Archipelago » qemu

/*

 * Block driver for the Virtual Disk Image (VDI) format

 *

 * Copyright (c) 2009 Stefan Weil

 *

 * This program is free software: you can redistribute it and/or modify

 * it under the terms of the GNU General Public License as published by

 * the Free Software Foundation, either version 2 of the License, or

 * (at your option) version 3 or any later version.

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 *

 * Reference:

 * http://forums.virtualbox.org/viewtopic.php?t=8046

 *

 * This driver supports create / read / write operations on VDI images.

 *

 * Todo (see also TODO in code):

 *

 * Some features like snapshots are still missing.

 *

 * Deallocation of zero-filled blocks and shrinking images are missing, too

 * (might be added to common block layer).

 *

 * Allocation of blocks could be optimized (less writes to block map and

 * header).

 *

 * Read and write of adjacents blocks could be done in one operation

 * (current code uses one operation per block (1 MiB).

 *

 * The code is not thread safe (missing locks for changes in header and

 * block table, no problem with current QEMU).

 *

 * Hints:

 *

 * Blocks (VDI documentation) correspond to clusters (QEMU).

 * QEMU's backing files could be implemented using VDI snapshot files (TODO).

 * VDI snapshot files may also contain the complete machine state.

 * Maybe this machine state can be converted to QEMU PC machine snapshot data.

 *

 * The driver keeps a block cache (little endian entries) in memory.

 * For the standard block size (1 MiB), a 1 TiB disk will use 4 MiB RAM,

 * so this seems to be reasonable.

 */

#include "qemu-common.h"

#include "block_int.h"

#include "module.h"

#if defined(CONFIG_UUID)

#include <uuid/uuid.h>

#else

/* TODO: move uuid emulation to some central place in QEMU. */

#include "sysemu.h"     /* UUID_FMT */

typedef unsigned char uuid_t[16];

void uuid_generate(uuid_t out);

int uuid_is_null(const uuid_t uu);

void uuid_unparse(const uuid_t uu, char *out);

#endif

/* Code configuration options. */

/* Enable debug messages. */

//~ #define CONFIG_VDI_DEBUG

/* Support write operations on VDI images. */

#define CONFIG_VDI_WRITE

/* Support non-standard block (cluster) size. This is untested.

 * Maybe it will be needed for very large images.

 */

//~ #define CONFIG_VDI_BLOCK_SIZE

/* Support static (fixed, pre-allocated) images. */

#define CONFIG_VDI_STATIC_IMAGE

/* Command line option for static images. */

#define BLOCK_OPT_STATIC "static"

#define KiB     1024

#define MiB     (KiB * KiB)

#define SECTOR_SIZE 512

#if defined(CONFIG_VDI_DEBUG)

#define logout(fmt, ...) \

                fprintf(stderr, "vdi\t%-24s" fmt, __func__, ##__VA_ARGS__)

#else

#define logout(fmt, ...) ((void)0)

#endif

/* Image signature. */

#define VDI_SIGNATURE 0xbeda107f

/* Image version. */

#define VDI_VERSION_1_1 0x00010001

/* Image type. */

#define VDI_TYPE_DYNAMIC 1

#define VDI_TYPE_STATIC  2

/* Innotek / SUN images use these strings in header.text:

 * "<<< innotek VirtualBox Disk Image >>>\n"

 * "<<< Sun xVM VirtualBox Disk Image >>>\n"

 * "<<< Sun VirtualBox Disk Image >>>\n"

 * The value does not matter, so QEMU created images use a different text.

