Intel Preparing The Linux Kernel For Cascade Lake AP Multi-Die Support

Intel developers have begun posting their Linux kernel patches for enabling multi-die/package topology support to the Linux kernel as part of their Cascade Lake AP upbringing.

Cascade Lake "Advanced Performance" is a multi-chip package of multiple Cascade Lake dies, expected to be up to 48 cores / 96 threads per package and twelve DDR4 memory channels. Cascade Lake SP and Cascade Lake X Linux support already has been in order -- or at least appears to be based upon previous commit activity -- while Cascade Lake AP is taking some additional work due to the new multi-die design. Cascade Lake dies are connected via Ultra Path Interconnect (UPI) links.

Sent out on Monday were 11 patches for the initial multi-die/package support, in order for the kernel to discover the multi-die/package topology, export the topology inside the kernel and to user-space via sysfs, and update the various bits of the kernel to differentiate between per-die and per-package machine specific registers (MSRs).

Hitting the mailing list today were the perf subsystem patches for handling the multi-die design of Cascade Lake AP.

Cascade Lake AP will also require updates to TurboStat, lscpu, and other user-space utilities though that work hasn't been submitted yet for review.

In going through these patches so far, no new details on Cascade Lake AP were revealed -- just prepping for the multi-chip package groundwork. If the patches are accepted promptly, this work could still appear in the upcoming Linux 5.1 merge window.