The guest will be destroyed after hot remove the VF from the guest.

[chao zhou]

Environment:
------------
Host OS (ia32/ia32e/IA64):ia32e
Guest OS (ia32/ia32e/IA64):ia32e
Guest OS Type (Linux/Windows):Linux
kvm.git Commit:9f6226a762c7ae02f6a23a3d4fc552dafa57ea23
qemu.git Commit:5a7348045091a2bc15d85bb177e5956aa6114e5a
Host Kernel Version:3.16.0-rc1
Hardware:Romley_EP, Ivytown_EP,Haswell_EP

Bug detailed description:
--------------------------
hot add the VF to the guest, then hot remove the VF from the guest, the guest will be destroyed.

note:
1. when hot add the VF with vfio, the hot remove the VF from the guest, the guest works fine.
2. this shoule be a qemu bug:
kvm + qemu = result
9f6226a7 + 5a734804 = bad
9f6226a7 + 9f862687 = good

Reproduce steps:
----------------
1. create guest
qemu-system-x86_64 --enable-kvm -m 1024 -smp 4 -net none rhel6u5.qcow -monitor pty
2. hot add the vf to guest
echo "device_add pci-assign,host=05:10.0,id=nic" >/dev/pts/x
cat /dev/pts/x
3. hot remove the VF froem guest
echo "device_del nic" >/dev/pts/x

Current result:
----------------
the guest willl be destroyed after hot remove the VF from the guest

Expected result:
----------------
the guest works fine after hot remove the VF from the guest

Basic root-causing log:
----------------------
[root@vt-snb9 qemu.git]# qemu-system-x86_64 -enable-kvm -m 1024 -smp 2 -net none rhel6u5.qcow -monitor pty
VNC server running on `::1:5900'
**
ERROR:qom/object.c:725:object_unref: assertion failed: (obj->ref > 0)
Aborted (core dumped)

[chao zhou (chao-zhou)]

the first bad commit is:
commit 22a893e4f55344f96e1aafc66f5fedc491a5ca97
Author: Paolo Bonzini <email address hidden>
Date: Wed Jun 11 10:58:06 2014 +0200

    memory: MemoryRegion: replace owner field with QOM parent

    The two are now the same.

    Reviewed-by: Peter Crosthwaite <email address hidden>
    Signed-off-by: Paolo Bonzini <email address hidden>

[chao zhou (chao-zhou)]

test on Ivytown_EP
kvm.git + qemu.git: c77dcacb_0e4a7737
kernel version: 3.16.0
after hot remove the VF from the guest, the guest works fine.