arch/i386/mm/highmem-xen.c

   1 #include <linux/highmem.h>
   2 #include <linux/module.h>
   3
   4 void *kmap(struct page *page)
   5 {
   6         might_sleep();
   7         if (!PageHighMem(page))
   8                 return page_address(page);
   9         return kmap_high(page);
  10 }
  11
  12 void kunmap(struct page *page)
  13 {
  14         if (in_interrupt())
  15                 BUG();
  16         if (!PageHighMem(page))
  17                 return;
  18         kunmap_high(page);
  19 }
  20
  21 /*
  22  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
  23  * no global lock is needed and because the kmap code must perform a global TLB
  24  * invalidation when the kmap pool wraps.
  25  *
  26  * However when holding an atomic kmap is is not legal to sleep, so atomic
  27  * kmaps are appropriate for short, tight code paths only.
  28  */
  29 static void *__kmap_atomic(struct page *page, enum km_type type, pgprot_t prot)
  30 {
  31         enum fixed_addresses idx;
  32         unsigned long vaddr;
  33
  34         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
  35         inc_preempt_count();
  36         if (!PageHighMem(page))
  37                 return page_address(page);
  38
  39         idx = type + KM_TYPE_NR*smp_processor_id();
  40         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
  41 #ifdef CONFIG_DEBUG_HIGHMEM
  42         if (!pte_none(*(kmap_pte-idx)))
  43                 BUG();
  44 #endif
  45         set_pte_at_sync(&init_mm, vaddr, kmap_pte-idx, mk_pte(page, prot));
  46
  47         return (void*) vaddr;
  48 }
  49
  50 void *kmap_atomic(struct page *page, enum km_type type)
  51 {
  52         return __kmap_atomic(page, type, kmap_prot);
  53 }
  54
  55 /* Same as kmap_atomic but with PAGE_KERNEL_RO page protection. */
  56 void *kmap_atomic_pte(struct page *page, enum km_type type)
  57 {
  58         return __kmap_atomic(page, type, PAGE_KERNEL_RO);
  59 }
  60
  61 void kunmap_atomic(void *kvaddr, enum km_type type)
  62 {
  63 #if defined(CONFIG_DEBUG_HIGHMEM) || defined(CONFIG_XEN)
  64         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
  65         enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
  66
  67         if (vaddr < FIXADDR_START) { // FIXME
  68                 dec_preempt_count();
  69                 preempt_check_resched();
  70                 return;
  71         }
  72 #endif
  73
  74 #if defined(CONFIG_DEBUG_HIGHMEM)
  75         if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN+idx))
  76                 BUG();
  77
  78         /*
  79          * force other mappings to Oops if they'll try to access
  80          * this pte without first remap it
  81          */
  82         pte_clear(&init_mm, vaddr, kmap_pte-idx);
  83         __flush_tlb_one(vaddr);
  84 #elif defined(CONFIG_XEN)
  85         /*
  86          * We must ensure there are no dangling pagetable references when
  87          * returning memory to Xen (decrease_reservation).
  88          * XXX TODO: We could make this faster by only zapping when
  89          * kmap_flush_unused is called but that is trickier and more invasive.
  90          */
  91         pte_clear(&init_mm, vaddr, kmap_pte-idx);
  92 #endif
  93
  94         dec_preempt_count();
  95         preempt_check_resched();
  96 }
  97
  98 /* This is the same as kmap_atomic() but can map memory that doesn't
  99  * have a struct page associated with it.
 100  */
 101 void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
 102 {
 103         enum fixed_addresses idx;
 104         unsigned long vaddr;
 105
 106         inc_preempt_count();
 107
 108         idx = type + KM_TYPE_NR*smp_processor_id();
 109         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 110         set_pte(kmap_pte-idx, pfn_pte(pfn, kmap_prot));
 111         __flush_tlb_one(vaddr);
 112
 113         return (void*) vaddr;
 114 }
 115
 116 struct page *kmap_atomic_to_page(void *ptr)
 117 {
 118         unsigned long idx, vaddr = (unsigned long)ptr;
 119         pte_t *pte;
 120
 121         if (vaddr < FIXADDR_START)
 122                 return virt_to_page(ptr);
 123
 124         idx = virt_to_fix(vaddr);
 125         pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 126         return pte_page(*pte);
 127 }
 128
 129 EXPORT_SYMBOL(kmap);
 130 EXPORT_SYMBOL(kunmap);
 131 EXPORT_SYMBOL(kmap_atomic);
 132 EXPORT_SYMBOL(kunmap_atomic);
 133 EXPORT_SYMBOL(kmap_atomic_to_page);