 */

#define VDI_TEXT "<<< QEMU VM Virtual Disk Image >>>\n"

/* Unallocated blocks use this index (no need to convert endianness). */

#define VDI_UNALLOCATED UINT32_MAX

#if !defined(CONFIG_UUID)

void uuid_generate(uuid_t out)

{

    memset(out, 0, sizeof(uuid_t));

}

int uuid_is_null(const uuid_t uu)

{

    uuid_t null_uuid = { 0 };

    return memcmp(uu, null_uuid, sizeof(uuid_t)) == 0;

}

void uuid_unparse(const uuid_t uu, char *out)

{

    snprintf(out, 37, UUID_FMT,

            uu[0], uu[1], uu[2], uu[3], uu[4], uu[5], uu[6], uu[7],

            uu[8], uu[9], uu[10], uu[11], uu[12], uu[13], uu[14], uu[15]);

}

#endif

typedef struct {

    BlockDriverAIOCB common;

    int64_t sector_num;

    QEMUIOVector *qiov;

    uint8_t *buf;

    /* Total number of sectors. */

    int nb_sectors;

    /* Number of sectors for current AIO. */

    int n_sectors;

    /* New allocated block map entry. */

    uint32_t bmap_first;

    uint32_t bmap_last;

    /* Buffer for new allocated block. */

    void *block_buffer;

    void *orig_buf;

    int header_modified;

    BlockDriverAIOCB *hd_aiocb;

    struct iovec hd_iov;

    QEMUIOVector hd_qiov;

    QEMUBH *bh;

} VdiAIOCB;

typedef struct {

    char text[0x40];

    uint32_t signature;

    uint32_t version;

    uint32_t header_size;

    uint32_t image_type;

    uint32_t image_flags;

    char description[256];

    uint32_t offset_bmap;

    uint32_t offset_data;

    uint32_t cylinders;         /* disk geometry, unused here */

    uint32_t heads;             /* disk geometry, unused here */

    uint32_t sectors;           /* disk geometry, unused here */

    uint32_t sector_size;

    uint32_t unused1;

    uint64_t disk_size;

    uint32_t block_size;

    uint32_t block_extra;       /* unused here */

    uint32_t blocks_in_image;

    uint32_t blocks_allocated;

    uuid_t uuid_image;

    uuid_t uuid_last_snap;

    uuid_t uuid_link;

    uuid_t uuid_parent;

    uint64_t unused2[7];

} VdiHeader;

typedef struct {

    /* The block map entries are little endian (even in memory). */

    uint32_t *bmap;

    /* Size of block (bytes). */

    uint32_t block_size;

    /* Size of block (sectors). */

    uint32_t block_sectors;

    /* First sector of block map. */

    uint32_t bmap_sector;

    /* VDI header (converted to host endianness). */

    VdiHeader header;

} BDRVVdiState;

/* Change UUID from little endian (IPRT = VirtualBox format) to big endian

 * format (network byte order, standard, see RFC 4122) and vice versa.

 */

static void uuid_convert(uuid_t uuid)

{

    bswap32s((uint32_t *)&uuid[0]);

    bswap16s((uint16_t *)&uuid[4]);

    bswap16s((uint16_t *)&uuid[6]);

}

static void vdi_header_to_cpu(VdiHeader *header)

{

    le32_to_cpus(&header->signature);

    le32_to_cpus(&header->version);

    le32_to_cpus(&header->header_size);

    le32_to_cpus(&header->image_type);

    le32_to_cpus(&header->image_flags);

    le32_to_cpus(&header->offset_bmap);

    le32_to_cpus(&header->offset_data);

    le32_to_cpus(&header->cylinders);

    le32_to_cpus(&header->heads);

    le32_to_cpus(&header->sectors);

    le32_to_cpus(&header->sector_size);

    le64_to_cpus(&header->disk_size);

    le32_to_cpus(&header->block_size);

    le32_to_cpus(&header->block_extra);

    le32_to_cpus(&header->blocks_in_image);

    le32_to_cpus(&header->blocks_allocated);

    uuid_convert(header->uuid_image);

    uuid_convert(header->uuid_last_snap);

    uuid_convert(header->uuid_link);

    uuid_convert(header->uuid_parent);

}

static void vdi_header_to_le(VdiHeader *header)

