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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com>,
 linuxppc-dev <linuxppc-dev@ozlabs.org>,
 Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: [PATCH] powerpc: Fix the corrupt r3 error during MCE handling.
In-Reply-To: <20130710130155.4993.61577.stgit@mars>
References: <20130710130155.4993.61577.stgit@mars>
Date: Wed, 10 Jul 2013 19:41:51 +0530
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Cc: Paul Mackerras <paulus@samba.org>, Anton Blanchard <anton@samba.org>
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Mahesh J Salgaonkar <mahesh@linux.vnet.ibm.com> writes:

> From: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
>
> During Machine Check interrupt on pseries platform, R3 generally points to
> memory region inside RTAS (FWNMI) area. We see r3 corruption because when RTAS
> delivers the machine check exception it passes the address inside FWNMI area
> with the top most bit set. This patch fixes this issue by masking top two bit
> in machine check exception handler.

I always got that error and used to wonder why I find FWNMI
corrupt. IS this a rtas bug or is it documented in papr ?


>
> Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
> ---
>  arch/powerpc/platforms/pseries/ras.c |    3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
> index 7b3cbde..721c058 100644
> --- a/arch/powerpc/platforms/pseries/ras.c
> +++ b/arch/powerpc/platforms/pseries/ras.c
> @@ -287,6 +287,9 @@ static struct rtas_error_log *fwnmi_get_errinfo(struct pt_regs *regs)
>  	unsigned long *savep;
>  	struct rtas_error_log *h, *errhdr = NULL;
>
> +	/* Mask top two bits */
> +	regs->gpr[3] &= ~(0x3UL << 62);
> +
>  	if (!VALID_FWNMI_BUFFER(regs->gpr[3])) {
>  		printk(KERN_ERR "FWNMI: corrupt r3 0x%016lx\n", regs->gpr[3]);
>  		return NULL;
>

-aneesh