_copy(available_mask,
 728                                      cpumask_of_node(primary->numa_node));
 729                         continue;
 730                 }
 731
 732                 if (primary->affinity_policy == HV_LOCALIZED) {
 733                         /*
 734                          * NOTE: in the case of sub-channel, we clear the
 735                          * sub-channel related bit(s) in
 736                          * primary->alloced_cpus_in_node in
 737                          * hv_process_channel_removal(), so when we
 738                          * reload drivers like hv_netvsc in SMP guest, here
 739                          * we're able to re-allocate
 740                          * bit from primary->alloced_cpus_in_node.
 741                          */
 742                         if (!cpumask_test_cpu(cur_cpu,
 743                                               &primary->alloced_cpus_in_node)) {
 744                                 cpumask_set_cpu(cur_cpu,
 745                                                 &primary->alloced_cpus_in_node);
 746                                 cpumask_set_cpu(cur_cpu, alloced_mask);
 747                                 break;
 748                         }
 749                 } else {
 750                         cpumask_set_cpu(cur_cpu, alloced_mask);
 751                         break;
 752                 }
 753         }
 754
 755         channel->target_cpu = cur_cpu;
 756         channel->target_vp = hv_cpu_number_to_vp_number(cur_cpu);
 757
 758         spin_unlock(&bind_channel_to_cpu_lock);
 759
 760         free_cpumask_var(available_mask);
 761 }
 762
 763 static void vmbus_wait_for_unload(void)
 764 {
 765         int cpu;
 766         void *page_addr;
 767         struct hv_message *msg;
 768         struct vmbus_channel_message_header *hdr;
 769         u32 message_type;
 770
 771         /*
 772          * CHANNELMSG_UNLOAD_RESPONSE is always delivered to the CPU which was
 773          * used for initial contact or to CPU0 depending on host version. When
 774          * we're crashing on a different CPU let's hope that IRQ handler on
 775          * the cpu which receives CHANNELMSG_UNLOAD_RESPONSE is still
 776          * functional and vmbus_unload_response() will complete
 777          * vmbus_connection.unload_event. If not, the last thing we can do is
 778          * read message pages for all CPUs directly.
 779          */
 780         while (1) {
 781                 if (completion_done(&vmbus_connection.unload_event))
 782                         break;
 783
 784                 for_each_online_cpu(cpu) {
 785                         struct hv_per_cpu_context *hv_cpu
 786                                 = per_cpu_ptr(hv_context.cpu_context, cpu);
 787
 788                         page_addr = hv_cpu->synic_message_page;
 789                         msg = (struct hv_message *)page_addr
 790                                 + VMBUS_MESSAGE_SINT;
 791
 792                         message_type = READ_ONCE(msg->header.message_type);
 793                         if (message_type == HVMSG_NONE)
 794                                 continue;
 795
 796                         hdr = (struct vmbus_channel_message_header *)
 797                                 msg->u.payload;
 798
 799                         if (hdr->msgtype == CHANNELMSG_UNLOAD_RESPONSE)
 800                                 complete(&vmbus_connection.unload_event);
 801
 802                         vmbus_signal_eom(msg, message_type);
 803                 }
 804
 805                 mdelay(10);
 806         }
 807
 808         /*
 809          * We're crashing and already got the UNLOAD_RESPONSE, cleanup all
 810          * maybe-pending messages on all CPUs to be able to receive new
 811          * messages after we reconnect.
 812          */
 813         for_each_online_cpu(cpu) {
 814                 struct hv_per_cpu_context *hv_cpu
 815                         = per_cpu_ptr(hv_context.cpu_context, cpu);
 816
 817                 page_addr = hv_cpu->synic_message_page;
 818                 msg = (struct hv_message *)page_addr + VMBUS_MESSAGE_SINT;
 819                 msg->header.message_type = HVMSG_NONE;
 820         }
 821 }
 822
 823 /*
 824  * vmbus_unload_response - Handler for the unload response.
 825  */
 826 static void vmbus_unload_response(struct vmbus_channel_message_header *hdr)
 827 {
 828         /*
 829          * This is a global event; just wakeup the waiting thread.
 830          * Once we successfully unload, we can cleanup the monitor state.
 831          */
 832         complete(&vmbus_connection.unload_event);
 833 }
 834
 835 void vmbus_initiate_unload(bool crash)
 836 {
 837         struct vmbus_channel_message_header hdr;
 838
 839         /* Pre-Win2012R2 hosts don't support reconnect */
 840         if (vmbus_proto_version < VERSION_WIN8_1)
 841                 return;
 842
 843         init_completion(&vmbus_connection.unload_event);
 844         memset(&hdr, 0, sizeof(struct vmbus_channel_message_header));
 845         hdr.msgtype = CHANNELMSG_UNLOAD;
 846         vmbus_post_msg(&hdr, sizeof(struct vmbus_channel_message_header),
 847                        !crash);
 848
 849         /*
 850          * vmbus_initiate_unload() is also called on crash and the crash can be
 851          * happening in an interrupt context, where scheduling is impossible.
