1/* 2 * Collaborative memory management interface. 3 * 4 * Copyright (C) 2008 IBM Corporation 5 * Author(s): Brian King (brking@linux.vnet.ibm.com), 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, write to the Free Software 19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 20 * 21 */ 22 23#include <linux/ctype.h> 24#include <linux/delay.h> 25#include <linux/errno.h> 26#include <linux/fs.h> 27#include <linux/gfp.h> 28#include <linux/init.h> 29#include <linux/kthread.h> 30#include <linux/module.h> 31#include <linux/oom.h> 32#include <linux/reboot.h> 33#include <linux/sched.h> 34#include <linux/stringify.h> 35#include <linux/swap.h> 36#include <linux/sysdev.h> 37#include <asm/firmware.h> 38#include <asm/hvcall.h> 39#include <asm/mmu.h> 40#include <asm/pgalloc.h> 41#include <asm/uaccess.h> 42#include <linux/memory.h> 43 44#include "plpar_wrappers.h" 45 46#define CMM_DRIVER_VERSION "1.0.0" 47#define CMM_DEFAULT_DELAY 1 48#define CMM_HOTPLUG_DELAY 5 49#define CMM_DEBUG 0 50#define CMM_DISABLE 0 51#define CMM_OOM_KB 1024 52#define CMM_MIN_MEM_MB 256 53#define KB2PAGES(_p) ((_p)>>(PAGE_SHIFT-10)) 54#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10)) 55/* 56 * The priority level tries to ensure that this notifier is called as 57 * late as possible to reduce thrashing in the shared memory pool. 58 */ 59#define CMM_MEM_HOTPLUG_PRI 1 60#define CMM_MEM_ISOLATE_PRI 15 61 62static unsigned int delay = CMM_DEFAULT_DELAY; 63static unsigned int hotplug_delay = CMM_HOTPLUG_DELAY; 64static unsigned int oom_kb = CMM_OOM_KB; 65static unsigned int cmm_debug = CMM_DEBUG; 66static unsigned int cmm_disabled = CMM_DISABLE; 67static unsigned long min_mem_mb = CMM_MIN_MEM_MB; 68static struct sys_device cmm_sysdev; 69 70MODULE_AUTHOR("Brian King <brking@linux.vnet.ibm.com>"); 71MODULE_DESCRIPTION("IBM System p Collaborative Memory Manager"); 72MODULE_LICENSE("GPL"); 73MODULE_VERSION(CMM_DRIVER_VERSION); 74 75module_param_named(delay, delay, uint, S_IRUGO | S_IWUSR); 76MODULE_PARM_DESC(delay, "Delay (in seconds) between polls to query hypervisor paging requests. " 77 "[Default=" __stringify(CMM_DEFAULT_DELAY) "]"); 78module_param_named(hotplug_delay, hotplug_delay, uint, S_IRUGO | S_IWUSR); 79MODULE_PARM_DESC(delay, "Delay (in seconds) after memory hotplug remove " 80 "before loaning resumes. " 81 "[Default=" __stringify(CMM_HOTPLUG_DELAY) "]"); 82module_param_named(oom_kb, oom_kb, uint, S_IRUGO | S_IWUSR); 83MODULE_PARM_DESC(oom_kb, "Amount of memory in kb to free on OOM. " 84 "[Default=" __stringify(CMM_OOM_KB) "]"); 85module_param_named(min_mem_mb, min_mem_mb, ulong, S_IRUGO | S_IWUSR); 86MODULE_PARM_DESC(min_mem_mb, "Minimum amount of memory (in MB) to not balloon. " 87 "[Default=" __stringify(CMM_MIN_MEM_MB) "]"); 88module_param_named(debug, cmm_debug, uint, S_IRUGO | S_IWUSR); 89MODULE_PARM_DESC(debug, "Enable module debugging logging. Set to 1 to enable. " 90 "[Default=" __stringify(CMM_DEBUG) "]"); 91 92#define CMM_NR_PAGES ((PAGE_SIZE - sizeof(void *) - sizeof(unsigned long)) / sizeof(unsigned long)) 93 94#define cmm_dbg(...) if (cmm_debug) { printk(KERN_INFO "cmm: "__VA_ARGS__); } 95 96struct cmm_page_array { 97 struct cmm_page_array *next; 98 unsigned long index; 99 unsigned long page[CMM_NR_PAGES]; 100}; 101 102static unsigned long loaned_pages; 103static unsigned long