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1 /******************************************************************************
2  * Xen balloon driver - enables returning/claiming memory to/from Xen.
3  *
4  * Copyright (c) 2003, B Dragovic
5  * Copyright (c) 2003-2004, M Williamson, K Fraser
6  * Copyright (c) 2005 Dan M. Smith, IBM Corporation
7  * Copyright (c) 2010 Daniel Kiper
8  *
9  * Memory hotplug support was written by Daniel Kiper. Work on
10  * it was sponsored by Google under Google Summer of Code 2010
11  * program. Jeremy Fitzhardinge from Citrix was the mentor for
12  * this project.
13  *
14  * This program is free software; you can redistribute it and/or
15  * modify it under the terms of the GNU General Public License version 2
16  * as published by the Free Software Foundation; or, when distributed
17  * separately from the Linux kernel or incorporated into other
18  * software packages, subject to the following license:
19  *
20  * Permission is hereby granted, free of charge, to any person obtaining a copy
21  * of this source file (the "Software"), to deal in the Software without
22  * restriction, including without limitation the rights to use, copy, modify,
23  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
24  * and to permit persons to whom the Software is furnished to do so, subject to
25  * the following conditions:
26  *
27  * The above copyright notice and this permission notice shall be included in
28  * all copies or substantial portions of the Software.
29  *
30  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
31  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
32  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
33  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
34  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
35  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
36  * IN THE SOFTWARE.
37  */
38
39 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
40
41 #include <linux/cpu.h>
42 #include <linux/kernel.h>
43 #include <linux/sched.h>
44 #include <linux/errno.h>
45 #include <linux/module.h>
46 #include <linux/mm.h>
47 #include <linux/bootmem.h>
48 #include <linux/pagemap.h>
49 #include <linux/highmem.h>
50 #include <linux/mutex.h>
51 #include <linux/list.h>
52 #include <linux/gfp.h>
53 #include <linux/notifier.h>
54 #include <linux/memory.h>
55 #include <linux/memory_hotplug.h>
56 #include <linux/percpu-defs.h>
57
58 #include <asm/page.h>
59 #include <asm/pgalloc.h>
60 #include <asm/pgtable.h>
61 #include <asm/tlb.h>
62
63 #include <asm/xen/hypervisor.h>
64 #include <asm/xen/hypercall.h>
65
66 #include <xen/xen.h>
67 #include <xen/interface/xen.h>
68 #include <xen/interface/memory.h>
69 #include <xen/balloon.h>
70 #include <xen/features.h>
71 #include <xen/page.h>
72
73 /*
74  * balloon_process() state:
75  *
76  * BP_DONE: done or nothing to do,
77  * BP_EAGAIN: error, go to sleep,
78  * BP_ECANCELED: error, balloon operation canceled.
79  */
80
81 enum bp_state {
82         BP_DONE,
83         BP_EAGAIN,
84         BP_ECANCELED
85 };
86
87
88 static DEFINE_MUTEX(balloon_mutex);
89
90 struct balloon_stats balloon_stats;
91 EXPORT_SYMBOL_GPL(balloon_stats);
92
93 /* We increase/decrease in batches which fit in a page */
94 static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)];
95 static DEFINE_PER_CPU(struct page *, balloon_scratch_page);
96
97
98 /* List of ballooned pages, threaded through the mem_map array. */
99 static LIST_HEAD(ballooned_pages);
100
101 /* Main work function, always executed in process context. */
102 static void balloon_process(struct work_struct *work);
103 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
104
105 /* When ballooning out (allocating memory to return to Xen) we don't really
106    want the kernel to try too hard since that can trigger the oom killer. */
107 #define GFP_BALLOON \
108         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
109
110 static void scrub_page(struct page *page)
111 {
112 #ifdef CONFIG_XEN_SCRUB_PAGES
113         clear_highpage(page);
114 #endif
115 }
116
117 /* balloon_append: add the given page to the balloon. */
118 static void __balloon_append(struct page *page)
119 {
120         /* Lowmem is re-populated first, so highmem pages go at list tail. */
121         if (PageHighMem(page)) {
122                 list_add_tail(&page->lru, &ballooned_pages);
123                 balloon_stats.balloon_high++;
124         } else {
125                 list_add(&page->lru, &ballooned_pages);
126                 balloon_stats.balloon_low++;
127         }
128 }
129
130 static void balloon_append(struct page *page)
131 {
132         __balloon_append(page);
133         adjust_managed_page_count(page, -1);
134 }
135
136 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
137 static struct page *balloon_retrieve(bool prefer_highmem)
138 {
139         struct page *page;
140
141         if (list_empty(&ballooned_pages))
142                 return NULL;
143
144         if (prefer_highmem)
145                 page = list_entry(ballooned_pages.prev, struct page, lru);
146         else
147                 page = list_entry(ballooned_pages.next, struct page, lru);
148         list_del(&page->lru);
149
150         if (PageHighMem(page))
