xen/balloon: Remove pr_info's and don't alter retry_count
[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 #include <asm/e820.h>
54
55 #include <asm/xen/hypervisor.h>
56 #include <asm/xen/hypercall.h>
57
58 #include <xen/xen.h>
59 #include <xen/interface/xen.h>
60 #include <xen/interface/memory.h>
61 #include <xen/xenbus.h>
62 #include <xen/features.h>
63 #include <xen/page.h>
64
65 #define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
66
67 #define BALLOON_CLASS_NAME "xen_memory"
68
69 /*
70  * balloon_process() state:
71  *
72  * BP_DONE: done or nothing to do,
73  * BP_EAGAIN: error, go to sleep,
74  * BP_ECANCELED: error, balloon operation canceled.
75  */
76
77 enum bp_state {
78         BP_DONE,
79         BP_EAGAIN,
80         BP_ECANCELED
81 };
82
83 #define RETRY_UNLIMITED 0
84
85 struct balloon_stats {
86         /* We aim for 'current allocation' == 'target allocation'. */
87         unsigned long current_pages;
88         unsigned long target_pages;
89         /* Number of pages in high- and low-memory balloons. */
90         unsigned long balloon_low;
91         unsigned long balloon_high;
92         unsigned long schedule_delay;
93         unsigned long max_schedule_delay;
94         unsigned long retry_count;
95         unsigned long max_retry_count;
96 };
97
98 static DEFINE_MUTEX(balloon_mutex);
99
100 static struct sys_device balloon_sysdev;
101
102 static int register_balloon(struct sys_device *sysdev);
103
104 static struct balloon_stats balloon_stats;
105
106 /* We increase/decrease in batches which fit in a page */
107 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
108
109 #ifdef CONFIG_HIGHMEM
110 #define inc_totalhigh_pages() (totalhigh_pages++)
111 #define dec_totalhigh_pages() (totalhigh_pages--)
112 #else
113 #define inc_totalhigh_pages() do {} while(0)
114 #define dec_totalhigh_pages() do {} while(0)
115 #endif
116
117 /* List of ballooned pages, threaded through the mem_map array. */
118 static LIST_HEAD(ballooned_pages);
119
120 /* Main work function, always executed in process context. */
121 static void balloon_process(struct work_struct *work);
122 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
123
124 /* When ballooning out (allocating memory to return to Xen) we don't really
125    want the kernel to try too hard since that can trigger the oom killer. */
126 #define GFP_BALLOON \
127         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
128
129 static void scrub_page(struct page *page)
130 {
131 #ifdef CONFIG_XEN_SCRUB_PAGES
132         clear_highpage(page);
133 #endif
134 }
135
136 /* balloon_append: add the given page to the balloon. */
137 static void __balloon_append(struct page *page)
138 {
139         /* Lowmem is re-populated first, so highmem pages go at list tail. */
140         if (PageHighMem(page)) {
141                 list_add_tail(&page->lru, &ballooned_pages);
142                 balloon_stats.balloon_high++;
143                 dec_totalhigh_pages();
144         } else {
145                 list_add(&page->lru, &ballooned_pages);
146                 balloon_stats.balloon_low++;
147         }
148 }
149
150 static void balloon_append(struct page *page)
151 {
152         __balloon_append(page);
153         totalram_pages--;
154 }
155
156 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
157 static struct page *balloon_retrieve(void)
158 {
159         struct page *page;
160
161         if (list_empty(&ballooned_pages))
162                 return NULL;
163
164         page = list_entry(ballooned_pages.next, struct page, lru);
165         list_del(&page->lru);
166
167         if (PageHighMem(page)) {
168                 balloon_stats.balloon_high--;
169                 inc_totalhigh_pages();
170         }
171         else
172                 balloon_stats.balloon_low--;
173
174         totalram_pages++;
175
176         return page;
177 }
178
179 static struct page *balloon_first_page(void)
180 {
181         if (list_empty(&ballooned_pages))
182                 return NULL;
183         return list_entry(ballooned_pages.next, struct page, lru);
184 }
185
186 static struct page *balloon_next_page(struct page *page)
187 {
188         struct list_head *next = page->lru.next;
189         if (next == &ballooned_pages)
190                 return NULL;
191         return list_entry(next, struct page, lru);
192 }
193
194 static enum bp_state update_schedule(enum bp_state state)
195 {
196         if (state == BP_DONE) {
197                 balloon_stats.schedule_delay = 1;
198                 balloon_stats.retry_count = 1;
199                 return BP_DONE;
200         }
201
202         ++balloon_stats.retry_count;
203
204         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
205                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
206                 balloon_stats.schedule_delay = 1;
207                 balloon_stats.retry_count = 1;
208                 return BP_ECANCELED;
