Bug 799180

Summary:	Sometimes guest become not to respond when change vcpu
Product:	Red Hat Enterprise Linux 6	Reporter:	yuping zhang <yupzhang>
Component:	kernel	Assignee:	Red Hat Kernel Manager <kernel-mgr>
Status:	CLOSED DUPLICATE	QA Contact:	Red Hat Kernel QE team <kernel-qe>
Severity:	medium	Docs Contact:
Priority:	high
Version:	6.2	CC:	acathrow, dallan, dyuan, eblake, imammedo, mzhan, rwu, tburke, zpeng
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2012-05-23 21:31:12 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:

Description yuping zhang 2012-03-02 03:17:24 UTC

Description of problem:
Perpare a rhel6.2 guest, then change the vcpu,sometimes the guest will become not to respond.

Version-Release number of selected component (if applicable):
qemu-kvm-0.12.1.2-2.234.el6.x86_64
libvirt-0.9.10-3.el6.x86_64
virt-manager-0.9.0-10.el6.x86_64

How reproducible:
90%

Steps to Reproduce:
1.Start a rhel6.2 guest.
#virsh dumpxml rhel6.2-new
...
<currentMemory>1048576</currentMemory>
<vcpu current='2'>4</vcpu>
...
2. Wait for the guest boot completely,then run
#virsh setvcpus rhel6.2-new 1 --live
#virsh setvcpus rhel6.2-new 3 --live
Or
You can use virt-manager to change the Current allocation of CPU,then apply.

3.Check the guest with virt-manager or virt-viewer.

Actual results:
The guest become no respond.

Expected results:
The guest works well and the vcpu will not update.
As we know,the qemu-kvm doesn't support vcpu hotplug now.The libvirt provide the API for it.
But I think the guest should not become not to respond at least.

Additional info:
1. I can reproduce this issue on rhel6 guest 100%,and can not reproduce on rhel5 guest.
2. You can change the vcpus several times if you can not reproduce this issue.

Comment 3 Dave Allan 2012-05-23 20:27:45 UTC

Based on the fact that the reproduction is completely dependent on the guest OS, I believe this BZ is not a libvirt problem, so I'm reassigning to kernel.  Please correct me if I'm wrong about that.

Comment 4 Igor Mammedov 2012-05-23 21:31:12 UTC

Closingas duplicate of bug 788562

Please re-test with RHEL6.3 kernel (kernel-2.6.32-235.el6 or later), where issue is fixed or disable kvm-clock in qemu to workaround issue on RHEL6.2.

Dor:
It might be good idea to clone bug 788562 for RHEL6.2 z stream.

*** This bug has been marked as a duplicate of bug 788562 ***