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