linux-kernel - Re: [patch] disable NMI watchdog by default

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Date:	Mon, 05 Mar 2007 11:02:45 -0500
From:	Bill Davidsen <davidsen@....com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Andi Kleen <ak@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [patch] disable NMI watchdog by default

Ingo Molnar wrote:
> From: Ingo Molnar <mingo@...e.hu>
> 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:[<c011a8ae>]    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.

I'm missing something, what limits this to systems running under kvm?

-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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