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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 if (!PageOffline(page))
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. */
164static 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
185static 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
193static 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
223static 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
236static 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
260static 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
340static 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
355static 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
363static struct notifier_block xen_memory_nb = {
364 .notifier_call = xen_memory_notifier,
365 .priority = 0
366};
367#else
368static 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
376static long current_credit(void)
377{
378 return balloon_stats.target_pages - balloon_stats.current_pages;
379}
380
381static bool balloon_is_inflated(void)
382{
383 return balloon_stats.balloon_low || balloon_stats.balloon_high;
384}
385
386static 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 /*
417 * Relinquish the page back to the allocator. Note that
418 * some pages, including ones added via xen_online_page(), might
419 * not be marked reserved; free_reserved_page() will handle that.
420 */
421 free_reserved_page(page);
422 }
423
424 balloon_stats.current_pages += rc;
425
426 return BP_DONE;
427}
428
429static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
430{
431 enum bp_state state = BP_DONE;
432 unsigned long i;
433 struct page *page, *tmp;
434 int ret;
435 LIST_HEAD(pages);
436
437 if (nr_pages > ARRAY_SIZE(frame_list))
438 nr_pages = ARRAY_SIZE(frame_list);
439
440 for (i = 0; i < nr_pages; i++) {
441 page = alloc_page(gfp);
442 if (page == NULL) {
443 nr_pages = i;
444 state = BP_EAGAIN;
445 break;
446 }
447 adjust_managed_page_count(page, -1);
448 xenmem_reservation_scrub_page(page);
449 list_add(&page->lru, &pages);
450 }
451
452 /*
453 * Ensure that ballooned highmem pages don't have kmaps.
454 *
455 * Do this before changing the p2m as kmap_flush_unused()
456 * reads PTEs to obtain pages (and hence needs the original
457 * p2m entry).
458 */
459 kmap_flush_unused();
460
461 /*
462 * Setup the frame, update direct mapping, invalidate P2M,
463 * and add to balloon.
464 */
465 i = 0;
466 list_for_each_entry_safe(page, tmp, &pages, lru) {
467 frame_list[i++] = xen_page_to_gfn(page);
468
469 xenmem_reservation_va_mapping_reset(1, &page);
470
471 list_del(&page->lru);
472
473 balloon_append(page);
474 }
475
476 flush_tlb_all();
477
478 ret = xenmem_reservation_decrease(nr_pages, frame_list);
479 BUG_ON(ret != nr_pages);
480
481 balloon_stats.current_pages -= nr_pages;
482
483 return state;
484}
485
486/*
487 * Stop waiting if either state is BP_DONE and ballooning action is
488 * needed, or if the credit has changed while state is not BP_DONE.
489 */
490static bool balloon_thread_cond(long credit)
491{
492 if (balloon_state == BP_DONE)
493 credit = 0;
494
495 return current_credit() != credit || kthread_should_stop();
496}
497
498/*
499 * As this is a kthread it is guaranteed to run as a single instance only.
500 * We may of course race updates of the target counts (which are protected
501 * by the balloon lock), or with changes to the Xen hard limit, but we will
502 * recover from these in time.