loaned_pages_target; 104static unsigned long oom_freed_pages; 105 106static struct cmm_page_array *cmm_page_list; 107static DEFINE_SPINLOCK(cmm_lock); 108 109static DEFINE_MUTEX(hotplug_mutex); 110static int hotplug_occurred; /* protected by the hotplug mutex */ 111 112static struct task_struct *cmm_thread_ptr; 113 114/** 115 * cmm_alloc_pages - Allocate pages and mark them as loaned 116 * @nr: number of pages to allocate 117 * 118 * Return value: 119 * number of pages requested to be allocated which were not 120 **/ 121static long cmm_alloc_pages(long nr) 122{ 123 struct cmm_page_array *pa, *npa; 124 unsigned long addr; 125 long rc; 126 127 cmm_dbg("Begin request for %ld pages\n", nr); 128 129 while (nr) { 130 /* Exit if a hotplug operation is in progress or occurred */ 131 if (mutex_trylock(&hotplug_mutex)) { 132 if (hotplug_occurred) { 133 mutex_unlock(&hotplug_mutex); 134 break; 135 } 136 mutex_unlock(&hotplug_mutex); 137 } else { 138 break; 139 } 140 141 addr = __get_free_page(GFP_NOIO | __GFP_NOWARN | 142 __GFP_NORETRY | __GFP_NOMEMALLOC); 143 if (!addr) 144 break; 145 spin_lock(&cmm_lock); 146 pa = cmm_page_list; 147 if (!pa || pa->index >= CMM_NR_PAGES) { 148 /* Need a new page for the page list. */ 149 spin_unlock(&cmm_lock); 150 npa = (struct cmm_page_array *)__get_free_page( 151 GFP_NOIO | __GFP_NOWARN | 152 __GFP_NORETRY | __GFP_NOMEMALLOC); 153 if (!npa) { 154 pr_info("%s: Can not allocate new page list\n", __func__); 155 free_page(addr); 156 break; 157 } 158 spin_lock(&cmm_lock); 159 pa = cmm_page_list; 160 161 if (!pa || pa->index >= CMM_NR_PAGES) { 162 npa->next = pa; 163 npa->index = 0; 164 pa = npa; 165 cmm_page_list = pa; 166 } else 167 free_page((unsigned long) npa); 168 } 169 170 if ((rc = plpar_page_set_loaned(__pa(addr)))) { 171 pr_err("%s: Can not set page to loaned. rc=%ld\n", __func__, rc); 172 spin_unlock(&cmm_lock); 173 free_page(addr); 174 break; 175 } 176 177 pa->page[pa->index++] = addr; 178 loaned_pages++; 179 totalram_pages--; 180 spin_unlock(&cmm_lock); 181 nr--; 182 } 183 184 cmm_dbg("End request with %ld pages unfulfilled\n", nr); 185 return nr; 186} 187 188/** 189 * cmm_free_pages - Free pages and mark them as active 190 * @nr: number of pages to free 191 * 192 * Return value: 193 * number of pages requested to be freed which were not 194 **/ 195static long cmm_free_pages(long nr) 196{ 197 struct cmm_page_array *pa; 198 unsigned long addr; 199 200 cmm_dbg("Begin free of %ld pages.\n", nr); 201 spin_lock(&cmm_lock); 202 pa = cmm_page_list; 203 while (nr) { 204 if (!pa || pa->index <= 0) 205 break; 206 addr = pa->page[--pa->index]; 207 208 if (pa->index == 0) { 209 pa = pa->next; 210 free_page((unsigned long) cmm_page_list); 211 cmm_page_list = pa; 212 } 213 214 plpar_page_set_active(__pa(addr)); 215 free_page(addr); 216 loaned_pages--; 217 nr--; 218 totalram_pages++; 219 } 220 spin_unlock(&cmm_lock); 221 cmm_dbg("End request with %ld pages unfulfilled\n", nr); 222 return nr; 223} 224 225/** 226 * cmm_oom_notify - OOM notifier 227 * @self: notifier block struct 228 * @dummy: not used 229 * @parm: returned - number of pages freed 230 * 231 * Return value: 232 * NOTIFY_OK 233 **/ 234static int cmm_oom_notify(struct notifier_block *self, 235 unsigned long dummy, void *parm) 236{ 237 unsigned long *freed = parm; 238 long nr = KB2PAGES(oom_kb); 239 240 cmm_dbg("OOM processing started\n"); 241 nr = cmm_free_pages(nr); 242 loaned_pages_target = loaned_pages; 243 *freed += KB2PAGES(oom_kb) - nr; 244 oom_freed_pages += KB2PAGES(oom_kb) - nr; 245 cmm_dbg("OOM processing complete\n"); 246 return NOTIFY_OK; 247} 248 249/** 250 * cmm_get_mpp - Read memory performance parameters 251 * 252 * Makes hcall to query the current page loan request from the hypervisor. 