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1/*
2 * VMware Balloon driver.
3 *
4 * Copyright (C) 2000-2010, VMware, Inc. All Rights Reserved.
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the
8 * Free Software Foundation; version 2 of the License and no later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
13 * NON INFRINGEMENT. See the GNU General Public License for more
14 * details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Maintained by: Dmitry Torokhov <dtor@vmware.com>
21 */
22
23/*
24 * This is VMware physical memory management driver for Linux. The driver
25 * acts like a "balloon" that can be inflated to reclaim physical pages by
26 * reserving them in the guest and invalidating them in the monitor,
27 * freeing up the underlying machine pages so they can be allocated to
28 * other guests. The balloon can also be deflated to allow the guest to
29 * use more physical memory. Higher level policies can control the sizes
30 * of balloons in VMs in order to manage physical memory resources.
31 */
32
33//#define DEBUG
34#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
35
36#include <linux/types.h>
37#include <linux/kernel.h>
38#include <linux/mm.h>
39#include <linux/sched.h>
40#include <linux/module.h>
41#include <linux/workqueue.h>
42#include <linux/debugfs.h>
43#include <linux/seq_file.h>
44#include <asm/hypervisor.h>
45
46MODULE_AUTHOR("VMware, Inc.");
47MODULE_DESCRIPTION("VMware Memory Control (Balloon) Driver");
48MODULE_VERSION("1.2.1.3-k");
49MODULE_ALIAS("dmi:*:svnVMware*:*");
50MODULE_ALIAS("vmware_vmmemctl");
51MODULE_LICENSE("GPL");
52
53/*
54 * Various constants controlling rate of inflaint/deflating balloon,
55 * measured in pages.
56 */
57
58/*
59 * Rate of allocating memory when there is no memory pressure
60 * (driver performs non-sleeping allocations).
61 */
62#define VMW_BALLOON_NOSLEEP_ALLOC_MAX 16384U
63
64/*
65 * Rates of memory allocaton when guest experiences memory pressure
66 * (driver performs sleeping allocations).
67 */
68#define VMW_BALLOON_RATE_ALLOC_MIN 512U
69#define VMW_BALLOON_RATE_ALLOC_MAX 2048U
70#define VMW_BALLOON_RATE_ALLOC_INC 16U
71
72/*
73 * Rates for releasing pages while deflating balloon.
74 */
75#define VMW_BALLOON_RATE_FREE_MIN 512U
76#define VMW_BALLOON_RATE_FREE_MAX 16384U
77#define VMW_BALLOON_RATE_FREE_INC 16U
78
79/*
80 * When guest is under memory pressure, use a reduced page allocation
81 * rate for next several cycles.
82 */
83#define VMW_BALLOON_SLOW_CYCLES 4
84
85/*
86 * Use __GFP_HIGHMEM to allow pages from HIGHMEM zone. We don't
87 * allow wait (__GFP_WAIT) for NOSLEEP page allocations. Use
88 * __GFP_NOWARN, to suppress page allocation failure warnings.
89 */
90#define VMW_PAGE_ALLOC_NOSLEEP (__GFP_HIGHMEM|__GFP_NOWARN)
91
92/*
93 * Use GFP_HIGHUSER when executing in a separate kernel thread
94 * context and allocation can sleep. This is less stressful to
95 * the guest memory system, since it allows the thread to block
96 * while memory is reclaimed, and won't take pages from emergency
97 * low-memory pools.
98 */
99#define VMW_PAGE_ALLOC_CANSLEEP (GFP_HIGHUSER)
100
101/* Maximum number of page allocations without yielding processor */
102#define VMW_BALLOON_YIELD_THRESHOLD 1024
103
104/* Maximum number of refused pages we accumulate during inflation cycle */
105#define VMW_BALLOON_MAX_REFUSED 16
106
107/*
108 * Hypervisor communication port definitions.
109 */
110#define VMW_BALLOON_HV_PORT 0x5670
111#define VMW_BALLOON_HV_MAGIC 0x456c6d6f
112#define VMW_BALLOON_PROTOCOL_VERSION 2
113#define VMW_BALLOON_GUEST_ID 1 /* Linux */
114
115#define VMW_BALLOON_CMD_START 0
116#define VMW_BALLOON_CMD_GET_TARGET 1
117#define VMW_BALLOON_CMD_LOCK 2
118#define VMW_BALLOON_CMD_UNLOCK 3
119#define VMW_BALLOON_CMD_GUEST_ID 4
120
121/* error codes */
122#define VMW_BALLOON_SUCCESS 0
123#define VMW_BALLOON_FAILURE -1
124#define VMW_BALLOON_ERROR_CMD_INVALID 1
125#define VMW_BALLOON_ERROR_PPN_INVALID 2
126#define VMW_BALLOON_ERROR_PPN_LOCKED 3
127#define VMW_BALLOON_ERROR_PPN_UNLOCKED 4
128#define VMW_BALLOON_ERROR_PPN_PINNED 5
129#define VMW_BALLOON_ERROR_PPN_NOTNEEDED 6
130#define VMW_BALLOON_ERROR_RESET 7
131#define VMW_BALLOON_ERROR_BUSY 8
132
133#define VMWARE_BALLOON_CMD(cmd, data, result) \
134({ \
135 unsigned long __stat, __dummy1, __dummy2; \
136 __asm__ __volatile__ ("inl (%%dx)" : \
137 "=a"(__stat), \
138 "=c"(__dummy1), \
139 "=d"(__dummy2), \
140 "=b"(result) : \
141 "0"(VMW_BALLOON_HV_MAGIC), \
142 "1"(VMW_BALLOON_CMD_##cmd), \
143 "2"(VMW_BALLOON_HV_PORT), \
144 "3"(data) : \
145 "memory"); \
146 result &= -1UL; \
147 __stat & -1UL; \
148})
149
150#ifdef CONFIG_DEBUG_FS
151struct vmballoon_stats {
152 unsigned int timer;
153
154 /* allocation statustics */
155 unsigned int alloc;
156 unsigned int alloc_fail;
157 unsigned int sleep_alloc;
158 unsigned int sleep_alloc_fail;
159 unsigned int refused_alloc;
160 unsigned int refused_free;
161 unsigned int free;
162
163 /* monitor operations */
164 unsigned int lock;
165 unsigned int lock_fail;
166 unsigned int unlock;
167 unsigned int unlock_fail;
168 unsigned int target;
169 unsigned int target_fail;
170 unsigned int start;
171 unsigned int start_fail;
172 unsigned int guest_type;
173 unsigned int guest_type_fail;
174};
175
176#define STATS_INC(stat) (stat)++
177#else
178#define STATS_INC(stat)
179#endif
180
181struct vmballoon {
182
183 /* list of reserved physical pages */
184 struct list_head pages;
185
186 /* transient list of non-balloonable pages */
187 struct list_head refused_pages;
188 unsigned int n_refused_pages;
189
190 /* balloon size in pages */
191 unsigned int size;
192 unsigned int target;
193
194 /* reset flag */
195 bool reset_required;
196
197 /* adjustment rates (pages per second) */
198 unsigned int rate_alloc;
199 unsigned int rate_free;
200
201 /* slowdown page allocations for next few cycles */
202 unsigned int slow_allocation_cycles;
203
204#ifdef CONFIG_DEBUG_FS
205 /* statistics */
206 struct vmballoon_stats stats;
207
208 /* debugfs file exporting statistics */
209 struct dentry *dbg_entry;
210#endif
211
212 struct sysinfo sysinfo;
213
214 struct delayed_work dwork;
215};
216
217static struct vmballoon balloon;
218
219/*
220 * Send "start" command to the host, communicating supported version
221 * of the protocol.
222 */
223static bool vmballoon_send_start(struct vmballoon *b)
224{
225 unsigned long status, dummy;
226
227 STATS_INC(b->stats.start);
228
229 status = VMWARE_BALLOON_CMD(START, VMW_BALLOON_PROTOCOL_VERSION, dummy);
230 if (status == VMW_BALLOON_SUCCESS)
231 return true;
232
233 pr_debug("%s - failed, hv returns %ld\n", __func__, status);
234 STATS_INC(b->stats.start_fail);
235 return false;
236}
237
238static bool vmballoon_check_status(struct vmballoon *b, unsigned long status)
239{
240 switch (status) {
241 case VMW_BALLOON_SUCCESS:
242 return true;
243
244 case VMW_BALLOON_ERROR_RESET:
245 b->reset_required = true;
246 /* fall through */
247
248 default:
249 return false;
250 }
251}
252
253/*
254 * Communicate guest type to the host so that it can adjust ballooning
255 * algorithm to the one most appropriate for the guest. This command
256 * is normally issued after sending "start" command and is part of
257 * standard reset sequence.
258 */
259static bool vmballoon_send_guest_id(struct vmballoon *b)
260{
261 unsigned long status, dummy;
262
263 status = VMWARE_BALLOON_CMD(GUEST_ID, VMW_BALLOON_GUEST_ID, dummy);
264
265 STATS_INC(b->stats.guest_type);
266
267 if (vmballoon_check_status(b, status))
268 return true;
269
270 pr_debug("%s - failed, hv returns %ld\n", __func__, status);
271 STATS_INC(b->stats.guest_type_fail);
272 return false;
273}
274
275/*
276 * Retrieve desired balloon size from the host.
277 */
278static bool vmballoon_send_get_target(struct vmballoon *b, u32 *new_target)
279{
280 unsigned long status;
281 unsigned long target;
282 unsigned long limit;
283 u32 limit32;
284
285 /*
286 * si_meminfo() is cheap. Moreover, we want to provide dynamic
287 * max balloon size later. So let us call si_meminfo() every
288 * iteration.
289 */
290 si_meminfo(&b->sysinfo);
291 limit = b->sysinfo.totalram;
292
293 /* Ensure limit fits in 32-bits */
294 limit32 = (u32)limit;
295 if (limit != limit32)
296 return false;
297
298 /* update stats */
299 STATS_INC(b->stats.target);
300
301 status = VMWARE_BALLOON_CMD(GET_TARGET, limit, target);
302 if (vmballoon_check_status(b, status)) {
303 *new_target = target;
304 return true;
305 }
306
307 pr_debug("%s - failed, hv returns %ld\n", __func__, status);
308 STATS_INC(b->stats.target_fail);
309 return false;
310}
311
312/*
313 * Notify the host about allocated page so that host can use it without
314 * fear that guest will need it. Host may reject some pages, we need to
315 * check the return value and maybe submit a different page.
316 */
317static bool vmballoon_send_lock_page(struct vmballoon *b, unsigned long pfn,
318 unsigned int *hv_status)
319{
320 unsigned long status, dummy;
321 u32 pfn32;
322
323 pfn32 = (u32)pfn;
324 if (pfn32 != pfn)
325 return false;
326
327 STATS_INC(b->stats.lock);
328
329 *hv_status = status = VMWARE_BALLOON_CMD(LOCK, pfn, dummy);
330 if (vmballoon_check_status(b, status))
331 return true;
332
333 pr_debug("%s - ppn %lx, hv returns %ld\n", __func__, pfn, status);
334 STATS_INC(b->stats.lock_fail);
335 return false;
336}
337
338/*
339 * Notify the host that guest intends to release given page back into
340 * the pool of available (to the guest) pages.
341 */
342static bool vmballoon_send_unlock_page(struct vmballoon *b, unsigned long pfn)
343{
344 unsigned long status, dummy;
345 u32 pfn32;
346
347 pfn32 = (u32)pfn;
348 if (pfn32 != pfn)
349 return false;
350
351 STATS_INC(b->stats.unlock);
352
353 status = VMWARE_BALLOON_CMD(UNLOCK, pfn, dummy);
354 if (vmballoon_check_status(b, status))
355 return true;
356
357 pr_debug("%s - ppn %lx, hv returns %ld\n", __func__, pfn, status);
358 STATS_INC(b->stats.unlock_fail);
359 return false;
360}
361
362/*
363 * Quickly release all pages allocated for the balloon. This function is
364 * called when host decides to "reset" balloon for one reason or another.
365 * Unlike normal "deflate" we do not (shall not) notify host of the pages
366 * being released.
367 */
368static void vmballoon_pop(struct vmballoon *b)
369{
370 struct page *page, *next;
371 unsigned int count = 0;
372
373 list_for_each_entry_safe(page, next, &b->pages, lru) {
374 list_del(&page->lru);
375 __free_page(page);
376 STATS_INC(b->stats.free);
377 b->size--;
378
379 if (++count >= b->rate_free) {
380 count = 0;
381 cond_resched();
382 }
383 }
384}
385
386/*
387 * Perform standard reset sequence by popping the balloon (in case it
388 * is not empty) and then restarting protocol. This operation normally
389 * happens when host responds with VMW_BALLOON_ERROR_RESET to a command.
