1 /* 2 * Page table allocation functions 3 * 4 * Copyright IBM Corp. 2016 5 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com> 6 */ 7 8 #include <linux/mm.h> 9 #include <linux/sysctl.h> 10 #include <asm/mmu_context.h> 11 #include <asm/pgalloc.h> 12 #include <asm/gmap.h> 13 #include <asm/tlb.h> 14 #include <asm/tlbflush.h> 15 16 #ifdef CONFIG_PGSTE 17 18 static int page_table_allocate_pgste_min = 0; 19 static int page_table_allocate_pgste_max = 1; 20 int page_table_allocate_pgste = 0; 21 EXPORT_SYMBOL(page_table_allocate_pgste); 22 23 static struct ctl_table page_table_sysctl[] = { 24 { 25 .procname = "allocate_pgste", 26 .data = &page_table_allocate_pgste, 27 .maxlen = sizeof(int), 28 .mode = S_IRUGO | S_IWUSR, 29 .proc_handler = proc_dointvec, 30 .extra1 = &page_table_allocate_pgste_min, 31 .extra2 = &page_table_allocate_pgste_max, 32 }, 33 { } 34 }; 35 36 static struct ctl_table page_table_sysctl_dir[] = { 37 { 38 .procname = "vm", 39 .maxlen = 0, 40 .mode = 0555, 41 .child = page_table_sysctl, 42 }, 43 { } 44 }; 45 46 static int __init page_table_register_sysctl(void) 47 { 48 return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM; 49 } 50 __initcall(page_table_register_sysctl); 51 52 #endif /* CONFIG_PGSTE */ 53 54 unsigned long *crst_table_alloc(struct mm_struct *mm) 55 { 56 struct page *page = alloc_pages(GFP_KERNEL, 2); 57 58 if (!page) 59 return NULL; 60 arch_set_page_dat(page, 2); 61 return (unsigned long *) page_to_phys(page); 62 } 63 64 void crst_table_free(struct mm_struct *mm, unsigned long *table) 65 { 66 free_pages((unsigned long) table, 2); 67 } 68 69 static void __crst_table_upgrade(void *arg) 70 { 71 struct mm_struct *mm = arg; 72 73 if (current->active_mm == mm) { 74 clear_user_asce(); 75 set_user_asce(mm); 76 } 77 __tlb_flush_local(); 78 } 79 80 int crst_table_upgrade(struct mm_struct *mm, unsigned long end) 81 { 82 unsigned long *table, *pgd; 83 int rc, notify; 84 85 /* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */ 86 VM_BUG_ON(mm->context.asce_limit < _REGION2_SIZE); 87 if (end >= TASK_SIZE_MAX) 88 return -ENOMEM; 89 rc = 0; 90 notify = 0; 91 while (mm->context.asce_limit < end) { 92 table = crst_table_alloc(mm); 93 if (!table) { 94 rc = -ENOMEM; 95 break; 96 } 97 spin_lock_bh(&mm->page_table_lock); 98 pgd = (unsigned long *) mm->pgd; 99 if (mm->context.asce_limit == _REGION2_SIZE) { 100 crst_table_init(table, _REGION2_ENTRY_EMPTY); 101 p4d_populate(mm, (p4d_t *) table, (pud_t *) pgd); 102 mm->pgd = (pgd_t *) table; 103 mm->context.asce_limit = _REGION1_SIZE; 104 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 105 _ASCE_USER_BITS | _ASCE_TYPE_REGION2; 106 } else { 107 crst_table_init(table, _REGION1_ENTRY_EMPTY); 108 pgd_populate(mm, (pgd_t *) table, (p4d_t *) pgd); 109 mm->pgd = (pgd_t *) table; 110 mm->context.asce_limit = -PAGE_SIZE; 111 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 112 _ASCE_USER_BITS | _ASCE_TYPE_REGION1; 113 } 114 notify = 1; 115 spin_unlock_bh(&mm->page_table_lock); 116 } 117 if (notify) 118 on_each_cpu(__crst_table_upgrade, mm, 0); 119 return rc; 120 } 121 122 void crst_table_downgrade(struct mm_struct *mm) 123 { 124 pgd_t *pgd; 125 126 /* downgrade should only happen from 3 to 2 levels (compat only) */ 127 VM_BUG_ON(mm->context.asce_limit != _REGION2_SIZE); 128 129 if (current->active_mm == mm) { 130 clear_user_asce(); 