drivers/xen/balloon.c

   1 /******************************************************************************
   2  * Xen balloon driver - enables returning/claiming memory to/from Xen.
   3  *
   4  * Copyright (c) 2003, B Dragovic
   5  * Copyright (c) 2003-2004, M Williamson, K Fraser
   6  * Copyright (c) 2005 Dan M. Smith, IBM Corporation
   7  * Copyright (c) 2010 Daniel Kiper
   8  *
   9  * Memory hotplug support was written by Daniel Kiper. Work on
  10  * it was sponsored by Google under Google Summer of Code 2010
  11  * program. Jeremy Fitzhardinge from Citrix was the mentor for
  12  * this project.
  13  *
  14  * This program is free software; you can redistribute it and/or
  15  * modify it under the terms of the GNU General Public License version 2
  16  * as published by the Free Software Foundation; or, when distributed
  17  * separately from the Linux kernel or incorporated into other
  18  * software packages, subject to the following license:
  19  *
  20  * Permission is hereby granted, free of charge, to any person obtaining a copy
  21  * of this source file (the "Software"), to deal in the Software without
  22  * restriction, including without limitation the rights to use, copy, modify,
  23  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  24  * and to permit persons to whom the Software is furnished to do so, subject to
  25  * the following conditions:
  26  *
  27  * The above copyright notice and this permission notice shall be included in
  28  * all copies or substantial portions of the Software.
  29  *
  30  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  31  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  32  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  33  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  34  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  35  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  36  * IN THE SOFTWARE.
  37  */
  38
  39 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
  40
  41 #include <linux/cpu.h>
  42 #include <linux/kernel.h>
  43 #include <linux/sched.h>
  44 #include <linux/errno.h>
  45 #include <linux/module.h>
  46 #include <linux/mm.h>
  47 #include <linux/bootmem.h>
  48 #include <linux/pagemap.h>
  49 #include <linux/highmem.h>
  50 #include <linux/mutex.h>
  51 #include <linux/list.h>
  52 #include <linux/gfp.h>
  53 #include <linux/notifier.h>
  54 #include <linux/memory.h>
  55 #include <linux/memory_hotplug.h>
  56 #include <linux/percpu-defs.h>
  57 #include <linux/slab.h>
  58 #include <linux/sysctl.h>
  59
  60 #include <asm/page.h>
  61 #include <asm/pgalloc.h>
  62 #include <asm/pgtable.h>
  63 #include <asm/tlb.h>
  64
  65 #include <asm/xen/hypervisor.h>
  66 #include <asm/xen/hypercall.h>
  67
  68 #include <xen/xen.h>
  69 #include <xen/interface/xen.h>
  70 #include <xen/interface/memory.h>
  71 #include <xen/balloon.h>
  72 #include <xen/features.h>
  73 #include <xen/page.h>
  74
  75 static int xen_hotplug_unpopulated;
  76
  77 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
  78
  79 static int zero;
  80 static int one = 1;
  81
  82 static struct ctl_table balloon_table[] = {
  83         {
  84                 .procname       = "hotplug_unpopulated",
  85                 .data           = &xen_hotplug_unpopulated,
  86                 .maxlen         = sizeof(int),
  87                 .mode           = 0644,
  88                 .proc_handler   = proc_dointvec_minmax,
  89                 .extra1         = &zero,
  90                 .extra2         = &one,
  91         },
  92         { }
  93 };
  94
  95 static struct ctl_table balloon_root[] = {
  96         {
  97                 .procname       = "balloon",
  98                 .mode           = 0555,
  99                 .child          = balloon_table,
 100         },
 101         { }
 102 };
 103
 104 static struct ctl_table xen_root[] = {
 105         {
 106                 .procname       = "xen",
 107                 .mode           = 0555,
 108                 .child          = balloon_root,
 109         },
 110         { }
 111 };
 112
 113 #endif
 114
 115 /*
 116  * Use one extent per PAGE_SIZE to avoid to break down the page into
 117  * multiple frame.
