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/vmalloc.h>
  38 #include <linux/uaccess.h>
  39
  40 #include <xen/interface/xen.h>
  41 #include <xen/page.h>
  42 #include <xen/grant_table.h>
  43
  44 #include <asm/pgtable.h>
  45 #include <asm/sync_bitops.h>
  46
  47
  48 /* External tools reserve first few grant table entries. */
  49 #define NR_RESERVED_ENTRIES 8
  50 #define GNTTAB_LIST_END 0xffffffff
  51 #define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry))
  52
  53 static grant_ref_t **gnttab_list;
  54 static unsigned int nr_grant_frames;
  55 static unsigned int boot_max_nr_grant_frames;
  56 static int gnttab_free_count;
  57 static grant_ref_t gnttab_free_head;
  58 static DEFINE_SPINLOCK(gnttab_list_lock);
  59
  60 static struct grant_entry *shared;
  61
  62 static struct gnttab_free_callback *gnttab_free_callback_list;
  63
  64 static int gnttab_expand(unsigned int req_entries);
  65
  66 #define RPP (PAGE_SIZE / sizeof(grant_ref_t))
  67
  68 static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
  69 {
  70         return &gnttab_list[(entry) / RPP][(entry) % RPP];
  71 }
  72 /* This can be used as an l-value */
  73 #define gnttab_entry(entry) (*__gnttab_entry(entry))
  74
  75 static int get_free_entries(unsigned count)
  76 {
  77         unsigned long flags;
  78         int ref, rc;
  79         grant_ref_t head;
  80
  81         spin_lock_irqsave(&gnttab_list_lock, flags);
  82
  83         if ((gnttab_free_count < count) &&
  84             ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
  85                 spin_unlock_irqrestore(&gnttab_list_lock, flags);
  86                 return rc;
  87         }
  88
  89         ref = head = gnttab_free_head;
  90         gnttab_free_count -= count;
  91         while (count-- > 1)
  92                 head = gnttab_entry(head);
  93         gnttab_free_head = gnttab_entry(head);
  94         gnttab_entry(head) = GNTTAB_LIST_END;
  95
  96         spin_unlock_irqrestore(&gnttab_list_lock, flags);
  97
  98         return ref;
  99 }
 100
 101 static void do_free_callbacks(void)
 102 {
 103         struct gnttab_free_callback *callback, *next;
 104
 105         callback = gnttab_free_callback_list;
 106         gnttab_free_callback_list = NULL;
 107
 108         while (callback != NULL) {
 109                 next = callback->next;
 110                 if (gnttab_free_count >= callback->count) {
 111                         callback->next = NULL;
 112                         callback->fn(callback->arg);
 113                 } else {
 114                         callback->next = gnttab_free_callback_list;
 115                         gnttab_free_callback_list = callback;
 116                 }
 117                 callback = next;
 118         }
 119 }
 120
 121 static inline void check_free_callbacks(void)
 122 {
 123         if (unlikely(gnttab_free_callback_list))
 124                 do_free_callbacks();
 125 }
 126
 127 static void put_free_entry(grant_ref_t ref)
 128 {
 129         unsigned long flags;
 130         spin_lock_irqsave(&gnttab_list_lock, flags);
 131         gnttab_entry(ref) = gnttab_free_head;
 132         gnttab_free_head = ref;
 133         gnttab_free_count++;
 134         check_free_callbacks();
 135         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 136 }
 137
 138 static void update_grant_entry(grant_ref_t ref, domid_t domid,
 139                                unsigned long frame, unsigned flags)
 140 {
 141         /*
 142          * Introducing a valid entry into the grant table:
 143          *  1. Write ent->domid.
 144          *  2. Write ent->frame:
 145          *      GTF_permit_access:   Frame to which access is permitted.
 146          *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
 147          *                           frame, or zero if none.
 148          *  3. Write memory barrier (WMB).
 149          *  4. Write ent->flags, inc. valid type.
