x86: nmi - nmi_watchdog boot param docs cleanup

Impact: documentation update

1) nmi_watchdog boot parameter is common to 32/64 bit modes. So
   move it from Documentation/x86/x86_64/boot-options.txt to
   Documentation/kernel-parameters.txt and integrate with.

2) Also fix [panic] keyword placement -- it ought to be at first
   position otherwise it will not be recognized.

3) Document lapic and ioapic keywords.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 14 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 343e0f0f84b6..6246220ac914 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1403,7 +1403,20 @@ and is between 256 and 4096 characters. It is defined in the file
                         when a NMI is triggered.
                         Format: [state][,regs][,debounce][,die]
 
-        nmi_watchdog=   [KNL,BUGS=X86-32] Debugging features for SMP kernels
+        nmi_watchdog=   [KNL,BUGS=X86-32,X86-64] Debugging features for SMP kernels
+                        Format: [panic,][num]
+                        Valid num: 0,1,2
+                        0 - turn nmi_watchdog off
+                        1 - use the IO-APIC timer for the NMI watchdog
+                        2 - use the local APIC for the NMI watchdog using
+                        a performance counter. Note: This will use one performance
+                        counter and the local APIC's performance vector.
+                        When panic is specified panic when an NMI watchdog timeout occurs.
+                        This is useful when you use a panic=... timeout and need the box
+                        quickly up again.
+                        Instead of 1 and 2 it is possible to use the following
+                        symbolic names: lapic and ioapic
+                        Example: nmi_watchdog=2 or nmi_watchdog=panic,lapic
 
         no387           [BUGS=X86-32] Tells the kernel to use the 387 maths
                         emulation library even if a 387 maths coprocessor