Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging

Block layer patches:

- qemu-storage-daemon: add --pidfile option
- qemu-storage-daemon: CLI error messages include the option name now
- vhost-user-blk export: Misc fixes
- docs: Improvements for qemu-storage-daemon documentation
- parallels: load bitmap extension
- backup-top: Don't crash on post-finalize accesses
- Improve error messages related to node-name options
- iotests improvements

# gpg: Signature made Mon 08 Mar 2021 17:01:41 GMT
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (30 commits)
  blockdev: Clarify error messages pertaining to 'node-name'
  block: Clarify error messages pertaining to 'node-name'
  docs: qsd: Explain --export nbd,name=... default
  MAINTAINERS: update parallels block driver
  iotests: add parallels-read-bitmap test
  iotests.py: add unarchive_sample_image() helper
  parallels: support bitmap extension for read-only mode
  block/parallels: BDRVParallelsState: add cluster_size field
  parallels.txt: fix bitmap L1 table description
  qcow2-bitmap: make bytes_covered_by_bitmap_cluster() public
  block/export: port virtio-blk read/write range check
  block/export: port virtio-blk discard/write zeroes input validation
  block/export: fix vhost-user-blk export sector number calculation
  block/export: use VIRTIO_BLK_SECTOR_BITS
  block/export: fix blk_size double byteswap
  libqtest: add qtest_remove_abrt_handler()
  libqtest: add qtest_kill_qemu()
  libqtest: add qtest_socket_server()
  vhost-user-blk: fix blkcfg->num_queues endianness
  docs: replace insecure /tmp examples in qsd docs
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

9 files changed, 477 insertions, 49 deletions

diff --git a/block/backup-top.c b/block/backup-top.c
index d1253e1aa6..589e8b651d 100644
--- a/block/backup-top.c
+++ b/block/backup-top.c
@@ -45,6 +45,12 @@ static coroutine_fn int backup_top_co_preadv(
         BlockDriverState *bs, uint64_t offset, uint64_t bytes,
         QEMUIOVector *qiov, int flags)
 {
+    BDRVBackupTopState *s = bs->opaque;
+
+    if (!s->active) {
+        return -EIO;
+    }
+
     return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
 }
 
@@ -54,6 +60,10 @@ static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
     BDRVBackupTopState *s = bs->opaque;
     uint64_t off, end;
 
+    if (!s->active) {
+        return -EIO;
+    }
+
     if (flags & BDRV_REQ_WRITE_UNCHANGED) {
         return 0;
     }
diff --git a/block/backup.c b/block/backup.c
index 94e6dcd72e..6cf2f974aa 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -103,6 +103,7 @@ static void backup_abort(Job *job)
 static void backup_clean(Job *job)
 {
     BackupBlockJob *s = container_of(job, BackupBlockJob, common.job);
+    block_job_remove_all_bdrv(&s->common);
     bdrv_backup_top_drop(s->backup_top);
 }
 
diff --git a/block/dirty-bitmap.c b/block/dirty-bitmap.c
index 9b9cd71238..a0eaa28785 100644
--- a/block/dirty-bitmap.c
+++ b/block/dirty-bitmap.c
@@ -726,6 +726,19 @@ uint64_t bdrv_dirty_bitmap_serialization_align(const BdrvDirtyBitmap *bitmap)
     return hbitmap_serialization_align(bitmap->bitmap);
 }
 
+/* Return the disk size covered by a chunk of serialized bitmap data. */
+uint64_t bdrv_dirty_bitmap_serialization_coverage(int serialized_chunk_size,
+                                                  const BdrvDirtyBitmap *bitmap)
+{
+    uint64_t granularity = bdrv_dirty_bitmap_granularity(bitmap);
+    uint64_t limit = granularity * (serialized_chunk_size << 3);
+
+    assert(QEMU_IS_ALIGNED(limit,
+                           bdrv_dirty_bitmap_serialization_align(bitmap)));
+    return limit;
+}
+
+
 void bdrv_dirty_bitmap_serialize_part(const BdrvDirtyBitmap *bitmap,
                                       uint8_t *buf, uint64_t offset,
                                       uint64_t bytes)
diff --git a/block/export/vhost-user-blk-server.c b/block/export/vhost-user-blk-server.c
index ab2c4d44c4..cb5d896b7b 100644
--- a/block/export/vhost-user-blk-server.c
+++ b/block/export/vhost-user-blk-server.c
@@ -20,8 +20,17 @@
 #include "sysemu/block-backend.h"
 #include "util/block-helpers.h"
 
