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1775826c | 1 | /****************************************************************************** |
1775826c JF |
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 | * | |
8 | * This program is free software; you can redistribute it and/or | |
9 | * modify it under the terms of the GNU General Public License version 2 | |
10 | * as published by the Free Software Foundation; or, when distributed | |
11 | * separately from the Linux kernel or incorporated into other | |
12 | * software packages, subject to the following license: | |
13 | * | |
14 | * Permission is hereby granted, free of charge, to any person obtaining a copy | |
15 | * of this source file (the "Software"), to deal in the Software without | |
16 | * restriction, including without limitation the rights to use, copy, modify, | |
17 | * merge, publish, distribute, sublicense, and/or sell copies of the Software, | |
18 | * and to permit persons to whom the Software is furnished to do so, subject to | |
19 | * the following conditions: | |
20 | * | |
21 | * The above copyright notice and this permission notice shall be included in | |
22 | * all copies or substantial portions of the Software. | |
23 | * | |
24 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
25 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
26 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
27 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
28 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING | |
29 | * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS | |
30 | * IN THE SOFTWARE. | |
31 | */ | |
32 | ||
33 | #include <linux/kernel.h> | |
1775826c JF |
34 | #include <linux/sched.h> |
35 | #include <linux/errno.h> | |
36 | #include <linux/mm.h> | |
37 | #include <linux/bootmem.h> | |
38 | #include <linux/pagemap.h> | |
39 | #include <linux/highmem.h> | |
40 | #include <linux/mutex.h> | |
1775826c | 41 | #include <linux/list.h> |
5a0e3ad6 | 42 | #include <linux/gfp.h> |
1775826c | 43 | |
1775826c JF |
44 | #include <asm/page.h> |
45 | #include <asm/pgalloc.h> | |
46 | #include <asm/pgtable.h> | |
1775826c | 47 | #include <asm/tlb.h> |
66946f67 | 48 | #include <asm/e820.h> |
1775826c | 49 | |
ecbf29cd JF |
50 | #include <asm/xen/hypervisor.h> |
51 | #include <asm/xen/hypercall.h> | |
1ccbf534 JF |
52 | |
53 | #include <xen/xen.h> | |
ecbf29cd | 54 | #include <xen/interface/xen.h> |
1775826c | 55 | #include <xen/interface/memory.h> |
803eb047 | 56 | #include <xen/balloon.h> |
1775826c JF |
57 | #include <xen/features.h> |
58 | #include <xen/page.h> | |
59 | ||
95d2ac4a DK |
60 | /* |
61 | * balloon_process() state: | |
62 | * | |
63 | * BP_DONE: done or nothing to do, | |
64 | * BP_EAGAIN: error, go to sleep, | |
65 | * BP_ECANCELED: error, balloon operation canceled. | |
66 | */ | |
1775826c | 67 | |
95d2ac4a DK |
68 | enum bp_state { |
69 | BP_DONE, | |
70 | BP_EAGAIN, | |
71 | BP_ECANCELED | |
1775826c JF |
72 | }; |
73 | ||
1775826c | 74 | |
1775826c | 75 | static DEFINE_MUTEX(balloon_mutex); |
1775826c | 76 | |
803eb047 DDG |
77 | struct balloon_stats balloon_stats; |
78 | EXPORT_SYMBOL_GPL(balloon_stats); | |
1775826c JF |
79 | |
80 | /* We increase/decrease in batches which fit in a page */ | |
81 | static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)]; | |
82 | ||
1775826c | 83 | #ifdef CONFIG_HIGHMEM |
1775826c JF |
84 | #define inc_totalhigh_pages() (totalhigh_pages++) |
85 | #define dec_totalhigh_pages() (totalhigh_pages--) | |
86 | #else | |
87 | #define inc_totalhigh_pages() do {} while(0) | |
