linux-kernel - Re: [PATCH -v3 5/6] x86, NMI, treat unknown NMI as hardware error

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Date:	Sun, 10 Oct 2010 16:13:11 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Huang Ying <ying.huang@...el.com>, Don Zickus <dzickus@...hat.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>,
	Robert Richter <robert.richter@....com>
Subject: Re: [PATCH -v3 5/6] x86, NMI, treat unknown NMI as hardware error

On Sun, Oct 10, 2010 at 03:07:13PM +0100, Alan Cox wrote:
> On Sat,  9 Oct 2010 14:49:46 +0800
> Huang Ying <ying.huang@...el.com> wrote:
> 
> > In general, unknown NMI is used by hardware and firmware to notify
> > fatal hardware errors to OS. So the Linux should treat unknown NMI as
> > hardware error and go panic upon unknown NMI for better error
> > containment.
> 
> Not entirely true. Older machines use NMI for all sorts of interesting
> purposes. In particular many 486 laptops trigger NMI as part of power
> manaagement, (Hence the choice of the dazed and confused message)

In general, on any post stone age x86 system, ...

> > These systems are identified via the presentation of APEI HEST or
> > some PCI ID of the host bridge. The PCI ID of host bridge instead of
> > DMI ID is used, so that the checking can be done based on the platform
> > type instead of motherboard. This should be simpler and sufficient.
> > 
> > The method to identify the platforms is designed by Andi Kleen.
> 
> Why not make the new flag also a boot option so you can force it on for
> platforms where we don't auto whitelist it.

You can already set it at run time using sysctl.

echo 1 > /proc/sys/kernel/panic_on_unrecovered_nmi
echo 1 > /proc/sys/kernel/panic_on_io_nmi

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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