390 */
391static void vmballoon_reset(struct vmballoon *b)
392{
393 /* free all pages, skipping monitor unlock */
394 vmballoon_pop(b);
395
396 if (vmballoon_send_start(b)) {
397 b->reset_required = false;
398 if (!vmballoon_send_guest_id(b))
399 pr_err("failed to send guest ID to the host\n");
400 }
401}
402
403/*
404 * Allocate (or reserve) a page for the balloon and notify the host. If host
405 * refuses the page put it on "refuse" list and allocate another one until host
406 * is satisfied. "Refused" pages are released at the end of inflation cycle
407 * (when we allocate b->rate_alloc pages).
408 */
409static int vmballoon_reserve_page(struct vmballoon *b, bool can_sleep)
410{
411 struct page *page;
412 gfp_t flags;
413 unsigned int hv_status;
414 bool locked = false;
415
416 do {
417 if (!can_sleep)
418 STATS_INC(b->stats.alloc);
419 else
420 STATS_INC(b->stats.sleep_alloc);
421
422 flags = can_sleep ? VMW_PAGE_ALLOC_CANSLEEP : VMW_PAGE_ALLOC_NOSLEEP;
423 page = alloc_page(flags);
424 if (!page) {
425 if (!can_sleep)
426 STATS_INC(b->stats.alloc_fail);
427 else
428 STATS_INC(b->stats.sleep_alloc_fail);
429 return -ENOMEM;
430 }
431
432 /* inform monitor */
433 locked = vmballoon_send_lock_page(b, page_to_pfn(page), &hv_status);
434 if (!locked) {
435 STATS_INC(b->stats.refused_alloc);
436
437 if (hv_status == VMW_BALLOON_ERROR_RESET ||
438 hv_status == VMW_BALLOON_ERROR_PPN_NOTNEEDED) {
439 __free_page(page);
440 return -EIO;
441 }
442
443 /*
444 * Place page on the list of non-balloonable pages
445 * and retry allocation, unless we already accumulated
446 * too many of them, in which case take a breather.
447 */
448 list_add(&page->lru, &b->refused_pages);
449 if (++b->n_refused_pages >= VMW_BALLOON_MAX_REFUSED)
450 return -EIO;
451 }
452 } while (!locked);
453
454 /* track allocated page */
455 list_add(&page->lru, &b->pages);
456
457 /* update balloon size */
458 b->size++;
459
460 return 0;
461}
462
463/*
464 * Release the page allocated for the balloon. Note that we first notify
465 * the host so it can make sure the page will be available for the guest
466 * to use, if needed.
467 */
468static int vmballoon_release_page(struct vmballoon *b, struct page *page)
469{
470 if (!vmballoon_send_unlock_page(b, page_to_pfn(page)))
471 return -EIO;
472
473 list_del(&page->lru);
474
475 /* deallocate page */
476 __free_page(page);
477 STATS_INC(b->stats.free);
478
479 /* update balloon size */
480 b->size--;
481
482 return 0;
483}
484
485/*
486 * Release pages that were allocated while attempting to inflate the
487 * balloon but were refused by the host for one reason or another.
488 */
489static void vmballoon_release_refused_pages(struct vmballoon *b)
490{
491 struct page *page, *next;
492
493 list_for_each_entry_safe(page, next, &b->refused_pages, lru) {
494 list_del(&page->lru);
495 __free_page(page);
496 STATS_INC(b->stats.refused_free);
497 }
498
499 b->n_refused_pages = 0;
500}
501
502/*
503 * Inflate the balloon towards its target size. Note that we try to limit
504 * the rate of allocation to make sure we are not choking the rest of the
505 * system.
506 */
507static void vmballoon_inflate(struct vmballoon *b)
508{
509 unsigned int goal;
510 unsigned int rate;
511 unsigned int i;
512 unsigned int allocations = 0;
513 int error = 0;
514 bool alloc_can_sleep = false;
515
516 pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
517
518 /*
519 * First try NOSLEEP page allocations to inflate balloon.
520 *
521 * If we do not throttle nosleep allocations, we can drain all
522 * free pages in the guest quickly (if the balloon target is high).
523 * As a side-effect, draining free pages helps to inform (force)
524 * the guest to start swapping if balloon target is not met yet,
525 * which is a desired behavior. However, balloon driver can consume
526 * all available CPU cycles if too many pages are allocated in a
527 * second. Therefore, we throttle nosleep allocations even when
528 * the guest is not under memory pressure. OTOH, if we have already
529 * predicted that the guest is under memory pressure, then we
530 * slowdown page allocations considerably.
531 */
532
533 goal = b->target - b->size;
534 /*
535 * Start with no sleep allocation rate which may be higher
536 * than sleeping allocation rate.
537 */
538 rate = b->slow_allocation_cycles ?
539 b->rate_alloc : VMW_BALLOON_NOSLEEP_ALLOC_MAX;
540
541 pr_debug("%s - goal: %d, no-sleep rate: %d, sleep rate: %d\n",
542 __func__, goal, rate, b->rate_alloc);
543
544 for (i = 0; i < goal; i++) {
545
546 error = vmballoon_reserve_page(b, alloc_can_sleep);
547 if (error) {
548 if (error != -ENOMEM) {
549 /*
550 * Not a page allocation failure, stop this
551 * cycle. Maybe we'll get new target from
552 * the host soon.
553 */
554 break;
555 }
556
557 if (alloc_can_sleep) {
558 /*
559 * CANSLEEP page allocation failed, so guest
560 * is under severe memory pressure. Quickly
561 * decrease allocation rate.
562 */
563 b->rate_alloc = max(b->rate_alloc / 2,
564 VMW_BALLOON_RATE_ALLOC_MIN);
565 break;
566 }
567
568 /*
569 * NOSLEEP page allocation failed, so the guest is
570 * under memory pressure. Let us slow down page
571 * allocations for next few cycles so that the guest
572 * gets out of memory pressure. Also, if we already
573 * allocated b->rate_alloc pages, let's pause,
574 * otherwise switch to sleeping allocations.
575 */
576 b->slow_allocation_cycles = VMW_BALLOON_SLOW_CYCLES;
577
578 if (i >= b->rate_alloc)
579 break;
580
581 alloc_can_sleep = true;
582 /* Lower rate for sleeping allocations. */
583 rate = b->rate_alloc;
584 }
585
586 if (++allocations > VMW_BALLOON_YIELD_THRESHOLD) {
587 cond_resched();
588 allocations = 0;
589 }
590
591 if (i >= rate) {
592 /* We allocated enough pages, let's take a break. */
593 break;
594 }
595 }
596
597 /*
598 * We reached our goal without failures so try increasing
599 * allocation rate.
600 */
601 if (error == 0 && i >= b->rate_alloc) {
602 unsigned int mult = i / b->rate_alloc;
603
604 b->rate_alloc =
605 min(b->rate_alloc + mult * VMW_BALLOON_RATE_ALLOC_INC,
606 VMW_BALLOON_RATE_ALLOC_MAX);
607 }
608
609 vmballoon_release_refused_pages(b);
610}
611
612/*
613 * Decrease the size of the balloon allowing guest to use more memory.
614 */
615static void vmballoon_deflate(struct vmballoon *b)
616{
617 struct page *page, *next;
618 unsigned int i = 0;
619 unsigned int goal;
620 int error;
621
622 pr_debug("%s - size: %d, target %d\n", __func__, b->size, b->target);
623
624 /* limit deallocation rate */
625 goal = min(b->size - b->target, b->rate_free);
626
627 pr_debug("%s - goal: %d, rate: %d\n", __func__, goal, b->rate_free);
628
629 /* free pages to reach target */
630 list_for_each_entry_safe(page, next, &b->pages, lru) {
631 error = vmballoon_release_page(b, page);
632 if (error) {
633 /* quickly decrease rate in case of error */
634 b->rate_free = max(b->rate_free / 2,
635 VMW_BALLOON_RATE_FREE_MIN);
636 return;
637 }
638
639 if (++i >= goal)
640 break;
641 }
642
643 /* slowly increase rate if there were no errors */
644 b->rate_free = min(b->rate_free + VMW_BALLOON_RATE_FREE_INC,
645 VMW_BALLOON_RATE_FREE_MAX);
646}
647
648/*
649 * Balloon work function: reset protocol, if needed, get the new size and
650 * adjust balloon as needed. Repeat in 1 sec.
651 */
652static void vmballoon_work(struct work_struct *work)
653{
654 struct delayed_work *dwork = to_delayed_work(work);
655 struct vmballoon *b = container_of(dwork, struct vmballoon, dwork);
656 unsigned int target;
657
658 STATS_INC(b->stats.timer);
659
660 if (b->reset_required)
661 vmballoon_reset(b);
662
663 if (b->slow_allocation_cycles > 0)
664 b->slow_allocation_cycles--;
665
666 if (vmballoon_send_get_target(b, &target)) {
667 /* update target, adjust size */
668 b->target = target;
669
670 if (b->size < target)
671 vmballoon_inflate(b);
672 else if (b->size > target)
673 vmballoon_deflate(b);
674 }
675
676 /*
677 * We are using a freezable workqueue so that balloon operations are
678 * stopped while the system transitions to/from sleep/hibernation.
679 */
680 queue_delayed_work(system_freezable_wq,
681 dwork, round_jiffies_relative(HZ));
682}
683
684/*
685 * DEBUGFS Interface
686 */
687#ifdef CONFIG_DEBUG_FS
688
689static int vmballoon_debug_show(struct seq_file *f, void *offset)
690{
691 struct vmballoon *b = f->private;
692 struct vmballoon_stats *stats = &b->stats;
693
694 /* format size info */
695 seq_printf(f,
696 "target: %8d pages\n"
697 "current: %8d pages\n",
698 b->target, b->size);
699
700 /* format rate info */
701 seq_printf(f,
702 "rateNoSleepAlloc: %8d pages/sec\n"
703 "rateSleepAlloc: %8d pages/sec\n"
704 "rateFree: %8d pages/sec\n",
705 VMW_BALLOON_NOSLEEP_ALLOC_MAX,
706 b->rate_alloc, b->rate_free);
707
708 seq_printf(f,
709 "\n"
710 "timer: %8u\n"
711 "start: %8u (%4u failed)\n"
712 "guestType: %8u (%4u failed)\n"
713 "lock: %8u (%4u failed)\n"
714 "unlock: %8u (%4u failed)\n"
715 "target: %8u (%4u failed)\n"
716 "primNoSleepAlloc: %8u (%4u failed)\n"
717 "primCanSleepAlloc: %8u (%4u failed)\n"
718 "primFree: %8u\n"
719 "errAlloc: %8u\n"
720 "errFree: %8u\n",
721 stats->timer,
722 stats->start, stats->start_fail,
723 stats->guest_type, stats->guest_type_fail,
724 stats->lock, stats->lock_fail,
725 stats->unlock, stats->unlock_fail,
726 stats->target, stats->target_fail,
727 stats->alloc, stats->alloc_fail,
728 stats->sleep_alloc, stats->sleep_alloc_fail,
729 stats->free,
730 stats->refused_alloc, stats->refused_free);
731
732 return 0;
733}
734
735static int vmballoon_debug_open(struct inode *inode, struct file *file)
736{
737 return single_open(file, vmballoon_debug_show, inode->i_private);
738}
739
740static const struct file_operations vmballoon_debug_fops = {
741 .owner = THIS_MODULE,
742 .open = vmballoon_debug_open,
743 .read = seq_read,
744 .llseek = seq_lseek,
745 .release = single_release,
746};
747
748static int __init vmballoon_debugfs_init(struct vmballoon *b)
749{
750 int error;
751
752 b->dbg_entry = debugfs_create_file("vmmemctl", S_IRUGO, NULL, b,
753 &vmballoon_debug_fops);
754 if (IS_ERR(b->dbg_entry)) {
755 error = PTR_ERR(b->dbg_entry);
756 pr_err("failed to create debugfs entry, error: %d\n", error);
757 return error;
758 }
759
760 return 0;
761}
762
763static void __exit vmballoon_debugfs_exit(struct vmballoon *b)
764{
765 debugfs_remove(b->dbg_entry);
766}
767
768#else
769
770static inline int vmballoon_debugfs_init(struct vmballoon *b)
771{
772 return 0;
773}
774
775static inline void vmballoon_debugfs_exit(struct vmballoon *b)
776{
777}
778
779#endif /* CONFIG_DEBUG_FS */
780
781static int __init vmballoon_init(void)
782{
783 int error;
784
785 /*
786 * Check if we are running on VMware's hypervisor and bail out
787 * if we are not.