151                 balloon_stats.balloon_high--;
152         else
153                 balloon_stats.balloon_low--;
154
155         adjust_managed_page_count(page, 1);
156
157         return page;
158 }
159
160 static struct page *balloon_first_page(void)
161 {
162         if (list_empty(&ballooned_pages))
163                 return NULL;
164         return list_entry(ballooned_pages.next, struct page, lru);
165 }
166
167 static struct page *balloon_next_page(struct page *page)
168 {
169         struct list_head *next = page->lru.next;
170         if (next == &ballooned_pages)
171                 return NULL;
172         return list_entry(next, struct page, lru);
173 }
174
175 static enum bp_state update_schedule(enum bp_state state)
176 {
177         if (state == BP_DONE) {
178                 balloon_stats.schedule_delay = 1;
179                 balloon_stats.retry_count = 1;
180                 return BP_DONE;
181         }
182
183         ++balloon_stats.retry_count;
184
185         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
186                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
187                 balloon_stats.schedule_delay = 1;
188                 balloon_stats.retry_count = 1;
189                 return BP_ECANCELED;
190         }
191
192         balloon_stats.schedule_delay <<= 1;
193
194         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
195                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
196
197         return BP_EAGAIN;
198 }
199
200 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
201 static long current_credit(void)
202 {
203         return balloon_stats.target_pages - balloon_stats.current_pages -
204                 balloon_stats.hotplug_pages;
205 }
206
207 static bool balloon_is_inflated(void)
208 {
209         if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
210                         balloon_stats.balloon_hotplug)
211                 return true;
212         else
213                 return false;
214 }
215
216 /*
217  * reserve_additional_memory() adds memory region of size >= credit above
218  * max_pfn. New region is section aligned and size is modified to be multiple
219  * of section size. Those features allow optimal use of address space and
220  * establish proper alignment when this function is called first time after
221  * boot (last section not fully populated at boot time contains unused memory
222  * pages with PG_reserved bit not set; online_pages_range() does not allow page
223  * onlining in whole range if first onlined page does not have PG_reserved
224  * bit set). Real size of added memory is established at page onlining stage.
225  */
226
227 static enum bp_state reserve_additional_memory(long credit)
228 {
229         int nid, rc;
230         u64 hotplug_start_paddr;
231         unsigned long balloon_hotplug = credit;
232
233         hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
234         balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
235         nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
236
237         rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
238
239         if (rc) {
240                 pr_info("%s: add_memory() failed: %i\n", __func__, rc);
241                 return BP_EAGAIN;
242         }
243
244         balloon_hotplug -= credit;
245
246         balloon_stats.hotplug_pages += credit;
247         balloon_stats.balloon_hotplug = balloon_hotplug;
248
249         return BP_DONE;
250 }
251
252 static void xen_online_page(struct page *page)
253 {
254         __online_page_set_limits(page);
255
256         mutex_lock(&balloon_mutex);
257
258         __balloon_append(page);
259
260         if (balloon_stats.hotplug_pages)
261                 --balloon_stats.hotplug_pages;
262         else
263                 --balloon_stats.balloon_hotplug;
264
265         mutex_unlock(&balloon_mutex);
266 }
267
268 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
269 {
270         if (val == MEM_ONLINE)
271                 schedule_delayed_work(&balloon_worker, 0);
272
273         return NOTIFY_OK;
274 }
275
276 static struct notifier_block xen_memory_nb = {
277         .notifier_call = xen_memory_notifier,
278         .priority = 0
279 };
280 #else
281 static long current_credit(void)
282 {
283         unsigned long target = balloon_stats.target_pages;
284
285         target = min(target,
286                      balloon_stats.current_pages +
287                      balloon_stats.balloon_low +
288                      balloon_stats.balloon_high);
289
290         return target - balloon_stats.current_pages;
291 }
292
293 static bool balloon_is_inflated(void)
294 {
295         if (balloon_stats.balloon_low || balloon_stats.balloon_high)
296                 return true;
297         else
298                 return false;
299 }
300
301 static enum bp_state reserve_additional_memory(long credit)
302 {
303         balloon_stats.target_pages = balloon_stats.current_pages;
304         return BP_DONE;
305 }
306 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
307
308 static enum bp_state increase_reservation(unsigned long nr_pages)
309 {
310         int rc;
311         unsigned long  pfn, i;
312         struct page   *page;
