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 <linux/set_memory.h>
  21#include <linux/export.h>
  22#include <asm/page.h>
  23#include <asm/mshyperv.h>
  24
  25#include "hyperv_vmbus.h"
  26
  27/*
  28 * hv_gpadl_size - Return the real size of a gpadl, the size that Hyper-V uses
  29 *
  30 * For BUFFER gpadl, Hyper-V uses the exact same size as the guest does.
  31 *
  32 * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the header
  33 * (because of the alignment requirement), however, the hypervisor only
  34 * uses the first HV_HYP_PAGE_SIZE as the header, therefore leaving a
  35 * (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap. And since there are two rings in a
  36 * ringbuffer, the total size for a RING gpadl that Hyper-V uses is the
  37 * total size that the guest uses minus twice of the gap size.
  38 */
  39static inline u32 hv_gpadl_size(enum hv_gpadl_type type, u32 size)
  40{
  41	switch (type) {
  42	case HV_GPADL_BUFFER:
  43		return size;
  44	case HV_GPADL_RING:
  45		/* The size of a ringbuffer must be page-aligned */
  46		BUG_ON(size % PAGE_SIZE);
  47		/*
  48		 * Two things to notice here:
  49		 * 1) We're processing two ring buffers as a unit
  50		 * 2) We're skipping any space larger than HV_HYP_PAGE_SIZE in
  51		 * the first guest-size page of each of the two ring buffers.
  52		 * So we effectively subtract out two guest-size pages, and add
  53		 * back two Hyper-V size pages.
  54		 */
  55		return size - 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
  56	}
  57	BUG();
  58	return 0;
  59}
  60
  61/*
  62 * hv_ring_gpadl_send_hvpgoffset - Calculate the send offset (in unit of
  63 *                                 HV_HYP_PAGE) in a ring gpadl based on the
  64 *                                 offset in the guest
  65 *
  66 * @offset: the offset (in bytes) where the send ringbuffer starts in the
  67 *               virtual address space of the guest
  68 */
  69static inline u32 hv_ring_gpadl_send_hvpgoffset(u32 offset)
  70{
  71
  72	/*
  73	 * For RING gpadl, in each ring, the guest uses one PAGE_SIZE as the
  74	 * header (because of the alignment requirement), however, the
  75	 * hypervisor only uses the first HV_HYP_PAGE_SIZE as the header,
  76	 * therefore leaving a (PAGE_SIZE - HV_HYP_PAGE_SIZE) gap.
  77	 *
  78	 * And to calculate the effective send offset in gpadl, we need to
  79	 * substract this gap.
  80	 */
  81	return (offset - (PAGE_SIZE - HV_HYP_PAGE_SIZE)) >> HV_HYP_PAGE_SHIFT;
  82}
  83
  84/*
  85 * hv_gpadl_hvpfn - Return the Hyper-V page PFN of the @i th Hyper-V page in
  86 *                  the gpadl
  87 *
  88 * @type: the type of the gpadl
  89 * @kbuffer: the pointer to the gpadl in the guest
  90 * @size: the total size (in bytes) of the gpadl
  91 * @send_offset: the offset (in bytes) where the send ringbuffer starts in the
  92 *               virtual address space of the guest
  93 * @i: the index
  94 */
  95static inline u64 hv_gpadl_hvpfn(enum hv_gpadl_type type, void *kbuffer,
  96				 u32 size, u32 send_offset, int i)
  97{
  98	int send_idx = hv_ring_gpadl_send_hvpgoffset(send_offset);
  99	unsigned long delta = 0UL;
 100
 101	switch (type) {
 102	case HV_GPADL_BUFFER:
 103		break;
 104	case HV_GPADL_RING:
 105		if (i == 0)
 106			delta = 0;
 107		else if (i <= send_idx)
 108			delta = PAGE_SIZE - HV_HYP_PAGE_SIZE;
 109		else
 110			delta = 2 * (PAGE_SIZE - HV_HYP_PAGE_SIZE);
 111		break;
 112	default:
 113		BUG();
 114		break;
 115	}
 116
 117	return virt_to_hvpfn(kbuffer + delta + (HV_HYP_PAGE_SIZE * i));
 118}
 119
 120/*
 121 * vmbus_setevent- Trigger an event notification on the specified
 122 * channel.
 123 */
 124void vmbus_setevent(struct vmbus_channel *channel)
 125{
 126	struct hv_monitor_page *monitorpage;
 127
 128	trace_vmbus_setevent(channel);
 129
 130	/*
 131	 * For channels marked as in "low latency" mode
 132	 * bypass the monitor page mechanism.
