POWER Changes On The Way To Linux 4.19 Include More Spectre Work

The POWER architecture changes have been submitted for the in-development Linux 4.19 kernel.

Highlights of the recent POWER activity of code making it into this next kernel cycle includes:

- A fix to their page table fragment allocator that could lead to memory corruption or other problems.

- Fixes to their pkey support that brings it in line with the x86 pkeys support.

- Drops support for POWER8 DDI and POWER9 DDI processors. As for these chips, the POWER code maintainer commented, "neither chip should be in use anywhere other than as a paper weight."

- Optimized "memcmp" for POWER7 and later using VMX instructions.

- Support for using the barrier no speculation on some NXP processors.

- Support for flushing the count cache on context switches for some IBM POWER CPUs as a Spectre Variant Two mitigation.

- Various other fixes and improvements.

The complete list of POWER patches for Linux 4.19 can be found via this mailing list post.