  We report on our study of the B \to D^(*) \ell \nu semileptonic decays at
zero and nonzero recoils in 2+1 flavor QCD. The M\"obius domain-wall action is
employed for light, charm and bottom quarks at lattice cutoffs 1/a = 2.5 and
3.6 GeV. We take bottom quark masses up to \approx 2.4 times the physical charm
mass to control discretization effects. The pion mass is as low as M_\pi \sim
310 MeV. We present our preliminary results for the relevant form factors and
discuss the violation of heavy quark symmetry, which is a recent important
isuue on the long-standing tension in the Cabibbo-Kobayashi-Maskawa matrix
element |V_{cb}| between the exclusive and inclusive decays.
