1 files changed, 1064 insertions, 0 deletions
diff --git a/block/vdi.c b/block/vdi.c
new file mode 100644
index 000000000..bdc58d726
--- /dev/null
+++ b/block/vdi.c
@@ -0,0 +1,1064 @@
+/*
+ * Block driver for the Virtual Disk Image (VDI) format
+ *
+ * Copyright (c) 2009, 2012 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 adjacent 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/osdep.h"
+#include "qemu/units.h"
+#include "qapi/error.h"
+#include "qapi/qobject-input-visitor.h"
+#include "qapi/qapi-visit-block-core.h"
+#include "block/block_int.h"
+#include "block/qdict.h"
+#include "sysemu/block-backend.h"
+#include "qemu/module.h"
+#include "qemu/option.h"
+#include "qemu/bswap.h"
+#include "migration/blocker.h"
+#include "qemu/coroutine.h"
+#include "qemu/cutils.h"
+#include "qemu/uuid.h"
+
+/* 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 SECTOR_SIZE 512
+#define DEFAULT_CLUSTER_SIZE 1048576
+/* Note: can't use 1 * MiB, because it's passed to stringify() */
+
+#if defined(CONFIG_VDI_DEBUG)
+#define VDI_DEBUG 1
+#else
+#define VDI_DEBUG 0
+#endif
+
+#define logout(fmt, ...) \
+    do {                                                                \
+        if (VDI_DEBUG) {                                                \
+            fprintf(stderr, "vdi\t%-24s" fmt, __func__, ##__VA_ARGS__); \
+        }                                                               \
+    } while (0)
+
+/* 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"
+
+/* A never-allocated block; semantically arbitrary content. */
+#define VDI_UNALLOCATED 0xffffffffU
+
+/* A discarded (no longer allocated) block; semantically zero-filled. */
+#define VDI_DISCARDED   0xfffffffeU
+
+#define VDI_IS_ALLOCATED(X) ((X) < VDI_DISCARDED)
+
+/* The bmap will take up VDI_BLOCKS_IN_IMAGE_MAX * sizeof(uint32_t) bytes; since
+ * the bmap is read and written in a single operation, its size needs to be
+ * limited to INT_MAX; furthermore, when opening an image, the bmap size is
+ * rounded up to be aligned on BDRV_SECTOR_SIZE.
+ * Therefore this should satisfy the following:
+ * VDI_BLOCKS_IN_IMAGE_MAX * sizeof(uint32_t) + BDRV_SECTOR_SIZE == INT_MAX + 1
+ * (INT_MAX + 1 is the first value not representable as an int)
+ * This guarantees that any value below or equal to the constant will, when
+ * multiplied by sizeof(uint32_t) and rounded up to a BDRV_SECTOR_SIZE boundary,
+ * still be below or equal to INT_MAX. */
+#define VDI_BLOCKS_IN_IMAGE_MAX \
+    ((unsigned)((INT_MAX + 1u - BDRV_SECTOR_SIZE) / sizeof(uint32_t)))
+#define VDI_DISK_SIZE_MAX        ((uint64_t)VDI_BLOCKS_IN_IMAGE_MAX * \
+                                  (uint64_t)DEFAULT_CLUSTER_SIZE)
+
+static QemuOptsList vdi_create_opts;
+
+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;
+    QemuUUID uuid_image;
+    QemuUUID uuid_last_snap;
+    QemuUUID uuid_link;
+    QemuUUID uuid_parent;
+    uint64_t unused2[7];
+} QEMU_PACKED VdiHeader;
+
+QEMU_BUILD_BUG_ON(sizeof(VdiHeader) != 512);
+
+typedef struct {
+    /* The block map entries are little endian (even in memory). */
+    uint32_t *bmap;
+    /* Size of block (bytes). */
+    uint32_t block_size;
+    /* First sector of block map. */
+    uint32_t bmap_sector;
+    /* VDI header (converted to host endianness). */
+    VdiHeader header;
+
+    CoRwlock bmap_lock;
+
+    Error *migration_blocker;
+} BDRVVdiState;
+
+static void vdi_header_to_cpu(VdiHeader *header)
+{
+    header->signature = le32_to_cpu(header->signature);
+    header->version = le32_to_cpu(header->version);
+    header->header_size = le32_to_cpu(header->header_size);
+    header->image_type = le32_to_cpu(header->image_type);
