Pileus Git - ~andy/linux/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 #include <linux/gfp.h>
  47
  48 #include <asm/page.h>
  49 #include <asm/pgalloc.h>
  50 #include <asm/pgtable.h>
  51 #include <asm/uaccess.h>
  52 #include <asm/tlb.h>
  53 #include <asm/e820.h>
  54
  55 #include <asm/xen/hypervisor.h>
  56 #include <asm/xen/hypercall.h>
  57
  58 #include <xen/xen.h>
  59 #include <xen/interface/xen.h>
  60 #include <xen/interface/memory.h>
  61 #include <xen/xenbus.h>
  62 #include <xen/features.h>
  63 #include <xen/page.h>
  64
  65 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
  66
  67 #define BALLOON_CLASS_NAME "xen_memory"
  68
  69 struct balloon_stats {
  70         /* We aim for 'current allocation' == 'target allocation'. */
  71         unsigned long current_pages;
  72         unsigned long target_pages;
  73         /* Number of pages in high- and low-memory balloons. */
  74         unsigned long balloon_low;
  75         unsigned long balloon_high;
  76 };
  77
  78 static DEFINE_MUTEX(balloon_mutex);
  79
  80 static struct sys_device balloon_sysdev;
  81
  82 static int register_balloon(struct sys_device *sysdev);
  83
  84 static struct balloon_stats balloon_stats;
  85
  86 /* We increase/decrease in batches which fit in a page */
  87 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
  88
  89 #ifdef CONFIG_HIGHMEM
  90 #define inc_totalhigh_pages() (totalhigh_pages++)
  91 #define dec_totalhigh_pages() (totalhigh_pages--)
  92 #else
  93 #define inc_totalhigh_pages() do {} while(0)
  94 #define dec_totalhigh_pages() do {} while(0)
  95 #endif
  96
  97 /* List of ballooned pages, threaded through the mem_map array. */
  98 static LIST_HEAD(ballooned_pages);
  99
 100 /* Main work function, always executed in process context. */
 101 static void balloon_process(struct work_struct *work);
 102 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
 103
 104 /* When ballooning out (allocating memory to return to Xen) we don't really
 105    want the kernel to try too hard since that can trigger the oom killer. */
 106 #define GFP_BALLOON \
 107         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 108
 109 static void scrub_page(struct page *page)
 110 {
 111 #ifdef CONFIG_XEN_SCRUB_PAGES
 112         clear_highpage(page);
 113 #endif
 114 }
 115
 116 /* balloon_append: add the given page to the balloon. */
 117 static void __balloon_append(struct page *page)
 118 {
 119         /* Lowmem is re-populated first, so highmem pages go at list tail. */
 120         if (PageHighMem(page)) {
 121                 list_add_tail(&page->lru, &ballooned_pages);
 122                 balloon_stats.balloon_high++;
 123                 dec_totalhigh_pages();
 124         } else {
 125                 list_add(&page->lru, &ballooned_pages);
 126                 balloon_stats.balloon_low++;
 127         }
 128 }
 129
 130 static void balloon_append(struct page *page)
 131 {
 132         __balloon_append(page);
 133         totalram_pages--;
 134 }
 135
 136 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 137 static struct page *balloon_retrieve(void)
 138 {
 139         struct page *page;
 140
 141         if (list_empty(&ballooned_pages))
 142                 return NULL;
 143
 144         page = list_entry(ballooned_pages.next, struct page, lru);
 145         list_del(&page->lru);
 146
 147         if (PageHighMem(page)) {
 148                 balloon_stats.balloon_high--;
 149                 inc_totalhigh_pages();
 150         }
 151         else
 152                 balloon_stats.balloon_low--;
 153
 154         totalram_pages++;
 155
 156         return page;
 157 }
 158
 159 static struct page *balloon_first_page(void)
 160 {
 161         if (list_empty(&ballooned_pages))
 162                 return NULL;
 163         return list_entry(ballooned_pages.next, struct page, lru);
 164 }
 165
 166 static struct page *balloon_next_page(struct page *page)
 167 {
 168         struct list_head *next = page->lru.next;
 169         if (next == &ballooned_pages)
 170                 return NULL;
 171         return list_entry(next, struct page, lru);
 172 }
 173
 174 static unsigned long current_target(void)
 175 {
 176         unsigned long target = balloon_stats.target_pages;
 177
 178         target = min(target,
 179                      balloon_stats.current_pages +
 180                      balloon_stats.balloon_low +