503 */
504static int balloon_thread(void *unused)
505{
506 long credit;
507 unsigned long timeout;
508
509 set_freezable();
510 for (;;) {
511 switch (balloon_state) {
512 case BP_DONE:
513 case BP_ECANCELED:
514 timeout = 3600 * HZ;
515 break;
516 case BP_EAGAIN:
517 timeout = balloon_stats.schedule_delay * HZ;
518 break;
519 case BP_WAIT:
520 timeout = HZ;
521 break;
522 }
523
524 credit = current_credit();
525
526 wait_event_freezable_timeout(balloon_thread_wq,
527 balloon_thread_cond(credit), timeout);
528
529 if (kthread_should_stop())
530 return 0;
531
532 mutex_lock(&balloon_mutex);
533
534 credit = current_credit();
535
536 if (credit > 0) {
537 if (balloon_is_inflated())
538 balloon_state = increase_reservation(credit);
539 else
540 balloon_state = reserve_additional_memory();
541 }
542
543 if (credit < 0) {
544 long n_pages;
545
546 n_pages = min(-credit, si_mem_available());
547 balloon_state = decrease_reservation(n_pages,
548 GFP_BALLOON);
549 if (balloon_state == BP_DONE && n_pages != -credit &&
550 n_pages < totalreserve_pages)
551 balloon_state = BP_EAGAIN;
552 }
553
554 update_schedule();
555
556 mutex_unlock(&balloon_mutex);
557
558 cond_resched();
559 }
560}
561
562/* Resets the Xen limit, sets new target, and kicks off processing. */
563void balloon_set_new_target(unsigned long target)
564{
565 /* No need for lock. Not read-modify-write updates. */
566 balloon_stats.target_pages = target;
567 wake_up(&balloon_thread_wq);
568}
569EXPORT_SYMBOL_GPL(balloon_set_new_target);
570
571static int add_ballooned_pages(unsigned int nr_pages)
572{
573 enum bp_state st;
574
575 if (xen_hotplug_unpopulated) {
576 st = reserve_additional_memory();
577 if (st != BP_ECANCELED) {
578 int rc;
579
580 mutex_unlock(&balloon_mutex);
581 rc = wait_event_interruptible(balloon_wq,
582 !list_empty(&ballooned_pages));
583 mutex_lock(&balloon_mutex);
584 return rc ? -ENOMEM : 0;
585 }
586 }
587
588 if (si_mem_available() < nr_pages)
589 return -ENOMEM;
590
591 st = decrease_reservation(nr_pages, GFP_USER);
592 if (st != BP_DONE)
593 return -ENOMEM;
594
595 return 0;
596}
597
598/**
599 * xen_alloc_ballooned_pages - get pages that have been ballooned out
600 * @nr_pages: Number of pages to get
601 * @pages: pages returned
602 * @return 0 on success, error otherwise
603 */
604int xen_alloc_ballooned_pages(unsigned int nr_pages, struct page **pages)
605{
606 unsigned int pgno = 0;
607 struct page *page;
608 int ret;
609
610 mutex_lock(&balloon_mutex);
611
612 balloon_stats.target_unpopulated += nr_pages;
613
614 while (pgno < nr_pages) {
615 page = balloon_retrieve(true);
616 if (page) {
617 pages[pgno++] = page;
618#ifdef CONFIG_XEN_HAVE_PVMMU
619 /*
620 * We don't support PV MMU when Linux and Xen is using
621 * different page granularity.
622 */
623 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
624
625 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
626 ret = xen_alloc_p2m_entry(page_to_pfn(page));
627 if (ret < 0)
628 goto out_undo;
629 }
630#endif
631 } else {
632 ret = add_ballooned_pages(nr_pages - pgno);
633 if (ret < 0)
634 goto out_undo;
635 }
636 }
637 mutex_unlock(&balloon_mutex);
638 return 0;
639 out_undo:
640 mutex_unlock(&balloon_mutex);
641 xen_free_ballooned_pages(pgno, pages);
642 /*
643 * NB: xen_free_ballooned_pages will only subtract pgno pages, but since
644 * target_unpopulated is incremented with nr_pages at the start we need
645 * to remove the remaining ones also, or accounting will be screwed.
646 */
647 balloon_stats.target_unpopulated -= nr_pages - pgno;
648 return ret;
649}
650EXPORT_SYMBOL(xen_alloc_ballooned_pages);
651
652/**
653 * xen_free_ballooned_pages - return pages retrieved with get_ballooned_pages
654 * @nr_pages: Number of pages
655 * @pages: pages to return
656 */
657void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
658{
659 unsigned int i;
660
661 mutex_lock(&balloon_mutex);
662
663 for (i = 0; i < nr_pages; i++) {
664 if (pages[i])
665 balloon_append(pages[i]);
666 }
667
668 balloon_stats.target_unpopulated -= nr_pages;
669
670 /* The balloon may be too large now. Shrink it if needed. */
671 if (current_credit())
672 wake_up(&balloon_thread_wq);
673
674 mutex_unlock(&balloon_mutex);
675}
676EXPORT_SYMBOL(xen_free_ballooned_pages);
677
678static void __init balloon_add_regions(void)
679{
680 unsigned long start_pfn, pages;
681 unsigned long pfn, extra_pfn_end;
682 unsigned int i;
683
684 for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++) {
685 pages = xen_extra_mem[i].n_pfns;
686 if (!pages)
687 continue;
688
689 start_pfn = xen_extra_mem[i].start_pfn;
690
691 /*
692 * If the amount of usable memory has been limited (e.g., with
693 * the 'mem' command line parameter), don't add pages beyond
694 * this limit.
