diff --git a/tests/qemu-iotests/017 b/tests/qemu-iotests/017
index 0a4b854e6520..585512bb296b 100755
--- a/tests/qemu-iotests/017
+++ b/tests/qemu-iotests/017
@@ -66,7 +66,7 @@ echo "Creating test image with backing file"
 echo

 TEST_IMG=$TEST_IMG_SAVE
-_make_test_img -b "$TEST_IMG.base" 6G
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 6G

 echo "Filling test image"
 echo
diff --git a/tests/qemu-iotests/017.out b/tests/qemu-iotests/017.out
index 8fc9241942e8..f439d3ece3a7 100644
--- a/tests/qemu-iotests/017.out
+++ b/tests/qemu-iotests/017.out
@@ -269,7 +269,7 @@ wrote 65536/65536 bytes at offset 4295032832
 No errors were found on the image.
 Creating test image with backing file

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Filling test image

 === IO: pattern 1
diff --git a/tests/qemu-iotests/018 b/tests/qemu-iotests/018
index c69ce0920920..191b461a4d29 100755
--- a/tests/qemu-iotests/018
+++ b/tests/qemu-iotests/018
@@ -66,7 +66,7 @@ echo "Creating test image with backing file"
 echo

 TEST_IMG="$TEST_IMG_SAVE.orig"
-_make_test_img -b "$TEST_IMG_SAVE.base" 6G
+_make_test_img -b "$TEST_IMG_SAVE.base" -F $IMGFMT 6G

 echo "Filling test image"
 echo
diff --git a/tests/qemu-iotests/018.out b/tests/qemu-iotests/018.out
index 5df966727f98..0ab664ca4b4c 100644
--- a/tests/qemu-iotests/018.out
+++ b/tests/qemu-iotests/018.out
@@ -269,7 +269,7 @@ wrote 65536/65536 bytes at offset 4295032832
 No errors were found on the image.
 Creating test image with backing file

-Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Filling test image

 === IO: pattern 1
diff --git a/tests/qemu-iotests/019 b/tests/qemu-iotests/019
index 813a84acac47..d3c11256dc0f 100755
--- a/tests/qemu-iotests/019
+++ b/tests/qemu-iotests/019
@@ -74,7 +74,7 @@ echo "Creating test image with backing file"
 echo

 TEST_IMG="$TEST_IMG_SAVE.orig"
-_make_test_img -b "$TEST_IMG_SAVE.base" 6G
+_make_test_img -b "$TEST_IMG_SAVE.base" -F $IMGFMT 6G

 echo "Filling test image"
 echo
@@ -98,7 +98,8 @@ for backing_option in "-B " "-o backing_file="; do
     echo
     echo Testing conversion with $backing_option"$TEST_IMG.base" | _filter_testdir | _filter_imgfmt
     echo
-    $QEMU_IMG convert -f $IMGFMT -O $IMGFMT $backing_option"$TEST_IMG.base" "$TEST_IMG.orig" "$TEST_IMG"
+    $QEMU_IMG convert -f $IMGFMT -O $IMGFMT $backing_option"$TEST_IMG.base" \
+        -o backing_fmt=$IMGFMT "$TEST_IMG.orig" "$TEST_IMG"

     echo "Checking if backing clusters are allocated when they shouldn't"
     echo
diff --git a/tests/qemu-iotests/019.out b/tests/qemu-iotests/019.out
index 17a7c036b989..0fa73bd69ab8 100644
--- a/tests/qemu-iotests/019.out
+++ b/tests/qemu-iotests/019.out
@@ -269,7 +269,7 @@ wrote 65536/65536 bytes at offset 4296015872
 No errors were found on the image.
 Creating test image with backing file

-Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT.orig', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Filling test image

 === IO: pattern 43
diff --git a/tests/qemu-iotests/020 b/tests/qemu-iotests/020
index 20f8f185d071..f9167527bea7 100755
--- a/tests/qemu-iotests/020
+++ b/tests/qemu-iotests/020
@@ -70,7 +70,7 @@ echo "Creating test image with backing file"
 echo

 TEST_IMG="$TEST_IMG_SAVE"
-_make_test_img -b "$TEST_IMG.base" 6G
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 6G

 echo "Filling test image"
 echo
diff --git a/tests/qemu-iotests/020.out b/tests/qemu-iotests/020.out
index 4b722b2dd022..3fad6a59e09b 100644
--- a/tests/qemu-iotests/020.out
+++ b/tests/qemu-iotests/020.out
@@ -269,7 +269,7 @@ wrote 65536/65536 bytes at offset 4295032832
 No errors were found on the image.
 Creating test image with backing file

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Filling test image

 === IO: pattern 1
diff --git a/tests/qemu-iotests/024 b/tests/qemu-iotests/024
index e2e766241e1a..3c5d57310e94 100755
--- a/tests/qemu-iotests/024
+++ b/tests/qemu-iotests/024
@@ -83,7 +83,7 @@ TEST_IMG="$TEST_IMG_SAVE"
 echo "Creating COW image"
 echo

-_make_test_img -b "$TEST_IMG.base_old" 1G
+_make_test_img -b "$TEST_IMG.base_old" -F $IMGFMT 1G
 io_pattern writev 0 $((4 * CLUSTER_SIZE)) 0 1 0x33
 io_pattern writev $((8 * CLUSTER_SIZE)) $((4 * CLUSTER_SIZE)) 0 1 0x33

@@ -109,7 +109,7 @@ io_pattern readv $((15 * CLUSTER_SIZE)) $CLUSTER_SIZE 0 1 0x00
 echo
 echo Rebase and test again
 echo
-$QEMU_IMG rebase -b "$TEST_IMG.base_new" "$TEST_IMG"
+$QEMU_IMG rebase -b "$TEST_IMG.base_new" -F $IMGFMT "$TEST_IMG"
 io_pattern readv $((0 * CLUSTER_SIZE)) $CLUSTER_SIZE 0 1 0x33
 io_pattern readv $((1 * CLUSTER_SIZE)) $CLUSTER_SIZE 0 1 0x33
 io_pattern readv $((2 * CLUSTER_SIZE)) $CLUSTER_SIZE 0 1 0x33
@@ -159,7 +159,7 @@ OVERLAY="$TEST_DIR/$OVERLAY_WREL"

 TEST_IMG=$BASE_OLD _make_test_img 1M
 TEST_IMG=$BASE_NEW _make_test_img 1M
-TEST_IMG=$OVERLAY _make_test_img -b "$BASE_OLD_OREL" 1M
+TEST_IMG=$OVERLAY _make_test_img -b "$BASE_OLD_OREL" -F $IMGFMT 1M

 echo

@@ -176,7 +176,7 @@ $QEMU_IO "$BASE_NEW" \
 echo

 pushd "$TEST_DIR" >/dev/null
-$QEMU_IMG rebase -f "$IMGFMT" -b "$BASE_NEW_OREL" "$OVERLAY_WREL"
+$QEMU_IMG rebase -f "$IMGFMT" -b "$BASE_NEW_OREL" -F $IMGFMT "$OVERLAY_WREL"
 popd >/dev/null

 # Verify the backing path is correct
diff --git a/tests/qemu-iotests/024.out b/tests/qemu-iotests/024.out
index 024dc786b3c4..f4fd77fd5b4d 100644
--- a/tests/qemu-iotests/024.out
+++ b/tests/qemu-iotests/024.out
@@ -33,7 +33,7 @@ wrote 131072/131072 bytes at offset 786432
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 Creating COW image

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 backing_file=TEST_DIR/t.IMGFMT.base_old
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 backing_file=TEST_DIR/t.IMGFMT.base_old backing_fmt=IMGFMT
 === IO: pattern 0x33
 wrote 262144/262144 bytes at offset 0
 256 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
@@ -146,7 +146,7 @@ read 65536/65536 bytes at offset 983040

 Formatting 'TEST_DIR/subdir/t.IMGFMT.base_old', fmt=IMGFMT size=1048576
 Formatting 'TEST_DIR/subdir/t.IMGFMT.base_new', fmt=IMGFMT size=1048576
-Formatting 'TEST_DIR/subdir/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=t.IMGFMT.base_old
+Formatting 'TEST_DIR/subdir/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=t.IMGFMT.base_old backing_fmt=IMGFMT

 wrote 131072/131072 bytes at offset 0
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
@@ -158,6 +158,7 @@ wrote 65536/65536 bytes at offset 196608
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

 backing file: t.IMGFMT.base_new (actual path: TEST_DIR/subdir/t.IMGFMT.base_new)
+backing file format: IMGFMT

 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
diff --git a/tests/qemu-iotests/028 b/tests/qemu-iotests/028
index 797dae535042..5d043cef9289 100755
--- a/tests/qemu-iotests/028
+++ b/tests/qemu-iotests/028
@@ -76,7 +76,7 @@ echo "Creating test image with backing file"
 echo

 TEST_IMG="$TEST_IMG_SAVE"
-_make_test_img -b "$TEST_IMG.base" $image_size
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $image_size

 echo "Filling test image"
 echo
@@ -101,7 +101,7 @@ io_zero readv $(( offset + 32 * 1024 )) 512 1024 32
 _check_test_img

 # Rebase it on top of its base image
-$QEMU_IMG rebase -b "$TEST_IMG.base" "$TEST_IMG"
+$QEMU_IMG rebase -b "$TEST_IMG.base" -F $IMGFMT "$TEST_IMG"

 echo
 echo block-backup
diff --git a/tests/qemu-iotests/028.out b/tests/qemu-iotests/028.out
index 37aed8443628..12f82c6a6c39 100644
--- a/tests/qemu-iotests/028.out
+++ b/tests/qemu-iotests/028.out
@@ -70,7 +70,7 @@ wrote 512/512 bytes at offset 3221225984
 No errors were found on the image.
 Creating test image with backing file

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294968832 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294968832 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Filling test image

 === IO: pattern 196
diff --git a/tests/qemu-iotests/030 b/tests/qemu-iotests/030
index aa911d266a13..322e31e2cd93 100755
--- a/tests/qemu-iotests/030
+++ b/tests/qemu-iotests/030
@@ -32,8 +32,12 @@ class TestSingleDrive(iotests.QMPTestCase):

     def setUp(self):
         iotests.create_image(backing_img, TestSingleDrive.image_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, mid_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % mid_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img,
+                 '-F', 'raw', mid_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % mid_img,
+                 '-F', iotests.imgfmt, test_img)
         qemu_io('-f', 'raw', '-c', 'write -P 0x1 0 512', backing_img)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0x1 524288 512', mid_img)
         self.vm = iotests.VM().add_drive("blkdebug::" + test_img,
@@ -199,7 +203,8 @@ class TestParallelOps(iotests.QMPTestCase):
         iotests.create_image(self.imgs[0], self.image_len)
         for i in range(1, self.num_imgs):
             qemu_img('create', '-f', iotests.imgfmt,
-                     '-o', 'backing_file=%s' % self.imgs[i-1], self.imgs[i])
+                     '-o', 'backing_file=%s' % self.imgs[i-1],
+                     '-F', 'raw' if i == 1 else iotests.imgfmt, self.imgs[i])

         # Put data into the images we are copying data from
         odd_img_indexes = [x for x in reversed(range(self.num_imgs)) if x % 2 == 1]
@@ -544,7 +549,8 @@ class TestQuorum(iotests.QMPTestCase):
             qemu_io('-f', iotests.imgfmt,
                     '-c', 'write -P 0x55 0 1024', backing_img)
             qemu_img('create', '-f', iotests.imgfmt,
-                     '-o', 'backing_file=%s' % backing_img, child_img)
+                     '-o', 'backing_file=%s' % backing_img,
+                     '-F', iotests.imgfmt, child_img)
             opts.append("children.%d.file.filename=%s" % (i, child_img))
             opts.append("children.%d.node-name=node%d" % (i, i))

@@ -585,7 +591,9 @@ class TestSmallerBackingFile(iotests.QMPTestCase):

     def setUp(self):
         iotests.create_image(backing_img, self.backing_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, test_img, str(self.image_len))
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img,
+                 '-F', 'raw', test_img, str(self.image_len))
         self.vm = iotests.VM().add_drive(test_img)
         self.vm.launch()

@@ -848,7 +856,9 @@ class TestStreamStop(iotests.QMPTestCase):
     def setUp(self):
         qemu_img('create', backing_img, str(TestStreamStop.image_len))
         qemu_io('-f', 'raw', '-c', 'write -P 0x1 0 32M', backing_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img,
+                 '-F', 'raw', test_img)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0x1 32M 32M', test_img)
         self.vm = iotests.VM().add_drive("blkdebug::" + test_img)
         self.vm.launch()
@@ -879,7 +889,9 @@ class TestSetSpeed(iotests.QMPTestCase):
     def setUp(self):
         qemu_img('create', backing_img, str(TestSetSpeed.image_len))
         qemu_io('-f', 'raw', '-c', 'write -P 0x1 0 32M', backing_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img,
+                 '-F', 'raw', test_img)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0x1 32M 32M', test_img)
         self.vm = iotests.VM().add_drive('blkdebug::' + test_img)
         self.vm.launch()
diff --git a/tests/qemu-iotests/034 b/tests/qemu-iotests/034
index da4cea1571e4..ac2d687c71da 100755
--- a/tests/qemu-iotests/034
+++ b/tests/qemu-iotests/034
@@ -58,7 +58,7 @@ $QEMU_IO -c "write -P 0x55 0 1M" "$TEST_IMG" | _filter_qemu_io

 TEST_IMG="$TEST_IMG_SAVE"

-_make_test_img -b "$TEST_IMG.base" 6G
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 6G

 echo
 echo "== zero write with backing file =="
diff --git a/tests/qemu-iotests/034.out b/tests/qemu-iotests/034.out
index 0764ead8b95d..478205ad2542 100644
--- a/tests/qemu-iotests/034.out
+++ b/tests/qemu-iotests/034.out
@@ -4,7 +4,7 @@ QA output created by 034
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
 wrote 1048576/1048576 bytes at offset 0
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == zero write with backing file ==
 wrote 196608/196608 bytes at offset 65536
diff --git a/tests/qemu-iotests/037 b/tests/qemu-iotests/037
index e6517acbd4cd..e1187ac24a0b 100755
--- a/tests/qemu-iotests/037
+++ b/tests/qemu-iotests/037
@@ -74,7 +74,7 @@ backing_io 0 256 write | $QEMU_IO "$TEST_IMG" | _filter_qemu_io

 TEST_IMG="$TEST_IMG_SAVE"

-_make_test_img -b "$TEST_IMG.base" 6G
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 6G

 echo
 echo "== COW in a single cluster =="
diff --git a/tests/qemu-iotests/037.out b/tests/qemu-iotests/037.out
index cd6710c90160..30ef989b64d6 100644
--- a/tests/qemu-iotests/037.out
+++ b/tests/qemu-iotests/037.out
@@ -514,7 +514,7 @@ wrote 512/512 bytes at offset 130048
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 512/512 bytes at offset 130560
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == COW in a single cluster ==
 wrote 2048/2048 bytes at offset 0
diff --git a/tests/qemu-iotests/038 b/tests/qemu-iotests/038
index 707e2d72e92d..a253231f5baf 100755
--- a/tests/qemu-iotests/038
+++ b/tests/qemu-iotests/038
@@ -71,7 +71,7 @@ backing_io 0 256 write | $QEMU_IO "$TEST_IMG" | _filter_qemu_io

 TEST_IMG="$TEST_IMG_SAVE"

-_make_test_img -b "$TEST_IMG.base" 6G
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 6G

 echo
 echo "== Some concurrent requests touching the same cluster =="
diff --git a/tests/qemu-iotests/038.out b/tests/qemu-iotests/038.out
index 0bdfb19faa63..fe2108593ae6 100644
--- a/tests/qemu-iotests/038.out
+++ b/tests/qemu-iotests/038.out
@@ -514,7 +514,7 @@ wrote 65536/65536 bytes at offset 16646144
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 16711680
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == Some concurrent requests touching the same cluster ==
 wrote 65536/65536 bytes at offset XXX
diff --git a/tests/qemu-iotests/039 b/tests/qemu-iotests/039
index ddce48ab4752..42f65031383a 100755
--- a/tests/qemu-iotests/039
+++ b/tests/qemu-iotests/039
@@ -133,7 +133,8 @@ echo "== Committing to a backing file with lazy_refcounts=on =="

 TEST_IMG="$TEST_IMG".base _make_test_img -o "compat=1.1,lazy_refcounts=on" $size

-_make_test_img -o "compat=1.1,lazy_refcounts=on,backing_file=$TEST_IMG.base" $size
+_make_test_img -o "compat=1.1,lazy_refcounts=on,backing_file=$TEST_IMG.base" \
+    -F $IMGFMT $size

 $QEMU_IO -c "write 0 512" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG commit "$TEST_IMG"
diff --git a/tests/qemu-iotests/039.out b/tests/qemu-iotests/039.out
index bdafa3ace360..e52484d4be1b 100644
--- a/tests/qemu-iotests/039.out
+++ b/tests/qemu-iotests/039.out
@@ -66,7 +66,7 @@ No errors were found on the image.

