Comment 5 for bug 1716028

Kevin,

Thanks for the information. A couple of points for feedback:

1) there doesn't appear to be a way to run qmp query-schema without spawning a qemu instance in -qmp mode and having a second client issue the query-schema; certainly a qemu-system-$arch -qmp-schema would be quite useful when examining feature availability. While I know the QMP/QAPI introspection is where most of the work has gone to describing how to interact with qemu it's quite cumbersome at best:

searching for blockdev-add, find arg-type: 48, read arg-type-48, find list of 'variants', know that locking feature is part of 'file', find type: 207, see member 'locking' in list[A], which is of type 296, find type: 296, which is an enum of 'on', 'off', 'auto'

A. Interesting enough, qapi says the default is None, however qemu certainly locks files by default which would seem to imply a mismatch between qapi defaults and qemu behavior.

That's pretty heavy; Maybe that warning message qemu prints could provide some hints as to what a user could do (or refer to a manpage on locking?).

2) share-rw appears to be a blockdev parameter (I see it available via most block devices via qemu-system-$arch -device {scsi-hd,ide-hd,virtio-blk}? However there is no equivalent -blockdev for dumping the default options that a -blockdev parameter takes. The qmp-schema also does not include any information about 'share-rw' w.r.t what values are available that I could find after dumping the schema.

Thanks smoser:

#!/bin/sh
qemu-system-x86_64 -S -nodefaults -nographic \
   -serial none -monitor none -qmp stdio <<EOF |
{ "execute": "qmp_capabilities" }
{ "execute": "query-qmp-schema" }
{ "execute": "quit" }
EOF
   python3 -c '
import json, sys
data = json.loads(sys.stdin.read().splitlines()[2])
print(json.dumps(data, indent=1, sort_keys=True,
                 separators=(",", ": ")))'