arch/powerpc/mm/pgtable.c

   1 /*
   2  * This file contains common routines for dealing with free of page tables
   3  * Along with common page table handling code
   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
  33 static DEFINE_PER_CPU(struct pte_freelist_batch *, pte_freelist_cur);
  34 static unsigned long pte_freelist_forced_free;
  35
  36 struct pte_freelist_batch
  37 {
  38         struct rcu_head rcu;
  39         unsigned int    index;
  40         pgtable_free_t  tables[0];
  41 };
  42
  43 #define PTE_FREELIST_SIZE \
  44         ((PAGE_SIZE - sizeof(struct pte_freelist_batch)) \
  45           / sizeof(pgtable_free_t))
  46
  47 static void pte_free_smp_sync(void *arg)
  48 {
  49         /* Do nothing, just ensure we sync with all CPUs */
  50 }
  51
  52 /* This is only called when we are critically out of memory
  53  * (and fail to get a page in pte_free_tlb).
  54  */
  55 static void pgtable_free_now(pgtable_free_t pgf)
  56 {
  57         pte_freelist_forced_free++;
  58
  59         smp_call_function(pte_free_smp_sync, NULL, 1);
  60
  61         pgtable_free(pgf);
  62 }
  63
  64 static void pte_free_rcu_callback(struct rcu_head *head)
  65 {
  66         struct pte_freelist_batch *batch =
  67                 container_of(head, struct pte_freelist_batch, rcu);
  68         unsigned int i;
  69
  70         for (i = 0; i < batch->index; i++)
  71                 pgtable_free(batch->tables[i]);
  72
  73         free_page((unsigned long)batch);
  74 }
  75
  76 static void pte_free_submit(struct pte_freelist_batch *batch)
  77 {
  78         INIT_RCU_HEAD(&batch->rcu);
  79         call_rcu(&batch->rcu, pte_free_rcu_callback);
  80 }
  81
  82 void pgtable_free_tlb(struct mmu_gather *tlb, pgtable_free_t pgf)
  83 {
  84         /* This is safe since tlb_gather_mmu has disabled preemption */
  85         struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
  86
  87         if (atomic_read(&tlb->mm->mm_users) < 2 ||
  88             cpumask_equal(mm_cpumask(tlb->mm), cpumask_of(smp_processor_id()))){
  89                 pgtable_free(pgf);
  90                 return;
  91         }
  92
  93         if (*batchp == NULL) {
  94                 *batchp = (struct pte_freelist_batch *)__get_free_page(GFP_ATOMIC);
  95                 if (*batchp == NULL) {
  96                         pgtable_free_now(pgf);
  97                         return;
  98                 }
  99                 (*batchp)->index = 0;
 100         }
 101         (*batchp)->tables[(*batchp)->index++] = pgf;
 102         if ((*batchp)->index == PTE_FREELIST_SIZE) {
 103                 pte_free_submit(*batchp);
 104                 *batchp = NULL;
 105         }
 106 }
 107
 108 void pte_free_finish(void)
 109 {
 110         /* This is safe since tlb_gather_mmu has disabled preemption */
 111         struct pte_freelist_batch **batchp = &__get_cpu_var(pte_freelist_cur);
 112
 113         if (*batchp == NULL)
 114                 return;
 115         pte_free_submit(*batchp);
 116         *batchp = NULL;
 117 }
 118
 119 /*
 120  * Handle i/d cache flushing, called from set_pte_at() or ptep_set_access_flags()
 121  */
 122 static pte_t do_dcache_icache_coherency(pte_t pte)
 123 {
 124         unsigned long pfn = pte_pfn(pte);
 125         struct page *page;
 126
 127         if (unlikely(!pfn_valid(pfn)))
 128                 return pte;
 129         page = pfn_to_page(pfn);
 130
 131         if (!PageReserved(page) && !test_bit(PG_arch_1, &page->flags)) {
 132                 pr_devel("do_dcache_icache_coherency... flushing\n");
 133                 flush_dcache_icache_page(page);
 134                 set_bit(PG_arch_1, &page->flags);
 135         }
 136         else
 137                 pr_devel("do_dcache_icache_coherency... already clean\n");
 138         return __pte(pte_val(pte) | _PAGE_HWEXEC);
 139 }
 140
 141 static inline int is_exec_fault(void)
 142 {
 143         return current->thread.regs && TRAP(current->thread.regs) == 0x400;
 144 }
 145
 146 /* We only try to do i/d cache coherency on stuff that looks like
 147  * reasonably "normal" PTEs. We currently require a PTE to be present
 148  * and we avoid _PAGE_SPECIAL and _PAGE_NO_CACHE
 149  */
 150 static inline int pte_looks_normal(pte_t pte)
 151 {
 152         return (pte_val(pte) &
 153                 (_PAGE_PRESENT | _PAGE_SPECIAL | _PAGE_NO_CACHE)) ==
 154                 (_PAGE_PRESENT);
 155 }
 156
 157 #if defined(CONFIG_PPC_STD_MMU)
 158 /* Server-style MMU handles coherency when hashing if HW exec permission
 159  * is supposed per page (currently 64-bit only). Else, we always flush
 160  * valid PTEs in set_pte.
