qcow2/qcow2_format.h

/*
 * Block driver for the QCOW version 2 format
 *
 * Copyright (c) 2004-2006 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#ifndef BLOCK_QCOW2_H
#define BLOCK_QCOW2_H

#ifdef __cplusplus
extern "C" {
#endif

#include "qemu_dep.h"

//#define DEBUG_ALLOC
//#define DEBUG_ALLOC2
//#define DEBUG_EXT

#define QCOW_MAGIC (('Q' << 24) | ('F' << 16) | ('I' << 8) | 0xfb)

#define QCOW_CRYPT_NONE 0
#define QCOW_CRYPT_AES  1
#define QCOW_CRYPT_LUKS 2

#define QCOW_MAX_CRYPT_CLUSTERS 32
#define QCOW_MAX_SNAPSHOTS 65536

/* Field widths in qcow2 mean normal cluster offsets cannot reach
 * 64PB; depending on cluster size, compressed clusters can have a
 * smaller limit (64PB for up to 16k clusters, then ramps down to
 * 512TB for 2M clusters).  */
#define QCOW_MAX_CLUSTER_OFFSET ((1ULL << 56) - 1)

/* 8 MB refcount table is enough for 2 PB images at 64k cluster size
 * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
#define QCOW_MAX_REFTABLE_SIZE (8 * MiB)

/* 32 MB L1 table is enough for 2 PB images at 64k cluster size
 * (128 GB for 512 byte clusters, 2 EB for 2 MB clusters) */
#define QCOW_MAX_L1_SIZE (32 * MiB)

/* Allow for an average of 1k per snapshot table entry, should be plenty of
 * space for snapshot names and IDs */
#define QCOW_MAX_SNAPSHOTS_SIZE (1024 * QCOW_MAX_SNAPSHOTS)

/* Maximum amount of extra data per snapshot table entry to accept */
#define QCOW_MAX_SNAPSHOT_EXTRA_DATA 1024

/* Bitmap header extension constraints */
#define QCOW2_MAX_BITMAPS 65535
#define QCOW2_MAX_BITMAP_DIRECTORY_SIZE (1024 * QCOW2_MAX_BITMAPS)

/* indicate that the refcount of the referenced cluster is exactly one. */
#define QCOW_OFLAG_COPIED     (1ULL << 63)
/* indicate that the cluster is compressed (they never have the copied flag) */
#define QCOW_OFLAG_COMPRESSED (1ULL << 62)
/* The cluster reads as all zeros */
#define QCOW_OFLAG_ZERO (1ULL << 0)

#define QCOW_EXTL2_SUBCLUSTERS_PER_CLUSTER 32

/* The subcluster X [0..31] is allocated */
#define QCOW_OFLAG_SUB_ALLOC(X)   (1ULL << (X))
/* The subcluster X [0..31] reads as zeroes */
#define QCOW_OFLAG_SUB_ZERO(X)    (QCOW_OFLAG_SUB_ALLOC(X) << 32)
/* Subclusters [X, Y) (0 <= X <= Y <= 32) are allocated */
#define QCOW_OFLAG_SUB_ALLOC_RANGE(X, Y) \
    (QCOW_OFLAG_SUB_ALLOC(Y) - QCOW_OFLAG_SUB_ALLOC(X))
/* Subclusters [X, Y) (0 <= X <= Y <= 32) read as zeroes */
#define QCOW_OFLAG_SUB_ZERO_RANGE(X, Y) \
    (QCOW_OFLAG_SUB_ALLOC_RANGE(X, Y) << 32)
/* L2 entry bitmap with all allocation bits set */
#define QCOW_L2_BITMAP_ALL_ALLOC  (QCOW_OFLAG_SUB_ALLOC_RANGE(0, 32))
/* L2 entry bitmap with all "read as zeroes" bits set */
#define QCOW_L2_BITMAP_ALL_ZEROES (QCOW_OFLAG_SUB_ZERO_RANGE(0, 32))

/* Size of normal and extended L2 entries */
#define L2E_SIZE_NORMAL   (sizeof(uint64_t))
#define L2E_SIZE_EXTENDED (sizeof(uint64_t) * 2)

/* Size of L1 table entries */
#define L1E_SIZE (sizeof(uint64_t))

/* Size of reftable entries */
#define REFTABLE_ENTRY_SIZE (sizeof(uint64_t))

#define MIN_CLUSTER_BITS 9
#define MAX_CLUSTER_BITS 21

/* Defined in the qcow2 spec (compressed cluster descriptor) */
#define QCOW2_COMPRESSED_SECTOR_SIZE 512U

