linux/drivers/hv/channel_mgmt.c
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   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/sched.h>
  25#include <linux/wait.h>
  26#include <linux/mm.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>
  32
  33#include "hyperv_vmbus.h"
  34
  35struct vmbus_channel_message_table_entry {
  36        enum vmbus_channel_message_type message_type;
  37        void (*message_handler)(struct vmbus_channel_message_header *msg);
  38};
  39
  40
  41/**
  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
  46 *
  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.
  50 *
  51 * The max_fw_version specifies the maximum framework version that
  52 * we can support and max _srv_version specifies the maximum service
  53 * version we can support. A special value MAX_SRV_VER can be
  54 * specified to indicate that we can handle the maximum version
  55 * exposed by the host.
  56 *
  57 * Mainly used by Hyper-V drivers.
  58 */
  59void vmbus_prep_negotiate_resp(struct icmsg_hdr *icmsghdrp,
  60                                struct icmsg_negotiate *negop, u8 *buf,
  61                                int max_fw_version, int max_srv_version)
  62{
  63        int icframe_vercnt;
  64        int icmsg_vercnt;
  65        int i;
  66
  67        icmsghdrp->icmsgsize = 0x10;
  68
  69        negop = (struct icmsg_negotiate *)&buf[
  70                sizeof(struct vmbuspipe_hdr) +
  71                sizeof(struct icmsg_hdr)];
  72
  73        icframe_vercnt = negop->icframe_vercnt;
  74        icmsg_vercnt = negop->icmsg_vercnt;
  75
  76        /*
  77         * Select the framework version number we will
  78         * support.
  79         */
  80
  81        for (i = 0; i < negop->icframe_vercnt; i++) {
  82                if (negop->icversion_data[i].major <= max_fw_version)
  83                        icframe_vercnt = negop->icversion_data[i].major;
  84        }
  85
  86        for (i = negop->icframe_vercnt;
  87                 (i < negop->icframe_vercnt + negop->icmsg_vercnt); i++) {
  88                if (negop->icversion_data[i].major <= max_srv_version)
  89                        icmsg_vercnt = negop->icversion_data[i].major;
  90        }
  91
  92        /*
  93         * Respond with the maximum framework and service
  94         * version numbers we can support.
  95         */
  96        negop->icframe_vercnt = 1;
  97        negop->icmsg_vercnt = 1;
  98        negop->icversion_data[0].major = icframe_vercnt;
  99        negop->icversion_data[0].minor = 0;
 100        negop->icversion_data[1].major = icmsg_vercnt;
 101        negop->icversion_data[1].minor = 0;
 102}
 103
 104EXPORT_SYMBOL_GPL(vmbus_prep_negotiate_resp);
 105
 106/*
 107 * alloc_channel - Allocate and initialize a vmbus channel object
 108 */
 109static struct vmbus_channel *alloc_channel(void)
 110{
 111        struct vmbus_channel *channel;
 112
 113        channel = kzalloc(sizeof(*channel), GFP_ATOMIC);
 114        if (!channel)
 115                return NULL;
 116
 117        spin_lock_init(&channel->inbound_lock);
 118
 119        channel->controlwq = create_workqueue("hv_vmbus_ctl");
 120        if (!channel->controlwq) {
 121                kfree(channel);
 122                return NULL;
 123        }
 124
 125        return channel;
 126}
 127
 128/*
 129 * release_hannel - Release the vmbus channel object itself
 130 */
 131static void release_channel(struct work_struct *work)
 132{
 133        struct vmbus_channel *channel = container_of(work,
 134                                                     struct vmbus_channel,
 135                                                     work);
 136
 137        destroy_workqueue(channel->controlwq);
 138
 139        kfree(channel);
 140}
 141
 142/*
 143 * free_channel - Release the resources used by the vmbus channel object
 144 */
 145static void free_channel(struct vmbus_channel *channel)
 146{
 147
 148        /*
 149         * We have to release the channel's workqueue/thread in the vmbus's
 150         * workqueue/thread context
 151         * ie we can't destroy ourselves.
