First handle the cases which do not need know the value of PlatformInfoHob->LowMemory (microvm and cloudhv). Then call PlatformGetSystemMemorySizeBelow4gb() to get LowMemory. Finally handle the cases (q35 and pc) which need to look at LowMemory, Signed-off-by: Gerd Hoffmann <kraxel@redhat.com> Reviewed-by: Laszlo Ersek <lersek@redhat.com>