mm: replace various uses of num_physpages by totalram_pages
[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 #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");