x86/mpx: Introduce a boot-time disable flag

MPX has the _potential_ to cause some issues.  Say part of your
init system tried to protect one of its components from buffer
overflows with MPX.  If there were a false positive, it's
possible that MPX could keep a system from booting.

MPX could also potentially cause performance issues since it is
present in hot paths like the unmap path.

Allow it to be disabled at boot time.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Hansen <dave@sr71.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150607183702.2E8B77AB@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 61ab1628a057..8b7e5c342302 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -937,6 +937,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         Enable debug messages at boot time.  See
                         Documentation/dynamic-debug-howto.txt for details.
 
+        nompx           [X86] Disables Intel Memory Protection Extensions.
+                        See Documentation/x86/intel_mpx.txt for more
+                        information about the feature.
+
         eagerfpu=       [X86]
                         on      enable eager fpu restore
                         off     disable eager fpu restore