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 /* 70 * balloon_process() state: 71 * 72 * BP_DONE: done or nothing to do, 73 * BP_EAGAIN: error, go to sleep, 74 * BP_ECANCELED: error, balloon operation canceled. 75 */ 76 77 enum bp_state { 78 BP_DONE, 79 BP_EAGAIN, 80 BP_ECANCELED 81 }; 82 83 #define RETRY_UNLIMITED 0 84 85 struct balloon_stats { 86 /* We aim for 'current allocation' == 'target allocation'. */ 87 unsigned long current_pages; 88 unsigned long target_pages; 89 /* Number of pages in high- and low-memory balloons. */ 90 unsigned long balloon_low; 91 unsigned long balloon_high; 92 unsigned long schedule_delay; 93 unsigned long max_schedule_delay; 94 unsigned long retry_count; 95 unsigned long max_retry_count; 96 }; 97 98 static DEFINE_MUTEX(balloon_mutex); 99 100 static struct sys_device balloon_sysdev; 101 102 static int register_balloon(struct sys_device *sysdev); 103 104 static struct balloon_stats balloon_stats; 105 106 /* We increase/decrease in batches which fit in a page */ 107 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)]; 108 109 #ifdef CONFIG_HIGHMEM 110 #define inc_totalhigh_pages() (totalhigh_pages++) 111 #define dec_totalhigh_pages() (totalhigh_pages--) 112 #else 113 #define inc_totalhigh_pages() do {} while(0) 114 #define dec_totalhigh_pages() do {} while(0) 115 #endif 116 117 /* List of ballooned pages, threaded through the mem_map array. */ 118 static LIST_HEAD(ballooned_pages); 119 120 /* Main work function, always executed in process context. */ 121 static void balloon_process(struct work_struct *work); 122 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process); 123 124 /* When ballooning out (allocating memory to return to Xen) we don't really 125 want the kernel to try too hard since that can trigger the oom killer. */ 126 #define GFP_BALLOON \ 127 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC) 128 129 static void scrub_page(struct page *page) 130 { 131 #ifdef CONFIG_XEN_SCRUB_PAGES 132 clear_highpage(page); 133 #endif 134 } 135 136 /* balloon_append: add the given page to the balloon. */ 137 static void __balloon_append(struct page *page) 138 { 139 /* Lowmem is re-populated first, so highmem pages go at list tail. */ 140 if (PageHighMem(page)) { 141 list_add_tail(&page->lru, &ballooned_pages); 142 balloon_stats.balloon_high++; 143 dec_totalhigh_pages(); 144 } else { 145 list_add(&page->lru, &ballooned_pages); 146 balloon_stats.balloon_low++; 147 } 148 } 149 150 static void balloon_append(struct page *page) 151 { 152 __balloon_append(page); 153 totalram_pages--; 154 } 155 156 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */ 157 static struct page *balloon_retrieve(void) 158 { 159 struct page *page; 160 161 if (list_empty(&ballooned_pages)) 162 return NULL; 163 164 page = list_entry(ballooned_pages.next, struct page, lru); 165 list_del(&page->lru); 166 167 if (PageHighMem(page)) { 168 balloon_stats.balloon_high--; 169 inc_totalhigh_pages(); 170 } 171 else 172 balloon_stats.balloon_low--; 173 174 totalram_pages++; 175 176 return page; 177 } 178 179 static struct page *balloon_first_page(void) 180 { 181 if (list_empty(&ballooned_pages)) 182 return NULL; 183 return list_entry(ballooned_pages.next, struct page, lru); 184 } 185 186 static struct page *balloon_next_page(struct page *page) 187 { 188 struct list_head *next = page->lru.next; 189 if (next == &ballooned_pages) 190 return NULL; 191 return list_entry(next, struct page, lru); 192 } 193 194 static enum bp_state update_schedule(enum bp_state state) 195 { 196 if (state == BP_DONE) { 197 balloon_stats.schedule_delay = 1; 198 balloon_stats.retry_count = 1; 199 return BP_DONE; 200 } 201 202 ++balloon_stats.retry_count; 203 204 if (balloon_stats.max_retry_count != RETRY_UNLIMITED && 205 balloon_stats.retry_count > balloon_stats.max_retry_count) { 206 balloon_stats.schedule_delay = 1; 207 balloon_stats.retry_count = 1; 208 return BP_ECANCELED; 209 } 210 211 balloon_stats.schedule_delay <<= 1; 212 213 if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay) 214 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay; 215 216 return BP_EAGAIN; 217 } 218 219 static unsigned long current_target(void) 220 { 221 unsigned long target = balloon_stats.target_pages; 222 223 target = min(target, 224 balloon_stats.current_pages + 225 balloon_stats.balloon_low + 226 balloon_stats.balloon_high); 227 228 return target; 229 } 230 231 static enum bp_state increase_reservation(unsigned long nr_pages) 232 { 233 int rc; 234 unsigned long pfn, i; 235 struct page *page; 236 struct xen_memory_reservation reservation = { 237 .address_bits = 0, 238 .extent_order = 0, 239 .domid = DOMID_SELF 240 }; 241 242 if (nr_pages > ARRAY_SIZE(frame_list)) 243 nr_pages = ARRAY_SIZE(frame_list); 244 245 page = balloon_first_page(); 246 for (i = 0; i < nr_pages; i++) { 247 if (!page) { 248 nr_pages = i; 249 break; 250 } 251 frame_list[i] = page_to_pfn(page); 252 page = balloon_next_page(page); 253 } 254 255 set_xen_guest_handle(reservation.extent_start, frame_list); 256 reservation.nr_extents = nr_pages; 257 rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation); 258 if (rc <= 0) 259 return BP_EAGAIN; 260 261 for (i = 0; i < rc; i++) { 262 page = balloon_retrieve(); 263 BUG_ON(page == NULL); 264 265 pfn = page_to_pfn(page); 266 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) && 267 phys_to_machine_mapping_valid(pfn)); 268 269 set_phys_to_machine(pfn, frame_list[i]); 270 271 /* Link back into the page tables if not highmem. */ 272 if (pfn < max_low_pfn) { 273 int ret; 274 ret = HYPERVISOR_update_va_mapping( 275 (unsigned long)__va(pfn << PAGE_SHIFT), 276 mfn_pte(frame_list[i], PAGE_KERNEL), 277 0); 278 BUG_ON(ret); 279 } 280 281 /* Relinquish the page back to the allocator. */ 282 ClearPageReserved(page); 283 init_page_count(page); 284 __free_page(page); 285 } 286 287 balloon_stats.current_pages += rc; 288 289 return BP_DONE; 290 } 291 292 static enum bp_state decrease_reservation(unsigned long nr_pages) 293 { 294 enum bp_state state = BP_DONE; 295 unsigned long pfn, i; 296 struct page *page; 297 int ret; 298 struct xen_memory_reservation reservation = { 299 .address_bits = 0, 300 .extent_order = 0, 301 .domid = DOMID_SELF 302 }; 303 304 if (nr_pages > ARRAY_SIZE(frame_list)) 305 nr_pages = ARRAY_SIZE(frame_list); 306 307 for (i = 0; i < nr_pages; i++) { 308 if ((page = alloc_page(GFP_BALLOON)) == NULL) { 309 nr_pages = i; 310 state = BP_EAGAIN; 311 break; 312 } 313 314 pfn = page_to_pfn(page); 315 frame_list[i] = pfn_to_mfn(pfn); 316 317 scrub_page(page); 318 319 if (!PageHighMem(page)) { 320 ret = HYPERVISOR_update_va_mapping( 321 (unsigned long)__va(pfn << PAGE_SHIFT), 322 __pte_ma(0), 0); 323 BUG_ON(ret); 324 } 325 326 } 327 328 /* Ensure that ballooned highmem pages don't have kmaps. */ 329 kmap_flush_unused(); 330 flush_tlb_all(); 331 332 /* No more mappings: invalidate P2M and add to balloon. */ 333 for (i = 0; i < nr_pages; i++) { 334 pfn = mfn_to_pfn(frame_list[i]); 335 set_phys_to_machine(pfn, INVALID_P2M_ENTRY); 336 balloon_append(pfn_to_page(pfn)); 337 } 338 339 set_xen_guest_handle(reservation.extent_start, frame_list); 340 reservation.nr_extents = nr_pages; 341 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); 342 BUG_ON(ret != nr_pages); 343 344 balloon_stats.current_pages -= nr_pages; 345 346 return state; 347 } 348 349 /* 350 * We avoid multiple worker processes conflicting via the balloon mutex. 