+/*
+ * Sector units are 512 bytes regardless of the
+ * virtio_blk_config->blk_size value.
+ */
+#define VIRTIO_BLK_SECTOR_BITS 9
+#define VIRTIO_BLK_SECTOR_SIZE (1ull << VIRTIO_BLK_SECTOR_BITS)
+
 enum {
     VHOST_USER_BLK_NUM_QUEUES_DEFAULT = 1,
+    VHOST_USER_BLK_MAX_DISCARD_SECTORS = 32768,
+    VHOST_USER_BLK_MAX_WRITE_ZEROES_SECTORS = 32768,
 };
 struct virtio_blk_inhdr {
     unsigned char status;
@@ -58,30 +67,102 @@ static void vu_blk_req_complete(VuBlkReq *req)
     free(req);
 }
 
+static bool vu_blk_sect_range_ok(VuBlkExport *vexp, uint64_t sector,
+                                 size_t size)
+{
+    uint64_t nb_sectors = size >> BDRV_SECTOR_BITS;
+    uint64_t total_sectors;
+
+    if (nb_sectors > BDRV_REQUEST_MAX_SECTORS) {
+        return false;
+    }
+    if ((sector << VIRTIO_BLK_SECTOR_BITS) % vexp->blk_size) {
+        return false;
+    }
+    blk_get_geometry(vexp->export.blk, &total_sectors);
+    if (sector > total_sectors || nb_sectors > total_sectors - sector) {
+        return false;
+    }
+    return true;
+}
+
 static int coroutine_fn
-vu_blk_discard_write_zeroes(BlockBackend *blk, struct iovec *iov,
+vu_blk_discard_write_zeroes(VuBlkExport *vexp, struct iovec *iov,
                             uint32_t iovcnt, uint32_t type)
 {
+    BlockBackend *blk = vexp->export.blk;
     struct virtio_blk_discard_write_zeroes desc;
-    ssize_t size = iov_to_buf(iov, iovcnt, 0, &desc, sizeof(desc));
+    ssize_t size;
+    uint64_t sector;
+    uint32_t num_sectors;
+    uint32_t max_sectors;
+    uint32_t flags;
+    int bytes;
+
+    /* Only one desc is currently supported */
+    if (unlikely(iov_size(iov, iovcnt) > sizeof(desc))) {
+        return VIRTIO_BLK_S_UNSUPP;
+    }
+
+    size = iov_to_buf(iov, iovcnt, 0, &desc, sizeof(desc));
     if (unlikely(size != sizeof(desc))) {
-        error_report("Invalid size %zd, expect %zu", size, sizeof(desc));
-        return -EINVAL;
+        error_report("Invalid size %zd, expected %zu", size, sizeof(desc));
+        return VIRTIO_BLK_S_IOERR;
+    }
+
+    sector = le64_to_cpu(desc.sector);
+    num_sectors = le32_to_cpu(desc.num_sectors);
+    flags = le32_to_cpu(desc.flags);
+    max_sectors = (type == VIRTIO_BLK_T_WRITE_ZEROES) ?
+                  VHOST_USER_BLK_MAX_WRITE_ZEROES_SECTORS :
+                  VHOST_USER_BLK_MAX_DISCARD_SECTORS;
+
+    /* This check ensures that 'bytes' fits in an int */
+    if (unlikely(num_sectors > max_sectors)) {
+        return VIRTIO_BLK_S_IOERR;
     }
 