 852          */
 853         if (!crash)
 854                 wait_for_completion(&vmbus_connection.unload_event);
 855         else
 856                 vmbus_wait_for_unload();
 857 }
 858
 859 /*
 860  * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
 861  *
 862  */
 863 static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 864 {
 865         struct vmbus_channel_offer_channel *offer;
 866         struct vmbus_channel *newchannel;
 867
 868         offer = (struct vmbus_channel_offer_channel *)hdr;
 869
 870         trace_vmbus_onoffer(offer);
 871
 872         /* Allocate the channel object and save this offer. */
 873         newchannel = alloc_channel();
 874         if (!newchannel) {
 875                 vmbus_release_relid(offer->child_relid);
 876                 atomic_dec(&vmbus_connection.offer_in_progress);
 877                 pr_err("Unable to allocate channel object\n");
 878                 return;
 879         }
 880
 881         /*
 882          * Setup state for signalling the host.
 883          */
 884         newchannel->sig_event = VMBUS_EVENT_CONNECTION_ID;
 885
 886         if (vmbus_proto_version != VERSION_WS2008) {
 887                 newchannel->is_dedicated_interrupt =
 888                                 (offer->is_dedicated_interrupt != 0);
 889                 newchannel->sig_event = offer->connection_id;
 890         }
 891
 892         memcpy(&newchannel->offermsg, offer,
 893                sizeof(struct vmbus_channel_offer_channel));
 894         newchannel->monitor_grp = (u8)offer->monitorid / 32;
 895         newchannel->monitor_bit = (u8)offer->monitorid % 32;
 896
 897         vmbus_process_offer(newchannel);
 898 }
 899
 900 /*
 901  * vmbus_onoffer_rescind - Rescind offer handler.
 902  *
 903  * We queue a work item to process this offer synchronously
 904  */
 905 static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 906 {
 907         struct vmbus_channel_rescind_offer *rescind;
 908         struct vmbus_channel *channel;
 909         struct device *dev;
 910
 911         rescind = (struct vmbus_channel_rescind_offer *)hdr;
 912
 913         trace_vmbus_onoffer_rescind(rescind);
 914
 915         /*
 916          * The offer msg and the corresponding rescind msg
 917          * from the host are guranteed to be ordered -
 918          * offer comes in first and then the rescind.
 919          * Since we process these events in work elements,
 920          * and with preemption, we may end up processing
 921          * the events out of order. Given that we handle these
 922          * work elements on the same CPU, this is possible only
 923          * in the case of preemption. In any case wait here
 924          * until the offer processing has moved beyond the
 925          * point where the channel is discoverable.
 926          */
 927
 928         while (atomic_read(&vmbus_connection.offer_in_progress) != 0) {
 929                 /*
 930                  * We wait here until any channel offer is currently
 931                  * being processed.
 932                  */
 933                 msleep(1);
 934         }
 935
 936         mutex_lock(&vmbus_connection.channel_mutex);
 937         channel = relid2channel(rescind->child_relid);
 938         mutex_unlock(&vmbus_connection.channel_mutex);
 939
 940         if (channel == NULL) {
 941                 /*
 942                  * We failed in processing the offer message;
 943                  * we would have cleaned up the relid in that
 944                  * failure path.
 945                  */
 946                 return;
 947         }
 948
 949         /*
 950          * Before setting channel->rescind in vmbus_rescind_cleanup(), we
 951          * should make sure the channel callback is not running any more.
 952          */
 953         vmbus_reset_channel_cb(channel);
 954
 955         /*
 956          * Now wait for offer handling to complete.
 957          */
 958         vmbus_rescind_cleanup(channel);
 959         while (READ_ONCE(channel->probe_done) == false) {
 960                 /*
 961                  * We wait here until any channel offer is currently
 962                  * being processed.
 963                  */
 964                 msleep(1);
 965         }
 966
 967         /*
 968          * At this point, the rescind handling can proceed safely.
 969          */
 970
 971         if (channel->device_obj) {
 972                 if (channel->chn_rescind_callback) {
 973                         channel->chn_rescind_callback(channel);
 974                         return;
 975                 }
 976                 /*
 977                  * We will have to unregister this device from the
 978                  * driver core.