/* Must be at least 2 to cover COW */
#define MIN_L2_CACHE_SIZE 2 /* cache entries */

/* Must be at least 4 to cover all cases of refcount table growth */
#define MIN_REFCOUNT_CACHE_SIZE 4 /* clusters */

#define DEFAULT_L2_CACHE_MAX_SIZE (32 * MiB)
#define DEFAULT_CACHE_CLEAN_INTERVAL 600  /* seconds */

#define DEFAULT_CLUSTER_SIZE 65536

#define QCOW2_OPT_DATA_FILE "data-file"
#define QCOW2_OPT_LAZY_REFCOUNTS "lazy-refcounts"
#define QCOW2_OPT_DISCARD_REQUEST "pass-discard-request"
#define QCOW2_OPT_DISCARD_SNAPSHOT "pass-discard-snapshot"
#define QCOW2_OPT_DISCARD_OTHER "pass-discard-other"
#define QCOW2_OPT_OVERLAP "overlap-check"
#define QCOW2_OPT_OVERLAP_TEMPLATE "overlap-check.template"
#define QCOW2_OPT_OVERLAP_MAIN_HEADER "overlap-check.main-header"
#define QCOW2_OPT_OVERLAP_ACTIVE_L1 "overlap-check.active-l1"
#define QCOW2_OPT_OVERLAP_ACTIVE_L2 "overlap-check.active-l2"
#define QCOW2_OPT_OVERLAP_REFCOUNT_TABLE "overlap-check.refcount-table"
#define QCOW2_OPT_OVERLAP_REFCOUNT_BLOCK "overlap-check.refcount-block"
#define QCOW2_OPT_OVERLAP_SNAPSHOT_TABLE "overlap-check.snapshot-table"
#define QCOW2_OPT_OVERLAP_INACTIVE_L1 "overlap-check.inactive-l1"
#define QCOW2_OPT_OVERLAP_INACTIVE_L2 "overlap-check.inactive-l2"
#define QCOW2_OPT_OVERLAP_BITMAP_DIRECTORY "overlap-check.bitmap-directory"
#define QCOW2_OPT_CACHE_SIZE "cache-size"
#define QCOW2_OPT_L2_CACHE_SIZE "l2-cache-size"
#define QCOW2_OPT_L2_CACHE_ENTRY_SIZE "l2-cache-entry-size"
#define QCOW2_OPT_REFCOUNT_CACHE_SIZE "refcount-cache-size"
#define QCOW2_OPT_CACHE_CLEAN_INTERVAL "cache-clean-interval"

typedef struct QCowHeader {
    uint32_t magic;
    uint32_t version;
    uint64_t backing_file_offset;
    uint32_t backing_file_size;
    uint32_t cluster_bits;
    uint64_t size; /* in bytes */
    uint32_t crypt_method;
    uint32_t l1_size; /* XXX: save number of clusters instead ? */
    uint64_t l1_table_offset;
    uint64_t refcount_table_offset;
    uint32_t refcount_table_clusters;
    uint32_t nb_snapshots;
    uint64_t snapshots_offset;

    /* The following fields are only valid for version >= 3 */
    uint64_t incompatible_features;
    uint64_t compatible_features;
    uint64_t autoclear_features;

    uint32_t refcount_order;
    uint32_t header_length;

    /* Additional fields */
    uint8_t compression_type;

    /* header must be a multiple of 8 */
    uint8_t padding[7];
} QEMU_PACKED QCowHeader;

//QEMU_BUILD_BUG_ON(!QEMU_IS_ALIGNED(sizeof(QCowHeader), 8));

typedef struct QEMU_PACKED QCowSnapshotHeader {
    /* header is 8 byte aligned */
    uint64_t l1_table_offset;

    uint32_t l1_size;
    uint16_t id_str_size;
    uint16_t name_size;

    uint32_t date_sec;
    uint32_t date_nsec;

    uint64_t vm_clock_nsec;

    uint32_t vm_state_size;
    uint32_t extra_data_size; /* for extension */
    /* extra data follows */
    /* id_str follows */
    /* name follows  */
} QCowSnapshotHeader;

typedef struct QEMU_PACKED QCowSnapshotExtraData {
    uint64_t vm_state_size_large;
    uint64_t disk_size;
    uint64_t icount;
} QCowSnapshotExtraData;


typedef struct Qcow2CryptoHeaderExtension {
    uint64_t offset;
    uint64_t length;
} QEMU_PACKED Qcow2CryptoHeaderExtension;

enum {
    QCOW2_FEAT_TYPE_INCOMPATIBLE    = 0,
    QCOW2_FEAT_TYPE_COMPATIBLE      = 1,
    QCOW2_FEAT_TYPE_AUTOCLEAR       = 2,
};