313         struct xen_memory_reservation reservation = {
314                 .address_bits = 0,
315                 .extent_order = 0,
316                 .domid        = DOMID_SELF
317         };
318
319 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
320         if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
321                 nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
322                 balloon_stats.hotplug_pages += nr_pages;
323                 balloon_stats.balloon_hotplug -= nr_pages;
324                 return BP_DONE;
325         }
326 #endif
327
328         if (nr_pages > ARRAY_SIZE(frame_list))
329                 nr_pages = ARRAY_SIZE(frame_list);
330
331         page = balloon_first_page();
332         for (i = 0; i < nr_pages; i++) {
333                 if (!page) {
334                         nr_pages = i;
335                         break;
336                 }
337                 frame_list[i] = page_to_pfn(page);
338                 page = balloon_next_page(page);
339         }
340
341         set_xen_guest_handle(reservation.extent_start, frame_list);
342         reservation.nr_extents = nr_pages;
343         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
344         if (rc <= 0)
345                 return BP_EAGAIN;
346
347         for (i = 0; i < rc; i++) {
348                 page = balloon_retrieve(false);
349                 BUG_ON(page == NULL);
350
351                 pfn = page_to_pfn(page);
352
353                 set_phys_to_machine(pfn, frame_list[i]);
354
355 #ifdef CONFIG_XEN_HAVE_PVMMU
356                 /* Link back into the page tables if not highmem. */
357                 if (xen_pv_domain() && !PageHighMem(page)) {
358                         int ret;
359                         ret = HYPERVISOR_update_va_mapping(
360                                 (unsigned long)__va(pfn << PAGE_SHIFT),
361                                 mfn_pte(frame_list[i], PAGE_KERNEL),
362                                 0);
363                         BUG_ON(ret);
364                 }
365 #endif
366
367                 /* Relinquish the page back to the allocator. */
368                 __free_reserved_page(page);
369         }
370
371         balloon_stats.current_pages += rc;
372
373         return BP_DONE;
374 }
375
376 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
377 {
378         enum bp_state state = BP_DONE;
379         unsigned long  pfn, i;
380         struct page   *page;
381         struct page   *scratch_page;
382         int ret;
383         struct xen_memory_reservation reservation = {
384                 .address_bits = 0,
385                 .extent_order = 0,
386                 .domid        = DOMID_SELF
387         };
388
389 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
390         if (balloon_stats.hotplug_pages) {
391                 nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
392                 balloon_stats.hotplug_pages -= nr_pages;
393                 balloon_stats.balloon_hotplug += nr_pages;
394                 return BP_DONE;
395         }
396 #endif
397
398         if (nr_pages > ARRAY_SIZE(frame_list))
399                 nr_pages = ARRAY_SIZE(frame_list);
400
401         scratch_page = get_balloon_scratch_page();
402
403         for (i = 0; i < nr_pages; i++) {
404                 page = alloc_page(gfp);
405                 if (page == NULL) {
406                         nr_pages = i;
407                         state = BP_EAGAIN;
408                         break;
409                 }
410
411                 pfn = page_to_pfn(page);
412                 frame_list[i] = pfn_to_mfn(pfn);
413
414                 scrub_page(page);
415
416 #ifdef CONFIG_XEN_HAVE_PVMMU
417                 if (xen_pv_domain() && !PageHighMem(page)) {
418                         ret = HYPERVISOR_update_va_mapping(
419                                 (unsigned long)__va(pfn << PAGE_SHIFT),
420                                 pfn_pte(page_to_pfn(scratch_page),
421                                         PAGE_KERNEL_RO), 0);
422                         BUG_ON(ret);
423                 }
424 #endif
425         }
426
427         /* Ensure that ballooned highmem pages don't have kmaps. */
428         kmap_flush_unused();
429         flush_tlb_all();
430
431         /* No more mappings: invalidate P2M and add to balloon. */
432         for (i = 0; i < nr_pages; i++) {
433                 pfn = mfn_to_pfn(frame_list[i]);
434                 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
435                         unsigned long p;
436                         p = page_to_pfn(scratch_page);
437                         __set_phys_to_machine(pfn, pfn_to_mfn(p));
438                 }
439                 balloon_append(pfn_to_page(pfn));
440         }
441
442         put_balloon_scratch_page();
443
444         set_xen_guest_handle(reservation.extent_start, frame_list);
445         reservation.nr_extents   = nr_pages;
446         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
447         BUG_ON(ret != nr_pages);
448
449         balloon_stats.current_pages -= nr_pages;
450
451         return state;
452 }
453
454 /*
455  * We avoid multiple worker processes conflicting via the balloon mutex.
