Bug 819014

Summary:	blockIoTune modifies live xml even on failure
Product:	Red Hat Enterprise Linux 6	Reporter:	Eric Blake <eblake>
Component:	libvirt	Assignee:	Eric Blake <eblake>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	high
Version:	6.3	CC:	acathrow, ajia, bsarathy, dallan, dyasny, dyuan, eblake, gsun, jyang, mjenner, mzhan, rwu, veillard, weizhan
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	libvirt-0.9.10-17.el6	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	770683	Environment:
Last Closed:	2012-06-20 06:57:57 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	770683
Bug Blocks:

Comment 1 Eric Blake 2012-05-04 15:41:48 UTC

Modifying the live xml even when the monitor command fails is problematic, because you can end up with corrupted xml that will prevent a managedsave/restore cycle on the domain.  The fix is a one-liner (move the change to the live xml to occur after the check for error).

Comment 2 Eric Blake 2012-05-04 15:59:32 UTC

Upstream patch proposed:
https://www.redhat.com/archives/libvir-list/2012-May/msg00322.html

Comment 4 Eric Blake 2012-05-04 23:35:55 UTC

In POST:
http://post-office.corp.redhat.com/archives/rhvirt-patches/2012-May/msg00096.html

Comment 6 dyuan 2012-05-11 09:04:16 UTC

Verified PASS with libvirt-0.9.10-18.el6.

# virsh blkdeviotune xp hda --total_bytes_sec 1000
error: Unable to change block I/O throttle
error: unsupported configuration: block I/O throttling not supported with this QEMU binary

# virsh dumpxml xp
...
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/var/lib/libvirt/images/winXP-32-virtio.qcow2'/>
      <target dev='hda' bus='ide'/>
      <alias name='ide0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
...

Reproduced it with libvirt-0.9.10-16.el6.

# virsh blkdeviotune xp hda --total_bytes_sec 1000
error: Unable to change block I/O throttle
error: internal error Unexpected error

# virsh dumpxml xp|grep disk -A 10
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='none'/>
      <source file='/var/lib/libvirt/images/winXP-32-virtio.qcow2'/>
      <target dev='hda' bus='ide'/>
      <iotune>
        <total_bytes_sec>1000</total_bytes_sec>
      </iotune>
      <alias name='ide0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>

Comment 8 errata-xmlrpc 2012-06-20 06:57:57 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHSA-2012-0748.html