Re: Linux 2.6.39-rc3

From: Andreas Herrmann
Date: Fri Apr 15 2011 - 10:04:55 EST

On Fri, Apr 15, 2011 at 03:11:52PM +0200, Joerg Roedel wrote:
> On Wed, Apr 13, 2011 at 07:33:40PM -0700, Linus Torvalds wrote:
> > we definitely want to also understand the reason for things not
> > working, even if we do revert..
> Okay, here it is.
> After experimenting with different configurations for the north-bridge
> it turned out that a GART related MCE fires at the time the machine
> reboots. BIOSes configure the machine to sync-flood in that case which
> causes a reboot.
> After decoding the MCE it turned out to be a GART TBL Wlk Error. Such
> errors can happen if devices (speculativly) access GART ranges mapped
> invalid. The AMD BKDG for Fam10h CPUs recommends to disable these errors
> at all. But unfortunatly some BIOSes (including the one on my laptop)
> forget to do this.
> Below is a patch which disables these errors if the BIOS didn't do it.
> It fixes the problem on my site.
> Alexandre, can you try this patch on your machine too, please?
> Regards,
> Joerg
> From aaacff8db50b6ed4345e337ecbe53e505699c7e5 Mon Sep 17 00:00:00 2001
> From: Joerg Roedel <joerg.roedel@xxxxxxx>
> Date: Fri, 15 Apr 2011 14:47:40 +0200
> Subject: [PATCH] x86/amd: Disable GartTlbWlkErr when BIOS forgets it
> This patch disables GartTlbWlk errors on AMD Fam10h CPUs if
> the BIOS forgets to do is (or is just too old). Letting
> these errors enabled can cause a sync-flood on the CPU
> causing a reboot.
> This patch is the fix for
> on my machine.
> Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>


What about tagging this patch for stable/longterm releases?

Potentially there are other cases where certain combinations of
hardware(GPUs)/drivers/whatsoever might trigger a GartTlbWlkErr. If
the BIOS doesn't follow the BKDG recommendation to mask these errors,
the system will hang/reboot. Thus I think having this quirk in .32 and
.38 (at least) is useful.

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