1 /*
2 * High memory handling common code and variables.
3 *
4 * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
5 * Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
6 *
7 *
8 * Redesigned the x86 32-bit VM architecture to deal with
9 * 64-bit physical space. With current x86 CPUs this
10 * means up to 64 Gigabytes physical RAM.
11 *
12 * Rewrote high memory support to move the page cache into
13 * high memory. Implemented permanent (schedulable) kmaps
14 * based on Linus' idea.
15 *
16 * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
17 */
18
19 #include <linux/mm.h>
20 #include <linux/export.h>
21 #include <linux/swap.h>
22 #include <linux/bio.h>
23 #include <linux/pagemap.h>
24 #include <linux/mempool.h>
25 #include <linux/blkdev.h>
26 #include <linux/init.h>
27 #include <linux/hash.h>
28 #include <linux/highmem.h>
29 #include <linux/kgdb.h>
30 #include <asm/tlbflush.h>
31
32
33 #if defined(CONFIG_HIGHMEM) || defined(CONFIG_X86_32)
34 DEFINE_PER_CPU(int, __kmap_atomic_idx);
35 #endif
36
37 /*
38 * Virtual_count is not a pure "count".
39 * 0 means that it is not mapped, and has not been mapped
40 * since a TLB flush - it is usable.
41 * 1 means that there are no users, but it has been mapped
42 * since the last TLB flush - so we can't use it.
43 * n means that there are (n-1) current users of it.
44 */
45 #ifdef CONFIG_HIGHMEM
46
47 /*
48 * Architecture with aliasing data cache may define the following family of
49 * helper functions in its asm/highmem.h to control cache color of virtual
50 * addresses where physical memory pages are mapped by kmap.
51 */
52 #ifndef get_pkmap_color
53
54 /*
55 * Determine color of virtual address where the page should be mapped.
56 */
get_pkmap_color(struct page * page)57 static inline unsigned int get_pkmap_color(struct page *page)
58 {
59 return 0;
60 }
61 #define get_pkmap_color get_pkmap_color
62
63 /*
64 * Get next index for mapping inside PKMAP region for page with given color.
65 */
get_next_pkmap_nr(unsigned int color)66 static inline unsigned int get_next_pkmap_nr(unsigned int color)
67 {
68 static unsigned int last_pkmap_nr;
69
70 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
71 return last_pkmap_nr;
72 }
73
74 /*
75 * Determine if page index inside PKMAP region (pkmap_nr) of given color
76 * has wrapped around PKMAP region end. When this happens an attempt to
77 * flush all unused PKMAP slots is made.
78 */
no_more_pkmaps(unsigned int pkmap_nr,unsigned int color)79 static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
80 {
81 return pkmap_nr == 0;
82 }
83
84 /*
85 * Get the number of PKMAP entries of the given color. If no free slot is
86 * found after checking that many entries, kmap will sleep waiting for
87 * someone to call kunmap and free PKMAP slot.
88 */
get_pkmap_entries_count(unsigned int color)89 static inline int get_pkmap_entries_count(unsigned int color)
90 {
91 return LAST_PKMAP;
92 }
93
94 /*
95 * Get head of a wait queue for PKMAP entries of the given color.
96 * Wait queues for different mapping colors should be independent to avoid
97 * unnecessary wakeups caused by freeing of slots of other colors.
98 */
get_pkmap_wait_queue_head(unsigned int color)99 static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
100 {
101 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
102
103 return &pkmap_map_wait;
104 }
105 #endif
106
107 unsigned long totalhigh_pages __read_mostly;
108 EXPORT_SYMBOL(totalhigh_pages);
109
110
111 EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
112
nr_free_highpages(void)113 unsigned int nr_free_highpages (void)
114 {
115 pg_data_t *pgdat;
116 unsigned int pages = 0;
117
118 for_each_online_pgdat(pgdat) {
119 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM],
120 NR_FREE_PAGES);
121 if (zone_movable_is_highmem())
122 pages += zone_page_state(
123 &pgdat->node_zones[ZONE_MOVABLE],
124 NR_FREE_PAGES);
125 }
126
127 return pages;
128 }
129
130 static int pkmap_count[LAST_PKMAP];
131 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
132
133 pte_t * pkmap_page_table;
134
135 /*
136 * Most architectures have no use for kmap_high_get(), so let's abstract
137 * the disabling of IRQ out of the locking in that case to save on a
138 * potential useless overhead.
