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/bootmem.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
  63 #include <asm/page.h>
  64 #include <asm/pgalloc.h>
  65 #include <asm/pgtable.h>
  66 #include <asm/tlb.h>
  67
  68 #include <asm/xen/hypervisor.h>
  69 #include <asm/xen/hypercall.h>
  70
  71 #include <xen/xen.h>
  72 #include <xen/interface/xen.h>
  73 #include <xen/interface/memory.h>
  74 #include <xen/balloon.h>
  75 #include <xen/features.h>
  76 #include <xen/page.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 static int xen_hotplug_unpopulated;
  85
  86 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
  87
  88 static int zero;
  89 static int one = 1;
  90
  91 static struct ctl_table balloon_table[] = {
  92         {
  93                 .procname       = "hotplug_unpopulated",
  94                 .data           = &xen_hotplug_unpopulated,
  95                 .maxlen         = sizeof(int),
  96                 .mode           = 0644,
  97                 .proc_handler   = proc_dointvec_minmax,
  98                 .extra1         = &zero,
  99                 .extra2         = &one,
 100         },
 101         { }
 102 };
 103
 104 static struct ctl_table balloon_root[] = {
 105         {
 106                 .procname       = "balloon",
 107                 .mode           = 0555,
 108                 .child          = balloon_table,
 109         },
 110         { }
 111 };
 112
 113 static struct ctl_table xen_root[] = {
 114         {
 115                 .procname       = "xen",
 116                 .mode           = 0555,
 117                 .child          = balloon_root,
 118         },
 119         { }
 120 };
 121
 122 #endif
 123
 124 /*
 125  * Use one extent per PAGE_SIZE to avoid to break down the page into
 126  * multiple frame.
 127  */
 128 #define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
 129
 130 /*
 131  * balloon_thread() state:
 132  *
 133  * BP_DONE: done or nothing to do,
 134  * BP_WAIT: wait to be rescheduled,
 135  * BP_EAGAIN: error, go to sleep,
 136  * BP_ECANCELED: error, balloon operation canceled.
 137  */
 138
 139 static enum bp_state {
 140         BP_DONE,
 141         BP_WAIT,
 142         BP_EAGAIN,
 143         BP_ECANCELED
 144 } balloon_state = BP_DONE;
 145
 146 /* Main waiting point for xen-balloon thread. */
 147 static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq);
 148
 149 static DEFINE_MUTEX(balloon_mutex);
 150
 151 struct balloon_stats balloon_stats;
 152 EXPORT_SYMBOL_GPL(balloon_stats);
 153
 154 /* We increase/decrease in batches which fit in a page */
 155 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
 156
 157
 158 /* List of ballooned pages, threaded through the mem_map array. */
 159 static LIST_HEAD(ballooned_pages);
 160 static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
 161
 162 /* When ballooning out (allocating memory to return to Xen) we don't really
 163    want the kernel to try too hard since that can trigger the oom killer. */
 164 #define GFP_BALLOON \
 165         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 166
 167 static void scrub_page(struct page *page)
 168 {
 169 #ifdef CONFIG_XEN_SCRUB_PAGES
 170         clear_highpage(page);
 171 #endif
 172 }
 173
 174 /* balloon_append: add the given page to the balloon. */
 175 static void __balloon_append(struct page *page)
 176 {
 177         /* Lowmem is re-populated first, so highmem pages go at list tail. */
 178         if (PageHighMem(page)) {
 179                 list_add_tail(&page->lru, &ballooned_pages);
 180                 balloon_stats.balloon_high++;
 181         } else {
 182                 list_add(&page->lru, &ballooned_pages);
 183                 balloon_stats.balloon_low++;
 184         }
 185         wake_up(&balloon_wq);
 186 }
 187
 188 static void balloon_append(struct page *page)
 189 {
 190         __balloon_append(page);
 191 }
 192
 193 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 194 static struct page *balloon_retrieve(bool require_lowmem)
 195 {
 196         struct page *page;
 197
 198         if (list_empty(&ballooned_pages))
 199                 return NULL;
 200
 201         page = list_entry(ballooned_pages.next, struct page, lru);
 202         if (require_lowmem && PageHighMem(page))
 203                 return NULL;
 204         list_del(&page->lru);
 205
 206         if (PageHighMem(page))
 207                 balloon_stats.balloon_high--;
 208         else
 209                 balloon_stats.balloon_low--;
 210
 211         return page;
 212 }
 213
 214 static struct page *balloon_next_page(struct page *page)
 215 {
 216         struct list_head *next = page->lru.next;
 217         if (next == &ballooned_pages)
 218                 return NULL;
 219         return list_entry(next, struct page, lru);
 220 }
 221
 222 static void update_schedule(void)
 223 {
 224         if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED)
 225                 return;