+    header->image_flags = le32_to_cpu(header->image_flags);
+    header->offset_bmap = le32_to_cpu(header->offset_bmap);
+    header->offset_data = le32_to_cpu(header->offset_data);
+    header->cylinders = le32_to_cpu(header->cylinders);
+    header->heads = le32_to_cpu(header->heads);
+    header->sectors = le32_to_cpu(header->sectors);
+    header->sector_size = le32_to_cpu(header->sector_size);
+    header->disk_size = le64_to_cpu(header->disk_size);
+    header->block_size = le32_to_cpu(header->block_size);
+    header->block_extra = le32_to_cpu(header->block_extra);
+    header->blocks_in_image = le32_to_cpu(header->blocks_in_image);
+    header->blocks_allocated = le32_to_cpu(header->blocks_allocated);
+    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
+    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
+    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
+    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
+}
+
+static void vdi_header_to_le(VdiHeader *header)
+{
+    header->signature = cpu_to_le32(header->signature);
+    header->version = cpu_to_le32(header->version);
+    header->header_size = cpu_to_le32(header->header_size);
+    header->image_type = cpu_to_le32(header->image_type);
+    header->image_flags = cpu_to_le32(header->image_flags);
+    header->offset_bmap = cpu_to_le32(header->offset_bmap);
+    header->offset_data = cpu_to_le32(header->offset_data);
+    header->cylinders = cpu_to_le32(header->cylinders);
+    header->heads = cpu_to_le32(header->heads);
+    header->sectors = cpu_to_le32(header->sectors);
+    header->sector_size = cpu_to_le32(header->sector_size);
+    header->disk_size = cpu_to_le64(header->disk_size);
+    header->block_size = cpu_to_le32(header->block_size);
+    header->block_extra = cpu_to_le32(header->block_extra);
+    header->blocks_in_image = cpu_to_le32(header->blocks_in_image);
+    header->blocks_allocated = cpu_to_le32(header->blocks_allocated);
+    header->uuid_image = qemu_uuid_bswap(header->uuid_image);
+    header->uuid_last_snap = qemu_uuid_bswap(header->uuid_last_snap);
+    header->uuid_link = qemu_uuid_bswap(header->uuid_link);
+    header->uuid_parent = qemu_uuid_bswap(header->uuid_parent);
+}
+
+static void vdi_header_print(VdiHeader *header)
+{
+    char uuidstr[37];
+    QemuUUID uuid;
+    logout("text        %s", header->text);
+    logout("signature   0x%08x\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 = header->uuid_image;
+    qemu_uuid_unparse(&uuid, uuidstr);
+    logout("uuid image  %s\n", uuidstr);
+    uuid = header->uuid_last_snap;
+    qemu_uuid_unparse(&uuid, uuidstr);
+    logout("uuid snap   %s\n", uuidstr);
+    uuid = header->uuid_link;
+    qemu_uuid_unparse(&uuid, uuidstr);
+    logout("uuid link   %s\n", uuidstr);
+    uuid = header->uuid_parent;
+    qemu_uuid_unparse(&uuid, uuidstr);
+    logout("uuid parent %s\n", uuidstr);
+}
+
+static int coroutine_fn vdi_co_check(BlockDriverState *bs, BdrvCheckResult *res,
+                                     BdrvCheckMode fix)
+{
+    /* TODO: additional checks possible. */
+    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
+    uint32_t blocks_allocated = 0;
+    uint32_t block;
+    uint32_t *bmap;
+    logout("\n");
+
+    if (fix) {
+        return -ENOTSUP;
+    }
+
+    bmap = g_try_new(uint32_t, s->header.blocks_in_image);
+    if (s->header.blocks_in_image && bmap == NULL) {
+        res->check_errors++;
+        return -ENOMEM;
+    }
+
+    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 (VDI_IS_ALLOCATED(bmap_entry)) {
+            if (bmap_entry < s->header.blocks_in_image) {
+                blocks_allocated++;