 152         */
 153        INIT_WORK(&channel->work, release_channel);
 154        queue_work(vmbus_connection.work_queue, &channel->work);
 155}
 156
 157
 158
 159/*
 160 * vmbus_process_rescind_offer -
 161 * Rescind the offer by initiating a device removal
 162 */
 163static void vmbus_process_rescind_offer(struct work_struct *work)
 164{
 165        struct vmbus_channel *channel = container_of(work,
 166                                                     struct vmbus_channel,
 167                                                     work);
 168        unsigned long flags;
 169        struct vmbus_channel_relid_released msg;
 170
 171        vmbus_device_unregister(channel->device_obj);
 172        memset(&msg, 0, sizeof(struct vmbus_channel_relid_released));
 173        msg.child_relid = channel->offermsg.child_relid;
 174        msg.header.msgtype = CHANNELMSG_RELID_RELEASED;
 175        vmbus_post_msg(&msg, sizeof(struct vmbus_channel_relid_released));
 176
 177        spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
 178        list_del(&channel->listentry);
 179        spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
 180        free_channel(channel);
 181}
 182
 183void vmbus_free_channels(void)
 184{
 185        struct vmbus_channel *channel;
 186
 187        list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
 188                vmbus_device_unregister(channel->device_obj);
 189                kfree(channel->device_obj);
 190                free_channel(channel);
 191        }
 192}
 193
 194/*
 195 * vmbus_process_offer - Process the offer by creating a channel/device
 196 * associated with this offer
 197 */
 198static void vmbus_process_offer(struct work_struct *work)
 199{
 200        struct vmbus_channel *newchannel = container_of(work,
 201                                                        struct vmbus_channel,
 202                                                        work);
 203        struct vmbus_channel *channel;
 204        bool fnew = true;
 205        int ret;
 206        unsigned long flags;
 207
 208        /* The next possible work is rescind handling */
 209        INIT_WORK(&newchannel->work, vmbus_process_rescind_offer);
 210
 211        /* Make sure this is a new offer */
 212        spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
 213
 214        list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
 215                if (!uuid_le_cmp(channel->offermsg.offer.if_type,
 216                        newchannel->offermsg.offer.if_type) &&
 217                        !uuid_le_cmp(channel->offermsg.offer.if_instance,
 218                                newchannel->offermsg.offer.if_instance)) {
 219                        fnew = false;
 220                        break;
 221                }
 222        }
 223
 224        if (fnew)
 225                list_add_tail(&newchannel->listentry,
 226                              &vmbus_connection.chn_list);
 227
 228        spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
 229
 230        if (!fnew) {
 231                free_channel(newchannel);
 232                return;
 233        }
 234
 235        /*
 236         * Start the process of binding this offer to the driver
 237         * We need to set the DeviceObject field before calling
 238         * vmbus_child_dev_add()
 239         */
 240        newchannel->device_obj = vmbus_device_create(
 241                &newchannel->offermsg.offer.if_type,
 242                &newchannel->offermsg.offer.if_instance,
 243                newchannel);
 244
 245        /*
 246         * Add the new device to the bus. This will kick off device-driver
 247         * binding which eventually invokes the device driver's AddDevice()
 248         * method.
 249         */
 250        ret = vmbus_device_register(newchannel->device_obj);
 251        if (ret != 0) {
 252                pr_err("unable to add child device object (relid %d)\n",
 253                           newchannel->offermsg.child_relid);
 254
 255                spin_lock_irqsave(&vmbus_connection.channel_lock, flags);
 256                list_del(&newchannel->listentry);
 257                spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
 258                kfree(newchannel->device_obj);
 259
 260                free_channel(newchannel);
 261        } else {
 262                /*
 263                 * This state is used to indicate a successful open
 264                 * so that when we do close the channel normally, we
 265                 * can cleanup properly
 266                 */
 267                newchannel->state = CHANNEL_OPEN_STATE;
 268        }
 269}
 270
 271enum {
 272        IDE = 0,
 273        SCSI,
 274        NIC,
 275        MAX_PERF_CHN,
 276};
 277
 278/*
 279 * This is an array of device_ids (device types) that are performance critical.