 118  */
 119 #define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
 120
 121 /*
 122  * balloon_process() state:
 123  *
 124  * BP_DONE: done or nothing to do,
 125  * BP_WAIT: wait to be rescheduled,
 126  * BP_EAGAIN: error, go to sleep,
 127  * BP_ECANCELED: error, balloon operation canceled.
 128  */
 129
 130 enum bp_state {
 131         BP_DONE,
 132         BP_WAIT,
 133         BP_EAGAIN,
 134         BP_ECANCELED
 135 };
 136
 137
 138 static DEFINE_MUTEX(balloon_mutex);
 139
 140 struct balloon_stats balloon_stats;
 141 EXPORT_SYMBOL_GPL(balloon_stats);
 142
 143 /* We increase/decrease in batches which fit in a page */
 144 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
 145
 146
 147 /* List of ballooned pages, threaded through the mem_map array. */
 148 static LIST_HEAD(ballooned_pages);
 149 static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
 150
 151 /* Main work function, always executed in process context. */
 152 static void balloon_process(struct work_struct *work);
 153 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
 154
 155 /* When ballooning out (allocating memory to return to Xen) we don't really
 156    want the kernel to try too hard since that can trigger the oom killer. */
 157 #define GFP_BALLOON \
 158         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 159
 160 static void scrub_page(struct page *page)
 161 {
 162 #ifdef CONFIG_XEN_SCRUB_PAGES
 163         clear_highpage(page);
 164 #endif
 165 }
 166
 167 /* balloon_append: add the given page to the balloon. */
 168 static void __balloon_append(struct page *page)
 169 {
 170         /* Lowmem is re-populated first, so highmem pages go at list tail. */
 171         if (PageHighMem(page)) {
 172                 list_add_tail(&page->lru, &ballooned_pages);
 173                 balloon_stats.balloon_high++;
 174         } else {
 175                 list_add(&page->lru, &ballooned_pages);
 176                 balloon_stats.balloon_low++;
 177         }
 178         wake_up(&balloon_wq);
 179 }
 180
 181 static void balloon_append(struct page *page)
 182 {
 183         __balloon_append(page);
 184         adjust_managed_page_count(page, -1);
 185 }
 186
 187 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 188 static struct page *balloon_retrieve(bool require_lowmem)
 189 {
 190         struct page *page;
 191
 192         if (list_empty(&ballooned_pages))
 193                 return NULL;
 194
 195         page = list_entry(ballooned_pages.next, struct page, lru);
 196         if (require_lowmem && PageHighMem(page))
 197                 return NULL;
 198         list_del(&page->lru);
 199
 200         if (PageHighMem(page))
 201                 balloon_stats.balloon_high--;
 202         else
 203                 balloon_stats.balloon_low--;
 204
 205         adjust_managed_page_count(page, 1);
 206
 207         return page;
 208 }
 209
 210 static struct page *balloon_next_page(struct page *page)
 211 {
 212         struct list_head *next = page->lru.next;
 213         if (next == &ballooned_pages)
 214                 return NULL;
 215         return list_entry(next, struct page, lru);
 216 }
 217
 218 static enum bp_state update_schedule(enum bp_state state)
 219 {
 220         if (state == BP_WAIT)
 221                 return BP_WAIT;
 222
 223         if (state == BP_ECANCELED)
 224                 return BP_ECANCELED;
 225
 226         if (state == BP_DONE) {
 227                 balloon_stats.schedule_delay = 1;
 228                 balloon_stats.retry_count = 1;
 229                 return BP_DONE;
 230         }
 231
 232         ++balloon_stats.retry_count;
 233
 234         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
 235                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
 236                 balloon_stats.schedule_delay = 1;
 237                 balloon_stats.retry_count = 1;
 238                 return BP_ECANCELED;
 239         }
 240
 241         balloon_stats.schedule_delay <<= 1;
 242
 243         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
 244                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
 245
 246         return BP_EAGAIN;
 247 }
 248
 249 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 250 static struct resource *additional_memory_resource(phys_addr_t size)
 251 {
 252         struct resource *res;
 253         int ret;
 254
 255         res = kzalloc(sizeof(*res), GFP_KERNEL);
 256         if (!res)
 257                 return NULL;
 258
 259         res->name = "System RAM";
 260         res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 261
 262         ret = allocate_resource(&iomem_resource, res,
 263                                 size, 0, -1,
 264                                 PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
 265         if (ret < 0) {
 266                 pr_err("Cannot allocate new System RAM resource\n");
