drivers/xen/grant-table.c

   1 /******************************************************************************
   2  * grant_table.c
   3  *
   4  * Granting foreign access to our memory reservation.
   5  *
   6  * Copyright (c) 2005-2006, Christopher Clark
   7  * Copyright (c) 2004-2005, K A Fraser
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License version 2
  11  * as published by the Free Software Foundation; or, when distributed
  12  * separately from the Linux kernel or incorporated into other
  13  * software packages, subject to the following license:
  14  *
  15  * Permission is hereby granted, free of charge, to any person obtaining a copy
  16  * of this source file (the "Software"), to deal in the Software without
  17  * restriction, including without limitation the rights to use, copy, modify,
  18  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  19  * and to permit persons to whom the Software is furnished to do so, subject to
  20  * the following conditions:
  21  *
  22  * The above copyright notice and this permission notice shall be included in
  23  * all copies or substantial portions of the Software.
  24  *
  25  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  26  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  27  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  28  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  29  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  30  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  31  * IN THE SOFTWARE.
  32  */
  33
  34 #include <linux/module.h>
  35 #include <linux/sched.h>
  36 #include <linux/mm.h>
  37 #include <linux/slab.h>
  38 #include <linux/vmalloc.h>
  39 #include <linux/uaccess.h>
  40 #include <linux/io.h>
  41
  42 #include <xen/xen.h>
  43 #include <xen/interface/xen.h>
  44 #include <xen/page.h>
  45 #include <xen/grant_table.h>
  46 #include <xen/interface/memory.h>
  47 #include <asm/xen/hypercall.h>
  48
  49 #include <asm/pgtable.h>
  50 #include <asm/sync_bitops.h>
  51
  52
  53 /* External tools reserve first few grant table entries. */
  54 #define NR_RESERVED_ENTRIES 8
  55 #define GNTTAB_LIST_END 0xffffffff
  56 #define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry))
  57
  58 static grant_ref_t **gnttab_list;
  59 static unsigned int nr_grant_frames;
  60 static unsigned int boot_max_nr_grant_frames;
  61 static int gnttab_free_count;
  62 static grant_ref_t gnttab_free_head;
  63 static DEFINE_SPINLOCK(gnttab_list_lock);
  64 unsigned long xen_hvm_resume_frames;
  65 EXPORT_SYMBOL_GPL(xen_hvm_resume_frames);
  66
  67 static struct grant_entry *shared;
  68
  69 static struct gnttab_free_callback *gnttab_free_callback_list;
  70
  71 static int gnttab_expand(unsigned int req_entries);
  72
  73 #define RPP (PAGE_SIZE / sizeof(grant_ref_t))
  74
  75 static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
  76 {
  77         return &gnttab_list[(entry) / RPP][(entry) % RPP];
  78 }
  79 /* This can be used as an l-value */
  80 #define gnttab_entry(entry) (*__gnttab_entry(entry))
  81
  82 static int get_free_entries(unsigned count)
  83 {
  84         unsigned long flags;
  85         int ref, rc = 0;
  86         grant_ref_t head;
  87
  88         spin_lock_irqsave(&gnttab_list_lock, flags);
  89
  90         if ((gnttab_free_count < count) &&
  91             ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
  92                 spin_unlock_irqrestore(&gnttab_list_lock, flags);
  93                 return rc;
  94         }
  95
  96         ref = head = gnttab_free_head;
  97         gnttab_free_count -= count;
  98         while (count-- > 1)
  99                 head = gnttab_entry(head);
 100         gnttab_free_head = gnttab_entry(head);
 101         gnttab_entry(head) = GNTTAB_LIST_END;
 102
 103         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 104
 105         return ref;
 106 }
 107
 108 static void do_free_callbacks(void)
 109 {
 110         struct gnttab_free_callback *callback, *next;
 111
 112         callback = gnttab_free_callback_list;
 113         gnttab_free_callback_list = NULL;
 114
 115         while (callback != NULL) {
 116                 next = callback->next;
 117                 if (gnttab_free_count >= callback->count) {
 118                         callback->next = NULL;
 119                         callback->fn(callback->arg);
 120                 } else {
 121                         callback->next = gnttab_free_callback_list;
 122                         gnttab_free_callback_list = callback;
 123                 }
 124                 callback = next;
 125         }
 126 }
 127
 128 static inline void check_free_callbacks(void)
 129 {
 130         if (unlikely(gnttab_free_callback_list))
 131                 do_free_callbacks();
 132 }
 133
 134 static void put_free_entry(grant_ref_t ref)
 135 {
 136         unsigned long flags;
 137         spin_lock_irqsave(&gnttab_list_lock, flags);
 138         gnttab_entry(ref) = gnttab_free_head;
 139         gnttab_free_head = ref;
 140         gnttab_free_count++;
 141         check_free_callbacks();
 142         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 143 }
 144
 145 static void update_grant_entry(grant_ref_t ref, domid_t domid,
 146                                unsigned long frame, unsigned flags)
 147 {
 148         /*
 149          * Introducing a valid entry into the grant table:
 150          *  1. Write ent->domid.