-    uint64_t range[2] = { le64_to_cpu(desc.sector) << 9,
-                          le32_to_cpu(desc.num_sectors) << 9 };
-    if (type == VIRTIO_BLK_T_DISCARD) {
-        if (blk_co_pdiscard(blk, range[0], range[1]) == 0) {
-            return 0;
+    bytes = num_sectors << VIRTIO_BLK_SECTOR_BITS;
+
+    if (unlikely(!vu_blk_sect_range_ok(vexp, sector, bytes))) {
+        return VIRTIO_BLK_S_IOERR;
+    }
+
+    /*
+     * The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for discard
+     * and write zeroes commands if any unknown flag is set.
+     */
+    if (unlikely(flags & ~VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
+        return VIRTIO_BLK_S_UNSUPP;
+    }
+
+    if (type == VIRTIO_BLK_T_WRITE_ZEROES) {
+        int blk_flags = 0;
+
+        if (flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP) {
+            blk_flags |= BDRV_REQ_MAY_UNMAP;
         }
-    } else if (type == VIRTIO_BLK_T_WRITE_ZEROES) {
-        if (blk_co_pwrite_zeroes(blk, range[0], range[1], 0) == 0) {
-            return 0;
+
+        if (blk_co_pwrite_zeroes(blk, sector << VIRTIO_BLK_SECTOR_BITS,
+                                 bytes, blk_flags) == 0) {
+            return VIRTIO_BLK_S_OK;
+        }
+    } else if (type == VIRTIO_BLK_T_DISCARD) {
+        /*
+         * The device MUST set the status byte to VIRTIO_BLK_S_UNSUPP for
+         * discard commands if the unmap flag is set.
+         */
+        if (unlikely(flags & VIRTIO_BLK_WRITE_ZEROES_FLAG_UNMAP)) {
+            return VIRTIO_BLK_S_UNSUPP;
+        }
+
+        if (blk_co_pdiscard(blk, sector << VIRTIO_BLK_SECTOR_BITS,
+                            bytes) == 0) {
+            return VIRTIO_BLK_S_OK;
         }
     }
 
-    return -EINVAL;
+    return VIRTIO_BLK_S_IOERR;
 }
 
 static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
@@ -128,6 +209,8 @@ static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
     switch (type & ~VIRTIO_BLK_T_BARRIER) {
     case VIRTIO_BLK_T_IN:
     case VIRTIO_BLK_T_OUT: {
+        QEMUIOVector qiov;
+        int64_t offset;
         ssize_t ret = 0;
         bool is_write = type & VIRTIO_BLK_T_OUT;
         req->sector_num = le64_to_cpu(req->out.sector);
@@ -137,13 +220,24 @@ static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
             break;
         }
 
-        int64_t offset = req->sector_num * vexp->blk_size;
-        QEMUIOVector qiov;
         if (is_write) {
             qemu_iovec_init_external(&qiov, out_iov, out_num);
-            ret = blk_co_pwritev(blk, offset, qiov.size, &qiov, 0);
         } else {
             qemu_iovec_init_external(&qiov, in_iov, in_num);
+        }
+
+        if (unlikely(!vu_blk_sect_range_ok(vexp,
+                                           req->sector_num,
+                                           qiov.size))) {
+            req->in->status = VIRTIO_BLK_S_IOERR;
+            break;
+        }
+
+        offset = req->sector_num << VIRTIO_BLK_SECTOR_BITS;
+
+        if (is_write) {
+            ret = blk_co_pwritev(blk, offset, qiov.size, &qiov, 0);
+        } else {
             ret = blk_co_preadv(blk, offset, qiov.size, &qiov, 0);
         }
         if (ret >= 0) {
@@ -170,19 +264,13 @@ static void coroutine_fn vu_blk_virtio_process_req(void *opaque)
     }
     case VIRTIO_BLK_T_DISCARD:
     case VIRTIO_BLK_T_WRITE_ZEROES: {
-        int rc;
-
         if (!vexp->writable) {
             req->in->status = VIRTIO_BLK_S_IOERR;
             break;
         }
 
