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

Block layer patches:

- Add block export infrastructure
- iotests improvements
- Document the throttle block filter
- Misc code cleanups

# gpg: Signature made Fri 02 Oct 2020 15:36:53 BST
# gpg:                using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg:                issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]
# Primary key fingerprint: DC3D EB15 9A9A F95D 3D74  56FE 7F09 B272 C88F 2FD6

* remotes/kevin/tags/for-upstream: (37 commits)
  qcow2: Use L1E_SIZE in qcow2_write_l1_entry()
  qemu-storage-daemon: Fix help line for --export
  iotests: Test block-export-* QMP interface
  iotests: Allow supported and unsupported formats at the same time
  iotests: Introduce qemu_nbd_list_log()
  iotests: Factor out qemu_tool_pipe_and_status()
  nbd: Deprecate nbd-server-add/remove
  nbd: Merge nbd_export_new() and nbd_export_create()
  block/export: Move writable to BlockExportOptions
  block/export: Add query-block-exports
  block/export: Create BlockBackend in blk_exp_add()
  block/export: Move blk to BlockExport
  block/export: Add BLOCK_EXPORT_DELETED event
  block/export: Add block-export-del
  block/export: Move strong user reference to block_exports
  block/export: Add 'id' option to block-export-add
  block/export: Add blk_exp_close_all(_type)
  block/export: Allocate BlockExport in blk_exp_add()
  block/export: Add node-name to BlockExportOptions
  block/export: Move AioContext from NBDExport to BlockExport
  ...

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

8 files changed, 313 insertions, 36 deletions

diff --git a/tests/check-block.sh b/tests/check-block.sh
index a5a6906..f6b1bda 100755
--- a/tests/check-block.sh
+++ b/tests/check-block.sh
@@ -46,6 +46,11 @@ if ! command -v bash >/dev/null 2>&1 ; then
     exit 0
 fi
 
+if LANG=C bash --version | grep -q 'GNU bash, version [123]' ; then
+    echo "bash version too old ==> Not running the qemu-iotests."
+    exit 0
+fi
+
 if ! (sed --version | grep 'GNU sed') > /dev/null 2>&1 ; then
     if ! command -v gsed >/dev/null 2>&1; then
         echo "GNU sed not available ==> Not running the qemu-iotests."
diff --git a/tests/qemu-iotests/140 b/tests/qemu-iotests/140
index 8d2ce5d..309b177 100755
--- a/tests/qemu-iotests/140
+++ b/tests/qemu-iotests/140
@@ -81,10 +81,17 @@ $QEMU_IO_PROG -f raw -r -c 'read -P 42 0 64k' \
     "nbd+unix:///drv?socket=$SOCK_DIR/nbd" 2>&1 \
     | _filter_qemu_io | _filter_nbd
 
+# The order of 'return' and the BLOCK_EXPORT_DELETED event is undefined. Just
+# wait until we've twice seen one of them. Filter the 'return' line out so that
+# the output is defined.
 _send_qemu_cmd $QEMU_HANDLE \
     "{ 'execute': 'eject',
        'arguments': { 'device': 'drv' }}" \
-    'return'
+    'return\|BLOCK_EXPORT_DELETED' |
+    grep -v 'return'
+
+_send_qemu_cmd $QEMU_HANDLE '' 'return\|BLOCK_EXPORT_DELETED' |
+    grep -v 'return'
 
