linux-kernel - [PATCH 5/5] kvm: ensure hard lockup detection is disabled by default

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Date:	Mon, 11 Aug 2014 10:49:27 -0400
From:	Don Zickus <dzickus@...hat.com>
To:	akpm@...ux-foundation.org
Cc:	kvm@...r.kernel.org, pbonzini@...hat.com, mingo@...hat.com,
	LKML <linux-kernel@...r.kernel.org>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	Andrew Jones <drjones@...hat.com>,
	Don Zickus <dzickus@...hat.com>
Subject: [PATCH 5/5] kvm: ensure hard lockup detection is disabled by default

From: Ulrich Obergfell <uobergfe@...hat.com>

Use watchdog_enable_hardlockup_detector() to set hard lockup detection's
default value to false. It's risky to run this detection in a guest, as
false positives are easy to trigger, especially if the host is
overcommitted.

Signed-off-by: Ulrich Obergfell <uobergfe@...hat.com>
Signed-off-by: Andrew Jones <drjones@...hat.com>
Signed-off-by: Don Zickus <dzickus@...hat.com>
---
 arch/x86/kernel/kvm.c |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 3dd8e2c..95c3cb1 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -35,6 +35,7 @@
 #include <linux/slab.h>
 #include <linux/kprobes.h>
 #include <linux/debugfs.h>
+#include <linux/nmi.h>
 #include <asm/timer.h>
 #include <asm/cpu.h>
 #include <asm/traps.h>
@@ -499,6 +500,13 @@ void __init kvm_guest_init(void)
 #else
 	kvm_guest_cpu_init();
 #endif
+
+	/*
+	 * Hard lockup detection is enabled by default. Disable it, as guests
+	 * can get false positives too easily, for example if the host is
+	 * overcommitted.
+	 */
+	watchdog_enable_hardlockup_detector(false);
 }
 
 static noinline uint32_t __kvm_cpuid_base(void)
-- 
1.7.1

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