of/xsysace: Fix OF probing on little-endian systems
[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 #include <linux/gfp.h>
47
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 <asm/xen/hypervisor.h>
55 #include <asm/xen/hypercall.h>
56
57 #include <xen/xen.h>
58 #include <xen/interface/xen.h>
59 #include <xen/interface/memory.h>
60 #include <xen/xenbus.h>
61 #include <xen/features.h>
62 #include <xen/page.h>
63
64 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
65
66 #define BALLOON_CLASS_NAME "xen_memory"
67
68 struct balloon_stats {
69         /* We aim for 'current allocation' == 'target allocation'. */
70         unsigned long current_pages;
71         unsigned long target_pages;
72         /*
73          * Drivers may alter the memory reservation independently, but they
74          * must inform the balloon driver so we avoid hitting the hard limit.
75          */
76         unsigned long driver_pages;
77         /* Number of pages in high- and low-memory balloons. */
78         unsigned long balloon_low;
79         unsigned long balloon_high;
80 };
81
82 static DEFINE_MUTEX(balloon_mutex);
83
84 static struct sys_device balloon_sysdev;
85
86 static int register_balloon(struct sys_device *sysdev);
87
88 static struct balloon_stats balloon_stats;
89
90 /* We increase/decrease in batches which fit in a page */
91 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
92
93 #ifdef CONFIG_HIGHMEM
94 #define inc_totalhigh_pages() (totalhigh_pages++)
95 #define dec_totalhigh_pages() (totalhigh_pages--)
96 #else
97 #define inc_totalhigh_pages() do {} while(0)
98 #define dec_totalhigh_pages() do {} while(0)
99 #endif
100
101 /* List of ballooned pages, threaded through the mem_map array. */
102 static LIST_HEAD(ballooned_pages);
103
104 /* Main work function, always executed in process context. */
105 static void balloon_process(struct work_struct *work);
106 static DECLARE_WORK(balloon_worker, balloon_process);
107 static struct timer_list balloon_timer;
108
109 /* When ballooning out (allocating memory to return to Xen) we don't really
110    want the kernel to try too hard since that can trigger the oom killer. */
111 #define GFP_BALLOON \
112         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
113
114 static void scrub_page(struct page *page)
115 {
116 #ifdef CONFIG_XEN_SCRUB_PAGES
117         clear_highpage(page);
118 #endif
119 }
120
121 /* balloon_append: add the given page to the balloon. */
122 static void balloon_append(struct page *page)
123 {
124         /* Lowmem is re-populated first, so highmem pages go at list tail. */
125         if (PageHighMem(page)) {
126                 list_add_tail(&page->lru, &ballooned_pages);
127                 balloon_stats.balloon_high++;
128                 dec_totalhigh_pages();
129         } else {
130                 list_add(&page->lru, &ballooned_pages);
131                 balloon_stats.balloon_low++;
132         }
133
134         totalram_pages--;
135 }
136
137 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
138 static struct page *balloon_retrieve(void)
139 {
140         struct page *page;
141
142         if (list_empty(&ballooned_pages))
143                 return NULL;
144
145         page = list_entry(ballooned_pages.next, struct page, lru);
146         list_del(&page->lru);
147
148         if (PageHighMem(page)) {
149                 balloon_stats.balloon_high--;
150                 inc_totalhigh_pages();
151         }
152         else
153                 balloon_stats.balloon_low--;
154
155         totalram_pages++;
156
157         return page;
158 }
159
160 static struct page *balloon_first_page(void)
161 {
162         if (list_empty(&ballooned_pages))
163                 return NULL;
164         return list_entry(ballooned_pages.next, struct page, lru);
165 }
166
167 static struct page *balloon_next_page(struct page *page)
168 {
169         struct list_head *next = page->lru.next;
170         if (next == &ballooned_pages)
171                 return NULL;
172         return list_entry(next, struct page, lru);
173 }
174
175 static void balloon_alarm(unsigned long unused)
176 {
177         schedule_work(&balloon_worker);
178 }
179
180 static unsigned long current_target(void)
181 {
182         unsigned long target = balloon_stats.target_pages;
183
184         target = min(target,
185                      balloon_stats.current_pages +
186                      balloon_stats.balloon_low +
187                      balloon_stats.balloon_high);
188
189         return target;
190 }
191
192 static int increase_reservation(unsigned long nr_pages)
193 {
194         unsigned long  pfn, i, flags;