+                if (!VDI_IS_ALLOCATED(bmap[bmap_entry])) {
+                    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++;
+    }
+
+    g_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 ret = 0;
+
+    logout("\n");
+
+    if (buf_size < sizeof(*header)) {
+        /* Header too small, no VDI. */
+    } else if (le32_to_cpu(header->signature) == VDI_SIGNATURE) {
+        ret = 100;
+    }
+
+    if (ret == 0) {
+        logout("no vdi image\n");
+    } else {
+        logout("%s", header->text);
+    }
+
+    return ret;
+}
+
+static int vdi_open(BlockDriverState *bs, QDict *options, int flags,
+                    Error **errp)
+{
+    BDRVVdiState *s = bs->opaque;
+    VdiHeader header;
+    size_t bmap_size;
+    int ret;
+    QemuUUID uuid_link, uuid_parent;
+
+    bs->file = bdrv_open_child(NULL, options, "file", bs, &child_of_bds,
+                               BDRV_CHILD_IMAGE, false, errp);
+    if (!bs->file) {
+        return -EINVAL;
+    }
+
+    logout("\n");
+
+    ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
+    if (ret < 0) {
+        goto fail;
+    }
+
+    vdi_header_to_cpu(&header);
+    if (VDI_DEBUG) {
+        vdi_header_print(&header);
+    }
+
+    if (header.disk_size > VDI_DISK_SIZE_MAX) {
+        error_setg(errp, "Unsupported VDI image size (size is 0x%" PRIx64
+                          ", max supported is 0x%" PRIx64 ")",
+                          header.disk_size, VDI_DISK_SIZE_MAX);
+        ret = -ENOTSUP;
+        goto fail;
+    }
+
+    uuid_link = header.uuid_link;
+    uuid_parent = header.uuid_parent;
+
+    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 = ROUND_UP(header.disk_size, SECTOR_SIZE);
+    }
+
+    if (header.signature != VDI_SIGNATURE) {
+        error_setg(errp, "Image not in VDI format (bad signature %08" PRIx32
+                   ")", header.signature);
+        ret = -EINVAL;
+        goto fail;
+    } else if (header.version != VDI_VERSION_1_1) {
+        error_setg(errp, "unsupported VDI image (version %" PRIu32 ".%" PRIu32
+                   ")", header.version >> 16, header.version & 0xffff);
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (header.offset_bmap % SECTOR_SIZE != 0) {
+        /* We only support block maps which start on a sector boundary. */
+        error_setg(errp, "unsupported VDI image (unaligned block map offset "
+                   "0x%" PRIx32 ")", header.offset_bmap);
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (header.offset_data % SECTOR_SIZE != 0) {
+        /* We only support data blocks which start on a sector boundary. */
+        error_setg(errp, "unsupported VDI image (unaligned data offset 0x%"
+                   PRIx32 ")", header.offset_data);
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (header.sector_size != SECTOR_SIZE) {
+        error_setg(errp, "unsupported VDI image (sector size %" PRIu32
+                   " is not %u)", header.sector_size, SECTOR_SIZE);
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (header.block_size != DEFAULT_CLUSTER_SIZE) {
+        error_setg(errp, "unsupported VDI image (block size %" PRIu32
+                         " is not %" PRIu32 ")",
+                   header.block_size, DEFAULT_CLUSTER_SIZE);
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (header.disk_size >
+               (uint64_t)header.blocks_in_image * header.block_size) {
+        error_setg(errp, "unsupported VDI image (disk size %" PRIu64 ", "
+                   "image bitmap has room for %" PRIu64 ")",
+                   header.disk_size,
+                   (uint64_t)header.blocks_in_image * header.block_size);
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (!qemu_uuid_is_null(&uuid_link)) {
