XSAVES Supervisor States For Linux 5.8 To Support Future Intel CPU Features

Queued up this weekend as part of the x86/fpu changes slated for the upcoming Linux 5.8 cycle is low-level functionality necessary for supporting other current and future Intel CPU features.

The XSAVES supervisor states (Save Processor Extended States Supervisor) support is now queued up ahead of the Linux 5.8 kernel. These patches have been on the mailing list for a while and now deemed ready for mainline inclusion after being queued by Borislav Petkov.

This XSAVES supervisor instruction handling was done as part of the Control-Flow Enforcement Technology kernel support (Intel CET). But beyond CET support, this low-level functionality can also be used by Processor Trace (PT), ENQCMD Process Address Space ID (coming with Sapphire Rapids), and other possible future features needing the supervisor xstates handling. So this feature may not be exciting itself, but it's a stepping stone to supporting other Intel CPU features moving forward.

The code is ready come the Linux 5.8 merge window expected at the start of June.