788 */
789 if (x86_hyper != &x86_hyper_vmware)
790 return -ENODEV;
791
792 INIT_LIST_HEAD(&balloon.pages);
793 INIT_LIST_HEAD(&balloon.refused_pages);
794
795 /* initialize rates */
796 balloon.rate_alloc = VMW_BALLOON_RATE_ALLOC_MAX;
797 balloon.rate_free = VMW_BALLOON_RATE_FREE_MAX;
798
799 INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);
800
801 /*
802 * Start balloon.
803 */
804 if (!vmballoon_send_start(&balloon)) {
805 pr_err("failed to send start command to the host\n");
806 return -EIO;
807 }
808
809 if (!vmballoon_send_guest_id(&balloon)) {
810 pr_err("failed to send guest ID to the host\n");
811 return -EIO;
812 }
813
814 error = vmballoon_debugfs_init(&balloon);
815 if (error)
816 return error;
817
818 queue_delayed_work(system_freezable_wq, &balloon.dwork, 0);
819
820 return 0;
821}
822module_init(vmballoon_init);
823
824static void __exit vmballoon_exit(void)
825{
826 cancel_delayed_work_sync(&balloon.dwork);
827
828 vmballoon_debugfs_exit(&balloon);
829
830 /*
831 * Deallocate all reserved memory, and reset connection with monitor.
832 * Reset connection before deallocating memory to avoid potential for
833 * additional spurious resets from guest touching deallocated pages.
834 */
835 vmballoon_send_start(&balloon);
836 vmballoon_pop(&balloon);
837}
838module_exit(vmballoon_exit);
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * VMware Balloon driver.
4 *
5 * Copyright (C) 2000-2018, VMware, Inc. All Rights Reserved.
6 *
7 * This is VMware physical memory management driver for Linux. The driver
8 * acts like a "balloon" that can be inflated to reclaim physical pages by
9 * reserving them in the guest and invalidating them in the monitor,
10 * freeing up the underlying machine pages so they can be allocated to
11 * other guests. The balloon can also be deflated to allow the guest to
12 * use more physical memory. Higher level policies can control the sizes
13 * of balloons in VMs in order to manage physical memory resources.
14 */
15
16//#define DEBUG
17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18
19#include <linux/types.h>
20#include <linux/io.h>
21#include <linux/kernel.h>
22#include <linux/mm.h>
23#include <linux/vmalloc.h>
24#include <linux/sched.h>
25#include <linux/module.h>
26#include <linux/workqueue.h>
27#include <linux/debugfs.h>
28#include <linux/seq_file.h>
29#include <linux/rwsem.h>
30#include <linux/slab.h>
31#include <linux/spinlock.h>
32#include <linux/balloon_compaction.h>
33#include <linux/vmw_vmci_defs.h>
34#include <linux/vmw_vmci_api.h>
35#include <asm/hypervisor.h>
36
37MODULE_AUTHOR("VMware, Inc.");
38MODULE_DESCRIPTION("VMware Memory Control (Balloon) Driver");
39MODULE_ALIAS("dmi:*:svnVMware*:*");
40MODULE_ALIAS("vmware_vmmemctl");
41MODULE_LICENSE("GPL");
42
43static bool __read_mostly vmwballoon_shrinker_enable;
44module_param(vmwballoon_shrinker_enable, bool, 0444);
45MODULE_PARM_DESC(vmwballoon_shrinker_enable,
46 "Enable non-cooperative out-of-memory protection. Disabled by default as it may degrade performance.");
47
48/* Delay in seconds after shrink before inflation. */
49#define VMBALLOON_SHRINK_DELAY (5)
50
51/* Maximum number of refused pages we accumulate during inflation cycle */
52#define VMW_BALLOON_MAX_REFUSED 16
53
54/* Magic number for the balloon mount-point */
55#define BALLOON_VMW_MAGIC 0x0ba11007
56
57/*
58 * Hypervisor communication port definitions.
59 */
60#define VMW_BALLOON_HV_PORT 0x5670
61#define VMW_BALLOON_HV_MAGIC 0x456c6d6f
62#define VMW_BALLOON_GUEST_ID 1 /* Linux */
63
64enum vmwballoon_capabilities {
65 /*
66 * Bit 0 is reserved and not associated to any capability.
67 */
68 VMW_BALLOON_BASIC_CMDS = (1 << 1),
69 VMW_BALLOON_BATCHED_CMDS = (1 << 2),
70 VMW_BALLOON_BATCHED_2M_CMDS = (1 << 3),
71 VMW_BALLOON_SIGNALLED_WAKEUP_CMD = (1 << 4),
72 VMW_BALLOON_64_BIT_TARGET = (1 << 5)
73};
74
75#define VMW_BALLOON_CAPABILITIES_COMMON (VMW_BALLOON_BASIC_CMDS \
76 | VMW_BALLOON_BATCHED_CMDS \
77 | VMW_BALLOON_BATCHED_2M_CMDS \
78 | VMW_BALLOON_SIGNALLED_WAKEUP_CMD)
79
80#define VMW_BALLOON_2M_ORDER (PMD_SHIFT - PAGE_SHIFT)
81
82/*
83 * 64-bit targets are only supported in 64-bit
84 */
85#ifdef CONFIG_64BIT
86#define VMW_BALLOON_CAPABILITIES (VMW_BALLOON_CAPABILITIES_COMMON \
87 | VMW_BALLOON_64_BIT_TARGET)
88#else
89#define VMW_BALLOON_CAPABILITIES VMW_BALLOON_CAPABILITIES_COMMON
90#endif
91
92enum vmballoon_page_size_type {
93 VMW_BALLOON_4K_PAGE,
94 VMW_BALLOON_2M_PAGE,
95 VMW_BALLOON_LAST_SIZE = VMW_BALLOON_2M_PAGE
96};
97
98#define VMW_BALLOON_NUM_PAGE_SIZES (VMW_BALLOON_LAST_SIZE + 1)
99
100static const char * const vmballoon_page_size_names[] = {
101 [VMW_BALLOON_4K_PAGE] = "4k",
102 [VMW_BALLOON_2M_PAGE] = "2M"
103};
104
105enum vmballoon_op {
106 VMW_BALLOON_INFLATE,
107 VMW_BALLOON_DEFLATE
108};
109
110enum vmballoon_op_stat_type {
111 VMW_BALLOON_OP_STAT,
112 VMW_BALLOON_OP_FAIL_STAT
113};
114
115#define VMW_BALLOON_OP_STAT_TYPES (VMW_BALLOON_OP_FAIL_STAT + 1)
116
117/**
118 * enum vmballoon_cmd_type - backdoor commands.
119 *
120 * Availability of the commands is as followed:
121 *
122 * %VMW_BALLOON_CMD_START, %VMW_BALLOON_CMD_GET_TARGET and
123 * %VMW_BALLOON_CMD_GUEST_ID are always available.
124 *
125 * If the host reports %VMW_BALLOON_BASIC_CMDS are supported then
126 * %VMW_BALLOON_CMD_LOCK and %VMW_BALLOON_CMD_UNLOCK commands are available.
127 *
128 * If the host reports %VMW_BALLOON_BATCHED_CMDS are supported then
129 * %VMW_BALLOON_CMD_BATCHED_LOCK and VMW_BALLOON_CMD_BATCHED_UNLOCK commands
130 * are available.
131 *
132 * If the host reports %VMW_BALLOON_BATCHED_2M_CMDS are supported then
133 * %VMW_BALLOON_CMD_BATCHED_2M_LOCK and %VMW_BALLOON_CMD_BATCHED_2M_UNLOCK
134 * are supported.
135 *
136 * If the host reports VMW_BALLOON_SIGNALLED_WAKEUP_CMD is supported then
137 * VMW_BALLOON_CMD_VMCI_DOORBELL_SET command is supported.
138 *
139 * @VMW_BALLOON_CMD_START: Communicating supported version with the hypervisor.
140 * @VMW_BALLOON_CMD_GET_TARGET: Gets the balloon target size.
141 * @VMW_BALLOON_CMD_LOCK: Informs the hypervisor about a ballooned page.
142 * @VMW_BALLOON_CMD_UNLOCK: Informs the hypervisor about a page that is about
143 * to be deflated from the balloon.
144 * @VMW_BALLOON_CMD_GUEST_ID: Informs the hypervisor about the type of OS that
145 * runs in the VM.
146 * @VMW_BALLOON_CMD_BATCHED_LOCK: Inform the hypervisor about a batch of
147 * ballooned pages (up to 512).
148 * @VMW_BALLOON_CMD_BATCHED_UNLOCK: Inform the hypervisor about a batch of
149 * pages that are about to be deflated from the
150 * balloon (up to 512).
151 * @VMW_BALLOON_CMD_BATCHED_2M_LOCK: Similar to @VMW_BALLOON_CMD_BATCHED_LOCK
152 * for 2MB pages.
153 * @VMW_BALLOON_CMD_BATCHED_2M_UNLOCK: Similar to
154 * @VMW_BALLOON_CMD_BATCHED_UNLOCK for 2MB
155 * pages.
156 * @VMW_BALLOON_CMD_VMCI_DOORBELL_SET: A command to set doorbell notification
157 * that would be invoked when the balloon
158 * size changes.
159 * @VMW_BALLOON_CMD_LAST: Value of the last command.
160 */
161enum vmballoon_cmd_type {
162 VMW_BALLOON_CMD_START,
163 VMW_BALLOON_CMD_GET_TARGET,
164 VMW_BALLOON_CMD_LOCK,
165 VMW_BALLOON_CMD_UNLOCK,
166 VMW_BALLOON_CMD_GUEST_ID,
167 /* No command 5 */
168 VMW_BALLOON_CMD_BATCHED_LOCK = 6,
169 VMW_BALLOON_CMD_BATCHED_UNLOCK,
170 VMW_BALLOON_CMD_BATCHED_2M_LOCK,
171 VMW_BALLOON_CMD_BATCHED_2M_UNLOCK,
172 VMW_BALLOON_CMD_VMCI_DOORBELL_SET,
173 VMW_BALLOON_CMD_LAST = VMW_BALLOON_CMD_VMCI_DOORBELL_SET,
174};
175
176#define VMW_BALLOON_CMD_NUM (VMW_BALLOON_CMD_LAST + 1)
177
178enum vmballoon_error_codes {
179 VMW_BALLOON_SUCCESS,
180 VMW_BALLOON_ERROR_CMD_INVALID,
181 VMW_BALLOON_ERROR_PPN_INVALID,
182 VMW_BALLOON_ERROR_PPN_LOCKED,
183 VMW_BALLOON_ERROR_PPN_UNLOCKED,
184 VMW_BALLOON_ERROR_PPN_PINNED,
185 VMW_BALLOON_ERROR_PPN_NOTNEEDED,
186 VMW_BALLOON_ERROR_RESET,
187 VMW_BALLOON_ERROR_BUSY
188};
189
190#define VMW_BALLOON_SUCCESS_WITH_CAPABILITIES (0x03000000)
191
192#define VMW_BALLOON_CMD_WITH_TARGET_MASK \
193 ((1UL << VMW_BALLOON_CMD_GET_TARGET) | \
194 (1UL << VMW_BALLOON_CMD_LOCK) | \
195 (1UL << VMW_BALLOON_CMD_UNLOCK) | \
196 (1UL << VMW_BALLOON_CMD_BATCHED_LOCK) | \
197 (1UL << VMW_BALLOON_CMD_BATCHED_UNLOCK) | \
198 (1UL << VMW_BALLOON_CMD_BATCHED_2M_LOCK) | \
199 (1UL << VMW_BALLOON_CMD_BATCHED_2M_UNLOCK))
200
201static const char * const vmballoon_cmd_names[] = {
202 [VMW_BALLOON_CMD_START] = "start",
203 [VMW_BALLOON_CMD_GET_TARGET] = "target",
204 [VMW_BALLOON_CMD_LOCK] = "lock",
205 [VMW_BALLOON_CMD_UNLOCK] = "unlock",
206 [VMW_BALLOON_CMD_GUEST_ID] = "guestType",
207 [VMW_BALLOON_CMD_BATCHED_LOCK] = "batchLock",
208 [VMW_BALLOON_CMD_BATCHED_UNLOCK] = "batchUnlock",
209 [VMW_BALLOON_CMD_BATCHED_2M_LOCK] = "2m-lock",
210 [VMW_BALLOON_CMD_BATCHED_2M_UNLOCK] = "2m-unlock",
211 [VMW_BALLOON_CMD_VMCI_DOORBELL_SET] = "doorbellSet"
212};
213
214enum vmballoon_stat_page {
215 VMW_BALLOON_PAGE_STAT_ALLOC,
216 VMW_BALLOON_PAGE_STAT_ALLOC_FAIL,
217 VMW_BALLOON_PAGE_STAT_REFUSED_ALLOC,
218 VMW_BALLOON_PAGE_STAT_REFUSED_FREE,
219 VMW_BALLOON_PAGE_STAT_FREE,
220 VMW_BALLOON_PAGE_STAT_LAST = VMW_BALLOON_PAGE_STAT_FREE
221};
222
223#define VMW_BALLOON_PAGE_STAT_NUM (VMW_BALLOON_PAGE_STAT_LAST + 1)
224
225enum vmballoon_stat_general {
226 VMW_BALLOON_STAT_TIMER,
227 VMW_BALLOON_STAT_DOORBELL,
228 VMW_BALLOON_STAT_RESET,
229 VMW_BALLOON_STAT_SHRINK,
230 VMW_BALLOON_STAT_SHRINK_FREE,
231 VMW_BALLOON_STAT_LAST = VMW_BALLOON_STAT_SHRINK_FREE
232};
233
234#define VMW_BALLOON_STAT_NUM (VMW_BALLOON_STAT_LAST + 1)
235
236static DEFINE_STATIC_KEY_TRUE(vmw_balloon_batching);
237static DEFINE_STATIC_KEY_FALSE(balloon_stat_enabled);
238
239struct vmballoon_ctl {
240 struct list_head pages;
241 struct list_head refused_pages;
242 struct list_head prealloc_pages;
243 unsigned int n_refused_pages;
244 unsigned int n_pages;
245 enum vmballoon_page_size_type page_size;
246 enum vmballoon_op op;
247};
248
249/**
250 * struct vmballoon_batch_entry - a batch entry for lock or unlock.
