xref: /openbmc/linux/mm/highmem.c (revision f3956ebb)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * High memory handling common code and variables.
4  *
5  * (C) 1999 Andrea Arcangeli, SuSE GmbH, andrea@suse.de
6  *          Gerhard Wichert, Siemens AG, Gerhard.Wichert@pdb.siemens.de
7  *
8  *
9  * Redesigned the x86 32-bit VM architecture to deal with
10  * 64-bit physical space. With current x86 CPUs this
11  * means up to 64 Gigabytes physical RAM.
12  *
13  * Rewrote high memory support to move the page cache into
14  * high memory. Implemented permanent (schedulable) kmaps
15  * based on Linus' idea.
16  *
17  * Copyright (C) 1999 Ingo Molnar <mingo@redhat.com>
18  */
19 
20 #include <linux/mm.h>
21 #include <linux/export.h>
22 #include <linux/swap.h>
23 #include <linux/bio.h>
24 #include <linux/pagemap.h>
25 #include <linux/mempool.h>
26 #include <linux/blkdev.h>
27 #include <linux/init.h>
28 #include <linux/hash.h>
29 #include <linux/highmem.h>
30 #include <linux/kgdb.h>
31 #include <asm/tlbflush.h>
32 #include <linux/vmalloc.h>
33 
34 /*
35  * Virtual_count is not a pure "count".
36  *  0 means that it is not mapped, and has not been mapped
37  *    since a TLB flush - it is usable.
38  *  1 means that there are no users, but it has been mapped
39  *    since the last TLB flush - so we can't use it.
40  *  n means that there are (n-1) current users of it.
41  */
42 #ifdef CONFIG_HIGHMEM
43 
44 /*
45  * Architecture with aliasing data cache may define the following family of
46  * helper functions in its asm/highmem.h to control cache color of virtual
47  * addresses where physical memory pages are mapped by kmap.
48  */
49 #ifndef get_pkmap_color
50 
51 /*
52  * Determine color of virtual address where the page should be mapped.
53  */
54 static inline unsigned int get_pkmap_color(struct page *page)
55 {
56 	return 0;
57 }
58 #define get_pkmap_color get_pkmap_color
59 
60 /*
61  * Get next index for mapping inside PKMAP region for page with given color.
62  */
63 static inline unsigned int get_next_pkmap_nr(unsigned int color)
64 {
65 	static unsigned int last_pkmap_nr;
66 
67 	last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK;
68 	return last_pkmap_nr;
69 }
70 
71 /*
72  * Determine if page index inside PKMAP region (pkmap_nr) of given color
73  * has wrapped around PKMAP region end. When this happens an attempt to
74  * flush all unused PKMAP slots is made.
75  */
76 static inline int no_more_pkmaps(unsigned int pkmap_nr, unsigned int color)
77 {
78 	return pkmap_nr == 0;
79 }
80 
81 /*
82  * Get the number of PKMAP entries of the given color. If no free slot is
83  * found after checking that many entries, kmap will sleep waiting for
84  * someone to call kunmap and free PKMAP slot.
85  */
86 static inline int get_pkmap_entries_count(unsigned int color)
87 {
88 	return LAST_PKMAP;
89 }
90 
91 /*
92  * Get head of a wait queue for PKMAP entries of the given color.
93  * Wait queues for different mapping colors should be independent to avoid
94  * unnecessary wakeups caused by freeing of slots of other colors.
