blob: 591bc29b55f5acf0f8dbe97e360ddd279020e9b2 [file] [log] [blame]
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -07001/******************************************************************************
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/highmem.h>
45#include <linux/list.h>
46#include <linux/sysdev.h>
47
48#include <asm/xen/hypervisor.h>
49#include <asm/page.h>
50#include <asm/pgalloc.h>
51#include <asm/pgtable.h>
52#include <asm/uaccess.h>
53#include <asm/tlb.h>
54
55#include <xen/interface/memory.h>
56#include <xen/balloon.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 "memory"
64
65struct 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
81static DEFINE_MUTEX(balloon_mutex);
82
83static struct sys_device balloon_sysdev;
84
85static 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 */
92static DEFINE_SPINLOCK(balloon_lock);
93
94static struct balloon_stats balloon_stats;
95
96/* We increase/decrease in batches which fit in a page */
97static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
98
99/* VM /proc information for memory */
100extern unsigned long totalram_pages;
101
102#ifdef CONFIG_HIGHMEM
103extern unsigned long totalhigh_pages;
104#define inc_totalhigh_pages() (totalhigh_pages++)
105#define dec_totalhigh_pages() (totalhigh_pages--)
106#else
107#define inc_totalhigh_pages() do {} while(0)
108#define dec_totalhigh_pages() do {} while(0)
109#endif
110
111/* List of ballooned pages, threaded through the mem_map array. */
112static LIST_HEAD(ballooned_pages);
113
114/* Main work function, always executed in process context. */
115static void balloon_process(struct work_struct *work);
116static DECLARE_WORK(balloon_worker, balloon_process);
117static struct timer_list balloon_timer;
118
119/* When ballooning out (allocating memory to return to Xen) we don't really
120 want the kernel to try too hard since that can trigger the oom killer. */
121#define GFP_BALLOON \
122 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
123
124static void scrub_page(struct page *page)
125{
126#ifdef CONFIG_XEN_SCRUB_PAGES
127 if (PageHighMem(page)) {
128 void *v = kmap(page);
129 clear_page(v);
130 kunmap(v);
131 } else {
132 void *v = page_address(page);
133 clear_page(v);
134 }
135#endif
136}
137
138/* balloon_append: add the given page to the balloon. */
139static void balloon_append(struct page *page)
140{
141 /* Lowmem is re-populated first, so highmem pages go at list tail. */
142 if (PageHighMem(page)) {
143 list_add_tail(&page->lru, &ballooned_pages);
144 balloon_stats.balloon_high++;
145 dec_totalhigh_pages();
146 } else {
147 list_add(&page->lru, &ballooned_pages);
148 balloon_stats.balloon_low++;
149 }
150}
151
152/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
153static struct page *balloon_retrieve(void)
154{
155 struct page *page;
156
157 if (list_empty(&ballooned_pages))
158 return NULL;
159
160 page = list_entry(ballooned_pages.next, struct page, lru);
161 list_del(&page->lru);
162
163 if (PageHighMem(page)) {
164 balloon_stats.balloon_high--;
165 inc_totalhigh_pages();
166 }
167 else
168 balloon_stats.balloon_low--;
169
170 return page;
171}
172
173static struct page *balloon_first_page(void)
174{
175 if (list_empty(&ballooned_pages))
176 return NULL;
177 return list_entry(ballooned_pages.next, struct page, lru);
178}
179
180static struct page *balloon_next_page(struct page *page)
181{
182 struct list_head *next = page->lru.next;
183 if (next == &ballooned_pages)
184 return NULL;
185 return list_entry(next, struct page, lru);
186}
187
188static void balloon_alarm(unsigned long unused)
189{
190 schedule_work(&balloon_worker);
191}
192
193static unsigned long current_target(void)
194{
195 unsigned long target = min(balloon_stats.target_pages, balloon_stats.hard_limit);
196
197 target = min(target,