131 __tlb_flush_mm(mm); 132 } 133 134 pgd = mm->pgd; 135 mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN); 136 mm->context.asce_limit = _REGION3_SIZE; 137 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 138 _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT; 139 crst_table_free(mm, (unsigned long *) pgd); 140 141 if (current->active_mm == mm) 142 set_user_asce(mm); 143 } 144 145 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits) 146 { 147 unsigned int old, new; 148 149 do { 150 old = atomic_read(v); 151 new = old ^ bits; 152 } while (atomic_cmpxchg(v, old, new) != old); 153 return new; 154 } 155 156 #ifdef CONFIG_PGSTE 157 158 struct page *page_table_alloc_pgste(struct mm_struct *mm) 159 { 160 struct page *page; 161 unsigned long *table; 162 163 page = alloc_page(GFP_KERNEL); 164 if (page) { 165 table = (unsigned long *) page_to_phys(page); 166 clear_table(table, _PAGE_INVALID, PAGE_SIZE/2); 167 clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2); 168 } 169 return page; 170 } 171 172 void page_table_free_pgste(struct page *page) 173 { 174 __free_page(page); 175 } 176 177 #endif /* CONFIG_PGSTE */ 178 179 /* 180 * page table entry allocation/free routines. 181 */ 182 unsigned long *page_table_alloc(struct mm_struct *mm) 183 { 184 unsigned long *table; 185 struct page *page; 186 unsigned int mask, bit; 187 188 /* Try to get a fragment of a 4K page as a 2K page table */ 189 if (!mm_alloc_pgste(mm)) { 190 table = NULL; 191 spin_lock_bh(&mm->context.lock); 192 if (!list_empty(&mm->context.pgtable_list)) { 193 page = list_first_entry(&mm->context.pgtable_list, 194 struct page, lru); 195 mask = atomic_read(&page->_mapcount); 196 mask = (mask | (mask >> 4)) & 3; 197 if (mask != 3) { 198 table = (unsigned long *) page_to_phys(page); 199 bit = mask & 1; /* =1 -> second 2K */ 200 if (bit) 201 table += PTRS_PER_PTE; 202 atomic_xor_bits(&page->_mapcount, 1U << bit); 203 list_del(&page->lru); 204 } 205 } 206 spin_unlock_bh(&mm->context.lock); 207 if (table) 208 return table; 209 } 210 /* Allocate a fresh page */ 211 page = alloc_page(GFP_KERNEL); 212 if (!page) 213 return NULL; 214 if (!pgtable_page_ctor(page)) { 215 __free_page(page); 216 return NULL; 217 } 218 arch_set_page_dat(page, 0); 219 /* Initialize page table */ 220 table = (unsigned long *) page_to_phys(page); 221 if (mm_alloc_pgste(mm)) { 222 /* Return 4K page table with PGSTEs */ 223 atomic_set(&page->_mapcount, 3); 224 clear_table(table, _PAGE_INVALID, PAGE_SIZE/2); 225 clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2); 226 } else { 227 /* Return the first 2K fragment of the page */ 228 atomic_set(&page->_mapcount, 1); 229 clear_table(table, _PAGE_INVALID, PAGE_SIZE); 230 spin_lock_bh(&mm->context.lock); 231 list_add(&page->lru, &mm->context.pgtable_list); 232 spin_unlock_bh(&mm->context.lock); 233 } 234 return table; 235 } 236 237 void page_table_free(struct mm_struct *mm, unsigned long *table) 238 { 239 struct page *page; 240 unsigned int bit, mask; 241 242 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 243 if (!mm_alloc_pgste(mm)) { 244 /* Free 2K page table fragment of a 4K page */ 245 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)); 246 spin_lock_bh(&mm->context.lock); 247 mask = atomic_xor_bits(&page->_mapcount, 1U << bit); 248 if (mask & 3) 249 list_add(&page->lru, &mm->context.pgtable_list); 