 == Committing to a backing file with lazy_refcounts=on ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 Image committed.
diff --git a/tests/qemu-iotests/040 b/tests/qemu-iotests/040
index 32c82b4ec68a..f58f50d023e6 100755
--- a/tests/qemu-iotests/040
+++ b/tests/qemu-iotests/040
@@ -80,8 +80,11 @@ class TestSingleDrive(ImageCommitTestCase):

     def setUp(self):
         iotests.create_image(backing_img, self.image_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, mid_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % mid_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', mid_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % mid_img,
+                 '-F', iotests.imgfmt, test_img)
         qemu_io('-f', 'raw', '-c', 'write -P 0xab 0 524288', backing_img)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xef 524288 524288', mid_img)
         self.vm = iotests.VM().add_drive(test_img, "node-name=top,backing.node-name=mid,backing.backing.node-name=base", interface="none")
@@ -305,10 +308,16 @@ class TestRelativePaths(ImageCommitTestCase):
             if exception.errno != errno.EEXIST:
                 raise
         iotests.create_image(self.backing_img_abs, TestRelativePaths.image_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % self.backing_img_abs, self.mid_img_abs)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % self.mid_img_abs, self.test_img)
-        qemu_img('rebase', '-u', '-b', self.backing_img, self.mid_img_abs)
-        qemu_img('rebase', '-u', '-b', self.mid_img, self.test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % self.backing_img_abs,
+                 '-F', 'raw', self.mid_img_abs)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % self.mid_img_abs,
+                 '-F', iotests.imgfmt, self.test_img)
+        qemu_img('rebase', '-u', '-b', self.backing_img,
+                 '-F', 'raw', self.mid_img_abs)
+        qemu_img('rebase', '-u', '-b', self.mid_img,
+                 '-F', iotests.imgfmt, self.test_img)
         qemu_io('-f', 'raw', '-c', 'write -P 0xab 0 524288', self.backing_img_abs)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xef 524288 524288', self.mid_img_abs)
         self.vm = iotests.VM().add_drive(self.test_img)
@@ -371,8 +380,11 @@ class TestSetSpeed(ImageCommitTestCase):

     def setUp(self):
         qemu_img('create', backing_img, str(TestSetSpeed.image_len))
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, mid_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % mid_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', mid_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % mid_img,
+                 '-F', iotests.imgfmt, test_img)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0x1 0 512', test_img)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xef 524288 524288', mid_img)
         self.vm = iotests.VM().add_drive('blkdebug::' + test_img)
@@ -410,9 +422,14 @@ class TestReopenOverlay(ImageCommitTestCase):

     def setUp(self):
         iotests.create_image(self.img0, self.image_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % self.img0, self.img1)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % self.img1, self.img2)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % self.img2, self.img3)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % self.img0, '-F', 'raw', self.img1)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % self.img1,
+                 '-F', iotests.imgfmt, self.img2)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % self.img2,
+                 '-F', iotests.imgfmt, self.img3)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xab 0 128K', self.img1)
         self.vm = iotests.VM().add_drive(self.img3)
         self.vm.launch()
@@ -435,8 +452,12 @@ class TestErrorHandling(iotests.QMPTestCase):

     def setUp(self):
         iotests.create_image(backing_img, self.image_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, mid_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % mid_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img,
+                 '-F', 'raw', mid_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % mid_img,
+                 '-F', iotests.imgfmt, test_img)

         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0x11 0 512k', mid_img)
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0x22 0 512k', test_img)
diff --git a/tests/qemu-iotests/041 b/tests/qemu-iotests/041
index 5d67bf14bfe8..547d75cc491a 100755
--- a/tests/qemu-iotests/041
+++ b/tests/qemu-iotests/041
@@ -44,7 +44,8 @@ class TestSingleDrive(iotests.QMPTestCase):

     def setUp(self):
         iotests.create_image(backing_img, self.image_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', test_img)
         self.vm = iotests.VM().add_drive(test_img, "node-name=top,backing.node-name=base")
         if iotests.qemu_default_machine == 'pc':
             self.vm.add_drive(None, 'media=cdrom', 'ide')
@@ -157,7 +158,8 @@ class TestSingleDrive(iotests.QMPTestCase):
         self.assert_no_active_block_jobs()

         qemu_img('create', '-f', iotests.imgfmt, '-o', 'cluster_size=%d,backing_file=%s'
-                        % (self.image_len, backing_img), target_img)
+                        % (self.image_len, backing_img),
+                 '-F', 'raw', target_img)
         result = self.vm.qmp(self.qmp_cmd, device='drive0', sync='full',
                              mode='existing', target=self.qmp_target)
         self.assert_qmp(result, 'return', {})
@@ -227,7 +229,8 @@ class TestSingleBlockdev(TestSingleDrive):

     def setUp(self):
         TestSingleDrive.setUp(self)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, target_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', target_img)
         args = {'driver': iotests.imgfmt,
                 'node-name': self.qmp_target,
                 'file': { 'filename': target_img, 'driver': 'file' } }
@@ -265,7 +268,8 @@ class TestMirrorNoBacking(iotests.QMPTestCase):

     def setUp(self):
         iotests.create_image(backing_img, TestMirrorNoBacking.image_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', test_img)
         self.vm = iotests.VM().add_drive(test_img)
         self.vm.launch()

@@ -282,7 +286,8 @@ class TestMirrorNoBacking(iotests.QMPTestCase):
     def test_complete(self):
         self.assert_no_active_block_jobs()

-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, target_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', target_img)
         result = self.vm.qmp('drive-mirror', device='drive0', sync='full',
                              mode='existing', target=target_img)
         self.assert_qmp(result, 'return', {})
@@ -297,7 +302,8 @@ class TestMirrorNoBacking(iotests.QMPTestCase):
     def test_cancel(self):
         self.assert_no_active_block_jobs()

-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, target_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', target_img)
         result = self.vm.qmp('drive-mirror', device='drive0', sync='full',
                              mode='existing', target=target_img)
         self.assert_qmp(result, 'return', {})
@@ -316,7 +322,8 @@ class TestMirrorNoBacking(iotests.QMPTestCase):
         qemu_img('create', '-f', iotests.imgfmt, '-o', 'size=%d'
                         %(TestMirrorNoBacking.image_len), target_backing_img)
         qemu_img('create', '-f', iotests.imgfmt, '-o', 'cluster_size=%d,backing_file=%s'
-                        % (TestMirrorNoBacking.image_len, target_backing_img), target_img)
+                        % (TestMirrorNoBacking.image_len, target_backing_img),
+                 '-F', iotests.imgfmt, target_img)

         result = self.vm.qmp('drive-mirror', device='drive0', sync='full',
                              mode='existing', target=target_img)
@@ -335,7 +342,8 @@ class TestMirrorResized(iotests.QMPTestCase):

     def setUp(self):
         iotests.create_image(backing_img, TestMirrorResized.backing_len)
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', test_img)
         qemu_img('resize', test_img, '2M')
         self.vm = iotests.VM().add_drive(test_img)
         self.vm.launch()
@@ -481,7 +489,9 @@ new_state = "1"
         # Test COW into the target image.  The first half of the
         # cluster at MIRROR_GRANULARITY has to be copied from
         # backing_img, even though sync='top'.
-        qemu_img('create', '-f', iotests.imgfmt, '-ocluster_size=131072,backing_file=%s' %(backing_img), target_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-ocluster_size=131072,backing_file=%s' %(backing_img),
+                 '-F', 'raw', target_img)
         result = self.vm.qmp('drive-mirror', device='drive0', sync='top',
                              on_source_error='ignore',
                              mode='existing', target=target_img)
@@ -501,7 +511,8 @@ new_state = "1"
         self.vm.shutdown()

         # Detach blkdebug to compare images successfully
-        qemu_img('rebase', '-f', iotests.imgfmt, '-u', '-b', backing_img, test_img)
+        qemu_img('rebase', '-f', iotests.imgfmt, '-u', '-b', backing_img,
+                 '-F', 'raw', test_img)
         self.assertTrue(iotests.compare_images(test_img, target_img),
                         'target image does not match source after mirroring')

@@ -573,7 +584,8 @@ new_state = "1"
         self.blkdebug_file = target_img + ".blkdebug"
         iotests.create_image(backing_img, TestWriteErrors.image_len)
         self.create_blkdebug_file(self.blkdebug_file, "write_aio", 5)
-        qemu_img('create', '-f', iotests.imgfmt, '-obacking_file=%s' %(backing_img), test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-obacking_file=%s' %(backing_img), '-F', 'raw', test_img)
         self.vm = iotests.VM().add_drive(test_img)
         self.target_img = 'blkdebug:%s:%s' % (self.blkdebug_file, target_img)
         qemu_img('create', '-f', iotests.imgfmt, '-osize=%d' %(TestWriteErrors.image_len), target_img)
@@ -668,7 +680,8 @@ class TestSetSpeed(iotests.QMPTestCase):

     def setUp(self):
         qemu_img('create', backing_img, str(TestSetSpeed.image_len))
-        qemu_img('create', '-f', iotests.imgfmt, '-o', 'backing_file=%s' % backing_img, test_img)
+        qemu_img('create', '-f', iotests.imgfmt,
+                 '-o', 'backing_file=%s' % backing_img, '-F', 'raw', test_img)
         self.vm = iotests.VM().add_drive(test_img)
         self.vm.launch()

diff --git a/tests/qemu-iotests/042 b/tests/qemu-iotests/042
index 0e85b356b76a..e8f23a174ce7 100755
--- a/tests/qemu-iotests/042
+++ b/tests/qemu-iotests/042
@@ -64,8 +64,8 @@ _check_test_img
 echo
 echo "== Rebasing the image =="

-$QEMU_IMG rebase -u -b "$TEST_IMG.orig" "$TEST_IMG"
-$QEMU_IMG rebase -b "$TEST_IMG.orig" "$TEST_IMG"
+$QEMU_IMG rebase -u -b "$TEST_IMG.orig" -F $IMGFMT "$TEST_IMG"
+$QEMU_IMG rebase -b "$TEST_IMG.orig" -F $IMGFMT "$TEST_IMG"
 _check_test_img

 # success, all done
diff --git a/tests/qemu-iotests/043 b/tests/qemu-iotests/043
index b102e49208b8..e4022b7044de 100755
--- a/tests/qemu-iotests/043
+++ b/tests/qemu-iotests/043
@@ -46,7 +46,7 @@ _supported_proto file

 size=128M
 _make_test_img $size
-$QEMU_IMG rebase -u -b "$TEST_IMG" "$TEST_IMG"
+$QEMU_IMG rebase -u -b "$TEST_IMG" -F $IMGFMT "$TEST_IMG"

 echo
 echo "== backing file references self =="
@@ -54,8 +54,8 @@ _img_info --backing-chain

 _make_test_img $size
 mv "$TEST_IMG" "$TEST_IMG.base"
-_make_test_img -b "$TEST_IMG.base" $size
-$QEMU_IMG rebase -u -b "$TEST_IMG" "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $size
+$QEMU_IMG rebase -u -b "$TEST_IMG" -F $IMGFMT "$TEST_IMG.base"

 echo
 echo "== parent references self =="
@@ -63,12 +63,12 @@ _img_info --backing-chain

 _make_test_img $size
 mv "$TEST_IMG" "$TEST_IMG.1.base"
-_make_test_img -b "$TEST_IMG.1.base" $size
+_make_test_img -b "$TEST_IMG.1.base" -F $IMGFMT $size
 mv "$TEST_IMG" "$TEST_IMG.2.base"
-_make_test_img -b "$TEST_IMG.2.base" $size
+_make_test_img -b "$TEST_IMG.2.base" -F $IMGFMT $size
 mv "$TEST_IMG" "$TEST_IMG.3.base"
-_make_test_img -b "$TEST_IMG.3.base" $size
-$QEMU_IMG rebase -u -b "$TEST_IMG.2.base" "$TEST_IMG.1.base"
+_make_test_img -b "$TEST_IMG.3.base" -F $IMGFMT $size
+$QEMU_IMG rebase -u -b "$TEST_IMG.2.base" -F $IMGFMT "$TEST_IMG.1.base"

 echo
 echo "== ancestor references another ancestor =="
@@ -76,9 +76,9 @@ _img_info --backing-chain

 _make_test_img $size
 mv "$TEST_IMG" "$TEST_IMG.1.base"
-_make_test_img -b "$TEST_IMG.1.base" $size
+_make_test_img -b "$TEST_IMG.1.base" -F $IMGFMT $size
 mv "$TEST_IMG" "$TEST_IMG.2.base"
-_make_test_img -b "$TEST_IMG.2.base" $size
+_make_test_img -b "$TEST_IMG.2.base" -F $IMGFMT $size

 echo
 echo "== finite chain of length 3 (human) =="
diff --git a/tests/qemu-iotests/043.out b/tests/qemu-iotests/043.out
index 0280f999ce12..7251e26d4ff9 100644
--- a/tests/qemu-iotests/043.out
+++ b/tests/qemu-iotests/043.out
@@ -4,20 +4,20 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
 == backing file references self ==
 qemu-img: Backing file 'TEST_DIR/t.IMGFMT' creates an infinite loop.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == parent references self ==
 qemu-img: Backing file 'TEST_DIR/t.IMGFMT' creates an infinite loop.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.1.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.2.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.3.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.1.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.2.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.3.base backing_fmt=IMGFMT

 == ancestor references another ancestor ==
 qemu-img: Backing file 'TEST_DIR/t.IMGFMT.2.base' creates an infinite loop.
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.1.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.2.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.1.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.2.base backing_fmt=IMGFMT

 == finite chain of length 3 (human) ==
 image: TEST_DIR/t.IMGFMT
@@ -25,12 +25,14 @@ file format: IMGFMT
 virtual size: 128 MiB (134217728 bytes)
 cluster_size: 65536
 backing file: TEST_DIR/t.IMGFMT.2.base
+backing file format: IMGFMT

 image: TEST_DIR/t.IMGFMT.2.base
 file format: IMGFMT
 virtual size: 128 MiB (134217728 bytes)
 cluster_size: 65536
 backing file: TEST_DIR/t.IMGFMT.1.base
+backing file format: IMGFMT

 image: TEST_DIR/t.IMGFMT.1.base
 file format: IMGFMT
@@ -40,6 +42,7 @@ cluster_size: 65536
 == finite chain of length 3 (json) ==
 [
     {
+        "backing-filename-format": "IMGFMT",
         "virtual-size": 134217728,
         "filename": "TEST_DIR/t.IMGFMT",
         "cluster-size": 65536,
@@ -49,6 +52,7 @@ cluster_size: 65536
         "dirty-flag": false
     },
     {
+        "backing-filename-format": "IMGFMT",
         "virtual-size": 134217728,
         "filename": "TEST_DIR/t.IMGFMT.2.base",
         "cluster-size": 65536,
diff --git a/tests/qemu-iotests/046 b/tests/qemu-iotests/046
index a066eec60598..7384136dc016 100755
--- a/tests/qemu-iotests/046
+++ b/tests/qemu-iotests/046
@@ -69,7 +69,7 @@ backing_io 0 32 write | $QEMU_IO "$TEST_IMG" | _filter_qemu_io

 mv "$TEST_IMG" "$TEST_IMG.base"