+        error_setg(errp, "unsupported VDI image (non-NULL link UUID)");
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (!qemu_uuid_is_null(&uuid_parent)) {
+        error_setg(errp, "unsupported VDI image (non-NULL parent UUID)");
+        ret = -ENOTSUP;
+        goto fail;
+    } else if (header.blocks_in_image > VDI_BLOCKS_IN_IMAGE_MAX) {
+        error_setg(errp, "unsupported VDI image "
+                         "(too many blocks %u, max is %u)",
+                          header.blocks_in_image, VDI_BLOCKS_IN_IMAGE_MAX);
+        ret = -ENOTSUP;
+        goto fail;
+    }
+
+    bs->total_sectors = header.disk_size / SECTOR_SIZE;
+
+    s->block_size = header.block_size;
+    s->bmap_sector = header.offset_bmap / SECTOR_SIZE;
+    s->header = header;
+
+    bmap_size = header.blocks_in_image * sizeof(uint32_t);
+    bmap_size = DIV_ROUND_UP(bmap_size, SECTOR_SIZE);
+    s->bmap = qemu_try_blockalign(bs->file->bs, bmap_size * SECTOR_SIZE);
+    if (s->bmap == NULL) {
+        ret = -ENOMEM;
+        goto fail;
+    }
+
+    ret = bdrv_pread(bs->file, header.offset_bmap, s->bmap,
+                     bmap_size * SECTOR_SIZE);
+    if (ret < 0) {
+        goto fail_free_bmap;
+    }
+
+    /* Disable migration when vdi images are used */
+    error_setg(&s->migration_blocker, "The vdi format used by node '%s' "
+               "does not support live migration",
+               bdrv_get_device_or_node_name(bs));
+    ret = migrate_add_blocker(s->migration_blocker, errp);
+    if (ret < 0) {
+        error_free(s->migration_blocker);
+        goto fail_free_bmap;
+    }
+
+    qemu_co_rwlock_init(&s->bmap_lock);
+
+    return 0;
+
+ fail_free_bmap:
+    qemu_vfree(s->bmap);
+
+ fail:
+    return ret;
+}
+
+static int vdi_reopen_prepare(BDRVReopenState *state,
+                              BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
+static int coroutine_fn vdi_co_block_status(BlockDriverState *bs,
+                                            bool want_zero,
+                                            int64_t offset, int64_t bytes,
+                                            int64_t *pnum, int64_t *map,
+                                            BlockDriverState **file)
+{
+    BDRVVdiState *s = (BDRVVdiState *)bs->opaque;
+    size_t bmap_index = offset / s->block_size;
+    size_t index_in_block = offset % s->block_size;
+    uint32_t bmap_entry = le32_to_cpu(s->bmap[bmap_index]);
+    int result;
+
+    logout("%p, %" PRId64 ", %" PRId64 ", %p\n", bs, offset, bytes, pnum);
+    *pnum = MIN(s->block_size - index_in_block, bytes);
+    result = VDI_IS_ALLOCATED(bmap_entry);
+    if (!result) {
+        return BDRV_BLOCK_ZERO;
+    }
+
+    *map = s->header.offset_data + (uint64_t)bmap_entry * s->block_size +
+        index_in_block;
+    *file = bs->file->bs;
+    return BDRV_BLOCK_DATA | BDRV_BLOCK_OFFSET_VALID |
+        (s->header.image_type == VDI_TYPE_STATIC ? BDRV_BLOCK_RECURSE : 0);
+}
+
+static int coroutine_fn
+vdi_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
+              QEMUIOVector *qiov, BdrvRequestFlags flags)
+{
+    BDRVVdiState *s = bs->opaque;
+    QEMUIOVector local_qiov;
+    uint32_t bmap_entry;
+    uint32_t block_index;
+    uint32_t offset_in_block;
+    uint32_t n_bytes;
+    uint64_t bytes_done = 0;
+    int ret = 0;
+
+    logout("\n");
+
+    qemu_iovec_init(&local_qiov, qiov->niov);
+
+    while (ret >= 0 && bytes > 0) {
+        block_index = offset / s->block_size;
+        offset_in_block = offset % s->block_size;
+        n_bytes = MIN(bytes, s->block_size - offset_in_block);
+
