1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Page table allocation functions 4 * 5 * Copyright IBM Corp. 2016 6 * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com> 7 */ 8 9 #include <linux/mm.h> 10 #include <linux/sysctl.h> 11 #include <asm/mmu_context.h> 12 #include <asm/pgalloc.h> 13 #include <asm/gmap.h> 14 #include <asm/tlb.h> 15 #include <asm/tlbflush.h> 16 17 #ifdef CONFIG_PGSTE 18 19 static int page_table_allocate_pgste_min = 0; 20 static int page_table_allocate_pgste_max = 1; 21 int page_table_allocate_pgste = 0; 22 EXPORT_SYMBOL(page_table_allocate_pgste); 23 24 static struct ctl_table page_table_sysctl[] = { 25 { 26 .procname = "allocate_pgste", 27 .data = &page_table_allocate_pgste, 28 .maxlen = sizeof(int), 29 .mode = S_IRUGO | S_IWUSR, 30 .proc_handler = proc_dointvec, 31 .extra1 = &page_table_allocate_pgste_min, 32 .extra2 = &page_table_allocate_pgste_max, 33 }, 34 { } 35 }; 36 37 static struct ctl_table page_table_sysctl_dir[] = { 38 { 39 .procname = "vm", 40 .maxlen = 0, 41 .mode = 0555, 42 .child = page_table_sysctl, 43 }, 44 { } 45 }; 46 47 static int __init page_table_register_sysctl(void) 48 { 49 return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM; 50 } 51 __initcall(page_table_register_sysctl); 52 53 #endif /* CONFIG_PGSTE */ 54 55 unsigned long *crst_table_alloc(struct mm_struct *mm) 56 { 57 struct page *page = alloc_pages(GFP_KERNEL, 2); 58 59 if (!page) 60 return NULL; 61 arch_set_page_dat(page, 2); 62 return (unsigned long *) page_to_phys(page); 63 } 64 65 void crst_table_free(struct mm_struct *mm, unsigned long *table) 66 { 67 free_pages((unsigned long) table, 2); 68 } 69 70 static void __crst_table_upgrade(void *arg) 71 { 72 struct mm_struct *mm = arg; 73 74 if (current->active_mm == mm) { 75 clear_user_asce(); 76 set_user_asce(mm); 77 } 78 __tlb_flush_local(); 79 } 80 81 int crst_table_upgrade(struct mm_struct *mm, unsigned long end) 82 { 83 unsigned long *table, *pgd; 84 int rc, notify; 85 86 /* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */ 87 VM_BUG_ON(mm->context.asce_limit < _REGION2_SIZE); 88 if (end >= TASK_SIZE_MAX) 89 return -ENOMEM; 90 rc = 0; 91 notify = 0; 92 while (mm->context.asce_limit < end) { 93 table = crst_table_alloc(mm); 94 if (!table) { 95 rc = -ENOMEM; 96 break; 97 } 98 spin_lock_bh(&mm->page_table_lock); 99 pgd = (unsigned long *) mm->pgd; 100 if (mm->context.asce_limit == _REGION2_SIZE) { 101 crst_table_init(table, _REGION2_ENTRY_EMPTY); 102 p4d_populate(mm, (p4d_t *) table, (pud_t *) pgd); 103 mm->pgd = (pgd_t *) table; 104 mm->context.asce_limit = _REGION1_SIZE; 105 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 106 _ASCE_USER_BITS | _ASCE_TYPE_REGION2; 107 } else { 108 crst_table_init(table, _REGION1_ENTRY_EMPTY); 109 pgd_populate(mm, (pgd_t *) table, (p4d_t *) pgd); 110 mm->pgd = (pgd_t *) table; 111 mm->context.asce_limit = -PAGE_SIZE; 112 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 113 _ASCE_USER_BITS | _ASCE_TYPE_REGION1; 114 } 115 notify = 1; 116 spin_unlock_bh(&mm->page_table_lock); 117 } 118 if (notify) 119 on_each_cpu(__crst_table_upgrade, mm, 0); 120 return rc; 121 } 122 123 void crst_table_downgrade(struct mm_struct *mm) 124 { 125 pgd_t *pgd; 126 127 /* downgrade should only happen from 3 to 2 levels (compat only) */ 128 VM_BUG_ON(mm->context.asce_limit != _REGION2_SIZE); 129 130 if (current->active_mm == mm) { 131 clear_user_asce(); 132 __tlb_flush_mm(mm); 133 } 134 135 pgd = mm->pgd; 136 mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN); 137 mm->context.asce_limit = _REGION3_SIZE; 138 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 139 _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT; 140 crst_table_free(mm, (unsigned long *) pgd); 141 142 if (current->active_mm == mm) 143 set_user_asce(mm); 144 } 145 146 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits) 147 { 148 unsigned int old, new; 149 150 do { 151 old = atomic_read(v); 152 new = old ^ bits; 153 } while (atomic_cmpxchg(v, old, new) != old); 154 return new; 155 } 156 157 #ifdef CONFIG_PGSTE 158 159 struct page *page_table_alloc_pgste(struct mm_struct *mm) 160 { 161 struct page *page; 162 unsigned long *table; 163 164 page = alloc_page(GFP_KERNEL); 165 if (page) { 166 table = (unsigned long *) page_to_phys(page); 167 clear_table(table, _PAGE_INVALID, PAGE_SIZE/2); 168 clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2); 169 } 170 return page; 171 } 172 173 void page_table_free_pgste(struct page *page) 174 { 175 __free_page(page); 176 } 177 178 #endif /* CONFIG_PGSTE */ 179 180 /* 181 * page table entry allocation/free routines. 182 */ 183 unsigned long *page_table_alloc(struct mm_struct *mm) 184 { 185 unsigned long *table; 186 struct page *page; 187 unsigned int mask, bit; 188 189 /* Try to get a fragment of a 4K page as a 2K page table */ 190 if (!mm_alloc_pgste(mm)) { 191 table = NULL; 192 spin_lock_bh(&mm->context.lock); 193 if (!list_empty(&mm->context.pgtable_list)) { 194 page = list_first_entry(&mm->context.pgtable_list, 195 struct page, lru); 196 mask = atomic_read(&page->_mapcount); 197 mask = (mask | (mask >> 4)) & 3; 198 if (mask != 3) { 199 table = (unsigned long *) page_to_phys(page); 200 bit = mask & 1; /* =1 -> second 2K */ 201 if (bit) 202 table += PTRS_PER_PTE; 203 atomic_xor_bits(&page->_mapcount, 1U << bit); 204 list_del(&page->lru); 205 } 206 } 207 spin_unlock_bh(&mm->context.lock); 208 if (table) 209 return table; 210 } 211 /* Allocate a fresh page */ 212 page = alloc_page(GFP_KERNEL); 213 if (!page) 214 return NULL; 215 if (!pgtable_page_ctor(page)) { 216 __free_page(page); 217 return NULL; 218 } 219 arch_set_page_dat(page, 0); 220 /* Initialize page table */ 221 table = (unsigned long *) page_to_phys(page); 222 if (mm_alloc_pgste(mm)) { 223 /* Return 4K page table with PGSTEs */ 224 atomic_set(&page->_mapcount, 3); 225 clear_table(table, _PAGE_INVALID, PAGE_SIZE/2); 226 clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2); 227 } else { 228 /* Return the first 2K fragment of the page */ 229 atomic_set(&page->_mapcount, 1); 230 clear_table(table, _PAGE_INVALID, PAGE_SIZE); 231 spin_lock_bh(&mm->context.lock); 232 list_add(&page->lru, &mm->context.pgtable_list); 233 spin_unlock_bh(&mm->context.lock); 234 } 235 return table; 236 } 237 238 void page_table_free(struct mm_struct *mm, unsigned long *table) 239 { 240 struct page *page; 241 unsigned int bit, mask; 242 243 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 244 if (!mm_alloc_pgste(mm)) { 245 /* Free 2K page table fragment of a 4K page */ 246 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)); 247 spin_lock_bh(&mm->context.lock); 248 mask = atomic_xor_bits(&page->_mapcount, 1U << bit); 249 if (mask & 3) 250 