Selective access to partitioned branch transfer buffer (BTB) content

The present disclosure is directed to systems and methods for mitigating or eliminating the effectiveness of a side channel attack, such as a Spectre type attack, by limiting the ability of a user-level branch prediction inquiry to access system-level branch prediction data. The branch prediction data stored in the BTB may be apportioned into a plurality of BTB data portions. BTB control circuitry identifies the initiator of a received branch prediction inquiry. Based on the identity of the branch prediction inquiry initiator, the BTB control circuitry causes BTB look-up circuitry to selectively search one or more of the plurality of BTB data portions.