...how registry virtualization is implemented by the Configuration Manager, which manages the registry in the operating systemkernel, Ntoskrnl.exe. As with file system virtualization, a legacy process creating a subkey of a virtualized key is redirected...
http://technet.microsoft.com/magazine/4ce22051-1ff9-49c1-ab06-d97658e993e0
...changes to the guest operating systemkernel. The first product to use binary...which a modified guest operating systemkernel communicates to the hypervisor...the underlying guest operating systemkernel. However in order to paravirtualize...
http://www.vmware.com/pdf/VMware_VMI_performance.pdf