95  */
96 static inline wait_queue_head_t *get_pkmap_wait_queue_head(unsigned int color)
97 {
98 	static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait);
99 
100 	return &pkmap_map_wait;
101 }
102 #endif
103 
104 atomic_long_t _totalhigh_pages __read_mostly;
105 EXPORT_SYMBOL(_totalhigh_pages);
106 
107 unsigned int __nr_free_highpages(void)
108 {
109 	struct zone *zone;
110 	unsigned int pages = 0;
111 
112 	for_each_populated_zone(zone) {
113 		if (is_highmem(zone))
114 			pages += zone_page_state(zone, NR_FREE_PAGES);
115 	}
116 
117 	return pages;
118 }
119 
120 static int pkmap_count[LAST_PKMAP];
121 static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock);
122 
123 pte_t *pkmap_page_table;
124 
125 /*
126  * Most architectures have no use for kmap_high_get(), so let's abstract
127  * the disabling of IRQ out of the locking in that case to save on a
128  * potential useless overhead.
129  */
130 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
131 #define lock_kmap()             spin_lock_irq(&kmap_lock)
132 #define unlock_kmap()           spin_unlock_irq(&kmap_lock)
133 #define lock_kmap_any(flags)    spin_lock_irqsave(&kmap_lock, flags)
134 #define unlock_kmap_any(flags)  spin_unlock_irqrestore(&kmap_lock, flags)
135 #else
136 #define lock_kmap()             spin_lock(&kmap_lock)
137 #define unlock_kmap()           spin_unlock(&kmap_lock)
138 #define lock_kmap_any(flags)    \
139 		do { spin_lock(&kmap_lock); (void)(flags); } while (0)
140 #define unlock_kmap_any(flags)  \
141 		do { spin_unlock(&kmap_lock); (void)(flags); } while (0)
142 #endif
143 
144 struct page *__kmap_to_page(void *vaddr)
145 {
146 	unsigned long addr = (unsigned long)vaddr;
147 
148 	if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) {
149 		int i = PKMAP_NR(addr);
150 
151 		return pte_page(pkmap_page_table[i]);
152 	}
153 
154 	return virt_to_page(addr);
155 }
156 EXPORT_SYMBOL(__kmap_to_page);
157 
158 static void flush_all_zero_pkmaps(void)
159 {
160 	int i;
161 	int need_flush = 0;
162 
163 	flush_cache_kmaps();
164 
165 	for (i = 0; i < LAST_PKMAP; i++) {
166 		struct page *page;
167 
168 		/*
169 		 * zero means we don't have anything to do,
170 		 * >1 means that it is still in use. Only
171 		 * a count of 1 means that it is free but
172 		 * needs to be unmapped
173 		 */
174 		if (pkmap_count[i] != 1)
175 			continue;
176 		pkmap_count[i] = 0;
177 
178 		/* sanity check */
179 		BUG_ON(pte_none(pkmap_page_table[i]));
180 
181 		/*
182 		 * Don't need an atomic fetch-and-clear op here;
183 		 * no-one has the page mapped, and cannot get at
184 		 * its virtual address (and hence PTE) without first
185 		 * getting the kmap_lock (which is held here).
186 		 * So no dangers, even with speculative execution.
