diff --git a/block/Makefile.objs b/block/Makefile.objs
index 2fc496ab69..f43ecbc044 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -2,7 +2,7 @@ block-obj-y += raw_bsd.o cow.o qcow.o vdi.o vmdk.o cloop.o dmg.o bochs.o vpc.o v
 block-obj-y += qcow2.o qcow2-refcount.o qcow2-cluster.o qcow2-snapshot.o qcow2-cache.o
 block-obj-y += qed.o qed-gencb.o qed-l2-cache.o qed-table.o qed-cluster.o
 block-obj-y += qed-check.o
-block-obj-$(CONFIG_VHDX) += vhdx.o vhdx-endian.o
+block-obj-$(CONFIG_VHDX) += vhdx.o vhdx-endian.o vhdx-log.o
 block-obj-y += parallels.o blkdebug.o blkverify.o
 block-obj-y += snapshot.o qapi.o
 block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
diff --git a/block/vhdx-log.c b/block/vhdx-log.c
new file mode 100644
index 0000000000..0284729ddf
--- /dev/null
+++ b/block/vhdx-log.c
@@ -0,0 +1,728 @@
+/*
+ * 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 v1.00", published 8/25/2012
+ *  by Microsoft:
+ *      https://www.microsoft.com/en-us/download/details.aspx?id=34750
+ *
+ * This file covers the functionality of the metadata log writing, parsing, and
+ * replay.
+ *
+ * This work is licensed under the terms of the GNU LGPL, version 2 or later.
+ * See the COPYING.LIB file in the top-level directory.
+ *
+ */
+#include "qemu-common.h"
+#include "block/block_int.h"
+#include "qemu/module.h"
+#include "block/vhdx.h"
+
+
+typedef struct VHDXLogSequence {
+    bool valid;
+    uint32_t count;
+    VHDXLogEntries log;
+    VHDXLogEntryHeader hdr;
+} VHDXLogSequence;
+
+typedef struct VHDXLogDescEntries {
+    VHDXLogEntryHeader hdr;
+    VHDXLogDescriptor desc[];
+} VHDXLogDescEntries;
+
+static const MSGUID zero_guid = { 0 };
+
+/* The log located on the disk is circular buffer containing
+ * sectors of 4096 bytes each.
+ *
+ * It is assumed for the read/write functions below that the
+ * circular buffer scheme uses a 'one sector open' to indicate
+ * the buffer is full.  Given the validation methods used for each
+ * sector, this method should be compatible with other methods that
+ * do not waste a sector.
+ */
+
+
+/* Allow peeking at the hdr entry at the beginning of the current
+ * read index, without advancing the read index */
+static int vhdx_log_peek_hdr(BlockDriverState *bs, VHDXLogEntries *log,
+                             VHDXLogEntryHeader *hdr)
+{
+    int ret = 0;
+    uint64_t offset;
+    uint32_t read;
+
+    assert(hdr != NULL);
+
+    /* peek is only supported on sector boundaries */
+    if (log->read % VHDX_LOG_SECTOR_SIZE) {
+        ret = -EFAULT;
+        goto exit;
+    }
+
+    read = log->read;
+    /* we are guaranteed that a) log sectors are 4096 bytes,
+     * and b) the log length is a multiple of 1MB. So, there
+     * is always a round number of sectors in the buffer */
+    if ((read + sizeof(VHDXLogEntryHeader)) > log->length) {
+        read = 0;
+    }
+
+    if (read == log->write) {
+        ret = -EINVAL;
+        goto exit;
+    }
+
+    offset = log->offset + read;
+
+    ret = bdrv_pread(bs->file, offset, hdr, sizeof(VHDXLogEntryHeader));
+    if (ret < 0) {
+        goto exit;
+    }
+
+exit:
+    return ret;
+}
+
+/* Index increment for log, based on sector boundaries */
+static int vhdx_log_inc_idx(uint32_t idx, uint64_t length)
+{
+    idx += VHDX_LOG_SECTOR_SIZE;
+    /* we are guaranteed that a) log sectors are 4096 bytes,
+     * and b) the log length is a multiple of 1MB. So, there
+     * is always a round number of sectors in the buffer */
+    return idx >= length ? 0 : idx;
+}
+
+
+/* Reset the log to empty */
+static void vhdx_log_reset(BlockDriverState *bs, BDRVVHDXState *s)
+{
+    MSGUID guid = { 0 };
+    s->log.read = s->log.write = 0;
+    /* a log guid of 0 indicates an empty log to any parser of v0
+     * VHDX logs */
+    vhdx_update_headers(bs, s, false, &guid);
+}
+
+/* Reads num_sectors from the log (all log sectors are 4096 bytes),
+ * into buffer 'buffer'.  Upon return, *sectors_read will contain
+ * the number of sectors successfully read.
+ *
+ * It is assumed that 'buffer' is already allocated, and of sufficient
+ * size (i.e. >= 4096*num_sectors).
+ *
+ * If 'peek' is true, then the tail (read) pointer for the circular buffer is
+ * not modified.
+ *
+ * 0 is returned on success, -errno otherwise.  */
+static int vhdx_log_read_sectors(BlockDriverState *bs, VHDXLogEntries *log,
