RE: [RFC PATCH 1/2] EDAC/ghes: Add EDAC device for the CPU caches

[Shiju Jose]

Hi Boris,

>-----Original Message-----
>From: Borislav Petkov [mailto:bp@xxxxxxxxx]
>Sent: 18 January 2021 18:37
>To: Shiju Jose <shiju.jose@xxxxxxxxxx>
>Cc: linux-edac@xxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; linux-
>kernel@xxxxxxxxxxxxxxx; james.morse@xxxxxxx;
>mchehab+huawei@xxxxxxxxxx; tony.luck@xxxxxxxxx; rjw@xxxxxxxxxxxxx;
>lenb@xxxxxxxxxx; rrichter@xxxxxxxxxxx; Jonathan Cameron
><jonathan.cameron@xxxxxxxxxx>; tanxiaofei <tanxiaofei@xxxxxxxxxx>;
>linuxarm@xxxxxxxxxxxxx
>Subject: Re: [RFC PATCH 1/2] EDAC/ghes: Add EDAC device for the CPU
>caches
>
>On Fri, Jan 15, 2021 at 11:06:30AM +0000, Shiju Jose wrote:
>> L2 cache corrected errors are detected occasionally on few of our
>> ARM64 hardware boards. Though it is rare, the probability of the CPU
>> cache errors frequently occurring can't be avoided.
>> The earlier failure detection by monitoring the cache corrected errors
>> for the frequent occurrences and taking preventive action could
>> prevent more serious hardware faults.
>>
>> On Intel architectures, cache corrected errors are reported and the
>> affected cores are offline in the architecture specific method.
>> http://www.mcelog.org/cache.html
>>
>> However for the firmware-first error reporting, specifically on
>> ARM64 architectures, there is no provision present for reporting the
>> cache corrected error count to the user-space and taking preventive
>> action such as offline the affected cores.
>
>How hard was it to write that in your first submission? What do you think
>would be the best way to persuade a patch reviewer/maintainer to take a
>look at your submission?
>
>> >Why a separate Kconfig item?
>> CONFIG_EDAC_GHES_CPU_CACHE_ERROR is added to make this feature
>> optional only for the platforms which need this and supported.
>>
>> >
>> >> +	depends on EDAC_GHES
>
>depends on EDAC_GHES hardly expresses which platforms need it/support it.
>
>If anything, depends on ARM64.
Sure. I will add dependency on ARM64.
This EDAC code for the cache errors is  architecture independent for the
firmware-first error reporting and  could be used for other architectures,
though now we need it for the ARM64. 

>
>> >Init stuff belongs into ghes_scan_system().
>> >
>> Did you mean calling  ghes_edac_create_cpu_device() in the
>ghes_scan_system()?
>
>I mean, all hardware discovery needs to happen in ghes_scan_system
>- you don't need to call those from outside the driver, in
>ghes_edac_register().

sure. Will modify.
>
>--
>Regards/Gruss,
>    Boris.

Thanks,
Shiju