+        logout("will read %u bytes starting at offset %" PRIu64 "\n",
+               n_bytes, offset);
+
+        /* prepare next AIO request */
+        qemu_co_rwlock_rdlock(&s->bmap_lock);
+        bmap_entry = le32_to_cpu(s->bmap[block_index]);
+        qemu_co_rwlock_unlock(&s->bmap_lock);
+        if (!VDI_IS_ALLOCATED(bmap_entry)) {
+            /* Block not allocated, return zeros, no need to wait. */
+            qemu_iovec_memset(qiov, bytes_done, 0, n_bytes);
+            ret = 0;
+        } else {
+            uint64_t data_offset = s->header.offset_data +
+                                   (uint64_t)bmap_entry * s->block_size +
+                                   offset_in_block;
+
+            qemu_iovec_reset(&local_qiov);
+            qemu_iovec_concat(&local_qiov, qiov, bytes_done, n_bytes);
+
+            ret = bdrv_co_preadv(bs->file, data_offset, n_bytes,
+                                 &local_qiov, 0);
+        }
+        logout("%u bytes read\n", n_bytes);
+
+        bytes -= n_bytes;
+        offset += n_bytes;
+        bytes_done += n_bytes;
+    }
+
+    qemu_iovec_destroy(&local_qiov);
+
+    return ret;
+}
+
+static int coroutine_fn
+vdi_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
+               QEMUIOVector *qiov, BdrvRequestFlags flags)
+{
+    BDRVVdiState *s = bs->opaque;
+    QEMUIOVector local_qiov;
+    uint32_t bmap_entry;
+    uint32_t block_index;
+    uint32_t offset_in_block;
+    uint32_t n_bytes;
+    uint64_t data_offset;
+    uint32_t bmap_first = VDI_UNALLOCATED;
+    uint32_t bmap_last = VDI_UNALLOCATED;
+    uint8_t *block = NULL;
+    uint64_t bytes_done = 0;
+    int ret = 0;
+
+    logout("\n");
+
+    qemu_iovec_init(&local_qiov, qiov->niov);
+
+    while (ret >= 0 && bytes > 0) {
+        block_index = offset / s->block_size;
+        offset_in_block = offset % s->block_size;
+        n_bytes = MIN(bytes, s->block_size - offset_in_block);
+
+        logout("will write %u bytes starting at offset %" PRIu64 "\n",
+               n_bytes, offset);
+
+        /* prepare next AIO request */
+        qemu_co_rwlock_rdlock(&s->bmap_lock);
+        bmap_entry = le32_to_cpu(s->bmap[block_index]);
+        if (!VDI_IS_ALLOCATED(bmap_entry)) {
+            /* Allocate new block and write to it. */
+            uint64_t data_offset;
+            qemu_co_rwlock_upgrade(&s->bmap_lock);
+            bmap_entry = le32_to_cpu(s->bmap[block_index]);
+            if (VDI_IS_ALLOCATED(bmap_entry)) {
+                /* A concurrent allocation did the work for us.  */
+                qemu_co_rwlock_downgrade(&s->bmap_lock);
+                goto nonallocating_write;
+            }
+
+            bmap_entry = s->header.blocks_allocated;
+            s->bmap[block_index] = cpu_to_le32(bmap_entry);
+            s->header.blocks_allocated++;
+            data_offset = s->header.offset_data +
+                          (uint64_t)bmap_entry * s->block_size;
+            if (block == NULL) {
+                block = g_malloc(s->block_size);
+                bmap_first = block_index;
+            }
+            bmap_last = block_index;
+            /* Copy data to be written to new block and zero unused parts. */
+            memset(block, 0, offset_in_block);
+            qemu_iovec_to_buf(qiov, bytes_done, block + offset_in_block,
+                              n_bytes);
+            memset(block + offset_in_block + n_bytes, 0,
+                   s->block_size - n_bytes - offset_in_block);
+
+            /* Write the new block under CoRwLock write-side protection,
+             * so this full-cluster write does not overlap a partial write
+             * of the same cluster, issued from the "else" branch.
