diff --git a/backends/cryptodev-vhost.c b/backends/cryptodev-vhost.c
index 8231e7f1bc..bc13e466b4 100644
--- a/backends/cryptodev-vhost.c
+++ b/backends/cryptodev-vhost.c
@@ -52,6 +52,7 @@ cryptodev_vhost_init(
 {
     int r;
     CryptoDevBackendVhost *crypto;
+    Error *local_err = NULL;
 
     crypto = g_new(CryptoDevBackendVhost, 1);
     crypto->dev.max_queues = 1;
@@ -66,8 +67,10 @@ cryptodev_vhost_init(
     /* vhost-user needs vq_index to initiate a specific queue pair */
     crypto->dev.vq_index = crypto->cc->queue_index * crypto->dev.nvqs;
 
-    r = vhost_dev_init(&crypto->dev, options->opaque, options->backend_type, 0);
+    r = vhost_dev_init(&crypto->dev, options->opaque, options->backend_type, 0,
+                       &local_err);
     if (r < 0) {
+        error_report_err(local_err);
         goto fail;
     }
 
diff --git a/backends/vhost-user.c b/backends/vhost-user.c
index b366610e16..10b39992d2 100644
--- a/backends/vhost-user.c
+++ b/backends/vhost-user.c
@@ -48,9 +48,9 @@ vhost_user_backend_dev_init(VhostUserBackend *b, VirtIODevice *vdev,
     b->dev.nvqs = nvqs;
     b->dev.vqs = g_new0(struct vhost_virtqueue, nvqs);
 
-    ret = vhost_dev_init(&b->dev, &b->vhost_user, VHOST_BACKEND_TYPE_USER, 0);
+    ret = vhost_dev_init(&b->dev, &b->vhost_user, VHOST_BACKEND_TYPE_USER, 0,
+                         errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "vhost initialization failed");
         return -1;
     }
 
diff --git a/block.c b/block.c
index 1d37f133a8..acd35cb0cb 100644
--- a/block.c
+++ b/block.c
@@ -84,12 +84,15 @@ static BlockDriverState *bdrv_open_inherit(const char *filename,
 
 static void bdrv_replace_child_noperm(BdrvChild *child,
                                       BlockDriverState *new_bs);
+static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
+                                              BdrvChild *child,
+                                              Transaction *tran);
 static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
                                             Transaction *tran);
 
 static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
                                BlockReopenQueue *queue,
-                               Transaction *set_backings_tran, Error **errp);
+                               Transaction *change_child_tran, Error **errp);
 static void bdrv_reopen_commit(BDRVReopenState *reopen_state);
 static void bdrv_reopen_abort(BDRVReopenState *reopen_state);
 
@@ -2249,12 +2252,14 @@ static TransactionActionDrv bdrv_replace_child_drv = {
 };
 
 /*
- * bdrv_replace_child
+ * bdrv_replace_child_tran
  *
  * Note: real unref of old_bs is done only on commit.
+ *
+ * The function doesn't update permissions, caller is responsible for this.
  */
-static void bdrv_replace_child(BdrvChild *child, BlockDriverState *new_bs,
-                               Transaction *tran)
+static void bdrv_replace_child_tran(BdrvChild *child, BlockDriverState *new_bs,
+                                    Transaction *tran)
 {
     BdrvReplaceChildState *s = g_new(BdrvReplaceChildState, 1);
     *s = (BdrvReplaceChildState) {
@@ -2768,6 +2773,8 @@ static TransactionActionDrv bdrv_attach_child_common_drv = {
  * @child is saved to a new entry of @tran, so that *@child could be reverted to
  * NULL on abort(). So referenced variable must live at least until transaction
  * end.
+ *
+ * Function doesn't update permissions, caller is responsible for this.
  */
 static int bdrv_attach_child_common(BlockDriverState *child_bs,
                                     const char *child_name,
@@ -2846,6 +2853,8 @@ static int bdrv_attach_child_common(BlockDriverState *child_bs,
 /*
  * Variable referenced by @child must live at least until transaction end.
  * (see bdrv_attach_child_common() doc for details)
+ *
+ * Function doesn't update permissions, caller is responsible for this.
  */
 static int bdrv_attach_child_noperm(BlockDriverState *parent_bs,
                                     BlockDriverState *child_bs,
@@ -3111,54 +3120,104 @@ static BdrvChildRole bdrv_backing_role(BlockDriverState *bs)
 }
 
 /*
- * Sets the bs->backing link of a BDS. A new reference is created; callers
- * which don't need their own reference any more must call bdrv_unref().
+ * Sets the bs->backing or bs->file link of a BDS. A new reference is created;
+ * callers which don't need their own reference any more must call bdrv_unref().
+ *
+ * Function doesn't update permissions, caller is responsible for this.
  */
-static int bdrv_set_backing_noperm(BlockDriverState *bs,
-                                   BlockDriverState *backing_hd,
-                                   Transaction *tran, Error **errp)
+static int bdrv_set_file_or_backing_noperm(BlockDriverState *parent_bs,
+                                           BlockDriverState *child_bs,
+                                           bool is_backing,
+                                           Transaction *tran, Error **errp)
 {
     int ret = 0;
-    bool update_inherits_from = bdrv_chain_contains(bs, backing_hd) &&
-        bdrv_inherits_from_recursive(backing_hd, bs);
+    bool update_inherits_from =
+        bdrv_inherits_from_recursive(child_bs, parent_bs);
+    BdrvChild *child = is_backing ? parent_bs->backing : parent_bs->file;
+    BdrvChildRole role;
 
-    if (bdrv_is_backing_chain_frozen(bs, child_bs(bs->backing), errp)) {
+    if (!parent_bs->drv) {
+        /*
+         * Node without drv is an object without a class :/. TODO: finally fix
+         * qcow2 driver to never clear bs->drv and implement format corruption
+         * handling in other way.
+         */
+        error_setg(errp, "Node corrupted");
+        return -EINVAL;
+    }
+
+    if (child && child->frozen) {
+        error_setg(errp, "Cannot change frozen '%s' link from '%s' to '%s'",
+                   child->name, parent_bs->node_name, child->bs->node_name);
         return -EPERM;
     }
 
-    if (bs->backing) {
-        /* Cannot be frozen, we checked that above */
-        bdrv_unset_inherits_from(bs, bs->backing, tran);
-        bdrv_remove_filter_or_cow_child(bs, tran);
+    if (is_backing && !parent_bs->drv->is_filter &&
+        !parent_bs->drv->supports_backing)
+    {
+        error_setg(errp, "Driver '%s' of node '%s' does not support backing "
+                   "files", parent_bs->drv->format_name, parent_bs->node_name);
+        return -EINVAL;
     }
 
-    if (!backing_hd) {
+    if (parent_bs->drv->is_filter) {
+        role = BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY;
+    } else if (is_backing) {
+        role = BDRV_CHILD_COW;
+    } else {
+        /*
+         * We only can use same role as it is in existing child. We don't have
+         * infrastructure to determine role of file child in generic way
+         */
+        if (!child) {
+            error_setg(errp, "Cannot set file child to format node without "
+                       "file child");
+            return -EINVAL;
+        }
+        role = child->role;
+    }
+
+    if (child) {
+        bdrv_unset_inherits_from(parent_bs, child, tran);
+        bdrv_remove_file_or_backing_child(parent_bs, child, tran);
+    }
+
+    if (!child_bs) {
         goto out;
     }
 
-    ret = bdrv_attach_child_noperm(bs, backing_hd, "backing",
-                                   &child_of_bds, bdrv_backing_role(bs),
-                                   &bs->backing, tran, errp);
+    ret = bdrv_attach_child_noperm(parent_bs, child_bs,
+                                   is_backing ? "backing" : "file",
+                                   &child_of_bds, role,
+                                   is_backing ? &parent_bs->backing :
+                                                &parent_bs->file,
+                                   tran, errp);
     if (ret < 0) {
         return ret;
     }
 
 
     /*
-     * If backing_hd was already part of bs's backing chain, and
-     * inherits_from pointed recursively to bs then let's update it to
+     * If inherits_from pointed recursively to bs then let's update it to
      * point directly to bs (else it will become NULL).
      */
     if (update_inherits_from) {
-        bdrv_set_inherits_from(backing_hd, bs, tran);
+        bdrv_set_inherits_from(child_bs, parent_bs, tran);
     }
 
 out:
-    bdrv_refresh_limits(bs, tran, NULL);
+    bdrv_refresh_limits(parent_bs, tran, NULL);
 
     return 0;
 }
 
+static int bdrv_set_backing_noperm(BlockDriverState *bs,
+                                   BlockDriverState *backing_hd,
+                                   Transaction *tran, Error **errp)
+{
+    return bdrv_set_file_or_backing_noperm(bs, backing_hd, true, tran, errp);
+}
+
 int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
                         Error **errp)
 {
@@ -4089,6 +4148,10 @@ int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
             refresh_list = bdrv_topological_dfs(refresh_list, found,
                                                 state->old_backing_bs);
         }
+        if (state->old_file_bs) {
+            refresh_list = bdrv_topological_dfs(refresh_list, found,
+                                                state->old_file_bs);
+        }
     }
 
     /*
@@ -4164,29 +4227,6 @@ int bdrv_reopen_set_read_only(BlockDriverState *bs, bool read_only,
     return ret;
 }
 
