arch/powerpc/mm/pgtable-hash64.c

   1 /*
   2  * Copyright 2005, Paul Mackerras, IBM Corporation.
   3  * Copyright 2009, Benjamin Herrenschmidt, IBM Corporation.
   4  * Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/sched.h>
  13 #include <linux/mm_types.h>
  14 #include <linux/mm.h>
  15
  16 #include <asm/pgalloc.h>
  17 #include <asm/pgtable.h>
  18 #include <asm/sections.h>
  19 #include <asm/mmu.h>
  20 #include <asm/tlb.h>
  21
  22 #include "mmu_decl.h"
  23
  24 #define CREATE_TRACE_POINTS
  25 #include <trace/events/thp.h>
  26
  27 #if H_PGTABLE_RANGE > (USER_VSID_RANGE * (TASK_SIZE_USER64 / TASK_CONTEXT_SIZE))
  28 #warning Limited user VSID range means pagetable space is wasted
  29 #endif
  30
  31 #ifdef CONFIG_SPARSEMEM_VMEMMAP
  32 /*
  33  * vmemmap is the starting address of the virtual address space where
  34  * struct pages are allocated for all possible PFNs present on the system
  35  * including holes and bad memory (hence sparse). These virtual struct
  36  * pages are stored in sequence in this virtual address space irrespective
  37  * of the fact whether the corresponding PFN is valid or not. This achieves
  38  * constant relationship between address of struct page and its PFN.
  39  *
  40  * During boot or memory hotplug operation when a new memory section is
  41  * added, physical memory allocation (including hash table bolting) will
  42  * be performed for the set of struct pages which are part of the memory
  43  * section. This saves memory by not allocating struct pages for PFNs
  44  * which are not valid.
  45  *
  46  *              ----------------------------------------------
  47  *              | PHYSICAL ALLOCATION OF VIRTUAL STRUCT PAGES|
  48  *              ----------------------------------------------
  49  *
  50  *         f000000000000000                  c000000000000000
  51  * vmemmap +--------------+                  +--------------+
  52  *  +      |  page struct | +--------------> |  page struct |
  53  *  |      +--------------+                  +--------------+
  54  *  |      |  page struct | +--------------> |  page struct |
  55  *  |      +--------------+ |                +--------------+
  56  *  |      |  page struct | +       +------> |  page struct |
  57  *  |      +--------------+         |        +--------------+
  58  *  |      |  page struct |         |   +--> |  page struct |
  59  *  |      +--------------+         |   |    +--------------+
  60  *  |      |  page struct |         |   |
  61  *  |      +--------------+         |   |
  62  *  |      |  page struct |         |   |
  63  *  |      +--------------+         |   |
  64  *  |      |  page struct |         |   |
  65  *  |      +--------------+         |   |
  66  *  |      |  page struct |         |   |
  67  *  |      +--------------+         |   |
  68  *  |      |  page struct | +-------+   |
  69  *  |      +--------------+             |
  70  *  |      |  page struct | +-----------+
  71  *  |      +--------------+
  72  *  |      |  page struct | No mapping
  73  *  |      +--------------+
  74  *  |      |  page struct | No mapping
  75  *  v      +--------------+
  76  *
  77  *              -----------------------------------------
  78  *              | RELATION BETWEEN STRUCT PAGES AND PFNS|
  79  *              -----------------------------------------
  80  *
  81  * vmemmap +--------------+                 +---------------+
  82  *  +      |  page struct | +-------------> |      PFN      |
  83  *  |      +--------------+                 +---------------+
  84  *  |      |  page struct | +-------------> |      PFN      |
  85  *  |      +--------------+                 +---------------+
  86  *  |      |  page struct | +-------------> |      PFN      |
  87  *  |      +--------------+                 +---------------+
  88  *  |      |  page struct | +-------------> |      PFN      |
  89  *  |      +--------------+                 +---------------+
  90  *  |      |              |
  91  *  |      +--------------+
  92  *  |      |              |
  93  *  |      +--------------+
  94  *  |      |              |
  95  *  |      +--------------+                 +---------------+
  96  *  |      |  page struct | +-------------> |      PFN      |
  97  *  |      +--------------+                 +---------------+
  98  *  |      |              |
  99  *  |      +--------------+
 100  *  |      |              |
 101  *  |      +--------------+                 +---------------+
 102  *  |      |  page struct | +-------------> |      PFN      |
 103  *  |      +--------------+                 +---------------+
 104  *  |      |  page struct | +-------------> |      PFN      |
 105  *  v      +--------------+                 +---------------+
 106  */
 107 /*
 108  * On hash-based CPUs, the vmemmap is bolted in the hash table.
