arch/powerpc/mm/book3s64/hash_pgtable.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright 2005, Paul Mackerras, IBM Corporation.
   4  * Copyright 2009, Benjamin Herrenschmidt, IBM Corporation.
   5  * Copyright 2015-2016, Aneesh Kumar K.V, IBM Corporation.
   6  */
   7
   8 #include <linux/sched.h>
   9 #include <linux/mm_types.h>
  10 #include <linux/mm.h>
  11
  12 #include <asm/pgalloc.h>
  13 #include <asm/pgtable.h>
  14 #include <asm/sections.h>
  15 #include <asm/mmu.h>
  16 #include <asm/tlb.h>
  17
  18 #include <mm/mmu_decl.h>
  19
  20 #define CREATE_TRACE_POINTS
  21 #include <trace/events/thp.h>
  22
  23 #if H_PGTABLE_RANGE > (USER_VSID_RANGE * (TASK_SIZE_USER64 / TASK_CONTEXT_SIZE))
  24 #warning Limited user VSID range means pagetable space is wasted
  25 #endif
  26
  27 #ifdef CONFIG_SPARSEMEM_VMEMMAP
  28 /*
  29  * vmemmap is the starting address of the virtual address space where
  30  * struct pages are allocated for all possible PFNs present on the system
  31  * including holes and bad memory (hence sparse). These virtual struct
  32  * pages are stored in sequence in this virtual address space irrespective
  33  * of the fact whether the corresponding PFN is valid or not. This achieves
  34  * constant relationship between address of struct page and its PFN.
  35  *
  36  * During boot or memory hotplug operation when a new memory section is
  37  * added, physical memory allocation (including hash table bolting) will
  38  * be performed for the set of struct pages which are part of the memory
  39  * section. This saves memory by not allocating struct pages for PFNs
  40  * which are not valid.
  41  *
  42  *              ----------------------------------------------
  43  *              | PHYSICAL ALLOCATION OF VIRTUAL STRUCT PAGES|
  44  *              ----------------------------------------------
  45  *
  46  *         f000000000000000                  c000000000000000
  47  * vmemmap +--------------+                  +--------------+
  48  *  +      |  page struct | +--------------> |  page struct |
  49  *  |      +--------------+                  +--------------+
  50  *  |      |  page struct | +--------------> |  page struct |
  51  *  |      +--------------+ |                +--------------+
  52  *  |      |  page struct | +       +------> |  page struct |
  53  *  |      +--------------+         |        +--------------+
  54  *  |      |  page struct |         |   +--> |  page struct |
  55  *  |      +--------------+         |   |    +--------------+
  56  *  |      |  page struct |         |   |
  57  *  |      +--------------+         |   |
  58  *  |      |  page struct |         |   |
  59  *  |      +--------------+         |   |
  60  *  |      |  page struct |         |   |
  61  *  |      +--------------+         |   |
  62  *  |      |  page struct |         |   |
  63  *  |      +--------------+         |   |
  64  *  |      |  page struct | +-------+   |
  65  *  |      +--------------+             |
  66  *  |      |  page struct | +-----------+
  67  *  |      +--------------+
  68  *  |      |  page struct | No mapping
  69  *  |      +--------------+
  70  *  |      |  page struct | No mapping
  71  *  v      +--------------+
  72  *
  73  *              -----------------------------------------
  74  *              | RELATION BETWEEN STRUCT PAGES AND PFNS|
  75  *              -----------------------------------------
  76  *
  77  * vmemmap +--------------+                 +---------------+
  78  *  +      |  page struct | +-------------> |      PFN      |
  79  *  |      +--------------+                 +---------------+
  80  *  |      |  page struct | +-------------> |      PFN      |
  81  *  |      +--------------+                 +---------------+
  82  *  |      |  page struct | +-------------> |      PFN      |
  83  *  |      +--------------+                 +---------------+
  84  *  |      |  page struct | +-------------> |      PFN      |
  85  *  |      +--------------+                 +---------------+
  86  *  |      |              |
  87  *  |      +--------------+
  88  *  |      |              |
  89  *  |      +--------------+
  90  *  |      |              |
  91  *  |      +--------------+                 +---------------+
  92  *  |      |  page struct | +-------------> |      PFN      |
  93  *  |      +--------------+                 +---------------+
  94  *  |      |              |
  95  *  |      +--------------+
  96  *  |      |              |
  97  *  |      +--------------+                 +---------------+
  98  *  |      |  page struct | +-------------> |      PFN      |
  99  *  |      +--------------+                 +---------------+
 100  *  |      |  page struct | +-------------> |      PFN      |
 101  *  v      +--------------+                 +---------------+
 102  */
 103 /*
 104  * On hash-based CPUs, the vmemmap is bolted in the hash table.