 226
 227         if (balloon_state == BP_DONE) {
 228                 balloon_stats.schedule_delay = 1;
 229                 balloon_stats.retry_count = 1;
 230                 return;
 231         }
 232
 233         ++balloon_stats.retry_count;
 234
 235         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
 236                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
 237                 balloon_stats.schedule_delay = 1;
 238                 balloon_stats.retry_count = 1;
 239                 balloon_state = BP_ECANCELED;
 240                 return;
 241         }
 242
 243         balloon_stats.schedule_delay <<= 1;
 244
 245         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
 246                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
 247
 248         balloon_state = BP_EAGAIN;
 249 }
 250
 251 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 252 static void release_memory_resource(struct resource *resource)
 253 {
 254         if (!resource)
 255                 return;
 256
 257         /*
 258          * No need to reset region to identity mapped since we now
 259          * know that no I/O can be in this region
 260          */
 261         release_resource(resource);
 262         kfree(resource);
 263 }
 264
 265 static struct resource *additional_memory_resource(phys_addr_t size)
 266 {
 267         struct resource *res;
 268         int ret;
 269
 270         res = kzalloc(sizeof(*res), GFP_KERNEL);
 271         if (!res)
 272                 return NULL;
 273
 274         res->name = "System RAM";
 275         res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 276
 277         ret = allocate_resource(&iomem_resource, res,
 278                                 size, 0, -1,
 279                                 PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
 280         if (ret < 0) {
 281                 pr_err("Cannot allocate new System RAM resource\n");
 282                 kfree(res);
 283                 return NULL;
 284         }
 285
 286 #ifdef CONFIG_SPARSEMEM
 287         {
 288                 unsigned long limit = 1UL << (MAX_PHYSMEM_BITS - PAGE_SHIFT);
 289                 unsigned long pfn = res->start >> PAGE_SHIFT;
 290
 291                 if (pfn > limit) {
 292                         pr_err("New System RAM resource outside addressable RAM (%lu > %lu)\n",
 293                                pfn, limit);
 294                         release_memory_resource(res);
 295                         return NULL;
 296                 }
 297         }
 298 #endif
 299
 300         return res;
 301 }
 302
 303 static enum bp_state reserve_additional_memory(void)
 304 {
 305         long credit;
 306         struct resource *resource;
 307         int nid, rc;
 308         unsigned long balloon_hotplug;
 309
 310         credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
 311                 - balloon_stats.total_pages;
 312
 313         /*
 314          * Already hotplugged enough pages?  Wait for them to be
 315          * onlined.
 316          */
 317         if (credit <= 0)
 318                 return BP_WAIT;
 319
 320         balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
 321
 322         resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
 323         if (!resource)
 324                 goto err;
 325
 326         nid = memory_add_physaddr_to_nid(resource->start);
 327
 328 #ifdef CONFIG_XEN_HAVE_PVMMU
 329         /*
 330          * We don't support PV MMU when Linux and Xen is using
 331          * different page granularity.
 332          */
 333         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 334
 335         /*
 336          * add_memory() will build page tables for the new memory so
 337          * the p2m must contain invalid entries so the correct
 338          * non-present PTEs will be written.
 339          *
 340          * If a failure occurs, the original (identity) p2m entries
 341          * are not restored since this region is now known not to
 342          * conflict with any devices.
 343          */
 344         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 345                 unsigned long pfn, i;
 346
 347                 pfn = PFN_DOWN(resource->start);
 348                 for (i = 0; i < balloon_hotplug; i++) {
 349                         if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
 350                                 pr_warn("set_phys_to_machine() failed, no memory added\n");
 351                                 goto err;
 352                         }
 353                 }
 354         }
 355 #endif
 356
 357         /*
 358          * add_memory_resource() will call online_pages() which in its turn
 359          * will call xen_online_page() callback causing deadlock if we don't
 360          * release balloon_mutex here. Unlocking here is safe because the
 361          * callers drop the mutex before trying again.