187 		 */
188 		page = pte_page(pkmap_page_table[i]);
189 		pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]);
190 
191 		set_page_address(page, NULL);
192 		need_flush = 1;
193 	}
194 	if (need_flush)
195 		flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP));
196 }
197 
198 void __kmap_flush_unused(void)
199 {
200 	lock_kmap();
201 	flush_all_zero_pkmaps();
202 	unlock_kmap();
203 }
204 
205 static inline unsigned long map_new_virtual(struct page *page)
206 {
207 	unsigned long vaddr;
208 	int count;
209 	unsigned int last_pkmap_nr;
210 	unsigned int color = get_pkmap_color(page);
211 
212 start:
213 	count = get_pkmap_entries_count(color);
214 	/* Find an empty entry */
215 	for (;;) {
216 		last_pkmap_nr = get_next_pkmap_nr(color);
217 		if (no_more_pkmaps(last_pkmap_nr, color)) {
218 			flush_all_zero_pkmaps();
219 			count = get_pkmap_entries_count(color);
220 		}
221 		if (!pkmap_count[last_pkmap_nr])
222 			break;	/* Found a usable entry */
223 		if (--count)
224 			continue;
225 
226 		/*
227 		 * Sleep for somebody else to unmap their entries
228 		 */
229 		{
230 			DECLARE_WAITQUEUE(wait, current);
231 			wait_queue_head_t *pkmap_map_wait =
232 				get_pkmap_wait_queue_head(color);
233 
234 			__set_current_state(TASK_UNINTERRUPTIBLE);
235 			add_wait_queue(pkmap_map_wait, &wait);
236 			unlock_kmap();
237 			schedule();
238 			remove_wait_queue(pkmap_map_wait, &wait);
239 			lock_kmap();
240 
241 			/* Somebody else might have mapped it while we slept */
242 			if (page_address(page))
243 				return (unsigned long)page_address(page);
244 
245 			/* Re-start */
246 			goto start;
247 		}
248 	}
249 	vaddr = PKMAP_ADDR(last_pkmap_nr);
250 	set_pte_at(&init_mm, vaddr,
251 		   &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot));
252 
253 	pkmap_count[last_pkmap_nr] = 1;
254 	set_page_address(page, (void *)vaddr);
255 
256 	return vaddr;
257 }
258 
259 /**
260  * kmap_high - map a highmem page into memory
261  * @page: &struct page to map
262  *
263  * Returns the page's virtual memory address.
264  *
265  * We cannot call this from interrupts, as it may block.
266  */
267 void *kmap_high(struct page *page)
268 {
269 	unsigned long vaddr;
270 
271 	/*
272 	 * For highmem pages, we can't trust "virtual" until
273 	 * after we have the lock.
274 	 */
275 	lock_kmap();
276 	vaddr = (unsigned long)page_address(page);
277 	if (!vaddr)
278 		vaddr = map_new_virtual(page);
279 	pkmap_count[PKMAP_NR(vaddr)]++;
280 	BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2);
281 	unlock_kmap();
282 	return (void *) vaddr;
283 }
284 EXPORT_SYMBOL(kmap_high);
285 
286 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
287 /**
288  * kmap_high_get - pin a highmem page into memory
289  * @page: &struct page to pin
290  *
291  * Returns the page's current virtual memory address, or NULL if no mapping
292  * exists.  If and only if a non null address is returned then a
293  * matching call to kunmap_high() is necessary.
294  *
295  * This can be called from any context.
296  */
297 void *kmap_high_get(struct page *page)
298 {
299 	unsigned long vaddr, flags;
300 
301 	lock_kmap_any(flags);
302 	vaddr = (unsigned long)page_address(page);
303 	if (vaddr) {
304 		BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1);
305 		pkmap_count[PKMAP_NR(vaddr)]++;
306 	}
307 	unlock_kmap_any(flags);
308 	return (void *) vaddr;
309 }
310 #endif
311 
312 /**
313  * kunmap_high - unmap a highmem page into memory
314  * @page: &struct page to unmap
315  *
316  * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called
317  * only from user context.
318  */
319 void kunmap_high(struct page *page)
320 {
321 	unsigned long vaddr;
322 	unsigned long nr;
323 	unsigned long flags;
324 	int need_wakeup;
325 	unsigned int color = get_pkmap_color(page);
326 	wait_queue_head_t *pkmap_map_wait;
327 
328 	lock_kmap_any(flags);
329 	vaddr = (unsigned long)page_address(page);
330 	BUG_ON(!vaddr);
331 	nr = PKMAP_NR(vaddr);
332 
333 	/*
334 	 * A count must never go down to zero
335 	 * without a TLB flush!
336 	 */
337 	need_wakeup = 0;
338 	switch (--pkmap_count[nr]) {
339 	case 0:
340 		BUG();
341 	case 1:
342 		/*
343 		 * Avoid an unnecessary wake_up() function call.
344 		 * The common case is pkmap_count[] == 1, but
345 		 * no waiters.
