A virtualization architecture for improving the performance of nested virtualization in a computer system. A virtualization instruction reads or writes data in a control structure used by a virtual machine monitor (VMM) to maintain state on a virtual machine (VM) to support transitions between a root mode of operation of a CPU in which the VMM executes and a non-root mode of operation of the CPU in which the VM executes. A privileged data access is made to a primary control structure according to the virtualization instruction if the CPU is in the root mode. A non-privileged data access is made to a secondary control structure according to the virtualization instruction if the CPU is in the non-root mode and a secondary control structure field in the primary control structure is enabled.