 151          *  2. Write ent->frame:
 152          *      GTF_permit_access:   Frame to which access is permitted.
 153          *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
 154          *                           frame, or zero if none.
 155          *  3. Write memory barrier (WMB).
 156          *  4. Write ent->flags, inc. valid type.
 157          */
 158         shared[ref].frame = frame;
 159         shared[ref].domid = domid;
 160         wmb();
 161         shared[ref].flags = flags;
 162 }
 163
 164 /*
 165  * Public grant-issuing interface functions
 166  */
 167 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
 168                                      unsigned long frame, int readonly)
 169 {
 170         update_grant_entry(ref, domid, frame,
 171                            GTF_permit_access | (readonly ? GTF_readonly : 0));
 172 }
 173 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);
 174
 175 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 176                                 int readonly)
 177 {
 178         int ref;
 179
 180         ref = get_free_entries(1);
 181         if (unlikely(ref < 0))
 182                 return -ENOSPC;
 183
 184         gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);
 185
 186         return ref;
 187 }
 188 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
 189
 190 int gnttab_query_foreign_access(grant_ref_t ref)
 191 {
 192         u16 nflags;
 193
 194         nflags = shared[ref].flags;
 195
 196         return nflags & (GTF_reading|GTF_writing);
 197 }
 198 EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
 199
 200 int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
 201 {
 202         u16 flags, nflags;
 203
 204         nflags = shared[ref].flags;
 205         do {
 206                 flags = nflags;
 207                 if (flags & (GTF_reading|GTF_writing)) {
 208                         printk(KERN_ALERT "WARNING: g.e. still in use!\n");
 209                         return 0;
 210                 }
 211         } while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) != flags);
 212
 213         return 1;
 214 }
 215 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
 216
 217 void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
 218                                unsigned long page)
 219 {
 220         if (gnttab_end_foreign_access_ref(ref, readonly)) {
 221                 put_free_entry(ref);
 222                 if (page != 0)
 223                         free_page(page);
 224         } else {
 225                 /* XXX This needs to be fixed so that the ref and page are
 226                    placed on a list to be freed up later. */
 227                 printk(KERN_WARNING
 228                        "WARNING: leaking g.e. and page still in use!\n");
 229         }
 230 }
 231 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
 232
 233 int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)
 234 {
 235         int ref;
 236
 237         ref = get_free_entries(1);
 238         if (unlikely(ref < 0))
 239                 return -ENOSPC;
 240         gnttab_grant_foreign_transfer_ref(ref, domid, pfn);
 241
 242         return ref;
 243 }
 244 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);
 245
 246 void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,
 247                                        unsigned long pfn)
 248 {
 249         update_grant_entry(ref, domid, pfn, GTF_accept_transfer);
 250 }
 251 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);
 252
 253 unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
 254 {
 255         unsigned long frame;
 256         u16           flags;
 257
 258         /*
 259          * If a transfer is not even yet started, try to reclaim the grant
 260          * reference and return failure (== 0).