209         }
210
211         balloon_stats.schedule_delay <<= 1;
212
213         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
214                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
215
216         return BP_EAGAIN;
217 }
218
219 static unsigned long current_target(void)
220 {
221         unsigned long target = balloon_stats.target_pages;
222
223         target = min(target,
224                      balloon_stats.current_pages +
225                      balloon_stats.balloon_low +
226                      balloon_stats.balloon_high);
227
228         return target;
229 }
230
231 static enum bp_state increase_reservation(unsigned long nr_pages)
232 {
233         int rc;
234         unsigned long  pfn, i;
235         struct page   *page;
236         struct xen_memory_reservation reservation = {
237                 .address_bits = 0,
238                 .extent_order = 0,
239                 .domid        = DOMID_SELF
240         };
241
242         if (nr_pages > ARRAY_SIZE(frame_list))
243                 nr_pages = ARRAY_SIZE(frame_list);
244
245         page = balloon_first_page();
246         for (i = 0; i < nr_pages; i++) {
247                 if (!page) {
248                         nr_pages = i;
249                         break;
250                 }
251                 frame_list[i] = page_to_pfn(page);
252                 page = balloon_next_page(page);
253         }
254
255         set_xen_guest_handle(reservation.extent_start, frame_list);
256         reservation.nr_extents = nr_pages;
257         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
258         if (rc <= 0)
259                 return BP_EAGAIN;
260
261         for (i = 0; i < rc; i++) {
262                 page = balloon_retrieve();
263                 BUG_ON(page == NULL);
264
265                 pfn = page_to_pfn(page);
266                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
267                        phys_to_machine_mapping_valid(pfn));
268
269                 set_phys_to_machine(pfn, frame_list[i]);
270
271                 /* Link back into the page tables if not highmem. */
272                 if (pfn < max_low_pfn) {
273                         int ret;
274                         ret = HYPERVISOR_update_va_mapping(
275                                 (unsigned long)__va(pfn << PAGE_SHIFT),
276                                 mfn_pte(frame_list[i], PAGE_KERNEL),
277                                 0);
278                         BUG_ON(ret);
279                 }
280
281                 /* Relinquish the page back to the allocator. */
282                 ClearPageReserved(page);
283                 init_page_count(page);
284                 __free_page(page);
285         }
286
287         balloon_stats.current_pages += rc;
288
289         return BP_DONE;
290 }
291
292 static enum bp_state decrease_reservation(unsigned long nr_pages)
293 {
294         enum bp_state state = BP_DONE;
295         unsigned long  pfn, i;
296         struct page   *page;
297         int ret;
298         struct xen_memory_reservation reservation = {
299                 .address_bits = 0,
300                 .extent_order = 0,
301                 .domid        = DOMID_SELF
302         };
303
304         if (nr_pages > ARRAY_SIZE(frame_list))
305                 nr_pages = ARRAY_SIZE(frame_list);
306
307         for (i = 0; i < nr_pages; i++) {
308                 if ((page = alloc_page(GFP_BALLOON)) == NULL) {
309                         nr_pages = i;
310                         state = BP_EAGAIN;
311                         break;
312                 }
313
314                 pfn = page_to_pfn(page);
315                 frame_list[i] = pfn_to_mfn(pfn);
316
317                 scrub_page(page);
318
319                 if (!PageHighMem(page)) {
320                         ret = HYPERVISOR_update_va_mapping(
321                                 (unsigned long)__va(pfn << PAGE_SHIFT),
322                                 __pte_ma(0), 0);
323                         BUG_ON(ret);
324                 }
325
326         }
327
328         /* Ensure that ballooned highmem pages don't have kmaps. */
329         kmap_flush_unused();
330         flush_tlb_all();
331
332         /* No more mappings: invalidate P2M and add to balloon. */
333         for (i = 0; i < nr_pages; i++) {
334                 pfn = mfn_to_pfn(frame_list[i]);
335                 set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
336                 balloon_append(pfn_to_page(pfn));
337         }
338
339         set_xen_guest_handle(reservation.extent_start, frame_list);
340         reservation.nr_extents   = nr_pages;
341         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
342         BUG_ON(ret != nr_pages);
343
344         balloon_stats.current_pages -= nr_pages;
345
346         return state;
347 }
348
349 /*
350  * We avoid multiple worker processes conflicting via the balloon mutex.