{

    cpu_to_le32s(&header->signature);

    cpu_to_le32s(&header->version);

    cpu_to_le32s(&header->header_size);

    cpu_to_le32s(&header->image_type);

    cpu_to_le32s(&header->image_flags);

    cpu_to_le32s(&header->offset_bmap);

    cpu_to_le32s(&header->offset_data);

    cpu_to_le32s(&header->cylinders);

    cpu_to_le32s(&header->heads);

    cpu_to_le32s(&header->sectors);

    cpu_to_le32s(&header->sector_size);

    cpu_to_le64s(&header->disk_size);

    cpu_to_le32s(&header->block_size);

    cpu_to_le32s(&header->block_extra);

    cpu_to_le32s(&header->blocks_in_image);

    cpu_to_le32s(&header->blocks_allocated);

    cpu_to_le32s(&header->blocks_allocated);

    uuid_convert(header->uuid_image);

    uuid_convert(header->uuid_last_snap);

    uuid_convert(header->uuid_link);

    uuid_convert(header->uuid_parent);

}

#if defined(CONFIG_VDI_DEBUG)

static void vdi_header_print(VdiHeader *header)

{

    char uuid[37];

    logout("text        %s", header->text);

    logout("signature   0x%04x\n", header->signature);

    logout("header size 0x%04x\n", header->header_size);

    logout("image type  0x%04x\n", header->image_type);

    logout("image flags 0x%04x\n", header->image_flags);

    logout("description %s\n", header->description);

    logout("offset bmap 0x%04x\n", header->offset_bmap);

    logout("offset data 0x%04x\n", header->offset_data);

    logout("cylinders   0x%04x\n", header->cylinders);

    logout("heads       0x%04x\n", header->heads);

    logout("sectors     0x%04x\n", header->sectors);

    logout("sector size 0x%04x\n", header->sector_size);

    logout("image size  0x%" PRIx64 " B (%" PRIu64 " MiB)\n",

           header->disk_size, header->disk_size / MiB);

    logout("block size  0x%04x\n", header->block_size);

    logout("block extra 0x%04x\n", header->block_extra);

    logout("blocks tot. 0x%04x\n", header->blocks_in_image);

    logout("blocks all. 0x%04x\n", header->blocks_allocated);

    uuid_unparse(header->uuid_image, uuid);

    logout("uuid image  %s\n", uuid);

    uuid_unparse(header->uuid_last_snap, uuid);

    logout("uuid snap   %s\n", uuid);

    uuid_unparse(header->uuid_link, uuid);

    logout("uuid link   %s\n", uuid);

    uuid_unparse(header->uuid_parent, uuid);

    logout("uuid parent %s\n", uuid);

}

#endif

static int vdi_check(BlockDriverState *bs, BdrvCheckResult *res)

{

    /* TODO: additional checks possible. */

    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;

    uint32_t blocks_allocated = 0;

    uint32_t block;

    uint32_t *bmap;

    logout("\n");

    bmap = qemu_malloc(s->header.blocks_in_image * sizeof(uint32_t));

    memset(bmap, 0xff, s->header.blocks_in_image * sizeof(uint32_t));

    /* Check block map and value of blocks_allocated. */

    for (block = 0; block < s->header.blocks_in_image; block++) {

        uint32_t bmap_entry = le32_to_cpu(s->bmap[block]);

        if (bmap_entry != VDI_UNALLOCATED) {

            if (bmap_entry < s->header.blocks_in_image) {

                blocks_allocated++;

                if (bmap[bmap_entry] == VDI_UNALLOCATED) {

                    bmap[bmap_entry] = bmap_entry;

                } else {

                    fprintf(stderr, "ERROR: block index %" PRIu32

                            " also used by %" PRIu32 "\n", bmap[bmap_entry], bmap_entry);

                    res->corruptions++;

                }

            } else {

                fprintf(stderr, "ERROR: block index %" PRIu32

                        " too large, is %" PRIu32 "\n", block, bmap_entry);

                res->corruptions++;

