Subject: Re: [PATCH] powerpc: Fix the corrupt r3 error during MCE handling.

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Wed, 10 Jul 2013 19:41:51 +0530

Mahesh J Salgaonkar <[email-masked]> writes:

> From: Mahesh Salgaonkar <[email-masked]>
>
> 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 <[email-masked]>
> ---
>  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