With software-based CPU virtualization, the guest application code runs directly on the processor, while the guest privileged code is translated and the translated code runs on the processor.
The translated code is slightly larger and usually runs more slowly than the native version. As a result, guest applications, which have a small privileged code component, run with speeds very close to native. Applications with a significant privileged code component, such as system calls, traps, or page table updates can run slower in the virtualized environment.