695 */
696 extra_pfn_end = min(max_pfn, start_pfn + pages);
697
698 for (pfn = start_pfn; pfn < extra_pfn_end; pfn++)
699 balloon_append(pfn_to_page(pfn));
700
701 balloon_stats.total_pages += extra_pfn_end - start_pfn;
702 }
703}
704
705static int __init balloon_init(void)
706{
707 struct task_struct *task;
708
709 if (!xen_domain())
710 return -ENODEV;
711
712 pr_info("Initialising balloon driver\n");
713
714#ifdef CONFIG_XEN_PV
715 balloon_stats.current_pages = xen_pv_domain()
716 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
717 : get_num_physpages();
718#else
719 balloon_stats.current_pages = get_num_physpages();
720#endif
721 balloon_stats.target_pages = balloon_stats.current_pages;
722 balloon_stats.balloon_low = 0;
723 balloon_stats.balloon_high = 0;
724 balloon_stats.total_pages = balloon_stats.current_pages;
725
726 balloon_stats.schedule_delay = 1;
727 balloon_stats.max_schedule_delay = 32;
728 balloon_stats.retry_count = 1;
729 balloon_stats.max_retry_count = 4;
730
731#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
732 set_online_page_callback(&xen_online_page);
733 register_memory_notifier(&xen_memory_nb);
734 register_sysctl_init("xen/balloon", balloon_table);
735#endif
736
737 balloon_add_regions();
738
739 task = kthread_run(balloon_thread, NULL, "xen-balloon");
740 if (IS_ERR(task)) {
741 pr_err("xen-balloon thread could not be started, ballooning will not work!\n");
742 return PTR_ERR(task);
743 }
744
745 /* Init the xen-balloon driver. */
746 xen_balloon_init();
747
748 return 0;
749}
750subsys_initcall(balloon_init);
751
752static int __init balloon_wait_finish(void)
753{
754 long credit, last_credit = 0;
755 unsigned long last_changed = 0;
756
757 if (!xen_domain())
758 return -ENODEV;
759
760 /* PV guests don't need to wait. */
761 if (xen_pv_domain() || !current_credit())
762 return 0;
763
764 pr_notice("Waiting for initial ballooning down having finished.\n");
765
766 while ((credit = current_credit()) < 0) {
767 if (credit != last_credit) {
768 last_changed = jiffies;
769 last_credit = credit;
770 }
771 if (balloon_state == BP_ECANCELED) {
772 pr_warn_once("Initial ballooning failed, %ld pages need to be freed.\n",
773 -credit);
774 if (time_is_before_eq_jiffies(last_changed + HZ * balloon_boot_timeout))
775 panic("Initial ballooning failed!\n");
776 }
777
778 schedule_timeout_interruptible(HZ / 10);
779 }
780
781 pr_notice("Initial ballooning down finished.\n");
782
783 return 0;
784}
785late_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#include <linux/kernel.h>
40#include <linux/sched.h>
41#include <linux/errno.h>
42#include <linux/mm.h>
43#include <linux/bootmem.h>
44#include <linux/pagemap.h>
45#include <linux/highmem.h>
46#include <linux/mutex.h>
47#include <linux/list.h>
48#include <linux/gfp.h>
49#include <linux/notifier.h>
50#include <linux/memory.h>
51#include <linux/memory_hotplug.h>
52
53#include <asm/page.h>
54#include <asm/pgalloc.h>
55#include <asm/pgtable.h>
56#include <asm/tlb.h>
57#include <asm/e820.h>
58
59#include <asm/xen/hypervisor.h>
60#include <asm/xen/hypercall.h>
61
62#include <xen/xen.h>
63#include <xen/interface/xen.h>
64#include <xen/interface/memory.h>
65#include <xen/balloon.h>
66#include <xen/features.h>
67#include <xen/page.h>
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
77enum bp_state {
78 BP_DONE,
79 BP_EAGAIN,
80 BP_ECANCELED
81};
82
83
84static DEFINE_MUTEX(balloon_mutex);
85
86struct balloon_stats balloon_stats;
87EXPORT_SYMBOL_GPL(balloon_stats);
88
89/* We increase/decrease in batches which fit in a page */
90static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
91
92#ifdef CONFIG_HIGHMEM
93#define inc_totalhigh_pages() (totalhigh_pages++)
94#define dec_totalhigh_pages() (totalhigh_pages--)
95#else
96#define inc_totalhigh_pages() do {} while(0)
97#define dec_totalhigh_pages() do {} while(0)
98#endif
99
100/* List of ballooned pages, threaded through the mem_map array. */
