text: The virtual machine control structure (VMCS) is a data structure in memory that exists exactly once per VM, while it is managed by the VMM. With every change of the execution context between different VMs, the VMCS is restored for the current VM, defining the state of the VM's virtual processor. As soon as more than one VMM or nested VMMs are used, a problem appears in a way similar to what required shadow page table management to be invented, as described above. In such cases, VMCS needs to be shadowed multiple times (in case of nesting) and partially implemented in software in case there is no hardware support by the processor. To make shadow VMCS handling more efficient, Intel implemented hardware support for VMCS shadowing.
  VIA virtualization (VIA VT)
  VIA Nano 3000 Series Processors and higher support VIA VT virtualization technology compatible with Intel VT-x. EPT is present in Zhaoxin ZX-C, a descendant of VIA QuadCore-E & Eden X4 similar to Nano C4350AL.
  Interrupt virtualization (AMD AVIC and Intel APICv)
  In 2012, AMD announced their Advanced Virtual Interrupt Controller (AVIC) targeting interrupt overhead reduction in virtualization environments. This technology, as announced, does not support x2APIC.
  In 2016, AVIC is available on the AMD family 15h models 6Xh