 150          */
 151         shared[ref].frame = frame;
 152         shared[ref].domid = domid;
 153         wmb();
 154         shared[ref].flags = flags;
 155 }
 156
 157 /*
 158  * Public grant-issuing interface functions
 159  */
 160 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
 161                                      unsigned long frame, int readonly)
 162 {
 163         update_grant_entry(ref, domid, frame,
 164                            GTF_permit_access | (readonly ? GTF_readonly : 0));
 165 }
 166 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);
 167
 168 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 169                                 int readonly)
 170 {
 171         int ref;
 172
 173         ref = get_free_entries(1);
 174         if (unlikely(ref < 0))
 175                 return -ENOSPC;
 176
 177         gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);
 178
 179         return ref;
 180 }
 181 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
 182
 183 int gnttab_query_foreign_access(grant_ref_t ref)
 184 {
 185         u16 nflags;
 186
 187         nflags = shared[ref].flags;
 188
 189         return (nflags & (GTF_reading|GTF_writing));
 190 }
 191 EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
 192
 193 int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
 194 {
 195         u16 flags, nflags;
 196
 197         nflags = shared[ref].flags;
 198         do {
 199                 flags = nflags;
 200                 if (flags & (GTF_reading|GTF_writing)) {
 201                         printk(KERN_ALERT "WARNING: g.e. still in use!\n");
 202                         return 0;
 203                 }
 204         } while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) != flags);
 205
 206         return 1;
 207 }
 208 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
 209
 210 void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
 211                                unsigned long page)
 212 {
 213         if (gnttab_end_foreign_access_ref(ref, readonly)) {
 214                 put_free_entry(ref);
 215                 if (page != 0)
 216                         free_page(page);
 217         } else {
 218                 /* XXX This needs to be fixed so that the ref and page are
 219                    placed on a list to be freed up later. */
 220                 printk(KERN_WARNING
 221                        "WARNING: leaking g.e. and page still in use!\n");
 222         }
 223 }
 224 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
 225
 226 int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)
 227 {
 228         int ref;
 229
 230         ref = get_free_entries(1);
 231         if (unlikely(ref < 0))
 232                 return -ENOSPC;
 233         gnttab_grant_foreign_transfer_ref(ref, domid, pfn);
 234
 235         return ref;
 236 }
 237 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);
 238
 239 void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,
 240                                        unsigned long pfn)
 241 {
 242         update_grant_entry(ref, domid, pfn, GTF_accept_transfer);
 243 }
 244 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);
 245
 246 unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
 247 {
 248         unsigned long frame;
 249         u16           flags;
 250
 251         /*
 252          * If a transfer is not even yet started, try to reclaim the grant
 253          * reference and return failure (== 0).
 254          */
 255         while (!((flags = shared[ref].flags) & GTF_transfer_committed)) {
 256                 if (sync_cmpxchg(&shared[ref].flags, flags, 0) == flags)
 257                         return 0;
 258                 cpu_relax();
 259         }
 260
 261         /* If a transfer is in progress then wait until it is completed. */
 262         while (!(flags & GTF_transfer_completed)) {
 263                 flags = shared[ref].flags;
 264                 cpu_relax();
 265         }
 266
 267         rmb();  /* Read the frame number /after/ reading completion status. */
 268         frame = shared[ref].frame;
 269         BUG_ON(frame == 0);
 270
 271         return frame;
 272 }
 273 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);
 274
 275 unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)
 276 {
 277         unsigned long frame = gnttab_end_foreign_transfer_ref(ref);
 278         put_free_entry(ref);
 279         return frame;
 280 }
 281 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);
 282
 283 void gnttab_free_grant_reference(grant_ref_t ref)
 284 {
 285         put_free_entry(ref);
 286 }
 287 EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);
 288
 289 void gnttab_free_grant_references(grant_ref_t head)
 290 {
 291         grant_ref_t ref;
 292         unsigned long flags;
 293         int count = 1;
 294         if (head == GNTTAB_LIST_END)