-static bool bdrv_reopen_can_attach(BlockDriverState *parent,
-                                   BdrvChild *child,
-                                   BlockDriverState *new_child,
-                                   Error **errp)
-{
-    AioContext *parent_ctx = bdrv_get_aio_context(parent);
-    AioContext *child_ctx = bdrv_get_aio_context(new_child);
-    GSList *ignore;
-    bool ret;
-
-    ignore = g_slist_prepend(NULL, child);
-    ret = bdrv_can_set_aio_context(new_child, parent_ctx, &ignore, NULL);
-    g_slist_free(ignore);
-    if (ret) {
-        return ret;
-    }
-
-    ignore = g_slist_prepend(NULL, child);
-    ret = bdrv_can_set_aio_context(parent, child_ctx, &ignore, errp);
-    g_slist_free(ignore);
-    return ret;
-}
-
 /*
  * Take a BDRVReopenState and check if the value of 'backing' in the
  * reopen_state->options QDict is valid or not.
@@ -4204,115 +4244,81 @@ static bool bdrv_reopen_can_attach(BlockDriverState *parent,
  *
  * Return 0 on success, otherwise return < 0 and set @errp.
  */
-static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state,
-                                     Transaction *set_backings_tran,
-                                     Error **errp)
+static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
+                                             bool is_backing, Transaction *tran,
+                                             Error **errp)
 {
     BlockDriverState *bs = reopen_state->bs;
-    BlockDriverState *overlay_bs, *below_bs, *new_backing_bs;
+    BlockDriverState *new_child_bs;
+    BlockDriverState *old_child_bs = is_backing ? child_bs(bs->backing) :
+                                                  child_bs(bs->file);
+    const char *child_name = is_backing ? "backing" : "file";
     QObject *value;
     const char *str;
 
-    value = qdict_get(reopen_state->options, "backing");
+    value = qdict_get(reopen_state->options, child_name);
     if (value == NULL) {
         return 0;
     }
 
     switch (qobject_type(value)) {
     case QTYPE_QNULL:
-        new_backing_bs = NULL;
+        assert(is_backing); /* The 'file' option does not allow a null value */
+        new_child_bs = NULL;
         break;
     case QTYPE_QSTRING:
         str = qstring_get_str(qobject_to(QString, value));
-        new_backing_bs = bdrv_lookup_bs(NULL, str, errp);
-        if (new_backing_bs == NULL) {
+        new_child_bs = bdrv_lookup_bs(NULL, str, errp);
+        if (new_child_bs == NULL) {
             return -EINVAL;
-        } else if (bdrv_recurse_has_child(new_backing_bs, bs)) {
-            error_setg(errp, "Making '%s' a backing file of '%s' "
-                       "would create a cycle", str, bs->node_name);
+        } else if (bdrv_recurse_has_child(new_child_bs, bs)) {
+            error_setg(errp, "Making '%s' a %s child of '%s' would create a "
+                       "cycle", str, child_name, bs->node_name);
             return -EINVAL;
         }
         break;
     default:
-        /* 'backing' does not allow any other data type */
+        /*
+         * The options QDict has been flattened, so 'backing' and 'file'
+         * do not allow any other data type here.
+         */
         g_assert_not_reached();
     }
 
-    /*
-     * Check AioContext compatibility so that the bdrv_set_backing_hd() call in
-     * bdrv_reopen_commit() won't fail.
-     */
-    if (new_backing_bs) {
-        if (!bdrv_reopen_can_attach(bs, bs->backing, new_backing_bs, errp)) {
-            return -EINVAL;
+    if (old_child_bs == new_child_bs) {
+        return 0;
+    }
+
+    if (old_child_bs) {
+        if (bdrv_skip_implicit_filters(old_child_bs) == new_child_bs) {
+            return 0;
+        }
+
+        if (old_child_bs->implicit) {
+            error_setg(errp, "Cannot replace implicit %s child of %s",
+                       child_name, bs->node_name);
+            return -EPERM;
         }
     }
 
-    /*
-     * Ensure that @bs can really handle backing files, because we are
-     * about to give it one (or swap the existing one)
-     */
-    if (bs->drv->is_filter) {
-        /* Filters always have a file or a backing child */
-        if (!bs->backing) {
-            error_setg(errp, "'%s' is a %s filter node that does not support a "
-                       "backing child", bs->node_name, bs->drv->format_name);
-            return -EINVAL;
-        }
-    } else if (!bs->drv->supports_backing) {
-        error_setg(errp, "Driver '%s' of node '%s' does not support backing "
-                   "files", bs->drv->format_name, bs->node_name);
+    if (bs->drv->is_filter && !old_child_bs) {
+        /*
+         * Filters always have a file or a backing child, so we are trying to
+         * change wrong child
+         */
+        error_setg(errp, "'%s' is a %s filter node that does not support a "
+                   "%s child", bs->node_name, bs->drv->format_name, child_name);
         return -EINVAL;
     }
 
-    /*
-     * Find the "actual" backing file by skipping all links that point
-     * to an implicit node, if any (e.g. a commit filter node).
-     * We cannot use any of the bdrv_skip_*() functions here because
-     * those return the first explicit node, while we are looking for
-     * its overlay here.
-     */
-    overlay_bs = bs;
-    for (below_bs = bdrv_filter_or_cow_bs(overlay_bs);
-         below_bs && below_bs->implicit;
-         below_bs = bdrv_filter_or_cow_bs(overlay_bs))
-    {
-        overlay_bs = below_bs;
+    if (is_backing) {
+        reopen_state->old_backing_bs = old_child_bs;
+    } else {
+        reopen_state->old_file_bs = old_child_bs;
     }
 
-    /* If we want to replace the backing file we need some extra checks */
-    if (new_backing_bs != bdrv_filter_or_cow_bs(overlay_bs)) {
-        int ret;
-
-        /* Check for implicit nodes between bs and its backing file */
-        if (bs != overlay_bs) {
-            error_setg(errp, "Cannot change backing link if '%s' has "
-                       "an implicit backing file", bs->node_name);
-            return -EPERM;
-        }
-        /*
-         * Check if the backing link that we want to replace is frozen.
-         * Note that
-         * bdrv_filter_or_cow_child(overlay_bs) == overlay_bs->backing,
-         * because we know that overlay_bs == bs, and that @bs
-         * either is a filter that uses ->backing or a COW format BDS
-         * with bs->drv->supports_backing == true.
-         */
-        if (bdrv_is_backing_chain_frozen(overlay_bs,
-                                         child_bs(overlay_bs->backing), errp))
-        {
-            return -EPERM;
-        }
-        reopen_state->replace_backing_bs = true;
-        reopen_state->old_backing_bs = bs->backing ? bs->backing->bs : NULL;
-        ret = bdrv_set_backing_noperm(bs, new_backing_bs, set_backings_tran,
-                                      errp);
-        if (ret < 0) {
-            return ret;
-        }
-    }
-
-    return 0;
+    return bdrv_set_file_or_backing_noperm(bs, new_child_bs, is_backing,
+                                           tran, errp);
 }
 
 /*
@@ -4334,7 +4340,7 @@ static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state,
  */
 static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
                                BlockReopenQueue *queue,
-                               Transaction *set_backings_tran, Error **errp)
+                               Transaction *change_child_tran, Error **errp)
 {
     int ret = -1;
     int old_flags;
@@ -4454,12 +4460,21 @@ static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
      * either a reference to an existing node (using its node name)
      * or NULL to simply detach the current backing file.
      */
-    ret = bdrv_reopen_parse_backing(reopen_state, set_backings_tran, errp);
+    ret = bdrv_reopen_parse_file_or_backing(reopen_state, true,
+                                            change_child_tran, errp);
     if (ret < 0) {
         goto error;
     }
     qdict_del(reopen_state->options, "backing");
 
+    /* Allow changing the 'file' option. In this case NULL is not allowed */
+    ret = bdrv_reopen_parse_file_or_backing(reopen_state, false,
+                                            change_child_tran, errp);
+    if (ret < 0) {
+        goto error;
+    }
+    qdict_del(reopen_state->options, "file");
+
     /* Options that are not handled are only okay if they are unchanged
      * compared to the old state. It is expected that some options are only
      * used for the initial open, but not reopen (e.g. filename) */
@@ -4564,17 +4579,16 @@ static void bdrv_reopen_commit(BDRVReopenState *reopen_state)
     bs->open_flags         = reopen_state->flags;
     bs->detect_zeroes      = reopen_state->detect_zeroes;
 
-    if (reopen_state->replace_backing_bs) {
-        qdict_del(bs->explicit_options, "backing");
-        qdict_del(bs->options, "backing");
-    }
-
     /* Remove child references from bs->options and bs->explicit_options.
      * Child options were already removed in bdrv_reopen_queue_child() */
     QLIST_FOREACH(child, &bs->children, next) {
         qdict_del(bs->explicit_options, child->name);
         qdict_del(bs->options, child->name);
     }
+    /* backing is probably removed, so it's not handled by previous loop */
+    qdict_del(bs->explicit_options, "backing");
+    qdict_del(bs->options, "backing");
+
     bdrv_refresh_limits(bs, NULL, NULL);
 }
 
@@ -4766,7 +4780,7 @@ static void bdrv_remove_filter_or_cow_child_abort(void *opaque)
     }
 
     /*
-     * We don't have to restore child->bs here to undo bdrv_replace_child()
+     * We don't have to restore child->bs here to undo bdrv_replace_child_tran()
      * because that function is transactionable and it registered own completion
      * entries in @tran, so .abort() for bdrv_replace_child_safe() will be
      * called automatically.
@@ -4787,22 +4801,23 @@ static TransactionActionDrv bdrv_remove_filter_or_cow_child_drv = {
 };
 
 /*
- * A function to remove backing-chain child of @bs if exists: cow child for
- * format nodes (always .backing) and filter child for filters (may be .file or
- * .backing)
+ * A function to remove backing or file child of @bs.
+ * Function doesn't update permissions, caller is responsible for this.
  */
-static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
-                                            Transaction *tran)
+static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
+                                              BdrvChild *child,
+                                              Transaction *tran)
 {
     BdrvRemoveFilterOrCowChild *s;
-    BdrvChild *child = bdrv_filter_or_cow_child(bs);
+
+    assert(child == bs->backing || child == bs->file);
 
     if (!child) {
         return;
     }
 
     if (child->bs) {
-        bdrv_replace_child(child, NULL, tran);
+        bdrv_replace_child_tran(child, NULL, tran);
     }
 
     s = g_new(BdrvRemoveFilterOrCowChild, 1);
@@ -4820,6 +4835,17 @@ static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
     }
 }
 
