On powerpc, we must only signal huge page support to the guest if
all memory areas are capable of supporting huge pages. The commit
2d103aae ("fix hugepage support when using memory-backend-file")
already fixed the case when the user specified the mem-path property
for NUMA memory nodes instead of using the global "-mem-path" option.
However, there is one more case where it currently can go wrong.
When specifying additional memory DIMMs without using NUMA, e.g.

 qemu-system-ppc64 -enable-kvm ... -m 1G,slots=2,maxmem=2G \
    -device pc-dimm,id=dimm-mem1,memdev=mem1 -object \
    memory-backend-file,policy=default,mem-path=/...,size=1G,id=mem1

the code in getrampagesize() currently assumes that huge pages
are possible since they are enabled for the mem1 object. But
since the main RAM is not backed by a huge page filesystem,
the guest Linux kernel then crashes very quickly after being
started. So in case the we've got "normal" memory without NUMA
and without the global "-mem-path" option, we must not announce
huge pages to the guest. Since this is likely a mis-configuration
by the user, also spill out a message in this case.
Signed-off-by: NThomas Huth <thuth@redhat.com>
Signed-off-by: NDavid Gibson <david@gibson.dropbear.id.au>