 105  *
 106  */
 107 int __meminit hash__vmemmap_create_mapping(unsigned long start,
 108                                        unsigned long page_size,
 109                                        unsigned long phys)
 110 {
 111         int rc;
 112
 113         if ((start + page_size) >= H_VMEMMAP_END) {
 114                 pr_warn("Outside the supported range\n");
 115                 return -1;
 116         }
 117
 118         rc = htab_bolt_mapping(start, start + page_size, phys,
 119                                pgprot_val(PAGE_KERNEL),
 120                                mmu_vmemmap_psize, mmu_kernel_ssize);
 121         if (rc < 0) {
 122                 int rc2 = htab_remove_mapping(start, start + page_size,
 123                                               mmu_vmemmap_psize,
 124                                               mmu_kernel_ssize);
 125                 BUG_ON(rc2 && (rc2 != -ENOENT));
 126         }
 127         return rc;
 128 }
 129
 130 #ifdef CONFIG_MEMORY_HOTPLUG
 131 void hash__vmemmap_remove_mapping(unsigned long start,
 132                               unsigned long page_size)
 133 {
 134         int rc = htab_remove_mapping(start, start + page_size,
 135                                      mmu_vmemmap_psize,
 136                                      mmu_kernel_ssize);
 137         BUG_ON((rc < 0) && (rc != -ENOENT));
 138         WARN_ON(rc == -ENOENT);
 139 }
 140 #endif
 141 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 142
 143 /*
 144  * map_kernel_page currently only called by __ioremap
 145  * map_kernel_page adds an entry to the ioremap page table
 146  * and adds an entry to the HPT, possibly bolting it
 147  */
 148 int hash__map_kernel_page(unsigned long ea, unsigned long pa, pgprot_t prot)
 149 {
 150         pgd_t *pgdp;
 151         pud_t *pudp;
 152         pmd_t *pmdp;
 153         pte_t *ptep;
 154
 155         BUILD_BUG_ON(TASK_SIZE_USER64 > H_PGTABLE_RANGE);
 156         if (slab_is_available()) {
 157                 pgdp = pgd_offset_k(ea);
 158                 pudp = pud_alloc(&init_mm, pgdp, ea);
 159                 if (!pudp)
 160                         return -ENOMEM;
 161                 pmdp = pmd_alloc(&init_mm, pudp, ea);
 162                 if (!pmdp)
 163                         return -ENOMEM;
 164                 ptep = pte_alloc_kernel(pmdp, ea);
 165                 if (!ptep)
 166                         return -ENOMEM;
 167                 set_pte_at(&init_mm, ea, ptep, pfn_pte(pa >> PAGE_SHIFT, prot));
 168         } else {
 169                 /*
 170                  * If the mm subsystem is not fully up, we cannot create a
 171                  * linux page table entry for this mapping.  Simply bolt an
 172                  * entry in the hardware page table.
 173                  *
 174                  */
 175                 if (htab_bolt_mapping(ea, ea + PAGE_SIZE, pa, pgprot_val(prot),
 176                                       mmu_io_psize, mmu_kernel_ssize)) {
 177                         printk(KERN_ERR "Failed to do bolted mapping IO "
 178                                "memory at %016lx !\n", pa);
 179                         return -ENOMEM;
 180                 }
 181         }
 182
 183         smp_wmb();
 184         return 0;
 185 }
 186
 187 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 188
 189 unsigned long hash__pmd_hugepage_update(struct mm_struct *mm, unsigned long addr,
 190                                     pmd_t *pmdp, unsigned long clr,
 191                                     unsigned long set)
 192 {
 193         __be64 old_be, tmp;
 194         unsigned long old;
 195
 196 #ifdef CONFIG_DEBUG_VM
 197         WARN_ON(!hash__pmd_trans_huge(*pmdp) && !pmd_devmap(*pmdp));
 198         assert_spin_locked(pmd_lockptr(mm, pmdp));
 199 #endif
 200
 201         __asm__ __volatile__(
 202         "1:     ldarx   %0,0,%3\n\
 203                 and.    %1,%0,%6\n\
 204                 bne-    1b \n\
 205                 andc    %1,%0,%4 \n\
 206                 or      %1,%1,%7\n\
 207                 stdcx.  %1,0,%3 \n\
 208                 bne-    1b"
 209         : "=&r" (old_be), "=&r" (tmp), "=m" (*pmdp)
 210         : "r" (pmdp), "r" (cpu_to_be64(clr)), "m" (*pmdp),
 211           "r" (cpu_to_be64(H_PAGE_BUSY)), "r" (cpu_to_be64(set))
 212         : "cc" );
 213
 214         old = be64_to_cpu(old_be);
 215
 216         trace_hugepage_update(addr, old, clr, set);
 217         if (old & H_PAGE_HASHPTE)
 218                 hpte_do_hugepage_flush(mm, addr, pmdp, old);
 219         return old;
 220 }
 221
 222 pmd_t hash__pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
 223                             pmd_t *pmdp)
 224 {
 225         pmd_t pmd;
 226
 227         VM_BUG_ON(address & ~HPAGE_PMD_MASK);
 228         VM_BUG_ON(pmd_trans_huge(*pmdp));
 229         VM_BUG_ON(pmd_devmap(*pmdp));
 230
 231         pmd = *pmdp;
 232         pmd_clear(pmdp);
 233         /*
 234          * Wait for all pending hash_page to finish. This is needed
 235          * in case of subpage collapse. When we collapse normal pages
 236          * to hugepage, we first clear the pmd, then invalidate all
 237          * the PTE entries. The assumption here is that any low level
 238          * page fault will see a none pmd and take the slow path that
 239          * will wait on mmap_sem. But we could very well be in a
 240          * hash_page with local ptep pointer value. Such a hash page
 241          * can result in adding new HPTE entries for normal subpages.
