Documentation: Add MDS vulnerability documentation

commit 5999bbe7a6ea3c62029532ec84dc06003a1fa258 upstream.

Add the initial MDS vulnerability documentation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jon Masters <jcm@redhat.com>
[bwh: Backported to 4.9: adjust filenames]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/Documentation/hw-vuln/l1tf.rst b/Documentation/hw-vuln/l1tf.rst
index 9af9773..31653a9 100644
--- a/Documentation/hw-vuln/l1tf.rst
+++ b/Documentation/hw-vuln/l1tf.rst
@@ -445,6 +445,7 @@
 line, then 'always' is enforced and the kvm-intel.vmentry_l1d_flush
 module parameter is ignored and writes to the sysfs file are rejected.
 
+.. _mitigation_selection:
 
 Mitigation selection guide
 --------------------------