Linux 6.5 Preps For IBM POWER's "DEXCR"

Written by Michael Larabel in Linux Kernel on 20 June 2023 at 06:14 AM EDT. 6 Comments
LINUX KERNEL
Patches being queued ahead of the upcoming Linux 6.5 kernel merge window prepare initial support for DEXCR that is found in recent Power ISA specifications.

DEXCR is short for the Dynamic Execution Control Register that allows for dynamically controlling execution behavior on a per-CPU basis. With the Dynamic Execution Control Register behavior around indirect branch target prediction and other speculation features can be changed, enabling of return-oriented-programming (ROP) protections, and other behavior can be modified via this special purpose register.

DEXCR was detailed in the Power ISA 3.1B (POWER 10) specification while to date it hasn't seen any specialized integration with the Linux kernel. But now there are patches slated to be introduced with Linux 6.5 begin adding in the DEXCR support. The initial patch has made it into powerpc/linux.git's "next" branch ahead of the Linux 6.5 kernel merge window. Besides that patch are several other patches related to this POWER DEXCR bring-up for those wishing more per-CPU core control over different behavior.


It's too bad though that POWER10 isn't as open-source friendly as POWER9 and thus remains out of reach for free software enthusiasts and the fully open hardware offerings produced by Raptor Computing.
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