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[~shefty/rdma-dev.git] / drivers / xen / balloon.c
1 /******************************************************************************
2  * Xen balloon driver - enables returning/claiming memory to/from Xen.
3  *
4  * Copyright (c) 2003, B Dragovic
5  * Copyright (c) 2003-2004, M Williamson, K Fraser
6  * Copyright (c) 2005 Dan M. Smith, IBM Corporation
7  * Copyright (c) 2010 Daniel Kiper
8  *
9  * Memory hotplug support was written by Daniel Kiper. Work on
10  * it was sponsored by Google under Google Summer of Code 2010
11  * program. Jeremy Fitzhardinge from Citrix was the mentor for
12  * this project.
13  *
14  * This program is free software; you can redistribute it and/or
15  * modify it under the terms of the GNU General Public License version 2
16  * as published by the Free Software Foundation; or, when distributed
17  * separately from the Linux kernel or incorporated into other
18  * software packages, subject to the following license:
19  *
20  * Permission is hereby granted, free of charge, to any person obtaining a copy
21  * of this source file (the "Software"), to deal in the Software without
22  * restriction, including without limitation the rights to use, copy, modify,
23  * merge, publish, distribute, sublicense, and/or sell copies of the Software,
24  * and to permit persons to whom the Software is furnished to do so, subject to
25  * the following conditions:
26  *
27  * The above copyright notice and this permission notice shall be included in
28  * all copies or substantial portions of the Software.
29  *
30  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
31  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
32  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
33  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
34  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
35  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
36  * IN THE SOFTWARE.
37  */
38
39 #include <linux/kernel.h>
40 #include <linux/sched.h>
41 #include <linux/errno.h>
42 #include <linux/module.h>
43 #include <linux/mm.h>
44 #include <linux/bootmem.h>
45 #include <linux/pagemap.h>
46 #include <linux/highmem.h>
47 #include <linux/mutex.h>
48 #include <linux/list.h>
49 #include <linux/gfp.h>
50 #include <linux/notifier.h>
51 #include <linux/memory.h>
52 #include <linux/memory_hotplug.h>
53
54 #include <asm/page.h>
55 #include <asm/pgalloc.h>
56 #include <asm/pgtable.h>
57 #include <asm/tlb.h>
58 #include <asm/e820.h>
59
60 #include <asm/xen/hypervisor.h>
61 #include <asm/xen/hypercall.h>
62
63 #include <xen/xen.h>
64 #include <xen/interface/xen.h>
65 #include <xen/interface/memory.h>
66 #include <xen/balloon.h>
67 #include <xen/features.h>
68 #include <xen/page.h>
69
70 /*
71  * balloon_process() state:
72  *
73  * BP_DONE: done or nothing to do,
74  * BP_EAGAIN: error, go to sleep,
75  * BP_ECANCELED: error, balloon operation canceled.
