SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 #include <asm/xen/hypercall.h>
  44
  45 #include <asm/pgtable.h>
  46 #include <asm/sync_bitops.h>
  47
  48
  49 /* External tools reserve first few grant table entries. */
  50 #define NR_RESERVED_ENTRIES 8
  51 #define GNTTAB_LIST_END 0xffffffff
  52 #define GREFS_PER_GRANT_FRAME (PAGE_SIZE / sizeof(struct grant_entry))
  53
  54 static grant_ref_t **gnttab_list;
  55 static unsigned int nr_grant_frames;
  56 static unsigned int boot_max_nr_grant_frames;
  57 static int gnttab_free_count;
  58 static grant_ref_t gnttab_free_head;
  59 static DEFINE_SPINLOCK(gnttab_list_lock);
  60
  61 static struct grant_entry *shared;
  62
  63 static struct gnttab_free_callback *gnttab_free_callback_list;
  64
  65 static int gnttab_expand(unsigned int req_entries);
  66
  67 #define RPP (PAGE_SIZE / sizeof(grant_ref_t))
  68
  69 static inline grant_ref_t *__gnttab_entry(grant_ref_t entry)
  70 {
  71         return &gnttab_list[(entry) / RPP][(entry) % RPP];
  72 }
  73 /* This can be used as an l-value */
  74 #define gnttab_entry(entry) (*__gnttab_entry(entry))
  75
  76 static int get_free_entries(unsigned count)
  77 {
  78         unsigned long flags;
  79         int ref, rc;
  80         grant_ref_t head;
  81
  82         spin_lock_irqsave(&gnttab_list_lock, flags);
  83
  84         if ((gnttab_free_count < count) &&
  85             ((rc = gnttab_expand(count - gnttab_free_count)) < 0)) {
  86                 spin_unlock_irqrestore(&gnttab_list_lock, flags);
  87                 return rc;
  88         }
  89
  90         ref = head = gnttab_free_head;
  91         gnttab_free_count -= count;
  92         while (count-- > 1)
  93                 head = gnttab_entry(head);
  94         gnttab_free_head = gnttab_entry(head);
  95         gnttab_entry(head) = GNTTAB_LIST_END;
  96
  97         spin_unlock_irqrestore(&gnttab_list_lock, flags);
  98
  99         return ref;
 100 }
 101
 102 static void do_free_callbacks(void)
 103 {
 104         struct gnttab_free_callback *callback, *next;
 105
 106         callback = gnttab_free_callback_list;
 107         gnttab_free_callback_list = NULL;
 108
 109         while (callback != NULL) {
 110                 next = callback->next;
 111                 if (gnttab_free_count >= callback->count) {
 112                         callback->next = NULL;
 113                         callback->fn(callback->arg);
 114                 } else {
 115                         callback->next = gnttab_free_callback_list;
 116                         gnttab_free_callback_list = callback;
 117                 }
 118                 callback = next;
 119         }
 120 }
 121
 122 static inline void check_free_callbacks(void)
 123 {
 124         if (unlikely(gnttab_free_callback_list))
 125                 do_free_callbacks();
 126 }
 127
 128 static void put_free_entry(grant_ref_t ref)
 129 {
 130         unsigned long flags;
 131         spin_lock_irqsave(&gnttab_list_lock, flags);
 132         gnttab_entry(ref) = gnttab_free_head;
 133         gnttab_free_head = ref;
 134         gnttab_free_count++;
 135         check_free_callbacks();
 136         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 137 }
 138
 139 static void update_grant_entry(grant_ref_t ref, domid_t domid,
 140                                unsigned long frame, unsigned flags)
 141 {
 142         /*
 143          * Introducing a valid entry into the grant table:
 144          *  1. Write ent->domid.
 145          *  2. Write ent->frame:
 146          *      GTF_permit_access:   Frame to which access is permitted.
 147          *      GTF_accept_transfer: Pseudo-phys frame slot being filled by new
 148          *                           frame, or zero if none.
 149          *  3. Write memory barrier (WMB).
 150          *  4. Write ent->flags, inc. valid type.