 181                      balloon_stats.balloon_high);
 182
 183         return target;
 184 }
 185
 186 static int increase_reservation(unsigned long nr_pages)
 187 {
 188         unsigned long  pfn, i;
 189         struct page   *page;
 190         long           rc;
 191         struct xen_memory_reservation reservation = {
 192                 .address_bits = 0,
 193                 .extent_order = 0,
 194                 .domid        = DOMID_SELF
 195         };
 196
 197         if (nr_pages > ARRAY_SIZE(frame_list))
 198                 nr_pages = ARRAY_SIZE(frame_list);
 199
 200         page = balloon_first_page();
 201         for (i = 0; i < nr_pages; i++) {
 202                 BUG_ON(page == NULL);
 203                 frame_list[i] = page_to_pfn(page);
 204                 page = balloon_next_page(page);
 205         }
 206
 207         set_xen_guest_handle(reservation.extent_start, frame_list);
 208         reservation.nr_extents = nr_pages;
 209         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
 210         if (rc < 0)
 211                 goto out;
 212
 213         for (i = 0; i < rc; i++) {
 214                 page = balloon_retrieve();
 215                 BUG_ON(page == NULL);
 216
 217                 pfn = page_to_pfn(page);
 218                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
 219                        phys_to_machine_mapping_valid(pfn));
 220
 221                 set_phys_to_machine(pfn, frame_list[i]);
 222
 223                 /* Link back into the page tables if not highmem. */
 224                 if (pfn < max_low_pfn) {
 225                         int ret;
 226                         ret = HYPERVISOR_update_va_mapping(
 227                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 228                                 mfn_pte(frame_list[i], PAGE_KERNEL),
 229                                 0);
 230                         BUG_ON(ret);
 231                 }
 232
 233                 /* Relinquish the page back to the allocator. */
 234                 ClearPageReserved(page);
 235                 init_page_count(page);
 236                 __free_page(page);
 237         }
 238
 239         balloon_stats.current_pages += rc;
 240
 241  out:
 242         return rc < 0 ? rc : rc != nr_pages;
 243 }
 244
 245 static int decrease_reservation(unsigned long nr_pages)
 246 {
 247         unsigned long  pfn, i;
 248         struct page   *page;
 249         int            need_sleep = 0;
 250         int ret;
 251         struct xen_memory_reservation reservation = {
 252                 .address_bits = 0,
 253                 .extent_order = 0,
 254                 .domid        = DOMID_SELF
 255         };
 256
 257         if (nr_pages > ARRAY_SIZE(frame_list))
 258                 nr_pages = ARRAY_SIZE(frame_list);
 259
 260         for (i = 0; i < nr_pages; i++) {
 261                 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
 262                         nr_pages = i;
 263                         need_sleep = 1;
 264                         break;
 265                 }
 266
 267                 pfn = page_to_pfn(page);
 268                 frame_list[i] = pfn_to_mfn(pfn);
 269
 270                 scrub_page(page);
 271
 272                 if (!PageHighMem(page)) {
 273                         ret = HYPERVISOR_update_va_mapping(
 274                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 275                                 __pte_ma(0), 0);
 276                         BUG_ON(ret);
 277                 }
 278
 279         }
 280
 281         /* Ensure that ballooned highmem pages don't have kmaps. */
 282         kmap_flush_unused();
 283         flush_tlb_all();
 284
 285         /* No more mappings: invalidate P2M and add to balloon. */
 286         for (i = 0; i < nr_pages; i++) {
 287                 pfn = mfn_to_pfn(frame_list[i]);
 288                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 289                 balloon_append(pfn_to_page(pfn));
 290         }
 291
 292         set_xen_guest_handle(reservation.extent_start, frame_list);
 293         reservation.nr_extents   = nr_pages;
 294         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 295         BUG_ON(ret != nr_pages);
 296
 297         balloon_stats.current_pages -= nr_pages;
 298
 299         return need_sleep;
 300 }
 301
 302 /*
 303  * We avoid multiple worker processes conflicting via the balloon mutex.
