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/cred.h>
  45 #include <linux/errno.h>
  46 #include <linux/freezer.h>
  47 #include <linux/kthread.h>
  48 #include <linux/mm.h>
  49 #include <linux/memblock.h>
  50 #include <linux/pagemap.h>
  51 #include <linux/highmem.h>
  52 #include <linux/mutex.h>
  53 #include <linux/list.h>
  54 #include <linux/gfp.h>
  55 #include <linux/notifier.h>
  56 #include <linux/memory.h>
  57 #include <linux/memory_hotplug.h>
  58 #include <linux/percpu-defs.h>
  59 #include <linux/slab.h>
  60 #include <linux/sysctl.h>
  61 #include <linux/moduleparam.h>
  62 #include <linux/jiffies.h>
  63
  64 #include <asm/page.h>
  65 #include <asm/tlb.h>
  66
  67 #include <asm/xen/hypervisor.h>
  68 #include <asm/xen/hypercall.h>
  69
  70 #include <xen/xen.h>
  71 #include <xen/interface/xen.h>
  72 #include <xen/interface/memory.h>
  73 #include <xen/balloon.h>
  74 #include <xen/features.h>
  75 #include <xen/page.h>
  76 #include <xen/mem-reservation.h>
  77
  78 #undef MODULE_PARAM_PREFIX
  79 #define MODULE_PARAM_PREFIX "xen."
  80
  81 static uint __read_mostly balloon_boot_timeout = 180;
  82 module_param(balloon_boot_timeout, uint, 0444);
  83
  84 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
  85 static int xen_hotplug_unpopulated;
  86
  87 static struct ctl_table balloon_table[] = {
  88         {
  89                 .procname       = "hotplug_unpopulated",
  90                 .data           = &xen_hotplug_unpopulated,
  91                 .maxlen         = sizeof(int),
  92                 .mode           = 0644,
  93                 .proc_handler   = proc_dointvec_minmax,
  94                 .extra1         = SYSCTL_ZERO,
  95                 .extra2         = SYSCTL_ONE,
  96         },
  97         { }
  98 };
  99
 100 static struct ctl_table balloon_root[] = {
 101         {
 102                 .procname       = "balloon",
 103                 .mode           = 0555,
 104                 .child          = balloon_table,
 105         },
 106         { }
 107 };
 108
 109 static struct ctl_table xen_root[] = {
 110         {
 111                 .procname       = "xen",
 112                 .mode           = 0555,
 113                 .child          = balloon_root,
 114         },
 115         { }
 116 };
 117
 118 #else
 119 #define xen_hotplug_unpopulated 0
 120 #endif
 121
 122 /*
 123  * Use one extent per PAGE_SIZE to avoid to break down the page into
 124  * multiple frame.
 125  */
 126 #define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
 127
 128 /*
 129  * balloon_thread() state:
 130  *
 131  * BP_DONE: done or nothing to do,
 132  * BP_WAIT: wait to be rescheduled,
 133  * BP_EAGAIN: error, go to sleep,
 134  * BP_ECANCELED: error, balloon operation canceled.
