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Description of problem: msr-tools does not contain the corresponding msr kernel module so values cannot be written using wrmsr Version-Release number of selected component (if applicable): 1.3 Steps to Reproduce: 1. install msr-tools 2. attempt to write (for example) an msr offset: sudo wrmsr 0x150 0x80000011ecc00000 Actual results: wrmsr: pwrite: Operation not permitted Expected results: value written Additional info: the msr kernel module necessary to write values is missing from the package/distro: lsmod| grep msr (returns nothing)
Kernels built for Fedora (and RHEL / CentOS) appear to have the msr module compiled directly into the kernel as opposed to being built as a separate module: [root@localhost ~]# grep CONFIG_X86_MSR /boot/config-4.16.3-301.fc28.x86_64 CONFIG_X86_MSR=y Because of the above, I'm not aware of any need for any separate module to be loaded, as the msr interface is already available: [root@localhost ~]# ls -l /dev/cpu/0/msr crw-------. 1 root root 202, 0 Jul 6 12:40 /dev/cpu/0/msr
>sudo wrmsr 0x150 0x80000011F9A00000 wrmsr: pwrite: Operation not permitted Based on googling, the error thrown was the same as when the msr module was missing. Based on your information I did some further research and found that by default the msr module does not play nicely with secure boot: https://github.com/intel/intel-cmt-cat/wiki/UEFI-Secure-Boot-Compatibility Looks like that was the issue all along.