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Date: Mon, 9 Sep 2013 14:30:16 +1000
From: Paul Mackerras <paulus@samba.org>
To: Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH v3 02/12] powerpc/book3s: Introduce exclusive
 emergency stack for machine check exception.
Message-ID: <20130909043016.GB6248@drongo>
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 <20130826193132.2855.85275.stgit@mars>
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Cc: linuxppc-dev <linuxppc-dev@ozlabs.org>,
 Jeremy Kerr <jeremy.kerr@au1.ibm.com>, Anton Blanchard <anton@samba.org>
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On Tue, Aug 27, 2013 at 01:01:32AM +0530, Mahesh J Salgaonkar wrote:
> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> 
> This patch introduces exclusive emergency stack for machine check exception.
> We use emergency stack to handle machine check exception so that we can save
> MCE information (srr1, srr0, dar and dsisr) before turning on ME bit and be
> ready for re-entrancy. This helps us to prevent clobbering of MCE information
> in case of nested machine checks.
> 
> The reason for using emergency stack over normal kernel stack is that the
> machine check might occur in the middle of setting up a stack frame which may
> result into improper use of kernel stack.
> 
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>

Acked-by: Paul Mackerras <paulus@samba.org>