+                                 uint32_t *sectors_read, void *buffer,
+                                 uint32_t num_sectors, bool peek)
+{
+    int ret = 0;
+    uint64_t offset;
+    uint32_t read;
+
+    read = log->read;
+
+    *sectors_read = 0;
+    while (num_sectors) {
+        if (read == log->write) {
+            /* empty */
+            break;
+        }
+        offset = log->offset + read;
+
+        ret = bdrv_pread(bs->file, offset, buffer, VHDX_LOG_SECTOR_SIZE);
+        if (ret < 0) {
+            goto exit;
+        }
+        read = vhdx_log_inc_idx(read, log->length);
+
+        *sectors_read = *sectors_read + 1;
+        num_sectors--;
+    }
+
+exit:
+    if (!peek) {
+        log->read = read;
+    }
+    return ret;
+}
+
+/* Validates a log entry header */
+static bool vhdx_log_hdr_is_valid(VHDXLogEntries *log, VHDXLogEntryHeader *hdr,
+                                  BDRVVHDXState *s)
+{
+    int valid = false;
+
+    if (memcmp(&hdr->signature, "loge", 4)) {
+        goto exit;
+    }
+
+    /* if the individual entry length is larger than the whole log
+     * buffer, that is obviously invalid */
+    if (log->length < hdr->entry_length) {
+        goto exit;
+    }
+
+    /* length of entire entry must be in units of 4KB (log sector size) */
+    if (hdr->entry_length % (VHDX_LOG_SECTOR_SIZE)) {
+        goto exit;
+    }
+
+    /* per spec, sequence # must be > 0 */
+    if (hdr->sequence_number == 0) {
+        goto exit;
+    }
+
+    /* log entries are only valid if they match the file-wide log guid
+     * found in the active header */
+    if (!guid_eq(hdr->log_guid, s->headers[s->curr_header]->log_guid)) {
+        goto exit;
+    }
+
+    if (hdr->descriptor_count * sizeof(VHDXLogDescriptor) > hdr->entry_length) {
+        goto exit;
+    }
+
+    valid = true;
+
+exit:
+    return valid;
+}
+
+/*
+ * Given a log header, this will validate that the descriptors and the
+ * corresponding data sectors (if applicable)
+ *
+ * Validation consists of:
+ *      1. Making sure the sequence numbers matches the entry header
+ *      2. Verifying a valid signature ('zero' or 'desc' for descriptors)
+ *      3. File offset field is a multiple of 4KB
+ *      4. If a data descriptor, the corresponding data sector
+ *         has its signature ('data') and matching sequence number
+ *
+ * @desc: the data buffer containing the descriptor
+ * @hdr:  the log entry header
+ *
+ * Returns true if valid
+ */
+static bool vhdx_log_desc_is_valid(VHDXLogDescriptor *desc,
+                                   VHDXLogEntryHeader *hdr)
+{
+    bool ret = false;
+
+    if (desc->sequence_number != hdr->sequence_number) {
+        goto exit;
+    }
+    if (desc->file_offset % VHDX_LOG_SECTOR_SIZE) {
+        goto exit;
+    }
+
+    if (!memcmp(&desc->signature, "zero", 4)) {
+        if (desc->zero_length % VHDX_LOG_SECTOR_SIZE == 0) {
+            /* valid */
+            ret = true;
+        }
+    } else if (!memcmp(&desc->signature, "desc", 4)) {
+            /* valid */
+            ret = true;
+    }
+
+exit:
+    return ret;
+}
+
+
+/* Prior to sector data for a log entry, there is the header
+ * and the descriptors referenced in the header:
+ *
+ * [] = 4KB sector
+ *
+ * [ hdr, desc ][   desc   ][ ... ][ data ][ ... ]
+ *
+ * The first sector in a log entry has a 64 byte header, and
+ * up to 126 32-byte descriptors.  If more descriptors than
+ * 126 are required, then subsequent sectors can have up to 128
+ * descriptors.  Each sector is 4KB.  Data follows the descriptor
+ * sectors.
+ *
+ * This will return the number of sectors needed to encompass
+ * the passed number of descriptors in desc_cnt.
+ *
+ * This will never return 0, even if desc_cnt is 0.
+ */
+static int vhdx_compute_desc_sectors(uint32_t desc_cnt)
+{
+    uint32_t desc_sectors;
+
+    desc_cnt += 2; /* account for header in first sector */
+    desc_sectors = desc_cnt / 128;
+    if (desc_cnt % 128) {
+        desc_sectors++;
+    }
+
+    return desc_sectors;
+}
+
+
+/* Reads the log header, and subsequent descriptors (if any).  This
+ * will allocate all the space for buffer, which must be NULL when
+ * passed into this function. Each descriptor will also be validated,
+ * and error returned if any are invalid. */
+static int vhdx_log_read_desc(BlockDriverState *bs, BDRVVHDXState *s,
+                              VHDXLogEntries *log, VHDXLogDescEntries **buffer)