 161  */
 162 static inline int pte_need_exec_flush(pte_t pte, int set_pte)
 163 {
 164         return set_pte && pte_looks_normal(pte) &&
 165                 !(cpu_has_feature(CPU_FTR_COHERENT_ICACHE) ||
 166                   cpu_has_feature(CPU_FTR_NOEXECUTE));
 167 }
 168 #elif _PAGE_HWEXEC == 0
 169 /* Embedded type MMU without HW exec support (8xx only so far), we flush
 170  * the cache for any present PTE
 171  */
 172 static inline int pte_need_exec_flush(pte_t pte, int set_pte)
 173 {
 174         return set_pte && pte_looks_normal(pte);
 175 }
 176 #else
 177 /* Other embedded CPUs with HW exec support per-page, we flush on exec
 178  * fault if HWEXEC is not set
 179  */
 180 static inline int pte_need_exec_flush(pte_t pte, int set_pte)
 181 {
 182         return pte_looks_normal(pte) && is_exec_fault() &&
 183                 !(pte_val(pte) & _PAGE_HWEXEC);
 184 }
 185 #endif
 186
 187 /*
 188  * set_pte stores a linux PTE into the linux page table.
 189  */
 190 void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_t pte)
 191 {
 192 #ifdef CONFIG_DEBUG_VM
 193         WARN_ON(pte_present(*ptep));
 194 #endif
 195         /* Note: mm->context.id might not yet have been assigned as
 196          * this context might not have been activated yet when this
 197          * is called.
 198          */
 199         pte = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
 200         if (pte_need_exec_flush(pte, 1))
 201                 pte = do_dcache_icache_coherency(pte);
 202
 203         /* Perform the setting of the PTE */
 204         __set_pte_at(mm, addr, ptep, pte, 0);
 205 }
 206
 207 /*
 208  * This is called when relaxing access to a PTE. It's also called in the page
 209  * fault path when we don't hit any of the major fault cases, ie, a minor
 210  * update of _PAGE_ACCESSED, _PAGE_DIRTY, etc... The generic code will have
 211  * handled those two for us, we additionally deal with missing execute
 212  * permission here on some processors
 213  */
 214 int ptep_set_access_flags(struct vm_area_struct *vma, unsigned long address,
 215                           pte_t *ptep, pte_t entry, int dirty)
 216 {
 217         int changed;
 218         if (!dirty && pte_need_exec_flush(entry, 0))
 219                 entry = do_dcache_icache_coherency(entry);
 220         changed = !pte_same(*(ptep), entry);
 221         if (changed) {
 222                 if (!(vma->vm_flags & VM_HUGETLB))
 223                         assert_pte_locked(vma->vm_mm, address);
 224                 __ptep_set_access_flags(ptep, entry);
 225                 flush_tlb_page_nohash(vma, address);
 226         }
 227         return changed;
 228 }
 229
 230 #ifdef CONFIG_DEBUG_VM
 231 void assert_pte_locked(struct mm_struct *mm, unsigned long addr)
 232 {
 233         pgd_t *pgd;
 234         pud_t *pud;
 235         pmd_t *pmd;
 236
 237         if (mm == &init_mm)
 238                 return;
 239         pgd = mm->pgd + pgd_index(addr);
 240         BUG_ON(pgd_none(*pgd));
 241         pud = pud_offset(pgd, addr);
 242         BUG_ON(pud_none(*pud));
 243         pmd = pmd_offset(pud, addr);
 244         BUG_ON(!pmd_present(*pmd));
 245         BUG_ON(!spin_is_locked(pte_lockptr(mm, pmd)));
 246 }
 247 #endif /* CONFIG_DEBUG_VM */
 248