With Advanced Performance Extensions (APX) on upcoming Intel processors doubling the number of general purpose registers (GPRs) among other advantages, Intel engineers are beginning to think of possible kernel uses for the extra registers.

To date there hasn’t been much thought given to kernel uses for these extra registers with the enablement thus far of APX primarily focused on user-space software. There is some thinking that these EGPRs (Extended General Purpose Registers) may be useful to help reduce kernel stack pressure. But it also needs to be decided among kernel developers just how much they plan to make use of these extra registers for knowing the best design for how to handle their use in sharing with user-space. Plus needing to keep assuming APX is optional for x86_64 Linux, maintaining legacy register use, etc.