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/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 }
 185
 186 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 187 static struct page *balloon_retrieve(bool require_lowmem)
 188 {
 189         struct page *page;
 190
 191         if (list_empty(&ballooned_pages))
 192                 return NULL;
 193
 194         page = list_entry(ballooned_pages.next, struct page, lru);
 195         if (require_lowmem && PageHighMem(page))
 196                 return NULL;
 197         list_del(&page->lru);
 198
 199         if (PageHighMem(page))
 200                 balloon_stats.balloon_high--;
 201         else
 202                 balloon_stats.balloon_low--;
 203
 204         return page;
 205 }
 206
 207 static struct page *balloon_next_page(struct page *page)
 208 {
 209         struct list_head *next = page->lru.next;
 210         if (next == &ballooned_pages)
 211                 return NULL;
 212         return list_entry(next, struct page, lru);
 213 }
 214
 215 static enum bp_state update_schedule(enum bp_state state)
 216 {
 217         if (state == BP_WAIT)
 218                 return BP_WAIT;
 219
 220         if (state == BP_ECANCELED)
 221                 return BP_ECANCELED;
 222
 223         if (state == BP_DONE) {
 224                 balloon_stats.schedule_delay = 1;
 225                 balloon_stats.retry_count = 1;
 226                 return BP_DONE;
 227         }
 228
 229         ++balloon_stats.retry_count;
 230
 231         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
 232                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
 233                 balloon_stats.schedule_delay = 1;
 234                 balloon_stats.retry_count = 1;
 235                 return BP_ECANCELED;
 236         }
 237
 238         balloon_stats.schedule_delay <<= 1;
 239
 240         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
 241                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
 242
 243         return BP_EAGAIN;
 244 }
 245
 246 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 247 static void release_memory_resource(struct resource *resource)
 248 {
 249         if (!resource)
 250                 return;
 251
 252         /*
 253          * No need to reset region to identity mapped since we now
 254          * know that no I/O can be in this region
 255          */
 256         release_resource(resource);
 257         kfree(resource);
 258 }
 259
 260 /*
 261  * Host memory not allocated to dom0. We can use this range for hotplug-based
 262  * ballooning.
 263  *
 264  * It's a type-less resource. Setting IORESOURCE_MEM will make resource
 265  * management algorithms (arch_remove_reservations()) look into guest e820,
 266  * which we don't want.
 267  */
 268 static struct resource hostmem_resource = {
 269         .name   = "Host RAM",
 270 };
 271
 272 void __attribute__((weak)) __init arch_xen_balloon_init(struct resource *res)
 273 {}
 274
 275 static struct resource *additional_memory_resource(phys_addr_t size)
 276 {
 277         struct resource *res, *res_hostmem;
 278         int ret = -ENOMEM;
 279
 280         res = kzalloc(sizeof(*res), GFP_KERNEL);
 281         if (!res)
 282                 return NULL;
 283
 284         res->name = "System RAM";
 285         res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 286
 287         res_hostmem = kzalloc(sizeof(*res), GFP_KERNEL);
 288         if (res_hostmem) {
 289                 /* Try to grab a range from hostmem */
 290                 res_hostmem->name = "Host memory";
 291                 ret = allocate_resource(&hostmem_resource, res_hostmem,
 292                                         size, 0, -1,
 293                                         PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
 294         }
 295
 296         if (!ret) {
 297                 /*
 298                  * Insert this resource into iomem. Because hostmem_resource
 299                  * tracks portion of guest e820 marked as UNUSABLE noone else
 300                  * should try to use it.