list_add(&page->lru, &mm->context.pgtable_list); 251 else 252 list_del(&page->lru); 253 spin_unlock_bh(&mm->context.lock); 254 if (mask != 0) 255 return; 256 } 257 258 pgtable_page_dtor(page); 259 atomic_set(&page->_mapcount, -1); 260 __free_page(page); 261 } 262 263 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table, 264 unsigned long vmaddr) 265 { 266 struct mm_struct *mm; 267 struct page *page; 268 unsigned int bit, mask; 269 270 mm = tlb->mm; 271 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 272 if (mm_alloc_pgste(mm)) { 273 gmap_unlink(mm, table, vmaddr); 274 table = (unsigned long *) (__pa(table) | 3); 275 tlb_remove_table(tlb, table); 276 return; 277 } 278 bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)); 279 spin_lock_bh(&mm->context.lock); 280 mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit); 281 if (mask & 3) 282 list_add_tail(&page->lru, &mm->context.pgtable_list); 283 else 284 list_del(&page->lru); 285 spin_unlock_bh(&mm->context.lock); 286 table = (unsigned long *) (__pa(table) | (1U << bit)); 287 tlb_remove_table(tlb, table); 288 } 289 290 static void __tlb_remove_table(void *_table) 291 { 292 unsigned int mask = (unsigned long) _table & 3; 293 void *table = (void *)((unsigned long) _table ^ mask); 294 struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 295 296 switch (mask) { 297 case 0: /* pmd, pud, or p4d */ 298 free_pages((unsigned long) table, 2); 299 break; 300 case 1: /* lower 2K of a 4K page table */ 301 case 2: /* higher 2K of a 4K page table */ 302 if (atomic_xor_bits(&page->_mapcount, mask << 4) != 0) 303 break; 304 /* fallthrough */ 305 case 3: /* 4K page table with pgstes */ 306 pgtable_page_dtor(page); 307 atomic_set(&page->_mapcount, -1); 308 __free_page(page); 309 break; 310 } 311 } 312 313 static void tlb_remove_table_smp_sync(void *arg) 314 { 315 /* Simply deliver the interrupt */ 316 } 317 318 static void tlb_remove_table_one(void *table) 319 { 320 /* 321 * This isn't an RCU grace period and hence the page-tables cannot be 322 * assumed to be actually RCU-freed. 323 * 324 * It is however sufficient for software page-table walkers that rely 325 * on IRQ disabling. See the comment near struct mmu_table_batch. 326 */ 327 smp_call_function(tlb_remove_table_smp_sync, NULL, 1); 328 __tlb_remove_table(table); 329 } 330 331 static void tlb_remove_table_rcu(struct rcu_head *head) 332 { 333 struct mmu_table_batch *batch; 334 int i; 335 336 batch = container_of(head, struct mmu_table_batch, rcu); 337 338 for (i = 0; i < batch->nr; i++) 339 __tlb_remove_table(batch->tables[i]); 340 341 free_page((unsigned long)batch); 342 } 343 344 void tlb_table_flush(struct mmu_gather *tlb) 345 { 346 struct mmu_table_batch **batch = &tlb->batch; 347 348 if (*batch) { 349 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu); 350 *batch = NULL; 351 } 352 } 353 354 void tlb_remove_table(struct mmu_gather *tlb, void *table) 355 { 356 struct mmu_table_batch **batch = &tlb->batch; 357 358 tlb->mm->context.flush_mm = 1; 359 if (*batch == NULL) { 360 *batch = (struct mmu_table_batch *) 361 __get_free_page(GFP_NOWAIT | __GFP_NOWARN); 362 if (*batch == NULL) { 363 __tlb_flush_mm_lazy(tlb->mm); 364 tlb_remove_table_one(table); 365 return; 366 } 367 (*batch)->nr = 0; 368 } 369 (*batch)->tables[(*batch)->nr++] = table; 370 if ((*batch)->nr == MAX_TABLE_BATCH) 371 tlb_flush_mmu(tlb); 372 } 373