On 3/6/23 08:46, Jiri Slaby wrote:
I use the intel-undervolt package that I maintain:
https://build.openbuildservice.org/package/show/hardware/intel-undervolt
Most undervolting tools do it by manipulating MSRs. Lockdown will break them.
Yeah, it definitely will as LOCKDOWN_MSR <= LOCKDOWN_INTEGRITY_MAX.
Funny enough is that the voltage MSR is not even documented in the intel manual -- as far as I can see. So as I understand it, they are playing with some undocumented MSR, using some reverse engineered values. This is something which should be disabled anyway :P.
If you really want to play with that register, you can implement a proper kernel module and sign it.
regards,
In any case, undervolting is very efficient when supported, to keep laptops cooler and more efficient. Windows tools such as ThrottleStop also manipulate MSRs. I think there was a discussion at some point by kernel people to provide a framework for undervolting tools that would not require manipulating MSRs in user-space but I do not know what the conclusion was...