IBM PowerKVM runs the OpenStack integration tests using a "CirrOS-like" image, a minimal Linux distribution that was designed for use as a test image on clouds.
This article shows how to build a custom cloud image for Power and how to use it on OpenStack Tempest suite.
The tiny image has less than 10MB and boots a custom mainline Kernel with built-in virtio drivers in less than 9 seconds. The rootfs is built with buildroot release 2014.05 and the resulting image is bundled with the scripts provided in CirrOS-0.3.2.
For more information about IBM PowerKVM refer to the Redbook.