251 *
252 * @status: the status of the operation, which is written by the hypervisor.
253 * @reserved: reserved for future use. Must be set to zero.
254 * @pfn: the physical frame number of the page to be locked or unlocked.
255 */
256struct vmballoon_batch_entry {
257 u64 status : 5;
258 u64 reserved : PAGE_SHIFT - 5;
259 u64 pfn : 52;
260} __packed;
261
262struct vmballoon {
263 /**
264 * @max_page_size: maximum supported page size for ballooning.
265 *
266 * Protected by @conf_sem
267 */
268 enum vmballoon_page_size_type max_page_size;
269
270 /**
271 * @size: balloon actual size in basic page size (frames).
272 *
273 * While we currently do not support size which is bigger than 32-bit,
274 * in preparation for future support, use 64-bits.
275 */
276 atomic64_t size;
277
278 /**
279 * @target: balloon target size in basic page size (frames).
280 *
281 * We do not protect the target under the assumption that setting the
282 * value is always done through a single write. If this assumption ever
283 * breaks, we would have to use X_ONCE for accesses, and suffer the less
284 * optimized code. Although we may read stale target value if multiple
285 * accesses happen at once, the performance impact should be minor.
286 */
287 unsigned long target;
288
289 /**
290 * @reset_required: reset flag
291 *
292 * Setting this flag may introduce races, but the code is expected to
293 * handle them gracefully. In the worst case, another operation will
294 * fail as reset did not take place. Clearing the flag is done while
295 * holding @conf_sem for write.
296 */
297 bool reset_required;
298
299 /**
300 * @capabilities: hypervisor balloon capabilities.
301 *
302 * Protected by @conf_sem.
303 */
304 unsigned long capabilities;
305
306 /**
307 * @batch_page: pointer to communication batch page.
308 *
309 * When batching is used, batch_page points to a page, which holds up to
310 * %VMW_BALLOON_BATCH_MAX_PAGES entries for locking or unlocking.
311 */
312 struct vmballoon_batch_entry *batch_page;
313
314 /**
315 * @batch_max_pages: maximum pages that can be locked/unlocked.
316 *
317 * Indicates the number of pages that the hypervisor can lock or unlock
318 * at once, according to whether batching is enabled. If batching is
319 * disabled, only a single page can be locked/unlock on each operation.
320 *
321 * Protected by @conf_sem.
322 */
323 unsigned int batch_max_pages;
324
325 /**
326 * @page: page to be locked/unlocked by the hypervisor
327 *
328 * @page is only used when batching is disabled and a single page is
329 * reclaimed on each iteration.
330 *
331 * Protected by @comm_lock.
332 */
333 struct page *page;
334
335 /**
336 * @shrink_timeout: timeout until the next inflation.
337 *
338 * After an shrink event, indicates the time in jiffies after which
339 * inflation is allowed again. Can be written concurrently with reads,
340 * so must use READ_ONCE/WRITE_ONCE when accessing.
341 */
342 unsigned long shrink_timeout;
343
344 /* statistics */
345 struct vmballoon_stats *stats;
346
347 /**
348 * @b_dev_info: balloon device information descriptor.
349 */
350 struct balloon_dev_info b_dev_info;
351
352 struct delayed_work dwork;
353
354 /**
355 * @huge_pages - list of the inflated 2MB pages.
356 *
357 * Protected by @b_dev_info.pages_lock .
358 */
359 struct list_head huge_pages;
360
361 /**
362 * @vmci_doorbell.
363 *
364 * Protected by @conf_sem.
365 */
366 struct vmci_handle vmci_doorbell;
367
368 /**
369 * @conf_sem: semaphore to protect the configuration and the statistics.
370 */
371 struct rw_semaphore conf_sem;
372
373 /**
374 * @comm_lock: lock to protect the communication with the host.
375 *
376 * Lock ordering: @conf_sem -> @comm_lock .
377 */
378 spinlock_t comm_lock;
379
380 /**
381 * @shrinker: shrinker interface that is used to avoid over-inflation.
382 */
383 struct shrinker shrinker;
384
385 /**
386 * @shrinker_registered: whether the shrinker was registered.
387 *
388 * The shrinker interface does not handle gracefully the removal of
389 * shrinker that was not registered before. This indication allows to
390 * simplify the unregistration process.
391 */
392 bool shrinker_registered;
393};
394
395static struct vmballoon balloon;
396
397struct vmballoon_stats {
398 /* timer / doorbell operations */
399 atomic64_t general_stat[VMW_BALLOON_STAT_NUM];
400
401 /* allocation statistics for huge and small pages */
402 atomic64_t
403 page_stat[VMW_BALLOON_PAGE_STAT_NUM][VMW_BALLOON_NUM_PAGE_SIZES];
404
405 /* Monitor operations: total operations, and failures */
406 atomic64_t ops[VMW_BALLOON_CMD_NUM][VMW_BALLOON_OP_STAT_TYPES];
407};
408
409static inline bool is_vmballoon_stats_on(void)
410{
411 return IS_ENABLED(CONFIG_DEBUG_FS) &&
412 static_branch_unlikely(&balloon_stat_enabled);
413}
414
415static inline void vmballoon_stats_op_inc(struct vmballoon *b, unsigned int op,
416 enum vmballoon_op_stat_type type)
417{
418 if (is_vmballoon_stats_on())
419 atomic64_inc(&b->stats->ops[op][type]);
420}
421
422static inline void vmballoon_stats_gen_inc(struct vmballoon *b,
423 enum vmballoon_stat_general stat)
424{
425 if (is_vmballoon_stats_on())
426 atomic64_inc(&b->stats->general_stat[stat]);
427}
428
429static inline void vmballoon_stats_gen_add(struct vmballoon *b,
430 enum vmballoon_stat_general stat,
431 unsigned int val)
432{
433 if (is_vmballoon_stats_on())
434 atomic64_add(val, &b->stats->general_stat[stat]);
435}
436
437static inline void vmballoon_stats_page_inc(struct vmballoon *b,
438 enum vmballoon_stat_page stat,
439 enum vmballoon_page_size_type size)
440{
441 if (is_vmballoon_stats_on())
442 atomic64_inc(&b->stats->page_stat[stat][size]);
443}
444
445static inline void vmballoon_stats_page_add(struct vmballoon *b,
446 enum vmballoon_stat_page stat,
447 enum vmballoon_page_size_type size,
448 unsigned int val)
449{
450 if (is_vmballoon_stats_on())
451 atomic64_add(val, &b->stats->page_stat[stat][size]);
452}
453
454static inline unsigned long
455__vmballoon_cmd(struct vmballoon *b, unsigned long cmd, unsigned long arg1,
456 unsigned long arg2, unsigned long *result)
457{
458 unsigned long status, dummy1, dummy2, dummy3, local_result;
459
460 vmballoon_stats_op_inc(b, cmd, VMW_BALLOON_OP_STAT);
461
462 asm volatile ("inl %%dx" :
463 "=a"(status),
464 "=c"(dummy1),
465 "=d"(dummy2),
466 "=b"(local_result),
467 "=S"(dummy3) :
468 "0"(VMW_BALLOON_HV_MAGIC),
469 "1"(cmd),
470 "2"(VMW_BALLOON_HV_PORT),
471 "3"(arg1),
472 "4"(arg2) :
473 "memory");
474
475 /* update the result if needed */
476 if (result)
477 *result = (cmd == VMW_BALLOON_CMD_START) ? dummy1 :
478 local_result;
479
480 /* update target when applicable */
481 if (status == VMW_BALLOON_SUCCESS &&
482 ((1ul << cmd) & VMW_BALLOON_CMD_WITH_TARGET_MASK))
483 WRITE_ONCE(b->target, local_result);
484
485 if (status != VMW_BALLOON_SUCCESS &&
486 status != VMW_BALLOON_SUCCESS_WITH_CAPABILITIES) {
487 vmballoon_stats_op_inc(b, cmd, VMW_BALLOON_OP_FAIL_STAT);
488 pr_debug("%s: %s [0x%lx,0x%lx) failed, returned %ld\n",
489 __func__, vmballoon_cmd_names[cmd], arg1, arg2,
490 status);
491 }
492
493 /* mark reset required accordingly */
494 if (status == VMW_BALLOON_ERROR_RESET)
495 b->reset_required = true;
496
497 return status;
498}
499
500static __always_inline unsigned long
501vmballoon_cmd(struct vmballoon *b, unsigned long cmd, unsigned long arg1,
502 unsigned long arg2)
503{
504 unsigned long dummy;
505
506 return __vmballoon_cmd(b, cmd, arg1, arg2, &dummy);
507}
508
509/*
510 * Send "start" command to the host, communicating supported version
511 * of the protocol.
512 */
513static int vmballoon_send_start(struct vmballoon *b, unsigned long req_caps)
514{
515 unsigned long status, capabilities;
516
517 status = __vmballoon_cmd(b, VMW_BALLOON_CMD_START, req_caps, 0,
518 &capabilities);
519
520 switch (status) {
521 case VMW_BALLOON_SUCCESS_WITH_CAPABILITIES:
522 b->capabilities = capabilities;
523 break;
524 case VMW_BALLOON_SUCCESS:
525 b->capabilities = VMW_BALLOON_BASIC_CMDS;
526 break;
527 default:
528 return -EIO;
529 }
530
531 /*
532 * 2MB pages are only supported with batching. If batching is for some
533 * reason disabled, do not use 2MB pages, since otherwise the legacy
534 * mechanism is used with 2MB pages, causing a failure.
535 */
536 b->max_page_size = VMW_BALLOON_4K_PAGE;
537 if ((b->capabilities & VMW_BALLOON_BATCHED_2M_CMDS) &&
538 (b->capabilities & VMW_BALLOON_BATCHED_CMDS))
539 b->max_page_size = VMW_BALLOON_2M_PAGE;
540
541
542 return 0;
543}
544
545/**
546 * vmballoon_send_guest_id - communicate guest type to the host.
547 *
548 * @b: pointer to the balloon.
549 *
550 * Communicate guest type to the host so that it can adjust ballooning
551 * algorithm to the one most appropriate for the guest. This command
552 * is normally issued after sending "start" command and is part of
553 * standard reset sequence.
554 *
555 * Return: zero on success or appropriate error code.
556 */
557static int vmballoon_send_guest_id(struct vmballoon *b)
558{
559 unsigned long status;
560
561 status = vmballoon_cmd(b, VMW_BALLOON_CMD_GUEST_ID,
562 VMW_BALLOON_GUEST_ID, 0);
563
564 return status == VMW_BALLOON_SUCCESS ? 0 : -EIO;
565}
566
567/**
568 * vmballoon_page_order() - return the order of the page
569 * @page_size: the size of the page.
