x86: add unknown_nmi_panic kernel parameter

It's not possible to enable the unknown_nmi_panic sysctl option
until init is run. It's useful to be able to panic the kernel
during boot too, this adds a parameter to enable this option.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 09ad745..06fbb3a 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2158,6 +2158,10 @@
 			Note that genuine overcurrent events won't be
 			reported either.
 
+	unknown_nmi_panic
+			[X86-32,X86-64]
+			Set unknown_nmi_panic=1 early on boot.
+
 	usbcore.autosuspend=
 			[USB] The autosuspend time delay (in seconds) used
 			for newly-detected USB devices (default 2).  This