Archipelago » qemu

/* BDRV_BLOCK_DATA: data is read from bs->file or another file

 * BDRV_BLOCK_ZERO: sectors read as zero

 * BDRV_BLOCK_OFFSET_VALID: sector stored in bs->file as raw data

 *

 * If BDRV_BLOCK_OFFSET_VALID is set, bits 9-62 represent the offset in

 * bs->file where sector data can be read from as raw data.

 *

 * DATA == 0 && ZERO == 0 means that data is read from backing_hd if present.

 *

 * DATA ZERO OFFSET_VALID

 *  t    t        t       sectors read as zero, bs->file is zero at offset

 *  t    f        t       sectors read as valid from bs->file at offset

 *  f    t        t       sectors preallocated, read as zero, bs->file not

 *                        necessarily zero at offset

 *  f    f        t       sectors preallocated but read from backing_hd,

 *                        bs->file contains garbage at offset

 *  t    t        f       sectors preallocated, read as zero, unknown offset

 *  t    f        f       sectors read from unknown file or offset

 *  f    t        f       not allocated or unknown offset, read as zero

 *  f    f        f       not allocated or unknown offset, read from backing_hd

 */

#define BDRV_BLOCK_DATA         1

#define BDRV_BLOCK_ZERO         2

#define BDRV_BLOCK_OFFSET_VALID 4

#define BDRV_BLOCK_OFFSET_MASK  BDRV_SECTOR_MASK