 301                  */
 302                 res->start = res_hostmem->start;
 303                 res->end = res_hostmem->end;
 304                 ret = insert_resource(&iomem_resource, res);
 305                 if (ret < 0) {
 306                         pr_err("Can't insert iomem_resource [%llx - %llx]\n",
 307                                 res->start, res->end);
 308                         release_memory_resource(res_hostmem);
 309                         res_hostmem = NULL;
 310                         res->start = res->end = 0;
 311                 }
 312         }
 313
 314         if (ret) {
 315                 ret = allocate_resource(&iomem_resource, res,
 316                                         size, 0, -1,
 317                                         PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
 318                 if (ret < 0) {
 319                         pr_err("Cannot allocate new System RAM resource\n");
 320                         kfree(res);
 321                         return NULL;
 322                 }
 323         }
 324
 325 #ifdef CONFIG_SPARSEMEM
 326         {
 327                 unsigned long limit = 1UL << (MAX_PHYSMEM_BITS - PAGE_SHIFT);
 328                 unsigned long pfn = res->start >> PAGE_SHIFT;
 329
 330                 if (pfn > limit) {
 331                         pr_err("New System RAM resource outside addressable RAM (%lu > %lu)\n",
 332                                pfn, limit);
 333                         release_memory_resource(res);
 334                         release_memory_resource(res_hostmem);
 335                         return NULL;
 336                 }
 337         }
 338 #endif
 339
 340         return res;
 341 }
 342
 343 static enum bp_state reserve_additional_memory(void)
 344 {
 345         long credit;
 346         struct resource *resource;
 347         int nid, rc;
 348         unsigned long balloon_hotplug;
 349
 350         credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
 351                 - balloon_stats.total_pages;
 352
 353         /*
 354          * Already hotplugged enough pages?  Wait for them to be
 355          * onlined.
 356          */
 357         if (credit <= 0)
 358                 return BP_WAIT;
 359
 360         balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
 361
 362         resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
 363         if (!resource)
 364                 goto err;
 365
 366         nid = memory_add_physaddr_to_nid(resource->start);
 367
 368 #ifdef CONFIG_XEN_HAVE_PVMMU
 369         /*
 370          * We don't support PV MMU when Linux and Xen is using
 371          * different page granularity.
 372          */
 373         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 374
 375         /*
 376          * add_memory() will build page tables for the new memory so
 377          * the p2m must contain invalid entries so the correct
 378          * non-present PTEs will be written.
 379          *
 380          * If a failure occurs, the original (identity) p2m entries
 381          * are not restored since this region is now known not to
 382          * conflict with any devices.
 383          */
 384         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 385                 unsigned long pfn, i;
 386
 387                 pfn = PFN_DOWN(resource->start);
 388                 for (i = 0; i < balloon_hotplug; i++) {
 389                         if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
 390                                 pr_warn("set_phys_to_machine() failed, no memory added\n");
 391                                 goto err;
 392                         }
 393                 }
 394         }
 395 #endif
 396
 397         /*
 398          * add_memory_resource() will call online_pages() which in its turn
 399          * will call xen_online_page() callback causing deadlock if we don't
 400          * release balloon_mutex here. Unlocking here is safe because the
 401          * callers drop the mutex before trying again.
 402          */
 403         mutex_unlock(&balloon_mutex);
 404         rc = add_memory_resource(nid, resource, memhp_auto_online);
 405         mutex_lock(&balloon_mutex);
 406
 407         if (rc) {
 408                 pr_warn("Cannot add additional memory (%i)\n", rc);
 409                 goto err;
 410         }
 411
 412         balloon_stats.total_pages += balloon_hotplug;
 413
 414         return BP_WAIT;
 415   err:
 416         release_memory_resource(resource);
 417         return BP_ECANCELED;
 418 }
 419
 420 static void xen_online_page(struct page *page)
 421 {
 422         __online_page_set_limits(page);
 423
 424         mutex_lock(&balloon_mutex);
 425
 426         __balloon_append(page);
 427
 428         mutex_unlock(&balloon_mutex);
 429 }
 430
 431 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
 432 {
 433         if (val == MEM_ONLINE)
 434                 schedule_delayed_work(&balloon_worker, 0);
 435
 436         return NOTIFY_OK;
 437 }
 438
 439 static struct notifier_block xen_memory_nb = {
 440         .notifier_call = xen_memory_notifier,
 441         .priority = 0
 442 };
 443 #else
 444 static enum bp_state reserve_additional_memory(void)
 445 {
 446         balloon_stats.target_pages = balloon_stats.current_pages;
 447         return BP_ECANCELED;
 448 }
 449 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 450
 451 static long current_credit(void)
 452 {
 453         return balloon_stats.target_pages - balloon_stats.current_pages;
 454 }
 455
 456 static bool balloon_is_inflated(void)
 457 {
 458         return balloon_stats.balloon_low || balloon_stats.balloon_high;
 459 }
 460
 461 static enum bp_state increase_reservation(unsigned long nr_pages)
 462 {
 463         int rc;
 464         unsigned long i;
 465         struct page   *page;
 466         struct xen_memory_reservation reservation = {
 467                 .address_bits = 0,
 468                 .extent_order = EXTENT_ORDER,
 469                 .domid        = DOMID_SELF
 470         };
 471
 472         if (nr_pages > ARRAY_SIZE(frame_list))
 473                 nr_pages = ARRAY_SIZE(frame_list);
 474
 475         page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
 476         for (i = 0; i < nr_pages; i++) {
 477                 if (!page) {
 478                         nr_pages = i;
 479                         break;
 480                 }
 481
 482                 /* XENMEM_populate_physmap requires a PFN based on Xen
 483                  * granularity.