 267                 kfree(res);
 268                 return NULL;
 269         }
 270
 271         return res;
 272 }
 273
 274 static void release_memory_resource(struct resource *resource)
 275 {
 276         if (!resource)
 277                 return;
 278
 279         /*
 280          * No need to reset region to identity mapped since we now
 281          * know that no I/O can be in this region
 282          */
 283         release_resource(resource);
 284         kfree(resource);
 285 }
 286
 287 static enum bp_state reserve_additional_memory(void)
 288 {
 289         long credit;
 290         struct resource *resource;
 291         int nid, rc;
 292         unsigned long balloon_hotplug;
 293
 294         credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
 295                 - balloon_stats.total_pages;
 296
 297         /*
 298          * Already hotplugged enough pages?  Wait for them to be
 299          * onlined.
 300          */
 301         if (credit <= 0)
 302                 return BP_WAIT;
 303
 304         balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
 305
 306         resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
 307         if (!resource)
 308                 goto err;
 309
 310         nid = memory_add_physaddr_to_nid(resource->start);
 311
 312 #ifdef CONFIG_XEN_HAVE_PVMMU
 313         /*
 314          * We don't support PV MMU when Linux and Xen is using
 315          * different page granularity.
 316          */
 317         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 318
 319         /*
 320          * add_memory() will build page tables for the new memory so
 321          * the p2m must contain invalid entries so the correct
 322          * non-present PTEs will be written.
 323          *
 324          * If a failure occurs, the original (identity) p2m entries
 325          * are not restored since this region is now known not to
 326          * conflict with any devices.
 327          */
 328         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 329                 unsigned long pfn, i;
 330
 331                 pfn = PFN_DOWN(resource->start);
 332                 for (i = 0; i < balloon_hotplug; i++) {
 333                         if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
 334                                 pr_warn("set_phys_to_machine() failed, no memory added\n");
 335                                 goto err;
 336                         }
 337                 }
 338         }
 339 #endif
 340
 341         rc = add_memory_resource(nid, resource);
 342         if (rc) {
 343                 pr_warn("Cannot add additional memory (%i)\n", rc);
 344                 goto err;
 345         }
 346
 347         balloon_stats.total_pages += balloon_hotplug;
 348
 349         return BP_WAIT;
 350   err:
 351         release_memory_resource(resource);
 352         return BP_ECANCELED;
 353 }
 354
 355 static void xen_online_page(struct page *page)
 356 {
 357         __online_page_set_limits(page);
 358
 359         mutex_lock(&balloon_mutex);
 360
 361         __balloon_append(page);
 362
 363         mutex_unlock(&balloon_mutex);
 364 }
 365
 366 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
 367 {
 368         if (val == MEM_ONLINE)
 369                 schedule_delayed_work(&balloon_worker, 0);
 370
 371         return NOTIFY_OK;
 372 }
 373
 374 static struct notifier_block xen_memory_nb = {
 375         .notifier_call = xen_memory_notifier,
 376         .priority = 0
 377 };
 378 #else
 379 static enum bp_state reserve_additional_memory(void)
 380 {
 381         balloon_stats.target_pages = balloon_stats.current_pages;
 382         return BP_ECANCELED;
 383 }
 384 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 385
 386 static long current_credit(void)
 387 {
 388         return balloon_stats.target_pages - balloon_stats.current_pages;
 389 }
 390
 391 static bool balloon_is_inflated(void)
 392 {
 393         return balloon_stats.balloon_low || balloon_stats.balloon_high;
 394 }
 395
 396 static enum bp_state increase_reservation(unsigned long nr_pages)
 397 {
 398         int rc;
 399         unsigned long i;
 400         struct page   *page;
 401         struct xen_memory_reservation reservation = {
 402                 .address_bits = 0,
 403                 .extent_order = EXTENT_ORDER,
 404                 .domid        = DOMID_SELF
 405         };
 406
 407         if (nr_pages > ARRAY_SIZE(frame_list))
 408                 nr_pages = ARRAY_SIZE(frame_list);
 409
 410         page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
 411         for (i = 0; i < nr_pages; i++) {
 412                 if (!page) {
 413                         nr_pages = i;
 414                         break;
 415                 }
 416
 417                 /* XENMEM_populate_physmap requires a PFN based on Xen
 418                  * granularity.