/* Incompatible feature bits */
enum {
    QCOW2_INCOMPAT_DIRTY_BITNR      = 0,
    QCOW2_INCOMPAT_CORRUPT_BITNR    = 1,
    QCOW2_INCOMPAT_DATA_FILE_BITNR  = 2,
    QCOW2_INCOMPAT_COMPRESSION_BITNR = 3,
    QCOW2_INCOMPAT_EXTL2_BITNR      = 4,
    QCOW2_INCOMPAT_DIRTY            = 1 << QCOW2_INCOMPAT_DIRTY_BITNR,
    QCOW2_INCOMPAT_CORRUPT          = 1 << QCOW2_INCOMPAT_CORRUPT_BITNR,
    QCOW2_INCOMPAT_DATA_FILE        = 1 << QCOW2_INCOMPAT_DATA_FILE_BITNR,
    QCOW2_INCOMPAT_COMPRESSION      = 1 << QCOW2_INCOMPAT_COMPRESSION_BITNR,
    QCOW2_INCOMPAT_EXTL2            = 1 << QCOW2_INCOMPAT_EXTL2_BITNR,

    QCOW2_INCOMPAT_MASK             = QCOW2_INCOMPAT_DIRTY
                                    | QCOW2_INCOMPAT_CORRUPT
                                    | QCOW2_INCOMPAT_DATA_FILE
                                    | QCOW2_INCOMPAT_COMPRESSION
                                    | QCOW2_INCOMPAT_EXTL2,
};

/* Compatible feature bits */
enum {
    QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR = 0,
    QCOW2_COMPAT_LAZY_REFCOUNTS       = 1 << QCOW2_COMPAT_LAZY_REFCOUNTS_BITNR,

    QCOW2_COMPAT_FEAT_MASK            = QCOW2_COMPAT_LAZY_REFCOUNTS,
};

/* Autoclear feature bits */
enum {
    QCOW2_AUTOCLEAR_BITMAPS_BITNR       = 0,
    QCOW2_AUTOCLEAR_DATA_FILE_RAW_BITNR = 1,
    QCOW2_AUTOCLEAR_BITMAPS             = 1 << QCOW2_AUTOCLEAR_BITMAPS_BITNR,
    QCOW2_AUTOCLEAR_DATA_FILE_RAW       = 1 << QCOW2_AUTOCLEAR_DATA_FILE_RAW_BITNR,

    QCOW2_AUTOCLEAR_MASK                = QCOW2_AUTOCLEAR_BITMAPS
                                        | QCOW2_AUTOCLEAR_DATA_FILE_RAW,
};

enum qcow2_discard_type {
    QCOW2_DISCARD_NEVER = 0,
    QCOW2_DISCARD_ALWAYS,
    QCOW2_DISCARD_REQUEST,
    QCOW2_DISCARD_SNAPSHOT,
    QCOW2_DISCARD_OTHER,
    QCOW2_DISCARD_MAX
};

typedef struct Qcow2Feature {
    uint8_t type;
    uint8_t bit;
    char    name[46];
} QEMU_PACKED Qcow2Feature;


typedef struct Qcow2BitmapHeaderExt {
    uint32_t nb_bitmaps;
    uint32_t reserved32;
    uint64_t bitmap_directory_size;
    uint64_t bitmap_directory_offset;
} QEMU_PACKED Qcow2BitmapHeaderExt;


/*
 * In images with standard L2 entries all clusters are treated as if
 * they had one subcluster so QCow2ClusterType and QCow2SubclusterType
 * can be mapped to each other and have the exact same meaning
 * (QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC cannot happen in these images).
 *
 * In images with extended L2 entries QCow2ClusterType refers to the
 * complete cluster and QCow2SubclusterType to each of the individual
 * subclusters, so there are several possible combinations:
 *
 *     |--------------+---------------------------|
 *     | Cluster type | Possible subcluster types |
 *     |--------------+---------------------------|
 *     | UNALLOCATED  |         UNALLOCATED_PLAIN |
 *     |              |                ZERO_PLAIN |
 *     |--------------+---------------------------|
 *     | NORMAL       |         UNALLOCATED_ALLOC |
 *     |              |                ZERO_ALLOC |
 *     |              |                    NORMAL |
 *     |--------------+---------------------------|
 *     | COMPRESSED   |                COMPRESSED |
 *     |--------------+---------------------------|
 *
 * QCOW2_SUBCLUSTER_INVALID means that the L2 entry is incorrect and
 * the image should be marked corrupt.
 */