253 * 254 * Return value: 255 * nothing 256 **/ 257static void cmm_get_mpp(void) 258{ 259 int rc; 260 struct hvcall_mpp_data mpp_data; 261 signed long active_pages_target, page_loan_request, target; 262 signed long total_pages = totalram_pages + loaned_pages; 263 signed long min_mem_pages = (min_mem_mb * 1024 * 1024) / PAGE_SIZE; 264 265 rc = h_get_mpp(&mpp_data); 266 267 if (rc != H_SUCCESS) 268 return; 269 270 page_loan_request = div_s64((s64)mpp_data.loan_request, PAGE_SIZE); 271 target = page_loan_request + (signed long)loaned_pages; 272 273 if (target < 0 || total_pages < min_mem_pages) 274 target = 0; 275 276 if (target > oom_freed_pages) 277 target -= oom_freed_pages; 278 else 279 target = 0; 280 281 active_pages_target = total_pages - target; 282 283 if (min_mem_pages > active_pages_target) 284 target = total_pages - min_mem_pages; 285 286 if (target < 0) 287 target = 0; 288 289 loaned_pages_target = target; 290 291 cmm_dbg("delta = %ld, loaned = %lu, target = %lu, oom = %lu, totalram = %lu\n", 292 page_loan_request, loaned_pages, loaned_pages_target, 293 oom_freed_pages, totalram_pages); 294} 295 296static struct notifier_block cmm_oom_nb = { 297 .notifier_call = cmm_oom_notify 298}; 299 300/** 301 * cmm_thread - CMM task thread 302 * @dummy: not used 303 * 304 * Return value: 305 * 0 306 **/ 307static int cmm_thread(void *dummy) 308{ 309 unsigned long timeleft; 310 311 while (1) { 312 timeleft = msleep_interruptible(delay * 1000); 313 314 if (kthread_should_stop() || timeleft) 315 break; 316 317 if (mutex_trylock(&hotplug_mutex)) { 318 if (hotplug_occurred) { 319 hotplug_occurred = 0; 320 mutex_unlock(&hotplug_mutex); 321 cmm_dbg("Hotplug operation has occurred, " 322 "loaning activity suspended " 323 "for %d seconds.\n", 324 hotplug_delay); 325 timeleft = msleep_interruptible(hotplug_delay * 326 1000); 327 if (kthread_should_stop() || timeleft) 328 break; 329 continue; 330 } 331 mutex_unlock(&hotplug_mutex); 332 } else { 333 cmm_dbg("Hotplug operation in progress, activity " 334 "suspended\n"); 335 continue; 336 } 337 338 cmm_get_mpp(); 339 340 if (loaned_pages_target > loaned_pages) { 341 if (cmm_alloc_pages(loaned_pages_target - loaned_pages)) 342 loaned_pages_target = loaned_pages; 343 } else if (loaned_pages_target < loaned_pages) 344 cmm_free_pages(loaned_pages - loaned_pages_target); 345 } 346 return 0; 347} 348 349#define CMM_SHOW(name, format, args...) \ 350 static ssize_t show_##name(struct sys_device *dev, \ 351 struct sysdev_attribute *attr, \ 352 char *buf) \ 353 { \ 354 return sprintf(buf, format, ##args); \ 355 } \ 356 static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL) 357 358CMM_SHOW(loaned_kb, "%lu\n", PAGES2KB(loaned_pages)); 359CMM_SHOW(loaned_target_kb, "%lu\n", PAGES2KB(loaned_pages_target)); 360 361static ssize_t show_oom_pages(struct sys_device *dev, 362 struct sysdev_attribute *attr, char *buf) 363{ 364 return