 419                  */
 420                 frame_list[i] = page_to_xen_pfn(page);
 421                 page = balloon_next_page(page);
 422         }
 423
 424         set_xen_guest_handle(reservation.extent_start, frame_list);
 425         reservation.nr_extents = nr_pages;
 426         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
 427         if (rc <= 0)
 428                 return BP_EAGAIN;
 429
 430         for (i = 0; i < rc; i++) {
 431                 page = balloon_retrieve(false);
 432                 BUG_ON(page == NULL);
 433
 434 #ifdef CONFIG_XEN_HAVE_PVMMU
 435                 /*
 436                  * We don't support PV MMU when Linux and Xen is using
 437                  * different page granularity.
 438                  */
 439                 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 440
 441                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 442                         unsigned long pfn = page_to_pfn(page);
 443
 444                         set_phys_to_machine(pfn, frame_list[i]);
 445
 446                         /* Link back into the page tables if not highmem. */
 447                         if (!PageHighMem(page)) {
 448                                 int ret;
 449                                 ret = HYPERVISOR_update_va_mapping(
 450                                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 451                                                 mfn_pte(frame_list[i], PAGE_KERNEL),
 452                                                 0);
 453                                 BUG_ON(ret);
 454                         }
 455                 }
 456 #endif
 457
 458                 /* Relinquish the page back to the allocator. */
 459                 __free_reserved_page(page);
 460         }
 461
 462         balloon_stats.current_pages += rc;
 463
 464         return BP_DONE;
 465 }
 466
 467 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 468 {
 469         enum bp_state state = BP_DONE;
 470         unsigned long i;
 471         struct page *page, *tmp;
 472         int ret;
 473         struct xen_memory_reservation reservation = {
 474                 .address_bits = 0,
 475                 .extent_order = EXTENT_ORDER,
 476                 .domid        = DOMID_SELF
 477         };
 478         LIST_HEAD(pages);
 479
 480         if (nr_pages > ARRAY_SIZE(frame_list))
 481                 nr_pages = ARRAY_SIZE(frame_list);
 482
 483         for (i = 0; i < nr_pages; i++) {
 484                 page = alloc_page(gfp);
 485                 if (page == NULL) {
 486                         nr_pages = i;
 487                         state = BP_EAGAIN;
 488                         break;
 489                 }
 490                 scrub_page(page);
 491                 list_add(&page->lru, &pages);
 492         }
 493
 494         /*
 495          * Ensure that ballooned highmem pages don't have kmaps.
 496          *
 497          * Do this before changing the p2m as kmap_flush_unused()
 498          * reads PTEs to obtain pages (and hence needs the original
 499          * p2m entry).
 500          */
 501         kmap_flush_unused();
 502
 503         /*
 504          * Setup the frame, update direct mapping, invalidate P2M,
 505          * and add to balloon.
 506          */
 507         i = 0;
 508         list_for_each_entry_safe(page, tmp, &pages, lru) {
 509                 /* XENMEM_decrease_reservation requires a GFN */
 510                 frame_list[i++] = xen_page_to_gfn(page);
 511
 512 #ifdef CONFIG_XEN_HAVE_PVMMU
 513                 /*
 514                  * We don't support PV MMU when Linux and Xen is using
 515                  * different page granularity.
