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Linux 5.9 and MSRs

Open alxchk opened this issue 4 years ago • 11 comments

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

Maybe it's worth to collaborate with upstream somehow?

alxchk avatar Oct 12 '20 10:10 alxchk

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

msr: Write to unrecognized MSR 0x150 by intel-undervolt
Please report to [email protected]

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)

rien333 avatar Oct 15 '20 10:10 rien333

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.

jthomme1 avatar Oct 19 '20 10:10 jthomme1

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.

antonvalletas avatar Oct 21 '20 13:10 antonvalletas

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

alxchk avatar Oct 21 '20 13:10 alxchk

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.

milos7250 avatar Jan 01 '21 11:01 milos7250

@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 [email protected]..

BachoSeven avatar Jan 01 '21 11:01 BachoSeven

Alright then, update it is :). Cheers :+1:

milos7250 avatar Jan 01 '21 11:01 milos7250

Relevant kernel thread:

https://lore.kernel.org/lkml/[email protected]/T/#m4bc3ddd4fcc1c1795d257ef887280dbfa9fec56c

saboya avatar Feb 10 '21 02:02 saboya

Hi, I found the msr: write to unrecognized ... error in my journalctl and found this issue. I am running 5.10.16, do I need to set the msr.allow_writes= to true in order to make it work or it works without it?

heretoenhance avatar Feb 14 '21 17:02 heretoenhance

@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.

BachoSeven avatar Feb 14 '21 17:02 BachoSeven

Got it, thanks

heretoenhance avatar Feb 14 '21 17:02 heretoenhance