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>

2 files changed, 11 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 09ad7450647b..06fbb3aa288c 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2158,6 +2158,10 @@ and is between 256 and 4096 characters. It is defined in the file
                         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
diff --git a/arch/x86/kernel/nmi.c b/arch/x86/kernel/nmi.c
index ec024b3baad0..e0b44b7b717a 100644
--- a/arch/x86/kernel/nmi.c
+++ b/arch/x86/kernel/nmi.c
@@ -448,6 +448,13 @@ nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 
 #ifdef CONFIG_SYSCTL
 
+static int __init setup_unknown_nmi_panic(char *str)
+{
+        unknown_nmi_panic = 1;
+        return 1;
+}
+__setup("unknown_nmi_panic", setup_unknown_nmi_panic);
+
 static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
 {
         unsigned char reason = get_nmi_reason();