Description of problem:
qemu-kvm hang after hot-unplug a vf from win2012r2. 
Note that:
Before hot-unplug this vf from guest, do the following operation: 
# echo 0 > /sys/bus/pci/devices/0000\:05\:00.0/sriov_numvfs

Version-Release number of selected component (if applicable):
qemu-kvm-rhev-1.5.3-21.el7.x86_64
3.10.0-61.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1.bring up vfs and unbind them from host, then assign to guest.
# cat init.sh 
#! /bin/sh

./insmod.sh
./reset_num_vfs.sh
./unbind_vf_from_host.sh
---
# cat insmod.sh 
#! /bin/sh

modprobe vfio
modprobe vfio-pci
lsmod |grep vfio

echo 1 > /sys/module/vfio_iommu_type1/parameters/allow_unsafe_interrupts
----
# cat reset_num_vfs.sh 
#! /bin/sh

#modprobe -r ixgbe; modprobe ixgbe max_vfs=1000

# Get max NO. of VFs driver supported:
cat /sys/bus/pci/devices/0000\:05\:00.0/sriov_totalvfs

echo 0 > /sys/bus/pci/devices/0000\:05\:00.0/sriov_numvfs
echo 16 > /sys/bus/pci/devices/0000\:05\:00.0/sriov_numvfs
echo 0 > /sys/bus/pci/devices/0000\:05\:00.1/sriov_numvfs
echo 16 > /sys/bus/pci/devices/0000\:05\:00.1/sriov_numvfs
---
# cat unbind_vf_from_host.sh 
#! /bin/sh

lspci -n -s 0000:05:00.0 | awk '{ print $3 }'

#echo 19a2 0710 > /sys/bus/pci/drivers/vfio-pci/new_id 


echo 0000:05:10.0 > /sys/bus/pci/devices/0000\:05\:10.0/driver/unbind
echo 0000:05:10.1 > /sys/bus/pci/devices/0000\:05\:10.1/driver/unbind
echo 0000:05:10.2 > /sys/bus/pci/devices/0000\:05\:10.2/driver/unbind
echo 0000:05:10.3 > /sys/bus/pci/devices/0000\:05\:10.3/driver/unbind
echo 0000:05:10.4 > /sys/bus/pci/devices/0000\:05\:10.4/driver/unbind
echo 0000:05:10.5 > /sys/bus/pci/devices/0000\:05\:10.5/driver/unbind
echo 0000:05:10.6 > /sys/bus/pci/devices/0000\:05\:10.6/driver/unbind
echo 0000:05:10.7 > /sys/bus/pci/devices/0000\:05\:10.7/driver/unbind



echo 0000:05:11.0 > /sys/bus/pci/devices/0000\:05\:11.0/driver/unbind
echo 0000:05:11.1 > /sys/bus/pci/devices/0000\:05\:11.1/driver/unbind
echo 0000:05:11.2 > /sys/bus/pci/devices/0000\:05\:11.2/driver/unbind
echo 0000:05:11.3 > /sys/bus/pci/devices/0000\:05\:11.3/driver/unbind
echo 0000:05:11.4 > /sys/bus/pci/devices/0000\:05\:11.4/driver/unbind
echo 0000:05:11.5 > /sys/bus/pci/devices/0000\:05\:11.5/driver/unbind
echo 0000:05:11.6 > /sys/bus/pci/devices/0000\:05\:11.6/driver/unbind
echo 0000:05:11.7 > /sys/bus/pci/devices/0000\:05\:11.7/driver/unbind


echo 8086 10ed > /sys/bus/pci/drivers/vfio-pci/new_id 
---
2.Boot guest with following cmd.
<cli>:
# /usr/libexec/qemu-kvm -S -M pc-i440fx-rhel7.0.0 -cpu SandyBridge,hv_spinlocks=0x1fff,hv_relaxed,hv_vapic -enable-kvm -m 2G -smp 2,sockets=2,cores=1,threads=1 -name juli -uuid 355a2475-4e03-4cdd-bf7b-5d6a59edaa68 -rtc base=localtime,clock=host,driftfix=slew -device virtio-scsi-pci,bus=pci.0,addr=0x5,id=scsi0 -drive file=/home/juli/win2012r2.raw,if=none,id=drive-scsi0-0-0,media=disk,cache=none,format=raw,werror=stop,rerror=stop,aio=native  -device scsi-hd,drive=drive-scsi0-0-0,bus=scsi0.0,scsi-id=0,lun=0,id=juli,bootindex=0 -drive file=/home/juli/ISO/en_windows_server_2012_r2_x64_dvd_2707946.iso,if=none,media=cdrom,format=raw,aio=native,id=drive-ide1-0-0 -device ide-drive,drive=drive-ide1-0-0,id=ide1-0-0,bus=ide.0,unit=0,bootindex=4 -drive file=/home/juli/virtio-win-prewhql-0.1-74.iso,if=none,media=cdrom,format=raw,aio=native,id=drive-ide1-0-1 -device ide-drive,drive=drive-ide1-0-1,id=ide1-0-1,bus=ide.0,unit=1,bootindex=6 -device virtio-balloon-pci,id=ballooning -global PIIX4_PM.disable_s3=0 -global PIIX4_PM.disable_s4=0 -k en-us -boot menu=on,reboot-timeout=-1,strict=on -qmp tcp:0:4499,server,nowait -serial unix:/tmp/ttyS0,server,nowait -vnc :8 -spice port=5961,disable-ticketing  -vga qxl -global qxl-vga.revision=3 -monitor stdio -monitor tcp:0:7766,server,nowait -monitor unix:/tmp/monitor1,server,nowait -netdev tap,id=tap1,vhost=on,queues=4,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown,ifname=tap-juli -device virtio-net-pci,netdev=tap1,id=nic1,mq=on,vectors=17,mac=1a:59:0a:4b:aa:94 -device vfio-pci,host=05:10.0,id=hostnet_VF
3.disable IOV via the following command.
# echo 0 > /sys/bus/pci/devices/0000\:05\:00.0/sriov_numvfs
4.hot-unplug vf from guest.
$ telnet 10.66.104.53 4499
{"execute":"qmp_capabilities"}
{"execute":"device_del","arguments":{"id":"hostnet_VF"}}

Actual results:
hot-unplug vf has returned via qmp, such as:
{"execute":"device_del","arguments":{"id":"hostnet_VF"}}
{"return": {}}
Note that: after this, qemu-kvm hang.

Expected results:
qemu-kvm works well. Or forbid hot-unplug vf when guest is using it.

Additional info: