1 /******************************************************************************
2 * Xen balloon driver - enables returning/claiming memory to/from Xen.
3 *
4 * Copyright (c) 2003, B Dragovic
5 * Copyright (c) 2003-2004, M Williamson, K Fraser
6 * Copyright (c) 2005 Dan M. Smith, IBM Corporation
7 * Copyright (c) 2010 Daniel Kiper
8 *
9 * Memory hotplug support was written by Daniel Kiper. Work on
10 * it was sponsored by Google under Google Summer of Code 2010
11 * program. Jeremy Fitzhardinge from Citrix was the mentor for
12 * this project.
13 *
14 * This program is free software; you can redistribute it and/or
15 * modify it under the terms of the GNU General Public License version 2
16 * as published by the Free Software Foundation; or, when distributed
17 * separately from the Linux kernel or incorporated into other
18 * software packages, subject to the following license:
19 *
20 * Permission is hereby granted, free of charge, to any person obtaining a copy
21 * of this source file (the "Software"), to deal in the Software without
22 * restriction, including without limitation the rights to use, copy, modify,
23 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
24 * and to permit persons to whom the Software is furnished to do so, subject to
25 * the following conditions:
26 *
27 * The above copyright notice and this permission notice shall be included in
28 * all copies or substantial portions of the Software.
29 *
30 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
31 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
32 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
33 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
34 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
35 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
36 * IN THE SOFTWARE.
37 */
38
39 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
40
41 #include <linux/cpu.h>
42 #include <linux/kernel.h>
43 #include <linux/sched.h>
44 #include <linux/cred.h>
45 #include <linux/errno.h>
46 #include <linux/freezer.h>
47 #include <linux/kthread.h>
48 #include <linux/mm.h>
49 #include <linux/memblock.h>
50 #include <linux/pagemap.h>
51 #include <linux/highmem.h>
52 #include <linux/mutex.h>
53 #include <linux/list.h>
54 #include <linux/gfp.h>
55 #include <linux/notifier.h>
56 #include <linux/memory.h>
57 #include <linux/memory_hotplug.h>
58 #include <linux/percpu-defs.h>
59 #include <linux/slab.h>
60 #include <linux/sysctl.h>
61 #include <linux/moduleparam.h>
62 #include <linux/jiffies.h>
63
64 #include <asm/page.h>
65 #include <asm/tlb.h>
66
67 #include <asm/xen/hypervisor.h>
68 #include <asm/xen/hypercall.h>
69
70 #include <xen/xen.h>
71 #include <xen/interface/xen.h>
72 #include <xen/interface/memory.h>
73 #include <xen/balloon.h>
74 #include <xen/features.h>
75 #include <xen/page.h>
76 #include <xen/mem-reservation.h>
77
78 #undef MODULE_PARAM_PREFIX
79 #define MODULE_PARAM_PREFIX "xen."
80
81 static uint __read_mostly balloon_boot_timeout = 180;
82 module_param(balloon_boot_timeout, uint, 0444);
83
84 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
85 static int xen_hotplug_unpopulated;
86
87 static struct ctl_table balloon_table[] = {
88 {
89 .procname = "hotplug_unpopulated",
90 .data = &xen_hotplug_unpopulated,
91 .maxlen = sizeof(int),
92 .mode = 0644,
93 .proc_handler = proc_dointvec_minmax,
94 .extra1 = SYSCTL_ZERO,
95 .extra2 = SYSCTL_ONE,
96 },
97 { }
98 };
99
100 #else
101 #define xen_hotplug_unpopulated 0
102 #endif
103
104 /*
105 * Use one extent per PAGE_SIZE to avoid to break down the page into
106 * multiple frame.
107 */
108 #define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
109
110 /*
111 * balloon_thread() state:
112 *
113 * BP_DONE: done or nothing to do,
114 * BP_WAIT: wait to be rescheduled,
115 * BP_EAGAIN: error, go to sleep,
116 * BP_ECANCELED: error, balloon operation canceled.
