Bug 1428893

+++ This bug was initially created as a clone of Bug #1427801 +++

Description of problem:
After a VCPU unplug request times out initially the domain definition is not updated once the guest actually unplugs the vCPUS.

Afterwards further vCPU unplug requests fail with: 
internal error: unable to execute QEMU command 'device_del': Device 'vcpu8' not found

Version-Release number of selected component (if applicable):
Upstream libvirt compiled at
Repo: https://github.com/libvirt/libvirt.git 
Branch: master 
Commit: ca1f38545750d597c75c9773723c716483b03e5c
#libvirtd --version
libvirtd (libvirt) 3.1.0

Also applies to 3.2.0.el7.


How reproducible:
Always

Steps to Reproduce:
1. Define a guest(Fedora25) with current 8 vcpus and 240 max vcpus with following topology
2. virsh setvcpus virt-tests-vm1 16 --live
3. virsh setvcpus virt-tests-vm1 8 --live
error: operation failed: vcpu unplug request timed out

^^ vcpu unplug took long, the command timed out, the failure is expected

4. the guest actually unplugs the vcpus

5. virsh setvcpus virt-tests-vm1 8 --live
error: internal error: unable to execute QEMU command 'device_del': Device 'vcpu8' not found

^^ this should not happen

Actual results:
Cpu unplug  errors out leaving hotplug/unplug operation not functional once a vcpu unplug request times out.


Expected results:
Cpu hotplug/unplug should work fine

Additional info:
It may be necessary to somehow make the guest deny the vcpu unplug. I could not reproduce it.
Note that the bug is not ppc64 specific. The same would happen on intel if the first attempt was rejected.

Guest XML:
<domain type='kvm' id='5'>
  <name>virt-tests-vm1</name>
  <uuid>496d2299-4a36-4403-a583-6e07bec87070</uuid>
  <memory unit='KiB'>33554432</memory>
  <currentMemory unit='KiB'>33554432</currentMemory>
  <vcpu placement='static' current='8'>240</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='ppc64le' machine='pseries-2.9'>hvm</type>
    <boot dev='hd'/>
  </os>
  <cpu>
    <topology sockets='2' cores='15' threads='8'/>
  </cpu>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/bin/qemu-kvm</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/home/sath/runAvocadoFVTTest/avocado-fvt-wrapper/data/avocado-vt/images/f25-ppc64le.qcow2'/>
      <backingStore/>
      <target dev='sda' bus='scsi'/>
      <alias name='scsi0-0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    </disk>
    <controller type='scsi' index='0' model='virtio-scsi'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </controller>
    <controller type='usb' index='0' model='pci-ohci'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </controller>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <alias name='virtio-serial0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </controller>
    <interface type='bridge'>
      <mac address='52:54:00:61:62:63'/>
      <source bridge='virbr0'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/0'/>
      <target port='0'/>
      <alias name='serial0'/>
      <address type='spapr-vio' reg='0x30000000'/>
    </serial>
    <console type='pty' tty='/dev/pts/0'>
      <source path='/dev/pts/0'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
      <address type='spapr-vio' reg='0x30000000'/>
    </console>
    <channel type='unix'>
      <source mode='bind' path='/var/lib/libvirt/qemu/f25ppc64le.agent'/>
      <target type='virtio' name='org.qemu.guest_agent.0' state='connected'/>
      <alias name='channel0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </memballoon>
    <panic model='pseries'/>
  </devices>
  <seclabel type='dynamic' model='selinux' relabel='yes'>
    <label>system_u:system_r:svirt_t:s0:c62,c845</label>
    <imagelabel>system_u:object_r:svirt_image_t:s0:c62,c845</imagelabel>
  </seclabel>
  <seclabel type='dynamic' model='dac' relabel='yes'>
    <label>+107:+107</label>
    <imagelabel>+107:+107</imagelabel>
  </seclabel>
</domain>