 979                  */
 980                 dev = get_device(&channel->device_obj->device);
 981                 if (dev) {
 982                         vmbus_device_unregister(channel->device_obj);
 983                         put_device(dev);
 984                 }
 985         }
 986         if (channel->primary_channel != NULL) {
 987                 /*
 988                  * Sub-channel is being rescinded. Following is the channel
 989                  * close sequence when initiated from the driveri (refer to
 990                  * vmbus_close() for details):
 991                  * 1. Close all sub-channels first
 992                  * 2. Then close the primary channel.
 993                  */
 994                 mutex_lock(&vmbus_connection.channel_mutex);
 995                 if (channel->state == CHANNEL_OPEN_STATE) {
 996                         /*
 997                          * The channel is currently not open;
 998                          * it is safe for us to cleanup the channel.
 999                          */
1000                         hv_process_channel_removal(channel);
1001                 } else {
1002                         complete(&channel->rescind_event);
1003                 }
1004                 mutex_unlock(&vmbus_connection.channel_mutex);
1005         }
1006 }
1007
1008 void vmbus_hvsock_device_unregister(struct vmbus_channel *channel)
1009 {
1010         BUG_ON(!is_hvsock_channel(channel));
1011
1012         /* We always get a rescind msg when a connection is closed. */
1013         while (!READ_ONCE(channel->probe_done) || !READ_ONCE(channel->rescind))
1014                 msleep(1);
1015
1016         vmbus_device_unregister(channel->device_obj);
1017 }
1018 EXPORT_SYMBOL_GPL(vmbus_hvsock_device_unregister);
1019
1020
1021 /*
1022  * vmbus_onoffers_delivered -
1023  * This is invoked when all offers have been delivered.
1024  *
1025  * Nothing to do here.
1026  */
1027 static void vmbus_onoffers_delivered(
1028                         struct vmbus_channel_message_header *hdr)
1029 {
1030 }
1031
1032 /*
1033  * vmbus_onopen_result - Open result handler.
1034  *
1035  * This is invoked when we received a response to our channel open request.
1036  * Find the matching request, copy the response and signal the requesting
1037  * thread.
1038  */
1039 static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr)
1040 {
1041         struct vmbus_channel_open_result *result;
1042         struct vmbus_channel_msginfo *msginfo;
1043         struct vmbus_channel_message_header *requestheader;
1044         struct vmbus_channel_open_channel *openmsg;
1045         unsigned long flags;
1046
1047         result = (struct vmbus_channel_open_result *)hdr;
1048
1049         trace_vmbus_onopen_result(result);
1050
1051         /*
1052          * Find the open msg, copy the result and signal/unblock the wait event
1053          */
1054         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
1055
1056         list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
1057                                 msglistentry) {
1058                 requestheader =
1059                         (struct vmbus_channel_message_header *)msginfo->msg;
1060
1061                 if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) {
1062                         openmsg =
1063                         (struct vmbus_channel_open_channel *)msginfo->msg;
1064                         if (openmsg->child_relid == result->child_relid &&
1065                             openmsg->openid == result->openid) {
1066                                 memcpy(&msginfo->response.open_result,
1067                                        result,
1068                                        sizeof(
1069                                         struct vmbus_channel_open_result));
1070                                 complete(&msginfo->waitevent);
1071                                 break;
1072                         }
1073                 }
1074         }
1075         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
1076 }
1077
1078 /*
1079  * vmbus_ongpadl_created - GPADL created handler.
1080  *
1081  * This is invoked when we received a response to our gpadl create request.
1082  * Find the matching request, copy the response and signal the requesting
1083  * thread.
1084  */
1085 static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr)
1086 {
1087         struct vmbus_channel_gpadl_created *gpadlcreated;
1088         struct vmbus_channel_msginfo *msginfo;
1089         struct vmbus_channel_message_header *requestheader;
1090         struct vmbus_channel_gpadl_header *gpadlheader;
1091         unsigned long flags;
1092
1093         gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr;
1094
1095         trace_vmbus_ongpadl_created(gpadlcreated);
1096
1097         /*
1098          * Find the establish msg, copy the result and signal/unblock the wait
1099          * event
1100          */
1101         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
1102
1103         list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
1104                                 msglistentry) {
1105                 requestheader =
1106                         (struct vmbus_channel_message_header *)msginfo->msg;
1107
1108                 if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) {
1109                         gpadlheader =
1110                         (struct vmbus_channel_gpadl_header *)requestheader;
1111
1112                         if ((gpadlcreated->child_relid ==
1113                              gpadlheader->child_relid) &&
1114                             (gpadlcreated->gpadl == gpadlheader->gpadl)) {
1115                                 memcpy(&msginfo->response.gpadl_created,
1116                                        gpadlcreated,
1117                                        sizeof(
1118                                         struct vmbus_channel_gpadl_created));
1119                                 complete(&msginfo->waitevent);
1120                                 break;
1121                         }
1122                 }
1123         }
1124         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
1125 }
1126
1127 /*
1128  * vmbus_ongpadl_torndown - GPADL torndown handler.
