quoted

diff --git a/arch/powerpc/include/asm/hv_gpci.h b/arch/powerpc/include/asm/hv_gpci.h

Any reason this can't just live in arch/powerpc/perf ?

Nope, it should be able to keep the header there for now. As this 
interface allows determination of the HW topology, we may have some code 
that exposes that (in sysfs) at some point, which doesn't really belong 
in arch/powerpc/perf (though we could just put it there anyhow).