device can't be hot-removed from the guest

[Yongjie Ren]

Environment:
------------
Host OS (ia32/ia32e/IA64): ia32e
Guest OS (ia32/ia32e/IA64): ia32e
Guest OS Type (Linux/Windows): Linux(RHEL6u1)
kvm.git Commit: ff92e9b5571b34f53cbfde0899cf6e6a579cb3fa
qemu-kvm Commit: aad3b517a1b83561f2755dc4451596a421399c19
Host Kernel Version: 3.2.0-rc7
Hardware: Romley-EP, WSM-EP

Bug detailed description:
--------------------------
Using the latest qemu-kvm and kvm upstream, PCI device can't be hot-removed from the guest.
I try to remove a VF, but the device can't be removed. The VF in guest still has IP, and its network is fine.
A normal NIC will have the same issue.
From my test, this should be a qemu-kvm bug.
kvm + qemu-kvm = result
ff92e9b5 + aad3b517 = bad
ff92e9b5 + fcfeed4a = good

some logs are attached.

Reproduce steps:
----------------
1. start up a host with kvm(commit: ff92e9b5) and use qmeu-kvm(commit:aad3b517 )
2. qemu-system-x86_64 -m 512 -smp 1 –hda /root/rhel6u1.img
3. ctrl+Alt+2 (switch to monitor)
4. device_add pci-assign,host=09:10.0,id=nic (hot-add a VF)
5. ctrl+Alt+1
6. check the device can get IP
7. ctrl+Alt+2
8. device_del nic (try to detach the VF)

Current result:
----------------
Cannot hot-remove the device.

Expected result:
----------------
The device can be hot-removed.

[Yongjie Ren (yongjie-ren)]

fixed by the following commit.

commit 024a6fbdb9d8cbc4d7f833b23db51c9d1004bc47
Author: Anthony Liguori <email address hidden>
Date: Fri Jan 13 07:45:55 2012 -0600

    qdev: fix device_del by refactoring reference counting

    Commit 8eb0283 broken device_del by having too overzealous reference counting
    checks. Move the reference count checks to qdev_free(), make sure to remove
    the parent link on free, and decrement the reference count on property removal.