+/*
+ * A function to remove backing-chain child of @bs if exists: cow child for
+ * format nodes (always .backing) and filter child for filters (may be .file or
+ * .backing)
+ */
+static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
+                                            Transaction *tran)
+{
+    bdrv_remove_file_or_backing_child(bs, bdrv_filter_or_cow_child(bs), tran);
+}
+
 static int bdrv_replace_node_noperm(BlockDriverState *from,
                                     BlockDriverState *to,
                                     bool auto_skip, Transaction *tran,
@@ -4842,7 +4868,7 @@ static int bdrv_replace_node_noperm(BlockDriverState *from,
                        c->name, from->node_name);
             return -EPERM;
         }
-        bdrv_replace_child(c, to, tran);
+        bdrv_replace_child_tran(c, to, tran);
     }
 
     return 0;
@@ -4866,7 +4892,7 @@ static int bdrv_replace_node_common(BlockDriverState *from,
     Transaction *tran = tran_new();
     g_autoptr(GHashTable) found = NULL;
     g_autoptr(GSList) refresh_list = NULL;
-    BlockDriverState *to_cow_parent;
+    BlockDriverState *to_cow_parent = NULL;
     int ret;
 
     if (detach_subchain) {
@@ -6553,9 +6579,13 @@ void bdrv_img_create(const char *filename, const char *fmt,
         }
         assert(full_backing);
 
-        /* backing files always opened read-only */
+        /*
+         * No need to do I/O here, which allows us to open encrypted
+         * backing images without needing the secret
+         */
         back_flags = flags;
         back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
+        back_flags |= BDRV_O_NO_IO;
 
         backing_options = qdict_new();
         if (backing_fmt) {
diff --git a/block/commit.c b/block/commit.c
index b7f0c7c061..42792b4556 100644
--- a/block/commit.c
+++ b/block/commit.c
@@ -119,24 +119,24 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
     uint64_t delay_ns = 0;
     int ret = 0;
     int64_t n = 0; /* bytes */
-    void *buf = NULL;
+    QEMU_AUTO_VFREE void *buf = NULL;
     int64_t len, base_len;
 
-    ret = len = blk_getlength(s->top);
+    len = blk_getlength(s->top);
     if (len < 0) {
-        goto out;
+        return len;
     }
     job_progress_set_remaining(&s->common.job, len);
 
-    ret = base_len = blk_getlength(s->base);
+    base_len = blk_getlength(s->base);
     if (base_len < 0) {
-        goto out;
+        return base_len;
     }
 
     if (base_len < len) {
         ret = blk_truncate(s->base, len, false, PREALLOC_MODE_OFF, 0, NULL);
         if (ret) {
-            goto out;
+            return ret;
         }
     }
 
@@ -174,7 +174,7 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
                 block_job_error_action(&s->common, s->on_error,
                                        error_in_source, -ret);
             if (action == BLOCK_ERROR_ACTION_REPORT) {
-                goto out;
+                return ret;
             } else {
                 n = 0;
                 continue;
@@ -190,12 +190,7 @@ static int coroutine_fn commit_run(Job *job, Error **errp)
         }
     }
 
-    ret = 0;
-
-out:
-    qemu_vfree(buf);
-
-    return ret;
+    return 0;
 }
 
 static const BlockJobDriver commit_job_driver = {
@@ -435,7 +430,7 @@ int bdrv_commit(BlockDriverState *bs)
     int ro;
     int64_t n;
     int ret = 0;
-    uint8_t *buf = NULL;
+    QEMU_AUTO_VFREE uint8_t *buf = NULL;
     Error *local_err = NULL;
 
     if (!drv)
@@ -556,8 +551,6 @@ int bdrv_commit(BlockDriverState *bs)
 
     ret = 0;
 ro_cleanup:
-    qemu_vfree(buf);
-
     blk_unref(backing);
     if (bdrv_cow_bs(bs) != backing_file_bs) {
         bdrv_set_backing_hd(bs, backing_file_bs, &error_abort);
diff --git a/block/io.c b/block/io.c
index dd93364258..cf177a9d2d 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3392,6 +3392,11 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
         return old_size;
     }
 
+    if (bdrv_is_read_only(bs)) {
+        error_setg(errp, "Image is read-only");
+        return -EACCES;
+    }
+
     if (offset > old_size) {
         new_bytes = offset - old_size;
     } else {
@@ -3408,11 +3413,6 @@ int coroutine_fn bdrv_co_truncate(BdrvChild *child, int64_t offset, bool exact,
     if (new_bytes) {
         bdrv_make_request_serialising(&req, 1);
     }
-    if (bdrv_is_read_only(bs)) {
-        error_setg(errp, "Image is read-only");
-        ret = -EACCES;
-        goto out;
-    }
     ret = bdrv_co_write_req_prepare(child, offset - new_bytes, new_bytes, &req,
                                     0);
     if (ret < 0) {
diff --git a/block/ssh.c b/block/ssh.c
index b51a031620..d008caf059 100644
--- a/block/ssh.c
+++ b/block/ssh.c
@@ -442,6 +442,9 @@ static int check_host_key(BDRVSSHState *s, SshHostKeyCheck *hkc, Error **errp)
         } else if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_SHA1) {
             return check_host_key_hash(s, hkc->u.hash.hash,
                                        SSH_PUBLICKEY_HASH_SHA1, errp);
+        } else if (hkc->u.hash.type == SSH_HOST_KEY_CHECK_HASH_TYPE_SHA256) {
+            return check_host_key_hash(s, hkc->u.hash.hash,
+                                       SSH_PUBLICKEY_HASH_SHA256, errp);
         }
         g_assert_not_reached();
         break;
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index c6210fad0c..ba13cb87e5 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -31,6 +31,8 @@
 #include "sysemu/sysemu.h"
 #include "sysemu/runstate.h"
 
+#define REALIZE_CONNECTION_RETRIES 3
+
 static const int user_feature_bits[] = {
     VIRTIO_BLK_F_SIZE_MAX,
     VIRTIO_BLK_F_SEG_MAX,
@@ -91,11 +93,13 @@ static int vhost_user_blk_handle_config_change(struct vhost_dev *dev)
     int ret;
     struct virtio_blk_config blkcfg;
     VHostUserBlk *s = VHOST_USER_BLK(dev->vdev);
+    Error *local_err = NULL;
 
     ret = vhost_dev_get_config(dev, (uint8_t *)&blkcfg,
-                               sizeof(struct virtio_blk_config));
+                               sizeof(struct virtio_blk_config),
+                               &local_err);
     if (ret < 0) {
-        error_report("get config space failed");
+        error_report_err(local_err);
         return -1;
     }
 
@@ -113,7 +117,7 @@ const VhostDevConfigOps blk_ops = {
     .vhost_dev_config_notifier = vhost_user_blk_handle_config_change,
 };
 
-static int vhost_user_blk_start(VirtIODevice *vdev)
+static int vhost_user_blk_start(VirtIODevice *vdev, Error **errp)
 {
     VHostUserBlk *s = VHOST_USER_BLK(vdev);
     BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
@@ -121,19 +125,19 @@ static int vhost_user_blk_start(VirtIODevice *vdev)
     int i, ret;
 
     if (!k->set_guest_notifiers) {
-        error_report("binding does not support guest notifiers");
+        error_setg(errp, "binding does not support guest notifiers");
         return -ENOSYS;
     }
 
     ret = vhost_dev_enable_notifiers(&s->dev, vdev);
     if (ret < 0) {
-        error_report("Error enabling host notifiers: %d", -ret);
+        error_setg_errno(errp, -ret, "Error enabling host notifiers");
         return ret;
     }
 
     ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, true);
     if (ret < 0) {
-        error_report("Error binding guest notifier: %d", -ret);
+        error_setg_errno(errp, -ret, "Error binding guest notifier");
         goto err_host_notifiers;
     }
 
@@ -141,27 +145,27 @@ static int vhost_user_blk_start(VirtIODevice *vdev)
 
     ret = vhost_dev_prepare_inflight(&s->dev, vdev);
     if (ret < 0) {
-        error_report("Error set inflight format: %d", -ret);
+        error_setg_errno(errp, -ret, "Error setting inflight format");
         goto err_guest_notifiers;
     }
 
     if (!s->inflight->addr) {
         ret = vhost_dev_get_inflight(&s->dev, s->queue_size, s->inflight);
         if (ret < 0) {
-            error_report("Error get inflight: %d", -ret);
+            error_setg_errno(errp, -ret, "Error getting inflight");
             goto err_guest_notifiers;
         }
     }
 
     ret = vhost_dev_set_inflight(&s->dev, s->inflight);
     if (ret < 0) {
-        error_report("Error set inflight: %d", -ret);
+        error_setg_errno(errp, -ret, "Error setting inflight");
         goto err_guest_notifiers;
     }
 
     ret = vhost_dev_start(&s->dev, vdev);
     if (ret < 0) {
-        error_report("Error starting vhost: %d", -ret);
+        error_setg_errno(errp, -ret, "Error starting vhost");
         goto err_guest_notifiers;
     }
     s->started_vu = true;
@@ -214,6 +218,7 @@ static void vhost_user_blk_set_status(VirtIODevice *vdev, uint8_t status)
 {
     VHostUserBlk *s = VHOST_USER_BLK(vdev);
     bool should_start = virtio_device_started(vdev, status);
+    Error *local_err = NULL;
     int ret;
 
     if (!vdev->vm_running) {
@@ -229,10 +234,9 @@ static void vhost_user_blk_set_status(VirtIODevice *vdev, uint8_t status)
     }
 
     if (should_start) {
-        ret = vhost_user_blk_start(vdev);
+        ret = vhost_user_blk_start(vdev, &local_err);
         if (ret < 0) {
-            error_report("vhost-user-blk: vhost start failed: %s",
-                         strerror(-ret));
+            error_reportf_err(local_err, "vhost-user-blk: vhost start failed: ");
             qemu_chr_fe_disconnect(&s->chardev);
         }
     } else {
@@ -270,6 +274,7 @@ static uint64_t vhost_user_blk_get_features(VirtIODevice *vdev,
 static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
 {
     VHostUserBlk *s = VHOST_USER_BLK(vdev);
+    Error *local_err = NULL;
     int i, ret;
 
     if (!vdev->start_on_kick) {
@@ -287,10 +292,9 @@ static void vhost_user_blk_handle_output(VirtIODevice *vdev, VirtQueue *vq)
     /* Some guests kick before setting VIRTIO_CONFIG_S_DRIVER_OK so start
      * vhost here instead of waiting for .set_status().
      */
-    ret = vhost_user_blk_start(vdev);
+    ret = vhost_user_blk_start(vdev, &local_err);
     if (ret < 0) {
-        error_report("vhost-user-blk: vhost start failed: %s",
-                     strerror(-ret));
+        error_reportf_err(local_err, "vhost-user-blk: vhost start failed: ");
         qemu_chr_fe_disconnect(&s->chardev);
         return;
     }
@@ -332,17 +336,16 @@ static int vhost_user_blk_connect(DeviceState *dev, Error **errp)
 
     vhost_dev_set_config_notifier(&s->dev, &blk_ops);
 
