f5bbd9e8341660a6d4f5195d1b42350db0288d5d
[linux-2.6.git] / drivers / xen / 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/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 /* VM /proc information for memory */
100 extern unsigned long totalram_pages;
101
102 #ifdef CONFIG_HIGHMEM
103 extern 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. */
112 static LIST_HEAD(ballooned_pages);
113
114 /* Main work function, always executed in process context. */
115 static void balloon_process(struct work_struct *work);
116 static DECLARE_WORK(balloon_worker, balloon_process);
117 static 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
124 static void scrub_page(struct page *page)
125 {
126 #ifdef CONFIG_XEN_SCRUB_PAGES
127         clear_highpage(page);
128 #endif
129 }
130
131 /* balloon_append: add the given page to the balloon. */
132 static void balloon_append(struct page *page)
133 {
134         /* Lowmem is re-populated first, so highmem pages go at list tail. */
135         if (PageHighMem(page)) {
136                 list_add_tail(&page->lru, &ballooned_pages);
137                 balloon_stats.balloon_high++;
138                 dec_totalhigh_pages();
139         } else {
140                 list_add(&page->lru, &ballooned_pages);
141                 balloon_stats.balloon_low++;
142         }
143 }
144
145 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
146 static struct page *balloon_retrieve(void)
147 {
148         struct page *page;
149
150         if (list_empty(&ballooned_pages))
151                 return NULL;
152
153         page = list_entry(ballooned_pages.next, struct page, lru);
154         list_del(&page->lru);
155
156         if (PageHighMem(page)) {
157                 balloon_stats.balloon_high--;
158                 inc_totalhigh_pages();
159         }
160         else
161                 balloon_stats.balloon_low--;
162
163         return page;
164 }
165
166 static struct page *balloon_first_page(void)
167 {
168         if (list_empty(&ballooned_pages))
169                 return NULL;
170         return list_entry(ballooned_pages.next, struct page, lru);
171 }
172
173 static struct page *balloon_next_page(struct page *page)
174 {
175         struct list_head *next = page->lru.next;
176         if (next == &ballooned_pages)
177                 return NULL;
178         return list_entry(next, struct page, lru);
179 }
180
181 static void balloon_alarm(unsigned long unused)
182 {
183         schedule_work(&balloon_worker);
184 }
185
186 static unsigned long current_target(void)
187 {
188         unsigned long target = min(balloon_stats.target_pages, balloon_stats.hard_limit);
189
190         target = min(target,
191                      balloon_stats.current_pages +
192                      balloon_stats.balloon_low +
193                      balloon_stats.balloon_high);
194
195         return target;
196 }
197
198 static int increase_reservation(unsigned long nr_pages)
199 {
200         unsigned long  pfn, i, flags;
201         struct page   *page;
202         long           rc;
203         struct xen_memory_reservation reservation = {
204                 .address_bits = 0,
205                 .extent_order = 0,
206                 .domid        = DOMID_SELF
207         };
208
209         if (nr_pages > ARRAY_SIZE(frame_list))
210                 nr_pages = ARRAY_SIZE(frame_list);
211
212         spin_lock_irqsave(&balloon_lock, flags);
213
214         page = balloon_first_page();
215         for (i = 0; i < nr_pages; i++) {
216                 BUG_ON(page == NULL);
217                 frame_list[i] = page_to_pfn(page);;
218                 page = balloon_next_page(page);
219         }
220
221         set_xen_guest_handle(reservation.extent_start, frame_list);
222         reservation.nr_extents = nr_pages;
223         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
224         if (rc < nr_pages) {
225                 if (rc > 0) {
226                         int ret;
227
228                         /* We hit the Xen hard limit: reprobe. */
229                         reservation.nr_extents = rc;
230                         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
231                                                    &reservation);
232                         BUG_ON(ret != rc);
233                 }
234                 if (rc >= 0)
235                         balloon_stats.hard_limit = (balloon_stats.current_pages + rc -
236                                                     balloon_stats.driver_pages);
237                 goto out;
238         }
239
240         for (i = 0; i < nr_pages; i++) {
241                 page = balloon_retrieve();
242                 BUG_ON(page == NULL);
243
244                 pfn = page_to_pfn(page);
245                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
246                        phys_to_machine_mapping_valid(pfn));
247
248                 set_phys_to_machine(pfn, frame_list[i]);
249
250                 /* Link back into the page tables if not highmem. */
251                 if (pfn < max_low_pfn) {
252                         int ret;
253                         ret = HYPERVISOR_update_va_mapping(
254                                 (unsigned long)__va(pfn << PAGE_SHIFT),
255                                 mfn_pte(frame_list[i], PAGE_KERNEL),
256                                 0);
257                         BUG_ON(ret);
258                 }
259
260                 /* Relinquish the page back to the allocator. */
261                 ClearPageReserved(page);
262                 init_page_count(page);
263                 __free_page(page);
264         }
265
266         balloon_stats.current_pages += nr_pages;
267         totalram_pages = balloon_stats.current_pages;
268
269  out:
270         spin_unlock_irqrestore(&balloon_lock, flags);
271
272         return 0;
273 }
274
275 static int decrease_reservation(unsigned long nr_pages)
276 {
277         unsigned long  pfn, i, flags;
278         struct page   *page;
279         int            need_sleep = 0;
280         int ret;
281         struct xen_memory_reservation reservation = {
282                 .address_bits = 0,
283                 .extent_order = 0,
284                 .domid        = DOMID_SELF
285         };
286
287         if (nr_pages > ARRAY_SIZE(frame_list))
288                 nr_pages = ARRAY_SIZE(frame_list);
289