 135  */
 136
 137 static enum bp_state {
 138         BP_DONE,
 139         BP_WAIT,
 140         BP_EAGAIN,
 141         BP_ECANCELED
 142 } balloon_state = BP_DONE;
 143
 144 /* Main waiting point for xen-balloon thread. */
 145 static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq);
 146
 147 static DEFINE_MUTEX(balloon_mutex);
 148
 149 struct balloon_stats balloon_stats;
 150 EXPORT_SYMBOL_GPL(balloon_stats);
 151
 152 /* We increase/decrease in batches which fit in a page */
 153 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
 154
 155
 156 /* List of ballooned pages, threaded through the mem_map array. */
 157 static LIST_HEAD(ballooned_pages);
 158 static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
 159
 160 /* When ballooning out (allocating memory to return to Xen) we don't really
 161    want the kernel to try too hard since that can trigger the oom killer. */
 162 #define GFP_BALLOON \
 163         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 164
 165 /* balloon_append: add the given page to the balloon. */
 166 static void balloon_append(struct page *page)
 167 {
 168         __SetPageOffline(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 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 182 static struct page *balloon_retrieve(bool require_lowmem)
 183 {
 184         struct page *page;
 185
 186         if (list_empty(&ballooned_pages))
 187                 return NULL;
 188
 189         page = list_entry(ballooned_pages.next, struct page, lru);
 190         if (require_lowmem && PageHighMem(page))
 191                 return NULL;
 192         list_del(&page->lru);
 193
 194         if (PageHighMem(page))
 195                 balloon_stats.balloon_high--;
 196         else
 197                 balloon_stats.balloon_low--;
 198
 199         __ClearPageOffline(page);
 200         return page;
 201 }
 202
 203 static struct page *balloon_next_page(struct page *page)
 204 {
 205         struct list_head *next = page->lru.next;
 206         if (next == &ballooned_pages)
 207                 return NULL;
 208         return list_entry(next, struct page, lru);
 209 }
 210
 211 static void update_schedule(void)
 212 {
 213         if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED)
 214                 return;
 215
 216         if (balloon_state == BP_DONE) {
 217                 balloon_stats.schedule_delay = 1;
 218                 balloon_stats.retry_count = 1;
 219                 return;
 220         }
 221
 222         ++balloon_stats.retry_count;
 223
 224         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
 225                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
 226                 balloon_stats.schedule_delay = 1;
 227                 balloon_stats.retry_count = 1;
 228                 balloon_state = BP_ECANCELED;
 229                 return;
 230         }
 231
 232         balloon_stats.schedule_delay <<= 1;
 233
 234         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
 235                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
 236
 237         balloon_state = BP_EAGAIN;
 238 }
 239
 240 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 241 static void release_memory_resource(struct resource *resource)
 242 {
 243         if (!resource)
 244                 return;
 245
 246         /*
 247          * No need to reset region to identity mapped since we now
 248          * know that no I/O can be in this region
 249          */
 250         release_resource(resource);
 251         kfree(resource);
 252 }
 253
 254 static struct resource *additional_memory_resource(phys_addr_t size)
 255 {
 256         struct resource *res;
 257         int ret;
 258
 259         res = kzalloc(sizeof(*res), GFP_KERNEL);
 260         if (!res)
 261                 return NULL;
 262
 263         res->name = "System RAM";
 264         res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 265
 266         ret = allocate_resource(&iomem_resource, res,
 267                                 size, 0, -1,
 268                                 PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
 269         if (ret < 0) {
 270                 pr_err("Cannot allocate new System RAM resource\n");
 271                 kfree(res);
 272                 return NULL;
 273         }
 274
 275         return res;
 276 }
 277
 278 static enum bp_state reserve_additional_memory(void)
 279 {
 280         long credit;
 281         struct resource *resource;
 282         int nid, rc;
 283         unsigned long balloon_hotplug;
 284
 285         credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
 286                 - balloon_stats.total_pages;
 287
 288         /*
 289          * Already hotplugged enough pages?  Wait for them to be
 290          * onlined.
 291          */
 292         if (credit <= 0)
 293                 return BP_WAIT;
 294
 295         balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
 296
 297         resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
 298         if (!resource)
 299                 goto err;
 300
 301         nid = memory_add_physaddr_to_nid(resource->start);
 302
 303 #ifdef CONFIG_XEN_HAVE_PVMMU
 304         /*
 305          * We don't support PV MMU when Linux and Xen is using
 306          * different page granularity.
 307          */
 308         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 309
 310         /*
 311          * add_memory() will build page tables for the new memory so
 312          * the p2m must contain invalid entries so the correct
 313          * non-present PTEs will be written.
 314          *
 315          * If a failure occurs, the original (identity) p2m entries
 316          * are not restored since this region is now known not to
 317          * conflict with any devices.
