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Jeremy Fitzhardinge17758262008-04-02 10:54:13 -07001/******************************************************************************
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>
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070044#include <linux/list.h>
45#include <linux/sysdev.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090046#include <linux/gfp.h>
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070047
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070048#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
Jeremy Fitzhardingeecbf29c2008-12-16 12:37:07 -080054#include <asm/xen/hypervisor.h>
55#include <asm/xen/hypercall.h>
Jeremy Fitzhardinge1ccbf532009-10-06 15:11:14 -070056
57#include <xen/xen.h>
Jeremy Fitzhardingeecbf29c2008-12-16 12:37:07 -080058#include <xen/interface/xen.h>
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070059#include <xen/interface/memory.h>
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070060#include <xen/xenbus.h>
61#include <xen/features.h>
62#include <xen/page.h>
63
64#define PAGES2KB(_p) ((_p)<<(PAGE_SHIFT-10))
65
Jeremy Fitzhardinge167e6cf2008-07-24 16:27:52 -070066#define BALLOON_CLASS_NAME "xen_memory"
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070067
68struct balloon_stats {
69 /* We aim for 'current allocation' == 'target allocation'. */
70 unsigned long current_pages;
71 unsigned long target_pages;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070072 /*
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
82static DEFINE_MUTEX(balloon_mutex);
83
84static struct sys_device balloon_sysdev;
85
86static int register_balloon(struct sys_device *sysdev);
87
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070088static struct balloon_stats balloon_stats;
89
90/* We increase/decrease in batches which fit in a page */
91static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
92
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070093#ifdef CONFIG_HIGHMEM
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -070094#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. */
102static LIST_HEAD(ballooned_pages);
103
104/* Main work function, always executed in process context. */
105static void balloon_process(struct work_struct *work);
106static DECLARE_WORK(balloon_worker, balloon_process);
107static 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
114static void scrub_page(struct page *page)
115{
116#ifdef CONFIG_XEN_SCRUB_PAGES
Jeremy Fitzhardinge26a3e992008-11-17 09:35:00 -0800117 clear_highpage(page);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700118#endif
119}
120
121/* balloon_append: add the given page to the balloon. */
122static 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 }
Gianluca Guida3d65c942009-07-30 22:54:36 +0100133
134 totalram_pages--;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700135}
136
137/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
138static 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
Gianluca Guida3d65c942009-07-30 22:54:36 +0100155 totalram_pages++;
156
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700157 return page;
158}
159
160static 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
167static 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
175static void balloon_alarm(unsigned long unused)
176{
177 schedule_work(&balloon_worker);
178}
179
180static unsigned long current_target(void)
181{
Ian Campbellbc2c0302009-06-05 11:58:37 +0100182 unsigned long target = balloon_stats.target_pages;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700183
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
192static 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
Alex Nixon19001c82009-02-09 12:05:46 -0800206 spin_lock_irqsave(&xen_reservation_lock, flags);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700207
208 page = balloon_first_page();
209 for (i = 0; i < nr_pages; i++) {
210 BUG_ON(page == NULL);
Joe Perchesa419aef2009-08-18 11:18:35 -0700211 frame_list[i] = page_to_pfn(page);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700212 page = balloon_next_page(page);
213 }
214
Isaku Yamahataa90971e2008-05-26 23:31:14 +0100215 set_xen_guest_handle(reservation.extent_start, frame_list);
Jeremy Fitzhardingefde28e82008-07-24 16:28:00 -0700216 reservation.nr_extents = nr_pages;
217 rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
Ian Campbellbc2c0302009-06-05 11:58:37 +0100218 if (rc < 0)
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700219 goto out;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700220
Ian Campbellbc2c0302009-06-05 11:58:37 +0100221 for (i = 0; i < rc; i++) {
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700222 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
Ian Campbellbc2c0302009-06-05 11:58:37 +0100247 balloon_stats.current_pages += rc;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700248
249 out:
Alex Nixon19001c82009-02-09 12:05:46 -0800250 spin_unlock_irqrestore(&xen_reservation_lock, flags);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700251
Ian Campbellbc2c0302009-06-05 11:58:37 +0100252 return rc < 0 ? rc : rc != nr_pages;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700253}
254
255static 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);
Dan Magenheimer1058a752009-01-22 14:36:08 -0800281
