linux-kernel - Re: [PATCH 11/11] EDAC/ghes: Create one memory controller per physical memory array

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Date:   Tue, 17 Mar 2020 16:34:32 +0000
From:   John Garry <john.garry@...wei.com>
To:     Borislav Petkov <bp@...en8.de>,
        Robert Richter <rrichter@...vell.com>
CC:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Tony Luck <tony.luck@...el.com>,
        James Morse <james.morse@....com>,
        Aristeu Rozanski <aris@...hat.com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Toshi Kani <toshi.kani@....com>,
        Xiaofei Tan <tanxiaofei@...wei.com>,
        Shiju Jose <shiju.jose@...wei.com>
Subject: Re: [PATCH 11/11] EDAC/ghes: Create one memory controller per
 physical memory array

On 16/03/2020 09:51, Borislav Petkov wrote:
> On Fri, Mar 06, 2020 at 04:13:18PM +0100, Robert Richter wrote:
>> The ghes driver only creates one memory controller for the whole
>> system. This does not reflect memory topology especially in multi-node
>> systems. E.g. a Marvell ThunderX2 system shows:
>>
>>   /sys/devices/system/edac/mc/mc0/dimm0
>>   /sys/devices/system/edac/mc/mc0/dimm1
>>   /sys/devices/system/edac/mc/mc0/dimm2
>>   /sys/devices/system/edac/mc/mc0/dimm3
>>   /sys/devices/system/edac/mc/mc0/dimm4
>>   /sys/devices/system/edac/mc/mc0/dimm5
>>   /sys/devices/system/edac/mc/mc0/dimm6
>>   /sys/devices/system/edac/mc/mc0/dimm7
>>   /sys/devices/system/edac/mc/mc0/dimm8
>>   /sys/devices/system/edac/mc/mc0/dimm9
>>   /sys/devices/system/edac/mc/mc0/dimm10
>>   /sys/devices/system/edac/mc/mc0/dimm11
>>   /sys/devices/system/edac/mc/mc0/dimm12
>>   /sys/devices/system/edac/mc/mc0/dimm13
>>   /sys/devices/system/edac/mc/mc0/dimm14
>>   /sys/devices/system/edac/mc/mc0/dimm15
>>
>> The DIMMs 9-15 are located on the 2nd node of the system. On
>> comparable x86 systems there is one memory controller per node. The
>> ghes driver should also group DIMMs depending on the topology and
>> create one MC per node.
>>
>> There are several options to detect the topology. ARM64 systems
>> retrieve the (NUMA) node information from the ACPI SRAT table (see
>> acpi_table_parse_srat()). The node id is later stored in the physical
>> address page. The pfn_to_nid() macro could be used for a DIMM after
>> determining its physical address. The drawback of this approach is
>> that there are too many subsystems involved it depends on. It could
>> easily break and makes the implementation complex. E.g. pfn_to_nid()
>> can only be reliable used on mapped address ranges which is not always
>> granted, there are various firmware instances involved which could be
>> broken, or results may vary depending on NUMA settings.
>>
>> Another approach that was suggested by James' is to use the DIMM's
>> physical memory array handle to group DIMMs [1]. The advantage is to
>> only use the information on memory devices from the SMBIOS table that
>> contains a reference to the physical memory array it belongs too. This
>> information is mandatory same as the use of DIMM handle references by
>> GHES to provide the DIMM location of an error. There is only a single
>> table to parse which eases implementation. This patch uses this
>> approach for DIMM grouping.
>>
>> Modify the DMI decoder to also detect the physical memory array a DIMM
>> is linked to and create one memory controller per array to group
>> DIMMs. With the change DIMMs are grouped, e.g. a ThunderX2 system
>> shows one MC per node now:
>>
>>   # grep . /sys/devices/system/edac/mc/mc*/dimm*/dimm_label
>>   /sys/devices/system/edac/mc/mc0/dimm0/dimm_label:N0 DIMM_A0
>>   /sys/devices/system/edac/mc/mc0/dimm1/dimm_label:N0 DIMM_B0
>>   /sys/devices/system/edac/mc/mc0/dimm2/dimm_label:N0 DIMM_C0
>>   /sys/devices/system/edac/mc/mc0/dimm3/dimm_label:N0 DIMM_D0
>>   /sys/devices/system/edac/mc/mc0/dimm4/dimm_label:N0 DIMM_E0
>>   /sys/devices/system/edac/mc/mc0/dimm5/dimm_label:N0 DIMM_F0
>>   /sys/devices/system/edac/mc/mc0/dimm6/dimm_label:N0 DIMM_G0
>>   /sys/devices/system/edac/mc/mc0/dimm7/dimm_label:N0 DIMM_H0
>>   /sys/devices/system/edac/mc/mc1/dimm0/dimm_label:N1 DIMM_I0
>>   /sys/devices/system/edac/mc/mc1/dimm1/dimm_label:N1 DIMM_J0
>>   /sys/devices/system/edac/mc/mc1/dimm2/dimm_label:N1 DIMM_K0
>>   /sys/devices/system/edac/mc/mc1/dimm3/dimm_label:N1 DIMM_L0
>>   /sys/devices/system/edac/mc/mc1/dimm4/dimm_label:N1 DIMM_M0
>>   /sys/devices/system/edac/mc/mc1/dimm5/dimm_label:N1 DIMM_N0
>>   /sys/devices/system/edac/mc/mc1/dimm6/dimm_label:N1 DIMM_O0
>>   /sys/devices/system/edac/mc/mc1/dimm7/dimm_label:N1 DIMM_P0
>>
>> [1] https://lkml.kernel.org/r/f878201f-f8fd-0f2a-5072-ba60c64eefaf@arm.com
>>
>> Suggested-by: James Morse <james.morse@....com>
>> Signed-off-by: Robert Richter <rrichter@...vell.com>
>> ---
>>   drivers/edac/ghes_edac.c | 137 ++++++++++++++++++++++++++++++---------
>>   1 file changed, 107 insertions(+), 30 deletions(-)
> 
> This is all fine and good but that change affects the one x86 platform
> we support so the whole patchset should be tested there too. Adding
> Toshi.
> 
> As a matter of fact, the final version of this set should be tested on
> all platforms which are using this thing. Adding John Garry too who
> reported issues with this driver recently on his platform.

Adding other RAS-centric guys for H.

Cheers,
John

> 
> Thx.
>