Improving the Latency of VMExit Forwarding in Recursive Virtualization for the x86 Architecture

As virtualization becomes more common, the need for recursive virtualization is also rising. However, performance degrades exponentially as we go deeper in the number of levels in recursive virtualization. In this paper, one of the biggest challenges of improving the performance of recursive virtualization is explored, namely bounding the time for VM Exit forwarding across the hierarchy of hypervisors, including VM Exits due to interrupts, exceptions and various other intercepts. The problem is analyzed in the context of the current x86 architecture. We argued that a purely software solution will likely fall short, and then proposed a simple hardware extension that could speed up the VM Exit delivery significantly.