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 #include <linux/kernel.h>
  40 #include <linux/sched.h>
  41 #include <linux/errno.h>
  42 #include <linux/module.h>
  43 #include <linux/mm.h>
  44 #include <linux/bootmem.h>
  45 #include <linux/pagemap.h>
  46 #include <linux/highmem.h>
  47 #include <linux/mutex.h>
  48 #include <linux/list.h>
  49 #include <linux/gfp.h>
  50 #include <linux/notifier.h>
  51 #include <linux/memory.h>
  52 #include <linux/memory_hotplug.h>
  53
  54 #include <asm/page.h>
  55 #include <asm/pgalloc.h>
  56 #include <asm/pgtable.h>
  57 #include <asm/tlb.h>
  58 #include <asm/e820.h>
  59
  60 #include <asm/xen/hypervisor.h>
  61 #include <asm/xen/hypercall.h>
  62
  63 #include <xen/xen.h>
  64 #include <xen/interface/xen.h>
  65 #include <xen/interface/memory.h>
  66 #include <xen/balloon.h>
  67 #include <xen/features.h>
  68 #include <xen/page.h>
  69
  70 /*
  71  * balloon_process() state:
  72  *
  73  * BP_DONE: done or nothing to do,
  74  * BP_EAGAIN: error, go to sleep,
  75  * BP_ECANCELED: error, balloon operation canceled.
  76  */
  77
  78 enum bp_state {
  79         BP_DONE,
  80         BP_EAGAIN,
  81         BP_ECANCELED
  82 };
  83
  84
  85 static DEFINE_MUTEX(balloon_mutex);
  86
  87 struct balloon_stats balloon_stats;
  88 EXPORT_SYMBOL_GPL(balloon_stats);
  89
  90 /* We increase/decrease in batches which fit in a page */
  91 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
  92
  93 #ifdef CONFIG_HIGHMEM
  94 #define inc_totalhigh_pages() (totalhigh_pages++)
  95 #define dec_totalhigh_pages() (totalhigh_pages--)
  96 #else
  97 #define inc_totalhigh_pages() do {} while(0)
  98 #define dec_totalhigh_pages() do {} while(0)
  99 #endif
 100
 101 /* List of ballooned pages, threaded through the mem_map array. */
 102 static LIST_HEAD(ballooned_pages);
 103
 104 /* Main work function, always executed in process context. */
 105 static void balloon_process(struct work_struct *work);
 106 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
 107
 108 /* When ballooning out (allocating memory to return to Xen) we don't really
 109    want the kernel to try too hard since that can trigger the oom killer. */
 110 #define GFP_BALLOON \
 111         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 112
 113 static void scrub_page(struct page *page)
 114 {
 115 #ifdef CONFIG_XEN_SCRUB_PAGES
 116         clear_highpage(page);
 117 #endif
 118 }
 119
 120 /* balloon_append: add the given page to the balloon. */
 121 static void __balloon_append(struct page *page)
 122 {
 123         /* Lowmem is re-populated first, so highmem pages go at list tail. */
 124         if (PageHighMem(page)) {
 125                 list_add_tail(&page->lru, &ballooned_pages);
 126                 balloon_stats.balloon_high++;
 127         } else {
 128                 list_add(&page->lru, &ballooned_pages);
 129                 balloon_stats.balloon_low++;
 130         }
 131 }
 132
 133 static void balloon_append(struct page *page)
 134 {
 135         __balloon_append(page);
 136         if (PageHighMem(page))
 137                 dec_totalhigh_pages();
 138         totalram_pages--;
 139 }
 140
 141 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 142 static struct page *balloon_retrieve(bool prefer_highmem)
 143 {
 144         struct page *page;
 145
 146         if (list_empty(&ballooned_pages))
 147                 return NULL;
 148
 149         if (prefer_highmem)
 150                 page = list_entry(ballooned_pages.prev, struct page, lru);
 151         else
 152                 page = list_entry(ballooned_pages.next, struct page, lru);
 153         list_del(&page->lru);
 154
 155         if (PageHighMem(page)) {
 156                 balloon_stats.balloon_high--;
 157                 inc_totalhigh_pages();
 158         }
 159         else
 160                 balloon_stats.balloon_low--;
 161
 162         totalram_pages++;
 163
 164         return page;
 165 }
 166
 167 static struct page *balloon_first_page(void)
 168 {
 169         if (list_empty(&ballooned_pages))
 170                 return NULL;
 171         return list_entry(ballooned_pages.next, struct page, lru);
 172 }
 173
 174 static struct page *balloon_next_page(struct page *page)
 175 {
 176         struct list_head *next = page->lru.next;
 177         if (next == &ballooned_pages)
 178                 return NULL;
 179         return list_entry(next, struct page, lru);
 180 }
 181
 182 static enum bp_state update_schedule(enum bp_state state)
 183 {
 184         if (state == BP_DONE) {
 185                 balloon_stats.schedule_delay = 1;
 186                 balloon_stats.retry_count = 1;
 187                 return BP_DONE;
 188         }
 189
 190         ++balloon_stats.retry_count;
 191