 295                 return;
 296         spin_lock_irqsave(&gnttab_list_lock, flags);
 297         ref = head;
 298         while (gnttab_entry(ref) != GNTTAB_LIST_END) {
 299                 ref = gnttab_entry(ref);
 300                 count++;
 301         }
 302         gnttab_entry(ref) = gnttab_free_head;
 303         gnttab_free_head = head;
 304         gnttab_free_count += count;
 305         check_free_callbacks();
 306         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 307 }
 308 EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
 309
 310 int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
 311 {
 312         int h = get_free_entries(count);
 313
 314         if (h < 0)
 315                 return -ENOSPC;
 316
 317         *head = h;
 318
 319         return 0;
 320 }
 321 EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);
 322
 323 int gnttab_empty_grant_references(const grant_ref_t *private_head)
 324 {
 325         return (*private_head == GNTTAB_LIST_END);
 326 }
 327 EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);
 328
 329 int gnttab_claim_grant_reference(grant_ref_t *private_head)
 330 {
 331         grant_ref_t g = *private_head;
 332         if (unlikely(g == GNTTAB_LIST_END))
 333                 return -ENOSPC;
 334         *private_head = gnttab_entry(g);
 335         return g;
 336 }
 337 EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);
 338
 339 void gnttab_release_grant_reference(grant_ref_t *private_head,
 340                                     grant_ref_t release)
 341 {
 342         gnttab_entry(release) = *private_head;
 343         *private_head = release;
 344 }
 345 EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);
 346
 347 void gnttab_request_free_callback(struct gnttab_free_callback *callback,
 348                                   void (*fn)(void *), void *arg, u16 count)
 349 {
 350         unsigned long flags;
 351         spin_lock_irqsave(&gnttab_list_lock, flags);
 352         if (callback->next)
 353                 goto out;
 354         callback->fn = fn;
 355         callback->arg = arg;
 356         callback->count = count;
 357         callback->next = gnttab_free_callback_list;
 358         gnttab_free_callback_list = callback;
 359         check_free_callbacks();
 360 out:
 361         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 362 }
 363 EXPORT_SYMBOL_GPL(gnttab_request_free_callback);
 364
 365 void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
 366 {
 367         struct gnttab_free_callback **pcb;
 368         unsigned long flags;
 369
 370         spin_lock_irqsave(&gnttab_list_lock, flags);
 371         for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
 372                 if (*pcb == callback) {
 373                         *pcb = callback->next;
 374                         break;
 375                 }
 376         }
 377         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 378 }
 379 EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
 380
 381 static int grow_gnttab_list(unsigned int more_frames)
 382 {
 383         unsigned int new_nr_grant_frames, extra_entries, i;
 384
 385         new_nr_grant_frames = nr_grant_frames + more_frames;
 386         extra_entries       = more_frames * GREFS_PER_GRANT_FRAME;
 387
 388         for (i = nr_grant_frames; i < new_nr_grant_frames; i++) {
 389                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
 390                 if (!gnttab_list[i])
 391                         goto grow_nomem;
 392         }
 393
 394
 395         for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames;
 396              i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)
 397                 gnttab_entry(i) = i + 1;
 398
 399         gnttab_entry(i) = gnttab_free_head;
 400         gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames;
 401         gnttab_free_count += extra_entries;
 402
 403         nr_grant_frames = new_nr_grant_frames;
 404
 405         check_free_callbacks();
 406
 407         return 0;
 408
 409 grow_nomem:
 410         for ( ; i >= nr_grant_frames; i--)
 411                 free_page((unsigned long) gnttab_list[i]);
 412         return -ENOMEM;
 413 }
 414
 415 static unsigned int __max_nr_grant_frames(void)
 416 {
 417         struct gnttab_query_size query;
 418         int rc;
 419
 420         query.dom = DOMID_SELF;
 421
 422         rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
 423         if ((rc < 0) || (query.status != GNTST_okay))
 424                 return 4; /* Legacy max supported number of frames */
 425
 426         return query.max_nr_frames;
 427 }
 428
 429 static inline unsigned int max_nr_grant_frames(void)
 430 {
 431         unsigned int xen_max = __max_nr_grant_frames();
 432
 433         if (xen_max > boot_max_nr_grant_frames)
 434                 return boot_max_nr_grant_frames;
