RCP: A Low-overhead Reversible Coherence Protocol

TL;DR

This paper introduces RCP, a low-overhead reversible coherence protocol enabling invisible speculative load execution with enhanced security, implemented in Gem5 and verified with Murphi, outperforming existing methods in overhead and protection.

Contribution

RCP is a novel reversible coherence protocol that systematically extends existing protocols to support low-overhead invisible speculative execution with stronger security guarantees.

Findings

RCP achieves lower overhead than STT/SDO/SPT.

RCP provides at least as strong protection as SPT.

Implementation in Gem5 verified with Murphi confirms effectiveness.

Abstract

This paper proposes RCP, a new reversible coherence protocol that ensures invisible speculative load execution (ISLE) with low overhead. RCP can be combined with processor mechanisms that eliminate the effects of speculative instructions on other instructions to achieve low overhead invisible speculative execution (ISE). ISE provides protection that is at least as strong as speculative privacy tracking (SPT) and stronger than speculative taint tracking (STT). RCP is designed by systematically extending the existing coherence protocol to incorporate speculative loads and states. The protocol is implemented in Gem5 and verified with Murphi. The results show that RCP based ISE incurs lower overhead than STT/SDO/SPT while providing similar/stronger protection.