346 		 * The tasks queued in the wait-queue are guarded
347 		 * by both the lock in the wait-queue-head and by
348 		 * the kmap_lock.  As the kmap_lock is held here,
349 		 * no need for the wait-queue-head's lock.  Simply
350 		 * test if the queue is empty.
351 		 */
352 		pkmap_map_wait = get_pkmap_wait_queue_head(color);
353 		need_wakeup = waitqueue_active(pkmap_map_wait);
354 	}
355 	unlock_kmap_any(flags);
356 
357 	/* do wake-up, if needed, race-free outside of the spin lock */
358 	if (need_wakeup)
359 		wake_up(pkmap_map_wait);
360 }
361 EXPORT_SYMBOL(kunmap_high);
362 
363 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
364 void zero_user_segments(struct page *page, unsigned start1, unsigned end1,
365 		unsigned start2, unsigned end2)
366 {
367 	unsigned int i;
368 
369 	BUG_ON(end1 > page_size(page) || end2 > page_size(page));
370 
371 	if (start1 >= end1)
372 		start1 = end1 = 0;
373 	if (start2 >= end2)
374 		start2 = end2 = 0;
375 
376 	for (i = 0; i < compound_nr(page); i++) {
377 		void *kaddr = NULL;
378 
379 		if (start1 >= PAGE_SIZE) {
380 			start1 -= PAGE_SIZE;
381 			end1 -= PAGE_SIZE;
382 		} else {
383 			unsigned this_end = min_t(unsigned, end1, PAGE_SIZE);
384 
385 			if (end1 > start1) {
386 				kaddr = kmap_atomic(page + i);
387 				memset(kaddr + start1, 0, this_end - start1);
388 			}
389 			end1 -= this_end;
390 			start1 = 0;
391 		}
392 
393 		if (start2 >= PAGE_SIZE) {
394 			start2 -= PAGE_SIZE;
395 			end2 -= PAGE_SIZE;
396 		} else {
397 			unsigned this_end = min_t(unsigned, end2, PAGE_SIZE);
398 
399 			if (end2 > start2) {
400 				if (!kaddr)
401 					kaddr = kmap_atomic(page + i);
402 				memset(kaddr + start2, 0, this_end - start2);
403 			}
404 			end2 -= this_end;
405 			start2 = 0;
406 		}
407 
408 		if (kaddr) {
409 			kunmap_atomic(kaddr);
410 			flush_dcache_page(page + i);
411 		}
412 
413 		if (!end1 && !end2)
414 			break;
415 	}
416 
417 	BUG_ON((start1 | start2 | end1 | end2) != 0);
418 }
419 EXPORT_SYMBOL(zero_user_segments);
420 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
421 #endif /* CONFIG_HIGHMEM */
422 
423 #ifdef CONFIG_KMAP_LOCAL
424 
425 #include <asm/kmap_size.h>
426 
427 /*
428  * With DEBUG_KMAP_LOCAL the stack depth is doubled and every second
429  * slot is unused which acts as a guard page
430  */
431 #ifdef CONFIG_DEBUG_KMAP_LOCAL
432 # define KM_INCR	2
433 #else
434 # define KM_INCR	1
435 #endif
436 
437 static inline int kmap_local_idx_push(void)
438 {
439 	WARN_ON_ONCE(in_hardirq() && !irqs_disabled());
440 	current->kmap_ctrl.idx += KM_INCR;
441 	BUG_ON(current->kmap_ctrl.idx >= KM_MAX_IDX);
442 	return current->kmap_ctrl.idx - 1;
443 }
444 
445 static inline int kmap_local_idx(void)
446 {
447 	return current->kmap_ctrl.idx - 1;
448 }
449 
450 static inline void kmap_local_idx_pop(void)