 280 * We attempt to distribute the interrupt load for these devices across
 281 * all available CPUs.
 282 */
 283static const struct hv_vmbus_device_id hp_devs[] = {
 284        /* IDE */
 285        { HV_IDE_GUID, },
 286        /* Storage - SCSI */
 287        { HV_SCSI_GUID, },
 288        /* Network */
 289        { HV_NIC_GUID, },
 290};
 291
 292
 293/*
 294 * We use this state to statically distribute the channel interrupt load.
 295 */
 296static u32  next_vp;
 297
 298/*
 299 * Starting with Win8, we can statically distribute the incoming
 300 * channel interrupt load by binding a channel to VCPU. We
 301 * implement here a simple round robin scheme for distributing
 302 * the interrupt load.
 303 * We will bind channels that are not performance critical to cpu 0 and
 304 * performance critical channels (IDE, SCSI and Network) will be uniformly
 305 * distributed across all available CPUs.
 306 */
 307static u32 get_vp_index(uuid_le *type_guid)
 308{
 309        u32 cur_cpu;
 310        int i;
 311        bool perf_chn = false;
 312        u32 max_cpus = num_online_cpus();
 313
 314        for (i = IDE; i < MAX_PERF_CHN; i++) {
 315                if (!memcmp(type_guid->b, hp_devs[i].guid,
 316                                 sizeof(uuid_le))) {
 317                        perf_chn = true;
 318                        break;
 319                }
 320        }
 321        if ((vmbus_proto_version == VERSION_WS2008) ||
 322            (vmbus_proto_version == VERSION_WIN7) || (!perf_chn)) {
 323                /*
 324                 * Prior to win8, all channel interrupts are
 325                 * delivered on cpu 0.
 326                 * Also if the channel is not a performance critical
 327                 * channel, bind it to cpu 0.
 328                 */
 329                return 0;
 330        }
 331        cur_cpu = (++next_vp % max_cpus);
 332        return hv_context.vp_index[cur_cpu];
 333}
 334
 335/*
 336 * vmbus_onoffer - Handler for channel offers from vmbus in parent partition.
 337 *
 338 */
 339static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 340{
 341        struct vmbus_channel_offer_channel *offer;
 342        struct vmbus_channel *newchannel;
 343
 344        offer = (struct vmbus_channel_offer_channel *)hdr;
 345
 346        /* Allocate the channel object and save this offer. */
 347        newchannel = alloc_channel();
 348        if (!newchannel) {
 349                pr_err("Unable to allocate channel object\n");
 350                return;
 351        }
 352
 353        /*
 354         * By default we setup state to enable batched
 355         * reading. A specific service can choose to
 356         * disable this prior to opening the channel.
 357         */
 358        newchannel->batched_reading = true;
 359
 360        /*
 361         * Setup state for signalling the host.
 362         */
 363        newchannel->sig_event = (struct hv_input_signal_event *)
 364                                (ALIGN((unsigned long)
 365                                &newchannel->sig_buf,
 366                                HV_HYPERCALL_PARAM_ALIGN));
 367
 368        newchannel->sig_event->connectionid.asu32 = 0;
 369        newchannel->sig_event->connectionid.u.id = VMBUS_EVENT_CONNECTION_ID;
 370        newchannel->sig_event->flag_number = 0;
 371        newchannel->sig_event->rsvdz = 0;
 372
 373        if (vmbus_proto_version != VERSION_WS2008) {
 374                newchannel->is_dedicated_interrupt =
 375                                (offer->is_dedicated_interrupt != 0);
 376                newchannel->sig_event->connectionid.u.id =
 377                                offer->connection_id;
 378        }
 379
 380        newchannel->target_vp = get_vp_index(&offer->offer.if_type);
 381
 382        memcpy(&newchannel->offermsg, offer,
 383               sizeof(struct vmbus_channel_offer_channel));
 384        newchannel->monitor_grp = (u8)offer->monitorid / 32;
 385        newchannel->monitor_bit = (u8)offer->monitorid % 32;
 386
 387        INIT_WORK(&newchannel->work, vmbus_process_offer);
 388        queue_work(newchannel->controlwq, &newchannel->work);
 389}
 390
 391/*
 392 * vmbus_onoffer_rescind - Rescind offer handler.