-        rc = vu_blk_discard_write_zeroes(blk, &elem->out_sg[1], out_num, type);
-        if (rc == 0) {
-            req->in->status = VIRTIO_BLK_S_OK;
-        } else {
-            req->in->status = VIRTIO_BLK_S_IOERR;
-        }
+        req->in->status = vu_blk_discard_write_zeroes(vexp, out_iov, out_num,
+                                                      type);
         break;
     }
     default:
@@ -347,17 +435,21 @@ vu_blk_initialize_config(BlockDriverState *bs,
                          uint32_t blk_size,
                          uint16_t num_queues)
 {
-    config->capacity = cpu_to_le64(bdrv_getlength(bs) >> BDRV_SECTOR_BITS);
+    config->capacity =
+        cpu_to_le64(bdrv_getlength(bs) >> VIRTIO_BLK_SECTOR_BITS);
     config->blk_size = cpu_to_le32(blk_size);
     config->size_max = cpu_to_le32(0);
     config->seg_max = cpu_to_le32(128 - 2);
     config->min_io_size = cpu_to_le16(1);
     config->opt_io_size = cpu_to_le32(1);
     config->num_queues = cpu_to_le16(num_queues);
-    config->max_discard_sectors = cpu_to_le32(32768);
+    config->max_discard_sectors =
+        cpu_to_le32(VHOST_USER_BLK_MAX_DISCARD_SECTORS);
     config->max_discard_seg = cpu_to_le32(1);
-    config->discard_sector_alignment = cpu_to_le32(config->blk_size >> 9);
-    config->max_write_zeroes_sectors = cpu_to_le32(32768);
+    config->discard_sector_alignment =
+        cpu_to_le32(blk_size >> VIRTIO_BLK_SECTOR_BITS);
+    config->max_write_zeroes_sectors
+        = cpu_to_le32(VHOST_USER_BLK_MAX_WRITE_ZEROES_SECTORS);
     config->max_write_zeroes_seg = cpu_to_le32(1);
 }
 
