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 #include <xen/interface/xen.h> 56 #include <xen/interface/memory.h> 57 #include <xen/xenbus.h> 58 #include <xen/features.h> 59 #include <xen/page.h> 60 61 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10)) 62 63 #define BALLOON_CLASS_NAME "xen_memory" 64 65 struct balloon_stats { 66 /* We aim for 'current allocation' == 'target allocation'. */ 67 unsigned long current_pages; 68 unsigned long target_pages; 69 /* We may hit the hard limit in Xen. If we do then we remember it. */ 70 unsigned long hard_limit; 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 } 140 141 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */ 142 static struct page *balloon_retrieve(void) 143 { 144 struct page *page; 145 146 if (list_empty(&ballooned_pages)) 147 return NULL; 148 149 page = list_entry(ballooned_pages.next, struct page, lru); 150 list_del(&page->lru); 151 152 if (PageHighMem(page)) { 153 balloon_stats.balloon_high--; 154 inc_totalhigh_pages(); 155 } 156 else 157 balloon_stats.balloon_low--; 158 159 return page; 160 } 161 162 static struct page *balloon_first_page(void) 163 { 164 if (list_empty(&ballooned_pages)) 165 return NULL; 166 return list_entry(ballooned_pages.next, struct page, lru); 167 } 168 169 static struct page *balloon_next_page(struct page *page) 170 { 171 struct list_head *next = page->lru.next; 172 if (next == &ballooned_pages) 173 return NULL; 174 return list_entry(next, struct page, lru); 175 } 176 177 static void balloon_alarm(unsigned long unused) 178 { 179 schedule_work(&balloon_worker); 180 } 181 182 static unsigned long current_target(void) 183 { 184 unsigned long target = min(balloon_stats.target_pages, balloon_stats.hard_limit); 185 186 target = min(target, 187 balloon_stats.current_pages + 188 balloon_stats.balloon_low + 189 balloon_stats.balloon_high); 190 191 return target; 192 } 193 194 static int increase_reservation(unsigned long nr_pages) 195 { 196 unsigned long pfn, i, flags; 197 struct page *page; 198 long rc; 199 struct xen_memory_reservation reservation = { 200 .address_bits = 0, 201 .extent_order = 0, 202 .domid = DOMID_SELF 203 }; 204 205 if (nr_pages > ARRAY_SIZE(frame_list)) 206 nr_pages = ARRAY_SIZE(frame_list); 207 208 spin_lock_irqsave(&balloon_lock, flags); 209 210 page = balloon_first_page(); 211 for (i = 0; i < nr_pages; i++) { 212 BUG_ON(page == NULL); 213 frame_list[i] = page_to_pfn(page); 214 page = balloon_next_page(page); 215 } 216 217 set_xen_guest_handle(reservation.extent_start, frame_list); 218 reservation.nr_extents = nr_pages; 219 rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation); 220 if (rc < nr_pages) { 221 if (rc > 0) { 222 int ret; 223 224 /* We hit the Xen hard limit: reprobe. */ 225 reservation.nr_extents = rc; 226 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, 227 &reservation); 228 BUG_ON(ret != rc); 229 } 230 if (rc >= 0) 231 balloon_stats.hard_limit = (balloon_stats.current_pages + rc - 232 balloon_stats.driver_pages); 233 goto out; 234 } 235 236 for (i = 0; i < nr_pages; i++) { 237 page = balloon_retrieve(); 238 BUG_ON(page == NULL); 239 240 pfn = page_to_pfn(page); 241 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) && 242 phys_to_machine_mapping_valid(pfn)); 243 244 set_phys_to_machine(pfn, frame_list[i]); 245 246 /* Link back into the page tables if not highmem. */ 247 if (pfn < max_low_pfn) { 248 int ret; 249 ret = HYPERVISOR_update_va_mapping( 250 (unsigned long)__va(pfn << PAGE_SHIFT), 251 mfn_pte(frame_list[i], PAGE_KERNEL), 252 0); 253 BUG_ON(ret); 254 } 255 256 /* Relinquish the page back to the allocator. */ 257 ClearPageReserved(page); 258 init_page_count(page); 259 __free_page(page); 260 } 261 262 balloon_stats.current_pages += nr_pages; 263 totalram_pages = balloon_stats.current_pages; 264 265 out: 266 spin_unlock_irqrestore(&balloon_lock, flags); 267 268 return 0; 269 } 270 271 static int decrease_reservation(unsigned long nr_pages) 272 { 273 unsigned long pfn, i, flags; 274 struct page *page; 275 int need_sleep = 0; 276 int ret; 277 struct xen_memory_reservation reservation = { 278 .address_bits = 0, 279 .extent_order = 0, 280 .domid = DOMID_SELF 281 }; 282 283 if (nr_pages > ARRAY_SIZE(frame_list)) 284 nr_pages = ARRAY_SIZE(frame_list); 285 286 for (i = 0; i < nr_pages; i++) { 287 if ((page = alloc_page(GFP_BALLOON)) == NULL) { 288 nr_pages = i; 289 need_sleep = 1; 290 break; 291 } 292 293 pfn = page_to_pfn(page); 294 frame_list[i] = pfn_to_mfn(pfn); 295 296 scrub_page(page); 297 298 if (!PageHighMem(page)) { 299 ret = HYPERVISOR_update_va_mapping( 300 (unsigned long)__va(pfn << PAGE_SHIFT), 301 __pte_ma(0), 0); 302 BUG_ON(ret); 303 } 304 305 } 306 307 /* Ensure that ballooned highmem pages don't have kmaps. */ 308 kmap_flush_unused(); 309 flush_tlb_all(); 310 311 spin_lock_irqsave(&balloon_lock, flags); 312 313 /* No more mappings: invalidate P2M and add to balloon. */ 314 for (i = 0; i < nr_pages; i++) { 315 pfn = mfn_to_pfn(frame_list[i]); 316 set_phys_to_machine(pfn, INVALID_P2M_ENTRY); 317 balloon_append(pfn_to_page(pfn)); 318 } 319 320 set_xen_guest_handle(reservation.extent_start, frame_list); 321 reservation.nr_extents = nr_pages; 322 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); 323 BUG_ON(ret != nr_pages); 324 325 balloon_stats.current_pages -= nr_pages; 326 totalram_pages = balloon_stats.current_pages; 327 328 spin_unlock_irqrestore(&balloon_lock, flags); 329 330 return need_sleep; 331 } 332 333 /* 334 * We avoid multiple worker processes conflicting via the balloon mutex. 335 * We may of course race updates of the target counts (which are protected 336 * by the balloon lock), or with changes to the Xen hard limit, but we will 337 * recover from these in time. 338 */ 339 static void balloon_process(struct work_struct *work) 340 { 341 int need_sleep = 0; 342 long credit; 343 344 mutex_lock(&balloon_mutex); 345 346 do { 347 credit = current_target() - balloon_stats.current_pages; 348 if (credit > 0) 349 need_sleep = (increase_reservation(credit) != 0); 350 if (credit < 0) 351 need_sleep = (decrease_reservation(-credit) != 0); 352 353 #ifndef CONFIG_PREEMPT 354 if (need_resched()) 355 schedule(); 356 #endif 357 } while ((credit != 0) && !need_sleep); 358 359 /* Schedule more work if there is some still to be done. */ 360 if (current_target() != balloon_stats.current_pages) 361 mod_timer(&balloon_timer, jiffies + HZ); 362 363 mutex_unlock(&balloon_mutex); 364 } 365 366 /* Resets the Xen limit, sets new target, and kicks off processing. */ 367 static void balloon_set_new_target(unsigned long target) 368 { 369 /* No need for lock. Not read-modify-write updates. */ 370 balloon_stats.hard_limit = ~0UL; 371 balloon_stats.target_pages = target; 372 schedule_work(&balloon_worker); 373 } 374 375 static struct xenbus_watch target_watch = 376 { 377 .node = "memory/target" 378 }; 379 380 /* React to a change in the target key */ 381 static void watch_target(struct xenbus_watch *watch, 382 const char **vec, unsigned int len) 383 { 384 unsigned long long new_target; 385 int err; 386 387 err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target); 388 if (err != 1) { 389 /* This is ok (for domain0 at least) - so just return */ 390 return; 391 } 392 393 /* The given memory/target value is in KiB, so it needs converting to 394 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10. 395 */ 396 balloon_set_new_target(new_target >> (PAGE_SHIFT - 10)); 397 } 398 399 static int balloon_init_watcher(struct notifier_block *notifier, 400 unsigned long event, 401 void *data) 402 { 403 int err; 404 405 err = register_xenbus_watch(&target_watch); 406 if (err) 407 printk(KERN_ERR "Failed to set balloon watcher\n"); 408 409 return NOTIFY_DONE; 410 } 411 412 static struct notifier_block xenstore_notifier; 413 414 static int __init balloon_init(void) 415 { 416 unsigned long pfn; 417 struct page *page; 418 419 if (!xen_pv_domain()) 420 return -ENODEV; 421 422 pr_info("xen_balloon: Initialising balloon driver.