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Description of problem:
Improve the error info when add the second balloon device

Version-Release number of selected component (if applicable):

Host:
# uname -r
3.10.0-205.el7.x86_64
# rpm -q qemu-kvm-rhev
qemu-kvm-rhev-2.1.2-8.el7.x86_64

Guest:win1012r2

How reproducible:
100%

Steps to Reproduce:
1.Boot guest with balloon device
..-device virtio-balloon-pci,bus=pci.0,id=balloon0..

2.Try to hotplug another balloon device
...
 { "execute": "device_add", "arguments": { "driver": "virtio-balloon-pci","id": "balloon1" } }
{"error": {"class": "GenericError", "desc": "Adding balloon handler failed"}}
..

3.

Actual results:

The error info is hard to diagnose 
.
Expected results:
{"error": {"class": "GenericError", "desc": "Adding balloon handler failed,another balloon device already registered"}}

Additional info:
Use HMP, will see
(qemu) device_add virtio-balloon-pci,id=balloon2
Another balloon device already registered
Adding balloon handler failed
Device initialization failed.
Device 'virtio-balloon-pci' could not be initialized

Yeah, we can improve the error message. But a second balloon device is not supported, so this is really minor. Moving to RHEL7.2.

Fix posted upstream:

http://lists.nongnu.org/archive/html/qemu-devel/2015-03/msg06208.html

Fix included in qemu-kvm-rhev-2.3.0-2.el7

reproduce:
host kernel:3.10.0-267.el7.x86_64
host qemu:  qemu-kvm-rhev-2.1.2-21.el7.x86_64

QE retested this bug on the above environment,then got the same result.
So, the bug is reproduced on the above environment.


verify:
host kernel:3.10.0-267.el7.x86_64
host qemu:  qemu-kvm-rhev-2.3.0-4.el7.x86_64

QE retested this bug on the above environment. Got explicitly error info:{"error": {"class": "GenericError", "desc": "Only one balloon device is supported"}}
So, the bug fixed.

Based on Comment 8, set this bug to VERIFIED.

Best regards,
Huiqing

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-2015-2546.html