570 *
571 * Return: the allocation order.
572 */
573static inline
574unsigned int vmballoon_page_order(enum vmballoon_page_size_type page_size)
575{
576 return page_size == VMW_BALLOON_2M_PAGE ? VMW_BALLOON_2M_ORDER : 0;
577}
578
579/**
580 * vmballoon_page_in_frames() - returns the number of frames in a page.
581 * @page_size: the size of the page.
582 *
583 * Return: the number of 4k frames.
584 */
585static inline unsigned int
586vmballoon_page_in_frames(enum vmballoon_page_size_type page_size)
587{
588 return 1 << vmballoon_page_order(page_size);
589}
590
591/**
592 * vmballoon_mark_page_offline() - mark a page as offline
593 * @page: pointer for the page.
594 * @page_size: the size of the page.
595 */
596static void
597vmballoon_mark_page_offline(struct page *page,
598 enum vmballoon_page_size_type page_size)
599{
600 int i;
601
602 for (i = 0; i < vmballoon_page_in_frames(page_size); i++)
603 __SetPageOffline(page + i);
604}
605
606/**
607 * vmballoon_mark_page_online() - mark a page as online
608 * @page: pointer for the page.
609 * @page_size: the size of the page.
610 */
611static void
612vmballoon_mark_page_online(struct page *page,
613 enum vmballoon_page_size_type page_size)
614{
615 int i;
616
617 for (i = 0; i < vmballoon_page_in_frames(page_size); i++)
618 __ClearPageOffline(page + i);
619}
620
621/**
622 * vmballoon_send_get_target() - Retrieve desired balloon size from the host.
623 *
624 * @b: pointer to the balloon.
625 *
626 * Return: zero on success, EINVAL if limit does not fit in 32-bit, as required
627 * by the host-guest protocol and EIO if an error occurred in communicating with
628 * the host.
629 */
630static int vmballoon_send_get_target(struct vmballoon *b)
631{
632 unsigned long status;
633 unsigned long limit;
634
635 limit = totalram_pages();
636
637 /* Ensure limit fits in 32-bits if 64-bit targets are not supported */
638 if (!(b->capabilities & VMW_BALLOON_64_BIT_TARGET) &&
639 limit != (u32)limit)
640 return -EINVAL;
641
642 status = vmballoon_cmd(b, VMW_BALLOON_CMD_GET_TARGET, limit, 0);
643
644 return status == VMW_BALLOON_SUCCESS ? 0 : -EIO;
645}
646
647/**
648 * vmballoon_alloc_page_list - allocates a list of pages.
649 *
650 * @b: pointer to the balloon.
651 * @ctl: pointer for the %struct vmballoon_ctl, which defines the operation.
652 * @req_n_pages: the number of requested pages.
653 *
654 * Tries to allocate @req_n_pages. Add them to the list of balloon pages in
655 * @ctl.pages and updates @ctl.n_pages to reflect the number of pages.
656 *
657 * Return: zero on success or error code otherwise.
658 */
659static int vmballoon_alloc_page_list(struct vmballoon *b,
660 struct vmballoon_ctl *ctl,
661 unsigned int req_n_pages)
662{
663 struct page *page;
664 unsigned int i;
665
666 for (i = 0; i < req_n_pages; i++) {
667 /*
668 * First check if we happen to have pages that were allocated
669 * before. This happens when 2MB page rejected during inflation
670 * by the hypervisor, and then split into 4KB pages.
671 */
672 if (!list_empty(&ctl->prealloc_pages)) {
673 page = list_first_entry(&ctl->prealloc_pages,
674 struct page, lru);
675 list_del(&page->lru);
676 } else {
677 if (ctl->page_size == VMW_BALLOON_2M_PAGE)
678 page = alloc_pages(__GFP_HIGHMEM|__GFP_NOWARN|
679 __GFP_NOMEMALLOC, VMW_BALLOON_2M_ORDER);
680 else
681 page = balloon_page_alloc();
682
683 vmballoon_stats_page_inc(b, VMW_BALLOON_PAGE_STAT_ALLOC,
684 ctl->page_size);
685 }
686
687 if (page) {
688 /* Success. Add the page to the list and continue. */
689 list_add(&page->lru, &ctl->pages);
690 continue;
691 }
692
693 /* Allocation failed. Update statistics and stop. */
694 vmballoon_stats_page_inc(b, VMW_BALLOON_PAGE_STAT_ALLOC_FAIL,
695 ctl->page_size);
696 break;
697 }
698
699 ctl->n_pages = i;
700
701 return req_n_pages == ctl->n_pages ? 0 : -ENOMEM;
702}
703
704/**
705 * vmballoon_handle_one_result - Handle lock/unlock result for a single page.
706 *
707 * @b: pointer for %struct vmballoon.
708 * @page: pointer for the page whose result should be handled.
709 * @page_size: size of the page.
710 * @status: status of the operation as provided by the hypervisor.
711 */
712static int vmballoon_handle_one_result(struct vmballoon *b, struct page *page,
713 enum vmballoon_page_size_type page_size,
714 unsigned long status)
715{
716 /* On success do nothing. The page is already on the balloon list. */
717 if (likely(status == VMW_BALLOON_SUCCESS))
718 return 0;
719
720 pr_debug("%s: failed comm pfn %lx status %lu page_size %s\n", __func__,
721 page_to_pfn(page), status,
722 vmballoon_page_size_names[page_size]);
723
724 /* Error occurred */
725 vmballoon_stats_page_inc(b, VMW_BALLOON_PAGE_STAT_REFUSED_ALLOC,
726 page_size);
727
728 return -EIO;
729}
730
731/**
732 * vmballoon_status_page - returns the status of (un)lock operation
733 *
734 * @b: pointer to the balloon.
735 * @idx: index for the page for which the operation is performed.
736 * @p: pointer to where the page struct is returned.
737 *
738 * Following a lock or unlock operation, returns the status of the operation for
739 * an individual page. Provides the page that the operation was performed on on
740 * the @page argument.
741 *
742 * Returns: The status of a lock or unlock operation for an individual page.
743 */
744static unsigned long vmballoon_status_page(struct vmballoon *b, int idx,
745 struct page **p)
746{
747 if (static_branch_likely(&vmw_balloon_batching)) {
748 /* batching mode */
749 *p = pfn_to_page(b->batch_page[idx].pfn);
750 return b->batch_page[idx].status;
751 }
752
753 /* non-batching mode */
754 *p = b->page;
755
756 /*
757 * If a failure occurs, the indication will be provided in the status
758 * of the entire operation, which is considered before the individual
759 * page status. So for non-batching mode, the indication is always of
760 * success.
761 */
762 return VMW_BALLOON_SUCCESS;
763}
764
765/**
766 * vmballoon_lock_op - notifies the host about inflated/deflated pages.
767 * @b: pointer to the balloon.
768 * @num_pages: number of inflated/deflated pages.
769 * @page_size: size of the page.
770 * @op: the type of operation (lock or unlock).
771 *
772 * Notify the host about page(s) that were ballooned (or removed from the
773 * balloon) so that host can use it without fear that guest will need it (or
774 * stop using them since the VM does). Host may reject some pages, we need to
775 * check the return value and maybe submit a different page. The pages that are
776 * inflated/deflated are pointed by @b->page.
777 *
778 * Return: result as provided by the hypervisor.
779 */
780static unsigned long vmballoon_lock_op(struct vmballoon *b,
781 unsigned int num_pages,
782 enum vmballoon_page_size_type page_size,
783 enum vmballoon_op op)
784{
785 unsigned long cmd, pfn;
786
787 lockdep_assert_held(&b->comm_lock);
788
789 if (static_branch_likely(&vmw_balloon_batching)) {
790 if (op == VMW_BALLOON_INFLATE)
791 cmd = page_size == VMW_BALLOON_2M_PAGE ?
792 VMW_BALLOON_CMD_BATCHED_2M_LOCK :
793 VMW_BALLOON_CMD_BATCHED_LOCK;
794 else
795 cmd = page_size == VMW_BALLOON_2M_PAGE ?
796 VMW_BALLOON_CMD_BATCHED_2M_UNLOCK :
797 VMW_BALLOON_CMD_BATCHED_UNLOCK;
798
799 pfn = PHYS_PFN(virt_to_phys(b->batch_page));
800 } else {
801 cmd = op == VMW_BALLOON_INFLATE ? VMW_BALLOON_CMD_LOCK :
802 VMW_BALLOON_CMD_UNLOCK;
803 pfn = page_to_pfn(b->page);
804
805 /* In non-batching mode, PFNs must fit in 32-bit */
806 if (unlikely(pfn != (u32)pfn))
807 return VMW_BALLOON_ERROR_PPN_INVALID;
808 }
809
810 return vmballoon_cmd(b, cmd, pfn, num_pages);
811}
812
813/**
814 * vmballoon_add_page - adds a page towards lock/unlock operation.
815 *
816 * @b: pointer to the balloon.
817 * @idx: index of the page to be ballooned in this batch.
818 * @p: pointer to the page that is about to be ballooned.
819 *
820 * Adds the page to be ballooned. Must be called while holding @comm_lock.
821 */
822static void vmballoon_add_page(struct vmballoon *b, unsigned int idx,
823 struct page *p)
824{
825 lockdep_assert_held(&b->comm_lock);
826
827 if (static_branch_likely(&vmw_balloon_batching))
828 b->batch_page[idx] = (struct vmballoon_batch_entry)
829 { .pfn = page_to_pfn(p) };
830 else
831 b->page = p;
832}
833
834/**
835 * vmballoon_lock - lock or unlock a batch of pages.
836 *
837 * @b: pointer to the balloon.
838 * @ctl: pointer for the %struct vmballoon_ctl, which defines the operation.
839 *
840 * Notifies the host of about ballooned pages (after inflation or deflation,
841 * according to @ctl). If the host rejects the page put it on the
842 * @ctl refuse list. These refused page are then released when moving to the
843 * next size of pages.
844 *
845 * Note that we neither free any @page here nor put them back on the ballooned
846 * pages list. Instead we queue it for later processing. We do that for several
847 * reasons. First, we do not want to free the page under the lock. Second, it
848 * allows us to unify the handling of lock and unlock. In the inflate case, the
849 * caller will check if there are too many refused pages and release them.
850 * Although it is not identical to the past behavior, it should not affect
851 * performance.
852 */
853static int vmballoon_lock(struct vmballoon *b, struct vmballoon_ctl *ctl)
854{
855 unsigned long batch_status;
856 struct page *page;
857 unsigned int i, num_pages;
858
859 num_pages = ctl->n_pages;
860 if (num_pages == 0)
861 return 0;
862
863 /* communication with the host is done under the communication lock */
864 spin_lock(&b->comm_lock);
865
866 i = 0;
867 list_for_each_entry(page, &ctl->pages, lru)
868 vmballoon_add_page(b, i++, page);
869
870 batch_status = vmballoon_lock_op(b, ctl->n_pages, ctl->page_size,
871 ctl->op);
872
873 /*
874 * Iterate over the pages in the provided list. Since we are changing
875 * @ctl->n_pages we are saving the original value in @num_pages and
876 * use this value to bound the loop.
877 */
878 for (i = 0; i < num_pages; i++) {
879 unsigned long status;
880
881 status = vmballoon_status_page(b, i, &page);
882
883 /*
884 * Failure of the whole batch overrides a single operation
885 * results.
886 */
887 if (batch_status != VMW_BALLOON_SUCCESS)
888 status = batch_status;
889
890 /* Continue if no error happened */
891 if (!vmballoon_handle_one_result(b, page, ctl->page_size,
892 status))
893 continue;
894
895 /*
896 * Error happened. Move the pages to the refused list and update
897 * the pages number.
898 */
899 list_move(&page->lru, &ctl->refused_pages);
900 ctl->n_pages--;
901 ctl->n_refused_pages++;
902 }
903
904 spin_unlock(&b->comm_lock);
905
906 return batch_status == VMW_BALLOON_SUCCESS ? 0 : -EIO;
907}
908
909/**
910 * vmballoon_release_page_list() - Releases a page list
911 *
912 * @page_list: list of pages to release.
913 * @n_pages: pointer to the number of pages.
914 * @page_size: whether the pages in the list are 2MB (or else 4KB).
915 *
916 * Releases the list of pages and zeros the number of pages.