 393 *
 394 * We queue a work item to process this offer synchronously
 395 */
 396static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)
 397{
 398        struct vmbus_channel_rescind_offer *rescind;
 399        struct vmbus_channel *channel;
 400
 401        rescind = (struct vmbus_channel_rescind_offer *)hdr;
 402        channel = relid2channel(rescind->child_relid);
 403
 404        if (channel == NULL)
 405                /* Just return here, no channel found */
 406                return;
 407
 408        /* work is initialized for vmbus_process_rescind_offer() from
 409         * vmbus_process_offer() where the channel got created */
 410        queue_work(channel->controlwq, &channel->work);
 411}
 412
 413/*
 414 * vmbus_onoffers_delivered -
 415 * This is invoked when all offers have been delivered.
 416 *
 417 * Nothing to do here.
 418 */
 419static void vmbus_onoffers_delivered(
 420                        struct vmbus_channel_message_header *hdr)
 421{
 422}
 423
 424/*
 425 * vmbus_onopen_result - Open result handler.
 426 *
 427 * This is invoked when we received a response to our channel open request.
 428 * Find the matching request, copy the response and signal the requesting
 429 * thread.
 430 */
 431static void vmbus_onopen_result(struct vmbus_channel_message_header *hdr)
 432{
 433        struct vmbus_channel_open_result *result;
 434        struct vmbus_channel_msginfo *msginfo;
 435        struct vmbus_channel_message_header *requestheader;
 436        struct vmbus_channel_open_channel *openmsg;
 437        unsigned long flags;
 438
 439        result = (struct vmbus_channel_open_result *)hdr;
 440
 441        /*
 442         * Find the open msg, copy the result and signal/unblock the wait event
 443         */
 444        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 445
 446        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
 447                                msglistentry) {
 448                requestheader =
 449                        (struct vmbus_channel_message_header *)msginfo->msg;
 450
 451                if (requestheader->msgtype == CHANNELMSG_OPENCHANNEL) {
 452                        openmsg =
 453                        (struct vmbus_channel_open_channel *)msginfo->msg;
 454                        if (openmsg->child_relid == result->child_relid &&
 455                            openmsg->openid == result->openid) {
 456                                memcpy(&msginfo->response.open_result,
 457                                       result,
 458                                       sizeof(
 459                                        struct vmbus_channel_open_result));
 460                                complete(&msginfo->waitevent);
 461                                break;
 462                        }
 463                }
 464        }
 465        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 466}
 467
 468/*
 469 * vmbus_ongpadl_created - GPADL created handler.
 470 *
 471 * This is invoked when we received a response to our gpadl create request.
 472 * Find the matching request, copy the response and signal the requesting
 473 * thread.