 133	 */
 134	if (channel->offermsg.monitor_allocated && !channel->low_latency) {
 135		vmbus_send_interrupt(channel->offermsg.child_relid);
 136
 137		/* Get the child to parent monitor page */
 138		monitorpage = vmbus_connection.monitor_pages[1];
 139
 140		sync_set_bit(channel->monitor_bit,
 141			(unsigned long *)&monitorpage->trigger_group
 142					[channel->monitor_grp].pending);
 143
 144	} else {
 145		vmbus_set_event(channel);
 146	}
 147}
 148EXPORT_SYMBOL_GPL(vmbus_setevent);
 149
 150/* vmbus_free_ring - drop mapping of ring buffer */
 151void vmbus_free_ring(struct vmbus_channel *channel)
 152{
 153	hv_ringbuffer_cleanup(&channel->outbound);
 154	hv_ringbuffer_cleanup(&channel->inbound);
 155
 156	if (channel->ringbuffer_page) {
 157		/* In a CoCo VM leak the memory if it didn't get re-encrypted */
 158		if (!channel->ringbuffer_gpadlhandle.decrypted)
 159			__free_pages(channel->ringbuffer_page,
 160			     get_order(channel->ringbuffer_pagecount
 161				       << PAGE_SHIFT));
 162		channel->ringbuffer_page = NULL;
 163	}
 164}
 165EXPORT_SYMBOL_GPL(vmbus_free_ring);
 166
 167/* vmbus_alloc_ring - allocate and map pages for ring buffer */
 168int vmbus_alloc_ring(struct vmbus_channel *newchannel,
 169		     u32 send_size, u32 recv_size)
 170{
 171	struct page *page;
 172	int order;
 173
 174	if (send_size % PAGE_SIZE || recv_size % PAGE_SIZE)
 175		return -EINVAL;
 176
 177	/* Allocate the ring buffer */
 178	order = get_order(send_size + recv_size);
 179	page = alloc_pages_node(cpu_to_node(newchannel->target_cpu),
 180				GFP_KERNEL|__GFP_ZERO, order);
 181
 182	if (!page)
 183		page = alloc_pages(GFP_KERNEL|__GFP_ZERO, order);
 184
 185	if (!page)
 186		return -ENOMEM;
 187
 188	newchannel->ringbuffer_page = page;
 189	newchannel->ringbuffer_pagecount = (send_size + recv_size) >> PAGE_SHIFT;
 190	newchannel->ringbuffer_send_offset = send_size >> PAGE_SHIFT;
 191
 192	return 0;
 193}
 194EXPORT_SYMBOL_GPL(vmbus_alloc_ring);
 195
 196/* Used for Hyper-V Socket: a guest client's connect() to the host */
 197int vmbus_send_tl_connect_request(const guid_t *shv_guest_servie_id,
 198				  const guid_t *shv_host_servie_id)
 199{
 200	struct vmbus_channel_tl_connect_request conn_msg;
 201	int ret;
 202
 203	memset(&conn_msg, 0, sizeof(conn_msg));
 204	conn_msg.header.msgtype = CHANNELMSG_TL_CONNECT_REQUEST;
 205	conn_msg.guest_endpoint_id = *shv_guest_servie_id;
 206	conn_msg.host_service_id = *shv_host_servie_id;
 207
 208	ret = vmbus_post_msg(&conn_msg, sizeof(conn_msg), true);
 209
 210	trace_vmbus_send_tl_connect_request(&conn_msg, ret);
 211
 212	return ret;
 213}
 214EXPORT_SYMBOL_GPL(vmbus_send_tl_connect_request);
 215
 216static int send_modifychannel_without_ack(struct vmbus_channel *channel, u32 target_vp)
 217{
 218	struct vmbus_channel_modifychannel msg;
 219	int ret;
 220
 221	memset(&msg, 0, sizeof(msg));
 222	msg.header.msgtype = CHANNELMSG_MODIFYCHANNEL;
 223	msg.child_relid = channel->offermsg.child_relid;
 224	msg.target_vp = target_vp;
 225
 226	ret = vmbus_post_msg(&msg, sizeof(msg), true);
 227	trace_vmbus_send_modifychannel(&msg, ret);
 228
 229	return ret;
 230}
 231
 232static int send_modifychannel_with_ack(struct vmbus_channel *channel, u32 target_vp)
 233{
 234	struct vmbus_channel_modifychannel *msg;
 235	struct vmbus_channel_msginfo *info;
 236	unsigned long flags;
 237	int ret;
 238
 239	info = kzalloc(sizeof(struct vmbus_channel_msginfo) +
 240				sizeof(struct vmbus_channel_modifychannel),
 241		       GFP_KERNEL);
 242	if (!info)
 243		return -ENOMEM;
 244
 245	init_completion(&info->waitevent);
 246	info->waiting_channel = channel;
 247
 248	msg = (struct vmbus_channel_modifychannel *)info->msg;
 249	msg->header.msgtype = CHANNELMSG_MODIFYCHANNEL;
 250	msg->child_relid = channel->offermsg.child_relid;
 251	msg->target_vp = target_vp;
 252
 253	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 254	list_add_tail(&info->msglistentry, &vmbus_connection.chn_msg_list);
 255	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 256
 257	ret = vmbus_post_msg(msg, sizeof(*msg), true);
 258	trace_vmbus_send_modifychannel(msg, ret);
 259	if (ret != 0) {
 260		spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 261		list_del(&info->msglistentry);
 262		spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 263		goto free_info;
 264	}
 265
 266	/*
 267	 * Release channel_mutex; otherwise, vmbus_onoffer_rescind() could block on
 268	 * the mutex and be unable to signal the completion.
 269	 *
 270	 * See the caller target_cpu_store() for information about the usage of the
 271	 * mutex.
 272	 */
 273	mutex_unlock(&vmbus_connection.channel_mutex);
 274	wait_for_completion(&info->waitevent);
 275	mutex_lock(&vmbus_connection.channel_mutex);
 276
 277	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 278	list_del(&info->msglistentry);
 279	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 280
 281	if (info->response.modify_response.status)
 282		ret = -EAGAIN;
 283
 284free_info:
 285	kfree(info);
 286	return ret;
 287}
 288
 289/*
 290 * Set/change the vCPU (@target_vp) the channel (@child_relid) will interrupt.
 291 *
 292 * CHANNELMSG_MODIFYCHANNEL messages are aynchronous.  When VMbus version 5.3
 293 * or later is negotiated, Hyper-V always sends an ACK in response to such a
 294 * message.  For VMbus version 5.2 and earlier, it never sends an ACK.  With-
 295 * out an ACK, we can not know when the host will stop interrupting the "old"
 296 * vCPU and start interrupting the "new" vCPU for the given channel.
 297 *
 298 * The CHANNELMSG_MODIFYCHANNEL message type is supported since VMBus version
 299 * VERSION_WIN10_V4_1.
