xen: fix scrub_page()
[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/xen/hypervisor.h>
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
54 #include <xen/interface/memory.h>
55 #include <xen/xenbus.h>
56 #include <xen/features.h>
57 #include <xen/page.h>
58
59 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
60
61 #define BALLOON_CLASS_NAME "xen_memory"
62
63 struct balloon_stats {
64         /* We aim for 'current allocation' == 'target allocation'. */
65         unsigned long current_pages;
66         unsigned long target_pages;
67         /* We may hit the hard limit in Xen. If we do then we remember it. */
68         unsigned long hard_limit;
69         /*
70          * Drivers may alter the memory reservation independently, but they
71          * must inform the balloon driver so we avoid hitting the hard limit.
72          */
73         unsigned long driver_pages;
74         /* Number of pages in high- and low-memory balloons. */
75         unsigned long balloon_low;
76         unsigned long balloon_high;
77 };
78
79 static DEFINE_MUTEX(balloon_mutex);
80
81 static struct sys_device balloon_sysdev;
82
83 static int register_balloon(struct sys_device *sysdev);
84
85 /*
86  * Protects atomic reservation decrease/increase against concurrent increases.
87  * Also protects non-atomic updates of current_pages and driver_pages, and
88  * balloon lists.
89  */
90 static DEFINE_SPINLOCK(balloon_lock);
91
92 static struct balloon_stats balloon_stats;
93
94 /* We increase/decrease in batches which fit in a page */
95 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
96
97 /* VM /proc information for memory */
98 extern unsigned long totalram_pages;
99
100 #ifdef CONFIG_HIGHMEM
101 extern unsigned long totalhigh_pages;
102 #define inc_totalhigh_pages() (totalhigh_pages++)
103 #define dec_totalhigh_pages() (totalhigh_pages--)
104 #else
105 #define inc_totalhigh_pages() do {} while(0)
106 #define dec_totalhigh_pages() do {} while(0)
107 #endif
108
109 /* List of ballooned pages, threaded through the mem_map array. */
110 static LIST_HEAD(ballooned_pages);
111
112 /* Main work function, always executed in process context. */
113 static void balloon_process(struct work_struct *work);
114 static DECLARE_WORK(balloon_worker, balloon_process);
115 static struct timer_list balloon_timer;
116
117 /* When ballooning out (allocating memory to return to Xen) we don't really
118    want the kernel to try too hard since that can trigger the oom killer. */
119 #define GFP_BALLOON \
120         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
121
122 static void scrub_page(struct page *page)
123 {
124 #ifdef CONFIG_XEN_SCRUB_PAGES
125         clear_highpage(page);
126 #endif
127 }
128
129 /* balloon_append: add the given page to the balloon. */
130 static void balloon_append(struct page *page)
131 {
132         /* Lowmem is re-populated first, so highmem pages go at list tail. */
133         if (PageHighMem(page)) {
134                 list_add_tail(&page->lru, &ballooned_pages);
135                 balloon_stats.balloon_high++;
136                 dec_totalhigh_pages();
137         } else {
138                 list_add(&page->lru, &ballooned_pages);
139                 balloon_stats.balloon_low++;
140         }
141 }
142
143 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
144 static struct page *balloon_retrieve(void)
145 {
146         struct page *page;
147
148         if (list_empty(&ballooned_pages))
149                 return NULL;
150
151         page = list_entry(ballooned_pages.next, struct page, lru);
152         list_del(&page->lru);
153
154         if (PageHighMem(page)) {
155                 balloon_stats.balloon_high--;
156                 inc_totalhigh_pages();
157         }
158         else
159                 balloon_stats.balloon_low--;
160
161         return page;
162 }
163
164 static struct page *balloon_first_page(void)
165 {
166         if (list_empty(&ballooned_pages))
167                 return NULL;
168         return list_entry(ballooned_pages.next, struct page, lru);
169 }
170
171 static struct page *balloon_next_page(struct page *page)
172 {
173         struct list_head *next = page->lru.next;
174         if (next == &ballooned_pages)
175                 return NULL;
176         return list_entry(next, struct page, lru);
177 }
178
179 static void balloon_alarm(unsigned long unused)
180 {
181         schedule_work(&balloon_worker);
182 }
183
184 static unsigned long current_target(void)
185 {
186         unsigned long target = min(balloon_stats.target_pages, balloon_stats.hard_limit);
187
188         target = min(target,
189                      balloon_stats.current_pages +
190                      balloon_stats.balloon_low +
191                      balloon_stats.balloon_high);
192
193         return target;
194 }
195
196 static int increase_reservation(unsigned long nr_pages)
197 {
198         unsigned long  pfn, i, flags;
199         struct page   *page;
200         long           rc;