 484                  */
 485                 frame_list[i] = page_to_xen_pfn(page);
 486                 page = balloon_next_page(page);
 487         }
 488
 489         set_xen_guest_handle(reservation.extent_start, frame_list);
 490         reservation.nr_extents = nr_pages;
 491         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
 492         if (rc <= 0)
 493                 return BP_EAGAIN;
 494
 495         for (i = 0; i < rc; i++) {
 496                 page = balloon_retrieve(false);
 497                 BUG_ON(page == NULL);
 498
 499 #ifdef CONFIG_XEN_HAVE_PVMMU
 500                 /*
 501                  * We don't support PV MMU when Linux and Xen is using
 502                  * different page granularity.
 503                  */
 504                 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 505
 506                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 507                         unsigned long pfn = page_to_pfn(page);
 508
 509                         set_phys_to_machine(pfn, frame_list[i]);
 510
 511                         /* Link back into the page tables if not highmem. */
 512                         if (!PageHighMem(page)) {
 513                                 int ret;
 514                                 ret = HYPERVISOR_update_va_mapping(
 515                                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 516                                                 mfn_pte(frame_list[i], PAGE_KERNEL),
 517                                                 0);
 518                                 BUG_ON(ret);
 519                         }
 520                 }
 521 #endif
 522
 523                 /* Relinquish the page back to the allocator. */
 524                 free_reserved_page(page);
 525         }
 526
 527         balloon_stats.current_pages += rc;
 528
 529         return BP_DONE;
 530 }
 531
 532 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 533 {
 534         enum bp_state state = BP_DONE;
 535         unsigned long i;
 536         struct page *page, *tmp;
 537         int ret;
 538         struct xen_memory_reservation reservation = {
 539                 .address_bits = 0,
 540                 .extent_order = EXTENT_ORDER,
 541                 .domid        = DOMID_SELF
 542         };
 543         LIST_HEAD(pages);
 544
 545         if (nr_pages > ARRAY_SIZE(frame_list))
 546                 nr_pages = ARRAY_SIZE(frame_list);
 547
 548         for (i = 0; i < nr_pages; i++) {
 549                 page = alloc_page(gfp);
 550                 if (page == NULL) {
 551                         nr_pages = i;
 552                         state = BP_EAGAIN;
 553                         break;
 554                 }
 555                 adjust_managed_page_count(page, -1);
 556                 scrub_page(page);
 557                 list_add(&page->lru, &pages);
 558         }
 559
 560         /*
 561          * Ensure that ballooned highmem pages don't have kmaps.
 562          *
 563          * Do this before changing the p2m as kmap_flush_unused()
 564          * reads PTEs to obtain pages (and hence needs the original
 565          * p2m entry).
 566          */
 567         kmap_flush_unused();
 568
 569         /*
 570          * Setup the frame, update direct mapping, invalidate P2M,
 571          * and add to balloon.
 572          */
 573         i = 0;
 574         list_for_each_entry_safe(page, tmp, &pages, lru) {
 575                 /* XENMEM_decrease_reservation requires a GFN */
 576                 frame_list[i++] = xen_page_to_gfn(page);
 577
 578 #ifdef CONFIG_XEN_HAVE_PVMMU
 579                 /*
 580                  * We don't support PV MMU when Linux and Xen is using
 581                  * different page granularity.