351  * We may of course race updates of the target counts (which are protected
352  * by the balloon lock), or with changes to the Xen hard limit, but we will
353  * recover from these in time.
354  */
355 static void balloon_process(struct work_struct *work)
356 {
357         enum bp_state state = BP_DONE;
358         long credit;
359
360         mutex_lock(&balloon_mutex);
361
362         do {
363                 credit = current_target() - balloon_stats.current_pages;
364
365                 if (credit > 0)
366                         state = increase_reservation(credit);
367
368                 if (credit < 0)
369                         state = decrease_reservation(-credit);
370
371                 state = update_schedule(state);
372
373 #ifndef CONFIG_PREEMPT
374                 if (need_resched())
375                         schedule();
376 #endif
377         } while (credit && state == BP_DONE);
378
379         /* Schedule more work if there is some still to be done. */
380         if (state == BP_EAGAIN)
381                 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
382
383         mutex_unlock(&balloon_mutex);
384 }
385
386 /* Resets the Xen limit, sets new target, and kicks off processing. */
387 static void balloon_set_new_target(unsigned long target)
388 {
389         /* No need for lock. Not read-modify-write updates. */
390         balloon_stats.target_pages = target;
391         schedule_delayed_work(&balloon_worker, 0);
392 }
393
394 static struct xenbus_watch target_watch =
395 {
396         .node = "memory/target"
397 };
398
399 /* React to a change in the target key */
400 static void watch_target(struct xenbus_watch *watch,
401                          const char **vec, unsigned int len)
402 {
403         unsigned long long new_target;
404         int err;
405
406         err = xenbus_scanf(XBT_NIL, "memory", "target", "%llu", &new_target);
407         if (err != 1) {
408                 /* This is ok (for domain0 at least) - so just return */
409                 return;
410         }
411
412         /* The given memory/target value is in KiB, so it needs converting to
413          * pages. PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
414          */
415         balloon_set_new_target(new_target >> (PAGE_SHIFT - 10));
416 }
417
418 static int balloon_init_watcher(struct notifier_block *notifier,
419                                 unsigned long event,
420                                 void *data)
421 {
422         int err;
423
424         err = register_xenbus_watch(&target_watch);
425         if (err)
426                 printk(KERN_ERR "Failed to set balloon watcher\n");
427
428         return NOTIFY_DONE;
429 }
430
431 static struct notifier_block xenstore_notifier;
432
433 static int __init balloon_init(void)
434 {
435         unsigned long pfn, extra_pfn_end;
436         struct page *page;
437
438         if (!xen_pv_domain())
439                 return -ENODEV;
440
441         pr_info("xen_balloon: Initialising balloon driver.\n");
442
443         balloon_stats.current_pages = min(xen_start_info->nr_pages, max_pfn);
444         balloon_stats.target_pages  = balloon_stats.current_pages;
445         balloon_stats.balloon_low   = 0;
446         balloon_stats.balloon_high  = 0;
447
448         balloon_stats.schedule_delay = 1;
449         balloon_stats.max_schedule_delay = 32;
450         balloon_stats.retry_count = 1;
451         balloon_stats.max_retry_count = RETRY_UNLIMITED;
452
453         register_balloon(&balloon_sysdev);
454
455         /*
456          * Initialise the balloon with excess memory space.  We need
457          * to make sure we don't add memory which doesn't exist or
458          * logically exist.  The E820 map can be trimmed to be smaller
459          * than the amount of physical memory due to the mem= command
460          * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
461          * on a system with memory which requires highmem to access,
462          * don't try to use it.