+{
+    int ret = 0;
+    uint32_t desc_sectors;
+    uint32_t sectors_read;
+    VHDXLogEntryHeader hdr;
+    VHDXLogDescEntries *desc_entries = NULL;
+    int i;
+
+    assert(*buffer == NULL);
+
+    ret = vhdx_log_peek_hdr(bs, log, &hdr);
+    if (ret < 0) {
+        goto exit;
+    }
+    vhdx_log_entry_hdr_le_import(&hdr);
+    if (vhdx_log_hdr_is_valid(log, &hdr, s) == false) {
+        ret = -EINVAL;
+        goto exit;
+    }
+
+    desc_sectors = vhdx_compute_desc_sectors(hdr.descriptor_count);
+    desc_entries = qemu_blockalign(bs, desc_sectors * VHDX_LOG_SECTOR_SIZE);
+
+    ret = vhdx_log_read_sectors(bs, log, &sectors_read, desc_entries,
+                                desc_sectors, false);
+    if (ret < 0) {
+        goto free_and_exit;
+    }
+    if (sectors_read != desc_sectors) {
+        ret = -EINVAL;
+        goto free_and_exit;
+    }
+
+    /* put in proper endianness, and validate each desc */
+    for (i = 0; i < hdr.descriptor_count; i++) {
+        vhdx_log_desc_le_import(&desc_entries->desc[i]);
+        if (vhdx_log_desc_is_valid(&desc_entries->desc[i], &hdr) == false) {
+            ret = -EINVAL;
+            goto free_and_exit;
+        }
+    }
+
+    *buffer = desc_entries;
+    goto exit;
+
+free_and_exit:
+    qemu_vfree(desc_entries);
+exit:
+    return ret;
+}
+
+
+/* Flushes the descriptor described by desc to the VHDX image file.
+ * If the descriptor is a data descriptor, than 'data' must be non-NULL,
+ * and >= 4096 bytes (VHDX_LOG_SECTOR_SIZE), containing the data to be
+ * written.
+ *
+ * Verification is performed to make sure the sequence numbers of a data
+ * descriptor match the sequence number in the desc.
+ *
+ * For a zero descriptor, it may describe multiple sectors to fill with zeroes.
+ * In this case, it should be noted that zeroes are written to disk, and the
+ * image file is not extended as a sparse file.  */
+static int vhdx_log_flush_desc(BlockDriverState *bs, VHDXLogDescriptor *desc,
+                               VHDXLogDataSector *data)
+{
+    int ret = 0;
+    uint64_t seq, file_offset;
+    uint32_t offset = 0;
+    void *buffer = NULL;
+    uint64_t count = 1;
+    int i;
+
+    buffer = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
+
+    if (!memcmp(&desc->signature, "desc", 4)) {
+        /* data sector */
+        if (data == NULL) {
+            ret = -EFAULT;
+            goto exit;
+        }
+
+        /* The sequence number of the data sector must match that
+         * in the descriptor */
+        seq = data->sequence_high;
+        seq <<= 32;
+        seq |= data->sequence_low & 0xffffffff;
+
+        if (seq != desc->sequence_number) {
+            ret = -EINVAL;
+            goto exit;
+        }
+
+        /* Each data sector is in total 4096 bytes, however the first
+         * 8 bytes, and last 4 bytes, are located in the descriptor */
+        memcpy(buffer, &desc->leading_bytes, 8);
+        offset += 8;
+
+        memcpy(buffer+offset, data->data, 4084);
+        offset += 4084;
+
+        memcpy(buffer+offset, &desc->trailing_bytes, 4);
+
+    } else if (!memcmp(&desc->signature, "zero", 4)) {
+        /* write 'count' sectors of sector */
+        memset(buffer, 0, VHDX_LOG_SECTOR_SIZE);
+        count = desc->zero_length / VHDX_LOG_SECTOR_SIZE;
+    }
+
+    file_offset = desc->file_offset;
+
+    /* count is only > 1 if we are writing zeroes */
+    for (i = 0; i < count; i++) {
+        ret = bdrv_pwrite_sync(bs->file, file_offset, buffer,
+                               VHDX_LOG_SECTOR_SIZE);
+        if (ret < 0) {
+            goto exit;
+        }
+        file_offset += VHDX_LOG_SECTOR_SIZE;
+    }
+
+exit:
+    qemu_vfree(buffer);
+    return ret;
+}
+
+/* Flush the entire log (as described by 'logs') to the VHDX image
+ * file, and then set the log to 'empty' status once complete.
+ *
+ * The log entries should be validate prior to flushing */
+static int vhdx_log_flush(BlockDriverState *bs, BDRVVHDXState *s,
+                          VHDXLogSequence *logs)
+{
+    int ret = 0;
+    int i;
+    uint32_t cnt, sectors_read;
+    uint64_t new_file_size;
+    void *data = NULL;
+    VHDXLogDescEntries *desc_entries = NULL;
+    VHDXLogEntryHeader hdr_tmp = { 0 };
+
+    cnt = logs->count;
+
+    data = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
+
