drivers/hv/channel.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (c) 2009, Microsoft Corporation.
   4  *
   5  * Authors:
   6  *   Haiyang Zhang <haiyangz@microsoft.com>
   7  *   Hank Janssen  <hjanssen@microsoft.com>
   8  */
   9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10
  11 #include <linux/kernel.h>
  12 #include <linux/sched.h>
  13 #include <linux/wait.h>
  14 #include <linux/mm.h>
  15 #include <linux/slab.h>
  16 #include <linux/module.h>
  17 #include <linux/hyperv.h>
  18 #include <linux/uio.h>
  19 #include <linux/interrupt.h>
  20 #include <asm/page.h>
  21 #include <asm/mshyperv.h>
  22
  23 #include "hyperv_vmbus.h"
  24
  25 /*
  26  * hv_gpadl_size - Return the real size of a gpadl, the size that Hyper-V uses
  27  *
  28  * For BUFFER gpadl, Hyper-V uses the exact same size as the guest does.
  29  *
  30  * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the header
  31  * (because of the alignment requirement), however, the hypervisor only
  32  * uses the first HV_HYP_PAGE_SIZE as the header, therefore leaving a
  33  * (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap. And since there are two rings in a
  34  * ringbuffer, the total size for a RING gpadl that Hyper-V uses is the
  35  * total size that the guest uses minus twice of the gap size.
  36  */
  37 static inline u32 hv_gpadl_size(enum hv_gpadl_type type, u32 size)
  38 {
  39         switch (type) {
  40         case HV_GPADL_BUFFER:
  41                 return size;
  42         case HV_GPADL_RING:
  43                 /* The size of a ringbuffer must be page-aligned */
  44                 BUG_ON(size % PAGE_SIZE);
  45                 /*
  46                  * Two things to notice here:
  47                  * 1) We're processing two ring buffers as a unit
  48                  * 2) We're skipping any space larger than HV_HYP_PAGE_SIZE in
  49                  * the first guest-size page of each of the two ring buffers.
  50                  * So we effectively subtract out two guest-size pages, and add
  51                  * back two Hyper-V size pages.
  52                  */
  53                 return size - 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
  54         }
  55         BUG();
  56         return 0;
  57 }
  58
  59 /*
  60  * hv_ring_gpadl_send_hvpgoffset - Calculate the send offset (in unit of
  61  *                                 HV_HYP_PAGE) in a ring gpadl based on the
  62  *                                 offset in the guest
  63  *
  64  * @offset: the offset (in bytes) where the send ringbuffer starts in the
  65  *               virtual address space of the guest
  66  */
  67 static inline u32 hv_ring_gpadl_send_hvpgoffset(u32 offset)
  68 {
  69
  70         /*
  71          * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the
  72          * header (because of the alignment requirement), however, the
  73          * hypervisor only uses the first HV_HYP_PAGE_SIZE as the header,
  74          * therefore leaving a (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap.
  75          *
  76          * And to calculate the effective send offset in gpadl, we need to
  77          * substract this gap.
  78          */
  79         return (offset - (PAGE_SIZE - HV_HYP_PAGE_SIZE)) >> HV_HYP_PAGE_SHIFT;
  80 }
  81
  82 /*
  83  * hv_gpadl_hvpfn - Return the Hyper-V page PFN of the @i th Hyper-V page in
  84  *                  the gpadl
  85  *
  86  * @type: the type of the gpadl
  87  * @kbuffer: the pointer to the gpadl in the guest
  88  * @size: the total size (in bytes) of the gpadl
  89  * @send_offset: the offset (in bytes) where the send ringbuffer starts in the
  90  *               virtual address space of the guest
  91  * @i: the index
  92  */
  93 static inline u64 hv_gpadl_hvpfn(enum hv_gpadl_type type, void *kbuffer,
  94                                  u32 size, u32 send_offset, int i)
  95 {
  96         int send_idx = hv_ring_gpadl_send_hvpgoffset(send_offset);
  97         unsigned long delta = 0UL;
  98
  99         switch (type) {
 100         case HV_GPADL_BUFFER:
 101                 break;
 102         case HV_GPADL_RING:
 103                 if (i == 0)
 104                         delta = 0;
 105                 else if (i <= send_idx)
 106                         delta = PAGE_SIZE - HV_HYP_PAGE_SIZE;
 107                 else
 108                         delta = 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
 109                 break;
 110         default:
 111                 BUG();
 112                 break;
 113         }
 114
 115         return virt_to_hvpfn(kbuffer + delta + (HV_HYP_PAGE_SIZE * i));
 116 }
 117
 118 /*
 119  * vmbus_setevent- Trigger an event notification on the specified
 120  * channel.
 121  */
 122 void vmbus_setevent(struct vmbus_channel *channel)
 123 {
 124         struct hv_monitor_page *monitorpage;
 125
 126         trace_vmbus_setevent(channel);
 127
 128         /*
 129          * For channels marked as in "low latency" mode
 130          * bypass the monitor page mechanism.
