From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751201AbXANJd7 (ORCPT ); Sun, 14 Jan 2007 04:33:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751184AbXANJd7 (ORCPT ); Sun, 14 Jan 2007 04:33:59 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:44583 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751201AbXANJd6 (ORCPT ); Sun, 14 Jan 2007 04:33:58 -0500 Date: Sun, 14 Jan 2007 10:29:26 +0100 From: Ingo Molnar To: Andrew Morton , Linus Torvalds Cc: Andi Kleen , linux-kernel@vger.kernel.org Subject: [patch] disable NMI watchdog by default Message-ID: <20070114092926.GA14465@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.6 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.6 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -2.6 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Ingo Molnar Subject: [patch] disable NMI watchdog by default there's a new NMI watchdog related problem: KVM crashes on certain bzImages because ... we enable the NMI watchdog by default (even if the user does not ask for it) , and no other OS on this planet does that so KVM doesnt have emulation for that yet. So KVM injects a #GP, which crashes the Linux guest: general protection fault: 0000 [#1] PREEMPT SMP Modules linked in: CPU: 0 EIP: 0060:[] Not tainted VLI EFLAGS: 00000246 (2.6.20-rc5-rt0 #3) EIP is at setup_apic_nmi_watchdog+0x26d/0x3d3 and no, i did /not/ request an nmi_watchdog on the boot command line! Solution: turn off that darn thing! It's a debug tool, not a 'make life harder' tool!! with this patch the KVM guest boots up just fine. And with this my laptop (Lenovo T60) also stops its sporadic hard hanging (sometimes in acpi_init(), sometimes later during bootup, sometimes much later during actual use) as well. It hung with both nmi_watchdog=1 and nmi_watchdog=2, so it's generally the fact of NMI injection that is causing problems, not the NMI watchdog variant, nor any particular bootup code. The patch is unintrusive. Signed-off-by: Ingo Molnar Index: linux/include/asm-i386/nmi.h =================================================================== --- linux.orig/include/asm-i386/nmi.h +++ linux/include/asm-i386/nmi.h @@ -33,7 +33,7 @@ extern int nmi_watchdog_tick (struct pt_ extern atomic_t nmi_active; extern unsigned int nmi_watchdog; -#define NMI_DEFAULT -1 +#define NMI_DEFAULT 0 #define NMI_NONE 0 #define NMI_IO_APIC 1 #define NMI_LOCAL_APIC 2 Index: linux/include/asm-x86_64/nmi.h =================================================================== --- linux.orig/include/asm-x86_64/nmi.h +++ linux/include/asm-x86_64/nmi.h @@ -63,7 +63,7 @@ extern int setup_nmi_watchdog(char *); extern atomic_t nmi_active; extern unsigned int nmi_watchdog; -#define NMI_DEFAULT -1 +#define NMI_DEFAULT 0 #define NMI_NONE 0 #define NMI_IO_APIC 1 #define NMI_LOCAL_APIC 2