@@ -383,7 +475,7 @@ static int vu_blk_exp_create(BlockExport *exp, BlockExportOptions *opts,
     if (vu_opts->has_logical_block_size) {
         logical_block_size = vu_opts->logical_block_size;
     } else {
-        logical_block_size = BDRV_SECTOR_SIZE;
+        logical_block_size = VIRTIO_BLK_SECTOR_SIZE;
     }
     check_block_size(exp->id, "logical-block-size", logical_block_size,
                      &local_err);
diff --git a/block/meson.build b/block/meson.build
index eeaefe5809..d21990ec95 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -57,7 +57,8 @@ block_ss.add(when: 'CONFIG_QED', if_true: files(
   'qed-table.c',
   'qed.c',
 ))
-block_ss.add(when: [libxml2, 'CONFIG_PARALLELS'], if_true: files('parallels.c'))
+block_ss.add(when: [libxml2, 'CONFIG_PARALLELS'],
+             if_true: files('parallels.c', 'parallels-ext.c'))
 block_ss.add(when: 'CONFIG_WIN32', if_true: files('file-win32.c', 'win32-aio.c'))
 block_ss.add(when: 'CONFIG_POSIX', if_true: [files('file-posix.c'), coref, iokit])
 block_ss.add(when: libiscsi, if_true: files('iscsi-opts.c'))
diff --git a/block/parallels-ext.c b/block/parallels-ext.c
new file mode 100644
index 0000000000..e0dd0975c6
--- /dev/null
+++ b/block/parallels-ext.c
@@ -0,0 +1,300 @@
+/*
+ * Support of Parallels Format Extension. It's a part of Parallels format
+ * driver.
+ *
+ * Copyright (c) 2021 Virtuozzo International GmbH
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "qapi/error.h"
+#include "block/block_int.h"
+#include "parallels.h"
+#include "crypto/hash.h"
+#include "qemu/uuid.h"
+
+#define PARALLELS_FORMAT_EXTENSION_MAGIC 0xAB234CEF23DCEA87ULL
+
+#define PARALLELS_END_OF_FEATURES_MAGIC 0x0ULL
+#define PARALLELS_DIRTY_BITMAP_FEATURE_MAGIC 0x20385FAE252CB34AULL
+
+typedef struct ParallelsFormatExtensionHeader {
+    uint64_t magic; /* PARALLELS_FORMAT_EXTENSION_MAGIC */
+    uint8_t check_sum[16];
+} QEMU_PACKED ParallelsFormatExtensionHeader;
+
+typedef struct ParallelsFeatureHeader {
+    uint64_t magic;
+    uint64_t flags;
+    uint32_t data_size;
+    uint32_t _unused;
+} QEMU_PACKED ParallelsFeatureHeader;
+
+typedef struct ParallelsDirtyBitmapFeature {
+    uint64_t size;
+    uint8_t id[16];
+    uint32_t granularity;
+    uint32_t l1_size;
+    /* L1 table follows */
+} QEMU_PACKED ParallelsDirtyBitmapFeature;
+
+/* Given L1 table read bitmap data from the image and populate @bitmap */
+static int parallels_load_bitmap_data(BlockDriverState *bs,
+                                      const uint64_t *l1_table,
+                                      uint32_t l1_size,
+                                      BdrvDirtyBitmap *bitmap,
+                                      Error **errp)
+{
+    BDRVParallelsState *s = bs->opaque;
+    int ret = 0;
+    uint64_t offset, limit;
+    uint64_t bm_size = bdrv_dirty_bitmap_size(bitmap);
+    uint8_t *buf = NULL;
+    uint64_t i, tab_size =
+        DIV_ROUND_UP(bdrv_dirty_bitmap_serialization_size(bitmap, 0, bm_size),
+                     s->cluster_size);
+
+    if (tab_size != l1_size) {
+        error_setg(errp, "Bitmap table size %" PRIu32 " does not correspond "
+                   "to bitmap size and cluster size. Expected %" PRIu64,
+                   l1_size, tab_size);
+        return -EINVAL;
+    }
+
+    buf = qemu_blockalign(bs, s->cluster_size);
+    limit = bdrv_dirty_bitmap_serialization_coverage(s->cluster_size, bitmap);
+    for (i = 0, offset = 0; i < tab_size; ++i, offset += limit) {
+        uint64_t count = MIN(bm_size - offset, limit);
+        uint64_t entry = l1_table[i];
+
+        if (entry == 0) {
+            /* No need to deserialize zeros because @bitmap is cleared. */
+            continue;
+        }
+
+        if (entry == 1) {
+            bdrv_dirty_bitmap_deserialize_ones(bitmap, offset, count, false);
+        } else {
+            ret = bdrv_pread(bs->file, entry << BDRV_SECTOR_BITS, buf,
+                             s->cluster_size);
+            if (ret < 0) {
+                error_setg_errno(errp, -ret,
+                                 "Failed to read bitmap data cluster");
+                goto finish;
+            }
+            bdrv_dirty_bitmap_deserialize_part(bitmap, buf, offset, count,
+                                               false);
+        }
+    }
+    ret = 0;
+
+    bdrv_dirty_bitmap_deserialize_finish(bitmap);
+
+finish:
+    qemu_vfree(buf);
+
+    return ret;
+}
+
+/*
+ * @data buffer (of @data_size size) is the Dirty bitmaps feature which
+ * consists of ParallelsDirtyBitmapFeature followed by L1 table.
+ */
+static BdrvDirtyBitmap *parallels_load_bitmap(BlockDriverState *bs,
+                                              uint8_t *data,
+                                              size_t data_size,
+                                              Error **errp)
+{
+    int ret;
+    ParallelsDirtyBitmapFeature bf;
+    g_autofree uint64_t *l1_table = NULL;
+    BdrvDirtyBitmap *bitmap;
+    QemuUUID uuid;
+    char uuidstr[UUID_FMT_LEN + 1];
+    int i;
+
+    if (data_size < sizeof(bf)) {
+        error_setg(errp, "Too small Bitmap Feature area in Parallels Format "
+                   "Extension: %zu bytes, expected at least %zu bytes",
+                   data_size, sizeof(bf));
+        return NULL;
+    }
+    memcpy(&bf, data, sizeof(bf));
+    bf.size = le64_to_cpu(bf.size);
