linux-kernel - Re: [RFC Patch 0/2] Slimdump framework using CRASH_REASON

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Date:	Wed, 30 Nov 2011 22:45:24 +0530
From:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
	"Luck, Tony" <tony.luck@...el.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>, anderson@...hat.com,
	tachibana@....nes.nec.co.jp, oomichi@....nes.nec.co.jp,
	Valdis.Kletnieks@...edu, Nick Bowler <nbowler@...iptictech.com>
Subject: Re: [RFC Patch 0/2] Slimdump framework using CRASH_REASON - v2

On Mon, Nov 28, 2011 at 09:24:02AM -0500, Vivek Goyal wrote:
> On Wed, Nov 23, 2011 at 11:03:18PM +0530, K.Prasad wrote:
> > On Mon, Nov 21, 2011 at 10:17:27AM -0500, Vivek Goyal wrote:
> > > On Mon, Nov 21, 2011 at 03:24:05PM +0530, K.Prasad wrote:
[snipped]
> > 
> > The kernel message buffers can be obtained by using the --dump-dmesg
> > option of makedumpfile but again that's risky. We wouldn't know if it'll
> > cause access to the faulty memory (which is how the previous method of having
> > a new elf-notes in a pristine location is much safer).
> > 
> > The method in this patch is quite primitive in that informs the user
> > nothing more than a one-line cause of crash. One should take help from other
> > tools (such as service processor/firmware/ACPI logs, or previous corrected
> > error logs) to infer the location of bad memory.
> 
> And how does one get to firmware/ACPI logs? Many system don't have service
> processor also.
> 
> I think extracting kernel buffers by default in case of MCE is reasonable.
> This should allow somebody to figure out some MCE related information.
> 
> You might want to modify makedumpfile so that it does not try to access
> pages marked poisoned.
>

I'm not sure how easy or difficult it would be to skip hw-poisoned pages
from user-space i.e. makedumpfile. I'll start working on the relevant
changes though, and keep the community posted with the patches.

Thanks,
K.Prasad

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