Re: [PATCH] Revert "EDAC/mce_amd: Do not load edac_mce_amd module on guests"

[Yazen Ghannam]

On 9/13/23 11:50 AM, Luck, Tony wrote:
>> Also, please note that the EDAC modules don't handle MCE events
>> directly. They act on information passed from the MCE subsystem.
>>
>> Furthermore, there are other EDAC modules that have the same !hypervisor
>> check, so why change only this one?
> 
> The older Intel EDAC drivers translated system physical addresses to DIMM
> addresses by digging around in the CONFIG and MMIO space of the memory
> controller devices. It would seem unwise for a VMM to give access to those
> addresses to a guest (in general ... perhaps OK for a Xen style "DOM0" guest that is
> handling many tasks for the VMM?).
> 
> What system resources do AMD EDAC drivers need access to? Could they
> work inside a guest?
>

The MCE decoder may access some newer MCA registers, or request info
from the MCE subsystem. But this is for informational error decoding. It
won't support any actions that a guest could take.

The AMD64 EDAC module reads system-specific memory controller registers
through non-architectural interfaces. So also unwise or not useful for a
guest to access.

Thanks,
Yazen