76  */
77
78 enum bp_state {
79         BP_DONE,
80         BP_EAGAIN,
81         BP_ECANCELED
82 };
83
84
85 static DEFINE_MUTEX(balloon_mutex);
86
87 struct balloon_stats balloon_stats;
88 EXPORT_SYMBOL_GPL(balloon_stats);
89
90 /* We increase/decrease in batches which fit in a page */
91 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
92
93 #ifdef CONFIG_HIGHMEM
94 #define inc_totalhigh_pages() (totalhigh_pages++)
95 #define dec_totalhigh_pages() (totalhigh_pages--)
96 #else
97 #define inc_totalhigh_pages() do {} while (0)
98 #define dec_totalhigh_pages() do {} while (0)
99 #endif
100
101 /* List of ballooned pages, threaded through the mem_map array. */
102 static LIST_HEAD(ballooned_pages);
103
104 /* Main work function, always executed in process context. */
105 static void balloon_process(struct work_struct *work);
106 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
107
108 /* When ballooning out (allocating memory to return to Xen) we don't really
109    want the kernel to try too hard since that can trigger the oom killer. */
110 #define GFP_BALLOON \
111         (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
112
113 static void scrub_page(struct page *page)
114 {
115 #ifdef CONFIG_XEN_SCRUB_PAGES
116         clear_highpage(page);
117 #endif
118 }
119
120 /* balloon_append: add the given page to the balloon. */
121 static void __balloon_append(struct page *page)
122 {
123         /* Lowmem is re-populated first, so highmem pages go at list tail. */
124         if (PageHighMem(page)) {
125                 list_add_tail(&page->lru, &ballooned_pages);
126                 balloon_stats.balloon_high++;
127         } else {
128                 list_add(&page->lru, &ballooned_pages);
129                 balloon_stats.balloon_low++;
130         }
131 }
132
133 static void balloon_append(struct page *page)
134 {
135         __balloon_append(page);
136         if (PageHighMem(page))
137                 dec_totalhigh_pages();
138         totalram_pages--;
139 }
140
141 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
142 static struct page *balloon_retrieve(bool prefer_highmem)
143 {
144         struct page *page;
145
146         if (list_empty(&ballooned_pages))
147                 return NULL;
148
149         if (prefer_highmem)
150                 page = list_entry(ballooned_pages.prev, struct page, lru);
151         else
152                 page = list_entry(ballooned_pages.next, struct page, lru);
153         list_del(&page->lru);
154
155         if (PageHighMem(page)) {
156                 balloon_stats.balloon_high--;
157                 inc_totalhigh_pages();
158         } else
159                 balloon_stats.balloon_low--;
160
161         totalram_pages++;
162
163         return page;
164 }
165
166 static struct page *balloon_first_page(void)
167 {
168         if (list_empty(&ballooned_pages))
169                 return NULL;
170         return list_entry(ballooned_pages.next, struct page, lru);
171 }
172
173 static struct page *balloon_next_page(struct page *page)
174 {
175         struct list_head *next = page->lru.next;
176         if (next == &ballooned_pages)
177                 return NULL;
178         return list_entry(next, struct page, lru);
179 }
180
181 static enum bp_state update_schedule(enum bp_state state)
182 {
183         if (state == BP_DONE) {
184                 balloon_stats.schedule_delay = 1;
185                 balloon_stats.retry_count = 1;
186                 return BP_DONE;
187         }
188
189         ++balloon_stats.retry_count;
190
191         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
192                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
193                 balloon_stats.schedule_delay = 1;
194                 balloon_stats.retry_count = 1;
195                 return BP_ECANCELED;
196         }
197
198         balloon_stats.schedule_delay <<= 1;
199
200         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
201                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
202
203         return BP_EAGAIN;
204 }
205
206 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
207 static long current_credit(void)
208 {
209         return balloon_stats.target_pages - balloon_stats.current_pages -
210                 balloon_stats.hotplug_pages;
211 }
212
213 static bool balloon_is_inflated(void)
214 {
215         if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
216                         balloon_stats.balloon_hotplug)
217                 return true;
218         else
219                 return false;
220 }
221
222 /*
223  * reserve_additional_memory() adds memory region of size >= credit above
224  * max_pfn. New region is section aligned and size is modified to be multiple
225  * of section size. Those features allow optimal use of address space and
226  * establish proper alignment when this function is called first time after
227  * boot (last section not fully populated at boot time contains unused memory
228  * pages with PG_reserved bit not set; online_pages_range() does not allow page
229  * onlining in whole range if first onlined page does not have PG_reserved
230  * bit set). Real size of added memory is established at page onlining stage.