+    ret = vhdx_user_visible_write(bs, s);
+    if (ret < 0) {
+        goto exit;
+    }
+
+    /* each iteration represents one log sequence, which may span multiple
+     * sectors */
+    while (cnt--) {
+        ret = vhdx_log_peek_hdr(bs, &logs->log, &hdr_tmp);
+        if (ret < 0) {
+            goto exit;
+        }
+        /* if the log shows a FlushedFileOffset larger than our current file
+         * size, then that means the file has been truncated / corrupted, and
+         * we must refused to open it / use it */
+        if (hdr_tmp.flushed_file_offset > bdrv_getlength(bs->file)) {
+            ret = -EINVAL;
+            goto exit;
+        }
+
+        ret = vhdx_log_read_desc(bs, s, &logs->log, &desc_entries);
+        if (ret < 0) {
+            goto exit;
+        }
+
+        for (i = 0; i < desc_entries->hdr.descriptor_count; i++) {
+            if (!memcmp(&desc_entries->desc[i].signature, "desc", 4)) {
+                /* data sector, so read a sector to flush */
+                ret = vhdx_log_read_sectors(bs, &logs->log, &sectors_read,
+                                            data, 1, false);
+                if (ret < 0) {
+                    goto exit;
+                }
+                if (sectors_read != 1) {
+                    ret = -EINVAL;
+                    goto exit;
+                }
+            }
+
+            ret = vhdx_log_flush_desc(bs, &desc_entries->desc[i], data);
+            if (ret < 0) {
+                goto exit;
+            }
+        }
+        if (bdrv_getlength(bs->file) < desc_entries->hdr.last_file_offset) {
+            new_file_size = desc_entries->hdr.last_file_offset;
+            if (new_file_size % (1024*1024)) {
+                /* round up to nearest 1MB boundary */
+                new_file_size = ((new_file_size >> 20) + 1) << 20;
+                bdrv_truncate(bs->file, new_file_size);
+            }
+        }
+        qemu_vfree(desc_entries);
+        desc_entries = NULL;
+    }
+
+    bdrv_flush(bs);
+    /* once the log is fully flushed, indicate that we have an empty log
+     * now.  This also sets the log guid to 0, to indicate an empty log */
+    vhdx_log_reset(bs, s);
+
+exit:
+    qemu_vfree(data);
+    qemu_vfree(desc_entries);
+    return ret;
+}
+
+static int vhdx_validate_log_entry(BlockDriverState *bs, BDRVVHDXState *s,
+                                   VHDXLogEntries *log, uint64_t seq,
+                                   bool *valid, VHDXLogEntryHeader *entry)
+{
+    int ret = 0;
+    VHDXLogEntryHeader hdr;
+    void *buffer = NULL;
+    uint32_t i, desc_sectors, total_sectors, crc;
+    uint32_t sectors_read = 0;
+    VHDXLogDescEntries *desc_buffer = NULL;
+
+    *valid = false;
+
+    ret = vhdx_log_peek_hdr(bs, log, &hdr);
+    if (ret < 0) {
+        goto inc_and_exit;
+    }
+
+    vhdx_log_entry_hdr_le_import(&hdr);
+
+
+    if (vhdx_log_hdr_is_valid(log, &hdr, s) == false) {
+        goto inc_and_exit;
+    }
+
+    if (seq > 0) {
+        if (hdr.sequence_number != seq + 1) {
+            goto inc_and_exit;
+        }
+    }
+
+    desc_sectors = vhdx_compute_desc_sectors(hdr.descriptor_count);
+
+    /* Read desc sectors, and calculate log checksum */
+
+    total_sectors = hdr.entry_length / VHDX_LOG_SECTOR_SIZE;
+
+
+    /* read_desc() will incrememnt the read idx */
+    ret = vhdx_log_read_desc(bs, s, log, &desc_buffer);
+    if (ret < 0) {
+        goto free_and_exit;
+    }
+
+    crc = vhdx_checksum_calc(0xffffffff, (void *)desc_buffer,
+                            desc_sectors * VHDX_LOG_SECTOR_SIZE, 4);
+    crc ^= 0xffffffff;
+
+    buffer = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
+    if (total_sectors > desc_sectors) {
+        for (i = 0; i < total_sectors - desc_sectors; i++) {
+            sectors_read = 0;
+            ret = vhdx_log_read_sectors(bs, log, &sectors_read, buffer,
+                                        1, false);
+            if (ret < 0 || sectors_read != 1) {
+                goto free_and_exit;
+            }
+            crc = vhdx_checksum_calc(crc, buffer, VHDX_LOG_SECTOR_SIZE, -1);
+            crc ^= 0xffffffff;
+        }
+    }
+    crc ^= 0xffffffff;
+    if (crc != desc_buffer->hdr.checksum) {
+        goto free_and_exit;
+    }
+
+    *valid = true;
+    *entry = hdr;
+    goto free_and_exit;
+
+inc_and_exit:
+    log->read = vhdx_log_inc_idx(log->read, log->length);