 151          */
 152         shared[ref].frame = frame;
 153         shared[ref].domid = domid;
 154         wmb();
 155         shared[ref].flags = flags;
 156 }
 157
 158 /*
 159  * Public grant-issuing interface functions
 160  */
 161 void gnttab_grant_foreign_access_ref(grant_ref_t ref, domid_t domid,
 162                                      unsigned long frame, int readonly)
 163 {
 164         update_grant_entry(ref, domid, frame,
 165                            GTF_permit_access | (readonly ? GTF_readonly : 0));
 166 }
 167 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access_ref);
 168
 169 int gnttab_grant_foreign_access(domid_t domid, unsigned long frame,
 170                                 int readonly)
 171 {
 172         int ref;
 173
 174         ref = get_free_entries(1);
 175         if (unlikely(ref < 0))
 176                 return -ENOSPC;
 177
 178         gnttab_grant_foreign_access_ref(ref, domid, frame, readonly);
 179
 180         return ref;
 181 }
 182 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_access);
 183
 184 int gnttab_query_foreign_access(grant_ref_t ref)
 185 {
 186         u16 nflags;
 187
 188         nflags = shared[ref].flags;
 189
 190         return (nflags & (GTF_reading|GTF_writing));
 191 }
 192 EXPORT_SYMBOL_GPL(gnttab_query_foreign_access);
 193
 194 int gnttab_end_foreign_access_ref(grant_ref_t ref, int readonly)
 195 {
 196         u16 flags, nflags;
 197
 198         nflags = shared[ref].flags;
 199         do {
 200                 flags = nflags;
 201                 if (flags & (GTF_reading|GTF_writing)) {
 202                         printk(KERN_ALERT "WARNING: g.e. still in use!\n");
 203                         return 0;
 204                 }
 205         } while ((nflags = sync_cmpxchg(&shared[ref].flags, flags, 0)) != flags);
 206
 207         return 1;
 208 }
 209 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access_ref);
 210
 211 void gnttab_end_foreign_access(grant_ref_t ref, int readonly,
 212                                unsigned long page)
 213 {
 214         if (gnttab_end_foreign_access_ref(ref, readonly)) {
 215                 put_free_entry(ref);
 216                 if (page != 0)
 217                         free_page(page);
 218         } else {
 219                 /* XXX This needs to be fixed so that the ref and page are
 220                    placed on a list to be freed up later. */
 221                 printk(KERN_WARNING
 222                        "WARNING: leaking g.e. and page still in use!\n");
 223         }
 224 }
 225 EXPORT_SYMBOL_GPL(gnttab_end_foreign_access);
 226
 227 int gnttab_grant_foreign_transfer(domid_t domid, unsigned long pfn)
 228 {
 229         int ref;
 230
 231         ref = get_free_entries(1);
 232         if (unlikely(ref < 0))
 233                 return -ENOSPC;
 234         gnttab_grant_foreign_transfer_ref(ref, domid, pfn);
 235
 236         return ref;
 237 }
 238 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer);
 239
 240 void gnttab_grant_foreign_transfer_ref(grant_ref_t ref, domid_t domid,
 241                                        unsigned long pfn)
 242 {
 243         update_grant_entry(ref, domid, pfn, GTF_accept_transfer);
 244 }
 245 EXPORT_SYMBOL_GPL(gnttab_grant_foreign_transfer_ref);
 246
 247 unsigned long gnttab_end_foreign_transfer_ref(grant_ref_t ref)
 248 {
 249         unsigned long frame;
 250         u16           flags;
 251
 252         /*
 253          * If a transfer is not even yet started, try to reclaim the grant
 254          * reference and return failure (== 0).
 255          */
 256         while (!((flags = shared[ref].flags) & GTF_transfer_committed)) {
 257                 if (sync_cmpxchg(&shared[ref].flags, flags, 0) == flags)
 258                         return 0;
 259                 cpu_relax();
 260         }
 261
 262         /* If a transfer is in progress then wait until it is completed. */
 263         while (!(flags & GTF_transfer_completed)) {
 264                 flags = shared[ref].flags;
 265                 cpu_relax();
 266         }
 267
 268         rmb();  /* Read the frame number /after/ reading completion status. */
 269         frame = shared[ref].frame;
 270         BUG_ON(frame == 0);
 271
 272         return frame;
 273 }
 274 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer_ref);
 275
 276 unsigned long gnttab_end_foreign_transfer(grant_ref_t ref)
 277 {
 278         unsigned long frame = gnttab_end_foreign_transfer_ref(ref);
 279         put_free_entry(ref);
 280         return frame;
 281 }
 282 EXPORT_SYMBOL_GPL(gnttab_end_foreign_transfer);
 283
 284 void gnttab_free_grant_reference(grant_ref_t ref)