-_make_test_img -b "$TEST_IMG.base" 6G
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 6G

 echo
 echo "== Some concurrent requests touching the same cluster =="
diff --git a/tests/qemu-iotests/046.out b/tests/qemu-iotests/046.out
index ca2c7404a914..1a9dfe200f6f 100644
--- a/tests/qemu-iotests/046.out
+++ b/tests/qemu-iotests/046.out
@@ -66,7 +66,7 @@ wrote 65536/65536 bytes at offset 1966080
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 2031616
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=6442450944 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == Some concurrent requests touching the same cluster ==
 blkdebug: Suspended request 'A'
diff --git a/tests/qemu-iotests/050 b/tests/qemu-iotests/050
index cdc53565410d..4b0a390c437c 100755
--- a/tests/qemu-iotests/050
+++ b/tests/qemu-iotests/050
@@ -58,13 +58,13 @@ $QEMU_IO -c "write -P 0x5a 0 1048576" "$TEST_IMG" | _filter_qemu_io

 TEST_IMG="$TEST_IMG_SAVE"

-_make_test_img -b "$TEST_IMG.old" $size
+_make_test_img -b "$TEST_IMG.old" -F $IMGFMT $size
 $QEMU_IO -c "write -z 0 1048576" "$TEST_IMG" | _filter_qemu_io

 echo
 echo "== Rebasing the image =="

-$QEMU_IMG rebase -b "$TEST_IMG.new" "$TEST_IMG"
+$QEMU_IMG rebase -b "$TEST_IMG.new" -F $IMGFMT "$TEST_IMG"
 $QEMU_IO -c "read -P 0x00 0 1048576" "$TEST_IMG" | _filter_qemu_io

 # success, all done
diff --git a/tests/qemu-iotests/050.out b/tests/qemu-iotests/050.out
index 3602d580dc05..ab3daeddca3e 100644
--- a/tests/qemu-iotests/050.out
+++ b/tests/qemu-iotests/050.out
@@ -7,7 +7,7 @@ wrote 1048576/1048576 bytes at offset 0
 Formatting 'TEST_DIR/t.IMGFMT.new', fmt=IMGFMT size=10485760
 wrote 1048576/1048576 bytes at offset 0
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=10485760 backing_file=TEST_DIR/t.IMGFMT.old
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=10485760 backing_file=TEST_DIR/t.IMGFMT.old backing_fmt=IMGFMT
 wrote 1048576/1048576 bytes at offset 0
 1 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

diff --git a/tests/qemu-iotests/051 b/tests/qemu-iotests/051
index 034d3a325077..bee26075b207 100755
--- a/tests/qemu-iotests/051
+++ b/tests/qemu-iotests/051
@@ -70,7 +70,7 @@ device_id="drive0"
 _make_test_img $size
 cp "$TEST_IMG" "$TEST_IMG.orig"
 mv "$TEST_IMG" "$TEST_IMG.base"
-_make_test_img -b "$TEST_IMG.base" $size
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $size

 echo
 echo === Unknown option ===
diff --git a/tests/qemu-iotests/051.out b/tests/qemu-iotests/051.out
index 554c5ca90a02..de4771bcb36d 100644
--- a/tests/qemu-iotests/051.out
+++ b/tests/qemu-iotests/051.out
@@ -1,6 +1,6 @@
 QA output created by 051
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 === Unknown option ===

diff --git a/tests/qemu-iotests/051.pc.out b/tests/qemu-iotests/051.pc.out
index 0ea80d35f0e2..0a261753faac 100644
--- a/tests/qemu-iotests/051.pc.out
+++ b/tests/qemu-iotests/051.pc.out
@@ -1,6 +1,6 @@
 QA output created by 051
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 === Unknown option ===

diff --git a/tests/qemu-iotests/060 b/tests/qemu-iotests/060
index 043f12904aab..2f0894e255ea 100755
--- a/tests/qemu-iotests/060
+++ b/tests/qemu-iotests/060
@@ -163,7 +163,7 @@ $QEMU_IO -c 'write 0k 64k' "$BACKING_IMG" | _filter_qemu_io
 # compat=0.10 is required in order to make the following discard actually
 # unallocate the sector rather than make it a zero sector - we want COW, after
 # all.
-_make_test_img -o 'compat=0.10' -b "$BACKING_IMG" 1G
+_make_test_img -o 'compat=0.10' -b "$BACKING_IMG" -F $IMGFMT 1G
 # Write two clusters, the second one enforces creation of an L2 table after
 # the first data cluster.
 $QEMU_IO -c 'write 0k 64k' -c 'write 512M 64k' "$TEST_IMG" | _filter_qemu_io
diff --git a/tests/qemu-iotests/060.out b/tests/qemu-iotests/060.out
index d27692a33c0d..6b0a3b360d41 100644
--- a/tests/qemu-iotests/060.out
+++ b/tests/qemu-iotests/060.out
@@ -100,7 +100,7 @@ read 512/512 bytes at offset 0
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1073741824
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 536870912
diff --git a/tests/qemu-iotests/061 b/tests/qemu-iotests/061
index 36b040491fef..5d3cbc5083b6 100755
--- a/tests/qemu-iotests/061
+++ b/tests/qemu-iotests/061
@@ -187,7 +187,7 @@ echo "=== Testing zero expansion on backed image ==="
 echo
 TEST_IMG="$TEST_IMG.base" _make_test_img -o "compat=1.1" 64M
 $QEMU_IO -c "write -P 0x2a 0 128k" "$TEST_IMG.base" | _filter_qemu_io
-_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" 64M
+_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" -F $IMGFMT 64M
 $QEMU_IO -c "read -P 0x2a 0 128k" -c "write -z 0 64k" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG amend -o "compat=0.10" "$TEST_IMG"
 _check_test_img
@@ -198,7 +198,7 @@ echo "=== Testing zero expansion on backed inactive clusters ==="
 echo
 TEST_IMG="$TEST_IMG.base" _make_test_img -o "compat=1.1" 64M
 $QEMU_IO -c "write -P 0x2a 0 128k" "$TEST_IMG.base" | _filter_qemu_io
-_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" 64M
+_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" -F $IMGFMT 64M
 $QEMU_IO -c "write -z 0 64k" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG snapshot -c foo "$TEST_IMG"
 $QEMU_IO -c "write -P 0x42 0 128k" "$TEST_IMG" | _filter_qemu_io
@@ -214,7 +214,7 @@ echo "=== Testing zero expansion on backed image with shared L2 table ==="
 echo
 TEST_IMG="$TEST_IMG.base" _make_test_img -o "compat=1.1" 64M
 $QEMU_IO -c "write -P 0x2a 0 128k" "$TEST_IMG.base" | _filter_qemu_io
-_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" 64M
+_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" -F $IMGFMT 64M
 $QEMU_IO -c "write -z 0 128k" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG snapshot -c foo "$TEST_IMG"
 $QEMU_IMG amend -o "compat=0.10" "$TEST_IMG"
@@ -237,7 +237,7 @@ echo
 echo "=== Testing progress report without snapshot ==="
 echo
 TEST_IMG="$TEST_IMG.base" _make_test_img -o "compat=1.1" 4G
-_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" 4G
+_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" -F $IMGFMT 4G
 $QEMU_IO -c "write -z 0  64k" \
          -c "write -z 1G 64k" \
          -c "write -z 2G 64k" \
@@ -249,7 +249,7 @@ echo
 echo "=== Testing progress report with snapshot ==="
 echo
 TEST_IMG="$TEST_IMG.base" _make_test_img -o "compat=1.1" 4G
-_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" 4G
+_make_test_img -o "compat=1.1" -b "$TEST_IMG.base" -F $IMGFMT 4G
 $QEMU_IO -c "write -z 0  64k" \
          -c "write -z 1G 64k" \
          -c "write -z 2G 64k" \
diff --git a/tests/qemu-iotests/061.out b/tests/qemu-iotests/061.out
index 8b3091a412bc..5963f0f91e95 100644
--- a/tests/qemu-iotests/061.out
+++ b/tests/qemu-iotests/061.out
@@ -395,7 +395,7 @@ read 131072/131072 bytes at offset 0
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 wrote 131072/131072 bytes at offset 0
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 read 131072/131072 bytes at offset 0
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 0
@@ -411,7 +411,7 @@ read 65536/65536 bytes at offset 65536
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 wrote 131072/131072 bytes at offset 0
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 0
@@ -430,7 +430,7 @@ read 65536/65536 bytes at offset 65536
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 wrote 131072/131072 bytes at offset 0
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 131072/131072 bytes at offset 0
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 No errors were found on the image.
@@ -454,7 +454,7 @@ read 67108864/67108864 bytes at offset 0
 === Testing progress report without snapshot ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=4294967296
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 1073741824
@@ -469,7 +469,7 @@ No errors were found on the image.
 === Testing progress report with snapshot ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=4294967296
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 65536/65536 bytes at offset 1073741824
diff --git a/tests/qemu-iotests/069 b/tests/qemu-iotests/069
index b997b127f025..a4da83b2d9da 100755
--- a/tests/qemu-iotests/069
+++ b/tests/qemu-iotests/069
@@ -46,7 +46,7 @@ echo
 echo "=== Creating an image with a backing file and deleting that file ==="
 echo
 TEST_IMG="$TEST_IMG.base" _make_test_img $IMG_SIZE
-_make_test_img -b "$TEST_IMG.base" $IMG_SIZE
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $IMG_SIZE
 _rm_test_img "$TEST_IMG.base"
 # Just open the image and close it right again (this should print an error message)
 $QEMU_IO -c quit "$TEST_IMG" 2>&1 | _filter_testdir | _filter_imgfmt
diff --git a/tests/qemu-iotests/069.out b/tests/qemu-iotests/069.out
index c78e8c2b7204..126b4d2d519b 100644
--- a/tests/qemu-iotests/069.out
+++ b/tests/qemu-iotests/069.out
@@ -3,6 +3,6 @@ QA output created by 069
 === Creating an image with a backing file and deleting that file ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=131072
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=131072 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 qemu-io: can't open device TEST_DIR/t.IMGFMT: Could not open backing file: Could not open 'TEST_DIR/t.IMGFMT.base': No such file or directory
 *** done
diff --git a/tests/qemu-iotests/073 b/tests/qemu-iotests/073
index 23a1bdf89056..1dce47870914 100755
--- a/tests/qemu-iotests/073
+++ b/tests/qemu-iotests/073
@@ -52,7 +52,7 @@ echo "== creating backing file =="

 TEST_IMG="$TEST_IMG.base" _make_test_img $size

-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT
 $QEMU_IO -c "write -P 0xa5 0 $size" "$TEST_IMG.base" | _filter_qemu_io

 echo
diff --git a/tests/qemu-iotests/073.out b/tests/qemu-iotests/073.out
index de5452492c70..7a718b525e68 100644
--- a/tests/qemu-iotests/073.out
+++ b/tests/qemu-iotests/073.out
@@ -2,7 +2,7 @@ QA output created by 073

 == creating backing file ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 134217728/134217728 bytes at offset 0
 128 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

diff --git a/tests/qemu-iotests/082 b/tests/qemu-iotests/082
index 3286c2c6dbb7..5ddd6427d206 100755
--- a/tests/qemu-iotests/082
+++ b/tests/qemu-iotests/082
@@ -83,8 +83,10 @@ run_qemu_img create -f $IMGFMT -o cluster_size=4k -o help "$TEST_IMG" $size
 run_qemu_img create -f $IMGFMT -o cluster_size=4k -o \? "$TEST_IMG" $size

 # Looks like a help option, but is part of the backing file name
-run_qemu_img create -f $IMGFMT -u -o backing_file="$TEST_IMG",,help "$TEST_IMG" $size
-run_qemu_img create -f $IMGFMT -u -o backing_file="$TEST_IMG",,\? "$TEST_IMG" $size
+run_qemu_img create -f $IMGFMT -u -o backing_file="$TEST_IMG",,help \
+    -F $IMGFMT "$TEST_IMG" $size
+run_qemu_img create -f $IMGFMT -u -o backing_file="$TEST_IMG",,\? \
+    -F $IMGFMT "$TEST_IMG" $size

 # Try to trick qemu-img into creating escaped commas
 run_qemu_img create -f $IMGFMT -o backing_file="$TEST_IMG", -o help "$TEST_IMG" $size
@@ -140,8 +142,8 @@ run_qemu_img convert -O $IMGFMT -o cluster_size=4k -o help "$TEST_IMG" "$TEST_IM
 run_qemu_img convert -O $IMGFMT -o cluster_size=4k -o \? "$TEST_IMG" "$TEST_IMG".base

 # Looks like a help option, but is part of the backing file name
-run_qemu_img convert -O $IMGFMT -o backing_file="$TEST_IMG",,help "$TEST_IMG" "$TEST_IMG".base
-run_qemu_img convert -O $IMGFMT -o backing_file="$TEST_IMG",,\? "$TEST_IMG" "$TEST_IMG".base
+run_qemu_img convert -O $IMGFMT -o backing_fmt=$IMGFMT,backing_file="$TEST_IMG",,help "$TEST_IMG" "$TEST_IMG".base
+run_qemu_img convert -O $IMGFMT -o backing_fmt=$IMGFMT,backing_file="$TEST_IMG",,\? "$TEST_IMG" "$TEST_IMG".base

 # Try to trick qemu-img into creating escaped commas
 run_qemu_img convert -O $IMGFMT -o backing_file="$TEST_IMG", -o help "$TEST_IMG" "$TEST_IMG".base
@@ -199,10 +201,12 @@ run_qemu_img amend -f $IMGFMT -o cluster_size=4k -o help "$TEST_IMG"
 run_qemu_img amend -f $IMGFMT -o cluster_size=4k -o \? "$TEST_IMG"

 # Looks like a help option, but is part of the backing file name
-run_qemu_img amend -f $IMGFMT -o backing_file="$TEST_IMG",,help "$TEST_IMG"
+run_qemu_img amend -f $IMGFMT \
+   -o backing_fmt=$IMGFMT,backing_file="$TEST_IMG",,help "$TEST_IMG"
 run_qemu_img rebase -u -b "" -f $IMGFMT "$TEST_IMG"

-run_qemu_img amend -f $IMGFMT -o backing_file="$TEST_IMG",,\? "$TEST_IMG"
+run_qemu_img amend -f $IMGFMT \
+   -o backing_fmt=$IMGFMT,backing_file="$TEST_IMG",,\? "$TEST_IMG"
 run_qemu_img rebase -u -b "" -f $IMGFMT "$TEST_IMG"

 # Try to trick qemu-img into creating escaped commas
diff --git a/tests/qemu-iotests/082.out b/tests/qemu-iotests/082.out
index 9d4ed4dc9d61..6ac32ad2d7b9 100644
--- a/tests/qemu-iotests/082.out
+++ b/tests/qemu-iotests/082.out
@@ -226,11 +226,11 @@ Supported options:
   refcount_bits=<num>    - Width of a reference count entry in bits
   size=<size>            - Virtual disk size

-Testing: create -f qcow2 -u -o backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2 128M
-Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=134217728 backing_file=TEST_DIR/t.qcow2,,help cluster_size=65536 lazy_refcounts=off refcount_bits=16
+Testing: create -f qcow2 -u -o backing_file=TEST_DIR/t.qcow2,,help -F qcow2 TEST_DIR/t.qcow2 128M
+Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=134217728 backing_file=TEST_DIR/t.qcow2,,help backing_fmt=qcow2 cluster_size=65536 lazy_refcounts=off refcount_bits=16

-Testing: create -f qcow2 -u -o backing_file=TEST_DIR/t.qcow2,,? TEST_DIR/t.qcow2 128M
-Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=134217728 backing_file=TEST_DIR/t.qcow2,,? cluster_size=65536 lazy_refcounts=off refcount_bits=16
+Testing: create -f qcow2 -u -o backing_file=TEST_DIR/t.qcow2,,? -F qcow2 TEST_DIR/t.qcow2 128M
+Formatting 'TEST_DIR/t.qcow2', fmt=qcow2 size=134217728 backing_file=TEST_DIR/t.qcow2,,? backing_fmt=qcow2 cluster_size=65536 lazy_refcounts=off refcount_bits=16

 Testing: create -f qcow2 -o backing_file=TEST_DIR/t.qcow2, -o help TEST_DIR/t.qcow2 128M
 qemu-img: Invalid option list: backing_file=TEST_DIR/t.qcow2,
@@ -506,10 +506,10 @@ Supported options:
   refcount_bits=<num>    - Width of a reference count entry in bits
   size=<size>            - Virtual disk size

-Testing: convert -O qcow2 -o backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
+Testing: convert -O qcow2 -o backing_fmt=qcow2,backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
 qemu-img: Could not open 'TEST_DIR/t.qcow2.base': Could not open backing file: Could not open 'TEST_DIR/t.qcow2,help': No such file or directory

-Testing: convert -O qcow2 -o backing_file=TEST_DIR/t.qcow2,,? TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
+Testing: convert -O qcow2 -o backing_fmt=qcow2,backing_file=TEST_DIR/t.qcow2,,? TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
 qemu-img: Could not open 'TEST_DIR/t.qcow2.base': Could not open backing file: Could not open 'TEST_DIR/t.qcow2,?': No such file or directory

 Testing: convert -O qcow2 -o backing_file=TEST_DIR/t.qcow2, -o help TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.base
@@ -805,11 +805,11 @@ Creation options for 'qcow2':

 Note that not all of these options may be amendable.

