Row Hammer (RH) is a circuit-level phenomenon where repetitive activation of a DRAM row causes bit-flips in adjacent rows. Prior studies that rely on extra refreshes to mitigate RH vulnerability demonstrate that bit-flips can be prevented effectively. However, its implementation is challenging due to the significant performance degradation and energy overhead caused by the additional extra refresh for the RH mitigation. To overcome challenges, some studies propose techniques to mitigate the RH attack without relying on extra refresh. These techniques include delaying the activation of an aggressor row for a certain amount of time or swapping an aggressor row with another row to isolate it from victim rows. Although such techniques do not require extra refreshes to mitigate RH, the activation delaying technique may result in high-performance degradation in false-positive cases, and the swapping technique requires high storage overheads to track swap information. We propose NoHammer , an efficient RH mitigation technique to prevent the bit-flips caused by the RH attack by utilizing Last-Level Cache (LLC) management. NoHammer temporarily extends the associativity of the cache set that is being targeted by utilizing another cache set as the extended set and keeps the cache lines of aggressor rows on the extended set under the eviction-based RH attack. Along with the modification of the LLC replacement policy, NoHammer ensures that the aggressor row's cache lines are not evicted from the LLC under the RH attack. In our evaluation, we demonstrate that NoHammer gives 6% higher performance than a baseline without any RH mitigation technique by replacing excessive cache misses caused by the RH attack with LLC hits through sophisticated LLC management, while requiring 45% less storage than prior proposals.

中文翻译：

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NoHammer：通过末级缓存管理防止行锤

行锤击 (RH) 是一种电路级现象，其中 DRAM 行的重复激活会导致相邻行中的位翻转。先前依赖额外刷新来缓解 RH 漏洞的研究表明，可以有效防止位翻转。然而，由于 RH 缓解所需的额外刷新会导致显着的性能下降和能源开销，因此其实施具有挑战性。为了克服挑战，一些研究提出了在不依赖额外刷新的情况下减轻 RH 攻击的技术。这些技术包括将攻击者行的激活延迟一定时间或将攻击者行与另一行交换以将其与受害者行隔离。尽管此类技术不需要额外的刷新来减轻RH，但激活延迟技术可能会导致误报情况下的高性能下降，并且交换技术需要高存储开销来跟踪交换信息。我们建议无锤 ，一种有效的 RH 缓解技术，通过利用末级缓存 (LLC) 管理来防止 RH 攻击引起的位翻转。无锤通过利用另一个高速缓存集作为扩展集来临时扩展作为目标的高速缓存集的关联性，并且在基于驱逐的RH攻击下保持扩展集上的攻击者行的高速缓存行。随着LLC更换政策的修改，无锤确保攻击者行的缓存行在 RH 攻击下不会从 LLC 中逐出。在我们的评估中，我们证明无锤通过复杂的 LLC 管理，用 LLC 命中替换由 RH 攻击引起的过多缓存未命中，与没有任何 RH 缓解技术的基准相比，性能提高 6%，同时比之前的建议减少 45% 的存储需求。