195         struct page   *page;
196         long           rc;
197         struct xen_memory_reservation reservation = {
198                 .address_bits = 0,
199                 .extent_order = 0,
200                 .domid        = DOMID_SELF
201         };
202
203         if (nr_pages > ARRAY_SIZE(frame_list))
204                 nr_pages = ARRAY_SIZE(frame_list);
205
206         spin_lock_irqsave(&xen_reservation_lock, flags);
207
208         page = balloon_first_page();
209         for (i = 0; i < nr_pages; i++) {
210                 BUG_ON(page == NULL);
211                 frame_list[i] = page_to_pfn(page);
212                 page = balloon_next_page(page);
213         }
214
215         set_xen_guest_handle(reservation.extent_start, frame_list);
216         reservation.nr_extents = nr_pages;
217         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
218         if (rc < 0)
219                 goto out;
220
221         for (i = 0; i < rc; i++) {
222                 page = balloon_retrieve();
223                 BUG_ON(page == NULL);
224
225                 pfn = page_to_pfn(page);
226                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
227                        phys_to_machine_mapping_valid(pfn));
228
229                 set_phys_to_machine(pfn, frame_list[i]);
230
231                 /* Link back into the page tables if not highmem. */
232                 if (pfn < max_low_pfn) {
233                         int ret;
234                         ret = HYPERVISOR_update_va_mapping(
235                                 (unsigned long)__va(pfn << PAGE_SHIFT),
236                                 mfn_pte(frame_list[i], PAGE_KERNEL),
237                                 0);
238                         BUG_ON(ret);
239                 }
240
241                 /* Relinquish the page back to the allocator. */
242                 ClearPageReserved(page);
243                 init_page_count(page);
244                 __free_page(page);
245         }
246
247         balloon_stats.current_pages += rc;
248
249  out:
250         spin_unlock_irqrestore(&xen_reservation_lock, flags);
251
252         return rc < 0 ? rc : rc != nr_pages;
253 }
254
255 static int decrease_reservation(unsigned long nr_pages)
256 {
257         unsigned long  pfn, i, flags;
258         struct page   *page;
259         int            need_sleep = 0;
260         int ret;
261         struct xen_memory_reservation reservation = {
262                 .address_bits = 0,
263                 .extent_order = 0,
264                 .domid        = DOMID_SELF
265         };
266
267         if (nr_pages > ARRAY_SIZE(frame_list))
268                 nr_pages = ARRAY_SIZE(frame_list);
269
270         for (i = 0; i < nr_pages; i++) {
271                 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
272                         nr_pages = i;
273                         need_sleep = 1;
274                         break;
275                 }
276
277                 pfn = page_to_pfn(page);
278                 frame_list[i] = pfn_to_mfn(pfn);
279
280                 scrub_page(page);
281
282                 if (!PageHighMem(page)) {
283                         ret = HYPERVISOR_update_va_mapping(
284                                 (unsigned long)__va(pfn << PAGE_SHIFT),
285                                 __pte_ma(0), 0);
286                         BUG_ON(ret);
287                 }
288
289         }
290
291         /* Ensure that ballooned highmem pages don't have kmaps. */
292         kmap_flush_unused();
293         flush_tlb_all();
294
295         spin_lock_irqsave(&xen_reservation_lock, flags);
296
297         /* No more mappings: invalidate P2M and add to balloon. */
298         for (i = 0; i < nr_pages; i++) {
299                 pfn = mfn_to_pfn(frame_list[i]);
300                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
301                 balloon_append(pfn_to_page(pfn));
302         }
303
304         set_xen_guest_handle(reservation.extent_start, frame_list);
305         reservation.nr_extents   = nr_pages;
306         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
307         BUG_ON(ret != nr_pages);
308
309         balloon_stats.current_pages -= nr_pages;
310
311         spin_unlock_irqrestore(&xen_reservation_lock, flags);
312
313         return need_sleep;
314 }
315
316 /*
317  * We avoid multiple worker processes conflicting via the balloon mutex.
318  * We may of course race updates of the target counts (which are protected
319  * by the balloon lock), or with changes to the Xen hard limit, but we will
320  * recover from these in time.