 300 */
 301int vmbus_send_modifychannel(struct vmbus_channel *channel, u32 target_vp)
 302{
 303	if (vmbus_proto_version >= VERSION_WIN10_V5_3)
 304		return send_modifychannel_with_ack(channel, target_vp);
 305	return send_modifychannel_without_ack(channel, target_vp);
 306}
 307EXPORT_SYMBOL_GPL(vmbus_send_modifychannel);
 308
 309/*
 310 * create_gpadl_header - Creates a gpadl for the specified buffer
 311 */
 312static int create_gpadl_header(enum hv_gpadl_type type, void *kbuffer,
 313			       u32 size, u32 send_offset,
 314			       struct vmbus_channel_msginfo **msginfo)
 315{
 316	int i;
 317	int pagecount;
 318	struct vmbus_channel_gpadl_header *gpadl_header;
 319	struct vmbus_channel_gpadl_body *gpadl_body;
 320	struct vmbus_channel_msginfo *msgheader;
 321	struct vmbus_channel_msginfo *msgbody = NULL;
 322	u32 msgsize;
 323
 324	int pfnsum, pfncount, pfnleft, pfncurr, pfnsize;
 325
 326	pagecount = hv_gpadl_size(type, size) >> HV_HYP_PAGE_SHIFT;
 327
 328	pfnsize = MAX_SIZE_CHANNEL_MESSAGE -
 329		  sizeof(struct vmbus_channel_gpadl_header) -
 330		  sizeof(struct gpa_range);
 331	pfncount = umin(pagecount, pfnsize / sizeof(u64));
 332
 333	msgsize = sizeof(struct vmbus_channel_msginfo) +
 334		  sizeof(struct vmbus_channel_gpadl_header) +
 335		  sizeof(struct gpa_range) + pfncount * sizeof(u64);
 336	msgheader =  kzalloc(msgsize, GFP_KERNEL);
 337	if (!msgheader)
 338		return -ENOMEM;
 339
 340	INIT_LIST_HEAD(&msgheader->submsglist);
 341	msgheader->msgsize = msgsize;
 342
 343	gpadl_header = (struct vmbus_channel_gpadl_header *)
 344		msgheader->msg;
 345	gpadl_header->rangecount = 1;
 346	gpadl_header->range_buflen = sizeof(struct gpa_range) +
 347				 pagecount * sizeof(u64);
 348	gpadl_header->range[0].byte_offset = 0;
 349	gpadl_header->range[0].byte_count = hv_gpadl_size(type, size);
 350	for (i = 0; i < pfncount; i++)
 351		gpadl_header->range[0].pfn_array[i] = hv_gpadl_hvpfn(
 352			type, kbuffer, size, send_offset, i);
 353	*msginfo = msgheader;
 354
 355	pfnsum = pfncount;
 356	pfnleft = pagecount - pfncount;
 357
 358	/* how many pfns can we fit in a body message */
 359	pfnsize = MAX_SIZE_CHANNEL_MESSAGE -
 360		  sizeof(struct vmbus_channel_gpadl_body);
 361	pfncount = pfnsize / sizeof(u64);
 362
 363	/*
 364	 * If pfnleft is zero, everything fits in the header and no body
 365	 * messages are needed
 366	 */
 367	while (pfnleft) {
 368		pfncurr = umin(pfncount, pfnleft);
 369		msgsize = sizeof(struct vmbus_channel_msginfo) +
 370			  sizeof(struct vmbus_channel_gpadl_body) +
 371			  pfncurr * sizeof(u64);
 372		msgbody = kzalloc(msgsize, GFP_KERNEL);
 373
 374		if (!msgbody) {
 375			struct vmbus_channel_msginfo *pos = NULL;
 376			struct vmbus_channel_msginfo *tmp = NULL;
 377			/*
 378			 * Free up all the allocated messages.
 379			 */
 380			list_for_each_entry_safe(pos, tmp,
 381				&msgheader->submsglist,
 382				msglistentry) {
 383
 384				list_del(&pos->msglistentry);
 385				kfree(pos);
 386			}
 387			kfree(msgheader);
 388			return -ENOMEM;
 389		}
 390
 391		msgbody->msgsize = msgsize;
 392		gpadl_body = (struct vmbus_channel_gpadl_body *)msgbody->msg;
 393
 394		/*
 395		 * Gpadl is u32 and we are using a pointer which could
 396		 * be 64-bit
 397		 * This is governed by the guest/host protocol and
 398		 * so the hypervisor guarantees that this is ok.
 399		 */
 400		for (i = 0; i < pfncurr; i++)
 401			gpadl_body->pfn[i] = hv_gpadl_hvpfn(type,
 402				kbuffer, size, send_offset, pfnsum + i);
 403
 404		/* add to msg header */
 405		list_add_tail(&msgbody->msglistentry, &msgheader->submsglist);
 406		pfnsum += pfncurr;
 407		pfnleft -= pfncurr;
 408	}
 409
 410	return 0;
 411}
 412
 413static void vmbus_free_channel_msginfo(struct vmbus_channel_msginfo *msginfo)
 414{
 415	struct vmbus_channel_msginfo *submsginfo, *tmp;
 416
 417	if (!msginfo)
 418		return;
 419
 420	list_for_each_entry_safe(submsginfo, tmp, &msginfo->submsglist,
 421				 msglistentry) {
 422		kfree(submsginfo);
 423	}
 424
 425	kfree(msginfo);
 426}
 427
 428/*
 429 * __vmbus_establish_gpadl - Establish a GPADL for a buffer or ringbuffer
 430 *
 431 * @channel: a channel
 432 * @type: the type of the corresponding GPADL, only meaningful for the guest.
 433 * @kbuffer: from kmalloc or vmalloc
 434 * @size: page-size multiple
 435 * @send_offset: the offset (in bytes) where the send ring buffer starts,
 436 *              should be 0 for BUFFER type gpadl
 437 * @gpadl_handle: some funky thing
 438 */
 439static int __vmbus_establish_gpadl(struct vmbus_channel *channel,
 440				   enum hv_gpadl_type type, void *kbuffer,
 441				   u32 size, u32 send_offset,
 442				   struct vmbus_gpadl *gpadl)
 443{
 444	struct vmbus_channel_gpadl_header *gpadlmsg;
 445	struct vmbus_channel_gpadl_body *gpadl_body;
 446	struct vmbus_channel_msginfo *msginfo = NULL;
 447	struct vmbus_channel_msginfo *submsginfo;
 448	struct list_head *curr;
 449	u32 next_gpadl_handle;
 450	unsigned long flags;
 451	int ret = 0;
 452
 453	next_gpadl_handle =
 454		(atomic_inc_return(&vmbus_connection.next_gpadl_handle) - 1);
 455
 456	ret = create_gpadl_header(type, kbuffer, size, send_offset, &msginfo);
 457	if (ret) {
 458		gpadl->decrypted = false;
 459		return ret;
 460	}
 461
 462	gpadl->decrypted = !((channel->co_external_memory && type == HV_GPADL_BUFFER) ||
 463		(channel->co_ring_buffer && type == HV_GPADL_RING));
 464	if (gpadl->decrypted) {
 465		/*
 466		 * The "decrypted" flag being true assumes that set_memory_decrypted() succeeds.
 467		 * But if it fails, the encryption state of the memory is unknown. In that case,
 468		 * leave "decrypted" as true to ensure the memory is leaked instead of going back
 469		 * on the free list.
