Heat stroke: power-density-based denial of service in SMT

In the past, there have been several denial of service (DOS) attacks which exhaust some shared resource (e.g., physical memory, process table, file descriptors, TCP connections) of the targeted machine. Though these attacks have been addressed, it is important to continue to identify and address new attacks because DOS is one of most prominent methods used to cause significant financial loss. A recent paper shows how to prevent attacks that exploit the sharing of pipeline resources (e.g., shared trace cache) in SMT to degrade the performance of normal threads. In this paper, we show that power density can be exploited in SMT to launch a novel DOS attack, called heat stroke. Heat stroke repeatedly accesses a shared resource to create a hot spot at the resource. Current solutions to hot spots inevitably involve slowing down the pipeline to let the hot spot cool down. Consequently, heat stroke slows down the entire SMT pipeline and severely degrades normal threads. We present a solution to heat stroke by identifying the thread that causes the hot spot and selectively slowing down the malicious thread while minimally affecting normal threads.