-Testing: amend -f qcow2 -o backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2
+Testing: amend -f qcow2 -o backing_fmt=qcow2,backing_file=TEST_DIR/t.qcow2,,help TEST_DIR/t.qcow2

 Testing: rebase -u -b  -f qcow2 TEST_DIR/t.qcow2

-Testing: amend -f qcow2 -o backing_file=TEST_DIR/t.qcow2,,? TEST_DIR/t.qcow2
+Testing: amend -f qcow2 -o backing_fmt=qcow2,backing_file=TEST_DIR/t.qcow2,,? TEST_DIR/t.qcow2

 Testing: rebase -u -b  -f qcow2 TEST_DIR/t.qcow2

diff --git a/tests/qemu-iotests/085 b/tests/qemu-iotests/085
index 46981dbb64ae..09137c70474e 100755
--- a/tests/qemu-iotests/085
+++ b/tests/qemu-iotests/085
@@ -105,7 +105,7 @@ add_snapshot_image()
 {
     base_image="${TEST_DIR}/$((${1}-1))-${snapshot_virt0}"
     snapshot_file="${TEST_DIR}/${1}-${snapshot_virt0}"
-    TEST_IMG=$snapshot_file _make_test_img -u -b "${base_image}" "$size"
+    TEST_IMG=$snapshot_file _make_test_img -u -b "${base_image}" -F $IMGFMT "$size"
     do_blockdev_add "$1" "'backing': null, " "${snapshot_file}"
 }

@@ -224,7 +224,7 @@ echo
 SNAPSHOTS=$((${SNAPSHOTS}+1))

 TEST_IMG="$TEST_IMG.base" _make_test_img "$size"
-_make_test_img -b "${TEST_IMG}.base" "$size"
+_make_test_img -b "${TEST_IMG}.base" -F $IMGFMT "$size"
 do_blockdev_add ${SNAPSHOTS} "" "${TEST_IMG}"
 blockdev_snapshot ${SNAPSHOTS} error

diff --git a/tests/qemu-iotests/085.out b/tests/qemu-iotests/085.out
index d94ad22f70ba..d5f482e01582 100644
--- a/tests/qemu-iotests/085.out
+++ b/tests/qemu-iotests/085.out
@@ -68,12 +68,12 @@ Formatting 'TEST_DIR/10-snapshot-v1.qcow2', fmt=qcow2 size=134217728 backing_fil

 === Create a couple of snapshots using blockdev-snapshot ===

-Formatting 'TEST_DIR/11-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/10-snapshot-v0.IMGFMT
+Formatting 'TEST_DIR/11-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/10-snapshot-v0.IMGFMT backing_fmt=IMGFMT
 { 'execute': 'blockdev-add', 'arguments': { 'driver': 'IMGFMT', 'node-name': 'snap_11', 'backing': null, 'file': { 'driver': 'file', 'filename': 'TEST_DIR/11-snapshot-v0.IMGFMT', 'node-name': 'file_11' } } }
 {"return": {}}
 { 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_11' } }
 {"return": {}}
-Formatting 'TEST_DIR/12-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/11-snapshot-v0.IMGFMT
+Formatting 'TEST_DIR/12-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/11-snapshot-v0.IMGFMT backing_fmt=IMGFMT
 { 'execute': 'blockdev-add', 'arguments': { 'driver': 'IMGFMT', 'node-name': 'snap_12', 'backing': null, 'file': { 'driver': 'file', 'filename': 'TEST_DIR/12-snapshot-v0.IMGFMT', 'node-name': 'file_12' } } }
 {"return": {}}
 { 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_12' } }
@@ -101,7 +101,7 @@ Formatting 'TEST_DIR/12-snapshot-v0.IMGFMT', fmt=IMGFMT size=134217728 backing_f
 === Invalid command - snapshot node has a backing image ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 { 'execute': 'blockdev-add', 'arguments': { 'driver': 'IMGFMT', 'node-name': 'snap_13', 'file': { 'driver': 'file', 'filename': 'TEST_DIR/t.IMGFMT', 'node-name': 'file_13' } } }
 {"return": {}}
 { 'execute': 'blockdev-snapshot', 'arguments': { 'node': 'virtio0', 'overlay':'snap_13' } }
diff --git a/tests/qemu-iotests/089 b/tests/qemu-iotests/089
index 059ad75e28d6..66c5415abe8c 100755
--- a/tests/qemu-iotests/089
+++ b/tests/qemu-iotests/089
@@ -84,7 +84,7 @@ echo
 echo "=== Testing correct handling of 'backing':null ==="
 echo

-_make_test_img -b "$TEST_IMG.base" $IMG_SIZE
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $IMG_SIZE

 # This should read 42
 $QEMU_IO -c 'read -P 42 0 512' "$TEST_IMG" | _filter_qemu_io
diff --git a/tests/qemu-iotests/089.out b/tests/qemu-iotests/089.out
index 20c8ce8f0ef4..15682c28862a 100644
--- a/tests/qemu-iotests/089.out
+++ b/tests/qemu-iotests/089.out
@@ -21,7 +21,7 @@ read 512/512 bytes at offset 0

 === Testing correct handling of 'backing':null ===

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 read 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 512/512 bytes at offset 0
diff --git a/tests/qemu-iotests/095 b/tests/qemu-iotests/095
index 155ae86aa780..77a5f0f3f597 100755
--- a/tests/qemu-iotests/095
+++ b/tests/qemu-iotests/095
@@ -51,9 +51,9 @@ size_larger=100M

 TEST_IMG="$TEST_IMG.base" _make_test_img $size_smaller

-TEST_IMG="$TEST_IMG.snp1" _make_test_img -b "$TEST_IMG.base" $size_larger
+TEST_IMG="$TEST_IMG.snp1" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT $size_larger

-_make_test_img -b "${TEST_IMG}.snp1" $size_larger
+_make_test_img -b "${TEST_IMG}.snp1" -F $IMGFMT $size_larger

 echo
 echo "=== Base image info before commit and resize ==="
diff --git a/tests/qemu-iotests/095.out b/tests/qemu-iotests/095.out
index 614e5ccbbb38..e66ced58f855 100644
--- a/tests/qemu-iotests/095.out
+++ b/tests/qemu-iotests/095.out
@@ -1,7 +1,7 @@
 QA output created by 095
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=5242880
-Formatting 'TEST_DIR/t.IMGFMT.snp1', fmt=IMGFMT size=104857600 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=104857600 backing_file=TEST_DIR/t.IMGFMT.snp1
+Formatting 'TEST_DIR/t.IMGFMT.snp1', fmt=IMGFMT size=104857600 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=104857600 backing_file=TEST_DIR/t.IMGFMT.snp1 backing_fmt=IMGFMT

 === Base image info before commit and resize ===
 image: TEST_DIR/t.IMGFMT.base
diff --git a/tests/qemu-iotests/097 b/tests/qemu-iotests/097
index 690f3d3ce1ed..d910a8b107ea 100755
--- a/tests/qemu-iotests/097
+++ b/tests/qemu-iotests/097
@@ -67,8 +67,8 @@ echo

 len=$((2100 * 1024 * 1024 + 512)) # larger than 2G, and not cluster aligned
 TEST_IMG="$TEST_IMG.base" _make_test_img $len
-TEST_IMG="$TEST_IMG.itmd" _make_test_img -b "$TEST_IMG.base" $len
-_make_test_img -b "$TEST_IMG.itmd" $len
+TEST_IMG="$TEST_IMG.itmd" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT $len
+_make_test_img -b "$TEST_IMG.itmd" -F $IMGFMT $len

 $QEMU_IO -c "write -P 1 0x7ffd0000 192k" "$TEST_IMG.base" | _filter_qemu_io
 $QEMU_IO -c "write -P 2 0x7ffe0000 128k" "$TEST_IMG.itmd" | _filter_qemu_io
diff --git a/tests/qemu-iotests/097.out b/tests/qemu-iotests/097.out
index f6705a1cc74a..3038ddab3100 100644
--- a/tests/qemu-iotests/097.out
+++ b/tests/qemu-iotests/097.out
@@ -3,8 +3,8 @@ QA output created by 097
 === Test pass 0 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
@@ -40,8 +40,8 @@ Offset          Length          File
 === Test pass 1 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
@@ -78,8 +78,8 @@ Offset          Length          File
 === Test pass 2 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
@@ -116,8 +116,8 @@ Offset          Length          File
 === Test pass 3 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
diff --git a/tests/qemu-iotests/098 b/tests/qemu-iotests/098
index 1e29d96b3d7e..f2ccdd790980 100755
--- a/tests/qemu-iotests/098
+++ b/tests/qemu-iotests/098
@@ -52,7 +52,7 @@ echo "=== $event ==="
 echo

 TEST_IMG="$TEST_IMG.base" _make_test_img 64M
-_make_test_img -b "$TEST_IMG.base" 64M
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT 64M

 # Some data that can be leaked when emptying the top image
 $QEMU_IO -c 'write 0 64k' "$TEST_IMG" | _filter_qemu_io
diff --git a/tests/qemu-iotests/098.out b/tests/qemu-iotests/098.out
index 7634d0e8b02b..14d3018ecce7 100644
--- a/tests/qemu-iotests/098.out
+++ b/tests/qemu-iotests/098.out
@@ -3,7 +3,7 @@ QA output created by 098
 === l1_update ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-img: Could not empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
@@ -12,7 +12,7 @@ No errors were found on the image.
 === empty_image_prepare ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-img: Could not empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
@@ -25,7 +25,7 @@ No errors were found on the image.
 === reftable_update ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-img: Could not empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
@@ -39,7 +39,7 @@ No errors were found on the image.
 === refblock_alloc ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 qemu-img: Could not empty blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error
diff --git a/tests/qemu-iotests/110 b/tests/qemu-iotests/110
index 139c02c2cf6b..f1813d0dfb50 100755
--- a/tests/qemu-iotests/110
+++ b/tests/qemu-iotests/110
@@ -50,7 +50,7 @@ echo '=== Reconstructable filename ==='
 echo

 TEST_IMG="$TEST_IMG.base" _make_test_img 64M
-_make_test_img -b "$TEST_IMG_REL.base" 64M
+_make_test_img -b "$TEST_IMG_REL.base" -F $IMGFMT 64M
 # qemu should be able to reconstruct the filename, so relative backing names
 # should work
 # (We have to filter the backing file format because vmdk always
@@ -91,7 +91,7 @@ echo '=== Backing name is always relative to the backed image ==='
 echo

 # omit the image size; it should work anyway
-_make_test_img -b "$TEST_IMG_REL.base"
+_make_test_img -b "$TEST_IMG_REL.base" -F $IMGFMT

 echo
 echo '=== Nodes without a common directory ==='
diff --git a/tests/qemu-iotests/110.out b/tests/qemu-iotests/110.out
index f835553a9930..cf8f6c025d60 100644
--- a/tests/qemu-iotests/110.out
+++ b/tests/qemu-iotests/110.out
@@ -3,7 +3,7 @@ QA output created by 110
 === Reconstructable filename ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=t.IMGFMT.base backing_fmt=IMGFMT
 image: TEST_DIR/t.IMGFMT
 file format: IMGFMT
 virtual size: 64 MiB (67108864 bytes)
@@ -18,7 +18,7 @@ backing file: t.IMGFMT.base (actual path: TEST_DIR/t.IMGFMT.base)

 === Backing name is always relative to the backed image ===

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=t.IMGFMT.base backing_fmt=IMGFMT

 === Nodes without a common directory ===

diff --git a/tests/qemu-iotests/122 b/tests/qemu-iotests/122
index f7a3ae684a7c..61a0d7aeec2a 100755
--- a/tests/qemu-iotests/122
+++ b/tests/qemu-iotests/122
@@ -52,9 +52,10 @@ echo
 echo "=== Check allocation status regression with -B ==="
 echo

-_make_test_img -b "$TEST_IMG".base
+_make_test_img -b "$TEST_IMG".base -F $IMGFMT
 $QEMU_IO -c "write -P 0x22 0 3M" "$TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
-$QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base "$TEST_IMG" "$TEST_IMG".orig
+$QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base \
+    -o backing_fmt=$IMGFMT "$TEST_IMG" "$TEST_IMG".orig
 $QEMU_IMG map "$TEST_IMG".orig | _filter_qemu_img_map


@@ -62,18 +63,22 @@ echo
 echo "=== Check that zero clusters are kept in overlay ==="
 echo

-_make_test_img -b "$TEST_IMG".base
+_make_test_img -b "$TEST_IMG".base -F $IMGFMT

 $QEMU_IO -c "write -P 0 0 3M" "$TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
-$QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base "$TEST_IMG" "$TEST_IMG".orig
+$QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base -o backing_fmt=$IMGFMT \
+    "$TEST_IMG" "$TEST_IMG".orig
 $QEMU_IO -c "read -P 0 0 3M" "$TEST_IMG".orig 2>&1 | _filter_qemu_io | _filter_testdir
-$QEMU_IMG convert -O $IMGFMT -c -B "$TEST_IMG".base "$TEST_IMG" "$TEST_IMG".orig
+$QEMU_IMG convert -O $IMGFMT -c -B "$TEST_IMG".base -o backing_fmt=$IMGFMT \
+    "$TEST_IMG" "$TEST_IMG".orig
 $QEMU_IO -c "read -P 0 0 3M" "$TEST_IMG".orig 2>&1 | _filter_qemu_io | _filter_testdir

 $QEMU_IO -c "write -z 0 3M" "$TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir
-$QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base "$TEST_IMG" "$TEST_IMG".orig
+$QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base -o backing_fmt=$IMGFMT \
+    "$TEST_IMG" "$TEST_IMG".orig
 $QEMU_IO -c "read -P 0 0 3M" "$TEST_IMG".orig 2>&1 | _filter_qemu_io | _filter_testdir
-$QEMU_IMG convert -O $IMGFMT -c -B "$TEST_IMG".base "$TEST_IMG" "$TEST_IMG".orig
+$QEMU_IMG convert -O $IMGFMT -c -B "$TEST_IMG".base -o backing_fmt=$IMGFMT \
+    "$TEST_IMG" "$TEST_IMG".orig
 $QEMU_IO -c "read -P 0 0 3M" "$TEST_IMG".orig 2>&1 | _filter_qemu_io | _filter_testdir


@@ -94,11 +99,11 @@ TEST_IMG="$TEST_IMG".base _make_test_img 256M
 # We do not want such a zero write, however, because we are past the
 # end of the backing file on the target as well, so we do not need to
 # write anything there.
-_make_test_img -b "$TEST_IMG".base 768M
+_make_test_img -b "$TEST_IMG".base 768M -F $IMGFMT

 # Use compat=0.10 as the output so there is no zero cluster support
 $QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base -o compat=0.10 \
-    "$TEST_IMG" "$TEST_IMG".orig
+    -o backing_fmt=$IMGFMT "$TEST_IMG" "$TEST_IMG".orig
 # See that nothing has been allocated past 64M
 $QEMU_IMG map "$TEST_IMG".orig | _filter_qemu_img_map

@@ -110,7 +115,7 @@ $QEMU_IO -c 'write -P 0x11 255M 1M' "$TEST_IMG".base 2>&1 | _filter_qemu_io
 $QEMU_IO -c 'write -P 0x22 600M 1M' "$TEST_IMG" 2>&1 | _filter_qemu_io

 $QEMU_IMG convert -O $IMGFMT -B "$TEST_IMG".base -o compat=0.10 \
-    "$TEST_IMG" "$TEST_IMG".orig
+    -o backing_fmt=$IMGFMT "$TEST_IMG" "$TEST_IMG".orig

