diff --git a/block/vhdx.c b/block/vhdx.c
new file mode 100644
index 0000000..96f8fc7
--- /dev/null
+++ b/block/vhdx.c
@@ -0,0 +1,814 @@
+/*
+ * Block driver for Hyper-V VHDX Images
+ *
+ * Copyright (c) 2013 Red Hat, Inc.,
+ *
+ * Authors:
+ *  Jeff Cody <jcody@redhat.com>
+ *
+ *  This is based on the "VHDX Format Specification v0.95", published 4/12/2012
+ *  by Microsoft:
+ *      https://www.microsoft.com/en-us/download/details.aspx?id=29681
+ *
+ * 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)
+ * any later version.
+ *
+ */
+
+#include "qemu-common.h"
+#include "block/block_int.h"
+#include "qemu/module.h"
+#include "migration/migration.h"
+#if defined(CONFIG_UUID)
+#include <uuid/uuid.h>
+#endif
+#include "qemu/crc32c.h"
+#include "block/vhdx.h"
+
+#define vhdx_nop(x) do { (void)(x); } while (0)
+
+/* Help macros to copy data from file buffers to header
+ * structures, with proper endianness.  These help avoid
+ * using packed structs */
+
+/* Do not use directly, see macros below */
+#define _hdr_copy(item, buf, size, offset, to_cpu) do { \
+    memcpy((item), (buf)+(offset), (size));        \
+    to_cpu((item));                                \
+    (offset) += (size); } while (0)
+
+/* for all of these, buf should be a uint8_t buffer */
+
+/* copy 16-bit header field */
+#define hdr_copy16(item, buf, offset) do { \
+    _hdr_copy((item), (buf), 2, (offset), (le16_to_cpus)); } while (0)
+
+/* copy 32-bit header field */
+#define hdr_copy32(item, buf, offset) do { \
+    _hdr_copy((item), (buf), 4, (offset), (le32_to_cpus)); } while (0)
+
+/* copy 64-bit header field */
+#define hdr_copy64(item, buf, offset) do { \
+    _hdr_copy((item), (buf), 8, (offset), (le64_to_cpus)); } while (0)
+
+/* copy variable-length header field, no endian swapping */
+#define hdr_copy(item, buf, size, offset) do { \
+    _hdr_copy((item), (buf), (size), (offset), vhdx_nop); } while (0)
+
+/* copies a defined msguid field, with correct endianness
+ * a msguid entry has 3 data types with endianness sensitivity,
+ * followed by a byte array */
+#define hdr_copy_guid(item, buf, offset) do {        \
+        hdr_copy32(&(item).data1, (buf), (offset));  \
+        hdr_copy16(&(item).data2, (buf), (offset));  \
+        hdr_copy16(&(item).data3, (buf), (offset));  \
+        hdr_copy(&(item).data4, (buf), sizeof((item).data4), (offset)); \
+        } while (0)
+
+
+/* Several metadata and region table data entries are identified by
+ * guids in  a MS-specific GUID format. */
+
+
+/* ------- Known Region Table GUIDs ---------------------- */
+static const ms_guid bat_guid =      { .data1 = 0x2dc27766,
+                                       .data2 = 0xf623,
+                                       .data3 = 0x4200,
+                                       .data4 = { 0x9d, 0x64, 0x11, 0x5e,
+                                                  0x9b, 0xfd, 0x4a, 0x08} };
+
+static const ms_guid metadata_guid = { .data1 = 0x8b7ca206,
+                                       .data2 = 0x4790,
+                                       .data3 = 0x4b9a,
+                                       .data4 = { 0xb8, 0xfe, 0x57, 0x5f,
+                                                  0x05, 0x0f, 0x88, 0x6e} };
+
+
+
+/* ------- Known Metadata Entry GUIDs ---------------------- */
+static const ms_guid file_param_guid =   { .data1 = 0xcaa16737,
+                                           .data2 = 0xfa36,
+                                           .data3 = 0x4d43,
+                                           .data4 = { 0xb3, 0xb6, 0x33, 0xf0,
+                                                      0xaa, 0x44, 0xe7, 0x6b} };
+
+static const ms_guid virtual_size_guid = { .data1 = 0x2FA54224,
+                                           .data2 = 0xcd1b,