139 */
140 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
141 #define lock_kmap() spin_lock_irq(&kmap_lock)
142 #define unlock_kmap() spin_unlock_irq(&kmap_lock)
143 #define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags)
144 #define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags)
145 #else
146 #define lock_kmap() spin_lock(&kmap_lock)
147 #define unlock_kmap() spin_unlock(&kmap_lock)
148 #define lock_kmap_any(flags) \
149 do { spin_lock(&kmap_lock); (void)(flags); } while (0)
150 #define unlock_kmap_any(flags) \
151 do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
152 #endif
153
kmap_to_page(void * vaddr)154 struct page *kmap_to_page(void *vaddr)
155 {
156 unsigned long addr = (unsigned long)vaddr;
157
158 if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
159 int i = PKMAP_NR(addr);
160 return pte_page(pkmap_page_table[i]);
161 }
162
163 return virt_to_page(addr);
164 }
165 EXPORT_SYMBOL(kmap_to_page);
166
flush_all_zero_pkmaps(void)167 static void flush_all_zero_pkmaps(void)
168 {
169 int i;
170 int need_flush = 0;
171
172 flush_cache_kmaps();
173
174 for (i = 0; i < LAST_PKMAP; i++) {
175 struct page *page;
176
177 /*
178 * zero means we don't have anything to do,
179 * >1 means that it is still in use. Only
180 * a count of 1 means that it is free but
181 * needs to be unmapped
182 */
183 if (pkmap_count[i] != 1)
184 continue;
185 pkmap_count[i] = 0;
186
187 /* sanity check */
188 BUG_ON(pte_none(pkmap_page_table[i]));
189
190 /*
191 * Don't need an atomic fetch-and-clear op here;
192 * no-one has the page mapped, and cannot get at
193 * its virtual address (and hence PTE) without first
194 * getting the kmap_lock (which is held here).
195 * So no dangers, even with speculative execution.
196 */
197 page = pte_page(pkmap_page_table[i]);
198 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
199
200 set_page_address(page, NULL);
201 need_flush = 1;
202 }
203 if (need_flush)
204 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
205 }
206
207 /**
208 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings
209 */
kmap_flush_unused(void)210 void kmap_flush_unused(void)
211 {
212 lock_kmap();
213 flush_all_zero_pkmaps();
214 unlock_kmap();
215 }
216
map_new_virtual(struct page * page)217 static inline unsigned long map_new_virtual(struct page *page)
218 {
219 unsigned long vaddr;
220 int count;
221 unsigned int last_pkmap_nr;
222 unsigned int color = get_pkmap_color(page);
223
224 start:
225 count = get_pkmap_entries_count(color);
226 /* Find an empty entry */
227 for (;;) {
228 last_pkmap_nr = get_next_pkmap_nr(color);
229 if (no_more_pkmaps(last_pkmap_nr, color)) {
230 flush_all_zero_pkmaps();
231 count = get_pkmap_entries_count(color);
232 }
233 if (!pkmap_count[last_pkmap_nr])
234 break; /* Found a usable entry */
235 if (--count)
236 continue;
237
238 /*
239 * Sleep for somebody else to unmap their entries
240 */
241 {
242 DECLARE_WAITQUEUE(wait, current);
243 wait_queue_head_t *pkmap_map_wait =
244 get_pkmap_wait_queue_head(color);
245
246 __set_current_state(TASK_UNINTERRUPTIBLE);
247 add_wait_queue(pkmap_map_wait, &wait);
248 unlock_kmap();
249 schedule();
250 remove_wait_queue(pkmap_map_wait, &wait);
251 lock_kmap();
252
253 /* Somebody else might have mapped it while we slept */
254 if (page_address(page))
255 return (unsigned long)page_address(page);
256
257 /* Re-start */
258 goto start;
259 }
260 }
261 vaddr = PKMAP_ADDR(last_pkmap_nr);
262 set_pte_at(&init_mm, vaddr,
263 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
264
265 pkmap_count[last_pkmap_nr] = 1;
266 set_page_address(page, (void *)vaddr);
267
268 return vaddr;
269 }
270
271 /**
272 * kmap_high - map a highmem page into memory
273 * @page: &struct page to map
274 *
275 * Returns the page's virtual memory address.
276 *
277 * We cannot call this from interrupts, as it may block.
278 */
kmap_high(struct page * page)279 void *kmap_high(struct page *page)
280 {
281 unsigned long vaddr;
282
283 /*
284 * For highmem pages, we can't trust "virtual" until
285 * after we have the lock.
286 */
287 lock_kmap();
288 vaddr = (unsigned long)page_address(page);
289 if (!vaddr)
290 vaddr = map_new_virtual(page);
291 pkmap_count[PKMAP_NR(vaddr)]++;
292 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
293 unlock_kmap();
294 return (void*) vaddr;
295 }
296
297 EXPORT_SYMBOL(kmap_high);
298
299 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
300 /**
301 * kmap_high_get - pin a highmem page into memory
302 * @page: &struct page to pin
303 *
304 * Returns the page's current virtual memory address, or NULL if no mapping
305 * exists. If and only if a non null address is returned then a
306 * matching call to kunmap_high() is necessary.
307 *
308 * This can be called from any context.
309 */
kmap_high_get(struct page * page)310 void *kmap_high_get(struct page *page)
311 {
312 unsigned long vaddr, flags;
313
314 lock_kmap_any(flags);
315 vaddr = (unsigned long)page_address(page);
316 if (vaddr) {
317 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
318 pkmap_count[PKMAP_NR(vaddr)]++;
319 }
320 unlock_kmap_any(flags);
321 return (void*) vaddr;
322 }
323 #endif
324
325 /**
326 * kunmap_high - unmap a highmem page into memory
327 * @page: &struct page to unmap
328 *
329 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
330 * only from user context.
