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

[Don Zickus]

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.

Signed-off-by: Don Zickus <dzickus@xxxxxxxxxx>
---
 Documentation/kernel-parameters.txt |    4 ++++
 arch/x86/kernel/smp.c               |    8 ++++++++
 2 files changed, 12 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 f54e07a..cc8026a 100644
--- a/arch/x86/kernel/smp.c
+++ b/arch/x86/kernel/smp.c
@@ -283,6 +283,14 @@ void smp_call_function_single_interrupt(struct pt_regs *regs)
 	irq_exit();
 }
 
+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

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