Performance and Accuracy in Soft-Error Resilience Evaluation using the Multi-Level Processor Simulator ETISS-ML

Soft errors are a major safety concern in many devices, e.g., in automotive, industrial, control or medical applications. Ideally, safety-critical systems should be resilient against the impact of soft errors, but at a low cost. This requires to evaluate the soft error resilience, which is typically done by extensive fault injection. In this paper, we present ETISS-ML, a multi-level processor simulator, which manages to achieve both accuracy and performance for fault simulation by intelligently switching the level of abstraction between an Instruction Set Simulator (ISS) and an RTL simulator. For a given software testcase and fault scenario, the software is first executed in ISS-mode until shortly before the fault injection. Then ETISS-ML switches to RTL-mode for accurate fault simulation. Whenever the impact of the fault is propagated completely out of the processor's micro-architecture, the simulation can switch back to ISS-mode. This paper describes the methods needed to preserve accuracy during both of these switches. Experimental results show that ETISS-ML obtains near to ISS performance with RTL accuracy. It is also shown that ETISS-ML can be used as the processor model in SystemC / TLM virtual prototypes (VPs) and, hence, allows to investigate the impact of soft errors at system level.