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