Building with the attached random configuration file,

  LD      init/built-in.o
drivers/built-in.o: In function `ib_init_ah_from_wc':
(.text+0xaaa957): undefined reference to `rdma_addr_find_dmac_by_grh'
drivers/built-in.o: In function `ib_resolve_eth_l2_attrs':
(.text+0xaab100): undefined reference to `rdma_addr_find_dmac_by_grh'
drivers/built-in.o: In function `ib_resolve_eth_l2_attrs':
(.text+0xaab134): undefined reference to `rdma_addr_find_smac_by_sgid'
make: *** [vmlinux] Error 1