The recent works such as InvisiSpec, SafeSpec, and Cleanup-Spec, among others, provided promising solutions to defend speculation induced (transient) attacks. However, they intro-duce delay either when a speculative load becomes safe in the redo approach or when it is squashed in the undo approach. We argue that it is due to the lack of fundamental mechanisms for reversing the effects of speculation in a cache coherence protocol. Based on mostly unmodified coherence protocol, the redo approach avoids leaving trace at the expense of double loads; the undo approach "stops the world" in recovery to avoid interference. This paper provides the first solution to the fundamental problem. Specifically, we propose ReversiSpec, a comprehensive solution to mitigate speculative induced attacks.ReversiSpec is a reversible approach that uses speculative buffers in all cache levels to record the effects of speculative execution. When a speculative load becomes safe, a merge operation adds the effects of speculative execution to the global state. When a speculative load is squashed, a purge operation clears the buffered speculative execution states from speculative buffer. The key problem solved by the paper is the first demonstration of a reversible cache coherence protocol that naturally rollbacks the effects of squashed speculative execution. We design two concrete coherence protocols, ReversiCC-Lazy and ReversiCC-Eager providing the same functionality with different trade-offs. Our solution closes a crucial gap in modern architecture: just like the mechanisms to roll back the speculation effects inside a processor, ReversiSpec provides the mechanisms to roll back the state of the whole coherence protocol.

中文翻译：

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ReversiSpec：用于防御瞬态攻击的可逆一致性协议

最近的工作，如 InvisiSpec、SafeSpec 和 Cleanup-Spec 等，为防御投机引发的（瞬态）攻击提供了有前景的解决方案。然而，当推测负载在重做方法中变得安全或在撤销方法中被压缩时，它们会引入延迟。我们认为这是由于缺乏在缓存一致性协议中逆转推测影响的基本机制。基于大部分未修改的一致性协议，重做方法避免了以双负载为代价留下痕迹；撤消方法在恢复中“停止世界”以避免干扰。本文提供了基本问题的第一个解决方案。具体来说，我们提出了 ReversiSpec，这是一种减轻投机诱导攻击的综合解决方案。ReversiSpec 是一种可逆方法，它在所有缓存级别中使用推测缓冲区来记录推测执行的效果。当推测加载变得安全时，合并操作会将推测执行的效果添加到全局状态。当推测负载被压缩时，清除操作从推测缓冲区中清除缓冲的推测执行状态。该论文解决的关键问题是首次演示了一种可逆缓存一致性协议，该协议可以自然地回滚被压扁的推测执行的影响。我们设计了两个具体的一致性协议，ReversiCC-Lazy 和 ReversiCC-Eager，提供相同的功能和不同的权衡。我们的解决方案弥补了现代架构中的一个关键差距：就像回滚处理器内部推测效应的机制一样，