 318          */
 319         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 320                 unsigned long pfn, i;
 321
 322                 pfn = PFN_DOWN(resource->start);
 323                 for (i = 0; i < balloon_hotplug; i++) {
 324                         if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
 325                                 pr_warn("set_phys_to_machine() failed, no memory added\n");
 326                                 goto err;
 327                         }
 328                 }
 329         }
 330 #endif
 331
 332         /*
 333          * add_memory_resource() will call online_pages() which in its turn
 334          * will call xen_online_page() callback causing deadlock if we don't
 335          * release balloon_mutex here. Unlocking here is safe because the
 336          * callers drop the mutex before trying again.
 337          */
 338         mutex_unlock(&balloon_mutex);
 339         /* add_memory_resource() requires the device_hotplug lock */
 340         lock_device_hotplug();
 341         rc = add_memory_resource(nid, resource, MHP_MERGE_RESOURCE);
 342         unlock_device_hotplug();
 343         mutex_lock(&balloon_mutex);
 344
 345         if (rc) {
 346                 pr_warn("Cannot add additional memory (%i)\n", rc);
 347                 goto err;
 348         }
 349
 350         balloon_stats.total_pages += balloon_hotplug;
 351
 352         return BP_WAIT;
 353   err:
 354         release_memory_resource(resource);
 355         return BP_ECANCELED;
 356 }
 357
 358 static void xen_online_page(struct page *page, unsigned int order)
 359 {
 360         unsigned long i, size = (1 << order);
 361         unsigned long start_pfn = page_to_pfn(page);
 362         struct page *p;
 363
 364         pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
 365         mutex_lock(&balloon_mutex);
 366         for (i = 0; i < size; i++) {
 367                 p = pfn_to_page(start_pfn + i);
 368                 balloon_append(p);
 369         }
 370         mutex_unlock(&balloon_mutex);
 371 }
 372
 373 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
 374 {
 375         if (val == MEM_ONLINE)
 376                 wake_up(&balloon_thread_wq);
 377
 378         return NOTIFY_OK;
 379 }
 380
 381 static struct notifier_block xen_memory_nb = {
 382         .notifier_call = xen_memory_notifier,
 383         .priority = 0
 384 };
 385 #else
 386 static enum bp_state reserve_additional_memory(void)
 387 {
 388         balloon_stats.target_pages = balloon_stats.current_pages +
 389                                      balloon_stats.target_unpopulated;
 390         return BP_ECANCELED;
 391 }
 392 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 393
 394 static long current_credit(void)
 395 {
 396         return balloon_stats.target_pages - balloon_stats.current_pages;
 397 }
 398
 399 static bool balloon_is_inflated(void)
 400 {
 401         return balloon_stats.balloon_low || balloon_stats.balloon_high;
 402 }
 403
 404 static enum bp_state increase_reservation(unsigned long nr_pages)
 405 {
 406         int rc;
 407         unsigned long i;
 408         struct page   *page;
 409
 410         if (nr_pages > ARRAY_SIZE(frame_list))
 411                 nr_pages = ARRAY_SIZE(frame_list);
 412
 413         page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
 414         for (i = 0; i < nr_pages; i++) {
 415                 if (!page) {
 416                         nr_pages = i;
 417                         break;
 418                 }
 419
 420                 frame_list[i] = page_to_xen_pfn(page);
 421                 page = balloon_next_page(page);
 422         }
 423
 424         rc = xenmem_reservation_increase(nr_pages, frame_list);
 425         if (rc <= 0)
 426                 return BP_EAGAIN;
 427
 428         for (i = 0; i < rc; i++) {
 429                 page = balloon_retrieve(false);
 430                 BUG_ON(page == NULL);
 431
 432                 xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
 433
 434                 /* Relinquish the page back to the allocator. */
 435                 free_reserved_page(page);
 436         }
 437
 438         balloon_stats.current_pages += rc;
 439
 440         return BP_DONE;
 441 }
 442
 443 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 444 {
 445         enum bp_state state = BP_DONE;
 446         unsigned long i;
 447         struct page *page, *tmp;
 448         int ret;
 449         LIST_HEAD(pages);
 450
 451         if (nr_pages > ARRAY_SIZE(frame_list))
 452                 nr_pages = ARRAY_SIZE(frame_list);
 453
 454         for (i = 0; i < nr_pages; i++) {
 455                 page = alloc_page(gfp);
 456                 if (page == NULL) {
 457                         nr_pages = i;
 458                         state = BP_EAGAIN;
 459                         break;
 460                 }
 461                 adjust_managed_page_count(page, -1);
 462                 xenmem_reservation_scrub_page(page);
 463                 list_add(&page->lru, &pages);
 464         }
 465
 466         /*
 467          * Ensure that ballooned highmem pages don't have kmaps.
