Selective restrictions to memory mapped registers using an emulator

A computer-readable storage having instructions thereon for executing a method of restricting access to memory mapped registers, the method comprising:

• executing instructions in a virtual machine;
• for a current instruction being executed, detecting an attempted access of a restricted memory page;
• in response to the detection, switching execution of the current instruction to an emulator that substantially functions like the virtual machine, but is not under control by the virtual machine;
• using the emulator, determining whether the attempted access to the memory page is to a restricted portion of the memory page or an unrestricted portion of the memory page;
• and
• allowing access by the current instruction to the unrestricted portion and not allowing access to the restricted portion.

A system for restricting access to memory mapped registers, comprising:

• a guest virtual machine executing on a partition in a multi-tenant environment of a service provider;
• a memory having at least one restricted area in which the guest virtual machine cannot access and unrestricted areas in which the guest virtual machine can access;
• a processor coupled to the memory and executing instructions of the guest virtual machine;
• and
• an emulator coupled to the processor for running at least one instruction of the guest virtual machine when the guest virtual machine attempts access to a restricted area of the memory, the emulator under the control of the service provider rather than the guest virtual machine, the emulator for selectively deciding whether or not to allow the virtual machine to access the restricted area of the memory.