Kumar Gala | 0186f47 | 2008-11-19 12:50:04 +0000 | [diff] [blame] | 1 | /* |
| 2 | * This file contains common routines for dealing with free of page tables |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 3 | * Along with common page table handling code |
Kumar Gala | 0186f47 | 2008-11-19 12:50:04 +0000 | [diff] [blame] | 4 | * |
| 5 | * Derived from arch/powerpc/mm/tlb_64.c: |
| 6 | * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) |
| 7 | * |
| 8 | * Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au) |
| 9 | * and Cort Dougan (PReP) (cort@cs.nmt.edu) |
| 10 | * Copyright (C) 1996 Paul Mackerras |
| 11 | * |
| 12 | * Derived from "arch/i386/mm/init.c" |
| 13 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| 14 | * |
| 15 | * Dave Engebretsen <engebret@us.ibm.com> |
| 16 | * Rework for PPC64 port. |
| 17 | * |
| 18 | * This program is free software; you can redistribute it and/or |
| 19 | * modify it under the terms of the GNU General Public License |
| 20 | * as published by the Free Software Foundation; either version |
| 21 | * 2 of the License, or (at your option) any later version. |
| 22 | */ |
| 23 | |
| 24 | #include <linux/kernel.h> |
| 25 | #include <linux/mm.h> |
| 26 | #include <linux/init.h> |
| 27 | #include <linux/percpu.h> |
| 28 | #include <linux/hardirq.h> |
| 29 | #include <asm/pgalloc.h> |
| 30 | #include <asm/tlbflush.h> |
| 31 | #include <asm/tlb.h> |
| 32 | |
Benjamin Herrenschmidt | a8f7758 | 2009-07-23 23:15:45 +0000 | [diff] [blame] | 33 | DEFINE_PER_CPU(struct mmu_gather, mmu_gathers); |
| 34 | |
Benjamin Herrenschmidt | c7cc58a | 2009-07-23 23:15:28 +0000 | [diff] [blame] | 35 | #ifdef CONFIG_SMP |
| 36 | |
| 37 | /* |
| 38 | * Handle batching of page table freeing on SMP. Page tables are |
| 39 | * queued up and send to be freed later by RCU in order to avoid |
| 40 | * freeing a page table page that is being walked without locks |
| 41 | */ |
| 42 | |
Kumar Gala | 0186f47 | 2008-11-19 12:50:04 +0000 | [diff] [blame] | 43 | static DEFINE_PER_CPU(struct pte_freelist_batch *, pte_freelist_cur); |
| 44 | static unsigned long pte_freelist_forced_free; |
| 45 | |
| 46 | struct pte_freelist_batch |
| 47 | { |
| 48 | struct rcu_head rcu; |
| 49 | unsigned int index; |
| 50 | pgtable_free_t tables[0]; |
| 51 | }; |
| 52 | |
| 53 | #define PTE_FREELIST_SIZE \ |
| 54 | ((PAGE_SIZE - sizeof(struct pte_freelist_batch)) \ |
| 55 | / sizeof(pgtable_free_t)) |
| 56 | |
| 57 | static void pte_free_smp_sync(void *arg) |
| 58 | { |
| 59 | /* Do nothing, just ensure we sync with all CPUs */ |
| 60 | } |
| 61 | |
| 62 | /* This is only called when we are critically out of memory |
| 63 | * (and fail to get a page in pte_free_tlb). |
| 64 | */ |
| 65 | static void pgtable_free_now(pgtable_free_t pgf) |
| 66 | { |
| 67 | pte_freelist_forced_free++; |
| 68 | |
| 69 | smp_call_function(pte_free_smp_sync, NULL, 1); |
| 70 | |
| 71 | pgtable_free(pgf); |
| 72 | } |
| 73 | |
| 74 | static void pte_free_rcu_callback(struct rcu_head *head) |
| 75 | { |
| 76 | struct pte_freelist_batch *batch = |
| 77 | container_of(head, struct pte_freelist_batch, rcu); |
| 78 | unsigned int i; |
| 79 | |
| 80 | for (i = 0; i < batch->index; i++) |
| 81 | pgtable_free(batch->tables[i]); |
| 82 | |
| 83 | free_page((unsigned long)batch); |
| 84 | } |
| 85 | |
| 86 | static void pte_free_submit(struct pte_freelist_batch *batch) |
| 87 | { |
| 88 | INIT_RCU_HEAD(&batch->rcu); |
| 89 | call_rcu(&batch->rcu, pte_free_rcu_callback); |
| 90 | } |