 131          */
 132         if (channel->offermsg.monitor_allocated && !channel->low_latency) {
 133                 vmbus_send_interrupt(channel->offermsg.child_relid);
 134
 135                 /* Get the child to parent monitor page */
 136                 monitorpage = vmbus_connection.monitor_pages[1];
 137
 138                 sync_set_bit(channel->monitor_bit,
 139                         (unsigned long *)&monitorpage->trigger_group
 140                                         [channel->monitor_grp].pending);
 141
 142         } else {
 143                 vmbus_set_event(channel);
 144         }
 145 }
 146 EXPORT_SYMBOL_GPL(vmbus_setevent);
 147
 148 /* vmbus_free_ring - drop mapping of ring buffer */
 149 void vmbus_free_ring(struct vmbus_channel *channel)
 150 {
 151         hv_ringbuffer_cleanup(&channel->outbound);
 152         hv_ringbuffer_cleanup(&channel->inbound);
 153
 154         if (channel->ringbuffer_page) {
 155                 __free_pages(channel->ringbuffer_page,
 156                              get_order(channel->ringbuffer_pagecount
 157                                        << PAGE_SHIFT));
 158                 channel->ringbuffer_page = NULL;
 159         }
 160 }
 161 EXPORT_SYMBOL_GPL(vmbus_free_ring);
 162
 163 /* vmbus_alloc_ring - allocate and map pages for ring buffer */
 164 int vmbus_alloc_ring(struct vmbus_channel *newchannel,
 165                      u32 send_size, u32 recv_size)
 166 {
 167         struct page *page;
 168         int order;
 169
 170         if (send_size % PAGE_SIZE || recv_size % PAGE_SIZE)
 171                 return -EINVAL;
 172
 173         /* Allocate the ring buffer */
 174         order = get_order(send_size + recv_size);
 175         page = alloc_pages_node(cpu_to_node(newchannel->target_cpu),
 176                                 GFP_KERNEL|__GFP_ZERO, order);
 177
 178         if (!page)
 179                 page = alloc_pages(GFP_KERNEL|__GFP_ZERO, order);
 180
 181         if (!page)
 182                 return -ENOMEM;
 183
 184         newchannel->ringbuffer_page = page;
 185         newchannel->ringbuffer_pagecount = (send_size + recv_size) >> PAGE_SHIFT;
 186         newchannel->ringbuffer_send_offset = send_size >> PAGE_SHIFT;
 187
 188         return 0;
 189 }
 190 EXPORT_SYMBOL_GPL(vmbus_alloc_ring);
 191
 192 /* Used for Hyper-V Socket: a guest client's connect() to the host */
 193 int vmbus_send_tl_connect_request(const guid_t *shv_guest_servie_id,
 194                                   const guid_t *shv_host_servie_id)
 195 {
 196         struct vmbus_channel_tl_connect_request conn_msg;
 197         int ret;
 198
 199         memset(&conn_msg, 0, sizeof(conn_msg));
 200         conn_msg.header.msgtype = CHANNELMSG_TL_CONNECT_REQUEST;
 201         conn_msg.guest_endpoint_id = *shv_guest_servie_id;
 202         conn_msg.host_service_id = *shv_host_servie_id;
 203
 204         ret = vmbus_post_msg(&conn_msg, sizeof(conn_msg), true);
 205
 206         trace_vmbus_send_tl_connect_request(&conn_msg, ret);
 207
 208         return ret;
 209 }
 210 EXPORT_SYMBOL_GPL(vmbus_send_tl_connect_request);
 211
 212 /*
 213  * Set/change the vCPU (@target_vp) the channel (@child_relid) will interrupt.
 214  *
 215  * CHANNELMSG_MODIFYCHANNEL messages are aynchronous.  Also, Hyper-V does not
 216  * ACK such messages.  IOW we can't know when the host will stop interrupting
 217  * the "old" vCPU and start interrupting the "new" vCPU for the given channel.
 218  *
 219  * The CHANNELMSG_MODIFYCHANNEL message type is supported since VMBus version
 220  * VERSION_WIN10_V4_1.
 221  */
 222 int vmbus_send_modifychannel(u32 child_relid, u32 target_vp)
 223 {
 224         struct vmbus_channel_modifychannel conn_msg;
 225         int ret;
 226
 227         memset(&conn_msg, 0, sizeof(conn_msg));
 228         conn_msg.header.msgtype = CHANNELMSG_MODIFYCHANNEL;
 229         conn_msg.child_relid = child_relid;
 230         conn_msg.target_vp = target_vp;
 231
 232         ret = vmbus_post_msg(&conn_msg, sizeof(conn_msg), true);
 233
 234         trace_vmbus_send_modifychannel(&conn_msg, ret);
 235
 236         return ret;
 237 }
 238 EXPORT_SYMBOL_GPL(vmbus_send_modifychannel);
 239
 240 /*
 241  * create_gpadl_header - Creates a gpadl for the specified buffer
 242  */
 243 static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
 244                                u32 size, u32 send_offset,
 245                                struct vmbus_channel_msginfo **msginfo)
 246 {
 247         int i;
 248         int pagecount;
 249         struct vmbus_channel_gpadl_header *gpadl_header;
 250         struct vmbus_channel_gpadl_body *gpadl_body;
 251         struct vmbus_channel_msginfo *msgheader;
 252         struct vmbus_channel_msginfo *msgbody = NULL;
 253         u32 msgsize;
 254
 255         int pfnsum, pfncount, pfnleft, pfncurr, pfnsize;
 256
 257         pagecount = hv_gpadl_size(type, size) >> HV_HYP_PAGE_SHIFT;
 258
 259         /* do we need a gpadl body msg */
 260         pfnsize = MAX_SIZE_CHANNEL_MESSAGE -
 261                   sizeof(struct vmbus_channel_gpadl_header) -
 262                   sizeof(struct gpa_range);
 263         pfncount = pfnsize / sizeof(u64);
 264
 265         if (pagecount > pfncount) {
 266                 /* we need a gpadl body */
 267                 /* fill in the header */
 268                 msgsize = sizeof(struct vmbus_channel_msginfo) +
 269                           sizeof(struct vmbus_channel_gpadl_header) +
 270                           sizeof(struct gpa_range) + pfncount * sizeof(u64);
 271                 msgheader =  kzalloc(msgsize, GFP_KERNEL);
 272                 if (!msgheader)
 273                         goto nomem;
 274
 275                 INIT_LIST_HEAD(&msgheader->submsglist);
 276                 msgheader->msgsize = msgsize;
 277
 278                 gpadl_header = (struct vmbus_channel_gpadl_header *)
 279                         msgheader->msg;
 280                 gpadl_header->rangecount = 1;
 281                 gpadl_header->range_buflen = sizeof(struct gpa_range) +
 282                                          pagecount * sizeof(u64);
 283                 gpadl_header->range[0].byte_offset = 0;
 284                 gpadl_header->range[0].byte_count = hv_gpadl_size(type, size);
 285                 for (i = 0; i < pfncount; i++)
 286                         gpadl_header->range[0].pfn_array[i] = hv_gpadl_hvpfn(
 287                                 type, kbuffer, size, send_offset, i);
 288                 *msginfo = msgheader;
 289
 290                 pfnsum = pfncount;
 291                 pfnleft = pagecount - pfncount;
 292
 293                 /* how many pfns can we fit */
 294                 pfnsize = MAX_SIZE_CHANNEL_MESSAGE -
 295                           sizeof(struct vmbus_channel_gpadl_body);
 296                 pfncount = pfnsize / sizeof(u64);
 297
 298                 /* fill in the body */
 299                 while (pfnleft) {
 300                         if (pfnleft > pfncount)
 301                                 pfncurr = pfncount;
 302                         else
 303                                 pfncurr = pfnleft;
 304
 305                         msgsize = sizeof(struct vmbus_channel_msginfo) +
 306                                   sizeof(struct vmbus_channel_gpadl_body) +
 307                                   pfncurr * sizeof(u64);
 308                         msgbody = kzalloc(msgsize, GFP_KERNEL);
 309
 310                         if (!msgbody) {
 311                                 struct vmbus_channel_msginfo *pos = NULL;
 312                                 struct vmbus_channel_msginfo *tmp = NULL;
 313                                 /*
 314                                  * Free up all the allocated messages.