 435         return xen_max;
 436 }
 437
 438 static int map_pte_fn(pte_t *pte, struct page *pmd_page,
 439                       unsigned long addr, void *data)
 440 {
 441         unsigned long **frames = (unsigned long **)data;
 442
 443         set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));
 444         (*frames)++;
 445         return 0;
 446 }
 447
 448 static int unmap_pte_fn(pte_t *pte, struct page *pmd_page,
 449                         unsigned long addr, void *data)
 450 {
 451
 452         set_pte_at(&init_mm, addr, pte, __pte(0));
 453         return 0;
 454 }
 455
 456 static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
 457 {
 458         struct gnttab_setup_table setup;
 459         unsigned long *frames;
 460         unsigned int nr_gframes = end_idx + 1;
 461         int rc;
 462
 463         frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC);
 464         if (!frames)
 465                 return -ENOMEM;
 466
 467         setup.dom        = DOMID_SELF;
 468         setup.nr_frames  = nr_gframes;
 469         setup.frame_list = frames;
 470
 471         rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
 472         if (rc == -ENOSYS) {
 473                 kfree(frames);
 474                 return -ENOSYS;
 475         }
 476
 477         BUG_ON(rc || setup.status);
 478
 479         if (shared == NULL) {
 480                 struct vm_struct *area;
 481                 area = alloc_vm_area(PAGE_SIZE * max_nr_grant_frames());
 482                 BUG_ON(area == NULL);
 483                 shared = area->addr;
 484         }
 485         rc = apply_to_page_range(&init_mm, (unsigned long)shared,
 486                                  PAGE_SIZE * nr_gframes,
 487                                  map_pte_fn, &frames);
 488         BUG_ON(rc);
 489         frames -= nr_gframes; /* adjust after map_pte_fn() */
 490
 491         kfree(frames);
 492
 493         return 0;
 494 }
 495
 496 static int gnttab_resume(void)
 497 {
 498         if (max_nr_grant_frames() < nr_grant_frames)
 499                 return -ENOSYS;
 500         return gnttab_map(0, nr_grant_frames - 1);
 501 }
 502
 503 static int gnttab_suspend(void)
 504 {
 505         apply_to_page_range(&init_mm, (unsigned long)shared,
 506                             PAGE_SIZE * nr_grant_frames,
 507                             unmap_pte_fn, NULL);
 508
 509         return 0;
 510 }
 511
 512 static int gnttab_expand(unsigned int req_entries)
 513 {
 514         int rc;
 515         unsigned int cur, extra;
 516
 517         cur = nr_grant_frames;
 518         extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) /
 519                  GREFS_PER_GRANT_FRAME);
 520         if (cur + extra > max_nr_grant_frames())
 521                 return -ENOSPC;
 522
 523         rc = gnttab_map(cur, cur + extra - 1);
 524         if (rc == 0)
 525                 rc = grow_gnttab_list(extra);
 526
 527         return rc;
 528 }
 529
 530 static int __devinit gnttab_init(void)
 531 {
 532         int i;
 533         unsigned int max_nr_glist_frames;
 534         unsigned int nr_init_grefs;
 535
 536         if (!is_running_on_xen())
 537                 return -ENODEV;
 538
 539         nr_grant_frames = 1;
 540         boot_max_nr_grant_frames = __max_nr_grant_frames();
 541
 542         /* Determine the maximum number of frames required for the
 543          * grant reference free list on the current hypervisor.
 544          */
 545         max_nr_glist_frames = (boot_max_nr_grant_frames *
 546                                GREFS_PER_GRANT_FRAME /
 547                                (PAGE_SIZE / sizeof(grant_ref_t)));
 548
 549         gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
 550                               GFP_KERNEL);
 551         if (gnttab_list == NULL)
 552                 return -ENOMEM;
 553
 554         for (i = 0; i < nr_grant_frames; i++) {
 555                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
 556                 if (gnttab_list[i] == NULL)
 557                         goto ini_nomem;
 558         }
 559
 560         if (gnttab_resume() < 0)
 561                 return -ENODEV;
 562
 563         nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME;
 564
 565         for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
 566                 gnttab_entry(i) = i + 1;
 567
 568         gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
 569         gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
 570         gnttab_free_head  = NR_RESERVED_ENTRIES;
 571
 572         printk("Grant table initialized\n");
 573         return 0;
 574
 575  ini_nomem:
 576         for (i--; i >= 0; i--)
 577                 free_page((unsigned long)gnttab_list[i]);
 578         kfree(gnttab_list);
 579         return -ENOMEM;
 580 }
 581
 582 core_initcall(gnttab_init);