88 | #define dec_totalhigh_pages() do {} while(0) | |
89 | #endif | |
90 | ||
91 | /* List of ballooned pages, threaded through the mem_map array. */ | |
92 | static LIST_HEAD(ballooned_pages); | |
93 | ||
94 | /* Main work function, always executed in process context. */ | |
95 | static void balloon_process(struct work_struct *work); | |
95170b2e | 96 | static DECLARE_DELAYED_WORK(balloon_worker, balloon_process); |
1775826c JF |
97 | |
98 | /* When ballooning out (allocating memory to return to Xen) we don't really | |
99 | want the kernel to try too hard since that can trigger the oom killer. */ | |
100 | #define GFP_BALLOON \ | |
101 | (GFP_HIGHUSER | __GFP_NOWARN | __GFP_NORETRY | __GFP_NOMEMALLOC) | |
102 | ||
103 | static void scrub_page(struct page *page) | |
104 | { | |
105 | #ifdef CONFIG_XEN_SCRUB_PAGES | |
26a3e991 | 106 | clear_highpage(page); |
1775826c JF |
107 | #endif |
108 | } | |
109 | ||
110 | /* balloon_append: add the given page to the balloon. */ | |
9be4d457 | 111 | static void __balloon_append(struct page *page) |
1775826c JF |
112 | { |
113 | /* Lowmem is re-populated first, so highmem pages go at list tail. */ | |
114 | if (PageHighMem(page)) { | |
115 | list_add_tail(&page->lru, &ballooned_pages); | |
116 | balloon_stats.balloon_high++; | |
1775826c JF |
117 | } else { |
118 | list_add(&page->lru, &ballooned_pages); | |
119 | balloon_stats.balloon_low++; | |
120 | } | |
9be4d457 | 121 | } |
3d65c948 | 122 | |
9be4d457 JF |
123 | static void balloon_append(struct page *page) |
124 | { | |
125 | __balloon_append(page); | |
09ca132a DK |
126 | if (PageHighMem(page)) |
127 | dec_totalhigh_pages(); | |
3d65c948 | 128 | totalram_pages--; |
1775826c JF |
129 | } |
130 | ||
131 | /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */ | |
b6f30679 | 132 | static struct page *balloon_retrieve(bool prefer_highmem) |
1775826c JF |
133 | { |
134 | struct page *page; | |
135 | ||
136 | if (list_empty(&ballooned_pages)) | |
137 | return NULL; | |
138 | ||
b6f30679 KRW |
139 | if (prefer_highmem) |
140 | page = list_entry(ballooned_pages.prev, struct page, lru); | |
141 | else | |
142 | page = list_entry(ballooned_pages.next, struct page, lru); | |
1775826c JF |
143 | list_del(&page->lru); |
144 | ||
145 | if (PageHighMem(page)) { | |
146 | balloon_stats.balloon_high--; | |
147 | inc_totalhigh_pages(); | |
148 | } | |
149 | else | |
150 | balloon_stats.balloon_low--; | |
151 | ||
3d65c948 GG |
152 | totalram_pages++; |
153 | ||
1775826c JF |
154 | return page; |
155 | } | |
156 | ||
157 | static struct page *balloon_first_page(void) | |
158 | { | |
159 | if (list_empty(&ballooned_pages)) | |
160 | return NULL; | |
161 | return list_entry(ballooned_pages.next, struct page, lru); | |
162 | } | |
163 | ||
164 | static struct page *balloon_next_page(struct page *page) | |
165 | { | |
166 | struct list_head *next = page->lru.next; | |
167 | if (next == &ballooned_pages) | |
168 | return NULL; | |
169 | return list_entry(next, struct page, lru); | |
170 | } | |
171 | ||
95d2ac4a | 172 | static enum bp_state update_schedule(enum bp_state state) |
1775826c | 173 | { |
95d2ac4a DK |
174 | if (state == BP_DONE) { |
175 | balloon_stats.schedule_delay = 1; | |
176 | balloon_stats.retry_count = 1; | |
177 | return BP_DONE; | |
178 | } | |
179 | ||
95d2ac4a DK |
180 | ++balloon_stats.retry_count; |
181 | ||
182 | if (balloon_stats.max_retry_count != RETRY_UNLIMITED && | |
183 | balloon_stats.retry_count > balloon_stats.max_retry_count) { | |
95d2ac4a DK |
184 | balloon_stats.schedule_delay = 1; |
185 | balloon_stats.retry_count = 1; | |
186 | return BP_ECANCELED; | |
