  We find a class of new supersymmetric dyonic black holes in four-dimensional
maximal gauged supergravity which are asymptotic to the ${\rm SU(3)}\times {\rm
U(1)}$ invariant AdS$_4$ Warner vacuum. These black holes can be embedded in
eleven-dimensional supergravity where they describe the backreaction of
M2-branes wrapped on a Riemann surface. The holographic dual description of
these supergravity backgrounds is given by a partial topological twist on a
Riemann surface of a three-dimensional $\mathcal{N}=2$ SCFT that is obtained by
a mass-deformation of the ABJM theory. We compute explicitly the topologically
twisted index of this SCFT and show that it accounts for the entropy of the
black holes.
