Linux 5.4 Preps For Intel Tiger Lake, Elkhart Lake & Lightning Mountain + Killing MPX

The Linux 5.4 x86/cpu changes are as busy as always on the Intel side.

The Linux 5.4 x86/cpu code changes include cleaning up the Intel CPU naming conventions within definitions in the code. The changes now provide a standardized convention for dealing with Intel CPU core names and their variations within the kernel code rather than the naming convention mess that had come about over the years. This doesn't impact end-users, but cleans up the kernel code to be less confusing.

There are also model IDs added for upcoming Intel CPU cores. This pull simply is about recognizing them / their model IDs but within the other subsystems of the kernel is where the actual CPU changes are worked out. The new models added are for:

Tiger Lake - The 10nm++ successor to Icelake. Most exciting for what we know of Tiger Lake at this point is the major graphics architecture changes for Gen 12 / Xe. Intel's open-source developers have already been volleying the initial "Gen12" graphics patches and more work is on the way. Other Tiger Lake kernel enablement continues but should all be settled in time with Tiger Lake CPUs still likely being the better part of a year away.

Elkhart Lake - The ultra-low power processors for SoCs and featuring Gen 11 graphics. Other Elkhart Lake enablement is already underway elsewhere in the kernel.

Lightning Mountain - A new SoC we spotted a few weeks ago. Lightning Mountain is a variant of 14nm Airmont.

Linux 5.4 is also adding AVX512 VP2INTERSECT support to the CPU features list for reporting via /proc/cpuinfo on supported CPUs, among other reporting use-cases. VP2INTERSECT comes with Tiger Lake.

Meanwhile Linux 5.4 is dropping support for the user-space APIs exposing Intel Memory Protection Extensions (MPX). The kernel has been working to remove MPX support since it isn't widely-used and now that GCC 9 removed MPX support, there isn't a compiler supporting it through for the kernel. Eventually more of the Intel MPX code will be stripped out of the Linux kernel while the initial change is dropping the exposed APIs.

So the x86/cpu work is busy as always. Meanwhile the smp/hotplug changes for Linux 5.4 end up being notable as well. There it has taken until 2019 to cache the number of online CPUs in the name of performance instead of evaluating it in each call to num_online_cpus().