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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#include <linux/kernel.h>
40#include <linux/sched.h>
41#include <linux/errno.h>
42#include <linux/mm.h>
43#include <linux/bootmem.h>
44#include <linux/pagemap.h>
45#include <linux/highmem.h>
46#include <linux/mutex.h>
47#include <linux/list.h>
48#include <linux/gfp.h>
49#include <linux/notifier.h>
50#include <linux/memory.h>
51#include <linux/memory_hotplug.h>
52
53#include <asm/page.h>
54#include <asm/pgalloc.h>
55#include <asm/pgtable.h>
56#include <asm/tlb.h>
57#include <asm/e820.h>
58
59#include <asm/xen/hypervisor.h>
60#include <asm/xen/hypercall.h>
61
62#include <xen/xen.h>
63#include <xen/interface/xen.h>
64#include <xen/interface/memory.h>
65#include <xen/balloon.h>
66#include <xen/features.h>
67#include <xen/page.h>
68
69/*
70 * balloon_process() state:
71 *
72 * BP_DONE: done or nothing to do,
73 * BP_EAGAIN: error, go to sleep,
74 * BP_ECANCELED: error, balloon operation canceled.
75 */
76
77enum bp_state {
78 BP_DONE,
79 BP_EAGAIN,
80 BP_ECANCELED
81};
82
83
84static DEFINE_MUTEX(balloon_mutex);
85
86struct balloon_stats balloon_stats;
87EXPORT_SYMBOL_GPL(balloon_stats);
88
89/* We increase/decrease in batches which fit in a page */
90static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
91
92#ifdef CONFIG_HIGHMEM
93#define inc_totalhigh_pages() (totalhigh_pages++)
94#define dec_totalhigh_pages() (totalhigh_pages--)
95#else
96#define inc_totalhigh_pages() do {} while(0)
97#define dec_totalhigh_pages() do {} while(0)
98#endif
99
100/* List of ballooned pages, threaded through the mem_map array. */
101static LIST_HEAD(ballooned_pages);
102
103/* Main work function, always executed in process context. */
104static void balloon_process(struct work_struct *work);
105static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
106
107/* When ballooning out (allocating memory to return to Xen) we don't really
108 want the kernel to try too hard since that can trigger the oom killer. */
109#define GFP_BALLOON \
110 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
111
112static void scrub_page(struct page *page)
113{
114#ifdef CONFIG_XEN_SCRUB_PAGES
115 clear_highpage(page);
116#endif
117}
118
119/* balloon_append: add the given page to the balloon. */
120static void __balloon_append(struct page *page)
121{
122 /* Lowmem is re-populated first, so highmem pages go at list tail. */
123 if (PageHighMem(page)) {
124 list_add_tail(&page->lru, &ballooned_pages);
125 balloon_stats.balloon_high++;
126 } else {
127 list_add(&page->lru, &ballooned_pages);
128 balloon_stats.balloon_low++;
129 }
130}
131
132static void balloon_append(struct page *page)
133{
134 __balloon_append(page);
135 if (PageHighMem(page))
136 dec_totalhigh_pages();
137 totalram_pages--;
138}
139
140/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
141static struct page *balloon_retrieve(bool prefer_highmem)
142{
143 struct page *page;
144
145 if (list_empty(&ballooned_pages))
146 return NULL;
147
148 if (prefer_highmem)
149 page = list_entry(ballooned_pages.prev, struct page, lru);
150 else
151 page = list_entry(ballooned_pages.next, struct page, lru);
152 list_del(&page->lru);
153
154 if (PageHighMem(page)) {
155 balloon_stats.balloon_high--;
156 inc_totalhigh_pages();
157 }
158 else
159 balloon_stats.balloon_low--;
160
161 totalram_pages++;
162
163 return page;
164}
165
166static struct page *balloon_first_page(void)
167{
168 if (list_empty(&ballooned_pages))
169 return NULL;
170 return list_entry(ballooned_pages.next, struct page, lru);
171}
172
173static struct page *balloon_next_page(struct page *page)
174{
175 struct list_head *next = page->lru.next;
176 if (next == &ballooned_pages)
177 return NULL;
178 return list_entry(next, struct page, lru);
179}
180
181static enum bp_state update_schedule(enum bp_state state)
182{
183 if (state == BP_DONE) {
184 balloon_stats.schedule_delay = 1;
185 balloon_stats.retry_count = 1;
186 return BP_DONE;
187 }
188
189 ++balloon_stats.retry_count;
190
191 if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
192 balloon_stats.retry_count > balloon_stats.max_retry_count) {
193 balloon_stats.schedule_delay = 1;
194 balloon_stats.retry_count = 1;
195 return BP_ECANCELED;
196 }
197
198 balloon_stats.schedule_delay <<= 1;
199
200 if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
201 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
202
203 return BP_EAGAIN;
204}
205
206#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
207static long current_credit(void)
208{
209 return balloon_stats.target_pages - balloon_stats.current_pages -
210 balloon_stats.hotplug_pages;
211}
212
213static bool balloon_is_inflated(void)
214{
215 if (balloon_stats.balloon_low || balloon_stats.balloon_high ||
216 balloon_stats.balloon_hotplug)
217 return true;
218 else
219 return false;
220}
221
222/*
223 * reserve_additional_memory() adds memory region of size >= credit above
224 * max_pfn. New region is section aligned and size is modified to be multiple
225 * of section size. Those features allow optimal use of address space and
226 * establish proper alignment when this function is called first time after
227 * boot (last section not fully populated at boot time contains unused memory
228 * pages with PG_reserved bit not set; online_pages_range() does not allow page
229 * onlining in whole range if first onlined page does not have PG_reserved
230 * bit set). Real size of added memory is established at page onlining stage.
