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 #include <linux/delay.h>
  42 #include <linux/hardirq.h>
  43
  44 #include <xen/xen.h>
  45 #include <xen/interface/xen.h>
  46 #include <xen/page.h>
  47 #include <xen/grant_table.h>
  48 #include <xen/interface/memory.h>
  49 #include <xen/hvc-console.h>
  50 #include <asm/xen/hypercall.h>
  51 #include <asm/xen/interface.h>
  52
  53 #include <asm/pgtable.h>
  54 #include <asm/sync_bitops.h>
  55
  56 /* External tools reserve first few grant table entries. */
  57 #define NR_RESERVED_ENTRIES 8
  58 #define GNTTAB_LIST_END 0xffffffff
  59
  60 static grant_ref_t **gnttab_list;
  61 static unsigned int nr_grant_frames;
  62 static unsigned int boot_max_nr_grant_frames;
  63 static int gnttab_free_count;
  64 static grant_ref_t gnttab_free_head;
  65 static DEFINE_SPINLOCK(gnttab_list_lock);
  66 unsigned long xen_hvm_resume_frames;
  67 EXPORT_SYMBOL_GPL(xen_hvm_resume_frames);
  68
  69 static union {
  70         struct grant_entry_v1 *v1;
  71         union grant_entry_v2 *v2;
  72         void *addr;
  73 } gnttab_shared;
  74
  75 /*This is a structure of function pointers for grant table*/
  76 struct gnttab_ops {
  77         /*
  78          * Mapping a list of frames for storing grant entries. Frames parameter
  79          * is used to store grant table address when grant table being setup,
  80          * nr_gframes is the number of frames to map grant table. Returning
  81          * GNTST_okay means success and negative value means failure.
  82          */
  83         int (*map_frames)(xen_pfn_t *frames, unsigned int nr_gframes);
  84         /*
  85          * Release a list of frames which are mapped in map_frames for grant
  86          * entry status.
  87          */
  88         void (*unmap_frames)(void);
  89         /*
  90          * Introducing a valid entry into the grant table, granting the frame of
  91          * this grant entry to domain for accessing or transfering. Ref
  92          * parameter is reference of this introduced grant entry, domid is id of
  93          * granted domain, frame is the page frame to be granted, and flags is
  94          * status of the grant entry to be updated.
  95          */
  96         void (*update_entry)(grant_ref_t ref, domid_t domid,
  97                              unsigned long frame, unsigned flags);
  98         /*
  99          * Stop granting a grant entry to domain for accessing. Ref parameter is
 100          * reference of a grant entry whose grant access will be stopped,
 101          * readonly is not in use in this function. If the grant entry is
 102          * currently mapped for reading or writing, just return failure(==0)
 103          * directly and don't tear down the grant access. Otherwise, stop grant
 104          * access for this entry and return success(==1).
 105          */
 106         int (*end_foreign_access_ref)(grant_ref_t ref, int readonly);
 107         /*
 108          * Stop granting a grant entry to domain for transfer. Ref parameter is
 109          * reference of a grant entry whose grant transfer will be stopped. If
 110          * tranfer has not started, just reclaim the grant entry and return
 111          * failure(==0). Otherwise, wait for the transfer to complete and then
 112          * return the frame.
 113          */
 114         unsigned long (*end_foreign_transfer_ref)(grant_ref_t ref);
 115         /*
 116          * Query the status of a grant entry. Ref parameter is reference of
 117          * queried grant entry, return value is the status of queried entry.
 118          * Detailed status(writing/reading) can be gotten from the return value
 119          * by bit operations.
 120          */
 121         int (*query_foreign_access)(grant_ref_t ref);
 122         /*
 123          * Grant a domain to access a range of bytes within the page referred by
 124          * an available grant entry. Ref parameter is reference of a grant entry
 125          * which will be sub-page accessed, domid is id of grantee domain, frame
 126          * is frame address of subpage grant, flags is grant type and flag
 127          * information, page_off is offset of the range of bytes, and length is
 128          * length of bytes to be accessed.
 129          */
 130         void (*update_subpage_entry)(grant_ref_t ref, domid_t domid,
 131                                      unsigned long frame, int flags,
 132                                      unsigned page_off, unsigned length);
 133         /*
 134          * Redirect an available grant entry on domain A to another grant
 135          * reference of domain B, then allow domain C to use grant reference
 136          * of domain B transitively. Ref parameter is an available grant entry
 137          * reference on domain A, domid is id of domain C which accesses grant
 138          * entry transitively, flags is grant type and flag information,
 139          * trans_domid is id of domain B whose grant entry is finally accessed
 140          * transitively, trans_gref is grant entry transitive reference of
 141          * domain B.
