drivers/xen/balloon/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/config.h>
  36 #include <linux/kernel.h>
  37 #include <linux/module.h>
  38 #include <linux/sched.h>
  39 #include <linux/errno.h>
  40 #include <linux/mm.h>
  41 #include <linux/mman.h>
  42 #include <linux/smp_lock.h>
  43 #include <linux/pagemap.h>
  44 #include <linux/bootmem.h>
  45 #include <linux/highmem.h>
  46 #include <linux/vmalloc.h>
  47 #include <xen/xen_proc.h>
  48 #include <asm/hypervisor.h>
  49 #include <xen/balloon.h>
  50 #include <xen/interface/memory.h>
  51 #include <asm/pgalloc.h>
  52 #include <asm/pgtable.h>
  53 #include <asm/uaccess.h>
  54 #include <asm/tlb.h>
  55 #include <linux/list.h>
  56
  57 #include <xen/xenbus.h>
  58
  59 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
  60
  61 #ifdef CONFIG_PROC_FS
  62 static struct proc_dir_entry *balloon_pde;
  63 #endif
  64
  65 static DECLARE_MUTEX(balloon_mutex);
  66
  67 /*
  68  * Protects atomic reservation decrease/increase against concurrent increases.
  69  * Also protects non-atomic updates of current_pages and driver_pages, and
  70  * balloon lists.
  71  */
  72 DEFINE_SPINLOCK(balloon_lock);
  73
  74 /* We aim for 'current allocation' == 'target allocation'. */
  75 static unsigned long current_pages;
  76 static unsigned long target_pages;
  77
  78 /* We increase/decrease in batches which fit in a page */
  79 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
  80
  81 /* VM /proc information for memory */
  82 extern unsigned long totalram_pages;
  83
  84 /* We may hit the hard limit in Xen. If we do then we remember it. */
  85 static unsigned long hard_limit;
  86
  87 /*
  88  * Drivers may alter the memory reservation independently, but they must
  89  * inform the balloon driver so that we can avoid hitting the hard limit.
  90  */
  91 static unsigned long driver_pages;
  92
  93 /* List of ballooned pages, threaded through the mem_map array. */
  94 static LIST_HEAD(ballooned_pages);
  95 static unsigned long balloon_low, balloon_high;
  96
  97 /* Main work function, always executed in process context. */
  98 static void balloon_process(void *unused);
  99 static DECLARE_WORK(balloon_worker, balloon_process, NULL);
 100 static struct timer_list balloon_timer;
 101
 102 /* When ballooning out (allocating memory to return to Xen) we don't really
 103    want the kernel to try too hard since that can trigger the oom killer. */
 104 #define GFP_BALLOON \
 105         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
 106
 107 #define PAGE_TO_LIST(p) (&(p)->lru)
 108 #define LIST_TO_PAGE(l) list_entry((l), struct page, lru)
 109 #define UNLIST_PAGE(p)                          \
 110         do {                                    \
 111                 list_del(PAGE_TO_LIST(p));      \
 112                 PAGE_TO_LIST(p)->next = NULL;   \
 113                 PAGE_TO_LIST(p)->prev = NULL;   \
 114         } while(0)
 115
 116 #define IPRINTK(fmt, args...) \
 117         printk(KERN_INFO "xen_mem: " fmt, ##args)
 118 #define WPRINTK(fmt, args...) \
 119         printk(KERN_WARNING "xen_mem: " fmt, ##args)
 120
 121 /* balloon_append: add the given page to the balloon. */
 122 static void balloon_append(struct page *page)
 123 {
 124         /* Lowmem is re-populated first, so highmem pages go at list tail. */
 125         if (PageHighMem(page)) {
 126                 list_add_tail(PAGE_TO_LIST(page), &ballooned_pages);
 127                 balloon_high++;
 128         } else {
 129                 list_add(PAGE_TO_LIST(page), &ballooned_pages);
 130                 balloon_low++;
 131         }
 132 }
 133
 134 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
 135 static struct page *balloon_retrieve(void)
 136 {
 137         struct page *page;
 138
 139         if (list_empty(&ballooned_pages))
 140                 return NULL;
 141
 142         page = LIST_TO_PAGE(ballooned_pages.next);
 143         UNLIST_PAGE(page);
