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Linux/arch/tile/mm/highmem.c

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  1 /*
  2  * Copyright 2010 Tilera Corporation. All Rights Reserved.
  3  *
  4  *   This program is free software; you can redistribute it and/or
  5  *   modify it under the terms of the GNU General Public License
  6  *   as published by the Free Software Foundation, version 2.
  7  *
  8  *   This program is distributed in the hope that it will be useful, but
  9  *   WITHOUT ANY WARRANTY; without even the implied warranty of
 10  *   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 11  *   NON INFRINGEMENT.  See the GNU General Public License for
 12  *   more details.
 13  */
 14 
 15 #include <linux/highmem.h>
 16 #include <linux/module.h>
 17 #include <linux/pagemap.h>
 18 #include <asm/homecache.h>
 19 
 20 #define kmap_get_pte(vaddr) \
 21         pte_offset_kernel(pmd_offset(pud_offset(pgd_offset_k(vaddr), (vaddr)),\
 22                 (vaddr)), (vaddr))
 23 
 24 
 25 void *kmap(struct page *page)
 26 {
 27         void *kva;
 28         unsigned long flags;
 29         pte_t *ptep;
 30 
 31         might_sleep();
 32         if (!PageHighMem(page))
 33                 return page_address(page);
 34         kva = kmap_high(page);
 35 
 36         /*
 37          * Rewrite the PTE under the lock.  This ensures that the page
 38          * is not currently migrating.
 39          */
 40         ptep = kmap_get_pte((unsigned long)kva);
 41         flags = homecache_kpte_lock();
 42         set_pte_at(&init_mm, kva, ptep, mk_pte(page, page_to_kpgprot(page)));
 43         homecache_kpte_unlock(flags);
 44 
 45         return kva;
 46 }
 47 EXPORT_SYMBOL(kmap);
 48 
 49 void kunmap(struct page *page)
 50 {
 51         if (in_interrupt())
 52                 BUG();
 53         if (!PageHighMem(page))
 54                 return;
 55         kunmap_high(page);
 56 }
 57 EXPORT_SYMBOL(kunmap);
 58 
 59 /*
 60  * Describe a single atomic mapping of a page on a given cpu at a
 61  * given address, and allow it to be linked into a list.
 62  */
 63 struct atomic_mapped_page {
 64         struct list_head list;
 65         struct page *page;
 66         int cpu;
 67         unsigned long va;
 68 };
 69 
 70 static spinlock_t amp_lock = __SPIN_LOCK_UNLOCKED(&amp_lock);
 71 static struct list_head amp_list = LIST_HEAD_INIT(amp_list);
 72 
 73 /*
 74  * Combining this structure with a per-cpu declaration lets us give
 75  * each cpu an atomic_mapped_page structure per type.
 76  */
 77 struct kmap_amps {
 78         struct atomic_mapped_page per_type[KM_TYPE_NR];
 79 };
 80 static DEFINE_PER_CPU(struct kmap_amps, amps);
 81 
 82 /*
 83  * Add a page and va, on this cpu, to the list of kmap_atomic pages,
 84  * and write the new pte to memory.  Writing the new PTE under the
 85  * lock guarantees that it is either on the list before migration starts
 86  * (if we won the race), or set_pte() sets the migrating bit in the PTE
 87  * (if we lost the race).  And doing it under the lock guarantees
 88  * that when kmap_atomic_fix_one_pte() comes along, it finds a valid
 89  * PTE in memory, iff the mapping is still on the amp_list.
 90  *
 91  * Finally, doing it under the lock lets us safely examine the page
 92  * to see if it is immutable or not, for the generic kmap_atomic() case.
 93  * If we examine it earlier we are exposed to a race where it looks
 94  * writable earlier, but becomes immutable before we write the PTE.
 95  */
 96 static void kmap_atomic_register(struct page *page, int type,
 97                                  unsigned long va, pte_t *ptep, pte_t pteval)
 98 {
 99         unsigned long flags;
100         struct atomic_mapped_page *amp;
101 
102         flags = homecache_kpte_lock();
103         spin_lock(&amp_lock);
104 
105         /* With interrupts disabled, now fill in the per-cpu info. */
106         amp = &__get_cpu_var(amps).per_type[type];
107         amp->page = page;
108         amp->cpu = smp_processor_id();
109         amp->va = va;
110 
111         /* For generic kmap_atomic(), choose the PTE writability now. */
112         if (!pte_read(pteval))
113                 pteval = mk_pte(page, page_to_kpgprot(page));
114 
115         list_add(&amp->list, &amp_list);
116         set_pte(ptep, pteval);
117 
118         spin_unlock(&amp_lock);
119         homecache_kpte_unlock(flags);
120 }
121 
122 /*
123  * Remove a page and va, on this cpu, from the list of kmap_atomic pages.
124  * Linear-time search, but we count on the lists being short.
125  * We don't need to adjust the PTE under the lock (as opposed to the
126  * kmap_atomic_register() case), since we're just unconditionally
127  * zeroing the PTE after it's off the list.