+                                           .data3 = 0x4876,
+                                           .data4 = { 0xb2, 0x11, 0x5d, 0xbe,
+                                                      0xd8, 0x3b, 0xf4, 0xb8} };
+
+static const ms_guid page83_guid =       { .data1 = 0xbeca12ab,
+                                           .data2 = 0xb2e6,
+                                           .data3 = 0x4523,
+                                           .data4 = { 0x93, 0xef, 0xc3, 0x09,
+                                                      0xe0, 0x00, 0xc7, 0x46} };
+
+static const ms_guid logical_sector_guid = {.data1 = 0x8141bf1d,
+                                            .data2 = 0xa96f,
+                                            .data3 = 0x4709,
+                                           .data4 = { 0xba, 0x47, 0xf2, 0x33,
+                                                      0xa8, 0xfa, 0xab, 0x5f} };
+
+static const ms_guid phys_sector_guid =  { .data1 = 0xcda348c7,
+                                           .data2 = 0x445d,
+                                           .data3 = 0x4471,
+                                           .data4 = { 0x9c, 0xc9, 0xe9, 0x88,
+                                                      0x52, 0x51, 0xc5, 0x56} };
+
+static const ms_guid parent_locator_guid = {.data1 = 0xa8d35f2d,
+                                            .data2 = 0xb30b,
+                                            .data3 = 0x454d,
+                                           .data4 = { 0xab, 0xf7, 0xd3, 0xd8,
+                                                      0x48, 0x34, 0xab, 0x0c} };
+
+
+
+#define META_FILE_PARAMETER_PRESENT      0x01
+#define META_VIRTUAL_DISK_SIZE_PRESENT   0x02
+#define META_PAGE_83_PRESENT             0x04
+#define META_LOGICAL_SECTOR_SIZE_PRESENT 0x08
+#define META_PHYS_SECTOR_SIZE_PRESENT    0x10
+#define META_PARENT_LOCATOR_PRESENT      0x20
+
+#define META_ALL_PRESENT    \
+    (META_FILE_PARAMETER_PRESENT | META_VIRTUAL_DISK_SIZE_PRESENT | \
+     META_PAGE_83_PRESENT | META_LOGICAL_SECTOR_SIZE_PRESENT | \
+     META_PHYS_SECTOR_SIZE_PRESENT)
+
+typedef struct vhdx_metadata_entries {
+    vhdx_metadata_table_entry file_parameters_entry;
+    vhdx_metadata_table_entry virtual_disk_size_entry;
+    vhdx_metadata_table_entry page83_data_entry;
+    vhdx_metadata_table_entry logical_sector_size_entry;
+    vhdx_metadata_table_entry phys_sector_size_entry;
+    vhdx_metadata_table_entry parent_locator_entry;
+    uint16_t present;
+} vhdx_metadata_entries;
+
+
+typedef struct BDRVVHDXState {
+    CoMutex lock;
+
+    int curr_header;
+    vhdx_header * headers[2];
+
+    vhdx_region_table_header rt;
+    vhdx_region_table_entry bat_rt;         /* region table for the BAT */
+    vhdx_region_table_entry metadata_rt;    /* region table for the metadata */
+    vhdx_region_table_entry *unknown_rt;
+    unsigned int unknown_rt_size;
+
+    vhdx_metadata_table_header  metadata_hdr;
+    vhdx_metadata_entries metadata_entries;
+
+    vhdx_file_parameters params;
+    uint32_t block_size_bits;
+    uint32_t sectors_per_block;
+    uint32_t sectors_per_block_bits;
+
+    uint64_t virtual_disk_size;
+    uint32_t logical_sector_size;
+    uint32_t physical_sector_size;
+
+    uint64_t chunk_ratio;
+    uint32_t chunk_ratio_bits;
+    uint32_t logical_sector_size_bits;
+
+    uint32_t bat_entries;
+    vhdx_bat_entry *bat;
+
+    /* TODO */
+
+} BDRVVHDXState;
+
+/* CRC-32C, Castagnoli polynomial, code 0x11EDC6F41 */
+static uint32_t vhdx_checksum(uint8_t *buf, size_t size)
+{
+    uint32_t chksum;
+    chksum =  crc32c(0xffffffff, buf, size);
+
+    return chksum;
+}
+
+/* validates the checksum of a region of table entries, substituting zero
+ * in for the in-place checksum field of the region.