198 balloon_stats.current_pages +
199 balloon_stats.balloon_low +
200 balloon_stats.balloon_high);
201
202 return target;
203}
204
205static int increase_reservation(unsigned long nr_pages)
206{
207 unsigned long pfn, i, flags;
208 struct page *page;
209 long rc;
210 struct xen_memory_reservation reservation = {
211 .address_bits = 0,
212 .extent_order = 0,
213 .domid = DOMID_SELF
214 };
215
216 if (nr_pages > ARRAY_SIZE(frame_list))
217 nr_pages = ARRAY_SIZE(frame_list);
218
219 spin_lock_irqsave(&balloon_lock, flags);
220
221 page = balloon_first_page();
222 for (i = 0; i < nr_pages; i++) {
223 BUG_ON(page == NULL);
224 frame_list[i] = page_to_pfn(page);;
225 page = balloon_next_page(page);
226 }
227
Isaku Yamahataa90971e2008-05-26 23:31:14 +0100228 set_xen_guest_handle(reservation.extent_start, frame_list);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700229 reservation.nr_extents = nr_pages;
230 rc = HYPERVISOR_memory_op(
231 XENMEM_populate_physmap, &reservation);
232 if (rc < nr_pages) {
233 if (rc > 0) {
234 int ret;
235
236 /* We hit the Xen hard limit: reprobe. */
237 reservation.nr_extents = rc;
238 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
239 &reservation);
240 BUG_ON(ret != rc);
241 }
242 if (rc >= 0)
243 balloon_stats.hard_limit = (balloon_stats.current_pages + rc -
244 balloon_stats.driver_pages);
245 goto out;
246 }
247
248 for (i = 0; i < nr_pages; i++) {
249 page = balloon_retrieve();
250 BUG_ON(page == NULL);
251
252 pfn = page_to_pfn(page);
253 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
254 phys_to_machine_mapping_valid(pfn));
255
256 set_phys_to_machine(pfn, frame_list[i]);
257
258 /* Link back into the page tables if not highmem. */
259 if (pfn < max_low_pfn) {
260 int ret;
261 ret = HYPERVISOR_update_va_mapping(
262 (unsigned long)__va(pfn << PAGE_SHIFT),
263 mfn_pte(frame_list[i], PAGE_KERNEL),
264 0);
265 BUG_ON(ret);
266 }
267
268 /* Relinquish the page back to the allocator. */
269 ClearPageReserved(page);
270 init_page_count(page);
271 __free_page(page);
272 }
273
274 balloon_stats.current_pages += nr_pages;
275 totalram_pages = balloon_stats.current_pages;
276
277 out:
278 spin_unlock_irqrestore(&balloon_lock, flags);
279
280 return 0;
281}
282
283static int decrease_reservation(unsigned long nr_pages)
284{
285 unsigned long pfn, i, flags;
286 struct page *page;
287 int need_sleep = 0;
288 int ret;
289 struct xen_memory_reservation reservation = {
290 .address_bits = 0,
291 .extent_order = 0,
292 .domid = DOMID_SELF
293 };
294
295 if (nr_pages > ARRAY_SIZE(frame_list))
296 nr_pages = ARRAY_SIZE(frame_list);
297
298 for (i = 0; i < nr_pages; i++) {
299 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
300 nr_pages = i;
301 need_sleep = 1;
302 break;
303 }
304
305 pfn = page_to_pfn(page);
306 frame_list[i] = pfn_to_mfn(pfn);
307
308 scrub_page(page);
309 }
310
311 /* Ensure that ballooned highmem pages don't have kmaps. */
312 kmap_flush_unused();
313 flush_tlb_all();
314
315 spin_lock_irqsave(&balloon_lock, flags);
316
317 /* No more mappings: invalidate P2M and add to balloon. */
318 for (i = 0; i < nr_pages; i++) {
319 pfn = mfn_to_pfn(frame_list[i]);
320 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
321 balloon_append(pfn_to_page(pfn));
322 }
323
Isaku Yamahataa90971e2008-05-26 23:31:14 +0100324 set_xen_guest_handle(reservation.extent_start, frame_list);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700325 reservation.nr_extents = nr_pages;
326 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
327 BUG_ON(ret != nr_pages);
328
329 balloon_stats.current_pages -= nr_pages;
330 totalram_pages = balloon_stats.current_pages;
331
332 spin_unlock_irqrestore(&balloon_lock, flags);
333
334 return need_sleep;
335}
336
337/*
338 * We avoid multiple worker processes conflicting via the balloon mutex.