typedef enum QCow2ClusterType {
    QCOW2_CLUSTER_UNALLOCATED,
    QCOW2_CLUSTER_ZERO_PLAIN,
    QCOW2_CLUSTER_ZERO_ALLOC,
    QCOW2_CLUSTER_NORMAL,
    QCOW2_CLUSTER_COMPRESSED,
} QCow2ClusterType;

typedef enum QCow2SubclusterType {
    QCOW2_SUBCLUSTER_UNALLOCATED_PLAIN,
    QCOW2_SUBCLUSTER_UNALLOCATED_ALLOC,
    QCOW2_SUBCLUSTER_ZERO_PLAIN,
    QCOW2_SUBCLUSTER_ZERO_ALLOC,
    QCOW2_SUBCLUSTER_NORMAL,
    QCOW2_SUBCLUSTER_COMPRESSED,
    QCOW2_SUBCLUSTER_INVALID,
} QCow2SubclusterType;

typedef enum QCow2MetadataOverlap {
    QCOW2_OL_MAIN_HEADER_BITNR      = 0,
    QCOW2_OL_ACTIVE_L1_BITNR        = 1,
    QCOW2_OL_ACTIVE_L2_BITNR        = 2,
    QCOW2_OL_REFCOUNT_TABLE_BITNR   = 3,
    QCOW2_OL_REFCOUNT_BLOCK_BITNR   = 4,
    QCOW2_OL_SNAPSHOT_TABLE_BITNR   = 5,
    QCOW2_OL_INACTIVE_L1_BITNR      = 6,
    QCOW2_OL_INACTIVE_L2_BITNR      = 7,
    QCOW2_OL_BITMAP_DIRECTORY_BITNR = 8,

    QCOW2_OL_MAX_BITNR              = 9,

    QCOW2_OL_NONE             = 0,
    QCOW2_OL_MAIN_HEADER      = (1 << QCOW2_OL_MAIN_HEADER_BITNR),
    QCOW2_OL_ACTIVE_L1        = (1 << QCOW2_OL_ACTIVE_L1_BITNR),
    QCOW2_OL_ACTIVE_L2        = (1 << QCOW2_OL_ACTIVE_L2_BITNR),
    QCOW2_OL_REFCOUNT_TABLE   = (1 << QCOW2_OL_REFCOUNT_TABLE_BITNR),
    QCOW2_OL_REFCOUNT_BLOCK   = (1 << QCOW2_OL_REFCOUNT_BLOCK_BITNR),
    QCOW2_OL_SNAPSHOT_TABLE   = (1 << QCOW2_OL_SNAPSHOT_TABLE_BITNR),
    QCOW2_OL_INACTIVE_L1      = (1 << QCOW2_OL_INACTIVE_L1_BITNR),
    /* NOTE: Checking overlaps with inactive L2 tables will result in bdrv
     * reads. */
    QCOW2_OL_INACTIVE_L2      = (1 << QCOW2_OL_INACTIVE_L2_BITNR),
    QCOW2_OL_BITMAP_DIRECTORY = (1 << QCOW2_OL_BITMAP_DIRECTORY_BITNR),
} QCow2MetadataOverlap;

/* Perform all overlap checks which can be done in constant time */
#define QCOW2_OL_CONSTANT \
    (QCOW2_OL_MAIN_HEADER | QCOW2_OL_ACTIVE_L1 | QCOW2_OL_REFCOUNT_TABLE | \
     QCOW2_OL_SNAPSHOT_TABLE | QCOW2_OL_BITMAP_DIRECTORY)

/* Perform all overlap checks which don't require disk access */
#define QCOW2_OL_CACHED \
    (QCOW2_OL_CONSTANT | QCOW2_OL_ACTIVE_L2 | QCOW2_OL_REFCOUNT_BLOCK | \
     QCOW2_OL_INACTIVE_L1)

/* Perform all overlap checks */
#define QCOW2_OL_ALL \
    (QCOW2_OL_CACHED | QCOW2_OL_INACTIVE_L2)

#define L1E_OFFSET_MASK 0x00fffffffffffe00ULL
#define L1E_RESERVED_MASK 0x7f000000000001ffULL
#define L2E_OFFSET_MASK 0x00fffffffffffe00ULL
#define L2E_STD_RESERVED_MASK 0x3f000000000001feULL

#define REFT_OFFSET_MASK 0xfffffffffffffe00ULL
#define REFT_RESERVED_MASK 0x1ffULL

#define INV_OFFSET (-1ULL)

#ifdef __cplusplus
}
#endif

#endif