No MangoHud power readings on MSI Claw 8 AI+ A2VM (Lunar Lake)

[matte-schwartz]

Your system information

• Steam client version: 1756242410
• SteamOS version: SteamOS 3.8 (20250826.1000)
• Opted into Steam client beta?: Yes
• Opted into SteamOS beta?: Yes, Main channel
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

On my MSI Claw 8 AI+ A2VM with Intel 258V chip (Lunar Lake), MangoHud readings for CPU and power consumption both show up as 0 ootb.

Per the MangoHud README, I had to create a simple udev rule to set this parameter:

deck@msi-claw8-a2vm ~> cat /etc/udev/rules.d/99-mangohud-rapl.rules 
ACTION=="add", SUBSYSTEM=="powercap", KERNEL=="intel-rapl:0", RUN+="/bin/chmod o+r /sys/class/powercap/intel-rapl:0/energy_uj"

although this is coupled with a warning that the method above is a potential security vulnerability.

Steps for reproducing this issue:

1. Install SteamOS Main on an MSI Claw w/ Intel chipset
2. Turn the performance overlay on to level 4

[flightlessmango]

What does cat /sys/class/powercap/intel-rapl:0/energy_uj return?

[matte-schwartz]

out of the box:

deck@steamdeck ~> cat /sys/class/powercap/intel-rapl:0/energy_uj
cat: '/sys/class/powercap/intel-rapl:0/energy_uj': Permission denied
deck@steamdeck ~ [1]> sudo cat /sys/class/powercap/intel-rapl:0/energy_uj
[sudo] password for deck: 
40289179452

[flightlessmango]

Can you run MANGOHUD_LOG_LEVEL=debug mangohud vkcube in desktop terminal and attach the logs?

[matte-schwartz]

mangohud.log

[matte-schwartz]

I'm also fine with rebuilding mangohud targeting SteamOS if you need me to try any patches.

[flightlessmango]

According to the log, it looks like it should work. The steamos mangohud is pretty old at this point, it would be great if you build and test latest git

[matte-schwartz]

mangohud-git.log no change on latest git

[matte-schwartz]

also, reading back my original report, I just wanted to clarify the empty readings are without a udev rule in place to set /bin/chmod o+r /sys/class/powercap/intel-rapl:0/energy_uj.

if I do run that command or use a udev rule for it, it mostly works as intended:

I filed this issue because SteamOS will need a way to set that without user intervention, unless that's not supposed to be needed anymore on Intel GPUs.

[flightlessmango]

Oh I see, that makes sense. I think this is probably best handled by mangohud transitioning into a client/server model, allowing us to access rapl without intervention.
But that is probably not in the near future

[matte-schwartz]

makes sense. I'll leave this open as a general tracker for this on SteamOS specifically.

for now, in case anyone else comes to this issue, the simplest solution if you really want some power readings and you don't care about the potential security vulnerability is /etc/udev/rules.d/99-mangohud-rapl.rules with the contents:

ACTION=="add", SUBSYSTEM=="powercap", KERNEL=="intel-rapl:0", RUN+="/bin/chmod o+r /sys/class/powercap/intel-rapl:0/energy_uj"

which can be preserved through SteamOS updates via whitelist in /etc (see: /etc/atomic-update.conf.d/example-additional-keep-list.conf for info)