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From: Kumar Gala <galak@kernel.crashing.org>
Date: Fri, 24 Oct 2008 10:39:05 -0500

> As for making it ARCH specific, that doesn't really help since not
> all PPC hw has the limitation I spoke of.  Not even all MPIC (in our
> cases) have the limitation.

Since the PPC code knows exactly which MPICs have the problem the
PPC code is where the constraining can occur.

I agree completely with the suggestion that the arch code has to
interpret the cpumask as appropriate for the hardware, since the
user can stick "illegal" values there anyways.