Re: [GIT PULL] EDAC pile for 5.4 -> AMD family 17h, model 70h support

["Ghannam, Yazen" <Yazen.Ghannam@amd.com>]

On 10/10/2019 9:41 AM, Borislav Petkov wrote:
> On Thu, Oct 10, 2019 at 08:48:20AM -0400, Jean-Frederic wrote:
>> I did recheck all menus in advanced mode several times. I used my bios
>> fairly often when I got this new system, I would also have seen it
>> before I would think.
> 
> I have the faint suspicion that our perfectly capable BIOS writers
> forgot to add a disable functionality. Let's see what Yazen finds out
> first, though.
> 

I believe PFEH is generally geared towards enterprise users which is why I
remembered it once you mentioned your system is EPYC. I don't really know if
it's being used for desktop/client systems. Of course, it's up to the vendor
which features they choose to implement. I haven't seen it in the client
documentation though.

There's no explicit way to check if PFEH is enabled from the kernel. The
feature is meant to be transparent to the OS.

However, MCA_MISC0 will be Read-as-Zero/Writes-Ignored for all MCA banks when
PFEH is enabled. So you can use this as an implicit check. This is just an
implementation detail though for current systems. It's not an architectural
requirement.

Jean-Frederic,
Please do the following if you'd like to try this check:
1) rdmsr 0xC0002003

This command will read the MCA_MISC0 register from MCA bank 0. If it is
non-zero, then we'll know that PFEH is not enabled.

The "rdmsr" command is usually found in the msr-tools package in many distros.
You will need to run it as root, and you may need to load the "msr" module
before using the command.

Thanks,
Yazen