 285 {
 286         put_free_entry(ref);
 287 }
 288 EXPORT_SYMBOL_GPL(gnttab_free_grant_reference);
 289
 290 void gnttab_free_grant_references(grant_ref_t head)
 291 {
 292         grant_ref_t ref;
 293         unsigned long flags;
 294         int count = 1;
 295         if (head == GNTTAB_LIST_END)
 296                 return;
 297         spin_lock_irqsave(&gnttab_list_lock, flags);
 298         ref = head;
 299         while (gnttab_entry(ref) != GNTTAB_LIST_END) {
 300                 ref = gnttab_entry(ref);
 301                 count++;
 302         }
 303         gnttab_entry(ref) = gnttab_free_head;
 304         gnttab_free_head = head;
 305         gnttab_free_count += count;
 306         check_free_callbacks();
 307         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 308 }
 309 EXPORT_SYMBOL_GPL(gnttab_free_grant_references);
 310
 311 int gnttab_alloc_grant_references(u16 count, grant_ref_t *head)
 312 {
 313         int h = get_free_entries(count);
 314
 315         if (h < 0)
 316                 return -ENOSPC;
 317
 318         *head = h;
 319
 320         return 0;
 321 }
 322 EXPORT_SYMBOL_GPL(gnttab_alloc_grant_references);
 323
 324 int gnttab_empty_grant_references(const grant_ref_t *private_head)
 325 {
 326         return (*private_head == GNTTAB_LIST_END);
 327 }
 328 EXPORT_SYMBOL_GPL(gnttab_empty_grant_references);
 329
 330 int gnttab_claim_grant_reference(grant_ref_t *private_head)
 331 {
 332         grant_ref_t g = *private_head;
 333         if (unlikely(g == GNTTAB_LIST_END))
 334                 return -ENOSPC;
 335         *private_head = gnttab_entry(g);
 336         return g;
 337 }
 338 EXPORT_SYMBOL_GPL(gnttab_claim_grant_reference);
 339
 340 void gnttab_release_grant_reference(grant_ref_t *private_head,
 341                                     grant_ref_t release)
 342 {
 343         gnttab_entry(release) = *private_head;
 344         *private_head = release;
 345 }
 346 EXPORT_SYMBOL_GPL(gnttab_release_grant_reference);
 347
 348 void gnttab_request_free_callback(struct gnttab_free_callback *callback,
 349                                   void (*fn)(void *), void *arg, u16 count)
 350 {
 351         unsigned long flags;
 352         spin_lock_irqsave(&gnttab_list_lock, flags);
 353         if (callback->next)
 354                 goto out;
 355         callback->fn = fn;
 356         callback->arg = arg;
 357         callback->count = count;
 358         callback->next = gnttab_free_callback_list;
 359         gnttab_free_callback_list = callback;
 360         check_free_callbacks();
 361 out:
 362         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 363 }
 364 EXPORT_SYMBOL_GPL(gnttab_request_free_callback);
 365
 366 void gnttab_cancel_free_callback(struct gnttab_free_callback *callback)
 367 {
 368         struct gnttab_free_callback **pcb;
 369         unsigned long flags;
 370
 371         spin_lock_irqsave(&gnttab_list_lock, flags);
 372         for (pcb = &gnttab_free_callback_list; *pcb; pcb = &(*pcb)->next) {
 373                 if (*pcb == callback) {
 374                         *pcb = callback->next;
 375                         break;
 376                 }
 377         }
 378         spin_unlock_irqrestore(&gnttab_list_lock, flags);
 379 }
 380 EXPORT_SYMBOL_GPL(gnttab_cancel_free_callback);
 381
 382 static int grow_gnttab_list(unsigned int more_frames)
 383 {
 384         unsigned int new_nr_grant_frames, extra_entries, i;
 385         unsigned int nr_glist_frames, new_nr_glist_frames;
 386
 387         new_nr_grant_frames = nr_grant_frames + more_frames;
 388         extra_entries       = more_frames * GREFS_PER_GRANT_FRAME;
 389
 390         nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
 391         new_nr_glist_frames =
 392                 (new_nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
 393         for (i = nr_glist_frames; i < new_nr_glist_frames; i++) {
 394                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_ATOMIC);
 395                 if (!gnttab_list[i])
 396                         goto grow_nomem;
 397         }
 398
 399
 400         for (i = GREFS_PER_GRANT_FRAME * nr_grant_frames;
 401              i < GREFS_PER_GRANT_FRAME * new_nr_grant_frames - 1; i++)
 402                 gnttab_entry(i) = i + 1;
 403
 404         gnttab_entry(i) = gnttab_free_head;
 405         gnttab_free_head = GREFS_PER_GRANT_FRAME * nr_grant_frames;
 406         gnttab_free_count += extra_entries;
 407
 408         nr_grant_frames = new_nr_grant_frames;
 409
 410         check_free_callbacks();
 411
 412         return 0;
 413
 414 grow_nomem:
 415         for ( ; i >= nr_glist_frames; i--)
