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 unsigned long totalhigh_pages __read_mostly; 48 EXPORT_SYMBOL(totalhigh_pages); 49 50 51 EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx); 52 53 unsigned int nr_free_highpages (void) 54 { 55 pg_data_t *pgdat; 56 unsigned int pages = 0; 57 58 for_each_online_pgdat(pgdat) { 59 pages += zone_page_state(&pgdat->node_zones[ZONE_HIGHMEM], 60 NR_FREE_PAGES); 61 if (zone_movable_is_highmem()) 62 pages += zone_page_state( 63 &pgdat->node_zones[ZONE_MOVABLE], 64 NR_FREE_PAGES); 65 } 66 67 return pages; 68 } 69 70 static int pkmap_count[LAST_PKMAP]; 71 static unsigned int last_pkmap_nr; 72 static __cacheline_aligned_in_smp DEFINE_SPINLOCK(kmap_lock); 73 74 pte_t * pkmap_page_table; 75 76 static DECLARE_WAIT_QUEUE_HEAD(pkmap_map_wait); 77 78 /* 79 * Most architectures have no use for kmap_high_get(), so let's abstract 80 * the disabling of IRQ out of the locking in that case to save on a 81 * potential useless overhead. 82 */ 83 #ifdef ARCH_NEEDS_KMAP_HIGH_GET 84 #define lock_kmap() spin_lock_irq(&kmap_lock) 85 #define unlock_kmap() spin_unlock_irq(&kmap_lock) 86 #define lock_kmap_any(flags) spin_lock_irqsave(&kmap_lock, flags) 87 #define unlock_kmap_any(flags) spin_unlock_irqrestore(&kmap_lock, flags) 88 #else 89 #define lock_kmap() spin_lock(&kmap_lock) 90 #define unlock_kmap() spin_unlock(&kmap_lock) 91 #define lock_kmap_any(flags) \ 92 do { spin_lock(&kmap_lock); (void)(flags); } while (0) 93 #define unlock_kmap_any(flags) \ 94 do { spin_unlock(&kmap_lock); (void)(flags); } while (0) 95 #endif 96 97 struct page *kmap_to_page(void *vaddr) 98 { 99 unsigned long addr = (unsigned long)vaddr; 100 101 if (addr >= PKMAP_ADDR(0) && addr < PKMAP_ADDR(LAST_PKMAP)) { 102 int i = PKMAP_NR(addr); 103 return pte_page(pkmap_page_table[i]); 104 } 105 106 return virt_to_page(addr); 107 } 108 EXPORT_SYMBOL(kmap_to_page); 109 110 static void flush_all_zero_pkmaps(void) 111 { 112 int i; 113 int need_flush = 0; 114 115 flush_cache_kmaps(); 116 117 for (i = 0; i < LAST_PKMAP; i++) { 118 struct page *page; 119 120 /* 121 * zero means we don't have anything to do, 122 * >1 means that it is still in use. Only 123 * a count of 1 means that it is free but 124 * needs to be unmapped 125 */ 126 if (pkmap_count[i] != 1) 127 continue; 128 pkmap_count[i] = 0; 129 130 /* sanity check */ 131 BUG_ON(pte_none(pkmap_page_table[i])); 132 133 /* 134 * Don't need an atomic fetch-and-clear op here; 135 * no-one has the page mapped, and cannot get at 136 * its virtual address (and hence PTE) without first 137 * getting the kmap_lock (which is held here). 138 * So no dangers, even with speculative execution. 139 */ 140 page = pte_page(pkmap_page_table[i]); 141 pte_clear(&init_mm, PKMAP_ADDR(i), &pkmap_page_table[i]); 142 143 set_page_address(page, NULL); 144 need_flush = 1; 145 } 146 if (need_flush) 147 flush_tlb_kernel_range(PKMAP_ADDR(0), PKMAP_ADDR(LAST_PKMAP)); 148 } 149 150 /** 151 * kmap_flush_unused - flush all unused kmap mappings in order to remove stray mappings 152 */ 153 void kmap_flush_unused(void) 154 { 155 lock_kmap(); 156 flush_all_zero_pkmaps(); 157 unlock_kmap(); 158 } 159 160 static inline unsigned long map_new_virtual(struct page *page) 161 { 162 unsigned long vaddr; 163 int count; 164 165 start: 166 