187 | } | |
188 | ||
189 | balloon_stats.schedule_delay <<= 1; | |
190 | ||
191 | if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay) | |
192 | balloon_stats.schedule_delay = balloon_stats.max_schedule_delay; | |
193 | ||
194 | return BP_EAGAIN; | |
1775826c JF |
195 | } |
196 | ||
83be7e52 | 197 | static long current_credit(void) |
1775826c | 198 | { |
bc2c0303 | 199 | unsigned long target = balloon_stats.target_pages; |
1775826c JF |
200 | |
201 | target = min(target, | |
202 | balloon_stats.current_pages + | |
203 | balloon_stats.balloon_low + | |
204 | balloon_stats.balloon_high); | |
205 | ||
83be7e52 | 206 | return target - balloon_stats.current_pages; |
1775826c JF |
207 | } |
208 | ||
95d2ac4a | 209 | static enum bp_state increase_reservation(unsigned long nr_pages) |
1775826c | 210 | { |
95d2ac4a | 211 | int rc; |
2f70e0ac | 212 | unsigned long pfn, i; |
1775826c | 213 | struct page *page; |
1775826c JF |
214 | struct xen_memory_reservation reservation = { |
215 | .address_bits = 0, | |
216 | .extent_order = 0, | |
217 | .domid = DOMID_SELF | |
218 | }; | |
219 | ||
220 | if (nr_pages > ARRAY_SIZE(frame_list)) | |
221 | nr_pages = ARRAY_SIZE(frame_list); | |
222 | ||
1775826c JF |
223 | page = balloon_first_page(); |
224 | for (i = 0; i < nr_pages; i++) { | |
95d2ac4a DK |
225 | if (!page) { |
226 | nr_pages = i; | |
227 | break; | |
228 | } | |
a419aef8 | 229 | frame_list[i] = page_to_pfn(page); |
1775826c JF |
230 | page = balloon_next_page(page); |
231 | } | |
232 | ||
a90971eb | 233 | set_xen_guest_handle(reservation.extent_start, frame_list); |
fde28e8f JF |
234 | reservation.nr_extents = nr_pages; |
235 | rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation); | |
40095de1 | 236 | if (rc <= 0) |
95d2ac4a | 237 | return BP_EAGAIN; |
1775826c | 238 | |
bc2c0303 | 239 | for (i = 0; i < rc; i++) { |
b6f30679 | 240 | page = balloon_retrieve(false); |
1775826c JF |
241 | BUG_ON(page == NULL); |
242 | ||
243 | pfn = page_to_pfn(page); | |
244 | BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) && | |
245 | phys_to_machine_mapping_valid(pfn)); | |
246 | ||
247 | set_phys_to_machine(pfn, frame_list[i]); | |
248 | ||
249 | /* Link back into the page tables if not highmem. */ | |
4dfe22f5 | 250 | if (xen_pv_domain() && !PageHighMem(page)) { |
1775826c JF |
251 | int ret; |
252 | ret = HYPERVISOR_update_va_mapping( | |
253 | (unsigned long)__va(pfn << PAGE_SHIFT), | |
254 | mfn_pte(frame_list[i], PAGE_KERNEL), | |
255 | 0); | |
256 | BUG_ON(ret); | |
257 | } | |
258 | ||
259 | /* Relinquish the page back to the allocator. */ | |
260 | ClearPageReserved(page); | |
261 | init_page_count(page); | |
262 | __free_page(page); | |
263 | } | |
264 | ||
bc2c0303 | 265 | balloon_stats.current_pages += rc; |
1775826c | 266 | |
95d2ac4a | 267 | return BP_DONE; |
1775826c JF |
268 | } |
269 | ||
b6f30679 | 270 | static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) |
1775826c | 271 | { |
95d2ac4a | 272 | enum bp_state state = BP_DONE; |
2f70e0ac | 273 | unsigned long pfn, i; |
1775826c | 274 | struct page *page; |
1775826c JF |
275 | int ret; |
276 | struct xen_memory_reservation reservation = { | |
277 | .address_bits = 0, | |
278 | .extent_order = 0, | |
279 | .domid = DOMID_SELF | |
280 | }; | |
281 | ||
282 | if (nr_pages > ARRAY_SIZE(frame_list)) | |
283 | nr_pages = ARRAY_SIZE(frame_list); | |
284 | ||
285 | for (i = 0; i < nr_pages; i++) { | |
b6f30679 | 286 | if ((page = alloc_page(gfp)) == NULL) { |
1775826c | 287 | nr_pages = i; |
95d2ac4a | 288 | state = BP_EAGAIN; |
1775826c JF |
289 | break; |
290 | } | |