-    ret = vhost_dev_init(&s->dev, &s->vhost_user, VHOST_BACKEND_TYPE_USER, 0);
+    ret = vhost_dev_init(&s->dev, &s->vhost_user, VHOST_BACKEND_TYPE_USER, 0,
+                         errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "vhost initialization failed");
         return ret;
     }
 
     /* restore vhost state */
     if (virtio_device_started(vdev, vdev->status)) {
-        ret = vhost_user_blk_start(vdev);
+        ret = vhost_user_blk_start(vdev, errp);
         if (ret < 0) {
-            error_setg_errno(errp, -ret, "vhost start failed");
             return ret;
         }
     }
@@ -422,10 +425,42 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event)
     }
 }
 
+static int vhost_user_blk_realize_connect(VHostUserBlk *s, Error **errp)
+{
+    DeviceState *dev = &s->parent_obj.parent_obj;
+    int ret;
+
+    s->connected = false;
+
+    ret = qemu_chr_fe_wait_connected(&s->chardev, errp);
+    if (ret < 0) {
+        return ret;
+    }
+
+    ret = vhost_user_blk_connect(dev, errp);
+    if (ret < 0) {
+        qemu_chr_fe_disconnect(&s->chardev);
+        return ret;
+    }
+    assert(s->connected);
+
+    ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg,
+                               sizeof(struct virtio_blk_config), errp);
+    if (ret < 0) {
+        qemu_chr_fe_disconnect(&s->chardev);
+        vhost_dev_cleanup(&s->dev);
+        return ret;
+    }
+
+    return 0;
+}
+
 static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
 {
+    ERRP_GUARD();
     VirtIODevice *vdev = VIRTIO_DEVICE(dev);
     VHostUserBlk *s = VHOST_USER_BLK(vdev);
+    int retries;
     int i, ret;
 
     if (!s->chardev.chr) {
@@ -466,23 +501,20 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
 
     s->inflight = g_new0(struct vhost_inflight, 1);
     s->vhost_vqs = g_new0(struct vhost_virtqueue, s->num_queues);
-    s->connected = false;
 
-    if (qemu_chr_fe_wait_connected(&s->chardev, errp) < 0) {
-        goto virtio_err;
-    }
+    retries = REALIZE_CONNECTION_RETRIES;
+    assert(!*errp);
+    do {
+        if (*errp) {
+            error_prepend(errp, "Reconnecting after error: ");
+            error_report_err(*errp);
+            *errp = NULL;
+        }
+        ret = vhost_user_blk_realize_connect(s, errp);
+    } while (ret == -EPROTO && retries--);
 
-    if (vhost_user_blk_connect(dev, errp) < 0) {
-        qemu_chr_fe_disconnect(&s->chardev);
-        goto virtio_err;
-    }
-    assert(s->connected);
-
-    ret = vhost_dev_get_config(&s->dev, (uint8_t *)&s->blkcfg,
-                               sizeof(struct virtio_blk_config));
     if (ret < 0) {
-        error_setg(errp, "vhost-user-blk: get block config failed");
-        goto vhost_err;
+        goto virtio_err;
     }
 
     /* we're fully initialized, now we can operate, so add the handler */
@@ -491,8 +523,6 @@ static void vhost_user_blk_device_realize(DeviceState *dev, Error **errp)
                              NULL, true);
     return;
 
-vhost_err:
-    vhost_dev_cleanup(&s->dev);
 virtio_err:
     g_free(s->vhost_vqs);
     s->vhost_vqs = NULL;
diff --git a/hw/display/vhost-user-gpu.c b/hw/display/vhost-user-gpu.c
index 6cdaa1c73b..389199e6ca 100644
--- a/hw/display/vhost-user-gpu.c
+++ b/hw/display/vhost-user-gpu.c
@@ -415,14 +415,16 @@ vhost_user_gpu_get_config(VirtIODevice *vdev, uint8_t *config_data)
     VirtIOGPUBase *b = VIRTIO_GPU_BASE(vdev);
     struct virtio_gpu_config *vgconfig =
         (struct virtio_gpu_config *)config_data;
+    Error *local_err = NULL;
     int ret;
 
     memset(config_data, 0, sizeof(struct virtio_gpu_config));
 
     ret = vhost_dev_get_config(&g->vhost->dev,
-                               config_data, sizeof(struct virtio_gpu_config));
+                               config_data, sizeof(struct virtio_gpu_config),
+                               &local_err);
     if (ret) {
-        error_report("vhost-user-gpu: get device config space failed");
+        error_report_err(local_err);
         return;
     }
 
diff --git a/hw/input/vhost-user-input.c b/hw/input/vhost-user-input.c
index 63984a8ba7..273e96a7b1 100644
--- a/hw/input/vhost-user-input.c
+++ b/hw/input/vhost-user-input.c
@@ -49,13 +49,15 @@ static void vhost_input_get_config(VirtIODevice *vdev, uint8_t *config_data)
 {
     VirtIOInput *vinput = VIRTIO_INPUT(vdev);
     VHostUserInput *vhi = VHOST_USER_INPUT(vdev);
+    Error *local_err = NULL;
     int ret;
 
     memset(config_data, 0, vinput->cfg_size);
 
-    ret = vhost_dev_get_config(&vhi->vhost->dev, config_data, vinput->cfg_size);
+    ret = vhost_dev_get_config(&vhi->vhost->dev, config_data, vinput->cfg_size,
+                               &local_err);
     if (ret) {
-        error_report("vhost-user-input: get device config space failed");
+        error_report_err(local_err);
         return;
     }
 }
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 44c1ed92dc..10a7780a13 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -22,6 +22,7 @@
 #include "standard-headers/linux/vhost_types.h"
 #include "hw/virtio/virtio-net.h"
 #include "net/vhost_net.h"
+#include "qapi/error.h"
 #include "qemu/error-report.h"
 #include "qemu/main-loop.h"
 
@@ -116,7 +117,7 @@ uint64_t vhost_net_get_features(struct vhost_net *net, uint64_t features)
 int vhost_net_get_config(struct vhost_net *net,  uint8_t *config,
                          uint32_t config_len)
 {
-    return vhost_dev_get_config(&net->dev, config, config_len);
+    return vhost_dev_get_config(&net->dev, config, config_len, NULL);
 }
 int vhost_net_set_config(struct vhost_net *net, const uint8_t *data,
                          uint32_t offset, uint32_t size, uint32_t flags)
@@ -157,6 +158,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     bool backend_kernel = options->backend_type == VHOST_BACKEND_TYPE_KERNEL;
     struct vhost_net *net = g_new0(struct vhost_net, 1);
     uint64_t features = 0;
+    Error *local_err = NULL;
 
     if (!options->net_backend) {
         fprintf(stderr, "vhost-net requires net backend to be setup\n");
@@ -187,8 +189,10 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     }
 
     r = vhost_dev_init(&net->dev, options->opaque,
-                       options->backend_type, options->busyloop_timeout);
+                       options->backend_type, options->busyloop_timeout,
+                       &local_err);
     if (r < 0) {
+        error_report_err(local_err);
         goto fail;
     }
     if (backend_kernel) {
diff --git a/hw/scsi/vhost-scsi.c b/hw/scsi/vhost-scsi.c
index 4d70fa036b..8c611bfd2d 100644
--- a/hw/scsi/vhost-scsi.c
+++ b/hw/scsi/vhost-scsi.c
@@ -219,10 +219,8 @@ static void vhost_scsi_realize(DeviceState *dev, Error **errp)
     vsc->dev.backend_features = 0;
 
     ret = vhost_dev_init(&vsc->dev, (void *)(uintptr_t)vhostfd,
-                         VHOST_BACKEND_TYPE_KERNEL, 0);
+                         VHOST_BACKEND_TYPE_KERNEL, 0, errp);
     if (ret < 0) {
-        error_setg(errp, "vhost-scsi: vhost initialization failed: %s",
-                   strerror(-ret));
         goto free_vqs;
     }
 
diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index 4666019442..1b2f7eed98 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -122,10 +122,8 @@ static void vhost_user_scsi_realize(DeviceState *dev, Error **errp)
     vqs = vsc->dev.vqs;
 
     ret = vhost_dev_init(&vsc->dev, &s->vhost_user,
-                         VHOST_BACKEND_TYPE_USER, 0);
+                         VHOST_BACKEND_TYPE_USER, 0, errp);
     if (ret < 0) {
-        error_setg(errp, "vhost-user-scsi: vhost initialization failed: %s",
-                   strerror(-ret));
         goto free_vhost;
     }
 
diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 31b33bde37..594d770b75 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -24,13 +24,15 @@ static int vhost_kernel_call(struct vhost_dev *dev, unsigned long int request,
                              void *arg)
 {
     int fd = (uintptr_t) dev->opaque;
+    int ret;
 
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_KERNEL);
 
-    return ioctl(fd, request, arg);
+    ret = ioctl(fd, request, arg);
+    return ret < 0 ? -errno : ret;
 }
 
