include/qemu/hbitmap.h

   1 /*
   2  * Hierarchical Bitmap Data Type
   3  *
   4  * Copyright Red Hat, Inc., 2012
   5  *
   6  * Author: Paolo Bonzini <pbonzini@redhat.com>
   7  *
   8  * This work is licensed under the terms of the GNU GPL, version 2 or
   9  * later.  See the COPYING file in the top-level directory.
  10  */
  11
  12 #ifndef HBITMAP_H
  13 #define HBITMAP_H
  14
  15 #include "bitops.h"
  16 #include "host-utils.h"
  17
  18 typedef struct HBitmap HBitmap;
  19 typedef struct HBitmapIter HBitmapIter;
  20
  21 #define BITS_PER_LEVEL         (BITS_PER_LONG == 32 ? 5 : 6)
  22
  23 /* For 32-bit, the largest that fits in a 4 GiB address space.
  24  * For 64-bit, the number of sectors in 1 PiB.  Good luck, in
  25  * either case... :)
  26  */
  27 #define HBITMAP_LOG_MAX_SIZE   (BITS_PER_LONG == 32 ? 34 : 41)
  28
  29 /* We need to place a sentinel in level 0 to speed up iteration.  Thus,
  30  * we do this instead of HBITMAP_LOG_MAX_SIZE / BITS_PER_LEVEL.  The
  31  * difference is that it allocates an extra level when HBITMAP_LOG_MAX_SIZE
  32  * is an exact multiple of BITS_PER_LEVEL.
  33  */
  34 #define HBITMAP_LEVELS         ((HBITMAP_LOG_MAX_SIZE / BITS_PER_LEVEL) + 1)
  35
  36 struct HBitmapIter {
  37     const HBitmap *hb;
  38
  39     /* Copied from hb for access in the inline functions (hb is opaque).  */
  40     int granularity;
  41
  42     /* Entry offset into the last-level array of longs.  */
  43     size_t pos;
  44
  45     /* The currently-active path in the tree.  Each item of cur[i] stores
  46      * the bits (i.e. the subtrees) yet to be processed under that node.
  47      */
  48     unsigned long cur[HBITMAP_LEVELS];
  49 };
  50
  51 /**
  52  * hbitmap_alloc:
  53  * @size: Number of bits in the bitmap.
  54  * @granularity: Granularity of the bitmap.  Aligned groups of 2^@granularity
  55  * bits will be represented by a single bit.  Each operation on a
  56  * range of bits first rounds the bits to determine which group they land
  57  * in, and then affect the entire set; iteration will only visit the first
  58  * bit of each group.
  59  *
  60  * Allocate a new HBitmap.
  61  */
  62 HBitmap *hbitmap_alloc(uint64_t size, int granularity);
  63
  64 /**
  65  * hbitmap_truncate:
  66  * @hb: The bitmap to change the size of.
  67  * @size: The number of elements to change the bitmap to accommodate.
  68  *
  69  * truncate or grow an existing bitmap to accommodate a new number of elements.
  70  * This may invalidate existing HBitmapIterators.
  71  */
  72 void hbitmap_truncate(HBitmap *hb, uint64_t size);
  73
  74 /**
  75  * hbitmap_merge:
  76  * @a: The bitmap to store the result in.
  77  * @b: The bitmap to merge into @a.
  78  * @return true if the merge was successful,
  79  *         false if it was not attempted.
  80  *
  81  * Merge two bitmaps together.
  82  * A := A (BITOR) B.
  83  * B is left unmodified.
  84  */
  85 bool hbitmap_merge(HBitmap *a, const HBitmap *b);
  86
  87 /**
  88  * hbitmap_empty:
  89  * @hb: HBitmap to operate on.
  90  *
  91  * Return whether the bitmap is empty.
  92  */
  93 bool hbitmap_empty(const HBitmap *hb);
  94
  95 /**
  96  * hbitmap_granularity:
  97  * @hb: HBitmap to operate on.
  98  *
  99  * Return the granularity of the HBitmap.
 100  */
 101 int hbitmap_granularity(const HBitmap *hb);
 102
 103 /**
 104  * hbitmap_count:
 105  * @hb: HBitmap to operate on.
 106  *
 107  * Return the number of bits set in the HBitmap.
 108  */
 109 uint64_t hbitmap_count(const HBitmap *hb);
 110
 111 /**
 112  * hbitmap_set:
 113  * @hb: HBitmap to operate on.
