[libvirt] Out of Memory Error

Hi, I am trying to attach a usb device to my virtualbox node using libvirt. My node is already running, I stop my node and then I am trying to add this usb device. I have a separate xml file defined for usb. It looks like this: *<device> <hostdev mode='subsystem' type='usb'> <source> <vendor id='0x4321'/> <product id='0xfeeb'/> </source> </hostdev> </device> * * * I am trying to attach it using code: *conn = libvirt.open("vbox:///session") if conn ==None: print 'Failed to open connection to the hypervisor' sys.exit(1) print 'connected to vbox hypervisor driver' domainInstance = conn.lookupByName('SampleNode') filed = open('/root/testFolder/usbSharedFolder.xml', 'r') config_str = filed.read() libvirt.virDomain.attachDevice(domainInstance, config_str)* When it is executed I am getting an error message saying: *libvir: VirtualBox Driver error : out of memory * * * Even with virsh it is giving the same error. I am using the below command: *attach-device SampleNode /root/testFolder/usbSharedFolder.xml* Can anyone tell me what is going wrong. It is really very important. Please do reply. Thanks in advance.