250 else 251 list_del(&page->lru); 252 spin_unlock_bh(&mm->context.lock); 253 if (mask != 0) 254 return; 255 } 256 257 pgtable_page_dtor(page); 258 atomic_set(&page->_mapcount, -1); 259 __free_page(page); 260 } 261 262 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table, 263 unsigned long vmaddr) 264 { 265 struct mm_struct *mm; 266 struct page *page; 267 unsigned int bit, mask; 268 269 mm = tlb->mm; 270 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 271 if (mm_alloc_pgste(mm)) { 272 gmap_unlink(mm, table, vmaddr); 273 table = (unsigned long *) (__pa(table) | 3); 274 tlb_remove_table(tlb, table); 275 return; 276 } 277 bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)); 278 spin_lock_bh(&mm->context.lock); 279 mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit); 280 if (mask & 3) 281 list_add_tail(&page->lru, &mm->context.pgtable_list); 282 else 283 list_del(&page->lru); 284 spin_unlock_bh(&mm->context.lock); 285 table = (unsigned long *) (__pa(table) | (1U << bit)); 286 tlb_remove_table(tlb, table); 287 } 288 289 static void __tlb_remove_table(void *_table) 290 { 291 unsigned int mask = (unsigned long) _table & 3; 292 void *table = (void *)((unsigned long) _table ^ mask); 293 struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 294 295 switch (mask) { 296 case 0: /* pmd, pud, or p4d */ 297 free_pages((unsigned long) table, 2); 298 break; 299 case 1: /* lower 2K of a 4K page table */ 300 case 2: /* higher 2K of a 4K page table */ 301 if (atomic_xor_bits(&page->_mapcount, mask << 4) != 0) 302 break; 303 /* fallthrough */ 304 case 3: /* 4K page table with pgstes */ 305 pgtable_page_dtor(page); 306 atomic_set(&page->_mapcount, -1); 307 __free_page(page); 308 break; 309 } 310 } 311 312 static void tlb_remove_table_smp_sync(void *arg) 313 { 314 /* Simply deliver the interrupt */ 315 } 316 317 static void tlb_remove_table_one(void *table) 318 { 319 /* 320 * This isn't an RCU grace period and hence the page-tables cannot be 321 * assumed to be actually RCU-freed. 322 * 323 * It is however sufficient for software page-table walkers that rely 324 * on IRQ disabling. See the comment near struct mmu_table_batch. 325 */ 326 smp_call_function(tlb_remove_table_smp_sync, NULL, 1); 327 __tlb_remove_table(table); 328 } 329 330 static void tlb_remove_table_rcu(struct rcu_head *head) 331 { 332 struct mmu_table_batch *batch; 333 int i; 334 335 batch = container_of(head, struct mmu_table_batch, rcu); 336 337 for (i = 0; i < batch->nr; i++) 338 __tlb_remove_table(batch->tables[i]); 339 340 free_page((unsigned long)batch); 341 } 342 343 void tlb_table_flush(struct mmu_gather *tlb) 344 { 345 struct mmu_table_batch **batch = &tlb->batch; 346 347 if (*batch) { 348 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu); 349 *batch = NULL; 350 } 351 } 352 353 void tlb_remove_table(struct mmu_gather *tlb, void *table) 354 { 355 struct mmu_table_batch **batch = &tlb->batch; 356 357 tlb->mm->context.flush_mm = 1; 358 if (*batch == NULL) { 359 *batch = (struct mmu_table_batch *) 360 __get_free_page(GFP_NOWAIT | __GFP_NOWARN); 361 if (*batch == NULL) { 362 __tlb_flush_mm_lazy(tlb->mm); 363 tlb_remove_table_one(table); 364 return; 365 } 366 (*batch)->nr = 0; 367 } 368 (*batch)->tables[(*batch)->nr++] = table; 369 if ((*batch)->nr == MAX_TABLE_BATCH) 370 tlb_flush_mmu(tlb); 371 } 372