+ * buf: buffer to compute crc32c over,
+ * size: size of the buffer to checksum
+ * crc_offset: offset into buf that contains the existing 4-byte checksum
+ */
+static int vhdx_validate_checksum(uint8_t *buf, size_t size, int crc_offset)
+{
+    uint32_t crc_orig;
+    uint32_t crc;
+
+    assert(buf != NULL);
+    assert(size > (crc_offset+4));
+
+    memcpy(&crc_orig, buf+crc_offset, sizeof(crc_orig));
+    memset(buf+crc_offset, 0, sizeof(crc_orig));
+
+    crc = vhdx_checksum(buf, size);
+
+    memcpy(buf+crc_offset, &crc_orig, sizeof(crc_orig));
+
+    crc_orig = le32_to_cpu(crc_orig);
+    return crc == crc_orig ? 0 : 1;
+}
+
+/*
+ * Per the MS VHDX Specification, for every VHDX file:
+ *      - The header section is fixed size - 1 MB
+ *      - The header section is always the first "object"
+ *      - The first 64KB of the header is the File Identifier
+ *      - The first uint64 (8 bytes) is the VHDX Signature ("vhdxfile")
+ *      - The following 512 bytes constitute a UTF-16 string identifiying the
+ *        software that created the file, and is optional and diagnostic only.
+ *
+ *  Therefore, we probe by looking for the vhdxfile signature "vhdxfile"
+ */
+static int vhdx_probe(const uint8_t *buf, int buf_size, const char *filename)
+{
+    if (buf_size >= 8 && !strncmp((char *)buf, "vhdxfile", 8)) {
+        return 100;
+    }
+    return 0;
+}
+
+
+static void vhdx_fill_header(vhdx_header *h, uint8_t *buffer)
+{
+    int offset = 0;
+    assert(h != NULL);
+    assert(buffer != NULL);
+
+    /* use memcpy to avoid unaligned data read */
+    hdr_copy32(&h->signature,       buffer, offset);
+    hdr_copy32(&h->checksum,        buffer, offset);
+    hdr_copy64(&h->sequence_number, buffer, offset);
+
+    hdr_copy_guid(h->file_write_guid, buffer, offset);
+    hdr_copy_guid(h->data_write_guid, buffer, offset);
+    hdr_copy_guid(h->log_guid, buffer, offset);
+
+    hdr_copy16(&h->log_version,     buffer,  offset);
+    hdr_copy16(&h->version,         buffer,  offset);
+    hdr_copy32(&h->log_length,      buffer,  offset);
+    hdr_copy64(&h->log_offset,      buffer,  offset);
+}
+
+
+/* opens the specified header block from the VHDX file header section */
+static int vhdx_parse_header(BlockDriverState *bs, BDRVVHDXState *s)
+{
+    int ret = 0;
+    vhdx_header *header1;
+    vhdx_header *header2;
+    uint64_t h1_seq = 0;
+    uint64_t h2_seq = 0;
+    uint8_t *buffer;
+
+    header1 = g_malloc(sizeof(vhdx_header));
+    header2 = g_malloc(sizeof(vhdx_header));
+
+    buffer = g_malloc(VHDX_HEADER_SIZE);
+
+    s->headers[0] = header1;
+    s->headers[1] = header2;
+
+    ret = bdrv_pread(bs->file, VHDX_HEADER1_OFFSET, buffer, VHDX_HEADER_SIZE);
+    if (ret < 0) {
+        goto fail;
+    }
+    vhdx_fill_header(header1, buffer);
+
+    if (vhdx_validate_checksum(buffer, VHDX_HEADER_SIZE, 4) == 0 &&
+        header1->signature == VHDX_HDR_MAGIC) {
+        printf("header1 is valid!\n");
+        h1_seq = header1->sequence_number;
+    }
+
+    ret = bdrv_pread(bs->file, VHDX_HEADER2_OFFSET, buffer, VHDX_HEADER_SIZE);
+    if (ret < 0) {
+        goto fail;
+    }
+    vhdx_fill_header(header2, buffer);
+
+    if (vhdx_validate_checksum(buffer, VHDX_HEADER_SIZE, 4) == 0 &&
+        header2->signature == VHDX_HDR_MAGIC) {
+        printf("header2 is valid!\n");
