aboutsummaryrefslogtreecommitdiff
path: root/drivers/xen/balloon.c
blob: 930fb68179012355952c20d759111a6755b3acbe (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
/******************************************************************************
 * Xen balloon driver - enables returning/claiming memory to/from Xen.
 *
 * Copyright (c) 2003, B Dragovic
 * Copyright (c) 2003-2004, M Williamson, K Fraser
 * Copyright (c) 2005 Dan M. Smith, IBM Corporation
 * Copyright (c) 2010 Daniel Kiper
 *
 * Memory hotplug support was written by Daniel Kiper. Work on
 * it was sponsored by Google under Google Summer of Code 2010
 * program. Jeremy Fitzhardinge from Citrix was the mentor for
 * this project.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version 2
 * as published by the Free Software Foundation; or, when distributed
 * separately from the Linux kernel or incorporated into other
 * software packages, subject to the following license:
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this source file (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/bootmem.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/mutex.h>
#include <linux/list.h>
#include <linux/gfp.h>
#include <linux/notifier.h>
#include <linux/memory.h>
#include <linux/memory_hotplug.h>

#include <asm/page.h>
#include <asm/pgalloc.h>
#include <asm/pgtable.h>
#include <asm/tlb.h>

#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>

#include <xen/xen.h>
#include <xen/interface/xen.h>
#include <xen/interface/memory.h>
#include <xen/balloon.h>
#include <xen/features.h>
#include <xen/page.h>

/*
 * balloon_process() state:
 *
 * BP_DONE: done or nothing to do,
 * BP_EAGAIN: error, go to sleep,
 * BP_ECANCELED: error, balloon operation canceled.
 */

enum bp_state {
	BP_DONE,
	BP_EAGAIN,
	BP_ECANCELED
};


static DEFINE_MUTEX(balloon_mutex);

struct balloon_stats balloon_stats;
EXPORT_SYMBOL_GPL(balloon_stats);

/* We increase/decrease in batches which fit in a page */
static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)];

#ifdef CONFIG_HIGHMEM
#define inc_totalhigh_pages() (totalhigh_pages++)
#define dec_totalhigh_pages() (totalhigh_pages--)
#else
#define inc_totalhigh_pages() do {} while (0)
#define dec_totalhigh_pages() do {} while (0)
#endif

/* List of ballooned pages, threaded through the mem_map array. */
static LIST_HEAD(ballooned_pages);

/* Main work function, always executed in process context. */
static void balloon_process(struct work_struct *work);
static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);

/* When ballooning out (allocating memory to return to Xen) we don't really
   want the kernel to try too hard since that can trigger the oom killer. */
#define GFP_BALLOON \
	(GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)

static void scrub_page(struct page *page)
{
#ifdef CONFIG_XEN_SCRUB_PAGES
	clear_highpage(page);
#endif
}

/* balloon_append: add the given page to the balloon. */
static void __balloon_append(struct page *page)
{
	/* Lowmem is re-populated first, so highmem pages go at list tail. */
	if (PageHighMem(page)) {
		list_add_tail(&page->lru, &ballooned_pages);
		balloon_stats.balloon_high++;
	} else {
		list_add(&page->lru, &ballooned_pages);
		balloon_stats.balloon_low++;
	}
}

static void balloon_append(struct page *page)
{
	__balloon_append(page);
	if (PageHighMem(page))
		dec_totalhigh_pages();
	totalram_pages--;
}

/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
static struct page *balloon_retrieve(bool prefer_highmem)
{
	struct page *page;

	if (list_empty(&ballooned_pages))
		return NULL;

	if (prefer_highmem)
		page = list_entry(ballooned_pages.prev, struct page, lru);
	else
		page = list_entry(ballooned_pages.next, struct page, lru);
	list_del(&page->lru);

	if (PageHighMem(page)) {
		balloon_stats.balloon_high--;
		inc_totalhigh_pages();
	} else
		balloon_stats.balloon_low--;

	totalram_pages++;

	return page;
}

static struct page *balloon_first_page(void)
{
	if (list_empty(&ballooned_pages))
		return NULL;
	return list_entry(ballooned_pages.next, struct page, lru);
}

static struct page *balloon_next_page(struct page *page)
{
	struct list_head *next = page->lru.next;
	if (next == &ballooned_pages)
		return NULL;
	return list_entry(next, struct page, lru);
}

static enum bp_state update_schedule(enum bp_state state)
{
	if (state == BP_DONE) {
		balloon_stats.schedule_delay = 1;
		balloon_stats.retry_count = 1;
		return BP_DONE;
	}

