Merge branches 'stable/hvc-console', 'stable/gntalloc.v6' and 'stable/balloon' of...
[linux-2.6.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  *
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>
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>
41 #include <linux/list.h>
42 #include <linux/gfp.h>
43
44 #include <asm/page.h>
45 #include <asm/pgalloc.h>
46 #include <asm/pgtable.h>
47 #include <asm/tlb.h>
48 #include <asm/e820.h>
49
50 #include <asm/xen/hypervisor.h>
51 #include <asm/xen/hypercall.h>
52
53 #include <xen/xen.h>
54 #include <xen/interface/xen.h>
55 #include <xen/interface/memory.h>
56 #include <xen/balloon.h>
57 #include <xen/features.h>
58 #include <xen/page.h>
59
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  */
67
68 enum bp_state {
69         BP_DONE,
70         BP_EAGAIN,
71         BP_ECANCELED
72 };
73
74
75 static DEFINE_MUTEX(balloon_mutex);
76
77 struct balloon_stats balloon_stats;
78 EXPORT_SYMBOL_GPL(balloon_stats);
79
80 /* We increase/decrease in batches which fit in a page */
81 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
82
83 #ifdef CONFIG_HIGHMEM
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);
96 static DECLARE_DELAYED_WORK(balloon_worker, balloon_process);
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
106         clear_highpage(page);
107 #endif
108 }
109
110 /* balloon_append: add the given page to the balloon. */
111 static void __balloon_append(struct page *page)
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++;
117                 dec_totalhigh_pages();
118         } else {
119                 list_add(&page->lru, &ballooned_pages);
120                 balloon_stats.balloon_low++;
121         }
122 }
123
124 static void balloon_append(struct page *page)
125 {
126         __balloon_append(page);
127         totalram_pages--;
128 }
129
130 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
131 static struct page *balloon_retrieve(bool prefer_highmem)
132 {
133         struct page *page;
134
135         if (list_empty(&ballooned_pages))
136                 return NULL;
137
138         if (prefer_highmem)
139                 page = list_entry(ballooned_pages.prev, struct page, lru);
140         else
141                 page = list_entry(ballooned_pages.next, struct page, lru);
142         list_del(&page->lru);
143
144         if (PageHighMem(page)) {
145                 balloon_stats.balloon_high--;
146                 inc_totalhigh_pages();
147         }
148         else
149                 balloon_stats.balloon_low--;
150
151         totalram_pages++;
152
153         return page;
154 }
155
156 static struct page *balloon_first_page(void)
157 {
158         if (list_empty(&ballooned_pages))
159                 return NULL;
160         return list_entry(ballooned_pages.next, struct page, lru);
161 }
162
163 static struct page *balloon_next_page(struct page *page)
164 {
165         struct list_head *next = page->lru.next;
166         if (next == &ballooned_pages)
167                 return NULL;
168         return list_entry(next, struct page, lru);
169 }
170
171 static enum bp_state update_schedule(enum bp_state state)
172 {
173         if (state == BP_DONE) {
174                 balloon_stats.schedule_delay = 1;
175                 balloon_stats.retry_count = 1;
176                 return BP_DONE;
177         }
178
179         ++balloon_stats.retry_count;
180
181         if (balloon_stats.max_retry_count != RETRY_UNLIMITED &&
182                         balloon_stats.retry_count > balloon_stats.max_retry_count) {
183                 balloon_stats.schedule_delay = 1;
184                 balloon_stats.retry_count = 1;
185                 return BP_ECANCELED;
186         }
187
188         balloon_stats.schedule_delay <<= 1;
189
190         if (balloon_stats.schedule_delay > balloon_stats.max_schedule_delay)
191                 balloon_stats.schedule_delay = balloon_stats.max_schedule_delay;
192
193         return BP_EAGAIN;
194 }
195
196 static unsigned long current_target(void)
197 {
198         unsigned long target = balloon_stats.target_pages;
199
200         target = min(target,
201                      balloon_stats.current_pages +
202                      balloon_stats.balloon_low +
203                      balloon_stats.balloon_high);
204
205         return target;
206 }
207
208 static enum bp_state increase_reservation(unsigned long nr_pages)
209 {
210         int rc;