231  */
232
233 static enum bp_state reserve_additional_memory(long credit)
234 {
235         int nid, rc;
236         u64 hotplug_start_paddr;
237         unsigned long balloon_hotplug = credit;
238
239         hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
240         balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
241         nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
242
243         rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
244
245         if (rc) {
246                 pr_info("xen_balloon: %s: add_memory() failed: %i\n", __func__, rc);
247                 return BP_EAGAIN;
248         }
249
250         balloon_hotplug -= credit;
251
252         balloon_stats.hotplug_pages += credit;
253         balloon_stats.balloon_hotplug = balloon_hotplug;
254
255         return BP_DONE;
256 }
257
258 static void xen_online_page(struct page *page)
259 {
260         __online_page_set_limits(page);
261
262         mutex_lock(&balloon_mutex);
263
264         __balloon_append(page);
265
266         if (balloon_stats.hotplug_pages)
267                 --balloon_stats.hotplug_pages;
268         else
269                 --balloon_stats.balloon_hotplug;
270
271         mutex_unlock(&balloon_mutex);
272 }
273
274 static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
275 {
276         if (val == MEM_ONLINE)
277                 schedule_delayed_work(&balloon_worker, 0);
278
279         return NOTIFY_OK;
280 }
281
282 static struct notifier_block xen_memory_nb = {
283         .notifier_call = xen_memory_notifier,
284         .priority = 0
285 };
286 #else
287 static long current_credit(void)
288 {
289         unsigned long target = balloon_stats.target_pages;
290
291         target = min(target,
292                      balloon_stats.current_pages +
293                      balloon_stats.balloon_low +
294                      balloon_stats.balloon_high);
295
296         return target - balloon_stats.current_pages;
297 }
298
299 static bool balloon_is_inflated(void)
300 {
301         if (balloon_stats.balloon_low || balloon_stats.balloon_high)
302                 return true;
303         else
304                 return false;
305 }
306
307 static enum bp_state reserve_additional_memory(long credit)
308 {
309         balloon_stats.target_pages = balloon_stats.current_pages;
310         return BP_DONE;
311 }
312 #endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
313
314 static enum bp_state increase_reservation(unsigned long nr_pages)
315 {
316         int rc;
317         unsigned long  pfn, i;
318         struct page   *page;
319         struct xen_memory_reservation reservation = {
320                 .address_bits = 0,
321                 .extent_order = 0,
322                 .domid        = DOMID_SELF
323         };
324
325 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
326         if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
327                 nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
328                 balloon_stats.hotplug_pages += nr_pages;
329                 balloon_stats.balloon_hotplug -= nr_pages;
330                 return BP_DONE;
331         }
332 #endif
333
334         if (nr_pages > ARRAY_SIZE(frame_list))
335                 nr_pages = ARRAY_SIZE(frame_list);
336
337         page = balloon_first_page();
338         for (i = 0; i < nr_pages; i++) {
339                 if (!page) {
340                         nr_pages = i;
341                         break;
342                 }
343                 frame_list[i] = page_to_pfn(page);
344                 page = balloon_next_page(page);
345         }
346
347         set_xen_guest_handle(reservation.extent_start, frame_list);
348         reservation.nr_extents = nr_pages;
349         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
350         if (rc <= 0)
351                 return BP_EAGAIN;
352
353         for (i = 0; i < rc; i++) {
354                 page = balloon_retrieve(false);
355                 BUG_ON(page == NULL);
356
357                 pfn = page_to_pfn(page);
358                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
359                        phys_to_machine_mapping_valid(pfn));
360
361                 set_phys_to_machine(pfn, frame_list[i]);
362
363                 /* Link back into the page tables if not highmem. */
364                 if (xen_pv_domain() && !PageHighMem(page)) {
365                         int ret;
366                         ret = HYPERVISOR_update_va_mapping(
367                                 (unsigned long)__va(pfn << PAGE_SHIFT),