101static LIST_HEAD(ballooned_pages);
102
103/* Main work function, always executed in process context. */
104static void balloon_process(struct work_struct *work);
105static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
106
107/* When ballooning out (allocating memory to return to Xen) we don't really
108 want the kernel to try too hard since that can trigger the oom killer. */
109#define GFP_BALLOON \
110 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
111
112static void scrub_page(struct page *page)
113{
114#ifdef CONFIG_XEN_SCRUB_PAGES
115 clear_highpage(page);
116#endif
117}
118
119/* balloon_append: add the given page to the balloon. */
120static void __balloon_append(struct page *page)
121{
122 /* Lowmem is re-populated first, so highmem pages go at list tail. */
123 if (PageHighMem(page)) {
124 list_add_tail(&page->lru, &ballooned_pages);
125 balloon_stats.balloon_high++;
126 } else {
127 list_add(&page->lru, &ballooned_pages);
128 balloon_stats.balloon_low++;
129 }
130}
131
132static void balloon_append(struct page *page)
133{
134 __balloon_append(page);
135 if (PageHighMem(page))
136 dec_totalhigh_pages();
137 totalram_pages--;
138}
139
140/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
141static struct page *balloon_retrieve(bool prefer_highmem)
142{
143 struct page *page;
144
145 if (list_empty(&ballooned_pages))
146 return NULL;
147
148 if (prefer_highmem)
149 page = list_entry(ballooned_pages.prev, struct page, lru);
150 else
151 page = list_entry(ballooned_pages.next, struct page, lru);
152 list_del(&page->lru);
153
154 if (PageHighMem(page)) {
155 balloon_stats.balloon_high--;
156 inc_totalhigh_pages();
157 }
158 else
159 balloon_stats.balloon_low--;
160
161 totalram_pages++;
162
163 return page;
164}
165
166static struct page *balloon_first_page(void)
167{
168 if (list_empty(&ballooned_pages))
169 return NULL;
170 return list_entry(ballooned_pages.next, struct page, lru);
171}
172
173static struct page *balloon_next_page(struct page *page)
174{
175 struct list_head *next = page->lru.next;
176 if (next == &ballooned_pages)
177 return NULL;
178 return list_entry(next, struct page, lru);
179}
180
181static enum bp_state update_schedule(enum bp_state state)
182{
183 if (state == BP_DONE) {
184 balloon_stats.schedule_delay = 1;
185 balloon_stats.retry_count = 1;
186 return BP_DONE;
187 }
188
189 ++balloon_stats.retry_count;
190
191 if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
192 balloon_stats.retry_count > balloon_stats.max_retry_count) {
193 balloon_stats.schedule_delay = 1;
194 balloon_stats.retry_count = 1;
195 return BP_ECANCELED;
196 }
197
198 balloon_stats.schedule_delay <<= 1;
199
200 if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
201 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
202
203 return BP_EAGAIN;
204}
205
206#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
207static long current_credit(void)
208{
209 return balloon_stats.target_pages - balloon_stats.current_pages -
210 balloon_stats.hotplug_pages;
211}
212
213static bool balloon_is_inflated(void)
214{
215 if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
216 balloon_stats.balloon_hotplug)
217 return true;
218 else
219 return false;
220}
221
222/*
223 * reserve_additional_memory() adds memory region of size >= credit above
224 * max_pfn. New region is section aligned and size is modified to be multiple
225 * of section size. Those features allow optimal use of address space and
226 * establish proper alignment when this function is called first time after
227 * boot (last section not fully populated at boot time contains unused memory
228 * pages with PG_reserved bit not set; online_pages_range() does not allow page
229 * onlining in whole range if first onlined page does not have PG_reserved
230 * bit set). Real size of added memory is established at page onlining stage.