 315                                  */
 316                                 list_for_each_entry_safe(pos, tmp,
 317                                         &msgheader->submsglist,
 318                                         msglistentry) {
 319
 320                                         list_del(&pos->msglistentry);
 321                                         kfree(pos);
 322                                 }
 323
 324                                 goto nomem;
 325                         }
 326
 327                         msgbody->msgsize = msgsize;
 328                         gpadl_body =
 329                                 (struct vmbus_channel_gpadl_body *)msgbody->msg;
 330
 331                         /*
 332                          * Gpadl is u32 and we are using a pointer which could
 333                          * be 64-bit
 334                          * This is governed by the guest/host protocol and
 335                          * so the hypervisor guarantees that this is ok.
 336                          */
 337                         for (i = 0; i < pfncurr; i++)
 338                                 gpadl_body->pfn[i] = hv_gpadl_hvpfn(type,
 339                                         kbuffer, size, send_offset, pfnsum + i);
 340
 341                         /* add to msg header */
 342                         list_add_tail(&msgbody->msglistentry,
 343                                       &msgheader->submsglist);
 344                         pfnsum += pfncurr;
 345                         pfnleft -= pfncurr;
 346                 }
 347         } else {
 348                 /* everything fits in a header */
 349                 msgsize = sizeof(struct vmbus_channel_msginfo) +
 350                           sizeof(struct vmbus_channel_gpadl_header) +
 351                           sizeof(struct gpa_range) + pagecount * sizeof(u64);
 352                 msgheader = kzalloc(msgsize, GFP_KERNEL);
 353                 if (msgheader == NULL)
 354                         goto nomem;
 355
 356                 INIT_LIST_HEAD(&msgheader->submsglist);
 357                 msgheader->msgsize = msgsize;
 358
 359                 gpadl_header = (struct vmbus_channel_gpadl_header *)
 360                         msgheader->msg;
 361                 gpadl_header->rangecount = 1;
 362                 gpadl_header->range_buflen = sizeof(struct gpa_range) +
 363                                          pagecount * sizeof(u64);
 364                 gpadl_header->range[0].byte_offset = 0;
 365                 gpadl_header->range[0].byte_count = hv_gpadl_size(type, size);
 366                 for (i = 0; i < pagecount; i++)
 367                         gpadl_header->range[0].pfn_array[i] = hv_gpadl_hvpfn(
 368                                 type, kbuffer, size, send_offset, i);
 369
 370                 *msginfo = msgheader;
 371         }
 372
 373         return 0;
 374 nomem:
 375         kfree(msgheader);
 376         kfree(msgbody);
 377         return -ENOMEM;
 378 }
 379
 380 /*
 381  * __vmbus_establish_gpadl - Establish a GPADL for a buffer or ringbuffer
 382  *
 383  * @channel: a channel
 384  * @type: the type of the corresponding GPADL, only meaningful for the guest.
 385  * @kbuffer: from kmalloc or vmalloc
 386  * @size: page-size multiple
 387  * @send_offset: the offset (in bytes) where the send ring buffer starts,
 388  *               should be 0 for BUFFER type gpadl
 389  * @gpadl_handle: some funky thing
 390  */
 391 static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 392                                    enum hv_gpadl_type type, void *kbuffer,
 393                                    u32 size, u32 send_offset,
 394                                    u32 *gpadl_handle)
 395 {
 396         struct vmbus_channel_gpadl_header *gpadlmsg;
 397         struct vmbus_channel_gpadl_body *gpadl_body;
 398         struct vmbus_channel_msginfo *msginfo = NULL;
 399         struct vmbus_channel_msginfo *submsginfo, *tmp;
 400         struct list_head *curr;
 401         u32 next_gpadl_handle;
 402         unsigned long flags;
 403         int ret = 0;
 404
 405         next_gpadl_handle =
 406                 (atomic_inc_return(&vmbus_connection.next_gpadl_handle) - 1);
 407
 408         ret = create_gpadl_header(type, kbuffer, size, send_offset, &msginfo);
 409         if (ret)
 410                 return ret;
 411
 412         init_completion(&msginfo->waitevent);
 413         msginfo->waiting_channel = channel;
 414
 415         gpadlmsg = (struct vmbus_channel_gpadl_header *)msginfo->msg;
 416         gpadlmsg->header.msgtype = CHANNELMSG_GPADL_HEADER;
 417         gpadlmsg->child_relid = channel->offermsg.child_relid;
 418         gpadlmsg->gpadl = next_gpadl_handle;
 419
 420
 421         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 422         list_add_tail(&msginfo->msglistentry,
 423                       &vmbus_connection.chn_msg_list);
 424
 425         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 426
 427         if (channel->rescind) {
 428                 ret = -ENODEV;
 429                 goto cleanup;
 430         }
 431
 432         ret = vmbus_post_msg(gpadlmsg, msginfo->msgsize -
 433                              sizeof(*msginfo), true);
 434
 435         trace_vmbus_establish_gpadl_header(gpadlmsg, ret);
 436
 437         if (ret != 0)
 438                 goto cleanup;
 439
 440         list_for_each(curr, &msginfo->submsglist) {
 441                 submsginfo = (struct vmbus_channel_msginfo *)curr;
 442                 gpadl_body =
 443                         (struct vmbus_channel_gpadl_body *)submsginfo->msg;
 444
 445                 gpadl_body->header.msgtype =
 446                         CHANNELMSG_GPADL_BODY;
 447                 gpadl_body->gpadl = next_gpadl_handle;
 448
 449                 ret = vmbus_post_msg(gpadl_body,
 450                                      submsginfo->msgsize - sizeof(*submsginfo),
 451                                      true);
 452
 453                 trace_vmbus_establish_gpadl_body(gpadl_body, ret);
 454
 455                 if (ret != 0)