 582                  */
 583                 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 584
 585                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 586                         unsigned long pfn = page_to_pfn(page);
 587
 588                         if (!PageHighMem(page)) {
 589                                 ret = HYPERVISOR_update_va_mapping(
 590                                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 591                                                 __pte_ma(0), 0);
 592                                 BUG_ON(ret);
 593                         }
 594                         __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 595                 }
 596 #endif
 597                 list_del(&page->lru);
 598
 599                 balloon_append(page);
 600         }
 601
 602         flush_tlb_all();
 603
 604         set_xen_guest_handle(reservation.extent_start, frame_list);
 605         reservation.nr_extents   = nr_pages;
 606         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 607         BUG_ON(ret != nr_pages);
 608
 609         balloon_stats.current_pages -= nr_pages;
 610
 611         return state;
 612 }
 613
 614 /*
 615  * As this is a work item it is guaranteed to run as a single instance only.
 616  * We may of course race updates of the target counts (which are protected
 617  * by the balloon lock), or with changes to the Xen hard limit, but we will
 618  * recover from these in time.
 619  */
 620 static void balloon_process(struct work_struct *work)
 621 {
 622         enum bp_state state = BP_DONE;
 623         long credit;
 624
 625
 626         do {
 627                 mutex_lock(&balloon_mutex);
 628
 629                 credit = current_credit();
 630
 631                 if (credit > 0) {
 632                         if (balloon_is_inflated())
 633                                 state = increase_reservation(credit);
 634                         else
 635                                 state = reserve_additional_memory();
 636                 }
 637
 638                 if (credit < 0)
 639                         state = decrease_reservation(-credit, GFP_BALLOON);
 640
 641                 state = update_schedule(state);
 642
 643                 mutex_unlock(&balloon_mutex);
 644
 645                 cond_resched();
 646
 647         } while (credit && state == BP_DONE);
 648
 649         /* Schedule more work if there is some still to be done. */
 650         if (state == BP_EAGAIN)
 651                 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
 652 }
 653
 654 /* Resets the Xen limit, sets new target, and kicks off processing. */
 655 void balloon_set_new_target(unsigned long target)
 656 {
 657         /* No need for lock. Not read-modify-write updates. */
 658         balloon_stats.target_pages = target;
 659         schedule_delayed_work(&balloon_worker, 0);
 660 }
 661 EXPORT_SYMBOL_GPL(balloon_set_new_target);
 662
 663 static int add_ballooned_pages(int nr_pages)
 664 {
 665         enum bp_state st;
 666
 667         if (xen_hotplug_unpopulated) {
 668                 st = reserve_additional_memory();
 669                 if (st != BP_ECANCELED) {
 670                         mutex_unlock(&balloon_mutex);
 671                         wait_event(balloon_wq,
 672                                    !list_empty(&ballooned_pages));
 673                         mutex_lock(&balloon_mutex);
 674                         return 0;
 675                 }
 676         }
 677
 678         st = decrease_reservation(nr_pages, GFP_USER);
 679         if (st != BP_DONE)
 680                 return -ENOMEM;
 681
 682         return 0;
 683 }
 684
 685 /**
 686  * alloc_xenballooned_pages - get pages that have been ballooned out
 687  * @nr_pages: Number of pages to get
 688  * @pages: pages returned
 689  * @return 0 on success, error otherwise
 690  */
 691 int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 692 {
 693         int pgno = 0;
 694         struct page *page;
 695         int ret;
 696
 697         mutex_lock(&balloon_mutex);
 698
 699         balloon_stats.target_unpopulated += nr_pages;
 700
 701         while (pgno < nr_pages) {
 702                 page = balloon_retrieve(true);
 703                 if (page) {
 704                         pages[pgno++] = page;
 705 #ifdef CONFIG_XEN_HAVE_PVMMU
 706                         /*
 707                          * We don't support PV MMU when Linux and Xen is using
 708                          * different page granularity.