 261          */
 262         while (!((flags = shared[ref].flags) & GTF_transfer_committed)) {
 263                 if (sync_cmpxchg(&shared[ref].flags, flags, 0) == flags)
 264                         return 0;
 265                 cpu_relax();
 266         }
 267
 268         /* If a transfer is in progress then wait until it is completed. */
 269         while (!(flags & GTF_transfer_completed)) {
 270                 flags = shared[ref].flags;
 271                 cpu_relax();
 272         }
 273
 274         rmb();  /* Read the frame number /after/ reading completion status. */
 275         frame = shared[ref].frame;
 276         BUG_ON(frame == 0);
 277
 278         return frame;
 279 }
 280 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);
 281
 282 unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)
 283 {
 284         unsigned long frame = gnttab_end_foreign_transfer_ref(ref);
 285         put_free_entry(ref);
 286         return frame;
 287 }
 288 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);
 289
 290 void gnttab_free_grant_reference(grant_ref_t ref)
 291 {
 292         put_free_entry(ref);
 293 }
 294 EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);
 295
 296 void gnttab_free_grant_references(grant_ref_t head)
 297 {
 298         grant_ref_t ref;
 299         unsigned long flags;
 300         int count = 1;
 301         if (head == GNTTAB_LIST_END)
 302                 return;
 303         spin_lock_irqsave(&gnttab_list_lock, flags);
 304         ref = head;
 305         while (gnttab_entry(ref) != GNTTAB_LIST_END) {
 306                 ref = gnttab_entry(ref);
 307                 count++;
 308         }
 309         gnttab_entry(ref) = gnttab_free_head;
 310         gnttab_free_head = head;
 311         gnttab_free_count += count;
 312         check_free_callbacks();
 313         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 314 }
 315 EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
 316
 317 int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
 318 {
 319         int h = get_free_entries(count);
 320
 321         if (h < 0)
 322                 return -ENOSPC;
 323
 324         *head = h;
 325
 326         return 0;
 327 }
 328 EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);
 329
 330 int gnttab_empty_grant_references(const grant_ref_t *private_head)
 331 {
 332         return (*private_head == GNTTAB_LIST_END);
 333 }
 334 EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);
 335
 336 int gnttab_claim_grant_reference(grant_ref_t *private_head)
 337 {
 338         grant_ref_t g = *private_head;
 339         if (unlikely(g == GNTTAB_LIST_END))
 340                 return -ENOSPC;
 341         *private_head = gnttab_entry(g);
 342         return g;
 343 }
 344 EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);
 345
 346 void gnttab_release_grant_reference(grant_ref_t *private_head,
 347                                     grant_ref_t release)
 348 {
 349         gnttab_entry(release) = *private_head;
 350         *private_head = release;
 351 }
 352 EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);
 353
 354 void gnttab_request_free_callback(struct gnttab_free_callback *callback,
 355                                   void (*fn)(void *), void *arg, u16 count)
 356 {
 357         unsigned long flags;
 358         struct gnttab_free_callback *cb;
 359
 360         spin_lock_irqsave(&gnttab_list_lock, flags);
 361
 362         /* Check if the callback is already on the list */
 363         cb = gnttab_free_callback_list;
 364         while (cb) {
 365                 if (cb == callback)
 366                         goto out;
 367                 cb = cb->next;
 368         }
 369
 370         callback->fn = fn;
 371         callback->arg = arg;
 372         callback->count = count;
 373         callback->next = gnttab_free_callback_list;
 374         gnttab_free_callback_list = callback;
 375         check_free_callbacks();
 376 out:
 377         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 378 }
 379 EXPORT_SYMBOL_GPL(gnttab_request_free_callback);
 380
 381 void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
 382 {
 383         struct gnttab_free_callback **pcb;
 384         unsigned long flags;
 385
 386         spin_lock_irqsave(&gnttab_list_lock, flags);
 387         for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
 388                 if (*pcb == callback) {
 389                         *pcb = callback->next;
 390                         break;
 391                 }
 392         }
 393         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 394 }
 395 EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
 396
 397 static int grow_gnttab_list(unsigned int more_frames)
 398 {
 399         unsigned int new_nr_grant_frames, extra_entries, i;
 400         unsigned int nr_glist_frames, new_nr_glist_frames;
 401
 402         new_nr_grant_frames = nr_grant_frames + more_frames;
 403         extra_entries       = more_frames * GREFS_PER_GRANT_FRAME;
 404
 405         nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
 406         new_nr_glist_frames =
 407                 (new_nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
 408         for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