 242          * That means we could be modifying the page content as we
 243          * copy them to a huge page. So wait for parallel hash_page
 244          * to finish before invalidating HPTE entries. We can do this
 245          * by sending an IPI to all the cpus and executing a dummy
 246          * function there.
 247          */
 248         serialize_against_pte_lookup(vma->vm_mm);
 249         /*
 250          * Now invalidate the hpte entries in the range
 251          * covered by pmd. This make sure we take a
 252          * fault and will find the pmd as none, which will
 253          * result in a major fault which takes mmap_sem and
 254          * hence wait for collapse to complete. Without this
 255          * the __collapse_huge_page_copy can result in copying
 256          * the old content.
 257          */
 258         flush_tlb_pmd_range(vma->vm_mm, &pmd, address);
 259         return pmd;
 260 }
 261
 262 /*
 263  * We want to put the pgtable in pmd and use pgtable for tracking
 264  * the base page size hptes
 265  */
 266 void hash__pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 267                                   pgtable_t pgtable)
 268 {
 269         pgtable_t *pgtable_slot;
 270
 271         assert_spin_locked(pmd_lockptr(mm, pmdp));
 272         /*
 273          * we store the pgtable in the second half of PMD
 274          */
 275         pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
 276         *pgtable_slot = pgtable;
 277         /*
 278          * expose the deposited pgtable to other cpus.
 279          * before we set the hugepage PTE at pmd level
 280          * hash fault code looks at the deposted pgtable
 281          * to store hash index values.
 282          */
 283         smp_wmb();
 284 }
 285
 286 pgtable_t hash__pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp)
 287 {
 288         pgtable_t pgtable;
 289         pgtable_t *pgtable_slot;
 290
 291         assert_spin_locked(pmd_lockptr(mm, pmdp));
 292
 293         pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
 294         pgtable = *pgtable_slot;
 295         /*
 296          * Once we withdraw, mark the entry NULL.
 297          */
 298         *pgtable_slot = NULL;
 299         /*
 300          * We store HPTE information in the deposited PTE fragment.
 301          * zero out the content on withdraw.
 302          */
 303         memset(pgtable, 0, PTE_FRAG_SIZE);
 304         return pgtable;
 305 }
 306
 307 /*
 308  * A linux hugepage PMD was changed and the corresponding hash table entries
 309  * neesd to be flushed.
 310  */
 311 void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
 312                             pmd_t *pmdp, unsigned long old_pmd)
 313 {
 314         int ssize;
 315         unsigned int psize;
 316         unsigned long vsid;
 317         unsigned long flags = 0;
 318
 319         /* get the base page size,vsid and segment size */
 320 #ifdef CONFIG_DEBUG_VM
 321         psize = get_slice_psize(mm, addr);
 322         BUG_ON(psize == MMU_PAGE_16M);
 323 #endif
 324         if (old_pmd & H_PAGE_COMBO)
 325                 psize = MMU_PAGE_4K;
 326         else
 327                 psize = MMU_PAGE_64K;
 328
 329         if (!is_kernel_addr(addr)) {
 330                 ssize = user_segment_size(addr);
 331                 vsid = get_user_vsid(&mm->context, addr, ssize);
 332                 WARN_ON(vsid == 0);
 333         } else {
 334                 vsid = get_kernel_vsid(addr, mmu_kernel_ssize);
 335                 ssize = mmu_kernel_ssize;
 336         }
 337
 338         if (mm_is_thread_local(mm))
 339                 flags |= HPTE_LOCAL_UPDATE;
 340
 341         return flush_hash_hugepage(vsid, addr, pmdp, psize, ssize, flags);
 342 }
 343
 344 pmd_t hash__pmdp_huge_get_and_clear(struct mm_struct *mm,
 345                                 unsigned long addr, pmd_t *pmdp)
 346 {
 347         pmd_t old_pmd;
 348         pgtable_t pgtable;
 349         unsigned long old;
 350         pgtable_t *pgtable_slot;
 351
 352         old = pmd_hugepage_update(mm, addr, pmdp, ~0UL, 0);
 353         old_pmd = __pmd(old);
 354         /*
 355          * We have pmd == none and we are holding page_table_lock.