-static int vhost_kernel_init(struct vhost_dev *dev, void *opaque)
+static int vhost_kernel_init(struct vhost_dev *dev, void *opaque, Error **errp)
 {
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_KERNEL);
 
diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
index 6f7f91533d..c595957983 100644
--- a/hw/virtio/vhost-user-fs.c
+++ b/hw/virtio/vhost-user-fs.c
@@ -235,9 +235,8 @@ static void vuf_device_realize(DeviceState *dev, Error **errp)
     fs->vhost_dev.nvqs = 1 + fs->conf.num_request_queues;
     fs->vhost_dev.vqs = g_new0(struct vhost_virtqueue, fs->vhost_dev.nvqs);
     ret = vhost_dev_init(&fs->vhost_dev, &fs->vhost_user,
-                         VHOST_BACKEND_TYPE_USER, 0);
+                         VHOST_BACKEND_TYPE_USER, 0, errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "vhost_dev_init failed");
         goto err_virtio;
     }
 
diff --git a/hw/virtio/vhost-user-vsock.c b/hw/virtio/vhost-user-vsock.c
index a6f08c26b9..6095ed7349 100644
--- a/hw/virtio/vhost-user-vsock.c
+++ b/hw/virtio/vhost-user-vsock.c
@@ -34,10 +34,12 @@ static void vuv_get_config(VirtIODevice *vdev, uint8_t *config)
 static int vuv_handle_config_change(struct vhost_dev *dev)
 {
     VHostUserVSock *vsock = VHOST_USER_VSOCK(dev->vdev);
+    Error *local_err = NULL;
     int ret = vhost_dev_get_config(dev, (uint8_t *)&vsock->vsockcfg,
-                                   sizeof(struct virtio_vsock_config));
+                                   sizeof(struct virtio_vsock_config),
+                                   &local_err);
     if (ret < 0) {
-        error_report("get config space failed");
+        error_report_err(local_err);
         return -1;
     }
 
@@ -108,16 +110,14 @@ static void vuv_device_realize(DeviceState *dev, Error **errp)
     vhost_dev_set_config_notifier(&vvc->vhost_dev, &vsock_ops);
 
     ret = vhost_dev_init(&vvc->vhost_dev, &vsock->vhost_user,
-                         VHOST_BACKEND_TYPE_USER, 0);
+                         VHOST_BACKEND_TYPE_USER, 0, errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "vhost_dev_init failed");
         goto err_virtio;
     }
 
     ret = vhost_dev_get_config(&vvc->vhost_dev, (uint8_t *)&vsock->vsockcfg,
-                               sizeof(struct virtio_vsock_config));
+                               sizeof(struct virtio_vsock_config), errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "get config space failed");
         goto err_vhost_dev;
     }
 
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index ee57abe045..1ac4a2ebec 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -1353,7 +1353,11 @@ static int vhost_user_get_u64(struct vhost_dev *dev, int request, uint64_t *u64)
 
 static int vhost_user_get_features(struct vhost_dev *dev, uint64_t *features)
 {
-    return vhost_user_get_u64(dev, VHOST_USER_GET_FEATURES, features);
+    if (vhost_user_get_u64(dev, VHOST_USER_GET_FEATURES, features) < 0) {
+        return -EPROTO;
+    }
+
+    return 0;
 }
 
 static int vhost_user_set_owner(struct vhost_dev *dev)
@@ -1364,7 +1368,7 @@ static int vhost_user_set_owner(struct vhost_dev *dev)
     };
 
     if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     return 0;
@@ -1856,7 +1860,8 @@ static int vhost_user_postcopy_notifier(NotifierWithReturn *notifier,
     return 0;
 }
 
-static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
+static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque,
+                                   Error **errp)
 {
     uint64_t features, protocol_features, ram_slots;
     struct vhost_user *u;
@@ -1880,7 +1885,7 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
         err = vhost_user_get_u64(dev, VHOST_USER_GET_PROTOCOL_FEATURES,
                                  &protocol_features);
         if (err < 0) {
-            return err;
+            return -EPROTO;
         }
 
         dev->protocol_features =
@@ -1891,14 +1896,14 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
             dev->protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG);
         } else if (!(protocol_features &
                     (1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) {
-            error_report("Device expects VHOST_USER_PROTOCOL_F_CONFIG "
-                    "but backend does not support it.");
-            return -1;
+            error_setg(errp, "Device expects VHOST_USER_PROTOCOL_F_CONFIG "
+                       "but backend does not support it.");
+            return -EINVAL;
         }
 
         err = vhost_user_set_protocol_features(dev, dev->protocol_features);
         if (err < 0) {
-            return err;
+            return -EPROTO;
         }
 
         /* query the max queues we support if backend supports Multiple Queue */
@@ -1906,12 +1911,12 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
             err = vhost_user_get_u64(dev, VHOST_USER_GET_QUEUE_NUM,
                                      &dev->max_queues);
             if (err < 0) {
-                return err;
+                return -EPROTO;
             }
         }
         if (dev->num_queues && dev->max_queues < dev->num_queues) {
-            error_report("The maximum number of queues supported by the "
-                         "backend is %" PRIu64, dev->max_queues);
+            error_setg(errp, "The maximum number of queues supported by the "
+                       "backend is %" PRIu64, dev->max_queues);
             return -EINVAL;
         }
 
@@ -1920,9 +1925,9 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
                     VHOST_USER_PROTOCOL_F_SLAVE_REQ) &&
                  virtio_has_feature(dev->protocol_features,
                     VHOST_USER_PROTOCOL_F_REPLY_ACK))) {
-            error_report("IOMMU support requires reply-ack and "
-                         "slave-req protocol features.");
-            return -1;
+            error_setg(errp, "IOMMU support requires reply-ack and "
+                       "slave-req protocol features.");
+            return -EINVAL;
         }
 
         /* get max memory regions if backend supports configurable RAM slots */
@@ -1932,15 +1937,15 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
         } else {
             err = vhost_user_get_max_memslots(dev, &ram_slots);
             if (err < 0) {
-                return err;
+                return -EPROTO;
             }
 
             if (ram_slots < u->user->memory_slots) {
-                error_report("The backend specified a max ram slots limit "
-                             "of %" PRIu64", when the prior validated limit was %d. "
-                             "This limit should never decrease.", ram_slots,
-                             u->user->memory_slots);
-                return -1;
+                error_setg(errp, "The backend specified a max ram slots limit "
+                           "of %" PRIu64", when the prior validated limit was "
+                           "%d. This limit should never decrease.", ram_slots,
+                           u->user->memory_slots);
+                return -EINVAL;
             }
 
             u->user->memory_slots = MIN(ram_slots, VHOST_USER_MAX_RAM_SLOTS);
@@ -1958,7 +1963,7 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque)
     if (dev->vq_index == 0) {
         err = vhost_setup_slave_channel(dev);
         if (err < 0) {
-            return err;
+            return -EPROTO;
         }
     }
 
@@ -2112,7 +2117,7 @@ static void vhost_user_set_iotlb_callback(struct vhost_dev *dev, int enabled)
 }
 
 static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
-                                 uint32_t config_len)
+                                 uint32_t config_len, Error **errp)
 {
     VhostUserMsg msg = {
         .hdr.request = VHOST_USER_GET_CONFIG,
@@ -2122,32 +2127,32 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
 
     if (!virtio_has_feature(dev->protocol_features,
                 VHOST_USER_PROTOCOL_F_CONFIG)) {
-        return -1;
+        error_setg(errp, "VHOST_USER_PROTOCOL_F_CONFIG not supported");
+        return -EINVAL;
     }
 
-    if (config_len > VHOST_USER_MAX_CONFIG_SIZE) {
-        return -1;
-    }
+    assert(config_len <= VHOST_USER_MAX_CONFIG_SIZE);
 
     msg.payload.config.offset = 0;
     msg.payload.config.size = config_len;
     if (vhost_user_write(dev, &msg, NULL, 0) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     if (vhost_user_read(dev, &msg) < 0) {
-        return -1;
+        return -EPROTO;
     }
 
     if (msg.hdr.request != VHOST_USER_GET_CONFIG) {
-        error_report("Received unexpected msg type. Expected %d received %d",
-                     VHOST_USER_GET_CONFIG, msg.hdr.request);
-        return -1;
+        error_setg(errp,
+                   "Received unexpected msg type. Expected %d received %d",
+                   VHOST_USER_GET_CONFIG, msg.hdr.request);
+        return -EINVAL;
     }
 
     if (msg.hdr.size != VHOST_USER_CONFIG_HDR_SIZE + config_len) {
-        error_report("Received bad msg size.");
-        return -1;
+        error_setg(errp, "Received bad msg size.");
+        return -EINVAL;
     }
 
     memcpy(config, msg.payload.config.region, config_len);
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 61ba313331..4fa414feea 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -245,10 +245,12 @@ static int vhost_vdpa_call(struct vhost_dev *dev, unsigned long int request,
 {
     struct vhost_vdpa *v = dev->opaque;
     int fd = v->device_fd;
+    int ret;
 
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
 
-    return ioctl(fd, request, arg);
+    ret = ioctl(fd, request, arg);
+    return ret < 0 ? -errno : ret;
 }
 
 static void vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
@@ -265,7 +267,7 @@ static void vhost_vdpa_add_status(struct vhost_dev *dev, uint8_t status)
     vhost_vdpa_call(dev, VHOST_VDPA_SET_STATUS, &s);
 }
 
-static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque)
+static int vhost_vdpa_init(struct vhost_dev *dev, void *opaque, Error **errp)
 {
     struct vhost_vdpa *v;
     assert(dev->vhost_ops->backend_type == VHOST_BACKEND_TYPE_VDPA);
@@ -521,7 +523,7 @@ static int vhost_vdpa_set_config(struct vhost_dev *dev, const uint8_t *data,
 }
 
 static int vhost_vdpa_get_config(struct vhost_dev *dev, uint8_t *config,
-                                   uint32_t config_len)
+                                   uint32_t config_len, Error **errp)
 {
     struct vhost_vdpa_config *v_config;
     unsigned long config_size = offsetof(struct vhost_vdpa_config, buf);
diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
index 8ddfb9abfe..777cafe70d 100644
--- a/hw/virtio/vhost-vsock.c
+++ b/hw/virtio/vhost-vsock.c
@@ -170,9 +170,8 @@ static void vhost_vsock_device_realize(DeviceState *dev, Error **errp)
     vhost_vsock_common_realize(vdev, "vhost-vsock");
 
     ret = vhost_dev_init(&vvc->vhost_dev, (void *)(uintptr_t)vhostfd,
-                         VHOST_BACKEND_TYPE_KERNEL, 0);
+                         VHOST_BACKEND_TYPE_KERNEL, 0, errp);
     if (ret < 0) {
-        error_setg_errno(errp, -ret, "vhost-vsock: vhost_dev_init failed");
         goto err_virtio;
     }
 