+        h2_seq = header2->sequence_number;
+    }
+
+    if (h1_seq > h2_seq) {
+        s->curr_header = 0;
+    } else if (h2_seq > h1_seq) {
+        s->curr_header = 1;
+    } else {
+        printf("NO VALID HEADER\n");
+        ret = -1;
+    }
+
+    ret = 0;
+
+    printf("current header is %d\n", s->curr_header);
+    goto exit;
+
+fail:
+    g_free(header1);
+    g_free(header2);
+    s->headers[0] = NULL;
+    s->headers[1] = NULL;
+exit:
+    g_free(buffer);
+    return ret;
+}
+
+static int vhdx_open_region_tables(BlockDriverState *bs, BDRVVHDXState *s)
+{
+    int ret = 0;
+    uint8_t *buffer;
+    int offset = 0;
+    vhdx_region_table_entry rt_entry;
+    int i;
+
+    /* We have to read the whole 64KB block, because the crc32 is over the
+     * whole block */
+    buffer = g_malloc(VHDX_HEADER_BLOCK_SIZE);
+
+    printf("reading region tables...\n");
+    ret = bdrv_pread(bs->file, VHDX_REGION_TABLE_OFFSET, buffer,
+                    VHDX_HEADER_BLOCK_SIZE);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    hdr_copy32(&s->rt.signature,   buffer, offset);
+    hdr_copy32(&s->rt.checksum,    buffer, offset);
+    hdr_copy32(&s->rt.entry_count, buffer, offset);
+    hdr_copy32(&s->rt.reserved,    buffer, offset);
+
+    if (vhdx_validate_checksum(buffer, VHDX_HEADER_BLOCK_SIZE, 4) ||
+        s->rt.signature != VHDX_RT_MAGIC) {
+        ret = -1;
+        printf("region table checksum and/or magic failure\n");
+        goto fail;
+    }
+
+    printf("Found %" PRId32 " region table entries\n", s->rt.entry_count);
+
+    for (i = 0; i < s->rt.entry_count; i++) {
+        hdr_copy_guid(rt_entry.guid, buffer, offset);
+
+        hdr_copy64(&rt_entry.file_offset,   buffer, offset);
+        hdr_copy32(&rt_entry.length,        buffer, offset);
+        hdr_copy32(&rt_entry.bitfield.data, buffer, offset);
+
+        /* see if we recognize the entry */
+        if (guid_cmp(rt_entry.guid, bat_guid)) {
+            s->bat_rt = rt_entry;
+            continue;
+        }
+
+        if (guid_cmp(rt_entry.guid, metadata_guid)) {
+            s->metadata_rt = rt_entry;
+            continue;
+        }
+
+        if (rt_entry.bitfield.bits.required) {
+            /* cannot read vhdx file - required region table entry that
+             * we do not understand.  per spec, we must fail to open */
+            printf("Found unknown region table entry that is REQUIRED!\n");
+            ret = -1;
+            goto fail;
+        }
+    }
+    ret = 0;
+
+fail:
+    g_free(buffer);
+    return ret;
+}
+
+
+static int vhdx_parse_metadata(BlockDriverState *bs, BDRVVHDXState *s)
+{
+    int ret = 0;
+    uint8_t *buffer;
+    int offset = 0;
+    int i = 0;
+    uint32_t block_size, sectors_per_block, logical_sector_size;
+    uint64_t chunk_ratio;
+    vhdx_metadata_table_entry md_entry;
+
+    buffer = g_malloc(VHDX_METADATA_TABLE_MAX_SIZE);
+
+    printf("reading metadata at offset 0x%" PRIx64 "\n",
+            s->metadata_rt.file_offset);
+    ret = bdrv_pread(bs->file, s->metadata_rt.file_offset, buffer,
+                     VHDX_METADATA_TABLE_MAX_SIZE);
+    if (ret < 0) {
+        goto fail_no_free;
+    }
+    hdr_copy64(&s->metadata_hdr.signature,   buffer, offset);
+    hdr_copy16(&s->metadata_hdr.reserved,    buffer, offset);