451 {
452 	current->kmap_ctrl.idx -= KM_INCR;
453 	BUG_ON(current->kmap_ctrl.idx < 0);
454 }
455 
456 #ifndef arch_kmap_local_post_map
457 # define arch_kmap_local_post_map(vaddr, pteval)	do { } while (0)
458 #endif
459 
460 #ifndef arch_kmap_local_pre_unmap
461 # define arch_kmap_local_pre_unmap(vaddr)		do { } while (0)
462 #endif
463 
464 #ifndef arch_kmap_local_post_unmap
465 # define arch_kmap_local_post_unmap(vaddr)		do { } while (0)
466 #endif
467 
468 #ifndef arch_kmap_local_map_idx
469 #define arch_kmap_local_map_idx(idx, pfn)	kmap_local_calc_idx(idx)
470 #endif
471 
472 #ifndef arch_kmap_local_unmap_idx
473 #define arch_kmap_local_unmap_idx(idx, vaddr)	kmap_local_calc_idx(idx)
474 #endif
475 
476 #ifndef arch_kmap_local_high_get
477 static inline void *arch_kmap_local_high_get(struct page *page)
478 {
479 	return NULL;
480 }
481 #endif
482 
483 #ifndef arch_kmap_local_set_pte
484 #define arch_kmap_local_set_pte(mm, vaddr, ptep, ptev)	\
485 	set_pte_at(mm, vaddr, ptep, ptev)
486 #endif
487 
488 /* Unmap a local mapping which was obtained by kmap_high_get() */
489 static inline bool kmap_high_unmap_local(unsigned long vaddr)
490 {
491 #ifdef ARCH_NEEDS_KMAP_HIGH_GET
492 	if (vaddr >= PKMAP_ADDR(0) && vaddr < PKMAP_ADDR(LAST_PKMAP)) {
493 		kunmap_high(pte_page(pkmap_page_table[PKMAP_NR(vaddr)]));
494 		return true;
495 	}
496 #endif
497 	return false;
498 }
499 
500 static inline int kmap_local_calc_idx(int idx)
501 {
502 	return idx + KM_MAX_IDX * smp_processor_id();
503 }
504 
505 static pte_t *__kmap_pte;
506 
507 static pte_t *kmap_get_pte(void)
508 {
509 	if (!__kmap_pte)
510 		__kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN));
511 	return __kmap_pte;
512 }
513 
514 void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot)
515 {
516 	pte_t pteval, *kmap_pte = kmap_get_pte();
517 	unsigned long vaddr;
518 	int idx;
519 
520 	/*
521 	 * Disable migration so resulting virtual address is stable
522 	 * across preemption.
523 	 */
524 	migrate_disable();
525 	preempt_disable();
526 	idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn);
527 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
528 	BUG_ON(!pte_none(*(kmap_pte - idx)));
529 	pteval = pfn_pte(pfn, prot);
530 	arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte - idx, pteval);
531 	arch_kmap_local_post_map(vaddr, pteval);
532 	current->kmap_ctrl.pteval[kmap_local_idx()] = pteval;
533 	preempt_enable();
534 
535 	return (void *)vaddr;
536 }
537 EXPORT_SYMBOL_GPL(__kmap_local_pfn_prot);
538 
539 void *__kmap_local_page_prot(struct page *page, pgprot_t prot)
540 {
541 	void *kmap;
542 
543 	/*
544 	 * To broaden the usage of the actual kmap_local() machinery always map
545 	 * pages when debugging is enabled and the architecture has no problems
546 	 * with alias mappings.
