Intel SERIALIZE, Dropping Of SGI UV Supercomputer, i386 Clang'ing Hit Linux 5.9

A number of x86-related changes were sent out today for the first full day of the Linux 5.9 merge window.

Among the x86 material sent in so far for Linux 5.9 includes:

- With x86/cpu there is now preparations for making use of Intel's new SERIALIZE instruction, split lock detection is now enabled for Sapphire Rapids and Alder Lake CPUs, the patch confirming Alder Lake as a hybrid Core/Atom design, a simplification to the Spectre logic, and other mundane changes.

- x86/asm has changes to build the Linux x86 32-bit kernel with Clang rather than GCC, complementing the existing support for x86_64 and AArch64.

- For the x86/platform code the SGI UV1 support is being removed which in turn allows some old EFI code to be removed as well. SGI UV1 is for SGI's super-computer from a decade ago (2009) based on Intel Nehalem. The original UV supercomputer support is eliminated but later UV generations of support remains within the kernel.

- On the x86/misc front there is support to filter MSR writes to the CPU machine specific registers. Currently the filtering is just over the EPB (Energy Performance Bias) bit but is expected to be extended in the future. This work was previously talked about in Linux To Begin Tightening Up Ability To Write To CPU MSRs From User-Space.

Linux 5.9 is shaping up to be another big kernel. The merge window is running for the next two weeks followed by roughly eight weeks of release candidates, putting the stable Linux 5.9 kernel in the October timeframe.