+    hdr_copy16(&s->metadata_hdr.entry_count, buffer, offset);
+    hdr_copy(&s->metadata_hdr.reserved2, buffer,
+             sizeof(s->metadata_hdr.reserved2), offset);
+
+    if (s->metadata_hdr.signature != VHDX_METADATA_MAGIC) {
+        ret = -1;
+        printf("metadata header signature did not match: 0x%" PRIx64 "\n",
+                s->metadata_hdr.signature);
+        goto fail_no_free;
+    }
+
+    printf("metadata section has %" PRId16 " entries\n",
+            s->metadata_hdr.entry_count);
+
+    s->metadata_entries.present = 0;
+
+    for (i = 0; i < s->metadata_hdr.entry_count; i++) {
+        hdr_copy_guid(md_entry.item_id,     buffer, offset);
+        hdr_copy32(&md_entry.offset,        buffer, offset);
+        hdr_copy32(&md_entry.length,        buffer, offset);
+        hdr_copy32(&md_entry.bitfield.data, buffer, offset);
+        hdr_copy32(&md_entry.reserved2,     buffer, offset);
+
+        if (guid_cmp(md_entry.item_id, file_param_guid)) {
+            s->metadata_entries.file_parameters_entry = md_entry;
+            s->metadata_entries.present |= META_FILE_PARAMETER_PRESENT;
+            continue;
+        }
+
+        if (guid_cmp(md_entry.item_id, virtual_size_guid)) {
+            s->metadata_entries.virtual_disk_size_entry = md_entry;
+            s->metadata_entries.present |= META_VIRTUAL_DISK_SIZE_PRESENT;
+            continue;
+        }
+
+        if (guid_cmp(md_entry.item_id, page83_guid)) {
+            s->metadata_entries.page83_data_entry = md_entry;
+            s->metadata_entries.present |= META_PAGE_83_PRESENT;
+            continue;
+        }
+
+        if (guid_cmp(md_entry.item_id, logical_sector_guid)) {
+            s->metadata_entries.logical_sector_size_entry = md_entry;
+            s->metadata_entries.present |= META_LOGICAL_SECTOR_SIZE_PRESENT;
+            continue;
+        }
+
+        if (guid_cmp(md_entry.item_id, phys_sector_guid)) {
+            s->metadata_entries.phys_sector_size_entry = md_entry;
+            s->metadata_entries.present |= META_PHYS_SECTOR_SIZE_PRESENT;
+            continue;
+        }
+
+        if (guid_cmp(md_entry.item_id, parent_locator_guid)) {
+            s->metadata_entries.parent_locator_entry = md_entry;
+            s->metadata_entries.present |= META_PARENT_LOCATOR_PRESENT;
+            continue;
+        }
+
+        if (md_entry.bitfield.bits.is_required) {
+            /* cannot read vhdx file - required region table entry that
+             * we do not understand.  per spec, we must fail to open */
+            printf("Found unknown metadata table entry that is REQUIRED!\n");
+            ret = -1;
+            goto exit;
+        }
+    }
+
+    if (s->metadata_entries.present != META_ALL_PRESENT) {
+        printf("Did not find all required metadata entry fields\n");
+        ret = -1;
+        goto exit;
+    }
+
+    offset = 0;
+    buffer = g_realloc(buffer,
+                       s->metadata_entries.file_parameters_entry.length);
+    ret = bdrv_pread(bs->file,
+                     s->metadata_entries.file_parameters_entry.offset
+                                         + s->metadata_rt.file_offset,
+                     buffer,
+                     s->metadata_entries.file_parameters_entry.length);
+
+    hdr_copy32(&s->params.block_size,    buffer, offset);