231 */
232
233static enum bp_state reserve_additional_memory(long credit)
234{
235 int nid, rc;
236 u64 hotplug_start_paddr;
237 unsigned long balloon_hotplug = credit;
238
239 hotplug_start_paddr = PFN_PHYS(SECTION_ALIGN_UP(max_pfn));
240 balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
241 nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
242
243 rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
244
245 if (rc) {
246 pr_info("xen_balloon: %s: add_memory() failed: %i\n", __func__, rc);
247 return BP_EAGAIN;
248 }
249
250 balloon_hotplug -= credit;
251
252 balloon_stats.hotplug_pages += credit;
253 balloon_stats.balloon_hotplug = balloon_hotplug;
254
255 return BP_DONE;
256}
257
258static void xen_online_page(struct page *page)
259{
260 __online_page_set_limits(page);
261
262 mutex_lock(&balloon_mutex);
263
264 __balloon_append(page);
265
266 if (balloon_stats.hotplug_pages)
267 --balloon_stats.hotplug_pages;
268 else
269 --balloon_stats.balloon_hotplug;
270
271 mutex_unlock(&balloon_mutex);
272}
273
274static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
275{
276 if (val == MEM_ONLINE)
277 schedule_delayed_work(&balloon_worker, 0);
278
279 return NOTIFY_OK;
280}
281
282static struct notifier_block xen_memory_nb = {
283 .notifier_call = xen_memory_notifier,
284 .priority = 0
285};
286#else
287static long current_credit(void)
288{
289 unsigned long target = balloon_stats.target_pages;
290
291 target = min(target,
292 balloon_stats.current_pages +
293 balloon_stats.balloon_low +
294 balloon_stats.balloon_high);
295
296 return target - balloon_stats.current_pages;
297}
298
299static bool balloon_is_inflated(void)
300{
301 if (balloon_stats.balloon_low || balloon_stats.balloon_high)
302 return true;
303 else
304 return false;
305}
306
307static enum bp_state reserve_additional_memory(long credit)
308{
309 balloon_stats.target_pages = balloon_stats.current_pages;
310 return BP_DONE;
311}
312#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
313
314static enum bp_state increase_reservation(unsigned long nr_pages)
315{
316 int rc;
317 unsigned long pfn, i;
318 struct page *page;
319 struct xen_memory_reservation reservation = {
320 .address_bits = 0,
321 .extent_order = 0,
322 .domid = DOMID_SELF
323 };
324
325#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
326 if (!balloon_stats.balloon_low && !balloon_stats.balloon_high) {
327 nr_pages = min(nr_pages, balloon_stats.balloon_hotplug);
328 balloon_stats.hotplug_pages += nr_pages;
329 balloon_stats.balloon_hotplug -= nr_pages;
330 return BP_DONE;
331 }
332#endif
333
334 if (nr_pages > ARRAY_SIZE(frame_list))
335 nr_pages = ARRAY_SIZE(frame_list);
336
337 page = balloon_first_page();
338 for (i = 0; i < nr_pages; i++) {
339 if (!page) {
340 nr_pages = i;
341 break;
342 }
343 frame_list[i] = page_to_pfn(page);
344 page = balloon_next_page(page);
345 }
346
347 set_xen_guest_handle(reservation.extent_start, frame_list);
348 reservation.nr_extents = nr_pages;
349 rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
350 if (rc <= 0)
351 return BP_EAGAIN;
352
353 for (i = 0; i < rc; i++) {
354 page = balloon_retrieve(false);
355 BUG_ON(page == NULL);
356
357 pfn = page_to_pfn(page);
358 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
359 phys_to_machine_mapping_valid(pfn));
360
361 set_phys_to_machine(pfn, frame_list[i]);
362
363 /* Link back into the page tables if not highmem. */
364 if (xen_pv_domain() && !PageHighMem(page)) {
365 int ret;
366 ret = HYPERVISOR_update_va_mapping(
367 (unsigned long)__va(pfn << PAGE_SHIFT),
368 mfn_pte(frame_list[i], PAGE_KERNEL),
369 0);
370 BUG_ON(ret);
371 }
372
373 /* Relinquish the page back to the allocator. */
374 ClearPageReserved(page);
375 init_page_count(page);
376 __free_page(page);
377 }
378
379 balloon_stats.current_pages += rc;
380
381 return BP_DONE;
382}
383
384static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
385{
386 enum bp_state state = BP_DONE;
