1. A computing device for multi-level virtualization, the computing device comprising: a processor having root virtualization mode support and non-root virtualization mode support; and one or more memory devices having stored therein a plurality of instructions that, when executed by the processor, cause the computing device to: receive, by a root hypervisor of the computing device, a virtual machine exit generated by a virtual machine of the computing device, wherein the virtual machine is hosted by a non-root hypervisor of the computing device; determine, by the root hypervisor in the root virtualization mode, whether a callback handler of the non-root hypervisor is registered for an exit reason of the virtual machine exit in response to receipt of the virtual machine exit; determine, by the root hypervisor in the root virtualization mode, whether a trigger condition associated with the callback handler is satisfied in response to a determination that the callback handler is registered; and execute the callback handler of the non-root hypervisor in response to a determination that the trigger condition is satisfied.