+    hdr_copy32(&s->params.bitfield.data, buffer, offset);
+
+
+    /* We now have the file parameters, so we can tell if this is a
+     * differencing file (i.e.. has_parent), is dynamic or fixed
+     * sized (leave_blocks_allocated), and the block size */
+
+    /* The parent locator required iff the file parameters has_parent set */
+    if (s->params.bitfield.bits.has_parent) {
+        if (s->metadata_entries.present & ~META_PARENT_LOCATOR_PRESENT) {
+            offset = 0;
+            buffer = g_realloc(buffer,
+                               s->metadata_entries.parent_locator_entry.length);
+            ret = bdrv_pread(bs->file,
+                             s->metadata_entries.parent_locator_entry.offset,
+                             buffer,
+                             s->metadata_entries.parent_locator_entry.length);
+
+            ret = -1; /* temp, until differencing files are supported */
+            /* TODO: parse  parent locator fields */
+
+        } else {
+            printf("Did not find all required metadata entry fields\n");
+            ret = -1;
+            goto exit;
+        }
+    }
+    /* determine virtual disk size, logical sector size,
+     * and phys sector size */
+
+    ret = bdrv_pread(bs->file,
+                     s->metadata_entries.virtual_disk_size_entry.offset
+                                           + s->metadata_rt.file_offset,
+                     &s->virtual_disk_size,
+                     sizeof(uint64_t));
+    ret = bdrv_pread(bs->file,
+                     s->metadata_entries.logical_sector_size_entry.offset
+                                             + s->metadata_rt.file_offset,
+                     &s->logical_sector_size,
+                     sizeof(uint32_t));
+    ret = bdrv_pread(bs->file,
+                     s->metadata_entries.phys_sector_size_entry.offset
+                                          + s->metadata_rt.file_offset,
+                     &s->physical_sector_size,
+                     sizeof(uint32_t));
+
+    le64_to_cpus(&s->virtual_disk_size);
+    le32_to_cpus(&s->logical_sector_size);
+    le32_to_cpus(&s->physical_sector_size);
+
+    /* both block_size and sector_size are guaranteed powers of 2 */
+    s->sectors_per_block = s->params.block_size / s->logical_sector_size;
+    s->chunk_ratio = (VHDX_MAX_SECTORS_PER_BLOCK) *
+                     (uint64_t)s->logical_sector_size /
+                     (uint64_t)s->params.block_size;
+
+
+
+    /* These values are ones we will want to division / multiplication
+     * with later on, and they are all guaranteed (per the spec) to be
+     * powers of 2, so we can take advantage of that */
+    logical_sector_size = s->logical_sector_size;
+    while (logical_sector_size >>= 1) {
+        s->logical_sector_size_bits++;
+    }
+    sectors_per_block = s->sectors_per_block;
+    while (sectors_per_block >>= 1) {
+        s->sectors_per_block_bits++;
+    }
+    chunk_ratio = s->chunk_ratio;
+    while (chunk_ratio >>= 1) {
+        s->chunk_ratio_bits++;
+    }
+    block_size = s->params.block_size;
+    while (block_size >>= 1) {
+        s->block_size_bits++;
+    }
+
+    printf("chunk ratio is %" PRId64 "\n", s->chunk_ratio);
+    printf("block size is %" PRId32 " MB\n", s->params.block_size/(1024*1024));
