[libvirt] How many functions that can't be used within libvirt

Hello, I've tested some functions of libvirt don't work. Could some people give me a reasonable explanation about these functions? Why do these function don't work? Or if there is anything wrong of my understanding. 1.virsh # migrate 1 xen+ssh://root@172.16.201.183/Password: error: POST operation failed: xend_post: error from xen daemon: (xend.err "can't connect: (-2, 'Name or service not known')") 2.virsh # dommemstat 5error: Failed to get memory statistics for domain 5error: this function is not supported by the hypervisor: virDomainMemoryStats 3.virsh # dump 5 fileerror: Failed to core dump domain 5 to fileerror: POST operation failed: xend_post: error from xen daemon: (xend.err 'Too many values for live') 4.virsh # iface-list error: Failed to list active interfaceserror: this function is not supported by the hypervisor: virConnectNumOfInterfaces 5.virsh # vncdisplay 5:1 virsh # vncdisplay 41:0 6.virsh # snapshot-create 42 snapshot.xml error: Failed to create snapshot snapshot.xml for domain 42 7.NWFILTER functions Thank you very much!