 142          */
 143         void (*update_trans_entry)(grant_ref_t ref, domid_t domid, int flags,
 144                                    domid_t trans_domid, grant_ref_t trans_gref);
 145 };
 146
 147 static struct gnttab_ops *gnttab_interface;
 148
 149 /*This reflects status of grant entries, so act as a global value*/
 150 static grant_status_t *grstatus;
 151
 152 static int grant_table_version;
 153 static int grefs_per_grant_frame;
 154
 155 static struct gnttab_free_callback *gnttab_free_callback_list;
 156
 157 static int gnttab_expand(unsigned int req_entries);
 158
 159 #define RPP (PAGE_SIZE / sizeof(grant_ref_t))
 160 #define SPP (PAGE_SIZE / sizeof(grant_status_t))
 161
 162 static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
 163 {
 164         return &gnttab_list[(entry) / RPP][(entry) % RPP];
 165 }
 166 /* This can be used as an l-value */
 167 #define gnttab_entry(entry) (*__gnttab_entry(entry))
 168
 169 static int get_free_entries(unsigned count)
 170 {
 171         unsigned long flags;
 172         int ref, rc = 0;
 173         grant_ref_t head;
 174
 175         spin_lock_irqsave(&gnttab_list_lock, flags);
 176
 177         if ((gnttab_free_count < count) &&
 178             ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
 179                 spin_unlock_irqrestore(&gnttab_list_lock, flags);
 180                 return rc;
 181         }
 182
 183         ref = head = gnttab_free_head;
 184         gnttab_free_count -= count;
 185         while (count-- > 1)
 186                 head = gnttab_entry(head);
 187         gnttab_free_head = gnttab_entry(head);
 188         gnttab_entry(head) = GNTTAB_LIST_END;
 189
 190         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 191
 192         return ref;
 193 }
 194
 195 static void do_free_callbacks(void)
 196 {
 197         struct gnttab_free_callback *callback, *next;
 198
 199         callback = gnttab_free_callback_list;
 200         gnttab_free_callback_list = NULL;
 201
 202         while (callback != NULL) {
 203                 next = callback->next;
 204                 if (gnttab_free_count >= callback->count) {
 205                         callback->next = NULL;
 206                         callback->fn(callback->arg);
 207                 } else {
 208                         callback->next = gnttab_free_callback_list;
 209                         gnttab_free_callback_list = callback;
 210                 }
 211                 callback = next;
 212         }
 213 }
 214
 215 static inline void check_free_callbacks(void)
 216 {
 217         if (unlikely(gnttab_free_callback_list))
 218                 do_free_callbacks();
 219 }
 220
 221 static void put_free_entry(grant_ref_t ref)
 222 {
 223         unsigned long flags;
 224         spin_lock_irqsave(&gnttab_list_lock, flags);
 225         gnttab_entry(ref) = gnttab_free_head;
 226         gnttab_free_head = ref;
 227         gnttab_free_count++;
 228         check_free_callbacks();
 229         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 230 }
 231
 232 /*
 233  * Following applies to gnttab_update_entry_v1 and gnttab_update_entry_v2.
 234  * Introducing a valid entry into the grant table:
 235  *  1. Write ent->domid.
 236  *  2. Write ent->frame:
 237  *      GTF_permit_access:   Frame to which access is permitted.
 238  *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
 239  *                           frame, or zero if none.
 240  *  3. Write memory barrier (WMB).
 241  *  4. Write ent->flags, inc. valid type.
 242  */
 243 static void gnttab_update_entry_v1(grant_ref_t ref, domid_t domid,
 244                                    unsigned long frame, unsigned flags)
 245 {
 246         gnttab_shared.v1[ref].domid = domid;
 247         gnttab_shared.v1[ref].frame = frame;
 248         wmb();
 249         gnttab_shared.v1[ref].flags = flags;
 250 }
 251
 252 static void gnttab_update_entry_v2(grant_ref_t ref, domid_t domid,
 253                                    unsigned long frame, unsigned flags)
 254 {
 255         gnttab_shared.v2[ref].hdr.domid = domid;
 256         gnttab_shared.v2[ref].full_page.frame = frame;
 257         wmb();
 258         gnttab_shared.v2[ref].hdr.flags = GTF_permit_access | flags;
 259 }
 260
 261 /*
 262  * Public grant-issuing interface functions
 263  */
 264 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
 265                                      unsigned long frame, int readonly)
 266 {
 267         gnttab_interface->update_entry(ref, domid, frame,
 268                            GTF_permit_access | (readonly ? GTF_readonly : 0));
 269 }
 270 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);
 271
 272 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 273                                 int readonly)
 274 {
 275         int ref;
 276
 277         ref = get_free_entries(1);
 278         if (unlikely(ref < 0))
 279                 return -ENOSPC;
 280
 281         gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);
 282
 283         return ref;
 284 }
 285 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
 286
 287 static void gnttab_update_subpage_entry_v2(grant_ref_t ref, domid_t domid,
 288                                            unsigned long frame, int flags,
 289                                            unsigned page_off, unsigned length)
 290 {
 291         gnttab_shared.v2[ref].sub_page.frame = frame;
 292         gnttab_shared.v2[ref].sub_page.page_off = page_off;
 293         gnttab_shared.v2[ref].sub_page.length = length;
 294         gnttab_shared.v2[ref].hdr.domid = domid;
 295         wmb();
 296         gnttab_shared.v2[ref].hdr.flags =
 297                                 GTF_permit_access | GTF_sub_page | flags;
 298 }
 299
 300 int gnttab_grant_foreign_access_subpage_ref(grant_ref_t ref, domid_t domid,
 301                                             unsigned long frame, int flags,
 302                                             unsigned page_off,
 303                                             unsigned length)
 304 {
 305         if (flags & (GTF_accept_transfer | GTF_reading |