331 */
kunmap_high(struct page * page)332 void kunmap_high(struct page *page)
333 {
334 unsigned long vaddr;
335 unsigned long nr;
336 unsigned long flags;
337 int need_wakeup;
338 unsigned int color = get_pkmap_color(page);
339 wait_queue_head_t *pkmap_map_wait;
340
341 lock_kmap_any(flags);
342 vaddr = (unsigned long)page_address(page);
343 BUG_ON(!vaddr);
344 nr = PKMAP_NR(vaddr);
345
346 /*
347 * A count must never go down to zero
348 * without a TLB flush!
349 */
350 need_wakeup = 0;
351 switch (--pkmap_count[nr]) {
352 case 0:
353 BUG();
354 case 1:
355 /*
356 * Avoid an unnecessary wake_up() function call.
357 * The common case is pkmap_count[] == 1, but
358 * no waiters.
359 * The tasks queued in the wait-queue are guarded
360 * by both the lock in the wait-queue-head and by
361 * the kmap_lock. As the kmap_lock is held here,
362 * no need for the wait-queue-head's lock. Simply
363 * test if the queue is empty.
364 */
365 pkmap_map_wait = get_pkmap_wait_queue_head(color);
366 need_wakeup = waitqueue_active(pkmap_map_wait);
367 }
368 unlock_kmap_any(flags);
369
370 /* do wake-up, if needed, race-free outside of the spin lock */
371 if (need_wakeup)
372 wake_up(pkmap_map_wait);
373 }
374
375 EXPORT_SYMBOL(kunmap_high);
376 #endif
377
378 #if defined(HASHED_PAGE_VIRTUAL)
379
380 #define PA_HASH_ORDER 7
381
382 /*
383 * Describes one page->virtual association
384 */
385 struct page_address_map {
386 struct page *page;
387 void *virtual;
388 struct list_head list;
389 };
390
391 static struct page_address_map page_address_maps[LAST_PKMAP];
392
393 /*
394 * Hash table bucket
395 */
396 static struct page_address_slot {
397 struct list_head lh; /* List of page_address_maps */
398 spinlock_t lock; /* Protect this bucket's list */
399 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
400
page_slot(const struct page * page)401 static struct page_address_slot *page_slot(const struct page *page)
402 {
403 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
404 }
405
406 /**
407 * page_address - get the mapped virtual address of a page
408 * @page: &struct page to get the virtual address of
409 *
410 * Returns the page's virtual address.
411 */
page_address(const struct page * page)412 void *page_address(const struct page *page)
413 {
414 unsigned long flags;
415 void *ret;
416 struct page_address_slot *pas;
417
418 if (!PageHighMem(page))
419 return lowmem_page_address(page);
420
421 pas = page_slot(page);
422 ret = NULL;
423 spin_lock_irqsave(&pas->lock, flags);
424 if (!list_empty(&pas->lh)) {
425 struct page_address_map *pam;
426
427 list_for_each_entry(pam, &pas->lh, list) {
428 if (pam->page == page) {
429 ret = pam->virtual;
430 goto done;
431 }
432 }
433 }
434 done:
435 spin_unlock_irqrestore(&pas->lock, flags);
436 return ret;
437 }
438
439 EXPORT_SYMBOL(page_address);
440
441 /**
442 * set_page_address - set a page's virtual address
443 * @page: &struct page to set
444 * @virtual: virtual address to use
445 */
set_page_address(struct page * page,void * virtual)446 void set_page_address(struct page *page, void *virtual)
447 {
448 unsigned long flags;
449 struct page_address_slot *pas;
450 struct page_address_map *pam;
451
452 BUG_ON(!PageHighMem(page));
453
454 pas = page_slot(page);
455 if (virtual) { /* Add */
456 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
457 pam->page = page;
458 pam->virtual = virtual;
459
460 spin_lock_irqsave(&pas->lock, flags);
461 list_add_tail(&pam->list, &pas->lh);
462 spin_unlock_irqrestore(&pas->lock, flags);
463 } else { /* Remove */
464 spin_lock_irqsave(&pas->lock, flags);
465 list_for_each_entry(pam, &pas->lh, list) {
466 if (pam->page == page) {
467 list_del(&pam->list);
468 spin_unlock_irqrestore(&pas->lock, flags);
469 goto done;
470 }
471 }
472 spin_unlock_irqrestore(&pas->lock, flags);
473 }
474 done:
475 return;
476 }
477
page_address_init(void)478 void __init page_address_init(void)
479 {
480 int i;
481
482 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
483 INIT_LIST_HEAD(&page_address_htable[i].lh);
484 spin_lock_init(&page_address_htable[i].lock);
485 }
486 }
487
488 #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
489