 192         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
 193                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
 194                 balloon_stats.schedule_delay = 1;
 195                 balloon_stats.retry_count = 1;
 196                 return BP_ECANCELED;
 197         }
 198
 199         balloon_stats.schedule_delay <<= 1;
 200
 201         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
 202                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
 203
 204         return BP_EAGAIN;
 205 }
 206
 207 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 208 static long current_credit(void)
 209 {
 210         return balloon_stats.target_pages - balloon_stats.current_pages -
 211                 balloon_stats.hotplug_pages;
 212 }
 213
 214 static bool balloon_is_inflated(void)
 215 {
 216         if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
 217                         balloon_stats.balloon_hotplug)
 218                 return true;
 219         else
 220                 return false;
 221 }
 222
 223 /*
 224  * reserve_additional_memory() adds memory region of size >= credit above
 225  * max_pfn. New region is section aligned and size is modified to be multiple
 226  * of section size. Those features allow optimal use of address space and
 227  * establish proper alignment when this function is called first time after
 228  * boot (last section not fully populated at boot time contains unused memory
 229  * pages with PG_reserved bit not set; online_pages_range() does not allow page
 230  * onlining in whole range if first onlined page does not have PG_reserved
 231  * bit set). Real size of added memory is established at page onlining stage.
 232  */
 233
 234 static enum bp_state reserve_additional_memory(long credit)
 235 {
 236         int nid, rc;
 237         u64 hotplug_start_paddr;
 238         unsigned long balloon_hotplug = credit;
 239
 240         hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
 241         balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
 242         nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
 243
 244         rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
 245
 246         if (rc) {
 247                 pr_info("xen_balloon: %s: add_memory() failed: %i\n", __func__, rc);
 248                 return BP_EAGAIN;
 249         }
 250
 251         balloon_hotplug -= credit;
 252
 253         balloon_stats.hotplug_pages += credit;
 254         balloon_stats.balloon_hotplug = balloon_hotplug;
 255
 256         return BP_DONE;
 257 }
 258
 259 static void xen_online_page(struct page *page)
 260 {
 261         __online_page_set_limits(page);
 262
 263         mutex_lock(&balloon_mutex);
 264
 265         __balloon_append(page);
 266
 267         if (balloon_stats.hotplug_pages)
 268                 --balloon_stats.hotplug_pages;
 269         else
 270                 --balloon_stats.balloon_hotplug;
 271
 272         mutex_unlock(&balloon_mutex);
 273 }
 274
 275 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
 276 {
 277         if (val == MEM_ONLINE)
 278                 schedule_delayed_work(&balloon_worker, 0);
 279
 280         return NOTIFY_OK;
 281 }
 282
 283 static struct notifier_block xen_memory_nb = {
 284         .notifier_call = xen_memory_notifier,
 285         .priority = 0
 286 };
 287 #else
 288 static long current_credit(void)
 289 {
 290         unsigned long target = balloon_stats.target_pages;
 291
 292         target = min(target,
 293                      balloon_stats.current_pages +
 294                      balloon_stats.balloon_low +
 295                      balloon_stats.balloon_high);
 296
 297         return target - balloon_stats.current_pages;
 298 }
 299
 300 static bool balloon_is_inflated(void)
 301 {
 302         if (balloon_stats.balloon_low || balloon_stats.balloon_high)
 303                 return true;
 304         else
 305                 return false;
 306 }
 307
 308 static enum bp_state reserve_additional_memory(long credit)
 309 {
 310         balloon_stats.target_pages = balloon_stats.current_pages;
 311         return BP_DONE;
 312 }
 313 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
 314
 315 static enum bp_state increase_reservation(unsigned long nr_pages)
 316 {
 317         int rc;
 318         unsigned long  pfn, i;
 319         struct page   *page;
 320         struct xen_memory_reservation reservation = {
 321                 .address_bits = 0,
 322                 .extent_order = 0,
 323                 .domid        = DOMID_SELF
 324         };
 325
 326 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 327         if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
 328                 nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
 329                 balloon_stats.hotplug_pages += nr_pages;