 304  * We may of course race updates of the target counts (which are protected
 305  * by the balloon lock), or with changes to the Xen hard limit, but we will
 306  * recover from these in time.
 307  */
 308 static void balloon_process(struct work_struct *work)
 309 {
 310         int need_sleep = 0;
 311         long credit;
 312
 313         mutex_lock(&balloon_mutex);
 314
 315         do {
 316                 credit = current_target() - balloon_stats.current_pages;
 317                 if (credit > 0)
 318                         need_sleep = (increase_reservation(credit) != 0);
 319                 if (credit < 0)
 320                         need_sleep = (decrease_reservation(-credit) != 0);
 321
 322 #ifndef CONFIG_PREEMPT
 323                 if (need_resched())
 324                         schedule();
 325 #endif
 326         } while ((credit != 0) && !need_sleep);
 327
 328         /* Schedule more work if there is some still to be done. */
 329         if (current_target() != balloon_stats.current_pages)
 330                 schedule_delayed_work(&balloon_worker, HZ);
 331
 332         mutex_unlock(&balloon_mutex);
 333 }
 334
 335 /* Resets the Xen limit, sets new target, and kicks off processing. */
 336 static void balloon_set_new_target(unsigned long target)
 337 {
 338         /* No need for lock. Not read-modify-write updates. */
 339         balloon_stats.target_pages = target;
 340         schedule_delayed_work(&balloon_worker, 0);
 341 }
 342
 343 static struct xenbus_watch target_watch =
 344 {
 345         .node = "memory/target"
 346 };
 347
 348 /* React to a change in the target key */
 349 static void watch_target(struct xenbus_watch *watch,
 350                          const char **vec, unsigned int len)
 351 {
 352         unsigned long long new_target;
 353         int err;
 354
 355         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
 356         if (err != 1) {
 357                 /* This is ok (for domain0 at least) - so just return */
 358                 return;
 359         }
 360
 361         /* The given memory/target value is in KiB, so it needs converting to
 362          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
 363          */
 364         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
 365 }
 366
 367 static int balloon_init_watcher(struct notifier_block *notifier,
 368                                 unsigned long event,
 369                                 void *data)
 370 {
 371         int err;
 372
 373         err = register_xenbus_watch(&target_watch);
 374         if (err)
 375                 printk(KERN_ERR "Failed to set balloon watcher\n");
 376
 377         return NOTIFY_DONE;
 378 }
 379
 380 static struct notifier_block xenstore_notifier;
 381
 382 static int __init balloon_init(void)
 383 {
 384         unsigned long pfn, extra_pfn_end;
 385         struct page *page;
 386
 387         if (!xen_pv_domain())
 388                 return -ENODEV;
 389
 390         pr_info("xen_balloon: Initialising balloon driver.\n");
 391
 392         balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
 393         balloon_stats.target_pages  = balloon_stats.current_pages;
 394         balloon_stats.balloon_low   = 0;
 395         balloon_stats.balloon_high  = 0;
 396
 397         register_balloon(&balloon_sysdev);
 398
 399         /*
 400          * Initialise the balloon with excess memory space.  We need
 401          * to make sure we don't add memory which doesn't exist or
 402          * logically exist.  The E820 map can be trimmed to be smaller
 403          * than the amount of physical memory due to the mem= command
 404          * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
 405          * on a system with memory which requires highmem to access,
 406          * don't try to use it.