            }

        }

    }

    if (blocks_allocated != s->header.blocks_allocated) {

        fprintf(stderr, "ERROR: allocated blocks mismatch, is %" PRIu32

               ", should be %" PRIu32 "\n",

               blocks_allocated, s->header.blocks_allocated);

        res->corruptions++;

    }

    qemu_free(bmap);

    return 0;

}

static int vdi_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)

{

    /* TODO: vdi_get_info would be needed for machine snapshots.

       vm_state_offset is still missing. */

    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;

    logout("\n");

    bdi->cluster_size = s->block_size;

    bdi->vm_state_offset = 0;

    return 0;

}

static int vdi_make_empty(BlockDriverState *bs)

{

    /* TODO: missing code. */

    logout("\n");

    /* The return value for missing code must be 0, see block.c. */

    return 0;

}

static int vdi_probe(const uint8_t *buf, int buf_size, const char *filename)

{

    const VdiHeader *header = (const VdiHeader *)buf;

    int result = 0;

    logout("\n");

    if (buf_size < sizeof(*header)) {

        /* Header too small, no VDI. */

    } else if (le32_to_cpu(header->signature) == VDI_SIGNATURE) {

        result = 100;

    }

    if (result == 0) {

        logout("no vdi image\n");

    } else {

        logout("%s", header->text);

    }

    return result;

}

static int vdi_open(BlockDriverState *bs, int flags)

{

    BDRVVdiState *s = bs->opaque;

    VdiHeader header;

    size_t bmap_size;

    logout("\n");

    if (bdrv_read(bs->file, 0, (uint8_t *)&header, 1) < 0) {

        goto fail;

    }

    vdi_header_to_cpu(&header);

#if defined(CONFIG_VDI_DEBUG)

    vdi_header_print(&header);

#endif

    if (header.disk_size % SECTOR_SIZE != 0) {

        /* 'VBoxManage convertfromraw' can create images with odd disk sizes.

           We accept them but round the disk size to the next multiple of

           SECTOR_SIZE. */

        logout("odd disk size %" PRIu64 " B, round up\n", header.disk_size);

        header.disk_size += SECTOR_SIZE - 1;

        header.disk_size &= ~(SECTOR_SIZE - 1);

    }

    if (header.version != VDI_VERSION_1_1) {

        logout("unsupported version %u.%u\n",

               header.version >> 16, header.version & 0xffff);

        goto fail;

    } else if (header.offset_bmap % SECTOR_SIZE != 0) {

        /* We only support block maps which start on a sector boundary. */

        logout("unsupported block map offset 0x%x B\n", header.offset_bmap);

        goto fail;

    } else if (header.offset_data % SECTOR_SIZE != 0) {

        /* We only support data blocks which start on a sector boundary. */

        logout("unsupported data offset 0x%x B\n", header.offset_data);

        goto fail;

    } else if (header.sector_size != SECTOR_SIZE) {

        logout("unsupported sector size %u B\n", header.sector_size);

        goto fail;

    } else if (header.block_size != 1 * MiB) {

        logout("unsupported block size %u B\n", header.block_size);

        goto fail;

    } else if (header.disk_size >

               (uint64_t)header.blocks_in_image * header.block_size) {

        logout("unsupported disk size %" PRIu64 " B\n", header.disk_size);

        goto fail;

    } else if (!uuid_is_null(header.uuid_link)) {

        logout("link uuid != 0, unsupported\n");

        goto fail;

    } else if (!uuid_is_null(header.uuid_parent)) {

        logout("parent uuid != 0, unsupported\n");

        goto fail;

    }

    bs->total_sectors = header.disk_size / SECTOR_SIZE;

    s->block_size = header.block_size;

    s->block_sectors = header.block_size / SECTOR_SIZE;

    s->bmap_sector = header.offset_bmap / SECTOR_SIZE;

    s->header = header;

    bmap_size = header.blocks_in_image * sizeof(uint32_t);

    bmap_size = (bmap_size + SECTOR_SIZE - 1) / SECTOR_SIZE;

    if (bmap_size > 0) {

        s->bmap = qemu_malloc(bmap_size * SECTOR_SIZE);