 330                 balloon_stats.balloon_hotplug -= nr_pages;
 331                 return BP_DONE;
 332         }
 333 #endif
 334
 335         if (nr_pages > ARRAY_SIZE(frame_list))
 336                 nr_pages = ARRAY_SIZE(frame_list);
 337
 338         page = balloon_first_page();
 339         for (i = 0; i < nr_pages; i++) {
 340                 if (!page) {
 341                         nr_pages = i;
 342                         break;
 343                 }
 344                 frame_list[i] = page_to_pfn(page);
 345                 page = balloon_next_page(page);
 346         }
 347
 348         set_xen_guest_handle(reservation.extent_start, frame_list);
 349         reservation.nr_extents = nr_pages;
 350         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
 351         if (rc <= 0)
 352                 return BP_EAGAIN;
 353
 354         for (i = 0; i < rc; i++) {
 355                 page = balloon_retrieve(false);
 356                 BUG_ON(page == NULL);
 357
 358                 pfn = page_to_pfn(page);
 359                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
 360                        phys_to_machine_mapping_valid(pfn));
 361
 362                 set_phys_to_machine(pfn, frame_list[i]);
 363
 364                 /* Link back into the page tables if not highmem. */
 365                 if (xen_pv_domain() && !PageHighMem(page)) {
 366                         int ret;
 367                         ret = HYPERVISOR_update_va_mapping(
 368                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 369                                 mfn_pte(frame_list[i], PAGE_KERNEL),
 370                                 0);
 371                         BUG_ON(ret);
 372                 }
 373
 374                 /* Relinquish the page back to the allocator. */
 375                 ClearPageReserved(page);
 376                 init_page_count(page);
 377                 __free_page(page);
 378         }
 379
 380         balloon_stats.current_pages += rc;
 381
 382         return BP_DONE;
 383 }
 384
 385 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
 386 {
 387         enum bp_state state = BP_DONE;
 388         unsigned long  pfn, i;
 389         struct page   *page;
 390         int ret;
 391         struct xen_memory_reservation reservation = {
 392                 .address_bits = 0,
 393                 .extent_order = 0,
 394                 .domid        = DOMID_SELF
 395         };
 396
 397 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 398         if (balloon_stats.hotplug_pages) {
 399                 nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
 400                 balloon_stats.hotplug_pages -= nr_pages;
 401                 balloon_stats.balloon_hotplug += nr_pages;
 402                 return BP_DONE;
 403         }
 404 #endif
 405
 406         if (nr_pages > ARRAY_SIZE(frame_list))
 407                 nr_pages = ARRAY_SIZE(frame_list);
 408
 409         for (i = 0; i < nr_pages; i++) {
 410                 if ((page = alloc_page(gfp)) == NULL) {
 411                         nr_pages = i;
 412                         state = BP_EAGAIN;
 413                         break;
 414                 }
 415
 416                 pfn = page_to_pfn(page);
 417                 frame_list[i] = pfn_to_mfn(pfn);
 418
 419                 scrub_page(page);
 420
 421                 if (xen_pv_domain() && !PageHighMem(page)) {
 422                         ret = HYPERVISOR_update_va_mapping(
 423                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 424                                 __pte_ma(0), 0);
 425                         BUG_ON(ret);
 426                 }
 427
 428         }
 429
 430         /* Ensure that ballooned highmem pages don't have kmaps. */
 431         kmap_flush_unused();
 432         flush_tlb_all();
 433
 434         /* No more mappings: invalidate P2M and add to balloon. */
 435         for (i = 0; i < nr_pages; i++) {
 436                 pfn = mfn_to_pfn(frame_list[i]);
 437                 __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 438                 balloon_append(pfn_to_page(pfn));
 439         }
 440
 441         set_xen_guest_handle(reservation.extent_start, frame_list);
 442         reservation.nr_extents   = nr_pages;
 443         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 444         BUG_ON(ret != nr_pages);
 445
 446         balloon_stats.current_pages -= nr_pages;
 447
 448         return state;
 449 }
 450
 451 /*
 452  * We avoid multiple worker processes conflicting via the balloon mutex.
 453  * We may of course race updates of the target counts (which are protected
 454  * by the balloon lock), or with changes to the Xen hard limit, but we will
 455  * recover from these in time.