 306                      GTF_writing | GTF_transitive))
 307                 return -EPERM;
 308
 309         if (gnttab_interface->update_subpage_entry == NULL)
 310                 return -ENOSYS;
 311
 312         gnttab_interface->update_subpage_entry(ref, domid, frame, flags,
 313                                                page_off, length);
 314
 315         return 0;
 316 }
 317 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage_ref);
 318
 319 int gnttab_grant_foreign_access_subpage(domid_t domid, unsigned long frame,
 320                                         int flags, unsigned page_off,
 321                                         unsigned length)
 322 {
 323         int ref, rc;
 324
 325         ref = get_free_entries(1);
 326         if (unlikely(ref < 0))
 327                 return -ENOSPC;
 328
 329         rc = gnttab_grant_foreign_access_subpage_ref(ref, domid, frame, flags,
 330                                                      page_off, length);
 331         if (rc < 0) {
 332                 put_free_entry(ref);
 333                 return rc;
 334         }
 335
 336         return ref;
 337 }
 338 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_subpage);
 339
 340 bool gnttab_subpage_grants_available(void)
 341 {
 342         return gnttab_interface->update_subpage_entry != NULL;
 343 }
 344 EXPORT_SYMBOL_GPL(gnttab_subpage_grants_available);
 345
 346 static void gnttab_update_trans_entry_v2(grant_ref_t ref, domid_t domid,
 347                                          int flags, domid_t trans_domid,
 348                                          grant_ref_t trans_gref)
 349 {
 350         gnttab_shared.v2[ref].transitive.trans_domid = trans_domid;
 351         gnttab_shared.v2[ref].transitive.gref = trans_gref;
 352         gnttab_shared.v2[ref].hdr.domid = domid;
 353         wmb();
 354         gnttab_shared.v2[ref].hdr.flags =
 355                                 GTF_permit_access | GTF_transitive | flags;
 356 }
 357
 358 int gnttab_grant_foreign_access_trans_ref(grant_ref_t ref, domid_t domid,
 359                                           int flags, domid_t trans_domid,
 360                                           grant_ref_t trans_gref)
 361 {
 362         if (flags & (GTF_accept_transfer | GTF_reading |
 363                      GTF_writing | GTF_sub_page))
 364                 return -EPERM;
 365
 366         if (gnttab_interface->update_trans_entry == NULL)
 367                 return -ENOSYS;
 368
 369         gnttab_interface->update_trans_entry(ref, domid, flags, trans_domid,
 370                                              trans_gref);
 371
 372         return 0;
 373 }
 374 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans_ref);
 375
 376 int gnttab_grant_foreign_access_trans(domid_t domid, int flags,
 377                                       domid_t trans_domid,
 378                                       grant_ref_t trans_gref)
 379 {
 380         int ref, rc;
 381
 382         ref = get_free_entries(1);
 383         if (unlikely(ref < 0))
 384                 return -ENOSPC;
 385
 386         rc = gnttab_grant_foreign_access_trans_ref(ref, domid, flags,
 387                                                    trans_domid, trans_gref);
 388         if (rc < 0) {
 389                 put_free_entry(ref);
 390                 return rc;
 391         }
 392
 393         return ref;
 394 }
 395 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_trans);
 396
 397 bool gnttab_trans_grants_available(void)
 398 {
 399         return gnttab_interface->update_trans_entry != NULL;
 400 }
 401 EXPORT_SYMBOL_GPL(gnttab_trans_grants_available);
 402
 403 static int gnttab_query_foreign_access_v1(grant_ref_t ref)
 404 {
 405         return gnttab_shared.v1[ref].flags & (GTF_reading|GTF_writing);
 406 }
 407
 408 static int gnttab_query_foreign_access_v2(grant_ref_t ref)
 409 {
 410         return grstatus[ref] & (GTF_reading|GTF_writing);
 411 }
 412
 413 int gnttab_query_foreign_access(grant_ref_t ref)
 414 {
 415         return gnttab_interface->query_foreign_access(ref);
 416 }
 417 EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
 418
 419 static int gnttab_end_foreign_access_ref_v1(grant_ref_t ref, int readonly)
 420 {
 421         u16 flags, nflags;
 422         u16 *pflags;
 423
 424         pflags = &gnttab_shared.v1[ref].flags;
 425         nflags = *pflags;
 426         do {
 427                 flags = nflags;
 428                 if (flags & (GTF_reading|GTF_writing))
 429                         return 0;
 430         } while ((nflags = sync_cmpxchg(pflags, flags, 0)) != flags);
 431
 432         return 1;
 433 }
 434
 435 static int gnttab_end_foreign_access_ref_v2(grant_ref_t ref, int readonly)
 436 {
 437         gnttab_shared.v2[ref].hdr.flags = 0;
 438         mb();
 439         if (grstatus[ref] & (GTF_reading|GTF_writing)) {
 440                 return 0;
 441         } else {
 442                 /* The read of grstatus needs to have acquire
 443                 semantics.  On x86, reads already have
 444                 that, and we just need to protect against
 445                 compiler reorderings.  On other
 446                 architectures we may need a full
 447                 barrier. */
 448 #ifdef CONFIG_X86
 449                 barrier();
 450 #else
 451                 mb();
 452 #endif
 453         }
 454
 455         return 1;
 456 }
 457
 458 static inline int _gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
 459 {
 460         return gnttab_interface->end_foreign_access_ref(ref, readonly);
 461 }
 462
 463 int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
 464 {
 465         if (_gnttab_end_foreign_access_ref(ref, readonly))
 466                 return 1;
 467         pr_warn("WARNING: g.e. %#x still in use!\n", ref);
 468         return 0;
 469 }
 470 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
 471
 472 struct deferred_entry {
 473         struct list_head list;
 474         grant_ref_t ref;
 475         bool ro;
 476         uint16_t warn_delay;
 477         struct page *page;
 478 };