count = LAST_PKMAP; 167 /* Find an empty entry */ 168 for (;;) { 169 last_pkmap_nr = (last_pkmap_nr + 1) & LAST_PKMAP_MASK; 170 if (!last_pkmap_nr) { 171 flush_all_zero_pkmaps(); 172 count = LAST_PKMAP; 173 } 174 if (!pkmap_count[last_pkmap_nr]) 175 break; /* Found a usable entry */ 176 if (--count) 177 continue; 178 179 /* 180 * Sleep for somebody else to unmap their entries 181 */ 182 { 183 DECLARE_WAITQUEUE(wait, current); 184 185 __set_current_state(TASK_UNINTERRUPTIBLE); 186 add_wait_queue(&pkmap_map_wait, &wait); 187 unlock_kmap(); 188 schedule(); 189 remove_wait_queue(&pkmap_map_wait, &wait); 190 lock_kmap(); 191 192 /* Somebody else might have mapped it while we slept */ 193 if (page_address(page)) 194 return (unsigned long)page_address(page); 195 196 /* Re-start */ 197 goto start; 198 } 199 } 200 vaddr = PKMAP_ADDR(last_pkmap_nr); 201 set_pte_at(&init_mm, vaddr, 202 &(pkmap_page_table[last_pkmap_nr]), mk_pte(page, kmap_prot)); 203 204 pkmap_count[last_pkmap_nr] = 1; 205 set_page_address(page, (void *)vaddr); 206 207 return vaddr; 208 } 209 210 /** 211 * kmap_high - map a highmem page into memory 212 * @page: &struct page to map 213 * 214 * Returns the page's virtual memory address. 215 * 216 * We cannot call this from interrupts, as it may block. 217 */ 218 void *kmap_high(struct page *page) 219 { 220 unsigned long vaddr; 221 222 /* 223 * For highmem pages, we can't trust "virtual" until 224 * after we have the lock. 225 */ 226 lock_kmap(); 227 vaddr = (unsigned long)page_address(page); 228 if (!vaddr) 229 vaddr = map_new_virtual(page); 230 pkmap_count[PKMAP_NR(vaddr)]++; 231 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 2); 232 unlock_kmap(); 233 return (void*) vaddr; 234 } 235 236 EXPORT_SYMBOL(kmap_high); 237 238 #ifdef ARCH_NEEDS_KMAP_HIGH_GET 239 /** 240 * kmap_high_get - pin a highmem page into memory 241 * @page: &struct page to pin 242 * 243 * Returns the page's current virtual memory address, or NULL if no mapping 244 * exists. If and only if a non null address is returned then a 245 * matching call to kunmap_high() is necessary. 246 * 247 * This can be called from any context. 248 */ 249 void *kmap_high_get(struct page *page) 250 { 251 unsigned long vaddr, flags; 252 253 lock_kmap_any(flags); 254 vaddr = (unsigned long)page_address(page); 255 if (vaddr) { 256 BUG_ON(pkmap_count[PKMAP_NR(vaddr)] < 1); 257 pkmap_count[PKMAP_NR(vaddr)]++; 258 } 259 unlock_kmap_any(flags); 260 return (void*) vaddr; 261 } 262 #endif 263 264 /** 265 * kunmap_high - unmap a highmem page into memory 266 * @page: &struct page to unmap 267 * 268 * If ARCH_NEEDS_KMAP_HIGH_GET is not defined then this may be called 269 * only from user context. 270 */ 271 void kunmap_high(struct page *page) 272 { 273 unsigned long vaddr; 274 unsigned long nr; 275 unsigned long flags; 276 int need_wakeup; 277 278 lock_kmap_any(flags); 279 vaddr = (unsigned long)page_address(page); 280 BUG_ON(!vaddr); 281 nr = PKMAP_NR(vaddr); 282 283 /* 284 * A count must never go down to zero 285 * without a TLB flush! 286 */ 287 need_wakeup = 0; 288 switch (--pkmap_count[nr]) { 289 case 0: 290 BUG(); 291 case 1: 292 /* 293 * Avoid an unnecessary wake_up() function call. 294 * The common case is pkmap_count[] == 1, but 295 * no waiters. 