1. A method of context switching in a virtualized system, the virtualized system having a plurality of globally unique domain identifiers, a plurality of different virtual machines, a plurality of translation lookaside buffer entries that control access to a memory, a plurality of globally unique application-space identifiers, a plurality of guest applications, and a domain access control register, the method comprising: associating a first domain identifier from the plurality of globally unique domain identifiers with a first virtual machine from the plurality of different virtual machines and associating a second domain identifier from the plurality of globally unique domain identifiers with a second virtual machine from the plurality of different virtual machines, wherein a third, predefined domain identifier from the plurality of globally unique domain identifiers is unassociated with any one virtual machine, wherein each domain identifier is different from every other domain identifier in the virtualized system, and wherein the domain access control register specifies whether translation lookaside buffer entries tagged with one of the domain identifiers are active; associating the plurality of globally unique application-space identifiers with the plurality of guest applications, wherein each application-space identifier is different from every other application-space identifier in the virtualized system, and wherein the plurality of guest applications reside in different virtual machines from the plurality of different virtual machines; conditioned upon a virtual user mode being active, switching from the first virtual machine to the second virtual machine by loading the third, predefined domain identifier into the domain access control register; and conditioned upon a virtual kernel mode being active, switching from the first virtual machine to the second virtual machine by loading the second domain identifier into the domain access control register.