+             */
+            ret = bdrv_pwrite(bs->file, data_offset, block, s->block_size);
+            qemu_co_rwlock_unlock(&s->bmap_lock);
+        } else {
+nonallocating_write:
+            data_offset = s->header.offset_data +
+                           (uint64_t)bmap_entry * s->block_size +
+                           offset_in_block;
+            qemu_co_rwlock_unlock(&s->bmap_lock);
+
+            qemu_iovec_reset(&local_qiov);
+            qemu_iovec_concat(&local_qiov, qiov, bytes_done, n_bytes);
+
+            ret = bdrv_co_pwritev(bs->file, data_offset, n_bytes,
+                                  &local_qiov, 0);
+        }
+
+        bytes -= n_bytes;
+        offset += n_bytes;
+        bytes_done += n_bytes;
+
+        logout("%u bytes written\n", n_bytes);
+    }
+
+    qemu_iovec_destroy(&local_qiov);
+
+    logout("finished data write\n");
+    if (ret < 0) {
+        g_free(block);
+        return ret;
+    }
+
+    if (block) {
+        /* One or more new blocks were allocated. */
+        VdiHeader *header;
+        uint8_t *base;
+        uint64_t offset;
+        uint32_t n_sectors;
+
+        g_free(block);
+        header = g_malloc(sizeof(*header));
+
+        logout("now writing modified header\n");
+        assert(VDI_IS_ALLOCATED(bmap_first));
+        *header = s->header;
+        vdi_header_to_le(header);
+        ret = bdrv_pwrite(bs->file, 0, header, sizeof(*header));
+        g_free(header);
+
+        if (ret < 0) {
+            return ret;
+        }
+
+        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;
+        base = ((uint8_t *)&s->bmap[0]) + bmap_first * SECTOR_SIZE;
+        logout("will write %u block map sectors starting from entry %u\n",
+               n_sectors, bmap_first);
+        ret = bdrv_pwrite(bs->file, offset * SECTOR_SIZE, base,
+                          n_sectors * SECTOR_SIZE);
+    }
+
+    return ret < 0 ? ret : 0;
+}
+
+static int coroutine_fn vdi_co_do_create(BlockdevCreateOptions *create_options,
+                                         size_t block_size, Error **errp)
+{
+    BlockdevCreateOptionsVdi *vdi_opts;
+    int ret = 0;
+    uint64_t bytes = 0;
+    uint32_t blocks;
+    uint32_t image_type;
+    VdiHeader header;
+    size_t i;
+    size_t bmap_size;
+    int64_t offset = 0;
+    BlockDriverState *bs_file = NULL;
+    BlockBackend *blk = NULL;
+    uint32_t *bmap = NULL;
+    QemuUUID uuid;
+
+    assert(create_options->driver == BLOCKDEV_DRIVER_VDI);
+    vdi_opts = &create_options->u.vdi;
+
+    logout("\n");
+
+    /* Validate options and set default values */
+    bytes = vdi_opts->size;
+
+    if (!vdi_opts->has_preallocation) {
+        vdi_opts->preallocation = PREALLOC_MODE_OFF;
+    }
+    switch (vdi_opts->preallocation) {
+    case PREALLOC_MODE_OFF:
+        image_type = VDI_TYPE_DYNAMIC;
+        break;
+    case PREALLOC_MODE_METADATA:
+        image_type = VDI_TYPE_STATIC;
+        break;
+    default:
+        error_setg(errp, "Preallocation mode not supported for vdi");
+        return -EINVAL;
+    }
+
+#ifndef CONFIG_VDI_STATIC_IMAGE
+    if (image_type == VDI_TYPE_STATIC) {
+        ret = -ENOTSUP;
+        error_setg(errp, "Statically allocated images cannot be created in "
+                   "this build");
+        goto exit;
+    }
+#endif
+#ifndef CONFIG_VDI_BLOCK_SIZE
+    if (block_size != DEFAULT_CLUSTER_SIZE) {
+        ret = -ENOTSUP;
+        error_setg(errp,
+                   "A non-default cluster size is not supported in this build");
+        goto exit;
+    }
+#endif
+
+    if (bytes > VDI_DISK_SIZE_MAX) {
+        ret = -ENOTSUP;
+        error_setg(errp, "Unsupported VDI image size (size is 0x%" PRIx64
+                          ", max supported is 0x%" PRIx64 ")",