463          */
464         extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
465                             (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
466         for (pfn = PFN_UP(xen_extra_mem_start);
467              pfn < extra_pfn_end;
468              pfn++) {
469                 page = pfn_to_page(pfn);
470                 /* totalram_pages doesn't include the boot-time
471                    balloon extension, so don't subtract from it. */
472                 __balloon_append(page);
473         }
474
475         target_watch.callback = watch_target;
476         xenstore_notifier.notifier_call = balloon_init_watcher;
477
478         register_xenstore_notifier(&xenstore_notifier);
479
480         return 0;
481 }
482
483 subsys_initcall(balloon_init);
484
485 static void balloon_exit(void)
486 {
487     /* XXX - release balloon here */
488     return;
489 }
490
491 module_exit(balloon_exit);
492
493 #define BALLOON_SHOW(name, format, args...)                             \
494         static ssize_t show_##name(struct sys_device *dev,              \
495                                    struct sysdev_attribute *attr,       \
496                                    char *buf)                           \
497         {                                                               \
498                 return sprintf(buf, format, ##args);                    \
499         }                                                               \
500         static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
501
502 BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
503 BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
504 BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
505
506 static SYSDEV_ULONG_ATTR(schedule_delay, 0444, balloon_stats.schedule_delay);
507 static SYSDEV_ULONG_ATTR(max_schedule_delay, 0644, balloon_stats.max_schedule_delay);
508 static SYSDEV_ULONG_ATTR(retry_count, 0444, balloon_stats.retry_count);
509 static SYSDEV_ULONG_ATTR(max_retry_count, 0644, balloon_stats.max_retry_count);
510
511 static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
512                               char *buf)
513 {
514         return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
515 }
516
517 static ssize_t store_target_kb(struct sys_device *dev,
518                                struct sysdev_attribute *attr,
519                                const char *buf,
520                                size_t count)
521 {
522         char *endchar;
523         unsigned long long target_bytes;
524
525         if (!capable(CAP_SYS_ADMIN))
526                 return -EPERM;
527
528         target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
529
530         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
531
532         return count;
533 }
534
535 static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
536                    show_target_kb, store_target_kb);
537
538
539 static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
540                               char *buf)
541 {
542         return sprintf(buf, "%llu\n",
543                        (unsigned long long)balloon_stats.target_pages
544                        << PAGE_SHIFT);
545 }
546
547 static ssize_t store_target(struct sys_device *dev,
548                             struct sysdev_attribute *attr,
549                             const char *buf,
550                             size_t count)
551 {
552         char *endchar;
553         unsigned long long target_bytes;
554
555         if (!capable(CAP_SYS_ADMIN))
556                 return -EPERM;
557
558         target_bytes = memparse(buf, &endchar);
559
560         balloon_set_new_target(target_bytes >> PAGE_SHIFT);
561
562         return count;
563 }
564
565 static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
566                    show_target, store_target);
567
568
569 static struct sysdev_attribute *balloon_attrs[] = {
570         &attr_target_kb,
571         &attr_target,
572         &attr_schedule_delay.attr,
573         &attr_max_schedule_delay.attr,
574         &attr_retry_count.attr,
575         &attr_max_retry_count.attr
576 };
577
578 static struct attribute *balloon_info_attrs[] = {
579         &attr_current_kb.attr,
580         &attr_low_kb.attr,
581         &attr_high_kb.attr,
582         NULL
583 };
584
585 static struct attribute_group balloon_info_group = {
586         .name = "info",
587         .attrs = balloon_info_attrs,
588 };
589
590 static struct sysdev_class balloon_sysdev_class = {
591         .name = BALLOON_CLASS_NAME,
592 };
593
594 static int register_balloon(struct sys_device *sysdev)
595 {
596         int i, error;
597
598         error = sysdev_class_register(&balloon_sysdev_class);
599         if (error)
600                 return error;
601
602         sysdev->id = 0;
603         sysdev->cls = &balloon_sysdev_class;
604
605         error = sysdev_register(sysdev);
606         if (error) {
607                 sysdev_class_unregister(&balloon_sysdev_class);
608                 return error;
609         }
610
611         for (i = 0; i < ARRAY_SIZE(balloon_attrs); i++) {
612                 error = sysdev_create_file(sysdev, balloon_attrs[i]);
613                 if (error)
614                         goto fail;
615         }
616
617         error = sysfs_create_group(&sysdev->kobj, &balloon_info_group);
618         if (error)
619                 goto fail;
620
621         return 0;
622
623  fail:
624         while (--i >= 0)
625                 sysdev_remove_file(sysdev, balloon_attrs[i]);
626         sysdev_unregister(sysdev);
627         sysdev_class_unregister(&balloon_sysdev_class);
628         return error;
629 }
630
631 MODULE_LICENSE("GPL");