+    printf("virtual disk size is %" PRId64 " MB\n",
+            s->virtual_disk_size/(1024*1024));
+    printf("logical sector size is %" PRId32 " bytes\n",
+            s->logical_sector_size);
+    printf("sectors per block is %" PRId32 "\n", s->sectors_per_block);
+
+    if (s->logical_sector_size != BDRV_SECTOR_SIZE) {
+        printf("VHDX error - QEMU only supports 512 byte sector sizes\n");
+        ret = -1;
+        goto exit;
+    }
+
+    ret = 0;
+
+exit:
+    g_free(buffer);
+fail_no_free:
+    return ret;
+}
+
+static int vhdx_open(BlockDriverState *bs, int flags)
+{
+    BDRVVHDXState *s = bs->opaque;
+    int ret = 0;
+    int i;
+
+    s->bat = NULL;
+
+    ret = vhdx_parse_header(bs, s);
+    if (ret) {
+        goto fail;
+    }
+
+    ret = vhdx_open_region_tables(bs, s);
+    if (ret) {
+        goto fail;
+    }
+
+    ret = vhdx_parse_metadata(bs, s);
+    if (ret) {
+        goto fail;
+    }
+
+    /* the VHDX spec dictates that virtual_disk_size is always a multiple of
+     * logical_sector_size */
+    bs->total_sectors = s->virtual_disk_size / s->logical_sector_size;
+
+    s->bat_entries = s->bat_rt.length / VHDX_BAT_ENTRY_SIZE;
+    s->bat = g_malloc(s->bat_rt.length);
+
+    ret = bdrv_pread(bs->file, s->bat_rt.file_offset, s->bat, s->bat_rt.length);
+
+    /* as it is a uint64_t bitfield, we need to have the right endianness */
+    for (i = 0; i < s->bat_entries; i++) {
+        le64_to_cpus(&s->bat[i].bitfield.data);
+    }
+
+    /* TODO: differencing files, r/w */
+    /* the below is obviously temporary */
+    if (flags & BDRV_O_RDWR) {
+        ret = -1;
+        goto fail;
+    }
+fail:
+    ret = 0;
+    return ret;
+}
+
+static int vhdx_reopen_prepare(BDRVReopenState *state,
+                               BlockReopenQueue *queue, Error **errp)
+{
+    return 0;
+}
+
+
+
+static int vhdx_read(BlockDriverState *bs, int64_t sector_num,
+                    uint8_t *buf, int nb_sectors)
+{
+    BDRVVHDXState *s = bs->opaque;
+    int ret = 0;
+    uint32_t sectors_avail;
+    uint32_t block_offset;
+    uint64_t offset;
+    uint32_t bat_idx;
+    uint32_t bytes_to_read;
+
+    while (nb_sectors > 0) {
+        /* We are a differencing file, so we need to inspect the sector bitmap
+         * to see if we have the data or not */
+        if (s->params.bitfield.bits.has_parent) {
+            /* not supported yet */
+            ret = -1;
+            goto exit;
+        } else {
+            bat_idx = sector_num >> s->sectors_per_block_bits;
+            /* effectively a modulo - this gives us the offset into the block
+             * (in sector sizes) for our sector number */
+            block_offset = sector_num - (bat_idx << s->sectors_per_block_bits);
+            /* the chunk ratio gives us the interleaving of the sector
+             * bitmaps, so we need to advance our page block index by the
+             * sector bitmaps entry number */
+            bat_idx += bat_idx >> s->chunk_ratio_bits;
+
+            /* the number of sectors we can read in this cycle */
+            sectors_avail = s->sectors_per_block - block_offset;
+
+            if (sectors_avail  > nb_sectors) {
+                sectors_avail = nb_sectors;
+            }
+
+            bytes_to_read = sectors_avail << s->logical_sector_size_bits;
