" then a full VM is your only guarantee" VM's on commercial and FOSS platforms have been unable to ensure security as far back as first pentest of VM/370. They

" then a full VM is your only guarantee" VM's on commercial and FOSS platforms have been unable to ensure security as far back as first pentest of VM/370. They were too complicated depending on a lot of privileged code. The founders of INFOSEC took aim at it with KVM/370 and VAX VMM Security Kernel. One example (see esp layering and assurance sections): http://lukemuehlhauser.com/wp-content/uploads/Karger-et-al-A-retrospective-on-the-VAX-VMM-security-kernel.pdf http://lukemuehlhauser.com/wp-content/uploads/Karger-et-al-A... Even those systems had too much complexity by our standards. They aimed for nearly-perfect implementation of the core kernels mediating everything. That led to separation kernels like INTEGRITY-178B, LynxSecure, seL4, and Muen. They're usually just 4-12Kloc. Whereas, projects trying to achieve similar assurance activities on KVM and Xen mostly gave up due to complexity. If aiming for correctness more than security, projects like Nova microhypervisor and GenodeOS show similar partitioning can still help. Although separation kernels succeeded, their requirements assumed hardware/firmware that was sane and would work correctly. What people are using for virtualized workloads has been overly complex with shoddy implementations. Bypasses keep happening via everything from CPU's to RAM to peripheral firmware. Although methods exist to assure them, the companies providing them are not using them. So, if you want anything close to a guarantee, you have to use physical separation with strongly-mediated, communications systems over optical links. The boards need to be electrically isolated from each other in their own TEMPEST boxes or safes. Alternatively, use old technique from separation kernel era of putting all the complex, enemy-facing stuff on their own boxes that interpret stuff down to requests in simple protocols interfacing with the trusted boxes on better hardware. Reduces hardware cost but what you get is nothing like a Google or Amazon cloud. It's more like a partitioned version of SoftLayer.