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=(",", ": ")))'
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1716028
Title:
qemu 2.10 locks images with no feature flag
Status in QEMU:
New
Status in qemu package in Ubuntu:
New
Bug description:
1) % lsb_release -rd
Description: Ubuntu Artful Aardvark (development branch)
Release: 17.10
2) % apt-cache policy qemu-system-x86
qemu-system-x86:
Installed: 1:2.10~rc3+dfsg-0ubuntu1
Candidate: 1:2.10+dfsg-0ubuntu1
Version table:
1:2.10+dfsg-0ubuntu1 500
500 http://archive.ubuntu.com//ubuntu devel/main amd64 Packages
*** 1:2.10~rc3+dfsg-0ubuntu1 100
100 /var/lib/dpkg/status
3) qemu locks image files with no way to discover this feature nor how
to disable it
4) qemu provides a way to query if it supports image locking, and what
the default value is, and how to disable the locking via cli
qemu 2.10 now will lock image files and warn if an image is currently
locked. This prevent qemu from running (and possibly corrupting said
image).
However, qemu does not provide any way to determine if a qemu binary
actually has this capability. Normally behavior changing features are
exposed via some change to the qemu help menu or QMP/QAPI output of
capabilities.
I believe this slipped through since libvirt already does image
locking, but direct cli users will be caught by this change.
In particular, we have a use-case where we simulate multipath disks by
creating to disks which point to the same file which now breaks
without adding the 'file.locking=off' to the -drive parameters; which
is also completely undocumented and unexposed.
Some parts of the cli like -device allow querying of settable options
(qemu-system-x86 -device scsi_hd,?) but nothing equivalent exists for
-drive parameters.
ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: qemu-system-x86 1:2.10~rc3+dfsg-0ubuntu1
ProcVersionSignature: Ubuntu 4.12.0-11.12-generic 4.12.5
Uname: Linux 4.12.0-11-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.6-0ubuntu7
Architecture: amd64
Date: Fri Sep 8 12:56:53 2017
JournalErrors:
Hint: You are currently not seeing messages from other users and the system.
Users in groups 'adm', 'systemd-journal' can see all messages.
Pass -q to turn off this notice.
-- Logs begin at Mon 2017-01-30 11:56:02 CST, end at Fri 2017-09-08 12:56:46
CDT. --
-- No entries --
KvmCmdLine: COMMAND STAT EUID RUID PID PPID %CPU COMMAND
MachineType: HP ProLiant DL360 Gen9
ProcEnviron:
TERM=xterm
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.12.0-11-generic
root=UUID=45354276-e0c0-4bf6-9083-f130b89411cc ro --- console=ttyS1,115200
SourcePackage: qemu
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 03/05/2015
dmi.bios.vendor: HP
dmi.bios.version: P89
dmi.chassis.type: 23
dmi.chassis.vendor: HP
dmi.modalias:
dmi:bvnHP:bvrP89:bd03/05/2015:svnHP:pnProLiantDL360Gen9:pvr:cvnHP:ct23:cvr:
dmi.product.family: ProLiant
dmi.product.name: ProLiant DL360 Gen9
dmi.sys.vendor: HP
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