 456                         goto cleanup;
 457
 458         }
 459         wait_for_completion(&msginfo->waitevent);
 460
 461         if (msginfo->response.gpadl_created.creation_status != 0) {
 462                 pr_err("Failed to establish GPADL: err = 0x%x\n",
 463                        msginfo->response.gpadl_created.creation_status);
 464
 465                 ret = -EDQUOT;
 466                 goto cleanup;
 467         }
 468
 469         if (channel->rescind) {
 470                 ret = -ENODEV;
 471                 goto cleanup;
 472         }
 473
 474         /* At this point, we received the gpadl created msg */
 475         *gpadl_handle = gpadlmsg->gpadl;
 476
 477 cleanup:
 478         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 479         list_del(&msginfo->msglistentry);
 480         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 481         list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
 482                                  msglistentry) {
 483                 kfree(submsginfo);
 484         }
 485
 486         kfree(msginfo);
 487         return ret;
 488 }
 489
 490 /*
 491  * vmbus_establish_gpadl - Establish a GPADL for the specified buffer
 492  *
 493  * @channel: a channel
 494  * @kbuffer: from kmalloc or vmalloc
 495  * @size: page-size multiple
 496  * @gpadl_handle: some funky thing
 497  */
 498 int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,
 499                           u32 size, u32 *gpadl_handle)
 500 {
 501         return __vmbus_establish_gpadl(channel, HV_GPADL_BUFFER, kbuffer, size,
 502                                        0U, gpadl_handle);
 503 }
 504 EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);
 505
 506 /**
 507  * request_arr_init - Allocates memory for the requestor array. Each slot
 508  * keeps track of the next available slot in the array. Initially, each
 509  * slot points to the next one (as in a Linked List). The last slot
 510  * does not point to anything, so its value is U64_MAX by default.
 511  * @size The size of the array
 512  */
 513 static u64 *request_arr_init(u32 size)
 514 {
 515         int i;
 516         u64 *req_arr;
 517
 518         req_arr = kcalloc(size, sizeof(u64), GFP_KERNEL);
 519         if (!req_arr)
 520                 return NULL;
 521
 522         for (i = 0; i < size - 1; i++)
 523                 req_arr[i] = i + 1;
 524
 525         /* Last slot (no more available slots) */
 526         req_arr[i] = U64_MAX;
 527
 528         return req_arr;
 529 }
 530
 531 /*
 532  * vmbus_alloc_requestor - Initializes @rqstor's fields.
 533  * Index 0 is the first free slot
 534  * @size: Size of the requestor array
 535  */
 536 static int vmbus_alloc_requestor(struct vmbus_requestor *rqstor, u32 size)
 537 {
 538         u64 *rqst_arr;
 539         unsigned long *bitmap;
 540
 541         rqst_arr = request_arr_init(size);
 542         if (!rqst_arr)
 543                 return -ENOMEM;
 544
 545         bitmap = bitmap_zalloc(size, GFP_KERNEL);
 546         if (!bitmap) {
 547                 kfree(rqst_arr);
 548                 return -ENOMEM;
 549         }
 550
 551         rqstor->req_arr = rqst_arr;
 552         rqstor->req_bitmap = bitmap;
 553         rqstor->size = size;
 554         rqstor->next_request_id = 0;
 555         spin_lock_init(&rqstor->req_lock);
 556
 557         return 0;
 558 }
 559
 560 /*
 561  * vmbus_free_requestor - Frees memory allocated for @rqstor
 562  * @rqstor: Pointer to the requestor struct
 563  */
 564 static void vmbus_free_requestor(struct vmbus_requestor *rqstor)
 565 {
 566         kfree(rqstor->req_arr);
 567         bitmap_free(rqstor->req_bitmap);
 568 }
 569
 570 static int __vmbus_open(struct vmbus_channel *newchannel,
 571                        void *userdata, u32 userdatalen,
 572                        void (*onchannelcallback)(void *context), void *context)
 573 {
 574         struct vmbus_channel_open_channel *open_msg;
 575         struct vmbus_channel_msginfo *open_info = NULL;
 576         struct page *page = newchannel->ringbuffer_page;
 577         u32 send_pages, recv_pages;
 578         unsigned long flags;
 579         int err;
 580
 581         if (userdatalen > MAX_USER_DEFINED_BYTES)
 582                 return -EINVAL;
 583
 584         send_pages = newchannel->ringbuffer_send_offset;
 585         recv_pages = newchannel->ringbuffer_pagecount - send_pages;
 586
 587         if (newchannel->state != CHANNEL_OPEN_STATE)
 588                 return -EINVAL;
 589
 590         /* Create and init requestor */
 591         if (newchannel->rqstor_size) {
 592                 if (vmbus_alloc_requestor(&newchannel->requestor, newchannel->rqstor_size))
 593                         return -ENOMEM;
 594         }
 595
 596         newchannel->state = CHANNEL_OPENING_STATE;
 597         newchannel->onchannel_callback = onchannelcallback;
 598         newchannel->channel_callback_context = context;
 599
 600         err = hv_ringbuffer_init(&newchannel->outbound, page, send_pages);
 601         if (err)
 602                 goto error_clean_ring;
 603
 604         err = hv_ringbuffer_init(&newchannel->inbound,
 605                                  &page[send_pages], recv_pages);
 606         if (err)
 607                 goto error_clean_ring;
 608
 609         /* Establish the gpadl for the ring buffer */
 610         newchannel->ringbuffer_gpadlhandle = 0;
 611
 612         err = __vmbus_establish_gpadl(newchannel, HV_GPADL_RING,
 613                                       page_address(newchannel->ringbuffer_page),
 614                                       (send_pages + recv_pages) << PAGE_SHIFT,
 615                                       newchannel->ringbuffer_send_offset << PAGE_SHIFT,
 616                                       &newchannel->ringbuffer_gpadlhandle);
 617         if (err)
 618                 goto error_clean_ring;
 619
 620         /* Create and init the channel open message */
 621         open_info = kmalloc(sizeof(*open_info) +
 622                            sizeof(struct vmbus_channel_open_channel),
 623                            GFP_KERNEL);
