xen/pciback: Register the owner (domain) of the PCI device.

When the front-end and back-end start negotiating we register
the domain that will use the PCI device. Furthermore during shutdown
of guest or unbinding of the PCI device (and unloading of module)
from pciback we unregister the domain owner.
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

drivers/xen/xen-pciback/pci_stub.c

@@ -90,6 +90,8 @@ static void pcistub_device_release(struct kref *kref)
 
 	dev_dbg(&psdev->dev->dev, "pcistub_device_release\n");
 
+	xen_unregister_device_domain_owner(psdev->dev);
+
 	/* Clean-up the device */
 	pciback_reset_device(psdev->dev);
 	pciback_config_free_dyn_fields(psdev->dev);

drivers/xen/xen-pciback/xenbus.c

@@ -10,6 +10,7 @@
 #include <linux/workqueue.h>
 #include <xen/xenbus.h>
 #include <xen/events.h>
+#include <asm/xen/pci.h>
 #include <linux/workqueue.h>
 #include "pciback.h"
 
@@ -221,6 +222,15 @@ static int pciback_export_device(struct pciback_device *pdev,
 	if (err)
 		goto out;
 
+	dev_dbg(&dev->dev, "registering for %d\n", pdev->xdev->otherend_id);
+	if (xen_register_device_domain_owner(dev,
+					     pdev->xdev->otherend_id) != 0) {
+		dev_err(&dev->dev, "device has been assigned to another " \
+			"domain! Over-writting the ownership, but beware.\n");
+		xen_unregister_device_domain_owner(dev);
+		xen_register_device_domain_owner(dev, pdev->xdev->otherend_id);
+	}
+
 	/* TODO: It'd be nice to export a bridge and have all of its children
 	 * get exported with it. This may be best done in xend (which will
 	 * have to calculate resource usage anyway) but we probably want to
@@ -251,6 +261,9 @@ static int pciback_remove_device(struct pciback_device *pdev,
 		goto out;
 	}
 
+	dev_dbg(&dev->dev, "unregistering for %d\n", pdev->xdev->otherend_id);
+	xen_unregister_device_domain_owner(dev);
+
 	pciback_release_pci_dev(pdev, dev);
 
 out: