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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
81static uint __read_mostly balloon_boot_timeout = 180;
82module_param(balloon_boot_timeout, uint, 0444);
83
84#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
85static int xen_hotplug_unpopulated;
86
87static 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#else
100#define xen_hotplug_unpopulated 0
101#endif
102
103/*
104 * Use one extent per PAGE_SIZE to avoid to break down the page into
105 * multiple frame.
106 */
107#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
108
109/*
110 * balloon_thread() state:
111 *
112 * BP_DONE: done or nothing to do,
113 * BP_WAIT: wait to be rescheduled,
114 * BP_EAGAIN: error, go to sleep,
115 * BP_ECANCELED: error, balloon operation canceled.
116 */
117
118static enum bp_state {
119 BP_DONE,
120 BP_WAIT,
121 BP_EAGAIN,
122 BP_ECANCELED
123} balloon_state = BP_DONE;
124
125/* Main waiting point for xen-balloon thread. */
126static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq);
127
128static DEFINE_MUTEX(balloon_mutex);
129
130struct balloon_stats balloon_stats;
131EXPORT_SYMBOL_GPL(balloon_stats);
132
133/* We increase/decrease in batches which fit in a page */
134static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
135
136
137/* List of ballooned pages, threaded through the mem_map array. */
138static LIST_HEAD(ballooned_pages);
139static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
140
141/* When ballooning out (allocating memory to return to Xen) we don't really
142 want the kernel to try too hard since that can trigger the oom killer. */
143#define GFP_BALLOON \
144 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
145
146/* balloon_append: add the given page to the balloon. */
147static void balloon_append(struct page *page)
148{
149 __SetPageOffline(page);
150
151 /* Lowmem is re-populated first, so highmem pages go at list tail. */
152 if (PageHighMem(page)) {
153 list_add_tail(&page->lru, &ballooned_pages);
154 balloon_stats.balloon_high++;
155 } else {
156 list_add(&page->lru, &ballooned_pages);
157 balloon_stats.balloon_low++;
158 }
159 wake_up(&balloon_wq);
160}
161
162/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
163static struct page *balloon_retrieve(bool require_lowmem)
164{
165 struct page *page;
166
167 if (list_empty(&ballooned_pages))
168 return NULL;
169
170 page = list_entry(ballooned_pages.next, struct page, lru);
171 if (require_lowmem && PageHighMem(page))
172 return NULL;
173 list_del(&page->lru);
174
175 if (PageHighMem(page))
176 balloon_stats.balloon_high--;
177 else
178 balloon_stats.balloon_low--;
179
180 __ClearPageOffline(page);
181 return page;
182}
183
184static struct page *balloon_next_page(struct page *page)
185{
186 struct list_head *next = page->lru.next;
187 if (next == &ballooned_pages)
188 return NULL;
189 return list_entry(next, struct page, lru);
190}
191
192static void update_schedule(void)
193{
194 if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED)
195 return;
196
197 if (balloon_state == BP_DONE) {
198 balloon_stats.schedule_delay = 1;
199 balloon_stats.retry_count = 1;
200 return;
201 }
202
203 ++balloon_stats.retry_count;
204
205 if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
206 balloon_stats.retry_count > balloon_stats.max_retry_count) {
207 balloon_stats.schedule_delay = 1;
208 balloon_stats.retry_count = 1;
209 balloon_state = BP_ECANCELED;
210 return;
211 }
212
213 balloon_stats.schedule_delay <<= 1;
214
215 if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
216 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
217
218 balloon_state = BP_EAGAIN;
219}
220
221#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
222static void release_memory_resource(struct resource *resource)
223{
224 if (!resource)
225 return;
226
227 /*
228 * No need to reset region to identity mapped since we now
229 * know that no I/O can be in this region
230 */
231 release_resource(resource);
232 kfree(resource);
233}
234
235static struct resource *additional_memory_resource(phys_addr_t size)
236{
237 struct resource *res;
238 int ret;
239
240 res = kzalloc(sizeof(*res), GFP_KERNEL);
241 if (!res)
242 return NULL;
243
244 res->name = "System RAM";
245 res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
246
247 ret = allocate_resource(&iomem_resource, res,
248 size, 0, -1,
249 PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
250 if (ret < 0) {
251 pr_err("Cannot allocate new System RAM resource\n");
252 kfree(res);
253 return NULL;
254 }
255
256 return res;
257}
258
259static enum bp_state reserve_additional_memory(void)
260{
261 long credit;
262 struct resource *resource;
263 int nid, rc;
264 unsigned long balloon_hotplug;
265
266 credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
267 - balloon_stats.total_pages;
268
269 /*
270 * Already hotplugged enough pages? Wait for them to be
271 * onlined.
272 */
273 if (credit <= 0)
274 return BP_WAIT;
275
276 balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
277
278 resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
279 if (!resource)
280 goto err;
281
282 nid = memory_add_physaddr_to_nid(resource->start);
283
284#ifdef CONFIG_XEN_HAVE_PVMMU
285 /*
286 * We don't support PV MMU when Linux and Xen is using
287 * different page granularity.
288 */
289 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
290
291 /*
292 * add_memory() will build page tables for the new memory so
293 * the p2m must contain invalid entries so the correct
294 * non-present PTEs will be written.
295 *
296 * If a failure occurs, the original (identity) p2m entries
297 * are not restored since this region is now known not to
298 * conflict with any devices.
299 */
300 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
301 unsigned long pfn, i;
302
303 pfn = PFN_DOWN(resource->start);
304 for (i = 0; i < balloon_hotplug; i++) {
305 if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
306 pr_warn("set_phys_to_machine() failed, no memory added\n");
307 goto err;
308 }
309 }
310 }
311#endif
312
313 /*
314 * add_memory_resource() will call online_pages() which in its turn
315 * will call xen_online_page() callback causing deadlock if we don't
316 * release balloon_mutex here. Unlocking here is safe because the
317 * callers drop the mutex before trying again.
318 */
319 mutex_unlock(&balloon_mutex);
320 /* add_memory_resource() requires the device_hotplug lock */
321 lock_device_hotplug();
322 rc = add_memory_resource(nid, resource, MHP_MERGE_RESOURCE);
323 unlock_device_hotplug();
324 mutex_lock(&balloon_mutex);
325
326 if (rc) {
327 pr_warn("Cannot add additional memory (%i)\n", rc);
328 goto err;
329 }
330
331 balloon_stats.total_pages += balloon_hotplug;
332
333 return BP_WAIT;
334 err:
335 release_memory_resource(resource);
336 return BP_ECANCELED;
337}
338
339static void xen_online_page(struct page *page, unsigned int order)
340{
341 unsigned long i, size = (1 << order);
342 unsigned long start_pfn = page_to_pfn(page);
343 struct page *p;
344
345 pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
346 mutex_lock(&balloon_mutex);
347 for (i = 0; i < size; i++) {
348 p = pfn_to_page(start_pfn + i);
349 balloon_append(p);
350 }
351 mutex_unlock(&balloon_mutex);
352}
353
354static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
355{
356 if (val == MEM_ONLINE)
357 wake_up(&balloon_thread_wq);
358
359 return NOTIFY_OK;
360}
361
362static struct notifier_block xen_memory_nb = {
363 .notifier_call = xen_memory_notifier,
364 .priority = 0
365};
366#else
367static enum bp_state reserve_additional_memory(void)
368{
369 balloon_stats.target_pages = balloon_stats.current_pages +
370 balloon_stats.target_unpopulated;
371 return BP_ECANCELED;
372}
373#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
374
375static long current_credit(void)
376{
377 return balloon_stats.target_pages - balloon_stats.current_pages;
378}
379
380static bool balloon_is_inflated(void)
381{
382 return balloon_stats.balloon_low || balloon_stats.balloon_high;
383}
384
385static enum bp_state increase_reservation(unsigned long nr_pages)
386{
387 int rc;
388 unsigned long i;
389 struct page *page;
390
391 if (nr_pages > ARRAY_SIZE(frame_list))
392 nr_pages = ARRAY_SIZE(frame_list);
393
394 page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
395 for (i = 0; i < nr_pages; i++) {
396 if (!page) {
397 nr_pages = i;
398 break;
399 }
400
401 frame_list[i] = page_to_xen_pfn(page);
402 page = balloon_next_page(page);
403 }
404
405 rc = xenmem_reservation_increase(nr_pages, frame_list);
406 if (rc <= 0)
407 return BP_EAGAIN;
408
409 for (i = 0; i < rc; i++) {
410 page = balloon_retrieve(false);
411 BUG_ON(page == NULL);
412
413 xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
414
415 /* Relinquish the page back to the allocator. */
416 free_reserved_page(page);
417 }
418
419 balloon_stats.current_pages += rc;
420
421 return BP_DONE;
422}
423
424static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
425{
426 enum bp_state state = BP_DONE;
427 unsigned long i;
428 struct page *page, *tmp;
429 int ret;
430 LIST_HEAD(pages);
431
432 if (nr_pages > ARRAY_SIZE(frame_list))
433 nr_pages = ARRAY_SIZE(frame_list);
434
435 for (i = 0; i < nr_pages; i++) {
436 page = alloc_page(gfp);
437 if (page == NULL) {
438 nr_pages = i;
439 state = BP_EAGAIN;
440 break;
441 }
442 adjust_managed_page_count(page, -1);
443 xenmem_reservation_scrub_page(page);
444 list_add(&page->lru, &pages);
445 }
446
447 /*
448 * Ensure that ballooned highmem pages don't have kmaps.
449 *
450 * Do this before changing the p2m as kmap_flush_unused()
451 * reads PTEs to obtain pages (and hence needs the original
452 * p2m entry).
453 */
454 kmap_flush_unused();
455
456 /*
457 * Setup the frame, update direct mapping, invalidate P2M,
458 * and add to balloon.
459 */
460 i = 0;
461 list_for_each_entry_safe(page, tmp, &pages, lru) {
462 frame_list[i++] = xen_page_to_gfn(page);
463
464 xenmem_reservation_va_mapping_reset(1, &page);
465
466 list_del(&page->lru);
467
468 balloon_append(page);
469 }
470
471 flush_tlb_all();
472
473 ret = xenmem_reservation_decrease(nr_pages, frame_list);
474 BUG_ON(ret != nr_pages);
475
476 balloon_stats.current_pages -= nr_pages;
477
478 return state;
479}
480
481/*
482 * Stop waiting if either state is BP_DONE and ballooning action is
483 * needed, or if the credit has changed while state is not BP_DONE.
484 */
485static bool balloon_thread_cond(long credit)
486{
487 if (balloon_state == BP_DONE)
488 credit = 0;
489
490 return current_credit() != credit || kthread_should_stop();
491}
492
493/*
494 * As this is a kthread it is guaranteed to run as a single instance only.
495 * We may of course race updates of the target counts (which are protected
496 * by the balloon lock), or with changes to the Xen hard limit, but we will
497 * recover from these in time.
498 */
499static int balloon_thread(void *unused)
500{
501 long credit;
502 unsigned long timeout;
503
504 set_freezable();
505 for (;;) {
506 switch (balloon_state) {
507 case BP_DONE:
508 case BP_ECANCELED:
509 timeout = 3600 * HZ;
510 break;
511 case BP_EAGAIN:
512 timeout = balloon_stats.schedule_delay * HZ;
513 break;
514 case BP_WAIT:
515 timeout = HZ;
516 break;
517 }
518
519 credit = current_credit();
520
521 wait_event_freezable_timeout(balloon_thread_wq,
522 balloon_thread_cond(credit), timeout);
523
524 if (kthread_should_stop())
525 return 0;
526
527 mutex_lock(&balloon_mutex);
528
529 credit = current_credit();
530
531 if (credit > 0) {
532 if (balloon_is_inflated())
533 balloon_state = increase_reservation(credit);
534 else
535 balloon_state = reserve_additional_memory();
536 }
537
538 if (credit < 0) {
539 long n_pages;
540
541 n_pages = min(-credit, si_mem_available());
542 balloon_state = decrease_reservation(n_pages,
543 GFP_BALLOON);
544 if (balloon_state == BP_DONE && n_pages != -credit &&
545 n_pages < totalreserve_pages)
546 balloon_state = BP_EAGAIN;
547 }
548
549 update_schedule();
550
551 mutex_unlock(&balloon_mutex);
552
553 cond_resched();
554 }
555}
556
557/* Resets the Xen limit, sets new target, and kicks off processing. */
558void balloon_set_new_target(unsigned long target)
559{
560 /* No need for lock. Not read-modify-write updates. */
561 balloon_stats.target_pages = target;
562 wake_up(&balloon_thread_wq);
563}
564EXPORT_SYMBOL_GPL(balloon_set_new_target);
565
566static int add_ballooned_pages(unsigned int nr_pages)
567{
568 enum bp_state st;
569
570 if (xen_hotplug_unpopulated) {
571 st = reserve_additional_memory();
572 if (st != BP_ECANCELED) {
573 int rc;
574
575 mutex_unlock(&balloon_mutex);
576 rc = wait_event_interruptible(balloon_wq,
577 !list_empty(&ballooned_pages));
578 mutex_lock(&balloon_mutex);
579 return rc ? -ENOMEM : 0;
580 }
581 }
582
583 if (si_mem_available() < nr_pages)
584 return -ENOMEM;
585
586 st = decrease_reservation(nr_pages, GFP_USER);
587 if (st != BP_DONE)
588 return -ENOMEM;
589
590 return 0;
591}
592
593/**
594 * xen_alloc_ballooned_pages - get pages that have been ballooned out
595 * @nr_pages: Number of pages to get
596 * @pages: pages returned
597 * @return 0 on success, error otherwise
598 */
599int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
600{
601 unsigned int pgno = 0;
602 struct page *page;
603 int ret;
604
605 mutex_lock(&balloon_mutex);
606
607 balloon_stats.target_unpopulated += nr_pages;
608
609 while (pgno < nr_pages) {
610 page = balloon_retrieve(true);
611 if (page) {
612 pages[pgno++] = page;
613#ifdef CONFIG_XEN_HAVE_PVMMU
614 /*
615 * We don't support PV MMU when Linux and Xen is using
616 * different page granularity.
617 */
618 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
619
620 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
621 ret = xen_alloc_p2m_entry(page_to_pfn(page));
622 if (ret < 0)
623 goto out_undo;
624 }
625#endif
626 } else {
627 ret = add_ballooned_pages(nr_pages - pgno);
628 if (ret < 0)
629 goto out_undo;
630 }
631 }
632 mutex_unlock(&balloon_mutex);
633 return 0;
634 out_undo:
635 mutex_unlock(&balloon_mutex);
636 xen_free_ballooned_pages(pgno, pages);
637 /*
638 * NB: xen_free_ballooned_pages will only subtract pgno pages, but since
639 * target_unpopulated is incremented with nr_pages at the start we need
640 * to remove the remaining ones also, or accounting will be screwed.
641 */
642 balloon_stats.target_unpopulated -= nr_pages - pgno;
643 return ret;
644}
645EXPORT_SYMBOL(xen_alloc_ballooned_pages);
646
647/**
648 * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
649 * @nr_pages: Number of pages
650 * @pages: pages to return
651 */
652void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
653{
654 unsigned int i;
655
656 mutex_lock(&balloon_mutex);
657
658 for (i = 0; i < nr_pages; i++) {
659 if (pages[i])
660 balloon_append(pages[i]);
661 }
662
663 balloon_stats.target_unpopulated -= nr_pages;
664
665 /* The balloon may be too large now. Shrink it if needed. */
666 if (current_credit())
667 wake_up(&balloon_thread_wq);
668
669 mutex_unlock(&balloon_mutex);
670}
671EXPORT_SYMBOL(xen_free_ballooned_pages);
672
673static void __init balloon_add_regions(void)
674{
675#if defined(CONFIG_XEN_PV)
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#endif
700}
701
702static int __init balloon_init(void)
703{
704 struct task_struct *task;
705
706 if (!xen_domain())
707 return -ENODEV;
708
709 pr_info("Initialising balloon driver\n");
710
711#ifdef CONFIG_XEN_PV
712 balloon_stats.current_pages = xen_pv_domain()
713 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
714 : get_num_physpages();
715#else
716 balloon_stats.current_pages = get_num_physpages();
717#endif
718 balloon_stats.target_pages = balloon_stats.current_pages;
719 balloon_stats.balloon_low = 0;
720 balloon_stats.balloon_high = 0;
721 balloon_stats.total_pages = balloon_stats.current_pages;
722
723 balloon_stats.schedule_delay = 1;
724 balloon_stats.max_schedule_delay = 32;
725 balloon_stats.retry_count = 1;
726 balloon_stats.max_retry_count = 4;
727
728#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
729 set_online_page_callback(&xen_online_page);
730 register_memory_notifier(&xen_memory_nb);
731 register_sysctl_init("xen/balloon", balloon_table);
732#endif
733
734 balloon_add_regions();
735
736 task = kthread_run(balloon_thread, NULL, "xen-balloon");
737 if (IS_ERR(task)) {
738 pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
739 return PTR_ERR(task);
740 }
741
742 /* Init the xen-balloon driver. */
743 xen_balloon_init();
744
745 return 0;
746}
747subsys_initcall(balloon_init);
748
749static int __init balloon_wait_finish(void)
750{
751 long credit, last_credit = 0;
752 unsigned long last_changed = 0;
753
754 if (!xen_domain())
755 return -ENODEV;
756
757 /* PV guests don't need to wait. */
758 if (xen_pv_domain() || !current_credit())
759 return 0;
760
761 pr_notice("Waiting for initial ballooning down having finished.\n");
762
763 while ((credit = current_credit()) < 0) {
764 if (credit != last_credit) {
765 last_changed = jiffies;
766 last_credit = credit;
767 }
768 if (balloon_state == BP_ECANCELED) {
769 pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
770 -credit);
771 if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout))
772 panic("Initial ballooning failed!\n");
773 }
774
775 schedule_timeout_interruptible(HZ / 10);
776 }
777
778 pr_notice("Initial ballooning down finished.\n");
779
780 return 0;
781}
782late_initcall_sync(balloon_wait_finish);
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
81static uint __read_mostly balloon_boot_timeout = 180;
82module_param(balloon_boot_timeout, uint, 0444);
83
84#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
85static int xen_hotplug_unpopulated;
86
87static 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
100static struct ctl_table balloon_root[] = {
101 {
102 .procname = "balloon",
103 .mode = 0555,
104 .child = balloon_table,
105 },
106 { }
107};
108
109static struct ctl_table xen_root[] = {
110 {
111 .procname = "xen",
112 .mode = 0555,
113 .child = balloon_root,
114 },
115 { }
116};
117
118#else
119#define xen_hotplug_unpopulated 0
120#endif
121
122/*
123 * Use one extent per PAGE_SIZE to avoid to break down the page into
124 * multiple frame.
125 */
126#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
127
128/*
129 * balloon_thread() state:
130 *
131 * BP_DONE: done or nothing to do,
132 * BP_WAIT: wait to be rescheduled,
133 * BP_EAGAIN: error, go to sleep,
134 * BP_ECANCELED: error, balloon operation canceled.
135 */
136
137static enum bp_state {
138 BP_DONE,
139 BP_WAIT,
140 BP_EAGAIN,
141 BP_ECANCELED
142} balloon_state = BP_DONE;
143
144/* Main waiting point for xen-balloon thread. */
145static DECLARE_WAIT_QUEUE_HEAD(balloon_thread_wq);
146
147static DEFINE_MUTEX(balloon_mutex);
148
149struct balloon_stats balloon_stats;
150EXPORT_SYMBOL_GPL(balloon_stats);
151
152/* We increase/decrease in batches which fit in a page */
153static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
154
155
156/* List of ballooned pages, threaded through the mem_map array. */
157static LIST_HEAD(ballooned_pages);
158static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
159
160/* When ballooning out (allocating memory to return to Xen) we don't really
161 want the kernel to try too hard since that can trigger the oom killer. */
162#define GFP_BALLOON \
163 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
164
165/* balloon_append: add the given page to the balloon. */
166static void balloon_append(struct page *page)
167{
168 __SetPageOffline(page);
169
170 /* Lowmem is re-populated first, so highmem pages go at list tail. */
171 if (PageHighMem(page)) {
172 list_add_tail(&page->lru, &ballooned_pages);
173 balloon_stats.balloon_high++;
174 } else {
175 list_add(&page->lru, &ballooned_pages);
176 balloon_stats.balloon_low++;
177 }
178 wake_up(&balloon_wq);
179}
180
181/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
182static struct page *balloon_retrieve(bool require_lowmem)
183{
184 struct page *page;
185
186 if (list_empty(&ballooned_pages))
187 return NULL;
188
189 page = list_entry(ballooned_pages.next, struct page, lru);
190 if (require_lowmem && PageHighMem(page))
191 return NULL;
192 list_del(&page->lru);
193
194 if (PageHighMem(page))
195 balloon_stats.balloon_high--;
196 else
197 balloon_stats.balloon_low--;
198
199 __ClearPageOffline(page);
200 return page;
201}
202
203static struct page *balloon_next_page(struct page *page)
204{
205 struct list_head *next = page->lru.next;
206 if (next == &ballooned_pages)
207 return NULL;
208 return list_entry(next, struct page, lru);
209}
210
211static void update_schedule(void)
212{
213 if (balloon_state == BP_WAIT || balloon_state == BP_ECANCELED)
214 return;
215
216 if (balloon_state == BP_DONE) {
217 balloon_stats.schedule_delay = 1;
218 balloon_stats.retry_count = 1;
219 return;
220 }
221
222 ++balloon_stats.retry_count;
223
224 if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
225 balloon_stats.retry_count > balloon_stats.max_retry_count) {
226 balloon_stats.schedule_delay = 1;
227 balloon_stats.retry_count = 1;
228 balloon_state = BP_ECANCELED;
229 return;
230 }
231
232 balloon_stats.schedule_delay <<= 1;
233
234 if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
235 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
236
237 balloon_state = BP_EAGAIN;
238}
239
240#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
241static void release_memory_resource(struct resource *resource)
242{
243 if (!resource)
244 return;
245
246 /*
247 * No need to reset region to identity mapped since we now
248 * know that no I/O can be in this region
249 */
250 release_resource(resource);
251 kfree(resource);
252}
253
254static struct resource *additional_memory_resource(phys_addr_t size)
255{
256 struct resource *res;
257 int ret;
258
259 res = kzalloc(sizeof(*res), GFP_KERNEL);
260 if (!res)
261 return NULL;
262
263 res->name = "System RAM";
264 res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
265
266 ret = allocate_resource(&iomem_resource, res,
267 size, 0, -1,
268 PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
269 if (ret < 0) {
270 pr_err("Cannot allocate new System RAM resource\n");
271 kfree(res);
272 return NULL;
273 }
274
275 return res;
276}
277
278static enum bp_state reserve_additional_memory(void)
279{
280 long credit;
281 struct resource *resource;
282 int nid, rc;
283 unsigned long balloon_hotplug;
284
285 credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
286 - balloon_stats.total_pages;
287
288 /*
289 * Already hotplugged enough pages? Wait for them to be
290 * onlined.
291 */
292 if (credit <= 0)
293 return BP_WAIT;
294
295 balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
296
297 resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
298 if (!resource)
299 goto err;
300
301 nid = memory_add_physaddr_to_nid(resource->start);
302
303#ifdef CONFIG_XEN_HAVE_PVMMU
304 /*
305 * We don't support PV MMU when Linux and Xen is using
306 * different page granularity.