211         unsigned long  pfn, i;
212         struct page   *page;
213         struct xen_memory_reservation reservation = {
214                 .address_bits = 0,
215                 .extent_order = 0,
216                 .domid        = DOMID_SELF
217         };
218
219         if (nr_pages > ARRAY_SIZE(frame_list))
220                 nr_pages = ARRAY_SIZE(frame_list);
221
222         page = balloon_first_page();
223         for (i = 0; i < nr_pages; i++) {
224                 if (!page) {
225                         nr_pages = i;
226                         break;
227                 }
228                 frame_list[i] = page_to_pfn(page);
229                 page = balloon_next_page(page);
230         }
231
232         set_xen_guest_handle(reservation.extent_start, frame_list);
233         reservation.nr_extents = nr_pages;
234         rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
235         if (rc <= 0)
236                 return BP_EAGAIN;
237
238         for (i = 0; i < rc; i++) {
239                 page = balloon_retrieve(false);
240                 BUG_ON(page == NULL);
241
242                 pfn = page_to_pfn(page);
243                 BUG_ON(!xen_feature(XENFEAT_auto_translated_physmap) &&
244                        phys_to_machine_mapping_valid(pfn));
245
246                 set_phys_to_machine(pfn, frame_list[i]);
247
248                 /* Link back into the page tables if not highmem. */
249                 if (!xen_hvm_domain() && pfn < max_low_pfn) {
250                         int ret;
251                         ret = HYPERVISOR_update_va_mapping(
252                                 (unsigned long)__va(pfn << PAGE_SHIFT),
253                                 mfn_pte(frame_list[i], PAGE_KERNEL),
254                                 0);
255                         BUG_ON(ret);
256                 }
257
258                 /* Relinquish the page back to the allocator. */
259                 ClearPageReserved(page);
260                 init_page_count(page);
261                 __free_page(page);
262         }
263
264         balloon_stats.current_pages += rc;
265
266         return BP_DONE;
267 }
268
269 static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
270 {
271         enum bp_state state = BP_DONE;
272         unsigned long  pfn, i;
273         struct page   *page;
274         int ret;
275         struct xen_memory_reservation reservation = {
276                 .address_bits = 0,
277                 .extent_order = 0,
278                 .domid        = DOMID_SELF
279         };
280
281         if (nr_pages > ARRAY_SIZE(frame_list))
282                 nr_pages = ARRAY_SIZE(frame_list);
283
284         for (i = 0; i < nr_pages; i++) {
285                 if ((page = alloc_page(gfp)) == NULL) {
286                         nr_pages = i;
287                         state = BP_EAGAIN;
288                         break;
289                 }
290
291                 pfn = page_to_pfn(page);
292                 frame_list[i] = pfn_to_mfn(pfn);
293
294                 scrub_page(page);
295
296                 if (!xen_hvm_domain() && !PageHighMem(page)) {
297                         ret = HYPERVISOR_update_va_mapping(
298                                 (unsigned long)__va(pfn << PAGE_SHIFT),
299                                 __pte_ma(0), 0);
300                         BUG_ON(ret);
301                 }
302
303         }
304
305         /* Ensure that ballooned highmem pages don't have kmaps. */
306         kmap_flush_unused();
307         flush_tlb_all();
308
309         /* No more mappings: invalidate P2M and add to balloon. */
310         for (i = 0; i < nr_pages; i++) {
311                 pfn = mfn_to_pfn(frame_list[i]);
312                 __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
313                 balloon_append(pfn_to_page(pfn));
314         }
315
316         set_xen_guest_handle(reservation.extent_start, frame_list);
317         reservation.nr_extents   = nr_pages;
318         ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
319         BUG_ON(ret != nr_pages);
320
321         balloon_stats.current_pages -= nr_pages;
322
323         return state;
324 }
325
326 /*
327  * We avoid multiple worker processes conflicting via the balloon mutex.
328  * We may of course race updates of the target counts (which are protected
329  * by the balloon lock), or with changes to the Xen hard limit, but we will
330  * recover from these in time.
