include/linux/mmu_notifier.h

   1 #ifndef _LINUX_MMU_NOTIFIER_H
   2 #define _LINUX_MMU_NOTIFIER_H
   3
   4 #include <linux/list.h>
   5 #include <linux/spinlock.h>
   6 #include <linux/mm_types.h>
   7
   8 struct mmu_notifier;
   9 struct mmu_notifier_ops;
  10
  11 #ifdef CONFIG_MMU_NOTIFIER
  12
  13 /*
  14  * The mmu notifier_mm structure is allocated and installed in
  15  * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
  16  * critical section and it's released only when mm_count reaches zero
  17  * in mmdrop().
  18  */
  19 struct mmu_notifier_mm {
  20         /* all mmu notifiers registerd in this mm are queued in this list */
  21         struct hlist_head list;
  22         /* to serialize the list modifications and hlist_unhashed */
  23         spinlock_t lock;
  24 };
  25
  26 struct mmu_notifier_ops {
  27         /*
  28          * Called either by mmu_notifier_unregister or when the mm is
  29          * being destroyed by exit_mmap, always before all pages are
  30          * freed. This can run concurrently with other mmu notifier
  31          * methods (the ones invoked outside the mm context) and it
  32          * should tear down all secondary mmu mappings and freeze the
  33          * secondary mmu. If this method isn't implemented you've to
  34          * be sure that nothing could possibly write to the pages
  35          * through the secondary mmu by the time the last thread with
  36          * tsk->mm == mm exits.
  37          *
  38          * As side note: the pages freed after ->release returns could
  39          * be immediately reallocated by the gart at an alias physical
  40          * address with a different cache model, so if ->release isn't
  41          * implemented because all _software_ driven memory accesses
  42          * through the secondary mmu are terminated by the time the
  43          * last thread of this mm quits, you've also to be sure that
  44          * speculative _hardware_ operations can't allocate dirty
  45          * cachelines in the cpu that could not be snooped and made
  46          * coherent with the other read and write operations happening
  47          * through the gart alias address, so leading to memory
  48          * corruption.
  49          */
  50         void (*release)(struct mmu_notifier *mn,
  51                         struct mm_struct *mm);
  52
  53         /*
  54          * clear_flush_young is called after the VM is
  55          * test-and-clearing the young/accessed bitflag in the
  56          * pte. This way the VM will provide proper aging to the
  57          * accesses to the page through the secondary MMUs and not
  58          * only to the ones through the Linux pte.
  59          */
  60         int (*clear_flush_young)(struct mmu_notifier *mn,
  61                                  struct mm_struct *mm,
  62                                  unsigned long address);
  63
  64         /*
  65          * Before this is invoked any secondary MMU is still ok to
  66          * read/write to the page previously pointed to by the Linux
  67          * pte because the page hasn't been freed yet and it won't be
  68          * freed until this returns. If required set_page_dirty has to
  69          * be called internally to this method.
  70          */
  71         void (*invalidate_page)(struct mmu_notifier *mn,
  72                                 struct mm_struct *mm,
  73                                 unsigned long address);
  74
  75         /*
  76          * invalidate_range_start() and invalidate_range_end() must be
  77          * paired and are called only when the mmap_sem and/or the
  78          * locks protecting the reverse maps are held. The subsystem
  79          * must guarantee that no additional references are taken to
  80          * the pages in the range established between the call to
  81          * invalidate_range_start() and the matching call to
  82          * invalidate_range_end().
  83          *
  84          * Invalidation of multiple concurrent ranges may be
  85          * optionally permitted by the driver. Either way the
  86          * establishment of sptes is forbidden in the range passed to
  87          * invalidate_range_begin/end for the whole duration of the
  88          * invalidate_range_begin/end critical section.
  89          *
  90          * invalidate_range_start() is called when all pages in the
  91          * range are still mapped and have at least a refcount of one.
  92          *
  93          * invalidate_range_end() is called when all pages in the
  94          * range have been unmapped and the pages have been freed by
  95          * the VM.
  96          *
  97          * The VM will remove the page table entries and potentially
  98          * the page between invalidate_range_start() and
  99          * invalidate_range_end(). If the page must not be freed
 100          * because of pending I/O or other circumstances then the
 101          * invalidate_range_start() callback (or the initial mapping
 102          * by the driver) must make sure that the refcount is kept
 103          * elevated.
 104          *
 105          * If the driver increases the refcount when the pages are
 106          * initially mapped into an address space then either
 107          * invalidate_range_start() or invalidate_range_end() may
 108          * decrease the refcount. If the refcount is decreased on
 109          * invalidate_range_start() then the VM can free pages as page
 110          * table entries are removed.  If the refcount is only
 111          * droppped on invalidate_range_end() then the driver itself
 112          * will drop the last refcount but it must take care to flush
 113          * any secondary tlb before doing the final free on the
 114          * page. Pages will no longer be referenced by the linux
 115          * address space but may still be referenced by sptes until
 116          * the last refcount is dropped.