387 unsigned long pfn, i;
388 struct page *page;
389 int ret;
390 struct xen_memory_reservation reservation = {
391 .address_bits = 0,
392 .extent_order = 0,
393 .domid = DOMID_SELF
394 };
395
396#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
397 if (balloon_stats.hotplug_pages) {
398 nr_pages = min(nr_pages, balloon_stats.hotplug_pages);
399 balloon_stats.hotplug_pages -= nr_pages;
400 balloon_stats.balloon_hotplug += nr_pages;
401 return BP_DONE;
402 }
403#endif
404
405 if (nr_pages > ARRAY_SIZE(frame_list))
406 nr_pages = ARRAY_SIZE(frame_list);
407
408 for (i = 0; i < nr_pages; i++) {
409 if ((page = alloc_page(gfp)) == NULL) {
410 nr_pages = i;
411 state = BP_EAGAIN;
412 break;
413 }
414
415 pfn = page_to_pfn(page);
416 frame_list[i] = pfn_to_mfn(pfn);
417
418 scrub_page(page);
419
420 if (xen_pv_domain() && !PageHighMem(page)) {
421 ret = HYPERVISOR_update_va_mapping(
422 (unsigned long)__va(pfn << PAGE_SHIFT),
423 __pte_ma(0), 0);
424 BUG_ON(ret);
425 }
426
427 }
428
429 /* Ensure that ballooned highmem pages don't have kmaps. */
430 kmap_flush_unused();
431 flush_tlb_all();
432
433 /* No more mappings: invalidate P2M and add to balloon. */
434 for (i = 0; i < nr_pages; i++) {
435 pfn = mfn_to_pfn(frame_list[i]);
436 __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
437 balloon_append(pfn_to_page(pfn));
438 }
439
440 set_xen_guest_handle(reservation.extent_start, frame_list);
441 reservation.nr_extents = nr_pages;
442 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
443 BUG_ON(ret != nr_pages);
444
445 balloon_stats.current_pages -= nr_pages;
446
447 return state;
448}
449
450/*
451 * We avoid multiple worker processes conflicting via the balloon mutex.
452 * We may of course race updates of the target counts (which are protected
453 * by the balloon lock), or with changes to the Xen hard limit, but we will
454 * recover from these in time.
455 */
456static void balloon_process(struct work_struct *work)
457{
458 enum bp_state state = BP_DONE;
459 long credit;
460
461 mutex_lock(&balloon_mutex);
462
463 do {
464 credit = current_credit();
465
466 if (credit > 0) {
467 if (balloon_is_inflated())
468 state = increase_reservation(credit);
469 else
470 state = reserve_additional_memory(credit);
471 }
472
473 if (credit < 0)
474 state = decrease_reservation(-credit, GFP_BALLOON);
475
476 state = update_schedule(state);
477
478#ifndef CONFIG_PREEMPT
479 if (need_resched())
480 schedule();
481#endif
482 } while (credit && state == BP_DONE);
483
484 /* Schedule more work if there is some still to be done. */
485 if (state == BP_EAGAIN)
486 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
487
488 mutex_unlock(&balloon_mutex);
489}
490
491/* Resets the Xen limit, sets new target, and kicks off processing. */
492void balloon_set_new_target(unsigned long target)
493{
494 /* No need for lock. Not read-modify-write updates. */
495 balloon_stats.target_pages = target;
496 schedule_delayed_work(&balloon_worker, 0);
497}
498EXPORT_SYMBOL_GPL(balloon_set_new_target);
499
500/**
501 * alloc_xenballooned_pages - get pages that have been ballooned out
502 * @nr_pages: Number of pages to get
503 * @pages: pages returned
504 * @return 0 on success, error otherwise
505 */
506int alloc_xenballooned_pages(int nr_pages, struct page** pages)
507{
508 int pgno = 0;
509 struct page* page;
510 mutex_lock(&balloon_mutex);
511 while (pgno < nr_pages) {
512 page = balloon_retrieve(true);
513 if (page) {
514 pages[pgno++] = page;
515 } else {
516 enum bp_state st;
517 st = decrease_reservation(nr_pages - pgno, GFP_HIGHUSER);
518 if (st != BP_DONE)
519 goto out_undo;
520 }
521 }
522 mutex_unlock(&balloon_mutex);
523 return 0;
524 out_undo:
525 while (pgno)
526 balloon_append(pages[--pgno]);
527 /* Free the memory back to the kernel soon */
528 schedule_delayed_work(&balloon_worker, 0);
529 mutex_unlock(&balloon_mutex);
530 return -ENOMEM;
531}
532EXPORT_SYMBOL(alloc_xenballooned_pages);