 $QEMU_IMG map "$TEST_IMG".orig | _filter_qemu_img_map
 $QEMU_IO -c 'read -P 0x11 255M 1M' \
@@ -199,7 +204,7 @@ $QEMU_IMG map --output=json "$TEST_IMG".orig | _filter_qemu_img_map
 TEST_IMG="$TEST_IMG".base _make_test_img 64M
 $QEMU_IO -c "write -P 0x11 0 32M" "$TEST_IMG".base 2>&1 | _filter_qemu_io | _filter_testdir

-_make_test_img -b "$TEST_IMG".base 64M
+_make_test_img -b "$TEST_IMG".base 64M -F $IMGFMT
 $QEMU_IO -c "write -P 0x22 0 3M" "$TEST_IMG" 2>&1 | _filter_qemu_io | _filter_testdir

 echo
diff --git a/tests/qemu-iotests/122.out b/tests/qemu-iotests/122.out
index 1a35951a80a8..513c34ef3b9d 100644
--- a/tests/qemu-iotests/122.out
+++ b/tests/qemu-iotests/122.out
@@ -5,7 +5,7 @@ wrote 67108864/67108864 bytes at offset 0

 === Check allocation status regression with -B ===

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 3145728/3145728 bytes at offset 0
 3 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 Offset          Length          File
@@ -14,7 +14,7 @@ Offset          Length          File

 === Check that zero clusters are kept in overlay ===

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 3145728/3145728 bytes at offset 0
 3 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 read 3145728/3145728 bytes at offset 0
@@ -31,7 +31,7 @@ read 3145728/3145728 bytes at offset 0
 === Converting to an overlay larger than its backing file ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=268435456
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=805306368 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=805306368 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Offset          Length          File

 wrote 1048576/1048576 bytes at offset 267386880
@@ -141,7 +141,7 @@ read 63963136/63963136 bytes at offset 3145728
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 wrote 33554432/33554432 bytes at offset 0
 32 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 3145728/3145728 bytes at offset 0
 3 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

diff --git a/tests/qemu-iotests/126 b/tests/qemu-iotests/126
index b7fce1e59dd3..dd5a2112278d 100755
--- a/tests/qemu-iotests/126
+++ b/tests/qemu-iotests/126
@@ -61,7 +61,7 @@ BASE_IMG="$TEST_DIR/image:base.$IMGFMT"
 TOP_IMG="$TEST_DIR/image:top.$IMGFMT"

 TEST_IMG=$BASE_IMG _make_test_img 64M
-TEST_IMG=$TOP_IMG _make_test_img -b ./image:base.$IMGFMT
+TEST_IMG=$TOP_IMG _make_test_img -b ./image:base.$IMGFMT -F $IMGFMT

 # (1) The default cluster size depends on the image format
 # (2) vmdk only supports vmdk backing files, so it always reports the
@@ -82,7 +82,7 @@ BASE_IMG="base.$IMGFMT"
 TOP_IMG="file:image:top.$IMGFMT"

 TEST_IMG=$BASE_IMG _make_test_img 64M
-TEST_IMG=$TOP_IMG _make_test_img -b "$BASE_IMG"
+TEST_IMG=$TOP_IMG _make_test_img -b "$BASE_IMG" -F $IMGFMT

 TEST_IMG=$TOP_IMG _img_info | grep -ve 'cluster_size' -e 'backing file format'

diff --git a/tests/qemu-iotests/126.out b/tests/qemu-iotests/126.out
index e3c4d619162d..7d6634685eb5 100644
--- a/tests/qemu-iotests/126.out
+++ b/tests/qemu-iotests/126.out
@@ -8,14 +8,14 @@ Formatting 'file:TEST_DIR/a:b.IMGFMT', fmt=IMGFMT size=67108864
 === Testing relative backing filename resolution ===

 Formatting 'TEST_DIR/image:base.IMGFMT', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/image:top.IMGFMT', fmt=IMGFMT size=67108864 backing_file=./image:base.IMGFMT
+Formatting 'TEST_DIR/image:top.IMGFMT', fmt=IMGFMT size=67108864 backing_file=./image:base.IMGFMT backing_fmt=IMGFMT
 image: TEST_DIR/image:top.IMGFMT
 file format: IMGFMT
 virtual size: 64 MiB (67108864 bytes)
 backing file: ./image:base.IMGFMT (actual path: TEST_DIR/./image:base.IMGFMT)

 Formatting 'base.IMGFMT', fmt=IMGFMT size=67108864
-Formatting 'file:image:top.IMGFMT', fmt=IMGFMT size=67108864 backing_file=base.IMGFMT
+Formatting 'file:image:top.IMGFMT', fmt=IMGFMT size=67108864 backing_file=base.IMGFMT backing_fmt=IMGFMT
 image: ./image:top.IMGFMT
 file format: IMGFMT
 virtual size: 64 MiB (67108864 bytes)
diff --git a/tests/qemu-iotests/127 b/tests/qemu-iotests/127
index a4fc8660381b..e2ac2f55364d 100755
--- a/tests/qemu-iotests/127
+++ b/tests/qemu-iotests/127
@@ -48,8 +48,8 @@ _require_devices virtio-scsi scsi-hd
 IMG_SIZE=64K

 _make_test_img $IMG_SIZE
-TEST_IMG="$TEST_IMG.overlay0" _make_test_img -b "$TEST_IMG" $IMG_SIZE
-TEST_IMG="$TEST_IMG.overlay1" _make_test_img -b "$TEST_IMG" $IMG_SIZE
+TEST_IMG="$TEST_IMG.overlay0" _make_test_img -b "$TEST_IMG" -F $IMGFMT $IMG_SIZE
+TEST_IMG="$TEST_IMG.overlay1" _make_test_img -b "$TEST_IMG" -F $IMGFMT $IMG_SIZE

 # So that we actually have something to mirror and the job does not return
 # immediately (which may be bad because then we cannot know whether the
diff --git a/tests/qemu-iotests/127.out b/tests/qemu-iotests/127.out
index 623d52bbd150..efd6cb327fe5 100644
--- a/tests/qemu-iotests/127.out
+++ b/tests/qemu-iotests/127.out
@@ -1,7 +1,7 @@
 QA output created by 127
 Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=65536
-Formatting 'TEST_DIR/t.IMGFMT.overlay0', fmt=IMGFMT size=65536 backing_file=TEST_DIR/t.IMGFMT
-Formatting 'TEST_DIR/t.IMGFMT.overlay1', fmt=IMGFMT size=65536 backing_file=TEST_DIR/t.IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.overlay0', fmt=IMGFMT size=65536 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.overlay1', fmt=IMGFMT size=65536 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
 wrote 42/42 bytes at offset 0
 42 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
diff --git a/tests/qemu-iotests/129 b/tests/qemu-iotests/129
index b0da4a5541ab..0e13244d850e 100755
--- a/tests/qemu-iotests/129
+++ b/tests/qemu-iotests/129
@@ -29,7 +29,8 @@ class TestStopWithBlockJob(iotests.QMPTestCase):

     def setUp(self):
         iotests.qemu_img('create', '-f', iotests.imgfmt, self.base_img, "1G")
-        iotests.qemu_img('create', '-f', iotests.imgfmt, self.test_img, "-b", self.base_img)
+        iotests.qemu_img('create', '-f', iotests.imgfmt, self.test_img,
+                         "-b", self.base_img, '-F', iotests.imgfmt)
         iotests.qemu_io('-f', iotests.imgfmt, '-c', 'write -P0x5d 1M 128M', self.test_img)
         self.vm = iotests.VM().add_drive(self.test_img)
         self.vm.launch()
diff --git a/tests/qemu-iotests/133 b/tests/qemu-iotests/133
index 6f7cacc0910b..4070fd9457b2 100755
--- a/tests/qemu-iotests/133
+++ b/tests/qemu-iotests/133
@@ -40,7 +40,7 @@ _supported_fmt qcow2
 _supported_proto file

 TEST_IMG="$TEST_IMG.base" _make_test_img 64M
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 echo
 echo "=== Check that node-name can't be changed ==="
diff --git a/tests/qemu-iotests/133.out b/tests/qemu-iotests/133.out
index 1491ef45a984..d70c2e8041ce 100644
--- a/tests/qemu-iotests/133.out
+++ b/tests/qemu-iotests/133.out
@@ -1,6 +1,6 @@
 QA output created by 133
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 === Check that node-name can't be changed ===

diff --git a/tests/qemu-iotests/139 b/tests/qemu-iotests/139
index 7120d3142b77..1452fd24b335 100755
--- a/tests/qemu-iotests/139
+++ b/tests/qemu-iotests/139
@@ -71,7 +71,7 @@ class TestBlockdevDel(iotests.QMPTestCase):
     def addBlockDriverStateOverlay(self, node):
         self.checkBlockDriverState(node, False)
         iotests.qemu_img('create', '-u', '-f', iotests.imgfmt,
-                         '-b', base_img, new_img, '1M')
+                         '-b', base_img, '-F', iotests.imgfmt, new_img, '1M')
         opts = {'driver': iotests.imgfmt,
                 'node-name': node,
                 'backing': None,
diff --git a/tests/qemu-iotests/141 b/tests/qemu-iotests/141
index 5192d256e314..21aa0b42d813 100755
--- a/tests/qemu-iotests/141
+++ b/tests/qemu-iotests/141
@@ -89,8 +89,8 @@ test_blockjob()


 TEST_IMG="$TEST_DIR/b.$IMGFMT" _make_test_img 1M
-TEST_IMG="$TEST_DIR/m.$IMGFMT" _make_test_img -b "$TEST_DIR/b.$IMGFMT" 1M
-_make_test_img -b "$TEST_DIR/m.$IMGFMT" 1M
+TEST_IMG="$TEST_DIR/m.$IMGFMT" _make_test_img -b "$TEST_DIR/b.$IMGFMT" -F $IMGFMT 1M
+_make_test_img -b "$TEST_DIR/m.$IMGFMT" 1M -F $IMGFMT

 _launch_qemu -nodefaults

diff --git a/tests/qemu-iotests/141.out b/tests/qemu-iotests/141.out
index 263b680bdfb3..08e0aecd65f4 100644
--- a/tests/qemu-iotests/141.out
+++ b/tests/qemu-iotests/141.out
@@ -1,7 +1,7 @@
 QA output created by 141
 Formatting 'TEST_DIR/b.IMGFMT', fmt=IMGFMT size=1048576
-Formatting 'TEST_DIR/m.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/b.IMGFMT
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/m.IMGFMT
+Formatting 'TEST_DIR/m.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/b.IMGFMT backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/m.IMGFMT backing_fmt=IMGFMT
 {'execute': 'qmp_capabilities'}
 {"return": {}}

diff --git a/tests/qemu-iotests/142 b/tests/qemu-iotests/142
index daefcbaa5878..69fd10ef5103 100755
--- a/tests/qemu-iotests/142
+++ b/tests/qemu-iotests/142
@@ -67,7 +67,7 @@ size=128M

 TEST_IMG="$TEST_IMG.base" _make_test_img $size
 TEST_IMG="$TEST_IMG.snap" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base" $size
+_make_test_img -b "$TEST_IMG.base" $size -F $IMGFMT

 echo
 echo === Simple test for all cache modes ===
diff --git a/tests/qemu-iotests/142.out b/tests/qemu-iotests/142.out
index 3667e38def8a..a92b948edd95 100644
--- a/tests/qemu-iotests/142.out
+++ b/tests/qemu-iotests/142.out
@@ -1,7 +1,7 @@
 QA output created by 142
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
 Formatting 'TEST_DIR/t.IMGFMT.snap', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 === Simple test for all cache modes ===

diff --git a/tests/qemu-iotests/153 b/tests/qemu-iotests/153
index 2b1311176801..4d41f25e2ced 100755
--- a/tests/qemu-iotests/153
+++ b/tests/qemu-iotests/153
@@ -94,7 +94,7 @@ for opts1 in "" "read-only=on" "read-only=on,force-share=on"; do

     echo
     echo "== Creating test image =="
-    _make_test_img -b "${TEST_IMG}.base"
+    _make_test_img -b "${TEST_IMG}.base" -F $IMGFMT

     echo
     echo "== Launching QEMU, opts: '$opts1' =="
@@ -125,7 +125,7 @@ for opts1 in "" "read-only=on" "read-only=on,force-share=on"; do
         _run_cmd $QEMU_IMG amend -o "" $L "${TEST_IMG}"
         _run_cmd $QEMU_IMG commit      $L "${TEST_IMG}"
         _run_cmd $QEMU_IMG resize      $L "${TEST_IMG}" $size
-        _run_cmd $QEMU_IMG rebase      $L "${TEST_IMG}" -b "${TEST_IMG}.base"
+        _run_cmd $QEMU_IMG rebase      $L "${TEST_IMG}" -b "${TEST_IMG}.base" -F $IMGFMT
         _run_cmd $QEMU_IMG snapshot -l $L "${TEST_IMG}"
         _run_cmd $QEMU_IMG convert     $L "${TEST_IMG}" "${TEST_IMG}.convert"
         _run_cmd $QEMU_IMG dd          $L if="${TEST_IMG}" of="${TEST_IMG}.convert" bs=512 count=1
@@ -135,7 +135,7 @@ for opts1 in "" "read-only=on" "read-only=on,force-share=on"; do
         # qemu-img create does not support -U
         if [ -z "$L" ]; then
             _run_cmd $QEMU_IMG create -f $IMGFMT "${TEST_IMG}" \
-                                      -b ${TEST_IMG}.base
+                                      -b ${TEST_IMG}.base -F $IMGFMT
             # Read the file format.  It used to be the case that
             # file-posix simply truncated the file, but the qcow2
             # driver then failed to format it because it was unable
@@ -168,9 +168,9 @@ done
 echo
 echo "== Creating ${TEST_IMG}.[abc] ==" | _filter_testdir
 (
-    $QEMU_IMG create -f qcow2 "${TEST_IMG}.a" -b "${TEST_IMG}"
-    $QEMU_IMG create -f qcow2 "${TEST_IMG}.b" -b "${TEST_IMG}"
-    $QEMU_IMG create -f qcow2 "${TEST_IMG}.c" -b "${TEST_IMG}.b"
+    $QEMU_IMG create -f qcow2 "${TEST_IMG}.a" -b "${TEST_IMG}" -F $IMGFMT
+    $QEMU_IMG create -f qcow2 "${TEST_IMG}.b" -b "${TEST_IMG}" -F $IMGFMT
+    $QEMU_IMG create -f qcow2 "${TEST_IMG}.c" -b "${TEST_IMG}.b" -F $IMGFMT
 ) | _filter_img_create

 echo
@@ -219,7 +219,7 @@ _send_qemu_cmd $QEMU_HANDLE \
 _run_cmd $QEMU_IO "${TEST_IMG}" -c 'write 0 512'

 echo "Creating overlay with qemu-img when the guest is running should be allowed"
-_run_cmd $QEMU_IMG create -f $IMGFMT -b "${TEST_IMG}" "${TEST_IMG}.overlay"
+_run_cmd $QEMU_IMG create -f $IMGFMT -b "${TEST_IMG}" -F $IMGFMT "${TEST_IMG}.overlay"

 echo "== Closing an image should unlock it =="
 _send_qemu_cmd $QEMU_HANDLE \
diff --git a/tests/qemu-iotests/153.out b/tests/qemu-iotests/153.out
index f7464dd8d345..24fcf78d63b2 100644
--- a/tests/qemu-iotests/153.out
+++ b/tests/qemu-iotests/153.out
@@ -6,7 +6,7 @@ QEMU_PROG: -drive if=none,file=null-co://,readonly=off,force-share=on: force-sha
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=33554432

 == Creating test image ==
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == Launching QEMU, opts: '' ==

@@ -68,7 +68,7 @@ _qemu_img_wrapper resize TEST_DIR/t.qcow2 32M
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

-_qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

@@ -92,10 +92,11 @@ _qemu_img_wrapper bench -w -c 1 TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

-_qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2
 qemu-img: TEST_DIR/t.qcow2: Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?
 file format: IMGFMT
+backing file format: IMGFMT

 == Running utility commands -U ==

@@ -130,7 +131,7 @@ _qemu_img_wrapper resize -U TEST_DIR/t.qcow2 32M
 qemu-img: unrecognized option '-U'
 Try 'qemu-img --help' for more information

-_qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

@@ -152,7 +153,7 @@ Round done
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=33554432

 == Creating test image ==
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == Launching QEMU, opts: 'read-only=on' ==

@@ -199,7 +200,7 @@ _qemu_img_wrapper resize TEST_DIR/t.qcow2 32M
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

-_qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

@@ -215,10 +216,11 @@ _qemu_img_wrapper bench -w -c 1 TEST_DIR/t.qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

-_qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2
 qemu-img: TEST_DIR/t.qcow2: Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?
 file format: IMGFMT
+backing file format: IMGFMT

 == Running utility commands -U ==

@@ -253,7 +255,7 @@ _qemu_img_wrapper resize -U TEST_DIR/t.qcow2 32M
 qemu-img: unrecognized option '-U'
 Try 'qemu-img --help' for more information

-_qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2
 qemu-img: Could not open 'TEST_DIR/t.qcow2': Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?

@@ -275,7 +277,7 @@ Round done
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=33554432

 == Creating test image ==
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT

 == Launching QEMU, opts: 'read-only=on,force-share=on' ==

@@ -309,7 +311,7 @@ _qemu_img_wrapper commit TEST_DIR/t.qcow2

 _qemu_img_wrapper resize TEST_DIR/t.qcow2 32M

-_qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper rebase TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2

 _qemu_img_wrapper snapshot -l TEST_DIR/t.qcow2

@@ -321,8 +323,9 @@ _qemu_img_wrapper bench -c 1 TEST_DIR/t.qcow2

 _qemu_img_wrapper bench -w -c 1 TEST_DIR/t.qcow2

-_qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper create -f qcow2 TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2
 file format: IMGFMT
+backing file format: IMGFMT

 == Running utility commands -U ==

@@ -357,7 +360,7 @@ _qemu_img_wrapper resize -U TEST_DIR/t.qcow2 32M
 qemu-img: unrecognized option '-U'
 Try 'qemu-img --help' for more information

-_qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base
+_qemu_img_wrapper rebase -U TEST_DIR/t.qcow2 -b TEST_DIR/t.qcow2.base -F qcow2

 _qemu_img_wrapper snapshot -l -U TEST_DIR/t.qcow2

@@ -398,9 +401,9 @@ Is another process using the image [TEST_DIR/t.qcow2]?
 == Two devices with the same image (read-only=on,force-share=on - read-only=on,force-share=on) ==

 == Creating TEST_DIR/t.qcow2.[abc] ==
-Formatting 'TEST_DIR/t.IMGFMT.a', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT
-Formatting 'TEST_DIR/t.IMGFMT.b', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT
-Formatting 'TEST_DIR/t.IMGFMT.c', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.b
+Formatting 'TEST_DIR/t.IMGFMT.a', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.b', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.c', fmt=IMGFMT size=33554432 backing_file=TEST_DIR/t.IMGFMT.b backing_fmt=IMGFMT

 == Two devices sharing the same file in backing chain ==

@@ -430,7 +433,7 @@ qemu-io: can't open device TEST_DIR/t.qcow2: Failed to get "write" lock
 Is another process using the image [TEST_DIR/t.qcow2]?
 Creating overlay with qemu-img when the guest is running should be allowed

-_qemu_img_wrapper create -f qcow2 -b TEST_DIR/t.qcow2 TEST_DIR/t.qcow2.overlay
+_qemu_img_wrapper create -f qcow2 -b TEST_DIR/t.qcow2 -F qcow2 TEST_DIR/t.qcow2.overlay
 == Closing an image should unlock it ==
 { 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'drive_del d0' } }
 {"return": ""}
diff --git a/tests/qemu-iotests/154 b/tests/qemu-iotests/154
index d68f66b9e058..7f1c0d9bd981 100755
--- a/tests/qemu-iotests/154
+++ b/tests/qemu-iotests/154
@@ -50,7 +50,7 @@ echo
 echo == backing file contains zeros ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Make sure that the whole cluster is allocated even for partial write_zeroes
 # when the backing file contains zeros
@@ -74,7 +74,7 @@ echo
 echo == backing file contains non-zero data before write_zeroes ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Single cluster; non-zero data at the cluster start
 # ... | XX -- 00 -- | ...
@@ -97,7 +97,7 @@ echo
 echo == backing file contains non-zero data after write_zeroes ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Single cluster; non-zero data directly after request
 # ... | -- 00 XX -- | ...
@@ -120,7 +120,7 @@ echo
 echo == write_zeroes covers non-zero data ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # non-zero data at front of request
 # Backing file: -- XX -- --
@@ -160,7 +160,7 @@ echo
 echo == spanning two clusters, non-zero before request ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Two clusters; non-zero data before request:
 # 1. At cluster start:          32k: XX -- -- 00 | 00 -- -- --
@@ -190,7 +190,7 @@ echo
 echo == spanning two clusters, non-zero after request ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Two clusters; non-zero data after request:
 # 1. Directly after request:    32k: -- -- -- 00 | 00 XX -- --
@@ -220,7 +220,7 @@ echo
 echo == spanning two clusters, partially overwriting backing file ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Backing file: -- -- XX XX | XX XX -- --
 # Active layer: -- -- XX 00 | 00 XX -- --
@@ -239,7 +239,7 @@ echo
 echo == spanning multiple clusters, non-zero in first cluster ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Backing file: 64k: XX XX -- -- | -- -- -- -- | -- -- -- --
 # Active layer: 64k: XX XX 00 00 | 00 00 00 00 | 00 -- -- --
@@ -255,7 +255,7 @@ echo
 echo == spanning multiple clusters, non-zero in intermediate cluster ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Backing file: 64k: -- -- -- -- | -- XX XX -- | -- -- -- --
 # Active layer: 64k: -- -- 00 00 | 00 00 00 00 | 00 -- -- --
@@ -270,7 +270,7 @@ echo
 echo == spanning multiple clusters, non-zero in final cluster ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Backing file: 64k: -- -- -- -- | -- -- -- -- | -- -- XX XX
 # Active layer: 64k: -- -- 00 00 | 00 00 00 00 | 00 -- XX XX
@@ -286,7 +286,7 @@ echo
 echo == spanning multiple clusters, partially overwriting backing file ==

 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Backing file: 64k: -- XX XX XX | XX XX XX XX | XX XX XX --
 # Active layer: 64k: -- XX 00 00 | 00 00 00 00 | 00 XX XX --
@@ -338,7 +338,7 @@ CLUSTER_SIZE=2048 TEST_IMG="$TEST_IMG.base" _make_test_img $((size + 1024))
 # Write at the front: sector-wise, the request is:
 # backing: 128m... | -- --
 # active:  128m... | 00 -- -- --
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $size 512" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -346,7 +346,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # Write at the back: sector-wise, the request is:
 # backing: 128m... | -- --
 # active:  128m... | -- -- -- 00
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $((size + 1536)) 512" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -354,7 +354,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # Write at middle: sector-wise, the request is:
 # backing: 128m... | -- --
 # active:  128m... | -- 00 00 --
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $((size + 512)) 1024" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -362,7 +362,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # Write entire cluster: sector-wise, the request is:
 # backing: 128m... | -- --
 # active:  128m... | 00 00 00 00
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -373,7 +373,7 @@ $QEMU_IO -c "write -z $size 512" "$TEST_IMG.base" | _filter_qemu_io
 # Write at the front: sector-wise, the request is:
 # backing: 128m... | 00 00
 # active:  128m... | 00 -- -- --
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $size 512" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -381,7 +381,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # Write at the back: sector-wise, the request is:
 # backing: 128m... | 00 00
 # active:  128m... | -- -- -- 00
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $((size + 1536)) 512" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -389,7 +389,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # Write at middle: sector-wise, the request is:
 # backing: 128m... | 00 00
 # active:  128m... | -- 00 00 --
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $((size + 512)) 1024" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -397,7 +397,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # Write entire cluster: sector-wise, the request is:
 # backing: 128m... | 00 00
 # active:  128m... | 00 00 00 00
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -z $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "alloc $size 2048" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
@@ -427,7 +427,7 @@ echo == unaligned image tail cluster, allocation required ==
 # Backing file: 128m... | XX --
 # Active layer: 128m... | -- -- 00 --
 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $((size + 1024))
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -P 1 $((size)) 512" "$TEST_IMG.base" | _filter_qemu_io
 $QEMU_IO -c "write -z $((size + 1024)) 512" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "read -P 1 $((size)) 512" "$TEST_IMG" | _filter_qemu_io
@@ -438,7 +438,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map
 # Backing file: 128m: ... | -- XX
 # Active layer: 128m: ... | 00 -- -- 00
 CLUSTER_SIZE=512 TEST_IMG="$TEST_IMG.base" _make_test_img $((size + 1024))
-_make_test_img -b "$TEST_IMG.base" $((size + 2048))
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $((size + 2048))
 $QEMU_IO -c "write -P 1 $((size + 512)) 512" "$TEST_IMG.base" | _filter_qemu_io
 $QEMU_IO -c "write -z $((size)) 512" "$TEST_IMG" | _filter_qemu_io
 $QEMU_IO -c "read -P 0 $((size)) 512" "$TEST_IMG" | _filter_qemu_io
diff --git a/tests/qemu-iotests/154.out b/tests/qemu-iotests/154.out
index fa3673317fd8..4863e2483864 100644
--- a/tests/qemu-iotests/154.out
+++ b/tests/qemu-iotests/154.out
@@ -2,7 +2,7 @@ QA output created by 154

 == backing file contains zeros ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 0
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 2048/2048 bytes at offset 10240
@@ -22,7 +22,7 @@ wrote 2048/2048 bytes at offset 27648

 == backing file contains non-zero data before write_zeroes ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 32768
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 1024/1024 bytes at offset 34816
@@ -49,7 +49,7 @@ read 2048/2048 bytes at offset 67584

 == backing file contains non-zero data after write_zeroes ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 34816
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 1024/1024 bytes at offset 33792
@@ -76,7 +76,7 @@ read 3072/3072 bytes at offset 40960

 == write_zeroes covers non-zero data ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 5120
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 2048/2048 bytes at offset 5120
@@ -113,7 +113,7 @@ read 4096/4096 bytes at offset 28672

 == spanning two clusters, non-zero before request ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 32768
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 2048/2048 bytes at offset 35840
@@ -155,7 +155,7 @@ read 5120/5120 bytes at offset 68608

 == spanning two clusters, non-zero after request ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 37888
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 2048/2048 bytes at offset 35840
@@ -197,7 +197,7 @@ read 1024/1024 bytes at offset 72704

 == spanning two clusters, partially overwriting backing file ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 4096/4096 bytes at offset 2048
 4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 2048/2048 bytes at offset 3072
@@ -217,7 +217,7 @@ read 2048/2048 bytes at offset 6144

 == spanning multiple clusters, non-zero in first cluster ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 65536
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 7168/7168 bytes at offset 67584
@@ -233,7 +233,7 @@ read 10240/10240 bytes at offset 67584

 == spanning multiple clusters, non-zero in intermediate cluster ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 70656
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 7168/7168 bytes at offset 67584
@@ -246,7 +246,7 @@ read 12288/12288 bytes at offset 65536

 == spanning multiple clusters, non-zero in final cluster ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 75776
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 7168/7168 bytes at offset 67584
@@ -262,7 +262,7 @@ read 2048/2048 bytes at offset 75776

 == spanning multiple clusters, partially overwriting backing file ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 10240/10240 bytes at offset 66560
 10 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 7168/7168 bytes at offset 67584
@@ -305,25 +305,25 @@ wrote 2048/2048 bytes at offset 134217728
 2048/2048 bytes allocated at offset 128 MiB
 [{ "start": 0, "length": 134219776, "depth": 0, "zero": true, "data": false}]
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134218752
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
 [{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
 { "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134219264
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
 [{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
 { "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 134218240
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
 [{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
 { "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 134217728
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
@@ -331,25 +331,25 @@ wrote 2048/2048 bytes at offset 134217728
 { "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
 [{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
 { "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134219264
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
 [{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
 { "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 1024/1024 bytes at offset 134218240
 1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
 [{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
 { "start": 134217728, "length": 2048, "depth": 0, "zero": true, "data": false}]
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2048/2048 bytes at offset 134217728
 2 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 2048/2048 bytes allocated at offset 128 MiB
@@ -377,7 +377,7 @@ read 1024/1024 bytes at offset 134217728

 == unaligned image tail cluster, allocation required ==
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134218752
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134217728
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 512/512 bytes at offset 134218752
@@ -389,7 +389,7 @@ read 1536/1536 bytes at offset 134218240
 [{ "start": 0, "length": 134217728, "depth": 1, "zero": true, "data": false},
 { "start": 134217728, "length": 2048, "depth": 0, "zero": false, "data": true, "offset": OFFSET}]
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134218752
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134219776 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 512/512 bytes at offset 134218240
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 512/512 bytes at offset 134217728
diff --git a/tests/qemu-iotests/155 b/tests/qemu-iotests/155
index f237868710e0..c62029189267 100755
--- a/tests/qemu-iotests/155
+++ b/tests/qemu-iotests/155
@@ -52,9 +52,12 @@ class BaseClass(iotests.QMPTestCase):

     def setUp(self):
         qemu_img('create', '-f', iotests.imgfmt, back0_img, '1440K')
-        qemu_img('create', '-f', iotests.imgfmt, '-b', back0_img, back1_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-b', back1_img, back2_img)
-        qemu_img('create', '-f', iotests.imgfmt, '-b', back2_img, source_img)
+        qemu_img('create', '-f', iotests.imgfmt, '-b', back0_img,
+                 '-F', iotests.imgfmt, back1_img)
+        qemu_img('create', '-f', iotests.imgfmt, '-b', back1_img,
+                 '-F', iotests.imgfmt, back2_img)
+        qemu_img('create', '-f', iotests.imgfmt, '-b', back2_img,
+                 '-F', iotests.imgfmt, source_img)

         self.vm = iotests.VM()
         # Add the BDS via blockdev-add so it stays around after the mirror block
@@ -72,7 +75,8 @@ class BaseClass(iotests.QMPTestCase):
         if self.existing:
             if self.target_backing:
                 qemu_img('create', '-f', iotests.imgfmt,
-                         '-b', self.target_backing, target_img, '1440K')
+                         '-b', self.target_backing, '-F', 'raw',
+                         target_img, '1440K')
             else:
                 qemu_img('create', '-f', iotests.imgfmt, target_img, '1440K')

diff --git a/tests/qemu-iotests/156 b/tests/qemu-iotests/156
index 5559df63a53e..7c69a6c3fa32 100755
--- a/tests/qemu-iotests/156
+++ b/tests/qemu-iotests/156
@@ -56,7 +56,7 @@ _unsupported_imgopts data_file

 # Create source disk
 TEST_IMG="$TEST_IMG.backing" _make_test_img 1M
-_make_test_img -b "$TEST_IMG.backing" 1M
+_make_test_img -b "$TEST_IMG.backing" -F $IMGFMT 1M

 $QEMU_IO -c 'write -P 1 0 256k' "$TEST_IMG.backing" | _filter_qemu_io
 $QEMU_IO -c 'write -P 2 64k 192k' "$TEST_IMG" | _filter_qemu_io
@@ -68,7 +68,7 @@ _send_qemu_cmd $QEMU_HANDLE \
     'return'

 # Create snapshot
-TEST_IMG="$TEST_IMG.overlay" _make_test_img -u -b "$TEST_IMG" 1M
+TEST_IMG="$TEST_IMG.overlay" _make_test_img -u -b "$TEST_IMG" -F $IMGFMT 1M
 _send_qemu_cmd $QEMU_HANDLE \
     "{ 'execute': 'blockdev-snapshot-sync',
        'arguments': { 'device': 'source',
@@ -85,7 +85,8 @@ _send_qemu_cmd $QEMU_HANDLE \
     'return'

 # Create target image
-TEST_IMG="$TEST_IMG.target.overlay" _make_test_img -u -b "$TEST_IMG.target" 1M
+TEST_IMG="$TEST_IMG.target.overlay" _make_test_img -u -b "$TEST_IMG.target" \
+    -F $IMGFMT 1M