 456  */
 457 static void balloon_process(struct work_struct *work)
 458 {
 459         enum bp_state state = BP_DONE;
 460         long credit;
 461
 462         mutex_lock(&balloon_mutex);
 463
 464         do {
 465                 credit = current_credit();
 466
 467                 if (credit > 0) {
 468                         if (balloon_is_inflated())
 469                                 state = increase_reservation(credit);
 470                         else
 471                                 state = reserve_additional_memory(credit);
 472                 }
 473
 474                 if (credit < 0)
 475                         state = decrease_reservation(-credit, GFP_BALLOON);
 476
 477                 state = update_schedule(state);
 478
 479 #ifndef CONFIG_PREEMPT
 480                 if (need_resched())
 481                         schedule();
 482 #endif
 483         } while (credit && state == BP_DONE);
 484
 485         /* Schedule more work if there is some still to be done. */
 486         if (state == BP_EAGAIN)
 487                 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
 488
 489         mutex_unlock(&balloon_mutex);
 490 }
 491
 492 /* Resets the Xen limit, sets new target, and kicks off processing. */
 493 void balloon_set_new_target(unsigned long target)
 494 {
 495         /* No need for lock. Not read-modify-write updates. */
 496         balloon_stats.target_pages = target;
 497         schedule_delayed_work(&balloon_worker, 0);
 498 }
 499 EXPORT_SYMBOL_GPL(balloon_set_new_target);
 500
 501 /**
 502  * alloc_xenballooned_pages - get pages that have been ballooned out
 503  * @nr_pages: Number of pages to get
 504  * @pages: pages returned
 505  * @highmem: highmem or lowmem pages
 506  * @return 0 on success, error otherwise
 507  */
 508 int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
 509 {
 510         int pgno = 0;
 511         struct page* page;
 512         mutex_lock(&balloon_mutex);
 513         while (pgno < nr_pages) {
 514                 page = balloon_retrieve(highmem);
 515                 if (page && PageHighMem(page) == highmem) {
 516                         pages[pgno++] = page;
 517                 } else {
 518                         enum bp_state st;
 519                         if (page)
 520                                 balloon_append(page);
 521                         st = decrease_reservation(nr_pages - pgno,
 522                                         highmem ? GFP_HIGHUSER : GFP_USER);
 523                         if (st != BP_DONE)
 524                                 goto out_undo;
 525                 }
 526         }
 527         mutex_unlock(&balloon_mutex);
 528         return 0;
 529  out_undo:
 530         while (pgno)
 531                 balloon_append(pages[--pgno]);
 532         /* Free the memory back to the kernel soon */
 533         schedule_delayed_work(&balloon_worker, 0);
 534         mutex_unlock(&balloon_mutex);
 535         return -ENOMEM;
 536 }
 537 EXPORT_SYMBOL(alloc_xenballooned_pages);
 538
 539 /**
 540  * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
 541  * @nr_pages: Number of pages
 542  * @pages: pages to return
 543  */
 544 void free_xenballooned_pages(int nr_pages, struct page** pages)
 545 {
 546         int i;
 547
 548         mutex_lock(&balloon_mutex);
 549
 550         for (i = 0; i < nr_pages; i++) {
 551                 if (pages[i])
 552                         balloon_append(pages[i]);
 553         }
 554
 555         /* The balloon may be too large now. Shrink it if needed. */
 556         if (current_credit())
 557                 schedule_delayed_work(&balloon_worker, 0);
 558
 559         mutex_unlock(&balloon_mutex);
 560 }
 561 EXPORT_SYMBOL(free_xenballooned_pages);
 562
 563 static void __init balloon_add_region(unsigned long start_pfn,
 564                                       unsigned long pages)
 565 {
 566         unsigned long pfn, extra_pfn_end;
 567         struct page *page;
 568
 569         /*
 570          * If the amount of usable memory has been limited (e.g., with
 571          * the 'mem' command line parameter), don't add pages beyond
 572          * this limit.
 573          */
 574         extra_pfn_end = min(max_pfn, start_pfn + pages);
 575
 576         for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
 577                 page = pfn_to_page(pfn);
 578                 /* totalram_pages and totalhigh_pages do not
 579                    include the boot-time balloon extension, so
 580                    don't subtract from it. */
 581                 __balloon_append(page);
 582         }
 583 }
 584
 585 static int __init balloon_init(void)
 586 {
 587         int i;
 588
 589         if (!xen_domain())
 590                 return -ENODEV;
 591
 592         pr_info("xen/balloon: Initialising balloon driver.\n");
 593
 594         balloon_stats.current_pages = xen_pv_domain()
 595                 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
 596                 : max_pfn;
 597         balloon_stats.target_pages  = balloon_stats.current_pages;
 598         balloon_stats.balloon_low   = 0;
 599         balloon_stats.balloon_high  = 0;
 600
 601         balloon_stats.schedule_delay = 1;
 602         balloon_stats.max_schedule_delay = 32;
 603         balloon_stats.retry_count = 1;
 604         balloon_stats.max_retry_count = RETRY_UNLIMITED;
 605
 606 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
 607         balloon_stats.hotplug_pages = 0;
 608         balloon_stats.balloon_hotplug = 0;
 609
 610         set_online_page_callback(&xen_online_page);
 611         register_memory_notifier(&xen_memory_nb);
 612 #endif
 613
 614         /*
 615          * Initialize the balloon with pages from the extra memory
 616          * regions (see arch/x86/xen/setup.c).
 617          */
 618         for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
 619                 if (xen_extra_mem[i].size)
 620                         balloon_add_region(PFN_UP(xen_extra_mem[i].start),
 621                                            PFN_DOWN(xen_extra_mem[i].size));
 622
 623         return 0;
 624 }
 625
 626 subsys_initcall(balloon_init);
 627
 628 MODULE_LICENSE("GPL");