	++balloon_stats.retry_count;

	if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
			balloon_stats.retry_count > balloon_stats.max_retry_count) {
		balloon_stats.schedule_delay = 1;
		balloon_stats.retry_count = 1;
		return BP_ECANCELED;
	}

	balloon_stats.schedule_delay <<= 1;

	if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
		balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;

	return BP_EAGAIN;
}

#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
static long current_credit(void)
{
	return balloon_stats.target_pages - balloon_stats.current_pages -
		balloon_stats.hotplug_pages;
}

static bool balloon_is_inflated(void)
{
	if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
			balloon_stats.balloon_hotplug)
		return true;
	else
		return false;
}

/*
 * reserve_additional_memory() adds memory region of size >= credit above
 * max_pfn. New region is section aligned and size is modified to be multiple
 * of section size. Those features allow optimal use of address space and
 * establish proper alignment when this function is called first time after
 * boot (last section not fully populated at boot time contains unused memory
 * pages with PG_reserved bit not set; online_pages_range() does not allow page
 * onlining in whole range if first onlined page does not have PG_reserved
 * bit set). Real size of added memory is established at page onlining stage.
 */

static enum bp_state reserve_additional_memory(long credit)
{
	int nid, rc;
	u64 hotplug_start_paddr;
	unsigned long balloon_hotplug = credit;

	hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
	balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
	nid = memory_add_physaddr_to_nid(hotplug_start_paddr);

	rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);

	if (rc) {
		pr_info("xen_balloon: %s: add_memory() failed: %i\n", __func__, rc);
		return BP_EAGAIN;
	}

	balloon_hotplug -= credit;

	balloon_stats.hotplug_pages += credit;
	balloon_stats.balloon_hotplug = balloon_hotplug;

	return BP_DONE;
}

static void xen_online_page(struct page *page)
{
	__online_page_set_limits(page);

	mutex_lock(&balloon_mutex);

	__balloon_append(page);

	if (balloon_stats.hotplug_pages)
		--balloon_stats.hotplug_pages;
	else
		--balloon_stats.balloon_hotplug;

	mutex_unlock(&balloon_mutex);
}

static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
{
	if (val == MEM_ONLINE)
		schedule_delayed_work(&balloon_worker, 0);

	return NOTIFY_OK;
}

static struct notifier_block xen_memory_nb = {
	.notifier_call = xen_memory_notifier,
	.priority = 0
};
#else
static long current_credit(void)
{
	unsigned long target = balloon_stats.target_pages;

	target = min(target,
		     balloon_stats.current_pages +
		     balloon_stats.balloon_low +
		     balloon_stats.balloon_high);

	return target - balloon_stats.current_pages;
}

static bool balloon_is_inflated(void)
{
	if (balloon_stats.balloon_low || balloon_stats.balloon_high)
		return true;
	else
		return false;
}

static enum bp_state reserve_additional_memory(long credit)
{
	balloon_stats.target_pages = balloon_stats.current_pages;
	return BP_DONE;
}
#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */

static enum bp_state increase_reservation(unsigned long nr_pages)
{
	int rc;
	unsigned long  pfn, i;
	struct page   *page;
	struct xen_memory_reservation reservation = {
		.address_bits = 0,
		.extent_order = 0,
		.domid        = DOMID_SELF
	};