296 * The tasks queued in the wait-queue are guarded 297 * by both the lock in the wait-queue-head and by 298 * the kmap_lock. As the kmap_lock is held here, 299 * no need for the wait-queue-head's lock. Simply 300 * test if the queue is empty. 301 */ 302 need_wakeup = waitqueue_active(&pkmap_map_wait); 303 } 304 unlock_kmap_any(flags); 305 306 /* do wake-up, if needed, race-free outside of the spin lock */ 307 if (need_wakeup) 308 wake_up(&pkmap_map_wait); 309 } 310 311 EXPORT_SYMBOL(kunmap_high); 312 #endif 313 314 #if defined(HASHED_PAGE_VIRTUAL) 315 316 #define PA_HASH_ORDER 7 317 318 /* 319 * Describes one page->virtual association 320 */ 321 struct page_address_map { 322 struct page *page; 323 void *virtual; 324 struct list_head list; 325 }; 326 327 static struct page_address_map page_address_maps[LAST_PKMAP]; 328 329 /* 330 * Hash table bucket 331 */ 332 static struct page_address_slot { 333 struct list_head lh; /* List of page_address_maps */ 334 spinlock_t lock; /* Protect this bucket's list */ 335 } ____cacheline_aligned_in_smp page_address_htable[1<<PA_HASH_ORDER]; 336 337 static struct page_address_slot *page_slot(const struct page *page) 338 { 339 return &page_address_htable[hash_ptr(page, PA_HASH_ORDER)]; 340 } 341 342 /** 343 * page_address - get the mapped virtual address of a page 344 * @page: &struct page to get the virtual address of 345 * 346 * Returns the page's virtual address. 347 */ 348 void *page_address(const struct page *page) 349 { 350 unsigned long flags; 351 void *ret; 352 struct page_address_slot *pas; 353 354 if (!PageHighMem(page)) 355 return lowmem_page_address(page); 356 357 pas = page_slot(page); 358 ret = NULL; 359 spin_lock_irqsave(&pas->lock, flags); 360 if (!list_empty(&pas->lh)) { 361 struct page_address_map *pam; 362 363 list_for_each_entry(pam, &pas->lh, list) { 364 if (pam->page == page) { 365 ret = pam->virtual; 366 goto done; 367 } 368 } 369 } 370 done: 371 spin_unlock_irqrestore(&pas->lock, flags); 372 return ret; 373 } 374 375 EXPORT_SYMBOL(page_address); 376 377 /** 378 * set_page_address - set a page's virtual address 379 * @page: &struct page to set 380 * @virtual: virtual address to use 381 */ 382 void set_page_address(struct page *page, void *virtual) 383 { 384 unsigned long flags; 385 struct page_address_slot *pas; 386 struct page_address_map *pam; 387 388 BUG_ON(!PageHighMem(page)); 389 390 pas = page_slot(page); 391 if (virtual) { /* Add */ 392 pam = &page_address_maps[PKMAP_NR((unsigned long)virtual)]; 393 pam->page = page; 394 pam->virtual = virtual; 395 396 spin_lock_irqsave(&pas->lock, flags); 397 list_add_tail(&pam->list, &pas->lh); 398 spin_unlock_irqrestore(&pas->lock, flags); 399 } else { /* Remove */ 400 spin_lock_irqsave(&pas->lock, flags); 401 list_for_each_entry(pam, &pas->lh, list) { 402 if (pam->page == page) { 403 list_del(&pam->list); 404 spin_unlock_irqrestore(&pas->lock, flags); 405 goto done; 406 } 407 } 408 spin_unlock_irqrestore(&pas->lock, flags); 409 } 410 done: 411 return; 412 } 413 414 void __init page_address_init(void) 415 { 416 int i; 417 418 for (i = 0; i < ARRAY_SIZE(page_address_htable); i++) { 419 INIT_LIST_HEAD(&page_address_htable[i].lh); 420 spin_lock_init(&page_address_htable[i].lock); 421 } 422 } 423 424 #endif /* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */ 425