917 */
918static void vmballoon_release_page_list(struct list_head *page_list,
919 int *n_pages,
920 enum vmballoon_page_size_type page_size)
921{
922 struct page *page, *tmp;
923
924 list_for_each_entry_safe(page, tmp, page_list, lru) {
925 list_del(&page->lru);
926 __free_pages(page, vmballoon_page_order(page_size));
927 }
928
929 if (n_pages)
930 *n_pages = 0;
931}
932
933
934/*
935 * Release pages that were allocated while attempting to inflate the
936 * balloon but were refused by the host for one reason or another.
937 */
938static void vmballoon_release_refused_pages(struct vmballoon *b,
939 struct vmballoon_ctl *ctl)
940{
941 vmballoon_stats_page_inc(b, VMW_BALLOON_PAGE_STAT_REFUSED_FREE,
942 ctl->page_size);
943
944 vmballoon_release_page_list(&ctl->refused_pages, &ctl->n_refused_pages,
945 ctl->page_size);
946}
947
948/**
949 * vmballoon_change - retrieve the required balloon change
950 *
951 * @b: pointer for the balloon.
952 *
953 * Return: the required change for the balloon size. A positive number
954 * indicates inflation, a negative number indicates a deflation.
955 */
956static int64_t vmballoon_change(struct vmballoon *b)
957{
958 int64_t size, target;
959
960 size = atomic64_read(&b->size);
961 target = READ_ONCE(b->target);
962
963 /*
964 * We must cast first because of int sizes
965 * Otherwise we might get huge positives instead of negatives
966 */
967
968 if (b->reset_required)
969 return 0;
970
971 /* consider a 2MB slack on deflate, unless the balloon is emptied */
972 if (target < size && target != 0 &&
973 size - target < vmballoon_page_in_frames(VMW_BALLOON_2M_PAGE))
974 return 0;
975
976 /* If an out-of-memory recently occurred, inflation is disallowed. */
977 if (target > size && time_before(jiffies, READ_ONCE(b->shrink_timeout)))
978 return 0;
979
980 return target - size;
981}
982
983/**
984 * vmballoon_enqueue_page_list() - Enqueues list of pages after inflation.
985 *
986 * @b: pointer to balloon.
987 * @pages: list of pages to enqueue.
988 * @n_pages: pointer to number of pages in list. The value is zeroed.
989 * @page_size: whether the pages are 2MB or 4KB pages.
990 *
991 * Enqueues the provides list of pages in the ballooned page list, clears the
992 * list and zeroes the number of pages that was provided.
993 */
994static void vmballoon_enqueue_page_list(struct vmballoon *b,
995 struct list_head *pages,
996 unsigned int *n_pages,
997 enum vmballoon_page_size_type page_size)
998{
999 unsigned long flags;
1000 struct page *page;
1001
1002 if (page_size == VMW_BALLOON_4K_PAGE) {
1003 balloon_page_list_enqueue(&b->b_dev_info, pages);
1004 } else {
1005 /*
1006 * Keep the huge pages in a local list which is not available
1007 * for the balloon compaction mechanism.
1008 */
1009 spin_lock_irqsave(&b->b_dev_info.pages_lock, flags);
1010
1011 list_for_each_entry(page, pages, lru) {
1012 vmballoon_mark_page_offline(page, VMW_BALLOON_2M_PAGE);
1013 }
1014
1015 list_splice_init(pages, &b->huge_pages);
1016 __count_vm_events(BALLOON_INFLATE, *n_pages *
1017 vmballoon_page_in_frames(VMW_BALLOON_2M_PAGE));
1018 spin_unlock_irqrestore(&b->b_dev_info.pages_lock, flags);
1019 }
1020
1021 *n_pages = 0;
1022}
1023
1024/**
1025 * vmballoon_dequeue_page_list() - Dequeues page lists for deflation.
1026 *
1027 * @b: pointer to balloon.
1028 * @pages: list of pages to enqueue.
1029 * @n_pages: pointer to number of pages in list. The value is zeroed.
1030 * @page_size: whether the pages are 2MB or 4KB pages.
1031 * @n_req_pages: the number of requested pages.
1032 *
1033 * Dequeues the number of requested pages from the balloon for deflation. The
1034 * number of dequeued pages may be lower, if not enough pages in the requested
1035 * size are available.
1036 */
1037static void vmballoon_dequeue_page_list(struct vmballoon *b,
1038 struct list_head *pages,
1039 unsigned int *n_pages,
1040 enum vmballoon_page_size_type page_size,
1041 unsigned int n_req_pages)
1042{
1043 struct page *page, *tmp;
1044 unsigned int i = 0;
1045 unsigned long flags;
1046
1047 /* In the case of 4k pages, use the compaction infrastructure */
1048 if (page_size == VMW_BALLOON_4K_PAGE) {
1049 *n_pages = balloon_page_list_dequeue(&b->b_dev_info, pages,
1050 n_req_pages);
1051 return;
1052 }
1053
1054 /* 2MB pages */
1055 spin_lock_irqsave(&b->b_dev_info.pages_lock, flags);
1056 list_for_each_entry_safe(page, tmp, &b->huge_pages, lru) {
1057 vmballoon_mark_page_online(page, VMW_BALLOON_2M_PAGE);
1058
1059 list_move(&page->lru, pages);
1060 if (++i == n_req_pages)
1061 break;
1062 }
1063
1064 __count_vm_events(BALLOON_DEFLATE,
1065 i * vmballoon_page_in_frames(VMW_BALLOON_2M_PAGE));
1066 spin_unlock_irqrestore(&b->b_dev_info.pages_lock, flags);
1067 *n_pages = i;
1068}
1069
1070/**
1071 * vmballoon_split_refused_pages() - Split the 2MB refused pages to 4k.
1072 *
1073 * If inflation of 2MB pages was denied by the hypervisor, it is likely to be
1074 * due to one or few 4KB pages. These 2MB pages may keep being allocated and
1075 * then being refused. To prevent this case, this function splits the refused
1076 * pages into 4KB pages and adds them into @prealloc_pages list.
1077 *
1078 * @ctl: pointer for the %struct vmballoon_ctl, which defines the operation.
1079 */
1080static void vmballoon_split_refused_pages(struct vmballoon_ctl *ctl)
1081{
1082 struct page *page, *tmp;
1083 unsigned int i, order;
1084
1085 order = vmballoon_page_order(ctl->page_size);
1086
1087 list_for_each_entry_safe(page, tmp, &ctl->refused_pages, lru) {
1088 list_del(&page->lru);
1089 split_page(page, order);
1090 for (i = 0; i < (1 << order); i++)
1091 list_add(&page[i].lru, &ctl->prealloc_pages);
1092 }
1093 ctl->n_refused_pages = 0;
1094}
1095
1096/**
1097 * vmballoon_inflate() - Inflate the balloon towards its target size.
1098 *
1099 * @b: pointer to the balloon.
1100 */
1101static void vmballoon_inflate(struct vmballoon *b)
1102{
1103 int64_t to_inflate_frames;
1104 struct vmballoon_ctl ctl = {
1105 .pages = LIST_HEAD_INIT(ctl.pages),
1106 .refused_pages = LIST_HEAD_INIT(ctl.refused_pages),
1107 .prealloc_pages = LIST_HEAD_INIT(ctl.prealloc_pages),
1108 .page_size = b->max_page_size,
1109 .op = VMW_BALLOON_INFLATE
1110 };
1111
1112 while ((to_inflate_frames = vmballoon_change(b)) > 0) {
1113 unsigned int to_inflate_pages, page_in_frames;
1114 int alloc_error, lock_error = 0;
1115
1116 VM_BUG_ON(!list_empty(&ctl.pages));
1117 VM_BUG_ON(ctl.n_pages != 0);
1118
1119 page_in_frames = vmballoon_page_in_frames(ctl.page_size);
1120
1121 to_inflate_pages = min_t(unsigned long, b->batch_max_pages,
1122 DIV_ROUND_UP_ULL(to_inflate_frames,
1123 page_in_frames));
1124
1125 /* Start by allocating */
1126 alloc_error = vmballoon_alloc_page_list(b, &ctl,
1127 to_inflate_pages);
1128
1129 /* Actually lock the pages by telling the hypervisor */
1130 lock_error = vmballoon_lock(b, &ctl);
1131
1132 /*
1133 * If an error indicates that something serious went wrong,
1134 * stop the inflation.
1135 */
1136 if (lock_error)
1137 break;
1138
1139 /* Update the balloon size */
1140 atomic64_add(ctl.n_pages * page_in_frames, &b->size);
1141
1142 vmballoon_enqueue_page_list(b, &ctl.pages, &ctl.n_pages,
1143 ctl.page_size);
1144
1145 /*
1146 * If allocation failed or the number of refused pages exceeds
1147 * the maximum allowed, move to the next page size.
1148 */
1149 if (alloc_error ||
1150 ctl.n_refused_pages >= VMW_BALLOON_MAX_REFUSED) {
1151 if (ctl.page_size == VMW_BALLOON_4K_PAGE)
1152 break;
1153
1154 /*
1155 * Split the refused pages to 4k. This will also empty
1156 * the refused pages list.
1157 */
1158 vmballoon_split_refused_pages(&ctl);
1159 ctl.page_size--;
1160 }
1161
1162 cond_resched();
1163 }
1164
1165 /*
1166 * Release pages that were allocated while attempting to inflate the
1167 * balloon but were refused by the host for one reason or another,
1168 * and update the statistics.
1169 */
1170 if (ctl.n_refused_pages != 0)
1171 vmballoon_release_refused_pages(b, &ctl);
1172
1173 vmballoon_release_page_list(&ctl.prealloc_pages, NULL, ctl.page_size);
1174}
1175
1176/**
1177 * vmballoon_deflate() - Decrease the size of the balloon.
1178 *
1179 * @b: pointer to the balloon
1180 * @n_frames: the number of frames to deflate. If zero, automatically
1181 * calculated according to the target size.
1182 * @coordinated: whether to coordinate with the host
1183 *
1184 * Decrease the size of the balloon allowing guest to use more memory.
1185 *
1186 * Return: The number of deflated frames (i.e., basic page size units)
1187 */
1188static unsigned long vmballoon_deflate(struct vmballoon *b, uint64_t n_frames,
1189 bool coordinated)
1190{
1191 unsigned long deflated_frames = 0;
1192 unsigned long tried_frames = 0;
1193 struct vmballoon_ctl ctl = {
1194 .pages = LIST_HEAD_INIT(ctl.pages),
1195 .refused_pages = LIST_HEAD_INIT(ctl.refused_pages),
1196 .page_size = VMW_BALLOON_4K_PAGE,
1197 .op = VMW_BALLOON_DEFLATE
1198 };
1199
1200 /* free pages to reach target */
1201 while (true) {
1202 unsigned int to_deflate_pages, n_unlocked_frames;
1203 unsigned int page_in_frames;
1204 int64_t to_deflate_frames;
1205 bool deflated_all;
1206
1207 page_in_frames = vmballoon_page_in_frames(ctl.page_size);
1208
1209 VM_BUG_ON(!list_empty(&ctl.pages));
1210 VM_BUG_ON(ctl.n_pages);
1211 VM_BUG_ON(!list_empty(&ctl.refused_pages));
1212 VM_BUG_ON(ctl.n_refused_pages);
1213
1214 /*
1215 * If we were requested a specific number of frames, we try to
1216 * deflate this number of frames. Otherwise, deflation is
1217 * performed according to the target and balloon size.
1218 */
1219 to_deflate_frames = n_frames ? n_frames - tried_frames :
1220 -vmballoon_change(b);
1221
1222 /* break if no work to do */
1223 if (to_deflate_frames <= 0)
1224 break;
1225
1226 /*
1227 * Calculate the number of frames based on current page size,
1228 * but limit the deflated frames to a single chunk
1229 */
1230 to_deflate_pages = min_t(unsigned long, b->batch_max_pages,
1231 DIV_ROUND_UP_ULL(to_deflate_frames,
1232 page_in_frames));
1233
1234 /* First take the pages from the balloon pages. */
1235 vmballoon_dequeue_page_list(b, &ctl.pages, &ctl.n_pages,
1236 ctl.page_size, to_deflate_pages);
1237
1238 /*
1239 * Before pages are moving to the refused list, count their
1240 * frames as frames that we tried to deflate.
1241 */
1242 tried_frames += ctl.n_pages * page_in_frames;
1243
1244 /*
1245 * Unlock the pages by communicating with the hypervisor if the
1246 * communication is coordinated (i.e., not pop). We ignore the
1247 * return code. Instead we check if all the pages we manage to
1248 * unlock all the pages. If we failed, we will move to the next
1249 * page size, and would eventually try again later.