+                          bytes, VDI_DISK_SIZE_MAX);
+        goto exit;
+    }
+
+    /* Create BlockBackend to write to the image */
+    bs_file = bdrv_open_blockdev_ref(vdi_opts->file, errp);
+    if (!bs_file) {
+        ret = -EIO;
+        goto exit;
+    }
+
+    blk = blk_new_with_bs(bs_file, BLK_PERM_WRITE | BLK_PERM_RESIZE,
+                          BLK_PERM_ALL, errp);
+    if (!blk) {
+        ret = -EPERM;
+        goto exit;
+    }
+
+    blk_set_allow_write_beyond_eof(blk, true);
+
+    /* We need enough blocks to store the given disk size,
+       so always round up. */
+    blocks = DIV_ROUND_UP(bytes, block_size);
+
+    bmap_size = blocks * sizeof(uint32_t);
+    bmap_size = ROUND_UP(bmap_size, SECTOR_SIZE);
+
+    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;
+    }
+    qemu_uuid_generate(&uuid);
+    header.uuid_image = uuid;
+    qemu_uuid_generate(&uuid);
+    header.uuid_last_snap = uuid;
+    /* There is no need to set header.uuid_link or header.uuid_parent here. */
+    if (VDI_DEBUG) {
+        vdi_header_print(&header);
+    }
+    vdi_header_to_le(&header);
+    ret = blk_pwrite(blk, offset, &header, sizeof(header), 0);
+    if (ret < 0) {
+        error_setg(errp, "Error writing header");
+        goto exit;
+    }
+    offset += sizeof(header);
+
+    if (bmap_size > 0) {
+        bmap = g_try_malloc0(bmap_size);
+        if (bmap == NULL) {
+            ret = -ENOMEM;
+            error_setg(errp, "Could not allocate bmap");
+            goto exit;
+        }
+        for (i = 0; i < blocks; i++) {
+            if (image_type == VDI_TYPE_STATIC) {
+                bmap[i] = i;
+            } else {
+                bmap[i] = VDI_UNALLOCATED;
+            }
+        }
+        ret = blk_pwrite(blk, offset, bmap, bmap_size, 0);
+        if (ret < 0) {
+            error_setg(errp, "Error writing bmap");
+            goto exit;
+        }
+        offset += bmap_size;
+    }
+
+    if (image_type == VDI_TYPE_STATIC) {
+        ret = blk_truncate(blk, offset + blocks * block_size, false,
+                           PREALLOC_MODE_OFF, 0, errp);
+        if (ret < 0) {
+            error_prepend(errp, "Failed to statically allocate file");
+            goto exit;
+        }
+    }
+
+    ret = 0;
+exit:
+    blk_unref(blk);
+    bdrv_unref(bs_file);
+    g_free(bmap);
+    return ret;
+}
+
+static int coroutine_fn vdi_co_create(BlockdevCreateOptions *create_options,
+                                      Error **errp)
+{
+    return vdi_co_do_create(create_options, DEFAULT_CLUSTER_SIZE, errp);
+}
+
+static int coroutine_fn vdi_co_create_opts(BlockDriver *drv,
+                                           const char *filename,
+                                           QemuOpts *opts,
+                                           Error **errp)
+{
+    QDict *qdict = NULL;
+    BlockdevCreateOptions *create_options = NULL;
+    BlockDriverState *bs_file = NULL;
+    uint64_t block_size = DEFAULT_CLUSTER_SIZE;
+    bool is_static = false;
+    Visitor *v;
+    int ret;
+
+    /* Parse options and convert legacy syntax.
+     *
+     * Since CONFIG_VDI_BLOCK_SIZE is disabled by default,
+     * cluster-size is not part of the QAPI schema; therefore we have
+     * to parse it before creating the QAPI object. */
+#if defined(CONFIG_VDI_BLOCK_SIZE)
+    block_size = qemu_opt_get_size_del(opts,
+                                       BLOCK_OPT_CLUSTER_SIZE,
+                                       DEFAULT_CLUSTER_SIZE);
+    if (block_size < BDRV_SECTOR_SIZE || block_size > UINT32_MAX ||
+        !is_power_of_2(block_size))
+    {
+        error_setg(errp, "Invalid cluster size");
+        ret = -EINVAL;
+        goto done;
+    }
+#endif