 709                          */
 710                         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 711
 712                         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 713                                 ret = xen_alloc_p2m_entry(page_to_pfn(page));
 714                                 if (ret < 0)
 715                                         goto out_undo;
 716                         }
 717 #endif
 718                 } else {
 719                         ret = add_ballooned_pages(nr_pages - pgno);
 720                         if (ret < 0)
 721                                 goto out_undo;
 722                 }
 723         }
 724         mutex_unlock(&balloon_mutex);
 725         return 0;
 726  out_undo:
 727         mutex_unlock(&balloon_mutex);
 728         free_xenballooned_pages(pgno, pages);
 729         return ret;
 730 }
 731 EXPORT_SYMBOL(alloc_xenballooned_pages);
 732
 733 /**
 734  * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
 735  * @nr_pages: Number of pages
 736  * @pages: pages to return
 737  */
 738 void free_xenballooned_pages(int nr_pages, struct page **pages)
 739 {
 740         int i;
 741
 742         mutex_lock(&balloon_mutex);
 743
 744         for (i = 0; i < nr_pages; i++) {
 745                 if (pages[i])
 746                         balloon_append(pages[i]);
 747         }
 748
 749         balloon_stats.target_unpopulated -= nr_pages;
 750
 751         /* The balloon may be too large now. Shrink it if needed. */
 752         if (current_credit())
 753                 schedule_delayed_work(&balloon_worker, 0);
 754
 755         mutex_unlock(&balloon_mutex);
 756 }
 757 EXPORT_SYMBOL(free_xenballooned_pages);
 758
 759 #ifdef CONFIG_XEN_PV
 760 static void __init balloon_add_region(unsigned long start_pfn,
 761                                       unsigned long pages)
 762 {
 763         unsigned long pfn, extra_pfn_end;
 764         struct page *page;
 765
 766         /*
 767          * If the amount of usable memory has been limited (e.g., with
 768          * the 'mem' command line parameter), don't add pages beyond
 769          * this limit.
 770          */
 771         extra_pfn_end = min(max_pfn, start_pfn + pages);
 772
 773         for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
 774                 page = pfn_to_page(pfn);
 775                 /* totalram_pages and totalhigh_pages do not
 776                    include the boot-time balloon extension, so
 777                    don't subtract from it. */
 778                 __balloon_append(page);
 779         }
 780
 781         balloon_stats.total_pages += extra_pfn_end - start_pfn;
 782 }
 783 #endif
 784
 785 static int __init balloon_init(void)
 786 {
 787         if (!xen_domain())
 788                 return -ENODEV;
 789
 790         pr_info("Initialising balloon driver\n");
 791
 792 #ifdef CONFIG_XEN_PV
 793         balloon_stats.current_pages = xen_pv_domain()
 794                 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
 795                 : get_num_physpages();
 796 #else
 797         balloon_stats.current_pages = get_num_physpages();
 798 #endif
 799         balloon_stats.target_pages  = balloon_stats.current_pages;
 800         balloon_stats.balloon_low   = 0;
 801         balloon_stats.balloon_high  = 0;
 802         balloon_stats.total_pages   = balloon_stats.current_pages;
 803
 804         balloon_stats.schedule_delay = 1;
 805         balloon_stats.max_schedule_delay = 32;
 806         balloon_stats.retry_count = 1;
 807         balloon_stats.max_retry_count = RETRY_UNLIMITED;
 808
 809 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 810         set_online_page_callback(&xen_online_page);
 811         register_memory_notifier(&xen_memory_nb);
 812         register_sysctl_table(xen_root);
 813
 814         arch_xen_balloon_init(&hostmem_resource);
 815 #endif
 816
 817 #ifdef CONFIG_XEN_PV
 818         {
 819                 int i;
 820
 821                 /*
 822                  * Initialize the balloon with pages from the extra memory
 823                  * regions (see arch/x86/xen/setup.c).
 824                  */
 825                 for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
 826                         if (xen_extra_mem[i].n_pfns)
 827                                 balloon_add_region(xen_extra_mem[i].start_pfn,
 828                                                    xen_extra_mem[i].n_pfns);
 829         }
 830 #endif
 831
 832         /* Init the xen-balloon driver. */
 833         xen_balloon_init();
 834
 835         return 0;
 836 }
 837 subsys_initcall(balloon_init);