290         for (i = 0; i < nr_pages; i++) {
291                 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
292                         nr_pages = i;
293                         need_sleep = 1;
294                         break;
295                 }
296
297                 pfn = page_to_pfn(page);
298                 frame_list[i] = pfn_to_mfn(pfn);
299
300                 scrub_page(page);
301
302                 if (!PageHighMem(page)) {
303                         ret = HYPERVISOR_update_va_mapping(
304                                 (unsigned long)__va(pfn << PAGE_SHIFT),
305                                 __pte_ma(0), 0);
306                         BUG_ON(ret);
307                 }
308
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
324         set_xen_guest_handle(reservation.extent_start, frame_list);
325         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  */
343 static 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. */
371 static void balloon_set_new_target(unsigned long target)
372 {
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
379 static struct xenbus_watch target_watch =
380 {
381         .node = "memory/target"
382 };
383
384 /* React to a change in the target key */
385 static 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
403 static 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
416 static struct notifier_block xenstore_notifier;
417
418 static int __init balloon_init(void)
419 {
420         unsigned long pfn;
421         struct page *page;
422
423         if (!xen_pv_domain())
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
457 subsys_initcall(balloon_init);
458
459 static void balloon_exit(void)
460 {
461     /* XXX - release balloon here */
462     return;
463 }
464
465 module_exit(balloon_exit);
466
467 #define BALLOON_SHOW(name, format, args...)                             \
468         static ssize_t show_##name(struct sys_device *dev,              \
469                                    struct sysdev_attribute *attr,       \
470                                    char *buf)                           \
471         {                                                               \
472                 return sprintf(buf, format, ##args);                    \
473         }                                                               \
474         static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
475
476 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
477 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
478 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
479 BALLOON_SHOW(hard_limit_kb,
480              (balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n",
481              (balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0);
482 BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
483
484 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
485                               char *buf)
486 {
487         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
488 }
489
490 static ssize_t store_target_kb(struct sys_device *dev,
491                                struct sysdev_attribute *attr,
492                                const char *buf,
493                                size_t count)
494 {
495         char *endchar;
496         unsigned long long target_bytes;
497
498         if (!capable(CAP_SYS_ADMIN))
499                 return -EPERM;
500
501         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
502
503         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
504
505         return count;
506 }
507
508 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
509                    show_target_kb, store_target_kb);
510
511
512 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
513                               char *buf)
514 {
515         return sprintf(buf, "%llu\n",
516                        (unsigned long long)balloon_stats.target_pages
517                        << PAGE_SHIFT);
518 }
519
520 static ssize_t store_target(struct sys_device *dev,
521                             struct sysdev_attribute *attr,
522                             const char *buf,
523                             size_t count)
524 {
525         char *endchar;
526         unsigned long long target_bytes;
527
528         if (!capable(CAP_SYS_ADMIN))
529                 return -EPERM;
530
531         target_bytes = memparse(buf, &endchar);
532
533         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
534
535         return count;
536 }
537
538 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
539                    show_target, store_target);
540
541
542 static struct sysdev_attribute *balloon_attrs[] = {
543         &attr_target_kb,
544         &attr_target,
545 };
546
547 static struct attribute *balloon_info_attrs[] = {
548         &attr_current_kb.attr,
549         &attr_low_kb.attr,
550         &attr_high_kb.attr,
551         &attr_hard_limit_kb.attr,
552         &attr_driver_kb.attr,
553         NULL
554 };
555
556 static struct attribute_group balloon_info_group = {
557         .name = "info",
558         .attrs = balloon_info_attrs,
559 };
560
561 static struct sysdev_class balloon_sysdev_class = {
562         .name = BALLOON_CLASS_NAME,
563 };
564
565 static int register_balloon(struct sys_device *sysdev)
566 {
567         int i, error;
568
569         error = sysdev_class_register(&balloon_sysdev_class);
570         if (error)
571                 return error;
572
573         sysdev->id = 0;
574         sysdev->cls = &balloon_sysdev_class;
575
576         error = sysdev_register(sysdev);
577         if (error) {
578                 sysdev_class_unregister(&balloon_sysdev_class);
579                 return error;
580         }
581
582         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
583                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
584                 if (error)
585                         goto fail;
586         }
587
588         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
589         if (error)
590                 goto fail;
591
592         return 0;
593
594  fail:
595         while (--i >= 0)
596                 sysdev_remove_file(sysdev, balloon_attrs[i]);
597         sysdev_unregister(sysdev);
598         sysdev_class_unregister(&balloon_sysdev_class);
599         return error;
600 }
601
602 MODULE_LICENSE("GPL");