321  */
322 static void balloon_process(struct work_struct *work)
323 {
324         int need_sleep = 0;
325         long credit;
326
327         mutex_lock(&balloon_mutex);
328
329         do {
330                 credit = current_target() - balloon_stats.current_pages;
331                 if (credit > 0)
332                         need_sleep = (increase_reservation(credit) != 0);
333                 if (credit < 0)
334                         need_sleep = (decrease_reservation(-credit) != 0);
335
336 #ifndef CONFIG_PREEMPT
337                 if (need_resched())
338                         schedule();
339 #endif
340         } while ((credit != 0) && !need_sleep);
341
342         /* Schedule more work if there is some still to be done. */
343         if (current_target() != balloon_stats.current_pages)
344                 mod_timer(&balloon_timer, jiffies + HZ);
345
346         mutex_unlock(&balloon_mutex);
347 }
348
349 /* Resets the Xen limit, sets new target, and kicks off processing. */
350 static void balloon_set_new_target(unsigned long target)
351 {
352         /* No need for lock. Not read-modify-write updates. */
353         balloon_stats.target_pages = target;
354         schedule_work(&balloon_worker);
355 }
356
357 static struct xenbus_watch target_watch =
358 {
359         .node = "memory/target"
360 };
361
362 /* React to a change in the target key */
363 static void watch_target(struct xenbus_watch *watch,
364                          const char **vec, unsigned int len)
365 {
366         unsigned long long new_target;
367         int err;
368
369         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
370         if (err != 1) {
371                 /* This is ok (for domain0 at least) - so just return */
372                 return;
373         }
374
375         /* The given memory/target value is in KiB, so it needs converting to
376          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
377          */
378         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
379 }
380
381 static int balloon_init_watcher(struct notifier_block *notifier,
382                                 unsigned long event,
383                                 void *data)
384 {
385         int err;
386
387         err = register_xenbus_watch(&target_watch);
388         if (err)
389                 printk(KERN_ERR "Failed to set balloon watcher\n");
390
391         return NOTIFY_DONE;
392 }
393
394 static struct notifier_block xenstore_notifier;
395
396 static int __init balloon_init(void)
397 {
398         unsigned long pfn;
399         struct page *page;
400
401         if (!xen_pv_domain())
402                 return -ENODEV;
403
404         pr_info("xen_balloon: Initialising balloon driver.\n");
405
406         balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
407         balloon_stats.target_pages  = balloon_stats.current_pages;
408         balloon_stats.balloon_low   = 0;
409         balloon_stats.balloon_high  = 0;
410         balloon_stats.driver_pages  = 0UL;
411
412         init_timer(&balloon_timer);
413         balloon_timer.data = 0;
414         balloon_timer.function = balloon_alarm;
415
416         register_balloon(&balloon_sysdev);
417
418         /* Initialise the balloon with excess memory space. */
419         for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) {
420                 page = pfn_to_page(pfn);
421                 if (!PageReserved(page))
422                         balloon_append(page);
423         }
424
425         target_watch.callback = watch_target;
426         xenstore_notifier.notifier_call = balloon_init_watcher;
427
428         register_xenstore_notifier(&xenstore_notifier);
429
430         return 0;
431 }
432
433 subsys_initcall(balloon_init);
434
435 static void balloon_exit(void)
436 {
437     /* XXX - release balloon here */
438     return;
439 }
440
441 module_exit(balloon_exit);
442
443 #define BALLOON_SHOW(name, format, args...)                             \
444         static ssize_t show_##name(struct sys_device *dev,              \
445                                    struct sysdev_attribute *attr,       \
446                                    char *buf)                           \
447         {                                                               \
448                 return sprintf(buf, format, ##args);                    \
449         }                                                               \
450         static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
451
452 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
453 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
454 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
455 BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
456
457 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
458                               char *buf)
459 {
460         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
461 }
462
463 static ssize_t store_target_kb(struct sys_device *dev,
464                                struct sysdev_attribute *attr,
465                                const char *buf,
466                                size_t count)
467 {
468         char *endchar;
469         unsigned long long target_bytes;
470
471         if (!capable(CAP_SYS_ADMIN))
472                 return -EPERM;
473
474         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
475
476         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
477
478         return count;
479 }
480
481 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
482                    show_target_kb, store_target_kb);
483
484
485 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
486                               char *buf)
487 {
488         return sprintf(buf, "%llu\n",
489                        (unsigned long long)balloon_stats.target_pages
490                        << PAGE_SHIFT);
491 }
492
493 static ssize_t store_target(struct sys_device *dev,
494                             struct sysdev_attribute *attr,
495                             const char *buf,
496                             size_t count)
497 {
498         char *endchar;
499         unsigned long long target_bytes;
500
501         if (!capable(CAP_SYS_ADMIN))
502                 return -EPERM;
503
504         target_bytes = memparse(buf, &endchar);
505
506         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
507
508         return count;
509 }
510
511 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
512                    show_target, store_target);
513
514
515 static struct sysdev_attribute *balloon_attrs[] = {
516         &attr_target_kb,
517         &attr_target,
518 };
519
520 static struct attribute *balloon_info_attrs[] = {
521         &attr_current_kb.attr,
522         &attr_low_kb.attr,
523         &attr_high_kb.attr,
524         &attr_driver_kb.attr,
525         NULL
526 };
527
528 static struct attribute_group balloon_info_group = {
529         .name = "info",
530         .attrs = balloon_info_attrs,
531 };
532
533 static struct sysdev_class balloon_sysdev_class = {
534         .name = BALLOON_CLASS_NAME,
535 };
536
537 static int register_balloon(struct sys_device *sysdev)
538 {
539         int i, error;
540
541         error = sysdev_class_register(&balloon_sysdev_class);
542         if (error)
543                 return error;
544
545         sysdev->id = 0;
546         sysdev->cls = &balloon_sysdev_class;
547
548         error = sysdev_register(sysdev);
549         if (error) {
550                 sysdev_class_unregister(&balloon_sysdev_class);
551                 return error;
552         }
553
554         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
555                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
556                 if (error)
557                         goto fail;
558         }
559
560         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
561         if (error)
562                 goto fail;
563
564         return 0;
565
566  fail:
567         while (--i >= 0)
568                 sysdev_remove_file(sysdev, balloon_attrs[i]);
569         sysdev_unregister(sysdev);
570         sysdev_class_unregister(&balloon_sysdev_class);
571         return error;
572 }
573
574 MODULE_LICENSE("GPL");