Improved AMD CPU Microcode Handling On Deck For Linux 4.21

With CPU microcode updates having become increasingly important over the past year in light of the Spectre vulnerabilities and other security updates, the Linux 4.21 kernel is bringing several improvements to the AMD CPU microcode update handling.

The AMD CPU microcode update handling now does more verification work to ensure it's not corrupted, the microcode loading code has been cleaned up and seen more unification of the code paths, and other improvements.

Borislav Petkov commented in the pull request, "The result is a set of verification routines which validate the microcode blobs before loading it on the CPU. In addition, the code is a lot more streamlined and unified. In the process, some of the aspects of patch handling and loading were simplified."