339 * We may of course race updates of the target counts (which are protected
340 * by the balloon lock), or with changes to the Xen hard limit, but we will
341 * recover from these in time.
342 */
343static void balloon_process(struct work_struct *work)
344{
345 int need_sleep = 0;
346 long credit;
347
348 mutex_lock(&balloon_mutex);
349
350 do {
351 credit = current_target() - balloon_stats.current_pages;
352 if (credit > 0)
353 need_sleep = (increase_reservation(credit) != 0);
354 if (credit < 0)
355 need_sleep = (decrease_reservation(-credit) != 0);
356
357#ifndef CONFIG_PREEMPT
358 if (need_resched())
359 schedule();
360#endif
361 } while ((credit != 0) && !need_sleep);
362
363 /* Schedule more work if there is some still to be done. */
364 if (current_target() != balloon_stats.current_pages)
365 mod_timer(&balloon_timer, jiffies + HZ);
366
367 mutex_unlock(&balloon_mutex);
368}
369
370/* Resets the Xen limit, sets new target, and kicks off processing. */
Adrian Bunk955d6f12008-05-26 23:31:17 +0100371static void balloon_set_new_target(unsigned long target)
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700372{
373 /* No need for lock. Not read-modify-write updates. */
374 balloon_stats.hard_limit = ~0UL;
375 balloon_stats.target_pages = target;
376 schedule_work(&balloon_worker);
377}
378
379static struct xenbus_watch target_watch =
380{
381 .node = "memory/target"
382};
383
384/* React to a change in the target key */
385static void watch_target(struct xenbus_watch *watch,
386 const char **vec, unsigned int len)
387{
388 unsigned long long new_target;
389 int err;
390
391 err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
392 if (err != 1) {
393 /* This is ok (for domain0 at least) - so just return */
394 return;
395 }
396
397 /* The given memory/target value is in KiB, so it needs converting to
398 * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
399 */
400 balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
401}
402
403static int balloon_init_watcher(struct notifier_block *notifier,
404 unsigned long event,
405 void *data)
406{
407 int err;
408
409 err = register_xenbus_watch(&target_watch);
410 if (err)
411 printk(KERN_ERR "Failed to set balloon watcher\n");
412
413 return NOTIFY_DONE;
414}
415
416static struct notifier_block xenstore_notifier;
417
418static int __init balloon_init(void)
419{
420 unsigned long pfn;
421 struct page *page;
422
423 if (!is_running_on_xen())
424 return -ENODEV;
425
426 pr_info("xen_balloon: Initialising balloon driver.\n");
427
428 balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
429 totalram_pages = balloon_stats.current_pages;
430 balloon_stats.target_pages = balloon_stats.current_pages;
431 balloon_stats.balloon_low = 0;
432 balloon_stats.balloon_high = 0;
433 balloon_stats.driver_pages = 0UL;
434 balloon_stats.hard_limit = ~0UL;
435
436 init_timer(&balloon_timer);
437 balloon_timer.data = 0;
438 balloon_timer.function = balloon_alarm;
439
440 register_balloon(&balloon_sysdev);
441
442 /* Initialise the balloon with excess memory space. */
443 for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
444 page = pfn_to_page(pfn);
445 if (!PageReserved(page))
446 balloon_append(page);
447 }
448
449 target_watch.callback = watch_target;
450 xenstore_notifier.notifier_call = balloon_init_watcher;
451
452 register_xenstore_notifier(&xenstore_notifier);