307 */
308 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
309
310 /*
311 * add_memory() will build page tables for the new memory so
312 * the p2m must contain invalid entries so the correct
313 * non-present PTEs will be written.
314 *
315 * If a failure occurs, the original (identity) p2m entries
316 * are not restored since this region is now known not to
317 * conflict with any devices.
318 */
319 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
320 unsigned long pfn, i;
321
322 pfn = PFN_DOWN(resource->start);
323 for (i = 0; i < balloon_hotplug; i++) {
324 if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
325 pr_warn("set_phys_to_machine() failed, no memory added\n");
326 goto err;
327 }
328 }
329 }
330#endif
331
332 /*
333 * add_memory_resource() will call online_pages() which in its turn
334 * will call xen_online_page() callback causing deadlock if we don't
335 * release balloon_mutex here. Unlocking here is safe because the
336 * callers drop the mutex before trying again.
337 */
338 mutex_unlock(&balloon_mutex);
339 /* add_memory_resource() requires the device_hotplug lock */
340 lock_device_hotplug();
341 rc = add_memory_resource(nid, resource, MHP_MERGE_RESOURCE);
342 unlock_device_hotplug();
343 mutex_lock(&balloon_mutex);
344
345 if (rc) {
346 pr_warn("Cannot add additional memory (%i)\n", rc);
347 goto err;
348 }
349
350 balloon_stats.total_pages += balloon_hotplug;
351
352 return BP_WAIT;
353 err:
354 release_memory_resource(resource);
355 return BP_ECANCELED;
356}
357
358static void xen_online_page(struct page *page, unsigned int order)
359{
360 unsigned long i, size = (1 << order);
361 unsigned long start_pfn = page_to_pfn(page);
362 struct page *p;
363
364 pr_debug("Online %lu pages starting at pfn 0x%lx\n", size, start_pfn);
365 mutex_lock(&balloon_mutex);
366 for (i = 0; i < size; i++) {
367 p = pfn_to_page(start_pfn + i);
368 balloon_append(p);
369 }
370 mutex_unlock(&balloon_mutex);
371}
372
373static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
374{
375 if (val == MEM_ONLINE)
376 wake_up(&balloon_thread_wq);
377
378 return NOTIFY_OK;
379}
380
381static struct notifier_block xen_memory_nb = {
382 .notifier_call = xen_memory_notifier,
383 .priority = 0
384};
385#else
386static enum bp_state reserve_additional_memory(void)
387{
388 balloon_stats.target_pages = balloon_stats.current_pages +
389 balloon_stats.target_unpopulated;
390 return BP_ECANCELED;
391}
392#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
393
394static long current_credit(void)
395{
396 return balloon_stats.target_pages - balloon_stats.current_pages;
397}
398
399static bool balloon_is_inflated(void)
400{
401 return balloon_stats.balloon_low || balloon_stats.balloon_high;
402}
403
404static enum bp_state increase_reservation(unsigned long nr_pages)
405{
406 int rc;
407 unsigned long i;
408 struct page *page;
409
410 if (nr_pages > ARRAY_SIZE(frame_list))
411 nr_pages = ARRAY_SIZE(frame_list);
412
413 page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
414 for (i = 0; i < nr_pages; i++) {
415 if (!page) {
416 nr_pages = i;
417 break;
418 }
419
420 frame_list[i] = page_to_xen_pfn(page);
421 page = balloon_next_page(page);
422 }
423
424 rc = xenmem_reservation_increase(nr_pages, frame_list);
425 if (rc <= 0)
426 return BP_EAGAIN;
427
428 for (i = 0; i < rc; i++) {
429 page = balloon_retrieve(false);
430 BUG_ON(page == NULL);
431
432 xenmem_reservation_va_mapping_update(1, &page, &frame_list[i]);
433
434 /* Relinquish the page back to the allocator. */
435 free_reserved_page(page);
436 }
437
438 balloon_stats.current_pages += rc;
439
440 return BP_DONE;
441}
442
443static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
444{
445 enum bp_state state = BP_DONE;
446 unsigned long i;
447 struct page *page, *tmp;
448 int ret;
449 LIST_HEAD(pages);
450
451 if (nr_pages > ARRAY_SIZE(frame_list))
452 nr_pages = ARRAY_SIZE(frame_list);
453
454 for (i = 0; i < nr_pages; i++) {
455 page = alloc_page(gfp);
456 if (page == NULL) {
457 nr_pages = i;
458 state = BP_EAGAIN;
459 break;
460 }
461 adjust_managed_page_count(page, -1);
462 xenmem_reservation_scrub_page(page);
463 list_add(&page->lru, &pages);
464 }
465
466 /*
467 * Ensure that ballooned highmem pages don't have kmaps.