 109  *
 110  */
 111 int __meminit hash__vmemmap_create_mapping(unsigned long start,
 112                                        unsigned long page_size,
 113                                        unsigned long phys)
 114 {
 115         int rc = htab_bolt_mapping(start, start + page_size, phys,
 116                                    pgprot_val(PAGE_KERNEL),
 117                                    mmu_vmemmap_psize, mmu_kernel_ssize);
 118         if (rc < 0) {
 119                 int rc2 = htab_remove_mapping(start, start + page_size,
 120                                               mmu_vmemmap_psize,
 121                                               mmu_kernel_ssize);
 122                 BUG_ON(rc2 && (rc2 != -ENOENT));
 123         }
 124         return rc;
 125 }
 126
 127 #ifdef CONFIG_MEMORY_HOTPLUG
 128 void hash__vmemmap_remove_mapping(unsigned long start,
 129                               unsigned long page_size)
 130 {
 131         int rc = htab_remove_mapping(start, start + page_size,
 132                                      mmu_vmemmap_psize,
 133                                      mmu_kernel_ssize);
 134         BUG_ON((rc < 0) && (rc != -ENOENT));
 135         WARN_ON(rc == -ENOENT);
 136 }
 137 #endif
 138 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 139
 140 /*
 141  * map_kernel_page currently only called by __ioremap
 142  * map_kernel_page adds an entry to the ioremap page table
 143  * and adds an entry to the HPT, possibly bolting it
 144  */
 145 int hash__map_kernel_page(unsigned long ea, unsigned long pa, unsigned long flags)
 146 {
 147         pgd_t *pgdp;
 148         pud_t *pudp;
 149         pmd_t *pmdp;
 150         pte_t *ptep;
 151
 152         BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE);
 153         if (slab_is_available()) {
 154                 pgdp = pgd_offset_k(ea);
 155                 pudp = pud_alloc(&init_mm, pgdp, ea);
 156                 if (!pudp)
 157                         return -ENOMEM;
 158                 pmdp = pmd_alloc(&init_mm, pudp, ea);
 159                 if (!pmdp)
 160                         return -ENOMEM;
 161                 ptep = pte_alloc_kernel(pmdp, ea);
 162                 if (!ptep)
 163                         return -ENOMEM;
 164                 set_pte_at(&init_mm, ea, ptep, pfn_pte(pa >> PAGE_SHIFT,
 165                                                           __pgprot(flags)));
 166         } else {
 167                 /*
 168                  * If the mm subsystem is not fully up, we cannot create a
 169                  * linux page table entry for this mapping.  Simply bolt an
 170                  * entry in the hardware page table.
 171                  *
 172                  */
 173                 if (htab_bolt_mapping(ea, ea + PAGE_SIZE, pa, flags,
 174                                       mmu_io_psize, mmu_kernel_ssize)) {
 175                         printk(KERN_ERR "Failed to do bolted mapping IO "
 176                                "memory at %016lx !\n", pa);
 177                         return -ENOMEM;
 178                 }
 179         }
 180
 181         smp_wmb();
 182         return 0;
 183 }
 184
 185 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 186
 187 unsigned long hash__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 188                                     pmd_t *pmdp, unsigned long clr,
 189                                     unsigned long set)
 190 {
 191         __be64 old_be, tmp;
 192         unsigned long old;
 193
 194 #ifdef CONFIG_DEBUG_VM
 195         WARN_ON(!hash__pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
 196         assert_spin_locked(pmd_lockptr(mm, pmdp));
 197 #endif
 198
 199         __asm__ __volatile__(
 200         "1:     ldarx   %0,0,%3\n\
 201                 and.    %1,%0,%6\n\
 202                 bne-    1b \n\
 203                 andc    %1,%0,%4 \n\
 204                 or      %1,%1,%7\n\
 205                 stdcx.  %1,0,%3 \n\
 206                 bne-    1b"
 207         : "=&r" (old_be), "=&r" (tmp), "=m" (*pmdp)
 208         : "r" (pmdp), "r" (cpu_to_be64(clr)), "m" (*pmdp),
 209           "r" (cpu_to_be64(H_PAGE_BUSY)), "r" (cpu_to_be64(set))
 210         : "cc" );
 211
 212         old = be64_to_cpu(old_be);
 213
 214         trace_hugepage_update(addr, old, clr, set);
 215         if (old & H_PAGE_HASHPTE)
 216                 hpte_do_hugepage_flush(mm, addr, pmdp, old);
 217         return old;
 218 }
 219
 220 pmd_t hash__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
 221                             pmd_t *pmdp)
 222 {
 223         pmd_t pmd;
 224
 225         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 226         VM_BUG_ON(pmd_trans_huge(*pmdp));
 227         VM_BUG_ON(pmd_devmap(*pmdp));
 228
 229         pmd = *pmdp;
 230         pmd_clear(pmdp);
 231         /*
 232          * Wait for all pending hash_page to finish. This is needed
 233          * in case of subpage collapse. When we collapse normal pages
 234          * to hugepage, we first clear the pmd, then invalidate all
 235          * the PTE entries. The assumption here is that any low level
 236          * page fault will see a none pmd and take the slow path that
 237          * will wait on mmap_sem. But we could very well be in a
 238          * hash_page with local ptep pointer value. Such a hash page
 239          * can result in adding new HPTE entries for normal subpages.