453
454 return 0;
455}
456
457subsys_initcall(balloon_init);
458
459static void balloon_exit(void)
460{
461 /* XXX - release balloon here */
462 return;
463}
464
465module_exit(balloon_exit);
466
467static void balloon_update_driver_allowance(long delta)
468{
469 unsigned long flags;
470
471 spin_lock_irqsave(&balloon_lock, flags);
472 balloon_stats.driver_pages += delta;
473 spin_unlock_irqrestore(&balloon_lock, flags);
474}
475
476static int dealloc_pte_fn(
477 pte_t *pte, struct page *pmd_page, unsigned long addr, void *data)
478{
479 unsigned long mfn = pte_mfn(*pte);
480 int ret;
481 struct xen_memory_reservation reservation = {
482 .nr_extents = 1,
483 .extent_order = 0,
484 .domid = DOMID_SELF
485 };
Isaku Yamahataa90971e2008-05-26 23:31:14 +0100486 set_xen_guest_handle(reservation.extent_start, &mfn);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700487 set_pte_at(&init_mm, addr, pte, __pte_ma(0ull));
488 set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY);
489 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
490 BUG_ON(ret != 1);
491 return 0;
492}
493
494static struct page **alloc_empty_pages_and_pagevec(int nr_pages)
495{
496 unsigned long vaddr, flags;
497 struct page *page, **pagevec;
498 int i, ret;
499
500 pagevec = kmalloc(sizeof(page) * nr_pages, GFP_KERNEL);
501 if (pagevec == NULL)
502 return NULL;
503
504 for (i = 0; i < nr_pages; i++) {
505 page = pagevec[i] = alloc_page(GFP_KERNEL);
506 if (page == NULL)
507 goto err;
508
509 vaddr = (unsigned long)page_address(page);
510
511 scrub_page(page);
512
513 spin_lock_irqsave(&balloon_lock, flags);
514
515 if (xen_feature(XENFEAT_auto_translated_physmap)) {
516 unsigned long gmfn = page_to_pfn(page);
517 struct xen_memory_reservation reservation = {
518 .nr_extents = 1,
519 .extent_order = 0,
520 .domid = DOMID_SELF
521 };
Isaku Yamahataa90971e2008-05-26 23:31:14 +0100522 set_xen_guest_handle(reservation.extent_start, &gmfn);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700523 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
524 &reservation);
525 if (ret == 1)
526 ret = 0; /* success */
527 } else {
528 ret = apply_to_page_range(&init_mm, vaddr, PAGE_SIZE,
529 dealloc_pte_fn, NULL);
530 }
531
532 if (ret != 0) {
533 spin_unlock_irqrestore(&balloon_lock, flags);
534 __free_page(page);
535 goto err;
536 }
537
538 totalram_pages = --balloon_stats.current_pages;
539
540 spin_unlock_irqrestore(&balloon_lock, flags);
541 }
542
543 out:
544 schedule_work(&balloon_worker);
545 flush_tlb_all();
546 return pagevec;
547
548 err:
549 spin_lock_irqsave(&balloon_lock, flags);
550 while (--i >= 0)
551 balloon_append(pagevec[i]);
552 spin_unlock_irqrestore(&balloon_lock, flags);
553 kfree(pagevec);
554 pagevec = NULL;
555 goto out;
556}
557
558static void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages)
559{
560 unsigned long flags;
561 int i;
562
563 if (pagevec == NULL)
564 return;
565
566 spin_lock_irqsave(&balloon_lock, flags);
567 for (i = 0; i < nr_pages; i++) {
568 BUG_ON(page_count(pagevec[i]) != 1);
569 balloon_append(pagevec[i]);
570 }
571 spin_unlock_irqrestore(&balloon_lock, flags);
572
573 kfree(pagevec);
574
575 schedule_work(&balloon_worker);
576}
577
578static void balloon_release_driver_page(struct page *page)
579{
580 unsigned long flags;
581
582 spin_lock_irqsave(&balloon_lock, flags);
583 balloon_append(page);