201         struct xen_memory_reservation reservation = {
202                 .address_bits = 0,
203                 .extent_order = 0,
204                 .domid        = DOMID_SELF
205         };
206
207         if (nr_pages > ARRAY_SIZE(frame_list))
208                 nr_pages = ARRAY_SIZE(frame_list);
209
210         spin_lock_irqsave(&balloon_lock, flags);
211
212         page = balloon_first_page();
213         for (i = 0; i < nr_pages; i++) {
214                 BUG_ON(page == NULL);
215                 frame_list[i] = page_to_pfn(page);;
216                 page = balloon_next_page(page);
217         }
218
219         set_xen_guest_handle(reservation.extent_start, frame_list);
220         reservation.nr_extents = nr_pages;
221         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
222         if (rc < nr_pages) {
223                 if (rc > 0) {
224                         int ret;
225
226                         /* We hit the Xen hard limit: reprobe. */
227                         reservation.nr_extents = rc;
228                         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
229                                                    &reservation);
230                         BUG_ON(ret != rc);
231                 }
232                 if (rc >= 0)
233                         balloon_stats.hard_limit = (balloon_stats.current_pages + rc -
234                                                     balloon_stats.driver_pages);
235                 goto out;
236         }
237
238         for (i = 0; i < nr_pages; i++) {
239                 page = balloon_retrieve();
240                 BUG_ON(page == NULL);
241
242                 pfn = page_to_pfn(page);
243                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
244                        phys_to_machine_mapping_valid(pfn));
245
246                 set_phys_to_machine(pfn, frame_list[i]);
247
248                 /* Link back into the page tables if not highmem. */
249                 if (pfn < max_low_pfn) {
250                         int ret;
251                         ret = HYPERVISOR_update_va_mapping(
252                                 (unsigned long)__va(pfn << PAGE_SHIFT),
253                                 mfn_pte(frame_list[i], PAGE_KERNEL),
254                                 0);
255                         BUG_ON(ret);
256                 }
257
258                 /* Relinquish the page back to the allocator. */
259                 ClearPageReserved(page);
260                 init_page_count(page);
261                 __free_page(page);
262         }
263
264         balloon_stats.current_pages += nr_pages;
265         totalram_pages = balloon_stats.current_pages;
266
267  out:
268         spin_unlock_irqrestore(&balloon_lock, flags);
269
270         return 0;
271 }
272
273 static int decrease_reservation(unsigned long nr_pages)
274 {
275         unsigned long  pfn, i, flags;
276         struct page   *page;
277         int            need_sleep = 0;
278         int ret;
279         struct xen_memory_reservation reservation = {
280                 .address_bits = 0,
281                 .extent_order = 0,
282                 .domid        = DOMID_SELF
283         };
284
285         if (nr_pages > ARRAY_SIZE(frame_list))
286                 nr_pages = ARRAY_SIZE(frame_list);
287
288         for (i = 0; i < nr_pages; i++) {
289                 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
290                         nr_pages = i;
291                         need_sleep = 1;
292                         break;
293                 }
294
295                 pfn = page_to_pfn(page);
296                 frame_list[i] = pfn_to_mfn(pfn);
297
298                 scrub_page(page);
299         }
300
301         /* Ensure that ballooned highmem pages don't have kmaps. */
302         kmap_flush_unused();
303         flush_tlb_all();
304
305         spin_lock_irqsave(&balloon_lock, flags);
306
307         /* No more mappings: invalidate P2M and add to balloon. */
308         for (i = 0; i < nr_pages; i++) {
309                 pfn = mfn_to_pfn(frame_list[i]);
310                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
311                 balloon_append(pfn_to_page(pfn));
312         }
313
314         set_xen_guest_handle(reservation.extent_start, frame_list);
315         reservation.nr_extents   = nr_pages;
316         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
317         BUG_ON(ret != nr_pages);
318
319         balloon_stats.current_pages -= nr_pages;
320         totalram_pages = balloon_stats.current_pages;
321
322         spin_unlock_irqrestore(&balloon_lock, flags);
323
324         return need_sleep;
325 }
326
327 /*
328  * We avoid multiple worker processes conflicting via the balloon mutex.
329  * We may of course race updates of the target counts (which are protected
330  * by the balloon lock), or with changes to the Xen hard limit, but we will
331  * recover from these in time.
