Original patch by Benjamin Herrenschmidt after debugging by Brian Hinz.

Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Brian Hinz <bphinz@hotmail.com>
Signed-off-by: H Peter Anvin <hpa@zytor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>