 114  * @start: First bit to set (0-based).
 115  * @count: Number of bits to set.
 116  *
 117  * Set a consecutive range of bits in an HBitmap.
 118  */
 119 void hbitmap_set(HBitmap *hb, uint64_t start, uint64_t count);
 120
 121 /**
 122  * hbitmap_reset:
 123  * @hb: HBitmap to operate on.
 124  * @start: First bit to reset (0-based).
 125  * @count: Number of bits to reset.
 126  *
 127  * Reset a consecutive range of bits in an HBitmap.
 128  */
 129 void hbitmap_reset(HBitmap *hb, uint64_t start, uint64_t count);
 130
 131 /**
 132  * hbitmap_reset_all:
 133  * @hb: HBitmap to operate on.
 134  *
 135  * Reset all bits in an HBitmap.
 136  */
 137 void hbitmap_reset_all(HBitmap *hb);
 138
 139 /**
 140  * hbitmap_get:
 141  * @hb: HBitmap to operate on.
 142  * @item: Bit to query (0-based).
 143  *
 144  * Return whether the @item-th bit in an HBitmap is set.
 145  */
 146 bool hbitmap_get(const HBitmap *hb, uint64_t item);
 147
 148 /**
 149  * hbitmap_serialization_granularity:
 150  * @hb: HBitmap to operate on.
 151  *
 152  * Granularity of serialization chunks, used by other serialization functions.
 153  * For every chunk:
 154  * 1. Chunk start should be aligned to this granularity.
 155  * 2. Chunk size should be aligned too, except for last chunk (for which
 156  *      start + count == hb->size)
 157  */
 158 uint64_t hbitmap_serialization_granularity(const HBitmap *hb);
 159
 160 /**
 161  * hbitmap_serialization_size:
 162  * @hb: HBitmap to operate on.
 163  * @start: Starting bit
 164  * @count: Number of bits
 165  *
 166  * Return number of bytes hbitmap_(de)serialize_part needs
 167  */
 168 uint64_t hbitmap_serialization_size(const HBitmap *hb,
 169                                     uint64_t start, uint64_t count);
 170
 171 /**
 172  * hbitmap_serialize_part
 173  * @hb: HBitmap to operate on.
 174  * @buf: Buffer to store serialized bitmap.
 175  * @start: First bit to store.
 176  * @count: Number of bits to store.
 177  *
 178  * Stores HBitmap data corresponding to given region. The format of saved data
 179  * is linear sequence of bits, so it can be used by hbitmap_deserialize_part
 180  * independently of endianness and size of HBitmap level array elements
 181  */
 182 void hbitmap_serialize_part(const HBitmap *hb, uint8_t *buf,
 183                             uint64_t start, uint64_t count);
 184
 185 /**
 186  * hbitmap_deserialize_part
 187  * @hb: HBitmap to operate on.
 188  * @buf: Buffer to restore bitmap data from.
 189  * @start: First bit to restore.
 190  * @count: Number of bits to restore.
 191  * @finish: Whether to call hbitmap_deserialize_finish automatically.
 192  *
 193  * Restores HBitmap data corresponding to given region. The format is the same
 194  * as for hbitmap_serialize_part.
 195  *
 196  * If @finish is false, caller must call hbitmap_serialize_finish before using
 197  * the bitmap.
 198  */
 199 void hbitmap_deserialize_part(HBitmap *hb, uint8_t *buf,
 200                               uint64_t start, uint64_t count,
 201                               bool finish);
 202
 203 /**
 204  * hbitmap_deserialize_zeroes
 205  * @hb: HBitmap to operate on.
 206  * @start: First bit to restore.
 207  * @count: Number of bits to restore.
 208  * @finish: Whether to call hbitmap_deserialize_finish automatically.
 209  *
 210  * Fills the bitmap with zeroes.
 211  *
 212  * If @finish is false, caller must call hbitmap_serialize_finish before using
 213  * the bitmap.
 214  */
 215 void hbitmap_deserialize_zeroes(HBitmap *hb, uint64_t start, uint64_t count,
 216                                 bool finish);
 217
 218 /**
 219  * hbitmap_deserialize_finish
 220  * @hb: HBitmap to operate on.
 221  *
 222  * Repair HBitmap after calling hbitmap_deserialize_data. Actually, all HBitmap
 223  * layers are restored here.