1129  *
1130  * This is invoked when we received a response to our gpadl teardown request.
1131  * Find the matching request, copy the response and signal the requesting
1132  * thread.
1133  */
1134 static void vmbus_ongpadl_torndown(
1135                         struct vmbus_channel_message_header *hdr)
1136 {
1137         struct vmbus_channel_gpadl_torndown *gpadl_torndown;
1138         struct vmbus_channel_msginfo *msginfo;
1139         struct vmbus_channel_message_header *requestheader;
1140         struct vmbus_channel_gpadl_teardown *gpadl_teardown;
1141         unsigned long flags;
1142
1143         gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr;
1144
1145         trace_vmbus_ongpadl_torndown(gpadl_torndown);
1146
1147         /*
1148          * Find the open msg, copy the result and signal/unblock the wait event
1149          */
1150         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
1151
1152         list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
1153                                 msglistentry) {
1154                 requestheader =
1155                         (struct vmbus_channel_message_header *)msginfo->msg;
1156
1157                 if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) {
1158                         gpadl_teardown =
1159                         (struct vmbus_channel_gpadl_teardown *)requestheader;
1160
1161                         if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) {
1162                                 memcpy(&msginfo->response.gpadl_torndown,
1163                                        gpadl_torndown,
1164                                        sizeof(
1165                                         struct vmbus_channel_gpadl_torndown));
1166                                 complete(&msginfo->waitevent);
1167                                 break;
1168                         }
1169                 }
1170         }
1171         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
1172 }
1173
1174 /*
1175  * vmbus_onversion_response - Version response handler
1176  *
1177  * This is invoked when we received a response to our initiate contact request.
1178  * Find the matching request, copy the response and signal the requesting
1179  * thread.
1180  */
1181 static void vmbus_onversion_response(
1182                 struct vmbus_channel_message_header *hdr)
1183 {
1184         struct vmbus_channel_msginfo *msginfo;
1185         struct vmbus_channel_message_header *requestheader;
1186         struct vmbus_channel_version_response *version_response;
1187         unsigned long flags;
1188
1189         version_response = (struct vmbus_channel_version_response *)hdr;
1190
1191         trace_vmbus_onversion_response(version_response);
1192
1193         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
1194
1195         list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
1196                                 msglistentry) {
1197                 requestheader =
1198                         (struct vmbus_channel_message_header *)msginfo->msg;
1199
1200                 if (requestheader->msgtype ==
1201                     CHANNELMSG_INITIATE_CONTACT) {
1202                         memcpy(&msginfo->response.version_response,
1203                               version_response,
1204                               sizeof(struct vmbus_channel_version_response));
1205                         complete(&msginfo->waitevent);
1206                 }
1207         }
1208         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
1209 }
1210
1211 /* Channel message dispatch table */
1212 const struct vmbus_channel_message_table_entry
1213 channel_message_table[CHANNELMSG_COUNT] = {
1214         { CHANNELMSG_INVALID,                   0, NULL },
1215         { CHANNELMSG_OFFERCHANNEL,              0, vmbus_onoffer },
1216         { CHANNELMSG_RESCIND_CHANNELOFFER,      0, vmbus_onoffer_rescind },
1217         { CHANNELMSG_REQUESTOFFERS,             0, NULL },
1218         { CHANNELMSG_ALLOFFERS_DELIVERED,       1, vmbus_onoffers_delivered },
1219         { CHANNELMSG_OPENCHANNEL,               0, NULL },
1220         { CHANNELMSG_OPENCHANNEL_RESULT,        1, vmbus_onopen_result },
1221         { CHANNELMSG_CLOSECHANNEL,              0, NULL },
1222         { CHANNELMSG_GPADL_HEADER,              0, NULL },
1223         { CHANNELMSG_GPADL_BODY,                0, NULL },
1224         { CHANNELMSG_GPADL_CREATED,             1, vmbus_ongpadl_created },
1225         { CHANNELMSG_GPADL_TEARDOWN,            0, NULL },
1226         { CHANNELMSG_GPADL_TORNDOWN,            1, vmbus_ongpadl_torndown },
1227         { CHANNELMSG_RELID_RELEASED,            0, NULL },
1228         { CHANNELMSG_INITIATE_CONTACT,          0, NULL },
1229         { CHANNELMSG_VERSION_RESPONSE,          1, vmbus_onversion_response },
1230         { CHANNELMSG_UNLOAD,                    0, NULL },
1231         { CHANNELMSG_UNLOAD_RESPONSE,           1, vmbus_unload_response },
1232         { CHANNELMSG_18,                        0, NULL },
1233         { CHANNELMSG_19,                        0, NULL },
1234         { CHANNELMSG_20,                        0, NULL },
1235         { CHANNELMSG_TL_CONNECT_REQUEST,        0, NULL },
1236 };
1237
1238 /*
1239  * vmbus_onmessage - Handler for channel protocol messages.