 416                 free_page((unsigned long) gnttab_list[i]);
 417         return -ENOMEM;
 418 }
 419
 420 static unsigned int __max_nr_grant_frames(void)
 421 {
 422         struct gnttab_query_size query;
 423         int rc;
 424
 425         query.dom = DOMID_SELF;
 426
 427         rc = HYPERVISOR_grant_table_op(GNTTABOP_query_size, &query, 1);
 428         if ((rc < 0) || (query.status != GNTST_okay))
 429                 return 4; /* Legacy max supported number of frames */
 430
 431         return query.max_nr_frames;
 432 }
 433
 434 static inline unsigned int max_nr_grant_frames(void)
 435 {
 436         unsigned int xen_max = __max_nr_grant_frames();
 437
 438         if (xen_max > boot_max_nr_grant_frames)
 439                 return boot_max_nr_grant_frames;
 440         return xen_max;
 441 }
 442
 443 static int gnttab_map(unsigned int start_idx, unsigned int end_idx)
 444 {
 445         struct gnttab_setup_table setup;
 446         unsigned long *frames;
 447         unsigned int nr_gframes = end_idx + 1;
 448         int rc;
 449
 450         frames = kmalloc(nr_gframes * sizeof(unsigned long), GFP_ATOMIC);
 451         if (!frames)
 452                 return -ENOMEM;
 453
 454         setup.dom        = DOMID_SELF;
 455         setup.nr_frames  = nr_gframes;
 456         set_xen_guest_handle(setup.frame_list, frames);
 457
 458         rc = HYPERVISOR_grant_table_op(GNTTABOP_setup_table, &setup, 1);
 459         if (rc == -ENOSYS) {
 460                 kfree(frames);
 461                 return -ENOSYS;
 462         }
 463
 464         BUG_ON(rc || setup.status);
 465
 466         rc = arch_gnttab_map_shared(frames, nr_gframes, max_nr_grant_frames(),
 467                                     &shared);
 468         BUG_ON(rc);
 469
 470         kfree(frames);
 471
 472         return 0;
 473 }
 474
 475 int gnttab_resume(void)
 476 {
 477         if (max_nr_grant_frames() < nr_grant_frames)
 478                 return -ENOSYS;
 479         return gnttab_map(0, nr_grant_frames - 1);
 480 }
 481
 482 int gnttab_suspend(void)
 483 {
 484         arch_gnttab_unmap_shared(shared, nr_grant_frames);
 485         return 0;
 486 }
 487
 488 static int gnttab_expand(unsigned int req_entries)
 489 {
 490         int rc;
 491         unsigned int cur, extra;
 492
 493         cur = nr_grant_frames;
 494         extra = ((req_entries + (GREFS_PER_GRANT_FRAME-1)) /
 495                  GREFS_PER_GRANT_FRAME);
 496         if (cur + extra > max_nr_grant_frames())
 497                 return -ENOSPC;
 498
 499         rc = gnttab_map(cur, cur + extra - 1);
 500         if (rc == 0)
 501                 rc = grow_gnttab_list(extra);
 502
 503         return rc;
 504 }
 505
 506 static int __devinit gnttab_init(void)
 507 {
 508         int i;
 509         unsigned int max_nr_glist_frames, nr_glist_frames;
 510         unsigned int nr_init_grefs;
 511
 512         if (!xen_domain())
 513                 return -ENODEV;
 514
 515         nr_grant_frames = 1;
 516         boot_max_nr_grant_frames = __max_nr_grant_frames();
 517
 518         /* Determine the maximum number of frames required for the
 519          * grant reference free list on the current hypervisor.
 520          */
 521         max_nr_glist_frames = (boot_max_nr_grant_frames *
 522                                GREFS_PER_GRANT_FRAME / RPP);
 523
 524         gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
 525                               GFP_KERNEL);
 526         if (gnttab_list == NULL)
 527                 return -ENOMEM;
 528
 529         nr_glist_frames = (nr_grant_frames * GREFS_PER_GRANT_FRAME + RPP - 1) / RPP;
 530         for (i = 0; i < nr_glist_frames; i++) {
 531                 gnttab_list[i] = (grant_ref_t *)__get_free_page(GFP_KERNEL);
 532                 if (gnttab_list[i] == NULL)
 533                         goto ini_nomem;
 534         }
 535
 536         if (gnttab_resume() < 0)
 537                 return -ENODEV;
 538
 539         nr_init_grefs = nr_grant_frames * GREFS_PER_GRANT_FRAME;
 540
 541         for (i = NR_RESERVED_ENTRIES; i < nr_init_grefs - 1; i++)
 542                 gnttab_entry(i) = i + 1;
 543
 544         gnttab_entry(nr_init_grefs - 1) = GNTTAB_LIST_END;
 545         gnttab_free_count = nr_init_grefs - NR_RESERVED_ENTRIES;
 546         gnttab_free_head  = NR_RESERVED_ENTRIES;
 547
 548         printk("Grant table initialized\n");
 549         return 0;
 550
 551  ini_nomem:
 552         for (i--; i >= 0; i--)
 553                 free_page((unsigned long)gnttab_list[i]);
 554         kfree(gnttab_list);
 555         return -ENOMEM;
 556 }
 557
 558 core_initcall(gnttab_init);