Bug 1133842

Description of problem:
balloon driver hit the same issue with rng device：https://bugzilla.redhat.com/show_bug.cgi?id=1131417,open a new bug to track balloon driver

Version-Release number of selected component (if applicable):
qemu-kvm-rhev-0.12.1.2-2.441.el6.x86_64
kernel-2.6.32-492.el6.x86_64
seabios-0.6.1.2-28.el6.x86_64
virtio-win-prewhql-90

How reproducible:
100%

Steps to Reproduce:
1.boot guest with balloon device:
/usr/libexec/qemu-kvm -drive file=win2k12r2.qcow2,if=none,cache=none,media=disk,format=qcow2,id=drive-ide0-0-1 -device ide-drive,id=ide0-0-1,drive=drive-ide0-0-1,bootindex=1 -boot menu=on -global PIIX4_PM.disable_s3=0 -global PIIX4_PM.disable_s4=0 -usb -device usb-tablet -monitor stdio -chardev file,path=/root/console.log,id=serial1 -device isa-serial,chardev=serial1,id=s1 -cpu SandyBridge -M rhel6.6.0 -smp 4,maxcpus=4,cores=2,threads=2,sockets=1 -m 4G -enable-kvm -qmp tcp:0:4444,server,nowait -vnc :0 -vga cirrus -device virtio-balloon-pci,id=balloon1
2.set the verifier with all the flags enabled,then reboot guest to make it effective:
cmd:verifier /flags 0x01FFFFFF /driver balloon.sys
3.Hot-plug/unplug balloon device in a loop
#!/bin/bash
# some simply scripts for balloon device hotplug/unplug in a loop
let i=0
exec 3<>/dev/tcp/localhost/4444 #note modify this to qmp port
echo -e "{ 'execute': 'qmp_capabilities' }" >&3
read response <&3
echo $response
while [ $i -lt 150 ]
do
    echo -e "{ 'execute': 'device_del', 'arguments': {'id': 'balloon1' }}">&3 ;
    sleep 2 ;
    read response <&3 ;
    echo "$i: $response"
    sleep 2 ;
     echo -e "{'execute':'device_add','arguments':{'driver':'virtio-balloon-pci','id':'balloon1','addr':'0x9'}}">&3 ;
    sleep 2 ;
    read response <&3
    echo "$i: $response"
    let i=$i+1
done

Actual results:
1.after hotplug/unplug about 60~80 times ,there is a yellow exclamation mark on device manager(as shown in the attachment);
2.balloon memory via qmp/hmp,balloon device does not work,memory keep at the original value

Expected results:
balloon device can function well after the hotplug loop ends 

Additional info:
set verifier with the standard settings cannot hit this issue:
cmd:verifier /standard /driver balloon.sys