 479 static LIST_HEAD(deferred_list);
 480 static void gnttab_handle_deferred(unsigned long);
 481 static DEFINE_TIMER(deferred_timer, gnttab_handle_deferred, 0, 0);
 482
 483 static void gnttab_handle_deferred(unsigned long unused)
 484 {
 485         unsigned int nr = 10;
 486         struct deferred_entry *first = NULL;
 487         unsigned long flags;
 488
 489         spin_lock_irqsave(&gnttab_list_lock, flags);
 490         while (nr--) {
 491                 struct deferred_entry *entry
 492                         = list_first_entry(&deferred_list,
 493                                            struct deferred_entry, list);
 494
 495                 if (entry == first)
 496                         break;
 497                 list_del(&entry->list);
 498                 spin_unlock_irqrestore(&gnttab_list_lock, flags);
 499                 if (_gnttab_end_foreign_access_ref(entry->ref, entry->ro)) {
 500                         put_free_entry(entry->ref);
 501                         if (entry->page) {
 502                                 pr_debug("freeing g.e. %#x (pfn %#lx)\n",
 503                                          entry->ref, page_to_pfn(entry->page));
 504                                 __free_page(entry->page);
 505                         } else
 506                                 pr_info("freeing g.e. %#x\n", entry->ref);
 507                         kfree(entry);
 508                         entry = NULL;
 509                 } else {
 510                         if (!--entry->warn_delay)
 511                                 pr_info("g.e. %#x still pending\n",
 512                                         entry->ref);
 513                         if (!first)
 514                                 first = entry;
 515                 }
 516                 spin_lock_irqsave(&gnttab_list_lock, flags);
 517                 if (entry)
 518                         list_add_tail(&entry->list, &deferred_list);
 519                 else if (list_empty(&deferred_list))
 520                         break;
 521         }
 522         if (!list_empty(&deferred_list) && !timer_pending(&deferred_timer)) {
 523                 deferred_timer.expires = jiffies + HZ;
 524                 add_timer(&deferred_timer);
 525         }
 526         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 527 }
 528
 529 static void gnttab_add_deferred(grant_ref_t ref, bool readonly,
 530                                 struct page *page)
 531 {
 532         struct deferred_entry *entry = kmalloc(sizeof(*entry), GFP_ATOMIC);
 533         const char *what = KERN_WARNING "leaking";
 534
 535         if (entry) {
 536                 unsigned long flags;
 537
 538                 entry->ref = ref;
 539                 entry->ro = readonly;
 540                 entry->page = page;
 541                 entry->warn_delay = 60;
 542                 spin_lock_irqsave(&gnttab_list_lock, flags);
 543                 list_add_tail(&entry->list, &deferred_list);
 544                 if (!timer_pending(&deferred_timer)) {
 545                         deferred_timer.expires = jiffies + HZ;
 546                         add_timer(&deferred_timer);
 547                 }
 548                 spin_unlock_irqrestore(&gnttab_list_lock, flags);
 549                 what = KERN_DEBUG "deferring";
 550         }
 551         printk("%s g.e. %#x (pfn %#lx)\n",
 552                what, ref, page ? page_to_pfn(page) : -1);
 553 }
 554
 555 void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
 556                                unsigned long page)
 557 {
 558         if (gnttab_end_foreign_access_ref(ref, readonly)) {
 559                 put_free_entry(ref);
 560                 if (page != 0)
 561                         free_page(page);
 562         } else
 563                 gnttab_add_deferred(ref, readonly,
 564                                     page ? virt_to_page(page) : NULL);
 565 }
 566 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
 567
 568 int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)
 569 {
 570         int ref;
 571
 572         ref = get_free_entries(1);
 573         if (unlikely(ref < 0))
 574                 return -ENOSPC;
 575         gnttab_grant_foreign_transfer_ref(ref, domid, pfn);
 576
 577         return ref;
 578 }
 579 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);
 580
 581 void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,
 582                                        unsigned long pfn)
 583 {
 584         gnttab_interface->update_entry(ref, domid, pfn, GTF_accept_transfer);
 585 }
 586 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);
 587
 588 static unsigned long gnttab_end_foreign_transfer_ref_v1(grant_ref_t ref)
 589 {
 590         unsigned long frame;
 591         u16           flags;
 592         u16          *pflags;
 593
 594         pflags = &gnttab_shared.v1[ref].flags;
 595
 596         /*
 597          * If a transfer is not even yet started, try to reclaim the grant
 598          * reference and return failure (== 0).
 599          */
 600         while (!((flags = *pflags) & GTF_transfer_committed)) {
 601                 if (sync_cmpxchg(pflags, flags, 0) == flags)
 602                         return 0;
 603                 cpu_relax();
 604         }
 605
 606         /* If a transfer is in progress then wait until it is completed. */
 607         while (!(flags & GTF_transfer_completed)) {
 608                 flags = *pflags;
 609                 cpu_relax();
 610         }
 611
 612         rmb();  /* Read the frame number /after/ reading completion status. */
 613         frame = gnttab_shared.v1[ref].frame;
 614         BUG_ON(frame == 0);
 615
 616         return frame;
 617 }
 618
 619 static unsigned long gnttab_end_foreign_transfer_ref_v2(grant_ref_t ref)
 620 {
 621         unsigned long frame;
 622         u16           flags;
 623         u16          *pflags;
 624
 625         pflags = &gnttab_shared.v2[ref].hdr.flags;
 626
 627         /*
 628          * If a transfer is not even yet started, try to reclaim the grant
 629          * reference and return failure (== 0).