+    bf.granularity = le32_to_cpu(bf.granularity) << BDRV_SECTOR_BITS;
+    bf.l1_size = le32_to_cpu(bf.l1_size);
+    data += sizeof(bf);
+    data_size -= sizeof(bf);
+
+    if (bf.size != bs->total_sectors) {
+        error_setg(errp, "Bitmap size (in sectors) %" PRId64 " differs from "
+                   "disk size in sectors %" PRId64, bf.size, bs->total_sectors);
+        return NULL;
+    }
+
+    if (bf.l1_size * sizeof(uint64_t) > data_size) {
+        error_setg(errp, "Bitmaps feature corrupted: l1 table exceeds "
+                   "extension data_size");
+        return NULL;
+    }
+
+    memcpy(&uuid, bf.id, sizeof(uuid));
+    qemu_uuid_unparse(&uuid, uuidstr);
+    bitmap = bdrv_create_dirty_bitmap(bs, bf.granularity, uuidstr, errp);
+    if (!bitmap) {
+        return NULL;
+    }
+
+    l1_table = g_new(uint64_t, bf.l1_size);
+    for (i = 0; i < bf.l1_size; i++, data += sizeof(uint64_t)) {
+        l1_table[i] = ldq_le_p(data);
+    }
+
+    ret = parallels_load_bitmap_data(bs, l1_table, bf.l1_size, bitmap, errp);
+    if (ret < 0) {
+        bdrv_release_dirty_bitmap(bitmap);
+        return NULL;
+    }
+
+    /* We support format extension only for RO parallels images. */
+    assert(!(bs->open_flags & BDRV_O_RDWR));
+    bdrv_dirty_bitmap_set_readonly(bitmap, true);
+
+    return bitmap;
+}
+
+static int parallels_parse_format_extension(BlockDriverState *bs,
+                                            uint8_t *ext_cluster, Error **errp)
+{
+    BDRVParallelsState *s = bs->opaque;
+    int ret;
+    int remaining = s->cluster_size;
+    uint8_t *pos = ext_cluster;
+    ParallelsFormatExtensionHeader eh;
+    g_autofree uint8_t *hash = NULL;
+    size_t hash_len = 0;
+    GSList *bitmaps = NULL, *el;
+
+    memcpy(&eh, pos, sizeof(eh));
+    eh.magic = le64_to_cpu(eh.magic);
+    pos += sizeof(eh);
+    remaining -= sizeof(eh);
+
+    if (eh.magic != PARALLELS_FORMAT_EXTENSION_MAGIC) {
+        error_setg(errp, "Wrong parallels Format Extension magic: 0x%" PRIx64
+                   ", expected: 0x%llx", eh.magic,
+                   PARALLELS_FORMAT_EXTENSION_MAGIC);
+        goto fail;
+    }
+
+    ret = qcrypto_hash_bytes(QCRYPTO_HASH_ALG_MD5, (char *)pos, remaining,
+                             &hash, &hash_len, errp);
+    if (ret < 0) {
+        goto fail;
+    }
+
+    if (hash_len != sizeof(eh.check_sum) ||
+        memcmp(hash, eh.check_sum, sizeof(eh.check_sum)) != 0) {
+        error_setg(errp, "Wrong checksum in Format Extension header. Format "
+                   "extension is corrupted.");
+        goto fail;
+    }
+
+    while (true) {
+        ParallelsFeatureHeader fh;
+        BdrvDirtyBitmap *bitmap;
+
+        if (remaining < sizeof(fh)) {
+            error_setg(errp, "Can not read feature header, as remaining bytes "
+                       "(%d) in Format Extension is less than Feature header "
+                       "size (%zu)", remaining, sizeof(fh));
+            goto fail;
+        }
+
+        memcpy(&fh, pos, sizeof(fh));
+        pos += sizeof(fh);
+        remaining -= sizeof(fh);
+
+        fh.magic = le64_to_cpu(fh.magic);
+        fh.flags = le64_to_cpu(fh.flags);
+        fh.data_size = le32_to_cpu(fh.data_size);
+
+        if (fh.flags) {
+            error_setg(errp, "Flags for extension feature are unsupported");
+            goto fail;
+        }
+
+        if (fh.data_size > remaining) {
+            error_setg(errp, "Feature data_size exceedes Format Extension "
+                       "cluster");
+            goto fail;
+        }
+
+        switch (fh.magic) {
+        case PARALLELS_END_OF_FEATURES_MAGIC:
+            return 0;
+
+        case PARALLELS_DIRTY_BITMAP_FEATURE_MAGIC:
+            bitmap = parallels_load_bitmap(bs, pos, fh.data_size, errp);
+            if (!bitmap) {
+                goto fail;
+            }
+            bitmaps = g_slist_append(bitmaps, bitmap);
+            break;
+
+        default:
+            error_setg(errp, "Unknown feature: 0x%" PRIu64, fh.magic);
+            goto fail;
+        }
+
+        pos = ext_cluster + QEMU_ALIGN_UP(pos + fh.data_size - ext_cluster, 8);
+    }
+
+fail:
+    for (el = bitmaps; el; el = el->next) {
+        bdrv_release_dirty_bitmap(el->data);
+    }
+    g_slist_free(bitmaps);
+
+    return -EINVAL;
+}
+
+int parallels_read_format_extension(BlockDriverState *bs,
+                                    int64_t ext_off, Error **errp)
+{
+    BDRVParallelsState *s = bs->opaque;
+    int ret;
+    uint8_t *ext_cluster = qemu_blockalign(bs, s->cluster_size);
+
+    assert(ext_off > 0);
+
+    ret = bdrv_pread(bs->file, ext_off, ext_cluster, s->cluster_size);
+    if (ret < 0) {
+        error_setg_errno(errp, -ret, "Failed to read Format Extension cluster");
+        goto out;
+    }
+
+    ret = parallels_parse_format_extension(bs, ext_cluster, errp);
+
+out:
+    qemu_vfree(ext_cluster);
+
+    return ret;
+}
diff --git a/block/parallels.c b/block/parallels.c
index 3c22dfdc9d..6ebad2a2bb 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -29,6 +29,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "block/block_int.h"
 #include "block/qdict.h"
@@ -421,7 +422,6 @@ static int coroutine_fn parallels_co_check(BlockDriverState *bs,
     int ret;
     uint32_t i;
     bool flush_bat = false;
-    int cluster_size = s->tracks << BDRV_SECTOR_BITS;
 