533
534/**
535 * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
536 * @nr_pages: Number of pages
537 * @pages: pages to return
538 */
539void free_xenballooned_pages(int nr_pages, struct page** pages)
540{
541 int i;
542
543 mutex_lock(&balloon_mutex);
544
545 for (i = 0; i < nr_pages; i++) {
546 if (pages[i])
547 balloon_append(pages[i]);
548 }
549
550 /* The balloon may be too large now. Shrink it if needed. */
551 if (current_credit())
552 schedule_delayed_work(&balloon_worker, 0);
553
554 mutex_unlock(&balloon_mutex);
555}
556EXPORT_SYMBOL(free_xenballooned_pages);
557
558static int __init balloon_init(void)
559{
560 unsigned long pfn, extra_pfn_end;
561 struct page *page;
562
563 if (!xen_domain())
564 return -ENODEV;
565
566 pr_info("xen/balloon: Initialising balloon driver.\n");
567
568 balloon_stats.current_pages = xen_pv_domain() ? min(xen_start_info->nr_pages, max_pfn) : max_pfn;
569 balloon_stats.target_pages = balloon_stats.current_pages;
570 balloon_stats.balloon_low = 0;
571 balloon_stats.balloon_high = 0;
572
573 balloon_stats.schedule_delay = 1;
574 balloon_stats.max_schedule_delay = 32;
575 balloon_stats.retry_count = 1;
576 balloon_stats.max_retry_count = RETRY_UNLIMITED;
577
578#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
579 balloon_stats.hotplug_pages = 0;
580 balloon_stats.balloon_hotplug = 0;
581
582 set_online_page_callback(&xen_online_page);
583 register_memory_notifier(&xen_memory_nb);
584#endif
585
586 /*
587 * Initialise the balloon with excess memory space. We need
588 * to make sure we don't add memory which doesn't exist or
589 * logically exist. The E820 map can be trimmed to be smaller
590 * than the amount of physical memory due to the mem= command
591 * line parameter. And if this is a 32-bit non-HIGHMEM kernel
592 * on a system with memory which requires highmem to access,
593 * don't try to use it.
594 */
595 extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
596 (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
597 for (pfn = PFN_UP(xen_extra_mem_start);
598 pfn < extra_pfn_end;
599 pfn++) {
600 page = pfn_to_page(pfn);
601 /* totalram_pages and totalhigh_pages do not include the boot-time
602 balloon extension, so don't subtract from it. */
603 __balloon_append(page);
604 }
605
606 return 0;
607}
608
609subsys_initcall(balloon_init);
610
611MODULE_LICENSE("GPL");
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/mm.h>
46#include <linux/bootmem.h>
47#include <linux/pagemap.h>
48#include <linux/highmem.h>
49#include <linux/mutex.h>
50#include <linux/list.h>
51#include <linux/gfp.h>
52#include <linux/notifier.h>
53#include <linux/memory.h>
54#include <linux/memory_hotplug.h>
55#include <linux/percpu-defs.h>
56#include <linux/slab.h>
57#include <linux/sysctl.h>
58
59#include <asm/page.h>
60#include <asm/pgalloc.h>
61#include <asm/pgtable.h>
62#include <asm/tlb.h>
63
64#include <asm/xen/hypervisor.h>
65#include <asm/xen/hypercall.h>
66
67#include <xen/xen.h>
68#include <xen/interface/xen.h>
69#include <xen/interface/memory.h>
70#include <xen/balloon.h>
71#include <xen/features.h>
72#include <xen/page.h>
73
74static int xen_hotplug_unpopulated;
75
76#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
77
78static int zero;
79static int one = 1;
80
81static struct ctl_table balloon_table[] = {
82 {
83 .procname = "hotplug_unpopulated",
84 .data = &xen_hotplug_unpopulated,
85 .maxlen = sizeof(int),
86 .mode = 0644,
87 .proc_handler = proc_dointvec_minmax,
88 .extra1 = &zero,
89 .extra2 = &one,
90 },
91 { }
92};
93
94static struct ctl_table balloon_root[] = {
95 {
96 .procname = "balloon",
97 .mode = 0555,
98 .child = balloon_table,
99 },
100 { }
101};
102
103static struct ctl_table xen_root[] = {
104 {
105 .procname = "xen",
106 .mode = 0555,
107 .child = balloon_root,
108 },
109 { }
110};
111
112#endif
113
114/*
115 * Use one extent per PAGE_SIZE to avoid to break down the page into
116 * multiple frame.
