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 set_user_asce(mm); 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 VM_BUG_ON(mm->context.asce_limit < _REGION2_SIZE); 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 == _REGION2_SIZE) { 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 = _REGION1_SIZE; 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 VM_BUG_ON(mm->context.asce_limit != _REGION2_SIZE); 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 = _REGION3_SIZE; 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 u64 *table; 161 162 page = alloc_page(GFP_KERNEL); 163 if (page) { 164 table = (u64 *)page_to_phys(page); 165 memset64(table, _PAGE_INVALID, PTRS_PER_PTE); 166 memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE); 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.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.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 arch_set_page_dat(page, 0); 218 /* Initialize page table */ 219 table = (unsigned long *) page_to_phys(page); 220 if (mm_alloc_pgste(mm)) { 221 /* Return 4K page table with PGSTEs */ 222 atomic_set(&page->_mapcount, 3); 223 memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE); 224 memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE); 225 } else { 226 /* Return the first 2K fragment of the page */ 227 atomic_set(&page->_mapcount, 1); 228 memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE); 229 spin_lock_bh(&mm->context.lock); 230 list_add(&page->lru, &mm->context.pgtable_list); 231 spin_unlock_bh(&mm->context.lock); 232 } 233 return table; 234 } 235 236 void page_table_free(struct mm_struct *mm, unsigned long *table) 237 { 238 struct page *page; 239 unsigned int bit, mask; 240 241 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 242 if (!mm_alloc_pgste(mm)) { 243 /* Free 2K page table fragment of a 4K page */ 244 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)); 245 spin_lock_bh(&mm->context.lock); 246 mask = atomic_xor_bits(&page->_mapcount, 1U << bit); 247 if (mask & 3) 248 list_add(&page->lru, &mm->context.pgtable_list); 249 else 250 list_del(&page->lru); 251 spin_unlock_bh(&mm->context.lock); 252 if (mask != 0) 253 return; 254 } 255 256 pgtable_page_dtor(page); 257 atomic_set(&page->_mapcount, -1); 258 __free_page(page); 259 } 260 261 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table, 262 unsigned long vmaddr) 263 { 264 struct mm_struct *mm; 265 struct page *page; 266 unsigned int bit, mask; 267 268 mm = tlb->mm; 269 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 270 if (mm_alloc_pgste(mm)) { 271 gmap_unlink(mm, table, vmaddr); 272 table = (unsigned long *) (__pa(table) | 3); 273 tlb_remove_table(tlb, table); 274 return; 275 } 276 bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)); 277 spin_lock_bh(&mm->context.lock); 278 mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit); 279 if (mask & 3) 280 list_add_tail(&page->lru, &mm->context.pgtable_list); 281 else 282 list_del(&page->lru); 283 spin_unlock_bh(&mm->context.lock); 284 table = (unsigned long *) (__pa(table) | (1U << bit)); 285 tlb_remove_table(tlb, table); 286 } 287 288 static void __tlb_remove_table(void *_table) 289 { 290 unsigned int mask = (unsigned long) _table & 3; 291 void *table = (void *)((unsigned long) _table ^ mask); 292 struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 293 294 switch (mask) { 295 case 0: /* pmd, pud, or p4d */ 296 free_pages((unsigned long) table, 2); 297 break; 298 case 1: /* lower 2K of a 4K page table */ 299 case 2: /* higher 2K of a 4K page table */ 300 if (atomic_xor_bits(&page->_mapcount, mask << 4) != 0) 301 break; 302 /* fallthrough */ 303 case 3: /* 4K page table with pgstes */ 304 pgtable_page_dtor(page); 305 atomic_set(&page->_mapcount, -1); 306 __free_page(page); 307 break; 308 } 309 } 310 311 static void tlb_remove_table_smp_sync(void *arg) 312 { 313 /* Simply deliver the interrupt */ 314 } 315 316 static void tlb_remove_table_one(void *table) 317 { 318 /* 319 * This isn't an RCU grace period and hence the page-tables cannot be 320 * assumed to be actually RCU-freed. 321 * 322 * It is however sufficient for software page-table walkers that rely 323 * on IRQ disabling. See the comment near struct mmu_table_batch. 324 */ 325 smp_call_function(tlb_remove_table_smp_sync, NULL, 1); 326 __tlb_remove_table(table); 327 } 328 329 static void tlb_remove_table_rcu(struct rcu_head *head) 330 { 331 struct mmu_table_batch *batch; 332 int i; 333 334 batch = container_of(head, struct mmu_table_batch, rcu); 335 336 for (i = 0; i < batch->nr; i++) 337 __tlb_remove_table(batch->tables[i]); 338 339 free_page((unsigned long)batch); 340 } 341 342 void tlb_table_flush(struct mmu_gather *tlb) 343 { 344 struct mmu_table_batch **batch = &tlb->batch; 345 346 if (*batch) { 347 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu); 348 *batch = NULL; 349 } 350 } 351 352 void tlb_remove_table(struct mmu_gather *tlb, void *table) 353 { 354 struct mmu_table_batch **batch = &tlb->batch; 355 356 tlb->mm->context.flush_mm = 1; 357 if (*batch == NULL) { 358 *batch = (struct mmu_table_batch *) 359 __get_free_page(GFP_NOWAIT | __GFP_NOWARN); 360 if (*batch == NULL) { 361 __tlb_flush_mm_lazy(tlb->mm); 362 tlb_remove_table_one(table); 363 return; 364 } 365 (*batch)->nr = 0; 366 } 367 (*batch)->tables[(*batch)->nr++] = table; 368 if ((*batch)->nr == MAX_TABLE_BATCH) 369 tlb_flush_mmu(tlb); 370 } 371