 $QEMU_IO_PROG -f raw -r -c close \
     "nbd+unix:///drv?socket=$SOCK_DIR/nbd" 2>&1 \
diff --git a/tests/qemu-iotests/140.out b/tests/qemu-iotests/140.out
index 86b985d..62d9c3a 100644
--- a/tests/qemu-iotests/140.out
+++ b/tests/qemu-iotests/140.out
@@ -11,7 +11,7 @@ wrote 65536/65536 bytes at offset 0
 read 65536/65536 bytes at offset 0
 64 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
 { 'execute': 'eject', 'arguments': { 'device': 'drv' }}
-{"return": {}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "drv"}}
 qemu-io: can't open device nbd+unix:///drv?socket=SOCK_DIR/nbd: Requested export not available
 server reported: export 'drv' not present
 { 'execute': 'quit' }
diff --git a/tests/qemu-iotests/223.out b/tests/qemu-iotests/223.out
index e1eaaed..f6eac23 100644
--- a/tests/qemu-iotests/223.out
+++ b/tests/qemu-iotests/223.out
@@ -45,7 +45,7 @@ exports available: 0
 {"execute":"nbd-server-add", "arguments":{"device":"nosuch"}}
 {"error": {"class": "GenericError", "desc": "Cannot find device=nosuch nor node_name=nosuch"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n"}}
-{"error": {"class": "GenericError", "desc": "NBD server already has export named 'n'"}}
+{"error": {"class": "GenericError", "desc": "Block export id 'n' is already in use"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b2"}}
 {"error": {"class": "GenericError", "desc": "Enabled bitmap 'b2' incompatible with readonly export"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b3"}}
@@ -102,8 +102,10 @@ read 2097152/2097152 bytes at offset 2097152
 {"execute":"nbd-server-remove", "arguments":{"name":"n"}}
 {"return": {}}
 {"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n"}}
 {"return": {}}
 {"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n2"}}
 {"error": {"class": "GenericError", "desc": "Export 'n2' is not found"}}
 {"execute":"nbd-server-stop"}
 {"return": {}}
@@ -126,7 +128,7 @@ exports available: 0
 {"execute":"nbd-server-add", "arguments":{"device":"nosuch"}}
 {"error": {"class": "GenericError", "desc": "Cannot find device=nosuch nor node_name=nosuch"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n"}}
-{"error": {"class": "GenericError", "desc": "NBD server already has export named 'n'"}}
+{"error": {"class": "GenericError", "desc": "Block export id 'n' is already in use"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b2"}}
 {"error": {"class": "GenericError", "desc": "Enabled bitmap 'b2' incompatible with readonly export"}}
 {"execute":"nbd-server-add", "arguments":{"device":"n", "name":"n2", "bitmap":"b3"}}
@@ -183,8 +185,10 @@ read 2097152/2097152 bytes at offset 2097152
 {"execute":"nbd-server-remove", "arguments":{"name":"n"}}
 {"return": {}}
 {"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n"}}
 {"return": {}}
 {"execute":"nbd-server-remove", "arguments":{"name":"n2"}}
+{"timestamp": {"seconds":  TIMESTAMP, "microseconds":  TIMESTAMP}, "event": "BLOCK_EXPORT_DELETED", "data": {"id": "n2"}}
 {"error": {"class": "GenericError", "desc": "Export 'n2' is not found"}}
 {"execute":"nbd-server-stop"}
 {"return": {}}
diff --git a/tests/qemu-iotests/307 b/tests/qemu-iotests/307
new file mode 100755
index 0000000..de7c25f
--- /dev/null
+++ b/tests/qemu-iotests/307
@@ -0,0 +1,132 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2020 Red Hat, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# Creator/Owner: Kevin Wolf <kwolf@redhat.com>
+#
+# Test the block export QAPI interfaces
+
+import iotests
+import os
+
+# Need a writable image format (but not vpc, which rounds the image size, nor
+# luks which requires special command lines)
+iotests.script_initialize(
+    supported_fmts=['generic'],
+    unsupported_fmts=['luks', 'vpc'],
+    supported_platforms=['linux'],
+)
+
+with iotests.FilePath('image') as img, \
+     iotests.FilePath('socket', base_dir=iotests.sock_dir) as socket, \
+     iotests.VM() as vm:
+
+    iotests.qemu_img('create', '-f', iotests.imgfmt, img, '64M')
+    iotests.qemu_io_log('-f', iotests.imgfmt, '-c', 'write -P 0x11 0 4k', img)
+
+    iotests.log('=== Launch VM ===')
+
+    virtio_scsi_device = iotests.get_virtio_scsi_device()
+
+    vm.add_object('iothread,id=iothread0')
+    vm.add_blockdev(f'file,filename={img},node-name=file')
+    vm.add_blockdev(f'{iotests.imgfmt},file=file,node-name=fmt')
+    vm.add_blockdev('raw,file=file,node-name=ro,read-only=on')
+    vm.add_device(f'id=scsi0,driver={virtio_scsi_device},iothread=iothread0')
+    vm.launch()
+
+    vm.qmp_log('nbd-server-start',
+               addr={'type': 'unix', 'data': {'path': socket}},