| 91 | |
| 92 | void pgtable_free_tlb(struct mmu_gather *tlb, pgtable_free_t pgf) |
| 93 | { |
| 94 | /* This is safe since tlb_gather_mmu has disabled preemption */ |
Kumar Gala | 0186f47 | 2008-11-19 12:50:04 +0000 | [diff] [blame] | 95 | struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur); |
| 96 | |
| 97 | if (atomic_read(&tlb->mm->mm_users) < 2 || |
Rusty Russell | 56aa412 | 2009-03-15 18:16:43 +0000 | [diff] [blame] | 98 | cpumask_equal(mm_cpumask(tlb->mm), cpumask_of(smp_processor_id()))){ |
Kumar Gala | 0186f47 | 2008-11-19 12:50:04 +0000 | [diff] [blame] | 99 | pgtable_free(pgf); |
| 100 | return; |
| 101 | } |
| 102 | |
| 103 | if (*batchp == NULL) { |
| 104 | *batchp = (struct pte_freelist_batch *)__get_free_page(GFP_ATOMIC); |
| 105 | if (*batchp == NULL) { |
| 106 | pgtable_free_now(pgf); |
| 107 | return; |
| 108 | } |
| 109 | (*batchp)->index = 0; |
| 110 | } |
| 111 | (*batchp)->tables[(*batchp)->index++] = pgf; |
| 112 | if ((*batchp)->index == PTE_FREELIST_SIZE) { |
| 113 | pte_free_submit(*batchp); |
| 114 | *batchp = NULL; |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | void pte_free_finish(void) |
| 119 | { |
| 120 | /* This is safe since tlb_gather_mmu has disabled preemption */ |
| 121 | struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur); |
| 122 | |
| 123 | if (*batchp == NULL) |
| 124 | return; |
| 125 | pte_free_submit(*batchp); |
| 126 | *batchp = NULL; |
| 127 | } |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 128 | |
Benjamin Herrenschmidt | c7cc58a | 2009-07-23 23:15:28 +0000 | [diff] [blame] | 129 | #endif /* CONFIG_SMP */ |
| 130 | |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 131 | static inline int is_exec_fault(void) |
| 132 | { |
| 133 | return current->thread.regs && TRAP(current->thread.regs) == 0x400; |
| 134 | } |
| 135 | |
| 136 | /* We only try to do i/d cache coherency on stuff that looks like |
| 137 | * reasonably "normal" PTEs. We currently require a PTE to be present |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 138 | * and we avoid _PAGE_SPECIAL and _PAGE_NO_CACHE. We also only do that |
| 139 | * on userspace PTEs |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 140 | */ |
| 141 | static inline int pte_looks_normal(pte_t pte) |
| 142 | { |
| 143 | return (pte_val(pte) & |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 144 | (_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE | _PAGE_USER)) == |
| 145 | (_PAGE_PRESENT | _PAGE_USER); |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 146 | } |
| 147 | |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 148 | struct page * maybe_pte_to_page(pte_t pte) |
| 149 | { |
| 150 | unsigned long pfn = pte_pfn(pte); |
| 151 | struct page *page; |
| 152 | |
| 153 | if (unlikely(!pfn_valid(pfn))) |
| 154 | return NULL; |
| 155 | page = pfn_to_page(pfn); |
| 156 | if (PageReserved(page)) |
| 157 | return NULL; |
| 158 | return page; |
| 159 | } |
| 160 | |
| 161 | #if defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 |
| 162 | |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 163 | /* Server-style MMU handles coherency when hashing if HW exec permission |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 164 | * is supposed per page (currently 64-bit only). If not, then, we always |
| 165 | * flush the cache for valid PTEs in set_pte. Embedded CPU without HW exec |
| 166 | * support falls into the same category. |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 167 | */ |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 168 | |