    }

    if (bdrv_read(bs->file, s->bmap_sector, (uint8_t *)s->bmap, bmap_size) < 0) {

        goto fail_free_bmap;

    }

    return 0;

 fail_free_bmap:

    qemu_free(s->bmap);

 fail:

    return -1;

}

static int vdi_is_allocated(BlockDriverState *bs, int64_t sector_num,

                             int nb_sectors, int *pnum)

{

    /* TODO: Check for too large sector_num (in bdrv_is_allocated or here). */

    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;

    size_t bmap_index = sector_num / s->block_sectors;

    size_t sector_in_block = sector_num % s->block_sectors;

    int n_sectors = s->block_sectors - sector_in_block;

    uint32_t bmap_entry = le32_to_cpu(s->bmap[bmap_index]);

    logout("%p, %" PRId64 ", %d, %p\n", bs, sector_num, nb_sectors, pnum);

    if (n_sectors > nb_sectors) {

        n_sectors = nb_sectors;

    }

    *pnum = n_sectors;

    return bmap_entry != VDI_UNALLOCATED;

}

static void vdi_aio_cancel(BlockDriverAIOCB *blockacb)

{

    /* TODO: This code is untested. How can I get it executed? */

    VdiAIOCB *acb = container_of(blockacb, VdiAIOCB, common);

    logout("\n");

    if (acb->hd_aiocb) {

        bdrv_aio_cancel(acb->hd_aiocb);

    }

    qemu_aio_release(acb);

}

static AIOPool vdi_aio_pool = {

    .aiocb_size = sizeof(VdiAIOCB),

    .cancel = vdi_aio_cancel,

};

static VdiAIOCB *vdi_aio_setup(BlockDriverState *bs, int64_t sector_num,

        QEMUIOVector *qiov, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque, int is_write)

{

    VdiAIOCB *acb;

    logout("%p, %" PRId64 ", %p, %d, %p, %p, %d\n",

           bs, sector_num, qiov, nb_sectors, cb, opaque, is_write);

    acb = qemu_aio_get(&vdi_aio_pool, bs, cb, opaque);

    if (acb) {

        acb->hd_aiocb = NULL;

        acb->sector_num = sector_num;

        acb->qiov = qiov;

        if (qiov->niov > 1) {

            acb->buf = qemu_blockalign(bs, qiov->size);

            acb->orig_buf = acb->buf;

            if (is_write) {

                qemu_iovec_to_buffer(qiov, acb->buf);

            }

        } else {

            acb->buf = (uint8_t *)qiov->iov->iov_base;

        }

        acb->nb_sectors = nb_sectors;

        acb->n_sectors = 0;

        acb->bmap_first = VDI_UNALLOCATED;

        acb->bmap_last = VDI_UNALLOCATED;

        acb->block_buffer = NULL;

        acb->header_modified = 0;

    }

    return acb;

}

static int vdi_schedule_bh(QEMUBHFunc *cb, VdiAIOCB *acb)

{

    logout("\n");

    if (acb->bh) {

        return -EIO;

    }

    acb->bh = qemu_bh_new(cb, acb);

    if (!acb->bh) {

        return -EIO;

    }

    qemu_bh_schedule(acb->bh);

    return 0;

}

static void vdi_aio_read_cb(void *opaque, int ret);

static void vdi_aio_read_bh(void *opaque)

{

    VdiAIOCB *acb = opaque;

    logout("\n");

    qemu_bh_delete(acb->bh);

    acb->bh = NULL;

    vdi_aio_read_cb(opaque, 0);

}

static void vdi_aio_read_cb(void *opaque, int ret)

{

    VdiAIOCB *acb = opaque;

    BlockDriverState *bs = acb->common.bs;

