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 rc = 0; 87 notify = 0; 88 while (mm->context.asce_limit < end) { 89 table = crst_table_alloc(mm); 90 if (!table) { 91 rc = -ENOMEM; 92 break; 93 } 94 spin_lock_bh(&mm->page_table_lock); 95 pgd = (unsigned long *) mm->pgd; 96 if (mm->context.asce_limit == _REGION2_SIZE) { 97 crst_table_init(table, _REGION2_ENTRY_EMPTY); 98 p4d_populate(mm, (p4d_t *) table, (pud_t *) pgd); 99 mm->pgd = (pgd_t *) table; 100 mm->context.asce_limit = _REGION1_SIZE; 101 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 102 _ASCE_USER_BITS | _ASCE_TYPE_REGION2; 103 } else { 104 crst_table_init(table, _REGION1_ENTRY_EMPTY); 105 pgd_populate(mm, (pgd_t *) table, (p4d_t *) pgd); 106 mm->pgd = (pgd_t *) table; 107 mm->context.asce_limit = -PAGE_SIZE; 108 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 109 _ASCE_USER_BITS | _ASCE_TYPE_REGION1; 110 } 111 notify = 1; 112 spin_unlock_bh(&mm->page_table_lock); 113 } 114 if (notify) 115 on_each_cpu(__crst_table_upgrade, mm, 0); 116 return rc; 117 } 118 119 void crst_table_downgrade(struct mm_struct *mm) 120 { 121 pgd_t *pgd; 122 123 /* downgrade should only happen from 3 to 2 levels (compat only) */ 124 VM_BUG_ON(mm->context.asce_limit != _REGION2_SIZE); 125 126 if (current->active_mm == mm) { 127 clear_user_asce(); 128 __tlb_flush_mm(mm); 129 } 130 131 pgd = mm->pgd; 132 mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN); 133 mm->context.asce_limit = _REGION3_SIZE; 134 mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH | 135 _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT; 136 crst_table_free(mm, (unsigned long *) pgd); 137 138 if (current->active_mm == mm) 139 set_user_asce(mm); 140 } 141 142 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits) 143 { 144 unsigned int old, new; 145 146 do { 147 old = atomic_read(v); 148 new = old ^ bits; 149 } while (atomic_cmpxchg(v, old, new) != old); 150 return new; 151 } 152 153 #ifdef CONFIG_PGSTE 154 155 struct page *page_table_alloc_pgste(struct mm_struct *mm) 156 { 157 struct page *page; 158 u64 *table; 159 160 page = alloc_page(GFP_KERNEL); 161 if (page) { 162 table = (u64 *)page_to_phys(page); 163 memset64(table, _PAGE_INVALID, PTRS_PER_PTE); 164 memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE); 165 } 166 return page; 167 } 168 169 void page_table_free_pgste(struct page *page) 170 { 171 __free_page(page); 172 } 173 174 #endif /* CONFIG_PGSTE */ 175 176 /* 177 * page table entry allocation/free routines. 178 */ 179 unsigned long *page_table_alloc(struct mm_struct *mm) 180 { 181 unsigned long *table; 182 struct page *page; 183 unsigned int mask, bit; 184 185 /* Try to get a fragment of a 4K page as a 2K page table */ 186 if (!mm_alloc_pgste(mm)) { 187 table = NULL; 188 spin_lock_bh(&mm->context.lock); 189 if (!list_empty(&mm->context.pgtable_list)) { 190 page = list_first_entry(&mm->context.pgtable_list, 191 struct page, lru); 192 mask = atomic_read(&page->_mapcount); 193 mask = (mask | (mask >> 4)) & 3; 194 if (mask != 3) { 195 table = (unsigned long *) page_to_phys(page); 196 bit = mask & 1; /* =1 -> second 2K */ 197 if (bit) 198 table += PTRS_PER_PTE; 199 atomic_xor_bits(&page->_mapcount, 1U << bit); 200 list_del(&page->lru); 201 } 202 } 203 spin_unlock_bh(&mm->context.lock); 204 if (table) 205 return table; 206 } 207 /* Allocate a fresh page */ 208 page = alloc_page(GFP_KERNEL); 209 if (!page) 210 return NULL; 211 if (!pgtable_page_ctor(page)) { 212 __free_page(page); 213 return NULL; 214 } 215 arch_set_page_dat(page, 0); 216 /* Initialize page table */ 217 table = (unsigned long *) page_to_phys(page); 218 if (mm_alloc_pgste(mm)) { 219 /* Return 4K page table with PGSTEs */ 220 atomic_set(&page->_mapcount, 3); 221 memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE); 222 memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE); 223 } else { 224 /* Return the first 2K fragment of the page */ 225 atomic_set(&page->_mapcount, 1); 226 memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE); 