 117          */
 118         void (*invalidate_range_start)(struct mmu_notifier *mn,
 119                                        struct mm_struct *mm,
 120                                        unsigned long start, unsigned long end);
 121         void (*invalidate_range_end)(struct mmu_notifier *mn,
 122                                      struct mm_struct *mm,
 123                                      unsigned long start, unsigned long end);
 124 };
 125
 126 /*
 127  * The notifier chains are protected by mmap_sem and/or the reverse map
 128  * semaphores. Notifier chains are only changed when all reverse maps and
 129  * the mmap_sem locks are taken.
 130  *
 131  * Therefore notifier chains can only be traversed when either
 132  *
 133  * 1. mmap_sem is held.
 134  * 2. One of the reverse map locks is held (i_mmap_lock or anon_vma->lock).
 135  * 3. No other concurrent thread can access the list (release)
 136  */
 137 struct mmu_notifier {
 138         struct hlist_node hlist;
 139         const struct mmu_notifier_ops *ops;
 140 };
 141
 142 static inline int mm_has_notifiers(struct mm_struct *mm)
 143 {
 144         return unlikely(mm->mmu_notifier_mm);
 145 }
 146
 147 extern int mmu_notifier_register(struct mmu_notifier *mn,
 148                                  struct mm_struct *mm);
 149 extern int __mmu_notifier_register(struct mmu_notifier *mn,
 150                                    struct mm_struct *mm);
 151 extern void mmu_notifier_unregister(struct mmu_notifier *mn,
 152                                     struct mm_struct *mm);
 153 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
 154 extern void __mmu_notifier_release(struct mm_struct *mm);
 155 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
 156                                           unsigned long address);
 157 extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
 158                                           unsigned long address);
 159 extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 160                                   unsigned long start, unsigned long end);
 161 extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 162                                   unsigned long start, unsigned long end);
 163
 164 static inline void mmu_notifier_release(struct mm_struct *mm)
 165 {
 166         if (mm_has_notifiers(mm))
 167                 __mmu_notifier_release(mm);
 168 }
 169
 170 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 171                                           unsigned long address)
 172 {
 173         if (mm_has_notifiers(mm))
 174                 return __mmu_notifier_clear_flush_young(mm, address);
 175         return 0;
 176 }
 177
 178 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
 179                                           unsigned long address)
 180 {
 181         if (mm_has_notifiers(mm))
 182                 __mmu_notifier_invalidate_page(mm, address);
 183 }
 184
 185 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 186                                   unsigned long start, unsigned long end)
 187 {
 188         if (mm_has_notifiers(mm))
 189                 __mmu_notifier_invalidate_range_start(mm, start, end);
 190 }
 191
 192 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 193                                   unsigned long start, unsigned long end)
 194 {
 195         if (mm_has_notifiers(mm))
 196                 __mmu_notifier_invalidate_range_end(mm, start, end);
 197 }
 198
 199 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 200 {
 201         mm->mmu_notifier_mm = NULL;
 202 }
 203
 204 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 205 {
 206         if (mm_has_notifiers(mm))
 207                 __mmu_notifier_mm_destroy(mm);
 208 }
 209
 210 /*
 211  * These two macros will sometime replace ptep_clear_flush.
 212  * ptep_clear_flush is impleemnted as macro itself, so this also is
 213  * implemented as a macro until ptep_clear_flush will converted to an
 214  * inline function, to diminish the risk of compilation failure. The
 215  * invalidate_page method over time can be moved outside the PT lock
 216  * and these two macros can be later removed.
 217  */
 218 #define ptep_clear_flush_notify(__vma, __address, __ptep)               \
 219 ({                                                                      \
 220         pte_t __pte;                                                    \
 221         struct vm_area_struct *___vma = __vma;                          \
 222         unsigned long ___address = __address;                           \
 223         __pte = ptep_clear_flush(___vma, ___address, __ptep);           \
 224         mmu_notifier_invalidate_page(___vma->vm_mm, ___address);        \
 225         __pte;                                                          \
 226 })
 227
 228 #define ptep_clear_flush_young_notify(__vma, __address, __ptep)         \
 229 ({                                                                      \
 230         int __young;                                                    \
 231         struct vm_area_struct *___vma = __vma;                          \
 232         unsigned long ___address = __address;                           \
 233         __young = ptep_clear_flush_young(___vma, ___address, __ptep);   \
 234         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
 235                                                   ___address);          \
 236         __young;                                                        \
 237 })
 238
 239 #else /* CONFIG_MMU_NOTIFIER */
 240
 241 static inline void mmu_notifier_release(struct mm_struct *mm)
 242 {
 243 }
 244
 245 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 246                                           unsigned long address)
 247 {
 248         return 0;
 249 }
 250
 251 static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
 252                                           unsigned long address)
 253 {
 254 }
 255
 256 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 257                                   unsigned long start, unsigned long end)
 258 {
 259 }
 260
 261 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 262                                   unsigned long start, unsigned long end)
 263 {
 264 }
 265
 266 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 267 {
 268 }
 269
 270 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 271 {
 272 }
 273
 274 #define ptep_clear_flush_young_notify ptep_clear_flush_young
 275 #define ptep_clear_flush_notify ptep_clear_flush
 276
 277 #endif /* CONFIG_MMU_NOTIFIER */
 278
 279 #endif /* _LINUX_MMU_NOTIFIER_H */