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