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[Qemu-devel] [Bug 1716028] Re: qemu 2.10 locks images with no feature fl
From: |
ChristianEhrhardt |
Subject: |
[Qemu-devel] [Bug 1716028] Re: qemu 2.10 locks images with no feature flag |
Date: |
Wed, 08 Nov 2017 16:10:24 -0000 |
We had a discussion today on how to workaround if you drive qmeu via libvirt.
While discussions often and up at the correctness of such setups they exists, I
think it is worth to document until libvirt supports that officially.
TL:DR:
- no native libvirt feature yet
- discussions if <shareable/> should set it
- workaround available via cmdline
Details on the workaround:
- To use the workaround you have to check your log usually in
/var/log/libvirt/qemu/<guestname>.log
- Get the id of the device that matters to you
- then use [1] to tweak qemu cmdline
- example is from [2] to [3]
[1]: http://blog.vmsplice.net/2011/04/how-to-pass-qemu-command-line-options.html
[2]: https://gist.github.com/anonymous/a2ce3cbf7878995537212f0dafd06d99
[3]: https://gist.github.com/anonymous/07a357af9e34172b60c83d410fe63fdd
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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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- [Qemu-devel] [Bug 1716028] Re: qemu 2.10 locks images with no feature flag,
ChristianEhrhardt <=