 362          */
 363         mutex_unlock(&balloon_mutex);
 364         /* add_memory_resource() requires the device_hotplug lock */
 365         lock_device_hotplug();
 366         rc = add_memory_resource(nid, resource, memhp_auto_online);
 367         unlock_device_hotplug();
 368         mutex_lock(&balloon_mutex);
 369
 370         if (rc) {
 371                 pr_warn("Cannot add additional memory (%i)\n", rc);
 372                 goto err;
 373         }
 374
 375         balloon_stats.total_pages += balloon_hotplug;
 376
 377         return BP_WAIT;
 378   err:
 379         release_memory_resource(resource);
 380         return BP_ECANCELED;
 381 }
 382
 383 static void xen_online_page(struct page *page)
 384 {
 385         __online_page_set_limits(page);
 386
 387         mutex_lock(&balloon_mutex);
 388
 389         __balloon_append(page);
 390
 391         mutex_unlock(&balloon_mutex);
 392 }
 393
 394 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
 395 {
 396         if (val == MEM_ONLINE)
 397                 wake_up(&balloon_thread_wq);
 398
 399         return NOTIFY_OK;
 400 }
 401
 402 static struct notifier_block xen_memory_nb = {
 403         .notifier_call = xen_memory_notifier,
 404         .priority = 0
 405 };
 406 #else
 407 static enum bp_state reserve_additional_memory(void)
 408 {
 409         balloon_stats.target_pages = balloon_stats.current_pages +
 410                                      balloon_stats.target_unpopulated;
 411         return BP_ECANCELED;
 412 }
 413 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 414
 415 static long current_credit(void)
 416 {
 417         return balloon_stats.target_pages - balloon_stats.current_pages;
 418 }
 419
 420 static bool balloon_is_inflated(void)
 421 {
 422         return balloon_stats.balloon_low || balloon_stats.balloon_high;
 423 }
 424
 425 static enum bp_state increase_reservation(unsigned long nr_pages)
 426 {
 427         int rc;
 428         unsigned long i;
 429         struct page   *page;
 430         struct xen_memory_reservation reservation = {
 431                 .address_bits = 0,
 432                 .extent_order = EXTENT_ORDER,
 433                 .domid        = DOMID_SELF
 434         };
 435
 436         if (nr_pages > ARRAY_SIZE(frame_list))
 437                 nr_pages = ARRAY_SIZE(frame_list);
 438
 439         page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
 440         for (i = 0; i < nr_pages; i++) {
 441                 if (!page) {
 442                         nr_pages = i;
 443                         break;
 444                 }
 445
 446                 /* XENMEM_populate_physmap requires a PFN based on Xen
 447                  * granularity.
 448                  */
 449                 frame_list[i] = page_to_xen_pfn(page);
 450                 page = balloon_next_page(page);
 451         }
 452
 453         set_xen_guest_handle(reservation.extent_start, frame_list);
 454         reservation.nr_extents = nr_pages;
 455         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
 456         if (rc <= 0)
 457                 return BP_EAGAIN;
 458
 459         for (i = 0; i < rc; i++) {
 460                 page = balloon_retrieve(false);
 461                 BUG_ON(page == NULL);
 462
 463 #ifdef CONFIG_XEN_HAVE_PVMMU
 464                 /*
 465                  * We don't support PV MMU when Linux and Xen is using
 466                  * different page granularity.
