The topic of virtualization has received renewed attention. Xen is a popular open source type-I hypervisor. The Xen hypervisor currently has limited capabilities for runtime modification to the core hypervisor, which impairs research into dynamic adaptation for system-level virtualization. This paper discusses recent investigations into the feasibility of extending Xen to support runtime adaptation for core hypervisor service, e.g., scheduler. Categories and Subject Descriptors D.4 [Software]: Operating Systems General Terms Virtualization, Adaptation Keywords Xen, Linux, Loadable modules