231 */
232
233static enum bp_state reserve_additional_memory(long credit)
234{
235 int nid, rc;
236 u64 hotplug_start_paddr;
237 unsigned long balloon_hotplug = credit;
238
239 hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
240 balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
241 nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
242
243 rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
244
245 if (rc) {
246 pr_info("xen_balloon: %s: add_memory() failed: %i\n", __func__, rc);
247 return BP_EAGAIN;
248 }
249
250 balloon_hotplug -= credit;
251
252 balloon_stats.hotplug_pages += credit;
253 balloon_stats.balloon_hotplug = balloon_hotplug;
254
255 return BP_DONE;
256}
257
258static void xen_online_page(struct page *page)
259{
260 __online_page_set_limits(page);
261
262 mutex_lock(&balloon_mutex);
263
264 __balloon_append(page);
265
266 if (balloon_stats.hotplug_pages)
267 --balloon_stats.hotplug_pages;
268 else
269 --balloon_stats.balloon_hotplug;
270
271 mutex_unlock(&balloon_mutex);
272}
273
274static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
275{
276 if (val == MEM_ONLINE)
277 schedule_delayed_work(&balloon_worker, 0);
278
279 return NOTIFY_OK;
280}
281
282static struct notifier_block xen_memory_nb = {
283 .notifier_call = xen_memory_notifier,
284 .priority = 0
285};
286#else
287static long current_credit(void)
288{
289 unsigned long target = balloon_stats.target_pages;
290
291 target = min(target,
292 balloon_stats.current_pages +
293 balloon_stats.balloon_low +
294 balloon_stats.balloon_high);
295
296 return target - balloon_stats.current_pages;
297}
298
299static bool balloon_is_inflated(void)
300{
301 if (balloon_stats.balloon_low || balloon_stats.balloon_high)
302 return true;
303 else
304 return false;
305}
306
307static enum bp_state reserve_additional_memory(long credit)
308{
309 balloon_stats.target_pages = balloon_stats.current_pages;
310 return BP_DONE;
311}
312#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
313
314static enum bp_state increase_reservation(unsigned long nr_pages)
315{
316 int rc;
317 unsigned long pfn, i;
318 struct page *page;
319 struct xen_memory_reservation reservation = {
320 .address_bits = 0,
321 .extent_order = 0,
322 .domid = DOMID_SELF
323 };
324
325#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
326 if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
327 nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
328 balloon_stats.hotplug_pages += nr_pages;
329 balloon_stats.balloon_hotplug -= nr_pages;
330 return BP_DONE;
331 }
332#endif
333
334 if (nr_pages > ARRAY_SIZE(frame_list))
335 nr_pages = ARRAY_SIZE(frame_list);
336
337 page = balloon_first_page();
338 for (i = 0; i < nr_pages; i++) {
339 if (!page) {
340 nr_pages = i;
341 break;
342 }
343 frame_list[i] = page_to_pfn(page);
344 page = balloon_next_page(page);
345 }
346
347 set_xen_guest_handle(reservation.extent_start, frame_list);