547 	 */
548 	if (!IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) && !PageHighMem(page))
549 		return page_address(page);
550 
551 	/* Try kmap_high_get() if architecture has it enabled */
552 	kmap = arch_kmap_local_high_get(page);
553 	if (kmap)
554 		return kmap;
555 
556 	return __kmap_local_pfn_prot(page_to_pfn(page), prot);
557 }
558 EXPORT_SYMBOL(__kmap_local_page_prot);
559 
560 void kunmap_local_indexed(void *vaddr)
561 {
562 	unsigned long addr = (unsigned long) vaddr & PAGE_MASK;
563 	pte_t *kmap_pte = kmap_get_pte();
564 	int idx;
565 
566 	if (addr < __fix_to_virt(FIX_KMAP_END) ||
567 	    addr > __fix_to_virt(FIX_KMAP_BEGIN)) {
568 		if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP)) {
569 			/* This _should_ never happen! See above. */
570 			WARN_ON_ONCE(1);
571 			return;
572 		}
573 		/*
574 		 * Handle mappings which were obtained by kmap_high_get()
575 		 * first as the virtual address of such mappings is below
576 		 * PAGE_OFFSET. Warn for all other addresses which are in
577 		 * the user space part of the virtual address space.
578 		 */
579 		if (!kmap_high_unmap_local(addr))
580 			WARN_ON_ONCE(addr < PAGE_OFFSET);
581 		return;
582 	}
583 
584 	preempt_disable();
585 	idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr);
586 	WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
587 
588 	arch_kmap_local_pre_unmap(addr);
589 	pte_clear(&init_mm, addr, kmap_pte - idx);
590 	arch_kmap_local_post_unmap(addr);
591 	current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0);
592 	kmap_local_idx_pop();
593 	preempt_enable();
594 	migrate_enable();
595 }
596 EXPORT_SYMBOL(kunmap_local_indexed);
597 
598 /*
599  * Invoked before switch_to(). This is safe even when during or after
600  * clearing the maps an interrupt which needs a kmap_local happens because
601  * the task::kmap_ctrl.idx is not modified by the unmapping code so a
602  * nested kmap_local will use the next unused index and restore the index
603  * on unmap. The already cleared kmaps of the outgoing task are irrelevant
604  * because the interrupt context does not know about them. The same applies
605  * when scheduling back in for an interrupt which happens before the
606  * restore is complete.
607  */
608 void __kmap_local_sched_out(void)
609 {
610 	struct task_struct *tsk = current;
611 	pte_t *kmap_pte = kmap_get_pte();
612 	int i;
613 
614 	/* Clear kmaps */
615 	for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
616 		pte_t pteval = tsk->kmap_ctrl.pteval[i];
617 		unsigned long addr;
618 		int idx;
619 
620 		/* With debug all even slots are unmapped and act as guard */
621 		if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
622 			WARN_ON_ONCE(!pte_none(pteval));
623 			continue;
624 		}
625 		if (WARN_ON_ONCE(pte_none(pteval)))
626 			continue;
627 
628 		/*
629 		 * This is a horrible hack for XTENSA to calculate the
630 		 * coloured PTE index. Uses the PFN encoded into the pteval
631 		 * and the map index calculation because the actual mapped
632 		 * virtual address is not stored in task::kmap_ctrl.
633 		 * For any sane architecture this is optimized out.