Ian Campbellff4ce8c2009-01-23 16:26:21 +0000282 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
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700289 }
290
291 /* Ensure that ballooned highmem pages don't have kmaps. */
292 kmap_flush_unused();
293 flush_tlb_all();
294
Alex Nixon19001c82009-02-09 12:05:46 -0800295 spin_lock_irqsave(&xen_reservation_lock, flags);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700296
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
Isaku Yamahataa90971e2008-05-26 23:31:14 +0100304 set_xen_guest_handle(reservation.extent_start, frame_list);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700305 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;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700310
Alex Nixon19001c82009-02-09 12:05:46 -0800311 spin_unlock_irqrestore(&xen_reservation_lock, flags);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700312
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 */
322static 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. */
Adrian Bunk955d6f12008-05-26 23:31:17 +0100350static void balloon_set_new_target(unsigned long target)
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700351{
352 /* No need for lock. Not read-modify-write updates. */
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700353 balloon_stats.target_pages = target;
354 schedule_work(&balloon_worker);
355}
356
357static struct xenbus_watch target_watch =
358{
359 .node = "memory/target"
360};
361
362/* React to a change in the target key */
363static 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
381static 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
394static struct notifier_block xenstore_notifier;
395
396static int __init balloon_init(void)
397{
398 unsigned long pfn;
399 struct page *page;
400
Jeremy Fitzhardinge6e833582008-08-19 13:16:17 -0700401 if (!xen_pv_domain())
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700402 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);
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700407 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;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700411
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
433subsys_initcall(balloon_init);
434
435static void balloon_exit(void)
436{
437 /* XXX - release balloon here */
438 return;
439}
440
441module_exit(balloon_exit);
442
Jeremy Fitzhardinge167e6cf2008-07-24 16:27:52 -0700443#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 } \
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700450 static SYSDEV_ATTR(name, S_IRUGO, show_##name, NULL)
451
452BALLOON_SHOW(current_kb, "%lu\n", PAGES2KB(balloon_stats.current_pages));
453BALLOON_SHOW(low_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_low));
454BALLOON_SHOW(high_kb, "%lu\n", PAGES2KB(balloon_stats.balloon_high));
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700455BALLOON_SHOW(driver_kb, "%lu\n", PAGES2KB(balloon_stats.driver_pages));
456
Jeremy Fitzhardinge167e6cf2008-07-24 16:27:52 -0700457static ssize_t show_target_kb(struct sys_device *dev, struct sysdev_attribute *attr,
458 char *buf)
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700459{
460 return sprintf(buf, "%lu\n", PAGES2KB(balloon_stats.target_pages));
461}
462
463static ssize_t store_target_kb(struct sys_device *dev,
Andi Kleen4a0b2b42008-07-01 18:48:41 +0200464 struct sysdev_attribute *attr,
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700465 const char *buf,
466 size_t count)
467{
Jeremy Fitzhardinge167e6cf2008-07-24 16:27:52 -0700468 char *endchar;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700469 unsigned long long target_bytes;
470
471 if (!capable(CAP_SYS_ADMIN))
472 return -EPERM;
473
Jeremy Fitzhardinge618b2c82009-01-28 16:50:20 -0800474 target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700475
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700476 balloon_set_new_target(target_bytes >> PAGE_SHIFT);
477
478 return count;
479}
480
481static SYSDEV_ATTR(target_kb, S_IRUGO | S_IWUSR,
482 show_target_kb, store_target_kb);
483
Jeremy Fitzhardinge618b2c82009-01-28 16:50:20 -0800484
485static ssize_t show_target(struct sys_device *dev, struct sysdev_attribute *attr,
486 char *buf)
487{
488 return sprintf(buf, "%llu\n",
Jan Beulich06926982009-05-05 13:57:52 +0100489 (unsigned long long)balloon_stats.target_pages
490 << PAGE_SHIFT);
Jeremy Fitzhardinge618b2c82009-01-28 16:50:20 -0800491}
492
493static 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
511static SYSDEV_ATTR(target, S_IRUGO | S_IWUSR,
512 show_target, store_target);
513
514
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700515static struct sysdev_attribute *balloon_attrs[] = {
516 &attr_target_kb,
Jeremy Fitzhardinge618b2c82009-01-28 16:50:20 -0800517 &attr_target,
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700518};
519
520static struct attribute *balloon_info_attrs[] = {
521 &attr_current_kb.attr,
522 &attr_low_kb.attr,
523 &attr_high_kb.attr,
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700524 &attr_driver_kb.attr,
525 NULL
526};
527
528static struct attribute_group balloon_info_group = {
529 .name = "info",
530 .attrs = balloon_info_attrs,
531};
532
533static struct sysdev_class balloon_sysdev_class = {
534 .name = BALLOON_CLASS_NAME,
535};
536
537static 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
Jeremy Fitzhardinge17758262008-04-02 10:54:13 -0700574MODULE_LICENSE("GPL");