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Bug 1178853

Summary: Allow disabling the PMU in the xml file
Product: Red Hat Enterprise Linux 7 Reporter: Luiz Capitulino <lcapitulino>
Component: libvirtAssignee: Martin Kletzander <mkletzan>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 7.2CC: dyuan, ehabkost, honzhang, juzhang, lcapitulino, lhuang, mkletzan, mtosatti, mzhan, rbalakri, xfu, zhwang
Target Milestone: rcKeywords: Upstream
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: libvirt-1.2.13-1.el7 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2015-11-19 06:06:27 UTC Type: Bug
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:    
Bug Blocks: 1175463    

Description Luiz Capitulino 2015-01-05 14:47:11 UTC 
Description of problem:

For real-time, we need to be able to disable the PMU. This is done by passing pmu=off to QEMU, like:

-cpu host,pmu=off

However, libvirt doesn't know the "pmu=off" flag.


Version-Release number of selected component (if applicable): libvirt-1.2.8-11.el7.x86_64
Comment 1 Martin Kletzander 2015-01-05 15:50:33 UTC 
Do all QEMU versions support this flag or only some of them?  If the latter is true, how can we get that support information from QMP?  We need that in order to error out properly before even starting QEMU.
Comment 2 Luiz Capitulino 2015-01-05 17:00:30 UTC 
I think Eduardo is the best person to answer this.
Comment 3 Martin Kletzander 2015-01-13 08:00:08 UTC 
Patches proposed upstream:

https://www.redhat.com/archives/libvir-list/2015-January/msg00308.html
Comment 4 Eduardo Habkost 2015-01-15 16:11:00 UTC 
(In reply to Martin Kletzander from comment #1)
> Do all QEMU versions support this flag or only some of them?  If the latter
> is true, how can we get that support information from QMP?  We need that in
> order to error out properly before even starting QEMU.

I believe there's no way to query for the availability of the "pmu" property yet, because we still don't have working CPU class introspection in QEMU. This should be implemented as part of bug 824987.
Comment 5 Martin Kletzander 2015-01-19 07:49:46 UTC 
Fixed upstream by commits v1.2.11-190-g1993901 and v1.2.11-191-g6514c04:

commit 199390117c9ad010c2cc84a152943a5f006ec2b1
Author: Martin Kletzander <mkletzan>
Date:   Mon Jan 5 16:21:51 2015 +0100

    docs, schema, conf: Add support for PMU feature

commit 6514c04c182f0c59ce8d491c37f0dc4b73703311
Author: Martin Kletzander <mkletzan>
Date:   Mon Jan 5 16:52:18 2015 +0100

    qemu: Add support for enabling/disabling PMU
Comment 7 Luyao Huang 2015-06-16 06:26:40 UTC 
Verify this issue with libvirt-1.2.16-1.el7.x86_64:

1. prepare a guest with xml like this:

...

  <features>
    <acpi/>
    <apic/>
    <pae/>
    <pmu state='off'/>
  </features>
... 

2. start the guest and recheck the xml and qemu CLI:

# virsh start test3
Domain test3 started
 

# virsh dumpxml test3

...

  <features>
    <acpi/>
    <apic/>
    <pae/>
    <pmu state='off'/>
  </features>
...

 

# ps aux|grep qemu

...

-cpu qemu64,pmu=off

...

3. do managedsave/restore :

# virsh managedsave rhel7.0

Domain rhel7.0 state saved by libvirt

# virsh start rhel7.0
Domain rhel7.0 started

4. recheck the xml and qemu CLI:

# virsh dumpxml test3

...

  <features>
    <acpi/>
    <apic/>
    <pae/>
    <pmu state='off'/>
  </features>
...

 

# ps aux|grep qemu

...

-cpu qemu64,pmu=off

...

5. restart libvirtd and recheck the xml still exist
Comment 9 errata-xmlrpc 2015-11-19 06:06:27 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.

https://rhn.redhat.com/errata/RHBA-2015-2202.html