 # Mirror snapshot
 _send_qemu_cmd $QEMU_HANDLE \
@@ -111,7 +112,7 @@ _send_qemu_cmd $QEMU_HANDLE \
 # Copy source backing chain to the target before completing the job
 cp "$TEST_IMG.backing" "$TEST_IMG.target.backing"
 cp "$TEST_IMG" "$TEST_IMG.target"
-$QEMU_IMG rebase -u -b "$TEST_IMG.target.backing" "$TEST_IMG.target"
+$QEMU_IMG rebase -u -b "$TEST_IMG.target.backing" -F $IMGFMT "$TEST_IMG.target"

 # Complete block job
 _send_qemu_cmd $QEMU_HANDLE \
diff --git a/tests/qemu-iotests/156.out b/tests/qemu-iotests/156.out
index 084be5ad7151..cce167b63fe3 100644
--- a/tests/qemu-iotests/156.out
+++ b/tests/qemu-iotests/156.out
@@ -1,20 +1,20 @@
 QA output created by 156
 Formatting 'TEST_DIR/t.IMGFMT.backing', fmt=IMGFMT size=1048576
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.backing
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.backing backing_fmt=IMGFMT
 wrote 262144/262144 bytes at offset 0
 256 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 196608/196608 bytes at offset 65536
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
-Formatting 'TEST_DIR/t.IMGFMT.overlay', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.overlay', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT backing_fmt=IMGFMT
 { 'execute': 'blockdev-snapshot-sync', 'arguments': { 'device': 'source', 'snapshot-file': 'TEST_DIR/t.IMGFMT.overlay', 'format': 'IMGFMT', 'mode': 'existing' } }
 {"return": {}}
 { 'execute': 'human-monitor-command', 'arguments': { 'command-line': 'qemu-io source "write -P 3 128k 128k"' } }
 wrote 131072/131072 bytes at offset 131072
 128 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 {"return": ""}
-Formatting 'TEST_DIR/t.IMGFMT.target.overlay', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.target
+Formatting 'TEST_DIR/t.IMGFMT.target.overlay', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.target backing_fmt=IMGFMT
 { 'execute': 'drive-mirror', 'arguments': { 'device': 'source', 'target': 'TEST_DIR/t.IMGFMT.target.overlay', 'mode': 'existing', 'sync': 'top' } }
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "created", "id": "source"}}
 {"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "JOB_STATUS_CHANGE", "data": {"status": "running", "id": "source"}}
diff --git a/tests/qemu-iotests/158 b/tests/qemu-iotests/158
index ba4db6116ac3..3175968e2b6a 100755
--- a/tests/qemu-iotests/158
+++ b/tests/qemu-iotests/158
@@ -64,7 +64,7 @@ echo "== verify pattern =="
 $QEMU_IO --object $SECRET -c "read -P 0xa 0 $size" --image-opts $IMGSPECBASE | _filter_qemu_io | _filter_testdir

 echo "== create overlay =="
-_make_test_img -u --object $SECRET -o "encryption=on,encrypt.key-secret=sec0" -b "$TEST_IMG_BASE" $size
+_make_test_img -u --object $SECRET -o "encryption=on,encrypt.key-secret=sec0" -b "$TEST_IMG_BASE" -F $IMGFMT $size

 echo
 echo "== writing part of a cluster =="
diff --git a/tests/qemu-iotests/158.out b/tests/qemu-iotests/158.out
index 6def216e5574..d999f51ec0c0 100644
--- a/tests/qemu-iotests/158.out
+++ b/tests/qemu-iotests/158.out
@@ -10,7 +10,7 @@ wrote 134217728/134217728 bytes at offset 0
 read 134217728/134217728 bytes at offset 0
 128 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 == create overlay ==
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base encryption=on encrypt.key-secret=sec0
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT encryption=on encrypt.key-secret=sec0

 == writing part of a cluster ==
 wrote 1024/1024 bytes at offset 0
diff --git a/tests/qemu-iotests/161 b/tests/qemu-iotests/161
index f572a19af28c..e270976d8783 100755
--- a/tests/qemu-iotests/161
+++ b/tests/qemu-iotests/161
@@ -49,8 +49,8 @@ IMG_SIZE=1M

 # Create the images
 TEST_IMG="$TEST_IMG.base" _make_test_img $IMG_SIZE | _filter_imgfmt
-TEST_IMG="$TEST_IMG.int" _make_test_img -b "$TEST_IMG.base" | _filter_imgfmt
-_make_test_img -b "$TEST_IMG.int" | _filter_imgfmt
+TEST_IMG="$TEST_IMG.int" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT | _filter_imgfmt
+_make_test_img -b "$TEST_IMG.int" -F $IMGFMT -F $IMGFMT | _filter_imgfmt

 # First test: reopen $TEST.IMG changing the detect-zeroes option on
 # its backing file ($TEST_IMG.int).
@@ -106,8 +106,8 @@ echo "*** Commit and then change an option on the backing file"
 echo
 # Create the images again
 TEST_IMG="$TEST_IMG.base" _make_test_img $IMG_SIZE | _filter_imgfmt
-TEST_IMG="$TEST_IMG.int" _make_test_img -b "$TEST_IMG.base" | _filter_imgfmt
-_make_test_img -b "$TEST_IMG.int" | _filter_imgfmt
+TEST_IMG="$TEST_IMG.int" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT| _filter_imgfmt
+_make_test_img -b "$TEST_IMG.int" -F $IMGFMT | _filter_imgfmt

 _launch_qemu -drive if=none,file="${TEST_IMG}"
 _send_qemu_cmd $QEMU_HANDLE \
diff --git a/tests/qemu-iotests/161.out b/tests/qemu-iotests/161.out
index aef9741ed31c..3d8d89a9da3f 100644
--- a/tests/qemu-iotests/161.out
+++ b/tests/qemu-iotests/161.out
@@ -1,7 +1,7 @@
 QA output created by 161
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1048576
-Formatting 'TEST_DIR/t.IMGFMT.int', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int
+Formatting 'TEST_DIR/t.IMGFMT.int', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int backing_fmt=IMGFMT

 *** Change an option on the backing file

@@ -29,8 +29,8 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.
 *** Commit and then change an option on the backing file

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1048576
-Formatting 'TEST_DIR/t.IMGFMT.int', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int
+Formatting 'TEST_DIR/t.IMGFMT.int', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int backing_fmt=IMGFMT
 { 'execute': 'qmp_capabilities' }
 {"return": {}}
 { 'execute': 'block-commit', 'arguments': { 'device': 'none0', 'top': 'TEST_DIR/t.IMGFMT.int' } }
diff --git a/tests/qemu-iotests/176 b/tests/qemu-iotests/176
index 117c8b695490..2565ff12eef8 100755
--- a/tests/qemu-iotests/176
+++ b/tests/qemu-iotests/176
@@ -84,8 +84,8 @@ echo

 len=$((2100 * 1024 * 1024 + 512)) # larger than 2G, and not cluster aligned
 TEST_IMG="$TEST_IMG.base" _make_test_img $len
-TEST_IMG="$TEST_IMG.itmd" _make_test_img -b "$TEST_IMG.base" $len
-_make_test_img -b "$TEST_IMG.itmd" $len
+TEST_IMG="$TEST_IMG.itmd" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT $len
+_make_test_img -b "$TEST_IMG.itmd" -F $IMGFMT $len
 # Update the top image to use a feature that is incompatible with fast path
 case $reason in
     snapshot) $QEMU_IMG snapshot -c snap "$TEST_IMG" ;;
diff --git a/tests/qemu-iotests/176.out b/tests/qemu-iotests/176.out
index cc33def96b25..9d09b6045202 100644
--- a/tests/qemu-iotests/176.out
+++ b/tests/qemu-iotests/176.out
@@ -3,8 +3,8 @@ QA output created by 176
 === Test pass snapshot.0 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
@@ -43,8 +43,8 @@ ID        TAG
 === Test pass snapshot.1 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
@@ -84,8 +84,8 @@ ID        TAG
 === Test pass snapshot.2 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
@@ -125,8 +125,8 @@ ID        TAG
 === Test pass snapshot.3 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 wrote 196608/196608 bytes at offset 2147287040
 192 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 131072/131072 bytes at offset 2147352576
@@ -163,8 +163,8 @@ ID        TAG
 === Test pass bitmap.0 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 QMP_VERSION
 {"return": {}}
 {"return": {}}
@@ -212,8 +212,8 @@ QMP_VERSION
 === Test pass bitmap.1 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 QMP_VERSION
 {"return": {}}
 {"return": {}}
@@ -262,8 +262,8 @@ QMP_VERSION
 === Test pass bitmap.2 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 QMP_VERSION
 {"return": {}}
 {"return": {}}
@@ -312,8 +312,8 @@ QMP_VERSION
 === Test pass bitmap.3 ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=2202010112
-Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd
+Formatting 'TEST_DIR/t.IMGFMT.itmd', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2202010112 backing_file=TEST_DIR/t.IMGFMT.itmd backing_fmt=IMGFMT
 QMP_VERSION
 {"return": {}}
 {"return": {}}
diff --git a/tests/qemu-iotests/177 b/tests/qemu-iotests/177
index 752d29f8ad50..c201a9d6c64a 100755
--- a/tests/qemu-iotests/177
+++ b/tests/qemu-iotests/177
@@ -51,7 +51,7 @@ echo "== setting up files =="

 TEST_IMG="$TEST_IMG.base" _make_test_img $size
 $QEMU_IO -c "write -P 11 0 $size" "$TEST_IMG.base" | _filter_qemu_io
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT
 $QEMU_IO -c "write -P 22 0 $size" "$TEST_IMG" | _filter_qemu_io

 # Limited to 64k max-transfer
diff --git a/tests/qemu-iotests/177.out b/tests/qemu-iotests/177.out
index e887542678ba..ba1e1e212e47 100644
--- a/tests/qemu-iotests/177.out
+++ b/tests/qemu-iotests/177.out
@@ -4,7 +4,7 @@ QA output created by 177
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
 wrote 134217728/134217728 bytes at offset 0
 128 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 134217728/134217728 bytes at offset 0
 128 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

diff --git a/tests/qemu-iotests/179 b/tests/qemu-iotests/179
index 9372dc30ef77..11a20cb1bfa8 100755
--- a/tests/qemu-iotests/179
+++ b/tests/qemu-iotests/179
@@ -49,7 +49,7 @@ echo '=== Testing write zeroes with unmap ==='
 echo

 TEST_IMG="$TEST_IMG.base" _make_test_img 64M
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 # Offsets chosen at or near 2M boundaries so test works at all cluster sizes
 # 8k and larger (smaller clusters fail due to non-contiguous allocations)
diff --git a/tests/qemu-iotests/179.out b/tests/qemu-iotests/179.out
index 80722b22891d..1f7680002ca6 100644
--- a/tests/qemu-iotests/179.out
+++ b/tests/qemu-iotests/179.out
@@ -3,7 +3,7 @@ QA output created by 179
 === Testing write zeroes with unmap ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 2097152/2097152 bytes at offset 2097152
 2 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 wrote 2097152/2097152 bytes at offset 6291456
diff --git a/tests/qemu-iotests/189 b/tests/qemu-iotests/189
index c9ce9d3bede3..99a900c998c2 100755
--- a/tests/qemu-iotests/189
+++ b/tests/qemu-iotests/189
@@ -65,7 +65,7 @@ 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" $size
+_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

 echo
 echo "== writing part of a cluster =="
diff --git a/tests/qemu-iotests/189.out b/tests/qemu-iotests/189.out
index a0b7c9c24c24..035068764f73 100644
--- a/tests/qemu-iotests/189.out
+++ b/tests/qemu-iotests/189.out
@@ -10,7 +10,7 @@ wrote 16777216/16777216 bytes at offset 0
 read 16777216/16777216 bytes at offset 0
 16 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 == create overlay ==
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=16777216 backing_file=TEST_DIR/t.IMGFMT.base encrypt.format=luks encrypt.key-secret=sec1 encrypt.iter-time=10
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=16777216 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT encrypt.format=luks encrypt.key-secret=sec1 encrypt.iter-time=10

 == writing part of a cluster ==
 wrote 1024/1024 bytes at offset 0
diff --git a/tests/qemu-iotests/191 b/tests/qemu-iotests/191
index b05db6814157..d17462e1e42b 100755
--- a/tests/qemu-iotests/191
+++ b/tests/qemu-iotests/191
@@ -54,8 +54,8 @@ echo

 TEST_IMG="${TEST_IMG}.base" _make_test_img $size
 TEST_IMG="${TEST_IMG}.mid" _make_test_img -o "backing_fmt=$IMGFMT" -b "${TEST_IMG}.base"
-_make_test_img -b "${TEST_IMG}.mid"
-TEST_IMG="${TEST_IMG}.ovl2" _make_test_img -b "${TEST_IMG}.mid"
+_make_test_img -b "${TEST_IMG}.mid" -F $IMGFMT
+TEST_IMG="${TEST_IMG}.ovl2" _make_test_img -b "${TEST_IMG}.mid" -F $IMGFMT

 $QEMU_IO -c 'write -P 0x55 1M 64k' "${TEST_IMG}.mid" | _filter_qemu_io

@@ -102,10 +102,10 @@ echo === Preparing and starting VM with -drive ===
 echo

 TEST_IMG="${TEST_IMG}.base" _make_test_img $size
-TEST_IMG="${TEST_IMG}.mid" _make_test_img -b "${TEST_IMG}.base"
-_make_test_img -b "${TEST_IMG}.mid"
-TEST_IMG="${TEST_IMG}.ovl2" _make_test_img -b "${TEST_IMG}.mid"
-TEST_IMG="${TEST_IMG}.ovl3" _make_test_img -b "${TEST_IMG}.ovl2"
+TEST_IMG="${TEST_IMG}.mid" _make_test_img -b "${TEST_IMG}.base" -F $IMGFMT
+_make_test_img -b "${TEST_IMG}.mid" -F $IMGFMT
+TEST_IMG="${TEST_IMG}.ovl2" _make_test_img -b "${TEST_IMG}.mid" -F $IMGFMT
+TEST_IMG="${TEST_IMG}.ovl3" _make_test_img -b "${TEST_IMG}.ovl2" -F $IMGFMT

 $QEMU_IO -c 'write -P 0x55 1M 64k' "${TEST_IMG}.mid" | _filter_qemu_io

diff --git a/tests/qemu-iotests/191.out b/tests/qemu-iotests/191.out
index 34cec7b9ecf3..11aaf3b691fd 100644
--- a/tests/qemu-iotests/191.out
+++ b/tests/qemu-iotests/191.out
@@ -4,8 +4,8 @@ QA output created by 191

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
 Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid
-Formatting 'TEST_DIR/t.IMGFMT.ovl2', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.ovl2', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 1048576
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
@@ -413,10 +413,10 @@ backing file format: IMGFMT
 === Preparing and starting VM with -drive ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid
-Formatting 'TEST_DIR/t.IMGFMT.ovl2', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid
-Formatting 'TEST_DIR/t.IMGFMT.ovl3', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.ovl2
+Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.ovl2', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT.ovl3', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.ovl2 backing_fmt=IMGFMT
 wrote 65536/65536 bytes at offset 1048576
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'qmp_capabilities' }
diff --git a/tests/qemu-iotests/195 b/tests/qemu-iotests/195
index 48984b7ac1ed..2351d55fe1f1 100755
--- a/tests/qemu-iotests/195
+++ b/tests/qemu-iotests/195
@@ -56,8 +56,8 @@ run_qemu()

 size=64M
 TEST_IMG="$TEST_IMG.base" _make_test_img $size
-TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base"
-_make_test_img -b "$TEST_IMG.mid"
+TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT
+_make_test_img -b "$TEST_IMG.mid" -F $IMGFMT

 echo
 echo "Change backing file of mid (opened read-only)"
@@ -75,7 +75,7 @@ echo
 echo "Change backing file of top (opened writable)"
 echo

-TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base"
+TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT

 run_qemu -drive if=none,file="$TEST_IMG",node-name=top <<EOF
 {"execute":"qmp_capabilities"}
diff --git a/tests/qemu-iotests/195.out b/tests/qemu-iotests/195.out
index e6df0d6781ba..ec84df5012a3 100644
--- a/tests/qemu-iotests/195.out
+++ b/tests/qemu-iotests/195.out
@@ -1,7 +1,7 @@
 QA output created by 195
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid
+Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT

 Change backing file of mid (opened read-only)

