Dual-OS communications allow a real-time operating system (RTOS) and a general-purpose operating system (GPOS)—sharing the same processor through virtualization—to collaborate in complex distributed applications. However, they also introduce new threats to the reliability (e.g., memory and time isolation) of the RTOS that need to be considered. Traditional dual-OS communication architectures follow essentially the same conservative approach which consists of extending the virtualization layer with new communication primitives. Although this approach may be able to address the aforementioned reliability threats, it imposes a rather big overhead on communications due to unnecessary data copies and context switches. In this paper, we propose a new dual-OS communications approach able to accomplish efficient communications without compromising the reliability of the RTOS. We implemented our architecture on a physical platform using a highly reliable dual-OS system (SafeG) which leverages ARM TrustZone hardware to guarantee the reliability of the RTOS. We observed from the evaluation results that our approach is effective at minimizing communication overhead while satisfying the strict reliability requirements of the RTOS.