SAFE public projects git trees. - safe/jmp/linux-2.6/blob - drivers/xen/balloon.c

   1 /******************************************************************************
   2  * balloon.c
   3  *
   4  * Xen balloon driver - enables returning/claiming memory to/from Xen.
   5  *
   6  * Copyright (c) 2003, B Dragovic
   7  * Copyright (c) 2003-2004, M Williamson, K Fraser
   8  * Copyright (c) 2005 Dan M. Smith, IBM Corporation
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License version 2
  12  * as published by the Free Software Foundation; or, when distributed
  13  * separately from the Linux kernel or incorporated into other
  14  * software packages, subject to the following license:
  15  *
  16  * Permission is hereby granted, free of charge, to any person obtaining a copy
  17  * of this source file (the "Software"), to deal in the Software without
  18  * restriction, including without limitation the rights to use, copy, modify,
  19  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  20  * and to permit persons to whom the Software is furnished to do so, subject to
  21  * the following conditions:
  22  *
  23  * The above copyright notice and this permission notice shall be included in
  24  * all copies or substantial portions of the Software.
  25  *
  26  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  27  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  28  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  29  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  30  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  31  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  32  * IN THE SOFTWARE.
  33  */
  34
  35 #include <linux/kernel.h>
  36 #include <linux/module.h>
  37 #include <linux/sched.h>
  38 #include <linux/errno.h>
  39 #include <linux/mm.h>
  40 #include <linux/bootmem.h>
  41 #include <linux/pagemap.h>
  42 #include <linux/highmem.h>
  43 #include <linux/mutex.h>
  44 #include <linux/list.h>
  45 #include <linux/sysdev.h>
  46
  47 #include <asm/page.h>
  48 #include <asm/pgalloc.h>
  49 #include <asm/pgtable.h>
  50 #include <asm/uaccess.h>
  51 #include <asm/tlb.h>
  52
  53 #include <asm/xen/hypervisor.h>
  54 #include <asm/xen/hypercall.h>
  55
  56 #include <xen/xen.h>
  57 #include <xen/interface/xen.h>
  58 #include <xen/interface/memory.h>
  59 #include <xen/xenbus.h>
  60 #include <xen/features.h>
  61 #include <xen/page.h>
  62
  63 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
  64
  65 #define BALLOON_CLASS_NAME "xen_memory"
  66
  67 struct balloon_stats {
  68         /* We aim for 'current allocation' == 'target allocation'. */
  69         unsigned long current_pages;
  70         unsigned long target_pages;
  71         /*
  72          * Drivers may alter the memory reservation independently, but they
  73          * must inform the balloon driver so we avoid hitting the hard limit.
  74          */
  75         unsigned long driver_pages;
  76         /* Number of pages in high- and low-memory balloons. */
  77         unsigned long balloon_low;
  78         unsigned long balloon_high;
  79 };
  80
  81 static DEFINE_MUTEX(balloon_mutex);
  82
  83 static struct sys_device balloon_sysdev;
  84
  85 static int register_balloon(struct sys_device *sysdev);
  86
  87 /*
  88  * Protects atomic reservation decrease/increase against concurrent increases.
  89  * Also protects non-atomic updates of current_pages and driver_pages, and
  90  * balloon lists.