 407          */
 408         extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
 409                             (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
 410         for (pfn = PFN_UP(xen_extra_mem_start);
 411              pfn < extra_pfn_end;
 412              pfn++) {
 413                 page = pfn_to_page(pfn);
 414                 /* totalram_pages doesn't include the boot-time
 415                    balloon extension, so don't subtract from it. */
 416                 __balloon_append(page);
 417         }
 418
 419         target_watch.callback = watch_target;
 420         xenstore_notifier.notifier_call = balloon_init_watcher;
 421
 422         register_xenstore_notifier(&xenstore_notifier);
 423
 424         return 0;
 425 }
 426
 427 subsys_initcall(balloon_init);
 428
 429 static void balloon_exit(void)
 430 {
 431     /* XXX - release balloon here */
 432     return;
 433 }
 434
 435 module_exit(balloon_exit);
 436
 437 #define BALLOON_SHOW(name, format, args...)                             \
 438         static ssize_t show_##name(struct sys_device *dev,              \
 439                                    struct sysdev_attribute *attr,       \
 440                                    char *buf)                           \
 441         {                                                               \
 442                 return sprintf(buf, format, ##args);                    \
 443         }                                                               \
 444         static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
 445
 446 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
 447 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
 448 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
 449
 450 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
 451                               char *buf)
 452 {
 453         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
 454 }
 455
 456 static ssize_t store_target_kb(struct sys_device *dev,
 457                                struct sysdev_attribute *attr,
 458                                const char *buf,
 459                                size_t count)
 460 {
 461         char *endchar;
 462         unsigned long long target_bytes;
 463
 464         if (!capable(CAP_SYS_ADMIN))
 465                 return -EPERM;
 466
 467         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
 468
 469         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 470
 471         return count;
 472 }
 473
 474 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
 475                    show_target_kb, store_target_kb);
 476
 477
 478 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
 479                               char *buf)
 480 {
 481         return sprintf(buf, "%llu\n",
 482                        (unsigned long long)balloon_stats.target_pages
 483                        << PAGE_SHIFT);
 484 }
 485
 486 static ssize_t store_target(struct sys_device *dev,
 487                             struct sysdev_attribute *attr,
 488                             const char *buf,
 489                             size_t count)
 490 {
 491         char *endchar;
 492         unsigned long long target_bytes;
 493
 494         if (!capable(CAP_SYS_ADMIN))
 495                 return -EPERM;
 496
 497         target_bytes = memparse(buf, &endchar);
 498
 499         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
 500
 501         return count;
 502 }
 503
 504 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
 505                    show_target, store_target);
 506
 507
 508 static struct sysdev_attribute *balloon_attrs[] = {
 509         &attr_target_kb,
 510         &attr_target,
 511 };
 512
 513 static struct attribute *balloon_info_attrs[] = {
 514         &attr_current_kb.attr,
 515         &attr_low_kb.attr,
 516         &attr_high_kb.attr,
 517         NULL
 518 };
 519
 520 static struct attribute_group balloon_info_group = {
 521         .name = "info",
 522         .attrs = balloon_info_attrs,
 523 };
 524
 525 static struct sysdev_class balloon_sysdev_class = {
 526         .name = BALLOON_CLASS_NAME,
 527 };
 528
 529 static int register_balloon(struct sys_device *sysdev)
 530 {
 531         int i, error;
 532
 533         error = sysdev_class_register(&balloon_sysdev_class);
 534         if (error)
 535                 return error;
 536
 537         sysdev->id = 0;
 538         sysdev->cls = &balloon_sysdev_class;
 539
 540         error = sysdev_register(sysdev);
 541         if (error) {
 542                 sysdev_class_unregister(&balloon_sysdev_class);
 543                 return error;
 544         }
 545
 546         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
 547                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
 548                 if (error)
 549                         goto fail;
 550         }
 551
 552         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
 553         if (error)
 554                 goto fail;
 555
 556         return 0;
 557
 558  fail:
 559         while (--i >= 0)
 560                 sysdev_remove_file(sysdev, balloon_attrs[i]);
 561         sysdev_unregister(sysdev);
 562         sysdev_class_unregister(&balloon_sysdev_class);
 563         return error;
 564 }
 565
 566 MODULE_LICENSE("GPL");