Since the introduction of Meltdown and Spectre, the research community has been tirelessly working on speculative side-channel attacks and on how to shield computer systems from them. To ensure that a system is protected not only from all the currently known attacks but also from future, yet to be discovered, attacks, the solutions developed need to be general in nature, covering a wide array of system components, while at the same time keeping the performance, energy, area, and implementation complexity costs at a minimum. One such solution is our own delay-on-miss, which efficiently protects the memory hierarchy by i) selectively delaying speculative load instructions and ii) utilizing value prediction as an invisible form of speculation. In this article we dive deeper into delay-on-miss, offering insights into why and how it affects the performance of the system. We also reevaluate value prediction as an invisible form of speculation. Specifically, we focus on the implications that delaying memory loads has in the memory level parallelism of the system and how this affects the value predictor and the overall performance of the system. We present new, updated results but more importantly, we also offer deeper insight into why delay-on-miss works so well and what this means for the future of secure speculative execution.

中文翻译：

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将选择性延迟理解为一种高效安全推测执行的方法

自从引入 Meltdown 和 Spectre 以来，研究界一直在不知疲倦地致力于推测性侧信道攻击以及如何保护计算机系统免受攻击。为确保系统不仅免受所有当前已知的攻击，而且免受未来尚未发现的攻击，开发的解决方案必须具有通用性，涵盖广泛的系统组件，同时将性能、能源、面积和实施复杂性成本保持在最低水平。一个这样的解决方案是我们自己的延迟未命中，它通过 i) 选择性地延迟推测加载指令和 ii) 利用值预测作为一种不可见的推测形式来有效地保护内存层次结构。在这篇文章中，我们深入探讨了延迟错过，提供有关它为什么以及如何影响系统性能的见解。我们还将价值预测重新评估为一种无形的投机形式。具体来说，我们关注延迟内存加载对系统内存级并行性的影响，以及这如何影响值预测器和系统的整体性能。我们提供了新的、更新的结果，但更重要的是，我们还提供了更深入的见解，了解为什么延迟未命中如此有效，以及这对安全推测执行的未来意味着什么。