 144
 145         if (PageHighMem(page))
 146                 balloon_high--;
 147         else
 148                 balloon_low--;
 149
 150         return page;
 151 }
 152
 153 static struct page *balloon_first_page(void)
 154 {
 155         if (list_empty(&ballooned_pages))
 156                 return NULL;
 157         return LIST_TO_PAGE(ballooned_pages.next);
 158 }
 159
 160 static struct page *balloon_next_page(struct page *page)
 161 {
 162         struct list_head *next = PAGE_TO_LIST(page)->next;
 163         if (next == &ballooned_pages)
 164                 return NULL;
 165         return LIST_TO_PAGE(next);
 166 }
 167
 168 static void balloon_alarm(unsigned long unused)
 169 {
 170         schedule_work(&balloon_worker);
 171 }
 172
 173 static unsigned long current_target(void)
 174 {
 175         unsigned long target = min(target_pages, hard_limit);
 176         if (target > (current_pages + balloon_low + balloon_high))
 177                 target = current_pages + balloon_low + balloon_high;
 178         return target;
 179 }
 180
 181 static int increase_reservation(unsigned long nr_pages)
 182 {
 183         unsigned long  pfn, i, flags;
 184         struct page   *page;
 185         long           rc;
 186         struct xen_memory_reservation reservation = {
 187                 .address_bits = 0,
 188                 .extent_order = 0,
 189                 .domid        = DOMID_SELF
 190         };
 191
 192         if (nr_pages > ARRAY_SIZE(frame_list))
 193                 nr_pages = ARRAY_SIZE(frame_list);
 194
 195         balloon_lock(flags);
 196
 197         page = balloon_first_page();
 198         for (i = 0; i < nr_pages; i++) {
 199                 BUG_ON(page == NULL);
 200                 frame_list[i] = page_to_pfn(page);;
 201                 page = balloon_next_page(page);
 202         }
 203
 204         set_xen_guest_handle(reservation.extent_start, frame_list);
 205         reservation.nr_extents   = nr_pages;
 206         rc = HYPERVISOR_memory_op(
 207                 XENMEM_populate_physmap, &reservation);
 208         if (rc < nr_pages) {
 209                 if (rc > 0) {
 210                         int ret;
 211
 212                         /* We hit the Xen hard limit: reprobe. */
 213                         reservation.nr_extents = rc;
 214                         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
 215                                         &reservation);
 216                         BUG_ON(ret != rc);
 217                 }
 218                 if (rc >= 0)
 219                         hard_limit = current_pages + rc - driver_pages;
 220                 goto out;
 221         }
 222
 223         for (i = 0; i < nr_pages; i++) {
 224                 page = balloon_retrieve();
 225                 BUG_ON(page == NULL);
 226
 227                 pfn = page_to_pfn(page);
 228                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
 229                        phys_to_machine_mapping_valid(pfn));
 230
 231                 /* Update P->M and M->P tables. */
 232                 set_phys_to_machine(pfn, frame_list[i]);
 233                 xen_machphys_update(frame_list[i], pfn);
 234
 235                 /* Link back into the page tables if not highmem. */
 236                 if (pfn < max_low_pfn) {
 237                         int ret;
 238                         ret = HYPERVISOR_update_va_mapping(
 239                                 (unsigned long)__va(pfn << PAGE_SHIFT),
 240                                 pfn_pte_ma(frame_list[i], PAGE_KERNEL),
 241                                 0);
 242                         BUG_ON(ret);
 243                 }
 244
 245                 /* Relinquish the page back to the allocator. */
 246                 ClearPageReserved(page);
 247                 init_page_count(page);
 248                 __free_page(page);
 249         }
 250
 251         current_pages += nr_pages;
