[libvirt] Libvirt error in Openstack Tempest attaching disk on arm64 system

Daniel P. Berrange berrange at redhat.com
Wed Jul 22 20:58:04 UTC 2015

On Wed, Jul 22, 2015 at 02:53:31PM -0500, Clark Laughlin wrote:
> I am running Openstack Tempest on an arm64 platform and am seeing some
> test failures related to attaching volumes to an instance.  This is an
> example of the disk XML generated by one of the tests:
> <disk type="block" device="disk"><driver name="qemu" type="raw"
> cache="none"/<source
> dev="/dev/disk/by-path/ip-"/><target
> bus="virtio" dev="vdb"/><serial>5a204339-80cb-4d06-aecf-2a8a2c970b0e</serial></disk>
> The test is failing with the error "XML error: No PCI buses
> available".  I am trying to find the relevent source locations for
> this functionality in either in the nova libvirt driver or in the
> libvirt source itself.  I am not sure why I am getting an error about
> no PCI buses when the bus specified in the XML is "virtio".
> I would appreciate any pointers / help.

virtio is just a guest/host device communication protocol that
can be run over multiple different transport. On x86 virtio has
always used PCI, but on s390 it uses either s390 or ccw bus,
and on arm7/aarch64 it uses mmio. I'm not sure that the mmio
bus supports hotplug, which could be why you see the error in
question. Very latest upstream QEMU does now support PCI with
aarch64 so in the near future it should have parity of functionality
with x86

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