348 reservation.nr_extents = nr_pages;
349 rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
350 if (rc <= 0)
351 return BP_EAGAIN;
352
353 for (i = 0; i < rc; i++) {
354 page = balloon_retrieve(false);
355 BUG_ON(page == NULL);
356
357 pfn = page_to_pfn(page);
358 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
359 phys_to_machine_mapping_valid(pfn));
360
361 set_phys_to_machine(pfn, frame_list[i]);
362
363 /* Link back into the page tables if not highmem. */
364 if (xen_pv_domain() && !PageHighMem(page)) {
365 int ret;
366 ret = HYPERVISOR_update_va_mapping(
367 (unsigned long)__va(pfn << PAGE_SHIFT),
368 mfn_pte(frame_list[i], PAGE_KERNEL),
369 0);
370 BUG_ON(ret);
371 }
372
373 /* Relinquish the page back to the allocator. */
374 ClearPageReserved(page);
375 init_page_count(page);
376 __free_page(page);
377 }
378
379 balloon_stats.current_pages += rc;
380
381 return BP_DONE;
382}
383
384static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
385{
386 enum bp_state state = BP_DONE;
387 unsigned long pfn, i;
388 struct page *page;
389 int ret;
390 struct xen_memory_reservation reservation = {
391 .address_bits = 0,
392 .extent_order = 0,
393 .domid = DOMID_SELF
394 };
395
396#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
397 if (balloon_stats.hotplug_pages) {
398 nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
399 balloon_stats.hotplug_pages -= nr_pages;
400 balloon_stats.balloon_hotplug += nr_pages;
401 return BP_DONE;
402 }
403#endif
404
405 if (nr_pages > ARRAY_SIZE(frame_list))
406 nr_pages = ARRAY_SIZE(frame_list);
407
408 for (i = 0; i < nr_pages; i++) {
409 if ((page = alloc_page(gfp)) == NULL) {
410 nr_pages = i;
411 state = BP_EAGAIN;
412 break;
413 }
414
415 pfn = page_to_pfn(page);
416 frame_list[i] = pfn_to_mfn(pfn);
417
418 scrub_page(page);
419
420 if (xen_pv_domain() && !PageHighMem(page)) {
421 ret = HYPERVISOR_update_va_mapping(
422 (unsigned long)__va(pfn << PAGE_SHIFT),
423 __pte_ma(0), 0);
424 BUG_ON(ret);
425 }
426
427 }
428
429 /* Ensure that ballooned highmem pages don't have kmaps. */
430 kmap_flush_unused();
431 flush_tlb_all();
432
433 /* No more mappings: invalidate P2M and add to balloon. */
434 for (i = 0; i < nr_pages; i++) {
435 pfn = mfn_to_pfn(frame_list[i]);
436 __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
437 balloon_append(pfn_to_page(pfn));
438 }
439
440 set_xen_guest_handle(reservation.extent_start, frame_list);
441 reservation.nr_extents = nr_pages;
442 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
443 BUG_ON(ret != nr_pages);
444
445 balloon_stats.current_pages -= nr_pages;
446
447 return state;
448}
449
450/*
451 * We avoid multiple worker processes conflicting via the balloon mutex.
452 * We may of course race updates of the target counts (which are protected
453 * by the balloon lock), or with changes to the Xen hard limit, but we will
454 * recover from these in time.