+               filters=(iotests.filter_qmp_testfiles, ))
+    vm.qmp_log('query-block-exports')
+
+    iotests.log('\n=== Create a read-only NBD export ===')
+
+    vm.qmp_log('block-export-add', id='export0', type='nbd', node_name='fmt')
+    vm.qmp_log('query-block-exports')
+
+    iotests.qemu_nbd_list_log('-k', socket)
+
+    iotests.log('\n=== Try a few invalid things ===')
+
+    vm.qmp_log('block-export-add', id='#invalid', type='nbd', node_name='fmt')
+    vm.qmp_log('block-export-add', id='export0', type='nbd', node_name='fmt')
+    vm.qmp_log('block-export-add', id='export1', type='nbd', node_name='ro',
+               writable=True)
+    vm.qmp_log('block-export-del', id='export1')
+    vm.qmp_log('query-block-exports')
+
+    iotests.log('\n=== Move export to an iothread ===')
+
+    vm.qmp_log('device_add', id='sda', driver='scsi-hd', drive='fmt')
+    vm.qmp_log('query-block-exports')
+    iotests.qemu_nbd_list_log('-k', socket)
+
+    iotests.log('\n=== Add a writable export ===')
+
+    # This fails because share-rw=off
+    vm.qmp_log('block-export-add', id='export1', type='nbd', node_name='fmt',
+               name='export1', writable=True, writethrough=True,
+               description='This is the writable second export')
+
+    vm.qmp_log('device_del', id='sda')
+    event = vm.event_wait(name="DEVICE_DELETED",
+                          match={'data': {'device': 'sda'}})
+    iotests.log(event, filters=[iotests.filter_qmp_event])
+    vm.qmp_log('device_add', id='sda', driver='scsi-hd', drive='fmt',
+               share_rw=True)
+
+    # Now it should work
+    vm.qmp_log('block-export-add', id='export1', type='nbd', node_name='fmt',
+               name='export1', writable=True, writethrough=True,
+               description='This is the writable second export')
+
+    vm.qmp_log('query-block-exports')
+    iotests.qemu_nbd_list_log('-k', socket)
+
+    iotests.log('\n=== Connect qemu-io to export1, try removing exports ===')
+
+    nbd_url = f'nbd+unix:///export1?socket={socket}'
+    qemu_io = iotests.QemuIoInteractive('-f', 'raw', nbd_url)
+
+    iotests.log(qemu_io.cmd('read -P 0x11 0 4k'),
+                filters=[iotests.filter_qemu_io])
+    iotests.log(qemu_io.cmd('write -P 0x22 4k 4k'),
+                filters=[iotests.filter_qemu_io])
+
+    vm.qmp_log('block-export-del', id='export1')
+    vm.qmp_log('block-export-del', id='export0')
+    iotests.log(vm.get_qmp_events_filtered())
+    qemu_io.close()
+
+    vm.qmp_log('query-block-exports')
+    iotests.qemu_nbd_list_log('-k', socket)
+
+    iotests.log('\n=== Connect qemu-io again, try force removing ===')
+
+    qemu_io = iotests.QemuIoInteractive('-f', 'raw', nbd_url)
+    vm.qmp_log('block-export-del', id='export1')
+    vm.qmp_log('block-export-del', id='export1', mode='hard')
+
+    # This should fail now
+    iotests.log(qemu_io.cmd('read -P 0x11 0 4k'))
+    qemu_io.close()
+
+    vm.qmp_log('query-block-exports')
+    iotests.qemu_nbd_list_log('-k', socket)
+
+    iotests.log('\n=== Shut down QEMU ===')
+    vm.shutdown()
diff --git a/tests/qemu-iotests/307.out b/tests/qemu-iotests/307.out
new file mode 100644
index 0000000..daa8ad2
--- /dev/null
+++ b/tests/qemu-iotests/307.out
@@ -0,0 +1,124 @@
+wrote 4096/4096 bytes at offset 0
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+=== Launch VM ===
+{"execute": "nbd-server-start", "arguments": {"addr": {"data": {"path": "SOCK_DIR/PID-socket"}, "type": "unix"}}}
+{"return": {}}
+{"execute": "query-block-exports", "arguments": {}}
+{"return": []}
+
+=== Create a read-only NBD export ===
+{"execute": "block-export-add", "arguments": {"id": "export0", "node-name": "fmt", "type": "nbd"}}
+{"return": {}}
+{"execute": "query-block-exports", "arguments": {}}
+{"return": [{"id": "export0", "node-name": "fmt", "shutting-down": false, "type": "nbd"}]}
+exports available: 1
+ export: 'fmt'
+  size:  67108864
+  flags: 0x58f ( readonly flush fua df multi cache )
+  min block: XXX
+  opt block: XXX
+  max block: XXX
+  available meta contexts: 1
+   base:allocation
+
+
+=== Try a few invalid things ===
+{"execute": "block-export-add", "arguments": {"id": "#invalid", "node-name": "fmt", "type": "nbd"}}
+{"error": {"class": "GenericError", "desc": "Invalid block export id"}}
+{"execute": "block-export-add", "arguments": {"id": "export0", "node-name": "fmt", "type": "nbd"}}
+{"error": {"class": "GenericError", "desc": "Block export id 'export0' is already in use"}}