468 *
469 * Do this before changing the p2m as kmap_flush_unused()
470 * reads PTEs to obtain pages (and hence needs the original
471 * p2m entry).
472 */
473 kmap_flush_unused();
474
475 /*
476 * Setup the frame, update direct mapping, invalidate P2M,
477 * and add to balloon.
478 */
479 i = 0;
480 list_for_each_entry_safe(page, tmp, &pages, lru) {
481 frame_list[i++] = xen_page_to_gfn(page);
482
483 xenmem_reservation_va_mapping_reset(1, &page);
484
485 list_del(&page->lru);
486
487 balloon_append(page);
488 }
489
490 flush_tlb_all();
491
492 ret = xenmem_reservation_decrease(nr_pages, frame_list);
493 BUG_ON(ret != nr_pages);
494
495 balloon_stats.current_pages -= nr_pages;
496
497 return state;
498}
499
500/*
501 * Stop waiting if either state is BP_DONE and ballooning action is
502 * needed, or if the credit has changed while state is not BP_DONE.
503 */
504static bool balloon_thread_cond(long credit)
505{
506 if (balloon_state == BP_DONE)
507 credit = 0;
508
509 return current_credit() != credit || kthread_should_stop();
510}
511
512/*
513 * As this is a kthread it is guaranteed to run as a single instance only.
514 * We may of course race updates of the target counts (which are protected
515 * by the balloon lock), or with changes to the Xen hard limit, but we will
516 * recover from these in time.
517 */
518static int balloon_thread(void *unused)
519{
520 long credit;
521 unsigned long timeout;
522
523 set_freezable();
524 for (;;) {
525 switch (balloon_state) {
526 case BP_DONE:
527 case BP_ECANCELED:
528 timeout = 3600 * HZ;
529 break;
530 case BP_EAGAIN:
531 timeout = balloon_stats.schedule_delay * HZ;
532 break;
533 case BP_WAIT:
534 timeout = HZ;
535 break;
536 }
537
538 credit = current_credit();
539
540 wait_event_freezable_timeout(balloon_thread_wq,
541 balloon_thread_cond(credit), timeout);
542
543 if (kthread_should_stop())
544 return 0;
545
546 mutex_lock(&balloon_mutex);
547
548 credit = current_credit();
549
550 if (credit > 0) {
551 if (balloon_is_inflated())
552 balloon_state = increase_reservation(credit);
553 else
554 balloon_state = reserve_additional_memory();
555 }
556
557 if (credit < 0) {
558 long n_pages;
559
560 n_pages = min(-credit, si_mem_available());
561 balloon_state = decrease_reservation(n_pages,
562 GFP_BALLOON);
563 if (balloon_state == BP_DONE && n_pages != -credit &&
564 n_pages < totalreserve_pages)
565 balloon_state = BP_EAGAIN;
566 }
567
568 update_schedule();
569
570 mutex_unlock(&balloon_mutex);
571
572 cond_resched();
573 }
574}
575
576/* Resets the Xen limit, sets new target, and kicks off processing. */
577void balloon_set_new_target(unsigned long target)
578{
579 /* No need for lock. Not read-modify-write updates. */
580 balloon_stats.target_pages = target;
581 wake_up(&balloon_thread_wq);
582}
583EXPORT_SYMBOL_GPL(balloon_set_new_target);
584
585static int add_ballooned_pages(unsigned int nr_pages)
586{
587 enum bp_state st;
588
589 if (xen_hotplug_unpopulated) {
590 st = reserve_additional_memory();
591 if (st != BP_ECANCELED) {
592 int rc;
593
594 mutex_unlock(&balloon_mutex);
595 rc = wait_event_interruptible(balloon_wq,
596 !list_empty(&ballooned_pages));
597 mutex_lock(&balloon_mutex);
598 return rc ? -ENOMEM : 0;
599 }
600 }
601
602 if (si_mem_available() < nr_pages)
603 return -ENOMEM;
604
605 st = decrease_reservation(nr_pages, GFP_USER);
606 if (st != BP_DONE)
607 return -ENOMEM;
608
609 return 0;
610}
611
612/**
613 * xen_alloc_ballooned_pages - get pages that have been ballooned out
614 * @nr_pages: Number of pages to get
615 * @pages: pages returned
616 * @return 0 on success, error otherwise
617 */
618int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
619{
620 unsigned int pgno = 0;
621 struct page *page;
622 int ret;
623
624 mutex_lock(&balloon_mutex);
625
626 balloon_stats.target_unpopulated += nr_pages;
627
628 while (pgno < nr_pages) {
629 page = balloon_retrieve(true);
630 if (page) {
631 pages[pgno++] = page;
632#ifdef CONFIG_XEN_HAVE_PVMMU
633 /*
634 * We don't support PV MMU when Linux and Xen is using
635 * different page granularity.