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 7b7bde7657..e8f85a5d2d 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1286,11 +1286,12 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq)
 }
 
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
-                   VhostBackendType backend_type, uint32_t busyloop_timeout)
+                   VhostBackendType backend_type, uint32_t busyloop_timeout,
+                   Error **errp)
 {
+    ERRP_GUARD();
     uint64_t features;
     int i, r, n_initialized_vqs = 0;
-    Error *local_err = NULL;
 
     hdev->vdev = NULL;
     hdev->migration_blocker = NULL;
@@ -1298,26 +1299,30 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     r = vhost_set_backend_type(hdev, backend_type);
     assert(r >= 0);
 
-    r = hdev->vhost_ops->vhost_backend_init(hdev, opaque);
+    r = hdev->vhost_ops->vhost_backend_init(hdev, opaque, errp);
     if (r < 0) {
+        if (!*errp) {
+            error_setg_errno(errp, -r, "vhost_backend_init failed");
+        }
         goto fail;
     }
 
     r = hdev->vhost_ops->vhost_set_owner(hdev);
     if (r < 0) {
-        VHOST_OPS_DEBUG("vhost_set_owner failed");
+        error_setg_errno(errp, -r, "vhost_set_owner failed");
         goto fail;
     }
 
     r = hdev->vhost_ops->vhost_get_features(hdev, &features);
     if (r < 0) {
-        VHOST_OPS_DEBUG("vhost_get_features failed");
+        error_setg_errno(errp, -r, "vhost_get_features failed");
         goto fail;
     }
 
     for (i = 0; i < hdev->nvqs; ++i, ++n_initialized_vqs) {
         r = vhost_virtqueue_init(hdev, hdev->vqs + i, hdev->vq_index + i);
         if (r < 0) {
+            error_setg_errno(errp, -r, "Failed to initialize virtqueue %d", i);
             goto fail;
         }
     }
@@ -1327,6 +1332,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
             r = vhost_virtqueue_set_busyloop_timeout(hdev, hdev->vq_index + i,
                                                      busyloop_timeout);
             if (r < 0) {
+                error_setg_errno(errp, -r, "Failed to set busyloop timeout");
                 goto fail_busyloop;
             }
         }
@@ -1365,9 +1371,8 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     }
 
     if (hdev->migration_blocker != NULL) {
-        r = migrate_add_blocker(hdev->migration_blocker, &local_err);
-        if (local_err) {
-            error_report_err(local_err);
+        r = migrate_add_blocker(hdev->migration_blocker, errp);
+        if (*errp) {
             error_free(hdev->migration_blocker);
             goto fail_busyloop;
         }
@@ -1384,9 +1389,9 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     QLIST_INSERT_HEAD(&vhost_devices, hdev, entry);
 
     if (used_memslots > hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
-        error_report("vhost backend memory slots limit is less"
-                " than current number of present memory slots");
-        r = -1;
+        error_setg(errp, "vhost backend memory slots limit is less"
+                   " than current number of present memory slots");
+        r = -EINVAL;
         goto fail_busyloop;
     }
 
@@ -1557,15 +1562,23 @@ void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
 }
 
 int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
-                         uint32_t config_len)
+                         uint32_t config_len, Error **errp)
 {
+    ERRP_GUARD();
+    int ret;
+
     assert(hdev->vhost_ops);
 
     if (hdev->vhost_ops->vhost_get_config) {
-        return hdev->vhost_ops->vhost_get_config(hdev, config, config_len);
+        ret = hdev->vhost_ops->vhost_get_config(hdev, config, config_len, errp);
+        if (ret < 0 && !*errp) {
+            error_setg_errno(errp, -ret, "vhost_get_config failed");
+        }
+        return ret;
     }
 
-    return -1;
+    error_setg(errp, "vhost_get_config not implemented");
+    return -ENOTSUP;
 }
 
 int vhost_dev_set_config(struct vhost_dev *hdev, const uint8_t *data,
diff --git a/include/block/block.h b/include/block/block.h
index 8e707a83b7..7ec77ecb1a 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -208,8 +208,8 @@ typedef struct BDRVReopenState {
     int flags;
     BlockdevDetectZeroesOptions detect_zeroes;
     bool backing_missing;
-    bool replace_backing_bs;  /* new_backing_bs is ignored if this is false */
     BlockDriverState *old_backing_bs; /* keep pointer for permissions update */
+    BlockDriverState *old_file_bs; /* keep pointer for permissions update */
     QDict *options;
     QDict *explicit_options;
     void *opaque;
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index 8a6f8e2a7a..8475c5a29d 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -37,7 +37,8 @@ struct vhost_scsi_target;
 struct vhost_iotlb_msg;
 struct vhost_virtqueue;
 
-typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque);
+typedef int (*vhost_backend_init)(struct vhost_dev *dev, void *opaque,
+                                  Error **errp);
 typedef int (*vhost_backend_cleanup)(struct vhost_dev *dev);
 typedef int (*vhost_backend_memslots_limit)(struct vhost_dev *dev);
 
@@ -97,7 +98,7 @@ typedef int (*vhost_set_config_op)(struct vhost_dev *dev, const uint8_t *data,
                                    uint32_t offset, uint32_t size,
                                    uint32_t flags);
 typedef int (*vhost_get_config_op)(struct vhost_dev *dev, uint8_t *config,
-                                   uint32_t config_len);
+                                   uint32_t config_len, Error **errp);
 
 typedef int (*vhost_crypto_create_session_op)(struct vhost_dev *dev,
                                               void *session_info,
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 21a9a52088..045d0fd9f2 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -104,7 +104,7 @@ struct vhost_net {
 
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
                    VhostBackendType backend_type,
-                   uint32_t busyloop_timeout);
+                   uint32_t busyloop_timeout, Error **errp);
 void vhost_dev_cleanup(struct vhost_dev *hdev);
 int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice *vdev);
 void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev);
@@ -130,8 +130,8 @@ int vhost_net_set_backend(struct vhost_dev *hdev,
                           struct vhost_vring_file *file);
 
 int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write);
-int vhost_dev_get_config(struct vhost_dev *dev, uint8_t *config,
-                         uint32_t config_len);
+int vhost_dev_get_config(struct vhost_dev *hdev, uint8_t *config,
+                         uint32_t config_len, Error **errp);
 int vhost_dev_set_config(struct vhost_dev *dev, const uint8_t *data,
                          uint32_t offset, uint32_t size, uint32_t flags);
 /* notifier callback in case vhost device config space changed
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index c3656b755a..c91a78b5e6 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -386,6 +386,21 @@ void *qemu_anon_ram_alloc(size_t size, uint64_t *align, bool shared,
 void qemu_vfree(void *ptr);
 void qemu_anon_ram_free(void *ptr, size_t size);
 
+/*
+ * It's an analog of GLIB's g_autoptr_cleanup_generic_gfree(), used to define
+ * g_autofree macro.
+ */
+static inline void qemu_cleanup_generic_vfree(void *p)
+{
+  void **pp = (void **)p;
+  qemu_vfree(*pp);
+}
+
+/*
+ * Analog of g_autofree, but qemu_vfree is called on cleanup instead of g_free.
+ */
+#define QEMU_AUTO_VFREE __attribute__((cleanup(qemu_cleanup_generic_vfree)))
+
 /*
  * Abstraction of PROT_ and MAP_ flags as passed to mmap(), for example,
  * consumed by qemu_ram_mmap().
diff --git a/qapi/block-core.json b/qapi/block-core.json
index a54f37dbef..3114ba69bb 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -3190,11 +3190,12 @@
 #
 # @md5: The given hash is an md5 hash
 # @sha1: The given hash is an sha1 hash
+# @sha256: The given hash is an sha256 hash
 #
 # Since: 2.12
 ##
 { 'enum': 'SshHostKeyCheckHashType',
-  'data': [ 'md5', 'sha1' ] }
+  'data': [ 'md5', 'sha1', 'sha256' ] }
 
 ##
 # @SshHostKeyHash:
diff --git a/tests/qemu-iotests/189 b/tests/qemu-iotests/189
index 4e463385b2..801494c6b9 100755
--- a/tests/qemu-iotests/189
+++ b/tests/qemu-iotests/189
@@ -67,7 +67,7 @@ echo "== verify pattern =="
 $QEMU_IO --object $SECRET0 -c "read -P 0xa 0 $size" --image-opts $IMGSPECBASE | _filter_qemu_io | _filter_testdir
 
 echo "== create overlay =="
-_make_test_img --object $SECRET1 -o "encrypt.format=luks,encrypt.key-secret=sec1,encrypt.iter-time=10" -u -b "$TEST_IMG_BASE" -F $IMGFMT $size
+_make_test_img --object $SECRET1 -o "encrypt.format=luks,encrypt.key-secret=sec1,encrypt.iter-time=10" -b "$TEST_IMG_BASE" -F $IMGFMT
 
 echo
 echo "== writing part of a cluster =="
diff --git a/tests/qemu-iotests/198 b/tests/qemu-iotests/198
index b333a8f281..1c93dea1f7 100755
--- a/tests/qemu-iotests/198
+++ b/tests/qemu-iotests/198
@@ -64,7 +64,7 @@ echo "== writing whole image base =="
 $QEMU_IO --object $SECRET0 -c "write -P 0xa 0 $size" --image-opts $IMGSPECBASE | _filter_qemu_io | _filter_testdir
 
 echo "== create overlay =="
-_make_test_img --object $SECRET1 -o "encrypt.format=luks,encrypt.key-secret=sec1,encrypt.iter-time=10" -u -b "$TEST_IMG_BASE" -F $IMGFMT $size
+_make_test_img --object $SECRET1 -o "encrypt.format=luks,encrypt.key-secret=sec1,encrypt.iter-time=10" -b "$TEST_IMG_BASE" -F $IMGFMT
 
 echo
 echo "== writing whole image layer =="
diff --git a/tests/qemu-iotests/207 b/tests/qemu-iotests/207
index f9f3fd7131..0f5c4bc8a0 100755
--- a/tests/qemu-iotests/207
+++ b/tests/qemu-iotests/207
@@ -73,6 +73,9 @@ with iotests.FilePath('t.img') as disk_path, \
     iotests.log("=== Test host-key-check options ===")
     iotests.log("")
 