  91  */
  92 static DEFINE_SPINLOCK(balloon_lock);
  93
  94 static struct balloon_stats balloon_stats;
  95
  96 /* We increase/decrease in batches which fit in a page */
  97 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
  98
  99 #ifdef CONFIG_HIGHMEM
 100 #define inc_totalhigh_pages() (totalhigh_pages++)
 101 #define dec_totalhigh_pages() (totalhigh_pages--)
 102 #else
 103 #define inc_totalhigh_pages() do {} while(0)
 104 #define dec_totalhigh_pages() do {} while(0)
 105 #endif
 106
 107 /* List of ballooned pages, threaded through the mem_map array. */
 108 static LIST_HEAD(ballooned_pages);
 109
 110 /* Main work function, always executed in process context. */
 111 static void balloon_process(struct work_struct *work);
 112 static DECLARE_WORK(balloon_worker, balloon_process);
 113 static struct timer_list balloon_timer;
 114
 115 /* When ballooning out (allocating memory to return to Xen) we don't really
 116    want the kernel to try too hard since that can trigger the oom killer. */
 117 #define GFP_BALLOON \
 118         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 119
 120 static void scrub_page(struct page *page)
 121 {
 122 #ifdef CONFIG_XEN_SCRUB_PAGES
 123         clear_highpage(page);
 124 #endif
 125 }
 126
 127 /* balloon_append: add the given page to the balloon. */
 128 static void balloon_append(struct page *page)
 129 {
 130         /* Lowmem is re-populated first, so highmem pages go at list tail. */
 131         if (PageHighMem(page)) {
 132                 list_add_tail(&page->lru, &ballooned_pages);
 133                 balloon_stats.balloon_high++;
 134                 dec_totalhigh_pages();
 135         } else {
 136                 list_add(&page->lru, &ballooned_pages);
 137                 balloon_stats.balloon_low++;
 138         }
 139
 140         totalram_pages--;
 141 }
 142
 143 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 144 static struct page *balloon_retrieve(void)
 145 {
 146         struct page *page;
 147
 148         if (list_empty(&ballooned_pages))
 149                 return NULL;
 150
 151         page = list_entry(ballooned_pages.next, struct page, lru);
 152         list_del(&page->lru);
 153
 154         if (PageHighMem(page)) {
 155                 balloon_stats.balloon_high--;
 156                 inc_totalhigh_pages();
 157         }
 158         else
 159                 balloon_stats.balloon_low--;
 160
 161         totalram_pages++;
 162
 163         return page;
 164 }
 165
 166 static struct page *balloon_first_page(void)
 167 {
 168         if (list_empty(&ballooned_pages))
 169                 return NULL;
 170         return list_entry(ballooned_pages.next, struct page, lru);
 171 }
 172
 173 static struct page *balloon_next_page(struct page *page)
 174 {
 175         struct list_head *next = page->lru.next;
 176         if (next == &ballooned_pages)
 177                 return NULL;
 178         return list_entry(next, struct page, lru);
 179 }
 180
 181 static void balloon_alarm(unsigned long unused)
 182 {
 183         schedule_work(&balloon_worker);
 184 }
 185
 186 static unsigned long current_target(void)
 187 {
 188         unsigned long target = balloon_stats.target_pages;
 189
 190         target = min(target,
 191                      balloon_stats.current_pages +
 192                      balloon_stats.balloon_low +
 193                      balloon_stats.balloon_high);
 194
 195         return target;
 196 }
 197
 198 static int increase_reservation(unsigned long nr_pages)
 199 {
 200         unsigned long  pfn, i, flags;
 201         struct page   *page;
 202         long           rc;
 203         struct xen_memory_reservation reservation = {
 204                 .address_bits = 0,
 205                 .extent_order = 0,
 206                 .domid        = DOMID_SELF
 207         };
 208
 209         if (nr_pages > ARRAY_SIZE(frame_list))
 210                 nr_pages = ARRAY_SIZE(frame_list);
 211
 212         spin_lock_irqsave(&balloon_lock, flags);
 213
 214         page = balloon_first_page();
 215         for (i = 0; i < nr_pages; i++) {
 216                 BUG_ON(page == NULL);
 217                 frame_list[i] = page_to_pfn(page);
 218                 page = balloon_next_page(page);
 219         }
 220
 221         set_xen_guest_handle(reservation.extent_start, frame_list);
 222         reservation.nr_extents = nr_pages;
 223         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
 224         if (rc < 0)
 225                 goto out;
 226
 227         for (i = 0; i < rc; i++) {
 228                 page = balloon_retrieve();
 229                 BUG_ON(page == NULL);
 230
 231                 pfn = page_to_pfn(page);
 232                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
 233                        phys_to_machine_mapping_valid(pfn));
 234
 235                 set_phys_to_machine(pfn, frame_list[i]);
 236
 237                 /* Link back into the page tables if not highmem. */
 238                 if (pfn < max_low_pfn) {
 239                         int ret;
 240                         ret = HYPERVISOR_update_va_mapping(
 241                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 242                                 mfn_pte(frame_list[i], PAGE_KERNEL),
 243                                 0);
 244                         BUG_ON(ret);
 245                 }
 246
 247                 /* Relinquish the page back to the allocator. */
 248                 ClearPageReserved(page);
 249                 init_page_count(page);
 250                 __free_page(page);