1250 */
1251 if (coordinated)
1252 vmballoon_lock(b, &ctl);
1253
1254 /*
1255 * Check if we deflated enough. We will move to the next page
1256 * size if we did not manage to do so. This calculation takes
1257 * place now, as once the pages are released, the number of
1258 * pages is zeroed.
1259 */
1260 deflated_all = (ctl.n_pages == to_deflate_pages);
1261
1262 /* Update local and global counters */
1263 n_unlocked_frames = ctl.n_pages * page_in_frames;
1264 atomic64_sub(n_unlocked_frames, &b->size);
1265 deflated_frames += n_unlocked_frames;
1266
1267 vmballoon_stats_page_add(b, VMW_BALLOON_PAGE_STAT_FREE,
1268 ctl.page_size, ctl.n_pages);
1269
1270 /* free the ballooned pages */
1271 vmballoon_release_page_list(&ctl.pages, &ctl.n_pages,
1272 ctl.page_size);
1273
1274 /* Return the refused pages to the ballooned list. */
1275 vmballoon_enqueue_page_list(b, &ctl.refused_pages,
1276 &ctl.n_refused_pages,
1277 ctl.page_size);
1278
1279 /* If we failed to unlock all the pages, move to next size. */
1280 if (!deflated_all) {
1281 if (ctl.page_size == b->max_page_size)
1282 break;
1283 ctl.page_size++;
1284 }
1285
1286 cond_resched();
1287 }
1288
1289 return deflated_frames;
1290}
1291
1292/**
1293 * vmballoon_deinit_batching - disables batching mode.
1294 *
1295 * @b: pointer to &struct vmballoon.
1296 *
1297 * Disables batching, by deallocating the page for communication with the
1298 * hypervisor and disabling the static key to indicate that batching is off.
1299 */
1300static void vmballoon_deinit_batching(struct vmballoon *b)
1301{
1302 free_page((unsigned long)b->batch_page);
1303 b->batch_page = NULL;
1304 static_branch_disable(&vmw_balloon_batching);
1305 b->batch_max_pages = 1;
1306}
1307
1308/**
1309 * vmballoon_init_batching - enable batching mode.
1310 *
1311 * @b: pointer to &struct vmballoon.
1312 *
1313 * Enables batching, by allocating a page for communication with the hypervisor
1314 * and enabling the static_key to use batching.
1315 *
1316 * Return: zero on success or an appropriate error-code.
1317 */
1318static int vmballoon_init_batching(struct vmballoon *b)
1319{
1320 struct page *page;
1321
1322 page = alloc_page(GFP_KERNEL | __GFP_ZERO);
1323 if (!page)
1324 return -ENOMEM;
1325
1326 b->batch_page = page_address(page);
1327 b->batch_max_pages = PAGE_SIZE / sizeof(struct vmballoon_batch_entry);
1328
1329 static_branch_enable(&vmw_balloon_batching);
1330
1331 return 0;
1332}
1333
1334/*
1335 * Receive notification and resize balloon
1336 */
1337static void vmballoon_doorbell(void *client_data)
1338{
1339 struct vmballoon *b = client_data;
1340
1341 vmballoon_stats_gen_inc(b, VMW_BALLOON_STAT_DOORBELL);
1342
1343 mod_delayed_work(system_freezable_wq, &b->dwork, 0);
1344}
1345
1346/*
1347 * Clean up vmci doorbell
1348 */
1349static void vmballoon_vmci_cleanup(struct vmballoon *b)
1350{
1351 vmballoon_cmd(b, VMW_BALLOON_CMD_VMCI_DOORBELL_SET,
1352 VMCI_INVALID_ID, VMCI_INVALID_ID);
1353
1354 if (!vmci_handle_is_invalid(b->vmci_doorbell)) {
1355 vmci_doorbell_destroy(b->vmci_doorbell);
1356 b->vmci_doorbell = VMCI_INVALID_HANDLE;
1357 }
1358}
1359
1360/**
1361 * vmballoon_vmci_init - Initialize vmci doorbell.
1362 *
1363 * @b: pointer to the balloon.
1364 *
1365 * Return: zero on success or when wakeup command not supported. Error-code
1366 * otherwise.
1367 *
1368 * Initialize vmci doorbell, to get notified as soon as balloon changes.
1369 */
1370static int vmballoon_vmci_init(struct vmballoon *b)
1371{
1372 unsigned long error;
1373
1374 if ((b->capabilities & VMW_BALLOON_SIGNALLED_WAKEUP_CMD) == 0)
1375 return 0;
1376
1377 error = vmci_doorbell_create(&b->vmci_doorbell, VMCI_FLAG_DELAYED_CB,
1378 VMCI_PRIVILEGE_FLAG_RESTRICTED,
1379 vmballoon_doorbell, b);
1380
1381 if (error != VMCI_SUCCESS)
1382 goto fail;
1383
1384 error = __vmballoon_cmd(b, VMW_BALLOON_CMD_VMCI_DOORBELL_SET,
1385 b->vmci_doorbell.context,
1386 b->vmci_doorbell.resource, NULL);
1387
1388 if (error != VMW_BALLOON_SUCCESS)
1389 goto fail;
1390
1391 return 0;
1392fail:
1393 vmballoon_vmci_cleanup(b);
1394 return -EIO;
1395}
1396
1397/**
1398 * vmballoon_pop - Quickly release all pages allocate for the balloon.
1399 *
1400 * @b: pointer to the balloon.
1401 *
1402 * This function is called when host decides to "reset" balloon for one reason
1403 * or another. Unlike normal "deflate" we do not (shall not) notify host of the
1404 * pages being released.
1405 */
1406static void vmballoon_pop(struct vmballoon *b)
1407{
1408 unsigned long size;
1409
1410 while ((size = atomic64_read(&b->size)))
1411 vmballoon_deflate(b, size, false);
1412}
1413
1414/*
1415 * Perform standard reset sequence by popping the balloon (in case it
1416 * is not empty) and then restarting protocol. This operation normally
1417 * happens when host responds with VMW_BALLOON_ERROR_RESET to a command.
1418 */
1419static void vmballoon_reset(struct vmballoon *b)
1420{
1421 int error;
1422
1423 down_write(&b->conf_sem);
1424
1425 vmballoon_vmci_cleanup(b);
1426
1427 /* free all pages, skipping monitor unlock */
1428 vmballoon_pop(b);
1429
1430 if (vmballoon_send_start(b, VMW_BALLOON_CAPABILITIES))
1431 goto unlock;
1432
1433 if ((b->capabilities & VMW_BALLOON_BATCHED_CMDS) != 0) {
1434 if (vmballoon_init_batching(b)) {
1435 /*
1436 * We failed to initialize batching, inform the monitor
1437 * about it by sending a null capability.
1438 *
1439 * The guest will retry in one second.
1440 */
1441 vmballoon_send_start(b, 0);
1442 goto unlock;
1443 }
1444 } else if ((b->capabilities & VMW_BALLOON_BASIC_CMDS) != 0) {
1445 vmballoon_deinit_batching(b);
1446 }
1447
1448 vmballoon_stats_gen_inc(b, VMW_BALLOON_STAT_RESET);
1449 b->reset_required = false;
1450
1451 error = vmballoon_vmci_init(b);
1452 if (error)
1453 pr_err_once("failed to initialize vmci doorbell\n");
1454
1455 if (vmballoon_send_guest_id(b))
1456 pr_err_once("failed to send guest ID to the host\n");
1457
1458unlock:
1459 up_write(&b->conf_sem);
1460}
1461
1462/**
1463 * vmballoon_work - periodic balloon worker for reset, inflation and deflation.
1464 *
1465 * @work: pointer to the &work_struct which is provided by the workqueue.
1466 *
1467 * Resets the protocol if needed, gets the new size and adjusts balloon as
1468 * needed. Repeat in 1 sec.
1469 */
1470static void vmballoon_work(struct work_struct *work)
1471{
1472 struct delayed_work *dwork = to_delayed_work(work);
1473 struct vmballoon *b = container_of(dwork, struct vmballoon, dwork);
1474 int64_t change = 0;
1475
1476 if (b->reset_required)
1477 vmballoon_reset(b);
1478
1479 down_read(&b->conf_sem);
1480
1481 /*
1482 * Update the stats while holding the semaphore to ensure that
1483 * @stats_enabled is consistent with whether the stats are actually
1484 * enabled
1485 */
1486 vmballoon_stats_gen_inc(b, VMW_BALLOON_STAT_TIMER);
1487
1488 if (!vmballoon_send_get_target(b))
1489 change = vmballoon_change(b);
1490
1491 if (change != 0) {
1492 pr_debug("%s - size: %llu, target %lu\n", __func__,
1493 atomic64_read(&b->size), READ_ONCE(b->target));
1494
1495 if (change > 0)
1496 vmballoon_inflate(b);
1497 else /* (change < 0) */
1498 vmballoon_deflate(b, 0, true);
1499 }
1500
1501 up_read(&b->conf_sem);
1502
1503 /*
1504 * We are using a freezable workqueue so that balloon operations are
1505 * stopped while the system transitions to/from sleep/hibernation.
1506 */
1507 queue_delayed_work(system_freezable_wq,
1508 dwork, round_jiffies_relative(HZ));
1509
1510}
1511
1512/**
1513 * vmballoon_shrinker_scan() - deflate the balloon due to memory pressure.
1514 * @shrinker: pointer to the balloon shrinker.
1515 * @sc: page reclaim information.
1516 *
1517 * Returns: number of pages that were freed during deflation.
1518 */
1519static unsigned long vmballoon_shrinker_scan(struct shrinker *shrinker,
1520 struct shrink_control *sc)
1521{
1522 struct vmballoon *b = &balloon;
1523 unsigned long deflated_frames;
1524
1525 pr_debug("%s - size: %llu", __func__, atomic64_read(&b->size));
1526
1527 vmballoon_stats_gen_inc(b, VMW_BALLOON_STAT_SHRINK);
1528
1529 /*
1530 * If the lock is also contended for read, we cannot easily reclaim and
1531 * we bail out.
1532 */
1533 if (!down_read_trylock(&b->conf_sem))
1534 return 0;
1535
1536 deflated_frames = vmballoon_deflate(b, sc->nr_to_scan, true);
1537
1538 vmballoon_stats_gen_add(b, VMW_BALLOON_STAT_SHRINK_FREE,
1539 deflated_frames);
1540
1541 /*
1542 * Delay future inflation for some time to mitigate the situations in
1543 * which balloon continuously grows and shrinks. Use WRITE_ONCE() since
1544 * the access is asynchronous.
1545 */
1546 WRITE_ONCE(b->shrink_timeout, jiffies + HZ * VMBALLOON_SHRINK_DELAY);
1547
1548 up_read(&b->conf_sem);
1549
1550 return deflated_frames;
1551}
1552
1553/**
1554 * vmballoon_shrinker_count() - return the number of ballooned pages.
1555 * @shrinker: pointer to the balloon shrinker.
1556 * @sc: page reclaim information.
1557 *
1558 * Returns: number of 4k pages that are allocated for the balloon and can
1559 * therefore be reclaimed under pressure.
1560 */
1561static unsigned long vmballoon_shrinker_count(struct shrinker *shrinker,
1562 struct shrink_control *sc)
1563{
1564 struct vmballoon *b = &balloon;
1565
1566 return atomic64_read(&b->size);
1567}
1568
1569static void vmballoon_unregister_shrinker(struct vmballoon *b)
1570{
1571 if (b->shrinker_registered)
1572 unregister_shrinker(&b->shrinker);
1573 b->shrinker_registered = false;
1574}
1575
1576static int vmballoon_register_shrinker(struct vmballoon *b)
1577{
1578 int r;
1579
1580 /* Do nothing if the shrinker is not enabled */
1581 if (!vmwballoon_shrinker_enable)
1582 return 0;
1583
1584 b->shrinker.scan_objects = vmballoon_shrinker_scan;
1585 b->shrinker.count_objects = vmballoon_shrinker_count;
1586 b->shrinker.seeks = DEFAULT_SEEKS;
1587
1588 r = register_shrinker(&b->shrinker, "vmw-balloon");
1589
1590 if (r == 0)
1591 b->shrinker_registered = true;
1592
1593 return r;
1594}
1595
1596/*
1597 * DEBUGFS Interface
1598 */
1599#ifdef CONFIG_DEBUG_FS
1600
1601static const char * const vmballoon_stat_page_names[] = {
1602 [VMW_BALLOON_PAGE_STAT_ALLOC] = "alloc",
1603 [VMW_BALLOON_PAGE_STAT_ALLOC_FAIL] = "allocFail",
1604 [VMW_BALLOON_PAGE_STAT_REFUSED_ALLOC] = "errAlloc",
1605 [VMW_BALLOON_PAGE_STAT_REFUSED_FREE] = "errFree",
1606 [VMW_BALLOON_PAGE_STAT_FREE] = "free"
1607};
1608
1609static const char * const vmballoon_stat_names[] = {
1610 [VMW_BALLOON_STAT_TIMER] = "timer",
1611 [VMW_BALLOON_STAT_DOORBELL] = "doorbell",
1612 [VMW_BALLOON_STAT_RESET] = "reset",
1613 [VMW_BALLOON_STAT_SHRINK] = "shrink",
1614 [VMW_BALLOON_STAT_SHRINK_FREE] = "shrinkFree"
1615};
1616
1617static int vmballoon_enable_stats(struct vmballoon *b)
1618{
1619 int r = 0;
1620
1621 down_write(&b->conf_sem);
1622
1623 /* did we somehow race with another reader which enabled stats? */
1624 if (b->stats)
1625 goto out;
1626
1627 b->stats = kzalloc(sizeof(*b->stats), GFP_KERNEL);
1628
1629 if (!b->stats) {
1630 /* allocation failed */
1631 r = -ENOMEM;
1632 goto out;
1633 }
1634 static_key_enable(&balloon_stat_enabled.key);
1635out:
1636 up_write(&b->conf_sem);
1637 return r;
1638}
1639
1640/**
1641 * vmballoon_debug_show - shows statistics of balloon operations.