\n"); 423 424 balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn); 425 totalram_pages = balloon_stats.current_pages; 426 balloon_stats.target_pages = balloon_stats.current_pages; 427 balloon_stats.balloon_low = 0; 428 balloon_stats.balloon_high = 0; 429 balloon_stats.driver_pages = 0UL; 430 balloon_stats.hard_limit = ~0UL; 431 432 init_timer(&balloon_timer); 433 balloon_timer.data = 0; 434 balloon_timer.function = balloon_alarm; 435 436 register_balloon(&balloon_sysdev); 437 438 /* Initialise the balloon with excess memory space. */ 439 for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) { 440 page = pfn_to_page(pfn); 441 if (!PageReserved(page)) 442 balloon_append(page); 443 } 444 445 target_watch.callback = watch_target; 446 xenstore_notifier.notifier_call = balloon_init_watcher; 447 448 register_xenstore_notifier(&xenstore_notifier); 449 450 return 0; 451 } 452 453 subsys_initcall(balloon_init); 454 455 static void balloon_exit(void) 456 { 457 /* XXX - release balloon here */ 458 return; 459 } 460 461 module_exit(balloon_exit); 462 463 #define BALLOON_SHOW(name, format, args...) \ 464 static ssize_t show_##name(struct sys_device *dev, \ 465 struct sysdev_attribute *attr, \ 466 char *buf) \ 467 { \ 468 return sprintf(buf, format, ##args); \ 469 } \ 470 static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL) 471 472 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages)); 473 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low)); 474 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high)); 475 BALLOON_SHOW(hard_limit_kb, 476 (balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n", 477 (balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0); 478 BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages)); 479 480 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr, 481 char *buf) 482 { 483 return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages)); 484 } 485 486 static ssize_t store_target_kb(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 = simple_strtoull(buf, &endchar, 0) * 1024; 498 499 balloon_set_new_target(target_bytes >> PAGE_SHIFT); 500 501 return count; 502 } 503 504 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR, 505 show_target_kb, store_target_kb); 506 507 508 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr, 509 char *buf) 510 { 511 return sprintf(buf, "%llu\n", 512 (unsigned long long)balloon_stats.target_pages 513 << PAGE_SHIFT); 514 } 515 516 static ssize_t store_target(struct sys_device *dev, 517 struct sysdev_attribute *attr, 518 const char *buf, 519 size_t count) 520 { 521 char *endchar; 522 unsigned long long target_bytes; 523 524 if (!capable(CAP_SYS_ADMIN)) 525 return -EPERM; 526 527 target_bytes = memparse(buf, &endchar); 528 529 balloon_set_new_target(target_bytes >> PAGE_SHIFT); 530 531 return count; 532 } 533 534 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR, 535 show_target, store_target); 536 537 538 static struct sysdev_attribute *balloon_attrs[] = { 539 &attr_target_kb, 540 &attr_target, 541 }; 542 543 static struct attribute *balloon_info_attrs[] = { 544 &attr_current_kb.attr, 545 &attr_low_kb.attr, 546 &attr_high_kb.attr, 547 &attr_hard_limit_kb.attr, 548 &attr_driver_kb.attr, 549 NULL 550 }; 551 552 static struct attribute_group balloon_info_group = { 553 .name = "info", 554 .attrs = balloon_info_attrs, 555 }; 556 557 static struct sysdev_class balloon_sysdev_class = { 558 .name = BALLOON_CLASS_NAME, 559 }; 560 561 static int register_balloon(struct sys_device *sysdev) 562 { 563 int i, error; 564 565 error = sysdev_class_register(&balloon_sysdev_class); 566 if (error) 567 return error; 568 569 sysdev->id = 0; 570 sysdev->cls = &balloon_sysdev_class; 571 572 error = sysdev_register(sysdev); 573 if (error) { 574 sysdev_class_unregister(&balloon_sysdev_class); 575 return error; 576 } 577 578 for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) { 579 error = sysdev_create_file(sysdev, balloon_attrs[i]); 580 if (error) 581 goto fail; 582 } 583 584 error = sysfs_create_group(&sysdev->kobj, &balloon_info_group); 585 if (error) 586 goto fail; 587 588 return 0; 589 590 fail: 591 while (--i >= 0) 592 sysdev_remove_file(sysdev, balloon_attrs[i]); 593 sysdev_unregister(sysdev); 594 sysdev_class_unregister(&balloon_sysdev_class); 595 return error; 596 } 597 598 MODULE_LICENSE("GPL"); 599