 252         totalram_pages = current_pages;
 253
 254  out:
 255         balloon_unlock(flags);
 256
 257         return 0;
 258 }
 259
 260 static int decrease_reservation(unsigned long nr_pages)
 261 {
 262         unsigned long  pfn, i, flags;
 263         struct page   *page;
 264         void          *v;
 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                 if (!PageHighMem(page)) {
 287                         v = phys_to_virt(pfn << PAGE_SHIFT);
 288                         scrub_pages(v, 1);
 289                         ret = HYPERVISOR_update_va_mapping(
 290                                 (unsigned long)v, __pte_ma(0), 0);
 291                         BUG_ON(ret);
 292                 }
 293 #ifdef CONFIG_XEN_SCRUB_PAGES
 294                 else {
 295                         v = kmap(page);
 296                         scrub_pages(v, 1);
 297                         kunmap(page);
 298                 }
 299 #endif
 300         }
 301
 302         /* Ensure that ballooned highmem pages don't have kmaps. */
 303         kmap_flush_unused();
 304         flush_tlb_all();
 305
 306         balloon_lock(flags);
 307
 308         /* No more mappings: invalidate P2M and add to balloon. */
 309         for (i = 0; i < nr_pages; i++) {
 310                 pfn = mfn_to_pfn(frame_list[i]);
 311                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
 312                 balloon_append(pfn_to_page(pfn));
 313         }
 314
 315         set_xen_guest_handle(reservation.extent_start, frame_list);
 316         reservation.nr_extents   = nr_pages;
 317         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 318         BUG_ON(ret != nr_pages);
 319
 320         current_pages -= nr_pages;
 321         totalram_pages = current_pages;
 322
 323         balloon_unlock(flags);
 324
 325         return need_sleep;
 326 }
 327
 328 /*
 329  * We avoid multiple worker processes conflicting via the balloon mutex.
 330  * We may of course race updates of the target counts (which are protected
 331  * by the balloon lock), or with changes to the Xen hard limit, but we will
 332  * recover from these in time.
 333  */
 334 static void balloon_process(void *unused)
 335 {
 336         int need_sleep = 0;
 337         long credit;
 338
 339         down(&balloon_mutex);
 340
 341         do {
 342                 credit = current_target() - current_pages;
 343                 if (credit > 0)
 344                         need_sleep = (increase_reservation(credit) != 0);
 345                 if (credit < 0)
 346                         need_sleep = (decrease_reservation(-credit) != 0);
 347
 348 #ifndef CONFIG_PREEMPT
 349                 if (need_resched())
 350                         schedule();
 351 #endif
 352         } while ((credit != 0) && !need_sleep);
 353
 354         /* Schedule more work if there is some still to be done. */
 355         if (current_target() != current_pages)
 356                 mod_timer(&balloon_timer, jiffies + HZ);
 357
 358         up(&balloon_mutex);
 359 }
 360
 361 /* Resets the Xen limit, sets new target, and kicks off processing. */
 362 static void set_new_target(unsigned long target)
 363 {
 364         /* No need for lock. Not read-modify-write updates. */
 365         hard_limit   = ~0UL;
 366         target_pages = target;
 367         schedule_work(&balloon_worker);
 368 }
 369
 370 static struct xenbus_watch target_watch =
 371 {
 372         .node = "memory/target"
 373 };
 374
 375 /* React to a change in the target key */
 376 static void watch_target(struct xenbus_watch *watch,
 377                          const char **vec, unsigned int len)
 378 {
 379         unsigned long long new_target;
 380         int err;
 381
 382         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
 383         if (err != 1) {
 384                 /* This is ok (for domain0 at least) - so just return */
 385                 return;
 386         }
 387