 468          *
 469          * Do this before changing the p2m as kmap_flush_unused()
 470          * reads PTEs to obtain pages (and hence needs the original
 471          * p2m entry).
 472          */
 473         kmap_flush_unused();
 474
 475         /*
 476          * Setup the frame, update direct mapping, invalidate P2M,
 477          * and add to balloon.
 478          */
 479         i = 0;
 480         list_for_each_entry_safe(page, tmp, &pages, lru) {
 481                 frame_list[i++] = xen_page_to_gfn(page);
 482
 483                 xenmem_reservation_va_mapping_reset(1, &page);
 484
 485                 list_del(&page->lru);
 486
 487                 balloon_append(page);
 488         }
 489
 490         flush_tlb_all();
 491
 492         ret = xenmem_reservation_decrease(nr_pages, frame_list);
 493         BUG_ON(ret != nr_pages);
 494
 495         balloon_stats.current_pages -= nr_pages;
 496
 497         return state;
 498 }
 499
 500 /*
 501  * Stop waiting if either state is BP_DONE and ballooning action is
 502  * needed, or if the credit has changed while state is not BP_DONE.
 503  */
 504 static bool balloon_thread_cond(long credit)
 505 {
 506         if (balloon_state == BP_DONE)
 507                 credit = 0;
 508
 509         return current_credit() != credit || kthread_should_stop();
 510 }
 511
 512 /*
 513  * As this is a kthread it is guaranteed to run as a single instance only.
 514  * We may of course race updates of the target counts (which are protected
 515  * by the balloon lock), or with changes to the Xen hard limit, but we will
 516  * recover from these in time.
 517  */
 518 static int balloon_thread(void *unused)
 519 {
 520         long credit;
 521         unsigned long timeout;
 522
 523         set_freezable();
 524         for (;;) {
 525                 switch (balloon_state) {
 526                 case BP_DONE:
 527                 case BP_ECANCELED:
 528                         timeout = 3600 * HZ;
 529                         break;
 530                 case BP_EAGAIN:
 531                         timeout = balloon_stats.schedule_delay * HZ;
 532                         break;
 533                 case BP_WAIT:
 534                         timeout = HZ;
 535                         break;
 536                 }
 537
 538                 credit = current_credit();
 539
 540                 wait_event_freezable_timeout(balloon_thread_wq,
 541                         balloon_thread_cond(credit), timeout);
 542
 543                 if (kthread_should_stop())
 544                         return 0;
 545
 546                 mutex_lock(&balloon_mutex);
 547
 548                 credit = current_credit();
 549
 550                 if (credit > 0) {
 551                         if (balloon_is_inflated())
 552                                 balloon_state = increase_reservation(credit);
 553                         else
 554                                 balloon_state = reserve_additional_memory();
 555                 }
 556
 557                 if (credit < 0) {
 558                         long n_pages;
 559
 560                         n_pages = min(-credit, si_mem_available());
 561                         balloon_state = decrease_reservation(n_pages,
 562                                                              GFP_BALLOON);
 563                         if (balloon_state == BP_DONE && n_pages != -credit &&
 564                             n_pages < totalreserve_pages)
