On some systems, hot-plug tests could hang forever waiting for cpu and
memory to be ready to be offlined. A special hot-plug target is created
to run full range of hot-plug tests. In default mode, hot-plug tests run
in safe mode with a limited scope. In limited mode, cpu-hotplug test is
run on a single cpu as opposed to all hotplug capable cpus, and memory
hotplug test is run on 2% of hotplug capable memory instead of 10%. In
addition to the above change, cpu-hotplug is chnged to change processor
affinity to cpu 0 so it doesn't impact itself while the test runs.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Michael Ellerman <michael@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This change adds a little documentation to the tests under
tools/testing/selftests/, based on akpm's explanation.

[akpm@linux-foundation.org: move from Documentation to tools/testing/selftests/README.txt]
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Cc: Dave Young <dyoung@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>