 516                  */
 517                 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 518
 519                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 520                         unsigned long pfn = page_to_pfn(page);
 521
 522                         if (!PageHighMem(page)) {
 523                                 ret = HYPERVISOR_update_va_mapping(
 524                                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 525                                                 __pte_ma(0), 0);
 526                                 BUG_ON(ret);
 527                         }
 528                         __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 529                 }
 530 #endif
 531                 list_del(&page->lru);
 532
 533                 balloon_append(page);
 534         }
 535
 536         flush_tlb_all();
 537
 538         set_xen_guest_handle(reservation.extent_start, frame_list);
 539         reservation.nr_extents   = nr_pages;
 540         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 541         BUG_ON(ret != nr_pages);
 542
 543         balloon_stats.current_pages -= nr_pages;
 544
 545         return state;
 546 }
 547
 548 /*
 549  * As this is a work item it is guaranteed to run as a single instance only.
 550  * We may of course race updates of the target counts (which are protected
 551  * by the balloon lock), or with changes to the Xen hard limit, but we will
 552  * recover from these in time.
 553  */
 554 static void balloon_process(struct work_struct *work)
 555 {
 556         enum bp_state state = BP_DONE;
 557         long credit;
 558
 559
 560         do {
 561                 mutex_lock(&balloon_mutex);
 562
 563                 credit = current_credit();
 564
 565                 if (credit > 0) {
 566                         if (balloon_is_inflated())
 567                                 state = increase_reservation(credit);
 568                         else
 569                                 state = reserve_additional_memory();
 570                 }
 571
 572                 if (credit < 0)
 573                         state = decrease_reservation(-credit, GFP_BALLOON);
 574
 575                 state = update_schedule(state);
 576
 577                 mutex_unlock(&balloon_mutex);
 578
 579                 cond_resched();
 580
 581         } while (credit && state == BP_DONE);
 582
 583         /* Schedule more work if there is some still to be done. */
 584         if (state == BP_EAGAIN)
 585                 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
 586 }
 587
 588 /* Resets the Xen limit, sets new target, and kicks off processing. */
 589 void balloon_set_new_target(unsigned long target)
 590 {
 591         /* No need for lock. Not read-modify-write updates. */
 592         balloon_stats.target_pages = target;
 593         schedule_delayed_work(&balloon_worker, 0);
 594 }
 595 EXPORT_SYMBOL_GPL(balloon_set_new_target);
 596
 597 static int add_ballooned_pages(int nr_pages)
 598 {
 599         enum bp_state st;
 600
 601         if (xen_hotplug_unpopulated) {
 602                 st = reserve_additional_memory();
 603                 if (st != BP_ECANCELED) {
 604                         mutex_unlock(&balloon_mutex);
 605                         wait_event(balloon_wq,
 606                                    !list_empty(&ballooned_pages));
 607                         mutex_lock(&balloon_mutex);
 608                         return 0;
 609                 }
 610         }
 611
 612         st = decrease_reservation(nr_pages, GFP_USER);
 613         if (st != BP_DONE)
 614                 return -ENOMEM;
 615
 616         return 0;
 617 }
 618
 619 /**
 620  * alloc_xenballooned_pages - get pages that have been ballooned out
 621  * @nr_pages: Number of pages to get
 622  * @pages: pages returned
 623  * @return 0 on success, error otherwise
 624  */
 625 int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 626 {
 627         int pgno = 0;
 628         struct page *page;
 629         int ret;
 630
 631         mutex_lock(&balloon_mutex);
 632
 633         balloon_stats.target_unpopulated += nr_pages;
 634
 635         while (pgno < nr_pages) {
 636                 page = balloon_retrieve(true);
 637                 if (page) {
 638                         pages[pgno++] = page;
 639 #ifdef CONFIG_XEN_HAVE_PVMMU
 640                         /*
 641                          * We don't support PV MMU when Linux and Xen is using
 642                          * different page granularity.
