Homogeneous manycore processors are emerging for tera-scale computation. Effective defect tolerance techniques are essential to improve the yield of such complex integrated circuits. In this paper, we propose to achieve fault tolerance by employing redundancy at the core-level instead of at the microarchitecture-level. When faulty cores existing on-chip in this architecture, how to reconfigure the processor with the most effective topology is a relevant research problem. We present novel solutions for this problem, which not only maximize the performance of the manycore processor, but also provide a unified topology to operating system and application software running on the processor. Experimental results show the effectiveness of the proposed techniques.