456  * We may of course race updates of the target counts (which are protected
457  * by the balloon lock), or with changes to the Xen hard limit, but we will
458  * recover from these in time.
459  */
460 static void balloon_process(struct work_struct *work)
461 {
462         enum bp_state state = BP_DONE;
463         long credit;
464
465         mutex_lock(&balloon_mutex);
466
467         do {
468                 credit = current_credit();
469
470                 if (credit > 0) {
471                         if (balloon_is_inflated())
472                                 state = increase_reservation(credit);
473                         else
474                                 state = reserve_additional_memory(credit);
475                 }
476
477                 if (credit < 0)
478                         state = decrease_reservation(-credit, GFP_BALLOON);
479
480                 state = update_schedule(state);
481
482 #ifndef CONFIG_PREEMPT
483                 if (need_resched())
484                         schedule();
485 #endif
486         } while (credit && state == BP_DONE);
487
488         /* Schedule more work if there is some still to be done. */
489         if (state == BP_EAGAIN)
490                 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
491
492         mutex_unlock(&balloon_mutex);
493 }
494
495 struct page *get_balloon_scratch_page(void)
496 {
497         struct page *ret = get_cpu_var(balloon_scratch_page);
498         BUG_ON(ret == NULL);
499         return ret;
500 }
501
502 void put_balloon_scratch_page(void)
503 {
504         put_cpu_var(balloon_scratch_page);
505 }
506
507 /* Resets the Xen limit, sets new target, and kicks off processing. */
508 void balloon_set_new_target(unsigned long target)
509 {
510         /* No need for lock. Not read-modify-write updates. */
511         balloon_stats.target_pages = target;
512         schedule_delayed_work(&balloon_worker, 0);
513 }
514 EXPORT_SYMBOL_GPL(balloon_set_new_target);
515
516 /**
517  * alloc_xenballooned_pages - get pages that have been ballooned out
518  * @nr_pages: Number of pages to get
519  * @pages: pages returned
520  * @highmem: allow highmem pages
521  * @return 0 on success, error otherwise
522  */
523 int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
524 {
525         int pgno = 0;
526         struct page *page;
527         mutex_lock(&balloon_mutex);
528         while (pgno < nr_pages) {
529                 page = balloon_retrieve(highmem);
530                 if (page && (highmem || !PageHighMem(page))) {
531                         pages[pgno++] = page;
532                 } else {
533                         enum bp_state st;
534                         if (page)
535                                 balloon_append(page);
536                         st = decrease_reservation(nr_pages - pgno,
537                                         highmem ? GFP_HIGHUSER : GFP_USER);
538                         if (st != BP_DONE)
539                                 goto out_undo;
540                 }
541         }
542         mutex_unlock(&balloon_mutex);
543         return 0;
544  out_undo:
545         while (pgno)
546                 balloon_append(pages[--pgno]);
547         /* Free the memory back to the kernel soon */
548         schedule_delayed_work(&balloon_worker, 0);
549         mutex_unlock(&balloon_mutex);
550         return -ENOMEM;
551 }
552 EXPORT_SYMBOL(alloc_xenballooned_pages);
553
554 /**
555  * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
556  * @nr_pages: Number of pages
557  * @pages: pages to return
558  */
559 void free_xenballooned_pages(int nr_pages, struct page **pages)
560 {
561         int i;
562
563         mutex_lock(&balloon_mutex);
564
565         for (i = 0; i < nr_pages; i++) {
566                 if (pages[i])
567                         balloon_append(pages[i]);
568         }
569
570         /* The balloon may be too large now. Shrink it if needed. */
571         if (current_credit())
572                 schedule_delayed_work(&balloon_worker, 0);
573
574         mutex_unlock(&balloon_mutex);
575 }
576 EXPORT_SYMBOL(free_xenballooned_pages);
577
578 static void __init balloon_add_region(unsigned long start_pfn,
579                                       unsigned long pages)
580 {
581         unsigned long pfn, extra_pfn_end;
582         struct page *page;
583
584         /*
585          * If the amount of usable memory has been limited (e.g., with
586          * the 'mem' command line parameter), don't add pages beyond
587          * this limit.