| 169 | static pte_t set_pte_filter(pte_t pte) |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 170 | { |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 171 | pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS); |
| 172 | if (pte_looks_normal(pte) && !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) || |
| 173 | cpu_has_feature(CPU_FTR_NOEXECUTE))) { |
| 174 | struct page *pg = maybe_pte_to_page(pte); |
| 175 | if (!pg) |
| 176 | return pte; |
| 177 | if (!test_bit(PG_arch_1, &pg->flags)) { |
| 178 | flush_dcache_icache_page(pg); |
| 179 | set_bit(PG_arch_1, &pg->flags); |
| 180 | } |
| 181 | } |
| 182 | return pte; |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 183 | } |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 184 | |
| 185 | static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, |
| 186 | int dirty) |
| 187 | { |
| 188 | return pte; |
| 189 | } |
| 190 | |
| 191 | #else /* defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0 */ |
| 192 | |
| 193 | /* Embedded type MMU with HW exec support. This is a bit more complicated |
| 194 | * as we don't have two bits to spare for _PAGE_EXEC and _PAGE_HWEXEC so |
| 195 | * instead we "filter out" the exec permission for non clean pages. |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 196 | */ |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 197 | static pte_t set_pte_filter(pte_t pte) |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 198 | { |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 199 | struct page *pg; |
| 200 | |
| 201 | /* No exec permission in the first place, move on */ |
| 202 | if (!(pte_val(pte) & _PAGE_EXEC) || !pte_looks_normal(pte)) |
| 203 | return pte; |
| 204 | |
| 205 | /* If you set _PAGE_EXEC on weird pages you're on your own */ |
| 206 | pg = maybe_pte_to_page(pte); |
| 207 | if (unlikely(!pg)) |
| 208 | return pte; |
| 209 | |
| 210 | /* If the page clean, we move on */ |
| 211 | if (test_bit(PG_arch_1, &pg->flags)) |
| 212 | return pte; |
| 213 | |
| 214 | /* If it's an exec fault, we flush the cache and make it clean */ |
| 215 | if (is_exec_fault()) { |
| 216 | flush_dcache_icache_page(pg); |
| 217 | set_bit(PG_arch_1, &pg->flags); |
| 218 | return pte; |
| 219 | } |
| 220 | |
| 221 | /* Else, we filter out _PAGE_EXEC */ |
| 222 | return __pte(pte_val(pte) & ~_PAGE_EXEC); |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 223 | } |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 224 | |
| 225 | static pte_t set_access_flags_filter(pte_t pte, struct vm_area_struct *vma, |
| 226 | int dirty) |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 227 | { |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 228 | struct page *pg; |
| 229 | |
| 230 | /* So here, we only care about exec faults, as we use them |
| 231 | * to recover lost _PAGE_EXEC and perform I$/D$ coherency |
| 232 | * if necessary. Also if _PAGE_EXEC is already set, same deal, |
| 233 | * we just bail out |
| 234 | */ |
| 235 | if (dirty || (pte_val(pte) & _PAGE_EXEC) || !is_exec_fault()) |
| 236 | return pte; |
| 237 | |
| 238 | #ifdef CONFIG_DEBUG_VM |
| 239 | /* So this is an exec fault, _PAGE_EXEC is not set. If it was |
| 240 | * an error we would have bailed out earlier in do_page_fault() |
| 241 | * but let's make sure of it |
| 242 | */ |
| 243 | if (WARN_ON(!(vma->vm_flags & VM_EXEC))) |
| 244 | return pte; |
| 245 | #endif /* CONFIG_DEBUG_VM */ |
