Re: Memory controller not showing half of the memory?

[reox <mailinglist@reox.at>]

Am 13.03.2025 um 18:31 schrieb Borislav Petkov:
> On Thu, Mar 13, 2025 at 06:21:28PM +0100, reox wrote:
>> Hello,
>>
>> I hope it is okay to ask such a question on this mailinglist, however there
>> is surprisingly little information on this topic (or I'm not deep enough in
>> the matter to understand everything correctly...).
>>
>> I have a server with a ASRockRack B665D4U-1L board. I'm running Debian with
>> bookworm-backports kernel 6.12.9-1~bpo12+1.
>> In the syslog I see the following output of EDAC:
>> # dmesg | grep -i EDAC
>> [    1.340448] EDAC MC: Ver: 3.0.0
>> [    4.705255] EDAC MC0: Giving out device to module amd64_edac controller
>> F19h_M70h: DEV 0000:00:18.3 (INTERRUPT)
>> [    4.705262] EDAC amd64: F19h_M70h detected (node 0).
>> [    4.705266] EDAC MC: UMC0 chip selects:
>> [    4.705267] EDAC amd64: MC: 0:     0MB 1:     0MB
>> [    4.705270] EDAC amd64: MC: 2:  8192MB 3:  8192MB
>> [    4.705273] EDAC MC: UMC1 chip selects:
>> [    4.705274] EDAC amd64: MC: 0:     0MB 1:     0MB
>> [    4.705277] EDAC amd64: MC: 2:  8192MB 3:  8192MB
>>
>> However, compare this to the real amount of memory (2×32GB):
>> # lshw -c memory  # shorted
>>    *-memory
>>         size: 64GiB
>>         capabilities: ecc
>>         configuration: errordetection=multi-bit-ecc
>>       *-bank:0
>>            description: [empty]
>>       *-bank:1
>>            description: DIMM Synchronous Unbuffered (Unregistered) 4800 MHz
>> (0.2 ns)
>>            product: HMCG88MEBEA081N
>>            vendor: SK Hynix
>>            size: 32GiB
>>       *-bank:2
>>            description: [empty]
>>       *-bank:3
>>            description: DIMM Synchronous Unbuffered (Unregistered) 4800 MHz
>> (0.2 ns)
>>            product: HMCG88MEBEA081N
>>            vendor: SK Hynix
>>            size: 32GiB
>>
>> I'm a bit confused here... Does EDAC simply miss half of the memory? Is this
>> output correct? Or the memory controller not fully implemented / bugged in
>> that kernel version (with the bookworm kernel it does not load EDAC at all)?
> 						^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> 
> What does that mean, exactly?
> 
> Are you force-loading the module?

Sorry, that was formulated a bit sloppy... I meant that with the current 
bookworm kernel (6.1.128) there was no memory controller detected. The 
module was loaded fine but reported nothing. As far as I can tell, 
support was added only with 6.5 with commit 6c79e42 (would the expected 
outcome in my case also be 4×16GB?).

by the way, if it helps, the CPU is a "AMD Ryzen 7 PRO 8700GE w/ Radeon 
780M Graphics".

> 
> You could send a full dmesg...

from 6.1.128 or 6.12.9?

> 
>> Unfortunately I cannot easily run a dev version of the kernel on that
>> machine - otherwise I would have probably already done that.
>>
>> Thanks in advance!
>> Best,
>> Sebastian
>>
>