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         return (unsigned long *) page_to_phys(page);
  61 }
  62
  63 void crst_table_free(struct mm_struct *mm, unsigned long *table)
  64 {
  65         free_pages((unsigned long) table, 2);
  66 }
  67
  68 static void __crst_table_upgrade(void *arg)
  69 {
  70         struct mm_struct *mm = arg;
  71
  72         if (current->active_mm == mm) {
  73                 clear_user_asce();
  74                 set_user_asce(mm);
  75         }
  76         __tlb_flush_local();
  77 }
  78
  79 int crst_table_upgrade(struct mm_struct *mm)
  80 {
  81         unsigned long *table, *pgd;
  82
  83         /* upgrade should only happen from 3 to 4 levels */
  84         BUG_ON(mm->context.asce_limit != (1UL << 42));
  85
  86         table = crst_table_alloc(mm);
  87         if (!table)
  88                 return -ENOMEM;
  89
  90         spin_lock_bh(&mm->page_table_lock);
  91         pgd = (unsigned long *) mm->pgd;
  92         crst_table_init(table, _REGION2_ENTRY_EMPTY);
  93         pgd_populate(mm, (pgd_t *) table, (pud_t *) pgd);
  94         mm->pgd = (pgd_t *) table;
  95         mm->context.asce_limit = 1UL << 53;
  96         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
  97                            _ASCE_USER_BITS | _ASCE_TYPE_REGION2;
  98         mm->task_size = mm->context.asce_limit;
  99         spin_unlock_bh(&mm->page_table_lock);
 100
 101         on_each_cpu(__crst_table_upgrade, mm, 0);
 102         return 0;
 103 }
 104
 105 void crst_table_downgrade(struct mm_struct *mm)
 106 {
 107         pgd_t *pgd;
 108
 109         /* downgrade should only happen from 3 to 2 levels (compat only) */
 110         BUG_ON(mm->context.asce_limit != (1UL << 42));
 111
 112         if (current->active_mm == mm) {
 113                 clear_user_asce();
 114                 __tlb_flush_mm(mm);
 115         }
 116
 117         pgd = mm->pgd;
 118         mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
 119         mm->context.asce_limit = 1UL << 31;
 120         mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
 121                            _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
 122         mm->task_size = mm->context.asce_limit;
 123         crst_table_free(mm, (unsigned long *) pgd);
 124
 125         if (current->active_mm == mm)
 126                 set_user_asce(mm);
 127 }
 128
 129 static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
 130 {
 131         unsigned int old, new;
 132
 133         do {
 134                 old = atomic_read(v);
 135                 new = old ^ bits;
 136         } while (atomic_cmpxchg(v, old, new) != old);
 137         return new;
 138 }
 139
 140 /*
 141  * page table entry allocation/free routines.
 142  */
 143 unsigned long *page_table_alloc(struct mm_struct *mm)
 144 {
 145         unsigned long *table;
 146         struct page *page;
 147         unsigned int mask, bit;
 148
 149         /* Try to get a fragment of a 4K page as a 2K page table */
 150         if (!mm_alloc_pgste(mm)) {
 151                 table = NULL;
 152                 spin_lock_bh(&mm->context.list_lock);
 153                 if (!list_empty(&mm->context.pgtable_list)) {
 154                         page = list_first_entry(&mm->context.pgtable_list,
 155                                                 struct page, lru);
 156                         mask = atomic_read(&page->_mapcount);
 157                         mask = (mask | (mask >> 4)) & 3;
 158                         if (mask != 3) {
 159                                 table = (unsigned long *) page_to_phys(page);
 160                                 bit = mask & 1;         /* =1 -> second 2K */
 161                                 if (bit)
 162                                         table += PTRS_PER_PTE;
 163                                 atomic_xor_bits(&page->_mapcount, 1U << bit);
 164                                 list_del(&page->lru);
 165                         }
 166                 }
 167                 spin_unlock_bh(&mm->context.list_lock);
 168                 if (table)
 169                         return table;
 170         }
 171         /* Allocate a fresh page */
 172         page = alloc_page(GFP_KERNEL|__GFP_REPEAT);
 173         if (!page)
 174                 return NULL;
 175         if (!pgtable_page_ctor(page)) {
 176                 __free_page(page);
 177                 return NULL;
 178         }
 179         /* Initialize page table */
 180         table = (unsigned long *) page_to_phys(page);
 181         if (mm_alloc_pgste(mm)) {
 182                 /* Return 4K page table with PGSTEs */
 183                 atomic_set(&page->_mapcount, 3);
 184                 clear_table(table, _PAGE_INVALID, PAGE_SIZE/2);
 185                 clear_table(table + PTRS_PER_PTE, 0, PAGE_SIZE/2);
 186         } else {
 187                 /* Return the first 2K fragment of the page */
 188                 atomic_set(&page->_mapcount, 1);
 189                 clear_table(table, _PAGE_INVALID, PAGE_SIZE);
 190                 spin_lock_bh(&mm->context.list_lock);
 191                 list_add(&page->lru, &mm->context.pgtable_list);