 624         if (!open_info) {
 625                 err = -ENOMEM;
 626                 goto error_free_gpadl;
 627         }
 628
 629         init_completion(&open_info->waitevent);
 630         open_info->waiting_channel = newchannel;
 631
 632         open_msg = (struct vmbus_channel_open_channel *)open_info->msg;
 633         open_msg->header.msgtype = CHANNELMSG_OPENCHANNEL;
 634         open_msg->openid = newchannel->offermsg.child_relid;
 635         open_msg->child_relid = newchannel->offermsg.child_relid;
 636         open_msg->ringbuffer_gpadlhandle = newchannel->ringbuffer_gpadlhandle;
 637         /*
 638          * The unit of ->downstream_ringbuffer_pageoffset is HV_HYP_PAGE and
 639          * the unit of ->ringbuffer_send_offset (i.e. send_pages) is PAGE, so
 640          * here we calculate it into HV_HYP_PAGE.
 641          */
 642         open_msg->downstream_ringbuffer_pageoffset =
 643                 hv_ring_gpadl_send_hvpgoffset(send_pages << PAGE_SHIFT);
 644         open_msg->target_vp = hv_cpu_number_to_vp_number(newchannel->target_cpu);
 645
 646         if (userdatalen)
 647                 memcpy(open_msg->userdata, userdata, userdatalen);
 648
 649         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 650         list_add_tail(&open_info->msglistentry,
 651                       &vmbus_connection.chn_msg_list);
 652         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 653
 654         if (newchannel->rescind) {
 655                 err = -ENODEV;
 656                 goto error_free_info;
 657         }
 658
 659         err = vmbus_post_msg(open_msg,
 660                              sizeof(struct vmbus_channel_open_channel), true);
 661
 662         trace_vmbus_open(open_msg, err);
 663
 664         if (err != 0)
 665                 goto error_clean_msglist;
 666
 667         wait_for_completion(&open_info->waitevent);
 668
 669         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 670         list_del(&open_info->msglistentry);
 671         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 672
 673         if (newchannel->rescind) {
 674                 err = -ENODEV;
 675                 goto error_free_info;
 676         }
 677
 678         if (open_info->response.open_result.status) {
 679                 err = -EAGAIN;
 680                 goto error_free_info;
 681         }
 682
 683         newchannel->state = CHANNEL_OPENED_STATE;
 684         kfree(open_info);
 685         return 0;
 686
 687 error_clean_msglist:
 688         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 689         list_del(&open_info->msglistentry);
 690         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 691 error_free_info:
 692         kfree(open_info);
 693 error_free_gpadl:
 694         vmbus_teardown_gpadl(newchannel, newchannel->ringbuffer_gpadlhandle);
 695         newchannel->ringbuffer_gpadlhandle = 0;
 696 error_clean_ring:
 697         hv_ringbuffer_cleanup(&newchannel->outbound);
 698         hv_ringbuffer_cleanup(&newchannel->inbound);
 699         vmbus_free_requestor(&newchannel->requestor);
 700         newchannel->state = CHANNEL_OPEN_STATE;
 701         return err;
 702 }
 703
 704 /*
 705  * vmbus_connect_ring - Open the channel but reuse ring buffer
 706  */
 707 int vmbus_connect_ring(struct vmbus_channel *newchannel,
 708                        void (*onchannelcallback)(void *context), void *context)
 709 {
 710         return  __vmbus_open(newchannel, NULL, 0, onchannelcallback, context);
 711 }
 712 EXPORT_SYMBOL_GPL(vmbus_connect_ring);
 713
 714 /*
 715  * vmbus_open - Open the specified channel.
 716  */
 717 int vmbus_open(struct vmbus_channel *newchannel,
 718                u32 send_ringbuffer_size, u32 recv_ringbuffer_size,
 719                void *userdata, u32 userdatalen,
 720                void (*onchannelcallback)(void *context), void *context)
 721 {
 722         int err;
 723
 724         err = vmbus_alloc_ring(newchannel, send_ringbuffer_size,
 725                                recv_ringbuffer_size);
 726         if (err)
 727                 return err;
 728
 729         err = __vmbus_open(newchannel, userdata, userdatalen,
 730                            onchannelcallback, context);
 731         if (err)
 732                 vmbus_free_ring(newchannel);
 733
 734         return err;
 735 }
 736 EXPORT_SYMBOL_GPL(vmbus_open);
 737
 738 /*
 739  * vmbus_teardown_gpadl -Teardown the specified GPADL handle
 740  */
 741 int vmbus_teardown_gpadl(struct vmbus_channel *channel, u32 gpadl_handle)
 742 {
 743         struct vmbus_channel_gpadl_teardown *msg;
 744         struct vmbus_channel_msginfo *info;
 745         unsigned long flags;
 746         int ret;
 747
 748         info = kmalloc(sizeof(*info) +
 749                        sizeof(struct vmbus_channel_gpadl_teardown), GFP_KERNEL);
 750         if (!info)
 751                 return -ENOMEM;
 752
 753         init_completion(&info->waitevent);
 754         info->waiting_channel = channel;
 755
 756         msg = (struct vmbus_channel_gpadl_teardown *)info->msg;
 757
 758         msg->header.msgtype = CHANNELMSG_GPADL_TEARDOWN;
 759         msg->child_relid = channel->offermsg.child_relid;
 760         msg->gpadl = gpadl_handle;
 761
 762         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 763         list_add_tail(&info->msglistentry,
 764                       &vmbus_connection.chn_msg_list);
 765         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 766
 767         if (channel->rescind)
 768                 goto post_msg_err;
 769
 770         ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_gpadl_teardown),
 771                              true);
 772
 773         trace_vmbus_teardown_gpadl(msg, ret);
 774
 775         if (ret)
 776                 goto post_msg_err;
 777
 778         wait_for_completion(&info->waitevent);
 779
 780 post_msg_err:
 781         /*
 782          * If the channel has been rescinded;
 783          * we will be awakened by the rescind
 784          * handler; set the error code to zero so we don't leak memory.