    BDRVVdiState *s = bs->opaque;

    uint32_t bmap_entry;

    uint32_t block_index;

    uint32_t sector_in_block;

    uint32_t n_sectors;

    logout("%u sectors read\n", acb->n_sectors);

    acb->hd_aiocb = NULL;

    if (ret < 0) {

        goto done;

    }

    acb->nb_sectors -= acb->n_sectors;

    if (acb->nb_sectors == 0) {

        /* request completed */

        ret = 0;

        goto done;

    }

    acb->sector_num += acb->n_sectors;

    acb->buf += acb->n_sectors * SECTOR_SIZE;

    block_index = acb->sector_num / s->block_sectors;

    sector_in_block = acb->sector_num % s->block_sectors;

    n_sectors = s->block_sectors - sector_in_block;

    if (n_sectors > acb->nb_sectors) {

        n_sectors = acb->nb_sectors;

    }

    logout("will read %u sectors starting at sector %" PRIu64 "\n",

           n_sectors, acb->sector_num);

    /* prepare next AIO request */

    acb->n_sectors = n_sectors;

    bmap_entry = le32_to_cpu(s->bmap[block_index]);

    if (bmap_entry == VDI_UNALLOCATED) {

        /* Block not allocated, return zeros, no need to wait. */

        memset(acb->buf, 0, n_sectors * SECTOR_SIZE);

        ret = vdi_schedule_bh(vdi_aio_read_bh, acb);

        if (ret < 0) {

            goto done;

        }

    } else {

        uint64_t offset = s->header.offset_data / SECTOR_SIZE +

                          (uint64_t)bmap_entry * s->block_sectors +

                          sector_in_block;

        acb->hd_iov.iov_base = (void *)acb->buf;

        acb->hd_iov.iov_len = n_sectors * SECTOR_SIZE;

        qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

        acb->hd_aiocb = bdrv_aio_readv(bs->file, offset, &acb->hd_qiov,

                                       n_sectors, vdi_aio_read_cb, acb);

        if (acb->hd_aiocb == NULL) {

            ret = -EIO;

            goto done;

        }

    }

    return;

done:

    if (acb->qiov->niov > 1) {

        qemu_iovec_from_buffer(acb->qiov, acb->orig_buf, acb->qiov->size);

        qemu_vfree(acb->orig_buf);

    }

    acb->common.cb(acb->common.opaque, ret);

    qemu_aio_release(acb);

}

static BlockDriverAIOCB *vdi_aio_readv(BlockDriverState *bs,

        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque)

{

    VdiAIOCB *acb;

    logout("\n");

    acb = vdi_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 0);

    if (!acb) {

        return NULL;

    }

    vdi_aio_read_cb(acb, 0);

    return &acb->common;

}

static void vdi_aio_write_cb(void *opaque, int ret)

{

    VdiAIOCB *acb = opaque;

    BlockDriverState *bs = acb->common.bs;

    BDRVVdiState *s = bs->opaque;

    uint32_t bmap_entry;

    uint32_t block_index;

    uint32_t sector_in_block;

    uint32_t n_sectors;

    acb->hd_aiocb = NULL;

    if (ret < 0) {

        goto done;

    }

    acb->nb_sectors -= acb->n_sectors;

    acb->sector_num += acb->n_sectors;

    acb->buf += acb->n_sectors * SECTOR_SIZE;

    if (acb->nb_sectors == 0) {

        logout("finished data write\n");

        acb->n_sectors = 0;

        if (acb->header_modified) {

            VdiHeader *header = acb->block_buffer;

            logout("now writing modified header\n");

            assert(acb->bmap_first != VDI_UNALLOCATED);

            *header = s->header;

            vdi_header_to_le(header);

            acb->header_modified = 0;

            acb->hd_iov.iov_base = acb->block_buffer;

            acb->hd_iov.iov_len = SECTOR_SIZE;

            qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

            acb->hd_aiocb = bdrv_aio_writev(bs->file, 0, &acb->hd_qiov, 1,

                                            vdi_aio_write_cb, acb);

            if (acb->hd_aiocb == NULL) {

                ret = -EIO;

                goto done;