117 */
118#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
119
120/*
121 * balloon_process() state:
122 *
123 * BP_DONE: done or nothing to do,
124 * BP_WAIT: wait to be rescheduled,
125 * BP_EAGAIN: error, go to sleep,
126 * BP_ECANCELED: error, balloon operation canceled.
127 */
128
129enum bp_state {
130 BP_DONE,
131 BP_WAIT,
132 BP_EAGAIN,
133 BP_ECANCELED
134};
135
136
137static DEFINE_MUTEX(balloon_mutex);
138
139struct balloon_stats balloon_stats;
140EXPORT_SYMBOL_GPL(balloon_stats);
141
142/* We increase/decrease in batches which fit in a page */
143static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)];
144
145
146/* List of ballooned pages, threaded through the mem_map array. */
147static LIST_HEAD(ballooned_pages);
148static DECLARE_WAIT_QUEUE_HEAD(balloon_wq);
149
150/* Main work function, always executed in process context. */
151static void balloon_process(struct work_struct *work);
152static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
153
154static void release_memory_resource(struct resource *resource);
155
156/* When ballooning out (allocating memory to return to Xen) we don't really
157 want the kernel to try too hard since that can trigger the oom killer. */
158#define GFP_BALLOON \
159 (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC)
160
161static void scrub_page(struct page *page)
162{
163#ifdef CONFIG_XEN_SCRUB_PAGES
164 clear_highpage(page);
165#endif
166}
167
168/* balloon_append: add the given page to the balloon. */
169static void __balloon_append(struct page *page)
170{
171 /* Lowmem is re-populated first, so highmem pages go at list tail. */
172 if (PageHighMem(page)) {
173 list_add_tail(&page->lru, &ballooned_pages);
174 balloon_stats.balloon_high++;
175 } else {
176 list_add(&page->lru, &ballooned_pages);
177 balloon_stats.balloon_low++;
178 }
179 wake_up(&balloon_wq);
180}
181
182static void balloon_append(struct page *page)
183{
184 __balloon_append(page);
185 adjust_managed_page_count(page, -1);
186}
187
188/* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
189static struct page *balloon_retrieve(bool require_lowmem)
190{
191 struct page *page;
192
193 if (list_empty(&ballooned_pages))
194 return NULL;
195
196 page = list_entry(ballooned_pages.next, struct page, lru);
197 if (require_lowmem && PageHighMem(page))
198 return NULL;
199 list_del(&page->lru);
200
201 if (PageHighMem(page))
202 balloon_stats.balloon_high--;
203 else
204 balloon_stats.balloon_low--;
205
206 adjust_managed_page_count(page, 1);
207
208 return page;
209}
210
211static struct page *balloon_next_page(struct page *page)
212{
213 struct list_head *next = page->lru.next;
214 if (next == &ballooned_pages)
215 return NULL;
216 return list_entry(next, struct page, lru);
217}
218
219static enum bp_state update_schedule(enum bp_state state)
220{
221 if (state == BP_WAIT)
222 return BP_WAIT;
223
224 if (state == BP_ECANCELED)
225 return BP_ECANCELED;
226
227 if (state == BP_DONE) {
228 balloon_stats.schedule_delay = 1;
229 balloon_stats.retry_count = 1;
230 return BP_DONE;
231 }
232
233 ++balloon_stats.retry_count;
234
235 if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
236 balloon_stats.retry_count > balloon_stats.max_retry_count) {
237 balloon_stats.schedule_delay = 1;
238 balloon_stats.retry_count = 1;
239 return BP_ECANCELED;
240 }
241
242 balloon_stats.schedule_delay <<= 1;
243
244 if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
245 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
246
247 return BP_EAGAIN;
248}
249
250#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
251static struct resource *additional_memory_resource(phys_addr_t size)
252{
253 struct resource *res;
254 int ret;
255
256 res = kzalloc(sizeof(*res), GFP_KERNEL);
257 if (!res)
258 return NULL;
259
260 res->name = "System RAM";
261 res->flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
262
263 ret = allocate_resource(&iomem_resource, res,
264 size, 0, -1,
265 PAGES_PER_SECTION * PAGE_SIZE, NULL, NULL);
266 if (ret < 0) {
267 pr_err("Cannot allocate new System RAM resource\n");
268 kfree(res);
269 return NULL;
270 }
271
272#ifdef CONFIG_SPARSEMEM
273 {
274 unsigned long limit = 1UL << (MAX_PHYSMEM_BITS - PAGE_SHIFT);
275 unsigned long pfn = res->start >> PAGE_SHIFT;
276
277 if (pfn > limit) {
278 pr_err("New System RAM resource outside addressable RAM (%lu > %lu)\n",
279 pfn, limit);
280 release_memory_resource(res);
281 return NULL;
282 }
283 }
284#endif
285
286 return res;
287}
288
289static void release_memory_resource(struct resource *resource)
290{
291 if (!resource)
292 return;
293
294 /*
295 * No need to reset region to identity mapped since we now
296 * know that no I/O can be in this region
297 */
298 release_resource(resource);
299 kfree(resource);
300}
301
302static enum bp_state reserve_additional_memory(void)
303{
304 long credit;
305 struct resource *resource;
306 int nid, rc;
307 unsigned long balloon_hotplug;
308
309 credit = balloon_stats.target_pages + balloon_stats.target_unpopulated
310 - balloon_stats.total_pages;
311
312 /*
313 * Already hotplugged enough pages? Wait for them to be
314 * onlined.