 388         /* The given memory/target value is in KiB, so it needs converting to
 389          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
 390          */
 391         set_new_target(new_target >> (PAGE_SHIFT - 10));
 392 }
 393
 394 static int balloon_init_watcher(struct notifier_block *notifier,
 395                                 unsigned long event,
 396                                 void *data)
 397 {
 398         int err;
 399
 400         err = register_xenbus_watch(&target_watch);
 401         if (err)
 402                 printk(KERN_ERR "Failed to set balloon watcher\n");
 403
 404         return NOTIFY_DONE;
 405 }
 406
 407 #ifdef CONFIG_PROC_FS
 408 static int balloon_write(struct file *file, const char __user *buffer,
 409                          unsigned long count, void *data)
 410 {
 411         char memstring[64], *endchar;
 412         unsigned long long target_bytes;
 413
 414         if (!capable(CAP_SYS_ADMIN))
 415                 return -EPERM;
 416
 417         if (count <= 1)
 418                 return -EBADMSG; /* runt */
 419         if (count > sizeof(memstring))
 420                 return -EFBIG;   /* too long */
 421
 422         if (copy_from_user(memstring, buffer, count))
 423                 return -EFAULT;
 424         memstring[sizeof(memstring)-1] = '\0';
 425
 426         target_bytes = memparse(memstring, &endchar);
 427         set_new_target(target_bytes >> PAGE_SHIFT);
 428
 429         return count;
 430 }
 431
 432 static int balloon_read(char *page, char **start, off_t off,
 433                         int count, int *eof, void *data)
 434 {
 435         int len;
 436
 437         len = sprintf(
 438                 page,
 439                 "Current allocation: %8lu kB\n"
 440                 "Requested target:   %8lu kB\n"
 441                 "Low-mem balloon:    %8lu kB\n"
 442                 "High-mem balloon:   %8lu kB\n"
 443                 "Xen hard limit:     ",
 444                 PAGES2KB(current_pages), PAGES2KB(target_pages),
 445                 PAGES2KB(balloon_low), PAGES2KB(balloon_high));
 446
 447         if (hard_limit != ~0UL) {
 448                 len += sprintf(
 449                         page + len,
 450                         "%8lu kB (inc. %8lu kB driver headroom)\n",
 451                         PAGES2KB(hard_limit), PAGES2KB(driver_pages));
 452         } else {
 453                 len += sprintf(
 454                         page + len,
 455                         "     ??? kB\n");
 456         }
 457
 458         *eof = 1;
 459         return len;
 460 }
 461 #endif
 462
 463 static struct notifier_block xenstore_notifier;
 464
 465 static int __init balloon_init(void)
 466 {
 467         unsigned long pfn;
 468         struct page *page;
 469
 470         if (!is_running_on_xen())
 471                 return -ENODEV;
 472
 473         IPRINTK("Initialising balloon driver.\n");
 474
 475         current_pages = min(xen_start_info->nr_pages, max_pfn);
 476         totalram_pages = current_pages;
 477         target_pages  = current_pages;
 478         balloon_low   = 0;
 479         balloon_high  = 0;
 480         driver_pages  = 0UL;
 481         hard_limit    = ~0UL;
 482
 483         init_timer(&balloon_timer);
 484         balloon_timer.data = 0;
 485         balloon_timer.function = balloon_alarm;
 486
 487 #ifdef CONFIG_PROC_FS
 488         if ((balloon_pde = create_xen_proc_entry("balloon", 0644)) == NULL) {
 489                 WPRINTK("Unable to create /proc/xen/balloon.\n");
 490                 return -1;
 491         }
 492
 493         balloon_pde->read_proc  = balloon_read;
 494         balloon_pde->write_proc = balloon_write;
 495 #endif
 496
 497         /* Initialise the balloon with excess memory space. */
 498         for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
 499                 page = pfn_to_page(pfn);
 500                 if (!PageReserved(page))
 501                         balloon_append(page);
