Co-simulation of a circuit design includes simulating a first subset of blocks of the circuit design on a software-based co-simulation platform, simulating a second subset of the blocks of the circuit design on a hardware-based co-simulation platform, and maintaining coherency for a memory block of the circuit design between a first representation of data in the memory block on the software-based co-simulation platform and a second representation of the data in the memory block on the hardware-based co-simulation platform. Coherency is maintained by managing mutually exclusive access to the memory block from the first subset of blocks and the second subset of blocks.