117 */
118
119 static enum bp_state {
120 BP_DONE,
121 BP_WAIT,
122 BP_EAGAIN,
123 BP_ECANCELED
124 } balloon_state = BP_DONE;
125
126 /* Main waiting point for xen-balloon thread. */
127 static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq);
128
129 static DEFINE_MUTEX(balloon_mutex);
130
131 struct balloon_stats balloon_stats;
132 EXPORT_SYMBOL_GPL(balloon_stats);
133
134 /* We increase/decrease in batches which fit in a page */
135 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
136
137
138 /* List of ballooned pages, threaded through the mem_map array. */
139 static LIST_HEAD(ballooned_pages);
140 static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
141
142 /* When ballooning out (allocating memory to return to Xen) we don't really
143 want the kernel to try too hard since that can trigger the oom killer. */
144 #define GFP_BALLOON \
145 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
146
147 /* balloon_append: add the given page to the balloon. */
balloon_append(struct page * page)148 static void balloon_append(struct page *page)
149 {
150 __SetPageOffline(page);
151
152 /* Lowmem is re-populated first, so highmem pages go at list tail. */
153 if (PageHighMem(page)) {
154 list_add_tail(&page->lru, &ballooned_pages);
155 balloon_stats.balloon_high++;
156 } else {
157 list_add(&page->lru, &ballooned_pages);
158 balloon_stats.balloon_low++;
159 }
160 wake_up(&balloon_wq);
161 }
162
163 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
balloon_retrieve(bool require_lowmem)164 static struct page *balloon_retrieve(bool require_lowmem)
165 {
166 struct page *page;
167
168 if (list_empty(&ballooned_pages))
169 return NULL;
170
171 page = list_entry(ballooned_pages.next, struct page, lru);
172 if (require_lowmem && PageHighMem(page))
173 return NULL;
174 list_del(&page->lru);
175
176 if (PageHighMem(page))
177 balloon_stats.balloon_high--;
178 else
179 balloon_stats.balloon_low--;
180
181 __ClearPageOffline(page);
182 return page;
183 }
184
balloon_next_page(struct page * page)185 static struct page *balloon_next_page(struct page *page)
186 {
187 struct list_head *next = page->lru.next;
188 if (next == &ballooned_pages)
189 return NULL;
190 return list_entry(next, struct page, lru);
191 }
192
update_schedule(void)193 static void update_schedule(void)
194 {
195 if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED)
196 return;
197
198 if (balloon_state == BP_DONE) {
199 balloon_stats.schedule_delay = 1;
200 balloon_stats.retry_count = 1;
201 return;
202 }
203
204 ++balloon_stats.retry_count;
205
206 if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
207 balloon_stats.retry_count > balloon_stats.max_retry_count) {
208 balloon_stats.schedule_delay = 1;
209 balloon_stats.retry_count = 1;
210 balloon_state = BP_ECANCELED;
211 return;
212 }
213
214 balloon_stats.schedule_delay <<= 1;
215
216 if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
217 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
218
219 balloon_state = BP_EAGAIN;
220 }
221
222 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
release_memory_resource(struct resource * resource)223 static void release_memory_resource(struct resource *resource)
224 {
225 if (!resource)
226 return;
227
228 /*
229 * No need to reset region to identity mapped since we now
230 * know that no I/O can be in this region
231 */
232 release_resource(resource);
233 kfree(resource);
234 }
235
additional_memory_resource(phys_addr_t size)236 static struct resource *additional_memory_resource(phys_addr_t size)
237 {
238 struct resource *res;
239 int ret;
240
241 res = kzalloc(sizeof(*res), GFP_KERNEL);
242 if (!res)
243 return NULL;
244
245 res->name = "System RAM";
246 res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
247
248 ret = allocate_resource(&iomem_resource, res,
249 size, 0, -1,
250 PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
251 if (ret < 0) {
252 pr_err("Cannot allocate new System RAM resource\n");
253 kfree(res);
254 return NULL;
255 }
256
257 return res;
258 }
259
reserve_additional_memory(void)260 static enum bp_state reserve_additional_memory(void)
261 {
262 long credit;
263 struct resource *resource;
264 int nid, rc;
265 unsigned long balloon_hotplug;
266
267 credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
268 - balloon_stats.total_pages;
269
270 /*
271 * Already hotplugged enough pages? Wait for them to be
272 * onlined.