 502         }
 503
 504         target_watch.callback = watch_target;
 505         xenstore_notifier.notifier_call = balloon_init_watcher;
 506
 507         register_xenstore_notifier(&xenstore_notifier);
 508
 509         return 0;
 510 }
 511
 512 subsys_initcall(balloon_init);
 513
 514 void balloon_update_driver_allowance(long delta)
 515 {
 516         unsigned long flags;
 517
 518         balloon_lock(flags);
 519         driver_pages += delta;
 520         balloon_unlock(flags);
 521 }
 522
 523 static int dealloc_pte_fn(
 524         pte_t *pte, struct page *pmd_page, unsigned long addr, void *data)
 525 {
 526         unsigned long mfn = pte_mfn(*pte);
 527         int ret;
 528         struct xen_memory_reservation reservation = {
 529                 .nr_extents   = 1,
 530                 .extent_order = 0,
 531                 .domid        = DOMID_SELF
 532         };
 533         set_xen_guest_handle(reservation.extent_start, &mfn);
 534         set_pte_at(&init_mm, addr, pte, __pte_ma(0));
 535         set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY);
 536         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
 537         BUG_ON(ret != 1);
 538         return 0;
 539 }
 540
 541 struct page *balloon_alloc_empty_page_range(unsigned long nr_pages)
 542 {
 543         unsigned long vstart, flags;
 544         unsigned int  order = get_order(nr_pages * PAGE_SIZE);
 545         int ret;
 546         unsigned long i;
 547         struct page *page;
 548
 549         vstart = __get_free_pages(GFP_KERNEL, order);
 550         if (vstart == 0)
 551                 return NULL;
 552
 553         scrub_pages(vstart, 1 << order);
 554
 555         balloon_lock(flags);
 556         if (xen_feature(XENFEAT_auto_translated_physmap)) {
 557                 unsigned long gmfn = __pa(vstart) >> PAGE_SHIFT;
 558                 struct xen_memory_reservation reservation = {
 559                         .nr_extents   = 1,
 560                         .extent_order = order,
 561                         .domid        = DOMID_SELF
 562                 };
 563                 set_xen_guest_handle(reservation.extent_start, &gmfn);
 564                 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
 565                                            &reservation);
 566                 if (ret == -ENOSYS)
 567                         goto err;
 568                 BUG_ON(ret != 1);
 569         } else {
 570                 ret = apply_to_page_range(&init_mm, vstart, PAGE_SIZE << order,
 571                                           dealloc_pte_fn, NULL);
 572                 if (ret == -ENOSYS)
 573                         goto err;
 574                 BUG_ON(ret);
 575         }
 576         current_pages -= 1UL << order;
 577         totalram_pages = current_pages;
 578         balloon_unlock(flags);
 579
 580         schedule_work(&balloon_worker);
 581
 582         flush_tlb_all();
 583
 584         page = virt_to_page(vstart);
 585
 586         for (i = 0; i < (1UL << order); i++)
 587                 init_page_count(page + i);
 588
 589         return page;
 590
 591  err:
 592         free_pages(vstart, order);
 593         balloon_unlock(flags);
 594         return NULL;
 595 }
 596
 597 void balloon_dealloc_empty_page_range(
 598         struct page *page, unsigned long nr_pages)
 599 {
 600         unsigned long i, flags;
 601         unsigned int  order = get_order(nr_pages * PAGE_SIZE);
 602
 603         balloon_lock(flags);
 604         for (i = 0; i < (1UL << order); i++) {
 605                 BUG_ON(page_count(page + i) != 1);
 606                 balloon_append(page + i);
 607         }
 608         balloon_unlock(flags);
 609
 610         schedule_work(&balloon_worker);
 611 }
 612
 613 EXPORT_SYMBOL_GPL(balloon_update_driver_allowance);
 614 EXPORT_SYMBOL_GPL(balloon_alloc_empty_page_range);
 615 EXPORT_SYMBOL_GPL(balloon_dealloc_empty_page_range);
 616
 617 MODULE_LICENSE("Dual BSD/GPL");