linux-kernel - RE: [PATCH RFC] NMI Re-introduce un[set]_nmi

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Date:	Thu, 4 Sep 2008 20:21:40 +0000
From:	"Mingarelli, Thomas" <Thomas.Mingarelli@...com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Vivek Goyal <vgoyal@...hat.com>, Don Zickus <dzickus@...hat.com>,
	Ingo Molnar <mingo@...e.hu>,
	Prarit Bhargava <prarit@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"arozansk@...hat.com" <arozansk@...hat.com>,
	"ak@...ux.intel.com" <ak@...ux.intel.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Maciej W. Rozycki" <macro@...ux-mips.org>
Subject: RE: [PATCH RFC] NMI Re-introduce un[set]_nmi_callback

The BIOS does the actual logging of the cause of the NMI. What kind of NMI:

PCI Bus Parity error
Double bit memory error
.
.
.
And so on.

The watchdog is a separate part of the driver. It can be enabled or not; most of our customers will want the NMI sourcing capability of the driver.
With Prarit's patch we no longer need to worry about the watchdog timer firing. However, yes that was troublesome before his patch. We could not distinguish between a REAL NMI and a watchdog timer tick.

The BIOS does not come into play until the hpwdt nmi handler gets called.

Tom

-----Original Message-----
From: Andi Kleen [mailto:andi@...stfloor.org]
Sent: Thursday, September 04, 2008 3:19 PM
To: Mingarelli, Thomas
Cc: Andi Kleen; Vivek Goyal; Don Zickus; Ingo Molnar; Prarit Bhargava; Peter Zijlstra; linux-kernel@...r.kernel.org; arozansk@...hat.com; ak@...ux.intel.com; Alan Cox; H. Peter Anvin; Thomas Gleixner; Maciej W. Rozycki
Subject: Re: [PATCH RFC] NMI Re-introduce un[set]_nmi_callback

On Thu, Sep 04, 2008 at 08:01:31PM +0000, Mingarelli, Thomas wrote:
> Exactly.
>
> The hpwdt driver is meant to be a catch-all for any NMI coming through on ProLiant HW only. Moreover, for newer ProLiant HW at that.
>
> Once the NMI comes in, we call into our BIOS for the true reason of the NMI. That message gets logged to the IML in NVRAM for the user to view. We then panic the system.

The BIOS tells you about the NMI reason and tells you if the
watchdog didn't fire?

If yes that's great. You can be a good NMI citizen then.
Just check if the NMI came from your watchdog and if not return
NOTIFY_DONE

-Andi

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