 240          * That means we could be modifying the page content as we
 241          * copy them to a huge page. So wait for parallel hash_page
 242          * to finish before invalidating HPTE entries. We can do this
 243          * by sending an IPI to all the cpus and executing a dummy
 244          * function there.
 245          */
 246         serialize_against_pte_lookup(vma->vm_mm);
 247         /*
 248          * Now invalidate the hpte entries in the range
 249          * covered by pmd. This make sure we take a
 250          * fault and will find the pmd as none, which will
 251          * result in a major fault which takes mmap_sem and
 252          * hence wait for collapse to complete. Without this
 253          * the __collapse_huge_page_copy can result in copying
 254          * the old content.
 255          */
 256         flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
 257         return pmd;
 258 }
 259
 260 /*
 261  * We want to put the pgtable in pmd and use pgtable for tracking
 262  * the base page size hptes
 263  */
 264 void hash__pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 265                                   pgtable_t pgtable)
 266 {
 267         pgtable_t *pgtable_slot;
 268
 269         assert_spin_locked(pmd_lockptr(mm, pmdp));
 270         /*
 271          * we store the pgtable in the second half of PMD
 272          */
 273         pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
 274         *pgtable_slot = pgtable;
 275         /*
 276          * expose the deposited pgtable to other cpus.
 277          * before we set the hugepage PTE at pmd level
 278          * hash fault code looks at the deposted pgtable
 279          * to store hash index values.
 280          */
 281         smp_wmb();
 282 }
 283
 284 pgtable_t hash__pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
 285 {
 286         pgtable_t pgtable;
 287         pgtable_t *pgtable_slot;
 288
 289         assert_spin_locked(pmd_lockptr(mm, pmdp));
 290
 291         pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
 292         pgtable = *pgtable_slot;
 293         /*
 294          * Once we withdraw, mark the entry NULL.
 295          */
 296         *pgtable_slot = NULL;
 297         /*
 298          * We store HPTE information in the deposited PTE fragment.
 299          * zero out the content on withdraw.
 300          */
 301         memset(pgtable, 0, PTE_FRAG_SIZE);
 302         return pgtable;
 303 }
 304
 305 /*
 306  * A linux hugepage PMD was changed and the corresponding hash table entries
 307  * neesd to be flushed.
 308  */
 309 void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
 310                             pmd_t *pmdp, unsigned long old_pmd)
 311 {
 312         int ssize;
 313         unsigned int psize;
 314         unsigned long vsid;
 315         unsigned long flags = 0;
 316
 317         /* get the base page size,vsid and segment size */
 318 #ifdef CONFIG_DEBUG_VM
 319         psize = get_slice_psize(mm, addr);
 320         BUG_ON(psize == MMU_PAGE_16M);
 321 #endif
 322         if (old_pmd & H_PAGE_COMBO)
 323                 psize = MMU_PAGE_4K;
 324         else
 325                 psize = MMU_PAGE_64K;
 326
 327         if (!is_kernel_addr(addr)) {
 328                 ssize = user_segment_size(addr);
 329                 vsid = get_user_vsid(&mm->context, addr, ssize);
 330                 WARN_ON(vsid == 0);
 331         } else {
 332                 vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
 333                 ssize = mmu_kernel_ssize;
 334         }
 335
 336         if (mm_is_thread_local(mm))
 337                 flags |= HPTE_LOCAL_UPDATE;
 338
 339         return flush_hash_hugepage(vsid, addr, pmdp, psize, ssize, flags);
 340 }
 341
 342 pmd_t hash__pmdp_huge_get_and_clear(struct mm_struct *mm,
 343                                 unsigned long addr, pmd_t *pmdp)
 344 {
 345         pmd_t old_pmd;
 346         pgtable_t pgtable;
 347         unsigned long old;
 348         pgtable_t *pgtable_slot;
 349
 350         old = pmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
 351         old_pmd = __pmd(old);
 352         /*
 353          * We have pmd == none and we are holding page_table_lock.