 470		 */
 471		ret = set_memory_decrypted((unsigned long)kbuffer,
 472					PFN_UP(size));
 473		if (ret) {
 474			dev_warn(&channel->device_obj->device,
 475				"Failed to set host visibility for new GPADL %d.\n",
 476				ret);
 477			vmbus_free_channel_msginfo(msginfo);
 478			return ret;
 479		}
 480	}
 481
 482	init_completion(&msginfo->waitevent);
 483	msginfo->waiting_channel = channel;
 484
 485	gpadlmsg = (struct vmbus_channel_gpadl_header *)msginfo->msg;
 486	gpadlmsg->header.msgtype = CHANNELMSG_GPADL_HEADER;
 487	gpadlmsg->child_relid = channel->offermsg.child_relid;
 488	gpadlmsg->gpadl = next_gpadl_handle;
 489
 490
 491	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 492	list_add_tail(&msginfo->msglistentry,
 493		      &vmbus_connection.chn_msg_list);
 494
 495	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 496
 497	if (channel->rescind) {
 498		ret = -ENODEV;
 499		goto cleanup;
 500	}
 501
 502	ret = vmbus_post_msg(gpadlmsg, msginfo->msgsize -
 503			     sizeof(*msginfo), true);
 504
 505	trace_vmbus_establish_gpadl_header(gpadlmsg, ret);
 506
 507	if (ret != 0)
 508		goto cleanup;
 509
 510	list_for_each(curr, &msginfo->submsglist) {
 511		submsginfo = (struct vmbus_channel_msginfo *)curr;
 512		gpadl_body =
 513			(struct vmbus_channel_gpadl_body *)submsginfo->msg;
 514
 515		gpadl_body->header.msgtype =
 516			CHANNELMSG_GPADL_BODY;
 517		gpadl_body->gpadl = next_gpadl_handle;
 518
 519		ret = vmbus_post_msg(gpadl_body,
 520				     submsginfo->msgsize - sizeof(*submsginfo),
 521				     true);
 522
 523		trace_vmbus_establish_gpadl_body(gpadl_body, ret);
 524
 525		if (ret != 0)
 526			goto cleanup;
 527
 528	}
 529	wait_for_completion(&msginfo->waitevent);
 530
 531	if (msginfo->response.gpadl_created.creation_status != 0) {
 532		pr_err("Failed to establish GPADL: err = 0x%x\n",
 533		       msginfo->response.gpadl_created.creation_status);
 534
 535		ret = -EDQUOT;
 536		goto cleanup;
 537	}
 538
 539	if (channel->rescind) {
 540		ret = -ENODEV;
 541		goto cleanup;
 542	}
 543
 544	/* At this point, we received the gpadl created msg */
 545	gpadl->gpadl_handle = gpadlmsg->gpadl;
 546	gpadl->buffer = kbuffer;
 547	gpadl->size = size;
 548
 549
 550cleanup:
 551	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 552	list_del(&msginfo->msglistentry);
 553	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 554
 555	vmbus_free_channel_msginfo(msginfo);
 556
 557	if (ret) {
 558		/*
 559		 * If set_memory_encrypted() fails, the decrypted flag is
 560		 * left as true so the memory is leaked instead of being
 561		 * put back on the free list.
 562		 */
 563		if (gpadl->decrypted) {
 564			if (!set_memory_encrypted((unsigned long)kbuffer, PFN_UP(size)))
 565				gpadl->decrypted = false;
 566		}
 567	}
 568
 569	return ret;
 570}
 571
 572/*
 573 * vmbus_establish_gpadl - Establish a GPADL for the specified buffer
 574 *
 575 * @channel: a channel
 576 * @kbuffer: from kmalloc or vmalloc
 577 * @size: page-size multiple
 578 * @gpadl_handle: some funky thing
 579 */
 580int vmbus_establish_gpadl(struct vmbus_channel *channel, void *kbuffer,
 581			  u32 size, struct vmbus_gpadl *gpadl)
 582{
 583	return __vmbus_establish_gpadl(channel, HV_GPADL_BUFFER, kbuffer, size,
 584				       0U, gpadl);
 585}
 586EXPORT_SYMBOL_GPL(vmbus_establish_gpadl);
 587
 588/**
 589 * request_arr_init - Allocates memory for the requestor array. Each slot
 590 * keeps track of the next available slot in the array. Initially, each
 591 * slot points to the next one (as in a Linked List). The last slot
 592 * does not point to anything, so its value is U64_MAX by default.
 593 * @size: The size of the array
 594 */
 595static u64 *request_arr_init(u32 size)
 596{
 597	int i;
 598	u64 *req_arr;
 599
 600	req_arr = kcalloc(size, sizeof(u64), GFP_KERNEL);
 601	if (!req_arr)
 602		return NULL;
 603
 604	for (i = 0; i < size - 1; i++)
 605		req_arr[i] = i + 1;
 606
 607	/* Last slot (no more available slots) */
 608	req_arr[i] = U64_MAX;
 609
 610	return req_arr;
 611}
 612
 613/*
 614 * vmbus_alloc_requestor - Initializes @rqstor's fields.