 467                  */
 468                 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 469
 470                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 471                         unsigned long pfn = page_to_pfn(page);
 472
 473                         set_phys_to_machine(pfn, frame_list[i]);
 474
 475                         /* Link back into the page tables if not highmem. */
 476                         if (!PageHighMem(page)) {
 477                                 int ret;
 478                                 ret = HYPERVISOR_update_va_mapping(
 479                                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 480                                                 mfn_pte(frame_list[i], PAGE_KERNEL),
 481                                                 0);
 482                                 BUG_ON(ret);
 483                         }
 484                 }
 485 #endif
 486
 487                 /* Relinquish the page back to the allocator. */
 488                 free_reserved_page(page);
 489         }
 490
 491         balloon_stats.current_pages += rc;
 492
 493         return BP_DONE;
 494 }
 495
 496 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 497 {
 498         enum bp_state state = BP_DONE;
 499         unsigned long i;
 500         struct page *page, *tmp;
 501         int ret;
 502         struct xen_memory_reservation reservation = {
 503                 .address_bits = 0,
 504                 .extent_order = EXTENT_ORDER,
 505                 .domid        = DOMID_SELF
 506         };
 507         LIST_HEAD(pages);
 508
 509         if (nr_pages > ARRAY_SIZE(frame_list))
 510                 nr_pages = ARRAY_SIZE(frame_list);
 511
 512         for (i = 0; i < nr_pages; i++) {
 513                 page = alloc_page(gfp);
 514                 if (page == NULL) {
 515                         nr_pages = i;
 516                         state = BP_EAGAIN;
 517                         break;
 518                 }
 519                 adjust_managed_page_count(page, -1);
 520                 scrub_page(page);
 521                 list_add(&page->lru, &pages);
 522         }
 523
 524         /*
 525          * Ensure that ballooned highmem pages don't have kmaps.
 526          *
 527          * Do this before changing the p2m as kmap_flush_unused()
 528          * reads PTEs to obtain pages (and hence needs the original
 529          * p2m entry).
 530          */
 531         kmap_flush_unused();
 532
 533         /*
 534          * Setup the frame, update direct mapping, invalidate P2M,
 535          * and add to balloon.
 536          */
 537         i = 0;
 538         list_for_each_entry_safe(page, tmp, &pages, lru) {
 539                 /* XENMEM_decrease_reservation requires a GFN */
 540                 frame_list[i++] = xen_page_to_gfn(page);
 541
 542 #ifdef CONFIG_XEN_HAVE_PVMMU
 543                 /*
 544                  * We don't support PV MMU when Linux and Xen is using
 545                  * different page granularity.
 546                  */
 547                 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 548
 549                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 550                         unsigned long pfn = page_to_pfn(page);
 551
 552                         if (!PageHighMem(page)) {
 553                                 ret = HYPERVISOR_update_va_mapping(
 554                                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 555                                                 __pte_ma(0), 0);
 556                                 BUG_ON(ret);
 557                         }
 558                         __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 559                 }
 560 #endif
 561                 list_del(&page->lru);
 562
 563                 balloon_append(page);
 564         }
 565
 566         flush_tlb_all();
 567
 568         set_xen_guest_handle(reservation.extent_start, frame_list);
 569         reservation.nr_extents   = nr_pages;
 570         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 571         BUG_ON(ret != nr_pages);
 572
 573         balloon_stats.current_pages -= nr_pages;
 574
 575         return state;
 576 }
 577
 578 /*
 579  * Stop waiting if either state is BP_DONE and ballooning action is
 580  * needed, or if the credit has changed while state is not BP_DONE.
 581  */
 582 static bool balloon_thread_cond(long credit)
 583 {
 584         if (balloon_state == BP_DONE)
 585                 credit = 0;
 586
 587         return current_credit() != credit || kthread_should_stop();
 588 }
 589
 590 /*
 591  * As this is a kthread it is guaranteed to run as a single instance only.
 592  * We may of course race updates of the target counts (which are protected
 593  * by the balloon lock), or with changes to the Xen hard limit, but we will
 594  * recover from these in time.
