Re: [RFC] x86, NMI, Treat unknown NMI as hardware error

From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Huang Ying <ying.huang@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Don Zickus <dzickus@redhat.com>,
	linux-kernel@vger.kernel.org, Andi Kleen <andi@firstfloor.org>,
	Robert Richter <robert.richter@amd.com>,
	Andi Kleen <ak@linux.intel.com>
Subject: Re: [RFC] x86, NMI, Treat unknown NMI as hardware error
Date: Fri, 13 May 2011 19:17:25 +0400	[thread overview]
Message-ID: <4DCD4B85.3040702@gmail.com> (raw)
In-Reply-To: <1305275018-20596-1-git-send-email-ying.huang@intel.com>

On 05/13/2011 12:23 PM, Huang Ying 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.
> 
> But there are some legacy machine which would randomly send unknown
> NMIs for no good reason.  To support these machines, a white list
> mechanism is provided to treat unknown NMI as hardware error only on
> some known working 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.
> 
> Signed-off-by: Huang Ying <ying.huang@intel.com>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: Don Zickus <dzickus@redhat.com>
> ---
...

Hi Ying,

just curious (regardless the concerns Don and Ingo have) -- if there still a need
for such semi-unknown nmi handling maybe it's worth to register a *notifier* for it
and we panic only when user *explicitly* specify how to treat this class of NMIs
(via say "hest-nmi-panic" boot option or something like that). Maybe such partially
modular scheme would be better? If only I don't miss anything.

-- 
            Cyrill