128  */
129 static void kmap_atomic_unregister(struct page *page, unsigned long va)
130 {
131         unsigned long flags;
132         struct atomic_mapped_page *amp;
133         int cpu = smp_processor_id();
134         spin_lock_irqsave(&amp_lock, flags);
135         list_for_each_entry(amp, &amp_list, list) {
136                 if (amp->page == page && amp->cpu == cpu && amp->va == va)
137                         break;
138         }
139         BUG_ON(&amp->list == &amp_list);
140         list_del(&amp->list);
141         spin_unlock_irqrestore(&amp_lock, flags);
142 }
143 
144 /* Helper routine for kmap_atomic_fix_kpte(), below. */
145 static void kmap_atomic_fix_one_kpte(struct atomic_mapped_page *amp,
146                                      int finished)
147 {
148         pte_t *ptep = kmap_get_pte(amp->va);
149         if (!finished) {
150                 set_pte(ptep, pte_mkmigrate(*ptep));
151                 flush_remote(0, 0, NULL, amp->va, PAGE_SIZE, PAGE_SIZE,
152                              cpumask_of(amp->cpu), NULL, 0);
153         } else {
154                 /*
155                  * Rewrite a default kernel PTE for this page.
156                  * We rely on the fact that set_pte() writes the
157                  * present+migrating bits last.
158                  */
159                 pte_t pte = mk_pte(amp->page, page_to_kpgprot(amp->page));
160                 set_pte(ptep, pte);
161         }
162 }
163 
164 /*
165  * This routine is a helper function for homecache_fix_kpte(); see
166  * its comments for more information on the "finished" argument here.
167  *
168  * Note that we hold the lock while doing the remote flushes, which
169  * will stall any unrelated cpus trying to do kmap_atomic operations.
170  * We could just update the PTEs under the lock, and save away copies
171  * of the structs (or just the va+cpu), then flush them after we
172  * release the lock, but it seems easier just to do it all under the lock.
173  */
174 void kmap_atomic_fix_kpte(struct page *page, int finished)
175 {
176         struct atomic_mapped_page *amp;
177         unsigned long flags;
178         spin_lock_irqsave(&amp_lock, flags);
179         list_for_each_entry(amp, &amp_list, list) {
180                 if (amp->page == page)
181                         kmap_atomic_fix_one_kpte(amp, finished);
182         }
183         spin_unlock_irqrestore(&amp_lock, flags);
184 }
185 
186 /*
187  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap
188  * because the kmap code must perform a global TLB invalidation when
189  * the kmap pool wraps.
190  *
191  * Note that they may be slower than on x86 (etc.) because unlike on
192  * those platforms, we do have to take a global lock to map and unmap
193  * pages on Tile (see above).
194  *
195  * When holding an atomic kmap is is not legal to sleep, so atomic
196  * kmaps are appropriate for short, tight code paths only.
197  */
198 void *kmap_atomic_prot(struct page *page, pgprot_t prot)
199 {
200         unsigned long vaddr;
201         int idx, type;
202         pte_t *pte;
203 
204         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
205         pagefault_disable();
206 
207         /* Avoid icache flushes by disallowing atomic executable mappings. */
208         BUG_ON(pte_exec(prot));
209 
210         if (!PageHighMem(page))
211                 return page_address(page);
212 
213         type = kmap_atomic_idx_push();
214         idx = type + KM_TYPE_NR*smp_processor_id();
215         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
216         pte = kmap_get_pte(vaddr);
217         BUG_ON(!pte_none(*pte));
218 
219         /* Register that this page is mapped atomically on this cpu. */
220         kmap_atomic_register(page, type, vaddr, pte, mk_pte(page, prot));
221 
222         return (void *)vaddr;
223 }
224 EXPORT_SYMBOL(kmap_atomic_prot);
225 
226 void *kmap_atomic(struct page *page)
227 {
228         /* PAGE_NONE is a magic value that tells us to check immutability. */
229         return kmap_atomic_prot(page, PAGE_NONE);
230 }
231 EXPORT_SYMBOL(kmap_atomic);
232 
233 void __kunmap_atomic(void *kvaddr)
234 {
235         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
236 
237         if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
238             vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
239                 pte_t *pte = kmap_get_pte(vaddr);
240                 pte_t pteval = *pte;
241                 int idx, type;
242 
243                 type = kmap_atomic_idx();
244                 idx = type + KM_TYPE_NR*smp_processor_id();
245 
246                 /*
247                  * Force other mappings to Oops if they try to access this pte
248                  * without first remapping it.  Keeping stale mappings around
249                  * is a bad idea.
250                  */
251                 BUG_ON(!pte_present(pteval) && !pte_migrating(pteval));
252                 kmap_atomic_unregister(pte_page(pteval), vaddr);
253                 kpte_clear_flush(pte, vaddr);
254                 kmap_atomic_idx_pop();
255         } else {
256                 /* Must be a lowmem page */
257                 BUG_ON(vaddr < PAGE_OFFSET);
258                 BUG_ON(vaddr >= (unsigned long)high_memory);
259         }
260 
261         pagefault_enable();
262 }
263 EXPORT_SYMBOL(__kunmap_atomic);
264 
265 /*
266  * This API is supposed to allow us to map memory without a "struct page".
267  * Currently we don't support this, though this may change in the future.
268  */
269 void *kmap_atomic_pfn(unsigned long pfn)
270 {
271         return kmap_atomic(pfn_to_page(pfn));
272 }
273 void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
274 {
275         return kmap_atomic_prot(pfn_to_page(pfn), prot);
276 }
277 
278 struct page *kmap_atomic_to_page(void *ptr)
279 {
280         pte_t *pte;
281         unsigned long vaddr = (unsigned long)ptr;
282 
283         if (vaddr < FIXADDR_START)
284                 return virt_to_page(ptr);
285 
286         pte = kmap_get_pte(vaddr);
287         return pte_page(*pte);
288 }
289 

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