 565                                 balloon_state = BP_EAGAIN;
 566                 }
 567
 568                 update_schedule();
 569
 570                 mutex_unlock(&balloon_mutex);
 571
 572                 cond_resched();
 573         }
 574 }
 575
 576 /* Resets the Xen limit, sets new target, and kicks off processing. */
 577 void balloon_set_new_target(unsigned long target)
 578 {
 579         /* No need for lock. Not read-modify-write updates. */
 580         balloon_stats.target_pages = target;
 581         wake_up(&balloon_thread_wq);
 582 }
 583 EXPORT_SYMBOL_GPL(balloon_set_new_target);
 584
 585 static int add_ballooned_pages(unsigned int nr_pages)
 586 {
 587         enum bp_state st;
 588
 589         if (xen_hotplug_unpopulated) {
 590                 st = reserve_additional_memory();
 591                 if (st != BP_ECANCELED) {
 592                         int rc;
 593
 594                         mutex_unlock(&balloon_mutex);
 595                         rc = wait_event_interruptible(balloon_wq,
 596                                    !list_empty(&ballooned_pages));
 597                         mutex_lock(&balloon_mutex);
 598                         return rc ? -ENOMEM : 0;
 599                 }
 600         }
 601
 602         if (si_mem_available() < nr_pages)
 603                 return -ENOMEM;
 604
 605         st = decrease_reservation(nr_pages, GFP_USER);
 606         if (st != BP_DONE)
 607                 return -ENOMEM;
 608
 609         return 0;
 610 }
 611
 612 /**
 613  * xen_alloc_ballooned_pages - get pages that have been ballooned out
 614  * @nr_pages: Number of pages to get
 615  * @pages: pages returned
 616  * @return 0 on success, error otherwise
 617  */
 618 int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
 619 {
 620         unsigned int pgno = 0;
 621         struct page *page;
 622         int ret;
 623
 624         mutex_lock(&balloon_mutex);
 625
 626         balloon_stats.target_unpopulated += nr_pages;
 627
 628         while (pgno < nr_pages) {
 629                 page = balloon_retrieve(true);
 630                 if (page) {
 631                         pages[pgno++] = page;
 632 #ifdef CONFIG_XEN_HAVE_PVMMU
 633                         /*
 634                          * We don't support PV MMU when Linux and Xen is using
 635                          * different page granularity.
 636                          */
 637                         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 638
 639                         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 640                                 ret = xen_alloc_p2m_entry(page_to_pfn(page));
 641                                 if (ret < 0)
 642                                         goto out_undo;
 643                         }
 644 #endif
 645                 } else {
 646                         ret = add_ballooned_pages(nr_pages - pgno);
 647                         if (ret < 0)
 648                                 goto out_undo;
 649                 }
 650         }
 651         mutex_unlock(&balloon_mutex);
 652         return 0;
 653  out_undo:
 654         mutex_unlock(&balloon_mutex);
 655         xen_free_ballooned_pages(pgno, pages);
 656         /*
 657          * NB: xen_free_ballooned_pages will only subtract pgno pages, but since
 658          * target_unpopulated is incremented with nr_pages at the start we need
 659          * to remove the remaining ones also, or accounting will be screwed.