368                                 mfn_pte(frame_list[i], PAGE_KERNEL),
369                                 0);
370                         BUG_ON(ret);
371                 }
372
373                 /* Relinquish the page back to the allocator. */
374                 ClearPageReserved(page);
375                 init_page_count(page);
376                 __free_page(page);
377         }
378
379         balloon_stats.current_pages += rc;
380
381         return BP_DONE;
382 }
383
384 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
385 {
386         enum bp_state state = BP_DONE;
387         unsigned long  pfn, i;
388         struct page   *page;
389         int ret;
390         struct xen_memory_reservation reservation = {
391                 .address_bits = 0,
392                 .extent_order = 0,
393                 .domid        = DOMID_SELF
394         };
395
396 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
397         if (balloon_stats.hotplug_pages) {
398                 nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
399                 balloon_stats.hotplug_pages -= nr_pages;
400                 balloon_stats.balloon_hotplug += nr_pages;
401                 return BP_DONE;
402         }
403 #endif
404
405         if (nr_pages > ARRAY_SIZE(frame_list))
406                 nr_pages = ARRAY_SIZE(frame_list);
407
408         for (i = 0; i < nr_pages; i++) {
409                 if ((page = alloc_page(gfp)) == NULL) {
410                         nr_pages = i;
411                         state = BP_EAGAIN;
412                         break;
413                 }
414
415                 pfn = page_to_pfn(page);
416                 frame_list[i] = pfn_to_mfn(pfn);
417
418                 scrub_page(page);
419
420                 if (xen_pv_domain() && !PageHighMem(page)) {
421                         ret = HYPERVISOR_update_va_mapping(
422                                 (unsigned long)__va(pfn << PAGE_SHIFT),
423                                 __pte_ma(0), 0);
424                         BUG_ON(ret);
425                 }
426
427         }
428
429         /* Ensure that ballooned highmem pages don't have kmaps. */
430         kmap_flush_unused();
431         flush_tlb_all();
432
433         /* No more mappings: invalidate P2M and add to balloon. */
434         for (i = 0; i < nr_pages; i++) {
435                 pfn = mfn_to_pfn(frame_list[i]);
436                 __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
437                 balloon_append(pfn_to_page(pfn));
438         }
439
440         set_xen_guest_handle(reservation.extent_start, frame_list);
441         reservation.nr_extents   = nr_pages;
442         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
443         BUG_ON(ret != nr_pages);
444
445         balloon_stats.current_pages -= nr_pages;
446
447         return state;
448 }
449
450 /*
451  * We avoid multiple worker processes conflicting via the balloon mutex.
452  * We may of course race updates of the target counts (which are protected
453  * by the balloon lock), or with changes to the Xen hard limit, but we will
454  * recover from these in time.
455  */
456 static void balloon_process(struct work_struct *work)
457 {
458         enum bp_state state = BP_DONE;
459         long credit;
460
461         mutex_lock(&balloon_mutex);
462
463         do {
464                 credit = current_credit();
465
466                 if (credit > 0) {
467                         if (balloon_is_inflated())
468                                 state = increase_reservation(credit);
469                         else
470                                 state = reserve_additional_memory(credit);
471                 }
472
473                 if (credit < 0)
474                         state = decrease_reservation(-credit, GFP_BALLOON);
475
476                 state = update_schedule(state);
477
478 #ifndef CONFIG_PREEMPT
479                 if (need_resched())
480                         schedule();
481 #endif
482         } while (credit && state == BP_DONE);
483
484         /* Schedule more work if there is some still to be done. */
485         if (state == BP_EAGAIN)
486                 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
487
488         mutex_unlock(&balloon_mutex);
489 }
490
491 /* Resets the Xen limit, sets new target, and kicks off processing. */
492 void balloon_set_new_target(unsigned long target)
493 {
494         /* No need for lock. Not read-modify-write updates. */
495         balloon_stats.target_pages = target;
496         schedule_delayed_work(&balloon_worker, 0);
497 }
498 EXPORT_SYMBOL_GPL(balloon_set_new_target);
