Post Silicon Validation of the MMU

Post silicon validation is a unique challenge in the design verification process. On one hand, it utilizes real silicon and is therefore able to cover a larger state-space. On the other, it suffers from debugging challenges due to a lack of observability into the design. These challenges dictate distinctive design choices, such as the simplicity of validation tools and a built-for-debugging software design methodology. The Memory Management Unit (MMU) is central to any design that uses virtual-memory, and creates complex verification challenges, especially in many-core designs. We propose a novel method for post silicon validation of the MMU that brings together previously undescribed techniques, based on several papers and patents. This method was implemented in Threadmill, a bare metal exerciser and was used in the verification of high-end industry-level POWER and ARM SoCs. It succeeded in increasing RTL coverage, hitting several hidden bugs, and saving hundreds of work-hours in the validation process.