With virtualization the VMM must be the most privileged. This means that it is running in ring 0. But the OS wants to run in ring 0! Something has to change so that the OS can run while the VMM is in ring 0. [[VMM requirements#Transparency|Transparency]] is a requirement of the VMM, meaning that the execution environment is identical. If we make modifications to the OS to resolve the ring 0 dilemma, we have changed the execution environment, failing to meet the requirements of the VMM. This leads to the idea of **para-virtualization**. We make the necessary changes, and now we call it para-virtualization instead of virtualization.