@@ -42,7 +42,7 @@ backing file format: IMGFMT

 Change backing file of top (opened writable)

-Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Testing: -drive if=none,file=TEST_DIR/t.IMGFMT,node-name=top
 {
     QMP_VERSION
diff --git a/tests/qemu-iotests/198 b/tests/qemu-iotests/198
index fb0d5a29d357..33853df1c8bd 100755
--- a/tests/qemu-iotests/198
+++ b/tests/qemu-iotests/198
@@ -62,7 +62,7 @@ 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" $size
+_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

 echo
 echo "== writing whole image layer =="
diff --git a/tests/qemu-iotests/198.out b/tests/qemu-iotests/198.out
index 831ce3a289d3..8bc39dd0d5ee 100644
--- a/tests/qemu-iotests/198.out
+++ b/tests/qemu-iotests/198.out
@@ -6,7 +6,7 @@ Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=16777216 encrypt.format=luk
 wrote 16777216/16777216 bytes at offset 0
 16 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 == create overlay ==
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=16777216 backing_file=TEST_DIR/t.IMGFMT.base encrypt.format=luks encrypt.key-secret=sec1 encrypt.iter-time=10
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=16777216 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT encrypt.format=luks encrypt.key-secret=sec1 encrypt.iter-time=10

 == writing whole image layer ==
 wrote 16777216/16777216 bytes at offset 0
@@ -78,6 +78,7 @@ image: json:{ /* filtered */ }
 file format: IMGFMT
 virtual size: 16 MiB (16777216 bytes)
 backing file: TEST_DIR/t.IMGFMT.base
+backing file format: IMGFMT
 Format specific information:
     encrypt:
         ivgen alg: plain64
diff --git a/tests/qemu-iotests/204 b/tests/qemu-iotests/204
index abb73dc381c9..6770fa9b9636 100755
--- a/tests/qemu-iotests/204
+++ b/tests/qemu-iotests/204
@@ -52,7 +52,7 @@ echo "== setting up files =="

 TEST_IMG="$TEST_IMG.base" _make_test_img $size
 $QEMU_IO -c "write -P 11 0 $size" "$TEST_IMG.base" | _filter_qemu_io
-_make_test_img -b "$TEST_IMG.base"
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT
 $QEMU_IO -c "write -P 22 0 110M" "$TEST_IMG" | _filter_qemu_io

 # Limited to 64k max-transfer
diff --git a/tests/qemu-iotests/204.out b/tests/qemu-iotests/204.out
index f3a10fbe9035..457f72df8f88 100644
--- a/tests/qemu-iotests/204.out
+++ b/tests/qemu-iotests/204.out
@@ -4,7 +4,7 @@ QA output created by 204
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
 wrote 134217728/134217728 bytes at offset 0
 128 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 wrote 115343360/115343360 bytes at offset 0
 110 MiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

diff --git a/tests/qemu-iotests/216 b/tests/qemu-iotests/216
index 372f042d3ebf..088b318a3755 100755
--- a/tests/qemu-iotests/216
+++ b/tests/qemu-iotests/216
@@ -53,7 +53,7 @@ with iotests.FilePath('base.img') as base_img_path, \
     assert qemu_img('create', '-f', iotests.imgfmt, base_img_path, '64M') == 0
     assert qemu_io_silent(base_img_path, '-c', 'write -P 1 0M 1M') == 0
     assert qemu_img('create', '-f', iotests.imgfmt, '-b', base_img_path,
-                    top_img_path) == 0
+                    '-F', iotests.imgfmt, top_img_path) == 0
     assert qemu_io_silent(top_img_path,  '-c', 'write -P 2 1M 1M') == 0

     log('Done')
diff --git a/tests/qemu-iotests/224 b/tests/qemu-iotests/224
index e91fb26fd8eb..94e412a680df 100755
--- a/tests/qemu-iotests/224
+++ b/tests/qemu-iotests/224
@@ -49,9 +49,9 @@ for filter_node_name in False, True:
         assert qemu_img('create', '-f', iotests.imgfmt,
                         base_img_path, '64M') == 0
         assert qemu_img('create', '-f', iotests.imgfmt, '-b', base_img_path,
-                        mid_img_path) == 0
+                        '-F', iotests.imgfmt, mid_img_path) == 0
         assert qemu_img('create', '-f', iotests.imgfmt, '-b', mid_img_path,
-                        top_img_path) == 0
+                        '-F', iotests.imgfmt, top_img_path) == 0

         # Something to commit
         assert qemu_io_silent(mid_img_path, '-c', 'write -P 1 0 1M') == 0
diff --git a/tests/qemu-iotests/228 b/tests/qemu-iotests/228
index 64bc82ee2346..98e92f750249 100755
--- a/tests/qemu-iotests/228
+++ b/tests/qemu-iotests/228
@@ -54,7 +54,8 @@ with iotests.FilePath('base.img') as base_img_path, \
     assert qemu_img('create', '-f', iotests.imgfmt, base_img_path, '64M') == 0
     # Choose a funny way to describe the backing filename
     assert qemu_img('create', '-f', iotests.imgfmt, '-b',
-                    'file:' + base_img_path, top_img_path) == 0
+                    'file:' + base_img_path, '-F', iotests.imgfmt,
+                    top_img_path) == 0

     vm.launch()

@@ -169,7 +170,7 @@ with iotests.FilePath('base.img') as base_img_path, \
     # filename unless the backing file is opened implicitly with the
     # overlay)
     assert qemu_img('create', '-f', iotests.imgfmt, '-b', base_img_path,
-                    top_img_path) == 0
+                    '-F', iotests.imgfmt, top_img_path) == 0

     # You can only reliably override backing options by using a node
     # reference (or by specifying file.filename, but, well...)
diff --git a/tests/qemu-iotests/245 b/tests/qemu-iotests/245
index 489bf78bd08a..554bbec00914 100755
--- a/tests/qemu-iotests/245
+++ b/tests/qemu-iotests/245
@@ -44,7 +44,8 @@ class TestBlockdevReopen(iotests.QMPTestCase):

     def setUp(self):
         qemu_img('create', '-f', iotests.imgfmt, hd_path[0], '3M')
-        qemu_img('create', '-f', iotests.imgfmt, '-b', hd_path[0], hd_path[1])
+        qemu_img('create', '-f', iotests.imgfmt, '-b', hd_path[0],
+                 '-F', iotests.imgfmt, hd_path[1])
         qemu_img('create', '-f', iotests.imgfmt, hd_path[2], '3M')
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xa0  0 1M', hd_path[0])
         qemu_io('-f', iotests.imgfmt, '-c', 'write -P 0xa1 1M 1M', hd_path[1])
diff --git a/tests/qemu-iotests/249 b/tests/qemu-iotests/249
index 2b99c9789ed2..68f13ed32896 100755
--- a/tests/qemu-iotests/249
+++ b/tests/qemu-iotests/249
@@ -49,8 +49,8 @@ IMG_SIZE=1M

 # Create the images: base <- int <- active
 TEST_IMG="$TEST_IMG.base" _make_test_img $IMG_SIZE | _filter_imgfmt
-TEST_IMG="$TEST_IMG.int" _make_test_img -b "$TEST_IMG.base" | _filter_imgfmt
-_make_test_img -b "$TEST_IMG.int" | _filter_imgfmt
+TEST_IMG="$TEST_IMG.int" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT | _filter_imgfmt
+_make_test_img -b "$TEST_IMG.int" -F $IMGFMT | _filter_imgfmt

 # Launch QEMU with these two drives:
 # none0: base (read-only)
diff --git a/tests/qemu-iotests/249.out b/tests/qemu-iotests/249.out
index 51307ed0f795..85acda4635b3 100644
--- a/tests/qemu-iotests/249.out
+++ b/tests/qemu-iotests/249.out
@@ -1,7 +1,7 @@
 QA output created by 249
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=1048576
-Formatting 'TEST_DIR/t.IMGFMT.int', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int
+Formatting 'TEST_DIR/t.IMGFMT.int', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1048576 backing_file=TEST_DIR/t.IMGFMT.int backing_fmt=IMGFMT
 { 'execute': 'qmp_capabilities' }
 {"return": {}}

diff --git a/tests/qemu-iotests/252 b/tests/qemu-iotests/252
index 83280c1715dc..6662f4c9dec7 100755
--- a/tests/qemu-iotests/252
+++ b/tests/qemu-iotests/252
@@ -101,7 +101,7 @@ $QEMU_IMG map --output=json "$TEST_IMG" | _filter_qemu_img_map

 echo

-$QEMU_IMG rebase -b "$TEST_IMG.base_new" "$TEST_IMG"
+$QEMU_IMG rebase -b "$TEST_IMG.base_new" -F $IMGFMT "$TEST_IMG"

 # Verify the data is correct
 $QEMU_IO "$TEST_IMG" \
diff --git a/tests/qemu-iotests/257 b/tests/qemu-iotests/257
index 004a433b8be2..e1e60772195e 100755
--- a/tests/qemu-iotests/257
+++ b/tests/qemu-iotests/257
@@ -238,7 +238,8 @@ def compare_images(image, reference, baseimg=None, expected_match=True):
     """
     expected_ret = 0 if expected_match else 1
     if baseimg:
-        assert qemu_img("rebase", "-u", "-b", baseimg, image) == 0
+        assert qemu_img("rebase", "-u", "-b", baseimg, '-F', iotests.imgfmt,
+                        image) == 0
     ret = qemu_img("compare", image, reference)
     log('qemu_img compare "{:s}" "{:s}" ==> {:s}, {:s}'.format(
         image, reference,
diff --git a/tests/qemu-iotests/267 b/tests/qemu-iotests/267
index 3146273eef33..e44be49c771d 100755
--- a/tests/qemu-iotests/267
+++ b/tests/qemu-iotests/267
@@ -73,7 +73,7 @@ size=128M
 run_test()
 {
     if [ -n "$BACKING_FILE" ]; then
-        _make_test_img -b "$BACKING_FILE" $size
+        _make_test_img -b "$BACKING_FILE" -F $IMGFMT $size
     else
         _make_test_img $size
     fi
@@ -149,7 +149,7 @@ echo
 echo "=== -blockdev with NBD server on the backing file ==="
 echo

-_make_test_img -b "$TEST_IMG.base" $size
+_make_test_img -b "$TEST_IMG.base" -F $IMGFMT $size
 cat <<EOF |
 nbd_server_start unix:$SOCK_DIR/nbd
 nbd_server_add -w backing-fmt
diff --git a/tests/qemu-iotests/267.out b/tests/qemu-iotests/267.out
index 8dddb4baa443..d6d80c099f94 100644
--- a/tests/qemu-iotests/267.out
+++ b/tests/qemu-iotests/267.out
@@ -128,7 +128,7 @@ ID        TAG                 VM SIZE                DATE       VM CLOCK
 === -blockdev with a backing file ===

 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=134217728
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Testing: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT.base,node-name=backing-file -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file -blockdev driver=IMGFMT,file=file,backing=backing-file,node-name=fmt
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
@@ -139,7 +139,7 @@ ID        TAG                 VM SIZE                DATE       VM CLOCK
 (qemu) loadvm snap0
 (qemu) quit

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Testing: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT.base,node-name=backing-file -blockdev driver=IMGFMT,file=backing-file,node-name=backing-fmt -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file -blockdev driver=IMGFMT,file=file,backing=backing-fmt,node-name=fmt
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) savevm snap0
@@ -158,7 +158,7 @@ Internal snapshots on backing file:

 === -blockdev with NBD server on the backing file ===

-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=134217728 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
 Testing: -blockdev driver=file,filename=TEST_DIR/t.IMGFMT.base,node-name=backing-file -blockdev driver=IMGFMT,file=backing-file,node-name=backing-fmt -blockdev driver=file,filename=TEST_DIR/t.IMGFMT,node-name=file -blockdev driver=IMGFMT,file=file,backing=backing-fmt,node-name=fmt
 QEMU X.Y.Z monitor - type 'help' for more information
 (qemu) nbd_server_start unix:SOCK_DIR/nbd
diff --git a/tests/qemu-iotests/270 b/tests/qemu-iotests/270
index b9a12b908c3e..00339c0f7833 100755
--- a/tests/qemu-iotests/270
+++ b/tests/qemu-iotests/270
@@ -53,7 +53,7 @@ $QEMU_IO -c 'write 0 512' "$TEST_IMG.base" | _filter_qemu_io
 # We need a large cluster size, see below for why (above the $QEMU_IO
 # invocation)
 _make_test_img -o cluster_size=2M,data_file="$TEST_IMG.orig" \
-    -b "$TEST_IMG.base" 4G
+    -b "$TEST_IMG.base" -F $IMGFMT 4G

 # We want a null-co as the data file, because it allows us to quickly
 # "write" 2G of data without using any space.
diff --git a/tests/qemu-iotests/270.out b/tests/qemu-iotests/270.out
index c7be1110142f..6dc3b23d5bfa 100644
--- a/tests/qemu-iotests/270.out
+++ b/tests/qemu-iotests/270.out
@@ -2,7 +2,7 @@ QA output created by 270
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=4294967296
 wrote 512/512 bytes at offset 0
 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 backing_file=TEST_DIR/t.IMGFMT.base data_file=TEST_DIR/t.IMGFMT.orig
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4294967296 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT data_file=TEST_DIR/t.IMGFMT.orig
 wrote 2147483136/2147483136 bytes at offset 768
 2 GiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 No errors were found on the image.
diff --git a/tests/qemu-iotests/273 b/tests/qemu-iotests/273
index 00ff79bcf8f8..41ffbf39c4ef 100755
--- a/tests/qemu-iotests/273
+++ b/tests/qemu-iotests/273
@@ -56,8 +56,8 @@ run_qemu()
 }

 TEST_IMG="$TEST_IMG.base" _make_test_img 64M
-TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base"
-_make_test_img -b "$TEST_IMG.mid"
+TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT
+_make_test_img -b "$TEST_IMG.mid" -F $IMGFMT

 run_qemu \
     -blockdev file,node-name=base,filename="$TEST_IMG.base" \
diff --git a/tests/qemu-iotests/273.out b/tests/qemu-iotests/273.out
index 684b8d6f777e..87d475850387 100644
--- a/tests/qemu-iotests/273.out
+++ b/tests/qemu-iotests/273.out
@@ -1,7 +1,7 @@
 QA output created by 273
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid
+Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT
 Testing: -blockdev file,node-name=base,filename=TEST_DIR/t.IMGFMT.base -blockdev file,node-name=midf,filename=TEST_DIR/t.IMGFMT.mid -blockdev {"driver":"IMGFMT","node-name":"mid","file":"midf","backing":null} -blockdev file,node-name=topf,filename=TEST_DIR/t.IMGFMT -blockdev {"driver":"IMGFMT","file":"topf","node-name":"top","backing":null}
 {
     QMP_VERSION
diff --git a/tests/qemu-iotests/279 b/tests/qemu-iotests/279
index 30d29b1cb2aa..5272c8fcfe0d 100755
--- a/tests/qemu-iotests/279
+++ b/tests/qemu-iotests/279
@@ -42,8 +42,8 @@ _unsupported_imgopts "subformat=monolithicFlat" \
                      "subformat=twoGbMaxExtentFlat" \

 TEST_IMG="$TEST_IMG.base" _make_test_img 64M
-TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base"
-_make_test_img -b "$TEST_IMG.mid"
+TEST_IMG="$TEST_IMG.mid" _make_test_img -b "$TEST_IMG.base" -F $IMGFMT
+_make_test_img -b "$TEST_IMG.mid" -F $IMGFMT

 echo
 echo '== qemu-img info --backing-chain =='
diff --git a/tests/qemu-iotests/279.out b/tests/qemu-iotests/279.out
index f4dc6c69cbb3..adb2e47a1a9c 100644
--- a/tests/qemu-iotests/279.out
+++ b/tests/qemu-iotests/279.out
@@ -1,7 +1,7 @@
 QA output created by 279
 Formatting 'TEST_DIR/t.IMGFMT.base', fmt=IMGFMT size=67108864
-Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base
-Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid
+Formatting 'TEST_DIR/t.IMGFMT.mid', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=67108864 backing_file=TEST_DIR/t.IMGFMT.mid backing_fmt=IMGFMT

 == qemu-img info --backing-chain ==
 image: TEST_DIR/t.IMGFMT
