diff -r 35a9ca776c34 tools/python/xen/util/pci.py
--- a/tools/python/xen/util/pci.py	Tue Jan 19 11:04:15 2010 +0100
+++ b/tools/python/xen/util/pci.py	Thu Jan 21 10:17:00 2010 +0100
@@ -441,6 +441,8 @@ def find_sysfs_mnt():
 
 def get_all_pci_names():
     sysfs_mnt = find_sysfs_mnt()
+    if sysfs_mnt is None:
+        return None
     pci_names = os.popen('ls ' + sysfs_mnt + SYSFS_PCI_DEVS_PATH).read().split()
     return pci_names
 
diff -r 35a9ca776c34 tools/python/xen/util/utils.py
--- a/tools/python/xen/util/utils.py	Tue Jan 19 11:04:15 2010 +0100
+++ b/tools/python/xen/util/utils.py	Thu Jan 21 10:17:00 2010 +0100
@@ -68,7 +68,9 @@ def find_sysfs_mount():
                 continue
             if sline[2] == 'sysfs':
                 sysfs_mount_point= sline[1]
-                return sysfs_mount_point
+                break
+        mounts_file.close()
+        return sysfs_mount_point
     except IOError, (errno, strerr):
         raise
 
diff -r 35a9ca776c34 tools/python/xen/util/vscsi_util.py
--- a/tools/python/xen/util/vscsi_util.py	Tue Jan 19 11:04:15 2010 +0100
+++ b/tools/python/xen/util/vscsi_util.py	Thu Jan 21 10:17:00 2010 +0100
@@ -123,6 +123,9 @@ def _vscsi_get_scsidevices_by_sysfs():
     except:
         return devices
 
+    if sysfs_mnt is None:
+        return devices
+
     for dirpath, dirnames, files in os.walk(sysfs_mnt + SYSFS_SCSI_PATH):
         for hctl in dirnames:
             paths = os.path.join(dirpath, hctl)