 630          */
 631         while (!((flags = *pflags) & GTF_transfer_committed)) {
 632                 if (sync_cmpxchg(pflags, flags, 0) == flags)
 633                         return 0;
 634                 cpu_relax();
 635         }
 636
 637         /* If a transfer is in progress then wait until it is completed. */
 638         while (!(flags & GTF_transfer_completed)) {
 639                 flags = *pflags;
 640                 cpu_relax();
 641         }
 642
 643         rmb();  /* Read the frame number /after/ reading completion status. */
 644         frame = gnttab_shared.v2[ref].full_page.frame;
 645         BUG_ON(frame == 0);
 646
 647         return frame;
 648 }
 649
 650 unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
 651 {
 652         return gnttab_interface->end_foreign_transfer_ref(ref);
 653 }
 654 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);
 655
 656 unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)
 657 {
 658         unsigned long frame = gnttab_end_foreign_transfer_ref(ref);
 659         put_free_entry(ref);
 660         return frame;
 661 }
 662 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);
 663
 664 void gnttab_free_grant_reference(grant_ref_t ref)
 665 {
 666         put_free_entry(ref);
 667 }
 668 EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);
 669
 670 void gnttab_free_grant_references(grant_ref_t head)
 671 {
 672         grant_ref_t ref;
 673         unsigned long flags;
 674         int count = 1;
 675         if (head == GNTTAB_LIST_END)
 676                 return;
 677         spin_lock_irqsave(&gnttab_list_lock, flags);
 678         ref = head;
 679         while (gnttab_entry(ref) != GNTTAB_LIST_END) {
 680                 ref = gnttab_entry(ref);
 681                 count++;
 682         }
 683         gnttab_entry(ref) = gnttab_free_head;
 684         gnttab_free_head = head;
 685         gnttab_free_count += count;
 686         check_free_callbacks();
 687         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 688 }
 689 EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
 690
 691 int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
 692 {
 693         int h = get_free_entries(count);
 694
 695         if (h < 0)
 696                 return -ENOSPC;
 697
 698         *head = h;
 699
 700         return 0;
 701 }
 702 EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);
 703
 704 int gnttab_empty_grant_references(const grant_ref_t *private_head)
 705 {
 706         return (*private_head == GNTTAB_LIST_END);
 707 }
 708 EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);
 709
 710 int gnttab_claim_grant_reference(grant_ref_t *private_head)
 711 {
 712         grant_ref_t g = *private_head;
 713         if (unlikely(g == GNTTAB_LIST_END))
 714                 return -ENOSPC;
 715         *private_head = gnttab_entry(g);
 716         return g;
 717 }
 718 EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);
 719
 720 void gnttab_release_grant_reference(grant_ref_t *private_head,
 721                                     grant_ref_t release)
 722 {
 723         gnttab_entry(release) = *private_head;
 724         *private_head = release;
 725 }
 726 EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);
 727
 728 void gnttab_request_free_callback(struct gnttab_free_callback *callback,
 729                                   void (*fn)(void *), void *arg, u16 count)
 730 {
 731         unsigned long flags;
 732         spin_lock_irqsave(&gnttab_list_lock, flags);
 733         if (callback->next)
 734                 goto out;
 735         callback->fn = fn;
 736         callback->arg = arg;
 737         callback->count = count;
 738         callback->next = gnttab_free_callback_list;
 739         gnttab_free_callback_list = callback;
 740         check_free_callbacks();
 741 out:
 742         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 743 }
 744 EXPORT_SYMBOL_GPL(gnttab_request_free_callback);
 745
 746 void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
 747 {
 748         struct gnttab_free_callback **pcb;
 749         unsigned long flags;
 750
 751         spin_lock_irqsave(&gnttab_list_lock, flags);
 752         for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
 753                 if (*pcb == callback) {
 754                         *pcb = callback->next;
 755                         break;
 756                 }
 757         }
 758         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 759 }
 760 EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
 761
 762 static int grow_gnttab_list(unsigned int more_frames)
 763 {
 764         unsigned int new_nr_grant_frames, extra_entries, i;
 765         unsigned int nr_glist_frames, new_nr_glist_frames;
 766
 767         BUG_ON(grefs_per_grant_frame == 0);
 768
 769         new_nr_grant_frames = nr_grant_frames + more_frames;
 770         extra_entries       = more_frames * grefs_per_grant_frame;
 771
 772         nr_glist_frames = (nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;
 773         new_nr_glist_frames =
 774                 (new_nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;
 775         for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
 776                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
 777                 if (!gnttab_list[i])
 778                         goto grow_nomem;
 779         }
 780
 781
 782         for (i = grefs_per_grant_frame * nr_grant_frames;
 783              i < grefs_per_grant_frame * new_nr_grant_frames - 1; i++)
 784                 gnttab_entry(i) = i + 1;
 785
 786         gnttab_entry(i) = gnttab_free_head;
 787         gnttab_free_head = grefs_per_grant_frame * nr_grant_frames;
 788         gnttab_free_count += extra_entries;
 789
 790         nr_grant_frames = new_nr_grant_frames;
 791
 792         check_free_callbacks();
 793
 794         return 0;
 795
 796 grow_nomem:
 797         for ( ; i >= nr_glist_frames; i--)
 798                 free_page((unsigned long) gnttab_list[i]);
 799         return -ENOMEM;
 800 }
 801
 802 static unsigned int __max_nr_grant_frames(void)
 803 {
 804         struct gnttab_query_size query;
 805         int rc;
 806
 807         query.dom = DOMID_SELF;
 808
 809         rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
 810         if ((rc < 0) || (query.status != GNTST_okay))
 811                 return 4; /* Legacy max supported number of frames */
 812
 813         return query.max_nr_frames;
 814 }
 815
 816 unsigned int gnttab_max_grant_frames(void)
 817 {
 818         unsigned int xen_max = __max_nr_grant_frames();
 819
 820         if (xen_max > boot_max_nr_grant_frames)
 821                 return boot_max_nr_grant_frames;
 822         return xen_max;
 823 }
 824 EXPORT_SYMBOL_GPL(gnttab_max_grant_frames);
 825
 826 /* Handling of paged out grant targets (GNTST_eagain) */
 827 #define MAX_DELAY 256
 828 static inline void
 829 gnttab_retry_eagain_gop(unsigned int cmd, void *gop, int16_t *status,
 830                                                 const char *func)
 831 {
 832         unsigned delay = 1;
 833
 834         do {
 835                 BUG_ON(HYPERVISOR_grant_table_op(cmd, gop, 1));
 836                 if (*status == GNTST_eagain)
 837                         msleep(delay++);
 838         } while ((*status == GNTST_eagain) && (delay < MAX_DELAY));
 839
 840         if (delay >= MAX_DELAY) {
 841                 printk(KERN_ERR "%s: %s eagain grant\n", func, current->comm);
 842                 *status = GNTST_bad_page;
 843         }
 844 }
 845
 846 void gnttab_batch_map(struct gnttab_map_grant_ref *batch, unsigned count)
 847 {
 848         struct gnttab_map_grant_ref *op;
 849
 850         if (HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, batch, count))
 851                 BUG();
 852         for (op = batch; op < batch + count; op++)
 853                 if (op->status == GNTST_eagain)
 854                         gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, op,
 855                                                 &op->status, __func__);
 856 }
 857 EXPORT_SYMBOL_GPL(gnttab_batch_map);
 858
 859 void gnttab_batch_copy(struct gnttab_copy *batch, unsigned count)
 860 {
 861         struct gnttab_copy *op;
 862
 863         if (HYPERVISOR_grant_table_op(GNTTABOP_copy, batch, count))
 864                 BUG();
 865         for (op = batch; op < batch + count; op++)
 866                 if (op->status == GNTST_eagain)
 867                         gnttab_retry_eagain_gop(GNTTABOP_copy, op,
 868                                                 &op->status, __func__);
 869 }
 870 EXPORT_SYMBOL_GPL(gnttab_batch_copy);
 871
 872 int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
 873                     struct gnttab_map_grant_ref *kmap_ops,
 874                     struct page **pages, unsigned int count)
 875 {
 876         int i, ret;
 877         bool lazy = false;
 878         pte_t *pte;
 879         unsigned long mfn;
 880
 881         ret = HYPERVISOR_grant_table_op(GNTTABOP_map_grant_ref, map_ops, count);
 882         if (ret)
 883                 return ret;
 884
 885         /* Retry eagain maps */
 886         for (i = 0; i < count; i++)
 887                 if (map_ops[i].status == GNTST_eagain)
 888                         gnttab_retry_eagain_gop(GNTTABOP_map_grant_ref, map_ops + i,
 889                                                 &map_ops[i].status, __func__);
 890
 891         if (xen_feature(XENFEAT_auto_translated_physmap))
 892                 return ret;
 893
 894         if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 895                 arch_enter_lazy_mmu_mode();
 896                 lazy = true;
 897         }
 898
 899         for (i = 0; i < count; i++) {
 900                 /* Do not add to override if the map failed. */
 901                 if (map_ops[i].status)
 902                         continue;
 903
 904                 if (map_ops[i].flags & GNTMAP_contains_pte) {
 905                         pte = (pte_t *) (mfn_to_virt(PFN_DOWN(map_ops[i].host_addr)) +
 906                                 (map_ops[i].host_addr & ~PAGE_MASK));
 907                         mfn = pte_mfn(*pte);
 908                 } else {
 909                         mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
 910                 }
 911                 ret = m2p_add_override(mfn, pages[i], kmap_ops ?
 912                                        &kmap_ops[i] : NULL);
 913                 if (ret)
 914                         return ret;
 915         }
 916
 917         if (lazy)
 918                 arch_leave_lazy_mmu_mode();
 919
 920         return ret;
 921 }
 922 EXPORT_SYMBOL_GPL(gnttab_map_refs);
 923
 924 int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
 925                       struct gnttab_map_grant_ref *kmap_ops,
 926                       struct page **pages, unsigned int count)
 927 {
 928         int i, ret;
 929         bool lazy = false;
 930
 931         ret = HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap_ops, count);
 932         if (ret)
 933                 return ret;
 934
 935         if (xen_feature(XENFEAT_auto_translated_physmap))
 936                 return ret;
 937
 938         if (!in_interrupt() && paravirt_get_lazy_mode() == PARAVIRT_LAZY_NONE) {
 939                 arch_enter_lazy_mmu_mode();
 940                 lazy = true;
 941         }
 942
 943         for (i = 0; i < count; i++) {
 944                 ret = m2p_remove_override(pages[i], kmap_ops ?
