Collective behaviors of multi-agent systems over signed graphs find applications in a variety of scenarios including social networks, predator-prey dynamics, which however have not been adequately addressed as their counterparts with nonnegative graphs. This paper studies bipartite consensus problem of general linear multi-agent systems over signed digraphs. First, we show that for general linear agents, bipartite consensus over signed graphs and ordinary consensus over nonnegative graphs are equivalent. This indicates that prevailing consensus controllers for nonnegative graphs can be adopted to solve bipartite consensus problems. Based on this observation, an existing Riccati equation based cooperative tracking controller is extended to solve the bipartite consensus problem for general linear systems.