Description of problem:
IDE disk with raw format image cannot be hot-plugged and hot-unplugged on Xen HVM

Version-Release number of selected component (if applicable):
virt-manager-0.6.1-14.el5
xen-3.0.3-130.el5
kernel-xen-2.6.18-259.el5

How reproducible:
Always

Steps to Reproduce:
1. Create a raw format volume in storage : raw.img
2. Open a running guest, here is rhel5.6, run #modprobe acpiphp
3. On the Hardware tab, click "Add Hardware"
4. Select "Storage" and forward
5. Browse raw.img as File(disk image), Device type is "IDE disk", Forward and Finish

6. Select "hdb" in the Hardware tab, and click "Remove"
  
Actual results:
After step5, There is no error, and the disk "hdb" is listed in Hardware tab, but on the guest console, run #ls /dev/hd* or #fdisk -l , there is no "hdb" disk.

After step6, the "hdb" is still in the list. Reboot the guest, "hdb" is disappeared.  

Expected results:
After step 5, the disk "hdb" should be added successfully. 
After step 6, the disk "hdb" should be removed successfully. We don't need to reboot guest.


Additional info:
It work well on virsh command:

# virsh attach-disk rhel5.6 /var/lib/libvirt/images/raw.img  hdb --driver file
Disk attached successfully

# virsh detach-disk rhel5.6 hdb
Disk detached successfully