331  */
332 static void balloon_process(struct work_struct *work)
333 {
334         enum bp_state state = BP_DONE;
335         long credit;
336
337         mutex_lock(&balloon_mutex);
338
339         do {
340                 credit = current_target() - balloon_stats.current_pages;
341
342                 if (credit > 0)
343                         state = increase_reservation(credit);
344
345                 if (credit < 0)
346                         state = decrease_reservation(-credit, GFP_BALLOON);
347
348                 state = update_schedule(state);
349
350 #ifndef CONFIG_PREEMPT
351                 if (need_resched())
352                         schedule();
353 #endif
354         } while (credit && state == BP_DONE);
355
356         /* Schedule more work if there is some still to be done. */
357         if (state == BP_EAGAIN)
358                 schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ);
359
360         mutex_unlock(&balloon_mutex);
361 }
362
363 /* Resets the Xen limit, sets new target, and kicks off processing. */
364 void balloon_set_new_target(unsigned long target)
365 {
366         /* No need for lock. Not read-modify-write updates. */
367         balloon_stats.target_pages = target;
368         schedule_delayed_work(&balloon_worker, 0);
369 }
370 EXPORT_SYMBOL_GPL(balloon_set_new_target);
371
372 /**
373  * alloc_xenballooned_pages - get pages that have been ballooned out
374  * @nr_pages: Number of pages to get
375  * @pages: pages returned
376  * @return 0 on success, error otherwise
377  */
378 int alloc_xenballooned_pages(int nr_pages, struct page** pages)
379 {
380         int pgno = 0;
381         struct page* page;
382         mutex_lock(&balloon_mutex);
383         while (pgno < nr_pages) {
384                 page = balloon_retrieve(true);
385                 if (page) {
386                         pages[pgno++] = page;
387                 } else {
388                         enum bp_state st;
389                         st = decrease_reservation(nr_pages - pgno, GFP_HIGHUSER);
390                         if (st != BP_DONE)
391                                 goto out_undo;
392                 }
393         }
394         mutex_unlock(&balloon_mutex);
395         return 0;
396  out_undo:
397         while (pgno)
398                 balloon_append(pages[--pgno]);
399         /* Free the memory back to the kernel soon */
400         schedule_delayed_work(&balloon_worker, 0);
401         mutex_unlock(&balloon_mutex);
402         return -ENOMEM;
403 }
404 EXPORT_SYMBOL(alloc_xenballooned_pages);
405
406 /**
407  * free_xenballooned_pages - return pages retrieved with get_ballooned_pages
408  * @nr_pages: Number of pages
409  * @pages: pages to return
410  */
411 void free_xenballooned_pages(int nr_pages, struct page** pages)
412 {
413         int i;
414
415         mutex_lock(&balloon_mutex);
416
417         for (i = 0; i < nr_pages; i++) {
418                 if (pages[i])
419                         balloon_append(pages[i]);
420         }
421
422         /* The balloon may be too large now. Shrink it if needed. */
423         if (current_target() != balloon_stats.current_pages)
424                 schedule_delayed_work(&balloon_worker, 0);
425
426         mutex_unlock(&balloon_mutex);
427 }
428 EXPORT_SYMBOL(free_xenballooned_pages);
429
430 static int __init balloon_init(void)
431 {
432         unsigned long pfn, nr_pages, extra_pfn_end;
433         struct page *page;
434
435         if (!xen_domain())
436                 return -ENODEV;
437
438         pr_info("xen/balloon: Initialising balloon driver.\n");
439
440         if (xen_pv_domain())
441                 nr_pages = xen_start_info->nr_pages;
442         else
443                 nr_pages = max_pfn;
444         balloon_stats.current_pages = min(nr_pages, max_pfn);
445         balloon_stats.target_pages  = balloon_stats.current_pages;
446         balloon_stats.balloon_low   = 0;
447         balloon_stats.balloon_high  = 0;
448
449         balloon_stats.schedule_delay = 1;
450         balloon_stats.max_schedule_delay = 32;
451         balloon_stats.retry_count = 1;
452         balloon_stats.max_retry_count = RETRY_UNLIMITED;
453
454         /*
455          * Initialise the balloon with excess memory space.  We need
456          * to make sure we don't add memory which doesn't exist or
457          * logically exist.  The E820 map can be trimmed to be smaller
458          * than the amount of physical memory due to the mem= command
459          * line parameter.  And if this is a 32-bit non-HIGHMEM kernel
460          * on a system with memory which requires highmem to access,
461          * don't try to use it.
462          */
463         extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
464                             (unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
465         for (pfn = PFN_UP(xen_extra_mem_start);
466              pfn < extra_pfn_end;
467              pfn++) {
468                 page = pfn_to_page(pfn);
469                 /* totalram_pages doesn't include the boot-time
470                    balloon extension, so don't subtract from it. */
471                 __balloon_append(page);
472         }
473
474         return 0;
475 }
476
477 subsys_initcall(balloon_init);
478
479 MODULE_LICENSE("GPL");