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

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Date:	Tue, 11 Oct 2011 11:24:46 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>, Andi Kleen <andi@...stfloor.org>,
	<x86@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Robert Richter <robert.richter@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	seiji.aguchi@....com, vgoyal@...hat.com, mjg@...hat.com,
	tony.luck@...el.com, gong.chen@...el.com, satoru.moriya@....com,
	avi@...hat.com, Don Zickus <dzickus@...hat.com>
Subject: [PATCH 3/3] x86, NMI: 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.

Signed-off-by: Don Zickus <dzickus@...hat.com>
---
 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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