 474 */
 475static void vmbus_ongpadl_created(struct vmbus_channel_message_header *hdr)
 476{
 477        struct vmbus_channel_gpadl_created *gpadlcreated;
 478        struct vmbus_channel_msginfo *msginfo;
 479        struct vmbus_channel_message_header *requestheader;
 480        struct vmbus_channel_gpadl_header *gpadlheader;
 481        unsigned long flags;
 482
 483        gpadlcreated = (struct vmbus_channel_gpadl_created *)hdr;
 484
 485        /*
 486         * Find the establish msg, copy the result and signal/unblock the wait
 487         * event
 488         */
 489        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 490
 491        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
 492                                msglistentry) {
 493                requestheader =
 494                        (struct vmbus_channel_message_header *)msginfo->msg;
 495
 496                if (requestheader->msgtype == CHANNELMSG_GPADL_HEADER) {
 497                        gpadlheader =
 498                        (struct vmbus_channel_gpadl_header *)requestheader;
 499
 500                        if ((gpadlcreated->child_relid ==
 501                             gpadlheader->child_relid) &&
 502                            (gpadlcreated->gpadl == gpadlheader->gpadl)) {
 503                                memcpy(&msginfo->response.gpadl_created,
 504                                       gpadlcreated,
 505                                       sizeof(
 506                                        struct vmbus_channel_gpadl_created));
 507                                complete(&msginfo->waitevent);
 508                                break;
 509                        }
 510                }
 511        }
 512        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 513}
 514
 515/*
 516 * vmbus_ongpadl_torndown - GPADL torndown handler.
 517 *
 518 * This is invoked when we received a response to our gpadl teardown request.
 519 * Find the matching request, copy the response and signal the requesting
 520 * thread.
 521 */
 522static void vmbus_ongpadl_torndown(
 523                        struct vmbus_channel_message_header *hdr)
 524{
 525        struct vmbus_channel_gpadl_torndown *gpadl_torndown;
 526        struct vmbus_channel_msginfo *msginfo;
 527        struct vmbus_channel_message_header *requestheader;
 528        struct vmbus_channel_gpadl_teardown *gpadl_teardown;
 529        unsigned long flags;
 530
 531        gpadl_torndown = (struct vmbus_channel_gpadl_torndown *)hdr;
 532
 533        /*
 534         * Find the open msg, copy the result and signal/unblock the wait event
 535         */
 536        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 537
 538        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
 539                                msglistentry) {
 540                requestheader =
 541                        (struct vmbus_channel_message_header *)msginfo->msg;
 542
 543                if (requestheader->msgtype == CHANNELMSG_GPADL_TEARDOWN) {
 544                        gpadl_teardown =
 545                        (struct vmbus_channel_gpadl_teardown *)requestheader;
 546
 547                        if (gpadl_torndown->gpadl == gpadl_teardown->gpadl) {
 548                                memcpy(&msginfo->response.gpadl_torndown,
 549                                       gpadl_torndown,
 550                                       sizeof(
 551                                        struct vmbus_channel_gpadl_torndown));
 552                                complete(&msginfo->waitevent);
 553                                break;
 554                        }
 555                }
 556        }
 557        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 558}
 559
 560/*
 561 * vmbus_onversion_response - Version response handler
 562 *
 563 * This is invoked when we received a response to our initiate contact request.
 564 * Find the matching request, copy the response and signal the requesting
 565 * thread.