1642 * @f: pointer to the &struct seq_file.
1643 * @offset: ignored.
1644 *
1645 * Provides the statistics that can be accessed in vmmemctl in the debugfs.
1646 * To avoid the overhead - mainly that of memory - of collecting the statistics,
1647 * we only collect statistics after the first time the counters are read.
1648 *
1649 * Return: zero on success or an error code.
1650 */
1651static int vmballoon_debug_show(struct seq_file *f, void *offset)
1652{
1653 struct vmballoon *b = f->private;
1654 int i, j;
1655
1656 /* enables stats if they are disabled */
1657 if (!b->stats) {
1658 int r = vmballoon_enable_stats(b);
1659
1660 if (r)
1661 return r;
1662 }
1663
1664 /* format capabilities info */
1665 seq_printf(f, "%-22s: %#16x\n", "balloon capabilities",
1666 VMW_BALLOON_CAPABILITIES);
1667 seq_printf(f, "%-22s: %#16lx\n", "used capabilities", b->capabilities);
1668 seq_printf(f, "%-22s: %16s\n", "is resetting",
1669 b->reset_required ? "y" : "n");
1670
1671 /* format size info */
1672 seq_printf(f, "%-22s: %16lu\n", "target", READ_ONCE(b->target));
1673 seq_printf(f, "%-22s: %16llu\n", "current", atomic64_read(&b->size));
1674
1675 for (i = 0; i < VMW_BALLOON_CMD_NUM; i++) {
1676 if (vmballoon_cmd_names[i] == NULL)
1677 continue;
1678
1679 seq_printf(f, "%-22s: %16llu (%llu failed)\n",
1680 vmballoon_cmd_names[i],
1681 atomic64_read(&b->stats->ops[i][VMW_BALLOON_OP_STAT]),
1682 atomic64_read(&b->stats->ops[i][VMW_BALLOON_OP_FAIL_STAT]));
1683 }
1684
1685 for (i = 0; i < VMW_BALLOON_STAT_NUM; i++)
1686 seq_printf(f, "%-22s: %16llu\n",
1687 vmballoon_stat_names[i],
1688 atomic64_read(&b->stats->general_stat[i]));
1689
1690 for (i = 0; i < VMW_BALLOON_PAGE_STAT_NUM; i++) {
1691 for (j = 0; j < VMW_BALLOON_NUM_PAGE_SIZES; j++)
1692 seq_printf(f, "%-18s(%s): %16llu\n",
1693 vmballoon_stat_page_names[i],
1694 vmballoon_page_size_names[j],
1695 atomic64_read(&b->stats->page_stat[i][j]));
1696 }
1697
1698 return 0;
1699}
1700
1701DEFINE_SHOW_ATTRIBUTE(vmballoon_debug);
1702
1703static void __init vmballoon_debugfs_init(struct vmballoon *b)
1704{
1705 debugfs_create_file("vmmemctl", S_IRUGO, NULL, b,
1706 &vmballoon_debug_fops);
1707}
1708
1709static void __exit vmballoon_debugfs_exit(struct vmballoon *b)
1710{
1711 static_key_disable(&balloon_stat_enabled.key);
1712 debugfs_remove(debugfs_lookup("vmmemctl", NULL));
1713 kfree(b->stats);
1714 b->stats = NULL;
1715}
1716
1717#else
1718
1719static inline void vmballoon_debugfs_init(struct vmballoon *b)
1720{
1721}
1722
1723static inline void vmballoon_debugfs_exit(struct vmballoon *b)
1724{
1725}
1726
1727#endif /* CONFIG_DEBUG_FS */
1728
1729
1730#ifdef CONFIG_BALLOON_COMPACTION
1731/**
1732 * vmballoon_migratepage() - migrates a balloon page.
1733 * @b_dev_info: balloon device information descriptor.
1734 * @newpage: the page to which @page should be migrated.
1735 * @page: a ballooned page that should be migrated.
1736 * @mode: migration mode, ignored.
1737 *
1738 * This function is really open-coded, but that is according to the interface
1739 * that balloon_compaction provides.
1740 *
1741 * Return: zero on success, -EAGAIN when migration cannot be performed
1742 * momentarily, and -EBUSY if migration failed and should be retried
1743 * with that specific page.
1744 */
1745static int vmballoon_migratepage(struct balloon_dev_info *b_dev_info,
1746 struct page *newpage, struct page *page,
1747 enum migrate_mode mode)
1748{
1749 unsigned long status, flags;
1750 struct vmballoon *b;
1751 int ret;
1752
1753 b = container_of(b_dev_info, struct vmballoon, b_dev_info);
1754
1755 /*
1756 * If the semaphore is taken, there is ongoing configuration change
1757 * (i.e., balloon reset), so try again.
1758 */
1759 if (!down_read_trylock(&b->conf_sem))
1760 return -EAGAIN;
1761
1762 spin_lock(&b->comm_lock);
1763 /*
1764 * We must start by deflating and not inflating, as otherwise the
1765 * hypervisor may tell us that it has enough memory and the new page is
1766 * not needed. Since the old page is isolated, we cannot use the list
1767 * interface to unlock it, as the LRU field is used for isolation.
1768 * Instead, we use the native interface directly.
1769 */
1770 vmballoon_add_page(b, 0, page);
1771 status = vmballoon_lock_op(b, 1, VMW_BALLOON_4K_PAGE,
1772 VMW_BALLOON_DEFLATE);
1773
1774 if (status == VMW_BALLOON_SUCCESS)
1775 status = vmballoon_status_page(b, 0, &page);
1776
1777 /*
1778 * If a failure happened, let the migration mechanism know that it
1779 * should not retry.
1780 */
1781 if (status != VMW_BALLOON_SUCCESS) {
1782 spin_unlock(&b->comm_lock);
1783 ret = -EBUSY;
1784 goto out_unlock;
1785 }
1786
1787 /*
1788 * The page is isolated, so it is safe to delete it without holding
1789 * @pages_lock . We keep holding @comm_lock since we will need it in a
1790 * second.
1791 */
1792 balloon_page_delete(page);
1793
1794 put_page(page);
1795
1796 /* Inflate */
1797 vmballoon_add_page(b, 0, newpage);
1798 status = vmballoon_lock_op(b, 1, VMW_BALLOON_4K_PAGE,
1799 VMW_BALLOON_INFLATE);
1800
1801 if (status == VMW_BALLOON_SUCCESS)
1802 status = vmballoon_status_page(b, 0, &newpage);
1803
1804 spin_unlock(&b->comm_lock);
1805
1806 if (status != VMW_BALLOON_SUCCESS) {
1807 /*
1808 * A failure happened. While we can deflate the page we just
1809 * inflated, this deflation can also encounter an error. Instead
1810 * we will decrease the size of the balloon to reflect the
1811 * change and report failure.
1812 */
1813 atomic64_dec(&b->size);
1814 ret = -EBUSY;
1815 } else {
1816 /*
1817 * Success. Take a reference for the page, and we will add it to
1818 * the list after acquiring the lock.
1819 */
1820 get_page(newpage);
1821 ret = MIGRATEPAGE_SUCCESS;
1822 }
1823
1824 /* Update the balloon list under the @pages_lock */
1825 spin_lock_irqsave(&b->b_dev_info.pages_lock, flags);
1826
1827 /*
1828 * On inflation success, we already took a reference for the @newpage.
1829 * If we succeed just insert it to the list and update the statistics
1830 * under the lock.
1831 */
1832 if (ret == MIGRATEPAGE_SUCCESS) {
1833 balloon_page_insert(&b->b_dev_info, newpage);
1834 __count_vm_event(BALLOON_MIGRATE);
1835 }
1836
1837 /*
1838 * We deflated successfully, so regardless to the inflation success, we
1839 * need to reduce the number of isolated_pages.
1840 */
1841 b->b_dev_info.isolated_pages--;
1842 spin_unlock_irqrestore(&b->b_dev_info.pages_lock, flags);
1843
1844out_unlock:
1845 up_read(&b->conf_sem);
1846 return ret;
1847}
1848
1849/**
1850 * vmballoon_compaction_init() - initialized compaction for the balloon.
1851 *
1852 * @b: pointer to the balloon.
1853 *
1854 * If during the initialization a failure occurred, this function does not
1855 * perform cleanup. The caller must call vmballoon_compaction_deinit() in this
1856 * case.
1857 *
1858 * Return: zero on success or error code on failure.
1859 */
1860static __init void vmballoon_compaction_init(struct vmballoon *b)
1861{
1862 b->b_dev_info.migratepage = vmballoon_migratepage;
1863}
1864
1865#else /* CONFIG_BALLOON_COMPACTION */
1866static inline void vmballoon_compaction_init(struct vmballoon *b)
1867{
1868}
1869#endif /* CONFIG_BALLOON_COMPACTION */
1870
1871static int __init vmballoon_init(void)
1872{
1873 int error;
1874
1875 /*
1876 * Check if we are running on VMware's hypervisor and bail out
1877 * if we are not.
1878 */
1879 if (x86_hyper_type != X86_HYPER_VMWARE)
1880 return -ENODEV;
1881
1882 INIT_DELAYED_WORK(&balloon.dwork, vmballoon_work);
1883
1884 error = vmballoon_register_shrinker(&balloon);
1885 if (error)
1886 goto fail;
1887
1888 /*
1889 * Initialization of compaction must be done after the call to
1890 * balloon_devinfo_init() .
1891 */
1892 balloon_devinfo_init(&balloon.b_dev_info);
1893 vmballoon_compaction_init(&balloon);
1894
1895 INIT_LIST_HEAD(&balloon.huge_pages);
1896 spin_lock_init(&balloon.comm_lock);
1897 init_rwsem(&balloon.conf_sem);
1898 balloon.vmci_doorbell = VMCI_INVALID_HANDLE;
1899 balloon.batch_page = NULL;
1900 balloon.page = NULL;
1901 balloon.reset_required = true;
1902
1903 queue_delayed_work(system_freezable_wq, &balloon.dwork, 0);
1904
1905 vmballoon_debugfs_init(&balloon);
1906
1907 return 0;
1908fail:
1909 vmballoon_unregister_shrinker(&balloon);
1910 return error;
1911}
1912
1913/*
1914 * Using late_initcall() instead of module_init() allows the balloon to use the
1915 * VMCI doorbell even when the balloon is built into the kernel. Otherwise the
1916 * VMCI is probed only after the balloon is initialized. If the balloon is used
1917 * as a module, late_initcall() is equivalent to module_init().
1918 */
1919late_initcall(vmballoon_init);
1920
1921static void __exit vmballoon_exit(void)
1922{
1923 vmballoon_unregister_shrinker(&balloon);
1924 vmballoon_vmci_cleanup(&balloon);
1925 cancel_delayed_work_sync(&balloon.dwork);
1926
1927 vmballoon_debugfs_exit(&balloon);
1928
1929 /*
1930 * Deallocate all reserved memory, and reset connection with monitor.
1931 * Reset connection before deallocating memory to avoid potential for
1932 * additional spurious resets from guest touching deallocated pages.
1933 */
1934 vmballoon_send_start(&balloon, 0);
1935 vmballoon_pop(&balloon);
1936}
1937module_exit(vmballoon_exit);