     size = bdrv_getlength(bs->file->bs);
     if (size < 0) {
@@ -472,7 +472,7 @@ static int coroutine_fn parallels_co_check(BlockDriverState *bs,
             high_off = off;
         }
 
-        if (prev_off != 0 && (prev_off + cluster_size) != off) {
+        if (prev_off != 0 && (prev_off + s->cluster_size) != off) {
             res->bfi.fragmented_clusters++;
         }
         prev_off = off;
@@ -487,10 +487,10 @@ static int coroutine_fn parallels_co_check(BlockDriverState *bs,
         }
     }
 
-    res->image_end_offset = high_off + cluster_size;
+    res->image_end_offset = high_off + s->cluster_size;
     if (size > res->image_end_offset) {
         int64_t count;
-        count = DIV_ROUND_UP(size - res->image_end_offset, cluster_size);
+        count = DIV_ROUND_UP(size - res->image_end_offset, s->cluster_size);
         fprintf(stderr, "%s space leaked at the end of the image %" PRId64 "\n",
                 fix & BDRV_FIX_LEAKS ? "Repairing" : "ERROR",
                 size - res->image_end_offset);
@@ -771,6 +771,7 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
         ret = -EFBIG;
         goto fail;
     }
+    s->cluster_size = s->tracks << BDRV_SECTOR_BITS;
 
     s->bat_size = le32_to_cpu(ph.bat_entries);
     if (s->bat_size > INT_MAX / sizeof(uint32_t)) {
@@ -843,6 +844,23 @@ static int parallels_open(BlockDriverState *bs, QDict *options, int flags,
         goto fail_options;
     }
 
