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Re: [PATCH] Proposed NMI handling interface...

To: "Steven J. Hill" <sjhill@realitydiluted.com>
Subject: Re: [PATCH] Proposed NMI handling interface...
From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 8 Oct 2003 18:06:00 +0200
Cc: linux-mips@linux-mips.org
In-reply-to: <3F832040.7070606@realitydiluted.com>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <3F832040.7070606@realitydiluted.com>
Sender: linux-mips-bounce@linux-mips.org
User-agent: Mutt/1.4.1i
On Tue, Oct 07, 2003 at 04:21:20PM -0400, Steven J. Hill wrote:

> I wanted to propose an NMI handling interface. I have attached
> the header file and patches to 'arch/mips/kernel/traps.c'. The
> user need only specify the offset address for the NMI vector
> code and then they can also specify their own desired NMI
> function. Comments?

That hook you're proposing isn't even necessary in generic code.  NMI
on MIPS hardware is a fairly odd type of exception - it goes straight to
0xbfc00000 which usually is a a firmware address - and lots of firmware
doesn't even offer an NMI hook.  So for those cases where it's possible,
you need to do something firmware anyway before jumping to Linux's NMI
handler.  An additional problem with the NMI design of MIPS is it's using
ErrorEPC, just like cache errors so you better pray - or simply design
systems only to rely on NMI for debugging and catastrophic failures.

  Ralf

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