+    iotests.log("--- no host key checking --")
+    iotests.log("")
+
     vm.launch()
     blockdev_create(vm, { 'driver': 'ssh',
                           'location': {
@@ -90,6 +93,9 @@ with iotests.FilePath('t.img') as disk_path, \
 
     iotests.img_info_log(remote_path)
 
+    iotests.log("--- known_hosts key checking --")
+    iotests.log("")
+
     vm.launch()
     blockdev_create(vm, { 'driver': 'ssh',
                           'location': {
@@ -115,6 +121,7 @@ with iotests.FilePath('t.img') as disk_path, \
     # Mappings of base64 representations to digests
     md5_keys = {}
     sha1_keys = {}
+    sha256_keys = {}
 
     for key in keys:
         md5_keys[key] = subprocess.check_output(
@@ -125,6 +132,10 @@ with iotests.FilePath('t.img') as disk_path, \
             'echo %s | base64 -d | sha1sum -b | cut -d" " -f1' % key,
             shell=True).rstrip().decode('ascii')
 
+        sha256_keys[key] = subprocess.check_output(
+            'echo %s | base64 -d | sha256sum -b | cut -d" " -f1' % key,
+            shell=True).rstrip().decode('ascii')
+
     vm.launch()
 
     # Find correct key first
@@ -150,6 +161,9 @@ with iotests.FilePath('t.img') as disk_path, \
         vm.shutdown()
         iotests.notrun('Did not find a key that fits 127.0.0.1')
 
+    iotests.log("--- explicit md5 key checking --")
+    iotests.log("")
+
     blockdev_create(vm, { 'driver': 'ssh',
                           'location': {
                               'path': disk_path,
@@ -164,6 +178,7 @@ with iotests.FilePath('t.img') as disk_path, \
                               }
                           },
                           'size': 2097152 })
+
     blockdev_create(vm, { 'driver': 'ssh',
                           'location': {
                               'path': disk_path,
@@ -182,6 +197,9 @@ with iotests.FilePath('t.img') as disk_path, \
 
     iotests.img_info_log(remote_path)
 
+    iotests.log("--- explicit sha1 key checking --")
+    iotests.log("")
+
     vm.launch()
     blockdev_create(vm, { 'driver': 'ssh',
                           'location': {
@@ -215,6 +233,42 @@ with iotests.FilePath('t.img') as disk_path, \
 
     iotests.img_info_log(remote_path)
 
+    iotests.log("--- explicit sha256 key checking --")
+    iotests.log("")
+
+    vm.launch()
+    blockdev_create(vm, { 'driver': 'ssh',
+                          'location': {
+                              'path': disk_path,
+                              'server': {
+                                  'host': '127.0.0.1',
+                                  'port': '22'
+                              },
+                              'host-key-check': {
+                                  'mode': 'hash',
+                                  'type': 'sha256',
+                                  'hash': 'wrong',
+                              }
+                          },
+                          'size': 2097152 })
+    blockdev_create(vm, { 'driver': 'ssh',
+                          'location': {
+                              'path': disk_path,
+                              'server': {
+                                  'host': '127.0.0.1',
+                                  'port': '22'
+                              },
+                              'host-key-check': {
+                                  'mode': 'hash',
+                                  'type': 'sha256',
+                                  'hash': sha256_keys[matching_key],
+                              }
+                          },
+                          'size': 4194304 })
+    vm.shutdown()
+
+    iotests.img_info_log(remote_path)
+
     #
     # Invalid path and user
     #
diff --git a/tests/qemu-iotests/207.out b/tests/qemu-iotests/207.out
index 1239d9d648..aeb8569d77 100644
--- a/tests/qemu-iotests/207.out
+++ b/tests/qemu-iotests/207.out
@@ -16,6 +16,8 @@ virtual size: 4 MiB (4194304 bytes)
 
 === Test host-key-check options ===
 
+--- no host key checking --
+
 {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"mode": "none"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 8388608}}}
 {"return": {}}
 {"execute": "job-dismiss", "arguments": {"id": "job0"}}
@@ -25,6 +27,8 @@ image: TEST_IMG
 file format: IMGFMT
 virtual size: 8 MiB (8388608 bytes)
 
+--- known_hosts key checking --
+
 {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"mode": "known_hosts"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 4194304}}}
 {"return": {}}
 {"execute": "job-dismiss", "arguments": {"id": "job0"}}
@@ -34,6 +38,8 @@ image: TEST_IMG
 file format: IMGFMT
 virtual size: 4 MiB (4194304 bytes)
 
+--- explicit md5 key checking --
+
 {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "wrong", "mode": "hash", "type": "md5"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 2097152}}}
 {"return": {}}
 Job failed: remote host key does not match host_key_check 'wrong'
@@ -49,6 +55,8 @@ image: TEST_IMG
 file format: IMGFMT
 virtual size: 8 MiB (8388608 bytes)
 
+--- explicit sha1 key checking --
+
 {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "wrong", "mode": "hash", "type": "sha1"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 2097152}}}
 {"return": {}}
 Job failed: remote host key does not match host_key_check 'wrong'
@@ -64,6 +72,23 @@ image: TEST_IMG
 file format: IMGFMT
 virtual size: 4 MiB (4194304 bytes)
 
+--- explicit sha256 key checking --
+
+{"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "wrong", "mode": "hash", "type": "sha256"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 2097152}}}
+{"return": {}}
+Job failed: remote host key does not match host_key_check 'wrong'
+{"execute": "job-dismiss", "arguments": {"id": "job0"}}
+{"return": {}}
+
+{"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"hash": "HASH", "mode": "hash", "type": "sha256"}, "path": "TEST_DIR/PID-t.img", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 4194304}}}
+{"return": {}}
+{"execute": "job-dismiss", "arguments": {"id": "job0"}}
+{"return": {}}
+
+image: TEST_IMG
+file format: IMGFMT
+virtual size: 4 MiB (4194304 bytes)
+
 === Invalid path and user ===
 
 {"execute": "blockdev-create", "arguments": {"job-id": "job0", "options": {"driver": "ssh", "location": {"host-key-check": {"mode": "none"}, "path": "/this/is/not/an/existing/path", "server": {"host": "127.0.0.1", "port": "22"}}, "size": 4194304}}}
diff --git a/tests/qemu-iotests/245 b/tests/qemu-iotests/245
index fc5297e268..0295129cbb 100755
--- a/tests/qemu-iotests/245
+++ b/tests/qemu-iotests/245
@@ -79,7 +79,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         for line in log.split("\n"):
             if line.startswith("Pattern verification failed"):
                 raise Exception("%s (command #%d)" % (line, found))
-            if re.match("read .*/.* bytes at offset", line):
+            if re.match("(read|wrote) .*/.* bytes at offset", line):
                 found += 1
         self.assertEqual(found, self.total_io_cmds,
                          "Expected output of %d qemu-io commands, found %d" %
@@ -146,8 +146,8 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         self.reopen(opts, {'driver': 'raw'}, "Cannot change the option 'driver'")
         self.reopen(opts, {'driver': ''}, "Invalid parameter ''")
         self.reopen(opts, {'driver': None}, "Invalid parameter type for 'driver', expected: string")
-        self.reopen(opts, {'file': 'not-found'}, "Cannot change the option 'file'")
-        self.reopen(opts, {'file': ''}, "Cannot change the option 'file'")
+        self.reopen(opts, {'file': 'not-found'}, "Cannot find device='' nor node-name='not-found'")
+        self.reopen(opts, {'file': ''}, "Cannot find device='' nor node-name=''")
         self.reopen(opts, {'file': None}, "Invalid parameter type for 'file', expected: BlockdevRef")
         self.reopen(opts, {'file.node-name': 'newname'}, "Cannot change the option 'node-name'")
         self.reopen(opts, {'file.driver': 'host_device'}, "Cannot change the option 'driver'")
@@ -443,7 +443,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # Illegal operation: hd2 is a child of hd1
         self.reopen(opts[2], {'backing': 'hd1'},
-                    "Making 'hd1' a backing file of 'hd2' would create a cycle")
+                    "Making 'hd1' a backing child of 'hd2' would create a cycle")
 
         # hd2 <- hd0, hd2 <- hd1
         self.reopen(opts[0], {'backing': 'hd2'})
@@ -454,8 +454,9 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # More illegal operations
         self.reopen(opts[2], {'backing': 'hd1'},
-                    "Making 'hd1' a backing file of 'hd2' would create a cycle")
-        self.reopen(opts[2], {'file': 'hd0-file'}, "Cannot change the option 'file'")
+                    "Making 'hd1' a backing child of 'hd2' would create a cycle")
+        self.reopen(opts[2], {'file': 'hd0-file'},
+                    "Permission conflict on node 'hd0-file': permissions 'write, resize' are both required by node 'hd0' (uses node 'hd0-file' as 'file' child) and unshared by node 'hd2' (uses node 'hd0-file' as 'file' child).")
 
         result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'hd2')
         self.assert_qmp(result, 'error/class', 'GenericError')
@@ -497,18 +498,18 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # Illegal: hd2 is backed by hd1
         self.reopen(opts[1], {'backing': 'hd2'},
-                    "Making 'hd2' a backing file of 'hd1' would create a cycle")
+                    "Making 'hd2' a backing child of 'hd1' would create a cycle")
 
         # hd1 <- hd0 <- hd2
         self.reopen(opts[2], {'backing': 'hd0'})
 
         # Illegal: hd2 is backed by hd0, which is backed by hd1
         self.reopen(opts[1], {'backing': 'hd2'},
-                    "Making 'hd2' a backing file of 'hd1' would create a cycle")
+                    "Making 'hd2' a backing child of 'hd1' would create a cycle")
 
         # Illegal: hd1 cannot point to itself
         self.reopen(opts[1], {'backing': 'hd1'},
-                    "Making 'hd1' a backing file of 'hd1' would create a cycle")
+                    "Making 'hd1' a backing child of 'hd1' would create a cycle")
 
         # Remove all backing files
         self.reopen(opts[0])
@@ -530,12 +531,119 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # Illegal: hd0 is a child of the blkverify node
         self.reopen(opts[0], {'backing': 'bv'},
-                    "Making 'bv' a backing file of 'hd0' would create a cycle")
+                    "Making 'bv' a backing child of 'hd0' would create a cycle")
 
         # Delete the blkverify node
         result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'bv')
         self.assert_qmp(result, 'return', {})
 
+    # Replace the protocol layer ('file' parameter) of a disk image
+    def test_replace_file(self):
+        # Create two small raw images and add them to a running VM
+        qemu_img('create', '-f', 'raw', hd_path[0], '10k')
+        qemu_img('create', '-f', 'raw', hd_path[1], '10k')
+
+        hd0_opts = {'driver': 'file', 'node-name': 'hd0-file', 'filename':  hd_path[0] }
+        hd1_opts = {'driver': 'file', 'node-name': 'hd1-file', 'filename':  hd_path[1] }
+
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **hd0_opts)
+        self.assert_qmp(result, 'return', {})
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **hd1_opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Add a raw format layer that uses hd0-file as its protocol layer
+        opts = {'driver': 'raw', 'node-name': 'hd', 'file': 'hd0-file'}
+
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Fill the image with data
+        self.run_qemu_io("hd", "read  -P 0 0 10k")
+        self.run_qemu_io("hd", "write -P 0xa0 0 10k")
+
+        # Replace hd0-file with hd1-file and fill it with (different) data
+        self.reopen(opts, {'file': 'hd1-file'})
+        self.run_qemu_io("hd", "read  -P 0 0 10k")
+        self.run_qemu_io("hd", "write -P 0xa1 0 10k")
+
+        # Use hd0-file again and check that it contains the expected data
+        self.reopen(opts, {'file': 'hd0-file'})
+        self.run_qemu_io("hd", "read  -P 0xa0 0 10k")
+
+        # And finally do the same with hd1-file
+        self.reopen(opts, {'file': 'hd1-file'})
+        self.run_qemu_io("hd", "read  -P 0xa1 0 10k")
+
+    # Insert (and remove) a throttle filter
+    def test_insert_throttle_filter(self):
+        # Add an image to the VM
+        hd0_opts = hd_opts(0)
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **hd0_opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Create a throttle-group object
+        opts = { 'qom-type': 'throttle-group', 'id': 'group0',
+                 'limits': { 'iops-total': 1000 } }
+        result = self.vm.qmp('object-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Add a throttle filter with the group that we just created.
+        # The filter is not used by anyone yet
+        opts = { 'driver': 'throttle', 'node-name': 'throttle0',
+                 'throttle-group': 'group0', 'file': 'hd0-file' }
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Insert the throttle filter between hd0 and hd0-file
+        self.reopen(hd0_opts, {'file': 'throttle0'})
+
+        # Remove the throttle filter from hd0
+        self.reopen(hd0_opts, {'file': 'hd0-file'})
+
+    # Insert (and remove) a compress filter
+    def test_insert_compress_filter(self):
+        # Add an image to the VM: hd (raw) -> hd0 (qcow2) -> hd0-file (file)
+        opts = {'driver': 'raw', 'node-name': 'hd', 'file': hd_opts(0)}
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Add a 'compress' filter
+        filter_opts = {'driver': 'compress',
+                       'node-name': 'compress0',
+                       'file': 'hd0'}
+        result = self.vm.qmp('blockdev-add', conv_keys = False, **filter_opts)
+        self.assert_qmp(result, 'return', {})
+
+        # Unmap the beginning of the image (we cannot write compressed
+        # data to an allocated cluster)
+        self.run_qemu_io("hd", "write -z -u 0 128k")
+
+        # Write data to the first cluster
+        self.run_qemu_io("hd", "write -P 0xa0 0 64k")
+
+        # Insert the filter then write to the second cluster
+        # hd -> compress0 -> hd0 -> hd0-file
+        self.reopen(opts, {'file': 'compress0'})
+        self.run_qemu_io("hd", "write -P 0xa1 64k 64k")
+
+        # Remove the filter then write to the third cluster
+        # hd -> hd0 -> hd0-file
+        self.reopen(opts, {'file': 'hd0'})
+        self.run_qemu_io("hd", "write -P 0xa2 128k 64k")
+
+        # Verify the data that we just wrote
+        self.run_qemu_io("hd", "read -P 0xa0    0 64k")
+        self.run_qemu_io("hd", "read -P 0xa1  64k 64k")
+        self.run_qemu_io("hd", "read -P 0xa2 128k 64k")
+
+        self.vm.shutdown()
+
+        # Check the first byte of the first three L2 entries and verify that
+        # the second one is compressed (0x40) while the others are not (0x80)
+        iotests.qemu_io_log('-f', 'raw', '-c', 'read -P 0x80 0x40000 1',
+                                         '-c', 'read -P 0x40 0x40008 1',
+                                         '-c', 'read -P 0x80 0x40010 1', hd_path[0])
+
     # Misc reopen tests with different block drivers
     @iotests.skip_if_unsupported(['quorum', 'throttle'])
     def test_misc_drivers(self):
@@ -563,7 +671,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         # You can't make quorum0 a backing file of hd0:
         # hd0 is already a child of quorum0.
         self.reopen(hd_opts(0), {'backing': 'quorum0'},
-                    "Making 'quorum0' a backing file of 'hd0' would create a cycle")
+                    "Making 'quorum0' a backing child of 'hd0' would create a cycle")
 
         # Delete quorum0
         result = self.vm.qmp('blockdev-del', conv_keys = True, node_name = 'quorum0')
@@ -878,7 +986,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # We can't remove hd1 while the stream job is ongoing
         opts['backing'] = None
-        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd0' to 'hd1'")
+        self.reopen(opts, {}, "Cannot change frozen 'backing' link from 'hd0' to 'hd1'")
 
         self.vm.run_job('stream0', auto_finalize = False, auto_dismiss = True)
 
@@ -910,7 +1018,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
         # We can't remove hd2 while the stream job is ongoing
         opts['backing']['backing'] = None
         self.reopen(opts['backing'], {'read-only': False},
-                    "Cannot change 'backing' link from 'hd1' to 'hd2'")
+                    "Cannot change frozen 'backing' link from 'hd1' to 'hd2'")
 
         # We can detach hd1 from hd0 because it doesn't affect the stream job
         opts['backing'] = None
@@ -933,11 +1041,11 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # We can't remove hd2 while the commit job is ongoing
         opts['backing']['backing'] = None
-        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd1' to 'hd2'")
+        self.reopen(opts, {}, "Cannot change frozen 'backing' link from 'hd1' to 'hd2'")
 
         # We can't remove hd1 while the commit job is ongoing
         opts['backing'] = None
-        self.reopen(opts, {}, "Cannot change 'backing' link from 'hd0' to 'hd1'")
+        self.reopen(opts, {}, "Cannot change frozen 'backing' link from 'hd0' to 'hd1'")
 
         event = self.vm.event_wait(name='BLOCK_JOB_READY')
         self.assert_qmp(event, 'data/device', 'commit0')
@@ -969,7 +1077,7 @@ class TestBlockdevReopen(iotests.QMPTestCase):
 
         # We can't remove hd1 while the commit job is ongoing
         opts['backing'] = None
-        self.reopen(opts, {}, "Cannot change backing link if 'hd0' has an implicit backing file")
+        self.reopen(opts, {}, "Cannot replace implicit backing child of hd0")
 
         # hd2 <- hd0
         self.vm.run_job('commit0', auto_finalize = False, auto_dismiss = True)
diff --git a/tests/qemu-iotests/245.out b/tests/qemu-iotests/245.out
index 99c12f4f98..daf1e51922 100644
--- a/tests/qemu-iotests/245.out
+++ b/tests/qemu-iotests/245.out
@@ -10,8 +10,15 @@
 {"return": {}}
 {"data": {"id": "stream0", "type": "stream"}, "event": "BLOCK_JOB_PENDING", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
 {"data": {"device": "stream0", "len": 3145728, "offset": 3145728, "speed": 0, "type": "stream"}, "event": "BLOCK_JOB_COMPLETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
-...............
+....read 1/1 bytes at offset 262144
+1 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 1/1 bytes at offset 262152
+1 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+read 1/1 bytes at offset 262160
+1 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+..............
 ----------------------------------------------------------------------
-Ran 21 tests
+Ran 24 tests
 
 OK
diff --git a/tests/unit/test-bdrv-drain.c b/tests/unit/test-bdrv-drain.c
index 892f7f47d8..ce071b5fc5 100644
--- a/tests/unit/test-bdrv-drain.c
+++ b/tests/unit/test-bdrv-drain.c
@@ -95,6 +95,7 @@ static int bdrv_test_change_backing_file(BlockDriverState *bs,
 static BlockDriver bdrv_test = {
     .format_name            = "test",
     .instance_size          = sizeof(BDRVTestState),
+    .supports_backing       = true,
 
     .bdrv_close             = bdrv_test_close,
     .bdrv_co_preadv         = bdrv_test_co_preadv,
diff --git a/tests/unit/test-bdrv-graph-mod.c b/tests/unit/test-bdrv-graph-mod.c
index 88f25c0cdb..a6e3bb79be 100644
--- a/tests/unit/test-bdrv-graph-mod.c
+++ b/tests/unit/test-bdrv-graph-mod.c
@@ -41,6 +41,7 @@ static void no_perm_default_perms(BlockDriverState *bs, BdrvChild *c,
 
 static BlockDriver bdrv_no_perm = {
     .format_name = "no-perm",
+    .supports_backing = true,
     .bdrv_child_perm = no_perm_default_perms,
 };