RE: [PATCH 1/1] RAS: Add CPU Correctable Error Collector to isolate an erroneous CPU core

[Shiju Jose]

Hi Boris,

>-----Original Message-----
>From: Borislav Petkov [mailto:bp@xxxxxxxxx]
>Sent: 01 September 2020 15:36
>To: Shiju Jose <shiju.jose@xxxxxxxxxx>
>Cc: linux-edac@xxxxxxxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; linux-
>kernel@xxxxxxxxxxxxxxx; tony.luck@xxxxxxxxx; rjw@xxxxxxxxxxxxx;
>james.morse@xxxxxxx; lenb@xxxxxxxxxx; Linuxarm
><linuxarm@xxxxxxxxxx>
>Subject: Re: [PATCH 1/1] RAS: Add CPU Correctable Error Collector to isolate
>an erroneous CPU core
>
>On Tue, Sep 01, 2020 at 03:01:40PM +0100, Shiju Jose wrote:
>> When the CPU correctable errors reported on an ARM64 CPU core too
>> often, it should be isolated. Add the CPU correctable error collector
>> to store the CPU correctable error count.
>>
>> When the correctable error count for a CPU exceed the threshold value
>> in a short time period, it will try to isolate the CPU core.
>> The threshold value, time period etc are configurable.
>>
>> Implementation details is added in the file.
>>
>> Signed-off-by: Shiju Jose <shiju.jose@xxxxxxxxxx>
>> ---
>>  Documentation/ABI/testing/debugfs-cpu-cec |  22 ++
>>  arch/arm64/ras/Kconfig                    |   8 +
>>  drivers/acpi/apei/ghes.c                  |  30 +-
>>  drivers/ras/Kconfig                       |   1 +
>>  drivers/ras/Makefile                      |   1 +
>>  drivers/ras/cpu_cec.c                     | 393 ++++++++++++++++++++++
>
>So instead of adding the ability to collect other error types to the CEC, you're
>duplicating the CEC itself?!
>
>Why?
CPU CEC derived the infrastructure of the CEC only and the logic used in the CEC for
CE count storage, CE count calculation and page isolation is very unique for the
memory pages,  which seems cannot be reusable for the CPU CEs. 
Also the values set for the parameters such as threshold, time period for the memory errors
and  CPU errors would be different.
Thus extending cec.c to support CPU CEs would include adding CPU CEC specific code
for storing error count, isolation etc which I thought would result the code less tidy and
less readable unless find more reusable logic.

>
>--
>Regards/Gruss,
>    Boris.
>
>https://people.kernel.org/tglx/notes-about-netiquette

Thanks,
Shiju