584 balloon_stats.driver_pages--;
585 spin_unlock_irqrestore(&balloon_lock, flags);
586
587 schedule_work(&balloon_worker);
588}
589
590
591#define BALLOON_SHOW(name, format, args...) \
592 static ssize_t show_##name(struct sys_device *dev, \
593 char *buf) \
594 { \
595 return sprintf(buf, format, ##args); \
596 } \
597 static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
598
599BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
600BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
601BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
602BALLOON_SHOW(hard_limit_kb,
603 (balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n",
604 (balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0);
605BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
606
607static ssize_t show_target_kb(struct sys_device *dev, char *buf)
608{
609 return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
610}
611
612static ssize_t store_target_kb(struct sys_device *dev,
613 const char *buf,
614 size_t count)
615{
616 char memstring[64], *endchar;
617 unsigned long long target_bytes;
618
619 if (!capable(CAP_SYS_ADMIN))
620 return -EPERM;
621
622 if (count <= 1)
623 return -EBADMSG; /* runt */
624 if (count > sizeof(memstring))
625 return -EFBIG; /* too long */
626 strcpy(memstring, buf);
627
628 target_bytes = memparse(memstring, &endchar);
629 balloon_set_new_target(target_bytes >> PAGE_SHIFT);
630
631 return count;
632}
633
634static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
635 show_target_kb, store_target_kb);
636
637static struct sysdev_attribute *balloon_attrs[] = {
638 &attr_target_kb,
639};
640
641static struct attribute *balloon_info_attrs[] = {
642 &attr_current_kb.attr,
643 &attr_low_kb.attr,
644 &attr_high_kb.attr,
645 &attr_hard_limit_kb.attr,
646 &attr_driver_kb.attr,
647 NULL
648};
649
650static struct attribute_group balloon_info_group = {
651 .name = "info",
652 .attrs = balloon_info_attrs,
653};
654
655static struct sysdev_class balloon_sysdev_class = {
656 .name = BALLOON_CLASS_NAME,
657};
658
659static int register_balloon(struct sys_device *sysdev)
660{
661 int i, error;
662
663 error = sysdev_class_register(&balloon_sysdev_class);
664 if (error)
665 return error;
666
667 sysdev->id = 0;
668 sysdev->cls = &balloon_sysdev_class;
669
670 error = sysdev_register(sysdev);
671 if (error) {
672 sysdev_class_unregister(&balloon_sysdev_class);
673 return error;
674 }
675
676 for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
677 error = sysdev_create_file(sysdev, balloon_attrs[i]);
678 if (error)
679 goto fail;
680 }
681
682 error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
683 if (error)
684 goto fail;
685
686 return 0;
687
688 fail:
689 while (--i >= 0)
690 sysdev_remove_file(sysdev, balloon_attrs[i]);
691 sysdev_unregister(sysdev);
692 sysdev_class_unregister(&balloon_sysdev_class);
693 return error;
694}
695
696static void unregister_balloon(struct sys_device *sysdev)
697{
698 int i;
699
700 sysfs_remove_group(&sysdev->kobj, &balloon_info_group);
701 for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++)
702 sysdev_remove_file(sysdev, balloon_attrs[i]);
703 sysdev_unregister(sysdev);
704 sysdev_class_unregister(&balloon_sysdev_class);
705}
706
707static void balloon_sysfs_exit(void)
708{
709 unregister_balloon(&balloon_sysdev);
710}
711
712MODULE_LICENSE("GPL");