| 246 | |
| 247 | /* If you set _PAGE_EXEC on weird pages you're on your own */ |
| 248 | pg = maybe_pte_to_page(pte); |
| 249 | if (unlikely(!pg)) |
| 250 | goto bail; |
| 251 | |
| 252 | /* If the page is already clean, we move on */ |
| 253 | if (test_bit(PG_arch_1, &pg->flags)) |
| 254 | goto bail; |
| 255 | |
| 256 | /* Clean the page and set PG_arch_1 */ |
| 257 | flush_dcache_icache_page(pg); |
| 258 | set_bit(PG_arch_1, &pg->flags); |
| 259 | |
| 260 | bail: |
| 261 | return __pte(pte_val(pte) | _PAGE_EXEC); |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 262 | } |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 263 | |
| 264 | #endif /* !(defined(CONFIG_PPC_STD_MMU) || _PAGE_EXEC == 0) */ |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 265 | |
| 266 | /* |
| 267 | * set_pte stores a linux PTE into the linux page table. |
| 268 | */ |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 269 | void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, |
| 270 | pte_t pte) |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 271 | { |
| 272 | #ifdef CONFIG_DEBUG_VM |
| 273 | WARN_ON(pte_present(*ptep)); |
| 274 | #endif |
| 275 | /* Note: mm->context.id might not yet have been assigned as |
| 276 | * this context might not have been activated yet when this |
| 277 | * is called. |
| 278 | */ |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 279 | pte = set_pte_filter(pte); |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 280 | |
| 281 | /* Perform the setting of the PTE */ |
| 282 | __set_pte_at(mm, addr, ptep, pte, 0); |
| 283 | } |
| 284 | |
| 285 | /* |
| 286 | * This is called when relaxing access to a PTE. It's also called in the page |
| 287 | * fault path when we don't hit any of the major fault cases, ie, a minor |
| 288 | * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have |
| 289 | * handled those two for us, we additionally deal with missing execute |
| 290 | * permission here on some processors |
| 291 | */ |
| 292 | int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address, |
| 293 | pte_t *ptep, pte_t entry, int dirty) |
| 294 | { |
| 295 | int changed; |
Benjamin Herrenschmidt | ea3cc33 | 2009-08-18 19:00:34 +0000 | [diff] [blame^] | 296 | entry = set_access_flags_filter(entry, vma, dirty); |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 297 | changed = !pte_same(*(ptep), entry); |
| 298 | if (changed) { |
Mel Gorman | af3e4ac | 2009-04-30 10:59:19 +0000 | [diff] [blame] | 299 | if (!(vma->vm_flags & VM_HUGETLB)) |
| 300 | assert_pte_locked(vma->vm_mm, address); |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 301 | __ptep_set_access_flags(ptep, entry); |
| 302 | flush_tlb_page_nohash(vma, address); |
| 303 | } |
| 304 | return changed; |
| 305 | } |
| 306 | |
| 307 | #ifdef CONFIG_DEBUG_VM |
| 308 | void assert_pte_locked(struct mm_struct *mm, unsigned long addr) |
| 309 | { |
| 310 | pgd_t *pgd; |
| 311 | pud_t *pud; |
| 312 | pmd_t *pmd; |
| 313 | |
| 314 | if (mm == &init_mm) |
| 315 | return; |
| 316 | pgd = mm->pgd + pgd_index(addr); |
| 317 | BUG_ON(pgd_none(*pgd)); |
| 318 | pud = pud_offset(pgd, addr); |
| 319 | BUG_ON(pud_none(*pud)); |
| 320 | pmd = pmd_offset(pud, addr); |
| 321 | BUG_ON(!pmd_present(*pmd)); |
Kumar Gala | 797a747 | 2009-08-18 15:21:40 +0000 | [diff] [blame] | 322 | assert_spin_locked(pte_lockptr(mm, pmd)); |
Benjamin Herrenschmidt | 8d30c14 | 2009-02-10 16:02:37 +0000 | [diff] [blame] | 323 | } |
| 324 | #endif /* CONFIG_DEBUG_VM */ |
| 325 | |