Systems, methods, and apparatuses relating to microarchitectural mechanisms for the prevention of side-channel attacks are disclosed herein. In one embodiment, a processor includes a core having a plurality of physical contexts to execute a plurality of threads, a plurality of structures shared by the plurality of threads, a context mapping structure to map context signatures to respective physical contexts of the plurality of physical contexts, each physical context to identify and differentiate state of the plurality of structures, and a context manager circuit to, when one or more of a plurality of fields that comprise a context signature is changed, search the context mapping structure for a match to another context signature, and when the match is found, a physical context associated with the match is set as an active physical context for the core.