[v2 PATCH 3/3] x86, NMI: knob to disable using NMI IPIs to stop cpus

[Don Zickus <dzickus@redhat.com>]

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 <dzickus@redhat.com>
---
 Documentation/kernel-parameters.txt |    4 ++++
 arch/x86/kernel/smp.c               |   13 +++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 6ca1f5c..dab6439 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1761,6 +1761,10 @@ 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 991d184..f96d32d 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -248,6 +248,11 @@ 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.
  */
@@ -279,6 +284,14 @@ 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,
-- 
1.7.6.4