AMD Zen-Based Hygon Dhyana CPU Support Queued Ahead Of Next Linux Cycle
Written by Michael Larabel in Hardware on 27 September 2018 at 06:09 PM EDT. Add A Comment
Support for the Hygon Dhyana, a Chinese x86 server CPU based on AMD Zen/EPYC, will find its way into the next Linux kernel cycle.

The partnership between AMD and Haiguang IT Co was announced earlier this year for creating x86 CPUs targeting the Chinese server market. Hygon "Dhyana" is the first family of these new x86 CPUs licensed from AMD and based upon their Zen / Family 17h architecture. For the past several months there have been rounds of kernel patches sent out for review adding this Hygon Dhyana support to the Linux kernel.

These patches have revealed just how similar Dhyana is to AMD Zen/EPYC, with most of the code just adding in new PCI IDs or recognizing these CPUs as a new "Family 18h" while mirroring all of the code-paths of existing AMD CPUs / Family 17h. As reported a few days ago, the patches were settling down following eight rounds of revision. Indeed, the patches appear ready now for mainline as they have been queued in the appropriate tree as its last stop before being sent in as a pull request to Linus Torvalds next kernel merge window.

SUSE developer (and formerly of AMD) Borislav Petkov queued today the Dhyana enablement patches authored by Hygon into the x86/cpu tree. This is the staging area of x86 CPU changes ahead of the next kernel cycle, which will be Linux 4.20 or 5.0 and be opening up around mid-October while that stable release will happen around year's end.

The AMD EPYC Linux support has been in great shape since launching last year, the Hygon Dhyana support is leveraging that existing support.

The support can be toggled via a new CPU_SUP_HYGON Kconfig build-time switch and adds a few hundred lines of code to the kernel while most of that is boilerplate code for re-using existing AMD CPU code-paths. There doesn't appear to be anything "new" to this Hygon driver/kernel code for functionality not currently supported by EPYC, just reinforcing that it's a facsimile of the current AMD CPU technology.

So unless something very dramatic were to occur where these patches would get dropped from the x86/cpu tree or rejected by Torvalds, the initial Hygon Dhyana support is all but certain to be in the Linux 4.20~5.0 kernel.
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