351 * We may of course race updates of the target counts (which are protected 352 * by the balloon lock), or with changes to the Xen hard limit, but we will 353 * recover from these in time. 354 */ 355 static void balloon_process(struct work_struct *work) 356 { 357 enum bp_state state = BP_DONE; 358 long credit; 359 360 mutex_lock(&balloon_mutex); 361 362 do { 363 credit = current_target() - balloon_stats.current_pages; 364 365 if (credit > 0) 366 state = increase_reservation(credit); 367 368 if (credit < 0) 369 state = decrease_reservation(-credit); 370 371 state = update_schedule(state); 372 373 #ifndef CONFIG_PREEMPT 374 if (need_resched()) 375 schedule(); 376 #endif 377 } while (credit && state == BP_DONE); 378 379 /* Schedule more work if there is some still to be done. */ 380 if (state == BP_EAGAIN) 381 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ); 382 383 mutex_unlock(&balloon_mutex); 384 } 385 386 /* Resets the Xen limit, sets new target, and kicks off processing. */ 387 static void balloon_set_new_target(unsigned long target) 388 { 389 /* No need for lock. Not read-modify-write updates. */ 390 balloon_stats.target_pages = target; 391 schedule_delayed_work(&balloon_worker, 0); 392 } 393 394 static struct xenbus_watch target_watch = 395 { 396 .node = "memory/target" 397 }; 398 399 /* React to a change in the target key */ 400 static void watch_target(struct xenbus_watch *watch, 401 const char **vec, unsigned int len) 402 { 403 unsigned long long new_target; 404 int err; 405 406 err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target); 407 if (err != 1) { 408 /* This is ok (for domain0 at least) - so just return */ 409 return; 410 } 411 412 /* The given memory/target value is in KiB, so it needs converting to 413 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10. 414 */ 415 balloon_set_new_target(new_target >> (PAGE_SHIFT - 10)); 416 } 417 418 static int balloon_init_watcher(struct notifier_block *notifier, 419 unsigned long event, 420 void *data) 421 { 422 int err; 423 424 err = register_xenbus_watch(&target_watch); 425 if (err) 426 printk(KERN_ERR "Failed to set balloon watcher\n"); 427 428 return NOTIFY_DONE; 429 } 430 431 static struct notifier_block xenstore_notifier; 432 433 static int __init balloon_init(void) 434 { 435 unsigned long pfn, extra_pfn_end; 436 struct page *page; 437 438 if (!xen_pv_domain()) 439 return -ENODEV; 440 441 pr_info("xen_balloon: Initialising balloon driver.\n"); 442 443 balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn); 444 balloon_stats.target_pages = balloon_stats.current_pages; 445 balloon_stats.balloon_low = 0; 446 balloon_stats.balloon_high = 0; 447 448 balloon_stats.schedule_delay = 1; 449 balloon_stats.max_schedule_delay = 32; 450 balloon_stats.retry_count = 1; 451 balloon_stats.max_retry_count = RETRY_UNLIMITED; 452 453 register_balloon(&balloon_sysdev); 454 455 /* 456 * Initialise the balloon with excess memory space. We need 457 * to make sure we don't add memory which doesn't exist or 458 * logically exist. The E820 map can be trimmed to be smaller 459 * than the amount of physical memory due to the mem= command 460 * line parameter. And if this is a 32-bit non-HIGHMEM kernel 461 * on a system with memory which requires highmem to access, 462 * don't try to use it. 463 */ 464 extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()), 465 (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size)); 466 for (pfn = PFN_UP(xen_extra_mem_start); 467 pfn < extra_pfn_end; 468 pfn++) { 469 page = pfn_to_page(pfn); 470 /* totalram_pages doesn't include the boot-time 471 balloon extension, so don't subtract from it. */ 472 __balloon_append(page); 473 } 474 475 target_watch.callback = watch_target; 476 xenstore_notifier.notifier_call = balloon_init_watcher; 477 478 register_xenstore_notifier(&xenstore_notifier); 479 480 return 0; 481 } 482 483 subsys_initcall(balloon_init); 