+
+free_and_exit:
+    qemu_vfree(buffer);
+    qemu_vfree(desc_buffer);
+    return ret;
+}
+
+/* Search through the log circular buffer, and find the valid, active
+ * log sequence, if any exists
+ * */
+static int vhdx_log_search(BlockDriverState *bs, BDRVVHDXState *s,
+                           VHDXLogSequence *logs)
+{
+    int ret = 0;
+    uint32_t tail;
+    bool seq_valid = false;
+    VHDXLogSequence candidate = { 0 };
+    VHDXLogEntryHeader hdr = { 0 };
+    VHDXLogEntries curr_log;
+
+    memcpy(&curr_log, &s->log, sizeof(VHDXLogEntries));
+    curr_log.write = curr_log.length;   /* assume log is full */
+    curr_log.read = 0;
+
+
+    /* now we will go through the whole log sector by sector, until
+     * we find a valid, active log sequence, or reach the end of the
+     * log buffer */
+    for (;;) {
+        uint64_t curr_seq = 0;
+        VHDXLogSequence current = { 0 };
+
+        tail = curr_log.read;
+
+        ret = vhdx_validate_log_entry(bs, s, &curr_log, curr_seq,
+                                      &seq_valid, &hdr);
+        if (ret < 0) {
+            goto exit;
+        }
+
+        if (seq_valid) {
+            current.valid     = true;
+            current.log       = curr_log;
+            current.log.read  = tail;
+            current.log.write = curr_log.read;
+            current.count     = 1;
+            current.hdr       = hdr;
+
+
+            for (;;) {
+                ret = vhdx_validate_log_entry(bs, s, &curr_log, curr_seq,
+                                              &seq_valid, &hdr);
+                if (ret < 0) {
+                    goto exit;
+                }
+                if (seq_valid == false) {
+                    break;
+                }
+                current.log.write = curr_log.read;
+                current.count++;
+
+                curr_seq = hdr.sequence_number;
+            }
+        }
+
+        if (current.valid) {
+            if (candidate.valid == false ||
+                current.hdr.sequence_number > candidate.hdr.sequence_number) {
+                candidate = current;
+            }
+        }
+
+        if (curr_log.read < tail) {
+            break;
+        }
+    }
+
+    *logs = candidate;
+
+    if (candidate.valid) {
+        /* this is the next sequence number, for writes */
+        s->log.sequence = candidate.hdr.sequence_number + 1;
+    }
+
+
+exit:
+    return ret;
+}
+
+/* Parse the replay log.  Per the VHDX spec, if the log is present
+ * it must be replayed prior to opening the file, even read-only.
+ *
+ * If read-only, we must replay the log in RAM (or refuse to open
+ * a dirty VHDX file read-only) */
+int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s, bool *flushed)
+{
+    int ret = 0;
+    VHDXHeader *hdr;
+    VHDXLogSequence logs = { 0 };
+
+    hdr = s->headers[s->curr_header];
+
+    *flushed = false;
+
+    /* s->log.hdr is freed in vhdx_close() */
+    if (s->log.hdr == NULL) {
+        s->log.hdr = qemu_blockalign(bs, sizeof(VHDXLogEntryHeader));
+    }
+
+    s->log.offset = hdr->log_offset;
+    s->log.length = hdr->log_length;
+
+    if (s->log.offset < VHDX_LOG_MIN_SIZE ||
+        s->log.offset % VHDX_LOG_MIN_SIZE) {
+        ret = -EINVAL;
+        goto exit;
+    }
+
+    /* per spec, only log version of 0 is supported */
+    if (hdr->log_version != 0) {
+        ret = -EINVAL;
+        goto exit;
+    }
+
+    /* If either the log guid, or log length is zero,
+     * then a replay log is not present */
+    if (guid_eq(hdr->log_guid, zero_guid)) {
+        goto exit;
+    }
+
+    if (hdr->log_length == 0) {
+        goto exit;
+    }
+
+    if (hdr->log_length % VHDX_LOG_MIN_SIZE) {
+        ret = -EINVAL;
+        goto exit;
+    }
+
+
+    /* The log is present, we need to find if and where there is an active
+     * sequence of valid entries present in the log.  */
+
+    ret = vhdx_log_search(bs, s, &logs);
+    if (ret < 0) {
+        goto exit;
+    }
+
+    if (logs.valid) {
+        /* now flush the log */
+        ret = vhdx_log_flush(bs, s, &logs);
+        if (ret < 0) {
+            goto exit;
+        }
+        *flushed = true;
+    }
+
+
+exit:
+    return ret;
+}
+
+
diff --git a/block/vhdx.c b/block/vhdx.c
index 3f06ce33ef..8fbfbd60a1 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -735,58 +735,22 @@ exit:
     return ret;
 }
 