 192                 spin_unlock_bh(&mm->context.list_lock);
 193         }
 194         return table;
 195 }
 196
 197 void page_table_free(struct mm_struct *mm, unsigned long *table)
 198 {
 199         struct page *page;
 200         unsigned int bit, mask;
 201
 202         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 203         if (!mm_alloc_pgste(mm)) {
 204                 /* Free 2K page table fragment of a 4K page */
 205                 bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
 206                 spin_lock_bh(&mm->context.list_lock);
 207                 mask = atomic_xor_bits(&page->_mapcount, 1U << bit);
 208                 if (mask & 3)
 209                         list_add(&page->lru, &mm->context.pgtable_list);
 210                 else
 211                         list_del(&page->lru);
 212                 spin_unlock_bh(&mm->context.list_lock);
 213                 if (mask != 0)
 214                         return;
 215         }
 216
 217         pgtable_page_dtor(page);
 218         atomic_set(&page->_mapcount, -1);
 219         __free_page(page);
 220 }
 221
 222 void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
 223                          unsigned long vmaddr)
 224 {
 225         struct mm_struct *mm;
 226         struct page *page;
 227         unsigned int bit, mask;
 228
 229         mm = tlb->mm;
 230         page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 231         if (mm_alloc_pgste(mm)) {
 232                 gmap_unlink(mm, table, vmaddr);
 233                 table = (unsigned long *) (__pa(table) | 3);
 234                 tlb_remove_table(tlb, table);
 235                 return;
 236         }
 237         bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
 238         spin_lock_bh(&mm->context.list_lock);
 239         mask = atomic_xor_bits(&page->_mapcount, 0x11U << bit);
 240         if (mask & 3)
 241                 list_add_tail(&page->lru, &mm->context.pgtable_list);
 242         else
 243                 list_del(&page->lru);
 244         spin_unlock_bh(&mm->context.list_lock);
 245         table = (unsigned long *) (__pa(table) | (1U << bit));
 246         tlb_remove_table(tlb, table);
 247 }
 248
 249 static void __tlb_remove_table(void *_table)
 250 {
 251         unsigned int mask = (unsigned long) _table & 3;
 252         void *table = (void *)((unsigned long) _table ^ mask);
 253         struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
 254
 255         switch (mask) {
 256         case 0:         /* pmd or pud */
 257                 free_pages((unsigned long) table, 2);
 258                 break;
 259         case 1:         /* lower 2K of a 4K page table */
 260         case 2:         /* higher 2K of a 4K page table */
 261                 if (atomic_xor_bits(&page->_mapcount, mask << 4) != 0)
 262                         break;
 263                 /* fallthrough */
 264         case 3:         /* 4K page table with pgstes */
 265                 pgtable_page_dtor(page);
 266                 atomic_set(&page->_mapcount, -1);
 267                 __free_page(page);
 268                 break;
 269         }
 270 }
 271
 272 static void tlb_remove_table_smp_sync(void *arg)
 273 {
 274         /* Simply deliver the interrupt */
 275 }
 276
 277 static void tlb_remove_table_one(void *table)
 278 {
 279         /*
 280          * This isn't an RCU grace period and hence the page-tables cannot be
 281          * assumed to be actually RCU-freed.
 282          *
 283          * It is however sufficient for software page-table walkers that rely
 284          * on IRQ disabling. See the comment near struct mmu_table_batch.
 285          */
 286         smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
 287         __tlb_remove_table(table);
 288 }
 289
 290 static void tlb_remove_table_rcu(struct rcu_head *head)
 291 {
 292         struct mmu_table_batch *batch;
 293         int i;
 294
 295         batch = container_of(head, struct mmu_table_batch, rcu);
 296
 297         for (i = 0; i < batch->nr; i++)
 298                 __tlb_remove_table(batch->tables[i]);
 299
 300         free_page((unsigned long)batch);
 301 }
 302
 303 void tlb_table_flush(struct mmu_gather *tlb)
 304 {
 305         struct mmu_table_batch **batch = &tlb->batch;
 306
 307         if (*batch) {
 308                 call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
 309                 *batch = NULL;
 310         }
 311 }
 312
 313 void tlb_remove_table(struct mmu_gather *tlb, void *table)
 314 {
 315         struct mmu_table_batch **batch = &tlb->batch;
 316
 317         tlb->mm->context.flush_mm = 1;
 318         if (*batch == NULL) {
 319                 *batch = (struct mmu_table_batch *)
 320                         __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
 321                 if (*batch == NULL) {
 322                         __tlb_flush_mm_lazy(tlb->mm);
 323                         tlb_remove_table_one(table);
 324                         return;
 325                 }
 326                 (*batch)->nr = 0;
 327         }
 328         (*batch)->tables[(*batch)->nr++] = table;
 329         if ((*batch)->nr == MAX_TABLE_BATCH)
 330                 tlb_flush_mmu(tlb);
 331 }