Linux 5.14 ARM64 Preps For When Not All The CPU Cores Support 32-bit Execution

The 64-bit ARM architecture changes were submitted this week for the ongoing Linux 5.14.

One of the recent ARM64/AArch64 themes has been making kernel preparations for upcoming platforms where not all of the CPU cores may support 32-bit execution but limited to just 64-bit execution. Some of those kernel changes are in place for Linux 5.14 while some other pieces haven't yet landed.

The ARM64 work for Linux 5.14 isn't the most exciting but some of the work this cycle includes:

- Continued preparations for where not all of the CPUs on the system may support 32-bit execution, at least not for 32-bit execution at the lowest levels of execution.

- The ARM64 entry code has been migrated into C and further hardened.

- Kernel Address Sanitizer (KASAN) optimizations when using ARM MTE (Memory Tagging Extensions) or the out-of-line software tagging.

- Support for configuring Pointer Authentication independent of the kernel and user-space.

- Optimized SVE (Scalable Vector Extension) switching for CPUs with the 128-bit implementation.

- Various other clean-ups and fixes.

The full set of ARM64 patches via this pull request.