 354          * So we can safely go and clear the pgtable hash
 355          * index info.
 356          */
 357         pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
 358         pgtable = *pgtable_slot;
 359         /*
 360          * Let's zero out old valid and hash index details
 361          * hash fault look at them.
 362          */
 363         memset(pgtable, 0, PTE_FRAG_SIZE);
 364         /*
 365          * Serialize against find_current_mm_pte variants which does lock-less
 366          * lookup in page tables with local interrupts disabled. For huge pages
 367          * it casts pmd_t to pte_t. Since format of pte_t is different from
 368          * pmd_t we want to prevent transit from pmd pointing to page table
 369          * to pmd pointing to huge page (and back) while interrupts are disabled.
 370          * We clear pmd to possibly replace it with page table pointer in
 371          * different code paths. So make sure we wait for the parallel
 372          * find_curren_mm_pte to finish.
 373          */
 374         serialize_against_pte_lookup(mm);
 375         return old_pmd;
 376 }
 377
 378 int hash__has_transparent_hugepage(void)
 379 {
 380
 381         if (!mmu_has_feature(MMU_FTR_16M_PAGE))
 382                 return 0;
 383         /*
 384          * We support THP only if PMD_SIZE is 16MB.
 385          */
 386         if (mmu_psize_defs[MMU_PAGE_16M].shift != PMD_SHIFT)
 387                 return 0;
 388         /*
 389          * We need to make sure that we support 16MB hugepage in a segement
 390          * with base page size 64K or 4K. We only enable THP with a PAGE_SIZE
 391          * of 64K.
 392          */
 393         /*
 394          * If we have 64K HPTE, we will be using that by default
 395          */
 396         if (mmu_psize_defs[MMU_PAGE_64K].shift &&
 397             (mmu_psize_defs[MMU_PAGE_64K].penc[MMU_PAGE_16M] == -1))
 398                 return 0;
 399         /*
 400          * Ok we only have 4K HPTE
 401          */
 402         if (mmu_psize_defs[MMU_PAGE_4K].penc[MMU_PAGE_16M] == -1)
 403                 return 0;
 404
 405         return 1;
 406 }
 407 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 408
 409 #ifdef CONFIG_STRICT_KERNEL_RWX
 410 static bool hash__change_memory_range(unsigned long start, unsigned long end,
 411                                       unsigned long newpp)
 412 {
 413         unsigned long idx;
 414         unsigned int step, shift;
 415
 416         shift = mmu_psize_defs[mmu_linear_psize].shift;
 417         step = 1 << shift;
 418
 419         start = ALIGN_DOWN(start, step);
 420         end = ALIGN(end, step); // aligns up
 421
 422         if (start >= end)
 423                 return false;
 424
 425         pr_debug("Changing page protection on range 0x%lx-0x%lx, to 0x%lx, step 0x%x\n",
 426                  start, end, newpp, step);
 427
 428         for (idx = start; idx < end; idx += step)
 429                 /* Not sure if we can do much with the return value */
 430                 mmu_hash_ops.hpte_updateboltedpp(newpp, idx, mmu_linear_psize,
 431                                                         mmu_kernel_ssize);
 432
 433         return true;
 434 }
 435
 436 void hash__mark_rodata_ro(void)
 437 {
 438         unsigned long start, end;
 439
 440         start = (unsigned long)_stext;
 441         end = (unsigned long)__init_begin;
 442
 443         WARN_ON(!hash__change_memory_range(start, end, PP_RXXX));
 444 }
 445
 446 void hash__mark_initmem_nx(void)
 447 {
 448         unsigned long start, end, pp;
 449
 450         start = (unsigned long)__init_begin;
 451         end = (unsigned long)__init_end;
 452
 453         pp = htab_convert_pte_flags(pgprot_val(PAGE_KERNEL));
 454
 455         WARN_ON(!hash__change_memory_range(start, end, pp));
 456 }
 457 #endif