xen/pciback: Move the PCI_DEV_FLAGS_ASSIGNED ops to the "[un|]bind"

operation instead of doing it per guest creation/disconnection. Without
this we could have potentially unloaded the vf driver from the
xen pciback control even if the driver was binded to the xen-pciback.
This will hold on to it until the user "unbind"s the PCI device using
SysFS.
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/xen-pciback/pci_stub.c

@@ -99,6 +99,7 @@ static void pcistub_device_release(struct kref *kref)
 	kfree(pci_get_drvdata(psdev->dev));
 	pci_set_drvdata(psdev->dev, NULL);
 
+	psdev->dev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
 	pci_dev_put(psdev->dev);
 
 	kfree(psdev);
@@ -331,6 +332,7 @@ static int __devinit pcistub_init_device(struct pci_dev *dev)
 	dev_dbg(&dev->dev, "reset device\n");
 	xen_pcibk_reset_device(dev);
 
+	dev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
 	return 0;
 
 config_release:

drivers/xen/xen-pciback/xenbus.c

@@ -241,7 +241,6 @@ static int xen_pcibk_export_device(struct xen_pcibk_device *pdev,
 		goto out;
 
 	dev_dbg(&dev->dev, "registering for %d\n", pdev->xdev->otherend_id);
-	dev->dev_flags |= PCI_DEV_FLAGS_ASSIGNED;
 	if (xen_register_device_domain_owner(dev,
 					     pdev->xdev->otherend_id) != 0) {
 		dev_err(&dev->dev, "device has been assigned to another " \
@@ -281,7 +280,6 @@ static int xen_pcibk_remove_device(struct xen_pcibk_device *pdev,
 	}
 
 	dev_dbg(&dev->dev, "unregistering for %d\n", pdev->xdev->otherend_id);
-	dev->dev_flags &= ~PCI_DEV_FLAGS_ASSIGNED;
 	xen_unregister_device_domain_owner(dev);
 
 	xen_pcibk_release_pci_dev(pdev, dev);