+{"execute": "block-export-add", "arguments": {"id": "export1", "node-name": "ro", "type": "nbd", "writable": true}}
+{"error": {"class": "GenericError", "desc": "Cannot export read-only node as writable"}}
+{"execute": "block-export-del", "arguments": {"id": "export1"}}
+{"error": {"class": "GenericError", "desc": "Export 'export1' is not found"}}
+{"execute": "query-block-exports", "arguments": {}}
+{"return": [{"id": "export0", "node-name": "fmt", "shutting-down": false, "type": "nbd"}]}
+
+=== Move export to an iothread ===
+{"execute": "device_add", "arguments": {"drive": "fmt", "driver": "scsi-hd", "id": "sda"}}
+{"return": {}}
+{"execute": "query-block-exports", "arguments": {}}
+{"return": [{"id": "export0", "node-name": "fmt", "shutting-down": false, "type": "nbd"}]}
+exports available: 1
+ export: 'fmt'
+  size:  67108864
+  flags: 0x58f ( readonly flush fua df multi cache )
+  min block: XXX
+  opt block: XXX
+  max block: XXX
+  available meta contexts: 1
+   base:allocation
+
+
+=== Add a writable export ===
+{"execute": "block-export-add", "arguments": {"description": "This is the writable second export", "id": "export1", "name": "export1", "node-name": "fmt", "type": "nbd", "writable": true, "writethrough": true}}
+{"error": {"class": "GenericError", "desc": "Conflicts with use by sda as 'root', which does not allow 'write' on fmt"}}
+{"execute": "device_del", "arguments": {"id": "sda"}}
+{"return": {}}
+{"data": {"device": "sda", "path": "/machine/peripheral/sda"}, "event": "DEVICE_DELETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}
+{"execute": "device_add", "arguments": {"drive": "fmt", "driver": "scsi-hd", "id": "sda", "share-rw": true}}
+{"return": {}}
+{"execute": "block-export-add", "arguments": {"description": "This is the writable second export", "id": "export1", "name": "export1", "node-name": "fmt", "type": "nbd", "writable": true, "writethrough": true}}
+{"return": {}}
+{"execute": "query-block-exports", "arguments": {}}
+{"return": [{"id": "export1", "node-name": "fmt", "shutting-down": false, "type": "nbd"}, {"id": "export0", "node-name": "fmt", "shutting-down": false, "type": "nbd"}]}
+exports available: 2
+ export: 'fmt'
+  size:  67108864
+  flags: 0x58f ( readonly flush fua df multi cache )
+  min block: XXX
+  opt block: XXX
+  max block: XXX
+  available meta contexts: 1
+   base:allocation
+ export: 'export1'
+  description: This is the writable second export
+  size:  67108864
+  flags: 0xced ( flush fua trim zeroes df cache fast-zero )
+  min block: XXX
+  opt block: XXX
+  max block: XXX
+  available meta contexts: 1
+   base:allocation
+
+
+=== Connect qemu-io to export1, try removing exports ===
+read 4096/4096 bytes at offset 0
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+wrote 4096/4096 bytes at offset 4096
+4 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+
+{"execute": "block-export-del", "arguments": {"id": "export1"}}
+{"error": {"class": "GenericError", "desc": "export 'export1' still in use"}}
+{"execute": "block-export-del", "arguments": {"id": "export0"}}
+{"return": {}}
+[{"data": {"id": "export0"}, "event": "BLOCK_EXPORT_DELETED", "timestamp": {"microseconds": "USECS", "seconds": "SECS"}}]
+{"execute": "query-block-exports", "arguments": {}}
+{"return": [{"id": "export1", "node-name": "fmt", "shutting-down": false, "type": "nbd"}]}
+exports available: 1
+ export: 'export1'
+  description: This is the writable second export
+  size:  67108864
+  flags: 0xced ( flush fua trim zeroes df cache fast-zero )
+  min block: XXX
+  opt block: XXX
+  max block: XXX
+  available meta contexts: 1
+   base:allocation
+
+
+=== Connect qemu-io again, try force removing ===
+{"execute": "block-export-del", "arguments": {"id": "export1"}}
+{"error": {"class": "GenericError", "desc": "export 'export1' still in use"}}
+{"execute": "block-export-del", "arguments": {"id": "export1", "mode": "hard"}}
+{"return": {}}
+read failed: Input/output error
+
+{"execute": "query-block-exports", "arguments": {}}
+{"return": []}
+exports available: 0
+
+
+=== Shut down QEMU ===
diff --git a/tests/qemu-iotests/group b/tests/qemu-iotests/group
index ff59cfd..9e4f7c0 100644
--- a/tests/qemu-iotests/group
+++ b/tests/qemu-iotests/group
@@ -314,3 +314,4 @@
 303 rw quick
 304 rw quick
 305 rw quick
+307 rw quick export
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index f484604..f212cec 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -65,7 +65,8 @@ if os.environ.get('QEMU_IO_OPTIONS_NO_FMT'):
     qemu_io_args_no_fmt += \
         os.environ['QEMU_IO_OPTIONS_NO_FMT'].strip().split(' ')
 