 409                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
 410                 if (!gnttab_list[i])
 411                         goto grow_nomem;
 412         }
 413
 414
 415         for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames;
 416              i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)
 417                 gnttab_entry(i) = i + 1;
 418
 419         gnttab_entry(i) = gnttab_free_head;
 420         gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames;
 421         gnttab_free_count += extra_entries;
 422
 423         nr_grant_frames = new_nr_grant_frames;
 424
 425         check_free_callbacks();
 426
 427         return 0;
 428
 429 grow_nomem:
 430         for ( ; i >= nr_glist_frames; i--)
 431                 free_page((unsigned long) gnttab_list[i]);
 432         return -ENOMEM;
 433 }
 434
 435 static unsigned int __max_nr_grant_frames(void)
 436 {
 437         struct gnttab_query_size query;
 438         int rc;
 439
 440         query.dom = DOMID_SELF;
 441
 442         rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
 443         if ((rc < 0) || (query.status != GNTST_okay))
 444                 return 4; /* Legacy max supported number of frames */
 445
 446         return query.max_nr_frames;
 447 }
 448
 449 unsigned int gnttab_max_grant_frames(void)
 450 {
 451         unsigned int xen_max = __max_nr_grant_frames();
 452
 453         if (xen_max > boot_max_nr_grant_frames)
 454                 return boot_max_nr_grant_frames;
 455         return xen_max;
 456 }
 457 EXPORT_SYMBOL_GPL(gnttab_max_grant_frames);
 458
 459 int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 460                         struct gnttab_map_grant_ref *kmap_ops,
 461                         struct page **pages, unsigned int count)
 462 {
 463         int i, ret;
 464         pte_t *pte;
 465         unsigned long mfn;
 466
 467         ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);
 468         if (ret)
 469                 return ret;
 470
 471         if (xen_feature(XENFEAT_auto_translated_physmap))
 472                 return ret;
 473
 474         for (i = 0; i < count; i++) {
 475                 /* Do not add to override if the map failed. */
 476                 if (map_ops[i].status)
 477                         continue;
 478
 479                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 480                         pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 481                                 (map_ops[i].host_addr & ~PAGE_MASK));
 482                         mfn = pte_mfn(*pte);
 483                 } else {
 484                         /* If you really wanted to do this:
 485                          * mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 486                          *
 487                          * The reason we do not implement it is b/c on the
 488                          * unmap path (gnttab_unmap_refs) we have no means of
 489                          * checking whether the page is !GNTMAP_contains_pte.
 490                          *
 491                          * That is without some extra data-structure to carry
 492                          * the struct page, bool clear_pte, and list_head next
 493                          * tuples and deal with allocation/delallocation, etc.
 494                          *
 495                          * The users of this API set the GNTMAP_contains_pte
 496                          * flag so lets just return not supported until it
 497                          * becomes neccessary to implement.
 498                          */
 499                         return -EOPNOTSUPP;
 500                 }
 501                 ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
 502                 if (ret)
 503                         return ret;
 504         }
 505
 506         return ret;
 507 }
 508 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 509
 510 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
 511                 struct page **pages, unsigned int count)
 512 {
 513         int i, ret;
 514
 515         ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
 516         if (ret)
 517                 return ret;
 518
 519         if (xen_feature(XENFEAT_auto_translated_physmap))
 520                 return ret;
 521
 522         for (i = 0; i < count; i++) {
 523                 ret = m2p_remove_override(pages[i], true /* clear the PTE */);
 524                 if (ret)
 525                         return ret;
 526         }
 527
 528         return ret;
 529 }
 530 EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
 531
 532 static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
 533 {
 534         struct gnttab_setup_table setup;
 535         unsigned long *frames;
 536         unsigned int nr_gframes = end_idx + 1;
 537         int rc;
 538
 539         if (xen_hvm_domain()) {
 540                 struct xen_add_to_physmap xatp;
 541                 unsigned int i = end_idx;
 542                 rc = 0;
 543                 /*
 544                  * Loop backwards, so that the first hypercall has the largest
 545                  * index, ensuring that the table will grow only once.