+    if (qemu_opt_get_bool_del(opts, BLOCK_OPT_STATIC, false)) {
+        is_static = true;
+    }
+
+    qdict = qemu_opts_to_qdict_filtered(opts, NULL, &vdi_create_opts, true);
+
+    /* Create and open the file (protocol layer) */
+    ret = bdrv_create_file(filename, opts, errp);
+    if (ret < 0) {
+        goto done;
+    }
+
+    bs_file = bdrv_open(filename, NULL, NULL,
+                        BDRV_O_RDWR | BDRV_O_RESIZE | BDRV_O_PROTOCOL, errp);
+    if (!bs_file) {
+        ret = -EIO;
+        goto done;
+    }
+
+    qdict_put_str(qdict, "driver", "vdi");
+    qdict_put_str(qdict, "file", bs_file->node_name);
+    if (is_static) {
+        qdict_put_str(qdict, "preallocation", "metadata");
+    }
+
+    /* Get the QAPI object */
+    v = qobject_input_visitor_new_flat_confused(qdict, errp);
+    if (!v) {
+        ret = -EINVAL;
+        goto done;
+    }
+    visit_type_BlockdevCreateOptions(v, NULL, &create_options, errp);
+    visit_free(v);
+    if (!create_options) {
+        ret = -EINVAL;
+        goto done;
+    }
+
+    /* Silently round up size */
+    assert(create_options->driver == BLOCKDEV_DRIVER_VDI);
+    create_options->u.vdi.size = ROUND_UP(create_options->u.vdi.size,
+                                          BDRV_SECTOR_SIZE);
+
+    /* Create the vdi image (format layer) */
+    ret = vdi_co_do_create(create_options, block_size, errp);
+done:
+    qobject_unref(qdict);
+    qapi_free_BlockdevCreateOptions(create_options);
+    bdrv_unref(bs_file);
+    return ret;
+}
+
+static void vdi_close(BlockDriverState *bs)
+{
+    BDRVVdiState *s = bs->opaque;
+
+    qemu_vfree(s->bmap);
+
+    migrate_del_blocker(s->migration_blocker);
+    error_free(s->migration_blocker);
+}
+
+static int vdi_has_zero_init(BlockDriverState *bs)
+{
+    BDRVVdiState *s = bs->opaque;
+
+    if (s->header.image_type == VDI_TYPE_STATIC) {
+        return bdrv_has_zero_init(bs->file->bs);
+    } else {
+        return 1;
+    }
+}
+
+static QemuOptsList vdi_create_opts = {
+    .name = "vdi-create-opts",
+    .head = QTAILQ_HEAD_INITIALIZER(vdi_create_opts.head),
+    .desc = {
+        {
+            .name = BLOCK_OPT_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "Virtual disk size"
+        },
+#if defined(CONFIG_VDI_BLOCK_SIZE)
+        {
+            .name = BLOCK_OPT_CLUSTER_SIZE,
+            .type = QEMU_OPT_SIZE,
+            .help = "VDI cluster (block) size",
+            .def_value_str = stringify(DEFAULT_CLUSTER_SIZE)
+        },
+#endif
+#if defined(CONFIG_VDI_STATIC_IMAGE)
+        {
+            .name = BLOCK_OPT_STATIC,
+            .type = QEMU_OPT_BOOL,
+            .help = "VDI static (pre-allocated) image",
+            .def_value_str = "off"
+        },
+#endif
+        /* TODO: An additional option to set UUID values might be useful. */
+        { /* end of list */ }
+    }
+};
+
+static BlockDriver bdrv_vdi = {
+    .format_name = "vdi",
+    .instance_size = sizeof(BDRVVdiState),
+    .bdrv_probe = vdi_probe,
+    .bdrv_open = vdi_open,
+    .bdrv_close = vdi_close,
+    .bdrv_reopen_prepare = vdi_reopen_prepare,
+    .bdrv_child_perm          = bdrv_default_perms,
+    .bdrv_co_create      = vdi_co_create,
+    .bdrv_co_create_opts = vdi_co_create_opts,
+    .bdrv_has_zero_init  = vdi_has_zero_init,
+    .bdrv_co_block_status = vdi_co_block_status,
+    .bdrv_make_empty = vdi_make_empty,
+
+    .bdrv_co_preadv     = vdi_co_preadv,
+#if defined(CONFIG_VDI_WRITE)
+    .bdrv_co_pwritev    = vdi_co_pwritev,
+#endif
+
+    .bdrv_get_info = vdi_get_info,
+
+    .is_format = true,
+    .create_opts = &vdi_create_opts,
+    .bdrv_co_check = vdi_co_check,
+};
+
+static void bdrv_vdi_init(void)
+{
+    logout("\n");
+    bdrv_register(&bdrv_vdi);
+}
+
+block_init(bdrv_vdi_init);