x86, NMI: Add knob to disable using NMI IPIs to stop cpus

Some machines may exhibit problems using the NMI to stop other
cpus. This knob just allows one to revert back to the original
behaviour to help diagnose the problem.

V2:
  make function static

Signed-off-by: Don Zickus <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Andi Kleen <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

2 files changed, 17 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index a0c5c5f4fce6..b4339e5a50da 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1796,6 +1796,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 	nomfgpt		[X86-32] Disable Multi-Function General Purpose
 			Timer usage (for AMD Geode machines).
 
+	nonmi_ipi	[X86] Disable using NMI IPIs during panic/reboot to
+			shutdown the other cpus.  Instead use the REBOOT_VECTOR
+			irq.
+
 	nopat		[X86] Disable PAT (page attribute table extension of
 			pagetables) support.
 
diff --git a/arch/x86/kernel/smp.c b/arch/x86/kernel/smp.c
index e72b1754a2d7..113acda5879e 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -249,6 +249,11 @@ static void native_irq_stop_other_cpus(int wait)
 	local_irq_restore(flags);
 }
 
+static void native_smp_disable_nmi_ipi(void)
+{
+	smp_ops.stop_other_cpus = native_irq_stop_other_cpus;
+}
+
 /*
  * Reschedule call back.
  */
@@ -280,6 +285,14 @@ void smp_call_function_single_interrupt(struct pt_regs *regs)
 	irq_exit();
 }
 
+static int __init nonmi_ipi_setup(char *str)
+{
+        native_smp_disable_nmi_ipi();
+        return 1;
+}
+
+__setup("nonmi_ipi", nonmi_ipi_setup);
+
 struct smp_ops smp_ops = {
 	.smp_prepare_boot_cpu	= native_smp_prepare_boot_cpu,
 	.smp_prepare_cpus	= native_smp_prepare_cpus,