315 */
316 if (credit <= 0)
317 return BP_WAIT;
318
319 balloon_hotplug = round_up(credit, PAGES_PER_SECTION);
320
321 resource = additional_memory_resource(balloon_hotplug * PAGE_SIZE);
322 if (!resource)
323 goto err;
324
325 nid = memory_add_physaddr_to_nid(resource->start);
326
327#ifdef CONFIG_XEN_HAVE_PVMMU
328 /*
329 * We don't support PV MMU when Linux and Xen is using
330 * different page granularity.
331 */
332 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
333
334 /*
335 * add_memory() will build page tables for the new memory so
336 * the p2m must contain invalid entries so the correct
337 * non-present PTEs will be written.
338 *
339 * If a failure occurs, the original (identity) p2m entries
340 * are not restored since this region is now known not to
341 * conflict with any devices.
342 */
343 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
344 unsigned long pfn, i;
345
346 pfn = PFN_DOWN(resource->start);
347 for (i = 0; i < balloon_hotplug; i++) {
348 if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
349 pr_warn("set_phys_to_machine() failed, no memory added\n");
350 goto err;
351 }
352 }
353 }
354#endif
355
356 /*
357 * add_memory_resource() will call online_pages() which in its turn
358 * will call xen_online_page() callback causing deadlock if we don't
359 * release balloon_mutex here. Unlocking here is safe because the
360 * callers drop the mutex before trying again.
361 */
362 mutex_unlock(&balloon_mutex);
363 rc = add_memory_resource(nid, resource, memhp_auto_online);
364 mutex_lock(&balloon_mutex);
365
366 if (rc) {
367 pr_warn("Cannot add additional memory (%i)\n", rc);
368 goto err;
369 }
370
371 balloon_stats.total_pages += balloon_hotplug;
372
373 return BP_WAIT;
374 err:
375 release_memory_resource(resource);
376 return BP_ECANCELED;
377}
378
379static void xen_online_page(struct page *page)
380{
381 __online_page_set_limits(page);
382
383 mutex_lock(&balloon_mutex);
384
385 __balloon_append(page);
386
387 mutex_unlock(&balloon_mutex);
388}
389
390static int xen_memory_notifier(struct notifier_block *nb, unsigned long val, void *v)
391{
392 if (val == MEM_ONLINE)
393 schedule_delayed_work(&balloon_worker, 0);
394
395 return NOTIFY_OK;
396}
397
398static struct notifier_block xen_memory_nb = {
399 .notifier_call = xen_memory_notifier,
400 .priority = 0
401};
402#else
403static enum bp_state reserve_additional_memory(void)
404{
405 balloon_stats.target_pages = balloon_stats.current_pages;
406 return BP_ECANCELED;
407}
408#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
409
410static long current_credit(void)
411{
412 return balloon_stats.target_pages - balloon_stats.current_pages;
413}
414
415static bool balloon_is_inflated(void)
416{
417 return balloon_stats.balloon_low || balloon_stats.balloon_high;
418}
419
420static enum bp_state increase_reservation(unsigned long nr_pages)
421{
422 int rc;
423 unsigned long i;
424 struct page *page;
425 struct xen_memory_reservation reservation = {
426 .address_bits = 0,
427 .extent_order = EXTENT_ORDER,
428 .domid = DOMID_SELF
429 };
430
431 if (nr_pages > ARRAY_SIZE(frame_list))
432 nr_pages = ARRAY_SIZE(frame_list);
433
434 page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
435 for (i = 0; i < nr_pages; i++) {
436 if (!page) {
437 nr_pages = i;
438 break;
439 }
440
441 /* XENMEM_populate_physmap requires a PFN based on Xen
442 * granularity.
443 */
444 frame_list[i] = page_to_xen_pfn(page);
445 page = balloon_next_page(page);
446 }
447
448 set_xen_guest_handle(reservation.extent_start, frame_list);
449 reservation.nr_extents = nr_pages;
450 rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
451 if (rc <= 0)
452 return BP_EAGAIN;
453
454 for (i = 0; i < rc; i++) {
455 page = balloon_retrieve(false);
456 BUG_ON(page == NULL);
457
458#ifdef CONFIG_XEN_HAVE_PVMMU
459 /*
460 * We don't support PV MMU when Linux and Xen is using
461 * different page granularity.