273 */
274 if (credit <= 0)
275 return BP_WAIT;
276
277 balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
278
279 resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
280 if (!resource)
281 goto err;
282
283 nid = memory_add_physaddr_to_nid(resource->start);
284
285 #ifdef CONFIG_XEN_HAVE_PVMMU
286 /*
287 * We don't support PV MMU when Linux and Xen is using
288 * different page granularity.
289 */
290 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
291
292 /*
293 * add_memory() will build page tables for the new memory so
294 * the p2m must contain invalid entries so the correct
295 * non-present PTEs will be written.
296 *
297 * If a failure occurs, the original (identity) p2m entries
298 * are not restored since this region is now known not to
299 * conflict with any devices.
300 */
301 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
302 unsigned long pfn, i;
303
304 pfn = PFN_DOWN(resource->start);
305 for (i = 0; i < balloon_hotplug; i++) {
306 if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
307 pr_warn("set_phys_to_machine() failed, no memory added\n");
308 goto err;
309 }
310 }
311 }
312 #endif
313
314 /*
315 * add_memory_resource() will call online_pages() which in its turn
316 * will call xen_online_page() callback causing deadlock if we don't
317 * release balloon_mutex here. Unlocking here is safe because the
318 * callers drop the mutex before trying again.
319 */
320 mutex_unlock(&balloon_mutex);
321 /* add_memory_resource() requires the device_hotplug lock */
322 lock_device_hotplug();
323 rc = add_memory_resource(nid, resource, MHP_MERGE_RESOURCE);
324 unlock_device_hotplug();
325 mutex_lock(&balloon_mutex);
326
327 if (rc) {
328 pr_warn("Cannot add additional memory (%i)\n", rc);
329 goto err;
330 }
331
332 balloon_stats.total_pages += balloon_hotplug;
333
334 return BP_WAIT;
335 err:
336 release_memory_resource(resource);
337 return BP_ECANCELED;
338 }
339
xen_online_page(struct page * page,unsigned int order)340 static void xen_online_page(struct page *page, unsigned int order)
341 {
342 unsigned long i, size = (1 << order);
343 unsigned long start_pfn = page_to_pfn(page);
344 struct page *p;
345
346 pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
347 mutex_lock(&balloon_mutex);
348 for (i = 0; i < size; i++) {
349 p = pfn_to_page(start_pfn + i);
350 balloon_append(p);
351 }
352 mutex_unlock(&balloon_mutex);
353 }
354
xen_memory_notifier(struct notifier_block * nb,unsigned long val,void * v)355 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
356 {
357 if (val == MEM_ONLINE)
358 wake_up(&balloon_thread_wq);
359
360 return NOTIFY_OK;
361 }
362
363 static struct notifier_block xen_memory_nb = {
364 .notifier_call = xen_memory_notifier,
365 .priority = 0
366 };
367 #else
reserve_additional_memory(void)368 static enum bp_state reserve_additional_memory(void)
369 {
370 balloon_stats.target_pages = balloon_stats.current_pages +
371 balloon_stats.target_unpopulated;
372 return BP_ECANCELED;
373 }
374 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
375
current_credit(void)376 static long current_credit(void)
377 {
378 return balloon_stats.target_pages - balloon_stats.current_pages;