636 */
637 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
638
639 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
640 ret = xen_alloc_p2m_entry(page_to_pfn(page));
641 if (ret < 0)
642 goto out_undo;
643 }
644#endif
645 } else {
646 ret = add_ballooned_pages(nr_pages - pgno);
647 if (ret < 0)
648 goto out_undo;
649 }
650 }
651 mutex_unlock(&balloon_mutex);
652 return 0;
653 out_undo:
654 mutex_unlock(&balloon_mutex);
655 xen_free_ballooned_pages(pgno, pages);
656 /*
657 * NB: xen_free_ballooned_pages will only subtract pgno pages, but since
658 * target_unpopulated is incremented with nr_pages at the start we need
659 * to remove the remaining ones also, or accounting will be screwed.
660 */
661 balloon_stats.target_unpopulated -= nr_pages - pgno;
662 return ret;
663}
664EXPORT_SYMBOL(xen_alloc_ballooned_pages);
665
666/**
667 * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
668 * @nr_pages: Number of pages
669 * @pages: pages to return
670 */
671void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
672{
673 unsigned int i;
674
675 mutex_lock(&balloon_mutex);
676
677 for (i = 0; i < nr_pages; i++) {
678 if (pages[i])
679 balloon_append(pages[i]);
680 }
681
682 balloon_stats.target_unpopulated -= nr_pages;
683
684 /* The balloon may be too large now. Shrink it if needed. */
685 if (current_credit())
686 wake_up(&balloon_thread_wq);
687
688 mutex_unlock(&balloon_mutex);
689}
690EXPORT_SYMBOL(xen_free_ballooned_pages);
691
692static void __init balloon_add_regions(void)
693{
694#if defined(CONFIG_XEN_PV)
695 unsigned long start_pfn, pages;
696 unsigned long pfn, extra_pfn_end;
697 unsigned int i;
698
699 for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
700 pages = xen_extra_mem[i].n_pfns;
701 if (!pages)
702 continue;
703
704 start_pfn = xen_extra_mem[i].start_pfn;
705
706 /*
707 * If the amount of usable memory has been limited (e.g., with
708 * the 'mem' command line parameter), don't add pages beyond
709 * this limit.
710 */
711 extra_pfn_end = min(max_pfn, start_pfn + pages);
712
713 for (pfn = start_pfn; pfn < extra_pfn_end; pfn++)
714 balloon_append(pfn_to_page(pfn));
715
716 balloon_stats.total_pages += extra_pfn_end - start_pfn;
717 }
718#endif
719}
720
721static int __init balloon_init(void)
722{
723 struct task_struct *task;
724
725 if (!xen_domain())
726 return -ENODEV;
727
728 pr_info("Initialising balloon driver\n");
729
730#ifdef CONFIG_XEN_PV
731 balloon_stats.current_pages = xen_pv_domain()
732 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
733 : get_num_physpages();
734#else
735 balloon_stats.current_pages = get_num_physpages();
736#endif
737 balloon_stats.target_pages = balloon_stats.current_pages;
738 balloon_stats.balloon_low = 0;
739 balloon_stats.balloon_high = 0;
740 balloon_stats.total_pages = balloon_stats.current_pages;
741
742 balloon_stats.schedule_delay = 1;
743 balloon_stats.max_schedule_delay = 32;
744 balloon_stats.retry_count = 1;
745 balloon_stats.max_retry_count = 4;
746
747#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
748 set_online_page_callback(&xen_online_page);
749 register_memory_notifier(&xen_memory_nb);
750 register_sysctl_table(xen_root);
751#endif
752
753 balloon_add_regions();
754
755 task = kthread_run(balloon_thread, NULL, "xen-balloon");
756 if (IS_ERR(task)) {
757 pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
758 return PTR_ERR(task);
759 }
760
761 /* Init the xen-balloon driver. */
762 xen_balloon_init();
763
764 return 0;
765}
766subsys_initcall(balloon_init);
767
768static int __init balloon_wait_finish(void)
769{
770 long credit, last_credit = 0;
771 unsigned long last_changed = 0;
772
773 if (!xen_domain())
774 return -ENODEV;
775
776 /* PV guests don't need to wait. */
777 if (xen_pv_domain() || !current_credit())
778 return 0;
779
780 pr_notice("Waiting for initial ballooning down having finished.\n");
781
782 while ((credit = current_credit()) < 0) {
783 if (credit != last_credit) {
784 last_changed = jiffies;
785 last_credit = credit;
786 }
787 if (balloon_state == BP_ECANCELED) {
788 pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
789 -credit);
790 if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout))
791 panic("Initial ballooning failed!\n");
792 }
793
794 schedule_timeout_interruptible(HZ / 10);
795 }
796
797 pr_notice("Initial ballooning down finished.\n");
798
799 return 0;
800}
801late_initcall_sync(balloon_wait_finish);