linux-kernel - Re: [PATCH] amd64_edac: Memory size reported double on processor family 0Fh

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Message-ID: <5050857F.5060207@akamai.com>
Date:	Wed, 12 Sep 2012 07:52:15 -0500
From:	Josh Hunt <johunt@...mai.com>
To:	Borislav Petkov <bp@...64.org>
CC:	"linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] amd64_edac: Memory size reported double on processor
 family 0Fh

On 09/12/2012 07:38 AM, Josh Hunt wrote:
> On 09/12/2012 03:51 AM, Borislav Petkov wrote:
>> On Tue, Sep 11, 2012 at 06:02:01PM -0500, Josh Hunt wrote:
>>> On 09/11/2012 05:52 PM, Josh Hunt wrote:
>>>> With recent kernels we noticed that edac was reporting double the memory size on
>>>> systems running with AMD family 0Fh processors. I'm not very familiar with the
>>>> code, but this resolves it from what I can see on my systems. At least in
>>>> amd64_debug_display_dimm_sizes() and k8_dbam_to_chip_select() there appeared
>>>> to be redundant shifts to the left by 1 when WIDTH_128 is present.
>>
>> Any chance you could enable CONFIG_EDAC_DEBUG, boot and send me your
>> whole dmesg? Privately is fine too.
>>
>> Thanks.
>>
> 
> Sure. Attached. This is booting with latest git.
> 
> Josh

I wanted to add that we started seeing this back in 3.0. I didn't go
back any farther, but know it was not occurring in 2.6.38. The issue in
3.0 appeared to be that we shift left k8_dbam_to_chip_select() and there
was also another shift in amd64_csrow_nr_pages(). It looks like that
second shift has been replaced by a more recent patch, which actually
checks to see if the csrow is enabled and then counts nr_pages again
adding that to the first calculation, still resulting in the size being
double.

Josh
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