+    if (ph.ext_off) {
+        if (flags & BDRV_O_RDWR) {
+            /*
+             * It's unsafe to open image RW if there is an extension (as we
+             * don't support it). But parallels driver in QEMU historically
+             * ignores the extension, so print warning and don't care.
+             */
+            warn_report("Format Extension ignored in RW mode");
+        } else {
+            ret = parallels_read_format_extension(
+                    bs, le64_to_cpu(ph.ext_off) << BDRV_SECTOR_BITS, errp);
+            if (ret < 0) {
+                goto fail;
+            }
+        }
+    }
+
     if ((flags & BDRV_O_RDWR) && !(flags & BDRV_O_INACTIVE)) {
         s->header->inuse = cpu_to_le32(HEADER_INUSE_MAGIC);
         ret = parallels_update_header(bs);
diff --git a/block/parallels.h b/block/parallels.h
index 5aa101cfc8..f22f43f988 100644
--- a/block/parallels.h
+++ b/block/parallels.h
@@ -48,7 +48,8 @@ typedef struct ParallelsHeader {
     uint64_t nb_sectors;
     uint32_t inuse;
     uint32_t data_off;
-    char padding[12];
+    uint32_t flags;
+    uint64_t ext_off;
 } QEMU_PACKED ParallelsHeader;
 
 typedef enum ParallelsPreallocMode {
@@ -79,9 +80,13 @@ typedef struct BDRVParallelsState {
     ParallelsPreallocMode prealloc_mode;
 
     unsigned int tracks;
+    unsigned int cluster_size;
 
     unsigned int off_multiplier;
     Error *migration_blocker;
 } BDRVParallelsState;
 
+int parallels_read_format_extension(BlockDriverState *bs,
+                                    int64_t ext_off, Error **errp);
+
 #endif
diff --git a/block/qcow2-bitmap.c b/block/qcow2-bitmap.c
index 5eef82fa55..42d81c44cd 100644
--- a/block/qcow2-bitmap.c
+++ b/block/qcow2-bitmap.c
@@ -278,18 +278,6 @@ static int free_bitmap_clusters(BlockDriverState *bs, Qcow2BitmapTable *tb)
     return 0;
 }
 
-/* Return the disk size covered by a single qcow2 cluster of bitmap data. */
-static uint64_t bytes_covered_by_bitmap_cluster(const BDRVQcow2State *s,
-                                                const BdrvDirtyBitmap *bitmap)
-{
-    uint64_t granularity = bdrv_dirty_bitmap_granularity(bitmap);
-    uint64_t limit = granularity * (s->cluster_size << 3);
-
-    assert(QEMU_IS_ALIGNED(limit,
-                           bdrv_dirty_bitmap_serialization_align(bitmap)));
-    return limit;
-}
-
 /* load_bitmap_data
  * @bitmap_table entries must satisfy specification constraints.
  * @bitmap must be cleared */
@@ -312,7 +300,7 @@ static int load_bitmap_data(BlockDriverState *bs,
     }
 
     buf = g_malloc(s->cluster_size);
-    limit = bytes_covered_by_bitmap_cluster(s, bitmap);
+    limit = bdrv_dirty_bitmap_serialization_coverage(s->cluster_size, bitmap);
     for (i = 0, offset = 0; i < tab_size; ++i, offset += limit) {
         uint64_t count = MIN(bm_size - offset, limit);
         uint64_t entry = bitmap_table[i];
@@ -1303,7 +1291,7 @@ static uint64_t *store_bitmap_data(BlockDriverState *bs,
     }
 
     buf = g_malloc(s->cluster_size);
-    limit = bytes_covered_by_bitmap_cluster(s, bitmap);
+    limit = bdrv_dirty_bitmap_serialization_coverage(s->cluster_size, bitmap);
     assert(DIV_ROUND_UP(bm_size, limit) == tb_size);
 
     offset = 0;