 615 * Index 0 is the first free slot
 616 * @size: Size of the requestor array
 617 */
 618static int vmbus_alloc_requestor(struct vmbus_requestor *rqstor, u32 size)
 619{
 620	u64 *rqst_arr;
 621	unsigned long *bitmap;
 622
 623	rqst_arr = request_arr_init(size);
 624	if (!rqst_arr)
 625		return -ENOMEM;
 626
 627	bitmap = bitmap_zalloc(size, GFP_KERNEL);
 628	if (!bitmap) {
 629		kfree(rqst_arr);
 630		return -ENOMEM;
 631	}
 632
 633	rqstor->req_arr = rqst_arr;
 634	rqstor->req_bitmap = bitmap;
 635	rqstor->size = size;
 636	rqstor->next_request_id = 0;
 637	spin_lock_init(&rqstor->req_lock);
 638
 639	return 0;
 640}
 641
 642/*
 643 * vmbus_free_requestor - Frees memory allocated for @rqstor
 644 * @rqstor: Pointer to the requestor struct
 645 */
 646static void vmbus_free_requestor(struct vmbus_requestor *rqstor)
 647{
 648	kfree(rqstor->req_arr);
 649	bitmap_free(rqstor->req_bitmap);
 650}
 651
 652static int __vmbus_open(struct vmbus_channel *newchannel,
 653		       void *userdata, u32 userdatalen,
 654		       void (*onchannelcallback)(void *context), void *context)
 655{
 656	struct vmbus_channel_open_channel *open_msg;
 657	struct vmbus_channel_msginfo *open_info = NULL;
 658	struct page *page = newchannel->ringbuffer_page;
 659	u32 send_pages, recv_pages;
 660	unsigned long flags;
 661	int err;
 662
 663	if (userdatalen > MAX_USER_DEFINED_BYTES)
 664		return -EINVAL;
 665
 666	send_pages = newchannel->ringbuffer_send_offset;
 667	recv_pages = newchannel->ringbuffer_pagecount - send_pages;
 668
 669	if (newchannel->state != CHANNEL_OPEN_STATE)
 670		return -EINVAL;
 671
 672	/* Create and init requestor */
 673	if (newchannel->rqstor_size) {
 674		if (vmbus_alloc_requestor(&newchannel->requestor, newchannel->rqstor_size))
 675			return -ENOMEM;
 676	}
 677
 678	newchannel->state = CHANNEL_OPENING_STATE;
 679	newchannel->onchannel_callback = onchannelcallback;
 680	newchannel->channel_callback_context = context;
 681
 682	if (!newchannel->max_pkt_size)
 683		newchannel->max_pkt_size = VMBUS_DEFAULT_MAX_PKT_SIZE;
 684
 685	/* Establish the gpadl for the ring buffer */
 686	newchannel->ringbuffer_gpadlhandle.gpadl_handle = 0;
 687
 688	err = __vmbus_establish_gpadl(newchannel, HV_GPADL_RING,
 689				      page_address(newchannel->ringbuffer_page),
 690				      (send_pages + recv_pages) << PAGE_SHIFT,
 691				      newchannel->ringbuffer_send_offset << PAGE_SHIFT,
 692				      &newchannel->ringbuffer_gpadlhandle);
 693	if (err)
 694		goto error_clean_ring;
 695
 696	err = hv_ringbuffer_init(&newchannel->outbound,
 697				 page, send_pages, 0, newchannel->co_ring_buffer);
 698	if (err)
 699		goto error_free_gpadl;
 700
 701	err = hv_ringbuffer_init(&newchannel->inbound, &page[send_pages],
 702				 recv_pages, newchannel->max_pkt_size,
 703				 newchannel->co_ring_buffer);
 704	if (err)
 705		goto error_free_gpadl;
 706
 707	/* Create and init the channel open message */
 708	open_info = kzalloc(sizeof(*open_info) +
 709			   sizeof(struct vmbus_channel_open_channel),
 710			   GFP_KERNEL);
 711	if (!open_info) {
 712		err = -ENOMEM;
 713		goto error_free_gpadl;
 714	}
 715
 716	init_completion(&open_info->waitevent);
 717	open_info->waiting_channel = newchannel;
 718
 719	open_msg = (struct vmbus_channel_open_channel *)open_info->msg;
 720	open_msg->header.msgtype = CHANNELMSG_OPENCHANNEL;
 721	open_msg->openid = newchannel->offermsg.child_relid;
 722	open_msg->child_relid = newchannel->offermsg.child_relid;
 723	open_msg->ringbuffer_gpadlhandle
 724		= newchannel->ringbuffer_gpadlhandle.gpadl_handle;
 725	/*
 726	 * The unit of ->downstream_ringbuffer_pageoffset is HV_HYP_PAGE and
 727	 * the unit of ->ringbuffer_send_offset (i.e. send_pages) is PAGE, so
 728	 * here we calculate it into HV_HYP_PAGE.
 729	 */
 730	open_msg->downstream_ringbuffer_pageoffset =
 731		hv_ring_gpadl_send_hvpgoffset(send_pages << PAGE_SHIFT);
 732	open_msg->target_vp = hv_cpu_number_to_vp_number(newchannel->target_cpu);
 733
 734	if (userdatalen)
 735		memcpy(open_msg->userdata, userdata, userdatalen);
 736
 737	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 738	list_add_tail(&open_info->msglistentry,
 739		      &vmbus_connection.chn_msg_list);
 740	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 741
 742	if (newchannel->rescind) {
 743		err = -ENODEV;
 744		goto error_clean_msglist;
 745	}
 746
 747	err = vmbus_post_msg(open_msg,
 748			     sizeof(struct vmbus_channel_open_channel), true);
 749
 750	trace_vmbus_open(open_msg, err);
 751
 752	if (err != 0)
 753		goto error_clean_msglist;
 754
 755	wait_for_completion(&open_info->waitevent);
 756
 757	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 758	list_del(&open_info->msglistentry);
 759	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 760
 761	if (newchannel->rescind) {
 762		err = -ENODEV;
 763		goto error_free_info;
 764	}
 765
 766	if (open_info->response.open_result.status) {
 767		err = -EAGAIN;
 768		goto error_free_info;
 769	}
 770
 771	newchannel->state = CHANNEL_OPENED_STATE;
 772	kfree(open_info);
 773	return 0;
 774
 775error_clean_msglist:
 776	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 777	list_del(&open_info->msglistentry);
 778	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 779error_free_info:
 780	kfree(open_info);
 781error_free_gpadl:
 782	vmbus_teardown_gpadl(newchannel, &newchannel->ringbuffer_gpadlhandle);
 783error_clean_ring:
 784	hv_ringbuffer_cleanup(&newchannel->outbound);
 785	hv_ringbuffer_cleanup(&newchannel->inbound);
 786	vmbus_free_requestor(&newchannel->requestor);
 787	newchannel->state = CHANNEL_OPEN_STATE;
 788	return err;
 789}
 790
 791/*
 792 * vmbus_connect_ring - Open the channel but reuse ring buffer
 793 */
 794int vmbus_connect_ring(struct vmbus_channel *newchannel,
 795		       void (*onchannelcallback)(void *context), void *context)
 796{
 797	return  __vmbus_open(newchannel, NULL, 0, onchannelcallback, context);
 798}
 799EXPORT_SYMBOL_GPL(vmbus_connect_ring);
 800
 801/*
 802 * vmbus_open - Open the specified channel.