455 */
456static void balloon_process(struct work_struct *work)
457{
458 enum bp_state state = BP_DONE;
459 long credit;
460
461 mutex_lock(&balloon_mutex);
462
463 do {
464 credit = current_credit();
465
466 if (credit > 0) {
467 if (balloon_is_inflated())
468 state = increase_reservation(credit);
469 else
470 state = reserve_additional_memory(credit);
471 }
472
473 if (credit < 0)
474 state = decrease_reservation(-credit, GFP_BALLOON);
475
476 state = update_schedule(state);
477
478#ifndef CONFIG_PREEMPT
479 if (need_resched())
480 schedule();
481#endif
482 } while (credit && state == BP_DONE);
483
484 /* Schedule more work if there is some still to be done. */
485 if (state == BP_EAGAIN)
486 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
487
488 mutex_unlock(&balloon_mutex);
489}
490
491/* Resets the Xen limit, sets new target, and kicks off processing. */
492void balloon_set_new_target(unsigned long target)
493{
494 /* No need for lock. Not read-modify-write updates. */
495 balloon_stats.target_pages = target;
496 schedule_delayed_work(&balloon_worker, 0);
497}
498EXPORT_SYMBOL_GPL(balloon_set_new_target);
499
500/**
501 * alloc_xenballooned_pages - get pages that have been ballooned out
502 * @nr_pages: Number of pages to get
503 * @pages: pages returned
504 * @return 0 on success, error otherwise
505 */
506int alloc_xenballooned_pages(int nr_pages, struct page** pages)
507{
508 int pgno = 0;
509 struct page* page;
510 mutex_lock(&balloon_mutex);
511 while (pgno < nr_pages) {
512 page = balloon_retrieve(true);
513 if (page) {
514 pages[pgno++] = page;
515 } else {
516 enum bp_state st;
517 st = decrease_reservation(nr_pages - pgno, GFP_HIGHUSER);
518 if (st != BP_DONE)
519 goto out_undo;
520 }
521 }
522 mutex_unlock(&balloon_mutex);
523 return 0;
524 out_undo:
525 while (pgno)
526 balloon_append(pages[--pgno]);
527 /* Free the memory back to the kernel soon */
528 schedule_delayed_work(&balloon_worker, 0);
529 mutex_unlock(&balloon_mutex);
530 return -ENOMEM;
531}
532EXPORT_SYMBOL(alloc_xenballooned_pages);
533
534/**
535 * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
536 * @nr_pages: Number of pages
537 * @pages: pages to return
538 */
539void free_xenballooned_pages(int nr_pages, struct page** pages)
540{
541 int i;
542
543 mutex_lock(&balloon_mutex);
544
545 for (i = 0; i < nr_pages; i++) {
546 if (pages[i])
547 balloon_append(pages[i]);
548 }
549
550 /* The balloon may be too large now. Shrink it if needed. */
551 if (current_credit())
552 schedule_delayed_work(&balloon_worker, 0);
553
554 mutex_unlock(&balloon_mutex);
555}
556EXPORT_SYMBOL(free_xenballooned_pages);
557
558static int __init balloon_init(void)
559{
560 unsigned long pfn, extra_pfn_end;
561 struct page *page;
562
563 if (!xen_domain())
564 return -ENODEV;
565
566 pr_info("xen/balloon: Initialising balloon driver.\n");
567
568 balloon_stats.current_pages = xen_pv_domain() ? min(xen_start_info->nr_pages, max_pfn) : max_pfn;
569 balloon_stats.target_pages = balloon_stats.current_pages;
570 balloon_stats.balloon_low = 0;
571 balloon_stats.balloon_high = 0;
572
573 balloon_stats.schedule_delay = 1;
574 balloon_stats.max_schedule_delay = 32;
575 balloon_stats.retry_count = 1;
576 balloon_stats.max_retry_count = RETRY_UNLIMITED;
577
578#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
579 balloon_stats.hotplug_pages = 0;
580 balloon_stats.balloon_hotplug = 0;
581
582 set_online_page_callback(&xen_online_page);
583 register_memory_notifier(&xen_memory_nb);
584#endif
585
586 /*
587 * Initialise the balloon with excess memory space. We need
588 * to make sure we don't add memory which doesn't exist or
589 * logically exist. The E820 map can be trimmed to be smaller
590 * than the amount of physical memory due to the mem= command
591 * line parameter. And if this is a 32-bit non-HIGHMEM kernel
592 * on a system with memory which requires highmem to access,
593 * don't try to use it.
594 */
595 extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
596 (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
597 for (pfn = PFN_UP(xen_extra_mem_start);
598 pfn < extra_pfn_end;
599 pfn++) {
600 page = pfn_to_page(pfn);
601 /* totalram_pages and totalhigh_pages do not include the boot-time
602 balloon extension, so don't subtract from it. */
603 __balloon_append(page);
604 }
605
606 return 0;
607}
608
609subsys_initcall(balloon_init);
610
611MODULE_LICENSE("GPL");