379 }
380
balloon_is_inflated(void)381 static bool balloon_is_inflated(void)
382 {
383 return balloon_stats.balloon_low || balloon_stats.balloon_high;
384 }
385
increase_reservation(unsigned long nr_pages)386 static enum bp_state increase_reservation(unsigned long nr_pages)
387 {
388 int rc;
389 unsigned long i;
390 struct page *page;
391
392 if (nr_pages > ARRAY_SIZE(frame_list))
393 nr_pages = ARRAY_SIZE(frame_list);
394
395 page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
396 for (i = 0; i < nr_pages; i++) {
397 if (!page) {
398 nr_pages = i;
399 break;
400 }
401
402 frame_list[i] = page_to_xen_pfn(page);
403 page = balloon_next_page(page);
404 }
405
406 rc = xenmem_reservation_increase(nr_pages, frame_list);
407 if (rc <= 0)
408 return BP_EAGAIN;
409
410 for (i = 0; i < rc; i++) {
411 page = balloon_retrieve(false);
412 BUG_ON(page == NULL);
413
414 xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
415
416 /* Relinquish the page back to the allocator. */
417 free_reserved_page(page);
418 }
419
420 balloon_stats.current_pages += rc;
421
422 return BP_DONE;
423 }
424
decrease_reservation(unsigned long nr_pages,gfp_t gfp)425 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
426 {
427 enum bp_state state = BP_DONE;
428 unsigned long i;
429 struct page *page, *tmp;
430 int ret;
431 LIST_HEAD(pages);
432
433 if (nr_pages > ARRAY_SIZE(frame_list))
434 nr_pages = ARRAY_SIZE(frame_list);
435
436 for (i = 0; i < nr_pages; i++) {
437 page = alloc_page(gfp);
438 if (page == NULL) {
439 nr_pages = i;
440 state = BP_EAGAIN;
441 break;
442 }
443 adjust_managed_page_count(page, -1);
444 xenmem_reservation_scrub_page(page);
445 list_add(&page->lru, &pages);
446 }
447
448 /*
449 * Ensure that ballooned highmem pages don't have kmaps.
450 *
451 * Do this before changing the p2m as kmap_flush_unused()
452 * reads PTEs to obtain pages (and hence needs the original
453 * p2m entry).
454 */
455 kmap_flush_unused();
456
457 /*
458 * Setup the frame, update direct mapping, invalidate P2M,
459 * and add to balloon.
460 */
461 i = 0;
462 list_for_each_entry_safe(page, tmp, &pages, lru) {
463 frame_list[i++] = xen_page_to_gfn(page);
464
465 xenmem_reservation_va_mapping_reset(1, &page);
466
467 list_del(&page->lru);
468
469 balloon_append(page);
470 }
471
472 flush_tlb_all();
473
474 ret = xenmem_reservation_decrease(nr_pages, frame_list);
475 BUG_ON(ret != nr_pages);
476
477 balloon_stats.current_pages -= nr_pages;
478
479 return state;
480 }
481
482 /*
483 * Stop waiting if either state is BP_DONE and ballooning action is
484 * needed, or if the credit has changed while state is not BP_DONE.
485 */
balloon_thread_cond(long credit)486 static bool balloon_thread_cond(long credit)
487 {
488 if (balloon_state == BP_DONE)
489 credit = 0;
490
491 return current_credit() != credit || kthread_should_stop();
492 }
493
494 /*
495 * As this is a kthread it is guaranteed to run as a single instance only.
496 * We may of course race updates of the target counts (which are protected
497 * by the balloon lock), or with changes to the Xen hard limit, but we will
498 * recover from these in time.