 945                                        &kmap_ops[i] : NULL);
 946                 if (ret)
 947                         return ret;
 948         }
 949
 950         if (lazy)
 951                 arch_leave_lazy_mmu_mode();
 952
 953         return ret;
 954 }
 955 EXPORT_SYMBOL_GPL(gnttab_unmap_refs);
 956
 957 static unsigned nr_status_frames(unsigned nr_grant_frames)
 958 {
 959         BUG_ON(grefs_per_grant_frame == 0);
 960         return (nr_grant_frames * grefs_per_grant_frame + SPP - 1) / SPP;
 961 }
 962
 963 static int gnttab_map_frames_v1(xen_pfn_t *frames, unsigned int nr_gframes)
 964 {
 965         int rc;
 966
 967         rc = arch_gnttab_map_shared(frames, nr_gframes,
 968                                     gnttab_max_grant_frames(),
 969                                     &gnttab_shared.addr);
 970         BUG_ON(rc);
 971
 972         return 0;
 973 }
 974
 975 static void gnttab_unmap_frames_v1(void)
 976 {
 977         arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
 978 }
 979
 980 static int gnttab_map_frames_v2(xen_pfn_t *frames, unsigned int nr_gframes)
 981 {
 982         uint64_t *sframes;
 983         unsigned int nr_sframes;
 984         struct gnttab_get_status_frames getframes;
 985         int rc;
 986
 987         nr_sframes = nr_status_frames(nr_gframes);
 988
 989         /* No need for kzalloc as it is initialized in following hypercall
 990          * GNTTABOP_get_status_frames.
 991          */
 992         sframes = kmalloc(nr_sframes  * sizeof(uint64_t), GFP_ATOMIC);
 993         if (!sframes)
 994                 return -ENOMEM;
 995
 996         getframes.dom        = DOMID_SELF;
 997         getframes.nr_frames  = nr_sframes;
 998         set_xen_guest_handle(getframes.frame_list, sframes);
 999
1000         rc = HYPERVISOR_grant_table_op(GNTTABOP_get_status_frames,
1001                                        &getframes, 1);
1002         if (rc == -ENOSYS) {
1003                 kfree(sframes);
1004                 return -ENOSYS;
1005         }
1006
1007         BUG_ON(rc || getframes.status);
1008
1009         rc = arch_gnttab_map_status(sframes, nr_sframes,
1010                                     nr_status_frames(gnttab_max_grant_frames()),
1011                                     &grstatus);
1012         BUG_ON(rc);
1013         kfree(sframes);
1014
1015         rc = arch_gnttab_map_shared(frames, nr_gframes,
1016                                     gnttab_max_grant_frames(),
1017                                     &gnttab_shared.addr);
1018         BUG_ON(rc);
1019
1020         return 0;
1021 }
1022
1023 static void gnttab_unmap_frames_v2(void)
1024 {
1025         arch_gnttab_unmap(gnttab_shared.addr, nr_grant_frames);
1026         arch_gnttab_unmap(grstatus, nr_status_frames(nr_grant_frames));
1027 }
1028
1029 static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
1030 {
1031         struct gnttab_setup_table setup;
1032         xen_pfn_t *frames;
1033         unsigned int nr_gframes = end_idx + 1;
1034         int rc;
1035
1036         if (xen_hvm_domain()) {
1037                 struct xen_add_to_physmap xatp;
1038                 unsigned int i = end_idx;
1039                 rc = 0;
1040                 /*
1041                  * Loop backwards, so that the first hypercall has the largest
1042                  * index, ensuring that the table will grow only once.
1043                  */
1044                 do {
1045                         xatp.domid = DOMID_SELF;
1046                         xatp.idx = i;
1047                         xatp.space = XENMAPSPACE_grant_table;
1048                         xatp.gpfn = (xen_hvm_resume_frames >> PAGE_SHIFT) + i;
1049                         rc = HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp);
1050                         if (rc != 0) {
1051                                 printk(KERN_WARNING
1052                                                 "grant table add_to_physmap failed, err=%d\n", rc);
1053                                 break;
1054                         }
1055                 } while (i-- > start_idx);
1056
1057                 return rc;
1058         }
1059
1060         /* No need for kzalloc as it is initialized in following hypercall
1061          * GNTTABOP_setup_table.
1062          */
1063         frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC);
1064         if (!frames)
1065                 return -ENOMEM;
1066
1067         setup.dom        = DOMID_SELF;
1068         setup.nr_frames  = nr_gframes;
1069         set_xen_guest_handle(setup.frame_list, frames);
1070
1071         rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
1072         if (rc == -ENOSYS) {
1073                 kfree(frames);
1074                 return -ENOSYS;
1075         }
1076
1077         BUG_ON(rc || setup.status);
1078
1079         rc = gnttab_interface->map_frames(frames, nr_gframes);
1080
1081         kfree(frames);
1082
1083         return rc;
1084 }
1085
1086 static struct gnttab_ops gnttab_v1_ops = {
1087         .map_frames                     = gnttab_map_frames_v1,
1088         .unmap_frames                   = gnttab_unmap_frames_v1,
1089         .update_entry                   = gnttab_update_entry_v1,
1090         .end_foreign_access_ref         = gnttab_end_foreign_access_ref_v1,
1091         .end_foreign_transfer_ref       = gnttab_end_foreign_transfer_ref_v1,
1092         .query_foreign_access           = gnttab_query_foreign_access_v1,
1093 };
1094
1095 static struct gnttab_ops gnttab_v2_ops = {
1096         .map_frames                     = gnttab_map_frames_v2,
1097         .unmap_frames                   = gnttab_unmap_frames_v2,
1098         .update_entry                   = gnttab_update_entry_v2,
1099         .end_foreign_access_ref         = gnttab_end_foreign_access_ref_v2,
1100         .end_foreign_transfer_ref       = gnttab_end_foreign_transfer_ref_v2,
1101         .query_foreign_access           = gnttab_query_foreign_access_v2,
1102         .update_subpage_entry           = gnttab_update_subpage_entry_v2,
1103         .update_trans_entry             = gnttab_update_trans_entry_v2,
1104 };
1105
1106 static void gnttab_request_version(void)
1107 {
1108         int rc;
1109         struct gnttab_set_version gsv;
1110
1111         if (xen_hvm_domain())
1112                 gsv.version = 1;
1113         else
1114                 gsv.version = 2;
1115         rc = HYPERVISOR_grant_table_op(GNTTABOP_set_version, &gsv, 1);
1116         if (rc == 0 && gsv.version == 2) {
1117                 grant_table_version = 2;
1118                 grefs_per_grant_frame = PAGE_SIZE / sizeof(union grant_entry_v2);
1119                 gnttab_interface = &gnttab_v2_ops;
1120         } else if (grant_table_version == 2) {
1121                 /*
1122                  * If we've already used version 2 features,
1123                  * but then suddenly discover that they're not
1124                  * available (e.g. migrating to an older
1125                  * version of Xen), almost unbounded badness
1126                  * can happen.
