arch/s390/mm/pgalloc.c

   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 }