-/* Parse the replay log.  Per the VHDX spec, if the log is present
- * it must be replayed prior to opening the file, even read-only.
- *
- * If read-only, we must replay the log in RAM (or refuse to open
- * a dirty VHDX file read-only */
-static int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s)
-{
-    int ret = 0;
-    int i;
-    VHDXHeader *hdr;
-
-    hdr = s->headers[s->curr_header];
-
-    /* either the log guid, or log length is zero,
-     * then a replay log is present */
-    for (i = 0; i < sizeof(hdr->log_guid.data4); i++) {
-        ret |= hdr->log_guid.data4[i];
-    }
-    if (hdr->log_guid.data1 == 0 &&
-        hdr->log_guid.data2 == 0 &&
-        hdr->log_guid.data3 == 0 &&
-        ret == 0) {
-        goto exit;
-    }
-
-    /* per spec, only log version of 0 is supported */
-    if (hdr->log_version != 0) {
-        ret = -EINVAL;
-        goto exit;
-    }
-
-    if (hdr->log_length == 0) {
-        goto exit;
-    }
-
-    /* We currently do not support images with logs to replay */
-    ret = -ENOTSUP;
-
-exit:
-    return ret;
-}
-
 
 static void vhdx_close(BlockDriverState *bs)
 {
     BDRVVHDXState *s = bs->opaque;
     qemu_vfree(s->headers[0]);
+    s->headers[0] = NULL;
     qemu_vfree(s->headers[1]);
+    s->headers[1] = NULL;
     qemu_vfree(s->bat);
+    s->bat = NULL;
     qemu_vfree(s->parent_entries);
+    s->parent_entries = NULL;
     migrate_del_blocker(s->migration_blocker);
     error_free(s->migration_blocker);
+    qemu_vfree(s->log.hdr);
+    s->log.hdr = NULL;
 }
 