 803 */
 804int vmbus_open(struct vmbus_channel *newchannel,
 805	       u32 send_ringbuffer_size, u32 recv_ringbuffer_size,
 806	       void *userdata, u32 userdatalen,
 807	       void (*onchannelcallback)(void *context), void *context)
 808{
 809	int err;
 810
 811	err = vmbus_alloc_ring(newchannel, send_ringbuffer_size,
 812			       recv_ringbuffer_size);
 813	if (err)
 814		return err;
 815
 816	err = __vmbus_open(newchannel, userdata, userdatalen,
 817			   onchannelcallback, context);
 818	if (err)
 819		vmbus_free_ring(newchannel);
 820
 821	return err;
 822}
 823EXPORT_SYMBOL_GPL(vmbus_open);
 824
 825/*
 826 * vmbus_teardown_gpadl -Teardown the specified GPADL handle
 827 */
 828int vmbus_teardown_gpadl(struct vmbus_channel *channel, struct vmbus_gpadl *gpadl)
 829{
 830	struct vmbus_channel_gpadl_teardown *msg;
 831	struct vmbus_channel_msginfo *info;
 832	unsigned long flags;
 833	int ret;
 834
 835	info = kzalloc(sizeof(*info) +
 836		       sizeof(struct vmbus_channel_gpadl_teardown), GFP_KERNEL);
 837	if (!info)
 838		return -ENOMEM;
 839
 840	init_completion(&info->waitevent);
 841	info->waiting_channel = channel;
 842
 843	msg = (struct vmbus_channel_gpadl_teardown *)info->msg;
 844
 845	msg->header.msgtype = CHANNELMSG_GPADL_TEARDOWN;
 846	msg->child_relid = channel->offermsg.child_relid;
 847	msg->gpadl = gpadl->gpadl_handle;
 848
 849	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 850	list_add_tail(&info->msglistentry,
 851		      &vmbus_connection.chn_msg_list);
 852	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 853
 854	if (channel->rescind)
 855		goto post_msg_err;
 856
 857	ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_gpadl_teardown),
 858			     true);
 859
 860	trace_vmbus_teardown_gpadl(msg, ret);
 861
 862	if (ret)
 863		goto post_msg_err;
 864
 865	wait_for_completion(&info->waitevent);
 866
 867	gpadl->gpadl_handle = 0;
 868
 869post_msg_err:
 870	/*
 871	 * If the channel has been rescinded;
 872	 * we will be awakened by the rescind
 873	 * handler; set the error code to zero so we don't leak memory.
 874	 */
 875	if (channel->rescind)
 876		ret = 0;
 877
 878	spin_lock_irqsave(&vmbus_connection.channelmsg_lock, flags);
 879	list_del(&info->msglistentry);
 880	spin_unlock_irqrestore(&vmbus_connection.channelmsg_lock, flags);
 881
 882	kfree(info);
 883
 884	if (gpadl->decrypted)
 885		ret = set_memory_encrypted((unsigned long)gpadl->buffer,
 886					PFN_UP(gpadl->size));
 887	else
 888		ret = 0;
 889	if (ret)
 890		pr_warn("Fail to set mem host visibility in GPADL teardown %d.\n", ret);
 891
 892	gpadl->decrypted = ret;
 893
 894	return ret;
 895}
 896EXPORT_SYMBOL_GPL(vmbus_teardown_gpadl);
 897
 898void vmbus_reset_channel_cb(struct vmbus_channel *channel)
 899{
 900	unsigned long flags;
 901
 902	/*
 903	 * vmbus_on_event(), running in the per-channel tasklet, can race
 904	 * with vmbus_close_internal() in the case of SMP guest, e.g., when
 905	 * the former is accessing channel->inbound.ring_buffer, the latter
 906	 * could be freeing the ring_buffer pages, so here we must stop it
 907	 * first.
 908	 *
 909	 * vmbus_chan_sched() might call the netvsc driver callback function
 910	 * that ends up scheduling NAPI work that accesses the ring buffer.
 911	 * At this point, we have to ensure that any such work is completed
 912	 * and that the channel ring buffer is no longer being accessed, cf.
 913	 * the calls to napi_disable() in netvsc_device_remove().
 914	 */
 915	tasklet_disable(&channel->callback_event);
 916
 917	/* See the inline comments in vmbus_chan_sched(). */
 918	spin_lock_irqsave(&channel->sched_lock, flags);
 919	channel->onchannel_callback = NULL;
 920	spin_unlock_irqrestore(&channel->sched_lock, flags);
 921
 922	channel->sc_creation_callback = NULL;
 923
 924	/* Re-enable tasklet for use on re-open */
 925	tasklet_enable(&channel->callback_event);
 926}
 927
 928static int vmbus_close_internal(struct vmbus_channel *channel)
 929{
 930	struct vmbus_channel_close_channel *msg;
 931	int ret;
 932
 933	vmbus_reset_channel_cb(channel);
 934
 935	/*
 936	 * In case a device driver's probe() fails (e.g.,
 937	 * util_probe() -> vmbus_open() returns -ENOMEM) and the device is
 938	 * rescinded later (e.g., we dynamically disable an Integrated Service
 939	 * in Hyper-V Manager), the driver's remove() invokes vmbus_close():
 940	 * here we should skip most of the below cleanup work.
 941	 */
 942	if (channel->state != CHANNEL_OPENED_STATE)
 943		return -EINVAL;
 944
 945	channel->state = CHANNEL_OPEN_STATE;
 946
 947	/* Send a closing message */
 948
 949	msg = &channel->close_msg;
 950
 951	msg->header.msgtype = CHANNELMSG_CLOSECHANNEL;
 952	msg->child_relid = channel->offermsg.child_relid;
 953
 954	ret = vmbus_post_msg(msg, sizeof(struct vmbus_channel_close_channel),
 955			     true);
 956
 957	trace_vmbus_close_internal(msg, ret);
 958
 959	if (ret) {
 960		pr_err("Close failed: close post msg return is %d\n", ret);
 961		/*
 962		 * If we failed to post the close msg,
 963		 * it is perhaps better to leak memory.
 964		 */
 965	}
 966
 967	/* Tear down the gpadl for the channel's ring buffer */
 968	else if (channel->ringbuffer_gpadlhandle.gpadl_handle) {
 969		ret = vmbus_teardown_gpadl(channel, &channel->ringbuffer_gpadlhandle);
 970		if (ret) {
 971			pr_err("Close failed: teardown gpadl return %d\n", ret);
 972			/*
 973			 * If we failed to teardown gpadl,
 974			 * it is perhaps better to leak memory.
 975			 */
 976		}
 977	}
 978
 979	if (!ret)
 980		vmbus_free_requestor(&channel->requestor);
 981
 982	return ret;
 983}
 984
 985/* disconnect ring - close all channels */
 986int vmbus_disconnect_ring(struct vmbus_channel *channel)
 987{
 988	struct vmbus_channel *cur_channel, *tmp;
 989	int ret;
 990
 991	if (channel->primary_channel != NULL)
 992		return -EINVAL;
 993
 994	list_for_each_entry_safe(cur_channel, tmp, &channel->sc_list, sc_list) {
 995		if (cur_channel->rescind)
 996			wait_for_completion(&cur_channel->rescind_event);
 997
 998		mutex_lock(&vmbus_connection.channel_mutex);
 999		if (vmbus_close_internal(cur_channel) == 0) {
1000			vmbus_free_ring(cur_channel);
1001
1002			if (cur_channel->rescind)
1003				hv_process_channel_removal(cur_channel);
1004		}
1005		mutex_unlock(&vmbus_connection.channel_mutex);
1006	}
1007
1008	/*
1009	 * Now close the primary.