462 */
463 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
464
465 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
466 unsigned long pfn = page_to_pfn(page);
467
468 set_phys_to_machine(pfn, frame_list[i]);
469
470 /* Link back into the page tables if not highmem. */
471 if (!PageHighMem(page)) {
472 int ret;
473 ret = HYPERVISOR_update_va_mapping(
474 (unsigned long)__va(pfn << PAGE_SHIFT),
475 mfn_pte(frame_list[i], PAGE_KERNEL),
476 0);
477 BUG_ON(ret);
478 }
479 }
480#endif
481
482 /* Relinquish the page back to the allocator. */
483 __free_reserved_page(page);
484 }
485
486 balloon_stats.current_pages += rc;
487
488 return BP_DONE;
489}
490
491static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
492{
493 enum bp_state state = BP_DONE;
494 unsigned long i;
495 struct page *page, *tmp;
496 int ret;
497 struct xen_memory_reservation reservation = {
498 .address_bits = 0,
499 .extent_order = EXTENT_ORDER,
500 .domid = DOMID_SELF
501 };
502 LIST_HEAD(pages);
503
504 if (nr_pages > ARRAY_SIZE(frame_list))
505 nr_pages = ARRAY_SIZE(frame_list);
506
507 for (i = 0; i < nr_pages; i++) {
508 page = alloc_page(gfp);
509 if (page == NULL) {
510 nr_pages = i;
511 state = BP_EAGAIN;
512 break;
513 }
514 scrub_page(page);
515 list_add(&page->lru, &pages);
516 }
517
518 /*
519 * Ensure that ballooned highmem pages don't have kmaps.
520 *
521 * Do this before changing the p2m as kmap_flush_unused()
522 * reads PTEs to obtain pages (and hence needs the original
523 * p2m entry).
524 */
525 kmap_flush_unused();
526
527 /*
528 * Setup the frame, update direct mapping, invalidate P2M,
529 * and add to balloon.
530 */
531 i = 0;
532 list_for_each_entry_safe(page, tmp, &pages, lru) {
533 /* XENMEM_decrease_reservation requires a GFN */
534 frame_list[i++] = xen_page_to_gfn(page);
535
536#ifdef CONFIG_XEN_HAVE_PVMMU
537 /*
538 * We don't support PV MMU when Linux and Xen is using
539 * different page granularity.
540 */
541 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
542
543 if (!xen_feature(XENFEAT_auto_translated_physmap)) {
544 unsigned long pfn = page_to_pfn(page);
545
546 if (!PageHighMem(page)) {
547 ret = HYPERVISOR_update_va_mapping(
548 (unsigned long)__va(pfn << PAGE_SHIFT),
549 __pte_ma(0), 0);
550 BUG_ON(ret);
551 }
552 __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
553 }
554#endif
555 list_del(&page->lru);
556
557 balloon_append(page);
558 }
559
560 flush_tlb_all();
561
562 set_xen_guest_handle(reservation.extent_start, frame_list);
563 reservation.nr_extents = nr_pages;
564 ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
565 BUG_ON(ret != nr_pages);
566
567 balloon_stats.current_pages -= nr_pages;
568
569 return state;
570}
571
572/*
573 * As this is a work item it is guaranteed to run as a single instance only.
574 * We may of course race updates of the target counts (which are protected
575 * by the balloon lock), or with changes to the Xen hard limit, but we will
576 * recover from these in time.
577 */
578static void balloon_process(struct work_struct *work)
579{
580 enum bp_state state = BP_DONE;
581 long credit;
582
583
584 do {
585 mutex_lock(&balloon_mutex);
586
587 credit = current_credit();
588
589 if (credit > 0) {
590 if (balloon_is_inflated())
591 state = increase_reservation(credit);
592 else
593 state = reserve_additional_memory();
594 }
595
596 if (credit < 0)
597 state = decrease_reservation(-credit, GFP_BALLOON);
598
599 state = update_schedule(state);
600
601 mutex_unlock(&balloon_mutex);
602
603 cond_resched();
604
605 } while (credit && state == BP_DONE);
606
607 /* Schedule more work if there is some still to be done. */
608 if (state == BP_EAGAIN)
609 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
610}
611
612/* Resets the Xen limit, sets new target, and kicks off processing. */
613void balloon_set_new_target(unsigned long target)
614{
615 /* No need for lock. Not read-modify-write updates. */
616 balloon_stats.target_pages = target;
617 schedule_delayed_work(&balloon_worker, 0);
618}
619EXPORT_SYMBOL_GPL(balloon_set_new_target);
620
621static int add_ballooned_pages(int nr_pages)
622{
623 enum bp_state st;
624
625 if (xen_hotplug_unpopulated) {
626 st = reserve_additional_memory();
627 if (st != BP_ECANCELED) {
628 mutex_unlock(&balloon_mutex);
629 wait_event(balloon_wq,
630 !list_empty(&ballooned_pages));
631 mutex_lock(&balloon_mutex);
632 return 0;
633 }
634 }
635
636 st = decrease_reservation(nr_pages, GFP_USER);
637 if (st != BP_DONE)
638 return -ENOMEM;
639
640 return 0;
641}
642
643/**
644 * alloc_xenballooned_pages - get pages that have been ballooned out
645 * @nr_pages: Number of pages to get
646 * @pages: pages returned
647 * @return 0 on success, error otherwise
648 */
649int alloc_xenballooned_pages(int nr_pages, struct page **pages)
650{
651 int pgno = 0;
652 struct page *page;
653 int ret;
654
655 mutex_lock(&balloon_mutex);
656
657 balloon_stats.target_unpopulated += nr_pages;
658
659 while (pgno < nr_pages) {
660 page = balloon_retrieve(true);
661 if (page) {
662 pages[pgno++] = page;
663#ifdef CONFIG_XEN_HAVE_PVMMU
664 /*
665 * We don't support PV MMU when Linux and Xen is using
666 * different page granularity.