sprintf(buf, "%lu\n", PAGES2KB(oom_freed_pages)); 365} 366 367static ssize_t store_oom_pages(struct sys_device *dev, 368 struct sysdev_attribute *attr, 369 const char *buf, size_t count) 370{ 371 unsigned long val = simple_strtoul (buf, NULL, 10); 372 373 if (!capable(CAP_SYS_ADMIN)) 374 return -EPERM; 375 if (val != 0) 376 return -EBADMSG; 377 378 oom_freed_pages = 0; 379 return count; 380} 381 382static SYSDEV_ATTR(oom_freed_kb, S_IWUSR| S_IRUGO, 383 show_oom_pages, store_oom_pages); 384 385static struct sysdev_attribute *cmm_attrs[] = { 386 &attr_loaned_kb, 387 &attr_loaned_target_kb, 388 &attr_oom_freed_kb, 389}; 390 391static struct sysdev_class cmm_sysdev_class = { 392 .name = "cmm", 393}; 394 395/** 396 * cmm_sysfs_register - Register with sysfs 397 * 398 * Return value: 399 * 0 on success / other on failure 400 **/ 401static int cmm_sysfs_register(struct sys_device *sysdev) 402{ 403 int i, rc; 404 405 if ((rc = sysdev_class_register(&cmm_sysdev_class))) 406 return rc; 407 408 sysdev->id = 0; 409 sysdev->cls = &cmm_sysdev_class; 410 411 if ((rc = sysdev_register(sysdev))) 412 goto class_unregister; 413 414 for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) { 415 if ((rc = sysdev_create_file(sysdev, cmm_attrs[i]))) 416 goto fail; 417 } 418 419 return 0; 420 421fail: 422 while (--i >= 0) 423 sysdev_remove_file(sysdev, cmm_attrs[i]); 424 sysdev_unregister(sysdev); 425class_unregister: 426 sysdev_class_unregister(&cmm_sysdev_class); 427 return rc; 428} 429 430/** 431 * cmm_unregister_sysfs - Unregister from sysfs 432 * 433 **/ 434static void cmm_unregister_sysfs(struct sys_device *sysdev) 435{ 436 int i; 437 438 for (i = 0; i < ARRAY_SIZE(cmm_attrs); i++) 439 sysdev_remove_file(sysdev, cmm_attrs[i]); 440 sysdev_unregister(sysdev); 441 sysdev_class_unregister(&cmm_sysdev_class); 442} 443 444/** 445 * cmm_reboot_notifier - Make sure pages are not still marked as "loaned" 446 * 447 **/ 448static int cmm_reboot_notifier(struct notifier_block *nb, 449 unsigned long action, void *unused) 450{ 451 if (action == SYS_RESTART) { 452 if (cmm_thread_ptr) 453 kthread_stop(cmm_thread_ptr); 454 cmm_thread_ptr = NULL; 455 cmm_free_pages(loaned_pages); 456 } 457 return NOTIFY_DONE; 458} 459 460static struct notifier_block cmm_reboot_nb = { 461 .notifier_call = cmm_reboot_notifier, 462}; 463 464/** 465 * cmm_count_pages - Count the number of pages loaned in a particular range. 466 * 467 * @arg: memory_isolate_notify structure with address range and count 468 * 469 * Return value: 470 * 0 on success 471 **/ 472static unsigned long cmm_count_pages(void *arg) 473{ 474 struct memory_isolate_notify *marg = arg; 475 struct cmm_page_array *pa; 476 unsigned long start = (unsigned long)pfn_to_kaddr(marg->start_pfn); 477 unsigned long end = start + (marg->nr_pages << PAGE_SHIFT); 478 unsigned long idx; 479 480 spin_lock(&cmm_lock); 481 pa = cmm_page_list; 482 while (pa) { 483 if ((unsigned long)pa >= start && (unsigned long)pa < end) 484 marg->pages_found++; 485 for (idx = 0; idx < pa->index; idx++) 486 if (pa->page[idx] >= start && pa->page[idx] < end) 487 marg->pages_found++; 488 pa = pa->next; 489 } 490 spin_unlock(&cmm_lock); 491 return 0; 492} 493 494/** 495 * cmm_memory_isolate_cb - Handle memory isolation notifier calls 496 * @self: notifier block struct 497 * @action: action to take 498 * @arg: struct memory_isolate_notify data for handler 499 * 500 * Return value: 501 * NOTIFY_OK or notifier error based on subfunction return value 502 **/ 503static int cmm_memory_isolate_cb(struct notifier_block *self, 504 unsigned long action, void *arg) 505{ 506 int ret = 0; 507 508 if (action == MEM_ISOLATE_COUNT) 509 ret = cmm_count_pages(arg); 510 511 if (ret) 512 ret = notifier_from_errno(ret); 513 else 514 ret = NOTIFY_OK; 515 516 return ret; 517} 518 519static struct notifier_block cmm_mem_isolate_nb = { 520 .notifier_call = cmm_memory_isolate_cb, 521 .priority = CMM_MEM_ISOLATE_PRI 522}; 523 524/** 525 * cmm_mem_going_offline - Unloan pages where memory is to be removed 526 * @arg: memory_notify structure with page range to be offlined 527 * 528 * Return value: 529 * 0 on success 530 **/ 531static int cmm_mem_going_offline(void *arg) 532{ 533 struct memory_notify *marg = arg; 534 unsigned long start_page = (unsigned long)pfn_to_kaddr(marg->start_pfn); 535 unsigned long end_page = start_page + (marg->nr_pages << PAGE_SHIFT); 536 struct cmm_page_array *pa_curr, *pa_last, *npa; 537 unsigned long idx; 538 unsigned long freed = 0; 539 540 cmm_dbg("Memory going offline, searching 0x%lx (%ld pages).\n", 541 start_page, marg->nr_pages); 542 spin_lock(&cmm_lock); 543 544 /* Search the page list for pages in the range to be offlined */ 545 pa_last = pa_curr = cmm_page_list; 546 while (pa_curr) { 547 for (idx = (pa_curr->index - 1); (idx + 1) > 0; idx--) { 548 if ((pa_curr->page[idx] < start_page) || 549 (pa_curr->page[idx] >= end_page)) 550 continue; 551 552 plpar_page_set_active(__pa(pa_curr->page[idx])); 553 free_page(pa_curr->page[idx]); 554 freed++; 555 loaned_pages--; 556 totalram_pages++; 557 pa_curr->page[idx] = pa_last->page[--pa_last->index]; 558 if (pa_last->index == 0) { 559 if (pa_curr == pa_last) 560 pa_curr = pa_last->next; 561 pa_last = pa_last->next; 562 free_page((unsigned long)cmm_page_list); 563 cmm_page_list = pa_last; 564 continue; 565 } 566 } 567 pa_curr = pa_curr->next; 568 } 569 570 /* Search for page list structures in the range to be offlined */ 571 pa_last = NULL; 572 pa_curr = cmm_page_list; 573 while (pa_curr) { 574 if (((unsigned long)pa_curr >= start_page) && 575 ((unsigned long)pa_curr < end_page)) { 576 npa = (struct cmm_page_array *)__get_free_page( 577 GFP_NOIO | __GFP_NOWARN | 578 __GFP_NORETRY | __GFP_NOMEMALLOC); 579 if (!npa) { 580 spin_unlock(&cmm_lock); 581 cmm_dbg("Failed to allocate memory for list " 582 "management. Memory hotplug " 583 "failed.\n"); 584 return ENOMEM; 585 } 586 memcpy(npa, pa_curr, PAGE_SIZE); 587 if (pa_curr == cmm_page_list) 588 cmm_page_list = npa; 589 if (pa_last) 590 pa_last->next = npa; 591 free_page((unsigned long) pa_curr); 592 freed++; 593 pa_curr = npa; 594 } 595 596 pa_last = pa_curr; 597 pa_curr = pa_curr->next; 598 } 599 600 spin_unlock(&cmm_lock); 601 cmm_dbg("Released %ld pages in the search range.\n", freed); 602 603 return 0; 604} 605 606/** 607 * cmm_memory_cb - Handle memory hotplug notifier calls 608 * @self: notifier block struct 609 * @action: action to take 610 * @arg: struct memory_notify data for handler 611 * 612 * Return value: 613 * NOTIFY_OK or notifier error based on subfunction return value 614 * 615 **/ 616static int cmm_memory_cb(struct notifier_block *self, 617 unsigned long action, void *arg) 618{ 619 int ret = 0; 620 621 switch (action) { 622 case MEM_GOING_OFFLINE: 623 mutex_lock(&hotplug_mutex); 624 hotplug_occurred = 1; 625 ret = cmm_mem_going_offline(arg); 626 break; 627 case MEM_OFFLINE: 628 case MEM_CANCEL_OFFLINE: 629 mutex_unlock(&hotplug_mutex); 630 cmm_dbg("Memory offline operation complete.