 356          * So we can safely go and clear the pgtable hash
 357          * index info.
 358          */
 359         pgtable_slot = (pgtable_t *)pmdp + PTRS_PER_PMD;
 360         pgtable = *pgtable_slot;
 361         /*
 362          * Let's zero out old valid and hash index details
 363          * hash fault look at them.
 364          */
 365         memset(pgtable, 0, PTE_FRAG_SIZE);
 366         /*
 367          * Serialize against find_current_mm_pte variants which does lock-less
 368          * lookup in page tables with local interrupts disabled. For huge pages
 369          * it casts pmd_t to pte_t. Since format of pte_t is different from
 370          * pmd_t we want to prevent transit from pmd pointing to page table
 371          * to pmd pointing to huge page (and back) while interrupts are disabled.
 372          * We clear pmd to possibly replace it with page table pointer in
 373          * different code paths. So make sure we wait for the parallel
 374          * find_curren_mm_pte to finish.
 375          */
 376         serialize_against_pte_lookup(mm);
 377         return old_pmd;
 378 }
 379
 380 int hash__has_transparent_hugepage(void)
 381 {
 382
 383         if (!mmu_has_feature(MMU_FTR_16M_PAGE))
 384                 return 0;
 385         /*
 386          * We support THP only if PMD_SIZE is 16MB.
 387          */
 388         if (mmu_psize_defs[MMU_PAGE_16M].shift != PMD_SHIFT)
 389                 return 0;
 390         /*
 391          * We need to make sure that we support 16MB hugepage in a segement
 392          * with base page size 64K or 4K. We only enable THP with a PAGE_SIZE
 393          * of 64K.
 394          */
 395         /*
 396          * If we have 64K HPTE, we will be using that by default
 397          */
 398         if (mmu_psize_defs[MMU_PAGE_64K].shift &&
 399             (mmu_psize_defs[MMU_PAGE_64K].penc[MMU_PAGE_16M] == -1))
 400                 return 0;
 401         /*
 402          * Ok we only have 4K HPTE
 403          */
 404         if (mmu_psize_defs[MMU_PAGE_4K].penc[MMU_PAGE_16M] == -1)
 405                 return 0;
 406
 407         return 1;
 408 }
 409 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 410
 411 #ifdef CONFIG_STRICT_KERNEL_RWX
 412 static bool hash__change_memory_range(unsigned long start, unsigned long end,
 413                                       unsigned long newpp)
 414 {
 415         unsigned long idx;
 416         unsigned int step, shift;
 417
 418         shift = mmu_psize_defs[mmu_linear_psize].shift;
 419         step = 1 << shift;
 420
 421         start = ALIGN_DOWN(start, step);
 422         end = ALIGN(end, step); // aligns up
 423
 424         if (start >= end)
 425                 return false;
 426
 427         pr_debug("Changing page protection on range 0x%lx-0x%lx, to 0x%lx, step 0x%x\n",
 428                  start, end, newpp, step);
 429
 430         for (idx = start; idx < end; idx += step)
 431                 /* Not sure if we can do much with the return value */
 432                 mmu_hash_ops.hpte_updateboltedpp(newpp, idx, mmu_linear_psize,
 433                                                         mmu_kernel_ssize);
 434
 435         return true;
 436 }
 437
 438 void hash__mark_rodata_ro(void)
 439 {
 440         unsigned long start, end;
 441
 442         start = (unsigned long)_stext;
 443         end = (unsigned long)__init_begin;
 444
 445         WARN_ON(!hash__change_memory_range(start, end, PP_RXXX));
 446 }
 447
 448 void hash__mark_initmem_nx(void)
 449 {
 450         unsigned long start, end, pp;
 451
 452         start = (unsigned long)__init_begin;
 453         end = (unsigned long)__init_end;
 454
 455         pp = htab_convert_pte_flags(pgprot_val(PAGE_KERNEL));
 456
 457         WARN_ON(!hash__change_memory_range(start, end, pp));
 458 }
 459 #endif