-qemu_nbd_args = [os.environ.get('QEMU_NBD_PROG', 'qemu-nbd')]
+qemu_nbd_prog = os.environ.get('QEMU_NBD_PROG', 'qemu-nbd')
+qemu_nbd_args = [qemu_nbd_prog]
 if os.environ.get('QEMU_NBD_OPTIONS'):
     qemu_nbd_args += os.environ['QEMU_NBD_OPTIONS'].strip().split(' ')
 
@@ -88,21 +89,30 @@ luks_default_secret_object = 'secret,id=keysec0,data=' + \
 luks_default_key_secret_opt = 'key-secret=keysec0'
 
 
-def qemu_img_pipe_and_status(*args: str) -> Tuple[str, int]:
+def qemu_tool_pipe_and_status(tool: str, args: Sequence[str],
+                              connect_stderr: bool = True) -> Tuple[str, int]:
     """
-    Run qemu-img and return both its output and its exit code
+    Run a tool and return both its output and its exit code
     """
-    subp = subprocess.Popen(qemu_img_args + list(args),
+    stderr = subprocess.STDOUT if connect_stderr else None
+    subp = subprocess.Popen(args,
                             stdout=subprocess.PIPE,
-                            stderr=subprocess.STDOUT,
+                            stderr=stderr,
                             universal_newlines=True)
     output = subp.communicate()[0]
     if subp.returncode < 0:
-        sys.stderr.write('qemu-img received signal %i: %s\n'
-                         % (-subp.returncode,
+        sys.stderr.write('%s received signal %i: %s\n'
+                         % (tool, -subp.returncode,
                             ' '.join(qemu_img_args + list(args))))
     return (output, subp.returncode)
 