 595  */
 596 static int balloon_thread(void *unused)
 597 {
 598         long credit;
 599         unsigned long timeout;
 600
 601         set_freezable();
 602         for (;;) {
 603                 switch (balloon_state) {
 604                 case BP_DONE:
 605                 case BP_ECANCELED:
 606                         timeout = 3600 * HZ;
 607                         break;
 608                 case BP_EAGAIN:
 609                         timeout = balloon_stats.schedule_delay * HZ;
 610                         break;
 611                 case BP_WAIT:
 612                         timeout = HZ;
 613                         break;
 614                 }
 615
 616                 credit = current_credit();
 617
 618                 wait_event_freezable_timeout(balloon_thread_wq,
 619                         balloon_thread_cond(credit), timeout);
 620
 621                 if (kthread_should_stop())
 622                         return 0;
 623
 624                 mutex_lock(&balloon_mutex);
 625
 626                 credit = current_credit();
 627
 628                 if (credit > 0) {
 629                         if (balloon_is_inflated())
 630                                 balloon_state = increase_reservation(credit);
 631                         else
 632                                 balloon_state = reserve_additional_memory();
 633                 }
 634
 635                 if (credit < 0) {
 636                         long n_pages;
 637
 638                         n_pages = min(-credit, si_mem_available());
 639                         balloon_state = decrease_reservation(n_pages,
 640                                                              GFP_BALLOON);
 641                         if (balloon_state == BP_DONE && n_pages != -credit &&
 642                             n_pages < totalreserve_pages)
 643                                 balloon_state = BP_EAGAIN;
 644                 }
 645
 646                 update_schedule();
 647
 648                 mutex_unlock(&balloon_mutex);
 649
 650                 cond_resched();
 651         }
 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         wake_up(&balloon_thread_wq);
 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                         int rc;
 671
 672                         mutex_unlock(&balloon_mutex);
 673                         rc = wait_event_interruptible(balloon_wq,
 674                                    !list_empty(&ballooned_pages));
 675                         mutex_lock(&balloon_mutex);
 676                         return rc ? -ENOMEM : 0;
 677                 }
 678         }
 679
 680         if (si_mem_available() < nr_pages)
 681                 return -ENOMEM;
 682
 683         st = decrease_reservation(nr_pages, GFP_USER);
 684         if (st != BP_DONE)
 685                 return -ENOMEM;
 686
 687         return 0;
 688 }
 689
 690 /**
 691  * alloc_xenballooned_pages - get pages that have been ballooned out
 692  * @nr_pages: Number of pages to get
 693  * @pages: pages returned
 694  * @return 0 on success, error otherwise
 695  */
 696 int alloc_xenballooned_pages(int nr_pages, struct page **pages)
 697 {
 698         int pgno = 0;
 699         struct page *page;
 700         int ret;
 701
 702         mutex_lock(&balloon_mutex);
 703
 704         balloon_stats.target_unpopulated += nr_pages;
 705
 706         while (pgno < nr_pages) {
 707                 page = balloon_retrieve(true);
 708                 if (page) {
 709                         pages[pgno++] = page;
 710 #ifdef CONFIG_XEN_HAVE_PVMMU
 711                         /*
 712                          * We don't support PV MMU when Linux and Xen is using
 713                          * different page granularity.
 714                          */
 715                         BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
 716
 717                         if (!xen_feature(XENFEAT_auto_translated_physmap)) {
 718                                 ret = xen_alloc_p2m_entry(page_to_pfn(page));
 719                                 if (ret < 0)
 720                                         goto out_undo;
 721                         }
 722 #endif
 723                 } else {
 724                         ret = add_ballooned_pages(nr_pages - pgno);
 725                         if (ret < 0)
 726                                 goto out_undo;
 727                 }
 728         }
 729         mutex_unlock(&balloon_mutex);
 730         return 0;
 731  out_undo:
 732         mutex_unlock(&balloon_mutex);
 733         free_xenballooned_pages(pgno, pages);
 734         /*
 735          * NB: free_xenballooned_pages will only subtract pgno pages, but since
 736          * target_unpopulated is incremented with nr_pages at the start we need
 737          * to remove the remaining ones also, or accounting will be screwed.
 738          */
 739         balloon_stats.target_unpopulated -= nr_pages - pgno;
 740         return ret;
 741 }
 742 EXPORT_SYMBOL(alloc_xenballooned_pages);
 743
 744 /**
 745  * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
 746  * @nr_pages: Number of pages
 747  * @pages: pages to return
 748  */
 749 void free_xenballooned_pages(int nr_pages, struct page **pages)
 750 {
 751         int i;
 752
 753         mutex_lock(&balloon_mutex);
 754
 755         for (i = 0; i < nr_pages; i++) {
 756                 if (pages[i])
 757                         balloon_append(pages[i]);
 758         }
 759
 760         balloon_stats.target_unpopulated -= nr_pages;
 761
 762         /* The balloon may be too large now. Shrink it if needed. */
 763         if (current_credit())
 764                 wake_up(&balloon_thread_wq);
 765
 766         mutex_unlock(&balloon_mutex);
 767 }
 768 EXPORT_SYMBOL(free_xenballooned_pages);
 769
 770 #ifdef CONFIG_XEN_PV
 771 static void __init balloon_add_region(unsigned long start_pfn,
 772                                       unsigned long pages)
 773 {
 774         unsigned long pfn, extra_pfn_end;
 775         struct page *page;
 776
 777         /*
 778          * If the amount of usable memory has been limited (e.g., with
 779          * the 'mem' command line parameter), don't add pages beyond
 780          * this limit.
