DDM: A Demand-Based Dynamic Mitigation for SMT Transient Channels

In this paper, we define a Simultaneous Multi-Threading(SMT) Transient Channel, stemmed from the sharing mechanism between multi threads running on the same core, which can be used to steal information by attackers. In order to alleviate this problem, we design a demand-based dynamic mitigation (DDM). The DDM writes the processes' security requirements to the CPU register sets, and then the operating system invokes the HLT(an assembly language instruction in X86 computer architecture) to dynamically turn hyper threading on or off according to the values of registers. We modify the Linux kernel and use MSR register groups of Intel processor to implement scheme. The evaluation results show that DDM can significantly protect key information against the SMT transient side-channel such as PortsMash that rely on SMT, and the performance loss of DDM is less than 8%.