Installing a CUDA-aware MPI in the defaults, e.g. with

spack install mpi+cuda

does not properly select openmpi+cuda but just the plain openmpi~cuda default.

Since "CUDA-Awareness" (yes/no) is a MPI property of nearly all popular MPI implementations, it would make sense to be able to define +cuda as a variant of the virtual mpi package.

CUDA Aware MPI implementations from the 2013 blog post above:

MVAPICH2 1.8/1.9b
OpenMPI 1.7 (beta)
CRAY MPI (MPT 5.6.2)
IBM Platform MPI (8.3)
SGI MPI (1.08)