 static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
@@ -797,6 +761,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
     uint32_t i;
     uint64_t signature;
     uint32_t data_blocks_cnt, bitmap_blocks_cnt;
+    bool log_flushed = false;
 
 
     s->bat = NULL;
@@ -820,24 +785,25 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
     vhdx_guid_generate(&s->session_guid);
 
     ret = vhdx_parse_header(bs, s);
-    if (ret) {
+    if (ret < 0) {
         goto fail;
     }
 
-    ret = vhdx_parse_log(bs, s);
-    if (ret) {
+    ret = vhdx_parse_log(bs, s, &log_flushed);
+    if (ret < 0) {
         goto fail;
     }
 
     ret = vhdx_open_region_tables(bs, s);
-    if (ret) {
+    if (ret < 0) {
         goto fail;
     }
 
     ret = vhdx_parse_metadata(bs, s);
-    if (ret) {
+    if (ret < 0) {
         goto fail;
     }
+
     s->block_size = s->params.block_size;
 
     /* the VHDX spec dictates that virtual_disk_size is always a multiple of
@@ -897,10 +863,7 @@ static int vhdx_open(BlockDriverState *bs, QDict *options, int flags,
 
     return 0;
 fail:
-    qemu_vfree(s->headers[0]);
-    qemu_vfree(s->headers[1]);
-    qemu_vfree(s->bat);
-    qemu_vfree(s->parent_entries);
+    vhdx_close(bs);
     return ret;
 }
 
diff --git a/block/vhdx.h b/block/vhdx.h
index 6c35737b07..584ebec8fc 100644
--- a/block/vhdx.h
+++ b/block/vhdx.h
@@ -326,7 +326,11 @@ typedef struct VHDXMetadataEntries {
 typedef struct VHDXLogEntries {
     uint64_t offset;
     uint64_t length;
-    uint32_t head;
+    uint32_t write;
+    uint32_t read;
+    VHDXLogEntryHeader *hdr;
+    void *desc_buffer;
+    uint64_t sequence;
     uint32_t tail;
 } VHDXLogEntries;
 
@@ -383,6 +387,7 @@ uint32_t vhdx_checksum_calc(uint32_t crc, uint8_t *buf, size_t size,
 
 bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset);
 
+int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s, bool *flushed);
 
 static inline void leguid_to_cpus(MSGUID *guid)
 {