Last year the Linux kernel began tightening up the ability to write to select CPU MSRs from user-space. That restricting of user-space access to select registers was done in the name of security as well as not wanting user-space to accidentally or maliciously poke some MSRs that could cause problems with kernel behavior. Now in kernel space there are some yet-to-be-merged patches that would place some new restrictions on kernel modules around poking certain registers or using select CPU instructions…

Source: Phoronix – Linux Patches Look To Restrict Modules From Poking Certain Registers, Using Select Instructions