Linux 5.9 and MSRs

[alxchk]

https://www.phoronix.com/scan.php?page=news_item&px=Linux-Filter-Tightening-MSRs

Maybe it's worth to collaborate with upstream somehow?

[rien333]

From what I gather, this dmesg message I recieve during login

msr: Write to unrecognized MSR 0x150 by intel-undervolt
Please report to x86@kernel.org

is thus an harmless warning for now, while MSR writing may be actually significantly restricted in the future?

And even with such restrictions in place, users could still turn off this behavior using the msr.allow_writes= writes kernel parameter?

(just to check)

[jthomme1]

I also have a big interest in this issue. Would really appreciate it if this awesome tool is not rendered useless with upcoming kernel updates.

[antonvalletas]

Is there anyway to confirm that it is actually working in kernel 5.9.1? I am also getting that error, and I don't want to loose undervolting.

[alxchk]

It works with 5.9.1.
The only problem you need to do something with log messages. I patched kernel a bit (added MSRs to exceptions).
Likely msr.allow_writes=on should also works for some time

[milos7250]

Has anyone tried updating to kernel 5.10? I'm curious if anything changed regarding this issue, as I'd love to continue undervolting (helps with battery a lot) and 5.9 is marked EOL. I don't know whether I should update or fall back to 5.4 LTS.

[BachoSeven]

@milos7250 I'm on 5.10.3, and the behaviour is still the same, it works but you get msr: Write to unrecognized MSR 0x150 by intel-undervolt (pid: XXX). Please report to x86@kernel.org..

[milos7250]

Alright then, update it is :). Cheers 👍

[saboya]

Relevant kernel thread:

https://lore.kernel.org/lkml/20200907094843.1949-1-Jason@zx2c4.com/T/#m4bc3ddd4fcc1c1795d257ef887280dbfa9fec56c

[BachoSeven]

@heretoenhance The warning from the kernel does not disallow writes to the MSR, in fact you will find the intel-undervolt is working nevertheless. However, if you wish to remove that warning, setting the msr.allow_writes=true parameter will do so.