 785          */
 786         if (channel->rescind)
 787                 ret = 0;
 788
 789         spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 790         list_del(&info->msglistentry);
 791         spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 792
 793         kfree(info);
 794         return ret;
 795 }
 796 EXPORT_SYMBOL_GPL(vmbus_teardown_gpadl);
 797
 798 void vmbus_reset_channel_cb(struct vmbus_channel *channel)
 799 {
 800         unsigned long flags;
 801
 802         /*
 803          * vmbus_on_event(), running in the per-channel tasklet, can race
 804          * with vmbus_close_internal() in the case of SMP guest, e.g., when
 805          * the former is accessing channel->inbound.ring_buffer, the latter
 806          * could be freeing the ring_buffer pages, so here we must stop it
 807          * first.
 808          *
 809          * vmbus_chan_sched() might call the netvsc driver callback function
 810          * that ends up scheduling NAPI work that accesses the ring buffer.
 811          * At this point, we have to ensure that any such work is completed
 812          * and that the channel ring buffer is no longer being accessed, cf.
 813          * the calls to napi_disable() in netvsc_device_remove().
 814          */
 815         tasklet_disable(&channel->callback_event);
 816
 817         /* See the inline comments in vmbus_chan_sched(). */
 818         spin_lock_irqsave(&channel->sched_lock, flags);
 819         channel->onchannel_callback = NULL;
 820         spin_unlock_irqrestore(&channel->sched_lock, flags);
 821
 822         channel->sc_creation_callback = NULL;
 823
 824         /* Re-enable tasklet for use on re-open */
 825         tasklet_enable(&channel->callback_event);
 826 }
 827
 828 static int vmbus_close_internal(struct vmbus_channel *channel)
 829 {
 830         struct vmbus_channel_close_channel *msg;
 831         int ret;
 832
 833         vmbus_reset_channel_cb(channel);
 834
 835         /*
 836          * In case a device driver's probe() fails (e.g.,
 837          * util_probe() -> vmbus_open() returns -ENOMEM) and the device is
 838          * rescinded later (e.g., we dynamically disable an Integrated Service
 839          * in Hyper-V Manager), the driver's remove() invokes vmbus_close():
 840          * here we should skip most of the below cleanup work.
 841          */
 842         if (channel->state != CHANNEL_OPENED_STATE)
 843                 return -EINVAL;
 844
 845         channel->state = CHANNEL_OPEN_STATE;
 846
 847         /* Send a closing message */
 848
 849         msg = &channel->close_msg.msg;
 850
 851         msg->header.msgtype = CHANNELMSG_CLOSECHANNEL;
 852         msg->child_relid = channel->offermsg.child_relid;
 853
 854         ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_close_channel),
 855                              true);
 856
 857         trace_vmbus_close_internal(msg, ret);
 858
 859         if (ret) {
 860                 pr_err("Close failed: close post msg return is %d\n", ret);
 861                 /*
 862                  * If we failed to post the close msg,
 863                  * it is perhaps better to leak memory.
 864                  */
 865         }
 866
 867         /* Tear down the gpadl for the channel's ring buffer */
 868         else if (channel->ringbuffer_gpadlhandle) {
 869                 ret = vmbus_teardown_gpadl(channel,
 870                                            channel->ringbuffer_gpadlhandle);
 871                 if (ret) {
 872                         pr_err("Close failed: teardown gpadl return %d\n", ret);
 873                         /*
 874                          * If we failed to teardown gpadl,
 875                          * it is perhaps better to leak memory.
 876                          */
 877                 }
 878
 879                 channel->ringbuffer_gpadlhandle = 0;
 880         }
 881
 882         if (!ret)
 883                 vmbus_free_requestor(&channel->requestor);
 884
 885         return ret;
 886 }
 887
 888 /* disconnect ring - close all channels */
 889 int vmbus_disconnect_ring(struct vmbus_channel *channel)
 890 {
 891         struct vmbus_channel *cur_channel, *tmp;
 892         int ret;
 893
 894         if (channel->primary_channel != NULL)
 895                 return -EINVAL;
 896
 897         list_for_each_entry_safe(cur_channel, tmp, &channel->sc_list, sc_list) {
 898                 if (cur_channel->rescind)
 899                         wait_for_completion(&cur_channel->rescind_event);
 900
 901                 mutex_lock(&vmbus_connection.channel_mutex);
 902                 if (vmbus_close_internal(cur_channel) == 0) {
 903                         vmbus_free_ring(cur_channel);
 904
 905                         if (cur_channel->rescind)
 906                                 hv_process_channel_removal(cur_channel);
 907                 }
 908                 mutex_unlock(&vmbus_connection.channel_mutex);
 909         }
 910
 911         /*
 912          * Now close the primary.
 913          */
 914         mutex_lock(&vmbus_connection.channel_mutex);
 915         ret = vmbus_close_internal(channel);
 916         mutex_unlock(&vmbus_connection.channel_mutex);
 917
 918         return ret;
 919 }
 920 EXPORT_SYMBOL_GPL(vmbus_disconnect_ring);
 921
 922 /*
 923  * vmbus_close - Close the specified channel
 924  */
 925 void vmbus_close(struct vmbus_channel *channel)
 926 {
 927         if (vmbus_disconnect_ring(channel) == 0)
 928                 vmbus_free_ring(channel);
 929 }
 930 EXPORT_SYMBOL_GPL(vmbus_close);
 931
 932 /**
 933  * vmbus_sendpacket() - Send the specified buffer on the given channel
 934  * @channel: Pointer to vmbus_channel structure
 935  * @buffer: Pointer to the buffer you want to send the data from.
