Additional block devices cannot be attached when libvirt driver is virtio-scsi

[J-P methot]

Description
===========

This bug is very specific as it will only affect instances using the virtio-scsi driver that were booted up with a cinder block device.

Once your VM is booted up, attaching a drive will make the following error appear in the nova-compute log: "libvirtError: internal error: unable to execute QEMU command '__com.redhat_drive_add': Duplicate ID 'drive-scsi0-0-0-0' for drive"

This bug seems to affect most storage backends, as long as you use cinder for all your block devices. It was tested with Ceph and iscsi backends in both Mitaka and Newton.

It may also affect config drives.

Steps to reproduce
==================
1. Assign the necessary options to the image you are going to use, so that libvirt uses the virtio-scsi driver

hw_scsi_model = virtio-scsi
hw_disk_bus = scsi

2. Create a VM by selecting to use "image" as a source and set "create a new volume" to yes. This will boot from a new volume created in cinder with the selected image on it.

3.Create a new volume in cinder and try to attach it to the instance.

Expected result
===============
The volume will attach itself to the instance.

Actual result
=============
The attach operation will fail and you will see the aforementioned error in the nova-compute logs.

Environment
===========
CentOS 7
RDO Newton
openstack-nova-compute-14.0.6-1.el7.noarch
KVM libvirt

rpm -qa | grep "qemu\|libvirt"
libvirt-daemon-config-network-2.0.0-10.el7_3.9.x86_64
libvirt-python-2.0.0-2.el7.x86_64
qemu-img-ev-2.6.0-28.el7_3.9.1.x86_64
libvirt-daemon-driver-network-2.0.0-10.el7_3.9.x86_64
libvirt-daemon-driver-lxc-2.0.0-10.el7_3.9.x86_64
qemu-kvm-ev-2.6.0-28.el7_3.9.1.x86_64
centos-release-qemu-ev-1.0-1.el7.noarch
libvirt-daemon-2.0.0-10.el7_3.9.x86_64
libvirt-daemon-driver-qemu-2.0.0-10.el7_3.9.x86_64
ipxe-roms-qemu-20160127-5.git6366fa7a.el7.noarch
libvirt-daemon-kvm-2.0.0-10.el7_3.9.x86_64
libvirt-2.0.0-10.el7_3.9.x86_64
libvirt-client-2.0.0-10.el7_3.9.x86_64
libvirt-daemon-driver-nwfilter-2.0.0-10.el7_3.9.x86_64
libvirt-daemon-driver-nodedev-2.0.0-10.el7_3.9.x86_64
libvirt-daemon-config-nwfilter-2.0.0-10.el7_3.9.x86_64
libvirt-daemon-driver-storage-2.0.0-10.el7_3.9.x86_64
libvirt-daemon-driver-interface-2.0.0-10.el7_3.9.x86_64
qemu-kvm-common-ev-2.6.0-28.el7_3.9.1.x86_64
libvirt-daemon-driver-secret-2.0.0-10.el7_3.9.x86_64

Storage: Dell iscsi but also confirmed to be present on Ceph
Network: Neutron + openvswitch

Logs & config
=====
See logs and config in attached txt file

[George (lmihaiescu)]

Confirmed same problem on Mitaka running on Ubuntu 16.04 with Ceph as a backend for Cinder.

[Jay Pipes (jaypipes)]

@lmihaiescu: Any chance you could post your exact log output so we can compare?

[Sean Dague (sdague)]

Automatically discovered version newton in description. If this is incorrect, please update the description to include 'nova version: ...'

[Lee Yarwood (lyarwood)]

I think Sahid is potentially fixing this as part of bug #1686116 and the following change https://review.openstack.org/#/c/459741/ correctly setting the unit in get_config for scsi volumes. I'll attempt to confirm this now.

[Vladyslav Drok (vdrok)]

Applying the chain up to https://review.openstack.org/#/c/459741/ seems to fix the issue for me

[Lee Yarwood (lyarwood)]

I've marked this as a duplicate of bug #1686116, if this is still required for Newton then please request a stable backport there.