+def qemu_img_pipe_and_status(*args: str) -> Tuple[str, int]:
+    """
+    Run qemu-img and return both its output and its exit code
+    """
+    full_args = qemu_img_args + list(args)
+    return qemu_tool_pipe_and_status('qemu-img', full_args)
+
 def qemu_img(*args: str) -> int:
     '''Run qemu-img and return the exit code'''
     return qemu_img_pipe_and_status(*args)[1]
@@ -263,19 +273,20 @@ def qemu_nbd(*args):
     '''Run qemu-nbd in daemon mode and return the parent's exit code'''
     return subprocess.call(qemu_nbd_args + ['--fork'] + list(args))
 
-def qemu_nbd_early_pipe(*args):
+def qemu_nbd_early_pipe(*args: str) -> Tuple[int, str]:
     '''Run qemu-nbd in daemon mode and return both the parent's exit code
        and its output in case of an error'''
-    subp = subprocess.Popen(qemu_nbd_args + ['--fork'] + list(args),
-                            stdout=subprocess.PIPE,
-                            universal_newlines=True)
-    output = subp.communicate()[0]
-    if subp.returncode < 0:
-        sys.stderr.write('qemu-nbd received signal %i: %s\n' %
-                         (-subp.returncode,
-                          ' '.join(qemu_nbd_args + ['--fork'] + list(args))))
-
-    return subp.returncode, output if subp.returncode else ''
+    full_args = qemu_nbd_args + ['--fork'] + list(args)
+    output, returncode = qemu_tool_pipe_and_status('qemu-nbd', full_args,
+                                                   connect_stderr=False)
+    return returncode, output if returncode else ''
+
+def qemu_nbd_list_log(*args: str) -> str:
+    '''Run qemu-nbd to list remote exports'''
+    full_args = [qemu_nbd_prog, '-L'] + list(args)
+    output, _ = qemu_tool_pipe_and_status('qemu-nbd', full_args)
+    log(output, filters=[filter_testfiles, filter_nbd_exports])
+    return output
 
 @contextmanager
 def qemu_nbd_popen(*args):
@@ -410,6 +421,9 @@ def filter_qmp_imgfmt(qmsg):
         return value
     return filter_qmp(qmsg, _filter)
 
+def filter_nbd_exports(output: str) -> str:
+    return re.sub(r'((min|opt|max) block): [0-9]+', r'\1: XXX', output)
+
 
 Msg = TypeVar('Msg', Dict[str, Any], List[Any], str)
 
@@ -1048,16 +1062,12 @@ def case_notrun(reason):
 
 def _verify_image_format(supported_fmts: Sequence[str] = (),
                          unsupported_fmts: Sequence[str] = ()) -> None:
-    assert not (supported_fmts and unsupported_fmts)
-
     if 'generic' in supported_fmts and \
             os.environ.get('IMGFMT_GENERIC', 'true') == 'true':
         # similar to
         #   _supported_fmt generic
         # for bash tests
-        if imgfmt == 'luks':
-            verify_working_luks()
-        return
+        supported_fmts = ()
 
     not_sup = supported_fmts and (imgfmt not in supported_fmts)
     if not_sup or (imgfmt in unsupported_fmts):
@@ -1141,20 +1151,14 @@ def verify_working_luks():
     if not working:
         notrun(reason)
 
-def qemu_pipe(*args):
+def qemu_pipe(*args: str) -> str:
     """
     Run qemu with an option to print something and exit (e.g. a help option).
 
     :return: QEMU's stdout output.
     """
-    args = [qemu_prog] + qemu_opts + list(args)
-    subp = subprocess.Popen(args, stdout=subprocess.PIPE,
-                            stderr=subprocess.STDOUT,
-                            universal_newlines=True)
-    output = subp.communicate()[0]
-    if subp.returncode < 0:
-        sys.stderr.write('qemu received signal %i: %s\n' %
-                         (-subp.returncode, ' '.join(args)))
+    full_args = [qemu_prog] + qemu_opts + list(args)
+    output, _ = qemu_tool_pipe_and_status('qemu', full_args)
     return output
 
 def supported_formats(read_only=False):