#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
	if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
		nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
		balloon_stats.hotplug_pages += nr_pages;
		balloon_stats.balloon_hotplug -= nr_pages;
		return BP_DONE;
	}
#endif

	if (nr_pages > ARRAY_SIZE(frame_list))
		nr_pages = ARRAY_SIZE(frame_list);

	page = balloon_first_page();
	for (i = 0; i < nr_pages; i++) {
		if (!page) {
			nr_pages = i;
			break;
		}
		frame_list[i] = page_to_pfn(page);
		page = balloon_next_page(page);
	}

	set_xen_guest_handle(reservation.extent_start, frame_list);
	reservation.nr_extents = nr_pages;
	rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
	if (rc <= 0)
		return BP_EAGAIN;

	for (i = 0; i < rc; i++) {
		page = balloon_retrieve(false);
		BUG_ON(page == NULL);

		pfn = page_to_pfn(page);
		BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
		       phys_to_machine_mapping_valid(pfn));

		set_phys_to_machine(pfn, frame_list[i]);

#ifdef CONFIG_XEN_HAVE_PVMMU
		/* Link back into the page tables if not highmem. */
		if (xen_pv_domain() && !PageHighMem(page)) {
			int ret;
			ret = HYPERVISOR_update_va_mapping(
				(unsigned long)__va(pfn << PAGE_SHIFT),
				mfn_pte(frame_list[i], PAGE_KERNEL),
				0);
			BUG_ON(ret);
		}
#endif

		/* Relinquish the page back to the allocator. */
		ClearPageReserved(page);
		init_page_count(page);
		__free_page(page);
	}

	balloon_stats.current_pages += rc;

	return BP_DONE;
}

static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
{
	enum bp_state state = BP_DONE;
	unsigned long  pfn, i;
	struct page   *page;
	int ret;
	struct xen_memory_reservation reservation = {
		.address_bits = 0,
		.extent_order = 0,
		.domid        = DOMID_SELF
	};

#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
	if (balloon_stats.hotplug_pages) {
		nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
		balloon_stats.hotplug_pages -= nr_pages;
		balloon_stats.balloon_hotplug += nr_pages;
		return BP_DONE;
	}
#endif

	if (nr_pages > ARRAY_SIZE(frame_list))
		nr_pages = ARRAY_SIZE(frame_list);

	for (i = 0; i < nr_pages; i++) {
		page = alloc_page(gfp);
		if (page == NULL) {
			nr_pages = i;
			state = BP_EAGAIN;
			break;
		}

		pfn = page_to_pfn(page);
		frame_list[i] = pfn_to_mfn(pfn);

		scrub_page(page);

#ifdef CONFIG_XEN_HAVE_PVMMU
		if (xen_pv_domain() && !PageHighMem(page)) {
			ret = HYPERVISOR_update_va_mapping(
				(unsigned long)__va(pfn << PAGE_SHIFT),
				__pte_ma(0), 0);
			BUG_ON(ret);
		}
#endif
	}

	/* Ensure that ballooned highmem pages don't have kmaps. */
	kmap_flush_unused();
	flush_tlb_all();

	/* No more mappings: invalidate P2M and add to balloon. */
	for (i = 0; i < nr_pages; i++) {
		pfn = mfn_to_pfn(frame_list[i]);
		__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
		balloon_append(pfn_to_page(pfn));
	}

	set_xen_guest_handle(reservation.extent_start, frame_list);
	reservation.nr_extents   = nr_pages;
	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
	BUG_ON(ret != nr_pages);

	balloon_stats.current_pages -= nr_pages;

	return state;
}

/*
 * We avoid multiple worker processes conflicting via the balloon mutex.
 * We may of course race updates of the target counts (which are protected
 * by the balloon lock), or with changes to the Xen hard limit, but we will
 * recover from these in time.
 */
static void balloon_process(struct work_struct *work)
{
	enum bp_state state = BP_DONE;
	long credit;

	mutex_lock(&balloon_mutex);

	do {
		credit = current_credit();

		if (credit > 0) {
			if (balloon_is_inflated())
				state = increase_reservation(credit);
			else
				state = reserve_additional_memory(credit);
		}

		if (credit < 0)
			state = decrease_reservation(-credit, GFP_BALLOON);

		state = update_schedule(state);

#ifndef CONFIG_PREEMPT
		if (need_resched())
			schedule();
#endif
	} while (credit && state == BP_DONE);