 643                          */
 644                         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 645
 646                         ret = xen_alloc_p2m_entry(page_to_pfn(page));
 647                         if (ret < 0)
 648                                 goto out_undo;
 649 #endif
 650                 } else {
 651                         ret = add_ballooned_pages(nr_pages - pgno);
 652                         if (ret < 0)
 653                                 goto out_undo;
 654                 }
 655         }
 656         mutex_unlock(&balloon_mutex);
 657         return 0;
 658  out_undo:
 659         mutex_unlock(&balloon_mutex);
 660         free_xenballooned_pages(pgno, pages);
 661         return ret;
 662 }
 663 EXPORT_SYMBOL(alloc_xenballooned_pages);
 664
 665 /**
 666  * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
 667  * @nr_pages: Number of pages
 668  * @pages: pages to return
 669  */
 670 void free_xenballooned_pages(int nr_pages, struct page **pages)
 671 {
 672         int i;
 673
 674         mutex_lock(&balloon_mutex);
 675
 676         for (i = 0; i < nr_pages; i++) {
 677                 if (pages[i])
 678                         balloon_append(pages[i]);
 679         }
 680
 681         balloon_stats.target_unpopulated -= nr_pages;
 682
 683         /* The balloon may be too large now. Shrink it if needed. */
 684         if (current_credit())
 685                 schedule_delayed_work(&balloon_worker, 0);
 686
 687         mutex_unlock(&balloon_mutex);
 688 }
 689 EXPORT_SYMBOL(free_xenballooned_pages);
 690
 691 static void __init balloon_add_region(unsigned long start_pfn,
 692                                       unsigned long pages)
 693 {
 694         unsigned long pfn, extra_pfn_end;
 695         struct page *page;
 696
 697         /*
 698          * If the amount of usable memory has been limited (e.g., with
 699          * the 'mem' command line parameter), don't add pages beyond
 700          * this limit.
 701          */
 702         extra_pfn_end = min(max_pfn, start_pfn + pages);
 703
 704         for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
 705                 page = pfn_to_page(pfn);
 706                 /* totalram_pages and totalhigh_pages do not
 707                    include the boot-time balloon extension, so
 708                    don't subtract from it. */
 709                 __balloon_append(page);
 710         }
 711
 712         balloon_stats.total_pages += extra_pfn_end - start_pfn;
 713 }
 714
 715 static int __init balloon_init(void)
 716 {
 717         int i;
 718
 719         if (!xen_domain())
 720                 return -ENODEV;
 721
 722         pr_info("Initialising balloon driver\n");
 723
 724         balloon_stats.current_pages = xen_pv_domain()
 725                 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
 726                 : get_num_physpages();
 727         balloon_stats.target_pages  = balloon_stats.current_pages;
 728         balloon_stats.balloon_low   = 0;
 729         balloon_stats.balloon_high  = 0;
 730         balloon_stats.total_pages   = balloon_stats.current_pages;
 731
 732         balloon_stats.schedule_delay = 1;
 733         balloon_stats.max_schedule_delay = 32;
 734         balloon_stats.retry_count = 1;
 735         balloon_stats.max_retry_count = RETRY_UNLIMITED;
 736
 737 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 738         set_online_page_callback(&xen_online_page);
 739         register_memory_notifier(&xen_memory_nb);
 740         register_sysctl_table(xen_root);
 741 #endif
 742
 743         /*
 744          * Initialize the balloon with pages from the extra memory
 745          * regions (see arch/x86/xen/setup.c).
 746          */
 747         for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
 748                 if (xen_extra_mem[i].n_pfns)
 749                         balloon_add_region(xen_extra_mem[i].start_pfn,
 750                                            xen_extra_mem[i].n_pfns);
 751
 752         return 0;
 753 }
 754
 755 subsys_initcall(balloon_init);
 756
 757 MODULE_LICENSE("GPL");