\n"); 631 break; 632 case MEM_GOING_ONLINE: 633 case MEM_ONLINE: 634 case MEM_CANCEL_ONLINE: 635 break; 636 } 637 638 if (ret) 639 ret = notifier_from_errno(ret); 640 else 641 ret = NOTIFY_OK; 642 643 return ret; 644} 645 646static struct notifier_block cmm_mem_nb = { 647 .notifier_call = cmm_memory_cb, 648 .priority = CMM_MEM_HOTPLUG_PRI 649}; 650 651/** 652 * cmm_init - Module initialization 653 * 654 * Return value: 655 * 0 on success / other on failure 656 **/ 657static int cmm_init(void) 658{ 659 int rc = -ENOMEM; 660 661 if (!firmware_has_feature(FW_FEATURE_CMO)) 662 return -EOPNOTSUPP; 663 664 if ((rc = register_oom_notifier(&cmm_oom_nb)) < 0) 665 return rc; 666 667 if ((rc = register_reboot_notifier(&cmm_reboot_nb))) 668 goto out_oom_notifier; 669 670 if ((rc = cmm_sysfs_register(&cmm_sysdev))) 671 goto out_reboot_notifier; 672 673 if (register_memory_notifier(&cmm_mem_nb) || 674 register_memory_isolate_notifier(&cmm_mem_isolate_nb)) 675 goto out_unregister_notifier; 676 677 if (cmm_disabled) 678 return rc; 679 680 cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread"); 681 if (IS_ERR(cmm_thread_ptr)) { 682 rc = PTR_ERR(cmm_thread_ptr); 683 goto out_unregister_notifier; 684 } 685 686 return rc; 687 688out_unregister_notifier: 689 unregister_memory_notifier(&cmm_mem_nb); 690 unregister_memory_isolate_notifier(&cmm_mem_isolate_nb); 691 cmm_unregister_sysfs(&cmm_sysdev); 692out_reboot_notifier: 693 unregister_reboot_notifier(&cmm_reboot_nb); 694out_oom_notifier: 695 unregister_oom_notifier(&cmm_oom_nb); 696 return rc; 697} 698 699/** 700 * cmm_exit - Module exit 701 * 702 * Return value: 703 * nothing 704 **/ 705static void cmm_exit(void) 706{ 707 if (cmm_thread_ptr) 708 kthread_stop(cmm_thread_ptr); 709 unregister_oom_notifier(&cmm_oom_nb); 710 unregister_reboot_notifier(&cmm_reboot_nb); 711 unregister_memory_notifier(&cmm_mem_nb); 712 unregister_memory_isolate_notifier(&cmm_mem_isolate_nb); 713 cmm_free_pages(loaned_pages); 714 cmm_unregister_sysfs(&cmm_sysdev); 715} 716 717/** 718 * cmm_set_disable - Disable/Enable CMM 719 * 720 * Return value: 721 * 0 on success / other on failure 722 **/ 723static int cmm_set_disable(const char *val, struct kernel_param *kp) 724{ 725 int disable = simple_strtoul(val, NULL, 10); 726 727 if (disable != 0 && disable != 1) 728 return -EINVAL; 729 730 if (disable && !cmm_disabled) { 731 if (cmm_thread_ptr) 732 kthread_stop(cmm_thread_ptr); 733 cmm_thread_ptr = NULL; 734 cmm_free_pages(loaned_pages); 735 } else if (!disable && cmm_disabled) { 736 cmm_thread_ptr = kthread_run(cmm_thread, NULL, "cmmthread"); 737 if (IS_ERR(cmm_thread_ptr)) 738 return PTR_ERR(cmm_thread_ptr); 739 } 740 741 cmm_disabled = disable; 742 return 0; 743} 744 745module_param_call(disable, cmm_set_disable, param_get_uint, 746 &cmm_disabled, S_IRUGO | S_IWUSR); 747MODULE_PARM_DESC(disable, "Disable CMM. Set to 1 to disable. " 748 "[Default=" __stringify(CMM_DISABLE) "]"); 749 750module_init(cmm_init); 751module_exit(cmm_exit); 752