634 		 */
635 		idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
636 
637 		addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
638 		arch_kmap_local_pre_unmap(addr);
639 		pte_clear(&init_mm, addr, kmap_pte - idx);
640 		arch_kmap_local_post_unmap(addr);
641 	}
642 }
643 
644 void __kmap_local_sched_in(void)
645 {
646 	struct task_struct *tsk = current;
647 	pte_t *kmap_pte = kmap_get_pte();
648 	int i;
649 
650 	/* Restore kmaps */
651 	for (i = 0; i < tsk->kmap_ctrl.idx; i++) {
652 		pte_t pteval = tsk->kmap_ctrl.pteval[i];
653 		unsigned long addr;
654 		int idx;
655 
656 		/* With debug all even slots are unmapped and act as guard */
657 		if (IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL) && !(i & 0x01)) {
658 			WARN_ON_ONCE(!pte_none(pteval));
659 			continue;
660 		}
661 		if (WARN_ON_ONCE(pte_none(pteval)))
662 			continue;
663 
664 		/* See comment in __kmap_local_sched_out() */
665 		idx = arch_kmap_local_map_idx(i, pte_pfn(pteval));
666 		addr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
667 		set_pte_at(&init_mm, addr, kmap_pte - idx, pteval);
668 		arch_kmap_local_post_map(addr, pteval);
669 	}
670 }
671 
672 void kmap_local_fork(struct task_struct *tsk)
673 {
674 	if (WARN_ON_ONCE(tsk->kmap_ctrl.idx))
675 		memset(&tsk->kmap_ctrl, 0, sizeof(tsk->kmap_ctrl));
676 }
677 
678 #endif
679 
680 #if defined(HASHED_PAGE_VIRTUAL)
681 
682 #define PA_HASH_ORDER	7
683 
684 /*
685  * Describes one page->virtual association
686  */
687 struct page_address_map {
688 	struct page *page;
689 	void *virtual;
690 	struct list_head list;
691 };
692 
693 static struct page_address_map page_address_maps[LAST_PKMAP];
694 
695 /*
696  * Hash table bucket
697  */
698 static struct page_address_slot {
699 	struct list_head lh;			/* List of page_address_maps */
700 	spinlock_t lock;			/* Protect this bucket's list */
701 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER];
702 
703 static struct page_address_slot *page_slot(const struct page *page)
704 {
705 	return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)];
706 }
707 
708 /**
709  * page_address - get the mapped virtual address of a page
710  * @page: &struct page to get the virtual address of
711  *
712  * Returns the page's virtual address.
713  */
714 void *page_address(const struct page *page)
715 {
716 	unsigned long flags;
717 	void *ret;
718 	struct page_address_slot *pas;
719 
720 	if (!PageHighMem(page))
721 		return lowmem_page_address(page);
722 
723 	pas = page_slot(page);
724 	ret = NULL;
725 	spin_lock_irqsave(&pas->lock, flags);
726 	if (!list_empty(&pas->lh)) {
727 		struct page_address_map *pam;
728 
729 		list_for_each_entry(pam, &pas->lh, list) {
730 			if (pam->page == page) {
731 				ret = pam->virtual;
732 				goto done;
733 			}
734 		}
735 	}
736 done:
737 	spin_unlock_irqrestore(&pas->lock, flags);
738 	return ret;
739 }
740 EXPORT_SYMBOL(page_address);
741 
742 /**
743  * set_page_address - set a page's virtual address
744  * @page: &struct page to set
745  * @virtual: virtual address to use
746  */
747 void set_page_address(struct page *page, void *virtual)
748 {
749 	unsigned long flags;
750 	struct page_address_slot *pas;
751 	struct page_address_map *pam;
752 
753 	BUG_ON(!PageHighMem(page));
754 
755 	pas = page_slot(page);
756 	if (virtual) {		/* Add */
757 		pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)];
758 		pam->page = page;
759 		pam->virtual = virtual;
760 
761 		spin_lock_irqsave(&pas->lock, flags);
762 		list_add_tail(&pam->list, &pas->lh);
763 		spin_unlock_irqrestore(&pas->lock, flags);
764 	} else {		/* Remove */
765 		spin_lock_irqsave(&pas->lock, flags);
766 		list_for_each_entry(pam, &pas->lh, list) {
767 			if (pam->page == page) {
768 				list_del(&pam->list);
769 				spin_unlock_irqrestore(&pas->lock, flags);
770 				goto done;
771 			}
772 		}
773 		spin_unlock_irqrestore(&pas->lock, flags);
774 	}
775 done:
776 	return;
777 }
778 
779 void __init page_address_init(void)
780 {
781 	int i;
782 
783 	for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) {
784 		INIT_LIST_HEAD(&page_address_htable[i].lh);
785 		spin_lock_init(&page_address_htable[i].lock);
786 	}
787 }
788 
789 #endif	/* defined(HASHED_PAGE_VIRTUAL) */
790