pci_piix3_xen_ide_unplug should completely unhook the unplugged
IDEDevice from the corresponding BlockBackend, otherwise the next call
to release_drive will try to detach the drive again.

Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---
 hw/ide/piix.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tools/qemu-xen/hw/ide/piix.c b/tools/qemu-xen/hw/ide/piix.c
index 40757eb..0524dce 100644
--- a/tools/qemu-xen/hw/ide/piix.c
+++ b/tools/qemu-xen/hw/ide/piix.c
@@ -172,6 +172,7 @@ int pci_piix3_xen_ide_unplug(DeviceState *dev)
     PCIIDEState *pci_ide;
     DriveInfo *di;
     int i = 0;
+    IDEDevice *idedev;
 
     pci_ide = PCI_IDE(dev);
 
@@ -184,6 +185,12 @@ int pci_piix3_xen_ide_unplug(DeviceState *dev)
             }
             bdrv_close(di->bdrv);
             pci_ide->bus[di->bus].ifs[di->unit].bs = NULL;
+            if (!(i % 2)) {
+                idedev = pci_ide->bus[di->bus].master;
+            } else {
+                idedev = pci_ide->bus[di->bus].slave;
+            }
+            idedev->conf.bs = NULL;
             drive_put_ref(di);
         }
     }
-- 
2.1.4