332  */
333 static void balloon_process(struct work_struct *work)
334 {
335         int need_sleep = 0;
336         long credit;
337
338         mutex_lock(&balloon_mutex);
339
340         do {
341                 credit = current_target() - balloon_stats.current_pages;
342                 if (credit > 0)
343                         need_sleep = (increase_reservation(credit) != 0);
344                 if (credit < 0)
345                         need_sleep = (decrease_reservation(-credit) != 0);
346
347 #ifndef CONFIG_PREEMPT
348                 if (need_resched())
349                         schedule();
350 #endif
351         } while ((credit != 0) && !need_sleep);
352
353         /* Schedule more work if there is some still to be done. */
354         if (current_target() != balloon_stats.current_pages)
355                 mod_timer(&balloon_timer, jiffies + HZ);
356
357         mutex_unlock(&balloon_mutex);
358 }
359
360 /* Resets the Xen limit, sets new target, and kicks off processing. */
361 static void balloon_set_new_target(unsigned long target)
362 {
363         /* No need for lock. Not read-modify-write updates. */
364         balloon_stats.hard_limit   = ~0UL;
365         balloon_stats.target_pages = target;
366         schedule_work(&balloon_worker);
367 }
368
369 static struct xenbus_watch target_watch =
370 {
371         .node = "memory/target"
372 };
373
374 /* React to a change in the target key */
375 static void watch_target(struct xenbus_watch *watch,
376                          const char **vec, unsigned int len)
377 {
378         unsigned long long new_target;
379         int err;
380
381         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
382         if (err != 1) {
383                 /* This is ok (for domain0 at least) - so just return */
384                 return;
385         }
386
387         /* The given memory/target value is in KiB, so it needs converting to
388          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
389          */
390         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
391 }
392
393 static int balloon_init_watcher(struct notifier_block *notifier,
394                                 unsigned long event,
395                                 void *data)
396 {
397         int err;
398
399         err = register_xenbus_watch(&target_watch);
400         if (err)
401                 printk(KERN_ERR "Failed to set balloon watcher\n");
402
403         return NOTIFY_DONE;
404 }
405
406 static struct notifier_block xenstore_notifier;
407
408 static int __init balloon_init(void)
409 {
410         unsigned long pfn;
411         struct page *page;
412
413         if (!xen_pv_domain())
414                 return -ENODEV;
415
416         pr_info("xen_balloon: Initialising balloon driver.\n");
417
418         balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
419         totalram_pages   = balloon_stats.current_pages;
420         balloon_stats.target_pages  = balloon_stats.current_pages;
421         balloon_stats.balloon_low   = 0;
422         balloon_stats.balloon_high  = 0;
423         balloon_stats.driver_pages  = 0UL;
424         balloon_stats.hard_limit    = ~0UL;
425
426         init_timer(&balloon_timer);
427         balloon_timer.data = 0;
428         balloon_timer.function = balloon_alarm;
429
430         register_balloon(&balloon_sysdev);
431
432         /* Initialise the balloon with excess memory space. */
433         for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
434                 page = pfn_to_page(pfn);
435                 if (!PageReserved(page))
436                         balloon_append(page);
437         }
438
439         target_watch.callback = watch_target;
440         xenstore_notifier.notifier_call = balloon_init_watcher;
441
442         register_xenstore_notifier(&xenstore_notifier);
443
444         return 0;
445 }
446
447 subsys_initcall(balloon_init);
448
449 static void balloon_exit(void)
450 {
451     /* XXX - release balloon here */
452     return;
453 }
454
455 module_exit(balloon_exit);
456
457 #define BALLOON_SHOW(name, format, args...)                             \
458         static ssize_t show_##name(struct sys_device *dev,              \
459                                    struct sysdev_attribute *attr,       \
460                                    char *buf)                           \
461         {                                                               \
462                 return sprintf(buf, format, ##args);                    \
463         }                                                               \
464         static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
465
466 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
467 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
468 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
469 BALLOON_SHOW(hard_limit_kb,
470              (balloon_stats.hard_limit!=~0UL) ? "%lu\n" : "???\n",
471              (balloon_stats.hard_limit!=~0UL) ? PAGES2KB(balloon_stats.hard_limit) : 0);
472 BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
473
474 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
475                               char *buf)
476 {
477         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
478 }
479
480 static ssize_t store_target_kb(struct sys_device *dev,
481                                struct sysdev_attribute *attr,
482                                const char *buf,
483                                size_t count)
484 {
485         char *endchar;
486         unsigned long long target_bytes;
487
488         if (!capable(CAP_SYS_ADMIN))
489                 return -EPERM;
490
491         target_bytes = memparse(buf, &endchar);
492
493         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
494
495         return count;
496 }
497
498 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
499                    show_target_kb, store_target_kb);
500
501 static struct sysdev_attribute *balloon_attrs[] = {
502         &attr_target_kb,
503 };
504
505 static struct attribute *balloon_info_attrs[] = {
506         &attr_current_kb.attr,
507         &attr_low_kb.attr,
508         &attr_high_kb.attr,
509         &attr_hard_limit_kb.attr,
510         &attr_driver_kb.attr,
511         NULL
512 };
513
514 static struct attribute_group balloon_info_group = {
515         .name = "info",
516         .attrs = balloon_info_attrs,
517 };
518
519 static struct sysdev_class balloon_sysdev_class = {
520         .name = BALLOON_CLASS_NAME,
521 };
522
523 static int register_balloon(struct sys_device *sysdev)
524 {
525         int i, error;
526
527         error = sysdev_class_register(&balloon_sysdev_class);
528         if (error)
529                 return error;
530
531         sysdev->id = 0;
532         sysdev->cls = &balloon_sysdev_class;
533
534         error = sysdev_register(sysdev);
535         if (error) {
536                 sysdev_class_unregister(&balloon_sysdev_class);
537                 return error;
538         }
539
540         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
541                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
542                 if (error)
543                         goto fail;
544         }
545
546         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
547         if (error)
548                 goto fail;
549
550         return 0;
551
552  fail:
553         while (--i >= 0)
554                 sysdev_remove_file(sysdev, balloon_attrs[i]);
555         sysdev_unregister(sysdev);
556         sysdev_class_unregister(&balloon_sysdev_class);
557         return error;
558 }
559
560 MODULE_LICENSE("GPL");