499 */
balloon_thread(void * unused)500 static int balloon_thread(void *unused)
501 {
502 long credit;
503 unsigned long timeout;
504
505 set_freezable();
506 for (;;) {
507 switch (balloon_state) {
508 case BP_DONE:
509 case BP_ECANCELED:
510 timeout = 3600 * HZ;
511 break;
512 case BP_EAGAIN:
513 timeout = balloon_stats.schedule_delay * HZ;
514 break;
515 case BP_WAIT:
516 timeout = HZ;
517 break;
518 }
519
520 credit = current_credit();
521
522 wait_event_freezable_timeout(balloon_thread_wq,
523 balloon_thread_cond(credit), timeout);
524
525 if (kthread_should_stop())
526 return 0;
527
528 mutex_lock(&balloon_mutex);
529
530 credit = current_credit();
531
532 if (credit > 0) {
533 if (balloon_is_inflated())
534 balloon_state = increase_reservation(credit);
535 else
536 balloon_state = reserve_additional_memory();
537 }
538
539 if (credit < 0) {
540 long n_pages;
541
542 n_pages = min(-credit, si_mem_available());
543 balloon_state = decrease_reservation(n_pages,
544 GFP_BALLOON);
545 if (balloon_state == BP_DONE && n_pages != -credit &&
546 n_pages < totalreserve_pages)
547 balloon_state = BP_EAGAIN;
548 }
549
550 update_schedule();
551
552 mutex_unlock(&balloon_mutex);
553
554 cond_resched();
555 }
556 }
557
558 /* Resets the Xen limit, sets new target, and kicks off processing. */
balloon_set_new_target(unsigned long target)559 void balloon_set_new_target(unsigned long target)
560 {
561 /* No need for lock. Not read-modify-write updates. */
562 balloon_stats.target_pages = target;
563 wake_up(&balloon_thread_wq);
564 }
565 EXPORT_SYMBOL_GPL(balloon_set_new_target);
566
add_ballooned_pages(unsigned int nr_pages)567 static int add_ballooned_pages(unsigned int nr_pages)
568 {
569 enum bp_state st;
570
571 if (xen_hotplug_unpopulated) {
572 st = reserve_additional_memory();
573 if (st != BP_ECANCELED) {
574 int rc;
575
576 mutex_unlock(&balloon_mutex);
577 rc = wait_event_interruptible(balloon_wq,
578 !list_empty(&ballooned_pages));
579 mutex_lock(&balloon_mutex);
580 return rc ? -ENOMEM : 0;
581 }
582 }
583
584 if (si_mem_available() < nr_pages)
585 return -ENOMEM;
586
587 st = decrease_reservation(nr_pages, GFP_USER);
588 if (st != BP_DONE)
589 return -ENOMEM;
590
591 return 0;
592 }
593
594 /**
595 * xen_alloc_ballooned_pages - get pages that have been ballooned out
596 * @nr_pages: Number of pages to get
597 * @pages: pages returned
598 * @return 0 on success, error otherwise
599 */
xen_alloc_ballooned_pages(unsigned int nr_pages,struct page ** pages)600 int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
601 {
602 unsigned int pgno = 0;
603 struct page *page;
604 int ret;
605
606 mutex_lock(&balloon_mutex);
607
608 balloon_stats.target_unpopulated += nr_pages;
609
610 while (pgno < nr_pages) {
611 page = balloon_retrieve(true);
612 if (page) {
613 pages[pgno++] = page;
614 #ifdef CONFIG_XEN_HAVE_PVMMU
615 /*
616 * We don't support PV MMU when Linux and Xen is using
617 * different page granularity.
618 */
619 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
620
621 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
622 ret = xen_alloc_p2m_entry(page_to_pfn(page));
623 if (ret < 0)
624 goto out_undo;
625 }
626 #endif
627 } else {
628 ret = add_ballooned_pages(nr_pages - pgno);
629 if (ret < 0)
630 goto out_undo;
631 }
632 }
633 mutex_unlock(&balloon_mutex);
634 return 0;
635 out_undo:
636 mutex_unlock(&balloon_mutex);
637 xen_free_ballooned_pages(pgno, pages);
638 /*
639 * NB: xen_free_ballooned_pages will only subtract pgno pages, but since
640 * target_unpopulated is incremented with nr_pages at the start we need
641 * to remove the remaining ones also, or accounting will be screwed.