 546                  */
 547                 do {
 548                         xatp.domid = DOMID_SELF;
 549                         xatp.idx = i;
 550                         xatp.space = XENMAPSPACE_grant_table;
 551                         xatp.gpfn = (xen_hvm_resume_frames >> PAGE_SHIFT) + i;
 552                         rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
 553                         if (rc != 0) {
 554                                 printk(KERN_WARNING
 555                                                 "grant table add_to_physmap failed, err=%d\n", rc);
 556                                 break;
 557                         }
 558                 } while (i-- > start_idx);
 559
 560                 return rc;
 561         }
 562
 563         frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC);
 564         if (!frames)
 565                 return -ENOMEM;
 566
 567         setup.dom        = DOMID_SELF;
 568         setup.nr_frames  = nr_gframes;
 569         set_xen_guest_handle(setup.frame_list, frames);
 570
 571         rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
 572         if (rc == -ENOSYS) {
 573                 kfree(frames);
 574                 return -ENOSYS;
 575         }
 576
 577         BUG_ON(rc || setup.status);
 578
 579         rc = arch_gnttab_map_shared(frames, nr_gframes, gnttab_max_grant_frames(),
 580                                     &shared);
 581         BUG_ON(rc);
 582
 583         kfree(frames);
 584
 585         return 0;
 586 }
 587
 588 int gnttab_resume(void)
 589 {
 590         unsigned int max_nr_gframes;
 591
 592         max_nr_gframes = gnttab_max_grant_frames();
 593         if (max_nr_gframes < nr_grant_frames)
 594                 return -ENOSYS;
 595
 596         if (xen_pv_domain())
 597                 return gnttab_map(0, nr_grant_frames - 1);
 598
 599         if (!shared) {
 600                 shared = ioremap(xen_hvm_resume_frames, PAGE_SIZE * max_nr_gframes);
 601                 if (shared == NULL) {
 602                         printk(KERN_WARNING
 603                                         "Failed to ioremap gnttab share frames!");
 604                         return -ENOMEM;
 605                 }
 606         }
 607
 608         gnttab_map(0, nr_grant_frames - 1);
 609
 610         return 0;
 611 }
 612
 613 int gnttab_suspend(void)
 614 {
 615         arch_gnttab_unmap_shared(shared, nr_grant_frames);
 616         return 0;
 617 }
 618
 619 static int gnttab_expand(unsigned int req_entries)
 620 {
 621         int rc;
 622         unsigned int cur, extra;
 623
 624         cur = nr_grant_frames;
 625         extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) /
 626                  GREFS_PER_GRANT_FRAME);
 627         if (cur + extra > gnttab_max_grant_frames())
 628                 return -ENOSPC;
 629
 630         rc = gnttab_map(cur, cur + extra - 1);
 631         if (rc == 0)
 632                 rc = grow_gnttab_list(extra);
 633
 634         return rc;
 635 }
 636
 637 int gnttab_init(void)
 638 {
 639         int i;
 640         unsigned int max_nr_glist_frames, nr_glist_frames;
 641         unsigned int nr_init_grefs;
 642
 643         nr_grant_frames = 1;
 644         boot_max_nr_grant_frames = __max_nr_grant_frames();
 645
 646         /* Determine the maximum number of frames required for the
 647          * grant reference free list on the current hypervisor.
 648          */
 649         max_nr_glist_frames = (boot_max_nr_grant_frames *
 650                                GREFS_PER_GRANT_FRAME / RPP);
 651
 652         gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
 653                               GFP_KERNEL);
 654         if (gnttab_list == NULL)
 655                 return -ENOMEM;
 656
 657         nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
 658         for (i = 0; i < nr_glist_frames; i++) {
 659                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
 660                 if (gnttab_list[i] == NULL)
 661                         goto ini_nomem;
 662         }
 663
 664         if (gnttab_resume() < 0)
 665                 return -ENODEV;
 666
 667         nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME;
 668
 669         for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
 670                 gnttab_entry(i) = i + 1;
 671
 672         gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
 673         gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
 674         gnttab_free_head  = NR_RESERVED_ENTRIES;
 675
 676         printk("Grant table initialized\n");
 677         return 0;
 678
 679  ini_nomem:
 680         for (i--; i >= 0; i--)
 681                 free_page((unsigned long)gnttab_list[i]);
 682         kfree(gnttab_list);
 683         return -ENOMEM;
 684 }
 685 EXPORT_SYMBOL_GPL(gnttab_init);
 686
 687 static int __devinit __gnttab_init(void)
 688 {
 689         /* Delay grant-table initialization in the PV on HVM case */
 690         if (xen_hvm_domain())
 691                 return 0;
 692
 693         if (!xen_pv_domain())
 694                 return -ENODEV;
 695
 696         return gnttab_init();
 697 }
 698
 699 core_initcall(__gnttab_init);