588          */
589         extra_pfn_end = min(max_pfn, start_pfn + pages);
590
591         for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
592                 page = pfn_to_page(pfn);
593                 /* totalram_pages and totalhigh_pages do not
594                    include the boot-time balloon extension, so
595                    don't subtract from it. */
596                 __balloon_append(page);
597         }
598 }
599
600 static int __cpuinit balloon_cpu_notify(struct notifier_block *self,
601                                     unsigned long action, void *hcpu)
602 {
603         int cpu = (long)hcpu;
604         switch (action) {
605         case CPU_UP_PREPARE:
606                 if (per_cpu(balloon_scratch_page, cpu) != NULL)
607                         break;
608                 per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
609                 if (per_cpu(balloon_scratch_page, cpu) == NULL) {
610                         pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
611                         return NOTIFY_BAD;
612                 }
613                 break;
614         default:
615                 break;
616         }
617         return NOTIFY_OK;
618 }
619
620 static struct notifier_block balloon_cpu_notifier __cpuinitdata = {
621         .notifier_call  = balloon_cpu_notify,
622 };
623
624 static int __init balloon_init(void)
625 {
626         int i, cpu;
627
628         if (!xen_domain())
629                 return -ENODEV;
630
631         for_each_online_cpu(cpu)
632         {
633                 per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
634                 if (per_cpu(balloon_scratch_page, cpu) == NULL) {
635                         pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
636                         return -ENOMEM;
637                 }
638         }
639         register_cpu_notifier(&balloon_cpu_notifier);
640
641         pr_info("Initialising balloon driver\n");
642
643         balloon_stats.current_pages = xen_pv_domain()
644                 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
645                 : max_pfn;
646         balloon_stats.target_pages  = balloon_stats.current_pages;
647         balloon_stats.balloon_low   = 0;
648         balloon_stats.balloon_high  = 0;
649
650         balloon_stats.schedule_delay = 1;
651         balloon_stats.max_schedule_delay = 32;
652         balloon_stats.retry_count = 1;
653         balloon_stats.max_retry_count = RETRY_UNLIMITED;
654
655 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
656         balloon_stats.hotplug_pages = 0;
657         balloon_stats.balloon_hotplug = 0;
658
659         set_online_page_callback(&xen_online_page);
660         register_memory_notifier(&xen_memory_nb);
661 #endif
662
663         /*
664          * Initialize the balloon with pages from the extra memory
665          * regions (see arch/x86/xen/setup.c).
666          */
667         for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
668                 if (xen_extra_mem[i].size)
669                         balloon_add_region(PFN_UP(xen_extra_mem[i].start),
670                                            PFN_DOWN(xen_extra_mem[i].size));
671
672         return 0;
673 }
674
675 subsys_initcall(balloon_init);
676
677 static int __init balloon_clear(void)
678 {
679         int cpu;
680
681         for_each_possible_cpu(cpu)
682                 per_cpu(balloon_scratch_page, cpu) = NULL;
683
684         return 0;
685 }
686 early_initcall(balloon_clear);
687
688 MODULE_LICENSE("GPL");