            }

            return;

        } else if (acb->bmap_first != VDI_UNALLOCATED) {

            /* One or more new blocks were allocated. */

            uint64_t offset;

            uint32_t bmap_first;

            uint32_t bmap_last;

            qemu_free(acb->block_buffer);

            acb->block_buffer = NULL;

            bmap_first = acb->bmap_first;

            bmap_last = acb->bmap_last;

            logout("now writing modified block map entry %u...%u\n",

                   bmap_first, bmap_last);

            /* Write modified sectors from block map. */

            bmap_first /= (SECTOR_SIZE / sizeof(uint32_t));

            bmap_last /= (SECTOR_SIZE / sizeof(uint32_t));

            n_sectors = bmap_last - bmap_first + 1;

            offset = s->bmap_sector + bmap_first;

            acb->bmap_first = VDI_UNALLOCATED;

            acb->hd_iov.iov_base = (void *)((uint8_t *)&s->bmap[0] +

                                            bmap_first * SECTOR_SIZE);

            acb->hd_iov.iov_len = n_sectors * SECTOR_SIZE;

            qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

            logout("will write %u block map sectors starting from entry %u\n",

                   n_sectors, bmap_first);

            acb->hd_aiocb = bdrv_aio_writev(bs->file, offset, &acb->hd_qiov,

                                            n_sectors, vdi_aio_write_cb, acb);

            if (acb->hd_aiocb == NULL) {

                ret = -EIO;

                goto done;

            }

            return;

        }

        ret = 0;

        goto done;

    }

    logout("%u sectors written\n", acb->n_sectors);

    block_index = acb->sector_num / s->block_sectors;

    sector_in_block = acb->sector_num % s->block_sectors;

    n_sectors = s->block_sectors - sector_in_block;

    if (n_sectors > acb->nb_sectors) {

        n_sectors = acb->nb_sectors;

    }

    logout("will write %u sectors starting at sector %" PRIu64 "\n",

           n_sectors, acb->sector_num);

    /* prepare next AIO request */

    acb->n_sectors = n_sectors;

    bmap_entry = le32_to_cpu(s->bmap[block_index]);

    if (bmap_entry == VDI_UNALLOCATED) {

        /* Allocate new block and write to it. */

        uint64_t offset;

        uint8_t *block;

        bmap_entry = s->header.blocks_allocated;

        s->bmap[block_index] = cpu_to_le32(bmap_entry);

        s->header.blocks_allocated++;

        offset = s->header.offset_data / SECTOR_SIZE +

                 (uint64_t)bmap_entry * s->block_sectors;

        block = acb->block_buffer;

        if (block == NULL) {

            block = qemu_mallocz(s->block_size);

            acb->block_buffer = block;

            acb->bmap_first = block_index;

            assert(!acb->header_modified);

            acb->header_modified = 1;

        }

        acb->bmap_last = block_index;

        memcpy(block + sector_in_block * SECTOR_SIZE,

               acb->buf, n_sectors * SECTOR_SIZE);

        acb->hd_iov.iov_base = (void *)block;

        acb->hd_iov.iov_len = s->block_size;

        qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

        acb->hd_aiocb = bdrv_aio_writev(bs->file, offset,

                                        &acb->hd_qiov, s->block_sectors,

                                        vdi_aio_write_cb, acb);

        if (acb->hd_aiocb == NULL) {

            ret = -EIO;

            goto done;

        }

    } else {

        uint64_t offset = s->header.offset_data / SECTOR_SIZE +

                          (uint64_t)bmap_entry * s->block_sectors +

                          sector_in_block;

        acb->hd_iov.iov_base = (void *)acb->buf;

        acb->hd_iov.iov_len = n_sectors * SECTOR_SIZE;

        qemu_iovec_init_external(&acb->hd_qiov, &acb->hd_iov, 1);

        acb->hd_aiocb = bdrv_aio_writev(bs->file, offset, &acb->hd_qiov,

                                        n_sectors, vdi_aio_write_cb, acb);

        if (acb->hd_aiocb == NULL) {

            ret = -EIO;

            goto done;

