Reducing world switches in virtualized environment with flexible cross-world calls

Modern computers are built with increasingly complex software stack crossing multiple layers (i.e., worlds), where cross-world call has been a necessity for various important purposes like security, reliability, and reduced complexity. Unfortunately, there is currently limited cross-world call support (e.g., syscall, vmcall), and thus other calls need to be emulated by detouring multiple times to the privileged software layer (i.e., OS kernel and hypervisor). This causes not only significant performance degradation, but also unnecessary implementation complexity.