667 */
668 BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
669
670 ret = xen_alloc_p2m_entry(page_to_pfn(page));
671 if (ret < 0)
672 goto out_undo;
673#endif
674 } else {
675 ret = add_ballooned_pages(nr_pages - pgno);
676 if (ret < 0)
677 goto out_undo;
678 }
679 }
680 mutex_unlock(&balloon_mutex);
681 return 0;
682 out_undo:
683 mutex_unlock(&balloon_mutex);
684 free_xenballooned_pages(pgno, pages);
685 return ret;
686}
687EXPORT_SYMBOL(alloc_xenballooned_pages);
688
689/**
690 * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
691 * @nr_pages: Number of pages
692 * @pages: pages to return
693 */
694void free_xenballooned_pages(int nr_pages, struct page **pages)
695{
696 int i;
697
698 mutex_lock(&balloon_mutex);
699
700 for (i = 0; i < nr_pages; i++) {
701 if (pages[i])
702 balloon_append(pages[i]);
703 }
704
705 balloon_stats.target_unpopulated -= nr_pages;
706
707 /* The balloon may be too large now. Shrink it if needed. */
708 if (current_credit())
709 schedule_delayed_work(&balloon_worker, 0);
710
711 mutex_unlock(&balloon_mutex);
712}
713EXPORT_SYMBOL(free_xenballooned_pages);
714
715static void __init balloon_add_region(unsigned long start_pfn,
716 unsigned long pages)
717{
718 unsigned long pfn, extra_pfn_end;
719 struct page *page;
720
721 /*
722 * If the amount of usable memory has been limited (e.g., with
723 * the 'mem' command line parameter), don't add pages beyond
724 * this limit.
725 */
726 extra_pfn_end = min(max_pfn, start_pfn + pages);
727
728 for (pfn = start_pfn; pfn < extra_pfn_end; pfn++) {
729 page = pfn_to_page(pfn);
730 /* totalram_pages and totalhigh_pages do not
731 include the boot-time balloon extension, so
732 don't subtract from it. */
733 __balloon_append(page);
734 }
735
736 balloon_stats.total_pages += extra_pfn_end - start_pfn;
737}
738
739static int __init balloon_init(void)
740{
741 int i;
742
743 if (!xen_domain())
744 return -ENODEV;
745
746 pr_info("Initialising balloon driver\n");
747
748 balloon_stats.current_pages = xen_pv_domain()
749 ? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
750 : get_num_physpages();
751 balloon_stats.target_pages = balloon_stats.current_pages;
752 balloon_stats.balloon_low = 0;
753 balloon_stats.balloon_high = 0;
754 balloon_stats.total_pages = balloon_stats.current_pages;
755
756 balloon_stats.schedule_delay = 1;
757 balloon_stats.max_schedule_delay = 32;
758 balloon_stats.retry_count = 1;
759 balloon_stats.max_retry_count = RETRY_UNLIMITED;
760
761#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
762 set_online_page_callback(&xen_online_page);
763 register_memory_notifier(&xen_memory_nb);
764 register_sysctl_table(xen_root);
765#endif
766
767 /*
768 * Initialize the balloon with pages from the extra memory
769 * regions (see arch/x86/xen/setup.c).
770 */
771 for (i = 0; i < XEN_EXTRA_MEM_MAX_REGIONS; i++)
772 if (xen_extra_mem[i].n_pfns)
773 balloon_add_region(xen_extra_mem[i].start_pfn,
774 xen_extra_mem[i].n_pfns);
775
776 return 0;
777}
778subsys_initcall(balloon_init);