arch/s390/mm/pgalloc.c

   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_minmax,
  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         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         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.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                 clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
 224                 clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
 225         } else {
 226                 /* Return the first 2K fragment of the page */
 227                 atomic_set(&page->_mapcount, 1);
 228                 clear_table(table, _PAGE_INVALID, PAGE_SIZE);
 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 }