291 | ||
292 | pfn = page_to_pfn(page); | |
293 | frame_list[i] = pfn_to_mfn(pfn); | |
294 | ||
295 | scrub_page(page); | |
1058a75f | 296 | |
4dfe22f5 | 297 | if (xen_pv_domain() && !PageHighMem(page)) { |
ff4ce8c3 IC |
298 | ret = HYPERVISOR_update_va_mapping( |
299 | (unsigned long)__va(pfn << PAGE_SHIFT), | |
300 | __pte_ma(0), 0); | |
301 | BUG_ON(ret); | |
302 | } | |
303 | ||
1775826c JF |
304 | } |
305 | ||
306 | /* Ensure that ballooned highmem pages don't have kmaps. */ | |
307 | kmap_flush_unused(); | |
308 | flush_tlb_all(); | |
309 | ||
1775826c JF |
310 | /* No more mappings: invalidate P2M and add to balloon. */ |
311 | for (i = 0; i < nr_pages; i++) { | |
312 | pfn = mfn_to_pfn(frame_list[i]); | |
6eaa412f | 313 | __set_phys_to_machine(pfn, INVALID_P2M_ENTRY); |
1775826c JF |
314 | balloon_append(pfn_to_page(pfn)); |
315 | } | |
316 | ||
a90971eb | 317 | set_xen_guest_handle(reservation.extent_start, frame_list); |
1775826c JF |
318 | reservation.nr_extents = nr_pages; |
319 | ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); | |
320 | BUG_ON(ret != nr_pages); | |
321 | ||
322 | balloon_stats.current_pages -= nr_pages; | |
1775826c | 323 | |
95d2ac4a | 324 | return state; |
1775826c JF |
325 | } |
326 | ||
327 | /* | |
328 | * We avoid multiple worker processes conflicting via the balloon mutex. | |
329 | * We may of course race updates of the target counts (which are protected | |
330 | * by the balloon lock), or with changes to the Xen hard limit, but we will | |
331 | * recover from these in time. | |
332 | */ | |
333 | static void balloon_process(struct work_struct *work) | |
334 | { | |
95d2ac4a | 335 | enum bp_state state = BP_DONE; |
1775826c JF |
336 | long credit; |
337 | ||
338 | mutex_lock(&balloon_mutex); | |
339 | ||
340 | do { | |
83be7e52 | 341 | credit = current_credit(); |
95d2ac4a | 342 | |
1775826c | 343 | if (credit > 0) |
95d2ac4a DK |
344 | state = increase_reservation(credit); |
345 | ||
1775826c | 346 | if (credit < 0) |
b6f30679 | 347 | state = decrease_reservation(-credit, GFP_BALLOON); |
95d2ac4a DK |
348 | |
349 | state = update_schedule(state); | |
1775826c JF |
350 | |
351 | #ifndef CONFIG_PREEMPT | |
352 | if (need_resched()) | |
353 | schedule(); | |
354 | #endif | |
95d2ac4a | 355 | } while (credit && state == BP_DONE); |
1775826c JF |
356 | |
357 | /* Schedule more work if there is some still to be done. */ | |
95d2ac4a DK |
358 | if (state == BP_EAGAIN) |
359 | schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ); | |
1775826c JF |
360 | |
361 | mutex_unlock(&balloon_mutex); | |
362 | } | |
363 | ||
364 | /* Resets the Xen limit, sets new target, and kicks off processing. */ | |
803eb047 | 365 | void balloon_set_new_target(unsigned long target) |
1775826c JF |
366 | { |
367 | /* No need for lock. Not read-modify-write updates. */ | |
1775826c | 368 | balloon_stats.target_pages = target; |
95170b2e | 369 | schedule_delayed_work(&balloon_worker, 0); |
1775826c | 370 | } |
803eb047 | 371 | EXPORT_SYMBOL_GPL(balloon_set_new_target); |
1775826c | 372 | |
b6f30679 KRW |
373 | /** |
374 | * alloc_xenballooned_pages - get pages that have been ballooned out | |
375 | * @nr_pages: Number of pages to get | |
376 | * @pages: pages returned | |
377 | * @return 0 on success, error otherwise | |
378 | */ | |
379 | int alloc_xenballooned_pages(int nr_pages, struct page** pages) | |
1775826c | 380 | { |
b6f30679 KRW |
381 | int pgno = 0; |
382 | struct page* page; | |
383 | mutex_lock(&balloon_mutex); | |
384 | while (pgno < nr_pages) { | |
385 | page = balloon_retrieve(true); | |
386 | if (page) { | |
387 | pages[pgno++] = page; | |
388 | } else { | |
389 | enum bp_state st; | |
390 | st = decrease_reservation(nr_pages - pgno, GFP_HIGHUSER); | |
391 | if (st != BP_DONE) | |
392 | goto out_undo; | |
393 | } | |
1775826c | 394 | } |
b6f30679 KRW |
395 | mutex_unlock(&balloon_mutex); |
396 | return 0; | |
397 | out_undo: | |
398 | while (pgno) | |
399 | balloon_append(pages[--pgno]); | |
400 | /* Free the memory back to the kernel soon */ | |
401 | schedule_delayed_work(&balloon_worker, 0); | |
402 | mutex_unlock(&balloon_mutex); | |
403 | return -ENOMEM; | |
1775826c | 404 | } |
b6f30679 | 405 | EXPORT_SYMBOL(alloc_xenballooned_pages); |
1775826c | 406 | |
b6f30679 KRW |
407 | /** |
408 | * free_xenballooned_pages - return pages retrieved with get_ballooned_pages | |
409 | * @nr_pages: Number of pages | |
410 | * @pages: pages to return | |
411 | */ | |
412 | void free_xenballooned_pages(int nr_pages, struct page** pages) | |
1775826c | 413 | { |
b6f30679 | 414 | int i; |
1775826c | 415 | |
b6f30679 | 416 | mutex_lock(&balloon_mutex); |
1775826c | 417 | |
b6f30679 KRW |
418 | for (i = 0; i < nr_pages; i++) { |
419 | if (pages[i]) | |
420 | balloon_append(pages[i]); | |
421 | } | |
422 | ||
423 | /* The balloon may be too large now. Shrink it if needed. */ | |
83be7e52 | 424 | if (current_credit()) |
b6f30679 | 425 | schedule_delayed_work(&balloon_worker, 0); |
1775826c | 426 | |
b6f30679 KRW |
427 | mutex_unlock(&balloon_mutex); |
428 | } | |
429 | EXPORT_SYMBOL(free_xenballooned_pages); | |
1775826c JF |
430 | |
431 | static int __init balloon_init(void) | |
432 | { | |
4dfe22f5 | 433 | unsigned long pfn, extra_pfn_end; |
1775826c JF |
434 | struct page *page; |
435 | ||
53d5522c | 436 | if (!xen_domain()) |
1775826c JF |
437 | return -ENODEV; |
438 | ||
803eb047 | 439 | pr_info("xen/balloon: Initialising balloon driver.\n"); |
1775826c | 440 | |
4dfe22f5 | 441 | balloon_stats.current_pages = xen_pv_domain() ? min(xen_start_info->nr_pages, max_pfn) : max_pfn; |
1775826c JF |
442 | balloon_stats.target_pages = balloon_stats.current_pages; |
443 | balloon_stats.balloon_low = 0; | |
444 | balloon_stats.balloon_high = 0; | |
1775826c | 445 | |
95d2ac4a DK |
446 | balloon_stats.schedule_delay = 1; |
447 | balloon_stats.max_schedule_delay = 32; | |
448 | balloon_stats.retry_count = 1; | |
40095de1 | 449 | balloon_stats.max_retry_count = RETRY_UNLIMITED; |
1775826c | 450 | |
2a4c92fa JF |
451 | /* |
452 | * Initialise the balloon with excess memory space. We need | |
453 | * to make sure we don't add memory which doesn't exist or | |
454 | * logically exist. The E820 map can be trimmed to be smaller | |
455 | * than the amount of physical memory due to the mem= command | |
456 | * line parameter. And if this is a 32-bit non-HIGHMEM kernel | |
457 | * on a system with memory which requires highmem to access, | |
458 | * don't try to use it. | |
459 | */ | |
460 | extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()), | |
66946f67 | 461 | (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size)); |
9be4d457 | 462 | for (pfn = PFN_UP(xen_extra_mem_start); |
66946f67 | 463 | pfn < extra_pfn_end; |
9be4d457 | 464 | pfn++) { |
1775826c | 465 | page = pfn_to_page(pfn); |
09ca132a | 466 | /* totalram_pages and totalhigh_pages do not include the boot-time |
9be4d457 JF |
467 | balloon extension, so don't subtract from it. */ |
468 | __balloon_append(page); | |
1775826c JF |
469 | } |
470 | ||
1775826c JF |
471 | return 0; |
472 | } | |
473 | ||
474 | subsys_initcall(balloon_init); | |
475 | ||
1775826c | 476 | MODULE_LICENSE("GPL"); |