论价值重构对无形投机的促进作用
On Value Recomputation to Accelerate Invisible Speculation
摘要：
解决推测性侧信道攻击的最新架构方法旨在防止软件暴露瞬态执行的微架构状态变化。未命中延迟（Delay-on-Miss）技术就是这样一种方法，其简单地延迟L1高速缓存中未命中的加载，直到它们变为非推测性的，从而导致存储层次结构中没有瞬时变化。然而，这会降低性能，促使使用值预测（VP）来重新获得一些延迟。然而，这个问题不能简单地通过引入一种新的投机（价值预测）来解决。值预测的加载必须经过验证，在加载变为非推测性之前不能开始验证。因此，值预测的负载占用相同量的宝贵核心资源（例如，重新排序缓冲器条目）作为未命中延迟。最终的结果是，VP只产生边际效益超过延迟错过。在本文中，我们的见解是，我们可以实现与VP相同的目标（通过提供未命中负载的值来提高性能），而不会产生其负面副作用（延迟宝贵资源的释放），如果我们可以安全地、非推测地、隔离地重新计算一个值（而不被外部看到），这样我们就不会通过经由存储层次结构传输这样的值而暴露任何信息。值重新计算，它交易的数据传输计算先前提出了一个完全不同的上下文中：以减少能源昂贵的数据传输在存储层次结构。在本文中，我们展示了价值重新计算的潜力与隐藏推测的延迟未命中方法有关，讨论了权衡，并表明我们可以实现相同的安全级别，达到93%的不安全基线性能（比延迟未命中高5%），并超过（3%）甚至是一个预言（100%的准确性和覆盖率）值预测器可以做的。
英文摘要：
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.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