1010	 */
1011	mutex_lock(&vmbus_connection.channel_mutex);
1012	ret = vmbus_close_internal(channel);
1013	mutex_unlock(&vmbus_connection.channel_mutex);
1014
1015	return ret;
1016}
1017EXPORT_SYMBOL_GPL(vmbus_disconnect_ring);
1018
1019/*
1020 * vmbus_close - Close the specified channel
1021 */
1022void vmbus_close(struct vmbus_channel *channel)
1023{
1024	if (vmbus_disconnect_ring(channel) == 0)
1025		vmbus_free_ring(channel);
1026}
1027EXPORT_SYMBOL_GPL(vmbus_close);
1028
1029/**
1030 * vmbus_sendpacket_getid() - Send the specified buffer on the given channel
1031 * @channel: Pointer to vmbus_channel structure
1032 * @buffer: Pointer to the buffer you want to send the data from.
1033 * @bufferlen: Maximum size of what the buffer holds.
1034 * @requestid: Identifier of the request
1035 * @trans_id: Identifier of the transaction associated to this request, if
1036 *            the send is successful; undefined, otherwise.
1037 * @type: Type of packet that is being sent e.g. negotiate, time
1038 *	  packet etc.
1039 * @flags: 0 or VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED
1040 *
1041 * Sends data in @buffer directly to Hyper-V via the vmbus.
1042 * This will send the data unparsed to Hyper-V.
1043 *
1044 * Mainly used by Hyper-V drivers.
1045 */
1046int vmbus_sendpacket_getid(struct vmbus_channel *channel, void *buffer,
1047			   u32 bufferlen, u64 requestid, u64 *trans_id,
1048			   enum vmbus_packet_type type, u32 flags)
1049{
1050	struct vmpacket_descriptor desc;
1051	u32 packetlen = sizeof(struct vmpacket_descriptor) + bufferlen;
1052	u32 packetlen_aligned = ALIGN(packetlen, sizeof(u64));
1053	struct kvec bufferlist[3];
1054	u64 aligned_data = 0;
1055	int num_vecs = ((bufferlen != 0) ? 3 : 1);
1056
1057
1058	/* Setup the descriptor */
1059	desc.type = type; /* VmbusPacketTypeDataInBand; */
1060	desc.flags = flags; /* VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED; */
1061	/* in 8-bytes granularity */
1062	desc.offset8 = sizeof(struct vmpacket_descriptor) >> 3;
1063	desc.len8 = (u16)(packetlen_aligned >> 3);
1064	desc.trans_id = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
1065
1066	bufferlist[0].iov_base = &desc;
1067	bufferlist[0].iov_len = sizeof(struct vmpacket_descriptor);
1068	bufferlist[1].iov_base = buffer;
1069	bufferlist[1].iov_len = bufferlen;
1070	bufferlist[2].iov_base = &aligned_data;
1071	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
1072
1073	return hv_ringbuffer_write(channel, bufferlist, num_vecs, requestid, trans_id);
1074}
1075EXPORT_SYMBOL(vmbus_sendpacket_getid);
1076
1077/**
1078 * vmbus_sendpacket() - Send the specified buffer on the given channel
1079 * @channel: Pointer to vmbus_channel structure
1080 * @buffer: Pointer to the buffer you want to send the data from.
1081 * @bufferlen: Maximum size of what the buffer holds.
1082 * @requestid: Identifier of the request
1083 * @type: Type of packet that is being sent e.g. negotiate, time
1084 *	  packet etc.
1085 * @flags: 0 or VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED
1086 *
1087 * Sends data in @buffer directly to Hyper-V via the vmbus.
1088 * This will send the data unparsed to Hyper-V.
1089 *
1090 * Mainly used by Hyper-V drivers.
1091 */
1092int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
1093		     u32 bufferlen, u64 requestid,
1094		     enum vmbus_packet_type type, u32 flags)
1095{
1096	return vmbus_sendpacket_getid(channel, buffer, bufferlen,
1097				      requestid, NULL, type, flags);
1098}
1099EXPORT_SYMBOL(vmbus_sendpacket);
1100
1101/*
1102 * vmbus_sendpacket_mpb_desc - Send one or more multi-page buffer packets
1103 * using a GPADL Direct packet type.
1104 * The desc argument must include space for the VMBus descriptor. The
1105 * rangecount field must already be set.
1106 */
1107int vmbus_sendpacket_mpb_desc(struct vmbus_channel *channel,
1108			      struct vmbus_packet_mpb_array *desc,
1109			      u32 desc_size,
1110			      void *buffer, u32 bufferlen, u64 requestid)
1111{
1112	u32 packetlen;
1113	u32 packetlen_aligned;
1114	struct kvec bufferlist[3];
1115	u64 aligned_data = 0;
1116
1117	packetlen = desc_size + bufferlen;
1118	packetlen_aligned = ALIGN(packetlen, sizeof(u64));
1119
1120	/* Setup the descriptor */
1121	desc->type = VM_PKT_DATA_USING_GPA_DIRECT;
1122	desc->flags = VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED;
1123	desc->dataoffset8 = desc_size >> 3; /* in 8-bytes granularity */
1124	desc->length8 = (u16)(packetlen_aligned >> 3);
1125	desc->transactionid = VMBUS_RQST_ERROR; /* will be updated in hv_ringbuffer_write() */
1126	desc->reserved = 0;
1127
1128	bufferlist[0].iov_base = desc;
1129	bufferlist[0].iov_len = desc_size;
1130	bufferlist[1].iov_base = buffer;
1131	bufferlist[1].iov_len = bufferlen;
1132	bufferlist[2].iov_base = &aligned_data;
1133	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
1134
1135	return hv_ringbuffer_write(channel, bufferlist, 3, requestid, NULL);
1136}
1137EXPORT_SYMBOL_GPL(vmbus_sendpacket_mpb_desc);
1138
1139/**
1140 * __vmbus_recvpacket() - Retrieve the user packet on the specified channel
1141 * @channel: Pointer to vmbus_channel structure
1142 * @buffer: Pointer to the buffer you want to receive the data into.