499
500 /**
501  * alloc_xenballooned_pages - get pages that have been ballooned out
502  * @nr_pages: Number of pages to get
503  * @pages: pages returned
504  * @highmem: highmem or lowmem pages
505  * @return 0 on success, error otherwise
506  */
507 int alloc_xenballooned_pages(int nr_pages, struct page **pages, bool highmem)
508 {
509         int pgno = 0;
510         struct page *page;
511         mutex_lock(&balloon_mutex);
512         while (pgno < nr_pages) {
513                 page = balloon_retrieve(highmem);
514                 if (page && PageHighMem(page) == highmem) {
515                         pages[pgno++] = page;
516                 } else {
517                         enum bp_state st;
518                         if (page)
519                                 balloon_append(page);
520                         st = decrease_reservation(nr_pages - pgno,
521                                         highmem ? GFP_HIGHUSER : GFP_USER);
522                         if (st != BP_DONE)
523                                 goto out_undo;
524                 }
525         }
526         mutex_unlock(&balloon_mutex);
527         return 0;
528  out_undo:
529         while (pgno)
530                 balloon_append(pages[--pgno]);
531         /* Free the memory back to the kernel soon */
532         schedule_delayed_work(&balloon_worker, 0);
533         mutex_unlock(&balloon_mutex);
534         return -ENOMEM;
535 }
536 EXPORT_SYMBOL(alloc_xenballooned_pages);
537
538 /**
539  * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
540  * @nr_pages: Number of pages
541  * @pages: pages to return
542  */
543 void free_xenballooned_pages(int nr_pages, struct page **pages)
544 {
545         int i;
546
547         mutex_lock(&balloon_mutex);
548
549         for (i = 0; i < nr_pages; i++) {
550                 if (pages[i])
551                         balloon_append(pages[i]);
552         }
553
554         /* The balloon may be too large now. Shrink it if needed. */
555         if (current_credit())
556                 schedule_delayed_work(&balloon_worker, 0);
557
558         mutex_unlock(&balloon_mutex);
559 }
560 EXPORT_SYMBOL(free_xenballooned_pages);
561
562 static void __init balloon_add_region(unsigned long start_pfn,
563                                       unsigned long pages)
564 {
565         unsigned long pfn, extra_pfn_end;
566         struct page *page;
567
568         /*
569          * If the amount of usable memory has been limited (e.g., with
570          * the 'mem' command line parameter), don't add pages beyond
571          * this limit.
572          */
573         extra_pfn_end = min(max_pfn, start_pfn + pages);
574
575         for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
576                 page = pfn_to_page(pfn);
577                 /* totalram_pages and totalhigh_pages do not
578                    include the boot-time balloon extension, so
579                    don't subtract from it. */
580                 __balloon_append(page);
581         }
582 }
583
584 static int __init balloon_init(void)
585 {
586         int i;
587
588         if (!xen_domain())
589                 return -ENODEV;
590
591         pr_info("xen/balloon: Initialising balloon driver.\n");
592
593         balloon_stats.current_pages = xen_pv_domain()
594                 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
595                 : max_pfn;
596         balloon_stats.target_pages  = balloon_stats.current_pages;
597         balloon_stats.balloon_low   = 0;
598         balloon_stats.balloon_high  = 0;
599
600         balloon_stats.schedule_delay = 1;
601         balloon_stats.max_schedule_delay = 32;
602         balloon_stats.retry_count = 1;
603         balloon_stats.max_retry_count = RETRY_UNLIMITED;
604
605 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
606         balloon_stats.hotplug_pages = 0;
607         balloon_stats.balloon_hotplug = 0;
608
609         set_online_page_callback(&xen_online_page);
610         register_memory_notifier(&xen_memory_nb);
611 #endif
612
613         /*
614          * Initialize the balloon with pages from the extra memory
615          * regions (see arch/x86/xen/setup.c).
616          */
617         for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
618                 if (xen_extra_mem[i].size)
619                         balloon_add_region(PFN_UP(xen_extra_mem[i].start),
620                                            PFN_DOWN(xen_extra_mem[i].size));
621
622         return 0;
623 }
624
625 subsys_initcall(balloon_init);
626
627 MODULE_LICENSE("GPL");