 251         }
 252
 253         balloon_stats.current_pages += rc;
 254
 255  out:
 256         spin_unlock_irqrestore(&balloon_lock, flags);
 257
 258         return rc < 0 ? rc : rc != nr_pages;
 259 }
 260
 261 static int decrease_reservation(unsigned long nr_pages)
 262 {
 263         unsigned long  pfn, i, flags;
 264         struct page   *page;
 265         int            need_sleep = 0;
 266         int ret;
 267         struct xen_memory_reservation reservation = {
 268                 .address_bits = 0,
 269                 .extent_order = 0,
 270                 .domid        = DOMID_SELF
 271         };
 272
 273         if (nr_pages > ARRAY_SIZE(frame_list))
 274                 nr_pages = ARRAY_SIZE(frame_list);
 275
 276         for (i = 0; i < nr_pages; i++) {
 277                 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
 278                         nr_pages = i;
 279                         need_sleep = 1;
 280                         break;
 281                 }
 282
 283                 pfn = page_to_pfn(page);
 284                 frame_list[i] = pfn_to_mfn(pfn);
 285
 286                 scrub_page(page);
 287
 288                 if (!PageHighMem(page)) {
 289                         ret = HYPERVISOR_update_va_mapping(
 290                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 291                                 __pte_ma(0), 0);
 292                         BUG_ON(ret);
 293                 }
 294
 295         }
 296
 297         /* Ensure that ballooned highmem pages don't have kmaps. */
 298         kmap_flush_unused();
 299         flush_tlb_all();
 300
 301         spin_lock_irqsave(&balloon_lock, flags);
 302
 303         /* No more mappings: invalidate P2M and add to balloon. */
 304         for (i = 0; i < nr_pages; i++) {
 305                 pfn = mfn_to_pfn(frame_list[i]);
 306                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 307                 balloon_append(pfn_to_page(pfn));
 308         }
 309
 310         set_xen_guest_handle(reservation.extent_start, frame_list);
 311         reservation.nr_extents   = nr_pages;
 312         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 313         BUG_ON(ret != nr_pages);
 314
 315         balloon_stats.current_pages -= nr_pages;
 316
 317         spin_unlock_irqrestore(&balloon_lock, flags);
 318
 319         return need_sleep;
 320 }
 321
 322 /*
 323  * We avoid multiple worker processes conflicting via the balloon mutex.
 324  * We may of course race updates of the target counts (which are protected
 325  * by the balloon lock), or with changes to the Xen hard limit, but we will
 326  * recover from these in time.
 327  */
 328 static void balloon_process(struct work_struct *work)
 329 {
 330         int need_sleep = 0;
 331         long credit;
 332
 333         mutex_lock(&balloon_mutex);
 334
 335         do {
 336                 credit = current_target() - balloon_stats.current_pages;
 337                 if (credit > 0)
 338                         need_sleep = (increase_reservation(credit) != 0);
 339                 if (credit < 0)
 340                         need_sleep = (decrease_reservation(-credit) != 0);
 341
 342 #ifndef CONFIG_PREEMPT
 343                 if (need_resched())
 344                         schedule();
 345 #endif
 346         } while ((credit != 0) && !need_sleep);
 347
 348         /* Schedule more work if there is some still to be done. */
 349         if (current_target() != balloon_stats.current_pages)
 350                 mod_timer(&balloon_timer, jiffies + HZ);
 351
 352         mutex_unlock(&balloon_mutex);
 353 }
 354
 355 /* Resets the Xen limit, sets new target, and kicks off processing. */
 356 static void balloon_set_new_target(unsigned long target)
 357 {
 358         /* No need for lock. Not read-modify-write updates. */
 359         balloon_stats.target_pages = target;
 360         schedule_work(&balloon_worker);
 361 }
 362
 363 static struct xenbus_watch target_watch =
 364 {
 365         .node = "memory/target"
 366 };
 367
 368 /* React to a change in the target key */
 369 static void watch_target(struct xenbus_watch *watch,
 370                          const char **vec, unsigned int len)
 371 {
 372         unsigned long long new_target;
 373         int err;
 374
 375         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
 376         if (err != 1) {
 377                 /* This is ok (for domain0 at least) - so just return */
 378                 return;
 379         }
 380
 381         /* The given memory/target value is in KiB, so it needs converting to
 382          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
 383          */
 384         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
 385 }
 386
 387 static int balloon_init_watcher(struct notifier_block *notifier,
 388                                 unsigned long event,
 389                                 void *data)
 390 {
 391         int err;
 392
 393         err = register_xenbus_watch(&target_watch);
 394         if (err)
 395                 printk(KERN_ERR "Failed to set balloon watcher\n");
 396
 397         return NOTIFY_DONE;
 398 }
 399
 400 static struct notifier_block xenstore_notifier;
 401
 402 static int __init balloon_init(void)
 403 {
 404         unsigned long pfn;
 405         struct page *page;
 406
 407         if (!xen_pv_domain())
 408                 return -ENODEV;
 409
 410         pr_info("xen_balloon: Initialising balloon driver.\n");
 411
 412         balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