 224  */
 225 void hbitmap_deserialize_finish(HBitmap *hb);
 226
 227 /**
 228  * hbitmap_free:
 229  * @hb: HBitmap to operate on.
 230  *
 231  * Free an HBitmap and all of its associated memory.
 232  */
 233 void hbitmap_free(HBitmap *hb);
 234
 235 /**
 236  * hbitmap_iter_init:
 237  * @hbi: HBitmapIter to initialize.
 238  * @hb: HBitmap to iterate on.
 239  * @first: First bit to visit (0-based, must be strictly less than the
 240  * size of the bitmap).
 241  *
 242  * Set up @hbi to iterate on the HBitmap @hb.  hbitmap_iter_next will return
 243  * the lowest-numbered bit that is set in @hb, starting at @first.
 244  *
 245  * Concurrent setting of bits is acceptable, and will at worst cause the
 246  * iteration to miss some of those bits.  Resetting bits before the current
 247  * position of the iterator is also okay.  However, concurrent resetting of
 248  * bits can lead to unexpected behavior if the iterator has not yet reached
 249  * those bits.
 250  */
 251 void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first);
 252
 253 /* hbitmap_iter_skip_words:
 254  * @hbi: HBitmapIter to operate on.
 255  *
 256  * Internal function used by hbitmap_iter_next and hbitmap_iter_next_word.
 257  */
 258 unsigned long hbitmap_iter_skip_words(HBitmapIter *hbi);
 259
 260 /* hbitmap_create_meta:
 261  * Create a "meta" hbitmap to track dirtiness of the bits in this HBitmap.
 262  * The caller owns the created bitmap and must call hbitmap_free_meta(hb) to
 263  * free it.
 264  *
 265  * Currently, we only guarantee that if a bit in the hbitmap is changed it
 266  * will be reflected in the meta bitmap, but we do not yet guarantee the
 267  * opposite.
 268  *
 269  * @hb: The HBitmap to operate on.
 270  * @chunk_size: How many bits in @hb does one bit in the meta track.
 271  */
 272 HBitmap *hbitmap_create_meta(HBitmap *hb, int chunk_size);
 273
 274 /* hbitmap_free_meta:
 275  * Free the meta bitmap of @hb.
 276  *
 277  * @hb: The HBitmap whose meta bitmap should be freed.
 278  */
 279 void hbitmap_free_meta(HBitmap *hb);
 280
 281 /**
 282  * hbitmap_iter_next:
 283  * @hbi: HBitmapIter to operate on.
 284  *
 285  * Return the next bit that is set in @hbi's associated HBitmap,
 286  * or -1 if all remaining bits are zero.
 287  */
 288 static inline int64_t hbitmap_iter_next(HBitmapIter *hbi)
 289 {
 290     unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1];
 291     int64_t item;
 292
 293     if (cur == 0) {
 294         cur = hbitmap_iter_skip_words(hbi);
 295         if (cur == 0) {
 296             return -1;
 297         }
 298     }
 299
 300     /* The next call will resume work from the next bit.  */
 301     hbi->cur[HBITMAP_LEVELS - 1] = cur & (cur - 1);
 302     item = ((uint64_t)hbi->pos << BITS_PER_LEVEL) + ctzl(cur);
 303
 304     return item << hbi->granularity;
 305 }
 306
 307 /**
 308  * hbitmap_iter_next_word:
 309  * @hbi: HBitmapIter to operate on.
 310  * @p_cur: Location where to store the next non-zero word.
 311  *
 312  * Return the index of the next nonzero word that is set in @hbi's
 313  * associated HBitmap, and set *p_cur to the content of that word
 314  * (bits before the index that was passed to hbitmap_iter_init are
 315  * trimmed on the first call).  Return -1, and set *p_cur to zero,
 316  * if all remaining words are zero.
 317  */
 318 static inline size_t hbitmap_iter_next_word(HBitmapIter *hbi, unsigned long *p_cur)
 319 {
 320     unsigned long cur = hbi->cur[HBITMAP_LEVELS - 1];
 321
 322     if (cur == 0) {
 323         cur = hbitmap_iter_skip_words(hbi);
 324         if (cur == 0) {
 325             *p_cur = 0;
 326             return -1;
 327         }
 328     }
 329
 330     /* The next call will resume work from the next word.  */
 331     hbi->cur[HBITMAP_LEVELS - 1] = 0;
 332     *p_cur = cur;
 333     return hbi->pos;
 334 }
 335
 336
 337 #endif