+
+            /*
+            printf("bat_idx: %d\n", bat_idx);
+            printf("sectors_avail: %d\n", bat_idx);
+            printf("bytes_to_read: %d\n", bat_idx);
+            */
+            /* check the payload block state */
+            switch (s->bat[bat_idx].bitfield.bits.state) {
+            case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
+            case PAYLOAD_BLOCK_UNMAPPED:    /* fall through */
+            case PAYLOAD_BLOCK_ZERO:
+                /* return zero */
+                memset(buf, 0, bytes_to_read);
+                break;
+            case PAYLOAD_BLOCK_UNDEFINED:   /* fall through */
+            case PAYLOAD_BLOCK_FULL_PRESENT:
+                offset = (block_offset << s->logical_sector_size_bits) +
+                         (s->bat[bat_idx].bitfield.bits.file_offset_mb
+                          * (1024 * 1024));
+                ret = bdrv_pread(bs->file, offset, buf, bytes_to_read);
+                if (ret != bytes_to_read) {
+                    ret = -1;
+                    goto exit;
+                }
+                break;
+            case PAYLOAD_BLOCK_PARTIALLY_PRESENT:
+                /* we don't yet support difference files, fall through
+                 * to error */
+            default:
+                ret = -1;
+                goto exit;
+                break;
+            }
+            nb_sectors -= sectors_avail;
+            sector_num += sectors_avail;
+            buf += bytes_to_read;
+        }
+    }
+    ret = 0;
+exit:
+    return ret;
+}
+
+static int vhdx_write(BlockDriverState *bs, int64_t sector_num,
+    const uint8_t *buf, int nb_sectors)
+{
+   /* BDRVVHDXState *s = bs->opaque; */
+
+    /* TODO */
+
+    return 0;
+}
+
+static coroutine_fn int vhdx_co_write(BlockDriverState *bs, int64_t sector_num,
+                                     const uint8_t *buf, int nb_sectors)
+{
+    int ret;
+    BDRVVHDXState *s = bs->opaque;
+    qemu_co_mutex_lock(&s->lock);
+    ret = vhdx_write(bs, sector_num, buf, nb_sectors);
+    qemu_co_mutex_unlock(&s->lock);
+
+    /* TODO */
+
+    return ret;
+}
+
+
+static int vhdx_create(const char *filename, QEMUOptionParameter *options)
+{
+
+    /* TODO */
+
+   return 0;
+}
+
+static void vhdx_close(BlockDriverState *bs)
+{
+    BDRVVHDXState *s = bs->opaque;
+
+    /* TODO */
+
+    g_free(s->headers[0]);
+    g_free(s->headers[1]);
+    g_free(s->bat);
+}
+
+static QEMUOptionParameter vhdx_create_options[] = {
+    {
+        .name = BLOCK_OPT_SIZE,
+        .type = OPT_SIZE,
+        .help = "Virtual disk size"
+    },
+    {
+        .name = BLOCK_OPT_SUBFMT,
+        .type = OPT_STRING,
+        .help =
+            ""
+    },
+    { NULL }
+};
+
+static BlockDriver bdrv_vhdx = {
+    .format_name    = "vhdx",
+    .instance_size  = sizeof(BDRVVHDXState),
+
+    .bdrv_probe             = vhdx_probe,
+    .bdrv_open              = vhdx_open,
+    .bdrv_close             = vhdx_close,
+    .bdrv_reopen_prepare    = vhdx_reopen_prepare,
+    .bdrv_create            = vhdx_create,
+    .bdrv_read              = vhdx_read,
+    .bdrv_write             = vhdx_co_write,
+    .create_options         = vhdx_create_options,
+};
+
+static void bdrv_vhdx_init(void)
+{
+    bdrv_register(&bdrv_vhdx);
+}
+
+block_init(bdrv_vhdx_init);
