Pre-Virtualization: Soft Layering for Virtual Machines

Despite its current popularity, para-virtualization has an enormous cost. Its deviation from the platform architecture abandons many of the benefits of traditional virtualization: stable and well-defined platform interfaces, hypervisor neutrality, operating system neutrality, and upgrade neutrality — in sum, modularity. Additionally, para-virtualization has a significant engineering cost. These limitations are accepted as inevitable for significantly better performance, and for the ability to provide virtualization-like behavior on non-virtualizable hardware such as x86.

Virtualization and its modularity solve many systems problems, and when combined with the performance of para-virtualization become even more compelling. We show how to achieve both together. We still modify the guest operating system, but according to a set of design principles that avoids lock-in, which we call soft layering. Additionally, our approach is highly automated and thus reduces the implementation and maintenance burden of para-virtualization, which is especially useful for enabling obsoleted operating systems. We demonstrate soft layering on x86 and Itanium: we can load a single Linux binary on a variety of hypervisors (and thus substitute virtual machine environments and their enhancements), while achieving essentially the same performance as para-virtualization with less effort.

By: Joshua LeVasseur; Volkmar Uhlig; Yaowei Yang; Matthew Chapman; Peter Chubb; Ben Leslie; Gernot Heiser

Published in: RC24692 in 2008


This Research Report is available. This report has been submitted for publication outside of IBM and will probably be copyrighted if accepted for publication. It has been issued as a Research Report for early dissemination of its contents. In view of the transfer of copyright to the outside publisher, its distribution outside of IBM prior to publication should be limited to peer communications and specific requests. After outside publication, requests should be filled only by reprints or legally obtained copies of the article (e.g., payment of royalties). I have read and understand this notice and am a member of the scientific community outside or inside of IBM seeking a single copy only.


Questions about this service can be mailed to .