arch/arm/mm/flush.c

   1 /*
   2  *  linux/arch/arm/mm/flush.c
   3  *
   4  *  Copyright (C) 1995-2002 Russell King
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/module.h>
  11 #include <linux/mm.h>
  12 #include <linux/pagemap.h>
  13
  14 #include <asm/cacheflush.h>
  15 #include <asm/system.h>
  16 #include <asm/tlbflush.h>
  17
  18 #ifdef CONFIG_CPU_CACHE_VIPT
  19 #define ALIAS_FLUSH_START       0xffff4000
  20
  21 #define TOP_PTE(x)      pte_offset_kernel(top_pmd, x)
  22
  23 static void flush_pfn_alias(unsigned long pfn, unsigned long vaddr)
  24 {
  25         unsigned long to = ALIAS_FLUSH_START + (CACHE_COLOUR(vaddr) << PAGE_SHIFT);
  26
  27         set_pte(TOP_PTE(to), pfn_pte(pfn, PAGE_KERNEL));
  28         flush_tlb_kernel_page(to);
  29
  30         asm(    "mcrr   p15, 0, %1, %0, c14\n"
  31         "       mcrr    p15, 0, %1, %0, c5\n"
  32             :
  33             : "r" (to), "r" (to + PAGE_SIZE - L1_CACHE_BYTES)
  34             : "cc");
  35 }
  36 #else
  37 #define flush_pfn_alias(pfn,vaddr)      do { } while (0)
  38 #endif
  39
  40 static void __flush_dcache_page(struct address_space *mapping, struct page *page)
  41 {
  42         struct mm_struct *mm = current->active_mm;
  43         struct vm_area_struct *mpnt;
  44         struct prio_tree_iter iter;
  45         pgoff_t pgoff;
  46
  47         /*
  48          * Writeback any data associated with the kernel mapping of this
  49          * page.  This ensures that data in the physical page is mutually
  50          * coherent with the kernels mapping.
  51          */
  52         __cpuc_flush_dcache_page(page_address(page));
  53
  54         /*
  55          * If there's no mapping pointer here, then this page isn't
  56          * visible to userspace yet, so there are no cache lines
  57          * associated with any other aliases.
  58          */
  59         if (!mapping)
  60                 return;
  61
  62         /*
  63          * This is a page cache page.  If we have a VIPT cache, we
  64          * only need to do one flush - which would be at the relevant
  65          * userspace colour, which is congruent with page->index.
  66          */
  67         if (cache_is_vipt()) {
  68                 if (cache_is_vipt_aliasing())
  69                         flush_pfn_alias(page_to_pfn(page),
  70                                         page->index << PAGE_CACHE_SHIFT);
  71                 return;
  72         }
  73
  74         /*
  75          * There are possible user space mappings of this page:
  76          * - VIVT cache: we need to also write back and invalidate all user
  77          *   data in the current VM view associated with this page.
  78          * - aliasing VIPT: we only need to find one mapping of this page.
  79          */
  80         pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
  81
  82         flush_dcache_mmap_lock(mapping);
  83         vma_prio_tree_foreach(mpnt, &iter, &mapping->i_mmap, pgoff, pgoff) {
  84                 unsigned long offset;
  85
  86                 /*
  87                  * If this VMA is not in our MM, we can ignore it.
  88                  */
  89                 if (mpnt->vm_mm != mm)
  90                         continue;
  91                 if (!(mpnt->vm_flags & VM_MAYSHARE))
  92                         continue;
  93                 offset = (pgoff - mpnt->vm_pgoff) << PAGE_SHIFT;
  94                 flush_cache_page(mpnt, mpnt->vm_start + offset, page_to_pfn(page));
  95         }
  96         flush_dcache_mmap_unlock(mapping);
  97 }
  98
  99 /*
 100  * Ensure cache coherency between kernel mapping and userspace mapping
 101  * of this page.
 102  *
 103  * We have three cases to consider:
 104  *  - VIPT non-aliasing cache: fully coherent so nothing required.
 105  *  - VIVT: fully aliasing, so we need to handle every alias in our
 106  *          current VM view.
 107  *  - VIPT aliasing: need to handle one alias in our current VM view.
 108  *
 109  * If we need to handle aliasing:
 110  *  If the page only exists in the page cache and there are no user
 111  *  space mappings, we can be lazy and remember that we may have dirty
 112  *  kernel cache lines for later.  Otherwise, we assume we have
 113  *  aliasing mappings.
 114  */
 115 void flush_dcache_page(struct page *page)
 116 {
 117         struct address_space *mapping = page_mapping(page);
 118
 119         if (cache_is_vipt_nonaliasing())
 120                 return;
 121
 122         if (mapping && !mapping_mapped(mapping))
 123                 set_bit(PG_dcache_dirty, &page->flags);
 124         else
 125                 __flush_dcache_page(mapping, page);
 126 }
 127 EXPORT_SYMBOL(flush_dcache_page);