 936  * @bufferlen: Maximum size of what the buffer holds.
 937  * @requestid: Identifier of the request
 938  * @type: Type of packet that is being sent e.g. negotiate, time
 939  *        packet etc.
 940  * @flags: 0 or VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED
 941  *
 942  * Sends data in @buffer directly to Hyper-V via the vmbus.
 943  * This will send the data unparsed to Hyper-V.
 944  *
 945  * Mainly used by Hyper-V drivers.
 946  */
 947 int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
 948                            u32 bufferlen, u64 requestid,
 949                            enum vmbus_packet_type type, u32 flags)
 950 {
 951         struct vmpacket_descriptor desc;
 952         u32 packetlen = sizeof(struct vmpacket_descriptor) + bufferlen;
 953         u32 packetlen_aligned = ALIGN(packetlen, sizeof(u64));
 954         struct kvec bufferlist[3];
 955         u64 aligned_data = 0;
 956         int num_vecs = ((bufferlen != 0) ? 3 : 1);
 957
 958
 959         /* Setup the descriptor */
 960         desc.type = type; /* VmbusPacketTypeDataInBand; */
 961         desc.flags = flags; /* VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED; */
 962         /* in 8-bytes granularity */
 963         desc.offset8 = sizeof(struct vmpacket_descriptor) >> 3;
 964         desc.len8 = (u16)(packetlen_aligned >> 3);
 965         desc.trans_id = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
 966
 967         bufferlist[0].iov_base = &desc;
 968         bufferlist[0].iov_len = sizeof(struct vmpacket_descriptor);
 969         bufferlist[1].iov_base = buffer;
 970         bufferlist[1].iov_len = bufferlen;
 971         bufferlist[2].iov_base = &aligned_data;
 972         bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 973
 974         return hv_ringbuffer_write(channel, bufferlist, num_vecs, requestid);
 975 }
 976 EXPORT_SYMBOL(vmbus_sendpacket);
 977
 978 /*
 979  * vmbus_sendpacket_pagebuffer - Send a range of single-page buffer
 980  * packets using a GPADL Direct packet type. This interface allows you
 981  * to control notifying the host. This will be useful for sending
 982  * batched data. Also the sender can control the send flags
 983  * explicitly.
 984  */
 985 int vmbus_sendpacket_pagebuffer(struct vmbus_channel *channel,
 986                                 struct hv_page_buffer pagebuffers[],
 987                                 u32 pagecount, void *buffer, u32 bufferlen,
 988                                 u64 requestid)
 989 {
 990         int i;
 991         struct vmbus_channel_packet_page_buffer desc;
 992         u32 descsize;
 993         u32 packetlen;
 994         u32 packetlen_aligned;
 995         struct kvec bufferlist[3];
 996         u64 aligned_data = 0;
 997
 998         if (pagecount > MAX_PAGE_BUFFER_COUNT)
 999                 return -EINVAL;
1000
1001         /*
1002          * Adjust the size down since vmbus_channel_packet_page_buffer is the
1003          * largest size we support
1004          */
1005         descsize = sizeof(struct vmbus_channel_packet_page_buffer) -
1006                           ((MAX_PAGE_BUFFER_COUNT - pagecount) *
1007                           sizeof(struct hv_page_buffer));
1008         packetlen = descsize + bufferlen;
1009         packetlen_aligned = ALIGN(packetlen, sizeof(u64));
1010
1011         /* Setup the descriptor */
1012         desc.type = VM_PKT_DATA_USING_GPA_DIRECT;
1013         desc.flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
1014         desc.dataoffset8 = descsize >> 3; /* in 8-bytes granularity */
1015         desc.length8 = (u16)(packetlen_aligned >> 3);
1016         desc.transactionid = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
1017         desc.reserved = 0;
1018         desc.rangecount = pagecount;
1019
1020         for (i = 0; i < pagecount; i++) {
1021                 desc.range[i].len = pagebuffers[i].len;
1022                 desc.range[i].offset = pagebuffers[i].offset;
1023                 desc.range[i].pfn        = pagebuffers[i].pfn;
1024         }
1025
1026         bufferlist[0].iov_base = &desc;
1027         bufferlist[0].iov_len = descsize;
1028         bufferlist[1].iov_base = buffer;
1029         bufferlist[1].iov_len = bufferlen;
1030         bufferlist[2].iov_base = &aligned_data;
1031         bufferlist[2].iov_len = (packetlen_aligned - packetlen);
1032
1033         return hv_ringbuffer_write(channel, bufferlist, 3, requestid);
1034 }
1035 EXPORT_SYMBOL_GPL(vmbus_sendpacket_pagebuffer);
1036
1037 /*
1038  * vmbus_sendpacket_multipagebuffer - Send a multi-page buffer packet
1039  * using a GPADL Direct packet type.
1040  * The buffer includes the vmbus descriptor.
1041  */
1042 int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
1043                               struct vmbus_packet_mpb_array *desc,
1044                               u32 desc_size,
1045                               void *buffer, u32 bufferlen, u64 requestid)
1046 {
1047         u32 packetlen;
1048         u32 packetlen_aligned;
1049         struct kvec bufferlist[3];
1050         u64 aligned_data = 0;
1051
1052         packetlen = desc_size + bufferlen;
1053         packetlen_aligned = ALIGN(packetlen, sizeof(u64));
1054
1055         /* Setup the descriptor */
1056         desc->type = VM_PKT_DATA_USING_GPA_DIRECT;
1057         desc->flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
1058         desc->dataoffset8 = desc_size >> 3; /* in 8-bytes granularity */
1059         desc->length8 = (u16)(packetlen_aligned >> 3);
1060         desc->transactionid = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
1061         desc->reserved = 0;
1062         desc->rangecount = 1;
1063
1064         bufferlist[0].iov_base = desc;
1065         bufferlist[0].iov_len = desc_size;
1066         bufferlist[1].iov_base = buffer;
1067         bufferlist[1].iov_len = bufferlen;
1068         bufferlist[2].iov_base = &aligned_data;
1069         bufferlist[2].iov_len = (packetlen_aligned - packetlen);
1070
1071         return hv_ringbuffer_write(channel, bufferlist, 3, requestid);
1072 }
1073 EXPORT_SYMBOL_GPL(vmbus_sendpacket_mpb_desc);
1074
1075 /**
1076  * __vmbus_recvpacket() - Retrieve the user packet on the specified channel
1077  * @channel: Pointer to vmbus_channel structure
1078  * @buffer: Pointer to the buffer you want to receive the data into.