1127                  */
1128                 panic("we need grant tables version 2, but only version 1 is available");
1129         } else {
1130                 grant_table_version = 1;
1131                 grefs_per_grant_frame = PAGE_SIZE / sizeof(struct grant_entry_v1);
1132                 gnttab_interface = &gnttab_v1_ops;
1133         }
1134         printk(KERN_INFO "Grant tables using version %d layout.\n",
1135                 grant_table_version);
1136 }
1137
1138 static int gnttab_setup(void)
1139 {
1140         unsigned int max_nr_gframes;
1141
1142         max_nr_gframes = gnttab_max_grant_frames();
1143         if (max_nr_gframes < nr_grant_frames)
1144                 return -ENOSYS;
1145
1146         if (xen_pv_domain())
1147                 return gnttab_map(0, nr_grant_frames - 1);
1148
1149         if (gnttab_shared.addr == NULL) {
1150                 gnttab_shared.addr = xen_remap(xen_hvm_resume_frames,
1151                                                 PAGE_SIZE * max_nr_gframes);
1152                 if (gnttab_shared.addr == NULL) {
1153                         printk(KERN_WARNING
1154                                         "Failed to ioremap gnttab share frames!");
1155                         return -ENOMEM;
1156                 }
1157         }
1158
1159         gnttab_map(0, nr_grant_frames - 1);
1160
1161         return 0;
1162 }
1163
1164 int gnttab_resume(void)
1165 {
1166         gnttab_request_version();
1167         return gnttab_setup();
1168 }
1169
1170 int gnttab_suspend(void)
1171 {
1172         gnttab_interface->unmap_frames();
1173         return 0;
1174 }
1175
1176 static int gnttab_expand(unsigned int req_entries)
1177 {
1178         int rc;
1179         unsigned int cur, extra;
1180
1181         BUG_ON(grefs_per_grant_frame == 0);
1182         cur = nr_grant_frames;
1183         extra = ((req_entries + (grefs_per_grant_frame-1)) /
1184                  grefs_per_grant_frame);
1185         if (cur + extra > gnttab_max_grant_frames())
1186                 return -ENOSPC;
1187
1188         rc = gnttab_map(cur, cur + extra - 1);
1189         if (rc == 0)
1190                 rc = grow_gnttab_list(extra);
1191
1192         return rc;
1193 }
1194
1195 int gnttab_init(void)
1196 {
1197         int i;
1198         unsigned int max_nr_glist_frames, nr_glist_frames;
1199         unsigned int nr_init_grefs;
1200         int ret;
1201
1202         gnttab_request_version();
1203         nr_grant_frames = 1;
1204         boot_max_nr_grant_frames = __max_nr_grant_frames();
1205
1206         /* Determine the maximum number of frames required for the
1207          * grant reference free list on the current hypervisor.
1208          */
1209         BUG_ON(grefs_per_grant_frame == 0);
1210         max_nr_glist_frames = (boot_max_nr_grant_frames *
1211                                grefs_per_grant_frame / RPP);
1212
1213         gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
1214                               GFP_KERNEL);
1215         if (gnttab_list == NULL)
1216                 return -ENOMEM;
1217
1218         nr_glist_frames = (nr_grant_frames * grefs_per_grant_frame + RPP - 1) / RPP;
1219         for (i = 0; i < nr_glist_frames; i++) {
1220                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
1221                 if (gnttab_list[i] == NULL) {
1222                         ret = -ENOMEM;
1223                         goto ini_nomem;
1224                 }
1225         }
1226
1227         if (gnttab_setup() < 0) {
1228                 ret = -ENODEV;
1229                 goto ini_nomem;
1230         }
1231
1232         nr_init_grefs = nr_grant_frames * grefs_per_grant_frame;
1233
1234         for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
1235                 gnttab_entry(i) = i + 1;
1236
1237         gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
1238         gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
1239         gnttab_free_head  = NR_RESERVED_ENTRIES;
1240
1241         printk("Grant table initialized\n");
1242         return 0;
1243
1244  ini_nomem:
1245         for (i--; i >= 0; i--)
1246                 free_page((unsigned long)gnttab_list[i]);
1247         kfree(gnttab_list);
1248         return ret;
1249 }
1250 EXPORT_SYMBOL_GPL(gnttab_init);
1251
1252 static int __gnttab_init(void)
1253 {
1254         /* Delay grant-table initialization in the PV on HVM case */
1255         if (xen_hvm_domain())
1256                 return 0;
1257
1258         if (!xen_pv_domain())
1259                 return -ENODEV;
1260
1261         return gnttab_init();
1262 }
1263
1264 core_initcall(__gnttab_init);