Recent architectural approaches that address speculative side-channel attacks aim to prevent software from exposing the microarchitectural state changes of transient execution. The Delay-on-Miss technique is one such approach, which simply delays loads that miss in the L1 cache until they become non-speculative, resulting in no transient changes in the memory hierarchy. However, this costs performance, prompting the use of value prediction (VP) to regain some of the delay. However, the problem cannot be solved by simply introducing a new kind of speculation (value prediction). Value-predicted loads have to be validated, which cannot be commenced until the load becomes non-speculative. Thus, value-predicted loads occupy the same amount of precious core resources (e.g., reorder buffer entries) as Delay-on-Miss. The end result is that VP only yields marginal benefits over Delay-on-Miss. In this paper, our insight is that we can achieve the same goal as VP (increasing performance by providing the value of loads that miss) without incurring its negative side-effect (delaying the release of precious resources), if we can safely, non-speculatively, recompute a value in isolation (without being seen from the outside), so that we do not expose any information by transferring such a value via the memory hierarchy. Value Recomputation, which trades computation for data transfer was previously proposed in an entirely different context: to reduce energy-expensive data transfers in the memory hierarchy. In this paper, we demonstrate the potential of value recomputation in relation to the Delay-on-Miss approach of hiding speculation, discuss the trade-offs, and show that we can achieve the same level of security, reaching 93% of the unsecured baseline performance (5% higher than Delay-on-miss), and exceeding (by 3%) what even an oracular (100% accuracy and coverage) value predictor could do.

中文翻译：

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价值计算加速无形投机

解决投机侧通道攻击的最新体系结构方法旨在防止软件暴露瞬态执行的微体系结构状态变化。缺少时延技术是一种这样的方法，它只是将L1缓存中未命中的负载延迟到它们成为非推测性负载之前，从而导致内存层次结构中没有任何瞬时变化。但是，这会降低性能，从而促使使用值预测（VP）来重新获得一些延迟。但是，仅通过引入一种新的推测（值预测）就无法解决该问题。必须对值预测的负载进行验证，直到负载成为非推测性负载后才能开始。因此，值预测的负载占用与Miss-on-Miss相同数量的宝贵核心资源（例如，重新排序缓冲区条目）。最终结果是，VP仅比“延迟时延”产生边际收益。在本文中，我们的见解是，如果我们能够安全，不费力地做到这一点，那么我们可以实现与VP相同的目标（通过提供错过的负载值来提高性能），而不会产生负面影响（延迟宝贵资源的释放）。 -推测性地，独立地重新计算一个值（不会从外部看到），这样我们就不会通过内存层次结构传递这样的值来公开任何信息。以前在完全不同的上下文中提出了将计算换取数据传输的Value Recomputation：减少内存层次结构中耗能的数据传输。在本文中，我们展示了与隐藏投机的Miss-on-Miss方法相关的价值重新计算的潜力，讨论了取舍，