1079  * @bufferlen: Maximum size of what the buffer can hold.
1080  * @buffer_actual_len: The actual size of the data after it was received.
1081  * @requestid: Identifier of the request
1082  * @raw: true means keep the vmpacket_descriptor header in the received data.
1083  *
1084  * Receives directly from the hyper-v vmbus and puts the data it received
1085  * into Buffer. This will receive the data unparsed from hyper-v.
1086  *
1087  * Mainly used by Hyper-V drivers.
1088  */
1089 static inline int
1090 __vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
1091                    u32 bufferlen, u32 *buffer_actual_len, u64 *requestid,
1092                    bool raw)
1093 {
1094         return hv_ringbuffer_read(channel, buffer, bufferlen,
1095                                   buffer_actual_len, requestid, raw);
1096
1097 }
1098
1099 int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
1100                      u32 bufferlen, u32 *buffer_actual_len,
1101                      u64 *requestid)
1102 {
1103         return __vmbus_recvpacket(channel, buffer, bufferlen,
1104                                   buffer_actual_len, requestid, false);
1105 }
1106 EXPORT_SYMBOL(vmbus_recvpacket);
1107
1108 /*
1109  * vmbus_recvpacket_raw - Retrieve the raw packet on the specified channel
1110  */
1111 int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
1112                               u32 bufferlen, u32 *buffer_actual_len,
1113                               u64 *requestid)
1114 {
1115         return __vmbus_recvpacket(channel, buffer, bufferlen,
1116                                   buffer_actual_len, requestid, true);
1117 }
1118 EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
1119
1120 /*
1121  * vmbus_next_request_id - Returns a new request id. It is also
1122  * the index at which the guest memory address is stored.
1123  * Uses a spin lock to avoid race conditions.
1124  * @rqstor: Pointer to the requestor struct
1125  * @rqst_add: Guest memory address to be stored in the array
1126  */
1127 u64 vmbus_next_request_id(struct vmbus_requestor *rqstor, u64 rqst_addr)
1128 {
1129         unsigned long flags;
1130         u64 current_id;
1131         const struct vmbus_channel *channel =
1132                 container_of(rqstor, const struct vmbus_channel, requestor);
1133
1134         /* Check rqstor has been initialized */
1135         if (!channel->rqstor_size)
1136                 return VMBUS_NO_RQSTOR;
1137
1138         spin_lock_irqsave(&rqstor->req_lock, flags);
1139         current_id = rqstor->next_request_id;
1140
1141         /* Requestor array is full */
1142         if (current_id >= rqstor->size) {
1143                 spin_unlock_irqrestore(&rqstor->req_lock, flags);
1144                 return VMBUS_RQST_ERROR;
1145         }
1146
1147         rqstor->next_request_id = rqstor->req_arr[current_id];
1148         rqstor->req_arr[current_id] = rqst_addr;
1149
1150         /* The already held spin lock provides atomicity */
1151         bitmap_set(rqstor->req_bitmap, current_id, 1);
1152
1153         spin_unlock_irqrestore(&rqstor->req_lock, flags);
1154
1155         /*
1156          * Cannot return an ID of 0, which is reserved for an unsolicited
1157          * message from Hyper-V.
1158          */
1159         return current_id + 1;
1160 }
1161 EXPORT_SYMBOL_GPL(vmbus_next_request_id);
1162
1163 /*
1164  * vmbus_request_addr - Returns the memory address stored at @trans_id
1165  * in @rqstor. Uses a spin lock to avoid race conditions.
1166  * @rqstor: Pointer to the requestor struct
1167  * @trans_id: Request id sent back from Hyper-V. Becomes the requestor's
1168  * next request id.
1169  */
1170 u64 vmbus_request_addr(struct vmbus_requestor *rqstor, u64 trans_id)
1171 {
1172         unsigned long flags;
1173         u64 req_addr;
1174         const struct vmbus_channel *channel =
1175                 container_of(rqstor, const struct vmbus_channel, requestor);
1176
1177         /* Check rqstor has been initialized */
1178         if (!channel->rqstor_size)
1179                 return VMBUS_NO_RQSTOR;
1180
1181         /* Hyper-V can send an unsolicited message with ID of 0 */
1182         if (!trans_id)
1183                 return trans_id;
1184
1185         spin_lock_irqsave(&rqstor->req_lock, flags);
1186
1187         /* Data corresponding to trans_id is stored at trans_id - 1 */
1188         trans_id--;
1189
1190         /* Invalid trans_id */
1191         if (trans_id >= rqstor->size || !test_bit(trans_id, rqstor->req_bitmap)) {
1192                 spin_unlock_irqrestore(&rqstor->req_lock, flags);
1193                 return VMBUS_RQST_ERROR;
1194         }
1195
1196         req_addr = rqstor->req_arr[trans_id];
1197         rqstor->req_arr[trans_id] = rqstor->next_request_id;
1198         rqstor->next_request_id = trans_id;
1199
1200         /* The already held spin lock provides atomicity */
1201         bitmap_clear(rqstor->req_bitmap, trans_id, 1);
1202
1203         spin_unlock_irqrestore(&rqstor->req_lock, flags);
1204         return req_addr;
1205 }
1206 EXPORT_SYMBOL_GPL(vmbus_request_addr);