484 485 static void balloon_exit(void) 486 { 487 /* XXX - release balloon here */ 488 return; 489 } 490 491 module_exit(balloon_exit); 492 493 #define BALLOON_SHOW(name, format, args...) \ 494 static ssize_t show_##name(struct sys_device *dev, \ 495 struct sysdev_attribute *attr, \ 496 char *buf) \ 497 { \ 498 return sprintf(buf, format, ##args); \ 499 } \ 500 static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL) 501 502 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages)); 503 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low)); 504 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high)); 505 506 static SYSDEV_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay); 507 static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay); 508 static SYSDEV_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count); 509 static SYSDEV_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count); 510 511 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr, 512 char *buf) 513 { 514 return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages)); 515 } 516 517 static ssize_t store_target_kb(struct sys_device *dev, 518 struct sysdev_attribute *attr, 519 const char *buf, 520 size_t count) 521 { 522 char *endchar; 523 unsigned long long target_bytes; 524 525 if (!capable(CAP_SYS_ADMIN)) 526 return -EPERM; 527 528 target_bytes = simple_strtoull(buf, &endchar, 0) * 1024; 529 530 balloon_set_new_target(target_bytes >> PAGE_SHIFT); 531 532 return count; 533 } 534 535 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR, 536 show_target_kb, store_target_kb); 537 538 539 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr, 540 char *buf) 541 { 542 return sprintf(buf, "%llu\n", 543 (unsigned long long)balloon_stats.target_pages 544 << PAGE_SHIFT); 545 } 546 547 static ssize_t store_target(struct sys_device *dev, 548 struct sysdev_attribute *attr, 549 const char *buf, 550 size_t count) 551 { 552 char *endchar; 553 unsigned long long target_bytes; 554 555 if (!capable(CAP_SYS_ADMIN)) 556 return -EPERM; 557 558 target_bytes = memparse(buf, &endchar); 559 560 balloon_set_new_target(target_bytes >> PAGE_SHIFT); 561 562 return count; 563 } 564 565 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR, 566 show_target, store_target); 567 568 569 static struct sysdev_attribute *balloon_attrs[] = { 570 &attr_target_kb, 571 &attr_target, 572 &attr_schedule_delay.attr, 573 &attr_max_schedule_delay.attr, 574 &attr_retry_count.attr, 575 &attr_max_retry_count.attr 576 }; 577 578 static struct attribute *balloon_info_attrs[] = { 579 &attr_current_kb.attr, 580 &attr_low_kb.attr, 581 &attr_high_kb.attr, 582 NULL 583 }; 584 585 static struct attribute_group balloon_info_group = { 586 .name = "info", 587 .attrs = balloon_info_attrs, 588 }; 589 590 static struct sysdev_class balloon_sysdev_class = { 591 .name = BALLOON_CLASS_NAME, 592 }; 593 594 static int register_balloon(struct sys_device *sysdev) 595 { 596 int i, error; 597 598 error = sysdev_class_register(&balloon_sysdev_class); 599 if (error) 600 return error; 601 602 sysdev->id = 0; 603 sysdev->cls = &balloon_sysdev_class; 604 605 error = sysdev_register(sysdev); 606 if (error) { 607 sysdev_class_unregister(&balloon_sysdev_class); 608 return error; 609 } 610 611 for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) { 612 error = sysdev_create_file(sysdev, balloon_attrs[i]); 613 if (error) 614 goto fail; 615 } 616 617 error = sysfs_create_group(&sysdev->kobj, &balloon_info_group); 618 if (error) 619 goto fail; 620 621 return 0; 622 623 fail: 624 while (--i >= 0) 625 sysdev_remove_file(sysdev, balloon_attrs[i]); 626 sysdev_unregister(sysdev); 627 sysdev_class_unregister(&balloon_sysdev_class); 628 return error; 629 } 630 631 MODULE_LICENSE("GPL"); 632