Comment 13 for bug 996840

You can see here that libvirt is attempting to run the 'drive_add' command, using QMP (JSON) monitor:

QEMU_MONITOR_IO_WRITE: mon=0x7f242c000a80 buf={"execute":"drive_add","arguments":{"pci_addr":"dummy","opts":"file=/dev/disk/by-path/ip-XXX.XXX.XXX.XXX:3260-iscsi-iqn.2010-10.org.openstack:volume-0000002b-lun-1,if=none,id=drive-virtio-disk5,format=raw,cache=none"},"id":"libvirt-7"}

The problem is that although it existed in the HMP monitor, the QEMU developers decided *not* to make drive_add available in QMP monitor.

They did however add a 'hmp_passthrough' command to let you invoke HMP commands via QMP. Assuming you have a new enough QEMU and new enough libvirt, libvirt will not use hmp_passthrough to invoke 'drive_add'.

Since this is not happening for the bug reporter, either their QEMU or libvirt (or both) packages must be too old.