linux-kernel - Re: [PATCH v2] platform/x86/intel/ifs: Allow non-default names for IFS image

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Message-ID: <26102aca-a730-ddf8-d024-2e7367696757@redhat.com>
Date:   Thu, 28 Jul 2022 20:48:00 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     "Luck, Tony" <tony.luck@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     "Joseph, Jithu" <jithu.joseph@...el.com>,
        "markgross@...nel.org" <markgross@...nel.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Shankar, Ravi V" <ravi.v.shankar@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: Re: [PATCH v2] platform/x86/intel/ifs: Allow non-default names for
 IFS image

Hi Tony,

On 7/28/22 17:12, Luck, Tony wrote:
>>>> Speculating myself as far as I understand IFS is not for factory
>>>> tests but for testing in the fields since big cloud vendors have
>>>> found that sometimes there are hard to catch CPU defects which
>>>> they only find out by running statistics which show that certain
>>>> tasks only crash when run on machine a, socket b, core c.
>>>
>>> Who knows, Intel doesn't say so we can't really guess :(
>>
>> Right, for version 3 the commit message and ABI documentation changes
>> really need to clarify why multiple test-pattern files may be needed
>> mucy better. If possible please also include 1 or 2 _clear_ examples
>> of cases where more then 1 test-pattern file may be used.
> 
> Sorry for the radio silence. We took Greg's suggestion to go back and
> thinks this out completely to heart. As he said, there is no rush to get
> this in. We need to do it right.

That (taking your time to get this right) is good to hear, thanks.

> Your summary above on how this works is completely correct.
> 
> The reason for adding more files is to cover more transistors in the
> core. The base file that we started with gets mumble-mumble percent
> of the transistors checked. Adding a few more files will increase that
> quite significantly.
> 
> So testing a system may look like:
> 
> 	for each scan file
> 	do
> 		load the scan file
> 		for each core
> 		do
> 			test the core with this set of tests
> 		done
> 	done
> 
> Our internal discussions on naming are following the same direction that
> you suggested, but likely even more restrictive. The "suffix" may just be
> a two-digit hex number (allowing for up to 256 files ... though for Sapphire
> Rapids we are looking at just 6).
> 
> So our current direction is to name six "parts" something like this:
> 
> 	06-8f-06-00.scan
> 	06-8f-06-01.scan
> 	06-8f-06-02.scan
> 	06-8f-06-03.scan
> 	06-8f-06-04.scan
> 	06-8f-06-05.scan
> 
> but we are still checking to make sure this will work for future CPUs. Once
> we have something solid we will come back to the mailing list.

Thanks, this sounds good to me.

> As also suggested in earlier thread we will change the name of the "reload"
> file (since skipping to a new file isn't a "reload"). The "load a scan file" will
> write the "part" number to this new file.

Regards,

Hans