227 spin_lock_bh(&mm->context.lock); 228 list_add(&page->lru, &mm->context.pgtable_list); 229 spin_unlock_bh(&mm->context.lock); 230 } 231 return table; 232 } 233 234 void page_table_free(struct mm_struct *mm, unsigned long *table) 235 { 236 struct page *page; 237 unsigned int bit, mask; 238 239 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 240 if (!mm_alloc_pgste(mm)) { 241 /* Free 2K page table fragment of a 4K page */ 242 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t)); 243 spin_lock_bh(&mm->context.lock); 244 mask = atomic_xor_bits(&page->_mapcount, 1U << bit); 245 if (mask & 3) 246 list_add(&page->lru, &mm->context.pgtable_list); 247 else 248 list_del(&page->lru); 249 spin_unlock_bh(&mm->context.lock); 250 if (mask != 0) 251 return; 252 } 253 254 pgtable_page_dtor(page); 255 atomic_set(&page->_mapcount, -1); 256 __free_page(page); 257 } 258 259 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table, 260 unsigned long vmaddr) 261 { 262 struct mm_struct *mm; 263 struct page *page; 264 unsigned int bit, mask; 265 266 mm = tlb->mm; 267 page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 268 if (mm_alloc_pgste(mm)) { 269 gmap_unlink(mm, table, vmaddr); 270 table = (unsigned long *) (__pa(table) | 3); 271 tlb_remove_table(tlb, table); 272 return; 273 } 274 bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t)); 275 spin_lock_bh(&mm->context.lock); 276 mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit); 277 if (mask & 3) 278 list_add_tail(&page->lru, &mm->context.pgtable_list); 279 else 280 list_del(&page->lru); 281 spin_unlock_bh(&mm->context.lock); 282 table = (unsigned long *) (__pa(table) | (1U << bit)); 283 tlb_remove_table(tlb, table); 284 } 285 286 static void __tlb_remove_table(void *_table) 287 { 288 unsigned int mask = (unsigned long) _table & 3; 289 void *table = (void *)((unsigned long) _table ^ mask); 290 struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT); 291 292 switch (mask) { 293 case 0: /* pmd, pud, or p4d */ 294 free_pages((unsigned long) table, 2); 295 break; 296 case 1: /* lower 2K of a 4K page table */ 297 case 2: /* higher 2K of a 4K page table */ 298 if (atomic_xor_bits(&page->_mapcount, mask << 4) != 0) 299 break; 300 /* fallthrough */ 301 case 3: /* 4K page table with pgstes */ 302 pgtable_page_dtor(page); 303 atomic_set(&page->_mapcount, -1); 304 __free_page(page); 305 break; 306 } 307 } 308 309 static void tlb_remove_table_smp_sync(void *arg) 310 { 311 /* Simply deliver the interrupt */ 312 } 313 314 static void tlb_remove_table_one(void *table) 315 { 316 /* 317 * This isn't an RCU grace period and hence the page-tables cannot be 318 * assumed to be actually RCU-freed. 319 * 320 * It is however sufficient for software page-table walkers that rely 321 * on IRQ disabling. See the comment near struct mmu_table_batch. 322 */ 323 smp_call_function(tlb_remove_table_smp_sync, NULL, 1); 324 __tlb_remove_table(table); 325 } 326 327 static void tlb_remove_table_rcu(struct rcu_head *head) 328 { 329 struct mmu_table_batch *batch; 330 int i; 331 332 batch = container_of(head, struct mmu_table_batch, rcu); 333 334 for (i = 0; i < batch->nr; i++) 335 __tlb_remove_table(batch->tables[i]); 336 337 free_page((unsigned long)batch); 338 } 339 340 void tlb_table_flush(struct mmu_gather *tlb) 341 { 342 struct mmu_table_batch **batch = &tlb->batch; 343 344 if (*batch) { 345 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu); 346 *batch = NULL; 347 } 348 } 349 350 void tlb_remove_table(struct mmu_gather *tlb, void *table) 351 { 352 struct mmu_table_batch **batch = &tlb->batch; 353 354 tlb->mm->context.flush_mm = 1; 355 if (*batch == NULL) { 356 *batch = (struct mmu_table_batch *) 357 __get_free_page(GFP_NOWAIT | __GFP_NOWARN); 358 if (*batch == NULL) { 359 __tlb_flush_mm_lazy(tlb->mm); 360 tlb_remove_table_one(table); 361 return; 362 } 363 (*batch)->nr = 0; 364 } 365 (*batch)->tables[(*batch)->nr++] = table; 366 if ((*batch)->nr == MAX_TABLE_BATCH) 367 tlb_flush_mmu(tlb); 368 } 369