How to check if Zenbleed mitigation(chicken bit) is properly set?

notme@lemmy.world to Linux@lemmy.ml – 28 points –

I'm a newb and ran the recommended mitigation code to set a chicken bit on my processor. After running it there was no indication that it worked. Is there a simple way to use rdmsr to check?

https://lock.cmpxchg8b.com/zenbleed.html#solution

7

echo $(($(rdmsr -c 0xc0011029) & (1<<9) ))

Should return 512. You might need a ‘sudo’ before the rdmsr (any permission errors in any of this means it didn’t work). Unfortunately, this needs to be done every time you reboot. The next security update for linux will do this automatically.

Thanks, it works. That's a bit worrying.

Do you think Ubuntu 22.04 will get the security update soon? I got a microcode update today but i think that's only a fix for server cpus and not desktop cpus.

For anyone having permission problems turn off secure boot in order for this to work.

Microcode fixes the issue as of 3 days ago

I thought that was only for Eypc processors with desktop processor fixes coming later this year. The articles are not very clear with what is fixed when.

I also read that fixes are being released now for the high-end chips, but the desktop fixes will be released significantly later