1. A method comprising: removing, by microcode of a processor, a lock that prevents alteration of a set of values by a macro-architectural agent of the processor, the lock corresponding to a lock indicator of a first memory region range register of the processor accessible to a region monitor of the processor, the set of values including a first set of values that define a first micro-architectural memory region of a system memory located within a computer system, wherein the first micro-architectural memory region is established subsequent to erasure of a previous micro-architectural memory region, the erasure effected by use of a scrubbing microcode; disabling, by the microcode, the first micro-architectural memory region from being accessible by one or more micro-architectural agent that previously had access to the first micro-architectural memory region by changing an enable indicator of the first memory region range register to indicate that the first micro-architectural memory region cannot be accessed; replacing, by the microcode, the first set of values with a second set of values to establish a default memory region of the system memory corresponding to a known, stable state in response to the microcode initiation of a reset of the first micro-architectural memory region; receiving a third set of values from the macro-architectural agent, the third set of values to define a second micro-architectural memory region, wherein the third set of values replace the second set of values to establish the second micro-architectural memory region subsequent to replacement of the first set of values with the second set of values by the scrubbing microcode; and thereafter updating the enable indicator of the first memory region range register to indicate that that the second micro-architectural memory region is enabled to be accessed by the one or more micro-architectural agent and updating the lock indicator of the first memory region range register.