 660          */
 661         balloon_stats.target_unpopulated -= nr_pages - pgno;
 662         return ret;
 663 }
 664 EXPORT_SYMBOL(xen_alloc_ballooned_pages);
 665
 666 /**
 667  * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
 668  * @nr_pages: Number of pages
 669  * @pages: pages to return
 670  */
 671 void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
 672 {
 673         unsigned int i;
 674
 675         mutex_lock(&balloon_mutex);
 676
 677         for (i = 0; i < nr_pages; i++) {
 678                 if (pages[i])
 679                         balloon_append(pages[i]);
 680         }
 681
 682         balloon_stats.target_unpopulated -= nr_pages;
 683
 684         /* The balloon may be too large now. Shrink it if needed. */
 685         if (current_credit())
 686                 wake_up(&balloon_thread_wq);
 687
 688         mutex_unlock(&balloon_mutex);
 689 }
 690 EXPORT_SYMBOL(xen_free_ballooned_pages);
 691
 692 static void __init balloon_add_regions(void)
 693 {
 694 #if defined(CONFIG_XEN_PV)
 695         unsigned long start_pfn, pages;
 696         unsigned long pfn, extra_pfn_end;
 697         unsigned int i;
 698
 699         for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
 700                 pages = xen_extra_mem[i].n_pfns;
 701                 if (!pages)
 702                         continue;
 703
 704                 start_pfn = xen_extra_mem[i].start_pfn;
 705
 706                 /*
 707                  * If the amount of usable memory has been limited (e.g., with
 708                  * the 'mem' command line parameter), don't add pages beyond
 709                  * this limit.
 710                  */
 711                 extra_pfn_end = min(max_pfn, start_pfn + pages);
 712
 713                 for (pfn = start_pfn; pfn < extra_pfn_end; pfn++)
 714                         balloon_append(pfn_to_page(pfn));
 715
 716                 balloon_stats.total_pages += extra_pfn_end - start_pfn;
 717         }
 718 #endif
 719 }
 720
 721 static int __init balloon_init(void)
 722 {
 723         struct task_struct *task;
 724
 725         if (!xen_domain())
 726                 return -ENODEV;
 727
 728         pr_info("Initialising balloon driver\n");
 729
 730 #ifdef CONFIG_XEN_PV
 731         balloon_stats.current_pages = xen_pv_domain()
 732                 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
 733                 : get_num_physpages();
 734 #else
 735         balloon_stats.current_pages = get_num_physpages();
 736 #endif
 737         balloon_stats.target_pages  = balloon_stats.current_pages;
 738         balloon_stats.balloon_low   = 0;
 739         balloon_stats.balloon_high  = 0;
 740         balloon_stats.total_pages   = balloon_stats.current_pages;
 741
 742         balloon_stats.schedule_delay = 1;
 743         balloon_stats.max_schedule_delay = 32;
 744         balloon_stats.retry_count = 1;
 745         balloon_stats.max_retry_count = 4;
 746
 747 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 748         set_online_page_callback(&xen_online_page);
 749         register_memory_notifier(&xen_memory_nb);
 750         register_sysctl_table(xen_root);
 751 #endif
 752
 753         balloon_add_regions();
 754
 755         task = kthread_run(balloon_thread, NULL, "xen-balloon");
 756         if (IS_ERR(task)) {
 757                 pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
 758                 return PTR_ERR(task);
 759         }
 760
 761         /* Init the xen-balloon driver. */
 762         xen_balloon_init();
 763
 764         return 0;
 765 }
 766 subsys_initcall(balloon_init);
 767
 768 static int __init balloon_wait_finish(void)
 769 {
 770         long credit, last_credit = 0;
 771         unsigned long last_changed = 0;
 772
 773         if (!xen_domain())
 774                 return -ENODEV;
 775
 776         /* PV guests don't need to wait. */
 777         if (xen_pv_domain() || !current_credit())
 778                 return 0;
 779
 780         pr_notice("Waiting for initial ballooning down having finished.\n");
 781
 782         while ((credit = current_credit()) < 0) {
 783                 if (credit != last_credit) {
 784                         last_changed = jiffies;
 785                         last_credit = credit;
 786                 }
 787                 if (balloon_state == BP_ECANCELED) {
 788                         pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
 789                                      -credit);
 790                         if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout))
 791                                 panic("Initial ballooning failed!\n");
 792                 }
 793
 794                 schedule_timeout_interruptible(HZ / 10);
 795         }
 796
 797         pr_notice("Initial ballooning down finished.\n");
 798
 799         return 0;
 800 }
 801 late_initcall_sync(balloon_wait_finish);