1240  *
1241  * This is invoked in the vmbus worker thread context.
1242  */
1243 void vmbus_onmessage(void *context)
1244 {
1245         struct hv_message *msg = context;
1246         struct vmbus_channel_message_header *hdr;
1247         int size;
1248
1249         hdr = (struct vmbus_channel_message_header *)msg->u.payload;
1250         size = msg->header.payload_size;
1251
1252         trace_vmbus_on_message(hdr);
1253
1254         if (hdr->msgtype >= CHANNELMSG_COUNT) {
1255                 pr_err("Received invalid channel message type %d size %d\n",
1256                            hdr->msgtype, size);
1257                 print_hex_dump_bytes("", DUMP_PREFIX_NONE,
1258                                      (unsigned char *)msg->u.payload, size);
1259                 return;
1260         }
1261
1262         if (channel_message_table[hdr->msgtype].message_handler)
1263                 channel_message_table[hdr->msgtype].message_handler(hdr);
1264         else
1265                 pr_err("Unhandled channel message type %d\n", hdr->msgtype);
1266 }
1267
1268 /*
1269  * vmbus_request_offers - Send a request to get all our pending offers.
1270  */
1271 int vmbus_request_offers(void)
1272 {
1273         struct vmbus_channel_message_header *msg;
1274         struct vmbus_channel_msginfo *msginfo;
1275         int ret;
1276
1277         msginfo = kmalloc(sizeof(*msginfo) +
1278                           sizeof(struct vmbus_channel_message_header),
1279                           GFP_KERNEL);
1280         if (!msginfo)
1281                 return -ENOMEM;
1282
1283         msg = (struct vmbus_channel_message_header *)msginfo->msg;
1284
1285         msg->msgtype = CHANNELMSG_REQUESTOFFERS;
1286
1287         ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_message_header),
1288                              true);
1289
1290         trace_vmbus_request_offers(ret);
1291
1292         if (ret != 0) {
1293                 pr_err("Unable to request offers - %d\n", ret);
1294
1295                 goto cleanup;
1296         }
1297
1298 cleanup:
1299         kfree(msginfo);
1300
1301         return ret;
1302 }
1303
1304 static void invoke_sc_cb(struct vmbus_channel *primary_channel)
1305 {
1306         struct list_head *cur, *tmp;
1307         struct vmbus_channel *cur_channel;
1308
1309         if (primary_channel->sc_creation_callback == NULL)
1310                 return;
1311
1312         list_for_each_safe(cur, tmp, &primary_channel->sc_list) {
1313                 cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
1314
1315                 primary_channel->sc_creation_callback(cur_channel);
1316         }
1317 }
1318
1319 void vmbus_set_sc_create_callback(struct vmbus_channel *primary_channel,
1320                                 void (*sc_cr_cb)(struct vmbus_channel *new_sc))
1321 {
1322         primary_channel->sc_creation_callback = sc_cr_cb;
1323 }
1324 EXPORT_SYMBOL_GPL(vmbus_set_sc_create_callback);
1325
1326 bool vmbus_are_subchannels_present(struct vmbus_channel *primary)
1327 {
1328         bool ret;
1329
1330         ret = !list_empty(&primary->sc_list);
1331
1332         if (ret) {
1333                 /*
1334                  * Invoke the callback on sub-channel creation.
1335                  * This will present a uniform interface to the
1336                  * clients.
1337                  */
1338                 invoke_sc_cb(primary);
1339         }
1340
1341         return ret;
1342 }
1343 EXPORT_SYMBOL_GPL(vmbus_are_subchannels_present);
1344
1345 void vmbus_set_chn_rescind_callback(struct vmbus_channel *channel,
1346                 void (*chn_rescind_cb)(struct vmbus_channel *))
1347 {
1348         channel->chn_rescind_callback = chn_rescind_cb;
1349 }
1350 EXPORT_SYMBOL_GPL(vmbus_set_chn_rescind_callback);