	/* Schedule more work if there is some still to be done. */
	if (state == BP_EAGAIN)
		schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);

	mutex_unlock(&balloon_mutex);
}

/* Resets the Xen limit, sets new target, and kicks off processing. */
void balloon_set_new_target(unsigned long target)
{
	/* No need for lock. Not read-modify-write updates. */
	balloon_stats.target_pages = target;
	schedule_delayed_work(&balloon_worker, 0);
}
EXPORT_SYMBOL_GPL(balloon_set_new_target);

/**
 * alloc_xenballooned_pages - get pages that have been ballooned out
 * @nr_pages: Number of pages to get
 * @pages: pages returned
 * @highmem: allow highmem pages
 * @return 0 on success, error otherwise
 */
int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
{
	int pgno = 0;
	struct page *page;
	mutex_lock(&balloon_mutex);
	while (pgno < nr_pages) {
		page = balloon_retrieve(highmem);
		if (page && (highmem || !PageHighMem(page))) {
			pages[pgno++] = page;
		} else {
			enum bp_state st;
			if (page)
				balloon_append(page);
			st = decrease_reservation(nr_pages - pgno,
					highmem ? GFP_HIGHUSER : GFP_USER);
			if (st != BP_DONE)
				goto out_undo;
		}
	}
	mutex_unlock(&balloon_mutex);
	return 0;
 out_undo:
	while (pgno)
		balloon_append(pages[--pgno]);
	/* Free the memory back to the kernel soon */
	schedule_delayed_work(&balloon_worker, 0);
	mutex_unlock(&balloon_mutex);
	return -ENOMEM;
}
EXPORT_SYMBOL(alloc_xenballooned_pages);

/**
 * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
 * @nr_pages: Number of pages
 * @pages: pages to return
 */
void free_xenballooned_pages(int nr_pages, struct page **pages)
{
	int i;

	mutex_lock(&balloon_mutex);

	for (i = 0; i < nr_pages; i++) {
		if (pages[i])
			balloon_append(pages[i]);
	}

	/* The balloon may be too large now. Shrink it if needed. */
	if (current_credit())
		schedule_delayed_work(&balloon_worker, 0);

	mutex_unlock(&balloon_mutex);
}
EXPORT_SYMBOL(free_xenballooned_pages);

static void __init balloon_add_region(unsigned long start_pfn,
				      unsigned long pages)
{
	unsigned long pfn, extra_pfn_end;
	struct page *page;

	/*
	 * If the amount of usable memory has been limited (e.g., with
	 * the 'mem' command line parameter), don't add pages beyond
	 * this limit.
	 */
	extra_pfn_end = min(max_pfn, start_pfn + pages);

	for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
		page = pfn_to_page(pfn);
		/* totalram_pages and totalhigh_pages do not
		   include the boot-time balloon extension, so
		   don't subtract from it. */
		__balloon_append(page);
	}
}

static int __init balloon_init(void)
{
	int i;

	if (!xen_domain())
		return -ENODEV;

	pr_info("xen/balloon: Initialising balloon driver.\n");

	balloon_stats.current_pages = xen_pv_domain()
		? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
		: max_pfn;
	balloon_stats.target_pages  = balloon_stats.current_pages;
	balloon_stats.balloon_low   = 0;
	balloon_stats.balloon_high  = 0;

	balloon_stats.schedule_delay = 1;
	balloon_stats.max_schedule_delay = 32;
	balloon_stats.retry_count = 1;
	balloon_stats.max_retry_count = RETRY_UNLIMITED;

#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
	balloon_stats.hotplug_pages = 0;
	balloon_stats.balloon_hotplug = 0;

	set_online_page_callback(&xen_online_page);
	register_memory_notifier(&xen_memory_nb);
#endif

	/*
	 * Initialize the balloon with pages from the extra memory
	 * regions (see arch/x86/xen/setup.c).
	 */
	for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
		if (xen_extra_mem[i].size)
			balloon_add_region(PFN_UP(xen_extra_mem[i].start),
					   PFN_DOWN(xen_extra_mem[i].size));

	return 0;
}

subsys_initcall(balloon_init);

MODULE_LICENSE("GPL");