 781          */
 782         extra_pfn_end = min(max_pfn, start_pfn + pages);
 783
 784         for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
 785                 page = pfn_to_page(pfn);
 786                 /* totalram_pages and totalhigh_pages do not
 787                    include the boot-time balloon extension, so
 788                    don't subtract from it. */
 789                 __balloon_append(page);
 790         }
 791
 792         balloon_stats.total_pages += extra_pfn_end - start_pfn;
 793 }
 794 #endif
 795
 796 static int __init balloon_init(void)
 797 {
 798         struct task_struct *task;
 799
 800         if (!xen_domain())
 801                 return -ENODEV;
 802
 803         pr_info("Initialising balloon driver\n");
 804
 805 #ifdef CONFIG_XEN_PV
 806         balloon_stats.current_pages = xen_pv_domain()
 807                 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
 808                 : get_num_physpages();
 809 #else
 810         balloon_stats.current_pages = get_num_physpages();
 811 #endif
 812         balloon_stats.target_pages  = balloon_stats.current_pages;
 813         balloon_stats.balloon_low   = 0;
 814         balloon_stats.balloon_high  = 0;
 815         balloon_stats.total_pages   = balloon_stats.current_pages;
 816
 817         balloon_stats.schedule_delay = 1;
 818         balloon_stats.max_schedule_delay = 32;
 819         balloon_stats.retry_count = 1;
 820         balloon_stats.max_retry_count = 4;
 821
 822 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 823         set_online_page_callback(&xen_online_page);
 824         register_memory_notifier(&xen_memory_nb);
 825         register_sysctl_table(xen_root);
 826 #endif
 827
 828 #ifdef CONFIG_XEN_PV
 829         {
 830                 int i;
 831
 832                 /*
 833                  * Initialize the balloon with pages from the extra memory
 834                  * regions (see arch/x86/xen/setup.c).
 835                  */
 836                 for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
 837                         if (xen_extra_mem[i].n_pfns)
 838                                 balloon_add_region(xen_extra_mem[i].start_pfn,
 839                                                    xen_extra_mem[i].n_pfns);
 840         }
 841 #endif
 842
 843         task = kthread_run(balloon_thread, NULL, "xen-balloon");
 844         if (IS_ERR(task)) {
 845                 pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
 846                 return PTR_ERR(task);
 847         }
 848
 849         /* Init the xen-balloon driver. */
 850         xen_balloon_init();
 851
 852         return 0;
 853 }
 854 subsys_initcall(balloon_init);
 855
 856 static int __init balloon_wait_finish(void)
 857 {
 858         long credit, last_credit = 0;
 859         unsigned long last_changed = 0;
 860
 861         if (!xen_domain())
 862                 return -ENODEV;
 863
 864         /* PV guests don't need to wait. */
 865         if (xen_pv_domain() || !current_credit())
 866                 return 0;
 867
 868         pr_notice("Waiting for initial ballooning down having finished.\n");
 869
 870         while ((credit = current_credit()) < 0) {
 871                 if (credit != last_credit) {
 872                         last_changed = jiffies;
 873                         last_credit = credit;
 874                 }
 875                 if (balloon_state == BP_ECANCELED) {
 876                         pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
 877                                      -credit);
 878                         if (jiffies - last_changed >= HZ * balloon_boot_timeout)
 879                                 panic("Initial ballooning failed!\n");
 880                 }
 881
 882                 schedule_timeout_interruptible(HZ / 10);
 883         }
 884
 885         pr_notice("Initial ballooning down finished.\n");
 886
 887         return 0;
 888 }
 889 late_initcall_sync(balloon_wait_finish);