 566 */
 567static void vmbus_onversion_response(
 568                struct vmbus_channel_message_header *hdr)
 569{
 570        struct vmbus_channel_msginfo *msginfo;
 571        struct vmbus_channel_message_header *requestheader;
 572        struct vmbus_channel_version_response *version_response;
 573        unsigned long flags;
 574
 575        version_response = (struct vmbus_channel_version_response *)hdr;
 576        spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 577
 578        list_for_each_entry(msginfo, &vmbus_connection.chn_msg_list,
 579                                msglistentry) {
 580                requestheader =
 581                        (struct vmbus_channel_message_header *)msginfo->msg;
 582
 583                if (requestheader->msgtype ==
 584                    CHANNELMSG_INITIATE_CONTACT) {
 585                        memcpy(&msginfo->response.version_response,
 586                              version_response,
 587                              sizeof(struct vmbus_channel_version_response));
 588                        complete(&msginfo->waitevent);
 589                }
 590        }
 591        spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 592}
 593
 594/* Channel message dispatch table */
 595static struct vmbus_channel_message_table_entry
 596        channel_message_table[CHANNELMSG_COUNT] = {
 597        {CHANNELMSG_INVALID,                    NULL},
 598        {CHANNELMSG_OFFERCHANNEL,               vmbus_onoffer},
 599        {CHANNELMSG_RESCIND_CHANNELOFFER,       vmbus_onoffer_rescind},
 600        {CHANNELMSG_REQUESTOFFERS,              NULL},
 601        {CHANNELMSG_ALLOFFERS_DELIVERED,        vmbus_onoffers_delivered},
 602        {CHANNELMSG_OPENCHANNEL,                NULL},
 603        {CHANNELMSG_OPENCHANNEL_RESULT, vmbus_onopen_result},
 604        {CHANNELMSG_CLOSECHANNEL,               NULL},
 605        {CHANNELMSG_GPADL_HEADER,               NULL},
 606        {CHANNELMSG_GPADL_BODY,         NULL},
 607        {CHANNELMSG_GPADL_CREATED,              vmbus_ongpadl_created},
 608        {CHANNELMSG_GPADL_TEARDOWN,             NULL},
 609        {CHANNELMSG_GPADL_TORNDOWN,             vmbus_ongpadl_torndown},
 610        {CHANNELMSG_RELID_RELEASED,             NULL},
 611        {CHANNELMSG_INITIATE_CONTACT,           NULL},
 612        {CHANNELMSG_VERSION_RESPONSE,           vmbus_onversion_response},
 613        {CHANNELMSG_UNLOAD,                     NULL},
 614};
 615
 616/*
 617 * vmbus_onmessage - Handler for channel protocol messages.
 618 *
 619 * This is invoked in the vmbus worker thread context.
 620 */
 621void vmbus_onmessage(void *context)
 622{
 623        struct hv_message *msg = context;
 624        struct vmbus_channel_message_header *hdr;
 625        int size;
 626
 627        hdr = (struct vmbus_channel_message_header *)msg->u.payload;
 628        size = msg->header.payload_size;
 629
 630        if (hdr->msgtype >= CHANNELMSG_COUNT) {
 631                pr_err("Received invalid channel message type %d size %d\n",
 632                           hdr->msgtype, size);
 633                print_hex_dump_bytes("", DUMP_PREFIX_NONE,
 634                                     (unsigned char *)msg->u.payload, size);
 635                return;
 636        }
 637
 638        if (channel_message_table[hdr->msgtype].message_handler)
 639                channel_message_table[hdr->msgtype].message_handler(hdr);
 640        else
 641                pr_err("Unhandled channel message type %d\n", hdr->msgtype);
 642}
 643
 644/*
 645 * vmbus_request_offers - Send a request to get all our pending offers.
 646 */
 647int vmbus_request_offers(void)
 648{
 649        struct vmbus_channel_message_header *msg;
 650        struct vmbus_channel_msginfo *msginfo;
 651        int ret, t;
 652
 653        msginfo = kmalloc(sizeof(*msginfo) +
 654                          sizeof(struct vmbus_channel_message_header),
 655                          GFP_KERNEL);
 656        if (!msginfo)
 657                return -ENOMEM;
 658
 659        init_completion(&msginfo->waitevent);
 660
 661        msg = (struct vmbus_channel_message_header *)msginfo->msg;
 662
 663        msg->msgtype = CHANNELMSG_REQUESTOFFERS;
 664
 665
 666        ret = vmbus_post_msg(msg,
 667                               sizeof(struct vmbus_channel_message_header));
 668        if (ret != 0) {
 669                pr_err("Unable to request offers - %d\n", ret);
 670
 671                goto cleanup;
 672        }
 673
 674        t = wait_for_completion_timeout(&msginfo->waitevent, 5*HZ);
 675        if (t == 0) {
 676                ret = -ETIMEDOUT;
 677                goto cleanup;
 678        }
 679
 680
 681
 682cleanup:
 683        kfree(msginfo);
 684
 685        return ret;
 686}
 687
 688/* eof */
 689
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