1143 * @bufferlen: Maximum size of what the buffer can hold.
1144 * @buffer_actual_len: The actual size of the data after it was received.
1145 * @requestid: Identifier of the request
1146 * @raw: true means keep the vmpacket_descriptor header in the received data.
1147 *
1148 * Receives directly from the hyper-v vmbus and puts the data it received
1149 * into Buffer. This will receive the data unparsed from hyper-v.
1150 *
1151 * Mainly used by Hyper-V drivers.
1152 */
1153static inline int
1154__vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
1155		   u32 bufferlen, u32 *buffer_actual_len, u64 *requestid,
1156		   bool raw)
1157{
1158	return hv_ringbuffer_read(channel, buffer, bufferlen,
1159				  buffer_actual_len, requestid, raw);
1160
1161}
1162
1163int vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
1164		     u32 bufferlen, u32 *buffer_actual_len,
1165		     u64 *requestid)
1166{
1167	return __vmbus_recvpacket(channel, buffer, bufferlen,
1168				  buffer_actual_len, requestid, false);
1169}
1170EXPORT_SYMBOL(vmbus_recvpacket);
1171
1172/*
1173 * vmbus_recvpacket_raw - Retrieve the raw packet on the specified channel
1174 */
1175int vmbus_recvpacket_raw(struct vmbus_channel *channel, void *buffer,
1176			      u32 bufferlen, u32 *buffer_actual_len,
1177			      u64 *requestid)
1178{
1179	return __vmbus_recvpacket(channel, buffer, bufferlen,
1180				  buffer_actual_len, requestid, true);
1181}
1182EXPORT_SYMBOL_GPL(vmbus_recvpacket_raw);
1183
1184/*
1185 * vmbus_next_request_id - Returns a new request id. It is also
1186 * the index at which the guest memory address is stored.
1187 * Uses a spin lock to avoid race conditions.
1188 * @channel: Pointer to the VMbus channel struct
1189 * @rqst_add: Guest memory address to be stored in the array
1190 */
1191u64 vmbus_next_request_id(struct vmbus_channel *channel, u64 rqst_addr)
1192{
1193	struct vmbus_requestor *rqstor = &channel->requestor;
1194	unsigned long flags;
1195	u64 current_id;
1196
1197	/* Check rqstor has been initialized */
1198	if (!channel->rqstor_size)
1199		return VMBUS_NO_RQSTOR;
1200
1201	lock_requestor(channel, flags);
1202	current_id = rqstor->next_request_id;
1203
1204	/* Requestor array is full */
1205	if (current_id >= rqstor->size) {
1206		unlock_requestor(channel, flags);
1207		return VMBUS_RQST_ERROR;
1208	}
1209
1210	rqstor->next_request_id = rqstor->req_arr[current_id];
1211	rqstor->req_arr[current_id] = rqst_addr;
1212
1213	/* The already held spin lock provides atomicity */
1214	bitmap_set(rqstor->req_bitmap, current_id, 1);
1215
1216	unlock_requestor(channel, flags);
1217
1218	/*
1219	 * Cannot return an ID of 0, which is reserved for an unsolicited
1220	 * message from Hyper-V; Hyper-V does not acknowledge (respond to)
1221	 * VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED requests with ID of
1222	 * 0 sent by the guest.
1223	 */
1224	return current_id + 1;
1225}
1226EXPORT_SYMBOL_GPL(vmbus_next_request_id);
1227
1228/* As in vmbus_request_addr_match() but without the requestor lock */
1229u64 __vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
1230			       u64 rqst_addr)
1231{
1232	struct vmbus_requestor *rqstor = &channel->requestor;
1233	u64 req_addr;
1234
1235	/* Check rqstor has been initialized */
1236	if (!channel->rqstor_size)
1237		return VMBUS_NO_RQSTOR;
1238
1239	/* Hyper-V can send an unsolicited message with ID of 0 */
1240	if (!trans_id)
1241		return VMBUS_RQST_ERROR;
1242
1243	/* Data corresponding to trans_id is stored at trans_id - 1 */
1244	trans_id--;
1245
1246	/* Invalid trans_id */
1247	if (trans_id >= rqstor->size || !test_bit(trans_id, rqstor->req_bitmap))
1248		return VMBUS_RQST_ERROR;
1249
1250	req_addr = rqstor->req_arr[trans_id];
1251	if (rqst_addr == VMBUS_RQST_ADDR_ANY || req_addr == rqst_addr) {
1252		rqstor->req_arr[trans_id] = rqstor->next_request_id;
1253		rqstor->next_request_id = trans_id;
1254
1255		/* The already held spin lock provides atomicity */
1256		bitmap_clear(rqstor->req_bitmap, trans_id, 1);
1257	}
1258
1259	return req_addr;
1260}
1261EXPORT_SYMBOL_GPL(__vmbus_request_addr_match);
1262
1263/*
1264 * vmbus_request_addr_match - Clears/removes @trans_id from the @channel's
1265 * requestor, provided the memory address stored at @trans_id equals @rqst_addr
1266 * (or provided @rqst_addr matches the sentinel value VMBUS_RQST_ADDR_ANY).
1267 *
1268 * Returns the memory address stored at @trans_id, or VMBUS_RQST_ERROR if
1269 * @trans_id is not contained in the requestor.
1270 *
1271 * Acquires and releases the requestor spin lock.
1272 */
1273u64 vmbus_request_addr_match(struct vmbus_channel *channel, u64 trans_id,
1274			     u64 rqst_addr)
1275{
1276	unsigned long flags;
1277	u64 req_addr;
1278
1279	lock_requestor(channel, flags);
1280	req_addr = __vmbus_request_addr_match(channel, trans_id, rqst_addr);
1281	unlock_requestor(channel, flags);
1282
1283	return req_addr;
1284}
1285EXPORT_SYMBOL_GPL(vmbus_request_addr_match);
1286
1287/*
1288 * vmbus_request_addr - Returns the memory address stored at @trans_id
1289 * in @rqstor. Uses a spin lock to avoid race conditions.
1290 * @channel: Pointer to the VMbus channel struct
1291 * @trans_id: Request id sent back from Hyper-V. Becomes the requestor's
1292 * next request id.
1293 */
1294u64 vmbus_request_addr(struct vmbus_channel *channel, u64 trans_id)
1295{
1296	return vmbus_request_addr_match(channel, trans_id, VMBUS_RQST_ADDR_ANY);
1297}
1298EXPORT_SYMBOL_GPL(vmbus_request_addr);