        }

    }

    return;

done:

    if (acb->qiov->niov > 1) {

        qemu_vfree(acb->orig_buf);

    }

    acb->common.cb(acb->common.opaque, ret);

    qemu_aio_release(acb);

}

static BlockDriverAIOCB *vdi_aio_writev(BlockDriverState *bs,

        int64_t sector_num, QEMUIOVector *qiov, int nb_sectors,

        BlockDriverCompletionFunc *cb, void *opaque)

{

    VdiAIOCB *acb;

    logout("\n");

    acb = vdi_aio_setup(bs, sector_num, qiov, nb_sectors, cb, opaque, 1);

    if (!acb) {

        return NULL;

    }

    vdi_aio_write_cb(acb, 0);

    return &acb->common;

}

static int vdi_create(const char *filename, QEMUOptionParameter *options)

{

    int fd;

    int result = 0;

    uint64_t bytes = 0;

    uint32_t blocks;

    size_t block_size = 1 * MiB;

    uint32_t image_type = VDI_TYPE_DYNAMIC;

    VdiHeader header;

    size_t i;

    size_t bmap_size;

    uint32_t *bmap;

    logout("\n");

    /* Read out options. */

    while (options && options->name) {

        if (!strcmp(options->name, BLOCK_OPT_SIZE)) {

            bytes = options->value.n;

#if defined(CONFIG_VDI_BLOCK_SIZE)

        } else if (!strcmp(options->name, BLOCK_OPT_CLUSTER_SIZE)) {

            if (options->value.n) {

                /* TODO: Additional checks (SECTOR_SIZE * 2^n, ...). */

                block_size = options->value.n;

            }

#endif

#if defined(CONFIG_VDI_STATIC_IMAGE)

        } else if (!strcmp(options->name, BLOCK_OPT_STATIC)) {

            if (options->value.n) {

                image_type = VDI_TYPE_STATIC;

            }

#endif

        }

        options++;

    }

    fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY | O_LARGEFILE,

              0644);

    if (fd < 0) {

        return -errno;

    }

    /* We need enough blocks to store the given disk size,

       so always round up. */

    blocks = (bytes + block_size - 1) / block_size;

    bmap_size = blocks * sizeof(uint32_t);

    bmap_size = ((bmap_size + SECTOR_SIZE - 1) & ~(SECTOR_SIZE -1));

    memset(&header, 0, sizeof(header));

    pstrcpy(header.text, sizeof(header.text), VDI_TEXT);

    header.signature = VDI_SIGNATURE;

    header.version = VDI_VERSION_1_1;

    header.header_size = 0x180;

    header.image_type = image_type;

    header.offset_bmap = 0x200;

    header.offset_data = 0x200 + bmap_size;

    header.sector_size = SECTOR_SIZE;

    header.disk_size = bytes;

    header.block_size = block_size;

    header.blocks_in_image = blocks;

    if (image_type == VDI_TYPE_STATIC) {

        header.blocks_allocated = blocks;

    }

    uuid_generate(header.uuid_image);

    uuid_generate(header.uuid_last_snap);

    /* There is no need to set header.uuid_link or header.uuid_parent here. */

#if defined(CONFIG_VDI_DEBUG)

    vdi_header_print(&header);

#endif

    vdi_header_to_le(&header);

    if (write(fd, &header, sizeof(header)) < 0) {

        result = -errno;

    }

    bmap = NULL;

    if (bmap_size > 0) {

        bmap = (uint32_t *)qemu_mallocz(bmap_size);

    }

    for (i = 0; i < blocks; i++) {

        if (image_type == VDI_TYPE_STATIC) {

            bmap[i] = i;

        } else {

            bmap[i] = VDI_UNALLOCATED;

        }