642 */
643 balloon_stats.target_unpopulated -= nr_pages - pgno;
644 return ret;
645 }
646 EXPORT_SYMBOL(xen_alloc_ballooned_pages);
647
648 /**
649 * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
650 * @nr_pages: Number of pages
651 * @pages: pages to return
652 */
xen_free_ballooned_pages(unsigned int nr_pages,struct page ** pages)653 void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
654 {
655 unsigned int i;
656
657 mutex_lock(&balloon_mutex);
658
659 for (i = 0; i < nr_pages; i++) {
660 if (pages[i])
661 balloon_append(pages[i]);
662 }
663
664 balloon_stats.target_unpopulated -= nr_pages;
665
666 /* The balloon may be too large now. Shrink it if needed. */
667 if (current_credit())
668 wake_up(&balloon_thread_wq);
669
670 mutex_unlock(&balloon_mutex);
671 }
672 EXPORT_SYMBOL(xen_free_ballooned_pages);
673
balloon_add_regions(void)674 static void __init balloon_add_regions(void)
675 {
676 unsigned long start_pfn, pages;
677 unsigned long pfn, extra_pfn_end;
678 unsigned int i;
679
680 for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
681 pages = xen_extra_mem[i].n_pfns;
682 if (!pages)
683 continue;
684
685 start_pfn = xen_extra_mem[i].start_pfn;
686
687 /*
688 * If the amount of usable memory has been limited (e.g., with
689 * the 'mem' command line parameter), don't add pages beyond
690 * this limit.
691 */
692 extra_pfn_end = min(max_pfn, start_pfn + pages);
693
694 for (pfn = start_pfn; pfn < extra_pfn_end; pfn++)
695 balloon_append(pfn_to_page(pfn));
696
697 balloon_stats.total_pages += extra_pfn_end - start_pfn;
698 }
699 }
700
balloon_init(void)701 static int __init balloon_init(void)
702 {
703 struct task_struct *task;
704
705 if (!xen_domain())
706 return -ENODEV;
707
708 pr_info("Initialising balloon driver\n");
709
710 #ifdef CONFIG_XEN_PV
711 balloon_stats.current_pages = xen_pv_domain()
712 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
713 : get_num_physpages();
714 #else
715 balloon_stats.current_pages = get_num_physpages();
716 #endif
717 balloon_stats.target_pages = balloon_stats.current_pages;
718 balloon_stats.balloon_low = 0;
719 balloon_stats.balloon_high = 0;
720 balloon_stats.total_pages = balloon_stats.current_pages;
721
722 balloon_stats.schedule_delay = 1;
723 balloon_stats.max_schedule_delay = 32;
724 balloon_stats.retry_count = 1;
725 balloon_stats.max_retry_count = 4;
726
727 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
728 set_online_page_callback(&xen_online_page);
729 register_memory_notifier(&xen_memory_nb);
730 register_sysctl_init("xen/balloon", balloon_table);
731 #endif
732
733 balloon_add_regions();
734
735 task = kthread_run(balloon_thread, NULL, "xen-balloon");
736 if (IS_ERR(task)) {
737 pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
738 return PTR_ERR(task);
739 }
740
741 /* Init the xen-balloon driver. */
742 xen_balloon_init();
743
744 return 0;
745 }
746 subsys_initcall(balloon_init);
747
balloon_wait_finish(void)748 static int __init balloon_wait_finish(void)
749 {
750 long credit, last_credit = 0;
751 unsigned long last_changed = 0;
752
753 if (!xen_domain())
754 return -ENODEV;
755
756 /* PV guests don't need to wait. */
757 if (xen_pv_domain() || !current_credit())
758 return 0;
759
760 pr_notice("Waiting for initial ballooning down having finished.\n");
761
762 while ((credit = current_credit()) < 0) {
763 if (credit != last_credit) {
764 last_changed = jiffies;
765 last_credit = credit;
766 }
767 if (balloon_state == BP_ECANCELED) {
768 pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
769 -credit);
770 if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout))
771 panic("Initial ballooning failed!\n");
772 }
773
774 schedule_timeout_interruptible(HZ / 10);
775 }
776
777 pr_notice("Initial ballooning down finished.\n");
778
779 return 0;
780 }
781 late_initcall_sync(balloon_wait_finish);
782