 413         balloon_stats.target_pages  = balloon_stats.current_pages;
 414         balloon_stats.balloon_low   = 0;
 415         balloon_stats.balloon_high  = 0;
 416         balloon_stats.driver_pages  = 0UL;
 417
 418         init_timer(&balloon_timer);
 419         balloon_timer.data = 0;
 420         balloon_timer.function = balloon_alarm;
 421
 422         register_balloon(&balloon_sysdev);
 423
 424         /* Initialise the balloon with excess memory space. */
 425         for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
 426                 page = pfn_to_page(pfn);
 427                 if (!PageReserved(page))
 428                         balloon_append(page);
 429         }
 430
 431         target_watch.callback = watch_target;
 432         xenstore_notifier.notifier_call = balloon_init_watcher;
 433
 434         register_xenstore_notifier(&xenstore_notifier);
 435
 436         return 0;
 437 }
 438
 439 subsys_initcall(balloon_init);
 440
 441 static void balloon_exit(void)
 442 {
 443     /* XXX - release balloon here */
 444     return;
 445 }
 446
 447 module_exit(balloon_exit);
 448
 449 #define BALLOON_SHOW(name, format, args...)                             \
 450         static ssize_t show_##name(struct sys_device *dev,              \
 451                                    struct sysdev_attribute *attr,       \
 452                                    char *buf)                           \
 453         {                                                               \
 454                 return sprintf(buf, format, ##args);                    \
 455         }                                                               \
 456         static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
 457
 458 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
 459 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
 460 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
 461 BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
 462
 463 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
 464                               char *buf)
 465 {
 466         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
 467 }
 468
 469 static ssize_t store_target_kb(struct sys_device *dev,
 470                                struct sysdev_attribute *attr,
 471                                const char *buf,
 472                                size_t count)
 473 {
 474         char *endchar;
 475         unsigned long long target_bytes;
 476
 477         if (!capable(CAP_SYS_ADMIN))
 478                 return -EPERM;
 479
 480         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
 481
 482         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 483
 484         return count;
 485 }
 486
 487 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
 488                    show_target_kb, store_target_kb);
 489
 490
 491 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
 492                               char *buf)
 493 {
 494         return sprintf(buf, "%llu\n",
 495                        (unsigned long long)balloon_stats.target_pages
 496                        << PAGE_SHIFT);
 497 }
 498
 499 static ssize_t store_target(struct sys_device *dev,
 500                             struct sysdev_attribute *attr,
 501                             const char *buf,
 502                             size_t count)
 503 {
 504         char *endchar;
 505         unsigned long long target_bytes;
 506
 507         if (!capable(CAP_SYS_ADMIN))
 508                 return -EPERM;
 509
 510         target_bytes = memparse(buf, &endchar);
 511
 512         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 513
 514         return count;
 515 }
 516
 517 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
 518                    show_target, store_target);
 519
 520
 521 static struct sysdev_attribute *balloon_attrs[] = {
 522         &attr_target_kb,
 523         &attr_target,
 524 };
 525
 526 static struct attribute *balloon_info_attrs[] = {
 527         &attr_current_kb.attr,
 528         &attr_low_kb.attr,
 529         &attr_high_kb.attr,
 530         &attr_driver_kb.attr,
 531         NULL
 532 };
 533
 534 static struct attribute_group balloon_info_group = {
 535         .name = "info",
 536         .attrs = balloon_info_attrs,
 537 };
 538
 539 static struct sysdev_class balloon_sysdev_class = {
 540         .name = BALLOON_CLASS_NAME,
 541 };
 542
 543 static int register_balloon(struct sys_device *sysdev)
 544 {
 545         int i, error;
 546
 547         error = sysdev_class_register(&balloon_sysdev_class);
 548         if (error)
 549                 return error;
 550
 551         sysdev->id = 0;
 552         sysdev->cls = &balloon_sysdev_class;
 553
 554         error = sysdev_register(sysdev);
 555         if (error) {
 556                 sysdev_class_unregister(&balloon_sysdev_class);
 557                 return error;
 558         }
 559
 560         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
 561                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
 562                 if (error)
 563                         goto fail;
 564         }
 565
 566         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
 567         if (error)
 568                 goto fail;
 569
 570         return 0;
 571
 572  fail:
 573         while (--i >= 0)
 574                 sysdev_remove_file(sysdev, balloon_attrs[i]);
 575         sysdev_unregister(sysdev);
 576         sysdev_class_unregister(&balloon_sysdev_class);
 577         return error;
 578 }
 579
 580 MODULE_LICENSE("GPL");