FSGSBASE Testing Is Encouraged Ahead Of Linux 5.9

A few days ago I mentioned that it looked like the FSGSBASE patches could finally land for Linux 5.9 and indeed this performance-sensitive x86_64 feature is on track for premiering the next kernel cycle. But additional testing is encouraged.

Addressed to Andy Lutomirski confirmed plans for landing FSGSBASE support in Linux 5.9. He is encouraging testing of the FSGSBASE-enabled kernel ahead of time particularly for relevant workloads in ensuring nothing is broken and in good shape.

The work is available from this x86/fsgsbase branch. When building a kernel from that code, the nofsgsbase kernel command line option is available for disabling the functionality without having to revert the patches and rebuild the kernel. More details on the testing via this mailing list message.

I am in the process of running some fresh FSGSBASE benchmarks and should have them out in the next few days. Great to see this work finally coming to fruition considering it can benefit CPUs going back to the days of Ivy Bridge and these patches have been worked on in varying degrees for several years now. It was a Microsoft developer that recently took up the work to get it over the finish line.