Bug 834365

Summary:	Improve error message when trying to change VM's processor count to 0
Product:	Red Hat Enterprise Linux 6	Reporter:	Peter Krempa <pkrempa>
Component:	libvirt	Assignee:	Peter Krempa <pkrempa>
Status:	CLOSED ERRATA	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	low	Docs Contact:
Priority:	medium
Version:	6.3	CC:	acathrow, dallan, dyasny, dyuan, honzhang, juzhang, mzhan, pkrempa, rwu, ydu
Target Milestone:	rc
Target Release:	---
Hardware:	Unspecified
OS:	Linux
Whiteboard:
Fixed In Version:	libvirt-0.9.13-3.el6	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:	832946	Environment:
Last Closed:	2013-02-21 07:18:01 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:

Description Peter Krempa 2012-06-21 16:28:38 UTC

+++ This bug was initially created as a clone of Bug #832946 +++

Description of problem:
Use setvcpus to hotplug vcpu for a guest, then the guest's CPU usage is 100% and guest hang there.
BTW, if set vcpu number to 0, it seems the error message is not correct.

Version-Release number of selected component (if applicable):
libvirt-0.9.10-21.el6_3.1.x86_64&libvirt-0.9.10-21.el6.x86_64
qemu-kvm-rhev-0.12.1.2-2.295.el6.x86_64
kernel-2.6.32-276.el6.x86_64


How reproducible:
100%

Steps to Reproduce:
1. Set the maximum cpu number to 4
#virsh dumpxml test
......
<vcpu placement='static' current='1'>4</vcpu>
.....
2. hotplug vcpus 
#virsh setvcpus test 2 

check the guest xml again
#virsh dumpxml test
......
<vcpu placement='static' current='2'>4</vcpu>
.....

3. After add step2, guest's CPU usage up to 100% and cann't conduct any operation in guest.

4. set vcpus to 0
# virsh setvcpus  test 0
error: invalid argument: virDomainSetVcpus
  
Actual results:
As steps 3&4.

Expected results:
Hotplug vcpu can succeed, and the error message should be improved when set vcpu to 0.

Additional info:
No error meesages in libvirtd.log

--- Additional comment from ydu on 2012-06-18 11:43:30 CEST ---

This bug can always reproduced with rhel6.2 guest(release version), but can't reproduce with rhel6.3 guest.

--- Additional comment from pkrempa on 2012-06-18 12:18:02 CEST ---

There's either a bug or the the guest OS is missing support for CPU hotplug, so that it cannot handle the CPU that has emerged in the emulated system. This part of this bug isn't a problem with libvirt. 

As of the error message, that probably is worth tweaking a little bit.

Comment 1 Peter Krempa 2012-06-21 16:30:38 UTC

Creating a clone of the original bug to track improvement of the error message.

Comment 2 Peter Krempa 2012-06-22 08:49:54 UTC

Error message improved upstream with two commits:

commit d91f3ef49741f1b9143865ff6ef9e2119fbeccc2
Author: Daniel P. Berrange <berrange>
Date:   Fri May 25 18:41:07 2012 +0100

    Santize the reporting of VIR_ERR_INVALID_ERROR

improving API error messages and 

commit de924ca90a0ff1ad8adeab460761f65b7a742d72
Author: Peter Krempa <pkrempa>
Date:   Thu Jun 21 18:34:32 2012 +0200

    virsh: Improve error when trying to change vm's cpu count 0

to point out the error directly without the need for the user to understand API variable names.

Comment 4 hongming 2012-07-25 06:04:40 UTC

Verify it using the following version.
kernel-2.6.32-276.el6.x86_64
qemu-kvm-0.12.1.2-2.295.el6.x86_64
libvirt-0.9.13-3.el6.x86_64


Steps
1. # virsh dumpxml rhel6
...
<vcpu placement='static' current='1'>4</vcpu>
...

2. # virsh setvcpus rhel6 2


3. # virsh dumpxml rhel6 |grep cpu
  <vcpu placement='static' current='2'>4</vcpu>


4. # virsh setvcpus rhel6 0
error: Invalid number of virtual CPUs

Results
It is expected result.so move its status to VERIFIED.

Comment 5 errata-xmlrpc 2013-02-21 07:18:01 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-2013-0276.html